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061987867 | summary | FIELD OF THE INVENTION This invention relates generally to the method of controlling reactor system pressure for a nuclear power plant and more particularly, to controlling the reactor system pressure of a boiling water reactor by reactor core power modulation. BACKGROUND OF THE INVENTION A conventional boiling water reactor (BWR) includes a pressure vessel containing a nuclear fuel core immersed in circulating coolant, i.e., water, which removes heat from the nuclear fuel. The water is boiled to generate steam for driving a steam turbine-generator for generating electric power. The steam is then condensed and the water is returned to the pressure vessel in a closed loop system. Piping circuits carry the heated water or steam to the steam generators and turbines and carry recirculated water or feedwater back to the pressure vessel that contains the nuclear fuel. The BWR includes several conventional closed-loop control systems that control various individual operations of the BWR in response to demands. For example a control rod drive control system (CRDCS) controls the position of the control rods within the reactor core and thereby controls the rod density within the core which determines the reactivity therein, and which in turn determines the output power of the reactor core. A conventional recirculation flow control system (RFCS) is used to control core flow rate, which changes the steam/water relationship in the core and can be used to change the output power of the reactor core. These two control systems work in conjunction with each other to control, at any given point in time, the output power of the reactor core and thereby establish the electrical power output of the electric generating plant. A turbine control system (TCS) controls steam flow from the BWR to the turbine based on pressure regulation or load demand. The operation of these systems, as well as other conventional systems, is controlled utilizing various monitoring parameters of the BWR. Some monitoring parameters include core flow and flow rate effected by the RFCS, reactor system pressure, which is the pressure of the steam discharged from the pressure vessel to the turbine that can be measured at the reactor dome or at the inlet to the turbine, neutron flux or core power, feedwater temperature and flow rate, steam flow rate provided to the turbine and various status indications of the BWR systems. Many monitoring parameters are measured directly by conventional sensors, while others, such as core thermal power, are conventionally calculated using measured parameters. Output from the conventional sensors and calculated parameters are input to an emergency protection system to assure safe shutdown of the plant, isolating the reactor from the outside environment if necessary, and preventing the reactor core from overheating during any emergency event. Conventional pressure control of the BWR is provided by automatically adjusting the position of the main turbine control valves, or steam admission flow control valves to the turbine. The control system must maintain control valve position margin below valves-wide-open (VWO) so as to provide adequate reactor pressure control should the pressure rise for any reason. If the reactor pressure rises, the steam admission control valves will open beyond the initial position, thus restoring the reactor system pressure to its desired value. For a conventional pressure control system, the margin in steam flow between the normal desired operating point of the steam admission flow control valves compared to the steam flow where the steam admission flow control valves are wide open is required to be about 3% of rated steam flow to maintain adequate performance. The main turbine control valves are controlled by a pressure regulation system and valve servo system which position the turbine inlet flow control valves. Also, several steam bypass valves are included in the plant design. These bypass valves are used for plant startup and to bypass excessive steam should the need arise. The pressure regulator uses system pressure as one input and pressure setpoint as the second input. Each of the main turbine control valves is typically controlled by a control valve servo loop which has a flow demand to valve position demand characterizer and the actual valve position as inputs to the control valve servo loop. The bypass valves are typically controlled by a similar servo loop. The bypass valves and in some cases, the main control valves are opened in a planned sequence according to steam flow demand needs. The current BWR reactor system pressure regulation requires the main turbine control valves to change position or modulate to maintain reactor system pressure. As noted above, when the reactor pressure decreases, the control valves close to restore reactor system pressure to the desired value, or conversely, if the reactor system pressure increases the control valves open to reduce reactor system pressure to the desired value. As an example, for many BWR types of plants, the main turbine valves are typically operated in full arc mode, i.e., all turbine flow control valves move together, with average position near 50% of wide open. Control valve modulation is around this average valve position. If operation greater than about 60% valve position is attempted, the pressure control system will become less effective and steady plant operation can not usually be maintained. Other BWR plants operate in partial arc mode in which the turbine control valves are opened in a planned sequential order. In partial arc mode, conventional pressure control at full power is primarily accomplished with all but one turbine control valve wide open. The last turbine control valve modulates at a partially open position, typically about 30% of wide open. When the main turbine control valves are operating near their normal full power position, i.e., 50% open in full arc mode, the turbine control valves are passing less steam flow to the main turbine than if the valves were wide open for the same system pressure, and as a result less electrical output is generated. It would be desirable to operate a BWR plant under conditions that maximize electrical output and still maintain reactor system pressure within acceptable limits. SUMMARY OF THE INVENTION These and other objects may be attained by a method of controlling the system pressure in a power generating system, having a turbine-generator and a BWR, that modulates the core thermal power of the reactor while maintaining the main turbine control valves in a constant steady position. The constant steady position may be wide open, but may be any position that is greater than 75 percent of wide open. The core thermal power may be adjusted by adjusting the control rod density within the reactor core. Alternatively, the core thermal power may be adjusted by adjusting the flow rate through the reactor which may be accomplished by modulating the speed of variable frequency recirculation pumps or by modulating recirculation flow control valves. The method includes transferring the power generation system from normal turbine control valve modulation pressure control to core thermal power modulation pressure control. Additionally the method includes modifying the bypass valve closure bias and the power control bias to accommodate the variances from core power modulation pressure control over normal pressure control. If pressure transients are outside of predetermined safety ranges, the method provides for transferring system pressure control back to the standard turbine control valve modulation pressure control. The above described method enables BWR plants to operate the main turbine control valves wide open while maintaining reactor system pressure within acceptable limits. Operating the control valves wide open enables the plant to produce increased electrical output without enlarging the turbine or the generator. |
055704689 | abstract | A method of effectively decontaminating a substance contaminated with radioactivity, in particular, shot blasting grit contaminated with radioactivity, and a decontaminating apparatus which makes it possible for a single apparatus to perform all of the decontamination processes without moving the contaminated substance from one apparatus to another for each process, thereby realizing reduction in the installation space and achieving an improvement in operational efficiency. The method comprises: decontaminating a contaminated substance by washing it with achelate liquid; draining the chelate liquid; raising the temperature of the substance to a level not lower than the boiling point of a solvent by means of hot air; supplying the solvent to the substance to result in rapid vaporization thereof; removing the remaining chelate fluid liquid by the force of this vaporization and draining the same;and drying the substance. |
description | This application claims priority to U.S. Patent Provisional Application 60/747,404, filed May 16, 2006, which is incorporated by reference herein. The invention described and claimed herein was made in part utilizing funds supplied by the U.S. Department of Energy under Contract No. DE-AC03-76SF00098, and more recently under DE-AC02-05CH11231. The government has certain rights in this invention. Most existing electron sources extract electrons from conductors. There are several disadvantages associated with currently-available electron beam sources. The Fermi temperature of the extracted electrons is significantly lower than the electrons remaining in the source, so the electron degeneracy δf (brightness in inverse Compton wavelength units) is close to 1, the maximum allowed by the Pauli exclusion principle. Other factors conspire together to reduce δf many orders of magnitude during extraction. Interactions with the collective electric field (space charge) and with randomly positioned electrons in the beam further decrease the beam brightness. In the case of field emitters, large inhomogeneities in the electric field near the tip also degrade brightness considerably. For example, a state of the art room-temperature field-emitter can produce a DC beam with δf≈10−5, while high-current pulsed RF photoinjector sources for high-energy accelerators strive to produce a beam with δf=2.5×10−12, both significantly lower than the theoretical limit. Herein, a new concept is described for building a novel electron source designed to produce a pulsed beam with δf≈0.6 and longitudinal emittance four orders of magnitude smaller than currently achieved values. This high brightness, low longitudinal emittance pulsed electron source enables a wide range of novel applications that utilize angstrom-scale spatial resolution and μeV-scale energy resolution. A novel scheme for a high-brightness pulsed electron source, which has the potential for many useful applications in electron microscopy, inverse photo-emission, low energy electron scattering experiments, and electron holography is disclosed herein. The source makes use of neutral atoms in an atomic beam. Each cycle of the source begins with a laser pulse that excites a single atom on average to a band of high-lying Rydberg nP states. The resulting valence electron Rydberg wave packet evolves in a nearly classical Kepler orbit. When the electron reaches apogee, an electric field pulse is applied that ionizes the atom and accelerates the electron away from its parent ion. The collection of electron wave packets thus generated in a series of cycles can occupy a phase volume near the quantum limit and it can possess very high brightness. Each wave packet can exhibit a considerable degree of coherence. In one arrangement, the electron energy is in the 10-100 eV range The source has the capability of approaching the brightness quantum limit and of lowering the effective temperature of the electrons orders of magnitude as compared to existing sources. Such a device can open the way for a wide range of novel applications that utilize angstrom-scale spatial resolution and μeV-scale energy resolution. Examples of applications include electron microscopy, inverse photo-emission, and low energy electron scattering experiments, electron holography, and investigations of dynamics on a picosecond time scale using pump-probe techniques. Without wishing to be bound to any particular theory, the concepts for such a source are disclosed below. Several phenomena taken into consideration for construction of the disclosed electron source are also discussed. The source can use, as starting material, an atomic beam of alkali atoms, such as Li, Na, K, Rb, and Cs. Exemplary embodiments of the invention are described with reference to a Cs source, but of course, embodiments using other alkali atoms are also possible. Cesium can be useful because of its high vapor pressure at room temperature. The high atomic weight and significant vapor pressure at low temperatures minimize the effective temperature of the electron due to the thermal motion of the atom. Without wishing to be bound to any particular theory, some physics background is presented. In the rest-frame of a beam of electrons propagating in the z direction, the dimensionless differential phase volume dΓ is: ⅆ Γ = 1 h 3 ⅆ x ⅆ p x ⅆ y ⅆ p y ⅆ z ⅆ p z = ⅆ x ⅆ β x ⅆ y ⅆ β y ⅆ z ⅆ β z ( 2 π ) 3 C 3 ( 1 ) where βx,y,z=νx,y,z/c and c is the velocity of light, and C=/mec=3.86×10−11 cm is the electron Compton wavelength. Assuming that the electron beam is described by a six-dimensional Gaussian distribution in phase space, the total dimensionless phase volume Γ occupied by the electron beam may be expressed in terms of the transverse emittances εx, y and longitudinal emittance εz as follows: Γ = ɛ x ɛ y ɛ z λ _ C 3 ( 2 ) where ɛ x = ( 〈 x 2 〉 - 〈 x 〉 2 ) 〈 β x 2 〉 - 〈 x β x 〉 2 ( 3 ) with similar definitions for εy and εz. Let Ne be the actual number of electrons, and consider the ratio: δ F = N e Γ = C 3 N e ɛ x ɛ y ɛ z = λ _ C 3 B ( 4 ) where B=Ne/εxεyεz is the “brightness”. The Pauli exclusion principle requires δF≦1 for electrons of a given spin polarization; hence εxεyεz≧ λc3. Typically, field emission electron guns of modern design achieve δF up to 5×10−6. For the present electron source it appears possible to reach δF≈2×10−2. The terms degeneracy and brightness are used interchangeably in this disclosure. The usual definition of brightness for a beam is: B = N ε x ε y ε z where N is the average number of electrons per pulse. However, emittances are expressed as dimensionless quantities in Compton wavelength units: λc2εx2= (x−{overscore (x)})2(βx−{overscore (β)}x)2− (x−{overscore (x)})(βx−{overscore (β)}x)2 Using this definition of emittance, brightness and degeneracy are equal. An exemplary embodiment of an electron source 100 is illustrated in FIG. 1. An effusive source 105, such as a Cesium (Cs) oven operating at a temperature of about 500K, generates a beam of neutral Cs atoms 110. The atomic beam 110 can be collimated by passing through a pinhole aperture 115 to reduce the transverse beam temperature to about 5K. Transverse cooling using the 62S1/2−6P3/2 Cs resonance line can be employed also to reduce this temperature to ≈0.01 K. The collimated atomic beam 110 continues into an interaction volume about 10×10×10 μm3 about midway between two plane parallel electrodes 120, 125 that are separated by a distance of about 1 cm and defined by three overlapping and mutually perpendicular laser beams 130, 135, 140, from lasers L1, L2, L3 (only beams are shown), respectively. Heating is avoided by using the laser beams 130, 135, 140 to excite one atom at a time, on average, to a very high lying band of nP Rydberg states (for example n≈800, Δn≈50). The laser beams 130, 135 are made from continuous wave (CW) lasers which excite about a quarter of the atoms through two transitions to the 7S1/2 state. FIG. 2 is a diagram of Cesium energy levels. The third laser 140 is a pulsed laser which excites on average about one atom per pulse up to an extreme Rydberg state (very close to vacuum—about −10−5 eV). For an exemplary embodiment using Cs atoms, the laser properties are shown in Table I. TABLE ILaser 1 (L1)Laser 2 (L2)Laser 3 (L3)Wavelength, λ852 nm1470 nm777 nmCs Transition6S1/2-6P3/26P3/2-7S1/27S1/2-nPModeCWCWPulsedAverage Power0.1 mW0.1 mWPeak Power30 WPulse Length2.5 nsFWHMRep. Rate10 MHz In the exemplary embodiment shown in FIG. 1, laser beam 135 along the beam axis can be used to select a narrow band of longitudinal velocities. Thus excited atoms can have a thermal energy spread ΔE≦10−6 eV, and if the valence electrons are optically excited to ionization threshold (ignoring subsequent space-charge heating), the electron energy spread is δE=(me/MCs)ΔE≦10−11 eV. On the other hand, if many atoms were excited in a given pulse, space-charge interactions would result in an electron temperature given by kT≈e2ne1/3 where ne is the electron density. For example, given a laser-atom interaction volume≈10−9 cm3 and ne≈1010 cm−3, so that only ≈10 electrons are generated simultaneously, space-charge interaction would yield δE≈10−4 eV. The electron in the excited atom has a large kinetic energy and starts to drift away from the atom. After the laser pulse, it takes the electron about 40 ns, in its extreme elliptical classical orbit, to travel from its initial position a few atomic radii from the Cs nucleus to approximately 65-70 μm from the Cs nucleus. In this position, the electron reaches the turning point (apogee) of its orbit where its kinetic energy is negligible. At the orbit apogee, the electron in the Rydberg state is nearly stationary with minimal momentum spread, and distributed within a thick spherical shell with angular distribution 1+3 cos(θ)2 about the polarization axis of the pulsed laser. At this point, a short pulsed voltage ionizes the atom, extracts the electron from the interaction region and moves the electron through the electrode 125. When an electron is at the apogee point as described above, a Cs atom can be ionized, for example, with a 1 ns pulse of a 30 V/cm electric field. For a pulse peak=100 V/cm and FWHM=0.5 ns, the final electron energy is E≈2 eV, with ΔE≈10−4 eV. Several ns after the accelerating pulse, the electron reaches electrode 125 and passes through a circular aperture. The diameter of the aperture can be chosen to minimize aberrations and simultaneously to maintain reasonable field uniformity in the excitation region. Because the electron is so far (approximately 65-70 μm) from the Cs ion, Coulomb interactions with the parent Cs ion introduce minimal increase in emittance and decrease in brightness. After ionization, the electron exits the interaction volume through an aperture in the electrode 125 and into a second region where it is accelerated by an electrode 150 with a DC field to the source operating energy. Then the electron leaves the second region and moves on to one or more electron optics modules (not shown) which can manipulate the distribution of the electron beam 160 in 6-D phase space as desired to form an electron beam suitable for an intended application. After the electron leaves the second region, a “clearing” pulsed field removes the residual ionized Cs atom from the interaction volume in preparation for receiving and ionizing another neutral Cs atom, i.e., before the beginning of the next cycle. Thus the residual ion is no longer in the interaction volume where it could interact with an electron produced in the next cycle. Since each ion is cleared away before the next electron is produced, Coulomb interactions between the electron and previously produced ions are eliminated. Because the electrons are produced one by one, space charge problems are eliminated. Since the electrons are nearly stationary when ionized by the homogeneous ionizing field, they emerge from the atom with very small temperature (approximately 10−9 eV). This more than compensates for the relatively large volume within which the electron is extracted. All these factors work together to yield a beam with δf≈0.6. A process for producing an electron beam, according to an embodiment of the invention, is outlined in FIG. 3. FIG. 4 is a time-line showing a timing sequence within one cycle of the method of FIG. 3. Each cycle of the device 100 begins with a laser pulse that excites a single Cs atom, on average, to a band of high-lying Rydberg nP states. The radial motion of the resulting shell-like valence-electron Rydberg wave packet is nearly classical, describing an elliptical orbit with very high eccentricity. When the electron reaches the orbit apogee far away from the parent atom, an electric field pulse is applied that ionizes the atom and accelerates the electron away from its parent ion. The electron bunch thus generated in a train or series of cycles can occupy a phase volume near the quantum limit and possess very high brightness. Appreciable phase coherence in each electron wave packet can be achieved. Thus the source may be employed to observe coherence effects, e.g., electron holography and other interferometric experiments. As in any coherence experiment involving electrons, interference occurs between different paths over a single electron wave-packet, and successive wave packets are mutually incoherent. However if these packets are similar enough to one another, an interference pattern with significant visibility emerges from the train of pulses. It is possible to achieve such an interference pattern in some embodiments of the invention. An electron source with these parameters can open a wide range of novel applications that utilize angstrom-scale spatial resolution and meV-scale energy resolution. Possible applications for this electron source include angstrom-scale resolution electron microscopy, electron holography, other interferometric experiments, and investigations of dynamics on a picosecond time scale using pump-probe techniques. By accelerating or decelerating the beam, one can adjust the energy and time uncertainties according to the requirements of the target application, subject to the constraint ΔEΔT/=εz≈1.2. In one example, the test beam has an energy spread of approximately 10−4 eV, which corresponds to about 30 ps jitter relative to the ionization pulse. The resulting valence-electron Rydberg wave packet forms a spherical shell that expands radially in Kepler-like motion, with half-period T = πℏ 3 m e e 4 n _ 3 . (The value n≈800 has been chosen as an example because in this case T≈40 ns, which makes possible a range of pulsed laser bandwidths convenient for chirping. However, n≈600 might also be practical). The oscillator strengths for Cs 7S-nP3/2 transitions are much larger than for 7S-nP1/2 when n≧15. Taking into account this spin-orbit effect and assuming that the 777 nm photons are linearly polarized along z, the probability density of the Rydberg wave packet is proportional to 1+3 cos2 θ, where θ is the angle between the z axis and the electron position vector r. The frequency of the 777 nm laser pulse can be chirped so that the classical Kepler orbits for various n values in the vicinity of n=800 all reach apogee simultaneously. The most favorable chirping parameters are found by optimizing a quantum mechanical calculation of laser excitation and subsequent time evolution of the Rydberg wave-packet. FIG. 5 shows radial probability distributions for a Rydberg wave at apogee for chirped and unchirped laser pulses. At apogee the wave packet fills a spherical shell centered on the remaining Cs ion, with mean shell radius <R>≈67 μm and shell half-thickness ΔR≈6 μm. It can be seen that is useful to have the shell width ΔR at apogee reasonably large, because this relaxes restrictions on V. Also it is desirable that the radial part F of the wave function describing the wave packet at apogee be real (apart from an arbitrary overall phase), so that the radial probability current density vanishes everywhere. These goals are achieved by suitable chirping in frequency of the 777 nm laser pulse. FIG. 6 shows the optimum laser intensity profile and frequency chirping for good performance. FIG. 7 shows curves of constant δ for two cases: a) the chirped laser pulse with n=800, ΔR=0.12R; b) an unchirped Gaussian laser pulse amplitude with time dependence exp ( - t 2 4 τ 2 ) .In one arrangement, τ=1 ns is chosen because it gives a wave packet with minimum uncertainty, ΔRΔpR at apogee as a function of τ for n=800. Here, ΔR≈0.02R. The unchirped laser pulse yields a radial wave function at apogee with an r-dependent phase factor, and thus a radial probability current density that does not vanish identically. It appears practical to achieve σ≈10 microns and ηc≈100 cm/s. Assuming this, FIG. 7 shows that for case a) δ≈0.6, while for case b) δ≈0.03. This shows the advantage of chirping and that substantial coherence effects can be realized. At apogee, an electric field pulse with peak value E0 and FWHM=τ0 can ionize the atom and accelerate the electron. It is desirable that E0 and τ0 satisfy the following criteria: ∫Edt is the same for all electrons regardless of θ at apogee; the acceleration is rapid enough that Coulomb interaction between the electron and residual Cs+ ion is minimal; and the final electron energy E is sufficiently large (≈1-10 eV) that electron-optical aberrations on passing through subsequent apertures are minimal. Typical acceptable values are E0=100 V/cm, τ=0.5 ns. Because the electrons are close to the quantum-degenerate limit, ΔEΔt˜h/2π where Δt is the spread in electron arrival times. By a “rotation” in phase space, it is possible to vary ΔE at the expense of Δt for as desired for individual applications. For example, in electron microscope and holographic experiments, very small ΔE (≈10−7 eV) is desirable, while for pump-probe experiments with sub-picosecond resolution, a larger ΔE (≈10−3 eV) can be used. For a Rydberg atom with principal quantum number n, the electric field required for spontaneous ionization is E I = e 16 a 0 2 n 4 ≈ 8 · 10 - 4 V / cm for n = 800. Such a field can be generated by an electronic charge at a distance s=0.014 cm. Therefore it is desirable that when the next laser pulse occurs, the residual ion from the present pulse is at a distance s′>>s from the interaction region. To achieve this, after the acceleration pulse another “ion clearing” electric field pulse can be applied to remove the residual Cs ion from the interaction region. Because the ion is massive, it is desirable to use a clearing pulse with sufficient duration (e.g., ≈100 ns for a pulse amplitude of ≈1 kV/cm). In this example, a cycle repetition rate≈3 MHz can be achieved. At an average of one electron per pulse, this gives an average source current of about 0.5 pA. Of course, other combinations of clearing pulse duration, amplitude, and repetition are possible. Different combinations can yield different average source currents. Stray electric fields and stray magnetic fields can cause undesirable perturbations that degrade brightness. It is desirable to reduce stray electric fields in the interaction region to a level ES=EI; that is to the level ES≦10−4 V/cm. Stray magnetic fields B can cause degradation unless the electron radius of curvature is much greater than R. It can be useful to reduce the ambient magnetic field to a level≦1 mG. This can be done by enclosing the interaction region in an appropriate magnetic shield. It is also desirable to avoid generation of photo-electrons by absorption of stray laser photons on electrode surfaces. Collisions between Rydberg atoms of interest and ground state atoms as well as molecules are unlikely to cause serious difficulties. The probability w for a scattering in the time T=40 ns between the laser pulse and the acceleration pulse is estimated to be about w<<n0σmaxuT≈2·10−5 where u≈2·104 cm/s is the mean relative velocity of the Rydberg atom and ground state atom. The cross-sections for collisions of the Rydberg atom with Cs2 and with background gas molecules are undoubtedly large, but the number densities of these molecules will be so small in ultra-high vacuum that they do not present serious problems. In conclusion, the proposed source can be used in a novel low-energy scanning electron microscope with a current density on the sample of several kA/cm2 and Angstrom resolution. Such resolution is achievable for two main reasons: chromatic aberration is minimized by extremely small energy spread and phase-space volume, and spherical aberration can be compensated by axial symmetric lenses. In fact, the well-defined time structure of the electron beam allows use of focusing or defocusing time-dependent fields, which allows for positive or negative spherical aberration. The ultra-bright pulsed electron source described herein improves brightness by two orders of magnitude and longitudinal emittance four orders of magnitude over existing sources. An electron source with these characteristics opens up new applications, in, for example, electron microscopy, sub-meV energy resolution, inverse photoemission spectroscopy, precise measurement of electric fields in orbital laboratories, energy exchange with tens of μeV accuracy in inelastic atomic and molecular scattering, and new ways of investigating chemical reactions and dynamics on a picosecond time scale using pump-probe techniques. Finally, the feasibility of significant phase coherence opens the possibility of electron holography and other interferometric experiments. |
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description | 1. Field of the Invention The present invention relates to a circulation system for a high refractive index liquid, used for circulating the high refractive index liquid in a pattern forming apparatus that includes a resist coating/developing section and an immersion light exposure section. The resist coating/developing section is structured to perform resist coating on a substrate, such as a semiconductor substrate, and development after light exposure. The immersion light exposure section is structured to subject a resist film formed on the substrate to light exposure in accordance with a predetermined pattern while immersing the resist film in the high refractive index liquid. The present invention further relates to a pattern forming apparatus and pattern forming method using a circulation system for a high refractive index liquid. 2. Description of the Related Art In the process of manufacturing semiconductor devices, photolithography techniques are used for forming circuit patterns on semiconductor wafers. Where a circuit pattern is formed by use of photolithography, the process steps are performed, as follows. Specifically, a resist liquid is first applied to a semiconductor wafer to form a resist film. Then, the resist film is irradiated with light to perform light exposure on the resist film in accordance with the circuit pattern. Then, the resist film is subjected to a developing process. In recent years, the integration degree of semiconductor devices becomes increasingly higher to improve the operation speed and so forth. Accordingly, photolithography techniques are required to increase the miniaturization level of circuit patterns formed on semiconductor wafers. As a photolithography technique for realizing a high resolution of a 45-nm node level, there has been proposed the following immersion light exposure (for example, see U.S. Patent Application Publication No. US 2006/0231206 A1). In this immersion light exposure, a light exposure liquid, such as purified water, having a refractive index higher than air is supplied between the semiconductor wafer and light exposure projection lens. The wavelength of light radiated from the projection lens is shortened by means of the refractive index of the light exposure liquid, so that the line width obtained by the light exposure is decreased. Further, in order to attain a higher resolution, there has been proposed a technique for performing immersion light exposure while using a high refractive index liquid as a light exposure liquid (see “Development of new high refractive index liquid (Delphi) for next-generation immersion light exposure in semiconductor manufacturing,—realizing micro-fabrication of 32 nano-meter line width—,” Sep. 12, 2005, Mitsui Chemicals, Inc. (authorship unknown); Internet [mitsui-chem.co.jp/whats/2005—0912.htm]). According to this technique, the high refractive index liquid is formed of a liquid compound comprising a cyclic hydrocarbon skeleton and having a higher refractive index than purified water, with which a high resolution of a 32-nm node level is realized. In general, cleaning (or rinsing) of a semiconductor wafer is performed by use of a cleaning liquid (or rinsing liquid), such as purified water, before and after immersion light exposure (for example, see Jpn. Pat. Appln. KOKAI Publication No. 2006-80403). Cleaning performed before immersion light exposure is conceived to improve the affinity relative to the light exposure liquid. Cleaning performed after immersion light exposure is conceived to remove part of the light exposure liquid left on the semiconductor wafer. However, where a high refractive index liquid is used as a light exposure liquid, as described above, the conventional cleaning may bring about following problems. Specifically, in the case of cleaning performed before immersion light exposure, the cleaning liquid and light exposure liquid come to be greatly different in physicality, so the resist film suffers bubbles and liquid residues generated during the immersion light exposure due to the residual part of the cleaning liquid. Further, since high refractive index liquids have a high viscosity, it may be difficult to satisfactorily remove the light exposure liquid by cleaning performed after the immersion light exposure. Accordingly, where a high refractive index liquid is used as a light exposure liquid, the conventional cleaning may deteriorate the process uniformity, when performed before and after the immersion light exposure. On the other hand, in light of the cost and environment, the consumption of the light exposure liquid and cleaning liquid should be smaller. Particularly, since high refractive index liquids are expensive in general, a process performed by use of a high refractive index liquid is strongly required to decrease the consumption thereof. In order to decrease the consumption of the light exposure liquid and cleaning liquid, these liquids may be recycled by circulation. However, where the light exposure liquid and cleaning liquid are recycled by circulation, each of these liquids requires a mechanism and treatment for regenerating used liquid, which complicate the entire apparatus and process. An object of the present invention is to provide a circulation system for a high refractive index liquid in a pattern forming apparatus, which can decrease the consumption of a cleaning liquid as well as the high refractive index liquid used as a light exposure liquid, without complicating the apparatus and process. Another object of the present invention is to provide a circulation system for a high refractive index liquid in a pattern forming apparatus, which can prevent the process uniformity on a substrate from being deteriorated. Another object of the present invention is to provide a pattern forming apparatus and pattern forming method using such a circulation system for a high refractive index liquid, and a computer readable storage medium that stores a control program for executing the pattern forming method. According to a first aspect of the present invention, there is provided a circulation system for a high refractive index liquid in a pattern forming apparatus for forming a predetermined resist pattern on a substrate, the apparatus comprising a resist coating/developing section configured to perform a series of processes including resist coating onto the substrate to form a resist film and development of the resist film after light exposure, and including a cleaning section configured to perform cleaning on the substrate after the resist coating and before the light exposure and/or the substrate after the light exposure and before the development, and an immersion light exposure section configured to perform the light exposure on the resist film in accordance with a predetermined pattern while immersing the resist film formed on the substrate in a high refractive index liquid having a refractive index higher than water, the circulation system comprising: a first collecting section configured to collect the high refractive index liquid used in the immersion light exposure section; a first supply section configured to supply the high refractive index liquid collected in the first collecting section to the cleaning section as the cleaning liquid; a second collecting section configured to collect the high refractive index liquid used in the cleaning section; a second supply section configured to supply the high refractive index liquid collected in the second collecting section to the immersion light exposure section; and a control section configured to control an operation of the circulation system, wherein the control section executes control for the high refractive index liquid to be circulated between the immersion light exposure section and the cleaning section, such that the high refractive index liquid is collected from the immersion light exposure section to the first collecting section, then supplied from the first supply section to the cleaning section for use in cleaning, then collected from the cleaning section to the second collecting section, and then supplied from the second supply section to the immersion light exposure section for use in immersion light exposure. In the first aspect of the present invention, the circulation system is preferably arranged such that at least one of the first collecting section and the first supply section and at least one of the second collecting section and the second supply section respectively include storage tanks configured to temporarily store the high refractive index liquid, and the storage tanks store a volatilization-preventive liquid for preventing the high refractive index liquid from being volatilized, the volatilization-preventive liquid having a smaller specific gravity than the high refractive index liquid and being separative from the high refractive index liquid. The circulation system preferably further comprises a filter configured to filtrate the high refractive index liquid after collection in the second collecting section and before supply from the second supply section. The circulation system preferably further comprises a degasifying member configured to degasify the high refractive index liquid after collection in the second collecting section and before supply from the second supply section. The circulation system preferably further comprises a temperature adjusting mechanism configured to adjust to a predetermined temperature the high refractive index liquid after collection in the second collecting section and before supply from the second supply section. In this case, the temperature adjusting mechanism may include, in order from a upstream side to a downstream side in a direction in which the high refractive index liquid flows, a first temperature adjusting portion configured to adjust the high refractive index liquid approximately to the predetermined temperature after collection in the second collecting section, and a second temperature adjusting portion configured to adjust the high refractive index liquid, which has been adjusted approximately to the predetermined temperature by the first temperature adjusting portion, precisely to the predetermined temperature. The high refractive index liquid preferably has a refractive index of 1.5 or higher. According to a second aspect of the present invention, there is provided a pattern forming apparatus for forming a predetermined resist pattern on a substrate, the apparatus comprising: a resist coating/developing section configured to perform a series of processes including resist coating onto the substrate to form a resist film and development of the resist film after light exposure, and including a cleaning section configured to perform cleaning on the substrate after the resist coating and before the light exposure and/or the substrate after the light exposure and before the development; an immersion light exposure section configured to perform the light exposure on the resist film in accordance with a predetermined pattern while immersing the resist film formed on the substrate in a high refractive index liquid having a refractive index higher than water; a high refractive index liquid circulation mechanism configured to circulate the high refractive index liquid in use; and a control section configured to control an operation of the pattern forming apparatus, wherein the cleaning section is configured to perform cleaning of the substrate by use of the high refractive index liquid, the high refractive index liquid circulation mechanism includes a first collecting section configured to collect the high refractive index liquid used in the immersion light exposure section, a first supply section configured to supply the high refractive index liquid collected in the first collecting section to the cleaning section as the cleaning liquid, a second collecting section configured to collect the high refractive index liquid used in the cleaning section, and a second supply section configured to supply the high refractive index liquid collected in the second collecting section to the immersion light exposure section, and the control section executes control for the high refractive index liquid to be circulated between the immersion light exposure section and the cleaning section, such that the high refractive index liquid is collected from the immersion light exposure section to the first collecting section, then supplied from the first supply section to the cleaning section for use in cleaning, then collected from the cleaning section to the second collecting section, and then supplied from the second supply section to the immersion light exposure section for use in immersion light exposure. In the second aspect of the present invention, the pattern forming apparatus may be arranged such that the resist coating/developing section includes a process station configured to perform a series of processes including resist coating onto the substrate to form a resist film and development of the resist film after light exposure, and an interface station interposed between the process station and the immersion light exposure section, and including the cleaning section disposed therein and a transfer mechanism configured to transfer the substrate between the process station, the immersion light exposure section, and the cleaning section, and wherein the immersion light exposure section is set at a positive pressure relative to the interface station, while the interface station is provided with a capture mechanism configured to capture volatilized components of the high refractive index liquid. In this case, the capture mechanism is preferably configured to extract an organic component from volatilized components of the high refractive index liquid captured therein, and to supply the organic component to at least one of the first collecting section, the first supply section, the second collecting section, and the second supply section. According to a third aspect of the present invention, there is provided a pattern forming method for forming a predetermined resist pattern, the method comprising: performing resist coating on a substrate by a resist coating section, thereby forming a resist film; performing light exposure on the resist film in accordance with a predetermined pattern by an immersion light exposure section, while immersing the resist film formed on the substrate in a high refractive index liquid having a refractive index higher than water; performing development of the resist film by a development section after light exposure; and performing cleaning by a cleaning section on the substrate after the resist coating and before the light exposure and/or the substrate after the light exposure and before the development, wherein the high refractive index liquid is circulated between the immersion light exposure section and the cleaning section, such that the high refractive index liquid used for the light exposure is collected from the immersion light exposure section and is then used for the cleaning, while the high refractive index liquid used for the cleaning is collected from the cleaning section and is then used for the light exposure. In the third aspect of the present invention, the pattern forming method preferably further comprises temporarily storing the high refractive index liquid, collected from the immersion light exposure section and the cleaning section, in respective storage tanks before use in the cleaning and the light exposure, wherein the storage tanks store a volatilization-preventive liquid for preventing the high refractive index liquid from being volatilized, the volatilization-preventive liquid having a smaller specific gravity than the high refractive index liquid and being separative from the high refractive index liquid. The pattern forming method preferably further comprises filtrating the high refractive index liquid collected from the cleaning section before use in the light exposure. The pattern forming method preferably further comprises degasifying the high refractive index liquid collected from the cleaning section before use in the light exposure. The pattern forming method preferably further comprises adjusting to a predetermined temperature the high refractive index liquid collected from the cleaning section before use in the light exposure. The high refractive index liquid preferably has a refractive index of 1.5 or higher. According to a fourth aspect of the present invention, there is provided a computer readable storage medium that stores a control program for execution on a computer, the control program, when executed, causing the computer to control a processing apparatus to conduct a pattern forming method for forming a predetermined resist pattern, the method comprising: performing resist coating on a substrate by a resist coating section, thereby forming a resist film; performing light exposure on the resist film in accordance with a predetermined pattern by an immersion light exposure section, while immersing the resist film formed on the substrate in a high refractive index liquid having a refractive index higher than water; performing development of the resist film by a development section after light exposure; and performing cleaning by a cleaning section on the substrate after the resist coating and before the light exposure and/or the substrate after the light exposure and before the development, wherein the high refractive index liquid is circulated between the immersion light exposure section and the cleaning section, such that the high refractive index liquid used for the light exposure is collected from the immersion light exposure section and is then used for the cleaning, while the high refractive index liquid used for the cleaning is collected from the cleaning section and is then used for the light exposure. Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentalities and combinations particularly pointed out hereinafter. An embodiment of the present invention will now be described with reference to the accompanying drawings. In the following description, the constituent elements having substantially the same function and arrangement are denoted by the same reference numerals, and a repetitive description will be made only when necessary. FIG. 1 is a plan view schematically showing a substrate processing apparatus or pattern forming apparatus according to an embodiment of the present invention. FIG. 2 is a perspective view schematically showing the pattern forming apparatus. The pattern forming apparatus 1 is designed to form a predetermined resist pattern on a semiconductor substrate or wafer W. This pattern forming apparatus 1 includes a cassette station 11 used as a transfer station for wafers W, a process station 12 comprising a plurality of processing units each for performing a predetermined process on a wafer W, a light exposure apparatus 14 for performing a light exposure process on a wafer W, and an interface station 13 for transferring wafers W between the process station 12 and light exposure apparatus 14. The cassette station 11, process station 12, interface station 13, and light exposure apparatus 14 are arrayed in series in this order in the longitudinal direction of the pattern forming apparatus 1 (Y-direction). The cassette station 11 includes a cassette table 11a for placing thereon wafer cassettes (CR) each storing a plurality of, e.g., 13 wafers W, and a wafer transfer mechanism 11c for transferring wafers W between the wafer cassettes (CR) placed on the cassette table 11a and a transition unit located in a third processing unit group G3 in the process station 12 described later. The cassette table 11a and wafer transfer mechanism 11c are arrayed in series in this order in the Y-direction. The cassette table 11a has a plurality of, e.g., five positioning portions 11b each for positioning a wafer cassette (CR), arrayed thereon in the width direction of the pattern forming apparatus 1 (X-direction). A wafer cassette (CR) is placed at each of the positioning portions 20a such that its transfer port faces an opening/closing portion 11e formed in a wall of the casing of the wafer transfer mechanism 11c. The wafer transfer mechanism 11c includes a transfer pick 11d disposed in the casing for handling wafers W, so that the wafers W are transferred by the transfer pick 11d between the wafer cassettes (CR) on the cassette table 11a and the transition unit. The process station 12 is arranged in a casing 15, on the front side of which (lower side in FIG. 1), the process station 12 includes a first processing unit group G1 and a second processing unit group G2 arrayed in this order from the cassette station 11 toward the interface station 13. On the rear side of the casing 15 (upper side in FIG. 1), the process station 12 includes a third processing unit group G3, a fourth processing unit group G4, and a fifth processing unit group G5 arrayed in this order from the cassette station 11 toward the interface station 13. Further, the process station 12 includes a first main transfer section A1 interposed between the third processing unit group G3 and fourth processing unit group G4, and a second main transfer section A2 interposed between the fourth processing unit group G4 and fifth processing unit group G5. The first processing unit group G1 includes a plurality of processing units stacked one on the other, which are formed of, e.g., two bottom coating units (BARC) for forming an anti-reflective coating that prevents reflection of light during light exposure on a wafer W, and three resist coating units (COT) for forming a resist film on a wafer W. The second processing unit group G2 includes a plurality of processing units stacked one on the other, which are formed of, e.g., three development units (DEV) for performing a developing process on a wafer W, and two top coating units (ITC) for forming a protection film having water repellency on a resist film formed on a wafer W. Each of the third processing unit group G3, fourth processing unit group G4, and fifth processing unit group G5 includes a plurality of processing units stacked one on the other, which are formed of, e.g., an adhesion unit for performing a hydrophobic process on a wafer W, a pre-baking unit for performing a heating process on a wafer W after resist coating, a post-baking unit for performing a heating process on a wafer W after development, a post-exposure baking unit for performing a heating process on a wafer W after light exposure and before development, and so forth. The third processing unit group G3 includes a transition unit through which wafers W are transferred between the cassette station 11 and first main transfer section A1. The fifth processing unit group G5 includes a transition unit through which wafers W are transferred between the second main transfer section A2 and a first wafer transfer member 21 used in the interface station 13 described later. The first main transfer section A1 is provided with a first main wafer transfer arm 16 for handling wafers W, which can selectively access the units located in the first processing unit group G1, third processing unit group G3, and fourth processing unit group G4. The second main transfer section A2 is provided with a second main wafer transfer arm 17 for handling wafers W, which can selectively access the units located in the second processing unit group G2, fourth processing unit group G4, and fifth processing unit group G5. Chemical solution pumps 18 are respectively disposed between the first processing unit group G1 and cassette station 11 and between the second processing unit group G2 and interface station 13, for supplying process liquids to the first and second processing unit groups G1 and G2. Chemical unit (CHM) are respectively disposed below the first and second processing unit groups G1 and G2, for supplying chemical solutions to the first and second processing unit groups G1 and G2. FIG. 3 is a perspective view schematically showing the interface station 13 used in the pattern forming apparatus 1. The interface station 13 has a casing that defines a first interface station 13a on the process station 12 side and a second interface station 13b on the light exposure apparatus 14 side. The first interface station 13a is provided with a first wafer transfer member 21 disposed to face an opening portion of the fifth processing unit group G5 for transferring wafers W. The second interface station 13b is provided with a second wafer transfer member 22 movable in the X-direction for transferring wafers W. A sixth processing unit group G6 is located on the front side of the first interface station 13a, and includes, e.g., a periphery light exposure unit (WEE), an incoming buffer cassette (INBR), an outgoing buffer cassette (OUTBR), a pre-cleaning unit (PRECLN), and a post-cleaning unit (POCLN), stacked one on the other. The periphery light exposure unit (WEE) is used for performing light exposure selectively only on the edge portion of a wafer W to remove unnecessary resist portion near the edge of the wafer. The incoming buffer cassette (INBR) is used for temporarily placing wafers W to be transferred into the light exposure apparatus 14. The outgoing buffer cassette (OUTBR) is used for temporarily placing wafers W transferred from the light exposure apparatus 14. The pre-cleaning unit (PRECLN) is used for cleaning a wafer to be transferred into the light exposure apparatus 14. The post-cleaning unit (POCLN) is used for cleaning a wafer transferred from the light exposure apparatus 14. A seventh processing unit group G7 is located on the rear side of the first interface station 13a, and includes, e.g., two high-precision temperature adjusting units (CPL), stacked one on the other, for adjusting the temperature of a wafer W with high precision. The first wafer transfer member 21 includes a fork 21a for transferring wafers W. The fork 21a can selectively access the units located in the fifth processing unit group G5, sixth processing unit group G6, and seventh processing unit group G7 to transfer wafers W between these units. The second wafer transfer member 22 includes a fork 22a for transferring wafers W. The fork 22a can selectively access the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN) of the sixth processing unit group G6, the units located in the seventh processing unit group G7, and an incoming stage 14a and an outgoing stage 14b of the light exposure apparatus 14 described later to transfer wafers W between these portions. A gas flow adjusting section 23 is disposed on top of the first interface station 13a to adjust the gas flow inside the first interface station 13a or interface station 13. A humidifier section 24 is disposed on top of the second interface station 13b to humidify the atmosphere inside the second interface station 13b or interface station 13 not to dry a wafer W transferred from the light exposure apparatus. As described above, the process station 12 includes the resist coating units (COT) for applying a resist onto a wafer W to form a film, the development units (DEV) for developing a resist film after light exposure performed by the light exposure apparatus 14, and so forth. The interface station 13 includes the pre-cleaning unit (PRECLN) for cleaning a wafer W after resist coating and before light exposure, and the post-cleaning unit (POCLN) for cleaning a wafer W after light exposure and before development. Accordingly, the process station 12 and interface station 13 constitute a resist coating/developing section. The light exposure apparatus 14 includes an incoming stage 14a for placing thereon wafers W transferred from the interface station 13, and an outgoing stage 14b for placing thereon wafers W to be transferred to the interface station 13. The light exposure apparatus 14 further includes an immersion light exposure section 30 structured to subject a resist film formed on a wafer W to light exposure while immersing the resist film in a predetermined liquid. A wafer transfer mechanism 25 is disposed to transfer wafers W between the incoming stage 14a, immersion light exposure section 30, and outgoing stage 14b. As shown in FIG. 2, a central control section 19 is located below the cassette station 11 and is used for controlling this pattern forming apparatus 1, as a whole, including a high refractive index liquid circulation mechanism 9 described later and so forth. As shown in FIG. 4, this central control section 19 includes a process controller 71 comprising a micro processor for controlling the respective components included in the pattern forming apparatus 1, such as the processing units and transfer mechanisms. The process controller 71 is connected to the user interface 72, which includes, e.g., a keyboard and a display, wherein the keyboard is used for a process operator to input commands for operating the respective components in the pattern forming apparatus 1, and the display is used for showing visualized images of the operational status of the respective components in the pattern forming apparatus 1. Further, the process controller 71 is connected to the storage portion 73, which stores control programs for realizing various processes performed in the pattern forming apparatus 1 under the control of the process controller 71, and programs or recipes for the respective components in the pattern forming apparatus 1 to perform processes in accordance with process conditions. Recipes are stored in the storage medium or media of storage portion 73. For example, the storage medium or media are formed of a hard disc, a semiconductor memory, and/or a portable medium, such as a CDROM, DVD, or flash memory. Further, recipes may be transmitted from another apparatus through, e.g., a dedicated line, as needed. A required recipe is retrieved from the storage portion 73 and executed by the process controller 71 in accordance with an instruction or the like input through the user interface 72. Consequently, each of various predetermined processes is performed in the pattern forming apparatus 1 under the control of the process controller 71. Each of the processing units is provided with its own subordinate unit controller, which controls the operation of the corresponding unit in accordance with instructions transmitted from the process controller 71. In the pattern forming apparatus 1 arranged as described above, wafers W are taken out one by one from a wafer cassette (CR) by the transfer pick 11d of the wafer transfer mechanism 11c. A wafer W thus taken out is transferred by the transfer pick 11d into the transition unit of the third processing unit group G3 of the process station 12. Then, the wafer W is sequentially transferred by the first and second main transfer sections A1 and A2 through predetermined units in the first to fifth processing unit groups G1 to G5, so that the wafer W is subjected to a series of processes in accordance with the order prescribed in the recipe. For example, the wafer W is subjected to an adhesion process in the adhesion unit, formation of a resist film in one of the resist coating units (COT), formation of a protection film in one of the top coating units (ITC), and a pre-baking process in the pre-baking unit in this order. In place of the adhesion process, the wafer W may be subjected to formation of an anti-reflective coating in one of the bottom coating units (BARC), or formation of an anti-reflective coating on a resist film and formation of a protection film on the anti-reflective coating. After the wafer W is subjected to a series of processes in the process station 12, the wafer W is transferred to the transition unit of the fifth processing unit group G5. Then, the wafer W is sequentially transferred by the first wafer transfer member 21 through the periphery light exposure unit (WEE), incoming buffer cassette (INBR), pre-cleaning unit (PRECLN), and high-precision temperature adjusting unit (CPL), so that the wafer W is subjected to a series of processes. Then, the wafer W is transferred by the second wafer transfer member 22 to the incoming stage 14a of the light exposure apparatus 14. Then, the wafer W is transferred by the wafer transfer mechanism 25 to the immersion light exposure section 30, in which the wafer W is subjected to a light exposure process. After the light exposure is finished in the immersion light exposure section 30, the wafer W is transferred by the wafer transfer mechanism 25 to the outgoing stage 14b. Then, the wafer W is transferred by the second wafer transfer member 22 to the post-cleaning unit (POCLN), in which the wafer W is subjected to cleaning. Thereafter, the wafer W is transferred by the first wafer transfer member 21 to the transition unit of the fifth processing unit group G5. Then, the wafer W is sequentially transferred by the first and second main transfer sections A1 and A2 through predetermined units in the first to fifth processing unit groups G1 to G5, so that the wafer W is subjected to a series of processes in accordance with the order prescribed in the recipe. For example, the wafer W is subjected to a post-exposure baking process in the post-exposure baking unit, a developing process in one of the development units (DEV), and a post-baking process in the post-baking unit in this order. Then, the wafer W is transferred to the transition unit of the third processing unit group G3, and is further transferred to a wafer cassette (CR) placed on the cassette station 11. Next, a detailed explanation will be given of the immersion light exposure section 30, pre-cleaning unit (PRECLN), and post-cleaning unit (POCLN) of the light exposure apparatus 14. FIG. 5 is a view schematically showing main portions of the interface station 13 and light exposure apparatus 14 of the pattern forming apparatus 1. FIG. 6 is a sectional view schematically showing the immersion light exposure section 30 of the light exposure apparatus 14. FIG. 7 is a sectional view schematically showing the pre-cleaning unit (PRECLN) located in the interface station 13. The immersion light exposure section 30 is designed to perform so-called immersion light exposure, i.e., to subject a resist film to light exposure in accordance with a predetermined pattern while immersing the resist film in a high refractive index liquid. The high refractive index liquid has a refractive index higher than purified water (having a refractive index of 1.44), and preferably has a refractive index of not less than 1.5. For example, this liquid is a liquid compound comprising a cyclic hydrocarbon skeleton (having a refractive index of 1.63). Each of the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN) is structured to perform cleaning on a wafer W by use of a high refractive index liquid the same as or of the same type as that used in the immersion light exposure section 30. For this reason, as shown in FIG. 5, a high refractive index liquid circulation mechanism 9 (a circulation system for the high refractive index liquid) is disposed over the interface station 13 and light exposure apparatus 14 to use the high refractive index liquid while circulating it between the immersion light exposure section 30 and the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN). The high refractive index liquid circulation mechanism 9 includes a first transportation line 41 for transporting the high refractive index liquid used in the immersion light exposure section 30 to the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN). The circulation mechanism 9 also include a second transportation line 42 for transporting the high refractive index liquid used in the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN) to the immersion light exposure section 30. A liquid regeneration mechanism 5 is disposed to regenerate the high refractive index liquid transported through the second transportation line 42. As shown in FIG. 6, the immersion light exposure section 30 includes an openable chamber (not shown) and a stage 31 located in the chamber for placing thereon a wafer W. A projection lens 32 is disposed to project a mask pattern image, obtained by irradiation with light exposure light from a light source (not shown), onto the wafer W placed on the stage 31 to perform light exposure. Supply ports 33 and collection ports 34 for the high refractive index liquid used as a light exposure liquid are formed in a light exposure liquid distribution member 35, such that the light exposure liquid is supplied from the supply ports 33 into the gap between the wafer W placed on the stage 31 and the projection lens 32, and is then collected from the collection ports 34. The stage 31 is movable in a horizontal direction and slightly rotatable. The stage 31 is provided with an annular projection to surround the wafer W placed thereon, so that the wafer W is held by the annular projection 36, and the light exposure liquid supplied on the wafer W is prevented from flowing out. The projection lens 32 magnifies and projects a mask pattern image at a predetermined magnification onto the wafer W for light exposure. As the light exposure light emitted from the light source, far ultraviolet light, such as KrF excimer laser light, or vacuum ultraviolet light, such as ArF excimer laser light, is used. The light exposure liquid distribution member 35 has an annular shape to surround the distal or lower end of the projection lens 32. The supply ports 33 and collection ports 34 are formed at intervals in annular directions on the bottom of the distribution member 35. The light exposure liquid distribution member 35 is connected to the first and second transportation lines 41 and 42 such that the supply ports 33 communicate with the second transportation line 42 and the collection ports 34 communicate with the first transportation line 41. Accordingly, the light exposure liquid transported through the second transportation line 42 is supplied from the supply ports 33, while the light exposure liquid collected from the collection ports 34 is transported through the first transportation line 41. The immersion light exposure section 30 having the structure described above is operated, as follows. Specifically, when a wafer W is placed on the stage 31 by the wafer transfer mechanism 25, the stage 31 and/or mask are horizontally moved, as needed. Further, the high refractive index liquid is supplied from the supply ports 33 of the light exposure liquid distribution member 35 into the gap between the wafer W and projection lens 32. In this state, a mask pattern image is projected from the projection lens 32 onto the wafer W to subject the wafer W to an immersion light exposure process. At this time, the high refractive index liquid supplied into the gap between the wafer W and projection lens 32 is collected through the collection ports 34 into the first transportation line 41. In this embodiment, since the high refractive index liquid is used for the immersion light exposure, the wavelength of the light exposure light is significantly shortened, thereby attaining a high resolution. After the immersion light exposure is performed for a predetermined time, supply of the light exposure liquid is stopped, and the wafer W is transferred from the stage 31 to the outgoing stage 14b by the wafer transfer mechanism 25. As shown in FIG. 7, the pre-cleaning unit (PRECLN) includes a chamber 60 for accommodating a wafer W, a spin chuck 61 located inside the chamber 60 to hold and rotate the wafer W in a horizontal state, and a lifter pins 62 movable up and down to transfer the wafer W between the first wafer transfer member 21 or second wafer transfer member 22 and the spin chuck 61. A showerhead 63 is disposed to deliver and supply a cleaning liquid comprising a high refractive index liquid, and a purge gas, such as nitrogen gas, onto the wafer W held by the spin chuck 61. The showerhead 63 is connected to a purge gas supply mechanism 68 for supplying the purge gas. A collection cup 64 is disposed to receive the cleaning liquid spilt from the wafer W and/or thrown off from the wafer W. The chamber 60 has transfer ports 65 formed in, e.g., sidewalls each with a shutter 65a for opening/closing it, to allow the first wafer transfer member 21 and second wafer transfer member 22 for transferring the wafer W to pass therethrough. The lifter pins 62 can be moved up and down by an elevating mechanism 66 to transfer the wafer W inside the chamber 60 between the first wafer transfer member 21 or second wafer transfer member 22 and the spin chuck 61. The spin chuck 61 is configured to hold the wafer W at the center of the back side (lower surface) of the wafer W by a vacuum attraction force, and rotate the wafer W by a rotary mechanism 67, such as a motor. The showerhead 63 is connected to the first transportation line 41, so that the cleaning liquid transported through the first transportation line 41 is supplied onto the front side (upper surface) of the wafer W held on the spin chuck 61. The collection cup 64 is disposed to surround the wafer W held on the spin chuck 61 and is connected to the second transportation line 42, so that the cleaning liquid received thereby is transported through the second transportation line 42. The post-cleaning unit (POCLN) has a structure equivalent to the pre-cleaning unit (PRECLN). The pre-cleaning unit (PRECLN) having the structure described above is operated, as follows. Specifically, when a wafer W is transferred from one transfer port 65 into the chamber 60, the elevating mechanism 66 is moved up and down to transfer the wafer W onto the spin chuck 61, and the shutter 65a is moved to close the transfer port 65. Then, while the wafer W is rotated by the spin chuck 61, the cleaning liquid is supplied from the showerhead 63 onto the wafer W to clean the wafer W. Then, while the wafer W is rotated, the purge gas is supplied from the showerhead 63 onto the wafer W to dry the wafer W. At this time, the cleaning liquid spilt or thrown off from the wafer W is received by the collection cup 64, and is collected through the second transportation line 42. After the wafer W is dried, the other shutter 65a is moved to open the other transfer port 65, and the wafer W is transferred out of the chamber 60 through the transfer port 65. According to this embodiment, the cleaning of the wafer W is performed before the immersion light exposure, while using as the cleaning liquid a high refractive index liquid the same as or of the same type as that used as the light exposure liquid in the immersion light exposure. Consequently, the affinity of the wafer W relative to the light exposure liquid is improved, so that the resist film is prevented from suffering bubbles and liquid residues generated during the immersion light exposure due to the residual part of the cleaning liquid. Further, since the high refractive index liquid has a high viscosity (higher than purified water) and easily adheres to the wafer W during the immersion light exposure, it would be difficult to satisfactorily remove the light exposure liquid by cleaning using purified water conventionally performed after the immersion light exposure. However, according to this embodiment, the cleaning of the wafer W is performed after the immersion light exposure, while using as the cleaning liquid a high refractive index liquid the same as or of the same type as that used as the light exposure liquid in the immersion light exposure. Consequently, even where the high refractive index liquid used as the light exposure liquid is left on the wafer W, the residual part can be satisfactorily removed by means of the liquid pressure and viscosity of the high refractive index liquid delivered from the showerhead 63. As shown in FIG. 5, the first transportation line 41 includes a first storage tank 41a located on the upstream side to store the high refractive index liquid, and a second storage tank 41b located on the downstream side to store the high refractive index liquid. A first pump 41c is disposed to send the high refractive index liquid used in the immersion light exposure section 30 to the first storage tank 41a. A second pump 41d is disposed to send the high refractive index liquid stored in the first storage tank 41a to the second storage tank 41b. A third pump 41e is disposed to send the high refractive index liquid stored in the second storage tank 41b to the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN). A first valve 41f is disposed to adjust the flow rate of the high refractive index liquid to be sent to the first storage tank 41a. A second valve 41g is disposed to adjust the flow rate of the high refractive index liquid to be sent to the pre-cleaning unit (PRECLN). A third valve 41h is disposed to adjust the flow rate of the high refractive index liquid to be sent to the post-cleaning unit (POCLN). On the other hand, the second transportation line 42 includes a first storage tank 42a located on the upstream side to store the high refractive index liquid, and a second storage tank 42b located on the downstream side to store the high refractive index liquid. A first pump 42c is disposed to send the high refractive index liquid collected from the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN) to the first storage tank 42a. A second pump 42d is disposed to send the high refractive index liquid stored in the first storage tank 42a to the second storage tank 42b. A third pump 42e is disposed to send the high refractive index liquid stored in the second storage tank 42b to the immersion light exposure section 30. A valve 42f is disposed to adjust the flow rate of the high refractive index liquid to be sent to the immersion light exposure section 30. In general, high refractive index liquids are highly volatile, each of the first storage tanks 41a and 42a and the second storage tanks 41b and 42b stores a volatilization-preventive liquid C to prevent volatilization of the high refractive index liquid. The volatilization-preventive liquid C is a substance, such as water, which has a specific gravity smaller than the high refractive index liquid and is separative from the high refractive index liquid. For example, the second pumps 41d and 42d are configured to send the high refractive index liquid inside the first storage tanks 41a and 42a to the second storage tanks 41b and 42b, respectively, when the high refractive index liquid exceeds a predetermined amount inside the first storage tanks 41a and 42a. The second storage tanks 41b and 42b are respectively connected to fresh liquid supply lines 43 and 44 for replenishing a fresh high refractive index liquid into the second storage tanks 41b and 42b. For example, the fresh liquid supply lines 43 and 44 are arranged to replenish a fresh high refractive index liquid set at a predetermined temperature into the second storage tanks 41b and 42b, respectively, when the high refractive index liquid inside the first storage tanks 41a and 42a becomes less than a predetermined amount, and the high refractive index liquid inside the second storage tanks 41b and 42b becomes less than a predetermined amount, at the same time. The upstream end side structure of the first transportation line 41 including the first storage tank 41a, first pump 41c, and first valve 41f constitutes a first collecting section 4a for collecting the high refractive index liquid used in the immersion light exposure section 30. The downstream end side structure of the first transportation line 41 including the second storage tank 41b, third pump 41e, second valve 41g, and third valve 41h constitutes a first supply section 4b for supplying the high refractive index liquid collected in the first collecting section to the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN), individually. The upstream end side structure of the second transportation line 42 including the first storage tank 42a and first pump 42c constitutes a second collecting section 4c for collecting the high refractive index liquid used in the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN). The downstream end side structure of the second transportation line 42 including the second storage tank 42b, third pump 42e, and valve 42f constitutes a second supply section 4d for supplying the high refractive index liquid collected in the second collecting section to the immersion light exposure section 30. The liquid regeneration mechanism 5 includes filters 51 for filtrating the high refractive index liquid flowing through the first transportation line 41 and second transportation line 42, respectively, a degasifying member 52 for degasifying the high refractive index liquid flowing through the second transportation line 42, and a temperature adjusting mechanism 53 for adjusting the high refractive index liquid flowing through the second transportation line 42 to a predetermined temperature. The filters 51 are used for filtration of the high refractive index liquid to be supplied to the immersion light exposure section 30, and filtration of the high refractive index liquid to be supplied to the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN). For example, the filters 51 are respectively located at a position downstream the second storage tank 41b of the first transportation line 41 and at a position downstream the second storage tank 42b of the second transportation line 42. The degasifying member 52 is located at a position, e.g., inside the first storage tank 42a to degasify the high refractive index liquid inside the first storage tank 42a. For example, the temperature adjusting mechanism 53 includes a first temperature adjusting portion 53a configured to adjust the high refractive index liquid approximately to a predetermined temperature inside the first storage tank 42a, and a second temperature adjusting portion 53b configured to adjust the high refractive index liquid, which has been adjusted approximately to the predetermined temperature by the first temperature adjusting portion 53a, precisely to the predetermined temperature inside the second storage tank 42b. The high refractive index liquid circulation mechanism 9 having the structure described above is operated, as follows. Specifically, the high refractive index liquid is collected from the immersion light exposure section 30 to the first collecting section 4a, and is then supplied from the first supply section 4b to the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN), individually, for use in cleaning. Then, the high refractive index liquid is collected from the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN) to the second collecting section 4c, and is then supplied from the second supply section 4d to the immersion light exposure section 30 for use in immersion light exposure. Thus, the high refractive index liquid is circulated between the immersion light exposure section 30 and the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN). The interface station 13 is provided with a capture mechanism 6 configured to capture volatilized components of the high refractive index liquid. The interior of the light exposure apparatus 14 (or the immersion light exposure section 30) is set at a positive pressure relative to the interface station 13. Since the high refractive index liquids is highly volatile, as described above, volatilized components of the high refractive index liquid could easily enter the interface station 13 and the process station 12 through the interface station 13. If volatilized components of the high refractive index liquid enter the process station 12, wafers W may be adversely affected. In this respect, according to this embodiment, the capture mechanism 6 is disposed to capture volatilized components of the high refractive index liquid inside the interface station 13 and volatilized components of the high refractive index liquid flowing from the light exposure apparatus 14 toward the interface station 13, thereby preventing wafers W from being adversely affected. Volatilized components of the high refractive index liquid captured by the capture mechanism 6 may be discarded after a detoxification process. However, in this embodiment, only organic components of volatilized components are extracted therefrom, and are supplied through a supply line 60 to at lease one of the first transportation line 41 and second transportation line 42, so that recycling efficiency of the high refractive index liquid is further improved. For example, the capture mechanism 6 may be designed such that, after organic components are extracted from volatilized components of the high refractive index liquid, the other gas is exhausted out of the apparatus. According to this embodiment, as described above, the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN) are disposed to perform cleaning of a wafer W by use of a high refractive index liquid, before and after the immersion light exposure process performed by the light exposure apparatus 14 or immersion light exposure section 30 by use the high refractive index liquid. Consequently, the affinity of the wafer W relative to the light exposure liquid is improved, while the light exposure liquid is satisfactorily removed from the wafer W, thereby preventing the process uniformity on the wafer W from being deteriorated. According to this embodiment, the high refractive index liquid used in the light exposure apparatus 14 or immersion light exposure section 30 is collected in the first transportation line 41, and is then supplied to the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN). Further, the high refractive index liquid used in the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN) is collected in the second transportation line 42, and is then supplied to the immersion light exposure section 30. Consequently, the high refractive index liquid is recycled by circulation between the immersion light exposure section 30 and the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN), so that the consumption of the light exposure liquid and cleaning liquid which comprise the high refractive index liquid can be decreased. Further, it becomes unnecessary to provide a mechanism and treatment for regenerating the light exposure liquid used in the light exposure apparatus 14 or immersion light exposure section 30, independently of a mechanism and treatment for regenerating the cleaning liquid used in the pre-cleaning unit (PRECLN) and post-cleaning unit (POCLN). In this case, the degasifying member 52 for regenerating the high refractive index liquid in circulation and the temperature adjusting mechanism 53 are required only for one of the first transportation line 41 and second transportation line 42, such as the second transportation line 42. This arrangement is preferable in light of the environment, and further allows the raw material cost to be decreased and the apparatus of the cluster tool type to be simplified. According to this embodiment, the first transportation line 41 and second transportation line 42 are provided with the storage tanks 41a, 41b, 42a, and 42b for temporarily storing the high refractive index liquid, and the storage tanks 41a, 41b, 42a, and 42b are configured to seal the high refractive index liquid by a volatilization-preventive liquid C, such as water (water seal type). In this case, the high refractive index liquid is prevented from being volatilized, thereby improving the recycling efficiency. According to this embodiment, the second transportation line 42 is provided with the filter 51 for filtrating the high refractive index liquid flowing therethrough, the degasifying member 52 for degasifying the high refractive index liquid flowing therethrough, and the temperature adjusting mechanism 53 for adjusting the high refractive index liquid flowing therethrough to a predetermined temperature. Consequently, the light exposure liquid to be used in the immersion light exposure section 30 is kept fresh, so as to maintain a high quality of the immersion light exposure process, which can be easily affected by the temperature and cleanliness of the light exposure liquid. According to this embodiment, the temperature adjusting mechanism 53 comprises, from the upstream side of the second transportation line 42 to the downstream side thereof, the first temperature adjusting portion 53a configured to adjust the high refractive index liquid roughly to a predetermined temperature, and the second temperature adjusting portion 53b configured to adjust the high refractive index liquid, which has been adjusted roughly to the predetermined temperature by the first temperature adjusting portion 53a, precisely to the predetermined temperature inside the second storage tank 42b. In this case, the light exposure liquid to be used in the immersion light exposure section 30 can be reliably adjusted to a predetermined temperature, so that the quality of the immersion light exposure process is further improved. The present invention is not limited to the embodiment described above, and it may be modified in various manners. For example, in the embodiment described above, the high refractive index liquid is circulated between the light exposure section and the pre-cleaning unit and post-cleaning unit. Alternately, the high refractive index liquid may be circulated between the light exposure section and only one of the pre-cleaning unit and post-cleaning unit. The degasifying member and temperature adjusting mechanism may be disposed on the first transportation line, as well as the second transportation line. The cleaning unit and high refractive index liquid circulation mechanism may be integrated with, e.g., the light exposure apparatus. Additional advantages and modifications 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. |
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056407041 | abstract | The present invention provides methods and processes for immobilizing and solidifying harmful heavy metal and radioactive species within a waste material. The processes of the present invention are also particularly advantageous for immobilizing and solidifying nitrate compounds with a waste material. One embodiment of the present invention is a method that can be carried out by admixing the waste material with cement and a complexant compound to form a grout admixture. Preferably, the complexant compound is an iron compound that can form a hydrated iron oxide in the presence of an aqueous solution. This grout admixture is then allowed to cure and solidify. The grout admixture is placed within a suitable containment vessel for final storage and disposal. |
039705170 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The drawing is a schematic representation of a container-arrangement as applied to the process in accordance with this invention. The container arrangement comprises a first container 1, containing a granulated or pulverous radio-active material 2, which has been pre-compacted, in a so-called hot-cell (a space protected against radio-activity, whereby the radio-active material can be handled from outside). At the same time the entire container arrangement and the charge thereof are exposed to mechanical vibrations for a given period of time, thereby already effecting a filling density of 50 - 60 per cent of the pulverous or granulated radio-active material. Such density can most certainly be obtained where the radio-active mass consists essentially of chemical compounds in the form of spherical granules. In this protected space of the hot-cell the container 1 made of a thin metal or plastic such as P.V.C., is closed within a porous cover 3, which then is welded according to the process described in said co-pending applications, preferably applying an electron-beam-welding apparatus comprising a vacuum chamber, wherein the welding of the porous cover 3 to the container-wall 4 can be effected. During this process a uniform welding bead 5 is formed between the cover 3 and the wall 4 in a short time while evacuating the container. Finally a pressure of 10.sup..sup.-1 torr or less is established in the container. The construction of the container 1 differs from the container disclosed in said co-pending application in that filling, pre-compacting, welding and simultaneous evacuation of the container of the present application are carried out in a space, protected against radio-activity, i.e. a hot cell. Thus, by closing the container 1, a body is produced filled with radio-active material within a hot-cell, a fact which is important for reasons of safety, etc. Next the container 1 is placed, within the aforementioned hot-cell into a second container 6, which is made of a compressible material as well, and filled with a pressure-transmitting medium, e.g. a liquid metal 7. In space the container 6 will be closed by a cover 8 under the same conditions as the container 1, closing being effected by at 9 the cover 8 to the container wall 6, by means of an electron-beam-welding apparatus. To center the container 1 in container 6, easily deformable supporting means 10 and 11 are applied. The container-arrangement 1,6, schematically represented in the drawing, is then compacted in a hydraulic press, the containers being exposed simultaneously to a high pressure and high temperature (hot-compacting process) for a given period of time. During compacting the second container functions as a safety-buffer-element, thereby preventing the leakage of radio-active material in the course of the hot-compacting process. Should there be leakage, for example, in container 6, i.e., leakage through the container 6 wall, compacting could take place only to a limited extend or not at all, since even a slight pressure-increase is followed by a pressure equalization between the container 6 and the pressure-room of the machine. Upon leakage of the container 1 that contains the radio-active material, liquid metal will seep through the leak into the container 1 during compacting. In this case the final product (the container arrangement or assembly 1,6) will not be compacted, because the pressure-transmitting medium, e.g. liquid metal 7, penetrated the container 1, thereby equalizing pressure. After-compacting, the compacted radio-active material can be used as an isotopic heat-source by removing the container 1 from the container 6, whereafter the compacted container 1 can easily be handled as an isotopic heat-bar. |
060524243 | abstract | A double-wall structure consisting of an inner wall, an outer wall surrounding said inner wall and reinforcing ribs that connect said outer and inner walls is produced by a piercing welding method in which an electron beam is externally applied at right angles to the outer wall, such that the welded structure of the outer wall and each rib is composed of at least two piercing weld beads that are spaced apart by an unwelded area, with the sum of the widths of the weld beads being at least 25% of the rib width and the length of the unwelded area exterior to the root of each bead being no more than 20% of plate thickness. The distortion in welding is sufficiently reduced to enable precise assembling of the double-wall structure that can be fabricated efficiently and which can reasonably withstand the large electromagnetic force caused by plasma disruption. |
054105765 | description | DESCRIPTION OF THE PREFERRED EMBODIMENT With reference now to the drawings, and in particular to FIG. 1 thereof, the preferred embodiment of the new and improved containers for disposing of low level radioactive waste and its detection embodying the principles and concepts of the present invention and generally designated by the reference numeral 10 will be described. Specifically, the container for disposing low level radio active waste, in its preferred embodiment is simply constructed of three major components, such components are the container 12, the lid 14 and the liner 16. These components function together for their intended purposes. More specifically, the first component of the container system is the container 12. The container has a cylindrical side wall 20 of an enlarged diameter and an enlarged height. The container also has a bottom wall 22. Its exterior periphery is circular and coupled to the lower edge of the side wall 20. Also formed as part of the container is a recess 24. The recess is located in the center of the bottom wall 22. It has an upwardly extending cylindrical support 26 with a closed top. Such cylindrical support is of a reduced diameter and shortened height so as to extend upwardly from the aperture of the bottom wall to an elevation neneath the upper edge of the side wall. The second component of the container system is the lid 14. The lid is simply a circular plate 30. It has downwardly extending flanges 32 around its periphery. The flanges are sized to be positioned over the exterior periphery of the container 12 around its upper edge and to have located therebetween the ridge of a liner secured to the container as will be described. The container 12 and liner 14 are preferably each molded of a one piece construction, suitable molding material include any rigid or semi-rigid elastomer such as polyurethane, polyethalene, polypropalene or silicone rubber. The last component of the system is the liner 16. The liner 16 is fabricated from a sheet of flexible material. It is preferably of a one piece construction. The liner is configured to fit interiorly of the side wall 20 of the container 12 with its upper edges extending over the over edge of the container. Note FIGS. 1, 2 and 3. The liner also is formed with a lower face 42. The lower face is adapted to be positioned on the interior or upper face of the bottom wall. The liner is also formed to have in its central extend an upwardly extending cylindrical extension 46 with a closed top. Such extension is adapted to be positioned over the upwardly extending interior cylinder of the container. The liner when positioned within the container as shown in FIG. 2 and when covered by the lid 14 thus provides a chamber for the receipt of material which may or may not have a low level of radio active waste therein. The interior of the upwardly extending cylindrical support 16 is adapted to receive a probe 50 of a dosemeter 52 as of a conventional type. With the probe located centrally of the container and waste, it is readily adapted to detect any radio active waste contained therein, even of a low level. Note FIG. 5. An alternate embodiment of the invention is shown in FIG. 6. In such embodiment, a holder 56 is secured to the exterior surface of the container at its lower extent. The holder has a lower support face 58, side faces 60 and a front face 62 with a U-shaped cut-out 64. The size and shape of the holder 56 is such as to hold the dosemeter 52 in proper position with respect to the container during operation and use. The cut-out 64 allows viewing the dial of the dosemeter when supported in holder 56. One of the biggest problems with disposing of low level radioactive waste is that the self-shielding quality of the solid waste makes it difficult to detect the low levels of radio active contamination that may be present. The style of the bags currently used to store this type of waste also contribute to this difficulty. The present invention is a new style storage container designed to eliminate this problem. The present invention consists of a rigid plastic container and a plastic liner. The present invention holds about 20 to 25 gallons of waste, is 5 to 7 millimeters thick and has a plastic tube molded into the bottom of the container that is large enough to allow a low level radiation detector to be inserted into it. The bag is made with a long cylindrical inset shaped to fit over the tube in the container. This design ensures that there will be a shaft in the center of the bag even after it is filled and removed from the container. After the bag is filled, it can be checked for low level radioactive contamination by inserting a radioactive detector, protected by this design, into the shaft. If the waste is found to be contaminated, the entire bag can then be disposed of properly. As to the manner of usage and operation of the present invention, the same should be apparent from the above description. Accordingly, no further discussion relating to the manner of usage and operation will be provided. With respect to the above description then, it is to be realized that the optimum dimensional relationships for the parts of the invention, to include variations in size, materials, shape, form, function and manner of operation, assembly and use, are deemed readily apparent and obvious to one skilled in the art, and all equivalent relationships to those illustrated in the drawings and described in the specification are intended to be encompassed by the present invention. Therefore, the foregoing is considered as illustrative only of the principles of the invention. Further, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described, and accordingly, all suitable modifications and equivalents may be resorted to, falling within the scope of the invention. |
summary | ||
description | This application claims the benefit of DE 10 2012 206 953.4, filed on Apr. 26, 2012, which is hereby incorporated by reference. The present embodiments relate to an adaptive x-ray filter and an associated method for changing a local intensity of x-ray radiation by locally changing a layer thickness of a fluid absorbing x-ray radiation. In examinations using x-ray radiation, the patient or organs of the patient in an area to be examined exhibit very different absorption behavior with respect to the applied x-ray radiation. For example, in thorax images, the attenuation in the area in front of the lungs is very large on account of the organs arranged in the area in the front of the lungs. The attenuation is very small in the area of the lungs itself. In order both to obtain a meaningful image and also, for example, to protect the patient, the applied dose may be adjusted depending on the area such that no more x-ray radiation than is required is supplied. This provides that a larger dose is to be applied in areas with a large attenuation than in areas with a lower attenuation. In addition, there are applications in which only part of the examined area is to be imaged with a good diagnostic quality (e.g., with little noise). The surrounding parts are important for the orientation but not for the actual diagnosis. These surrounding areas may therefore be imaged with a lower dose in order to reduce the overall dose applied. Filters are used to attenuate x-ray radiation. A filter of this type is known, for example, from DE 44 22 780 A1. The filter has a housing with a controllable electrode matrix, by which an electric field that acts on the fluid connected to the electrode matrix, in which fluid ions absorbing x-ray radiation are present, is generated. These are freely moveable and move around as a function of the applied field. By virtue of the corresponding electrical field, more or fewer ions may be accumulated correspondingly in the area of one or several electrodes in order to locally change the absorption behavior of the filter. The scope of the present invention is defined solely by the appended claims and is not affected to any degree by the statements within this summary. The present embodiments may obviate one or more of the drawbacks or limitations in the related art. For example, an adaptive x-ray filter and an associated method that attenuate x-ray radiation as a function of location in a simple, safe, precise and stable manner are provided. Positioning elements that are arranged in a honeycomb shape or orthogonally and may be moved hydraulically are able to locally change a layer thickness of a first fluid absorbing x-ray radiation. This changes the local absorption behavior of the filter. More x-ray radiation reaches an object with a minimal layer thickness than with a greater layer thickness. The x-ray radiation may therefore be modulated in two dimensions. In one embodiment, an adaptive x-ray filter for changing the local intensity of x-ray radiation is provided. The x-ray filter includes a first fluid absorbing x-ray radiation (e.g., Galinstan), and hydraulically-moveable positioning elements that change the layer thickness of the first fluid at the location of the respective positioning element by at least partly displacing the first fluid. One or more of the present embodiments are advantageous in that the radiation field of x-ray radiation may be modulated in a simple, precise and rapid manner. In one development, the positioning elements may be arranged in a plane at right angles to the x-ray radiation. The positioning elements therefore form a matrix that may be embodied in the manner of honeycomb. In a further embodiment, the x-ray filter includes a flexible first membrane that is transparent for x-ray radiation and separates the first fluid from the positioning elements. The first membrane is moved by the positioning elements. The layer thickness of the first fluid is therefore changed locally with the aid of the first membrane. The x-ray filter includes a cover plate arranged above the first fluid, in the direction of which the first membrane is pressed by the positioning elements. The cover plate and the first membrane form a chamber, in which the first fluid is located. In a further embodiment, the x-ray filter includes a second fluid arranged below the first membrane, in which the positioning elements are arranged. The second fluid has similar x-ray radiation-absorbing properties to the positioning elements. This avoids unwanted structures through the positioning elements in the x-ray images. In one development, the positioning element may be embodied in the shape of a mushroom and includes a cap and a stem. The positioning elements may be surrounded by the second fluid. The x-ray filter may include a flexible second membrane arranged below the positioning elements. The flexible second membrane may be moved hydraulically in a location-dependent manner in the direction of the positioning elements. As a result, the positioning element moves in the direction of the first fluid such that the positioning elements locally displace the layer thickness of the first fluid. The second membrane causes the second fluid to be held in a type of chamber. In a further embodiment, the x-ray filter includes a distributor plate arranged below the second membrane having supply lines for a third fluid. With the aid of the supply lines for the third fluid, a hydraulic pressure is exerted on the positioning elements. The positioning elements may thus be moved hydraulically. The third fluid may flow into and out of the supply lines via mini valves. A method for changing the local intensity of x-ray radiation using an adaptive x-ray filter is also provided. Positioning elements of the adaptive x-ray filter arranged in a plane are moved hydraulically. The layer thickness of a first x-ray radiation-absorbing fluid irradiated by x-ray radiation is thus changed at the location of the respective positioning element by the positioning elements being able to at least partly displace the first fluid. FIG. 1 shows the basic principle of location-dependent attenuation of x-ray radiation 2 through an adaptive x-ray filter 1. The x-ray radiation 2 is generated by an x-ray source 16, penetrates one embodiment of an adaptive x-ray filter 1, penetrates a patient 17, and is measured by an x-ray detector 18. The local attenuation of the x-ray radiation 2 is controlled by the adaptive x-ray filter 1 using a control unit 19. An intensity profile 20 of the x-ray radiation 2 upstream of the adaptive x-ray filter 1 is shown schematically at the top right in FIG. 1. The intensity y is shown across axis x, which specifies the location. An almost even shape of the intensity y is shown in FIG. 1. The intensity profile 21, after passage through the adaptive x-ray filter 1, is shown schematically at the bottom right in FIG. 1. The change in local intensity y caused by the adaptive x-ray filter 1 is shown by the shape of the intensity profile 21. FIG. 2 shows one embodiment of an adaptive x-ray filter 1 in a cross-sectional view. A distributor plate 13 is arranged on a base plate 15 made of carbon fiber-reinforced plastic. The distributor plate 13 has a plurality of tubular supply lines 15, through which a fluid 4 (e.g., a second fluid) may flow in and out. The supply lines 14 end below positioning elements 8 arranged in the shape of a honeycomb so as to be moveable in a plane. A flexible second membrane 7 is located between the positioning elements 8 and the distributor plate 13 as a switching membrane. If a third fluid 5 is supplied via mini valves (not shown), the switching membrane 7 is lifted locally, and the positioning element 8 therefore moves hydraulically upwards (e.g., in the direction of an incident x-ray radiation 2). The positioning elements 8 are embodied in the shape of mushrooms and have a cap 11 and a stem 12. The positioning elements 8 (e.g., the caps 11) are disposed in the second fluid 4, which has similar x-ray absorption properties to the positioning elements 8. This prevents unwanted structures formed by the positioning elements 8 from being visible in the x-ray image. The caps 11 are almost flush with one another. A flexible first membrane 6, as a separating membrane, is arranged opposite to the direction of the incident x-ray radiation 2 above the positioning element 8. A cover plate 10 made of carbon fiber-reinforced plastic is located at a distance above the separating membrane 6. The cover plate 10 and the separating membrane 6 form a chamber in which a first fluid 3 absorbing x-ray radiation (e.g., a liquid metal such as Galinstan or colloidal solutions with x-ray absorbing elements) is enclosed. If the positioning element 8 is moved hydraulically upwards, the separating membrane 6 is moved upwards by the cap 11 of the positioning element 8 at a location of the cap 11 and thus displaces the first fluid 3 at the location of the cap 11. The x-ray radiation absorption herewith changes locally at the location of the cap 11, since a layer thickness 9 of the first fluid 3 is reduced. The honeycomb-type arrangement of the positioning elements 8 thus enables each profile to be approximated with respect to the location-dependent attenuation of x-ray radiation. The local resolution increases where smaller caps 11 are used for the positioning elements 8 and where the positioning elements 8 are packed tighter. On account of a low pass effect, the separating membrane 6 prevents strong transitions (e.g., high frequency transitions) in the x-ray image, which is favorable for imaging. The first fluid 3 and the second fluid 4 may not be filled through inlet openings (not shown). A differential pressure may also be applied to the separating membrane 6 through the inlet openings. Depending on the deflection of the separating membrane 6, the first fluid 3 and the second fluid 4 may be fed in or discharged. In other words, the positioning elements 8 are moved hydraulically in the direction of the separating membrane 6 by a fluid pressure being applied via the supply lines 14 in the distributor plate 13. The supply lines 14 are controlled via mini valves (not shown). The positioning elements 8 are returned by applying a counter pressure via the first fluid 3 and the separating membrane 6 when the mini valves are open. All positioning elements 8 are extended in the normal state and press against the separating membrane 6. This allows the first fluid 3 to escape from the chamber formed by the cover plate 10 and the separating membrane 6. The mini valves are closed. The adaptive x-ray filter 1 has the lowest absorption. In order to achieve an absorption modulation, the corresponding mini valves are opened, and a counter pressure is applied to the separating membrane 6 via the first fluid 3. The positioning elements 8 with associated opened mini valves are pushed back, the separating membrane 6 is deflected, and the first fluid 3 flows in therebehind. The absorbing layer thickness 9 of the first fluid 3 may therefore be locally modulated, and a non-uniform x-ray radiation field may therefore be set. FIG. 3 shows a top view of one embodiment of an adaptive x-ray filter 1. The letters “C” and “V”, which are formed by the extended positioning elements 8, are shown. The honeycomb structure of the positioning elements 8 arranged in a plane is shown. The adaptive x-ray filter 1 includes a base plate 15, upon which the distributor plate 13 with the supply lines 14 is arranged. The switching membrane 7 is disposed above the distributor plate 13. A layer with the positioning elements 8 that push on the separating membrane 6 lies above the switching membrane 7. A cover plate 10 closes the adaptive x-ray filter 1 at the top. The first fluid 3 is located between the cover plate 10 and the separating membrane 6. The positioning elements 8 lie in the second fluid 4, which is disposed between the separating membrane 6 and the switching membrane 7. FIG. 4 shows a bottom view of one embodiment of an adaptive x-ray filter 1 in accordance with FIG. 3. For improved representation, the individual layers are shown in a partly transparent manner. FIG. 4 shows, from top down, the base plate 15, the distributor plate 13 with the supply lines 14 for applying pressure to the positioning elements 8, the switching membrane 7, the plane with the positioning elements 8, the separating membrane 6, and the cover plate 10. The supply lines 14 are arranged such that a supply line leads to each positioning element 8. It is to be understood that the elements and features recited in the appended claims may be combined in different ways to produce new claims that likewise fall within the scope of the present invention. Thus, whereas the dependent claims appended below depend from only a single independent or dependent claim, it is to be understood that these dependent claims can, alternatively, be made to depend in the alternative from any preceding or following claim, whether independent or dependent, and that such new combinations are to be understood as forming a part of the present specification. While the present invention has been described above by reference to various embodiments, it should be understood that many changes and modifications can be made to the described embodiments. It is therefore intended that the foregoing description be regarded as illustrative rather than limiting, and that it be understood that all equivalents and/or combinations of embodiments are intended to be included in this description. |
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043308651 | summary | BACKGROUND OF THE INVENTION This invention relates to non destructive test apparatus and provides a free roving vehicle for carrying inspection instrumentation over a remote surface. A vehicle according to the invention finds application in the inspection of a primary vessel of a construction of liquid metal cooled nuclear reactor of the pool kind. Such a nuclear reactor construction comprises a nuclear fuel assembly submerged in a pool of liquid metal coolant contained in the primary vessel which is housed in a concrete containment vault. In use the primary vessel is subject to irradiation and to severe thermal stress so that periodic inspection of the vessel is required to ensure its continued integrity. Inspection of the primary vessel is difficult because it must be carried out on its external surface by remotely operated apparatus. SUMMARY OF THE INVENTION According to the invention a vehicle for carrying non destructive test instrumentation over a remote surface comprises a bridge structure having a plurality of support pads pivotally mounted thereon, each support pad having suction means for adhering the vehicle to an inclined or inverted surface and fluid thrust means arranged in opposition to the suction means to facilitate lateral sliding displacement of the vehicle and a resiliently flexible tubular tie member for suspending the bridge structure and conducting fluid supplies thereto. According to another aspect of the invention a method of inspecting the primary vessel of a liquid metal cooled nuclear reactor of the pool kind housed in a closed vault comprises mounting inspection instrumentation including a television camera on a vehicle, suspending the vehicle and instrumentation in an interspace bounded by the primary vessel and the vault, adhering the vehicle to the vessel by suction means, vertically displacing the vehicle in step wise manner and intermittently anchoring the vehicle to the surface of the vessel by the suction means prior to inspection of the surrounding terrain. |
042973040 | description | The invention will now be explained by way of the examples which follow without, however, being limited to these examples. EXAMPLE 1 The chemical composition of a highly active nitric acid waste solution which is obtained during reprocessing of spent fuel elements in a light water nuclear reactor where 33,000 MWd/t fuel are burnt was simulated in its main components by chemically similar inactive isotopes. The nitric acid waste solution was denitrated with formic acid such that a pH of 2.5 resulted. The pH of the solution was then adjusted by the addition of 1 M sodium liquor, to a value of 6 and was concentrated by way of distillation. After this pretreatment, the solution or suspension, respectively, had the following chemical composition: ______________________________________ (a) water content: 700 g H.sub.2 O (b) residual nitrate content: 109 g NO.sub.3.sup.- (c) residue after heating: 91.2 g Gd.sub.2 O.sub.3 35.0 g ZrO.sub.2 36.5 g MoO.sub.3 23.4 g Na.sub.2 O 18.8 g BaO 28.5 g Ag 8.0 g MnO.sub.2 4.0 g Te 12.8 g Pb.sub.3 O.sub.4 20.8 g Fe.sub.3 O.sub.4 3.7 g Cr.sub.2 O.sub.3 g NiO 285.9 g Total ______________________________________ This solution or suspension, respectively was kneaded in a kneading vessel together with 981 grams of a mixture of portland cement and Hirschau kaolin (weight ratio 1:8) to form a dough. By pressing the doughy mixture through a tube, molded bodies were produced having a diameter of 25 mm and a height of about 20 mm. Further, cylindrical bodies having a diameter of 80 mm and a height of 80 mm were shaped from the doughy mixture in polyethylene beakers. These latter bodies could be removed from the beakers after only 3 days due to shrinkage of the mass. All of the molded bodies were dried in air for 20 to 30 days then rinsed with water and thereafter dried, calcined and sintered in a furnace at increasing temperatures. The heating schedule for the furnace is shown in the table below. ______________________________________ Temperature Time (.degree.C.) (Hours) ______________________________________ 20-150 15 150-800 30 800-1150 5 1150-1280 10 ______________________________________ The sintered end product exhibited an elevated hardness of 6 to 7 according to the Mohs scale, and poor solubility in water. The water solubility at room temperature is less than 10.sup.-6 g of the product with reference to 1 cm.sup.2 of surface per day. The table below gives the chemical composition of the product. ______________________________________ Components Weight - % ______________________________________ SiO.sub.2 38.8 Al.sub.2 O.sub.3 26.8 CaO 6.2 Fe.sub.3 O.sub.4 0.9 TiO.sub.2 0.3 MgO 0.7 Na.sub.2 O 0.1 K.sub.2 O 1.9 Fission product oxides 24.3 (See heat treatment residue (c)) ______________________________________ The stoichiometry of this sintered body end product corresponds approximately to that of anorthite or nepheline, respectively, which are known as very stable natural minerals. EXAMPLE 2 Medium activity waste solutions which are the result of the reprocessing of nuclear fuels contain up to 90% sodium nitrate as salt ballast. To simulate this category of waste, a sodium nitrate solution was made into a dough with a cement/kaolin mixture (weight ratio of 1:10). The chemical compositions of the dough was as follows: ______________________________________ simulated waste solution: 184 g NaNO.sub.3 300 g Water portland cement: 50 g Geisenheim kaolin 500 g ______________________________________ As in Example 1, molded bodies were again produced by extruding and molding. Air drying and rinsing with water were effected as in Example 1. The heating schedule for the drying, calcination and sintering steps is given in the table below: ______________________________________ Temperature Time (.degree.C.) (Hours) ______________________________________ 20-150 12 150-400 20 400-450 25 450-800 15 800-1150 10 1150-1200 10 ______________________________________ The sintered end product has a hardness of 5 to 6 on the Mohs scale. The water solubility at room temperature is about 10.sup.-6 g of the product with reference to 1 cm.sup.2 of surface per day. The chemical composition of the sintered end product is shown in the table below: ______________________________________ Component Weight - % ______________________________________ SiO.sub.2 45.8 Al.sub.2 O.sub.3 31.9 CaO 5.9 Fe.sub.2 O.sub.3 1.0 TiO.sub.2 0.4 MgO 0.4 K.sub.2 O 2.3 Na.sub.2 O (From sodium nitrate solution) 12.3 ______________________________________ The stoichiometry of this sintered body end product corresponds approximately to that of nepheline which is known as a very stable natural mineral. EXAMPLE 3 Actinide concentrates which are formed as radioactive wastes during the manufacture of plutonium containing fuel elements are either evaporated solutions or combustion ashes obtained from the combustion of organic materials. They contain as radioactive components relatively large quantities of plutonium and americium which is produced during the radioactive decay of the relatively short-lived plutonium isotope Pu.sup.241. These actinide concentrates can be easily bound into a ceramic matrix according to the present invention since the chemical nature of the waste components themselves comes close to the heat treatment residues of the high activity waste solutions listed in Example 1. To simulate this category of waste, a suspension of 2.94 g americium dioxide powder in 7 g water was mixed into a dough with a mixture of 10 g portland cement and Hirschau kaolin (weight ratio 1:10). The doughy mass was pressed through a polyethylene tube so that a cylindrical molded body resulted which had a diameter of 20 mm and a height of 30 mm. The molded body was dried for 10 days at room temperature. In the same manner, a molded body was produced from 7 g of water and 10 g of a mixture of portland cement and Hirschau kaolin, (weight ratio 1:10) but without americium dioxide and likewise dried for 10 days at room temperature. Both molded bodies exhibited the same shrinkage of 28.+-.2% after drying compared to the starting volume during manufacture. This proves that radiolysis gas development and decomposition heat are without influence on the manufacturing process. The molded body containing AmO.sub.2 was dried in a furnace at increasing temperatures and sintered according to the heating program below: ______________________________________ Temperature Time (.degree.C.) (Hours) ______________________________________ 20-150 8 150-800 24 800-1150 10 1150-1300 10 ______________________________________ After sintering, a product resulted having a stoichiometry corresponding to anorthite or nepheline. The weight loss of the sintered product during leaching with water at room temperature is less than 10.sup.-7 g per cm.sup.2 surface. per day. The chemical composition of the sintered product is shown in the table below: ______________________________________ Component Weight - % ______________________________________ SiO.sub.2 39.2 Al.sub.2 O.sub.3 27.3 CaO 5.0 Fe.sub.2 O.sub.3 0.8 TiO.sub.2 0.3 MgO 0.4 Na.sub.2 O 0.1 K.sub.2 O 1.9 AmO.sub.2 25.0 ______________________________________ The specific alpha activity of the sintered body is 715 mCi/g, the specific decay heat is about 22 mW/g. EXAMPLE 4 In addition to dry combustion with oxygen from the air, the organic radioactive wastes from the production of plutonium containing fuel elements can also be concentrated by wet combustion methods. One of these methods is based on the carbonization of organic wastes in concentrated sulfuric acid at temperatures above 200.degree. C. and subsequent oxidation of the carbon with chemical oxidation means such as nitric acid. This produces combustion residues having high sulfate contents which, mainly after neutralization with sodium liquor, contain large amounts of sodium sulfate but also sodium chloride from the combustion of polyvinyl chloride. In Example 2 it was shown that sodium nitrate solutions can be solidified into a sintered body to form a chemical compound which stoichiometrically corresponds to the natural mineral nepheline. It is, moreover, possible to solidify sodium sulfate and sodium chloride containing sodium nitrate solutions in the same manner where the absorption capability of nepheline for sodium sulfate is limited to 14 percent by weight and for sodium chloride to 12 percent by weight. The crystallic phases formed thereby correspond to the natural stable minerals noselite which contains sodium sulfate and sodalite which contains sodium chloride. EXAMPLE 5 100 ml of a solution containing 5 weight-% sodium sulfate were mixed with 180 g of kaolin with and without addition of 4 weight-% BaO with respect to the kneaded mass and solidified to a sintered body. It was qualitatively demonstrated by condensing the foam evolved upon sintering that the BaO-containing sample had a very low release of sulfate with respect to the reference sample. EXAMPLE 6 100 ml of a solution containing 10 weight-% cesium nitrate were kneaded with 200 g of kaolin. To half of this batch, 10 g of TiO.sub.2 -powder were additionally added. Both samples were solidified to sintered bodies in the same manner. The foam evolved during the sintering process was condensed and analyzed for its cesium content. The TiO.sub.2 containing product had a cesium volatility of less than two orders of magnitude lower than the reference sample. It will be understood that the above description of the present invention is susceptible to various modifications, changes and adaptations, and the same are intended to be comprehended within the meaning and range of equivalents of the appended claims. |
claims | 1. A computer system for load testing, the computer system comprising:a first computer connected to a network;a computer program, embedded in a non-transitory computer-readable medium, executed by the first computer, the computer program comprising instructions for:assessing web instances running on one or more web browsers running on the first computer; andlisting some or all of the assessed web instances for selection by a user of the computer system,wherein said instructions for assessing web instances running on one or more web browsers comprises instructions for:connecting to a web browser shell interface of a web browser running on the first computer;listing shell instances running on the web browser shell interface;determining if each of the shell instances support a COM interface; andlisting the shell instances that support the COM interface. 2. A computer system for load testing, the computer system comprising:a first computer connected to a network;a computer program, embedded in a non-transitory computer-readable medium, executed by the first computer, the computer program comprising instructions for:automatically cataloguing web instances currently running on one or more web browsers running on the first computer;listing some or all of the catalogued web instances for selection by a user of the computer system;allowing a user to select one or more of the listed web instances as a test case URL;displaying parameter values of the selected test case URLs; andallowing the user to select one or more parameters whose values are to be varied within the selected test case URLs;wherein said instructions for varying the values of the selected parameters utilize syntax, wherein said syntax comprises:a symbolic character opening a varying part from a static part;a command that specifies how to vary the varying part;a plurality of arguments to the command; anda symbolic character closing the varying part. 3. The computer system of claim 2, wherein said symbolic character opening the varying part from the static part is left parentheses, and wherein said symbolic character closing the varying part is right parentheses. |
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039393666 | claims | 1. A device for converting radioactive energy to electric energy, said device comprising in combination, a first, second and third magnetic body, a plurality of InSb monocrystalline semi-conductor bodies stacked vertically between said first and second and between said second and third magnetic body, each stacked plurality of semi-conductor bodies being separated from the magnetic body by an insulating plate, a layer of .sup.210 Po radioactive substance sandwiched between adjacent semi-conductor bodies and disposed to produce electron hole pairs in said semi-conductor bodies, wherein said electron hole pairs diffuse toward an unirradiated region of said semi-conductor bodies to eleminate the differences in density between electrons and holes in each of said semiconductor bodies, said magnetic bodies separating said electrons and said holes from each other by means of the resultant magnetic field wherein said electrons and holes are caused to move in a direction perpendicular to the direction of diffusion of the electron-hole pairs, and a U-shaped plate member of high magnetic permeability disposed by the leg members thereof on the outer surfaces of said first and third magnetic bodies, said U-shaped plate member supporting the magnetic bodies and said stacked semi-conductor bodies in association, each of said semi-conductor bodies having electrodes on opposite sides thereof to receive separated electron-hole pairs of electric energy generated within each of the semi-conductor bodies. |
051732483 | abstract | A remote control apparatus for maintaining a tokamak type nuclear fusion reactor comprises a rail having a plurality of arcuated links to be extended in a circumferential direction and a plurality of joints for pivotally connecting the adjacent arcuated links, a vehicle running on the rail extended so as to form a continuous arc with its center substantially coinciding with the center of the torus space, and at least one handling device mounted on the vehicle, for handling the in-vessel components. The remote control apparatus is further provided with a rail housing device for receiving the arcuated links in a folded state when they are not in use, a rail mounting device for sending out said arcuated links in succession into the torus space, extending them so that they form a continuous arc and supporting the arcuated link on the proximal end of the rail, and a rail supporting device for supporting the central portion of the rail extended in the torus space. |
053176090 | claims | 1. Apparatus for installing fuel rods in a nuclear fuel assembly skeleton, defining fuel rod locations distributed in a predetermined array, said apparatus comprising: fixed skeleton receiving means for receiving a skeleton devoid of end nozzles; a magazine for storing fuel rods in alignment with said locations in the skeleton placed on a longitudinal side of said receiving means; a longitudinal displacement mechanism located on the other longitudinal side of said receiving means, said displacement mechanism having a plurality of mutually parallel pull bars and means for displacing said pull bars longitudinally towards the magazine and away from the magazine, the pull bars being terminated by clamps for grasping a plurality of fuel rods to be inserted into said skeleton; a cap-placing assembly interposed between the skeleton receiving means and the longitudinal displacement mechanism, said cap-placing assembly having a fixed support and a removable receptacle formed with housing distributed in an array that reproduces said array of fuel rod locations; and, a plurality of caps adapted to be received each in one of said housings, the shape of the caps being such that they are adapted to fit over the clamps of the pull bars when the clamps are closed nd the pull bars are moved forwardly toward the magazine. placing a skeleton devoid of end nozzles horizontally between a storage magazine for storing rods in alignment with rod-receiving locations in the skeleton and a longitudinal displacement mechanism for displacing pull bars terminated by rod-grasping clamps towards the magazine and away from the magazine; passing said pull bars through the skeleton until they reach the magazine and grasping respective rods; and pulling said pull rods through the skeleton; further comprising the steps of: loading caps in housings in a receptacle, said housings being distributed in the same array as the rods; locating the receptacle between the displacement mechanism and the skeleton; moving the pull bars forwardly to engage the clamps in the caps as they pass through the receptacle and prior to going through the skeleton; and removing the caps when they leave the receptacle without manual intervention prior to moving the clamps up to the magazine. 2. Apparatus according to claim 1, wherein the removable receptacle comprises a perforated body arranged to be secured to the support, passages formed through the body and distributed in an array identical to said array of fuel rods, and a closure plate formed with holes that holds captive a grid formed with housings for receiving said caps. 3. Apparatus according to claim 2, wherein the removable receptacle further comprises a perforated backing plate co-operating with the body to define a passage for receiving a moving plate between a position in which holes thereof coincide with the housings and a position in which said holes are offset relative to the housings thereby preventing the caps from moving out of the receptacle. 4. Apparatus according to claim 3, wherein the moving plate is provided with guide means and is connected to an actuator for displacement in a direction at 45.degree. to the rows of housings. 5. Apparatus according to claim 1, further including a cap-removing assembly interposed between the skeleton-receiving means and the magazine, the cap-removing assembly having a frame carrying cap-retaining jaws that are displaceable transversely to the displacement direction of the pull bars between a position in which they engage at least some of the caps and a position in which they release said caps. 6. Apparatus according to claim 5, wherein the frame is displaceable transversely to the direction of the pull bars to allow the pull bars to pass, and to enable the clamps to advance to grasp rods placed in the magazine. 7. Apparatus according to claim 5, wherein the frame is mounted on fixed brackets so as to be vertically movable and is connected to the brackets by vertical displacement means enabling the frame to be brought to a level where the jaws vertically straddle followed by the pull bars through any one of the rows of housings. 8. Apparatus according to claim 7, wherein the jaws are designed to engage simultaneously all caps in a same row. 9. Apparatus according to claim 7, wherein the vertical displacement means are designed to bring the frame to a level where the jaws face pressurized air nozzles for ejecting the caps. 10. Apparatus according to claim 5, wherein the frame carries a cap-collecting tank. 11. A method of installing fuel rods in a skeleton of a nuclear fuel assembly, comprising the steps of: 12. A method according to claim 11, comprising the further steps of: moving the clamps between open jaws; clamping the jaws onto the caps; moving back the pull bars to disengage them from the jaws; lowering and opening the jaws; moving the pull bars forwardly again until the clamps engage terminal plugs of the fuel rods, closing the clamps, and simultaneously pulling all rods of a layer through the skeleton. 13. A method according to claim 11, wherein said loading step is carried out at a location remote from said magazine. |
abstract | A power battery using the energy from a radioactive material. The arrangement uses ZnO as a semiconductor, with energy generated a metal-semiconductor junction. The ZnO is arranged in thin layers. This allows for good durability and relatively high power production. |
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abstract | There are provided an apparatus and method for separating radioactive nuclides from a waste salt and recovering a refined salt, which are able to maximize process efficiency and operating efficiency of a process of regenerating a waste salt produced during a pyrochemical process of used nuclear fuel by converting the waste salt into a thermally stable form and distilling the waste salt under a reduced pressure using a single apparatus having two top covers which are mountable to replace radioactive nuclides included in the waste salt, and highly improve applicability and utility in a remote operation facility for disposal of a radioactive waste by further simplifying operation/handling compared with conventional processes. |
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abstract | An illumination system is used to illuminate a specified illumination field of an object surface with EUV radiation. The illumination system has an EUV source and a collector to concentrate the EUV radiation in the direction of an optical axis. A first optical element is provided to generate secondary light sources, and a second optical element is provided at the location of these secondary light sources, the second optical element being part of an optical device which includes further optical elements, and which images the first optical element into an image plane into the illumination field. Between the collector and the illumination field, a maximum of five reflecting optical elements are arranged. These optical elements reflect the main beam either grazingly or steeply. The optical axis, projected onto an illumination main plane, is deflected by more than 30° between a source axis portion and a field axis portion. In a first variant of the illumination system, at least an axis portion between at least two of the reflecting optical elements is inclined relative to the illumination main plane. In a second variant of the illumination system, the optical device, in addition to the second optical element includes precisely three further optical elements, i.e. a third optical element, a fourth optical element and a fifth optical element. |
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abstract | A proton beam guidance apparatus and a method of providing proton beams having sub-micron beam width and MeV energies. The apparatus is a structure having an enclosed channel that can reflect or guide protons by grazing incidence interactions. The enclosed channel is in some embodiments an annular channel. The enclosed channel is shaped to provide a helical path for each proton in the beam. Protons are provided to an input port of the channel, and after multiple grazing incidence interactions with the walls of the channel, are provided as an output beam having dimensions comparable to the cross sectional dimensions of the channel. The channels can have cross sectional dimensions of tens of nanometers or less. No externally applied electromagnetic fields are needed to guide the proton beam. Contemplated applications include use of the exit proton beams to provide medical treatment to patients. |
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description | This invention relates to a designing method and device for phase shift mask, and in particular, relates to an art for correcting drawing data for designing a trench-type, Levenson-type phase shift mask to be used for manufacture of semiconductor devices. Semiconductor devices are being made higher in density from year to year and the integrated circuit patterns formed on semiconductor wafers are becoming even finer. Exposure using a photomask is normally performed in forming an integrated circuit pattern on a semiconductor wafer, and the pattern on a photomask inevitably becomes finer as the pattern to be exposed becomes finer. Especially since the latter half of the 1990's, technical developments are actively being made towards forming fine shapes of sizes shorter than the light source wavelength of an exposure tool on a semiconductor wafer. Generally in forming a fine pattern of a size near or no more than an exposure tool's light source wavelength on a semiconductor wafer, the diffraction phenomenon of light cannot be ignored. Specifically, in a case where a pair of mutually adjacent apertures are formed as a photo mask pattern, the lights transmitted through the pair of apertures diffract and interfere with each other, causing exposure even at parts that are supposed to be shielded from light. Thus with a photomask on which a fine pattern is formed, measures must be devised in consideration of the diffraction phenomenon of light. A phase shift mask is known as a type of photomask with which such a measure is taken. The basic principle of a phase shift mask is that a structure, with which the phases of the light transmitted through a pair of adjacently disposed apertures will be opposite each other, is employed to cancel out the interference of light. As a method of shifting the phase of light that is transmitted through one of the apertures by 180 degrees with respect to the phase of light that is transmitted through the other aperture, a method of forming a trench in the substrate that makes up the photomask has been proposed. For example, Laid-open Japanese Patent Publication No. 2002-40624 discloses a trench-type, Levenson-type phase shift mask as a typical example of such a phase shift mask. As mentioned above, with a phase shift mask, since the shape of a fine pattern must be determined in consideration of the diffraction phenomenon of light, the design work is complicated. Especially with a trench-type, Levenson-type phase shift mask, in which a trench is formed in a substrate, since the part at which the trench is formed takes on a three-dimensional structure, two-dimensional analysis is insufficient and the need to perform three-dimensional analysis arises. Much labor and time were thus required to design a single phase shift mask. An object of this invention is thus to provide a designing method and device for phase shift mask which enable the work load to be lightened and the working time to be shortened. (1) The first feature of the present invention resides in the method for designing a phase shift mask, having a substrate with a transparent property, and an opaque layer formed on the substrate and having an opaque property, wherein a plurality of rectangular apertures are formed in the opaque layer, a two-dimensional layout pattern is formed by opaque parts comprising regions at which the opaque layer is formed, and transparent parts comprising regions at which the apertures are formed, and for a pair of adjacently disposed apertures, so that a phase of light transmitted through one of the pair of adjacent apertures will be shifted by 180 degrees with respect to a phase of light transmitted through the other of the pair of adjacent apertures, a trench, having a predetermined depth and an outline greater than an outline of the one aperture, is formed on a portion of the substrate at which the one aperture is formed, the phase shift mask designing method comprising the steps of: a two-dimensional layout designing step of defining an XY plane on a surface of the substrate, determining a width Wx in the X-axis direction and a width Wy in the Y-axis direction of each aperture and a width Ws of each opaque part, and positioning a plurality of apertures of the same size at least along the X-axis to thereby design a two-dimensional layout on the XY plane; a three-dimensional structure determination step of determining, for each of the plurality of apertures, whether or not phase shifting is to be performed and determining, for the apertures with which phase shifting is to be performed, a trench depth d and an undercut amount Uc, which indicates a distance between a position of the outline of the trench and a position of the outline of the aperture, to thereby determine a three-dimensional structure; a three-dimensional analysis step of using a three-dimensional structural body, which is defined by the two-dimensional layout and the three-dimensional structure, to determine a light intensity deviation D, which indicates, for a case where light is transmitted under the same exposure conditions through a pair of adjacent apertures that have been designed to realize a phase shift of 180 degrees with respect to each other, a deviation in intensities of light transmitted through the respective apertures; a two-dimensional analysis step of using a two-dimensional structural body, which is defined by the two-dimensional layout, to determine, in a case where, for the pair of adjacent apertures, a light transmittance of one aperture is set to 100% and a light transmittance of the other aperture is set to T %, a transmittance T such that a deviation in intensities of light transmitted through each of the pair of adjacent apertures will be equal to the light intensity deviation D; and a layout correction step of correcting the two-dimensional layout based on the transmittance T. (2) The second feature of the present invention resides in the phase shift mask designing method according to the first feature, wherein in the two-dimensional analysis step, a light intensity deviation D is determined for each of a plurality of transmittances and a transmittance, which provides a result matching the light intensity deviation D determined in the three-dimensional analysis step, is determined as the transmittance T. (3) The second feature of the present invention resides in the phase shift mask designing method according to the second feature, wherein in the two-dimensional analysis step, a database, with which a value of the light intensity deviation D is determined for each of various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the transmittance T, is prepared in advance, and in determining a light intensity deviation D for a specific two-dimensional structural body, the database is searched to determine the light intensity deviation D. (4) The fourth feature of the present invention resides in the phase shift mask designing method according to the first feature, wherein in the three-dimensional analysis step, a database, with which a value of the light intensity deviation D is determined for each of various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the undercut amount Uc, is prepared in advance, and in determining a light intensity deviation D for a specific three-dimensional structural body, the database is searched to determine the light intensity deviation D. (5) The fifth feature of the present invention resides in the phase shift mask designing method according to the first feature, wherein in the layout correction step, a database, with which an optimal correction amount δ is determined for each of various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the transmittance T, is prepared in advance, and in performing a correction of a specific two-dimensional layout, with which a specific transmittance is defined, the database is searched to determine the optimal correction amount δ. (6) The sixth feature of the present invention resides in the phase shift mask designing method according to the first to the third features, wherein a database, having the width Wy in the Y-axis direction of each aperture in addition as a parameter value, is prepared. (7) The seventh feature of the present invention resides in the phase shift mask designing method according to the first to the third features, wherein in a case where a combination of parameter values that matches the search conditions does not exist among combinations of parameters prepared inside the database, an interpolation operation using parameter values that are close is performed. (8) The eighth feature of the present invention resides in the phase shift mask designing method according to the first to the third features, wherein in the two-dimensional layout designing step, a plurality of apertures are positioned in two-dimensional matrix form in the X-axis direction and the Y-axis direction, and as the width Ws of the opaque parts, two parameters of a width Wsx in the X-axis direction of an opaque part existing between apertures that are adjacent in the X-axis direction and a width Wsy in the Y-axis direction of an opaque part existing between apertures that are adjacent in the Y-axis direction are used. (9) The ninth feature of the present invention resides in the phase shift mask designing method according to the first feature, wherein in the three-dimensional structure determination step, apertures with which phase shifting is to be performed are determined so that every other aperture of the plurality of apertures that are positioned along the X-axis direction or the Y-axis direction are selected. (10) The tenth feature of the present invention resides in the phase shift mask designing method according to the first feature, wherein a part or all of the process of determining the light intensity deviation D in the three-dimensional analysis step, the process of determining the transmittance T in the two-dimensional analysis step, and the correction process in the layout correction step are executed using computer simulation. (11) The eleventh feature of the present invention resides in the phase shift mask designing method according to the first feature, wherein a part or all of the process of determining the light intensity deviation D in the three-dimensional analysis step, the process of determining the transmittance T in the two-dimensional analysis step, and the correction process in the layout correction step are executed by experimentation using an actually manufactured phase shift mask. (12) The twelfth feature of the present invention resides in the device for designing a phase shift mask, having a substrate with a transparent property, and an opaque layer formed on the substrate and having an opaque property, wherein a plurality of rectangular apertures are formed in the opaque layer, a two-dimensional layout pattern is formed by opaque parts comprising regions at which the opaque layer is formed, and transparent parts comprising regions at which the apertures are formed, and for a pair of adjacently disposed apertures, so that a phase of light transmitted through one of the pair of adjacent apertures will be shifted by 180 degrees with respect to a phase of light transmitted through the other of the pair of adjacent apertures, a trench, having a predetermined depth and an outline greater than an outline of the one aperture, is formed on a portion of the substrate at which the one aperture is formed, the phase shift mask designing device comprising: a two-dimensional layout determination tool, which, based on instructions from an operator, determines a width Wx in the X-axis direction and a width Wy in the Y-axis direction of each aperture and a width Ws of each opaque part on an XY plane defined on a surface of the substrate and positions a plurality of apertures of the same size at least along the X-axis to determine a two-dimensional layout on the XY plane; a three-dimensional structure determination tool, which, based on instructions from an operator, determines whether or not phase shifting is to be performed for each of the plurality of apertures and determines, for apertures with which phase shifting is to be performed, a trench depth d and an undercut amount Uc, which indicates a distance between a position of the outline of the trench and a position of the outline of the aperture, to thereby determine a three-dimensional structure; a three-dimensional simulator, which performs a three-dimensional analysis process of executing a three-dimensional simulation using a three-dimensional structural body, which is defined by the two-dimensional layout and the three-dimensional structure, as a model to determine a light intensity deviation D that indicates a deviation of intensities of light transmitted through each of a pair of adjacent apertures, designed to realize a phase shift of 180 degrees with respect to each other, when light is transmitted through the apertures under the same conditions; and a two-dimensional simulator, which performs a two-dimensional analysis process of executing two-dimensional simulations using a two-dimensional structural body, which is defined by the two-dimensional layout, as a model to determine a transmittance T, such that, when for a pair of adjacent apertures, a light transmittance of one aperture is set to 100% and a light transmittance of the other aperture is set to T %, a deviation in intensities of light transmitted through each of the pair of adjacent apertures becomes equal to the light intensity deviation D, and performs a layout correction process of executing two-dimensional simulations using a model, with which the transmittance T is applied to the two-dimensional structural body defined by the two-dimensional layout, to correct the two-dimensional layout. (13) The thirteenth feature of the present invention resides in the phase shift mask designing device according to the twelfth feature, wherein when the two-dimensional simulator performs the two-dimensional analysis process, a light intensity deviation D is determined for each of a plurality of transmittances, and a transmittance, which provides a result matching the light intensity deviation D determined by the three-dimensional analysis process performed by the three-dimensional simulator, is determined as the transmittance T. (14) The fourteenth feature of the present invention resides in the phase shift mask designing device according to the twelfth feature, wherein a database, in which light intensity deviations D, each defined as a value that indicates a deviation of intensities of light transmitted through each of a pair of adjacent apertures, which are of a predetermined three-dimensional structural body and are designed to realize a phase shift of 180 degrees with respect to each other, when light is transmitted through the apertures under the same conditions, are stored according to various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the undercut amount Uc; and a light intensity deviation determination tool, which determines a specific light intensity deviation D by searching the database using specific parameter values determined by the two-dimensional layout determination tool and the three-dimensional structure determination tool; are provided as an alternative means to the three-dimensional simulator. (15) The fifteenth feature of the present invention resides in the phase shift mask designing device according to the twelfth feature, wherein a database, in which light intensity deviations D, each defined as a value that indicates a deviation of intensities of light transmitted through each of a pair of adjacent apertures, which are of a predetermined two-dimensional structural body and with which a transmittance of one has been set to 100% and a transmittance of the other has been set to T %, when light is transmitted through the apertures under the same conditions, are stored according to various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the transmittance T; and a transmittance determination tool, which searches the database using specific parameter values determined by the two-dimensional layout determination tool and a specific light intensity deviation D determined by the three-dimensional simulator to determine a transmittance T, by which a light intensity deviation equal to the specific light intensity deviation D is obtained; are provided as an alternative means to the two-dimensional simulator for executing the two-dimensional analysis process. (16) The sixteenth feature of the present invention resides in the phase shift mask designing device according to the twelfth feature, wherein a database, in which correction amounts δ, each of which concerns widths of the respective apertures and is required to make equal the intensities of light transmitted under the same conditions through each of a pair of adjacent apertures, which are of a predetermined two-dimensional structural body, are of the same size, and with which a transmittance of one has been set to 100% and a transmittance of the other has been set to T %, are stored according to various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the transmittance T; and a correction amount determination tool, which searches the database using specific parameter values determined by the two-dimensional layout determination tool and a specific transmittance T determined by the two-dimensional analysis process performed by the two-dimensional simulator to determine a correction amount δ for the two-dimensional layout; are provided as an alternative means to the two-dimensional simulator for executing the layout correction process. (17) The seventeenth feature of the present invention resides in the device for designing a phase shift mask, having a substrate with a transparent property, and an opaque layer formed on the substrate and having an opaque property, wherein a plurality of rectangular apertures are formed in the opaque layer, a two-dimensional layout pattern is formed by opaque parts comprising regions at which the opaque layer is formed, and transparent parts comprising regions at which the apertures are formed, and for a pair of adjacently disposed apertures, so that a phase of light transmitted through one of the pair of adjacent apertures will be shifted by 180 degrees with respect to a phase of light transmitted through the other of the pair of adjacent apertures, a trench, having a predetermined depth and an outline greater than an outline of the one aperture, is formed on a portion of the substrate at which the one aperture is formed, the phase shift mask designing device comprising: a two-dimensional layout determination tool, which, based on instructions from an operator, determines a width Wx in the X-axis direction and the width Wy in the Y-axis direction of each aperture and a width Ws of each opaque part on an XY plane defined on a surface of the substrate and positions a plurality of apertures of the same size at least along the X-axis to determine a two-dimensional layout on the XY plane; a three-dimensional structure determination tool, which, based on instructions from an operator, determines whether or not phase shifting is to be performed for each of the plurality of apertures and determines, for apertures with which phase shifting is to be performed, a trench depth d and an undercut amount Uc, which indicates a distance between a position of the outline of the trench and a position of the outline of the aperture, to thereby determine a three-dimensional structure; a first database, in which light intensity deviations D, each defined as a value that indicates a deviation of intensities of light transmitted through each of a pair of adjacent apertures, which are of a predetermined three-dimensional structural body and are designed to realize a phase shift of 180 degrees with respect to each other, when light is transmitted through the apertures under the same conditions, are stored according to various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the undercut amount Uc; a light intensity deviation determination tool, which determines a specific light intensity deviation D by searching the first database using specific parameter values determined by the two-dimensional layout determination tool and the three-dimensional structure determination tool; a second database, in which light intensity deviations D, each defined as a value that indicates a deviation of intensities of light transmitted through each of a pair of adjacent apertures, which are of a predetermined two-dimensional structural body and with which a transmittance of one has been set to 100% and a transmittance of the other has been set to T %, when light is transmitted through the apertures under the same conditions, are stored according to various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the transmittance T; a transmittance determination tool, which searches the second database using specific parameter values determined by the two-dimensional layout determination tool and a specific light intensity deviation D determined by the light intensity deviation determination tool to determine a transmittance T, by which a light intensity deviation equal to the specific light intensity deviation D is obtained; a third database, in which correction amounts, each of which concerns widths of the respective apertures and is required to make equal the intensities of light transmitted under the same conditions through each of a pair of adjacent apertures, which are of a predetermined two-dimensional structural body, are of the same size, and with which a transmittance of one has been set to 100% and a transmittance of the other has been set to T %, are stored according to various different combinations of parameter values of the width Wx in the X-direction of each aperture, the width Ws of each opaque part, and the transmittance T; and a correction amount determination tool, which searches the third database using specific parameter values determined by the two-dimensional layout determination tool and a specific transmittance T determined by the transmittance determination tool to determine a correction amount δ for the two-dimensional layout. (18) The eighteenth feature of the present invention resides in the phase shift mask designing device according to the fourteenth to the seventeenth features, wherein a database, having the width Wy in the Y-axis direction of each aperture in addition as a parameter value, is prepared. (19) The nineteenth feature of the present invention resides in the phase shift mask designing device according to the fourteenth to the seventeenth features, wherein in order to accommodate for a two-dimensional layout, with which a plurality of apertures are positioned in two-dimensional matrix form in the X-axis direction and the Y-axis direction, two parameters of a width Wsx in the X-axis direction of an opaque part existing between apertures that are adjacent in the X-axis direction and a width Wsy in the Y-axis direction of an opaque part existing between apertures that are adjacent in the Y-axis direction are used as parameter values in the database as the width Ws of the opaque parts. (20) The twentieth feature of the present invention resides in the phase shift mask designing device according to the fourteenth to the seventeenth features, wherein in a case where a combination of parameter values that matches the search conditions does not exist among combinations of parameters prepared inside the database, the light intensity deviation determination tool, transmittance determination tool, or correction amount determination tool performs an interpolation operation using parameter values that are close to determine the light intensity deviation D, transmittance T, or correction amount δ. This invention shall now be described based on the illustrated embodiments. <<<§ 1. Basic Structure of a Phase Shift Mask>>> A photomask used for forming an integrated circuit pattern on a semiconductor wafer is basically a two-dimensional layout pattern arranged from opaque parts and transparent parts. FIG. 1 is a plan view, showing a photomask with such a two-dimensional layout pattern. An opaque layer 100 is formed on the upper surface of this photomask and this opaque layer has the two regions of transparent parts 110 and opaque parts 120. As illustrated, each transparent part 110 is arranged as a rectangular aperture and opaque parts 120 are arranged in the form of a frame that surrounds these apertures. The hatched parts in the Figure indicate the regions of opaque parts 120 and not cross sections. FIG. 2 is a sectional side view, showing the section along line 2-2 of the photomask shown in FIG. 1. As is illustrated, this photomask is arranged from a transparent substrate 200 and an opaque layer 100, which has an opaque property and is formed on substrate 200. Substrate 200 is formed of a material such as quartz glass, etc., and opaque layer 100 is formed of a material such as a metal film of chromium, etc. Transparent parts 110 are aperture parts formed in opaque layer 100. When light from an exposure tool is illuminated under predetermined illumination conditions onto this photomask, the light is shielded at the portions of opaque parts 120 and transmitted only through the portions of transparent parts 110. FIG. 3 is a sectional side view, illustrating the exposure work that is performed using this photomask. As is illustrated, the photomask is normally positioned so that substrate 200 will be at the upper side and opaque layer 100 will be at the lower side and the light L from the exposure tool is illuminated from above. Also, a prescribed optical system 300 (indicated as a block in the Figure) is disposed below the photomask, and the light that is transmitted through the photomask is illuminated onto an exposed surface 400 of a semiconductor wafer via this optical system 300. As a result, exposed surface 400 is exposed to a two-dimensional layout pattern, such as that shown in FIG. 1. For the sake of convenience, the X-axis shall be set, as shown in FIG. 1, in the transverse direction of the Figure, the Y-axis shall be set in the vertical direction of the Figure, the XY plane shall be defined as the surface of substrate 200, and the two-dimensional layout pattern formed by opaque layer 100 shall be the pattern defined on this XY plane in the description that follows. As shown in FIG. 2, the Z-axis is thus defined in the direction perpendicular to the main surface of substrate 200 and the light L from the exposure tool is thus illuminated in the Z-axis direction. The two-dimensional layout pattern shown in FIG. 1 is a typical pattern called a “line and space pattern” with which a plurality of apertures of the same size are disposed along the X-axis. This invention is premised on designing a photomask containing such a two-dimensional layout pattern in which a plurality of rectangular apertures of the same size are disposed along the X-axis. A two-dimensional layout pattern for an actual semiconductor integrated circuit is not necessarily arranged from just such a pattern in which a plurality of rectangular apertures of the same size are disposed and it is not rare for a pattern to take on a form where L-shaped apertures, U-shaped apertures, and other apertures of irregular shape coexist as necessary. However, a “line and space pattern” in which a plurality of rectangular apertures of the same size are disposed, is a pattern that is most frequently used in practical applications as a two-dimensional layout pattern for a general semiconductor integrated circuit and it is not an overstatement to say that most regions are taken up by such a “line and space pattern”. The designing method of the present invention is an art that can be used widely in designing such a “line and space pattern” part and is an art of extremely high value of use in designing a photomask for a general semiconductor integrated circuit. Though for the sake of convenience, the example shown in FIG. 1 is a comparatively simple example in which rectangular apertures are formed at five locations, in actuality, a layout pattern, with which a larger number of apertures are disposed along the X-axis at a predetermined pitch, is generally used. In a case where a photomask such as that shown in FIG. 1 is prepared with the dimensions that are actually indicated in the drawing, the light L that is illuminated from the exposure tool in FIG. 3 behaves as particles and the light that is transmitted through an aperture of opaque layer 100 proceeds rectilinearly as it is and exposes the surface of exposed surface 400. An exposure pattern equivalent to the two-dimensional layout pattern shown in FIG. 1 is thus obtained on the exposed surface 400. However, circumstances will differ if the respective parts of the pattern of a photomask such as that shown in FIG. 1 are prepared with a size near or no more than the wavelength of the light source of the exposure tool. When the size of an aperture becomes close to the wavelength of light, the light L that is illuminated from the exposure tool begins to behave as a wave and the diffraction phenomenon that occurs in the process of transmission through the aperture becomes non-negligible. FIG. 4 shows diagrams that illustrate the behavior of light transmitted through apertures of a photomask with the diffraction phenomenon taken into consideration, the upper diagram being a partially enlarged sectional side view of the photomask, the middle diagram showing graphs of the amplitude intensity distributions of the light transmitted through the photomask, and the lower diagram showing a graph of the light intensity distribution of the light transmitted through the photomask. As shown in the upper diagram of the Figure, though illumination light L1, L2, and L3 from the exposure tool are respectively transmitted through apertures 111, 112, and 113 and proceed toward the exposed surface below the photomask, since the diffraction phenomenon of light occurs in this process, parts of the transmitted light become diffracted towards portions of opaque parts 121, 122, 123, and 124. As a result, the amplitude intensity of light (here, the amplitude intensity that takes the sign into consideration is illustrated) will be as shown in the graph of the middle diagram. The abscissa of these graphs corresponds to the spatial position in the X-axis direction of the photomask, and it can be seen that amplitude intensities with peaks at the central positions of the respective apertures 111, 112, and 113 are obtained. Since all of the light that are thus transmitted through the photomask are light of the same phase, they intensify each other at the overlapping parts of the graphs of the middle diagram of the Figure, and consequently, the light intensity distribution of the transmitted light will be that of the graph of the lower diagram of the Figure that is obtained by adding the amplitude intensity values of the respective graphs. That is, though the light intensity at the regions of the exposed surface of the semiconductor wafer that correspond to the respective apertures 111, 112, and 113 will be relatively high, the light intensity will also come to take on a certain magnitude even at regions corresponding to opaque parts 121, 122, 123, and 124. Thus, if for example the threshold value Th of the light intensity that is necessary for exposing a resist layer that is formed on the exposed surface is of the value indicated in the graph of the lower diagram of the Figure, all regions of the exposed surface will be exposed in the case of the illustrated example and the image of the original pattern will not be formed. A phase shift mask is used as a method for counteracting such a problem. FIG. 5 shows diagrams that illustrate the behavior of light transmitted through apertures of a phase shift mask under predetermined conditions and with the occurrence of diffraction phenomenon taken into consideration, the upper diagram being a partially enlarged sectional side view of the phase shift mask, the middle diagram showing graphs of the amplitude intensity distributions of the light transmitted through this phase shift mask, and the lower diagram being a graph, showing the light intensity distribution of the light transmitted through this phase shift mask. The difference between the ordinary photomask shown in the upper diagram of FIG. 4 and the phase shift mask shown in the upper diagram of FIG. 5 is that, with the latter, a trench 210 of a depth d is formed at apart of substrate 200. With the illustrated example, trench 210 is formed at a region in which aperture 112 is formed and a trench is not formed at regions in which apertures 111 and 113 are formed. Here, trench 210 serves to shift the phase of light L2 that is transmitted through aperture 112 by 180 degrees. In other words, the depth d of trench 210 is set to a length that is necessary for shifting the phase of light of the wavelength of the light source of the exposure tool by just 180 degrees. When illumination light L1, L2, and L3 from the exposure tool are illuminated onto such a phase shift mask, though these light are transmitted through apertures 111, 112, and 113 and proceed toward the exposed surface below the photomask, the light L2 that is transmitted through aperture 112 will be shifted in phase by just 180 degrees. Here, the phases φ of the light L1 and L3 that are transmitted through apertures 111 and 113 are indicated as taking on the reference value of 0 degree and the phase of the light L2 that is transmitted through aperture 112 is indicated as being 180 degrees. When a phase shift occurs with part of such light that are transmitted through the phase shift mask, the amplitude intensities that take the signs of the transmitted light into consideration will be as shown by the graphs of the middle diagram of the Figure. Since the phase of light L2 is inverted with respect to the phases of light L1 and L3, the sign of its amplitude will be inverted as well. Consequently, the overlapping parts of the graphs shown in the middle diagram of the Figure weaken each other and the synthesized amplitude will be a result of addition of the amplitude intensity values of the graphs in consideration of the signs of the values. Since the light intensity distribution of transmitted light is the square of the amplitude, it will be as shown in the graph of the lower diagram of the Figure. The light intensity will thus be relatively high at regions of the exposed surface of the semiconductor wafer that correspond to the respective apertures 111, 112, and 113 and be relatively low at regions corresponding to opaque parts 121, 122, 123, and 124. If such an adequate difference in light intensity can be obtained between regions corresponding to apertures and regions corresponding to opaque parts, an image of the originally intended pattern can be formed on the exposed surface. The basic principle of a phase shift mask is thus to employ a structure, such that the phases of light transmitted through a pair of adjacently disposed apertures will be inverted, to cancel out the interference of light at the opaque parts. With a trench type phase shift mask, the method, wherein, for a pair of adjacently disposed apertures, a trench, having a predetermined depth d, is formed at the substrate part at which one of the apertures is formed so that the phase of the light transmitted through this one aperture will be shifted by 180 degrees with respect to the phase of the light transmitted through the other aperture, is taken. However, it is known that, in actuality, when a trench 210 such as that shown in the upper diagram of FIG. 5 is formed, an ideal light intensity distribution such as that shown in the lower diagram of FIG. 5 will not be obtained. FIG. 6 shows diagrams that illustrate the real behavior of light transmitted through apertures of a phase shift mask. With the middle diagram of FIG. 6, though the graph indicated by a broken line indicates the ideal amplitude intensity distribution shown in FIG. 5, in actuality, the amplitude intensity will be smaller as indicated by the solid line in this diagram. Likewise, with the lower diagram of FIG. 6, though the graph indicated by a broken line indicates the ideal light intensity distribution shown in FIG. 5, in actuality, the light intensity will be smaller as indicated by the solid line in this diagram. Such lowering of the amplitude intensity of light transmitted through trench 210 is due to the existence of light L4 that proceed downwards from the side faces of trench 210 as shown in the upper diagram of FIG. 6. That is, since the light L4, which leak from the side faces of trench 210 are light that differ in phase from the light L2 that proceeds in the vertical direction from the upper side to the lower side of the diagram inside trench 210, the two types of light cancel each other out. As a result, the amplitude intensity of light L2 transmitted through aperture 112 is decreased. Meanwhile, for light L1 and L2 that are transmitted through apertures 111 and 113 in which a trench is not formed, the amplitude intensities do not decrease since such a canceling-out phenomenon does not occur. Consequently, a circumstance arises wherein, in comparison to the intensity of light transmitted through an aperture with a phase setting of φ=0 degree (an aperture in which a trench is not formed), the intensity of light transmitted through an aperture with a phase setting of φ=180 degrees (an aperture in which a trench is formed) is decreased. This thus results in differences in the sizes of aperture patterns formed on the exposed surface despite performing exposure using a photomask with apertures of the same size. In order to resolve such a problem, with a trench-type, Levenson-type (or Alternating Aperture type) phase shift mask, such a method is taken, wherein, for a pair of adjacently disposed apertures, a trench of a predetermined depth d is formed at the substrate part at which one of the apertures is formed so that the phase of the light transmitted through this one aperture will be shifted by 180 degrees with respect to the phase of the light transmitted through the other aperture and the outline of this trench is set to be greater than the outline of the aperture. FIG. 7 shows diagrams that illustrate the real behavior of light transmitted through apertures of a trench-type, Levenson-type phase shift mask. The graphs of amplitude intensity distribution and light intensity distribution shown in the middle and lower diagrams, respectively, of FIG. 7 are the same as the ideal graphs shown in FIG. 5. This is due to the outline (outline on the XY plane) of trench 220 being set to be greater than the outline (outline on the XY plane) of aperture 112 as shown in the sectional side view of the upper diagram of FIG. 7. With such a structure, since the side faces of trench 220 will be retreated with respect to the outline portion of aperture 112, the light L4 that leak out from the side faces of trench 220 can be prevented from interfering with the light L2 that is transmitted through aperture 112. Though with the Figures of the present application, specific graphs concerning light transmitted through a phase shift mask shall be indicated for the sake of convenience of description, the forms of these graphs will differ according to various condition settings. In general, the behavior of light transmitted through a phase shift mask will be affected by the design conditions (two-dimensional dimensions of the apertures, opaque parts, etc.), exposure condition (the values of exposure wavelength, numerical aperture, illumination, etc.), and three-dimensional structures, such as the undercut amount to be described later and the trench depth, etc. The graphs shown in the Figures of the present application illustrate results that are obtained when these various conditions are set to specific conditions. <<<§ 2. Problem Concerning the Undercut Amount>>> As was mentioned already in § 1, by use of a trench-type, Levenson-type phase shift mask with a three-dimensional structure such as that shown in the upper diagram of FIG. 7, the phases of transmitted light can be inverted for a pair of adjacently disposed apertures (the pair of apertures 111 and 112 or the pair of apertures 112 and 113 in the case of the illustrated example) and the influence of interference of the light L4 that leak out from the side from the side faces of the trench can be restrained. However, in actuality, in order to restrain the influence of interference of the light L4 completely, a predetermined value or more must be secured for the distance between the outline position of trench 220 and the outline position of the aperture. FIG. 8 shows a sectional side view (upper diagram), showing a part of the phase shift mask of the upper diagram of FIG. 7 in a further enlarged manner, and a graph (lower diagram), showing the intensity of the light transmitted through this phase shift mask. As shown in the upper diagram, a trench 220 of a predetermined depth d is formed in a substrate 220 and the outline of this trench 220 is set to be greater than the outline of aperture 112. That is, the position C1 of the outline of the left side (left side face) of trench 220 is retreated slightly to the left of the left-side outline position C2 of aperture 112 (right-end position of opaque part 122) and the position C4 of the outline of the right side (right side face) of trench 220 is retreated slightly to the right of the right-side outline position C3 of aperture 112 (left-end position of opaque part 123). Here, the distance between the outline position of trench 220 and the outline position of aperture 112 shall be referred as the undercut amount Uc as shown in the Figure. Put in another way, this undercut amount Uc corresponds to being the width of the eaves portions of opaque parts 122 and 123 that are formed at the opening portions of trench 220. In terms of restraining the influence of interference of the light that leak out from the side faces of trench 220, the greater this undercut amount Uc, the more preferable. Actually, by setting the undercut amount Uc to at least a predetermined value, the influence of interference of the light L4 that leak out from the side faces of trench 220 can be restrained completely as in the example shown in FIG. 7, and the intensities of the light L1, L2, and L3 that are transmitted through the three apertures 111, 112, and 113 will be equal. However, as the two-dimensional layout pattern that is formed on substrate 200 becomes finer, it becomes more difficult to secure an adequate undercut amount Uc. This is because as the layout pattern is made finer, the width Wx in the X-axis direction of apertures 111 and 112 and the width Ws in the X-axis direction of opaque parts 121, 122, and 123, shown in the upper diagram of FIG. 8, become smaller and thus the areas of contact between opaque parts 121, 122, and 123 and substrate 200 inevitably become smaller. As mentioned above, whereas substrate 200 is normally formed of a layer of transparent material, such as quartz glass, opaque layer 100 is formed of a layer of chromium or other metal material with an opaque property. Opaque layer 100 is thus more readily separated from substrate 200 the less the contact area between the two material layers. Consequently, in order to manufacture a phase shift mask with adequate integrity for withstanding an actual exposure process to be performed on a semiconductor wafer, a contact area of a certain magnitude or more has to be secured between the two material layers. In other words, unless a contact dimension (Ws−Uc) of a certain magnitude or more is secured between opaque layer 122 and substrate 200 in the upper diagram of FIG. 8, opaque layer 122 may separate from substrate 200. It is thus inevitable that the undercut amount Uc that can actually be secured becomes smaller as the layout pattern becomes finer (as the width Ws of opaque layer 122 becomes smaller). Actually, with a fine pattern with which the width Ws of opaque layer 122 is a few hundred nm's, it becomes difficult to secure an adequate undercut amount Uc. Obviously, the influence of interference of light leaking out from the side faces of trench 220 then becomes non-negligible and the intensity of light transmitted through trench 220 decreases. The graph of the lower diagram of FIG. 8 shows an example where the intensity of light transmitted through aperture 112 (light with a phase φ=180 degrees) is decreased in comparison to the light transmitted through aperture 111 (light with a phase φ=0 degree) due to the influence of such interference. Though the apertures 111 and 112 formed in opaque layer 100 are rectangular apertures of the same size of width Wx as shown in the upper diagram of FIG. 8, the intensities of the light transmitted through the respective apertures under a predetermined condition will differ as shown in the graph of the lower diagram of FIG. 8. Here, the difference in the intensities of the light that are transmitted through such a pair of adjacently disposed apertures 111 and 112 shall be defined and handled quantitatively as a light intensity deviation. As long as the difference in the magnitudes of two light intensity distributions, such as those shown in the lower diagram of FIG. 8, can be indicated quantitatively, the light intensity deviation may be defined in any way. For example, the areas of the two graphs may be determined and the ratio or the difference of the areas may be defined as the light intensity deviation. Or, the peak values of the two graphs may be determined and the ratio or the difference of the values may be defined as the light intensity deviation. Here, as shown in the lower diagram of FIG. 8, a predetermined threshold value Th is set for the light intensity, a level line (the line indicated by the alternate long and short dash line in the Figure) corresponding to this threshold value Th is drawn on the two-dimensional coordinate system, the intersections of this level line with the respective graphs are defined as Q1, Q2, Q3, and Q4, the distance Wa between the two points Q1 and Q2 and the distance Wb between the two points Q3 and Q4 are determined, and the difference, D=Wa−Wb is defined as the light intensity deviation D for the illustrated embodiment. In this case, since the value of light intensity deviation D will vary depending on how the threshold value Th is set, threshold value Th is set to a value such that the distance between the two points Q2 and Q3 will be equal to the width Ws of opaque part 122. In other words, when a graph such as that shown in the lower diagram of FIG. 8 is obtained, a level line that is parallel to the X-axis is defined so that the distance between the two points Q2 and Q3 will be equal to the width Ws of opaque part 122, the distance Wa and Wb are determined based on this level line, and the light intensity difference D is defined as the difference D=Wa−Wb. By defining the light intensity deviation D by such a method, light intensity deviation D will be determined uniquely for a graph such as that shown in the lower diagram of FIG. 8. Though as mentioned above, the light intensity deviation may be defined in any way in putting this invention into practice as long as it can quantitatively indicate the difference between the transmitted light intensity for phase φ=0 degree and the transmitted light intensity for phase φ=180 degrees, the use of the light intensity deviation D defined as the difference D=Wa−Wb as indicated in the present embodiment is extremely practical. This is because, when the light intensity deviation is defined by a method of comparing the areas of the graphs, there is the demerit that the computing load for determining the areas becomes large, and when the light intensity deviation is defined by a method of comparing the peak values of the graphs, there is the demerit that the precision of comparison will be low. The light intensity deviation D that is defined as the difference D=Wa−Wb employs a method of comparing the widths of the graphs at a predetermined level position and is thus low in computing load and also provides the merit of enabling the securing of certain level of precision of comparison. Such a light intensity deviation D that is defined as the difference D=Wa−Wb is, in general, referred to as a “Walking Distance”. Consequently, when due to the layout pattern becoming fine, an adequate undercut amount Uc cannot be secured, a light intensity deviation D will arise for the light transmitted through a pair of adjacent apertures 111 and 112 as shown in the lower diagram of FIG. 8, even with a trench-type, Levenson-type phase shift mask, such as that shown in the upper diagram of FIG. 8. In order to prevent such a light intensity deviation D from occurring in the exposure of a semiconductor wafer, dimensional corrections considering the occurrence of light intensity deviation D in advance are applied to the two-dimensional layout pattern formed on the phase shift mask. Specifically, in the case of the example illustrated in FIG. 8, corrections must be applied to the sizes of apertures 111 and 112. For example, with the example shown in FIG. 8, the light intensity deviation D arises as a result of aperture 111, for which the phase of transmitted light is such that φ=0 degree (in other words, the aperture with which a trench is not formed), and aperture 112, for which the phase of transmitted light is such that φ=180 degrees (in other words, the aperture with which a trench is formed), being set to the same width Wx. By performing a correction by which the width Wx of aperture 111 is slightly narrowed and performing a correction by which the width Wx of aperture 112 is slightly widened, the intensity of light transmitted through aperture 111 can be decreased and the intensity of light transmitted through aperture 112 can be increased. The light intensity deviation D can thus be made zero if the correction amounts of the widths can be set appropriately. However, as a realistic problem, a vast amount of labor and time is required for determining optimal correction amounts for making the light intensity deviation D zero. This is because, as shown in the sectional side view of the upper diagram of FIG. 8, with a trench-type, Levenson-type phase shift mask in which a trench is formed in substrate 200, the part at which trench 220 is formed takes on a three-dimensional structure, making two-dimensional analysis inadequate and necessitating the performing of a three-dimensional analysis. For example, with the illustrated example, though the intensity of light transmitted through aperture 112 will obviously increase if the width Wx of aperture 112 is widened by a small amount, how much the light intensity will increase cannot be known unless a photomask of the exact design dimensions is actually manufactured and experimented with or a three-dimensional simulation using a computer is executed. Thus in designing a single phase shift mask, a vast amount of labor and time will be consumed in determining an optimal correction amount for making the light intensity deviation D zero by trial and error. An object of this invention is to provide a designing method and device for phase shift mask that will enable such a work load to be lightened and the working time to be shortened. The basic principles of the designing method of this invention shall now be described. <<<§ 3. Basic Principle of Designing Method of Invention>>> The inventor of the present application recognized that in a case of performing three-dimensional analysis to determine the light intensity deviation D for a three-dimensional structure, such as that shown in the upper diagram of FIG. 8, the respective parameters to be described below are involved. Consider a case where a two-dimensional layout pattern such as that shown in FIG. 9 (the same pattern as that shown in FIG. 1) is formed on opaque layer 100 itself. In this example, rectangular apertures 110 of the same size are formed at five locations and frame-shaped opaque parts 120 surround these apertures 110. Here, a setting for performing a phase shift (a setting by which φ=180 degrees) is applied to every other aperture of the respective apertures 110 that are aligned in the X-axis direction, and a trench 220 is formed at the region of each aperture that has been subject to this setting. If for this two-dimensional layout pattern, a two-dimensional, XY coordinate system is defined as illustrated, the width in the X-axis direction and the width in the Y-axis direction of each aperture 110 are defined as Wx and Wy, respectively, and the width in the X-axis direction of each opaque part 120 is defined as Ws, all of these dimension values Wx, Wy, and Ws will be parameters that affect the value of light intensity deviation D. Needless to say, the undercut amount Uc, shown in the upper diagram of FIG. 8, will also be a parameter that affects the value of light intensity deviation D. The inventor of this application considers that, in performing three-dimensional analysis of the behavior of light from an exposure tool for a trench-type, Levenson-type phase shift mask, these four parameters Wx, Wy, Ws, and Uc are the major parameters that determine the value of light intensity deviation D. As mentioned above, the behavior of light transmitted through a phase shift mask is affected by the design conditions (two-dimensional dimensions of the apertures, opaque parts, etc.), exposure condition (the values of exposure wavelength, numerical aperture, illumination, etc.), and three-dimensional structures, such as the undercut amount, trench depth, etc. However, the exposure condition is a condition determined by the exposure tool used in the process of forming a pattern on a semiconductor wafer and is not a condition that can be set freely in designing a phase shift mask. Also, though the depth d of trench 220 may be a parameter that defines the three-dimensional structure, this depth d must be set to a length that is necessary for shifting the phase of transmitted light by 180 degrees. The depth d is thus an amount that is determined by the wavelength of the light source of the exposure tool used and is thus not a parameter that can be set as suited. Thus if it is premised that a specific exposure tool is used to execute a pattern forming process on a semiconductor wafer, the predetermined exposure condition is already determined, the value of the depth d of the trench is uniquely determined, and consequently, the parameters that are variable in the designing step of a phase shift mask are the parameters, Wx, Wy, and Ws and the undercut amount Uc that correspond to being a designing condition. As shall be described later, with the present invention, a three-dimensional analysis and a two-dimensional analysis for tracing the behavior of light transmitted through a phase shift mask are performed by conducting a three-dimensional simulation and a two-dimensional simulation. Since these analyses are all premised on executing a pattern forming process onto a semiconductor wafer using a specific exposure tool, a condition that is unique to the specific exposure tool is set in regard to the exposure condition. The inventor of this application carried out three-dimensional simulations of cases of varying the combinations of the values of the abovementioned four parameters Wx, Wy, Ws, and Uc in various ways for a three-dimensional structure, such as that shown in the upper diagram of FIG. 8 and determined the light intensity deviation D for each case. As mentioned above, with regard to the exposure condition, a condition that is unique to a specific exposure tool was set. For example, the graphs of FIG. 10 are graphs of the relationship between the undercut amount Uc (unit: nm) and the light intensity deviation D (unit: nm) when, in the three-dimensional structure shown in the upper diagram of FIG. 8, the width Ws in the X-axis direction of an opaque part 122 is set equal to 200 nm, the width Wy in the Y-axis direction (in FIG. 8, the width in the direction perpendicular to the paper surface) of each of apertures 111 and 112 is set equal to 100 nm, and the width Wx in the X-axis direction of each of apertures 111 and 112 is set equal to the two values of 200 nm and 300 nm. The light intensity deviation D is the greatest when the undercut amount Uc is 0 (corresponding to the structure shown in the upper diagram of FIG. 5), and the light intensity deviation D decreases as the undercut amount Uc is made larger. And when the undercut amount Uc becomes equal to or greater than a predetermined length, the light intensity deviation D becomes zero. In the illustrated example, the light intensity deviation D can be restrained to zero when the undercut amount Uc exceeds 180 nm. It can also be seen that even if the undercut amount Uc is the same, the light intensity deviation D is smaller in the case where the width Wx in the X-axis direction of an aperture is 300 nm than in the case where the width Wx is 200 nm. Though the graphs of FIG. 10 are graphs with which Ws and Wy are fixed at Ws=200 nm and Wy=1000 nm, if various combinations are made for Ws and Wy, similar graphs will be obtained for the respective combinations. Though needless to say predetermined exposure condition must be set to perform such three-dimensional simulations, in regard to parameters concerning the structure of a phase shift mask, the value of the light intensity deviation D can be determined if the abovementioned four parameters Wx, Wy, Ws, and Uc (and trench depth d) are determined. With the example illustrated in the graphs of FIG. 10, the light intensity deviation D can be restricted to zero if the undercut amount Uc is set so that Uc=180 nm or more, and ideal light transmission characteristics, such as those shown in FIG. 7, can thereby be obtained. However, as was mentioned already, as the layout pattern becomes finer, the need to restrain the separation of the opaque layer makes it more difficult to secure an adequate undercut amount Uc. This invention proposes a new method for performing layout designing by which the light intensity deviation D is made closer to zero under designing conditions in which such an adequate undercut amount Uc cannot be secured. Put in another way, this invention provides a method of making the light intensity deviation D closer to zero by applying predetermined corrections to a layout pattern with which the undercut amount Uc is within a range of less than 180 nm in the graph shown in FIG. 10. The correction according to the present invention is a two-dimensional correction performed on the two-dimensional layout pattern, and it is premised that no correction is applied to depth d of trench 220 of the three-dimensional structure shown in the upper diagram of FIG. 8 and no correction is applied to undercut amount Uc. Such a premise is actually obvious in consideration of the object of this invention. That is, since depth d of trench 220 is uniquely determined by the light source wavelength of the exposure tool, it cannot be changed arbitrarily for the reason of “making the light intensity deviation D zero”. With regard to the undercut amount Uc, the maximum value thereof is determined automatically by the need to satisfy the physical requirement of preventing the separation of the opaque layer. As is clear from the upper diagram of FIG. 8, as the undercut amount Uc becomes greater, the adjacent dimension of opaque part 122 with respect to substrate 200 becomes smaller and separation becomes more frequent. For practical purposes, the maximum value of the undercut amount Uc having some degree of manufacturing tolerance must be set in adequate consideration of the yield of manufacture of a phase shift mask. Thus the undercut amount Uc cannot be set to a large value arbitrarily for the reason of “making the light intensity deviation D zero”. Thus, in the present invention, the trench depth d and the undercut amount Uc are determined with the first priority, and the light intensity deviation D should be approximated to zero with maintaining the values of d and Uc. Suppose now that a designer of a photomask makes a design in which rectangular apertures 111 and 112 of the same size, such as shown in FIG. 11, are disposed on a two-dimensional layout pattern. As mentioned above, since the pair of apertures 111 and 112 are disposed adjacently, if the phase of the light transmitted through one aperture 111 is such that φ=0 degree, measures must be taken to make the phase of the light transmitted through the other aperture 112 such that φ=180 degrees in order to cancel out the influence of light that diffracts into the region of opaque part 122 by the diffraction phenomenon. Specifically, a trench 220 must be formed in the substrate for aperture 112 to set the phase φ=180 degrees as was mentioned above as well. Here, the pair of apertures 111 and 112 are rectangular open patterns of the same size and are equal in both the width Wx in the X-axis direction and the width Wy in the Y-axis direction. The designer of the photomask positioned such rectangular apertures 111 and 112 of the same size intending to make a photomask that can form rectangular exposure patterns of the same size on the exposed surface of a semiconductor wafer. However, as mentioned above, unless an adequate undercut amount Uc can be secured, the transmitted light intensity of aperture 112 will be lower in comparison to the transmitted light intensity of aperture 111 and it will not be possible to form rectangular exposure patterns of the same size on the exposed surface of a semiconductor wafer as the designer intended. Suppose that corrections are thus applied to the two-dimensional layout pattern shown in FIG. 11 and a pattern such as that shown in FIG. 12 is obtained. With this correction, the width Wx in the X-axis direction is changed with each of apertures 111 and 112. That is, aperture 111, for which φ=0 degree, is narrowed in width by just δ at both the left and right sides and changed to an aperture 111* and aperture 112, for which φ=180 degrees, is broadened in width by just δ at both the left and right sides and changed to an aperture 112*. Each aperture is not changed in regard to the width Wy in the Y-axis direction. Consequently, the width Wxa in the X-axis direction of aperture 111* after the change is made smaller than the width Wx prior to the change by just 2 δ, and the width Wxb in the X-axis direction of aperture 112* after the change is made larger than the width Wx prior to the change by just 2 δ. As a result, the total amount of light transmitted through aperture 111* decreases and the total amount of light transmitted through aperture 112* increases. Here, as the correction amount δ is increased gradually from 0, the difference in the sizes of the pair of graphs (the graph for φ=0 degree and the graph for φ=180 degrees) shown in the lower diagram of FIG. 8 decreases gradually. Thus by setting the correction amount δ to an appropriate amount, the pair of graphs can be made equal in size and rectangular exposure patterns of the same size can be formed on the exposed surface of a semiconductor wafer. This is the basic principle of the correction that is carried out in this invention. That is, with this invention, when a two-dimensional layout pattern such as that shown in FIG. 11 is designed by a designer, the corrections of narrowing the width of an aperture with which a phase shift is not performed (an aperture for which φ=0 degree) and widening the width of an aperture with which a phase shift is performed (an aperture for which φ=180 degrees) are made to cancel out the decrease of light intensity that occurs, due to the existence of a trench, at just the aperture with which a phase shift is performed. With the pattern after correction, shown in FIG. 12, though the two apertures 111* and 112* have different widths Wxa and Wxb, when exposure is actually performed using the phase shift mask, rectangular exposure patterns of the same size can be formed on the exposed surface of a semiconductor wafer. In correcting the widths of the respective apertures, corrections are preferably made so that the center positions of the respective positions will always be fixed. For example, the center positions in the X-axis direction of the apertures 111 and 112 shown in FIG. 11 match the center positions in the X-axis direction of the apertures 111* and 112* shown in FIG. 12. Put in another way, aperture 111* is obtained by applying a correction that narrows the width of aperture 111 uniformly from both sides, and aperture 112* is obtained by applying a correction that widens the width of aperture 112 uniformly at both sides. As a result, the width Ws of opaque part 122* after correction will be matched with the width Ws of opaque part 122 prior to correction (the position will be shifted slightly) and there will thus be no changes in the width of the opaque part. With regard to the pitch of apertures, whereas a pitch P in the case of the pattern shown in FIG. 11 is such that “P=Wx+Ws”, a pitch P* in the case of the pattern after correction that is shown in FIG. 12 will be “P*=Wxa+Ws (in the case of an odd number pitch)” or “P*=Wxb+Ws (in the case of an even number pitch)”, and thus an odd number pitch will be narrow and an even number pitch will be wide. However, the sum of an odd number pitch and an even number pitch will not differ before and after the corrections. That is, with regard to the plan view shown in FIG. 9, though some changes will be made in terms of pitch P by the corrections, no changes will be made in terms of pitch 2P by the corrections. The change of the layout pitch of the apertures that results from the above-described correction therefore will not give rise to a major problem in terms of practical use. Thus in principle, by correcting the layout pattern shown in FIG. 11 to the layout pattern shown in FIG. 12, a phase shift mask, by which a designer's intended exposure pattern can be obtained, can be realized even if the undercut amount Uc is inadequate. However in actuality, there remains the problem of how to determine an appropriate correction amount δ. The reason for this is that, as was mentioned above, with a trench-type, Levenson-type phase shift mask, with which a trench is formed in substrate 200, the part at which trench 220 is formed takes on a three-dimensional structure, thus making two-dimensional analysis inadequate and making three-dimensional analysis necessary. As mentioned above, though this three-dimensional analysis can be executed by a method of determining the four parameters Wx, Wy, Ws, and Uc and determining the value of the light intensity deviation D, a vast amount of labor and time are required to determine, by trial and error, an optimal correction amount δ that makes the light intensity deviation D zero. The most characteristic point that this invention makes note of is to apply two-dimensional analysis in place of three-dimensional analysis in the determination of the correction amount d. As mentioned above, the root cause of occurrence of the light intensity deviation D lies in the three-dimensional structure in which a trench is formed in one of the apertures. Thus primarily, three-dimensional analysis must be performed as the analysis for determining the light intensity deviation D. There is no way for the concept of a three-dimensional trench to fall under the scope of two-dimensional analysis, and it thus seems at first sight that the phenomenon that gives rise to the light intensity deviation D cannot be handled by the two-dimensional analysis. However, the inventor of the present application found that by introducing the virtual parameter of “transmittance”, the three-dimensional phenomenon that gives rise to the light intensity deviation D can be handled by replacement by a two-dimensional model. The characteristic of the method and device for designing a phase shift mask of the present invention lies in this change of way of thinking. Here, consider a two-dimensional model, such as that shown in the upper diagram of FIG. 13. This model illustrates a two-dimensional layout pattern with a pair of apertures 111 and 112 of the same size (Wx×Wy). Though the pattern of each aperture is exactly the same as that shown in the plan view of FIG. 11, whereas the plan view of FIG. 11 shows the planar pattern of opaque layer 100 of a phase shift mask with a three-dimensional structure (structure with a trench), the plan view of the upper diagram of FIG. 13 illustrates the planar pattern of a virtual two-dimensional phase shift mask without thickness. Here, suppose that a transmittance of 100% is set for aperture 111 at the left side of the diagram and a transmittance T of 85% is set for aperture 112 at the right side of the diagram. If two-dimensional analysis under predetermined exposure conditions is then performed with the assumption that the width Wx in the X-axis direction of each of the apertures 111 and 112 and the width Ws in the X-axis direction of an opaque part 122 take on values close to the wavelength of light (that is, if analysis is performed with the premise that light diffracts to the lower surface of opaque part 122 due to the diffraction phenomenon), a light intensity graph, such as shown in the lower diagram of FIG. 13 can be obtained. In the field of photomask designing, such two-dimensional analysis method itself is a known art and the setting of a predetermined transmittance for each aperture is already practiced. The graphs of the lower diagram of FIG. 13 and the graphs of the lower diagram of FIG. 8 share the feature of being graphs of intensity distributions of light transmitted through a pair of adjacently disposed apertures 111 and 112. In both cases, a light intensity deviation D of a certain value can be determined by setting a level line, which is parallel to the X-axis and is such that the distance between the two points Q2 and Q3 will be equal to the width Ws of opaque part 122, determining the distance Wa and Wb based on this level line, and determining the light intensity deviation D as the deviation D=Wa−Wb. Needless to say, the result shown in the lower diagram of FIG. 8 is obtained by three-dimensional analysis using the three-dimensional structure shown in the upper diagram of FIG. 8 as a model, and the occurrence of the light intensity deviation D is caused by a trench not being formed at the aperture 111 side while there being a trench 220 formed at the aperture 112 side. On the other hand, the result shown in the lower diagram of FIG. 13 is obtained by a two-dimensional analysis using the virtual two-dimensional model shown in the upper diagram of FIG. 13, and the light intensity deviation D is caused by the transmittance of the aperture 111 side being set to 100% while the transmittance T of the aperture 112 side being set equal to 85%. The primary cause by which the light intensity deviation D occurs differs completely between the three-dimensional analysis illustrated in FIG. 8 and the two-dimensional analysis illustrated in FIG. 13. However, the phenomenon that the light intensity deviation D occurs for light transmitted through a pair of apertures in a case where a pair of apertures 111 and 112, each with widths Wx and Wy, are adjacently disposed across opaque part 122, with a width of Ws, is equivalent to both. The inventor of the present application thus noted that by replacing the three-dimensional model, which is shown in FIG. 8 and is subject to three-dimensional analysis, by the two-dimensional model, shown in FIG. 13, and determining an appropriate correction amount δ using a two-dimensional analysis method, the total work load can be lightened and the working time can be shortened. In order to make the light intensity deviation D, which occurs in the two-dimensional model shown in FIG. 13, zero, a correction, such as that shown in the upper diagram of FIG. 14, may be performed. The correction itself is exactly the same as the correction illustrated in FIG. 12 and the widths Wx in the X-axis direction of the respective apertures 111 and 112 are changed. That is, aperture 111 with a transmittance of 100% is changed to an aperture 111* with which the width has been narrowed by just δ from both the left and right sides, and aperture 112 with a transmittance T=85% is changed to an aperture 112* with which the width has been widened by just δ at both the left and right sides. With each aperture, there is no change of the width Wy in the Y-axis direction. Consequently, the width Wxa in the X-axis direction of aperture 111* after the change is reduced by just 2 δ in comparison to the width Wx prior to the change, and the width Wxb in the X-axis direction of aperture 112* after the change is enlarged by just 2 δ in comparison to the width Wx prior to the change. As a result, the total amount of light transmitted through aperture 111* is reduced and the total amount of light transmitted through aperture 112* is increased. Thus even with the above-described two-dimensional model, if the correction amount δ can be set to an appropriate value, the size of the graph that indicates the intensity distribution of light transmitted through aperture 111* can be made equal to the size of the graph that indicates the intensity distribution of light transmitted through aperture 112* as shown in the lower diagram of FIG. 14, thereby making the light intensity deviation D zero and enabling rectangular exposure patterns of the same size to be obtained on the exposed surface of a semiconductor surface. As mentioned above, in correcting the width of each aperture, it is preferable to perform a correction with which the central position of each aperture will be a fixed position at all times. As mentioned above, in determining the light intensity deviation D by a three-dimensional analysis method using a three-dimensional model, such as that shown in the upper diagram of FIG. 8, the four parameters Wx, Wy, Ws, and Uc must be determined. Meanwhile, in determining the light intensity deviation D by a two-dimensional analysis method using a two-dimensional model, such as that shown in the upper diagram of FIG. 13, the four parameters Wx, Wy, Ws, and T must be determined. A comparison of the parameters that are necessary in the two cases shows that whereas the parameters Wx, Wy, and Ws (these are all parameters that indicate dimensions of a two-dimensional layout pattern) are used in common in both cases, the cases differ in that the undercut amount Uc is needed as the fourth parameter for three-dimensional analysis and the transmittance T is needed as the fourth parameter for two-dimensional analysis. This is because whereas with the three-dimensional model, the undercut amount Uc is an important parameter that affects the light intensity deviation D, with the two-dimensional model, the transmittance T is introduced as a parameter in place of the undercut amount Uc since there is no such concept as the undercut amount Uc to start with in the two-dimensional model. Since, under predetermined exposure conditions, the light intensity deviation D can be determined by determining the four parameters of Wx, Wy, Ws, and Uc in the case of three-dimensional analysis and the light intensity deviation D can be determined by determining the four parameters of Wx, Wy, Ws, and T in the case of two-dimensional analysis, it may seem that there will not be much difference in using one or the other analysis method. However, three-dimensional analysis requires a vast amount of labor and time in comparison to two-dimensional analysis. For example, if typical parameter values are provided and the respective analysis methods are executed by computer simulation using a general personal computer, whereas a computation time in the order of minutes is required to determine the light intensity deviation D by three-dimensional analysis, a computation time of merely in the order of msec is required to determine the light intensity deviation D by two-dimensional analysis. The replacement of three-dimensional analysis by two-dimensional analysis is thus extremely significant for practical use. A key point of this invention is that by replacing the three-dimensional model, which is shown in FIG. 8 and is subject to three-dimensional analysis, by the two-dimensional model shown in FIG. 13 and using a two-dimensional analysis method to determine an appropriate correction amount δ, the total work load is lightened and the working time is shortened. Specific procedures for this method shall now be described in § 4. <<<§ 4. Specific Method and Device for Designing Phase Shift Mask of the Invention>>> FIG. 15 is a flowchart, showing the procedures of a phase shift mask designing method of a basic embodiment of this invention. First in step S1, designing of the two-dimensional layout of the phase mask to be designed is performed. This is a task of designing a two-dimensional layout pattern, such as that shown in the plan view of FIG. 9, and is normally a task performed using a dedicated design tool on a computer. In this task, an XY plane is defined on the surface of a substrate on which a phase shift mask is to be formed and a plurality of apertures of the same size are positioned at least along the X-axis. Though FIG. 9 shows an example wherein five apertures are positioned, in actuality, a larger number of apertures of the same size are positioned at a fixed pitch in the X-axis direction to form a “line and space pattern.” Needless to say, in putting this invention to practice, it is sufficient that a two-dimensional layout pattern with at least two apertures can be defined. Specifically in this task of step S1, the width Wx in the X-axis direction and the width Wy in the Y-axis direction of each aperture and the width Ws of each opaque part must be determined. Next in step S2, the three-dimensional structure of the phase mask that is to be designed is determined. Here, as a first matter that must be determined, whether or not phase shifting is to be performed must be determined for each of the plurality of apertures included in the layout pattern designed in step S1. In a case where a plurality of apertures are positioned in the X-axis direction as shown in FIG. 9, the phase is to be shifted at every other aperture in accordance to the order of alignment. In the case of the example of FIG. 9, the “determination that phase shifting is not to be performed (the determination of setting f=0 degree)” is made for the first, third, and fifth apertures and the “determination that phase shifting is to be performed (the determination of setting f=180 degrees)” is made for the second and fourth apertures. The second matter that must be determined in the step S2 is the specific three-dimensional structure of a trench to be dug in the substrate at the position of each aperture for which the “determination that phase shifting is to be performed (the determination of setting f=180 degrees)” has been made. That is, the depth d and the undercut amount Uc of the trench 220, shown in the upper diagram of FIG. 8, are determined. Here, the depth d of the trench is determined as the length necessary for shifting the phase of the light source wavelength of the exposure tool by just 180 degrees. Meanwhile, as the undercut amount Uc, an adequately large amount is determined while securing an adequate allowance in terms of the manufacturing process such that, in consideration of the width Ws of opaque part 122, etc., opaque part 122 will not become removed from an actual phase shift mask. The undercut amount Uc that is determined here will not be corrected in subsequent steps and thus becomes the final undercut amount Uc that is determined in the designing method of the present invention. Next in step S3, three-dimensional analysis is performed based on the design data at the present point in time to determine the light intensity deviation D. That is, since a specific three-dimensional structural body is defined by the two-dimensional layout designed in step S1 (for example, the pattern of FIG. 9) and the three-dimensional structure determined in step S2 (for example, the structure of trench 220 shown in the upper diagram of FIG. 8), three-dimensional analysis is performed using this specific three-dimensional structural body as a three-dimensional model. Specifically, the task of providing the four parameters Wx, Wy, Ws, and Uc, the predetermined exposure conditions, and the trench depth d to a three-dimensional simulator using a computer, carrying out a simulation concerning the behavior of transmitted light in a case where light is transmitted under the same conditions through a pair of adjacent apertures designed to realize a phase shift of 180 degrees with respect to each other, determining a graph, such as that shown in the lower diagram of FIG. 8, by computation, and determining the light intensity deviation D that indicates the deviation of the intensities of the light transmitted through the respective apertures is performed. As mentioned above, with the present embodiment, the light intensity deviation is defined as D=Wa−Wb, that is, the difference in the transverse width of graphs. Though such a three-dimensional simulation actually requires a long computation time, in step S3, a computation, of determining the light intensity deviation D when a single set of parameter values Wx, Wy, Ws, and Uc are provided, needs to be executed just once. In the subsequent step S4, the process of replacing the three-dimensional model, subject to three-dimensional analysis in step S3, by a two-dimensional model is performed. That is, a three-dimensional model, such as that shown in the upper diagram of FIG. 8, is replaced by a two-dimensional model, such as that shown in the upper diagram of FIG. 13. Here, in regard to the parameters concerning the two-dimensional layout, the parameters of the three-dimensional model can be used as they are in the two-dimensional model. That is, the sizes Wx and Wy of each aperture and the width Ws of each opaque part in the three-dimensional model shown in the upper diagram of FIG. 8 can be used as the sizes Wx and Wy of each aperture and the width Ws of each opaque part in the two-dimensional model shown in the upper diagram of FIG. 13. Needless to say, the same conditions are used as they are in regard to the exposure conditions. A key point of this replacement process of step S4 is the method of replacing the parameters of trench depth d and undercut amount Uc of the trench in the three-dimensional model by the parameter of transmittance T in the two-dimensional model. At the present level of the art, an efficient method of directly converting the dimensional parameters of d and Uc in the three-dimensional model to the transmittance parameter T in the two-dimensional model has not been found. The inventor of the present application thus reached a new method of performing such a conversion using light intensity deviation D as an intermediary. By this method, the dimensional parameters of d and Uc in the three-dimensional model can be converted to the transmittance parameter T in the two-dimensional model by the following procedure. First, of the parameters of the three-dimensional model, the sizes Wx and Wy of each aperture and the width Ws of each opaque part are used as they are in the two-dimensional model. As a result, a two-dimensional layout, such as that shown in the upper diagram of FIG. 13 can be defined. However, the transmittance T of aperture 112 at the right side, when the transmittance of aperture 111 at the left side is set to 100%, is still indeterminate. A plurality of arbitrary values are thus set for this transmittance T, and for each case, two-dimensional analysis is performed and light intensity distributions, such as those shown in the lower diagram of FIG. 13, are determined to determine light intensity deviations. Consequently, a light intensity deviation is determined by computation for each of a plurality of transmittances T. Among the plurality of light intensity deviations obtained in this manner, one which matches the light intensity deviation D determined in step S3 is selected and here, the transmittance T that provides this matching result becomes the transmittance that is to be determined. Specifically, the transmittance is set, for example, at 1% increments such that T=99%, 98%, 97%, . . . , 51%, 50%, and for each of the cases, wherein, for a pair of apertures having the predetermined sizes Wx, Wy, and Ws, such as shown in the upper diagram of FIG. 13, the transmittance of the left aperture 111 is set to 100% and the transmittance of the right aperture 112 is varied at 1% increments in the range of 99% to 50%, a two-dimensional simulation is performed to determine a light intensity deviation for each case, and the transmittance with which a value closest to the light intensity deviation D determined by three-dimensional analysis in step S3 is set as the transmittance T of the two-dimensional model. That is, this method can be said to be a so-called trial-and-error method wherein two-dimensional analysis is performed for each of a plurality of transmittances to determine a light intensity deviation D for each case, and a transmittance, by which a result matches the light intensity deviation D obtained in the three-dimensional analysis step, is determined as the transmittance T. As mentioned above, since a two-dimensional simulation is extremely light in computation load and extremely short in computation time in comparison to a three-dimensional simulation, even if such a trial-and-error method is adopted, there will be no problems in terms of practical use. Consequently, the task performed in step S4 is to determine a transmittance T such that, when a two-dimensional structural body defined by the two-dimensional layout designed in step S1 is used and, with a pair of adjacent apertures, the light transmittance of one aperture is set to 100% and the light transmittance of the other is set to T %, the deviation in the intensities of light transmitted through each of the pair of adjacent apertures becomes equal to the light intensity deviation D determined in step S3. A two-dimensional model which is equivalent to the three-dimensional model that is subject to three-dimensional analysis in step S3, is thus determined. Lastly, in step S5, correction of the two-dimensional layout is performed using this equivalent two-dimensional model. That is, based on the specific transmittance T determined in step S4, a correction amount δ is determined for the width of each aperture of the two-dimensional layout designed in step S1. Specifically, as mentioned already, a correction, such as that shown in the upper diagram of FIG. 14, is performed on a two-dimensional model shown in the upper diagram of FIG. 13, so that the widths Wx of the apertures 111 and 113 are corrected to Wxa and Wxb, respectively. Here, the correction amount δ is set to an appropriate value by which the intensity distribution graphs of the light transmitted through the apertures 111* and 112* after correction will be equal as shown in the lower diagram of FIG. 14 (by which the light intensity deviation D will be made zero). A trial-and-error type two-dimensional simulation may be employed as a method of determining an optimal correction amount δ in a condition when values of widths Wx and Wy of each aperture, width Ws of each opaque part, and transmittance T of one aperture with respect to the other aperture are given. For example, a plurality of correction amounts δ are set, a two-dimensional simulation of determining a light intensity deviation D is executed under predetermined exposure conditions (the same exposure conditions as those of the simulations performed up until now) for each case, and a correction amount δ, with which light intensity deviation D will be closest to zero, is determined. When step S5 is thus completed, a corrected two-dimensional layout, such as that shown in the upper diagram of FIG. 14 is obtained, and the three-dimensional structure determined in step S2 (trench depth d and undercut amount Uc) is applied to this corrected two-dimensional layout to determine a corrected three-dimensional structural body. Since in this case, the undercut amount Uc indicates the distance between the position of the outline of a trench and the position of the outline of an aperture after correction, in a case where for example as shown in the upper diagram of FIG. 14, the width in the X-axis direction of aperture 112* is widened by just 2 δ by the correction, the trench width is also widened by just 2 δ. Since the width in the X-axis direction of aperture 111* is oppositely narrowed by just 2 δ and the width Ws in the X-axis direction of opaque part 122* is therefore not changed, the dimensions of the parts of contact with substrate 200 of opaque part 122* will not be changed. Though the widths of apertures are thus corrected by this correction of step S5, since the undercut amount Uc and the dimensions of the contacting parts of the opaque part are kept at the initially designed values, the problem of removal will not occur. Also as mentioned above, though the pitch P of apertures in the two-dimensional layout shown in FIG. 9 will be changed slightly, since the pitch 2P for two periods will be kept fixed, the essential characteristics of the “line and space pattern” will not be affected. Thus, whereas conventionally, a computation of determining the optimal correction amount δ is performed by executing three-dimensional simulations on the three-dimensional model determined in steps S1 and S2, with the design method illustrated in FIG. 15, the optimal correction amount δ can be determined by performing the tasks of steps S3 and S4 to replace the three-dimensional model with a two-dimensional model and executing two-dimensional simulations on this two-dimensional model in step S5. Since as already mentioned, a two-dimensional simulation is significantly lighter in load than a three-dimensional simulation, the designing method for phase mask of the present invention enables the work load of designing a phase shift mask to be lightened and the working time to be shortened. FIG. 16 is a block diagram, showing the arrangement of a phase shift mask designing device of a basic embodiment of this invention. As illustrated, this designing device comprises a two-dimensional layout determination tool 10, a three-dimensional structure determination tool 20, a three-dimensional simulator 30, and a two-dimensional simulator 40. All of these components, indicated as four blocks, are actually arranged using a computer and this designing device can be realized by incorporating software having processing functions as the respective components in the same computer. Two-dimensional layout determination tool 10 is a component for executing the process of step S1 of the flowchart shown in FIG. 15 and, based on instructions from an operator, determines the width Wx in the X-axis direction and the width Wy in the Y-axis direction of each aperture and the width Ws of each opaque part on an XY plane defined on the surface of a substrate for forming a phase shift mask and positions a plurality of apertures of the same size at least along the X-axis to determine a two-dimensional layout on the XY plane. In the Figure, a simple example of a two-dimensional layout pattern 11 that has been determined by this two-dimensional layout determination tool 10 is illustrated for the sake of description. This two-dimensional layout pattern 11 is a pattern of the initial stage of design and is subsequently subject to correction. To determine the illustrated two-dimensional pattern 11, operator's instructions, indicating the respective dimensional values of Wx, Wy, and Ws, the total number of apertures, the direction of positioning, etc., are input. Three-dimensional structure determination tool 20 is a component for executing the process of step S2 of the flowchart shown in FIG. 15 and, based on instructions from an operator, executes the process of determining whether or not phase shifting is to be performed for each of the plurality of apertures in two-dimensional layout pattern 11 and determining, for apertures with which phase shifting is to be performed, the trench depth d and the undercut amount Uc, which indicates the distance between the position of the outline of a trench and the position of the outline of an aperture, to thereby determine the three-dimensional structure. The trench depth d may be computed automatically based on the light source wavelength of the exposure tool. In the Figure, a simple example of a three-dimensional structure 21 that has been determined by this three-dimensional structure determination tool 20 is illustrated for the sake of description. Three-dimensional simulator 30 is a component for executing the process of step S3 of the flowchart shown in FIG. 15 and executes the three-dimensional analysis process of using a three-dimensional structural body, which is defined by two-dimensional layout pattern 11 determined by two-dimensional layout determination tool 10 and three-dimensional structure 21 determined by three-dimensional structure determination tool 20, as a model to execute a three-dimensional simulation under predetermined exposure conditions to determine a light intensity deviation D that indicates the deviation of the intensities of light transmitted by each of a pair of adjacent apertures, which are designed to realize a phase shift of 180 degrees with respect to each other, when light is transmitted under the same conditions. Though the three-dimensional analysis process executed by this three-dimensional simulator 30 is a process of considerably large computation load, the purpose of the three-dimensional analysis process executed here is to determine the light intensity deviation D for the three-dimensional model with a specific structure (structure defined by the specific parameter values Wx, Wy, Ws, d, and Ux) and is not a process such as that performed for determining an optimal correction amount δ. The computation load is thus far smaller in comparison to the case of a three-dimensional analysis process for determining the correction amount δ. Two-dimensional simulator 40 is a component for executing the processes of steps S4 and S5 of the flowchart shown in FIG. 15. That is, as the two-dimensional analysis process of step S4, a two-dimensional structural body, defined by two-dimensional layout pattern 11 determined by two-dimensional layout determination tool 10, is used as a model and two-dimensional simulations are executed under the same exposure conditions as those of the above-described three-dimensional simulation. By this two-dimensional simulation, a transmittance T is determined such that, when for a pair of adjacent apertures, the light transmittance of one aperture is set to 100% and the light transmittance of the other aperture is set to T %, the deviation in the intensities of light transmitted through each of these pair of adjacent apertures becomes equal to the light intensity deviation D determined by three-dimensional simulator 30. This process can thus be said to be a process of replacing the three-dimensional model, used in three-dimensional simulator 30, by a two-dimensional model. Specifically, a light intensity deviation D is determined for each of plurality of transmittances and the transmittance, which provides a result that matches the light intensity deviation D determined by the three-dimensional analysis process performed by three-dimensional simulator 30, is determined as the transmittance T. Meanwhile, two-dimensional simulator 40 also has a function of executing the layout correction process, indicated in step S5 of the flowchart shown in FIG. 15. That is, a two-dimensional model, obtained by applying the transmittance T, determined by the above-described process, to the two-dimensional structural body defined by two-dimensional layout pattern 11, which is determined by two-dimensional layout determination tool 10, is used to perform two-dimensional simulations under the same exposure conditions as the exposure conditions used up until now to determine an optimal correction amount δ. The contents of the process of determining the correction amount δ are as have been described above in regard to the process of step S5. By using the correction amount 6 thus determined to perform layout correction on two-dimensional layout pattern 11, a corrected two-dimensional layout pattern 12 can be obtained as illustrated. The final phase shift mask structure is thus determined from three-dimensional structure 21, determined by three-dimensional structure determination tool 20, and two-dimensional layout pattern 12, corrected by two-dimensional simulator 40. <<<§ 5. More Practical Designing Method and Device>>> With the basic embodiment described in § 4, three-dimensional analysis and two-dimensional analysis must be executed each time a new phase shift mask is to be designed. For example, with the flowchart of FIG. 15, a three-dimensional simulation using the given predetermined parameter values Wx, Wy, Ws, and Uc (the values of the exposure conditions and the trench depth d, etc., are also necessary in addition to these values) is performed to determine a light intensity deviation D. In step S4, two-dimensional simulations using the given predetermined parameter values Wx, Wy, and Ws, and a plurality of transmission settings T's (the values of the exposure conditions, etc., are also necessary in addition to these values) are performed to determine light intensity deviations D's so that a transmittance T, which provides a result that matches the light intensity deviation D determined in step S3, is determined. Furthermore in step S5, two-dimensional simulations using the given predetermined parameter values Wx, Wy, Ws, and T (the values of the exposure conditions, etc., are also necessary in addition to these values) are performed to determine an optimal correction value δ and a process of changing the widths Wx of the respective apertures to Wxa or Wxb is performed. However, in terms of work, in cases where several phase shift masks must be designed, it is not necessarily efficient to perform the simulation tasks of steps S3, S4, and S5 each time. The practical embodiments described in this section incorporate measures for simplifying the simulation task performed in these steps. The basic concepts of these measure shall now be described. First, consider the three-dimensional analysis in step S3. Here, if the light source wavelength of the exposure tools using a phase shift mask designed by this invention is fixed at a predetermined wavelength value and the optical conditions for the exposure task are also fixed (in other words, if the exposure conditions are fixed), the variable parameters of the three-dimensional simulation performed in step S3 will be the four parameters of the width Wx in the X-axis direction and the width Wy in the Y-axis direction of each aperture, the width Ws of each opaque part, and the undercut amount Uc. Thus if three-dimensional simulations are executed in advance on respective cases wherein the combinations of these four parameter values are differed variously and the values of the obtained light intensity deviation D are made available in the form of a database, when specific parameter values Wx, Wy, Ws, and Uc are provided, the light intensity deviation D that is needed can be obtained by just performing the task of searching the database and without having to perform a three-dimensional simulation. For example, the graphs of FIG. 17 show the results of determining the light intensity deviation D for cases where Ws is set to 200 nm, Wx is set to 250 nm, Wy is varied among the six values of 100, 200, 300, 400, 500, and 600 nm, and Uc is varied among the four values of 70, 90, 110, and 130. In other words, shown here are the results of executing three-dimensional simulations in advance on a total of 24 combinations of parameter values and determining the light intensity deviation D for each combination. Needless to say, in actuality, similar graphs are prepared by varying the parameters Ws and Wx in a plurality of ways as well. Though the computation load for determining the values of the light intensity deviation D by three-dimensional simulation for all combinations becomes vast as the number of combinations of parameters increases, once such computations are performed and the results are stored in a database, it becomes possible thereafter to determine the light intensity deviation D for an arbitrary combination of parameter values by simply searching the database and without having to execute a three-dimensional simulation. For example, in the case where a specific combination of parameters of Ws=200 nm, Wx=250 nm, Wy=300 nm, and Uc=70 nm is provided, by referencing the ordinate value of the point P1 that corresponds to the abscissa value Wy=300 nm of graph G1 (the graph for Uc=70 nm) of FIG. 17, the result of light intensity deviation D=31 nm can be obtained. Since in actuality, graphs are not referenced but a database is simply searched based on the four parameter values, the required light intensity deviation D can be determined by an extremely simple process in comparison to the case of determining the light intensity deviation by actually performing a three-dimensional simulation. This method may also be applied to the two-dimensional analysis in step S4. That is, the variable parameters in the two-dimensional simulations carried out in step S4 are the four parameters of the width Wx in the X-axis direction and the width Wy in the Y-axis direction of each aperture, the width Ws of each opaque part, and the transmittance T. Thus if two-dimensional simulations are executed in advance on respective cases wherein the combinations of these four parameter values are differed variously and the values of the obtained light intensity deviation D are made available in the form of a database, when specific parameter values Wx, Wy, Ws, and T are provided, the light intensity deviation D that is needed can be obtained by just performing the task of searching the database and without having to perform two-dimensional simulations. For example, the graphs of FIG. 18 show the results of determining the light intensity deviation D for cases where Ws is set to 200 nm, Wx is set to 250 nm, Wy is varied among the six values of 100, 200, 300, 400, 500, and 600 nm, and T is varied among the four values of 60%, 70%, 80% and 90%. In other words, shown here are the results of executing two-dimensional simulations in advance on a total of 24 combinations of parameter values and determining the light intensity deviation D for each combination. Needless to say, in actuality, similar graphs are prepared by varying the parameters Ws and Wx in a plurality of ways as well. Once such computations are performed and the results are stored in a database, it becomes possible thereafter to determine the light intensity deviation D for an arbitrary combination of parameter values by simply searching the database and without having to execute two-dimensional simulations. For example, in the case where a specific combination of parameters of Ws=200 nm, Wx=250 nm, Wy=300 nm, and T=70% is given, by referencing the ordinate value of the point P2 that corresponds to the abscissa value Wy=300 nm of graph G6 (the graph for T=70%) of FIG. 18, the result, light intensity deviation D=31 nm, can be obtained. The primary purpose of the process of step S4 is not to determine a light intensity deviation D from a combination of the four parameters of Ws, Wx, Wy, and T. The primary purpose of the process of step S4 is to determine a transmittance T, with which the same light intensity deviation as the light intensity deviation D determined in the process of step S3 can be obtained. The method using a database, described in this § 5 is extremely convenient for such a process of determining the transmittance T. For example, as mentioned above, when, in the process of step S3, a specific combination of parameters such that Ws=200 nm, Wx=250 nm, Wy=300 nm, and Uc=70 nm is given, the result, light intensity deviation D=31 nm, is determined from the ordinate value of the point P1 on the graph G1 (graph of Uc=70 nm) of FIG. 17. The purpose of step S4 is to determine a transmittance T by which the thus-determined light intensity deviation D=31 nm can be obtained. For this purpose, the graph of FIG. 18 that corresponds to the parameter values of Ws=200 nm and Wx=250 nm is referenced and a point P2 having an abscissa value of Wy=300 nm and an ordinate value of D=31 nm is searched. With the example of FIG. 18, since point P2 is a point on graph G6, the transmittance T to be determined is T=70%. Though with the example shown in FIG. 18, the point P2 happened to be a point on graph G6 and the transmittance T=70% was obtained immediately, in a case where point P2 is not a point on any of the graphs, the nearest graph may be selected and the transmittance T of this graph may be selected. Though the graphs of FIG. 18 are determined for 10% increments of transmittance T, if, for example, graphs are determined at 1% increments, a selection of a nearby graph will enable an accurate transmittance T to be determined at a unit of 1%. If an even more accurate value is required, the increment width is set even more finely. Thus if the parameter values of Ws=200 nm, Wx=250 nm, and Wy=300 nm are determined in the step of two-dimensional layout designing of step S1 and the parameter value of Uc=70 nm is determined in the step of three-dimensional structure determination of step S2, the light intensity deviation value of D=31 nm can be determined in step S3 by just a process of searching the ordinate value of a point P1 on the graph of FIG. 17 that is prepared as a database, and a transmittance value of T=70% can be determined in step S4 by just a process of searching, from a database, of a graph G6 near a point P2 having the parameter D=31 nm as the ordinate value and having Wy=300 nm as the abscissa value. This method of using a database can also be applied to the two-dimensional layout correction process of step S5. That is, the variable parameters for the two-dimensional simulation for determining an appropriate correction amount δ in step S5 are the four parameters of the width Wx in the X-axis direction and the width Wy in the Y-axis direction of each aperture, the width Ws of each opaque part, and the transmittance T. Thus by performing two-dimensional simulations with a plurality of correction amounts δ being set for each of various different combinations of the four parameters, it becomes possible to determine to what value the correction amount δ should be set to enable an appropriate correction (that is, a correction by which the light intensity deviation D for the transmitted light of both apertures will be zero). Here, by determining appropriate correction amounts δ for combinations of specific parameter values Wx, Wy, Ws, and T in advance and preparing a database according to combination, the required correction amount δ can be obtained thereafter by just a task of searching this database and without having to perform two-dimensional simulations. As mentioned above, in a case where the method of executing two-dimensional simulations or three-dimensional simulations in advance for various combinations of parameters and storing the results in the form of a database, a more detailed database can be prepared by making the increment widths of the parameters finer and searching of such a database enables more accurate results to be obtained. However, there arises the problem that as the increment widths of the parameters are made finer, the number of parameter combinations to be subject to simulation becomes vast. Interpolation operations are effective for preventing such a problem. That is, in a case where a parameter value that matches the search condition does not exist among the combinations of parameter values prepared in a database, a more accurate value can be determined by performing an interpolation operation using parameter values that are close. For instance, with the example illustrated in FIG. 18, the transmittances T are made available only at 10% increments. Here, if the need to determine the transmittance T corresponding to the point P3 in the Figure arises, one of either graph G6 or G7 is selected as the graph close to P3 and for the transmittance T, T=70% or T=80% is determined. In such a case, by selecting both graphs G6 and G7 as graphs close to point P3 and determining, for example, a value of transmittance T=75% by an interpolation operation, a more accurate value can be obtained. Next, a phase shift designing device, which enables the work of designing each individual phase shift mask to be made more efficient by the preparation of such databases, shall be described. FIG. 19 is a block diagram, showing the basic arrangement of such a designing device. As illustrated, this designing device comprises a two-dimensional layout determination tool 10, a three-dimensional structure determination tool 20, a light intensity deviation determination tool 50, a first database 55, a transmittance determination tool 60, a second database 65, a correction amount determination tool 70, and a third database 75. The three-dimensional simulator 30 and two-dimensional simulator 40 that are shown in the Figure are components used for preparing the respective databases 55, 65, and 75 and are not components that make up the phase shift mask designing device of the present invention itself. In other words, once the respective databases 55, 65, and 75 have been prepared, three-dimensional simulator 30 and two-dimensional simulator 40 become unnecessary. Here, two-dimensional layout determination tool 10 and three-dimensional structure determination tool 20 are exactly the same components shown in FIG. 16 and detailed descriptions thereof shall be omitted. As mentioned above, a desired two-dimensional layout pattern 11 is determined when an operator instructs the dimensions of each aperture and opaque part, etc., to two-dimensional layout determination tool 10. Also, a desired three-dimensional structure 21 is determined when the operator instructs the undercut amount Uc, etc., to three-dimensional structure determination tool 20. Meanwhile, light intensity deviation determination tool 50 is a component for executing the process corresponding to step S3 of the flowchart of FIG. 15 without performing a three-dimensional simulation and enables the process of determining the required light intensity deviation D to be performed by the searching of first database 55. That is, light intensity deviation determination tool 50 has the function of determining a specific light intensity deviation D by searching first database 55 using the specific parameter values determined at two-dimensional layout determination tool 10 and three-dimensional structure determination tool 20. In first database 55, values of the light intensity deviation D, each defined as a value that indicates the deviation of the intensities of light transmitted through each of a pair of adjacent apertures, of a predetermined three-dimensional structural body and being designed to realize a phase shift of 180 degrees with respect to each other, when light is transmitted through the apertures under the same conditions, are stored according to various different combinations of the four parameter values of the width Wx in the X-direction and the width Wy in the Y-axis direction of each aperture, the width Ws of each opaque part, and the undercut amount Uc. Specifically, values of the light intensity deviation D for cases where the four parameter values are differed variously as shown by the graphs in FIG. 17 are stored in the form of a database. As mentioned above, such a database can be prepared by performing three-dimensional simulations in advance by means of three-dimensional simulator 30. Transmittance determination tool 60 is a component for executing the process corresponding to step S4 of the flowchart of FIG. 15 without performing two-dimensional simulations and enables the process of determining the required transmittance T to be performed by the searching of second database 65. That is, transmittance determination tool 60 has the function of searching second database 65 using the specific parameter values determined at two-dimensional layout determination tool 10 and the specific light intensity deviation D determined at light intensity deviation determination tool 50 to determine a transmittance T, by which a light intensity deviation equal to the specific light intensity deviation D is obtained. In second database 65, values of the light intensity deviation D, each defined as a value that indicates the deviation of the intensities of light transmitted through each of a pair of adjacent apertures, which are of a predetermined two-dimensional structural body and with which the transmittance of one has been set to 100% and the transmittance of the other has been set to T %, when light is transmitted through the apertures under the same conditions, are stored according to various different combinations of the four parameter values of the width Wx in the X-direction and the width Wy in the Y-axis direction of each aperture, the width Ws of each opaque part, and the transmittance T. Specifically, values of the light intensity deviation D for cases where the four parameter values are differed variously as shown by the graphs in FIG. 18 are stored in the form of a database. As mentioned above, such a database can be prepared by performing two-dimensional simulations in advance by means of two-dimensional simulator 40. Lastly, correction amount determination tool 70 is a component for executing the process corresponding to step S5 of the flowchart of FIG. 15 without performing two-dimensional simulations and enables the process of determining the required correction amount δ to be performed by the searching of third database 75. That is, correction amount determination tool 70 has the function of searching third database 75 using the specific parameter values determined at two-dimensional layout determination tool 10 and the specific transmittance T determined at transmittance determination tool 60 to determine a correction amount δ for two-dimensional layout pattern 11 and outputting the corrected two-dimensional layout pattern 12. In third database 75, values of the correction amount δ, each of which concerns the widths of the respective apertures and is required to make equal the intensities of light transmitted under the same conditions through each of a pair of adjacent apertures, which are of a predetermined two-dimensional structural body, are of the same size, and with which the transmittance of one has been set to 100% and the transmittance of the other has been set to T %, are stored according to various different combinations of the four parameter values of the width Wx in the X-direction and the width Wy in the Y-axis direction of each aperture, the width Ws of each opaque part, and the transmittance T. As mentioned above, such a database can be prepared by performing two-dimensional simulations in advance by means of two-dimensional simulator 40. By incorporating the above-described interpolation operation function in light intensity deviation determination tool 50, transmittance determination tool 60, and correction amount determination tool 70, the light intensity deviation D, transmittance T, and correction amount δ can be determined more accurately by interpolation operations using close parameter values in cases where values that match the search conditions do not exist among the combinations of parameter values prepared inside the corresponding databases 55, 65, and 75. With the above-described embodiment, the data prepared in advance in the respective databases 55, 65, and 75 are data obtained based on results of simulations performed for specific exposure conditions by using a specific exposure tool. Thus in a case where phase shift masks that are to be used with a plurality of mutually differing exposure tools are to be designed, simulations are executed for each case in which the exposure wavelength, numerical aperture, illumination, etc., are changed and the respective results are prepared as separate databases according to exposure conditions. In this case, when a phase shift mask suited to a specific set of exposure conditions is to be designed, the specific database that was obtained based on results of simulations under this set of exposure conditions is selected and used. Though in FIG. 19, the respective components are indicated as blocks, that is, as mutually independent tools for the sake of description, in actuality, all of these components are realized by incorporation of predetermined software in a computer and in terms of hardware, the same computer may be used to realize the respective components. Furthermore, though with the designing device shown in FIG. 19, all of steps S3, S4, and S5 in the flowchart of FIG. 15 are executed as search processes using first database 55, second database 65, and third database 75, such a method of using database search need not be performed in all of steps S3, S4, and S5 and may be employed selectively in the necessary steps. For example, if a method is to be employed wherein a database search is to be used only for the process of determining the light intensity deviation D by three-dimensional analysis (the process of step S3), arrangements may be made so that the process of step S3 is executed by searching of first database 55 by means of light intensity deviation determination tool 50, while the processes of steps S4 and S5 are executed by the two-dimensional simulator 40 shown in FIG. 16. <<<§ 6. Other Modification Examples>>> Lastly, modification examples of the designing method and device for phase shift mask of the present invention shall be described. (1) Though with the embodiments described up until now, the two parameters of the width Wx in the X-axis direction and the width Wy in the Y-axis direction were used as parameters for indicating the width of an aperture, these two parameters do not have to be used necessarily in putting this invention to practice. For example, in a case of a “line and space pattern” wherein a plurality of apertures 110, with each of which the width Wy in the Y-axis direction is comparatively large in comparison to the width Wx in the X-axis direction, are aligned in the X-axis direction as shown in FIG. 9, a large error will not occur even if the width Wy in the Y-axis direction is handled as being infinite. FIG. 20 is a plan view, illustrating the concept of such handling. With this example, four apertures 110 and opaque parts 120 are positioned alternatively in the X-axis direction, and for the respective apertures 110, φ is set equal to 0 degree and 180 degrees alternatively. Here, though finite, actual dimension values are set for both the width Wx in the X-axis direction of each aperture 110 and the width Ws in the X-axis direction of each opaque part 120, an imaginary dimensional setting of infinity is set for the width Wy in the Y-axis direction of each aperture 110. Though obviously a finite actual dimension must be set for the width Wy with the actual two-dimensional layout pattern, by setting the width Wy to infinity in carrying out a three-dimensional simulation or a two-dimensional simulation, the width Wy can be eliminated from among the parameters to be considered. By thus eliminating the width Wy from among the parameters to be considered, for example, it becomes possible, in the three-dimensional analysis of step S3 in the flowchart of FIG. 15, to determine the light intensity deviation D using just the three parameters Wx, Ws, and Uc, and it also becomes possible, in the two-dimensional analysis of steps S4 and S5, to perform analysis using just the three parameters Wx, Ws, and Uc. Needless to say, in a case of an embodiment with which databases are to be prepared in advance, it is sufficient to prepare databases with which the width Wy has been excluded from the parameters. (2) Though with the embodiments described up until now, only examples where a layout, with which a plurality of apertures are aligned in the X-axis direction, is prepared in the two-dimensional layout designing step was described, this invention is also applicable to a layout, wherein a plurality of apertures are positioned in a two-dimensional matrix form in the X-axis direction and the Y-axis direction. For example, FIG. 21 shows a two-dimensional layout pattern, in which four apertures 130 of the same size are aligned in the X-axis direction and three apertures 130 are aligned in the Y-axis direction. When such a layout is designed with apertures 130 being positioned in a two-dimensional matrix form, the determination that phase shifting is to be performed with every other aperture in both the X-axis direction and the Y-axis direction is made for the plurality of apertures aligned in either the X-axis direction or the Y-axis direction in the three-dimensional structure determination step. As a result, apertures with which phase shifting is not to be performed (apertures with the setting, φ=0 degree) and apertures with which phase shifting is to be performed (apertures with the setting, φ=180 degrees) are positioned in the form of a checkered pattern. In a case where, as in the example of FIG. 21, the width Wsx in the X-axis direction of an opaque part 140 existing between apertures that are adjacent in the X-axis direction differs from the width Wsy in the Y-axis direction of an opaque part 150 existing between apertures that are adjacent in the Y-axis direction, analysis using these two parameters Wsx and Wsy must be performed in each simulation process. (3) With the embodiments described up until now, the process of determining the light intensity deviation D in the three-dimensional analysis step of step S3 shown in FIG. 15, the process of determining the transmittance T in the two-dimensional analysis step of step S4, and the correction process of the layout correction step of step S5 were all described with the premise of being executed using computer simulation. However, these processes do not have to be executed necessarily by computer simulation, and a part or all of these processes may be executed by experiments using an actually manufactured phase shift mask. In particular with regard to three-dimensional analysis, since a three-dimensional simulation by a computer requires a considerable amount of computation time, it may be more effective in some cases to actually manufacture a phase shift mask with dimensions that are in accordance to the given parameters and to actually measure the light intensity deviation D by actually performing an experiment of illuminating light. Needless to say, the method for preparing the respective databases 55, 65, and 75 shown in FIG. 19 is also not limited to a computer simulation method. That is, the data may be actually measured in experiments using actually manufactured phase shift masks and the measured data may be stored in the databases. As described above, the designing method and device for phase shift mask of the present invention enable the work load spent on designing a phase shift mask to be lightened and the working time to be shortened. This invention is thus an art that is widely applicable in the field of semiconductor manufacturing processes. |
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048448397 | claims | 1. An in situ method of treating hazardous waste in a disposal site having hazardous waste randomly distributed therein comprising the steps of: (a) agitating a downwardly extending zone of particles of said hazardous waste at a first station on said site; (b) maintaining said zone out of communication with the ambient atmosphere; (c) analyzing vapors and gases which are liberated from said zone during said agitating to determine the identity of the toxic components therein; (d) separating toxic gases and vapors identified by said sampling from said particles in said zone; (e) detoxifying said separated toxic gases and vapors; (f) injecting at least one treatment agent selected in accordance with the determined identity of the toxic components into said particles in said agitating zone; (g) terminating said method when said sampling indicates said particles have been treated to a desired degree; and (h) repeating said method at a second station at said disposal site that overlaps said first section. injecting pressurized fluid into the agitating volume of soil. 2. The method of claim 1, wherein said agitating step comprises rotating a plurality of adjacently disposed cutters downwardly through said zone. 3. The method of claim 2, wherein said cutters include a pair of oppositely pitched blades to impart a downward and upward screwing action to said hazardous waste to obtain optimum homogenization thereof. 4. The method of claim 1, 2 or 3, wherein said treating step comprises injecting an agent into said zone to render water soluble toxic compounds therein insoluble. 5. The method of claim 4, further comprising the step of selecting a detoxifying agent that is effective in detoxifying particles of the composition found in the sample. 6. The method of claim 5, wherein said agent is selected from the group consisting of calcium oxide, sodium bisulfate and sodium hydrosulfite. 7. The method of claim 5, further comprising the step of establishing a pH of from 8.0 to 11.0 in said zone to facilitate the oxidizing of soluble salts of toxic metals therein to a substantially insoluble state. 8. The method of claim 5, wherein an agent is injected into said zone to interact with water therein and to provide an exothermic reaction in which radioactive products in said zone are transformed to a solid water insoluble mass. 9. The method of claim 8, wherein a plurality of said zones are arranged to provide an insoluble liner around the periphery and under said waste disposal site. 10. The method of claim 5, wherein said treating step comprises saponifying waste hydrocarbon products in said zone to an insoluble mass and oxidizing soluble salts of toxic metals present in said zone to a substantially insoluble state, collecting gases from said saponifying and oxidizing in a confined space, and scrubbing said gases in said confined space. 11. The method of claim 5, wherein said treating step comprises discharging a liquid media of microorganisms and a nutrient therefor into said zone, said microorganisms being of a species that biodegrades toxic substances in said zone to nontoxic material that remains in place in said zone. 12. The method of claim 1, 2 or 3 wherein said treating step comprises subjecting said particles in said zone to the action of at least one plasma arc to define a solid, vitrified, insoluble mass of substantial strength. 13. The method of claim 12, wherein a plurality of said zones are arranged to provide an insoluble liner around the periphery and under said waste disposal site. 14. The method of claim 4, wherein said treating step comprises discharging a plurality of liquid jets into said zone to further reduce said particles in size and provide a liquid seal that minimizes the flow of toxic gas from said zone. 15. The method of claim 5, in which said hazardous waste may contain radium 226 and thorium 230 from which radon is emitted due to radioactive decay, with said agent being added in an amount sufficient to precipitate said radium and thorium to transform them and said hazardous waste into a solid, inert insoluble mass of such high density that the rate of migration of radon therethrough is slowed to the extent that the major portion of the radon transforms to a solid radionuclide element prior to reaching the ambient atmosphere to contaminate the latter, with waste radionuclide element being rendered insoluble by contact with said agent and remaining in place in said insoluble mass. 16. The method of claim 1 further comprising the step of: 17. The method of claim 16, wherein said pressurized fluid is heated. 18. The method of claim 17, wherein said pressurized fluid is steam. 19. The method of claim 17, wherein said pressurized fluid is hot air. 20. The method of claim 17, wherein said volume of soil is agitated by a rotary cutter and said pressurized fluid is injected into said volume of soil near the lower end of the volume of agitating soil. 21. The method of claim 17, wherein said volatile gases are captured in a shroud and further comprising the step of maintaining said shroud in sealing contact with the soil surface during said method to prevent escape to atmosphere of said gases collected in said shroud. 22. The method of claim 21, wherein said gases are scrubbed with wash liquid and contaminant-laden wash liquid is conducted to automatic equipment for determining selected contaminants in said wash liquid and selected physical properties thereof and generating computer-usable data representative of said properties. 23. The method of claim 22 comprising the further steps of: routing said acquired data to a treatment menu programmer interface; determining therein the amount of detoxifying agent necessary to treat the detected contaminants; and generating therein a signal which triggers a feeder for the programmed feeding of selected detoxifying agent to detoxify the soil in situ. 24. The method of claim 23, comprising the further steps of: using motor driven rotary cutter means to agitate the soil; collecting information signals representative of the power load of the cutter drive motor and vertical travel distance of the cutter means; passing said signals to said treatment menu programmer; and using said information signals to determine preferred treatment of contaminated soil. |
summary | ||
047939648 | claims | 1. A pressurized nuclear reactor with circulation by natural convection, comprising: a main vessel adapted to be filled with water and to be surmounted by a pressurized steam layer, said vessel containing in a lower part thereof a reactor core and in an upper part thereof a steam generator, a first ferrule surrounding the reactor core and a second ferrule located within the steam generator, said ferrules adapted to channel water between the core and the steam generator, a confinement enclosure externally duplicating the main vessel and defining with the latter an intermediate space, the main vessel being thermally uninsulated, the intermediate space having an upper zone adapted to be filled with pressurized neutral gas, an intermediate zone adapted to be filled with water and communicating with the upper zone and defined between the enclosure and a fluid-tight ferrule sealingly connecting the confinement enclosure to the vessel, above the reactor core, and a lower zone adapted to be filled with water and defined between the fluid-tight ferrule, the vessel and the enclosure, the confinement enclosure being adapted to be immersed in an external cooling liquid and internally equipped with thermal insulation in the lower zone of the intermediate space, except in a lower part of the confinement enclosure located at a level below the reactor core. 2. A nuclear reactor according to claim 1, wherein in the upper zone of the intermediate space is formed in a spherical upper part of the confinement enclosure. 3. A nuclear reactor according to claim 2, wherein, outside the upper spherical part of the confinement enclosure, the main vessel and confinement enclosure have a cylindrical configuration centered on a common vertical axis, said fluid-tight ferrule also having a cylindrical configuration centered on said axis and having an upper end fixed to the confinement enclosure at a bottom of said upper spherical part and having a lower end fixed to the main vessel. 4. A nuclear reactor according to claim 1, wherein pressure balancing means are provided between the lower zone and the upper and intermediate zones of the intermediate space. 5. A nuclear reactor according to claim 4, wherein said pressure balancing means comprise a swanneck tube projecting upwards into the intermediate zone from the fluid-tight ferrule. 6. A nuclear reactor according to claim 1, wherein the main vessel also contains an annular reflector surrounding the reactor core, said reflector being formed from several separate sectors normally located level with the core, each sector being able to move upwards with the aid of elastic means during a slope of the reactor exceeding a given angle. 7. A nuclear reactor according to claim 1, wherein the main vessel contains at least one system of absorbing elements able to move in guides provided in the reactor core during operation of control means outside the main vessel, said control means creating a rotary movement transmitted to a threaded rod located in the vessel and on which is mounted a nut carrying said system, via a mechanism incorporating at least one magnetic coupler ensuring transmission of the rotary movement through the vessel. 8. A nuclear reactor according to claim 7, wherein the control means are placed outside the confinement enclosure, said mechanism incorporating a second coupler ensuring transmission of the rotary movement through the confinement enclosure. 9. A nuclear reactor according to claim 7, wherein means are provided for automatically disconnecting said system from the nut when the pressure in the vessel exceeds a given pressure and when the water level in the vessel drops below a given level. 10. A nuclear reactor according to claim 9, wherein a tube connects the upper part of the vessel to the outside of the enclosure, said tube being equipped with a burster disk and normally closed by sealing means. 11. A nuclear reactor according to claim 7, wherein the reactor core has an active part of given height h, the guides passing beyond said active part by half said height h in downwards direction and once said height h in upwards direction. 12. A nuclear reactor according to claim 11, wherein the absorbing elements have a length equal to one and a half times the height h of the active part of the core, half said elements being absorbing over their entire length and the other half being absorbing over the upper two thirds of their length. |
description | The invention relates to a technical installation with a number of system components supported in each case by a number of girders and with a number of pressure-carrying lines. It relates especially to a nuclear power plant. In many technical plants, especially nuclear power plants, pressure-carrying lines may be used, for example for carrying a flow medium. Depending on the design characteristic of the respective technical installation, the selected design pressure of the flow medium carried in such lines may be very high, and therefore, in the event of the mechanical failure of the lines or of individual line elements, a considerable mechanical load on the immediate vicinity of the respective lines may occur. In order to make an accident scenario easy to handle in such situations, the pressure-carrying lines may be provided, in particular, with what may be referred to as failure fixed points, so that, in the event of mechanical failure, at least the location and the immediate vicinity of an accident can be planned and therefore can be controlled. In the event of a mechanical failure of such a line provided, in particular, with a predetermined breaking point, which may lead, in particular, to a complete pipe break, the pipe ends which are free after the pipe break may be exposed to considerable mechanical deformations as a result of the possibly high design pressure of the flow medium carried in the lines and may in this case act with considerable forces on surrounding components, “beating pipe ends”, as they may be referred to. This may lead, in particular, to the partial or complete destruction of system components arranged in the vicinity of the pressure-carrying lines. Particularly in the case where system components are supported in the vicinity of the pressure-carrying lines via a number of girders, as may be provided particularly with regard to operating or access platforms, as they are known, the action of such a pipe end which has been freed on one or some of the girders may lead, due to the deformation transferred via these, even to the destruction of the respective system component, in which case the latter may itself involve further components, such as, for example, further pressure lines or measuring lines, which are arranged in its vicinity. Consequently, in an accident caused by the mechanical failure of a pressure-carrying line, comparatively serious secondary damage to further system components may occur beyond its immediate vicinity. The object on which the invention is based, therefore, is to specify a technical installation of the abovementioned type, which is protected to an especial extent against further damage to system components even in the event of a mechanical break of a pressure-carrying line. This object is achieved, according to the invention, in that at least one of the girders has a segmented design in a target region expected in the event of a pipe break in a pressure-carrying line. The invention proceeds, in this context, from the consideration that the overall damage to be expected in the event of a pipe break in a pressure-carrying line can be kept particularly low, in that the transfer of the forces and deformations of system components, transmitted by the beating pipe ends in the event of a pipe break, to further system components is as far as possible prevented. An especially suitable starting point for such a prevention of the transfer of introduced forces is girders, such as, for example, steel girders, used for supporting the system components. For example, in the case of a beating pipeline of a high-pressure system, the impingement of a freed pipeline end onto a girder of this type may lead to the deformation of the system component as a whole, which is supported overall by the girder, so that an unwanted transfer of the forces and constrained routes also into further components, such as, for example, pipelines or measuring lines, could proceed via this system component. In order, therefore, to prevent the transmission of the forces from the girders into the respective system component, the girders are designed, at least in an expected target region capable of being delimited, in particular, by analysis of the predetermined breaking points possibly provided, in such a way that, instead of a transfer of the introduced forces, an avoidance of individual system parts is possible. For this purpose, the respective girders have a segmented design in the manner of adapter pieces in the expected target region, so that, if required, individual segments can be knocked out from the freed pipeline end, without secondary effects on the adjacent segments or, for example, on the system component as a whole being capable of occurring. Advantageously, adjacent segment of the or each girder of segmented design are in this case connected to one another in such a way that the connection points can be loaded at most with a predetermined limiting shear force. What can be achieved thereby is that, normally, that is to say without bursting or beating pipelines, the girder still has, overall, a sufficient load-bearing force and can therefore be used in the functionally appropriate way. If, however, the accident, to be precise a pipeline break, then to be treated in design-related terms, occurs, with a freed line end acting upon the respective girder, then, as a result of the forces which act on the respective segment in this case by virtue of the design pressure of the entrained flow medium and which lead to shear forces at the connection points, the consequence is that the respective adapter piece or middle segment is knocked out. The limiting shear force provided for maximum load is in this case therefore expediently selected below the shear force at the connection points which is to be expected in such an accident. An especially simple possibility for mounting such a girder structure selected to be segmented can be achieved, in that adjacent segments of the or each girder of segmented design are connected to one another advantageously via screw connections. In order in this case, if required, that is to say for a freed pipeline end to butt against the respective segment in a way provided in design-related terms, to ensure that this segment is reliably released from the overall composite structure, the connecting screws of the or each screw connection are advantageously guided in a number of long holes. These make it possible to release the respective segment in an especially reliable way, in that, in a further advantageous embodiment, the or each long hole is designed to be open in a direction of avoidance expected in the event of an impingement of a line component onto the respective segment. The long holes provided in this way ensure, in particular, that, in the event of release, there are sufficiently free routes, so that there is no substantial influence exerted on the continuous process or on the tied systems. The functioning capacity of the connection is in this case expediently ensured by correspondingly dimensioned screws with a corresponding shank for transmitting the transverse forces limited in this way. For this purpose, if required, a controlled prestressing of the structure, in particular by means of spring rings, may expediently also be provided. In a particularly advantageous embodiment, the girders of segmented design, provided according to the invention, are used in a nuclear power plant. In this case, in particular, there may be provision for providing system fittings, not safety-relevant as such, within the pressure vessel or the outer jacket of the nuclear power plant with girders of this type. Advantageously, in this case, an access or operating platform is designed as a system component supported by a number of girders segmented in this way. To be precise, it is exactly on the access or operating platforms normally provided in a nuclear power plant where a multiplicity of measuring or test lines may be led along, which, in the event of the destruction of the respective platform, could likewise be torn off in the manner of secondary damage. A protection of lines of this type is possible in an especially effective way, in that it is exactly the girders provided for supporting such platforms which have a segmented design in the expected target regions. The advantages achieved by means of the invention are, in particular, that, owing to the segmented design of girders for system components, even in the event of a line break with freed pipeline ends, a transfer of the forces thus released and of routes into components located at a greater distance is reliably ruled out in the nearby region or vicinity of pressure-carrying lines. To be precise, this segmented design of the girders ensures that, in the event of an impact, the respective segment is merely knocked out of the girder, without a deformation of the system component as a whole, supported by the girders, along with secondary damage correspondingly to be expected, being capable of occurring in this situation. Thus, the steel structure as a whole does not experience any significant plastic deformation which could influence the overall primary load-bearing capacity. Furthermore, consequential breaks in the beating pipeline system are avoided in a controlled way, since no significant kickback into the line system is to be expected in the event of the impingement of the freed line ends onto the respective girder. Furthermore, on account of the segmented design of the girders, special anchorages, special structures or shock-absorber elements may be dispensed with, even in a system design meeting stringent safety requirements, thus resulting, in particular, in simple retrofitting possibilities. Identical parts are given the same reference symbols in all the figures. The girder 1 according to FIG. 1 is provided for supporting an operating or access platform, not illustrated in any more detail, in a nuclear plant 12. An operating or access platform of this type is arranged within the reactor building, in order, as required, to give the operating personnel possibilities for movement at the corresponding points. Furthermore, an operating or access platform of this type is normally also used for the routing and retention of measuring or other operating lines arranged on it. Furthermore, the girder 1 is arranged in the vicinity of pressure-carrying lines 16 of the high-pressure system of the nuclear power plant 12. Consequently, in the event of a pipe break 18 in the pressure-carrying system, beating pipe ends, as they may be referred to, could occur, which could act with considerable forces on components located in their vicinity. The girder 1 is designed with the aim, in the event of such an accident, of strictly preventing the transfer of the introduced forces and constrained routes into the operating or access platform and, via this, into further lines arranged on it and thus of keeping secondary damage particularly low even in the event of a pipe break 18 in the pressure-carrying system of the nuclear power plant 12. For this purpose, the girder 1 has a segmented design and comprises, as seen in its longitudinal direction, a number of successively arranged segments 2a, 2b, 2c connected to one another at their connection points. This segmented design of the girder 1 is in this case selected such that, in the event of a pipe break in the pressure-carrying system, the middle segment 2b can be knocked comparatively easily out of its position between the segments 2a and 2c. The girder 1 is thus designed in the manner of an avoidance system, so that, even in the event of the impingement of a freed pipeline end onto the segment 2b, a transfer of forces into the segments 2a and 2c adjacent to this is avoided. Adjacent segments 2a, 2b, 2c of the girder 1 of segmented design are in this case connected to one another in such a way that the connection points can be loaded at most with a predetermined limiting shear force which is selected below the actually occurring shear force expected for such a pipe break. Adjacent segments 2a, 2b, 2c of the girder 1 of segmented design are in this case connected to one another via screw connections 4. The girder 1 is shown in the region of its first segment 2a in FIG. 2 and in the region of its middle segment 2b in FIG. 3, in each case in cross section. As may be gathered from these illustrations, the end flanges 6 provided for making the connection between adjacent segments 2a, 2b, 2c are provided with long holes 8 for receiving the connecting screws of the screw connections 4. The long holes 8 are in this case designed to be kept open in such a way that, in the event of the impingement of a freed pipe end, they allow a comparatively unimpeded avoiding movement of the middle segment 2b in an expected direction of avoidance indicated by the arrow 10. For this purpose, as shown in FIG. 2, the long holes 8 arranged in the end flange 6 of the first segment 2a are designed to be open at their rear end, as seen in terms of the expected direction of impingement of the pipeline end, in order thereby to allow an unimpeded emergence of the screws in the direction of avoidance. Furthermore, as can be seen in FIG. 3, the front long holes 8 of the connecting flange 6 of the middle segment 2b, as seen in terms of the expected direction of impingement of the pipeline end, are designed to be open, so that, here too, an unimpeded emergence of the connecting screws guided therein is possible in the event of the impingement of the free pipeline end. FIG. 4 shows the final state which can be reached as a result of this segmented design of the girder 1 after the impingement of a freed pipeline end. The middle segment 2b of the girder 1 is displaced with respect to its adjacent segments 2a, 2c, as seen in the expected direction of impingement, represented by the arrow 10, of a freed pipeline end. The introduced force is thus converted into a displacement of the segment 2b, without a transfer of forces into the adjacent segments 2a, 2c or a deformation of the girder 1 as a whole and consequently also of the system component or operating platforms supported by it taking place. FIG. 5 shows a nuclear power plant 12 with a plurality of girders 1 supporting a system component 14, such as, for example, an operating or access platform. One of the pressure-carrying lines 16 of the high-pressure system has a pipe break 18, which causes the broken ends of the pressure-carrying line 16 to beat against the target region 20 of one of the plurality of girders 1. 1 Girder 2a, 2b, 2c Segment 4 Screw connection 6 End flange 8 Long hole 10 Arrow |
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054913454 | description | DESCRIPTION Turning now to the drawings, and in particular to FIGS. 1 and 2, which illustrate a vacuum canister 10 embodying the present invention for picking up and containing a fluid or a particulate material, in which vacuum canister 10 includes a housing 20 having a predetermined vacuum pressure, a valve 40, and a conduit 50. Vacuum canister 10, by depressing valve 40, is effective to displace a fluid or a particulate material through conduit 50 for containment within housing 20. As shown in FIG. 2, a liquid 60 and a particulate material 62 are contained within vacuum canister 10. Referring specifically to FIG. 2, housing 20 includes cylindrical side wall 24 attached at its lower end to a bottom 22 and attached to its upper end to a top 26 to define within housing 20 a vacuum chamber 30. Attached to top 26 is valve 40. Preferably, for containing hazardous material, housing 20 includes a protective layer 28 disposed in substantially covering relationship to vacuum chamber 30. Specifically, protective layer 28 is disposed in covering relationship on an inner surface of bottom 22, cylindrical side wall 24, and top 26. Particularly, for containing radioactive material, protective layer 28 is a predetermined thickness of lead that is effective to shield radiation from radioactive material contained within housing 20. Particularly, for containing a corrosive agent material, protective layer 28 is a predetermined thickness of glass that is effective to contain acids and bases within housing 20. When vacuum canister 10 is used to pick up and contain hazardous material, vacuum canister 10 can be labeled as shown in FIG. 1 with the words "HAZARDOUS MATERIAL" or as shown in FIG. 1 with a symbol for radioactivity. Referring now to FIGS. 3 and 4, valve 40 includes a first port 41 for fluid communication with vacuum chamber 30 and a second port 42 for receiving a fluid or a particulate material. Valve 40 is operable between a first or sealed position as shown in FIG. 3, and a second or open position as shown in FIG. 4. Specifically, valve 40 is operable between a first position to seal vacuum chamber 30 and retain a predetermined vacuum within vacuum chamber 30, and a second position to permit a vacuum fluid flow through valve 40 from second port 42. Referring specifically to FIG. 3, valve 40 is shown in the first or sealed position, in which a shoulder 43 on stem 44 is forced tightly against a seat or gasket 45 by a biasing means such as a spring 46. Specifically, spring 46 applies force on shoulder 43 to counteract the force applied on shoulder 43 due to a vacuum within vacuum chamber 30. A predetermined vacuum pressure can be suitably formed within vacuum chamber 30 by depressing valve 40 to access vacuum chamber 30 while valve 40 is attached to a suitable vacuum pump. Valve 40 is then raised to seal the vacuum within vacuum chamber 30. Referring now to FIG. 4, valve 40 is shown in the second position, in which shoulder 43 is pushed down away from seat 45. In operation of valve 40 in the second position, fluid flows into second port 42, thence through a hollow portion 44a of stem 44 and through first port 41; thus passing through top 26, protective layer 28 and into vacuum chamber 30. When a fluid or a particulate material is located adjacent port 42, the vacuum fluid flow through valve 40 is effective to displace a fluid or a particulate material through valve 40 and into vacuum chamber 30 in housing 20. Preferably, biasing means for biasing valve 40 toward the first position to seal vacuum chamber 30 permits valve 40 to be selectively and repetitively moved to the second position to access vacuum chamber 30 and to permit fluid flow through valve 40. In this embodiment, instead of a single use in which the vacuum pressure is equalized with or toward atmospheric pressure, a single vacuum pressure is incrementally equalized with atmospheric pressure to incrementally displace fluid or particulate materials through valve 40 and into vacuum chamber 30 in housing 20. It will be appreciated that other suitable conventional valves could be equally well employed to seal vacuum chamber 30 in a first position and permit vacuum fluid flow through valve 40 in a second position. Referring again to FIG. 1, conduit 50 is disposed to the exterior of valve 40 and conduit 50 has one end in fluid communication with second port 32 of valve 40. Conduit 50 enables a person to easily place the other or free end of conduit 50 adjacent a fluid or a particulate material to be displaced through valve 40 and into vacuum chamber 30 in housing 20 for containment. Upon depressing valve 40, a fluid vacuum flow is created to displace a fluid or a particulate material through valve 40 and into vacuum chamber 30. Advantageously, conduit 50 contains a small diameter passageway to limit the amount of vacuum fluid flow through conduit 50 when valve 40 is repetitively moved to the second position to access vacuum chamber 30 and to permit fluid flow through valve 40, thereby providing for multiple uses of vacuum canister 10 for picking up and containing a fluid or particulate material. Preferably, vacuum canister 10 is sized and configured to fit within a person's hand along with being operable by depressing valve 40 with a finger. When not in use vacuum canister can be easily rested on a table. It is appreciated that housing 20 for retaining the predetermined vacuum can be configured to have a thicker side wall, concave bottom, etc. to better retain the predetermined vacuum. In another embodiment of the invention for picking up and containing at least one of a fluid and a particulate material, vacuum canister 10, instead of having a predetermined vacuum pressure, further includes a vacuum means for establishing a predetermined vacuum pressure within vacuum chamber 30. As shown in FIG. 2, the vacuum means for creating a vacuum within the vacuum chamber includes a preselected substance 29 disposed in communication with vacuum chamber 30 for causing a reaction with a gas within vacuum chamber 30 to establish a predetermined vacuum. Preselected substance 29 may include sulfur, potassium nitrate or other ignitable substance, or a substance that naturally reacts with a gas such as air within vacuum chamber 30 to form a vacuum pressure. Suitable ignitable substances can be contacted with a high resistance wire having an applied electrical current to cause the high resistance wire to heat up and ignite the substance within vacuum chamber 30 and establish a predetermined vacuum. A vacuum pressure can be established in vacuum chamber 30 before using vacuum canister 10. Still another embodiment of the present invention is shown in FIG. 5. As shown in FIG. 5, vacuum canister 10a includes an alternative embodiment of a vacuum means for establishing a predetermined vacuum pressure within vacuum chamber 30a. Specifically, the vacuum means includes a slidable housing member 70 in which member 70 can be moved to increase the volume of vacuum chamber 30a. Member 70 includes an upper section 72 having a gasket or seal 74 that forms a seal against the inner surface of housing 20a, and a lower section 76 having external threads 78 that mates with an internally threaded bore 79 in the bottom of housing 20a. Downward movement of member 70, in the direction of the arrow as shown in FIG. 5, increases the volume of vacuum chamber 30a. In operation, member 70 can be moved to establish a vacuum in vacuum chamber 30 before operating valve 40 (not shown in FIG. 5) or member 70 can be moved to establish a vacuum in vacuum chamber 30 while operating valve 40 (not shown). The method according to the present invention for picking up and containing a fluid or a particulate material comprises the steps of: providing a housing having therein a sealed vacuum chamber, providing a valve having a first port in fluid communication with the vacuum chamber and a second port for receiving at least one of a fluid and a particulate material, the valve being operable between a first position to seal the vacuum chamber and retain a vacuum within the vacuum chamber, and a second position to permit fluid flow through the valve from the second port to the first port, establishing a predetermined vacuum pressure within the vacuum chamber, locating at least one of a fluid and a particulate material adjacent the second port, and placing the valve in the second position to displace along with fluid flow through the valve at least one of a fluid and a particulate material into the vacuum chamber. The vacuum canister is desirably suitable for picking up and containing hazardous material and most desirably suitable for picking up and containing radioactive material. Preferably, the step of providing a housing includes the step of providing a protective layer having a predetermined thickness that is effective to contain the hazardous material within said housing, said protective layer being disposed in substantially covering relationship to said vacuum chamber. Also preferably, the step of providing a valve includes the step of providing biasing means for biasing the valve toward the first position to seal the vacuum chamber. In this embodiment the valve is operable to be selectively or repetitively moved to the second position to repetitively permit fluid flow through the valve. Thus, while only several embodiments of the present invention have been shown and described, it is obvious that many changes and modification may be made thereunto without departing from the spirit and scope of the invention. |
summary | ||
summary | ||
description | This application is based on and claims the benefit of priority to Korean Patent Application No. 10-2014-0058572, filed on May 15, 2014 in the Korean Intellectual Property Office, the disclosure of which is incorporated herein in its entirety by reference. The present disclosure relates to a management equipment transfer apparatus, and more particularly, to a management equipment transfer apparatus capable of easily installing and transferring management equipment independent of a size of a nuclear reactor vessel. Generally, a nuclear reactor means an apparatus which controls a chain reaction to emit a large amount of mass defect energy which is instantly emitted as a result of a chain nuclear fission reaction so as to use heat energy generated from nuclear fission as power. To secure safety and reliability of an atomic power plant, there is a need to periodically test a pipe or a nuclear reactor vessel. The test is performed by ultrasonic testing, and the like which mainly uses an ultrasonic wave. A testing system and a maintenance system of the nuclear reactor vessel are installed using a fixed platform, in which the fixed platform is fixedly mounted to the nuclear reactor vessel by a multi-axis manipulator manner. However, the fixed platform needs to include a separate bracket for adjusting a length when the size of the nuclear reactor vessel is increased. In addition, the fixed platform may not change the multi-axis manipulator which is attached to a lower end thereof, such that the number of nuclear reactors which may be tested is limited and the fixed platform may hardly be decomposed/assembled and transferred/installed. Japanese Patent Laid-Open Publication No. 2000-321255 The present disclosure has been made to solve the above-mentioned problems occurring in the prior art while advantages achieved by the prior art are maintained intact. An aspect of the present disclosure provides a management equipment transfer apparatus capable of installing management equipment independent of a size of a nuclear reactor vessel. Another aspect of the present disclosure provides a management equipment transfer apparatus capable of being replaced by required test and maintenance equipment depending on working conditions. Still another aspect of the present disclosure provides a management equipment transfer apparatus capable of reducing a weight and a volume of management equipment. Yet still another aspect of the present disclosure provides a management equipment transfer apparatus capable of automatically transferring management equipment. According to an exemplary embodiment of the present disclosure, a management equipment transfer apparatus which transfers management equipment, which tests and maintains an inside of a nuclear reactor vessel, inside the nuclear reactor vessel while being locked to the management equipment and the nuclear reactor vessel includes: a cross beam configured to be lengthily disposed inside the nuclear reactor vessel in a transverse direction; a rod configured to be connected to a cross beam lengthily disposed inside the nuclear reactor vessel in a longitudinal direction; a bracket configured to be mounted in the rod to fix the management equipment; an arm configured to extend toward an inner peripheral surface of the nuclear reactor vessel and be connected to the cross beam; and rolling parts configured to be disposed at ends of the arm and the cross beam, contact the inner peripheral surface of the nuclear reactor vessel, and rotatably support the cross beam and the arm. At least any one of the arm and the cross beam may be formed to be expanded and contracted in a length direction so as to control an interval between the rolling part and the nuclear reactor vessel. An expansion and contraction direction of the arm or the cross beam may be a radius direction of the nuclear reactor vessel. The rod may be coupled with the cross beam to move in an up and down direction of the nuclear reactor vessel. The rod may be coupled with the bracket to move the bracket in an up and down direction of the nuclear reactor vessel. The rod may be coupled with the cross beam to move the bracket in a transverse direction of the nuclear reactor vessel. The rolling part may include: a roller configured to rotate by being supplied with power; and a wheel configured to rotate by a friction force with the nuclear reactor vessel. The arm and the cross beam may be hinged with each other to control an angle at a connection point between the arm and the cross beam. The bracket may detachably fix the management equipment. The management equipment transfer apparatus may further include: a first actuator configured to supply power so as to expand and contract the arm or the cross beam; a second actuator configured to supply power so as to move the bracket in an up and down direction of the nuclear reactor vessel; and a third actuator configured to supply a rotating force to the rolling part. Various advantages and features of the present disclosure and methods accomplishing thereof will become apparent from the following detailed description of embodiments with reference to the accompanying drawings. However, the present disclosure is not be limited to the embodiments set forth herein but may be implemented in many different forms. The present embodiments may be provided so that the disclosure of the present disclosure will be complete, and will fully convey the scope of the disclosure to those skilled in the art and therefore the present disclosure will be defined within the scope of claims. Like reference numerals throughout the description denote like elements. Hereinafter, a management equipment transfer apparatus according to exemplary embodiments of the present disclosure will be described with reference to the accompanying drawings. FIG. 1 is a longitudinal cross-sectional view of a nuclear reactor vessel according to an exemplary embodiment of the present disclosure. FIG. 2 is a perspective view of a management equipment transfer apparatus according to an exemplary embodiment of the present disclosure which is disposed in the nuclear reactor vessel. FIG. 3 is a perspective view of the management equipment transfer apparatus according to the exemplary embodiment of the present disclosure. FIG. 4 is a plan view of the management equipment transfer apparatus according to the exemplary embodiment of the present disclosure. Referring to FIGS. 1 to 4, a management equipment transfer apparatus 100 according to an exemplary embodiment of the present disclosure which transfers management equipment 10, which tests and maintains an inside of a nuclear reactor vessel 1, inside the nuclear reactor vessel 1 while being locked to management equipment 10 and the nuclear reactor vessel 1 includes: a cross beam 120 configured to be lengthily disposed inside the nuclear reactor vessel 1 in a transverse direction (W) which is the same as a radius direction (D) of the nuclear reactor vessel 1; a rod 110 configured to be connected to a cross beam 120 lengthily disposed inside the nuclear reactor vessel 1 in a longitudinal direction (H) which is the same as an up and down direction (H) of the nuclear reactor vessel 1; a bracket 115 configured to be mounted in the rod 110 to fix the management equipment 10; an arm 130 configured to extend toward an inner peripheral surface of the nuclear reactor vessel 1 and be connected to the cross beam 120; and rolling parts 150 configured to be disposed at ends of the arm 130 and the cross beam 120, contact the inner peripheral surface of the nuclear reactor vessel 1, and rotatably support the cross beam 120 and the arm 130. The nuclear reactor uses mass defect energy which is generated as a result of nuclear fission reaction. Unlike a thermal power reactor which automatically expands combustion by combustion heat, the nuclear reactor performs the nuclear fission reaction using neutrons emitted at the time of nuclear fission of fuel as a medium. The nuclear fission reaction of the nuclear reactor controls the number of neutrons absorbed into nuclear fuel to be able to control the combustion of nuclear fuel. To sustain the nuclear fission within the nuclear reactor, the number of neutrons, which is again absorbed into the nuclear fuel to again start the nuclear fission, among neutrons emitted at the time of the nuclear fission needs to be at least one. When the number of neutrons is 1, the nuclear fission reaction is not decreased and increased and is constantly kept, which is referred to as a critical of the nuclear reactor. Further, when the number of neutrons exceeds 1, the number of nuclear fission reactions is gradually increased, which is referred to as a supercritical state and the reverse case is a subcritical state. A method for keeping the nuclear reactor in a critical state when the nuclear reactor is operated at a constant output or absorbing extra neutrons into a control rod when the nuclear reactor slightly exceeds the critical is used. The number of neutrons emitted at the time of one-time nuclear fission is 2 in average in the case of uranium 235, but all the neutrons do not contribute to the nuclear fission again but the number of neutrons is decreased due to leakage to an outside of the nuclear reactor, absorption into a nonnuclear fissionable material, and the like. Therefore, to continuously operate the nuclear reactor, it is important to minimize a loss of neutrons. As a method for preventing the loss of neutrons, there are a method for increasing an absorption probability by increasing an amount of nuclear fissionable material or decelerating fast neutron emitted at the time of nuclear fission to a thermal neutron level, a method for sufficiently increasing a size of a nuclear reactor to minimize leakage to an outside of a reactor core, and a method for minimizing absorption into another nonnuclear fissionable material, and the like. The neutron emitted at the moment of the nuclear fission is less likely to be absorbed into nuclear fuel as the fast neutron having high energy and therefore it is important to increase the absorption probability by decelerating the fast neutron. The neutron reactor is controlled by controlling the number of neutrons by putting or extracting a material having a large neutron absorption cross section such as cadmium and boron into or from the nuclear reactor core and is controlled by a method for changing an amount of reflector or moderator. The nuclear reactor vessel 1 accommodates a nuclear fuel rod and water. Here, the water is heat-exchanged to absorb energy generated by a nuclear fission reaction and thus is phase-changed to steam. The nuclear reactor vessel 1 needs to keep an airtight state and therefore a state of a wall surface needs to be tested. The testing of the nuclear reactor vessel 1 is performed by ultrasonic testing (VT, UT, PAUT, and the like) and the defective portion is performed by maintenance (cutting, machining, welding, and the like). The management equipment 10 includes at least one of ultrasonic testing equipment and maintenance equipment. The bracket 115 is mounted with the management equipment 10 and is coupled with the rod 110 to be described below. The rod 110 fixes the bracket 115 and is disposed in a longitudinal direction. The rod 110 is disposed in the up and down direction (H) which is parallel to a longitudinal central line (C-C) of the nuclear reactor vessel 1. The cross beam 120 is disposed in a left and right direction. The cross beam 120 is disposed in the radius direction (D) which is orthogonal to the longitudinal central line C-C of the nuclear reactor vessel 1. The cross beam 120 supports a load of the rod 110 and the management equipment 10. The bracket 115 detachably fixes the management equipment 10 so that the management equipment 10 may be replaced. The bracket 115 may be disposed at an end of a lower portion of the rod 110. The bracket 115 may also be formed in a tong shape to fix the management equipment 10. Any one of the bracket 115 and the management equipment 10 is provided with a protrusion and the other one thereof is provided with an insertion into which the protrusion is inserted, and as a result, the bracket 115 and the management equipment 10 may be coupled with each other. The bracket 115 may also be screw-connected to the management equipment 10. The arm 130 is connected to the cross beam 120. The arm 130 may extend in the same direction as a length direction of the cross beam 120 and may also be connected to the cross beam 120, while forming a tilt to the length direction of the cross beam 120. The arm 130 supports the load of the cross beam 120, the rod 110, and the management equipment 10. The rolling part 150 is disposed to be rolled along an inner peripheral surface of the nuclear reactor vessel. The rolling part may be disposed at each of the ends of the arm 130 and the cross beam 120. The rolling part 150 changes sliding friction to rolling friction to reduce resistance generated at the time of the movement of the cross beam 120 and the arm 130. Therefore, a manager of the nuclear reactor vessel 1 may transfer the management equipment 10 with a smaller force. The cross beam 120 and the arm 130 may rotate, and thus the management equipment 10 and the rod 110 may rotate based on the longitudinal central line C-C of the nuclear reactor vessel 1. At least any one of the arm 130 and the cross beam 120 may be expanded and contracted to control an interval between the rolling part 150 and the nuclear reactor vessel 1 in a length direction. The arm 130 and the cross beam 120 may be extended or reduced in a length direction. A length of the arm 130 and the cross beam 120 is differently adjusted depending on the size of the nuclear reactor vessel 1. The arm 130 and the cross beam 120 may include a cylinder and a piston. The arm 130 and the cross beam 120 may be extended until a contact area between the rolling part 150 and the nuclear reactor vessel 1 is maximized. When the operation of the management equipment 10 ends, the arm 130 and the cross beam 120 may be contracted in the length direction, thereby minimizing the volume of the management equipment 10. Therefore, the management equipment 10 may be easily transferred, installed, and stored. The expansion and contraction direction of the arm 130 or the cross beam 120 may be the radius direction (D) of the nuclear reactor vessel 1. The rod 110 may be coupled with the cross beam 120 to move in an up and down direction (H) of the nuclear reactor vessel 1. The length direction of the arm 130 and the cross beam 120 is toward or passes through the longitudinal central line C-C of the nuclear reactor vessel 1. The nuclear reactor vessel 1 supports the load of the arm 130 and the cross beam 120 and therefore the arm 130 and the cross beam 120 are fixed to the nuclear reactor vessel 1 to be structurally stabilized. The length direction of the arm 130 and the cross beam 120 may be formed to be vertical to the contact surface of the nuclear reactor vessel 1. FIGS. 5A and 5B are perspective views of a ball screw and a lead screw according to the exemplary embodiment of the present disclosure. Referring to FIGS. 5A and 5B, the rod 110 may be coupled with the bracket 115 to move the bracket 115 in the up and down direction (H) of the nuclear reactor vessel 1. The rod 110 itself may control the height of the bracket while moving vertically and the rod 110 is fixed to the cross beam 120 and only the bracket may vertically move in the length direction of the rod 110. A method for coupling the rod 110 with the cross beam 120 to vertically move the rod 110 may be various. As the example, the rod 110 includes the piston and the cylinder and the bracket may be coupled with the piston to adjust the height of the bracket depending on the insertion depth of the piston. As another example, the height of the bracket may be adjusted by the ball screw 193 or the lead screw 191. The rod 110 may be coupled with the cross beam 120 to move the bracket 115 in the transverse direction (W) of the nuclear reactor vessel 1. A method for coupling the rod 110 with the cross beam 120 to move the rod 110 in the transverse direction (W) may be various. According to one exemplary embodiment, a rack may be provided in the length direction of the cross beam 120 in the cross beam 120 and a pinion rotating while being engaged with the rack may be disposed at the rod 110. A rotation shaft of the pinion may be vertically disposed to the length direction of the rod 110. The rolling part 150 includes a roller 153 configured to receive power to rotate for oneself and a wheel 151 configured to rotate by a friction force with the nuclear reactor vessel 1. The roller 153 may be supplied with power from a third actuator 163. The third actuator 163 may be a motor. The rolling part 150 may include a roller which may rotate by the motor. The third actuator 163 and the roller 153 are coupled with each other by a direct connection type and thus a rotation shaft of the third actuator 163 and a rotation shaft of the roller 153 may be disposed on the same line. The rotation shaft of the third actuator 163 and the rotation shaft of the roller 153 may be connected to each other by a gear or a belt to be able transfer power. The rolling part 150 is disposed in plural and at least one of the plurality of rolling parts 150 includes the roller 153. The arm 130 and the cross beam 120 may be hinged with each other to control an angle at a connection point (J) between the arm 130 and the cross beam 120. Since the arm 130 and the cross beam 120 may be hinged with each other, the arm 130 and the cross beam 120 are unfolded when being disposed in the nuclear reactor vessel 1 and when the examination and testing of the nuclear reactor vessel 1 end, the arm 130 and the cross beam 120 are folded to reduce the volume, thereby facilitating the storage and delivery. The cross beam 120 is connected to the rod 110 and therefore the cross beam 120 may be provided in a single number and the arm 130 may be provided in plural. When the number of arms 130 is increased, the structural stability is increased. However, the weight and volume of the management equipment transfer apparatus 100 are increased and the storage thereof is inconvenient, such that the arm 130 may be configured in two. The two arms 130 and the cross beam 120 may be connected to each other, forming an angle of 60°. The bracket 115 detectably fixes the management equipment 10. The manager may replace the management equipment 100 in a working order. For example, the ultrasonic testing equipment (VT, UT, PAUT, and the like) is fixed to the bracket 115 to perform the test and then finds out the defective portion and is replaced by the maintenance equipment (cutting, machining, welding equipment). The manager continuously performs the operation using the replaced equipment. FIG. 6 is a block diagram of a controller according to the exemplary embodiment of the present disclosure and components therearound. Referring to FIG. 6, the management equipment transfer apparatus 100 according to the exemplary embodiment of the present disclosure includes: a first actuator 161 configured to supply power so as to expand and contract the arm 130 or the cross beam 120; a second actuator 162 configured to supply power so as to move the bracket 115 in the up and down direction (H) of the nuclear reactor vessel 1; and the third actuator 163 configured to supply a rotating force to the rolling part 150. The first actuator 161, the second actuator 162, and the third actuator 163 generate power using oil pressure, air pressure, or electric power and supply the generated power to each member. For example, the first actuator 161 may be a hydraulic apparatus which uses a fluid pressure like oil. The second actuator 162 and the third actuator 163 may be a motor which generates a rotating force using power. A rotation shaft of the motor may be directly connected to the rolling part 150 and may be indirectly connected to the rolling part 150, the bracket 115, and the rod 110 by the belt or the gear. The controller 170 generates a control signal which operates the first actuator 161, the second actuator 162, and the third actuator 163. The controller 170 is connected to an input device 180. The input device 180 is to input information to the controller 170. The input device 180 may be a keyboard, a mouse, a joystick, and the like. The manager operates the input device 180 to control an operation amount of the first actuator 161, the second actuator 162, and the third actuator 163. The controller 170 operates the input device 180 to transfer the position of the management equipment 10 to a desired place. FIG. 7 is a diagram illustrating a disposition relationship of a rolling part according to an exemplary embodiment of the present disclosure. Referring to FIG. 7, the wheel 151 is disposed to be locked to a locking jaw 3 which is formed on an inner side wall 5 of the nuclear reactor vessel and the roller 153 is disposed to rotate, contacting the inner side wall 5 which is formed on the inner side wall 5 of the nuclear reactor vessel. The roller 153 is supplied with power from the third actuator 163 to rotate. The wheel 151 rotates by a friction force with the nuclear reactor vessel. A rotation shaft of the wheel 151 may be formed in the radius direction of the nuclear reactor vessel. The wheel 151 rotates, contacting the locking jaw 3 of the nuclear reactor vessel horizontally formed. The roller 153 rotates, contacting the inner side wall 5 of the nuclear reactor vessel which approximately vertically stands. The roller 153 is disposed so that the rotation shaft of the roller 153 longitudinally stands. When the roller 153 rotates, the management equipment transfer apparatus 100 rotates by the friction force of the roller 153 and the inner side wall. Therefore, a disposition angle of the management equipment 10 may be controlled. The arm 230 may be expanded and contracted in the radius direction of the nuclear reactor vessel and therefore the roller 153 may be extended until the roller 153 contacts the inner side wall 5 of the nuclear reactor vessel. Further, a roller support part 197 may move the roller 153 or the rolling part 150 until the roller 153 contacts the inner side wall 5 of the nuclear reactor vessel. The roller support part 197 is configured to include the cylinder and the piston and may be extended. A sufficient friction force is generated and thus the roller 153 contacts the inner side wall 5 of the nuclear reactor vessel to prevent an idle of the roller 153. FIG. 8 is a perspective view of a management equipment transfer apparatus 200 according to another exemplary embodiment of the present disclosure. Referring to FIG. 8, the cross beam 220 and the arm 230 may be connected to each other to form a straight line to have a length increased or decreased in one shaft direction. The cross beam 220 and the arm 230 may be formed in a three-leg form and a straight line. That is, any one of the cross beam 220 and the arm 230 is inserted into the other thereof and thus the overall length thereof may also be changed depending on the inserted degree. The overall length of the cross beam 220 and the arm 230 is changed depending on a diameter of the nuclear reactor vessel. The exemplary embodiment of the present disclosure has at least one of the following effects. First, it is possible to provide the transfer apparatus which may be expanded and contracted to be fitted for the size of the nuclear reactor vessel. Second, it is possible to provide the transfer apparatus which may be replaced by the required test and maintenance equipment depending on working conditions. Third, it is possible to reduce the weight and the volume of the management equipment. Fourth, it is possible to automatically transfer the management equipment. However, effects of the present disclosure are not limited to the foregoing matters and other effects of the present disclosure which are not mentioned may be clearly understood to those skilled in the art. Hereinabove, the exemplary embodiments of the present disclosure are illustrated and described, but the present disclosure is not limited to the foregoing specific exemplary embodiments and therefore it is apparent that various modifications can be made to those skilled in the art without departing from the spirit of the present disclosure described in the appended claims and these various modifications should not be individually construed from the technical ideas or prospects of the present disclosure. |
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039420230 | abstract | A radiological screen for placing on a patient's skin comprising a flat jacket containing a fine particulate filler and a settable resin binder, the fine particulate filler being of a material which absorbs medical radiation, and the jacket including a window to transmit such radiation through the flat jacket. |
abstract | The present invention discloses a method for determining the mineral content represented by the entire SEM-EDS dataset, including initially unknown data points. SEM-EDS data points are taken and compared to a set of known data points. Any data point that is not sufficiently similar to the known data point is classified as unknown and clustered with like unknown data points. After all data points are analyzed, any clusters of unknown data points with a sufficient number of data points are further analyzed to determine their characteristics. All clusters of unknown data points with an insufficient number of data points to allow further analysis are considered outliers and discarded. |
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abstract | Charged-particle-beam projection-exposure apparatus and methods are disclosed that achieve improved pattern-transfer accuracy, especially when using a segmented stencil reticle. To such end, the pattern field of a reticle pattern is divided into multiple exposure units that are individually and sequentially exposed onto corresponding regions on a substrate (e.g., semiconductor wafer). Any exposure units defining a feature surrounding an island region are split into complementary exposure units. Boundaries between adjacent exposure units are placed so as not to cross features or feature portions in the respective exposure units, defined by xe2x80x9cwhitexe2x80x9d regions of the reticle. Thus, when images of the exposure units are stitched together on the wafer, improved feature registration, alignment, and linewidth control are achieved. |
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abstract | The present invention provides a passive residual heat removal system and an atomic power plant comprising the same, the passive heat removal system comprising: a plate-type heat exchanger for causing heat exchange between a primary system fluid or a secondary system fluid which, in order to remove sensible heat from an atomic reactor cooling material system and residual heat from a reactor core, has received the sensible heat and the residual heat, and a cooling fluid which has been introduced from outside of a containment unit; and circulation piping for connecting the atomic reactor cooling material system to the plate-type heat exchanger, thereby forming a circulation channel of the primary system fluid, or connecting a steam generator, which is arranged at the boundary between the primary and secondary systems, to the plate-type heat exchanger, thereby forming a circulation channel of the secondary system fluid. |
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06188748& | claims | 1. A contour collimator for radiotherapy, comprising a plurality of plate-shaped diaphragm elements provided in a guiding block and movably arranged with respect to one another to form a contour diaphragm for a radiation beam emitted by a radiation source towards the collimator, and comprising at least one drive for moving the diaphragm elements, wherein a drive of its own is associated with each diaphragm element, the drives of a group of diaphragm elements are arranged substantially adjacent to one another, and a driving transmission of its own is provided between each drive and the associated diaphragm element, wherein the drives are arranged substantially in a semi-circle. 2. The contour collimator according to claim 1, wherein at least one displacement pickup for detecting the position of the corresponding diaphragm element is associated with each drive. 3. The contour collimator according to claim 1, wherein each driving transmission has a flexible but tension-resistant and pressure-resistant power-transmitting element one end of which is connected with the associated diaphragm element and the other end of which is connected with the associated drive and which is supported in a moving guide in translatorily movable fashion. 4. The contour collimator according to claim 3, wherein each power-transmitting element is detachably coupled to the associated diaphragm element via a coupling linkage. 5. The contour collimator according to claim 3, wherein each power-transmitting element is detachably coupled to the associated drive via a further coupling linkage. 6. The contour collimator according to claim 3, wherein each power-transmitting element has a spring band. 7. The contour collimator according to claim 1, wherein each drive comprises a linearly acting motor. 8. The contour collimator according to claim 7, wherein the motor is an electric linear motor. 9. The contour collimator according to claim 7, wherein the motor is an electric motor having a linearly acting gearing selected from the group consisting of a rack-and-pinion gear and a spindle gearing. 10. The contour collimator according to claim 1, wherein the guiding block has upper and lower guide plates which are each provided with a plurality of upper guide grooves and lower guide grooves, respectively, for the diaphragm elements. 11. The contour collimator according to claim 10, wherein the upper and lower guide plates are each provided with a rectangular opening which determine the maximum diaphragm opening and have a common middle plane extending substantially rectangularly with respect to the longitudinal direction of the guide grooves. 12. A contour collimator for radiotherapy, comprising a plurality of plate-shaped diaphragm elements provided in a guiding block and movably arranged with respect to one another to form a contour diaphragm for a radiation beam emitted by a radiation source towards the collimator, and comprising at least one drive for moving the diaphragm elements, wherein a drive of its own is associated with each diaphragm element, the drives of a group of diaphragm elements are arranged substantially adjacent to one another, and a driving transmission of its own is provided between each drive and the associated diaphragm element, wherein each driving transmission has a flexible but tension-resistant and pressure-resistant power-transmitting element one end of which is connected with the associated diaphragm element and the other end of which is connected with the associated drive and which is supported in a moving guide in translatorily movable fashion, and wherein the moving guides are arranged substantially side by side in a moving guide block and have moving guide gaps diverging in fan-shaped and bent fashion, in which one power-transmitting element is accommodated in translatorily movable fashion. 13. A contour collimator for radiotherapy, comprising a plurality of plate-shaped diaphragm elements provided in a guiding block and movably arranged with respect to one another to form a contour diaphragm for a radiation beam emitted by a radiation source towards the collimator, and comprising at least one drive for moving the diaphragm elements, wherein a drive of its own is associated with each diaphragm element, the drives of a group of diaphragm elements are arranged substantially adjacent to one another, and a driving transmission of its own is provided between each drive and the associated diaphragm element, wherein two superposed planes of drive arrangements are associated with each moving guide block, on power-transmitting element, accommodated in adjacent moving guides, being applied by two superposed drives each. 14. The contour collimator according claim 1, wherein two opposite groups of tanslatorily drivable diaphragm elements are provided in the guiding block, two opposite diaphragm elements each being guided in lower and upper common guide grooves. 15. The contour collimator according to claim 1, wherein each diaphragm element of a pair of opposite diaphragm elements is movable with its free edge facing away from the respective beyond the common middle plane of openings in upper and lower guide plates. 16. The contour collimator according to claim 12, wherein the displacement pickup comprises a potentiometer. 17. The contour collimator according to claim 2, wherein the displacement pickup comprising a moving potentiometer which can be actuated translatorily. 18. A contour collimator for radiotherapy, comprising a plurality of plate-shaped diaphragm elements provided in a guiding block and movably arranged with respect to one another to form a contour diaphragm for a radiation beam emitted by a radiation source towards the collimator, and comprising at least one drive for moving the diaphragm elements, wherein a drive of its own is associated with each diaphragm element, the drives of a group of diaphragm elements are arranged substantially adjacent to one another, and a driving transmission of its own is provided between each drive and the associated diaphragm element, wherein at least one of the diaphragm elements located in the region of the central middle ray of the radiation beam is provided with at least one thickening rib extending in the translational direction. 19. The contour collimator according to claim 18, wherein each thickening rib engages a corresponding groove in the adjacent diaphragm element. |
description | This application is a divisional of U.S. application Ser. No. 12/385,665 filed on Apr. 15, 2009, the contents of which is incorporated by reference in its entirety. 1. Field The invention relates to a capsule and methods of fabricating and using the capsule. The capsule is designed to fit within a nuclear reactor's neutron flux so that a material within the capsule may be irradiated in the reactor's core. The capsule is further designed to be used straight from the neutron flux source and used as an elution column to remove ions from within the capsule that were generated by the irradiation decay process. 2. Description of the Related Art Technetium-99m (m is metastable) is a radionuclide used in nuclear medical diagnostic imaging. Technetium-99m is injected into a patient which, when used with certain equipment, is used to image the patient's internal organs. However, technetium-99m has a halflife of only six (6) hours, therefore, readily available sources of technetium-99m are desired. A method for obtaining technetium-99m uses a minimum of a two-step process. First, titanium molybdate is placed in a capsule, which is then irradiated in a nuclear reactor. Molybdenum-98 within the titanium molybdate absorbs a neutron during the irradiation process and becomes molybdenum-99 (Mo-99). Mo-99 is unstable and decays with a 66-hour half-life to technetium-99m (m is metastable). After the irradiation step, the irradiated titanium molybdate is removed from the capsule and placed in a column for elution. Subsequently, saline is passed through the irradiated titanium molybdate to remove the technetium-99m ions from the irradiated titanium molybdate. At least one example embodiment relates to an elution capsule. In accordance with the example embodiment, an elution capsule may include a tube with a first end portion having a first inside diameter, a second end portion having a second inside diameter, and a middle portion between the first end portion and the second end portion having an inside diameter smaller than the inside diameters of the first and second end portions. The interface between the first end portion and the middle portion forms a first shoulder and the interface between the second end portion and the middle portion forms a second shoulder. The elution capsule may also include a first washer inside the first end portion contacting the first shoulder, a first filter inside the first end portion contacting the first washer, and a second filter inside the first end portion such that the first filter is between the first washer and the second filter. The first end may be sealed by a first end cap. The elution capsule may also include a second washer inside the second end portion contacting the second shoulder, a third filter inside the second end portion contacting the second washer, and a fourth filter inside the second end portion such that the third filter is between the second washer and the fourth filter. The second end portion may be sealed by a second end cap. In accordance with at least one example embodiment, a method of irradiating a material within an elution capsule is disclosed. In accordance with the example embodiment, the elution capsule may include a tube with a first end portion having a first inside diameter, a second end portion having a second inside diameter, and a middle portion having an inside diameter smaller than the inside diameters of the first and second end portions. The middle portion is between the first end portion and the second end portion and is configured to hold the material. The interface between the first end portion and the middle portion forms a first shoulder and the interface between the second end portion and the middle portion forms a second shoulder. A first washer may be inside the first end portion and may contact the first shoulder. A first filter may be inside the first end portion and may contact the first washer. A second filter may be inside the first end portion and may be positioned such that the first filter is between the first washer and the second filter. A first end cap may be provided in the first end portion to seal-off the first end portion. A second washer may be inside the second end portion and may contact the second shoulder. A third filter may be inside the second end portion and may contact the second washer. A fourth filter inside the second end portion may be provided such that the third filter is between the second washer and the fourth filter. A second end cap may be provided in the second portion to seal-off the second end portion. The method, according to the example embodiment, may include placing the sealed elution capsule, with the material in the middle portion of the elution capsule in a neutron flux source and irradiating the capsule and its contents in the reactor's core. At least one example embodiment related to a method of eluting a material enclosed in a sealed elution capsule is provided. The method includes placing the sealed elution capsule enclosing the material into a nuclear reactor, irradiating the sealed elution capsule and material in a reactor, removing the sealed elution capsule and irradiated material from the reactor, and performing an elution step by puncturing a first end portion of the elution capsule with a needle to supply a solution to the elution capsule and puncturing a second end portion with a needle to provide a vacuum to draw the solution through the irradiated material to collect the eluant. Example embodiments of the invention will now be described more fully with reference to the accompanying drawings, in which example embodiments are shown. The invention may, however, be embodied in different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of the invention to those skilled in the art. In the drawings, the sizes of components may be exaggerated for clarity. It will be understood that when an element or layer is referred to as being “on”, “connected to”, or “coupled to” another element or layer, it can be directly on, connected to, or coupled to the other element or layer or intervening elements or layers that 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. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It will be understood that, although the terms first, second, 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, and/or section from another element, component, region, layer, and/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, such as “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 will 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 exemplary term “below” can 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. Embodiments described herein will refer to plan views and/or cross-sectional views by way of ideal schematic views. Accordingly, the views may be modified depending on manufacturing technologies and/or tolerances. Therefore, example embodiments are not limited to those shown in the views, but include modifications in configuration formed on the basis of manufacturing processes. Therefore, regions exemplified in figures have schematic properties and shapes of regions shown in figures exemplify specific shapes or regions of elements, and do not limit example embodiments. FIGS. 1-3 represent an example embodiment of the present invention. The example embodiment, as shown in FIGS. 1-3, includes a hollow cylindrically shaped multidiameter tube 10. The tube 10 is hollow such that a cross-section of the multidiameter tube has an annular shape. The tube 10 has a constant outer diameter D1, however, the inner diameter of the tube 10 varies along the length of the tube 10. For example, the tube, as shown in FIG. 1, includes three portions: a first end portion 12 located at one end of the multidiameter tube 10, a second end portion 14 located at another end of the multidiameter tube 10, and a middle portion 16 between the first end portion 12 and the second end portion 14. In this example embodiment of the invention, the inner diameter D4 of the middle portion 16 may be smaller than the inner diameters D2 and D3 of the end portions 12 and 14. In addition, the inner diameter of the first end portion D2 and the inner diameter of the second end portion D3 may be equal. The first end portion 12 and the second end portion 14 may have lengths P1 and P2, respectively. As shown in FIG. 3, the lengths P1 and P2 may be equal. The interface between the first end portion 12 and the middle portion 16 forms a first shoulder 100 and the interface between the second end portion 14 and the middle portion 16 forms a second shoulder 110. Because the lengths P1 and P2 may be equal and because the diameters D2 and D3 may likewise be equal, the multidiameter tube 10 illustrated in FIGS. 1-3 may have a symmetric configuration. The example capsule 1 for holding, irradiating and eluting a material in accordance with FIGS. 1-3 also includes first and second washers 20 and 60 positioned inside the first end portion 12 and the second end portion 14, respectively. The washers 20 and 60, as shown in FIGS. 1, 2, 4 and 5, are short hollow cylinders with annular cross-sections. The washer 20 has an outside diameter D6 larger than the inside diameter D4 of the middle portion 16 and smaller than the inside diameter D2 of the first end portion 12. The washer 20 has an inside diameter D5 that may be smaller, equal to, or larger than the diameter of the inside diameter D4 of the middle portion 16. The washer 60 has an outside diameter D8 larger than the inside diameter D4 of the middle portion 16 and smaller than the inside diameter D3 of the second end portion 14. The washer 60 has an inside diameter D7 that may be smaller, equal to, or larger than the diameter of the inside diameter D4 of the middle portion 16. As shown in FIGS. 1-2, the washer 20 is placed inside the first end portion 12 and against the shoulder 100. The washer 60 is placed in the second end portion 14 and against the shoulder 110. The example capsule 1 for holding, irradiating, and eluting a material may also include first and second filters 30 and 40 in the first end portion 12 and third and fourth filters 70 and 80 in the second end portion 14 of the multidiameter tube 10. The first filter 30 may be placed in the first end portion such that the washer 20 is between the first filter 30 and the shoulder 100 and the second filter 40 may be placed in the first end portion 12 such that the first filter 30 is between the second filter 40 and the washer 20. The third filter 70 may be placed in the second end portion 14 such that the washer 60 is between the third filter 70 and the shoulder 110 and the fourth filter 80 may be placed in the second end portion 14 such that the third filter 70 is between the fourth filter 80 and the washer 60. The first through fourth filters may be made of various materials. For example, the first filter 30 and the third filter 70 may be made from glass wool. The glass wool may be made from a borosilicate or quartz glass. The second filter 40 and the fourth filter 80, may be circular glass frits as shown in FIGS. 1, 2, and 6-7 which resemble short cylinders or disks. The glass fits may be made from various materials such as borosilicate glass, quartz glass, polyethylene, resin, or some other material that will structurally support a material within the elution tube and act as a filter to prevent material from traversing down a flow path through the elution tube. The circular glass frit 40 has an outer diameter D9 smaller than the inner diameter D2 of the first end portion 12 but greater than the inner diameter D5 of the washer 20. The circular glass frit 80 has an outer diameter D10 smaller than the inner diameter D3 of the second end portion 14 but larger than the inner diameter D7 of the washer 60. Although circular glass frits are used as second and fourth filters 40 and 80, the invention is not limited thereto. The example capsule 1 for holding, irradiating, and eluting a material may also include end caps 50 and 90 configured to seal the first end portion 12 and the second end portion 14 of the multidiameter tube 10, respectively. In accordance with the example embodiment illustrated in FIGS. 1-2, the end caps 50 and 90 may include tapered hollow cylindrical body parts 52 and 92 with covers 53 and 93 as shown in FIGS. 1, 2 and 8-13, allowing the end caps 50 and 90 to be press fit into the first and second end portions 12 and 14 of the multidiameter tube 10. Because the ends of the multidiameter tube 10 are sealed by press fitting the end caps 50 and 90 into the first and second end portions 12 and 14, the end caps 50 and 90 should be made from a soft material which will accommodate yielding during the press fit process. For example, the end caps may be made of aluminum. The hollow cylindrical body part 52 may be tapered so that the outer diameter D12 of a portion of the hollow cylindrical body part 52 facing the center of the multidiameter tube 10 is smaller than an outer diameter D14 of the hollow cylindrical body part 52 attached to the cover 53. The diameter D12 must be smaller than the inner diameter D2 of the first end portion 12 of the multidiameter tube 10 so that the end of the hollow body part 52 facing the center of the multidiameter tube 10 may enter the first end portion 12. However, the outer diameter D14 of the cylindrical body part 52 attached to the cover 53 should be slightly larger than the inner diameter D2 of the first end portion 12 of the multidiameter tube 10 so that when the end cap 50 is press fit into the first end portion 12 of the multidiameter tube 10 the first end portion is sealed. Additionally, the inner diameter D11 of the hollow body part 52 should be smaller than the diameter D9 of the frit 40 to prevent the frit 40 from passing into the hollow body part 52. The length L1 of the hollow body part 52 should be long enough to accommodate a needle which may be passed through the cover 53 during an elution process. The length L1 of the hollow body part 52, therefore, should be at least as long as the needle used to introduce or remove a liquid into or from the example capsule 1 for holding, irradiating, and eluting a material. Because the length L1 of the hollow body part 52 is at least as long as the aforementioned needle, the hollow body part protects the first and second filter from being damaged by the needle as the needle is introduced into the capsule. The cover 53 of the end cap 50 has a diameter D15 larger than the inner diameter D2 of the first end portion 12 of the multidiameter tube to prevent the end cap 50 from completely passing into the first end portion 12. Because the cover 53 acts as a stop, the first and second filters 30 and 40 may be protected from being crushed by the hollow body 52 of the end cap 50 during the press fit process. Additionally, the cover 53 of the end cap 50 should be thin enough to allow puncture by a needle used in an elution process. The hollow cylindrical body part 92 may be tapered so that the outer diameter D16 of a portion of the hollow cylindrical body part 92 facing the center of the multidiameter tube 10 is smaller than an outer diameter D18 of the hollow cylindrical body part 92 attached to the cover 93. The diameter D16 must be smaller than the inner diameter D3 of the second end portion 14 of the multidiameter tube 10 so that the end of the hollow body part 92 facing the center of the multidiameter tube 10 may enter the second end portion 14. However, the outer diameter D18 of the cylindrical body part 92 attached to the cover 93 should be slightly larger than the inner diameter D3 of the second end portion 14 of the multidiameter tube 10 so that when the end cap 90 is press fit into the second end portion 14 of the multidiameter tube 10 the second end portion 14 forms a mechanical seal. Additionally, the inner diameter D17 of the hollow body part 92 should be smaller than the diameter D10 of the frit 80 to prevent the frit 80 from passing into the hollow body part 92. The length L2 of the hollow body part 92 should be long enough to accommodate a needle which may be passed through the cover 93 during an elution process. The length L2 of the hollow body part 92, therefore, should be at least as long as the needle used to introduce or remove a liquid into or from the example capsule for holding, irradiating, and eluting a material. Because the length L2 of the hollow body part 92 is at least as long as the aforementioned needle, the hollow body part 92 protects the third and fourth filters 70 and 80 from being damaged by the needle as the needle is introduced into the capsule. The cover 93 of the end cap 90 has a diameter D19 larger than the inner diameter D3 of the second end portion 14 of the multidiameter tube 10 to prevent the end cap 90 from completely passing into the second end portion 14. Because the cover 93 acts as a stop, the third and fourth filters 70 and 80 may be protected from being crushed by the hollow body 92 of the end cap 90 during the press fit process. Additionally, the cover 93 of the end cap 90 should be thin enough to allow puncture by a needle used in an elution process. An adhesive may be applied to the outer surfaces of the hollow body parts 52 and 92 before the end caps 50 and 90 are press fit into the first and second end portions 12 and 14. The adhesive may provide additionally sealing to prevent materials in the capsule from escaping. The example capsule 1 for holding, irradiating, and eluting a material may also include a first and second seals 200 and 300 for covering the end caps 50 and 90 after the end caps 50 and 90 have been press fit into the first and second end portions 12 and 14, respectively. Examples of the seals 200 and 300 are illustrated in FIG. 14. The first and second seals include a hollow cylindrical body parts 210 and 310 and are closed at one end by end parts 220 and 320. The seals may be made from a flexible material, for example, a non-hardening rubber, so that the seals 200 and 300 can be snug fit over the first and second end portions 12 and 14 to create a second seal. The end parts 220 and 320 of the seals 200 and 300 must be thin enough to allow puncture by a needle used in an elution process. Additionally, the seals 200 and 300 may be epoxied onto the ends of the multidiameter tube 10 by applying epoxy to the inner surfaces of the cylindrical body parts 210 and 310 before the seals 200 and 300 are fitted over the first and second end portions of 12 and 14. The epoxy applied to the inner surfaces of the cylindrical body parts 210 and 310 may provide an extra seal to prevent materials within the capsule 1 from escaping. The multidiameter tube 10, the end caps 50 and 90, and the washers 20 and 60, should be made from materials that have a low nuclear cross section to avoid absorbing neutrons. Examples of such materials include zirconium, quartz, aluminum or alloys including zirconium, quartz, glass and aluminum. For example, the multidiameter tube 10, end caps 50 and 90, and the washers 20 and 60, may be made from zircaloy-2 or alternatively from aluminum 6061, high purity aluminum, and 4N and 5N aluminum. Materials having low nuclear cross section are readily available from manufacturers and are often provided as bar stock. For example, cylinders of zirconium are readily available. The multidiameter tube 10 may be fabricated by implementing a series of boring operations on a solid cylinder, for example, a solid cylinder of zirconium. The cylinder may have an outer diameter D1 and a length. The length of the cylinder may be determined based on the size of the nuclear reactor in which the cylinder will be irradiated and/or the size of a generator used in an elution process. A center of the cylinder may be bored out to a diameter of D4 transforming the solid cylinder into a hollow cylindrical tube. The hollow cylindrical tube may have a constant annular cross section with an inner diameter D4 and an outer diameter D1. One end of the hollow tube may have the diameter increased by a second boring operation to form a first end portion 12 having a length of P1 and an inner diameter of D2. A second end of the hollow tube may likewise have the diameter increased by a third boring operation to form a second end portion 14 having a length P2 and an inner diameter D3. The length P1 should be deep enough to accommodate the above described filters 30 and 40, the washer 20, and the hollow part 52 of the end cap 50. Likewise, the length P2 should be deep enough to accommodate the above described filters 70 and 80, the washer 60, and the hollow part 92 of the end cap 90. The second and third boring operations transform the hollow cylindrical tube into a hollow multidiameter cylindrical tube 10 (see FIG. 3). The first end portion 12 has an annular cross section with an inner diameter D2 and an outer diameter D1 and the second end portion 14 has an annular cross section with an inner diameter D3 and an outer diameter D1. The portion of the tube between the first end portion 12 and the second end portion 14 constitutes a middle portion 16 with an annular cross section having an inner diameter D4 and an outer diameter D1. The depths P1 and P2 of the first end portion and the second end portion 12 and 14 of the multidiameter tube 10 by the second and third boring operations may be the same. In addition, the inner diameters D2 and D3 of the first and second end portions 12 and 14 may be the same. Accordingly, the multidiameter tube 10 may be fabricated to produce a symmetrical structure. The washers 20 and 60 may be fabricated by processes similar to those used in making the multidiameter tube 10. Because the washers 20 and 60 may be made by the same process, the process for making washer 60 is omitted for the sake of brevity. As a starting point, washers may be fabricated from a cylinder of zirconium having an outer diameter of D6 may be provided. The diameter D6 should be smaller than the diameter D2 associated with the first end portion 12 of the multidiameter tube 10. The cylinder may have a length that should be at least as long as a desired thickness for the washer. The cylinder may have the middle bored out to create a hollow tube. The tube has an annular cross section with an inner diameter D5 and an outer diameter D6 (see FIG. 4). An end portion of the tube may be cut along a cut line to form the washer 20 with a desired thickness. The end caps 50 and 90 may be fabricated by processes similar to those used in making the multidiameter tube 10. Because the end caps 50 and 90 may be made by the same process, the process for making the end cap 90 is omitted for the sake of brevity. As a starting point, end caps may be fabricated by a cylinder of zirconium having an outer diameter D14 may be provided. The diameter D14 should be larger than the diameter D2 of the first end portion 12 of the multidiameter tube 10 (see FIG. 3). The cylinder is slightly longer than a length of a needle used to introduce or remove saline solution into or from the capsule 1 during the elution process. The cylinder may be placed in a die which fixes a portion of the cylinder. A first force may be applied to one end of the cylinder to deform the end of the cylinder to create a cover 53. The cover has a diameter D15 larger than the diameter D14 of the cylindrical body 52. After the cover 53 has been formed, a portion of the cylinder below the cover 53 may be bored out to create a hollow body portion. The hollow body portion resembles a circular tube having an annular cross section with an inner diameter D11 and an outer diameter D14. After the hollow body portion is formed, a second force may be applied laterally to the hollow body portion to deform the hollow body portion into a tapered shape. Application of the second force transforms the hollow body portion into a tapered hollow body 52. The end of the tapered hollow body 52 away from the cover 53 has an annular cross section having an inner diameter D11 and an outer diameter D12. The outer diameter D12 should be formed to be smaller than the inner diameter D2 of the first end portion 12 in order to allow the end cap 50 to enter into the first end portion 12. Having fabricated the multidiameter tube 10, the washers 20 and 60, and the end caps 50 and 90 the capsule 1 may be assembled as shown in FIG. 2. The washer 20 may be placed into the first end portion 12 so that the washer 20 bears up against the first shoulder 100. A first filter 30, for example, glass wool made from borosilicate glass, may be placed in the first end portion 12 so that washer 20 is between the first filter 30 and the shoulder 100. A second filter 40, for example, a glass frit made of borosilicate glass, may be provided in the first end portion 12 so that first filter 30 is between the second filter 40 and the washer 20. The end cap 50 may be inserted and press fit into the first end portion 12 thus sealing the first end portion 12. An epoxy may be provided on the outer surfaces of the hollow body part 52 of the end cap 50 before the press fitting operation to provide an extra added sealing means. Formation of the capsule is completed by sealing the second end. The washer 60 may be placed into the second end portion 14 so that the washer 60 bears up against the second shoulder 110. A third filter 70, for example, glass wool made from borosilicate glass, may be placed in the second end portion 14 so that washer 60 is between the third filter 70 and the shoulder 110. A fourth filter 80, for example, a glass frit made of borosilicate glass, may be provided in the second end portion 14 so that third filter 70 is between the fourth filter 80 and the washer 60. The end cap 90 may be inserted and press fit into the second end portion 14 thus sealing the second end portion 14. An epoxy may be provided on the outer surfaces of the hollow body part 92 of end cap 90 before the press fitting operation to provide an extra added sealing means. In addition to the above steps for fabricating the example capsule 1, extra seals 200 and 300 (see FIGS. 2 and 14) may be provided and placed on the ends of the capsule 1 after the first and second end portions 12 and 14 are sealed. The seals 200 and 300 may be provided for an extra seal. These seals may be made from a flexible material such as rubber and may be fabricated to provide a snug fit over the end portions of 12 and 14, of the capsule 1. The seals may include hollow body parts 210 and 310 and cover parts 220 and 320. The cover parts 220 and 320 should be sufficiently thin to allow for puncture by a needle in an elution process. In addition, epoxy may be applied to the inside surfaces of the hollow body parts 210 and 310 before the seals 200 and 300 are placed on the end portions 12 and 14 to provide for extra means for sealing the end portions of 12 and 14, of capsule 1. As disclosed, the example capsule 1 includes a multidiameter tube 10 with a first end portion 12, a second end portion 14, and a middle portion 16 between the end portion 12 and 14. When the tube is in use, the middle portion 16 holds a material for an irradiation process. For example, the middle portion 16 may hold titanium molybdate, zirconium molybdate, titanium tungstenate, zirconyl tungstenate, or other ion exchange resin/gel matrix for elution. The material, for example, may be added to the middle portion 16 after the first end portion 12 has been assembled and sealed by the end cap 50 as described above. After the material is added to the middle portion 16, the second end portion 14 may be assembled and sealed as described above. The sealed capsule 1 (without the seals 200 and 300) including the material to be irradiated may be irradiated in a nuclear reactor. After the irradiation step, the capsule may be removed from the reactor and the seals 200 and 300 may be fixed to the capsule as described above. Referring to FIGS. 15 and 16 a method of eluting the ions generated by the irradiation step and subsequent radioactive decay is described. As shown in FIGS. 15 and 16, the capsule 1 includes an irradiated substance 6000. The elution process comprises two steps. The first step includes puncturing one end of the capsule 1 with a needle 7100 attached to a device 7000 for supplying a liquid, for example, distilled water, deionized water, saline, oxidizers, acids, bases, or any other water based solution, to the example capsule 1. As shown in FIG. 15, the seal 200 and the end cap 50 may be punctured by the needle 7100. However, because the length of the needle is shorter than the length of the hollow body portion 52, the first and second filters 30 and 40 of capsule 1, are not damaged by the needle. In order to draw the liquid through the irradiated substance 6000 as shown in FIG. 16, a needle 8100 attached to a vacuum system 8000, e.g. a vacuum bottle, punctures the end cap 90 and the seal 300. However, because the needle 8100 is shorter than the length of the hollow body 92 of the end cap 90, the third and fourth filters 70 and 80 of capsule 1, are not damaged by the needle 8100. The vacuum from the vacuum system 8000 draws the fluid from the device 7000, through the irradiated material 6000, and into the vacuum system 8000. Accordingly, ions generated during the irradiation decay process may be collected in the vacuum system 8000. While example embodiments have been particularly shown and described with reference to example embodiments thereof, it will be understood by those of ordinary skill in the art that various changes in form and details may be made therein without departing from the spirit and scope of the following claims. |
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056639937 | summary | TECHNICAL FIELD This invention relates generally to fuel bundle assemblies for boiling water nuclear reactors, and specifically to water rod configurations within such assemblies. BACKGROUND Conventional boiling water reactor fuel bundle assemblies utilize one or more water rods extending upwardly through the bundle to provide a source of coolant/moderator to maintain a more uniform distribution of power throughout the bundle. For convenience, reference will be made to water rods in the plural, recognizing that a single water rod bundle is also well known in the art. Typically, the water rods are closed at both ends by end plugs received in upper and lower tie plates of the bundle assembly. Side entry and exit holes are formed in the lower and upper portions, respectively, of each rod to allow a portion of the liquid coolant flowing upwardly through the bundle to pass through the rods. In some cases, the water rods transition at both ends to a larger diameter center section which extends for most of the axial lengths of the rods. It has been attempted to combine side entry holes and a metering device within the lower diameter transition, but this arrangement has not always permitted the accurate regulation of coolant within the water rod, and because of the location of the metering device, is relatively expensive to manufacture. In all cases, it is desirable to accurately meter the flow through the water rods to the amount required to prevent boiling within the rods. If there is too little flow, the coolant will boil within the rods, thus negating the purpose of the rods which is to distribute non-boiling water throughout the bundle length. Too much flow, on the other hand, starves the region around the fuel rods, outside the water rods. DISCLOSURE OF THE INVENTION We now have determined that incorporation of a coolant flow metering device within the water rod end plugs is not only a more cost effective solution to the problem than using entry and exit holes and a separate metering device within the tube, but also a more accurate method in terms of coolant flow regulation. In the exemplary embodiment, a lower end plug construction for water rods is provided which includes a relatively large entry bore, a reduced diameter center bore and an enlarged diameter exit bore. The end plugs are preferably welded to the lower ends of the water rods about annular shoulders formed on the end plugs. The plugs are also provided with external screw threads so that the water rods can be threadably secured to the lower tie plate, but other fastening means may be employed. Accordingly, in its broadest aspects, the present invention relates to a nuclear fuel rod assembly comprising a plurality of fuel rods and at least one water rod held together in a bundle, and wherein end plugs at the lower ends of the fuel rods and the at least one water rod engage a lower tie plate, the improvement wherein the end plug at the lower end of the water rod is hollow and includes a multi-diameter flow metering bore for regulating coolant flow into the water rod. Additional objects and advantages of the invention will become apparent from the detailed description which follows. |
052251500 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to the perspective drawing of FIG. 1 and the cross section of FIG. 2, an integrated head package 22 is provided for a nuclear reactor. The reactor includes a reactor vessel 24 containing nuclear fuel rods carried in a plurality of fuel assemblies 26 between an upper core plate 28 and a lower core plate 32. Each of the fuel assemblies 26 has certain thimble tubes occupying gaps in the pattern of fuel rods, aligned to guide tubes which extend between an upper support plate 34 (shown in FIG. 3) and the upper core plate 28. Control rods 36 as well as instrumentation tubes 42 are movably mounted to be extendable though penetrations 44, 48 in the reactor vessel head 50. The reactor vessel head 50 is a substantial structure, and must withstand pressures in the reactor vessel 24 on the order of 150 bars or about 2,200 psi. The head 50 is sealingly clamped to the reactor vessel 24 by bolts 54. The penetrations 44 for the control rod positioning mechanisms 56 and the penetrations 48 for the instrumentation tubes 42 are capable of withstanding such pressures. Examples of appropriate penetration or seal structures are disclosed, for example, in U.S. patent U.S. Pat. No. 4,983,351--Tower et al; U.S. Pat. No. 3,853,702--Bevilacqua et al, etc. The mechanism 56 for raising and lowering the control rods 36 relative to the fuel assemblies 26 includes control rod positioning shafts 58, which pass through the penetrations 44 in the reactor vessel head 50. A control rod drive coupled to the control rod positioning shafts 58 is disposed above the reactor vessel head 50, but is not shown in order to simply the drawing. The instrumentation tube structures 42 contain sensor arrangements such as a plurality of axially spaced sensors responsive to neutron and gamma radiation, and preferably at least one temperature sensor. The instrumentation tubes 42 can be lowered into certain of the thimble tubes in the fuel assemblies 26 which are not occupied by control rods 36, for placing the sensors in proximity with the fuel rods as well as the coolant in the reactor vessel 24. Electrical couplings for the sensor arrangements extend upwardly through the reactor vessel head 50, the instrumentation tubes 42 and/or their electrical connections likewise passing through penetrations 48 in the reactor vessel head 50 such that the sensor arrangement is retractable relative to the fuel assemblies 26. In the area above the reactor vessel head 50, a seismic support plate 62 is arranged at a space from the reactor vessel head. The seismic support plate 62 provides means for restraining the top of the control rod drive mechanism pressure housing. The seismic support plate 62 must remain precisely positioned relative to the fuel assemblies 26 in the reactor core, so that the control rod positioning shafts 58 always align with their respective thimbles, permitting correct positioning of the control rods 36 even in the event of a seismic disturbance. This preserves the possibility that the reactor can be "scrammed" by fully inserting the control rods 36 into the fuel assemblies 26 to provide maximum damping of nuclear flux. Normally, it would be necessary to couple the seismic support plate 62 to the vessel head 50 by a number of lift rods; however, according to the invention the seismic support plate 62 and the reactor vessel head 50 are coupled by a structurally sound shroud 70, which also provides shielding advantages and provides a means for cooling the mechanisms disposed over the vessel head 50. The shroud 70 is attached to the reactor vessel head 50 and substantially encloses the control rod guide mechanism 56 and at least a portion of the instrumentation tube structures when retracted. The shroud 70 and the reactor vessel head 50 to which the shroud 70 is attached form a structural element of sufficient strength to support the vessel head 50, the control rod guide mechanism 56 and the instrumentation tube structure 42. This arrangement enables the whole integrated head package 22 to be removed from the reactor as a unit for servicing the contents of the reactor vessel 24. At its bottom 72, adjacent the reactor vessel head 50, the shroud 70 is substantially thicker than at its top 74. For example, the shroud 70 can be on the order of five inches (13 cm) thick at the bottom 72, and three inches (8 cm) thick at the top 74. The shroud 70 is shaped as a cylindrical tube, and is attached by welding or bolts to the reactor vessel head 50. The bottom edge of the shroud can be reinforced or provided with a structure which assists in effecting the structural attachment of the shroud and the vessel head. As shown in FIGS. 1 and 2, the bottom edge of the shroud can have a flange 76 providing an attachment to the vessel head 50, preferably including a collar member 82 which is welded to the vessel head 50 and to the flange 76 on the shroud 70, respectively. When it is necessary to remove the reactor head 50 for servicing the reactor contents, the control rods 36 are lowered and the instrumentation tubes 42 are retracted upwardly from the fuel assemblies. The lowermost portions of these structures are the most heavily irradiated because they are placed in close proximity to the fuel rods when the reactor is operational. The reactor vessel 24 is depressurized, and the reactor head 50 is unbolted from its attachment to the vessel. As shown in FIG. 3, a lifting apparatus such as the polar crane normally provided in the reactor containment building is then engaged with the integrated head structure 22, and the entire head structure is lifted away. A pedestal-like support over a pool of water can be provided to support the vessel head, the control rod drive mechanisms and the instrumentation tube structures. The thickest and therefore most effective shielding portions of the shroud protect against escape of radiation from the lowermost, most heavily irradiated portions. Preferably, the head structure includes a lifting rig 92 disposed over the seismic support plate 62, and attached thereto, with the withdrawn instrumentation tube connecting lines 86 passing along the spreader frame 84. At the top of the lifting rig 92, a clevis 88 or similar fitting is provided for coupling to the polar crane, e.g., using a connecting pin. The spreader frame, however, does not support the weight of the integrated head structure 22. For this purpose, a plurality of lift rods 92 couple between the crane clevis 88 and the seismic support plate 62. For example, three lift rods at 120.degree. spacing can be provided between the crane clevis 88 and the seismic support plate 62. The seismic support plate 62 is rigidly fixed to the top edge 94 of the shroud 70, and accordingly the force exerted by the polar crane or other lifting apparatus is applied at the seismic support plate 62 and top shroud edge 94 to lift the head structure 22 away from the reactor vessel 24. In the embodiment shown, the top edge 94 of the shroud 70 is thickened via buttress fittings 96 for each of the lift rods 92. The buttress fittings 96 comprise a downwardly opening channel enclosing over the inside and outside of the shroud 70 at the top 94. The uppermost portion of the buttress fittings is bored and threaded for receipt of a connecting bolt 97 that protrudes through the seismic support plate 62. Nuts 98 provided on the connecting bolt over and under the seismic support plate 62 allow accurate positioning of the seismic support plate 62 as well as a means for rigidly fixing the seismic support plate 62 to the shroud 70. The buttress fittings 96 can be welded to the shroud 70. The shroud 70 is made of steel or similar material which attenuates radiation. Although the shroud 70 in the embodiment shown has two stepwise variations in thickness, it would also be possible to provide additional steps, or a continuous decrease in thickness from the lower portion adjacent the vessel head 50 proceeding upwardly, whereby lower portions of the instrumentation tubes 42 and the like are preferentially shielded by the shroud. FIG. 3 shows the integrated head package 22 of the invention as engaged using the overhead crane or similar lifting apparatus 102, for example having a travelling winch 104. The lifting apparatus 102 is coupled to the clevis fitting 88 at the top of the head package 22. The reactor head 50 is unbolted from the reactor vessel and the entire head package 22 can be lifted away from the reactor, for example to be placed on support 110 therefor. The connection between the lifting apparatus is structurally secure due to the rigid connection defined by the clevis fitting 88, lift rods 92, seismic support plate 62, shroud 70 and reactor head 50. Insofar as the lower more irradiated portions of the instrumentation tubes 42 can be retracted to where they reside above the reactor head 50, the thicker lower section 72 of the shroud 70 shields against escape of radiation. This arrangement can be supplemented using a support structure as shown, having an internal shielded area 112 for the extreme lowermost portions 114 of the instrumentation tubes, which may still extend below the reactor head. The invention having been disclosed in connection with preferred embodiments, a number of variations according to the invention will now become apparent to persons skilled in the art. Whereas the invention is intended to cover a reasonable range of variations in addition to the preferred embodiments discussed in detail, reference should be made to the appended claims rather than the foregoing specification, in order to assess the scope of the invention in which exclusive rights are claimed. |
054523346 | abstract | A new configuration of a pressurized water reactor nuclear fuel assembly having a disengaging upper tie plate corner portion (60) which will disengage if the fuel assembly is unintentionally lifted, thus precluding the lifting of the fuel assembly from the reactor core and thereby avoiding the potential risk of dropping the irradiated nuclear fuel assembly. |
047770112 | summary | The invention relates to a method for checking the dimensions of a nuclear reactor fuel assembly in a water tank, with two mutually parallel probes carrying ultrasonic test heads which are disposed at the free ends thereof, which have acoustic direction directed towards each other and which are movable relative to the fuel assembly, one ultrasonic test head emitting the acoustic waves and the other ultrasonic test head receiving the emitted acoustic waves. Such a method is known from Published European Application No. 0 080 418. In that method the spacing between two fuel rods is determined by means of the pulse/echo method. For this purpose an arm equipped with a transmitting/receiving test head is led past two oppositely situated fuel assembly sides. The echos returning from the fuel rods of the outer row of fuel rods are analyzed in relation to their transit time and provide information on the position of the fuel rods relative to one another or to a normal axis. One of the ultrasonic test heads is used as a transmitter and the other as a receiver, solely as a correction for the temperature-dependent propagation velocity in water. In contrast to this, it is an object of the invention to provide a method and device for checking the dimensions of a fuel assembly for nuclear reactors, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and by means of which the outer contours of a fuel assembly can be measured. With the foregoing and other objects in view there is provided, in accordance with the invention, a method for checking the dimensions of a nuclear reactor fuel assembly in a water tank, with two mutually parallel probes each having a first probe side carrying an ultrasonic test head at a free end thereof with acoustic directions directed towards each other and each having a second probe side facing away from the ultrasonic test head, which comprises transmitting acoustic waves with one of the ultrasonic test heads, receiving the transmitted acoustic waves with the other ultrasonic test head, bringing one of the second probe sides into contact with or placement near a given region of the fuel assembly to be checked, moving the probes towards each other in the direction of the acoustic waves due to contact pressure with the fuel assembly, indicating and assessing or determining the probe movement by a reduction of transit time of the acoustic waves between the test heads, and deriving the actual dimension of the fuel assembly region to be checked while accounting for or considering the dimension of probe movement. A precise measurement of the fuel assembly parts is achieved and damage to the fuel assembly is avoided through the combination of an elastic stop or guide with an indicator of the point in time of contact and of the deflection of the finger of the guide or stop. In order to carry out the method, there is provided a device for checking the dimensions of a nuclear reactor fuel assembly in a water tank, comprising two mutually parallel probes having free ends, first probe sides facing toward each other and second probe sides facing away from each other, ultrasonic test heads each being disposed on a respective one of the first probe sides at the free end of one of the probes, the ultrasonic test heads having acoustic directions directed towards each other, one of the ultrasonic test heads transmitting acoustic waves and the other of the ultrasonic test heads receiving the transmitted acoustic waves, a feeler or sensor disposed on one of the second probe sides, a roller connected to the feeler, means for bringing the roller into contact with a given region of the fuel assembly to be checked causing the probes to be moved closer together in the direction of the acoustic waves due to contact pressure with the fuel assembly, means for indicating and assessing movement of the probes by a reduction of transit time of the acoustic waves between the test heads, and means for deriving the actual dimension of the given fuel assembly region to be checked while accounting for dimensions of movement of the probes. In addition to a gentle treatment of the fuel assembly surface, the roller construction provides the possibility of checking a fuel assembly region for alignment deviations. 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 a method and device for checking the dimensions of a fuel assembly for nuclear reactors, 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. |
053435079 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention The invention relates to the field of cooling arrangements for nuclear reactors when in a shutdown mode. In particular, the invention provides a cooling system that is separately powered and operable independently of the residual heat removal system of the reactor, and is arranged to cool the seals of the primary reactor coolant pump(s) and the primary core coolant. 2. Prior Art Pressurized water and boiling water nuclear reactors having a number of cooling systems operable during different phases of reactor operation to remove heat produced by nuclear fission in the reactor core. The primary operational function of the reactor is to heat a liquid coolant that is pumped through a primary coolant circuit having the reactor vessel in series with means for converting the heat energy in the coolant to motive energy, for example to operate an electrical generator. This primary operational function can be considered a cooling function, i.e., cooling the reactor core, as well as an energy transfer function. In a pressurized water reactor, the primary coolant circuit includes a stream generator in series with the reactor, for producing stream in coolant water that is isolated from the primary coolant by a heat exchanger. The steam produced by the steam generator drives a turbine coupled to an electric generator. Thus the primary coolant circuit removes heat energy from the reactor core and moves it to the stream generator. In a pressurized water reactor, the primary coolant circuit is operated at substantial pressure (e.g., 150 bar) such that the water does not boil at the substantial temperature to which the coolant is heated (e.g., 30.degree. C.). One or more reactor coolant pumps circulates the coolant in the loop including the respective heating and heating-dissipating (energy extracting) elements. This coolant pump requires shaft sealing to maintain the pressure barrier, and the coolant pump seals can be cooled by a further flow of coolant (normally from a different source than the primary coolant circuit), to maintain the integrity of the seals. A second cooling funtion is provided for safety reasons, to deal with the possibility of a loss of primary coolant circuit function during operation of the reactor. A breach in the primary coolant circuit, for example, could allow the core to overheat, resulting in damage to the nuclear fuel. A pressurizer arrangement injects additional coolant into the circuit to maintain operational pressure and to replace coolant that may be lost through a minor breach or leak in the coolant circuit. Various techniques are known for cooling the reactor core in the event of a major breach such as the rupture of a conduit in the primary coolant circuit. Neutron absorbing control rods can be inserted into the fuel array quickly to damp the nuclear reaction, for example when the sensed coolant pressure drops. However, it remains necessary to cool the operationally-heated fuel. A volume of emergency cooling water can be maintained, to be pumped or released by gravity into reactor vessel, such that the emergency cooling water can cool the core. Such an arrangement can involve circulating the emergency coolant, such as by condening and recycling stream released from the coolant water when boiledby the hot core. Alternatively or in additiion, one or more heat exchangers can be used to move heat from the coolant to some external sink. A third cooling function applies when the reactor is not operational but the nuclear fuel in the reactor vessel continues to generate heat due to nuclear decay. Residual heat removal arrangements, such as disclosed in U.S. Pat. No. 4,113,561-Fidler et al, provide additional conduits, pumps and heat exchangers for removing heat from the core when the reactor is not operating to generate electric power. Such systems may be coupled directly to the primary coolant circuit as in Fidler et al, or coupled through heat exchangers as in U.S. Pat. No. 4,830,815-Gluntz. Arrangements for emergency cooling and those for residual heat removal are similar to one another and similar to operational power generation in that each is directed to moving heat energy away from the core. However, the source of the cooling water employed, the manner in which the particular cooling system is powered, the pressure at which the system must operate, the cooling capacity required in view of precisely how the reactor is cooled, the relative gravity of the situation, and other aspects are quite different. Most nuclear power plants have several sources of electric power, including the power generated locally the turbine/generator, offsite power from the normal electric power grid, and emergency power generated by emergency diesel generators. Typically, two emergency diesel generators are provided such that one generator is available if the other should fail to operate. The emergency generators are "safety grade," and in design planning to prepare for potential accidents and similar contingencies, at least one of the emergency generators typically is assumed to be available for powering shutdown functions and emergency cooling in the event of a design basis accident during operation of the reactor. Similarly, at least one diesel generator is assumed to be available for powering residual heat removal functions when the reactor is not generating operational power, that is, during shutdown. As with many safety systems employed with nuclear reactors, the emergency generators are designed for high reliability and automatic actuation. The generators are physically separated from one another to reduce the likelihood that both will be damaged by a forseeable, if unlikely, accident. Nevertheless, the assumption that at least one emergency power source will always be available is questionable. During shutdown, power generated locally by the reactor is not available. It is not inconceivable that in the event of a major disruption, power from the power grid and both of the two emergency generators may be unavailable as well. (An actual occurrence of this situation is described in US NRC Document NUREG-1410.) If none of the respective power source is available, there are two primary concerns applicable durnig shutdown. If the reactor coolant system is hot and pressurized, a first concern is cooling the seals of the reactor coolant pumps to maintain the pressure barrier. With loss of cooling, the hot reactor coolant seals degrade from the effects of hot coolant, causing increased leakage of coolant and unintended depressurization. When the reactor core is in shutdown and depressurized, a further concern is removal of decay heat that is still being generated by the core. If all poer is lost and cooling functoins are disabled, the reactor coolant system will reheat, and could boil away the coolant, leaving the reactor core without any means to remove heat generated by the core. Whereas existing nuclear power plant designs provide pump seal cooling and residual heat removal functions using the primary valves, pumps, heat exchangers and other service elements that operate when power is available, it would be advantageous to provide a cooling system that is not dependent on the design basis emergency backup diesel generators, and is useful during shutdown to maintain minimal cooling functions, including at least cooling of the reactor coolant pump seals, even when all other sources of power are lost. SUMMARY OF THE INVENTION It is an object of the invention to provide a shutdown system for maintaining critical cooling functions in the event of a loss of design basis electrical power. It is also an object of the inventioin to remove normal decay ehat from a nuclear reactor for protecting the reactor pump selas, suing a dedicated automatically actuated cooling system driven from a power source that is independent of backup emergenc power sources. It is a further object of the invention to provide independent reactor pump seal cooling using an auxiliary cooling water source and a dedicated cooling pump, coupled by automatic start logic to a dedicated power source that is independent of general backup power systems. These and other objects are accomplished by a shutdown cooling system for operation during lapse of power. The system has a high pressure pump operable to deliver cooling water to the reactor coolant pump seals, a low pressure pump for core coolant circulation, and a cooling mechanism for decay heat removal. Power for the pumps and all necessary electrical equipment is provided by an independent dedicated power source, thereby providing decay heat removal and protection of the coolant pump seals regardless of operational status and emergency power availability from the backup emergency generators. |
description | This application claims the benefit of priority to U.S. Provisional Application Ser. No. 60/412,931, filed Sep. 23, 2002, and entitled “Improved Gas Cluster Ion Beam Processing and Apparatus Therefor” which is incorporated herein by reference. The present invention relates generally to the formation of and application of increased-current gas-cluster ion beams (GCIB's) for processing the surfaces of workpieces, and, more particularly to reducing space charge effects in GCIB's, reducing workpiece charging, and to improving the measurement accuracy of GCIB currents and doses. The use of GCIB's for processing surfaces is known (see for example, U.S. Pat. No. 5,814,194, Deguchi et al.) in the art. For purposes of this discussion, gas clusters are nano-sized aggregates of materials that are gaseous under conditions of standard temperature and pressure. Such clusters typically consist of aggregates of from a few to several thousand molecules loosely bound to form the cluster. The clusters can be ionized by electron bombardment or other means, permitting them to be formed into directed beams of controllable energy. Such ions typically carry positive charges of q×e (where e is the electronic charge and q is an integer greater than or equal to one). The larger-sized clusters are often the most useful because of their ability to carry substantial energy per cluster ion, while yet having only modest energy per molecule. The clusters disintegrate on impact, with each individual molecule carrying only a small fraction of the total cluster energy. Consequently the impact effects of large clusters are substantial, but are limited to a very shallow surface region. This makes ion clusters effective for a variety of surface modification processes, without the tendency to produce deeper subsurface damage characteristic of conventional monomer ion beam processing. Means for creation of and acceleration of such GCIBs are described in the reference (U.S. Pat. No. 5,814,194) previously cited. Presently available ion cluster sources produce clusters ions having a wide distribution of sizes, N (where N=the number of molecules in each cluster—in the case of monatomic gases like argon, an atom of the monatomic gas will be referred to as a molecule and an ionized atom of such a monatomic gas will be referred to as a molecular ion—or simply a monomer ion—throughout this discussion). Many useful surface processing effects can be achieved by bombarding surfaces with GCIB's. These processing effects include, but are not necessarily limited to, smoothing, etching, and film growth. In many cases it is found that in order to achieve industrially practical throughputs in such processes, GCIB currents on the order of hundreds to thousands of microamps are required. Space charge effects in ion beams are expected when Poissance as defined by A. T. Forrester in Large Ion Beams, Wiley, New York (1987) approaches unity. In the case of a 400 μA beam with an N/q ratio of 5000, the Poissance varies with the GCIB acceleration voltage up to about 0.3 or so depending on exact operating conditions. Accordingly, some space charge beam expansion would be expected and is observed. Particularly at low acceleration voltages, providing a degree of space charge neutralization to the beam by providing a source of low energy electrons enhances the ability to transport larger gas-cluster ion beam currents and reduces beam spot size. In the beamline of a practical production GCIB processing tool, to minimize beam loss due to space charge expansion of the beam, it is useful to keep the beamline as short as practical (˜50 cm) and the beam size at the workpiece is nevertheless relatively large (˜6 cm). In the prior art, a simple thermionic electron emitter in the vicinity of the beam has been used to provide space charge neutralizing electrons. In order to achieve successful transport of higher beam currents (compared to the typical hundred or so microamps in practical prior art GCIB tools) it is highly desirable to achieve more effective space charge neutralization in the GCIB. Another important consideration in extending the useful GCIB beam currents to increase processing throughput is the fact that the workpiece can be charged up by the effects of the GCIB bombardment. This is especially important when the workpieces are semiconductor substrates, magnetic memory sensors, or other charge sensitive materials. Workpiece surface charge neutralization is required for successful GCIB processing. In some applications, such as magnetic memory smoothing, the requirements are even more stringent than for semiconductor devices and a maximum surface charging of ±6 volts or even less is required for successful processing. Low energy electrons supplied to the GCIB and the workpiece surface can provide surface charging control as well as GCIB space charge control, but in order to achieve low workpiece charging potentials under varying conditions, such electrons must be low energy. In the past it has not been practical to achieve satisfactory space charge neutralization and to simultaneously control workpiece surface charging at acceptably low potentials. Simple thermionic filament electron sources act as space-charge-limited-diodes, and thus do not readily emit adequate quantities of electrons. It is possible to dramatically reduce the space-charge-limited-diode effect by using an accelerating potential to extract electrons from a thermionic filament's space charge region. This can dramatically increase electron current emission, but results in an increased electron energy problem and in unacceptable risk of workpiece negative charging by energetic electrons if the GCIB should fluctuate momentarily or be momentarily interrupted. Thus, while an accelerated electron source can provide suitably high electron currents, the risk of high energy electrons charging the workpiece make the method unacceptable in many sensitive applications. For GCIB process control purposes, it is important to be able to measure and control the GCIB intensity. One convenient way of achieving this is by measuring the GCIB current. Faraday cups have traditionally been used as ion beam current measuring devices and are well known in the art of conventional monomer ion beams and have been used successfully for low current GCIB measurement. Inherently, a gas-cluster ion beam transports gas. For an argon beam having a beam current, IB, the gas flow, F (SCCM), in the beam is F = 2.23 × 10 - 18 ( N q ) ( I B e ) ( Eqn . 1 ) With a beam current of 400 μA and an N/q ratio of 5000, the beam conducts a gas flow of 27 SCCM. In a typical GCIB processing tool the ionizer and the workpiece being processed are each typically contained in separate chambers. This provides for better control of the substrate processing pressure. However, a major area of difficulty with beams carrying large amounts of gas occurs in terms of beam current measurement. The entire gas load is released when the cluster beam strikes the inside of the faraday cup. Charge exchange and gas ionization by the beam within the confines of the faraday cup become extreme and significant measurement errors occur with conventional faraday cup designs. It is therefore an object of this invention to provide a neutralizer capable of providing large neutralizing electron currents but having low electron energy. It is also an object of this invention to provide a method of effective space charge neutralization of a high current GCIB. It is a further object of this invention to provide an improved method of limiting the charging of the surface of a workpiece being processed by GCIB. Another object of this invention is to provide an improved faraday cup for beam current measurement in beams having high gas transport. A still further object of this invention is to provide a method for accurate measurement of gas-cluster ion beam current in GCIBs transporting large amounts of gas. The objects set forth above as well as further and other objects and advantages of the present invention are achieved by the embodiments of the invention described hereinbelow. An improved GCIB neutralizing apparatus is comprised of an array of one or more thermionic filaments disposed around a GCIB axis. A cylindrical mesh acceleration electrode draws the thermionic electrons away from the filament(s), directing them toward the GCIB axis, helping to overcome the well known space-charge-limited-diode effect. A second cylindrical mesh deceleration electrode decelerates the accelerated electrons, causing them to travel into the GCIB with a very low energy. This acceleration/deceleration (Accel/Decel) electron source provides high electron emission, while delivering the space charge neutralizing electrons with very low energies. Thus, the electrons are especially effective at reducing GCIB space charge effects including the beam expansion problem that otherwise tends to limit the ability to deliver high GCIB currents to the workpiece. Additionally, the low energy electrons are transported by the beam potential-well to the workpiece to neutralize any charging that might otherwise tend to occur at the workpiece. Because copious quantities electrons are available, beam induced charging is minimal. Because the electrons have very low energies due to their Accel/Decel generation, they do not tend to charge the workpiece excessively negatively if the beam momentarily fluctuates. Thus, both positive and negative workpiece charging is limited to less than a few volts. The effective space charge neutralization in the GCIB results in the ability to transport larger GCIB currents. The larger GCIB currents cause an increased mass flow of gas clusters to the workpiece and to the beam current measuring device. To avoid impairment of beam current measurement accuracy due to the large gas load that is accordingly released in the beam current measuring device, an improved faraday cup is utilized. The improved faraday cup is vented to facilitate the efficient removal of the beam-transported gas by the system's vacuum pumping system. It also has a novel biasing scheme and geometry that reduces measurement errors that would otherwise result. The improved faraday cup is cylindrical and consists of flat disk-electrodes stacked together with gaps between them to allow the beam transported gas to escape. The spacing between the disks is smaller than their radial extent so that electrical suppression fields fill the gaps. The suppression rings nearest the beam strike plate are biased by a supply with the positive terminal connected to the metering circuit. These rings suppress secondary electrons from the target plate and at the same time collect ions produced by charge exchange. Since the bias field needed to suppress to the center of the beam necessitates several kilovolts of bias, secondary ions striking the floating suppression ring set can generate secondary electrons, a portion of which could potentially escape between the rings. To collect these electrons an intermediate ring set is connected to the faraday cup strike plate and a slight negative bias is added on the outside rings opposite these intermediate rings. To encourage gas to escape laterally from the faraday cup, the strike plate incorporates grooving on its surface, preferably concentric circular grooves. To test the improved faraday cup, a much smaller and more conventional faraday cup with a very narrow slit to limit gas loading was scanned in front of the improved faraday cup and comparative measurements were made. This smaller conventional faraday cup included means for gas removal and its signal was integrated as it scanned across the beam, to determine total current in the beam. The two faraday cups agreed within about 2% with most of the difference attributable to systematic errors in the smaller conventional faraday cup. For a better understanding of the present invention, together with other and further objects thereof, reference is made to the accompanying drawings and detailed description. Preferred embodiments of the present invention will now be described with reference to the several figures of the drawing. FIG. 1 shows a schematic of the basic elements of a typical configuration for a GCIB processor 100 of a form known in prior art, and which may be described as follows: a vacuum vessel 102 is divided into three communicating chambers, a source chamber 104, an ionization/acceleration chamber 106, and a processing chamber 108. The three chambers are evacuated to suitable operating pressures by vacuum pumping systems 146a, 146b, and 146c, respectively. A condensable source gas 112 (for example argon or N2) stored in a gas storage cylinder 111 is admitted under pressure through gas metering valve 113 and gas feed tube 114 into stagnation chamber 116 and is ejected into the substantially lower pressure vacuum through a properly shaped nozzle 110. A supersonic gas jet 118 results. Cooling, which results from the expansion in the jet, causes a portion of the gas jet 118 to condense into clusters, each comprised of from several to several thousand weakly bound atoms or molecules. A gas skimmer aperture 120 partially separates the gas molecules that have not condensed into a cluster jet from the cluster jet so as to minimize pressure in the downstream regions where such higher pressures would be detrimental (e.g., ionizer 122, high voltage electrodes 126, and process chamber 108). Suitable condensable source gases 112 include, but are not necessarily limited to argon, nitrogen, carbon dioxide, oxygen, and other gases. After the supersonic gas jet 118 containing gas clusters has been formed, the clusters are ionized in an ionizer 122. The ionizer 122 is typically an electron impact ionizer that produces thermoelectrons from one or more incandescent filaments 124 and accelerates and directs the electrons causing them to collide with the gas clusters in the gas jet 118, where the jet passes through the ionizer 122. The electron impact ejects electrons from the clusters, causing a portion the clusters to become positively ionized. A set of suitably biased high voltage electrodes 126 extracts the cluster ions from the ionizer, forming a beam, then accelerates them to a desired energy (typically from 1 keV to several tens of keV) and focuses them to form a GCIB 128. Filament power supply 136 provides voltage VF to heat the ionizer filament 124. Anode power supply 134 provides voltage VA to accelerate thermoelectrons emitted from filament 124 to cause them to irradiate the cluster containing gas jet 118 to produce ions. Extraction power supply 138 provides voltage VE to bias a high voltage electrode to extract ions from the ionizing region of ionizer 122 and to form a GCIB 128. Accelerator power supply 140 provides voltage VACC to bias a high voltage electrode with respect to the ionizer 122 so as to result in a total GCIB acceleration energy equal to VACC electron volts (eV). One or more lens power supplies (142 and 144 shown for example) may be provided to bias high voltage electrodes with potentials (VL1 and VL2 for example) to focus the GCIB 128. A workpiece 152, which may be a semiconductor wafer or other workpiece to be processed by GCIB processing, is held on a workpiece holder 150, disposed in the path of the GCIB 128. Since most applications contemplate the processing of large workpieces with spatially uniform results, a scanning system is desirable to uniformly scan the GCIB 128 across large areas to produce spatially homogeneous results. Two pairs of orthogonally oriented electrostatic scan plates 130 and 132 can be utilized to produce a raster or other scanning pattern across the desired processing area. When beam scanning is performed, the GCIB 128 is converted into a scanned GCIB 148, which scans the entire surface of workpiece 152. FIG. 2 shows a schematic of the basic elements of a prior art GCIB processing apparatus 200 having a stationary beam with a mechanically scanned workpiece 152, and having a conventional faraday cup for beam measurement and a conventional thermionic neutralizer. GCIB formation is similar to as is shown in FIG. 1, but in the mechanically scanning GCIB processor 200 of FIG. 2, the GCIB 128 is stationary (not scanned) and the workpiece 152 is mechanically scanned through the GCIB 128 to distribute the effects of the GCIB 128 over a surface of the workpiece 152. An X-scan actuator 202 provides linear motion of the workpiece holder 150 in the direction of X-scan motion 208 (into and out of the plane of the paper). A Y-scan actuator 204 provides linear motion of the workpiece holder 150 in the direction of Y-scan motion 210, which is typically orthogonal to the X-scan motion 208. The combination of X-scanning and Y-scanning motions moves the workpiece 152, held by the workpiece holder 150 in a raster-like scanning motion through GCIB 128 to cause a uniform irradiation of a surface of the workpiece 152 by the GCIB 128 for uniform processing of the workpiece 152. The workpiece holder 150 disposes the workpiece 152 at an angle with respect to the axis of the GCIB 128 so that the GCIB 128 has an angle of beam incidence 206 with respect to the workpiece 152 surface. The angle of beam incidence 206 may be 90 degrees or some other angle, but is typically 90 degrees or very near 90 degrees. During Y-scanning, the workpiece 152 held by workpiece holder 150 moves from the position shown to the alternate position “A”, indicated by the designators 152A and 150A respectively. Notice that in moving between the two positions, the workpiece 152 is scanned through the GCIB 128 and in both extreme positions, is moved completely out of the path of the GCIB 128 (over-scanned). Though not shown explicitly in FIG. 2, similar scanning and over-scan is performed in the (typically) orthogonal X-scan motion 208 direction (in and out of the plane of the paper). A beam current sensor 222 is disposed beyond the workpiece holder 150 in the path of the GCIB 128 so as to intercept a sample of the GCIB 128 when the workpiece holder 150 is scanned out of the path of the GCIB 128. The beam current sensor 222 is typically a faraday cup or the like, closed except for a beam-entry opening, and is affixed to the wall of the vacuum vessel 102 with an electrically insulating mount 212. A controller 220, which may be a microcomputer based controller connects to the X-scan actuator 202 and the Y-scan actuator 204 through electrical cable 216 and controls the X-scan actuator 202 and the Y-scan actuator 204 so as to place the workpiece 152 into or out of the GCIB 128 and to scan the workpiece 152 uniformly relative to the GCIB 128 to achieve uniform processing of the workpiece 152 by the GCIB 128. Controller 220 receives the sampled beam current collected by the beam current sensor 222 by way of lead 214 and thereby monitors the GCIB and controls the GCIB dose received by the workpiece 152 by removing the workpiece 152 from the GCIB 128 when a predetermined desired dose has been delivered. FIG. 3 shows a schematic 250 illustrating an improved neutralizer 270 provided by the present invention and an associated neutralizer electronic system 352 containing supporting power supplies, measurement, and data communication and control cables. Improved neutralizer 270 is disposed so as to surround the beam axis 304 of GCIB 128. GCIB 128 travels through the neutralizer in the direction 306. The improved neutralizer 270 comprises three substantially concentric electrodes and an array of one or more thermionic filaments. In FIG. 3, the improved neutralizer 270 is shown schematically in longitudinal section view. Although 3 to 6 filaments are preferably employed, in FIG. 3, two filaments 252A and 252B are shown to facilitate viewing and understanding. FIG. 4 illustrates a possible arrangement for a 6-filament embodiment. Referring again to FIG. 3, neutralizer electron acceleration electrode 254 is an approximately cylindrical, electrically conductive mesh with high transparency, preferably 90% transparent or more. Neutralizer electron deceleration electrode 256 is a second approximately cylindrical, electrically conductive mesh with high transparency, preferably 90% transparent or more. Neutralizer electron repeller electrode 258 is a third approximately cylindrical, electrically conductive electrode. Electrodes 256, 254, and 258 are substantially concentric, approximately centered on nominal beam axis 304. Neutralizer electronic system 352 contains neutralizer filament power supply 264, which provides neutralizer filament power supply voltage VNF. The negative terminal of neutralizer filament power supply 264 is connected via an electrical lead in cable 354 to the negative ends of filaments 252A and 252B (for example). The positive terminal of neutralizer filament power supply 264 is connected via electrical leads in cable 354 to the positive ends of filaments 252A and 252B (for example) and to neutralizer electron deceleration electrode 256. The positive terminal of neutralizer filament power supply 264 is also connected via electrical leads to the positive terminal of neutralizer electron repeller electrode bias power supply 262 and to the negative terminal of neutralizer electron acceleration power supply 260 and to a terminal of neutralizer emission current transducer/indicator 266. The negative terminal of neutralizer electron repeller electrode bias power supply 262 is connected via an electrical lead in cable 354 to neutralizer electron repeller electrode 258. The positive terminal of neutralizer electron acceleration power supply 260 is connected via an electrical lead in cable 354 to neutralizer electron acceleration electrode 254. Neutralizer filament power supply voltage VNF is typically a few volts and is chosen to heat the filaments to incandescence for thermionic emission of electrons. Filament diameters are chosen to be such that less than 10 volts (preferably less than 6 volts) is dropped across the filaments. Thus, VNF is less than 10 volts (preferably less than 6 volts). Electrons (symbolized e-) 268A, 268B, and 268C (shown for example) emitted by the filaments 252A and 252B are attracted and accelerated by neutralizer electron acceleration electrode 254, which extracts them from the space charge cloud surrounding the filaments 252A and 252B, increasing the electron emission well beyond the space-charge-limited-diode condition that would otherwise prevail. Between the neutralizer electron acceleration electrode 254 and the neutralizer electron deceleration electrode 256 the electron is decelerated. Since the neutralizer electron deceleration electrode 256, is biased with the potential of the positive end of the filaments 252A and 252B, the electron are decelerated to thermal energy plus, at most, VNF, that is less than 10 (preferably less than 6) electron volts. When VNF is less than 6 volts, the extracted electrons do not charge surfaces they strike in excess of approximately 6 volts. Neutralizer electron repeller electrode bias voltage VNR is approximately 120 volts (for example) and biases the neutralizer electron repeller electrode 258 so as to cause any electrons 268D (symbolized e-) emitted in a direction away from the GCIB 128 to be reflected back toward the GCIB 128 so as to be accelerated and then decelerated into the beam path. Electrons, which pass through the beam, enter the grids on the opposite side and are re-circulated back through the beam. Neutralizer electron acceleration power supply 260 provides neutralizer electron acceleration voltage VNA and is approximately 50 to 250 volts (for example). It biases the neutralizer electron acceleration electrode 254 so as to extract electrons from the space charge cloud surrounding the filaments 252A and 252B. Neutralizer emission current transducer/indicator 266 measures the total emission current of the filaments, IEMIS With two or three filaments of approximately 10 cm length, emission currents of several milliamps of low energy electrons can be achieved, more than enough to effectively space charge neutralize GCIBs of at least several hundred microamps. After orbiting within the neutralizer, these electrons escape through the ends of the neutralizer cylinder and travel along the beam potential well to provide space charge neutralization up- and down-stream. The down-stream current is also available for minimizing workpiece charging during GCIB processing. Neutralizer electron acceleration power supply 260, neutralizer electron repeller electrode bias power supply 262, neutralizer filament power supply 264, and neutralizer emission current transducer/indicator 266 are all preferably remotely controllable and readable instruments or circuits and may communicate data and control signals with a higher level system controller. They have their control and data connections supplied to such higher level system controller by electrical connections in cable 356. FIG. 4 shows a schematic of an end view of the improved neutralizer 270 of the invention (looking in the direction of GCIB 128 travel). This view clarifies that the improved neutralizer 270 electrodes are substantially cylindrical and substantially concentric. In this figure, a case of six filaments 252A, 252B, 252C, 252D, 252E, and 252F is illustrated. The filaments are seen in end view in this figure and are typically (though not necessarily) parallel to the GCIB 128 (also seen in end view in this figure). The improved neutralizer 270 has a clear aperture 272 for beam transmission. It is recognized that other quantities of filaments are practical, with two to sixteen being preferred. When there are multiple filaments it is preferable to dispose them equally spaced on the circumference of a mounting circle (as shown in this figure for a case of six filaments). FIG. 5 shows a schematic 300 of the improved faraday cup 302 of the invention and its associated faraday cup electronic system 358 including power supplies and measurement electronics. The improved faraday cup 302 is a vented faraday cup with novel biasing to assure accuracy of beam current measurements for GCIBs that transport a high gas load to the faraday cup. The improved faraday cup 302 is cylindrical, substantially concentric with the GCIB beam axis 304, and consists of several sets of flat disks stacked with gaps between them to allow the GCIB-transported gas to escape. The disks are held and maintained in their proper positions with insulating supports, not shown in FIG. 5. The GCIB 128, traveling in direction 306, enters through the opening in the defining aperture 320 and strikes a circular beam strike plate 308. Strike plate 308 is grooved with a series of saw-tooth grooves 310, which are preferably circular grooves concentric with the beam axis 304. These grooves facilitate lateral direction of the gas deposited on the strike plate by the GCIB 128. The beam strike plate 308 is electrically connected via a lead in cable 362 to the beam current (IB) measurement system 330. The beam current, IB, flows through the measurement system 330 to ground. The conventional beam current measurement system 330 maintains the strike plate 308 potential at a virtual ground potential. The flat concentric disks that form the faraday cup are arranged and electrically connected in several groups. The group of suppression rings 312 nearest the strike plate 308 are biased negative with respect to the beam strike plate by a floating (isolated from ground) power supply 328 by a potential VS1. The positive terminal of power supply 328 is connected to the beam strike plate 308. This group of suppression rings 312 suppress secondary electrons from the beam strike plate 308 and at the same time collect positive ions produced by charge exchange between the GCIB and the gas in the faraday cup. Since the bias field needed to suppress to the center of the beam necessitates several kilovolts of bias (VS1 is for example about 3.5 kV), ions striking the group of suppression rings 312 may generate secondary electrons, a portion of which could potentially escape between the rings of the group of suppression rings 312. To collect these electrons an intermediate group of suppression rings 314 is connected to the beam strike plate 308. A third group of suppression rings 316 has a small negative bias, VS2 applied by power supply 326. The group of suppression rings 316 is outermost and returns any secondary electrons escaping the group of suppression rings 312 to the group of suppression rings 314. Generally, the correction due to these secondary electrons is small and in some cases it may be acceptable to eliminate power supply 326 by instead grounding the group of suppression rings 316. When power supply 326 is used, VS2 may typically be set at about 50 volts. Power supply 324 provides voltage VS3 to bias a fourth group of suppression rings 318 negative by several kilovolts (VS3 is typically about 3.5 kV). This bias prevents secondary electrons from the beam strike plate 308 from escaping the faraday cup and prevents electrons outside of the faraday cup from entering. The entrance defining aperture 320 and the group of rings 322 are all grounded via an electrical lead in cable 362 and serve to terminate the electric field from the group of suppression rings 318. The negative terminal of power supply 324 connects to group of suppression rings 318 via an electrical lead in cable 362. The negative terminal of power supply 326 connects to group of suppression plates 316 via an electrical lead in cable 362. Power supply 324, power supply 326, power supply 328, and beam current measurement system 330 are all preferably remotely controllable and readable instruments or circuits and may communicate data and control signals with a higher level system controller. They have their control and data connections made available to such higher level system controller by electrical connections in cable 360. FIG. 6 shows a schematic of the improved GCIB processing system 350 of the invention, including the improved neutralizer 270 and the improved faraday cup 302 as well as their associated support electronics. GCIB formation, mechanical scanning, and other general features are similar to as shown in the prior art of FIG. 2. The improved faraday cup 302 is disposed beyond the workpiece holder 150 in the path of the GCIB 128 so as to intercept a sample of the GCIB 128 when the workpiece holder 150 is scanned out of the path of the GCIB 128. The improved faraday cup 302 is affixed to the wall of the vacuum vessel 102 with an electrically insulating mount 212. A cable 362 provides the electrical connections between the improved faraday cup 302 and its associated faraday cup electronic system 358. A controller 368, which may be a microcomputer based controller connects to the X-scan actuator 202 and the Y-scan actuator 204 through electrical cable 216 and controls the X-scan actuator 202 and the Y-scan actuator 204 so as to place the workpiece 152 into or out of the GCIB 128 and to scan the workpiece 152 uniformly relative to the GCIB 128 to achieve uniform processing of the workpiece 152 by the GCIB 128. Controller 368 receives the sampled beam current collected by the improved faraday cup 302 beam current sensor and its associated faraday cup electronic system 358 including power supplies and measurement electronics. The controller 368 receives the current measurement data and sends control signals to the faraday cup electronic system 358 via electrical cable 360. Controller 368 thereby monitors the GCIB and controls the GCIB dose received by the workpiece 152 by removing the workpiece 152 from the GCIB 128 when a predetermined desired dose has been delivered. Controller 368 receives the measured neutralizer emission current, IEMIS, provided by the improved neutralizer 270 and measured by the neutralizer electronic system 352 via signals on electrical cable 356. Controller 368 also controls the power supplies in the neutralizer electronic system 352 via signals on electrical cable 356, and thus controls the operation of the improved neutralizer. Electrons (364 and 366 for example), symbolized as e-, escape the improved neutralizer along the GCIB 128 and travel up- and down-stream providing GCIB space charge neutralization to improve beam transport and increase available beam current at the workpiece. Electrons (366 for example) traveling along the GCIB 128 in the down-stream direction and having low energy travel to the workpiece and provide a copius source (potentially greater than the GCIB current) of low energy neutralizing electrons to reduce or eliminate workpiece charging during beam processing. The actual amount of electrons traveling to the workpiece is determined by the electrostatic attraction of electrons from the beam due to the onset of workpiece charging. Although the invention has been described with respect to various embodiments, it should be realized this invention is also capable of a wide variety of further and other embodiments within the spirit of the invention. |
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summary | ||
abstract | A combined makeup tank and passive residual heat removal system that places a tube and shell heat exchanger within the core makeup tank. An intake to the tube side of the heat exchanger is connected to the hot leg of the reactor core and the outlet of the tube side is connected to the cold leg of the reactor core. The shell side of the heat exchanger is connected to a separate heat sink through a second heat exchanger. |
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claims | 1. A multi-leaf collimator comprising:a controller and two leaf sets, the two leaf sets being arranged opposite to each other, whereineach of the two leaf sets comprises a plurality of leaves, at least one leaf in the two leaf sets being a small irradiation field leaf, wherein at least one irradiation field hole is provided on the small irradiation field leaf; andthe controller driving the leaves of the two leaf sets is configured to:move the leaves of the two leaf sets so as to form a first irradiation field through which a radioactive beam is permitted to pass, anddrive the small irradiation field leaf to move such that the irradiation field hole moves in a same direction as the small irradiation field leaf and forms a second irradiation field through which the radioactive beam is permitted to pass. 2. The multi-leaf collimator according to claim 1, where the small irradiation field leaf is provided at the central position of the leaf sets. 3. The multi-leaf collimator according to claim 1, wherein the at least one irradiation field hole includes more than one irradiation field hole that is provided on the small irradiation field leaf in an equally-spaced manner. 4. The multi-leaf collimator according to claim 1, wherein the at least one irradiation field hole includes more than one irradiation field hole that has different diameters. 5. The multi-leaf collimator according to claim 1, wherein the at least one irradiation field hole includes more than one irradiation field hole that is provided on the small irradiation field leaf in size order. 6. The multi-leaf collimator according to claim 1, wherein the at least one irradiation field hole includes more than one irradiation field hole that is provided from the center of the small irradiation field leaf to two sides of the small irradiation field leaf in size order sequentially. 7. The multi-leaf collimator according to claim 1, wherein the controller comprises a first control module for controlling and driving the leaves to move along a plane intersecting the radiation beam so as to form the first irradiation field when a desired irradiation field is larger than or equal to the minimum value of the first irradiation field and a second control module for controlling and driving a second irradiation field hole with a desired size in the small irradiation field leaf to move so as to form the second irradiation field when the desired irradiation field is smaller than the minimum value of the first irradiation field. 8. The multi-leaf collimator according to claim 1, wherein widths of the small irradiation field leaves are greater than those of other leaves. 9. A collimation system, comprising:a radioactive source;a pre-collimator; anda multi-leaf collimator; and, whereinthe pre-collimator is arranged below the radioactive source and is configured to guide a radioactive beam emitted by the radioactive source into the multi-leaf collimator; andthe multi-leaf collimator is arranged below the pre-collimator and comprises a controller and two leaf sets, the two leaf sets being arranged opposite to each other, whereineach of the leaf sets comprises a plurality of leaves, at least one leaf in the two leaf sets being a small irradiation field leaf, wherein at least one irradiation field hole is provided on the small irradiation field leaf; andthe controller driving the leaves of the two leaf sets is configured to:move the leaves of the two leaf sets so as to form a first irradiation field through which the radioactive beam is permitted to pass, anddrive the small irradiation field leaf to move such that the irradiation field hole moves in a same direction as the small irradiation field leaf and forms a second irradiation field through which the radioactive beam is permitted to pass. 10. A therapy head, wherein the therapy head comprises;a source body provided with a plurality of radioactive sources;a plurality of pre-collimators; anda plurality of multi-leaf collimators; and, whereinthe plurality of the radioactive sources are arranged below the plurality of the pre-collimators, wherein each of the plurality of the radioactive sources is provided with a corresponding one of the plurality of the pre-collimators and a corresponding one of the plurality of the multi-leaf collimators, and wherein radioactive beams emitted by the plurality of the radioactive sources are focused in a same area through the corresponding pre-collimators and multi-leaf collimators; and,a given one of the multi-leaf collimators comprises a controller and two leaf sets, the two leaf sets being arranged opposite to each other, whereineach of the leaf sets comprises a plurality of leaves, at least one leaf in the two leaf sets being a small irradiation field leaf, wherein at least one irradiation field hole is provided on the small irradiation field leaf; andthe controller driving the leaves of the two leaf sets is configured to:move the leaves of the two leaf sets so as to form a first irradiation field through which a radioactive beam emitted by the radioactive source corresponding to the multi-leaf collimator is permitted to pass, anddrive the small irradiation field leaf to move such that the irradiation field hole moves in a same direction as the small irradiation field leaf and forms a second irradiation field through which the radioactive beam emitted by the radioactive source corresponding to the multi-leaf collimator is permitted to pass. |
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claims | 1. A method of increasing the thermal emissivity of a surface of an object comprising the step of: forming a cavity structure on the surface defining a plurality of cavities, said cavity structure further defining a plurality of cavity apertures and cavity surfaces, wherein said cavity structure has an average cavity area aspect ratio of at least 8. 2. The method of claim 1 , wherein said forming comprises selectively removing material from the surface of the object. claim 1 3. The method of claim 1 , wherein said forming comprises selectively adding material to the surface of the object. claim 1 4. The method of claim 1 , wherein the ratio of the cumulative cross-sectional area of said plurality of cavity apertures to surface area that is not occupied by said plurality of cavity apertures is greater than about 1:4. claim 1 5. The method of claim 4 , wherein the ratio of the cumulative cross-sectional area of said plurality of cavity apertures to surface area that is not occupied by said plurality of cavity apertures is greater than about 2:1. claim 4 6. The method of claim 1 , wherein said plurality of cavity apertures form a geometric array on the surface of the object. claim 1 7. The method of claim 1 , wherein said plurality of cavity apertures are circular in shape. claim 1 8. The method of claim 7 , wherein said plurality of cavity apertures have approximately the same diameter. claim 7 9. The method of claim 1 , wherein the average effective diameter of said plurality of cavity apertures is at least 10 xcexcm. claim 1 10. The method of claim 1 , further comprising the step of backfilling at least a portion of said plurality of cavities in said cavity structure with a material that is substantially transparent to incident and emitted radiation. claim 1 11. A method of controlling the amount of radiation transferred between a surface of an object and its environment in situ, comprising the steps of: forming a cavity structure on the surface defining a plurality of cavities, said cavity structure further defining a plurality of cavity apertures and cavity surfaces, wherein said cavity structure has an average cavity area aspect ratio of at least 8; and changing the degree of blackbody behavior of the surface by changing a physical characteristic of said cavity structure in situ. 12. The method of claim 11 , wherein said physical characteristic is selected from the group consisting of cavity area aspect ratio, cavity longitudinal axis orientation, and combinations thereof. claim 11 13. The method of claim 12 , wherein changing the cavity area aspect ratio is by changing the area of at least a portion of said plurality of cavity apertures. claim 12 14. The method of claim 13 , wherein changing the area of at least a portion of said plurality of cavity apertures is by moving at least one cap proximate said portion of cavity apertures. claim 13 15. The method of claim 14 , wherein said at least one cap incorporates an activate element selected from the group consisting of bimetallic, shape memory, piezoelectric, magnetic, magnetostrictive, and combinations thereof. claim 14 16. The method of claim 13 , wherein changing the area of at least a portion of said plurality of cavity apertures is by deforming said portion of cavity apertures. claim 13 17. The method of claim 12 , wherein changing the cavity area aspect ratio is by changing the area of at least a portion of said plurality of cavity surfaces. claim 12 18. The method of claim 17 , wherein changing the area of at least a portion of said plurality of cavity surfaces is by changing the level of a selector contained in said portion of said plurality of cavities. claim 17 19. The method of claim 11 , further comprising the step of backfilling at least a portion of said plurality of cavities in said cavity structure with a selector, wherein said selector is selected from the group consisting of luminescent materials, liquid crystals, photochromes, electrochromes, and combinations thereof. claim 11 20. The method of claim 11 , wherein changing said physical characteristic is caused by a stimulus selected from the group consisting of temperature, chemistry, biology, humidity, pressure, electrical current, electric field, voltage, magnetic field, electromagnetic radiation, particle radiation, mechanical force, and combinations thereof. claim 11 21. The method of claim 11 , wherein the average effective diameter of said plurality of cavity apertures is at least 10 xcexcm. claim 11 22. A surface structure that increases the thermal emissivity of a surface of an object, comprising: a cavity structure defining a plurality of cavities, said cavity structure further defining a plurality of cavity apertures and cavity surfaces, wherein said cavity structure has an average cavity area aspect ratio of at least 8. 23. The surface structure of claim 22 , wherein the ratio of the cumulative cross-sectional area of said plurality of cavity apertures to surface area that is not occupied by said plurality of cavity apertures is greater than about 1:4. claim 22 24. The surface structure of claim 23 , wherein the ratio of the cumulative cross-sectional area of said plurality of cavity apertures to surface area that is not occupied by said plurality of cavity apertures is greater than about 2:1. claim 23 25. The surface structure of claim 22 , wherein said plurality of cavity apertures form a geometric array on the surface. claim 22 26. The surface structure of claim 22 , wherein said plurality of cavity apertures are circular in shape. claim 22 27. The surface structure of claim 26 , wherein said plurality of cavity apertures have approximately the same diameter. claim 26 28. The surface structure of claim 22 , wherein the average effective diameter of said plurality of cavity apertures is at least 10 xcexcm. claim 22 29. The surface structure of claim 22 , further comprising a material that backfills at least a portion of said plurality of cavities in said cavity structure, said material substantially transparent to incident and emitted radiation. claim 22 30. A controllable surface structure for controlling the amount of radiation transferred between a surface of an object and its environment in situ, comprising: a cavity structure defining a plurality of cavities, said cavity structure further defining a plurality of cavity apertures and cavity surfaces, wherein said cavity structure has an average cavity area aspect ratio of at least 8; and a means to change a physical characteristic of said cavity structure in situ to control the degree of blackbody behavior of the surface. 31. The controllable surface structure of claim 30 , wherein said physical characteristic is selected from the group consisting of cavity area aspect ratio, cavity longitudinal axis orientation, and combinations thereof. claim 30 32. The controllable surface structure of claim 30 , wherein said means is selected from the group consisting of electrical, mechanical, and combinations thereof. claim 30 33. The controllable surface structure of claim 30 , wherein the average effective diameter of said plurality of cavity apertures is at least 10 xcexcm. claim 30 34. The controllable surface structure of claim 30 , further comprising a selector in at least a portion of said plurality of cavities. claim 30 35. The controllable surface structure of claim 34 , wherein said selector is selected from the group consisting of luminescent materials, liquid crystals, photochromes, electrochromes, and combinations thereof. claim 34 |
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041486080 | description | While the invention will be described in connection with certain preferred embodiments, it will be understood that it is not intended to limit the invention to these particular embodiments. On the contrary, it is intended to cover all alternatives, modifications and equivalent arrangements as may be included within the spirit and scope of the invention as defined by the appended claims. Turning now to the drawings, in FIG. 1 there is illustrated a sample preparation system for use in the preparation of samples for radioactive isotope tracer studies, such as studies involving tissue distribution and residue levels of drugs in plants and animals. In the preparation of such samples, a sample of the starting material containing the radioactive isotope tracer, such as a sample of the plant or animal tissue, is burned to convert the carbon in the starting material to carbon dioxide and the hydrogen to water, and the radioactive isotope tracer is then recovered from the resulting combustion products. For example, if the particular radioactive isotope tracer employed is .sup.14 C, it appears in the combustion products as .sup.14 CO.sub.2 gas; if the tracer is tritium (.sup.3 H), it appears in the combustion products as .sup.3 H.sub.2 O in the form of a condensable vapor. Although .sup.14 C and .sup.3 H are the most commonly employed tracers, it will be understood that a number of other radioactive isotopes may be employed, such as .sup.35 S which is converted to sulfate during combustion. In order to provide samples which can be analyzed for radioactivity, the compounds containing the isotope tracers are recovered from the combustion products, and separated from any materials therein which might interfere with the radioactivity determination. For example, the .sup.3 H.sub.2 O is recovered by cooling the combustion products to condense the vapors therein, including the .sup.3 H.sub.2 O, after which the condensed vapors are separated from the remaining gases. The .sup.14 CO.sub.2 may also be recovered by condensation or freezing at extremely low temperatures, such as by the use of liquid nitrogen for example, but it is more conventional to react the .sup.14 CO.sub.2 with a liquid trapping agent such as ethanolamine; the resulting reaction product is then recovered and mixed with a liquid scintillator to provide a sample suitable for use in making a radioactivity determination. Referring now more specifically to FIG. 1, the sample to be burned is placed in a sample basket 10 which forms a part of the electrical ignition system, and also functions as a catalyst for efficient combustion for the sample contained therein. The basket 10 is suitably made of platinum or a platinum-rhodium alloy, so that the basket can be used both as an electrical resistor in the ignition system and as a catalyst for the combustion of the sample. A pair of electrical conductors 11 and 12 extend upwardly from a mounting plate 13, to support the basket 10 at the upper and lower ends thereof, while also making electrical contact with the basket to connect it into the electrical ignition system. The conductors 11 and 12 extend vertically down through the plate 13 and terminate in depending connector pins beneath the plate 13. In order to facilitate the loading of successive samples, the mounting plate 13 is supported on the top of a small platform 14 threaded on to the end of a pneumatic piston rod 15. To load a sample in the basket 10, the pneumatic cylinder and piston assembly 16 associated with the rod 15 is actuated to retract the piston rod 15, thereby lowering the basket 10 through an opening 17 in the bottom of a combustion chamber 18. The sample is then loaded in the basket, and the cylinder and piston assembly 16 is actuated to advance the rod 15 and thereby raise the basket 10 through the opening 17 into the combustion chamber 18. As the platform 14 enters the opening 17, a sealing ring 19 mounted in a groove in the outer periphery of the platform 14 engages the tapered walls of the opening 17 to form a gas-tight seal therewith, as shown in FIGS. 1 and 2. For the purpose of igniting a sample contained in the basket 10 after it has been raised into the combustion chamber 18, the connector pins depending from the plate 13 fit into complementary electrical receptacles 20 in the top of the platform 14. The receptacles 20, in turn, are connected to an electrical igniter circuit including a power source such as battery 21 and an ignition switch 22 for applying an electrical voltage across the basket 10, which serves as a resistive type heating element in the igniter system. Thus, the sample is ignited by simply closing the switch 22, which is opened again as soon as combustion has been initiated. In order to supply the oxygen required for combustion of the sample contained in the basket 10, pure oxygen is supplied to the combustion chamber 18 through a valve 23, a flow meter 24, and a pair of cooperating passageways 25 and 26 formed in the platform 14 and the plate 13. The gas discharge passageway 26 in the plate 13 is positioned directly beneath the center of the basket 10, so that the oxygen is fed directly into the combustion zone. The oxygen flow rate is adjusted, via the valve 23 and flow meter 24, to a level slightly above that required to support combustion of the sample in the basket 10, so that there is a slight excess of oxygen within the combustion chamber. Consequently, there is generally a relatively thin layer of an oxygen-rich atmosphere between the combustion flame and the inside walls of the combustion chamber 18, as indicated by the arrows in FIG. 1. This excess oxygen rises through the combustion chamber and is exhausted from the combustion chamber 18 along with the combustion products through a lateral exit 27 at the top of the chamber. In accordance with one aspect of the present invention, the combustion chamber is open at the upper end thereof with the sidewalls extending upwardly and inwardly above the sample basket so as to approximate the shape of the flame of a burning sample, thereby minimizing the volume of oxygen-rich atmosphere around the flame, and the walls of the combustion chamber are preheated so as to maintain the wall temperature above the condensation temperature of the vapors contained in the combustion products. With this design, the combustion products tend to be swept directly into the exit 27, with the rising layer of oxygen-rich atmosphere along the chamber sidewalls tending to isolate the combustion products from the sidewalls. Moreover, any combustion products that do contact the chamber walls remain in the gas state, even during initiation of the combustion, because the walls are pre-heated and maintained at a temperature above the condensation temperature. Thus, in the illustrative embodiment of the combustion chamber illustrated in FIGS. 1 and 2, the walls of the combustion chamber 18 extend vertically upwardly past the sample basket 10, and then slope inwardly above the basket so as to approximate the shape of the flame represented in broken lines. Surrounding the combustion chamber 18 is a cylindrical vessel 30 which defines an annular cavity around the outer surface of the chamber 18 for receiving a preheating fluid. To center the combustion chamber 18 within the vessel 30, the upper end thereof meshes with a complementary mounting element 31, while the lower end fits into a complementary hole in the bottom wall of the vessel 30. Prior to ignition of the sample contained in the basket 10, the fluid contained in the annular cavity between the combustion chamber 18 and the vessel 30 is heated by means of a heating coil 32 at the lower end of the cavity. The fluid distributes this heat along the walls of the combustion chamber 18 so that the walls are uniformly heated to a temperature above the condensation temperature of the vapors contained in the combustion products to be produced. It has been found that the preheating of the combustion chamber walls to maintain the combustion products in gaseous form even during ignition, combined with the flame-shaped configuration of the chamber, permits the combustion products to be exhausted from the combustion chamber, on a continuous basis, so efficiently that there is virtually no residue of combustion products deposited on the chamber walls. The illustrative system also prevents condensation within the exit 27 of the combustion chamber 18, since the exit is also surrounded by the preheated fluid in the annular cavity between the combustion chamber 18 and the surrounding vessel 31. As the exhausted gases leave the exit 27, they enter a transfer tube 34 which is insulated to maintain the fluids passing therethrough in a gaseous state. In the particular embodiment illustrated, the transfer tube 34 is double walled with a metallic inner shell and an insulating outer shell to minimize the heat loss therethrough. From the transfer tube 34, the gaseous combustion products are passed through a T connection 40 into a heat exchanger 41 for cooling the exhausted combustion products to condense the vapors therein. The heat exchanger 41 includes an inner member 42 forming a fluid passageway for receiving the combustion products from the tube 34, and an outer shell 43 defining an annular cavity around the inner member 42 for receiving a cooling liquid to maintain the walls of the inner passageway at a temperature at least as low as the condensation temperature of the vapors passing therethrough. When the radioactive isotope tracer is in the form of a condensable vapor, such as .sup.3 H.sub.2 O for example, the heat exchanger 41 functions to convert the tracer from a vapor to liquid form. In cases where the radioactive isotope tracer is in the form of a gas to be reacted with a trapping agent, for example, the heat exchanger 41 functions to remove the condensable vapors from the tracer gas before it is reacted with the trapping agent. In accordance with another significant aspect of this invention, the fluid passageway of the heat exchanger is, formed of thermally conductive material designed to provide laminar flow of gases and vapors passing therethrough in the absence of condensation, and the cross section of the fluid passageway is sufficiently small in at least one direction transverse to the fluid flow to provide capillary attraction on the type of liquid condensed within the passageway. Thus, in one preferred embodiment of the invention, the inner member 42 comprises a straight thin walled metal tube having an inside diameter of about 0.05 inch, with a wall thickness of about 0.004 inch, and a length of about 5 inches. Although both the volume and the heat transfer surface area of such a tube are obviously very small, it has been found that such a heat exchanger is capable of reducing the temperature of the combustion gases to the condensation temperature with such a high degree of efficiency that virtually 100% of the condensable vapors can be recovered in liquid form at the outlet end of the heat exchanger. Moreover, this heat transfer is effected without producing a high backpressure or otherwise inhibiting the exhaustion of the combustion products from the combustion chamber directly upstream of the heat exchanger inlet. Although it is not intended to limit this aspect of the invention to any particular theory, it is believed that the fluid passageway designed in accordance with this invention causes droplets of liquid condensate to form along the walls of the passageway, thereby providing extremely efficient heat transfer conditions. This drop-wise condensation may be caused or promoted by the capillary nature of the fluid passageway. When the fluid passageway in the heat exchanger is in tubular form as in the illustrative embodiment, a pulsating pressure is detected at the inlet of the passageway, and it is believed that dropwise condensation may account for this pulsating pressure. It will be appreciated, however, that the fluid passageway may have forms other than tubular, such as a narrow slot, since capillary attraction is present whenever the surface of a liquid where it is in contact with a solid is elevated by the relative attraction of the molecules of the liquid for each other and for those of the solid. As another feature of the present invention, a separating means is connected to the outlet end of the heat exchanger for receiving the combustion products, including the condensed vapors, from the heat exchanger and separating the condensed vapors from the remaining gas products, and control means are associated with the combustion chamber for terminating the oxygen supply and supplying an inert gas to the combustion chamber upon completion of the burning of each sample so as to sweep any residual combustion products out of the chamber and on through the heat exchanger into the separating means. Thus, in the illustrative system, a resilient connector 50 is provided at the lower end of the heat exchanger 41 for connecting the outlet of the fluid passageway member 42 to a conventional sample or counting vial 51. The vial 51 is supported on a platform 52 which is biased upwardly against the connector 50 by means of a biasing spring 53 to provide a gas-tight seal around the upper periphery of the vial. As the combustion products are discharged from the lower end of the heat exchanger 41, they flow downwardly into the sample vial 51 so that the liquids are retained in the vial by gravity, while the gases continue on through a discharge passageway 54 formed in the resilient connector 50. When the combustion of a given sample has been completed, the valve 23 is closed to terminate the oxygen supply to the combustion chamber, and a valve 60 is opened to supply an inert gas such as nitrogen to the combustion chamber via the same flow meter 24 and passageways 25, 26 previously used to supply the oxygen. This inert gas, which is supplied under a slight pressure, sweeps upwardly through the combustion chamber 18 so as to purge the chamber of any remaining combustion products, and continues on through the chamber exit 27, the transfer tube 34, and the heat exchanger 41. Consequently, it can be seen that the entire system from the combustion chamber 18 to the sample vial 51 is immediately purged of all gaseous combustion products following each sample combustion, and the purging gas also tends to sweep any remaining liquid condensate out of the heat exchanger. Moreover, since the inert purging gas is discharged from the heat exchanger 41 into the headspace of the sample vial 51 which is used as a part of the liquid-gas separating means, it may also be used to purge oxygen from the vial headspace to avoid the quenching effect of such oxygen during analysis of the resultant sample for radioactivity. Thus, when the sample vial 51 is disconnected from the resilient connector 50 to place a sealing cap on the vial, the throat of the vial may be maintained directly under the nitrogen discharge from the connector 50 by simply tilting the vial laterally, so that the nitrogen purges the headspace of the vial by displacing any oxygen remaining therein to the atmosphere. As will be apparent to those familiar with this art, this is an important feature because oxygen is a severe quenching agent, i.e., it distorts the radioactivity measurements made by liquid scintillation counting techniques unless certain steps are taken to compensate for the effect of the quenching agent. Although several means of compensating for such quenching effects are known, they complicate the radioactivity measuring procedure. After the purging of the combustion chamber and the heat exchanger, the inert purging gas is preferably turned off by closing the valve 60, and the inlet of the heat exchanger 41 may be sequentially connected to a pair of liquid supply systems generally indicated at 61 and 62. The first supply system 61 includes a supply vessel 63 containing a liquid solvent of the type conventionally used in the preparation of samples to be subjected to sub-freezing temperatures, so as to maintain the sample in a liquid state. It will be understood that this first liquid supply system 61 is not normally used in the preparation of samples to be handled at above-freezing temperature. Referring now more specifically to the liquid supply system 61, an inert gas such as nitrogen is supplied to the headspace of the supply vessel 63 under a slight pressure, so as to force the liquid solvent through a valve 64 into a metering dispenser 65 including a movable piston 65a. As long as the valve 64 remains in the position illustrated in FIG. 1, the piston 65a in the metering dispenser 65 remains in the position illustrated in FIG. 1 and no liquid flows out of the dispenser because the output thereof is effectively closed. However, when the valve 64 is turned 90.degree. to its second position, the pressure of the fluid from the supply vessel 63 urges the piston 65a to the left as viewed in FIG. 1 until it reaches a preselected stop position, thereby metering a preselected quantity of liquid through the valve 64 and the T connection 40 into the heat exchanger 41. As the piston 65a moves to the left, the supply of liquid within the dispenser 65 is continuously replenished through the right hand end thereof. Thus, when the metered quantity of liquid solvent has been dispensed, the system is ready to dispense the same preselected quantity of liquid the next time the valve 64 is turned 90.degree.. It will be understood that the piston 65a moves alternately to the left and to the right during successive dispensing operations. The second liquid supply system 62 is used to feed a preselected quantity of liquid scintillator into the heat exchanger 41 in the same manner described above for the solvent supply system 61. Thus, the liquid scintillator is fed from a supply vessel 66 through a four-way valve 67 into a metering dispenser 68, and is dispensed alternately from opposite ends of the dispenser in response to successive 90.degree. turns of the valve 67. From the valve 67, the liquid flows into the T connection 40 and then downwardly through the heat exchanger 41 into the vial 51. In order to insure that all the liquid supplied to the T connection 40 from the liquid supply systems 61, 62 flows downwardly through the heat exchanger 41, a restriction (not shown) may be formed in the transfer line 34 to prevent liquid from backing up into the line 34 from the T connection 40. As the liquids from the systems 61, 62 flow downwardly through the heat exchanger 41, they are discharged through the connector 50 into the sample vial 51, where they are retained along with the condensed vapors collected previously. It will be appreciated that the connection of the two liquid supply systems to the heat exchanger inlet not only provides a convenient means of supplying these liquids to the sample vial connected to the outlet of the heat exchanger, but also insures that substantially all the condensed vapors are recovered from the walls of the heat exchanger tube 42. In this connection, one of the important advantages of the illustrative system is that the radioactive tracer never passes through any valves or other devices having movable parts, thereby facilitating recovery of the tracer and elimination of equipment memory. Moreover, due to the small volume of the heat exchanger, any fluid contained therein changes at a relatively high rate when fluid is flowing therethrough. To insure that all the liquids fed into the heat exchanger 41 are discharged therefrom, it is preferred to resume the nitrogen flow through the heat exchanger, via the combustion chamber, for a short interval of about five seconds, for example, after the liquid flow from the two systems 61, 62 has been terminated. (This nitrogen flow can also be used to purge the headspace of the vial 51 as it is removed from the connector 50, prior to placement of the cap thereon, in the manner described previously.) With this system, it has been found that essentially 100% of the radioactive isotope tracer present in the starting material can be recovered in the sample vial 51, when the isotope is in the form of a condensable vapor. In accordance with a further important aspect of this invention for recovering tracers by reaction with a trapping agent, the gases which are separated from the condensed vapors are passed into a reaction column including means for receiving a liquid trapping agent and reacting the gases with the trapping agent as the gases flow through the column. The reaction column is also provided with means for reversing the direction of the gas flow through the column for discharging the trapping agent and the reaction product from the column, and a sample vial is connected to the reaction column for receiving the trapping agent and reaction product from the column in response to the reversal of the gas flow. Thus, in the illustrative system, the gases discharged from the first sample vial 51 through the discharge passageway 54 in the resilient connector 50 are passed through a valve 70 which, when in the position shown in FIG. 1, conducts the gases through a connector 71 into a second sample via 72. From the sample vial 72, the gases enter the lower end of a depending stem 73 of a reaction column 74 comprising a series of smoothly contoured reaction chambers 74a interconnected by smoothly contoured necked down portions 74b with the interconnecting walls of the chambers 74a and the necked down portions 74b forming a smooth curvilinear configuration. When the reaction column 74 is used, i.e., when a radioactive isotope tracer is to be recovered by reaction with a trapping agent, a valve 75 is turned 90.degree. from the position shown in FIG. 1 so as to feed a preselected amount of liquid trapping agent into an inlet stem in the middle of the reaction column 74 just after the oxygen supply to the combustion chamber 18 is turned on. Thus, gas is already flowing upwardly through the reaction column 74 when the liquid trapping agent first enters the column. With the particular configuration of reaction column provided by this invention, it has been found that the liquid trapping agent becomes uniformly distributed throughout the various reaction chambers 74a, and such distribution is maintained, as long as gas flows continuously up through the column 74. That is, the upward gas flow through the reaction column causes the liquid trapping agent to become distributed along the walls of the bulbous or enlarged reaction chambers 74a while preventing the trapping agent from flowing down through the elongated depending stem 73 at the bottom of the reaction column, so that no liquid trapping agent enters the vial 72. In order to feed a preselected amount of trapping agent to the reaction column, the liquid is supplied by means of a metering device 77 having a movable piston therein with a predetermined stop position. Thus, the piston 77a is stopped at the same position during each feeding operation, so that the same amount of liquid trapping agent will be supplied for each sample. As long as the valve 75 is in the position illustrated in FIG. 1, the piston 77a in the metering device 77 remains in the position shown in FIG. 1 and no liquid flows into the inlet stem 76. When the valve is turned 90.degree. clockwise, the output of the device 77 is connected to the inlet stem 76, and subsequent advancement of the plunger 77a dispenses a preselected quantity of trapping agent into the reaction column 74; although a manually actuated plunger 77a is shown in the drawings, it will be understood that the dispensing of the liquid trapping agent could be made automatically responsive to the turning of the valve 75. After the metered amount of trapping agent has been fed into the reaction column, the valve 75 is returned to its normal position as illustrated in FIG. 1, and the metering device 77 is automatically refilled with liquid trapping agent from a supply bottle 78, the liquid being fed from the bottle 78 into the metering device 77 by means of pressurized nitrogen in the headspace of the supply bottle 78. As the gases containing the radioactive isotope tracer, such as .sup.14 CO.sub.2 for example, are passed upwardly through the reaction column, the radioactive compound is reacted with the trapping agent, such as ethanolamine for example, to form a reaction product which is held within the reaction chambers 74a along with the liquid trapping agent. The amount of reaction product contained in the series of reaction chambers 74a varies along the length of the reaction column, but it has been found that the reaction effected by the particular reaction column configuration provided by this invention traps over 99% of the isotope tracer. The unreactd gases are exhausted from the upper end of the reaction column through a connector member 79 and vented to the atmosphere through a valve 80. To control the reaction temperature within the column 74, a heat transfer fluid is passed through an annular jacket surrounding the column 74. In this connection, it has been found that the reaction column provided by this invention provides effective heat transfer with a high degree of efficiency when used to carry out gas-liquid reactions. It is believed that the interaction of the upwardly flowing gas with the liquid that is held within the enlarged reaction chambers 74a brings all portions of the liquid into intimate contact with the column walls, thereby effecting efficient heat transfer between the liquid and the column walls. After the sample combustion has been completed, the flow of nitrogen gas is continued for a suitable purging period, e.g. 30 seconds, and the valve 70 is then turned 90.degree. so as to conduct the purging nitrogen gas into the upper end of the reaction column 74, thereby effecting a reversal of the direction of gas flow through the column. As the gas flows downwardly through the reaction column 74, it sweeps the liquids contained therein, including the reaction product formed by reaction of the liquid trapping agent with the gas compound containing the isotope tracer, into the sample vial 72. The gases are discharged from the vial 72 upwardly through the connector 71 and vented to the atmosphere through the valve 70 via passageway 70a therein. The valve 70 is then returned to its original position to resume the gas flow upwardly through the reaction column, and the connector 79 at the upper end of the reaction column 74 may be sequentially connected to a pair of liquid supply systems generally indicated at 81 and 82. The first supply system 81 includes a supply vessel 83 containing a liquid solvent to be used to dissolve the reaction product formed by reaction of the isotope compound with the trapping agent; the solvent may also serve to maintain the resultant sample in a liquid condition where it is to be handled at sub-freezing temperatures, as described previously in connection with the liquid supply system 61. An inert gas such as nitrogen is supplied to the headspace of the supply vessel 83 under a slight pressure so as to force the liquid solvent through a valve 84 into a metering dispenser 85 including a movable piston 85a. As described previously in connection with the liquid dispensers 65 and 68, the piston 85a moves back and forth within the dispenser 85 in response to successive 90.degree. turns of the valve 84, so as to feed a preselected quantity of liquid solvent through the valve 84 into the connector 79 each time the valve 84 is turned 90.degree.. This liquid flows downwardly into the reaction column 74 and is distributed therethrough in the same manner described previously for the liquid trapping agent supplied through the inlet stem 76. It has been found that the combination of the upward gas flow and the liquid input at the top of the column, provides a scrubbing action on the inside walls of the reaction column so that substantially all the reaction produce contained therein is recovered in the sample vial 72. In fact, it has been found that the recovery effected by this reaction column is so efficient that it has substantially no memory whatever, and over 99% of the isotope tracer is recovered in the vial 72. After the first liquid has been dispensed into the top of the reaction column, the nitrogen flow is continued upwardly through the column for a period of about 15 to 45 seconds, depending upon the concentration of CO.sub.2 relative to the trapping agent. The valve 70 is then again turned 90.degree. to reverse the gas flow through the reaction column, thereby sweeping the liquid solvent downwardly through the reaction column into the sample vial 72. The valve 70 is then again returned to its original position so that the inert purging gas once again flows upwardly through the reaction column, and the liquid scintillator is metered into the upper end of the reaction column from the second liquid supply system 82. More particularly, liquid scintillator is fed from a supply bottle 86 through a four-way valve 87 into a metering dispenser 88. When the valve 87 is turned 90.degree. from the position illustrated in FIG. 1, with the dispenser piston 88a in the position shown, a preselected quantity of liquid scintillator is forced out of the dispenser by the pressure of the nitrogen in the headspace of the bottle 86, thereby advancing the piston 88a to the left to force liquid through the valve 87 into the connector 79 at the top of the reaction column 74. Due to the upward gas flow through the reaction column, this liquid again provides a scrubbing action on the walls of the reaction column 74. After the liquid has been dispersed into the column, the upward nitrogen flow is continued for about 5 to 10 seconds, at which time the gas flow is again reversed in the column 74, by turning the valve 70, to discharge the liquid scintillator into the vial 72. In addition to providing a convenient means of admitting the liquid scintillator into the vial 72, the liquid supply systems associated with the reaction column 74 provide a rapid and efficient means of achieving recoveries in excess of 99% with attendant low memories of 1/1000 or less. Moreover, it will be appreciated that the isotope tracer is passed through only a single valve 70, and then only while it is in the gas form, thereby further facilitating complete recovery of the radioactive tracer. In one example of the invention, ten one-gram samples of tritium-labelled samples were combusted in sequence in the same equipment, with a blank sample, i.e., a sample containing no radioactive tracer, being combusted after each labelled sample. The combustion of each sample was initiated by the electrical igniter, heated to a temperature of about 1500.degree. C., and the oxygen flow rate was set at about two liters per minute. The pressure inside the combustion chamber during combustion was less than 0.1 atmosphere above atmospheric pressure. The walls of the combustion chamber were pre-heated and thermostatically maintained at approximately 170.degree. C. which was sufficient to prevent any noticeable condensation of the combustion products on the inside walls of the combustion chamber. During combustion, the combustion products were continuously exhausted through the upper end of the combustion chamber into a heat exchanger, comprising a straight tube of stainless steel having an inside diameter of 0.080 inch, a wall thickness of 0.020 inch, and a length of 10.00 inches. The walls of the tube were maintained at a temperature of about 0.degree. C. From the heat exchanger, condensed vapors including condensed .sup.3 H.sub.2 O dripped into the counting vial connected to the lower end of the heat exchanger, while the remaining gases passed on through the vial and were vented to the atmosphere. The combustion of each sample was completed in about 45 seconds, after which the oxygen was turned off and the nitrogen supply to the combustion chamber was turned on so that nitrogen was fed into the combustion chamber at a rate of seven liters per minute for about five to ten seconds. The nitrogen was then shut off and a selected quantity of dioxane (liquid scintillator) was fed from the netering dispenser into the inlet of the heat exchanger. The metering dispenser was preset to feed ten milliliters of the liquid scintillator into the heat exchanger over a period of about five seconds, after which the liquid supply line to the inlet of the heat exchanger was closed, and the nitrogen feed to the combustion vessel was resumed for an additional five seconds at a rate of about four liters per minute. During this final nitrogen feed, the counting vial was removed from the resilient connector at the outlet of the heat exchanger and tilted with the open mouth of the vial positioned below the passageway from the heat exchanger outlet so that the nitrogen supplied to the counting vial during this interval purged the vial of oxygen. The vial cap was then quickly threaded onto the vial to seal the sample contained therein in a nitrogen atmosphere, and the sample was analyzed for radioactivity. The radioactivity level of the tracer in the starting material placed in the combustion chamber was 100,000 disintegrations per minute (dpm). When the sample collected in the counting vial was analyzed for radioactivity, a count of 42,000 counts per minute (cpm) was measured. The counting efficiency of the analytical method was determined to be 42% so that the measured count of 42,000 cpm indicated that there was no loss whatever, i.e., there was 100% recovery of the radioactive material. To check the accuracy of the radioactivity measurement made for the recovered material, the same amount and type of radioactive isotope tracer that was injected into the original starting material was placed in a second counting vial and analyzed for radioactivity in the same equipment used to analyze the recovered sample. The count measured for this second counting vial was identical to the measurement for the first sample, i.e., the count was 42,000 cpm in each case, thereby confirming that the recovery was in fact 100%. Over the series of ten samples, the standard deviation of recovery was determined to be 0.7%, which is about the same degree of variability accounted for by statistical variations in the samples plus the accuracy of the analytical instrument without automatic standardization. Based on a comparison of the counts of the radioactive samples and the alternate blank samples, a memory of 1/10,000 or less was obtained consistently throughout the entire series of samples. The 42% counting efficiency compares with maximum efficiencies of 25% to 36% obtainable by comparable methods used previously, the improvement being due in large measure to the fact that there was little or no oxygen present in the sample so that quenching effects were minimized or perhaps even eliminated. In addition to the increase in efficiency, there was a corresponding reduction in background, so that the resulting figure of merit (efficiency squared divided by background) was significantly increased. For example, with the 42% efficiency, the background was 27 so that the figure of merit was 650, which compares with a figure of merit of 370 obtainable by the conventional previous methods. The total time required to prepare the above samples was such that about 30 to 40 samples could be prepared per hour. In another example of the invention, 300 milligrams of double-labelled (.sup.3 H and .sup.14 C) material was placed in the combustion chamber and burned in the same manner described above in the previous example. The only differences in the combustion step of this example were that the oxygen flow rate was initially set at about 0.1 liter per minute, and immediately after the oxygen was turned on 2.7 milliliters of ethanolamine (trapping agent) were manually injected into the reaction column. After the ethanolamine was injected into the reaction column, the oxygen feed rate was gradually increased to one liter per minute, and at the same time the pressure in the gas feed line to the reaction column was increased by turning the valve in the atmosphere vent line toward the closed position until the pressure reached 0.3 atmosphere above atmospheric pressure. At this point, the sample was ignited in the combustion chamber in the same manner described in the example above. A white flame was initially produced due to the burning of hydrogen (which burns more rapidly than the carbon and produces a white flame). As this white flame began to diminish, the oxygen flow rate was gradually decreased to about 0.3 liters per minute to complete the combustion of the carbon. The exhaust gases from the combustion chamber were initially rich in water due to the combustion of the hydrogen, and subsequently become richer in carbon dioxide due to the combustion of the carbon. The water was condensed and collected in the first counting vial, while the CO.sub.2 gas was passed on to the reaction column containing ethanolamine as a trapping agent; as the CO.sub.2 passed upwardly through the reaction column, it reacted with the ethanolamine to form a carbamate reaction product. After the combustion was completed, the oxygen was turned off and the nitrogen turned on at a flow rate of 0.3 liters per minute and maintained for about 15 seconds to purge the system of gaseous combustion products. With the nitrogen flow continuing, the valve connected between the first vial and the reaction column was turned to its second position so that the nitrogen flow was fed into the top of the reaction column rather than the bottom, thereby reversing the nitrogen flow through the column to sweep the liquid reaction product, as well as any unreacted trapping agent, downwardly through the reaction column and into the second counting vial. The excess gases were discharged through the connector 71 and the valve 70. After the reaction product was collected in the second counting vial, the valve 70 was returned to its original position, with the nitrogen flow rate being maintained at about 0.3 liter per minute. The nitrogen was then turned off, and the liquid scintillator was fed into the inlet of the heat exchanger in the same manner described above. The nitrogen feed was then turned on again to purge the headspace of the first counting vial in the same manner described above, after which the vial was then removed and replaced with a new vial which simply served as a conduit for the nitrogen gas to be flowed through the system for the balance of the preparation procedure. At this point, the four-way valve associated with the metering device for the liquid solvent was turned to connect the output of the metering device to the top of the reaction column so that the pressure in the headspace of the solvent supply bottle forced a preselected quantity of liquid solvent into the reaction column. As this liquid passed downwardly through the column, the upwardly passing nitrogen gas coacted with the downwardly flowing liquid to create a turbulent condition within the reaction column. The nitrogen flow was maintained for 15 seconds and then again switched to the top of the reaction column so as to sweep the liquid downwardly through the column and into the counting vial. At this point, the valve 70 was returned to its original position so that the nitrogen flow once again entered the bottom of the column and flowed upwardly therethrough. At the same time, the four-way valve associated with the liquid scintillator supply system was turned to connect the output of the metering device to the top of the reaction column so as to feed a preselected metered amount of liquid scintillator into the top of the reaction column in the same manner described previously for the liquid solvent, except that the nitrogen flow was maintained for only 5 seconds, after which the valve 70 was again switched to its second position to conduct the nitrogen into the top of the column and sweep the liquid down into the counting vial. The nitrogen flow rate was then increased to a level of four liters per minute, and the second counting vial was removed from its stopper and tilted thereunder to purge the vial headspace in the same manner described previously for the first counting vial. At this point, the nitrogen flow was shut off and the sample preparation procedure was complete. The amount of liquid solvent fed into the reaction vessel was eight milliliters, and the amount of liquid scintillator was the same. The total sample preparation time for this double-labelled sample was such that 10 to 15 samples could be prepared per hour. The counting efficiency was 70%, the recovery was in excess of 99%, the standard deviation of recovery was 0.9%, and the memory was a maximum of 1/1000. The background was 37, so that the figure of merit was 133. It will be understood from the foregoing description that the illustrative sample preparation system may be used to prepare samples from starting materials labelled with only a single tracer to be recovered either as a condensed vapor or by reaction with a trapping agent, or from double-labelled samples containing tracers to be recovered by both means. In the event that the material is labelled with only a single tracer to be recovered as a condensed vapor, the gases discharged from the first sample vial 51 are, of course, simply passed on through the balance of the system and vented to the atmosphere. In the case of a sample labelled with only a single tracer to be recovered by reaction with a trapping agent, it is not necessary to supply a liquid scintillator to the heat exchanger 41, although it may be desired to feed some other liquid through the heat exchanger in order to remove the condensed vapors therefrom between successive combustions. Similarly, there is no need to feed any liquids whatever into the reaction column 74 when the sample is labelled with only a single tracer to be recovered as a condensed vapor, since the gas is discharged from the vial 51 will normally be vented to the atmosphere via valve 70 during the preparation of such samples. If it is desired to prepare only tritium-labelled samples, for example, that portion of the system downstream of the vial 51 may even be eliminated. It will also be appreciated that any of the manual operations required in the illustrative system may be readily converted to automatic operation. For example, the opening and closing of the oxygen and nitrogen valves 23 and 60, respectively, may be controlled by timing mechanisms according to a predetermined time schedule for particular types of samples. Similarly, the valves 64, 67, 75, 84, and 87 associated with the various liquid supply systems, as well as the valve 70, could be controlled by timing mechanisms according to predetermined time schedules. As can be seen from the foregoing detailed description, this invention provides an improved sample preparation method and apparatus which reduce the sample preparation time far below the preparation times required by the methods and apparatus previously known for the preparation of such samples, with corresponding increases in the sample preparation rate. Consequently, a technician using this system can prepare a much greater number of samples in any given work period, thereby improving the efficiency and reducing the cost of such preparation procedures. This invention significantly increases the efficiency of the isotope recovery from the starting material, permitting recoveries of essentially 100% of the isotope present in the starting material. As a result, the memory of the sample preparation equipment is virtually eliminated, so that the reliability of the resultant samples and the data derived therefrom are greatly improved. The invention also permits the preparation of samples which contain little or no oxygen, thereby minimizing quenching effects. The improved heat exchanger used to recover the condensable vapors provides an extremely high heat transfer with only a small volume and surface area and in a very short time period, and the improved reaction column achieves a high reaction rate between the gas and liquid for the recovery of isotopes to be reacted in gas form with a liquid trapping agent. |
abstract | Technology is described for a collimator assembly for a radiation collimator. In one example, the collimator assembly includes a base and a shutter assembly. The shutter assembly includes a lower shutter and a shutter control. The lower shutter includes a yoke, a control pin, and an inner extension extending from a first end of the yoke and supports the control pin. The shutter control includes a ramp feature that is slidably engaged with the control pin. The yoke rotates as the control pin slides along the ramp feature, and the shutter control is slidably engaged with the base. |
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claims | 1. An apparatus for ultrasonically examining a weld in a nuclear steam supply system, comprising: an elongated guide rod; a collapsible shoe positioned on an end of said elongated guide rod, said collapsible shoe including a first shoe half aligned with a second shoe half, said shoe halves movable between an expanded state and a collapsed state; an ultrasonic transducer positioned within said collapsible shoe; a biasing mechanism biasing said shoe halves continuously against the inner wall of a pipe at a weld location in said pipe, said biasing mechanism comprising two or more aligned biasing elements, said biasing elements being placed within aligned bias chambers in said shoe halves, said biasing elements pressing said collapsible shoe into said expanded state such that is forced against said pipe to ensure ultrasonic coupling between said pipe and said ultrasonic transducer through said collapsible shoe; and a transducer well located in said first shoe half, said transducer well accommodating said ultrasonic transducer when said shoe halves are in said collapsed state. 2. The apparatus of claim 1 wherein said pipe is connected to a cast stainless steel component of said nuclear steam supply system. claim 1 3. The apparatus of claim 2 wherein said pipe is formed in a reactor coolant pump of said nuclear steam supply system. claim 2 4. The apparatus of claim 3 wherein said pipe is a seal injection line. claim 3 5. The apparatus of claim 3 wherein said pipe is a coolant line. claim 3 6. The apparatus of claim 1 wherein said elongated guide rod includes measurement indicia indicating the distance said elongated rod is placed in said pipe. claim 1 7. The apparatus of claim 1 wherein said collapsible shoe includes tapered ends to facilitate transition between a first pipe circumference and a second pipe circumference. claim 1 8. The apparatus of claim 1 wherein the angle at which said ultrasonic transducer is positioned within said collapsible shoe may be altered to produce longitudinal waves between 45xc2x0 and 60xc2x0. claim 1 9. The apparatus of claim 1 wherein the angle at which said ultrasonic transducer is positioned within said collapsible shoe may be altered to produce shear waves at 45xc2x0. claim 1 10. The apparatus of claim 1 wherein said two or more biasing elements are springs. claim 1 |
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046631291 | summary | BACKGROUND OF THE INVENTION This invention relates generally to an isotopic generator system as a source of bismuth-212 and lead-212 radionuclides. More particularly, the invention relates to an isotopic generator system which uses thorium-228 starting material in a radiologically contained portion of the system for producing radionuclides of bismuth-212 and lead-212 from an ion exchange column in an accessible generator portion of the system. The practice of medical radiotherapy has previously involved the use of short lived .alpha.-emitting isotopes, such as .sup.211 At, and a .beta. emitter, such as .sup.131 I (see, for example, Zucchini et al., "Isotopic Generator for .sup.212 Pb and .sup.212 Bi", International J. Nucl. Med. Biol. 9, 83 (1982); and Gansow et al., "Generator Produced Bi-212", American Chemical Society Symposium Series No. 214, January, 1984, which are incorporated by reference herein). In the case of cancer therapy, isotopes of lead-212 and bismuth-212 are combined in a chelated form with monoclonal antibodies which have a high specificity for cancer cells (see Zucchini and Gansow). However, in the case of .sup.211 At and .sup.131 I because both are halogens, there is a covalent reaction with tyrosine residues present in the antibody material, and there can be a consequent diminishment in activity and in the specificity for cancer cells. Furthermore, .sup.131 I delivers only low linear energy transfer .beta..sup.- radiation which is not as effective as high linear energy transfer radiation, such as .alpha.-particles. Further, .sup.131 I emits .gamma. rays which have the undesired effect of nonlocalized destruction of cells somewhat removed from the origin of the .gamma. emIssIon. The .sup.211 At aIso must be produced by .alpha.-particle irradiation of bismuth in a cyclotron which limits the quantity of material produceable at a reasonable price. More recently, a chelated form of lead-212 has been used for immune suppression purposes, (see, M. K. Rosenow, "Properties of Liposomes Containing Pb-212", Intl. J. Nucl. Med. Biol. 10. 189-197, 1983). Further, a chelated form of bismuth-212 has been combined with monoclonal antibodies to provide a more stable radiotherapy agent with a high specificity for cancer cells. (see, p. 83 of Zucchini et al., cited hereinbefore). The bismuth-212 radionuclide is generated from decay of thorium-228 into radium-224 and radon-220 gas. The radon-220 gas is dissolved in water and separated from the thorium-228. Radon-220 has a half life of about one minute, and decay of the radon-220 leads to formation of lead-212 and consequent decay to bismuth-212. The short time for the decay of the radon-220 to form the desired lead-212 and its decay product, bismuth-212, makes it necessary to maintain the entire column as one unit. The long half life of 1.9 years for thorium-228 and the high level of radioactivity associated with the thorium-228, requires the use of a containment unit, such as a shielded facility or shielded glove box, for safe handling of the generator system. Furthermore, the ion exchange column used to retain the thorium-228 and the radium-224 undergoes substantial radiation damage degradation which requires periodic disassembly and reconstruction of the generator system. This particular prior art thorium-228 based generator system also necessitates periodic repurification of the thorium-228 source. It is therefore an object of the invention to provide an improved method and apparatus for producing bismuth-212 and lead-212 radionuclides. It is a further object of the invention to provide an improved generator system for producing bismuth-212 and lead-212 radionuclides from thorium-228 starting material. It is another object of the invention to provide an improved radionuclide generator system having a radiologically contained portion with a plurality of valves for collection of radium-224 to enable formation and withdrawal of bismuth-212 and lead-212 from an ion exchange column in an accessible portion of the system which can be removed and utilized apart from the contained portion of the system. It is an additional object of the invention to provide an improved radionuclide generator system which uses thorium-228 starting material disposed in a radiologically contained portion for producing radium-224 in an ion exchange column in an accessible generator portion which is removable from the contained portion and wherein a cation exchange media is used to retain the radium-224 to enable selective removal of bismuth-212 and lead-212. SUMMARY OF THE INVENTION In accordance with the present invention the radionuclide generator system utilizes thorium-228 starting material in a radiologically contained portion of the system to produce bismuth-212 and lead-212 radionuclides in a coupled, accessible generator portion of the system. A nitric acid carrier solution and thorium-228 is charged to the radiologically contained portion, and an anion exchange column is used to separate thorium-228 from radium-224. The thorium-228 remains on the anion exchange resin of the column, and the solution of nitric acid and radium-224 is transported to an evaporation unit wherein the acid solution is removed. A water solution of radium nitrate is formed and transferred from the evaporation unit to the accessible generator portion which is used for producing the bismuth-212 and lead-212 radionuclides. The accessible generator portion is a cation exchange column which retains the radium-224, and natural radioactive decay produces the desired bismuth-212 and lead-212 end products. In another aspect of the invention the radium nitrate solution can be output to the accessible generator portion by dispensing predetermined aliquots by a calibrated burette or pipette. In this manner a predetermined number of individual accessible generator portions can be dispensed and removed for end user application. Further objects and advantages of the present invention, together with the organization and manner of operation thereof, will become apparent from the following detailed description of the invention when taken in conjunction with the accompanying drawings. |
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abstract | One embodiment relates to a dynamic pattern generator for reflection electron beam lithography which includes conductive pixel pads, an insulative border surrounding each conductive pixel pad so as to electrically isolate the conductive pixel pads from each other, and conductive elements coupled to the conductive pixel pads for controllably applying voltages to the conductive pixel pads. The conductive pixel pads are advantageously cup shaped with a bottom portion, a sidewall portion, and an open cavity. Another embodiment relates to a pattern generating apparatus which includes a well structure with sidewalls and a cavity configured above each conductive pixel pad. The sidewalls may include alternating layers of conductive and insulative materials. Other embodiments, aspects and feature are also disclosed. |
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abstract | The present application relates to a collimator for radio surgery or radio therapy comprising a plurality of leaves; guiding members for guiding a movement of the leaves; a pressing unit for causing a press contact between the leaves and the guiding members; wherein the pressing unit comprises pressing members which are at least configured to allow for a rolling press contact between the pressing members and the leaves. |
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abstract | A method of monitoring a condition of a nuclear reactor pressure vessel disposed in a radioactive environment is provided. The method includes the steps of sensing a condition of the reactor pressure vessel with an instrument, transmitting a signal indicative of the condition of the reactor pressure vessel from the instrument to a powered wireless transmitting modem disposed in the radioactive environment, wirelessly transmitting a signal indicative of the condition of the reactor pressure vessel from the transmitting modem to a receiving modem in the line of sight of the transmitting modem, transmitting a signal indicative of the condition of the reactor pressure vessel from the receiving modem to a signal processing unit, and determining the condition of the reactor pressure vessel from the wirelessly transmitted signal. |
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description | This application claims the benefit of U.S. Provisional Application No. 61/625,326 filed Apr. 17, 2012. U.S. Provisional Application No. 61/625,326 filed Apr. 17, 2012 is hereby incorporated by reference in its entirety. The following relates to the nuclear power reactor arts, nuclear reaction coolant system arts, nuclear power safety arts, and related arts. Light water nuclear reactors are known for maritime and land based power generation applications and for other applications. In such reactors, a nuclear reactor core comprising a fissile material (for example, 235U) is disposed in a pressure vessel and immersed in primary coolant water. The radioactive core heats the primary coolant in the pressure vessel, and the pressure vessel (or an external pressurizer connected with the pressure vessel by piping) includes suitable devices, such as heaters and spargers, for maintaining the primary coolant at a designed pressure and temperature, e.g. in a subcooled state in typical pressurized water reactor (PWR) designs, or in a pressurized boiling water state in boiling water reactor (BWR) designs. Various vessel penetrations take primary coolant into and out of the pressure vessel. For example, in some PWR designs primary coolant is passed through large-diameter penetrations to and from an external steam generator to generate steam for driving a turbine to generate electrical power. Alternatively, an integral steam generator is located inside the reactor pressure vessel, which has advantages such as compactness, reduced likelihood of a severe loss of coolant accident (LOCA) event due to the reduced number and/or size of pressure vessel penetrations, retention of the radioactive primary coolant entirely within the reactor pressure vessel, and so forth. Additional smaller diameter vessel penetrations are provided to add primary coolant (i.e., a makeup line) or remove primary coolant (i.e., a letdown line). These lines are typically connected with an external reactor coolant inventory and purification system (RCIPS) that maintains a reservoir of purified primary coolant. Further vessel penetrations may be provided to connect with an external steam generator, an emergency condenser, or for other purposes. Light water reactors are evaluated to determine their response in the event that a pipe outside of the reactor vessel breaks and a loss of coolant accident (LOCA) occurs. The compact integral reactor design was developed, in part, to minimize the consequence of an external pipe break by eliminating large-diameter piping leading to and from external steam generators. However, integral reactors still utilize small bore connecting piping that transports reactor coolant to and from the reactor vessel. For example, in reactors with an integral pressurizer the reactor vessel has penetrations at the top for pressurizer spray and venting. Some emergency core cooling system (EGGS) designs include piping connecting with an emergency condenser. The vessel also has makeup and letdown penetrations for coolant makeup, letdown, and decay heat removal. These lines run from the vessel to one of two valve rooms where isolation valves act to limit loss of water for breaks down stream of the valve rooms. This arrangement results in three categories of LOCAs. Type 1 LOCAs result from a leak between the vessel and the valve room. Type 2 LOCAs result from a least at penetrations in the upper vessel. Type 3 LOCAs result from leaks that occur in the valve rooms. Type 2 and Type 3 LOCAs do not drain the reactor water storage tanks RWSTs at the end of the LOCA and result in long term cooling using the water left in the RWSTs. Type 1 LOCAs drain coolant into the refueling cavity, draining the RWSTs. The present disclosure sets forth apparatuses for reducing or eliminating Type 1 LOCAs. In accordance with one aspect, a nuclear reactor comprises a nuclear reactor core comprising a fissile material, a pressure vessel containing the nuclear reactor core immersed in primary coolant disposed in the pressure vessel, and an isolation valve assembly including, an isolation valve vessel having a single open end with a flange, a spool piece having a first flange secured to a wall of the pressure vessel and a second flange secured to the flange of the isolation valve vessel, a fluid flow line passing through the spool piece to conduct fluid flow into or out of the first flange wherein a portion of the fluid flow line is disposed in the isolation valve vessel, and at least one valve disposed in the isolation valve vessel and operatively connected with the fluid flow line. The spool piece and the isolation valve vessel can cooperatively define a sealed volume capable of withstanding an operating pressure of the pressure vessel of the nuclear reactor. The at least one valve can be a check valve preventing fluid flow out of the pressure vessel. The fluid flow line can be a makeup line for supplying reactor coolant to the pressure vessel and the at least one valve is a check valve preventing primary coolant from flowing out of the pressure vessel through the fluid flow line. The at least one valve can comprise at least two valves arranged in series on the fluid flow line. At least one valve can include an actuator for moving the valve between open and closed positions. The actuator can be an electric, hydraulic, pneumatic or manual actuator. The fluid flow line can be a letdown line that removes reactor coolant from the pressure vessel responsive to the actuator opening the at least one valve. An end of the fluid flow line can be disposed coaxially inside the spool piece. A redundant valve can be disposed outside of the isolation valve vessel and operatively connected with the fluid flow line. In accordance with another aspect, an apparatus comprises an isolation valve assembly including an isolation valve vessel, a mounting flange sealing with the isolation valve vessel to define a sealed volume, a fluid flow line in fluid communication with the mounting flange to flow fluid through the mounting flange, and a valve disposed in the isolation valve vessel inside the sealed volume and operatively connected with the fluid flow line. The isolation valve assembly can further include a forging including the mounting flange and a second flange to which the isolation valve vessel is secured, the forging having a passageway extending between the mounting flange and the second flange through which the fluid flow line passes. The valve can be a check valve allowing flow out of the mounting flange and blocking flow into the mounting flange. The valve can include first and second valves disposed in the isolation valve vessel inside the sealed volume and arranged in series along the fluid flow line. The isolation valve assembly can further include an external isolation valve disposed outside the isolation valve vessel and outside the sealed volume and operatively connected with the fluid flow line. The valve can include an actuator for moving the valve between open and closed positions. The actuator can be an electric, hydraulic, pneumatic or manual actuator. The apparatus can further comprise a nuclear reactor comprising (i) a pressure vessel including a mating flange and (ii) a nuclear reactor core comprising fissile material disposed in the pressure vessel, wherein the mounting flange of the isolation valve is connected with the mating flange of the pressure vessel of the nuclear reactor. The fluid flow line can be a makeup line of a reactor coolant inventory and purification system (RCIPS) and the valve can be a check valve preventing backflow of reactor coolant from the pressure vessel into the makeup line. The fluid flow line can be a coolant letdown line of a reactor coolant inventory and purification system (RCIPS) and the valve can be an actuated valve. In accordance with still another aspect, a nuclear reactor comprises a nuclear reactor core comprising a fissile material, a pressure vessel containing the nuclear reactor core immersed in primary coolant disposed in the pressure vessel, and an isolation valve assembly including a valve cover having a single open end with a flange, a spool piece including a first flange and a second flange secured with the flange of the valve cover to define a sealed volume enclosed by the valve cover, a fluid flow line passing through the spool piece and flowing fluid into or out of the first flange, and a valve supported in the sealed volume and operatively connected with the fluid flow line. The reactor can further comprise a reactor coolant inventory and purification system (RCIPS), wherein the fluid flow line is a makeup line supplying makeup coolant water from the RCIPS to the pressure vessel and the valve is a check valve preventing backflow of coolant water from the pressure vessel to the RCIPS. In another embodiment, the reactor can further comprise a reactor coolant inventory and purification system (RCIPS), wherein the fluid flow line is a letdown line and the valve is an actuated valve that is opened by an actuation signal to initiate flow of coolant water through the letdown line from the pressure vessel to the RCIPS. FIG. 1 is a schematic illustration of a nuclear reactor including a pressure vessel 10. The pressure vessel 10 contains a nuclear reactor core 11 (shown in phantom) disposed at or near the bottom of the pressure vessel 10 and immersed in primary coolant water also disposed in the pressure vessel 10. The pressure vessel 10 further contains numerous internal components that are not shown in FIG. 1 but which are known in the art, such as structures defining a primary coolant flow circuit, e.g. a hollow cylindrical central riser defining a hot leg inside the riser and a cold leg in a downcomer annulus (e.g., flow region) defined between the central riser and the pressure vessel 10, and neutron-absorbing control rods and associated drive mechanisms for controlling reactivity of the nuclear reactor core. Some embodiments, e.g. integral pressurized water reactor (PWR) designs, also include one or more steam generators disposed inside the pressure vessel, typically in the downcomer annulus. A reactor coolant inventory and purification system (RCIPS) 12 is provided to maintain the quantity and purity of primary coolant inside the pressure vessel. A letdown line 14 removes primary coolant water from the pressure vessel 10 into the RCIPS 12, and a makeup line 16 delivers makeup primary coolant water from the RCIPS 12 to the pressure vessel 10. The RCIPS 12 includes a pump 17 and other water processing components (not shown) for purifying and storing reserve primary coolant, injecting optional additives such as a soluble boron compound (a type of neutron poison optionally used to trim the reactivity), or so forth. Isolation valves 20, 21 are provided at respective vessel penetration locations where the letdown line 14 and makeup line 16, respectively, pass through an outer wall 18 of the pressure vessel 10. During ordinary operation, makeup water flows into, and/or letdown water flows out of, the pressure vessel 10 through the letdown line 14 and makeup line 16 to maintain desired operating volume and composition (e.g, purity) of the primary coolant water in the pressure vessel 10. However, if a break occurs in one of the fluid flow lines 14, 16, or elsewhere, such that a LOCA is initiated and uncontrolled primary coolant water discharge might occur, then flow of coolant out of the pressure vessel 10 is automatically blocked by the affected valve 20, 21. With reference to FIG. 2, an exemplary letdown isolation valve assembly 20 includes an isolation valve vessel (IVV) with a small pressure boundary containing redundant isolation valves. The pressure boundary is designed to withstand operating pressure and temperature conditions of primary coolant inside the pressure vessel 10. The isolation valve vessel is mounted to the side of the lower vessel with a flanged arrangement 32, which in the illustrative example is a spool piece 32. As used herein, a spool piece includes two flanges connected by piping or another passageway. The spool piece is rated to withstand the operating pressure of the pressure vessel 10, and in some embodiments the spool piece 32 is a forging. One flange of the spool piece 32 is connected with a mating flange of the pressure vessel 10 to connect the isolation valve assembly 20 directly to the wall 18 of the pressure vessel 10. The other flange of the spool piece 32 is connected with a flanged open end of the isolation valve vessel to define a sealed volume. Any leakage at the valves is contained within this sealed volume. With additional reference to FIG. 3, the details of the exemplary isolation valve assembly 20 in accordance with the disclosure will be described. The illustrated valve assembly 20 is a letdown isolation valve that can be used to control the flow of fluid out of the reactor core. However, it will be appreciated that the valve 20 could also be installed on a makeup line for adding fluid to the reactor core, or in another fluid line feeding into and/or out of the pressure vessel 10. The valve 20 includes the spool piece 32 and an isolation valve vessel 34 secured together via a mating flange 36 at a (single) open end of the isolation valve vessel 34 and a flange 38 of the spool piece 32. The spool piece 32 also includes a mounting flange 42 having a centrally located inlet/outlet 44 and a plurality of bolt holes surrounding the inlet/outlet 44 for securing the valve assembly 20 to a mating flange 48 of a pressure vessel, such as pressure vessel 10. Thus, the spool piece 32 includes a first flange (namely the mounting flange 42) and a second flange (namely the flange 38 that connects with the isolation valve vessel 34). The spool piece 32 further includes a passageway 46 connecting the first and second flanges 42, 38. In the illustrative example, the mounting flange 42 is spaced apart from the flange 38 and connected by the passageway 46 which is a reduced diameter section. The isolation valve vessel 34 includes a hemispherical or elliptical head 52 (e.g., a valve cover) having flange 36 which connects with the flange 38 of the spool piece 32. The connection of the isolation valve vessel 32 and the flange 36 defines a sealed volume contained by the isolation valve vessel 32. A fluid flow line 54 includes a “U”-shaped portion disposed inside the isolation valve vessel 32 and then continues on coaxially inside the spool piece 32 to flow fluid into or out of the flange 42. In the illustrative example of letdown valve assembly 20, fluid flows from the pressure vessel 10 through the fluid flow line 54 and into the letdown line 14 (see FIG. 1) to reduce the quantity of primary coolant in the pressure vessel 10. When the letdown valve assembly 20 is mounted to pressure vessel 10, the inlet/outlet 44 serves as an inlet that is in fluid communication with the interior of the pressure vessel 10 such that primary coolant can flow from the pressure vessel 10 through the letdown valve assembly 20 via valve fluid line 54 to an inlet/outlet 56 of the valve assembly 20. In the illustrative case of letdown valve assembly 20, the inlet/outlet 56 serves as an outlet that is connected to the letdown line 14 of the RCIPS 12. The illustrated “U”-shaped portion of the fluid flow line 54 inside the isolation valve vessel 34 advantagely accommodates thermal expansion. isolation valve vessel 34 together with the flange 38 define a sealed interior volume or chamber C in which a pair of valves 60 and 62 are supported. (In view of this, the hemispherical or elliptical head 52 is alternatively referred to herein as valve cover 52). In the illustrative example of letdown valve assembly 20 which is configured for a letdown application, the valves 60 and 62 are suitably actuated valves which are opened (or closed) by an actuation signal. Typically, it is preferable to have the valves 60, 62 be “normally closed” valves such that the actuation signal causes the valves to open so that the valves are closed in the passive state, although a “normally open” configuration is also contemplated. In some embodiments the valves 60, 62 are pneumatically actuated ball valves, although valves employing electrical, hydraulic, or manual actuation are also contemplated, as are valves other than ball valves. In the makeup valve configuration (e.g., the makeup valve assembly 21 of FIG. 1), the valves 60 and 62 can be swing check valves or another type of check valve, which is configured to prevent fluid flow into the flange 42 (i.e., configured to prevent flow of primary coolant out of the pressure vessel 10). The valves 60 and 62 are arranged in series for redundancy, and it will be appreciated that additional valves, or a single valve, could be provided in the chamber C as desired. The isolation valve vessel 32 optionally includes various penetrations for the plant instrument air system to pressurize the chamber C for vessel leak testing, and for air lines 64 for piloting/actuating the pneumatic actuators in case of pneumatically actuated valves. An optional internal support structure 68 is secured to flange 38 to support the actuated valves 60 and 62 (or to support the check valves in the case of makeup isolation valve assembly 21). The support structure 68 optionally also serves as a mechanical guide for installing the valve cover 52 so that it does not impact any internal components (e.g., valves and/or actuators, etc.) when it is removed and/or installed to allow maintenance access. Thermal insulation, although not illustrated, can be provided and its location will depend on the design of the actuator and/or position indicators. If high temperature actuators are utilized, the insulation can be placed on the outside of the support structure 68 and cover 52. If actuator temperature limitations prevent such positioning of the insulation, multi-layer metal insulation can be provided on the piping and a component cooling water line can be added to actively cool the valve 20 to assure acceptable temperatures. The support structure 68 is optional—in some embodiments the “U” shaped portion of the fluid flow line 54 has sufficient rigidity to support the valves 60, 62. In the illustrated embodiment, an optional third isolation valve 70 disposed outside of the chamber C is provided to isolate the valve fluid line 54 in the event of a pipe break inside of the isolation valve vessel 34. The external valve 70 can be pneumatically operated, for example, and configured to close the valve fluid line 54 in the event of a leak within the valve 20. The third isolation valve 70 can be used, for example, to block flow through the valve fluid line in the event the other valves are disabled due to flooding of the chamber C during an internal pipe break and/or leakage event. Third isolation valve 70 provides a level of redundancy. Turning to FIGS. 4 and 5, another exemplary isolation valve assembly 100 in accordance with the disclosure is illustrated. In this embodiment, the valve assembly 100 is similar to the valve assembly 20 of FIGS. 2 and 3. However, the valve assembly 100 has valves supported by the “U”-shaped portion of the fluid flow line (i.e., the support structure 68 is omitted), and valve actuators are mounted external to the pressure vessel. To this end, the valve 100 generally includes a spool piece 104 and an isolation valve vessel 108 comprising a valve cover 112 including a flange 116 that is removably secured to a mating flange 120 of the spool piece 104 with bolts or other fasteners (not shown). The valve assembly 100 is mountable to a pressure vessel of a nuclear reactor or other component via a mounting flange 124 of the spool piece 104 that is axially spaced from flange 120 of the spool piece 104 by a passageway 122. A fluid flow line 128 fluidly connects an inlet/outlet (not shown) of the mounting flange 124 with an inlet/outlet 132. As with valve assembly 20, the valve assembly 100 includes an interior chamber C formed by the valve cover 112 and the flange 120 secured to the flange 120 of the spool assembly 104, and a pair of valves 140 and 142 are supported inside the chamber C. Valves 140 and 142 are supported by valve fluid line 128 and are arranged in series for redundantly blocking flow through the valve fluid line 128. In embodiment of FIGS. 4 and 5, externally mounted valve actuators 146 and 148 are provided for actuating valves 140 and 142. To this end, the actuators 146 and 148 are mounted to respective actuator flanges 152 and 154 on the valve cover 112 with bolts or other suitable fasteners (not shown). A connecting shaft 156 (see FIG. 5) extends from the valves 140 through the valve cover 112 for coupling with the actuator 146. In one embodiment having ball valves, rotation of the connecting shaft 156 by the actuator 146 moves a ball of the valve 140 between respective open and closed positions. Valves 142 includes a similar configuration, although its connecting shaft is not visible in the drawings. This configuration places the actuators 146, 148 outside of the relatively harsh environment of the chamber C, and therefore can increase component longevity and/or allow the use of conventional actuators. This generally simplifies the design and potentially eliminates the need for thermal insulation inside the pressure vessel. The connecting shafts for connecting the actuators to the valve member introduce the potential for some leakage around the connecting shafts, but leakage up to several gallons per minute or more can be accommodated while still achieving acceptable performance. As an alternative approach, a wireless actuation signal is also contemplated, which would eliminate the penetrations through the valve cover 112. The isolation valve vessel of the present disclosure provides isolation for any pipe break of the makeup or letdown lines, assuming any active component failure. The makeup lines with check valves will automatically close if flow reverses, isolating the LOCA. The letdown lines require closure of the ball valves which is effected via the pneumatic actuators and occurs on a low RCS pressure signal. Elimination of the low break LOCA simplifies design basis accident analysis and eliminates sump recirculation after a LOCA. The valves in the vessel would isolate the broken line and long term makeup and letdown would continue using the non-effected lines. Because of the limited volume of the vessel, the amount of debris that can flow into the RCS is significantly limited, reducing concerns of debris plugging of flow passages in the fuel assemblies. It will now be appreciated that the present disclosure provides at least one or more of the following advantages: 1. Eliminates the two separate valve rooms used in conventional reactors. 2. Eliminates the Type 1 LOCA described above. Type 1 LOCA is generally considered the most difficult type of failure in which to provide long term cooling because most of the water spills on the refueling cavity floor. The RWST level drops to approximately 8 ft above the lower vessel penetrations minimizing the driving head to inject water. 3. The higher driving head allows greater flexibility in automatic depressurization valve sizing because very low differential pressures (e.g., less than 5 psi) are not required for long term injection. 4. During long-term cooling, there is a potential for water to flow through the break back into the reactor vessel. The invention limits the water that can flow back into the vessel and, because it is a closed structure, limits the amount of fibrous debris that can be mixed with the water. 5. By eliminating the Type 1 LOCA and its low passive injection pressure, the ADV and upper vessel penetration sizes may be reduced, making any upper breaks more benign. 6. The vessel reduces the length of ASME Class I piping. The exemplary embodiment has been described with reference to the preferred embodiments. Obviously, modifications and alterations will occur to others upon reading and understanding the preceding detailed description. It is intended that the exemplary embodiment be construed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof. |
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abstract | The invention relates to a positioning device for positioning a patient in a medical device comprising a patient receiving device for placing a patient and a robot arm having a plurality of movement axes for positioning the patient receiving device in a room. The positioning device can be placed into a manual operating mode in which a position of the patient receiving device in the room can be changed manually. The invention also relates to a method for operating the positioning device, comprising: providing a normal operating mode for positioning the patient receiving device automatically at a position predefined by a control device; providing a manual operating mode for manually changing a position of the patient receiving device; and switching from the normal operating mode into the manual operating mode if a switchover condition is present. The invention further relates to an irradiation device having the positioning device. |
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claims | 1. The scintillator material, comprising a composition of one of the following formulas:A′(1-x)B′xCa(1-y)EuyC′3 (1),A′3(1-x)B′3xM′Br6(1-y)Cl6y (2),A′(1-x)B′xM′2Br7(1-y)Cl7y (3),A′(1-x)B′xM″1-yEuyI3 (4),A′3(1-x)B′3xM″1-yEuyI5 (5),A′(1-x)B′xM″2(1-y)Eu2yI5 (6),A′3(1-x)B′3xM′Cl6 (7),A′(1-x)B′xM′2Cl7 (8), andM′(1-x)B′xC′3 (9),where:A′=Li, Na, K, Rb, Cs or any combination thereof,B′is selected from the group consisting of B, Al, Ga, In, Tl or any combination thereof,C′═Cl, Br, I or any combination thereof,M′ consist of Ce, Sc, V, La, Lu, Gd, Pr, Tb, Yb, Nd or any combination of them,M″ consists of Sr, Ca, Ba or any combination of thereof,x is in the range: 0<x<1, andy is in the range: 0<y<1. 2. The scintillator material of claim 1, wherein B′ comprises thallium (Tl). 3. A scintillator material, comprising: a metal halide; a first rare-earth element; and a group-13 element, wherein the group-13 element comprises thallium (Tl). |
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041586069 | description | DETAILED DESCRIPTION The inventive concept of this invention is based on the discovery that effective concentrations of silicon, titanium, and zirconium in certain stainless steel alloy formulations within prescribed silicon and titanium concentration limits of both elements result in an alloy having improved resistance to swelling due to voids induced by fast neutrons. The void suppressive effect provided by additions of silicon and titanium may be termed synergistic since the improvements in void formation observed after using silicon and titanium together within prescribed concentrations are greater than any void suppressive effect noted by the use of one in the absence of the other. We have found that small amounts of titanium and silicon have a profound effect in suppressing the void formation in austenitic stainless steels which result from prolonged exposure of such steels to a fast neutron flux at elevated temperatures. Because the effective amounts of silicon and titanium necessary to achieve void suppression is small, the inventive concept permits formulation of alloys whose otherwise desirable physical and mechanical properties are not thereby adversely affected. In general, the benefits of this invention are achieved by additions of silicon in the range 0.70 to 2: and titanium additions in the range 0.10 to 0.5: will result in significant void suppression. The exact amount of Si and Ti may vary from one austenitic composition to another and will represent a compromise between maximum achievable void suppression and mineral adverse metallurgical effects of Ti and Si or interaction of these additives with other alloy components. Thus, in 304 and 316 stainless steel, maximum void suppression and maximum strength are achieved at a Ti concentration in the range of 0.2 to 0.46% and a Si concentration which should not exceed 2%. While further void suppression may be expected at higher Ti and Si concentrations, other adverse metallurgical factors come into play. Futher embodiments of Ti lead to a reduction in strength while further increases in Si lead to the formation of low-melting Si-containing entities. The void suppression behavior of Si and Ti is most pronounced in the austenitic stainless steels encompassed within the quadrilateral area ABCD of the tenary Fe-Cr-Ni system shown in FIG. 3. To achieve maximum void suppression while maintaining austenitic stability, the Cr concentration should not exceed 22% nor should the minimum Ni content fall below 8%. Stainless (oxidation resistance) quality and strength dictate that minimum Cr concentration should not fall below 5%. It has been found that swelling decreases with increasing Ni content (greater than about 30% Ni) in Fe-Cr-Ni austenitic alloys. The extent to which Si and Ti additions decrease voids in such high (greater than 30%) nickel alloys may be academic since high Ni alloys suffer from several disadvantages for LMFBR application. The high Ni alloys are susceptable to corrosion by liquid sodium, are highly susceptible to fission product attack, and (compared to the alloys within ABCD of FIG. 3) result in reduced neutron economy. The void suppression effect will be illustrated in the following representative examples in which the advantages in the herein-disclosed inventive concept are utilized, as a best mode, to convert a type 316 stainless steel and other stainless steels known to exhibit very large swelling into a low-swelling alloy by minor modifications in titanium and silicon. In each case, the modified alloy was prepared and the swelling behavior tested in accordance with the following procedure. Approximately two pounds of each alloy tested were prepared by melting high purity alloy constituents under an inert gas atmosphere. The alloys were cast into 1/2 inch bar and subsequently rolled into a sheet of the desired thickness. Small samples (about 1/8 inch .times. 1/8 inch .times. 0.060 inch thickness) were cut and mounted in a specimen holder which allows the simultaneous irradiation of several samples. In this way, a direct comparision of the behavior of several alloys was obtained. Specimen surfaces were prepared by mounting the specimens in the holder and simultaneously polishing all specimens with successively finer abrasives. Swelling is inferred from measurement of the step which occurs on the surface of the sample when a portion of the surface is shielded during ion irradiation by a 0.010 inch mask. The area under the mask is protected from the ion beam and does not swell while the unmasked area does. The size of the step on the specimen at the interface between the masked (unbombarded) and unmasked (bombarded) regions is a measure of the degree of swelling. Swelling or volume increase was estimated using an empirical correlation published by Johnston et al. in J. Nuclear Material. Vol. 54, pp. 24-40. A step height of 60 A corresponds to a swelling of 1% at the peak of the damage curve. Because of the higher damage rate in an ion simulation experiment (vacancies and interstitials are produced about 10.sup.3 times faster in an ion irradiation than in a neutron irradiation), the temperature at which peak swelling occurs is shifted upwards about 100.degree. C. Thus, irradiation at about 655.degree. C. with ions corresponds to irradiation at about 555.degree. C. with neutrons. Step heights were measured with a Detak surface profilometer; a minimum of six measurements were made on each specimen. After step height measurement, the mask was moved to another region of the specimen for the next dose increment. Helium pre-injection was carried out using Ca.sub.2 .sup.244 O.sub.3 source which emits a 5.8 MeV.alpha.-particle. The source geometry was arranged to give a flat helium profile over the first 4-5 .mu. of range. EXAMPLE 1 A series of experimental alloys were prepared in accordance with the above-described procedure. Swelling behavior of the experimental alloys LS1 and LS2 was measured and compared with commercially available austenitic types 316, TiM-315, Nimonic PE-616, and FV-548. The compositions of the experimental and several commercially available alloys are given in Table I. Heat treatments and resulting grain size for LS1, LS2 and the commercial alloys are shown in Table II. TABLE I __________________________________________________________________________ Alloy Fe* Cr Ni Mo Mn Si Ti Al Nb V Co Zr W Cu C N __________________________________________________________________________ P7 17.0 16.7 2.5 0.03 0.10 0.01 0.02 0.02 -- 0.03 -- -- 0.02 0.001 -- 316 17.6 14.1 2.5 1.67 0.36 0.01 0.005 -- 0.05 0.02 0.01 -- -- 0.03 0.018 Tim 316 17.5 14.0 2.5 1.41 0.03 0.29 0.02 -- 0.03 0.02 -- -- -- 0.06 0.004 FY 548 16.7 11.5 1.4 1.08 0.45 -- -- 0.73 -- -- -- 0.10 -- 0.08 P.E. 16 16.7 43.8 3.38 0.13 0.26 1.03 1.10 -- -- -- -- -- -- 0.06 A7 (LS1) 16.3 13.4 1.9 1.9 1.0 0.10 -- 0.03 0.2 0.05 0.04 0.05 0.15 0.05 0.02 B7 (LS2) 8.7 19.4 2.3 1.9 1.0 0.27 -- 0.05 0.15 0.07 0.10 0.15 0.15 0.04 H7 10.9 15.4 1.9 1.76 1.06 0.16 -- -- -- -- 0.07 -- -- 0.04 0.02 K-7 11.8 14.3 2.1 1.80 1.04 0.17 -- -- -- -- -- 0.07 -- 0.04 0.02 L7 11.8 15.1 2.0 1.84 1.08 0.17 -- -- -- -- -- -- 0.08 0.04 0.02 M7 12.2 15.6 2.1 1.91 1.06 0.17 -- -- 0.07 -- -- -- -- 0.04 0.02 N7 11.8 14.4 2.0 1.86 1.02 0.17 -- -- -- -- -- -- -- 0.04 0.02 __________________________________________________________________________ *Balance Iron TABLE II __________________________________________________________________________ Heat Treatments Average Grain Alloy Heat Treatment Diameter .mu.m __________________________________________________________________________ 316 Annealed 1050.degree. C. 15 min. 12 C.W. 316 1050.degree. C. 15 min. + 20% Cold Work 12 Ti Modified 316 1050.degree. C. 15 min. 15 F.V. 548 1075.degree. C. 3 min. + 850.degree. C. 3 hr -- PE 16 1050.degree. C. 3 min. + 900 1 hr. + 750.degree. C. 8 25 LS1 1050.degree. C. 1 hr 45 LS2 1050.degree. C. 1 hr 45 __________________________________________________________________________ The results of swelling tests are displayed in FIG. 1 where the alloy specimens were injected to 10 parts per million helium and in FIG. 2 where the alloy specimens were injected to 20 parts per million helium. As shown in FIGS. 1 and 2, the alloys fall into two groups, a high-swelling group consisting of PE 16, a virtually silicon-free stainless steel FV548; annealed 316; 20% cold-worked 316 and a 0.29% titanium-modified 316, all commercially available alloys. The low-swelling group consisted of PE 16, a commercially available high (43.87%) nickel precipitation-hardened austenitic alloy and annealed LS1 and LS2 wherein LS1 corresponds to a type 316 steel modified to contain void suppressing concentrations of silicon and titanium. LS2 is a low-chromium stainless steel alloy in the iron-chromium-nickel region that normally exhibits very large swelling, with the silicon and titanium modifications to produce an alloy which shows a low degree of swelling comparable to the high nickel PE 16 alloy. From FIG. 1 it is seen that LS1 and LS2 under expected LMFBR conditions, at a fluence of 30.times. 10.sup.22, swell less than 10% while TiM 316 swells about 30% and FV348 swells about 50%. The data displayed in FIG. 2 further emphasizes the remarkable differences between the LS1 and LS 2 formulations and other austenitic alloys of similar composition. At an injection of 20 ppm He, the TiM 316 swelling has risen beyond FV548 and the PE 16 swelling has increased from about 5 to 15% while the LS1 and LS2 formulations remained fairly stable. The synergistic void depressant quality of Si and Ti is seen from a comparison of type 316 stainless steel which contains 0.36 Si, but not an effective concentration of Ti and TiM 316 which contains Ti, but not an effective concentration of Si. Both alloys exhibit large swelling. This is to be compared LS1 and LS2 which contain effective concentrations of both Si and Ti to produce, in each case, a low-swelling austenitic stainless steel. Comparing the compositions of the low-swelling LS1 and LS2 alloys with the commercial 316 series stainless steel, it is seen that the silicon and titanium content in the commercial formulations was well below those prescribed by the present invention and exhibited very high void swelling. On the other hand, it is seen that by only slight variations in the minor constituents of the 316 iron-chromium-nickel composition to comply with the concentrations prescribed by the present invention as represented by the LS1 and LS2 formulations an alloy results having a markedly low swelling in iron-chromium-nickel regions that have previously been regarded as inherently high swelling and not subject to modification in swelling behavior by minor compositional variations. EXAMPLE II An additional way of identifying the role of silicon and titanium as well as other elements which may contribute to or suppress void swelling of LS1 and LS2 may be seen by reference to alloys H-7, K-7, L-7, M-7, and N-7 in Table I, all of which contain chromium and nickel concentrations between LS1 and LS2. In formulating these alloys they were modified to contain nominally 1% silicon and 0.2% titanium. In addition, certain of the melts were made up to contain small additions of 0.1% zirconium (H-7), tungsten (K-7) copper (L-7), and vanadium (M-7). These alloys were fabricated into strips, mounted in ion bombardment holder, together with specimens LS1 and LS2, and a high purity 316 alloy (P-7) containing 0.1% silicon and 0.01% titanium. The alloys were then polished, pre-injected with 10 parts per million helium, followed by bombardment with 4 MeV nickel ions at 655.degree. C. and 705.degree. C. to 140 and 210 displacements per atom (dpa). Step height measurements are shown in Table III. TABLE III ______________________________________ Wt % Wt % Wt % Step Height, A Alloy Si Ti Minor Element 640.degree. C. 705.degree. C. ______________________________________ P 7 0.10 0.01 All <0.02 4550 6700 H 7 1.06 0.16 0.07 Zr 372 <200 K 7 1.07 0.17 0.07 W 550 <200 L 7 1.08 0.17 0.08 Cu 535 <200 M 7 1.06 0.17 0.06 V 645 <200 N 7 1.02 0.17 All <0.02 440 <200 LS1 0.93 0.11 0.15V, 0.05W, 0.15Cu, 350 250 0.05Zr LS2 1.10 0.27 0.15V, 0.15W, 0.15Cu, <200 <200 0.10Zr ______________________________________ As a guide to the amount of induced swelling, a step height of 60 A corresponds to about 1% of swelling. It is seen that void swelling as indicated by the step height measurement of the N-7 alloy was lower by more than an order of magnitude than the P-7 alloy which contains only trace amounts of silicon and titanium. Alloy N-7 which contains chromium and nickel concentrations midway between those of compositions LS1 and LS2 shows very little swelling when compared with annealed or cold-worked 316 stainless steel, see FIGS. 1 and 2. The addition of zirconium produced a slight reduction in swelling (H-7) whereas additions of copper (L-7), tungsten (K-7), or vanadium (M-7) all produced increases in swelling relative to N-7. These data show that according to the inventive concept, silicon and titanium levels present in LS1 and LS2 as well as in iron-chromium-nickel alloys having intermediate composition levels result in a decrease in swelling. Individual additions of tungsten, vanadium, or copper at the levels present in LS 1 and LS2 do not appear to have a significant effect on swelling. On the other hand, minor zirconium additions appear to aid in void suppression. When present together and in sufficient quantities, silicon and titanium are effective void suppressant combination as reflected by a resultant reduction in swelling. In accordance with the herein-described invention concept, we have shown that minor compositional modifications of a type 316 stainless steel (in the region of the iron-chromium-nickel system that has previous to this invention exhibited very large swelling) has been modified to exhibit swelling characteristics known only for the high nickel-containing alloys. By recognizing the role of minor additions of silicon and titanium is suppressing void formation reactor material, engineers are now provided with options to select or formulate other low-swelling candidate alloys in low nickel-containing (less than 25%) region of the iron-chromium-nickel system which have desirable mechanical properties. Thus, in accordance with our invention, such low Ni-containing stainless steels as the type 304, 321, 318 series as well as other austenitic stainless steel alloys can now be modified to contain void depressing amounts of silicon and titanium to produce low-swelling alloys previously thought unattainable. Typical make-up of commercial stainless steel compositions which may be modified with void depressing concentrations of Si and Ti are as follows: Type 304-- 18-20 Cr, 8-11 Ni, up to 0.08 C. up to 2 Mn, and the balance Fe. PA1 Type 316-- 16-18 Cr, 10-14 Ni, 2--3 Mo, 0.04-0.06C, 1.5-2 Mn, up to 0.75 Si, and the balance Fe. PA1 Type 321-- 17-19 Cr, 8-11 Ni, up to 2 Mn, up to 0.08 C, minimum Ti= 5 C, and the balance Fe. PA1 12R72HV-- 14.8 Cr, 15 Ni, 1.96 Mn, 1.1 Mo. 0.48 Ti, 0.33 Si, and the balance Fe. It should be understood that this invention contemplates minor modifications in Si and Ti in other austenitic stainless steels by adjustments of Si and Ti to void depressing concentrations to achieve reductions in swelling to a greater or lesser degree than that demonstrated for LS1 and LS2. Furthermore, to the extent that the composition of known austenitic steels contain void depressing concentrations of Si and Ti, the basic invention concept herein disclosed extends to and contemplates a process for the selection of such alloys to fabricate clad nuclear fuels and to resultant compositions and articles as intended for use under fast neutron flux void-forming and hence swelling conditions. And finally, while we have identified a formula for developing low-swelling alloys by specific minor compositional variations, it is within the scope of this invention to induce structural modifications which exhibit swelling to an even further extent. For example, such structural modifications as cold working, and/or grain refinement in combination with the herein-described compositional modifications should produce an alloy which inhibits void swelling to an even greater extent than that effected by the minor compositional variations. As used herein "an austenitic stainless steel alloy" designated as "consisting essentially of " means an austenitic stainless steel containing Fe, Cr, Ni, up to 3% Mo, up to 2% Mn, up to 0.08% C. and a void depressing concentration of silicon and titanium. Any designated alloy may also contain unspecified incidental ingredients which we define as ingredients which may be introduced in or accompany the process of alloy manufacture in accordance with common steel-making processes, and do not materially affect the basic and novel characteristics of the claimed alloy. Such incidental impurities may include, as a maximum, 0.01 N, 0.05 Al, 0.03 As, 0.001 B, 0.05 Co, 0.05 Cb, 0.1 Cu, 0.02 P, 0.01 S and 0.2 V. |
056420145 | claims | 1. A radio isotopic power source, comprising: a first arrangement of semiconductor materials including a first N+ portion having a first N+ surface area, a first P- portion in contact with said first N+ portion to form a first PN junction and a first P+ portion in contact with said first P- portion; a second arrangement of semiconductor materials including a second P+ portion having a P+ surface area that is electrically connected to the first N+ surface area, a second N+ portion having a second N+ surface area, an N portion in contact with said second P+ portion to form a second PN junction and with said second N+ portion and a second P- portion in contact with said second N portion; and a radioactive element disposed in a vicinity of said first N+ surface area and said P+ surface area. a first arrangement of semiconductor materials including a first P+ portion having a first P+ surface area, a first N- portion in contact with said first P+ portion to form a first PN junction and a first N+ portion in contact with said first N- portion; a second arrangement of semiconductor materials including a second N+ portion having an N+ surface area that is electrically connected to the first P+ surface area, a second P+ portion having a second P+ surface area, a P portion in contact with said second N+ portion to form a second PN junction and with said second P+ portion and a second N- portion in contact with said second P portion; and a radioactive element disposed in a vicinity of said first P+ surface area and said N+ surface area. 2. A radio isotopic power source according to claim 1, wherein said radioactive element has a pair of opposite radioactive surfaces defining a thickness therebetween whereby one of said radioactive surfaces contacts said first N+ surface area and the other of said radioactive surfaces contacts said P+ surface area. 3. A radio isotopic power source according to claim 2, wherein said first N+ surface area and said second P+ surface area envelope said radioactive element. 4. A radio isotopic power source according to claim 1, wherein said first and second arrangements of semiconductor materials are one of releasably connected to each other and integrally connected together to form a unitary construction. 5. A radio isotopic power source according to claim 1, wherein said first N+ portion is embedded into said first P- portion and wherein said second P+ portion is embedded into said second N portion. 6. A radio isotopic power source according to claim 5, wherein said second N+ portion has a second N+ surface area and wherein said second N+ portion is embedded into said N portion. 7. A radio isotopic power source according to claim 6, wherein said first P+ portion is embedded into said P- portion and wherein said N portion is embedded into said second P- portion. 8. A radio isotopic power source according to claim 1, further comprising an N+ electrode connected to said first N+ portion and a P+ electrode connected to said second P+ portion. 9. A radio isotopic power source according to claim 1, further comprising a first electrode connected to said first P+ portion and a second electrode connected to said second N+ portion. 10. A radio isotopic power source according to claim 1, wherein at least one of said first and second arrangements of semiconductor materials is a cap. 11. A radio isotopic power source according to claim 1, wherein at least one of said first and second arrangements of semiconductor materials is an integrated circuit. 12. A radio isotopic power source according to claim 1, wherein a voltage potential produced by the power source is approximately 1.4 volts. 13. A radio isotopic power source, comprising: |
abstract | This invention relates to a computational system and method for performing a safety analysis of a postulated Loss of Coolant Accident in a nuclear reactor for a full spectrum of break sizes including various small, intermediate and large breaks. Further, modeling and analyzing the postulated small break, intermediate break and large break LOCAs are performed with a single computer code and a single input model properly validated against relevant experimental data. Input and physical model uncertainties are combined following a random sampling process, e.g., a direct Monte Carlo approach (ASTRUM-FS) and advanced statistical procedures are utilized to show compliance with Nuclear Regulatory Commission 10 CFR 50.46 criteria. |
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041561473 | description | In FIG. 1 there is illustrated a typical neutron absorbing article, in the form of a long thin plate. For example, plate 19 may be of a length of about 93 cm., a width of about 22 cm. and a thickness of about 3 to 5 mm. The neutron absorbing plate 11 includes finely divided particles of boron carbide and diluent material in a matrix of cured and cross-linked phenolic polymer. Although the drawing illustrates particles 13 therein and shows areas 15 therebetween, separate boron carbide and diluent particles will not be identified because they are too closely intermixed and it should be realized that although area 15 may be taken as representative of the cured phenolic polymer, really there are no large areas of polymer or matrix alone because the particular materials are intimately blended in the polymer matrix. In the plate illustrated the presence of individual boron carbide and diluent particles is evident and such can be felt when the plates are handled although the particles are covered by cured polymer which binds them together, thereby helping to prevent accidental loss of particles during use and helping to maintain the neutron absorbing properties of the plates (or other articles) constant at design level. In use in a storage rack for spent nuclear fuels, the present "poison plates" may be stacked one above the other, to a total of about four or five plates, to a height of about 3.7 to 4.7 meters, for example. Usually such stacking will be within the walls of a stainless steel or other suitable enclosure to protect the plates from contact with the spent nuclear fuel or other nuclear material and from contact with an aqueous pool in which such material is being stored. In the diagrammatic illustration of FIG. 2 there is shown a preferred method for the manufacture of the present neutron absorbers. Initially, weighed quantities of boron carbide and diluent particles are mixed together in operation 17 in a paddle mixer type of apparatus, following which resin particles are mixed with the premix, usually in the same mixer, in operation 19. After uniform blending of the mentioned components a predetermined proportion of liquid is mixed in with the previous dry mix in operation 21. After such mixing is completed and the liquid is well distributed throughout the product the mix is screened at 23 (to break up any lumps and to increase product uniformity) into drying trays to a desired thickness and in drying operation 25 is allowed to dry to a desired extent, preferably in a controlled environment, so that it is desirably "tacky" for molding, yet not too fluid so that it can distort objectionably during heating in the curing operation. Preferably the mentioned drying is effected at about room temperature, e.g., 10.degree. to 35.degree. C., preferably 20.degree. to 25.degree. C., and at normal relative humidities, e.g., 10 to 75%, preferably 35 to 65%, but other conditions can also be used to produce the same results. Next, the product is screened in operation(s) 27 and is added to a mold and pressed for a short period of time, which combined molding and pressing operation is designated 29. After pressing, the mold is unloaded and the pressed green article is cured, as represented by numeral 31 (preferably in a forced air oven), at an elevated temperature in a curing cycle which comparatively slowly increases the temperature to the desired elevated level, maintains it at such level and gradually lowers it to about room temperature. The products made are of desired density, uniformity of neutron absorbing capability, flexibility and other required and desired physical properties, look like that of FIG. 1 and are capable of being incorporated in any of various types of storage racks for spent nuclear fuel, such as are illustrated in FIG'S. 1 and 2 in U.S. patent application Ser. No. 854,966 of McMurtry et al., previously mentioned. The manufacturing method described above and illustrated diagrammatically in FIG. 2 is that of a co-pending patent application of Dean P. Owens, Ser. No. 866,102, entitled Method for Manufacture of Neutron Absorbing Articles, filed Dec. 30, 1977. Another method for the manufacture of the present articles is illustrated in FIG. 3 and corresponds substantially to that described in U.S. patent application Ser. No. 854,966 for Neutron Absorbing Article and Method for Manufacture of Such Article of McMurtry, Naum, Owens and Hortman, previously referred to in this specification and, with the mentioned Owens and Storm applications (see the following description of FIG. 4), hereby incorporated by reference. In such method, a two-stage curing process, the boron carbide particles and diluent particles are mixed at 49, after which liquid resin is mixed in with the premix at 51 until a substantially uniform blend is obtained, following which the blend is screened at 53, dried (55), screened again (57), molded and pressed (59), cured in operation 61, impregnated with additional liquid resin (63) and subsequently dried (65) and cured (67). In FIG. 4 there is shown an alternative method for the manufacture of the present absorber plates. Following such method, which is largely described in detail in U.S. patent application Ser. No. 856,378 of Roger S. Storm, for One-Step Curing Method for Manufacture of Neutron Absorbing Plates, filed Dec. 1, 1977, a mixture of boron carbide particles and diluent particles is mixed in operation 33, after which, usually in the same mixer, resin particles will be admixed therewith in operation 35, to be followed by addition of liquid resin and mixing 37, still in the original preferred paddle-type mixing apparatus. Subsequently the mix is screened, dried, screened, pressed and cured in operations identified by numerals 39, 41, 43, 45, 47, respectively, corresponding to those previously described and mentioned in the Storm applications. The various methods described for the manufacture of the present articles all result in useful and commercially acceptable neutron absorbers but at the present time the order of preference is that of the numerical order of the representative figures, largely because of the improved efficiency, simplicity, lower breakage and shorter times attending the practice of the more preferred procedures. Of course, variations may be made in the described methods and in some cases additions, mixing procedures, screenings and dryings are varied in types, amounts and orders or are omitted in the interest of improving processing and the production of a more desirable product. For example, using the method of FIG. 2, when moisture content is reduced to the minimum or near the minimum to obtain a form-retaining green pressed item, preliminary drying before curing may be omitted. Whether the present products are made by any of the foregoing methods or equivalently satisfactory processes, an important advantage of the neutron absorbing article of this invention is that it contains a high proportion of a total of boron carbide and diluent particles, with such proportion normally being more than half of the article. Also, by varying the proportion of diluent particles to boron carbide particles products of various neutron absorbing activities may be made without requiring changes in manufacturing techniques or in the apparatuses in which the absorbers are to be utilized. Such variations in neutron absorbing capabilities may be made without changing the thicknesses of the articles to be employed, which allows the use of a variety of absorbing articles of different absorption powers in the same type of holder or rack, as may be desired. Due to the uniformity of distribution of the boron carbide particles and diluent in the phenolic polymer matrix the neutron absorbing capabilities of the articles made may be controlled, enabling engineers to design storage racks to high degrees of precision, thereby allowing a wide range of planned effective loadings of storage racks for spent nuclear fuel when the present neutron absorbing articles are parts thereof. The present absorbing articles are operable over temperature ranges at which the spent nuclear fuel is normally stored in storage racks. The articles withstand thermal cyclings from repeated spent fuel insertions and removals and withstand radiation from spent nuclear fuel over long periods of time without losing desirable neutron absorbing and physical properties. They are normally sufficiently chemically inert in water or in other aqueous media in which the spent fuel may be stored so as to retain effective neutron absorbing properties even when a leak occurs which allows the entry of such liquid into the enclosure for the neutron absorbing article in the storage rack and into contact with such article. The present plates do not galvanically corrode and are sufficiently flexible so as to withstand operational basis earthquake and safe shutdown seismic events without losing neutron absorbing capability and desirable physical properties when installed in a storage rack. Additionally, the high level of product consistency with any of a variety of design specifications for absorbing power, etc., provide a much needed technical validity for the present products. The boron carbide employed should be in finely divided particulate form. This is important for several reasons, among which are the intimate mixing of such particles with finely divided diluent particles, preferably also in finely divided particulate form, the production of effective bonds to the phenolic polymer cured about the particles, the production of a continuous bonding of polymer with the boron carbide particles at the article surface and the obtaining of a uniformly distributed boron carbide content in the polymeric matrix. It has been found that the particle sizes of the boron carbide should be such that substantially all of it (over 95%, preferably over 99% and more preferably over 99.9%) or all passes through a No. 20 (more preferably No. 35) screen. Preferably, substantially all of such particles, at least 90%, more preferably at least 95%, passes through a No. 60 U.S. Sieve Series screen and at least 50% passes through a No. 120 screen. Although there is no essential lower limit on the particle sizes (effective diameters) usually it will be desirable from a processing viewpoint and to avoid objectionable dusting during manufacture for no more than 25% and preferably less than 15% of the particles to pass through No. 325 and/or No. 400 U.S. Sieve Series screens and normally no more than 50% thereof should pass through a No. 200 U.S. Sieve Series screen, preferably less than 40%. Boron carbide often contains impurities, of which iron (including iron compounds) and B.sub.2 O.sub.3 (or impurities which can readily decompose to B.sub.2 O.sub.3 on heating) are among the more common. Both of such materials, especially B.sub.2 O.sub.3, have been found to have deleterious effects on the present products and therefore contents thereof are desirably limited therein. For example, although as much as 3% of iron (metallic or salt) may be tolerable in the boron carbide particles of high boron carbide content absorbers, preferably the iron content is held to 2%, more preferably to 1% and most preferably is less than 0.5%. Similarly, to obtain stable absorbing articles, especially when they are of long, thin plate form, it is important to limit the B.sub.2 O.sub.3 content (including boric acid, etc., as B.sub.2 O.sub.3), usually to no more than 2%, preferably to less than 1%, more preferably to less than 0.5% and most preferably to less than 0.2%. Of course, the lower the iron and B.sub.2 O.sub.3 contents the better. The boron carbide particles utilized will usually contain the normal isotopic ratio of B.sup.10 but may also contain more than such proportion to make even more effective neutron absorbers. Of course, it is also possible to use boron carbide with a lower than normal percentage of B.sup.10 (the normal percentage being about 18.3%, weight basis, of the boron present) but such products are rarely encountered and are less advantageous with respect to neutron absorbing activities. Other than the mentioned impurities, normally boron carbide should not contain significant amounts of components than than B.sub.4 C (boron and carbon in ideal combination) and minor variants of such formula unless the B.sub.4 C is intentionally diminished in concentration by use of a diluent or filler material, such as silicon carbide, as described herein. For satisfactory absorbing effectiveness at least 90% of the boron carbide particles should be boron carbide, preferably at least 94% and more preferably at least 97% and the B.sup.10 content of the article (from the boron carbide) for best absorption characteristics, will be at least 12%, preferably at least 14% (14.3% B.sup.10 in pure B.sub.4 C). To maintain the stability of the boron carbide-diluent-phenolic polymer article made it is considered to be important to severely limit the contents of halogen, mercury, lead and sulfur and compounds thereof, such as halides, in the final product and so of course, such materials, sometimes found present in impure phenolic resins, solvents, fillers and plasticizers, will be omitted from those and will also be omitted from the composition of the boron carbide particles to the extent this is feasible. At the most, such materials will contain no more of such impurities than would result in the final product just meeting the upper limits of contents allowed, which will be mentioned in more detail in a subsequent discussion with respect to the phenolic polymer and the resins from which it is made. The diluent or filler materials employed in the present articles to diminish the neutron absorbing activities thereof will be such as are compatible with the other components of the present article, principally the boron carbide particles and the phenolic resin and will be able to withstand the conditions of use thereof. Thus, the "diluents" will usually be inert or essentially or substantially inert particulate solids which are insoluble in water and aqueous media to which the neutron absorbing articles might become exposed during use. Such materials should be heat resistant, substantially inert chemically and of comparatively low coefficients of thermal expansion. Generally, inorganic materials such as carbon and compounds, such as carbides and oxides, best satisfy these requirements and the most preferred diluents and fillers are silicon carbide, alumina, silica, graphite ad amorphous carbon although two-component and multi-component mixtures of such materials may also be utilized. Usually, the materials to be employed should be anhydrous, although they may contain small proportions, such as 0.5 to 3%, e.g., 1% e.g., 1%, of moisture, but hydrates may be utilized if the water content thereof is satisfactorily volatilized during curing of the phenolic polymer of the present articles at elevated temperature. Normally the diluents employed will be in particulate form and the powders thereof will be of particle size characteristics like those previously described for the boron carbide particles. It has been found that best flexural strength characteristics are obtained when the diluent particles are of the same particle sizes as the boron carbide particles. Finer particles cause a lessening of flexural strength although products resulting may pass specifications and it is believed that when the filler particles are too coarse similar strength diminutions will result. While such particle sizes are generally preferred, it is also within the invention to utilize more finely divided fillers, usually however providing that the particle sizes are not so small as to cause excessive dusting. Thus, while as much as 95% or more of the diluent particles may pass a 200 mesh sieve it will usually be preferred that no more than 50% of the particles, preferably less than 25% and more preferably, less than 15%, pass through a No. 325 sieve. With respect to impurities, as was previously mentioned, both the boron carbide particles and diluent particles should have low contents, if any at all, of B.sub.2 O.sub.3, iron, halogen, mercury, lead and sulfur and compounds thereof. Although it is desirable that each component of the present composition have less of such impurities than the particular proportions given with respect to the boron carbide and the resin, it is considered that the important factor is the total content of such materials and providing that the total content is maintained within the specifications, variations in impurities contents of the components may be tolerated. The solid irreversibly cured phenolic polymer, cured to a continuous matrix about the boron carbide and diluent particles and binding them together in the neutron absorbing articles, is preferably made from a phenolic resin which is in solid form at normal temperatures, e.g., room temperature, 20.degree.-25.degree. C. The phenolic resins constitute a class of well-known thermosetting resins, most and are condensation products of phenolic compounds and aldehydes. Of the phenolic compounds phenols and lower alkyl- and hydroxyl-lower alkyl-substituted phenols are preferred. Thus, the lower alkyl-substituted phenols may be of 1 to 3 substituents on the benzene ring, usually in ortho and/or para positions and will be of 1 to 3 carbon atoms, preferably methyl, and the hydroxy-lower alkyls present will similarly be 1 to 3 in number and of 1 to 3 carbon atoms each, preferably methylol. Mixed lower alkyls and hydroxy-lower alkyls may also be employed but the total of substitutent groups, not counting the phenolic hydroxyl, is preferably no more than 3. Although it is possible to make a useful product with the phenol of the phenol aldehyde resin being essentially all substituted phenol, some phenol may also be present with it, e.g., 5 to 50%. For ease of expression the terms "phenolic type resins", "phenol-aldehyde type resins" and "phenol-formaldehyde type resins" may be employed in this specification to denote more broadly then "phenol-formaldehyde resins" the acceptable types of matrials described which have properties equivalent to or similar to those of phenol-formaldehyde resins and trimethylol phenol formaldehyde resins when employed to produce thermosetting polymers in conjunction with boron carbide (plus diluent) particles, as described herein. Specific examples of useful "phenols" which may be employed in the practice of this invention, other than phenol, include cresol, xylenol and mesitol and the hydroxylower alkyl compounds preferred include mono-, di- and trimethylol phenols, preferably with the substitution at the positions previously mentioned. Of course, ethyl and ethylol substitution instead of methyl and methylol substitution and mixed substitutions wherein the lower alkyls are both ethyl and methyl, the alkylols are both methylol and ethylol and wherein the alkyl and alkylol substituents are also mixed, are also useful. In short, with the guidance of this specification and the teaching herein that the presently preferred phenols are phenol and trimethylol phenol, other compounds, such as those previously described, may also be utilized providing that the effects obtained are similarly acceptable. This also applies to the selection of aldehydes and sources of aldehyde moieties employed but generally the only aldehyde utilized will be formaldehyde (compounds which decompose to produce formaldehyde may be substituted). The phenolic or phenol formaldehyde type resins utilized are employed as either resols or novolaks. The former are generally called one-stage or single-stage resins and the latter are two-stage resins. The major difference is that the single-stage resins include sufficient aldehyde moieties in the partially polymerized lower molecular weight resin to completely cure the hydroxyls of the phenol to a cross-linked and thermoset polymer upon application of sufficient heat for a sufficient curing time. The two-stage resins or novolaks are initially partially polymerized to a lower molecular weight resin without sufficient aldehyde present for irreversible cross-linking so that a source of aldehyde, such as hexamethylenetetramine, has to be added to them in order for a complete cure to be obtained by subsequent heating. Either type of resin may be employed to make phenolic polymers such as those described herein. When the polymerization reaction in which the resin is formed is acid catalyzed HCl will be avoided (to minimize chloride content in the resin) and formic acid or other suitable chlorine-free acid may be used. The solid state resin preferably employed is of a molecular weight sufficient to result in the resin being a solid, which will generally be in the range of 1,200 to 10,000, preferably 5,000 to 8,000 and more preferably 6,000 to 7,000, e.g., 6,500. The resin may have a small proportion of water present with it, which, if present, is usually adsorbed thereon and usually is less than 3% of the total resin or resin plus formaldehyde donor weight. If the resin is a resol it already contains sufficient formaldehyde for a complete cross-linking cure but if it is a novolak or two-stage resin it may have with it a formaldehyde donor such as hexamethylenetetramine, in sufficient quantity to cross-link the resin to irreversible polymerization (a thermoset). The quantity of cross-linking agent may vary but usually 0.02 to 0.2 part per part of resin will suffice. To avoid ammonia production during curing nitrogen-free formaldehyde donors may be employed, such as paraldehyde or a two-stage resin may be mixed with a one-stage resin containing excess combined or uncombined formaldehyde. Normally the particle sizes of the solid state two-stage or one-stage resins employed will be less than 140 mesh, U.S., Sieve series and preferably over 95% will be of particle sizes less than 200 mesh, to promote ready mixing with the boron carbide particles, even dispersion of the resin and such particles and good continuous resin cures. Among the useful phenolic resin materials that may be employed in such particulate form that which is presently most preferred is Arofene-877, manufactured by Ashland Chemical Company, but other such resins, such as Arofenes 7214; 6745; 6753; 6781; 24780; 75678; 877LF; and 890LF; all made by Ashland Chemical Company, and PA-108 manufactured by Polymer Applications, Inc. and various other solid state phenolic resins, such as described at pages 478 and 479 of the 1975-1976 Modern Plastics Encyclopedia, the manufacturers of which resins are listed at page 777 thereof, may be substituted. Many of such resins are two-stage resins, with hexamethylenetetramine (HMT) incorporated but single stage solids may also be used, as may be two-stage resins with other aldehyde sources included and those dependent on addition of aldehyde. Although the mentioned resins are preferred, a variety of other equivalent phenolic type resins, especially phenolformaldehydes, of other manufacturers and of other types may also be employed providing that they satisfy the requirements for making the molded neutron absorbing articles set forth in this specification. In the preferred method of manufacturing, described in FIG. 2, the liquid medium employed, the function of which is to assist in temporarily binding the powdered resin to the boron carbide and diluent particles, may be any of suitable liquids which can be volatilized off from the curing mixture at a temperature below the curing temperature. Because the curing temperature is normally below about 200.degree. C. it is highly preferable that the liquid medium be of a material or materials which can be volatilized or boiled off at a temperature below 200.degree. C. Most preferable of all such materials is water but aqueous solutions or even dispersions of other volatilizable, decomposable or reactant materials may also be employed. Thus, aqueous alcoholic liquids may be utilized, such as blends of water and ethanol, water and methanol, water and isopropanol. It may be desirable to employ aqueous solutions of formaldehyde or of hexamethylenetetramine, too. Additionally, phenol may be present in aqueous or aqueous alcoholic solution. Instead of using aqueous solution of alcohol the alcohols and other solvents may be utilized alone but generally this is not preferred because of expense, solvent recovery requirements and flammability hazards. When water is employed it will preferably be used alone or will be a major proportion of any mixed liquid, preferably being from 50 to 95% thereof, more preferably 70 to 95% thereof. Care should be taken to make sure that the water used is sufficiently pure (deionized or distilled water may be preferred) so as not to add any objectionable quantities of undesirable impurities to the final product. The powdered resin described above is also useful in the practice of the process of FIG. 4 of the drawing. In such process liquid state phenolic resins are also employed and such liquid resins are also utilized in carrying out the process of FIG. 3. The liquid state resins or mixtures thereof employed in the practice of this invention are normally of the same types as the solid state particulate resins or mixtures thereof previously described but may also be of different types within the previous description. They are of low molecular weight, usually being the monomer, dimer or trimer. Generally the molecular weight of such resins will be in the range of 200 to 1,000, preferably 200 to 750 and most preferably 200 to 500. Such a resin will usually be employed as an aqueous, alcoholic, aqueous alcoholic or other solvent solution so as to facilitate "wetting" of the boron carbide and inert diluent particles and creation of a formable mass. Although water solutions are preferred, lower alkanolic solutions such as methanol, ethanol and isopropanol solutions or aqueous solvent(s) solutions or dispersions are also usable. Generally the resin content of the liquid state resin preparation employed will be from 50 to 90%, preferably about 55 to 85%. The solvent content, usually principally water, may be from 5 to 30%, usually being from 7 to 20%, e.g., 8%, 10%, 15%, with the balance of liquid components normally including aldehyde and phenolic compound. Thus, for example, in a liquid unmodified phenolic resin of the single-stage type based principally on the condensation product of trimethylolphenol and formaldehyde, there may be present about 82% of dimer, about 4% of monomer, about 2% of trimethylol phenol, about 4% of formaldehyde and about 8% of water. When two-stage resins are employed the curing agent may also be included with the resin, in sufficient quantity to completely or partially cure (cross-link) it. Such quantity (for a complete cure) can be 0.02 to 0.2 part per part of resin. To avoid ammonia production during curing a sufficient quantity of an aqueous solution of an aldehyde or another suitable source thereof which does not release ammonia may be used for curing novolaks instead of the usual hexamethylenetetramine. Also, excess formaldehyde which may be present with a one-stage resin may be utilized to help to cure a two-stage resin. The liquid state resins employed are usually in liquid state because of the low molecular weight of the condensation products which are the main components thereof but also sometimes due to the presence of liquid media, such as water, other solvents and other liquids which may be present. Generally the viscosity of such resins at 25.degree. C. will be in the range of 200 to 700 centipoises, preferably 200 to 500 centipoises. Usually the liquid state resin will have a comparatively high water tolerance, generally being from 200 to 2,000 or more percent and preferably will have a water tolerance of at least 300%, e.g., at least 1,000%. Among the useful liquid products that may be employed are Arotap 352-W-70; Arotap 352-W-71; Arotap 8082-Me-56; Arotap 8095-W-50; Arofene 744-W-55; Arofene 986-Al-50; Arofene 536-E-56; and Arofene 72155, all manufactured by Ashland Chemical Company; PA-149, manufactured by Polymer Applications, Inc.; and B-178; R3 and R3A, all manufactured by The Carborundum Company. All such resins will be modified when desirable (when contents of the following impurities are too high) to omit halides, especially chloride, halogens, mercury, lead and sulfur and compounds thereof or to reduce proportions thereof present to acceptable limits. In some cases the procedure for manufacture of the resin will be changed accordingly, for example, formic acid may be used as a polymerization catalyst instead of hydrochloric acid. Different phenolic resins may be utilized for the solid particulate resins and liquid resins and mixtures may be employed in either case. However, very satisfactory products result when the particulate solid resin is a phenol formaldehyde polymer and the normally liquid state resin is a trimethylol phenol formaldehyde polymer. Although various ratios of boron carbide particles to diluent particles may be employed in the making of the present neutron absorbing articles it is generally preferable that the weight ratio thereof be in the range of 1:19 to 19:1 and usually such range will be from 1:9 to 9:1. Because a neutron absorbing capability corresponding to more than 2% of B.sup.10 is normally more desirable the ratio of boron carbide particles to diluent particles will usually be from 1:5 to 5:1, e.g., 1:2 to 2:1. Thus, while the B.sup.10 content of the final product may be in the range of about 0.5 to 12% and is controllable over such range, it will preferably be at least 3%, e.g., 4 to 6%. Additional control of neutron absorbing power may be obtained by adjusting the dimensions of the article made, such as the thickness thereof, especially when the article is in flat plate form and is intended to be utilized as a wall about neutron emitting nuclear material. Instead of utilizing only one type of diluent material with the boron carbide particles, various such inert, high temperature resistant, water insoluble products may be employed in mixture, often of about equal parts of such diluent particles in two- or multi-component mixtures, such as in ratios of 1:2 to 2:1 when two such diluents are employed and in ratios of about 1 to 2:1 to 2:1 to 2, when three components are present. Of course, more than three components may also be utilized. The proportions of the total of boron carbide and diluent particles to irreversibly cured phenol formaldehyde type polymer in the neutron absorbing article will normally be about 60 to 80% of the former and 20 to 40% of the latter, preferably with the total about 100%. Preferably, the component proportions will be 65 to 80% and 20 to 35%, with the presently most preferred proportions being about 70% and 30% or 74% and 26% and with essentially no other components in the neutron absorber (the water or liquid medium is essentially all volatilized off during curing). Within the proportions described the product made has the desirable physical characteristics for use in storage racks for spent nuclear fuel, which characteristics will be detailed later. Also, the described ratios of the total of boron carbide and diluent particles to phenolic resin permit manufacture by the simple, inexpensive, yet effective method of this invention. As was previously mentioned, various objectionable impurities will preferably be omitted from the present articles and the components thereof. Additionally, for most successful production of the present neutron absorbers, which should contain only very limited amounts, if any at all, of halogens, mercury, lead and sulfur, the content of B.sub.2 O.sub.3, which may tend to interfere with curing, sometimes causing the "green" molded article to lose its shape during the cure, and which can have adverse effects on the finished article, and the content of iron will also preferably be limited. Generally, less than 0.1% of each of the mentioned impurities (except the B.sub.2 O.sub.3 and iron) is in the final article, preferably less than 0.01% and most preferably less than 0.005%, and contents thereof in the resins are limited accordingly, e.g., to 0.4%, preferably 0.04%, etc. To assure the absence of such impurities the phenol and aldehyde employed will initially be free of them, at least to such an extent as to result in less than the limiting quantities recited, and the catalysts, tools and equipment used in the manufacture of the resins will be free of them, too. To obtain such desired results the tools and equipment will preferably be made of stainless steel or aluminum or similarly effective non-adulterating material but steel mixers have been found to be useful and not objectionably contaminating. Preferably impurities such as water, solvent, filler, plasticizer, halide or halogen, mercury, lead and sulfur should not be present or if any is present, the amount thereof will be limited as previously described and otherwise held to no more than 5% total in the final product. Generally, non-volatile plasticizers and various other components sometimes employed with resins will be omitted. To manufacture the present neutron absorbers by a preferred method the boron carbide particles, diluent particles and powdered resin are mixed together as previously mentioned, moisture is applied to the surface of such mix by suitable means so as to bring it into contact with all the particles, the moistened mix is compressed to green plate form and is then cured to final product. A useful method of manufacture is described in detail in the Owens application previously mentioned, and therefore little detail of such method will be given herein. Normally, dry mixing times will be from 1 minute to 20 minutes, preferably 2 to 10 minutes, after which moisture is mixed in and mixing is continued for about an equal period of time until the blend appears to be uniform. It may then be allowed to dry out somewhat, normally removing from 1/2 to 3/4 of the mixture weight as moisture over a period of five minutes to one hour, and then is screened, if desirable, to remove any small lumps. The desired pre-calculated weight of boron carbide-diluent-resin mix next is screened into a clean mold cavity of desired shape through a screen of about 4 to 20 mesh on top of a bottom plunger, aluminum setter plate and glazed paper, glazed side to the mix, and is leveled in the mold cavity by sequentially running across the major surface thereof a plurality of graduated strikers. This gently compacts the material in the mold, while leveling it, thereby distributing the boron carbide and resin evenly throughout the mold so that when such mix is compressed it will be of uniform density and B.sup.10 concentration throughout. A sheet of glazed paper is placed on top of the leveled charge, glazed side against the charge, and atop this there are placed a top setter plate and a top plunger, after which the mold is inserted in a hydraulic press and is pressed at a pressure of about 20 to 500 kg./sq. cm., preferably 35 to 150 kg./sq. cm., for a time of about 1 to 30 seconds, preferably 2 to 5 seconds. Plungers and plates on both sides of the pressed mixture, together with the pressed mixture, are removed from the mold together, the plungers and the setter plates are removed and the release papers are stripped from the pressed mixture. Fiberglass cloths are placed next to the molded item and then the green absorber plate and setter plate(s), usually of aluminium, are reassembled, with fiberglass cloth(s) between them. The assemblies are then inserted in a curing oven and the resin is cured. The cure may be effected with a plurality of sets of setter plates and green plates atop one another, usually three to ten, but curing may also be effected without such stacking, with only a lower setter plate being used for each green plate. Also, because the present mixes are not objectionably sticky, use of the fiberglass cloths may be omitted and in some cases use of the glazed paper may be omitted during pressing, at least for the portion of the mix in contact with the bottom setter plate, which supports the green plate during curing. The cure may be carried out in a pressurized oven, sometimes called an autoclave, but good absorber plates may also be made without the use of pressure during the curing cycle. The curing temperature is usually between 130 and 200.degree. C., preferably 140 to 160 or 180.degree. C. and the curing usually takes from 2 to 20 hours, preferably 2 to 10 hours and most preferably 3 to 7 hours. For best results the oven will be warmed gradually to curing temperature, which facilitates the gradual evaporation of some liquid from the green articles before the curing temperature is reached, thereby helping to prevent excessive softening of the green plate and loss of shape thereof. A typical warming period is one wherein over about 1 to 5 hours, preferably 2 to 4 hours, the temperature is gradually increased from room temperature (10 to 35.degree. C.) to curing temperature, e.g., 149.degree. C., at which temperature the green plate is held for a curing period, and after which it is cooled to room temperature at a regular rate over about 1 to 6 hours, preferably 2 to 4 hours, after which the cured article may be removed from the oven. When the oven is pressurized the pressure may often be from about 2 to 30 kg./sq. cm., preferably 5 to 10 kg./sq. cm. gas pressure (not compressing or compacting pressure). Instead of heating from room temperature to curing temperature in the allotted period described above, if it is considered desirable to improve the physical state of the green plate before curing it may be subjected to heating and drying in the oven at a temperature of about 40 to 60.degree. C., e.g., 52.degree. C., for about 6 to 48 hours, e.g., 24 hours, before such temperature is raised to curing level. Instead of following the preferred procedure, alternative methods may also be utilized, such as are described in the Storm and McMurtry et al. patent applications, previously mentioned. Following the one-step processing of the Storm application the boron carbide and diluent particles are mixed, particulate resin powder is admixed with them and liquid resin is blended with the mix, after which, the molding, pressing and curing processes of the previously described process are followed, with screening, etc., as desirable. Normally the proportion of liquid state phenolic resin to solid state phenolic resin in the curable mixture thereof with the boron carbide and diluent particles is within the range of 1:0.5 to 1:4. Another method which may be employed for the manufacture of the present absorbing articles, that of the McMurtry et al. application, involves utilizing about 1/5 to 2/3 preferably 1/4 to 1/2 of the resin, in liquid state, in initial mixture with all the boron carbide and diluent particles, pressing and curing a green plate of desired initial composition and then impregnating it with additional liquid resin, followed by curing. The various methods described all result in the production of useful neutron absorbing articles, preferably in plate form, which have desirable characteristics for such a product. Although the neutron absorbing articles made in accordance with the invented process may be of various shapes, such as arcs, cylinders, tubes (including cylinders and tubes of rectangular cross-section), normally they are preferably made as comparatively thin, flat plates which may be long plates or which may be used a plurality at a time, preferably erected end to end, to obtain the neutron absorbing properties of a longer plate. To obtain adequately high neutron absorbing capability the articles will usually be from 0.2 to 1 cm. thick and plates thereof will have a width which is 10 to 100 times the thickness and a length which is 20 to 500 times such thickness. Preferably, the width will be from 30 to 80 times the thickness and the length will be from 100 to 400 times that thickness. The neutron absorbing articles made in accordance with this invention are of a desirable density, normally within the range of about 1.2 g./cc. to about 2.8 g./cc., preferably 1.3 to 2 g./cc., e.g., 1.6 g./cc. They are of satisfactory resistance to degradation due to temperature and due to changes in temperature. They withstand radiation from spent nuclear fuel over exceptionally long periods of time without losing their desirable properties. They are designed to be sufficiently chemically inert in water so that a spent fuel storage rack in which they are utilized could continue to operate without untoward incident in the event that water leaked into their stainless steel container. They do not galvanically corrode with aluminum and stainless steel and are sufficiently flexible to withstand seismic events of the types previously mentioned. Thus, they are of a modulus of rupture (flexural) which is at least 100 kg./sq. cm. at room temperature, 38.degree. C. and 149.degree. C., a crush strength which is at least 750 kg./sq. cm. at 38.degree. C. and 149.degree. C., a modulus of elasticity which is less than 3.times.10.sup.5 kg./sq. cm. at 38.degree. C. and a coefficient of thermal expansion at 66.degree. C. which is less than 1.5.times.10.sup.-5 cm./cm. .degree. C. The absorbing articles made, when employed in a storage rack for spent fuel, as in an arrangement like that shown at FIG'S. 1-3 of the McMurtry et al. patent application, previously mentioned, are designed to give the desired extent of absorption of slow moving neutrons, prevent active or runaway nuclear reactions and allow an increase in storage capacity of a conventional pool for spent fuel storage. The designed system is one wherein the aqueous medium of the pool is usually water at a slightly acidic or neutral pH or is an aqueous solution of a boron compound, such as an aqueous solution of boric acid or buffered boric acid, which is in contact with the spent fuel rods although such rods are maintained out of contact with the present boron carbide-diluent-phenolic polymer neutron absorber plates. In other words, although the spent fuel is submerged in a pool of water or suitable aqueous medium and although the neutron absorber plates are designed to surround it they are normally intended to be protected by a sealed metallic or similar enclosure from contact with both the pool medium and the spent fuel. Of course, the particular composition of the absorber plates will be regulated so that they will be resistant to chemical interaction with the storage pool. The absorber plates made in accordance with this invention by the methods described above are subjected to stringent tests to make sure they possess the desired resistances to radiation, galvanic corrosion, temperature changes and physical shocks, as from seismic events. Because canisters or compartments in which they can be utilized might leak they also should be inert or substantially inert to long term exposure to storage pool water, which, for example, could have a pH in the range of about 4 to 6, a fluoride ion concentration of up to 0.1 p.p.m., a total suspended solids concentration of up to 1 p.p.m. and a boric acid content in the range of 0 to 2,000 p.p.m. of boron. Also, the "poison plates" of this invention should be capable of operation at normal pool temperatures, which may be about 27.degree. to 93.degree. C., and even in the event of a leak in the canister should be able to operate in such temperature range for relatively long periods of time, which could be up to six months or sometimes, a year. Further, the products should be able to withstand 1.times.10.sup.11 rads and preferably, 2.times.10.sup.11 rads total radiation, should not be galvanically corroded in use and should not cause such corrosion of metals or alloys employed. In this respect, while normally ordinary No's. 304 or 316 stainless steels may be used for structural members when seismic events are not contemplated, where such must be taken into consideration in the design of storage racks utilizing the present absorbers high strength stainless steels will preferably be used. The absorbers made may be of the lengths described in the McMurtry et al. application, e.g., 0.8 to 1.2 meters, so few joints are needed when plates are stacked one atop the other to form a continuous longer absorbing wall, or they may be made of other lengths. The desirable effects reported are obtainable using a variety of the phenolic resins described, alone or in combination, some of which may be one-stage and others of which may be two-stage, and a variety of the described diluents, either alone or in mixture, is also satisfactory. However, other resins and diluents outside the preferred class do not appear to have properties which allow the successful manufacture of stable and long lasting neutron absorbers by such simple methods and at reasonable costs. The following examples illustrate but do not limit the invention. In the examples and in this specification all parts are by weight and all temperatures are in .degree.C., unless otherwise indicated. EXAMPLE 1 3,200 Grams of boron carbide powder and 4,080 grams of silicon carbide powder are mixed together in a steel paddle mixer at room temperature (25.degree. C.) for five minutes and over another five minute period there are admixed therewith 2,450 grams of Ashland Chemical Company Arofene 877 powdered phenol formaldehyde resin. The boron carbide powder is one which has been previously washed with hot water and/or appropriate other solvents, e.g., methanol, ethanol, to reduce the boric oxide and any boric acid content thereof to less than 0.5% (actually 0.16%) of boric oxide and/or boric acid, as boric oxide. The powder analyzes 75.5% of boron and 97.5% of boron plus carbon (from the boron carbide) and the isotopic analysis of the boron present is 18.3 weight percent B.sup.10 and 81.7% B.sup.11. The boron carbide particles contain less than 2% of iron (actually 1.13%), and less than 0.05% each of halogen, mercury, lead and sulfur. The particle size distribution is 0% on a 35 mesh sieve, 0.4% on 60 mesh, 41.3% on 120 mesh and 58.3% through 120 mesh, with less than 15% through 325 mesh. The silicon carbide powder is a mixture of equal parts by weight of a silicon carbide powder which passes through a 50 mesh U.S. Sieve Series screen and fails to pass a 100 mesh sieve, and such a powder which passes a 100 mesh sieve. The more finely divided powder will usually have less than 25% thereof passing through a 325 mesh sieve. The contents of impurities in the silicon carbide particles will be maintained the same as or essentially the same as those of the boron carbide particles. The Arofene 877 powder (sometimes called 877 or PDW-877) is a two-stage phenolic resin powder of about 90% solids content (based on final cross-linked polymer) having an average molecular weight of 6,000 to 7,000 and a particle size distribution such that at least 98% passes through a 200 mesh sieve, and containing about 9% of hexamethylenetetramine (HMT). The resinous component is a condensation product of phenol and formaldehyde but instead of the phenol there may be substituted various other phenolic compounds, preferred among which is trimethylol phenol. The Arofene 877 resin may be characterized as an unmodified, short-flow, powdered, two-step phenolic resin. It exhibits an inclined plate flow of 25-40 mm., a reactivity (hot plate cure at 150.degree. C.) of 60-90 seconds and a softening point (ring and ball, Dennis bar) of 80 to 95.degree. C. and is of an apparent density of about 0.32 g./cc. It contains about 1% of volatile material. Instead of Arofene 877, in the present example there may be substituted Arofene 890 or Arofene 1877. After mixing together of the powdered materials 300 grams of water are admixed with them by adding the water onto the moving surfaces of the mix, while it is being agitated in the paddle mixer. Spray nozzles may be employed to distribute the water better and in such cases the spray nozzle and the droplet sizes of the spray will be in the 0.5 to 2 mm. diameter range. However, it has been found that it is not required to spray the water or other liquid onto the surfaces of the particulate mixture and actually the water can be poured onto the moving surfaces or dripped onto them, with good mixing and distribution throughout the particulate material. After completion of mixing the mix may be screened through a 10 mesh (or 4 to 40 mesh) screen and may be allowed to stand for about an hour and then screened through a 10 mesh opening (or 4 to 40 mesh) screen, after which it may be filled into a mold, preferably after being leveled, and then pressed to green article shape, which shape is preferably that of a long thin flat plate, suitable for use in storage racks for spent nuclear fuel. Alternatively instead of screening, drying and screening, as described above, the screening may be done directly into the mold. The mold employed comprises four sides of case hardened steel (brake die steel) pinned and tapped at all four corners to form an enclosure, identical top and bottom plungers about 2.5 cm. thick made of T-61 aluminum and 1.2 cm. thick top and bottom aluminum tool and jig setter plates, each weighing about one kg. The molds, which had been used previously, are prepared by cleaning of the inside surfaces thereof and insertions of the bottom plunger, the bottom setter plate on top of the plunger and a piece of glazed paper, glazed side up, on the setter plate. A charge (675 grams) of the boron carbide particles-silicon carbide particles-powdered resin-water mix fills the mold and is leveled in the mold cavity by means of a series of graduated strikers, the dimensions of which are such that they are capable of leveling from about a 12 mm. thickness to a desired 9 mm., with steps about every 0.8 mm. A special effort is made to make sure to fill the mold at the ends thereof so as to maintain uniformity of boron carbide (and silicon carbide) distribution throughout. Thus, the strikers are initially pushed toward the ends and then moved toward the more central parts of the molds and they are employed sequentially so that each strike further levels the mix in the mold. A piece of glazed paper is then placed on top of the leveled charge, glazed side down and the top setter plate and top plunger, both of aluminum, are inserted. The mold is then placed in a hydraulic press and the powder-resin mix is pressed. The size of the "green" plate made is about 14.7 cm. by 77.2 cm. by 3.6 mm. and the density thereof is about 1.6 g./cc. The pressure employed is about 143 kg./sq. cm. and it is held for three seconds. The pressure may be varied so long as the desired initial "green" article thickness and density are obtained. After completion of pressing the mold is removed from the press and at an unloading station a ram and a fixture force the plungers, setter plates and pressed mixture upwardly and through the mold cavity. The plungers, setter plates and glazed papers are then removed and the pressed mixture, in green article form, is placed between setter plates and intermediate layers of fiberglass cloth and is cured. Curing is effected by heating from room temperature to 149.degree. C. gradually and regularly over a period of three hours, holding at 149.degree. C. for four hours and cooling to room temperature at a uniform rate for three hours. After curing, the plate weighs 640 grams and its dimensions are essentially the same as after being pressed to green plate form. The finished plate is of about 72% of a total of boron carbide and diluent particles (31.6% of boron carbide and 40.4% of silicon carbide) and 28% of phenolic polymer. It appears to have the same desirable properties (except for lower neutron absorbing capability) of a similar product in which the silicon carbide particles are replaced by boron carbide particles. Thus, when tested it will be found to have a modulus of rupture (flexural) of at least 100 kg./sq. cm. at room temperature, 38.degree. C. and 149.degree. C. (actually 496 kg./sq. cm. at room temperature), a crush strength of at least 750 kg./sq. cm. at 38.degree. C. and 149.degree. C., a modulus of elasticity less than 3.times.10.sup.5 kg./sq. cm. at 38.degree. C. (actually 1.2.times.10.sup.5 kg./sq. cm. at room temperature) and a coefficient of thermal expansion at 66.degree. C. which is less than 1.5.times.10.sup.-5 cm./cm..degree. C. The neutron absorbing plates made will be of satisfactory resistance to degradation due to temperature and changes in temperature such as may be encountered in normal uses as neutron absorbers, as in fuel racks for spent nuclear fuels. They are designed to withstand radiation from spent nuclear fuel over long periods of time without losing desirable properties and similarly are designed to be sufficiently chemically inert in water so that a spent fuel storage rack could continue to operate without untoward incident in the event that water should leak into a stainless steel or other suitable metal or other container in which they are contained in such a rack. They do not galvanically corrode and are sufficiently flexible, when installed in a spent nuclear fuel rack, to survive seismic events of the types previously mentioned. In other words, they will be of essentially the same properties as the neutron absorbing plates described in the Owens patent application previously referred except that they are of a lesser neutron absorbing capability due to being diluted with the silicon carbide particles. When the experiment of Example 1 is repeated, with the silicon carbide being replaced by amorphous carbon, graphite, alumina or silica of essentially the same particle sizes and distributions or with equal mixtures of diluent components in 2-component or multi-component mixtures, e.g., amorphous carbon and graphite, amorphous carbon and silicon carbide, or amorphous carbon, graphite and silicon carbide, the same type of useful neutron absorber may be made. Also, when component proportions are varied, .+-.10%, .+-.20%, and .+-.30%, while being maintained within the ranges given in the foregoing specification, useful neutron absorbers may be made while varying the processing conditions, as taught above. Thus, neutron absorbers of any of a desired range of activities may be readily produced. EXAMPLE 2 A neutron absorber of essentially the same neutron absorbing and stability characteristics as that described in Example 1 is made by mixing together the same quantities of the same boron carbide and silicon carbide particles in the same manner but instead of mixing dry resin and water with them a lesser quantity, 750 grams, of liquid state phenolformaldehyde type resin (primarily trimethylol phenol formaldehyde) is utilized. The resin employed is Ashland Chemical Company Arotap Resin 358-W-70 and it is mixed with the mixture of boron carbide and silicon carbide powder for 30 minutes to produce a homogeneous mixture in which the resin appears to be substantially uniformly distributed over the surfaces of the particles. The Arotap resin solution employed, a thick liquid, having a viscosity of 200 to 500 centipoises at 25.degree. C. and a water tolerance of about 1,000%, is principally a condensation product of trimethylolphenol and formaldehyde and contains about 82% of dimer, about 4% of monomer, about 2% of trimethylolphenol, about 4% of formaldehyde and about 8% of water. The resin contains less than 0.01% of each of halogen, mercury, lead and sulfur, including compounds thereof. After completion of mixing, which is effected in a suitable stainless steel or aluminum paddle mixer, the mix is screened through a 3 mesh sieve and is allowed to dry for 16 hours at room temperature (15.degree. to 30.degree. C.) and normal humidity (35 to 65% R.H.). The loss in weight is about 55 to 70% of the volatiles and moisture content or about 6% of the weight of the resin, which corresponds to about 0.6% of the weight of the total mixture. The mix is next screened through a ten mesh screen and is ready for use. The molds employed are those previously described, as is the pressing method. The size of the green plate made is about 14.7 cm. by 77.2 cm. by 2.8 mm. and the density is about 1.7 g./cc. After completion of pressing and removal of release paper from the molded article the green plate, resting on the bottom setter plate, is placed flat in an oven, with the major surface thereof facing upwardly and the initial cure thereof is commenced. This is effected by increasing the temperature gradually by about 40.degree. C. per hour from room temperature to 149.degree. C. over a period of about three hours, holding for four hours at 149.degree. C. and then cooling at a rate of about 40.degree. C./hr. for three hours, back to room temperature. The total cycle is about ten hours and is automatically controlled. At the end of the curing cycle (the initial cure) the pressed plate can be easily removed from the setter plate and is independently form retaining. When weighed it is noted that it has lost additional weight, often losing an average of about 20 grams, so that it weighs about 510 grams. The density of the plate is about 1.6 g./cc. After completion of the initial cure the pressed plate, removed from the setter plate, is positioned vertically in a basket with various other such plates, standing on ends therein and separated by wires or screening and the basket is inserted into an impregnating vessel, which includes connections to sources of vacuum, pressurized air and liquid resin. The stainless steel vessel is then sealed and a vacuum of about 660 mm. of mercury is drawn on the tank over a period of about five minutes, after which the valve to the resin supply is opened and liquid resin (Arotap 358-W-70) is drawn into the tank and is allowed to completely cover all of the plates therein. Such addition of resin takes place over a period of about 1 to 5 minutes, after which the connection to the vacuum source is closed and the plates, submerged in the liquid resin, are allowed to absorb such resin over a period of 1 to 5 minutes. Then the resin is forced from the tank by compressed air at a pressure of about 260 mm. Hg gauge. The vessel is then opened and the basket containing the impregnated plates is removed therefrom. The plates are taken out of the baskets, are placed on their thin sides on drying racks separated by lengths of stainless steel or aluminum wire or clips and are dried at 52.degree. C. for a period of about 60 hours. During this drying operation there is a weight loss of about 1/12 of the approximately thirty additional percent of liquid state phenolic resin impregnating the plates (about 1.9% of the weight of the plates). The resin add-on is about 3/5 to 3/4 of the total resin content. The dried impregnated plates are next placed on setter plates of the type previously described, form-retaining flat aluminum, with fiberglass cloth separators covering the impregnated plates, and are stacked six high, flat sides up and down, on carts, which are then placed in a pressurizable oven, which is sealed and pressurized to about 6.4 kg./sq. cm. gauge. The temperature in the pressurized oven is raised to 149.degree. C. gradually over a seven hour period with one hour holds at 79.degree. C., 93.degree. C. and 121.degree. C. After holding for four hours at 149.degree. C. the temperature is gradually decreased to room temperature over a period of five hours, dropping at about 26.degree. C. per hour. Thus, the total pressurized curing cycle takes sixteen hours, after which the cured plates are removed from the carts and are inspected. They weigh 637 grams. The finished plates are of about the same composition as those of Example 1 and of about such dimensions and density. On testing they will be found to have a modulus of rupture (flexural) of at least 100 kg./sq. cm. at 25.degree. C., 38.degree. C. and 149.degree. C. (actually 350 kg./sq. cm. at room temperature), a crush strength of at least 750 kg./sq. cm. at 38.degree. C. and 149.degree. C., a modulus of elasticity of less than 3.times.10.sup.5 kg./sq. cm. at 38.degree. C. (actually 1.5.times.10.sup.5 kg./sq. cm. at room temperature) and a coefficient of thermal expansion at 66.degree. C. which is less than 1.5.times.10.sup.-5 cm./cm..degree. C. Like the products of Example 1, they are useful poison plates for absorption of neutrons from radioactive materials, especially spent nuclear fuel in rack storage in aqueous pools. They will be capable of resisting seismic conditions, as previously described, temperature and temperature changes experienced in spent fuel storage racks and other stresses and strains normally placed on them in such applications. The above experiment is repeated for verification of the reproducibility of the results and the modulus of rupture and modulus of elasticity of the products resulting are measured. The modulus of rupture is found to be 321 kg./sq. cm. at room temperature and the modulus of elasticity is measured as 1.5.times.10.sup.5 kg./sq. cm. at room temperature. The product appears to be of the same desirable physical and chemical characteristics as that described above in this example. When the composition of the plates is changed, as in Example 1, preferably when amorphous carbon or graphite is substituted for a silicon carbide or is employed in conjunction with it, and when the shapes thereof are changed, such as to curved shapes, as described previously in the specification, interchangeably useful products of predictable and controllable neutron absorbing capabilities may be made. EXAMPLE 3 When the procedures of Examples 1 and 2 are varied, as described in the Storm patent application previously referred to, similarly useful articles are producible. Such are made when instead of boron carbide particles being utilized, 44:56 mixtures of boron carbide and silicon carbide are utilized in the processes of the Storm working examples. Also, similarly useful products are producible when instead of silicon carbide, amorphous carbon, graphite, alumina and silica or a mixture thereof is utilized and when the proportions of boron carbide to inert diluent particles are varied, as previously mentioned. In practicing the invention as described in the foregoing specification and as is illustrated in the working examples, components of the products will be chosen so as to result in the production of satisfactory products, of sufficient neutron absorbing capability to be useful, of controllable neutron absorbing capabilities and of properties resistant to the environment in which they are intended to be employed. Thus, for example, diluents and other components utilized will be resistant to elevated temperature, rapid temperature changes and to extended radiation exposure. Similarly, with respect to workability and processing characteristics, the components will be chosen so as to facilitate mixing, blending, maintenance of structural integrity after pressing into green plate form and maintenance of such form during curing. One of skill in the art with this specification before him will be able to select particular components and processing conditions, such as temperatures, humidities, pressures and times, so as to able to manufacture the desired products quickly, efficiently and satisfactorily. 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 before him will be able to utilize substitutes and equivalents without departing from the spirit of the invention. |
description | 1. Field of the Invention The present invention relates to a passive containment air cooling device and system with an isolated pressure boundary, and more particularly, to a passive containment air cooling device and system with an isolated pressure boundary, in which a radioactive substance in a containment is prevented from being discharged out of the containment even though an internal or external part is broken. 2. Description of the Related Art When a leakage accident of cooling water occurs in a nuclear power plant, the cooling water is confined in a containment to manage the accident, and an internal part of the containment is cooled in order to prevent the internal pressure of the containment from being increased. In a light water reactor, generally, when the internal pressure of the containment is increased after a nuclear reactor accident, a vapor in the containment is condensed by using a spray pump, or a large-sized water tank is provided outside the containment and a heat exchanger is provided in the containment to condense a vapor in the heat exchanger and thus reduce the pressure of the containment. Referring to FIGS. 1 and 2, in a typical containment cooling system, when a portion of a heat exchanger 20 positioned inside or outside a containment 10 is broken, a radioactive substance 30 in the containment 10 may be discharged through the broken heat exchanger 20 into the atmosphere. This type is used in most of containment cooling systems, and an example thereof includes Korean Patent No. 10-1224024. In order to solve the aforementioned limitation, the present invention proposes a passive containment air cooling device with an isolated pressure boundary. In order to achieve the objects, the present invention provides a passive containment air cooling device with an isolated pressure boundary, including: a heat exchanger positioned inside and outside a containment, penetrating through an outer wall of the containment to be connected to the containment through a pipe and thus form a closed loop, and including a coolant; an air induction duct circulating air outside the heat exchanger; and a cooled air exhaust unit formed in the air induction duct to increase cooling efficiency of the heat exchanger. The heat exchanger may include: a containment internal heat exchanger exposed to an inside of the containment; a containment external heat exchanger exposed to an outside of the containment; a gas phase (vapor) connection pipe penetrating through the outer wall of the containment and connecting a side of an upper part of the containment internal heat exchanger and a side of an upper part of the containment external heat exchanger; and a liquid phase (water) connection pipe penetrating through the outer wall of the containment and connecting a side of a lower part of the containment internal heat exchanger and a side of a lower part of the containment external heat exchanger. The containment internal heat exchanger, the containment external heat exchanger, the gas phase (vapor) connection pipe, and the liquid phase (water) connection pipe may constitute a closed loop. The containment internal heat exchanger and the containment external heat exchanger may have a heat exchanger tube assembly structure enduring internal and external pressures. The gas phase (vapor) connection pipe may be inclined at a slope of (+)5° or more to a ground surface from the inside of the containment to the outside, and the liquid phase (water) connection pipe may be inclined at a slope of (−)5° or less to the ground surface from the outside of the containment to the inside. The containment internal heat exchanger may vaporize a coolant in the containment internal heat exchanger due to internal heat of the containment. The containment external heat exchanger may emit heat to external air to condense a coolant in the containment external heat exchanger. The cooled air exhaust unit may be selectively provided on any one of upper, lower, and middle portions inside the air induction duct. The present invention also provides a passive containment air cooling system with an isolated pressure boundary, including the passive containment air cooling devices with the isolated pressure boundary according to any one of claims 1 to 8 provided on each quadrant of an outer part of one containment. The passive containment air cooling device with the isolated pressure boundary may be respectively provided with air induction ducts, wherein the air induction ducts are converged into one in an upper part of the containment and have a single air outlet. Hereinafter, a passive containment air cooling device and system with an isolated pressure boundary according to the present invention will be described in detail with reference to the accompanying drawings. In this case, constitutions and functions of the present invention illustrated in the drawings and described with reference to the drawings are illustrated as at least one embodiment, and the technical spirit, and the essential constitution and function of the present invention are not limited thereto. Extensively used general terms at this time are selected as terms used in the present invention in consideration of a function thereof in the present invention, but the terms may be changed according to an intention of a person with ordinary skill in the art, the custom, or the emergence of a novel technology. Further, in a special case, terms arbitrarily selected by an applicant may be used, and in this case, the meaning of the terms will be described in detail in the corresponding description of the invention. Accordingly, it should be noted that the terms used in the present invention are not simple names of the terms, but should be defined based on the meaning of the terms and entire contents of the present invention. FIG. 3 is a vertical cross-sectional view of a passive containment air cooling device with an isolated pressure boundary according to an embodiment of the present invention. Referring to FIG. 3, the passive containment air cooling device with the isolated pressure boundary according to the embodiment of the present invention may include a heat exchanger 300, an air induction duct 400, and a cooled air exhaust unit 500. The heat exchanger 300 may be formed through an outer wall of a containment 100, and may be exposed to the inside and outside of the containment 100. The heat exchanger 300 may be configured with a closed loop. The heat exchanger 300 exposed to the inside of the containment 100 absorbs vapor heat in the containment 100 to cool high-temperature vapor in the containment. In this case, a liquid coolant in the heat exchanger is vaporized to flow toward the heat exchanger 300 outside the containment 100. The coolant may be made of a material having high specific heat, and may be preferably water. The heat exchanger 300 exposed to the outside of the containment 100 emits heat absorbed inside the containment 100 to air outside the containment 100. In this case, the heat exchanger outside the containment 100 is cooled by ambient air to condense high-temperature vapor in the heat exchanger into a liquid phase and thus allow the liquid phase to flow from the heat exchanger outside the containment 100 to the heat exchanger inside the containment 100 due to a head difference, thereby forming a closed loop natural circulation. For the heat exchanger 300, the heat exchanger 300 exposed to the outside of the containment 100 may be cooled by the air induction duct 400 and the cooled air exhaust unit 500 which will be described later. The coolant may fill the heat exchanger 300 in a content of 30 to 70% of an internal volume of the heat exchanger 300, but the volume is not limited thereto. When the content of the coolant is greater than 70% of the internal volume of the heat exchanger 300, internal pressure of the heat exchanger 300 may be excessively increased due to vaporization of the coolant; and when the content of the coolant is less than 30% of the internal volume of the heat exchanger 300, cooling efficiency of a cooling system of the containment may be reduced. The heat exchanger 300 will be described later with reference to FIG. 4. The air induction duct 400 is a passage pipe formed outside the containment 100 to induce a flow of air, and external air may flow through an inlet and be exhausted through an outlet. The air induction duct 400 may be formed outside the heat exchanger 300. The air induction duct 400 is a hollow pipe vertically formed outside the containment 100, and may have a shape corresponding to that of the outer wall of the containment 100. Due to the aforementioned constitution, a temperature of relatively cold air flowing through the inlet of the air induction duct 400 may be increased due to heat of the heat exchanger 300, and for the flow of air in the air induction duct 400, a density difference serving as driving force of the flow of air may be naturally formed due to heat of the heat exchanger 300. Air in the air induction duct 400 may have a stack effect. Further, the vaporized coolant positioned in the heat exchanger 300 may be cooled due to the flow of air and then liquefied. The cooled air exhaust unit 500 may include an electromotive fan 510 and a driver 550. The cooled air exhaust unit 500 may be provided in the air induction duct 400, and increase an amount of the flow of air naturally formed in the air induction duct 400. As the amount of the flow of air in the air induction duct 400 is increased due to the cooled air exhaust unit 500, cooling efficiency of the coolant positioned in the heat exchanger 300 may be increased. The electromotive fan 510 is a fan rotating by the driver 550, and may be a device forming the flow of air. The driver 550 is a power device performing a rotation motion and may be a motor, but is not limited thereto. FIG. 4 is a vertical cross-sectional view of the heat exchanger of the passive containment air cooling device with the isolated pressure boundary according to the embodiment of the present invention. Referring to FIG. 4, the heat exchanger 300 may include a containment internal heat exchanger 310, a containment external heat exchanger 320, a gas phase (vapor) connection pipe 330, and a liquid phase (water) connection pipe 340. The containment internal heat exchanger 310, which is a pipe positioned in the containment and of which at least a portion is formed perpendicular to a ground surface, may receive internal heat of the containment. Cooling water included in the containment internal heat exchanger 310 may absorb the internal heat of the containment to be vaporized, and in this case, vapor of vaporized cooling water may be positioned at an upper part of the containment internal heat exchanger 310. Further, the containment internal heat exchanger 310 may have a heat exchanger tube assembly structure capable of enduring the internal pressure of the containment. If the containment internal heat exchanger 310 is not formed to have the heat exchanger tube assembly structure, the containment internal heat exchanger 310 may be broken due to internal pressure of the containment or pressure of the vaporized coolant in the containment internal heat exchanger 310. Thus, it is desirable that the containment internal heat exchanger 310 be formed to have the heat exchanger tube assembly structure made of metal having high thermal conductivity to facilitate heat exchange, but the containment internal heat exchanger 310 is not limited thereto. The containment external heat exchanger 320, which is a pipe positioned outside the containment and of which at least a portion is formed perpendicular to the ground surface, may emit heat of vapor of the cooling water circulated through the gas phase (vapor) connection pipe 330 in the containment internal heat exchanger 310 to the outside. Vapor of the cooling water, from which heat is emitted, may be cooled in the containment external heat exchanger 320, and the vapor may be liquefied to be accumulated at a lower part of the containment external heat exchanger 320. Further, the containment external heat exchanger 320 has the heat exchanger tube assembly structure capable of enduring a pressure. If the containment external heat exchanger 320 is not a heat exchanger tube capable of enduring a pressure, the containment external heat exchanger 320 may be broken due to pressure of vapor of cooling water flowing from the containment internal heat exchanger 310. Thus, it is preferable that the containment external heat exchanger 320 be formed to have the heat exchanger tube assembly structure. Further, it is preferable that the containment external heat exchanger 320 be a heat exchanger tube made of metal having high thermal conductivity in order to facilitate heat exchange, but the containment external heat exchanger is not limited thereto. The gas phase (vapor) connection pipe 330 is a pipe connecting an end of an upper part of the containment internal heat exchanger 310 and an end of an upper part of the containment external heat exchanger 320, and a flow path of a gas phase (vapor) coolant. The liquid phase (water) connection pipe 340 is a pipe connecting an end of a lower part of the containment internal heat exchanger 310 and an end of a lower part of the containment external heat exchanger 320, and may be a flow path of a liquid phase (water) coolant. The gas phase (vapor) connection pipe 330 and the liquid phase (water) connection pipe 340 may be elements which penetrate through the outer wall of the containment to slantly connect a containment internal element and a containment external element such that a natural circulation is achieved between the containment internal element and the containment external element. The gas phase (vapor) connection pipe 330 is inclined so that a direction of the containment external heat exchanger 320 is higher than a direction of the containment internal heat exchanger 310, and a slope may be (+)5° or more. Vapor of cooling water generated in the containment internal heat exchanger 310 may flow into the containment external heat exchanger 320 due to the slope, and flowing may be performed in a natural circulation manner without a separate controlling device due to the rising effect of high-temperature gas. In this case, when the slope of the gas phase (vapor) connection pipe 330 is less than (+)5°, vapor of cooling water may not flow smoothly. The liquid phase (water) connection pipe 340 is inclined so that the direction of the containment internal heat exchanger 310 is higher than the direction of the containment external heat exchanger 320, and the slope may be (−)5° or less. When the slope of the liquid phase (water) connection pipe 340 is greater than (−)5°, the sufficient slope is not obtained, and thus condensed cooling water may not flow smoothly. Cooling water condensed in the containment external heat exchanger 320 may flow into the containment internal heat exchanger 310 due to the slope, and flowing may be performed in a natural circulation manner due to a head difference caused by a difference in density between cooling water and vapor. Cooling water accumulated in the containment external heat exchanger 320 may flow into the containment internal heat exchanger 310 due to a difference between the head of the coolant in the containment internal heat exchanger 310 and the head of the coolant in the containment external heat exchanger 320, and resultantly the coolant may be circulated. By virtue of the aforementioned constitution of the containment heat exchanger 300, the coolant in the containment heat exchanger 300 may be vaporized in the containment internal heat exchanger 310 positioned in the containment due to the internal heat of the containment, and the vapor of the coolant flow into the containment external heat exchanger 320 through the gas phase (vapor) connection pipe 330. Then, the vapor of the coolant may be condensed, and be naturally re-circulated through the liquid phase (water) connection pipe 340 to the lower part of the containment internal heat exchanger 310. The gas phase (vapor) connection pipe 330 and the liquid phase (water) connection pipe 340 may be preferably configured with pressure pipes, but are not limited thereto. The containment internal heat exchanger 310, the containment external heat exchanger 320, the gas phase (vapor) connection pipe 330, and the liquid phase (water) connection pipe 340 constitute the closed loop to independently form an internal pressure. Accordingly, the closed loop forms a pressure boundary to internal pressure of the containment inside the containment, and also forms a pressure boundary to an atmospheric pressure outside the containment. Accordingly, even when the closed loop is broken inside or outside the containment, a radioactive substance in the containment may be prevented from being leaked to the atmosphere outside the containment. A description thereof will be described in more detail with reference to FIGS. 6 and 7. FIG. 5 is a horizontal cross-sectional view illustrating a passive containment air cooling system with an isolated pressure boundary formed on a quadrant according to the embodiment of the present invention. The passive containment air cooling system with the isolated pressure boundary according to the embodiment of the present invention may include at least two heat exchanging units 600. Preferably, the passive containment air cooling system may include the heat exchanging unit 600 formed on each quadrant of the containment 100, but is not limited thereto. If one heat exchanging unit 600 is provided in the containment 100, the containment 100 is unable to be cooled when the heat exchanging unit 600 is broken. Thus, when the plurality of heat exchanging units 600 are provided, it is possible to prepare for the case some of the heat exchanging units 600 are disabled. FIGS. 6 and 7 are vertical cross-sectional views illustrating the case where an external portion or an internal portion of a heat exchanger of the passive containment air cooling system with the isolated pressure boundary according to the embodiment of the present invention is broken. Referring to FIG. 6, the case where the containment external heat exchanger 320 of the heat exchanger 300 is broken (A) may occur. In this case, the heat exchanger 300 has a closed loop shape, and thus the radioactive substance generated in the containment 100 does not flow into the heat exchanger 300, and may be prevented from being leaked to the outside of the containment. Referring to FIG. 7, the case where the containment internal heat exchanger 310 of the closed loop is broken (B) may occur. In this case, the radioactive substance generated in the containment may flow into the closed loop, but the pressure boundary of the containment external heat exchanger 320 is blocked from the atmosphere, and thus the radioactive substance in the containment may be prevented from being leaked to the atmosphere. According to embodiments of the present invention, it is possible to cool a containment through a cooling pipe of a closed loop, and prevent a radioactive substance in the containment from being leaked to the external atmosphere because a pressure boundary between the internal pressure of the containment and the external atmosphere is preserved even though the cooling pipe is partially broken. Since a heat exchanger outside the containment can be an air cooling type, an additional supplement of cooling water is not required. Furthermore, the cooling pipe of the closed loop is driven through natural circulation, and thus driving and operation controlling devices are not required separately, thereby reducing equipment maintenance costs for a containment cooling system. According to the aforementioned constitution, in the passive containment air cooling device and system with the isolated pressure boundary according to the present invention, a related art water cooling type of containment cooling system continuously requiring a supplement of cooling water can be replaced by an air cooling type of passive containment air cooling device with the isolated pressure boundary which does not require a supplement of cooling water, and thus a high effect is obtained even with simple equipment. Further, the passive containment air cooling device and system with the isolated pressure boundary according to the present invention can prevent a radioactive substance in a containment from being leaked to the outside through a cooling pipe of a closed loop when a heat exchanger is partially broken. Moreover, in the passive containment air cooling device and system with the isolated pressure boundary according to the present invention, since a coolant in the heat exchanger is naturally circulated due to internal heat of the containment, a separate controlling device circulating the coolant is not required, thereby reducing costs. |
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054229227 | claims | 1. A fuel assembly comprising a plurality of fuel rods which are composed of cladding tubes wherein a plurality of fuel pellets including fissile material are inserted, and at least a moderating rod which is filled with moderator for moderating neutrons generated by nuclear fissions, characterized in that a ratio of a sum of transversal cross section area of portions of said moderating rods which are filled with moderator to a sum of transversal cross section area of said fuel pellets averaged in an axial direction of the fuel assembly is at least 0.4. the transversal cross section area of portions filled with moderator per moderating rod is in a range of 14-50 cm.sup.2. a ratio of a sum of transversal cross section area of said moderator in a transversal cross section surrounded with imaginary planes which are extended downwards from outer edges of an upper tie plate which bundles said plurality of fuel rods to a sum of transversal cross section area of said fuel pellets is a value. in a range 2.7-3.4. at least one of said moderating rods is a double wall water rod wherein water level moves up or down depending on a flow rate of the moderator. a ratio of a sum of transversal cross section area of said moderator filled in a water gap region around said fuel assemblies to the sum of transversal cross section area of said fuel pellets is utmost 0.7. a control rod which is composed of a plurality of absorbing rods including neutron absorber bundled in a form having a cruciform cross section, and is inserted into a water gap region around said fuel assemblies, wherein a ratio of a sum of surface area of said absorbing rods to a sum of surface area of said fuel rods is at least 0.2. a control rod which is composed of a plurality of absorbing rods including neutron absorber bundled in a form having a cruciform cross section, and is inserted into a water gap region around said fuel assemblies, wherein a ratio of a sum of transversal cross section area of said absorbing rods to a sum of transversal cross section area of said water gap region is at least 0.4. a ratio of a sum of transversal cross section area of said moderator to the sum of transversal cross section area of said fuel pellets is a value in a range 3.0-3.5. 2. A fuel assembly claimed in claim 1, wherein 3. A fuel assembly claimed in claim 1, wherein 4. A fuel assembly claimed in claim 1, wherein 5. A reactor core comprising any one of the fuel assemblies claimed in any of claims from claim 1 to claim 4. 6. A reactor core claimed in claim 5, wherein 7. A reactor core claimed in claim 5, comprising 8. A reactor core claimed in claim 5, comprising 9. A reactor core claimed in claim 5, wherein |
abstract | A new interface between the cladding and the stack of pellets in a nuclear control rod. According to the invention, an interface joint made of a material transparent to neutrons, in the form of a structure with a high thermal conductivity and open pores, adapted to deform by compression across its thickness, is inserted between the cladding and the stack of pellets made of B4C neutron absorber material over at least the height of the stack. The invention also relates to associated production methods. |
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abstract | A shielding (11) for reducing the amount of radiation passing through the shielding comprises a first part (111) and a second part (112), wherein the first part is arranged for being withdrawn from the second part and wherein said first and second parts comprise abutments. At least one pair of corresponding abutments of said first and second parts has a transverse section which is curvilinearly shaped along a portion of at least half of said transverse section. |
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042232244 | claims | 1. 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 comprising at least one damped oscillator means coupled to said specimen holder at approximately the point of maximum vibration amplitude of said specimen holder, to eliminate interfering soil vibrations within said specimen holder. 2. The improvement recited in claim 1, wherein said oscillator means comprises a damped uni-axial oscillator means. 3. The improvement recited in claim 1, wherein said oscillator means comprises a damped multi-axial oscillator means. 4. The improvement recited in claim 1, wherein said oscillator means comprises a bi-axial oscillator consisting of a resilient rod which is unilaterally coupled to said specimen holder and is surrounded by energy-consuming material disposed on said rod, the resonance frequency of said oscillator in the two axes thereof being approximately equal to the corresponding resonance frequencies of said specimen holder. 5. The improvement recited in claim 4, wherein said rod has a circular cross-section and said energy-consuming material comprises an elastomer tube disposed on said rod. 6. The improvement recited in claims 4 or 5, further comprising a weight member disposed on said rod near a free end thereof. 7. The improvement recited in claim 1, wherein said oscillator means comprises a tri-axial oscillator comprising a first rigid mass located in the center of a second mass which is resilient in all three axes and is fabricated of energy-consuming material, the resonance frequency of said oscillator in said individual axes being approximately equal to the corresponding resonance frequencies of said specimen holder. |
summary | ||
047918012 | summary | BACKGROUND OF THE INVENTION This invention relates to nuclear power reactor fuel assembly repair and more particularly to a reversible fuel assembly grid tab repair tool having a bending member for remotely reforming fuel assembly grid tabs, wherein the tool has means for fine alignment of the bending member with the grid tab to be reformed. A nuclear power reactor is an apparatus for producing heat by the controlled fission of fissile nuclear material such as uranium-235. The nuclear material is typically formed into relatively small cylindrical fuel pellets which are stacked end to end in an elongated hollow cylindrical fuel rod which serves as cladding for the fuel rods. In the case of a pressurized water reactor, a plurality of fuel rods are bundled together by a plurality of rectangular grids each grid having generally rectangular cells therethrough for receiving each fuel rod so that the distance between fuel rods in adjacent cells obtains a predetermined pitch. The grids, which are fastened to a plurality of guide thimble tubes disposed in the fuel assembly, which thimble tubes extend the length of the fuel rods, are spaced along the length of the fuel rod bundle for securing the fuel rods in the bundle configuration by the friction engagement of a plurality of grid dimples which are integrally attached to each grid cell. A plurality of grid tabs are integrally attached to a rectangularly-shaped grid strap which wraps the outermost perimeter of the grid cells and thus binds the fuel rods in the grid. The grid tabs assist in directing cooling water flow over the fuel rods. The top and bottom of the fuel rod bundle are connected to a top nozzle and a bottom nozzle respectively for providing structural support to the fuel rod bundle. The combination of the fuel rod bundle, guide thimble tubes, grids, top nozzle and bottom nozzle form a fuel assembly. A plurality of fuel assemblies are disposed in a predetermined pattern in a nuclear reactor core which is positioned in a reactor pressure vessel. Heat due to fission of the nuclear fuel is carried away from the fuel assemblies by water circulating over each fuel assembly, which heat is transferred to a turbine for generating electricity in a manner well known in the art of nuclear power production. On occasion, a nuclear fuel rod requires replacement prior to the end of the operating life of the fuel rod. For example, the fuel rod may experience localized rod cladding breakage. Such breakage may be caused, for instance, by a phenomenon known in the art as baffle jetting wherein high pressure coolant water jets through a deformed joint of a core baffle which surrounds the reactor core and impinges one or more of the fuel rods located near the joint. If this happens, a fuel rod near the deformed joint may experience cladding damage due to the force of the impinging water. Such a joint must be reformed and the damaged fuel rod must be replaced with an undamaged fuel rod to avoid release of radioactive material from the damaged fuel rod into the cooling water. After the damaged fuel rod is withdrawn from its fuel assembly grid cell, an undamaged fuel rod is inserted into that cell. However, occasionally a fuel assembly grid tab, which is attached to the grid strap, is unintentionally deformed or bent when the undamaged fuel rod is inserted into a fuel assembly grid cell located adjacent the grid tab. In this manner, grid tabs may become bent from a nominal 43 degrees to as much as 90 degrees or more. When a grid tab is deformed in the manner described immediately above, the replacement fuel rod may vibrate against its adjacent deformed grid tab during reactor operation thereby increasing the likelihood that the bent grid tab may damage the fuel rod cladding. The vibration of the fuel rod is caused by the velocity and force of the coolant water flowing through and about the grid during reactor operation. Therefore, to preclude the possible undesirable effects of such a bent grid tab, the grid tab must be reformed by bending the grid tab so that the grid tab can not vibrate against the fuel rod in a manner which can cause fuel rod cladding damage. An appropriate grid tab crimping or bending tool capable of being remotely operated may be used for this purpose. A crimping tool adapted for crimping the edges of a panel for an automobile or the like is disclosed in U.S. Pat. No. 3,180,128, invented by O. V. Faulkner and issued Apr. 27, 1965. The Faulkner device comprises an elongated cylindrical body member having an elongated actuating member extending through the cylindrical body. A laterally projecting crimping element is carried by the actuating member in position to extend in spaced, parallel relation to a transverse plate which is carried by the cylindrical body member. The panel to be crimped is engaged between a relatively small crimping element and a relatively wide holding surface, thereby preventing damage to a finished surface which is placed in contact with the holding surface. The crimping element is urged by spring means away from the transverse plate whereby the crimping element always returns to a position to receive a member to be crimped. An adjustable stop means is also provided for varying the effective length of the actuating member. Although the Faulkner patent discloses a crimping tool most applicable to automobile panels, the Faulkner patent does not appear to disclose a tool suitable for bending or crimping a nuclear fuel assembly grid tab in the manner of the present invention which is a remotely operable and reversible fuel assembly grid tab repair tool. U.S. Pat. No. 4,614,106 issued Sept. 30, 1986 to D. Forget and entitled "Tab Lifting And Crimping Tool" discloses a tab lifting tool suitable for use on radiators of a type commonly used to cool motor vehicle engine cooling water. The tool includes a casing having a pair of openings at opposite ends thereof and an elongated tool channel inside the casing which communicates with the openings. An elongated tool member slidably mounted in the tool channel has a tab lifting finger proximate a tab lifting end of the casing and a tab crimping face proximate a tab crimping end of the casing. A flange gripping finger is affixed to the tab crimping end of the casing while a trigger is pivotally mounted in the casing. Biasing means are also located in the casing and engage the tool member for urging the tab lifting finger away from the casing and the tab crimping face towards the casing. Even though the Forget patent discloses a tool for lifting and crimping automobile radiator tabs, the Forget patent does not appear to disclose a tool for remotely bending or crimping a nuclear fuel assembly grid tab in the fashion of the present invention. U.S. Pat. No. 3,570,299 issued Mar. 16, 1971 to A. W. Wieters and entitled "Internal Duct Crimper" discloses a crimping device for bending and clenching edges of laterally extending ducts to main ducts including a bifurcated arm structure with a clenching device and anvil provided on the end of one of the arms with means for shifting the clenching member into clenching position against the anvil through the utilization of a connected arm and lever device. The apparatus provides a duct crimper wherein the crimping mechanism, including a shoe and anvil device, is carried completely on one leg of the unit. Although the Wieters patent discloses a tool for bending and clenching edges of laterally extending ducts to main ducts, the Wieters patent does not appear to disclose a reversible device configured for remotely bending or reforming nuclear fuel assembly grid tabs as provided by the present invention. A remotely operable device for studying fission gases generated within fuel rods during reactor operation is disclosed by U.S. Pat. No. 4,428,903 issued Jan. 31, 1984 in the name of James E. Kasik et al. and entitled "Fuel Rod Fission Gas Crimping Arrangement And Method". To study these gases, irradiated fuel rods are individually punctured in a subaqueous environment to release the fission gases for capture and examination. In this regard, a selected fuel rod is withdrawn from its bundle for penetration. After withdrawal from the bundle, and after penetration and capture of fission gas, the selected fuel rod is stored underwater for an indefinite period of time. The Kasik et al. device remotely and sealingly crimps a malleable sleeve over the puncture hole through which fission gases escape in order to prevent further release of fission gasses when the fuel rod is stored. According to the Kasik et al. disclosure, a hydraulically operated crimping mechanism forms a pair of sealing ridges (one on each side of the puncture hole) between the malleable sleeve and the punctured fuel rod by crimping the malleable sleeve with its jaws. At the appropriate moment, the jaws clench, securing the malleable sleeve onto the fuel rod and over the puncture hole. Although the Kasik et al. patent discloses a remotely operable crimping tool suitable for use on a nuclear fuel assembly component (e.g., a nuclear fuel rod), the Kasik et al. patent does not appear to disclose a reversible tool having a bending means for reforming a fuel assembly grid tab in combination with a spring biasing means connected to the bending means and does not appear to disclose an anvil surface on the tool against which the grid tab can be bent or reformed. Moreover, the Kasik et al. patent does not appear to disclose a device having means for fine alignment of a bending mechanism with the grid tab to be reformed. Consequently, while the prior art discloses crimping devices for crimping elements or tabs, the prior art does not disclose a reversible device having a bending member which is suitable for remotely bending or reforming a fuel assembly grid tab, wherein the device has means for fine alignment of the bending mechanism with the grid tab to be reformed. Therefore, what is needed is a reversible fuel assembly grid tab repair tool having a bending member for remotely reforming a fuel assembly grid tab, wherein the repair tool has means for fine alignment of the bending member with the grid tab to be reformed. SUMMARY OF THE INVENTION Disclosed herein is a reversible fuel assembly grid tab repair tool having a hook-shaped grid tab bending member for remotely bending or reforming deformed fuel assembly grid tabs, wherein the repair tool includes means for fine alignment of the grid tab bending member proximate the grid tab to be bent or reformed. The grid tabs may be disposed on the top and bottom edges of a grid strap which wraps a plurality of fuel rods disposed in the fuel assembly. The repair tool comprises a frame having an outwardly extending alignment blade which is capable of being interposed between two fuel rods adjacent each side of the grid tab for fine alignment of the bending member proximate the grid tab. The repair tool further comprises an anvil surface thereon for bending the grid tab thereagainst, the anvil surface having a plurality of outwardly extending register pins sized to matingly abut either the top or the bottom edge of the grid strap on each side of the grid tab to be reformed for fine alignment of the bending member proximate the grid tab. A lever member, which is pivotally connected to the frame and fixedly attached to the bending member, translates the bending member towards the anvil surface, when the lever member is pivoted, so that the grid tab bends if the grid tab is interposed between the bending member and the anvil surface. The repair tool includes a biasing means for biasing the bending member away from the anvil surface to receive another grid tab to be bent. |
claims | 1. A central column for a toroidal field coil, the central column comprising a plurality of segments (1001), each segment comprising first and second sets of parallel arrays of HTS tapes, the HTS tapes arranged such that c-axes of ReBCO crystal structures of the HTS tapes within each array are parallel to each other, and such that planes of the HTS layers of the HTS tapes within each segment are perpendicular to a respective radius (1010) of the central column which passes through the segment, wherein:each HTS tape has a c-angle which is an angle between a perpendicular to a plane of an HTS layer of the HTS tape and the c-axis of the ReBCO crystal structure of the tape;the HTS tapes of each array (1013) within the first set of arrays are HTS tapes having a first c-angle;the HTS tapes of each array (1011, 1012) within the second set of arrays are HTS tapes having a second c-angle which is greater than the first c-angle;wherein, within each segment, the first set of arrays are arranged closer to the respective radius than the second set of arrays. 2. A central column according to claim 1, wherein the each segment comprises one or more further sets of arrays comprising HTS tape having respective further c-angles, and wherein, within each segment, each set of arrays is arranged closer to the respective radius than sets of arrays comprising HTS tape having greater c-angles. 3. A central column according to claim 1, wherein each set of arrays is arranged such that a further radius of the central column passes through at least one array of the set of arrays, the further radius being at an angle from the respective radius equal to a c-angle of the HTS tape of that set of arrays. 4. A central column according to claim 1, and comprising two layers of segments, wherein a first layer of segments is located radially outward of a second layer of segments. 5. A toroidal field coil comprising a central column according to claim 4, wherein return limbs of the toroidal field coil which are connected to HTS assemblies of the second layer have a greater vertical extent than return limbs of the toroidal field coil which are connected to HTS assemblies of the first layer. 6. A central column according to claim 1, and comprising joints at either end of the central column. 7. A toroidal field coil comprising a central column according to claim 1. 8. A toroidal field coil comprising a central column according to claim 1, wherein each array of HTS tapes is an arc of a wound HTS coil. |
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047724463 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, and particularly to FIG. 1, there is shown an elevational view of a gripper assembly 10 of the invention disposed above a nuclear reactor fuel assembly 12, represented in vertically foreshortened form. The fuel assembly 12 includes a number of longitudinally extending guide tubes or thimbles 14 which project upwardly from a bottom nozzle (not shown). The assembly 12 further includes an organized array of elongated fuel rods 16 transversely spaced and supported by axially spaced transverse grids. The assembly 12 has a top nozzle 18 removably attached to the upper ends of the guide thimbles 14 to form an integral assembly capable of being conventionally handled without damaging the assembly parts. As mentioned above, the fuel rods 16 in the array thereof in the fuel assembly 12 are held in spaced relationship with one another by grids spaced along the fuel assembly length. Each fuel rod 16 includes nuclear fuel pellets and the opposite ends of the rod are closed by upper and lower end plugs to hermetically seal the rod. The fuel pellets, composed of fissile material, are responsible for creating the reactive power of the nuclear reactor. A liquid moderator/coolant such as water, or water containing boron, is pumped upwadly through the fuel assemblies of the core in order to extract heat generated therein for the production of useful work. In the operation of a nuclear reactor, it is common practice to provide an excess of reactivity initially in the reactor core and, at the same time, provide means to maintain the reactivity relatively constant over its lifetime. Such means commonly takes the form of control rods (not shown) supported for movement into the guide thimbles of some fuel assemblies in the core and burnable absorber rods 20 supported stationarily in the guide thimbles 14 of other fuel assemblies in the core. The stationary absorber rods 20 assist the movable control rods in maintaining a substantially constant level of neutron flux or reactivity in the core throughout its operating cycle. Before describing the means of the present invention for releasably engaging a burnable absorber rod, the means for stationarily attaching the burnable absorber rods 20 to the top nozzle 18 will be briefly described. As illustrated in FIGS. 3, 6, 7 and 8, the top nozzle 18 includes a lower adapter plate 22 having a plurality of passageways 24 (only one being shown) formed therethrough. Each guide thimble 14 has its uppermost end portion coaxially positioned within one passageway 24 in the adapter plate 22 and is removably connected to the adapter plate 22 by attaching structure 26, which provides a plurality of structural joints between the top nozzle 18 and the guide thimbles 14 of the fuel assembly skeleton. The attaching structure 26 is generally the same as illustrated and described in U.S. Pat. Nos. 4,631,500 and 4,684,500 cross-referenced above. Absorber rods 20 are disposed within guide thimbles 14 and extend through passageways 24 of adapter plate 22. The absorber rods 20 are releasably secured to adapter plate 22 by releasable latching structures 28. Releasable latching structure 28 is more fully described in U.S. Pat. No. 4,684,499 cross-referenced above, but will be described herein to the extent necessary to facilitate an understanding of the present invention. Releasable latching structure 28 includes a generally cylindrical mounting body 30 (FIGS. 3, 4 and 5) and a generally cylindricaly spring latch 32. The mounting body 30 is composed of a generally cylindrical lower plug portion 34 attached to and sealing the upper end of the absorber rod 20 and a generally cylindrical upper end portion 36 having an annular circumferential groove 38 defined thereabout. An undercut cavity 40 formed in the uppermost surface of the upper end portion 36 of the mounting body 30 is configured to receive the gripper assembly 10 of the invention for use in the insertion and removal of the absorber rods 20 from guide thimbles 14. The mounting body 30 has a generally conical configuration tapering inwardly from the upper end portion 36 to the lower plug portion 34 so as to define a tapering recessed void region 42, which surrounds the mounting body 30 at the middle portion thereof. Mounting body 30 has a plurality, preferably four, circumferentially spaced projections 44 disposed at 90 degree intervals about its lower end just above plug portion 34. Projections 44 are designed to extend over the top surface of adapter plate 22 when an absorber rod 20 is disposed within a guide thimble 14. The spring latch 32 of the latching structure 28 is composed of a generally cylindrical outer ring portion 46 disposed about the upper end portion 36 of the mounting body 30 and a plurality, preferably four, circumferentially spaced latch fingers 48 connected at their upper ends to the outer ring portion 46 in cantilever fashion and extending downwardly therefrom along the mounting body 30. Latching fingers 48 are disposed at 90 degree intervals and extend downwardly between projections 44 (FIG. 5). The outer ring portion 46 has an annular circumferential groove 50 associated annular circumferential bulge 52 defined therein. Circumferential bulge 52 coacts with to the circumferential groove 38 in the upper end portion 36 of latching structure 28 so as to connect the spring latch 32 to the mounting body 30. The latch fingers 48 have external latching keys 54 defined on their lower ends and are radially deflectible toward and away from the mounting body 30 between a outer latching position as seen in FIG. 3 and an inner unlatching position as seen in FIGS. 6, 7 and 8. The normal relaxed position to which each of the fingers 48 is biased to return is the latching position. When releasable latching structure 28 is holding absorber rods 20 in place within guide thimbles 14, latch fingers 48 are in their outer latching position and the latching keys 54 are engaged within recess 56 of a passageway 24 in adapter plate 22. As shown in FIG. 1, gripper assembly 10 is housed within support frame 58, which is disposed above fuel assembly 12. Gripper assembly 10 is attached to the lower portion of mast 60 by a bracket 62. Mast 60 is moved vertically between an upper and lower position by a mechanism, not shown, to raise and lower gripper assembly 10 with respect to fuel assembly 12. Comb assembly 64 provides some guidance and support for absorber rods 20 as they are raised from or lowered into fuel assembly 12. A recess is provided in each of the four lower corners of frame 58 to receive a guide pin 66, mounted on top of the fuel assembly 12 to orient the frame 58 as it is lowered onto fuel assembly 12 for use. As shown in FIGS. 2, 3, 6, 7 and 8, the gripper assembly 10 of the present invention includes actuator plate 68 and lower plate 70 disposed below and spaced apart from actuator plate 68. Actuator plate 68 is movable vertically with respect to lower plate 70 between a first distance and a closer second distance. A center support 72 is fixedly secured to actuator plate 68 and extends through bores in the center of both actuator plate 68 and lower plate 70, thus securing the plates 68 and 70 together. Center support 72 includes a circumferential flange 74 at its lower end which is capable of supporting lower plate 70 when the gripper assembly 10 is not engaging an absorber rod 20. Lower plate 70 includes a plurality of hollow cylindrical actuating sleeves 76 extending downwardly from lower plate 70. Actuating sleeves 76 are spaced so that they will extend over an absorber rod 20 as gripper assembly 10 is lowered over fuel assembly 12. Actuating sleeves 76 are of a size appropriate for causing keys 54 of latch fingers 48 to disengage from adapter plate 22 of the top nozzle 18 of the fuel assembly 12 as an actuating sleeve 76 is lowered over an absorber rod 20. Each actuating sleeve 76 further includes an annular circumferential bulge 78 on its inner surface which engages an annular circumferential groove 50 of a spring latch 32 as actuating sleeves 76 are lowered over absorber rods 20. Hollow cylindrical positioning sleeves 80 are attached to lower plate 70 and extend part way through the hollow portions 82 of actuating sleeves 76. The bottom surface 81 of each positioning sleeve 80 rests on the upper surface 83 of a mounting body 30 of a releasable latching structure 28 when gripper assembly 10 is lowered over absorber rods 20. Contact between bottom surfaces 81 of positioning sleeves 80 and the upper surfaces 83 of mounting bodies 30 prevents further downward motion of gripper assembly 10. Gripper flexures 84 extend through the hollow portions 86 of positioning sleeves 80 past the bottom surfaces 81 of positioning sleeves 80. Gripper flexures 84 include grippers 88 which are received within undercut cavities 40 of mounting bodies 30 as gripper assembly 10 is lowered over absorber rods 20. Actuator rods 90 extend from actuator plate 68 downwardly through hollow portions 92 between gripper flexures 84. As actuator plate 68 moves downwardly with respect to lower plate 70 between the first and second distance, actuator rod 90 contacts shoulders 91 and then inner surfaces 93 of grippers 88 to spread grippers 88 of gripper flexures 84 apart. Thus, when grippers 88 of gripper flexures 84 are disposed within undercut cavities 40 of mounting bodies 30, actuator rods 90 spread grippers 88 of gripper flexures 84 apart to securely engage the sides of undercut cavities 40. As shown in FIGS. 1, 2, 9 and 10, a plurality of latches 94 are attached to actuator plate 68 by pins 96. Each latch includes upper and lower fins 98 and 100, respectively. Latches 94 are normally biased in the locked position by a torsion spring 102. Lower fins 100 of latches 94 include flat shelf portions 104, which support lower plate 70 when latches 94 are oriented in the locked position and the distance between actuator plate 68 and lower plate 70 is the second distance (FIG. 10). Actuators 106 are used to release latches 94 from their locked positions. Actuators 106 include a stem portion 108 by which actuators 106 are attached to frame 58 through mounting means 110. Enlarged portions 112 at the lower ends of stems 108 contact upper fins 98 of latches 94 to unlock latches 94 (FIG. 9). Actuators 106 are attached to frame 58 so that they are movable along a vertical path between a lower, normal position (FIG. 10) and a raised, operating position (FIG. 9). Actuators 106 can be activated only when the gripper assembly 10 is at the lower end of its travel. In order to remove an absorber rod 20 from the top nozzle 18 of a fuel assembly 12, the gripper assembly 10 is lowered onto fuel assembly top nozzle 18. Actuator plate 68 and lower plate 70 are held in a first spaced relationship. Actuator plate 68 is supported by bracket 62 and lower plate 70 is supported by flange 74 of center support 72. As the gripper assembly 10 is lowered onto fuel assembly top nozzle 18, actuating sleeves 76 are lowered over releasable latching structures 28, which are releasably securing absorber rods 20 to adapter plate 22 of top nozzle 18 (FIG. 3). As each actuating sleeve 76 moves down over a releasable latching structure 28, an annular circumferential bulge 78 of an actuating sleeve 76 is eventually retained within an annular circumferential groove 50 of an outer ring portion 46 of a spring latch 32. Fingers 48 of each spring latch 32 are gradually forced inward toward a mounting body 30 until the latching keys 54 are disengaged from a recess 56 in passageway 24 in adapter plate 22. At the same time, each gripper flexure 84 gradually enters an undercut cavity 40 of a mounting body 30. Downward movement of gripper assembly 10 stops when the bottom surfaces 81 of positioning sleeves 80 contact the uppermost surfaces 83 of the upper end portions 36 of mounting bodies 30 of releasable latching structures 28 (FIG. 6). Use of positioning sleeves 80 prevents gripper flexures 84 from bottoming out in the undercut cavities 40 of the releasable latching structures 28, thus ensuring smooth operation of the gripper flexures 84. The actuator plate 68 is then lowered with respect to lower plate 70. As actuator plate 68 is lowered, each actuating rod 90 gradually enters hollow portions 92 between gripper flexures 84 contacts shoulders 91 and then inner surfaces 93 of grippers 88 and gradually pushes grippers 88 apart to a position wherein the grippers 88 of gripper flexures 84 are securely engaged within undercut cavities 40 of mounting bodies 30 of releasable latching structures 28 (FIG. 7). Absorber rods 20 can then be withdrawn from guide thimbles 14 and removed from the fuel assembly 12 by raising the gripper assembly 10 (FIG. 8). The actuator plate, 68 and the lower plate 70 are held together in this closer, spaced relationship as the gripper assembly 10 is raised by latches 94. After lower plate 70 reaches its lowest point of travel, actuators 106 are raised to their operating position (FIG. 9). As the actuator plate 68 is lowered with respect to the lower plate 70, so that gripper flexures 84 securely engage absorber rods 20, actuators 106 contact upper fins 98 of latches 94 causing latches 94 to rotate counterclockwise (FIG. 9). As a result, flat shelf portions 104 of latches 94 clear the top surface and outer edges of lower plate 70 and snap under lower plate 70 so that flat shelf portions 104 of latches 94 support the lower surface of lower plate 70 (FIG. 10). In order to insert an absorber rod into the fuel assembly top nozzle 18, the gripper assembly 10 is lowered onto fuel assembly top nozzle 18 with actuator plate 68 and lower plate 70 held in their second spaced apart relationship with latches 94 in their locked position and flat shelf portions 104 of latches 94 supporting the lower plate 70. Absorber rods 20 are secured by gripper assembly 10 as actuator rods 90 are disposed within hollow portions 92 between gripper flexures 84 keeping grippers 88 in their spaced apart position so that they are securely engaged within cavities 40 of mounting bodies 30 of releasable latching structures 28. Downward movement of gripper assembly 10 stops when the bottom surfaces 77 of actuating sleeves 76 contact the upper surface 23 of top nozzle adapter plate 22. In this position, absorber rods 20 are inserted within passageways 24 of top nozzle adapter plate 22 but are still secured by grippers 88 of gripper assembly 10 (FIG. 7). Actuators 106 are then raised until they contact upper fins 98 of latches 94 causing latches 94 to rotate counterclockwise (FIG. 9). As a result, flat sheet portions 104 of latches 94 clear the lower surface and outer edges of lower plate 70 releasing lower plate 70 (FIG. 9). As gripper assembly 10 is raised, actuator plate 68 is raised with respect to lower plate 70 until actuator plate 68 and lower plates 70 are in their first spaced apart relationship whereby actuator plate is supported by bracket 62 and lower plate 70 is supported by flange 74 on center support 72. As actuator plate 68 is raised with respect to lower plate 70, actuator rods 90 are withdrawn from recesses 92 between gripper flexures 84 so that grippers 88 no long securely engage undercut cavities 40 of mounting bodies 30 of releasable latching mechanisms 28 (FIG. 6). Further upward movement of the gripper assembly 10 raises actuator sleeves 76 from the upper surface of top nozzle adapter plate 22. As actuator sleeves 76 are raised, latch fingers 48 of releasable latching structure 28 are released and keys 54 of latch fingers 48 engage recesses 56 in passageway 24 in adapter plate 22, thus, securing absorber rods 20 to top nozzle adapter plate 22 through releasable latching structures 28 (FIG. 3). |
summary | ||
047626666 | claims | 1. A nuclear reactor tip off assembly, comprising: (a) a nozzle; (b) a closure assembly body connected to said nozzle and having an inlet adjacent said nozzle, an outlet adapted to receive a nozzle cap, and a through bore connecting said inlet and outlet, said inlet, outlet and through bore being dimensioned to permit passage of a fuel charge driven by fluid pressure in said nozzle from said nozzle through said inlet, through bore, and outlet; (c) a swing gate in said body and moveable between a first position in which said swing gate does not seal said through bore and a second position in which said swing gate seals said through bore, said swing gate being moved to said first position by said fuel charge during said passage; and (d) means in said body and in fluid communication with said inlet for hydraulically moving said swing gate to said second position in the absence of said fuel charge regardless of the presence of said fluid pressure in said closure assembly. (a) a nozzle; (b) a closure assembly body connected to said nozzle and having an inlet adjacent said nozzle, an outlet adapted to receive a nozzle cap, and a through bore connecting said inlet and outlet, said inlet, through bore, and outlet being dimensioned to permit passage of a fuel charge driven by fluid pressure in said nozzle from said nozzle through said inlet, through bore, and outlet; (c) an upper chamber in said closure assembly body, above said through bore; (d) a swing gate having an upper substantially planar surface defining a bottom surface of said upper chamber, an arcuate surface facing said outlet and having a first center of curvature, and a substantially concave surface facing said inlet, said swing gate being pivotable about a first horizontal axis perpendicular to said through bore, adjacent said inlet, and offset from said first center of curvature, and adapted to be movable by the passage of a fuel charge through said through bore to a first position in which said swing gate does not obstruct said through bore, and, in the absence of a fuel charge in said through bore regardless of the presence of said fluid pressure, to a second position sealing said through bore; (e) orifice means in said swing gate for providing fluid communication between said upper chamber and said inlet; and (f) a closure assembly seat in said closure assembly body adapted to form a seal with said swing gate. (a) a nozzle; (b) a closure assembly body connected to said nozzle and having an inlet adjacent said nozzle, an outlet adapted to receive a nozzle cap, and a through bore connecting said inlet and outlet, said inlet, through bore, and outlet being dimensioned to permit passage of a fuel charge driven by fluid pressure in said nozzle from said nozzle through said inlet, through bore, and outlet; (c) an upper chamber in said closure assembly body, above through bore; (d) a swing gate having an upper sustantially planar surface defining a bottom surface of said upper chamber, an arcuate surface facing said outlet and having a first center of curvature, and a substantially concave surface facing said inlet, said swing gate being pivotable about a first horizontal axis perpendicular to said through bore, adjacent said inlet, and offset from said first center of curvature, and adapted to be movable by the passage of a fuel charge through said through bore to a first position in which said swing gate does not obstruct said through bore, and, in the absence of a fuel charge in said through bore, and regardless of the presence of said fluid pressure, to a second position sealing said through bore; (e) orifice means in said body for providing fluid communication between said upper chamber and said inlet; and (f) a closure assembly seat in said closure assembly body adapted to form a seal with said swing gate. (a) a closure assembly body connected to said nozzle and having an inlet adjacent said nozzle, an outlet adapted to receive a nozzle cap, and a through bore connecting said inlet and outlet, said inlet, through bore, and outlet being dimensioned to permit passage of a fuel charge driven by fluid pressure in said nozzle from said nozzle through said inlet, through bore, and outlet; (b) an upper chamber in said closure assembly body, above said through bore; (c) a swing gate having an upper substantially planar surface defining a bottom surface of said upper chamber, an arcuate surface facing said outlet and having a first center of curvature, and a substantially concave surface facing said inlet, said swing gate being pivotable about a first horizontal axis perpendicular to said through bore, adjacent said inlet, and offset from said first center of curvature, and adapted to be movable by the passage of a fuel charge through said through bore to a first position in which said swing gate does not obstruct said through bore, and, in the absence of a fuel charge in said through bore, to a second position sealing said through bore; (d) orifice means in said swing gate for providing fluid communication between said upper chamber and said inlet; (e) a closure assembly seat in said closure assembly body adapted to form a seal with said swing gate; and (f) plunger means received in said outlet for locking said swing gate in said second position. (a) a closure assembly body connected to said nozzle and having an inlet adjacent said nozzle, an outlet adapted to receive a nozzle cap, and a through bore connecting said inlet and outlet, said inlet, through bore, and outlet being dimensioned to permit passage of a fuel charge driven by fluid pressure in said nozzle from said nozzle through said inlet, through bore, and outlet; (b) an upper chamber in said closure assembly body, above said through bore; (c) a swing gate having an upper substantially planar surface defining a bottom surface of said upper chamber, an arcuate surface facing said outlet and having a first center of curvature, and a substantially concave surface facing said inlet and being convoluted about a second horizontal axis perpendicular to said through bore to form an upward projection, said swing gate being pivotable about a first horizontal axis perpendicular to said through bore, adjacent said inlet, and offset from said first center of curvature, and adapted to be movable by the passage of a fuel charge through said through bore to a first position in which said swing gate does not obstruct said through bore, and, in the absence of a fuel charge in said through bore, to a second position sealing said through bore; (d) orifice means in said swing gate for providing fluid communication between said upper chamber and said inlet; and (e) a closure assembly seat in said closure assembly body adapted to form a seal with said swing gate. 2. A swing gate closure assembly as claimed in claim 1 wherein said means comprises a chamber within said body and having a greater volume when said swing gate is in said second position than when said swing gate is in said first position. 3. A swing gate closure assembly as claimed in claim 2 wherein said means further comprises a curved surface on a portion of said swing gate facing said inlet when said swing gate is in said second position. 4. A swing gate closure assembly as claimed in claim 1, wherein said swing gate is arranged to pivot between said first and second position about a first axis. 5. A swing gate closure assembly as claimed in claim 4 wherein said swing gate has an arcuate surface facing said outlet when said swing gate is in said second position, said arcuate surface having an axis of curvature parallel to and displaced from said first axis. 6. A nuclear reactor tip off assembly, comprising: 7. A swing gate closure assembly as claimed in claim 6, further comprising plunger means received in said outlet for locking said swing gate in said second position. 8. A swing gate closure assembly as claimed in claim 6, wherein said concave surface is convoluted about a second horizontal axis perpendicular to said through bore to form an upward projection. 9. A nuclear reactor tip off assembly, comprising: 10. A swing gate closure assembly as claimed in claim 9, further comprising plunger means received in said outlet for locking said swing gate in said second position. 11. A swing gate closure assembly as claimed in claim 9, wherein said concave surface is convoluted about a second horizontal axis perpendicular to said through bore to form an upward projection. 12. A swing gate closure assembly for a nozzle of a nuclear reactor tip off assembly, comprising: 13. A swing gate closure assembly for a nozzle of a nuclear reactor tip off assembly, comprising: |
abstract | An ion implantation apparatus with multiple operating modes is disclosed. The ion implantation apparatus has an ion source and an ion extraction means for extracting a ribbon-shaped ion beam therefrom. The ion implantation apparatus includes a magnetic analyzer for selecting ions with specific mass-to-charge ratio to pass through a mass slit to project onto a substrate. Multipole lenses are provided to control beam uniformity and collimation. A two-path beamline in which a second path incorporates a deceleration or acceleration system incorporating energy filtering is disclosed. Finally, methods of ion implantation are disclosed in which the mode of implantation may be switched from one-dimensional scanning of the target to two-dimensional scanning. |
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054208998 | claims | 1. A grapple for use with a fuel bundle channel of a nuclear reactor wherein the channel is provided with a pair of gussets in opposite diagonal corners of an upper end of the channel, each gusset having a hole therein, the grapple comprising: a pair of lever arms, each provided with a channel lifting foot at a lower end of the respective lever arm, said lever arms movable in opposite directions to a channel lifting position wherein said lifting foot of each lever arm is located under a respective one of the pair of channel gussets, and wherein the lifting foot of each lever arm is provided with a pair of laterally spaced lifting elements such that said lifting foot may engage the underside of the gusset on either side of the gusset hole. 2. The grapple of claim 1 wherein means are provided for moving said lever arms between said channel lifting position and a non-operative position permitting said lifting feet to be moved into and out of the channel by means of a lifting device. 3. The grapple of claim 1 wherein a slider is located between said pair of lifting elements of each channel lifting foot, said slider having a hole at one end thereof, and said slider movable relative to said lifting elements to permit said hole to be aligned with the hole in the channel gusset. 4. The grapple of claim 1 and including a shaft having an upper end and a threaded lower end; a fixed cross piece on said shaft; and wherein said lever arms are pivotally secured to opposite ends of said fixed cross piece. 5. The grapple of claim 4 wherein a second, movable cross piece is threadably secured to the threaded lower end of the shaft, said movable cross piece having cam pins fixed thereto at opposite ends of said movable cross piece, said cam pins slidably received within slots formed in said lever arms. 6. The grapple of claim 5 wherein a knob is fixed to said shaft to enable rotation of said shaft relative to said fixed cross piece and said movable cross piece, thereby causing said movable cross piece to move axially along said shaft. 7. The grapple of claim 3 and including a shaft having an upper end and a threaded lower end; a fixed cross piece on said shaft; and wherein said lever arms are pivotally secured to opposite ends of said fixed cross piece. 8. The grapple of claim 7 wherein a second, movable cross piece is threadably secured to the threaded lower end of the shaft, said movable cross piece having cam pins fixed thereto at opposite ends of said movable cross piece, said cam pins slidably received within slots formed in said lever arms. 9. The grapple of claim 8 wherein a knob is fixed to said shaft to enable rotation of said shaft relative to said fixed cross piece and said movable cross piece, thereby causing said movable cross piece to move axially along said shaft. 10. The grapple of claim 4 and including a swivel coupling mounted on the upper end of said shaft for attaching the grapple to a lifting device. 11. The grapple of claim 3 and including means for securing each of said sliders to a respective one of said gussets. 12. The grapple of claim 11 wherein said means comprises a ball lock pin insertable into said aligned holes. |
abstract | A substrate processing apparatus and an information storage server are connected with each other through a network. A storage part of the substrate processing apparatus stores set information and a control program, for controlling operation of the substrate processing apparatus according to the set information and the control program. The substrate processing apparatus is provided with a schedule function, for transmitting a backup instructional command according to the schedule. In response to this instructional command, the substrate processing apparatus generates a duplicate of specified information stored in the aforementioned storage part and transfers the duplicate information to the information storage server through the network. The information storage server stores the received duplicate information in a hard disk as backup data. The information storage server can also store only differential data of the duplicate information. Thus, information for controlling the operation of the substrate processing apparatus can be efficiently backed up without burdening the user. |
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050358537 | claims | 1. Nuclear reactor fuel assembly, comprising at least one uprightly disposed spacer having a grid of intersecting sheet-metal struts defining meshes therebetween, mutually parallel rods each being disposed in a respective one of said meshes, and strip-like contact springs being parallel to the rods and each having a side facing toward and a side facing away from a respective one of said struts, each of said contact springs being disposed in a respective one of said meshes and having two strip ends both being retained on said one strut, each of said contact springs having a contact location being resilient relative to said one strut for contacting a rod, said contact location being spaced apart from both of said strip ends, each of said contact springs having an undulatory transverse curve disposed at said contact location on said side of said contact spring facing toward said one strut, and said contact springs being continuously smooth and flat from said contact location to said strip ends resting on said one strut, wherein said undulatory transverse curve is in the form of a single curve disposed at said contact location, and said contact spring has transition locations adjacent said undulatory transverse curve being unequally spaced apart from said one strut on which said contact spring is retained. 2. Nuclear reactor fuel assembly, comprising at least one uprightly disposed spacer having a grid of intersecting sheet-metal struts defining meshes therebetween for receiving mutually parallel rods in a respective one of said meshes, and strip-like contact springs being parallel to the rods and each having a side facing toward and a side facing away from a respective one of said struts, each of said contact springs being disposed in a respective one of said meshes and having a) two strip ends both resting on said one strut and being retained thereon, b) two border regions, at least one of which to be contacted by a rod, c) two smooth intermediate strip parts each extending from one of said strip ends to a respective one of said border regions, d) a contact location having an two undulatory transverse curves, said contact location being resilient relative to said one strut and including said two border regions, said border regions being curved towards said one strut, and e) said smooth intermediate strip parts being continuously flat before a rod is disposed in the respective mesh. a) two strip ends both resting on said one strut and being retained thereon, b) a first and a second border region disposed at given respective first and second distances from said strut, said first and second distances being different from each other, c) a continuously smooth first intermediate strip part extending from one of said strip ends to said first border region, d) a contact location for contacting a respective one of the rods having an undulatory transverse curve in the form of a single curve, said contact location being resilient relative to said one strut and including said first border region, said second border region being curved towards said one strut, and e) a continuously smooth second intermediate strip part extending from said second border region to the other of said strip ends. 3. Nuclear reactor fuel assembly according to claim 2, wherein said smooth intermediate strip parts are slightly bent when said contact location contacts a rod. 4. Nuclear reactor fuel assembly according to claim 2, wherein at least some of said rods are fuel rods containing nuclear fuel. 5. Nuclear reactor fuel assembly, comprising at least one uprightly disposed spacer having a grid of intersecting sheet-metal struts defining meshes therebetween for receiving mutually parallel rods in a respective one of said meshes, and strip-like contact springs being parallel to the rods and each having a side facing toward and a side facing away from a respective one of said struts, each of said contact springs being disposed in a respective one of said meshes and having |
claims | 1. A nuclear plant, comprising:a nuclear reactor;a containment structure having one or more inner surfaces at least partially defining a containment environment in which the nuclear reactor is located;a passive containment cooling system, includinga coolant reservoir configured to hold a coolant fluid,a coolant channel coupled to the containment structure such that the coolant channel extends vertically from a coolant channel inlet at a bottom of the coolant channel to a coolant channel outlet at a top of the coolant channel,a coolant supply conduit extending downwards from an inlet of the coolant supply conduit that is open to a lower region of the coolant reservoir, an outlet of the coolant supply conduit is coupled to the coolant channel inlet, such that the coolant supply conduit is configured to direct a flow of the coolant fluid downwards out of the lower region of the coolant reservoir and into the bottom of the coolant channel via the coolant channel inlet according to gravity, such that the coolant fluid rises through the coolant channel from the bottom of the coolant channel to the top of the coolant channel according to a change in buoyancy of the coolant fluid based on the coolant fluid absorbing heat rejected from the nuclear reactor in the containment environment via at least the containment structure, anda coolant return conduit having an inlet coupled to the coolant channel outlet at the top of the coolant channel, the coolant return conduit extending upwards from the inlet of the coolant return conduit to an outlet of the coolant return conduit that is open to an upper region of the coolant reservoir that is above the lower region of the coolant reservoir, such that the coolant return conduit is configured to direct a flow of the coolant fluid to rise out of the top of the coolant channel via the coolant channel outlet and into the upper region of the coolant reservoir according to increased buoyancy of the coolant fluid at the top of the coolant channel over buoyancy of the coolant fluid at the bottom of the coolant channel; anda first check valve assembly at a first vertical depth below a top surface of the coolant fluid in the coolant reservoir, the first check valve assembly in fluid communication with the coolant reservoir through the coolant channel and in fluid communication with the containment environment, whereinthe first check valve assembly includes one or more check valves coupled between a first check valve assembly inlet and a first check valve assembly outlet, the first check valve assembly inlet being open to the containment environment, the first check valve assembly outlet being in fluid communication with the coolant reservoir through the coolant channel,the one or more check valves are configured to open in response to a pressure at an inlet of the one or more check valves being equal to or greater than a first threshold magnitude, the first threshold magnitude at least partially corresponding to a hydrostatic pressure of the coolant fluid at the first check valve assembly outlet at the first vertical depth, andthe first check valve assembly is configured to selectively enable one-way flow of a containment fluid, from the containment environment via the first check valve assembly inlet to the coolant reservoir through the coolant channel via the first check valve assembly outlet and the coolant channel, based on the one or more check valves opening in response to a pressure of the containment environment at the first check valve assembly inlet at the first vertical depth being equal to or greater than the first threshold magnitude. 2. The nuclear plant of claim 1, wherein the first threshold magnitude is greater than a reference hydrostatic pressure of the coolant fluid at the first vertical depth below the top surface of the coolant fluid in the coolant reservoir that results from the coolant reservoir being filled to a reference reservoir depth. 3. The nuclear plant of claim 1, whereinthe first check valve assembly is configured to, subsequently to selectively enabling the one-way flow, inhibit the one-way flow of the containment fluid based on the one or more check valves closing in response to the pressure of the containment environment at the first check valve assembly inlet being less than the first threshold magnitude. 4. The nuclear plant of claim 1, whereinthe one or more check valves include a series connection of a plurality of check valves between the first check valve assembly inlet and the first check valve assembly outlet,each check valve of the plurality of check valves is configured to open in response to a pressure at an inlet of the check valve being equal to or greater than the first threshold magnitude, andthe first check valve assembly is configured to selectively enable the one-way flow based on all check valves of the series connection of the plurality of check valves opening. 5. The nuclear plant of claim 1, whereinthe one or more check valves include a parallel connection of a plurality of sets of one or more check valves between the first check valve assembly inlet and one or more check valve assembly outlets,each check valve of the plurality of sets of one or more check valves is configured to open in response to a pressure at an inlet of the check valve being equal to or greater than the first threshold magnitude, andthe first check valve assembly is configured to selectively enable the one-way flow based on any set of one or more check valves of the parallel connection of the plurality of sets of one or more check valves. 6. The nuclear plant of claim 1, whereinthe first check valve assembly includes a burst disc coupled in series with the inlet of the one or more check valves and the first check valve assembly inlet, the burst disc configured to rupture in response to the pressure of the containment environment at the first check valve assembly inlet being equal to or greater than a particular set point pressure magnitude. 7. The nuclear plant of claim 1, further comprising:a second check valve assembly at a second vertical depth below the top surface of the coolant fluid in the coolant reservoir, the second check valve assembly in fluid communication with the coolant reservoir through the coolant channel and in fluid communication with the containment environment, the second vertical depth being less than the first vertical depth,wherein the second check valve assembly is configured to selectively enable one-way flow of the containment fluid, from the containment environment to the coolant reservoir through the coolant channel, based on one or more check valves of the second check valve assembly opening in response to a pressure of the containment environment at an inlet of the second check valve assembly being equal to or greater than a second threshold magnitude, the second threshold magnitude at least partially corresponding to a hydrostatic pressure of the coolant fluid at an outlet of the second check valve assembly at the second vertical depth. 8. The nuclear plant of claim 1, whereinthe first check valve assembly extends through the containment structure and into the coolant channel at the first vertical depth, and the first check valve assembly is open to the coolant channel, andthe first check valve assembly is configured to selectively enable the one-way flow of the containment fluid, from the containment environment via the first check valve assembly inlet, to the coolant channel via the first check valve assembly outlet. 9. The nuclear plant of claim 1, further comprising:a fusible plug in fluid communication with the coolant reservoir through the coolant channel and in fluid communication with the containment environment at a bottom vertical depth below the top surface of the coolant fluid in the coolant reservoir, the bottom vertical depth being greater than the first vertical depth, such that a hydrostatic pressure of the coolant fluid at the bottom vertical depth is greater than the hydrostatic pressure of the coolant fluid at the first check valve assembly outlet at the first vertical depth,wherein the fusible plug is configured to at least partially melt in response to a temperature in the containment environment at an end of the fusible plug that is open to the containment environment being equal to or greater than a threshold temperature, such that the fusible plug exposes a flow conduit extending between the coolant reservoir into the containment environment through the coolant channel to at least partially flood the containment environment with at least some of the coolant fluid. 10. The nuclear plant of claim 9, wherein the first check valve assembly is configured to, based on selectively enabling the one-way flow of the containment fluid in response to the pressure in the containment environment at the first check valve assembly inlet being equal to or greater than the first threshold magnitude, maintain a pressure in the containment environment at the bottom vertical depth at a magnitude that is less than the hydrostatic pressure of the coolant fluid at the bottom vertical depth, to enable flow of the coolant fluid through the exposed flow conduit and into the containment environment through the coolant channel in response to the fusible plug at least partially melting. 11. The nuclear plant of claim 5, whereineach separate set of one or more check valves between the first check valve assembly inlet and the one or more check valve assembly outlets includes a series connection of check valves between the first check valve assembly inlet and the first check valve assembly outlet,each check valve of each series connection of check valves is configured to open in response to a pressure at an inlet of the check valve being equal to or greater than the first threshold magnitude, andthe first check valve assembly is configured to selectively enable the one-way flow based on all check valves of at least one series connection of check valves opening. |
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055090397 | claims | 1. A manual measuring system for measuring a length of a nuclear fuel pellet stack segment along a longitudinal axis thereof, said system comprising: manually movable measuring head means having two legs; positioning means for positioning said manually movable measuring head means to at least one position along the longitudinal axis of the pellet stack segment, said manually movable measuring head means providing a compression force for comprising the pellet stack segment; measuring means for measuring the length of the pellet stack segment from the position of said manually movable measuring head means; compression means for compression by the compression force of said manually movable measuring head means, said compression means having a predetermined compression force; probe means cooperating with said compression means for contacting an end of the pellet stack segment and applying the compression force of said manually movable measuring head means to the end of the pellet stack segment, said probe means including slider block means for compressing said compression means and also including a probe member attached to the slider block means for contacting the end pellet stack segment, said compression means and the slider block means being located between the legs of said manually movable measuring head means, the slider block means sliding toward one of the legs of said manually movable measuring head means in response to the compression force of said manually movable measuring head means; and sensing means cooperating with said manually movable measuring head means for sensing a position of the slider block means and outputting a signal, representative of the position of the slider block means, for triggering a measurement by said measuring means of the length of the pellet stack segment, whenever the compression force of said manually movable measuring head means is at least equal to the predetermined compression force of said compression means. 2. The measuring system as recited in claim 1, wherein said compression means is a compression spring which is biased between the slider block means and one of the legs of said manually movable measuring head means. 3. The measuring system as recited in claim 2, wherein the compression spring is compressed and the slider block means is slidably mobile with respect to said manually movable measuring head means along the longitudinal axis of the pellet stack segment. 4. The measuring system as recited in claim 3, wherein the probe member is attached to a surface of the slider block means, and extends beyond the surface of the slider block means and outside the legs of said manually movable measuring head means. 5. The measuring system as recited in claim 4, wherein the probe member is cylindrical and has a diameter generally the same as a diameter of the pellet stack segment. 6. The measuring system as recited in claim 1, wherein said sensing means includes fiber optic sensor means having a bore associated with said movable measuring head means; wherein the slider block means includes pin means attached thereto and moveable therewith, the pin means including a trip screw for tripping the fiber optic sensor means in the bore thereof after the compression force of said manually movable measuring head means exceeds the predetermined compression force of said compression means. 7. The measuring system as recited in claim 6, wherein the slider block means has a bore running therethrough, and wherein the pin means and said compression means are positioned within the bore of the slider block means. 8. The measuring system as recited in claim 7, wherein the trip screw means has an adjustable position within the bore of the slider block means, in order that the output signal representative of the position of the pin means triggers the measurement by said measuring means of the length of the pellet stack segment after the application of the predetermined compression force. 9. The measuring system as recited in claim 7, wherein the pin means further includes a set screw, and wherein the trip screw means has a head which is positioned adjacent the set screw within the bore of the slider block means, in order to prevent a back-off the trip screw means. 10. The measuring system as recited in claim 9, wherein one of the legs of said manually movable measuring head means has a a bore running therethrough, wherein the trip screw means also has a shaft which is positioned within the bore of the slider block means and within the bore of said one of the legs of said manually movable measuring head means. 11. The measuring system as recited in claim 10, wherein said manually movable measuring head means has spacing means for blocking movement of said manually movable measuring head means toward the slider block means, the spacing means having a hole, the shaft of the trip screw means passing through the hole of the spacing means, the spacing means adjacent one of the legs of said manually movable measuring head means and abutting an end of said compression means. 12. The measuring system as recited in claim 6, wherein said manually movable measuring head means moves, with respect to the slider block means and the trip screw means, in a direction generally parallel to the longitudinal axis of the pellet stack segment and generally toward the end of the pellet stack segment. 13. The measuring system as recited in claim 1, wherein said sensing means includes a fiber optic sensor. 14. The measuring system as recited in claim 13, wherein the length of the pellet stack segment is measured on a longitudinal axis of the pellet stack segment, wherein the fiber optic sensor has a light beam which is generally perpendicular to the longitudinal axis of the pellet stack segment, and wherein the light beam is intercepted by the pin means, in order to trigger a measurement by said measuring means of the length of the pellet stack segment at a positive adjustable time after the compression force of said manually movable measuring head means is at least equal to the predetermined compression force of said compression means. 15. The measuring system as recited in claim 14, wherein said pin means includes a trip screw having a shaft, and wherein the light beam of the fiber optic sensor is broker by a movement of said manually movable measuring head means toward the shaft of the trip screw. 16. The measuring system as recited in claim 1 wherein said positioning means is a positioning table means for positioning said manually movable measuring 17. The measuring system as recited in claim 1 wherein said sensing means includes foot switch means for triggering a measurement by said measuring means of the length of the pellet stack segment after the foot switch means is closed. 18. The measuring system as recited in claim 17, wherein said sensing means also includes a fiber optic sensor with a light beam which is broken by movement of the slider block means, said sensing means triggering a measurement by said measuring means of the length of the pellet stack segment whenever the foot switch means is closed and the light beam is broken. |
description | 1. Field of the Invention The present invention relates to a control rod for nuclear reactors such as boiling water reactors and also relates to a method for manufacturing such a control rod. 2. Related Art One example of a conventional control rod having a long life for boiling water reactor (BWR) is shown in FIGS. 30 to 32 with reference numeral of 200 as disclosed in Japanese Unexamined Patent Application Publication No. 63-8594 (hereinafter referred to as Patent Document 1) or a publication by M. Ueda, T. Tanzawa, and R. Yoshioka of “Critical Experiment on a Flux-Trap-Type Hafnium Control Rod for BWR”, Transaction of the American Nuclear Society, vol. 55, p. 616 (1987) (hereinafter referred to as Non-patent Document 1). Each control rod 200 includes four wings 207, each of them including a sheath 201, made of stainless steel (SUS), having a U-shape in cross section. Namely, FIG. 30 shows a control rod 200 for a nuclear reactor such as boiling water reactor (BWR). The control rod 200 includes, for example, a tie rod 202 connecting a front end structural member 203 to a terminal end structural member 204, the wings 207 radially extending from the tie rod 202, and a plurality of neutron absorbers 210 arranged in parallel to the axis of the tie rod 202. The front end structural member 203 includes guide rollers 203a and a handle 211 located at an end of the front end structural member 203. Each of the wings 207 includes a sheath 201 having an outer end portion with a U-shape in cross section and has cooling holes 209. The neutron absorbers 8 are accommodated in the sheaths 201. The control rod 200 shown in FIGS. 31 and 32 is a conventional flux trap-type hafnium control rod 200, which is known to have a long life. The flux trap-type hafnium control rod 200 includes the wings 207 including sheaths 201, hafnium plates 205 accommodated in these sheaths 201, and a tie rod 202. The hafnium plates 205 function as neutron absorbers, are made of hafnium or a hafnium alloy, and are disposed in separated sections of each wing 207 that are arranged in parallel to the axis of the wing 207. Each pair of the hafnium plates 205 are opposed to each other. The respective hafnium plates 205 have different thicknesses depending on the amount of neutrons absorbed by the separated sections. This allows the hafnium plates 205 to have a uniform life. With reference to FIGS. 31 and 32, the hafnium plates 205 are fixed to the inner surfaces of these sheaths 201, which form shells of these wings 207, with fixing pieces 208 by welding. These sheaths 201 are fixed to this tie rod 202 by means of spot welding. In the flux trap-type hafnium control rod 200, since the fixing pieces 208 are fixed to these sheaths 201 by means of welding, these sheaths 201 are slightly recessed toward the hafnium plates 205 because of welding distortion. This can eliminate spaces between the hafnium plates 205 and these sheaths 201 and can cause these sheaths 201 and the hafnium plates 205 to be tightly fixed to each other. In this case, any space for absorbing a corrosive component is not present between the hafnium plate 205 and these sheath 201 and a large stress may be applied to the sheath 201 because the hafnium plate 205 cannot be displaced from the sheath 201 although the thermal expansion and irradiation growth of the hafnium plate 205 are different from that of the sheath 201. In the flux trap-type hafnium control rod 200, the hafnium plate 205 is fixed to the sheath 201 with the fixing piece 208 by welding as described above. The welded portion receive relatively large load such as scrum load during operation. The fixing of the fixing piece 208 by means of welding can develop residual tensile stress around the welded portion to cause stress corrosion cracking in the sheath 201 located near the welded portion. This leads to a reduction in the life of the flux trap-type hafnium control rod 200 and may threaten the safety of nuclear reactor. Japanese Unexamined Patent Application Publication No. 9-113664 (hereinafter referred to as Patent Document 2) also discloses a control rod, manufactured by means of welding, for the BWR. However, Patent Document 1 discloses no technique for reducing residual stresses caused by welding. In the flux trap-type hafnium control rod 200, each pair of the hafnium plates 205, which are opposed to each other, are disposed in one of the sheaths 201 and a distance between each hafnium plate 205 and the corresponding sheath 201 is maintained with the fixing pieces 208. The welding of the sheaths 201 to upper portions of the fixing pieces 208 causes thin portions of the sheaths 201 to be recessed toward the hafnium plates 205 to develop the residual tensile stress in the sheaths 201. If the flux trap-type hafnium control rod 200 is used in such a state, the residual tensile stress may cause stress corrosion cracking in the sheaths 201 in cooperation with high-temperature water. The distortion of the sheaths 201 due to welding may eliminate spaces between the sheaths 201 and the hafnium plates 205 to cause crevice corrosion. This leads to a reduction in the reliability of the flux trap-type hafnium control rod 200. Furthermore, the sheath 201 has an aperture fitted over a projecting portion of the narrow tie rod 202 having a cross shape in cross section and also has an inner space containing the pair of hafnium plates 205 that are neutron absorbers. Each of the wings 207 has a leading portion 211 bonded to a front end structural member 203 and a tailing portion bonded to a terminal end structural member 204. In the control rod 200, the space between the hafnium plates is filled with water in a nuclear reactor. The reactor water moderates neutrons, which are therefore efficiently absorbed by the hafnium plates 205. Therefore, the hafnium plates 205, which are expensive and heavy, can be saved because of the presence of the reactor water between the hafnium plates 205. The space therebetween is called a trap or a trap space. The hafnium plates 205 are spaced from each other in the axial direction of the control rod 200, which is inserted into or withdrawn or removed from the nuclear reactor, because the amount of hafnium contained in the hafnium plates 205 located closer to the entrance of the nuclear reactor may be small. The hafnium plates 205 are fixed to the sheaths 201 with fixing pieces 208, referred to as space/load-retaining members, disposed therebetween. No techniques for preventing stress corrosion cracking are disclosed in conventional technical documents. The hafnium plates 205 are spaced from each other in the axial direction of the control rod 200 and have different thicknesses. However, there are problems in that an increase in the number of the hafnium plates 205 leads to an increase in manufacturing cost and the hafnium plates 205 are nonuniform in mechanical strength in the axial direction (that is, the hafnium plates 205 located at lower positions have lower mechanical strength). The sheaths 201 are located close to the hafnium plates 205 and therefore the control rod 200 is under corrosive conditions because the stainless steel used to make the sheaths 201 has electrochemical properties different from those of hafnium in the hafnium plates 205. Furthermore, the control rod 200 suffers from corrosion because the atmosphere in the nuclear reactor is corrosive. Japanese Unexamined Patent Application Publication No. 58-147687 (hereinafter referred to as Patent Document 3) discloses a hafnium control rod including no sheath. The hafnium control rod has a structure for solving a problem that hafnium and stainless steel cannot be welded to each other. The hafnium control rod includes a tie rod made of stainless steel. However, no measure against corrosion or no measure against a problem, called blade history, are disclosed in Patent Document 3. A long-life control rod is mostly inserted in a nuclear reactor in high-power operation. Therefore, portions of fuel assemblies that are adjacent to neutron absorbers have a low neutron flux level and therefore burn slowly. Hence, fissionable content in the fuel assembly portions is relatively large. When the long-life control rod is withdrawn from nuclear reactor, a large amount of energy is generated. This influences on the health of the fuel assemblies. This problem may be called blade history. The prevention of a reduction in neutron flux is effective in solving this problem and usually reduces the reactivity worth of the long-life control rod, thereby causing a shortage in reactivity worth. Conventional control rods have been used in commercial reactors to exhibit satisfactory irradiation resistance. However, it has become clear that the conventional control rods are susceptible to stress corrosion cracking and are electrochemically activated. In order to use the conventional control rods in nuclear reactors for a long time, problems caused by a difference in irradiation growth or a difference in thermal expansion need to be solved and the following problem also needs to be solved in such a manner that a reduction in reactivity worth is suppressed, i.e., a problem that fuel assemblies adjacent to the conventional control rods generate a large amount of power when the conventional control rods are removed from the nuclear reactors (that is, a problem that blade history is serious). Furthermore, it is desired that neutron-absorbing plates are improved in manufacturability, have a uniform structure in the axial direction thereof, and are reduced in manufacturing cost. The present invention was conceived in consideration of the circumstances encountered in the prior art mentioned above and an object of the present invention is to provide a control rod, having a long life, for nuclear reactors and also provide a method of manufacturing such control rod. The present invention is effective in preventing stress corrosion cracking, effective in reducing electrochemical activation, effective in reducing blade history, effective in improving axial mechanical strength distribution, and effective in enhancing manufacturability. The above and other objects can be achieved according to the present invention by providing, in one aspect, a control rod for a nuclear reactor including a neutron absorber of a composite member including a hafnium plate and at least one zirconium plate bonded to the hafnium plate. This aspect may include the following embodiments. The neutron absorber may have a cross shape in horizontal cross section. The zirconium plate may be disposed on a surface of the neutron absorber which contacts reactor water. The control rod may further include wings fixed with fixing members in a thickness direction of each wing, wherein the fixing members are disposed at positions in a vicinity of bases of the wings and arranged in a longitudinal direction. The control rod may further include wings fixed with fixing members in a direction of a base of each wing, wherein the fixing members are disposed at positions arranged in a longitudinal direction and located at the bases of the wings which are opposed to each other. The control rod may further includes a terminal end structural member and a front end structural member including a handle, wherein the wings are formed from the composite member so as to provide a cross shape and the front end structural member is fixed to upper portions of the wings with the fixing members or the terminal end structural member is fixed to lower portions of the wings with the fixing members. The front end structural member may be formed from the composite member. The above object can be also achieved by providing, in another aspect, a method for manufacturing the control rod, which includes a neutron absorber of a composite member including a hafnium plate and at least one zirconium plate bonded to the hafnium plate, the method including the steps of: shaping the composite member such that the composite member have a rectangular tubular shape and the zirconium plate is located outside the hafnium plate; forming a rectangular tube by welding both end portions of the composite member to each other, the end portions being arranged in a longitudinal direction of the composite member; and shaping the rectangular tube such that the rectangular tube has a cross shape in horizontal cross section. This aspect may include the following preferred embodiments. The manufacturing method may further include a step of placing fixing members for fixing in a thickness direction of each wing of the neutron absorber at positions located in a vicinity of bases of the wings and arranged in a longitudinal direction to prevent distortion of a rectangular tube having a cross shape in horizontal cross section. The manufacturing method may further include a step of placing fixing members for fixing in a direction of a base of each wing at positions arranged in a longitudinal direction and located at the bases of the wings which are opposed to each other to prevent distortion of a rectangular tube having a cross shape in horizontal cross section. The above object can be achieved also by providing, in a further aspect, a control rod for nuclear reactors including: four wings including neutron absorbers containing hafnium; a front end structural member which has a cross shape in cross section and includes brackets bonded to leading ends of the wings; and a terminal end structural member which has a cross shape in cross section and includes brackets bonded to tailing ends of the wings, wherein the four wings are bonded to a wing bonding member including a cross-shaped center shaft so as to form a cross shape in such a manner that the wings are spaced from each other at predetermined intervals in an axial direction, at least the front end structural member and the wing bonding member are made of a zirconium alloy containing hafnium of which the hafnium content is greater than or equal to that of natural compositions, the wings have principal portions including neutron absorbing plates having neutron absorbing portions made of a hafnium-zirconium alloy diluted with hafnium or zirconium and each have an outer surface which is opposed to a fuel assembly and at which a hafnium-zircaloy composite member covered with zircaloy is disposed, the neutron-absorbing plates are opposed to each other in such a manner that trap spaces in which reactor water is present are disposed between the neutron absorbing plates, and a thickness of each neutron absorbing plate is substantially uniform in a direction in which the control rod inserted or withdrawn. In this aspect, the following preferred embodiment may be further provided. The control rod may further include tie rods, disposed in the wings, for connecting the front end structural member and the terminal end structural member to each other, wherein the neutron-absorbing plates are mounted in the wings so as to slide from the leading ends toward the tailing ends of the wings or from the tailing ends toward the leading ends of the wings. The tie rods may be made of hafnium. The control rod may further include wing end reinforcing members which are disposed in the trap spaces between the neutron absorbing plates and which slides in the axial direction of the control rod. The wing end reinforcing members may be made of hafnium. Each of the neutron absorbing portions may have a first portion extending from the leading end of the neutron-absorbing portion and having a length equal to 1/24 to 2/24 of a length of the neutron absorbing portion, a second portion extending from the first portion and having a length equal to a difference obtained by subtracting the length of the first portion from ¼ to ½ of the length of the neutron absorbing portion, and a third portion extending from the tailing end of the neutron absorbing portion, in which the second portion has a width greater than that of the third portion, and an outer end of a leading portion of each wing is aligned with that of a tailing portion of the wing. The first portion may have a width less than that of the second portion. The control rod may further include a hafnium-zircaloy composite material and short narrow hafnium rods, wherein the hafnium-zircaloy composite material is repeatedly mount-folded and valley-folded so as to provide mount-folded and valley-folded portions which are arranged at equal intervals and which extend in parallel to each other, the valley-folded folded portions are brought close to each other so that the folded hafnium-zircaloy composite material has a cross shape in horizontal cross section, and the hafnium rods are arranged in end portions of the wings in form of spacers. The control rod may further include a tie cross made of zircaloy, wherein the valley-folded portions partially have longitudinal holes regularly and intermittently arranged in the axial direction and portions of the tie cross are arranged above and below the longitudinal holes so as to maintain the cross shape and improve mechanical strength. The control rod may further include short narrow hafnium rods functioning as spacers, wherein the four hafnium-zircaloy composite members are bent so as to provide an L-shape, bent portions of the hafnium-zircaloy composite members are brought close to each other so as to be directed to a center of a cross shape, and the hafnium rods are attached to end portions of the bent hafnium-zircaloy composite members. The control rod may further include a tie cross made of zircaloy, wherein the bent portions partially have longitudinal holes regularly and intermittently arranged in the axial direction and portions of the tie cross are arranged above and below the longitudinal holes so as to maintain the cross shape and improve mechanical strength. Each of the wings may be formed so that two of the hafnium-zircaloy composite members are opposed to each other with a space therebetween and spacers for keeping spaces are fixed to both ends of the hafnium-zircaloy composite members in an inserting or withdrawing direction and a perpendicular direction, and the four wings are bonded to a tie cross including a cross-shaped center shaft so as to form a cross shape in such a manner that the wings are spaced from each other at predetermined intervals in the axial direction. Each of the wings may be formed so that one of the hafnium-zircaloy composite members is bent so as to provide a U-shape with a space, and a plurality of short spacers are fixed to end portions of the bent hafnium-zircaloy composite member located on the side close to a cross-shaped center shaft included in a tie cross, the tie cross is spaced from the wing at a predetermined distance in the axial direction, and the four wings are bonded to each other so as to form a cross shape. Each of the wings may be formed so that one of the hafnium-zircaloy composite members is bent so as to provide a cylindrical shape, both end portions of the bent hafnium-zircaloy composite member are bonded to each other to form a cylinder, which is then pressed into a flattened tube, and a plurality of short spacers are fixed to outer end portions and inner portions of the flattened tube, the inner portions being located on the side close to a cross-shaped center shaft, which is included in a tie cross, and the four wings are bonded to form a cross shape so that the tie cross is spaced from the wings at a predetermined distance in the axial direction. The wings may be fixed with members, located in a vicinity of end portions of the cross-shaped center shaft for preventing the wings from being opened. The spacers, made of hafnium, disposed in the outer end portions of the wings may be short rods and center portions of the short rods are fixed to the hafnium-zircaloy composite members. According to the present invention of the characters mentioned above, the control rod is effective in suppressing stress corrosion cracking and/or electrochemical activation. When the control rod is used in a nuclear reactor, the inconveniences, encountered in the prior art, caused by a difference in irradiation growth or a difference in thermal expansion can be solved and the reduction in reactivity worth is suppressed, which can solve a problem that a fuel assembly adjacent to the control rod generate a large amount of power when the control rod is removed from the nuclear reactor (i.e. a problem of serious blade history). The neutron-absorbing plates can be processed so as to have a uniform thickness in the axial direction, thereby improving manufacturability, reducing manufacturing cost, and enhancing mechanical health. The nature and further characteristic features of the present invention will be made clearer from the following descriptions made with reference to the accompanying drawings. Control rods, according to embodiments of the present invention, for nuclear reactors will now be described with reference to the accompanying drawings. Further, it is to be noted that terms “upper”, “lower”, “right”, “left” and like terms are used herein with reference to the illustrations of the drawings or in an actual charged state of a control rod. FIG. 1 is a partial sectional view of a neutron absorber 16 included in a control rod 15 according to a first embodiment of the present invention. The control rod 15 itself has a general structure such as shown in FIG. 30. The neutron absorber 16 includes a hafnium plate 20 bonded to a zirconium plate 21 by means of hot rolling or the like. The hafnium plate 20 and the zirconium plate 21 form a composite member 22. A conventional control rod, of the structure mentioned with reference to FIGS. 30 to 32, for example, includes U-shaped sheaths having fitting portions, hafnium plates, and supporting pieces having projecting portions bonded to the fitting portions by TIG welding. If the conventional control rod is exposed to high-temperature water in a nuclear reactor in such a state that the U-shaped sheaths have high residual tensile stress due to welding, stress corrosion cracking occurs in the U-shaped sheaths to deteriorate the performance of the conventional control rod. However, according to this embodiment, the control rod 15 includes the composite member 22, which includes the hafnium plate 20 and the zirconium plate 21 bonded to each other. Since the zirconium plate 21 functions as a fuel cover and has good irradiation properties, the control rod 15 has high corrosion resistance. Therefore, stress corrosion cracking can be prevented from occurring in the control rod 15 though the control rod 15 contacts high-temperature water. According to this embodiment, in the control rod 15, the composite member 22 is shaped into a cross-shaped structure, and hence, portions of the control rod 15 have low residual stress, low distortion and a long life. Therefore, the control rod 15 has high reliability and quality. FIG. 2 is a partial sectional view of a neutron absorber 16 included in a control rod 15 according to a second embodiment of the present invention. In this embodiment, the neutron absorber 16 includes a composite member 23 including a hafnium plate 20 and zirconium plates 21 bonded to both surfaces of the hafnium plate 20 by means of hot rolling or the like as shown in FIG. 2. The hafnium plate 20 is protected from high-temperature, high-pressure water that is a moderator, and hence, the corrosion of the neutron absorber 16 can be prevented and the creation of oxides in the control rod 15 can be suppressed. This allows the control rod 15 to have a long life. A third embodiment of the present invention provides a method of manufacturing the control rod 15 according to the first embodiment. The control rod 15 includes the composite member 22, which includes the hafnium plate 20 and the zirconium plate 21. As shown in FIG. 3, after the composite member 22, which has been prepared by bonding the hafnium plate 20 and the zirconium plate 21 together by means of rolling, for example, is shaped so as to have such a box shape that the zirconium plate 21 is located outside the hafnium plate 20, end portions of the composite member 22 are bonded to each other with a welding member 24 or the like, whereby a rectangular tube A is prepared. As shown in FIG. 4, the rectangular tube A is molded into a cross-shaped tube B such that the zirconium plate 21 is located outside the hafnium plate 20. The cross-shaped tube B has an inner space 25 which has a cross shape in cross section and through which water used as a moderator can flow. As shown in FIG. 30, a front end structural member 203 including a handle 211 is welded to an upper portion of the cross-shaped tube B and a terminal end structural member is welded to a lower portion thereof, whereby the control rod 15 is obtained. This allows cooling water used as a moderator to smoothly flow through the control rod 15. The inner space 25 contains no obstacle, and hence, no corrosive product is accumulated in the inner space 25. This allows the control rod 15 to have a long life. A fourth embodiment of the present invention provides a method of manufacturing the control rod 15 according to the second embodiment. The control rod 15 includes the composite member 23, which includes the hafnium plate 20 and the zirconium plates 21 bonded to both surfaces of the hafnium plate 20. The method of this embodiment is similar to that of the third embodiment. In the control rod 15, the hafnium plate 20 is covered with the zirconium plates 21 and therefore can be prevented from being corroded. This allows the control rod 15 to have a long life. FIG. 5 shows a control rod 15 according to a fifth embodiment of the present invention. The control rod 15 of this embodiment has a cross shape in cross section and includes a plurality of (four, in this embodiment) wings 2 fixed with rivets 26 that are fixing members for preventing distortion. The rivets 26 are disposed at positions which are arranged in the longitudinal direction and which are located near the base portions of the wings 2. Therefore, if the control rod 15 is used for a long time, the thickness direction of each wing 2 can be fixed by the presence of the rivets 26. This prevents the distortion of the control rod 15. If bolts are used instead of the rivets 26, the distortion of the control rod 15 can be prevented. This allows the control rod 15 to have a long life. A sixth embodiment of the present invention provides a method of preventing the distortion of the control rod 15 described in the third or fourth embodiment. The control rod 15 has a cross shape in cross section. With reference to FIG. 6, the control rod 15 includes wings 2 fixed with rivets 27 that are as fixing members for preventing distortion. The rivets 27 are disposed at positions which are arranged in the longitudinal direction of the control rod 15 and which are located near the base portions of the wings 2. Each rivet 27 and the longitudinal axis of each wing 2 form an angle of 45 degrees. The distortion of the control rod 15 can be prevented if the control rod 15 is used for a long time. If bolts are used instead of the rivets 27, the distortion of the control rod 15 can be prevented. This allows the control rod 15 to have a long life. A control rod 15 according to a seventh embodiment of the present invention is similar to that described in the third or fourth embodiment. With reference to FIG. 7, the control rod 15 includes a front end structural member 4 fixed with rivets 28 that are fixing members. Since the welding is not performed to fix the front end structural member 4, the front end structural member 4 has no residual welding stress and can be prevented from being distorted. If bolts are used instead of the rivets 28, the distortion of the control rod 15 can be prevented. This allows the control rod 15 to have a long life. A control rod 15 according to an eighth embodiment of the present invention includes a front end structural member integrally molded from the hafnium-zirconium composite member 22 or 23 described in the first or second embodiment. Therefore, the control rod 15 is stable and uniform and can have a long life. A control rod 15 according to a ninth embodiment of the present invention is similar to that described in the third or fourth embodiment. The control rod 15 includes a terminal end structural member fixed with rivets that are fixing members. Since the welding is not performed to fix the terminal end structural member, the terminal end structural member has no residual welding stress and can be prevented from being distorted. If bolts are used instead of the rivets, the distortion of the control rod 15 can be prevented. This allows the control rod 15 to have a long life. As described above, the present invention of the first to ninth embodiments provides a control rod for a nuclear reactor and a method of manufacturing the same. The control rod includes a composite member including a hafnium plate functioning as a neutron absorber and a zirconium plate bonded to the hafnium plate. Therefore, the control rod can be prevented from being deteriorated and can be prevented from being corroded by high-temperature water. This allows the control rod to have high reliability and quality. The followings are further embodiments of the control rods according to the present invention. Beforehand the description of the further preferred embodiments, critical experiments performed for the embodiments will be described with reference to FIGS. 8 to 10. FIGS. 8, 9 and 10A to 10C are illustrations showing critical experiments performed to evaluate the arrangement of neutron absorbers according to the present invention. In particular, FIG. 8 is an illustrated plan view showing an inside of a nuclear reactor used for the experiments, FIG. 9 is an enlarged view of a portion represented by B in FIG. 8, and FIGS. 10A to 10C are graphs showing the results obtained from the experiments. In the experiments, a cross-shaped control rod 111 having the same cross section as that of an existing control rod is placed at the center of a core tank 110 of a nuclear critical assembly (NCA), and four fuel assemblies 112 different from channel boxes are arranged around the control rod 111 as shown in FIGS. 8 and 9. Furthermore, fuel rods 113 are symmetrically arranged outside the fuel assemblies 112 so as to form a square in horizontal cross section until the core of the NCA reaches a critical point. All the fuel rods 113 have an enrichment of 2%. The control rod 111 includes neutron-absorbing rods prepared by packing podiatry boron carbide (B4C) in stainless steel (SUS) tubes having an outer diameter of 4.8 mm and an inner diameter of 3.5 mm at a theoretical density of about 70% and also includes hafnium (Hf rods having substantially the same outer diameter and reactivity worth as those of the neutron-absorbing rods. A control rod 111a located in the first row in FIG. 10A includes B4C-filled SUS tubes 114 and water-filled SUS tubes 115 (this configuration is hereinafter referred to as Configuration “a”), the water-filled SUS tubes 115 being marked with Symbol X. A control rod 111b located in the second row in FIG. 10A included Hf rods 116 and the water-filled SUS tubes 115 (this configuration is hereinafter referred to as Configuration “b”). A control rod 111c located in the third row in FIG. 10A includes acrylic rectangular rods 117 and the B4C-filled SUS tubes 114 (this configuration is hereinafter referred to as Configuration “c”), the acrylic rectangular rods 117 being marked with Symbol X. A control rod 111d located in the fourth row in FIG. 10A includes the B4C-filled SUS tubes 114 only (this configuration is hereinafter referred to as Configuration “d”). The control rods 111a to 111d includes sheaths 118, made of stainless steel, having a thickness of about 1.4 mm and a U-shape in horizontal cross section. The control rod 111 includes a center member (tie rod) located at the center thereof. In the Configuration “d”, a tie rod is present. In the Configuration “a”, three absorbing rods which are arranged in each wing and which located on the side close to the side surface of a tie rod are replaced with three of the water-filled SUS tubes 115. In the Configuration “b”, the water-filled SUS tubes 115 and the Hf rods 116 are alternately arranged in each wing so as to be located on the side close to a tie rod such that the water-filled SUS tubes 115 and the Hf rods 116 occupy two thirds of this wing. In the Configuration “c”, a tie rod is removed such that a region occupied by this tie rod is filled with water. In the experiments, four types of control rods having any one of the Configurations “a” to “d” are used to measure the activation of copper foil to determine the neutron flux distribution of the surfaces of the control rods as shown in FIGS. 10B and 10C. Strips of the copper foil are tightly attached to the sheaths 118, the core tank 110 is supplied with water, the core is made critical; and the copper foil strips are irradiated with neutrons, removed from the core tank 110, and then cut into pieces. Beta rays emitted from each piece are measured, whereby the induced radioactivity of the piece is determined. FIG. 10C shows radioactivity intensity distribution normalized with a point (a normalization point in this figure) that is hardly affected by the variation of the configuration of each control rod. FIG. 10B shows the ratio of the radioactivity intensity distribution of each configuration to that of the Configuration “a”. The activation of copper is caused by neutrons with low thermal energy, and therefore, can be assumed to be thermal neutron flux distribution. Neutron flux distribution sharply increases at an about 15-mm outer end portion of a wing. The neutron flux of a region near the tie rod of the Configuration “d” is slightly high. The neutron flux of the Configuration “c” is very high because a region containing no tie rod occupies by water. The neutron flux of one of the fuel rods that is located near the center axis of the control rod of the Configuration “a” is very high. The neutron flux of the Configuration “b” is high over a wide range. The power output from the fuel rods located near the control rod is not sharply varied as compared with the neutron flux distribution but similar variation is caused. It is therefore an object of the present invention to increase a neutron flux over a wide range without greatly reducing the reactivity worth of a control rod. As is clear from the measurement results, in the Configuration “c” having a preferable neutron flux distribution, the reactivity worth is lowest and the reduction in reactivity worth is about 8%, which is allowable. However, it is not preferable that the reactivity worth of the control rod be reduced by 8%, and hence, this configuration is used only in a necessary area. In the design of an ordinary control rod, it is unallowable that the reactivity worth of this control rod be reduced by greater than 10%. In the Configuration “a”, the reduction in reactivity worth is about 3.5%. In the Configuration “c”, the reactivity worth is increased. The life and reactivity worth of the control rod can be enhanced by arranging a large number of the neutron absorbers in an end portion of each wing because the wing end portion has particularly a high neutron flux. In an actual control rod, the end portions of the neutron absorbers arranged in each wing are irradiated with a high dose of neutrons. Therefore, when a long-life control rod is designed, long-life neutron absorbers are arranged. When a control rod with a high reactivity worth is designed, neutron absorbers with high neutron-absorbing effect are arranged. Conditions for selecting neutron absorbers arranged in a center portion of each wing are relatively easy. Hereunder, embodiments of preferable control rods will be described on the basis of the above measurements with reference to the accompanying drawings of FIGS. 11 to 29. FIG. 11 shows a control rod 111 according to a tenth embodiment of the present invention. The right half of this figure is a sectional view of a part of the control rod 111. FIG. 12A is a sectional view of the control rod 111 taken along the line A1-A1 of FIG. 11, FIG. 12B is a sectional view of the control rod 111 taken along the line B1-B1 of FIG. 11, and FIG. 12C is a sectional view of the control rod 111 taken along the line C1-C1 of FIG. 11. With reference to FIG. 11, the control rod 111 includes a front end structural member 121, located on the control rod insertion side (the upper side in this figure), having a cross shape in horizontal cross section and a terminal end structural member 122, located on the tailing side that is the control rod withdrawal (removal) side (the lower side in this figure), having a cross shape in horizontal cross section. The front end structural member 121 and the terminal end structural member 122 are connected to each other with a long tie cross 123 serving as a wing-bonding member. The tie cross 123 includes a center shaft 123a and has a cross shape in horizontal cross section. At least the front end structural member 121 and the tie cross 123 are made of a zirconium alloy containing hafnium. The hafnium content of the zirconium alloy may be greater than or equal to that of natural compositions. Four wings 124 are connected to the tie cross 123 so as to form a cross shape in horizontal cross section. Upper end portions of the wings 124 are engaged with a lower portion of the front end structural member 121 and fixed thereto through welding portions 125. Each wing 124 includes a pair of plates opposed to each other. The plates sandwich each bracket portion of the tie cross 123. The wing 124 has a principal portion including neutron absorbing plates having neutron absorbing portions made of a hafnium-zirconium alloy diluted with hafnium or zirconium. The wing 124 is narrow and tabular and has an edge section, opposed to the tie cross 123, having a narrow lower portion. The wing 124 has a lower end portion which is engaged with an upper end portion of the terminal end structural member 122 with a gap 130, located therebetween, having a predetermined size and which is supported with the upper end portion thereof so as to be horizontally slidable. This allows the wing 124 to be expanded or shrunk due to irradiation growth or the like during fuel burning. The front end structural member 121 and the terminal end structural member 122 each include four brackets connected to the wings 124. A plurality of short hafnium rods 128, functioning as wing end reinforcing members, are vertically arranged in a side end portion of each wing 124 with spaces, located therebetween, for absorbing thermal expansion. The hafnium rods 128 are fixed to the wing 124 with pins 129 and can vertically slide together with the wing 124 when the wing 124 is expanded or shrunk. The wing 124 has end portions located on the tie cross side. The end portions of the wing 124 sandwich tabular portions 131, vertically arranged, extending from each bracket of the tie cross 123 and are fixed to the tabular portions 131 with pins 132. FIG. 11 shows one welding line 141 formed by welding an upper portion and lower portion of the wing 124 together (an actual control rod has a plurality of welding lines). FIG. 12A shows an upper portion of the control rod 111 in cross section taken along the line A1-A1 of FIG. 11. FIG. 12B shows a lower portion of the control rod 111 in cross section taken along the line B1-B1 of FIG. 11. The two opposed plates included in the wing 124 are neutron absorbing plates 135 each including a composite member including a zircaloy sheet 133 and a hafnium sheet 134 bonded to the zircaloy sheet 133 by means of hot rolling or the like. The zircaloy sheet 133 is located outside the hafnium sheet 134. The neutron absorbing plates 135 are opposed to each other with a trap space 136 therebetween and have substantially a uniform thickness in the axial direction of the control rod 111. A tie rod 137 extends in the wing 124, which includes the neutron absorbing plates 135. The tie rod 137 functions as a connecting rod for connecting the front end structural member 121 to the terminal end structural member 122 and has welding portions 138 and 139 bonded to the front end structural member 121 and the terminal end structural member 122. With reference to FIG. 10C, one of the pins 132 is bonded to the zircaloy sheets 133 and the hafnium sheets 134 with welding portions located therebetween. The neutron absorbing plates 135 are mounted in the wing 124 so as to be slidable from the leading end toward the tailing end of the wing 124 or from the tailing end toward the leading end of the wing 124. The hafnium rods 128 are arranged in the trap space 136 between the neutron absorbing plates 135 in the axial direction of the control rod 111. The front end structural member 121 and the terminal end structural member 122 are fixed to each other with the tie rod 137. That is, in this embodiment, the front end structural member 121 and the terminal end structural member 122 are not fixed to each other with an intersection (center shaft) of the four wings 124 but are fixed to each other using the trap spaces 136 in the wings 124 without using a conventional tie rod (center member). A primary function of the tie rod 137, as well as that of the conventional tie rod, is to maintain the mechanical strength. The tie rod 137 is located at a position different from that of the conventional tie rod. This is because the a configuration similar to the Configuration “c” shown in FIG. 10C is obtained such that the burning of fuel rods located near the control rod 111 is prevented from being delayed during the insertion of the control rod 111 by preventing the reduction of a thermal neutron flux near the center shaft 123a. Since the tie rods 137 are disposed in the wings 124, water is removed from a zone occupied by each tie rod 137, and hence, the neutrons are moderated, and therefore, the absorption of the neutrons is reduced. This provides a neutron absorber removal effect similar to that obtained from the Configuration “b”. That is, an advantage due to the Configuration “c” can be obtained, as well as an advantage due to the Configuration “b”. The Configurations “b” and “c” are effective in preventing the burning of the fuel rods located near the control rod 111 from being delayed. This effect depends on design conditions such as the size and positions of the tie rods 137 in the wings 124. In this embodiment, each wing 124 includes the neutron absorbing plates 135, which are opposed to each other and which include the composite members including the zircaloy sheets 133 and the hafnium sheets 134. The zircaloy sheets 133 have a thickness of about 0.2 to 0.5 mm and are each located at an outer surface (a fuel assembly-side surface) of one of the wings 124. The composite members have a thickness of about 2 to 2.5 mm. The wings 124 are retained with the hafnium rods 128, the tie cross 123, and the pins 132. The hafnium rods 128 have a wing end spacer function, a reinforcing function, and a neutron-absorbing function and function as wing end-reinforcing members. The tie cross 123 is a member for bonding portions of the wings 124 located on the center shaft side. The pins 132 are members for preventing the wings 24 from being opened. Principal portions of the wings 124 are the composite members. The tie cross 123 retains the front end structural member 121 and the terminal end structural member 122 and also retains the four wings 124 such that the wings 124 form a cross shape. The pins 132 are located at positions where the tie cross 123 is not present so as to prevent the wings 124 from being opened. In this embodiment, the thickness of each neutron absorbing plate 135 is uniform in the axial direction of the control rod 111. It is known that the bending resistance of a plate is proportional to the cube of the thickness of the plate and proportional to the square of the width thereof, the leading half of a neutron-absorbing plate preferably has a high ability to absorb neutrons, and the tailing half thereof preferably has a low ability to absorb neutrons. Conventional neutron-absorbing plates have thin tailing portions, which have low strength. In this embodiment, however, the neutron absorbing plates 135 have a uniform thickness as described above and the neutron-absorbing ability of the neutron absorbing plates 135 is adjusted by varying the width of tailing portions of the neutron absorbing plates 135. The insertion or withdrawal of the control rod 111 is interrupted if the side end of a leading portion of each wing 124 is not aligned with that of a tailing portion of the wing 124. Hence, the portions located on the center shaft side are removed from the neutron absorbing plates 135, which provides the effect of preventing the reduction of a thermal neutron flux as described with reference to FIG. 10. Therefore, the sharp increase of the output can be prevented during the removal of the control rod 111, thereby improving fuel health (improving the blade history phenomenon). According to this embodiment, the control rod 111 has increased mechanical strength, and therefore, the fuel health can be improved. In this embodiment, the neutron absorbing plates 135 are uniform in thickness, and therefore, the type of the neutron absorbing plates 135 is single. Hence, the neutron absorbing plates 135 can be manufactured at low cost. The tie rod 137 is also uniform in thickness, and hence, the tie rod 137 has good sliding properties and can be manufactured at low cost. The sliding performance of the tie rod 137 relates to the absorption of a difference in the thermal expansion and a difference in the irradiation growth. Each neutron absorbing plate 135 may be manufactured from a single material and a portion located on the center shaft 123a may be then removed from the tailing portion of the neutron absorbing plate 135. Alternatively, the leading and tailing portions of the neutron absorbing plate 135 may be separately manufactured and then welded to each other. In the case where the leading and tailing portions thereof are welded to each other, the health of the welding portion can be improved in such a manner that the welding portion is set a position shifted from the center of the neutron absorbing plate 135 toward the tailing end thereof such that the neutron irradiation dose of the welding portion is reduced, because the neutron irradiation dose of a portion located below the center of the neutron absorbing plate 135 is significantly less than that of a center portion of the neutron absorbing plate 135. In the neutron absorbing plate 135, the outer surface of the hafnium sheet 134 is covered with the zircaloy sheet 133 and the inner surface thereof is polished so as to provide less irregularity and a reduced area. In view of manufacture, both surfaces of the hafnium sheet 134 are preferably covered in some cases. This, however, reduces the trap space 136 in each wing 124 and causes the following disadvantages of a reduction in the reactivity worth of the control rod 111, a reduction in the diameter of the tie cross 123, and the like. The purpose of covering both surfaces of the hafnium sheet 134 and reducing the surface area of the hafnium sheets 134 is to suppress or prevent the hafnium sheet 134 from corroding during the long-term use of the control rod 111 in a nuclear reactor. Products of the corrosion of the hafnium sheet 134 are radioactive and therefore need to be suppressed from being generated. On the other hand, products of the corrosion of the zircaloy sheet 133 are very slightly radioactive. Although the hafnium sheet 134 has high corrosion resistance, corrosion products are generated on the hafnium sheet 134 while the hafnium sheet 134 is being used in high-temperature water for a long time. It has been known that the corrosion products fall away from the hafnium sheet 134 because of some causes. The corrosion products are radioactive. A principal nuclide in the corrosion products is Hf181, which has a half-life of 43 days and emits gamma-rays with relatively low energy (482, 346, or 133 keV). A slight amount of Ta182, which has a half-life of 111 days and emits a 1.2 MeV gamma-ray, is produced. The water quality of the current BWR is greatly improved as compared to that of the conventional BWR. Since the radioactivity of the water in the current BWR is extremely low, the low radioactivity of Hf181 can be measured. Although the environmental damage caused by Hf181 has not been confirmed because the half-life thereof is relatively short, it has become clear that the radioactivity in nuclear reactor buildings needs to be reduced. Therefore, in this embodiment, the outer surface of the hafnium sheet 134 is covered with the zircaloy sheet 133 and the inner surface thereof is polished so as to provide less irregularity. Outer surfaces of the control rod 111 are rubbed with zircaloy channel boxes of the fuel assemblies opposed to the control rod 111 because of the movement of the control rod 111, so that the corrosion products may fall away from the outer surfaces thereof. Therefore, the zircaloy sheets 133 are located at the outer surfaces thereof. The corrosion products present on the inner surfaces of the hafnium sheets 134 may fall away due to the impact caused by scrum, earthquake or the like to contaminate the cooling water in a nuclear reactor through water channels. Hence, the inner surfaces thereof are polished. The zircaloy sheets 133 and the hafnium sheets 134 are manufactured by processes different from those of manufacturing the neutron absorbing plates 135, the tie rods 137 and the hafnium rods 128 because of characteristics of crystal grains in the zircaloy sheets 133 and the hafnium sheets 134, and therefore, are different in irradiation growth from the neutron absorbing plates 135, the tie rods 137 and the hafnium rods 128. An increase in irradiation dose may exert a negative influence on the health of the control rod 111. In this embodiment, various measures are taken against the negative influence. In particular, the wings 124 and the tie rods 137 are slidable. The leading portions of wings 124 are fixed to the front end structural member 121 by welding (another technique such as pinning may be used) and the tailing portions thereof slidably sandwich the thin portions of the terminal end structural member 122. The hafnium rods 128 are short and center portions thereof are pinned with the pins 129. The hafnium rods 128 are fixed to the neutron absorbing plates 135 with the pins 129 and the upper and lower end portions of the hafnium rods 128 can be freely expanded or shrunk. The tie cross 123 and the pins 132 located on the center shaft 123a side are short, and therefore, have no problem due to the expansion or shrinkage of the wings. If slight differences are caused by the expansion or shrinkage of the wings 124, a problem caused by the slight differences can be solved in such a way that small clearances are formed or rotatability is employed. The wings 124 and the tie rods 137 may slide from the terminal end structural member 122 toward the front end structural member 121 or may longitudinally expand or contract. The wings 124 may include U-shaped composite absorbing plates instead of the hafnium rods 128. FIG. 13A is a plan view of a control rod 111 according to an eleventh embodiment of the present invention. FIG. 13B is another plan view of the control rod 111. FIG. 13C is a sectional view of the control rod 111 taken along the line C21-C21 of FIG. 13A. FIG. 13D is a side view of one of neutron absorbing plates 135 each used to form one wing. FIG. 14A is a sectional view of the neutron absorbing plate 135 taken along the line A2-A2 of FIG. 13C. FIG. 14B a sectional view of the neutron absorbing plate 135 taken along the line B2-B2 of FIG. 13C. FIG. 14C is a sectional view of the neutron absorbing plate 135 taken along the line C22-C22 of FIG. 13C. In this embodiment, the neutron absorbing plate (composite absorbing plate) 135 includes a first zircaloy sheet 133a, a second zircaloy sheet 133b, and a hafnium sheet 134 sandwiched therebetween. The same components as those described in the tenth embodiment will not be described herein in detail. With reference to FIGS. 13A and 13B, the control rod 111 has a cross shape in a plan view and includes wings 124. With reference to FIG. 13C, a first tie rod 137a and a second tie rod 137b extend through each wing 124. The leading end of the wing 124 is fixed to a front end structural member 121. The wing 124 has a small clearance located near the leading end of the neutron absorbing plate 135 and pinned with pins 132. A tailing portion of the first tie rod 137a and a tailing portion of the second tie rod 137b are fitted in a first recess 142a and second recess 142b, respectively, disposed in a thin portion of a terminal end structural member 122, the thin portion being sandwiched between portions of the wing 124. The tailing portions of the first and second tie rods 137a and 137b can slide such that differences in the irradiation growth between the wing 124 and the first and second tie rods 137a and 137b can be absorbed. The first tie rod 137a is located on the wing tip side and is made of hafnium so as to have high neutron absorbing properties. The second tie rod 137b is located near the center axis and is made of zirconium such that the neutron-absorbing effect due to the removal of water is slightly suppressed. As shown in FIG. 13D, the neutron absorbing plate 135 is bent along dashed line O so as to have substantially an L-shape in a plan view. The bent neutron absorbing plate 135 forms surfaces of the two adjacent wings 124 as indicated by imaginary line (D) in FIG. 13B (that is, four of the neutron absorbing plates 135 form outer surfaces of the control rod 111). One of the wings 124 made from the neutron absorbing plates 135 has a closed configuration in which end portions 135C of two of the neutron absorbing plates 135 are bent so as to oppose to each other and fixed to each other with a welding portion 150 as shown in FIGS. 14A, 14B, and 14C. As shown in FIG. 13C, each neutron absorbing plate 135 has a first portion 143, a second portion 144, a third portion 145 and a fourth portion 146. The first portion 143 extends from the leading end of the neutron absorbing plate 135 and has a length equal to one 24th ( 1/24) of the length of the neutron absorbing plate 135 (it is known that no problem occurs if the reactivity worth is reduced to a certain extent, because the length of the first portion 143 is about 15 to 16 cm). The second portion 144 extends from the tailing end of the neutron absorbing plate 135, has a length equal to one half (½) of the length of the neutron absorbing plate 135 and is relatively greatly recessed from the center axis to have a small width. The third portion 145 extends from the first portion 143, has a length equal to the difference obtained by subtracting the length of the first portion from one fourth (¼) of the length of the neutron absorbing plate 135 and is not recessed because the third portion 145 is the most important in reactivity worth. The fourth portion 146 extends from the fourth portion 145 to the second portion 144 and is slightly recessed because the fourth portion 146 needs to have a good balance between reactivity worth and measures against blade history. The whole of the neutron absorbing plate 135 is shown in FIG. 13D. The neutron absorbing plate 135 has an upper notch 151, located at the leading end thereof (the upper end of FIG. 13D), having a large width and also has a lower notch 151a. The upper notch 151 corresponds to the first portion 143 shown in FIG. 13C and the lower notch 151a corresponds to the second, third and fourth portions 144, 145 and 146 shown in FIG. 13C. This configuration is used for measures against the blade history because no reactivity worth is required. A tie cross, which is not shown, is fixed to portions of the wings 124 located close to the center axis of the control rod 111. Pins 132 functioning as members for preventing the wings 124 from being opened may be arranged as required. End portions 135c of the neutron absorbing plates 135, as well as those described in the first embodiment, are fixed to the welding portions 150 in such a state that the end portions 135c thereof are bent so that the insertion or withdrawal of the control rod 111 is not prevented. The leading ends of the wings 124 are fixed to the front end structural member 121 and the tailing ends thereof are fixed to the terminal end structural member 122. The first tie rod 137a is located on the wing tip side and is made of hafnium so as to have high neutron-absorbing properties. The second tie rod 137b is located close to the center axis and is made of zirconium so that the neutron-absorbing effect due to the removal of water is slightly suppressed. In this embodiment, the same advantages as those described in the tenth embodiment are obtainable. The first and second zircaloy sheets 133a and 133b have a uniform width and may have a nonuniform width depending on design conditions. This may be applied to following embodiments. FIG. 15 is a vertical sectional view of one of wings 124 included in a control rod according to a twelfth embodiment of the present invention. FIG. 16A is a sectional view of the wing 124 taken along the line A3-A3 of FIG. 15. FIG. 16B is a sectional view of the wing 124 taken along the line B3-B3 of FIG. 15. FIG. 16C is a sectional view of the wing 124 taken along the line C3-C3 of FIG. 15. The control rod of this embodiment has a configuration similar to that of the eleventh embodiment have a similar configuration, but both the control rods are different from each other in that a single slidable tie rod 137 is located near the side end of the wing 124, and the wing 124 has a configuration different from that of the wings 124 in the control rod 111 of the eleventh embodiment. With reference to FIG. 15, the wing 124 includes a neutron absorbing plate 135 as absorbing plate. The neutron absorbing plate 135 has a first portion 143, a second portion 144 and a third portion. The first portion 143 extends from the leading end of the neutron absorbing plate 135 and has a length equal to one 24th ( 1/24) of the length of the neutron absorbing plate 135. The second portion 144 extends from the tailing end of the neutron absorbing plate 135 and has a length equal to one half (½) of the length of the neutron absorbing plate 135. The first portion 143 and the second portion 144 are configured of two sheets opposed to each other. The third portion extends from the first portion 143 and has a length equal to the difference obtained by subtracting the length of the first portion from one half (½) of the length of the neutron absorbing plate 135. The neutron absorbing plate 135, as well as that described in the eleventh embodiment, is bent to an L-shape to form the wing 124. The outer surface of the neutron absorbing plate 135 is covered with zircaloy and the inner surface thereof is polished so as to have a reduced effective area. Therefore, the corrosion area of the neutron absorbing plate 135 can be reduced. In this embodiment, no zircaloy coating which eliminates trap water is present on the inner surface of the neutron absorbing plate 135. This configuration is suitable for thin control rods that need to include thin wings. A plurality of short spacers 152 are located near the center axis of the control rod. Center portions of the spacers 152 are fixed to a tie cross 123 by means of pins 129. With reference to FIGS. 16A, 16B, and 16C, the wing 124 has an outer end portion 153 bent at a relatively large angle. The outer end portion 153 is fixed to the neutron absorbing plate 135 through a welding portion 139 disposed therebetween. A portion of the wing 124 that is located near the center axis of the control rod is fixed by means of the pins 129. The spacers 152 are made of hafnium so as to have a small weight when the reactivity worth is primarily desired. The spacers 152 are made of zircaloy when measures against blade history are primarily desired. The spacers 152 are alternately arranged in the axial direction of the control rod so as to partially overlap with each other. This is because the spacers 152 are short and the bending strength of boundaries between the spacers 152 is prevented from being reduced. In this embodiment, other components and advantages are substantially the same as those described in the tenth or eleventh embodiment. FIG. 17 is a vertical sectional view of one of wings 124 included in a control rod according to a thirteenth embodiment of the present invention. FIG. 18A is a sectional view of the wing 124 taken along the line A4-A4 of FIG. 17. FIG. 18B is a sectional view of the wing 124 taken along the line B4-B4 of FIG. 17. FIG. 18C is a sectional view of the wing 124 taken along the line C4-C4 of FIG. 17. The control rod of this embodiment has a configuration similar to that of the control rod of the twelfth embodiment. The outer surface of the hafnium sheet included in the neutron absorbing plate 135 of the twelfth embodiment is covered with the zircaloy sheet. Each neutron absorbing plate 135 which is a composite absorbing plate and which is included in the control rod of this thirteenth embodiment includes zircaloy sheets 133 and a hafnium sheet 134 sandwiched therebetween. The configuration of this embodiment is suitable for control rods in which trap water regions between the absorbing plates 135 can be kept within a desired range and is particularly suitable for thick control rods. Other components and advantages are substantially the same as those described in the twelfth embodiment, and therefore, will not be described. FIG. 19 is a vertical sectional view of one of wings 124 included in a control rod 111 according to a fourteenth embodiment of the present invention. FIG. 20A is a sectional view of the wing 124 taken along the line A5-A5 of FIG. 19. FIG. 20B is a sectional view of the wing 124 taken along the line B5-B5 of FIG. 19. FIG. 20C is a sectional view of the wing 124 taken along the line C5-C5 of FIG. 19. With reference to FIG. 19, a lower end portion of the wing 124 has substantially the same size and configuration of an end portion thereof. The upper and lower end portions of the wing 124 need not have the same size and configuration and may have different sizes and configurations. The optimum sizes of the upper and lower end portions of the wing 124 may be designed. With reference to FIGS. 19, 20A, 20B and 20C, the control rod 111 has a cross shape in cross section and there is no significant difference in configuration between the control rod 111 of this embodiment and those of the above-mentioned embodiments. Therefore, FIGS. 19, 20A, 20B and 20C will not be described herein in detail. This embodiment focuses on a method of manufacturing the control rod 111 and measures against the blade history in view of the transverse cross-sectional structure of the control rod 111. FIG. 21 is a developed view of a hafnium sheet included in the control rod 111 and shows the configuration of a material 161, having four parts, for manufacturing the control rod 111. The material 161 is a composite absorbing plate and includes the hafnium sheet covered with zircaloy. With reference to FIG. 21, the material 161 has not been bent to a cross shape and has been punched. The material 161 includes four composite absorbing plate elements 162a to 162d having the same shape as that of the neutron-absorbing plates 135 which are shown in FIG. 13D described with reference to the tenth embodiment and which are composite absorbing plates. The composite absorbing plate elements 162a to 162d have notches 164 and 165 having the same shape as that of notches present in the neutron absorbing plate 135 indicated by the broken line in FIG. 19. The composite absorbing plate elements 162a to 162d have folding lines 171a to 171h. The material 161 is valley-folded at a right angle along the folding lines 171a, 171c, 171e and 171g passing through the notches 164 and 165 and is mountain-folded at a right angle along the folding lines 171b, 171d, 171f and 171h passing through regions between the notches 164 and 165. This allows the material 161 to have a wavy shape with mountain portions and valley portions. The resulting material 161 is further folded, whereby the control rod 111 having a cross shape in cross section can be formed. With reference to FIG. 21, the leftmost and rightmost composite absorbing plate elements 162a and 162d, respectively, have different widths. This allows welding portions of the finally assembled material 161 not to be located at an end portion of one of the wings 124 but to be located at a flat portion thereof. The welding portions are welded to each other, whereby workability and strength properties can be enhanced. FIG. 22 shows a principal portion of the material 161 shown in FIG. 21. With reference to FIG. 22, the material 161, which is used to manufacture the control rod 111, has a length of about 3.6 m and a width of about 1 m. If the size of the material 161 is too large to manufacture the control rod 111, the composite absorbing plates 135 prepared by cutting the material 161 along the line connecting the center of the line α-α and that of the line β-β in FIG. 21 may be welded into one piece. The reason why the material 161 is cut along the line connecting the center of the line a-a and that of the line β-β is to avoid the welding portions from being located at mountain- or valley-folded portions of the control rod 111 having a cross shape. The line α-β is determined on the basis of the same concept as described above. The tailing end of a front end structural member is located at a position represented by the dotted line present in a leading end portion of the material 161 and the leading end of a terminal end structural member is located at a position represented by the dotted line present in a tailing end portion of the material 161. The material 161 has a first portion “c”, a second portion “d”, and a third portion “e”. The first portion “c” extends from the leading end of the material 161 and has a length equal to about one 24th ( 1/24) of the length of the material 161. The second portion “d” extends from the first portion “c” and has a length equal to the difference obtained by subtracting the length of the first portion “c” from one fourth (¼) of the length of the material 161. The third portion “e” extends from the tailing end of the material 161. The first portion “c” has wide notches located at the valley-folded portions. The second portion “d” has no notch. The third portion “e” has wide notches located at the valley-folded portions and also has narrow notches extending from a position apart from the leading end of the material 161 at a distance equal to one fourth (¼) of the length of the material 161 to a position apart from the leading end of the material 161 at a distance equal to two fourth ( 2/4) of the length of the material 161. The above notches are eliminated from portions that need to have high reactivity worth but are arranged in portions that may have slightly low reactivity worth so that the reactivity worth and measures against blade history are balanced. This concept is consistent herein. The need of the first portion “c” is low in view of reactivity worth during the shutdown of a nuclear reactor. The first portion “c” is not provided in the control rod 111 of the tenth embodiment because the first portion “c” is supposed to influence scrum properties at the moment of the insertion of the control rod 111 of the first embodiment when the insertion rate of the control rod 111 of the first embodiment is not large. Short rod-shaped portions 166, horizontally extending, surrounded by dotted lines show a wing-bonding member, that is, a tie cross 123 for keeping a cross shape. The wing-bonding member is not attached to the material 161 when the material 161 is plate-shaped but is attached to the material 161 after the material 161 is folded to a cross shape. The method of this embodiment will now be described. In a first step, the hafnium sheet covered with zircaloy is processed in advance such that the material 161 is formed as shown in FIGS. 21 to 23, the material 161 is mountain-folded at a right angle along the folding lines 171b, 171d, 171f and 171h passing through the regions between the notches 164 and 165, and both ends of the material 161 represented by the line α-β are welded to each other, whereby an object, not shown, having a square shape in cross section is obtained. In a second step, the object is valley-folded at a right angle along the folding lines 171a, 171c, 171e and 171g passing through the notches 164 and 165. A welding line corresponding to the line α-β is located between one of mountain-folded portions and one of valley-folded portions. This is probably because metal crystals in the welding portion are reformed by the welding and the presence of the welding line at the mountain- or valley-folded portion may cause the deterioration of health due to irradiation. In the second step, the mountain-folded portions are further folded at an angle of 180 degrees to form outer end portions of the wings 124 and the valley-folded portions are further folded at an angle of 90 degrees to form portions of the wings 124 that are located near the center axis of the control rod 111. With reference to FIG. 23, outer rods, that is, short hafnium rods 128 that are wing end-reinforcing members are pinned to the mountain-folded portions. The tie crosses 123 are pinned using pairs of holes 174 located between window-shaped holes (longitudinal holes) that are intermittently arranged in the valley-folded portions in the axial direction of the control rod 111. The pins used are made of zircaloy or hafnium. The control rod 111 shown in FIGS. 19 and 20 is obtained. The distance between the line α-αβ and line β-β shown in FIG. 21 need to be 3 m or more, and the line α-α usually have a length of about 1 m. Therefore, the control rod 111 may be manufactured so as to have a length exceeding 3 m so that a plurality of neutron absorbing plates 135 are prepared, processed as shown in FIG. 21, and then welded to each other in the axial direction thereof. In this case, the same nucleic properties (blade history-improving properties) as described in the twelfth or thirteenth embodiment can be obtained in such a manner that holes disposed in valley-folded portions are varied in size in the axial direction of the control rod 111 (the holes located closer to the tailing end of the control rod 111 have larger sizes in the wing end direction). The hafnium sheet may be replaced with a hafnium-zirconium alloy sheet. FIG. 24 is a sectional view of one of wings 124 included in a control rod according to a fifteenth embodiment of the present invention. FIG. 25A is a sectional view of the wing 124 taken along the line A6-A6 of FIG. 24. FIG. 25B is a sectional view of the wing 124 taken along the line B6-B6 of FIG. 24. FIG. 25C is a sectional view of the wing 124 taken along the line C6-C6 of FIG. 24. This embodiment focuses on a method of manufacturing the control rod and measures against the blade history in view of the transverse cross-sectional structure of the control rod. The method of this embodiment is simpler than that described with reference to FIGS. 19 to 23. FIGS. 24 and 25A to 25C are substantially the same as FIGS. 19 and 20A to 20C and therefore will not be described herein. In this embodiment, longitudinal holes are intermittently provided in folded portions, pairs of small holes for fixing a tie cross 123 are provided between the longitudinal holes, and the folded portions are valley-folded. Mountain-folded portions are to be finally formed into the ends of the wings 124. Short hafnium rods 128 are attached to the mountain-folded portions with pins 129, made of zircaloy or hafnium, inserted in the fitting holes. In this embodiment, the wings 124 usually have a width of 50 cm or less and therefore may be separately manufactured. The wings 124 can be manufactured from a single material if the wings 124 have a length exceeding 3 m. Holes, as well as those described in the above embodiments, located closer to the tailing end of the control rod preferably expand toward the wing ends. FIG. 26 is a sectional view of one of wings 124 included in a control rod, according to a sixteenth embodiment of the present invention, for nuclear reactors. FIG. 27A is a sectional view of the wing 124 taken along the line A7-A7 of FIG. 26. FIG. 27B is a sectional view of the wing 124 taken along the line B7-B7 of FIG. 26. FIG. 27C is a sectional view of the wing 124 taken along the line C7-C7 of FIG. 26. This control rod has substantially the same configuration as that of the control rod of the fifteenth embodiment. In this embodiment, as shown in FIG. 26, a zircaloy coating 133a is provided on a surface of each hafnium sheet 134, another surface of the hafnium sheet 134 opposing to the zircaloy coating 133a is polished so as to have a reduced effective area, the hafnium sheet 134 is rolled into a cylindrical shape so that the zircaloy coating 133a is located outside, and end portions of the rolled hafnium sheet 134 are then welded to each other, whereby a cylinder is formed. The cylinder is pressed into a flattened tube 181 as shown in this figure. Three types of cylinders having different diameters are prepared and then formed into the flattened tubes 181 as shown in FIG. 27A, 27B or 27C. A notch fitting over a tie cross 123 is provided in a portion of the flattened tube 181 located near the center axis of this control rod. The center axis-side portion of the flattened tube 181 is fixed to short spacers 152, which is fixed to the composite absorbing plate. The distance from the center axis thereof to a first portion of each flattened tube 181 is large as shown in FIG. 27A, the first portion extending from the leading end of the flattened tube 181 and having a length equal to one 24th ( 1/24) of the length of the flattened tube 181. The distance from the center axis thereof to a second portion of the flattened tube 181 is also large, the second portion extending from the tailing end of the flattened tube 181 and having a length equal to one half (½) of the length of the flattened tube 181. The distance from the center axis thereof to a third portion of the flattened tube 181 is the least as shown in FIG. 27B, the third portion extending from the first portion and having a length equal to one fourth (¼) of the length of the flattened tube 181. As shown in FIG. 27C, the distance from the center axis thereof to a fourth portion of the flattened tube 181 is between that shown in FIG. 27A and that shown in FIG. 27B, the fourth portion extending from the third portion. This configuration is determined on the basis of the same concept as that described in the above embodiments. FIG. 28A is a vertical sectional view of a leading portion (an upper portion) of one of wings 124 included in a control rod, according to a seventeenth embodiment of the present invention, for nuclear reactors. FIG. 28B is a sectional view of the wing 124 taken along the line B8-B8 of FIG. 28A. FIG. 29A is a vertical sectional view of a tailing portion (a lower portion) of the wing 124. FIG. 29B is a sectional view of the wing 124 taken along the line B9-B9 of FIG. 29A. The control rod of this embodiment has substantially the same configuration as that described in the sixteenth embodiment except that the distance from the center axis of the control rod to a leading portion of the composite absorbing plate 135 is different from that from the center axis thereof to a leading portion thereof. With reference to FIGS. 28A and 28B, in the upper half of the wing 124, short hafnium rods 137 are fixed to an outer end portion of the wing 124 by means of the pins 132 located near the centers of the hafnium rods 137. Short spacers 191 made of hafnium are fixed to a portion of the wing 124 with the pins 132, the portion being located near the center axis of the control rod. Each portion of the tie cross 123 is fixed between the spacers 191 adjacent to each other in the axial direction of the control rod with one or three of the pins 132. In order to solve a problem caused by the difference in the irradiation growth, one of the pins 132 may be preferably used in some cases. Three of the pins 132 may be used to solve this problem if an appropriate clearance is formed. With reference to FIGS. 29A and 29B, the control rod has substantially the same configuration as that described in the seventh embodiment except that the distance from the center axis of the control rod to the leading portion of the composite absorbing plate 135 is different from that from the center axis thereof to the leading portion thereof. In the lower half of the wing 124, the short hafnium rods 137 are fixed to an outer end portion of the wing 124 with the pins 132 located near the centers of the hafnium rods 137. Short zircaloy spacers 191 are fixed to a portion of the wing 124 with the pins 132, the portion being located near the center axis of the control rod. Each portion of the tie cross 123 is fixed between the zircaloy spacers 191 adjacent to each other in the axial direction of the control rod with one or three of the pins 132. In order to solve a problem caused by the difference in the irradiation growth, one of the pins 132 may be preferably used in some cases. Three of the pins 132 can be used to solve this problem if an appropriate clearance is formed. |
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abstract | Charged-particle-beam (CPB)-optical systems, and CPB microlithography systems including such CPB-optical systems, are disclosed that exhibit improved shielding against external stray magnetic fields. For example, the systems and apparatus exhibit improved shielding against stray magnetic fields from peripheral conductors or moving conductors, such as linear motors used to drive the reticle stage and/or substrate stage. To such end, a magnetic shield can be attached to the downstream-facing edge of a vacuum wall covering the downstream-facing surface of the wafer-side projection lens. Similarly, a magnetic shield can be attached to the upstream-facing edge of a vacuum wall covering the upstream-facing surface of the reticle-side projection lens. The axis-facing surface of the magnetic shield can have a conical profile, and the magnetic shield can be situated just outside a zone for passage of a light beam for a Z-position sensor. |
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046648690 | claims | 1. A method for simultaneously preparing a mixture of about equal amounts of .sup.211 Rn and .sup.125 Xe, and a second mixture of about equal amounts of .sup.211 At and .sup.123 I with a proton-irradiation procedure followed by a one-step chemical procedure, said method comprising; (a) irradiating a body of material selected from the group consisting of .sup.232 Th and .sup.238 U for about 15 hours with protons that have been accelerated to at least 2 GeV, (b) promptly dissolving said irradiated body of material in a vessel containing a mixture of hydrochloric acid, nitric acid and hydrofluoric acid, (c) forcing a stream of helium (He) carrier gas into the vessel at a predetermined flow rate to entrain radionuclides of gaseous .sup.210 Rn, .sup.211 Rn, .sup.123 Xe and .sup.125 Xe and trace amounts of radiohalogens and remove them from said vessel, (d) passing the stream of helium carrier gas and entrained radionuclides through a silver mesh trap that is maintained at a temperature of about 0.degree. C., thereby to eliminate radiohalogens from said stream of gases, (e) passing said stream of gases through a second trap that is maintained at a temperature of about -196.degree. C., thereby to entrap .sup.211 Rn and .sup.125 Xe in said second trap, (f) continuing to pass said carrier gas and any entrained radionuclides through a combination chromatographic separator and detector that is operated to first pass essentially of the .sup.123 Xe and .sup.125 Xe into a first collecting chamber that is maintained at about -196.degree. C., and that is subsequently operated to pass .sup.210 Rn .sup.211 Rn into a second collecting chamber that is maintained at about -196.degree. C., (g) allowing the radionuclides in said first and second collecting chamber to decay for about 10 to 15 hours, thereby to produce .sup.123 I from the .sup.123 Xe in said first chamber and to produce .sup.211 At from the .sup.211 Rn in said second chamber, (h) transferring .sup.125 Xe and the remainder of the .sup.211 Rn from said first collecting chamber into a third collecting chamber that is maintained at about -196.degree. C., and then transferring .sup.211 At from the second collecting chamber, through a trap to remove .sup.210 At, into said first collecting chamber, thereby to leave about equal amounts of .sup.123 I and .sup.211 At in said first chamber, while leaving about equal amounts of .sup.211 Rn and .sup.125 Xe in said third chamber. (g') transferring substantially pure .sup.211 Rn from the second chamber to the first chamber and allowing further decay of substantially all of the .sup.123 Xe and of some .sup.211 Rn, to .sup.123 I and .sup.211 At, respectively. (a) irradiating a body of material selected from the group consisting of .sup.232 Th and .sup.238 U for about 15 hours with protons accelerated to at least 2 GeV, (b) discontinuing irradiation of said body for a period of about 15 hours to permit decay of radionuclides having lives shorter than that period, (c) disssolving said body in a vessel containing a mixture of hydrochloric acid, nitric acid and trace amounts of hydrofluoric acid, (d) removing gaseous .sup.211 Rn and .sup.125 Xe from said vessel by forcing a stream of helium carrier gas into the vessel at a flow rate of about 1 to 3 milliliters per minute, (e) passing the stream of carrier gas and entrained .sup.211 Rn and .sup.125 Xe gases through a silver mesh trap that is maintained at a temperature of about 0.degree. C., thereby to eliminate radio-halogens from the stream of carrier gas and entrained radionuclides, (f) passing said stream of gases through a second trap that is maintained at a temperature of about -196.degree. C., thereby to entrap the radionuclides in said second trap, (g) discontinuing the stream of carrier gas through said first trap, and vacuum transferring the .sup.211 Rn and .sup.125 Xe radionuclides from said second trap into a storage vessel that is maintained at about -196.degree. C., thereby to provide about equal amounts of said to radionuclides in said storage vessel. 2. A method as defined in claim 1 wherein said .sup.232 Th is irradiated for about 15 hours with protons accelerated to about 28 GeV. 3. A method as defined in claim 1, except that rather than irradiating .sup.232 Th, said body of irradiated material is .sup.238 U, and said irradiation is continued for about 15 hours with protons accelerated to at least 3 GeV. 4. A method as defined in claim 1 wherein said mixture of acids comprises about ninety percent concentrated hydrochloric acid, about ten percent nitric acid, with a trace amount of hydrofluoric acid therein. 5. A method as defined in claim 2 wherein said radiohalogens that are eliminated from the carrier gas by said first trap comprise .sup.210 At and .sup.211 At. 6. A method as defined in claim 5 wherein said predetermined flow rate of the carrier gas is about 1 to 3 milliliters per minute. 7. A method as defined in claim 5 wherein said second trap contains activated carbon or a silica gel mesh. 8. A method as defined in claim 1, including the following step after step (g), which is effective to eliminate .sup.210 Rn and .sup.210 At from the first collecting chamber; 9. A method for simultaneously preparing about equal amounts of .sup.211 Rn and .sup.125 Xe, using a proton irradiation procedure followed by a one-step chemical procedure, said method comprising; 10. A method as defined in claim 9 wherein said second trap contains activated charcoal that is maintained at about -196.degree. C. 11. A method as defined in claim 9 wherein said second trap contains silica gel mesh. 12. A method as defined in claim 9, except that said body of irradiated material consists of .sup.238 U, rather than of .sup.232 Th, and is irradiated for about 15 hours with protons accelerated to at least 3 GeV. 13. A method as defined in claim 12 wherein said .sup.238 U is irradiated with protons accelerated to about 28.5 GeV. |
042886988 | description | SPECIFIC DESCRIPTION FIGS. 1 and 2 show a transport and/or storage vessel for radioactive materials, e.g. wastes of a nuclear power plant. Basically the vessel comprises a body 1 formed with upright walls 1a, a bottom 1b and a cover 2 fitted into a recess 1c formed in the top of this vessel. While the vessel is shown as generally cylindrical in FIGS. 1 and 2, it can also have a generally rectangular plan configuration with rounded vertical edges as shown in some of the aforementioned copending applications. The vessel defines an inner compartment 1d which is designed to receive the radioactive waste and is composed of a cast material such as cast iron or spherolitic cast iron, suitable as a gamma-radiation shield. The cover 2 has a plug portion 2a which fits tightly into the recess 1c and a flange 2b which overlies an upper face of the vessel and is bolted thereto, e.g. by the bolts 2c. The walls 1a are formed with vertically extending spaced apart circular cross-sectional passages 3 which receive the moderator material 4, e.g. water. The outer surface of the vessel is formed with unitarily cast cooling ribs 5 which, while playing a role in the gamma-shielding, can otherwise be disregarded for the purpose of determining the volume of the passages 3 and hence of the moderator material actually used. Reference may now be made to FIG. 3 which shows an imaginary vessel 1' whose wall thickness T can correspond in gamma-shielding effectiveness to the wall thickness of the vessel 1 of FIGS. 1 and 2 and whose perimeter P corresponds to the perimeter of the vessel 1. For any given radioactive material having a neutron emission, one can imagine a layer 6 of a moderating material which will achieve a given attenuation of the neutron flux. In FIG. 3 which also represents a horizontal section in the plane II--II, this layer has a thickness t and the layer has a volume v. We found that, when the total volume of the bores 3 is equal to or greater than v and the spacing 7 between the bores is at least twice the D thereof, the vessel 1' will have the same radiation-shielding effectiveness as the vessel 1 notwithstanding the large spacing between the passages. Preferably the distance 7 ranges between 2D and 4D. The volume v can thus be equal to or less than (n.times.L.times..pi.D.sup.2 /4) where n is the number of bores 3 filled with the same moderator material as that of the imaginary layer 6, L is the height of each bore and D has been defined above as the diameter. This means that in a horizontal cross section through the vertical axis of the vessel, the total cross-sectional area of the bores 3 (FIG. 2) is at least equal to the cross-sectional area of the layer 6 for the same moderating material. The wall structure of the vessel is thus highly compartmented and mechanically stable. In addition, the cover 2 and at least a central portion 8 of the bottom 1b below the chamber 1d can be formed with bores, channels or chambers 8 containing the moderating material, each of these chambers having a semicylindrical bottom 9a and an outwardly extending portion defined between parallel flanks 9b. The channels open at the surface of the cover and the bottom respectively and are there closed by cover plates 10 and 11 set into recesses 12 and 13 of the body 1 and bolted at 14, 15 in place. As can be seen from FIG. 4, which represents a modification of FIG. 2, the passages can extend in two or more rows around the periphery of the vessel with the passages of each row lying in the gaps between the passages of the other row. |
053735412 | abstract | A nuclear fuel rod cladding for a water moderated and nuclear reactor comprises an inner portion of Zircaloy 4 and an outer portion of a zirconium-based alloy which contains by weight, besides zirconium and unavoidable impurities:. 0.35% to 0.65% tin PA1 0.18% to 0.25% iron PA1 0.07% to 0.13% chromium, and PA1 0.19% to 0.23% oxygen,. with the sum of the iron, chromium, tin, and oxygen contents being less than 1.26% by weight. It may alternatively or additionally comprise 0.80% to 1.20% by weight niobium and then the oxygen content is in the range 0.10% to 0.16% by weight. The thickness of the outer layer is 10% to 25% of the total thickness of the cladding. In a modification, up to 0.5% of iron, chromium, niobium is replaced by an equivalent content of vanadium. |
description | Referring to FIGS. 1a and 1b, nuclear reactor 10 includes a reactor vessel 12 that contains the reactor core 14. The reactor core 14 contains nuclear fuel 16 that is disposed on a support structure 18. The nuclear fuel 16 undergoes a fission reaction that generates the heat that is used to generate electric power. The reactor 10 further includes a plurality of control rods 20 that can be inserted into the nuclear fuel 16 in order to control the reaction. The control rods 20 are preferably arranged in a honeycomb configuration, but can be arranged in any configuration known to those skilled in the art. The fission reaction generates a significant amount of heat. That heat is transferred to reactor coolant water that is present inside the vessel 12. A plurality of steam generators 22 may also be included inside the vessel 12, for example, eight steam generators 22 may be included. Preferably, the steam generators are disposed along the inside walls of the vessel 12. The steam generators 22 are essentially heat exchangers, such as a shell and tube heat exchanger, designed to extract the heat from the reactor coolant. Feedwater is supplied to the steam generator 22 through a feedwater inlet pipe 24. The feedwater passes through the steam generator 22 on the outside of pipes 26, where it absorbs the heat from the reactor coolant flowing through pipes 26 until it becomes steam. The steam leaves the steam generator 22 and the vessel 12 through a steam outlet pipe 28. The steam is eventually utilized in a plurality of turbines (not shown) to produce electric power. Alternatively, the steam generator 22 may be located outside the vessel, with piping connecting the steam generator 22 to the vessel 12. In accordance with an embodiment of the present invention, the reactor coolant is circulated to the steam generator 22 by a spool pump 30 connected to steam generator 22. The spool pump 30 and steam generator 22 are located inside the vessel 12. The spool pump 30 draws coolant from the vessel 12 and pumps it through the steam generator 22. The coolant flows through pipes 26 as it passes through the steam generator 22, and heat is transferred from the coolant to the feedwater occurs across the walls of the pipes 26. Once cooled, the feedwater flows out of the steam generator 22 and back into the coolant in vessel 12. FIG. 2 illustrates an embodiment of the spool pump 30 used to pump the coolant through the steam generator 22. The pump 30 includes a generally cylindrical housing 34 having a generally cylindrical passage 36 extending therethrough. The housing 34 also includes end caps 38, 40 for connecting the housing 34 in series with the steam generator 22 (as shown in FIG. 1a). The pump 30 further includes a hermetically sealed annular stator 42 mounted inside the housing 34. The stator 42 has a terminal gland 44 thereon for connecting the stator 42 to a source of electrical power located outside the vessel 12. The stator 42 is hermetically sealed by a stator can 46. Impeller assembly 58 is rotatably mounted inside the passage 36 of the housing 34 The impeller assembly 58 comprises an axial flow impeller 60 and an annular rotor 64 mounted around the perimeter of the impeller 60 on a cylindrical shaft 62. The rotor 64 and the stator 42 cooperate to form an induction motor. The rotor 64 is preferably a squirrel cage rotor, so that no electrical connections to the rotor are required. It will be appreciated by those skilled in the art, however, that the motor could be a synchronous motor or a permanent magnet motor. If a squirrel cage motor design is used, the rotor 64 will comprise steel laminations and copper alloy rotor bars, as is known in the art. If a synchronous motor is employed, the rotor 64 may be comprised of permanent magnets. The rotor 64 is hermetically sealed by a rotor can 66. Both the stator can 46 and the rotor can 66 preferably comprise thin-walled alloy cans such as Inconel or Hastelloy cans. The impeller 60 has a plurality of blades 68 mounted on and extending radially outwardly from a cylindrical hub 70. In a preferred embodiment, 5 to 9 blades 68 are provided. It will be appreciated, however, that the optimum number of blades will depend on the desired performance of the pump 30 and may be determined in a manner known to those skilled in the art. The blades 68 are pitched so as to create an axial flow in the pumped fluid in the direction F through the passage 36 in the housing 34 when the impeller 60 is rotated. The impeller 60 is preferably a high specific speed impeller. Specific speed (NS) is a non-dimensional design index used to classify pump impellers as to type and proportion. It is defined as the speed in revolutions per minute at which a geometrically similar impeller would operate if it were of such a size to deliver one gallon per minute against one foot head. NS is calculated using the formula: N S = NQ 1 / 2 H 3 / 4 where N=pump impeller speed in revolutions per minute Q=capacity in gallons per minute at the best efficiency point H=total head per stage at the best efficiency point. In the embodiment illustrated in FIG. 1a, the impeller 60 is of a configuration to yield a specific speed of about 9,000 or higher at a speed of 1800 rpm. As noted above, the nuclear reaction generates a significant amount of heat, which is transferred to the reactor coolant water, which is the fluid pumped by the spool pump 30. The coolant temperature will often exceed 300xc2x0 C. At that temperature, the water used as the coolant has a very low viscosity. The higher the specific speed of the impeller, the steeper the pump characteristic curve, with the thrust load being the greatest at zero flow, or what is called xe2x80x9cshut off flow.xe2x80x9d The higher specific speed requires a larger thrust bearing to accommodate the high thrust at shut off flow. In accordance with an embodiment of the present invention, a double acting thrust bearing 72 is located on one side of impeller 68. The thrust bearing 72 comprises a thrust bearing runner 74 and two sets of bearing pads 76, 78. The thrust bearing runner 74 is a carbon graphite-based ring that is shrink fitted on to the shaft 62. The thrust bearing runner 74 may also be manufactured from another hard solid material such as a carbide, a nitride, stainless steel or another appropriate material that is known to those skilled in the art. Two bearing pads 76, 78 form the self-aligning tilt pad design and are positioned on opposite sides of the thrust bearing runner 74. The bearing pads 76, 78 are made from 431 stainless steel (or a comparable alloy) that is chrome plated or hard faced, for both corrosion and wear resistance. A plurality of thrust pad retainers 77 are also included in order to keep the thrust bearing pads 76 and 78 in place. The thrust pad retainers are located outside of the bearing pads 76, 78. FIGS. 2 and 3 illustrate radial bearings 80 that are employed to rotatably support the rotor 64. Radial bearings 80 are mounted between housing 34 and the cylindrical shaft 62. Preferably, radial bearings 80 are located both upstream and downstream of the impeller 60. If the pump 30 is installed such that the coolant flow is vertical, then the radial bearings 80 are self-aligning, pivoted pad type bearings. If the pump 30 is installed such that the coolant flow is horizontal, then the radial bearings 80 may be self-aligning, pivoted pad type bearings, or may be simple solid journal bearings. The configuration shown in FIGS. 2 and 3 is for self-aligning, pivoted pad bearings. Preferably, the radial bearing journal 82 will be shrink fitted to the cylindrical shaft 62 and will be a 431 stainless steel (or comparable alloy) insert that has been chrome plated or hard faced for corrosion resistance and improved wear properties. When the cylindrical shaft 62 rotates, the radial bearing journal 82 wears against a radial bearing pad 84. The radial bearing pad 84 which may be ceramic material such as carbon graphite sits on a radial bearing retainer 86, which in turn, is mounted into a radial bearing flange 88. The radial bearing flange 88 is mounted to the housing 34. The radial bearing retainer 86 also sits on the radial bearing seat 90, which allows the bearing retainer 86 to pivot, and thus, self-align, as is known in the art. Referring to FIG. 4, when the stator 42 is energized, it causes the impeller assembly 58 to rotate. Pump parts that rotate include the rotor 64, the rotor can 66, the thrust bearing runner 74 (that is shrink fitted on the rotor 64) the radial bearing journal 82 (which is also shrink fitted on the rotor 64), impeller 60 and shaft 62. All other pump parts ideally remain stationary to the impeller assembly 58. The cylindrical shaft 62 has a forward end 63 that forms a forward gap 65 relative to the end cap 38 on the inlet side of the impeller assembly 58. The cylindrical shaft 62 also has an aft end 67 that forms an aft gap 69 relative to the end cap 40. During operation, water flowing through the cylindrical shaft 62 enters the aft gap 69. The water flows between the thrust bearing runner 74 and the bearing pad 76, and thereby lubricates the thrust bearing runner 74 as it moves relative to the bearing pad 76. Likewise, the water proceeds to flow between, and thereby, lubricate, the bearing pad 78 and the bearing runner 74. The water proceeds to flow between the radial bearing journal 82 and the radial bearing pad 84 of the radial bearing 80 located on the downstream side of impeller assembly 58. In this way, the water also lubricates and cools the radial bearing 80. The water proceeds through the gap between the rotor can 66 and the stator can 46, thereby cooling the rotor 64 and the stator 42. The water flows between the radial bearing journal 82 and the radial bearing pad 84 of the radial bearing 80 located on the upstream side of impeller assembly 58, thereby lubricating and cooling the radial bearing 80. Finally, the water proceeds through the forward gap 65 and back into the cylindrical passage 36. Due to the high reactor coolant temperature mentioned above, as well as the heat generated by the stator windings 41, the stator 42 must have adequate insulation or cooling, otherwise the stator windings 41 may be damaged. Therefore, in accordance with an embodiment of the present invention, the pump 30 further includes insulation 43. The insulation material 43 is disposed around the stator windings 41. The insulation material preferably is rated at 500xc2x0 C., and comprises a combination of mica, glass and ceramics. The insulation material preferably comprises a plurality of solid pieces of insulation that are shaped so as to fit inside the stator 42 and around the stator windings 41. In prior systems, strips of insulation were laid upon, or taped to, the stator windings. Resin was used to fill the remainder of the stator and hold the insulation in place on the stator windings. However, due to the high temperatures to which the pump 30 will be subjected, resin cannot be used, as it will likely degrade under high temperatures. Thus, in accordance with the present invention, the insulation material will be formed as a plurality of solid pieces that are shaped to fit snugly around the stator windings, similar to pieces of a three-dimensional jigsaw puzzle. In this way, the insulation material will not need resin in order to keep it in contact with the stator windings. As shown in further detail in FIG. 5, the terminal gland 44 connects the pump 30 to a source of electrical power outside the vessel 12, such as an electric generator (not shown). Terminal gland 44 is part of the pump pressure barrier. As such, the terminal gland 44 must be constructed to withstand design pressures up to approximately 2500 psi. As illustrated in FIG. 5, the terminal gland 44 comprises a body 48 that provides the capability of welding the terminal gland 44 to the housing 34. Preferably, the body 48 is made of stainless steel. The body 48 encases a cylindrical ceramic insulator 50, and is connected to the ceramic insulator 50 by a cylindrical first glass preform 52. Preferably, a ceramic insulator 50 may be used. The ceramic insulator 50, in turn, encases a terminal gland stud 54 through which electrical wires pass though to provide the electrical power to the stator 42. The ceramic insulator 50 is also connected to the terminal gland stud 54 by a second glass preform 56. Preferably, the terminal gland stud 54 is made of a conducting material such as molybdenum or copper. An external ceramic insulating sleeve 55 surrounds the upper portion of the terminal gland stud 54, while an internal ceramic insulating sleeve 57 surrounds the lower portion of the terminal gland stud 54. Due to the various thermal expansion rates of the several materials, the assembly is held together in compression. The compression must be great enough to provide the required sealing integrity. The compression achieved is dictated by the selection of the glass material used for the first and second glass preforms 52, 56. A grade of glass must be chosen such that the terminal gland 44 may operate in a temperature range of between approximately 350xc2x0 C. and approximately 400xc2x0 C. Electrical strike and creep distances for air operation is maintained by the ceramic insulator 50 and first and second glass preforms 52, 56 configuration. Should further motor cooling be desirable, the pump 30 may be provided with cooling tubes 92, as illustrated in FIG. 6. The cooling tubes 92 act as a heat exchanger to transfer heat from the stator 42 to the reactor coolant. The cooling tubes 92 are disposed within the end cap 40 of the downstream end of the pump 30, run through the housing 34, through the xe2x80x9cback ironxe2x80x9d area of the stator 42, and through the end cap 38 at the upstream end of the pump 30. The reactor coolant enters the cooling tubes 92 at the downstream end of the pump 30, where the reactor coolant is at a higher pressure than at the upstream end of the pump 30. The pressure difference is enough to drive the reactor coolant through the cooling tubes 92. Preferably, the cooling tubes 92 are made from stainless steel, Inconel or other non-magnetic alloy. The reactor coolant flows through the cooling tubes 92 and absorbs heat from the stator 42, which will typically be operating at a higher temperature than the reactor coolant. If a higher cooling capacity is required, cooling tubes may be installed in the stator slots. Externally-supplied cooling water, from outside reactor vessel 12, may also be provided, if necessary. An alternate embodiment of the present invention is illustrated in FIG. 7. It is noted that the embodiments illustrated in FIGS. 7 and 8 are comparable to the embodiments illustrated in FIGS. 2 and 3, respectively, with similar parts referenced by similar reference numbers, increased by a factor of 100. In this embodiment, the impeller assembly 158 is designed to produce a mixed flow, as is known to those of skill in the art. Generally, the cylindrical hub 170, is moved downstream relative to the blades 168. Further, the blades are pitched so as to create a mixed flow in the pumped fluid in the direction F through the passage 136 in the housing 134 when the impeller assembly 158 is rotated. Also, the cylindrical shaft 162 is narrowed in most areas except for the area corresponding to the position of the cylindrical hub 170, as illustrated in FIG. 7. In this configuration, the impeller assembly 158 yields a specific speed of about 5,000 to about 9,000 at a speed of 1800 rpm. Should further motor cooling be desirable for the pump 130 illustrated in FIG. 7, the pump 130 may be provided with cooling tubes 190, as illustrated in FIG. 8. The cooling tubes 190 act as a heat exchanger to transfer heat from the stator 142 to the reactor coolant. The cooling tubes 190 are disposed within the end cap 140 of the downstream end of the pump 130, run through the housing 134, through the xe2x80x9cback ironxe2x80x9d area of the stator 130, and through the end cap 138 at the upstream end of the pump 130. The reactor coolant enters the cooling tubes 190 at the downstream end of the pump 130, where the reactor coolant is at a higher pressure than at the upstream end of the pump 130. The pressure difference is enough to drive the reactor coolant through the cooling tubes 190. Preferably, the cooling tubes 190 are made from stainless steel, Inconel or other non-magnetic alloy. The reactor coolant flows through the cooling tubes 190 and absorbs heat from the stator 142, which will typically be operating at a higher temperature than the reactor coolant. If a higher cooling capacity is required, cooling tubes may be installed in the stator slots. Externally-supplied cooling water may also be provided, if necessary. While specific embodiments and methods for practicing this invention have been described in detail, those skilled in the art will recognize various manifestations and details that could be developed in light of the overall teachings herein. Accordingly, the particular mechanisms disclosed are meant to be illustrative only and not to limit the scope of the invention which is to be given the full breadth of the following claims and any and all embodiments thereof. |
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description | The present invention relates generally to the field of electromagnetic radiation shielding and in particular to a method of producing a garment having at least one electromagnetic radiation shielded zone and a corresponding garment. The number of wireless devices in use is currently estimated at around 7.9 billion globally and it is expected that it will continue growing to around 11.6 billion by the end of 2020. It is suspected that a long-term exposure to electromagnetic radiation emitted by such wireless devices can have harmful effects on human body. Despite that, their use has become indispensable for our modern life and people will continue to use them more and more extensively. Proper shielding can help protect against electromagnetic radiation and the resulting harmful effects. Different solutions related to electromagnetic radiation shielding have been developed in this area during the past years. They were designed to shield electromagnetic radiation in the form of a case on the wireless device, by affixing a shielding layer to the garment, as a radiation blocking portable pouch, or through the use of a hands-free device. For instance, the prior art document US Pub. No. 2014/0130243 A1 to Falken et al. discloses a garment with a sewn-in one-layer pocket which creates a shield between the wearer and a wireless device placed inside the pocket. Another prior art document US Pub. No. 2012/0047631 A1 to Kohler Connolly discloses a garment outfitted with a liner insert for a pocket to be shielded, said liner insert being attached to the inner side of the pocket either by ironing, applying pressure, stitching, or using Velcro. However, known prior art electromagnetic radiation protection solutions do not provide the necessary protection in a convenient manner. In particular, the prior art solutions require that an electromagnetic radiation shielding layer be incorporated as a replacement part of a garment (like the inner side of the pocket in US Pub. No. 2014/0130243 A1 to Falken et al.), or as an additional layer to a part of a garment (like the liner in US Pub. No. 2012/0047631 A1 to Kohler Connolly), presenting a means to house a wireless device in a manner that changes the traditional construction of the garment and impairs the convenience of wearing. The present invention thus aims at providing a solution to the technical problems identified above. The present invention provides a method of producing a garment having at least one electromagnetic, EM, radiation shielded zone and a corresponding garment as set out in respective independent claims. Preferred embodiments are defined by the appended dependent claims. The present invention is described herein in the context of an EM radiation shielding arrangement for a back pocket for jeans, although those skilled in the art will recognize that the invention may also be used in various other garments, like formal or casual trousers, jackets, shirts, coats, skirts, dresses, suits, underwear, etc. Referring to FIG. 1, a conventional garment, such as jeans, is shown. In particular, FIG. 1 illustrates the back view of an upper-right portion of conventional jeans including a body (100), a waistband (110) and a pocket (120) with an opening on top, all made of a suitable fabric. In the following, the first aspect of the present invention is described referring to FIGS. 2a to 2c. It relates to the method of producing a garment having at least one EM radiation shielded zone. First, at least one EM radiation shielded zone (240) of a garment is determined in relation to at least one designated area (230) of said garment as shown in FIG. 2a. The designated area defines an area of said garment designated to form the inner side of a pocket suitable to accommodate a device emitting EM radiation. The inner side of the pocket may be defined as the area covered by the outer side of the pocket. Thus, said designated area represents an area defining the placement of the pocket on the garment. For one garment, it may be desired to design the right back pocket to be the pocket providing EM radiation shielding, for another garment, it may be desired to design the left back pocket to be the pocket providing EM radiation shielding. Multiple pockets, for instance both left and right pockets, may be desired to be designed to provide EM radiation shielding. The at least one EM radiation shielded zone represents the area of said garment which physically exhibits EM radiation shielding properties. There may be just one EM radiation shielded zone in relation to said at least one designated area, or there may be multiple EM radiation shielded zones in relation to said at least one designated area. In one example, said at least one EM radiation shielded zone may be identical to said at least one designated area. In another example, said at least one EM radiation shielded zone may be formed within said at least one designated area. In yet another example, said at least one EM radiation shielded zone may be formed outside said at least one designated area. In yet another example, said at least one EM radiation shielded zone may extend said at least one designated area. In yet another example, said at least one EM shielded radiation zone may have a smaller surface than said at least one designated area. In yet another example, said at least one EM shielded radiation zone may have a larger surface than said at least one designated area. In one aspect of the present invention, said at least one EM radiation shielded zone is determined based on predicted location of the wireless device's at least one antenna. Next, an EM radiation shielding treatment to at least a part of said at least one EM radiation shielded zone is applied. Applying an EM radiation shielding treatment to said at least a part of said at least one EM radiation shielded zone may comprise applying a pattern to said at least a part of said at least one EM radiation shielded zone. In other words, a pattern which exhibits EM radiation shielding properties is applied to said at least a part of said at least one EM radiation shielded zone. Said pattern may be formed of a conductive yarn. Any conductive yarn can be used to form said pattern, for instance cotton, or polyester with micro fine stainless steel fibres, such as Bekinox BK 50/2, or Bekinox BK 50/1 made by Bekaert NV, Belgium. Other types of conductive yarns may be employed, which incorporate conductive fibres (metal, carbon, nanotubes, or other, or a combination thereof). In principle, a pattern formed of any type of a conductive yarn will exhibit EM radiation shielding properties. It is however preferred that the conductive yarn is resistant to machine and hand washing. There are various options of how said pattern may be applied. These may be stitching, sewing, embroidering, or any combination thereof. In detail, a conductive yarn is repeatedly passed through the fabric of a garment, either with use of a needle or a similar device, from one (outer) side of the fabric to the other (inner) side of the fabric and vice versa, to form said pattern. Stitching, sewing and embroidering represent various well-known techniques of how the yarn is passed through a fabric and will not be explained here in detail. The pattern may be of a substantially polygonal shape. It may also be of a substantially circular shape, of a substantially ellipsoidal shape, of a substantially radial shape, or of substantially any other geometrical shape. A combination of multiple shapes is also possible, for instance a combination of any of a substantially polygonal, a substantially circular, a substantially ellipsoidal, a substantially radial and a substantially any other geometrical shapes. The pattern may however also be fully, or partially, random. In one particular example, said pattern (250) is a grid, as shown in FIG. 2b without the outer side of the pocket applied. This pattern is especially convenient to implement, as it is relatively easy to apply and it provides a good predicted shielding efficiency. In detail, the shielding efficiency of a grid pattern may be approximately defined as: for far fields, d ≥ λ 2 π : SE E , H [ dB ] = 20 k log ( λ 2 g ) ( Eq . 1 ) for near fields, d < λ 2 π : SE E [ dB ] = 20 k log ( λ 2 4 π d g ) ( Eq . 2 ) SE H [ dB ] = 20 k log ( π d g ) ( Eq . 3 ) wherein λ, is the wavelength of the EM radiation waves, g is the grid spacing and d is the distance between the EM radiation source and the EM shielding grid. Parameter k is related to the grid conductivity, i.e. the conductivity of the yarn and the grid's connecting points, and can have a value between 0 and 1. If the grid conductivity is very high, the k approaches 1. Due to the logarithmic nature of the Equations 1 to 3, a shielding efficiency of 6 dB represents an attenuation of the signal strength of 50%, a shielding efficiency of 20 dB represents an attenuation of the signal strength of 90%. Referring to FIG. 2c, the detailed perspective view of the garment pocket (220) with the EM radiation shielding produced according to the method of the present invention is shown. As can be seen in FIG. 2c, the upper-left corner of the pocket is flipped open to better illustrate the application of the pattern (in this particular example the grid illustrated in FIG. 2b) to said at least a part of said at least one EM radiation shielded zone (240) according to the inventive concept underlying the present invention. In another particular example, said pattern is a mesh. Various other patterns are possible, as previously explained. FIG. 2d illustrates an another example of a pattern applied to said at least a part of said at least one EM radiation shielded zone shown without the outer side of the pocket applied. Said EM radiation shielding treatment may be applied to at least a part of said at least one EM radiation shielded zone as previously explained, but may also be applied to substantially whole said at least one EM radiation shielded zone. Referring to FIG. 3, a cross-sectional view of the pocket (220) with the EM radiation shielding according to the present invention is shown. The pocket is formed of two opposite walls, attached to each other along its edges to form a pocket space (300) between them. The first wall (350) is referred to as the inner side of the pocket and the second wall (360) is referred to as the outer side of the pocket. Solid lines in FIG. 3 are used to depict a fabric whereas dotted lines are used to depict a yarn. There are various arrangements of the pockets possible. For a conventional sewn-in pocket, both walls hang on the inner side of the garment, adjacent the inner side of the garment fabric. This is a usual arrangement for a more formal type of garment. For a conventional sewn-on pocket, such as the one illustrated in FIG. 3, the inner side of the pocket is formed on the garment body itself and the outer side of the pocket is sewn onto the garment body such that it faces exactly the inner side of the pocket. This arrangement is usual for a more casual, or less formal, type of garment, such as jeans. The present invention can equally be applied to both sewn-in as well as sewn-on types of pockets. Referring back to FIG. 3, said pattern (250) is shown in the cross-sectional view of the pocket (220) to be formed of a conductive yarn being repeatedly passed through the fabric of the garment. In this particular example, one line of a grid is shown in the cross-sectional view in FIG. 3 being stitched in the garment fabric. The method of producing a garment according to the present invention is suitable for producing the garment during the industrial production process as well as for producing the garment after the industrial production process has been completed. It is however preferable to apply the method during the production process as the determined EM radiation shielded zones are easier to access. Referring now to FIG. 4, the application of the method during the industrial garment production process is explained. First, at least one EM radiation shielded zone (240) of a garment is determined in relation to at least one designated area (not shown) of said garment. As previously explained, the designated area defines an area of said garment designated to form the inner side of a pocket suitable to accommodate a device emitting EM radiation. In other words, said designated area defines the inner side of the pocket providing EM radiation shielding. In the example of FIG. 4, the right back pocket is desired to be designed to be the pocket providing EM radiation shielding. As previously explained, the at least one EM radiation shielded zone represents the area on said garment which physically exhibits EM radiation shielding properties. Next, an EM radiation shielding treatment to at least a part of said at least one EM radiation shielded zone is applied, as previously explained. The subsequent steps in garment production process remain the same as those of a conventional garment production, i.e. cutting, sewing-on the outer sides of the pockets including the outer sides of the pockets to be sewn onto the at least one designated area, assembling, etc. Various modifications to the present invention described will be obvious to a person skilled in the art without departing from the scope of the invention as defined by the appended claims. |
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abstract | A mirror, in particular for a microlithographic projection exposure apparatus, has a mirror substrate (101), a reflection layer system (102) configured to reflect electromagnetic radiation that is incident on the optically effective surface (100a), and a capping layer (104), which is arranged on the side of the reflection layer system (102) facing the optically effective surface. The capping layer is produced from a first material. Particles (105) of a second material, either individually or in clusters, are applied onto this capping layer, wherein the second material differs from the first material. |
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claims | 1. A network analyzer that is connected to a test set that comprises network analyzer side ports, device under test side ports that are connected to a device under test, and a port connecter that selects any one of the device under test side ports, and connects the selected device under test side port to one of the network analyzer side ports, wherein the device under test side ports constitute a main port group and a sub port group whose connection to the network analyzer side ports is independently set, the network analyzer comprising:transmission and reception ports that are connected to the network analyzer side ports one by one, and are used to transmit and receive a signal;a transmission tracking error determiner that determines a transmission tracking error of a combination of one of the possible connections of the main port group and one of the possible connections of the sub port group for all the possible connections of the main port group based on a signal prior to transmission by said transmission and reception port, and a reception signal; anda transmission tracking error deriver that derives a transmission tracking error other than the transmission tracking errors determined by said transmission tracking error determiner based on the transmission tracking error determined by said transmission tracking error determiner. 2. The network analyzer according to claim 1,wherein said transmission tracking error deriver uses two connections other than connections at a start point and an endpoint of the transmission tracking error to be derived to derive the transmission tracking error for a combination of one of the possible connections of the main port group and another possible connection of the sub port group. 3. The network analyzer according to claim 2, wherein:the main port group includes three of the device under test side ports connected to two of the network analyzer side ports;the sub port group includes three of the device under test side ports connected to one of the network analyzer side ports; andtwo of the sub port groups exist. 4. The network analyzer according to claim 2, further comprising:a transmission signal measurer that measures a transmission signal parameter relating to a transmission signal transmitted from said transmission and reception port before a measuring system error factor is generated; anda reception signal measurer that measures a reception signal parameter relating to a reception signal received by said transmission and reception port. 5. The network analyzer according to claim 4, wherein the reception signal includes a reflected signal which is a reflected transmission signal. 6. The network analyzer according to claim 1, wherein:the main port group includes three of the device under test side ports connected to two of the network analyzer side ports;the sub port group includes three of the device under test side ports connected to one of the network analyzer side ports; andtwo of the sub port groups exist. 7. The network analyzer according to claim 1, further comprising:a transmission signal measurer that measures a transmission signal parameter relating to a transmission signal transmitted from said transmission and reception port before a measuring system error factor is generated; anda reception signal measurer that measures a reception signal parameter relating to a reception signal received by said transmission and reception port. 8. The network analyzer according to claim 7,wherein the reception signal includes a reflected signal which is a reflected transmission signal. 9. A transmission tracking error measuring method of measuring a transmission tracking error of a network analyzer that is connected to a test set that comprises network analyzer side ports, device under test side ports that are connected to a device under test, and a port connecter that selects any one of the device under test side ports, and connects the selected device under test side port to one of the network analyzer side ports, wherein the device under test side ports constitute a main port group and a sub port group whose connection to the network analyzer side ports is independently set, the network analyzer comprising transmission and reception ports that are connected to the network analyzer side ports one by one, and are used to transmit/receive a signal, the transmission tracking error measuring method comprising:realizing, in a connection operation, a combination of one of the possible connections of the main port group and one of the possible connections of the sub port group for all the possible connections of the main port group;realizing all couplings for one combination of two ports for the device under test side ports connected to the network analyzer side ports if the combination is realized by said connection operation;measuring a signal prior to being transmitted by transmission and reception port, and a resulting signal after said signal has been transmitted;determining a transmission tracking error of the coupling realized by said device under test side port coupling realizing based on a measured result of said signal measuring; andderiving a transmission tracking error other than the transmission tracking error determined by said transmission tracking error determining based on the transmission tracking error determined by said transmission tracking error determining. 10. The transmission tracking error measuring method according to claim 9,wherein said device under test side port coupling realizing is realized by a four-port calibrator which can couple all combinations of two ports out of four ports. 11. A network analyzing method of analyzing the network by using a network analyzer that is connected to a test set that comprises network analyzer side ports, device under test side ports that are connected to a device under test, and a port connecter that selects any one of the device under test side ports, and connects the selected device under test side port to one of the network analyzer side ports, wherein the device under test side ports constitute a main port group and a sub port group whose connection to the network analyzer side ports is independently set, the network analyzer comprising: transmission and reception ports that are connected to the network analyzer side ports one by one, and are used to transmit/receive a signal; the network analyzing method comprising:determining a transmission tracking error of a combination of one of the possible connections of the main port group and one of the possible connections of the sub port group for all the possible connections of the main port group based on a signal before transmitted by said transmission and reception port, and a reception signal; andderiving a transmission tracking error other than the transmission tracking errors determined by said transmission tracking error determining based on the transmission tracking error determined by said transmission tracking error determining. 12. A computer-readable medium having a program of instructions for execution by the computer to perform a processing for analyzing a network by using a network analyzer that is connected to a test set that comprises network analyzer side ports, device under test side ports that are connected to a device under test, and a port connecter that selects any one of the device under test side ports, and connects the selected device under test side port to one of the network analyzer side ports, wherein the device under test side ports constitute a main port group and a sub port group whose connection to the network analyzer side ports is independently set, the network analyzer comprising: transmission and reception ports that are connected to the network analyzer side ports one by one, and are used to transmit and receive a signal; said processing comprising:determining a transmission tracking error of a combination of one of the possible connections of the main port group and one of the possible connections of the sub port group for all the possible connections of the main port group based on a signal before transmitted by said transmission and reception port, and a reception signal; andderiving a transmission tracking error other than the transmission tracking errors determined by said transmission tracking error determining based on the transmission tracking error determined by said transmission tracking error determining. |
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claims | 1. A passive spent fuel cooling system operable to remove decay heat from a fuel handling area of a nuclear reactor plant, comprising:a spent fuel pool,wherein the spent fuel pool contains water,wherein the spent fuel pool contains spent fuel removed from a core of a nuclear reactor of the nuclear reactor plant,wherein the spent fuel generates decay heat, andwherein the spent fuel pool is located in the fuel handling area and,wherein in a boiling event, the water boils to generate steam that mixes with air in the fuel handling area to form a mixture,the mixture containing particulates;a filtration system configured to at least partially remove the particulates, comprising:a discharge path having a first end connected to the fuel handling area and a second end connected to atmosphere;a first vent mechanism positioned in the fuel handling area at an interface of the fuel handling area and the first end of the discharge path,the first vent mechanism comprising at least one temperature-actuated damper that is operable to release the mixture from the fuel handling area into the discharge path;an air filtration unit located in the discharge path,the air filtration unit comprising at least one passive particulate air filter,the at least one passive particulate air filter comprising at least one fiber-containing mat, the at least one fiber-containing mat is structured to trap at least a portion of the particulates from the mixture in the at least one fiber-containing mat to produce a filtered mixture, responsive to the mixture being forced through the at least one passive particulate air filter due to a differential pressure generated in the fuel handling area; anda second vent mechanism located downstream of the at least one passive particulate air filter,the second vent mechanism is structured to release the filtered mixture to the atmosphere. 2. The passive spent fuel cooling system of claim 1 further comprisingat least one drain connected to the air filtration unit,the at least one drain is structured to return to the fuel handling area or other discharge point, condensate generated from the steam and air mixture in the air filtration unit. 3. The passive spent fuel cooling system of claim 2 wherein the at least one drain is two drains. 4. The passive spent fuel cooling system of claim 3wherein one drain of the two drains is located upstream of the at least one passive filter, andwherein the other drain of the two drains is located downstream of the at least one passive filter. 5. The passive spent fuel cooling system of claim 1 wherein the second vent mechanism comprises at least one fail open or gravity operated damper. 6. The passive spent fuel cooling system of claim 1 wherein the first and second vent mechanisms each comprise two dampers. 7. The passive spent fuel cooling system of claim 1 wherein the mixture released from the first vent mechanism has a higher level of particulates as compared to the filtered mixture released from the second vent mechanism. 8. The passive spent fuel cooling system of claim 1 wherein the nuclear reactor is eithera pressurized water nuclear reactor, ora boiling water nuclear reactor. 9. The passive spent fuel cooling system of claim 1 wherein the particulates comprises radioactive particulates. |
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059600500 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1, there is shown a schematic illustration of a test holder, generally denoted 10, used in accordance with the method of the present invention to determine fission heat flux for a Uranium 235 fuel-bearing specimen used in a nuclear reactor. The test holder 10 is positioned in a conventional pressurized test loop (not shown) of an ATR reactor to take experimental data used in deriving the absolute value of the thermal fission flux of a prime specimen. Test holder 10 is an SW101-type F 2.times.3 holder and is shown in cross-section as having a series of components positioned in a row. Specifically, the following components are positioned in a row proceeding from left to right: a first bulk water channel (WC) 12; a prime specimen (PRIME) 14; a second WC 12; a first thermocouple test specimen (TC) 16; a third WC 12; a first Zirconium specimen (Zr) 18; a fourth WC 12; a second TC 16; a fifth WC 12; a second Zr specimen 18; and a sixth WC 12. As discussed above, the TC's 16 must be positioned at the same level and this is accomplished by using the test holder 10. FIG. 2 illustrates the composition of each TC 16 and shows in cross section that TC 16 comprises a central backclad (BC) 22. Two outer clads (CLAD) 26 and two fuel fillers (FF) 24 are disposed between the backclad 22 and the two outer clads 26, respectively. Two WC's 12 are shown in dashed lines to help illustrate the positioning of WC's 12 in test holder 10. As mentioned above and as discussed in more detail below, various temperature data is required to ultimately determine the fission flux; FIG. 2 illustrates that the temperature (TM) is measured at the interface between backclad 22 and fuel filler 24. The maximum temperature (T.sub.MAX) of backclad 22 is also measured, as is temperature of the bulk WC (T.sub.W). The temperature (T.sub.C) at the interface between fuel filler 24 and clad 26, and the temperature (T.sub.S) between clad 26 and WC 12 is to be determined later. FIG. 3 illustrates the composition of prime specimen 14 and shows in cross-section that prime specimen 14 comprises a fuel filler 30 disposed adjacent, and between, a pair of clad 32. The first and second WC's 12 are shown in dashed lines to help illustrate the positioning of prime specimen 14 in test holder 10. Since there is no backclad in prime specimen 14, the temperature of the prime specimen 14 is assumed to be the same as the maximum temperature for this type of specimen (i.e., T.sub.M =T.sub.MAX) and the temperature (T.sub.C) is that determined at the interface between clad 32 and fuel filler 30. FIG. 4 illustrates a second embodiment of test holder 10 which is an SE93-type B 2.times.4 holder. The configuration is similar to that illustrated in FIG. 1, except after the fourth WC (proceeding left to right), there is disposed the second Zr specimen 18, the fifth WC 12, the second TC 16, the sixth WC 12, a third Zr specimen 18, and lastly a seventh WC 12. The method of the present invention will be discussed below as part of a mathematical proof which demonstrates that the method does indeed yield a reliable value for the fission heat flux of a prime specimen, e.g., corresponding to specimen 14 based on readily obtainable experimental data. As mentioned above, the method of the present invention requires that two TC's 16 be located at the same elevation. In addition, it is also necessary to measure the temperatures of the WC's 12, and the temperatures of the TC's 16 and to measure the gamma-scan count ratio of the TC's 16 and the prime specimen 14. The transfer heat coefficient (H.sub.COEF) for the water channel flow is also required, and can be calculated from the measured flow rate of the water channels 12. The thickness of the backclad 22, fuel filler 24, and clad 26 of the TC's 16 must also be determined. Further, the ATR reactor lobe power (POWER) and axial factor for gamma heat (AXF) is used to separate the fission heat from the total heat so that the absolute value of the fission heat fluxes of the TC's 16 can then be determined. Once the absolute value of the fission heat fluxes of the TC's 16 is determined, the absolute value of the fission heat flux of the prime specimen can then be easily determined as shown below. To facilitate the explanation of the method of the invention, Zirconium (Zr) is assumed for the clad and backclad material. The thermal conductivity for the Zr regions can be expressed as a linear function of the average temperature. In addition to the heat generated from fission, there is also gamma heat throughout the specimen. Set forth below is a somewhat detailed derivation for the linearly varying conductivity versus temperature case. For clarification of the derivation, it may be helpful to note the following term abbreviations. Term Abbreviations P=Prime Specimen PA0 TC=Thermocouple Test Specimen PA0 WC=Water Channel PA0 FF=Fuel filler PA0 BC=Backclad PA0 H=Transfer heat coefficient for WC flow PA0 a=6, b=5e-3; ab=a/b=1200 (material constants for Zr) PA0 T.sub.w =Bulk WC temperature PA0 T.sub.s =Temperature at interface between the outer clad and WC in a TC or the temperature between the clad and WC in a prime specimen PA0 T.sub.L =Linear average temperature over fuel PA0 T.sub.M =Temperature at interface between the BC and FF in a TC, or maximum temperature of a prime specimen PA0 k.sub.w =Pseudo WC thermal conductivity PA0 k.sub.s =Pseudo WC film thermal conductivity PA0 k.sub.c =Clad thermal conductivity PA0 k.sub.m =Pseudo thermal conductivity based on T.sub.M PA0 Q.sub.T =Total heat generation for BC, FF, Clad PA0 Q.sub.G =Gamma heat generation PA0 Q.sub.F Fission heat generation PA0 S.sub.C =Clad heat source PA0 S.sub.F =Fuel heat source PA0 t.sub.s =Total specimen thickness PA0 t.sub.c =Thickness of outer clad of TC PA0 t.sub.f =Thickness of fuel filler of TC PA0 t.sub.bc =Thickness of backclad of TC PA0 a.sub.c =t.sub.c /t.sub.s =Clad gamma heat multiplication factor PA0 a.sub.f =(2t.sub.c -t.sub.b)/t.sub.s =Fuel filler gamma heat multiplication factor PA0 a.sub.bc =t.sub.bc /t.sub.s =Backclad gamma heat multiplication factor PA0 A.sub.p =Intercept in conductivity equation for prime specimen PA0 A.sub.i =Intercept in conductivity equation for TC's 1, 2 PA0 B=Slope in conductivity equation for specimens PA0 1,2,P=Subscripts for TC.sub.1, TC.sub.2, prime specimen PA0 AXF=Axial Factor for Gamma Heat PA0 Power=Reactor power PA0 T.sub.MAX =Maximum temperature of backclad in a TC or T.sub.M for prime specimen PA0 T.sub.c =Temperature at interface between FF and outer clad in a TC or temperature at interface between FF and clad in a prime specimen PA0 k=Average thermal conductivity PA0 S.sub.BC =Backclad heat source PA0 T.sub.BC =Backclad temperature PA0 R.sub.TC =Measured scan count ratios of the thermocouple specimens PA0 R.sub.P =Measured scan count ratio of the prime specimen The following statement definitions are also helpful in understanding the derivation which follows: ##EQU1## where: S=heat source term which is a function of fission and/or gamma heat plus the specimen material thicknesses. k=Average thermal conductivity EQU k=a+bT EQU T=(T.sub.2 +T.sub.1)/2=AVERAGE TEMPERATURE BETWEEN SURFACES 2 AND 1 a, b=average material constants where the material may contain Zr, U235, etc. As a result of an adiabatic heat surface in the backclad, the backclad heat source, denoted S.sub.BC, depends only on the material gamma heat and the backclad thickness (t.sub.bc). Since the thermocouple well is contained in the backclad (e.g., corresponding to backclad 22 of FIG. 2), it follows that T.sub.BC =(T.sub.MAX +T.sub.M)/2, and, therefore, the temperature drop across the backclad can be considered constant throughout the derivation for a particular TC. Using the fact that the average thermal conductivity is assumed to vary similarly with temperature for both TC's (1 and 2), then EQU (dk/dT.sub.L).sub.2 =(dk/dT.sub.L).sub.1 =(dk/dT.sub.L).sub.P wherein, in this last equation, the P refers to a prime specimen. As mentioned above, test holders such as the types F (2.times.3) and B (2.times.4), shown in FIGS. 1 and 4, generally contain two fueled thermocouple specimens (TC's 16) and one or more prime specimens (specimens 14). The derivation or proof set forth below is for simplest case whereby the conductivity in the fuel region is assumed to vary linearly with temperature. Conductivities for the clad and backclad are also assumed to vary linearly with temperature which is a very good assumption for Zr material. Moreover, the heat transfer is assumed as being one-dimensional. The composition of the prime specimen 14 and the TC's 16 was discussed previously. For purposes of the derivation which follows, it is assumed that all specimens have the same clad and backclad material and that the backclad 22 and clad 26 are Zr material with a linear conductivity temperature dependence. A further assumption is that dk/dT is the same for all fuel fillers. In the derivation or proof which follows, equations for the clad and fuel regions are set up in turn. It should be noted that a thermal adiabatic surface occurs in the backclad region 22. Consequently, since the conductivity temperature dependence is known, the temperature drop to the fuel surface fuel filler 24 depends only on the backclad thickness (t.sub.bc), gamma heat rate (Q.sub.G), and the TC temperature reading in the backclad. Some of the variables in the equations are symbolic to facilitate the derivation. Clad Region Let ##EQU2## It follows that EQU k.sub.c.sup.2 -k.sub.s.sup.2 =2bS.sub.c Eq (1) By differentiation of Eq (1) and using the equation for S.sub.c, then ##EQU3## Fuel Region Let ##EQU4## By differentiation of the last equation and using Eq (2) ##EQU5## where T.sub.M is fixed and Eq (2) has been used. It follows that ##EQU6## Let k.sub.w =a+bT.sub.w, then ##EQU7## From rules of differentiation and noting that T.sub.L =(T.sub.C +T.sub.M)/2 ##EQU8## By definition ##EQU9## Canceling constants it follows that ##EQU10## Next, we need to determine the variables k.sub.s, k.sub.c. From Eq (1) and Eq (3) ##EQU11## Solving the quadratic in k.sub.s yields ##EQU12## Let k.sub.s +t.sub.c H/12=X, k.sub.c =a+bT.sub.c and k.sub.m =a+bT.sub.M. Note that the only unknown variable on the right side of Eq (7) is k.sub.c. Eq (6) may be written in terms of X, k.sub.m and k.sub.c as follows ##EQU13## The total heat generation is Q.sub.T =Q.sub.F +Q.sub.G. Since ##EQU14## Then it follows that ##EQU15## Here R.sub.TC is the measured gamma scan ratio of the TCs. Equations (7), (8), (9) are independent. The T.sub.M as defined here is not the measured T.sub.MAX since there is a slight temperature rise to the middle of the backclad. The temperature T.sub.M as a function of T.sub.MAX is determined as follows. ##EQU16## and therefore ##EQU17## Solving the resulting quadratic equation yields for T.sub.M ##EQU18## Since T.sub.MAX is measured, and all other quantities are known, the T.sub.M for the TC is determined as is k.sub.m =a+bT.sub.M. Noting that k.sub.c from Eq (7) may be written in terms of X, then ##EQU19## for either TC. Therefore, it follows Eq (8) that ##EQU20## After applying Eq (11) to Eq (12), and using Eq (9) and (13) then the X value for either TC is determined. From the value of X and Eq (7), k.sub.s, k.sub.c and hence T.sub.S, T.sub.C are determined. Since, by definition EQU Q.sub.T.sbsb.1 =H.sub.1 (T.sub.S.sbsb.1 -T.sub.W.sbsb.1); Q.sub.F.sbsb.1 =Q.sub.T.sbsb.1 -Q.sub.G.sbsb.1 Eq (14) and similarly for TC.sub.2. The Q.sub.F values are therefore determined. From the TC value (T.sub.MAX), the delta T across the filler, T.sub.M -T.sub.C, is known. Since ##EQU21## the value of k is hence determined for either TC. The additional required equation, namely, Q.sub.G, may be written simply as EQU Q.sub.G =25773.times.POWER.times.0.3.times.AXF.times.t.sub.SEq (16) The above set of equations have been derived for the TC's. The following gives equations for the prime specimens. The gamma scan ratio of the prime specimen, R.sub.P is a measured quantity, i.e. ##EQU22## Since R.sub.p, Q.sub.F.sbsb.1 are known, the Q.sub.F.sbsb.P is determined. From the specimen dimensions, Q.sub.G.sbsb.P is found and hence Q.sub.T.sbsb.P. By analogy from the preceding equations for the CLAD region and FUEL region, the T.sub.C.sbsb.P, T.sub.S.sbsb.P are readily found. Since there is no backclad for the prime specimen, T.sub.M.sbsb.P is the maximum value. Therefore, for a linear temperature dependence of the thermal conductivity in the fuel filler, and noting that ##EQU23## we have found from Eq (8) ##EQU24## Since Y.sub.1 for TC.sub.1 is known, and X.sub.p, k.sub.c.sbsb.P is determined from T.sub.C.sbsb.P, T.sub.S.sbsb.P, Q.sub.T.sbsb.P then the only remaining variable in Eq (18) is k.sub.m.sbsb.P. Solving for k.sub.m.sbsb.P which is the pseudo filler thermal conductivity for the prime specimen, and then using the following ##EQU25## and k.sub.p, B, T.sub.M.sbsb.P, T.sub.C.sbsb.P are known, then the intercept A.sub.p for the prime specimen can be determined. Substituting the appropriate variables in Eq (21), the A.sub.i values for the TC's are similarly determined. A computer program was written in MS pro-basic to run on an IBM type 486 computer. The program listing plus the input for the ATR SW101 and SE93 test trains are attached. A comparison of results with the measured results is given in Table 1. Following Table 1 is a listing of the prompts for input and the values entered for both of the disclosed embodiments. Lastly, there is a listing of the computer program itself. TABLE 1 __________________________________________________________________________ COMPARISON OF INVENTION WITH THE MEASURED RESULTS Specimen T.sub.W T.sub.S T.sub.C T.sub.W T.sub.WAX Q.sub.F .times. 10.sup.-6 Percent ID M I M I M I M I M I M I Diff __________________________________________________________________________ SW101 Prime 224 224 467 472 828 840 1167 1142 1167 1142 2.01 2.05 +2.0 TC.sub.2 221 221 447 454 781 794 -- 1073 1084 1084 1.77 1.81 +2.3 TC.sub.1 215 215 364 369 599 607 -- 840 854 853 1.15 1.17 +1.7 SE93 Prime 492 492 558 559 764 767 -- 935 936 935 .836 .846 +1.2 TC.sub.2 492 492 558 559 714 718 -- 901 909 910 .784 .794 +1.3 TC.sub.1 489 489 543 543 672 674 -- 837 845 846 .633 .641 +1.3 __________________________________________________________________________ Invention I Measured Results M __________________________________________________________________________ PROMPTS FOR INPUT AND ENTERED VALUES INPUT TRAIN ID, SPECIMEN ID'S PRIME TC, ALT TC SW101, XX, YY INPUT POWER, GAMMA AXF, FISS RAT PRIME TO ALT TC, AND SIDE TO ALT TC 41, .939, 1.545, 1.751 INPUT BW, TMAX, HCOEF, THICC, THICF, THICBC, SWEL FOR PRIME TC 221, 1084, 8141, .0198, .064, .1453, 0 INPUT BW, TMAX, HCOEF, THICC, THICF, THICBC, SWEL FOR ALT TC 215, 853, 8141, .0195, .0637, .1458, .0048 INPUT SPEC ID, BW, HCOEF, THICC, THICF, THICBC, SWEL FOR SIDE SPECIMEN ZZ, 224, 8387, .0197, .0685, 0, .0334 INPUT TRAIN ID, SPECIMEN ID'S PRIME TC, ALT TC SE93, XX, YY INPUT POWER, GAMMA AXF, FISS RAT PRIME TO ALT TC, AND SIDE TO ALT TC 31.8, .951, 1.2385, 1.3207 INPUT BW, TMAX, HCOEF, THICC, THICF, THICBC, SWEL FOR PRIME TC 492, 910, 12820, .0206, .0682, .1404, .02284 INPUT BW, TMAX, HCOEF, THICC, THICF, THICBC, SWEL FOR ALT TC 489, 846, 12900, .0204, .0682, .1403, .02728 INPUT SPEC ID, BW, HCOEF, THICC, THICF, THICBC, SWEL FOR SIDE SPECIMEN ZZ, 492, 13100, .0268, .0673, 0, .04053 PROGRAM LISTING 9 OPEN "LPT1" FOR OUTPUT AS #1 10 PRINT "INPUT TRAIN ID, SPECIMEN ID'S PRIME TC, ALT TC" 20 INPUT Idt$, Id2$, Id1$ 30 PRINT "INPUT POWER, GAMMA AXF, FISS RAT PRIME TO ALT TC, AND SIDE TO ALT TC" 40 INPUT P, Axf, R, Rs 50 IF Axf > 1 THEN Axf = COS(.05775 * Axf) 60 PRINT "INPUT BW, TMAX, HCOEF, THICC, THICF, THICBC, SWEL FOR PRIME TC" 70 INPUT Tw2, Tmax2, H2, Tc2, Tf2, Tbc2, Sw2 80 INPUT "INPUT BW, TMAX, HCOEF, THICC, THICF, THICBC, SWEL FOR ALT TC" 90 INPUT Tw1, Tmax1, H1, Tc1, Tf1, Tbc1, Sw1: REM Sw1 = 0.273: SW2 = .0228 100 A = 6: B = .005; Ab = A/B: Tf2s = Tf2*(1 + Sw2): Tf1s = TF1*(1 + Sw1) 110 Ts2 = 2*Tc2 + Tf2 + Tbc2: Qg2 = 25773*P*.3*Axf*Ts2: Kw2 = A + B*Tw2: Kch2 = Tc2*H2/12 120 Ts1 = 2*Tc1 + Tf1 + Tbc1: Qg1 = 25773*P.3*Axf*Ts1: Kw1 = A + B*Tw1: Kch1 = Tc1*H1/12 130 Kfh2 = Tf2*H2/48: Kfh1 = Tf1*H1/48: Kgh2 = B*Qg2/H2 Kgh1 = B*Qg1/H1: Kwb1 = Kw1 + Kgh1 140 Ac2 = Tc2/Ts2: Af2 = (2*Tc2 - Tbc2)/Ts2: Kwb2 = Kw2 + Kgh2 150 Ac1 = Tc1/Ts1: Af1 = (2*Tc1 - Tbc1)/Ts1 160 Kwc2 = Kw2 + Ac2*Kgh2: Kwc1 = Kw1 + Ac1*Kgh1: Kwf2 = Kw2 + Af2*Kgh2: Kwf1 = Kw1 + Af1*Kgh1 170 Al1 = Kfh1*KWf1: G1 = Kch1 + Kwf1: G12 = Kch2 + Kwf2: G3 = Kch1 2 + 2*Kch1*Kwc1: G31 = G3 180 G32 = Kch2 2 + 2*Kch2*Kwc2: : P1 = Kwb1 + Kch1: P2 = Kwb2 + Kch2: Pw1 = Kwc1/B: Pw2 = Kwc2/B 190 Ph1 = (Kwc1 + .5*Kch1)/B: Ph2 = (Kwc2 + .5*Kch2)/B 200 IF Rs = 0 THEN 260 210 PRINT "INPUT SPEC ID, BW, HCOEF, THICC, THICF, THICBC, SWEL FOR SIDE SPECIMEN" 220 INPUT Ids$, Tws, Hs, Tcs, Tfs, Tbcs, Sws: REM Sws = .0405: Tfss = Tfs*(1 + Sws) 230 Tst = 2*Tcs + Tfs + Tbcs: Qgs = 25773*P*.3*Axf*Tst: Acs = Tcs/Tst: Afs = (2*Tcs - Tbcs)/Tst 240 Kchs = Tcs*Hs/12: Kfhs = Tfs*Hs/48: Kghs = B*Qgs/Hs: Kws = A + B*Tws: Kwcs = Kws + Acs*Kghs 250 Kwbs = Kws + Kghs 260 PRINT #1, : PRINT #1, "*******THE TRAIN ID IS"; Idt$; "*******" 270 PRINT #1, : PRINT #1, "SPECIMEN ID FOR PRIME ALT TC'S ARE": Id2$; "AND"; Id1$ 280 IF Rs <> 0 THEN PRINT #1, "SPECIMEN ID FOR SIDE SPECIMEN IS"; Ids$ 290 REM*******DETERMINED BCLAD DT AND FUEL/BCLAD INTERFACE TEMPERATURE******** 300 Tm2 = (-A + SQR((A + B*Tmax2) 2-B*Qg2*Tbc2 2/(24*T12)))/B: Dtb2 = Tmax2 - Tm2 310 Tm1 = (-A + SQR((A + B*Tmax1) 2-B*Qg1*Tbc1 2/(24*Ts1)))/B: Dtb1 = Tmaxl - Tm1 320 PRINT #1, : PRINT #1, "AXF ="; Axf; "tm2 ="; Tm2: "dtb2 ="; Dtb2; "tm1 ="; Tm1; "dtb1 ="; Dtb1 330 Kc1 = A + .002*Tm1: Dk = .001: Km2 = A + B*Tm2: Km1 = A + B*Tm1 340 C3 = Kwf2 2 + Kch2*Kgh2*(Af2 - Ac2) - Km2 2: C4 = Kwf1 2 + Kch1*Kgh1*(Af1 - Ac1) - Km1 2 350 FOR M = 1 TO 1000 360 Tcn1 = Kc1/B - Ab: Ks1 = -Kch1 + SQR(Kch1 2 + 2*Kch1*(Kw1 + Ac1*Kgh1) + Kc1 2) 370 Tsxl = Ks1/B - Ab: Ks2 = Kw2 + (Ks1 - Kw1 - Kgh1)*R*H1/H2 + Kgh2: Tsx2 = Ks2/B - Ab 380 Qt1 = H1*(Tsx1 - Tw1): Qf1 = Qt1 - Qg1: Qt2 = H2*(Tsx2 - Tw2): Qf2 = Qt2 - Qg2 390 Qct1 = Qt1 - AC1*Qg1: Qct2 = Qt2 - Ac2*Qg2: Qft1 = Qt1 - Af1*Qg1: Qft2 = Qf2 - Af2*Qg2 400 Dtl = Tm1 - Tcn1: S2 = Tf2*Qft2/48: S1 = Tf1*Qft1/48: K1 = S1/Dt1 410 Kc2 + SQR(Ks2 2 + 2*Kch2*(Ks2 - Kwc2)): Tcn2 = Kc2/B - Ab: Dt2 = Tm2 - Tcn2: K2 = S2/Dt2 420 Y2 = B*Kfh2*((Ks2 - Kwf2)/(Km2 - Kc2) 2 + Kc2/((Km2 - Kc2)*(Ks2 + Kch2))) 430 Y1 = B*Kfh1*((Ks1 - Kwf1(/(Km1 - Kc1) 2 + Kc1/((Km1 - Kc1)*(Ks1 + Kch1))):Ra = Y2/Y1 440 IF ABS(Ra - 1) < .001 THEN 480 450 IF M = 1 THEN 470 460 S1 = (1 - Ra)/(Ra - Rao): Kc1 = Kc1 + .5*S1*Dk: Me = M + S1: REM PRINT M; Me; Ra; Kc1; K2; K1 470 Kc1 = Kc1 + Dk: Y1o = Y1: Y2o = Y2: Rao = Y2o/Y1o: NEXT M 480 IF Rs = 0 THEN 560 490 Kss = Kws + (Ks1 - Kw1 - Kgh1)*Rs*H1/Hs + Hghs: Tsxs = Kss/B - Ab 500 Kcs = SQR(Kss 2 + 2*Kchs*(Kss - Kws - Acs*Kghs)) Tcns = Kcs/B - Ab 510 Ps = B*Kfhs*Kcs/(Kss + Kchs) 520 Kms = Kcs + .5*(Ps + SQR(Ps 2 + 4*Y1*B*Kfhs*(Kss - Kws - Afs*Kghs)))/Y1 530 Tms = Kms/B - Ab: Qfs = Rs*Qf1: Qts = Qfs + Qgs: Qfts = Qts - Afs*Qgs 540 Tmaxs = (-A + SQR((A + B*Tms) 2 + B *Qgs*Tbcs 2/(24*Tst)))/B: Dtbs = Tmaxs - Tms 550 Ks = Tfs*Qfts/(48*(Tms - Tcns)): PRINT #1, "TINTS ="; Tcns; "TMAXS ="; Tmaxs 560 PRINT #1, ".sub.-------------------- " 570 PRINT #1, "THE FOLLOWING VALUES WERE FOUND AFTER" M; "ITERATIONS" 580 PRINT #1, "me, RAT"; Me; Ra; "K2 ,K1, Ks"; K2; K1; Ks; "QF2, QF1, QFS"; Qf2, Qf1; Qfs 590 PRINT #1, "TSX1, TSX2, TSXS, TCN1, TCN2, TCNS"; Tsx1; Tsx2; Tsxs; Tcn1; Tcn2; Tcns 600 T1 = .5*(Tm1 + Tcn1): T2 = .5*(Tm2 + Tcn2): Q = Tf2*Qft2*(Tm1 - T1)/(Tf1*Qft1*(Tm2 - T2)) 610 S1 = (K2 - K1)/(T2 - T1): PRINT "SLOPE ="; S1; "INT ="; (T2 - Q*T1)*S1/(Q - 1) 620 Rh = H1*R/H2: Bb1 = Kch1*(Kch1 + 2*Kwc1): Ff = Kch2 + Kwb2 - Rh*(Kch1 + Kwb1) 630 Bb2 = Kch2*(Kch2 + 2*Kwc2): Kc1 = A + B*Tcn1: U1 = (Kc1 2 + Bb1)*Rh 2: Kc2o = Kc2 640 U2 = (Ff + SQR(U1)) 2: Kc2 = SQR(U2 - Bb2): Tcn2n = Kc2/B - Ab: K2ra = K2/K1 650 Cc = Tf2*Qft2/(Tf1*K2ra*Qft1): Sx = (Cc/Rh) 2 - 1: Ax = Sx 2: Kmd2 = (Km2 - Cc*Km1) 2 660 Hh = Ff 2 - Kmd2 + Bb1*Cc 2 - Bb2: Cx = Hh 2 + 4*Bb1*Kmd2*Cc 2 670 Bx = -4*Kmd2*(Cc/Rh) 2 - 2*Hh*Sx = 4*Ff 2: G4 = Ax 2: G3 = 2*Ax*Bx - 16*(Sx*Ff) 2 680 G2 = Bx 2 + 2*Cx*Ax + 32*Hh*Sx*Ff 2: G1 = 2*Bx*Cx - 16*(Hh*Ff) 2: G0 = Cx 2 681 Gx = SQR(SQR(G0)): Y1 = U1/Gx: G3 = G3/Gx: G2 = G2/Gx 2: G1 = G1/Gx 3: GO = 1: Y1 = .9086 690 Eq = G4*Y1 4 + G3*Y1 3 + G2*Y1 2 + G1*Y1 + GO: PRINT Eq; G4; G3; G2; G1; GO 700 PRINT #1, Kc2o; Kc2; Tcn2; Tcn2n; Tcn2n - Tcn2 701 PRINT #1, Kc1; SQR(U1/Rh 2 - Bb1); Tcn1; SQR(U1/Rh 2 - Bb1)/B - Ab 702 PRINT #1, : PRINT #1, "THE ABOVE FLUX ESTIMATES ARE THE LEAST REQUIRED CALCULATION" 703 PRINT #1, : "********************************************" 704 PRINT 710 REM*******FIND INITIAL INTERCEPT AND SLOPE FOR CONDUCTIVITY EQUATION***** 720 REM NOTE K2 VERSUS K1 IS GENERAL; T2 - T1 DEPENDS ON LINEAR AVERAGE 730 REM PRINT "INPUT INITIAL KBAR1 ESTIMATE": INPUT K1 740 L = L + 1: PRINT #1, : PRINT #1, "-------FOR L ="; L; "-------" 750 F1 = .5*Kch1 + Kfh1*(Km1 + A11/K1)/K1 760 Term = (1 - (Kfh1/K1) 2)*(Kch1*Kwc1 + (Km1 + A11/K1) 2) 770 G1 = (-F1 + SQR(F1 2 + Term))/(1 - (Kfh1/K1) 2) - Kwb1 780 Krgh = R*G1*H1/H2: S = Kwb2 + Krgh 790 D1 = SQR((S + .5*Kch2) 2 - .5*Kch2*(.5*Kch2 + 2*Kwc2)) 800 K2t = Kfh2*(Krgh + Kwb2 - Kwf2)/(Km2 - D1) 810 B3 = (Kwf2 + .5*Kch2 + Kfh2*Km2/K2)*2*B*K2/Kfh2 820 B4 = (Kwf1 + .5*Kch1 + Kfh1*Km1/K1)*2*B*K1/Kfh1 830 A3 = 4*B 2*((K2/Kfh2) 2 - 1): A4 = 4*B 2*((K1/Kfh1) 2 - 1) 840 IF L = 1 THEN 860 850 Sloo = Slo: T2o = T2: T1o = T1: Tcno2 = Tcn2: Tcno1 = Tcn1 860 T2 = Tm2 + B3/A3 + SQR((B3/A3) 2 - C3/A3): T1 = Tm1 + B4/A4 + SQR((B4/A4) 2 - C4/A4) 870 Slo = (K2 - K1)/(T2 - T1) 880 Q = Tf2*Qft2*(Tm1 - T1)/(Tf1*Qft1*(Tm2 - T2)): Nt = (T2 - Q*T1)*Slo/(Q - 1) 890 PRINT #1, : PRINT #1, "*******SLOPE ="; Slo; "INT ="; Nt; "******": PRINT #1, 900 PRINT #1, : Qt2 = Qft2 + Af2*Qg2: Qtl = Qft1 + Af1*Qg1: Qf2 = Qt2 - Qg2: Qf1 = Qt1 - Qg1 910 S2 = Tf2*Qft2/48: S1 = Tf1*Qft1/48 920 PRINT #1, "K2 ="; K2; "K1 ="; K1; ".backslash.QF2"; Qf2; "QF1 ="; Qf1 930 PRINT #1, "QT2 ="; Qt2; "Qt1 ="; Qt1; ".backslash.QFT2 ="; Qft2; "QFT1 ="; Qft1 940 PRINT #1, "R ="; R; "R EST ="; Qf2/Qf1; "R RATIO ="; R*Qf1/Qf2 950 PRINT #1, "S2 ="; S2; "S1 ="; S1; ".backslash.TBR2 ="; T2; "TBR1 ="; T1 960 Cc = 1: Qfol = Qf1: FOR M = 1 TO 200 970 IF M > = 2 THEN Cc = .9999*Cc 980 Qf1 = Cc*Qfo1: Qf2 = R*Qf1 990 Qt1 = Qf1 + Qg1: Qt2 = Qf2 + Qg2: Qct1 = Qt1 - Ac1*Qg1: Qct2 = Qt2 - Ac2*Qg2 1000 Tsx1 = Tw1 + Qt1/H1: Tcx1 = -Ab + SQR(Ab 2 + Tsx1 2 + 2*Ab*Tsx1 + 2*Tc1*Qct1/(12*B)) 1010 Tsx2 = Tw2 + Qt2/H2: Tcx2 = -Ab + SQR(Ab 2 + Tsx2 2 + 2*Ab*Tsx2 + 2*Tc2*Qct2/(12*B)) 1020 Ps2 = Qf1 *R/H2 + (Kwb2 + .5 *Kch2)/B: Tcn2 = -Ab + SQR(Ps2 2 - Ph2 2 + Pw2 2) 1030 Ps1 = Qf1/H1 + (Kwb1 + .5*Kch1)/B: Tcn1 = -Ab + SQR(Ps1 2 - Ph1 2 + Pw1 2) 1040 S2 = Tf2*(R*Qf1 + (1 - Af2)*Qg2)/48: S1 = Tf1*(Qf1 + (1 - Af1)*Qg1)/48 1050 Nu = (Tcn2 2 - Tm2 2 + 2*S2/B)*(Tm1 - Tcn1): Den = (Tcn1 2 - Tm1 2 + 2*S1/B)*(Tm2 - Tcn2) 1060 Ratio = Nu/Den: K2 = Tf2*(Qf2 + (1 - Af2)*Qg2)/(48*(Tm2 - Tcx2)) 1070 K1 = Tf1*(Qf1 + (1 - Af1)*Qg1)/(48*(Tm1 - Tcx1)) 1080 K2 = Tf2*(Qf2 + (1 - Af2)*Qg2)/(48*(Tm2 - Tcx2)) 1090 IF M > = 2 THEN Cc = Cc + .5*(1 - Ratio)*(Cc - Cco)/(Ratio - Rato) 1100 Rato = Ratio: Cco = Cc 1110 IF ABS(Ratio - 1) < = .0001 THEN 1130 1120 NEXT M 1130 PRINT #1, "--------------------------------------------" 1140 PRINT #1, "THE FOLLOWING VALUES WERE FOUND FOR L ="; L, "AFTER"; M; "ITERATIONS" 1150 PRINT #1, "C, Rat"; Cc; Ratio; "K2, K1"; K2; K1; "QF2, QF1"; Qf2; Qf1; "K2R"; K2t/K2 1160 Qft1 = Qf1 + (1 - Af1)*Qg1: Qft2 = Qf2 + (1 - Af2)*Qg2: Tcxo2 = Tcx2: Tcxo1 = Tcx1 1170 IF L = 1 THEN 1500 1180 Qf2 = Qt1 + Qg2: Qt1 = Qf1 + Qg1 1190 C2 = B*Tf2*H2/(K2t*48): D2 = Km2 + Af2*C2*Qg2/H2 1200 Term2 = C*D2 + B*Kw2 + 4*Tc2*C2*K2t/Tf2 1210 Term22 = D2 2 - Kw2 2 + 8*Tc2*K2t*C2*Ac2*Qg2/H2 1220 Qf2 = H2*(Term2 - SQR(Term2 2 - (C2 2 - B 2)*Term22))/(C2 2 - B 2) - Qg2:Qf1 = Qf2/R 1230 Qt1 = Qf1 + Qg1: Tcx1 = SQR((Kw1 + B*Qt1/H1) 2 + 2*B*Tc1*(Qt1 - Ac1*Qg1)/12)/B - Ab 1240 Qt2 = Qf2 + Qg2: Tcx2 = Tm2 - Tf2*(Qt2 - Af2*Qg2)/(48*K2t) 1250 K1t = Tf1*(Qt1 - Af1*Qg1)/(48*(Tm1 - Tcx1)): K1 = K1t 1260 K2 = Tf2*(Qt2 - A12*Qg2)/(48*(Tm2 - Tcx2)) 1270 Qft2 = Qt2 - Af2*Qg2: Qft1 = Qt1 - Af1*Qg1: Qct2 = Qt2 - Ac2*Qg2: Qct1 = Qt1 - Ac1*Qg1 1280 Dd = S2*K1/(S1*K2):Tcx2c = Tm2 - Tm1*Dd + Dd*Tcx1 1290 Gf = (Tm2*Tcx2 - Tm1*Tcx1)/(T2 - T1): Gfo = (Tm2*Tcxo2 - Tm1*Tcxo1)/(T2o - T1o) 1300 Ks1 = A + B*(Tw1 + Qt1/H1): Dt1 = Tm1 - Tcx1: Y1 = Tf1*H1*(Ks1 - Kw1 - B*Af1*Qg1/H1)/Dt1 2 1310 Kcx1 = A + B*Tcx1: Y1 = Y1 + Tf1*B*Kcx1/(Dt1*(Ks1/H1 + Tc1/12)): Kcx2 = A + B*Tcx2 1320 Ks2 = A + B*(Tw2 + Qt2/H2): Dt2 = Tm2 - Tcx2: Y2 = Tf2*H2*(Ks2 - Kw2 - B*Af2*Qg2/H2)/Dt2 2 1330 Y2 = Y2 + Tf2*B*(A + B*Tcx2)/(Dt2*(Ks2/H2 + Tc2/12)): PRINT "Y2, Y1"; Y2; Y1; Y2/Y1 1340 X1 = SQR(G31 + Kcx1 2): Z1 = 2*X1 1350 Kcx = SQR((P2 + (X1 - P1)*H1*R/H2) 2 - G32): X2 = SQR(G32 + Kcx 2): Z2 = 2*X2 1360 Trad = Km2 - SQR((2*G32 + Km2 2 + Kcx 2 - Z2*G12)/(1 + Z2*Y1/(B 2*Tf2*H2))): Trat = Kcx/Trad 1370 PRINT #1, "TRAT1 ="; Trat 1380 1F Rs = 0 THEN 1500 1390 Qfs = Rs*Qf1:Qts = Qfs + Qgs: Qfcs = Qts - Acs*Qgs: Qffs = Qts - Afs*Qgs 1400 Tss = Tws + Qts/Hs: Tes = -Ab + SQR(Tss + Ab) 2 + 2*Tcs*Qfcs/(12*B)): Tsum1 = Tm1 + Tcx1 1410 Tcb = K1/Slo: Tps = Tcb - Tsum1/2: Tms = -Tps + SQR((Tps + Tes) 2 + 2*Tfs*Qffs/(48*Slo)) 1420 F1 = .5*Kch1 + Kfh1*(Km1 + A11/K1)/K1 1430 Term = (1 - (Kfh1/K1) 2)*(Kch1*Kwc1 + (Km1 + A11/K1) 2) 1440 G1 = (-F1 + SQR(F1 2 + Term))/(1 - (Kfh1/K1) 2) - Kwb1:Krghs = Rs*G1*H1/Hs 1450 Fs = Tfs*Hs*(Krgs + (1 - Afs)*Kghs): Kws = A + B*Tws 1460 Ss = Kwbs + Krghs: Srs = Tfs*Qffs/48 1470 Ds = SQR(Ss + .5*Kchs) 2 - .5*Kchs*(.5*Kchs + 2*Kwcs)) 1480 Tmss = ((Ds - A)*Tfs*Qfffs - Fs*Tes)/(B*Tfs*Qffs - Fs): K = Tfs*Qffs/(48*(Tmss - Tes)) 1490 PRINT #1, "TRUE TMAX ="; Tmss; "TRUE KBARS ="; K; K2: K2t 1500 IF ABS(K2 - K2t) < .001 THEN 1521 1510 IF L = 2 THEN 1521 1520 GOTO 740 1521 LPRINT CHR$(27) + "E" 1530 PRINT #1, "--------------------------------------------" 1540 PRINT #1, "********TEMPERATURES FOR PRIME TC*******" 1550 PRINT #1, "BW2 ="; Tw2; "TSURF2 ="; Tsx2; "TINT2 ="; Tcx2; "TM2 ="; Tm2; TMAX2 ="; Tmax2 1560 PRINT #1, "DTS2 ="; Tsx2 - Tw2; "DTC2 ="; Tcx2 - Tsx2; "DTF2 ="; Tm2 - Tcx2; "DTBC2 ="; Dtb2 1570 PRINT #1, : PRINT #1, "*******TEMPERATURES FOR ALTERNATE TC*******" 1580 PRINT #1, "BW1 ="; Tw1; "TSURF ="; Tsx1; "TINT1 ="; Tcx1; "TM1 ="; Tm1; "TMAX ="; Tmax1 1590 PRINT #1, "DTS1 ="; Tsx1 - Tw1; "DTC1 ="; Tcx1 - Tsx1; "DTF1 ="; Tm1 - Tcx1; "DTBC1 ="; Dbt1 1600 PRINT #1, : PRINT #1, "*******FLUXES FOR BOTH TC'S*******" 1610 PRINT #1, "QT2 ="; Qt2; "QT1 ="; Qt1; "QF2 ="; Qf2; "QF1 ="; Qf1; "QG2 ="; Qg2; "QG1 ="; Qg1 1620 PRINT #1, : PRINT #1, "*******CONDUCTIVITIES AND TBAR'S FOR BOTH TC'S" 1630 PRINT #1, "KBAR2 ="; K2; "KBAR1 ="; K1: Tb12 = Tcx2 + .5*S2/K2:Tb11 = Tcx1 + .5*S1/K1 1640 PRINT #1, "TBLIN2 ="; Tbl2; Tm2 - Dd*Tm1 + Dd*Tbl1; "TBLIN ="; Tbl1 1650 Tt2 = .5*(Tm2 + Tcx2): Tt1 = .5*(Tm1 + Tcx1) 1660 IF Rs = 0 THEN 1780 1670 IF Tbcs = 0 THEN 1690 1680 Kms = A + B*Tms: Tmaxs = (-A + SQR(Kms 2 + 2*B*Qgs*Tbcs 2/(24*Tst)))/ B:Bs = Tmaxs - Tms 1690 PRINT #1, "--------------------------------------------" 1700 PRINT #1, "PRINT #1, "*******TEMPERATURES FOR SIDE SPECIMEN*******" 1710 PRINT #1, "BWS ="; Tws; "TSURFS ="; Tss; "TINTS ="; Tes; "TMS ="; Tms: "TMAXS ="; Tms + Bs 1720 PRINT #1, "DTSS ="; Tss. - Tws; "DTCS ="; Tes - Tss; "DFTS ="; Tms - Tes; "DTBCS ="; Bs 1730 PRINT #1, : PRINT #1, "*******FLUXES FOR SIDE SPECIMEN**************" 1740 PRINT #1, "QTS ="; Qts; "QFS ="; Qfs; "QGS ="; Qgs: Tbar1 = .5*(Tes + Tms): Zqs = Tbar1*Dq 1750 PRINT #1, : PRINT #1, "*******CONDUCITIVITIES AND TBAR'S FOR SIDE SPECIMEN*******" 1760 Ks = Tfs*Qffs/(48*(Tms - Tes)): PRINT #1, "KBARS ="; Ks: Sqs = 1 + (Tms/Tbar1 - 1) 2/3 1770 PRINT #1, "TBLINS ="; Tbar1; "TBARS ="; Tbar1*(1 + Zqs*Sqs)/(1 + Zqs) 1780 STOP __________________________________________________________________________ Although the present invention has been described to specific exemplary embodiments thereof, it will be understood by those skilled in the art that variations and modifications can be effected in these exemplary embodiments without departing from the scope and spirit of the invention. |
058959262 | claims | 1. In a radiation beam therapy system comprising a radiation beam source, a plurality of radiation beam treatment locations, and a multiplexed switchyard and beam transport system for directing the radiation beam to a selected one of the radiation beam treatment locations, a method of radiation beam security comprising the steps of: (a) receiving a beam request signal from a selected treatment location; (b) deriving a beam path configuration signal from said beam request signal indicative of a selected beam path for said radiation beam from said source to said selected treatment location; (c) selecting the switchyard and beam transport system configuration in accordance with said beam path configuration signal by enabling a first set comprising of less than all of a plurality of switchyard and beam transport elements to provide a path for transport of said radiation beam to said selected treatment location; (d) sensing the configuration of the switchyard and beam transport system to verify that (i) all of said first set of elements of the switchyard and beam transport elements are enabled so that the switchyard and beam transport system configuration allows radiation beam transport to said selected treatment locations along said selected beam path and (ii) all of the elements of said plurality of elements not in said first set are not enabled so that the switchyard and the beam transport system configuration does not allow radiation beam transport along a non-selected beam path of said plurality of beam paths; and (e) in response to step (d), providing radiation beam transport to said selected treatment location. deriving a switchyard and beam transport system configuration signal from said sensing step; comparing the switchyard and beam transport system configuration signal to said selected beam path configuration signal; verifying that every element of the selected beam path configuration signal is contained in the switchyard and beam transport system configuration signal; and verifying that every element of the switchyard and beam transport system configuration signal is contained in said beam path configuration signal. denying beam transport in the absence of verification of step (d). sensing the temperature of electrical load bearing components within said switchyard and beam transport system to determine an over-temperature condition; and denying beam transport in the event of said over temperature condition. sensing potential human contact with said beam transport system; and denying beam transport in the event of said potential human contact. transmitting said selected beam path configuration signal by mutual logical complementary redundant communication paths; transmitting said switchyard and beam transport system configuration signal by mutual logical complementary redundant communication paths; comparing said respective mutual logical complementary redundant communication paths to determine a communication link failure; and denying beam transport in the event of said communication link failure. comparing said switchyard and beam transport system configuration signal to said selected beam path configuration signal to determine a beam path error, in each of said logical complimentary redundant communication paths; and denying beam transport in the event of said beam path error. comparing said mutual logical complimentary redundant communication paths to determine a communication link failure; and denying beam transport in the event of said communication link failure. (a) means for receiving a beam request signal from a selected treatment location; (b) means for deriving a beam path configuration signal from said beam request signal; (c) means for selecting a switchyard and beam transport system configuration in accordance with said selected beam path configuration signal by enabling a first set comprising less than all of a plurality of switchyard and beam transport elements to provide a path for transport of said radiation beam to said selected treatment location; (d) means for sensing the configuration of the switchyard and beam transport system to verify that (i) all of said first set of said switchyard and beam transport elements are enabled and (ii) all elements of said plurality of elements not in said first set are not enabled so that the switchyard and beam transport system configuration allow radiation beam transport to only said selected treatment location; and (e) means for providing radiation beam transport to said selected treatment location. a plurality of switches having a first state and a second state wherein said plurality of switches are capable of being arranged divided into a plurality of sets of one or more switches and wherein each set of switches directs said radiation beam along one of said plurality of paths when each of said one or more switches in said set are in said first state; a plurality of sensors which provide signals indicative of the status of said plurality of switches; and a switch controller which receives said signals from said plurality of sensors and also receives a signal indicative of a desired beam path wherein said switch controller allows transport of said radiation beam by said radiation beam along said desired beam path to said radiation treatment location when both (i) said plurality of sensors indicate that a set of said plurality of switches corresponding to said desired beam path are in said first state and (ii) said plurality of sensors indicate that the switches in said plurality of switches that are not in said set of switches corresponding to said desired beam path are in said second state. receiving a beam request signal from a selected treatment location; inducing a selected set of said plurality of switches to enter a first state in response to said beam request signal whereby said treatment beam will be directed along one of said plurality of paths to said selected beam treatment location; verifying that said selected set of said plurality of switches are in said first state; verifying that said switches not in said selected set do not direct said beam along other of said plurality of paths; and allowing beam transport along said one beam path in response to said verifying steps. comparing the mutual logical complimentary redundant communication path to determine a communication link failure; and denying beam transport int he event of said communication link failure. 2. The method of claim 1, wherein step (d) comprises: 3. The method of claim 2, further comprising: 4. The method of claim 3, further comprising: 5. The method of claim 3, further comprising: 6. The method of claim 2, further comprising: 7. The method of claim 6, further comprising: 8. The method of claim 1, comprising transmitting sensed information by redundant communication paths. 9. The method of claim 8, wherein said redundant communication paths are mutual logical compliments. 10. The method of claim 9, further comprising: 11. The method of claim 8, further comprising the step of sensing potential faults in communications links which transmit sensed information. 12. In a radiation beam therapy system comprising a radiation beam source, a plurality of radiation beam treatment locations, and a multiplexed switchyard and beam transport system for directing the radiation beam to a selected one of the radiation beam treatment locations, an apparatus for radiation beam security comprising: 13. The apparatus of claim 12, wherein said means for receiving a beam request signal from a selected treatment location comprises a central control computer that receives said beam request signals. 14. The apparatus of claim 12, wherein said means for selecting the switchyard and beam transport system configuration is comprised of a switch controller and wherein said plurality of switchyard and beam transport components are comprised of switches which control magnets that steer said radiation beam. 15. The apparatus of claim 14, further comprising sensing means for sensing the state of said plurality of switches and wherein said switch controller receives signals from said sensing means indicative of the state of said plurality of switches. 16. The apparatus of claim 12, wherein said means for interrupting said providing of transport of said radiation beam to said selected treatment room interrupts said providing of said radiation beam in response to said sensing means sensing that one of said selected elements has become disabled during said beam transport. 17. An apparatus for providing radiation beam security for a radiation beam treatment system having a radiation source, a plurality of radiation treatment locations and a plurality of paths connecting said radiation source to said plurality of radiation treatment locations, said apparatus comprising: 18. The apparatus of claim 17, wherein said switch controller halts transport of said beam when said plurality of sensors indicates that one or more of said switches in said set of switches corresponding to said desired beam path enters said second state. 19. The apparatus of claim 17, wherein said radiation beam is comprised of a proton radiation beam and said plurality of switches are comprised of switching magnets having a first position and a second position which steer said proton beam along one of said plurality of paths in said first position. 20. The apparatus of claim 19, further comprising a plurality of dipole switches corresponding to said plurality of magnets, each of said plurality of dipole switches having a first position and a second position which provide power to said switching magnets to induce said switching magnets to change between said first position and said second position. 21. The apparatus of claim 20, wherein said plurality of sensors sense the status of said plurality of dipole switches. 22. The apparatus of claim 21, wherein said plurality of dipole switches are comprised of SCR switches. 23. The apparatus of claim 17, further comprising a central computer that receives a beam request signal from a treatment location and provides a signal to said switch controller indicative of said desired beam path. 24. The apparatus of claim 23, wherein said central computer determines if said beam request signal is in error prior to providing a signal to said switch controller indicative of said desired beam path. 25. The apparatus of claim 23, wherein said central computer determines that said beam request signal is in error if said beam request signal directs said radiation beam to more than one beam treatment location simultaneously and, if said beam request signal is in error, said central computer does not send said signal to said switch controller indicative of said desired beam path. 26. A method of radiation beam security for a radiation beam therapy system having a radiation beam source, a plurality of radiation beam treatment locations and a plurality of beam treatment paths between said radiation beam source and said plurality of treatment locations wherein said radiation beam therapy system includes a plurality of switches for directing said treatment beam along said plurality of paths, said method comprising: 27. The method of claim 26, wherein said step of sensing said state of said switches not in said selected set comprises sensing whether said switches not in said selected set are in said first state and wherein said method comprises interrupting transport of said beam upon sensing that one or more of said switches that are not in said selected state are in said first state. 28. The method of claim 27, further comprising the step of transmitting sensed information about the plurality of switches to a controller via redundant communication links. 29. The method of claim 28, further comprising the step of sensing potential faults in the communication links which transmit the sensed information. 30. The method of claim 28, wherein the step of transmitting sensed information via redundant communication links comprises transmitting the sensed information via mutual logical complimentary redundant communication links. 31. The method of claim 30 wherein the step of sensing potential faults in the communication links comprises: |
claims | 1. A method of replacing a cesium trap, the method comprising:freezing a first cesium trap at least partially containing cesium therein, wherein the first cesium trap is located within a shielded cell;decoupling the first cesium trap from the shielded cell, wherein decoupling the first cesium trap comprises remotely decoupling a cell anchor extending from the shielded cell from a trap anchor extending from the first cesium trap, and wherein remotely decoupling the cell anchor from the trap anchor comprises removing a connection member that couples the cell anchor extending from the shielded cell to the trap anchor extending from the first cesium trap;removing the first cesium trap from the shielded cell;inserting a second cesium trap into the shielded cell; andattaching the second cesium trap to the shielded cell. 2. The method of claim 1, wherein decoupling the first cesium trap further comprises at least one of:remotely decoupling the first cesium trap from a sodium processing circuit; andremotely disconnecting electrical power and instrument control attachments extending between the first cesium trap and the shielded cell. 3. The method of claim 2, wherein remotely decoupling the first cesium trap from a sodium processing circuit comprises:crimping at least one sodium line extending from the first cesium trap; andcutting the at least one sodium line adjacent the crimped portion such that a first portion of the at least one sodium line extends from a top portion of the first cesium trap and a second portion of the at least one sodium line remains part of the sodium processing circuit. 4. The method of claim 2, wherein remotely disconnecting electrical power and instrument control attachments comprises unplugging at least one of an electrical power attachment and an instrument control attachment from a corresponding receiver disposed on a top portion of the first cesium trap. 5. The method of claim 1, wherein the connection member is at least one of a pin and a bolt. 6. The method of claim 1, wherein removing the first cesium trap comprises:releasably coupling the first cesium trap to a lifting tool; andlifting, via the lifting tool, the first cesium trap out of the shielded cell such that a base of the first cesium trap slidably disengages with at least one locating pin extending from a bottom of the shielded cell. 7. The method of claim 6, wherein lifting the first cesium trap separates a cooling line inlet extending from the first cesium trap from a fixed cooling line extending from the shielded cell. 8. The method of claim 6, wherein releasably coupling the first cesium trap to a lifting tool comprises rotating and lifting at least one hook of the lifting tool into a corresponding lifting eye disposed on the first cesium trap. 9. The method of claim 1, wherein inserting the second cesium trap comprises:releasably coupling the second cesium trap to a lifting tool, wherein the lifting tool includes at least one hook and the second cesium trap includes at least one corresponding lifting eye;placing, via the lifting tool, the second cesium trap into the shielded cell;aligning a base of the second cesium trap with at least one locating pin extending from a bottom of the shielded cell; andlowering the base of the second cesium trap onto the at least one locating pin. 10. The method of claim 9, wherein lowering the second cesium trap slidably couples a cooling line inlet extending from the second cesium trap to a fixed cooling line extending from the shielded cell. 11. The method of claim 1, wherein attaching the second cesium trap comprises at least one of:coupling a cell anchor extending from the shielded cell to a trap anchor extending from the second cesium trap forming at least one lateral support anchor extending between the first cesium trap and the shielded cell;welding at least one first sodium line extending from the second cesium trap to at least one second sodium line extending from a sodium processing circuit; andconnecting electrical power and instrument control attachments via plugging the attachments into a corresponding receiver disposed on a top portion of the second cesium trap. 12. The method of claim 1, wherein the first cesium trap contains a predetermined amount of cesium and the second cesium trap contains no amount of cesium. 13. The method of claim 1, wherein the shielded cell is an individualized shielded cell. 14. A method of replacing a cesium trap, the method comprising:freezing a first cesium trap at least partially containing cesium therein, wherein the first cesium trap is located within a shielded cell;decoupling the first cesium trap from the shielded cell;removing the first cesium trap from the shielded cell, wherein removing the first cesium trap comprises:releasably coupling the first cesium trap to a lifting tool; andlifting, via the lifting tool, the first cesium trap out of the shielded cell such that a base of the first cesium trap slidably disengages with at least one locating pin extending from a bottom of the shielded cell, wherein lifting the first cesium trap separates a cooling line inlet extending from the first cesium trap from a fixed cooling line extending from the shielded cell;inserting a second cesium trap into the shielded cell; andattaching the second cesium trap to the shielded cell. 15. The method of claim 14, wherein decoupling the first cesium trap comprises at least one of:remotely decoupling a cell anchor extending from the shielded cell from a trap anchor extending from the first cesium trap;remotely decoupling the first cesium trap from a sodium processing circuit; andremotely disconnecting electrical power and instrument control attachments extending between the first cesium trap and the shielded cell. 16. The method of claim 15, wherein remotely decoupling the cell anchor from the trap anchor comprises removing a connection member that couples the cell anchor extending from the shielded cell to the trap anchor extending from the first cesium trap. 17. The method of claim 16, wherein the connection member is at least one of a pin and a bolt. 18. The method of claim 15, wherein remotely decoupling the first cesium trap from a sodium processing circuit comprises:crimping at least one sodium line extending from the first cesium trap; andcutting the at least one sodium line adjacent the crimped portion such that a first portion of the at least one sodium line extends from a top portion of the first cesium trap and a second portion of the at least one sodium line remains part of the sodium processing circuit. 19. The method of claim 15, wherein remotely disconnecting electrical power and instrument control attachments comprises unplugging at least one of an electrical power attachment and an instrument control attachment from a corresponding receiver disposed on a top portion of the first cesium trap. 20. The method of claim 14, wherein releasably coupling the first cesium trap to a lifting tool comprises rotating and lifting at least one hook of the lifting tool into a corresponding lifting eye disposed on the first cesium trap. 21. The method of claim 14, wherein inserting the second cesium trap comprises:releasably coupling the second cesium trap to a lifting tool, wherein the lifting tool includes at least one hook and the second cesium trap includes at least one corresponding lifting eye;placing, via the lifting tool, the second cesium trap into the shielded cell;aligning a base of the second cesium trap with at least one locating pin extending from a bottom of the shielded cell; andlowering the base of the second cesium trap onto the at least one locating pin. 22. The method of claim 21, wherein lowering the second cesium trap slidably couples a cooling line inlet extending from the second cesium trap to a fixed cooling line extending from the shielded cell. 23. The method of claim 14, wherein attaching the second cesium trap comprises at least one of:coupling a cell anchor extending from the shielded cell to a trap anchor extending from the second cesium trap forming at least one lateral support anchor extending between the first cesium trap and the shielded cell;welding at least one first sodium line extending from the second cesium trap to at least one second sodium line extending from a sodium processing circuit; andconnecting electrical power and instrument control attachments via plugging the attachments into a corresponding receiver disposed on a top portion of the second cesium trap. 24. The method of claim 14, wherein the first cesium trap contains a predetermined amount of cesium and the second cesium trap contains no amount of cesium. 25. The method of claim 14, wherein the shielded cell is an individualized shielded cell. |
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description | The present disclosure is a continuation-in-part application of the international patent application No. PCT/CN2017/082560 filed on Apr. 28, 2017, which claims priority to Chinese patent application No. 201610339632.X filed on May 23, 2016. The contents of the above applications are hereby incorporated by reference. The present disclosure relates to the technical field of radioactive waste disposal, in particular to a method of oxidative digestion of a radioactively contaminated carbonaceous material (carbonaceous material) in liquid phase. A great amount of radioactively contaminated carbonaceous materials are produced during nuclear-related processes, for example, graphitic layers in nuclear reactors for moderating/reflecting neutrons, graphite crucibles and graphite molds used in smelting, casting and analyzing radioactive materials, resin used in the disposal of radioactive waste liquid and so forth. For the disposal of radioactively contaminated carbon materials, there is no thorough and mature solution so far. Existing incineration technology can barely be used for volume reduction of a carbonaceous material with a low level of radioactive contamination. However, once a carbonaceous material with a relatively high level of radioactive contamination is involved, e.g. graphite crucibles and graphite molds contaminated by uranium, the incineration of such radioactively contaminated carbonaceous materials is infeasible due to the fact that the current incinerator cannot ensure that the uranium aerosol is thoroughly cut off. Carbon, especially high-purity carbon used in the nuclear industry, is an excellent heat conductor, and this property renders carbon unable to store heat, and if carbon is to be oxidized through incineration, persistent high energy input is required to maintain the temperature of carbon above 1000° C., this process is of high energy consumption and the deterioration of the sealing performance of the device at a high temperature would be accompanied by the risk of radioactive aerosol leakage. Steam reforming utilizes high-temperature steam to oxidize carbon into a gas (C+H2O→CO+CO+H2), which may also be a disposal mode for radioactively contaminated carbonaceous materials. However, the significant oxidation of carbon by water occurs at a temperature above 1000° C., while it is highly likely for matching failure to occur to a connecting piece of the device under such condition due to thermal expansion, hereby resulting in a radioactive aerosol leakage. Accordingly, as for the volume-reduction and weight-reduction disposal of radioactively contaminated carbonaceous materials, it is necessary to moderate the reaction conditions as much as possible, to inhibit the generation of radioactive aerosol, and to ensure a safe, stable and reliable disposal process. An object of the present disclosure is to provide a technical solution for a method of oxidative digestion of a radioactively contaminated carbonaceous material in liquid phase, in the light of the deficiencies existing in the prior art, wherein the technical solution utilizes thermal treatment to make carbon enter the space between molybdenum atoms, which reduces the particle size of carbon and enhances the chemical reactivity of carbon. Consequently, carbon in the space between molybdenum atoms is oxidized in liquid phase into a gas by an oxidant, and simultaneously, the molybdenum-containing moiety is converted into a water-soluble substance, hereby achieving effects of mild reaction conditions, low energy consumption, high operational safety and conduciveness to recovery of elements attached to the carbonaceous material. The present solution is realized through the following technical measures: A method of oxidative digestion of a radioactively contaminated carbonaceous material in liquid phase, comprising the following steps: a. milling a mixture of a molybdenum-containing substance and a carbonaceous material by using a planetary ball mill with a fixed ball mill revolution speed, to provide first-stage powders; b. placing the first-stage powders obtained in Step a) into a heating furnace, thermally treating the first-stage powders under a flowing gas, and then naturally cooling the first-stage powders to provide second-stage powders; and c. adding the second-stage powders to water, and adding an oxidant, such that carbon contained therein is oxidized into a gas, and the molybdenum-containing moiety is converted into a water-soluble substance. Preferably in the present solution: the component ratio between the carbonaceous material and the molybdenum-containing substance in Step a) is, in parts by weight, 1 part of the carbonaceous material to 2-50 parts of the molybdenum-containing substance. Preferably in the present solution: the component ratio between the carbonaceous material and the molybdenum-containing substance in Step a) is, in parts by weight, 1 part of the carbonaceous material to 3.5-50 parts of the molybdenum-containing substance. Preferably in the present solution: the component ratio between the carbonaceous material and the molybdenum-containing substance in Step a) is, in parts by weight, 1 part of the carbonaceous material to 2 parts, 3 parts, 3.5 parts, 10 parts, 15 parts, 20 parts, 30 parts, 40 parts or 50 parts of the molybdenum-containing substance. Preferably in the present solution: the gas in Step b) is an inert gas or a gas mixture of hydrogen and an inert gas. Preferably in the present solution: the oxidant in Step c) is one from ozone, hydrogen peroxide, permanganates, dichromates, or a free combination thereof. Preferably in the present solution: the molybdenum-containing substance is one from molybdenum trioxide, molybdenum dioxide, hexaammonium molybdate, phosphomolybdic acid, silicomolybdic acid, and metallic molybdenum, or a free combination thereof. Preferably in the present solution: the carbonaceous material is activated carbon or carbon nanotubes or graphite or carbon fibers or carbon black or resin. Preferably in the present solution: the inert gas is argon, helium or nitrogen. Preferably in the present solution: the thermal treatment in Step b) is realized at a temperature rise rate of 0.5-20° C./min, till a temperature of 500-1100° C., with the temperature being maintained for 1-6 hours. Preferably in the present solution: the thermal treatment in Step b) is realized at a temperature rise rate of 0.5-20° C./min, till a temperature of 900-1100° C., with the temperature being maintained for 1-6 hours. Preferably in the present solution: the thermal treatment in Step b) is realized at a temperature rise rate of 0.5° C./min, 1° C./min, 2° C./min, 5° C./min, 10° C./min or 20° C./min. Preferably in the present solution: the heating in Step b) is performed till a temperature of 500° C., 600° C., 700° C., 750° C., 800° C., 900° C., 1000° C. or 1100° C. Preferably in the present solution: the duration of temperature maintenance of the high temperature condition during the thermal treatment in Step b) is 1 hour, 2 hours, 4 hours, 5 hours or 6 hours. The beneficial effects of the present solution can be determined from the preceding statement of the solution, the technical solution utilizes thermal treatment to make carbon enter the space between molybdenum atoms, which reduces the particle size of carbon and enhances the chemical reactivity of carbon. Consequently, carbon in the space between molybdenum atoms can be oxidized in liquid phase into a gas by an oxidant, and simultaneously, the molybdenum-containing moiety is converted into a water-soluble substance, hereby achieving effects of mild reaction conditions, low energy consumption, high operational safety and conduciveness to recovery of elements attached to the carbonaceous material. Accordingly, compared with the prior art, the present disclosure has a substantive feature and represents a progress, and the beneficial effects of its implementation are also apparent. Except for mutually exclusive features and/or steps, all the features or all the steps in the method or the process disclosed in the present specification may be combined with each other in any manner. Unless expressly stated otherwise, any feature disclosed in the specification (including any appended claims, the abstract or the drawings) can be replaced by any other alternative feature that is equivalent or has a similar object. That is to say, unless expressly stated otherwise, each feature is only one example of a series of equivalent or similar features. A method of oxidative digestion of a radioactively contaminated carbonaceous material in liquid phase, comprising the following steps: (1) milling a mixture of a molybdenum-containing substance and a carbonaceous material by using a planetary ball mill at a fixed ball mill revolution speed, to provide first-stage powders; (2) placing the first-stage powders obtained in Step (1) into a heating furnace, performing thermal treatment to the first-stage powders under a flowing gas, and then naturally cooling the same to provide second-stage powders; (3) adding the second-stage powders to water, and adding an oxidant, such that carbon contained therein is oxidized into a gas, and molybdenum-containing moiety is converted into a water-soluble substance. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:20, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:20, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Activated carbon and molybdenum trioxide were mixed in a weight ratio of 1:15, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 700° C. at a temperature rise rate of 5° C./min in a helium-hydrogen mixture with the helium having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 2 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % potassium permanganate water solution, and the digestion rate of the activated carbon was determined as 60% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:10, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and hexaammonium molybdate were mixed in a weight ratio of 1:40, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:30, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 600° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 48% after 1 hour. (1) Graphite and phosphomolybdic acid were mixed in a weight ratio of 1:30, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and molybdenum dioxide were mixed in a weight ratio of 1:20, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and silicomolybdic acid were mixed in a weight ratio of 1:50, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 20° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 1 hour, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:5, and then placed in a ball mill pot and milled for 1 hour by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 500° C. at a temperature rise rate of 1° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 22% after 1 hour. (1) D152 macroporous weak acid cation exchange resin and molybdenum trioxide were mixed in a weight ratio of 1:30, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 1000° C. at a temperature rise rate of 2° C./min in a helium-hydrogen mixture with the helium having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the D152 macroporous weak acid cation exchange resin was determined as 100% after 1 hour. (1) 717-type strong base anion exchange resin and molybdenum trioxide were mixed in a weight ratio of 1:30, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 1000° C. at a temperature rise rate of 2° C./min in a helium-hydrogen mixture with the helium having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the 717-type strong base anion exchange resin was determined as 100% after 1 hour. (1) Graphite and phosphomolybdic acid were mixed in a weight ratio of 1:40, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 0.5° C./min in a helium-hydrogen mixture with the helium having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Natural flake graphite and metallic molybdenum were mixed in a weight ratio of 1:20, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 1100° C. at a temperature rise rate of 1° C./min in a helium-hydrogen mixture with the helium having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:5, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in argon with a flowing rate of 100 ml/min, wherein the temperature was maintained for 6 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 200 ml of water acidized by nitric acid, and after blowing ozone therein at a velocity of 10 g/h for 5 hours, the digestion rate of the graphite was determined as 98%. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:4, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 5 ml/min and the hydrogen having a flowing rate of 95 ml/min, wherein the temperature was maintained for 6 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 0.5 hour. (1) Activated carbon and molybdenum trioxide were mixed in a weight ratio of 1:10, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 700° C. at a temperature rise rate of 5° C./min in a helium-hydrogen mixture with the helium having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 100 ml of 30 wt % potassium permanganate water solution, and the digestion rate of the activated carbon was determined as 40% after 1 hour. (1) D152 macroporous weak acid cation exchange resin and molybdenum trioxide were mixed in a weight ratio of 1:6, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 1100° C. at a temperature rise rate of 0.5° C./min in argon with a flowing rate of 100 ml/min, wherein the temperature was maintained for 6 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 200 ml of water alkalized by sodium hydroxide, and after blowing ozone therein at a velocity of 10 g/h for 5 hours, the digestion rate of the resin was determined as 98%. (1) Graphite and hexaammonium molybdate were mixed in a weight ratio of 1:50, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 1000° C. at a temperature rise rate of 5° C./min in argon with a flowing rate of 100 ml/min, wherein the temperature was maintained for 6 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 96% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:2, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 20° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 1 hour, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 62% after 1 hour. (1) Graphite and phosphomolybdic acid were mixed in a weight ratio of 1:30, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 5° C./min in a nitrogen-hydrogen mixture with the nitrogen having a flowing rate of 5 ml/min and the hydrogen having a flowing rate of 95 ml/min, wherein the temperature was maintained for 6 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 90% after 1 hour. (1) Graphite and molybdenum dioxide were mixed in a weight ratio of 1:10, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in nitrogen with a flowing rate of 100 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 200 ml of water acidized by nitric acid, and after blowing ozone therein at a velocity of 10 g/h for 5 hours, the digestion rate of the graphite was determined as 85%. (1) Graphite and silicomolybdic acid were mixed in a weight ratio of 1:50, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 700° C. at a temperature rise rate of 20° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 39% after 1 hour. (1) 717-type strong base anion exchange resin and molybdenum trioxide were mixed in a weight ratio of 1:10, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 2° C./min in a helium-hydrogen mixture with the helium having a flowing rate of 5 ml/min and the hydrogen having a flowing rate of 95 ml/min, wherein the temperature was maintained for 6 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the 717-type strong base anion exchange resin was determined as 100% after 1 hour. (1) Natural flake graphite and metallic molybdenum were mixed in a weight ratio of 1:50, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 1° C./min in helium with a flowing rate of 100 ml/min, wherein the temperature was maintained for 6 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 78% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:3.5, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 20° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 1 hour, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and silicomolybdic acid were mixed in a weight ratio of 1:50, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 900° C. at a temperature rise rate of 20° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 100% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:1.5, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 600° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 11% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:10, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 400° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 5% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:10, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 600° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 30 minutes, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 18% after 1 hour. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:10, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 600° C. at a temperature rise rate of 25° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 200 ml of water alkalized by sodium hydroxide, and after blowing ozone therein at a velocity of 10 g/h for 5 hours, the digestion rate of the graphite was determined as 16%. (1) Graphite and palladium oxide were mixed in a weight ratio of 1:1, and then placed in a ball mill pot and milled for 5 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 600° C. at a temperature rise rate of 2° C./min in an argon-hydrogen mixture with the argon having a flowing rate of 30 ml/min and the hydrogen having a flowing rate of 50 ml/min, wherein the temperature was maintained for 5 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the loss rate of the graphite was determined after 1 hour as 53%. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:1, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 500° C. at a temperature rise rate of 2° C./min in argon with a flowing rate of 100 ml/min, wherein the temperature was maintained for 6 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 200 ml of water acidized by nitric acid, and after blowing ozone therein at a velocity of 10 g/h for 5 hours, the digestion rate of the graphite was determined as 10%. (1) Graphite and molybdenum trioxide were mixed in a weight ratio of 1:10, and then placed in a ball mill pot and milled for 3 hours by using a planetary ball mill at a revolution speed of 300 r/min; (2) 2 g of the obtained powders was placed in a tube furnace and heated to 400° C. at a temperature rise rate of 2° C./min in argon with a flowing rate of 100 ml/min, wherein the temperature was maintained for 4 hours, then the gas was turned off, and powders were obtained after natural cooling; and (3) 1 g of the obtained powders was added to 20 ml of 30 wt % hydrogen peroxide, and the digestion rate of the graphite was determined as 8% after 1 hour. Compared with the above comparative examples conducted under non-preferred conditions, it can be determined that the digestion rate of carbon materials is significantly improved and the treatment efficiency is significantly increased, when the amount of a molybdenum oxide group-containing substances, the ball mill revolution speed of the planetary ball mill, the milling duration of the planetary ball mill, the temperature maintained under the high temperature condition during the thermal treatment and the duration of temperature maintenance under the high temperature condition during the thermal treatment fall within the preferred condition ranges according to the present disclosure, hereby achieving the technical effects of mild reaction conditions, low energy consumption, high operational safety and conduciveness to recovery of elements attached to the carbonaceous material. The present disclosure is not limited to the foregoing detailed description of the embodiments. The present disclosure extends to any novel feature disclosed in this specification or any novel combination thereof, as well as any step in a novel method or process disclosed or any novel combination thereof. The present disclosure discloses a method of oxidative digestion of a radioactively contaminated carbonaceous material in liquid phase, wherein the method achieves mild reaction conditions, low energy consumption, and high operational safety, and significantly improves the efficiency of the digestive disposal of a carbonaceous material, which is conducive to recovery of elements attached to the carbonaceous material. |
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053512774 | abstract | A method of constructing the top slab of a nuclear reactor container in which a flange for mounting the top head of the container is prepared separately from the sleeve of the container. When the outside diameter of the flange is greater than the inside diameter of a doughnut-shaped steel; reinforcement structure assembled on the container, the steel reinforcement structure is situated in place and then the flange is welded to the sleeve, thus shortening the construction period. Disclosed also is a nuclear reactor container constructed by this method. |
045368821 | summary | BACKGROUND OF THE INVENTION 1. Field of the Invention This invention is directed to X-ray lithography masks, in general, and to a mask having the X-ray absorber material embedded in the mask, per se. 2. Prior Art There are many known masks which have been produced for use with X-ray lithography techniques. The known masks generally comprise a thin supporting membrane which is transparent to X-rays, a patterned absorber layer of dense material which is substantially opaque to soft X-rays supported on the membrane, and mechanical support means such as a peripheral ring bonded to the membrane. The known masks noted above are typically fabricated in a sequence wherein a membrane is bonded to a support ring, the membrane is coated with an absorber layer (for example heavy metal), and the absorber is patterned using suitable lithography and/or etching steps. However, the known masks and methods of making same are not totally satisfactory. That is, in the known masks the patterned absorber typically protrudes above the membrane surface leading to problems with mechanical damage and/or wear as well as significant problems with adhesion of contamination and particulate matter. More importantly, however, the known masks and method require that the absorber material be deposited in such a manner that, when patterned, non uniform strain in the thin membrane occurs. PRIOR ART 1. E. Bassous, R. Feder, E. Spiller, and J. Topalian, Solid State Technology, September 1976, p. 55. PA0 2. Suzuki et al., Japan J. Appl. Phys., 17, 1978, p. 1,447. PA0 3. P. L. Spears, H. I. Smith, and R. Stern, U.S. Pat. No. 3,742,230, June 28, 1973. PA0 4. Coquin et al., U.S. Pat. No. 3,892,973. SUMMARY OF THE INVENTION This invention is directed to a mask and method of making same. The mask is, typically, useful in the X-ray lithography, or charged particle lithography fields. The mask uses a temporary substrate as a template and support for the mask membrane, an X-ray absorber layer and a supporting membrane layer. A separate support structure can be provided for the mask. In addition, an adhesion promoting layer may be optionally utilized between the absorber layer and the membrane layer, and a capping layer provided to completely seal the absorber pattern, either an etch stop layer or a parting agent layer can be disposed between the substrate and the absorber layer or capping layer depending upon the ultimate structural arrangement of the mask as may be defined by the optional support structure. |
summary | ||
053234332 | description | PREFERRED EMBODIMENT OF THE INVENTION A first embodiment will be explained in the following with reference to FIGS. 1 to 22. In the following description, the axial direction is the direction parallel to the axis of the short rod-shaped pellets and the radial direction is the direction at right angles to the axial direction. FIG. 1 illustrates the overall arrangement of the first embodiment, in which the reference numeral 1 refers to a pellet supply section which supplies a plurality of pellets P (in the subsequent description, P is omitted). The pellet supply section 1 is connected to a wet grinding machine 2, and the pellets dimensioned by the wet grinding machine 2 are transported along the transport route 3 with the pellets axis in the axial direction by an endless grinder belt 4 which traverses a pellet collection section 10. An endless drying belt 300 of a drying section 30 is connected to the endless grinder belt 4 via a transfer section 20. The drying section 30 not only dries the pellets but also changes the direction of movement of the pellets so that pellets are now transported in the radial direction. The dried and re-directed pellets are forwarded to a pellet inspection section 40. The pellets inspected by the pellet inspection section 40 are forwarded to the visual confirmation section 70 by a pellet transport device 50 via pellet posting section 60 for visual confirmation of the surface condition of the pellets. Then, the pellets are arranged on pellet trays T in the tray posting section 5, and the trays T fully loaded with the pellets are stored in the tray storage racks 6 by the tray loading device 80. As shown in FIG. 2, the pellet collection section 10 is provided with a first pellet stopper 100 which can freely approach or move away from the pellet entering-end of the endless drying belt 300. The pellet collection section 10 is also provided with a second pellet stopper 101 which can freely approach or move away from the pellet discharging-end of the endless grinder belt 4. The pellets on the grinder belt 4 are transported as a group to the pellet collection device 103 by the pellet pick-up device 102. A pellet collection device 103 is disposed below the transport route 3 (refer to FIGS. 5 and 6). The pellet pick-up device 102 comprises, as shown in FIGS. 3 and 4: an opposing pair of plate-shaped pick-up fingers 102a; a pair of closer/opener devices 102c provided with a spring and a pressure cylinder 102b to operate the pick-up fingers 102a; a pair of elevator cylinders 102d, 102e which freely elevatably support the closer/opener devices 102c; and a horizontal pressure cylinder 102f which support the elevator cylinders 102e horizontally. The pellet collection device 103 comprises, as shown in FIGS. 5 and 6, a plurality of pulleys 103a driving three endless transport belt 103b to move one tray T. The three trays T are connected to and driven by one tray driving motor 103d via a transmission section 103c. The transfer section 20 comprises, as shown in FIGS. 7 and 8, a guide member 200 having a V-groove disposed between the grinder belt 4 and the drying belt 300; and a linear feeder 201 which transports the pellets, guided along the V-groove, in the axial direction. The travelling speed of the drying belt 300 is set higher than that of the grinder belt 4. Therefore, the pellets which are in contact with each other on the grinder belt 4 become separated when transferred on the drying belt 300 by the action of a spacer device 7 shown in FIG. 2, and shown in more detail in FIGS. 7 and 8. On both sides of the grinder belt 4 and the drying belt 300, there are disposed V-groove guides, as in the above mentioned V-grooves for the guide member 200, to prevent the pellets from shifting sideways. Next, the configuration of the pellet drying section will be explained. As shown in FIG. 9, the drying belt 300 in the drying section 30 is driven by an ultrasonic motor 301. On the extension of the drying belt 300, there is disposed a laser-operated pellet displacement monitor 302 which determines the position of a pellet being transported on the drying belt 300, by the reflection of a laser beam reflected from the planar end surface of the pellet. Above the drying belt, there is disposed a rotation disc 303 which is freely rotatable about a disc axis parallel to the direction of movement of the drying belt 300. The rotation disc 303 is connected to a pulse driven motor 304, via an attachment plate 305, which drives the rotation disc 303 in steps. At the intersection point (pellet direction change position) of the drying belt 300 and the rotation disc 303, there is disposed a transmission type pellet position sensor 307 consisting essentially of a laser beam transmitter 307a and a laser beam receiver 307b disposed on each side of the drying belt 300 (refer to FIG. 10). The planar end surface of the pellet is detected by the pellet position sensor 307 when a laser beam transmits through a space between the channels disposed in the ratchet teeth 303a of the rotation disc 303. The side surfaces of the rotation disc 303 are provided with a pair of end covers 308 which surround a middle cover 309 which encloses the outer circumferential surface of the rotation disc 303. All the covers, 308 and 309 are provided with gas circulation device 310. The outer circumferential surface of the rotation disc 303 is provided with ratchet teeth 303a, separated at an equal regular spacing, with the sharp end of the teeth facing the forward rotational direction. Each ratchet teeth 303a is branched into three teeth portions with two grooves interposed in the width direction of the rotation disc 303, as shown in FIG. 11. Viewed in the axial direction of the pellets as shown in FIG. 12, the ratchet teeth 303a are disposed at regular spacing along the circumferential periphery of the rotation disc 303, and the ratchet teeth 303a is formed between two pellet pockets 303b. The pellet pocket 303b consists of a pellet retention space 303c and a radially extending vacant space 303d. The laser beam from the pellet displacement monitor 302 is radiated onto the planar end surface of the pellet through a rectangular slit 308a (refer to FIGS. 10 and 13), to match the shape of the vacant space 303d, formed on the cover 308 in a location to correspond with the pellet direction change position. The pellet displacement monitor 302 operates by radiating a laser beam to and measuring the reflected laser beam back from the planar end surface of a pellet approaching the monitor 302 with the pellet axis directed to the monitor 302. The measured distance data are converted into analogue signals, and are inputted into a control device (not shown) which controls the ultrasonic motor 301 for driving the drying belt 300 and the pulse driven motor 304 for driving the rotation disc 303. The analogue signal inputted into the control device are conditioned, and forwarded to the ultrasonic motor 301 which operates to transport the pellets at an optimum speed. When the control device confirms that the pellet has reached the direction change position, according to the output signal from the monitor 302 or sensor 307, the control device nullifies the action of the pellet displacement monitor 302 until the completion of the direction change so as to prevent erroneous action of the ultrasonic motor 301 caused by such false signals as the laser beam reflecting from the rotation disc 303 instead of the planar end surface of the pellets. At the same time, the signal from the pellet position sensor 307 is conditioned and applied as a square wave signal to the pulse driven motor 304, thereby moving the rotation disc 303 through a given angle. When a large surface defect such as a missing piece is present on a pellet, the signal from the monitor 302 or the sensor 307 may be deflected away from the correct path, and may cause problems in activating the pellet direction change. To counter such a situation, the control device receives an ON/OFF signal from the monitor 302 or sensor 307, so that even if one of them becomes unstable, the direction change operation can be performed without hindrance. The gas circulation device 310 is shown in FIGS. 13 and 14, and comprises four sets of end-chambers 310a of an arc shape which are formed inside the covers 308 and on opposing sides of the middle cover 309. The covers 308 are provided with air-in connectors 310b and the air-out connectors 310c. The chambers are constructed such that three in-ports 310d communicating the three neighboring pellet pockets 303b are provided in one end-chamber 310a, and three out-ports 310e communicating the three neighboring pellet pockets 303b are provided in the other end-chamber 310a. The in-ports 310d and the out-ports 310e are disposed opposite to each other. Inside the middle cover 309, there is formed an arc shaped mid-chamber 310f which receives the air discharged from the air connector 310g. The mid-chamber 310f and the three neighboring pellet pocket 303b are communicated with an outflow port 310h. The air discharged from the outflow port 310h is expelled from the underside of the pellet in the pellet pocket 303b. The four sets of end-chambers 310a described above are arranged so that the air intake and air exhaust operations are performed alternatingly between the left and right end covers 308. It is preferable that the air used in the dryer operation be dried using a membrane type dryer. On the walls of the four sets of air chambers 310a having the out-port 310e, there are provided gas passage grooves 310i which extend at right angles to the out-port 310e. The width of the grooves 310i is larger than the diameter of the out-port 310e, and its length is longer than the outer diameter of the pellets. Further, the groove is disposed eccentrically with respect to the out-port 310e so that its bottom dimension is larger than the top dimension. Next, the pellet inspection section 40, illustrated chiefly in FIGS. 15 and 16, will be explained. The pellet inspection section 40 is arranged such that a pellet discharged from the rotation disc 303 of the pellet drying section 30 is rolled down on a first inclined channel 400, and is charged into and housed in a V-groove 401 of a transport disc 402. The transport disc 402 has a plurality of V-grooves 401 on its outer periphery, and rotates in discrete steps. The end surfaces of the pellets are recorded with a pair of end-surface recording devices 410 which are disposed so as not to interfere visually with each other. The end-surface recording device 410 determines acceptance or rejection of each pellet on the basis of the recorded image. FIG. 15 shows the location of a first pellet rejection device 403 which is provided near the transport disc 402 for removing a pellet which has been determined to be a reject by the pair of end-surface recording devices 410 from the transport disc 402. The accepted pellet from the transport disc 402 rolls down a second inclined channel 404, as shown in FIG. 15, and is supplied periodically to a pellet rotation device 406 via a pellet supply device 405 which rotates stepwise at a specific time interval. The cylindrical side surface of the pellet is examined by the side-surface recording device 411, and the acceptance or rejection of a pellet is determined by the side-surface recording device 411 on the basis of the recorded image. In the vicinity of the pellet rotation device 406, there is a third inclined channel 407, for rolling down the pellet from the rotation device 406. A second pellet rejection device 408 (refer to FIG. 17) is used for removing the pellet rejected by the side-surface recording device 411 from the third inclined surface 407. The second pellet rejection device 408 operates by activating a discharge member 408a which is disposed, freely movably in the vertical direction, on the third inclined channel 407. At the discharge end of the third inclined channel 407 is disposed a guide device 409 for guiding the pellet to downstream work stations. The first pellet rejection device 403, shown in FIG. 15, comprises a rotation device 403a disposed above the transport disc 402 and a rejector member 403b disposed on the axis of the rotation device 403a. When the rejector member 403b rotates, the pellet disposed on a V-groove 401 of the transport disc 402 is removed off the V-groove 401 to one side. The pellet supply device 405 comprises, as shown in FIG. 17, a pellet guiding vane 405a of a cross-shape which is freely rotatable, and a freely pivoting pressing member 405b which presses down on the pellet from above. Opposing the second inclined channel 404, there is a stopper device 405c which clamps the pellet between itself and the second inclined channel 404 when an emergency situation develops. The stopper device 405c is provided with a stopper member 405d, operated by an air cylinder 405e, and is freely movable vertically. The pellet rotation device 406 comprises a small diameter cylindrical roller 406a, and a large diameter roller 406c, provided with a plurality of hook shaped discharge pocket 406b (three are shown in FIG. 15, and four in FIG. 17), in which both rollers 406a, 406c are rotatable in the counter clockwise direction. In the vicinity and between the rollers 406a, 406c, there is a vacuum suction device 406d which provides a suction force to hold the pellet in place. The number of the hook shaped discharge pocket 406b of the large diameter roller 406c is chosen in accordance with the inspection speed of the pellets. The guide device 409, as shown in FIG. 18, is provided with a fixed guide pin 409a at the discharge end of the third inclined channel 407 to prevent the pellets from jumping up. A freely idlable guide pin 409b is provided below and to one side of the fixed guide pin 409a to assist in placing the pellet stably on a pellet collection belt 500 of the pellet transport device 50. As shown in FIG. 16, one end-surface recording device 410 is disposed on each side of the transport disc (402), and comprises: a support plate 410a erected on both sides of the transport disc 402; illumination device 410b attached to the support plate 410a for illuminating a planar end surface of a pellet disposed on a V-groove 401; and a CCD camera 410d which records the surface condition of the end surface of the pellet, and determines acceptance or rejection of the pellet in accordance with the recorded image. The side-surface recording device 411 is disposed above the rollers 406a, 406c, as shown in FIGS. 15, and comprises: an illumination device 411b attached to a support stand 411a; a half-mirror 411c; and a line sensor camera 411d. The illumination can be made either through the half mirror 411c or directly from above. The line sensor camera 411d records the entire side surface of the illuminated and rotating pellet, and produces a linearly translated image of the side surface of the pellet, and determines surface defects from the linearly translated image of the recorded image of the side surface of the pellet. The pellet transport device 50 comprises: a pellet collection (endless) belt 500 having a plurality of V-grooves 501 for placing a plurality of pellets thereon; a grip transporting device 502 which grips the plurality of pellets placed on the V-grooves 501, and transports the pellets to the pellet posting section 60; and a transport device 503 which transfers the pellets on the pellet posting section 60 to the visual confirmation section 70, and thence to the tray posting section 5. The grip transporting device 502 comprises: as shown in FIGS. 15, 16 in general and in 19 in detail, a pair of opposing holding plates 502a; a plurality (twenty five for each holding plate 502a in this embodiment) of opposing holding fingers 502b made of a spring type material, attached to the holding plates 502a at an equal spacing in the axial direction; a pair of steel balls 502c attached to the opposing surfaces of the holding fingers 502b; a pair of closer/opener device attached to ends of the holding plates 502a for closing and opening thereof; an elevator device 502e for freely raising or lowering the closer/opener device 502d; and a level support device 502f for freely translating the elevator device 502e in the horizontal direction. The steel balls 502c engage with the depressions section (dish section) formed on the planar end surfaces of the pellets, thus enabling to grasp the entire twenty five lines of pellets simultaneously, even if there are dimensional differences in the various lines of pellets. The transport device 503 comprises: as shown in FIG. 21, twenty five sets of gripping units 503d having a closer/opener device 503c comprising a cylinder 503b for closing and opening a pair of opposed gripping claws 503a, and a counter spring 503f; and an attachment section 503e for attaching the gripping units 503d. The attachment section 503e is disposed so as to be freely movable vertically, as well as freely translatable in an L-shape pattern among the pellet posting section 60, visual confirmation section 70 and the tray posting section 5. The arrangement of the above noted sections are illustrated in FIG. 20. As shown in FIG. 20, the entire pellets disposed on one tray T can thus be transported by the transport section 503. The pellet posting section 60 comprises: as shown in FIG. 20, twenty six guide axes 600 detachably attached to a guide frame 601; and a pellet aligning plate 602 which pushes the twenty five laterally arranged pellets on the pellet posting section 60 towards the visual inspection section 70, simultaneously, until the pellet posting section 60 becomes fully loaded with twenty fine lines of twenty five laterally arranged pellets. The aligning plate 602 is disposed near the grip transporting device 502, and is able to travel from the entry end to the visual inspection section end. The visual inspection section 70 is constructed by detachably attaching twenty six revolving axes 700 which are freely rotatable about the axis 700, to a frame 701. The revolving axes 700 are connected to a driving device (not shown) via gears and belt and other associated power transmission members. The tray loading device 80 is shown in FIG. 22. The tray loading device 80 comprises: an elevator plate 801 disposed in the elevator section 800 of the tray loading device 80 so as to be freely raised or lowered; a first table 803 disposed on tray rails 802 of the elevator plate 801; and a driving motor 804 which slides the first table 803 horizontally; a tray elevator 805 disposed on the first table 803 so as to be freely raised or lowered; and a tray cylinder 806 which raises or lowers the tray elevator 805. A second table 808 can be slid horizontally by a tray motor 809 on the tray rails 807 which are disposed roughly parallel to the first table 803. A tray support table 810 is fixed on the second table 808, and at one end of the tray support table 810, there is disposed a tray clamp 811 which can detachably hold the tray T. On a support member 812 of the elevator plate 801, there is disposed a pair of area sensors 813 which determine the tray storage space 6a and the availability of space for the tray T of the tray storage rack 6. There is also a magnetic sensor 814 disposed on the support member 812 for sensing the leading end of the tray T which passes by the side of the tray T. The tray T is transported to the initial location in the tray storage racks 6 by a slide plate (not shown) which moves horizontally between the tray loading device 80 and the tray posting section 5. The above completes the description of the surface inspection facility of the present embodiment. Next, the steps of handling the pellets will be explained, such as drying a large number of pellets, arranging the pellets on the trays T and storing the trays in the tray storage racks 6 using the surface inspection facility of the present embodiment. The pellets supplied from the pellet supply section are ground to dimension by the wet grinding machine 2. The pellets are then transported, via transport route 3, with the pellet axis aligned in the axial direction by the (endless) grinder belt 4, which is disposed so as to cross the pellet collection section 10. The pellets are transferred to the drying (endless) belt 300 of the drying section 30 from the grinder endless belt 4 via the transfer section 20. In this transfer process, even though the wet pellets may be disposed in contact with each other on the grinder belt 4, they become properly separated at a specific separation distance on the drying belt 300, because the speed of the drying belt 300 is set faster than that of the grinder belt 4, and because the guide member 200 of the transfer section 20 is operated by the linear feeder 201 (refer to FIGS. 7 and 8). The reflective type pellet displacement monitor 302, shown in FIG. 9, detects the leading end face of the leading pellet of the plurality of pellets being transported by the drying belt 300, and the position data is inputted as an analogue signal into a control device (not shown) for controlling the action of the ultrasonic motor 301 and the pulse driven motor 304, respectively, for operating the pellet transport belt drive and the rotation disc drive. The control device controls the voltage applied to the ultrasonic motor 301 so as to maintain the speed of the drying belt 300 at its optimum. Therefore, when a pellet on the drying belt 300 approaches the intersection (pellet direction change position) between the drying belt 300 and the rotation disc 303, the action of the ultrasonic motor 301 is controlled so as to slow down the drying belt 300 and position the pellet correctly at the pellet direction change position. In the above control, the upper limit of voltage applied to the ultrasonic motor 301 is limited by the voltage control diode so that the speed of the drying belt 300 is always maintained at a specific speed and never becomes unnecessarily high. When the pellet reaches the direction change position, the control device temporarily nullifies the operation of the reflective type pellet displacement monitor 302 until the pellet is properly positioned. Therefore, even if reflections occur, for example from the rotation disc 303, there is no danger of erroneous operation of the ultrasonic motor 301. The control device also controls the voltage of square wave signal applied to the pulse driven motor 304, based on an input signal from the transmission type pellet position sensor 307 to control the rotation disc 303 so as to produce slow start/stop actions through one angular displacement operation (1pitch). Thus, a pellet stopped at the direction change position is correctly picked up by the ratchet teeth 303a and is housed in a pellet pocket 303b. The control device is able to performs pellet direction change operation according to one ON/OFF signal from either the monitor 302 or the sensor 307 when a pellet having a large surface defect should be transported on the drying belt 300. If one of the devices 302, 307 detects the presence of a defective pellet, even if the other device did not detect the presence, the direction change operation can be performed normally. As described above, a plurality of pellets are successively brought to the direction change position, housed in the pellet pockets 303b of the rotation disc 303, and are transported upward. As shown in FIGS. 13 and 14, when a pellet is placed in the pellet pocket 303b, air is supplied to the end chambers 310a disposed in one end cover 308 via the air-in connector 310b, and is directed at one end surface of the pellet via the in-port 310d. In the other end chamber 310a disposed in the other end cover 308, air is exhausted via the air-out connector 310c via out-port 310e, and the other end surface of the pellet in the pellet pocket 303b makes an intimate contact with the wall surface of the end cover 308 having the out-port 310e. In this embodiment, there is a gas passage grooves 310i are provided for each out-port 310e. The reason for this is that if air is exhausted only through the out-port 310e, the pellet is sucked tightly to the out-port 310e, and the end surface sticks to the wall surface of the end cover 308, thereby subjecting the depressions (dish section) to a vacuum, and stopping air flow. In the initial stage of drying, moisture is present in the depressions, and they are not eliminated effectively with a vacuum evaporation effect only. Further, the pellet stuck to the wall surface of the end cover 308 represents a drag load on the rotation disc 303 when it tries to rotate upward, thus preventing a smooth operation of the rotation disc 303. The width of the gas passage grooves 310i is larger than the diameter of the out-port 310e, and its length is longer than the diameter of the pellet. Further, the groove 310i is disposed eccentrically with respect to the out-port 310e, the air inside the pellet pocket 303b passes preferentially through the bottom region of the groove 310i which is longer than its top region. The result is that the air flow in the pellet pockets 303b is preferentially exhausted through the longer bottom region of the groove 310i and flows out from the out-port 310e. The arrangement described above enables to efficiently eliminate the moisture which is apt to collect at the bottom region of the depression of the pellet, thereby assuring that the moisture is positively eliminated from the entire pellets. This arrangement also serves to lower the drag load on the rotation disc 303. The four sets of end chambers 310a formed inside the opposing end covers 308 are disposed so as to alternately perform air-intake and air-exhaust functions. In other words, as illustrated in FIG. 14, the direction of air flow, directed at a group of three pellets being dried within an end chamber 310a, is alternatingly changed from one chamber to another. Every time the rotation disc 303 moves, the pellet is subjected to an air flow directed in the opposite direction so that it moves from a left position in one chamber, in which the pellets stick to the left wall of the end cover 308, to a right position in the next chamber, in which the pellets stick to the right wall of the end cover 308. Therefore, both end surfaces are exposed equally to the air flow which sweeps over the end surfaces, thus promoting efficient drying of both end surfaces of the pellets. By exhausting the air flow coming from the in-port 310d through the out-port 310e, scattering of particulate matters, such as pellet powder, can be prevented. Also, air is supplied to the air connector 310g provided in the mid-chamber 310f of the middle cover 309 (refer to FIG. 13). The air sweeps over the side surfaces of the pellets and is discharged through the bottom region of the pellets housed in the pellet pockets 303b via the outflow ports 310h. This action of the flowing air lifts and floats the pellet in the pellet pocket 303b, thereby promoting drying of the bottom region of the side surface of the pellet as well as to facilitate the sideways movement of the pellets within the pellet pocket 303b. Next, the pellet is discharged from the pellet pocket 303b as the rotation disc turns stepwise (refer to FIG. 15) periodically. The pellet rolls down the first inclined channel 400, and is housed in a V-groove of the transport disc 402, from which it is forwarded one at a time to the next operation. When the pellet is stopped for the inspection of the end surfaces, the illumination devices 410b illuminate the end surfaces of the pellet and the CCD cameras 410d record the conditions of the end surfaces. The presence of absence of end surface defects is determined by the end-surface recording device 410, on the basis of the recorded images by the CCD cameras. If a pellet is determined to have an end surface defect by the end-surface recording device 410, then the reject pellet is removed to one side from the transport disc 402 by the action of the rotating device 403b operated by the rotation device 403a of the first pellet rejection device 403. The accepted pellet discharged from the transport disc 402 rolls down the second inclined channel 404, and is supplied periodically to the pellet rotation device 406 by the action of the guiding vane 405a and the pressing member 405b of the pellet supply device 405. The pellet is disposed between the small diameter roller 406a and the large diameter roller 406c of the pellet rotation device 406, and is rotated by the rollers 406a 406c (refer to FIG. 17). The rollers 406a, 406c are rotated in the same direction at the same peripheral speed. The pellet is held in the space between the rollers 406a, 406c by means of the vacuum suction provided by the vacuum suction device 406d. This is to prevent the pellet from jumping up by the force of impact when it is dropped into the space, thereby permitting the pellet to rotate smoothly and stably between the roller 406a, 406c. The above arrangement enables to record the condition of the side surface of the pellet rotating at a stable high speed, and to prevent scattering of particle matters such as pellet powder by positively eliminating them with the vacuum suction device 406d. After the side surface has been examined with the side-surface recording device 411, the pellet is housed in the pellet discharge pocket 406b of the large diameter roller 406c, and is discharged into the third inclined channel 407. If a pellet is determined to be defective by the side-surface recording device 411, the defective pellet is removed by operating the discharge member 408a of the second pellet rejection device 408 downward (refer to FIG. 17). The operation of the discharge member 408a is synchronized with the speed of rotation of the large diameter roller 406c to discharge the reject pellet. The accepted pellet rolls down to the end of the third inclined channel 407, and is disposed on a V-groove of the collection belt 500 reliably guided by the fixed guide pin 409a and the idlable guide pin 409b of the guiding device 409. The cooperative action of the fixed guide pin 409a and the idlable guide pin 409b positively prevents the occurrence of improper sequencing of the succeeding pellet, caused by such accidents as a succeeding pellet jumping over the preceding pellet, or pellet being bounced by hitting a protrusion on the V-grooves while the accepted pellet is being placed on the V-groove. As more and more accepted pellets are placed on the V-grooves 501 of the collection belt 500, the pellets gradually move toward the downstream side of the grip transporting device 502 to form a line of pellets. When a certain number of pellets (twenty five in this embodiment) is accumulated, the collection belt 500 is stopped and one line of pellets are placed directly below the holding finger 502b of the grip transporting device 502. By operating the holding plate 502a with the closer/opener device 502d of the grip transporting device 502, a line of pellets are held between the steels balls 502c of one pair of the holding fingers 502b (refer to FIG. 19). As other pellet lines are formed, the same process is repeated to place the pellet line below the steels balls 502c. The line of pellets is lifted by the elevator device 502e, translated by the level support device 502f and are placed between the twenty six guide axes 600 of the pellet posting section 60. The laterally arranged twenty five pellets are pushed out by the aligning plate 602 toward the visual confirmation section 70. By repeating this process for the next twenty four lines of pellets, lines of pellets is placed successively on the guide axes 600, and a tray T becomes fully loaded with twenty five lines of pellets in the pellet posting section 60. By operating the twenty five units of gripping unit 503d of the transport device 503, shown in FIG. 21, the entire lot of pellets to be arranged on the tray T are gripped at once, and by operating the attachment member 503e to elevate and translate horizontally, the entire lot of pellets are placed between the twenty six revolving axes 700 of the visual confirmation section 70. In the visual confirmation section 70, the revolving axes 700 makes the pellets to revolve, and an inspector can examine the pellet surfaces visually to confirm that there are no abnormalities. Upon completion of the visual inspection, the entire lot of pellets on one tray T are placed at once on a tray T in the tray posting section 5. Next, the tray T is transported horizontally by the slide plate (not shown) from the tray posting facility 5 to the initial position of the tray loading device shown in FIG. 22. When the tray T is stopped above the tray elevator 805 of the tray loading device, the tray elevator 805 is raised by the tray cylinder 806, and is moved away from the slide plate, permitting the slide plate to be returned to its original position. The tray T is clamped by the tray clamp 811 attached to the end of the tray support table 810 (refer to FIG. 22). The tray T is moved vertically in the tray elevator section 800, and is stopped in front of a potential tray storage space 6a of the pellet storage racks 6. In this condition, the area sensor 813 checks the tray storage space 6a to confirm the location and its availability. Next, the driving motor 804 operates to advance the first table 803 and the leading end of the tray T approaches the magnetic sensor 814, disposed close to the tray storage rack 6, which confirms the position of the leading end of the tray T. Next, unless the magnetic sensor 814 detects an abnormality, the driving motor 804 is activated to advance the tray T, and insert the leading end of the tray T into the storage space 6a. When the leg section Ta of the tray T is inside the tray storage space 6a, the movement of the first table 803 is stopped, the tray elevator 805 is lowered, and the leading end of the tray T is supported in the tray storage space 6a. The tray clamp 811 attached to the base end of the tray T is advanced by the tray motor 809 to push the tray T into the tray storage space 6a. When the tray T has been inserted to a specified position, the tray motor 809 is stopped, and the tray clamp 811 is gradually released. At the same time, the second table 808 retracts along with the tray support table 810 and the tray clamp 811. According to the steps presented above, the tray T is stored in the tray storage space 6a of the tray storage rack 6. After the completion of the storage process of one tray T, an empty tray T stored in another location of the tray storage spaces 6a of the tray storage rack 6 is pulled out by following the reverse steps to the tray insertion process presented above. The empty tray T is placed on the tray posting section 5, and the process is repeated to place a new lot of pellets thereon. Next, the process of recovering the pellets when some problems arise in some section after the drying section 30 will be explained. For example, if a problem arises in the grip transporting device 502, first the pellet inspection section 40 is shut down, followed by the drying section 30. Then, the following steps are carried out to efficiently recover the pellets forwarded from the wet grinding machine 2. When a pellet recovery command is issued, the first pellet stopper 100, shown in FIG. 2, is activated through the space between the pellets. The first stopper rises above the drying belt 300, and stops the flow of the pellets. The position of the first stopper 100 is set so that the tip of the pellet pick-up device 102 comes between the boundary of closely contacting pellets. This is done to prevent the pellet pick-up device 102 to lift the pellets in some abnormal condition, such as a tilted condition, thereby efficiently lifting many pellets. In the above condition, the pellets become arranged in close contact on the transfer section 20 and the grinder belt 4, starting from the first stopper 100 and heading towards the backward direction. The pick-up device 102 is thus able to lift many pellets positively. When a sufficient number of pellets, which can be lifted by the pick-up device 102, are lined up on the grinder belt 4, the grinder belt 4 is stopped. The pellets on the grinder belt 4 are picked up by a pair of pick-up fingers 102a by operating the closer/opener device 102c, and grasping the pellets therebetween. The pellets are lifted and transported onto the grooves of the tray T on the transport belt 103b of the pellet on device 103, by operating the elevator cylinder 102d, 102e and the horizontal pressure cylinder 102f. In the meantime, the first stopper 100 is retreated from the drying belt 300, and the linear feeder is operated to move the pellets on the transfer section 20 towards the drying belt 300. Next, the grinding belt 4 is activated and the second stopper 101 projects beyond the transport belt 4, which results in a certain number of pellets being lined up on the grinder belt 4. The pick-up device 102 is operated to lift the lined up pellets, and as before, these pellets are transferred onto the tray T on the transport belt 103b of the pellet collection device 103. The tray T disposed on the transport belt 103b of the pellet collection device 103 is moved one pitch by the tray driving motor 103d so as to position an empty groove in a specified position (pellet placement position for the pick-up device 102). The above described steps are repeated until the problem which arose after the drying section 30 is resolved, and the pellet recovery command is cancelled. In a second embodiment representing a variation of the first embodiment, the arrangement of the pellet inspection section 40 may be that the side surface inspection section A is disposed before the end surface inspection section B as shown in FIG. 23. In this embodiment, the pellet inspection section 40 is a continuous process facility, and a large number of accepted pellets are continuously discharged from the pellet inspection section 40. On the other hand, because the grip transporting device 502 is a batch-operated process, it is necessary that the collection belt 500, having twenty five pellets lined up thereon at certain spacing, be stopped temporarily. When the collection belt 500 is stopped, many succeeding pellets become bunched at the entry end to the collection belt 500. Therefore, the succeeding pellets which are discharged from the pellet inspection section 40 may knock against the preceding pellets bunched at the entry end to the collection belt 500. To reduce the shock impact, the rolling distance from the pellet inspection section 40 is minimized, but there is an addition device of a middle belt C (a flat stainless steel belt) is provided between the discharge end of the end surface inspection section B and the pellet transport device 50 for moderating the impact. Also, the speed of transport is adjusted to avoid impacting the preceding pellet with the succeeding pellets. By such measures, the effect of mechanical damage to the inspected pellets is reduced if the collection belt 500 should stop. |
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