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	description	This application claims priority to U.S. Provisional Application Ser. No. 60/711,139 (entitled BETAVOLTAIC CELL, filed Aug. 25, 2005) which is incorporated herein by reference. The invention described herein was made with U.S. Government support under Contract No W31P4Q-04-1-R002 awarded by Defense Advanced Research Project Agency (DARPA). The United States Government has certain rights in the invention. Modern society is experiencing an ever-increasing demand for energy to power a vast array of electrical and mechanical devices. Since the invention of the transistor, semiconductor devices that convert the energy of nuclear particles or solar photons to electric current have been investigated. Two dimensional planar diode structures have been used for such conversion. However, such two dimensional structures exhibit a number of inherent deficiencies that result in relatively low energy-conversion efficiencies. In the following description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments which may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the invention, and it is to be understood that other embodiments may be utilized and that structural, logical and electrical changes may be made without departing from the scope of the present invention. The following description is, therefore, not to be taken in a limited sense, and the scope of the present invention is defined by the appended claims. Three dimensional semiconductor based structures are used to improve power density in betavoltaic cells by providing large surface areas in a small volume. A radioactive emitting material may be placed on and/or within gaps in the structures to provide fuel for a cell. The characteristics of the structures, such as spacing and width of protrusions may be determined by a self-absorption depth in the radiation source and the penetration depth in the semiconductor respectively. In one embodiment, the semiconductor comprises silicon carbide (SiC), which is suitable for use in harsh conditions due to temperature stability, high thermal conductivity, radiation hardness and good electronic mobility. The wide bandgap of 4H hexagonal polytype (3.3 eV) provides very low leakage currents. In one embodiment, SiC pillars are formed of n-type SiC. P or n type dopants may be formed on the pillars or any SiC structure in various known manners. In one embodiment, p-type doping utilizes a borosilicate glass boron source formed on the pillars. The borosilicate glass may then be removed, such as by immersion in hydrofluoric acid followed by a deionized water rinse or by plasma etch. Both substitutional and vacancy mediated diffusion occurs. Other boron sources, such as boron nitride or any other boron-containing ceramic may be used in place of the borosilicate glass. The doping results in shallow planar p-n junctions in sic. The following text and figures describe one embodiment utilizing high aspect ratio micromachined pillars in semiconductors. The formation of PN junctions and provision of a radioactive beta-emitting material may be placed within gaps between the pillars to provide fuel for a cell are also described. A method for doping SiC is then described that utilizes an easily removable sacrificial layer. Some example results and calculations are then described. FIGS. 1A, 1B, 1C, 1D and 1E illustrate formation of an example betavoltaic cell. In one embodiment, a silicon carbide substrate 110 is used. Other semiconductor substrates may be used if desired, such as silicon. Photolithography and etching may be used to provide a structure 115 that has a larger surface area than a smooth substrate as shown in FIG. 1B. In one embodiment, the structure 115 comprises etched pillars 120 separated by gaps 125 between the pillars. Standard plasma etching techniques may be used to provide good control over sidewall profiles of the etched pillars 120. The roughness of the sidewalls resulting from electrochemical etching may provide traps for current flow. Photolithography may be used to pattern high aspect ratio pillars, yielding good control over the geometry of the device. This allows for better optimization of power conversion efficiency, and also may lead to better process control in commercialization. To form the pillars in one embodiment, a semiconductor wafer is patterned using standard photolithography techniques. The pattern is then transferred using plasma etching techniques such as electron cyclotron resonance (ECR) etching. These techniques can etch deep with good control over the sidewall profile, allowing for the realization of high aspect ratio structures. Other structures may also be used such as stripes 210 in FIG. 2 and scalloped stripes 310 in FIG. 3. In a further embodiment, pores in a semiconductor substrate may formed with junctions to form a porous three dimensional porous silicon diode having conformal junctions. Pore sizes may range from less than 2 nm to greater than 50 nm. Just about any structure that increases the surface area of the resulting battery may be used, High aspect ratio structures that may be doped to provide shallow junctions tend to provide the greatest increase in power density. Using the high aspect ratio pillars to form shallow junctions may lead to higher power densities over planar approaches. By etching through a typical half millimeter thick wafer, using a Tritium radiation source, this approach may yield power density increases of up to or more than 500 times planar or two dimensional approaches. Either solid source or gas source diffusion may be used to diffuse impurities 130 into the etched pillars 120, forming a p-n junction over substantially the entire length of the pillar or surface of the structure. Ohmic contacts 135, 140 compatible with the semiconductor, such as aluminum are deposited as shown in FIG. 1D. In one embodiment, contacts are formed on the tops of the pillars as indicated at 135, and on the bottom side of the substrate as indicated at 140. These serve as a cathode and anode for the resulting cell or battery. FIG. 1E provides a planar view of contact layout to minimize series resistance and simplify packaging. The device can then be mounted in a package and interfaced with the external world via wire-bonding. Gaps between the pillars may be filled with radioactive fuel, such as tritiated water (T2O), Ni-63 or other beta emitting source, such as promethium as indicated 410 in FIG. 4. In one embodiment, a metal radioactive source such as Ni-63 may be introduced by electroless/electroplating or evaporation techniques. In further embodiments, the source may be introduced before contact formation. The package can then be sealed or left open for characterization purposes. Aspect rations of up to 10:1 or higher, such as the entire thickness of the wafer, may be utilized. In a further embodiment as illustrated in FIGS. 5A and 5B, the fuel may take the form of a fluid—liquid or gas, such as T2O or solutions of radioactive salts. A cap 510 or container is formed on a cell 515, such as the cell illustrated in FIGS. 1A-1E. The cap may be formed using many different semiconductor techniques, such as PDMS, SU8, etc. A capillary or other fill device 515 may be used to introduce the fluid fuel into a resulting chamber 520. In further embodiments, the fluid fuel can be introduced by injection or otherwise. In further embodiments, a graded junction may be grown by crystal growth techniques, such as chemical vapor deposition (CVD) or implemented by diffusion from solid or gaseous sources on a planar semiconductor substrate, or by ion implantation as described below. The graded junction can then be etched to form high aspect ratio junctions. Batteries with power density of ˜5 mW/cm2 over a period of 20 years may be obtained. These may be useful to power sensors in low accessibility areas, such as pacemakers, sensor nodes in bridges, tags in freight containers and many other applications. In one embodiment, the pillars are approximately 1 um in width, with approximately 1 um between them. They may be 5 um to 500 um deep, or deeper, depending on the thickness of the substrate. The dimensions may vary significantly, and may also be a function of the self-absorption depth in the radiation source and the penetration depth in the semiconductor respectively. In one embodiment, the semiconductor comprise silicon carbide (SiC), which is suitable for use in harsh conditions due to temperature stability, high thermal conductivity, radiation hardness and good electronic mobility. The wide bandgap of 4H hexagonal polytype (3.3 eV) provides very low leakage currents. In one embodiment, SiC pillars are formed of n-type SiC. P type dopant, such a boron is performed from a borosilicate glass boron source formed on the pillars. The borosilicate glass may then be removed, such as by immersion in hydrofluoric acid followed by a deionized water rinse or by plasma etch. Both substitutional and vacancy mediated diffusion occurs. The doping results in shallow planar p-n junctions in SiC. Doping levels in one embodiment are approximately 1×1015 cm−3 for the n-type doping, and approximately 1×1017 cm−3 for the p-type doping. These doping densities may vary significantly in further embodiments. In still further embodiments, the pillars may cover substantially the entire wafer. At current densities of approximately 3 nanoamps/cm2, they may be used to form batteries with significant power capabilities. In still further embodiments, the pillars may be p-type and the dopant formed on the pillars may be n-type to form junctions. In one example, a dopant glass, such as Borosilicate glass, PSG, BPSG, etc., is deposited on the SiC pillars and annealed at high temperature, such as ˜1600° C. or greater than approximately 1300° C. to drive in the dopants. This process may also be used on any type of SiC structure, including planar substrates for circuit formation. The presence of the glass on the surface, and lower temperature than diffusing from vapor sources, reduces the effect of surface roughening through sublimation. For short diffusions, decomposition of the borosilicate glass appears to be minimal, as is surface roughening of the SiC. The resulting SiC surfaces may be smooth. In further embodiments as illustrated in FIGS. 6A, 6B, and 6C, a SiC substrate 600, which may or may not contain structures, is used as a starting point. Dopant glass 610, either p or n-type may be deposited on the SiC either by chemical vapor deposition or spin-on glass methods among other methods. The glass coated SiC is then annealed, either in vacuum or an ambient to diffuse the boron into the SiC as represented at 620, from approximately 1300° C. to approximately 1800° C. The glass 610 may then be removed by immersion in hydrofluoric acid followed by a deionized water rinse or by a plasma etch. In a further embodiment, dopant containing glass can be deposited on the SiC using a plasma enhanced chemical vapor deposition (PECVD). It may then be annealed in a vacuum at approximately greater than 1300° C. and removed by immersion in hydrofluoric acid followed by a deionized water rinse or by a plasma etch. Other boron sources, such as boron nitride or any other boron-containing ceramic may be used in place of the borosilicate glass to obtain p-type doping. It should be noted that glass was originally believed to be unstable at such high temperatures based on Si data. However, on SiC, it remains stable enough for this sacrificial application. Temperatures below 1300° C. may provide some drive in of dopants, and may be included in the phrase approximately greater than in some embodiments. FIGS. 7A, 7B, 7C, and 7D illustrate formation of a pn junction by ion implantation. A SiC substrate 710 in FIG. 7A is implanted with dopant 715, such as boron. Other p and n-type dopants may also be used. A glass 720 is then deposited on top of the implanted substrate as seen in FIG. 7B. An activation anneal is performed as illustrated in FIG. 7C, to activate the dopant, such as by ensuring dopants achieve proper locations within the crystalline lattice structure of the SiC. In FIG. 7D, the glass may be removed by acid, such as HF, or plasma etch. In one embodiment, the boron doped SiC forms a betavoltaic cell as described above. 4H SiC may be used in one embodiment. The p-n diode structure may be used to collect the charge from a 1 mCi Ni-63 source located between the pillars. The following results are provided for example only and may vary significantly dependent upon the actual structure used. An open circuit voltage of 0.72V and a short circuit current density of 16 nA/cm2 were measured in a single p-n junction. An efficiency of 5.76% was obtained. A simple photovoltaic-type model was used to explain the results. Fill factor and backscattering effects were included in the efficiency calculation. The performance of the device may be limited by edge recombination. Silicon carbide (SiC) is a wide bandgap semiconductor that has been used for high power applications in harsh conditions due to its temperature stability, high thermal conductivity, radiation hardness and good electronic mobility. The wide bandgap of the 4H hexagonal polytype (3.3 eV) provides very low leakage currents. This is advantageous for extremely low power applications. The availability of good quality substrates, along with recent advances in bulk and epitaxial growth technology, allow full exploitation of the properties of SiC. Radioactive isotopes emitting β-radiation such as Ni-63 and tritium (H-3) have been used as fuel for low power batteries. The long half-lives of these isotopes, their insensitivity to climate, and relatively benign nature make them very attractive candidates for nano-power sources. The radiation hardness of SiC4 ensures the long-term stability of a radiation cell fabricated from it. A 4H SiC p-n diode may be used as a betavoltaic radiation cell. Due to its wide bandgap, the expected open circuit voltage and thus realizable efficiency are higher than in alternative materials such as silicon. The operation of a radiation cell is very similar to that of a solar cell. Electron-hole (e-h) pairs are generated by high-energy β-particles instead of photons. These generated carriers are then collected in and around the depletion region of a diode and give rise to usable power. The dynamics of high-energy electron stopping in semiconductors are well known, with about ⅓ of the total energy of the radiation generating usable power through the creation of electron hole pairs. The remaining energy is lost through phonon interactions and X-rays. A mean “e-h pair creation energy or effective ionization parameter” in a semiconductor, takes into account all possible loss mechanisms in the bulk for an incident high-energy electron. This e-h pair creation energy is treated as independent of the incident electron energy. The effective ionization energy was calculated to be 8.4 eV for 4H SiC5. In one embodiment, doping values of 1016 cm−3 and 100% charge collection efficiency (CCE) were assumed. Calculations were performed for a 4 mCi/cm2 nickel-63 radiation source corresponding to an ideal incident β-electron current density of 20 pA/cm2, which was the source used in this work. Backscattering losses and fill factor effects are included in these calculations. The expected performance for ideal junctions (ideality factor n=1) is compared with junctions where current transport is dominated by depletion and/or edge and surface recombination (n=2). The performances realized in SiC in this work and in silicon previously are compared below. A p+4H SiC <0001> substrate cut 8° off-axis purchased from Cree Inc. was used in this study. A 4 μm thick active p layer background doped at 3×1015 cm−3, followed by a 0.25 μm thick n layer nitrogen doped at 2×1018 cm3, were grown by chemical vapor deposition (CVD) at 1600° C. and 200 Torr at a nominal growth rate of 2.5 μm/hr. Silane and propane were used as precursors with hydrogen as the carrier gas. The thickness of the active layer was chosen to match the average penetration depth of β-electrons from Ni-63 (which is about 3 μm), in order to provide good charge collection. All doping levels were experimentally determined by capacitance-voltage measurements. Test diodes (500×500 μm2) were patterned by photolithography and isolated by electron cyclotron resonance (ECR) etching in chlorine (Cl2). Backside Al/Ti contacts were evaporated by an electron beam in vacuum. They were then annealed at 980° C. to render them ohmic. 50×50 μM2 nickel contacts occupying only 1% of the active device area were then patterned and annealed at 980° C. in order to minimize backscattering losses from the high Z metal. A LEO DSM982 scanning electron microscope (SEM) at an accelerating voltage of 17 kV (corresponding to the mean energy of β-electrons from Ni-63) and a current of 0.72 nA was used to simulate an intense radiation source. An electrical feed-through connected to a probe tip was used to contact the isolated devices. The substrate was contacted to the stage with copper tape. The incident beam current density was varied by running the SEM in TV mode and changing the effective illumination area with constant beam current. The open circuit voltage (Voc) and short circuit current (Isc) were measured as a function of the incident beam current density Jbeam. In separate measurements, a 1 mCi Ni-63 source placed 6 mm from the devices was used to test the cell in air. The measured output current density of the source was 6 pA/cm2. The output of the cell was monitored for a period of one week. The leakage currents of the diodes were extracted from the forward active region of the current voltage (IV) characteristic. A typical value of the leakage current was J0=10−12 A/cm2 with an ideality factor of n=3 for 500 μm square diodes. The n=3 behavior is believed to be an artifact from high resistance contacts. A few of the diodes exhibited leakage currents of ˜10−17 A/cm2 with an ideality of n=2. The diodes were uniform in their characteristics, with the exception of those exhibiting n=2 behavior. Voc and Jsc are connected by the well-known photovoltaic relation derived from the diode equation with constant electron-hole pair generation, Voc = nV th ⁢ ln ⁡ ( Jsc J 0 ) ⁢ ⁢ for ⁢ ⁢ Jsc ⪢ J 0 ( 1 ) where J0 is the reverse leakage current density of the diode, Vth is the thermal voltage and n is the ideality factor. The voltage thus calculated from equation (1) using the measured value of J0 is 0.76 V for the Ni-63 source. There is good agreement between the open circuit voltage extracted from the above equation and the 0.72 V measured under β-electron illumination. Furthermore, the dependence of Voc on the illumination current density also exhibits an ideality of n=3, suggesting that the betavoltaic cell does indeed function in a manner analogous to a photovoltaic cell. The radiation cell was thus modeled with the following simple equation for a 500×500 μm2 diode: P = ⁢ IV = ⁢ I 0 ⁡ ( exp ⁡ ( V nV th ) - 1 ) ⁢ V - IscV ≅ ⁢ I 0 ( exp ⁢ ( V nV th ) ⁢ V - IscV ⁢ ⁢ ⁢ for ⁢ ⁢ Isc ⪢ I 0 ( 2 ) where P is the power obtained from the cell. We have used I0=(25×10−4)(1×10−12)A, n=3 and Isc=(25×10−4)(16×10−9) A for one example device. Series resistance is neglected in equation (2) as the currents being dealt with are so low. The current multiplication factor under monochromatic electron illumination is ˜1000, which is less than the total 2000 predicted by Klein's model. This is believed to stem from surface recombination, an effect well documented for SiC diodes. It was observed that when the illumination area was far from the edges of the diode, confined to its center, the current multiplication factor was ˜2000 vs. 1000 for blanket illumination, indicating that edge and surface recombination play a role in reducing collection efficiency despite the relatively large size of the devices (500×500 μm2). The highest efficiency of 14.5% and a current multiplication factor of ˜2000 were observed for an illumination area smaller than the area of the diode. It is thus expected that surface passivation techniques may improve the efficiency of the cell. Under Ni-63 irradiation, however, an enhancement in current multiplication to ˜2400 was observed. This is believed to stem from the details of the distribution characteristics of the β-radiation compared with monochromatic SEM electron illumination. No change in the open circuit voltage or short circuit current was observed during the one-week monitoring period, indicating that radiation damage did not occur over that time. This is consistent with the radiation damage threshold in SiC4. The overall efficiency of the radiation cell may be computed from Efficiency = FF ⁢ VocJsc V mean ⁢ J beam ⁢ ⁢ where ( 3 ) FF = V p ⁢ J p VocJsc ( 4 ) where Vp and Jp are the voltage and current density at the maximum power point, respectively. These were calculated numerically from equation (2) or directly from the measured data in FIG. 2c). Vmean=17 kV corresponds to the average energy of a β-particle from Ni-63 (17 keV) and Jbeam is the current density from the radiation source or from the SEM. Table 1 shows a comparison of the values of various salient parameters obtained by measurement and extraction from the model in equation (2). Fairly good correspondence is seen with the model despite the fact that the Ni-63 irradiation measurement was performed in air, implying that our model is an adequate first order description of the radiation cell. The discrepancy of the fill factor at the low currents from Ni-63 is believed to have arisen from suboptimal tunneling contacts. The measured fill factors approached their ideal values at currents>80 nA/cm2. TABLE 1ParameterMeasuredModelJ0 (A/cm2) 1 × 10−12Used measured valuen3 Used measured valueJsc (A/cm2) 1.6 × 10−8Used measured valueVoc (V)0.720.76Vp (V)0.600.60Jp (A/cm2)0.98 × 10−81.38 × 10−8FF0.510.68 Despite the low currents from the Ni-63 source, devices were obtained with a voltage of 0.72V and an efficiency of 5.76%, which can be used directly in circuits. By comparison, the use of silicon, which gives much lower voltages (˜100 mV3), necessitates multiple cells in series for usable power, complicating device geometry. Leakage currents as low as 10−24 A/cm2 have been reported for SiC PN junctions. With leakage currents of ˜10−24 A/cm2 and n=2, one can expect a voltage of ˜1.93 V and an efficiency of ˜13%. The Abstract is provided to comply with 37 C.F.R. §1.72(b) to allow the reader to quickly ascertain the nature and gist of the technical disclosure. The Abstract is submitted with the understanding that it will not be used to interpret or limit the scope or meaning of the claims.
	description	This application is a national phase entry under 35 U.S.C. §371 of PCT/CN2010/000085 filed Jan. 20, 2010, which claims priority to Chinese Patent Application No. 200910243721.4 filed Dec. 23, 2009, the entirety of each of which is incorporated by this reference. The present invention relates to the field of nuclear power, more particularly, to a high-temperature gas-cooled reactor steam generating system and method. As a clean, safe and eco-friendly energy, nuclear power is of great significance to the mitigation of energy safety and global climate change. After the setbacks of the Three Mile Island meltdown and the former Soviet Union's Chernobyl nuclear accident, people are still actively developing a safer and more economical nuclear power generation technology. Currently, the third-generation nuclear power technology has been basically mature. In the developing fourth-generation nuclear energy system, a high-temperature gas-cooled reactor (HTGR) can achieve a high outlet temperature, high generating efficiency and high-grade heat supply capacity, which has aroused widespread concern. HTGR adopts ceramic type coated particle fuel elements, uses helium as a coolant and graphite as a moderator. The core outlet temperature may reach 700° C. to 950° C. HTGR is a type of reactor with good safety property due to the following reasons: 1) excellent performance of the fuel elements; 2) large thermal capacity of the graphite core; 3) a full range of negative reactivity temperature coefficient; and 4) the coolant helium being a chemically stable inert gas without phase transition occurring. The international development of HTGR began in the early 1960, three experimental reactors have been built successively in Britain, Germany and the United States, and two prototype power plants of 330 MW and 300 MW electric power were built and run in the United States and Germany respectively by the 1970s. Without taking any special measures, the maximal core temperature of an early HTGR may exceed 2000° C. under the accident condition of losing coolant, so a dedicated emergency core cooling system is required to prevent overheating damage to the fuel elements. In order to further improve the safety of reactor, the concept of “modular” high-temperature gas-cooled reactor came into being. The modular HTGR refers specifically to the HTGR with inherent safety characteristics and relatively small single reactor power level. The basic features of such reactor are: under any accident conditions, the residual heat of the reactor core can be discharged through passive way, and the highest temperature of the core fuel would not exceed the allowable limit. Since the possibility of core melt is avoided, even if a beyond design basis accident of very low probability occurs, the radioactive dose outside the nuclear power plant still remains within the limits, the off-site emergency plan does not have to be carried out technically. Depending on the different shapes of fuel elements, HTGR is classified into the pebble-bed reactor and prismatic reactor. For the former, the coated particle fuels together with the graphite substrate are pressed into fuel pellets of a diameter of 6 cm, to form a flowable pebble bed reactor core and implement the on-load refueling. For the latter, the coated particle fuels together with graphite are pressed into cylindrical pellets, which are then put into a hexagonal prismatic fuel assembly, to form a fixed prismatic core. Comparing with the prismatic reactor, the pebble-bed HTGR has the following characteristics: 1) on-load handling of fuel elements, high availability rate of power plant; 2) small core excess reactivity, easy reactivity control, high neutron economy; 3) uniform and high discharge burnup, high fuel efficiency; 4) low temperature of fuel particles during normal operation, easy to further enhance the reactor outlet temperature. As a commercial power plant for on-grid power generation, besides adequate safety, it should possess sufficient competitive economy. The limit of the modular HTGR in the economy mainly comes from safety considerations. The inherent safety of the modular HTGR requires that the decay heat can be discharged from the core by a passive way after the accident, the maximal fuel temperature is ensured to not exceed the design limits, and that the restrictions on the power density and total power of a single core are put forward technically. How to achieve a better economy under the limit of a small single reactor power has become an issue which must be considered in the processes of design and commercial promotion of the HTGR nuclear power plant. An object of the invention is to provide a HTGR steam generating system and method achieving economy while ensuring safety, to overcome the technical defects of the prior art. To obtain the above object, a HTGR steam generating system in accordance with an embodiment of the invention is provided, which includes: a plurality of nuclear steam supply systems, a high-pressure turbine, a low-pressure turbine, a condenser, a condensate pump, a low-pressure heater, a deaerator, a water supply pump, and a high-pressure heater which are connected end to end to form a close steam loop. Preferably, a steam reheater and an intermediate-pressure turbine are in turn connected between the high-pressure turbine and low-pressure turbine in the HTGR steam generating system. Preferably, the outlet of the high-pressure heater is connected to a preliminary heating section of the steam reheater, and the inlet of a steam generator is connected to the preliminary heating section of the steam reheater. Preferably, the outlet of the high-pressure turbine is connected to a reheating portion of the steam generator. Preferably, the high-pressure turbine is connected to a reheater and the intermediate-pressure turbine respectively, the outlet of the intermediate-pressure turbine is connected to the reheater, and the reheater is connected to the low-pressure turbine. Preferably, the nuclear steam supply system comprises a reactor and a steam generator provided separately in two pressure vessels, the reactor and the steam generator are connected by a hot gas duct, and a primary helium circulator is provided on the upper part of a shell of the steam generator. Preferably, the reactor has a core designed as a flowable pebble bed structure, in which fuel elements are located and may flow from the top of the core toward the bottom of the core. Preferably, the reactor has a fixed arrangement core of prismatic structure, in which fuel elements are located. Preferably, the fuel elements adopt full ceramic type coated particle fuel elements. Preferably, the steam generator is a once-through steam generator, using a spiral tube structure. Preferably, the hot gas duct uses a ring structure, in which the outer ring is a cold helium flow channel for the helium flowing from the steam generator to the reactor, while the inner ring is a hot helium flow channel for the helium flowing from the reactor to the steam generator. The present invention also provides a HTGR steam generating method, including the steps of: S1, generating steam by means of a plurality of the nuclear steam supply systems; S2, connecting the seam in parallel and feeding it into a high-pressure turbine and a low-pressure turbine in turn to do work, in order to drive a generator; S3, the wet steam having done work entering a condenser for heat release, then entering a steam generator through a condensate pump, a low-pressure heater, a deaerator, a water supply pump and a high-pressure heater in turn, to complete a thermodynamic cycle; S4, repeating the steps S1-S3. Preferably, in step S2, after the steam being fed into the high-pressure turbine and having done work, the steam flowing out of the high-pressure turbine is sent into a steam reheater to be heated, and then successively into an intermediate-pressure turbine and the low-pressure turbine to do work. Preferably, in step S3, wet steam having done work is sent into a preliminary heating section of a steam reheater to be heated before entering the steam generator. Preferably, in step S2, after the steam being fed into the high-pressure turbine and having done work, the steam flowing out of the high-pressure turbine is sent into a reheating portion of the steam generator to be heated, and then successively into an intermediate-pressure turbine and the low-pressure turbine to do work. Preferably, in step S2, after the steam being fed into the high-pressure turbine and having done work, a part of the steam flowing out of the high-pressure turbine is sent into a reheater to be heated directly, another part of the steam flowing out of the high-pressure turbine is sent into an intermediate-pressure turbine to do work and then the outlet steam is heated by the reheater, and finally the steam heated directly as well as the steam heated after doing work in the intermediate-pressure turbine is sent into the low-pressure turbine to do work. The above technical solutions have the following advantages: taking a reactor core, a pressure vessel together with a steam generator as a standard module, thus to form the nuclear steam supply system (NSSS) module. NSSS module is copied to provide steam en masse for a large steam turbine generating system, i.e., multiple NSSS modules match a steam turbine, to achieve the configuration mode of “multiple NSSS modules driving one turbine”. A relatively small-scale individual module can reduce the difficulty of manufacture, and NSSS modules reduce the cost due to batch copy. In addition, NSSS modules share some auxiliary systems which improve the utilization of the auxiliary systems, and further reduce the cost. A plurality of generator units of “multiple NSSS modules driving one turbine” can also be configured within a plant site, to further share the auxiliary facility in power plant, and to reduce the construction and operating costs. In this way, on one hand, the inherent safety of the reactor is guaranteed and the system is simplified with such inherent safety; on the other hand, the scale economy of the steam engine system and that of other systems of a whole power station is guaranteed through batch copy, a shared auxiliary system and a scale effect. In which, 1: reactor; 2: reactor core; 3: cold helium flow channel; 4: hot helium flow channel; 5: top of the core; 6: bottom of the core; 7: high temperature and high pressure steam; 8: secondary circuit water; 9: steam generator; 10: primary helium circulator; 11: NSSS module; 12: nuclear power plant auxiliary system; 13: steam power system; 14: generator; 15: steam reheater; 21: high-pressure turbine; 22: low-pressure turbine; 23: condenser; 24: condensate pump; 25: low-pressure heater; 26: deaerator; 27: water supply pump; 28: high-pressure heater; 29: intermediate-pressure turbine; 30: reheater; 32: hot gas duct; 33: fuel elements. In combination with the attached drawings and examples, the specific embodiments of the present invention will be further described in details below. The following embodiments intend to illustrate the invention but not to limit the scope of the invention. FIG. 1 shows a steam generating system with a nuclear steam supply system (NSSS) module of the present invention. Taking a reactor core, a pressure vessel together with a steam generator as a standard module, thus to form the nuclear steam supply system (NSSS) module. A plurality of NSSS modules 11 share nuclear power plant auxiliary systems 12 and together provide steam to a steam power system 13 to drive generator 14 to generate electricity. The nuclear power plant auxiliary systems 12 mainly include: a fuel handling and storage system, a primary circuit pressure release system, a helium purification and helium auxiliary system, a gas sampling and analysis system, a residual heat removal system, a steam generator accidental release system, a component cooling water system, a reactor building ventilation and air conditioning system, a liquid waste processing system, a solid waste processing and storage system, a nuclear island fire protection system and so on. FIG. 2 is a structure schematic diagram of the nuclear steam supply system (NSSS) module according to an embodiment of the present invention. In NSSS module 11, a reactor 1 and a steam generator 9 are disposed separately in two pressure vessels, between which a hot gas duct 32 is connected, to constitute a “side by side” arrangement. The pressure vessel of the reactor 1, the shell of the steam generator 9 and the shell of the hot gas duct 32 constitute a primary circuit pressure boundary installed in a concrete shield compartment. The hot gas duct 32 uses a ring structure, of which the inner ring is a hot helium flow channel 4, having a flow direction from the reactor 1 to the steam generator 9. The outer ring is a cold helium flow channel 3, having a flow direction from the steam generator 9 to the reactor 1. A primary helium circulator 10 is provided on the upper part of the shell of the steam generator 9. High-temperature helium gas heated in the reactor 1 heats the secondary circuit water 8 in the steam generator 9, resulting in high temperature and high pressure steam 7, which is fed to the steam power system 13. The steam generator 9 is a once-through steam generator, using a spiral tube structure. The reactor core 2 is designed as a flowable pebble bed structure, in which the spherical fuel elements 33 flow from the top down. The reactor core 2 also may be a prismatic structure of fixed arrangement, and the fuel elements 33 are located in the core 2. Full ceramic type coated particle fuel elements 33 are adopted, being loaded from the top 5 of the core and unloaded from the bottom 6 of the core. Taking burnup measurements for the unloaded fuel elements 33 one by one, and discharging the fuel elements 33 having reached the discharge burnup out of the reactor for storage, while re-loading the fuel elements having not reached the discharge burnup into the core 2, to realize multiple recycles of fuel elements. FIG. 3 is a structure schematic diagram of one embodiment of the HTGR steam generating system of the present invention. Said system providing steam for the steam power system includes: nuclear steam supply systems, a high-pressure turbine 21, a low-pressure turbine 22, a condenser 23, a condensate pump 24, a low-pressure heater 25, a deaerator 26, a water supply pump 27 and a high-pressure heater 28 which are connected end to end to form a close steam loop, wherein the nuclear steam supply system is the above-mentioned one according to the embodiment of the invention. This embodiment of the present invention is a cycle solution that steam directly generates electricity. Being connected in parallel, the steam generated by the plurality of NSSS modules 11 enters the high-pressure turbine 21 and the low-pressure turbine 22 in turn to do work, in order to drive the generator 14. The wet steam having done work releases heat in the condenser 23, flows through the condensate pump 24 and then the low-pressure heater 25, the deaerator 26, the water supply pump 27 as well as the high-pressure heater 28, and is sent into the steam generator 9, to complete a thermodynamic cycle. FIG. 4 is a structure schematic diagram of another embodiment of the HTGR steam generating system of the present invention. Said system providing steam for the steam power system includes: nuclear steam supply systems, a high-pressure turbine 21, a low-pressure turbine 22, a condenser 23, a condensate pump 24, a low-pressure heater 25, a deaerator 26, a water supply pump 27 and a high-pressure heater 28 which are connected end to end to form a close steam loop, a steam reheater 15 and an intermediate-pressure turbine 29 are in turn connected between the high-pressure turbine 21 and low-pressure turbine 22, wherein the nuclear steam supply system is the above-mentioned one according to the embodiment of the invention. This embodiment of the present invention is a cycle solution that uses reheat steam supplied by special reheat nuclear steam supply system module to generate electricity. One or more reheat nuclear steam supply system modules 11 are specially provided, equipped with the steam reheater 15 to reheat the steam. Being connected in parallel, the steam generated by the plurality of NSSS modules 11 enters the high-pressure turbine 21 firstly to do work. The steam flowing out of the high-pressure turbine 21 enters the dedicated steam reheater 15 to be heated, and then successively into the intermediate-pressure turbine 29 and the low-pressure turbine 22 to do work, in order to drive the generator 14. The wet steam having done work releases heat in the condenser 23, flows through the condensate pump 24 and then the low-pressure heater 25, the deaerator 26, the water supply pump 27 as well as the high-pressure heater 28, and is sent into the steam generator 9, to complete a thermodynamic cycle. FIG. 5 is a structure schematic diagram of still another embodiment of the HTGR steam generating system of the present invention. Said system providing steam for the steam power system includes: nuclear steam supply systems, a high-pressure turbine 21, a low-pressure turbine 22, a condenser 23, a condensate pump 24, a low-pressure heater 25, a deaerator 26, a water supply pump 27 and a high-pressure heater 28 which are connected end to end to form a close steam loop, a steam reheater 15 and an intermediate-pressure turbine 29 are in turn connected between the high-pressure turbine 21 and low-pressure turbine 22, the outlet of the high-pressure heater 28 is connected to a preliminary heating section of the steam reheater 15, and the inlet of the steam generator 9 is connected to the preliminary heating section of the steam reheater 15, wherein the nuclear steam supply system is the above-mentioned one according to the embodiment of the invention. This embodiment of the present invention is an improvement of the last embodiment. One or more reheat nuclear steam supply system modules 11 are specially provided, and the equipped steam reheater 15 is further used for preliminary heating of the fed water other than heating the steam. The preliminarily heated fed water enters the evaporation NSSS module 11 to be further heated. Being connected in parallel, the steam generated by the plurality of NSSS modules 11 enters the high-pressure turbine 21 firstly to do work. The steam flowing out of the high-pressure turbine 21 enters the dedicated steam reheater 15 to be heated, and then successively into the intermediate-pressure turbine 29 and the low-pressure turbine 22 to do work, in order to drive the generator 14. The wet steam having done work releases heat in the condenser 23, flows through the condensate pump 24 and then the low-pressure heater 25, the deaerator 26, the water supply pump 27 as well as the high-pressure heater 28, and is sent into the preliminary heating section of the steam reheater 15, to complete a thermodynamic cycle. FIG. 6 is a structure schematic diagram of yet another embodiment of the HTGR steam generating system of the present invention. Said system providing steam for the steam power system includes: nuclear steam supply systems, a high-pressure turbine 21, a low-pressure turbine 22, a condenser 23, a condensate pump 24, a low-pressure heater 25, a deaerator 26, a water supply pump 27 and a high-pressure heater 28 which are connected end to end to form a close steam loop, the outlet of the high-pressure turbine 21 is connected to a reheating portion of the steam generator 9, wherein the nuclear steam supply system is the above-mentioned one according to the embodiment of the invention. This embodiment of the present invention is a cycle solution that uses reheat steam in the reactor to generate electricity. Being connected in parallel, the steam generated by the plurality of NSSS modules 11 enters the high-pressure turbine 21 firstly to do work. The steam flowing out of the high-pressure turbine 21 enters the reheating portion of the steam generator 9 again to be heated, and then successively into an intermediate-pressure turbine 29 and the low-pressure turbine 22 to do work, in order to drive the generator 14. The wet steam having done work releases heat in the condenser 23, flows through the condensate pump 24 and then the low-pressure heater 25, the deaerator 26, the water supply pump 27 as well as the high-pressure heater 28, and is sent into the steam generator 9, to complete a thermodynamic cycle. FIG. 7 is a structure schematic diagram of yet another embodiment of the HTGR steam generating system of the present invention. Said system providing steam for the steam power system includes: nuclear steam supply systems, a high-pressure turbine 21, a low-pressure turbine 22, a condenser 23, a condensate pump 24, a low-pressure heater 25, a deaerator 26, a water supply pump 27 and a high-pressure heater 28 which are connected end to end to form a close steam loop, the high-pressure turbine 21 is connected to a reheater 30 and an intermediate-pressure turbine 29 respectively, the outlet of the intermediate-pressure turbine 29 is connected to the reheater 30, and the reheater 30 is connected to the low-pressure turbine 22, wherein the nuclear steam supply system is the above-mentioned one according to the embodiment of the invention. The reheater 15 is a helium-steam reheater, while the reheater 30 is a steam-steam reheater. This embodiment of the present invention is a cycle solution that uses reheat steam out of the reactor to generate electricity. Being connected in parallel, the steam generated by the plurality of NSSS modules 11 enters the high-pressure turbine 21 firstly to do work. One part of the steam flowing out of the high-pressure turbine 21 enters the intermediate-pressure turbine 29 to do work, and the other part enters the reheater 30 to heat the outlet steam of the intermediate-pressure turbine 29. Then the heated steam enters the low-pressure turbine 22 to do work, in order to drive the generator 14. The wet steam having done work releases heat in the condenser 23, flows through the condensate pump 24 and then the low-pressure heater 25, the deaerator 26, the water supply pump 27 as well as the high-pressure heater 28, and is sent into the steam generator 9, to complete a thermodynamic cycle. The economic advantages of the modular pebble-bed HTGR are mainly embodied in: 1) high core outlet temperature, and correspondingly high generating efficiency; 2) on-load handling of fuel elements, high availability rate of power plant; 3) it does not need an emergency core cooling system, thus the system is simplified; 4) modular manufacturing; 5) if the solution of “multiple nuclear steam supply system (NSSS) modules driving one turbine” recommended in accordance with the present invention is adopted, the scale of unit power is increased, so that the economy can be further improved. The heat power of a single NSSS module of the modular HTGR is generally between 200-600 MW, typically corresponding to the electric power of more than hundreds of thousands kilowatts, and the electric power of the steam turbine generator units may run up to million-kilowatt level. According to the requirements of the input power of the steam turbine, several NSSS modules are connected in parallel to match one steam turbine unit, that is, using “multiple NSSS modules driving one turbine”, in order to achieve a matching between the modular HTGR and high-power steam generating units. By the mode of batch copy of NSSS modules, the scale effect is realized. Taking full advantage of the “high temperature” feature of HTGR, a supercritical steam cycle is achieved, and the generating efficiency is increased. Combination of the HTGR technology with the widely applied steam power cycle supercritical generating technology, is a supercritical cycle nuclear power plant most likely to be realized. As a high-quality “boiler”, HTGR may provide a heat source higher than 900° C., which may be coupled with the supercritical steam power cycle technology to obtain the generating efficiency more than other types of reactor. Even compared with a conventional fossil-fueled power plant with the same capacity, there is no loss of tail smoke since the primary circuit of HTGR is closed, and thus HTGR has the potential to achieve higher efficiency than a supercritical thermal power plant. The above description involves only the preferred embodiments of the present invention. It should be noted that for those skilled in the art, some improvements and modifications can be made without departing from the technology principle of the invention, which improvements and modifications should also be regarded as the protection scope of the present invention. In the present invention, the nuclear steam supply system (NSSS) module is formed by taking a reactor core, a pressure vessel together with a steam generator as a standard module. NSSS module is copied to provide steam en masse for a large steam turbine generating system, that is, multiple NSSS modules match a steam turbine, to achieve the configuration mode of “multiple NSSS modules driving one turbine”. A relatively small-scale individual module can reduce the difficulty of manufacture, and NSSS modules reduce the cost due to batch copy. In addition, NSSS modules share some auxiliary systems, which improves the utilization of the auxiliary systems, and further reduces the cost. A plurality of “multiple NSSS modules driving one turbine” generating units can also be configured within a plant site, to further share the auxiliary facility in power plant, and to reduce the construction and operating costs. In this way, on one hand, the inherent safety of the reactor is guaranteed and the system is simplified with such inherent safety; on the other hand, the scale economy of the steam engine system and other systems of a whole power station is guaranteed through batch copy, a shared auxiliary system and a scale effect.
	claims	1. A nuclear reactor assembly comprising a bottom nozzle, a top nozzle, a plurality of fuel rods extending axially between the top and bottom nozzles, channels defined in at least the bottom nozzle for passage of coolant past the fuel rods, and each fuel rod having at least a bottom end plug, the nuclear reactor assembly comprising:a plurality of recesses in the bottom nozzle, each recess configured for seating the bottom end plug of one of the plurality of fuel rods, and each recess defining a central axis therethrough;a plurality of first engagement surfaces on the bottom nozzle, one engagement surface for each fuel road;a second engagement surface on the bottom end plug of each fuel rod;the first and second engagement surfaces being configured for engagement with each other for axially retaining each fuel rod within the nuclear reactor assembly; andthe first engagement surface comprising at least one retainer projecting upwardly from the recess for engagement with the second engagement surface of the bottom end plug, wherein the retainer comprises at least one boss member having a stem portion extending axially relative to the central axis from the recess and a flanged portion extending radially outwardly from the stem portion. 2. The nuclear reactor assembly of claim 1 wherein the second engagement surface of the bottom end plug is segmented. 3. The nuclear reactor assembly of claim 1 wherein the boss member is comprised of segmented sections of the stem portion and flanged portions spaced from each other equidistant from the central axis of the recess. 4. The nuclear reactor assembly of claim 1 wherein each second engagement surface is comprised of a cavity for receiving the boss member, the cavity having end portions for engagement with the flanged portion of the boss member. 5. The nuclear reactor assembly of claim 4 wherein one of the first and second engagement surfaces is flexible for enabling movement thereof, in use, during engagement of the first and second engagement surfaces. 6. The nuclear reactor assembly of claim 5 wherein the cavity comprises at least one longitudinal gap therein for enabling flexible movement of the end portions of the cavity. 7. The nuclear reactor assembly of claim 6 wherein the boss member is rigid. 8. The nuclear reactor assembly of claim 5 wherein the boss member comprises a pair of stem and flanged portions spaced from each other for enabling flexible movement of the stem portions. 9. The nuclear reactor assembly of claim 8 wherein the cavity and end portions thereof are rigid. 10. The nuclear reactor assembly of claim 1 further comprising at least one second retainer projecting upwardly from the periphery of the recess for lateral retention, in use, of the fuel rod. 11. The nuclear reactor assembly of claim 10 wherein the second retainer comprises an arm portion and a clip portion. 12. The nuclear reactor assembly of claim 11 further comprising a groove around the exterior of the bottom end plug for receiving the clip portion of the second retainer. 13. The nuclear reactor assembly of claim 12 wherein the arm portion is biased inwardly towards the central axis of the recess for securing the clip portion, in use, in the groove of the bottom end plug. 14. The nuclear reactor assembly of claim 10 further comprising a plurality of second retainers projecting from each recess. 15. The nuclear reactor assembly of claim 1 further comprising a debris deflector positioned in each of a plurality of the channels in the bottom nozzle. 16. The nuclear reactor assembly of claim 15 wherein the debris deflectors comprise ribs.
	summary
	claims	1. An ion accelerator for accelerating ions traveling along a path in an ion implantation system, the accelerator comprising: a first accelerating stage comprising a first series of energizable electrodes spaced from one another along the path, each energizable electrode being spaced from an adjacent energizable electrode in a direction parallel with the path; and a first variable frequency RE power source and a first variable frequency RE resonator comprising a first terminal electrically connected with every other energizable electrode in the first series and a second terminal electrically connected with remaining electrodes in the first series, the first variable frequency RF power source operable to apply alternating potentials of a controlled frequency and amplitude to the first and second terminals, the alternating potentials at the first and second terminals being out of phase with one another. 2. The ion accelerator of claim 1 , wherein the variable frequency RF power source and the variable frequency RF resonator are each adjustable in a range from about 4 MHz to about 40 MHz. claim 1 3. The ion accelerator of claim 1 , further comprising a variable frequency ion buncher stage located upstream of the first accelerating stage along the path, and operable to provide bunched ions to the first accelerating stage along the path. claim 1 4. The ion accelerator of claim 3 , wherein variable frequency ion buncher stage comprises an energizable electrode located upstream of the first accelerating stage along the path and a variable frequency buncher RF system operable to energize the energizable electrode of the ion buncher stage at a controlled frequency corresponding to the frequency of the first accelerating stage and a controlled phase with respect to the first accelerating stage to create an alternating electric field to provide bunched ions to the first accelerating stage along the path. claim 3 5. The ion accelerator of claim 1 , wherein the alternating potentials at the first and second terminals are out of phase with one another by about 180 degrees. claim 1 6. The ion accelerator of claim 1 , further comprising: claim 1 a second accelerating stage spaced from and downstream of the first accelerating stage along the path, wherein the second accelerating stage comprises a second series of energizable electrodes spaced from one another along the path; and a second variable frequency RF power source and a second variable frequency RF resonator comprising a first terminal electrically connected with every other energizable electrode in the second series and a second terminal electrically connected with remaining electrodes in the second series, the second variable frequency RF power source being operable to apply alternating potentials to the first and second terminals of a controlled frequency corresponding to a harmonic of the frequency of the first accelerating stage, the alternating potentials at the first and second terminals being out of phase with one another. 7. The ion accelerator of claim 6 , wherein the first and second variable frequency RF power sources are operable to fix relative phasing between the alternative potentials in the first and second accelerating stages. claim 6 8. The ion accelerator of claim 6 , wherein the first and second variable frequency RF power sources are operable to adjust the relative phasing between the alternative potentials in the first and second accelerating stages. claim 6 9. The ion accelerator of claim 6 , wherein the first variable frequency RF power source is adjustable to provide the alternating potential in a frequency range between a first frequency and about ten times the first frequency. claim 6 10. The ion accelerator of claim 6 , further comprising a variable frequency ion buncher stage located upstream of the first accelerating stage along the path, and operable to provide bunched ions to the first accelerating stage along the path. claim 6 11. The ion accelerator of claim 10 , wherein the variable frequency ion buncher stage comprises an energizable electrode located upstream of the first accelerating stage along the path and a variable frequency buncher RF system operable to energize the energizable electrode of the ion buncher stage at a controlled frequency corresponding to the frequency of the first accelerating stage and a controlled phase with respect to the first accelerating stage to create an alternating electric field to provide bunched ions to the first accelerating stage along the path. claim 10 12. An ion accelerator for accelerating ions traveling along a path in an ion implantation system, the accelerator comprising: an accelerating stage comprising: one or more energizable electrodes spaced from one another along the path, each energizable electrode being spaced from an adjacent energizable electrode in a direction parallel with the path; and two or more constant potential electrodes arranged along the path with a first constant potential electrode located upstream of the energizable electrodes, and a second constant potential electrode located downstream of the energizable electrodes, wherein the constant potential electrodes are spaced from adjacent energizable electrodes to define accelerating gaps therebetween; a variable frequency RE system electrically connected with the energizable electrodes and operable to apply an alternating potential of a controlled frequency in a range between about 4 MHz and about 40 MHz to the energizable electrodes to create alternating electric fields in the accelerating gaps in a controlled fashion in order to accelerate ions through the accelerating stage along the path; and a variable frequency ion buncher stage located upstream of the accelerating stage along the path, and operable to provide bunched ions to the accelerating stage along the path. 13. The ion accelerator of claim 12 , wherein the variable frequency ion buncher stage comprises an energizable electrode located upstream of the accelerating stage along the path and a variable frequency buncher RF system operable to energize the energizable electrode of the ion buncher stage at a controlled frequency corresponding to the frequency of the accelerating stage and a controlled phase with respect to the accelerating stage to create an alternating electric field along the path. claim 12 14. The ion accelerator of claim 13 , wherein the variable frequency RF system of the accelerating stage comprises a variable frequency RF power source adjustable in a range between about 4 MHz and about 40 MHz and a variable frequency resonator adjustable in a range between about 4 MHz and about 40 MHz. claim 13 15. An ion accelerator for accelerating ions traveling along a path in an ion implantation system, the accelerator comprising: a first accelerating stage comprising: a first energizable electrode along the path; and two or more constant potential electrodes arranged along the path with a first constant potential electrode located upstream of the energizable electrode, and a second constant potential electrode located downstream of the energizable electrode, wherein the constant potential electrodes are spaced from the energizable electrode to define accelerating gaps therebetween; and a first variable frequency RF system electrically connected with the energizable electrode and operable to apply an alternating potential of a controlled frequency and amplitude to create alternating electric fields in the accelerating gaps in a controlled fashion in order to accelerate ions through the first accelerating stage along the path; and a second accelerating stage comprising: a second energizable electrode along the path; and two or more constant potential electrodes spaced from the energizable electrode along the path to define accelerating gaps therebetween; and a second variable frequency RF system electrically connected with the second energizable electrode and operable to apply an alternating potential of a controlled amplitude and a controlled frequency corresponding to a harmonic of the frequency of the first accelerating stage to create alternating electric fields in the accelerating gaps in a controlled fashion. 16. The ion accelerator of claim 15 , further comprising a variable frequency ion buncher stage located upstream of and providing bunched ions to the first accelerating stage along the path. claim 15 17. The ion accelerator of claim 16 , wherein variable frequency ion buncher stage comprises an energizable electrode located upstream of the first accelerating stage along the path and a variable frequency buncher RF system operable to energize the energizable electrode of the ion buncher stage at a controlled frequency corresponding to the frequency of the first accelerating stage and a controlled phase with respect to the first accelerating stage to create an alternating electric field to provide bunched ions to the first accelerating stage along the path. claim 16 18. The ion accelerator of claim 15 , wherein the first and second variable frequency RF systems are operable to fix relative phasing between the alternative potentials in the first and second accelerating stages. claim 15 19. The ion accelerator of claim 15 , wherein the first and second variable frequency RF systems are operable to adjust the relative phasing between the alternative potentials in the first and second accelerating stages. claim 15 20. The ion accelerator of claim 15 , wherein the first and second variable frequency RF systems are adjustable to provide alternating potentials in a frequency range between a first frequency and about ten times the first frequency. claim 15 21. The ion accelerator of claim 15 , wherein the first and second variable frequency RF systems each comprise a variable frequency RF power source and a variable frequency resonator, wherein the variable frequency RF power source and the variable frequency resonator are each adjustable between about 4 MHz and about 40 MHz. claim 15 22. An ion implantation system comprising: an ion source operable to direct charged ions having an initial energy along a path; an ion accelerator for accelerating the charged ions from the initial energy to a second energy along the path, the ion accelerator comprising: a first accelerating stage comprising a first series of energizable electrodes spaced from one another along the path, each energizable electrode being spaced from an adjacent energizable electrode in a direction parallel with the path; and a first variable frequency RF power source and a first variable frequency RE resonator comprising a first terminal electrically connected with every other energizable electrode in the first series and a second terminal electrically connected with remaining electrodes in the first series, the first variable frequency RF power source operable to apply alternating potentials of a controlled frequency and amplitude to the first and second terminals, the alternating potentials at the first and second terminals being out of phase with one another; an end station operable to position a workpiece so that charged ions accelerated to the second energy impact the workpiece; and a controller operatively connected with the variable frequency RE power source to control the frequency and amplitude of the alternating potential. 23. The ion implantation system of claim 22 , further comprising a variable frequency ion buncher stage located upstream of the first accelerating stage along the path, and operable to provide bunched ions to the first accelerating stage along the path. claim 22 24. The ion implantation system of claim 23 , wherein variable frequency ion buncher stage comprises an energizable electrode located upstream of the first accelerating stage along the path and a variable frequency buncher RF system operable to energize the energizable electrode of the ion buncher stage at a controlled frequency corresponding to the frequency of the first accelerating stage and a controlled phase with respect to the first accelerating stage to create an alternating electric field to provide bunched ions to the first accelerating stage along the path. claim 23 25. An ion implantation system comprising: an ion source operable to direct charged ions having an initial energy along a path; an ion accelerator for accelerating the charged ions from the initial energy to a second energy along the path, the ion accelerator comprising: a first accelerating stage comprising: a first energizable electrode along the path; and two or more constant potential electrodes arranged along the path with a first constant potential electrode located upstream of the energizable electrode, and a second constant potential electrode located downstream of the energizable electrode, wherein the constant potential electrodes are spaced from the energizable electrode to define accelerating gaps therebetween; a first variable frequency RF system electrically connected with the energizable electrode and operable to apply an alternating potential of a controlled frequency and amplitude to create alternating electric fields in the accelerating gaps in a controlled fashion in order to accelerate ions through the first accelerating stage along the path; and a second accelerating stage comprising: a second energizable electrode along the path; and two or more constant potential electrodes spaced from the energizable electrode along the path to define accelerating gaps therebetween; and a second variable frequency RF system electrically connected with the second energizable electrode and operable to apply an alternating potential of a controlled amplitude and a controlled frequency corresponding to a harmonic of the frequency of the first accelerating stage to create alternating electric fields in the accelerating gaps in a controlled fashion; an end station operable to position a workpiece so that charged ions accelerated to the second energy impact the workpiece; and a controller operatively connected with the variable frequency RF system to control the frequency and amplitude of the alternating potential. 26. A method of accelerating ions traveling along a path in an ion implantation system, comprising: providing a plurality of energizable electrodes spaced from one another in series along the path to define a plurality of accelerating gaps therebetween; and creating a plurality of alternating electric fields in the plurality of accelerating gaps using a variable frequency RF system electrically connected with the plurality of energizable electrodes. 27. The method of claim 26 , wherein creating the plurality of alternating electric fields comprises applying an alternating potential of a controlled frequency and amplitude to the plurality of energizable electrodes using a variable frequency RF power source and a variable frequency resonator electrically connected with the plurality of energizable electrodes. claim 26 28. The method of claim 27 , further comprising: claim 27 bunching ions from a generally DC ion beam using an ion buncher; and providing bunched ions from the ion buncher to the plurality of energizable electrodes along the path. 29. The method of claim 27 , further comprising adjusting the frequency of the variable frequency RF power source in a frequency range, wherein the frequency range includes a first frequency and frequencies of between about one and ten times the first frequency. claim 27
	summary
	claims	1. A method for manufacturing a high melting point metal based object, the method comprising:providing a powder consisting of only a pure, high melting point metal;fabricating a green object from the powder consisting of only the pure, high melting point metal, by way of partially melting the powder using a laser sintering technique;after fabricating the green object, providing an infiltration treatment to the green object by positioning the green object in a container and adding a metal solution to the container; andafter providing the infiltration treatment, positioning the infiltrated green object in a heating pressure device to provide a heating pressure treatment to the infiltrated green object, wherein a temperature applied to the infiltrated green object is controlled to a re-sintering point of the green object, and wherein a pressure of the heating pressure treatment combines the infiltrated green object having partially melted powder with completely dissolved metal in the metal solution. 2. The method of claim 1, wherein the metal solution comprises a Cu or Ni solution, wherein the Cu or Ni is completely dissolved in the metal solution. 3. The method of claim 1, wherein the powder consists of pure tungsten. 4. The method of claim 3, wherein the high melting point metal based object comprises a fabricated section having a thickness ranging from about 0.1 mm to about 0.5 mm. 5. The method of claim 4, wherein the high melting point metal based object comprises a collimator. 6. The method of claim 5, wherein a thickness of the collimator is about 0.1 mm to about 0.2 mm. 7. The method of claim 6, wherein providing the heating pressure treatment comprises:providing the heating pressure treatment to the infiltrated green object at a temperature between 2300-3000 degrees Celsius, and at a pressure above 100 MPa. 8. The method of claim 7, wherein the heating pressure device is an oven comprising a temperature and pressure control. 9. The method of claim 1, wherein fabricating comprises:a. applying a layer of the powder on a fabrication platform;b. scanning the layer by a laser beam to sinter the layer of powder;c. lowering the fabrication platform for a predetermined distance; andd. optionally repeating steps a) to c).
048250899	description	DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a view in partial section of a pair of ceiling joists 2 with a ceiling 4 of sheet rock or wall board (Gypsum) disposed beneath the ceiling joists 2. The view is through a typical attic, in which the ceiling 4 pertains to the room beneath the attic, and the ceiling joists 2 are disposed in the attic. Between the ceiling joists 2, and on top of the sheet rock, are radiant barrier elements 10 of the present invention. The radiant barrier elements 10 comprise many elements, one of which is shown in perspective in FIG. 2 and in cross section in FIG. 3. The elements 10 reflect long wave radiation in the infra red portion of the electromagnetic spectrum. A radiant barrier element 10 comprises a chip, which is generally flat and is relatively small, preferably about one inch square. However, a chip may be larger or even smaller, if desired. A plurality of the chips, in random layers, as illustrated in FIG. 1, comprise a substantial barrier to long wave infra red radiation, or heat, flowing into the attic. (Radiation in the infra red portion of the electromagnetic spectrum, or long wave infra red radiation, will simply be referred to as "long wave radiation" hereinafter.) The barrier prevents the radiant heat energy from flowing downwardly into the room beneath the ceiling 4. As best illustrated in FIG. 3, each chip 10 comprises a base film substrate 12, which is preferably polyester film, or the like, coated or metallized with aluminum or similar substance on both sides. In FIG. 3, the base layer 12 is shown with a top, metallized, layer 14 and a bottom, metallized, layer 16. The polyester film substrate 12, which actually may be of any appropriate or desired relatively thin plastic substrate, may be made in relatively large sheets and may be aluminized or metallized by well known processes prior to being cut into the individual squares or chips. If desired, the base film or substrate may also be paper, etc. The substrate, whatever it may be, includes the metallized layer on both sides to provide a radiant barrier regardless of its orientation. As shown in FIG. 1, the chips 10 are disposed in a loose fill type orientation, and they are disposed in, and consist of, many layers. The layers provide substantially continuous coverage, and with respect to the apparatus of the present invention, or to the elements of the present invention, coverage appears to be more important than a specific thickness. FIG. 4 is a perspective view of a crinkled chip 20, which comprises an alternate embodiment of the chip 10 of FIG. 2. The cross-sectional configuration of the chip 20 is substantially identical to the cross-sectional configuration of the chip 10 as illustrated in FIG. 3. However, the chip 20 is crinkled, as opposed or compared to the smooth chip 10 of FIG. 2. The crinkling provides a separation between chips to prevent them sticking one to another, and thus enhances the coverage of the chips in a relatively uniform manner in loose fill applications. In FIG. 5, layers of the crinkled chips 20 are shown disposed between the ceiling joists 2 and on top of the ceiling 4. FIG. 6 is a perspective view of an alternate embodiment of the element of the present invention, comprising a gaseous bag 30. FIG. 7 is a view in partial section of a portion of an attic in which a plurality of gaseous bags 30 are disposed on the ceiling 4 and between ceiling joists 2. FIG. 8 is a view in partial section through a bag 30 taken generally along line 8--8 of FIG. 6. For the following discussion of the gaseous bag 30 embodiment, reference will be directed to FIGS. 6, 7, and 8. The gaseous bag 30 is made of two layers of a polyester film or other appropriate thin plastic substrate, aluminized or metallized on both sides, with a pair of such elements being sealed or secured together at their outer peripheries and filled with some type of gas. In FIG. 8, the gaseous bag 30 is shown made of an upper base substrate 32, with an outer aluminized or metallized layer 34 and an inner metallized or aluminized layer 36. The gaseous bag 30 also includes a lower base substrate 38 with an outer aluminized or metallized layer 40 and an inner aluminized or metallized layer 42. The two layers 34 and 42 are secured together at a common outer periphery 44. The bag 30 includes a gas filled interior 46. The gas may be air, argon, or the like. Preferably, a substantially inert gas, such as argon is used. The common outer periphery 44 of the layers may be appropriately secured or sealed together by any well known means. Preferably, gaseous bags may be made in large sheets of gaseous bags and cut in a grid like fashion through the middle of the sealed outer peripheries of what becomes the individual bag elements. If desired, the sheets of the bags may be used as illustrated and discussed below in conjunction with FIGS. 11, 12, and 13. The gas-filled bags 30 include advantages not found with the chip 10, or the crinkled chip 20. The gaseous bags 30 provide substantial separation between layers, and the gas filled interior 46 introduces a captive gaseous barrier for insulation purposes. However, the aluminized or metallized layers still provide the primary radiant barrier for the reflection of long wave radiation or heat. FIG. 9 is a perspective view of a wrinkled wafer or fan folded chip 50, which comprises another alternate embodiment of the apparatus of the present invention. The wrinkled wafer 50 includes a base or substrate which is preferably thicker than the typical polyester film of which the wafer 10, the crinkled wafer 20, and the gaseous bag 30 is made. The reason for the thicker base film is that it must retain the wrinkled or fan folded shape illustrated in FIG. 9. The base or substrate is metallized or aluminized on both sides, as shown in FIG. 3. After metallizing or aluminizing, the substrate or base is wrinkled, as shown in FIG. 9. Again, it is the metallized exterior which reflects long wave radiation. The reflection of the long wave radiation from the wrinkled wafer 50 may provide advantages as well as disadvantages over the chip 10, the crinkled chip 20, or the wrinkled wafer or fan folded chip 50, in loose fill applications. In FIG. 10, a plurality of wrinkled or fan folded chips 50 is shown between the joists 2 and on the ceiling 4. FIG. 11 is a perspective view of a room 1 with a plurality of vertically extending wall studs 6 shown extending along a wall. The room 1 is insulated with an alternate embodiment of the apparatus of the present invention, comprising sheets of gaseous bags 60 of radiant barrier apparatus. The sheets of gaseous bags 60, which may be referred to as bubble packs, comprise sheets of gaseous bags, such as the gaseous bag 30 illustrated and discussed above in conjunction with FIGS. 6, 7, and 8. FIG. 12 is a view in partial section through a sheet of gaseous bags 60 taken generally along line 12--12 of FIG. 11. FIG. 13 is a view in partial section taken generally along line 13--13 of FIG. 11, schematically showing the sheets of gaseous bags 60 secured to the wall studs 6, and with sheets of wall board 8 and 9 secured to the studs over the sheets 60. In FIG. 11, parts of the wall boards 8 and 9 are broken away to show the sheets 60, and some of the sheets 60 are broken away to show the studs and the other related elements. For the following discussion of the sheets of gaseous bags 60, reference will be made to FIGS. 11, 12, and 13. In FIG. 12, which is an enlarged view in partial section, three separate bubbles or gaseous bags are illustrated, and they are secured together. The bubble packs include a first generally continuous film layer 62 and a second generally continuous film layer 72, which are preferably polyester film or some other type of plastic film substrates. On the film layer or substrate 62 there is an outer aluminized or metallized layer 64 and an inner aluminized or metallized layer 66. In other words, the continuous film layer 62 is metallized or aluminized on both sides. The film layer 62 comprises a substrate for the metal layers 64 and 66. The second continuous film layer 72 is substantially identical to the film layer 62. The film layer 72 also includes an outer layer 74 and an inner layer 76. The layers 74 and 76 are, of course, metallized or aluminized layers so that the film 72, with its layers, is substantially identical to the layer 62. The two film layers 62 and 72 are appropriately secured together in a grid type of pattern, as illustrated in FIG. 11. The layers join at horizontal connecting or lines 70 and vertical connecting lines 78. Within the grid of the connecting lines 70 and 78 are gas-filled interiors 80. The gas used to fill the interior of the bubble pack or sheet 60 may be air, argon, or some other relatively inert gas, as discussed above. It will be noted that both sides of the base film layer in each of the above-discussed embodiments is metallized or aluminized on both sides. This insures the proper reflection of long wave radiation, even though one side may be subjected to dust, dirt, etc. Obviously, with the gas filled embodiments 30 and 60, the interior of each bubble or bag is substantially sealed so that dust, etc., cannot penetrate. Accordingly, the interior metallized layer always provides a reflective surface for the radiant energy. FIG. 14 illustrates another alternate embodiment of the apparatus of the present invention in which a single metallic layer is deposited between a pair of films or film substrates. FIG. 14 comprises a view in partial section of an alternate embodiment radiant barrier apparatus 90 disposed on top of a ceiling joist 2. The alternate embodiment 90 includes a layer of expanded polystyrene foam, or the like, base 92. Appropriately bonded to the foam base 92 is a relatively thin layer or sheet 94, which may be a one-half mil polystyrene film substrate. A metallized layer 96 is appropriately secured to the film 94. A film layer 98 is in turn disposed on the metal layer 96. The layer 98 is a relatively thick protective film layer, protecting the metallized layer 96, as well as the bottom film layer 94. The thickness of the film layer 98 may be about two mils, or about four times as thick as the layer 94. The layer 98, and also the layer 94, should both be clear film layers to insure that the metal coating layer 96, sandwiched between the two film layers 94 and 98, is highly reflective, and with relatively low emissivity, for long wave radiant energy. It is known and understood that an aluminized layer may oxidize in time. With an aluminized layer sandwiched between two film layers, as the metal layer 96 is sandwiched between the layers 94 and 98, the likelihood of oxidation is substantially reduced due to the sandwich construction. The expanded polystyrene layer 92, or other appropriate base layer, provides the structural strength for supporting the metallized sandwich film layers and also provides additional insulation to help protect the room beneath the ceiling joist(s) 2 from the penetration of radiant heat. The film layers 94 and 98 have been discussed as being substantially clear, and the other film layers involved, as discussed above, should similarly be substantially clear to provide for maximum reflectivity of the metallized or aluminized layers. In place of the substrate discussed above in conjunction with the chip 10 and the crinkled chips 20, paper or the like could be used as a substrate, if desired. However, such paper substrate obviously would not be clear, but rather would be opaque. FIG. 15 is a perspective view of an expanded polystyrene base element 100, which is part of an alternate embodiment of the apparatus of the present invention. FIG. 16 is an end view of the base element polystyrene block 100, with a metallized film layer 120, shown in partial section, spaced apart from the block 100. FIG. 17 is an end view of an alternate embodiment 150 of the apparatus of the present invention, comprising a pair of base elements 100, with metallized film layers secured to the blocks. The top block layer is inverted and the blocks are disposed against each other and are appropriately secured together. For the following discussion of the alternate embodiment 150, reference will primarily be directed to FIGS. 15, 16, and 17. The block 100 is preferably a generally rectangular block support layer or base having a flat bottom 102 and four relatively flat sides. The sides include a side 104 and a side 106, shown in FIG. 15, and a side 110, shown in FIG. 16, along with the side 104 and a side 106. The top of the block 100 includes a plurality of generally parallel and diagonally extending rounded grooves 112, or a plurality of alternating convex and concave linear elements. The grooves 112 extend diagonally with respect to the four sides of the rectangular block 100. The tops of the linear elements 112 are generally parallel and are aligned with each other, and the bottoms of the grooves are at a common depth, all as best shown in FIGS. 16 and 17. In FIG. 16, a flexible film layer 120 is shown spaced above the grooves 112 of the block 100. The film layer 120 includes a substrate 122 that is appropriately metallized on both its top side and its bottom side. The metallized layers include a top metal layer 124 and a bottom metal layer 126. The metallized layers may be any appropriate metal, as discussed above. As previously indicated, the film layer 120, with its substrate 122 and metallized layers 124 and 126, is flexible. The metallized film layer 120 is appropriately secured to the top of the block 100, or on the diagonally extending and rounded grooves 112. The completed unit comprises a radiant barrier thermal block 130. In FIG. 17, two radiant barrier thermal blocks 130 are shown disposed against each other in a facing relationship and defining radiant barrier apparatus 150. The base block are disposed with the metallized film layers 120, on the grooves 112, facing each other. It will be understood that, because the grooves 112 are cut on a diagonal, the contact between the grooves will be in a diagonal spot-type relationship, rather than in a parallel relationship along the tops of the rounded grooves. Thus, rather than defining tubes, as would be the case if the tops of the grooves, or the lands, were in direct contact with each other, there is a series of discontinuous or separated air pockets in the center of the radiant barrier apparatus 150. It will be understood that the radiant barrier apparatus 150, in addition to comprising a radiant barrier, also comprises relatively good insulation for all types of heat transfer, rather than merely a barrier for radiant energy. The general similarity between the component elements 130 of the barrier apparatus 150 to the radiant barrier apparatus 90 of FIG. 14 is apparent. However, the expanded foam base 92 of the radiant barrier apparatus 90 is flat on both its top and bottom sides, and accordingly, the metallized substrate is relatively flat. However, in the barrier apparatus 130, the bottom 102 is flat, but the top consists of diagonally extending gently rounded grooves, thus providing a uniformly curved surface on the top. When the metallized film or substrate layer 120 is placed thereon, the film or substrate layer takes the configuration of the grooved top and accordingly is not flat. FIG. 18 is a view in partial section of another alternate embodiment of the apparatus of the present invention, comprising a flexible radiant barrier apparatus 160. The radiant barrier apparatus 160 includes a metallized film layer 170 appropriately secured to a mesh support layer 180. The film layer 170 includes a substrate or film layer 172, with a metallized layer 174 on the top and a metallized layer 176 on the bottom of the film or substrate layer 172. The mesh layer 180 is appropriately secured to the top of the film layer 170. A second mesh layer 190 is shown appropriately secured to the bottom of the film layer 172, or to the metal layer 176, which is the bottom metallized layer of the film substrate 172. If desired, there could be an additional metallized film layer 200 secured to the bottom mesh layer 190. The metallized film layer 200 includes a film or substrate 202 with a top metallized layer 204 and a bottom metallized layer 206 secured thereto. The three layers comprise the metallized film layer 200. Secured to the bottom metal layer 206 of the metallized layer 200 is another mesh layer 210. The apparatus 160, as illustrated in FIG. 18, includes outer, or top and bottom, mesh layers 180 and 210, and a mesh layer 190 disposed between the two metallized film layers. Thus, the metallized layers 170 and 200 include mesh layers on opposite sides of them. The mesh layers of the radiant barrier apparatus 160 provide flexibility and the support required for the barrier apparatus 160 to enable the barrier apparatus 160 to be wrapped around rounded objects, such as pipes, cylindrical water heaters, and the like. The apparatus 160 accordingly provides radiant barrier apparatus with the flexibility to conform to non linear or non flat surfaces, as desired. The primary purpose of the mesh is to separate the radiant barrier, the metallized film, from a heat source. For example, if the apparatus 160 is used to insulate a water heater, the mesh layer against the water heater provides contact between the water heater and the metallized film layer. Similarly, if the apparatus 160 is used as a flat radiant barrier, as on a wall, an outer mesh layer separates the heat source from the radiant barrier metallized film layer. It will be further understood that, while only two metallized layers 170 and 200 are shown in FIG. 18, there could be additional alternate layers of metallized film and support mesh to provide the desired thickness required for various applications. If desired, the outermost layer, or the layer farthest from the heat source, need not be a mesh layer, but may be a metallized film layer. The purpose of the grooves 112 (see FIGS. 15, 16, and 17) is to prevent the film layers from touching each other over an extended area. The only contact points are at the intersections of the tops of the oppositely extending diagonal grooves (or lands). The convex outer surface configuration of the bubbles 30, or of the bubble packs or sheets 60, prevents the metallized film layers from touching each other, or prevents touching over an extended area, and prevents the metallized film layers from touching or contacting a heat source, or minimizes any such touching. The various configurations of the film layer bases, including the mesh, actually minimizes contact, if not outright preventing contact. While the principles of the invention have been made clear in illustrative embodiments, there will be immediately obvious to those skilled in the art many modifications of structure, arrangements, proportions, the elements, materials, and components used in the practice of the invention, and otherwise, which are particularly adapted for specific environments and operative requirements without departing from those principles. The appended claims are intended to cover and embrace any and all such modifications, within the limits only of the true spirit and scope of the invention. This specification and the appended claims have been prepared in accordance with the applicable patent laws and the rules promulgated under the authority thereof.
	description	FIG. 4 is a diagram illustrating the entire configuration of an X-ray reduction projection exposure apparatus. In FIG. 4, X-rays (vacuum-ultraviolet rays or soft X-rays) are emitted from an undulator source 101, serving as a radiation source. The optical path of the X-rays is deflected by an illuminating system comprising a convex total-reflection mirror 102 and a concave multilayer-film reflecting mirror 103, and the X-rays are then projected onto a reflection mask 104. A multilayer film for effecting regular reflection of X-rays is formed on the reflection mask 104, and a predetermined circuit pattern is formed on the multilayer film. The X-rays reflected by the reflection mask 104 reach a wafer 106 after passing through a reduction projection optical system 105 having a plurality of reflection mirrors, to image the circuit pattern on the wafer 106 with a predetermined projection magnification (for example, ⅕). The reflection mask 104 is fixed and held on a mask stage 107, and the wafer 106 is fixed and held on a wafer stage 108. The reflection mask 104 and the wafer 106 are aligned with each other by the mask stage 107 and the wafer stage 108, respectively, and the scanning movement of the mask stage 107 holding the reflection mask 104 and the wafer stage 108 holding the wafer 106 is performed in a synchronized manner. Since the wavelength of the X-rays used for exposure is between about 20 nm and 4 nm, the theoretical resolution determined by the wavelength of the exposure light is improved. Since vacuum-ultraviolet rays and soft X-rays are greatly attenuated by a gas, the inside of the entire apparatus is held in a vacuum or in a reduced pressure of a light-element gas, such as helium or the like. In the present invention, an electrostatic chuck (unipolar type) which is suitable for the use in a vacuum or in a reduced pressure is used for a mechanism for fixing and holding the reflection mask 104 on the mask stage 107. The electrostatic chuck functions based on the principle that charges having a sign opposite to that of an electrode are excited on an insulator provided on the chuck""s surface to cause a dielectric polarization phenomenon to occur, so that an electrostatic force is applied to an object to be attracted. The attracting force F of the electrostatic chuck is represented by the following expression: F=S/2xc3x97∈xc3x97(V/d)2, where S is the area of the electrode of the electrostatic chuck, ∈ is the dielectric constant of the insulator, V is the applied voltage, and d is the thickness of the insulator on the surface. The above-described expression may be modified in accordance with various conditions. In a bipolar electrostatic chuck which is easy to handle and in which an object to be attracted need not be grounded, the attracting force is less than half the value of the above-described electrostatic chuck (unipolar type). For example, when using high-purity Al2O3, which is little contaminated with metal, for the insulator on the surface, the attracting force is about 25 g/cm2. If the pattern region of the reflection mask is 200 mm square with a thickness of a few xcexcm, and the base is 210 mm square with a thickness of 10 mm and is made of Si, the mass of the reflection mask is about 1 Kg. If a time period of 0.5 sec is required for exposure of one shot, it is necessary to scan a distance of 200 mm in a time period equal to or less than 0.5 sec. Hence, if a scanning speed of 400 mm/sec is obtained within 0.05 sec, the maximum acceleration of the mask stage is 8 m/sec2. When the mask is supported in a direction parallel to the direction of gravity, the maximum acceleration applied to the mask after adding the acceleration due to gravity is about 18 m/sec2, i.e., the force applied to the mask in the scanning direction is 18 N. Since the attracting force of the electrostatic chuck is 21xc3x9721xc3x970.025xc3x979.8 =100 N, the coefficient of friction must be equal to or greater than 0.18 N in order to prevent the reflection mask from dropping. In general, the surface of the electrostatic chuck is very precisely processed to an excellent flatness, and therefore has a low coefficient of friction. Hence, the mask may drop in the worst case. Accordingly, in the present invention, the attracting force of the mask by the electrostatic chuck is changed-in accordance with a situation in order to prevent the mask from dropping. A specific configuration for that purpose will now be described. First Embodiment FIG. 1 is a cross-sectional view as seen from the side, illustrating the configuration of a mask supporting device, which is used in a mask stage of an X-ray projection exposure apparatus, according to a first embodiment of the present invention. In FIG. 1, a reflection X-ray mask 1, serving as an optical element, comprises a base 1a comprising an Si substrate, and a pattern region 1b. The pattern region 1b is formed on the base 1a according to a thin-film forming method, such as magnetron sputtering, or the like. The pattern region 1b comprises a region having a low reflectivity for X-rays, such as vacuum-ultraviolet rays or soft X-rays, and a pattern portion having a high reflectivity for the X-rays. The pattern portion comprises an X-ray absorbing member (for example, made of gold or tungsten) formed on a patterned X-ray reflecting multilayer film obtained by alternately laminating at least two kinds of substances having different refractive indices for vacuum-ultraviolet rays or soft X-rays. The mask supporting device for holding the mask 1 comprises an electrostatic chuck 2 for attracting the mask 1, a plurality of pin-shaped projections 6 formed on portions thereof, a pressure sensor (attracting-force detection means) 11 for detecting an attracting force for the mask 1, an attraction control unit 12 for calculating the attracting force from the result of detection of the pressure sensor 11, a voltage control unit 10 for outputting a voltage for controlling the attracting force from the attracting force calculated by the attraction control unit 12, and a driving control unit 9 for effecting scanning movement of the mask 1. A supply tube 7 for supplying voids formed between the projections 6 with a cooling gas (such as helium or the like), and a recovering tube 8 for recovering the gas introduced into the voids are also provided. The electrostatic chuck 2 comprises a first insulating layer 3 and a second insulating layer 4. A first electrode 5a and a second electrode 5b for generating the attracting force are formed between the first insulating layer 3 and the second insulating layer 4, and the pin-shaped projections 6 are formed on the first insulating layer 3. In this configuration, when a voltage is applied from the voltage control unit 10 to the first electrode 5a and the second electrode 5b of the electrostatic chuck 2, static electricity is generated and charges having a sign different from that of the voltage are excited on the surface of the first insulating layer 3. At that time, the dielectric polarization phenomenon appears on the surface of the first insulating layer 3, and an electrostatic force is applied to the mask 1. The mask 1 is thereby attracted and fixed by being supported on the pin-shaped projections 6 formed on the electrostatic chuck 2. Since a so-called pin-chuck shape is provided in the above-described manner and the ratio of the area of portions of the distal ends of the pin-shaped projections 6 contacting the back of the mask 1 to the entire area of the mask 1 is arranged to be equal to or less than 10% (more preferably, less than 2%), the deformation of the mask 1 due to the presence of dust between the mask 1 and the electrostatic chuck 2 is prevented. In addition, since cooling gas flows in the voids between the projections 6, the mask 1, placed in a vacuum in which cooling is difficult to perform, is effectively cooled from the back to suppress the distortion of the mask pattern. The pressure sensor 11 for detecting the attracting force for the mask 1 is disposed on the surface of the electrostatic chuck 2, and the attracting force for the mask 1 is calculated by the attraction control unit 12 from a detection signal from the pressure sensor 11. In order to increase the illuminating region for the mask 1, the electrostatic chuck 2 is subjected to scanning movement by the control of the driving control unit 9. The attraction control unit 12 calculates the acceleration of the electrostatic chuck 2 from position information relating to the electrostatic chuck 2 detected by the driving control unit 9, and transmits an instruction to the voltage control unit 10 so that the following relationship is satisfied: {(the mass of the mask)xc3x97(acceleration due to gravity+the maximum acceleration of the mask while being moved)/(the maximum coefficient of static friction between the mask and the mask chuck)}xc3x97(safety factor) less than the attracting forcexe2x80x83xe2x80x83(1), wherein (the attracting force) is defined by: (the generating electrostatic force)xe2x88x92(the differential pressure between the pressure of the cooling gas and the atmosphere pressure of the inside of the entire apparatus). The voltage control unit 10 controls the attracting force by changing the voltage applied to the first electrode 5a and the second electrode 5b in accordance with the instruction from the attraction control unit 12. Expression (1) may be satisfied by controlling the attracting force to be constant and controlling the acceleration instead of the attracting force by providing an instruction from the attraction control unit 12 to the driving control unit 9. According to the above-described configuration, the drop of the mask 1 from the electrostatic mask 2 is prevented. Second Embodiment FIGS. 2(a) and 2(b) are diagrams illustrating the configuration of a mask supporting device according to a second embodiment of the present invention: FIG. 2(a) is a perspective view; and FIG. 2(b) is a cross-sectional view as seen from the side. In the mask supporting device of the first embodiment, a bipolar electrostatic chuck is used. In the mask supporting device of the second embodiment, a unipolar electrostatic chuck having a strong attracting force is used. By using such a unipolar electrostatic chuck, reliability in the attraction of the mask is improved. The second embodiment has the same structure as the first embodiment, except as noted below. In FIGS. 2(a) and 2(b), only the configuration of components added in the second embodiment which are not found in the first embodiment, is illustrated, and the attraction control unit, the voltage control unit and the driving control unit shown in the first embodiment are not illustrated. Since the operations of these units are the same as in the first embodiment, a description thereof will be omitted. When attracting a mask on the unipolar electrostatic chuck, the mask must be grounded. However, since the mask is conveyed within the exposure apparatus and is mounted on and detachable from the electrostatic chuck, it is difficult to always ground the mask. Accordingly, in the mask supporting device of the second embodiment, the mask is grounded only when it is attracted on the electrostatic chuck so as not to hinder the conveyance of the mask. In FIGS. 2(a) and 2(b), a mask 21 comprises a base 2a comprising an Si substrate, and a pattern region 2b which is formed on the base 2a. The mask supporting device for attracting and holding the mask 21 comprises an electrostatic chuck 22 for attracting the mask 21, and an earth pawl 26 for grounding the mask 21. The electrostatic chuck 22 comprises a first insulating layer 23 and a second insulating layer 24, and an electrode 25, for generating an attracting force, is formed between the first insulating layer 23 and the second insulating layer 24. The earth pawl 26 is connected to a minus (xe2x88x92) terminal of a power supply 27, and a plus (+) terminal of the power supply 27 is connected to the electrode 25. In this configuration, when the plus (+) potential of the power supply 27 is applied to the electrode 25 of the electrostatic chuck 22, charges of a different sign are excited on the surface of the first insulating layer 23. At that time, the dielectric polarization phenomenon appears on the surface of the first insulating layer 23, and an electrostatic force is applied to the mask 21. The mask 21 is thereby attracted and fixed to the electrostatic chuck 22. The earth pawl 26 is fixed relative to the electrostatic chuck 22 so as to be movable in the z direction shown in FIG. 2(b) to contact the base 2a of the mask 21, so that the mask 21 can be grounded and masks having different thicknesses can be attracted. By disposing the earth pawl 26 at a side of the base 2a, the earth pawl 26 also has the function of preventing the mask 21 from dropping. An object which can be attracted by the electrostatic chuck 22 is a conductor or a semiconductor. When attracting a mask 21 having a base 2a made of an insulator, the mask 21 is attracted by forming a conductive layer of a metal on the back and the sides of the mask 21 by vacuum deposition or the like and contacting the conductive layer to the earth pawl 26. According to the above-described configuration, a unipolar electrostatic chuck having a strong attracting force can be used for the mask supporting device, and reliability in the attraction of the mask can be improved. Since a sufficient attracting force can be obtained even with a material having a relatively low dielectric constant, a material with low metal contamination can be adopted. When semiconductor devices are manufactured using an exposure apparatus including the mask supporting device of the second embodiment, the production yield of the devices can be increased. Furthermore, since masks having different thicknesses can be attracted, the tolerances in the thickness of the mask required in the manufacture of the mask can be increased. Hence, the cost in the manufacture of the mask can be reduced. Since the earth pawl 26 also has the function of preventing the mask 21 from dropping, reliability in the attraction of the mask is improved. In addition, since a grounding mechanism which does not hinder the conveyance of the mask 21 is adopted, reliability in the conveyance of the mask is also improved. Third Embodiment FIG. 3 is a cross-sectional view as seen from a side illustrating the configuration of a mask supporting device according to a third embodiment of the present invention. The mask supporting device of the third embodiment includes temperature control means for controlling an electrostatic chuck to be a desired temperature. The third embodiment has the same structure as the first embodiment, except as noted below. In FIG. 3, only the configuration of components added in the third embodiment, which are not found in the first embodiment, is illustrated, and the attraction control unit and the voltage control unit shown in the first embodiment are not illustrated. Since the operations of these units are the same as in the first embodiment, a description thereof will be omitted. In FIG. 3, a mask 31 comprises a base 31a comprising a Si substrate, and a pattern region 31b which is formed on the base 31a. The mask supporting device for attracting and holding the mask 31 comprises an electrostatic chuck 32 for attracting the mask 31, a chuck base 38 having a low coefficient of linear expansion and high stiffness on which the electrostatic chuck 32 is fixed, a temperature sensor 37 for detecting the temperature of the chuck base 38, a temperature-adjusting-medium supply device 42 containing a temperature-adjusting or controlled medium for changing the temperature of the chuck base 38 by changing the temperature of the temperature adjusting or controlled medium, a temperature control unit 41 for controlling the temperature-adjusting-medium supply device 42 based on a detection signal from the temperature sensor 37, and a driving control unit 44 for effecting scanning movement of the electrostatic chuck 32. The electrostatic chuck 32 comprises a first insulating layer 33 and a second insulating layer 34. An electrode 35 for generating an attracting force is formed between the first insulating layer 33 and the second insulating layer 34. A plurality of pin-shaped projections 36 are formed on the surface of the first insulating layer 33. In addition, a supply tube 45 for supplying voids formed between projections 36 with a cooling gas, and a recovering tube 46 for recovering the gas introduced into the voids are provided. In this configuration, when a voltage is applied from a voltage control unit (not shown) to the electrode 35 of the electrostatic chuck 32, charges having a sign different from that of the voltage are excited on the surface of the first insulating layer 33. At that time, the dielectric polarization phenomenon appears on the surface of the first insulating layer 33, and an electrostatic force is applied to the mask 31. The mask 31 is thereby attracted and fixed on the pin-shaped projections 36 formed on the electrostatic chuck 32. The temperature sensor 37 comprises, for example, a platinum resistance temperature sensor, and has a resolution of about 0.01xc2x0 C. By being directly buried at a sufficiently deep position in the chuck base 38, the temperature sensor 37 can very precisely detect the temperature of the chuck base 38. A channel 39 is provided in the chuck base 38 in order to receive a temperature-adjusting or controlled medium subjected to temperature control. The temperature-adjusting or controlled medium is supplied from the temperature-adjusting-medium supply device 42 via flexible tubes 43 made of a metal or Teflon which has a low gas discharge rate in a vacuum. The chuck base 38 comprises, for example, a ceramic material, such as SiC, SiN or the like, or low-thermal-expansion glass, in which thermal strain is very small due to a low coefficient of linear expansion. The temperature control unit 41 controls the temperature-adjusting-medium supply device 42 based on an output signal from the temperature sensor 37 in order to control the temperature of the temperature-adjusting or controlled medium to be supplied to the chuck base 38. The electrostatic chuck 32 generates a sufficient force to attract the mask 31, and prevents the thermal expansion of the mask 31, having absorbed exposure light in lateral directions, by the attracting forcexc3x97the coefficient of friction of the electrostatic chuck 32. In order to prevent position deviation in lateral directions due to thermal expansion, the temperature of the electrostatic chuck 32 is very precisely controlled. More specifically, variations in the temperature of the electrostatic chuck 32 are very precisely controlled within a range equal to or less than 0.01xc2x0 C. In general, in an exposure apparatus, exposure is performed after very precisely aligning a mask with a wafer. In order to precisely perform the alignment, as disclosed in Japanese Patent Laid-Open Application (Kokai) No. 2-100311 (1990), a fine movement mechanism using a displacement member, comprising an elastic member having a low stiffness, such as a leaf spring or the like, and an actuator, comprising a piezoelectric element, are required for a mechanism for driving the wafer or the mask. The fine movement mechanism vibrates when the temperature adjusting medium flows because of its low stiffness, thereby degrading accuracy in the line width of the transferred pattern. In order to solve such a problem, the mask supporting device of the third embodiment uses only a coarse movement mechanism having a high stiffness for the driving mechanism, and a fine movement mechanism is provided in a mechanism for driving the wafer. The device also includes means for measuring the amount of shift of the interval between patterns on the exposed wafer, and expanding or contracting the electrostatic chuck by changing the temperature of the electrostatic chuck so as to minimize the amount of the shift. When the electrostatic chuck 32 is expanded or contracted, since the mask 31, attracted and constrained thereon, is simultaneously expanded or contracted, it is possible to correct the position deviation of the pattern of the mask 31. The temperature of the electrostatic chuck 32 is corrected by measuring, in advance, the relationship between the amount of shift of the pattern of the wafer after exposure and the change in the temperature of the electro-static chuck 32, and by controlling the temperature of the electrostatic chuck 32 by the temperature control unit 41 so as to minimize the amount of shift of the interval between patterns on the wafer based on the obtained data. The amount of shift of the interval between patterns on the wafer may be obtained from a signal from alignment adjusting means (not shown) for performing alignment between the mask and the wafer, instead of measuring the interval between exposed patterns. Instead of using a temperature adjusting medium, the temperature of the electrostatic chuck 32 may be adjusted by precisely controlling the temperature at a high speed using, for example, a Peltier-effect element as disclosed in Japanese Patent Laid-Open Application (Kokai) No. 5-21308 (1993). Embodiment of Device Manufacturing Method FIG. 5 is a flow chart of a method for manufacturing semiconductor devices (semiconductor chips of ICs (integrated circuits), LSIs (large-scale integrated circuits) or the like, liquid-crystal panels, CCDs (charge-coupled devices) or the like) using the above-described X-ray projection exposure apparatus. In step 1 (circuit design), circuit design of semiconductor devices is performed. In step 2 (mask manufacture), masks, on which designed circuit patterns are formed, are manufactured. In step 3 (wafer manufacture), wafers are manufactured using a material, such as silicon or the like. Step 4 (wafer process) is called a preprocess, in which actual circuits are formed on the wafers by means of photolithography using the above-described masks and wafers. Step 5 (assembly) is called a postprocess which manufactures semiconductor chips using the wafers manufactured in step 4, and includes an assembling process (dicing and bonding), a packaging process (chip encapsulation), and the like. In step 6, (inspection), inspection operations, such as operation-confirming tests, durability tests, and the like, of the semiconductor devices manufactured in step 5 are performed. The manufacture of semiconductor devices is completed after passing through the above-described processes, and the manufactured devices are shipped (step 7). FIG. 6 is a detailed flow diagram of the above-described wafer process (step 4). In step 11 (oxidation), the surface of the wafer is oxidized. In step 12 (CVD (chemical vapor deposition)), an insulating film is formed on the surface of the wafer. In step 13 (electrode formation), electrodes are formed on the surface of the wafer by vacuum deposition. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive material is coated on the wafer. In step 16 (exposure), the circuit pattern on the mask is exposed and printed on the wafer using the above-described X-ray projection exposure apparatus. In step 17 (development), the exposed wafer is developed. In step 18 (etching), portions other than the developed resist image are etched off. In step 19 (resist separation), the resist, which becomes unnecessary after the completion of the etching, is removed. By repeating these steps, a final circuit pattern made of multiple patterns is formed on the wafer. The individual components shown in outline or designated by blocks in the drawings are all well known in the X-ray projection exposure apparatus and device manufacturing method arts and their specific construction and operation are not critical to the operation or the best mode for carrying out the invention. While the present invention has been described with respect to what are presently considered to be preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. To the contrary, the present invention is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions.
	claims	1. An X-ray apparatus which includes an X-ray source ( 1 ) for producing X-rays ( 2 ), an X-ray detector ( 4 ) for detecting the X-rays, and a filter ( 14 ) which is arranged between the X-ray source and the X-ray detector and includes a plurality of tubular filter elements ( 13 ) having a longitudinal direction z and a circumference, wherein each filter element has an internal volume ( 21 ) for receiving a liquid filling ( 22 ) which contains at least one electrically conductive and one X-ray absorbing liquid component, the X-ray absorptivity of said filter element being dependent on the quantity of X-ray absorbing liquid component present in the internal volume ( 21 ), each filter element is provided with a first electrode ( 23 ) for applying a first electric voltage to a wall ( 28 ) of the filter element and a second electrode ( 29 ) for applying a second electric voltage to the internal volume ( 21 ) of the filter element, the first electrode is electrically isolated from the internal volume ( 21 ) of the filter element by means of an isolator layer ( 34 ) in such a manner that an electric capacitance per unit of surface area of the filter element exists between the first electrode ( 23 ) and the electrically conductive liquid component when a quantity of the electrically conductive liquid component is present in at least a part of the internal volume of the filter element ( 13 ), the X-ray absorptivity of each filter element ( 13 ) is adjustable by step-wise control of a surface level of the X-ray absorbing liquid component in the longitudinal direction z of each filter element, characterized in that the electric capacitance per unit of surface area of the wall ( 28 ) of the filter element ( 13 ) varies substantially in the longitudinal direction z of the filter element. 2. An X-ray apparatus as claimed in claim 1 , wherein the first electrode ( 23 ) includes a number of electrically interconnected first and second electrode segments, each of which extends at least over a part of the circumference of the tubular filter element ( 13 ), the first and the second electrode segments being arranged so as to succeed one another in the longitudinal direction z of the filter element and that the first electrode segment ( 37 ) extends over a larger part of the circumference of the filter element in comparison with the second electrode segment ( 39 ). claim 1 3. An X-ray apparatus as claimed in claim 1 , wherein the isolator layer ( 134 ) includes a number of first and second isolator segments, the first and second isolator segments succeeding one another in the longitudinal direction z of the filter element ( 13 ), the first isolator segment ( 136 ) having a dielectric constant which is higher than that of the second isolator segment ( 138 ). claim 1 4. An X-ray apparatus as claimed in claim 1 , wherein the isolator layer ( 234 ) includes a number of first and second isolator layer segments, the first and second isolator layer segments succeeding one another in the longitudinal direction z of the filter element ( 13 ) and the first isolator layer segment ( 236 ) having a layer thickness which is larger than that of the second isolator layer segment ( 238 ). claim 1
051494949	description	In FIG. 1 numeral 11 represents the emissions absorbing portion of an apparatus of this invention, and the remainder of the apparatus, for carrying off and consuming the energy generated in portion 11, is designated by numeral 13. In portion 11 radioactive waste material 15, suitably shaped in spherical form (although other forms may also be employed and held in a suitable interior container 16, preferably of compatible material, is positioned inside an inner spherical shell of electrically conductive material (such as aluminum), and is separated from such material by dielectric 19, which may be a suitable dielectric, solid or gaseous, e.g., alumina, mica, air. An enveloping sphere 21 surrounds sphere 17 and is separated from it by dielectric 23. Sphere 21 is preferably of an electrically conductive material, such as a metal of higher atomic number than the material of sphere shell 17. Suitable such materials are copper and silver, with copper normally being preferred, but other metals may also be used. When solid dielectrics are utilized they may be the sole means for separating the spheres but when gaseous dielectrics, such as air (or a high vacuum) are employed, mechanical means (not shown), preferably of electrically insulating material, will be employed. Electrical conductors 25 and 27, which will usually be insulated copper, and/or silver wires, conduct electricity to a variable resistance 29 and/or a battery 31. Diode 33 is provided to act as a check switch on current flow, preventing battery 31 from delivering electricity to part 11 of the apparatus. Other switches (not shown) may also be provided to separate the variable resistance and the battery from the rest of the system, if desired, and the variable resistance may be made automatically variable to draw a relatively small current, due to the difference in the electrical potentials of the spherical shells 17 and 21, drawing more current when the potential difference is sufficiently high and being of decreased resistance so as to allow and promote current flow when the potential difference is lower. Also, means may be provided for automatically reversing the polarity of the battery so as initially to stimulate or induce electrical current flow between spherical shells 17 and 21. While spherical shells are shown, these may be of other suitable shapes, such as cylindrical, cubical, tetrahedronal and ellipsoidal too, and in some instances the shells may desirably be perforated to allow release (through suitable absorbers or safety means, not shown) of gaseous materials generated from the radioactive waste or generated by expansion of gases present, as heat is released from the waste. Sometimes the inner shells may be perforated to permit some radiant energy flow through such openings, as when plural pairs of shields or electrodes are employed, e.g., 4 to 200 concentric metal spheres, with separating dielectrics. In the illustration a single apparatus is illustrated but banks of such devices may be connected together, with the current produced flowing through single or multiple resistances and/or being employed to charge one or more batteries. In FIG. 1 the nuclear waste is in a suitable metal container 16 but it is contemplated that other materials of construction may be employed and sometimes it can be omitted Concrete enclosing container 35 encloses the waste, the container for the waste, and the pair of spherical shells of electrically conductive material, but other suitable exterior containers may also be utilized. While this invention is not bound or limited by the following theory of operation, it is considered that alpha particles emitted by the radioactive waste (which usually is a complex mixture of various radioactive isotopes) tend to make the charge of the first metal absorber positive whereas beta particles and gamma rays, being more penetrating, tend to make the charge of the next contacted electrically conductive material negative, as illustrated in FIG. 1. When plural pairs of absorbers are employed the metals of low density will tend to be negative relative to the high density metals. Metals of low density, if sufficiently thick, will react with more beta particles reaching them than will metals of higher density because the high density metals, if sufficiently thin, will reflect some of the lower frequency radiation back to the more absorbing low density metal and transmit some to the next set of shielding levels. If the wastes emit gamma rays there should be several layers of combinations of insulator, low density conductor, insulator, high density conductor, etc. For example, aluminum and copper may be employed, as may be other metals and alloys, and combinations of metals (or alloys) outside the ranges specified in the Ritter patent. Magnesium, aluminum and/or titanium may be employed as the low atomic number metal, together with vanadium, chromium, manganese, iron, cobalt, nickel, copper or zinc as the higher atomic number metal. Similarly, magnesium or aluminum may be used with titanium. Also, for example, vanadium, chromium, manganese or iron may be used with cobalt, nickel, copper or zinc, with preference being to employing such combinations with atomic numbers further apart within such groups. Other such combinations that are useful include vanadium, chromium, manganese, iron, cobalt, nickel, copper or zinc with molybdenum, silver, tin, platinum, gold, mercury and/or lead. In some applications alloys or amalgams may be employed. Also, with respect to the higher atomic number materials, silver, cadmium and tin may be used with lead. Thus, while, within the broader aspects of this invention it is possible to utilize as the absorber or shield materials metals with atomic numbers below 23 in combination with those of atomic numbers above 46, it is also possible to utilize combinations of metals outside such ranges and still obtain the radiation absorbing and energy consuming effects desired. In FIG. 2 heterogeneous nuclear waste 41, in a suitable metal container 43, is surrounded by concentric absorbing materials and dielectrics, all of which are in spherical shape conforming to the shape of waste 41 and container 43. Thus, between the container for the radioactive waste and the first radiation absorbing sphere 45 of electrically conductive material there is a dielectric layer or sphere 47 and subsequently, in order, about the sphere 45 area spherical layer 49 of dielectric, another absorbing sphere 51 of electrically conductive material, another dielectric layer 53, another metal layer 55, a dielectric layer 57 and an outer metal layer 59. Spheres 45 and 55 are of aluminum or copper, as shown, and spheres 51 and 59 are of copper or lead, respectively. The same dielectric, mica, alumina or other suitable solid, or air, may be used between the various metal spheres. Of course, other shapes than spherical may also be employed. As illustrated, in normal operation spheres 45 and 55 will usually be relatively negative and spheres 51 and 59 will be relatively positive. Conductors 61 and 63 connect the "negative" potentials of spheres 45 and 55 to line 65, which line connects to an electrical power consuming part of the circuit, not shown herein, but like that of FIG. 1. Lines 67 and 69 act to transmit the "positive" potentials from parts 51 and 59 to line 71, which is also connected to the energy consuming parts of the circuit. Of course, lines 61, 63, 65, 67, 69 and 71 are insulated to avoid any short circuits. While only two sets of pairs of electrodes, shields, or electrically conductive spheres are illustrated in FIG. 2, a multiplicity of such pairs may also be employed. Also, container 43 and/or waste 41 may be connected to line 71. In FIG. 3 there is shown a nuclear installation, battery or other source of electrical power 73, which also is a source of harmful radiation due to the presence therein of radioactive material. Numeral 75 designates a multilayered shield of alternating high Z and low Z metals, separated by dielectrics. For example, electrically conductive metal sheets 77 and 81 may be of a low Z material, such as aluminum, and sheets 79 and 83 may be of a higher Z material, such as copper or lead. Between the sheets are dieletric layers, which may be of suitable dielectric material, such as alumina, mica, silica, glass and in some cases, synthetic organic polymeric plastics. If gaseous materials are employed for the dielectric, air or high vacuum is usually preferred. Electrical connections of the more negative first and third layers and the more positive second and fourth layers and the insulated metal surface of source 73 can be made to a power consuming portion of the circuitry, 85, which includes lines 87 and 89, a variable load 91, batteries to be charged, such as that at 93, and a diode 95 to prevent batteries from discharging through the radioactive source. As is seen from the drawing, voltages from energy converting device 73 and shield 75 may be combined via conductors 97 and 99, and 101 and 103 respectively. Thus, shielding 75 can protect humans and the environment from nuclear installation 73 and can be employed to help consume the radiation energy from the nuclear material in such installation. Of course, shielding 75 may be used to enclose the source of radiation 73 or may be employed to enclose and protect a "target" of such radiation, such as a room in which personnel are located, near the nuclear installation. FIG. 4 illustrates another embodiment of the invention in which an aluminum electrode 111, or "shield", in the form of an empty truncated sphere, with a few small holes in it, and insulated from surrounding container 113, has another conductive sphere 115, made of copper or silver, inside it. Radioactive waste 117 is in the container surrounding the spheres, and arrows, such as that identified by numeral 119, show some paths of radioactive emissions from a particular location 121 of the radioactive material. Instead of aluminum, other conductive materials, preferably metals, can be used as the material of the outer sphere as long as they are stable at the temperature obtaining within container 113 and as long as they are dense enough to absorb alpha particles emitted from the heterogeneous nuclear waste. Among such materials may be mentioned magnesium, titanium, copper, iron, chromium and nickel. Outer shell 111 does not have to be spherical in shape but a sphere presents the greatest variety of directional surfaces and is an excellent target for emitted radiation. Inner electrode 115, preferably of silver or copper, may also be of other conductive metals, with the identity of its electrode material depending to some extent on that of the other electrode material. For example, it is preferred that "the high Z" and "low Z" metals should be at least five atomic members apart, more preferably at least ten atomic numbers apart and most preferably twenty or more atomic numbers apart. Also, relatively high and low Z materials may be employed. Thus, two "high Z" metals or alloys may be used so long as they are a sufficient atomic number difference apart and are operative in the present invention. Electrical conductors 123 and 125, together with the outer shell source of electrical potential and the inner shell source of electrical potential, can be communicated through a load or resistance, such as that shown at 127, and the current flowing can be read by an ammeter, such as that at 129. Absorbing of alpha particles by conductors 123 and 125 may send a positive charge through the circuit but relatively high Z shield 115 will tend to be more charged than low Z 111 due to 111's greater photoelectron reactivity and its greater absorption of electrons. Also, as illustrated, the electrical potential from either of the metal spheres may be transmitted to a sink, represented by metal plate 131, in pond 133, which plate serves as a ground. At 135 is shown a battery which may be employed to induce the flow of electricity between the metal spheres or from the metal spheres to the metal plate 131. Switches for cutting off the auxiliary battery 135 are present, but are not illustrated in the drawing. As is seen from the previous description the present process affects dangerous emissions from the heterogeneous radioactive or comparable radiation source, which are converted to electrical energy, which is consumed. Thereby radiation is removed from the environment and is changed to a harmless energy form. It is well known that huge sums of money have been expended in research efforts to solve nuclear waste storage problems but despite all such efforts no prior art disclosure taught the process of this invention. Prior art efforts were directed to containing the nuclear waste, usually after concentration thereof, by storing it in a container or matrix in a remote area or deep in the earth. Often shielding was utilized which, in effect, merely contains the radiation or is itself affected by absorption of such radiation. When containment is the only effect of the shielding dangerous energy levels can be produced and when conversion of the shielding material takes place due to energy absorption, the nature of the material may change, leading to deterioration thereof. Before the present invention it was known that certain types of radiation could be converted into electrical energy (but many experts refused to believe that gamma rays could be so transformed). Still, the prior art did not teach the use of any of such conversion mechanisms for shielding the environment from dangerous emissions. In fact, such apparatuses could leak primary emissions and could generate dangerous secondary emissions. Also, for satisfactory operation of various prior art nuclear devices for producing electrical energy, such as that of the Ritter patent, purified sources of radioactivity had to be used, rather than heterogeneous wastes'such as usual nuclear wastes. The present invention allows the treatment and shielding of such wastes and also allows the protection of various sources of complex radioactive emissions, such as decommissioned nuclear plants, pools of highly radioactive materials, radioactive mill tailings, nuclear wastes being transported, nuclear wastes being processed, and stored solidified wastes that have been "vitrefied", encased in a synthetic organic resin, or embedded in ceramics or concrete. The present invention also incorporates several safety features not suggested by the prior art. For example, by drawing off radiant energy from shield material the invention allows for stabilization of such material and thereby increases its shielding life. Also, whereas in the Ritter patent an object has been to build up high voltages, thus putting a strain on the shielding and increasing the danger of accident, such is not necessary nor is it an object of the present invention, which allows for regulation of the resistance to maintain a current flow and thereby to aid the conversion of radioactivity to electricity. In other words, there is no "back pressure" on the system due to any requirement to produce a high voltage, and the present apparatus acts as a safety valve, allowing the flow of more electricity in response to any flare-ups or sudden emissions of radioactivity. The embodiment of the invention described uses form-retaining electrically conductive metal shields but such shields may also be made in the form of a flexible blanket which can be easily placed over a source of radiation or over a subject to be protected from such radiation. In such and other instances the intervening dielectric material, which will then preferably be a solid, may be molded or otherwise attached to the electrically conductive materials. Of course, in such blankets suitable conductors will be provided to carry off electricity from the shielding metals to an electrical load, where it is consumed. In employing the invention modifications may be made depending on the particular type of heterogeneous waste being utilized and its state of "decay". If the predominant emission is of alpha particles the load should be across contacts with the first layer of shielding and the rest of the shielding. If the predominant emission is of beta rays it is considered best to have a high Z outermost shielding layer and/or a ground as one electrode and all the other layers as the other electrode. When gamma rays are the principal radiation it is considered best to employ thin layers of relatively high Z material with thicker layers of relatively low Z material, in repeating pairs, with the current flow being between such high Z and low Z layers. Usually the various shield layers are at different distances from the radioactive source but it is also within the invention to utilize different shield electrodes at the same distance from such source. For conversion of gamma rays to harmless electricity a honeycomb form of shielding is considered to be efficient, and it is also effective for absorption of beta rays. However, in some cases, as when the metal shields deteriorate after use (some reduced amount of deterioration may be observed) only a single type of metal shielding material may sometimes be best employed, with dependence being on direct conversion, photoelectricity, Compton effect and ion pair formation for conversion of the radiation energy. Normally, as when a source of radiation is aboveground, as in a decommissioned nuclear power plant, the shielding may have to be changed as time goes by. Such changing may also be dictated by the changing nature of the radiation source, and it will be preferable to utilize shieldings for greatest effects versus various types of radiation, for example, radioactive cobalt 60 during the first years after decommissioning, and isotopes of nickel and niobium many years later (each having different peak frequencies of radiation). As described, shields may be used around a nuclear reactor or installation, and above the installation they may be in staggered form to allow air circulation (but any air emitted will be filtered and monitored for leakage of radionuclides). Liquid wastes may be shielded by means of the present invention, as may be radioactive wastes being transported in containers. Such containers may be made of shielding materials and the electrical load may be a part of the electrical system of the transporting vehicle. For example, the electricity generated from the waste being carried may be used to operate electric lights on a truck or trailer being employed, which lights will blink on and off to act as a warning that radioactive material is present. The present invention is useful for protecting humans and the environment. Even if it had been known that electricity could be produced from heterogeneous radiation including gamma rays, such "new use" of such process would be patentable, especially in the absence of any suggestion thereof in the art. Especially in view of the long felt need for such a process and the great number of researchers attempting to invent it it is considered that the process was not merely inherent in the prior art and was not obvious to those of ordinary skill in such art. Apparently the closest "prior art" to the present invention is U.S. Pat. No. 4,178,524, to Ritter. Ritter does not mention the employment of his apparatus to absorb radiation and protect the environment. In fact, he utilizes a lead housing to attenuate the radiation emitted by the source thereof. It may be inferred that the Ritter apparatus creates additional emissions. Ritter uses particular types of radioactive sources, emitting energies less than a million electron volts. Such radioactive sources of Ritter appear to be relatively pure isotopes, not heterogeneous nuclear wastes emitting large amounts of radiations of different types. Ritter specifies the employment of his particular high and low-Z materials whereas the present invention allows the use of a wide variety of such materials, for example, nuclear wastes include alpha and beta radiation emitters, but Ritter's device is limited to a source of gamma rays with less than 1 Mev power. Ritter tries to produce maximum voltage whereas such is not the purpose of this invention and in fact, preventing voltage build-up is very important. Ritter's invention is a "remote electrical generator" whereas the present apparatus is intended for use in or next to power plants, hospitals, waste processing centers or other places that generate or house nuclear wastes, and allows treatment of the wastes at such sites, thereby, at least in part, obviating the need to transport them to a dump. Finally, the Ritter patent makes no mention of consuming the energy developed in the load, especially one of variable resistance, which makes the apparatus adaptable for use with radioactive wastes of different strengths and of changing activities. Unlike the Ritter apparatus, which requires the regulation of the energy the radioactive source can emit so as to maintain it low, the present apparatus is capable of operations with high energy sources and is adaptable to consume whatever electrical energy is produced by such source, thereby aiding in continuous conversion of radiation to electrical energy. The invention has been described with respect to various illustrations and embodiments thereof but is not to be limited to these because it is evident that one of skill in the art, with the present specification and drawings before him, will be able to utilize substitutes and equivalents without departing from the invention.
	claims	1. A method for handling nuclear waste using a nuclear waste capsule system, the method comprising:(a) disassembling spent nuclear fuel assemblies into nuclear waste cores, wherein each nuclear waste core is a bundle of preexisting fuel rods disassembled from the spent nuclear fuel assemblies;(b) attaching at least one external support to each nuclear waste core;(c) inserting each nuclear waste core, with the at least one external support, into a carrier tube of pre-determined length and diameter, wherein the at least one external support suspends the nuclear waste core coaxially within the carrier tube;(d) filling a void space substantially around each nuclear waste core, with the at least one external support, and within the carrier tube, with a protective-medium through an injector port in communication with the carrier tube, wherein the protective-medium protects the nuclear waste capsule system from degradation by absorbing radioactive emissions and by absorbing heat emissions;(e) sealing the carrier tube with mechanical plugs at terminal ends of the carrier tube;(f) repeating steps (b) through (e) to form at least two different sealed carrier tubes;(g) attaching the at least two different sealed carrier tubes to each other to form a waste-string;(h) inserting the waste-string into a wellbore at a predetermined depth; and(i) sealing the wellbore. 2. The method according to claim 1, wherein the disassembling of the spent nuclear fuel assemblies uses safe robotic mechanical processes. 3. The method according to claim 1, wherein a given spent nuclear fuel assembly, selected from the spent nuclear fuel assemblies, is disassembled along at least one dividing-plane of the spent nuclear fuel assembly. 4. The method according to claim 1, wherein the carrier tube is constructed from one or more of the following, used singly or compositely in combination: steel, stainless steel, aluminum, cooper, or zircalloy. 5. The method according to claim 1, wherein the terminal ends of the carrier tube is two opposing ends, wherein the injector port is located on at least one such terminal end. 6. The method according to claim 5, wherein the carrier tube comprises an overflow port, wherein the overflow port is located on at least one of the two opposing terminal ends; wherein the overflow port permits excess of the protective-medium to drain from the carrier tube. 7. The method according to claim 1, wherein the protective-medium is selected from one or more of: high temperature hydrocarbon derived products, tar, bitumen, heavy crude oil, or bentonite clay suspensions. 8. The method according to claim 1, wherein the sealing of the carrier tube is by welding a given mechanical plug to its respective terminal end. 9. The method according to claim 1, wherein the wellbore of step (h) is lined with at least one layer of pipe; wherein it is this at least one layer of pipe that receives the waste-string. 10. The method according to claim 9, wherein the at least one layer of pipe is fitted with a plurality of centralizers at selected determined points externally to the at least one layer of pipe; such that an axis of this at least one layer of pipe is substantially concentric with an axis of the wellbore. 11. The method according to claim 9, wherein between an exterior of this at least one layer of pipe and an interior of the wellbore is a cement casing that is installed by pumping uncured cement slurring through an interior of this at least one layer of pipe and through a bottom of this at least one layer of pipe prior to inserting of the waste-string. 12. The method according to claim 9, wherein the at least one layer of pipe is formed from pre-determined lengths of pipe; wherein each these predetermined lengths of pipe are joined together via pipe-couplings. 13. The method according to claim 9, wherein the least one layer of pipe comprises an outer pipe and an inner pipe disposed within the outer pipe, such that the outer pipe and the inner pipe are substantially coaxial with respect to each other. 14. The method according to claim 13, wherein the waste-string is inserted into the inner pipe. 15. The method according to claim 13, wherein between an exterior of the inner pipe and an interior of the outer pipe is a cement layer that is installed by pumping uncured cement slurry through an interior of the inner pipe and through a bottom of the inner pipe prior to inserting of the waste-string into the inner pipe. 16. The method according to claim 1, wherein step (g) further comprises attaching the at least two different sealed carrier tubes to each other by use of at least one non-waste-bearing-spacer disposed between and attached to each of the at least two different sealed carrier tubes for controlling heat load dissemination from the nuclear waste cores. 17. The method according to claim 1, wherein the predetermined depth is at least 10,000 ft. 18. The method according to claim 1, wherein prior to step (a), the method comprises a step of harvesting the spent nuclear fuel assemblies from surface storage that then progresses into step (a).
	description	The present application is a U.S. national stage application under 35 U.S.C. 371 of PCT Application No. PCT/US2013/037228, filed on Apr. 18, 2013, which claims the benefit of U.S. Provisional Patent Application 61/625,869, filed Apr. 18, 2012, the disclosures of which are incorporated herein by reference in their entireties. The field of the present invention relates systems and methods for storing high level waste (“HLW”), such as spent nuclear fuel, in ventilated vertical modules. The storage, handling, and transfer of HLW such as spent nuclear fuel, requires special care and procedural safeguards. For example, in the operation of nuclear reactors, it is customary to remove fuel assemblies after their energy has been depleted down to a predetermined level. Upon removal, this spent nuclear fuel is still highly radioactive and produces considerable heat, requiring that great care be taken in its packaging, transporting, and storing. In order to protect the environment from radiation exposure, spent nuclear fuel is first placed in a canister. The loaded canister is then transported and stored in large cylindrical containers called casks. A transfer cask is used to transport spent nuclear fuel from location to location while a storage cask is used to store spent nuclear fuel for a determined period of time. In a typical nuclear power plant, an open empty canister is first placed in an open transfer cask. The transfer cask and empty canister are then submerged in a pool of water. Spent nuclear fuel is loaded into the canister while the canister and transfer cask remain submerged in the pool of water. Once fully loaded with spent nuclear fuel, a lid is typically placed atop the canister while in the pool. The transfer cask and canister are then removed from the pool of water, the lid of the canister is welded thereon and a lid is installed on the transfer cask. The canister is then properly dewatered and filled with inert gas. The transfer cask (which is holding the loaded canister) is then transported to a location where a storage cask is located. The loaded canister is then transferred from the transfer cask to the storage cask for long term storage. During transfer from the transfer cask to the storage cask, it is imperative that the loaded canister is not exposed to the environment. One type of storage cask is a ventilated vertical overpack (“VVO”). A VVO is a massive structure made principally from steel and concrete and is used to store a canister loaded with spent nuclear fuel (or other HLW). VVOs stand above ground and are typically cylindrical in shape and extremely heavy, weighing over 150 tons and often having a height greater than 16 feet. VVOs typically have a flat bottom, a cylindrical body having a cavity to receive a canister of spent nuclear fuel, and a removable top lid. In using a VVO to store spent nuclear fuel, a canister loaded with spent nuclear fuel is placed in the cavity of the cylindrical body of the VVO. Because the spent nuclear fuel is still producing a considerable amount of heat when it is placed in the VVO for storage, it is necessary that this heat energy is able to escape from the VVO cavity. This heat energy is removed from the outside surface of the canister by ventilating the VVO cavity. In ventilating the VVO cavity, cool air enters the VVO chamber through inlet ventilation ducts, flows upward past the loaded canister, and exits the VVO at an elevated temperature through outlet ventilation ducts. While it is necessary that the VVO cavity be vented so that heat can escape from the canister, it is also imperative that the VVO provide adequate radiation shielding and that the spent nuclear fuel not be directly exposed to the external environment. U.S. Pat. No. 7,933,374, issued Apr. 26, 2011, the disclosure of which is incorporated herein by reference in its entirety, discloses a VVO which meets these shielding needs. The effect of wind on the thermal performance of a ventilated system can also be a serious drawback that, to some extent, afflicts all systems in use in the industry at the present time. Storage VVO's with only two inlet or outlet ducts are especially vulnerable. While axisymmetric air inlet and outlet ducts behave extremely well in quiescent air, when the wind is blowing, the flow of air entering and leaving the system is skewed, frequently leading to at reduced heat rejection capacity. A module for storing high level radioactive waste includes an outer shell having a hermetically closed bottom end and an inner shell disposed inside the outer shell so as to form a space between the inner shell and the outer shell. At least one divider extends from a top of the inner shell to a bottom of the inner shell, the at least one divider creating a plurality of inlet passageways through the space, each inlet passageway connecting to a bottom portion of the cavity. A plurality of inlet ducts each connect at least one of the inlet passageways to ambient atmosphere. The inlet ducts are configured such that when the module is inset into the ground, the air pressure about each inlet duct is substantially the same. A removable lid is positioned on the inner shell, and the lid having at least one outlet passageway connecting the cavity and the ambient atmosphere. The lid and the top of the inner shell are respectively configured to form a hermetic seal at a top of the cavity. In a first separate aspect of the present invention, each inlet duct comprises an inlet duct cover affixed over a surrounding inlet wall, with the inlet wall being peripherally perforated. The inlet wall may be peripherally perforated to have a minimum of 60% open area. In a second separate aspect of the present invention, the lid further includes an outlet duct connecting the at least one outlet passageway and the ambient atmosphere. The outlet duct includes an outlet duet cover affixed over a surrounding outlet wall, with the outlet wall being peripherally perforated. The outlet wall may be peripherally perforated to have a minimum of 60% open area. In a third separate aspect of the present invention, a hermetically sealed canister for containing high-level waste is positioned within the cavity, wherein the cavity has a horizontal cross-section that accommodates no more than one canister. In a fourth separate aspect of the present invention, the top of the upper shield extends to or above the inlet ducts. In a fourth separate aspect of the present invention, at least four dividers extend from a top of the inner shell to a bottom of the inner shell, thereby forming a plurality of the inlet passageways, and each divider includes an extension portion extending into the cavity, the extension portion configured as a positioning flange for a canister disposed within the cavity. In a fifth separate aspect of the present invention, each of the inlet ducts maintains an intake air pressure independently of each of the other inlet ducts. In a sixth separate aspect of the present invention, each of the inlet ducts maintains an intake air pressure substantially the same as each of the other inlet ducts. In a seventh separate aspect of the present invention, a system including a plurality of the modules is employed, with the inlet ducts of a first of the modules maintains air pressure independently of the inlet ducts of a second of the modules. In an eighth separate aspect of the present invention, a method of storing high level waste includes providing a module having an outer shell having a hermetically closed bottom end and an inner shell disposed inside the outer shell so as to form a space between the inner shell and the outer shell. At least one divider extends from a top of the inner shell to a bottom of the inner shell, the at least one divider creating a plurality of inlet passageways through the space, each inlet passageway connecting to a bottom portion of the cavity. A plurality of inlet ducts each connect at least one of the inlet passageways to ambient atmosphere. The inlet ducts are configured such that when the module is inset into the ground, the air pressure at each inlet duct is substantially the same, and the air pressure at each inlet duct is independent of the air pressure at the other inlet ducts. A canister containing high level radioactive waste is placed into the cavity. A lid is positioned over the cavity, with the lid having at least one outlet passageway connecting the cavity and the ambient atmosphere. The lid and the top of the inner shell are respectively configured to form a hermetic seal at a top of the cavity. In a ninth separate aspect of the present invention, one or more of the preceding separate aspects may be employed in combination. Advantages of the improvements will be apparent from the drawings and the description of the preferred embodiment. The description of illustrative embodiments according to principles of the present invention is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. In the description of embodiments of the invention disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,” “above,” “below,” “up,” “down,” “left,” “right,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation unless explicitly indicated as such. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. Moreover, the features and benefits of the invention are illustrated by reference to the preferred embodiments. Accordingly, the invention expressly should not be limited to such preferred embodiments illustrating some possible non-limiting combinations of features that may exist alone or in other combinations of features; the scope of the invention being defined by the claims appended hereto. FIG. 1 illustrates a high level waste (“HLW”) storage container 10, encased in surrounding concrete 11, as it would be in an installation. FIG. 2 illustrates the storage container 10 in a sectional view, still with the surrounding concrete 101. While the HLW storage container 10 will be described in terms of being used to store a canister of spent nuclear fuel, it will be appreciated by those skilled in the art that the systems and methods described herein can be used to store any and all kinds of HLW. The HLW storage container 10 is designed to be a vertical, ventilated dry system for storing HLW such as spent fuel. The HLW storage container 10 is fully compatible with 100 ton and 125 ton transfer casks for HLW transfer procedures, such as spent fuel canister transfer operations. All spent fuel canister types engineered for storage in free-standing, below grade, and/or anchored overpack models can be stored in the HLW storage container 10. As used herein the term “canister” broadly includes any spent fuel containment apparatus, including, without limitation, multi-purpose canisters and thermally conductive casks. For example, in some areas of the world, spent fuel is transferred and stored in metal casks having a honeycomb grid-work/basket built directly into the metal cask. Such casks and similar containment apparatus qualify as canisters, as that term is used herein, and can be used in conjunction with the HLW storage container 10 as discussed below. The HLW storage container 10 can be modified/designed to be compatible with any size or style of transfer cask. The HLW storage container 10 can also be designed to accept spent fuel canisters for storage at an Independent Spent Fuel Storage installations (“ISFSI”). ISFSIs employing the HLW storage container 10 can be designed to accommodate any number of the HLW storage container 10 and can be expanded to add additional HLW storage containers 100 as the need arises. In ISFSIs utilizing a plurality of the HLW storage container 10, each HLW storage container 10 functions completely independent form any other HLW storage container 10 at the ISFSI. The HLW storage container 10 has a body 20 and a lid 30. The lid 30 rests atop and is removable/detachable from the body 20. Although an HLW storage container can be adapted for use as an above grade storage system, by incorporating design features found in U.S. Pat. No. 7,933,374, this HLW storage container 10, as shown, is designed for use as a below grade storage system. Referring to FIG. 2, the body 20 includes an outer shell 21 and an inner shell 22. The outer shell 21 surrounds the inner shell 22, forming a space 23 therebetween. The outer shell 21 and the inner shell 22 are generally cylindrical in shape and concentric with one another. As a result, the space 23 is an annular space. While the shape of the inner and outer shells 22, 21 is cylindrical in the illustrated embodiment, the shells can take on any shape, including without limitation rectangular, conical, hexagonal, or irregularly shaped. In some embodiments, the inner and outer shells 22, 22 will not be concentrically oriented. The space 23 formed between the inner shell 22 and the outer shell 21 acts as a passageway for cool air. The exact width of the space 23 for any HLW storage container 10 is determined on a case-by-case design basis, considering such factors as the heat load of the HLW to be stored, the temperature of the cool ambient air, and the desired fluid flow dynamics. In some embodiments, the width of the space 23 will be in the range of 1 to 6 inches. While the width of space 23 can vary circumferentially, it may be desirable to design the HLW storage container 10 so that the width of the space 23 is generally constant in order to effectuate symmetric cooling of the HLW container and even fluid flow of the incoming air. As discussed in greater detail below, the space 23 may be divided up into a plurality of passageways. The inner shell 22 and the outer shell 21 are secured atop a floor plate 50. The floor plate 50 is hermetically sealed to the outer shell 21, and it may take on any desired shape. A plurality of spacers 51 are secured atop the floor plate 50 within the space 23. The spacers 51 support a pedestal 52, which in turn supports a canister. When a canister holding HLW is loaded into the cavity 24 for storage, the bottom surface of the canister rests atop the pedestal 52, forming an inlet air plenum between the underside of the pedestal 52 and the floor of cavity 24. This inlet air plenum contributes to the fluid flow and proper cooling of the canister. Preferably, the outer shell 21 is seal joined to the floor plate 50 at all points of contact, thereby hermetically sealing the HLW storage container 10 to the ingress of fluids through these junctures. In the case of weldable metals, this seal joining may comprise welding or the use of gaskets. Most preferably, the outer shell 21 is integrally welded to the floor plate 50. An upper flange 77 is provided around the top of the outer shell 21 to stiffen the outer shell 21 so that it does not buckle or substantially deform under loading conditions. The upper flange 77 can be integrally welded to the top of the outer shell 21. The inner shell 22 is laterally and rotationally restrained in the horizontal plane at its bottom by support legs 27 which straddle lower ribs 53. The lower ribs 53 are preferably equispaced about the bottom of the cavity 24. The inner shell 22 is preferably not welded or otherwise permanently secured to the bottom plate 50 or outer shell 21 so as to permit convenient removal for decommissioning, and if required, for maintenance. The inner shell 22, the outer shell 21, the floor plate 50, and the upper flange 77 are preferably constructed of a metal, such as a thick low carbon steel, but can be made of other materials, such as stainless steel, aluminum, aluminum-alloys, plastics, and the like. Suitable low carbon steels include, without limitation, ASTM A516, Gr. 70, A515 Gr. 70 or equal. The desired thickness of the inner and outer shells 22, 21 is matter of design choice and will determined on a case-by-case basis. The inner shell 22 forms a cavity 24. The size and shape of the cavity 24 is also a matter of design choice. However, it is preferred that the inner shell 22 be designed so that the cavity 24 is sized and shaped so that it can accommodate a canister of spent nuclear fuel or other HLW. While not necessary, it is preferred that the horizontal cross-sectional size and shape of the cavity 24 be designed to generally correspond to the horizontal cross-sectional size and shape of the canister-type that is to be used in conjunction with a particular HLW storage container. More specifically, it is desirable that the size and shape of the cavity 24 be designed so that when a canister containing HLW is positioned in the cavity 24 for storage (as illustrated in FIG. 4A), a small clearance exists between the outer side walls of the canister and the side walls of the cavity 24. Designing the cavity 24 so that a small clearance is formed between the side walls of the stored canister and the side walls of the cavity 24 limits the degree the canister can move within the cavity during a catastrophic event, thereby minimizing damage to the canister and the cavity walls and prohibiting the canister from tipping over within the cavity. This small clearance also facilitates flow of the heated air during HLW cooling. The exact size of the clearance can be controlled/designed to achieve the desired fluid flow dynamics and heat transfer capabilities for any given situation. In some embodiments, for example, the clearance may be 1 to 3 inches. A small clearance also reduces radiation streaming. The inner shell 22 is also equipped with multiple sets of equispaced longitudinal ribs 54, 55, in addition to the lower ribs 53 discussed above. One set of ribs 54 are preferably disposed at an elevation that is near the top of a canister of HLW placed in the cavity 24. This set of ribs 54 may be shorter in length in comparison to the height of the cavity 24 and a canister. Another set of ribs 55 are set below the first set of ribs 54. This second set of ribs 55 is more elongated than the first set of ribs 54, and these ribs 55 extend to, or nearly to, the bottom of the cavity 24. These ribs 53, 54, 55 serve as guides for a canister of HLW is it is lowered down into the cavity 24, helping to assure that the canister properly rests atop the pedestal 52. The ribs also serve to limit the canister's lateral movement during an earthquake or other catastrophic event to a fraction of an inch. A plurality of openings 25 are provided in the inner shell 22 at or neat its bottom between the support legs 27. Each opening 25 provides a passageway between the annular space 23 and the bottom of the cavity 24. The openings 25 provide passageways by which fluids, such as air, can pass from the annular space 23 into the cavity 24. The openings 25 are used to facilitate the inlet of cooler ambient air into the cavity 24 for cooling a stored HLW having a heat load. As illustrated, eight openings 25 are equispaced about the bottom of the inner shell 22. However, any number of openings 25 can be included, and they may have any spacing desired. The exact number and spacing will be determined on a case-by-case basis and will dictated by such considerations as the beat load of the HLW, desired fluid flow dynamics, etc. Moreover, while the openings 25 are illustrated as being located in the side wall of the inner shell 22, the openings can be provided in the floor plate in certain modified embodiments of the HLW storage container. The openings 25 in the inner shell 22 are sufficiently tall to ensure that if water enters the cavity 24, the bottom region of a canister resting on the pedestal 52 would be submerged for several inches before the water level reaches the top edge of the openings 25. This design feature helps ensure thermal performance of the system under accidental flooding of the cavity 24. With reference to FIG. 3, a layer of insulation 26 is provided around the outside surface of the inner shell 22 within the annular space 23. The insulation 26 is provided to minimize heating of the incoming cooling air in the space 23 before it enters the cavity 24. The insulation 26 helps ensure that the heated air rising around a canister situated in the cavity 24 causes minimal pre-heating of the downdraft cool air in the annular space 23. The insulation 26 is preferably chosen so that it is water and radiation resistant and undegradable by accidental wetting. Suitable forms of insulation include, without limitation, blankets of alumina-silica fire clay (Kaowool Blanket), oxides of alimuna and silica (Kaowool S Blanket), alumina-silica-zirconia fiber (Cerablanket), and alumina-silica-chromia (Cerachrome Blanket). The desired thickness of the layer of insulation 26 is matter of design and will be dictated by such considerations such as the heat load of the HLW, the thickness of the shells, and the type of insulation used. In some embodiments, the insulation will have a thickness in the range ½ to 6 inches. As shown in FIGS. 2 and 3, inlet ducts 60 are disposed on the top surface of the upper flange 77. Each inlet duct 60 connects to two inlet passageways 61 which continue from under the upper flange 77, into the space 23 between the outer and inner shells 21, 22, and then connect to the cavity 24 by lower openings 62 in the bottom of the inner shell 22. Within the space 23, the inlet passageways 61 are separated by dividers 63 to keep cooling air flowing through each inlet passageway 61 separate from the other inlet passageways 61 until the cooling air emerges into the cavity 24. FIGS. 4A and 4B illustrate the configuration of the inlet passageways 61 and the dividers 63. Each inlet passageway 61 connects with the space 23 by openings 64 in the top of the outer shell 21. From the openings 64, the cooling air continues down the in the space, via the individual inlet passageways 61 created by the dividers 64, and into the cavity 24, where it is used to cool a placed HLW canister. The dividers 63 are equispaced within the space 23 to aid in balancing the air pressure entering the space 23 from each inlet duct and inlet passageway. Also, as shown in the figures, each of the lower ribs 53 is integrated with one of the dividers 63, such that the lower ribs form an extension of the dividers, extending into the cavity 24. Referring back to FIG. 3, each inlet duct 60 includes a duct cover 65, to help prevent rain water or other debris from entering and/or blocking the inlet passageways 61, affixed on top of an inlet wall 66 that surrounds the inlet passageways 61 on the top surface of the upper flange 77. The inlet wall 66 is peripherally perforated around the entire periphery of the opening of the inlet passageways 61. At least a portion of the lower part of the inlet ducts are left without perforations, to aid in preventing rain water from entering the HLW storage container. Preferably, the inlet wall 66 is perforated over 60% or more of its surface, and the perforations can be made in any shape, size, and distribution in accordance with design preferences. When the inlet ducts 60 are formed with the inlet wall 66 peripherally perforated, each of the inlet ducts has been found to maintain an intake air pressure independently of each of the other inlet ducts, even in high wind conditions, and each of the inlet ducts has been found to maintain an intake air pressure substantially the same as each of the other inlet ducts, again, even in high wind conditions. The lid 30 rests atop and is supported by the upper flange 77 and a shell flange 78, the latter being disposed on and connected to the tops edge of the inner shell 22. The lid 30 encloses the top of the cavity 24 and provides the necessary radiation shielding so that radiation does not escape from the top of the cavity 24 when a canister loaded with HLW is stored therein. The lid 30 is designed to facilitate the release of heated air from the cavity 24. FIG. 5A illustrates the HLW storage container 10 with a canister 13 placed within the cavity 24. As shown in the FIG. 5B detailed view, the bottom of the canister 13 sits on the pedestal 52, and the lower ribs 53 maintain a space between the bottom of the canister 13 and the inner shell 22. Similarly, the FIG. 5C detailed view shows that the upper ribs 54 maintain a space between the top of the canister 13 and the inner shell 22. The FIG. 5D detailed view shows the lid 30 resting atop the upper flange 77 and the shell flange 78. The lid 30 includes a closure gasket 31 which forms a seal against the upper flange 77 when the lid 30 is seated, and a leaf spring gasket 32 which forms a seal against the shell flange 78. FIGS. 6 and 7 illustrate the lid 30 removed from the body of the HLW storage container. Referring first to FIG. 6, the lid 30 is preferably constructed of a combination of low carbon steel and concrete (or another radiation absorbing material) in order to provide the requisite radiation shielding. The lid 30 includes an upper lid part 33 and a lower lid part 34. The upper lid part 33 preferable extends at least as high as, if not higher than, the top of each inlet duct 60. Each lid pan. 33, 34 includes an external shell 35, 36 encasing an upper concrete shield 37 and a lower concrete shield 38. One or more outlet passageways 39 are formed within and around the body parts 33, 34 to connect the cavity with the outlet duct 40 formed on the top surface of the lid 30. The outlet passageways 39 pass over the lower lid part 34, between the upper and lower lid parts 33, 34, and up through a central aperture within the upper lid part 34. The outlet duct 40 covers this central aperture to better control the heated air as it rises up out of the. By being disposed on the top of the lid 30, the outlet duct 40 may also be raised up significantly higher than the inlet ducts, using any desired length of extension for the outlet duct. By raising up the outlet duct higher, mixing between the heated air emitted from the outlet duct and cooler air being drawn into the inlet ducts can be significantly reduced, if not eliminated altogether. The outlet duct 40, which is constructed similar to the inlet ducts, includes a duct cover 41, to help prevent rain water or other debris from entering and/or blocking the outlet passageways 39, affixed on top of an outlet wall 42 that surrounds the outlet passageways 39 on the top surface of the upper lid pan 33. The outlet wall 42 is peripherally perforated around the entire periphery of the opening of the outlet passageways 39. At least a portion of the lower part of the outlet duct is left without perforations, to aid in preventing rain water from entering the HLW storage container. Preferably, the outlet wall 42 is perforated over 60% or more of its surface, and the perforations can be made in any shape, size, and distribution in accordance with design preferences. The external shell of the lid 30 may be constructed of a wide variety of materials, including without limitation metals, stainless steel, aluminum, aluminum-alloys, plastics, and the like. The lid may also be constructed of a single piece of material, such as concrete or steel for example, so that it has no separate external shell. When the lid 30 is positioned atop the body 20, the outlet passageways 39 are in spatial cooperation with the cavity 24. As a result, cool ambient air can enter the HLW storage container 10 through the inlet ducts 60, flow into the space 23, and into the bottom of the cavity 24 via the openings 62. When a canister containing HLW having a heat load is supported within the cavity 24, this cool air is warmed by the HLW canister, rises within the cavity 24, and, exits the cavity 24 via the outlet ducts 40. Because the inlet ducts 60 are placed on different sides of the lid 30, and the dividers separate the inlet passageways associated with the different inlet ducts, the hydraulic resistance to the incoming air flow, a common limitation in ventilated modules, is minimized. This configuration makes the HLW storage container less apt to build up heat internally under high wind conditions. A plurality of HLW storage containers 100 can be used at the same ISFSI site and situated in arrays as shown in FIG. 8. Although the HLW storage containers 100 are closely spaced, the design permits a canister in each HLW storage container 10 to be independently accessed and retrieved easily. In addition, the design of the individual storage containers 100, and particularly the design and positioning of the inlet and outlet ducts, enables the inlet ducts of a first of the storage containers to maintain air pressure independently of the inlet ducts of a second of the storage containers. Each storage container therefore will operate independently of each of the other storage containers, such that the failure of one storage container is unlikely to lead directly to the failure of other surrounding storage containers in the array. While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention. Thus, the spirit and scope of the invention should be construed broadly as set forth in the appended claims.
042971691	abstract	Rupture of boiling water reactor nuclear fuel cladding resulting from embrittlement caused by fission product cadmium is prevented by adding the stoichiometrically equivalent amount of CuFe.sub.2 O.sub.4 or CuTiO.sub.3 to the fuel.
042808740	summary	BACKGROUND OF THE INVENTION The present invention relates to a structure of a nuclear reactor core and, more particularly, to a structure of a reactor core which can facilitate the operation of the nuclear reactor. In the existing boiling water reactor (BWR), the reactivity and the power distribution in the core are controlled by means of control rods, flow rate of the coolant through the core and the gadolinea (Gd.sub.2 O.sub.3) which is a burnable poison. In a construction of a reactor core which provides reactivity and power distribution control relying upon the control rods, an extraordinarily large change in power peaking is caused when the control rods are extracted, resulting in a deteriorated soundness of the fuel rods. More specifically, the fuel assembly is constituted by a plurality of fuel rods each of which consists of UO.sub.2 pellets (fuel pellets) packed in a cladding tube. As the power of the reactor is increased, the volume of the UO.sub.2 pellet is increased due to swelling and thermal expansion so that the diameter of the UO.sub.2 pellet is increased at both ends thereof. Consequently, the UO.sub.2 pellet is deformed so as to contact at its central portion. When the deformed UO.sub.2 pellet contacts the wall of the cladding tube, a Pellet Cladding Mechanical Interaction (PCMI) is caused, often incurring a danger of breakage of the cladding tube. The possibility of the breakage of the cladding tube is large especially when the withdrawal of the control rods in the core is made while the reactor is operated to produce a high power. A countermeasure which has been taken conventionally for securing the soundness of the fuel rod will be described hereinunder with specific reference to a boiling water reactor. The core of the boiling water reactor is usually constituted by fuel assemblies having an uniform axial enrichment distribution. The increase of the power of this reactor is initiated by withdrawing the control rods, which have been inserted into the core, until the density of the control rods in the core reaches 20%. This density of the control rod corresponds to the linear heat generation rate at which the PCMI is commenced, and the withdrawal of the control rods beyond this control rod density may incur the breakage of the fuel rods. It is therefore essential to stop the withdrawal of the control rods when the density thereof in the core has decreased to 20%. Then, the flow rate of the cooling water flowing through the reactor core is gradually increased to increase the power to a preselected level at a rate smaller than the critical rate as shown in U.S. Pat. No. 4,057,466 at which the PCMI is caused. The reduction of the power of the nuclear reactor due to an elapse of time is prevented, as disclosed in U.S. Pat. No. 762,248, by an increase of the flow rate of the cooling water so that the power of the nuclear reactor is maintained at a preselected level. When the reactor core is operated with a constant density of control rods, an uneconomical exposure assymmetry is caused. In order to avoid this, it is necessary to effect a change of the control rod pattern as shown in U.S. Pat. No. 762,248 once in a period of from a month to two months. The change of the control rod pattern cannot be made when the reactor is operated at high power, because such a change necessitates the withdrawal of the control rods. Therefore, the change of the control rod pattern is made by withdrawing the control rods while reducing the flow rate of the cooling water and decreasing the power down to the level below the linear heat generation rate at which the PCMI is commenced. Then, after the change of the control rod pattern, the power of the nuclear reactor is gradually increased to the preset level. During this step, in order to minimize the rate of change in the thermal load on the fuel rods during the increase of the power, the power is increased at an extemely small rate by increasing the flow rate of the cooling water. The above described manner of operation is extremely complicated and troublesome. The specification of U.S. Pat. No. 3,799,839 and Japanese Patent Publication No. 12793/1976 disclose an example of a reactor core structure in which the concentration of gadolinea is varied in the axial and radial directions of the core. Although this arrangement considerably flattens the axial and radial power distribution in the core, the operation of this core still requires the aforementioned change of the control rod pattern, causing various inconveniences as stated before in connection with the power control by control rods. SUMMARY OF THE INVENTION It is therefore an object of the invention to simplify the operation of the nuclear reactor. It is another object of the invention to improve the availability factor of operation of the nuclear reactor. It is still another object of the invention to facilitate the refueling activities in the nuclear reactor. To these ends, according to the invention, a fuel assembly is composed of a plurality of first fuel rods each of which includes a fissile material and a burnable poison and a plurality of second fuel rods each of which contains a fissile material but no burnable poison. The core of the reactor is loaded with such a fuel assembly that the amount of the fissile material is larger at the upper part of the core than at the lower part of the core. At the same time, the number of the first fuel rods and the concentration of the burnable poison in the same are made substantially proportional to the power density at the positions where the fuel assembly is loaded in the reactor core. Preferably first fuel assemblies each of which includes both of the first and second fuel rods and second fuel assemblies each of which includes only the second fuel rods are placed in the core, such that the ratio of the number of the first fuel assemblies to that of the second fuel assemblies is 1:3.
047284889	summary	The present nvention pertains to ESD (electrospark deposited) coated zirconium base alloy structural elements for use in water reactors. It especially relates to water displacer rods having an ESD coating to minimize wear. In pressurized water reactor internals design it is required that Zircaloy components come into contact with AISI 304 stainless steel and other non-zirconium base alloy components in an environment of flowing high temperature, high pressure borated and non-borated water. Under these conditions, vibrations may be produced in these contacting components causing repeated impacts and fretting wear to occur in the Zircaloy component, thereby reducing the in reactor lifetime of the Zircaloy component or causing complex and costly structural design changes to reduce the wear rate (if feasible). Water displacer rodlets are low neutron cross section rods having a tubular Zircaloy cladding containing ZrO.sub.2 pellets and helium. These rods may be moveably held above a fuel assembly in a water reactor and are lowered into guide thimbles within the fuel assemblies as needed during reactor operation to displace water (coolant). Typically 16 to 24 water displacer rods are held suspended above a fuel assembly by a spider vane. There may be 88 such vanes in a reactor. The tubular Zircaloy cladding is hermetically sealed at both ends and may typically have an outer diameter of about 0.914 inch and a length in excess of about 140 inches. It is now readily apparent that because of the slender structure of the water displacement rods, support is required along their length to minimize vibration due to the flowing coolant while also keeping them aligned with their respective thimble tubes in the fuel assembly. Examples of water displacer rods, spider vanes and their use are provided in Trevor A. Francis' U.S. patent application Ser. No. 595,154 filed Jan. 13, 1984, and Robert K. Gjertsen et al. U.S. patent application Ser. No. 570,551 filed Jan. 13, 1984 (both assigned to the assignee herein,the Westinghouse Electric Corporation. These patent applications are hereby incorporated by reference. One area where we have found wear rates to be particularly significant is where water displacer rodlets (i.e. rods) come into contact with AISI 304 stainless (304SS) steel guide supports. We have observed, in fretting wear tests, that while the primary purpose of the 304SS guide supports is to support and protect the rods from excessive wear, the Zircaloy tubular member forming the rod is susceptible to wear due to the relatively poor wear characteristics of the Zircaloy on the 304SS in the pressurized water reactor environment. ESD coatings are being evaluated as a means to reduce wear between rubbing ferrous base articles in elevated temperature liquid sodium environments. In this regard the reader is referred to: Roger N. Johnson, U.S. patent application Ser. No. 703,856 filed on Feb. 21, 1985; and Gary L. Sheldon, U.S. Pat. No. 4,405,851. The foregoing documents are hereby incorporated by reference. We propose that the foregoing water reactor wear problems can be minimized by metallurgically bonding as ESD coating to the zirconium base alloy member in the area of contact with the non-zirconium base alloy member. Preferably the zirconium base alloy member is Zircaloy-2 or 4 and the ESD coating is a Cr.sub.2 C.sub.3 coating of about 1-2 mils in thickness. Preferably that non-zirconium base alloy component is also coated in the area of contact with an ESD coating.
	description	1. Field The disclosure relates to devices for maintaining a desired position of a fuel bundle within a fuel assembly. 2. Description of Related Art FIG. 1 illustrates an example of a conventional fuel assembly 100 of a boiling water reactor (BWR), including a fuel bundle 105 and a fuel channel 160. As shown in FIG. 1, the fuel bundle 105 encloses a plurality of fuel rods 110. The fuel rods 110 within the fuel bundle 105 are supported at a lower end by a lower tie plate 120, along a length thereof by one or more spacers 130, and at the top by an upper tie plate 140. The fuel bundle 105 includes a bail handle for transporting the fuel bundle 105. The fuel assembly 100 also includes a fuel channel 160, which encloses the fuel bundle 105, and a nosepiece 190 which allows water to flow into and through the fuel bundle 105. In addition to fuel rods 110, the conventional fuel bundle 105 typically includes water rods near the center of the fuel bundle 105 that allow the coolant to flow therethrough for neutron moderation. During the operation of a boiling water reactor, water is supplied to a fuel bundle through the entrance on the nosepiece 190. Ideally, the water exits the fuel bundle as pure steam which is used to drive a turbine. One or more embodiments relate to a bundle retention clip for maintaining a desired position of a fuel bundle within a fuel assembly; a fuel assembly including the bundle retention clip and a method of installing the bundle retention clip a fuel assembly. According to at least one example embodiment, a fuel assembly may include a channel nosepiece; a lower tie plate positioned above the channel nosepiece; and at least one bundle retention clip connected to the channel nosepiece and the lower tie plate and configured to resist movement of the lower tie plate away from the channel nosepiece. The lower tie plate may include at least one slot, and the at least one bundle retention clip may include an engagement region configured to be inserted into the slot. The at least one slot and the engagement region may be configured such that once the engagement region is inserted into the slot, the retention clip responds to vertical separation of the lower tie plate and the bundle retention clip by causing a force to be exerted on the lower tie plate in a direction towards the channel nosepiece. The engagement region may include at least one spring member. The at least one spring member may include a first protrusion extending outward from a central axis of the retention clip. The first protrusion may include a first edge angled with respect to the central axis at a first angle such that application of a force to the first angled edge, the force being parallel to the central axis, causes the spring member to contract, the central axis being defined as an axis extending down a center of the retention clip along a length of the retention clip. The at least one bundle retention clip may further include a base region connected to the engagement region, at least a portion of the base region being wider than a remainder of the retention clip in a direction perpendicular to the central axis. The first angle may be between 45° and 52°. The at least one spring member may include a second protrusion extending outward from the central axis and spaced apart from the first protrusion. The at least one spring member may be arranged as a cantilever spring capable of rotating inwards towards the central axis and configured to respond to the inward rotation by exerting an outward, lateral force. The at least one spring member may include first and second spring members formed at opposite sides of the central axis. The engagement region may further includes a middle member formed in between the first and second spring members such that a first gap exists between the middle member and the first spring member, and a second gap exists between the middle member and the second spring member. According to at least one example embodiment, a retention clip may include an engagement region. The engagement region may include at least one spring member. The at least one spring member may include a first protrusion extending outward from a central axis of the retention clip. The first protrusion may include a first edge angled with respect to the central axis at a first angle such that application of a force to the first angled edge, the force being parallel to the central axis, causes the spring member to contract, the central axis being defined as an axis extending down a center of the retention clip along a length of the retention clip. The retention clip may further include a base region connected to the engagement region, at least a portion of the base region being wider than a remainder of the retention clip in a direction perpendicular to the central axis. The first angle may be between 45° and 52°. The at least one spring member may include a second protrusion extending outward from the central axis and spaced apart from the first protrusion. The at least one spring member may be arranged as a cantilever spring capable of rotating inwards towards the central axis and configured to respond to the inward rotation by exerting an outward, lateral force. The at least one spring member may include first and second spring members formed at opposite sides of the central axis. The engagement region may further include a middle member formed in between the first and second spring members such that a first gap exists between the middle member and the first spring member, and a second gap exists between the middle member and the second spring member. According to at least one example embodiment, a method of assembling a fuel assembly, the fuel assembly including a channel nosepiece; a lower tie plate positioned above the channel nosepiece; and at least one bundle retention clip connected to the channel nosepiece and the lower tie plate and configured to resist movement of the lower tie plate away from the channel nosepiece, the channel nosepiece including an opening, the lower tie plate including a slot, the at least one bundle retention clip including a base region configured to fit into the opening and an engagement region configured to be inserted into the slot, may include inserting the base region of bundle retention clip into the opening of the channel nosepiece; and placing the lower tie plate onto the bundle retention clip such that the engagement region of the bundle retention clip enters the slot of the lower tie plate. It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. In boiling water reactor (BWR) plants having higher power levels and higher flow rates, it is possible that under certain transient conditions the vertical hydraulic forces on a fuel bundle could overcome the bundle weight and cause the lower tie plate 120 of the conventional fuel bundle 105 to lift from its normal seated position on the channel nosepiece 190. A modified fuel assembly configured to counteract this lift condition will now be discussed. Modified Fuel Assembly FIGS. 2A-2E illustrate a portion of a modified fuel assembly 100′ according to an example embodiment from various side angles. The modified fuel assembly 100′ includes a modified lower tie plate 120′, a modified channel nosepiece 190′, and first through fourth bundle retention clips 200A-D. First through fourth bundle retention clips 200A-D may be composed of, for example, alloy X750. FIGS. 2A and 2B illustrate the modified fuel assembly 100′ with the modified lower tie plate 120′ in an assembled state in a seated position atop the modified channel nosepiece 190′. FIGS. 2C and 2D illustrate the modified fuel assembly 100′ with modified lower tie plate 120′ in an unassembled state just prior to assuming the seated position atop the modified channel nosepiece 190′. FIG. 2E illustrates a portion of the modified fuel assembly 100′ from a viewpoint above the modified lower tie plate 120′ in the assembled state seated atop the modified channel nosepiece 190′ and the first bundle retention clip 200A. Further, as is illustrated in FIG. 2E, the modified fuel assembly 100′ also includes a channel 160′ which surrounds the modified lower tie plate 120′, the first bundle retention clip 200A, which is located under an upper surface of the lower tie plate 120′ as indicated by the dashed line in FIG. 2E, and at least a portion of the modified channel nosepiece 190′. Though not illustrated, the channel 160′ also surrounds the second through fourth bundle retention clips 200B-D. The channel 160′ is omitted from FIGS. 2A-D in order to illustrate the relationship between the modified lower tie plate 120′, modified channel nosepiece 190′, and the first bundle retention clip 200A. As will be discussed in greater detail below, according to at least one example embodiment, the first through fourth bundle retention clips 200A-D provide additional margin to the aforementioned fuel bundle lift scenario by increasing the amount of upward force necessary to displace the modified lower tie plate 120′ from its seated position on top of the nosepiece 190′. Referring to FIGS. 2A-2E, as in conventional fuel assembly 100 of FIG. 1, in the modified fuel assembly 100′, in an assembled state, the modified lower tie plate 120′ sits atop the modified channel nosepiece 190′. However, modified channel nosepiece 190′ includes an opening 195 which holds the first bundle retention clip 200A. As is illustrated in FIGS. 2A-D, an upper portion of the first bundle retention clip 200A extends above an upper surface of modified channel nosepiece 190′. Further, the modified lower tie plate 120′ includes a slot 125 with which the lower tie plate receives the portion of the first bundle retention clip 200A that extends beyond the upper surface of the modified channel nosepiece 190′ when the modified lower tie plate 120′ is placed on top of the modified channel nosepiece 190′ during assembly of the modified fuel assembly 100′. The first bundle retention clip 200A will now be discussed in greater detail below with reference to FIGS. 3A-3C. The opening 195 of the modified channel nosepiece 190′ and the slot 125 of the modified lower tie plate 120′ corresponding to the first bundle retention clip 200A will be discussed in greater detail below with respect to FIGS. 4 and 5 respectively. Though the modified fuel assembly 100′ is discussed above as including four bundle retention clips 200A-D, the fuel assembly 100′ according to an example embodiment may have any number of bundle retention clips including, for example, 1, 2, 4 or 8, each of which may have the same structure and function as the first bundle retention clip 200A which will be discussed in greater detail below. Further, though, for the purpose of simplicity, only the opening 195 of the modified channel nosepiece 190′ corresponding to the first bundle retention clip 200A is described in detail below, according to an example embodiment, for each bundle retention clip installed into the modified channel nosepiece 190′, the modified channel nosepiece 190′ may include a corresponding opening structured in the same manner as the opening 195. Further, though, for the purpose of simplicity, only the slot 125 of the modified lower tie plate 120′ corresponding to the first bundle retention clip 200A is described in detail below, according to an example embodiment, for each bundle retention clip installed into the modified channel nosepiece 190′, the modified lower tie plate 120′ may include a corresponding slot structured in the same manner as the slot 125. Bundle Retention Clip FIGS. 3A-3C illustrate various views of the first bundle retention clip 200A according to an example embodiment. According to example embodiments, second through third bundle retention clips 200B-D may have the same structure and function as the first bundle retention clip 200A. As is discussed above, first through fourth bundle retention clips 200A-D may be composed of, for example, alloy X750. FIG. 3A illustrates the first bundle retention clip 200A from a top view. FIG. 3B illustrates an enlarged portion of FIG. 3A. FIG. 3C illustrates a side view of the first bundle retention clip 200A. Referring to FIGS. 3A-3C, the first bundle retention clip 200A includes a base region 225 and an engagement region 205. As will be discussed in greater detail below with reference to FIG. 4, the base region 225 is configured to fit stably within the opening 195 of the modified channel nosepiece 190′. According to at least one example embodiment, the base region 225 of the first bundle retention clip 200A includes varying widths W2 and W1 such that the base region 225 has an inverted ‘T’ shape. As will be discussed in greater detail below with reference to FIG. 5, the engagement region 205 is configured to fit within the slot 125 of the modified lower tie plate 120′ such that the bundle retention clip connects with the modified lower tie plate 120′. The engagement region 205 is configured such that the bundle retention clip can be separated from the modified lower tie plate 120′ once a sufficient amount of upward force is applied. Referring to FIGS. 3A-3C, the engagement region 205 of the first bundle retention clip 200A may include one or more spring members 210. According to at least one example embodiment, the engagement region 205 may also include a middle member 230. In the example illustrated in FIGS. 3A-3C the first bundle retention clip 200A includes two spring members 210 positioned at both sides of a central axis 201 of the first bundle retention clip 200A. As is illustrated in FIGS. 3A-3C, the central axis is defined as an axis extending down a center of the retention clip in a lengthwise direction of the retention clip. The middle member 230 is positioned in between the two spring members 210. According to at least one example embodiment, each of the two spring members 210 are spaced apart from the middle member 230 by a width W3. The spring members 210 may be arranged as cantilever springs with respect to the rest of the first bundle retention clip 200A. For example, the spring members 210 may be configured to respond to rotational displacement inward towards the central axis 201 with a force in an outward direction away from the central axis 201. Each of the spring members 210 includes a first projection 215. The first projections 215 may be located on an extreme end of the first bundle retention clip 200A opposite from the base region 225 and may extend outwards in a direction perpendicular to the central axis 201 of the first bundle retention clip 200A. According to at least one example embodiment, the first projections 215 may be trapezoidal in shape. Referring to FIG. 3B, the first projections 215 of the spring members 210 may each include first through third edges 216A-216C. The first and third edges may be angled with respect to the central axis 201 at an angle θ1. The second edge 216B may be parallel with respect to the central axis 201. The angle θ1 may be selected such that application of a force F1 in a direction parallel to the central axis 201 of the first bundle retention clip 200A to the first edge 216A of the first projection 215 causes the spring member 210 to contract or rotate inwards towards the central axis 201. The angle θ1 may be any angle which achieves the above-referenced effect including, for example, 48±3° The engagement region 205 of the first bundle retention clip 200A may include a tip region 235. The tip region 235 may include extreme portions of the spring members 210 and the middle member 230 farthest away from the base region 225. As is illustrated in FIG. 3C, the portions of the spring members 210 and middle member 230 which fall within the tip region 235 may be tapered. For example, with reference to the central axis 201, edges of spring members 210 and the middle member 230 within the tip region 235 may be angled at an angle θ2. The angle θ2 may be, for example, 30±5°. Returning to FIG. 3A, the spring members 210 may optionally include second projections 220. The second projections are located in between the first projections 215 and the base region 225 and may extend outwards, for example, in a direction perpendicular to the central axis 201 of the first bundle retention clip 200A. The second projections may have any shape including, for example, the same trapezoidal shape of the first projections 215. As will be discussed in greater detail below with reference to FIG. 4, the second projections 220 may prevent incorrect installation of the first bundle retention clip 200A into the opening 195 of the modified channel nosepiece 190′. Though, in the examples discussed above the first bundle retention clip 200A is described as including two spring members 210, the first bundle retention clip 200A may have any number of spring members. For example, the bundle retention clip may have only one spring member, or more than two spring members. Further, though in the examples discussed above the first bundle retention clip 200A is described as including a middle member 230, the middle member 230 may be omitted and the engagement region 205 of the bundle retention clip may include, for example, only spring members. The modified channel nosepiece 190′ will now be discussed in greater detail below with reference to FIG. 4. Modified Channel Nosepiece FIG. 4 illustrates an enlarged view of the opening 195 of the modified channel nosepiece 190′. The opening 195 is configured to hold the base region 225 of the first bundle retention clip 200A upon installation of the retention clip 200 in the modified channel nosepiece 190′. The base region 225 and the opening 195 may be configured such that, after the first bundle retention clip 200A is installed in the modified channel nosepiece 190′, movement of the first bundle retention clip 200A with respect to the modified channel nosepiece 190′ is prevented. Accordingly, the opening 195 may have a shape corresponding to a shape of the base region 225 of the first bundle retention clip 200A so the base region 225 is held firmly by the opening 195 of the modified channel nosepiece 190′. For example, as is illustrated in FIG. 4, the opening 195 of the modified channel nosepiece 190′ may have an inverted ‘T’ shape corresponding to the inverted ‘T’ shape of the base region 225 of the first bundle retention clip 200A. Dimensions of the opening 195 may be configured to allow easy installation of the first bundle retention clip 200A. For example, dimensions of the opening 195 may be set such that a lateral gap between the opening 195 and base region 225 is 0.33±0.26 mm. These dimensions provide a minimum lateral gap of 0.07 mm. Dimensions of the opening 195 may be set such that a horizontal gap between the opening 195 and base region 225 is, for example, 0.33±0.26 mm. These dimensions provide a minimum horizontal gap of 0.07 mm. Further, because the opening 195 has the same inverted ‘T’ shape as the base region 225 of the bundle retention clip, the second projections 230 of the first bundle retention clip 200A will not allow the engagement region 205 of the first bundle retention clip 200A to fit into the opening 195. Accordingly, an incorrect, upside down installation of the first bundle retention clip 200A into the opening 195 of the modified channel nosepiece 190′ is prevented. The modified lower tie plate 120′ will now be discussed in greater detail below with reference to FIGS. 5 and 6. Modified Lower Tie Plate FIG. 5 illustrates an enlarged view of the slot 125 of the modified lower tie plate 120′. FIG. 6 illustrates an enlarged view of a portion of the engagement region 205 of the first bundle retention clip 200A inserted into the slot 125 of the modified lower tie plate 120′. Referring to FIG. 5, the slot 125 is configured to accept entry of the engagement region 205 of the first bundle retention clip 200A. The slot 125 is further configured such that after entry of the engagement region 205 in the slot 125 of the modified lower tie plate 120′, the engagement region 205 resists upward movement of the modified lower tie plate 120′ away from the channel nosepiece. For example, the slot 125 may have three regions of varying width including a slot opening region 126, a slot middle region 127, and a slot end region 128. As is illustrated in FIG. 5, the slot opening region 126 has a tapered width which may decrease gradually from the bottom of the modified lower tie plate 120′ towards the top of the modified lower tie plate 120′. According to at least one example embodiment, an opening end of the opening region 126 may be wider than a total width of both spring members 210, including the first projection 215, in order to facilitate initial entry of the engagement region 205 of the first bundle retention clip 200A into the slot 125 of the modified lower tie plate 120′, and to accommodate the second projections 230 which may be optionally included in the spring members 210. The slot middle region 127 has a width which decreases sharply with respect to a width of an upper portion of the slot opening region. The slot end region 128 has a width which increases sharply with respect to the width of the slot middle region 127. With this configuration, during entry of the first bundle retention clip 200A into the slot 125 of the modified lower tie plate 120′, the spring members 210, including the first projections 215, fit into the opening region 126 of the slot 125 and are forced to contract, or rotate, inwards towards the central axis 201 upon reaching the slot middle region 127 of the slot 125. Further, upon reaching the slot end region 128 of the slot 125, the increased width of the slot end region 128 relative to the slot middle region 127 allows the spring members 201 to rotate outwards back towards their original position. Referring to FIG. 6, the width of the slot end region 128 of the slot 125 may be wide enough to allow the spring members 210 of the first bundle retention clip 200A to assume their original position relative to the central axis 201, the original position being the position of the spring member 210 before entry into the slot 125. Further, as is illustrated in FIG. 6, edges of an upper portion of the slot middle region 127 may be angled at the same angle θ1 of the first edges 216A discussed above. Accordingly, after entry of the engagement region 205 into the slot end region 128 of the slot 125, the first edges 216A of the first projections 215 of the first bundle retention clip 200A may overlap with the edges of the slot 125 in both the vertical and horizontal directions. Due to this overlap, upward motion of the modified lower tie plate 120′ relative to the first bundle retention clip 200A will cause the modified lower tie plate 120′ to exert an upward force on the first edges 216A of the first projections 215. Due to the angle θ1 of the first edges 216A of the first projections 215, the upward force exerted by the modified lower tie plate 120′ will cause the spring members 210 of the first bundle retention clip 200A to contract or rotate inwards towards the central axis 201 of the first bundle retention clip 200A. The angle θ1 of the first edges 216A of the first projections 215 will also cause the inward rotation of the spring members 210 to increase as the upward movement of the lower tie plate 120 relative to bundle retention clip 200 increases. Due to the cantilever spring arrangement of the spring members 210, the inward rotation of the spring member 210 will cause the spring members 210 to respond by exerting an outward, lateral force away from the central axis 201 on the edges of the slot 125. Further, as the inward rotation of the spring members 210 towards the central axis 201 increases, so will the outward lateral force exerted by the spring members 210 on the edges of the slot 125. The angled edges within the slot middle region 127 of the slot 125 will convert the lateral force exerted by the spring members 210 into a downward force applied to the modified lower tie plate 120′. This downward force will increasingly resist the upward movement of the modified lower tie plate 120′ relative to the first bundle retention clip 200A until the upward movement of the modified lower tie plate 120′ is sufficient to remove the engagement region 205 of the first bundle retention clip 200A from the slot end region 128 and the slot middle region 127 of the slot 125. At this point, the engagement region 205 of the first bundle retention clip 200A may no longer provide substantial resistance to the upward movement of the modified lower tie plate 120′. According to at least one example embodiment, dimensions of the slot 125 may be selected such that after entry of the engagement region 205 of the first bundle retention clip 200A into the slot end region 128 of the slot 125, and before any upward movement of the modified lower tie plate 120′, the spring members 120′ are not forced inwards towards the central axis 210. Accordingly, the spring members 210 may exert no lateral force on the modified lower tie plate 120′ when the lateral tie plate 120′ is in its seated position atop the modified channel nosepiece 190′. A method of assembling a fuel assembly including a bundle retention clip according to example embodiments will now be discussed below with reference to FIG. 7. FIG. 7 is a flowchart illustrating a method of assembling a fuel assembly including a bundle retention clip according to an example embodiment. For the purpose of simplicity, FIG. 7 will be described below with reference to the first bundle retention clip 200A, modified lower tie plate 120′ and modified channel nosepiece 190′ of the modified fuel assembly 100′. However, the method illustrated in FIG. 7 may be applied to each of first through fourth bundle retention clips 200A-D. Referring to FIG. 7, in step S705 the bundle retention clip 200A is inserted into the opening 195 of the modified channel nosepiece 190′. For example, the base region 225 of the first bundle retention clip 200A is placed into the opening 195. In step S710, the modified lower tie plate 120′ is placed on the bundle retention clip 200A such that the engagement region 205 of the first bundle retention clip 200A enters slot 125 of the modified lower tie plate 120′. For example, the lower tie plate 120′ may be lowered to a seated position atop the channel nosepiece 190′ such that the engagement region 205 of the first bundle retention clip 200A enters the slot end region 128 of the slot 125. Thus, the slot 125 of the modified lower tie plate 120′ and the engagement region 205 of the first bundle retention clip 200A are configured such that, though removal of the modified lower tie plate 120′ from the modified channel nosepiece 190′ is resisted, the modified lower tie plate 120′ can be removed from its seated position atop the modified channel nosepiece 190′ upon application of sufficient upward force. Accordingly, using the first through fourth bundle retention clips 200A-D, a plant operator can assemble the modified fuel assembly 100′ by attaching the modified lower tie plate 120′ to the modified channel nosepiece 190′ in a manner that prevents unintentional displacement of the modified lower tie plate 120′ from its seated position atop the modified channel nosepiece 190′ while allowing intentional removal of the modified lower tie plate 120′ from the modified channel nosepiece 190′ when desired. While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
	summary
	abstract	Process and system for processing a thin film sample, as well as at least one portion of the thin film structure are provided. Irradiation beam pulses can be shaped to define at least one line-type beam pulse, which includes a leading portion, a top portion and a trailing portion, in which at least one part has an intensity sufficient to at least partially melt a film sample. Irradiating a first portion of the film sample to at least partially melt the first portion, and allowing the first portion to resolidify and crystallize to form an approximately uniform area therein. After the irradiation of the first portion of the film sample, irradiating a second portion using a second one of the line-type beam pulses to at least partially melt the second portion, and allowing the second portion to resolidify and crystallize to form an approximately uniform area therein. A section of the first portion impacted by the top portion of the first one of the line-type beam pulses is prevented from being irradiated by trailing portion of the second one of the line-type beam pulses.
	description	The present invention relates generally to a shielding apparatus and method for an operating room equipped with x-ray diagnostic equipment and more particularly to such a method and apparatus wherein an x-ray shield panel includes at least two segments, capable of turning relative to each other about a substantially vertical axis. Modern operating rooms typically include a table on which a patient lies during the operating procedure, and diagnostic equipment in the form of an x-ray source and an x-ray detector, is located on a gantry with the patient and operating table between the x-ray source and detector. The gantry is rotatable about a horizontal axis so that a surgeon viewing a display responsive to the detector is provided with real time display of the tissue being operated on. During the procedure, the patient is irradiated by x-rays for prolonged intervals and is moved relative to the source of x-rays by providing the table with motors and a linkage that move the table and patient relative to the platform in a plane parallel to the floor. At other times, it is essential that the table and patient remain stationary, a result achieved by providing the table with a braking arrangement for holding the table in situ relative to the platform. The x-ray source can be activated to different intensity levels. The x-ray source is activated to a high intensity level, referred to as the cine mode, to provide an intensity sufficient to expose cine film and to provide fluoroscopy. The x-ray source is activated to a lower intensity, referred to as the fluoroscopy mode, when only fluoroscopy and no exposure of cine film is required. Typically, there is approximately a 4:1 ratio between the intensity level of the cine and fluoroscopy modes. Because the surgeon and one or more assistants stand next to the operating table, they are constantly exposed to x-rays back-scattered from the patient and/or table unless adequate shielding is provided. The accumulated effect of the back-scattered radiation over many years of conducting surgical procedures may have deleterious effects on the health of the surgeon and assistant(s), and may induce cancer. In an attempt to reduce the x-ray exposure to a surgeon and assistant(s) standing next to the side of an operating table while an x-ray source is irradiating a patient, the surgeon and assistant(s) usually wear leaded eyeglasses, a lead thyroid covering and a lead apron which covers the chest, abdomen and thighs but leaves uncovered the arms, hands, legs below the knees and head. The radiation protection is only partially effective in blocking radiation and leaves substantial parts of the body uncovered. The amount of back-scattered x-ray radiation incident on the surgeon and assistant(s), particularly during the cine mode, is believed to be substantial enough to cause damage to the surgeon and assistant(s) over a prolonged time period. In some instances, the surgeon and assistant(s) stand behind lead shield panels that are transparent to optical energy but substantially opaque to x-rays. The lead shield panels are typically unitary structures fixedly mounted on frames carrying casters, as disclosed in my U.S. Pat. No. 5,185,778, incorporated herein by reference. The panels are made of lead glass having sufficient thickness to substantially attenuate the back-scattered x-rays and thereby protect the surgeon and assistants. The panels do not enable the surgeon and/or assistants easy access to the patient during the operating procedure. Consequently, if access to the patient is necessary during the procedure and while the patient is being x-rayed, there is a high likelihood of sensitive body portions of the surgeon and/or assistant(s) being irradiated with undesirable doses of back-scattered x-ray radiation. It is, accordingly, an object of the present invention to provide a new and improved method of and apparatus for shielding surgeons and/or assistants from x-rays during surgery while x-rays are being used for diagnostic purposes. An additional object of the present invention is to provide a new and improved method of and apparatus for shielding critical body parts of surgeons and/or assistant(s) during an operating procedure that is accompanied by a patient being exposed to diagnostic x-rays, wherein the shield arrangement enables relatively easy access to the patient. Another object of the present invention is to provide a new and improved shield panel arrangement for an operating room including x-ray diagnostic equipment, wherein the shield panel arrangement includes moving parts that are relatively easily moved, despite the substantial weight and density of the shield panels. According to one aspect of the invention, there is provided an apparatus for reducing back-scattered x-rays incident on a person working with a patient on an operating table, wherein the patient is exposed to x-rays from an x-ray source while on the table so that the back-scattered x-rays result from x-rays from the source being incident on the patient and/or table. The apparatus comprises an upper x-ray shield panel and a lower x-ray shield panel arrangement. The upper x-ray shield panel and the lower x-ray shield panel arrangement have thicknesses between front and back faces thereof and respectively have lower and upper edges in close enough proximity to each other to substantially attenuate the back-scattered x-rays incident on (a) the front face of the upper x-ray shield panel, (b) the lower x-ray shield panel arrangement, and (c) a gap between the edges while the front faces of the upper x-ray shield panel and lower x-ray shield panel arrangement are aligned and parallel to a proximate edge of the operating table. The upper shield panel is transparent to visible optical energy and pivotable about a vertical axis relative to the lower shield panel arrangement to enable one or both hands and one or both forearms of a person standing behind the back faces of the upper and lower shield panels to extend through an open region between the lower and upper edges. The opening results from pivoting of the upper x-ray shield panel relative to the lower x-ray shield panel arrangement about the vertical axis. The upper x-ray shield panel and lower x-ray shield panel arrangement together have a height and widths sufficiently greater than the height and width of the person standing behind the back faces of the upper panel and lower panel arrangement to substantially prevent the back-scattered x-rays incident on the front faces of the upper x-ray shield panel and the lower x-ray shield panel arrangement from being incident on the portion of the person behind the back faces while the front faces are aligned. Preferably, the upper x-ray shield panel and the lower x-ray shield panel arrangement have aligned vertically extending edges that are substantially coincident with the vertical axis. Another x-ray shield panel is preferably provided. The another x-ray shield panel has front and back faces and a vertically extending edge in sufficiently close proximity to the aligned vertically extending edges of the upper x-ray shield panel and lower x-ray shield panel arrangement to substantially attenuate the back-scattered x-rays incident on (1) the aligned vertically extending edges of the upper x-ray shield panel and the lower x-ray shield panel arrangement and (2) the vertically extending edge of the another x-ray shield panel. The front face of the another x-ray shield panel is positionable at a non-zero angle, e.g. 90°, relative to the front faces of the upper x-ray shield panel and the lower x-ray shield panel arrangement. The another x-ray shield panel preferably has a height equal to or greater than the combined heights of the upper x-ray shield panel and the lower x-ray shield panel arrangement. The vertically extending edge of the another x-ray shield panel is preferably pivotable relative to the aligned vertically extending edges of the upper x-ray shield panel and the lower x-ray shield panel arrangement to enable the another panel to be turned by a suitable angle, e.g., 90°, relative to the aligned upper panel and lower panel arrangement and the proximate edge of the operating table. Preferably, to maximize attenuation of back-scattered x-rays, the another x-ray shield panel has a horizontal extent substantially at a right angle to the faces and a first segment extending slightly beyond the front faces toward the operating table and a second segment extending by a substantial distance beyond the back faces away from the operating table. In one embodiment, the lower x-ray shield panel arrangement includes a single x-ray shield panel. In a second embodiment, the lower x-ray shield panel arrangement includes first and second x-ray shield panels, arranged so the first panel is generally above the second panel. The first x-ray shield panel has (1) a lower edge and (2) an upper edge corresponding with the upper edge of the lower x-ray shield panel arrangement. The second x-ray shield panel has an upper edge below the lower edge of the first x-ray shield panel and a lower edge in close proximity to the floor or on the floor. The first and upper x-ray shield panels are arranged so they can have different vertical positions so that the gap between the upper edge of the first x-ray shield panel and the lower edge of the upper x-ray shield panel is maintained constant at the different vertical positions. The first and second x-ray shield panels are arranged so that (1) the upper and lower edges of the second x-ray shield panel are maintained at the same vertical position while the first and upper x-ray shield panels are at all of the different vertical positions, and (2) the upper edge of the second x-ray shield panel is above the lower edge of the first x-ray shield panel at all of the different vertical positions. Preferably, the upper and first x-ray shield panels are drivingly connected to a pulley arrangement so the upper and first x-ray shield panels can be driven to the different vertical positions. The pulley arrangement includes a wheel and a counterweight. The counterweight is on a side of the wheel different from the upper and first x-ray shield panels and weighs about the same as the combined weights of the upper and first x-ray shield panels. Another aspect of the invention relates to a method of using the foregoing apparatus to reduce back-scattered x-rays incident on a person working with a patient on an operating table. The method comprises forming the open region between the bottom edge of the upper panel and the upper edge of the lower panel arrangement by causing the upper x-ray shield panel to be turned toward the operating table while maintaining the lower x-ray shield panel arrangement substantially parallel to a proximate edge of the table while the patient is exposed to x-rays from the x-ray source. One or both hands and one or both forearms of a person located behind the shield panels are extended through the open region while the patient is exposed to x-rays from the x-ray source while the remainder of the person is behind the back faces. In those embodiments wherein the lower x-ray shield panel arrangement includes the first and second x-ray shield panels, the method preferably further comprises abutting the lower edge of the upper x-ray shield panel against an upper surface of the patient on the operating table after the table has been vertically locked in position for the comfort of the surgeon. Such a position of the upper panel aids in reducing back-scattered x-rays incident on the person while the patient is exposed to x-rays from the x-ray source and one or both hands and one or both forearms of the person extend through the open region while the remainder of the person is behind the back faces of the shield panels. The above and still further objects, features and advantages of the present invention will become apparent upon consideration of the following detailed description of specific embodiments thereof, especially when taken in conjunction with the accompanying drawings. The preferred embodiment of the present invention is described in conjunction with a cardiac catheterization procedure. It is to be understood, however, that the principles of the invention are applicable to any surgical or radiological procedure wherein a patient is subject to x-ray radiation for prolonged time periods and an operator and assistant(s) attending the patient, e.g., a surgeon or radiologist and nurse(s), are subject to x-rays back-scattered from the patient and/or operating table on which the patient is lying. Reference is now made to FIG. 1 of the drawing wherein operating table 11 is mounted on platform 12, in turn fixedly mounted on floor 13 so that the operating table extends in a horizontal plane parallel to the floor. Platform 12 includes X-Y linkages (not shown) for moving table 11 in the horizontal plane in directions of X and Y axes and motors, as well as a braking mechanism, and an elevator (not shown) for driving table 11 up and down, i.e., in the direction of the z axis; the linkages, motors, braking mechanism and elevator are well known to those skilled in the art. The linkages and motors for the X and Y axes enable forces manually applied by the surgeon to the table during the procedure to move the table in the horizontal plane, even though a relatively heavy patient is lying on table 11. The X-Y linkages and motor in platform 12 are controlled by the surgeon selectively activating a button, so that when the button is pushed, the manually-imparted forces cause table 11 to move in the horizontal plane. When the button is not activated, the X-Y linkages and the motors in platform 12 are braked by the braking mechanism in the platform to prevent movement of table 11 relative to platform 12 and the floor 13. The z axis position of table 11 is established prior to the procedure being initiated so that the patient is at a height above floor 13 that enables the operator to perform the procedure with the greatest ease and comfort. X-ray source 14 and x-ray detector 15, in the form of an image intensifier, are mounted on gantry 16 so that the tube and detector are mounted on opposite sides of table 11 while the patient is on the table. Gantry 16 is mounted for rotation on column 17, located on floor 13. Circuitry in x-ray source 14 and image-intensifier 15 is controlled by electric power and signals coupled to them from an x-ray controller (not shown) via cable 19. The x-ray image is transmitted via cable 20 from an x-ray controller (not shown) through the ceiling to video display 18. Power for the cine recorder is provided by cable 21. Typically, x-ray source 14 is activated to one of two different intensity levels, respectively referred to as the fluoroscopy and cine modes, such that the cine mode has an intensity level four times greater than that of the fluoroscopy mode. Control console 22 for the movement of table 11 as well as for x-ray source 14 is fixedly mounted on one end of operating table 11. In a typical operating room, one or more lead impregnated plastic, optically transparent vertically extending x-ray shield panel(s) 24 is located in proximity to proximate side 23 of table 11. Each shield panel 24 is mounted on bracing structure 25, on which are mounted casters 26 for enabling the shield panel to be easily moved relative to platform 12 on floor 13. Shield panel 24 extends from about a foot above floor 13 to about 6½ feet above the floor and for about 3 feet from side to side so the entire body of a surgeon standing behind the panel is effectively shielded from x-rays back-scattered from table 11 and the patient lying on the table. One or more additional shield panels 30 (only one of which is included in FIG. 1 for clarity) somewhat similar to shield panel 24 are usually included, such that one additional shield panel 30 is provided for each assistant to the operator who is standing next to table 11. Additional shield panel 30 does not include controllers for the movement of table 11 that are included on panel 24. In the prior art, the additional panel 30 is a planar, structure that is mounted on casters. Panel 30 of the prior art does not enable the person standing behind the panel to assist the surgeon who is standing behind panel 24 while x-ray source 14 is activated, unless such a person is willing to step around panel 30 and risk x-ray exposure. Hence, during the cine operation, while x-ray source 15 is activated, body parts of the persons who should be standing behind prior art panel 30 are irradiated by x-ray radiation back-scattered from the patient and table 11. Over a prolonged period of many years, such a person is likely to be subjected to considerable amounts of x-ray radiation back-scattered from the table and patients on which the cardiac catheterization procedure has been performed. The accumulated effects of the back-scattered radiation on the persons may lead to the persons becoming cancer victims. As a result of the present invention, the prior art panel 30 is modified so persons standing behind an x-ray shield panel located around table 11 can participate with his/her hands in the procedure while x-ray source 14 is activated. The modified panel is such that one or both hands and forearms are the only parts of the person exposed to the back-scattered x-ray radiation. Exposure to x-rays by one or both hands and forearms is much less likely to result in cancer than exposure to x-rays by other body parts. Reference is now made to FIGS. 2-6 of the drawing, illustrations of a first embodiment of a shield panel that can be placed where shield panel 30 is illustrated in FIG. 1. The shield panel of FIGS. 2-6 includes base 32, center leg 34 and exterior legs 36-39, fixedly connected to leg 34 and arranged so that legs 36 and 37 extend in opposite directions from one end of center leg 34 and legs 38, 39 extend in opposite directions from the other end of center leg 34. Opposite ends of legs 36-39 carry casters 42 that enable the shield panel of FIGS. 2-6 to be easily moved around the operating room. Rectangular, x-ray shield panel 44 is fixedly mounted on and aligned with center leg 34 so panel 44 extends from the center leg upwardly in the vertical plane. The periphery of panel 44 is circumscribed by metal frame 46, having a vertically extending edge 48 that is substantially aligned with legs 38 and 39 and carries piano hinge 50. The upper portion of hinge 50 is attached to frame 52 that circumscribes upper x-ray shield panel 54. The lower part of hinge 50 is attached to a vertically extending edge of frame 56 that circumscribes lower x-ray shield panel 58 that can be considered as a lower x-ray shield panel arrangement. Typically, x-ray shield panels 44, 54 and 58 are plastic panels embedded with lead so that they have a 1.0 or 2.0 mm lead equivalent, causing the plastic panels to be 22 or 46 mm thick. Frames 52 and 56 are hung on hinge 50 such that there is a gap 60 between the upper edge of frame 56 and the lower edge of frame 52. Because x-ray shield panels 54 and 58 extend within frames 52 and 56 virtually to the opposite sides of gap 60, gap 60 can be considered as the gap between the lower edge of shield panel 54 and the upper edge of shield panel 58. In a typical embodiment, gap 60 has a vertical extent, i.e., height, of ¾ inch. The thicknesses of panels 54 and 58 and the vertical length of gap 60 are such that back-scattered x-rays incident on the front face of panel 54, the front face of panel 58 and gap 60 are substantially attenuated and are not harmful to a person standing behind panels 54 and 58, when the panels are aligned in a plane, such that the front faces of the panels are approximately 2 inches from proximate edge 23 of operating table 11. Upper shield panel 54 and lower shield panel 58 are dimensioned to cause a person standing behind panels 54 and 58 to be protected from back-scattered radiation from the patient being operated on and/or from table 11. To this end, in one embodiment panels 54 and 58 respectively have heights of 28½ and 44 inches, so that the total height of panels 54 and 58 and gap 60 is 73¼ inches, the same height as panel 44. Panels 54 and 58 have the same length in the horizontal plane of 24 inches while panel 44 has a length in the horizontal place of 30 inches. These dimensions are such that when panels 54 and 58 are aligned, panel 54 protects the head, upper torso, part of the midsection and arms and legs of the person, while panel 58 protects the remainder of the midsection, lower torso, legs and feet of the person. It is to be understood that the aforementioned dimensions are the preferred dimensions, but can be changed, as necessary, depending upon the height and girth of the person standing behind panels 54 and 58. Panel 54 is transparent to visible optical energy, so that the person standing behind panels 54 and 58 can see what is happening on operating table 11 and participate in the operation, as necessary. Panels 44 and 58 can be transparent or opaque to visible optical energy, as desired. In use, panel 44 is located at right angles to proximate edge 23 of operating table 11, so that one face of panel 44 abuts or is in very close proximity to an edge of panel 24. Panel 58 is positioned so that the front planar surface thereof is parallel to spaced approximately 2 inches from proximate 23 edge of operating table 11. When the person standing behind panels 54 and 58 is only observing what is happening on operating table 11, panel 54 is aligned with panel 58, so that both panels 54 and 58 are parallel to and approximately 2 inches from proximate edge 23 of operating table 11. When the person standing behind panels 54 and 58 needs to participate in the operation, panel 54 is turned about hinge 50 to such an extent that the person standing behind panels 54 and 58 can place one or both of its hands and one or both of its forearms through the opening between panels 54 and 58 created by panel 54 being turned toward the proximate edge 23 of operating table 11. Preferably, the height of table 11 is adjusted so the lower edge of panel 54 lies on a body part of the patient on operating table 11, typically the legs of the patient, to minimize radiation back-scattered from the patient and/or table 11 through the opening resulting from panel 54 being turned about hinge 50. If necessary, panel 54 can be turned 90 degrees relative to panel 58, so that panels 44 and 54 are both at right angles to the proximate edge 23 of operating table 11. If necessary or desirable, panel 58 is turned about hinge 50 so that the vertical edge of panel 58 that is remote from hinge 50 contacts proximate edge 23 of operating table 11. According to a modification of the shield arrangement of FIGS. 2-6, the upper shield panel and lower shield panel arrangement are such that the lower edge of the upper shield panel can always be turned so that it contacts the body of the patient and the gap between the lower edge of the upper shield panel and the upper edge of the lower shield arrangement is maintained constant. Such a modification is illustrated in FIGS. 7-9. In the embodiment of FIGS. 7-9, base 32 and casters 42 are identical to the arrangement of FIGS. 2-6. In the embodiment of FIGS. 7-9, shield panel 68 is similar, but slightly different from panel 44, but upper shield panel 70 is identical to upper shield panel 54 of the embodiment of FIGS. 2-6. However, mounting of upper shield panel 70 is quite different from mounting of shield panel 54. Lower shield panel arrangement 72 in the embodiment of FIGS. 7-9 includes a first, upper panel 74 and a second, lower panel 76. Panel 74 is mounted relative to panel 70 so that the upper edge of panel 74 and the lower edge of panel 70 have a ¾ inch constant height gap 78 between them, despite the fact that panels 70 and 74 can be raised together and the lower edge of panel 70 can be swung outwardly to engage an upper surface of the body of the patient, such as the top of the patient's legs. Panel 76 is fixedly mounted so that the bottom edge thereof abuts or is slightly above the operating room floor on which casters 42 rest. Panels 74 and 76 are dimensioned and mounted so that the upper edge of panel 76 is always above the lower edge of panel 74 and the back planar face of panel 74 and the front planar face of panel 76 always remain parallel and in close proximity to each other, so that the person standing behind panels 70, 74 and 76 is shielded from back-scattered x-rays incident on the front face of panel 74. When panels 70, 74 and 76 are parallel to each other, panel 70 protects the head, upper torso, arms and hands of the person, panel 74 protects the midsection and the upper and middle leg portions of the person and panel 76 protects the middle and lower leg portions and feet of the person. In one preferred embodiment, panels 68, 70, 74 and 76 have the same thickness of 22 or 46 mm. Panel 68 has a height of 73¼ inches and a width of 32 inches between its vertical edges; each of panels 70, 74 and 76 has a width of 30 inches between its vertical edges; panel 70 has a height of 28½ inches; panel 74 has a height of 34 inches and panel 76 has a height of 26 inches; and the gap between the top edge of panel 76 and the bottom edge of panel 74 is ¾ inch. Such dimensions provide the required protection for most persons who stand behind panels 70, 74 and 76. Panels 70, 74 and 76 are coupled to panel 68 and panel 68 is constricted in such a manner that front edge 77 of panel 68 extends to the proximate edge 23 of table 11 when the front, planar faces of panels 70, 74 and 76 are parallel to and spaced from the proximate edge 23 of table 11 by a distance of 2 inches. Because of the abutting relationship of front edge 77 of panel 68 with the proximate edge 23 of table 11, the amount of back-scattered radiation from the table and patient that is incident on the person standing behind panels 70, 74 and 76 is substantially reduced. The structure 80 for coupling panels 70, 74 and 76 to panel 68 includes rod or tube 82 that is fixedly connected to the top of panel 68 and includes leg 83 that extends upwardly from the top edge of panel 68 by a suitable distance, e.g., 1 foot. The connection point of tube 82 to the top edge of panel 68 is horizontally aligned with panels 70, 74 and 76 when panels 70, 74 and 76 are positioned so that the front faces thereof are parallel to proximate edge 23 of table 11, i.e., the base of tube 82 is 2 inches from the edge of panel 68 that abuts the proximate edge 23 of table 11. Tube 82 has a right angle bend 12 inches above the top edge of panel 68, to form leg 85 that extends horizontally in a plane aligned with panels 70, 74 and 76. The horizontal extent of leg 85 is 2 inches, to another right angle bend, at which tube 82 extends downwardly in the vertical plane to form leg 87. Leg 87 extends downwardly to a point aligned with base 32, where tube 82 has a further right angle bend to form leg 89 that extends horizontally in a plane aligned with the plane of panels 74 and 76. The end of leg 89 remote from panels 76 and 78 is fixedly connected to base 82. Tube 82 thus forms a rigid structure that ultimately carries panels 70, 74 and 76 so panel 70 can turn about a vertical axis defined by the axis of leg 87. Panels 74 and 76 are mounted so they stay in planes substantially parallel to proximate edge 23 of table 11. To enable panels 70 and 74 to be raised and lowered together and to enable panel 70 to be turned about the vertical axis of leg 87 while panels 74 and 76 remain parallel to edge 23, panels 70 and 74 are respectively fixedly mounted on sleeves 90 and 92 that are concentric with and slidable relative to the length of long leg 87 of tube 82. The bottom portion of sleeve 90 is connected to the top portion of sleeve 92 by flexible coupling 93 that enables sleeve 90 to turn about leg 87 relative to sleeve 92 while maintaining a constant vertical separation of ¾ inch between the bottom edge of sleeve 90 and the top edge of sleeve 92. To this end, the bottom portion of sleeve 90 is fixedly connected to the top portion of flexible coupling 93 and the top portion of sleeve 92 is fixedly connected to the bottom portion of coupling 93. Coupling 93 has sufficient lengthwise stiffness, i.e., stiffness in the vertical direction, to maintain the distance between the lower edge of panel 70 and the upper edge of panel 74 constant, even though the coupling is turned through an angle about its longitudinal axis in excess of 90°. As described infra, panel 76 remains in situ while panels 90 and 92 are moved up and down together and panel 70 is turned relative to panels 74 and 76. Sleeves 90 and 92 are connected to the proximate edges of panels 70 and 74 by clamps 95 and 96, respectively. Clamp 96 rigidly and fixedly holds panel 74 to sleeve 92, while clamp 95 is arranged so that one end thereof is fixedly connected to panel 70 and the other end is selectively fastened and released from sleeve 90. Clamp 95 is released from sleeve 90 while panel 70 is turned about leg 87 of rod 82. When panel 70 has been turned to the desired angle about leg 87, clamp 95 is fastened to sleeve 90 so panel 70 remains at the desired angular position relative to leg 87; for example, panel 70 can be turned so that at a first position panels 70 and 74 are aligned and at a second position, panel 70 is turned 90° relative to panel 74 so the faces of panels 68 and 70 are in parallel planes. Pulley system 102 that includes metal pulley cable 100 enables panels 70 and 74 to be raised and lowered together so that gap 78 between the upper edge of panel 74 and the lower edge of panel 70 remains constant. Opposite ends of pulley cable 100 are connected to the top edge of panel 70 and counterweight 106 so that panels 70 and 76 are raised and lowered by moving pulley cable 100 up and down. Pulley system 102 also includes pulley wheel assembly 104, mounted on by swivel 103 horizontally extending leg 105 that is aligned with leg 85 of rod 82, so that assembly 104 is free to turn as panel 70 turns. Pulley wheel assembly 104 comprises pulley wheel 108 having a circumferential groove about which cable 100 is wound and a cable brake (not shown). The cable brake of pulley wheel assembly 104 is applied when the bottom edge of panel 70 is at the desired position, i.e., at a position so that the bottom edge of panel 70 contacts the body of the person being operated on. Adjustment of the height of the bottom edge of panel 70 is easily provided in a precise manner by appropriate selection of the weight of counterweight 102, so that the counterweight and the combined weights of panels 70 and 74, that can exceed 1,000 pounds, are closely matched. Rack 110, fixedly mounted to rod 82 by pins 112, maintains panels 74 and 76 in planes parallel to each other and parallel to the proximate edge 23 of operating table 11. Rack 110 enables panel 74 to be driven up and down by cable 82, but holds panel 76 firmly in place. Rack 110 has a height less than the minimum height of the upper edge of panel 74 above the operating room floor so that a portion of panel 74 always extends above the upper edge of rack 110. Rack 110 includes base 116 that is fixedly positioned slightly above the operating room floor when the shield arrangement of FIGS. 7-9 is in place. The bottom edge of panel 76 rests on base 116, and the side edges of panel 76 are fixedly captured by interior surfaces of vertically extending channels 118 and 120 (FIG. 9), such that flanges 122 of channels 118 and 120 capture the front and back faces of panel 76, and the interior surfaces of the elongated, vertically extending bases 126 of channels 118 and 120 capture the opposite vertically extending edges of panel 76. Rack 110 also includes channels 128 and 130 that hold panel 74 in place. Channels 128 and 130 include flanges 132 that capture the front and back faces of panel 74, as well as elongated, vertically extending bases 134 that capture the opposite edges of panel 74. The interior flanges 124 and 132 of channels 118, 120, 128 and 130 have abutting faces that are welded together so that rack 110 is formed as a unitary structure in which panel 76 is maintained at a fixed, constant position, while panel 74 is free to move up and down relative to panel 76, but panel 74 can not turn appreciably relative to panel 76 due to the way panel 74 fits in channels 128 and 130. Prior to an operation on a patient commencing, the surgeon adjusts the height of table 11 above the operating room floor so that the patient is located at a position where the surgeon is comfortable while operating on the patient. Then, the shield assembly of FIGS. 7-9 is wheeled into place so that the forward edge 77 of panel 68 abuts the proximate edge 23 of operating table 11, while panels 70, 74 and 76 are locked in place at a position, such that (1) the front faces of panels 70, 74 and 76 are parallel to the proximate edge 23 of operating table 11, and (2) the upper edge of panel 74 and the lower edge of panel 70 are above the legs of the person being operated on. Hence, clamp 95 is fixedly connected to sleeve 90 and the brake of pulley wheel assembly 104 is engaged at this time. Then, clamp 95 is released and sleeve 90 is turned about leg 87 of cable 82, so that panel 70 extends above the patient on the operating table. Then, clamp 95 is locked to sleeve 90, so that flexible coupling 93 is twisted through an angle equal to the angular displacement of panel 70 from panel 74. Then, the brake of pulley wheel assembly 104 is released and leg 87 of cable 82 is pulled downwardly until the bottom edge of panel 70 rests on the legs of the person being operated on. Then, the brake of pulley wheel assembly 104 is activated, to lock cable 100 at a fixed vertical position, so that the fixed vertical positions of panels 70 and 74 are locked. Then, clamp 95 is released and panel 70 is turned about leg 87 of tube 82, so that the front face of panel 70 is parallel to proximate edge 23 of operating table 11. If the person standing behind panels 70, 74 and 76 is required to participate in the operation, clamp 95 is released and panel 70 is turned toward operating table 11, about leg 87 of tube 82, until panel 70 is at the required angle. Then, clamp 95 is tightened, so that panel 70 is maintained at the desired angle, to provide an opening through which the hand or hands and forearm or forearms of the person standing behind panels 70, 74 and 76 can extend to enable such a person to participate in the operation. Flexible coupling 93 is then twisted through an angle equal to the angular displacement of panel 70 from panel 74. When it is desired to re-align panels 70 and 74 or upon completion of the operation, the foregoing steps are reversed. While a specific embodiment of the invention has been described and illustrated, variations regarding details of the embodiments specifically illustrated and described may be made without departing from the true spirit and scope of the invention as defined in the appended claims. For example, standard controllers, as well as the controllers described in my aforementioned patent, can be mounted on the panels of both embodiments, if necessary or appropriate. In addition, the spacing between the bottom edge of panel 54 and the top edge of panel 58 and the spacing between the bottom edge of panel 70 and the top edge of panel 74 can be any suitable distance less than ¾ inch, as long is there is sufficient spacing between these edges to enable the upper panel to turn relative to the lower panel.
	description	This application is a continuation-in-part of, claims priority to, and incorporates by reference in its entirety PCT Patent Application Serial No. PCT/US02/17936, filed Jun. 5, 2002. This application also claims priority to, and incorporates by reference in its entirety, pending U.S. application Ser. No. 60/339,773, filed Dec. 17, 2001. This application incorporates by reference herein in its entirety pending U.S. patent application Ser. No. 10/282,402, filed Oct. 29, 2002, and titled “Devices, Methods, and Systems Involving Cast Collimators”. Certain exemplary embodiments of the present invention can combine certain techniques of stack lamination with certain molding processes to manufacture a final product. As a result of the stack lamination techniques, precision micro-scale cavities of predetermined shapes can be engineered into the stack lamination. Rather than have the stack lamination embody the final product, however, the stack lamination can be used as an intermediate in a casting or molding process. In certain exemplary embodiments of the present invention, the stack lamination (“laminated mold”) can be made up of layers comprising metallic, polymeric, and/or ceramic material. The mold can be a positive replication of a predetermined end product or a negative replication thereof. The mold can be filled with a first cast material and allowed to solidify. A first cast product can be demolded from the mold. The first cast material can comprise a flexible polymer such as silicone rubber. Certain exemplary embodiments of a method of the present invention can further include surrounding the first cast product with a second casting material and allowing the second cast material to solidify. Still further, a second cast product can be demolded from the first cast product. Some exemplary embodiments of the present invention can further include positioning an insert into the cavity prior to filling the mold with the first cast material, wherein the insert occupies only a portion of the space defined by the cavity. The second cast product can be nonplanar. The end product and/or the mold cavity can have an aspect ratio greater that 100:1. The end product can be attached to the substrate or it can be a free-standing structure. Certain exemplary embodiments of the present invention comprise a cast collimator descended from a stack lamination mold, said mold comprising a plurality of metallic foils. Certain embodiments of the present invention comprise a method comprising filling a mold having a stacked plurality of micro-machined metallic foil layers with a first casting material to form a first cast product; demolding the first cast product from the mold; filling the first cast product with a second casting material to form a cast collimator; and demolding the cast collimator from the first cast product. In certain exemplary embodiments, the cast collimator can be a computed-tomography collimator, a nuclear medicine collimator, and/or a mammography collimator, etc. In certain exemplary embodiments, the collimator can be descended from a lithographically-derived micro-machined metallic foil stack lamination mold. FIG. 1 is a flowchart of an exemplary embodiment of a method 1000 of the present invention. At activity 1010, a mold design is determined. At activity 1020, the layers of the mold (“laminations”) are fabricated. At activity 1030, the laminations are stacked and assembled into a mold (a derived mold could be produced at this point as shown in FIG. 1). At activity 1060, a first casting is cast. At activity 1070, the first casting is demolded. FIG. 2 is a flow diagram of exemplary items fabricated during a method 2000 of the present invention. Layers 2010 can be stacked to form a mold or stacked lamination 2020. A molding or casting material can be applied to mold 2020 to create a molding or casting 2030, that can be demolded from mold 2020. FIG. 3 is a perspective view of an exemplary molding 3000 of the present invention that demonstrates a parameter referred to herein as “aspect ratio” which is described below. Molded block 3010 has numerous through-holes 3020, each having a height H and a diameter or width W. For the purposes of this application, aspect ratio is defined as the ratio of height to width or H/W of a feature, and can apply to any “negative” structural feature, such as a space, channel, through-hole, cavity, etc., and can apply to a “positive” feature, such as a wall, projection, protrusion, etc., with the height of the feature measured along the Z-axis. Note that all features can be “bordered” by at least one “wall”. For a positive feature, the wall is part of the feature. For a negative feature, the wall at least partially defines the feature. FIG. 3 also demonstrates the X-, Y-, and Z-directions or axes. For the purposes of this application, the dimensions measured in the X- and Y-directions define a top surface of a structure (such as a layer, a stack lamination mold, or negative and/or positive replications thereof) when viewed from the top of the structure. The Z-direction is the third dimension perpendicular to the X-Y plane, and corresponds to the line of sight when viewing a point on a top surface of a structure from directly above that point. Certain embodiments of a method of the present invention can control aspect ratios for some or all features in a laminated mold, derived mold, and/or cast item (casting). The ability to attain relatively high aspect ratios can be affected by a feature's geometric shape, size, material, and/or proximity to another feature. This ability can be enhanced using certain embodiments of the present invention. For example, through-features of a mold, derived mold, and/or final part, having a width or diameter of approximately 5 microns, can have a dimension along the Z axis (height) of approximately 100 microns, or approximately 500 microns, or any value in the range there between (implying an aspect ratio of approximately 20:1, 100:1, or any value in the range therebetween, including, for example: 20:1 to 30:1, 20:1 to 40:1, 20:1 to 50:1, 20:1 to 60:1, 20:1 to 70:1, 20:1 to 80:1, 20:1 to 90:1, 20:1 to 100:1, 30:1 to 40:1, 30:1 to 50:1, 30:1 to 60:1, 30:1 to 70:1, 30:1 to 80:1, 30:1 to 90:1, 30:1 to 100:1, 40:1 to 50:1, 40:1 to 60:1, 40:1 to 70:1, 40:1 to 80:1, 40:1 to 90:1, 40:1 to 100:1, 50:1 to 60:1, 50:1 to 70:1, 50:1 to 80:1, 50:1 to 90:1, 50:1 to 100:1, 60:1 to 70:1, 60:1 to 80:1, 60:1 to 90:1, 60:1 to 100:1, 70:1 to 80:1, 70:1 to 90:1, 70:1 to 100:1, 80:1 to 90:1, 80:1 to 100:1, etc). As another example, a through slit having a width of approximately 20 microns can have a height of approximately 800 microns, or approximately 1600 microns, or any value in the range therebetween (implying an aspect ratio of approximately 40:1, 80:1, or any value in the range therebetween, including, for example: 40:1 to 50:1, 40:1 to 60:1, 40:1 to 70:1, 40:1 to 80:1, 50:1 to 60:1, 50:1 to 70:1, 50:1 to 80:1, 60:1 to 70:1, 60:1 to 80:1, 70:1 to 80:1, etc). As yet another example, the same approximately 20 micron slit can be separated by an approximately 15 micron wide wall in an array, where the wall can have a dimension along the Z axis (height) of approximately 800 microns, or approximately 1600 microns, or any value in the range therebetween (implying an aspect ratio of approximately 53:1, 114:1, or any value in the range therebetween, including, for example: 53:1 to 60:1, 53:1 to 70:1, 53:1 to 80:1, 53:1 to 90:1, 53:1 to 100:1, 53:1 to 110:1, 53:1 to 114:1, 60:1 to 70:1, 60:1 to 80:1, 60:1 to 90:1, 60:1 to 100:1, 60:1 to 110:1, 60:1 to 114:1, 70:1 to 80:1, 70:1 to 90:1, 70:1 to 100:1, 70:1 to 110:1, 70:1 to 114:1, 80:1 to 90:1, 80:1 to 100:1, 90:1 to 110:1, 90:1 to 114:1, 90:1 to 100:1, 90:1 to 110:1, 90:1 to 114:1, 100:1 to 110:1, 100:1 to 114:1, etc.). Still another example is an array of square-shaped openings having sides that are approximately 0.850 millimeters wide, each opening separated by approximately 0.150 millimeter walls, with a dimension along the Z axis of approximately 30 centimeters. In this example the approximately 0.850 square openings have an aspect ratio of approximately 353:1, and the approximately 0.150 walls have an aspect ratio of approximately 2000:1, with lesser aspect ratios possible. Thus, the aspect ratio of the openings can be approximately 10:1, or approximately 350:1, or any value in the range therebetween, including for example: 10:1 to 20:1, 10:1 to 30:1, 10:1 to 40:1, 10:1 to 50:1, 10:1 to 60:1, 10:1 to 70:1, 10:1 to 80:1, 10:1 to 90:1, 10:1 to 100:1, 10:1 to 150:1, 10:1 to 200:1, 10:1 to 250:1, 10:1 to 300:1, 10:1 to 350:1, 20:1 to 30:1, 20:1 to 40:1, 20:1 to 50:1, 20:1 to 60:1, 20:1 to 70:1, 20:1 to 80:1, 20:1 to 90:1, 20:1 to 100:1, 20:1 to 150:1, 20:1 to 200:1, 20:1 to 250:1, 20:1 to 300:1, 20:1 to 350:1, 30:1 to 40:1, 30:1 to 50:1, 30:1 to 60:1, 30:1 to 70:1, 30:1 to 80:1, 30:1 to 90:1, 30:1 to 100:1, 30:1 to 150:1, 30:1 to 200:1, 30:1 to 250:1, 30:1 to 300:1, 30:1 to 350:1, 40:1 to 50:1, 40:1 to 60:1, 40:1 to 70:1, 40:1 to 80:1, 40:1 to 90:1, 40:1 to 100:1, 40:1 to 150:1, 40:1 to 200:1, 40:1 to 250:1, 40:1 to 300:1, 40:1 to 350:1, 50:1 to 60:1, 50:1 to 70:1, 50:1 to 80:1, 50:1 to 90:1, 50:1 to 100:1, 50:1 to 150:1, 50:1 to 200:1, 50:1 to 250:1, 50:1 to 300:1, 50:1 to 350:1, 75:1 to 80:1, 75:1 to 90:1, 75:1 to 100:1, 75:1 to 150:1, 75:1 to 200:1, 75:1 to 250:1, 75:1 to 300:1, 75:1 to 350:1, 100:1 to 150:1, 100:1 to 200:1, 100:1 to 250:1, 100:1 to 300:1, 100:1 to 350:1, 150:1 to 200:1, 150:1 to 250:1, 150:1 to 300:1, 150:1 to 350:1, 200:1 to 250:1, 200:1 to 300:1, 200:1 to 350:1, 250:1 to 300:1, 250:1 to 350:1, 300:1 to 350:1, etc. Moreover, the aspect ratio of the walls can be approximately 10:1, or approximately 2000:1, or any value in the range therebetween, including for example: 10:1 to 20:1, 10:1 to 30:1, 10:1 to 40:1, 10:1 to 50:1, 10:1 to 100:1, 10:1 to 200:1, 10:1 to 500:1, 10:1 to 1000:1, 10:1 to 2000:1, 20:1 to 30:1, 20:1 to 40:1, 20:1 to 50:1, 20:1 to 100:1, 20:1 to 200:1, 20:1 to 500:1, 20:1 to 1000:1, 20:1 to 2000:1, 30:1 to 40:1, 30:1 to 50:1, 30:1 to 100:1, 30:1 to 200:1, 30:1 to 500:1, 30:1 to 1000:1, 30:1 to 2000:1, 40:1 to 50:1, 40:1 to 100:1, 40:1 to 200:1, 40:1 to 500:1, 40:1 to 1000:1, 40:1 to 2000:1, 50:1 to 100:1, 50:1 to 200:1, 50:1 to 500:1, 50:1 to 1000:1, 50:1 to 2000:1, 100:1 to 200:1, 100:1 to 500:1, 100:1 to 1000:1, 100:1 to 2000:1, 200:1 to 500:1, 200:1 to 1000:1, 200:1 to 2000:1, 500:1 to 1000:1, 500:1 to 2000:1, 1000:1 to 2000:1, etc. Another example of aspect ratio is the space between solid (positive) features of a mold, derived mold, and/or casting. For example, as viewed from the top, a casting can have two or more solid rectangles measuring approximately 50 microns wide by approximately 100 microns deep with an approximately 5 micron space therebetween (either width-wise or depth-wise). The rectangles can have a height of 100 microns, or 500 microns, or any value in the range therebetween (implying an aspect ratio of 20:1, or 100:1, or any value therebetween, including, for example: 20:1 to 30:1, 20:1 to 40:1, 20:1 to 50:1, 20:1 to 60:1, 20:1 to 70:1, 20:1 to 80:1, 20:1 to 90:1, 20:1 to 100:1, 30:1 to 40:1, 30:1 to 50:1, 30:1 to 60:1, 30:1 to 70:1, 30:1 to 80:1, 30:1 to 90:1, 30:1 to 100:1, 40:1 to 50:1, 40:1 to 60:1, 40:1 to 70:1, 40:1 to 80:1, 40:1 to 90:1, 40:1 to 100:1, 50:1 to 60:1, 50:1 to 70:1, 50:1 to 80:1, 50:1 to 90:1, 50:1 to 100:1, 60:1 to 70:1, 60:1 to 80:1, 60:1 to 90:1, 60:1 to 100:1, 70:1 to 80:1, 70:1 to 90:1, 70:1 to 100:1, 80:1 to 90:1, 80:1 to 100:1, etc). In another example the same rectangles can have a space there between of approximately 20 microns, and the rectangles can have dimensions along the Z axis of approximately 800 microns, or approximately 5000 microns, or any value therebetween (implying an aspect ratio of approximately 40:1, or 250:1, or any value therebetween, including, for example: 40:1 to 50:1, 40:1 to 75:1, 40:1 to 100:1, 40:1 to 150:1, 40:1 to 200:1, 40:1 to 250:1, 75:1 to 100:1, 75:1 to 150:1, 75:1 to 200:1, 75:1 to 250:1, 100:1 to 150:1, 100:1 to 200:1, 100:1 to 250:1, 150:1 to 200:1, 150:1 to 250:1, 200:1 to 250:1, etc). FIG. 4 is an assembly view of an exemplary assembly 4000 of the present invention that includes mold 4010 and cast part 4020 formed from mold 4010. Because certain exemplary embodiments of the present invention can utilize lithographically-derived micro-machining techniques (or in some cases, non-lithographically-derived micro-machining techniques, such as laser machining) combined with molding and/or casting, laminated molds can be conceived as negatives 4010 or positives 4020 of the desired end product. The terms “negative” or “positive” replications can be subjective terms assigned to different stages of reaching an end product. For certain embodiments, any intermediate or the end product can be considered a negative or positive replication depending on a subject's point of view. For the purpose of this application, a “positive” replication is an object (whether an intermediate or an end product) that geometrically resembles at least a portion of the spatial form of the end product. Conversely, a “negative” replication is a mold that geometrically defines at least a portion of the spatial form of the end product. The following parameters are described for the purpose of demonstrating some of the potential design parameters of certain embodiments of a method of the present invention. Layer Thickness One design parameter can be the thickness of the micro-machined layers of the stack lamination mold. According to certain exemplary embodiments of the present invention, to achieve high-aspect ratios, multiple micro-machined foils or layers can be stacked in succession and bonded together. In certain exemplary embodiments of the present invention, the layer thickness can have a dimensional role in creating the desired shape in the third dimension. FIG. 5A is a top view of an exemplary stack lamination mold 5000. FIGS. 5B-5E are exemplary alternative cross-sectional views of exemplary stack lamination mold 5000 taken at section lines 5-5 of FIG. 5A. As shown in FIG. 5B and FIG. 5D, respectively, stacks 5010 and 5020 utilize relatively thick layers. As shown in FIG. 5C and FIG. 5E, respectively, stacks 5030 and 5040 utilize relatively thinner layers in succession to smooth out resolution along the z-axis. Specific layers can have multiple functions that can be achieved through their thickness or other incorporated features described herein. Cross-sectional Shape of Layer One design parameter can be the cross sectional shape of a given layer in the mold. Through the use of etching and/or deposition techniques, many cross sectional shapes can be obtained. FIG. 6 is an unassembled cross-sectional view of an alternative exemplary stack lamination mold 5000 taken at section lines 5-5 of FIG. 5A. Each of exemplary layers 6010, 6020, 6030, and 6040 of FIG. 6 define an exemplary through-feature 6012, 6022, 6032, 6042, respectively, each having a different shape, orientation, and/or configuration. These through-features 6012, 6022, 6032, 6042 are bordered by one or more “sidewalls” 6014, 6024, 6034, and 6044, respectively, as they are commonly referred to in the field of lithographic micro-machining. Etching disciplines that can be utilized for a layer of the mold can be broadly categorized as isotropic (non-linear) or anisotropic (linear), depending on the shape of the remaining sidewalls. Isotropic often refers to those techniques that produce one or more radial or hour glassed shaped sidewalls, such as those shown in layer 6010. Anisotropic techniques produce one or more sidewalls that are more vertically straight, such as those shown in layer 6020. Additionally, the shape of a feature that can be etched through a foil of the mold can be controlled by the depth of etching on each surface and/or the configuration of the photo-mask. In the case of photo-chemical-machining, a term such as 90/10 etching is typically used to describe the practice of etching 90% through the foil thickness, from one side of the foil, and finishing the etching through the remaining 10% from the other side, such as shown on layer 6030. Other etch ratios can be obtained, such as 80/20, 70/30, and/or 65/35, etc., for various foils and/or various features on a given foil. Also, the practice of displacing the positional alignment of features from the top mask to the bottom mask can be used to alter the sidewall conditions for a layer of the mold, such as shown in layer 6040. By using these and/or other specific conditions as design parameters, layers can be placed to contribute to the net shape of the 3-dimensional structure, and/or provide specific function to that region of the device. For example, an hourglass sidewall could be used as a fluid channel and/or to provide structural features to the device. FIG. 7 is a cross-sectional view of an alternative exemplary stack lamination mold taken at section line 5-5 of FIG. 5A. FIG. 7 shows a laminated mold 5000 having layers 7010, 7020, 7030, 7040 that define cavity 7060. To achieve this, layers 7010, 7020 are etched anisotropically to have straight sidewalls, while layer 7030 is thicker than the other layers and is etched isotropically to form the complex shaped cross-section shown. Cross-sectional Surface Condition of Layer Another design parameter when creating advanced three-dimensional structures can be the cross-sectional surface condition of the layers used to create a laminated mold. As is the case with sidewall shape, surface condition can be used to provide additional function to a structure or a particular region of the structure. FIG. 8 is a perspective view of a generic laminated mold 8000. FIG. 9 is a cross-section of mold 8000 taken at lines 9-9 of FIG. 8. Any sidewall surface, top or bottom surface can be created with one or more specific finish conditions on all layers or on selected layers, such as for example, forming a relatively rough surface on at least a portion of a sidewall 9100 of certain through-features 9200 of layer 9300. As another example, chemical and/or ion etching can be used to produce very smooth, polished surfaces through the use of selected materials and/or processing techniques. Similarly, these etching methods can also be manipulated to produce very rough surfaces. Secondary techniques, such as electro-plating and/or passive chemical treatments can also be applied to micromachined surfaces (such as a layer of the mold) to alter the finish. Certain secondary techniques (for example, lapping or superfinishing) can also be applied to non-micromachined surfaces, such as the top or bottom surfaces of a layer. In any event, using standard profile measuring techniques, described as “roughness average” (Ra) or “arithmetic average” (AA), the following approximate ranges for surface finish (or surface conditions) are attainable using micromachining and/or one or more secondary techniques according to certain embodiments of the present invention (units in microns): 50 to any of: 25, 12.5, 6.3, 3.2, 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025, 25 to any of: 12.5, 6.3, 3.2, 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025, 12.5 to any of: 6.3, 3.2, 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025, 6.3 to any of: 3.2, 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025, 3.2 to any of: 1.6, 0.80, 0.40, 0.20, 0.10, 0.050, 0.025, 1.6 to any of: 0.80, 0.40, 0.20, 0.10, 0.050, 0.025, 0.80 to any of: 0.40, 0.20, 0.10, 0.050, 0.025, 0.40 to any of: 0.20, 0.10, 0.050, 0.025, 0.20 to any of: 0.10, 0.050, 0.025, 0.10 to any of: 0.050, 0.025, 0.050 to any of: 0.025, etc. Additional Layer Features Certain exemplary embodiments of the present invention can include layer features that can be created through the use of lithographic etching and/or deposition. These embodiments can include the size, shape, and/or positional orientation of features relative to the X- and/or Y-axes of a layer and/or their relationship to features on neighboring layers along the Z-axis of the assembled laminated mold. These parameters can define certain geometric aspects of the structure. For example, FIG. 10A is a top view of a layer 10010 having a pattern of repeating features (a redundant array of shapes), and FIG. 10B is a top view of a layer 10020 having a variety of differently shaped features (a non-redundant collection of shapes). Although not shown, a layer can have both redundant and non-redundant features. The terms “redundant” and/or “non-redundant” can refer to either positive or negative features. Thus, these parameters also can define the shapes and/or spatial forms of features, the number of features in a given area, secondary structures and/or spaces incorporated on or around a feature, and/or the spaces between features. The control of spacing between features can provide additional functionality and, for instance, allow integration of devices with micro-electronics. For example, conductive micro features could be arrayed (redundantly or non-redundantly) to align accurately with application specific integrated circuits (ASIC) to control features. Also, features could be arrayed for applications where non-linear spacing between features could enhance device functionality. For example, filtration elements could be arrayed in such a way as to match the flow and pressure profile of a fluid passing over or through a filtration media. The spacing of the filtration elements could be arrayed to compensate for the non-linear movement of the fluid. Cavity Definition Using Lithography A cavity formed in accordance with certain exemplary embodiments of the present invention can assume a shape and/or spatial form that includes one or more predetermined “protruding undercuts”. Imaginarily rotating the X-Y plane about its origin to any particular fixed orientation, a cavity is defined as having a “protruding undercut” when a first section of the cavity taken perpendicular to the Z-axis (i.e., parallel to the X-Y plane) has a predetermined dimension in the X- and/or Y-direction greater than the corresponding dimension in the X- and/or Y-direction of a second section of the cavity taken perpendicular to the Z-axis, the second section further along in the direction of eventual demolding of a cast part relative to the mold (assuming the demolding operation involves pulling the cast part free from the mold). That is, the X-dimension of the first section is intentionally greater than the X-dimension of the second section by a predetermined amount, or the Y-dimension of the first section is intentionally greater than the Y-dimension of the second section by a predetermined amount, or both. In still other words, for the purposes of this patent application, the term protruding undercut has a directional component to its definition. FIG. 11 is a top view of an exemplary stacked laminated mold 11000. FIG. 12 is a cross-sectional view of a mold 11000 taken at section lines 12-12 of FIG. 11, and showing the layers 12010-12060 of mold 11000 that cooperatively define a cavity having protruding undercuts 12022 and 12042. Direction A is the relative direction in which a part cast using mold 11000 will be demolded, and/or pulled away, from mold 11000. FIG. 12 also shows that certain layers 12020, 12040 of mold 12000 have been formed by controlled depth etching. FIG. 13 is a side view of a cast part 13000 formed using mold 11000. To make layers for certain embodiments of a laminated mold of the present invention, such as layers 2010 of FIG. 2, a photo-sensitive resist material coating (not shown) can be applied to one or more of the major surfaces (i.e., either of the relatively large planar “top” or “bottom” surfaces) of a micro-machining blank. After the blank has been provided with a photo-resist material coating on its surfaces, “mask tools” or “negatives” or “negative masks”, containing a negative image of the desired pattern of openings and registration features to be etched in the blank, can be applied in alignment with each other and in intimate contact with the surfaces of the blank (photo-resist materials are also available for positive patterns). The mask tools or negatives can be made from glass, which has a relatively low thermal expansion coefficient. Materials other than glass can be used provided that such materials transmit radiation such as ultraviolet light and have a reasonably low coefficient of thermal expansion, or are utilized in a carefully thermally-controlled environment. The mask tools can be configured to provide an opening of any desired shape and further configured to provide substantially any desired pattern of openings. The resulting sandwich of two negative masks aligned in registration and flanking both surfaces of the blank then can be exposed to radiation, typically in the form of ultraviolet light projected on both surfaces through the negative masks, to expose the photo-resist coatings to the radiation. Typically, the photo-resist that is exposed to the ultraviolet light is sensitized while the photo-resist that is not exposed is not sensitized because the light is blocked by each negative masks' features. The negative masks then can be removed and a developer solution can be applied to the surfaces of the blank to develop the exposed (sensitized) photo-resist material. Once the photo-resist is developed, the blanks can be micro-machined using one or more of the techniques described herein. For example, when using photo-chemical-machining, an etching solution can react with and remove the layer material not covered by the photo-resist to form the precision openings in the layer. Once etching or machining is complete, the remaining unsensitized photo-resist can be removed using a chemical stripping solution. Sub-Cavities on Layers Cavities can include sub-cavities, which can be engineered and incorporated into the molding and casting scheme using several methods. FIG. 14 is a top view of a laminated mold 14000. FIG. 15 is a cross-sectional view of mold 14000 taken at section lines 15-15 of FIG. 14, and showing the sub-cavities 15010 within layer 15030 of mold 14000. Note that because layer 15030 is sandwiched between layers 15020 and 15040, sub-cavities 15010 can be considered “sandwiched”, because sub-cavities are at least partially bounded by a ceiling layer (e.g., 15020) and a floor layer (e.g., 15040). Note that, although not shown, a sub-cavity can extend to one or more outer edges of its layer, thereby forming, for example, a sandwiched channel, vent, sprew, etc. FIG. 16 is a perspective view of cast part 16000 formed using mold 14000, and having protrusions 16010 that reflectively (invertedly) replicate sandwiched sub-cavities 15010. Because cast part can very accurately reflect the geometries of sub-cavities, such sub-cavities can be used to produce secondary features that can be incorporated with a desired structure. Examples of secondary features include fluid channels passing through or between features, protrusions such as fixation members (similar to Velcro-type hooks), reservoirs, and/or abrasive surfaces. Moreover, a secondary feature can have a wall which can have predetermined surface finish, as described herein. There are a number of methods for producing sub-cavities in a laminated mold. For example, in the field of photo-chemical-machining, the practice of partially etching features to a specified depth is commonly referred to as “controlled depth etching” or CDE. CDE features can be incorporated around the periphery of an etched feature, such as a through-diameter. Because the CDE feature is partially etched on, for example, the top surface of the layer, it can become a closed cavity when an additional layer is placed on top. Another method could be to fully etch the sub-cavity feature through the thickness of the layer. A cavity then can be created when the etched-through feature is sandwiched between layers without the features, such as is shown in FIG. 15. Combinations of micro-machining techniques can be used to create sub-cavities. For example, photo-chemical-machining (PCM) can be used to create the etched-through feature in the layer, while ion etching could be applied as a secondary process to produce the sub-cavities. By combined etching techniques, the sub-cavities can be etched with much finer detail than that of PCM. Micro-structures, Features, and Arrays on Non-Planar Surfaces Certain exemplary embodiments of the present invention can allow the production of complex three-dimensional micro-devices on contoured surfaces through the use of a flexible cavity mold insert. One activity of such a process can be the creation of a planar laminated mold (stack lamination), which can define the surface or 3-dimensional structures. A second mold (derived mold) can be produced from the lamination using a flexible molding material such as silicone RTV. The derived mold can be produced having a thin backing or membrane layer, which can act as a substrate for the 3-dimensional surface or features. The membrane then can be mechanically attached to the contoured surface of a mold insert, which can define the casting's final shape with the incorporated 3-dimensional features or surface. Because a mold can be derived from a series of previous molds, any derived mold can be considered to be descended from each mold in that series. Thus, a given derived mold can have a “parent” mold, and potentially a “grandparent” mold, etc. Likewise, from a stack lamination can descend a first derived, descendant, or child mold, from which a second derived, descendent, or grandchild mold can be descended, and so forth. Thus, as used herein to describe the relationship between molds and castings, the root verbs “derive” and “descend” are considered to be synonymous. As an example, FIG. 17 is a top view of a planar laminated mold 17010 having an array of openings 17020. FIG. 18 is a top view of a flexible casting or mold insert 18010 molded using laminated mold 17010. Flexible mold insert 18010 has an array of appendages 18020 corresponding to the array of openings 17020, and a backing layer 18030 of a controlled predetermined thickness. FIG. 19 is a top view of a mold fixture 19010 having an outer diameter 19020 and an inner diameter 19030. Placed around a cylinder or mandrel 19040 within mold fixture 19010 is flexible mold insert 18010, defining a pour region 19050. Upon filling pour region 19050, a casting is formed that defines a cylindrical tube having a pattern of cavities accessible from its inner diameter and corresponding to and formed by the array of appendages 18020 of flexible mold insert 18010. As another example, FIG. 20 is a top view of a planar laminated mold 20010 having an array of openings 20020. FIG. 21 is a top view of a flexible casting or mold insert 21010 molded using laminated mold 20010. Flexible mold insert 21010 has an array of appendages 21020 corresponding to the array of openings 20020, and a backing layer 21030 of a controlled predetermined thickness. FIG. 22 is a top view of a mold fixture 22010 having an outer diameter 22020 and an inner diameter 22030. Placed around the inside diameter 22030 within mold fixture 22010 is flexible mold insert 21010, defining a pour region 22050. Upon filling pour region 22050, a casting is formed that defines a cylindrical tube having a pattern of cavities accessible from its outer diameter and corresponding to and formed by the array of appendages 21020 of flexible mold insert 21010. Through these and related approaches, the 3-dimensional structure or surface can be built-up at the planar stage, and can be compensated for any distortions caused by forming the membrane to the contoured surface. The fabrication of the laminated mold can use specific or combined micro-machining techniques for producing the layers that define the aspect-ratio and 3-dimensional geometry. Micro-surfaces and/or structures can be transferred to many contours and/or shapes. For example, micro-patterns can be transferred to the inside and/or outside diameter of cylinders or tubes. Specific examples demonstrating the capabilities of this method are provided later in this document. Cavity Inserts The term mold insert is used herein to describe a micro-machined pattern that is used for molding and/or fabrication of a cast micro-device, part, and/or item. The laminated or derived mold described in this document also can be considered a mold insert. Cavity inserts are described here as a subset of a mold insert. Cavity inserts are objects and/or assemblies that can be placed within a cavity section of a mold but that do not take up the entire cavity space, and that provide further features to a 3-dimensional mold. As an example, FIG. 23 is a perspective view of a laminated mold 23010 having an array of cylindrical cavities 23020, each extending from top to bottom of mold 23010. FIG. 24 is a close-up perspective view of a single cylindrical cavity 23020 of mold 23010. Suspended and extending within cavity 23020 are a number of cavity inserts 23030. FIG. 25 is a perspective view of a cast part 25010 having numerous cavities 25020 formed by cavity inserts 23030. A cavity insert can also be produced using certain embodiments of the present invention. This is further explained later in the section on non-planar molds. An insert can be a portion of a mold in the sense that the insert will be removed from the cast product to leave a space having a predetermined shape within the product. An insert alternatively can become part of a final molded product. For instance, if it is desirable to have a composite end product, then a process can be engineered to leave an insert in place in the final molded product. As an example of a cavity insert, a 3-dimensional mold insert can be produced using one or more embodiments of the present invention, the insert having an array of cavities that are through-diameters. The cast part derived from this mold can reverse the cavities of the mold as solid diameters having the shape, size and height defined by the mold. To further enhance functionality, cavity inserts can be added to the mold before the final casting is produced. In this case, the cavity insert can be a wire formed in the shape of a spring. The spring can have the physical dimensions required to fit within a cavity opening of the mold, and can be held in position with a secondary fixture scheme. The spring-shaped cavity insert can be removed from the cast part after the final casting process is completed. Thus, the cavity section of the mold can define the solid shape of the casting while the cavity insert can form a channel through the solid body in the shape and width of the insert (the spring). The cavity can serve as, for example, a reservoir and/or a fluid flow restrictor. The examples given above demonstrate the basic principle of a cavity insert. Additional design and fabrication advances can be realized by using this method to create cavity inserts. For example, photo-chemical-machining can be used to create a mold that has larger cavity openings, while reactive-ion-etching can be used to create finer features on a cavity insert. Fabricating the Laminated Mold Certain exemplary embodiments of the present invention can involve the fabrication of a laminated mold which is used directly and/or as an intermediate mold in one or more subsequent casting and/or molding processes. FIG. 26 is a block diagram illustrating various devices formed during an exemplary method 26000 for fabricating a laminated mold having micro-machined layers that can be patterned and/or etched, and stacked to create a 3-dimensional mold. The laminated mold can be produced as a negative or positive replication of the desired finished casting. For the purpose of creating a laminated mold, any of three elements can be implemented: 1) creating a lithographic mask 26010 defining the features of each unique layer, 2) using lithographic micro-machining techniques and/or micro-machining techniques to produce patterned layers 26020, and/or 3) aligning, stacking, and/or laminating the patterned layers into a stack 26030 in order to achieve the desired 3-dimensional cavity shape, aspect ratios, and/or mold parameters desired for a laminated mold 26040.Lithographic Techniques Using lithography as a basis for layer fabrication, parts and/or features can be designed as diameters, squares, rectangles, hexagons, and/or any other shape and/or combination of shapes. The combinations of any number of shapes can result in non-redundant design arrays (i.e. patterns in which not all shapes, sizes, and/or spacings are identical, as shown in FIG. 10). Lithographic features can represent solid or through aspects of the final part. Such feature designs can be useful for fabricating micro-structures, surfaces, and/or any other structure that can employ a redundant and/or non-redundant design for certain micro-structural aspects. Large area, dense arrays can be produced through the lithographic process, thereby enabling creation of devices with sub-features or the production of multiple devices in a batch format. Lithography can also allow the creation of very accurate feature tolerances since those features can be derived from a potentially high-resolution photographic mask. The tolerance accuracy can include line-width resolution and/or positional accuracy of the plotted features over the desired area. In certain embodiments, such tolerance accuracy can enable micro-scale fabrication and/or accurate integration of created micro-mechanical devices with microelectronics. Photographic masks can assist with achieving high accuracy when chemical or ion-etched, or deposition-processed layers are being used to form a laminated mold through stack lamination. Because dimensional changes can occur during the final casting process in a mold, compensation factors can be engineered at the photo-mask stage, which can be transferred into the mold design and fabrication. These compensation factors can help achieve needed accuracy and predictability throughout the molding and casting process. Photographic masks can have a wide range of potential feature sizes and positional accuracies. For example, when using an IGI Maskwrite 800 photoplotter, an active plotting area of 22.8×31.5 inches, minimum feature size of 5 microns, and positional accuracy of +−1 micron within a 15+15 inch area is possible. Using higher resolution lithographic systems for mask generation, such as those employed for electron beam lithography, feature sizes as small as 0.25 microns are achievable, with positional tolerances similar to the Maskwrite plotter, within an area of 6×6 inches. Layer Machining and Material Options Another aspect to fabricating the laminated mold can be the particular technique or techniques used to machine or mill-out the features or patterns from the layer material. In certain embodiments, combining lithographic imaging and micro-machining techniques can improve the design and fabrication of high-aspect-ratio, 3-dimensional structures. Some of the micro machining techniques that can be used to fabricate layers for a laminated mold include photo-etching, laser machining, reactive ion etching, electroplating, vapor deposition, bulk micro-machining, surface micro-machining, and/or conventional machining. In certain exemplary embodiments, a laminated mold need only embody the mechanical features (e.g., size, shape, thickness, etc.) of the final casting. That is, it does not have to embody the specific functional properties (i.e. density, conductivity) that are desired to fulfill the application of the final casting. This means that any suitable techniques or materials can be used to produce the layers of the mold. Thus, there can be a wide variety of material and fabrication options, which can allow for a wide variety of engineered features of a layer, laminated mold, and/or derived mold. For instance, although photo-chemical machining can be limited to metallic foils, by using laser machining or reactive ion etching, the choice of materials can become greatly expanded. With regard to laser machining, Resonetics, Inc. of Nashua, N.H. commercially provides laser machining services and systems. For laser machining, a very wide range of materials can be processed using UV and infra-red laser sources. These materials include ceramics, metals, plastics, polymers, and/or inorganics. Laser micro-machining processes also can extend the limits of chemical machining with regards to feature size and/or accuracy. With little or no restriction on feature geometry, sizes on the order of 2 microns can be achievable using laser machining. When a wide variety of materials are available for making the laminated mold, process-compatibility issues can be resolved when choosing the material from which to create the mold. An example of this would be to match the thermal properties of casting materials with those of the laminated mold, in instances where elevated temperatures are needed in the casting or molding process. Also the de-molding properties of the mold and/or casting material can be relevant to the survival of the mold. This, for example, might lead one to laser-machine the layers from a material such as Teflon, instead of a metal. The laser machining process could be compatible with the Teflon and the Teflon could have greater de-molding capabilities than a metallic stack lamination. In certain exemplary embodiments of the present invention, only a single laminated stack is needed to produce molds or castings. Also, in certain exemplary embodiments of the present invention, molds and/or castings can be produced without the need for a clean-room processing environment. For certain exemplary embodiments of the present invention, the ability to create a single laminated mold and then cast the final parts can allow for using much thinner foils or advanced etching methods for producing the individual layers. Since feature size can be limited by the thickness of each foil, using thinner foils can allow finer features to be etched. Certain exemplary embodiments of the present invention can combine various micro-machining techniques to create layers that have very specific functional features that can be placed in predetermined locations along the Z-axis of the mold assembly. For example, photo-chemical-machining can be used to provide larger features and high resolution ion-etching for finer features. Various methods, as described above, can be used to produce layers for a laminated mold. The following examples are given to demonstrate dimensional feature resolution, positional accuracy, and/or feature accuracy of the layers. Ion etching: when using a Commonwealth Scientific Millitron 8000 etching system, for example, a uniform etch area of 18 inches by 18 inches is achievable. Feature widths from 0.5 microns and above are attainable, depending on the lithographic masks and imaging techniques used. A feature, for example a 5 micron wide slot, etched to a depth of 10 microns can be etched to a tolerance of +−1.25 microns in width, and +−0.1 microns in depth. The positional tolerance of features would be the same as those produced on the lithographic masks. Photo-chemical-machining: when using an Attotech XL 547 etching system, for example, a uniform etch area of 20 inches by 25 inches is achievable. Etched through-feature widths from 20 microns and above are attainable, with solid features widths of 15 microns and above also being attainable. A feature, for example a micron diameter etched through 25 microns of copper, can be etched to a tolerance of +−2.5 microns or 10% of the foil thickness. The positional tolerance of such features would be the same as those produced on the lithographic masks. Laser micromachining: when using a PIVOTAL laser micromachining system, for example, a uniform machining area of 3 inches by 3 inches is achievable. Machined through-feature sizes from 5 microns and above are attainable. A feature, for example a 5 micron wide slit machined through 25 microns of stainless steel, can be machined to a tolerance of +−1 micron. Positional tolerance of +−3 microns is achievable over the 3 inch by 3 inch area. Electro-forming: depending on the size limitations of the photographic masks used for this process, electro-forming over areas as large as 60 inches by 60 inches is attainable. Electro-formed layers having thickness of 2 microns to 100 microns is achievable. A feature, for example a 5 micron wide slit, 15 microns deep, can be formed to a tolerance of +−1 micron. Positional tolerance of features would be the same as those produced on the lithographic masks. Layer Assembly and Lamination As described above, in certain exemplary embodiments of the present invention, layers can be designed and produced so that feature shape and placement from layer to layer define the desired geometry along the X-, Y-, and/or Z-axes of a mold. The total number (and thickness) of layers in the assembly can define the overall height and aspect ratio of the feature. A feature can be either the solid shape or the space between given structural components. What follows are several exemplary methods of bonding the layers together to form the laminated mold. One exemplary method used to bond layers together is a metal-to-metal brazing technique. This technique can provide a durable mold that can survive high volume production casting and/or can provide efficient release properties from the castings. Prior to assembly, the layers can have 0.00003 inches of a eutectic braze alloy deposited on the top and bottom surfaces of the layers, using standard electro-plating techniques. An example of a braze material is CuSil™, which is comprised of copper and silver, with the percentage of each being variable for specific applications. CuSil™ can be designed specifically to lower the temperatures needed to flow the alloy during the brazing process. One of the potential concerns during the laminating process is to maintain accurate registration of the assembly layers, and/or control the movement of the layers and the bonding fixture when brought to the elevated temperatures needed to flow the braze material. Several methods can be used to achieve this registration and/or control. The first can involve the practice of having two or more alignment features on the layers. FIG. 27 is a perspective view of a plurality of exemplary layers 27000. As illustrated in FIG. 27, one such alignment feature can be a diameter 27010, and the other alignment feature can be an elongated slot 27020. The slot and the diameter can be positioned on each layer one hundred eighty degrees opposed, for example, and can be parallel in orientation with the grain and/or perpendicular to the plane of the layer material. FIG. 28 is a perspective view of an exemplary laminating fixture 28000, which can be fabricated from graphite, for example, and can have two graphite diameter pins 28010 that can be fixed to the lamination fixture at the same distance apart as the diameter 27010 and slot 27020 on the etched layers 27000. The layers can be placed over the pins 28010 so that each layer is orientated accurately to the layer below, using the slot and diameter to align each layer. Alternatively, two or more diameters can be provided on the layers 27000, each of which corresponds to a pin of laminating fixture 28000. During the brazing process, the layered assembly can be heated in a hydrogen atmosphere to a temperature of 825 degrees Celsius, which can cause the CuSil™ braze to flow. As the temperatures elevate, the layers and the fixture material can expand. The slotted alignment feature 27020 can allow the fixture 28000 material to expand or move at a dissimilar rate than the layers, by the presence of the elongated slot on the layer 27000. The slot 27020 can be greater in length than the diameter of pin 28010 in the fixture. The additional length of the slot can be determined by the different coefficient for expansion between the graphite and the assembly layers. Other methods for maintaining the layer alignment during a heated bonding process can include fabricating the bonding fixture from the same material as the assembly layers, which can thus limit the dissimilar movement of the layers and fixture. The alignment and bonding fixture can also be made so that the alignment pins fit nearly perfectly to alignment features on the layers, but the pins in the fixture are allowed to float while being held perpendicular to the face of the alignment fixture. In order to minimize positional errors when bonding layers (stacking errors), tolerances on certain features can be controlled. Referring to FIG. 27, the positional accuracy of features 27010 and 27020 can be controlled by the photographic masks used to produce the layers (exemplary tolerances for masks are provided in the section titled “Lithographic Techniques”, above). The geometric size and tolerance of features 27010 and 27020 can be governed by the layer thickness and/or micromachining method used to produce them (exemplary tolerances for various micromachining techniques are provided in the section titled “Layer Machining and Material Options”, above). When producing a laminated mold, numerous factors can be an influence on the overall tolerances of the features of the mold and/or the casting. For example, when using a stacking fixture, any of the laminating fixture's surface flatness, the laminating fixture's perpendicularity, and the laminating fixture's parallelism can be an influence. Also, the dimensional tolerance of the alignment feature(s) of a layer and/or the positional tolerance of that feature(s) can be an influence. For example, if an alignment pin, protrusion, or other “male” feature will engage a corresponding hole, indentation, or “female” feature to assist in aligning two or more layers, the dimensional tolerance and/or vocational tolerance of male and/or female feature can be an influence on the overall tolerances. For example, referring to FIG. 28, bonding fixture 28000 can include alignment pins 28010 fitted into the top surface of fixture 28000. In a particular experiment, through the use of a surface grinding process, followed by a planetary lapping and polishing process, the sides and top surface of bonding fixture 28000 were parallel and perpendicular to a tolerance of +−2 microns, with the top surface finish being optically flat to +− one half the wavelength of visible light (400 to 700 nanometers), or about 200 to 350 nanometers. The positional accuracy of the alignment pins and the machined diameters through fixture 28000 was +−5 microns, and the pins were perpendicular to the surface of the fixture to +−2 microns, measured at a pin height of 2 to 5 millimeters. The surface of the described fixture measured 6×6 inches, and was produced using an SIP 5000 Swiss jig boring milling center. Hardened steel alignment pins, having a diameter of 0.092 inches, were precisely ground to a tolerance of +−1.25 microns using a standard grinding operation. The process of laminating the layers can include placing the processed layers over the alignment pins until the desired number of layers have been assembled. The assembled layers and fixture then can be placed in a brazing furnace with uniform weight applied to the top of the fixture. The furnace temperature can be raised to a temperature of 825 degrees Celsius, in a hydrogen atmosphere (a vacuum atmosphere has also been shown to work) for 45 minutes. This temperature can be sufficient to allow the braze material to uniformly flow and connect the layers together at all contact points. The fixture then can be cooled in the hydrogen atmosphere for 2 hours and removed for disassembly. The graphite pins can be removed, freeing the bonded structure from the lamination fixture. The brazed lamination now can be ready for the final process step, which can be to coat the entire assembly with a hard nickel surface. The nickel coating can be applied to the laminated assembly using electro-plating techniques, which can deposits 0.0001 inches of nickel. The nickel-plated surface can act as an interface material that can enhance the release and durability properties of the assembled mold. Another exemplary method that can be used to bond layers can make use of a thermo-cured epoxy rather than metal-to-metal brazing. Prior to assembly, the layers can be coated with an epoxy, MAGNA-TAC® model E645, diluted 22:1 with acetone. The thinned epoxy can be applied to the top and bottom surfaces of the layers using a standard atomizing spray gun. The layers can be spray coated in such a way that the coverage of the epoxy will bond the layers without filling the micro-machined features. A dot coverage of 50% has shown to work. The parameters for dilution and coverage can be provided by the epoxy manufacture, such as the Beacon Chemical Company. The layers then can be assembled to a bonding fixture using, for example, the same technique described in the braze process. The assembled fixture then can be placed in a heated platen press, such as a Carver model #4122. The assembled layers and fixture can be compressed to 40 pounds per square inch and held at a temperature of 350 degrees F. for 3 hours, and allowed to cool to room temperature under constant pressure. The assembly then can be removed from the fixture using, for example, the same technique used for the brazed assembly. In certain embodiments, the technique described in the second example can be considerably less expensive and time consuming than that used for the first. Using the epoxy process, savings can be realized due to the cost of the plating and the additional requirement imposed by the hydrogen braze process compared to epoxy stack laminating. The master derived from the first example can provide more efficient de-molding properties and also can survive a greater number of castings than the epoxy bonded mold. The epoxy-bonded mold can demonstrate a cost effective alternative to brazing and can be used for prototyping or when smaller production quantities are required. Casting and Molding Process Exemplary embodiments of the present invention can involve the creation of a high-resolution casting mold, having high-aspect-ratio, as well as 3-dimensional features and shapes. A precision stack lamination, comprised of micro-machined layers, can be used as a laminated mold. The laminated mold can be used to produce advanced micro-devices and structures (a.k.a., “micro-electro-mechanical structures” and “MEMS”) and/or can be used to create second (or greater) generation derived molds. The following paragraphs describe the casting process in terms of the materials, fixtures, and/or methods that can be used to produce second-generation molds and final castings. Mold Duplication and Replication For certain exemplary embodiments of the present invention, the process options for producing molds and cast parts can be numerable. For example, molds can be made as negative 4010 or positive 4020 replications of the desired cast part as shown in FIG. 4. If the mold is made as a positive, a second-generation mold can be created. If the mold is made as a negative, the final part can be cast directly from the mold. For certain exemplary embodiments of the present invention, the process used to create the layers for the laminated mold can be a determining factor. For example, some production situations can require a second- (or even third) generation derived version of the laminated mold. In certain situations, process parameters can be greatly enhanced by combining molding and casting materials having certain predetermined values for physical properties such as durometer, elasticity, etc. For example, if the cast part is extremely rigid, with poor release properties, a second-generation consumable mold can be used to create the final casting. Further specific examples of this practice, and how they relate to 3-dimensional micro-fabrication are described later in this document. Feature size and positional accuracy for molds and produced parts can be compensated for at the layer production stage of the process. For example, known material properties such as thermal expansion or shrinkage can be accurately accounted for due to, for example, the accuracy levels of the photographic masks and/or laser machining used to produce mold layers. Feature resolution, using various mold making and casting materials, can be accurately replicated for features having a size of 1 micron and greater. Surface finishes have also been reproduced and accurately replicated. For example, layers have been used to form a laminated mold which was used to produce a derived silicone RTV mold. The surface finish of a 0.0015 inch thick stainless steel layer (specified finish as 8-10 micro inches RA max) and a 0.002 inch thick copper layer (specified finish as 8-20 micro inches RA max ) were easily identified on the molded surfaces of the derived RTV mold. The surfaces were observed at 400× magnification using a Nikon MM11 measuring scope. The same surface finishes were also easily identified when cast parts were produced from the derived mold using a casting alloy CERROBASE™. Very smooth surface finishes, such as those found on glass, have also been reproduced in molds and castings. Materials for Molds and Castings For certain exemplary embodiments of the present invention, there can be hundreds, if not thousands of material options for mold making and casting. Described below are some potential considerations regarding the selection of mold and casting materials that can meet the requirements of, for instance, 3-dimensional MEMS. To insure the accuracy and repeatability of certain cast micro-devices, the casting material can have the capability to resolve the fine 3-dimensional feature geometries of the laminated mold. Typical dimensions of MEMS can range from microns to millimeters. Other structures having micro features can have much larger dimensions. For certain embodiments, the mold's cavity geometry can influence the release properties between the mold and the casting, thereby potentially implicating the flexibility (and/or measured durometer) of the materials used. Other material compatibility issues also can be considered when using a casting process. Certain exemplary embodiments of a process of the present invention have been developed in order to enable the production of 3-dimensional micro-structures from a wide range of materials, tailored to specific applications. The ability to use various materials for molds and castings can greatly expand the product possibilities using this technique. One material that has been successfully used for creating castings from a laminated mold is an elastomeric product, referred to generally as RTV silicone rubber, although other materials could also be successful depending on process or product requirements. A wide range of silicone-based materials designed for various casting applications are commercially available through the Dow Corning Corporation of Midland, Michigan. For example, the Silastic® brand products have proven successful, possibly because of their resolution capability, release characteristics, flexibility, durability, and/or the fact that they work in a wide range of process temperatures. Although other types of silicone rubber products could be used, each of the Dow Corning Silastic® brand products that have been used consists of two components; a liquid silicone rubber and a catalyst or curing agent. Of the Dow Corning Silastic® brand products, there are two basic curing types: condensation, and addition cure. The two types can allow for a range of variations in material viscosities and cure times. The three primary products used in the earliest tests are Silastic® J RTV Silicone Rubber, Silastic® M RTV Silicone Rubber, and Silastic® J RTV Silicone Rubber. Product specifications are provided in several of the examples at the end of this document. The Dow Coming Silastic® products used thus far have similar specifications regarding shrinkage, which increases from nil up to 0.3 percent if the silicone casting is vulcanized. Vulcanization can be accomplished by heating the silicone to a specific elevated temperature (above the casting temperature) for a period of 2 hours. Vulcanizing can be particularly useful when the casting is to be used as a regenerated mold, and will be subjected to multiple castings. In addition to RTV silicone rubber, urethanes and other materials also have properties that can be desirable for laminated molds, derived molds, and/or castings, depending on the specific requirement. For example, when producing certain 3-dimensional micro-structures with extreme aspect ratios, very fine features, or extreme under-cuts, de-molding can be difficult. In certain situations, the rigidity of the mold also can be relevant, especially in certain cases where mold features have high-aspect ratios. For example, the practice of sacrificing or dissolving laminated second or third generation molds can be used when castings require very rigid molds, and/or where the de-molding of castings becomes impossible. There are several families of materials that can be used for producing laminated molds, derived molds, and/or final cast devices including, for example: Acrylics: such as, for example, PMMA acrylic powder, resins, and/or composites, as well as methacrylates such as butyl, lauryl, stearyl, isobutyl, hydroxethyl, hydroxpropyl, glycidyl and/or ethyl, etc. Plastic polymerics: such as, for example, ABS, acetal, acrylic, alkyd, flourothermoplastic, liquid crystal polymer, styrene acrylonitrile, polybutylene terephthalate, thermoplastic elastomer, polyketone, polypropylene, polyethylene, polystyrene, PVC, polyester, polyurethane, thermoplastic rubber, and/or polyamide, etc. Thermo-set plastics: such as, for example, phenolic, vinyl ester, urea, and/or amelamine, etc. Rubber: such as, for example, elastomer, natural rubber, nitrile rubber, silicone rubber, acrylic rubber, neoprene, butyl rubber, flurosilicone, TFE, SBR, and/or styrene butadiene, etc. Ceramics: such as, for example, silicon carbide, alumina, silicon carbide, zirconium oxide, and/or fused silica, calcium sulfate, luminescent optical ceramics, bio-ceramics, and/or plaster, etc. Alloys: such as, for example, aluminum, copper, bronze, brass, cadmium, chromium, gold, iron, lead, palladium, silver, sterling, stainless, zinc platinum, titanium, magnesium, anatomy, bismuth, nickel, and/or tin, etc. Wax: such as, for example, injection wax, and/or plastic injection wax, etc. There can be many material options within these groups that can be utilized when employing certain embodiments of the present invention. For example, in certain embodiments, metals and metal alloys can be primarily used as structural materials of final devices, but also can add to function. Exemplary functional properties of metals and/or alloys can include conductivity, magnetism, and/or shape memory. Polymers also can be used as structural and/or functional materials for micro-devices. Exemplary functional properties can include elasticity, optical, bio-compatibility, and/or chemical resistivity, to name a few. Materials having dual (or more) functionality, often referred to as engineered “smart” materials, could be incorporated into a final molded product or a mold. Additional functionality could utilize electrostatic, mechanical, thermal, fluidic, acoustic, magnetic, dynamic, and/or piezo-electric properties. Ceramics materials also can be used for applications where specialty requirements may be needed, such as certain high-temperature environments. Depending on the material that is chosen, there can be many alterative methods to solidify the casting material. The term “solidify” includes, but is not limited to, methods such as curing, vulcanizing, heat-treating, and/or chemically treating, etc. Mold Fixtures, Planar and Contoured For certain exemplary embodiments of the present invention, there can be a wide range of engineering options available when designing a casting mold. The casting process and geometry of the final product can determine certain details and features of the mold. Options can be available for filling and/or venting a mold, and/or for releasing the casting from the mold. Two basic approaches have been used for demonstrating the certain exemplary methods for mold design and fabrication. These approaches can be categorized as using a single-piece open-face mold or a two-part closed mold. In certain exemplary embodiments of the present invention, each of the mold types can include inserting, aligning, and assembling the laminated mold (or duplicate copy) in a fixture. The fixture can serve several purposes, including bounding and/or defining the area in which to pour the casting material, capturing the casting material during the curing process, allowing the escape of air and/or off-gases while the casting material is degassed, and/or enabling mechanical integration with the casting apparatus. The fixture can be configured in such a way that all sides surrounding the mold insert are equal and common, in order to, for example, equalize and limit the effects of thermal or mechanical stresses put on the mold during the casting process. The mold fixture also can accommodate the de-molding of the casting. Certain exemplary embodiments of this method can provide the ability to mold 3-dimensional structures and surfaces on contoured surfaces. The basic technique is described earlier in this document in the design parameter section. One element of the technique can be a flexible mold insert that can be fixed to a contoured surface as shown in FIGS. 19 and 22. The mold insert can be made with a membrane or backing thickness that can allow for integration with various fixture schemes that can define the contoured shape. For non-planar molds, the contour of the mold fixture can be produced by standard machining methods such as milling, grinding, and/or CNC machining, etc. The flexible mold insert can be attached to the surface of the mold using any of several methods. One such method is to epoxy bond the flexible insert to the fixture using an epoxy that can be applied with a uniform thickness, which can be thin enough to accommodate the mold design. Other parameters that can be considered when choosing the material to fix a membrane to a fixture include durability, material compatibility, and/or temperature compatibility, etc. A detailed description of a non-planar mold is given as an example further on. Casting and Molding Processes Various techniques can be used for injecting or filling cavity molds with casting materials, including injection molding, centrifugal casting, and/or vibration filling. An objective in any of these techniques can be to fill the cavity with the casting material in such a way that all of the air is forced out of the mold before the cast material has solidified. The method used for filling the cavity mold can depend on the geometry of the casting, the casting material, and/or the release properties of the mold and/or the cast part. As has been described earlier, an open face mold, using flexible RTV rubber has been found to work effectively. In certain embodiments, an open face mold can eliminate the need for having carefully designed entrance sprue and venting ports. The open face mold can be configured to create an intermediate structure that can have a controlled backing thickness which can serve any of several purposes: 1) it can be an open cavity section in the casting mold which can serve as an entrance point in which to fill the mold; 2) it can serve as a degassing port for the air evacuation during the vacuum casting process; 3) it can create a backing to which the cast part or parts can be attached and/or which can be grasped to assist in de-molding the casting from the flexible mold. In casting processes in which the casting material is heated, the mold temperature and the cooling of the casting can be carefully controlled. For example, when casting a lead casting alloy such as CERROBASE, the alloy can be held at a temperature of 285 degrees F., while the mold material can be preheated 25-30 degrees higher (310-315 degrees F.). The molten alloy can be poured and held at or above the melting point until it is placed in the vacuum environment. The mold then can be placed in a vacuum bell jar, and held in an atmosphere of 28 inches of mercury for 3-4 minutes. This can remove any air pockets from the molten metal before the alloy begins to solidify. As soon as the air has been evacuated, the mold can be immediately quenched or submersed in cold water to rapidly cool the molten metal. This can help minimize shrinkage of the cast metal. In certain exemplary embodiments of the present invention, no vent holes or slots are provided in the mold, and instead, air can be evacuated from the mold prior to injection. In certain exemplary embodiments of the present invention, temperature variation and its effect on the micro-structure can be addressed via enhanced heating and cooling controls in or around the mold. In certain exemplary embodiments of the present invention, heat can be eliminated from the curing process by replacing the molding materials with photo-curing materials. Some of the methods that can be used for micro-molding and casting include micro-injection molding, powder injection molding, metal injection molding, photo molding, hot embossing, micro-transfer molding, jet molding, pressure casting, vacuum casting, and/or spin casting, etc. Any of these methods can make use of a laminated or derived mold produced using this method. De-Molding and Finish Machining A controlled backing thickness can be incorporated into the casting to create an intermediate structure. One purpose of the intermediate can be to create a rigid substrate or backing, that allows the casting to be grasped for removal from the mold without distorting the casting. The thickness of the backing can be inversely related to the geometry of the pattern or features being cast. For example, fine grid patterns can required a thicker backing while coarse patterns can have a thinner backing. The backing can be designed to have a shape and thickness that can be used to efficiently grasp and/or pull the cast part from the mold. Following de-molding, the intermediate can be machined to remove the backing from the casting. Because the thickness of the backing can be closely controlled, the backing can be removed from the cast structure by using various precision machining processes. These processes can include wire and electrode EDM (electrode discharge machining), surface grinding, lapping, and/or fly cutting etc. In instances where extremely fine, fragile patterns have been cast, a dissolvable filler or potting material can be poured and cured in the cast structure prior to the removal of the backing from the grid. The filler can be used to stabilize the casting features and eliminate possible damage caused by the machining process. The filler can be removed after machining-off the backing. A machinable wax has been found to be effective for filling, machining, and dissolving from the casting. In some part designs, de-molding the casting from the mold might not be possible, due to extreme draft angles or extremely fine features. In these cases, the mold can remain intact with the cast part or can be sacrificed by dissolving the mold from casting. A wide range of three-dimensional micro-devices can be fabricated through the use of one or more embodiments of various fabrication processes of the present invention, as demonstrated in some of the following examples. This example demonstrates fabrication of an array of complex 3-dimensional cavity features having high aspect ratio. This example makes use of a second-generation derived mold for producing the final part, which is an array of sub-millimeter feedhorns. A feedhorn is a type of antenna that can be used to transmit or receive electromagnetic signals in the microwave and millimeter-wave portion of the spectrum. At higher frequencies (shorter wavelengths) the dimensions can become very small (millimeters and sub-millimeter) and fabrication can become difficult. Using certain exemplary embodiments of the present invention, a single horn, an array of hundreds or thousands of identical horns, and/or an array of hundreds or thousands of different horns can be fabricated. FIG. 29 is a top view of stack lamination mold 29000 that defines an array of cavities 29010 for fabricating feedhorns. FIG. 30 is a cross-section of a cavity 29010 taken along section lines 30-30 of FIG. 29. As shown, cavity 29010 is corrugated, having alternating cavity slots 30010 separated by mold ridges 30020 of decreasing dimensions, that can be held to close tolerances. In an exemplary embodiment, an array of feedhorns contains one thousand twenty identical corrugated feedhorns, each designed to operate at 500 GHz, and the overall dimensions of the feed horn array are 98 millimeters wide by 91 millimeters high by 7.6 millimeters deep. The fabrication of this exemplary array can begin with the creation of a laminated mold, comprised of micro-machined layers, and assembled into a precision stack lamination. Step 1: Creating the laminated mold: The laminated mold in this example was made of 100 layers of 0.003″ thick beryllium copper (BeCu) sheets that were chemically etched and then laminated together using an epoxy bonding process. Infinite Graphics, Inc. of Minneapolis, Minn. was contracted to produce the photo-masks needed for etching the layers. The masks were configured with one thousand twenty diameters having a center-to-center spacing of 2.5 millimeters. An IGI Lazerwrite photo plotter was used to create the masks, which were plotted on silver halite emulsion film. The plotter resolution accuracy was certified to 0.5 micrometers and pattern positional accuracy of plus or minus 0.40 micrometers per lineal inch. The layers were designed so that horn diameters were different from layer to layer, so that when the layers were assembled, the layers achieved the desired cross-section taper, slot, and ridge features shown in simplified form in FIG. 30. A total of 100 layers were used to create a stacked assembly 7.6 millimeters thick. The layers were processed by Tech Etch, Inc. of Plymouth, Mass., using standard photo-etching techniques and were etched in such a way that the cross-sectional shape of the etched walls for each layer are perpendicular to the top and bottom surfaces of the layer (commonly referred to as straight sidewalls). In this example, the method chosen to bond the etched layers together used a thermo-cured epoxy (MAGNA-TAC model E645), using the process and fixturing described earlier in the section on layer assembly and lamination. The assembled fixture was then placed in a 12 inch×12 inch heated platen press, Carver model No. 4122. The fixture was compressed to 40 pounds per square inch and held at a temperature of 350 degrees F. for 3 hours, then allowed to cool to room temperature under constant pressure. The assembly was then removed from the fixture and the alignment pins removed, leaving the bonded stack lamination. The laminated mold (stack lamination) was then used to produce the final casting mold. Step 2: Creating the casting mold: The second step of the process was the assembly of the final casting mold, which used the precision stack lamination made during step 1 as a laminated mold. The casting mold created was a negative version of the lamination, as shown in perspective view for a single feed horn 31000 in FIG. 31. Also shown is a feedhorn ridge 31010 that can correspond to a cavity slot 30010, and a feedhorn base 31020. For this example, Silastic® J RTV Silicone Rubber was used to make the final casting mold. This product was chosen because it is flexible enough to allow easy release from the laminated mold without damaging the undercut slots and rings inside the feedhorns, and because of its high-resolution capability. Described below are the product specifications. Silastic ® J:Durometer Hardness:56 Shore A pointsTensile Strength, psi:900Linear Coefficient of Thermal Expansion:6.2 × 10−4Cure Time at 25 C.:24 hours The Silastic® J Silicone RTV was prepared in accordance with the manufacturer's recommendations. This included mixing the silicone and the curing agent and evacuating air (degassing) from the material prior to filling the mold-making fixture. At the time the example was prepared, the most effective way of degassing the Silicone prior to filling the mold fixture was to mix the two parts of the Silicone and place them in a bell jar and evacuate the air using a dual stage vacuum pump. The material was pumped down to an atmosphere of 28 inches of mercury and held for 5 minutes beyond the break point of the material. The Silicone was then ready to pour into the mold fixture. As shown in the side view of FIG. 32, an open-face fixture 32000 was prepared, the fixture having a precision-machined aluminum ring 32010, precision ground glass plate 32030, rubber gaskets 32040, 32050 and the laminated mold 32060. The base 32020 of the fixture was thick plexiglass. On top of the plexiglass base was a glass substrate 32030. Rubber gasket 32040 separated the glass base and the glass substrate. An additional rubber gasket 32050 was placed on the top surface of the glass substrate 32030 and the laminated mold 32060 was placed on the top gasket. The rubber gaskets were used to prevent unwanted flashing of material during casting. A precision-machined aluminum ring 32010 was placed over the laminated mold subassembly and interfaced with the lower rubber gasket 32040. Generally, the height of the ring and dimensions of the above pieces can depend upon the dimensions of the specific structure to be cast. The ring portion 32010 of the fixture assembly served several purposes, including bounding and defining the area in which to pour mold material, capturing the material during the curing process, and providing an air escape while the mold material was degassed using vacuum. The fixture was configured in a way that all sides surrounding the laminated mold 32060 were equal and common, in order to equalize and limit the effects of thermal or mechanical stresses put on the lamination from the mold material. An open-face mold was used for this example. The mold insert and molding fixture were assembled and filled with the silicone RTV, then the air was evacuated again using a bell jar and vacuum pump in an atmosphere of 28 inches of mercury. After allowing sufficient time for the air to be removed from the silicone, the mold was then heat-cured by placing it in a furnace heated to and held at a constant temperature of 70 degrees F. for 16 hours prior to separating the laminated mold from the derived RTV mold. The molding fixture was then prepared for disassembly, taking care to remove the laminated mold from the RTV mold without damaging the lamination, since the lamination can be used multiple times to create additional RTV molds. The resulting RTV mold was a negative version of the entire feedhorn array consisting of an array of one thousand twenty negative feedhorns, similar to the simplified single horn 31010 shown in perspective view in FIG. 31. Step 3: Casting the feedhorn array: In this example, the cast feedhorn arrays were made of a silver loaded epoxy, which is electrically conductive. In certain exemplary embodiments of the present invention, binders and/or metallic (or other) powders can be combined and/or engineered to satisfy specific application and/or process specifications. The conductive epoxy chosen for this example provided the electrical conductivity needed to integrate the feedhorn array with an electronic infrared detector array. The conductive epoxy was purchased from the company BONDLINE™ of San Jose, Calif., which designs and manufactures engineered epoxies using powdered metals. Certain of its composite metal epoxies can be cured at room temperature, have high shear strength, low coefficient of thermal expansion, and viscosities suited for high-resolution casting. Exemplary embodiments of the present invention can utilize various techniques for injecting or filling cavity molds with casting materials. In this example, a pressure casting method was used. The BONDLINE™ epoxy was supplied fully mixed and loaded with the silver metallic powder, in a semi-frozen state. The loaded epoxy was first normalized to room temperature and then pre-heated per the manufacturer's specification. In the pre-heated state the epoxy was uncured and ready to be cast. The uncured epoxy was then poured into the open-face mold to fill the entire mold cavity. The mold was then placed in a pressurized vessel with an applied pressure of 50 psi using dry nitrogen, and held for one hour, which provided sufficient time for the epoxy to cure. The mold was then removed from the pressure vessel and placed in an oven for 6 hours at 225 degrees F., which fully cured the conductive epoxy. Step 4. Demolding and finish machining: After the cast epoxy had been cured, it was ready for disassembly and demolding from the casting fixture and mold. The mold material (RTV silicone) was chosen to be flexible enough to allow the cast feedhorn array to be removed from the casting mold without damaging the undercuts formed by the slots and ridges. When done carefully, the mold could be reused several times to make additional feedhorn arrays. The backing thickness 31020 of the RTV mold shown in FIG. 31 came into play during the de-molding process. The backing was cast thick enough to allow easy grasping to assist with separating the casting mold from the cast piece. In this example, the RTV casting mold was flexible and allowed easy separation without damaging the undercut slots and rings inside the cast feedhorns. Depending on the piece being cast, machining, coating, and/or other finish work can be desirable after de-molding. In this example, a final grinding operation was used on the top surface (pour side of the mold) of the feedhorn array because an open face mold was used. This final grinding operation could have been eliminated by using a closed, two-part mold. This example makes use of certain exemplary embodiments of the present invention to demonstrate the production of sub-millimeter feedhorns in a batch process. The example uses the same part design and fabrication process described in example 1, with several modifications detailed below. Process Modifications: The process detailed in example 1 was used to produce an array of one thousand twenty feedhorns. The first modification to the process was the casting material used to produce the array. The casting material for this example was a two-part casting polymer sold through the Synair Corporation of Chattanooga, Tenn. Product model “Mark 15 Por-A-Kast” was used to cast the feedhorn array and was mixed and prepared per the manufacturer's specifications. The polymer was also cast using the pressure filling method described in example 1. The next modification was a surface treatment applied to the cast polymer array. A conductive gold surface was deposited onto the polymer array in order to integrate the feedhorns with the detector electronics. The gold surface was applied in two stages. The first stage was the application of 0.5 microns of conduction gold, which was sputter-coated using standard vacuum deposition techniques. The first gold surface was used for a conductive surface to allow a second stage electro-deposition or plating of gold to be applied. The second gold plating was applied with a thickness of 2 microns using pure conductive gold. The final modification was to dice or cut the feedhorns from the cast and plated array into individual feedhorns, that were then suitable for detector integration. A standard dicing saw, used for wafer cutting, was used to cut the feedhorns from the cast array. Process steps 1 and 2 described in example 1 were used to produce a large area array of micro-structures, which are described as negatives of the feedhorn cavities, shown as a single feedhorn in FIG. 31. The laminated mold and molding fixture was used to cast the micro-structures using Dow Coming's Silastic® M RTV Silicone Rubber. This product was chosen because it is flexible enough to release from the mold insert, without damaging the circular steps in the structure, but has the hardness needed to maintain the microstructures in a standing position after being released from the mold. Described below are the product specifications. Silastic ®MDurometer Hardness:59 Shore A pointsTensile Strength, psi:650Linear Coefficient of Thermal Expansion:6.2 × 10−4Cure Time at 25 C.:16 hours The Silicone RTV was prepared in accordance with the manufacturer's recommendations, using the process described earlier in example 1, step 2. The laminated mold and molding fixture were assembled and filled with the silicone RTV, using the process described earlier in example 1, step 2. The molding fixture was then prepared for disassembly, taking care to separate the mold insert from the cast silicone array. The resulting casting was an array consisting of one thousand twenty 3-dimensional micro-structures. The shape and dimension of a single structure is shown in simplified form in FIG. 31. Certain exemplary embodiments of the present invention have been used to produce a 2.5 centimeter length of clear urethane tubing, having 3-dimensional micro-fluid channels on the inside diameter of the tubing. The fluidic tubing was produced using a flexible cavity insert with a controlled backing thickness. The following example demonstrates how the cavity insert can enable the production of three-dimensional features on the inside and outside diameters of cylindrical tubing. Step 1: Creating the mold insert: The first step in the process was to fabricate the micro-machined layers used to produce the cavity insert. The cast tubing was 2.5 centimeters long, having a 3.0 millimeter outside diameter and a 2.0 millimeter inside diameter, with 50 three-dimensional micro-fluidic channels, equally spaced around the interior diameter of the tube. FIG. 33 shows a side view of the tubing 33000, the wall of which defines numerous fluidic channels 33010. Although each fluidic channel could have different dimensions, in this example each channel was 0.075 mm in diameter at the entrance of the channel from the tube, and each channel extended 0.075 mm deep. Each channel tapered to a diameter of 0.050 mm, the taper beginning 0.025 mm from the bottom of each channel. Photo-chemical machining was used to fabricate the layers for the laminated mold. FIG. 34 is a top view of a such a laminated mold 34000, which was created using several photo masks, one of which with a similar top view. Mold 34000 includes an array of fluidic channels 34010 In this particular experiment, the length of channels 34010 was approximately 25 millimeters, and the width of each collection of channels was approximately 6.6 millimeters. FIG. 35 is a cross-section of mold 34000 taken at section lines 35-35 of FIG. 34. To the cross-sectional shape of channel 34010, a first copper foil 35010 having a thickness of 0.025 mm, and a second copper foil 35020 having a thickness of 0.050 mm, were chemically etched and then laminated together using a metal-to-metal brazing process. Each of the layers used in the laminated mold assembly used a separate photo-mask. The masks used for layer 35020 were configured with a 9.50×0.075 mm rectangular open slot, arrayed redundantly in 50 places, a portion of which are illustrated in FIG. 34. To achieve the desired taper, two masks were used for layer 35010. The bottom mask was configured with a 9.50×0.075 mm rectangular open slot and the top mask was configured with a 9.50×0.050 rectangular open slot, each of the slots were also redundantly arrayed in 50 places. The photo-masks were produced to the same specifications, by the same vendor as those described in example 1, step 1. The layers were designed so that the slot placement was identical from layer to layer, which when assembled, produced the cross-sectional shape for the channels as shown in FIG. 35. The final thickness of the lamination was specified at 0.083 millimeters, which required one 0.025 layer of copper foil, and one 0.050 thick layer of copper foil, leaving a total thickness amount of 0.002 millimeters for braze material on each side of each etched layer. The layers were photo-etched by the same vendor, and same sidewall condition as those described in example 1, step 1. The method chosen to bond the grid layers together was a metal-to-metal brazing technique described earlier, in detail as one of two exemplary methods of bonding layers together (eutectic braze alloy) Step 2: Creating the flexible cavity insert: The next step of the process was to create a flexible cavity insert from the brazed layered assembly. FIG. 36 is a side view of cavity insert 36000, which was produced from the brazed assembly with a backing 36010 having a thickness of 0.050 millimeters. The cavity insert 36000 was produced using Silastic® S RTV Silicone Rubber as the base material. The RTV Silicone Rubber was used because of its resolution capability, release properties, dimensional repeatability, and its flexibility to form the insert to a round pin that would be assembled to the final molding fixture. The material properties of Silastic® S are shown below. Silastic ®SDurometer Hardness:26 Shore A pointsTensile Strength, psi:1000Linear Coefficient of Thermal Expansion:6.2 × 10−4Cure Time at 25 C.:24 hoursThe casting fixture used to create the RTV cavity insert was similar to that shown in FIG. 32 and is described in detail in the prior examples. A modification was made to the fixture assembly, which was a top that was placed over the pour area of the mold fixture. This top was placed and located to close the mold after air evacuation and reduce the backing thickness 36010 of the RTV insert to a thickness of 0.050 millimeters, shown in FIG. 36. The Silastic® S RTV Silicone Rubber used for the cavity insert fabrication was prepared in accordance with the manufacturers recommendations, using the process described earlier in example 1, step 2. Step 3: Assembling the molding fixture: The final molding fixture was then ready to be assembled. The molding fixture included a base plate (FIG. 37), the cavity inserts (FIG. 38), and a top plate (FIG. 40). FIG. 37 is a top view of the base plate 37000, which was made from a 0.25 inch aluminum plate that was ground flat and machined using standard CNC machining techniques. The base had six machined diameters 37010 through the plate. These six diameters would accept the cavity insert pins described later. The plate also had machined diameters through the plate, which would accept dowel pins 37020 that were used to align and assemble the top plate and the base plate, as well as 4 bolt diameters 37030 to hold the top and bottom plates together. FIG. 38 is a side view of an insert fixture 38000, that includes the flexible cavity insert 36000 attached to a 3 centimeter long, 1.900 millimeter diameter steel pin 38010. The pin 38010 was ground to the desired dimensions using standard machine grinding techniques. The RTV cavity insert 36000 was cut to the proper size before being attached to the pin. The RTV insert 36000 was attached to outside diameter of the pin 38010 using a controlled layer of two-part epoxy. FIG. 39 is a side view of several insert fixtures 39000 that have been attached to a base plate 37000. Each insert 36000 was attached its corresponding pin 38010 so that the end of pin 38010 could be assembled to a corresponding machined diameter 37010 of base plate 37000 without interference from insert 36000. Once each insert 36000 was attached around the diameter of its corresponding pin 38010 and the pin placed in the corresponding through-diameter of base plate 37010, the pin was held perpendicular to base plate 37000 and in alignment with a top plate of the fixture. FIG. 40 is a top view of a top plate 40000 of the fixture, which was also fabricated of aluminum and machined using CNC techniques. There were six 3.0 millimeter diameters 40010 milled through the thickness of plate 40000, which was 3.0 centimeters thick. Diameters 40010 defined the cavity areas of the mold that would be filled during the final casting process, and aligned to the pins assembled to the base plate. Also incorporated into the top plate were bolt features 40020 and dowel features 40030 needed to align and assemble the top plate 40000 to the base plate 37000. The thickness of top plate 40000 was specified to slightly exceed the desired length of the final cast tubing, which was cut to its final length after casting. The casting fixture was then assembled, first by assembling the cavity insert 38000 to the base plate 37000, followed by assembling the top plate 40000 to the base using bolts and dowels. The top view of a representative cavity section for an assembled fixture is shown in FIG. 19. Step 4: Casting the fluidic tubes: Several fluidic tubes were produced using the assembled casting fixture. A clear urethane was used for the final casting because of its high-resolution, low shrink factor, and transparent properties, which allowed for final inspection of the interior diameter features through the clear wall of the tube. The casting material was purchased from the Alumilite Corporation of Kalamazoo, Mich., under the product name Water Clear urethane casting system. The manufacturer described the cured properties as follows: Hardness, Shore D:82Density (gm/cc)1.04Shrinkage (in/in/) maximum0.005Cure Time (150 degrees F.)16 hr The urethane was prepared in accordance with the manufacturer's recommendations. This included the mixing and evacuation of air (degassing) from the material prior to filling the mold. The most effective way found for degassing the urethane prior to filling the mold fixture was to mix parts A and B, place them in a bell jar, and evacuate the air using a dual stage vacuum pump. The mixture was pumped down to an atmosphere of 28 inches of mercury and held for 15 minutes beyond the break point of the material The urethane was then ready to pour into the mold fixture. The assembled mold fixture was heated to 125 degrees F. prior to filling the cavities with the urethane. The pre-heating of the mold helped the urethane to flow and fill the cavities of the mold, and aided in the degassing process. The cavity sections of the mold were then filled with the urethane, and the air was evacuated again using a bell jar and vacuum pump in an atmosphere of 28 inches of mercury. After allowing sufficient time for the air to be removed from the urethane, the mold was then removed from the vacuum bell jar and placed in an oven. The mold was heated and held at a constant temperature of 150-180 degrees F. for 16 hours prior to separating the cast tubes from the mold. The molding fixture was then disassembled and the cast tubes were separated from the cavity inserts. The inserts were first removed from the base plate of the fixture. The tubes were easily separated from the cavity insert assembly due to the flexibility and release properties of the silicone RTV, combined with the hardness of the urethane tubes. Example # 4 described the method used for producing cast urethane tubing with micro-fluidic features on the inside diameter of the tube. The current example demonstrates how that process can be altered to produce tubing with the micro-fluidic channels on the outside diameter of the tubing. This example uses a similar part design and the fabrication process described in example 4, with several modifications detailed below. One process modification involved step 3, assembling the molding fixture. For this step, a modification was made to the fixture design that enabled the molded features to be similar to that shown in FIGS. 20-22. The first modification was in the size of the machined diameters in the base plate and the top plate of the fixture described in example 4. The flexible RTV cavity insert that was attached to a pin in example 4 was instead attached to the inside diameters of the top fixture plate, similar to that shown in FIG. 22. In order to accommodate the existing RTV cavity insert, the cavity diameters of the top plate were milled to a size of 1.900 millimeters. The RTV cavity insert was then attached to the milled diameter of the top plate using the same epoxy technique described in example 4. The base plate of the fixture was also modified to accept a 1.0 millimeter diameter pin, and was assembled similar to the that shown in FIG. 22. The same casting process was used as described in example 4. After following the final casting process, with the altered molding fixture, the urethane tubes were produced having the same fluidic channels located on the outside diameter of the cast tube. Additional Embodiments—X-Ray and Gamma-Ray Collimators, Grids, and Detector Arrays Certain exemplary embodiments of the present invention can provide methods for fabricating grid structures having high-resolution and high-aspect ratio, which can be used for radiation collimators, scatter reduction grids, and/or detector array grids. Such devices can be used in the field of radiography to, for example, enhance image contrast and quality by filtering out and absorbing scattered radiation (sometimes referred to as “off-axis” radiation and/or “secondary” radiation). Certain embodiments of such devices can be used in nearly every type of imaging, including astronomy, land imaging, medical imaging, magnetic resonance imaging, tomography, fluoroscopy, non-destructive inspection, non-destructive testing, optical scanning (e.g., scanning, digital copying, optical printing, optical plate-making, faxing, and so forth), photography, ultra-violet imaging, etc. Thus, certain embodiments of such devices can be comprised in telescopes, satellites, imaging machines, inspection machines, testing machines, scanners, copiers, printers, facsimile machines, cameras, etc. Moreover, these machines can process images using analog and/or digital techniques. For the purposes of this description, the term “collimator” is used generally to describe what may also be referred to as a radiation collimator, x-ray grid, scatter reduction grid, detector array grid, or any other grid used in an imaging apparatus and/or process. Certain collimators fabricated according to one or more exemplary embodiments of the present invention can be placed between the object and the image receptor to absorb and reduce the effects of scattered x-rays. Moreover, in certain exemplary embodiments, such collimators can be used in a stationary fashion, like those used in SPECT (Single Photon Emission Computed Tomography) imaging, or can be moved in a reciprocating or oscillating motion during the exposure cycle to obscure the grid lines from the image, as is usually done in x-ray imaging systems. Grids that are moved are known as Potter-Bucky grids. X-ray grid configurations can be specified by grid ratio, which can be defined as the ratio of the height of the grid to the distance between the septa. The density, grid ratio, cell configuration, and/or thickness of the structure can have a direct impact on the grid's ability to absorb off-axis radiation and/or on the energy level of the x-rays that the grid can block. Certain exemplary embodiments of the present invention can allow for the use of various materials, including high-density grid materials. Also, certain exemplary can make use of a production mold, which can be derived from a laminated mold. Numerous additional aspects can be fabricated according to certain exemplary embodiments of the present invention. For example, the laminated mold can be produced from a stack lamination or other method, as discussed above. Moreover, X-ray absorbent material, such as lead, lead alloys, dense metallic composites, and/or epoxies loaded with dense metallic powders can be cast into a mold to produce x-ray absorbing grids. High-temperature ceramic materials also can be cast using a production mold. In addition, the open cells of the ceramic grid structure can be filled with detector materials that can be accurately registered to a collimator. The molds and grids can be fabricated having high-resolution grid geometries that can be made in parallel or focused configurations. The mold can remain assembled to the cast grid to provide structural integrity for grids with very fine septal walls, or can be removed using several methods, and produce an air-cell grid structure. FIG. 41 is a block diagram illustrating an exemplary embodiment of a method 41000 of the present invention Method 41000 can include the following activities: 1) creating a lithographic mask 41010 defining the features of each unique layer, 2) using lithographic micro-machining techniques and/or micro-machining techniques to produce patterned layers 41020, and 3) aligning, stacking, and/or laminating the patterned layers 41030 in order to achieve the desired 3-dimensional cavity shape, high-aspect ratios, and/or other device features desired for the laminated mold 41040, 4) fabricating a casting mold 41050 derived from the laminated mold, and/or 5) casting x-ray grids (or other parts) 41060 using the derived casting mold.The following discussion describes in detail exemplary activities involved in fabricating certain exemplary embodiments of a laminated mold, fabricating a derived mold from the laminated mold, and finally casting a collimator from the derived mold. Certain variations in the overall process, its activities, and the resulting collimator are noted throughout. In certain exemplary embodiments, the final collimator can be customized as a result of the casting process. For instance, conventional collimators have two separated flat major sides that are parallel to each other, thereby forming a flat, generally planar grid structure. Although certain exemplary embodiments of the present invention includes methods for forming these collimators, exemplary embodiments of the invention also can be used to form non-planar collimators. An exemplary embodiment of a method of the present invention can begin with the acquisition, purchase, and/or fabrication of a first collimator. This first collimator can serve as the master collimator from which one or more molds can be formed. The master collimator can be made by any means, including stack lamination, but there is no limitation with respect to how the first or master collimator can be made. Also, as will be explained in more detail, because the master collimator is not necessarily going to be a collimator used in radiography, it is possible to customize this master collimator to facilitate mold formation. The mold itself can be fabricated of many materials. When formed of a flexible material, for example, it is possible to use the mold to make a non-planar collimator. The material of the mold can be customized according to cost and performance requirements. In some embodiments, it is possible to make a mold of material that is substantially transparent to radiation transmission. The mold could be left embedded in the final cast collimator. This particular variation can be applicable when the final collimator has very narrow septal walls and the mold is needed to provide support and definition for the collimator. The mold generally also can be reused to form multiple final (or second) collimators to achieve economies of manufacturing scale. Radiation Opaque Casting Materials for Collimators and Grids A broad selection of base materials can be used for the fabrication of parts, such as x-ray collimators and scatter reduction grids. One potential characteristic of a grid material is sufficient absorption capacity so that it can block selective x-rays or gamma photons from reaching an image detector. In certain embodiments of the present invention, this characteristic can require high density and/or high atomic number (high z) materials. Certain exemplary embodiments of the present invention can utilize lead, tungsten, and/or various lead alloys for grid fabrication, but also can include the practice of loading various binders or alloys with dense powder metals, such as tungsten. The binders can be epoxies, polymers, and/or dense alloys which are described in detail below. For certain exemplary embodiments of the present invention, lead can be used for casting purposes because of its high density and low melting point, which can allow the molten lead to be poured or injected into a mold. In certain situations, however, pure lead can shrink and/or pull away from molds when it solidifies, which can inhibit the casting of fine features. This can be overcome by using lead alloys, made from high-density materials, which can allow the metal alloy to flow at lower temperatures than pure lead while reducing shrink factors. A typical chief component in a lead alloy is bismuth, a heavy, coarse crystalline metal that can expand by 3.3% of its volume when it solidifies. The presence of bismuth can expand and/or push the alloy into the fine features of the mold, thus enabling the duplication of fine features. The chart below shows the physical properties of pure lead and two lead alloys that were used to produce collimators. The alloys were obtained from Cerro Metal Products Co. of Bellefonte, Pa. Many other alloys exist that can be used to address specific casting and application requirements. BASEDENSITYMATERIALCOMPOSITIONMELT POINT(g/cc)Pure LeadPb621.7 degrees F.11.35CERROBASE ™55.5% BI, 44.5% Pb 255 degrees F.10.44CERROLOW-44.7% BI, 22.6% Pb, 117 degrees F. 9.16117 ™19.1% In, 8.3% Sn, 5.3% Cd, The physical properties of lead alloys can be more process-compatible when compared to pure lead, primarily because of the much lower melting point. For example, the low melt point of CERROBASE™ can allow the use of rubber-based molds, which can be helpful when casting fine-featured pieces. This can be offset in part by a slightly lower density (about 8%). The somewhat lower density, can be compensated for, however, by designing the grid structure with an increased thickness and/or slightly wider septal walls. Also, the alloy can be loaded with dense powder metals, such as tungsten, gold, and/or tantalum, etc., to increase density. Similarly, epoxy binders can be loaded with a metallic powder such as, for example, powdered tungsten, which has a density of 19.35 grams per cubic centimeter. In this approach, tungsten particles ranging in size from 1-150 microns, can be mixed and distributed into a binder material. The binder material can be loaded with the tungsten powder at sufficient amounts needed to achieve densities ranging between 8 and 14 grams per cubic centimeter. The tungsten powder is commercially available through the Kulite Tungsten Corporation of East Rutherford N.J., in various particle sizes, at a current cost of approximately $20-$25 dollars per pound. The binders and metallic powders can be combined and engineered to satisfy specific application and process issues. For example, tungsten powder can be added to various epoxies and used for casting. The company BONDLINE™ of San Jose, Calif., designs and manufactures engineered adhesives, such as epoxies, using powdered metals. Such composite metal epoxies can be cured at room temperature, can have high shear strength, low coefficient of thermal expansion, and viscosities that can be suited for high-resolution casting. Powdered materials combined with epoxy can be stronger than lead or lead alloys, but can be somewhat lower in density, having net density ranging from 7-8 grams per cubic centimeter. This density range can be acceptable for some collimator applications. In applications where material density is critical the practice of loading a lead alloy can be used. For example, tungsten powder can be combined with CERROBASE™ to raise the net density of the casting material from 10.44 up to 14.0 grams per cubic centimeter. Certain exemplary embodiments of the present invention also include the casting of grid structures from ceramic materials, such as alumina, silicon carbide, zirconium oxide, and/or fused silica. Such ceramic grid structures can be used to segment radiation imaging detector elements, such as scintillators. The Cotronics Corporation of Brooklyn, N.Y., manufactures and commercially distributes Rescor™ Cer-Cast ceramics that can be cast at room temperature, can have working times of 30-45 minutes, can have cure times of 16 hours, and can withstand temperatures ranging from 2300 to 4000 degrees F. Additional Embodiments—Anti-scatter Grids for Mammography and General Radiography One or more exemplary embodiments of the present invention can provide cellular air cross grids for blocking scattered X-ray radiation in mammography applications. Such cross grids can be interposed between the breast and the film-screen or digital detector. In some situations, such cross grids can tend to pass only the primary, information-containing radiation to the film-screen while absorbing secondary and/or scattered radiation which typically contains no useful information about the breast being irradiated. Certain exemplary embodiments of the present invention can provide focused grids. Grids can be made to focus to a line or a point. That is, each wall defining the grid can be placed at a unique angle, so that if an imaginary plane were extended from each seemingly parallel wall, all such planes would converge on a line or a point at a specific distance above the grid center—the distance of that point from the grid known as the grid focal distance. A focused grid can allow the primary radiation from the x-ray source to pass through the grid, producing the desired image, while the off-axis scattered rays are absorbed by the walls of the grid (known as septal walls). In certain embodiments, the septal walls can be thick enough to absorb the scattered x-rays, but also can be as thin as possible to optimize the transmission ratio (i.e., the percentage of open cell area to the total grid area including septal walls) and minimize grid artifacts (the shadow pattern of grid lines on the x-ray image) in the radiograph. The relation of the height of the septal walls to the distance between the walls can be known as the grid ratio. Higher grid ratios can yield a higher scatter reduction capability, and thus a higher Contrast Improvement Factor (CIF), which can be defined as the ratio of the image contrast with and without a grid. A higher grid ratio can require, however, a longer exposure time to obtain the same contrast, thus potentially exposing the patient to more radiation. This dose penalty, known as the Bucky factor (BF), is given by BF=CIF/Tp, where Tp is the fraction of primary radiation transmitted. Certain exemplary embodiments of the present invention can provide a grid design that arrives at an optimal and/or near-optimal combination of these measures. One or more exemplary embodiments of the present invention can include fine-celled, focused, and/or large area molded cross-grids, which can be sturdily formed from a laminated mold formed of laminated layers of metal selectively etched by chemical milling or photo-etching techniques to provide open focused passages through the laminated stack of etched metal layers. In certain applications, such molded and/or cast cross grids can maximize contrast and accuracy of the resulting mammograms when produced with a standard radiation dosage. In certain exemplary embodiments, the laminated mold for the molded cross grids can be fabricated using adhesive or diffusion bonding to join abutting edges of thin partition portions of the laminated abutting layers with minimum intrusion of bonding material into the open focused passages. Exemplary embodiments of the present invention can utilize any of a wide number of different materials to fabricate such molded and/or cast cross grids. A specific application can result in any of the following materials being most appropriate, depending on, for example, the net density and the cell and septa size requirements: Lead or lead alloy alone can offer a density of 9-11 grams per cc; Lead alloy can be loaded with a dense composite (e.g., tungsten, tantalum, and/or gold, etc.) powder to form a composite having a density of 12-15 grams per cc; Polymer can be loaded with a dense composite (e.g., lead, tungsten, tantalum, and/or gold, etc.) powder to form a composite having a density of 8-9 grams per cc; The cast grid made of lead alloy or any of the above combinations can be encapsulated in a low density polymer such that the transmission is minimally affected but scatter is significantly reduced. In addition, certain embodiments of the present invention can be employed to fabricate grids and/or collimators for which the mold can be pre-loaded with dense powder, followed by alloy or polymer. Alternatively, polymer or alloy can be pre-loaded with dense powder then injected into the mold. In certain embodiments, the casting can be removed from a flexible mold. In other embodiments, the mold can be dissolved or consumed to de-mold the casting. In certain embodiments, a master can be removed layer-by-layer from rigid mold. Alternatively, the lost wax approach can be used in which the model is dissolvable wax, dissolvable PMMA, dissolvable polyurethane, dissolvable high-resolution ceramic, and/or some other dissolvable material. Additional Embodiments—Computed Tomography Collimator and Detector Array Certain exemplary embodiments of the present invention can provide a system that includes an x-ray source, a scatter collimator, and a radiation detector array having a plurality of reflective scintillators. Such a system can be used for computer-assisted tomography (“CT”). Computed tomography is often performed using a CT scanner, which can also be known as a CAT scanner. In certain embodiments, the CT scanner can look like a large doughnut, having a square outer perimeter and a round hole. The patient can be positioned in a prone position on a table that can be adjusted up and down, and can be slid into and out of the hole of the CT scanner. Within the chassis of the CT scanner is an x-ray tube on a rotating gantry which can rotate around the patient's body to produce the images. On the opposite side of the gantry from the x-ray tube can be mounted an array of x-ray detectors. In certain exemplary embodiments of the present invention, the x-ray source can project a fan-shaped beam, which can be collimated to lie within an X-Y plane of a Cartesian coordinate system, referred to as the “imaging plane”. The x-ray beam can pass through the object being imaged, such as a patient. The beam, after being attenuated by the object, can impinge upon the array of radiation detectors. The intensity of the attenuated beam radiation received at the detector array can be dependent upon the attenuation of the x-ray beam by the object. Each detector element of the array can produce a separate electrical signal that can provide a measurement of the beam attenuation at the detector location. The attenuation measurements from all the detectors can be acquired separately to produce an x-ray transmission profile of the object. For certain exemplary embodiments of the present invention, the detector array can include a plurality of detector elements, and can be configured to attach to the housing. The detector elements can include scintillation elements, or scintillators, which can be coated with a light-retaining material. Moreover, in certain exemplary embodiments, the scintillators can be coated with a dielectric coating to contain within the scintillators any light events generated in the scintillators. Such coated scintillators can reduce detector element output gain loss, and thereby can extend the operational life of a detector element and/or array, without significantly increasing the costs of detector elements or detector arrays. In certain exemplary embodiments of the present invention, the x-ray source and the detector array can be rotated with a gantry within the imaging plane and around the object to be imaged so that the angle at which the x-ray beam intersects the object can constantly change. A group of x-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle can be referred to as a “view”, and a “scan” of the object can comprise a set of views made at different gantry angles during one revolution of the x-ray source and detector. In an axial scan, the projection data can be processed to construct an image that corresponds to a two-dimensional slice taken through the object. In certain exemplary embodiments of the present invention, images can be reconstructed from a set of projection data according to the “filtered back projection technique”. This process can convert the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units”, which can be used to control the brightness of a corresponding pixel on a cathode ray tube display. In certain exemplary embodiments of the present invention, detector elements can be configured to perform optimally when impinged by x-rays traveling a straight path from the x-ray source to the detector elements. Particularly, exemplary detector elements can include scintillation crystals that can generate light events when impinged by an x-ray beam. These light events can be output from each detector element and can be directed to photoelectrically responsive materials in order to produce an electrical signal representative of the attenuated beam radiation received at the detector element. The light events can be output to photomultipliers or photodiodes that can produce individual analog outputs. Exemplary detector elements can output a strong signal in response to impact by a straight path x-ray beam. Without a collimator, X-rays can scatter when passing through the object being imaged. Particularly, the object can cause some, but not all, x-rays to deviate from the straight path between the x-ray source and the detector. Therefore, detector elements can be impinged by x-ray beams at varying angles. System performance can be degraded when detector elements are impinged by these scattered x-rays. When a detector element is subjected to multiple x-rays at varying angles, the scintillation crystal can generate multiple light events. The light events corresponding to the scattered x-rays can generate noise in the scintillation crystal output, and thus can cause artifacts in the resulting image of the object. To, for example, reduce the effects of scattered x-rays, scatter collimators can be disposed between the object of interest and the detector array. Such collimators can be constructed of x-ray absorbent material and can be positioned so that scattered x-rays are substantially absorbed before impinging upon the detector array. Such scatter collimators can be properly aligned with both the x-ray source and the detector elements so that substantially only straight path x-rays impinge on the detector elements. Also, such scatter collimators can shield from x-ray radiation damage certain detector elements that can be sensitive at certain locations, such as the detector element edges. Certain exemplary embodiments of a scatter collimator of the present invention can include a plurality of substantially parallel attenuating blades and a plurality of substantially parallel attenuating wires located within a housing. In certain exemplary embodiments, the attenuating blades, and thus the openings between adjacent attenuating blades, can be oriented substantially on a radial line emanating from the x-ray source. That is, each blade and opening can be focally aligned. The blades also can be radially aligned with the x-ray source. That is, each blade can be equidistant from the x-ray source. Scattered x-rays, that is, x-rays diverted from radial lines, can be attenuated by the blades. The attenuating wires can be oriented substantially perpendicular to the blades. The wires and blades thus can form a two-dimensional shielding grid for attenuating scattered x-rays and shielding the detector array. At least one embodiment of the invention can include a feature that provides any of at least 5 functions: 1) separation of the collimator by a predetermined distance from an array of radiation detection elements; 2) alignment of the collimator to the array of radiation detection elements (or vice versa); 3) attachment of the collimator to the array of radiation detection elements; 4) attach the collimator to a gantry or other detector sub-assembly; and/or 5) align the collimator to a gantry or other detector sub-assembly. As an illustrative example, one embodiment of such a feature could resemble “stilts” that can be formed independently or integrally to a collimator and that can separate the collimator by a predetermined distance from an array of radiation detection elements. In another embodiment, one or more of the stilts could serve as an alignment pin to align the collimator with the array of radiation detection elements. In another embodiment, one or more of the stilts could include and/or interface with an attachment mechanism to attach the collimator to the array of radiation detection elements. For example, an end of a stilt could slide into, via an interference fit, a socket of the array of radiation detection elements. As example, a stilt could include a hemispherical protrusion that snaps into a corresponding hemispherical indentation in a socket of the array of radiation detection elements. As another illustrative example, one embodiment of such a feature could invert the description of the previous paragraph by providing “holes” in the collimator that interface with “stilts” attached to or integral with the radiation detection elements. As yet another illustrative example, an embodiment of the feature could be manifested in a collimator having an array of through-holes, each having a square cross-section. At one end of all or certain through-holes could be the feature, such as a groove that extends around a perimeter of the square through-hole. A radiation detection element could have a square outer perimeter that includes a lip having corresponding dimensions to the groove that allows the radiation detection element to snap into the through-hole of the collimator via an interference fit, thereby fixing the position of the radiation detection element with respect to the collimator, aligning the radiation detection element with the collimator, and attaching the radiation detection element to the collimator. Moreover, a modular collection of radiation detection elements, potentially cast according to an embodiment of the present invention, could attach to a collimator via one or more attachment features, any of which could be formed independently of, or integrally with, either the radiation detection module and/or the collimator. Depending on the embodiment, the scatter collimator can include blades and wires, open air cells, and/or encapsulated cells. Certain exemplary embodiments can be fabricated as a true cross grid having septa in both radial and axial directions. The cross-grid structure can be aligned in the radial and axial directions or it can be rotated. Thus, the cross grid can be aligned in two orthogonal directions. Depending on the grid design, it might not be practical and/or possible to remove the mold from the cast grid because of its shape or size, e.g., if very thin septa or severe undercuts are involved. In such cases, a material with a low x-ray absorptivity can be used for the mold and the final grid can be left encapsulated within the mold. Materials used for encapsulation can include, but are not limited to, polyurethanes, acrylics, foam, plastics etc. Because certain exemplary embodiments of the present invention can utilize photolithography in creating the laminated mold, great flexibility can be possible in designing the shape of the open cells. Thus, round, square, hexagonal, and/or other shapes can be incorporated. Furthermore, the cells do not all need to be identical (a “redundant pattern”). Instead, they can vary in size, shape, and/or location (“non-redundant” pattern) as desired by the designer. In addition, because of the precision stack lamination of individual layers that can be employed in fabricating the master, the cell shapes can vary in the third dimension, potentially resulting in focused, tapered, and/or other shaped sidewalls going through the cell. Because the cell shape can vary in the third dimension (i.e. going through the cell), the septa wall shape can also vary. For example, the septa can have straight, tapered, focused, bulging, and/or other possible shapes. Furthermore, the septa do not all need to be identical (a “redundant pattern”). Instead, they can vary in cross-sectional shape (“non-redundant” pattern) as desired by the designer. Certain exemplary embodiments of the present invention can provide a collimator or section of a collimator as a single cast piece, which can be inherently stronger than either a laminated structure or an assembly of precisely machined individual pieces. Such a cast collimator can be designed to withstand any mechanical damage from the significant g-forces involved in the gantry structure that can rotate as fast as 4 revolutions per second. Furthermore, such a cast structure can be substantially physically stable with respect to the alignment between collimator cells and detector elements. Some exemplary embodiments of the present invention can provide a collimator or section of a collimator as a single cast collimator in which cells and/or cell walls can be focused in the radial direction, and/or in which cells and/or cells walls can be accurately aligned in the axial direction. Conversely, certain exemplary embodiments of the present invention can provide a collimator or section of a collimator as a single cast collimator in which cells and/or cell walls can be focused (by stacking layers having slightly offset openings) in the axial direction, and/or in which cells and/or cells walls can be curved (and focused) in the radial direction. Exemplary embodiments of the present invention can utilize any of a wide number of different materials to fabricate the scatter collimator. A specific application can result in any of the following materials being most appropriate, depending on, for example, the net density and the cell and septa size requirements. Lead or lead alloy alone can offer a density of 9-11 grams per cc; Lead alloy can be loaded with a dense composite (e.g., tungsten, tantalum, and/or gold, etc.) powder to form a composite having a density of 12-15 grams per cc; Polymer can be loaded with a dense composite (e.g., lead, tungsten, tantalum, and/or gold, etc.) powder to form a composite having a density of 8-9 grams per cc; The cast grid made of lead alloy or any of the above combinations can be encapsulated in a low density polymer such that the transmission is minimally affected but scatter is significantly reduced. In addition, certain embodiments of the present invention can be employed to fabricate grids and/or collimators for which the mold can be pre-loaded with dense powder, followed by alloy or polymer. Alternatively, polymer or alloy can be pre-loaded with dense powder then injected into the mold. In certain embodiments, the casting can be removed from a flexible mold. In other embodiments, the mold can be dissolved or consumed to de-mold the casting. In certain embodiments, a master can be removed layer-by-layer from rigid mold. Alternatively, the lost wax approach can be used in which the model is dissolvable wax, dissolvable PMMA, dissolvable polyurethane, dissolvable high-resolution ceramic, and/or some other dissolvable material. The above description and examples have covered a number of aspects of certain exemplary embodiments of the invention including, for example, cell size and shape, different materials and densities, planar and non-planar orientations, and focused and unfocused collimators. Additional Embodiments—Nuclear Medicine (SPECT) Collimator and Detector Array In conventional X-ray or CT examinations, the radiation is emitted by a machine and then passes through the patient's body. In nuclear medicine exams, however, a radioactive material is introduced into the patient's body (by injection, inhalation or swallowing), and is then detected by a machine, such as a gamma camera or a scintillation camera. The camera can have a detector and means to compute the detected image. The detector can have at least one a scintillator crystal, which typically is planar. The scintillator can absorb the gamma radioactive radiation, and emit a luminous scintillation in response, which can be detected by an array of photomultiplier tubes of the detector. The computation means can determine the coordinates of a locus of interaction of the gamma rays in the scintillator, which can reveal the projected image of the body. Because the radiation source in the patient can emit radiation omnidirectionally, a collimator can be located between the body and the scintillator. This collimator can prevent the transmission of those radioactive rays that are not propagating in a chosen direction. Certain embodiments of the present invention can be used to fabricate structures useful for nuclear medicine. For example, collimators used in nuclear medicine, including pinhole, parallel-hole, diverging, and converging collimators, can be fabricated according to one or more exemplary methods of the present invention. As another example, exemplary methods of the present invention can be used to fabricate high precision, high attenuation collimators with design flexibility for hole-format, which can improve the performance of pixelated gamma detectors. Certain exemplary embodiments of certain casting techniques of the present invention can be applied to the fabrication of other components in detector systems. FIG. 47 is an assembly view of components of a typical pixelated gamma camera. Embodiments of certain casting techniques of the present invention can be used to produce collimator 47010, scintillator crystals segmentation structure 47020, and optical interface 47030 between scintillator array (not visible) and photo-multiplier tubes 47040. In an exemplary embodiment, collimator 47010 can be fabricated from lead, scintillator crystals segmentation structure 47020 can be fabricated from a ceramic, and optical interface 47030 can be fabricated from acrylic. In certain exemplary embodiments, through the use of a common fabrication process, two or more of these components can be made to the same precision and/or positional accuracy. Moreover, two or more of these components can be designed to optimize and/or manage seams and/or dead spaces between elements, thereby potentially improving detector efficiency for a given choice of spatial resolution. For example, in a pixelated camera with non-matched detector and collimator, if the detector's open area fraction (the fraction of the detector surface that is made up of converter rather than inter-converter gap) is 0.75, and the collimator's open area fraction (the fraction of the collimator surface that is hole rather than septum) is 0.75, the overall open area fraction is approximately (0.75)=0.56. For a similar camera in which the collimator holes are directly aligned with the pixel converters, the open area fraction is 0.75, giving a 33% increase in detection efficiency without reduction in spatial resolution. Certain embodiments of the present invention can provide parallel hole collimators and/or collimators having non-parallel holes, such as fan beam, cone beam, and/or slant hole collimators. Because certain embodiments of the present invention use photolithography in creating the master, flexibility is possible in designing the shape, spacing, and/or location of the open cells. For example, round, square, hexagonal, or other shapes can be incorporated. In addition, because certain embodiments of the present invention use precision stack lamination of individual layers to fabricate a laminated mold, the cell shapes can vary in the third dimension, resulting in focused, tapered, and/or other shaped sidewalls going through the cell. Furthermore, the cells do not all need to be identical (“redundant”). Instead, they can vary in size, shape or location (“non-redundant”) as desired by the designer, which in some circumstances can compensate for edge effects. Also, because a flexible mold can be used with certain embodiments of the present invention, collimators having non-planar surfaces can be fabricated. In some cases, both surfaces are non-planar. However, certain embodiments of the present invention also allow one or more surfaces to be planar and others non-planar if desired. Certain embodiments of the present invention can fabricate a collimator, or section of a collimator, as a single cast piece, which can make the collimator less susceptible to mechanical damage, more structurally stable, and/or allow more accurate alignment of the collimator with the detector. Certain embodiments of the present invention can utilize any of a number of different materials to fabricate a collimator or other component of an imaging system. A specific application could result in any of the following materials being chosen, depending, in the case of a collimator, on the net density and the cell and septa size requirements: Lead or lead alloy alone can offer a density of 9-11 grams per cc Polymer can be loaded with tungsten powder to form a composite having a density comparable to lead or lead alloys Polymer can also be combined with other dense powder composites such as tantalum or gold to yield a density comparable to lead or lead alloys Polymer can be combined with two or more dense powders to form a composite having a density comparable to lead or lead alloys Lead alloy can be loaded with tungsten powder to form a composite having a density of 12-15 grams per cc Lead alloy can be loaded with another dense composites (tantalum, gold, other) to form a composite having a density of 12-15 grams per cc Lead alloy can be combined with two or more dense powders to form composites having a density of 12-15 grams per cc (atomic number and attenuation) The cast grid made of lead alloy or any of the above combinations can be encapsulated in a low-density material such that the transmission is minimally affected but scatter is reduced. Thus, depending on the specific application, certain embodiments of the present invention can create any of a wide range of densities for the cast parts. For example, by adding tungsten (or other very dense powders) to lead alloys, net densities greater than that of lead can be achieved. In certain situations, the use of dense particles can provide high “z” properties (a measure of radiation absorption). For certain embodiments of the present invention, as radiation absorption improves, finer septa walls can be made, which can increase imaging resolution and/or efficiency. In addition, certain embodiments of the present invention can be employed to fabricate grids and/or collimators for which the mold can be pre-loaded with dense powder, followed by alloy or polymer. Alternatively, polymer or alloy can be pre-loaded with dense powder then injected into the mold. In certain embodiments, the casting can be removed from a flexible mold. In other embodiments, the mold can be dissolved or consumed to de-mold the casting. In certain embodiments, a master can be removed layer-by-layer from rigid mold. Alternatively, the lost wax approach can be used in which the model is dissolvable wax, dissolvable PMMA, dissolvable polyurethane, dissolvable high-resolution ceramic, and/or some other dissolvable material. With certain embodiments of the present invention, the stack-laminated master does not need to embody the net density of the final grid. Instead, it can have approximately the same mechanical shape and size. Similarly, the final grid can be cast from relatively low cost materials such as lead alloys or polymers. Furthermore, these final grids can be loaded with tungsten or other dense powders. As discussed previously, using certain embodiments of the invention, multiple molds can be made from a single master and multiple grids can be cast at a time, if desired. Such an approach can lead to consistency of dimensions and/or geometries of the molds and/or grids. Because of the inherent precision of the lithographic process, certain embodiments of the present invention can prevent and/or minimize assembly build up error, including error buildup across the surface of the grid and/or assembly buildup error as can occur in collimators in which each grid is individually assembled from photo-etched layers. In addition, process errors can be compensated for in designing the laminated mold. Step 1: Creating the laminated mold: In this exemplary process, 0.05 mm thick copper foils were chemically etched and then laminated together using a metal-to-metal brazing process, for producing a laminated mold. Photo-masks were configured with a 2.0×2.0 millimeter square open cell, with a 0.170 mm septal wall separating the cells. The cells were arrayed having 10 rows and 10 columns, with a 2 mm border around the cell array. Photo-masks were produced to the same specifications, by the same vendor as those described in example 1, step 1. The layers were designed so that the cell placement was identical from layer to layer, which when assembled, produced a parallel cross-sectional shape. FIG. 42A is a top view of an x-ray grid 42000 having an array of cells 42002 separated by septal walls 42004. FIG. 42B is a cross-sectional view of x-ray grid 42000 taken along section lines 42-42 of FIG. 42B showing that the placement of cells 42002 can also be dissimilar from layer to layer 42010-42050, so that when assembled, cells 42002 are focused specifically to a point source 42060 at a known distance from x-ray grid 42000. The total number of layers in the stack lamination defined the thickness of the casting mold and final cast grid. The final thickness of the lamination was specified at 0.118 inches, which required 57 layers of copper foil, leaving a total thickness amount of 0.00007 inches between each layer for a braze material. The layers were processed by Tech Etch of Plymouth Mass., using standard photo-etching techniques and were etched in such a way that the cross-sectional shape of the etched walls were perpendicular to the top and bottom surfaces of the foil (commonly referred to as straight sidewalls). The method chosen to bond the grid layers together was a metal-to-metal brazing technique described earlier in detail as one of two exemplary methods of bonding layers together (eutectic braze alloy). The brazed lamination was then electro-plated with a coating of hard nickel, also described earlier. Step 2: Creating a derived mold: An RTV mold was made from the stack laminated mold from step 1. Silastic® M RTV Silicone Rubber was chosen as the base material for the derived mold. This particular material was used to demonstrate the resolution capability, release properties, multiple castings, and dimensional repeatability of the derived mold from the laminated mold. Silastic M has the hardest durometer of the Silastic® family of mold making materials. The derived mold was configured as an open face mold. The fixture used to create the derived casting mold is shown in FIG. 32 and was comprised of a precision machined aluminum ring 32010, precision ground glass plates 32020 and 32030, rubber gaskets 32040 and 32050, and the laminated mold 32060. The base of the fixture 32020 was a 5 inch square of 1 inch thick plexiglass. On the top surface of the plexiglass base was a 1″ thick, 3 inch diameter glass substrate 32030. The base and the glass substrate were separated by a 1/16 inch thick, 4.5 inch diameter rubber gasket 32040. An additional 3.0 inch rubber gasket 32050 was placed on the top surface of the glass substrate 32030. The rubber gaskets helped prevent unwanted flashing of molten material when casting. The laminated mold 32060 was placed on the top gasket. The shape and thickness of the glass created the entrance area where the casting material was poured into the mold. The material formed in this cavity was referred to as a controlled backing. It served as a release aid for the final casting, and could later be removed from the casting in a final machining process. A precision machined aluminum ring 32010 having a 4.5 inch outside diameter and a 4 inch inside diameter was placed over the master subassembly and interfaced with the lower 4.5 inch diameter rubber gasket. As illustrated in FIG. 32, the height of the ring was configured so that the distance from the top surface of the master to the top of the ring was twice the distance from the base of the fixture to the top of the laminated mold. The additional height allowed the RTV material to rise up during the degassing process. The ring portion of the fixture assembly was used to locate the pouring of the mold material into the assembly, captivate the material during the curing process, and provide an air escape while the mold material was degassed using vacuum. The fixture was configured in such a way that all sides surrounding the laminated mold were equal and common, in order to limit the effects or stresses put on the lamination from the mold material. The Silastic® M RTV Silicone Rubber used for the mold fabrication was prepared in accordance with the manufacturer's recommendations, using the process described earlier in example 1, step 2. The laminated mold was characterized, before and after the mold-making process, by measuring the average pitch distance of the cells, the septal wall widths, overall distance of the open grid area, and the finished thickness of the part. These dimensions were also measured on the derived casting mold and compared with the laminated mold before and after the mold-making process. The following chart lists the dimensions of the lamination before and after the mold-making and the same dimensions of the derived RTV mold. All dimensions were taken using a Nikon MM-11 measuring scope at 200× magnification. These dimensions demonstrated the survivability of the master and the dimensional repeatability of the mold. MasterMasterLaminationLamination(beforeRTV Mold(afterGrid Featuremold-making)Silastic ® Mmold-making)Septal Wall0.1700.1610.170Width (mm)Cell Width2.000 × 2.0002.010 × 2.0102.000 × 2.000(mm)Cell Pitch2.170 × 2.1702.171 × 2.1712.170 × 2.170(mm)Pattern area21.530 × 21.53021.549 × 21.54921.530 × 21.530(mm)Thickness2.8622.8332.862(mm) Step 3: Casting the final collimator: A fine-featured lead collimator was produced from the derived RTV silicone mold described in step 2. FIG. 43 is a side view of an assembly 43000 that includes an open face mold 43010 that was used to produce a casting 43020 from CERROBASE™ alloy. Casting 43020 was dimensionally measured and compared to the laminated mold 43010. The backing 43030 of casting 43020 was 6 millimeters in thickness and was removed using a machining process. Grid FeaturesMaster LaminationCast CollimatorSeptal Wall Width (mm)0.1700.165Cell Width (mm)2.000 × 2.0002.005 × 2.005Cell Pitch (mm)2.170 × 2.1702.170 × 2.170 The first step of the casting process was to pre-heat the derived RTV mold to a temperature of 275 degrees F., which was 20 degrees above the melting point of the CERROBASE™ alloy. The mold was placed on a heated aluminum substrate, which maintained the mold at approximately 275 degrees F. when it was placed in the vacuum bell jar. In certain casting procedures, the material can be forced into the mold in a rapid fashion, and cooled and removed quickly. In this case, the casting process was somewhat slowed in order to fully fill and evacuate the air from the complex cavity geometry of the mold. The CERROBASE™ was then heated in an electric melting pot to a temperature of 400 degrees F., which melted the alloy sufficiently above its melt point to remain molten during the casting process. The next step was to pour the molten alloy into the mold, in such a way as to aid in the displacement of any air in the cavity. This was accomplished by tilting the mold at a slight angle and beginning the pour at the lowest point in the cavity section of the mold. It was found that if the mold was placed in a flat orientation while pouring the molten alloy, significant amounts of air were trapped, creating problems in the degassing phase of the process. Instead, once the mold was sufficiently filled with the molten alloy, the mold was slightly vibrated or tapped in order to expel the largest pockets of air. The mold, on the heated aluminum substrate, was then placed in the vacuum bell jar, pumped down to atmosphere of 25-28 inches of mercury for 2 minutes, which was sufficient time to evacuate any remaining air pockets. The mold was then removed from the vacuum bell jar and submersed in a quenching tank filled with water cooled to a temperature of 50 degrees F. The rapid quench produced a fine crystalline grain structure when the casting material solidified. The casting was then removed from the flexible mold by grasping the backing 43030, by mechanical means or by hand, and breaking the casting free of the mold using an even rotational force, releasing the casting gradually from the mold. The final process step was removing the backing 43030 from the attached surface of the grid casting 43020 to the line shown in FIG. 43. Prior to removing the backing, the grid structure of the final casting 43020 was filled or potted with a machineable wax, which provided the structural integrity needed to machine the backing without distorting the fine walls of the grid casting. The wax was sold under the product name MASTER™ Water Soluble Wax by the Kindt-Collins Corporation, of Cleveland, Ohio. The wax was melted at a temperature of 160-180 degrees F., and poured into the open cells of the cast grid. Using the same technique described above, the wax potted casting was placed in vacuum bell jar and air evacuated before being cooled. The wax was cooled to room temperature and was then ready for the machining of the backing. A conventional surface grinder was used to first rough cut the backing from the lead alloy casting. The remaining casting was then placed on a lapping machine and lapped on the non-backing side of the casting using a fine abrasive compound and lapping wheel. The non-backing side of the casting was lapped first so that the surface was flat and parallel to within 0.010-0.015 millimeters to the adjacent cast grid cells. The rough-cut backing surface was then lapped using the same abrasive wheel and compound so that it was flat and parallel to within 0.100-0.015 millimeters of the non-backing side of the casting. A thickness of 2.750 millimeters was targeted as the final casting thickness. Upon completion of the lapping process, the casting was placed in an acid solution, comprised of 5% dilute HCL and water, with mild agitation until the wax was fully dissolved from the cells of the casting. In an alternative embodiment, individual castings could also be stacked, aligned, and/or bonded to achieve thicker, higher aspect ratio collimators. Such collimators, potentially having a thicknesses measured in centimeters, can be used in nuclear medicine. A non-planar collimator can have several applications, such as, for example, in a CT environment. To create such an example of such a collimator, the following process was followed: Step 1: Creating a laminated mold: For this example, a laminated mold was designed and fabricated using the same process and vendors described in Example 1, step 1. The laminated mold was designed to serve as the basis for a derived non-planar casting mold. The laminated mold was designed and fabricated with outside dimensions of 73.66 mm×46.66 mm, a 5 mm border around a grid area having 52×18 open cell array. The cells were 1 mm×1.980 mm separated by 0.203 septal walls. The layers for the laminated mold were bonded using the same process described in Example 1, step 1 (thermo-cured epoxy). The dimensions of the laminated mold were specified to represent a typical collimator for CT x-ray scanning. Silastic® J RTV Silicone Rubber was chosen as a base material to create a derived non-planar casting mold because of its durometer which allowed it to more easily be formed into a non-planar configuration. The laminated mold and fixture was configured as an open face mold. Step 2: Creating a derived non-planar mold: Silastic® J RTV Silicone Rubber was used for the derived mold fabrication and was prepared in accordance with the manufacturers recommendations, using the process described earlier in example 1, step 2. FIG. 44 is a top view of casting assembly 44000. FIG. 45 is a side view of casting assembly 44000. The derived RTV mold 44010 was then formed into a non-planar configuration as shown in FIG. 45. The surface 44020 of casting fixture base 44030 defined a 1-meter radius arc to which mold 44010 was attached. A 1-meter radius was chosen because it is a common distance from the x-ray tube to the collimator in a CT scanner. Mold 44010 was fastened to the convex surface 44020 of casting base 44030 with a high temperature epoxy adhesive. A pour frame 44040 was placed around casting fixture base 44030. Pour frame 44040 had an open top to allow pouring the casting material to a desired fill level and to allow evacuating the air from the casting material. The laminated mold was characterized, before and after producing the derived non-planar mold, by measuring the average pitch distance of the cells, the septal wall widths, overall distance of the open grid area, and the finished thickness of the part. These dimensions were also measured on the derived non-planar mold and compared with the master before and after the mold-making process. The following chart lists the dimensions of the master lamination before and after the mold-making and the same dimensions of the RTV mold in the planar state and curved state. All dimensions are in millimeters and were taken using a Nikon MM-11 measuring scope at 200× magnification. MasterLaminationRTV MoldRTV MoldGrid(before(planar)(curved)Featuresmold-making)Silastic ® JSilastic ® JSeptal Wall0.2030.1830.193Cell Width1.980 × 1.0002.000 × 1.0202.000 × 1.020Cell Pitch2.183 × 1.2032.183 × 1.2032.183 × 1.213Pattern area39.091 × 62.35339.111 × 62.37339.111 × 62.883Thickness7.6207.5447.544 measured in the direction of curvature. Step 3: Casting a non-planar collimator: The derived non-planar RTV mold described in step 2, was used to create castings. Using the derived non-planar mold, the castings were produced from CERROBASE™ alloy and were dimensionally measured and compared to the laminated mold. Grid FeaturesMaster LaminationCast CollimatorSeptal Wall Width (mm)0.2030.197Cell Width (mm)1.000 × 1.9801.006 × 1.986Cell Pitch (mm)1.203 × 2.1831.203 × 2.183measured in the direction of curvature. The process used to fill the derived non-planar mold with the casting alloy and the de-molding of the casting was the same process described in Example 6. The final process step included the removal of the backing from the grid casting. A wire EDM (electrode discharge machining) process was found to be the most effective way to remove the backing from the casting, primarily due to the curved configuration of the casting. The wire EDM process used an electrically charged wire to burn or cut through the casting material, while putting no physical forces on the parts. In this case, a fine 0.003 inch molybdenum wire was used to cut the part, at a cutting speed of 1 linear inch per minute. This EDM configuration was chosen to limit the amount of recast material left behind on the cut surface of the part, leaving the finished septal walls with a smooth surface finish. The casting was fixtured and orientated so that the radial cutting of the backing was held parallel to the curved surface of the casting, which was a 1 meter radius. Another exemplary application of embodiments of the present invention is the fabrication of a mammography scatter reduction grid. In this example, a derived clear urethane mold for a fine-featured focused grid was made using a photo-etched stack lamination for the master model. For making this mold, the master was designed and fabricated using the lamination process detailed in Example 7. A clear urethane casting material was chosen as an example of a cast grid in which the mold was left intact with the casting as an integral part of the grid structure. This provided added strength and eliminated the need for a fragile or angled casting to be removed from the mold. Step 1: Creating a laminated mold: The laminated mold was fabricated from photo-etched layers of copper. The mold was designed to have a 63 mm outside diameter, a 5 mm border around the outside of the part, and a focused 53 mm grid area. FIG. 46 is a top view of a grid area 46000, which was comprised of hexagonal cells 46010 that were 0.445 mm wide, separated by 0.038 mm septal walls 46020. The cells were focused from the center of the grid pattern to a focal point of 60 centimeters, similar to that shown in FIG. 42B. The grid was made from 35 layers of 0.050 mm thick stainless steel, which when assembled created a 4:1 grid ratio. Each grid layer utilized a separate photo-mask in which the cells are arrayed out from the center of the grid pattern at a slightly larger distance from layer to layer. This created the focused geometry as shown in FIG. 42B. With this cell configuration, the final casting produced a hexagonal focused grid with a transmission of about 82%. The photo-masks and etched layers were produced using the same vendors and processes described in example 1, step 1. Step 2: Creating a derived urethane mold: Urethane mold material was chosen for its high-resolution, low shrink factor, and low density. Because of its low density, the urethane is somewhat transparent to the transmission of x-rays. The mold material, properties, and process parameters were as described earlier in example 4, step 4. The fixture used to create the derived urethane casting mold was the same as that described in Example 6, step 2. Before assembling the mold fixture, the laminated mold was sprayed with a mold release, Stoner E236. The fixture was assembled as shown in FIG. 32 and heated to 125 degrees F. Then it was filled with the Water Clear urethane and processed using the same parameters described in example 4, step 4. The laminated mold was characterized, before and after making the derived mold, by measuring the average pitch distance of the cells, the septal wall widths, overall distance of the open grid area, and the finished thickness of the lamination. These dimensions were also measured on the derived urethane casting mold and compared with the lamination before and after the mold-making process. The following chart lists the dimensions-of the lamination before and after the mold-making and the same dimensions of the urethane mold. All dimensions were in millimeters and were taken using a Nikon MM-11 measuring scope at 200× magnification. MasterMasterLaminationUrethaneLamination(beforeCasting System(afterGrid Featuresmold-making)Water Clearmold-making)Septal Wall Width0.0380.0370.038Cell Width0.4450.4460.445(hexagonal)(hexagonal)(hexagonal)Cell Pitch0.4830.4830.483Pattern area (mm2)53.000 52.735 53.000 Thickness1.7501.7291.750 Step 3: Casting the anti-scatter grid: A focused scatter reduction grid was produced by casting a lead alloy, CERROLOW-117™ alloy into the derived urethane mold described in step 2. The backing thickness of the casting was 2 millimeters and was removed using a surface grinding process. The first step of the process was to pre-heat the derived urethane mold to a temperature of 137 degrees F., which was 20 degrees above the 117 degree melting point of the CERROLOW™ alloy. The mold was placed on a heated aluminum substrate, which maintained the mold to approximately 117 degrees F. when it was placed in the vacuum bell jar. The CERROLOW™ was then heated in an electric melting pot to a temperature of 120 degrees F., which melted the alloy sufficiently above the melt point of the material, keeping the material molten during the casting process. The process steps for filling the mold were the same as those described in Example 6, step 3. The CERROLOW™ alloy was chosen for casting because of its high resolution capability, low melting point, and relatively high density. The urethane mold was left remaining to provide structural integrity for the fine lead alloy features. The urethane is also somewhat transparent to x-rays because of its low density (1 g/cm3) compared to the casting alloy. Additional collimator samples have been produced using the same process described in Example 6 above, with the exception of the casting alloy and that it was loaded with tungsten powder prior to the casting process. The tungsten powder (KMP115) was purchased through the Kulite Tungsten Corporation of East Rutherford, N.J. CERROLOW™ alloy was loaded to raise the net density of the alloy from a density of 9.16 grams per cubic centimeter to 13 grams per cubic centimeter. In certain radiological applications, elimination of secondary scattered radiation, also known as Compton scatter, and shielding can be an objective. The base density of the CERROLOW™ alloy can be sufficient on its own to absorb the scattered radiation, but the presence of the tungsten particles in the septal walls can increase the density and improve the scatter reduction performance of the part. The casting was dimensionally measured and compared to the laminated mold used to create the derived RTV mold. Grid FeaturesMaster LaminationCast CollimatorMaterialCopperCERROLOW-117 PlusTungsten PowderDensity (g/cc)8.96 12.50 Septal Wall Width0.0380.036Cell Width0.4450.447(hexagonal)(hexagonal)Cell Pitch0.4830.483*all dimensions are in millimeters. Prior to casting, the tungsten powder was loaded or mixed into the CERROLOW™ alloy. The first step was to super-heat the alloy to 2-3 times its melting point temperature (between 234-351 degrees F.), and to maintain this temperature. The tungsten powder, having particle sizes ranging from 1-15 microns in size, was measured by weight to 50% of the base alloy weight in a furnace crucible. A resin-based, lead-compatible soldering flux was added to the tungsten powder to serve as a wetting agent when combining the powder and the alloy. The resin flux was obtained from the Indium Corporation of America of Utica N.Y., under the name Indalloy Flux # 5RMA. The flux and the powder were heated to a temperature of 200 degrees F. and mixed together after the flux became liquid. The heated CERROLOW™ alloy and the fluxed powder then were combined and mixed using a high-shear mixer at a constant temperature of 220 degrees F. The net density of the alloy loaded with the powder was measured at 12.5 grams per cubic centimeter. The loaded alloy was molded into the derived RTV mold, and finished machined using the same process described in Example 6. This example demonstrates a structure that could be co-aligned with a cast collimator. The structure could be filled with detector materials, such as a scintillator, for pixilation purposes. Ceramic was chosen for high temperature processing of the scintillator materials, which are normally crystals. Additional cast samples have been produced using a castable silica ceramic material using the same mold described in Example 7 above. The ceramic material, Rescor™-750, was obtained from the Cotronics Corporation of Brooklyn, N.Y. The ceramic material was prepared prior to casting per the manufacturer's instructions. This included mixing the ceramic powder with the supplied activator. Per the manufacturer's instructions, an additional 2% of activator was used to reduce the viscosity of the mixed casting ceramic, in order to aid in filling the fine cavity features of the mold. The mold was filled and degassed using a similar process and the same mold and non-planar fixture as Example 7 above, covered with a thin sheet of plastic, and allowed to cure for 16 hours at room temperature. The ceramic casting then was removed from the RTV mold and post cured to a temperature of 1750 degrees F., heated at a rate of 200 degrees F. per hour. Post-curing increased the strength of the cast grid structure. The ceramic casting then was ready for the final grinding and lapping process for the removal of the backing. Additional Fields of Use Additional exemplary fields of use, illustrative functionalities and/or technology areas, and representative devices are contemplated for various embodiments of the invention, as partially listed below. Note that any such device, and many others not specifically listed, can utilize any aspect of any embodiment of the invention as disclosed herein to provide any of the functionalities in any of the fields of use. For example, in the automotive industry, inertial measurement can be provided by an accelerometer, at least a component of which that has been fabricated according to a method of the present invention. Likewise, in the telecommunications field, one or more components of an optical switch, and possibly an entire optical switch, can be fabricated according to a method of the present invention. Moreover, note that unless stated otherwise, any device fabricated according to any method disclosed herein can have any dimension, aspect ratio, geometric shape, configuration, feature, attribute, material of construction, functionality, and/or property disclosed herein. Among the many conceivable fields of use, technology areas, and devices are: Automotive Industry Technology Areas: Inertial measurement Micro-scale Power generation Pressure measurement Fluid dynamics Representative Devices: accelerometers rate sensors vibration sensors pressure sensors fuel cells fuel processors nozzle technology valves and regulators pumps filters relays actuators heaters Avionics Industry Technology Areas: Inertial measurement RF technology Communications Active structures and surfaces Representative Devices: conformable MEMS (active and passive) micro-satellite components micro-thrusters RF switches antennas phase shifters displays optical switches accelerometers rate sensors vibration sensors pressure sensors fuel cells fuel processors nozzle technology valves and regulators pumps filters relays actuators heaters Biological and Biotechnology Technology Areas: Micro-fluidics Microbiology DNA assays Chemical testing Chemical processing Lab-on-a-chip Tissue engineering Analytical instrumentation Bio-filtration Test and measurement Bio-computing Biomedical imaging Representative Devices: biosensors bioelectronic components reaction wells microtiterplates pin arrays valves pumps bio-filters tissue scaffolding cell sorting and filtration membranes Medical (diagnostic and therapeutic) Technology Areas: Imaging Computed tomography Angiography Fluoroscopy Radiography Interventional radiography Orthopedic Cardiac and vascular devices Catheter based tools and devices Non-invasive surgical devices Medical tubing Fasteners Surgical cutting tools Representative Devices: airways balloon catheters clips compression bars drainage tubes ear plugs hearing aids electrosurgical hand pieces and tubing feeding devices balloon cuffs wire/fluid coextrusions lumen assemblies infusion sleeves/test chambers introducer tips/flexible sheaths seals/stoppers/valves septums stents shunts membranes electrode arrays ultra-sound transducers infra-red radiation sensors radiopaque targets or markers collimators scatter grids detector arrays Military Technology Areas: Weapon safeing Arming and fusing Miniature analytical instruments Biomedical sensors Inertial measurement Distributed sensing and control Information technology Representative Devices: MEMS fuse/safe-arm devices ordinance guidance and control devices gyroscopes accelerometers disposable sensors spectrometers active MEMS surfaces (large area) micro-mirror MEMS displays Telecommunications Technology Areas: Optical switches Displays Adaptive optics Representative Devices: micro-relays optical attenuators photonic switches micro-channel plates optical switches displays Additional detailed examples of some of the many possible embodiments of devices and/or device components that can be fabricated according to a method of the present invention are now provided. Microvalves Microvalves can be enabling components of many microfluidic systems that can be used in many industry segments. Microvalves are generally classified as passive or active valves, but can share similar flow characteristics through varied orifice geometries. Diaphragm microvalves can be useful in many fluidic applications. FIG. 48A is a top view of an array 48010 of generic microdevices 48000. FIG. 48B is a cross section of a particular microdevice 48000 in this instance a diaphragm microvalve, taken along section lines 48-48 of FIG. 48A, the microvalve including diaphragm 48010 and valve seat 48020, as shown in the open position. FIG. 49 is a cross section of the diaphragm microvalve 48000, again taken along section lines 48-48 of FIG. 48A, the microvalve in the closed position. The flow rate through diaphragm microvalve 48000 can be controlled via the geometric design of the valve seat, which is often referred to as gap resistance. The physical characteristics of the valve seat, in combination with the diaphragm, can affect flow characteristics such as fluid pressure drop, inlet and outlet pressure, flow rate, and/or valve leakage. For example, the length, width, and/or height of the valve seat can be proportional to the pressure drop across the microvalve's diaphragm. Additionally, physical characteristics of the diaphragm can influence performance parameters such as fluid flow rate, which can increase significantly with a decrease in the Young's modulus of the diaphragm material. Valve leakage also can become optimized with a decrease in the Young's modulus of the diaphragm, which can enable higher deflection forces, further optimizing the valve's overall performance and/or lifetime. Typical microvalve features and specifications can include a valve seat: The valve seat, which is sometimes referred to as the valve chamber, can be defined by its size and the material from which it is made. Using an exemplary embodiment of a method of the present invention, the dimensions of the chamber can be as small as about 10 microns by about 10 microns if square, about 10 microns in diameter if round, etc., with a depth in the range of about 5 microns to millimeters or greater. Thus, aspect ratios of 50, 100, or 200:1 can be achieved. The inner walls of the chamber can have additional micro features and/or surfaces which can influence various parameters, such as flow resistance, Reynolds number, mixing capability, heat exchange fouling factor, thermal and/or electrical conductivity, etc. The chamber material can be selected for application specific uses. As examples, a ceramic material can be used for high temperature gas flow, or a chemical resistant polymer can be used for chemical uses, and/or a bio-compatible polymer can be used for biological uses, to name a few. Valve chambers can be arrayed over an area to create multi-valve configurations. Each valve chamber can have complex inlet and outlet channels and/or ports to further optimize functionality and/or provide additional functionality. Typical microvalve features and specifications can also include a diaphragm: The diaphragm can be defined by its size, shape, thickness, durometer (Young's modulus), and/or the material from which it is made. Using an exemplary embodiment of a method of the present invention, the dimensions of the diaphragm can be as small as about 25 microns by about 25 microns if square, about 25 microns in diameter if round, etc., with thickness of about 1 micron or greater. The surface of one side or both sides of the diaphragm could have micro features and/or surfaces to influence specific parameters, such as diaphragm deflection and/or flow characteristics. The diaphragm can be fabricated as a free form device that is attached to the valve in a secondary operation, and/or attached to a substrate. Diaphragms can be arrayed to accurately align to a matching array of valve chambers. Potential performance parameters can include valve seat and diaphragm material, diaphragm deflection distance, inlet pressure, flow, and/or lifetime. Micropumps FIGS. 50 and 51 are cross-sectional views of a particular micro-device 48000, in this case a typical simplified micropump, taken along section lines 48-48 of FIG. 48A. Micropumps can be an enabling component of many microfluidic systems that can be used in many industry segments. Reciprocating diaphragm pumps are a common pump type used in micro-fluidic systems. Micropump 50000 includes two microvalves 50010 and 50020, a pump cavity 50030, valve diaphragms 50040 and 50050, and actuator diaphragm 50060. At the initial state of pump 50000, the actuation is off, both inlet and outlet valves 50010 and 50020 are closed, and there is no fluid flow through pump 50000. Once actuator diaphragm 50060 is moved upwards, the cavity volume will be expanded causing the inside pressure to decrease, which opens inlet valve 50010 and allows the fluid to flow into and fill pump cavity 50030, as seen in FIG. 50. Then actuator diaphragm 50060 moves downward, shrinking pump cavity 50030, which increases the pressure inside cavity 50030. This pressure opens outlet valve 50020 and the fluid flows out of the pump cavity 50030 as seen in FIG. 51. By repeating the above steps, continuous fluid flow can be achieved. The actuator diaphragm can be driven using any of various drives, including pneumatic, hydraulic, mechanical, magnetic, electrical, and/or piezoelectrical, etc. drives. Typical microvalve features and specifications can include any of the following, each of which are similar to those features and specifications described herein under Microvalves: Valve seats Valve actuators (diaphragm) Cavity chamber Actuator diaphragm Potential performance parameters can include valve seat, chamber material, actuator diaphragm material, valve diaphragm material, deflection distance for actuator, deflection distance for valve diaphragms, inlet pressure, outlet pressure, chamber capacity, flow rate, actuator drive characteristics (pulse width, frequency, and/or power consumption, etc.), and/or lifetime. Microwells and Microwell Arrays Microwells can be an enabling component in many devices used for micro-electronics, micro-mechanics, micro-optics, and/or micro-fluidic systems. Precise arrays of micro-wells, potentially having hundreds to thousands of wells, can further advance functionality and process capabilities. Microwell technology can be applied to DNA micro-arrays, protein micro-arrays, drug delivery chips, microwell detectors, gas proportional counters, and/or arterial stents, etc. Fields of use can include drug discovery, genetics, proteomics, medical devices, x-ray crystallography, medical imaging, and/or bio-detection, to name a few. For example, using exemplary embodiments of the present invention, microwells can be engineered in the third (Z) dimension to produce complex undercuts, pockets, and/or sub-cavities. Wells can also be arrayed over various size areas as redundant or non-redundant arrays. These features can include the dimensional accuracies and/or tolerances described earlier. Also, a range of surface treatments within the well structure are possible that can enhance the functionality of the well. DNA Microarrays: Scientists can rely on DNA microarrays for several purposes, including 1) to determine gene identification, presence, and/or sequence in genotype applications by comparing the DNA on a chip; 2) to assess expression and/or activity level of genes; and/or 3) to measure levels of proteins in protein based arrays, which can be similar to DNA arrays. DNA microarrays can track tens of thousands of reactions in parallel on a single chip or array. Such tracking is possible because each probe (a gene or shorter sequence of code) can be deposited in an assigned position within the cell array. A DNA solution, representing a DNA sample that has been chopped into constituent sequences of code, can be poured over the entire array (DNA or RNA). If any sequence of the sample matches a sequence of any probe, the two will bind, and non-binding sequences can be washed away. Because each sequence in the sample or each probe can be tagged or labeled with a fluorescent, any bound sequences will remain in the cell array and can be detected by a scanner. Once an array has been scanned, a computer program can convert the raw data into a color-coded readout. Protein Microarrays: The design of a protein array is similar to that of a DNA chip. Hundreds to thousand of fluorescently labeled proteins can be placed in specific wells on a chip. The proteins can be deposited on the array via a pin or array of pins that are designed to draw fluidic material from a well and deposit it on the inside of the well of the array. The position and configuration of the cells on the array, the pins, and the wells are located with the accuracy needed to use high-speed pick-and-place robotics to move and align the chip over the fluidic wells. A blood sample is applied to the loaded array and scanned for bio-fluorescent reactions using a scanner. Certain embodiments of the invention enable DNA or Protein microarrays having a potentially large number of complex 3-dimensional wells to be fabricated using any of a range of materials. For example, structures can be fabricated that combine two or more types of material in a microwell or array. Additional functionality and enhancements can be designed into a chip having an array of microwells. Wells can be produced having cavities capable of capturing accurate amounts of fluids and/or high surface-to-volume ratios. Entrance and/or exit configurations can enhance fluid deposition and/or provide visual enhancements to scanners when detecting fluorescence reactions. Very precise well locations can enable the use of pick and place robotics when translating chips over arrays of fluidic wells. Certain embodiments of the invention can include highly engineered pins and/or pin arrays that can be accurately co-aligned to well arrays on chips and/or can have features capable of efficiently capturing and/or depositing fluids in the wells. Arterial Stents: Stents are small slotted cylindrical metal tubes that can be implanted by surgeons to prevent arterial walls from collapsing after surgery. Typical stents have diameters in the 2 to 4 millimeter range so as to fit inside an artery. After insertion of a stent, a large number of patients experience restenosis—a narrowing of the artery—because of the build-up of excess cells around the stent as part of the healing process. To minimize restenosis, techniques are emerging involving the use of radioactive elements or controlled-release chemicals that can be contained within the inner or outer walls of the stent. Certain embodiments of the invention can provide complex 3-dimensional features that can be designed and fabricated into the inside, outside, and/or through surfaces of tubing or other generally cylindrical and/or contoured surfaces. Examples 4 and 5 teach such a fabrication technique for a 3 mm tube. Certain embodiments of the invention can allow the manufacture of complex 2-dimensional and/or 3-dimensional features through the wall of a stent. Micro surfaces and features can also be incorporated into the stent design. For example, microwells could be used to contain pharmaceutical materials. The wells could be arrayed in redundant configurations or otherwise. The stent features do not have to be machined into the stent surface one at a time, but can be applied essentially simultaneously. From a quality control perspective, features formed individually typically must be 100% inspected, whereas features produced in a batch typically do not. Furthermore, a variety of application specific materials (e.g., radio-opaque, biocompatible, biosorbable, biodissolvable, shape-memory) can be employed. Microwell Detectors: Microwells and microwell arrays can be used in gas proportional counters of various kinds, such as for example, in x-ray crystallography, in certain astrophysical applications, and/or in medical imaging. One form of microwell detector consists of a cylindrical hole formed in a dielectric material and having a cathode surrounding the top opening and anode at the bottom of the well. Other forms can employ a point or pin anode centered in the well. The microwell detector can be filled with a gas such as Xenon and a voltage can be applied between the cathode and anode to create a relatively strong electric field. Because of the electric field, each x-ray striking an atom of the gas can initiate a chain reaction resulting in an “avalanche” of hundreds or thousands of electrons, thereby producing a signal that can be detected. This is known as a gas electron multiplier. Individual microwell detectors may be used to detect the presence and energy level of x-rays, and if arrays of microwell detectors are employed, an image of the x-ray source can be formed. Such arrays can be configured as 2-dimensional and/or 3-dimensional arrays. Certain embodiments of the invention can enable arrays of complex 3-dimensional wells to be fabricated and bonded or coupled to other structures such as a cathode material and anode material. It is also possible to alter the surface condition of the vertical walls of the wells, which can enhance the laminar flow of electrons in the well. A number of possible materials can be used to best meet the needs of a particular application, enhancing parameters such as conductivity, die-electrical constant, and/or density. Certain embodiments of the invention can further enable the hybridizing of micro-electronics to a well array, in particular because of accurate co-alignment between the micro-electronic feature(s), and/or the structural elements of the well. Typical Microwell Features, Specifications and Potential Performance Parameters FIG. 52 is a top view of an exemplary microwell array 52000, showing microwells 52010, and the X- and Y-axes. Array 52000 is shown as rectangle, but could be produced as a square, circle, or any other shape. Either of the array's dimensions as measured along the X- or Y-axes can range from 20 microns to 90 centimeters. Microwells 52010 are shown having circular perimeters, but could also be squares, rectangles, or any other shape. Array 52000 is shown having a redundant array of wells 52010, but could be produced to have non-redundant wells. The positional accuracy of wells 52010 can be accurate to the specifications described herein for producing lithographic masks. Wells can range in size from 0.5 microns to millimeters, with cross-sectional configurations as described herein. Using certain embodiments of a method of the present invention, certain materials can be used to produce microwell arrays for specific uses. For example, a ceramic material can be used for high-temperature gas flow, a chemical resistant polymer can be used for chemical uses, and/or a bio-compatible polymer can be used for biological uses, to name a few. Specialty composite materials can enhance application specific functionality by being conductive, magnetic, flexible, hydrophilic, hydrophobic, piezoelectric, to name a few. Using an embodiment of a method of the present invention, microwells with certain 3-dimensional cross-sectional shapes can be produced. FIG. 52 is a top view of an exemplary array 52000 of microwells 52010. FIG. 53 is a cross-sectional view, taken at section lines 52-52 of FIG. 52, of an exemplary microwell 53000 having an entrance 53010. Entrance 53010 is shown having a tapered angle, which could be angled from 0 degrees to nearly 180 degrees. Entrance 53010 is also shown having a different surface than well area 53020. Well area 53020 can be square, round, rectangular, or any other shape. Well area 53020 can range in size from 0.5 microns to millimeters in width and can be dimensionally controlled in the Z-axis to have aspect ratios of from about 50:1 to about 100:1. FIG. 54 is a cross-sectional view, taken at section lines 52-52 of FIG. 52, of an alternative exemplary microwell 54000 that defines an entrance 54010, a well 54020, and an exit 54030. Microwell 54000 can be used in applications that require fluids that are conveyed from below or above the entrance 54010 and/or exit 54030, and deposited in well 54020. Using an embodiment of a method of the present invention, microwell 54000 can be produced so that well 54020 is hydrophilic and entrance 54010 and exit 54030 are hydrophobic to, for example, enable the deposition of fluid into well 54020, and discourage the fluid deposition, retention, and/or accumulation on entrance 54010, on exit 54030, and/or on the chip's surface. For uses where microelectronic controls or chips are employed, the material surrounding and/or defining entrance 54010 and/or 54030 can be conductive or non-conductive, as required. Well 54020 can be dimensioned to accurately contain a pre-determined amount of fluid. The shape and size of corner feature 54040 can be defined to encourage the discharge of a fluid material from a fluidic channel on a pin, when a pin is produced using any of certain embodiments of the invention. For example, pins can be produced having fluidic channels or undercuts that are positioned radially at the end of the pin. The undercuts can serve as reservoirs that increase surface area-to-volume ratios and/or hold accurate amounts of fluids. If the undercuts are designed to be relatively flexible and larger than the opening dimension at feature 54040, fluid can be squeezed from the reservoir as the fluid passes by corner feature 54040. Entrance 54010 can have an angle that promotes the visibility of a material, such as a fluid, in well 54020. The material surrounding and/or defining well 54020 can be fabricated to have micro-surface features to increase the well's surface area-to-volume ratio. FIG. 55 is a top view of an exemplary microwell 55000 showing a well area 55010 and sub-cavities 55020. FIG. 56 is a cross-sectional view, taken at section lines 56-56 of FIG. 55, of microwell 55000 showing well 55010 and sub-cavities 55020. Well 55010 can extend through the material that defines it, as shown in FIG. 56, or can be a closed well having a solid floor. Sub-cavities 55020 can be incorporated within a well to, for example, increase an area of the surface(s) bordering the well, a volume, and/or surface area-to-volume ratio of the well. Sub-cavities 55020 can be continuous rings as shown in FIG. 55. Alternatively, sub-cavities 55020 can be discrete pockets forming sub-wells within well 55010. Sub-cavities 55020 can be positioned on a horizontal floor or subfloor of well 55010 as shown in FIG. 55, on the vertical walls of well 55010, and/or on another surface. Sub-cavities 55020 can have circular, square, rectangular, and/or any of a variety of other cross-sectional shapes. Sub-cavities 55020 can also be positioned to provide an enhanced visual perspective of a deposited material from which could be angled from 0 degrees to nearly 180 degrees, such as an approximately perpendicular angle, so as to enhance scanning performance or resolution. Filtration Filtration can be an important element in many industries including medical products, food and beverage, pharmaceutical and biological, dairy, waste water treatment, chemical processing, textile, and/or water treatment, to name a few. Filters are generally classified in terms of the particle size that they can separate. Micro-filtration generally refers to separation of particles in the range of approximately 0.01 microns through 20 microns. Separation of larger particles than approximately 10-20 microns is typically referred to as particle separation. There are two common forms of filtration, cross-flow and dead-end. In cross-flow separation, a fluid stream runs parallel to a membrane of a filter while in dead-end separation, the filter is perpendicular to the fluid flow. There are a very large number of different shapes, sizes, and materials used for filtration depending on the particular application. Certain embodiments of the invention can be filters suitable for micro-filtration and/or particle filtration applications. Certain embodiments of the invention allow fabrication of complex 2-dimensional and/or 3-dimensional filters offering redundant or non-redundant pore size, shape, and/or configuration. For example, a circular filter can have an array of redundant generally circular through-features, each through-feature having a diameter slightly smaller than a target particle size. Moreover, the through-feature can have a tapered, countersunk, and/or undercut entrance, thereby better trapping any target particle that encounters the through-feature. Further, the cylindrical walls defined by the through-feature can have channels defined therein that are designed to allow a continued and/or predetermined amount of fluid flow around a particle once the particle encounters the through-feature. The fluid flow around the particle can create eddys vortices, and/or other flow patterns that better trap the particle against the filter. Certain embodiments of the filter can have features that allow the capture of particles of various sizes at various levels of the filter. For example, an outer layer of the filter can capture larger particles, a middle layer can capture mid-sized particles, and a final layer can capture smaller particles. There are numerous techniques for accomplishing such particle segregation, including providing through-features having tapered, stepped, and/or diminishing cross-sectional areas. In certain embodiments, the filter can include means for detecting a pressure drop across the filter, and/or across any particular area, layer, and/or level of the filter. For example, in a filter designed to filter a gas such as air, micro pitot tubes can be fabricated into each layer of the filter (or into selected layers of the filter). Such pressure measurement devices can be used to determine the pressure drop across each layer, to detect the level of “clogging” of that layer, and/or to determine what size and/or concentration of particles are entrapped in the filter. Further, certain embodiments of the invention allow for fabrication of filters in a wide range of materials including metals, polymers, plastics, ceramics, and/or composites thereof. In biomedical applications, for instance, a biocompatible material can be used that will allow filtration of blood or other body fluids. Using certain embodiments of the invention, filtration schemes can be engineered as planar or non-planar configurations. Sorting Sorting can be considered a special type of filtration in which particles, solids, and/or solids are separated by size. In biomedical applications for example, it may be desirable to sort blood or other types of cells by size and deliver different sizes to different locations. Certain embodiments of the invention can enable the fabrication of complex 3-dimensional structures that allow cells to be sorted by size (potentially in a manner similar to that discussed herein for filters) and/or for cells of different sizes to be delivered through different size micro-channels or between complex 3-dimensional structures. Structures can be material specific and on planar or non-planar surfaces. Membranes Membranes can offer filtration via pore sizes ranging from nanometers to a few microns in size. Membrane filtration can be used for particles in the ionic and molecular range, such as for reverse osmosis processes to desalinate water. Membranes are generally fabricated of polymers, metals, or ceramics. Micro-filtration membranes can be divided into two broad types based on their pore structure. Membranes having capillary-type pores are called screen membranes, and those having so-called tortuous-type pores are called depth membranes. Screen membranes can have nearly perfectly round pores that can be dispersed randomly over the outer surface of the membrane. Screen membranes are generally fabricated using a nuclear track and etch process. Depth membranes offer a relatively rough surface where there appear to be openings larger than the rated size pore, however, the fluid must follow a random tortuous path deeper into the membrane to achieve their pore-size rating. Depth membranes can be fabricated of silver, various cellulosic compounds, nylon, and/or polymeric compounds. Certain embodiments of the invention enable fabrication of membranes having complex 3-dimensional shapes, sizes, and/or configurations made of polymers, plastics, metals, and/or ceramics, etc. Furthermore, such membranes can embody redundant or non-redundant pores, and can be fabricated to be flexible, rigid, and/or non-planar depending upon the material and/or application requirements. Although the invention has been described with reference to specific embodiments thereof, it will be understood that numerous variations, modifications and additional embodiments are possible, and accordingly, all such variations, modifications, and embodiments are to be regarded as being within the spirit and scope of the invention. Also, references specifically identified and discussed herein are incorporated by reference as if fully set forth herein.
051986809	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a collimator to be used in a nuclear medical apparatus such as a SPECT (Single Photon Emission Computed Tomography) apparatus, and a method for manufacturing such a collimator. 2. Description of the Background Art In a nuclear medical apparatus such as a SPECT apparatus, .gamma. rays emitted from radioactive materials deposited inside a body to be examined are detected, and an image of a distribution of the radioactive materials inside the body is obtained on a basis of the detected .gamma. ray signals, where the obtained image is utilized in the diagnosis of a cancer and a tumor. In such a nuclear medical apparatus, a collimator is attached on a detector device in order to selectively collect the .gamma. rays from the radioactive materials inside the body at the detector device. The .gamma. rays selectively collected at the detector device by using the collimator are then converted into light signals and then into electric signals by using a scintillator, and the obtained electric signals corresponding to the detected .gamma. rays are utilized as the image data in the image reconstruction process. For such a collimator to be used in a nuclear medical apparatus, there are several types including a parallel hole collimator in which all the holes arranged in an array are parallel to each other, and a single focus (fan beam) collimator in which each hole in an array is provided with a prescribed inclination angle such that the collimator as a whole has a focal line in order to improve the sensitivity and the resolution of the collimator. In the SPECT apparatus for the head portion diagnosis, three such collimators are used in an arrangement in which each collimator is located on each side of an equilateral triangle formed by detectors arranged around the head portion of a patient. Among the various types of such a collimator, the parallel hole collimator has conventionally been manufactured by the following methods relatively easily. (1) A method of folded foil construction in which corrugated thin plates made of lead are piled up to form a collimator body. (2) A method in which pipe shaped members made of lead are glued together to form a collimator body. On the other hand, the single focus collimator has been more difficult to manufacture conventionally, because each hole in the array must be manufactured to be oriented toward a single focal line, and the following manufacturing methods have been employed for the single focus collimator conventionally. (1) A method using pins in which approximately thirty to fifty thousand pins each in a shape of a hole of a collimator to be manufactured are mounted between two templates with pre-manufactured pin positions in an array such that all the pins are oriented toward a predetermined single focal line, and then the lead is casted between the templates with the pins mounted, such that a desired single focus collimator body with all the holes arranged in an array oriented toward the predetermined single focal line can be obtained by pulling out all the pins after the lead casting. (2) A method using tungsten plates as disclosed in U.S. patent application Ser. No. 07/538,763, in which one type of tungsten plates are provided with fan shape patterned grooves oriented toward a common focal point while the other type of tungsten plates are provided with parallel grooves, such that these two types of tungsten plates can be assembled into a lattice shape by perpendicularly engaging the fan shaped grooves on one type of the tungsten plates with the parallel grooves of the other type of the tungsten plates, so as to form a desired single focus collimator body with all the holes arranged in an array oriented toward the predetermined single focal line. However, such conventional methods of manufacturing a single focus collimator have been associated with the following problems. First of all, as for the method using pins, the following three problems exited. (1) Each of the normally thirty to fifty thousand pins used in manufacturing one single focus collimator must be applied with a tapering process in order to facilitate an easy pulling out operation after the lead casting, so that a number of processes for preparing the pins can be enormously large as well as ineconomical. (2) Each of the normally thirty to fifty thousand pins used in manufacturing one single focus collimator must be mounted between the templates one by one and them pulled out after the lead casting one by one, all manually, so that the amount of work required for the worker can be enormously large as well as ineconomical. (3) The precision of the manufactured single focus collimator is often deteriorated by the bending of the very thin templates due to the weights of the pins, and by the inaccuracy of the pin orientation due to the looseness of the fitting of the pins at the pin positions on the templates. On the other hand, as for the method using tungsten plates, the following two problems exited. (1) Each plate to form a collimator body is required to have a thickness of approximately 0.2 mm, so that the material for each plate must have a sufficient rigidity to be able to maintain its shape in such a thin thickness, along with a sufficient .gamma. ray shielding property. For this reason, the tungsten is an only presently available metallic material for each plate. However, the tungsten is a rare metal which is very expensive, so that the cost for manufacturing the collimator inevitably becomes very high. In this regard, if the lead which has the sufficient .gamma. ray shielding property and is relatively inexpensive is to be used for the material for each plate, the plate manufactured in a thickness of approximately 0.2 mm would not be able to maintain its shape in the assembling operation because the lead does not have the sufficient rigidity. (2) In order to cut the tungsten plates to form the grooves thereon, it becomes necessary to utilize the wire cut electric spark manufacturing process because of the high rigidity of the tungsten. However, such a wire cut electric spark manufacturing process is very time consuming, and therefore the cost for manufacturing the collimator inevitably becomes high. Moreover, the conventional single focus collimator is also associated with the problem that the sensitivity becomes higher in a central region compared with peripheral regions, such that the appropriate correction of the detector output has been necessary. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide a method for manufacturing a single focus collimator in a high precision, without increasing a cost for manufacturing. It is another object of the present invention to provide a single focus collimator which can be manufactured in a high precision inexpensively. Furthermore, it is another object of the present invention to provide a single focus collimator with a uniform sensitivity, which can be manufactured in a high precision inexpensively. According to one aspect of the present invention there is provided a method for manufacturing a single focus collimator, comprising the steps of: forming grooves on a surface of a bulk block member; casting a metallic material having a sufficient .gamma. ray shielding property into said grooves formed on said bulk block member; and immersing said bulk block member with said metallic material casted into said grooves into a solvent capable of dissolving said bulk block member but not said metallic material, such that a collimator body formed by said metallic material in a shape of said grooves is obtained as said bulk block member is dissolved by said solvent. According to another aspect of the present invention there is provided a single focus collimator, comprising: first septa members arranged in a fan shape pattern in which all the first septa members are oriented toward a common focal line; and second septa members arranged to be parallel to each other, which are perpendicularly crossing with the first septa members in a lattice shape such that holes are defined between each adjacent first septa members and each adjacent second septa members; wherein the first and second septa members are arranged with such intervals that the holes have larger size toward a center of said collimator body. Other features and advantages of the present invention will become apparent from the following description taken in conjunction with the accompanying drawings.
	description	This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2017-135673, filed on Jul. 11, 2017; the entire contents of which are incorporated herein by reference. The embodiment of the invention relates to a radiation detector. There is an X-ray detector as one example of a radiation detector. The X-ray detector is provided with, for example, an array substrate including a plurality of photoelectric conversion parts, and a scintillator provided on the plurality of photoelectric conversion parts and converting an X-ray to fluorescence. The photoelectric conversion part is provided with a photoelectric conversion element converting the fluorescence from the scintillator to a charge, a thin film transistor performing switching of storing and release of the charge, a storing capacitor storing the charge, and the like. In general, the X-ray detector reads out an image data as follows. First, the detector recognizes X-ray incidence from a signal input externally. Next, the detector reads out the stored charge as the image data by turning on a thin film transistor of the photoelectric conversion part performing reading after the passage of a pre-determined time. However, in this way, since the start of the operation of the X-ray detector depends on a signal from the outside, there is a problem that a processing time becomes longer due to a time lag or the like. Here, when the thin film transistor of a semiconductor element is irradiated with the X-ray, a current flows between a drain electrode and a source electrode, even if the thin film transistor is in an off state. The drain electrode of the thin film transistor is electrically connected to a data line. Thus, a technique is proposed, the thin film transistor is set to the off state, and then based on a difference between a value of the current flowing in the data line when the X-ray is irradiated and a value of the current flowing in the data line when the X-ray is not irradiated, a start time of the X-ray incidence is detected. However, the value of the current flowing in the data line when the thin film transistor is in the off state becomes extremely small. Furthermore, since a large amount of X-ray irradiation to a human body has an adverse effect on health, the X-ray irradiation to the human body is suppressed to the minimum necessary. Therefore, in the case of the X-ray detector used for medical application, the intensity of the incident X-ray is extremely weak, and the value of the current flowing in the data line becomes further small when the thin film transistor is in the off state. Therefore, there is a fear that even if the value of the current flowing in the data line is detected when the thin film transistor is in the off state, it is difficult to detect accurately the start time of the X-ray incidence. Thus, it has been desired to develop a radiation detector capable of detecting accurately the start time of the radiation incidence. According to one embodiment of the invention, a radiation detector includes a substrate, a plurality of control lines provided on the substrate and extending in a first direction, a plurality of data lines provided on the substrate and extending in a second direction crossing the first direction, a plurality of detection parts including a thin film transistor electrically connected to the corresponding control lines and the corresponding data lines, and detecting radiation directly or in cooperation with a scintillator, a control circuit switching an on state and an off state of the thin film transistor, a signal detection circuit reading out an image data in the on state of the thin film transistor, and an incident radiation detection part judging a start time of radiation incidence based on a value of the image data read out in the on state of the thin film transistor. The embodiment will be described with reference to the accompanying drawings. In the drawings, similar components are marked with like reference numerals, and the detailed description is omitted as appropriate. The radiation detector according to the embodiment can be applied to various radiations such as a γ-ray other than an X-ray. Here, the case of the X-ray as a representative of radiations is described as one example. Therefore, the detector can be also applied to other radiation by replacing “X-ray” of the following embodiments with “other radiation”. The X-ray detector 1 illustrated below is an X-ray plane sensor detecting an X-ray image which is a radiation image. The X-ray plane sensor includes a direct conversion method and an indirect conversion method broadly. The direct conversion method is a method that a photoconductive charge (charge) generated inside a photoconductive film by the X-ray incidence is introduced directly to a storing capacitor for charge storage. The indirect conversion method is a method that the X-ray is converted to fluorescence (visible light) by a scintillator, the fluorescence is converted to the charge by a photoelectric conversion element such as a photodiode, and the charge is introduced to the storing capacitor. In the following, the X-ray detector 1 of the indirect conversion method is illustrated as one example, however the invention can be applied to the X-ray detector of the indirect conversion method as well. That is, the X-ray detector may be a detection part as long as it includes a detection part converting the X-ray to electric information. The X-ray detection part can be, for example, a detector that detects the X-ray directly or in cooperation with the scintillator. Since an already known art can be applied to the X-ray detector of the direct conversion method, the detailed description will be omitted. The X-ray detector 1 can be used for, for example, general medical application or the like, and the application is not limited. FIG. 1 is a schematic view for illustrating the X-ray detector 1. In FIG. 1, a bias line 2c3 or the like is omitted. FIG. 2 is a block diagram of the X-ray detector 1. FIG. 3 is a circuit diagram of an array substrate 2. As shown in FIG. 1 to FIG. 3, the X-ray detector 1 is provided with the array substrate 2, a signal processing part 3, an image processing part 4, a scintillator 5, an incident X-ray detection part 6, and a memory 7. The array substrate 2 converts the fluorescence converted from the X-ray by the scintillator 5 to an electric signal. The array substrate 2 includes a substrate 2a, a photoelectric conversion part 2b, a control line (or gate line) 2c1, a data line (or signal line) 2c2, a bias line 2c3, a wiring pad 2d1, a wiring pad 2d2, and a protection layer 2f or the like. In the embodiment, the photoelectric conversion part 2b serves as a detection part detecting the X-ray in cooperation with the scintillator 5. The number of the photoelectric conversion part 2b, the control line 2c1, the data line 2c2, and the bias line 2c3 or the like is not limited to the illustration. The substrate 2a is plate-shaped, and is formed from a light transmissive material such as a non-alkali glass. The photoelectric conversion part 2b is provided in a plurality on one surface of the substrate 2a. The photoelectric conversion part 2b is provided in a region drawn by the control line 2c1 and the data line 2c2. The plurality of photoelectric conversion parts 2b are arranged in a matrix. One photoelectric conversion part 2b corresponds to one picture element (pixel) in the X-ray image. Each of the plurality of photoelectric conversion parts 2b is provided with a photoelectric conversion element 2b1, and a thin film transistor (TFT) 2b2. As shown in FIG. 3, a storing capacitor 2b3 to which the charge converted by the photoelectric conversion element 2b1 is supplied can be provided. The storing capacitor 2b3 is, for example, rectangular flat plate-shaped, and can be provided under the respective thin film transistor 2b2. However, depending on a capacity of the photoelectric conversion element 2b1, the photoelectric conversion element 2b1 can serve as the storing capacitor 2b3. In the case where the photoelectric conversion element 2b1 serves as the storing capacitor 2b3 (the case where the storing capacitor 2b3 is omitted), storing and release of the charge is performed in the photoelectric conversion element 2b1. In this case, the charge is released from the photoelectric conversion part 2b by turning on the thin film transistor 2b2, and the charge is stored by turning off the thin film transistor 2b2. In the case where the storing capacitor 2b3 is provided, a definite charge is stored in the storing capacitor 2b3 from the bias line 2c3 if the thin film transistor 2b2 is turned off, and the stored charge stored in the storing capacitor 2b3 is released if the thin film transistor is turned on. In the following, the case where the storing capacitor 2b3 is provided is illustrated as one example. The photoelectric conversion element 2b1 can be, for example, a photodiode or the like. The thin film transistor 2b2 performs switching of storing and release of the charge to the storing capacitor 2b3. The thin film transistor 2b2 can include a semiconductor material such as amorphous silicon (a-Si) or polysilicon (p-Si). The thin film transistor 2b2 includes a gate electrode 2b2a, a drain electrode 2b2b and a source electrode 2b2c. The gate electrode 2b2a of the thin film transistor 2b2 is electrically connected to the corresponding control line 2c1. The drain electrode 2b2b of the thin film transistor 2b2 is electrically connected to the corresponding data line 2c2. That is, the thin film transistor 2b2 is electrically connected to the corresponding control line 2c1 and the corresponding data line 2c2. The source electrode 2b2c of the thin film transistor 2b2 is electrically connected to the corresponding photoelectric conversion element 2b1 and the storing capacitor 2b3. The storing capacitor 2b3 and the anode side of the photoelectric conversion element 2b1 are electrically connected to the corresponding bias line 2c3 (see FIG. 3). The control line 2c1 is provided in a plurality to be parallel to each other with a prescribed spacing. The control lines 2c1 extend, for example, in a row direction (corresponding to one example of a first direction). One control line 2c1 is electrically connected to one of a plurality of wiring pads 2d1 provided near the periphery of the substrate 2a. One wiring pad 2d1 is electrically connected to one of the plurality of wirings provided on the flexible printed board 2e1. Other ends of the plurality of wirings provided on the flexible printed board 2e1 are electrically connected to a control circuit 31 provided in the signal processing part 3, respectively. The data line 2c2 is provided in a plurality to be parallel to each other with a prescribed spacing. The data lines 2c2 extend, for example, in a column direction (corresponding to one example of a second direction) orthogonal to the row direction. One data line 2c2 is electrically connected to one of a plurality of wiring pads 2d2 provided near the periphery of the substrate 2a. One of the plurality of wirings provided on the flexible printed board 2e2 is electrically connected to one wiring pad 2d2. Other ends of the plurality of wirings provided on the flexible printed board 2e2 are electrically connected to a signal detection circuit 32 provided in the signal processing part 3, respectively. As shown in FIG. 3, the bias line 2c3 is provided to be parallel to the data line 2c2. The bias line 2c3 is electrically connected to a bias power source not shown. The bias power source not shown can be provided, for example, on the signal processing part 3 or the like. The bias line 2c3 is not always necessary, and may be provided as necessary. In the case where the bias line 2c3 is not provided, the storing capacitor 2b3 and the anode side of the photoelectric conversion element 2b1 are electrically connected to the ground in place of the bias line 2c3. The control line 2c1, the data line 2c2, and the bias line 2c3 can be formed based on, for example, a low resistance metal such as aluminum and chromium or the like. A protection layer 2f covers the photoelectric conversion part 2b, the control line 2c1, the data line 2c2, and the bias line 2c3. The protection layer 2f includes, for example, at least one of an oxide insulating material, a nitride insulating material, oxynitride insulating material, and a resin material. The signal processing part 3 is provided on an opposite side of the array substrate 2 to the scintillator 5. The signal processing part 3 is provided with the control circuit 31 and the signal detection circuit 32. The control circuit 31 switches between the on state and the off state of the thin film transistor 2b2. As shown in FIG. 2, the control circuit 31 includes a plurality of gate drivers 31a and a column selection circuit 31b. A control signal S1 is input from the image processing part 4 or the like to the column selection circuit 31b. The column selection circuit 31b inputs the control signal S1 to the corresponding gate driver 31a in accordance with a scanning direction of the X-ray image. The gate driver 31a inputs the control signal S1 to the corresponding control line 2c1. For example, the control circuit 31 inputs the control signal S1 sequentially to every control line 2c1 via the flexible printed board 2e1. The thin film transistor 2b2 is turned on by the control signal S1 inputted to the control line 2c1, and the charge (image data signal S2) from the photoelectric conversion part 2b (storing capacitor 2b3) can be received. In the specification, the data read out when the thin film transistor 2b2 is in the on state is referred to as “image data S2”, and the data read out when the thin film transistor 2b2 is in the off state is referred to as “correction data”. The signal detection circuit 32 reads out the charge (image data S2) from the photoelectric conversion part 2b (storing capacitor 2b3) when the thin film transistor 2b2 is in the on state. The signal detection circuit 32 converts the read out image data S2 (analog signal) to digital signals sequentially. The signal detection circuit 32 reads out further the correction data S3 when the thin film transistor 2b2 is in the off state. The signal detection circuit 32 converts the read out correction data S3 (analog signal) to digital signals sequentially. The signal detection circuit 32 can read out the correction data S3 either before reading out the image data S2, after reading out the image data S2, or before reading out the image data S2 and after reading out the image data S2. The control circuit 31 can input the control signal S1 switching the on state and the off state of the thin film transistor 2b2 for each of the plurality of control lines 2c1. The signal detection circuit 32 can read out the correction data S3 every time the control signal S1 is input. The signal detection circuit 32 can give an image index for coupling the image data S2 with the read out correction data S3 either before reading out the relevant image data S2, after reading out the relevant image data S2, or before reading out the relevant image data S2 and after reading out the relevant image data S2. The signal detection circuit 32 can also convert a differential output of the read out image data S2 and the read out correction data S1 to the digital signal, and transmit to the image processing part 4. In this way, since the corrected image data can be input to the image processing part 4, real-time performance can be improved. In the case where the incident radiation detection part 6 judges the incidence of the X-ray starts, the signal detection circuit 32 can further read out the image data S2 when the thin film transistor 2b2 is in the on state. The image data S2, the correction data S3, and the image index will be described later in detail. As described previously, during the incidence of the X-ray, the current from the thin film transistor 2b2 in the off state flows in. Therefore, during the incidence of the X-ray, a sampling time (time of first sampling signal 21) of reading out the image data S2 and a sampling time (time of second sampling signal 22) of reading out the correction data S3 are preferable to be short. On the other hand, after the end of the X-ray incidence, the current from the thin film transistor 2b2 in the off state does not flow in. Therefore, after the end of the X-ray incidence, even if the sampling time of reading out the image data S2 and a time during which the thin film transistor 2b2 is in the on state are lengthened, an image spot does not occur. If the sampling time of reading out the image data S2 and the time during which the thin film transistor 2b2 is in the on state are lengthened, quality of the X-ray image can be improved. In this case, since the irradiation time of the X-ray is short, the sampling time of reading out the image data S2 and the time during which the thin film transistor 2b2 is in the on state after the detection of the incidence of the X-ray can be more lengthened than the sampling time of reading out the image data S2 and the sampling, time of reading out the correction data S3 before the detection of the X-ray. In this way, the occurrence of the image spot can be suppressed and the quality of the X-ray image can be improved. The memory 7 is electrically connected between the signal detection circuit 32 and the image processing part 4. The memory 7 saves temporarily the image data S2 and the correction data S3 converted to the digital signal. At this time, it is possible that the image data S2 and the correction data S3 to which an image index is given are saved. The image processing part 4 configures the X-ray image based on the image data S2 saved in the memory 7. The image processing part 4 corrects the image data S2 by using the correction data S3. At this time, the image processing part 4 extracts the correction data S3 based on the image index, and can correct the image data S2 coupling with the correction data S3 by using the extracted correction data S3. The image processing part 4, the memory 7 and the incident X-ray detection part 6 may be integrated with the signal processing part 3. The scintillator 5 is provided on a plurality of photoelectric conversion elements 2b1, and converts the incident X-ray to fluorescence. The scintillator 5 is provided to cover a region (effective pixel region) where a plurality of photoelectric conversion parts on the substrate 2b are provided. The scintillator 5 can be formed based on, for example, cesium iodide (CsI):thallium (TI), or sodium iodide (NaI):thallium (TI) or the like. In this case, if the scintillator 5 is formed by using a vacuum deposition method or the like, the scintillator 5 made of a plurality of columnar crystal aggregations is formed. The scintillator 5 can be also formed by using, for example, oxysulfide gadolinium (Gd2O2S) or the like. In this case, a groove portion in a matrix can be provided so that the quadrangular prismatic scintillator 5 is provided every the plurality of photoelectric conversion parts 2b. The groove portion can be filled with an atmosphere (air) or an inactive gas such as antioxidant nitrogen gas. Or the groove portion may be in a vacuum state. Other, in order to increase a utilization efficiency of the fluorescence and improve sensitivity characteristics, a reflection layer not shown can be provided so as to cover a surface side (incident surface side of X-ray) of the scintillator 5. In order to suppress deterioration of the characteristics of the scintillator 5 and the characteristics of the reflection layer due to water vapor included in air, a moistureproof body not shown covering the scintillator 5 and the reflection layer can be provided. Here, the X-ray detector 1 can configure the X-ray image as follows. First, the control circuit 3 turns the thin film transistor 2b2 off. The thin film transistor 2b2 is turned off, and thus the definite charge is stored in the storing capacitor 2b3 via the bias line 2c3. Next, when the X-ray is irradiated, the X-ray is converted to the fluorescence by the scintillator 5. When the fluorescence is incident on the photoelectric conversion element 2b1, charges (electron and hole) are produced by the photoelectric effect, the produced charges and the stored charges (heterogeneous charge) combine and the stored charges decrease. Next, the control circuit 31 turns the thin film transistors 2b2 on sequentially. The signal detection circuit 32 reads out the stored charge stored (image data S2) in each storing capacitor 2b3 in accordance with the sampling signal via the data line 2c2. The signal detection circuit 32 converts the read image data S2 (analog signal) to the digital signal sequentially. The signal detection circuit 32 converts a value of the current flowing in the data line 2c2 when the thin film transistor 2b2 is in the off state. The memory 7 saves temporarily the data obtained in the on state of the thin film transistor 2b2 as the image data S2. The memory 7 saves the data obtained in the off state of the thin film transistor 2b2 as the correction data S3. The image processing part 4 configures the X-ray image based on the image data S2 saved in the memory 7. The image processing part 4 performs correction for suppressing the image spot described later by using the correction data S3 saved in the memory 7 when configuring the X-ray image. The data of the X-ray image having the correction for suppressing the image spot performed are output from the image processing part 4 toward an external equipment or the like. Here, in a general X-ray detector, image operation starts as follows. First, incidence of the X-ray into the X-ray detector is recognized by the signal from the external equipment such as an X-ray source. Next, the thin film transistor 2b2 of the photoelectric conversion part 2b performing the reading is turned on after the passage of a predetermined time, and the stored charge is read out. That is, in the general X-ray detector, actual incidence of the X-ray into the X-ray detector is not detected. Therefore, a prescribed time is needed to be provided between a time when the signal from the external equipment is input and a time when the reading operation is started. As a result, a time lag or the like occurs and a processing time is lengthened. If the thin film transistor 2b2 of a semiconductor element is irradiated with the X-ray, a current flows between a drain electrode 2b2b and a source electrode 2b2c, even if the thin film transistor 2b2 is in the off state. The drain electrode 2b2b of the thin film transistor 2b2 is electrically connected to a data line 2c2. Therefore, based on a difference between a value of the current flowing in the data line 2c2 on the X-ray irradiation and a value of the current flowing, in the data line 2c2 on no X-ray irradiation, a start time of the X-ray incidence can be detected. If the start time of the X-ray incidence can be detected directly, the time lag or the like does not occur, and thus the processing time can be suppressed from being lengthened. However, the value of the current flowing in the data line 2c2 when the thin film transistor 2b2 is in the off state becomes extremely small. Furthermore, since a large amount of X-ray irradiation to a human body has an adverse effect on health, the X-ray irradiation to the human body is suppressed to the minimum necessary. Therefore, in the case of the X-ray detector used for medical application, the intensity of the incident X-ray is extremely weak, and the value of the current flowing in the data line 2c2 becomes further small when the thin film transistor 2b2 is in the off state. As a result, there is a fear that if the start time of the X-ray incidence is detected based on the value of the current flowing in the data line 2c2 when the thin film transistor 2b2 is in the off state, it is difficult to detect accurately the start time of the X-ray incidence. Thus, the X-ray detector 1 according to the embodiment is provided with the following incident X-ray detection part 6. The incident X-ray detection part 6 is electrically connected to the signal detection circuit 32. The incident X-ray detection part 6 judges the start time of the X-ray incidence based on the value of the current flowing in the data line 2c2 electrically connected to the thin film transistor 2b2 when the thin film transistor 2b2 is in the on state. That is, the incident X-ray detection part 6 judges the start time of the X-ray incidence based on the value of the image data S2 read out in the on state of the thin film transistor. For example, the incident X-ray detection part 6 can judge that the X-ray is incident, in the case where the X-ray detection part 6 detects the current flowing in the data line 2c2 connected to the thin film transistor 2b2 in the on state, and the value of the detected current exceeds a prescribed threshold value. The prescribed value can be set previously based on a difference between the value of the current flowing in the data line 2c2 on the X-ray irradiation and the value of the current flowing in the data line 2c2 on no X-ray irradiation. If the thin film transistor 2b2 is in the on state, an electrical resistance can be small compared with the case of the off state, and thus the value of the current flowing in the data line 2c2 becomes large. Therefore, it is easy to detect the start time of the X-ray. As described above, in the case of the X-ray detector used for medical application, the intensity of the incident X-ray is extremely weak. However, if the start time of the X-ray incidence is detected in the on state of the thin film transistor 2b2, it is possible to detect accurately the incident start time of the X-ray. However, since the current from other thin film transistor 2b2 in the off state also flows in the data line 2c2 connected to the thin film transistor 2b2 in the on state, a new problem of occurrence of the image spot arises. In this case, the current from the other thin film transistor 2b2 does not flow in the data line 2c2 connected to the thin film transistor 2b2 turned on after the irradiation of the X-ray is finished. Therefore, the image spot can be suppressed if the data at the start of the X-ray incidence are discarded and the X-ray image is configured by using only data after the irradiation of the X-ray is finished. However, in this way, since the data at the start of the X-ray incidence are lost, that will result in a decline in quality of the X-ray image. Thus, the incident X-ray detection part 6 detects the current flowing in the data line 2c2 in at least one of the off state before turning on the thin film transistor 2b2 and the off state after turning on the thin film transistor 2b2. As previously described, it is considered that the occurrence of the image spot is mainly caused by the current from the thin film transistor 2b2 in the off state. Therefore, if the current flowing in the data line 2c2 connected to the thin film transistor 2b2 in the on state is detected in the off state at least one of before and after the on state, and the image data acquired at the on state is corrected by the correction data S3 acquired at the off state, the image spot can be suppressed drastically. In this way, since the image data S2 at the start of the X-ray incidence can be used, the decline of quality of the X-ray image can be suppressed. That is, if the incident X-ray detection part 6 is provided, the start time of the X-ray incidence can be detected and deterioration of the quality of the X-ray image can be suppressed. FIG. 4 is a timing chart for illustrating reading of the image data S2 and the correction data S3. FIG. 4 shows the case where n control lines 2c1 and m data lines 2c2 are provided. First, the first sampling signal 21 is input to the signal detection circuit 32 from the image processing part 4 or the like. As shown in FIG. 4, the first sampling signal 21 is turned on, and thus the signal detection circuit 32 starts sampling for the data line (1)˜the data line (m). The first sampling signal 21 is turned off after the passage of the prescribed time. On the other hand, while the first sampling signal 21 is on, the control signal S1 is input to the control line (1) from the image processing part 4 or the like via the control circuit 31. The control signal S1 is turned on, and then the thin film transistor 2b2 electrically connected to the control line (1) is turned on. The control signal S1 is turned off after the passage of the prescribed time. The signal detection circuit 32 reads out sequentially the image data S2 from the data line (1)˜the data line (m) when the thin film transistor 2b2 is in the on state. The incident X-ray detection part 6 judges the start time of the X-ray incidence based on the value of the current flowing in the data line 2c2 when the first sampling signal 21 is on. Next, after the first sampling signal 21 is turned off, the second sampling signal 22 is input to the signal detection circuit 32 from the image processing part 4 or the like. The second sampling signal 22 is turned on, and then the signal detection circuit 32 starts sampling for the data line (1)˜the data line (m). The second sampling signal 22 is turned off after the passage of the prescribed time. In this case, the control signal S1 is not input to the control line (1), and the thin film transistor 2b2 electrically connected to the control line (1) remains to be in the off state. The signal detection circuit 32 detects the current flowing in the data line (1)˜the data line (m) when the thin film transistor 2b2 is in the off state. After that, the above procedure is performed for the control line (2)˜the data line (n). The data acquired in this way are saved in the memory 7. The data acquired when the thin film transistor 2b2 is in the on state serve as the image data S2 of n rows and m columns. The data acquired when the thin film transistor 2b2 is in the off state serve as the correction data S3 of n rows and m columns. The case where the image data S2 and the correction data S3 are saved in the same memory 7 is illustrated, however the image data S2 and the correction data S3 may be saved in separate memories. When the data serving as the image data S2 and the data serving as the correction data S3 are saved in the memory 7, the image indexes can be given. In the case illustrated in FIG. 4, an image index TFTon1 is given to the image data S2, and an image index TFToff1 is given to the correction data S3 coupling with the image data S2. In this case, the image index TFTon1 represents the image data S2 firstly acquired, and the TFToff1 represents the correction data S3 coupling with this. The image indexes can be given to the data with respect to the control line (1)˜the control line (n), respectively. In FIG. 4, the second sampling signal 22 is turned on after the first sampling signal 21 is turned off, however the first sampling signal 21 may be turned on after the second sampling signal 22 is turned off. That is, in FIG. 4, the correction data S3 is acquired after acquiring the image data S2, however the image data S2 may be acquired after acquiring the correction data S3. When the control signal S1 is input to one control line, the second sampling signal 22, the first sampling signal 21, and the second sampling signal 22 may be sequentially input to the signal detection circuit 32. In this case, it is possible that when the control signal S1 is input to the next signal line, only the first sampling signal 21 is input to the signal detection circuit 32, when the control signal S1 is input to the still next control line, the second sampling signal 22, the first sampling signal 21, and the second sampling signal 22 can be input to the signal detection circuit 32, sequentially. That is, the first sampling signal 21 and the second sampling signal 22 are only necessary to be input alternately. In FIG. 4, the first sampling signal 21 is turned on before turning the control signal S1 on, however the control signal S1 and the first sampling signal may be turned on simultaneously, and the first sampling signal 21 may be turned on after turning the control signal S1 on. In FIG. 4, the first sampling signal 21 is turned off after turning the control signal S1 off, however the control signal S1 and the first sampling signal 21 may be turned off simultaneously, and the first sampling signal 21 may be turned off before turning the control signal S1 off. Next, alternate input of the first sampling signal 21 and the second sampling signal 22 (alternate reading the image data S2 and the correction data S3) will be further described. FIG. 5 is a schematic view for illustrating the current flowing in the data line 2c2 when the X-ray is irradiated. “Circle” in FIG. 5 represent timing when the first sampling signal 21 is turned on, and “cross” represents timing when the second sampling signal 22 is turned on. When the X-ray detector 1 is irradiated with the X-ray, a wave current as illustrated in FIG. 5 flows in the data line 2c2. In this case, a change of a current value per unit time becomes large in a region A or a region C. On the other hand, a change of a current value per unit time becomes small in a region B. Here, the correction data S3 described previously is favorably acquired under the same condition as the image data S2 when possible. Therefore, the first sampling signal 21 and the second sampling signal 22 are favorably input in the region B. However, since it is unknown when the start time of the X-ray incidence is, it is difficult to input the first sampling signal 21 and the second sampling signal 22 in the region B. Thus, in the X-ray detector 1 according to the embodiment, the first sampling signal 21 and the second sampling signal 22 are input alternately. For example, in the case illustrated in FIG. 5, as shown in FIG. 4, the first sampling, signal 21 about the control line (1) is input, and subsequently the second sampling signal 22 is input. Next, the first sampling signal 21 about the control line (2) is input, and subsequently the second sampling signal 22 is input. Below, in the same way, the first sampling signal 21 and the second sampling signal 22 are input alternately. In this way, with respect to one image data, the correction data S3 before and after that can be obtained. If the before and after correction data S3 can be acquired, for example, a average value can be determined. Therefore, even if the change of the current value per unit time is large, the acquisition condition of the correction data S3 can be close to acquisition condition of the image data S2. As a result, since the correction accuracy can be improved, the image spot is suppressed easily. FIG. 6 is a flow chart for illustrating the process of the X-ray detector 1. As shown in FIG. 6, in a reading process 28, the control line 2c1 is scanned, and the image data S2 is read out in the ON state of the thin film transistor 2b2. The correction data S3 is read out in the OFF state of the thin film transistor 2b2. The image data S2 and the correction data S3 of every control line 2c1 are saved in the memory 7 with attaching the image indexes. Next, the incidence of the X-ray is judged based on the image data S2 saved in the memory 7. For example, when the image numbers exceeding a predetermined threshold value are counted and the image numbers reaches a predetermined count number, it can be judged that the X-ray is incident. In the above, the judge of the X-ray incidence is performed by using the image data S2 when the thin film transistor 2b2 is in the ON state, however the signal of the integration period in the process of reading the image data S2 in the ON state of the thin film transistor 2b2 and recharging the charge may be used for judge of X-ray incidence. In this way, the X-ray incidence can be known in an earlier stage. When it is judged that the X-ray is not incident, the image index is updated and the scanning of the control line 2c1 is reset. That is, the scanning is started from the control line (1), and the above procedure is repeated. When it is judged that the X-ray is incident, after the scanning of the control line 2c1 in the next period is finished, at the stage where the image data S2 and the correction data S3 are saved in the memory 7, the save into the memory 7 is interrupted. The save into the memory 7 is interrupted, and thereby already saved image data S2 and the correction data S3 are prevented from being overwritten. Subsequently, the image data S2 and the correction data S3 after the incidence of the X-ray are extracted based on the image index given in the period when the X-ray is judged to be incident, and the X-ray image is configured by the image processing part 4. At this time, the image spot is suppressed by correcting the image data S2 by using the correction data S3. Next, the suppression of the image spot will be further described. As described previously, when the control line 2c1 is scanned sequentially in the ON state of the thin film transistor 2b2 and the incidence of the X-ray is judged from the obtained image data S2, the image spot occurs. The image spot is considered to be caused mainly as follows. A plurality of thin film transistors are electrically connected to one data line 2c2. In the case where the control line 2c1 is scanned and the thin film transistors 2b2 electrically connected to the desired control line 2c1 is in the on state, the thin film transistors 2b2 electrically connected to other control lines 2c1 is in the OFF state. If the thin film transistor 2b2 is in the OFF state, a current does not flow between the source electrode 2b2c and the drain electrode 2b2b. However, the thin film transistor 2b2 is irradiated with the X-ray or the fluorescence converted by the scintillator 5, the resistance value between the source electrode 2b2c and the drain electrode 2b2b decreases. If the resistance value decreases, a portion of charges stored in the storing capacitor 2b3 is released to the data line 2c2 and serves as the current flowing in the data line 2c2. The image spot is considered to occur due to this current. Here, the resistance value between the source electrode 2b2c and the drain electrode 2b2b changes by strength of the X-ray incident to the X-ray detector 1. For example, the strength of the X-ray incident to the X-ray detector 1 changes drastically at the start time or the end time of the X-ray incidence. Therefore, the resistance value between the source electrode 2b2c and the drain electrode 2b2b changes also drastically at the start time or the end time of the X-ray incidence. In this case, as illustrated in FIG. 5, the current flowing in the data line 2c2 also changes drastically. In order to suppress the image spot effectively, in the case where the thin film transistor 2b2 electrically connected to the desired control line 2c1 is in the on state, it is necessary to know the resistance value change of the thin film transistor 2b2 in the off state electrically connected to other control lines 2c1. As described previously, if at a timing before and after tuning the thin film transistor 2b2 ON (turning the first sampling signal on), all thin film transistors 2b2 is in the OFF state, the second sampling signal 22 is on, and currents flowing in all data lines 2c2 are detected, it is possible to know the resistance value change. If the correction data S3 made from the currents in all data lines 2c2 is used, the image spot can be suppressed effectively. The number of the data lines 2c2 of the general X-ray detector is not less than 500 lines, however many thin film transistors 2b2 are in the OFF state, and thus the image spot can be, corrected accurately. If the correction is made in the above procedure, it is possible to correct the image spot in real time. If ON time of the first sampling signal 21 and the second sampling signal 22 are changed, the value of the current integral value illustrated in FIG. 5 variates. On the other hand, the value of the current integral value illustrated in FIG. 5 has no relation to a time during which the thin film transistor 2b2 is in the on state (ON time of control signal S1). When the first sampling, signal 21 is turned ON, integration of the current flowing in the data line 2c2 starts, and when the first sampling signal 21 is turned OFF, the integration ends. The current value which flows during the ON time of the first sampling signal 21 is integrated to be output as the digital signal (current integral value). There is a fear that the quality of the X-ray image may be deteriorated unless the time during which the thin film transistor 2b2 is in the on state is made long, to some extent. However, while the X-ray is irradiated, it is not necessary to lengthen the time during which the thin film transistor 2b2 is in the on state, and it is preferable to shorten the time during which the thin film transistor 2b2 is in the on state and decrease the current integral value in order to decrease the influence of the leak current. On the other hand, after the X-ray irradiation is finished, there is no leak current, and thus it is preferable to lengthen the time during which the thin film transistor 2b2 is in the on state. In this case, since the irradiation time of the X-ray is short, the sampling time for reading out the image data S2 and the time during which the thin film transistor 2b2 is in the on state after the incidence of the X-ray is detected can be longer than the sampling time for reading out the image data S2 and the sampling time for reading out the correction data S3 before the incidence of the X-ray is detected. In this way, the occurrence of the image spot can be suppressed and the quality of the X-ray image can be improved. FIG. 7 is a flow chart for illustrating, other process. As shown in FIG. 7, in the case where the X-ray is judged not to be incident, standby process 29 for standing by for a definite time can be provided before going back to a reading process 28. In the standby process 29, the scanning of the control line 2c1, and acquisition of the image data S2 and the correction data S3 are interrupted. In the case where the X-ray is irradiated in the state of the standby process 29, the control line 2c1 is not scanned, and thus the image spot due to the change of the resistance value described above does not occur. In this case, it can be decided whether the correction of the image data S2 is necessary or not based on the correction data S3 in the reading process 28. While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the invention. Moreover, above-mentioned embodiments can be combined mutually and can be carried out.
053717740	claims	1. A method for imaging an X-ray lithography beamline from an X-ray source emitting an X-ray beam along a y axis and diverging along x and z axes, respectively, where the x, y and z axes are orthogonal to each other, comprising: providing a mirror having a reflecting surface reflecting the X-ray beam to an imaging plane orthogonal to the y axis and spaced from the mirror along the y axis; determining the optical path function F from the source A to the image B by determining the optical path function from the source A to the mirror P, and from the mirror P to the image B, according to EQU F=AP+PB=((x.sub.A -x).sup.2 +(y.sub.A -y).sup.2 +(z.sub.A -z).sup.2).sup.1/2 +((x.sub.B -x).sup.2 +(y.sub.B -y).sup.2 +(z.sub.B -z).sup.2).sup.1/2 determining the partial derivatives of the optical path function F, .differential.F/.differential.x, .differential.F/.differential.y, .differential.F/.differential.z, wherein determining a grid on said reflecting surface comprising a plurality of grid points; and modifying the slope at said grid points such that the displacement of the reflected rays from the image line vanishes. 2. The method according to claim 1 comprising eliminating discontinuities in said reflecting surface by varying surface coordinates in z to smooth the surface. 3. The method according to claim 2 comprising modifying the surface recursively until it provides a smooth line image in the image plane along the x axis. 4. The method according to claim 3 comprising modifying the surface recursively according to ##EQU4## where n is the polynomial order, and c is the coefficient of the polynomials.
	summary
	summary
	claims	1. Nuclear power station comprising:a plurality of high temperature reactors (2), each comprising a core (4) in which a plurality of fuel elements (5) are arranged;for each reactor (2), a dedicated storage installation (14, 16, 18, 20, 22) for the fuel elements (5) for said reactor (2);means (32) for transferring the fuel elements (5) between the core (4) and the storage installation (14, 16, 18, 20, 22);wherein the transfer means (32) comprise:a tunnel (34), of which a first portion (36) is situated near the core (4) and a second portion (38) is situated in or near the storage installation (14, 16, 18, 20, 22);first transfer means (48, 58) suitable for transferring at least one fuel element (5) between the core (4) and the first portion (36);second transfer means (78) suitable for transferring at least one fuel element (5) between the second portion and the storage installation (14, 16, 18, 20, 22);means (66) for transferring at least one fuel element (5) along the tunnel (34) between the first and second portions (36, 38); andmeans (86, 88) for moving the tunnel (34) between a plurality of service positions each corresponding to one of the reactors (2), the first portion (36) of the tunnel (34) being situated in each service position near the core of the corresponding reactor and the second portion (38) of the tunnel (34) being situated in or near the dedicated storage installation (14, 16, 18, 20) for said reactor (2). 2. Nuclear power station according to claim 1, wherein the first portion (36) is situated above the core (4). 3. Nuclear power station according to claim 1, wherein the first transfer means (48, 58) comprise first connection means substantially sealed between the core (4) and the first portion (36), the second transfer means (78) comprise second connection means (74) substantially sealed between the second portion (38) and the storage installation (14, 16, 18, 20, 22), the tunnel (34) forming with the first and second connection means a continuous sealed path for the fuel elements (5) from the core (4) to the storage installation (14, 16, 18, 20, 22). 4. Nuclear power station according to claim 1, wherein it comprises a first biological protection slab (26) situated above the reactor core (4), the tunnel (34) being arranged at least in part beneath or in the first biological protection slab (26). 5. Nuclear power station according to claim 4, wherein the first biological protection slab (26) comprises an aperture (40) perpendicular to the core (4), the power station comprising a support stopper (42) arranged removably in the aperture (40), the first portion (36) of the tunnel (34) being arranged in the support stopper (42). 6. Nuclear power station according to claim 4, wherein it comprises a second biological protection slab (29) situated above the storage installation (14, 16, 18, 20, 22), the second portion (38) of the tunnel (34) being situated at a lower elevation than that of the second biological protection slab (29). 7. Nuclear power station according claim 1, wherein it comprises a first biological protection slab (26) situated above the reactor core (4), the tunnel (34) being arranged at least in part above the first biological protection slab (26). 8. Nuclear power station according to claim 7, wherein the first biological protection slab (26) comprises an aperture (40) perpendicular to the core (4), the power station comprising a support stopper (42) arranged removably in the aperture (40), the first portion (36) of the tunnel (34) being arranged above the support stopper (42). 9. Nuclear power station according to claim 7, wherein it comprises a second biological protection slab (29) situated above the storage installation (14, 16, 18, 20, 22), the second portion (38) of the tunnel (34) being situated above the second biological protection slab (29). 10. Nuclear power station according to claim 1, wherein it comprises:a plurality of connection tunnels (110) connecting each two storage installation (14, 16, 18, 20) to each other, each connection tunnel (110) comprising a first portion situated near one of the two corresponding storage installations (14, 16, 18, 20) and a second portion situated in or near the other of the two corresponding storage installations (14, 16, 18, 20);for each connection tunnel (110), first transfer means suitable for transferring at least one fuel element (5) between the corresponding storage installation (14, 16, 18, 20) and the first portion;for each connection tunnel (110), second transfer means suitable for transferring at least one fuel element (5) between the second portion and the corresponding storage installation (14, 16, 18, 20);for each connection tunnel (110), means for transferring at least one fuel element (5) along the connection tunnel (110) between the first and second portions. 11. Nuclear power station according to claim 10, wherein it comprises a biological protection slab (29) situated above each storage installation (14, 16, 18, 20), the first and second portions of each connection tunnel (110) being situated at respective elevations lower than those of the biological protection slabs (29) of the corresponding storage installations (14, 16, 18, 20). 12. Nuclear power station according to claim 10, wherein the storage installations (14, 16, 18, 20) are arranged in a line, each connection tunnel (110) connecting two adjacent storage installations (14, 16, 18, 20) along the line. 13. Nuclear power station according to claim 1, wherein the core contains a given number of fuel elements, the storage installation having a storage capacity of at least one sixth of said given number of fuel elements.
	claims	1. Device for conditioning of nuclear fuel assemblies comprising:an inner leak tight metallic receptacle including a loading opening for receiving and conditioning solid nuclear fuel assemblies placed in a basket, wherein a plurality of baskets are vertically stacked within the inner leak tight metallic receptacle; andan outer leak tight receptacle that contains the inner leak tight metallic receptacle, the outer leak tight receptacle at least including a bottom and an open end, such that when the inner leak tight metallic receptacle is located in the outer receptacle, a passage remains free between the two receptacles from the open end to the bottom of the outer receptacle, said passage including means for draining water from the outer receptacle and/or for controlling the leak tightness of the outer receptacle. 2. Device according to claim 1 wherein the inner receptacle is adjusted in the outer receptacle. 3. Device according to claim 1 wherein the passage is a duct located in the inner receptacle leading to the outside. 4. Device according to claim 3, the inner receptacle and the duct of which are cylindrical-shaped with a circular cross section. 5. Device according to claim 4, the duct of which is located on the centreline of the inner receptacle. 6. Device according to claim 1 for which the inner receptacle is cylindrical-shaped and the outer receptacle comprises a protuberance delimiting said passage. 7. Device according to claim 1 comprising a shielded plug that can be fixed in a leak tight manner to the open end of the inner receptacle and such that the passage passes through the plug. 8. Device according to claim 7 comprising at least one closing plate that can be assembled such that the inner receptacle is leak tight. 9. Device according claim 1 such that the outer receptacle comprises a leak tight cover and means for draining the outer receptacle and/or controlling its leak tightness, capable of facing the passage when the inner receptacle is placed in the outer receptacle. 10. Device according to claim 1 comprising means for draining the outer receptacle including a dip tube. 11. Device according to claim 1, the outer receptacle of which is a storage package for which the sidewalls are radiation shielding. 12. Device according to claim 1 the outer receptacle of which is a leak tight metallic receptacle for conditioning of nuclear fuel assemblies. 13. Device according to claim 12 further comprising a transfer package for which the sidewalls are radiation shielding and capable of containing the outer receptacle. 14. Method of conditioning nuclear fuel assemblies under water, including placement of the assemblies into the inner leak tight metallic receptacle of the device according to claim 13, the device itself being located in the outer leak tight metallic receptacle that is itself located in the transfer package. 15. Method according to claim 14 in which a seal is used to ensure leak tightness between the outer receptacle and the transfer package. 16. Method of conditioning nuclear fuel assemblies under water, comprising placement of the assemblies into the inner leak tight metallic receptacle of the device according to claim 1, the device itself being located in the outer receptacle. 17. Method of draining an outer receptacle for radioactive material comprising:inserting an inner leak tight metallic receptacle into the outer receptacle, the inner leak tight metallic receptacle comprising a loading opening for receiving a plurality of vertically stacked baskets, wherein each basket contains a plurality of solid nuclear fuel assemblies therein, the inner leak tight metallic receptacle and the outer receptacle having dimensions to define a passage remaining free between the two receptacles;confining the radioactive material in the inner leak tight receptacle; anddraining water from the outer receptacle through the passage. 18. Method according to claim 17 for which the outer receptacle is drained through the same end of the outer receptacle as the confinement of the inner receptacle. 19. Method according to claim 17, for which drainage is performed through a dip tube descending down to the bottom of the outer receptacle. 20. Method according to claim 17, for which the confinement of the inner leak tight metallic receptacle is performed by welding of at least one closing plate. 21. Method for double confinement of radioactive material including the drainage method according to claim 17, then confinement of the outer receptacle. 22. Method according to claim 21, wherein the outer receptacle is an outer leak tight metallic receptacle the confinement of which is performed by welding of at least one closing plate. 23. Method according to claim 22 wherein the outer receptacle is integrated to a transfer package with radiation shielding sidewalls. 24. Metallic receptacle for conditioning solid nuclear fuel assemblies, comprising a non-removable bottom and an open end, and further comprising a duct opening up in the non-removable bottom, said duct enabling drainage of water from between an adjusted receptacle, positioned within the metallic receptacle, and the metallic receptacle, wherein the adjusted receptacle contains a plurality of baskets vertically stacked within the adjusted receptacle, each basket containing one or more solid fuel assemblies therein.
	abstract	Portable user devices are provided that communicate wirelessly with base stations. A user device may include a transceiver, a power amplifier, a voltage supply, and a global positioning system (GPS) unit. The device may transmit signals at a certain transmit power to a neighboring base station. The device may log the time spent transmitting at each power level. Each data point may be tagged with the current location of the device. The logs of each device may be aggregated by a power optimization server. The power optimization server may calculate optimum power settings for each region and for each type of device. A region may be any desirable size ranging from the size of a single cell to an entire continent. Device users may download updated optimum settings. A device may automatically detect and select the optimum transmit power setting during operation depending on its current location.
	abstract	A moving module of a wafer ion-implanting machine includes a wafer carrier, a moving shaft, a base, a pair of first magnets, a fixture body, and a plurality of second magnets. One end of the wafer carrier is pivotally connected to a wafer tray; and the other end is fixed onto one end of the moving shaft. The base is fixed to the other end of the moving shaft. The moving shaft drives the wafer carrier and the base to move lengthwise. The pair of first magnets is fixed to the base. The fixture body is located between the pair of first magnets. The second magnets are fixed onto the fixture body and one of them forms compelling magnetic force between one of the first magnets. Thereby, the friction generated by contacting any of the first magnets with the fixture body can be prevented, thus increasing the production yield.
	abstract	In an externally integrated steam generator type small modular reactor, a steam generator is arranged along the circumference of a reactor vessel cylindrical shell, and a steam drum is arranged along the circumference of the steam generator. The small modular reactor includes: a nuclear reactor including a hemispherical upper head, the reactor vessel cylindrical shell coupled to the upper head and extending downward from the upper head in a cylindrical shape, and a hemispherical lower head provided on a lower portion of the reactor vessel cylindrical shell, wherein a core is placed in the nuclear reactor; the steam generator surrounding all around the reactor vessel cylindrical shell and including a first penetration hole communicating with an inside of the nuclear reactor; and the steam drum surrounding the circumference of the steam generator and including a second penetration hole communicating with an inside of the steam generator.
	summary
	description	This is a continuation, under 35 U.S.C. §120, of copending international application No. PCT/EP2006/011097, filed Nov. 20, 2006, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German patent application No. DE 10 2005 057 249.9, filed Nov. 29, 2005; the prior applications are herewith incorporated by reference in their entirety. The invention relates to an injection system for a neutron-poison containing an absorber liquid, in particular for the emergency shutdown of a nuclear reactor, containing a reservoir vessel for the absorber liquid. The invention furthermore relates to a method for making an absorber liquid which is under an operating pressure available in such an injection system. The invention additionally relates to a method for injecting the absorber liquid into a component, which is connected downstream of the reservoir vessel, of a plant, for example into a nuclear reactor. Finally, the invention relates to a nuclear power plant, in particular a boiling-water nuclear power plant containing an injection system of this type. In nuclear engineering plants, generally an injection system for a so-called absorber liquid is provided as a safety-relevant device. In particular in a boiling-water nuclear power plant it is necessary to make available rapidly acting measures for the emergency shutdown of the reactor core, if for example the drive of the control rods, which are used to control the nuclear reaction in the normal case, fails. For this purpose, introduction of an absorber liquid with a high absorption cross section for neutrons may be provided in the case of an incident. Usually, a boron solution is used for this purpose, wherein the boron, which is in this context also referred to as a neutron poison, effects the absorption of free neutrons. In this manner, the reactor core is, in an incident situation, safely converted to a subcritical state. By making available the absorber liquid in a reservoir vessel of the injection system at a high pressure, quick initiation of the injection process into the reactor core is possible at all times without the need to first activate active system components which are prone to failure, such as conveying pumps. In order to achieve this passive safety concept, it is therefore necessary to make available the absorber liquid possibly for years at a comparatively high operating pressure. In accordance with a known concept, the pressure in a reservoir vessel, which is in the form of a pressure accumulator, for the absorber liquid could build up by way of a nitrogen cushion which is located above the liquid. To this end however a complex nitrogen distribution system is necessary. A disadvantage in the case of the high operating pressure which is envisaged according to the design is also the relatively high space requirement for the nitrogen cushion relative to the volume of the absorber liquid. Furthermore, over time the nitrogen dissolves at least partially in the absorber liquid (usually boric acid), with the result that, when liquid is injected, a non-condensable gas is also introduced into the reactor, which among others negatively affects the cooling effect of condensers or emergency condensers. Published, non-prosecuted German patent application DE 198 46 459 A1, corresponding to U.S. Pat. No. 6,895,068, discloses an injection system for cooling liquid for the emergency cooling of a nuclear reactor, which achieves the necessary operating pressure by heating the cooling liquid, which is stored in a pressure accumulator vessel, using a heating apparatus arranged in the pressure accumulator vessel. In the process, a vapor cushion is formed over the liquid level by evaporating the liquid as a function of the original filling height. If it is needed, that is to say in a reactor incident situation, the vapor cushion pushes the cooling liquid, with simultaneous relief, into the reactor core through a supply line which is connected in the bottom region of the pressure vessel. Arranging the heating apparatus in an upper section of the accumulator vessel effects a temperature layering of the cooling liquid, with the result that, if needed, first comparatively cold and later increasingly hot cooling liquid flows out of the accumulator vessel. The application of this concept in the context of a boron injection system in which a boron-containing liquid is used not only for cooling purposes but primarily for the emergency shutdown of a nuclear reactor is likewise known. Chemical tests have now concluded, however, that if the absorber liquid, which can advantageously be in the form of a boron solution, is stored for a number of years at the temperatures which are necessary to generate pressure and which are envisaged according to the design within the context of the described concept, a progressive chemical dissociation of the absorber liquid must be expected. Additionally an increased interaction between the absorber liquid and the material of the vessel walls could occur, which under certain circumstances has a disadvantageous effect on the pressure stability or the leak tightness of the reservoir vessel. It is accordingly an object of the invention to provide an injection system and an associated operating method which overcomes the above-mentioned disadvantages of the prior art devices and methods of this general type, which injection system ensures, while keeping the configuration simple, permanently high operational reliability and avoids the stated disadvantages of the known systems. Furthermore, a method which is particularly suitable for operating the injection system will be specified—to be precise in each case for the storage period and for the actual injection process. With the foregoing and other objects in view there is provided, in accordance with the invention, an injection system for a neutron-poison for an emergency shutdown of a nuclear reactor. The injection system contains an absorber liquid, a pressure vessel filled with a propelling fluid, an overflow line, and a reservoir vessel for the absorber liquid. The reservoir vessel is connected, via the overflow line, to the pressure vessel. With respect to the injection system, the stated object is achieved according to the invention by virtue of the fact that the reservoir vessel is connected, via an overflow line, to a pressure vessel, with the pressure vessel being filled with a propelling fluid. The invention is here based on the idea that in order to achieve high operational reliability, chemical decomposition of the absorber liquid or other chemical reactions within the absorber liquid or with the walls of the surrounding reservoir vessel and thus possible corrosion of the wall materials should also largely be avoided if the absorber liquid is stored for a relatively long time over a period of several years or even decades. However, since chemical reactivity generally likewise increases with an increase in temperature, the absorber liquid should be stored in a comparatively cool manner, that is to say approximately at room temperature. On the other hand, the absorber liquid in the reservoir vessel should be able to be kept at a prespecified operating pressure for the entire storage period, so that if it is needed, it can be injected into a reactor cooling system or into a reactor core as quickly and completely as possible. The measures which are necessary to generate pressure should here lead to as little influence on the absorber liquid with respect to its other physical or chemical characteristics as possible. This is achieved in the present case by virtue of a pressure vessel with a propelling fluid which is under operating pressure, which pressure vessel is physically separate from the reservoir vessel and is connected to the reservoir vessel via an overflow line which effects pressure equalization. Therefore on the one hand, due to the overflow line, the pressure in the two vessels is always the same, and on the other hand, the physical separation of the two functions “storage of the absorber liquid” and “maintaining a pressure cushion” using a propelling fluid has the consequence that either of the two vessels can be matched and configured, with respect to its chemical compatibility or other characteristics, specifically to the liquid (absorber liquid or propelling fluid) it contains. The interactive influence between the absorber liquid and the propelling fluid is here extremely low due to the physical separation. Advantageously, the pressure vessel of the injection system has a heating device. In a preferred embodiment, the heating device can be regulated and is configured with respect to its heating output for generating and maintaining an adjustable pressure, wherein preferably the pressure represents the reference variable of the regulation. The actual pressure generation can thus be effected analogously to known systems by virtue of the fact that the pressure vessel is filled up to a prespecifiable filling height (i.e. not completely) with a propelling fluid. Some of the propelling fluid is evaporated by the heating device so that a vapor cushion is formed in the upper region of the pressure vessel and the pressure is maintained by the vapor cushion. The advantage of the vapor cushion is that the operating pressure can very easily be adjusted to, and also maintained at, a desired value, for example the saturated vapor pressure of the propelling fluid. Since the vapor is compressible, a slight temperature increase does not lead to an overproportional pressure increase, as inevitably occurs in a pressure accumulator vessel, for example, which is filled completely with an incompressible liquid. Overall, a known and already proven technology together with the associated know-how can therefore be used for the pressure generation, by which the emergency injection system according to the novel concept can be realized particularly simply and cost-effectively. In particular, if the overflow line, which will be described in more detail below, is configured and dimensioned accordingly, a largely thermal decoupling of reservoir vessel and pressure vessel is ensured with the result that the propelling fluid can also be stored under an operating temperature which is high as compared to the absorber liquid, to the extent that this is expedient for simple generation and maintenance or regulation of the operating pressure, or desired for reasons of other considerations. In a preferred development, the overflow line, which is provided for pressure equalization and for guidance of the propelling fluid, connects the bottom region of the pressure vessel to the ceiling region of the reservoir vessel. In other words, the connector, which is provided at the pressure vessel, of the overflow line is arranged in a lower wall section near the vessel bottom. The other end of the overflow line issues on the side of the reservoir vessel in an upper section of the vessel wall. In particular, this connector can also be guided through a ceiling of the reservoir vessel, which is in the form of a dome. Preferably, the overflow line has in the region of its end, which faces the pressure vessel, a lower partial section which is guided in the manner of a siphon and has a low point which lies below the bottom of the pressure vessel. That end of the overflow line which is connected to the pressure vessel, that is to say that end which is located at the entrance with respect to the direction of flow during the injection process, is therefore in the form of a downpipe piece near the connector. At the (exit) side, which faces the reservoir vessel, the overflow line preferably has an upper partial section with a high point which is arranged above the ceiling of the reservoir vessel, with the result that here on the connector side a downpipe piece is likewise provided. The lower and upper partial sections of the overflow line are preferably connected to one another by a nearly vertical riser piece. This type of line guidance is extremely advantageous for the already mentioned thermal decoupling of the fluids which are stored in the pressure vessel and in the reservoir vessel, respectively, since in particular the lower siphon-type partial section is used to largely suppress convective heat flow or heat conduction to the reservoir vessel (in particular due to the downpipe pieces). The line arrangement also has the advantage that when the injection system is activated, first cooler, liquid propelling fluid from the bottom region of the pressure vessel, later hot, liquid propelling fluid and only then vaporous propelling fluid, which originally forms the vapor cushion in the ceiling region of the pressure vessel, flows over into the reservoir vessel for the absorber liquid. In this manner, the walls of the reservoir vessel are comparatively gently preheated when the propelling fluid enters. This reduces the condensation of the propelling fluid vapor, which would otherwise very quickly heat the previously cold walls of the reservoir vessel. A temperature shock is thus avoided. Additionally, the vapor pressure decreases comparatively slowly during the injection procedure due to the preheating effect caused by the liquid propelling fluid. Even after a large part of the absorber liquid has already been introduced into the reactor, sufficient residual pressure is therefore left to completely displace the absorber liquid from the reservoir vessel. Preferably, an outflow opening provided for the on-demand removal of absorber liquid, for example in the form of an outlet connection provided with a shut-off valve, is arranged in the bottom region of the reservoir vessel. The exit of the absorber liquid is here supported by the hydrostatic pressure of the liquid column in the reservoir vessel. In a preferred embodiment, the pressure-loaded components of the injection system, that is to say in particular the pressure vessel, the reservoir vessel and the overflow line, are configured for an operating pressure of more than 100 bar, in particular for an operating pressure of approximately 150 bar. This corresponds to a pressure value which includes sufficient contingency reserves and is particularly expedient for use as emergency injection system in a nuclear power plant. In order to generate and maintain the desired operating pressure which preferably corresponds to the saturated vapor pressure of the propelling fluid, the propelling fluid is heated, with matching to the provided geometry of the pressure vessel, to an operating temperature of over 300° C., in particular to about 340° C. In another advantageous refinement, the pressure vessel is therefore also configured in terms of its material selection for a permanent provision of pressurized propelling fluid with such a high temperature. The reservoir vessel for the absorber liquid does not need to fulfill any particular requirements in terms of temperature resistance in the regular case, i.e. during the storage period or the standby time until a reactor incident, since the absorber liquid is merely at approximately room temperature. The overflowing hot propelling fluid causes a comparatively short temperature load only during the actual injection procedure. The reservoir vessel can therefore be made of a material which is of a lower quality with respect to its heat resistance than the pressure vessel and is thus cheaper. The injection system is, due to its design principles (in particular passivity and longevity), suitable particularly for making available an absorber liquid for on-demand emergency shutdown of a nuclear power plant. To this end, the reservoir vessel of the injection system is preferably dimensioned such that it can hold a quantity of absorber liquid which is sufficient for shutting down a nuclear reactor. The pressure vessel is preferably dimensioned in this case such that it can hold a quantity of propelling fluid which is sufficient to completely displace the absorber liquid from the reservoir vessel, with this quantity being dependent inter alia on the desired operating pressure and the desired operating temperature and on the type of fluids. An aqueous boron solution has proven particularly suitable as the absorber liquid for emergency shutdown and/or emergency cooling of a nuclear reactor. In particular, an approximately 13% boron solution, for example a sodium pentaborate solution, can be provided as the absorber liquid. As opposed to other conceivable absorber liquids with a high absorption cross section for neutrons, a boron solution is distinguished at least at temperatures which are not too high by a long shelf life and relatively good chemical compatibility with respect to the walls of the reservoir vessel, which are usually made of steel. Water is preferably provided as an easy-to-store propelling fluid which has particularly good compatibility with the boron solution. In the evaporated form, i.e. in the vapor cushion of the pressure vessel, the water is present as water vapor. The object relating to the method for making available an absorber liquid under an operating pressure is achieved by virtue of the fact that the operating pressure is generated by heating the propelling fluid in the pressure vessel of the injection system. The propelling fluid is here advantageously stored in a lower region of the pressure vessel in liquid form. The action of the heating device which can preferably be in the form of an electric heating device or of a heat exchanger system causes some of the quantity of liquid to evaporate, so that a vapor cushion is formed in the upper region of the pressure vessel. In a particularly preferred refinement, the heating device is a constituent part of a regulating system and is additionally dimensioned with respect to its achievable heating output to be sufficiently large so that a vapor cushion with an adjustable, temporally constant pressure can be permanently maintained. If a vapor cushion is present, the adjustment and maintenance of the desired pressure value can be effected significantly more easily in comparison with a pressure accumulator which is completely filled with liquid. In case of necessity, the absorber liquid which is made available under an operating pressure is injected into a component, which is connected downstream of the reservoir vessel, of a plant, in particular into a nuclear reactor. Such a case of necessity exists for example if the control elements or control rods, which are normally provided to control the neutron flow, cannot be inserted into the core due to a fault in the drive or in the actuation. In this case, a valve or a shut-off apparatus of the reservoir vessel is opened, so that the pressurized absorber liquid is introduced via a connection line into the reactor pressure vessel. Preferably, due to the relief of the vapor cushion, which is formed from evaporated propelling fluid, in the pressure vessel, first liquid and then vaporous propelling fluid flows into the reservoir vessel, wherein the absorber liquid which was originally present therein is more and more displaced. To the extent that water or water vapor is used as the propelling fluid, thus first preferably hot water, then saturated water and finally saturated vapor flows from the pressure vessel into the reservoir vessel, with the vessel pressure decreasing at the same time. A temperature shock on the walls of the reservoir vessel is avoided by this advantageous sequence. In another advantageous development, the overflow speed of the propelling fluid during such an injection process is adjusted such that although on the one hand as high a throughput per unit time as possible is achieved and thus the reactor can be shut down quickly, on the other hand mixing of the propelling fluid with the absorber liquid is substantially prevented. Such a value of the overflow speed can be adjusted for instance by way of a suitable throttle device or can be predefined already by way of the dimensioning of the overflow line itself. The advantage of the injection method carried out in this manner is that the temperature layering, which is established due to the density differences in the reservoir vessel, of cold absorber liquid and, above the latter, hot propelling liquid remains. Therefore only cold absorber liquid is introduced into the reactor core. Once the absorber liquid is fully displaced from the reservoir vessel, the pressure in the injection system has advantageously decreased so strongly that the flow processes stop automatically. In this way, the hot propelling fluid is kept away from the reactor core. Expediently, the injection system is a constituent part of a nuclear power plant. It is preferably in the form of a so-called poison injection system which can be used to shut down the nuclear reaction in a boiling-water reactor if, in the case of a serious incident situation, the control rods can no longer be inserted into the reactor core. Alternatively, or additionally, provision could be made for the fluid which is made available at high pressure by the injection system to be used for the emergency driving of the control rods themselves, by way of which a hydraulic drive system is realized which is redundant with respect to the usually electric driving of the control rods. The liquid stored in the reservoir vessel of the injection system should in this case therefore be regarded as drive liquid for the control rods. In another alternative, the injection fluid is supplied in an expedient manner to an emergency cooling system of a pressurized-water nuclear power plant as emergency cooling fluid (usually emergency cooling water). The injection system is therefore preferably used as a so-called accumulator for the emergency cooling water in a pressurized-water nuclear power plant. The advantages achieved with the invention are in particular that, by physically separating the functions “liquid storage” and “pressure generation” in the form of a reservoir vessel and a pressure vessel which are in each case provided for holding purposes, an effective chemical and thermal decoupling of the absorber liquid from the propelling fluid can be achieved, wherein the overflow line which connects the two components of the injection system ensures that the absorber liquid is stored at operating pressure such that it can be removed at any time. Such a configuration of an injection system, in which in particular heating of the reservoir vessel for the absorber liquid is prevented, provides a particularly high operational reliability also for permanent operation or standby mode over many years since a chemical reaction of the absorber liquid with the reservoir vessel and thus also a chemical dissociation of the absorber liquid is kept extremely low. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in an injection system and an associated operating method, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings. Identical parts are provided with the same reference symbols in both figures. Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is shown an injection system 2 which is used to make available and to inject in an on-demand manner pressurized absorber liquid 4 into a component, which is connected downstream of the injection system 2, of a plant, in particular into a nuclear reactor. In the exemplary embodiment, the absorber liquid 4 is a 13% sodium pentaborate solution which, in the case of an incident in a boiling-water reactor (not illustrated further here), is to be introduced into the reactor core, wherein the boron atoms of the boron solution capture free neutrons on account of their comparatively high absorption cross section for neutrons. In this way, the reactor can be reliably shut down in a relatively short period of time (approximately 20 seconds after the injection of the absorber liquid 4). In order to store the absorber liquid 4, a pressure-stable reservoir vessel 6 is provided, which reservoir vessel is completely filled with the absorber liquid 4 during the storage period. Here, the reservoir vessel 6 is an upright cylindrical tank with a bottom region 8 and a ceiling region 10 which are in each case in the shape of a semi-sphere. A structural height H and a diameter D and thus also the volume of the reservoir vessel 6 are matched to the intended use in a nuclear power plant and have, for example, the values H=7.0 m and D=0.8 m. The capacity of the reservoir vessel 6 thus corresponds to the quantity of absorber liquid 4 which is provided for the emergency shutdown of the reactor core. A vessel wall 12 is made from a particularly pressure-stable and corrosion-resistant steel wall of a high-grade steel, for example of an austenitic steel. In accordance with the configuration of the injection system 2 as a passive safety system, the absorber liquid 4 must be stored permanently under an operating pressure of preferably about 150 bar over the storage period which may last many years, that is to say in standby mode, as it were. The temperature of the absorber liquid 4 here should, however, not substantially exceed room temperature in order to avoid increased reactivity which could lead to corrosion of the surrounding vessel wall 12 and to a decomposition of the boron solution. In the exemplary embodiment, storage of the absorber liquid 4 at a temperature of about 30° C. is therefore envisaged. Because of the comparatively low temperature of the absorber liquid 4, the injection system 2 is configured for a particularly high operational reliability during the standby mode, wherein furthermore any influence on the absorber liquid 4 due to the measures necessary to generate pressure should, if possible, be avoided. In order to realize the stated temperature and pressure conditions in the reservoir vessel, the generation and maintenance of a pressure cushion, which are based on the evaporation of a propelling fluid 14 and associated with a strong development of heat, are therefore decoupled from the reservoir vessel 6. To this end, a separate pressure vessel 16 is provided which is configured in the exemplary embodiment similarly to the reservoir vessel 6 and also has approximately the same dimensions. The pressure vessel 16 here therefore has the same structural height H and the same diameter D′=D as the reservoir vessel 6. Both vessels are additionally arranged at the same height. While the volume of the pressure vessel 16 is subject to boundary conditions which, as far as possible, are prespecified by the intended use (in particular by the operating pressure to be realized, the quantity of absorber liquid 4 to be displaced and, if appropriate, by further design criteria), there is a far-reaching design freedom with respect to the concrete shape and arrangement of the pressure vessel 16 similar to the case of the reservoir vessel 6. The pressure vessel 16 is filled in the case of operation up to a filling height h with the liquid propelling fluid 14. The propelling fluid 14, in this case water, is heated by a heating device 18, which can be regulated, and evaporates partially in the process, with the result that a vapor cushion 20 forms over the liquid level, in this case therefore a water vapor cushion, which, owing to its compressibility, effects the actual pressure storage. The regulation of the heating device 18, which is formed for example by electric heating elements or by a heat exchanger system and is preferably arranged in a lower region of the pressure vessel 16, is effected such that approximately constant operating pressure of about 150 bar is maintained over the entire standby time. To this end, provision is made to heat the water located in the pressure vessel 16 to an average temperature of about 340° C. These values correspond to the saturated vapor pressure and the saturated temperature. A vessel wall 12′ of the pressure vessel 16 must therefore not only be particularly pressure-stable, but also comparatively heat-resistant. In order to reduce the heat losses (especially on account of heat radiation), the pressure vessel 16 is provided on its outside with a thermal insulation (not illustrated in further detail). The pressure vessel 16 is, on the medium side, connected via an overflow line 22 to the reservoir vessel 6, by which the same pressure conditions prevail in the entire injection system 2. Here, the overflow line 22 is guided out of the bottom region 8′ of the pressure vessel 16 in the manner of a siphon. The overflow line 22 therefore has a lower partial section 23 with a low point which is located below the bottom of the pressure vessel 16. Connected to the lower partial section 23, viewed in the direction of flow of the propelling fluid 14 (with reference to the injection process), is a vertical riser 24 which finally merges into a substantially arched upper partial section 25. The high point of the upper partial section 25 here lies above the ceiling of the reservoir vessel 6. The overflow line 22 is, in the direction of the reservoir vessel 6, guided into a connection flange 26 which projects out of the dome-type ceiling region 10 of the reservoir vessel 6. Due to the pressure exerted by the vapor cushion 20, the liquid propelling fluid 14 completely fills the overflow line 22. Any air cushion which may have originally been present in the overflow line was already displaced during the preceding heating process at approximately 100° C. At a boundary surface 27 between the absorber liquid 4 (boron solution with comparatively high density) and the propelling fluid 14 (water with lower density), the two liquids do not mix owing to the difference in densities. Rather, a layered liquid column is formed there. Due to the way the line is guided, a convective transport of heat inside the overflow line 22 can, if the line diameter is appropriately dimensioned, be neglected just like the conduction of heat. In other words: the liquid propelling fluid 14, which is located in an issue region 28 to the reservoir vessel 6 or just above in the overflow line 22, has approximately the same temperature as the absorber liquid 4 inside the reservoir vessel 6, that is to say approximately 30° C. The temperature of the fluid in the overflow line 22 rises continuously in the direction of the pressure vessel 16. The absorber liquid 4 is therefore not heated due to the substantially stationary temperature distribution inside the overflow line 22. If the injection system 2 is activated, a shut-off valve or other shut-off apparatus 30 which has been kept shut up until then is opened so that the pressurized absorber liquid 4 can emerge from an outflow opening 32 arranged in the bottom region 8 of the reservoir vessel 6. Connected to the outflow opening 32 is a connection line 34 to the component which is to be supplied with absorber liquid 4, for example a bypass of a reactor core. The shut-off apparatus 30 can, as shown here, be integrated into the connection line 34 or else directly into the outflow opening 32. During the injection process, the pressure of the vapor cushion 20, which has previously built up in the ceiling region 10′ of the pressure vessel 16, is relieved and in the process pushes the hot water, which is located under the cushion and acts as propelling fluid 14, into the overflow line 22 and then into the reservoir vessel 6. During this process, first the hot water, which is originally in the bottom region 8′ of the pressure vessel 16, then the saturated water, which is present directly below the vapor cushion 20, and finally the saturated vapor itself, which forms the vapor cushion 20, flows from the pressure vessel 16 into the reservoir vessel 6, with the vessel pressure decreasing at the same time. When the hot water enters the reservoir vessel 6, its vessel wall 12 is heated comparatively gently, in any case more gently than in the case of a direct entry of hot vapor. This avoids a temperature shock and associated material stresses. Additionally, the vapor pressure does not decrease as quickly as would be the case in a direct condensation of the vapor at the cold vessel wall 12 of the reservoir vessel 6. The hot propelling fluid 14 flows into the reservoir vessel 6 preferably in a manner such that a swirling or mixing with the cold absorber liquid 4 is avoided and the temperature layering which occurred originally due to the difference in densities therefore remains. That means that there is a relatively sharply defined boundary surface 27 between the cold absorber liquid 4 and the hot propelling fluid 14, which also remains intact over the course of the inflow process and in the process continuously wanders downwards. For this purpose, the issue region 28 of the overflow line 22 into the reservoir vessel 6 has a throttle element 36, provided with a large number of exit nozzles 35 (arranged for example on a cylinder outer surface), for suitably influencing the flow. A screening sheet 38 is also arranged in the throttle element 36. The injection system 2 with the stated dimensions is suited particularly as a quickly activatable boron injection system in a nuclear power plant, in particular in a boiling-water nuclear power plant. The two pressure vessels connected via the overflow line 22 (reservoir vessel 6 and pressure vessel 16) are in this case comparatively slim and tall, so that the vessel walls 12, 12′ can be kept thin. In this case, owing to the quick heating of the reservoir vessel 6 during the injection process, the thermal loads are lower than in the case of a shorter vessel with correspondingly greater wall thickness. Volume conditions which are different from those mentioned above can be more expedient for other intended uses. FIG. 2 shows a schematic detail from a boiling-water nuclear power plant 39 with an injection system 2 according to FIG. 1. A reactor pressure vessel 42 with a core region 44 is arranged in a containment 40. The reactor pressure vessel 42 is partially filled with a cooling liquid 46. Above the cooling liquid 46, there is vapor 48 which is conducted via a vapor line 50 out of the containment 40 and is guided to a turbine (not illustrated in more detail). Cooled cooling liquid 46 is recycled to the reactor pressure vessel 42 via a line 52. The performance of the nuclear reactor can be regulated by inserting and removing the control rods 54 into and out of the core region 44. The control rods 54 are in this case moved by a drive system 56 which is designed in a redundant manner. If the incident-free ability to manipulate the control rods 54 is no longer ensured in the case of a serious incident situation, the nuclear reaction can be interrupted by way of injecting boric acid 58 into the core region 44 of the boiling-water reactor (so-called poison injection system). The boric acid 58 is stored under high pressure in the reservoir vessel 6 of the emergency injection system 2 according to FIG. 1. The injection system 2 has for this purpose the pressure vessel 16, which is connected via the overflow line 22 to the reservoir vessel 6 for the boric acid 58 and in which a saturated vapor cushion 62 is produced by heating of water 60. The injection system 2 and the associated operating method allow preferably in boiling-water nuclear power plants and in particular in the case of incident situations a reliable supply of the absorber liquid 4, in particular boric acid, intended for an emergency shutdown to the reactor core, wherein, during the preceding storage period, corrosion of the reservoir vessel 6 and/or dissociation of the absorber liquid 4 is avoided.
060977795	summary	FIELD OF THE INVENTION This invention relates generally to nuclear reactors and, more particularly, to a fuel bundle and control rod assembly for such reactors. BACKGROUND OF THE INVENTION A reactor pressure vessel (RPV) of a boiling water reactor (BWR) typically has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide typically is spaced above a core plate within the RPV. A core shroud, or shroud, typically surrounds the core plate and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds the both the core plate and the top guide. The top guide includes several openings, and fuel bundles are inserted through the openings and are supported by the core plate. A plurality of openings are formed in the bottom head dome so that components, such as control rod drive assemblies, can extend within the RPV. As an example, for a control rod drive assembly, a control rod drive housing, e.g., a tube, is inserted through the bottom head dome opening and a control rod drive is inserted through the control rod drive housing. The control rod drive is coupled to a control rod to position the control rod within the core. A nuclear reactor core includes individual fuel assemblies that have different characteristics that affect the strategy for operation of the core. For example, a nuclear reactor core has many, e.g., several hundred, individual fuel bundles that have different characteristics. Such bundles preferably are arranged within the reactor core so that the interaction between the fuel bundles satisfies all regulatory and reactor design constraints, including governmental and customer specified constraints. In addition to satisfying the design constraints, since the core loading arrangement determines the cycle energy, i.e., the amount of energy that the reactor core generates before the core needs to be refreshed with new fuel elements, the core loading arrangement preferably optimizes the core cycle energy. In order to furnish the required energy output, the reactor core is periodically refueled with fresh fuel assemblies. To optimize core cycle energy, the higher reactivity bundles may be positioned at an inner core location. To satisfy some design constraints, however, higher reactivity bundles generally are positioned at an outer core location. The most depleted fuel bundles, i.e., the bundles with the least remaining energy content, are removed from the reactor. The interval between refuelings is referred to as a cycle of operation. During the course of the cycle of operation, the excess reactivity, which defines the energy capability of the core, is controlled in two ways. Specifically, a burnable poison, e.g., gadolinia, is incorporated in the fresh fuel. The quantity of initial burnable poison is determined by design constraints typically set by the utility and by the NRC. The burnable poison controls most, but not all, of the excess reactivity. Control rods also control the excess reactivity. Specifically, the reactor core contains control rods which assure safe shutdown and provide the primary mechanism for controlling the maximum power peaking factor. The total number of control rods available varies with core size and geometry, and is typically between 50 and 205. The position of the control rods, i.e., fully inserted, fully withdrawn, or somewhere between, is based on the need to control the excess reactivity and to meet other operational constraints, such as the maximum core power peaking factor. One known control rod includes a central portion having four radially extending blades. The blades define four fuel bundle channels, and when inserting the control rod into the core, the control rod is positioned so that one fuel bundle is positioned within each channel. Therefore, for example, approximately 100 control rods are included in a reactor having 400 fuel bundles. To reduce the number of control rods necessary for efficient operation, one known reactor includes fuel bundles with an interior water gap arranged in a K-lattice configuration. Each fuel bundle in such reactor is substantially larger than a conventional size fuel bundle, and represents twice the pitch as the conventional BWR fuel configuration. The larger fuel bundles facilitate increasing the peaking factor of the BWR core. Particularly, the maximum channel integrated power, i.e., highest radial peaking factor, is greater for such large twice pitch K-lattice fuel bundle core than for a core loaded with conventional size fuel bundles. The maximum channel peaking factor for the large twice pitch bundle core, for example, is approximately 1.7, whereas the maximum channel peaking factor for a conventional core typically is approximately about 1.4 or 1.5. Such larger fuel bundles also facilitate reducing the number of control rod drives, and thus reduce the capital cost of the reactor. Particularly, fuel assemblies including such twice pitch bundles are approximately four times the size of conventional fuel assemblies. Accordingly, fewer twice pitch bundles may be installed in nuclear reactor as compared to standard size fuel bundles. Fewer control rods, therefore, are needed to control radiation between the fewer twice pitch bundles as compared to standard size fuel bundles. Power is generated with fewer twice pitch fuel bundles as compared to standard size fuel bundles. In addition, refueling time is decreased due to the reduced number of fuel bundles. The twice pitch bundles provide for a nuclear reactor having a reduced number of control rod drives and a substantial reduction in capital cost as compared with a conventional reactor utilizing conventional fuel bundles. However, such larger bundles typically also require substantial redesign of the fuel assembly, (e.g., with a twice pitch bundle design, the fuel assembly is approximately four times the size of a conventional fuel assembly). Similarly, the larger bundles typically impose more parasitic material in the core, and are more susceptible to bow and bulge. In addition, the ability to perform sub-bundle shuffling, i.e., the ability to reposition individual fuel bundles within the core or remove individual fuel bundles from the core, is substantially compromised with the larger fuel bundles. It would be desirable to reduce the number of control rod drives without requiring substantial redesign of a fuel assembly. It also would be desirable to reduce the number of control rod drives without substantially compromising the ability to perform sub-bundle shuffling. SUMMARY OF THE INVENTION These and other objects may be attained by a nuclear reactor which, in one embodiment, includes at least one large control rod and conventional size fuel assemblies. Particularly, and in accordance with one embodiment of the present invention, at least one large control rod is sized to provide poison control (e.g., negative reactivity) for sixteen conventional size fuel bundles. The large control rod includes four channels defined by a central portion having four blades extending radially therefrom. The channels each are sized to receive one set of four conventional size fuel bundles. The fuel bundles are positioned in a "K" lattice configuration, and each set of four fuel bundles represents approximately twice the pitch of a single conventional size fuel bundle. The above-described reactor facilitates sub-bundle shuffling for maximum fuel cycle optimization. Such reactor also facilitates reducing refueling time. In addition, such reactor reduces the number of control rod drives by about one-half, as compared to a conventional reactor, and permits refueling four or more conventional fuel assemblies at one time, with an overall reduction in capital cost of the plant and reduced outage time.
	claims	1. An air distribution system for supplying filtered air to an isolator working volume, the system comprising:an inlet including a HEPA filter; andan outlet including a slidably mounted sintered panel,wherein the slidably mounted panel is positioned between the HEPA filter and the isolator working volume, and wherein the sintered panel is slidable between a first, closed position directly under the HEPA filter, and a second, open position enabling access to the HEPA filter. 2. The air distribution system of claim 1 further comprising tracks for mounting the sintered panel, the sintered panel being slidable on the track. 3. The air distribution system of claim 1 wherein the sintered panel is made of stainless steel. 4. The air distribution system of claim 1 wherein the isolator is a radionuclide generator hot cell. 5. The air distribution system of claim 4 wherein the hot cell includes a manufacturing area, and wherein the system is configured to provide uniform air flow over the manufacturing area. 6. A method for supplying filtered air to an isolator working volume, the method comprising:filtering the air through a HEPA filter into a plenum chamber defined by the volume between (i) an outlet surface of the HEPA filter, (ii) an inlet surface of a slidably mounted sintered panel, and (iii) walls of the isolator, wherein the slidably mounted sintered panel is positioned between the HEPA filter and the working volume of the isolator,controlling an air pressure in the plenum chamber to be greater than an air pressure in the isolator working volume. 7. The method of claim 6 wherein the isolator working volume is negatively pressurized and the plenum is positively pressurized. 8. The method of claim 6 wherein the sintered panel is made of stainless steel. 9. The method of claim 6 wherein the isolator is a radionuclide generator hot cell. 10. An air distribution system for supplying filtered air to an isolator working volume, the system comprising:a HEPA filter for filtering air to the isolator;a track mounted between the HEPA filter and the working volume, and a sintered panel slidably mounted on the track; anda plenum defined by the volume between the HEPA filter outlet surface, the sintered panel inlet surface, and the isolator walls,the sintered panel being slidable between a first closed position directly under the HEPA filter, and a second open position enabling access to the HEPA filter. 11. The air distribution system of claim 10 comprising a second HEPA filter, a second track mounted between the second HEPA filter and the working volume, and a second sintered panel slidably mounted on the second track, the second sintered panel being slidable between a first closed position directly under the second HEPA filter, and a second open position enabling access to the second HEPA filter. 12. The air distribution system of claim 10 wherein the isolator is a radionuclide generator hot cell. 13. The air distribution system of claim 1 comprising a second HEPA filter and a second slidably mounted sintered panel, wherein the second slidably mounted panel is positioned between the second HEPA filter and the isolator working volume. 14. The air distribution system of claim 2 comprising a second track for mounting a second sintered panel, the second sintered panel slidable on the track, wherein the second track is positioned at a different elevation than the track such that the second sintered panel is slidable under or over the sintered panel. 15. The method of claim 6 wherein the isolator walls are constructed of radiation shielding material. 16. The air distribution system of claim 10 wherein the sintered panel is made of stainless steel. 17. The air distribution system of claim 10 wherein the isolator walls are constructed of radiation shielding material. 18. The air distribution system of claim 11 wherein the sintered panel and the second sintered panel are made of stainless steel. 19. The air distribution system of claim 11 wherein the second track is positioned at a different elevation than the track such that the second sintered panel is slidable under or over the sintered panel.
059303182	abstract	The present invention provides a method and apparatus for fuel handling in a nuclear reactor. The nuclear reactor has a reactor vessel comprising a reactor core with a plurality of fuel assemblies and control rods. A fuel pool is arranged adjacent to the reactor vessel. A group comprising at least a plurality of fuel assemblies is simultaneously lifted out of or into the reactor vessel with a single gripper, the gripper having a plurality of gripping devices. The group is transported between the reactor vessel and the fuel pool by means of the gripper.
050135201	description	Referring now to the figures of the drawings in detail and first, particularly, to FIGS. 1 and 2 thereof, there is seen an apparatus having two guide rails 2 for a base plate 3. The guide rails 2 are stationary with respect to a frame 4 on which a support plate 5 is secured. The base plate 3 has an opening or duct 6 formed therein, through which an elongated can 7 of square cross section extends, so as to form a holder for the can. The longitudinal axis of the can 7 is at right angles to the base plate 3 and to the guide rails 2, which are parallel to one another. A cylinder 8 that can be acted upon by compressed air is mounted on the base plate 3 and contains a piston that can be displaced at right angles to the base plate 3. A lever 9 is articulated on the piston and secured to an elongated, rotatable eccentric shaft 10. The eccentric shaft 10 has an axis of rotation parallel to the base plate 3 and to one side wall 7a of the can 7, and the eccentric shaft is rotatably supported on the base plate 3 about the axis of rotation thereof. A bevel gear 11 is also mounted on one end of the eccentric shaft 10, concentrically with the axis of rotation of the eccentric shaft 10. The bevel gear 11 meshes with a further bevel gear 12. The bevel gear 12 is mounted on a shaft 13, which is likewise rotatably supported on the base plate 3 with an axis of rotation parallel to the base plate 3. The axes of rotation of the eccentric shaft 10 and of the shaft 13 are at right angles to one another. An eccentric 15 guided in a connecting link 14 is mounted on the shaft 13. A hollow rod 16 with a support element 17 is located at the connecting link 14. A non-illustrated die rod is guided inside the hollow rod 16 and secured on the rod 16 by a pin 18. A retaining die 19 is mounted outside the hollow rod 16, on one end of the die rod, and the retaining die is capable of resting flat on a side wall 7b of the can 7 adjacent the side wall 7a. Between the support element 17 and the retaining die 19 on the die rod is a spring assembly being formed of plate springs 20. Two blocks 25 and 26 are disposed on the support plate 5. A rail 27 is attached to the block 25, and a rail 28 is attached to the block 26. The rails 27 and 28 are at right angles to the support plate 5 and thus to the base plate 3 as well, and they are parallel to the longitudinal direction of the can 7. A carriage 31 or 32, provided with respective guide rollers 29 or 30, is displaceably guided on each rail 27 or 28, respectively, parallel to the longitudinal direction of the can 7. A respective fuel rod positioning arm 33 or 34 is attached to each carriage 31 and 32. The fuel rod positioning arms 33 and 34 are parallel to the support plate 5 and the base plate 3 and are at right angles to the longitudinal axis of the can 7. Each fuel rod positioning arm 33 and 34 forms an insertion end for insertion into the can 7, through a crosswise slit 7c in the side wall 7d opposite the side wall 7a of the can 7. A support structure 35 for fuel rods 36 to be inserted into the can 7 is attached to the two insertion ends of the fuel rod positioning arms 33 and 34. The support structure 35 is pivotable back and forth about a pivot axis of a shaft 37, which is at right angles to the insertion direction of the fuel rod positioning arms 33 and 34 into the can 7 and at right angles to the longitudinal direction of the can 7. The pivot axis 37 is also parallel to the side walls 7a and 7d of the can 7. A shaft 38 is supported in both carriages 31 and 32 and is parallel to the pivot axis 37 of the support structure 35. Mounted on the shaft 38 are two levers 39 and 40, each of which has two lever arms. A rod is pivotably connected to each lever arm of the two levers 39 and 40. Of the four rods connected to the lever arms, rods 42 and 44 on the lever 40 and a rod 41 on the lever 39 are seen in FIG. 1. The other ends of the four rods are pivotably connected to holders 45 and 46, which are secured to the side of the support structure 35. As can be seen particularly from FIG. 3, the support structure 35 is a tubular half-shell. Within a pivot angle sigma as measured from the pivot axis 37, the support structure 35 has a plurality of fuel rod support surfaces 47 and 48 on its jacket surface which are offset from and alongside one another in the direction of the pivot axis 37. One fuel rod support surface 47 changes from a segment in which it has a shorter radial spacing 49 from the pivot shaft 37 than the two fuel rod support surfaces 48 adjacent thereto, into a different segment in which it has a greater radial spacing 49 from the pivot axis 37 than the adjacent support surfaces 48. The radial spacings 49 and 50 of the two adjacent support surfaces 47 and 48 from the pivot axis 37 also increases in an infinitely graduated manner in opposite directions within the pivot angle sigma. A plate 49' is secured to the blocks 25 and 26 and a cylinder 50' that can be subjected to compressed air is located on the underside of the plate 49'. Inside the cylinder 50' is a piston, which is displaceable at right angles to the support plate 5 and has a piston rod 51 that is secured to a transverse plate 52. The transverse plate 52 is in turn secured to the fuel rod positioning arms 33 and 34. Finally, a gear wheel 53 that meshes with a rack 54 is mounted on the shaft 38. The rack 54 is mounted on a plate 55, which stands vertically on the support plate 5 and is secured to the support plate 5 and to the plate 49. Thus the rack 54 is likewise at right angles to the support plate 5. The eccentric shaft 10 is a counterpart structure to the support structure 35. Accordingly, the eccentric shaft 10 has grooves 56 formed therein in the circumferential direction thereof, which form an external toothing on the jacket surface. By rotation of the eccentric shaft 10, these grooves 56 forming the toothing can be inserted into the can 7 through a transverse slit 7e in the side 7a of the can 7. The transverse slit 7e is located at the same height as the transverse slit 7c in the opposite side wall 7d of the can 7. When the grooves 56 of the eccentric shaft 7 forming the toothing are inserted into the transverse slit 7e, a support surface 57 on the jacket surface of the eccentric shaft 10 for holding the can simultaneously presses against the edge of the side wall 7b in the transverse slit 7e. After the insertion of the can 7 into the opening 6, the cylinder 8 is subjected to compressed air. This rotates the eccentric shaft 10 so that the grooves 56 forming the toothing are inserted into the transverse slit 7e of the can 7. At the same time, the retaining die 19 is pressed externally against the side wall 7b of the can 7, so that the can 7 is firmly retained in a holder formed by the base plate 3, with its longitudinal axis at right angles to the base plate 3. A spindle 60 is driven by switching on a non-illustrated electric motor. The spindle 60 has a spindle nut 61 associated therewith, which is secured on a tube 62. A stop element 63 is secured to the tube 62. A slide block 64 is displaceably disposed on the tube 62 between the spindle nut 61 and the stop element 63, and secured to the underside of the base plate 3. Mounted on the tube between the spindle nut 61 and the sliding block 64 is a compression spring acting as a resilient restoring element 65, which is braced in a direction toward both the spindle nut 61 and the sliding block 64. The base plate 3 is therefore displaced on the guide rails 2 toward the support plate 5, so that the fuel rod positioning arms 33 and 34 with the support structure 35 pass through the transverse slit 7c of the can 7 into the can 7 until the support structure 35 comes to a stop at the eccentric shaft 10. The support surfaces 47 of the support structure 35 and the grooves 56 of the toothing of the eccentric shaft 10 then form guide conduits 59 in the longitudinal direction of the can 7 on the inner surface of the side wall 7a of the can 7. The fuel rods 36 are then introduced into these guide channels 59 from the top end of the can 7. The cylinder 50' is then subjected to compressed air, and the piston rod 51 is moved into another of two terminal positions. In this waY the carriages 31 and 32 are displaced on the plate 49'. At the same time, the gear wheel 53 rolls along the rack 54 and pivots the levers 39 and 40. As a result, the support structure 35 is pivoted through the rods 41-44 about the pivot shaft 37 by the pivot angle sigma. The support structure 35 rolls along the fuel rods 36, and with the fuel rods 36 located on the inside of the side wall 7a of the can 7, forms new guide channels in the longitudinal direction of the can 7. Each new guide channel is located between two fuel rods 36 resting on the inside of the side wall 7a. During this pivoting process, the base plate 3, which is the holder for the can 7, is thrust away from the support plate 5 on the guide rails 2 counter to the compression spring acting as the resilient restoring element 65. Further fuel rods are thereupon inserted into the new channels. Next, after the electric motor is switch on, the compression spring is relieved by moving the base plate 3 toward the guide rails 2, away from the base plate 5. Thereupon the cylinder 50' is subjected to compressed air in such a way that the piston rod 51 moves to its opposite terminal position. As a result the support structure 35 pivots back again by the pivot angle sigma and rolls along the fuel rods located in the can 7 into the position shown in FIG. 1. As a result, guide channels are again formed in the longitudinal direction of the can 7, between the most recently inserted fuel rods, for the insertion of new fuel rods. By repeating this alternation and gradually increasing the distance of the base plate 3 from the support plate 5, the can 7 can finally be completely filled with fuel rods in a close-packed structure. The foregoing is a description corresponding in substance to European Application 88 11 3815.0, dated Aug. 24, 1988, the International priority of which is being claimed for the instant application, and which is hereby made part of this application. Any material discrepancies between the foregoing specification and the aforementioned corresponding German application are to be resolved in favor of the latter.
	abstract
	claims	1. A zirconium-based alloy having one of improved corrosion resistance and improved creep resistance, for use in an elevated temperature environment of a nuclear reactor, comprising an alloying composition:0.2 to 1.5 weight percent niobium;0.01 to 0.6 weight percent iron;0.0 to 0.8 weight percent tin;0.0 to 0.5 weight percent chromium;0.0 to 0.3 weight percent copper;0.0 to 0.3 weight percent vanadium;0.0 to 0.1 weight percent nickel; anda balance at least 97 weight percent zirconium, including impurities, the zirconium-based alloy formed by a process, comprising:(a) melting the alloying composition to produce a melted alloy material;(b) forging the melted alloy material to produce a forged alloy material;(c) quenching the forged alloy material to produce a quenched alloy material;(d) extruding the quenched alloy material to produce a tube-shell alloy material;(e) pilgering the tube-shell alloy material to produce a reduced tube-shell alloy material;(f) annealing the reduced tube-shell alloy material to produce an annealed alloy material;(g) repeating steps (e) and (f) to produce a final alloy material; and(h) subjecting the final alloy material to a final heat treatment selected to provide the zirconium-based alloy exhibiting one of improved corrosion resistance and improved creep resistance,wherein for providing the zirconium-based alloy exhibiting improved corrosion resistance, the final alloy material is subjected to a final heat treatment selected from a final heat treatment of partial recrystallization to produce an amount of recrystallization from about 15% to about 20% with the remainder being stress relief annealed or a final heat treatment of stress relief annealed, andwherein for providing the zirconium-based alloy exhibiting improved creep resistance, the final alloy material is subjected to a final heat treatment of partial recrystallization to produce an amount of recrystallization from about 80% to about 95% recrystallization with the remainder being stress relief annealed. 2. The zirconium-based alloy of claim 1, wherein said alloy is formed into an article. 3. The zirconium-based alloy of claim 2, wherein said article is selected from the group consisting of cladding. 4. The zirconium-based alloy of claim 1, wherein the alloy comprises:0.6 to 1.5 weight percent niobium;0.01 to 0.1 weight percent iron;0.15 to 0.35 weight percent chromium;0.02 to 0.3 weight percent copper; anda balance at least 97 weight percent zirconium, including impurities. 5. The zirconium-based alloy of claim 1, wherein the alloy comprises:0.2 to 1.5 weight percent niobium;0.25 to 0.45 weight percent iron;0.05 to 0.4 weight percent tin;0.15 to 0.35 weight percent chromium;0.01 to 0.1 weight percent nickel; anda balance at least 97 weight percent zirconium, including impurities. 6. The zirconium-based alloy of claim 1, wherein the alloy comprises:0.4 to 1.5 weight percent niobium;0.01 to 0.1 weight percent iron;0.05 to 0.4 weight percent tin;0.0 to 0.5 weight percent chromium;0.02 to 0.3 weight percent copper;0.12 to 0.3 weight percent vanadium; anda balance at least 97 weight percent zirconium, including impurities. 7. The zirconium-based alloy of claim 6, wherein the chromium is present in an amount from 0.05 to 0.5. 8. The zirconium-based alloy of claim 1, wherein the alloy comprises:0.4 to 1.5 weight percent niobium;0.01 to 0.6 weight percent iron;0.1 to 0.8 weight percent tin;0.0 to 0.5 weight percent chromium; anda balance at least 97 weight percent zirconium, including impurities. 9. The zirconium-based alloy of claim 8, wherein the chromium is present in an amount from 0.05 to 0.5. 10. A method of making a zirconium-based alloy which exhibits one of improved corrosion resistance and improved creep resistance for use in an elevated temperature environment of a nuclear reactor, comprising the steps:(a) combining:0.2 to 1.5 weight percent niobium;0.01 to 0.6 weight percent iron;0.0 to 0.8 weight percent tin;0.0 to 0.5 weight percent chromium;0.0 to 0.3 weight percent copper;0.0 to 0.3 weight percent vanadium;0.0 to 0.1 weight percent nickel; anda balance at least 97 weight percent zirconium, including impurities, to provide an alloy mixture;(b) melting the alloy mixture to produce a melted alloy material;(c) forging the melted alloy material to produce a forged alloy material;(d) quenching the forged alloy material to produce a quenched alloy material;(e) extruding the quenched alloy material to produce a tube-shell alloy material;(f) pilgering the tube-shell alloy material to produce a reduced tube-shell alloy material;(g) annealing the tube-shell alloy material to produce an annealed alloy material;(h) repeating steps (f) and (g) to produce a final alloy material; and(i) subjecting the final alloy material to a final heat treatment selected to provide a zirconium-based alloy exhibiting one of improved corrosion resistance and improved creep resistance,wherein for providing the zirconium-based alloy exhibiting improved corrosion resistance, the final alloy material is subjected to a final heat treatment selected from a final heat treatment of partial recrystallization to produce an amount of recrystallization from about 15% to 20% with the remainder being stress relief annealed or a final heat treatment of stress relief annealed, andwherein for providing the zirconium-based alloy exhibiting improved creep resistance, the final alloy material is subjected to a final heat treatment of partial recrystallization to produce an amount of recrystallization from about 80% to 95% recrystallization with the remainder being stress relief annealed. 11. The method of making the zirconium-based alloy of claim 10, wherein said method further comprises forming the alloy into an article. 12. The zirconium-based alloy of claim 11, wherein said article is selected from the group consisting of cladding. 13. The method of making the zirconium-based alloy of claim 10, wherein the annealing is conducted at a temperature from about 960 to 1105° F. 14. The method of making the zirconium-based alloy of claim 13, wherein the annealing is conducted at a temperature from about 1030 to 1070° F. 15. A zirconium-based alloy for use in an elevated temperature environment of a nuclear reactor, comprising an alloying composition:0.2 to 1.5 weight percent niobium;0.01 to 0.6 weight percent iron;0.0 to 0.8 weight percent tin;0.0 to 0.5 weight percent chromium;0.0 to 0.3 weight percent copper;0.0 to 0.3 weight percent vanadium;0.0 to 0.1 weight percent nickel; anda balance at least 97 weight percent zirconium, including impurities, the zirconium-based alloy formed by a process, comprising:(a) melting the alloying composition to produce a melted alloy material;(b) forging the melted alloy material to produce a forged alloy material;(c) quenching the forged alloy material to produce a quenched alloy material;(e) rolling the quenched alloy material to produce a rolled alloy material;(f) annealing the rolled alloy material to produce a conditioned alloy material;(g) repeating steps (e) and/or (f) to produce a final alloy material; and(h) subjecting the final alloy material to a final heat treatment selected to provide the zirconium based alloy exhibiting one of improved corrosion resistance and improved creep resistance,wherein for providing the zirconium-based alloy exhibiting improved corrosion resistance, the final alloy material is subjected to a final heat treatment selected from a final heat treatment of partial recrystallization to produce an amount of recrystallization from about 15% to about 20% with the remainder being stress relief annealed or a final heat treatment of stress relief annealed, andwherein for providing the zirconium-based alloy exhibiting improved creep resistance, the final alloy material is subjected to a final heat treatment of partial recrystallization to produce an amount of recrystallization from about 80% to about 95% recrystallization with the remainder being stress relief annealed. 16. The zirconium-based alloy of claim 15, wherein said alloy is formed into an article. 17. The zirconium-based alloy of claim 16, wherein said article is strip. 18. The zirconium-based alloy of claim 15, wherein the forged alloy material has a rectangular cross-section.
	abstract	A supplementary injection device is installed in a nuclear power plant to draw coolant and inject coolant using an entraining fluid. The injection device can be a venturi or other passive device operable at relatively low fluid pressure that draws coolant through suction at the venturi narrowing point and mixes the coolant with the fluid for injection. The injection device is operable with a known BWR design, where the device is attached to a steam connection to the main steam line of the reactor, a coolant connection drawing from suction lines to a suppression cool or condensate tank, and an outlet connection injecting into the main feedwater lines. In a BWR, the injection device is operable without electricity and at a wide range of pressures, even less than 50 pounds per square inch, to maintain coolant levels in the reactor.
	abstract	A method of determining the shape of a radiation beam of a radiotherapy system at a treatment position, the system comprising a radiation source and a multi-leaf collimator disposed between the radiation source and the treatment position. The multi-leaf collimator includes an array of moveable leaves positioned to intersect and block parts of the radiation beam to define the shape of the radiation beam at the treatment position. The leaves of a group are aligned such that the planes of the leaves in that group converge at a point displaced laterally from the radiation source. The method includes, for each leaf in the array positioned to intersect the radiation beam, determining a projected width with respect to the radiation beam, the projected width being greater than the thickness of the respective leaf, and using the projected leaf width to determine the shape of the radiation beam at the treatment position.
	claims	1. A device for guiding a charged particle beam comprising a superconducting nano-channel consisting essentially of a superconducting material in the form of a tube having a proximal end, a distal end, and a bend disposed between said proximal end and said distal end. 2. The device as recited in claim 1 , wherein said bend is between zero degrees, and about 180 degrees. claim 1 3. The device as recited in claim 1 , wherein said bend is about 90 degrees. claim 1 4. The device as recited in claim 1 , further comprising an electron-transparent window sealed to said distal end of said tube. claim 1 5. The device as recited in claim 4 , wherein said window is substantially planar. claim 4 6. The device as recited in claim 4 , wherein said window is a semispherical end cap. claim 4 7. The device as recited in claim 4 , further comprising an electron beam emitter sealed to said proximal end of said tube. claim 4 8. The device as recited in claim 7 , wherein said electron beam emitter comprises a first superconducting nanotube. claim 7 9. The device as recited in claim 7 , wherein said tube, said window, and said electron beam emitter form an ultra-high vacuum region. claim 7 10. A device for guiding a charged particle beam comprising a first superconducting nano-channel formed by a substrate, a first area of superconducting material coated on said substrate and having a first edge, a second area of superconducting material coated on said substrate and having a second edge, wherein said first edge of said first area of superconducting material and said second edge of said second area of superconducting material are substantially parallel. 11. The device as recited in claim 10 , further comprising a first area of non-conductive material disposed on said first area of superconducting material, and a second area of non-conductive material disposed on said second area of superconducting material. claim 10 12. The device as recited in claim 11 , further comprising a third area of superconducting material disposed on said first area of non-conductive material, and a fourth area of superconducting material disposed on said second area of non-conductive material. claim 11 13. The device as recited in claim 10 , further comprising a second superconducting nano-channel formed by said substrate, a third area of superconducting material coated on said substrate and having a third edge, a fourth area of superconducting material coated on said substrate and having a fourth edge, wherein said third edge of third area of superconducting material and said fourth edge of fourth area of superconducting material are substantially parallel. claim 10 14. A device for guiding a charged particle beam comprising a superconducting nano-channel formed by a plurality of nano-scale superconducting rods disposed around a central region. 15. The device as recited in claim 14 , wherein said plurality of nano-scale superconducting rods is comprised of four rods. claim 14 16. The device as recited in claim 14 , wherein said plurality of nano-scale superconducting rods is comprised of six rods. claim 14 17. The device as recited in claim 16 , further comprising a seventh nano-scale superconducting rod disposed in said central region. claim 16 18. The device as recited in claim 14 , wherein said rods have a substantially circular cross section. claim 14 19. A device for guiding a charged particle beam comprising a superconducting nano-channel comprising a first split and a second split disposed parallel to the central axis of said nano-channel, said first and second splits forming a first section and a second section of said nano-channel. 20. The device as recited in claim 19 , wherein said superconducting nano-channel is a superconducting nano-cylinder. claim 19 21. The device as recited in claim 20 , wherein said first split and said second split are parallel. claim 20 22. The device as recited in claim 20 , wherein said first section and said second sections are half-cylinders. claim 20 23. The device as recited in claim 22 , wherein said first section comprises a first inner surface, and said second section comprises a second inner surface, and wherein said first section comprise a first layer of conductive material disposed on said first inner surface, and said second section comprise a second layer of conductive material disposed on said second inner surface. claim 22 24. The device as recited in claim 20 , wherein said first split and said second split are helical. claim 20
	summary
	claims	1. A method of separating material floating on a fluid's surface from the fluid comprising:applying acoustic pressure shock waves to the material and the fluid's surface such that acoustic pressure shock waves are propagated in liquid medium of the fluid and in gas medium above the fluid's surface; andcollecting the material pushed by the acoustic pressure shock waves. 2. The method of claim 1, wherein the material includes a contaminant selected from the group consisting of foam, foamy sludge, oil and grease. 3. The method of claim 2, wherein the liquid medium includes water. 4. The method of claim 3, wherein the gas medium includes air. 5. The method of claim 4, wherein the acoustic pressure shock waves are applied horizontally and along the fluid's surface from electrodes enclosed in a membrane. 6. The method of claim 1, wherein the acoustic pressure shock waves are applied horizontally and along the fluid's surface from electrodes enclosed in a membrane. 7. The method of claim 6, further comprising focusing the acoustic pressure shock waves along the fluid's surface with a reflector adjacent the electrodes. 8. The method of claim 5, further comprising focusing the acoustic pressure shock waves along the fluid's surface with a reflector adjacent the electrodes. 9. The method of claim 8, further comprising collecting water cleaned of the material. 10. The method of claim 5, further comprising collecting water cleaned of the material. 11. The method of claim 3, further comprising collecting water cleaned of the material. 12. A method of separating material floating on a fluid's surface from the fluid comprising applying acoustic pressure shock waves to the material and the fluid's surface sufficient to create a velocity differential above and below the fluid's surface that generates shear forces which push the material along and away from the fluid's surface. 13. The method of claim 12, wherein the material includes a contaminant selected from the group consisting of foam, foamy sludge, oil and grease. 14. The method of claim 13, wherein the fluid includes water. 15. A system for separating material floating on a fluid's surface from the fluid comprising:an acoustic pressure shock wave generator;a membrane enclosing electrodes and an acoustic pressure shock wave reflector adjacent the electrodes, wherein the electrodes are operatively coupled to the shock wave generator; anda fluid containment containing liquid medium having with material floating on the fluid surface, wherein the containment includes a material outlet and the acoustic pressure shock wave reflector is supported adjacent the fluid surface and oriented to focus acoustic pressure shock waves horizontally across the fluid surface and push the material floating on the fluid's surface to the material outlet. 16. The system of claim 15, wherein the fluid surface is an interface between the liquid medium and a gas medium above the liquid medium and the acoustic pressure shock wave reflector is oriented to focus acoustic pressure shock waves into both the liquid medium and the gas medium. 17. The system of claim 16, wherein the material includes at least one contaminant selected from the group consisting of foam, sludge, oil and grease and the material outlet is positioned near the fluid surface and adjacent a reservoir positioned to collect the material. 18. The system of claim 17, wherein the containment includes liquid medium outlet positioned below the material outlet. 19. The system of claim 15, wherein the containment includes a contaminated fluid inlet and a liquid medium outlet positioned below the material outlet. 20. The system of claim 16, wherein the containment includes a contaminated fluid inlet and a liquid medium outlet positioned below the material outlet.
	abstract	Apparatus and methods for collimation of x-ray beams. According to various embodiments, an x-ray apparatus may comprise a first rotatable disk comprising a first plurality of angled slots and a first shutter comprising a first plurality of protruding members. At least one of the first plurality of protruding members may be positioned within a first angled slot of the first plurality of angled slots, and at least one of the first plurality of protruding members may be positioned within a second angled slot of the first plurality of angled slots. The first shutter may at least partially define an x-ray collimation aperture, and the apparatus may be configured such that rotation of the first rotatable disk results in movement of the first shutter to alter a size of the x-ray collimation aperture.
	abstract	The invention relates to a nuclear reactor primary circuit comprising a primary pipeline (30), which defines an internal volume (32) and in which a primary nuclear reactor coolant downwardly runs, an additional pipeline (26) which is branched to the primary pipeline (30) and defines an internal volume communicating with the internal volume (32) of the primary pipeline (30) and a cuff (36) whose first end (50) is connected to the additional pipeline (26) and the second free end (52) is positioned in the internal volume (32) of the primary pipeline (30). According to said invention, the second end (52) is delimited by a free peripherial edge (53) comprising at least one upstream and downstream sections (56, 58) which are oriented towards the upstream, wherein the upstream section (56) penetrates into the internal volume (32) deeper from the primary pipeline (30) than the downstream section (58).
	abstract	In a plant including a system which is provided with a steam generator 2, a turbine 3, 5, a condenser 6 and a heater 7 and in which non-deaerated water circulates, and a pipe, the steam generator 2, the heater 7 and 8 of the system which comes into contact with the non-deaerated water is deposited with a protective substance.
047572094	claims	1. A neutron chopper comprising: a chopper rotor, bearings at each end of the chopper rotor supporting the rotor for rotation about an axis transverse to the neutron beam to be chopped, and a motor for driving the chopper rotor, the motor including: a hollow cylindrical steel rotor coaxially arranged with respect to the chopper rotor, the motor rotor surrounding the bearing at one end of the chopper rotor but the motor rotor being radially spaced from the bearing which it surrounds, so that the motor rotor is not directly supported by said bearing, and a ring of non-magnetic material fixed to, and coaxial with, said one end of the chopper rotor, the motor rotor being fixed to the ring, whereby the ring serves to interconnect the chopper and motor rotors. 2. A neutron chopper as defined in claim 1 wherein one end of the motor rotor is fixed to the ring, the other end of the motor rotor being free of attachment to any other part of the neutron chopper. 3. A neutron chopper as defined in claim 1 including a stator concentrically surrounding the motor rotor. 4. A neutron chopper as defined in claim 3 wherein the stator is embedded in an electrically insulating material which is resistant to neutron radiation. 5. A neutron chopper as defined in claim 1 wherein the motor rotor is press fit on to the ring. 6. A neutron chopper as defined in claim 1 wherein the motor is a hysteresis type motor.
053435060	claims	1. A nuclear reactor installation, comprising: a reactor pressure vessel, a reactor core in said reactor pressure vessel; a supporting and protective structure supporting said reactor pressure vessel and surrounding said reactor pressure vessel on the bottom and laterally, said supporting and protective structure having a bottom region and a circumferential wall; a core catcher device for said reactor core having a collecting basin for a core melt being installed below said reactor pressure vessel, said collecting basin having a bottom wall and a jacket wall being respectively separated from said bottom region and said circumferential wall of said supporting and protective structure by a spacing gap; cooling channels disposed in said spacing gap at said bottom wall and said jacket wall for exterior cooling of said collecting basin with a cooling liquid; and turbulence bodies disposed in a surface region of said bottom wall for generating a turbulent flow of the cooling liquid flowing from the inside to the outside over said bottom wall toward said jacket wall. a. a lower insulating portion lining said sacrificial layer of said collecting basin and enclosing said bottom cup of said reactor pressure vessel, b. a central insulating portion lining said inner periphery of said shielding ring, and c. an upper insulating portion extending from said shielding ring to the area of said cover portion gap of said reactor pressure vessel and being penetrated by said main coolant connection. the outer periphery of said upper insulating portion and the inner periphery of said circumferential wall of said supporting and protective wall, the outer surfaces of said support ring structure, and said outlet ring channels leading into said containment and said exhaust air filter installation. a reactor pressure vessel, a reactor core in the reactor pressure vessel, a primary circuit having main coolant lines leading to the reactor pressure vessel, pressure reservoirs communicating with the main coolant lines; a supporting and protective structure supporting the reactor pressure vessel and surrounding the reactor pressure vessel on the bottom and laterally, the supporting and protective structure having a bottom region and a circumferential wall; a core catcher device for the reactor core having a collecting basin for a core melt being installed below the reactor pressure vessel, the collecting basin having a bottom wall and a jacket wall being respectively separated from the bottom region and the circumferential wall of the supporting and protective structure by a spacing gap; a collecting basin cooling system having cooling channels disposed in the spacing gap at the bottom wall and the jacket wall for exterior cooling of the collecting basin with a cooling liquid; turbulence bodies disposed in a surface region of the bottom wall for generating a turbulent flow of the cooling liquid flowing from the inside to the outside over the bottom wall toward the jacket wall; and a cooling water reservoir disposed outside the supporting and protective structure, an inlet channel configuration connecting the cooling channels at the bottom wall to the cooling water reservoir and an outlet channel configuration connecting the cooling channels at the jacket wall to the cooling water reservoir, with a lift generating a naturally circulating flow through the cooling channels when the collecting basin is hot and the cooling channels are filled with water; the method which comprises: maintaining a cooling water level of the cooling water reservoir at a low water level, during normal operation of the nuclear reactor installation, at which no cooling water can reach the inlet channel configuration of the collecting basin cooling system, feeding emergency cooling water, when a leak occurs in the primary circuit, from the pressure reservoirs to be activated as a function of pressure of the primary circuit into the main coolant lines of the reactor pressure vessel, by feeding the emergency cooling water through the leak location and, if necessary, parallel thereto through further feed locations into the cooling water reservoir, and maintaining a sufficient water volume in the pressure reservoirs to lift the cooling water level of the cooling water reservoir up to a high water level for causing cooling water from the cooling water reservoir to reach the inlet channel configuration and from there the spacing gap of the collecting basin cooling system for filling the cooling system up to the level of the outlet channel configuration, for starting a naturally circulating flow, when the collecting basin is hot, from the cooling water reservoir through the inlet channel configuration to the cooling channels at the bottom wall and the jacket wall of the cooling system and from there through the outlet channel configuration back to the cooling water reservoir. 2. The nuclear reactor installation according to claim 1, including a cooling water reservoir disposed outside said supporting and protective structure, an inlet channel configuration connecting said cooling channels at said bottom wall to said cooling water reservoir and an outlet channel configuration connecting said cooling channels at said jacket wall to said cooling water reservoir, said cooling water reservoir forming a reactor housing sump. 3. The nuclear reactor installation according to claim 1, including a cooling water reservoir disposed outside said supporting and protective structure, an inlet channel configuration connecting said cooling channels at said bottom wall to said cooling water reservoir and an outlet channel configuration connecting said cooling channels at said jacket wall to said cooling water reservoir, with a lift generating a naturally circulating flow through said cooling channels when said collecting basin is hot and said cooling channels are filled with water. 4. The nuclear reactor installation according to claim 1, including a reactor cavern being bounded by said bottom region and said circumferential wall of said supporting and protective structure, said reactor pressure vessel being disposed in said reactor cavern at vertical and lateral distances from said bottom region and said circumferential wall, said reactor pressure vessel being seated in said supporting and protective structure, and said jacket wall of said collecting basin being disposed at a height extending at least approximately to a lower edge of said reactor core. 5. The nuclear reactor installation according to claim 1, wherein said collecting basin is seated on said bottom region of said supporting and protective structure by said turbulence bodies. 6. The nuclear reactor installation according to claim 1, including support bodies with which said collecting basin is seated on said bottom region of said supporting and protective structure. 7. The nuclear reactor installation according to claim 1, including separate support bodies, said collecting basin being seated on said bottom region of said supporting and protective structure by said turbulence bodies and said separate support bodies. 8. The nuclear reactor installation according to claim 1, wherein said collecting basin is constructed in the form of a crucible with said bottom wall being curved towards the bottom and the outside, said collecting basin has an upper edge, said collecting basin has a rounded-off edge area forming a transition from said bottom wall to said jacket wall, and said jacket wall tapers slightly conically from said rounded-off edge area to said upper edge. 9. The nuclear reactor installation according to claim 8, wherein said bottom wall of said collecting basin has a lowest central area and widens in the shape of a flat envelope of a cone from said lowest central area to said edge area defining intersecting surfaces being located in axial-radial intersecting planes and extending with a slight angle of slope relative to the horizontal. 10. The nuclear reactor installation according to claim 9, including a cooling water reservoir disposed outside said supporting and protective structure, an inlet channel configuration connecting said cooling channels at said bottom wall to said cooling water reservoir and an outlet channel configuration connecting said cooling channels at said jacket wall to said cooling water reservoir, and an inlet chamber through which said inlet channel configuration discharges into said cooling channels at said bottom wall in said central area, said cooling channels at said bottom wall extending outwardly from said inlet chamber as far as said edge area of said collecting basin, and one of said cooling channels at said jacket wall extending upward, adjoins said edge area at said jacket wall and terminating in said outlet channel configuration. 11. The nuclear reactor installation according to claim 10, including a chamber receiving said cooling water reservoir, said inlet channel configuration penetrating through said bottom region of said supporting and protective structure and extending from said chamber as far as said central area of said bottom wall of said collecting basin, and said outlet channel configuration penetrating through said circumferential wall of said supporting and protective structure, forming a continuation of said cooling channel at said jacket wall and terminating in the vicinity of an upper level of said cooling water reservoir. 12. The nuclear reactor installation according to claim 1, wherein said collecting basin includes: a base body in the form of a crucible being formed of a temperature-resistant steel alloy material, a protective shell lining said bottom wall and said jacket wall inside said crucible for protecting said crucible material against attacks by the melt, and a sacrificial material deposit following said protective shell as another protective layer on said crucible, said sacrificial material deposit being sufficient in amount for reacting with a maximally possible volume of the core melt entering said collecting basin in case of a possible malfunction. 13. The nuclear reactor installation according to claim 12, wherein said protective shell is formed of at least one alloy selected from the group consisting of MgO, UO.sub.2 and ThO.sub.2. 14. The nuclear reactor installation according to claim 12, wherein said sacrificial material deposit is a masonry structure of shielding concrete blocks. 15. The nuclear reactor installation according to claim 1, wherein said turbulence bodies are delta wings in the shape of prisms having triangular surfaces being fastened on said bottom region of said supporting and protective structure opposite said collecting basin bottom wall with a cooling gap therebetween. 16. The nuclear reactor installation according to claim 1, wherein said turbulence bodies are pipe sockets having ends facing said bottom wall of said collecting basin, said ends of said pipe sockets having channel recesses formed therein for generating partial cooling water flows bathing said bottom wall in the area of said pipe sockets. 17. The nuclear reactor installation according to claim 16, wherein said channel recesses are U-shaped, each of said pipe sockets has two of said U-shaped channel recesses aligned in the flow direction, and said pipe sockets have angular ends at said U-shaped recesses for increasing turbulence. 18. The nuclear reactor installation according to claim 1, including a shielding ring being installed above and adjoining said collecting basin between said circumferential wall of said supporting and protective structure and the outer periphery of said reactor pressure vessel. 19. The nuclear reactor installation according to claim 18, wherein said shielding ring is anchored on said circumferential wall of said supporting and protective structure. 20. The nuclear reactor installation according to claim 18, wherein said supporting and protective structure is formed of prestressed concrete with a steel reinforcement, and said shielding ring is formed of shielding concrete and a steel reinforcement being united with said steel reinforcement of said supporting and protective structure into a uniform steel reinforcement system. 21. The nuclear reactor installation according to claim 12, wherein said reactor pressure vessel has an outer periphery, a lower part with a bottom cup, a cover portion gap and a main coolant connection, and including a shielding ring having an inner periphery, being installed above and adjoining said collecting basin between said circumferential wall of said supporting and protective structure and the outer periphery of said reactor pressure vessel, and a heat insulation surrounding said lower part of said reactor pressure vessel at a distance and being substantially divided into three insulating portions merging into each other, said insulating portions being: 22. The nuclear reactor installation according to claim 1, including a cooling water reservoir disposed outside said supporting and protective structure, an inlet channel configuration connecting said cooling channels at said bottom wall to said cooling water reservoir and an outlet channel configuration connecting said cooling channels at said jacket wall to said cooling water reservoir, a dual air and water exterior cooling system of said collecting basin for air cooling of said reactor pressure vessel during normal operation of the nuclear reactor installation when said exterior cooling system is dry, a cooling air source connected to said inlet channel configuration, and a cooling air sink connected to said outlet channel configuration. 23. The nuclear reactor installation according to claim 1, including a cooling water reservoir disposed outside said supporting and protective structure, an inlet channel configuration connecting said cooling channels at said bottom wall to said cooling water reservoir and an outlet channel configuration connecting said cooling channels at said jacket wall to said cooling water reservoir, a thermal insulation enclosing said reactor pressure vessel, a dual air and water exterior cooling system of said collecting basin for air cooling of said thermal insulation during normal operation of the nuclear reactor installation when said exterior cooling system is dry, a cooling air source connected to said inlet channel configuration, and a cooling air sink connected to said outlet channel configuration. 24. The nuclear reactor installation according to claim 23, including a containment, an exhaust air filter installation, a shielding ring being installed above and adjoining said collecting basin between said circumferential wall of said supporting and protective structure and the outer periphery of said reactor pressure vessel, said circumferential wall having an inner periphery, a support ring structure for said reactor pressure vessel having outer surfaces, a heat insulation for said reactor pressure vessel having a lower insulating portion, a central insulating portion and an upper insulating portion with an outer periphery, main coolant lines for said reactor pressure vessel having an outer periphery, wall openings in said supporting and protective structure having an inner periphery, outlet ring channels formed between the outer periphery of said main coolant lines and said inner periphery of said wall openings, and a further air cooling system for said reactor pressure vessel in addition to said exterior dual cooling system, having inlet channels for supplying air to said further air cooling system, said inlet channels penetrating said circumferential wall of said supporting and protective structure and said shielding ring and terminating in an upper cooling air chamber, said upper cooling air chamber extending outside said upper insulating portion to said support ring structure, for guiding upwardly flowing cooling air in several partial flows along cooling surfaces, said cooling surfaces being: 25. The nuclear reactor installation according to claim 24, wherein the outer surfaces of said support ring structure include support arms, lug supports of the reactor pressure vessel being supported by said support arms, and seats of said support ring structure. 26. The nuclear reactor installation according to claim 12, wherein said collecting basin has a multi-layer construction and said crucible has a wall, and including a heat insulation for said reactor pressure vessel having a lower insulating portion, a central insulating portion and an upper insulating portion, a cooling liquid reservoir disposed outside said supporting and protective structure, at least one melt cooling tube penetrating said collecting basin in an upper half of said jacket wall and extending through said crucible wall, said protective layer, said sacrificial material deposit and said thermal insulation, said at least one melt cooling tube having an inlet side, an inner end and a melting plug sealing said inner end, said at least one melt cooling tube extending with a gradient from the outside to the inside and communicating on said inlet side with said cooling liquid reservoir, for heating said melting plug to its melting temperature with the core melt present in said collecting basin, causing said melting plug to melt and opening a flow channel to the surface of the core melt for cooling liquid. 27. A method for starting and maintaining exterior cooling of a core catcher device of a nuclear reactor installation having:
050892169	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Because critical path down time currently costs up to $1 million per day, optimization of the chemical decontamination process, both in terms of timing and cost, is very important. The time period between decontamination cycles will vary depending upon the particular plant and the materials that were used in constructing that plant. Older nuclear plants utilize more expensive materials that did not give rise to many of the corrosion problems that have arisen with subsequent plants. In order to utilize the two current decontamination process technologies (CAN-DEREM and LOMI), as well as any other future chemical processes that are developed, the operating capability of the RCS of a nuclear reactor, and of any auxiliary systems associated with the RCS, must be adaptable to the requirements of these chemical processes in terms of flow, temperature, pressure, and mass inventory. Ideally, this should be accomplished with as few hardware and operational changes as possible. Another significant question in considering full RCS decontamination is whether or not the process should be conducted with the fuel in or out of the reactor. The industry is currently trying to qualify a process for decontamination without spent fuel in the reactor vessel. The additional cost and analysis necessary to resolve these safety concerns for decontamination with fuel in place makes the decontamination of the fuel a non-preferred option at the present time. Nevertheless, after a decontamination is performed without fuel in the vessel, the next step would be to investigate the possibilities for qualifying with fuel in. Therefore, any decontamination design should allow for the possibility of fuel-in decontamination. The primary interface requirements that must be met to integrate current chemical decontamination processes with a nuclear steam supply system include at least the following: (1) temperature control in the range of 150.degree.-240.degree. F. (65.degree.-115.degree. C.) for proper utilization of the chemical processes involved; (2) provision for a number of discrete steps requiring injection and subsequent removal of chemicals; and (3) provision for continuous chemical circulation to ensure a uniform system chemistry, temperature, and a minimum system velocity during chemical decontamination processing. Current decontamination processes require approximately 99% removal of the particular chemicals in each of several process steps. Since the RCS cannot be "transfused," i.e., have total replacement of processed fluid, because of its large volume (on the order of 100,000 gallons (380 cubic meters)), a feed and bleed process is required. Standard mass balances around the processing system establish a processing rate relationship with processing time that reaches a point of diminishing return around 1,000 gallons (3,800 liters) per minute. Flow rates of this magnitude will typically provide system clean-up to an acceptable level in about 7 hours. Thus, the interface with the clean-up system must provide a flow of this magnitude. In addition, the interface will have to provide a means to cool the flow as well as a driving head to return the flow to the RCS. As existing Chemical and Volume Control Systems (CVCS) have capacities of only about 120 gallons (450 liters) they are clearly inadequate for optimum chemical decontamination. Thus, an alternate means for supplying the required flow and cooling must be utilized. In addition to the interface requirements listed above, an optimum chemical decontamination process will also preferably meet the following criteria: (1) an outside containment location due to the significant building space and time required for constructing such process equipment, which is typically beyond any space available inside containment, and to allow easy access for removal of solid waste; (2) providing for cooling of processed fluids prior to chemical removal in order to optimize demineralizer performance (preferable operating temperatures for resin beds are on the order of 140.degree. F. (60.degree. C.)); and (3) maximization of use of existing equipment and connections to the primary system in order to minimize overall cost. The apparatus and method of the present invention meets each of the necessary and preferred criteria and optimizes the chemical decontamination process as a whole. It has been discovered that the residual heat removal (RHR) system is the optimum interface for the decontamination processing system. The proposed configuration, described below, requires only one additional containment penetration, supplies more than adequate cooling capacity by use of the RHR heat exchanger, and provides more than adequate pressure by use of the RHR pump to drive the process flow to, and through, the processing system and to return it to the RCS. The CAN-DEREM process requires temperatures of 240.degree. F. (116.degree. C.).+-.10.degree. F. (6.degree. C.) and 194.degree. F. (90.degree. C.).+-.10.degree. F. (6.degree. C.) depending upon the particular chemical step. The LOMI process requires a constant temperature of 194.degree. F. (90.degree. C.).+-.10.degree. F. (6.degree. C.). Thus, the chemical decontamination system interfacing with the primary system must be capable of withstanding temperatures of approximately 250.degree. F. (120.degree. C.). Nevertheless, even though the chemical decontamination processes require a slightly elevated temperature, the primary system must be totally cooled down to remove fuel if the decontamination is to be performed with the fuel out. Thus, typical preliminary steps will involve total system cool down, fuel removal, and reheating of the primary system up to the appropriate temperature for decontamination. If the decontamination process is to proceed with the fuel in place, it is only necessary to cool down the primary system to the appropriate decontamination temperature. Decontamination with fuel in place can result in a time savings of up to 15 days of avoided outage time since the need for total cool-down and fuel removal is eliminated. The RHR system is typically used only during cool down or start up of the nuclear reactor. Even then, the RHR system is not activated until the reactor temperature has decreased to approximately 350.degree. F. (175.degree. C.). Prior to that point, heat is removed by dumping steam. Turning now in detail to the drawing, where like numbers refer to like items, the single FIGURE represents a schematic flow diagram of one preferred embodiment of the present invention. Other configurations are possible and do not affect the method and apparatus of the present invention. Processed fluids from the RCS 10 of a nuclear reactor are fed to the RHR system 11 by means of a pair of RHR pumps 12. The chemical decontamination processes occur at a temperature in the range of 15.degree.-240.degree. F. (65.degree.-115.degree. C.), as discussed above. Nevertheless, the decontamination removal system proposed to be used optimally should operate at a temperature in the range of 140.degree. F. (60.degree. C.). (Such a decontamination removal system is described in detail in co-pending application Ser. No. 07/62/129, entitled "Clean-up Sub-system For Chemical Decontamination Of Nuclear Reactor Primary Systems," and incorporated herein by reference.) Thus, heat removal prior to decontaminate removal is required. Heat removal will occur by steady state heat losses and, further, by cooling of the process fluids in one or more RHR heat exchangers 14 and 15. Since an RHR pump 12 is typically designed for pumping on the order of 3,000 gallons (11.4 cubic meters) per minute, only one RHR pump 12 would be required to provide the 1,000 gallons (3.79 cubic meters) per minute process flow desired within the decontamination process. The second RHR pump 12 would be reserved as a back-up. In a typical arrangement, one RHR pump 12 and RHR heat exchanger 14 would be dedicated to cooling the process flow 10 while the second RHR pump 12 and RHR heat exchanger 15 would remove any excess heat required to maintain a proper heat balance in the RCS 10. The scheme can be utilized with or without the fuel installed. In operation, a reactor coolant pump, or pumps, part of the RCS 10, provides a source of heat, in conjunction with any decay heat from the reactor core (if installed), to establish appropriate operating temperatures for the chemical decontamination throughout the RCS 10, as well assisting in circulation of the coolant. The reactor coolant pumps are the only source of heat if the core is removed during decontamination. In addition, operation of at least one reactor coolant pump is required for circulation, since the flow from the auxiliary RHR pumps 12 cannot ensure uniform chemistry and temperature in the RCS 10 as a whole. If it were possible for one RHR train of an RHR pump 12 and the RHR heat exchanger 15 to keep up with decay and reactor coolant pump heat input shortly after standard RHR initiation at approximately 350.degree. F. (175.degree. C.), then the other RHR train could be isolated and the tap-off to the chemical processing system installed while the other RHR train cooled the RCS from 350.degree. F. to 240.degree. F. (175.degree. C. to 116.degree. C.). Thus, with reference to the drawing, valves 16 and 20 would remain open to allow process fluid flow cool-down in RHR heat exchanger 15 while valves 18 and 22 would be closed to isolate the RHR heat exchanger 14 and its accompanying piping for installation of the chemical decontamination processing system. Using such a single RHR train for cool-down, a temperature of 240.degree. F. (116.degree. C.) will typically be reached within approximately 25 hours after reactor shut-down. Alternatively, if two RHR trains are available, the target temperature will be reached within about 6 hours after shut-down. To connect the chemical decontamination system 34 to the RHR system 11, a tap-in line 28 is connected just downstream of RHR heat exchanger 14. Valves 24 and 26 can be operated to divert flow from the RHR system 11 to the chemical decontamination system 34 when desired. In order to minimize penetration of the containment structure of the nuclear reactor 30, in one preferred embodiment, the process line leading to the high head safety injection pumps 32 is utilized for flow to the chemical decontamination system 34. Valves 36 and 38 in conjunction with connection piping 40 are used to divert process fluid flow from the high head safety injection pump line 32 to the chemical decontamination system 34. After passing through the chemical decontamination system 34, wherein dissolved contaminant metals and suspended contaminant solids are removed by means of demineralizers and filters as more fully described, for example in co-pending application Ser. No. 07/62/129, decontamination chemicals are thereafter injected as needed using injection means 35 and the process fluids are returned to the RHR system 11, and thereafter to the cold leg injection 44 by means of return line 42. An alternative method of utilizing the RHR system 11 is to tap off of the discharge of RHR pumps 12 outside of containment structure 30 and direct the flow directly to the processing system 34 and injection means 35, returning the processed fluids to the primary system by means of the high head safety injection pump line 32. This method would save a containment penetration, but would also require another heat exchanger along with a sizeable cooling water supply in order to reduce the process fluids temperature sufficiently to optimize use of the chemical decontamination resin beds. The cost of this option would typically be much higher than that of the preferred embodiments described herein. In addition to the primary interfacing of the chemical decontamination system 34 and injection means 35 with the RCS 10, additional sources of decontaminated fluids can be directed to the chemical decontamination system 34. While pump seal leakage is a constantly occurring phenomenon during nuclear reactor operation, the leakage becomes critical during decontamination since the leaked fluids will contain chemicals and activated crud. Thus, leak-offs from the reactor coolant pump #2 seals, valve leak-offs, and miscellaneous equipment drains are all typically directed to a reactor coolant drain tank 46 via line 48. The contents of the reactor coolant drain tank 46 would normally be directed thereafter to the boron recycle system holdup tanks 50 by means of one or more reactor coolant drain tank pumps 52. In conjunction with the apparatus of the present invention, however, the stream can preferably be diverted by means of valves 54 and 56 and combined with flow from the reactor coolant pump #3 seal leakoffs 58 that has been collected in containment sump 60 and pumped thereafter by containment sump pump 62 in line 64. The combined streams can be directed to the waste disposal system holdup tank 66, but are preferably diverted by valve 68 and 70 to the chemical decontamination system 34. Once in the chemical decontamination system 34, the combined stream of fluid can either be purified and returned to the primary system via return line 42, or removed with other decontamination wastes, thus minimizing the risk of personnel radiation exposure. Operation of one or more reactor coolant pumps, as called for in a preferred embodiment of the present invention, requires a minimum pressure in the RCS system 10 of approximately 400 psig (29 Kg/cm.sup.2) to ensure proper operation of the reactor coolant pump #1 seal. During normal plant operation, the RCS pressure is controlled using a steam bubble in the primary system pressurizer. However, the use of a steam bubble during decontamination is not feasible because the steam saturation temperature at 400 psig (29 Kg/cm.sup.2) of 447.degree. F. (230.degree. C.) is too high to be used with either of the current decontamination processes, which call for temperatures in the 150.degree.-240.degree. F. (65.degree.-116.degree. C.) range. The higher temperature would not only preclude the circulation of decontamination chemicals throughout the spray lines and into the pressurizer, but would result in accelerated corrosion rates of several RCS materials of construction. In some cases, pressure can be controlled with the pressurizer "water solid" during the latter stages of plant cool-down and the initial stages of plant heat-up. Water solid pressure control, however, is not a desirable method of pressure control for long periods of time such as are required for full decontamination (days), since minor system perturbations will result in a significant pressure transient. Because of the problems with steam or water-solid pressure control, an alternative means for pressurizing the RCS 10 during chemical decontamination is required. In one preferred embodiment of the present invention, a nitrogen gas bubble in the pressurizer, which is part of the RCS 10, is used to maintain system pressure at, or above, the necessary pressure at the lowered temperatures required for decontamination. An air bubble is not feasible because of the very stringent dissolved oxygen requirements for both the CAN-DEREM and LOMI processes. Nitrogen is preferable because of its inertness, general availability, low cost, and low impact if venting to the containment atmosphere were to become necessary. In addition, the quantity of nitrogen required is available on-site by installing a temporary cross-connection between the pressurizer and a safety injection system accumulator nitrogen supply line. In order to utilize a nitrogen bubble, nitrogen is admitted to the gas space of the pressurizer in the RCS 10 during the RCS cool down from 350.degree. F. (175.degree. C.). Spray flow condenses the steam and slowly drops the pressure. The pressure drop is compensated for by the nitrogen. Alternatively, the high pressure accumulator fill line can be routed to the pressurizer. Nitrogen pressure control permits full circulation through the pressurizer so that the spray lines, pressurizer, and surge line can be decontaminated and maintained in thermal equilibrium with the RCS loops. The nitrogen bubble will not preclude substantial decontamination of the pressurizer, since most of the activated crud will accumulate in the bottom of the pressurizer vessel. However, maximum spray flow should preferably be maintained. Thus, by using a nitrogen bubble, high pressure at the lower temperatures required for chemical decontamination is readily achieved. As an additional result of the relatively high pressures required for RCS operation during chemical decontamination, the potential exists for steam generator tube leakage into the secondary system. Such leakage is undesirable since it allows process fluids containing crud and other decontamination chemicals into the secondary system. Such leakage can preferably be prevented by pressurizing the shell side of the steam generators to a pressure above the primary system pressure, thereby precluding leakage from the primary side to the secondary side. One method of easily accomplishing such higher secondary side pressures is to maintain the secondary side water-solid during decontamination. Secondary side pressure can be maintained with a small positive displacement pump connected to a sampling or blow down line. Some allowance, as would be known to those of ordinary skill in the art, must be made to maintain proper mass inventory within the primary system during chemical decontamination. Thus, the normal let-down and charging path of the CVCS of the nuclear reactor primary system will preferably remain in service during decontamination in order to maintain RCS mass inventory and to provide seal injection cooling for the reactor coolant pumps. The typical let-down system capability, including storage in the CVCS holdup tanks, is more than adequate to compensate for any chemical addition associated with either of the current decontamination processes. This is true even if clean seal injection is required from either the refueling water storage tank or from the primary makeup water storage tank. Thus, a system for integrating a chemical decontamination system within a nuclear reactor primary system has been disclosed that optimizes use of existing equipment, minimizes containment penetration, and optimizes the time required for decontamination. It utilizes known technology in a unique arrangement to provide chemical decontamination in a timely manner so as to minimize the overall scheduled requirements for large, full system decontamination. Having thus described the invention, it is to be understood that the invention is not limited to the embodiments set forth herein for purposes of exemplification. It is to be limited only by the scope of the attached claims, including a full range of equivalents to which each claim thereof is entitled.
	abstract	The present disclosure discloses a radiation inspection system and a radiation inspection method. The radiation inspection system comprises a radiation source and a beam modulating device. The beam modulating device comprises a first collimating structure disposed at a beam exit side of the radiation source and a second collimating structure disposed at a beam exit side of the first collimating structure. The second collimating structure is movable relative to the first collimating structure to change a relative position of the first collimating port of the first collimating structure with the second collimating port of the second collimating structure, and the beam modulating device is shifted between a first operational state in which the beam modulating device modulates an initial beam into a fan beam, and a second operational state in which the beam modulating device modulates the initial beam into a pencil beam variable in position.
	description	This application is a continuation of U.S. patent application Ser. No. 11/039,960, filed on Jan. 24, 2005, now abandoned the entire disclosure of which is hereby incorporated by reference herein. 1. Field of the Invention The present invention relates to ion beam delivery equipment and ion beam delivery method, which are used to produce and deliver ion beam, e.g., proton or carbon ions, to a tumor for treatment. 2. Description of the Related Art There is known a method for delivering ion beam, e.g., proton or carbon ions, to a tumor, such as a cancer, in the body of a patient. The ion beam delivery equipment for such treatment comprises an ion beam generator to produce the said ion beam and accelerate it to a needed energy, a beam transport system, and an beam delivery nozzle. An ion beam accelerated by the beam generator reaches the beam delivery nozzle, which is installed in a rotating gantry to monitor and shape the therapeutic radiation field, through a first beam transport system and a second ion beam transport system, the latter being installed in the rotating gantry. The ion beam reached the beam delivery nozzle is delivered to the tumor in the patient body from the beam delivery nozzle. Known examples of the beam generator include a synchrotron (quasi-circular accelerator) provided with an extraction deflector for extracting the ion beam from the orbit (see, e.g., Patent Reference 1; U.S. Pat. No. 5,363,008). In radiation therapy using an ion beam, e.g., with a proton beam delivering a radiation dosage to a tumor, by utilizing characteristics that most of the energy of the proton beam is released just before protons come to rest, namely that a Bragg peak is formed just before the stop of protons, the energy of the proton beam is selected to stop protons in the tumor so that the beam energy is released most to cells within the tumor or its microscopic extensions. Usually, the tumor has a certain thickness in the direction of depth, i.e. along the direction of the ion beam, from the body surface of a patient (hereinafter referred to simply as “the direction of depth”). To effectively irradiate the ion beam over the entire thickness of the tumor in the direction of depth, the width of the Bragg peak must be spread out in the direction of depth. The spread-out width of the Bragg peak is called a Bragg peak width. To obtain the required Bragg peak width, the energy of the ion beam must be modulated. From that point of view, a range modulation wheel (RMW) has already been proposed in which a plurality of blades each having a thickness varied step by step in the circumferential direction are installed around a rotating shaft (see, e.g., Non-patent Reference 1; “REVIEW OF SCIENTIFIC INSTRUMENTS”, Vol. 64, No. 8, pp 2074-2084 (FIGS. 30 and 31) issued in August, 1993). The plural blades are mounted to the rotating shaft. In the RMW, a through opening is formed between adjacent sets of the blades. For example, when the RMW is rotated from a state in which the opening is positioned on a path of the ion beam (hereinafter referred to simply as a “beam path”), the opening and the blade alternately intersect the beam path. At the time when the ion beam passes through the opening, the energy of the ion beam is not attenuated and therefore the Bragg peak is produced in the deepest position inside the patient body. At the time when the ion beam passes through a blade, the energy of the ion beam is attenuated more as the ion beam passes through the blade having a larger thickness, and therefore the Bragg peak is produced in a portion of the tumor near the body surface of the patient. With the rotation of the RMW, the position in the direction of depth where the Bragg peak is formed varies cyclically. As a result, the Bragg peak width being comparatively wide and flat in the direction of depth of the tumor can be obtained, looking at the beam energy integrated over time. The known method described above has the problem as follows. Patients have body dimensions different from one another and tumor sizes also differ from one another. Accordingly, the Bragg peak width optimum for treatment of the tumor differs for each of the patients. With the known method, however, only one set Bragg peak width is obtained from one RMW. This has invited the necessity of forming and preparing a different RMW for each patient and replacing the RMW whenever the patient is changed, and hence has caused a difficulty in efficiently treating a large number of patients. It is an objective of the present invention to provide an ion beam delivery equipment and an ion beam delivery method, which can increase the number of patients treatable using one wheel having a thickness varied in the rotating direction to change energy of the ion beam passing the wheel. To achieve the above objective, the present invention is featured in that start and stop of extraction of the ion beam accelerated in the beam generator is controlled during rotation of a wheel having a thickness varied in the rotating direction to change energy of the ion beam passing the wheel. By controlling the start and stop of extraction of the ion beam from the beam generator during the rotation of the wheel, a region of the wheel where the ion beam passes the wheel can be changed in the rotating direction. It is therefore possible to form a plurality of spread-out beam peak (Bragg peak) widths (hereinafter referred to as “SOBP widths”) having different values in the direction of depth from the body surface of a patient by using one modulation wheel, and to employ one wheel for a plurality of patients. In other words, various patients having tumors with different thickness can be treated with one modulation wheel. Preferably, a synchrotron is used as the beam generator. Preferably, the wheel is provided with a plurality of blades each having a thickness varied in the rotating direction. Preferably, the control of the start and stop of extraction of the ion beam from the beam generator is done by using the information for the SOBP width sent from the treatment planning software through communication network. According to the present invention, since the modulation wheel has the thickness varied in the rotating direction to change energy of the ion beam passing the wheel, the number of patients treatable using one modulation wheel can be increased. Embodiments of the present invention will be described in detail below with reference to the drawings. Proton beam delivery equipment 7 as ion beam delivery equipment of this embodiment comprises, as shown in FIG. 1, a beam generator 1, a beam transport system 2, and an beam delivery nozzle 15, the latter two being connected downstream of the beam generator 1. The beam generator 1 comprises an ion (proton) source (not shown), a pre-accelerator 3, and a synchrotron 4 serving as a main accelerator. The synchrotron 4 includes an RF-applying device 5 having a pair of electrodes and an RF-accelerating cavity 6. The RF-applying device 5 and the RF-accelerating cavity 6 are installed on an orbit of a circulating ion beam. A first RF-power supply 8 is connected to the electrodes of the RF-applying device 5 through an on/off switch 9. A second RF-power supply (not shown) for applying an RF power to the RF-accelerating cavity 6 is separately provided. Ions (e.g., proton ions (or carbon ions)) generated by the ion source are accelerated by the pre-accelerator 3 (e.g., a linear accelerator). An ion beam emitted from the pre-accelerator 3 enters the synchrotron 4. The ion beam (corpuscular beam) is accelerated by an electromagnetic field generated in the RF-accelerating cavity 6 with application of the RF power supplied from the second RF-power supply. The ion beam circulating in the synchrotron 4 is extracted from the synchrotron 4 upon closing of the on/off switch 9, as described later, after energy of the ion beam has been increased up to a setting level (e.g., 70 to 250 MeV). More specifically, an RF power is applied to the circulating ion beam from the first RF-power supply 8 through the RF-applying device 5 when the on/off switch 9 is closed. With the application of the RF power, the ion beam circulating within a stability limit is forced to exceed the stability limit and extracted from the synchrotron 4 through a beam extraction deflector 10. At the time of extracting the ion beam, currents supplied to quadrupole magnets 11 and bending magnets 12 both installed in the synchrotron 4 are held at setting current values, and hence the stability limit of the circulation is also held substantially constant. The extraction of the ion beam from the synchrotron 4 is stopped by opening the on/off switch 9 to stop the application of the RF power to the RF-applying device 5. The ion beam extracted from the synchrotron 4 is transported to a downstream of the beam transport system 2. The beam transport system 2 includes quadrupole magnets 13 and a bending magnet 14, and the beam duct 16 connected to the beam delivery nozzle 15. The beam delivery nozzle 15 and the beam duct 16 are both mounted to a rotating gantry (not shown) installed in a treatment room (not shown). A quadrupole magnet 17, a quadrupole magnet 18, a bending magnet 19, and a bending magnet 20 are installed along the beam duct 16 in this order. The ion beam is transported along the beam duct 16 to the beam delivery nozzle 15 by these magnets. A patient 32 lies on a treatment couch 34 properly positioned in a treatment cage (not shown) that is formed within the rotating gantry. The ion beam emitted from the beam delivery nozzle 15 is delivered to a tumor, such as a cancer, in the body of the patient 32. The beam duct 16 with magnets, such as the quadrupole magnet 17, can also be regarded as a beam transport system. The beam delivery nozzle 15 has a casing 21 (see FIG. 2) mounted to the rotating gantry. Also, the beam delivery nozzle 15 has a first scatterer device 24, a second scatterer device 25, an RMW (range modulation wheel) device 26 serving as a Bragg peak spreading-out device, and a dose monitor 23 as shown in FIG. 2. The first scatterer device 24, the second scatterer device 25, the RMW device 26, and the dose monitor 23 are installed in the casing 21 in this order from the upstream side and are mounted to the casing 21. A bolus 27 and a collimator 28 each formed into a desired shape for each patient are also mounted to the casing 21. The first scatterer device 24 has a scatterer 24A for spreading out the ion beam in the direction perpendicular to a beam axis A, i.e., a beam path within the casing 21. The scatterer 24A is mounted to the casing 21 through a support member 24B. The scatterer 24A is generally made of a substance (such as lead or tungsten) having the large atomic number, which has a small energy loss with respect to a scattering rate of the ion beam. The first scatterer device 24 is installed such that the scatterer 24A is positioned on the beam axis A. The second scatterer device 25 has the function of converting the ion beam having a dose distribution, which has been spread into the Gaussian form by the first scatterer device 24, into a uniform dose distribution. The second scatterer device 25 has a scatterer 25A and a support member 25B for mounting the scatterer 25A to the casing 21. The second scatterer device 25 is installed such that the scatterer 25A is positioned on the beam axis A. The RMW device 26 comprises an RMW 29, a rotating device (e.g., a motor) 30 for rotating the RMW 29, and an angle sensor 31 for detecting a rotational phase (angle) of the RMW 29. As shown in FIG. 3, the RMW 29 comprises a plurality of blades (three in this embodiment) 37, a rotating shaft 40, and a cylindrical member 39. The cylindrical member 39 is disposed concentrically with the rotating shaft 40. The plurality of blades 37 (three 37A, 37B and 37C in this embodiment) mounted to the rotating shaft 40 are extended in the radial direction of the RMW 29. An outer end of each of the blades 37 is attached to the cylindrical member 39. Each blade 37 has a circumferential width larger at one end nearer to the cylindrical member 39 than at the other end nearer to the rotating shaft 40. An opening 42 is formed between adjacent two of the blades 37 in the circumferential direction of the RMW 29. Although the RMW of the present embodiment has the opening 42, it is possible that a thin blade with a certain thickness instead of the opening can be applied. In this case, a small amount of energy loss due to the thinnest blade has to be considered. Each blade 37 has a plurality of plane areas (stepped portions) 43 arranged in the form of stairs in the circumferential direction (rotating direction) of the RMW 29. Each of the plane areas 43 has a different thickness relative to a bottom surface of the RMW 29 in the axial direction of the rotating shaft 40 (i.e., the direction of the beam axis A). The thickness of each plane area 43 is called here the plane area thickness. More specifically, the plane area thickness of the blade 37 is increased in a stepwise way from each of the plane areas 43 adjacent to the opening 42, which are positioned on both sides of the blade 37 in the circumferential direction, toward the plane area 43 positioned at a top portion 44 having the largest thickness in the direction of the beam axis A. Each plane area 43 is extended from the rotating shaft 40 toward the cylindrical member 39. In one unit of the RMW 29, three openings 42 are present between the three blades 37. The rotating shaft 40 is detachably mounted to a support member 45 (FIG. 2) fixed to the casing 21. The rotating shaft 40 has a through hole 41 formed to penetrate the rotating shaft 40 in the axial direction. A rotating shaft 30A of the rotating device 30 mounted to the support member 45 is fitted to the through hole 41. The angle sensor 31 is also mounted on the support member 45. The RMW 29 may be of a structure having the first scatterer integrally attached to the RMW 29 (e.g., a scatterer affixed to an overall area of the wheel against which the ion beam impinges). Alternatively, a compensator may be attached to the wheel so as to compensate for a difference in scattering rate between the plane areas having large and small values in the thickness distribution. In the proton beam delivery equipment of this embodiment, a plurality of SOBP (Spread-out Bragg Peak) widths can be produced by making extraction-on/off control of the ion beam from the beam generator 1 in accordance with a rotational angle of the RMW 29. The principle of that operation will be described below with reference to FIGS. 4, 5 and 6. At the time when the ion beam passes the opening 42 of the RMW 29, the beam energy is not attenuated and therefore the Bragg peak is formed in a deep first position away from the body surface. At the time when the ion beam passes the plane area 43 of the blade 37 which is positioned at the top portion 44 and has the largest thickness, the beam energy is maximally attenuated and therefore the Bragg peak is formed in a shallow second position close to the body surface. At the time when the ion beam passes the plane area 43 positioned between the opening 42 and the top portion 44, the beam energy is attenuated to an extent to the thickness of the blade at the position where the relevant plane area 43 is present, and therefore the Bragg peak is formed in a third position between the first position and the second position. Accordingly, when the ion beam is always in the beam-on state all over a 360°-region of the rotational angle in the circumferential direction of the RMW 29 as the case a shown in FIGS. 4 and 5, the Bragg peak cyclically varies between the first position and the second position with the rotation of the RMW 29. As a result, looking at the dose integrated over time, the case a) can provide a comparatively wide SOBP width ranging from a position near the body surface to a deep position as indicated by a dose distribution a) in the direction of depth, as shown in FIG. 6. The term “beam-on state” means a state in which the ion beam is extracted from the synchrotron 4 and emitted from the beam delivery nozzle 15 after passing the RMW 29. On the other hand, the term “beam-off state” means a state in which the ion beam is neither extracted from the synchrotron 4 nor emitted from the beam delivery nozzle 15. In the case b) shown in FIGS. 4 and 5, the ion beam is brought into the beam-off state in a comparatively thick region (near the top portion 44) of each blade 37 in the circumferential direction of the RMW 29, while the ion beam is brought into the beam-on state in the other region of the rotational angle. Because no Bragg peak is formed in a shallow portion near the body surface, the case b) can provide a SOBP width indicated by a dose distribution b) in the direction of depth and having a narrower flat zone than the dose distribution a) as shown in FIG. 6. In the case c) shown in FIGS. 4 and 5, the ion beam is brought into the beam-on state in the opening 42 and a comparatively thin region of each blade 37 near the opening 42 in the circumferential direction of the RMW 29, while the ion beam is brought into the beam-off state in the other region of the rotational angle. Because the attenuation of the beam energy is small as a whole, the Bragg peak is formed in a deep position away from the body surface. Therefore, the case c) can provide a SOBP width indicated by a dose distribution c) in the direction of depth and having a narrower flat zone than the dose distribution b) as shown in FIG. 6. Thus, the proton beam delivery equipment 7 can form a plurality of different SOBP widths with one RMW 29 by making extraction-on/off control of the ion beam in accordance with the rotational angle of the RMW 29 as described above. Returning to FIG. 2, the dose monitor 23 measures dose of the ion beam in the irradiation field formed by the SOBP device 26, etc. The bolus 27 has the function of making the penetration depth distribution of the ion beam match distal depth variation of a diseased part (i.e., a tumor or a cancer) 33 in the body of the patient 32 under treatment. Stated another way, the bolus 27 adjusts the penetrating range distribution of the ion beam to the shape of the tumor 33 as an irradiation target in the direction of depth. The bolus 27 is also called a range compensating device, an energy compensator, or a compensator. The collimator 28 shapes the ion beam at each position in match with the shape of the tumor 33 in the direction perpendicular to the beam path (beam axis A). Prior to starting irradiation of the ion beam from the beam delivery nozzle 15, the treatment couch 34 on which the patient is lying is moved by a couch driving device (not shown) into the treatment cage. The rotating gantry is rotated by a motor (not shown) to direct the beam path within the beam delivery nozzle 15 toward the tumor 33 in the body of the patient 32 lying on the treatment couch 34. Further, the treatment couch 34 is positioned relative to the beam delivery nozzle 15 so that the tumor in the body of the patient is aligned with the beam path within the beam delivery nozzle 15 at high accuracy. Then, the ion beam introduced to the beam delivery nozzle 15 through the beam passage 16 is delivered to the tumor 33 after passing the first scatterer device 24, the second scatterer device 25, the RMW device 26 in which the RMW 29 is rotating, the bolus 27, and the collimator 28, which are all installed in the beam delivery nozzle 15. The RMW 29 is rotated by the rotating device 30. The extraction-on/off control of the ion beam during the rotation of the RMW 29 in this embodiment will be described in more detail below. The term “extraction-on of the ion beam” means the start of extraction of the ion beam from the synchrotron 4, and the term “extraction-off of the ion beam” means the stop of extraction of the ion beam from the synchrotron 4. First, a tomogram of the tumor 33 in the body of the patient 32 and thereabout is taken by using an X-ray CT apparatus (not shown). A physician makes a diagnosis based on the obtained tomogram to confirm the position and size of the tumor 33, and determines the direction of irradiation of the ion beam, the maximum irradiation depth, etc., followed by inputting them to a treatment planning unit 35. Based on the input data such as the direction of irradiation of the ion beam and the maximum irradiation depth, the treatment planning unit 35 computes factors necessary for the treatment, such as the SOBP width, the irradiation field size, and the target dose to be irradiated to the tumor 33, by using treatment planning software. Further, by using the treatment planning software, the treatment planning unit 35 computes various operation parameters (such as the beam energy when the ion beam is extracted from the synchrotron 4 (i.e., the extraction energy), the angle of the rotating gantry, patient couch position and the rotational angles of the RMW 29 when the extraction of the ion beam is turned on and off), and then selects the RMW 29 having a thickness distribution and an angular width in the circumferential direction suitable for the treatment. Various items of treatment plan information computed by the treatment planning unit 35, such as the extraction energy, the SOBP width, the irradiation field size, the rotational angles, the patient couch position and the irradiation dose, are inputted to a central processing unit 36 of the proton beam delivery equipment 7 and stored in a memory (not shown) of the central processing unit 36. Those various items of treatment plan information are displayed on a display of the treatment planning unit 35 and on a display installed in a control room of the proton beam delivery equipment 7. Then, the RMW 29, the bolus 27, and the collimator 28 suitable for the patient 32, who is going to take treatment, are installed in the casing 21 of the beam delivery nozzle 15 by an operator, as shown in FIG. 2. An irradiation controller 38 receives, from the central processing unit 36, setting values of required treatment plan information, i.e., rotational angles (e.g., α1 to α6 described later) of the RMW 29, a target dose, an angle of the rotating gantry, and a patient couch position and then stores the input data in the memory (not shown) of the irradiation controller 38. A gantry controller (not shown) receives the rotating gantry angle information from the irradiation controller 38 and rotates the rotating gantry based on the rotating gantry angle information, as described above, so that the beam path within the beam delivery nozzle 15 is directed toward the tumor 33. Based on information of the extraction energy irradiated to the patient 32, the central processing unit 36 sets control commands for currents (i.e., current setting values) introduced to the respective magnets of the beam generator 1 and the beam transport system 2. In accordance with the current setting values, a magnet power supply controller (not shown) controls respective power supplies for the corresponding magnets and adjusts values of excitation currents supplied to the respective magnets of the beam generator 1 and the beam transport system 2. Preparations for introducing the ion beam to the beam generator 1 and the beam transport system 2 are thereby completed. The magnet power supply controller is connected to the central processing unit 36. The synchrotron 4 is operated by repeating the steps of injecting the ion beam from the pre-accelerator 3, and then accelerating, extracting and decelerating (preparation of next injecting) the ion beam. When the ion beam is accelerated until reaching the desired extraction energy at a setting level, the acceleration of the ion beam is brought to an end and the ion beam comes into a state ready for extraction from the synchrotron 4 (i.e., an ion beam extractable state). Information indicating the end of acceleration of the ion beam is transmitted to the central processing unit 36 from the magnet power supply controller that monitors states of the magnets, etc. of the synchrotron 4 using status sensors (not shown). The extraction-on/off control of the ion beam for forming the SOBP width in the proton beam delivery equipment 7 will be described below with reference to FIGS. 1, 2, 4 and 7. The following description of the extraction-on/off control of the ion beam is made, by way of example, in connection with the case b shown in FIG. 4. In the example of the case b), points 45A, 45B and 45C each represent the timing of the extraction-on (start of extraction) of the ion beam, while points 46A, 46B and 46C each represent the timing of the extraction-off (stop of extraction) of the ion beam. When the irradiation controller 38 executes the control for the case b, it receives beforehand the rotational angles α1 to α6 (α3 to α6 are not shown), i.e., the setting values of the rotational angles, from the central processing unit 36. The rotational angle α1 represents an angle from a reference line 22 to the point 45A, and the rotational angle α2 represents an angle from the reference line 22 to the point 46A. The rotational angle α3 represents an angle from the reference line 22 to the point 45B, and the rotational angle α4 represents an angle from the reference line 22 to the point 46B. The rotational angle α5 represents an angle from the reference line 22 to the point 45C, and the rotational angle α6 represents an angle from the reference line 22 to the point 46C. The rotational angles α1 to α6 each represent an angle on the basis of the state in which the reference line 22 is positioned on the beam axis A. The irradiation controller 38 executes the extraction-on/off control of the ion beam in accordance with a control flow shown in FIG. 7. First, the irradiation controller 38 receives a signal indicating the end of acceleration in the accelerator (synchrotron 4) (i.e., a signal indicating that the ion beam is in the extractable state) (step 51). The end-of-acceleration signal is inputted from the central processing unit 36. The irradiation controller 38 outputs a start-of-rotation signal to the rotating device 30 (step 52). The rotating device 30 is rotated in accordance with a drive signal outputted from the irradiation controller 38. The torque of the rotating device 30 is transmitted to the rotating shaft 40 of the RMW 29 through the rotating shaft 30A, whereby the RMW 29 is rotated. The number of rotations of the RMW 29 is set to the range of 10 to 20 rotations per second. It is determined whether a measured value of the rotational angle matches with a first setting value of the rotational angle (step 53). More specifically, the measured value of the rotational angle of the RMW 29 measured by the angle sensor 31 is inputted to the irradiation controller 38. It is then determined whether the input measured value matches with the first setting value of the rotational angle (any of the rotational angles α1, α3 and α5) at which a beam extraction start signal is to be outputted. If the measured value of the rotational angle matches with the first setting value, the beam extraction start signal is outputted (step 54). The on/off switch 9 is closed in response to the beam extraction start signal. An RF power from the RF-applying device 5 is applied to the circulating ion beam, whereupon the ion beam is extracted from the synchrotron 4. The extracted ion beam is transported to the beam delivery nozzle 15. After passing the rotating RMW 29, etc. within the beam delivery nozzle 15, the ion beam is emitted from the beam delivery nozzle 15 along the beam axis A and then delivered to the tumor 33. In FIG. 4, a black circle represents the position where the extraction of the ion beam is started. It is determined whether a dose delivered to the tumor 33 has reached the target dose (step 55). Further, it is determined whether the measured value of the rotational angle matches with a second setting value of the rotational angle (step 56). The dose irradiated to the tumor 33, which is measured by the dose monitor 23, and the measured value of the rotational angle are always inputted to the irradiation controller 38. In step 55, it is determined whether an accumulated value of the measured dose has reached the target dose. If this determination result is “YES”, the processing of step 60 is executed in precedence to the processing of step 56 and a beam extraction stop signal is outputted. In response to the beam extraction stop signal, the on/off switch 9 is opened to stop the supply of the RF power to the RF-applying device 5. Accordingly, the extraction of the ion beam from the synchrotron 4 is stopped and the irradiation of the ion beam toward the patient 32 lying on the treatment couch 34 is brought to an end. A stop-of-rotation signal is then outputted to the rotating device 30 (step 61). Thereby, the rotation of the rotating device 30 is stopped and the rotation of the RMW 29 is also stopped. If the determination result in step 55 is “NO”, the processing of step 56 is executed. If it is determined in step 56 that the measured value of the rotational angle matches with the second setting value of the rotational angle (any of the rotational angles α2, α4 and α6) at which the beam extraction stop signal is to be outputted, the beam extraction stop signal is outputted (step 57). In response to the beam extraction stop signal, as mentioned above, the on/off switch 9 is opened and the extraction of the ion beam from the synchrotron 4 is stopped. In FIG. 4, a white circle represents the position where the extraction of the ion beam is stopped. The period from the output of the beam extraction start signal in step 54 to the output of the beam extraction stop signal in step 57 represents a period during which, for example, a region from the plane area 43A of the blade 37A to the plane area 43B of the blade 37B intersects the beam axis A along which the ion beam travels, i.e., an effective beam-on period. The time taken from the closing of the on/off switch 9 to the start of extraction of the ion beam from the synchrotron 4 is not longer than 1/1000 sec, and conversely the time taken from the opening of the on/off switch 9 to the stop of extraction of the ion beam is also not longer than 1/1000 sec. In step 58, it is determined again whether the dose irradiated to the tumor 33 has reached the target dose. If this determination result is “NO”, the processing of step 59 is executed. Stated another way, it is determined whether a sufficient amount of the ion beam exists in the synchrotron 4 after the end of the beam-on period. The amount of the ion beam (i.e., the current density of the ion beam) is monitored by the magnet power supply controller based on a value measured by a sensor (not shown) disposed in the synchrotron 4. The measured value of the current density of the ion beam is inputted to the irradiation controller 38 via the central processing unit 36. The determination in step 59 is made using the measured value of the current density. If the determination result in step 59 is “YES”, the processing of steps 53 to 58 is executed again. The period from the output of the beam extraction start signal in step 54 to the output of the beam extraction stop signal in step 57 in this repeated process represents a period during which, for example, a region from the plane area 43C of the blade 37B to the plane area 43D of the blade 37C intersects the beam axis A, i.e., an effective beam-on period. The period during which, for example, a region from the plane area 43E of the blade 37C to the plane area 43F of the blade 37A intersects the beam axis A in the next repeated process of steps 53 to 58 also represents an effective beam-on period. Between the two beam-on periods adjacent to each other, there is a beam-off period as shown in FIG. 5. If, during the repeated process of steps 53 to 58, it is determined in step 55 or 58 that an accumulated value of the measured dose has reached the target dose, the processing of step 61 is executed and the irradiation of the ion beam toward the patient 32 is brought to and end. If the determination result in step 59 is “NO”, the processing subsequent to step 51 is executed. More specifically, if the current density of the ion beam circulating within the synchrotron 4 lowers and the extraction of the ion beam is disabled, the ion beam in the synchrotron 4 is decelerated. The magnet power supply controller reduces the current values supplied to the magnets disposed in the synchrotron 4, the beam transport system 2, etc. The current values supplied to those magnets are held in the state allowing the ion beam to enter. The ion beam is introduced to the synchrotron 4 from the pre-accelerator 3. Then, the ion beam is accelerated until reaching the extraction energy, as described above. After the end of acceleration of the ion beam, the processing subsequent to step 51 is executed by the irradiation controller 38. Because the determination in step 55 is made between steps 54 and 56, the extraction of the ion beam can be stopped when the accumulated value of the measured dose has reached the target dose during the period in which the ion beam passes the rotating RMW 29. It is hence possible to prevent the ion beam from being excessively delivered to the tumor 33. For example, if the determination result in step 55 is made “YES” when the opening 42 between the blade 37A and the blade 37B, shown in FIG. 4, is positioned on the beam axis A, the extraction of the ion beam can be stopped immediately. Therefore, the irradiation of the ion beam to the tumor 33 can be avoided during the period from the time at which the opening 42 is positioned on the beam axis A to the time at which the point 46A corresponding to the second setting value of the rotational angle is positioned on the beam axis A. In the example of the case b) described above, the region from the point 45A to the point 46A, the region from the point 45B to the point 46B, and the region from the point 45C to the point 46C each represent an ion beam passage region in the RMW 29. The region from the point 46A to the point 45B, the region from the point 46B to the point 45C, and the region from the point 46C to the point 45A each represent a region in the RMW 29 where the ion beam does not pass (i.e., an ion beam non-passage region). While the above description is made, by way of example, in connection with the case b, various SOBP widths can be formed by changing, for one unit of the RWM 29, the first setting values of the rotational angle at each of which the beam extraction start signal is to be outputted and the second setting values of the rotational angle at each of which the beam extraction stop signal is to be outputted. While the ion beam passes the opening 42 in each of the “beam-on” periods shown in FIG. 5, the irradiation controller 38 may execute control such that the ion beam passes the top portion 44 of the blade in each of the “beam-on” periods instead of passing the opening 42. In such a case, for example, the irradiation controller 38 outputs the beam extraction start signal when the point 46C shown in FIG. 4 has reached the position of the beam axis A, and outputs the beam extraction stop signal when the point 45A shown in FIG. 4 has reached the position of the beam axis A. With the proton beam delivery equipment 7 of this embodiment, since the on/off control of the ion beam is performed with the RMW 29 being rotated, the region in the RMW 29 where the ion beam passes the RMW 29 can be varied in the rotating direction of the RMW 29. Accordingly, a plurality of SOBP widths having different values in the direction of depth from the body surface of the patient 32 can be formed by using one RMW 29, and one RMW 29 can be used for a plurality of patients. In other words, the number of patients treatable using one RMW 29 is increased. Also, since a plurality of SOBP widths can be formed by using one RMW 29, it is possible to reduce the number of RMWs to be prepared in a cancer treatment center equipped with the proton beam delivery equipment 7. Further, since a plurality of SOBP widths can be formed by using one RMW 29, it is possible to reduce the number of times at which the RMW installed in the beam delivery nozzle 15 is to be replaced. This is advantageous in cutting the time required for preparations of the treatment and in increasing the number of patients treated by the proton beam delivery equipment 7. Especially, in this embodiment, since the on/off control of the ion beam is performed in accordance with the rotational angle (specifically the measured values and the setting values of the rotational angle) of the RMW 29, each particular SOBP width can be formed at high accuracy. By changing the rotational angle of the RMW in the on/off control of the ion beam, the SOBP widths having various values can be formed. In the synchrotron 4, the number of accelerated ions is constant. Therefore, even when the beam-on period is shortened, the current density of the ion beam extracted from the synchrotron 4 during the beam-on period can be increased by increasing the RF power supplied from the first RF-power supply 8 to the RF-applying device 5. Hence, the dose rate for irradiation to the patient (i.e., the radiation dose irradiated to the patient per unit time and per unit volume) can be increased even in a short beam-on period. In other words, the irradiation time of the ion beam can be reduced for the patient 32 having the tumor 33 with a small thickness or a small volume by irradiating the ion beam having the increased current density. This reduction of the irradiation time contributes to reducing the burden imposed on the patient 32 and increasing the number of patients treated per year. Further, even in the case of shortening the beam-on period, all of the circulating ion beam can be essentially extracted from the synchrotron 4 by increasing the RF power for the beam extraction as mentioned above. As a result, the degree of radiation accumulated in the components, such as the synchrotron 4, can be reduced. As an accelerator, a cyclotron may also be used, instead of the synchrotron, for introducing an ion beam extracted from the cyclotron to the beam delivery nozzle 15. However, the cyclotron does not include the decelerating step unlike the synchrotron, and performs steps of entering, accelerating and extracting the ion beam in succession. Accordingly, if the “beam-on” period is shortened, the number of ions extracted from the beam delivery nozzle 15 per unit time is reduced, while the rate of dose irradiated to the tumor 33 is not changed. This results in a reduction of the SOBP width and is hence equivalent to a reduction of the volume subjected to the irradiation. As a result, even when the “beam-on” period is shortened, the irradiation time of the ion beam is not changed for the patient 32 having the tumor 33 with a small thickness or a small volume. If the extraction of the ion beam is turned off during or after the step of accelerating the ion beam in the cyclotron, the amount of the ion beam discarded is increased and the degree of radiation accumulated in the components, such as various units of the cyclotron, is increased. A description is now made of a modification of the first embodiment in which another RMW 62 shown in FIG. 8 is used instead of the RMW 29. The RMW 62 has three blades 63A, 63B and 63C. Numerals 64A, 64B and 64C denote respective top portions of the blades 63A, 63B and 63C. The blades 63A, 63B and 63C have different values of thickness from their bottom surfaces to their top portions. As shown in FIG. 9, the thickness of the blade 63A is maximum, the thickness of the blade 63B is medium, and the thickness of the blade 63C is minimum. Similarly to the RMW 29, each of the blades 63A, 63B and 63C has a plurality of plane areas. The other construction of the RMW 62 is the same as that of the RMW 29. While all the top portions of the blades of the RMW 29 have the same height, the top portions of the blades of the RMW 62 have heights different from one another. The RMW 62 is also detachably mounted to the support member 45 within the beam delivery nozzle 15. When the RMW 62 is installed in the beam delivery nozzle 15, the extraction-on/off control of the ion beam is performed in three cases described below. In case d), the beam extraction start signal is outputted at the rotational angle indicated by the position of a point 65A, and the beam extraction stop signal is outputted at the rotational angle indicated by the position of a point 66A, thereby providing the “beam-on” state in a region including the blade 63A. In case e), the beam extraction start signal is outputted at the rotational angle indicated by the position of a point 65B, and the beam extraction stop signal is outputted at the rotational angle indicated by the position of a point 66B, thereby providing the “beam-on” state in a region including the blade 63B. In case f), the beam extraction start signal is outputted at the rotational angle indicated by the position of a point 65C, and the beam extraction stop signal is outputted at the rotational angle indicated by the position of a point 66C, thereby providing the “beam-on” state in a region including the blade 63C. The points 65A to 65C and 66A to 66C are each positioned in a corresponding one of the openings 42. In any case, the ion beam is in the “beam-off” state in the other region than the “beam-on” state. The extraction-on/off control of the ion beam in the case d) to f) is executed by the irradiation controller 38 through the processing in accordance with the flowchart shown in FIG. 7. The modification using the RMW 62 can also provide similar advantages to those described above in connection with the first embodiment. In short, the RMW 62 enables three different SOBP widths corresponding to the blades 63A, 63B and 63C to be formed by using one RMW. While the RMW 62 has the three blades having different heights from one another, it may have two, four or more blades having different heights from one another. Also, while the “beam-on” region in the RMW 62 is set only in the region including only one blade, the “beam-on” region may be set over two or more adjacent blades having different heights from one another. In such a case, when the “beam-on” region is set over, e.g., the blades 63A and 63B, a resulting dose distribution is one obtained by superimposing respective dose distributions with each other, which are obtained by separately irradiating the ion beam to those blades. Additionally, the “beam-on” region is not always required to include the whole of any of the blades, and the “beam-on” region may be set to cover parts of the adjacent blades as in the RMW 29. Proton beam delivery equipment according to a second embodiment, i.e., another embodiment of the present invention, will be described below. In the proton beam delivery equipment of this second embodiment, an RMW 67 shown in FIG. 10 is substituted for the RMW 29 installed in the beam delivery nozzle 15 in the proton beam delivery equipment 7 of the first embodiment. The other construction of the proton beam delivery equipment of this second embodiment is the same as that of the proton beam delivery equipment 7. In the proton beam delivery equipment of this second embodiment, as shown in FIG. 11, the beam extraction-on/off control is performed for each stepped portion (plane area) of the RMW 67. The RMW 67 includes one blade 68 having a plurality of plane areas 43 formed such that a thickness of each plane area in the axial direction is increased step by step from the opening 42 having a thickness being 0 to a top portion 70 having a maximum thickness in a direction opposed to the rotating direction of the RMW 67. The other construction of the RMW 67 is the same as that of the RMW 29 and hence is not described here. The extraction-on/off control of the ion beam executed by the irradiation controller 38 in this embodiment will be described below with reference to a control flow shown in FIG. 12. Of the control flow shown in FIG. 12, the same part as that of the control flow shown in FIG. 7 is not described here. The irradiation controller 38 receives beforehand, as treatment plan information, information indicating a beam-on region Ri (i=1, 2, . . . , n) (where n is an integer) from the central processing unit 36. The treatment plan information further includes a setting value Ai (i=1, 2, . . . , n) of the rotational angle and a target dose value Di (i=1, 2, . . . , n), both described later, which are also inputted beforehand to the irradiation controller 38 from the central processing unit 36. In a treatment example described here, the beam-on region Ri is set to, e.g., R11, namely 11 regions ranging from the region R1 to the region R11 as shown in FIG. 10. The setting n=11 is also applied to the setting value Ai of the rotational angle and the target dose value Di. The region R1 is positioned in the opening 42. The region R2 to the region R11 circumferentially cover the blade 68 from the plane area 43 located at a position 69 where the blade thickness is minimum, to the plane area 43 located at a position 71 where the blade thickness is third largest. Also, the rotational angles A1 to A11, i.e., the setting values of the rotational angle, each represent an angle from a reference line 22 to the position of a corresponding black circle; namely, the rotational angle A1 represents an angle from the reference line 22 to a point 72A, the rotational angle A2 represents an angle from the reference line 22 to a point 72B, and the rotational angle A11 represents an angle from the reference line 22 to a point 72K. Alternatively, depending on the size of the tumor 33 in the body of the patient 32 and the position of the tumor from the body surface, the beam-on region Ri (i=1, 2, . . . , n) may be set to cover, for example, from the region R4 to the top portion 70, or from the region R3 to the region R9 in FIG. 10. The irradiation controller 38 receives a signal indicating the end of acceleration in the accelerator (synchrotron 4) (step 51). Then, the irradiation controller 38 outputs a start-of-rotation signal to the rotating device 30 (step 52). The rotating device 30 rotates the RMW 67 at the number of, e.g., six rotations per second. It is determined whether a measured value GAi (i=1, 2, . . . , n) of the rotational angle matches with a setting value Ai (i=1, 2, . . . , n) of the rotational angle (step 73). If the measured value GAi of the rotational angle of the RMW 67 measured by the angle sensor 31, for example, matches with the setting value Ai of the rotational angle, a beam extraction start signal is outputted (step 54). As one example, at the time when the measured value GA1 matches with the setting value A1, the beam extraction start signal is outputted. The on/off switch 9 is closed in response to the beam extraction start signal, whereupon the ion beam is extracted from the synchrotron 4. The extracted ion beam is irradiated to the tumor 33 after passing the region Ri (e.g., the region R1 corresponding to the opening 42) of the RMW 67. It is determined whether a measured dose value RDi (i=1, 2, . . . , n) for the region Ri matches with the target dose Di (i=1, 2, . . . , n) for the same region Ri (step 74). The measured dose value RDi of the ion beam irradiated to the tumor 33, which is obtained from the dose monitor 23, is inputted to the irradiation controller 38. If the measured dose value RDi matches with the target dose Di, a beam extraction stop signal is outputted (step 57). For example, at the time when the measured dose value RD1 for the region R1 matches with the target dose D1 for the same region R1, the beam extraction stop signal is outputted. In response to the beam extraction stop signal, the on/off switch 9 is opened to stop the extraction of the ion beam from the synchrotron 4. With the above-described processing of steps 73, 54, 74 and 57, the ion beam passes the region R1 in the range of the rotational angle from the black-circle point 72A to a white-circle point 77A for irradiation to the tumor 33. The ion beam having passed the region R1 (i.e., the opening 42) is irradiated to the deepest position of the tumor 33 because beam energy is not attenuated by the RMW 67. If the determination result in step 75 is “NO” (i.e., if the region Rn is not yet reached), the processing of steps 73, 54, 74, 57 and 75 is repeatedly executed for the regions R2, R3, . . . , Rn in succession. In this example, the processing is repeated until reaching the region R11. With the processing of steps 73, 54, 74 and 57 repeated, the ion beam passes successively the region R2 in the range of the rotational angle from a black-circle point 72B to a white-circle point 77B, the region R3 in the range of the rotational angle from a black-circle point 72C to a white-circle point 77C, . . . , and finally the region R11 in the range of the rotational angle from a black-circle point 72K to a white-circle point 77K. In this example, because the extraction of the ion beam is turned off in a plane area 43Z corresponding to the flat portion 70 of the RMW 67 and a plane area 43Y at a level one step lower than the flat portion 70, the ion beam does not pass those plane areas 43Z, 43Y. If the determination result in step 75 is “YES” (i.e., if the region Rn has been reached), the processing of step 76 is executed to determine whether an accumulated value TRDi (i=1, 2, . . . , n) of the measured dose for the region Ri has reached a dose setting value TDi (i=1, 2, . . . , n) for the same region Ri. If the determination result in step 76 is “NO”, the determination in step 59 is made. If the determination result in step 59 is “YES”, the processing of steps 73, 54, 74, 57, 75 and 76 is repeated. If the determination result in step 59 is “NO”, the processing of steps 51 to 76 shown in FIG. 12 is repeated. If the determination result in step 76 is “YES”, a stop-of-rotation signal is outputted to the rotating device 30 (step 61) and the irradiation of the ion beam to the patient 32 is brought to an end. With reference to FIG. 13, a description is now made of the target dose Di (i=1, 2, . . . , n) and the dose setting value TDi (i=1, 2, . . . , n) for each region Ri (i=1, 2, . . . , n). The SOBP width, i.e., the zone where the total dose has a uniform distribution in the direction of depth from the body surface of the patient 32, is set so as to include the width of the tumor (target area) 33 in the direction of depth. The total dose means a total of dose irradiated in the form of the ion beam to the tumor 33. As shown in FIG. 13, the ion beam having passed the region R1 (i.e., the opening 42) of the RMW 67 forms a Bragg peak at the deepest position of the tumor 33. The dose of a Bragg peak BP1 shown in FIG. 13 represents a total dose irradiated to the tumor 33 as the ion beam having passed the region R1 until the irradiation of the ion beam to the tumor 33 is completed. The dose of the Bragg peak BP1 provides the dose setting value TD1. As the thickness of the RMW 67 from the bottom surface thereof increases in the order of the regions R2, R3, . . . , R11, the energy of the ion beam is attenuated at a larger rate and hence the position at which the Bragg peak is formed shifts toward the body surface of the patient. Thus, Bragg peaks BPa, BPb, BPc, etc. are formed as shown in FIG. 13. The dose of the Bragg peak BPa represents a total dose irradiated to the tumor 33 as the ion beam having passed the region Ra until the irradiation of the ion beam to the tumor 33 is completed. The dose of a Bragg peak BPc represents a total dose irradiated to the tumor 33 as the ion beam having passed the region Rc until the irradiation of the ion beam to the tumor 33 is completed. Hence, the dose of the Bragg peak BPa provides the dose setting value TDa, the dose of the Bragg peak BPb provides the dose setting value TDb, and the dose of the Bragg peak BPc provides the dose setting value TDc. In such a way, the dose setting value TDi for a certain patient 32, e.g., each of the dose setting values TD1 to TD11, is determined. The target dose Di (i=1, 2, . . . , n) is determined based on the dose setting value TDi (i=1, 2, . . . , n) and the number of rotations of the RMW 67 during a period from the start of irradiation of the ion beam to the tumor 33 to the end of the irradiation. When the number of rotations of the RMW 67 during such an irradiation period is 10, for example, a relationship of Di=TDi/10 is obtained. In particular, the target dose is preferably determined using the number of rotations at which the dose can be irradiated at the maximum setting value TD1. This second embodiment can also provide similar advantages to those obtainable with the first embodiment. In this second embodiment, the dose distribution can be more finely adjusted than in the first embodiment by changing the target dose Di (i=1, 2, . . . , n) for each stepped portion (plane area). Accordingly, the dose distribution in the direction of depth can be adjusted to become uniform for a plurality of ion beams having different levels of energy (or different amounts by which a range adjuster is inserted, or different irradiation field sizes). Further, with this second embodiment, the number of rotations of the RMW can be set smaller than that in the first embodiment. Because the RMW is rotated during the irradiation for treatment in the beam delivery nozzle 15 at a position close to the patient 32, a reduction in the number of rotations contributes to improving safety. In the first embodiment, the number of the RMW's 29 to be prepared can be reduced in comparison with the related art, but several kinds of the RMW's 29 must be prepared so as to accommodate different irradiation field sizes adapted for tumors having various sizes. In contrast, this second embodiment enables one kind of the RMW 67, shown in FIG. 10, to be used for irradiation of the ion beam to tumors at different irradiation field sizes in treatment. Hence, the number of RMW's to be prepared for treatments can be remarkably reduced.
	description	This U.S. non-provisional patent application claims priority under 35 U.S.C. §119 of Korean Patent Application 10-2006-0015792 filed on Feb. 17, 2006, the entire contents of which are hereby incorporated by reference. The subject matter described herein is generally concerned with air purification technology that employs new and improved photocatalyst materials especially efficient in decomposing volatile organic compounds that may be present in an air stream, with methods for manufacturing such photocatalyst materials, and with methods and apparatus for using such materials to clean and purify air streams. A specific application for the photocatalyst materials of this invention is to treat an air stream drawn from a “clean room” environment to remove and/or decompose organic contaminants before recycling the treated air stream back to the “clean room.” It is known in the art of air purification to prepare photocatalytic materials based on metals or metal oxides having semiconductor-like characteristics for removing contaminants from air. For example, the metals titanium (Ti), zirconium (Zr), tin (Sn), zinc (Zn), and similar metals, and the oxides of these metals, e.g., TiO2, ZrO2, SnO2, and ZnO2, are known to demonstrate the semiconductor characteristic of exhibiting at least two possible energy levels which may be referred to as a valence band state and a conduction band state. Thus, when excited or activated by light energy of a suitable wavelength, these materials respond by exciting electrons into the conduction band and leaving electron “holes” in the valence band. Depending on the photocatalytic material, solar light, fluorescent light, ultraviolet light, or other forms of light irradiation may be used effectively to activate the photocatalytic material. The field known as heterogeneous photocatalysis has attracted considerable attention in recent years. A comprehensive overview of heterogeneous photocatalysis using titanium dioxide (TiO2) appears in a 1995 Chemical Reviews article by A. L. Linsebigler et al. entitled “Photocatalysis on TiO2 Surfaces: Principles, Mechanisms, and Selected Results,” which article is incorporated herein by reference. This article discusses the potential application of TiO2-based photocatalysts to destroying organic compounds found in polluted air and wastewaters. The above-cited article provides the following useful summary of how photocatalysis operates to decompose a contaminant such as an organic compound: “In a heterogeneous photocatalysis system, photo-induced molecular transformations or reactions take place at the surface of a catalyst . . . . The initial excitation of the system is followed by subsequent electron transfer and/or energy transfer. It is the subsequent deexcitation processes (via electron transfer or energy transfer) that leads to chemical reactions in the heterogeneous photocatalysis process . . . . Photocatalysis processes involve the initial absorption of photons by a molecule or the substrate to produce highly reactive electronically excited states. The efficiency of the photoinduced chemistry is controlled by the system's light absorption characteristics.” When the photocatalytic material is activated by light energy, the electrons generated tend to form “super oxide” anions (typically represented as O2−) and the holes form hydroxide (OH−) radicals, with the result that the activated photocatalyst has an unusually strong oxidation capability. Specifically, the O2− and OH− radicals are capable of rapidly and effectively oxidizing an organic contaminant contacted at the surface of the photocatalyst thereby converting the contaminant into water (H2O) and carbon dioxide (CO2) or, sometimes, to small amounts of relatively harmless mineral acids, for example HCl. Thus, volatile organic contaminants in an air stream can be effectively decomposed and removed from the environment by contacting the air stream with the light-activated photocatalyst. The phenomenon known as “band-gap photoexcitation” is described in more technical terms in the previously cited Chemical Reviews article as follows: “Unlike metals which have a continuum of electronic states, semiconductors possess a void energy region where no energy levels are available to promote recombination of an electron and hole produced by photoactivation in the solid. The void region which extends from the top of the filled valence band to the bottom of the vacant conduction band is called the band gap. Once excitation occurs across the band gap there is a sufficient lifetime, in the nanosecond regime, for the created electron-hole pair to undergo charge transfer to adsorbed species on the semiconductor surface from solution or gas phase contact. If the semiconductor remains intact and the charge transfer to the adsorbed species is continuous and exothermic the process is termed heterogeneous photocatalysis.” The Chemical Reviews article then further explains how one of the deexcitation pathways for the electrons and holes is a photoinduced chemical reaction at the semiconductor surface: “The photoinduced electron transfer to adsorbed organic or inorganic species or to the solvent results from migration of electrons and holes to the semiconductor surface. The electron transfer process is more efficient if the species are preadsorbed on the surface. While at the surface the semiconductor can donate electrons to reduce an electron acceptor (usually oxygen in an aerated solution) (pathway C); in turn, a hole can migrate to the surface where an electron from a donor species can combine with the surface hole oxidizing the donor species (pathway D).” As also taught in the art, however, the electrons and holes generated by exciting a photocatalyst with light energy have a tendency to quickly recombine thereby neutralizing the powerful oxidation capacity of the activated photocatalyst. Thus, the Chemical Reviews article further teaches that: “In competition with charge transfer to adsorbed species is electron and hole recombination.” Photocatalytic efficiency is therefore generally improved if the photocatalyst can be prepared so as to remain in an excited state (with “free” electrons and holes) for a longer period of time to preserve the high oxidation capability of the material. An increase in the oxidation capability of a photocatalyst can therefore be achieved by decreasing the rate at which recombination of electrons and holes occurs. This effect can sometimes be achieved by doping a photocatalyst with a relatively small amount of a suitable dopant or dopants, for example with a noble metal. For example, a suitable dopant molecule in a photocatalyst can act as an electron trap side to, at least temporarily, bind a free electron and thereby slow its tendency to recombine with a hole. Similarly, a suitable dopant molecule in a photocatalyst can act as a hole trap site to, at least temporarily, block a hole and thereby slow its tendency to recombine with an electron. Another means of improving the photocatalytic efficiency of a particular photocatalyst is by increasing the band-gap energy of the photocatalyst. This effect can also sometimes be achieved by doping a photocatalyst with a relatively small amount of a suitable dopant or dopants. Thus, it is known in the art to improve the photocatalytic efficiency of a metal oxide photocatalyst by doping it with a noble metal. For example, a metal oxide photocatalyst based on Ti, Zr, Sn, Zn, or a similar metal, typically made from a metal alkoxide precursor, can be advantageously doped with a noble metal such as platinum (Pt), gold (Au) or silver (Ag) to provide trap sites in the photocatalyst. Metal alkoxides suitable as precursors in forming these photocatalysts typically have the general chemical formula [M-O-alkyl] in which M is a suitable metal, O is oxygen, and the alkyl group is selected from methyl, ethyl, and similar alkyl groups typically having 6 or fewer carbon atoms. In a typical application of this preparation process, a noble metal precursor, such as a solution or dispersion of a noble metal in a suitable solvent or dispersant, is prepared. The metal oxide photocatalyst is then doped with the noble metal by any of several familiar methods such as a dipping method, a deposition method, a co-precipitation method, an impregnation method, or a Sol-gel method. In the typical dipping method, the metal oxide photocatalyst is briefly immersed in a bath of the noble metal precursor and then withdrawn. Particles of the noble metal become deposited on and/or within the photocatalyst as the solvent or dispersant evaporates and/or drips off the photocatalyst. The dipping procedure may have to be repeated multiple times to achieve effective doping of the photocatalyst. By comparison with the dipping method, however, the Sol-gel doping method tends to be a very complicated and lengthy (slow) process. This prior art technique, however, suffers from numerous limitations, drawbacks and disadvantages. One important drawback of the prior art approach is the high costs of the materials. Nobel metals such as Pt, Au, and Ag are also precious metals, which are very expensive. Even the metal alkoxide precursors are relatively expensive industrial commodities. A second disadvantage of the prior art technique is that it is relatively complicated—involving preparation of two precursors—and relatively lengthy. Another important limitation of the above-described conventional method, however, is that it is very difficult, if not impossible, to reliably prepare nano-sized metal oxide particles for use as the photocatalyst using the metal alkoxide precursor technique. It has been found that the particle size of the photocatalyst is highly inversely correlated with photocatalytic efficiency. Specifically, it has been found that smaller photocatalytic particle size is associated with greater efficiency in decomposing contaminants, presumably because smaller particle size correlates with greater surface area and therefore with a larger active contact area between the photocatalyst and an air stream being treated. More recent developments in photocatalyst technology have used TiO2 doped with various dopants to prepare useful photocatalyst materials. U.S. Pat. No. 6,627,173, which is incorporated herein by reference, for example, teaches a process for preparing doped, pyrogenically prepared titanium dioxide, doped with zinc oxide, platinum oxide, magnesium oxide or aluminum oxide for use as a photocatalyst or UV absorber. In this patent, the titanium dioxide is doped by injecting an aerosol of the oxide into the production stream. This process, however, requires relatively complex production equipment, does not insure a thorough, homogeneous doping of the TiO2, and does not produce optimally-sized photocatalyst particles. U.S. Pat. No. 6,365,007, which is also incorporated herein by reference, teaches preparation of a photocatalyst consisting of TiO2 doped with at least one lanthanide metal oxide. The photocatalyst is prepared by forming a titanium-containing gel followed by the steps of drying the gel and subjecting it to calcinations. This process, however, employs relatively uncommon and expensive “inner-transition” lanthanide series elements and relatively high processing temperatures in both the drying and calcination steps. These and other problems with and limitations of the prior art approaches in this field are addressed in whole or at least in part by the products, methods and apparatus of this invention. Accordingly, a general object of this invention is to provide new and improved photocatalyst materials useful in decomposing/removing organic contaminants from a fluid stream. Another general object of this invention is to provide methods for preparing such new photocatalyst materials. Another general object of this invention is to provide methods and apparatus for using such new photocatalyst materials to treat fluid streams to decompose/remove contaminants. A principal object of this invention is to provide relatively inexpensive photocatalyst materials having a high level of photocatalytic efficiency in treating air or other fluid streams to remove/decompose organic contaminants in the fluid stream without the presence of a noble metal, methods of preparing such photocatalytic materials, and methods and apparatus for using these materials. A specific object of this invention is to provide photocatalyst materials comprising a first-metal oxide, said first-metal having photo-induced semiconductor-like characteristics, with an effective amount of ions of a second-metal being dispersed throughout the first-metal oxide to provide doping characteristics, said second-metal being a dopant. Another specific object of this invention is to provide methods of preparing photocatalyst materials comprising at least a step of mixing a first-metal precursor, comprising an inorganic chloride of a first-metal selected from a group of metals having photo-induced semiconductor-like characteristics, with a second-metal precursor comprising an inorganic chloride of a second-metal selected from a group of dopants. Still another specific object of this invention is to provide methods of preparing photocatalyst materials comprising the sequential steps of mixing first-metal and second-metal precursors, removing unessential ions from the precursor mixture, drying the treated mixture, and calcinating the dried mixture. Yet another specific object of this invention is to provide air purification methods for using photocatalyst materials according to this invention for treating air streams to decompose/remove organic contaminants present in the air streams. Still a further specific object of this invention is to provide air purification apparatus using photocatalyst materials according to this invention for treating air streams to decompose/remove organic contaminants present in the air streams. These and other objects and advantages of this invention will be more fully explained in the following portions of this application. One aspect of the present invention is directed to new photocatalyst materials having a high photocatalytic efficiency in decomposing organic contaminants. Photocatalytic materials in accordance with this invention consist essentially of an oxide of a first-metal having photo-induced semiconductor-like characteristics doped with an effective dopant amount of a second-metal selected from a group of dopants. As used herein, the term “metal having photo-induced semiconductor-like characteristics” is used to mean a metal that possesses a void energy region where no energy levels are available to promote recombination of an electron and hole produced by photoactivation in the solid, as defined in the previously cited Chemical Reviews article. Also, as used herein, the term “dopant” is used to mean a metal that functions as a dopant and has a full continuum of electronic states, as defined in the previously cited Chemical Reviews article. Carbon is specifically excluded from both the “metal having photo-induced semiconductor-like characteristics” as used herein and also from the “dopant” as used herein. As a result of the precursor materials utilized to provide the first-metal and the second-metal, and also as a result of the sequential series of method steps used to prepare the photocatalyst material from the precursor materials, the photocatalyst materials according to this invention are comprised substantially completely of quantum- (nano-) sized particles having a mean particle diameter of about 10 nm or less. Such nano-sized photocatalyst particles significantly increase the efficiency and effectiveness of the photocatalyst material in decomposing volatile organic compounds by dramatically increasing the surface/contact area between the photocatalyst and an air stream containing the volatile organic compounds. Although the previously cited Chemical Reviews article teaches the general concept that doping a TiO2 photocatalyst with a transition metal such as iron (Fe+3) or copper (Cu+2) can improve trapping of electrons to inhibit electron-hole recombination during illumination, this art does not teach the preparation method of this invention. The first-metal precursor in accordance with this invention can be represented by the general chemical formula M1xCly in which: M1 (the first-metal) is a non-carbon metal having photo-induced semiconductor-like characteristics, preferably selected from the group consisting of titanium (Ti), zirconium (Zr), tin (Sn), zinc (Zn), and alloys or mixtures thereof; Cl is chloride ion; and x and y are positive integers typically ranging from 1 to about 6. Specific examples of the first-metal precursor include TiCl4, ZrCl2, SnCl4, and ZnCl2. Because carbon is regarded as a contaminant for purposes of this invention, the definition herein of M1 specifically excludes carbon even if it might otherwise be regarded as a “semiconductor metal.” The second-metal precursor in accordance with this invention can be represented by the general chemical formula M2xCly in which: M2 (the second-metal) is a non-carbon dopant, preferably selected from the group consisting of iron (Fe), tungsten (W), manganese (Mn), vanadium (V), and alloys and mixtures thereof; Cl is chloride ion; and x and y are positive integers typically ranging from 1 to about 6. Specific examples of the second metal precursor include FeCl2, FeCl3 or Fe2Cl6, MnCl2, MnCl3, WCl2, WCl4, WCl5, WCl6, VCl2, VCl3 and VCl4. Because carbon is regarded as a contaminant for purposes of this invention, the definition herein of M2 specifically excludes carbon even if it might otherwise be regarded as a “dopant.” In the photocatalysts of this invention, it has been found that the second-metal component plays a role similar to that served by the much more expensive noble metal dopants of the prior art photocatalysts as described above. In particular, the second-metal component provides a trap site for free electrons and electron holes thereby slowing the tendency for recombination and helping to preserve a high oxidation capability for the light-activated photocatalyst. Photocatalysts prepared in accordance with this invention will thus contain an effective proportion of the second-metal relative to the first-metal, the amount being effective to serve a dopant function of trapping electrons and holes to measurably slow recombination as compared with an undoped photocatalyst. In a preferred invention embodiment, that effective proportion of second-metal relative to first-metal will range from about 0.1 to about 10 mol %. A second aspect of this invention is a method for preparing the photocatalyst materials such that the final product is comprised substantially completely of particles having a 10 nm or less mean particle diameter, as described above. The method comprises four sequential steps: (1) mixing the first-metal precursor with the second-metal precursor in the proper proportions of second-metal to first-metal; (2) removing the unessential/unnecessary ion(s) from the precursor mixture to form a sol, gel or powder of a preliminary product; (3) drying the preliminary product resulting from step (2) under particular temperature and pressure conditions to obtain a dried product comprising particles substantially all of which have a mean particle diameter of about 10 nm or less; and (4) subjecting the dried product particles to a calcinations (heat treatment) under controlled temperature and time conditions to produce a final photocatalyst product. It has been found that the step of removing the unessential/unnecessary ions (typically chloride ions) from the precursor mixture according to this invention results in the formation of an oxide of the first-metal with ions of the second-metal dispersed throughout the lattice structure of the first-metal oxide. This constitutes a “preliminary product” which needs to be dried and calcinated in accordance with the invention method to produce a final photocatalyst material. A third aspect of this invention is an air purification method and associated air purification apparatus that use a photocatalyst material according to this invention to decompose/remove organic contaminants from an air stream. These several aspects and embodiments of this invention will be better understood from the following detailed Description and the accompanying drawings/figures as described below. Photocatalysts according to the present invention are prepared by a four-step method as schematically illustrated in FIG. 1. Only photocatalysts prepared according to the steps shown in FIG. 1 have been found to have all of the advantageous properties described herein, particularly the property of a high photocatalytic efficiency. Such a high photocatalytic efficiency, at least in significant part, results from producing photocatalyst comprised substantially completely of nano-sized particles having a mean particle diameter of about 10 nm or less. Accordingly, a material having substantially the same chemical composition as a photocatalyst of this invention, but prepared by a different method of preparation than that illustrated in FIG. 1, would not be expected to demonstrate all of the advantageous physical and chemical properties as the photocatalysts of this invention. As illustrated in FIG. 1, the first step (S1) of the method of this invention is a mixing step wherein a first-metal precursor is mixed with a second-metal precursor, said first-metal and second-metal precursors being selected from the groups of compounds as previously described. In a representative embodiment of carrying out the S1 mixing step, a measured molar quantity of the second-metal precursor may be dissolved in a suitable solvent (e.g., water, hydrochloric acid, acetone, ether, or ethanol), preferably at a relatively low temperature of about 0 to 1° C., to form a solution of the second-metal precursor. Then, a suitable measured molar quantity of the first-metal precursor, for example in powdered form, may be added to the solution until the molar concentration of the second-metal relative to the first-metal is in a range of about 0.1 to 10 mol %. Although a particular mixing step embodiment was described above for illustrative purposes, it will be understood by those skilled in this art that other substantially equivalent approaches to thoroughly and intimately mixing the first-metal and second-metal precursors in suitable proportions may also be effectively employed in this step, and all such substantially equivalent alternative mixing methods are intended to be included within the scope of the S1 mixing step. The second step (S2) of the method of this invention is a dialysis or ion removal step wherein the unnecessary ion or ions, typically chloride ion (Cl−), is extracted from the mixture of first-metal and second-metal precursors. In an exemplary embodiment of carrying out the S2 dialysis/ion removal step, the mixture from step S1 is placed in a contained fabricated at least in part from a semi-permeable membrane that is permeable to chloride ion but impermeable to the first-metal and the second-metal, and the membrane container is then floated in a surrounding water bath for a suitable length of time (e.g., about one hour). During this period, chloride ion is drawn out of the precursor mixture, passes through the semi-permeable membrane, and is dispersed into the water bath creating a dilute chloride ion solution. The water bath may contain a material that binds with the chloride ions extracted from the precursor solution. Such a dialysis/ion removal step can be carried out effectively at about room temperature. If this step is permitted to run for about one hour, or perhaps a bit longer, a sol or gel or powder consisting essentially of an oxide of the first-metal containing ions of the second-metal in the desired proportions is typically formed in the membrane container. If the dialysis/ion removal step is not run for a sufficient length of time, however, the maximum sol yield may not be obtained because of interference caused by remaining chloride ions. Although a particular dialysis/ion removal step embodiment was described above for illustrative purposes, it will be understood by those skilled in this art that other substantially equivalent approaches to extracting the unnecessary ion(s) from the mixture of the first-metal and second-metal precursors may also be effectively employed in this step, and all such substantially equivalent alternative ion removal methods are intended to be included within the scope of the S2 dialysis/ion removal step. The third step (S3) of the method of this invention is a drying step for drying the preliminary product in the form of the sol, gel or powder produced by the S2 dialysis/ion removal step. In a preferred embodiment, the S3 drying step is a vacuum drying step carried out under at least partial vacuum conditions at a pressure of about 10−3 to about 10−4 torr and at a generally ambient temperature of about 20° C. to obtain the desired quantum- (nano-) sized photocatalyst particles. As discussed above, it is preferred to produce photocatalyst particles according to this invention wherein substantially all of the particles are nano-sized particles because such nano-sized particles increase photocatalytic activity by increasing the ability of the photocatalyst to adsorb volatile organic compound due to the increased surface area of the photocatalyst. Specifically, in a preferred invention embodiment, the product produced by the S3 drying step consists of particles having a mean particle diameter of about 10 nm or less. Although a particular drying step embodiment was described above for illustrative purposes, it will be understood by those skilled in this art that other substantially equivalent approaches to drying the sol, gel or powder product from step S2 may also be effectively employed in this step, and all such substantially equivalent alternative drying methods are intended to be included within the scope of the S3 drying step. The fourth step (S4) of the method of this invention is a calcination or heat treatment step. This step has been found to serve multiple purposes in completing the preparation of photocatalysts in accordance with this invention. First, the S4 calcination step helps to remove residual contaminants that may be present in the dried product of step S3 as a result of earlier processing steps. The presence of such contaminants can impair the photocatalytic activity of the photocatalyst. In addition, it has been found that the S4 calcination step induces a degree of crystal growth of the anatase state of the photocatalyst. It has been found that the anatase state of the photocatalysts of this invention generally has the highest degree of photoactivity leading to greater photocatalytic efficiency. On the other hand, it has also been found that carrying out step S4 at too high a temperature and/or for too long a period of time can lead to a deterioration in the properties of the photocatalyst. Accordingly, a balance needs to be found in carrying out the S4 calcination step to optimize the effectiveness of this step in improving the photocatalyst properties. In general, the S4 calcination step may be effectively carried out at temperatures ranging from about 50° C. to about 600° C. for a period of about 3 to about 5 hours. In a preferred embodiment, the S4 calcination step is carried out at a temperature between about 100° C. and about 500° C., and in an even more preferred embodiment between about 300° C. to 500° C. It has been found that a calcinations step temperature below about 50° C. generally is not effective in driving off contaminants from the photocatalyst. It has also been found that a calcinations step temperature above about 600° C. results in converting a significant portion of the photocatalyst from the desired anatase state to an undesired rutile state. This results in a loss of photocatalytic efficiency caused by a decrease in both surface area and pore volume which results from partial sintering of the photocatalyst particles. Within the broad time and temperature ranges stated above, the S4 calcination step may be carried out under varying time/temperature conditions so as to optimize the desirable properties of the resulting photocatalyst product. The above-described method of production results in a photocatalyst material consisting essentially of an oxide of the first-metal with ions of the second-metal dispersed throughout the lattice structure of the first-metal oxide. The ions of the second-metal act effectively as trap sites for the electrons and holes that are formed when the photocatalyst is exposed to light energy. As a result, recombination of the conduction band electrons and the valence band holes is significantly slowed, and the light-activated photocatalyst maintains its high oxidation capability for a longer period of time. Furthermore, because the photocatalysts of this invention are formed as nano-sized particles, the photocatalytic efficiency of these materials in decomposing volatile organic contaminants is greatly enhanced. This illustrative example demonstrates the preparation of a first photocatalyst in accordance with this invention. The completed first photocatalyst consists essentially of titanium dioxide (TiO2) with interstitial iron (Fe) ions dispersed through the TiO2 lattice. Four aqueous solutions of iron chloride (FeCl2) in distilled water were prepared as follows: Example 1a: 0.1 mol % FeCl2 Example 1b: 0.5 mol % FeCl2 Example 1c: 1 mol % FeCl2 Example 1d: 10 mol % FeCl2 Titanium chloride (TiCl4) was mixed into each of the four iron chloride solutions (step S1) and allowed to mix for a period of about 1 hour. Next, the S2 dialysis step was performed on each of the four mixtures for a period of about 1 hour in order to form sols. Next, the S3 vacuum drying step was performed on each of the four sols at a pressure of about 10−3 to about 10−4 torr and at a temperature of about 10° C. to about 20° C. The resulting four photocatalyst products were each divided into four portions (sixteen portions in all). Each portion was then subjected to the S4 calcination step. One portion of each of the four photocatalyst products was subjected to a calcination step at a temperature of 30° C. (essentially no calcination); a second portion of each product was calcinated at 100° C.; a third portion of each product was calcinated at 300° C.; and, the fourth portion of each product was calcinated at 500° C. These sixteen completed photocatalyst products were used to carry out subsequent experimental testing as described below. This illustrative example demonstrates the preparation of a second photocatalyst in accordance with this invention. The completed second photocatalyst consists essentially of titanium dioxide (TiO2) with interstitial tungsten (W) ions dispersed throughout the TiO2 lattice. This example was carried out in the same manner as described above for Example 1 except that four aqueous solutions of tungsten chloride (WCl2) were substituted for the aqueous solutions of iron chloride. These sixteen completed photocatalyst products were used to carry out subsequent experimental testing as described below. This example illustrates the relationship between mean particle size of the photocatalyst and the concentration of the second metal ion under conditions of different calcinations step temperatures. In these tests, particle sizes were measured using a dynamic light scattering method. The results of this experimental testing are illustrated in FIGS. 3A to 3D, as described below. FIG. 3A shows the relationship between mean particle size and the second-metal ion concentration for the iron-doped and tungsten-doped titanium dioxide photocatalysts of Examples 1 and 2 “before calcination.” FIG. 3A shows that, at each of the four tested mol % concentrations for both the iron-doped and tungsten-doped photocatalysts, the mean particle size was well below 10 nm. FIG. 3B shows similar results but with slightly higher mean particle sizes following calcination at 100° C. FIG. 3C also shows results generally similar to FIGS. 3A and 3B with calcination carried out at 300° C.; but in FIG. 3C, at a 10 mol % concentration of the second-metal, the mean particle sizes for both the iron-doped and the tungsten-doped photocatalysts are starting to approach 10 nm. FIG. 3D showing results for calcination at 500° C. shows that mean particle size at every mol % concentration is close to or, at 10 mol %, perhaps even slightly exceeds 10 nm. This example illustrates the relationship between absorption intensity and absorption wavelength for photocatalyst materials prepared according to Examples 1 and 2 above to see what material has the highest band gap energy and to compare this property for the photocatalysts of this invention with the band gap energy of undoped titanium dioxide. The equation for band gap energy (Eg) is Eg=v, where v=c/λ. Thus, Eg=c/λ. In this equation, λ can be obtained from UV-vis spectrum, while and c are known constants. Therefore, Eg can be calculated. An increase in band gap energy Eg leads to the inhibition of recombination, which can be improved by the photoactivation step. The results of the band gap energy experimental testing are illustrated in FIGS. 4A and 4B, as described below. FIG. 4A is a graph that plots absorption intensity as a function of absorption wavelength for the iron-doped titanium oxide photocatalysts of Example 1 for each of the four mol % concentrations. This graph shows that the band gap for the iron-doped TiO2 at every tested mol % concentration (ranging from a band gap energy of 3.78 eV to a band gap energy of 3.66 eV) is greater than that of undoped TiO2 (which is 3.2 eV). FIG. 4B is a graph similar to FIG. 4A except that it shows testing of the tungsten-doped titanium dioxide photocatalyst of Example 2. Here again, the graph shows that the band gap for the tungsten-doped TiO2 at every tested mol % concentration (ranging from a band gap energy of 3.75 eV to a band gap energy of 3.6 eV) is greater than that of undoped TiO2 (namely 3.2 eV). This example illustrates the relationship between calcination temperature and the light activation response of the resulting photocatalyst owing principally to increased anatase crystallization growth at higher calcination temperatures up to 500° C. using the photocatalyst materials prepared according to Examples 1 and 2. The results of this experimental testing are illustrated in FIGS. 5A and 5B, as described below. FIG. 5A is a graph showing the results of X-ray diffraction analysis for 0.1 mol % iron-doped titanium dioxide photocatalysts prepared according to Example 1 at calcination temperatures of 30° C., 100° C., 300° C. and 500° C. respectively. Correspondingly, FIG. 5B is a graph showing the results of X-ray diffraction analysis for 0.5 mol % tungsten-doped titanium dioxide photocatalysts prepared according to Example 2 at calcination temperatures of 30° C., 100° C., 300° C. and 500° C. respectively. These graphs illustrate that, as the calcination step temperature increases (up to about 500° C.), more anatase crystallization growth is induced, which is favorable to the light activation responsiveness of the completed photocatalyst material. In general, the order of photoactivity, as illustrated by this Example, can be summarized as follows: TiO2 (anatase phase)>TiO2 (Rutile phase)>ZnO>ZrO2>SnO2, etc. For example, it has been confirmed with TiO2 anatase phase calcined at 500° C. Calcination temperatures up to about 500° C. increase photoactivity. The X axes of the XRD patterns are 2 Theta (θ) which can be induced from Bragg's law, namely, nλ=2d sin θ. Therefore, sin θ=nλ/(2d). From the above equation, one can obtain the θ with n, λ and d from fixed value in XRD equipment. The Y axes of the XRD patterns are merely intensity which means the crystallinity. This example compares the efficiency of various photocatalysts prepared according to this invention with one another in decomposing toluene, a common and representative volatile organic contaminant, and it also compares the decomposition performance of photocatalysts prepared according to this invention with the performance of a commercially available photocatalyst known in the trade as P-25, manufactured by Degussa Co. The chemical composition of the commercial photocatalysts used herein are as follows: P25: TiO2 (Gas-phase oxidation method) ST-01: TiO2 (Sol-gel method). The results of this set of experimental tests are illustrated in FIGS. 6A and 6B. In order to carry out this set of experimental tests, a laboratory line gas chromatography system as schematically shown in FIG. 2 was assembled. FIG. 2 shows a closed-loop air circulation system for continuously circulating a stream of air. A pump 5 is used to maintain flow of the air stream. An external supply 1 of the volatile organic contaminant (toluene) is connected by a supply line, which includes a valve element, to the closed-loop air circulation system so as to supply a controlled amount of the contaminant to the air stream at a location that is upstream from a contaminant decomposition unit in said closed-loop system. The contaminant decomposition unit as shown in FIG. 2 comprises a UV lamp 2 to provide ultraviolet radiation to a reaction compartment through a UV-transparent window such as a quartz window. Inside the reaction compartment is a bed of photocatalyst 3 dispersed on a quartz plate A which is exposed to UV light when the lamp 2 is on. Downstream of the contaminant decomposition unit is a valve 4 by which a sample portion of the circulating air stream can be continuously or periodically withdrawn from the closed-loop system for testing using detector 6 to determine the effectiveness of the decomposition unit in removing the toluene contaminant. For purposes of this set of experimental tests, a first photocatalyst was prepared according to this invention consisting essentially of TiO2 doped with 0.1 mol % of Fe ions. One portion of this photocatalyst was left uncalcinated, while other portions were calcinated at 100° C., 300° C. and 500° C. A second photocatalyst was prepared according to this invention consisting essentially of TiO2 doped with 0.5 mol % of W ions. One portion of this photocatalyst was left uncalcinated, while other portions were calcinated at 100° C., 300° C. and 500° C. 2 g of each prepared photocatalyst as well as a commercial photocatalyst was dispersed on separate quartz plates, each plate having a size of 2.5×7 cm2, and each plate with photocatalyst was in turn installed in the reaction chamber of the system for testing. An air mixture containing 100 ppm of toluene was circulated through the photocatalyst being tested at a speed of 50 cc/min. The UV lamp produced UV light at a wavelength of 150 nm. The following testing parameters were used for this set of tests: reaction pressure=1 atm; reaction temperature=room temperature; reaction time=20 mins. Detector 6 was used to periodically monitor the toluene content of the air stream downstream of the reactor/photocatalyst bed over a period of 200 minutes from the starting time. The results of these tests are plotted in the graphs of FIGS. 6A and 6B. FIG. 6A shows test results using the laboratory apparatus as illustrated in FIG. 2 with different photocatalysts for photocatalyst bed 3 of FIG. 2 as follows: (a) the commercial photocatalyst; (b) a 0.1 mol % iron-doped TiO2 photocatalyst according to Example 1 before calcination; (c) a 0.1 mol % iron-doped TiO2 photocatalyst according to Example 1 processed at a calcination temperature of 100° C.; (d) a 0.1 mol % iron-doped TiO2 photocatalyst according to Example 1 processed at a calcination temperature of 300° C.; and (e) a 0.1 mol % iron-doped TiO2 photocatalyst according to Example 1 processed at a calcination temperature of 500° C. In FIG. 6A, the y-axis shows the after reaction concentration of contaminant in the air stream (as measured by detector 6) divided by the initial concentration of contaminant in the air stream based on the amount/rate of contaminant addition (i.e., the after/before contaminant ratio). The x-axis of FIG. 6A is time measured from when the contaminant was added to the circulating air stream. Thus, FIG. 6A shows how efficient the different photocatalysts tested are in decomposing the toluene contaminant. For example, FIG. 6A shows that the commercial photocatalyst (a) (plotted with open squares) performs as well as or better than the 0.1 mol % iron-doped TiO2 photocatalyst (b) before calcination (plotted with solid triangles). Even after 200 minutes of reaction time, however, the commercial photocatalyst has only decomposed about 70% of the toluene contaminant in the air stream. The 0.1 mol % iron-doped TiO2 photocatalyst of this invention that was subjected to calcination at 100° C. (c) (plotted with solid circles) performed significantly better than the “before calcination” photocatalyst (b), but performed about the same as the commercial photocatalyst. By contrast, the photocatalysts according to this invention including calcination at 300° C. (d) (plotted with solid squares) and at 500° C. (e) (plotted with solid diamonds) performed substantially better than the others. Using either the (d) or (e) photocatalysts achieved substantially complete decomposition of the toluene contaminant after about 160 minutes. Furthermore, FIG. 6A shows that the (d) and (e) photocatalysts operate much more quickly than the other photocatalysts tested by decomposing at least half of the toluene contaminant in about 30 minutes or less, and decomposing 90% or more of the contaminant in 20 minutes (photocatalyst (d)) or 60 minutes (photocatalyst (e)). Photocatalyst (d) is seen to decompose the contaminant substantially faster than photocatalyst (e), which may reflect some of the adverse effects discussed above of carrying out the calcination step at a temperature as high as 500° C. FIG. 6B is similar to FIG. 6A except that in FIG. 6B the commercial photocatalyst is compared with four tungsten-doped photocatalysts. Thus, FIG. 6B shows plots using: (a) the commercial photocatalyst; (b) a 0.5 mol % tungsten-doped TiO2 photocatalyst according to Example 2 before calcination; (c) a 0.5 mol % tungsten-doped TiO2 photocatalyst according to Example 2 processed at a calcination temperature of 100° C.; (d) a 0.5 mol % tungsten-doped TiO2 photocatalyst according to Example 2 processed at a calcination temperature of 300° C.; and (e) a 0.5 mol % tungsten-doped TiO2 photocatalyst according to Example 2 processed at a calcination temperature of 500° C. Although the results shown in FIG. 6B are generally consistent with those of FIG. 6A, the most significant difference is that the performance characteristics of the (d) and (e) photocatalysts hardly differ at all, and both of these photocatalysts perform dramatically better than either the commercial photocatalyst (a) or the tungsten-doped photocatalysts either before calcination (b) or processed at a calcination temperature of 100° C. These experimental results confirm both the importance of the calcination step and the need to carefully control the calcination temperature to obtain optimum performance characteristics. Based on the teachings of this application, one skilled in this art could readily determine an optimum calcination temperature for a particular combination of first-metal oxide, a second-metal dopant, and a given mol % of the second-metal. This Example and accompanying FIG. 7 illustrate the loading effect of dopants. The photocatalysts tested in this Example were prepared by a process in accordance with the present invention with calcination carried out at 100° C. Photoactivity of the photocatalyst is seen to be enhanced at low concentration of dopant due to dispersion of the dopant throughout the lattice of TiO2. However, at heavy concentrations of dopant, photoactivity is seen to decrease. This effect is theorized to be caused by the formation of clusters which play a role of facilitating recombination or by interfering with light to the TiO2. The preceding examples confirm that doping a first-metal oxide with a relatively small proportion of ions of a second-metal according to the preparation method of this invention produces an efficient and effective photocatalyst material having a very small particle size, a relatively high band gap energy, and a high capability of decomposing volatile organic contaminants by photocatalyzed oxidation. With lower calcination temperatures, particle sizes will be smaller, but higher calcination temperatures (at least up to about 500° C.) promote anatase crystallization growth that is favorable to enhancing light activation responsiveness of the photocatalyst. On the other hand, certain negative performance effects from calcinating at the high end of the acceptable temperature range may lead one to try to optimize the photocatalyst manufacturing method by selecting an intermediate calcination temperature, for example about 300° C. In general, however, the examples show that effective photocatalysts in accordance with this invention may be produced by doping a first-metal oxide with about 0.1 to 10 mol % of a second-metal ion, and by performing a calcination step at a temperature of about 50° C. to 600° C., preferably a temperature of about 100° C. to 500° C., more preferably about 300° C. to 500° C. FIG. 8 schematically illustrates a “clean” room that utilizes a photocatalyst in accordance with this invention to purify a closed-loop circulating air stream by removing contaminants prior to recirculating the air stream. Such closed-loop air recirculation clean room environments are commonplace in industrial applications where it is necessary to maintain a workplace substantially free of any contamination and/or where environmentally unacceptable byproducts are produced as part of the industrial operation. The manufacture of modern semiconductor devices is a good example of a workplace that necessitates a clean room environment. Because of their widespread use as solvents, cleaning agents, and reagents in industrial applications, volatile organic compounds are a common contaminant in the recirculating air stream of a clean room. The photocatalysts of this invention have special utility in such clean room applications. Thus, FIG. 8 schematically shows a clean room 12 suitable to semiconductor manufacturing including a ceiling region 14, an under floor region 16 and a cooling coil 20. The sidewalls, ceiling and floor of clean room 12 define an air circulation path 18. At some point along air circulation path 18, for example in ceiling region 14, is located an array of fan filter units through which the air stream must pass. The fan filter units are designed to treat the circulating air stream as it passes through the units so as to supply a fresh stream of purified air to the clean room. In one application of the present invention, each fan filter unit in an array of such units includes a volatile organic contaminant decomposition system comprising a bed of photocatalyst according to this invention in combination with a light source suitable for activating the photocatalyst. A variety of fan filter unit configurations as illustrated in FIGS. 9A to 9D can readily be adapted for use in combination with the photocatalysts of this invention. The fan filter unit configurations of FIGS. 9A to 9D are disclosed and discussed in greater detail in Korean laid open application on 2005-75927, which is hereby incorporated herein by reference. Each of the fan filter configurations of FIGS. 9A to 9D includes a housing that houses a fan 110, a particle filter 130, and a chemical filter element 120, 220, 320 and 420, respectively, in FIGS. 9A to 9D. During operation, an air stream, possibly containing volatile organic compounds, ammonia, ozone, and perhaps other contaminants, is drawn by the fan elements 110 into the fan filter housings. The volatile organic compounds, ammonia, and ozone, if present, are chemically dissolved or decomposed by the chemical filter elements. Particulates are then removed by the particle filter elements 130, and fresh, purified air is supplied to the clean room. In an embodiment of the present invention, chemical filter elements 120, 220, 320 and 420 respectively in FIGS. 9A to 9D comprise a volatile organic contaminant decomposition system incorporating a photocatalyst material according to the present invention. Such chemical filter elements may be formed by coating the photocatalyst material of this invention on a surface of a suitably sized and shaped support member fashioned of a certain or comparable material. For example, the support member may be selected from glass, silica gel, silica alumina, zeolite, a honeycomb monolith substrate made of metal, or a ball and a coil type of molecular structure. Additionally, a chemical filter element in accordance with this invention comprises a source of light energy, for example a UV lamp, positioned near and oriented toward the photocatalyst-coated surface of the support member so as to activate the photocatalyst. The photocatalyst of the present invention may also or alternatively be coated in predetermined regions on interior and/or exterior walls of the clean room system where it will be light-activated and come into contact with the air stream. Embodiments of the present invention include applications in antibiotic manufacturing, semiconductor fabrication, and other industrial applications where a “clean” room environment is necessary or at least desirable. The photocatalyst materials of the present invention are relatively inexpensive to manufacture, especially in comparison with prior art photocatalysts employing noble (precious) metals as the dopant. The methods for manufacturing the photocatalysts of this invention are relatively simple—comprising a mixing step, a dialysis step, a drying step, and a calcinations step—and do not require expensive, specially-designed equipment. In addition, only a single cycle of the method is required to produce a finished, ready-to-use photocatalyst product. The preparation methods of this invention also use low temperature synthesis and low temperature vacuum drying, which also contribute to a low-cost photocatalyst product. The photocatalyst materials produced according to the methods of this invention have a number of advantageous physical and chemical properties. The photocatalysts of this invention demonstrate band gap widening properties and slower recombination speeds, which leads to elevated photocatalytic activity and enhancement of oxidation capability. The photocatalysts of this invention also have the benefit of being produced as nano-sized particles which present a greater surface area for contacting an air stream, which thereby further enhances the effectiveness of these materials in decomposing volatile organic compounds. The above-disclosed subject matter is to be considered illustrative, and not restrictive, and the appended claims are intended to cover all such modifications, enhancements, and other embodiments, which fall within the true spirit and scope of the present invention. Thus, to the maximum extent allowed by law, the scope of the present invention is to be determined by the broadest permissible interpretation of the following claims and their equivalents, and should not be restricted or limited by the foregoing detailed description.
062087126	abstract	Method and system aspects for utilizing portal images in a virtual wedge treatment during radiation treatment by a radiation-emitting device are described. In a method aspect, and system for achieving same, the method includes utilizing an image dose with a static jaw gap position to initiate a virtual wedge treatment with portal imaging. The method further includes continuing with the virtual wedge treatment from a reduced jaw gap position with a dynamic dose and dynamic jaw positioning. In addition, the virtual wedge treatment in completed with a static dose in the static jaw gap position.
047626615	summary	BACKGROUND AND SUMMARY OF THE INVENTION The invention relates to an upper end piece of a nuclear fuel assembly for a pressurized water reactor, which assembly comprises a lower end piece secured to a structural element belonging to the upper end piece by guide tubes for receiving a cluster of control elements. The invention is particularly suitable for use in spectral shift reactors in which the energy spectrum of the neutrons in the core is modified as the fuel burns up. This modification is obtained by changing the proportion of moderator in the core, by means of clusters of elements whose role is to replace moderating water in some at least of the guide tubes of an assembly (French No. 82 18011). The fuel assemblies of the above-defined type generally comprise means for damping the fall of the control element clusters upon shut down of the reactor. These means often operate by throttling outflow of water contained in the guide tubes when the control elements approach their lower position. The throttling action may be obtained by a restriction in the lower part of the guide tubes. The damping means have the disadvantage of considerably complicating the manufacture of the guide tubes because of the accuracy required in adjusting the damping effect. To complete the damping effect of the head loss impressed to the outflow, it has been proposed to add resilient means which are compressed by the cluster at the end of movement (French Nos. 2 106 373 and 2 070 373). The resilient means are integrated in the device controlling the cluster and consequently must have a small volume and a correspondingly low damping effect. Consequently, they only have a truly significant effect when the cluster is of moderate weight and so comprises a small number of control elements. The nuclear fuel assemblies for use in spectral shift reactors raise an additional problem, because each assembly must be adaptated for receiving a cluster of control elements controlling the reactor moderation rate in addition to the usual cluster of absorbing control elements or in place thereof. It is an object of the invention to provide an improved upper end piece; it is a more specific object to provide an end piece for satisfactory damping during fall of the control sclusters or "scram", using resilient means whose design does not contradict space considerations. To this end, there is provided an upper end piece for a nuclear fuel assembly which comprises an abutting member for receiving the cluster at the end of its fall, means for guiding said abutting member parallel to the axis of the guide tubes and resilient means within the end piece and disposed between the structural member and the abutting member for absorbing the energy of the cluster at the end of the fall thereof. In the case of an end piece for a spectral shift reactor assembly, adapted for receiving a cluster of absorbent elements and/or a cluster of elements for modifying the moderation rate by driving out the water contained in guide tubes, the resilient means of the end piece may comprise two springs and two abutment elements each cooperating with one of the clusters, one of which is formed by a plate constituting said abutting member. The springs may be disposed so that only one of the two is compressed by the fall of a particular one of the clusters, whereas the two springs are compressed and provide a damping function upon fall of the other cluster. The two springs may be disposed coaxially to each other. The end piece may be completed by additional resilient means located to receive an upper core plate and thus to complete the hold-down function of the coaxial springs, i.e. to oppose raising of the assembly by the upward flow of the water serving as moderator and coolant, during operation of the reactor. In an advantageous embodiment of the invention, the end piece forms a block independent of the rest of the assembly which comprises, in addition to the lower end piece and guide tubes, a simple upper perforated table fixed permanently to the guide tubes. Thus it is possible to replace the end piece should it be damaged or, on the contrary, to use the end piece successively on several assemblies, the end piece being easily removed from a completely exhausted assembly or a defective assembly. The invention will be better understood from reading the following description of particular embodiments given by way of non limitative examples.
062918281	summary	FIELD OF THE INVENTION The present invention relates generally to ion implantation systems and more particularly to the use of quartz or quartz-like beamline components in an ion implanter to prevent film coating thereof and subsequent voltage breakdowns. BACKGROUND OF THE INVENTION Ion implantation has become the technology preferred by industry to dope semiconductors with impurities in the large-scale manufacture of integrated circuits. High-energy ion implanters are used for deep implants into a substrate. Such deep implants are required to create, for example, retrograde wells. Eaton GSD/HE and GSD/VHE ion implanters are examples of such high-energy implanters. These implanters can provide ion beams at energy levels up to 5 MeV (million electron volts). U.S. Pat. No. 4,667,111, assigned to the assignee of the present invention, Eaton Corporation, describes such a high-energy ion implanter. Ion implanters operate at very high voltage levels. Typically, ions in the beam are accelerated and decelerated by electrodes and other components in the implanter that reside at differing voltage levels. For example, positive ions are extracted from an ion source and accelerated by electrodes having increasingly negative potentials. In a high-energy ion implanter, the ion beam accelerates as it passes through a radio frequency (RF) linear accelerator (linac). The ion beam progresses through the RF linac by passing through a series of acceleration stages (resonator modules) in which accelerating fields are produced by synchronizing the frequency of the RF voltage to the ion beam velocity. In known RF linac resonator modules, an RF signal is coupled to a low-voltage end of an inductor coil, and an accelerating electrode is directly coupled to an opposing high-voltage end of the inductor coil. Each accelerating electrode is mounted between two grounded electrodes and separated by gaps. When the resonator module achieves a state of resonance, a sinusoidal voltage of large magnitude is provided at the location of the accelerating electrode. The accelerating electrode and the ground electrodes on either side operate in a known "push-pull" manner to accelerate the ion beam passing therethrough, which has been "bunched" into "packets". During the negative half cycle of the RF sinusoidal electrode voltage, a positively charged ion packet is accelerated (pulled by the accelerating electrode from the upstream grounded electrode across the first gap). At the transition point in the sinusoidal cycle, wherein the electrode voltage is neutral, the packet drifts through the electrode (also referred to as a "drift tube") and is not accelerated. During the positive half cycle of the RF sinusoidal electrode voltage, positively charged ion packets are further accelerated (pushed by the accelerating electrode) toward the downstream grounded electrode across the second gap. This push-pull acceleration mechanism is repeated at subsequent resonator modules having accelerating electrodes that also oscillate at a high-voltage radio frequency, thereby further accelerating the ion beam packets by adding energy thereto. In each of the first and second accelerating gaps, electric field lines produce radial focusing in the first gap and radial defocusing in the second gap. If the gap is operating at a phase which keeps the particles bunched in the axial direction, more often than not the electric field is increasing in magnitude, through its RF cycle, when a particle is passing through the gap. Consequently, the electric radial defocusing forces in the second gap are greater than the radial focusing forces in the first gap, resulting in a net radial defocusing as the ion beam passes through a particular resonator module. Accordingly, to refocus the ion beam, magnetic or electrostatic quadruples are 20 positioned intermediate each of resonator modules in an RF linac. These magnetic or electrostatic quadruples include a plurality of magnets or high-voltage electrodes, respectively, through or by which the ion beam passes. In the case of an electrostatic quadrupole, the high-voltage electrodes, which operate between +20 kilovolts (KV) and -20 KV, are typically made of graphite, which is subject to sputtering when struck by the ion beam. Sputtered graphite material tends to coat the insulating standoffs (e.g., alumina (Al.sub.2 O.sub.3)) that mount the high-voltage electrode to the electrically grounded quadrupole housing. If a sufficient amount of sputtered material coats the standoffs, it can lead to voltage breakdown between the electrode and the grounded housing by creating an electrical current path therebetween. It is an object of the present invention, then, to provide ion implanter components that reduce the chance of being coated with material that can cause electrical shorts and resulting arcing. It is another object of the invention to provide such components in the form of electrical insulators that mount electrodes within the beamline. It is a further object to provide such components in the form of insulating standoffs that are used to mount electrostatic quadrupole electrodes in the linear accelerator portion of a high-energy ion implanter. SUMMARY OF THE INVENTION An electrostatic quadrupole lens assembly is provided for an ion implanter having an axis along which an ion beam passes, comprising: (i) four electrodes oriented radially outward from the axis, approximately 90.degree. apart from each other, such that a first pair of electrodes oppose each other approximately 180.degree. apart, and a second pair of electrodes also oppose each other approximately 180.degree. apart; (ii) a housing having a mounting surface for mounting the assembly to the implanter, the housing at least partially enclosing the four electrodes; (iii) a first electrical lead for providing electrical power to the first pair of electrodes; (iv) a second electrical lead for providing electrical power to the second pair of electrodes; and (v) a plurality of electrically insulating members formed of a glass-like material, comprising at least a first electrically insulating member for attaching the first pair of electrodes to the housing, and at least a second electrically insulating member for attaching the second pair of electrodes to the housing. The plurality of electrically insulating members are preferably comprised of quartz (SiO.sub.2), or a heat resistant and chemical resistant glass material such as Pyrex.RTM.. The members resist accumulation of material such as graphite sputtered off of the electrodes by the ion beam, thus reducing the occurrence of high voltage breakdown and electrical current breakdown.
	description	The present application claims the benefit under 35 USC 119(e) of U.S. Provisional Application No. 61/606,408 filed Mar. 3, 2012; the full disclosure of which is incorporated herein by reference in its entirety. Not Applicable Not Applicable The invention generally relates to radiation therapy and more particularly to systems and methods for very high electron energy radiation therapy. Major technical advances in radiation therapy in the past two decades have provided effective sculpting of 3-D dose distributions and spatially accurate dose delivery by imaging verification. These technologies, including intensity modulated radiation therapy (IMRT), hadron therapy, and image guided radiation therapy (IGRT) have translated clinically to decreased normal tissue toxicity for the same tumor control, and more recently, focused dose intensification to achieve high local control without increased toxicity, as in stereotactic ablative radiotherapy (SABR) and stereotactic body radiotherapy (SBRT). One key remaining barrier to precise, accurate, highly conformal radiation therapy is patient, target and organ motion from many sources including musculoskeletal, breathing, cardiac, organ filling, peristalsis, etc. that occurs during treatment delivery, currently 15-90 minutes per fraction for state-of-the-art high-dose radiotherapy. As such, significant effort has been devoted to developing “motion management” strategies, e.g., complex immobilization, marker implantation, respiratory gating, and dynamic tumor tracking. A fundamentally different approach to managing motion is to deliver the treatment so rapidly that no significant physiologic motion occurs between verification imaging and completion of treatment. According to certain embodiments of the invention, an accelerator, more preferably a compact high-gradient, very high energy electron (VHEE) linear accelerator, which may be a standing wave linear accelerator, together with a delivery system capable of treating patients from multiple beam directions, potentially using all-electromagnetic or radiofrequency deflection steering is provided, that can deliver an entire dose or fraction of high-dose (e.g., 20-30 Gy) radiation therapy sufficiently fast to freeze physiologic motion, yet with a better degree of dose conformity or sculpting than conventional photon therapy. The term “sufficiently fast to freeze physiologic motion” in this document means preferably faster than one human breath hold, more preferably less than 10 seconds, even more preferably less than 5 seconds, even more preferably less than one heartbeat and most preferably less than a second. In addition to the unique physical advantages of extremely rapid radiation delivery, there may also be radiobiological advantages in terms of greater tumor control efficacy for the same physical radiation dose. Certain embodiments of the invention can also treat non-tumor targets, such as, by way of nonlimiting example, ablation or other treatment of: (1) nerves or facet joints for pain control; (2) foci in the brain for neuromodulation of neurologic conditions including pain, severe depression, and seizures; (3) portions of the lung with severe emphysema; and/or (4) abnormal conductive pathways in the heart to control refractory arrhythmias. According to certain embodiments of the invention, there is provided a system for delivering very high electron energy beam to a target in a patient, comprising: An accelerator capable of generating a very high electron energy beam; A beam steering device capable of receiving the beam from the accelerator and steering the beam to the target from multiple directions; and A controller capable of controlling length of time that the beam irradiates the target, the length of time sufficiently fast to freeze physiologic motion, and to control the directions in which the beam steering device steers the beam to the target. According to some embodiments, the controller is configured to receive information from an imaging device and use the information from the imaging device to control the directions in which the beam steering device steers the beam to the target. According to some embodiments, the accelerator is a linear accelerator capable of generating a beam having energy of between 1 and 250 Mev, more preferably 50 and 250 MeV and most preferably between 75 and 100 MeV. According to some embodiments, the time period is preferably faster than one human breath hold, more preferably less than 10 seconds, even more preferably less than 5 seconds, even more preferably less than one heartbeat and most preferably less than a second. According to some embodiments, the beam steering device is an electro-magnetic device. According to some embodiments, the beam steering device is a radiofrequency deflector device. According to some embodiments, the beam steering device includes a gantry, the gantry including multiple beam ports. According to some embodiments, the beam steering device includes a continuous annular gantry. According to some embodiments, the beam steering device is capable of providing thin pencil beam raster scanning. According to some embodiments, the beam steering system is capable of providing volume filling scanning. According to some embodiments, the beam steering device includes no mechanical moving parts. According to other embodiments, there is provided a system for delivering very high electron energy beam to a target in a patient, comprising: An accelerator capable of generating a very high electron energy beam; A beam steering device capable of receiving the beam from the accelerator and steering the beam to the target from multiple directions; A controller capable of controlling length of time that the beam irradiates the target, the length of time sufficiently fast to freeze physiologic motion, and to control the directions in which the beam steering device steers the beam to the target; and An imaging device capable of generating images of the target and providing information from the imaging device to the controller to control the directions in which the beam steering device steers the beam to the target. According to some embodiments, the imaging device is capable of providing information to the controller to trigger when the system delivers the beam to the target. According to some embodiments, using information from the imaging device, the system is capable of automatically delivering the beam to the target from multiple predetermined directions at multiple predetermined points in time. According to some embodiments, the accelerator is a linear accelerator capable of generating a beam having energy of between 1 and 250 Mev, more preferably 50 and 250 MeV and most preferably between 75 and 100 MeV. According to some embodiments, the time period is preferably faster than one human breath hold, more preferably less than 10 seconds, even more preferably less than 5 seconds, even more preferably less than one heartbeat and most preferably less than a second. According to some embodiments, the beam steering device is an electro-magnetic device. According to some embodiments, the beam steering device is a radiofrequency deflector device. According to some embodiments, the beam steering device includes no mechanical moving parts. According to other embodiments, there is provided a method for delivering a beam of very high electron energy to a target in a patient, comprising: Providing a system for delivering very high electron energy beam to a target in a patient, the system comprising: An accelerator capable of generating a very high electron energy beam; A beam steering device capable of receiving the beam from the accelerator and steering the beam to the target from multiple directions; and A controller capable of controlling length of time that the beam irradiates the target, the length of time sufficiently fast to freeze physiologic motion, and to control the directions in which the beam steering device steers the beam to the target; and Actuating the system to cause it to deliver the beam to the target. According to some embodiments, providing the system includes providing an accelerator that is capable of generating a beam having energy of between 1 and 250 Mev, more preferably 50 and 250 MeV and most preferably between 75 and 100 MeV. According to some embodiments, providing the system includes providing a controller capable of controlling length of time that the beam irradiates the target, the time period preferably faster than one human breath hold, more preferably less than 10 seconds, even more preferably less than 5 seconds, even more preferably less than one heartbeat and most preferably less than a second. According to some embodiments, providing the system includes providing a beam steering device that is an electro-magnetic device. According to some embodiments, providing the system includes providing a beam steering device that is a radiofrequency deflector device. According to some embodiments, providing the system includes providing a beam steering device that includes no mechanical moving parts. According to some embodiments, there is further provided a controller that is configured to receive information from an imaging device and use the information from the imaging device to control the directions in which the beam steering device steers the beam to the target. According to some embodiments, there is further provided an imaging device capable of generating images of the target and providing information from the imaging device to the controller to control the directions in which the beam steering device steers the beam to the target. According to some embodiments, providing the imaging device includes providing an imaging device that is capable of providing information to the controller to trigger when the system delivers the beam to the target. According to some embodiments, providing the imaging device includes providing an imaging device wherein, using information from the imaging device, the system is capable of automatically delivering the beam to the target from multiple predetermined directions at multiple predetermined points in time. According to other embodiments, there is also provided a system for delivering a transverse-modulated electron beam to a target in a patient, comprising: A photoelectron gun configured to generate a transverse-modulated electron beam from an optical image produced by a light source such as a laser and projected on a photocathode; An accelerator capable of increasing the energy level of the transverse-modulated electron beam to a predetermined level; A beam steering device capable of receiving the transverse-modulated electron beam from the accelerator and steering the transverse-modulated electron beam to the target from multiple directions; and A controller capable of controlling length of time that the transverse-modulated electron beam irradiates the target, the length of time sufficiently fast to freeze physiologic motion, and to control the directions in which the beam steering device steers the transverse-modulated electron beam to the target. A. Significance In the U.S., cancer has surpassed heart disease as the leading cause of death in adults under age 85, and of the 1.5 million patients diagnosed with cancer each year, about two thirds will benefit from radiation therapy (RT) at some point in their treatment, with nearly three quarters of those receiving RT with curative intent. Worldwide, the global burden of cancer is increasing dramatically owing to the aging demographic, with an incidence of nearly 13 million per year and a projected 60% increase over the next 20 years, and the number of patients who could benefit from RT far exceeds its availability. Moreover, even when RT is administered with curative intent, tumor recurrence within the local radiation field is a major component of treatment failure for many common cancers. Thus, improvements in the efficacy of and access to RT have tremendous potential to save innumerable lives. Although there have been major technological advances in radiation therapy in recent years, a fundamental remaining barrier to precise, accurate, highly conformal radiation therapy is patient, target, and organ motion from many sources including musculoskeletal, breathing, cardiac, organ filling, peristalsis, etc. that occurs during treatment delivery. Conventional radiation delivery times are long relative to the time scale for physiologic motion, and in fact, more sophisticated techniques tend to prolong the delivery time, currently 15-90 minutes per fraction for state-of-the-art high-dose radiotherapy. The very fastest available photon technique (arc delivery with flattening filter free mode) requires a minimum of 2-5 min to deliver 25 Gy. Significant motion can occur during these times. Even for organs unaffected by respiratory motion, e.g., the prostate, the magnitude of intrafraction motion increases significantly with treatment duration, with 10% and 30% of treatments having prostate displacements of >5 mm and >3 mm, respectively, by only 10 minutes elapsed time. As such, considerable effort has been devoted to developing “motion management” strategies in order to suppress, control, or compensate for motion. These include complex immobilization, fiducial marker implantation, respiratory gating, and dynamic tumor tracking, and in all cases still require expansion of the target volume to avoid missing or undertreating the tumor owing to residual motion, at the cost of increased normal tissue irradiation. Several factors contribute to long delivery times in existing photon therapy systems. First, production of x-rays by Bremsstrahlung is inefficient, with less than 1% of the energy of the original electron beam being converted to useful radiation. Second, collimation, and particularly intensity modulation by collimation, is similarly inefficient as the large majority of the beam energy is blocked by collimation. Third, using multiple beam angles or arcs to achieve conformal dose distributions requires mechanical gantry motion, which is slow. Treatment using protons or other heavier ions has dosimetric advantages over photon therapy, and these particles can be electromagnetically scanned very rapidly across a given treatment field. However changing beam directions still requires mechanical rotation of the massive gantry, which is much larger and slower than for photon systems. The cost and size of these systems also greatly limits their accessibility. Very high-energy electrons (VHEE) in the energy range of 50-250 MeV have shown favorable dose deposition properties intermediate between megavoltage (MV) photons and high-energy protons. Without the need for inefficient Bremsstrahlung conversion or physical collimation, and with a smaller steering radius than heavier charged particles, treatment can be multiple orders of magnitude faster than any existing technology in a form factor comparable to conventional medical linacs. According to certain embodiments of the invention, a compact high-gradient VHEE accelerator and delivery system is provided that is capable of treating patients from multiple beam directions with great speed, using electro-magnetic, radiofrequency deflection or other beam steering devices. Such embodiments may deliver an entire dose or fraction of high-dose radiation therapy sufficiently fast to freeze physiologic motion, yet with a better degree of dose conformity or sculpting, and decreased integral dose and consequently decreased risk of late toxicities and secondary malignancies, than the best MV photon therapy. Suitable energy ranges in accordance with certain embodiments of the invention are 1-250 MeV, more preferably 50-250 MeV, and most preferably 75-100 MeV. Again, as described in the Summary section above, the term “sufficiently fast to freeze physiologic motion” in this document means preferably faster than one human breath hold, more preferably less than 10 seconds, even more preferably less than 5 seconds, even more preferably less than one heartbeat and most preferably less than a second. According to some embodiments, a major technological advance is extremely rapid or near instantaneous delivery of high dose radiotherapy that can eliminate the impact of target motion during RT, affording improved accuracy and dose conformity and potentially radiobiological effectiveness that will lead to improved clinical outcomes. Rapid imaging and treatment can also lead to greater clinical efficiency and patient throughput. For standard treatments, the room occupancy time can be reduced to less than 5 minutes. There can also be a great practical advantage for special populations like pediatric patients who normally require general anesthesia for adequate immobilization during long treatments, and who can instead be treated with only moderate sedation for such rapid treatments. Such advantages can be achieved, according to some embodiments, in a compact physical form factor and low cost comparable to conventional photon therapy systems, and much lower than hadron therapy systems. One embodiment is shown in FIG. 1, which shows a system wherein beam access from a large number of axial directions is achieved by electromagnetic steering without moving parts or with a minimum of moving parts, for extremely fast highly conformal radiotherapy. The system shown in FIG. 1 includes a compact linear accelerator, a beam steering device, and a controller for controlling the very high electron energy beam that is delivered to the patient. The embodiment can also include an integrated imaging device that obtains images of portions of the patient including the tumor or other site to be treated. The imaging device can also provide information to allow for control of the beam steering device in order to control directions from which the beam is delivered, and timing of the beam, among other variables. Furthermore, the prolonged treatment times of conventional highly conformal RT are sufficiently long for repair of sublethal chromosomal damage to occur during treatment, potentially reducing the tumoricidal effect of the radiation dose. Thus in addition to the unique physical advantages of extremely rapid radiation delivery, there may also be dose advantages. It is hypothesized that the treatment times sufficiently fast to freeze physiologic motion that are made possible by certain embodiments of the invention may be more biologically effective, producing enhanced tumor cell killing for the same physical dose. Differences between certain embodiments of the invention and conventional photon therapy that impact biological effectiveness include a much faster delivery time and differences in the radiation quality. Dose rate effects are well described in the radiobiology literature, in which prolongation of delivery times results in decreased cell killing. The main mechanism known to be responsible for this effect is repair of potentially lethal DNA double strand breaks (DSB) during the interval over which a given dose of radiation is delivered. Several in vitro studies have demonstrated significantly decreased cell killing when delivery is protracted from a few minutes to tens of minutes. However, there is a lack of consensus in the literature regarding the kinetics of sublethal damage (SLD) repair, with some studies suggesting that components of SLD repair may have repair half-times of as little as a few minutes. If so, shortening the delivery times even from a few minutes to a time period sufficiently fast to freeze physiologic motion has the potential to increase tumor cell killing. B. Beam Steering Some embodiments of the invention take advantage of the fact that electrons are relatively easier to manipulate using electric and magnetic fields. Charged particles such as electrons and protons can be produced as spatially coherent beams that can be steered electromagnetically or with radiofrequency deflection with high rapidity. Thus, direct treatment with scanned charged particle beams can eliminate the inefficiencies of Bremsstrahlung photon multiple beams from different directions toward the target in the patient. All conventional radiation therapy systems accomplish multidirectional treatment by mechanically rotating a gantry, or an entire compact linac, or even cyclotron, directing radiation to the target from one direction at a time. As a preliminary matter, at the end of the accelerator structure the beam must be deflected and then transported to the exit port and toward a target in or on the patient, such as a tumor in the patient. At the exit port the beam must be steered again to change the exit angle and/or beam size to adapt to the treatment plan. Electro-magnetic and/or RF deflector steering systems will manipulate the electron beam. A variety of gantry designs are potentially available, from simple to complex, ranging from multiple discrete beam ports arranged around the patient to a continuous annular gantry to allow arbitrary incident axial beam angles. The design depends on a number of factors, including scanning strategies such as thin pencil beam raster scanning vs. volume filling with non-isocentric variable-size shots, or use of transverse modulation of the electron beam profile. According to one embodiment, the steering system of the electron beam starts at the end of the accelerator structure with a two-dimensional deflector, which guides the beam into one of multiple channels. Once the beam enters a specific channel it is guided all the way to the exit of the channel, which is perpendicular to the axis of the patient. The guidance through the channels is achieved using low aberration electron optics. At the exit of each channel another small 2-D deflector can be added to scan the beam over a target. The number of channels can then be about 10-50. For a given channel width, a larger initial deflection would increase the number of channel entry ports that fit into the circumference swept by the beam. Thus if the field strength were increased, the number of channels could be increased to 100 or more. Because a linear accelerator will typically consume 50 to 100 MW of peak power to achieve 100 MeV of acceleration, over a length of 2 to 1 m respectively, potential RF deflectors can be considered. These have the advantage of being ultra-fast and permit capitalization on the RF infrastructure that is used for the main accelerator structure. In any event, the delivery system is preferably optimized to achieve high-dose treatment times sufficiently fast to freeze physiologic motion. Beam steering systems according to certain embodiments of the invention adopt a design that uses a smaller number of discrete beam channels, for example 3-10, that are mechanically rotated with the gantry around the patient. The initial deflector at the exit of the accelerator rapidly steers beams into the channels as they rotate. Although the ideal is to eliminate the need for any mechanical moving parts, some advantages of this design include: arbitrary rotational angular resolution despite a fixed number of beam channels; reduced complexity and possibly cost given the smaller number of beam channels needed to achieve equivalent angular coverage; and the larger space between beam channels which makes it more straightforward to incorporate an x-ray source and detecting array for imaging, which when rotated provides integrated computed tomography imaging. The rate of mechanical rotation preferably provides full angular coverage sufficiently fast to freeze physiologic motion. The greater the number of beam channels, the less rotational speed required to meet this condition as a general matter. One innovation of certain embodiments of the invention is to eliminate mechanical gantry rotation, thus a beam steering system with no mechanical moving parts. One such embodiment is illustrated in FIG. 1, in which there is a gantry through which a charged particle beam is electromagnetically steered or steered using radiofrequency deflection to the target from any axial direction and a limited range of non-coplanar directions in addition. An alternative implementation is to use multiple discrete beam ports arranged radially around the patient, with the beam being steered through each of the ports to the target for multidirectional beam arrangements. Another alternative implementation is to have multiple accelerating structures, one for each of a set of beam ports arranged radially around the patient. Such novel treatment system geometries and steering systems can greatly enhance the treatment delivery speed of radiation therapy using any type of charged particle. Combining it with high-energy electrons in the 1-250 MeV range, more preferably the 50-250 MeV range, most preferably the 75-100 MeV range, has the following additional advantages: (1) Conformal dose distributions to both superficial and deep targets in patients superior to what can be achieved with conventional high-energy photon therapy; (2) Compactness of the source and power supply, which by using high-gradient accelerator designs such as those based wholly or partially on accelerators developed or in development at the SLAC National Accelerator Laboratory (SLAC) as described in Section C.iii below can accelerate electrons up to these energies in less than 2 meters; (3) Compactness of the gantry/beam ports compared to protons or ions because of the smaller electro-magnetic fields needed for electrons. This results in a system of comparable cost and physical size to existing conventional photon radiotherapy treatment systems, yet with better dose distributions and far faster dose delivery. If treatment with photon beams is still desired, an alternative embodiment is to incorporate in this geometry an array of high density targets and collimator grid in place of a single target/multi-leaf collimator combination, one per beam port in the case of discrete beam ports, or mounted on a rapidly rotating closed ring and targeted by the scanned electron beam in the case of an annular beam port, in order to produce rapidly scanned, multidirectional photon beams. While this approach may be subject to the inefficiency of Bremsstrahlung conversion, the speed limitations of conventional mechanical gantry and multi-leaf collimator motions may be essentially eliminated. The main potential advantage of this implementation is that existing commercial electron linacs in a lower energy range could be used as the source. In addition to extremely rapid dose delivery, certain embodiments of the invention naturally facilitate rapid image-guidance to ensure accuracy. By adjusting the energy of the scanned electron beam and directing it to an annular target or a fixed array of targets, with an appropriately arranged detector array, extremely fast x-ray computed tomography (CT) or digital tomosynthesis images can be obtained and compared to pre-treatment planning images immediately before delivery of the dose. Alternative embodiments can include integration of more conventional x-ray imaging or other imaging modalities, positron emission tomography and other options described in Section D.3 below. C. Monte Carlo Simulation Design Considerations One approach in designing certain embodiments of the invention is to proceed using some or all of the following: (1) Monte Carlo simulations to determine optimal operating parameters; (2) experimental measurements of VHEE beams to validate and calibrate the Monte Carlo codes; (3) implementation factors for practical, cost-efficient and compact designs for the systems; and (4) experimental characterization of key radiobiological aspects and effects. 1. Monte Carlo (MC) Simulation MC simulations of VHEE of various energies have been performed on a sample case to estimate the range of electron energies needed to produce a plan comparable to optimized photon therapy. Dose distributions were calculated for a simulated lung tumor calculated on the CT data set of an anthropomorphic phantom. Specifically, an optimized 6 MV photon beam Volumetric Modulated Arc Therapy Stereotactic Ablative Body Radiotherapy (VMAT SABR) plan calculated in the Eclipse treatment planning system, and simplistic conformal electron arc plans with 360 beams using a commonly available 20 MeV energy and a very high 100 MeV energy calculated with the EGSnrc MC code [Walters B, Kawrakow I, and Rogers DWO, DOSXYZnrc, Users Manual, 2011, Ionizing Radiation Standards National Research Council of Canada. p. 1-109. (http://irs.inms.nrc.ca/software/beamnrc/documentation/pirs794/), incorporated herein by this reference], were compared. FIG. 2 shows axial images of simulation of SABR for an early stage lung tumor: dose distribution in an anthropomorphic phantom for a state-of-the-art 6 MV photon VMAT plan (FIG. 2a), a conformal electron arc plan using currently available 20 MeV electron beam (FIG. 2b), and a conformal electron arc plan using a 100 MeV electron beam as might be delivered by an embodiment of the invention (FIG. 2c). A graphical representation shows dose volume histogram (“DVH”) of the planning target volume (“PTV”) (delineated in black in the axial images) and critical organs: DVHs for 6 MV photons are shown in solid, 20 MeV electrons in dotted, and 100 MeV electrons in crossed lines (FIG. 2d). The plans were normalized to produce the same volumetric coverage of the PTV by the prescription dose. While conventional 20 MeV electrons results in poor conformity, the 100 MeV electron plan, even without optimization, is slightly more conformal than the 6 MV photon VMAT plan. Simulating conformal electron arcs across an energy range of 50-250 MeV (FIGS. 2e, 2f) demonstrates that both the high (100%) and intermediate (50%) dose conformity indices (CI100% and CI50%) as well as the mean lung dose and total body integral dose are superior for electron energies of ˜80 MeV and higher for this selected clinical scenario. With inverse optimization, superior plans with even lower electron energies should be possible. As shown in FIG. 2, the axial views of the dose distributions demonstrate that when all the plans are normalized to produce the same volumetric coverage of the target, the dose conformity of the 20 MeV beam is poor whereas the 100 MeV electron beam, even without inverse optimization, generates a dose distribution equivalent to the state-of-the-art 6 MV photon beam VMAT plan. In fact, the DVH's of the target and critical structures for the three beams demonstrate slightly better sparing of critical structures with the 100 MeV electron plan compared to the 6 MV photon plan. As shown in FIGS. 2e and 2f, at electron energies above ˜80 MeV, simple conformal electron arc plans (normalized to produce the same volumetric coverage of the target) are superior to the optimized 6 MV photon VMAT plan in terms of conformity, with conformity index defined as the ratio of the given percent isodose volume to the PTV, and the normal organ doses (mean lung dose) and total body integral dose (expressed in arbitrary units normalized to the photon plan). In preliminary simulations of this selected clinical scenario, the inventors have found electron energies of 75-100 MeV to produce plans of comparably high to superior quality compared to the best photon plans, and anticipate that plan optimization will produce superior plans with even lower electron energies. For example, the inventors have used Monte Carlo simulations to demonstrate that an 8 cc lung tumor could be treated with 100 MeV electrons to a dose of 10 Gy in 1.3 seconds. Further optimization of the electron plan can help to define the minimum electron beam energy with a comparable dose distribution to the best photon VMAT plan. In preliminary simulations of this selected clinical scenario, the inventors have found electron energies of 75-100 MeV to produce plans of comparably high quality to the best photon plans, and anticipate superior plans with plan optimization. 2. Experimental Measurement of VHEE Beams a. Monte Carlo Simulations To demonstrate the accuracy of Monte Carlo calculations with VHEE beams, the inventors experimentally measured the dose distribution and depth dose profiles at the NLCTA facility at SLAC. Of note, the NLCTA employs compact high-gradient linear accelerator structures which can produce beams that are relevant to those potentially suitable for certain embodiments of the invention. The inventors assembled a dosimetry phantom by sandwiching GAFCHROMIC EBT2 films (International Specialty Products, Wayne, N.J.) between slabs of tissue equivalent polystyrene as shown in FIG. 3. FIG. 3a is a schematic and FIG. 3b is a photograph of the experimental setup for film measurements (FIG. 3c) of very high-energy electron beams at the NLCTA beam line at SLAC. Monte Carlo simulations and film measurements of percentage depth dose curves (FIG. 3d) and 2-D dose distributions taken at 6 mm depth (FIG. 3e) for 50 MeV and 70 MeV beams demonstrate a high degree of agreement between calculation and measurement. By way of procedure and in greater detail, the phantom as shown in FIG. 3a was irradiated with 50 MeV and 70 MeV beams. Three beam sizes ranging from 3.35 to 6.15 mm were tested for each energy level. The energy was measured by a spectrometer upstream from the location of the experiment and the beam size was measured by two scintillating screens using two cameras just before and after the phantom with the phantom removed from the beam line (FIG. 3b). The films were calibrated with a clinical electron beam at 12 MeV. MC simulations have demonstrated no energy dependence of the film response at electron energies above 1 MeV. The number of particles required to irradiate the films to dose levels between 1-5 Gy to match the dynamic range of the film was determined for each beam size using MC simulations and used in the experiment. The charge was set to 30 pC/pulse corresponding to 1.9×108 electrons and the pulse rate was reduced to 1 Hz for easier control of the exposure. The number of pulses varied from 2 to 40 pulses depending on the beam size. The experimental and calibration films were read out in a flatbed scanner (Epson Perfection V500, Long Beach, Calif.) with 0.1 mm pixels 24 hours after irradiation (FIG. 3c) and central axis percentage depth dose (PDD) curves and 2-dimensional dose distributions at various depths were plotted. The experimental setup was simulated in the MCNPX 5.0 MC code [Palowitz D B, MCNPX User's Manual, Version 2.7.0, 2011 (http://mcnpx.lanl.gov/documents.html) incorporated herein by this reference]. The simulations are compared to measurements in FIG. 3d-e. Good agreement was observed for both the PDD curves and beam profiles for 50 and 70 MeV. These preliminary results indicate that dose from VHEE beams can be measured with GAFCHROMIC films and that VHEE beams can be accurately simulated with the GEANT4 code. In the arrangement shown in FIG. 3b, a 50-μm vacuum window made of stainless steel was used to interface the accelerator line with open air, in which the dose phantom (FIG. 2a) was placed. The stainless window was found to cause significant angular beam spreading, so that the simulations were also performed with a beryllium window which imparted less beam spreading. While a vacuum window is necessary to separate the vacuum of the accelerator beam line from the open air and the patient, significant angular spread will adversely affect beam performance and clinical accuracy. The angular spread from a thinner beryllium window was still present but it was much smaller than steel, due to beryllium's low atomic number. b. Cross Validation of Monte Carlo Codes The inventors performed Monte Carlo simulations using three independent codes for identical geometries to determine the consistency of calculated doses. The dose deposition of a number of rectangular electron beams incident on a 20×20×30 cm water phantom (as shown in FIG. 7a) was simulated in the GEANT4, MCNPX, and EGSnrc MC codes. The simulated electron beam energies were 50, 75, 100, and 150 MeV with beam sizes of 1×1 cm and 2×2 cm. The central-axis PDDs were plotted and compared for all three MC codes. Excellent agreement was found between the codes for all of these comparisons, as shown in FIG. 4, which shows PDD for a 2×2 cm 100 MeV electron beam, simulated using the three Monte Carlo codes. c. VHEE Tissue Interactions Monte Carlo simulations were performed to evaluate the impact of various tissue heterogeneities on VHEE beams relative to MV photon beams. FIG. 5 shows PDD curves for 2×2 cm 50 and 150 MeV electron beams compared to 6 MV photons in a water phantom with 2 cm thick heterogeneous tissue at 10 cm depth, normalized to identical dose at 3 cm depth. As shown in FIG. 5, the 50 and 150 MeV VHEE beams are less sensitive to tissue heterogeneity over the density range from lung tissue to titanium prosthetic implants compared to 6 MV photons. Contribution of secondary particles produced by Bremsstrahlung and electronuclear interactions to the dose from VHEE beams were also analyzed. FIG. 6 shows relative contribution to dose from a 100 MeV electron beam vs. secondary generated particles (log scale). As shown in FIG. 6, for a 100 MeV electron beam, nearly all the deposited dose is due to electrons, with a minor contribution from Bremsstrahlung x-rays, and far lower dose from protons and neutrons. FIG. 6 also shows that dose from neutrons is far less than with 15-18 MV photons or high-energy protons. This holds for 50 and 70 MeV electrons as well (not shown). For a 25 Gy SABR treatment of a 2 cm diameter target, an upper limit of total body neutron dose is estimated to be 0.6 mSv based on MC simulations. This is in contrast to more than 1-2 orders of magnitude greater estimated neutron doses of 9-170 mSv for scanning beam proton therapy and 15-18 MV photon IMRT for the same clinical scenario, based on published measurements of ambient neutron doses [Schneider U, Agosteo S, Pedroni E, and Besserer J., “Secondary neutron dose during proton therapy using spot scanning,” International Journal of Radiation Oncology Biology Physics, 2002; 53(1): 244-251. (PMID: 12007965); Howell R M, Ferenci M S, Hertel N E, Fullerton G D, Fox T, and Davis L W, “Measurements of secondary neutron dose from 15 MV and 18 MV IMRT,” Radiation Protection Dosimetry, 2005; 115(1-4): 508-512. (PMID: 16381776) both of which are incorporated herein by this reference]. An advantage of such potential designs according to certain embodiments compared to >8 MV photon and scanning beam or passive scattering proton therapies is elimination of need for beam modifying structures prior to beam incidence on the patient, in which most neutrons are generated with existing modalities. d. Tissue Inhomogeneities The effect of tissue inhomogeneities on dose deposition of VHEE beams has been studied by the inventors. A 20×20×25 cm3 water phantom with 0.5×0.5×0.1 cm3 voxels and a 2-cm thick inhomogeneity placed at 10 cm depth was built (FIG. 7b). The 2-cm thick slab was consequently filled with lung with mass density p of 0.368 g/cm3, adipose (p=0.950 g/cm3), ribs (p=1.410 g/cm3), and cortical bone (p=1.920 g/cm3) tissue to assess the effect of human tissue inhomogeneities. The tissue composition was obtained from the ICRU-44 document [ICRU. Tissue substitutes in radiation dosimetry and measurement, 1989 (incorporated herein by this reference)]. Moreover, the effect of metals, such as hip prostheses, dental fillings, and surgical clips, was investigated by simulating a steel slab (ρ=8.030 g/cm3). Doses deposited by 50, 100, and 150 MeV electron beams, as well as 6 MV photon beam interacting with the inhomegeneity slab were simulated. The DOSXYZnrc code was chosen for this task due to its simplicity of use and its shortest calculation times. The statistical uncertainties in all central axis voxels were below 1%. 3. Ultra-High Gradient Accelerator Structure Design Pluridirectional very high electron energy radiation therapy systems and processes according to various embodiments of the invention can be created with various types of electron source. There are a number of potential sources of very high-energy electrons in the range of, for example, up to about 250 MeV. A non-exhaustive list includes cyclotrons, synchrotrons, linacs (which can include more conventional designs with greater length), racetrack microtrons, dielectric wall accelerators, and laser plasma wakefield accelerator sources. Some of these are large and would need to be housed in a separate room. Some are not very mature technologies. In terms of goals of certain embodiments of the invention which can include any or all of compactness (entire system fitting within existing medical linac vaults without a separate room), power requirements, cost, repetition rates, compatibility with intensity modulation techniques described in this document, and other practical considerations, compact very high-gradient standing wave linear accelerators such as those developed at SLAC as described in the two paragraphs immediately below, or derivatives of them, may be at least a logical starting point, although other currently existing or future options should not be ruled out. Highly efficient π-mode standing wave accelerator structures have been developed at SLAC for the project formerly known as the Next Linear Collider, a positron-electron collider at 500 GeV energy for high-energy physics research [Dolgashev V, Tantawi S, Higashi Y, and Spataro B, “Geometric dependence of radio-frequency breakdown in normal conducting accelerating structures,” Applied Physics Letters, 2010; 97(17). (http://apl.aip.org/resource/1/applab/v97/i17/p171501_s1) incorporated herein by this reference (hereinafter sometimes “Dolgashev 2010”]. Such accelerators are capable of accelerating electrons to 100 MeV within 1 meter [Id.] using an optimized accelerating waveguide powered by a 50 MW 11.4 GHz microwave generator (klystron) [Caryotakis G. Development of X-band klystron technology at SLAC. Proceedings of the 1997 Particle Accelerator Conference, 1997; 3: 2894-2898. (http://ieeexplore.ieee.org/xpls/abs_all.jsp?arnumber=752852) incorporated herein by this reference]. In order to produce a practical system in terms of cost and size, optimized designs according to certain embodiments of the invention allow both economical production and high performance to minimize the treatment time while allowing maximum possible flexibility in beamlet shapes, directionality, and energy. Furthermore, it has been shown that coupling a series of small sections of standing-wave accelerators with a distributed radiofrequency (RF) network makes it possible to design a system without any reflection to the RF source [Tantawi S G, “rf distribution system for a set of standing-wave accelerator structures,” Physical Review Special Topics-Accelerators and Beams, 2006; 9(11) (http://prst-ab.aps.org/abstract/PRSTAB/v9/i11/e112001) incorporated herein by this reference (hereinafter, “Tantawi 2006”]. Building on these developments, a practical implementation of a standing-wave accelerator structure has been designed [Neilson J, Tantawi S, and Dolgashev V, “Design of RF feed system and cavities for standing-wave accelerator structure,” Nuclear Instruments and Methods in Physics Research A: Accelerators, Spectrometers, Detectors and Associated Equipment, 2011; 657(1): 52-54. (http://www.sciencedirect.com/science/article/pii/S0168900211008898) incorporated herein by this reference (hereinafter, “Neilson 2011”] that is designed to accelerate electrons to 100 MeV within one meter. Such accelerators can serve as a basis for or be relevant to certain embodiments of the invention. D. Other Design Issues 1. Design Options for the Injector System To inject the required low charge bunch into accelerators according to certain embodiments of the invention, several possibilities are available. Those include a photo-injector RF gun. Additional options can be considered to reduce the cost and size of the system, including a variety of field emitter configurations and RF thermionic guns. 2. Optimization of the RF Source by the Addition of a Pulse Compression System RF source requirements depend ultimately, at least in part, on the accelerator design. With the optimized cavities as described above, it is projected that a 50 MW source at X-band will be sufficient for a 2 meter accelerator operating at 50 MV/m. This type of source is available at SLAC and is being commercialized by Communications & Power Industries (Palo Alto, Calif.). With the use of a pulse compression system it may be possible to either reduce the cost and sophistication of the RF source dramatically or make the accelerator structure more compact by reducing the length to 1 meter. Because the typical filling time of such a structure is about 100 ns and the RF source typically provides several μs long pulses, one can use a compact pulse compressor with a high compression ratio and a power gain of about 3.5 to reduce the required RF source power to only about 14 MW, which opens the door for a variety of sources, including sources that are commercially available now, and including those that include a pulse compression system. 3. Imaging and Target Position Verification Options Given that treatment according to certain embodiments of the invention is delivered sufficiently fast to freeze physiologic motion, it is important to verify that the target is in the planned position at the time the treatment is triggered or administered. Several dynamic or “real-time” imaging or other localization technologies can be integrated into certain embodiments of the invention for this purpose. Potential such implementations can include any of the following, alone or in combination: a. Integration of two or more x-ray fluoroscopic imaging devices, forming at least one orthogonal pair, to permit real-time 3-dimensional verification of alignment of bony anatomy and/or implanted radio-opaque fiducial markers. b. Dynamic optical surface scanning, ideally combined with an internal imaging modality such as CT or fluoroscopy, providing real-time correlation of the external surface to the internal target position. c. Integration of fast x-ray computed tomography. This can be accomplished by the addition of a relatively conventional multi-detector CT system within the gantry of the treatment system. Alternatively, if a continuous ring gantry design is used for the treatment delivery system, the treatment system itself can be used to scan a low energy (around 100 keV) electron beam across a ring-shaped target introduced into the beam path to produce a rapidly moving x-ray source for very fast CT scanning, known as “electron beam CT” immediately before switching to the high energy treatment beam. d. Implantable radiofrequency beacons, whose 3-dimensional position can be read out in real time by an external antenna array. Beacons can be implanted in or near the target and serve as surrogates for the target position. e. Integration of ultrasound. For certain anatomic locations, for example the upper abdomen and pelvis, ultrasound can provide continuous real-time 3-dimensional localization of targets. f. While the most technologically complex to implement, magnetic resonance imaging may be implemented, which can provide real-time 3-dimensional localization of targets. Integration of MRI with conventional photon therapy systems is already commercially available or under development by multiple vendors. In any of these implementations, dynamic visualization and/or automated image analysis tools can be used to permit either manual triggering of the treatment by the operator, or automated triggering with manual override. 4. Implementation of Intensity Modulation According to certain embodiments of the invention, which may be used with various types of accelerators in accordance with the invention, and in order to achieve highly conformal volumetric dose shaping, radiation fields from each of multiple beam directions can cover an area with varying beam intensity across the field, with the intensity patterns optimized to produce the desired 3-dimensional dose distribution when summed across all beam directions. Such intensity modulation may be produced by raster scanning individual beamlets of varying intensity across the field from each beam direction. Alternatively, it may be produced by using a 2-dimensional intensity-modulated electron pattern at the source, effectively an array of beamlets of varying intensity, and accelerate and steer the entire array to the target volume. This eliminates the need for a raster scanning mechanism at the exit of each of the beam channels, greatly simplifying the design and reducing the bulk and cost of those components, and increases the treatment delivery speed by delivering beamlets in parallel within a much smaller number of electron pulses or bunches. According to some embodiments, the intensity modulation of the electron source may be produced by using a photocathode illuminated by a light source with the corresponding intensity pattern, in effect, an optical image. One implementation is to use a laser as the light source, and a digital light processing (DLP) micromirror array or other intensity modulating device to produce the charge image on the photocathode to be accelerated and steered. The electron beam optics can be designed to maintain the pattern with high fidelity until it reaches the target. According to one nonlimiting embodiment as shown in FIG. 8, a short, typically picosecond-long pulse with uniform transverse profile is generated by a laser (1). The wavelength of the laser is matched with specific photocathode material to obtain required charge and emittance. The laser pulse (2) falls on a digital-micro-mirror device (3). Pixels of this micro-mirror device are controlled by a computer and will reflect a portion of the laser pulse (4) thus creating an image that is then transferred to the photocathode (6) using precision projection optics (5). Although various types of accelerators may be used with this embodiment, high gradient pulsed devices with a few milliseconds between pulses are preferable. The computer modulates the mirror array thus creating a new image for each consequent pulse. A laser pulse with amplitude-modulated transverse profile that impacts the photocathode (6) will create an electron replica of the laser pulse transverse profile (8). The photocathode (6) is a part of photo-electron gun (7). The gun creates an electric field on the photocathode which accelerates the transverse-modulated electron beam. The gun also provides initial focusing for the electron beam. The electron beam then passes through the low-aberration focusing system toward accelerator (10). The accelerator increases energy of the beam to a desired value. The electron beam then passes through focusing optics (11) toward horizontal (12) and vertical (13) fast deflectors. The deflectors are controlled by a computer and are able to send the electron beam in different directions for each consecutive accelerator pulse. The desired direction will depend on (among other things) specific realization of the gantry's beam lines, number of the beam lines and whether they are movable or not. For clarity only one gantry beam line is shown in FIG. 8. After the deflectors, the electron beam passes through bending magnets (14, 16, 18) and electron optics (15, 17) and is directed through electron-beam monitoring system (19) toward the target (20). The transversely modulated electron beam irradiates the target with required distribution of the dose. After passing through the target, the beam is sent toward beam dump (21) in order to reduce unwanted radiation exposure of the target. Of note, a greater degree of intensity modulation will produce more conformal dose distributions. However, with conventional photon therapy where intensity modulation is delivered in a serial fashion over time, more modulation comes at a cost of longer delivery time, more leakage dose to the patient, and greater uncertainty in delivered dose because of target and organ motion during the longer treatment delivery time and its interplay. With VHEE technology according to certain embodiments of the invention, all of these problems are circumvented: arbitrarily complex intensity modulation can be produced through optical imaging, and rapid parallel delivery eliminates uncertainty from interplay effects. The concept of conversion of an optical intensity pattern into a radiation intensity pattern within a patient is considered to be unique, and also uniquely applicable to electron beam therapy in accordance with embodiments of the invention as opposed, for example, to photon or proton or other particle therapies. E. General Numerous specific details are set forth herein to provide a thorough understanding of the claimed subject matter. However, those skilled in the art will understand that the claimed subject matter may be practiced without these specific details. In other instances, methods, apparatuses or systems that would be known by one of ordinary skill have not been described in detail so as not to obscure subject matter that may be claimed. While the present subject matter has been described in detail with respect to specific embodiments thereof, it will be appreciated that those skilled in the art, upon attaining an understanding of the foregoing may readily produce alterations to, variations of, and equivalents to such embodiments. Accordingly, it should be understood that the present disclosure has been presented for purposes of example rather than limitation, and does not preclude inclusion of such modifications, variations and/or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.
	abstract	A transfer cask for maximizing the radiation shielding for spent nuclear fuel during cask transfer procedures has a cylindrical inner shell forming a cavity within which a spent nuclear fuel canister can be placed; a cylindrical outer shell concentric with and surrounding the inner shell to form an annulus with the inner shell, the annulus adapted for receiving gamma absorbing material; a jacket shell concentric with and surrounding the second shell to form a jacket for holding a neutron absorbing liquid; the jacket shell having filling and drainage systems; and a removable bottom lid so that a canister can be lowered from the cavity into a transport cask or permanent storage cask.
050911430	summary	BACKGROUND OF THE INVENTION The present invention relates to a natural circulation reactor and, more particularly, to a natural circulation reactor suitable for maintaining a reactor core submerged under coolant even on the supposition of breakage of any pipe connected to a pressure vessel of the reactor. As described in "Annual Meeting of 1987", Japanese Nuclear Society, Corp., (at Nagoya University, Apr. 1-3, 1987), E44, Conceptual Study of Natural Circulation BWR - (1) Plant Outline, a conventional natural circulation reactor has been designed to inject light water from a tank of an accumulated coolant injection system on the supposition of breakage of any pipe connected to a pressure vessel of the reactor. SUMMARY OF THE INVENTION On the supposition of breakage of any pipe connected to the reactor pressure vessel in the aforementioned reactor of prior art, a coolant, i.e., light water, within the reactor pressure vessel would be flushed in response to abrupt decompression caused by blowdown upon breakage of any pipe of large diameter, or in response to abrupt decompression caused by startup of an automatic decompressing system (ADS) upon breakage of any pipe of small diameter, whereby a large amount of coolant is discharged from the reactor pressure vessel. Accordingly, there is a possibility of exposing a top portion of the reactor core temporarily during an intermediate period before actuation of the accumulated coolant injection system to start injecting of a coolant into the reactor core, because the coolant level in the reactor is lowered as voids fail to occur after the completion of flushing. Further, in long-term cooling situations when a residual heat removal system is actuated in a core cooling mode to inject a coolant within a pressure suppressing chamber into the reactor core after the reactor has been decompressed completely, the coolant level in the reactor is elevated with the coolant injected, and the coolant is flown out from the broken part. At this time, there is a possibility that a portion of the coolant may be flown out from the broken part directly as it remains at a low temperature without acting to cool the reactor core, and hence the decay heat generated from the reactor core may not be removed efficiently. Accordingly, the prior art has been required to set a flow rate of the residual heat removal system and the capacity of a heat exchanger as to leave a sufficient allowance. It is an object of the present invention to provide a natural circulation reactor which can maintain a core in a reactor pressure vessel submerged under coolant even on the supposition of breakage of any pipe connected to the reactor pressure vessel. To achieve the above object, the present invention provides a natural circulation reactor having a reactor pressure vessel with a core housed therein, the core being disposed in such a location that a top portion of the core is submerged under coolant even in the event that any pipe connected to said reactor pressure vessel is broken and then a coolant level in the reactor pressure vessel is lowered due to flushing. In accordance with the present invention as arranged above, the reactor core will be submerged under coolant and hence will never be exposed even during an intermediate period before actuation of the accumulated coolant injection system subsequent to flushing, although the coolant present in the reactor core would be flushed and lost from the reactor pressure vessel in response to abrupt decompression caused by blowdown through the broken part of any pipe or by start-up of an automatic decompressing system (ADS), thereby lowering a coolant level in the reactor after the completion of flushing, on the supposition of breakage of any pipe connected to the reactor pressure vessel. Furthermore, after the completion of flushing, the accumulated coolant injection system is actuated to inject a coolant from an accumulated coolant injection tank, and then a residual heat removal system starts its operation to inject a coolant in a pressure suppressing chamber. The coolant thus injected into the reactor pressure vessel is flown out of the reactor pressure vessel while keeping the reactor core submerged under coolant. The outflowing coolant is transferred to a lower drywell surrounding a lower portion of the reactor pressure vessel for filling the lower drywell with the coolant. Herein, the reactor core is disposed below a level of passage holes of the lower drywell, while as the amount of the coolant filled in the lower drywell is increased, the resulting level of the coolant is elevated beyond a position of the reactor core. Afterward, the coolant is flown out through the passage holes into the pressure suppressing chamber. Accordingly, although a portion of the coolant injected into the reactor pressure vessel is flown out of the reactor pressure vessel from the broken part directly as it remains at a low temperature without removing any decay heat of the reactor core, the coolant at a low temperature is pooled in the lower drywell and utilized to cool the wall surface of the reactor pressure vessel from its outside, thereby in turn cooling the reactor core. Thus, the decay heat generated from the reactor core is removed reliably and efficiently.
	claims	1. An apparatus for projection lithography comprising: a lens system comprising at least one magnetic doublet lens and a back focal plane filter positioned in the back focal plane or some equivalent conjugate plane of the magnetic doublet lens in the lens system, the back focal plane filter having a first aperture which is adapted to transmit insignificantly scattered radiation from a radiation source therethrough wherein the magnetic doublet lens system has a pair of ferromagnetic clamps, a first clamp associated with the first lens in the magnetic doublet lens system and a second clamp associated with the second lens in the magnetic lens, wherein the first clamp and the second clamp are configured to substantially separate the magnetic field of the first lens from the magnetic field of the second lens. 2. The apparatus of claim 1 wherein the magnetic clamps are made of a magnetic material. claim 1 3. The apparatus of claim 1 wherein the back focal plane filter is placed between the two lenses of the magnetic doublet lens and wherein the clamps are placed and configured to prevent the magnetic fields of the first and second lens from extending to the back focal plane filter. claim 1 4. The apparatus of claim 2 wherein the magnetic material is a ferromagnetic material. claim 2 5. The apparatus of claim 1 wherein the magnetic doublet lens has a symmetry for image magnification or demagnification and wherein the first and second clamps have a geometry and dimensions that are selected to preserve the symmetry of the magnetic doublet lens. claim 1 6. The apparatus of claim 5 wherein the magnetic doublet lens provides 4:1 image demagnification and the first clamp and the second clamp have a dimensional relationship such that the dimensions of the first clamp are four times the dimensions of the second clamp. claim 5
	summary
	claims	1. A vehicle diagnostic device for deriving and displaying vehicle-specific diagnostic reset procedures, the device comprising:an image capturing device for capturing an optical image of vehicle data;an optical character recognition module in communication with the image capturing device for converting the captured image into a first data signal representative of the captured image;a vehicle decoder module in communication with the optical character recognition module for receiving and converting the first data signal into vehicle identifying information;the vehicle decoder module further being in communication with a reset procedure database for communicating the vehicle identifying information to the reset procedure database for accessing diagnostic reset procedures associated with the vehicle identifying information; anda display module in communication with the reset procedure database for displaying the diagnostic reset procedures accessed from the reset procedure database. 2. The device recited in claim 1, wherein the image capturing device is a camera. 3. The device recited in claim 2, wherein the camera, the optical character recognition module, and the display module are disposed in a mobile communication device. 4. The device recited in claim 1, wherein the captured image is an optical image of one of a vehicle identification number and a license plate number. 5. The device as recited in claim 4, wherein the captured image is an optical image of a bar code image representative of a vehicle identification number. 6. The device recited in claim 4, wherein the vehicle identifying information includes vehicle year, make, model, and engine information. 7. A vehicle diagnostic device for deriving and communicating vehicle-specific diagnostic reset procedures to a vehicle diagnostic port in communication with a vehicle's electronic control unit, the device comprising:an image capturing device for capturing an optical image of vehicle data;an optical character recognition module in communication with the image capturing device for converting the captured image into a first data signal;a vehicle decoder module in communication with the optical character recognition module for converting the first data signal into vehicle identifying information;the vehicle decoder module being in communication with a reset procedure database for communicating the vehicle identifying information to the reset procedure database for accessing a diagnostic reset procedure associated with the vehicle's vehicle identification number; anda local wireless communication circuit in communication with the reset procedure database for receiving the reset procedure and communicating the reset procedure to a vehicle diagnostic port. 8. The device as recited in claim 7 further including a display module in communication with the reset procedure database for displaying the diagnostic reset procedures accessed from the reset procedure database. 9. A system for deriving and displaying vehicle-specific diagnostic reset procedures on a vehicle diagnostic device, the system comprising:an image capturing device configured to capture an optical image of vehicle data;an optical character recognition module in communication with the image capturing device for converting the captured image into a first data signal representative of the captured image;a vehicle decoder module in communication with the optical character recognition module for converting the first data signal into vehicle identifying information;a reset procedure database in communication with the vehicle decoder module for receiving the vehicle identifying information, wherein the reset procedure database stores a plurality of vehicle-specific diagnostic reset procedures, and is operative to access a diagnostic reset procedure associated with the vehicle identifying information; anda display module in communication with the reset procedure database for displaying the diagnostic reset procedures accessed from the reset procedure database. 10. The system as recited in claim 9, wherein the optical character recognition module is disposed on a remote server. 11. The system as recited in claim 9, wherein the reset procedure database is disposed on a remote server. 12. The system as recited in claim 9, wherein the captured image is an optical image of one of a vehicle's vehicle identification number and a vehicle's license plate number. 13. The system as recited in claim 9, wherein the reset procedure database being in communication with the vehicle decoder module for accessing vehicle-specific diagnostic reset procedures associated with the vehicle identifying identification number from the plurality of diagnostic reset procedures. 14. The system as recited in claim 9, wherein the camera, the optical character recognition module, and the display module are disposed in a mobile communication device. 15. A system for deriving and communicating vehicle-specific diagnostic reset procedures to a vehicle diagnostic port in communication with a vehicle's electronic control unit, the system comprising:an image capturing device configured to capture an optical image of vehicle identifying information;an optical character recognition module in communication with the image capturing device, wherein the optical character recognition module is configured to convert the captured image into a first data signal representative of the vehicle identifying information;a reset procedure database in communication with the optical character recognition module for receiving the first data signal, wherein the reset procedure database stores a plurality of vehicle-specific diagnostic reset procedures, and is operative to access a vehicle specific diagnostic reset procedure associated with the vehicle identifying information from the plurality of diagnostic reset procedures; anda local wireless connectivity circuit is in communication with the vehicle diagnostics port and the reset procedure database for communicating the vehicle specific diagnostic reset procedure to the diagnostic port. 16. The system recited in claim 15, further comprising:a vehicle decoder module in communication with the vehicle diagnostic port for receiving information representative of a vehicle's vehicle identification number and converting the received information into a second data signal representative of the vehicle's vehicle identification information;the reset procedure database being in communication with the vehicle decoder module for receiving the second data signal and accessing vehicle-specific diagnostic reset procedures associated with the vehicle's vehicle identification number from the plurality of diagnostic reset procedures. 17. The system recited in claim 16, wherein the vehicle decoder module is disposed in a mobile communication device. 18. A method of deriving and displaying vehicle-specific diagnostic reset procedures, the method comprising the steps of:capturing an optical image of vehicle identifying information;communicating the captured image to an optical character recognition module;converting the captured image into a data signal representative of the vehicle identifying information;communicating the data signal to a reset procedure database, wherein the reset procedure database stores a plurality of vehicle-specific diagnostic reset procedures;accessing a diagnostic reset procedure associated with the vehicle identifying information from the plurality of vehicle-specific diagnostic reset procedures;communicating the accessed diagnostic reset procedure from the reset procedure database to a display module; andcommunicating the accessed diagnostic reset procedure to an electronic control unit associated with the vehicle. 19. The method recited in claim 18, wherein capturing an optical image step includes capturing an image of one of a vehicle's vehicle identification number, a vehicle's bar code identifier, and a vehicle's license plate number. 20. The method as recited in claim 18, wherein the vehicle decoder module is disposed in a mobile communication device. 21. A method of deriving and communicating diagnostic reset procedures to a vehicle diagnostic port in communication with a vehicle's electronic control unit, the method comprising the steps of:receiving vehicle identifying information from a vehicle diagnostic port;converting the received information into a data signal representative of the vehicle identifying information;communicating the data signal to a reset procedure database, wherein the reset procedure database stores a plurality of vehicle-specific diagnostic reset procedures;accessing a diagnostic reset procedure associated with the vehicle's vehicle identification number from the plurality of vehicle-specific diagnostic reset procedures;communicating the accessed diagnostic reset procedures from the reset procedure database to the vehicle diagnostic port; andcommunicating the accessed diagnostic reset procedures received from the vehicle diagnostic port to the electronic control unit.
	abstract	A compound of Chemical Formula 1, and an organic photoelectric device, an image sensor, and an electronic device including the same are disclosed:
	description	This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2009-212779 filed on Sep. 15, 2009 in Japan, the entire contents of which are incorporated herein by reference. 1. Field of the Invention The present invention relates to a charged particle beam writing method and a charged particle beam writing apparatus. For example, it relates to a writing method and a writing apparatus employed when writing patterns of a plurality of chips having different writing conditions onto a target workpiece. 2. Description of Related Art The microlithography technique which advances microminiaturization of semiconductor devices is extremely important as being the unique process whereby patterns are formed in the semiconductor manufacturing. In recent years, with the high integration of LSI, the line width (critical dimension) required for semiconductor device circuits is decreasing year by year. In order to form a desired circuit pattern on semiconductor devices, a master or “original” pattern (also called a mask or a reticle) of high precision is needed. Then, the electron beam writing technique intrinsically having excellent resolution is used for producing such a highly precise master pattern. FIG. 10 is a schematic diagram for illustrating operations of a variable-shaped electron beam (EB) writing apparatus. As shown in the figure, the variable-shaped electron beam writing apparatus operates as follows: A first aperture plate 410 has a quadrangular such as rectangular opening 411 for shaping an electron beam 330. A second aperture plate 420 has a variable-shaped opening 421 for shaping the electron beam 330 that passed through the opening 411 into a desired rectangular shape. The electron beam 330 emitted from a charged particle source 430 and having passed through the opening 411 is deflected by a deflector to pass through a part of the variable-shaped opening 421 and thereby to irradiate a target workpiece or “sample” 340 mounted on a stage which continuously moves in one predetermined direction (e.g. X direction) during writing or “drawing”. In other words, a rectangle shape as a result of passing through both the opening 411 and the variable-shaped opening 421 is written in the writing region of the target workpiece 340 on the stage. This method of shaping a given shape by letting beams pass through both the opening 411 of the first aperture plate 410 and the variable-shaped opening 421 of the second aperture plate 420 is referred to as a VSB (Variable Shaped Beam) method. It is generally performed to write patterns of a plurality of chips onto a mask being a target workpiece. Then, writing conditions may often vary depending upon the chips. For example, a certain chip is written by one-time writing (multiplicity=1), and another certain chip is written by multiple writing (e.g., multiplicity=2) while the position of a boundary between stripe regions is shifted (refer to, e.g., Japanese Patent Application Laid-open (JP-A) No. 11-274036). Conventionally, in the electron beam pattern writing apparatus, when writing patterns of a plurality of chips onto a mask, a writing group is configured by collecting chips whose writing conditions with respect to layout within a certain range are identical with each other, and then writing is performed for each writing group. Thus, when writing is performed in one writing group, the writing is carried out under the same writing conditions. FIG. 11 is a schematic diagram for illustrating writing groups and a writing order. FIG. 11 illustrates the case where three chips A, B, and C are arranged as shown in the figure. In this case, chip A and chip B are written with multiplicity 1, and chip C is written with multiplicity 2. That is, chips A and B having the same writing conditions configure a writing group G1, and chip C configures a writing group G2. In the writing group G1, merge processing is performed on chips A and B, and the merged region is divided into stripe regions of a predetermined height. The case of dividing the merged region into two stripes of the stripe G1S1 and the stripe G1S2 is shown in FIG. 11. On the other hand, in the writing group G2, the region of chip C is divided into stripe regions of a predetermined height. Since chip C is written with multiplicity 2, two stripe layers are configured: a stripe layer for the first time writing, and another stripe layer for the second time writing which is divided at the location shifted by half the stripe height. That is, they are stripes G2S1 and G2S2, and stripes G′2S1 to G′2S3. Thus, in FIG. 11, the writing group G2 is divided into five stripes. When writing, the two stripes of the writing group G1 are firstly written in order. Then, after having written all the stripes of the writing group G1, the five stripes of the writing group G2 are written in order. As described above, when writing is performed for each writing group, one writing processing is completed by firstly writing the two stripes of the writing group G1 in order and then writing all the stripes of the writing group G1. Then, writing processing of the writing group G2 is started. Thus, the writing is performed treating a writing group as a unit of writing processing. Therefore, it is necessary to have a fixed time needed for information generation between the writing processing, and a processing time, such as an initialization time, needed between the writing processing. Furthermore, since writing of the writing group G2 starts after having completed the writing of all the stripes of the writing group G1 and having returned to the writing starting position of the writing group G2, it is necessary to have a time for moving the stage with a target workpiece thereon from the final position of the writing group G1 to the starting position of the writing group G2. If this distance between the final position and the staring position is long, the stage movement time also becomes long in accordance with the distance. Since such time is added to the writing time, there is a problem causing a delay of writing time as a whole. Particularly, if the number of chips having different writing conditions increases, since the number of writing groups also increases according to it, each above-mentioned time becomes necessary in accordance with the increase of the number of writing groups, thereby further causing a delay of the writing time. In accordance with one aspect of the present invention, a charged particle beam writing method includes inputting layout information of a plurality of chips on which pattern formation is to be achieved, setting, using the layout information, a plurality of writing groups each being composed of at least one of the plurality of chips and each having writing conditions differing from each other, setting, for each of the plurality of writing groups, a frame which encloses a whole of all chip regions in the each of the plurality of writing groups, virtually dividing the frame into a plurality of stripe regions in a predetermined direction, with respect to the each of the plurality of writing groups, setting, using the plurality of stripe regions of all the plurality of writing groups, an order of each of the plurality of stripe regions such that a reference position of the each of the plurality of stripe regions is located in order in the predetermined direction regardless of the plurality of writing groups, and writing a pattern in the each of the plurality of stripe regions onto a target workpiece according to the order which has been set, by using a charged particle beam. In accordance with another aspect of the present invention, a charged particle beam writing apparatus includes a storage device configured to input layout information of a plurality of chips on which pattern formation is to be achieved, and store the layout information, a writing group setting unit configured to set, using the layout information, a plurality of writing groups each being composed of at least one of the plurality of chips and each having writing conditions differing from each other, a frame setting unit configured to set, for each of the plurality of writing groups, a frame which encloses a whole of all chip regions in the each of the plurality of writing groups, a region dividing unit configured to virtually divide the frame into a plurality of stripe regions in a predetermined direction, with respect to the each of the plurality of writing groups, an order setting unit configured to set, using the plurality of stripe regions of all the plurality of writing groups, an order of each of the plurality of stripe regions such that a reference position of the each of the plurality of stripe regions is located in order in the predetermined direction regardless of the plurality of writing groups, and a writing unit configured to write a pattern in the each of the plurality of stripe regions onto a target workpiece according to the order which has been set, by using a charged particle beam. In the following Embodiments, there is described a structure using an electron beam as an example of a charged particle beam. However, the charged particle beam is not limited to the electron beam. Other charged particle beam, such as an ion beam, may also be used. Moreover, a variable-shaped writing apparatus will be described as an example of a charged particle beam apparatus. FIG. 1 is a schematic diagram showing an example of the structure of a writing apparatus according to Embodiment 1. In FIG. 1, a writing apparatus 100 includes a writing unit 150 and a control unit 160. The writing apparatus 100 is an example of a charged particle beam writing apparatus. Particularly, it is an example of the variable-shaped writing apparatus. The writing unit 150 includes an electron lens barrel 102 and a writing chamber 103. In the electron lens barrel 102, there are arranged an electron gun assembly 201, an illumination lens 202, a first aperture plate 203, a projection lens 204, a deflector 205, a second aperture plate 206, an objective lens 207, a main deflector 208, and a sub-deflector 209. In the writing chamber 103, there is arranged an XY stage 105, on which a target workpiece 101, such as a mask, serving as a writing object is placed. The target workpiece 101 is, for example, a photomask used for exposure in manufacturing semiconductor devices. The target workpiece 101 may be a mask blank where no patterns are formed. The control unit 160 includes a writing group setting unit 108, a control computer unit 110, a control circuit 120, and storage devices, such as magnetic disk drives, 140, 142, 144, 146, and 148. They are connected with each other by a bus (not shown). In the control computer unit 110, there are arranged a memory 111, a frame setting unit 112, a stripe dividing unit 114, an order setting unit 116, and a data conversion processing unit 118. The frame setting unit 112, the stripe dividing unit 114, the order setting unit 116, and the data conversion processing unit 118 may be configured by hardware such as an electric circuit, or may be configured by software such as a program implementing these functions. Alternatively, they may be configured by a combination of hardware and software. Information (data) which is input/output to/from the frame setting unit 112, the stripe dividing unit 114, the order setting unit 116, and the data conversion processing unit 118, and information (data) which is being calculated are stored in the memory 111 each time. Particularly, since the amount of data processed by the data conversion processing unit 118 may be enormous, it is preferable for the data conversion processing unit 118 to be configured by a plurality of CPUs (not shown), a plurality of memories (not shown), etc. Further, the writing group setting unit 108 may be configured by hardware such as an electric circuit, or may be configured by software such as a program implementing these functions. Alternatively, it may be configured by a combination of hardware and software. With respect to the storage device 140, a plurality of chip data used as layout data is input into it from the outside of the apparatus so as to be stored. For example, the chip data of chip A, the chip data of chip B, the chip data of chip C, and so forty are stored to be used when pattern forming of each chip is performed. With respect to the storage device 142, a writing parameter indicating writing conditions of each chip is input into it from the outside of the apparatus so as to be stored, for example. As the writing conditions, there can be cited multiplicity for multiple writing, a stage movement path of the XY stage 105, a stage speed of the XY stage 105, a stripe height or “stripe width” (dividing height or “dividing width”), a subfield (SF) size, and an irradiation amount (dose), for example. The stripe height or “stripe width” for dividing indicates a dimension of the stripe in the y direction. The stage movement path includes a path which defines the writing direction of writing each stripe in order, such as forward-forward (FF), forward-backward (FB), backward-forward (BF), or backward-backward (BB). Moreover, the stage speed includes, for example, a bundle optimization speed, a speed for constant velocity writing, a speed for variable velocity writing, and a speed for step-and-repeat (S&R) writing. With respect to the storage device 144, layout structure data (layout information) indicating a layout structure of each chip is input into it from the outside of the apparatus so as to be stored, for example. FIG. 1 shows a structure which is necessary for describing Embodiment 1. Other structure elements generally necessary for the pattern writing apparatus 100 may also be included. For example, although the main and sub two-stage deflectors, namely the main deflector 208 and the sub-deflector 209, are used for deflecting a position, a one-stage deflector instead of the two-stage deflector may also be applied to the position deflection. FIG. 2 is a flowchart showing the main steps of the writing method according to Embodiment 1. In FIG. 2, the writing method of Embodiment 1 executes a series of steps: a writing group setting step (S102), a frame setting step (S104), a stripe dividing step (S106), an order setting step (S108), a data conversion processing step (S110), and a writing step (S112). FIG. 3 is a schematic diagram for illustrating a writing group and a combined stripe layer according to Embodiment 1. In the case of FIG. 3, the three chips A, B, and C are arranged as shown in the figure. In the example of FIG. 3, the rectangular chip C is arranged in the center. Then, two rectangular chips A which are long in the Y direction (vertically long) are arranged such that they sandwich chip C and two chips B, from the right and left respectively. The length in the Y direction of chip A is defined to be the same as the total length in the Y direction of chip C and two chips B. Two chips B which are long in the X direction (horizontally long) are arranged such that they sandwich chip C from the upper and lower sides respectively. The length in the X direction of chip B is made to be the same as the length in the X direction of chip C. In this case, chips A and B are written with multiplicity 1, and chip C is written with multiplicity 2. Other writing conditions of chip A and chip B shall be identical with each other. In S102, as the writing group setting step, the writing group setting unit 108 reads a writing parameter of each chip from the storage device 142 and layout structure data from the storage device 144. Using the layout structure data, the writing group setting unit 108 virtually lays out each chip, and sets a writing group composed of at least one chip by collecting chips whose writing parameters are the same. For example, it is preferable to collect chips having the same writing parameters in a predetermined region. In this way, the writing group setting unit 108 sets a plurality of writing groups which have writing conditions differing from each other. In the example of FIG. 3, writing group P is composed of chips A and B whose writing conditions are identical with each other, and writing group Q is composed of chip C. Therefore, FIG. 3 shows the case of setting two writing groups P and Q. Then, group information on the set writing group and writing conditions of each writing group are output to the storage device 146 to be stored. Next, in S104, as the frame setting step, the frame setting unit 112 reads group information on a writing group and writing conditions of each writing group from the storage device 146, and sets, for each writing group, a frame which encloses the whole of all the chip regions in the writing group concerned. The frame according to Embodiment 1 is set such that it encloses the whole of all the chip regions in the writing group concerned while circumscribing the chip regions located at the outer peripheral side. In the example of FIG. 3, with respect to the writing group P, a circumscribing frame 10 formed to be rectangular is set such that it contacts the outer peripheral sides of two chips A and two chips B. With respect to the writing group Q, a circumscribing frame 12 formed to be rectangular is set such that it contacts the outer peripheral side of chip C. Thus, by applying the circumscribing frame, it becomes possible to set a rectangular frame of the minimum size enclosing the whole of all the chip regions in the writing group. Next, in S106, as the stripe dividing step, the stripe dividing unit 114 virtually divides, for each writing group, the frame into a plurality of stripe regions being strip-like in a predetermined direction. In the example of FIG. 3, with respect to the writing group P, the circumscribing frame 10 is virtually divided by the stripe height or “stripe width” set by a writing parameter (writing conditions), into two stripe regions 20 to be strip-like in the Y direction. A first stripe layer (STL_P1) is composed of the two stripe regions 20. Since the writing group P is written with multiplicity N=1, only the first stripe layer (STL_P1) is set. With respect to the writing group Q, since it is written with multiplicity N=2, first, the circumscribing frame 12 is virtually divided by the stripe height specified by a writing parameter (writing conditions) into three stripe regions 30 to be strip-like in the Y direction for the first time writing layer (first stripe layer: STL_Q1). The first stripe layer is composed of the three stripe regions 30. A frame whose length is obtained by respectively adding one-half (½) of the stripe height, in the Y direction and in the −Y direction, to the circumscribing frame 12, is divided into the three stripe regions 30. In this case, since the multiplicity is N=2, one-half of the stripe height is added. For example, if the case is multiplicity N=4, three-fourth (¾) of the stripe height will be added. Furthermore, with respect to the writing group Q, the circumscribing frame 12 is virtually divided by the stripe height specified by a writing parameter (writing conditions) into two stripe regions 32 to be strip-like in the Y direction for the second time writing layer (second stripe layer: STL_Q2). The second stripe layer is composed of the two stripe regions 32. As mentioned above, the example of FIG. 3 is composed of the three stripe layers. Conventionally, the first stripe layer (STL_P1) of the writing group P and the first and the second stripe layers (STL_Q1 and STL_Q2) of the writing group Q are written as separate writing processing. However, according to Embodiment 1, they are combined to be written as one writing processing. In S108, as the order setting step, using a plurality of regions of all the writing groups, the order setting unit 116 sets an order of each stripe region such that the reference position of each stripe region is located in order in a predetermined direction (in this case, the Y direction) regardless of the writing group. FIG. 4 is a schematic diagram for illustrating the writing order of a plurality of stripe regions according to Embodiment 1. With respect to the two stripe regions 20, the three stripe regions 30, and the two stripe regions 32 shown in FIG. 3, an ascending sort is performed, for example, treating the position of the lower left corner as a reference position, so that reference positions may be sorted according to the Y coordinate in the ascending order. Consequently, as shown in FIG. 4, the sorting is performed to have the order of the stripe region Q1S1 of the first stripe layer of the writing group Q at the head, the stripe region P1S1 of the first stripe layer of the writing group P, the stripe region Q2S1 of the second stripe layer of the writing group Q, the stripe region Q1S2 of the first stripe layer of the writing group Q, the stripe region P1S2 of the first stripe layer of the writing group P, the stripe region Q2S2 of the second stripe layer of the writing group Q, and the stripe region Q1S3 of the first stripe layer of the writing group Q at the last. Thus, the order setting unit 116 sets the order of each stripe region as just described above. In S110, as the data conversion processing step, the data conversion processing unit 118 reads layout data corresponding to each stripe region from the storage device 140, performs conversion processing of a plurality of steps to generate shot data for each stripe region, and stores it in the storage device 148. It is preferable for the data conversion processing unit 118 to perform data conversion so that shot data of each stripe region may be temporarily stored according to the order described above. However, since layout data is a large amount, it is preferable to further divide each stripe region into a plurality of small regions and to perform parallel processing of data of the plurality of small regions. In that case, data conversion processing of data on the plurality of stripe regions may be carried out at the same time period. In S112, as the writing step, the control circuit 120 reads shpt data in each stripe region from the storage device 148 according to the order which has been set, and writes a pattern of each stripe region by controlling the writing unit 150 onto the target workpiece 101 according to the set order by using an electron beam 200. When writing each stripe region, the writing is respectively performed under the writing conditions set by writing parameters. The writing unit 150 specifically operates as follows: The electron beam 200 emitted from the electron gun assembly 201 (emitting unit) irradiates the entire first aperture plate 203 having a quadrangular, such as a rectangular, opening by the illumination lens 202. At this point, the electron beam 200 is shaped to be a quadrangle such as a rectangle. Then, after having passed through the first aperture plate 203, the electron beam 200 of a first aperture image is projected onto the second aperture plate 206 by the projection lens 204. The first aperture image on the second aperture plate 206 is deflection-controlled by the deflector 205 so as to change the shape and size of the beam. After having passed through the second aperture plate 206, the electron beam 200 of a second aperture image is focused by the objective lens 207 and deflected by the main deflector 208 and the sub-deflector 209, and reaches a desired position on the target workpiece 101 on the XY stage 105 which continuously moves. FIG. 1 shows the case where a multi-stage deflection of the main and sub two-stage is used for the position deflection. In such a case, what is needed is to deflect the electron beam 200 to the reference position of a subfield (SF), being a small region made by virtually dividing the stripe region, by the main deflector 208 while following the stage movement, and to deflect the beam reaching each irradiation position in the SF by the sub-deflector 209. FIG. 5 shows examples of a plurality of chips, writing groups, and writing conditions of each writing group according to Embodiment 1. In this case, chips A, B, and C are arranged such that the writing group I is composed of chips A and B and the writing group II is composed of chip C. As the writing conditions with respect to the writing group I, dividing is performed by the stripe height of 200 μm, the stage movement path of the XY stage 105 proceeds in the order of forward(FWD)-backward(BWD), writing is performed with multiplicity N=1, and the XY stage 105 moves at a constant speed. As the writing conditions with respect to the writing group II, dividing is performed by the stripe height of 200 μm, the stage movement path of the XY stage 105 proceeds in the order of forward(FWD)-forward(FWD), writing is performed with multiplicity N=2, and the XY stage 105 moves at a variable speed. FIG. 6 is a schematic diagram showing a plurality of chips, a plurality of writing groups, and the stripe region of each writing group of FIG. 5. As shown in FIG. 6, the writing group I composed of chips A and B is divided into four stripe regions 51, 52, 53, and 54. The writing group II composed of chip C is divided into two stripe regions 61 and 62 of the first stripe layer, and two stripe regions 71 and 72 of the second stripe layer. FIG. 7 is a schematic diagram showing a writing order of plurality of chips of FIG. 6. In Embodiment 1, since an ascending sort is performed according to the Y coordinate with respect to all the stripe regions 51, 52, 53, 54, 61, 62, 71, and 72, treating the lower left corner as a reference position, for example, thereby writing proceeds in the order shown in FIG. 7. In FIG. 7, first, the stripe region 51 of the writing group I is written in the X direction (FWD). Next, the stripe region 52 of the writing group I is written in the −X direction (BWD). Next, the stripe region 61 of the writing group II is written in the X direction (FWD). Next, the stripe region 71 of the writing group II is written in the X direction (FWD). Next, the stripe region 53 of the writing group I is written in the X direction (FWD). Next, the stripe region 62 of the writing group II is written in the X direction (FWD). Next, the stripe region 72 of the writing group II is written in the X direction (FWD). Then, lastly, the stripe region 54 of the writing group II is written in the −X direction (BWD). That is, in the writing group I, the writing is performed in the order of FWD→BWD→FWD→BWD according to the writing conditions shown in FIG. 5, and in the writing group II, the writing is performed in the order of FWD→FWD→FWD→FWD according to the writing conditions shown in FIG. 5. When at least part of regions of different writing groups overlap each other, after the region of the writing group whose reference position is precedingly located at the Y coordinate has been written, the region of the other writing group is written. In Embodiment 1, as described above, an ascending sort is performed in the Y direction, for example, with respect to the stripes of all the stripe layers of a plurality of writing groups, regardless of the writing conditions, and then, writing is carried out according to the sorted order. Thereby, the writing can be executed by one-time writing processing. Therefore, it is possible to save a fixed time conventionally needed for information generation of writing processing between writing groups, and a processing time, such as an initialization time, conventionally needed between writing processing. Thus, it is possible to reduce the writing processing time to the time of one-time writing processing. Moreover, it is possible to reduce the movement time of the XY stage 105 with the target workpiece 101 thereon when shifting from the final position of a certain writing group to the starting position of the next writing group. Therefore, the writing time in the case of writing a plurality of writing groups having different writing conditions can be shortened. In Embodiment 1, the circumscribing frame is set, for each writing group, such that it circumscribes a chip in the writing group concerned. However, it is not limited thereto. In Embodiment 2, the case of setting a frame by other method will be described. In Embodiment 2, the apparatus structure is the same as that in FIG. 1, each step of the writing method is the same as that in FIG. 2, and the content of each step is the same as that described in Embodiment 1 except for the points described below. FIG. 8 is a schematic diagram for illustrating a writing group and a combined stripe layer according to Embodiment 2. En the case of FIG. 8, the three chips A, B, and C are arranged as shown in the figure. In the example of FIG. 8, similar to FIG. 3, the rectangular chip C is arranged in the center. Then, two rectangular chips A which are long in the Y direction (vertically long) are arranged such that they sandwich chip C and two chips B, from the right and left respectively. The length in the Y direction of chip A is defined to be the same as the total length in the Y direction of chip C and two chips B. Two chips B which are long in the X direction (horizontally long) are arranged such that they sandwich chip C from the upper and lower sides respectively. The length in the X direction of chip B is made to be the same as the length in X direction of chip C. In this case, chips A and B are written with multiplicity 1, and chip C is written with multiplicity 2. Other writing conditions of chip A and chip B shall be identical with each other. Moreover, the content of the writing group setting step (S102) is the same as that described in Embodiment 1. Next, in S104, as the frame setting step, the frame setting unit 112 reads group information on a writing group and writing conditions of each writing group from the storage device 146, and sets, for each writing group, a frame which encloses the whole of all the chip regions in all the writing groups. The frame according to Embodiment 2 is set such that it encloses the whole of all the chip regions in all the writing groups while circumscribing the chip regions located at the outer peripheral side. In FIG. 8, with respect to the writing group P, since chip C is arranged inside the two chips A and two chips B, consequently, the circumscribing frame 10 formed to be rectangular is set such that it contacts the outer peripheral sides of two chips A and two chips B similarly to Embodiment 1. However, with respect to the writing group Q, since not only chip C but also two chips A and two chips B are enclosed, consequently, a circumscribing frame 14, being the same size as the circumscribing frame 10 formed to be rectangular, is set such that it contacts the outer peripheral sides of two chips A and two chips B. Thus, by applying the circumscribing frame, it becomes possible to set a rectangular frame of the minimum size enclosing the whole of all the chip regions in all the writing groups. Next, in S106, as the stripe dividing step, the stripe dividing unit 114 virtually divides each writing group into a plurality of stripe regions in a predetermined direction. In the example of FIG. 8, with respect to the writing group P, similarly to Embodiment 1, the circumscribing frame 10 is virtually divided by the stripe height set by a writing parameter (writing conditions), into two stripe regions 20 to be strip-like in the Y direction. The first stripe layer (STL_P1) is composed of the two stripe regions 20. On the other hand, with respect to the writing group Q, since it is written with multiplicity N=2, first, the circumscribing frame 14 is virtually divided by the stripe height specified by a writing parameter (writing conditions) into three stripe regions 34 to be strip-like in the Y direction for the first time writing layer (first stripe layer: STL_Q1). The first stripe layer composed of the three stripe regions 34. A frame whose length is obtained by respectively adding one-half (½) of the stripe height, in the Y direction and in the −Y direction, to the circumscribing frame 14 is divided into the three stripe regions 34. In this case, since the multiplicity is N=2, one-half of the stripe height is added. For example, if the case is multiplicity N=4, three-fourth (¾) of the stripe height will be added. Furthermore, with respect to the writing group Q, the circumscribing frame 14 is virtually divided by the stripe height specified by a writing parameter (writing conditions) into two stripe regions 36 to be strip-like in the Y direction for the second time writing layer (second stripe layer: STL_Q2). The second stripe layer is composed of the two stripe regions 36. Since the example of FIG. 8 shows the case where both the writing groups P and Q have the same stripe height, consequently, the two stripe regions 20 and the two stride regions 36 are the same regions. As mentioned above, the example of FIG. 8 is composed of the three stripe layers. Conventionally, the first stripe layer (STL_P1) of the writing group P and the first and the second stripe layers (STL_Q1 and STL_Q2) of the writing group Q are written as separate writing processing. However, according to Embodiment 2, they are combined to be written as one writing processing. In S108, as the order setting step, using a plurality of regions of all the writing groups, the order setting unit 116 sets an order of each stripe region such that the reference position of each stripe region is located in order in a predetermined direction (in this case, the Y direction) regardless of the writing group. FIG. 9 is a schematic diagram for illustrating the writing order of a plurality of stripe regions according to Embodiment 2. With respect to the two stripe regions 20, the three stripe regions 34, and the two stripe regions 36 shown in FIG. 8, an ascending sort is performed, for example, treating the position of the lower left corner as a reference position, so that reference positions may be sorted according to the Y coordinate in the ascending order. Consequently, as shown in FIG. 9, the sorting is performed to have the order of the stripe region Q1S1 of the first stripe layer of the writing group Q at the head, the stripe region Q2S1 of the second stripe layer of the writing group Q, the stripe region P1S1 of the first stripe layer of the writing group P, the stripe region Q1S2 of the first stripe layer of the writing group Q, the stripe region Q2S2 of the second stripe layer of the writing group Q, the stripe region P1S2 of the first stripe layer of the writing group P, and the stripe region Q1S3 of the first stripe layer of the writing group Q at the last. Thus, the order setting unit 116 sets the order of each stripe region as just described above. In the example of FIG. 9, since the two stripe regions 20 and the two stripe regions 36 have the same positional relationship, whichever of them may be sorted first. Then, the data conversion processing step (S110) and the writing step (S112) may be carried out similarly to Embodiment 1. Thus, according to Embodiment 2, it is possible to make the circumscribing frame be in common as mentioned above, in addition to the effects according to Embodiment 1. Therefore, the amount of data on the circumscribing frame can be reduced. According to Embodiments described above, each region is written in a predetermined direction regardless of the writing group. Therefore, it is enough for the length of stage movement to be short. Then, the time of stage movement can be shortened. Moreover, according to the configuration described above, writing processing can be performed not as writing processing for each writing group but as a series of writing processing for all the writing groups collected. Therefore, it is possible to save a fixed time needed for information generation between writing processing, and a processing time, such as an initialization time, needed between writing processing. Thus, it is possible to reduce the writing time in the case of writing a plurality of writing groups having different writing conditions. Referring to specific examples, Embodiments have been described above. However, the present invention is not limited to these examples. While description of the apparatus structure, control method, etc. not directly required for explaining the present invention is omitted, some or all of them may be suitably selected and used when needed. For example, although the structure of the control unit for controlling the writing apparatus 100 is not described, it should be understood that a necessary control unit structure is to be selected and used appropriately. In addition, any other charged particle beam writing apparatus and method that include elements of the present invention and that can be appropriately modified by those skilled in the art are included within the scope of the present invention. Additional advantages and modification will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents.
	summary
	description	Referring now to the drawings, wherein like reference numerals designate identical or corresponding parts throughout the several views, the embodiments of this invention will be described below. A first embodiment of this invention is described with reference to FIGS. 1 through 4. FIG. 1 schematically shows an example of core arrangement of a boiling water reactor of 1,300 MWe class in a plan view. In the nuclear core, there is strings where detector assemblies are arranged. In each of the detector assemblies, local power range monitor (LPRM) detectors for monitoring in-core neutron flux level are arranged at approximately equal intervals in an axial direction of the reactor core, as shown in FIG. 2B. As shown in FIGS. 1 and 2A, a control rod 3 having a xe2x80x9ccrossxe2x80x9d in cross-section is configured to be inserted in a center of corresponding four fuel assemblies 2 from beneath the reactor core (not illustrated), and detector assemblies 1 each comprising the four LPRM detectors 4 are arranged at approximately equal intervals in a diametrical parallel direction, in a proportion of one detector assembly 1 to sixteen fuel assemblies 2 and a proportion of one detector assembly 1 to four control rods 3. FIG. 2A, which is an enlarged potion of FIG. 1, shows the positions of the fuel assemblies 2, the control rods 3 and the detector assemblies 1 as a part of a reactor core, and FIG. 2B shows the composition inside the detector assembly 1 shown in FIG. 2A in an axial direction. As shown in FIG. 2B, in the detector assembly 1, four LPRM detectors 4, LPRM-A, LPRM-B, LPRM-C and LPRM-D from bottom to top, are arranged at approximately equal intervals in an axial direction. The LPRM detector further comprises a TIP calibration channel 5 containing a traversing incore probe (TIP) (not shown) for calibrating the LPRM detectors 4 and for continuously monitoring neutron flux distribution or gamma flux distribution in an axial direction, where the TIP moves inside the TIP calibration channel 5. Hereinafter, a node designates a length of a fuel effective length, in which nuclear fuel material is filled, divided by twenty-four or twenty-five. In the detecting assembly 1 illustrated in FIG. 2B, LPRM detector A is located at a pitch level of approximately the center of the third node and the fourth node from the bottom of the fuel effective length, LPRM detector B is located at a pitch level of approximately the center of the ninth node and the tenth node, LPRM detector C is located at a pitch level of approximately the center of the fifteenth node and the sixteenth node, and LPRM detector D is located at a pitch level of approximately the center of the twenty-first node and the twenty-second node. Each LPRM detector 4 detects neutron flux level at a corresponding pitch level. Accordingly, a linear power heat generation rate, that is, an output per unit length of fuel at a pitch level corresponding to each LPRM detector, of a fuel assembly adjacent to the LPRM detector, is approximately proportional to a changing rate of a value indicated this LPRM detector. And an output of a fuel assembly adjacent to the LPRM detectors is approximately proportional to an average of changing rates of four LPRM detectors belonging to a corresponding string. By using this correlation, thermal characteristics of a fuel assembly arranged around a string can be computed easily by changing rates of values indicated by the LPRM detectors, on the basis of calculation result of power distribution calculated by the three-dimensional reactor core simulator and the LPRM detectors and an actual measurement of plant data. That is, the linear heat generation rate and the critical power ratio around a string can be expressed with the following equations: Linear Heat Generation Rate MFLPDAT(K,ISTR)=MFLPDIN(K,ISTR)xc2x7(1+(1/FK(K))xc2x7(LPRMAT(K,ISTR)/LPRMIN(K,ISTR)xe2x88x921))xe2x80x83xe2x80x83(1), where, MFLPDAT(K,ISTR) is a ratio of the maximum linear heat generation rate of four fuel assemblies measured by means of the LPRM detectors around a string in the string position ISTR and at the pitch level K to an operational limit thereof, LPRMAT(K,ISTR) is a value indicated by LPRM detector in the string position ISTR and at the pitch level K, MFLPDIN(K,ISTR) is a ratio of the maximum linear heat generation rate of four fuel assemblies computed by power distribution calculation around a string in the string position ISTR and at the pitch level K to an operational limit thereof, LPRMIN(K,ISTR) is a value indicated by LPRM detector in the power distribution calculation in the string position ISTR and at the pitch level K, and FK(K) is a safety coefficient in calculation of the linear heat generation rate at the pitch level K. Critical Power Ratio MFLCPAT(ISTR)=MFLCPIN(ISTR)xc2x7(1+(1/FC)xc2x7(LPAVAT(ISTR)/LPAVIN(ISTR)xe2x88x921))xe2x80x83xe2x80x83(2), where MFLCPAT(ISTR) is a ratio of an operational limit of the critical power ratio to the minimum critical power ratio of four fuel assemblies measured by means of the LPRM detectors around a string in the string position ISTR, MFLCPIN(ISTR) is a ratio of an operational limit of the critical power ratio to the minimum critical power ratio of four fuel assemblies computed in power distribution calculation measured around a string in the string position ISTR, LPAVAT(ISTR) is a weighted-average of values indicated by four LPRM detectors, LPRM-A through LPRM-D, belonging to a string in the string position ISTR, LPAVIN(ISTR) is a weighted-average of values indicated by four LPRM detectors, LPRM-A through LPRM-D, in the power distribution calculation belonging to a string in the string position ISTR, and FC is a safety coefficient in calculation of the critical power ratio. Thus, in this embodiment concerning an incore monitoring method, the thermal characteristics can be computed using previously calculated values MFLPDIN(K, ISTR) and LPRMIN(K, ISTR) in equation (1) and MFLCPIN(ISTR) and LPAVIN(ISTR) in equation (2), and need not rely on power distribution calculation at the time of operating of control rods or adjusting of the reactor core flow rate. This result is shown in FIG. 3, which should be compared with FIG. 14. In FIG. 3, it is not necessary to stop operation of the control of the control rods and the adjustment of the reactor core flow rate, because the power distribution calculation, which takes a long time, is not performed every cycle but rather equations (1) and (2) are used which provide a fast solution using previously calculated power distribution values and current values of the LPRM detectors. That is, as shown as a solid line C1 in FIG. 3, cycles of calculation of the thermal characteristics at times when the power distribution calculation is not carried out and in operating of the control rods or adjusting of the reactor core flow rate, which is simplified calculation are performed continuously. And cycles of calculation of the thermal characteristics of power calculation performed in the power distribution calculation, shown as a dashed line C2 in FIG. 3, are performed frequently at fixed time interval or in response to a demand. In equations (1) and (2), only the severest situation concerning the thermal characteristics among four fuel assemblies around each string is analyzed. This is because the thermal characteristics of fuel assemblies arranged in symmetrical positions are equal to each other due to the symmetry of the loading pattern of fuel assemblies and control rods mentioned above, and thus it is sufficient to monitor only the severest one. Generally, a reactor core has a symmetrical property over one quarter of the core, or further one eighth symmetry, and the fuel assemblies loading pattern is determined so that the non-symmetrical portion is kept at a minimum when the symmetry cannot be ensured due to a kind or number of the fuel assemblies constructing reactor core. Symmetrically-arranged control rods are operated simultaneously, and the control rods operation pattern is arranged symmetrically. This is because the symmetric arrangement reduces power peaking in a radial direction and improves thermal characteristics, and because management of the fuel assemblies and the control rods becomes easier since burn-up histories of symmetrically-positioned fuel assemblies and neutron irradiation histories of symmetrically-positioned control rods are the same. In FIG. 1, the detector assemblies are labeled 1 through 52. In case of number 1 of the detector assembly shown in FIG. 1, thermal characteristics of the four fuel assemblies loaded in the fuel-assembly coordinates (27,04), (29,04), (27,06) and (29,06) designated by X-Y coordinates, are similar to the thermal characteristics of the four fuel assemblies loaded in the coordinates (03, 42), (03, 40), (05, 42) and (5,40), the four fuel assemblies located in the coordinates (41, 66), (39, 66), (41, 64) and (39, 64), or the four fuel assemblies located in the coordinates (65, 28), (65, 30), (63, 28) and (63, 30). Taken such symmetry into consideration, the thermal characteristics of all the fuel assemblies in a reactor core will be computed only by the detector assemblies shown in FIG. 1, except for a part of the fuel assemblies that are located outermost in a diametrical parallel direction of a reactor core. And the thermal characteristics of the outermost fuel assemblies are not severe because the power thereof is low due to a low neutron flux. Thus, according to this embodiment, if the thermal characteristics of fuel assemblies around strings are computed, the severest of the thermal characteristics can be extracted and confirmed not to exceed an operational limit; and thus it is not necessary to suspend operation of control rods or reactor core flow rate. Next, incore monitoring equipment for performing an incore monitoring method according to this embodiment is explained with reference to FIG. 4. In FIG. 4, a core shroud 9 surrounds a reactor core and forms a coolant flow channel in a nuclear reactor pressure vessel 6. The reactor core comprises fuel assemblies 2, detector assemblies 1 and control rods 3 inserted from beneath the reactor core. A steam separator 8 which separates steam generated in the nuclear core from coolant, and a steam dryer 7 which removes moisture from steam, are installed above the core shroud 9. Internal pumps 11 are installed in a lower part of the nuclear reactor pressure vessel 6 to control coolant flow in a reactor core, that is a core flow rate, by the adjusting rotational speed of the internal pumps 11. A plurality of control rod drive mechanisms 10 are installed under the nuclear reactor pressure vessel 6 and penetrate a lower part of the nuclear reactor pressure vessel 6 to control positions of the control rods 3. Control rod operation system 14 adjusts the position of control rods 3 via the control rod drive mechanisms 10, and recirculation flow control system 13 adjusts reactor core flow rate by changing frequencies of the internal pumps 11. In increasing power or adjusting control rod patterns, incore monitoring unit 16 outputs a command signal to the recirculation flow control system 13 and/or the control rod operation system 14 to adjust the reactor core flow rate and/or the control rod patterns, respectively. Plant data stored in plant database 18 is composed of data groups of sensor values concerning flow rate of a nuclear reactor, control rod patterns, incore pressure, main steam flow rate, feedwater temperature, and so forth, and these are updated periodically. Incore instrumentation system 12 equalizes a plurality of signals from the LPRM detectors, some of which is incore neutron flux instrumentation, processes signals from an average power range monitor (APRM) calibrated equivalent to a core thermal power. By receiving signals from the incore instrumentation system 12, the process computer 15 calculates power distribution, and the incore monitoring device 16 calculates thermal characteristics. The incore instrumentation system 12 also has an alert function and a function to output a command signal to stop the plant by rapidly inserting all control rods into the nuclear core. A process computer 15 receives plant data from plant database 18 and actual measurement data from the incore instrumentation system 12, performs power distribution calculations by the three-dimensional reactor core simulator built in the process computer 15, and thereby computes thermal characteristics and a void fraction distribution of each fuel assembly. This power distribution is calculated at regular fixed time interval or in response to a request from an operator. In an automatic power adjustment system 17, operating procedures of reactor core flow rate and control rod patterns at the time of starting-up, adjusting of control rod patterns and shutdown are preliminary installed. The automatic power adjustment system 17 automatically outputs a command signal of reactor core flow rate control and a command signal of control rod adjustment to the recirculation flow control system 13 and the control rod control system 14, respectively according to the procedures, thereby the reactor core flow rate and the control rods are adjusted automatically and followed by the procedures. The incore monitoring unit 16 receives results of power distribution calculation by the process computer 15, plant data corresponding to the time of the power distribution calculation from the process computer 15, and values indicated by the LPRM detectors from the incore instrument system 12, and continuously receives updated plant data and values indicated by the LPRM detectors, and continuously computes the thermal characteristics of fuel assemblies around a string according to the equations (1) and (2). When the computed thermal characteristics deviate from an operational limit, the incore monitoring device 16 outputs an operator alarm, transmits an automation stop signal to automatic output adjustment system 17, and transmits a command signal to stop control the reactor core flow rate and a command signal to prohibit adjusting of the control rods to the recirculation flow control system 13 and the control rod control system 14, respectively, thus adjustment of the reactor core flow rate and the operation of the control rods is stopped. In effect, the adjustments which were having the effect of increasing power output are now stopped until the thermal characteristics no longer exceed the operational limit. Next, concrete examples of this embodiment concerning incore monitoring method is explained below. In a first example of this embodiment, achieved by the incore monitoring system shown in FIG. 4, the process computer 15 calculates power distribution at fixed time intervals or in response to request of an operator, and the incore monitoring device 16 computes MLHGR and MCPR at a moment when these factors have not yet been calculated and the reactor core flow rate or the control rods is controlled, by using the equations (1) and (2) and based on the calculation result of the process computer 15. Moreover, if these computed thermal characteristics exceed corresponding operational limit, an alarm is activated and the control of the reactor core flow rate and the control rods is stopped. Here, when the incore monitoring device 16 receives linear power generation rates around a string in calculating power distribution from the process computer 15, the linear power generation rates in pitch levels correspond to the four LPRM detectors. LPRM-A is located between the third node, from the bottom of fuel effective length, which is divided by twenty-four or twenty-five as one node, and the fourth node, LPRM-B located between the ninth node and the tenth node, LPRM-C located between the fifteenth node and the sixteenth node, and LPRM-D located between the twenty-first node and the twenty-second node. Each LPRM detector is located at almost the middle point between two nodes, and receives a linear power generation rate at the corresponding pitch level. Alternatively, the higher value of two linear heat generation rates corresponding to two nodes arranged adjacent up and down may be received, that is, for example, an LPRM detector receives a higher one of the linear heat generation rates at the third node as compared to the fourth node. Also, the highest value may be taken among six linear heat generation rates corresponding to six sequential nodes by allocating each LPRM detector together with the TIP detector in the TIP channel 5 to six sequential nodes. In addition, when the fuel effective length is divided by twenty-five, the twenty-fifth node, which is the highest, may correspond to LPRM-D which is the highest of the four LPRM detectors, or can be ignored in calculation of the thermal characteristics of twenty-four nodes because the linear heat generation rate at the top node is relatively low. The incore monitoring device 16 calculates a linear heat generation rate at any pitch level by using a rate of change of values indicated by the LPRM detectors based on the received linear power generation rates. In a second example of this embodiment, acquired by a modification of the above-mentioned first example, when the incore monitoring device 16 receiving thermal characteristics as a basis computed by the power distribution calculation, the incore monitoring device 16 receives the severest factors, that is, the minimum value of the critical power ratio of four fuel assemblies arranged adjacent to each string and other fuel assemblies arranged symmetrically to the four fuel assemblies, and the maximum value of the linear heat generation rates at pitch levels corresponding that of LPRM detectors, to calculate thermal characteristics. If symmetry of fuel loading patterns cannot be completely assured, then thermal characteristics even for symmetrically arranged fuel assemblies will differ from each other. However, this second example uses the property that a rate of change of thermal characteristics in operation of the control rods or the reactor core flow rate at one position is approximately equal to that at a corresponding symmetrical position. The control rods are operated in a symmetric manner thus maintaining the equality of the rate of change of the thermal characteristics of symmetric fuel assemblies. In this second example, the severest factors, that is, the minimum value of the critical power ratios and the maximum value of the linear heat generation rates of four fuel assemblies arranged adjacent to each string and other fuel assemblies arranged symmetrically to the four fuel assemblies, are computed based on a changing rate of values indicated by LPRM detectors. If this computation is performed at every strings, the severest factors, that is, the minimum values of the critical power ratios and the maximum values of the linear heat generation rates of all fuel assemblies except a part at peripheries of the reactor core, can be found by the computation. In a third example of this embodiment, acquired by a modification of the above-mentioned second example, in computation of the critical power ratio, the critical power ratio is compensated by taking into account the fact that the critical power ratio is changed due to a change of the reactor core flow rate. The critical power ratio is defined as a ratio of critical power in which boiling transition arises to an output power of a fuel assembly. If the coolant discharge increases, the critical power also increases because of an increase in the cooling capacity. FIG. 5 shows a relation of flow rate of coolant in a fuel assembly and a critical power of a corresponding fuel assembly, both of which are of no quantity unit. Here, a value of 1.0 (no unit of quantity) of flow rate in a fuel assembly is equivalent to a coolant discharge inside a fuel assembly per one fuel assembly in rated reactor core flow rate. As known by the relation shown in FIG. 5, without consideration of effect that the critical power increases in accordance with the increase in the reactor core flow rate, the computed ratio of the operation limit of the critical power ratio to the critical power ratio acquired from the equation (2) is overestimated compared with an actual ratio at the time of an increase in the reactor core flow rate, and is underestimated compared with an actual ratio at the time of a decrease in the reactor core flow rate. Then, in this third example, a correlation of a reactor core flow rate and critical power is approximated with a polynomial or a function, based on the reactor core flow rates (discharges inside a fuel assembly) at which time when the power distribution is computed at periodic fixed times or in response to a request from an operator, and when the reactor core monitoring device 16 calculates thermal characteristics, that is, when the critical power ratio is calculated. That is, a reactor core flow rate and a corresponding critical power at each point is acquired, thereby by this acquired correlation, a polynomial or function may be obtained which approximates a curve as shown in FIG. 5 or a plotted line chart. Next, with this approximated polynomial or function, a ratio of a critical power corresponding to a reactor core flow rate in calculating the power distribution to a critical power corresponding to a reactor core flow rate in calculating the minimum critical power ratio, is calculated as a correction coefficient, and compensated critical power is calculated by multiplying a right side member of the above-mentioned equation (2) by this correction coefficient, thereby the critical power ratio can be corrected and be acquired as a value in which a change of critical power due to a change of the reactor core flow rate is reflected. In a fourth example of this embodiment, acquired by a modification of the above-mentioned first example or second example, in computation of the linear heat generation rate, the linear heat generation rate is compensated by considering a percentage change of a linear heat generation rate and a percentage change of values indicated by LPRM detector. As already mentioned, although a linear heat generation rate at a vicinity of LPRM detector is approximately proportional to a percentage change of values indicated by the LPRM detector, the correlation of the linear heat generation rate and the percentage change of values indicated by the LPRM detector varies comparatively, from one locality of a control rod to another. FIG. 6 shows a correlation of an insertion position of a control rod and a ratio of the maximum of changing rates (e.g. increasing rates) of the linear heat generation rates (at pitch level of LPRM-A) of four fuel assemblies arranged adjacent in one string, to the a changing rate of values indicated by LPRM-A, where one control rod adjacent to the string has been extracted from a state where an effective length of the control rod is fully inserted, that is, a control rod position is set to zero, to a state that all of the control rod is fully pulled out, that is, the control rod position is set to 200. Apparently recognized from FIG. 6, the ratio of a changing rate of the heat generation rate to a changing rate of values indicated by LPRM detector is approximately 1.0. However, the ratio deceases a little between 150 and 200 of the control rod position. That is, in this range, the increasing rate of the linear power heat generation rate becomes smaller compared with the increasing rate of values indicated by the LPRM detector. Thus, the changing rate (e.g. increasing rate) of the linear heat power generation rate at the pitch level of each LPRM detector is designated as a function of the changing rate (e.g. increasing rate) of values indicated by the corresponding LPRM detector and a control rod position, by a graph as shown in FIG. 6. As for the LPRM-A as shown in FIG. 6, the changing rate of values indicated by LPRM detector is almost equal to the changing rate of the linear heat generation rate in case of the control rod position being between 0 and 150. In this fourth example as a modification of the first or second example, when the maximum linear heat generation rate at the pitch level of each LPRM detector of the four fuel assemblies arranged adjacent to one string is calculated (see FIG. 2A), a changing rate (an increasing rate) of the linear power generation rate is acquired as a function of a changing rate of values indicated by these LPRM detectors and control rod position, based on positions of the control rod corresponding to when the power distribution is calculated at periodic fixed times or in response to a request from an operator (i.e., a first time), and when the maximum linear heat generation rate is calculated, that is, when the incore monitoring device 16 calculates thermal characteristics (i.e., a second, subsequent time). That is, by approximating a curved graph or plotted polygonal line, such as one shown in FIG. 6, showing a correlation of the control rod position and a ratio of a changing rate of the linear heat generation rate and a changing rate of values indicated by a LPRM detector, the changing rate of the linear heat generation rate is designated as a function of two parameters composed of the changing rate of values indicated by the LPRM detector and a rate of insertion of the control rod. In this way, the maximum linear heat generation rate calculated by equation (1) is compensated with a function acquired as discussed above. For example, an changing rate of the linear heat generation rate is calculated from the control rod position and an changing rate of values indicated by the LPRM detector at the above-mentioned first and second times (see FIG. 6), and the maximum linear heat generation rate is acquired by multiplying the calculated increasing rate by the value calculated by the equation (1), thereby, the maximum linear heat generation rate can be compensated, and thus, the maximum linear heat generation rate can acquire a value reflected by a change of values indicated by the LPRM detector due to a change of insertion position of the control rod. FIG. 6 shows as a result of acquiring a correlation of control rod positions and a ratio of a changing rate of the linear heat power generation rate to a changing rate of values indicated by the LPRM detector at pitch level of LPRM detector A, however, correlations at pitch level of LPRM-B, LPRM-C and LPRM-D corresponding to this figure can be acquired in the same way mentioned above, and thereby the linear heat generation rate can be compensated more appropriately. In a fifth example of this embodiment, acquired by a modification of the above-mentioned first example or second example, in computation of the linear heat generation rate at focused node position which is not adjacent a pitch level of a LPRM detector, the linear heat generation rate at such focused node position is calculated by using a value acquired by interpolation of changing rates of values indicated by LPRM detectors being above and below the focused node position, while utilizing fact that linear heat generation rate transits continuously in an axial direction. In the detector assembly shown in FIG. 2B, LPRM-A is between the third node, from the bottom of fuel effective length, and the fourth node, LPRM-B is between the ninth node and the tenth node, LPRM-C is between the fifteen node and the sixteen node, and LPRM-D is between the twenty-first node and the twenty-second node, each of which is in the middle of corresponding two nodes. When LPRM detectors are arranged as mentioned above, suppose that the linear heat generation rate locally changes at a certain rate, as a simplified example, a percentage change of the linear heat generation rate is applied to the interpolation. When the computed percentage changes of linear heat generation rates at node positions of LPRM-A and LPRM-B are a and b, respectively, the percentage change of linear heat generation rate at pitch level of a middle point of the sixth node and the seventh node, that is just between the two LPRM detectors, is, a+(bxe2x88x92a)/2=(a+b)/2, and similarly, the percentage change of linear heat generation rate at pitch level of a middle point of the seventh node and the eighth node is, a+2xc2x7(bxe2x88x92a)/3=(a+2b)/3. In addition, with regard to the first node and the second node at the bottom and the twenty-third node and the twenty-fourth node at the top, though no LPRM is arranged near these nodes, output is low due to leakage of neutrons from the bottom or top of the reactor core, therefore these nodes are never a maximum of the linear heat generation rate and it is not necessary to monitor there nodes. In this example, using four LPRM detectors, the linear heat generation rate at focused pitch level can be calculated with high precision, without directly detecting at the focused pitch level. LPRM detectors may be in a bypass state in which signals are intentionally intercepted and not used due to failure such as leakage of an electrolytic-dissociation gas, or disconnection, or due to inspection. In this case, the reactor core monitor 16 cannot receive suitable values directed by a LPRM detector in a failure or a bypass state from the reactor core instrumentation system 12, and thermal characteristics of fuel assemblies adjacent to a string including the LPRM detector cannot be calculated. As shown In FIG. 1, since strings exist with c-cxe2x80x2 as an axis of symmetric, when one of LPRM detectors included in a string is in a failure or a bypass state and the string is not a string on the axis of symmetric c-cxe2x80x2, there is another LPRM detector in the same pitch level of, and symmetric to, the LPRM detector in a failure or a bypass state. In a sixth example of this embodiment, acquired by a modification of the above-mentioned first example or second example, utilizing symmetric properties of the LPRM detectors, thermal characteristics around a string including a LPRM detector being in a failure or a bypass state is calculated by a substituted the value of a changing rate of values indicated by the corresponding LPRM detector in the same pitch level of, and symmetric to, the LPRM detector in the failure or bypass state. This example utilizes symmetric properties of control rod patterns, that is, a fact that a changing rate of values indicated by one LPRM detector is equal to that of values indicated by a symmetrically-arranged LPRM detector. In this sixth example, when LPRM-A included in a string numbered 1 in FIG. 1 is in a failure or a bypass state, the incore monitoring device 16 receives values indicated by LPRM-A included in a string numbered 17, symmetric to the number 1 around the axis of symmetry c-cxe2x80x2, and the incore monitoring device 16 treats the values received from LPRM-A of the number 17 as a substituted values for LPRM-A of the number 1 and the calculation is performed. Thus, even if a part of LPRM detectors is in a failure or a bypass state, the thermal characteristics of fuel assemblies adjacent to a string including such a LPRM detector can be computed with high accuracy. In the above-mentioned sixth example, since a LPRM detector on the axis of symmetry c-cxe2x80x2 does not have another alternative LPRM detector, if such LPRM detector on the c-cxe2x80x2 axis is in a failure or a bypass state, a substitution value cannot be acquired. Moreover, a substitution value cannot be calculated when two or more LPRM detectors at symmetrical positions are in failure or a bypass state simultaneously. This seventh example of this embodiment can be applied to this situation in the sixth embodiment, by considering expanding string positions with two axes of symmetry a-axe2x80x2 and b-bxe2x80x2 shown in FIG. 1. FIG. 7 shows a plain view of a reactor core expanding strings. In FIG. 7, square designates a control rod and four fuel assemblies adjacent to the control rod, that is, a control rod cell, and each number in upper left corner of a square grid is a string number. Circled strings in FIG. 7, numbers 1 through 52, designates strings in which a detector assembly 1 exists, that is, real-strings, and except for these real-strings, corresponding numbers designate numbers of real-strings expanded in rotational symmetry. In FIG. 7, expanded strings adjacent to a string number 6A are strings numbered 23A, 34A, 26A and 24A. That is, in view of symmetry, strings number 23A, 34A, 26A and 34A, which are closest to the string number 6a, surrounds the string number 6A. Thus, if one LPRM detector of the string number 6A is in a failure or a bypass state, an average of a changing rate of values indicated by at least one LPRM detector included in a string adjacent to the string number 6a in a symmetrical expansion, at the same pitch level of the failed LPRM detector, is used as a substitution. For example, one LPRM detector may be substituted in string number 26B or 34B adjacent expanded string 6B or one LPRM detector may be substituted in string number 23C or 24C adjacent expanded string 6C. Additionally, as a modification of this example, when detector assemblies are arranged symmetrically in the reactor core, one LPRM detector is in a failure or a bypass state, values outputted from one LPRM detector which is in the same pitch level of, and symmetrical to, the failed LPRM detector is used for a substitute to calculate thermal characteristics. In this embodiment including seven examples explained above, it is also possible to suitably combine two or more examples. Next, as an effect of this embodiment of an incore monitoring method in this invention, a result of an off-line three-dimensional reactor core simulator acquired in response to the incore monitoring method is described. FIGS. 8A through 8I show reactor core status 1 through 9 in the middle of gaining a power output, with a legend as shown in FIG. 8J. Since a control rod pattern is symmetrical in one fourth core regions, each status figure of FIGS. 8A through 8I shows one fourth of ranges of a reactor core, and the power output and the flow rate are shown as a percentage by setting a rated thermal power output and rated reactor core flow rate as 100%. Power distribution calculation is carried out in a reactor core status 1 shown in FIG. 8A, and then, thermal characteristics in reactor core status 2 through 6 in FIGS. 8B through 8F, respectively, are calculated by the incore monitoring method, based on a calculation result of the reactor core status 1. These results are compared with the calculation result of thermal characteristics in respective status by the off-line three-dimensional reactor core simulator. Moreover, suppose that a power distribution calculation is carried out in a reactor core status 6 shown in FIG. 8F. The thermal characteristics in reactor core status 7 through 9 in FIGS. 8G through 8I, respectively, are calculated by the incore monitoring method based on a calculation result of the reactor core status 6, and the results are compared with the calculation result of thermal characteristics in the respective status by the off-line three-dimensional reactor core simulator. FIGS. 9 through 12 show the calculation results of linear heat generation rates at a pitch level of each LPRM detector based on a changing rate of values indicated by the respective LPRM detector included in the detector assembly number 26 shown in FIG. 1. FIGS. 9 through 12 show behaviors of a ratio of the linear heat generation rate to an operational limit of the linear heat generation rate, which is instead of, and as significant as, the linear heat generation rate as such, and reactor status 1 through 9 corresponds to the above-mentioned status in FIGS. 8A through 8I, respectively. Here, a solid line shows the ratio acquired from the response by the incore monitoring method of this invention, and a dotted line shows the ratio calculated by the three-dimensional reactor core simulator based on actual linear heat generation rates. FIG. 9 corresponds to pitch level of LPRM-A, and here the linear heat generation rate is the maximum of the linear heat generation rates of fuel assemblies around a string between the third node and the fourth node. Similarly, FIG. 10 corresponds to pitch level of LPRM-B, and here the linear heat generation rate is the maximum of the linear heat generation rates of fuel assemblies around a string between the ninth node and the tenth node. FIG. 11 corresponds to pitch level of LPRM-C, and here the linear heat generation rate is the maximum of the linear heat generation rates of fuel assemblies around a string between the fifteenth node and the sixteenth node. FIG. 12 corresponds to pitch level of LPRM-D, and here the linear heat generation rate is the maximum of the linear heat generation rates of fuel assemblies around a string between the twenty-first node and the twenty-second node. In addition, in FIGS. 9 through 12, calculation result of the linear heat generation rate by the incore monitoring method according to equation (1), without compensation of control rod positions as mentioned in the fourth embodiment. FIGS. 9 through 12 show that in the reactor core monitoring method, the acquired result is better in accuracy than that based on a changing rate of values indicated by the LPRM detectors, throughout in the reactor core states 1 through 9. Although the linear heat generation rate at pitch level of LPRM-A in reactor core states 3 through 6, calculated by this incore monitoring method, is a little overestimated, the accuracy comes better by compensating in accordance with control rods position as mentioned in the fourth example. Correspondingly, FIG. 13 shows the transition of the minimum critical power ratios of four fuel assemblies adjacent to the detector assembly number 23 shown in FIG. 1. FIG. 13 shows a ratio of operation limit of the critical power ratio to the calculated critical power ratio, instead of showing the critical power ratio as such. Here, a solid line designates a ratio acquired by the critical power ratio calculated by the incore monitoring method in this invention, and a dotted line designates a result of the actual power distribution calculated by the three-dimensional reactor core simulator. Here, the calculation of the critical power ratio by this incore monitoring method in this invention is based on equation (2), LPRM-A through LPRM-D have the same weights in a weighted average of values indicated by the LPRM detectors, and compensation of change of the critical power due to a change of the reactor core flow rate is carried out according to the correlation shown in FIG. 5. As shown in FIG. 13, according to the incore monitoring method of this invention, the critical power ratio can be computed with sufficient accuracy according to a reactor core state. According to this invention, thermal characteristics at a the time when the power distribution calculation is not performed in operation of control rods or reactor core fuel rate, can be acquired instantly and concisely, and the thermal characteristics can be monitored continuously with high accuracy based on continuously-updated plant data and values indicated by LPRM detectors. Moreover, fuel soundness can be maintained by suspending automatic operation of the control rods or reactor core flow rate in case of deviating of the thermal characteristics out of the critical limit, and time necessary for starting-up or pattern adjustment can be shortened because the power distribution calculation performed after stopping operation for checking the thermal characteristics in starting-up or adjusting of control rods pattern is not necessary.
059582340	summary	BACKGROUND OF THE INVENTION The present invention relates generally to the field of suction strainers, and more particularly to the field of suction strainers employed in the suppression pools of boiling water reactor (BWR) nuclear power plants. A suction strainer employed in a suppression pool removes solids from a flow of liquid (e.g., water) being drawn into an emergency core cooling system (ECCS) pump. The flow of water is drawn through the suction strainer and then Into the suction line of the ECCS pump. Employment of suction strainers is desirable because solid debris drawn into the suction line of a pump can degrade pump performance by accumulating in the pump or its suction or discharge lines, or by impinging upon and damaging internal pump components. While almost any pump degradation can be characterized as being costly, the degradation of ECCS pump performance at BWR nuclear plants can be detrimental to safe plant shutdown following a loss of coolant accident (LOCA). At a BWR nuclear power plant following a LOCA, it is critical for the ECCS pumps to operate for an extended period of time in an undegraded fashion. In one mode of operation, the ECCS pumps are operated to recirculate water from the suppression pool back to the reactor core for the purpose of core cooling. A LOCA results from a high pressure pipe rupturing with such great force that large quantities of debris, such as pipe and vessel insulating material, and other solids, may be washed into the suppression pool. Conventional ECCS suction strainers currently installed in BWR plants would have a tendency to become clogged by such debris due to their small size and poor design. Also, when the large pressure pipes rupture with great force, suction strainers in the suppression pool are subjected to great hydrodynamic forces that can damage the suction strainers as well as subject the attachment recirculation piping to large reactive forces. These structural considerations, and space constraints, limit the size and shape of suction strainers in suppression pools. Conventional BWR plant suction strainers are typically constructed and arranged in a manner such that, under full flow conditions, localized high entrance velocities are established through that portion of the suction strainer that is most proximate to the suction line of the pump, while low entrance velocities are established through that portion of the suction strainer that is more distant from the suction line of the pump. The high entrance velocities may draw more solid debris into contact with the suction strainer causing the portions of the suction strainer experiencing the high entrance velocities to experience higher head loss. As the portion of the suction strainer most proximate to the suction line collects debris, high entrance velocities are established at the portion of the suction strainer that is next closest to the suction line causing that portion to collect debris. This process often continues until the entire suction strainer has collected debris in varying quantities, resulting in a non-uniform build-up of debris on the outer surface of the strainer. Localized high entrance velocities can be detrimental even when solids are not present in the liquid being pumped. For example, high entrance velocities can result in turbulent flow which tends to create greater pressure losses than laminar flow. Any such pressure losses reduce the net positive suction head (NPSH) available to a pump. As the NPSH available decreases, pump cavitation may occur. Similarly, localized high entrance velocities can cause vortexing. When a suction strainer is not sufficiently submerged, the vortexing can cause air ingestion which can severely degrade pump performance. Attempts have been made to resolve certain of the problems associated with suction strainer-like devices in other applications. For example, cylindrical suction flow control pipes have been encircled with screen material and employed in water wells. Such wells typically employ a well pump above the ground surface and a riser pipe extending from the well pump to the water table. The suction flow control pipe is connected to the end of the riser pipe and extends further below the water table. Openings are defined through the side wall of the suction flow control pipe such that there is somewhat less open area near the riser pipe and somewhat more open area distant from the riser pipe. As a result, when water is drawn into the flow control pipe through the openings, a substantially uniform inflow distribution is defined along the length of the flow control pipe. While such suction flow control pipes offer some advantages, they are not suitable for all applications. Attempts have been made, totally separate from flow control pipes, to increase filtering surface areas of BWR ECCS suction strainers in an effort to decrease pressure losses and thereby prevent pump cavitation. For example, such suction strainers may include a plurality of spaced, coaxial, stacked filtering disks. More particularly, such stacked disk suction strainers typically include an annular flange for attachment to the corresponding flange on the pump suction line. The stacked disk suction strainer provides an enhanced surface area and defines a longitudinal axis that is encircled by the attachment flange. A first disk is attached to the attachment flange. The first disk includes a pair of a radially extending, circular, disk walls, each of which encircle the longitudinal axis, and define a central hole. A first disk wall of the pair of disk walls is connected to the attachment flange. The first and second disk wall of the pair of disk walls face one another and are separated by a slight longitudinal distance. The first disk further includes an outer annular wall that encircles the longitudinal axis. The outer annular wall includes an annular first edge and an annular second edge. The entirety of the annular first edge of the outer annular wall is connected to the entire peripheral edge of the first perforated disk wall; and the entirety of the annular second edge of the outer annular wall is connected to the entire peripheral edge of the second perforated disk wall such that the pair of disk walls are connected at their periphery. The stacked disk suction strainer further includes a plurality of inner annular walls that encircle the longitudinal axis, each of which includes an annular first edge and an annular second edge. The annular first edge of one of the inner annular walls is connected around the periphery of the central hole of the second disk wall. The annular second edge of that inner annular wall is connected around the periphery of the central hole of a disk wall of a second disk. The first and second disk walls, and the outer and inner annular walls are perforated and comprise the filtering surface of the stacked disk suction strainer. Additional perforated disks and inner annular walls are attached to one another in the above manner until the last disk is attached, wherein the outer disk wall of the last disk does not include a central hole. The stacked disk suction strainers may incorporate separate structural members to maintain the structural integrity of the stacked disk suction strainer. However, the conventional stacked disk suction strainers do not incorporate an internal core tube and related components, whereby the conventional stacked disk suction strainers are difficult to structurally reinforce and are susceptible to vortexing and the detrimental non-uniform localized entrance velocities discussed above. There is, therefore, a need in the industry for an improved suction strainer. SUMMARY OF THE INVENTION Briefly described, the preferred embodiments of the of the present invention include a suction strainer that includes a filtering device with a strategically enlarged filtering surface and an internal core. The internal core is preferably in the form of an internal core tube, which is preferably an internal pipe with flow openings. In accordance with the preferred embodiments of the present invention, the internal core tube structurally reinforces the filtering device. In accordance with the preferred embodiments of the present invention, the structural reinforcement provided by the internal core tube is enhanced by reinforcing structural members that extend radially from the internal core tube. The reinforcing structural members are preferably connected to and extend radially from and angularly around the internal core tube to structurally support the filtering surfaces of the external filtering structure. The internal core tube, in conjunction with the structural members, seeks to prevent air ingestion and vortexing. The suction strainer preferably extends away from the suction line of an ECCS pump to define a length, and in accordance with certain examples the preferred embodiments of the present invention, the internal core tube seeks to promote controlled inflow along the length to preclude the establishment of non-uniform localized entrance velocities through the filtering surface. In accordance with other examples of the preferred embodiments of the present invention, the internal core tube is not constructed to specifically promote such a uniform inflow along the length. In accordance with the preferred embodiments of the present invention, the suction strainer is constructed in a manner that seeks to enlarge the filtering surface while minimizing the projected area of the suction strainer. The minimization of the projected area as well as structural reinforcement of the suction strainer enables the suction strainer to withstand high levels of hydrodynamic impact loading following a LOCA. The suction strainer also serves to minimize the bending moment and other reactive forces on the attachment ECCS piping in the BWR suppression pool. In accordance with the preferred embodiments of the present invention, the filtering surface is defined by an external filtering structure that is attached to, extends from, and is built around the internal core tube and the reinforcing structural members. When the suction strainer is connected to the suction of a pump and submerged, a liquid flow path is established through the internal core tube and external filtering structure. The liquid originates exterior to the external filtering structure and is drawn through the filtering surfaces of the external filtering structure. The filtering surfaces separate solids from the liquid. The size of the filtering surface is enlarged by virtue of the fact that the filtering surface defines protrusions such that the distance that the filtering surface extends from the internal core tube alternates. The resulting enlarged filtering surface seeks to decrease average flow velocities through the filtering surface and thereby spread the collected solid debris in thinner layers, thereby decreasing overall pressure losses associated with the suction strainer. Once the liquid flows through the filtering surface, the liquid is drawn through the internal core tube and into the suction of the pump. In accordance with the preferred embodiments of the present invention, the protrusions of the external filtering structure are in the form of a plurality of filtering plate assemblies that are connected to and extend radially from the internal core tube. Each plate assembly includes a pair of plate walls that face one another, define a distance therebetween, and are connected at their peripheries by an outer wall that surrounds the internal core tube. A separation distance is defined between neighboring plate assemblies. Inner walls connect between neighboring plate assemblies and extend around the internal core tube at a radius less than the radius of the outer walls. The outer and inner walls as well as the plate walls are perforated and comprise the filtering surfaces of the suction strainer. In accordance with first and second preferred embodiments of the present invention, the plurality of plate assemblies are preferably in the form of stacked disks that are spaced to defined troughs therebetween. In accordance with other embodiments, the plate assemblies are in other forms that increase the surface area of the suction strainer. In accordance with preferred embodiments of the present invention, the internal core tube has a downstream end for connection to the pump suction flange and an upstream end distant from the downstream end. The internal core tube defines a longitudinal axis extending between the upstream and downstream ends. In accordance with the preferred embodiments of the present invention, a plurality of openings are defined through the side wall of the internal core tube. In accordance with certain examples of the preferred embodiments, the openings are constructed and arranged such that there is somewhat less open area near the downstream end than the upstream end, and the amount of open area tapers between the upstream end and the downstream end. As a result, when water flows into the internal core tube through the openings, a substantially uniform flow rate distribution is defined along substantially the entire length of the internal core tube. It is therefore an object of the present invention to provide an improved BWR ECCS suction strainer. Another object of the present invention is to increase safety by improving the operability of the ECCS of a BWR nuclear plant following a LOCA. Yet another object of the present invention is to structurally reinforce a suction strainer sufficiently so that it can withstand the hydrodynamic forces following a LOCA in the suppression pool at a BWR nuclear plant. Still another object of the present invention is to minimize reactive forces on the attachment ECCS piping following a LOCA. Still another object of the present invention is to maximize the total strainer surface area within a limited geometric profile while providing a maximum strength strainer. Still another object of the present invention is to simultaneously minimize both the thickness of collected debris on the strainer and the average entrance velocities to minimize the resultant NPSH of the ECCS following a LOCA. Still another object of the present invention is to maximize the amount of time required to reach a particular head loss across the strainer. Still another object of the present invention is to control the distribution of fluid flow over the strainer so as to collect debris uniformly, from disk to disk or from trough to trough, to allow scaling of the strainer for other flow rates with similar, but different size, strainers with different water flow rates. Still another object of the present invention is to prevent vortexing and air ingestion. Other objects, features and advantages of the present invention will become apparent upon reading and understanding this specification, taken in conjunction with the accompanying drawings.
062755684	claims	1. An X-ray examination apparatus for forming X-ray images of an object, which apparatus includes an X-ray source for generating an X-ray beam, an X-ray filter which is provided with filter elements which are arranged to contain an adjustable quantity of X-ray absorbing liquid in order to adjust an intensity profile on an object, and with a supply duct for connecting the filter elements to a reservoir for the X-ray absorbing liquid, an X-ray detector for receiving a part of the X-ray beam, having traversed the object, in order to detect an X-ray image, characterized in that the supply duct includes sub-ducts, and that each of the sub-ducts connects at least one of the filter elements to the reservoir. 2. An X-ray examination apparatus as claimed in claim 1, in which the sub-ducts are arranged so as to extend parallel to one another. 3. An X-ray examination apparatus as claimed in claim 1, the X-ray examination apparatus being provided with adjusting means for keeping the X-ray source, the X-ray filter and the detector oriented along a first axis and for adjusting an orientation of the first axis relative to a horizontal plane, the X-ray examination apparatus also including means for rotating the X-ray filter about the first axis. 4. An X-ray examination apparatus as claimed in claim 3, in which the means for rotating the X-ray filter include a collimator which accommodates the X-ray filter. 5. An X-ray examination apparatus as claimed in claim 1, which is provided with means for generating a signal which represents an angle of inclination between a longitudinal axis of one of the sub-ducts and a horizontal plane. 6. An X-ray examination apparatus as claimed in claim 5, in which the means for generating the signal representing the angle of inclination include a roll-independent inclinometer. 7. An X-ray examination apparatus as claimed in claim 3, in which the means for rotating the X-ray filter include an electrically controllable drive and the X-ray examination apparatus is provided with control means which are arranged to generate control signals for the electrically controllable drive in order to orient a longitudinal axis of one of the sub-ducts horizontally in dependence on the signal representing the angle of inclination. 8. An X-ray examination apparatus as claimed in claim 1, in which the X-ray filter contains the reservoir which is arranged outside the X-ray beam to be generated, the reservoir containing chambers and each chamber being connected to at least one of the subducts. 9. An X-ray examination apparatus as claimed in claim 1 which is provided with means for generating a control signal whereby the adjustable quantity of X-ray absorbing liquid in the filter elements is adjusted. 10. An X-ray examination apparatus as claimed in claim 9 which is provided with means for generating a compensation signal which is dependent on the orientation of the X-ray filter, and with means for correcting the control signal by way of the compensation signal. 11. An X-ray filter provided with filter elements which are arranged to contain an adjustable quantity of X-ray absorbing liquid in order to adjust an intensity profile on an object, and a supply duct for connecting the filter elements to a reservoir for the X-ray absorbing liquid, characterized in that the supply duct includes sub-ducts, each of which connects at least one of the filter elements to the reservoir. 12. An X-ray filter as claimed in claim 10, which X-ray filter contains the reservoir which includes chambers, each chamber being connected to at least one of the sub-ducts.
051456397	abstract	A nuclear energy plant housing a boiling-water reactor utilizes an isolation condenser in which a single chamber is partitioned into a distributor plenum and a collector plenum. Steam accumulates in the distributor plenum and is conveyed to the collector plenum through an annular manifold that includes tubes extending through a condenser pool. The tubes provide for a transfer of heat from the steam, forming a condensate. The chamber has a disk-shaped base, a cylindrical sidewall, and a semispherical top. This geometry results in a compact design that exhibits significant performance and cost advantages over prior designs.
039705170	claims	1. A process carried out in a hot-cell which includes therein a chamber and means for drawing a partial vacuum within said chamber and an electronic-beam welding apparatus, comprising the steps carried out within said chamber and under partial vacuum conditions, of (a) filling a compressible inner container with granulated radio-active material, (b) applying said vacuum pressure to said material within said container, (c) with said welding apparatus, welding a first lid onto said container to seal same against radio-active leakage, and (d) placing said sealed inner container within a compressible outer container with a space defined between said containers and surrounding said inner container, (e) filling said space with liquid metal, and (f) welding a second lid onto said outer container to seal same, thus providing a container assembly and performing compaction on said container assembly, by applying a pressure upon said sealed outer container which being compressible applies pressure onto said liquid metal which transmits said pressure equally in all directions onto said inner container which being compressible compacts said radio-active material therein. 2. A process according to claim 1 wherein said liquid metal comprises lead or a lead compound. 3. A process according to claim 1 wherein said welding apparatus is an electron beam welding apparatus. 4. A process according to claim 1 wherein said compaction on said container assembly comprises applying pressure of at least 1000 bar and simultaneously maintaining said assembly at a temperature of at least 1200.degree.C. 5. In a process of compacting a granular radio-active material into a solid body, where said material is precompacted in a compressible inner container and sealed against radio-active leakage by welding under partial vacuum conditions, the improvement in combination therewith comprising the steps: (a) providing a hot-cell, (b) placing within said hot-cell said inner container, a larger compressible container and lid for same, and welding means operable within partial vacuum conditions, (c) placing said inner container within said outer container, with a space defined between said containers and surrounding said inner container, (d) filling said space with liquid metal, (e) drawing a partial vacuum within said hot-cell and welding said lid on said outer container to seal same, thus providing a container assembly, and comprising the further step of performing compaction on said container assembly, by applying a pressure upon said sealed outer container which being compressible applies said pressure onto said liquid metal which transmits said pressure equally in all directions onto said inner container which being compressible compacts said radio-active material therein. 6. A process according to claim 5 wherein said liquid metal is lead or a lead compound. 7. A process according to claim 5 wherein said compaction on said container assembly comprises applying pressure of at least 1000 bar and simultaneously maintaining said assembly at a temperature of at least 1200.degree.C. 8. A container of radio-active material which material has a theoretical density based upon the chemical compound thereof, and an actual density greater than 95% of said theoretical density made by the process defined in claim 5. 9. A process for compacting a granular radio-active material into a solid isotopic heat source, comprising the steps: (a) filling a compressible inner container with said granular radio-active material, (b) partially evacuating said filler inner container and (c) welding a first lid onto said inner container and thereby sealing same against radio-active leakage, (d) placing said sealed inner container into a compressible larger outer container, with a space defined between said containers, (e) filling said space with a pressure-transmitting medium, (f) welding a second lid onto said outer container and thereby sealing same against leakage of the pressure-transmitting medium, providing a container assembly and also providing a second seal against radio-active leakage from said inner container, (g) performing compaction on said container assembly by applying pressure with a hydraulic press onto said outer container while maintaining said inner container in a heated condition whereby said pressure is transmitted via said compressible outer container into said pressure-transmitting medium and thence into said sealed inner container which being compressible compacts said radio-active material therein.
	claims	1. A method of providing fresh meat products, comprising:irradiating the meat products in a first controlled atmosphere;packaging the irradiated meat products downstream from the irradiation area in a second controlled atmosphere having a modified oxygen concentration; and distributing the packaged irradiated meat products to a retail store; wherein the first controlled atmosphere excludes oxygen. 2. The method of claim 1, wherein the second controlled atmosphere is high in oxygen. 3. The method of claim 1, wherein the steps of irradiating the meat products in the first controlled atmosphere and packaging the irradiated meat products in the second controlled atmosphere are performed in the same meat packing facility. 4. The method of claim 1, further comprising:adding an antioxidant to the meat products prior to the step of irradiating the meat products in the first controlled atmosphere. 5. The method of claim 4, wherein the antioxidant is a rosemary extract. 6. The method of claim 4, wherein the package irradiated meat products have a color-life of over three weeks. 7. The method of claim 6, wherein the retail store is a convenience store. 8. The method of claim 1, further comprising:topically applying an antioxidant to the irradiated meat products prior to the step of packaging the irradiated meat products in the second controlled atmosphere. 9. The method of claim 8, wherein the antioxidant is a rosemary extract. 10. The method of claim 8, wherein the packaged irradiated meat products have a shelf-life and a color-life of over three weeks. 11. The method of claim 10, wherein the retail store is a convenience store. 12. The method of claim 1, wherein the retail store is a superstore that does not include an in-store meat processing department. 13. The method of claim 1, further comprising:providing a clean curtain between a meat processing area where the step of irradiating meat products is performed and a meat packaging area where the step of packaging the irradiated meat products is performed. 14. The method of claim 1, wherein the step of irradiating meat products is performed in a sealed conduit having the first controlled atmosphere therein. 15. The method of claim 14, wherein the step of irradiating meat products comprises:conveying the meat products to be irradiated through a processing area in the sealed conduit;controlling the first controlled atmosphere in the sealed conduit to be different from an ambient atmosphere; andapplying radiation to the meat products in the processing area. 16. The method of claim 15, wherein the first controlled atmosphere in the sealed conduit excludes oxygen. 17. The method of claim 16, wherein controlling the first controlled atmosphere in the sealed conduit comprises filling the sealed conduit with a gas selected from the group consisting of nitrogen and carbon dioxide.
	description	This PCT patent application claims priority to U.S. patent application Ser. No. 61/228,104, entitled ‘Nuclear Battery Based on Hydride/Thorium Fuel”, filed on Jul. 23, 2009, the contents of which are incorporated herein by reference in their entirety. This technology relates generally to portable nuclear fuel reactors. Presently, there are approximately 150 metric tons of known weapons grade plutonium and approximately 850 metric tons of known reactor-grade plutonium in the world, with 50 metric tons of reactor-grade plutonium being produced every year. There is likely to be more such plutonium in the world that is unaccounted for. Since these types of plutonium can be used to make weapons of mass destruction, such as thermonuclear bombs and dirty bombs, it is desirable to process any such plutonium so as to render the plutonium difficult to use in making a weapon of mass destruction or to transform any such plutonium into a form that is difficult to use in making any kind of weapon of mass destruction. Currently, there are two approaches to processing weapons-grade and reactor-grade plutonium such that the end product is either difficult or substantially impossible to use in constructing a weapon of mass destruction. The first approach is to immobilize the plutonium. Typically, this approach involves immobilizing plutonium powder in a glass matrix and then placing the plutonium/glass matrix in a secure storage location. The second approach is to incorporate the plutonium in a nuclear fuel that is burned at a nuclear power plant. The burning of such a fuel results in much of the plutonium being transformed into an isotope that is unsuitable for use in a weapon of mass destruction. Presently, a plutonium-based nuclear fuel that is being used to reduce the supply of plutonium that might be used to produce a weapon is a blend of plutonium-239 and natural or depleted uranium, which is commonly referred to as a mixed oxide fuel (MOX). There are plutonium-based nuclear fuels suitable for use in a light water reactor (LWR) generating electricity and in which ordinary water is used as a coolant and a moderator to slow down neutrons to the point where their energy ranges fall into the range of higher fission probability. There are two types of LWR, namely, a pressurized water reactor (PWR) and a boiling water reactor (BWR). The plutonium-based nuclear fuel is comprised of plutonium, zirconium hydride, and thorium, which may act as a moderator inside the fuel. In one embodiment, the zirconium hydride comprises 20-50% by weight of the fuel. Alternatively, the plutonium is less than 10% by weight of the fuel; the zirconium hydride is 20-50% by weight of the fuel; and the thorium is 20-50% by weight of the fuel. Further alternatives of the fuel, have about 40-94% of the plutonium in the fuel as plutonium-239. Other alternative fuel a comprises a zirconium hydride in which the hydrogen to zirconium ratio is in the range of about 1.6-1.8. These fuels may also be used in an LWR reactor, e.g., a TRIGA reactor (Training Research Isotopes General Atomics). There are benefits to using zirconium hydride alloy fuel in nuclear reactors, at least in part because of its safety characteristics. In fuel the moderator and fuel are intimately mixed. Among the research reactors that commonly use this type is the TRIGA reactor. The NERI program in applying this fuel to the LWR (Z. Shayer and E. Greenspan “Physics Characteristic of U-ZrH1.6Fueled PWR Cores”, PHYSOR 2004, Chicago, Ill., Apr. 25-29, 2004) The introduction of hydrogen within the fuel permits attainment of neutron moderation to aid plutonium incineration by thermalizing more neutrons, enhancing the neutron absorption probability in the 0.3 eV resonance peak of Pu-239. Use of this fuel may have several advantages over the existing MOX (Mixed Oxide fuel, blends of Uranium and Plutonium oxide) fuel: (a) increased core-life; (b) increased energy generation per fuel loading; (c) reduced waste volume and toxicity due to higher discharge number and to partial utilization of thorium; (d) utilization of thorium resources; (e) improved safety due to the large negative temperature coefficient; (f) improved proliferation resistance by burning up more plutonium and use of thorium; (g) additional significant benefits of the proposed zirconium hydride matrix are better thermal conductivity and fuel storage heat capacity; and (h) the reported experiments with TRIGA fuels indicated low fission gas release. The neutronic parametric study previously reported is limited directed mainly to infinite pin cell calculations that were performed by WIMSD-5B (WIMSD-5B (98/11), “Deterministic Code System for Reactor-Lattice Calculations”, RSICC CCC-656, user manual (1998), (WIMSD-5B stands for Winfrith Improved Multigroup Scheme Version D-5B, computer code) a deterministic code for reactor core lattice calculations. This code was benchmarked for hydride fuel applications against the well-established codes such as MCNP4B2 and SCALE4.4 codes to provide additional justification of the applicability of the code for the hydride fuel parametric study. Generally there was very good agreement between the codes for various ranges of neutronic parameters and spectrum (Z. Shayer, Neutronic Parametric Analysis: U-ZrH1.6 Unit Cell in PWR NERI Project—Rev.4, NERIO2-189-TM 2 (2003). The initial analysis shows significant advantages of the proposed fuel over the MOX for incineration of plutonium. Several calculations were performed by the WIMSD-5B to determine the benefit of Pu/ZrHx/Th matrix fuel. FIG. 1 is a sample of the results obtained from this study, which shows the variation of K∞ (Kinf Infinite—Multiplication factor for neutrons)) versus burnup (in GWd/Te ihm; GW days per ton equivalent initial heavy metal [U or Th]) for several fuel types (MOX and oxide fuel). The presence of some Th-232 provides additional fissile material through conversion of Th-232 to U-233, which increases the discharge burnup values to around 80,000 MWd/Te as compared to MOX fuel with LEU (Low Enriched Uranium) that reached only to 65,000 MWd/Te (At K∞=1.03 for a single batch). For a comparison, the discharge burnup value of HEU oxide fuel is only about 45,000 MWd/Te. From FIG. 2 we can see that the destruction rate of Pu-239 is significantly better fast compared to the destruction rate of than the MOX fuel, at 50,000 MWd/Te for MOX fuel, only about 50% of initial Pu-239 is consumed as compared to about 70% for the proposed fuel. This value is increase to 92% for the Pu/ZrHx/Th matrix fuel as compare to only 63% for MOX at 80,000 MWd/Te. The preliminary results show that this fuel is may be suitable ideal for the non-proliferation program to dispose of weapon and power grades plutonium. In this example the calculations were performed for typical PWR rods. The fuel, clad and water temperatures were assumed to be 978 K, 607 K and 579 K, respectively. Initial results indicated that this Pu/ZrHx/Th matrix fuel would may be very attractive to the disposition of weapon and power grades plutonium. The fuel destruction rates measured in the non-limiting examples described above, were is almost an order of magnitude higher than conventional MOX fuel of containing plutonium. Due to the higher discharge burnup in a smaller core volume, with beneficial safety characteristics and a high prompt reactivity coefficient, a Pu/ZrHx/Th matrix fuel with Zr or SS cladding offers excellent advantages over the conventional MOX fuel for plutonium disposition. The present disclosure is directed to transportable nuclear batteries comprising, sealed reactor shell; a reactor core; and a generator. The transportable nuclear battery may further comprises a nuclear fuel comprising in the reactor core wherein the fuel comprises plutonium, carbon, hydrogen, zirconium and, thorium. The fuel may further comprise hydrogen containing glass microspheres, wherein the glass microspheres, may be coated with a burnable poison, and other coating materials that may aid in keeping the hydrogen within the microsphere glass at relatively high temperature. The use of nuclear battery to serve remote sites without ready access to fuel is not new. In the 1960s, the U.S. Army Portable Nuclear Power Program deployed several small nuclear plants at locations such as Greenland and Antarctica. Since then several advanced concept studies, sponsored by government and industry, have addressed the problem with similar conclusions, i.e., it is extremely difficult for small nuclear plants to be cost-competitive with diesel generators and gas turbines, even with high fuel and maintenance costs. The main reason is that previous small nuclear plant concepts were burdened with the same safety requirements and sophisticated technical infrastructure as large nuclear plants. Additional concerns for security and nonproliferation generally have made small, remotely-sited nuclear reactors unattractive. Nevertheless, it may be time to re-examine the “small reactor dream.” There are two reasons: there is greater incentive for reducing the economic disparity between remote and central communities, and the available technology for solving problems unique to small remote reactors has evolved substantially in the last decade. The Nuclear Thorium/Hydride Fuel Battery (NTHFB) is a novel reactor concept based in part on the fuel element depicted in FIG. 3. In this reactor, fission-generated heat may be transferred to gas turbine to generate electricity. This may allow the reactor module to have a simplified design, and to provide electricity, heat or hydrogen to the remote areas, or to serves as backup system to the renewable energy systems such as, without limitation, wind or solar. The NTHFB module may be fabricated and fueled in the factory and transported to the site sealed, for example, without limitation, by welding. The NTHFB may operate for 10-20 years without refueling and with limited reactivity swing. After its operational life, it may be replaced by another module, and the old module may be transported to a nuclear waste repository site or a fuel recycling system. The electricity range of the proposed battery may be 0.1-50 MWe (MegaWatt electricity). The proposed small reactor may be also useful for space exploration program. The proposed Nuclear Battery may provide for various benefits such as, without limitation, a sealed module that may never need to be opened on site, it may provide enough power for 10-30 years, it may be capable of being removed & refueled, or buried underground out of sight without risk to environment, the proposed battery may also be transportable by train, ship, truck, and may in some cases lack mechanical parts in the core to malfunction thus leading to an inherent safety. The proposed battery may also not produce greenhouse gases which may lead to global warming emissions. The proposed Nuclear Battery may further aid in providing inherently safe, secure power to remote communities, hospital, and military bases. The proposed battery may be able to provide steady-state power in the range of 10 to 100 MWe. This power range may be sufficient for communities of 10,000 to 50,000 people. In addition, the battery could provide heat for district heating or for desalination of seawater, or hydrogen production. The battery and associated equipment may be transportable by truck over rural roads. The battery may also be monitored from a central point through a variety of communications methods for example, satellite uplink, cellular phone, or radio. The fuel may be made from ultra-high quality coated particle fuel and may aid in preventing radioactive contamination of power equipment and may also aid in preventing radioactivity releases even in the event of accidents. The proposed nuclear battery may serve as an energy source for a variety of methods and for various purposes including without limitation, electricity through Bryton cycle (with efficiency of 50%), thermoelectric, heat, water desalination, or hydrogen production. In solid hydride fuel, the moderator (hydrogen) may be placed inside the fuel. The hydride fuel may be based on, for example, Uranium, Plutonium and Thorium. Very Light fuel may be beneficial for applications in space, which may include without limitation, power production for propulsion, electronic systems, optics systems as well as electric batteries for stationary settlements, manned and unmanned, on planets or satellites of solar system. Space exploration may benefit from power systems able to provide electricity in the range of hundreds to thousands of KWe (KiloWatt electricity). The light weight fission based system may provide a viable compact technology system that may provide electricity in these ranges of power, and may do so in a safe reliable and economical manner. The present disclosure is directed toward a light nuclear power reactor that may feed an electric engine, for example without limitation, on board a space craft for nuclear electric propulsion or for use at manned or unmanned stationary settlements. The present disclosure may also provide reliable reactor for long-time operability (for example in some embodiments for 15 years or longer) with little or no intervention (with minimum control requirements). The presently disclosed system may be based on, for example without limitation, reactor technology developed for modular high temperature gas cooled reactors (HTGR). In some embodiments the present disclosure may provide for one or more of the following: minimization of overall mass and volume; using medium U-235 enrichment or plutonium for nuclear spent fuel (the use of plutonium may also alleviate nuclear waste problems); electrical power in the range of 100-5000 KWe; operating life time may be up to, or greater than 15 years; low core power density; and minimal use of fluids in the system, or no fluid at all. In various embodiments, the reactor design may be based on the modular version of high temperature gas cooled reactor with, for example, the Brayton cycle. Fuel composition may be based on hydride fuel type, for example without limitation, those used in TRIGA research reactor. In some embodiments, the moderator may be present in both the fuel and the coolant. Use of moderator in the fuel and coolant may impact the neutronic and safety characteristic of this core. The uranium-zirconium hydride fuel, in which the hydrogen moderator may be homogeneously distributed within a fuel, may lead to the large prompt negative fuel temperature coefficient of reactivity and may help to mitigate accidental reactivity insertion events and prevent fuel from melting. In some embodiments, the density of this fuel may be around 8.2 g/cm3 as compare to 10.2 g/cm3 of UO2, which is commonly used today in commercial nuclear power plants. The presently disclosed fuel may save about 20% in weight of the reactor compared to other fuel types. In addition TRIGA-type fuels, on which the presently disclosed fuel may be based, are considered to be inherently safe fuel types which may possess highly thermalized neutrons inside the fuel due to the presence of moderator within the fuel. The presently disclosed fuel formulation may be based on TRIGA fuel compositions, for example without limitation a Pu/ZrHx/Th matrix fuel. This formulation may further reduce the mass of the core by additional 10-15%, due to the lower density of thorium (11.72 g/cc as compare to 19.2 g/cc of uranium). The neutronic behavior of one embodiment of the currently disclosed fuel formulation may be described in Table 1. Table 1 fissile isotopes are presented at thermal neutron energy of 0.0253 eV. Where, a is the ratio of capture-to-fission cross-section, and η is the number of fission produced per neutron absorption, and υ is the number of neutrons produced per fission. The number of neutrons produced per neutron absorption, η, may provide a factor in determining the system's operational life-time and may indicate the ability to produced fissile isotopes for each fissile atom destroyed. Furthermore, in some embodiments, some neutrons may be absorbed in non-fuel material or may leak out from the reactor core, therefore Table 1 also lists the quantity of η-2 which the prospective fissile materials to breed fissile atoms. TABLE 1Basic nuclear data related to fissionable isotopes U-233, U-235, Pu-239 and Pu-241Nuclear DataU-233U-235Pu-239Pu-241σγ (barns)45.598.3269.3358.2σf (barns)529.1582.6748.11001.1α0.0860.1690.3600.354η2.2962.0752.1151.169η-20.2960.0750.1150.169υ2.492.422.882.94Energy per191194200202Fission The currently disclosed fuel formulation may be used in at least two types of hydride based pellets fuel: First type of fuel is Pu/ZrHx/Th fuel matrix as described above, and Conventional microsphere fuel types, for example without limitation, those similar to types used in Pebble Bed reactor or GA prismatic fuel (TRISO, tri-structural isotropic, particles) with highly enriched uranium or weapon grade/power grade plutonium in the form oxide or carbon (for example without limitation; UO2, UC, UCO, PuO2, PuC, PuCO). The fuel microsphere dimensions may be in the same range as conventional TRISO particles, for example without limitation, 300-350 μm. This microsphere fuel may be protected by as many as four carbon based layers. The carbon layers may comprise a low density carbon buffer, a high density pyrolitic carbon layer, a silicon carbide layer, and a high density pyrolitic carbon. The overall microsphere dimensions of the entire fuel particles may be in the range of 750-800 μm. In addition to the TRISO particles described above, microsphere glass, filled with hydrogen, may be used as a moderator (replacing the hydride fuel in form of ZrHx) and to control the reactivity of the reactor core. The hydrogen-containing microspheres may be coated with burnable poison film, such as boron carbide or boron, erbium, etc. A schematic view of one possible embodiment of the microsphere glass is depicted in the FIG. 4. The, at least, two types of microsphere particles may be mixed together randomly or may be layered with graphite powder and then compacted to the cylindrical fuel pellets. In one embodiment, compact cylindrical pellets may be formed in the range of about two centimeters in length and about 1 cm in diameter. These pellet embodiments may be inserted into holes which may, for example, without limitation be drilled in a hexagonal graphite moderator block. This embodiment is illustrated in the FIG. 5. In one embodiment of the hexagonal graphite moderator block, the center hydride fuel rod may be surrounded by six fertile material pellets. In this embodiment, the pellets may be made of thorium, such as for example without limitation, various forms of oxide, carbonate or hydrides (ThO2, ThC, Th2 . . . ). The fuel pellets may be made from this fuel formulation in various ways, such as for example, directly or in the form of TRISO particles and/or microsphere glass filled with hydrogen configuration as describe above. In a further embodiment, where only fuel kernel replaced by fertile materials (thorium or U-238). Then the mixing these fertile fuels with microsphere glasses filled with hydrogen and thin film of burnable poison will be also examined in this study. The productions of the fertile pellets are similar to that of fuel pellets. In some embodiments, a reactor core that may be capable of producing power in the ranges of couple of hundred KWth up to few MWth may be assembled with fuels described above. In some embodiments, the reactor may be comprised of several hundred hexagonal graphite blocks. In further embodiments, holes may be drilled for helium cooling system (FIG. 5 shows six holes, but the number may be greater or smaller in other embodiments). In some embodiments, the active core may be surrounded by reflector. The reflector thickness may vary from about two cm in some embodiments to more than two or less than two in other embodiments. In further embodiments, microsphere glass may be embedded in the reflector to aid reactivity control. TRISO particles may reach 100 MWd/kg burnup without fission gas release or damage. The temperature and pressure will be determined by more detail analysis, including the coupling between the heat source (reactor core) and entire plant balance. In some embodiments, values of 800° C. may be achieved, however further embodiments may achieve temperatures above 900° C. In various embodiments, a reduction in power density may provide for continuous operation time above 20 years, further embodiments may have a duration time of 30 years. In various embodiments, an electrical generator may be used, for example without limitation a thermoelectric generator or a Brayton cycle. Embodiments that include microsphere glass benefit from the control the reactivity, changes in the neutron spectra, or shifting the neutron energy profile during the reactor operation. In some embodiments, the neutron spectrum may be harder (more high energetic neutrons exist in the system). The hardness of the neutron spectrum may be due to presence of a thermal neutron absorber in the system (for example, without limitation burnable poison film). The thermal neutron absorber may tend to increase the absorption rate in the fertile thorium materials (high capture rate of neutrons in the resonance energy range). In some embodiments, depletion of a burnable poison during reactor operation may shift the neutron energy spectrum toward more softer spectrum (more low neutron energy). This shifting may be due to exposing more neutron to slowing down process with hydrogen collisions, for example, without limitation inside the microsphere glasses, this may improve the fuel utilization of the fissile material U-233, generated from neutrons absorption rate in Th-232. Microsphere Glass Technology The filling process of hydrogen may be aided by heating the spheres which may result in the permeability to hydrogen increasing. This heating, may provides the ability to fill the spheres by placing the warmed spheres in a high-pressure hydrogen environment. The hoop stresses achievable for glass microspheres can range from 345 Mpa (50,000 psi) to 1,034 Mpa (150,000 psi). Once cooled the spheres may lock the hydrogen inside. The fill rates of microspheres may be related to the properties of the glass used to construct the spheres, and may also vary with the temperature at which the gas is absorbed (for example without limitation, between 150° C. and 40° C., or greater than 150° C.) and may also vary with the pressure of the gas during absorption process. Fill rates may be directly proportional to the permeability of the glass spheres to hydrogen which increases with increasing temperature. For example, fill rate at 225° C. may be approximately 1 hour and at 300° C. it may be approximately 15 minutes. This increase in hydrogen permeability with temperature may allow the microspheres to maintain low hydrogen losses at storage conditions while providing sufficient hydrogen flow when needed. Engineered microspheres may provide for high density storage of hydrogen. For example, without limitation, a bed of 50 μm diameter engineered microspheres may be able to store hydrogen at 62 Mpa (9000 psi) with a safety factor of 1.5 and a hydrogen mass fraction of 10%. This may produce a hydrogen density of 20 kg/m3. FIG. 6 shows how the hydrogen mass fraction and volumetric density may change under various storage pressures. This figure was taken from NASA report NASA/CR-2002-211867 “Hydrogen Storage for Aircraft Application Overview. TABLE 2Some Non-Limiting Examples of Fuel Elements Zones and DimensionsRadiusDensityZone(cm)Material(g/cm3)Fuel0.622515% reactor/weapon grade Pu, 7.6555% ZrH1.6 30% Th by massGap0.6308HeliumCladding0.6808Zircaloy4 = 0.98 Zr, 0.015 Sn, 6.560.002 Fe, 0.001 CrGraphite0.750Carbon1.75Coolant0.807Helium<0.003Blanket1.707Thorium carbide = ThC10.67 TABLE 3Density and Mass Fraction of Elements in Some Non-Limiting Pu/ZrH1.6/Th MatrixFuelsPuZrH1.6ThDensityPu-238Pu239Pu-240Pu-241Pu-242Wt %Wt %Wt %gram/cm3Wt %Wt %Wt %Wt %Wt %TotalPower Grade Plutonium555407.4527630.053.11.10.60.1557.55537.57.50150.0754.651.650.90.2257.51055357.5508790.16.22.21.20.31012.55532.57.6009120.1257.752.751.50.37512.51555307.6516120.159.33.31.80.4515Weapon Grade Plutonium555407.45290404.680.30.02057.55537.57.50171507.020.450.0307.51055357.55116909.360.60.0401012.55532.57.601279011.70.750.05012.51555307.652059014.040.90.06015 Possible reactivity swing during the burnup for some non-limiting examples is provided in FIGS. 7-10. As can be seen from these figures reactivity may vary between 0.1 to 5%. In some cases, reactivity may be controlled, for example, without limitation, by the use of a burnable poison or automated movement of graphite. Reactor Control In one embodiment of the reactor control design, reactivity may be controlled by dividing the graphite region into, for example without limitation, slices or leaves. In these design embodiments, the slices or leaves may move in and out of the active core region and may accommodate changes in the reactivity. The Effect of Plutonium Content within the Pu/ZrH1.6/Th matrix on the Reactivity As a part of the parametric study we examine the effect of plutonium content inside the matrix fuel. These calculations are presented in the FIG. 11. The graph in FIG. 11 shows that the for weapon grade plutonium a relatively small amount of plutonium quantity is required to achieved a strong neutron source, while for power grade plutonium (plutonium that came out of nuclear spent fuel) at less 15% of plutonium is required to have a strong neutron source for the entire fuel irradiation. The presence of thorium within the fuel indicates that this strong neutron source will be kept even during burnup due to partially compensation of depleted plutonium by building up of U-233, which has better neutronic characteristic than Pu-239 and U-235, in addition to other advantage as it was discussed in my proposal. Safety Aspects of Pu/ZrH1.6/Th Matrix Fuel The reactivity coefficient of fuel temperature (Doppler Effect) is given in the equation below. The results also depicted in the FIG. 12 below for various plutonium grades and quantities of plutonium (within the Pu/ZrH1.6/Th matrix fuel). Table 4 shows also the comparison of the proposed fuel with the common fuels used in LWR and Gas cooled reactor. As can be seen this fuel is safer from reactivity stand point view more than uranium oxide fuel. Since the moderator is within the fuel, the impact of the graphite temperature is insignificant. The proposed fuel can be also considered as inherently safe fuel. δρ δ ⁢ ⁢ T = K ∞ ⁢ ⁢ T 2 - K ∞ ⁢ ⁢ T 1 ( T 2 - T 1 ) * ( K ∞ ⁢ ⁢ T 2 * K ∞ ⁢ ⁢ T 1 ) TABLE 4Comparison with Other Thermal ReactorsBWRPWRHTGR(Pu/ZrH1.6/Th)Doppler (×10−6)−4 to −1−4 to −1−7−55 to −25Moderator (×10−6)−50 to −8 −50 to −8 +1−0.08 to −0.01
	claims	1. An indirect-drive apparatus for inertial confinement fusion utilizing laser beams, comprising:an outer shell,an ablation layer inside the outer shell,a layer of fuel inside the ablation layer,wherein the fuel comprises deuterium-tritium,an inner volume of deuterium-tritium gas inside the layer of fuel,a hohlraum around the outer shell,wherein the hohlraum is located in a position to the receive the laser beams,wherein the hohlraum has an axis,a power supply operably connected to the hohlraum,wherein the power supply employs the hohlraum as a single turn solenoid,wherein the solenoid provides a magnetic field directed to the fuel,an insulating slot in the solenoid to insulate a current supply,wherein the insulating slot is parallel to the hohlraum axis.
	abstract	A radioactive substance is effectively suppressed by an oxide-film removal step of removing an oxide film on a metallic material surface with which a coolant containing the radioactive substance comes in contact, and a titanium-oxide deposition step of depositing a titanium oxide on the metallic material surface after the oxide film has been removed.
052971740	description	DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 is a schematic representation of a nuclear steam supply system 1 incorporating a typical pressurized water reactor (PWR) 3 in which the present invention is implemented to detect dropped control rods and malfunctioning thermocouples. The PWR 3 includes a reactor vessel 5 which forms a pressurized container when sealed by a head assembly 7. The reactor vessel 5 houses a reactor core 9 made up of a matrix of fuel assemblies 11. The fuel assemblies in turn contain a number of fuel rods 13 containing fissionable material. Fission reactions within the fuel rods 13 generate heat which is absorbed by a pressurized reactor coolant, for example light water, which is passed through the core 9. The reactor coolant enters the vessel 5 through inlet 15 and flows downward through an annular down-comer 17 and then upward through the fuel assemblies 11 where it is heated by the heat of the fission reactions. The heated reactor coolant flows upward out of the reactor core and through an outlet 19 into the hot leg 21 of a primary loop 23. The hot leg 21 delivers the heated reactor coolant to a steam generator 25 where feed water is converted into steam which is circulated in a secondary loop 27 to drive a turbine-generator 29 which generates electric power. Reactor coolant is returned to the inlet 15 through a cold leg 31 by a reactor coolant pump 33. Only one steam generator 25 in one primary loop 23 is shown in FIG. 1 for clarity; however, as is known, the typical PWR nuclear steam supply system 1 has two to four primary loops, each with its own steam generator 25 generating steam, and a comparable number of secondary loops 27 driving the single turbine-generator 29. The reactivity of the reactor core 9 is controlled by regulation of the concentration of a neutron absorber dissolved in the reactor coolant by a reactor chemical and volume control system CVCS 34 and by control rods 35 which are inserted into and withdrawn from the reactor core 9 by a rod control system 37 as discussed above. The rod control system 37 inserts and withdraws banks of control rods under the direction of a reactor control and protection system 39. Inputs to the reactor control and protection system 39 include hot and cold leg reactor coolant temperatures measured by temperature sensors such as RTDs 41 and 43, respectively. Additional monitored reactor parameters include core exit temperatures measured at selected fuel assemblies as discussed below by core exit thermocouples 45. An in-core detector system 47 maps power distribution in the core on a periodic basis. The dropped rod detection system 49 utilizes the signals generated by the hot leg and cold leg temperature sensors 41 and 43 and the core exit thermocouples 45 to detect a dropped control rod 35 and generate a signal which is applied to the rod control system 37 to block the withdrawal of control rods. The exemplary PWR 3 is an advanced system which, as discussed previously, is designed to load follow primarily through movement of the control rods rather than through regulation of the concentration of neutron absorber in the reactor coolant. Such reactors have in addition to control rods containing neutron absorbing material, gray rods with more moderate neutron absorbing materials which are provided to maintain appropriate power distribution in the core 9. FIG. 2 illustrates the arrangement of fuel assemblies 11 in the reactor core 9 of the exemplary PWR 3 with the conventional rods 35 depicted by the letter C, and the gray rods 35' indicated by the letter G. For purposes of this description, references to control rods 35 will include both the conventional control rods (C) and the gray rods (G) unless otherwise specified. The control rods 35 in a single fuel assembly form a cluster operated by a common mechanism, while groups of clusters are ganged together electrically to form banks of control rods, as is well known. The arrangement of the control rods into banks is not specified in FIG. 2 as it is not necessary to an understanding of the invention. The core exit thermocouples 45 are mounted in instrumentation thimbles provided in about a quarter of the fuel assemblies 11. As illustrated in FIG. 2, the core exit thermocouples are distributed in a regular pattern across the fuel assemblies 11 so that core exit thermocouples 45 are located in fuel assemblies that are laterally adjacent to every one of the conventional control rods clusters C and all but two of the gray rod clusters G. The only exceptions are two gray rod clusters G on the periphery of the core 9, each of which has one core exit thermocouple in a laterally adjacent fuel assembly. In addition, there are at least two, and more commonly, four core exit thermocouples 45 in fuel assemblies located a chess knight's move from each control rod C and gray rod cluster G location. Hence, a system divided into two completely independent trains of core exit thermocouples can readily be supported. However, the preferred embodiment of the invention adopts a four train system which requires an internal mutual exchange of information among the trains at one point in the computational process. The exemplary PWR 3 utilizes single core exist thermocouples distributed in four trains in the pattern indicated by the numerals 1-4 next to the thermocouples 45 in FIG. 2. In order for the dropped rod detection system of the invention to qualify as safety system grade, the entire system, including the core exit thermocouples 45, must be certifiable as meeting full Class IEEE-603 standards. The temperatures measured by thermocouples 45 are determined primarily by the power distribution. When thermocouple readings exhibit sudden changes, they may be caused by either: (a) a sudden change in the core condition; or (b) thermocouple malfunctions. In the former case, the thermocouple readings change and their spatial distribution must be governed by physical principles. However, in the latter case, a controlling physical principle is not applicable. In order to simplify the evaluation between these possibilities, a new parameter is introduced, the Relative Power Deviation, RD, which is defined by: ##EQU1## where: (L,M)=Thermocouple location .DELTA.T=Temperature rise in assembly PA1 .DELTA.T.sub.O =Temperature rise in assembly at reference condition PA1 .DELTA.T.sub.Avg =Temperature rise across reactor vessel PA1 .DELTA.T.sub.O.sbsb.Avg =Temperature rise across reactor vessel at reference condition PA1 a relatively high positive or negative CI value at the thermocouple location. PA1 smaller but still fairly large CI values (typically about one-fourth of the center CI value) and of opposite sign to the center CI value in most (frequently all) of the four laterally adjacent fuel assembly locations. PA1 noise level, random sign values of CI in the four diagonally adjacent fuel assembly locations. PA1 virtual disappearance of the relatively large, opposite sign values of CI in the four laterally adjacent fuel assembly locations if the RD value at the suspect thermocouple location is given a high lack of confidence value (i.e., ignored), the RD spline fit is rerun, and the CI's reevaluated. PA1 again, a relatively high positive or negative CI value at the location of a control rod or gray rod (in the exemplary reactor thermocouples and control or gray rods never share a common location). PA1 much smaller CI values of the same or opposite sign as the center CI value in the laterally and diagonally adjacent fuel locations. (Whether the CI values are of the same or opposite sign depends on which thermocouples are operational in the near vicinity, i.e., the values of nearby CI's are influenced to some degree by the spline fit algorithm. It should be noted that although RD values are defined herein in terms of temperature, the definitions could also be cast in terms of enthalpy. While RD can be calculated by Eq. 1 only for those fuel assemblies 11 having core exit thermocouples, RD values for all fuel assemblies can be interpolated through use of a surface spline fit, as is well known in the art. Each thermocouple 45 measures an assembly exit temperature, which defines a temperature rise with respect to the inlet temperature. RD represents the percent change in the normalized power distribution, with respect to the reference shape. It is important to note that if the power spatial distribution is unchanged, RD remains at the value zero, regardless of power level. As the power distribution changes from the reference shape, RD values become non-zero. The spatial distribution of RD is governed by the neutron diffusion equation. When the power distribution experiences a large change, by insertion of control rods 35 for example, RD also changes by a large amount; however, its spatial variation is smooth, except at the rod insertion location. This is similar to the behavior of the neutron flux distribution. In order to quantify the smoothness of the distribution, another parameter, the Curvature Index, CI, is introduced. CI is defined as follows in an x-y array of assemblies indexed by the coordinates (i,j): EQU CI(i, 1j)=4*RD(i,j)-[RD(i-1,j)+RD(i+1, j)+RD(i, j-1)+RD(i,j+1)](Eq. 2) Mathematically, CI approximates the negative of the spatial second derivative of RD. When the power distribution changes due to control rod insertion, a large value of CI occurs only at the rodded location. In other locations, the value of CI should be small, in spite of a large variation of RD throughout a wide area. However, if a large value of RD is the result of a thermocouple malfunction, CI of the surrounding assemblies will also be large. In the validation of thermocouple signals, this is the principle used to distinguish true changes in the physical condition of the core from detector malfunctions. When looking for "bad thermocouple" signatures, the most meaningful CI values are those found in the location of the location of the suspect thermocouple and in the four laterally adjacent fuel locations. The characteristics of a "bad thermocouple" signature are: The sign of the center CI value is indicative of the direction of the thermocouple signal error--positive indicates error high. The magnitude of the center CI value is roughly proportional to the magnitude of the signal error. If a moved (including "dropped") control rod is suspected, the CI values in all nine of the fuel locations in the 3.times.3 array centered on the rod location contribute to the signature pattern. The characteristics of the "moved control rod" signature are: The sign of the center CI value reflects the direction of movement of the control rod--a negative center CI value indicates rod insertion. The magnitude of the center CI value is roughly proportional to the amount of reactivity (positive or negative) inserted locally by rod movement. Important keys to the signature differentiation process are two: (1) is the maximum CI value at a thermocouple location or on a control rod/grey rod location? If at a control rod/grey rod location, almost certainly the rod has moved. (2) if the maximum CI value is at a thermocouple location, reprocessing the RD fit and CI evaluation with the suspect RD value discarded will show a recognizable change in the CI values at laterally adjacent fuel assembly locations. An example of the ability of the invention to distinguish between a dropped rod and a malfunctioning thermocouple is illustrated by FIGS. 3, and 4A and 4B which plot the values of CI for the fuel assemblies in the vicinity of a dropped rod, and in the vicinity of a failed thermocouple respectively. Each (-) and (+) represent an arbitrary unit of CI, while the dots represent partial units of random sign. As can be seen from FIG. 3, there is a large negative CI at the location of a dropped rod in the center of the figure in the fuel assembly 11 outlined in heavy line. It will be noticed that the CI's in the laterally and diagonally adjacent fuel assemblies are of either sign and are much smaller in magnitude than the CI of the assembly with the dropped rod. Also, it will be noted that the CI's of the fuel assemblies 360.degree. around and several assemblies away from the assembly with the dropped rod are affected. On the other hand, it can be seen in FIG. 4A that only the CI's for the fuel assemblies laterally spaced on the cardinal axes from the fuel assembly with a failed thermocouple are affected. Most importantly, it can be seen that the CI's for the laterally adjacent fuel assemblies are always of opposite sign from that of the fuel assembly with the failed thermocouple, and that the function falls off more rapidly than in the case of a dropped rod. FIG. 4B illustrates the distribution of CI values calculated from RD values generated from a surface spline fit in which the RD value for the suspect thermocouple is given a high lack of confidence factor. As can be seen, only very small disturbances even at the location of the suspect thermocouple are indicate. Again, the disturbances only extend to the four laterally adjacent fuel assembly locations. FIG. 5 is a block diagram of one of four trains 51 of the dropped rod detector system 49. The illustrated train 51 of the dropped rod detector system 49 includes a front end hot leg RTD signal processor 53. This processor digitizes ohm signals received from the hot leg RTD's 41 (typically three) in the train and converts the digital ohm signals to degrees Fahrenheit. The processor 53 then generates an average T.sub.hot temperature for the train. This average temperature T.sub.hot, is sent to all of the other trains. The processor 53 receives the average hot leg temperatures T.sub.hot generated by all of the other trains and generates therefrom an average, average T.sub.hot signal. Each train 51 also includes a front end cold leg RTD signal processor 54 which similarly digitizes ohm signals from the cold leg RTDs 43 in the train and converts them to degrees Fahrenheit. The processor 54 then generates train average T.sub.cold signal which is sent to all of the other trains. The processor 54 then generates an average, average cold leg temperature T.sub.cold from the T.sub.cold signals from all of the trains. A calculator 55 generates from the T.sub.hot and T.sub.cold signals a .DELTA.T.sub.core signal which is the average temperature rise across the core. The train 51 also includes a front end thermocouple (TC) signal processor 57 which, when the train is in service, digitizes voltage signals generated at each of the thermocouples in the train having coordinates L,M and converts them from millivolts to degrees Fahrenheit. The T/C signal processor 57 also identifies obviously failed thermocouples, both failed open and failed closed. In both cases, the processor 57 sets a lack of confidence, or tolerance, factor C (L,M) used in the surface spline fit to a large value (approximately 1,000, for example). As is well known, the lack of confidence factor C smooths out the surface spline fit by allowing the surface generated to deviate at a data point by an amount which is a function of the magnitude of the lack of confidence factor C at that point. The T/C signal processor 57 computes for each thermocouple a .DELTA.T.sub.T/C (L,M) which is the difference between the thermocouple reading and the average inlet temperature reading, T.sub.cold, provided by the processor 54. These .DELTA.T.sub.T/C (L,M) values and C (L,M) values for the train are sent to all the other trains. Similarly, the processor 57 receives the same values from the other trains and outputs all of them to an RD and CI calculator 59. If the train 51 is not in service, because of train failure or because it is in the test mode, the front end T/C signal processor 57 sets all the .DELTA.T.sub.T/C (L,M) in the train to .DELTA.T.sub.core. In addition, all C (L,M) in the train are set to a large value (approximately 1,000). Again, these values are sent to all the other trains and the corresponding values from all the other trains are received to generate a complete set of values which is sent to the calculator 59. As will be discussed in more detail below, RD and CI calculator 59 utilizes the .DELTA.T.sub.T/C and C signals from the T/C signal processor 57 and the .DELTA.T.sub.core from the calculator 55 together with reference values for .DELTA.T.sub.T/C and .DELTA.T.sub.core to generate the CI values for all of the fuel assemblies 11 which are then used by a CI evaluator 61 which identifies any dropped rods. The dropped rod signal is applied to a safety system grade rod withdrawal stop generation module 63 which generates a rod stop signal for the train. The CI evaluator 61 also identifies failed thermocouples. The front end processor 57, in effect, throws out obviously failed thermocouples by setting their C values to a large number. As a result, the CI evaluator will essentially ignore such thermocouples and concentrate on the questionable thermocouples. This would include those which are not completely failed but are unreliable. The identification of malfunctioning thermocouples is stored in a library 65 together with the large C values for such failed thermocouples. The library 65 also stores the identification of failed thermocouples detected by the processor 57. As discussed previously, the structure 51 illustrated in FIG. 5 is provided for each of the four trains of the dropped rod protection system. As shown in FIG. 6, the rod stop signals generated by the stop generators 63-1 to 63-4 for each of the four trains is input to voting logic 67 which, as is well known in the art, generates a block rod withdrawal signal in the presence of a selected combination of train rod stop signals such as, for example, two out of four, or if one train is out of service, two out of three. The block rod withdrawal signal is applied to the rod control system 37 to prevent withdrawal of the control rods in response to a dropped rod. As shown in FIG. 7, a common reference transmitter 69 provides .DELTA.T.sub.core/REF and .DELTA.T.sub.T/C (L,M).sub.REF values for all thermocouple locations to each of the four trains of the dropped rod protection system. As the banks of control rods move, maps of the CI values across the core will show progressively greater symmetric distortion, reflecting the deviation of the current rod configuration from that under which reference conditions were established. This is perfectly normal, but none the less highly confusing to a computer. Accordingly, it is highly desirable to periodically update the reference values of .DELTA.T.sub.core/REF and .DELTA.T.sub.T/C (L,M).sub.REF. These references values are updated, utilizing a software core surveillance program such as BEACON, which is typically run at, for example, 15 minute intervals. BEACON, which is available from Westinghouse Commercial Nuclear Fuels Divisions, is an analytical tool which calculates a three dimensional nodal power distribution in the core utilizing either excore power range detectors and core exit thermocouples or fixed incore detectors. Since the reference transmitter 69, and BEACON which interfaces with it, are not safety system grade, the reference signals provided by the reference transmitters 69 are subject to human approval as shown functionally by the switch 71 in FIG. 5. If there is reason for the operator to believe that the reference values are not valid, approval of the reference values can be withheld. Also, as discussed in connection with FIG. 11 below, updating of the references can be prevented by a block indicated at 70 when misalignment of a control rod is detected. A method for updating the reference values is to (a) monitor the CI values at symmetric control rod locations of the controlling groups. These values will steadily increase in absolute magnitude as the control rods are moved farther and farther from the positions they were at when the last reference set of values was established. (b) when the monitored CI values reach a preselected absolute magnitude, display to the operator the bank position that corresponded to the still current reference values and an indication of the net direction of bank movement from that position. The operator must then attempt to confirm, using the rod position indicators, that the dropped rod protection septum has successfully tracked the trend of control bank movement. If no alarms to the contrary exist and if he is satisfied that the protection system is at least trending properly, he must authorize replacing the set of reference values that had been in use with the current set of those parameters. The key ingredient here is the operator's verification that the system is apparently working correctly. (c) if one of the "anomalous train behavior" or anomalous rod/bank movement type alarms is generated, an update "block" is activated and the current values can not be made reference values. If the operator is not satisfied that the system is trending properly he must withhold approval to update the reference values. In either event, and assuming that any system malfunctions have been corrected, the operator must verify that the BEACON core surveillance system is running correctly, i.e., no significant differences exist between various measurable aspects of core power distribution such as incore detector signals and the equivalent analytically predicted values. If BEACON is seen to be generating a reliable estimate of core power distribution, the operator can authorize the current BEACON estimates of .DELTA.T.sub.core and .DELTA.T.sub.T/C for all thermocouples to be established as the new set of reference values for the dropped rod protection system. Since BEACON runs continuously on-line it is always current with core operations. (d) if the reference values cannot be updated when needed, administrative controls, such as setting very conservative rod insertion limits to insure that the core will survive one or more dropped rods without damage, must be imposed until the situation is corrected. FIG. 8 illustrates a flow chart for the RD and CI calculator 59. Utilizing the information from the .DELTA.T calculator 55 and the T/C signal processor 57 as well as the reference information from the reference transmitted 69, the calculator 59 computes RD (L,M) at all thermocouple locations using equation 1 as indicated at 71. Using these RD values and the corresponding lack of confidence factors C for those locations, a surface spline fit is used at 73 to generate the relative power deviation RD for all fuel assemblies (i,j). These values are then used to calculate the curvature indices CI (i,j) for all fuel assemblies 11 using equation 2 as indicated at 75. The curvature indices are then ranked by magnitude at 77. The system, of course, also detects normal movement of the control rods. Periodically, such as for example, every 10 minutes, as determined at 79, the status of flags indicating rod movement is stored at 81, the flags are reset at 83 and a timer for the period is reset at 85. The flow chart for the CI evaluator 61 is shown in FIGS. 9A-9C with an insert which is FIG. 10. The CI evaluator cycles through the ranked CIs in descending absolute order as indicated at 87. Only those absolute CI values which are greater than a first limit as determined at 89 are examined. This limit 1 is selected so that only signals above the expected noise level need be examined. When all of the significant CIs have been examined, the CI evaluator is exited and the program transfers to the rod movement analyzer shown in FIGS. 11A and 11B. If the evaluator cycles through all of the CIs, indicating that all of the CIs are above the first limit, which is not a valid condition, "an anomalous train behavior" alarm is generated at 91. For those CI signals above the noise level at locations (i,j) at which there are thermocouples as determined at 93, the CI evaluator performs the routine shown in FIG. 10 which checks for a malfunctioning thermocouple at the cited location by eliminating the reading from the thermocouple. As shown in FIG. 10, the current lack of confidence factor C for the thermocouple in question, and the current curvature index CI array calculated with that thermocouple value, are stored at 97 and 99, respectively. The lack of confidence factor C for the thermocouple in question is then set to a high value at 101 and the surface spline fit for RD at all fuel assembly locations is regenerated at 103. The new RD values are then used at 105 to recalculate the CIs. The CIs in the local region around the thermocouple in question are then evaluated at 107 in the manner discussed above. If a bad thermocouple signature is detected at 107, the originally stored values of C and the CI array are restored at 109 and 111 and the program returns to FIG. 9A at the "yes" branch from the insert. If a bad thermocouple signature is not detected at 107, the C value for the location under examination and the original CI array are restored at 113 and 115 and the program returns to FIG. 9A and the "no" branch from the insert. Returning to FIG. 9A from the "yes" branch from the insert, if the location under examination is a location of a thermocouple in this train as determined at 117, then the confidence factor C for this fuel assembly is changed in the library 65 to a large value, such as for example, 1,000, and a "new bad T/C in this train" message is generated at 121. If the location under examination at 117 is not in this train, a "new bad T/C in another train" message is generated at 123. Whether the fuel assembly being examined has a thermocouple or not, if there is a control rod at this location, as determined at 125 in FIG. 9B, the CIs in the region surrounding this fuel assembly are examined at 127 to determine if they show a moved rod signature. If they do, the absolute value of the CI is examined at 129 in FIG. C to determine whether it is compatible with normal control rod movement or a dropped rod. As soon as a dropped rod is detected, a safety system grade rod withdrawal stop signal is generated at 131 and transmitted to the rod control system at 133 and a "rod withdrawal stop actuated" alarm is generated at 135. If the magnitude of CI at 129 is less than the limit 2, a rod movement flag for the rod at the coordinates R,S is set at 137. This flag contains the CI value and rod group assignment. The program then loops back to FIG. 9A to examine the next fuel assembly location. If the fuel assembly being examined has a CI value above the limit 1, but is not the location of a thermocouple or a control rod, a determination is made at 139 in FIG. 9B as to whether the fuel assembly is within a five by five assembly array of a control rod which has moved. If the fuel assembly is within the proximity of a moved control rod which would explain the CI value, the program loops back to FIG. 9A to examine the next fuel assembly. If this fuel assembly is not within the proximity of an identified moved control rod, or a moved control rod signature was not identified at 127, then a "anomalous train behavior" alarm is generated at 141 before the program loops back to 87. FIGS. 11A and 11B illustrate the flowchart for the rod movement analyzer. As indicated in connection with the description of FIG. 9A, when all the fuel assemblies with significant CI values have been evaluated, this routine is called to analyze detected rod movements. This is done by cycling through the rod banks in the order of insertion sequence as indicated at 143 in FIG. 11A to determine if there are any flags set indicating a movement of a control rod in the bank as indicated at 145. If only one rod movement flag is set in the bank as determined at 147, then an "apparent misalignment of rod (R,S) in bank X" message is generated at 149 and the "reference update" block is set at 151. This prevents changing of the references at 70 in FIG. 7. If the movement of more than one but not all of the rods in the bank have been detected at 153, then an "anomalous movement of bank X rods" message is generated at 155. If there are indications that all of the rods in the bank have moved at 153, and the time has arrived for a bank movement update as indicated at 157, the current rod movement flag data is compared on a rod by rod basis with the stored data on that bank. If recent bank movement is indicated at 159 in FIG. 11B and that movement is indicated as being a withdrawal at 161, a "bank X withdrawn during last.sub.-- minutes" message is generated at 163. For a rod insertion, a corresponding message is generated at 165. The rod movement analyzer does not provide precise information on rod movement, but rather, provides an indication of which rods have moved and in which direction which can be compared with the rod position indicator system. The rod analyzer functions primarily serve as a confidence builder for the operator by providing information on rod movement which can be cross-checked against other systems to provide an indication of the reliability of the system. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular arrangements disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
	description	This application is the U.S. National Stage of International Application No. PCT/US2016/045987, filed Aug. 8, 2016, which claims the benefit of U.S. Provisional Application No. 62/202,390, filed Aug. 7, 2015, which is incorporated by reference herein in its entirety. This disclosure relates to the field of radiographic imaging for medical applications, and more particularly to methods and devices for filtering and shaping a radiation beam based on a shape of a target object. X-ray imaging is a consolidated technology that has reached high levels of excellence during more than a century of refinement. Conventional x-ray imaging systems include many individual components that function together to produce high quality radiographic images with the lowest possible radiation dose. Many x-ray imaging systems use a solid, stationary, beam-shaping filter—traditionally called a static bow-tie filter (see, e.g., FIG. 1A)—to differentially attenuate the central region and the periphery of the x-ray beam to compensate for the shape of the human body (or other object) cross-section, which is usually thicker in the center and thinner in the sides as seen from the x-ray source/focal spot. A traditional static bow-tie filter can serve several function, for example: reduction of the dose to the patient by avoiding unnecessary overexposure of the side of the body, reduction of the scatter coming from the overexposed areas, optimization of the detector dynamic range by avoiding saturation of the detector response in the periphery of the body, and generation of a uniform quantum noise level at substantially every pixel of the image (and correspondingly a uniform signal-to-noise-level). The ideal shape of a static bow-tie filter is determined by the shape and material composition of the imaged object and the x-ray energy spectrum to be used. Imaging systems using a static bow-tie filter are therefore optimized to operate exclusively with a particular object size, shape, orientation, composition, and x-ray energy, and the performance of the system is reduced if the imaging parameters deviate from the ideal design parameters. To partially address this limitation, some clinical systems provide a small set of filters for the user to choose from, such as one filter for an adult person torso, one for head scans, or one for pediatric patients. However, these application-specific filters still fail to match the attenuation profile of most patients and do not provide optimal performance. An imaging modality in which filters are of particular interest is computed tomography. In computed tomography, a filter can significantly reduce the radiation dose and mitigate some undesirable artifacts in the reconstructed images such as cupping. However, the practical performance of a static bow-tie filter is limited because the shape of the filter has to be designed assuming that the patient has a circular cross section and a fixed diameter. In this case, the same filter is used for most patients and for substantially every angle of rotation of the x-ray source around the patient. Since none of the human body parts have a circular cross section, the performance of the system is suboptimal. A technique known as automatic exposure control (or tube current modulation in tomographic imaging) can be used to scale the x-ray intensity used at each individual projection, and therefore compensate for the different maximum attenuation at different angles. However, this technique cannot correct for the different object profiles at different angles. The performance of a static bow-tie filter is further degraded in clinical practice for patients that are not perfectly centered on the axis of rotation of the scanner, which corresponds to the center of the symmetry of a static bow-tie filter. Disclosed herein are adaptive filters, radiographic systems, and methods for controlling the radiation exposure of a target object during a radiographic imaging procedure. An exemplary system comprises a radiation source, a radiation detector, and an adaptive filter positioned between the radiation source and the radiation detector. The system is configured to include a target object positioned between the adaptive filter and the radiation detector such that the target object can be radiologically imaged. The adaptive filter comprises first and second collimators (or just one collimator or more than two collimators) that block substantially all (or at least some) of the radiation that is incident upon the collimators, but allow radiation to pass between the collimators to reach the target object and radiation detector. The system is operable to move the first and second collimators apart from each other during a radiation emission from the radiation source such that the motion of the collimators allows different amounts of radiation from the radiation source to pass between the two collimators to each portion of the target object during the radiation emission. Alternatively, the collimators can be moved from an open position to a closed position during the radiation exposure. The amounts of radiation allowed to reach each portion of the target object can be determined based on the thickness of each portion of the target object, as measured in the direction the radiation travels. The movement of the collimators can be such that the radiation detector receives a generally uniform distribution of radiation through a target object of varying thickness, such as for target objects that have a continuous reduction of thickness from the thickest part to the thinnest part (such as the path from the center to the periphery of a circle). In some embodiments, the system is operable to move the first and second collimators apart from each other in opposite directions along curved paths about a common pivot axis. The common pivot axis can be generally perpendicular to the direction radiation travels. In other embodiments, the collimates move along linear paths toward and apart from each other. In some embodiments, the adaptive filter includes a first motor to drive the first collimator and a second motor to drive the second collimator. For example, the collimators can be positioned between the two motors along the pivot axis. In some embodiments, the system is operable to move the first and second collimators apart from each other from an initial closed position, wherein no radiation is allowed to reach the target object, to a plurality of increasingly further spaced apart positions that allow an increasingly greater portion of the target object to be exposed to the radiation. In some embodiments, the first and second collimators begin to move apart from each other near in time to when the radiation source begins to emit radiation toward the target object, and the first and second collimators reach a maximum separation from each other near in time to when the radiation source stops emitting radiation toward the target object. An opposite closing motion can alternatively be used, where the collimators start fully open and end closed together. The collimators can move in a smooth, continuous motion or in a plurality of small steps such that the collimators stop briefly between each step. For example, the collimators can be moved about a pivot axis in 30 or more steps of less than 1° per step, and 1 millisecond or less can elapse between each step. Each step can be also subdivided in 8 or more smaller micro-steps, and 20 microseconds or less can elapse between each micro-step. The precise control of the collimators' rate of motion (determined by the changes in motor speed, or by the delay between consecutive motor steps), and the synchronization of the motion with the radiation exposure are fundamental components of certain systems and methods disclosed herein. In some situations the effect that the adaptive filter has on the acquired x-ray projection image has to be corrected to recover a faithful radiography of the target object for clinical evaluation. Numerically combining the acquired image with the known spatial exposure time modulation profile produced by the adaptive filter allows the recovery of the radiographic image as it would look like without the filter. The correction process is similar to the standard flat field (or flood field) correction used with regular bow-tie filters. The spatial exposure time modulation profile of the adaptive filter can be experimentally measured by acquiring an image with the filter moving but no object inside the field of view, or it can be computationally estimated based on the pre-determined or measured collimator movement profile. Even in the non-ideal case in which the filter movement does not completely match the target object profile—due to mechanical limitations in the movement mechanism, or an irregular object shape—the corrected image will still keep some of positive features provided by the adaptive filter, such as a more uniform variance in the pixel values, fewer saturated pixels, and reduced object dose. The foregoing and other objects, features, and advantages of the disclosed technology will become more apparent from the following detailed description, which proceeds with reference to the accompanying figures. Disclosed herein are dynamic filters, and related systems and methods, that shape the radiation field using one or more completely (or partially) radio-opaque collimators that move during the image acquisition to modify the exposure time in different parts of the image. This concept is referred to herein as “spatial exposure time modulation.” The concept is different from previous methods used to shape a radiation field that are based on a differential attenuation of the beam in different locations (with a substantially constant exposure time at every location). The disclosed dynamic filters that utilize spatial exposure time modulation are referred to herein as “adaptive bow-tie filters” or simply “adaptive filters.” An adaptive filter provides many advantages of an ideal static bow-tie filter as well as the additional capability to adapt its motion in real-time during x-ray exposure to correspond to the profile of the imaged object (patient specific) instead of assuming a simple, fixed geometry for the object, like a traditional static bow-tie filter. The described adaptive filters have conceptual similarities to a shutter in a photographic camera, but with a fundamental difference that the movable collimators in the adaptive filters can actively change the speed of the collimators during x-ray exposure following a pre-computed acceleration/motion profile to selectively block or attenuate the radiation emitted to different parts of the subject object, for example at the exact moment when the prescribed exposure has been reached. Contrary to a static bow-tie filter (see example static bow-tie system in FIG. 1A), the motions of the disclosed adaptive filters (see, e.g., FIGS. 1B-1E) can be synchronized with the start and/or the end of the x-ray exposure to provide the intended modulation. The synchronization can be implemented in an x-ray imaging system by coordinating the radiation source and the adaptive filter using a controller and/or control software. During the interval of time when the adaptive filter blocks all the field of view, the x-ray exposure to the object can be effectively null, or at least significantly reduced. Thus, an adaptive filter can also be used as an alternative method to implement automatic exposure control. The disclosed adaptive filters and related systems and methods can be configured to reproduce profiles of many object shapes encountered in practical medical imaging applications. For example, a simple embodiment with a single movable collimator can reproduce the attenuation profile of an object with monotonically increasing attenuation, including angular views in a breast tomosynthesis system, without increasing the total exposure time (the total time can be determined by the most attenuating part of the object). The use of two collimators moving in opposite directions can reproduce the profile of an object with an attenuation profile increasing from the periphery to the center, such as an object with a circular or elliptical cross section. More complex attenuation profiles can be reproduced by adjusting the speed, attenuation, and shape of the collimators. The adaptive filters can also be applicable for a fan-beam and for a cone-beam x-ray source. With a conical source, curved collimator edges may be used to modulate the beam. Additionally, a static bow-tie filter can be used concurrently with the disclosed adaptive filter to provide a baseline beam shaping. One or two collimators rotated 90 degrees with respect to the two initial collimators could also be used to modulate the radiation exposure in the perpendicular direction. An example clinical implementation of the disclosed technology to improve the performance of computed tomography scanners includes a combination of software and hardware that compensates for the projection profile of an elliptical cylinder as seen from different rotation angles. The operator of the system (or an automatic system) can measure the principal axes of the ellipse that most closely resembles the shape of the part of the patient being scanned, and determine the location of the geometric center of the ellipse with respect to the center of rotation of the scanner. Using this information and other known parameters (such as the source-to-filter distance, the source-to-detector distance, the x-ray energy spectrum, an estimation of the average attenuation of the object, and the total exposure time) the software can compute the ideal dynamic filter movement sequence that would modulate the exposure time at each individual acquisition angle to compensate for the predicted shape of the ellipse as seen from the rotating source. A mathematical model of the attenuation profile for a target object having any shape can be used to compute an ideal adaptive filter movement profile at each source rotation angle (i.e., at each acquisition angle in a computed tomography scan). The profile of a non-cylindrical target object can change significantly at different angles, and therefore a fixed filter will not be able to adequately compensate for the object attenuation at more than one angle. An adaptive filter described herein can dynamically reproduce several different bow-tie filter profiles to provide improved system performance at every acquisition angle. FIGS. 1B-1D show plan view diagrams illustrating an exemplary radiological imaging system 10 including an exemplary rotational adaptive filter 14 positioned between a radiation source 12 and a test object 16, with a radiation detector 18 positioned behind the test object. FIG. 2 shows an exemplary clinical embodiment of the imaging system 10 configured for breast imaging. FIG. 1E is a plan view diagram illustrating another exemplary radiological imaging system 50 that includes an exemplary linear adaptive filter 54 positioned between a radiation source 52 and a test object 56, with a radiation detector 58 positioned behind the test object. Instead of the collimators of the adaptive filter moving in rotational motion, as in the system 10, in the system 50 the collimators of the adaptive filter 54 move toward and apart from each other in linear motions, such as in a common plane. They can be driven by linear actuators 62A, 62B, such a voice coil actuators, for example, rather than a rotational motor. FIGS. 3A, 3B, and 4 illustrate an exemplary rotational adaptive filter 14 that comprises two stepper motors 26 rotating in opposite directions and two collimators or shields 22 (or other radio-opaque shields) coupled to coaxial motor shafts 24 via retainers 20. In other embodiments, a single motor can control both collimators. In some embodiments, the collimators 22 can block substantially all of the radiation that is incident upon them, as opposed to attenuating the radiation so that a portion of radiation gets through. In other embodiments, the collimators can block a portion of the radiation incident upon them and allow a portion to pass through them. In such embodiments, the algorithm used to compute the motion profile of the collimators can take into account the amount of radiation that travels through the collimators in order to produce the desired beam shaping. Constructing the collimators with an appropriate combination of materials (such as aluminum, copper, carbon, polymers, and/or other materials), the energy spectrum of the radiation traveling through the collimators can be customized to reproduce the energy spectrum of the radiation traveling through a certain radiographic thickness of the patient tissue in a way that minimizes the beam hardening effect artifact (e.g., producing a substantially uniform energy spectrum at substantially every pixel of the detector, both at the center and at the periphery of the object). The motors 26 can rotate the two collimators 22 in opposite directions in order to open or close the field of view window 28 of the object 16 as seen from the radiation source 12. Two separate motor controllers can be used to independently regulate the speed of rotation of each collimator 22. If the device is constructed with stepper motors, the speed of the stepper motors 26 can be effectively modulated by modifying the time period between consecutive micro-step pulses, producing an effectively smooth rotation movement with continuously varying speed. If the device is constructed with motion mechanisms other than stepper motors (such as regular electric motors with or without gears, linear actuators, magnetic solenoids, or shape-memory alloys) alternative electronic speed control methods can be employed. The adaptive filter 14 is located near the exit window of the radiation source 12, and before the object 16 (pre-patient collimation). FIG. 3A shows the adaptive filter 14 with the rotatable collimators 22 completely closed and FIG. 3B shows the adaptive filter with the rotating collimators open to provide a window 28. During the x-ray image acquisition, the accurately timed movement of the edges of the collimators 22 limits the beam width starting from the center of the object 16 towards the periphery to compensate for the known object profile. The radio-opaque collimators 22 can comprise, for example, lead panels. The collimators can have any thickness sufficient for the amount of radiation present, such as a thickness of 2 mm or more, to provide complete or partial x-ray attenuation as desired. The collimators 22 can be mounted in and/or coupled to structural retainers 20 as illustrated. This thickness of collimators can be sufficient to fully attenuate the x-ray beam quality used in an example breast imaging procedure. The retainers 20 can comprise any material, such as a 3-D printed or molded polymeric material, and can couple the collimators 22 to the motor shafts 24. The collimators 22 can also be directly coupled to the motor shafts 24 in some embodiments. The collimators 22 can have straight, parallel opposing edges, as shown, or can have other non-straight edge profiles. The motors 26 can be configured to move the collimators 22 in a step-by-step motion, or in a continuous analog motion. The motors 26 can comprise stepper motors that can move the collimators 22 any rotational distance per step, such as less than 2.0° per step, less than 1.0° per step, and/or from about 0.8° to about 0.9° per step. The motor drivers can be set to divide each full motor step into a plurality of smaller steps, such as 32 micro-steps, for high resolution motion. In some embodiments, the motors can comprise or be coupled to a gearing system that reduces the motor's rotational motion to slower, more precise motions for the collimators. In embodiments with linear actuators driving the collimators toward and apart in linear paths, such as the system 50, the collimators can analogously be moved in incremental linear steps. In some embodiments, the motors, the collimators, the retainers, and/or other system components can include position encoders for implementation of a closed-loop feedback and control system to measure and validate the collimator edge position (e.g., the collimator edge rotation position and angle in a rotational embodiment, or linear position in a linear embodiments). For example, the rotational device 14 shown in FIGS. 3A and 3B can include a position encoder 29. In some embodiments, the shaft of each motor can extend above/below the motor enclosure to allow the optical encoder 29 to accurately measure its rotation. The encoder 29 can be electrically coupled to a control system 30 (see FIG. 4). In some embodiments, end-stop switches (e.g., optical end-stop switches) can be added to the system to reliably position the collimators at a known angle (for example, to position the collimators in a closed position corresponding to angle 0), and to prevent an accidental collision between the collimators (depending on the construction of the device such a collision might or might not be physically possible). In some embodiments, the system can comprise a voice coil actuator that uses an analogic resistor as a position encoder (not optical), which can provide absolute position information at 10 micron resolution for example. FIG. 3C shows a variation of the rotational adaptive filter 14 that includes optical end-stops 40 coupled to the retainers 20 and stationary optical sensors 42 that sense the position of the end-stops 40 to enable a more accurate and reliable positioning of the collimators 22 at high speeds. Coupled with one or more optical encoders, the end-stops and sensors can be used to optically detect the exact position of each collimator in real time and feed the position data back to the controller for more precise control of the collimators. Sensors or encoders that directly measure the real motion profile of the collimators provide information that can be used to validate that the device has moved according to the pre-computed profile, and/or to estimate the degree of deviation between the pre-computed and real profiles. Accurate knowledge of the real device motion, and the corresponding beam shaping, can be important in applications where the radiographic images have to be normalized by a flat field image (e.g., an image of the filter doing the same motion profile but without the object). As shown in FIG. 4, the disclosed systems can also include a control system 30 that includes a microcontroller and stepper motor drivers that are electrically and/or optically coupled to the motors of the adaptive filter. The microcontroller can, for example, calculate and execute a step-by-step movement sequence of the collimators (a movement profile) sufficient to compensate for a particular object shape. The object parameters can be pre-programmed or input by a user, or can be sensed or determined prior to radiological imaging using an optical or non-optical detection system, or using an initial x-ray scout radiograph of the patient, for example. In some systems, the object's profile is determined by an optical system that includes one or more optical cameras, and the determined profile is communicated to the control system 30 for the adaptive filter to determine the movement profile that the collimators will move through during a radiation exposure (whether rotational or linear or otherwise). The system can optionally include a manual movement trigger button 32 (FIG. 4). In other embodiments, the system can comprise automatic triggering, and control of the adaptive filter can be achieved by coupling the control system 30 to the radiation source trigger output. Alternatively, an electronic radiation sensor, such as a diode or phototransistor connected to the filter's microcontroller, could be used to independently detect the start of the x-ray irradiation and trigger the collimator movement. For example, the collimator movement can begin automatically when incoming radiation is detected. FIG. 4 also shows an example of a conventional static bow-tie filter 34 (e.g., made of aluminum) for comparison. Such a static filter is suitable only for a specific object size, distance, orientation, and energy spectrum. The partial attenuation of the beam with a static bow-tie filter can also produce unwanted scatter contamination that is avoided with the disclosed adaptive filter, which can provide a binary 100% or 0% transmission technology. FIG. 1B is a plan view diagram illustrating the system 10 with relevant dimensions and angles labeled. In this view, the adaptive filter 14 is shown in horizontal cross-section with the two collimators 22A, 22B being movable along a circumferential path having a radius Rb. Each collimator 22A, 22B has a curved profile matching the curvature of the circumferential path, and an arc length between 0° and 90°. In some embodiments, the arc length of each collimator is from 0° to 60°, from 0° to 45°, from 0° to 30°, from 30° to 60°, about 45°, and/or other arc lengths. The two collimators can have the same arc length or different arc lengths. As the two collimators 22A, 22B move apart from each other, the angle β for one or both of the collimators increases from 0°. At the same time, the aperture window 28 opens and the angle α increases corresponding to an increasingly wider and wider sector of radiation that is allowed to pass through the adaptive filter 14 to the object 16. The relationship between the angles α and β is dependent on at least the radius Rb of the adaptive filter and the distance sbd between the radiation source 12 and the center axis of the adaptive filter 14. During a radiation exposure, the collimators 22A, 22B can move with a velocity and acceleration that is predetermined based on the cross-sectional shape profile of the object 16, as well as the object's position relative to the source 12 and filter 14. The angles α and β can also depend on the distance sod from the source to the object 16 and/or the distance sdd from the source to the detector 18. FIG. 1C shows the system with the collimators 22A, 22B closed, such that α=0 and β=0 and no radiation passes through the filter 14. FIG. 1D shows the system with the collimators 22A, 22B rotating apart in opposite circumferential directions so that radiation passes through the aperture window 28. In FIG. 1D, the right collimator 22B is at an angle β and the left collimator 22A is at a similar angle, though the two collimators can be at asymmetric positions depending on the shape of the object 16. In some methods, during a single radiation exposure, the collimators 22A, 22B can move from a closed position (FIG. 1C) at the beginning of the radiation exposure to a maximum open position (e.g., FIG. 1D) at the end of the radiation exposure. In other methods, the collimators 22A, 22B can move from a starting open position (e.g., FIG. 1D) at the beginning of the radiation exposure to a closed position at the end of the radiation exposure. In other methods, the collimators 22A, 22B can move from a closed position at the beginning of the radiation exposure to a maximum open position and then back to a closed position at the end of the radiation exposure. For example, the final closed position can be the same as the starting closed position (including a change of direction at the maximum open position), or the final closed position can be with the collimators on the opposite side of the circumferential path from where they started (e.g., they can start closer to the radiation source and end closer to the object). Similarly, in other methods, the collimators can start open, move to or toward a closed position and then move back to an open position at the end of the radiation exposure. If multiple images are acquired sequentially in a short amount of time, for example during a computed tomography scan, the images can be acquired with alternating opening and closing motions of the collimators to avoid repositioning the collimators between exposures. For some objects such as objects with an elliptic cross-section, an accurate beam shaping is more relevant near the edges (where the curvature is large) than in the center (where the curvature is low, and the object thickness is nearly constant). In this situation, the collimators can be moved only for a short distance near the periphery of the object, shaping the beam only in the edge of the object where it is most relevant. With less travel distance for the same exposure time, the peak speed of the collimators can be reduced. More complex movement profiles during an exposure are also achievable with the disclosed technology. In addition, the two collimators 22A and 22B can move independently of each other and in asymmetric movement profiles. The motion of each collimator can depend on the shape of the portion of the object 16 that is behind each collimator. If the object has a symmetric profile, such as a circle or an ellipse that has its major or minor axis aligned with the longitudinal axis of the system (the axis passing through the source point 12 and the rotation center axis of the adaptive filter 14), then the two collimators 22A, 22B may move with motions that are symmetric about the longitudinal axis. However, if the object is not symmetric about the longitudinal axis (such as the object 16 shown in FIG. 1B, or if the object is shifted laterally out of line with the longitudinal axis), then the two collimators can have asymmetric motions with different speed profiles to provide a desirably even radiation dose across the asymmetric object. In addition, with an asymmetric object, the maximum opening angle β max can be different for each collimator. In an extreme example, if the object 16 is located entirely on one side (e.g., to the right side) of the longitudinal axis of the system, one of the collimators (e.g., the left collimator) may not move at all while the other collimator moves during the exposure. For objects that are not aligned with the imaging system central axis, the closed position of the filter can be modified by rotating both motors a certain amount of degrees in the same direction to make sure that the most attenuating part of the object is always irradiated for the longest time. Due to these independent motions available for each of the collimators, and the precisely controllable speed and timing of the collimator motion, the disclosed system can be used for x-ray imaging of a wide variety of object shapes, whether they are aligned or misaligned with the longitudinal axis, and can do so while providing a more even radiation dose across the whole object and/or a more even radiation level received at the x-ray detector 18 behind the object 16. The presence of the adaptive filter 14 in the imaging system 10 modifies the appearance of the x-ray image acquired by the detector 18. The effect of the filter can be corrected to recover a faithful radiography of the target object that can be used for evaluation of the internal object geometry. A possible method to perform this correction would be similar to the standard flat field correction used with regular bow-tie filters. In this process, the acquired image is combined with the known spatial exposure time modulation profile produced by the adaptive filter to recover the image that would have been produced if the filter had not spatially modified the exposure time. The spatial exposure time modulation profile of the adaptive filter can be experimentally measured by acquiring an image with the filter moving without any object inside the field of view (an image typically called a flat field or a flood field). The profile can also be computationally estimated based on the pre-determined collimator movement profile, or based on the actual movement profiled measured during the image acquisition. The collimators 22A, 22B can have various shapes. They can be curved about a center rotation axis as shown, or can have other curvatures, such as three-dimensional curvatures (e.g., spherical curvature), or can be flat plates without any curvature. The collimators 22A, 22B can have straight, vertical edges as shown, or can have straight, non-vertical edges or non-straight, curved edges. The edges may or may not be parallel. For example, for a cone-shaped radiation beam, the collimators can have curved adjoining edges that form a circle, ellipse, or other joint shape from the view point of the radiation source. In some embodiments, the collimators 22A, 22B can move linearly rather than in a circular motion (as in the system 50 shown in FIG. 1E). In some embodiments, the collimators can move in a curved but non-circular motion. In some embodiments, the collimators can move in three dimensions. Regardless of the motion path, whether curved or linear, the principles and methods disclosed herein can be equally, or at least analogously, applied. In some embodiments, two rotational collimators can start on opposite sides of the circumferential path illustrated in FIG. 1B and can move in the same circumferential direction during the exposure. For example, the collimator 22A can start at the position shown in FIG. 1C while the other collimator 22B can start at a position at the rear of the circumferential path that is diametrically opposite from the position of the collimator 22A. As the collimator 22A moves clockwise rearwardly around the left side of the path, the collimator 22B can move clockwise forwardly around the right side of the path. In some embodiments, only one collimator is present, and the single collimator can have at least one position where it fully blocks the view of the object from the radiation source, and can move to another position where it fully exposes the object from the view point of the radiation source. In other embodiments, the adaptive filter can comprise three or more collimators. For example, two pairs of collimators moving at the same time along two perpendicular directions could be used to modulate the beam shape in two dimensions (e.g., in the vertical and horizontal directions). In some embodiments, both of the collimators 22A, 22B are driven by motors located on the same end of the rotation axis, such as both of the motors 26 being above the collimators or both of the motors being below the collimators. In such embodiments, the two motor shafts 24 can be concentrically position with one within the other. In some embodiments, a single motor 26 and/or a single motor shaft 24 can drive both of the collimators 22A, 22B. In other embodiments, linear movement actuators can move the collimators within a plane (as in FIG. 1E). An exemplary adaptive filter technique was evaluated using computer simulations. A Monte Carlo simulation code MC-GPU was used to estimate the radiation dose distribution inside two test objects, with and without the adaptive filter. A typical case representative of a breast computed tomography acquisition was simulated. The mathematical function used to model the adaptive filter spatial exposure time modulation profile in the simulations is the same implemented in the prototype adaptive filter microcontroller's firmware to guide the collimator motion profile. The simulation results presented in FIGS. 5-7 show that the use of an ideal filter that closely matches the imaged object shape and size can produce a reduction of the average dose received by the object between 28% and 68% for a single projection image, and between 28% and 55% for a complete tomographic acquisition. The peak dose in the tomography is reduced more than 50% due to a more uniform distribution of the x-ray flux. The disclosed dynamic filtering scheme proved to work equally well with a cylindrical object and an elliptical object, contrary to a static filter that is not able to compensate for an asymmetric shape. This limitation of static filters is visualized in FIG. 1A by the fact that the angle alpha is fixed (e.g., equal in both sides), and the fan beam aperture is substantially larger than the object. FIGS. 5A-5D are simulation results showing 2D dose distribution in a cylindrical object with a 5 cm radius for a single x-ray projection at 0 degrees with the adaptive filter (5B) and with no filter (5A); and graphs showing corresponding average and peak dose values in a single projection (5C) and the cumulative dose deposited in the object by 360 projections acquired around the object in one degree increments reproducing a computed tomography scan. FIGS. 6A-6C are simulation results showing 2D dose distribution in an elliptical object (5 cm and 3 cm radii) for a single x-ray projection at 0 degrees with the adaptive filter (6A) and with no filter (6B); and a graph showing corresponding average and peak dose values (6C). FIGS. 7A-7C are simulation results showing 2D dose distribution in an elliptical object (5 cm and 3 cm radii) for 360 tomographic projections around the object (source-to-rotation axis distance 50 cm) with the adaptive filter (7A) and with no filter (7B); and a graph showing corresponding average and peak dose values (7C). FIG. 8 shows theoretical x-ray profiles detected by a one dimensional detector behind an elliptical object, with and without the adaptive filter, at 0° and 90° acquisitions. Embodiments of the disclosed adaptive filters can produce a uniform profile at any acquisition angle. The uniform intensity of the image with an adaptive filter can match the lowest intensity obtained without the adaptive filter at the maximum attenuation projection (90°), for example. In clinical practice, the irradiation parameters may be set to produce a valid image at the maximum attenuation projection, and all other less-attenuating projections can receive more radiation than the minimum required. Overexposure can translate into a noise level unnecessarily below the minimum noise acceptable for the task at the cost of increased dose to the patient. With the disclosed adaptive filters, substantially all of the projections can have about the same noise level and the dose is minimized. An additional feature of some adaptive filters is that they can block substantially all, or most, radiation outside the lateral edges of the object, where the signal intensity would be largest without the adaptive filter. Stopping the unnecessary radiation outside the sides of the patient prevents undesired effects on the detector that can reduce the system performance such as detector saturation, optical glare contamination, and backscatter. The adaptive filter of FIG. 3C was tested in a bench-top x-ray imaging system in two different validation experiments. In both, an x-ray source with a tungsten anode operated at 45 kVp, 32 mA, and 500 ms exposure time was used. The source-to-adaptive filter distance was 14 cm, and the source-to-detector distance 100 cm. During each x-ray exposure the adaptive filter opened in 160 ms following the computed movement profile from a closed position up to the expected edge of the object, and then closed in 160 ms more, producing an effective exposure time of 320 ms at the center of the object (and a lower exposure time at the periphery). The opening and closing movements were each divided in 2000 micro-step movements, approximately. In a first experiment, x-ray flood-field images of the filter compensating for the expected attenuation of cylinders with radii 2, 3, 4, 5 and 6 cm were acquired. The images, shown in FIGS. 9A-9F, demonstrate that the adaptive filter can modulate the x-ray beam fluence in a similar way as a traditional attenuating bow-tie for different object diameters. FIG. 10 shows five line profiles taken at the center of the flood-field images of FIGS. 9B-9F, normalized by the profile with the static, open collimators of FIG. 9A. The line profiles show the smooth modulation of the x-ray fluence for the five different sized cylinders generated by the motion of the dynamic collimators. In a second experiment, images of the adaptive filter compensating for a 5 cm radius cylinder composed of a liquid mixture equivalent to 60% adipose, 40% glandular breast tissue were acquired. FIG. 11A shows the imaged object and FIGS. 11B-11D show corresponding x-ray projections. FIG. 11B shows the x-ray projection with just the cylinder object and no filter. FIG. 11C shows the x-ray projection with just the adaptive filter and without the cylinder object. FIG. 11D shows the x-ray profile with both the cylinder object and the adaptive filter. FIG. 12 presents the line profiles at the center of the projections. The flat intensity profile obtained when imaging the cylinder object and the adaptive filter together (labeled “Cylinder and bowtie”) demonstrates that the adaptive filter successfully corrects for the expected attenuation of the cylinder. Dividing this profile by the adaptive filter flood-field profile, the original cylinder profile is recovered, as expected. With the adaptive filter, the sufficient detector dynamic range can be substantially smaller (e.g., maximum pixel intensity 20% of the original maximum intensity), which can be useful to prevent saturation and pile-up in photon counter detectors, the dose to the object can be lower, and the pixel variance in the image can be substantially constant (due to an almost constant intensity detected in substantially every pixel inside the object projection). The adaptive filter can also block irrelevant radiation outside the object to limit the saturation of the detector, and reduce the amount of scatter and veiling glare. Alternative driving mechanisms, such as voice-coil actuators, can also be used to provide the different speed and repeatability characteristics of the device motion. FIG. 13 is a flow chart 100 illustrating an exemplary algorithm for computing/determining an opening movement profile for one of the collimator motors for an exemplary embodiment of the disclosed x-ray system shown in FIG. 1B. At 102, the controller determines a time to move the motor to each step along a full opening movement profile (starting from a closed position) during a single exposure, using various input parameters derived from the geometry of the system set up, the geometry of the object, radiation exposure timing parameters, etc. At 104, the algorithm is advanced to the next iteration corresponding to each step along the opening movement profile. At 106, the controller computes various angles, probabilities, times, and other values that determine the amount of time that the motor has to wait before advancing to the next step, based on the input parameters and times determined at 102 and/or other factors. At 108, the algorithm determines if the thickness of the object at the given step angle is greater than 0 or not, and if so, it returns to 104 to compute the next iteration for the next step. Otherwise, at 110, the controller marks that the collimator has reached the edge of the object, in which case the computation of the opening profile for that motor is complete. The same process can be performed for the other motor. The algorithm 100 can be used to calculate the exact time at which each motor has to advance one step to compensate for the attenuation of the exemplary elliptical object shown in FIG. 1B. The movement profile can be computed independently for each one of the motors, and can be re-calculated whenever the object orientation changes (e.g., for each projection in a computed tomography scan). An equivalent algorithm can be used to compute the movement profile in the opposite direction to close the collimators from a starting open position, or to successively open and close the collimators during the exposure to finish the movement back at the starting position. FIG. 14 is a flow chart 200 illustrating a general algorithm for controlling a radiological imaging system including an adaptive filter as disclosed herein in a typical computed tomography or tomosynthesis application in which multiple images are acquired at different orientations. At 202, the controller reads imaging system parameters and initializes the adaptive filter. At 204, the controller computes the movement profile for each motor for the next object orientation. This step 204 can be performed, for example, by using the algorithm 100 shown in FIG. 13 for each motor. At 206, the motors are rotated until the collimators are closed, if not already. At 208, the system waits for an image acquisition trigger indicating the radiation source is ready to emit radiation for the current object orientation. At 210, the controller moves the adaptive filter in synchrony with the radiation exposure, modulating the speed and position of the collimators according to the computed movement profile during the radiation exposure for that object orientation. This process can then be repeated for each exposure at another object orientation. The movement profiles of each collimator can be actively monitored/audited and/or adjusted if needed during an exposure using a feedback loop that includes position encoders/sensors coupled to the collimators to determine the exact current position of each collimator in live time. Data including the input parameters, system geometry, object shape and other properties, the computed collimator movement profiles, and/or other information can be stored in a database, memory, and/or other data storage system for future use and/or analysis. The adaptive filter 14 can move quickly between each step in a collimator movement profile to provide a smoother, more accurate and effective filtering result. In some embodiments, each collimator moves through at least 30 steps from closed to fully open positions. Each step can be less than 1°, for example. In one example, the opening movement profile for a collimator has 32 sub-steps for each full-step of 0.8°. The entire opening motion (e.g., about 30° divided in 1200 sub-steps) can take 25.0 millisecond or less in some embodiments. In one example, each step takes 20 microseconds or less. In other examples, each step takes 10 microseconds or less. Shorter steps can take less time, and thus including more, shorter steps to achieve the entire opening motion can be desirable. In still other embodiments, the collimators can move in a continuous, analog motion that does not include discrete steps, or can comprise a great many, or substantially infinite, number of very small steps. The disclosed adaptive filter and related systems and methods provide for spatial exposure-time modulation as a means for radiation beam shaping. Other known static or adaptive bow-tie filters are based on the idea of differentially attenuating the intensity of the radiation beam using partially radio-opaque components with a particular shape (e.g., wedges, cylinders). Contrarily, the disclosed technology uses collimators that typically block 100% of the incoming radiation, though some embodiments may block less than 100% of the radiation. The intensity modulation is therefore not produced by a differential attenuation but by a precise timing of the transmission and blocking of the radiation field at different emission angles. Some of the alternative adaptive bow-tie filters and region-of-interest collimators move between discrete exposures of a computed tomography acquisition, but remain static during each radiation exposure. The operation of the disclosed device has to be synchronized with the emission of the radiation from the source using a controller in signal communications with the computerized imaging system. In the fields of photography and radiation therapy there are devices that use moving radiation blockers, such as focal-plane shutters and multi-leaf collimators. However, a unique characteristic of the disclosed technology is that the adaptive filter does not simply translate the collimators at a fixed speed to open or close a field of view, but instead actively modulates the speed and acceleration of the collimator to produce a pre-computed exposure time distribution. Furthermore, an aim of the disclosed technology is to homogenize the radiation arriving at the detector, as opposed to other filter technologies that aim to modulate the dose distribution inside the patient (as it is the case in radiotherapy). Additional advantages of the disclosed technology with respect to static bow-tie filters can include adaptability to patient size, patient off-center position, x-ray energy variation, patient geometric distance variation, and source rotation angle variation relative to the patient. Compared to other dynamic bow-tie designs, the disclosed technology can be adapted to any patient size and patient location inside the imaging system, reduce or eliminate scatter contamination coming from the device, and can produce more flexible and smoother profiles than those that can be generated by filters using discrete attenuating wedges. For purposes of this description, certain aspects, advantages, and novel features of the embodiments of this disclosure are described herein. The disclosed methods, apparatuses, and systems should not be construed as limiting in any way. Instead, the present disclosure is directed toward all novel and nonobvious features and aspects of the various disclosed embodiments, alone and in various combinations and sub-combinations with one another. The methods, apparatuses, and systems are not limited to any specific aspect or feature or combination thereof, nor do the disclosed embodiments require that any one or more specific advantages be present or problems be solved. Integers, characteristics, materials, and other features described in conjunction with a particular aspect, embodiment, or example of the disclosed technology are to be understood to be applicable to any other aspect, embodiment or example described herein unless incompatible therewith. All of the features disclosed in this specification (including any accompanying claims, abstract and drawings), and/or all of the steps of any method or process so disclosed, may be combined in any combination, except combinations where at least some of such features and/or steps are mutually exclusive. The invention is not restricted to the details of any foregoing embodiments. The invention extends to any novel one, or any novel combination, of the features disclosed in this specification (including any accompanying claims, abstract and drawings), or to any novel one, or any novel combination, of the steps of any method or process so disclosed. Although the operations of some of the disclosed methods are described in a particular, sequential order for convenient presentation, it should be understood that this manner of description encompasses rearrangement, unless a particular ordering is required by specific language. For example, operations described sequentially may in some cases be rearranged or performed concurrently. Moreover, for the sake of simplicity, the attached figures may not show the various ways in which the disclosed methods can be used in conjunction with other methods. As used herein, the terms “a”, “an”, and “at least one” encompass one or more of the specified element. That is, if two of a particular element are present, one of these elements is also present and thus “an” element is present. The terms “a plurality of” and “plural” mean two or more of the specified element. As used herein, the term “and/or” used between the last two of a list of elements means any one or more of the listed elements. For example, the phrase “A, B, and/or C” means “A”, “B,”, “C”, “A and B”, “A and C”, “B and C”, or “A, B, and C.” As used herein, the term “coupled” generally means physically coupled or linked and does not exclude the presence of intermediate elements between the coupled items absent specific contrary language. In view of the many possible embodiments to which the principles of the disclosed technology may be applied, it should be recognized that the illustrated embodiments are only examples and should not be taken as limiting the scope of the disclosure. Rather, the scope of the disclosure is at least as broad as the following claims. I therefore claim at least all that comes within the scope of these claims.
042232244	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a charged-particle beam optical apparatus including a specimen holder which is mounted in at least one support member of the apparatus and vibrates when the support member is subjected to shock. 2. Description of the Prior Art Charged-particle beam optical apparatus of the foregoing type are known in the art. See, for example, U.S. Pat. No. 4,058,731 which relates to an electron microscope of the foregoing type. The cause of such vibrations are, among other things, interfering soil vibrations which are first transmitted to the housing of the charged-particle beam optical apparatus and from there via the support of the specimen holder to the latter itself. At the support of the specimen holder, these interfering soil vibrations have on the average an amplitude between 1 and 10 .mu.m. The vibrations are transmitted to the housing and the support in a most pronounced manner if the frequency of the vibrations is in the neighborhood of the resonance frequency of the housing support, namely 1 to 10 Hz, and resonance peaking is then obtained. The reason a resolution of a few Anstroems is possible in electron microscopes in spite of a vibration amplitude of the specimen holder of several .mu.m is the friction coupling of the important parts of such microscopes to each other which vibrate in phase and with the same amplitude. Thus, for example, part of the specimen holder is mounted, friction-coupled, in its support which in turn can be mounted, friction-coupled, on a specimen stage. The specimen stage in turn rests, friction-coupled, on the upper pole piece of the objective lens of the particle beam apparatus. Elongated parts of the specimen holder which are not friction-coupled to adjacent parts, on the other hand, can be excited by the support vibrations to resonance vibrations which lead to a change of position of these parts of the specimen holder relative to the support of the specimen holder. If, for example, the specimen holder consists of a rod which passes through the wall of the electron microscope and is secured there in a first support and the other end of which, situated in the interior of the apparatus, engages a counter-support which is part of an adjustable specimen stage, then the portion of the rod-shaped specimen holder between the two supports can be excited to flexural vibrations in the two directions perpendicular to the rod axis. Additional vibrations can also be excited in the rod direction since at least one support must have spring action in the rod direction for adjusting the specimen holder in this direction without play. The higher the resolution or the accelerating voltage of the electron microscope, the thicker the required magnetic lenses of the microscope must be. This, however, leads to a longer rod-shaped specimen holder and, thus, to a lowering of its resonance frequency. This resonance frequency thereby approaches the resonance frequency of the microscope column, whereby the vibrations of the latter are again transmitted more strongly to the rod-shaped specimen holder. For maximum resolution (1 A), the position of the specimen must not change more than 0.1 A. Since the amplitude ratio of the interfering vibration of the specimen holder to the forcing support vibration is inversely proportional to the square of the lowest resonance frequency to the excitation frequency, it has already been attempted to make the amplitude of the interfering specimen holder vibration small by keeping the vibration frequency of the column low compared to the resonance frequency of the specimen holder vibration. For this purpose, a low-frequency microscope support, for example, an elaborate air spring system, is known. SUMMARY OF THE INVENTION It is therefore an object of the present invention to overcome the aforementioned disadvantages of heretofore known apparatus and to provide an improved charged-particle beam optical apparatus in which the interfering amplitude of the non-frictionally coupled parts of the specimen holder is limited to a degree permissible for maximum resolution in a simple manner and independently of position. These and other objects of the invention are achieved in a charged-particle beam optical apparatus including a specimen holder which is mounted in at least one support member of the apparatus and vibrates when the support member is subjected to shock. The improvement comprises at least one damped supplemental oscillator means coupled to the specimen holder at approximately the point of maximum vibration amplitude of the specimen holder. Attaching the supplemental oscillator, i.e., vibration damper, of the invention to the specimen holder approximately at the point of maximum vibration amplitude, i.e., vibration antinode, contrary to known low-frequency supports through which it has been attempted to eliminate the undesired vibration of the specimen holder by either selecting a location with extremely low soil vibrations or by not allowing the soil vibrations to be transmitted to the charged-particle beam optical apparatus itself by an elaborate air spring system, eliminates the effect of the interfering soil vibrations in the immediate vicinity of the specimen. The principle of such damped supplemental oscillators is known. The resonance frequency of the supplemental oscillator in this invention is in the vicinity of the resonance frequency of the specimen holder. With optimum damping, a flat amplitude response curve is obtained with respect to the interference frequency without pronounced resonance maxima. The interference vibrations of the specimen holder are best suppressed with a given mass ratio .rho.=m.sub.Z /m.sub.S, where m.sub.Z represents the mass of the supplemental oscillator and m.sub.S the mass of the specimen holder which is free to vibrate, when the damping .phi. of the supplemental oscillator and the frequency ratio .alpha. of the resonance frequency of the supplemental oscillator to the resonance frequency of the free-swinging part of the specimen holder are optimally set. According to "Shock and Vibration Handbook" by Harris and Crede, 2nd Ed., 1976, Section 6, pages 1 to 17, optimum damping is obtained in accordance with the equation .phi.=(.mu./2(1+.mu.)).sup.1/2 and the optimum frequency ratio from the equation .alpha. .sub.opt =1/(1+.mu.). Examples of applications of damped supplemental oscillators are bridges and foundations of buildings. Supplemental oscillators are also known in connection with open-air power lines in which case a rod spring is fastened at one end to the open-air line; at the other end the line has a plate as a swinging mass. The amplitudes of the vibrations of this plate are damped by the air resistance exerted on the plate. It is also known to provide for tubular bus bar lines a tri-axial undamped or also damped supplemental oscillator in the interior of the tubular line. See German Pat. No. 20 56 164. In all known examples, the amplitudes of the interference vibrations to be reduced are in the centimeter, or at least in the millimeter range. The purpose of a vibration damper on the specimen holder of a charged-particle beam optical apparatus, on the other hand, is to limit vibration amplitude to a value of a few tenths of an Angstroem. If the interfering specimen holder vibrations occur only in one direction, then only a uniaxially damped supplemental oscillator is necessary to reduce them. Suitable for this purpose is, for example, a leaf spring which can be considered rigid for all practical purposes in the plane of the spring leaf and is resilient only perpendicular to this plane. If interference vibrations along several axes must be suppressed, or at least if their amplitudes are to be reduced, then a separate uniaxial supplemental oscillator can be provided for each axis. It is more advantageous in such a case, however, to use a single, multi-axial supplemental oscillator. For a rod-shaped unilaterally supported specimen holder, it is advantageous if the supplemental oscillator is bi-axial and comprises a spring rod which is unilaterally fastened to such a specimen holder and is surrounded by energy-consuming material, and the resonance frequencies of which are approximately equal in both axes to the corresponding resonance frequencies of the specimen holder. It is assumed in this case that the rod-shaped specimen holder does not vibrate with an objectionable amplitude in the rod direction. The two possible directions of vibration of this specimen holder are in the plane perpendicular to the axis of the rod. The possible directions of vibration of the supplemental oscillator must also lie in the same plane, which is achieved by disposing the supplemental oscillator parallel to the rod-shaped specimen holder. To the extent possible, the supplemental oscillator should be fastened in the vicinity of the free end of the specimen holder, since in the case of a cantilevered rod, a vibration antinode is located at this point and, thus, a maximum amount of energy is transmitted to the supplemental oscillator. If the rod-shaped specimen holder has a rectangular-shaped cross-section, then different resonance frequencies are obtained due to the different spring stiffness in the two principal directions parallel to the sides of the cross-section. For optimum effectiveness of the supplemental oscillator in the two axes, i.e., in this case, in the two principal directions, it has been found to be most advantageous if the supplemental oscillator also has a rectangular-shaped cross-section with approximately the same sides ratio as the specimen holder. With appropriate length and appropriate choice of material, i.e., a specific modul of elasticity and specific weight, the resonance frequencies of the supplemental oscillator in the two principal directions will again be close to the corresponding resonance frequencies of the specimen holder. However, this also means that, with all other parameters entering into the equation for the resonance frequency being constant, the ratio of the area moments of inertia in the two axes of the supplemental oscillator must be approximately equal to the corresponding ratio of the area moments of inertia of the specimen holder. Material suitable for the supplemental oscillator includes all non-magnetic, resilient materials such as alloy steel, bronze, tungsten or vanadium. The material directly surrounding the supplemental oscillator must consume energy when deformed in order to have a damping effect. This material may comprise, for example, natural or synthetic rubber or fluorine-containing polymers such as, for example, polytetrafluoroethylene. A material which develops little gas in a high vacuum is preferred. Besides the mentioned and similar materials, it is also possible to apply to the supplemental oscillator a thick layer of varnish or lead. If the vibrating part of the specimen holder has a circular cross-section, it is then advantageous if the rod forming the supplemental oscillator also has circular cross-section and a tube of elastomer material is shrunk onto the rod. With a correspondingly small mass ratio .mu. of the mass of the supplemental oscillator m.sub.Z and the vibrating mass m.sub.S of the specimen holder, the supplemental oscillator can consist in the simplest case of a spring wire. This wire may, for example, be soldered at one end to a holder which is screwed to the rod. In one embodiment of the invention, a weight is movably disposed on the rod. This weight may comprise, for example, nuts which are screwed with a tight fit on a section of the rod provided with a thread. By means of this additional movable weight, the resonance frequency of the supplemental oscillator can be varied and can therefore be adapted more easily to the optimal conditions for reducing the amplitude of the interference vibrations. If the interfering vibrations of the specimen holder are to be reduced in all three spatial directions, an advantageous further embodiment of the invention is obtained if the supplemental oscillator is tri-axial and consists of a rigid mass which is located in the center of a mass which is resilient in all three axes and consists of energy-consuming material, and if the resonance frequency of the supplemental oscillator in the individual axes is approximately equal to the corresponding resonance frequencies of the specimen holder. Again, a single supplemental oscillator is sufficient. This tri-axial supplemental oscillator can be attached to the specimen holder in a particularly simple manner if the latter is at least partially tubular shaped. The supplemental oscillator is then located inside this tube, the outer rim of the resilient and energy-consuming mass being rigidly connected to the inside wall of the tube. This supplemental oscillator may comprise, for example, a sphere of elastomer material in the center of which a piece of metal is located as the rigid vibrating mass. Likewise, the shape of the supplemental oscillator may be that of a disc which is also constructed of an elastomer and contains in the center a rigid mass comprising, for example, metal. The dimensions of this supplemental oscillator depend on the required resonance frequencies in the different directions. These and other novel features and advantages of the invention will be discussed in greater detail in the following detailed description.
049842595	abstract	An X-ray exposure apparatus comprises an X-ray source, a reflecting mirror for deflecting an X-ray beam radiated from the X-ray source to an object, and mechanisms for rotating the reflecting mirror about an axis of rotation apart from a reflecting surface of the reflecting mirror. The reflecting mirror has such a shape that the angle of incidence remains constant relative to the X-ray beam at given angles of rotation.
	summary
	summary
	description	The present invention relates to a fuel assembly for a pressurized water nuclear reactor, of the type comprising fuel rods which are arranged at the nodes of a substantially regular network having a polygonal outer contour, the fuel rods containing uranium which is enriched in isotope 235 and not containing any plutonium before the assembly is used in a reactor. The invention is used for assemblies which are intended for pressurized water reactors (PWR), in contrast to boiling water reactors (BWR), and whose nuclear fuel is uranium which is enriched in isotope 235. These assemblies are generally designated UO2 assemblies, with reference to the nature of their fuel. This term UO2 is used in contrast to assemblies having fuel with mixed uranium and plutonium oxide which are generally designated MOx assemblies. MOx assemblies of this type allow the plutonium which originates from the reprocessing of UO2 assemblies to be reused. Document FR-2 693 023 describes a MOx assembly of this type. UO2 assemblies and MOx assemblies have different neutron behaviour. In order to nonetheless allow MOx and UO2 assemblies to be simultaneously loaded in the same reactor, this document has proposed that rods with different plutonium contents be used in the MOx assemblies. “Zoned” MOx assemblies are therefore referred to since these assemblies comprise zones in which the rods have different plutonium contents. As has already been indicated above, the present invention does not relate to MOx assemblies but instead applies to UO2 assemblies which do not have zone arrangements of this type, the enrichment in isotope 235 being uniform in this case. It is true that EP-799 484, for example, discloses UO2 assemblies of which a few isolated rods are contaminated with gadolinium and have an enrichment in uranium 235 which is less than that of the adjacent rods. However, these are not zoned assemblies in the strict sense. A UO2 assembly comprises a skeleton for retaining the fuel rods in the nodes of a regular network which generally has a square base. The skeleton comprises a lower end, an upper end, guiding tubes which connect the two ends and grids for retaining the fuel rods. Within the core of a pressurized water nuclear reactor, the UO2 assemblies are arranged beside each other with a slight lateral spacing in the order of 2 mm. This spacing in particular allows the assemblies to be raised and lowered during operations for loading and unloading the core. The cooling and moderation water flows in the gaps which result from this spacing and forms layers of water at that location. The height of assemblies of this type is great and can be up to three or four metres. Owing to production tolerances, the actual thickness of the layers of water could, at least locally, be different from the nominal thickness of 2 mm. Furthermore, assemblies which are placed in a reactor could theoretically become deformed owing to irradiation resulting in, for example, C, S or W-like shapes. Deformations of this type would present a number of problems. During operation, they would make it more difficult to insert the control and stop rod clusters of the nuclear reactor in the guiding tubes. During handling, these deformations would increase the risks of the assemblies becoming hooked together, for example, during operations for loading the core of the reactor. The actual behaviour of the UO2 assemblies could thus be different from that which is desired, at least in mechanical terms. An objective of the present invention is to overcome this problem by providing an assembly of the above-mentioned type which allows a reduction in the risks, in mechanical terms, of the behaviour of the assembly being different from the desired behaviour thereof. To this end, the invention relates to an assembly of the above-mentioned type, characterised in that the rods are distributed in at least: a first central group which is constituted by fuel rods which have a first level of nuclear reactivity, and an outer peripheral layer of fuel rods having a level/levels of nuclear reactivity which is/are strictly less than the first level of nuclear reactivity. According to specific embodiments, the assembly may comprise one or more of the following features, taken in isolation or according to all technically possible combinations: the rods of the peripheral layer are distributed in: a second group of fuel rods which extend along the faces of the outer contour of the network and which have a second level of nuclear reactivity which is strictly less than the first level of nuclear reactivity; and a third group of fuel rods which are arranged at the corners of the outer contour of the network and which have a third level of nuclear reactivity which is strictly less than the second level of nuclear reactivity; the second group extends, for each face of the outer contour of the network of fuel rods, from one corner to the other of the face in question, and the third group comprises only the fuel rods which are arranged in the corners of the outer contour of the network of fuel rods; the different levels of nuclear reactivity of the fuel rods of the various groups are obtained by different masses of uranium 235 in the fuel rods; the different levels of nuclear reactivity of the fuel rods of the various groups are obtained by the fuel rods having different levels of enrichment in uranium 235; the rods of the first group have a first level of enrichment e1 in uranium 235, the rods of the second group have a second level of enrichment e2 in uranium 235 which is strictly less than the first level of enrichment e1, and the rods of the third group have a third level of enrichment in uranium 235 which is strictly less than the second level of enrichment e3; the second level of enrichment e2 is between e1—0.8% and e1—0.2%; the third level of enrichment e3 is between e1—1.8% and e1—0.6%; and the first level of enrichment e1 is between 3% and 6%. The invention also relates to a nuclear reactor core, characterised in that it comprises fuel assemblies as defined above. FIG. 1 illustrates a quarter of the core 1 of a pressurized water nuclear reactor (PWR). This reactor is therefore cooled and moderated by pressurized water. Conventionally, the core 1 has quad symmetry, the axes of symmetry being illustrated with dot-dash lines. The core 1 comprises fuel assemblies 3 which are arranged beside each other with a mutual lateral spacing. Between the assemblies 3, gaps are consequently produced which are filled by the cooling and moderation water. The assemblies 3 are thus delimited laterally by layers 5 of water which extend over the entire height of the assemblies 3. Typically, the nominal thickness of those water layers 5 is 2 mm. The assemblies 3 are UO2 assemblies which have uranium enriched in isotope 235 as nuclear fuel. The fuel of the assemblies 3 does not therefore contain any plutonium before they are used in the core 1. The general structure of the assemblies 3 is conventional and will not therefore be described in detail. It should be noted simply that each assembly 3 comprises fuel rods and a skeleton for supporting and retaining these rods at the nodes of a substantially regular network. In the example of FIG. 2, the regular network has a square base and a square outer contour. The skeleton comprises a lower end, an upper end and guiding tubes 6 which connect these two ends and which are intended to receive the rods of a control rod cluster for controlling the operation of the core 1. The skeleton further comprises grids 7 for retaining the fuel rods at the nodes of the regular network. These grids 7 comprise sets of interlinked plates which together delimit cells 9 which are centred on the nodes of the regular network. Each cell 9 is intended to receive a fuel rod or a guiding tube 6, the central cell 9 itself receiving an instrumentation tube 11. In the example of FIG. 2, the retaining grids 7 comprise 17 cells 9 per side. The outer contour of the network is therefore a square comprising 17 side cells. In other variants, the number of cells 9 may be different, for example, 14×14 or 15×15. The fuel rods are distributed in three groups, that is to say: a first central group whose rods occupy the cells 9 which are shown empty in FIG. 2, a second group of side rods which occupy the cells 9 which are marked with a cross in FIG. 2, and a third group of corner rods which occupy the cells 9 which are illustrated with cross-hatching in FIG. 2. In the example illustrated, the first group comprises 200 fuel rods. This first group occupies the entire rod network, apart from the peripheral layer 13 of rods. This first group therefore corresponds to a square having 15 side cells, including 25 cells 9 which are occupied by the guiding tubes 6 and the instrumentation tube 11. The rods of this first group contain, as nuclear fuel, uranium which is enriched in isotope 235 with a first level of enrichment e1. This first level of enrichment e1 is approximately 4.11%. This enrichment is defined as being the mass ratio of the isotope U235 and the total amount of uranium present in the nuclear fuel of these rods. The second group of rods comprises 60 rods which are distributed over the four faces 15 of the peripheral layer 13. More precisely, for each outer face 15 of the fuel rod network, the 15 rods which are located between the two corner rods of the face 15 in question belong to the second group. The fuel rods of the second group contain as nuclear fuel uranium which is enriched in isotope 235 with a second level of enrichment e2. This second level of enrichment e2 in uranium 235 is approximately 3.7%. The third group comprises 4 rods which occupy the outer corners of the fuel rod network, that is to say, the corners of the peripheral layer 13. The nuclear fuel of the rods of the third group has a third level of enrichment e3 in uranium 235 of approximately 2.8%. Each face 15 of the peripheral layer 13 thus comprises, at the two ends thereof, two rods of the third group and, as for the remainder, comprises rods of the second group. The remainder of the network is occupied by rods of the first group. The rods of the peripheral layer 13 which extends continuously over the periphery of the assembly 3, therefore have lower levels of enrichment than the rods at the center of the assembly. The fuel rods of the first, second and third groups which have similar shapes but different levels of enrichment in isotope 235 therefore contain different masses of isotope 235. The assembly 3 thus has, before use, a “zoned” configuration with corner rods which have a low level of nuclear reactivity, rods which are located along the outer faces 15 between the corners having an intermediate level of nuclear reactivity, and the other rods, which are arranged at the center of the network, which have a high level of nuclear reactivity. As will now be set out, a zoned arrangement of this type allows satisfactory individual neutron behaviour of the assembly 3 to be ensured, even when the actual geometry of the assembly 3 differs relative to the nominal geometry thereof. FIG. 3A thus illustrates the distribution of linear power in a fuel assembly with uranium which is enriched in isotope 235 in accordance with the prior art, that is to say, with a uniform enrichment in all the rods thereof. The thickness of the layers 5 of water which surround the assembly in question is assumed to be homogeneous and equal to 2 mm, that is to say, the nominal value. It should be noted that power values on the Y axis have been standardised relative to the mean linear power in the assembly. This power distribution has been calculated for a depletion of 150 MWj/t which corresponds to the period in the operational cycles of the assembly referred to as the “beginning of the xenon equilibrium period”. This is the time at which the power distribution is supposed to be the most heterogeneous. In the case of FIG. 3A, the power distribution is homogeneous and the form factor which corresponds to the ratio of the maximum linear power in the assembly to the mean linear power within the assembly is approximately 1.053. The form factor value which is approximately 1 confirms that the power distribution is homogeneous and satisfactory. FIG. 3B is a similar chart for the assembly 3 of FIG. 2. As provided in this Figure, the linear power of the rods of the third group, that is to say, at the corners of the assembly, is much lower than that of the central rods of the first group, owing to the low nuclear reactivity level of the rods of the third group. In the same manner, the linear power provided by the rods of the second group located along the outer faces 15 of the assembly 3 is between that provided by the rods of the first group, that is to say, at the center of the assembly 3, and that provided by the rods of the third group of corner rods. The form factor is therefore approximately 1.068. It is therefore slightly higher than in the prior art. However, the value of the power factor remains acceptable and the assembly 3 of FIG. 2 is completely suitable for use in a reactor. FIGS. 4A and 4B correspond to FIGS. 3A and 3B, but with water layers 5 having a homogeneous thickness of 7 mm. As provided, the form factor increases significantly in the case of the assembly according to the prior art (FIG. 4A) to reach a value of 1.186. The power distribution is therefore highly heterogeneous, which must be prevented in a nuclear reactor core. This fact may be explained a posteriori by the fact that the greater thickness of water in the region of the layers 5 retards the neutrons to a greater extent so that the rods which are located at the sides, and even more so those located in the corners, are more exposed to thermal neutrons which are capable of bringing about fissions and therefore generating power. As provided in FIG. 4B, the zone arrangement of the assembly 3 of FIG. 2 allows the linear power to be reduced at the corners of the assembly 3 and along the outer faces 15 thereof in order to achieve a much more homogeneous distribution. The form factor is thus brought to a value of 1.078 which is completely satisfactory. The same phenomenon can be seen for an even greater homogeneous thickness of the water layer 5, for example, 12 mm, as illustrated in FIGS. 5A and 5B. In the case of an assembly according to the prior art, the form factor is thus approximately 1.342, whilst it is approximately 1.181 in the assembly 3 of FIG. 2. Adopting the structure of the assembly 3 of FIG. 2 therefore allows it to be ensured that the power distribution would be more homogeneous if the layers 5 of water were to have a thickness which deviated from the nominal value thereof, albeit only locally, without for all that significantly impairing this distribution if the thickness of the water layers 5 were to correspond to the nominal value. The assembly 3 of FIG. 2 therefore allows the consequences in terms of neutrons to be reduced which the mechanical deformations of the assemblies or their production tolerances could have. In some cases, the assembly 3 may also comprise, in particular in the first group thereof, fuel rods which contain a neutron contaminant such as gadolinium. The rods concerned may then have an enrichment in isotope 235 less than or equal to that of the group to which they belong. In a variant which is illustrated in FIG. 6, the third group comprises, in addition to the four corner rods, the eight rods which are directly adjacent to the peripheral layer 13. The third group of rods thus comprises 12 rods. However, this variant is found to be less advantageous since it more significantly impairs the power distribution if the thickness of the layers of water is equal to the nominal thickness. In specific exemplary variants, the second level of enrichment e2 may be between e1—0.8% and e1—0.2% and the third level of enrichment e3 between e1—1.8% and e1—0.6%. The first level of enrichment e1 is between 3% and 6%, for example. It is also possible in one variant for the second and third group to be constituted by rods which have the same level of enrichment in isotope 235. That is to say, e2 and e3 are equal. The rods having a low level of reactivity then occupy all the peripheral layer 13 and form a group which extends continuously at the periphery of the assembly 3. In yet another variant, the various levels of nuclear reactivity within the various groups of fuel rods may be achieved, not with different levels of enrichment in isotope 235, but instead with different diameters for the fuel rods, which also allows different masses of isotope 235 to be achieved in the rods of the different groups. The rods of the first group thus have a first diameter, the fuel rods of the second group have a second diameter which is strictly less than the first diameter, and the fuel rods of the third group have a third diameter which is less than or equal to the second diameter. The masses of isotope 235 contained in the rods of the first, second and third groups are therefore less, as are their levels of nuclear reactivity. More generally, the fuel rods may be arranged within the assembly in order to form a network having a polygonal outer contour other than a square.
	abstract	A nuclear power system includes a reactor vessel that includes a reactor core mounted therein. The reactor core includes nuclear fuel assemblies configured to generate a nuclear fission reaction. The reaction vessel does not include any control rod assemblies therein. The nuclear power system further includes a riser positioned above the reactor core, a primary coolant flow path, a primary coolant that circulates through the primary coolant flow path to receive heat from the nuclear fission reaction and release the received heat to generate electric power in a power generation, and a control system communicably coupled to the power generation system and configured to control a power output of the nuclear fission reaction independent of any control rod assemblies.
	description	This disclosure relates to the core technology and battery management technology for the kilowatt-class advanced Pressurized Water Reactor (PWR) nuclear power plant, also relates to the integrated optimization of energy saving technology which is combination of the core technology and battery management technology for the kilowatt-class advanced PWR nuclear power plant. Nuclear Power Plant (NPP) is the power generating station using the energy generated from Nuclear Fission or Nuclear Fusion reaction to produce electricity. In order to protect the health of working personnel and the around residents from being irradiated, the design, construction and operation of NPP all follow the defense-in-depth principle, thus multiple protection are provided through the devices and means to ensure the effective control of the output power of the reactors. When various natural disasters, such as earthquake, tsunami, flood, or artificially accidents caused by fire, explosion happen, the fuel assembly of the reactor could be cooled down adequately ensuring the radioactive material not emitting to the environment. The power supply should reflect the defense-in-depth idea either from the configuration or operation since it acts as the source of power. In order to achieve the high reliability of the power supply of NPP, emergency power supplies should be equipped with the especially important power consumption devices or devices of special requirements, multiple and independent configuration should be done to avoid the failure of the emergency power supply in case of the common mode fault. The emergency power supply system and the normal power supply system together constitute the station power system, providing safe and reliable power supply for all the power consumption devices. Plenty of redundant power supplies are equipped with NPP, including dedicated emergency powers, e.g., out-station main power, out-station auxiliary power and emergency stationary diesel, which do their own duties and cooperate mutually. These emergency power supplies are not only in various forms but configured in layers and multiple redundant, providing the reliable power supply for NPP to the maximum degree. Currently, the operation modes of the station power system are as followed: Under the normal working conditions, the power distribution system of the whole station power system are power supplied by the 26 KV busbar of generating set through the high voltage station transformer; When the generating set is in operation, 26 KV busbar is power supplied by the main generator; When the generator is shutdown, 26 KV busbar is down power supplied by the 400/500 KV power grid through the main transformer; In case that 26 KV busbar loses power supply or high voltage station transformer, i.e. out-station main power, 220 KV power grid provides power supply for the safety auxiliary devices which should remain operational through auxiliary transformer to maintain the reactor in thermal shutdown state; In case that the out-station main power and out-station auxiliary lose power supplies, the stationary diesel generator should provide power supply to the emergency ancillary equipment which enables the reactor enter cold-shutdown state; In case that any one set of the emergency diesel generators is disabled, the additional emergency diesel unit take the place to perform the function of the emergency diesel generators, to provide the power supply for the dedicated safety devices, removal of the resident heat of the reactor core and spent fuel pool. However, there are some limitations to the stationary diesel generator units. In case of the power supply failure, as the final emergency power supply, the stationary diesel generator units could not survive the flooding disaster such as floods, tsunami, typhoon, etc., due to its characteristics. In case that the extreme natural disaster exceeding the design standard happens, the stationary diesel units are easy to lose the power supply capability, are incapable of providing the power supply for the removal of the resident heat of the reactor core and spent fuel pool, resulting in disastrous consequences. The present invention aims to overcome the deficiencies of the prior art described above, providing a method and system to supply emergency power to the nuclear power plant. In order to achieve the above objects, according to one aspect of present disclosure, the present disclosure provides a method to supply emergency power to the nuclear power plant, comprising: providing accumulator battery system, which connects to the emergency bus, an online monitoring system monitors the accumulator battery system; in case of loss of power in the electrical equipment of the nuclear power plant, the online monitoring system actuates the accumulator battery system to provide the power supply to the electrical equipments through the emergency bus. According to the other aspect of present disclosure, a system supplying emergency power to the nuclear power plant corresponding to the above method is provided. The method and system to supply emergency power to the nuclear power plant provided by the present disclosure could withstand the conditions beyond design basis like serious natural disasters, such as earthquake plus tsunami, which the current emergency power supply system could not survive. The method and system to supply emergency power to the nuclear power plant provided by the present disclosure takes the design basis and beyond design basis of the nuclear power plant into consideration, enables the nuclear power plant work normally under serious natural disaster circumstance, decrease the melting probability of the reactor core, thus improves the safety of the nuclear power plant. As shown in FIG. 1, the method to provide emergency power supply for the nuclear power plant according one embodiment of the present invention includes, providing accumulator battery system 2100, which is connected to emergency bus 2910, an online monitoring system monitors the accumulator battery system 2100; in case of power loss of the electrical devices of the nuclear power plant, the online monitoring system actuates the accumulator battery system 2100 to provide power supply for the electrical devices of the nuclear power plant through the emergency bus 2910. The electrical devices includes cooling system, electronic instruments, control system, monitoring system or lighting system, etc. In this embodiment, the system to provide emergency power supply for the nuclear power plant is used to provide power supply for the station emergency devices to ensure the normal power supply of the station emergency devices under extreme conditions. In one embodiment, a system corresponding to the method in above embodiment to supply the emergency power for the nuclear power plant is provided, which comprises: accumulator battery system 2100 and online monitoring system electrically connected to the accumulator battery system 2100, which is connected to the electrical devices of the nuclear power plant through the emergency bus 2910. The online monitoring system can be used to monitor the accumulator battery system 2100 and the states of other related circuits and devices; under normal circumstances, the accumulator battery system 2100 can be charged using the proper means like station power grid or external power grid, is thus readily available. Once emergency happens or the other emergency power supplies are damaged or don't work normally, the accumulator battery system 2100 could provide power supply for the relating electrical devices of the nuclear power plant to maintain the relating electrical devices in normal working states, resulting in ensuring the safety of the nuclear power plant effectively. The states of the relating devices such as single battery, converter, battery array, could be inspected in real time via the setting of the online monitoring system, and the automatic intellectual switch functionality of the relating devices could be realized, such as fault diagnosis, self-healing of the relating faulty devices, automatic isolation of the faulty devices, to avoid the fault to expand which may result in system failure. In one embodiment, the system to provide emergency power supply for the nuclear power plant is located in appropriate place which is higher than the sea level and distant from the reactor of the nuclear power plant appropriately. The accumulator battery system is configured to have one set or at least two sets. In case of two sets, each set of the accumulator battery systems is connected to the independent emergency bus respectively; accordingly, the accumulator battery systems could be distributed in different locations. Since the single accumulator battery system could satisfy the design requirements of the nuclear power plant, at least two sets of the accumulator battery systems are configured to ensure that the other accumulator battery system could undertake the power supply under emergency circumstances even though one set of the accumulator battery may be damaged in the extreme natural disaster. Additionally, at least two sets of the accumulator battery systems are set to extend the power supply time at least twice under emergency conditions, thus extending the time limit for removing the emergency and facilitating the safety of the nuclear power plant. In one embodiment, the accumulator battery system 2100 comprises of multiple parallel accumulator system modules 2110 which are used to reach the required capacity. The accumulator system module 2110 is electrically connected to the online monitoring system and to the emergency bus 2910 through the bus rod 2920. In one embodiment, accumulator system modules 2110 are all in parallel connection to the emergency bus rod 2920. In specific applications, corresponding quantity of the accumulator system modules 2110 could be selected according to the design supply duration of the accumulator battery system 2100. The design capacity of the accumulator battery system 2100 should be more than the actual required capacity, even though some accumulator system modules fail or are damaged, these faulty modules could be disconnected from the bus rod 2920 through the online monitoring system, the remaining accumulator system modules 2110 could work reliably and satisfy the actual requirements, ensuring the reliability of the accumulator battery system 2100, thus ensuring the reliability of the power supply under emergency conditions, resulting in achieving the design goal of increasing the safety of the nuclear power plant. The accumulator system modules utilize the modular design which makes the adjustment of the quantity of the accumulator system modules connected to the bus rod 2920 to be convenient. In one embodiment, the corresponding interfaces and wiring could be reserved on the bus rod 2920, on the one hand, the accumulator battery system 2100 could be flexibly designed to be adapted to the different power and capacity requirements according to the actual situation like different loads, on the other hand, the redundant design requirements could be conveniently followed, the amount of the accumulator system modules 2110 could be increased according to the actual situation, and the only thing to do is to connect the additional accumulator system modules to the bus rod 2920, which makes the expansion, upgrade, use, maintenance to be significantly convenient. In one embodiment, accumulator system module 2110 comprises of converter 2111 and battery array 2112, the battery array 2112 is connected to bus rod 2920 through converter 2111. The battery array 2112 includes multiple battery units 2101, the multiple battery units 2101 is parallel to the converter 2111 through DC bus 2930 to increase the capacity of the battery array 2112. Even though one of the battery units fails, the faulty battery unit could be disconnected with the DC bus and the other backup battery unit in normal working state could be parallel to the DC bus, which does not influence the power supply from the battery array, as a result, the operation safety of the nuclear power plant can be further improved. Modular design could be done to the battery array 2112, with which appropriate number of battery units 2101 are connected to the DC bus 2930, on the one hand, the battery array 2112 could be flexibly designed to be adapted to different power and capacity requirements, on the other hand, the redundant design requirements of the nuclear power plant could be followed conveniently. In case that the battery units 2101 are to be added according to the actual situation, the only thing to do is to connect the additional battery units 2101 to the DC bus, which makes the expansion, upgrade, maintenance of the accumulator battery system 2100 to be significantly convenient. With the converter 2111 and online monitoring system configured, the operation modes of the accumulator system modules 2110 can be flexible, different accumulator system module can either work in synchronization or work independently. For example, some accumulator system modules 2110 can be discharged to the load, at the same time, the other accumulator system modules 2110 can be charged or standby. Alternately, one or more accumulator system module 2110 can charge the other one or more accumulator system module 2110, which brings great convenience to maintenance, use and testing. In one embodiment, the battery units 2101 comprise of single batteries which are in series and/or parallel connection. Since the voltage, current and capacity of single battery are all low, the voltage of battery units can be increased in series connection, and current of battery units can be increased in parallel connection. For example, the voltage of single battery is 2V, the design voltage of the battery unit 2101 is 600V, 300 single batteries in series connection are needed to form the 600V battery unit 2101. In one embodiment, a first switch control unit 2160 is configured between the accumulator system modules 2110 and bus rod 2920. The first switch control unit 2160 is connected to the online monitoring system and controlled by the online monitoring system to switch accumulator system modules 2110 automatically. A second switch control unit 2150 is configured between the battery units and converter. The second switch control unit 2150 is connected to the online monitoring system and controlled by the online monitoring system to switch the battery units 2101 automatically. With this design, once the online monitoring system detects that the parameters such as voltage, current, capacity or temperature of any accumulator system module or battery unit is out of the predefined extent, it could switch to the backup accumulator system module or battery unit, thus the system has high reliability. In one embodiment, manual operation mechanism is configured in the first switch control unit 2160, with which the operator could connect or disconnect the accumulator 2110 to the bus rod 2920 manually. In case of unexpected accident, the operator could connect the accumulator system module 2110 to the emergency 2910 manually to provide power supply to the emergency devices, or; manual operation mechanism is configured in the second switch control unit 2150, with which the operator could connect or disconnect the battery units to the DC bus manually. In one embodiment, low-voltage switch 2120 is connected to the bus rod 2920, transformer 2130 is connected to the low-voltage switch 2120, which increases the output voltage of the accumulator battery system 2100 to appropriate level. The transformer 2130 is connected to the emergency 2910 via medium-voltage switch or high-voltage switch. In this embodiment, the output voltage of accumulator battery system 2100 is 380V, which is converted to 6.6 KV high voltage via transformer 2130 to supply the emergency bus 2910. In one embodiment, wherein an accumulator system module could be used to charge another accumulator system module if necessary. Because battery not charging or discharging for long time may influence their performance and life, the accumulator system modules are to be charged or discharged under artificial control in periodic inspection or testing of the devices of the nuclear power plant. With this kind of design, when the accumulator system module is needed to be charged or discharged, the designated accumulator system module is connected to a load for complete discharging, then one another accumulator system module may charge the discharged accumulator system module until fully charged, and so on. For example, accumulator system module A is connected to a load or in other appropriate way to be discharged, accumulator system module B is set to forced discharge mode to charge accumulator system module A, after accumulator system module B is discharged, accumulator system module C is set to forced discharge mode to charge accumulator system module B, and so on, the last discharged accumulator system module could be charged by the internal power grid or in other appropriate way, thus, very small amount of power is needed for charging and discharging of all the accumulator system modules. Especially, in case of MW level of the capacity of the accumulator battery system, the charging cost may be high and it is not environmentally friendly if all the storage battery units are connected to the internal power grid or external power grid for charging. With the above-mentioned embodiment, not only the requirements of inspection, testing and maintenance can be met, but the operation cost could be cut. Additionally, in the charging and discharging process, only a few accumulator system modules are in the state of no power, as long as the number of the accumulator system modules of no power is no more than the design margin of the redundant design, the accumulator system modules in the state of power of the accumulator battery system can meet the requirements of emergency power supply even though the disaster beyond the design basis happens in the process of charging and discharging. So the accumulator battery system can provide power supply for the emergency devices whenever it is in normal working state or in charging and discharging state. The operation modes include but are not limited to the following besides the normal charging and discharging (the following operation modes could be realized with the selection of operation modes of converter): (1) Average charge: when the battery array needs to be charged after the capacity decreases to some extent or the discharging process is accomplished, average charge mode is set for the accumulator system module, which not only makes the battery array store as much power as possible, but facilitates to extend the service life of the accumulator system module. (2) Forced charge: In case that the nuclear power plant faces power loss risk, e.g. online monitoring system detects that the emergency system power supply duration is below the predefined safe value, the forced charging should be done to the battery array to ensure the battery array to store as much power as possible in minimum time, which may influence the service life of the battery array somehow, but ensure the power supply safety of the nuclear power plant to the maximum extent with the extension of the supply time of the accumulator battery system. (3) Forced discharge: under normal working conditions, forced discharge could realize the discharging testing of a accumulator system module and transferring the power to one another accumulator system module; in case of emergency, forced discharge could make the accumulator system module to output power as much as possible until the battery array is damaged. Although the service life of battery array may be shorten, the supply time of the accumulator battery system could be extended to the maximum extent. In one embodiment, the power supply modes from the accumulator battery system to the electrical device of the nuclear power plant started by the online monitoring system include isolated island operation mode and non-isolated island operation mode, the steps to control power supply include: online monitoring system determines plant-wide power failure of the Nuclear power plant, sending isolated island start command to accumulator battery system to enter isolated island operation mode, controlling the accumulator battery system to provide power supply to the power loss devices, wherein the steps of controlling the accumulator battery system to provide power supply to the power loss devices include: controlling accumulator battery system to drive the Hydrotest Pump Turbine Generator Set and its control system to work normally; controlling the accumulator battery system to drive auxiliary feed-water system to work normally; In case that the power grid is retrieved and the grid side voltage of the breaker of the grid is normal and maintains for predefined time, the outlet breaker of the accumulator battery system is switched off, entering non-isolated island operation mode. In the isolated island operation mode, accumulator system provides power supply to the Hydrotest Pump Turbine Generator Set through the emergency bus automatically to ensure the water supply to the main pump shaft seal and power supply to the instrument control system of the main control room, and power supply to the control system of the accumulator system itself to ensure the normal working of the accumulator system. Because the accumulator system enters with-load condition instantaneously when entering isolated island operation mode, the voltage of 380V AC may have sag phenomenon, after the accumulator system passes the self-inspection and feedbacks normal voltage of the power supply, the power switch of the auxiliary watering system could be actuated manually. Once the accumulator enters planning isolated island operation mode, it may be continuously discharged until totally discharged unless the external power grid retrieves. In one embodiment, after the accumulator system enters non-isolated island operation mode, the voltage of the accumulator battery system and the first voltage threshold value are determined, in case that the voltage of the accumulator battery system is less than the first threshold value, the accumulator battery system is controlled to be charged with the external power grid, then the voltage of the accumulator battery system and the second voltage threshold value, in case that the voltage of the accumulator battery system is more than the first voltage threshold value and equal to the second voltage threshold value, the charging of the accumulator battery system could be terminated. In one embodiment, the online monitoring system also inspects the voltage and frequency of the external power grid in real time, determines whether the voltage or frequency of the external power grid reaches predefined protection threshold value or not; in case that any one of the voltage and frequency of the external power grid reaches the predefined protection threshold value, the online monitoring system determines whether the isolated island operation mode starting command is received or not, if not, anti-non-planned isolated island protection signal is output to prevent the accumulator battery system from entering non-planned isolated island mode. In one embodiment, the system to provide the emergency power supply for the nuclear power plant further includes portable accumulator battery system, the portable accumulator battery system includes more than one vehicle-mounted accumulator system modules, the vehicle-mounted accumulator system module includes accumulator battery modules and portable vehicle-mounted carrier, the online monitoring system is further used to connect at least one vehicle-mounted accumulator system module when the total capacity of the accumulator battery system could not afford the load capacity under current working conditions. For example, the portable accumulator battery system is used to charge the stationary accumulator battery system, or the vehicle-mounted accumulator modules are connected to the electrical devices of the nuclear power plant through the emergency bus. The capacity inspection and switch control of the vehicle-mounted accumulator system modules could be performed referring to the stationary accumulator system modules. In one embodiment, portable vehicle-mounted carrier includes vehicle-mounted shell, the battery compartment fixed on the vehicle-mounted shell, at least two wheels or rollers disposed at the bottom of the vehicle-mounted shell. FIG. 2 illustrated a process the online monitoring system monitors the accumulator battery system according to one embodiment of the present invention, the steps are: In step S101, the performance parameters of the batteries in accumulator system are acquired. The performance parameters are at least one of the performance parameters of single battery, the performance parameters of battery units or performance parameters of battery array. The performance parameters include but are not limited to the capacity, voltage, current, temperature, internal resistance of the collected objects. In one embodiment, the acquisition devices are connected to the battery units through the field bus and used to collect the performance parameters of the batteries in accumulator system. In one embodiment, the acquisition devices are connected to the pin type terminal block of the single battery of the accumulator system via field measurement bus to collect the voltage and temperature of each single battery in accumulator system, and the voltage and temperature of the battery units as well. Wherein the acquisition devices are any devices capable of collecting the above-mentioned information, such as acquisition interface board, I/O communication unit or data acquisition card, not limited to the above examples. In another embodiment, the accumulator system includes battery unit monitor 3008 which can monitor and control the state of each battery unit 2101. The battery unit monitor 3008 could be used to read the performance parameters, as shown in FIG. 3. Wherein the battery unit monitor 3008 is the device that does the information collection and communicates with the online monitoring system 3040. In step S102, the total capacity is calculated according to the performance parameters. Because the performance parameters include at least one of the capacity of each single battery, capacity of battery unit, capacity of the battery array composed of plurality of battery units, the total capacity of the accumulator could be calculated according to the performance parameters of the batteries. For example, summation of the capacity of all single batteries could deduce the total capacity of the accumulator system, or summation of the capacity of all battery units could deduce the total capacity of the accumulator system, or summation of the capacity of the battery array could deduce the total capacity of the accumulator system. In step S103, the working conditions of the nuclear power plant is inspected and the load capacity under current working conditions could be calculated according to the working conditions of the nuclear power plant. Wherein the working conditions of the nuclear power plant includes but is not limited to normal operation and power loss mode, reactor shutdown and power loss mode, safety injection and power loss mode, loss of coolant accident of reactor and power loss mode, and extreme accident mode. Wherein the normal operation and power loss mode is that the external power supply is lost when the power of the reactor is between 0% and 100% of the design power; the safety injection and power loss mode is that the external power supply is lost when there is the safety injection signal of starting safety injection system and auxiliary watering system; LOCA and power loss mode is that the external power supply is lost when there is the safety injection signal of starting safety injection system and auxiliary watering system and the signal of starting containment spray system; the extreme accident mode is that the external power supply is lost when there is leakage of radioactive material. In one embodiment, the following steps are followed to inspect the working conditions of the nuclear power plant: inspecting whether the external power supply is lost; inspecting the temperature, pressure and boron concentration of the coolant of the reactor cooling system, the safety injection signal of the safety injection system, and containment pressure signal of the containment spray system; comparing the above inspected signals with the pre-stored correspondence between the working conditions and signals to deduce the current working conditions of the nuclear power plant. In one embodiment, the load capacity under current working conditions is calculated according to the relationship between the working conditions and the load capacity of the nuclear power plant. The relationship between the working conditions and the load capacity of the nuclear power plant is the minimum load capacity provided to the nuclear power plant under each working conditions. For example, Normal operation and power loss mode: LHA (6.6 KV AC Emergency Power Distribution—Train A) bus supplies 5005 KW, LHB bus supplies 4545 KW, i.e., when the nuclear power plant is in normal operation mode, if the accumulator system provides power supply through LHA bus, the load capacity is 5005 KW, if the accumulator system provides power supply through LHB (6.6 kV AC Emergency Power Distribution—Train B) bus, the load capacity is 4545 KW. Reactor shutdown and power loss mode: LHA bus supplies 4705 KW, LHB bus supplies 4240 KW; Safety injection and power loss mode: LHA bus supplies 5230 KW, LHB bus supplies 4770 KW; LOCA and power loss mode: LHA bus supplies 4990 KW, LHB bus supplies 4595 KW; Extreme accident mode: a RIS (Safety Injection System) pump needs power supply of 355 KW, a SEC (Essential Service Water) pump needs power supply of 315 KW, a RRI (Component Cooling) pump needs 600 KW, LNE (Uninterrupted 220V AC Power) 306CR (Marshalling Box) needs power supply of 16 KW. When the nuclear power plant is in extreme accident mode, the load capacity is 355 KW+315 KW+600 KW+16 KW=1286 KW. In other embodiments, the power of each device of the nuclear power plant under various working conditions included in nuclear power plant accident procedures could be read. The nuclear power plant accident procedures regulates what devices should be power supplied, what devices may not be power supplied, how much power should be supplied under different working conditions. The load capacity could be calculated through the summation of the power of each device of the nuclear power plant under current working conditions. In step S104, the remaining discharging time under current working conditions is calculated and output according to the total capacity of the accumulator system and load capacity of the nuclear power plant. With the key operation parameters being inspected in real time, the issues that the key operation parameters of the nuclear power plant are not able to be inspected by the online monitoring system and the operation states especially the accident states can not be determined are solved. According to the predetermined relationship between the working conditions and the load capacity of the nuclear power plant combined with the remaining discharging time of the accumulator system under current working conditions of the nuclear power plant, the issue that the current online monitoring system of the accumulator system can not provide the remaining discharging time of the accumulator system acting as the emergency power supply of the nuclear power plant has been solved. In other embodiments, after the remaining discharging time of the accumulator system under current working conditions is determined according to the total capacity of the accumulator system and load capacity of the nuclear power plant, comprising: uploading the remaining discharging time of the accumulator system, working conditions of the nuclear power plant and total capacity of the accumulator system to the main control room or the emergency command center of the nuclear power plant. With the relating information being uploaded to the main control room and the emergency command center of the nuclear power plant, the remaining discharging time could be monitored under different working conditions by the operators, providing the information support for instant and high efficient and accurate artificial control to the accumulator system and nuclear power generating units of nuclear power plant, which is also the prerequisite to avoid major safety accident or limit the expansion of accident, resulting in greatly improving the operation safety of the nuclear power plant. With the relating information being uploaded to the main control room and the emergency command center of the nuclear power plant, in case that serious nuclear accident happens, the emergency command experts in the emergency command center of the nuclear power plant can also be aware of the power storage status of the accumulator system in time, and make rapid determination of emergency strategy and emergency response plan, which may limit the further deterioration or upgrade of the serious nuclear accident, preventing the people from being hurt by the leakage of the nuclear radiation. In other embodiments, after the remaining discharging time of the accumulator system under current working conditions is determined according to the total capacity of the accumulator system and load capacity of the nuclear power plant, further comprising: uploading the total capacity of the accumulator system to the recorder of the main control room, which could output the total capacity of the accumulator system instantly and display the historical trends of the total capacity of the accumulator system, making the operator of the nuclear power plant to do the comprehensive monitoring of the total capacity in real time instantly and efficiently, resulting in improving the safety of the nuclear power plant. In other embodiments, after the performance parameters of the batteries in the accumulator system are collected, further comprising: determining whether the state of each single battery of the accumulator system is normal or not, in case of determination of being abnormal, locating the physical position of the single battery whose state is abnormal. In one embodiment, when the performance parameters meet at least one of the following conditions, the single battery is determined to be abnormal: the current of DC bus is more than the normal discharging current; the voltage is lower than the cut-off voltage or higher than the allowable voltage; the temperature is higher than the rated temperature. In one embodiment, the address of the abnormal signal representing the single battery whose state is abnormal, the physical position of the single battery whose state is abnormal is located according to the address of the abnormal signal. In other embodiments, after the performance parameters of the batteries in the accumulator system are collected, further comprising: determining whether the battery units are defective or not, in case that the battery units are defective, the faulty battery unit is isolated, for example, disconnecting second switch control unit between the faulty battery unit and DC bus, put the backup battery units into operation. In one embodiment, the steps to determine whether the battery units are defective are as followed: whether the state of each single battery in accumulator system is abnormal or not is determined according to the performance parameters of the batteries in accumulator system; in case that the change of voltage or current of the battery unit is beyond the predetermined allowable error range due to the single battery abnormalities, the battery unit wherein the single batteries are abnormal is determined to be faulty. In other embodiments, after the faulty battery units are isolated, further comprising: resetting the battery units after troubleshooting manually or automatically. In other embodiments, the process further comprises: in case of inspection of abnormal single battery, local alarm is given to the faulty single battery, in case of inspection of faulty battery units, local alarm and remote alarm of main control room are given to the faulty battery units. In other embodiments, the process further comprises: receiving the instructions of main control room and putting the battery units in the accumulator system into operation or cut off the battery units. For example: the structure of the accumulator system is output from the display devices in main control room through the interactive interface, the user could click any one of the second switch control units in the interactive interface to input the command to put the battery unit into operation or to cut off the battery unit, the online monitoring system would close the corresponding second switch control unit according to the command of putting the battery unit into operation from the main control room to control the corresponding battery unit to be put into operation, and open the corresponding second switch control unit 2150 according to the command of cutting off the battery unit from the main control room to control the corresponding battery unit to be cut off. In other embodiments, the process further comprises: monitoring the voltage of the emergency bus, in case that the duration of the power loss of the emergency bus is beyond the predetermined time, the signal to put into operation is generated, the accumulator system is put into operation acting as the emergency power supply according to the system signal of putting into operation. Wherein the system signal of putting into operation is used to instruct that the accumulator system is needed to put into operation as emergency power supply. In one embodiment, the predetermined time could be 9.7 s. In other embodiment, the process further comprises: In case that no signal of putting into operation is generated, and the voltage of the accumulator system modules in accumulator system is lower than the predefined charging voltage, and the converter of that accumulator system module is available, the accumulator system module is charged. Accordingly the battery units in accumulator system could be charged with external power supply instantly, ensuring the accumulator to be full of the power which can handle the five power supplies loss accident and the single battery to be in best condition which makes the accumulator system to reach the maximum design life. In one embodiment, the procedure of putting the accumulator system into operation as the emergency power supply according to the system putting in operation signal includes: Firstly, the first accumulator system module of the accumulator system is put into operation. Wherein the first accumulator system module is the accumulator system module which is put into operation in the first place, which could be any one of the accumulator system modules. In one embodiment, the first switch control unit between the converter of the first accumulator system module and bus rod could be closed directly to put the first accumulator system module into operation. In other embodiments, in order to get better effect of putting into operation, before the first accumulator system module is put into operation, the process further includes: step A: determining whether the converter in the first accumulator system module is available or not, performing step B if available, performing step C if not; step B: putting the first accumulator system module into operation; step C: reselecting one accumulator system module of the accumulator system as the first accumulator system module, restarting to put the first accumulator system module into operation. The accumulator system module put into operation could be ensured to provide power supply normally with the above determination process. In other embodiment, after that the first accumulator system module is determined to be available, the process further includes: monitoring the voltage of the first accumulator system module and determining whether the voltage of the first accumulator system module reaches the cut-off voltage, if not, putting the first accumulator system module into operation, otherwise, reselecting one accumulator system module as the first accumulator system module and putting it into operation. Because the voltage of the accumulator system module reaching the cut-off voltage represents that it is difficult to make the accumulator system module to achieve good power supply, which should not be put into operation, resulting in further improving the supply efficiency and stability of the accumulator system. In other embodiments, when the voltage of the first accumulator system module is determined to not reach the cut-off voltage, the process further includes: determining whether the first switch control unit of the first accumulator system module is closed, if yes, representing the putting into operation is a success, otherwise closing the first switch control unit of the first accumulator system module. After the first accumulator system module is put into operation, the second accumulator system module is to be put into operation, the above step is executed in loop until all the accumulator system modules are put into operation or the accumulator meets the power requirements. In one embodiment, whether the power requirement of the accumulator system is met could be determined through inspecting the power of bus rod, wherein the power requirements of the accumulator system is the total power of the load of the current bus rod. The second accumulator system module is the accumulator system module other than the first accumulator system module. In one embodiment, the process to put the second accumulator system module includes: step A: determining whether the converter of the second accumulator system module is available or not, if yes, performing step B, otherwise, performing step C; step B: putting the second accumulator system module into operation and parallel in the grid. For example, inspecting the frequency and phase angle of the bus rod, and the frequency and phase angle of the second accumulator system module; once the frequency difference and phase angle difference between the second accumulator system module and the bus rod are less than the predefined values respectively, putting the second accumulator system module. Step C: reselecting one accumulator system module as the second accumulator system module and putting it into operation. Through the above determination, the second accumulator system module put into operation could be ensured to provide power supply normally. In other embodiments, in case that the converter of the second accumulator system module is determined to be available, the process further includes: monitoring the voltage of the second accumulator system module and determining whether the voltage reaches the cut-off voltage, if not, putting the second accumulator system module, otherwise, reselecting one accumulator system module from the accumulator system as the second accumulator system module and putting it into operation. The above process could further improve the power efficiency and stability of the accumulator system. In other embodiments, in case that the voltage of the second accumulator system module is determined to not reach the cut-off voltage, the process further includes: determining whether the first switch control unit of the second accumulator system module is closes or not, if yes, representing that the putting into operation is a success, otherwise, closing the first switch control unit of the second accumulator system module. In other embodiments, after the accumulator system is put into operation, the process further includes: in case that the difference between the power of the bus rod and power requirement of the accumulator system exceeding the power of single accumulator system module is inspected, disconnecting a accumulator system module from the accumulator system modules put into operation, the above step is performed in loop until the difference between the power of the bus rod and the power requirement of the accumulator system is less than the power of single accumulator system module. In case that the extreme natural disaster beyond the design basis happens, the nuclear reactor might probably be terminated completely and the station power might be lost, and the transmission lines connected to the external power grid might probably be interrupted due to the wire rod collapse caused by earthquake, typhoon, and the external emergency power supplies don't work either. Under such conditions, comparing with the stationary diesel generator unit as final emergency power supply, the accumulator battery system provided by this application has obvious advantages: firstly, the batteries can word in a completely isolated space not influenced by the disasters. Considering the heat generated by the charging and discharging of the batteries, air-conditioners or water cooling system or heat pipe radiator or hot plate radiator are used to exhaust heat. Specifically, evaporator end of the heat pipe or the hot plate is in close contact with batteries or the appropriate locations, the condensing side is placed outside of the isolated space, the heat pipe or hot plate is through the walls of the isolated space and sealed. The heat generated by the batteries evaporates the fluids in the heat pipe or hot plate and liquefies the steam, thus the heat generated by the charging and discharging of the batteries is exhausted, and the fluids of condensing side flow back to the evaporator through the capillary to form cooling cycle. Secondly, the system to supply emergency power to the nuclear power plant provided by this application could add the accumulator system module to the accumulator battery system or replace the faulty accumulator system module conveniently with the modular design, ensuring the reliable operation even in worst case. Thirdly, for the system to supply emergency power to the nuclear power plant provided by this application, the batteries supply the power instantaneously with no time interval, which is of great significance for the station emergency devices with non-interruption requirements. In one embodiment, lithium batteries are selected as the minimum unit of the power storage for the accumulator battery system, which have advantages such as good safety, small volume, long maintenance cycle, high reliability, long life. In one embodiment, the converter could have functionalities of input reverse protection, Input over-voltage protection, output overload protection, output short circuit protection, overheating protection, ensuring the working safety of itself. The converter could also have functionalities of abnormal grid voltage protection, grid frequency abnormal protection, ground fault protection, islanding protection, ensuring the safety and reliability of the grid connected operation. The system to supply emergency power to the nuclear power plant provided by this application could be started automatically or manually by the operator through being monitored by the online monitoring system, once the trigger condition is achieved, which could take over or complement the other emergency power supplies in the nuclear power plant to provide power supply to the station emergency devices of the nuclear power plant, greatly enhancing the capability of nuclear power plant against the disasters beyond the design basis. According to the safety probability analysis calculation of the nuclear power plant, the baseline total risk CDF (per reactor per year) is decreased to 1.67E-05 from 2.13E-05, which decreases the core meltdown probability of the reactor of the nuclear power plant about 21.6%, providing important guarantee for the safety of the nuclear power plant. Refer to FIG. 4, in one embodiment, the battery module 2101 could comprise of plurality of battery pack 3044 in serial and/or parallel connection in order to facilitate the dismounting and maintenance of the batteries. The battery pack 3044 is a module formed by plurality of single battery 3028 in serial connection. The above-mentioned construction could not only facilitate the connection, combination of the single batteries, packing, transportation and installation, but configure the needed capacity flexibly according to power supply and the safety protection requirements of the nuclear power plant. Each single battery 3028 could be arranged in row or in column serial connection, flexible pad or at least two vertical flexible strips 3030 are disposed between two adjacent single batteries 3028, which are used to prevent the damage caused by the collision between the batteries and complement the machining error of the outer surface of each single battery 3028, while the gap between the flexible strips could facilitate the air circulation to achieve cooling effect. The positive and negative pole 3025 of each adjacent single battery is electrically connected through the flexible connecting piece 3029. Refer to FIG. 5, in one embodiment, the flexible connection piece 3029 includes flexible wire 3033 and metal joint 3036 connected to the two ends of the flexible wire. The metal head 3032 of the positive, negative pole 3025 of each single battery is provided with screw hole, through which the metal joints 3036 at two ends of the flexible connecting piece 3029 could be compacted on the corresponding metal head 3032 with a bolt 3034. After the bolt 3034 is fixed, a insulation cover is used to cover it. In case of the external impact to the entire battery module 2101, such as earthquake, the flexible electric cable 3033 could withstand or absorb the impact to ensure the reliable conductivity, enabling that the battery module 2101 can be used normally. The temperature collection element and voltage collection element are disposed in the single battery 3028, which are used to send the collected temperature and voltage signal of the single battery 3028 to the signal port 3031 of the battery 3028. The signals of the signal port 3031 are sent to the aggregated terminal row of the pin type signal processing module 3027 of the battery pack, the signal processing module 3027 is connected to the battery module monitor 3008 through data transmission line, as shown in FIG. 3. In one embodiment, after the terminal row of the signal processing module 3027 is pulled out, all the corresponding single batteries 3028 are disconnected to the signal processing module 3027, which facilitates the dismounting and changing of the battery pack with the reduction of the reduction of the wiring workload. Refer to FIG. 6, in one embodiment, In order to facilitate the convenient installation and changing, plurality of battery packs could be changeably fixed in a battery cabin 3042 (or battery rack), in which plurality of parallel bulkheads 3024 are provided with to form plurality of battery compartments 3010, the pin type signal processing module 3027 is located in the battery compartment 3010 to facilitate one-time plug of each single battery. Wiring compartment 3011 is vertically disposed on the side of battery cabin 3042, which is used to aggregate and fix various cables to prevent the cables from being scattered and intertwisted and short circuit. The battery module monitor 3008 is located inside the cabin body to facilitate the operator to observe the state parameters of each single battery of battery module 2101, and data could be transferred between the battery module monitor 3008 and online monitoring system via CAN bus communication. Refer to FIG. 6, in one embodiment, the battery pack is first placed in battery basket 3012 having a opening at one end, then mounted on the battery compartment 3010. The battery basket 3012 is provided with a elastic piece in flexible contact with the outer side of the battery pack, which is used to prevent the battery pack mounted in the battery basket 3012 from shaking due to shock. The battery basket 3012 is provided with the second connecting piece to connect the fastening strips 3019 which is used to fasten each single battery arranged in the battery basket 3012. In order to facilitate the battery basket 3012 to be fixed in the basket compartment 3010, the fixation ear 3016 is provided on the back above the battery basket 3012, which is fixed on the localization ear 3015 of the battery compartment; fixation ear 3018 is provided in the front middle position of the battery basket 3012, which is fixed on the localization ear 3017 inside the battery compartment; there are four feet 3020 at the two ends of the bottom of battery basket 3012, which are fixed on the force bearing beam 3021. In order to make the battery pack in the battery basket 3012 not to move up and down, the battery compartment is provided with depression bar 3013 inside which is fixed on the angle steel 3014 to compress the battery pack tightly. To facilitate the change and maintenance of the battery pack, the battery basket 3012 is provided with at least two wheels 3022 (or rollers) at the bottom; the battery pack in the battery compartment could be extracted or introduced conveniently. The cabin body of the battery cabin includes four pieces of U-steel 3023 located inside the four vertical edges and steel frame structure on the two sides of the battery compartment, and reinforced steel beam welded to the side of the cabin body; the across corners of the reinforced steel beam are welded to the adjacent U-steel to improve the structure stability of the battery cabin, even under harsh conditions such as high intensity earthquake, the reliability of the battery pack inside the battery cabin could be ensured. Bulkhead 3024 is fixed in connection with the four U-steels via retaining pieces, which could ensure reliable fixation even under extreme conditions such as earthquake. In one embodiment, the retaining pieces use the bolts above 6.8 level to ensure the structure reliability. In other embodiments, the battery pack could be placed inside a shell, and then mounted into the battery compartment. In order to make the battery pack mounted in the shell not to shake due to the vibration, flexible pieces in flexible contact with the outer surface of the battery pack is equipped with the inner wall of the shell. In order to fix each single battery more tightly, the shell is provided with a end cap which is used to depress and fix the single battery inside the shell tightly. In order to improve the cooling performance of the battery module inside the shell, heat radiating grooves are disposed at the side and bottom of the shell. The first connecting piece is equipped at the two sides of the shell which could be fixed to the battery compartment; each battery pack could be fixed inside the battery compartment with the first connecting piece. To facilitate the change and maintenance of the battery pack, the shell is provided with at least two wheels or rollers at the bottom, the battery pack in the battery compartment could be extracted or introduced conveniently by the operator. Refer to FIG. 7, in one embodiment, the battery cabin 3042 is provided with mounting component at the bottom, the cabin body of the battery cabin is fixed to the cement platform 3026 in which there are embedded parts, the embedded parts are provided with screw holes. The mounting component at the bottom of the battery cabin is locked tightly into the screw holes of the embedded parts via fasteners. In one embodiment, the fasteners are bolts with anti-loosing spring washer to facilitate the reliability of the construction. The battery cabin 3042 is provided with lifting ears 3005 at the top to facilitate the lifting in installation phase. The battery cabin 3042 is provided with cable holes 3006 at the top which are used to fix the cables. The cable holes 3006 are blocked with fireproof material. There are doors 3043 in the front and at the rear end. After the two doors are open, the operations in two directions could be performed to the devices inside the battery cabin 3042. The doors 3043 are provided with upper and lower locking handles. There are air admission shutters at the rear end of the battery 3042 and exhaust fan on the top of the battery 3042 to exhaust the heat inside the cabin, improving the cooling performance of each battery module 2101 and the service life of the batteries. Refer to FIGS. 8 and 9, in one embodiment, the accumulator battery system 2100 of present application is fixed inside a storage device which is waterproof, shockproof and temperature adjustable to ensure its reliability. The storage device includes a shockproof accommodating cavity which can be cast by reinforced concrete or made of metal material or the combination of the shockproof, press-proof, waterproof material. The structure intensity of the cavity should meet the requirement of maintaining integrity under the conditions of flooding or impact of other objects. The cavity is provided with flame resist material at the inner surface which is used to prevent the cavity from being damaged by the fire. The accommodating cavity has the cavity accommodating the battery cabin 3042, converter 2111and monitoring devices 4301 used by the online monitoring system 3040, wherein the cavity accommodating the battery cabin 3042 is sealed around to withstand flooding and impact of other objects. The storage location of the converter 2111 and monitoring devices 4301 is higher than the storage location of the battery cabin 3042. For example, the accommodating cavity is divided into two layers, wherein the first layer cavity 4001 located on the lower layer is used to accommodate plurality of battery cabins 3042, while the second layer located on the upper layer is further divided into two cavities 4003, 4004, wherein the cavity 4004 is used to accommodate the converter 2111 electrically connected to the battery cabin 3042 and distribution devices 4402. The converter 2111 has the following functionalities: (1) AC-DC conversion function; (2) function to increase or decrease the electrical energy; (3) distribution for the accumulation system itself; (4) receiving high voltage of external grid during normal operation and converting to AC of voltage level required by the converter station; (5) In case that the external grid needs power supply, converting AC output from converter 2111 to high voltage. For anti-earthquake purpose, the converter 2111 is provided with impact-resist components as internal components, spring or plastic gasket are added to the fixation bolts of the plates and components to avoid being loosened under earthquake or vibration conditions. In order to ensure the anti-earthquake performance of the devices, the battery cabin 3042, converter 2111 and monitoring devices 4301 are provided with plurality of flexible electrical connection interface. The other cavity of the second layer is a control chamber to accommodate the monitoring device 4301 which is used to monitor the state of the entire accumulator system and operate and adjust the input and output of the accumulator power. Moreover, maintenance room could be equipped to accommodate tools and backup battery modules. The accommodating cavity could be provided with ladder 4002 outside which is used to facilitate the personnel to access the second layer. The first layer cavity 4001 used to accommodate the battery cabin 3042 is provided with access opening at the sidewall to facilitate the transportation of devices and operator access. The access opening is sealed with waterproof gate 4104 to make the first layer cavity to form an enclosed cavity, preventing the battery cabin 3042 and other electrical components from being damaged by the flooding and mudslides caused by disaster. In other embodiments, as shown in FIG. 10, the access opening could be located on the top of the first layer cavity 4001, the height of which should ensure that the flooding, tsunami or mudslides could not enter under the disaster condition. On the top of the access opening, there is a device transportation compartment 4009, on the top of which a lifting mechanism 4901 is equipped to lift the battery cabin 3042 into or out of the first layer cavity 4001. The first layer cavity could be provided with ladder 4001 inside which is used to facilitate the operator or maintenance personnel to access the access opening. The first layer cavity is provided with base 4102 at the bottom which is higher than the bottom surface to fix the battery cabin 3042, e.g. the cement platform 3026 as shown in FIG. 7, preventing the battery cabin from being damaged by water and impurity at the bottom. Elastic pad could be added to the joint face of the base 4102 and the battery cabin 3042 to fix the battery cabin on the base 4102 tightly, which is also used to avoid the mutual impact of the base 4102 and the battery cabin 3042, resulting in ensuring the safety and reliability of the entire accumulator system. In one embodiment, the base 4102 could use high strength, corrosion resistance, strong anti-earthquake performance materials, which also needs to be in good attaching with the bottom surface of the first layer cavity. Moreover, the base could comprise of plurality of lugs combination, each of the lugs could be frustum-like structure, such as truncated cone, Polygonal frustum or trapezoidal cone, forming a drainage slope, the upper surface of the lug is non-slip surface to facilitate the fixation of the battery cabin. In another embodiment, the base could comprise of base stand having plurality of hollow areas, the bottom of the battery cabin is fixed to the solid part of the base stand. In case that there are water infiltrating into the first layer cavity due to the flooding, tsunami, or mudslides, the hollow area facilitates the overflow of the water, thus improving the reliability of the battery cabin. A water pit is disposed on the ground of the first layer cavity 4001. In order to avoid too much water spreading to the ground, drainage devices 4108 are equipped, which are used to extract the water into the pipe 4130 extending outside the accommodating cavity to drain via the control valve 4106. To ensure the safety of the battery cabin under fire condition, a plurality of nozzles which could inject water in fire are disposed on top of the location where the battery cabin 3042 are mounted, each nozzle 4105 could be disposed on a water pipe fixed on the top of the first layer cavity 4001. The water pipe has two branches, one of those is connected to the water tank 4007 located outside the accommodating cavity with a pump 4601 and control valve 4008 equipped, the other branch extends to the water pit 4109, whose inlet is placed into the water pit 4109, with a control valve 4107 equipped. Through the water pipe 4158, the water in water tank 4007 could be introduced to the nozzles to extinguish the fire. In case that the water in water tank 4007 is not enough, the water in water pit 4109 could be introduced to the nozzles to extinguish the fire via control valve 4107. At that time, the water pit 4109 could also be used to collect the water from the nozzles which can be backup fire water. Filter devices could be equipped in the water pit 4109, the spray water and stagnant water could be filtered through coarse filter and enter the water pit 4109, then be filtered through fine filter and enter the inlet of the pump 4108, which ensures the reliability of the pumping equipment. The first layer cavity should be ventilated and heat dissipated to ensure the normal operation of the battery cabin 3042 wherein and increase its service life. The ventilation is mainly used to exhaust the indoor gas, and adjust the room temperature as well, maintaining the temperature of the first layer cavity to be between 10° C. and 30° C. The first layer cavity is provided with a waterproof vent 4005 at the top, which is connected to ventilation device 4501 located outside of the accommodating cavity. Ventilation exhaust pipe should be introduced outside the accommodating cavity to the location higher than the top. The air inlet should be equipped with air filtration device to ensure the battery cabin to be in normal working state. In order to ensure the normal operation of the electrical devices located inside the two cavities 4003, 4004 of the second layer, air conditioner could be equipped outside the accommodating cavity used to do heat dissipation for the two cavities 4003, 4004 of the second layer. Refer to FIG. 11, in one embodiment, the converter includes plurality of converter units, plurality of internal controllers 5400, plurality of DC filter unit 5700, AC sampling unit 5200, DC sampling unit 5300 and central controller 5500. Wherein each converter is bidirectional converter 5100, the AC side of each bidirectional converter 5100 is connected to bus rod via a AC filter unit 5600, the DC side is connected to DC bus via a DC filter unit 5700. The AC sampling unit 5200 is connected to the AC side of each bidirectional converter 5100 respectively, while the DC sampling unit 5300 is connected to the DC side of each bidirectional converter 5100 respectively. Each bidirectional converter 5100 is connected to an internal controller 5400, a plurality of internal controllers 5400 are used to control the complete synchronization of the turn-on and turn-off of the IGBT switches of a plurality of bidirectional converters 5100 respectively, which makes flow equalization and voltage stabilization of the plurality of bidirectional converter 5100 to work synchronously. The central controller 5500 is connected to AC sampling unit 5200, DC sampling unit 5300 and the plurality of internal controllers 5400 respectively, used to control the operation of the plurality of internal controllers 5400 according to electrical signals collected in AC sampling unit 5200, such as AC voltage, AC current and phase angle, and electrical signals collected in DC sampling unit 5300, such as DC voltage and DC current. The central controller uses DSP or programmable advanced controller. In one embodiment, the central controller is connected to the plurality of internal controllers via CAN-BUS in two-wire serial communication. Refer to FIG. 12, in one embodiment, the internal controller 5400 includes: AC sampling module 54001 connected to the AC side of a bidirectional converter, DC sampling module 54002 connected to the AC side of the bidirectional converter, control module 54003 connected to the AC sampling module 54001, the DC sampling module 54002, the central controller 5500 and the bidirectional converter respectively, which is used to make the electrical signals output from the bidirectional converter to be same as predefined value according to the electrical signals collected in the AC sampling module 54001 and the DC sampling module 54002 and the control signals of the central controller 5500. In other embodiments, the plurality of converter units in the converter device could be a plurality of rectifiers, in that case, comparing with the converter device as shown in FIG. 11, there is no AC sampling unit, the central controller controls the plurality of internal controllers according to the electrical signals collected in the DC sampling unit. The corresponding internal controllers are not provided with AC sampling unit any more, the control module of internal controller makes the electrical signals output from the connected rectifier to be same as predefined value according to the electrical signals collected in the DC sampling module and the control signals of the central controller. In other embodiments, the plurality of converter units in the converter device could be a plurality of inverters, in that case, comparing with the converter device as shown in FIG. 11, there is no DC sampling unit, the central controller controls the plurality of internal controllers according to the electrical signals collected in the AC sampling unit. The corresponding internal controllers are not provided with DC sampling unit any more, the control module of internal controller makes the electrical signals output from the connected inverter to be same as predefined value according to the electrical signals collected in the AC sampling module and the control signals of the central controller. In one embodiment, the control method for synchronous working of the converter device are as followed: the plurality of internal controllers collect the electrical signals output from the plurality of converter units respectively; the central controller calculated the average value of the electrical signals; sampling unit collects the real time parallel average value of the electrical signals output by the plurality of the converter units; the central controller calculates the average difference value of the electrical signals according to the calculated average value of the electrical signals and the real time parallel average value of the electrical signals, then decomposes the average difference value to get compensation value; the plurality of internal controller could get the compensation value and control the electrical signals output by the corresponding converter unit to synchronize the electrical signals output by the plurality of converter units. In one embodiment, the working modes of the converter device are two as followed: one mode is to convert AC to DC, the other one is to convert DC to AC. The mode selection is controlled by the mode selector, which determines the working mode of the bidirectional converter via automatic detection, or receiving the signals of online monitoring system, or manual signals. It should be understood that the above embodiments is used to assist in the understanding of the present application, which should not be understood as any limitations. For the skilled in the art, modifications could be done to the above embodiments based on the spirit of the present application.
048470406	abstract	A nuclear power plant with a gas cooled high temperature reactor, installed in a prestressed concrete pressure vessel with the operational and decay heat removal systems. The prestressed concrete pressure vessel has a thermal protection system, with a thermal insulating layer and a liner cooling system. The liner cooling system, which is includes water carrying cooling pipes, which along with intermediate heat exchangers and cooling water pumps make up a closed intermediate cooling loop used for removal of the decay heat in case a failure of the decay heat removal systems. The elements of the invention assure an adequate water flow for the removal of decay heat in the liner cooling system in any situation, i.e. such that the decay heat may also be removed by natural convection. These element insure a sufficient driving pressure differences and minimize pressure losses in the intermediate cooling loop.
	summary
	description	This invention relates to a particle beam irradiation chamber in which a particle beam irradiation device which aims to irradiate a charged particle beam which is accelerated by an accelerator to a target is provided. A charged particle beam is circulated and accelerated by an accelerator (circular accelerator) such as a synchrotron, the charged particle beam which is accelerated to be high-energy (mainly, a proton or a carbon ion) is extracted from the circulating orbit, the charged particle beam which becomes a beam-state (will be also referred to as a charged particle beam, or a particle beam) is utilized in a physics experiment or a particle beam therapy such as a cancer treatment in which the charged particle beam is transported by a beam transport system so as to irradiate to an intended object. In a particle beam therapy by an accelerated charged particle beam (hereinafter, will be referred to as a particle beam), a particle beam is transported to an irradiation device which is provided in a particle beam irradiation chamber. In an irradiation device, a thin beam-like particle beam is scanned and spread by, for example, two sets of deflection electromagnet in directions of two axis which are perpendicular to a beam travelling direction, then, is passed through a scatterer to be spread further, is finally cut out to be a shape of a cancer by a collimator so as to irradiate to a person to be treated. A depth direction irradiation of a particle beam is adjusted to be a depth direction width of a cancer part of a person to be treated by passing the particle beam through a splinter-like filter, for example, so called a ridge filter and spreading a width of energy. The above-mentioned irradiation method of a particle beam is called as a spreading irradiation method. Further, recently, a scanning irradiation method, in which a particle beam whose state is kept thine beam state is scanned only by two sets of deflection electromagnets for beam scanning and is irradiated to a cancer part, is performed. In a case of a spreading irradiation method, when a particle beam which is accelerated to be high-energy collides with a scatterer or a collimator, finally a body of a person to be treated, radiation such as a neutron beam or a photon beam is generated secondarily. A spot where particle beams which are accelerated to be high-energy are collided and a neutron beam or a photon beam is generated secondarily is called a source of radiation. At this time, a neutron beam which is generated secondarily has energy distribution to the vicinity of energy of incident charged particle beam at most (in a case of particle beam treatment, per nucleon, several hundred MeV). Also, in a case of a scanning irradiation method, frequency of collision with a particle beam and a collimator or a scatterer is low, however, a particle beam is finally irradiated to inside of a body of a person to be treated. Therefore, total amount of a neutron or a photon beam which is generated secondarily is small in comparison with that of a spreading irradiation method, however, high-energy neutron beam or a photon beam is generated. In a facility where radiation such as a neutron beam or a photon beam is generated, dose limit is specified by laws and regulations. In a particle beam therapy facility, in order to make effective dose of outside a particle beam irradiation chamber to be in a legally permissible range, the intensity of a neutron is attenuated by thickening a thickness of a concrete wall or making a passage from a treatment bed where a person to be treated (patient) is placed in a particle beam irradiation chamber to a door of an entrance of an irradiation chamber to be a labyrinth-like shape (for example, refer to Patent Document 1). When a particle beam irradiation chamber is designed in shielding manner, two kinds of shielding effects, that is, an effect of bulk shielding and streaming should be considered. Bulk shielding is an effect to attenuate the dose equivalent of a neutron beam or a photon beam which is reached from a source of radiation passing through a concrete wall. In general, when a wall is thick and density of wall material is high, a shielding effect is high. Streaming is an effect of leaking a neutron beam or a photon beam, which is passed through a passage which connects inside and outside of a particle beam irradiation chamber, to the outside chamber. In general, when a passage is longer, cross section of a passage is smaller, and the time of bending is larger, dose equivalent of a neutron beam or a photon beam which leaks outside chamber is reduced by streaming is smaller. In a case where a shielding design in which a passage is utilized is performed, dose in the vicinity of an entrance of a passage which is a side of a radiation source is maximum dose, and after that dose is attenuated by a distance. Therefore, it is preferable such that dose at the radiation source entrance side of the passage is made to be small as possible. In general, energy of a neutron which is reached without being shielded on the way from a radiation source is not attenuated, therefore contribution to equivalent dose is large. (In strictly speaking, the degree of contribution to dose is different depending on energy, however, in a case of a neutron which is generated in a particle beam therapy, several hundred MeV neutron is generated at most, and contribution to a neutron in a range of several MeV to several hundred MeV is large). Consequently, it is important to attenuate an irradiation dose which intrudes in a passage by reducing the speed of a particle beam with a shielding wall and scattering. Conventionally, not only by making a passage to be a labyrinth-like form but also by forming a convex wall in a labyrinth-like passage, a neutron beam, which is reached from a radiation source to a gateway outside a particle beam irradiation chamber, is attenuated (for example, refer to Patent Document 2). Patent Document 1: JP2012-50843A (P12, FIG. 1) Patent Document 2: JP-H05-223987A (P6, FIG. 1, FIG. 2, FIG. 3) However, according to conventional shielding design, a passage which is surrounded by a shielding wall is formed to be a labyrinth-like passage, therefore, there is a problem such that an occupation area is large. For example, in a charged particle beam therapy or a photon beam therapy, an amount of radiation which is generated and energy is changed depending on a kind of a particle to be used for a therapy and energy. Consequently, in a case where an area of a particle beam irradiation chamber is compared, it is necessary to compare by considering a particle to be used for a therapy and energy. In comparison with a photon beam therapy, in a particle beam therapy, a neutron having higher energy is generated. Consequently, in order to attenuate radiation, it is necessary to form a thicker shielding wall and a longer passage. Further, a passage which is surrounded by a shielding wall is formed to be a labyrinth-like passage, therefore, a traffic line of a patient who moves from an entrance of a particle beam irradiation chamber to a treatment bed or a traffic line of medical personnel is complicated. Consequently, it takes longer time before starting treatment or it takes longer time for a patient to leave the chamber after treatment. As a result, there is a problem such that throughput of treatment is low. In order to solve the above-mentioned problem, this invention aims to improve throughput of treatment by making an occupation area smaller and shortening a traffic line of a patient and medical personnel. In a particle beam irradiation chamber of this invention, it is configured such that a passage having a first opening part at the side of an inner wall and a second opening part at the side of an outer wall is provided, an isocenter is provided inside the particle beam irradiation chamber, wherein a first line segment which connects the center of the first opening part and the center of the second opening part does not intersect two side walls constituting the passage, and when a vector which starts from the isocenter to the center of the first opening part is designated as a first vector and a vector which starts from the center of the first opening part to the center of the second opening part is designated as a second vector, a component of the first vector which is parallel to a line segment which connects both ends of the first opening part and a component of the second vector which is parallel to a line segment which connects both ends of the first opening are in an opposite direction. According to this invention, it is configured such that a first line segment which connects the center of a first opening and the center of a second opening does not intersect two side walls constituting a passage, and when a vector which starts from an isocenter to the center of the first opening part is designated as a first vector and a vector which starts from the center of the first opening to the center of the second opening part is designated as a second vector, it is configured such that a component, which is parallel to a line segment which connects both ends of the first opening part of the first vector, and a component, which is parallel to a line segment which connects both ends of the first opening part of the second vector are in an opposite direction. That is, according to this invention, it is configured such that from the first opening part to the second opening part of a passage which is surrounded by a shielding wall is tilted. Therefore, in the second opening part, amount of radiation can be decreased and an occupation area of a particle beam irradiation chamber can be reduced. Further, a distance between opening parts of a passage is short. Therefore, a traffic line of a patient or medical personnel from outside an irradiation room to the vicinity of the isocenter is short and the time of bending is small. Consequently, throughput of treatment can be improved. FIG. 1 is a top view showing a particle beam irradiation chamber in Embodiment 1 of this invention. Four sides of a particle beam irradiation chamber 1 in Embodiment 1 are surrounded by a shielding wall 2, and at one part of the shielding wall 2, a passage 3 is provided. In the particle beam irradiation chamber 1, a treatment table 4 is arranged. Further, a particle beam irradiation nozzle 5 for irradiating a particle beam to a patient who is laid down on the treatment table 4 is provided. A particle beam which is accelerated by an accelerator such as a synchrotron (not shown in FIG.) is transported by a beam transport system to the particle beam irradiation nozzle 5. A target of a particle beam which is irradiated from the particle beam irradiation nozzle 5 is determined on an affected part of the patient who is laid down on the treatment table 4, and a position of the target is called an isocenter 6. The isocenter means the irradiation center which is an intersection point of a particle beam or radiation when a particle beam or radiation is irradiated to a target site (an affected part) from different angles, and the isocenter conforms to the rotation center of the particle beam irradiation nozzle 5. That is, the isocenter is a position where a neutron beam or a photon beam is generated in a particle beam therapy. Further, in Embodiment 1, the particle beam irradiation nozzle 5 is not rotated around the isocenter 6 but is fixed. A particle beam which is transported to an irradiation chamber is formed to be a shape of an affected part, and the particle beam is irradiated by the particle beam irradiation nozzle 5 to the isocenter 6. A particle beam is irradiated to an affected part of a patient which is in the vicinity of the isocenter 6, therefore, a neutron beam or a photon beam which is generated secondarily is generated from the vicinity of the isocenter 6. Therefore, when neutron shielding design in a particle beam irradiation chamber is performed, in many cases, the isocenter 6 is considered as a radiation source. Radiation which is generated from the vicinity of the isocenter 6 includes not only a neutron beam but also a photon beam, and the limit of total of effective dose of the above-mentioned radiation is determined by law. A limit value set by law of effective dose of radiation in a particle beam irradiation chamber is different from that of outside a particle beam irradiation chamber. In order to reduce the effective dose outside a particle beam irradiation chamber, design of the passage 3 is important. It is necessary to attenuate the effective dose in a gateway outside the passage 3 so as to be lower than a limit value of the effective dose of radiation outside a particle beam irradiation chamber. In general particle beam therapy, it is known such that regarding the effective dose of radiation, a neutron dose is dominant, therefore, it is important to attenuate a neutron dose to be lower than a limit value set by law in shielding design of a particle beam irradiation chamber. Hereinafter, description of Embodiments of this invention will be made primarily based on shielding of a neutron. Next, the configuration of the passage 3 in Embodiment 1 will be described referring FIG. 1. Among two gateways of the passage 3, a gateway at the side of the inner wall of the shielding wall 2 is designated as a first opening part 7, and a gateway at the side of the outer wall of the shielding wall 2 is designated as a second opening part 8. In this time, it is configured such that a first line segment 9 which connects the center of the first opening part 7 and the center of the second opening part 8 does not intersect both walls of the passage 3. Further, when a vector which starts from the isocenter 6 to the center of the first opening part 7 is designated as a first vector 9a, a vector which starts from the center of the first opening part 7 to the center of the second opening part 8 is designated as a second vector 9b and a line segment which connects both ends of the first opening part 7 is designated as a line segment 10, it is configured such that both of a component P of the first vector 9a in a line segment direction 10 and a component Q of the second vector 9b in a line segment direction 10 are non-zero and the component P and the component Q are in the opposite direction. Further, in other words, in a case where a line segment which connects the isocenter and the center of the first opening part is designated as a first line segment and a line segment which connects the center of the first opening part and the center of the second opening part is designated as a second line segment, it is configured such that the first line segment and the second line segment are formed to be a shape of symbol of a sign of inequality, “” or “”. In the passage 3 having the above-mentioned configuration, a gateway inside the particle beam irradiation chamber 1 (the first opening part) can be seen from a gateway outside the particle beam irradiation chamber 1 (the second opening part). Further, in a case where a width of the first opening part and that of the second opening part are same, a width of the passage 3 is narrower than that of the first opening part and that of the second opening part. In other words, in a case where the shielding wall 2 of the particle beam irradiation chamber 1 is formed to be a rectangle as shown in FIG. 1, the passage 3 has an oblique shape. FIG. 2 is a view for describing a shielding effect in a particle beam irradiation chamber in Embodiment 1 of this invention. In FIGS. 2, A and C are points of both ends of a gateway inside the particle beam irradiation chamber 1, and B and D are points of both ends of a gateway outside the particle beam irradiation chamber 1. A length of a perpendicular line which starts from the isocenter 6 to a straight line E which connects both ends of a gateway inside the particle beam irradiation chamber 1 is designated as a. A length of a perpendicular line which starts from the isocenter to a straight line F which is perpendicular to the straight line E, which connects both ends of a gateway inside the particle beam irradiation chamber 1, and passes a point which is farther away from the isocenter 6 among points of both ends of a gateway inside the particle beam irradiation chamber 1, (in a case of FIG. 2, a point of A) is designated as b. It is assumed such that inner walls of both sides of the passage part are parallel planes, and a distance between the wall surfaces is designated as t. Further, an angle which is formed by the straight line F which is perpendicular to the straight line E which connects both ends of a gateway inside the particle beam irradiation chamber 1 and an inner wall of a passage part is designated as θ. It is known such that as shown in the Literature “shielding calculation practical manual 2007 2-13 to 2-14”, a neutron dose obeys following formula (1) and (2) of Nakamura-Uemino. In order to use the formulas of Nakamura-Uemino, it is necessary to set a virtual source at a gateway inside a particle beam irradiation chamber (a first opening part). A position of a virtual source is a point where the square attenuation of the distance in the passage 3 starts, and the point is set to be point α, that is, a point which is shifted to the side of inside of a particle beam irradiation chamber by the half of a passage from the center of gravity of a surface of a passage width in a line segment which connects the isocenter and a point X which is a critical point where radiation can be reached directly in the passage. Dose H0 in the virtual source α is obtained by the following formula (1). Here, D0 is a standardization constant (dose in the distance from a source of 1 m), R is a distance from a radiation source (isocenter) to a virtual radiation source α, s is a value which is obtained by dividing the geometric mean of a breadth and a depth of an irradiation chamber by 2, S is the total surface area of an inner surface of a particle beam irradiation chamber and S′ is the surface area of an inner surface of a particle beam irradiation chamber which can be looked directly from a virtual radiation source position. H 0 = D 0 ⁡ ( 1 R 2 + 4 R 2 + 4 ⁢ s 2 - 2 ⁢ 2 ⁢ Rs ⁢ S ′ S ) ( 1 ) Further, dose I(r) of radiation in a passage is obtained by a numerical formula (2). Here, r is a distance from a virtual radiation source α. I ⁡ ( r ) = H 0 ⁢ ( t / 2 ) 2 r 2 ( 2 ) As can be seen from formula (2), dose in a passage is attenuated by a reciprocal number of square of a distance, therefore, when a distance between X and B is longer, dose in a second opening part (a gateway outside a particle irradiation chamber) can be reduced. Dose H0 at a position of a virtual radiation source α is smaller when a distance from an isocenter (radiation source) to a virtual radiation source α is longer. However, as can be seen such that the second member is in parentheses of formula (1), attenuation of whole of H0 is smaller than square of a distance. The second member is a member for showing an influence of scattering in a particle beam irradiation chamber. Therefore, in a case where whole distance of a route from outside an irradiation chamber to an isocenter 6 in a chamber is fixed, accordingly, dose in the vicinity of a gateway outside a particle beam irradiation chamber can be reduced not by keeping a position of a virtual radiation source α away from a radiation source but by making a distance r0 from a virtual radiation source α to a second opening part 8 longer. In other words, whether dose can be suppressed to be in a range of a isocenter or not is practically determined by a length of r0. Consequently, under the condition such that r0 is fixed, a length of a route of a passage is shorter when a passage is formed to have an oblique shape as shown in Embodiment 1. A distance r0 from a virtual radiation source α to a second opening part 8 can be obtained by calculating using following formula (3), a, b, d, t and θ which are parameters showing the configuration of a particle beam irradiation chamber. d = at 2 ⁢ ( asin ⁢ ⁢ θ + b ⁢ ⁢ cos ⁢ ⁢ θ - t ) ⁢ cos ⁢ ⁢ θ + r 0 - t 2 ( 3 ) FIG. 3 shows a length d of the passage which is obtained by calculating with formula (3) using θ as a parameter. For example, a=5.5 m, b=6.5 m, t=2.5 m, r0=4 m. As can be seen from formula (3), when θ satisfies following formula (4), a value of d is smaller in comparison with a case of θ=0°.(a sin θ+b cos θ−t)cos θ>b−t (4) Therefore, θ is a value which satisfies θ°<θ<90° and formula (4) (a range of β in FIG. 3), in comparison with a case of θ=0°, the same level of shielding effect can be obtained with a shorter length of d. Further, θ>0° means such that a straight line E which connects both ends of a gateway inside a particle beam irradiation chamber does not intersect wall surfaces of both sides of a passage by an angle which is not perpendicular, and a passage having the above-mentioned is expressed as an oblique passage in Embodiment 1. By arranging an oblique passage 3 as above-mentioned, in a case where dose outside an irradiation chamber is suppressed to be lower than a certain value, under the condition in which a distance r0 for attenuating in a passage is fixed, a length of a passage d can be shortened, as a result, an occupation area can be reduced. Further, as a passage is not bending, a traffic line of a patient which is from an entrance of a particle beam irradiation room to a treatment bed and a traffic line of medical personnel are not complicated. Consequently, the time which is required before starting treatment or the time which is required for a patient to leave a chamber after treatment can be shortened, as a result, throughput of treatment can be improved. FIG. 4 is a top view showing a particle beam irradiation chamber in Embodiment 2 of this invention. The configuration of a particle beam irradiation chamber 1 in Embodiment 2 is same as that of a particle beam irradiation chamber 1 in Embodiment 1. However, unlike Embodiment 1, side walls of both sides constituting a passage 3 are configured by a combination of two plane surfaces, respectively. In addition to that, a position of a particle beam irradiation nozzle 5 is different. In Embodiment 2, the particle beam irradiation nozzle 5 is provided at a surface opposing a surface of a shielding wall where the passage 3 is provided. It is known such that regarding a neutron beam which is generated by an interaction of a particle beam and a target, the strength of high-energy neutron beam which is generated per a solid angle is stronger at a direction which is nearer to a travelling direction of an original incident particle beam. As the energy of a neutron beam is higher, the probability of passing through a shielding wall is higher. Consequently, at a position of a particle beam irradiation nozzle in Embodiment 2 (a direction of an incident beam), the strength of a neutron beam which reaches a shielding wall at a side of a passage (a number of a neutron) and the energy is larger than that at a position of a particle beam irradiation nozzle in Embodiment 1. Therefore, it is preferable such that a thickness of a part 13 of a shielding wall which shields a neutron beam which directly reaches a passage and a gateway outside a particle beam irradiation chamber is secured. Regarding a particle beam irradiation chamber in Embodiment 2, as shown in FIG. 4, one side of a side wall 11 of the passage 3 is constituted by a plane surface 11a and a plane surface 11b, and another side of a side wall 12 of the passage 3 is constituted by a plane surface 12a and a plane surface 12b. However, in the same as that of Embodiment 1, it is configured such that a first line segment 9 which connects the center of a first opening part 7 and the center of a second opening part 8 does not intersect both sides of side walls of the passage 3. That is, the passage 3 is gently bended on the way. When an angle which is formed by the plane surface 11a and a direction in a thickness of a shielding wall is designated as θ1, and an angle which is formed by the plane surface 11b and a direction in a thickness of a shielding wall is designated as θ2, by making the condition to be θ1<θ2, a thickness of the part 13 of a shielding wall can be thicker. By constituting a particle beam irradiation chamber as above-mentioned, in the same way as that of Embodiment 1, an occupation area can be reduced. Further, a length of a passage is shorter and the passage is not bended greatly. Therefore, a traffic line of a patient which is from an entrance of a particle beam irradiation room to a treatment bed and a traffic line of medical personnel are not complicated. Consequently, the time which is required before starting treatment or the time which is required for a patient to leave a chamber after treatment can be shortened, as a result, throughput of treatment can be improved. Further, in Embodiment 2, both sides of side walls constituting a passage are constituted by a combination of two plane surfaces. Therefore, in comparison with a thickness of a particle beam irradiation chamber in Embodiment 1, a thickness of the shielding wall 2 of the part 13 of a shielding wall in the vicinity of the first opening part 7 can be made thicker. As a result, radiation which passes through the part of a shielding wall 13 to be incident on the passage 3 can be further attenuated. FIG. 5 is a top view showing a particle beam irradiation chamber in Embodiment 3 of this invention. The configuration of a particle beam irradiation chamber 1 in Embodiment 3 is same as that of a particle beam irradiation chamber 1 in Embodiment 2, however, unlike Embodiment 2, configured such that side walls of both sides constituting a passage 3 are configured by a curved surface. As shown in FIG. 5, regarding a particle beam irradiation chamber in Embodiment 3, both sides of side walls of the passage 3 are constituted by a gentle curved surface. However, in the same way as that in Embodiment 1, it is configured such that a first line segment 9 which connects the center of a first opening part 7 and the center of a second opening part 8 passes the inside of the passage 3. That is, by making the passage 3 to be a gentle curved line, a thickness of a part 13 of a shielding wall can be thicker. As constituting a particle beam irradiation chamber as the above-mentioned, in the same way as that of Embodiment 1, an occupation area of a particle beam irradiation chamber can be reduced. Further, a length of a passage is shorter and the passage is not bended greatly. Therefore, a traffic line of a patient which is from an entrance of a particle beam irradiation room to a treatment bed and a traffic line of medical personnel are not complicated. Consequently, the time which is required before starting treatment or the time which is required for a patient to leave a chamber after treatment can be shortened, as a result, throughput of treatment can be improved. Further, in Embodiment 2, both sides of side walls constituting a passage are constituted by a curved surface. Therefore, in comparison with a thickness of a particle beam irradiation chamber in Embodiment 1, a thickness of a part 13 of a shielding wall 2 in the vicinity of a first opening part 7 can be made thicker. As a result, radiation which passes through to be incident on the passage 3 can be further attenuated. FIG. 6 is a top view showing a particle beam irradiation chamber in Embodiment 4 of this invention. The configuration of a particle beam irradiation chamber 1 in Embodiment 4 is same as that of a particle beam irradiation chamber 1 in Embodiment 1, however, unlike Embodiment 1, it is configured such that a rotary gantry device 14 is provided instead of a particle beam irradiation nozzle. Further, as shown in FIG. 6, four corners of an inner surface of a shielding wall 2 are designated as A, G, H and J. A rotary gantry device comprises a particle beam irradiation nozzle and a group of electromagnets for transporting a particle beam, the particle beam irradiation nozzle can be rotated by approximately 360 degrees, in the rotation center, a hollow space is provided, and in the hollow space, a treatment bed 4 is arranged. Regarding the rotary gantry device 14, treatment can be performed by rotating a particle beam irradiation nozzle around the treatment table 4 so as to irradiate a particle beam from a desired angle. Consequently, an isocenter 6 in Embodiment 4 is the rotation center (irradiation center) of the rotary gantry device 14. FIG. 6 shows a section including the isocenter 6, and an axis of rotation of the rotary gantry device 14 is designated as a straight line 15. In Embodiment 4, as shown in FIG. 6, it is configured such that the first opening part 7 is not on a plane surface which passes through the isocenter and is perpendicular to the axis of rotation of the rotary gantry device 14. It is further preferable such that an intersection point of the straight line 15 which is parallel to an axis of rotation of the rotary gantry device 14 and is extended from the isocenter 6 to a side of a passage, and a first line segment 9 which connects the center of a first opening part 7 and the center of a second opening part 8 is in a passage 3. It is simply that an arrangement direction of the rotary gantry 14 is determined. A neutron beam which is generated from a target (isocenter) is influenced by momentum of an incident particle beam. For example, in a case where a particle beam is irradiated to a target from right above, the strength of the high-energy neutron beam in a direction of right under (in a direction toward a floor) is high. On the contrary, in a case where a particle beam is irradiated to a target from right under, the high-energy having high strength in a direction of a ceiling is generated. From the point of view of a neutron dose in a passage, by preventing the high-energy neutron beam which is generated from an isocenter to a direction of an angle which is approximately parallel to an incident direction of a particle beam from reaching directly a passage, especially a first opening part 7, the dose at an outside of the second opening part 8 can be decreased. As described in Embodiment 4, by arranging a rotary gantry device, in a case where a particle beam is irradiated from a direction which is parallel to a floor face, designated by arrow 16, the—high energy neutron beam which is generated from an isocenter is emitted to a direction which includes a side wall between AG of a shielding wall 2. On the other hand, in a case where a particle beam is irradiated from a direction which is parallel to a floor face, designated by arrow 17, the—high energy neutron beam which is generated from an isocenter is emitted to a direction which includes a side wall between HJ of the shielding wall 2. As above-mentioned, by specifying the positional relationship of the a rotary gantry device and a passage, the strength of a direct neutron beam which is emitted to a direction of a first opening part 7 becomes smaller relatively, as a result, in comparison with a case in which the positional relationship between a rotary gantry device and a passage is not considered, a neutron dose in a second opening part 8 can be reduced. FIG. 7 is a top view showing a particle beam irradiation chamber in Embodiment 5 of this invention. The configuration of a particle beam irradiation chamber 1 in Embodiment 5 is same as that of a particle beam irradiation chamber 1 in Embodiment 4. In Embodiment 5, a positioning chamber 18 is arranged in front of a particle beam irradiation chamber 1. In Embodiment 5, in front of a gateway outside a particle beam irradiation chamber (second opening part) 8, a gateway 19 of the positioning chamber 18 is arranged adjoiningly. A positioning chamber is a chamber where the relative relationship between a perspective image of a body of a person to be treated (patient) and a treatment table is photographed in advance by an x-ray imaging device, for example. In advance, the relative relationship between a body of a patient and a treatment table is photographed in the positioning chamber 18, just before a particle beam therapy, a patient who is laid on a treatment table is carried in a particle beam irradiation chamber 1, and the treatment table is set at a position of an isocenter 6. The relationship between the treatment table 4 which is fixed on a position of the isocenter 6 and the isocenter 6 is determined in advance. Accordingly, by doing the above-mentioned, it is not necessary to adjust a position of an isocenter and that of a patient in the particle beam irradiation chamber 1, or even in a case where it is necessary to adjust a position of an isocenter and that of a patient, only fine adjustment is required. Consequently, the time which is required for adjustment is shorter in comparison with conventional particle beam irradiation chambers. In this time, it is necessary to carry a patient who is laid on a treatment table to a predetermined position in a particle beam irradiation chamber 1 after a perspective image of a body of a patient is photographed in advance by using an x-ray imaging device. In some cases, the relationship between a body of a patient and a treatment table may be changed by movement of a patient. In a conventional case in which a passage is bended, it is necessary to change a direction of a treatment table many times, and in a case in which a moving distance is long, the probability of changing the relative positional relationship between a body of a patient and a treatment may be higher. As described in Embodiment 5, by forming a passage 3 in a particle beam irradiation chamber 1 to be a linear passage, a traffic line can be shortened. In addition to that, a treatment table can be moved linearly. Consequently, it is only necessary to change a direction of a treatment table once while moving to an isocenter. As a result, the probability of changing the relative positional relationship between a body of a patient and a treatment table can be reduced. In a conventional particle beam therapy, an x-ray imaging device is provided in a particle beam irradiation chamber and an x-ray penetrative photographing for positioning is performed while a patient is laid on a treatment table in an isocenter. After that, particle beam therapy is performed. However, as an x-ray penetrative photographing for positioning and a particle beam therapy are performed in the same particle beam irradiation chamber, there is a problem such that an occupation time in a particle beam irradiation chamber per one therapy is long. As described in Embodiment 5, when an x-ray penetrative photographing for positioning is performed in a positioning chamber in advance, and only a particle beam therapy is performed in a particle beam irradiation chamber, improvement of throughput of treatment can be expected. Especially, in a small facility having only one particle beam irradiation chamber, during therapy of one patient in a particle beam irradiation chamber, positioning of subsequent patient can be performed in a positioning chamber, therefore therapy can be performed more effectively. 1. particle beam irradiation chamber 2. shielding wall 3. passage 4. treatment table 5. particle beam irradiation nozzle 6. isocenter 7. first opening part 8. second opening part 9. first line segment 9a. first vector 9b. second vector 10. line segment 11, 12. side wall 13. a part of a shielding wall 14. rotary gantry device 15. straight line 16, 17. arrow 18. positioning chamber 19. gateway
048715093	abstract	A spring retainer is disclosed for use in retaining fuel pellets in a fuel rod both during fabrication and shipment to prevent the fuel pellets from being moved from their design location before installation within a reactor. The cylindrical and solid nuclear pellets containing the reactor fuel are placed within the fuel rods (or cladding) and have an outside diameter slightly less than the inside diameter of the fuel rod. Once the pellets are in place, a two-part spring holder is inserted into the end of the fuel rod. A first compression spring part of the coil spring holder is a conventional coil spring which, acting in compression, bears against the fuel pellets with a preselected force typically forcing the pellets when in the horizontal position into a compacted disposition when the fuel rod is horizontal. This conventional coil spring has a diameter which is less than the inside diameter of the fuel rod. A second locking spring part of the coil spring holder is a coil spring having a diameter which exceeds the inside diameter of the fuel rod. This helical locking spring is spirally wound down to an outside diameter less than that of the inside diameter of the fuel rod for insertion into the rod and released to key to the inside diameter of the rod. Winding occurs through a special tool which attaches to the respective ends of the coil spring.
045004889	description	DETAILED DESCRIPTION OF THE SUBJECT INVENTION An encapsulated fuel unit 10 is illustrated in FIG. 1 and includes an exterior case or housing 12 and in interior fuel piece 14 contained within the housing. The fuel piece 14 can typically have a very thin cross section, perhaps between 1/64 and 1/8 inch thick, and otherwise can be sized as a rectangular block 1 or 2 inches wide by 2, 3 or perhaps 4 inches long. The housing 12 is formed as a generally elongated tube-like body or structure 16 having an interior through-opening 17 that is only slightly larger (perhaps with only 0.001-0.01 inch clearance on each face) than the fuel piece 14, so that the housing itself is perhaps between 1/16 and 3/16 of an inch thick. The housing 12 would typically be made perhaps 4, 6 or 8 inches long so that one or several fuel piece(s) 14 can be put end-to-end into a single housing. An end cap 18 is welded across each open end of the tube-like structure 16, at least one of the end caps being welded after the fuel piece(s) have been loaded inside the structure, thereby virtually confining the fuel piece(s) 14 therein and defining the encapsulated fuel unit 10. While the encapsulated fuel unit could have general utility with any nuclear fuel, it has particular utility for the storage of uranium enriched to varying levels, perhaps with .sup.235 U being as high as 90-95%. In this regard, such fuel is commonly used in test reactors where specific quantities and combinations of uranium, plutonium and other fuels are disposed at varying placements within a reactor core. The fuels thus have to be stored in relatively small quantities to allow for fine-tuning of such placement and the needed versatility for the tests. Of utmost importance to the subject invention is the fact that the end caps 18 are formed of a material having micron size pores which allows the confined fuel piece(s) 14 to breath in the encapsulated fuel unit 10. This extends the shelf life of the fuel unit 10 without dangerous chemical change as might take place with a voiding of oxygen, avoids pressure build-up due to the release of fission gases, and further precludes release or escape of uranium or oxide exteriorly of the unit for contaminating adjacent structures. One material successfully used for the end caps 18 is the porous T-316-L stainless steel sold by Pall Trinity of Villa Park, Ill. This material has pores of the order of 5 microns in size, although pore sizes in the range between 2 and 10 microns would appear suitable also. End caps 1/16 of an inch thick have allowed sufficient breathing of the confined uranium fuel piece(s) without adjacent contamination. Each end cap 18 is sized slightly smaller than the opening 17 of the tube-like structure 16 to allow penetration thereinto, and the exposed end cap is then preferably welded with an annular filet type weld 19. The tube-like structure 16 is illustrated as being formed from two C-shaped channels 20. Each channel 20 is formed from very thin flat sheet stock, such as stainless steel between 0.002 and 0.01 of an inch (although 0.005 of an inch thick sheet stock might be preferred). The sheet stock is first sheared to the proper length and width and then small side legs 22 are press broke 90.degree. from intermediate wall 24 to define the channel shape. Each leg 22 is only slightly longer than half the thickness of the fuel plate(s) 14 to be supported within the housing allowing for the slight clearance between the fuel plate and housing. The free ends 26 of corresponding pairs of channel legs 22 meet or butt precisely along the entire length of the channels so that welds 28 can be made along these seam to secure the channels 20 together as the tube-like structure 16. The technique to be disclosed now has proven to be most successful in welding these thin stainless steel channels to define the tube-like structure, even though the structure has a low thickness to width ratio (1/16 to 2 inches for example) and a low thickness to length ratio (1/16 to 6 inches for example). In this regard, the welds between the two channels 20 are made by a beam welder (such as manufactured by Hamilton Standard of Windsor Lock Company, Conn., a division of United Aircraft) in a protected atmosphere, either a vacuum or an inert gas, where a high energy beam directed towards the butted edges to be joined together directly fuses the channels themselves together. In using a beam welder (not shown), chill blocks are used to fixture the channels 20 and to dissipate excess heat away from the channel portions adjacent the welds. To form the tube-like housing structure 16, an expandable interior chill block 30 is used which can be snugged flush against the inside of the channel legs 22 before welding and can then be collapsed to allow endward removal from the structure after the welds have been made; and separate exterior chill blocks 32a and 32b sandwich the channels 20 against the interior chill block while the welds are being made. The interior chill block 30 is made the precise thickness across the opposite parallel faces 34 so that the intermediate channel walls 24 lie flush against the chill block while correspondingly the free ends of the channel legs 22 just butt one another. The interior chill block 30 is actually formed of two wedges 36a and 36b having parallel outer face 38a and 38b and angled faces 40a and 40b that slide on one another. Thus, by axially shifting the wedges 36a and 36b along the angled faces 40, the width across the outer faces 38a and 38b of the interior chill block 30 is adjusted. Two half-holes 42a and 42b are formed in the angled faces 40a and 40b of the wedges 36a and 36b, respectively, and become aligned to form a full circular opening 44 when the block wedges are shifted to the expanded position thereof where the outer faces 38 are precisely snugged against the inside faces of the channel legs 22; and positioning pin means 46 is used, to be inserted in the opening 44, so as to lock the wedges in this expanded position. With this keying arrangement, it is relatively easy to repeatedly expand the interior chill block wedges 36a and 36b for fixturing different pairs of channels 20 while maintaining the same critical dimensions. The collapsible interior chill block 30 is needed since the welding process shrinks the channels 20 slightly over the interior chill block, and a noncollapsible interior chill block would be quite difficult to remove without exerting large separating forces that might disrupt the tolerances of the finished tube-like structure 16. In a preferred embodiment, the interior chill block wedges 36a and 36b are manually brought into or removed from operative relative assembly from opposite ends of the channels 20 or finished tube-like structure 16. Each exterior chill block 32a and 32b similarly has a flat intermediate face 50 that butts flush against the intermediate wall 24 of the channel 20, and side shoulders 52 that engage and locate the corners of the channels at the channel legs 22. End stops 56a and 56b are secured by bolts 58 to corresponding ends of the exterior chill blocks 32, each stop projecting away from the intermediate face 50 a distance just less than the thickness of the channel 20 (0.004 of an inch projection versus 0.005 of an inch thick channel, for example). Thus the channel can be slid along and within the exterior chill block until it butts against the stop, whereby each channel is properly positioned then relative to its exterior chill block. The exterior chill blocks 32a and 32b are located relative to one another by means of a U-shaped stop 60 secured by bolts 62 to the opposite end of chill blocks 32b where the end legs 64 of the stop 60 span across and butt the corresponding end of the other chill block 32a. Thus, it is easy to repeatedly and accurately locate the interior and exterior chill blocks relative to one another and to the channels 20 on different sets of channels. A preferred arrangement provides that many pairs of exterior and interior chill blocks, each butted against and sandwiching its two channels that will be joined to form each tube-like housing, can be stacked back-to-back against one another and fixtured or clamped snuggly together. Thus, ten such paired chill block assemblies might be fixtured together on a table (not shown) in the beam welder so that the butted end edge seams to be welded are all exposed and parallel to one another. The table can then be moved automatically according to the indexing program of the welder, to cause each butted end edge on successive passes to be moved past the electron beam for welding each successive seam. Afterwards, the entire stack of chill block assemblies can be flipped over 180.degree. to weld the opposite side seams. The chill blocks associated with a conventional beam welder have typically been made of copper. However, copper chill blocks were found inadequate in fabricating this tube-like structure, with the thin gauge material and very high width and length to thickness ratios, as they did not retain accurate dimensions under the thermal fluctuations of the beam welder. This appeared to be particularly evident regarding the interior chill block wedges having the thin but relatively long and wide shapes. However, chill blocks formed of hardened and ground tool steel unexpectedly proved to be most adequate, allowing for very accurate initial fabrication and further providing exceptional dimensional stability and durability during repeated use. This is even so with respect to the separate interior chill block wedges, with the thin cross section extended over much greater width and length and further that must be handled extensively both before welding and after welding. Thus successive tube-like structures can be made according to the proposed technique with high accuracy and very low rejection rate. The end cap weld 19 can be performed by a skilled aritsan in the open atmosphere using heliarc equipment. Again, exterior chill blocks (not shown) are used to fixture the tube-like housing 16 during this welding. Because this end cap weld 19 is confined to a relatively small axial direction and the weld is made relative to a substantially stocky or heavy (1/16 of an inch) end cap 18, thermal warpage is of only minor concern. It can readily be appreciated that this tube-like structure 16 is most suited to enclose the very thin fuel piece(s) 14 for protecting them against breakage and the possibility of spreading radioactive contamination upon contacting adjacent structures. The porous end caps 18 allow some fuel breathing for extended shelf life, without the problems commonly experienced with oxygen voiding of the fuel pieces, and also allow the release of fission gases to minimize pressure build-ups of the encapsulated fuel unit. While a particular embodiment of the present invention has been shown and described, it will be apparent to those skilled in the art that changes and modifications may be made therein without departing from the invention in its broader aspects. The aim of the appended claims, therefore, is to cover the invention in the spirit of the actual disclosure and all such changes and modifications thereof.
	claims	1. A dry cooling system, comprising:an air duct; anda heat pipe including an evaporator section configured to be in contact with a heat source and a condenser section connected to the evaporator section,the condenser section being located in the air duct,the dry cooling system further comprising:an opening disposed below the air duct such that an air enters through the opening and flows to the condenser section; anda heat source flow duct including the heat source,the evaporator section being located inside the heat source flow duct,the heat source flow duct including a baffle providing a serpentine flow path, andthe evaporator section being located in the serpentine flow path. 2. The dry cooling system according to claim 1, further comprising a window disposed in an upper portion of the air duct. 3. The dry cooling system according to claim 2, further comprising a solar absorbing element disposed in the air duct and corresponding to the window. 4. The dry cooling system according to claim 3, the window being a side window disposed in a side surface of the air duct. 5. The dry cooling system according to claim 4, the side window bent from the side surface of the air duct. 6. The dry cooling system according to claim 3, the window being a top window covering the air duct. 7. The dry cooling system according to claim 3, the solar absorbing element including a thermal energy storage material. 8. The dry cooling system according to claim 3, further comprising a partition between the solar absorbing element and the condenser section. 9. The dry cooling system according to claim 3, further comprising a solar collector providing a solar beam to the solar absorbing element through the window. 10. The dry cooling system according to claim 1, further comprising a fan disposed over the condenser section. 11. A dry cooling system, comprising:a heat source flow duct;an air duct disposed over the heat source flow duct;an opening between the heat source flow duct and the air duct such that an air flows through the opening; anda heat pipe including an evaporator section disposed in the heat source flow duct and a condenser section disposed in the air duct,the air flowing from the opening to the condenser section,the dry cooling system further comprising side window disposed on a side surface of the air duct and a solar absorbing element disposed over the condenser section, andthe solar absorbing element including a thermal energy storage material and an air flow space which the air flows through. 12. The dry cooling system according to claim 11, further comprising a solar collector providing a solar beam to the solar absorbing element through the side window. 13. The dry cooling system according to claim 11, further comprising a fan disposed over the solar absorbing element. 14. The dry cooling system according to claim 11, the heat source flow duct including at least one of a steam in a condenser of a power plant, a cooling water of the power plant, a cooling water of an air conditioning system or a refrigeration system, and a vapor in a condenser of the air conditioning system or the refrigeration system. 15. A dry cooling system, comprising:a heat source flow duct including a heat source;an air duct disposed over the heat source flow duct;an opening between the heat source flow duct and the air duct;a heat pipe including an evaporator section disposed in the heat source of the heat source flow duct and a condenser section disposed in the air duct;a window disposed on the air duct;a solar absorbing element disposed over the condenser section; anda fan disposed over the solar absorbing element,the dry cooling system being configured to allow an air to flow from the opening to outside of the air duct through the condenser section, the solar absorbing element, and the fan, andthe solar absorbing element including a thermal energy storage material and an air flow space which the air flows through.
	summary
062748777	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT An exposure apparatus according to this embodiment is a multi-electron beam exposure apparatus which draws a desired pattern by irradiating a plurality of electron beams onto a substrate via an electron optical system, and adjusts the focal point of the electron optical system in correspondence with the number of electron beams irradiated onto the substrate, which sequentially changes in accordance with the pattern to be drawn. With this apparatus, an electron beam image blurred by the Coulomb effect can be corrected, and a pattern can be drawn at high resolution. In the multi-electron beam exposure apparatus, a plurality of electron beams irradiated onto the substrate are concentrated on a narrow range or uniformly distributed depending on the pattern to be drawn. Even when the number of electron beams irradiated onto the substrate remains the same, since the former case has a higher effective current density per unit area than the latter case, an electron beam image is blurred larger by the Coulomb effect. FIGS. 14A and 14B exemplify the patterns to be drawn on the substrate. In FIGS. 14A and 14B, the full circles indicate the actual irradiation positions of the electron beams, and the open circles indicate non-irradiation positions of the electron beams. The patterns shown in FIGS. 14A and 14B have the same number of electron beams to be irradiated onto the substrate (equivalent to the sum total of currents irradiated onto the substrate). However, in a region L in FIG. 14B, an electron beam image is blurred larger due to the Coulomb effect since a plurality of electron beams are concentrated within a narrower range than in FIG. 14A. On the other hand, in a region S in FIG. 14B, an electron beam image is blurred less due to the Coulomb effect since the electron beam density irradiated is smaller than that in FIG. 14A. The different degrees of blurring of an electron beam image due to the Coulomb effect arising from the distribution of electron beams irradiated onto the substrate also apply to, e.g., the patterns shown in FIGS. 15A and 15B. Hence, in order to accurately correct blurring of an electron beam due to the Coulomb effect, not only the number of electron beams to be irradiated onto the substrate (the sum total of currents irradiated onto the substrate) but also the distribution of electron beams are preferably taken into consideration. In the following description, an electron beam exposure apparatus which adjusts the focal point of an electron optical system in consideration of not only the number of electron beams to be irradiated onto the substrate but also the distribution of electron beams will be disclosed as a preferred embodiment of the present invention. (Explanation of Constituting Elements of Electron Beam Exposure Apparatus) FIG. 1 is a schematic view showing the principal part of an electron beam exposure apparatus according to the present invention. Referring to FIG. 1, reference numeral 1 denotes an electron gun made up of a cathode 1a, grid 1b, and anodes 1c. Electrons emitted by the cathode 1a form a crossover image between the grid 1b and anode 1c. The crossover image will be referred to as an electron source hereinafter. Electrons coming from this electron source are converted into nearly collimated electron beams by a condenser lens 2 whose front-side focal point position is located at the electron source position. The nearly collimated electron beams enter an elementary electron optical system array 3. The elementary electron optical system array 3 is formed by arranging a plurality of elementary electron optical systems, each consisting of an aperture, an electron optical system, and a blanking electrode, in directions perpendicular to an optical axis AX. The elementary electron optical system 3 will be explained in detail later. The elementary electron optical system array 3 forms a plurality of intermediate images of the electron source. These intermediate images are projected in a reduced scale by a reduction electron optical system 4 (to be described later), and form images of the electron source on a wafer 5. In this case, the individual elements of the elementary electron optical system array 3 are set so that the spacing between adjacent electron source images formed on the wafer 5 equals an integer multiple of the size of each electron source image. Furthermore, the elementary electron optical system array 3 makes the positions of the individual intermediate images differ in the optical axis direction in correspondence with the curvature of field of the reduction electron optical system 4, and corrects in advance any aberrations expected to be produced when the individual intermediate images are projected onto the wafer 5 in a reduced scale by the reduction electron optical system 4. The reduction electron optical system 4 comprises a symmetric magnetic doublet consisting of a first projection lens 41 (43) and second projection lens 42 (44). If f1 represents the focal length of the first projection lens 41 (43), and f2 represents the focal length of the second projection lens 42 (44), the distance between these two lenses is f1+f2. The object point on the optical axis AX is located at the focal point position of the first projection lens 41 (43), and its image point is formed at the focal point of the second projection lens 42 (44). This image is reduced to -f2/f1. Since two lens magnetic fields are determined to act in opposite directions, the Seidel aberrations and chromatic aberrations pertaining to rotation and magnification theoretically cancel each other, except for five aberrations, i.e., spherical aberration, isotropic astigmatism, isotropic coma, curvature of field, and on-axis chromatic aberration. Reference numeral 6 denotes a deflector for deflecting a plurality of electron beams coming from the elementary electron optical system array 3 to displace a plurality of electron source images by nearly equal displacement amounts in the X- and Y-directions on the wafer 5. The deflector 6 comprises a main deflector 61 used when the deflection width is large, and a sub deflector 62 used when the deflection width is small. The main deflector 61 is an electromagnetic type deflector, and the sub deflector 62 is an electrostatic type deflector. Reference numeral 7 denotes a dynamic focus coil that corrects any deviations of the focus positions of the electron source images arising from deflection aberration produced upon operation of the deflector 6; and 8, a dynamic stigmatic coil that corrects astigmatism of deflection aberration produced upon deflection as in the dynamic focus coil 7. Reference numeral 9 denotes a refocus coil for adjusting the focal point position of the reduction electron optical system 4 to correct blurring of electron beams due to the Coulomb effect produced when the number of a plurality of electron beams to be irradiated onto a wafer or the sum total of currents to be irradiated onto the wafer becomes large. Reference numeral 10 denotes a Faraday cup having two single knife edges respectively extending in the X- and Y-directions. The Faraday cup detects the charge amount of images formed by the electron beams coming from the elementary electron optical systems. Reference numeral 11 denotes a .theta.-Z stage that carries a wafer, and is movable in the direction of the optical axis AX (Z-axis) and in the direction of rotation about the Z-axis. A stage reference plate 13 and the Faraday cup 10 are fixed on the stage 11. Reference numeral 12 denotes an X-Y stage which carries the .theta.-Z stage and is movable in the X- and Y-directions perpendicular to the direction of the optical axis AX (Z-axis). The elementary electron optical system array 3 will be explained below with reference to FIG. 2. In the elementary electron optical system array 3, a plurality of elementary electron optical systems form a group (subarray), and a plurality of subarrays are formed. In this embodiment, five subarrays A1 to A5 are formed. In each subarray, a plurality of elementary electron optical systems are two-dimensionally arranged, and 27 elementary electron optical systems (e.g., A3 (1,1) to A3 (3,9)) are formed in each subarray of this embodiment. FIG. 3 is a sectional view of each elementary electron optical system. Referring to FIG. 3, a substrate AP-P is irradiated with electron beams nearly collimated by the condenser lens 2. The substrate AP-P has an aperture (AP1) that defines the shape of electron beams to be transmitted, and is common to other elementary electron optical systems. That is, the substrate AP-P is a substrate having a plurality of apertures. Reference numeral 301 denotes a blanking electrode which is made up of a pair of electrodes and has a deflection function; and 302, a substrate which has an aperture (AP2) and is common to other elementary electron optical systems. On the substrate 302, the blanking electrode 301 and a wiring layer (W) for turning on/off the electrodes are formed. That is, the substrate 302 has a plurality of apertures and a plurality of blanking electrodes. Reference numeral 303 denotes an electron optical system, which uses two unipotential lenses 303a and 303b. Each unipotential lens is made up of three aperture electrodes, and has a convergence function by setting the upper and lower electrodes at the same potential as an acceleration potential V0, and keeping the intermediate electrode at another potential V1 or V2. The individual aperture electrodes are stacked on a substrate via insulating materials, and the substrate is common to other elementary electron optical systems. That is, the substrate has a plurality of electron optical systems 303. The upper, intermediate, and lower electrodes of the unipotential lens 303a and the upper and lower electrodes of the unipotential lens 303b have a shape shown in FIG. 4A, and the upper and lower electrodes of the unipotential lenses 303a and 303b are set at common potential in all the elementary electron optical systems by a first focal point/astigmatism control circuit 15 (to be described later). Since the potential of the intermediate electrode of the unipotential lens 303a can be set by the first focal point/astigmatism control circuit 15 in units of elementary electron optical systems, the focal length of the unipotential lens 303a can be set in units of elementary electron optical systems. The intermediate electrode of the unipotential lens 303b is made up of four electrodes, as shown in FIG. 4B, and the potentials of these electrodes can be set independently and also individually in units of elementary electron optical systems by the first focal point/astigmatism control circuit 15. Hence, the unipotential lens 303b can have different focal lengths in a section perpendicular to its optical axis and can set them individually in units of elementary electron optical systems. As a consequence, by respectively controlling the potentials of the intermediate electrodes of the electron optical systems 303, the electron optical characteristics (the intermediate image forming positions and astigmatism) of the elementary electron optical systems can be controlled. Upon controlling the intermediate image forming positions, since the size of each intermediate image is determined by the ratio between the focal lengths of the condenser lens 2 and each electron optical system 303, the intermediate image forming position is moved by setting a constant focal length of each electron optical system 303 and moving its principal point position. With this control, the intermediate images formed by all the elementary electron optical systems can have nearly equal sizes and different positions in the optical axis direction. Each nearly collimated electron beam output from the condenser lens 2 forms an intermediate image of the electron source via the aperture (AP1) and electron optical system 303. Note that the aperture (AP1) is located at or in the vicinity of the front-side focal point position of the corresponding electron optical system 303, and the blanking electrode 301 is located at or in the vicinity of the intermediate image forming position (rear-side focal point position) of the corresponding electron optical system 303. For this reason, if no electric field is applied across the electrodes of the blanking electrode 301, the electron beam is not deflected, as indicated by an electron beam 305 in FIG. 3. On the other hand, if an electric field is applied across the electrodes of the blanking electrode 301, the electron beam is deflected, as indicated by an electron beam 306 in FIG. 3. Since the electron beams 305 and 306 have different angle distributions on the object plane of the reduction electron optical system 4, they become incident on different regions at the pupil position (on a plane P in FIG. 1) of the reduction electron optical system 4. Hence, a blanking aperture BA that transmits the electron beam 305 alone is formed at the pupil position (on the plane P in FIG. 1) of the reduction electron optical system. The electron optical systems 303 of the elementary electron optical systems individually set the potentials of their two intermediate electrodes so as to correct the curvature of field and astigmatism produced when the intermediate images formed thereby are projected in a reduced scale onto the surface to be exposed by the reduction electron optical system 4, thereby making the electron optical characteristics (intermediate image forming positions and astigmatism) of the elementary electron optical systems different. However, in this embodiment, in order to decrease the number of wiring lines between the intermediate electrodes and the first focal point/astigmatism control circuit 15, the elementary electron optical systems included in a single subarray have identical electron optical characteristics, and the electron optical characteristics (intermediate image forming positions and astigmatism) of the elementary electron optical systems are controlled in units of subarrays. Furthermore, in order to correct distortion produced when a plurality of intermediate images are projected in a reduced scale onto the surface to be exposed by the reduction electron optical system 4, the distortion characteristics of the reduction electron optical system 4 are detected in advance, and the positions of the elementary electron optical systems in the direction perpendicular to the optical axis of the reduction electron optical system 4 are set based on the detected characteristics. FIG. 5 shows the system arrangement of this embodiment. A blanking control circuit 14 individually ON/OFF-controls the blanking electrodes of the elementary electron optical systems in the elementary electron optical system array 3, and the first focal point/astigmatism control circuit 15 individually controls the electron optical characteristics (intermediate image forming positions and astigmatism) of the elementary electron optical systems in the elementary electron optical system array 3. A second focal point/astigmatism control circuit 16 controls the focal point position and astigmatism of the reduction electron optical system 4 by controlling the dynamic stigmatic coil 8 and dynamic focus coil 7. A deflection control circuit 17 controls the deflector 6. A magnification adjustment circuit 18 adjusts the magnification of the reduction electron optical system 4. A refocus control circuit 19 controls currents to be supplied to the refocus coil 9 to adjust the focal point position of the reduction electron optical system 4. A stage drive control circuit 20 controls driving of the .theta.-Z stage, and also controls driving of the X-Y stage 12 in collaboration with a laser interferometer 21 that detects the position of the X-Y stage 12. A control system 22 synchronously controls the plurality of control circuits described above and Faraday cup 10 to attain exposure and alignment based on exposure control data from a memory 23. The control system 22 is controlled by a CPU 25 for controlling the entire electron beam exposure apparatus via an interface 24. (Explanation of Operation) The operation of the electron beam exposure apparatus of this embodiment will be explained below with the aid of FIG. 5. Upon reception of pattern data to be formed on the wafer by exposure, the CPU 25 determines the minimum deflection amount the sub deflector 62 gives to the electron beams, on the basis of the minimum line width, types of line widths, and shapes of the pattern to be formed on the wafer by exposure. The CPU 25 divides the pattern data into those in units of exposure regions of the individual elementary electron optical systems, sets a common matrix made up of matrix elements FME using the minimum deflection amount as a matrix spacing, and converts the divided pattern data into those expressed on the common matrix in units of elementary electron optical systems. The processing pertaining to pattern data upon exposure using two elementary electron optical systems a and b will be described below for the sake of simplicity. FIGS. 6A and 6B show patterns Pa and Pb to be exposed by the neighboring elementary electron optical systems a and b on a common deflection matrix DM. More specifically, each elementary electron optical system irradiates an electron beam onto the wafer by turning off its blanking electrode at matrix positions denoted by hatched pattern portions. For this purpose, the CPU 25 determines first regions FF (solid black portions) consisting of the matrix positions corresponding to exposure positions of at least one of the elementary electron optical systems a and b, and second regions NN (blank portions) consisting of matrix positions where neither of the elementary electron optical systems a and b commonly perform exposure, as show in FIG. 6C, on the basis of the matrix position data to be exposed in units of elementary electron optical systems shown in FIGS. 6A and 6B. When a plurality of electron beams are located on the first region FF on the matrix, exposure is done by deflecting the electron beams by the sub deflector 62 in units of minimum deflection amounts (the matrix spacings), thus forming all the patterns to be drawn on the wafer by exposure. When a plurality of electron beams are located on the second region NN on the matrix, they are deflected without settling their positions, thereby attaining exposure while eliminating unnecessary deflection of the electron beams. Subsequently, the CPU 25 determines the matrix positions of matrix elements to be exposed on the basis of data pertaining to the regions FF and NN shown in FIG. 6C. Also, the CPU 25 determines the ON/OFF patterns of blanking electrodes corresponding to the matrix positions to be settled of the electron beams in units of elementary electron optical systems on the basis of data representing the patterns shown in FIGS. 6A and 6B. Consequently, the CPU 25 forms exposure data including, as elements, the matrix positions to be exposed by at least one beam, and ON/OFF states of blanking electrodes of each elementary electron optical system at the matrix positions, as shown in FIG. 7. Two examples that pertain to the method of correcting blurring produced by the Coulomb effect will be explained below. (First Correction Method) The CPU 25 executes evaluation shown in FIG. 8 on the basis of the formed exposure control data so as to correct blurring produced by the Coulomb effect. In the evaluation shown in FIG. 8, a distribution coefficient C for each subarray, which represents the distribution state of a plurality of electron beams irradiated onto the wafer, is calculated in the following sequence in units of matrix positions to be settled. (Step S101) The matrix position (x, y) to be settled is selected. (Step S102) The numbers N1 to N5 (the numbers of OFF blanking electrodes in subarrays) of electron beams that can reach the wafer without being intercepted in the subarrays A1 to A5 are checked. More specifically, the number of electron beams to be irradiated onto the wafer coming from each subarray, as an electron beam group made up of a plurality of electron beams, is checked. (Step S103) A distribution coefficient Ci for each subarray Ai is calculated by: ##EQU1## where Ni is the number of electron beams to be irradiated onto the wafer by the subarray Ai checked in step S102, K is a constant determined by, e.g., the size of the subarray, and Di,j is the distance between the centers of subarrays Ai and Aj. With the above equation, even when the number of all electron beams to be irradiated onto the wafer remains the same, the distribution coefficient Ci of the subarray Ai becomes larger as the number of electron beams to be irradiated onto the wafer in the subarray Ai is larger. Even when the number of electron beams to be irradiated onto the wafer in the subarray Ai remains the same, the distribution coefficient Ai of the subarray Ci becomes larger if the number of electron beams in another subarray is large. (Step S104) The calculated distribution coefficients Ci in units of subarrays are stored as refocus control data. (Step S105) It is checked if the processing in steps S102 to S104 is complete for all the matrix positions (x, y) to be settled. If non-processed matrix positions (x, y) to be settled are found, the flow returns to step S101 to select the next non-processed matrix position (x, y). (Step S106) Upon completion of the above processing for all the matrix positions (x, y) to be settled, the evaluation shown in FIG. 8 ends, and refocus control data including distribution coefficients Ci in units of subarrays corresponding to the matrix positions to be settled is stored, as shown in FIG. 9. In this embodiment, these processing steps are executed by the CPU 25 of the electron beam exposure apparatus. Alternatively, the above steps may be executed by another processing device, and the obtained exposure control data and refocus control data may be transferred to the CPU 25 to achieve the above object and to obtain the same effects as above. The CPU 25 then instructs the control system 22 to "execute exposure" via the interface 24. In response to this instruction, the control system 22 executes the following steps on the basis of the data on the memory 23 that stores the exposure control data and refocus control data. (Step S201) The control system 22 directs the deflection control circuit 17 to deflect a plurality of electron beams coming from the elementary electron optical system array by the sub deflector 62 of the deflector 6 so as to settle their positions, on the basis of the exposure control data transferred from the memory 23 in synchronism with internal reference clocks. The control system 22 directs the first focal point/astigmatism control circuit 15 to control the intermediate image forming positions of the elementary electron optical systems, in units of sub arrays, on the basis of the refocus control data transferred in the same manner as the exposure control data. More specifically, the control system 22 sets, on the basis of the distribution coefficients Ci in units of subarrays, the intermediate image forming positions of the elementary electron optical system of each subarray to be closer to the electron gun 1 side as the distribution coefficient Ci is larger. As a result, the imaging position of an electron beam on the wafer, which moves to a position farther from the reduction electron optical system 4 owing to the Coulomb effect as the distribution coefficient Ci is larger, approaches the reduction electron optical system 4, thus correcting blurring produced by the Coulomb effect. The moving amount (correction amount) of the imaging position of each electron beam on the wafer is called a refocus amount. The relationship between the refocus amount and distribution coefficient C is obtained in advance by numerical simulations or experiments, and the electron optical characteristics of the elementary electron optical systems in units of subarrays are controlled to obtain desired refocus amounts on the basis of the distribution coefficients C. Furthermore, the control system 22 directs the blanking control circuit 14 to turn on/off the blanking electrodes of the elementary electron optical systems in correspondence with the pattern to be exposed. At this time, the X-Y stage 12 is continuously moving in the X-direction, and the deflection control circuit 17 controls the deflection positions of the electron beams in consideration of the moving amount of the X-Y stage 12. As a result, an electron beam coming from one elementary electron optical system scans and exposes an exposure field (EF) on the wafer 5 to have a full square as a start point, as shown in FIG. 10A. Also, as shown in FIG. 10B, the exposure fields (EF) of the plurality of elementary electron optical systems in each subarray are set adjacent to each other. Consequently, a subarray exposure field (SEF) including a plurality of exposure fields (EF) is exposed on the wafer 5. At the same time, a subfield made up of subarray exposure fields (SEF) respectively formed by the subarrays A1 to A5 is exposed on the wafer 5, as shown in FIG. 11A. (Step S202) The control system 22 directs the deflection control circuit 17 to deflect a plurality of electron beams coming from the elementary electron optical system array using the main deflector 61 of the deflector 6, so as to expose subfield 2 after subfield 1, as shown in FIG. 11B. At that time, the control system 22 directs the second focal point/astigmatism control circuit 16 to control the dynamic focus control 7 on the basis of dynamic focus correction data obtained in advance, and to control the dynamic stigmatic coil 8 on the basis of dynamic stigmatic correction data obtained in advance, thereby correcting astigmatism of the reduction electron optical system. Then, the control system 22 executes the operation in step S201 to expose subfield 2. By repeating steps S201 and S202 above, subfields are sequentially exposed like subfields 3, 4, . . . , as shown in FIG. 11B, thereby exposing the entire surface of the wafer. In the above-mentioned correction method, the refocus amount of electron beams for each subarray is set by adjusting the electron optical characteristics of the elementary electron optical systems of each subarray. Alternatively, the average value of the refocus amounts in units of subarrays may be calculated, the refocus amount corresponding to the calculated average value may be set by the refocus coil 6, and the elementary electron optical systems of respective subarrays may set refocus amounts as differences obtained by subtracting the average value from the refocus amounts to be set. In the above-mentioned correction method, every time the sub deflector 62 deflects a plurality of electron beams coming from the elementary electron optical system array to settle their positions, the refocus amounts of electron beams in units of subarrays are changed. Alternatively, during exposure of one subfield, a constant refocus amount of the electron beams for each subarray may be used, and when the subfield to be exposed is switched to the next one, the refocus amount of electron beams for each subarray may be changed. In this case, the distribution coefficient C in units of subarrays can use the average value of the distribution coefficients C at the respective matrix positions in the subfield to be exposed. In other words, the imaging positions of the electron beams can be corrected in units of subarrays on the basis of the evaluation values in units of a plurality of subarray in each deflection region (subfield). (Second Correction Method) The CPU 25 executes evaluation shown in FIG. 16 on the basis of the formed exposure control data so as to correct blurring produced by the Coulomb effect. In the evaluation shown in FIG. 16, the distribution coefficient C representing the distribution state of a plurality of electron beams irradiated onto the wafer is calculated in the following procedure at each matrix position to be settled. (Step S301) The matrix position (x, y) to be settled is selected. (Step S302) The position, on the elementary electron optical system, of an elementary electron optical system that outputs an electron beam to be irradiated onto the wafer at the selected matrix position (x, y) is checked (the position, on the wafer, of that electron beam to be irradiated onto the wafer may be checked, as a matter of course). For example, if n represents the number of electron beams to be irradiated onto the wafer, a position Pi =(Xi, Yi) (for i=1 to n, Xi is the X-coordinate value on the elementary electron optical system array, and Yi is the Y-coordinate value on the elementary electron optical system array) of each beam is checked. (Step S303) The distribution coefficient C is calculated by: ##EQU2## As can be seen from the above equation, among all the different combinations of pairs of electron beams which are irradiated onto the wafer without being intercepted, the reciprocal value of the value obtained by calculating the square of the spacing between the pair of electron beams is calculated, and the sum total of the calculated values is the distribution coefficient C. Hence, as the number of electron beams irradiated onto the wafer is larger, the distribution coefficient C becomes larger. Even when the number of electron beams irradiated onto the wafer remains the same, if the electron beams are concentrated on a narrow range, the distribution coefficient C also becomes larger. (Step S304) The calculated distribution coefficient C is stored as refocus control data. (Step S305) It is checked if the processing in steps S302 to S304 is complete for all the matrix positions (x, y) to be settled. If non-processed matrix positions (x, y) to be settled are found, the flow returns to step S301 to select the next non-processed matrix position (x, y). (Step S306) Upon completion of the above processing for all the matrix positions (x, y) to be settled, the evaluation shown in FIG. 16 ends, and refocus control data including distribution coefficients C corresponding to the matrix positions to be settled is stored, as shown in FIG. 17. In this embodiment, these processing steps are executed by the CPU 25 of the electron beam exposure apparatus. Alternatively, the above steps may be executed by another processing device, and the obtained exposure control data and refocus control data may be transferred to the CPU 25 to achieve the above objective and to obtain the same effects as above. The CPU 25 then instructs the control system 22 to "execute exposure" via the interface 24. In response to this instruction, the control system 22 executes the following steps on the basis of the data on the memory 23 that stores the exposure control data and refocus control data. (Step S401) The control system 22 directs the deflection control circuit 17 to deflect a plurality of electron beams coming from the elementary electron optical system array by the sub deflector 62 of the deflector 6 so as to settle their positions, on the basis of the exposure control data transferred from the memory 23 in synchronism with internal reference clocks. The control system 22 directs the refocus control circuit 19 to control the focal point position of the reduction electron optical system 4 on the basis of the refocus control data transferred in the same manner as the exposure control data. More specifically, the control system 22 sets the focal point position of the reduction electron optical system 4 to be closer to the reduction electron optical system 4 as the distribution coefficient C is larger. As a result, the imaging position of an electron beam on the wafer, which moves to a position farther from the reduction electron optical system 4 owing to the Coulomb effect as the distribution coefficient C is larger, approaches the reduction electron optical system 4, thus correcting blurring produced by the Coulomb effect. The moving amount of the imaging position of each electron beam on the wafer is called a refocus amount. The relationship between the refocus amount and distribution coefficient C is obtained in advance by numerical simulations or experiments, and the currents to be supplied to the refocus coil 9 are controlled to obtain desired refocus amounts on the basis of the distribution coefficient C. Furthermore, the control system 22 directs the blanking control circuit 14 to turn on/off the blanking electrodes of the elementary electron optical systems in correspondence with the pattern to be exposed. At this time, the X-Y stage 12 is continuously moving in the X-direction, and the deflection control circuit 17 controls the deflection positions of the electron beams in consideration of the moving amount of the X-Y stage 12. As a result, an electron beam coming from one elementary electron optical system scans and exposes an exposure field (EF) on the wafer 5 to have a full square as a start point, as shown in FIG. 10A. Also, as shown in FIG. 10B, the exposure fields (EF) of the plurality of elementary electron optical systems in each subarray are set adjacent to each other. Consequently, a subarray exposure field (SEF) including a plurality of exposure fields (EF) is exposed on the wafer 5. At the same time, a subfield made up of subarray exposure fields (SEF) respectively formed by the subarrays A1 to A5 is exposed on the wafer 5, as shown in FIG. 11A. (Step S402) The control system 22 directs the deflection control circuit 17 to deflect a plurality of electron beams coming from the elementary electron optical system array using the main deflector 61 of the deflector 6, so as to expose subfield 2 after subfield 1, as shown in FIG. 11B. At that time, the control system 22 directs the second focal point/astigmatism control circuit 16 to control the dynamic focus control 7 on the basis of dynamic focus correction data obtained in advance, and to control the dynamic stigmatic coil 8 on the basis of dynamic stigmatic correction data obtained in advance, thereby correcting astigmatism of the reduction electron optical system. Then, the control system 22 executes the operation in step S401 to expose subfield 2. By repeating steps S401 and S402 above, subfields are sequentially exposed like subfields 3, 4, . . . , as shown in FIG. 11B, thereby exposing the entire surface of the wafer. In the above correction method, every time the sub deflector 62 deflects a plurality of electron beams coming from the elementary electron optical system array to settle their positions, the refocus amount of each electron beam (the focal point position adjustment amount of the reduction electron optical system 4 by the refocus coil 9) is changed. Alternatively, during exposure of one subfield, a constant refocus amount of the electron beams for each subarray may be used, and when the subfield to be exposed is switched to the next one, the refocus amount of electron beam may be changed. In this case, the control system 22 can use, as the distribution coefficient C, the average value of the distribution coefficients C at the respective matrix positions in the subfield to be exposed. In other words, the focal point position of the reduction electron optical system 4 is adjusted on the basis of the evaluation values of the respective matrix positions in each deflection region (subfield). (Embodiment of Device Manufacturing Method) An embodiment of a device manufacturing method using the above-mentioned electron beam exposure apparatus will be explained below. FIG. 12 shows the flow in the manufacture of a microdevice (semiconductor chips such as ICs, LSIs, liquid crystal devices, CCDs, thin film magnetic heads, micromachines, and the like). In step 1 (circuit design), the circuit design of a semiconductor device is done. In step 2 (generate exposure control data), the exposure control data of the exposure apparatus is generated based on the designed circuit pattern. Separately, in step 3 (manufacture wafer), a wafer is manufactured using materials such as silicon and the like. Step 4 (wafer process) is called a pre-process, and an actual circuit is formed by lithography on the wafer using the exposure apparatus input with the prepared exposure control data, and the manufactured wafer. The next step 5 (assembly) is called a post-process, in which semiconductor chips are assembled using the wafer obtained in step 4, and includes an assembly process (dicing, bonding), a packaging process (encapsulating chips), and the like. In step 6 (inspection), inspections such as operation tests, durability tests, and the like of semiconductor devices assembled in step 5 are conducted. Semiconductor devices are completed via these processes, and are delivered (step 7). FIG. 13 shows the detailed flow of the wafer process. In step 11 (oxidation), the surface of the wafer is allowed to oxidize. In step 12 (CVD), an insulating film is formed on the wafer surface. In step 13 (electrode formation), electrodes are formed by deposition on the wafer. In step 14 (ion implantation), ions are implanted into the wafer. In step 15 (resist process), a photosensitive agent is applied on the wafer. In step 16 (exposure), the circuit pattern on the mask is printed on the wafer by exposure using the above-mentioned exposure apparatus. In step 17 (development), the exposed wafer is developed. In step 18 (etching), a portion other than the developed resist image is removed by etching. In step 19 (remove resist), the resist film which has become unnecessary after the etching is removed. By repetitively executing these steps, multiple circuit patterns are formed on the wafer. According to the manufacturing method of this embodiment, a highly integrated semiconductor device which is not easy to manufacture by the conventional method can be manufactured at low cost. According to the present invention, a pattern can be drawn at high resolution by correcting blurring of an electron beam image produced by the Coulomb effect in accordance with the pattern to be exposed. The present invention is not limited to the above embodiments and various changes and modifications can be made within the spirit and scope of the present invention. Therefore, to apprise the public of the scope of the present invention the following claims are made.
	abstract	Techniques and tools for rating computer products are described. For example, software ratings are based on subjective evaluations to determine computer system requirements for a positive user experience, while a computer running a capability tool rates a computer system's (or hardware component's) ability to run software. A capability rating for hardware is determined by comparing a set of features and performance results with capability rating requirements. In another aspect, a capability rating is communicated using a standardized presentation. In another aspect, capability rating level requirements are proposed (e.g., by a ratings board) and then finalized. A capability rating level is determined for computer products (e.g., by a testing organization) based on the finalized requirements and analysis of the products (e.g., by a computer running a capability tool). In another aspect, a software system comprises an inventory module, a performance testing module, and an inventory and performance evaluator module.
	abstract	A cask cushioning body includes an end-surface side member (2) in which a plurality of plates (21, 22) made of steel are formed at a distance between plate surfaces of the plates (21, 22) that face each other, and in which the plate surfaces of the plates (21, 22) are arranged along an end surface (100a) of a cask (100), and a circumferential-surface side member (3) that forms a cylindrical body (31) made of steel, one end of which is connected to a periphery of the end-surface side member (2), and that is arranged along an end-portion outer-circumferential surface (100b), wherein an impact absorber (4) that absorbs an impact by deforming is provided outside of the end-surface side member (2) and the circumferential-surface side member (3).
	abstract	A bi-alloy spacer grid (BASG) is provided with grid straps and springs made using different zirconium alloys. The grid straps are made from a relatively low growth zirconium alloy, and the springs are made from a relatively high growth zirconium alloy. The springs are coupled to the grid straps by welding, mechanical interference, or secondary forming in place. When subjected to irradiation, the springs grow relative to the grid straps thereby maintaining contact with the fuel rod cladding, while the grid straps resist growth to maintain structural stability of the entire fuel assembly. The optimized balance of the high growth springs and low growth grid straps mitigates the formation of gaps between the fuel rods and grid support structures). The growth properties of the grid straps and springs may be further controlled through optional different fabrication processes.
	description	The invention relates to a method for checking the operability of a rotary encoder, when said encoder is in operation, said method comprising comparing at least one pair of measuring signals, which are shifted in phase relative to one another and which are representative of an amount of rotation, such as an angular position of a shaft, with at least one reference information stored in the rotary encoder. The invention further relates to a rotary encoder having integrated therein a sensor unit through which at least one pair of sinusoidal measuring signals, which are shifted in phase relative to one another, can be generated during operation, and a monitoring unit which is connected to the sensor unit in a measuring signal-transmitting manner and which is adapted to output, during operation, at least one monitoring signal representative of the operability of said rotary encoder. Rotary encoders are generally known and are often used for determining a rotary angle value in the case of controlled drives. If an error occurs in the rotary encoder or in a signal-transmitting connection between the rotary encoder and a reception unit for the signals of said rotary encoder, it cannot readily be found out whether the source of error is to be searched for in the connection or in the rotary encoder or whether the rotary angle value monitored has changed unexpectedly. An error in the connection may e.g. be a short-circuited signal transmission line. In the rotary encoder a plurality of potential error sources may exist. For example, movable or non-movable parts, such as magnets, light sources, sensors or incremental disks, may detach themselves from their intended position and may perhaps collide with one another. In addition, components in the rotary encoder may get dirty in the course of time or within a short period of time. In many cases, the errors cause, already prior to a failure of the rotary encoder, changes in the measuring signals generated in the sensor unit. When the measuring signals, which are generated as sinusoidal signals and in pairs and which have a fixed phase relationship with each other, pass through signal processing components in the rotary encoder, these signal processing components may fail as well. Also other electrical, mechanical or thermal causes may lead to one of the above-mentioned error patterns. In order to be able to identify an error source and to thus take effective countermeasures, EP 0 883 249 B1 and EP 1 006 663 B1 teach that the respective maximum values of the two amplitudes of the measuring signals, which change with the rotary angle value, are compared individually with predetermined maximum values. If, for example, a transparent area of an incremental disk gets dirty, the amplitude of the measuring signal will decrease and the previous maximum level of the measuring signal will no longer be reached. When the measuring signals are converted into square wave signals, these square wave signals often have an amplitude which is, within certain limits, independent of the maximum achievable amplitude of the measuring signal underlying the square wave signal. Hence, EP 1 006 663 B1 teaches that the adequate functioning of a signal processing unit or a signal converter forming square wave signals from sinusoidal measuring signals can be determined on the basis of the number or sequence of the rectangles or of the edges of the square wave signal. A plurality of square wave signals can be combined such that the sequence of the rectangles or of their edges will have a predetermined pattern when there is a change in the rotary angle value, such as a rotation through an angle within a certain period of time. If the measurement deviates from this predetermined pattern, conclusions with respect to the error source can be drawn from this circumstance. For identifying e.g. short-circuited signal lines, EP 1 006 663 B1 discloses that the output current of the rotary encoder is measured. It is shown that a low-ohmic resistor is connected in series with the signal line in the signal output. If an electric current flows through this resistor, a corresponding voltage will drop across the resistor according to Ohm's law, and this voltage is measured. If the flow of current increases due to a short circuit in e.g. an external signal transmission line, the voltage dropping across the resistor will increase as well; this is recognized and evaluated. Also an electric resistor, whose value of resistance increases as the temperature increases, may heat when the current flowing therethrough increases. The resistance value of this resistor will therefore increase, and this leads to a limitation of the flow of current. Also passive fuses may, for example, be used for interrupting, in the way described hereinbefore, signal transmission in the case of a short circuit. However, the above-described courses of action have the disadvantage that the rotary encoder must rotate so as to allow the measurements to be carried out. On the one hand, the maximum amplitudes of the measuring signals are applied to e.g. the sensor unit only in exceptional cases, and, on the other hand, the number of edges of the square wave signal can only be counted if they are actually generated. Also to this end, the rotary encoder must rotate, i.e. the movable part, e.g. the incremental disk which is connected to the rotary shaft, must be rotated by the latter. In addition, different signals, e.g. the sinusoidal measuring signals and the derived square wave signals, are evaluated in different ways. This increases the complexity and, consequently, the costs of a rotary encoder. It is therefore the object of the present invention to provide a rotary encoder comprising internal error control and a method therefor, wherein the function of the rotary encoder can also be ascertained when a constant rotary angle value, e.g. a constant angular position, is applied to the rotary encoder. As regards the method referred to at the beginning, the present invention achieves this object in that in the rotary encoder the amplitude values of the measuring signal pair are combined in a characteristic value, and that the characteristic value has associated therewith at least one reference information, which is stored in the rotary encoder as a quality value and which is representative of the admissible amplitude value combinations, and that a monitoring signal is outputted in dependence upon the quality value. As regards the rotary encoder referred to at the beginning, the object is achieved in that the monitoring unit comprises a computing module by means of which a characteristic value can be generated from the measuring signal pair, a memory unit in which at least one quality value can be stored, a verification device by means of which a quality value can be associated with the characteristic value, and an alarm unit which is controllable in dependence upon the result of the association executed by the verification device and in which the monitoring signal can be generated. These measures allow the function of the rotary encoder to be checked at any time when the rotary encoder is in operation, in particular also when it is stationary in any angular position, since amplitude values from which said characteristic value can be formed are always available. The solution according to the present invention can be further improved by various embodiments which can be combined in an arbitrary manner and each individual of which is advantageous. These embodiments and the resultant advantages will be described in the following. The amplitude values of the measuring signal pair can e.g. be combined with one another by means of an arithmetic function. If the measuring signal is present in the form of two sinusoidal signals which are shifted in phase by 90°, one of the measuring signal can be referred to as sinusoidal signal and the other one can be referred to as cosinoidal signal. When the arithmetic function comprises that the amplitude values of the measuring signals are squared and the results added, the sum obtained will be constant for all the rotary angle values that may occur when the rotary encoder is in operation. Since the sum, which will be referred to as characteristic value in the following, is especially also constant when the rotary encoder is stationary, the rotary encoder does not need to carry out any relative movements for checking itself. If the amplitude value of one of the measuring signals is correct and has its maximum magnitude and if the amplitude value of the second measuring signal is also correct and equal to zero, a characteristic value representative of an adequate functioning of the rotary encoder will be ascertained also in this case. An impairment of e.g. an optical component participating in the generation of the second measuring signal may, however, not be recognizable in this case. If the current amplitude values of the measuring signal pair, however, deviate from predetermined amplitude values and in particular if they are larger or smaller than the predetermined values, the characteristic value will change accordingly and allow conclusions with respect to defects or dirt within the rotary encoder. A change of said one characteristic value may also be indicative of ageing or loosening of components participating in signal generation, such as LEDs or magnets, and of a resultant change in position of the components in question. An increase in the characteristic value may indicate that the above-mentioned loosened components may move towards one another or towards other components, and this may, in the final analysis, result in damage due to collision when the rotary encoder is in operation. It may, however, also be possible that the rotary encoder is still functioning well even with impaired amplitude values of the measuring signal pair, since e.g. the parts with the maximum admissible tolerance cooperate. The characteristic values ascertained from such a rotary encoder may deviate from the ideal, constant characteristic value without an error existing. Hence, it will be of advantage when the characteristic values ascertained are compared with individual quality values stored in the rotary encoder. These quality values may be representative of an unimpaired function of the specific rotary encoder. Furthermore, additional quality values can be defined, which are representative of an only impaired function of the rotary encoder. It may, for example, happen that e.g. optical components get increasingly dirty during operation, so that a failure of the rotary encoder is foreseeable, although it is still functioning well at the moment. For this case, quality values can be provided, a value of which lies between a quality value representative of function failure and a quality value representative of unimpaired operability. Hence, quality values can be representative of a condition of the rotary encoder in which said rotary encoder no longer functions or is just still functioning. In order to avoid the necessity of storing all the quality values that are possible, the quality values may be stored in the rotary encoder in the form of threshold values. Hence, it will suffice to check whether a characteristic value lies within an interval delimited by the threshold values. The quality values can be ascertained in the rotary encoder itself, e.g. in a self-learning process. To this end, the characteristic values or a certain number of characteristic values can be collected and evaluated in the rotary encoder at a specific time, e.g. upon initial operation or upon servicing. In this way, changes which may occur in the measuring signals can be ascertained more precisely and expressed in the quality values. Such a self-learning process may also make sense when the otherwise fault-free rotary encoder does not correspond to an ideal rotary encoder, i.e. when e.g. the measuring signals of a measuring signal pair have different maximum amplitudes or when their phase shift differs from predetermined values. One cause for this behaviour may reside in the use of differently shining LEDs or of detectors having different sensitivities or it may reside in the use of inaccurately manufactured or mounted material measures. This may e.g. be the case if the LEDs used having a different luminosity, if the detectors used have different sensitivities or if the incremental disk is perfectly manufactured or mounted. In such a rotary encoder, a predetermined minimum number of characteristic values can be stored, e.g. when the rotary encoder is operated for the first time. These characteristic values are evaluated in the rotary encoder, and the quality values can then be derived on the basis of a predetermined likelihood of occurrence. The quality values are in this way calibrated to the individual rotary encoder. In order to be able to adapt the quality values even more effectively to each rotary encoder, the quality values, and also the amplitude values of the measuring signal pair, can depend on the rotary angle value. A representation of the quality values of a perfect rotary encoder which, due to its simplicity, is particularly advantageous is obtained, when all the occurring amplitude values of the measuring signals of the measuring signal pair are plotted on a respective axis of a coordinate system. In this case, one of the measuring signals of the measuring signal pair may e.g. plotted on one axis, here referred to as X-axis, and the second measuring signal may be plotted on the second axis, here referred to as Y-axis. When the amplitude value vectors are added, characteristic values will be obtained, which form a ring for all characteristic values in the coordinate system, said ring having a radius whose absolute value corresponds to the sum of the squared amplitudes and a centre that coincides with the origin of the coordinate system. If the amplitude values deviate from the perfect amplitude values already in the unimpaired condition of the rotary encoder or if the phase of the two signals of the measuring signal pair does not correspond to the predetermined values, the shape of the ring will change and become e.g. an ellipse. This can be taken into account when the rotary encoder is being calibrated. Additional fluctuations or deviations of the measuring signals, which may be caused e.g. by soiling, enlarge in this mode of representation the width of the lines which are delimited by the ring or the ellipse, and quality value intervals are formed. If a characteristic value deviates from the quality value unexpectedly, it will lie beside the enlarged boundary of the ring or of the ellipse comprising good quality values. Also in this case, a plurality of ring-shaped or elliptical-shaped areas, which can be represented by different quality values, may be representative of e.g. the functional states of the rotary encoder, including “good”, “still good” or “poor”. If the measuring signal pair is processed e.g. in digitized form, the amplitude values thereof can be assigned to discrete representation values, e.g. in the form of binary digits. These representation values are again combined so as to form a characteristic value, which, in a further embodiment, is used as a characteristic value memory address. Under this characteristic value memory address, a value is stored, which is representative of the functional state of the rotary encoder, such as “good”, “still good” or “poor”, and which may e.g. have a different binary code, depending on the respective status. This value, which corresponds to the former quality value, is read from a digital memory and evaluated. The memory means may especially be part of the verification device. A method for representing the digitized amplitude values, which, due to its simplicity, is particularly advantageous, is given when both representation values are used for addressing the columns and lines of a memory. The calculated memory address represents the characteristic value. In the address space of the memory, admissible quality values are again stored in the above-described elliptical-shaped ring or circular ring. The functional state of the rotary encoder corresponds to the content of the addressed memory location. The characteristic value may also be calculated on the basis of some other combination of the two digitized amplitude values. For example, the “good” and the “still good” quality values may fill the whole address space of the memory. If the amplitude values represent a “poor” functional state of the rotary encoder, the characteristic value memory address can here lie outside of the defined region, since it is a “poor” quality value, and can be interpreted accordingly. If the measuring signal pair is converted into a pair of square wave signals in the rotary encoder, also the function of a signal converter executing the conversion can be checked on the basis of the amplitude values of the two square wave signals. In so doing, the respective amplitude value of one of the two square wave signals is examined in comparison with a quality value. The shape of the square wave signals with amplitude values which are, at least sectionwise, substantially constant allows a process in which it is at least examined whether the square wave signal is either larger than an upper or smaller than a lower quality value. Which square wave signal is examined in comparison with which quality value is decided in the monitoring unit in dependence upon the amplitude values of the measuring signal pair and the characteristic value, respectively. If the angular position changes, the amplitude values of the measuring signal pair as well as those of the pair of square wave signals will change accordingly. The signal pairs pass through four sectors delimited by sector boundaries. The sector boundaries can be defined by amplitude values of the measuring signal pair having identical magnitudes. Also other pairs of amplitude values of the two measuring signals of the measuring signal pair can be used for defining the sector boundaries. Between two sector boundaries it can be determined, especially in dependence upon the ratio of the amplitude values of the measuring signal of the measuring signal pair, which of the square wave signals is examined in which way and in comparison with which quality value. If the phase of the square wave signals is not equal to zero with respect to the measuring signals underlying the square wave signals, the sector boundaries can be shifted by this phase. Since the amplitude values applied at the moment in question are, also in this case, used for checking the function of the rotary encoder or of the signal converter integrated in the rotary encoder, the check can also be carried out when the rotary encoder is stationary. In order to identify also short-circuited signal transmission lines which, in the direction of signal flow downstream of the rotary encoder, connect the latter e.g. with an evaluation unit for rotary encoder signals, the amplitude values of the signals of the pairs of signals can be used also in this case. Since the rotary encoder outputs the measuring signal pair directly and/or as a pair of square wave signals derived from said measuring signal pair, it will be advantageous to apply the method described hereinbelow to both types of signals. Due to short circuiting at least one of the signal transmission lines, the output voltage will collapse in a signal processing unit connected to the signal output. It may also be that the signal processing unit prevents transmission of the signal completely. When, according to a further embodiment, the amplitude values of the signals are, downstream of the signal processing unit when seen in the direction of signal flow, combined individually or as a characteristic value in pairs and compared with the amplitude values or characteristic values of the associated signals or pairs of signals upstream of the signal processing unit, and when the signals downstream of the signal processing unit deviate more than expected from the signals upstream of the signal processing unit, the short circuit of at least one of the signal transmission lines can be detected. When the rotary encoder generates more than one measuring signal pair and, consequently, possibly also more than one pair of square wave signals, the methods described here can be applied to each signal pair. On the basis of the result of the comparison between the characteristic values or amplitude values and the quality values or other characteristic values or amplitude values, respectively, the rotary encoder can output the monitoring signal which depends on said result and which can be used e.g. for a visual display by means of at least one LED, which may also be multicoloured, or for transmission to a control unit, e.g. a PLC. The monitoring signal can represent e.g. the various functional states “good”, “still good” or “poor”. A rotary encoder for executing the above-described method steps comprises a monitoring unit which is adapted to have supplied thereto at least one measuring signal pair and/or at least one pair of square wave signals. On the basis of the amplitude values of the signal pairs, the monitoring unit generates the monitoring signal representative of the function of the rotary encoder. For generating the monitoring signal, the monitoring unit comprises at least one computing module, a verification means, a memory unit and an alarm unit. The computing module can be connected to the sensor unit in such a way that the measuring signal pairs can be transmitted to the computing module. If the measuring signal pairs are converted, e.g. into pairs of square wave signals, by the signal converter which is also provided in the rotary encoder, also these pairs of square wave signals can be transmittable to the computing module e.g. via separate signal lines. In the computing module, a characteristic value can be determined for each signal pair supplied to the module. The characteristic value can be transmitted via signal lines connecting the computing module with the verification means. If a plurality of characteristic values is to be transmitted, these characteristic values can be transmitted via separate lines or via a common line, e.g. as a multi-plex signal. The verification device is preferably adapted to have supplied thereto at least one of the quality values from the memory unit, said quality value being then compared with the characteristic value by the verification device. The verification device may also be adapted to have supplied thereto amplitude values, e.g. the pair of square wave signals, which can then be compared with the quality values in said verification device. Also the memory unit can be adapted to have supplied thereto the characteristic values from the computing module as well as amplitude values, such as the amplitude values of the pair of square wave signals of the signal converter. In the verification means, at least one verification signal can be generated e.g. on the basis of a comparison between at least one characteristic value and at least one quality value. This verification signal can be supplied to the alarm unit which is controllable by the verification signal. On the basis of the verification signal, one monitoring signal or more per verification signal can be generated in the alarm unit. The monitoring signals can be applied individually to a respective monitoring signal output or as at least two monitoring signals to at least one signal output of the alarm unit. Furthermore, the monitoring unit may also comprise a signal comparison unit and an acceleration measuring device, said elements being, in turn, able to produce verification signals which can be supplied at least to the alarm unit. The signal comparison unit can be adapted to have supplied thereto the amplitude values of the measuring signal pairs and/or of the pairs of the square wave signals from the sensor unit or from the signal converter. In addition, the signal comparison unit can be adapted to have supplied thereto the signal pairs applied to the output of the rotary encoder. The signal comparison unit may also be integrated in the verification means. The alarm unit can be connected directly to an error control display for displaying the functional state of the rotary encoder e.g. via at least one LED. Alternatively, the monitoring signal may also be transmittable to a data processing unit, such as a machine control unit or a monitoring signal processing unit. It is also possible that, instead of the monitoring signals, the verification signals are transmittable directly. To begin with, the structural design and the function of a rotary encoder according to the present invention are described with reference to the embodiment according to FIG. 1. Said FIG. 1 shows schematically the structural design of a rotary encoder according to the present invention comprising a sensor unit 1 and a monitoring module 2. The sensor unit 1 transmits a measuring signal pair P1 comprising two sinusoidal and phase-shifted measuring signals M1 and M2 via measuring signal lines 3, 4 and via an electronic signal processing unit T to the signal output 5 of the rotary encoder. A respective further line 6, 7 branches off from the two lines 3, 4, said further lines 6, 7 transmitting the measuring signal pair P1 to signal inputs of the monitoring unit 2. The sensor unit may also be provided with separate signal outputs for outputting the measuring signal pair P1 to the signal input of the monitoring unit 2. In the monitoring unit 2 the measuring signal pair P1 is first supplied to the measuring signal inputs of a computing module 8. In said computing module 8 the measuring signal pair P1 has assigned thereto a characteristic value K, which is supplied to a memory unit 10 via a signal output of a verification device 9 and via a line L, i.e. the measuring signal pair is reduced to a characteristic value. Said characteristic value K is examined in the verification device 9 in comparison with expected characteristic values or quality values E stored in a memory unit 10, which communicates in a quality value-transmitting manner with the verification device 9. A verification signal V representative of the result of this examination controls an alarm unit 11, which is also integrated in the monitoring unit 2 and the signal input of which has supplied thereto via a line 12 the verification signal V from the verification device 9. A signal output 13 of the alarm unit 11 has applied thereto a monitoring signal U which depends on the verification signal V. FIG. 2 shows a further embodiment; elements which correspond to the elements of the embodiment according to FIG. 1 with respect to function and structural design are here designated by the same reference numerals. For the sake of brevity, only the features which are different from those of the embodiment according to FIG. 1 will be discussed. Here, the computing module 8 outputs, via an additional signal output, the characteristic value K also to the memory unit 10 which is connected to the computing module 8 via a line 14. However, said line 14 may also branch off from the line which interconnects the computing module 8 and the verification device 9 in a signal-transmitting manner, or it may be looped through the verification device 9 and then routed to the memory unit 10. The memory unit 10 may also be part of the verification device 9, as indicated by the dot-and-dash line. FIG. 3 shows a third embodiment; elements which correspond to the elements of the embodiments according to FIGS. 1 and 2 with respect to function and structural design are here designated by the same reference numerals. For the sake of brevity, only the features which are different from those of the embodiments according to FIGS. 1 and 2 will be discussed. In FIG. 3 a signal converter 15 is additionally shown, said signal converter 15 being integrated in the rotary encoder. The signal converter 15 has here supplied thereto the measuring signal pair P1 via separate measuring signal outputs of the sensor unit and via lines 16, 17. Said lines 16, 17 may also branch off from the lines 3, 4 which transmit the measuring signal pair P1 from the signal output of the sensor unit 1 to the signal output 5 of the rotary encoder. In the signal converter 15 the sinusoidal measuring signal pair P1 is converted into a pair P2 of square wave signals R1, R2. The square wave signal pair P2 is supplied via lines 18, 19 to additional connections of the signal output 5 of the rotary encoder. Here, two lines 20, 21 branch off from the lines 18, 19, a respective one of the square wave signals R1, R2 of the square wave signal pair P2 being supplied to the verification device via 9 said lines 20, 21. Also in this case, a separate pair of signal outputs of the signal converter 15 may be connected to the signal output 5 of the rotary encoder, an additional pair of signal outputs being then directly connected to the verification device 9 via said lines 20, 21, so that also the square wave signal P2 can be output. In order to allow an examination of the square wave signal pair P2 in the verification device 9, said verification device 9 has supplied thereto a second quality value E2 from the memory unit 10 via line 22. FIG. 4 shows a fourth embodiment; elements which correspond to the elements of the embodiments according to the preceding figures with respect to function and structural design are here designated by the same reference numerals. For the sake of brevity, only the features which are different from those of the embodiments according to the figures that have already been described will be discussed. Here, lines 20, 21 connect the signal converter 15 not to the verification device 9 but to the computing module 8. A second characteristic value K2 is ascertained from the square wave signal pair P2 supplied to the computing module 8, said second characteristic value K being supplied to the verification device 9 via a separate line 23 and to the memory unit 10 via an additional line 24. A signal output of the computing module 8 can, of course, have connected thereto the verification device 9 as well as the memory unit 10. A fifth embodiment is shown in FIG. 5; also in the case of this embodiment, elements which correspond to the elements of the embodiments according to the preceding figures with respect to function and structural design are designated by the same reference numerals. For the sake of brevity, only the features which are different from those of the embodiments according to the figures that have already been described will be discussed. The monitoring unit 2 has here added thereto two further functional units, viz. a signal comparison unit 25 and an acceleration measuring device 26. Both said elements are connected to the alarm unit 11 via a common line. The verification signals generated here can, of course, also be supplied to a respective signal input of the alarm unit via separate lines. The alarm unit 11 has supplied thereto four verification signals representative of the function of four functional units, and, for each of these signals, a monitoring signal U is here outputted at one of the signal outputs 13a-d of the alarm unit 11. The verification device 9 transmits, via line 12, a verification signal V1 representative of the function of the sensor unit 1 and, via line 28, a verification signal V2 representative of the signal converter 15 to the alarm unit 11. Each of the signal outputs 13a-d has applied thereto monitoring signals U a-d, which can be supplied to LEDs, by way of example. For example, three LEDs can be accessed for each of the functional units 1, 15, 25, 26 monitored, so that the operability of the functional units 1, 15, 25, 26 of the rotary encoder can be indicated e.g. via a green, a yellow and a red LED. The monitoring signals U a-d can also be adapted to be transmitted to a data processing unit in which the state of the rotary encoder can be stored in a database and/or displayed on a screen. In particular the verification signal of the signal comparison unit 25 can also be used for recognizing error sources outside of the rotary encoder. For example, a rise in temperature in the area of the signal processing unit T, which may comprise up to one output driver per signal output and at least one temperature sensor, may indicate that, e.g. due to a short circuit outside of the rotary encoder, an inadmissible high current flows through one of the signal outputs 5. For recognizing this fault, it is possible to execute in the signal comparison unit 25, which is connected to the signal outputs 5a-d of the sensor unit 1 and the signal converter 15 in a signal-transmitting manner, a comparison between the amplitude values AM1, AM2, AR1, AR2 of the signal pairs P1, P2 at the signal output 5a-d and the amplitude values AM1, AM2, AR1, AR2 of the signal pairs P1, P2 applied to the signal outputs of the sensor unit 1 and/or the signal converter 15. In order to be able to execute this comparison, characteristic values K, K2 and/or information can be supplied to the signal comparison unit 25 from the computing module 8 for the selection of the square wave signal to be examined. In addition, quality values E, E2 can be supplied to the signal comparison unit 25 from the computing module 8. A verification signal representative of the result of the comparison can be outputted to the alarm unit 11. The acceleration measuring device 26, which comprises e.g. a one-, two- or three-dimensional absolute acceleration sensor, is able to convert shocks or vibration into a further verification signal V, whereby e.g. collisions between components connected to the rotary encoder and other components, or other mechanical faults that generate mechanical vibrations, such as e.g. an incorrect mounting of the rotary encoder or defective ball bearings, can be recognized. FIG. 6 shows a sixth embodiment; also in the case of this embodiment, elements which correspond to the elements of the embodiments according to the preceding figures with respect to function and structural design are designated by the same reference numerals. For the sake of brevity, only the features which are different from those of the embodiments according to the figures that have already been described will be discussed. The flow chart shown here illustrates the method for checking the operability of the rotary encoder on the basis of the measuring signal pair P1. The amplitude values of the measuring signals M1, M2 depending on the angular position φ have here e.g. the form AM1=U cos(kφ) and AM2=U sin(kφ), k being the number of increments. The current amplitude values AM1, AM2 of the measuring signal pair P1, which can be generated in step 29, can here be linked by an arithmetic function so as to obtain the characteristic value K in the characteristic value determination step 30. In the case of the above-mentioned angular function forms of the measuring signals M1, M2, the arithmetic function may e.g. comprise that squares of the amplitude values AM1, AM2 are summed up. In a perfectly constructed and operating rotary encoder, the ideal characteristic value Ki=(AM1)2+(AM2)2=U2 cos2(kφ)+U2 sin2(kφ)=U2 is constant at any moment of operation of the rotary encoder. Due to functional deviations of the rotary encoder in the generation of the measuring signal pair P1 in step 29, which deviations may be caused e.g. by different light densities of the light sources or by a soiled sensor system used for optical rotary encoders, the ascertained characteristic value K may also deviate from the ideal, constant characteristic value Ki. If the measuring signal pair P1, whose deviation from the ideal value causes the deviation of the characteristic value K from the ideal characteristic value Ki, is still good enough for guaranteeing an adequate functioning of the rotary encoder, a verification signal V can be generated upon verifying 31 the characteristic value K, said verification signal V being representative of the functional states of the rotary encoder. In method step 32, the monitoring signal U can be generated in dependence upon the verification signal V. It is also possible to use the verification signal V as a monitoring signal U. If the deviation between the characteristic value K and the ideal characteristic value Ki is too large, so that the function of the rotary encoder can, for example, not be guaranteed for the future, the respective verification signal V can e.g. be used as a basis for outputting a monitoring signal U as a warning or servicing signal. If the deviation between the characteristic value K and the ideal characteristic value Ki is too large, which may e.g. be caused by a measuring signal pair P1 with at least one insufficient amplitude AM1, AM2, a monitoring signal U can be emitted as an error signal on the basis of which e.g. a machine, in which the rotary encoder is installed, is impaired in function. Instead of ascertaining the difference between the ascertained characteristic value K and the ideal characteristic value Ki, the characteristic value K may also be examined in comparison with characteristic value classes Ki, K+, K−. The characteristic value classes Ki, K+, K− define ranges which represent e.g. measuring signals M1, M2 having a “good”, “still good” or “poor” quality. In the embodiments of the figures which have been described so far, these characteristic value classes can be stored e.g. in the memory unit 10 as quality values E, E2 through which also the quality value intervals can be delimited. For establishing individual quality values E, E2 for each rotary encoder, the characteristic values K ascertained in step 30 can be fed to a characteristic value collection and processing step 33, which can be executed in the computing module 8 or in the memory unit 10. Characteristic values K which are collected in a specific period of time, e.g. upon initial operation or upon servicing, can be statistically evaluated in this step 33. The classification of the characteristic value classes Ki, K+, K− or quality values E can here be determined on the basis of a predetermined likelihood of occurrence. In order to exclude, by way of example, that good quality values E ascertained in step 33 represent a measuring signal pair P1 with e.g. at least one insufficient amplitude value AM1, AM2, the quality values E ascertained can, for the purpose of checking, be compared with absolute limit values which may e.g. have been stored in the memory unit 10 in advance. In the seventh embodiment shown in FIG. 7, elements which correspond to the elements of the embodiments according to the preceding figures with respect to function and structural design are again designated by the same reference numerals. For the sake of brevity, only the features which are different from those of the embodiments according to the figures that have already been described will be discussed. The measuring signal pair P1 can here be converted into a pair of square wave signals P2 in a signal conversion step 34. Amplitude values AR1, AR2 of the square wave signals R1, R2 can here be fed directly to the verification step 31 as characteristic values. In the verification step 31, at least one of the amplitude values AR1, AR2 of a pair of square wave signals P2 can be compared with at least one quality value E2. The selection of one of the square wave signals R1, R2 can be executed on the basis of the amplitude values AM1, AM2 of the measuring signal pair P1. Rotary angle values at which the measuring signal pair P1 comprises measuring signals M1, M2 with amplitude values AM1, AM2 of identical absolute value delimit sectors S1 to S4 in which a respective one of the square wave signals R1, R2 is to be examined. In particular, it can be examined whether the amplitude value AR1, AR2 is larger or smaller than an upper or lower quality value E2. If the square wave signals R1, R2 are shifted in phase relative to the measuring signals M1, M2, the sector limits will have to be shifted accordingly. A table illustrating the selection of the square wave signal to be examined is shown in FIG. 11. In the verification step 31, a second verification signal V2 is here generated, which is representative of “good”, “still good” or “poor” amplitude values AR1, AR2 or other functional features also for the square wave signal pair P2 and on the basis of which the monitoring signal U can be generated. The characteristic values K, K2 are here fed to the verification step 31 and to the memory unit 10. An eighth embodiment is shown in FIG. 8; also in the case of this embodiment, elements which correspond to the elements of the embodiments according to the preceding figures with respect to function and structural design are designated by the same reference numerals. For the sake of brevity, only the features which are different from those of the embodiments according to the figures that have already been described will be discussed. FIG. 8 shows a further method for ascertaining the characteristic value K from the amplitude values AM1, AM2. The characteristic value K can here be ascertained more easily, since the amplitude values AM1, AM2 need not be squared. FIG. 8 shows a coordinate system comprising axes X and Y, which are arranged at right angles to one another and which both have the same scale. If a respective one of the amplitude values is plotted on these axes X and Y as a vector, in the present case e.g. amplitude value AM1 on the X-axis and amplitude value AM2 on the Y-axis, the sum vector will point to the characteristic value K. If the characteristic value K represents good amplitude values AM1, AM2, it will lie in a range of good quality values arranged in the quality value ring 35. Quality values E which are still good are represented by the quality value rings 36 and 37, poor quality values E lie outside of the regions 38 and 39. The number of characteristic values stored can depend on the resolution of the participating ND converters, i.e. it may comprise a field of 1024×1024. Alternatively, parts of the ND converter may also be masked so as to reduce memory requirements. For an individual calibration of the quality values E, E2 to a rotary encoder, a certain number of characteristic values K can be stored and evaluated in the rotary encoder. If e.g. 5000 characteristic values K are evaluated, this can be considered as a spot sample from a large number of possible characteristic values K. If the histogram of the 5000 characteristic values K has a normal distribution with a standard deviation, e.g. an upper and a lower quality value E, E2 can be determined, said upper and lower quality values E, E2 defining together e.g. the “still good” range for the characteristic values K. The quality values E, E2 may be spaced apart at a distance corresponding to six times the standard deviation of the characteristic values K. If a characteristic value K ascertained later on should lie outside of this range, the rotary encoder can output a monitoring signal U indicating this event. If the histogram of the 5000 characteristic values K should have a different distribution, the quality values E will have to be ascertained in some other suitable way. Such a spot sample can also be ascertained and evaluated when the rotary encoder is being serviced. A change in phase between the measuring signals M1, M2 of the measuring signal pair P1 can also be detected when the rotary encoder is stationary. During this self-learning process, quality values E, E2 of working, but not perfectly working rotary encoders, whose measuring signal pair P1 comprises e.g. measuring signals M1, M2 having different maximum amplitude values AM1, AM2, can be ascertained individually. FIG. 9 shows a ninth embodiment; elements which correspond to the elements of the embodiments according to the preceding figures with respect to function and structural design are designated by the same reference numerals. For the sake of brevity, only the features which are different from those of the embodiments according to the figures that have already been described will be discussed. The quality value rings 35 to 39 may also be imaged in an at least two-dimensional characteristic diagram, i.e. a digital memory by way of example. The digitized amplitude values AM1, AM2 correspond here to memory addresses which are adapted to be combined with one another for calculating a characteristic value memory address Ks. The characteristic value memory address Ks comprises preferably more than two states or more than one bit so as to be able to classify the quality values stored under this characteristic value memory address Ks as “good”, “still good”, “poor”, etc., each status having assigned thereto one or more quality values E. If a classification as “good” and “poor” does suffice, this can also be represented in two states, e.g. as 0 or 1. The digital amplitude values AM1, AM2 may also be combined in some other form, so that the quality values E are not imaged in the memory as quality value rings 35 to 39. For example, the quality values E2 which are at least still good may, together with the good quality values E, occupy the whole memory, and ascertained characteristic value memory addresses Ks, which are ascertained on the basis of poor amplitude values AM1, AM2, may lie outside of the valid address space. The selected square wave signal R1, R2 can be examinable in a comparable manner, analogously according to FIG. 8 or digitally according to FIG. 9. Said examination can be based on amplitude values AR1, AR2 or on characteristic values E2. The verification means 10 is able to read, especially on the basis of the characteristic value memory address Ks ascertained in the computing module 8, the content of this address in the memory unit 10. A tenth embodiment is shown in FIG. 10; also in the case of this embodiment, elements which correspond to the elements of the embodiments according to the preceding figures with respect to function and structural design are designated by the same reference numerals. For the sake of brevity, features which are different from those of the embodiments according to the figures that have already been described will be discussed. The coordinate system according to FIG. 8 is here shown once more. In addition, the sectors S1 to S4, which are delimited by sector boundaries 40, 41 and in which the amplitude value AR1, AR2 of a respective one of the square wave signals R1, R2 has to be examined, are shown. When the measuring signals M1, M2 of the measuring signal pair P1 are shifted in phase by 90° relative one another, the axes X, Y and the sector boundaries 40, 41 define an angle of 45°, the cosinoidal measuring signal M1 being here plotted on the X-axis and the sinusoidal measuring signal M2 on the Y-axis. FIG. 11 shows an eleventh embodiment; in the case of this embodiment, elements which correspond to the elements of the embodiments according to the preceding figures with respect to function and structural design are designated by the same reference numerals. For the sake of brevity, the features which are different from those of the embodiments according to the figures that have already been described will be discussed. Here, a table is shown, which illustrates the determination of the sectors S1 to S4 on the basis of the ratio of the amplitude values AM1, AM2 of the measuring signal pair P1. The sector boundaries 40 and 41 are determined by amplitude values AM1, AM2 of the measuring signal pair P1 which are absolutely equal or equal in terms of their absolute value. In order to be able to assign the sectors S1 to S4, it is here defined that the measuring signal M1 is converted into the square wave signal R1, said measuring signal M1 and said square wave signal R1 having the same frequency and being not shifted in phase relative to one another. The measuring signal M2 is converted into the square wave signal R2. The square wave signal R2 is not shifted in phase relative to the measuring signal M2 either, and both signals have the same frequency. In sector 1, the absolute value of the amplitude value AM2 of the measuring signal M2 is smaller than the amplitude value AM1 of the measuring signal 1. In the thus defined sector 1, it is examined whether the amplitude value AR1 of the square wave signal R1 is larger than an upper quality value. In sector 2, the magnitude of the amplitude value AM1 is smaller than the amplitude value AM2. In this sector it is examined whether the amplitude value AR2 is larger than an upper quality value. In sector S3, the negative amplitude value AM1 is larger than the absolute value of the amplitude value AM2. In sector S4, the negative absolute value of the amplitude value AM2 is larger than the amplitude value AM1. In this sector it is examined whether the amplitude value AR2 is smaller than a lower quality value.
	description	1. Field of the Invention The present invention relates generally to spacer grids for nuclear fuel assemblies for reducing flow-induced vibrations and, more particularly, to a spacer grid for a nuclear fuel assembly which is formed from grid strips of an improved structure, thus reducing flow-induced vibration. 2. Description of the Related Art A nuclear reactor refers to a device that is designed to exert artificial control over the chain reaction of the nuclear fission of fissile materials and use thermal energy generated from the nuclear fission as power. Generally, nuclear fuel that is used in a nuclear reactor is formed in such a way that enriched uranium is molded into a cylindrical pellet of a predetermined size and many pellets are inserted into fuel rods. The fuel rods constitute a nuclear fuel assembly. The nuclear fuel assembly is loaded in a core of the nuclear reactor before it is burned up in a nuclear reaction. Referring to FIG. 1, a typical nuclear fuel assembly includes a plurality of fuel rods 10 which are located in an axial direction, a plurality of spacer grids 20 which are provided in a transverse direction of the fuel rods 10 and support the fuel rods 10, a plurality of guide thimbles 30 which are fixed to the spacer grid 20 and form a framework of the assembly, and a top nozzle 40 and a bottom nozzle 50 which respectively support upper and lower ends of the guide thimbles 30. About 200 or more fuel rods 10 are used to form the nuclear fuel assembly. Enriched uranium is molded into a pellet of a predetermined size and installed in each fuel rod 10. The top nozzle 40 and the bottom nozzle 50 support the upper and lower ends of the guide thimbles 30. The top nozzle 40 is provided with elastic bodies to push down an upper end of the nuclear fuel assembly, thus preventing the pressure of a coolant flowing from a lower end of the nuclear fuel assembly towards the upper end thereof from lifting up the nuclear fuel assembly. The bottom nozzle 50 supports the lower ends of the guide thimbles 30. A plurality of flow holes through which the coolant is supplied into the nuclear fuel assembly are formed in the bottom nozzle 50. The several spacer grids 20 are arranged at predetermined intervals with respect to the axial direction of the fuel rods 10. According to the arrangement location and function, the spacer grids 20 are classified into medial spacer grids, mixing spacer grids which enhance the performance of mixing the coolant, and a protective spacer grid which filters out foreign substances. Referring to FIG. 2, the spacer grids are commonly formed by a plurality of grid strips assembled in a lattice shape. In each spacer grid, a single fuel rod or guide thimble is disposed in each of the lattice cells. In detail, the spacer grid 20 includes a plurality of an outer grid strip 21 which forms an outer frame of a structure, and horizontal grid strips 22 and vertical grid strips 23 which are arranged and fixed inside the outer grid strip 21 and form a lattice shape. The fuel rods are disposed in the corresponding lattice cells 20a formed in the spacer grid 20 having the above-mentioned construction. Further, guide thimble lattice cells 20b into which the guide thimbles are inserted are formed in the spacer grid 20. The fuel rods are assembled with the spacer grid in such a way that dimples and springs are provided on the grid strips that form the lattice cells so that the grid strips elastically support the fuel rods. Each guide thimble may be welded to the spacer grid or may be mechanically fixed thereto by a sleeve. Meanwhile, during a process of supplying a coolant into the flow hole of the bottom nozzle 50, foreign substances, for example, pieces of metal, chips or shavings which are created when cooling equipment or piping equipment is produced, installed or repaired, may enter, along with the coolant, through the flow hole of the bottom nozzle 50. If such foreign substances enter the assembly along with the coolant, they may damage the jacket tubes. Therefore, foreign substances along with the coolant must be prevented from entering the nuclear fuel assembly. Among the spacer grids, the protective spacer grid that is disposed adjacent to the bottom nozzle 50 functions not only to support the fuel rods but also to filter out foreign substances which may be drawn, along with the coolant, into a nuclear reactor during the process of circulating the coolant. The protective spacer grid is also named a filtering spacer grid. For instance, protective spacer grids were proposed in Korean Patent Registration No. 10-0898114 (date: May 11, 2009), No. 10-0918486 (date: Sep. 15, 2009), No. 10-0907634 (date: Jul. 7, 2009), No. 10-0907635 (date: Jul. 7, 2009), No. 10-0982302 (date: Sep. 8, 2010), No. 10-0927133 (date: Nov. 10, 2009) which are filed by the applicant of the present invention. The conventional protective spacer grids are provided with filtering parts which protrude from surfaces of grid strips in bent shapes so as to filter out foreign substances from a spacer grid. In particular, the purpose of the conventional protective spacer grids is not only to improve the performance of filtering out foreign substances that pass through a flow hole of a bottom nozzle but also to minimize a pressure drop that is caused by a reduction in the cross-sectional area of the flow hole. FIG. 3 is a perspective view illustrating a protective spacer grid according to a conventional technique. Only one of lattice cells formed from a plurality of grid strips is shown in this drawing. Referring to FIG. 3, the conventional spacer grid 60 includes dimples 62 which are formed in the grid strips 61 to support a corresponding fuel rod, and filtering parts 63 which bend and protrude in arc-shapes so as to filter out foreign substances. A separate spring may be provided to elastically support the fuel rod, although it is not shown in the drawing. To more reliably prevent foreign substances from entering the fuel assembly, the shape of each filtering part 63 of the protective spacer grid may be complicated, or the cross-sectional area of the filtering part 63 may be widened, thus reducing the size of the space so that foreign substances cannot pass it. However, because pressure drop of the coolant is proportional to the cross-sectional area of the spacer grid when seen in the axial direction, the shape of the filtering parts cannot be designed just to be complex, even though the complex design can enhance the performance of filtering out foreign substances. As such, the shape and structure of the filtering parts or the dimples of the protective spacer grid are susceptible to pressure drop of a coolant. Thereby, flow-induced vibration may be caused by the coolant that is drawn into the fuel assembly at high speed. When the natural frequency of the protective spacer grid and the frequency of flow-induced vibration attributable to turbulence formed around the edges of the grid strips of the protective spacer grid are within the same range, the protective spacer grid is subject to large vibrations because of resonance. If the protective spacer grid undergoes large vibrations for a long period of time, fatigue damage or rupture occurs, acting as a mechanism of damaging the nuclear fuel assembly. Hence, the spacer grids, in particular, the protective spacer grid which is disposed adjacent to the bottom nozzle, must be designed to reduce flow-induced vibrations. Accordingly, the present invention has been made keeping in mind the above problems occurring in the prior art, and an object of the present invention is to provide a spacer grid for a nuclear fuel assembly which is formed from grid strips of an improved structure, thus reducing flow-induced vibrations. In order to accomplish the above object, the present invention provides a spacer grid provided in a lower end of a nuclear fuel assembly and having a dimple for supporting a fuel rod, the spacer grid including a plurality of grid strips assembled in a lattice shape to form lattice cells, each of the grid strips having at least one hole formed separately from the dimple. The hole may be formed in a planar surface of each of the grid strips above or below the dimple. Each of the grid strips may include a filtering part formed by slitting a portion of a surface of the grid strip, the filtering part perpendicularly protruding from the surface of the grid strip to filter out foreign substances. Preferably, the hole may be formed in the planar surface of the grid strip above the dimple, or between the dimple and the filtering part, or below the filtering part. The hole may comprise two or more holes formed in a surface of the grid strip and arranged with respect to a horizontal direction. More preferably, each of the holes may be circular or elliptical. The invention now will be described more fully hereinafter with reference to the accompanying drawings, in which various embodiments are shown. Specific structures or a functional description described in the embodiments are given only to explain the embodiments according to the concept of the present invention. This invention may be embodied in many different forms, and should not be construed as being limited to the embodiments set forth herein. All possible modifications, additions and substitutions must be considered as falling within the scope and spirit of the invention. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another element. For instance, a first element discussed below could be termed a second element without departing from the teachings of the present invention. Similarly, the second element could also be termed the first element. It will be understood that when an element is referred to as being “coupled” or “connected” to another element, it can be directly coupled or connected to the other element or intervening elements may be present therebetween. On the other hand, it should be understood that when an element is referred to as being “directly coupled” or “directly connected” to another element, there are no intervening elements present. Other expressions for describing a relationship between elements, e.g. “between” and “directly between” or “adjacent to” and “directly adjacent to”, must also be construed in the same way. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting. As used herein, the singular forms “a,” “an” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprise”, “include”, “have”, etc. when used in this specification, specify the presence of stated features, integers, steps, operations, elements, components, and/or combinations of them but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or combinations thereof. Hereinafter, a preferred embodiment of the present invention will be explained in detail with reference to the attached drawings. For reference, although a protective spacer grid having a separate filtering part for filtering out foreign substances will be explained in this embodiment, the present invention is not limited to this embodiment. For example, the present invention may be applied to a general spacer grid of a nuclear fuel assembly in the same way. Referring to FIG. 4, a protective spacer grid 100 according to the present invention is provided under a lower end of a nuclear fuel assembly and includes dimples 110 for supporting a fuel rod in the same manner as that of the conventional technique. The protective spacer grid 100 further includes filtering parts 120 which filter out foreign substances. Although it is not shown in the drawings, a spring for elastically supporting the fuel rod may be provided in the protective spacer grid 100. Particularly, the protective spacer grid of this embodiment is formed from a plurality of grid strips 101 which form lattice cells, wherein each grid strip 101 has at least one hole 130 which is formed separately from the dimples 110 or the filtering parts 120. Each of the dimples 110 and the filtering parts 120 is formed by slitting portions of the corresponding grid strip 101 and protruding inwards or outwards a portion defined by the slit so that it has an arc shape. Here, although the slits are formed in the grid strips 101 to form the dimples 110 and the filtering parts 120, the holes 130 must be interpreted as being separately formed in the grid strips 101 regardless of the dimple 110 and the filtering part 120. As such, because the holes 130 are formed in the grid strips 101 that form the spacer grid, when the coolant is drawn into the fuel assembly, a pressure difference between opposite sides of the holes 130 is reduced, and friction generated between cut edges of the holes 130 and the coolant reduces the magnitude of vibrations and causes a damping effect, thus resulting in a reduction of flow-induced vibrations. Furthermore, the purpose of the holes 130 formed in the grid strips 101 is to widen the range of the frequency of flow-induced vibration caused by vortex sheddings formed around the edges of the grid strips, thus reducing the possibility of the generation of resonance with the natural frequency of the protective spacer grid. In the present invention, a variety of modifications of the structure of the holes formed in the grid strips of the spacer grid are possible. For example, although FIG. 4 illustrates that the holes 130 of the same size are formed in each of the four grid strips 101 of a unit lattice cell at the same positions, the present invention is not limited to this. In other words, holes of different sizes may be formed in each grid strip at different positions. As another example, a single large hole may be formed in a predetermined portion of each grid strip. However, if the same area is given, forming several small holes is effective at preventing the structural strength of the grid strip from being reduced. FIGS. 5A and 5B are views showing other embodiments of the protective spacer grid of the nuclear fuel assembly of the present invention. As shown in FIG. 5A, a plurality of holes 130 may be formed in each grid strip above the dimples 110, between the dimples 110 and the filtering parts 120, and below the filtering parts 120. Furthermore, holes 130 may be formed in some of the above-stated portions. Alternatively, as shown in FIG. 5B, a single large elongated hole 130, rather than a plurality of holes, may be formed. In the present invention, given the structure of the dimples, the filtering parts or the spring, the positions, sizes or shapes of the holes formed in the grid strip can be modified in a variety of manners, without reducing the structural strength of the grid strip. Within such conditions, it will be preferable that an effective area of holes formed in the grid strip be set to be large. As described above, in a spacer grid for a nuclear fuel assembly according to the present invention, a dimple and a filtering part are formed by slitting portions of each of grid strips that form lattice cells and by protruding them from the surface of the grid strip. Each grid strip has holes which are formed separately from the dimple or the filtering part. Therefore, when a coolant is drawn into the fuel assembly, the pressure difference between opposite sides of the holes is reduced, and friction generated between cut edges of the holes and the coolant reduces the magnitude of the vibration and causes a damping effect, thus resulting in a reduction of the flow-induced vibration. Furthermore, the holes formed in the grid strip function to widen the range of the frequency of the flow-induced vibration caused by vortex sheddings formed around the edges of the grid strip, thus reducing the possibility of the generation of resonance with the natural frequency of the spacer grid. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
	abstract	A programmable actuator having multiple programmable functions is provided. The programmable actuator may be used on an off-board tool. In accordance with an embodiment, an off-board tool, OBT, including a user-defined programmable actuator is provided. In accordance with another embodiment, an OBT includes a processor, an internal memory, a programmable actuator, program logic and perform function logic. In accordance with yet another embodiment, a method of actuating performance of a user-defined series of functions for a OBT is provided. The method includes the step of actuating a programmable actuator of the OBT with a single actuating action.
	claims	1. A method of making a storage/transport container for radioactive material, the method comprising the step of: subdividing a chamber formed between an inner shell and an outer shell into first and second compartments by means of a foraminous partition having a predetermined maximum mesh size; introducing into one of the compartments an aggregate of a predetermined minimum particle size greater than the predetermined maximum mesh size; and introducing into the first compartment a suspension of cement and water such that the aggregate remains in the one compartment and the cement and water flow through the partition into the second compartment 7 . 2. The container-making method defined in claim 1 wherein the partition is formed by a perforated screen, plate, or netting. claim 1 3. The container-making method defined in claim 1 wherein the mesh size is between 2 mm and 4 mm. claim 1 4. The container-making method defined in claim 1 , further comprising the step of claim 1 supporting the partition between the shells on webs bridging the chamber and bearing on the shells. 5. The container-making method defined in claim 1 further comprising the step of claim 1 supporting the partition between the shells on an inner array of inner webs and an outer array of outer webs. 6. The container-making method defined in claim 5 wherein the partition is shaped to fit complementarily with the inner and outer webs. claim 5 7. The container-making method defined in claim 5 wherein the inner and outer webs are arrayed in pairs interconnected by respective inner and outer bridges secured to the respective shells. claim 5 8. The container-making method defined in claim 5 wherein the partition is welded to the webs. claim 5 9. The container-making method defined in claim 1 wherein the one compartment is the second compartment, whereby the aggregate and cement/water suspension are introduced into the same compartment. claim 1 10. The container-making method defined in claim 9 wherein the one and second compartment are an inner compartment adjacent the inner shell, the other and first compartment being an outer compartment adjacent the outer shell. claim 9
	claims	1. An apparatus for inspecting and testing a startup range neutron monitoring system, the apparatus comprising:a neutron-flux detector that detects neutron flux existing in a pressure vessel of a nuclear reactor;a preamplifier that amplifies an electric signal output from the neutron-flux detector;a pulse measurement unit that counts times when electric signal output from the preamplifier exceeds a discrimination voltage;a discrimination-voltage setting unit that applies the discrimination voltage to the pulse measurement unit;a voltage-setting unit that applies a voltage to the neutron-flux detector;an arithmetic processing unit that calculates an output power of the nuclear reactor based upon an output signal of the pulse measurement unit;an output unit that outputs data representing the output power of the nuclear reactor, calculated by the arithmetic processing unit; andan inspecting/testing unit that sets the discrimination voltage and the voltage to be applied by the voltage-setting unit. 2. The apparatus according to claim 1, whereinthe inspecting/testing unit sets different voltages at regular time intervals. 3. The apparatus according to claim 2, whereinthe inspecting/testing unit is configured to arbitrarily set a voltage range of voltages, voltage intervals, and time intervals at which the voltages are applied. 4. The apparatus according to claim 1, whereinthe inspecting/testing unit has a function of storing parameters used for operations, supplied from the arithmetic processing unit or from the output unit, the data being processed, and the calculated output power of the nuclear reactor. 5. The apparatus according to claim 1, further comprising a transfer unit that is connected to a data terminal to receive and supply data from and to the inspecting/testing unit. 6. The apparatus according to claim 1, wherein:the arithmetic processing unit calculates the output power of the nuclear reactor based upon the output signal of the pulse measurement unit during an activation period of nuclear reactor. 7. The apparatus according to claim 6, wherein:the activation period of nuclear reactor corresponds to an output power of 10−9% to 10−4% of that of a normal operation of the nuclear reactor. 8. The apparatus according to claim 1, wherein:the arithmetic processing unit calculates the output power of the nuclear reactor based upon the output signal of the pulse measurement unit during an activation period of nuclear reactor; andthe arithmetic processing unit calculates the output power of the nuclear reactor based upon an output signal of a Campbell measurement unit during an operational period of nuclear reactor that follows the activation period. 9. The apparatus according to claim 8, wherein:the activation period of nuclear reactor corresponds to an output power of 10−9% to 10−4% of that of a normal operation of the nuclear reactor; andthe operational period of nuclear reactor corresponds to an output power of 10−5% to 10% of that of the normal operation of the nuclear reactor.
	claims	1. An electron beam detecting device, by which a state of an electron beam radiated by an electron beam radiation device is detected, the electron beam detecting device comprising:a plurality of conductors disposed such that each one of the plurality of conductors is arranged corresponding to each one of a plurality of filaments, the plurality of filaments are provided in the electron beam radiation device to radiate thermal electrons, the conductors being electrically insulated from each other, in the area in which the electron beams are radiated;a plurality of measuring units, each measuring unit corresponding to one conductor, the plurality of measuring units measuring the current value flowing through each one of the conductors; anda determining unit determining the radiation level of the electron beams by receiving a signal output by each of the plurality of measuring units, the determining unit judging that when one of the measuring units measures a decrease in the electrical current value, an abnormal condition exists in the filament corresponding to the conductor in which the lower current value is detected. 2. The electron beam detecting device according to claim 1,wherein the plurality of conductors are disposed in parallel to the plurality of filaments. 3. The electron beam detecting device according to claim 1,wherein the plurality of conductors are attached to an outer surface of a radiation window for outputting the electron beams from the electron beam radiation device to the outside thereof. 4. The electron beam detecting device according to claim 3,wherein the plurality of conductors are attached to an insulator fixed to the radiation window to enclose the radiation window.

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