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053751493	description	DESCRIPTION OF THE PREFERRED EMBODIMENT As shown generally in the drawings, the invention provides a method of extracting energy from energetic ions produced by nuclear fusion within a tokamak fusion reactor 10. FIG. 1 is a cross-sectional, top view of the tokamak 10, wherein a toroidal plasma 11 is confined within a strong helical magnetic field created by the superposition of an externally generated toroidal magnetic field with a poloidal magnetic field generated by a toroidal current 12 within the plasma 11. Energy from the tokamak 10 is released when fuel ions, deuterium and tritium, within the toroidal plasma 11 fuse to form energetic ions, .alpha.-particles and protons, and neutrons. Energy is extracted from the energetic ions by injecting waves 13 of predetermined frequency and phase into the plasma 11 by means of antennas or wave guides 14 to diffuse the energetic ions towards the periphery 15 of the plasma 11. The energetic ions, while diffusing towards the periphery 15, impart energy to the waves 13 to amplify the waves 13. The amplified waves 13, in turn, convey energy to electrons and fuel ions to enhance respectively, the toroidal plasma current 12 and fuel ion reactivity. As shown in FIG. 2, the energetic ions are produced generally within the central region 20 of the toroidal plasma 11 to create a steep spatial gradient 21 of energetic ions. The spatial gradient 21 arises naturally from the fusion production rate which is proportional to the square of the fuel ion density and, approximately, to the square of the plasma temperature. Since heat and particles are lost from the plasma at its periphery 15, both the fuel ion density and plasma temperature is greatest near the plasma center 20. Accordingly, the production of energetic ions is greatest near the plasma center 20 such that the energetic ion density peaks near the center 20 and falls off rapidly towards the plasma periphery 15. The steep gradient provides a source of free energy that may be tapped by allowing the energetic ions to expand radially outward toward the plasma periphery 15. However, the free expansion energy of the energetic ions is difficult to harness because the energetic ions are confined within the strong magnetic field which confines the plasma 11. In the absence of external forces, the energetic ions will not expand towards the periphery 15 of the plasma 11, but instead, they will gyrate around the toroidal or z-directed lines of the magnetic field B 30 in what are called Larmor or gyroorbits 31 as shown in FIG. 3, which displays a cross-section of the plasma 11 in an r-.theta.-z coordinate system. Consequently, these confined energetic ions become diffused primarily by colliding with electrons which are traveling toroidally within the tokamak 10. These collisions, by slowing down the electrons, rob the tokamak reactor 10 of useful energy by reducing the plasma current 12 and the collisional or resistive heating available to the fuel ions. Nonetheless, it is possible to extract the energy of these energetic ions if they are diffused by a noncollisional means such as by interaction with an intense wave 13 deliberately injected into the tokamak 10 as shown in FIGS. 1 and 2. Under the influence of suitable waves 13, such as an electrostatic wave with substantial poloidal momentum, the centrally located energetic ions would tend to diffuse in energy-configuration space to the less energetic peripheral region 15. Although there may be other, possibly even more suitable, waves 13 for extracting the expansion energy of the energetic ions, in the preferred embodiment described herein, the lower hybrid wave is disclosed. Additionally, the invention herein considers and further discloses .alpha.-particles since in the first most likely achievable fusion reaction of deuterium-tritium (D-T), .alpha.-particles will be the primary energetic ions which are produced. Referring again to FIG. 3, the lower hybrid wave 32 can be made electrostatic with wavenumbers K predominantly in a direction perpendicular to both the magnetic field 30 and the gradient 21 of the energetic ions, which for a tokamak with circular cross section would mean a large k.sub..theta., where .theta. is the azimuthal, or poloidal, direction. Additionally, it is possible to concentrate the wave amplitude in the radial direction r to allow the wave 32 to interact with the energetic ions in a nonlinear manner and in the region in which the gradient 21 is greatest. To illustrate the mechanism by which the energetic ions are diffused, consider, as shown in FIG. 3, a lower hybrid wave 32 traveling along a wave trajectory with wavenumber k in the .theta. direction, interacting with .alpha.-particles in a strong z-directed magnetic field B 30 pointing into the plane of FIG. 3. As described earlier and shown in FIG. 2, the .alpha.-particles are concentrated towards the central region 20 of the plasma 11 with a gradient 21 in the r direction. The .alpha.-particles are magnetically confined in the plasma 11, i.e. .rho..sub..alpha. /a <1, where .rho..sub..alpha. is the .alpha.-particle gyroradius and a is the minor cross-section of the tokamak 10. The .alpha.-particles, however, are not magnetized with respect to the wave 32, i.e. k.sub..theta. .rho..sub..alpha. >1, where k.sub..theta. is the wave wavenumber in the poloidal direction. Thus, if due to the wave 32, the .alpha.-particle momentum changes by m.sub..alpha. .DELTA.v.sub..theta., where m.sub..alpha. is the .alpha.-particle mass and v.sub..theta. the .alpha.-particle poloidal velocity, then the change in the .alpha.-particle energy is .DELTA.E=m.sub..alpha. v.sub..theta. .DELTA.v.sub..theta., and the change in the gyrocenter or position of the .alpha.-particle in the r-direction is .DELTA.r.sub.gc =.DELTA.v.sub..theta. /.OMEGA..sub..alpha., where .OMEGA..sub..alpha. =2eB/m.sub..alpha. is the gyrofrequency and where e is the charge on a proton. The wave-particle resonance is .omega.=k.sub..theta. v.sub..theta., so upon exchanging energy .DELTA.E with the wave, the .alpha.-particle moves .DELTA.r.sub.gc =.DELTA.Ek.sub..theta. /m.sub..alpha. .OMEGA..sub..alpha. .omega.. As can be seen in FIG. 3, in an r-.theta.-z coordinate system the lower hybrid wave 32 can travel either in the positive or negative .theta.-direction, meaning that the wave 32 wavenumber k.sub..theta. can be either positive or negative. From the equation above, .DELTA.r.sub.gc =.DELTA.Ek.sub..theta. /m.sub..alpha. .OMEGA..sub..alpha. .omega., it can be readily seen that if the .alpha.-particle interacts with a lower hybrid wave 32 traveling in the negative .theta.-direction, i.e. the wave 32 wavenumber k.sub..theta. is negative, then the .alpha.-particle will move radially inward if it gains energy while if it loses energy it will move radially outward. Physically, what is happening is that the .alpha.-particle is in resonance with the wave 32 when the .alpha.-particle is traveling in the negative .theta.-direction, or, in other words, on the radially inward portion of its gyroorbit 31, such that if the .alpha.-particle is pushed to higher energy, it migrates radially inward while if it loses energy, it migrates radially outward. Precisely the opposite occurs when wave 32 wavenumber k.sub..theta. is chosen to be in the positive .theta.-direction. Because of the random nature of wave-particle interactions, the .alpha.-particle in interacting with the wave 32 will gain energy as often as it loses energy with the net effect of being diffused in both energy and gyrocenter radius. However, because the radial concentration of the .alpha.-particles is near the center 20 of the plasma 11, the diffusion of .alpha.-particles in energy-radius space will be on average to larger radius and lower energy when a wave 32 traveling in the negative .theta.-direction is allowed to interact with the .alpha.-particles. The net result is that the wave 32, in absorbing the energy lost by the .alpha.-particles, is amplified. To diffuse the energetic ions and extract their energy as described in the foregoing, lower hybrid waves 32 of predetermined frequency and phase which encircle the plasma center 20 poloidally in the negative .theta.-direction are injected into the plasma 11. The waves 32 are adapted to satisfy a resonance condition with the energetic ions such that .omega.-k.sub..vertline. v.sub.i.vertline. -k.sub..perp. v.sub.i.perp. .ltoreq.0, where .omega. is the wave frequency, k.sub..vertline. is the wave wavenumber parallel to said toroidal magnetic field, k.sub..perp. is the wave wavenumber perpendicular to said toroidal magnetic field, v.sub.i.vertline. is the ion parallel velocity and v.sub.i.perp. is the ion perpendicular velocity. The resonance condition ensures that the perpendicular wave phase velocity .omega./k.sub..perp. is less than the energetic ion perpendicular velocity v.sub.i.perp., as seen by an ion moving with the ion parallel velocity v.sub.i.vertline., and thus allows the waves 32 to fully interact with the ion. The lower hybrid wave 32 can be generated by launching rf waves into the plasma 11 be means of waveguides 14 with various toroidal and poloidal phasing as shown in FIGS. 1 and 2. Methods of launching rf waves into a plasma 11 to generate the various waves, such as the lower hybrid wave 32, are well known in the art. Alternate methods of launching rf waves include the use of antenna arrays and other slow wave structures. The lower hybrid waves 32, having been or while being amplified by the diffusion of energetic ion as described in the foregoing, can be used as a mechanism to provide power, in situ, directly to the toroidal plasma current 12. Because lower hybrid waves 32 traveling poloidally in the .theta.-direction can also travel in the toroidal or z direction, they can enhance and/or generate the toroidal plasma current 12 by increasing the energy of electrons traveling in one toroidal direction. To increase preferentially the energy of the electrons, the injected lower hybrid waves 32, while in resonance or possibly subsequent to being in resonance with energetic ions, are adapted to also satisfy a resonance condition with the electrons, such that .omega.-k.sub..vertline. v.sub.c.vertline. =0, where .omega. is the wave frequency, k.sub..vertline. is the wave wavenumber parallel to the toroidal magnetic field, and v.sub.c.vertline. is the parallel velocity of electrons. The waves 32 are launched by an endfire array of waveguides such that the wave parallel phase velocity .omega./k.sub..vertline. is substantially unidirectional and in the direction opposite the desired flow of toroidal current 12. To efficiently generate the plasma current 12, damping of the lower hybrid waves 32 by fuel ions must be avoided. To avoid damping on the bulk fuel ion population, the wave phase velocity in the direction perpendicular to the magnetic field must be made much greater than the thermal velocity of the bulk fuel ions, i.e. .omega./k.sub..perp. >v.sub.Tf is the average thermal velocity of the fuel ions and k.sub..perp. is the perpendicular wavenumber which in the main region of wave-particle interaction is chosen to be substantially in the poloidal direction. Since only fuel ions with perpendicular speeds much greater than that of the perpendicular wave phase velocity can resonate, very few fuel ions will participate in the damping. The amplified lower hybrid wave 32 can also be used to enhance the fusion reactivity of the plasma 11 by damping on fuel ions instead of electrons. To damp on fuel ions the lower hybrid wave 32 is adapted to satisfy a resonance condition with fuel ions such that .omega.-k.sub..vertline. v.sub.f.vertline. -k.sub..perp. v.sub.f.perp. .ltoreq.0, where .omega. is the wave frequency, k.sub..vertline. is the wave wavenumber parallel to the toroidal magnetic field, v.sub.f.vertline. is the fuel ion parallel velocity, k.sub..perp. is the wave wavenumber perpendicular to the magnetic field, and v.sub.f.vertline. is the fuel ion perpendicular velocity. For optimal wave damping by fuel ions, the wave 32 perpendicular phase velocity should be about four times the fuel ion perpendicular velocity, .omega./k.sub..perp. -4v.sub.Tf. Also, the wave 32 parallel velocity .omega./k.sub..vertline. should be large enough to avoid electron damping in comparison to ion damping. The foregoing damping of fuel ions is possible because, although fuel ions are diffused in space and energy in essentially the same manner as energetic ions, the energetic ions tend to lose energy and move radially outwardly while the fuel ions tend to gain energy and move radially inwardly. This is due to the fact that the energy and density distribution of fuel ions are different from that of energetic ions. For example, as shown in FIG. 4, both paths (a) and (b) are typical diffusion paths of ions that interact with a wave with poloidal phase velocity .omega./k.sub..theta., wherein r is the ion radial distance from the center of the plasma and .epsilon..sub..perp. is the ion perpendicular energy. Here .epsilon..sub.f =m.sub.f (.omega./k.sub..theta.).sup.2 /2 and .epsilon..sub.i =m.sub.i (.omega./k.sub..theta.).sup.2 /2 are, respectively, the threshold energies for interaction of the wave with ions with masses m.sub.f and m.sub.i. Therefore, if the wave poloidal velocity is chosen such that .epsilon..sub.f .perspectiveto.80-100 KeV, in a D-T fusion reactor operating at a temperature about 20 KeV, it is clear that not many fuel ions will have energy greater than .epsilon..sub.f. Thus, upon interaction with the waves 32, the fuel ions tend to gain energy and move inwardly while the energetic ions, in this case .alpha.-particles, being born at about 3.5 MeV and initially having substantially greater energies than .epsilon..sub.i are much less likely to gain energy. Moreover, the energetic ions being concentrated near the tokamak center 20, or r=0, are more likely to diffuse along (b) to lower energy .epsilon..sub.i than fuel ions. Energetic ions, on the other hand, are more likely to diffuse along (a) to higher energy and smaller radii. In this manner, through the wave intermediary, energy from the energetic ions are transferred to the fuel ions to increase the fusion reactivity of the plasma 11. In the embodiment disclosed thus far, the techniques of using energetic ion energy to enhance the plasma current 12 or fusion reactivity have been disclosed. However, in a further adaptation of the invention as disclosed herein, it is possible to use the energetic ion energy to simultaneously increase fusion reactivity while generating or enhancing the toroidal plasma current 12. One such known method is described in U.S. Pat. No. 4,423,001 (Fisch) entitled, "System and Method for Generating Current by Selective Minority Species Heating." To simultaneously increase fuel reactivity while generating plasma current, waves 32 of predetermined frequency and phase traveling in one poloidal direction and in one toroidal direction are injected into the plasma 11 which has been prepared to includes both minority and majority ions having different charge states. The waves are injected such that they are resonant with superthermal minority ions, such that (.omega.-.OMEGA..sub.m)/k.sub..vertline. .perspectiveto.4v.sub.Tm, where .OMEGA..sub.f is the minority fuel ion gyrofrequency and v.sub.Tm the minority fuel ion thermal velocity. The waves 32, while or subsequent to extracting energy from energetic ions, are preferentially absorbed by minority species ions traveling in one toroidal direction which increases the energy of the minority ions and serves to heat the minority ions and generate and/or enhance the toroidal plasma current 12. To maintain a steep spatial gradient of energetic ions and prevent diffusion of energetic ions back into the central region 20 of the plasma 11, it is advantageous to remove the energetic ions that diffuse into the peripheral region 15 of the plasma 11. Accordingly, in the preferred embodiment of the invention, an absorbing boundary at the low-energy end of the diffusion path would efficiently remove energetic ions and allow continuous diffusion of energetic ions from the central region 20 of the plasma 11 to its periphery 15. Absorbing boundaries may be effectuated by ash removal schemes which remove energetic ions as they approach the periphery 15 of the plasma 11. Ash removal schemes such as the use of diverter plates to skim off the outer layer of plasma 11 or by inducing a magnetic ripple or turbulence on the outer surface of the plasma without causing significant interior agitation are known and effective methods of ion removal. Under favorable circumstances, namely in conjunction with ash removal schemes, the invention, as described in the preferred embodiment herein, should be able to extract much of the perpendicular energy of the energetic ions. The consequence of being able to tap the energy of energetic ions as described in the invention is very advantageous for tokamak operations because the energy gain is obtained by a direct, in situ, conversion of the ion energy as contrasted with the traditional method of converting fusion energy to heat, then to electricity, and then to lower hybrid waves 32 to power the current drive or to increase fuel ion reactivity. Note that the energy savings in a D-T tokamak reactor by the use of the invention herein can be large. For example, if 5% of the total fusion energy is to be recirculated to drive the plasma current 12, and if 10-20% of the .alpha.-particle power, which is approximately 20% of the total fusion energy, can be channeled to directly to the plasma current 12, then the recirculating power can be reduced to only about 1-3% of the total fusion energy. The efficiency of the current drive mechanism is enhanced by a factor of 1.7 to 5. Another advantage is that since, by the practice of this invention, energetic ions are diffused to the periphery 15 of the plasma 11, unwanted helium ash is removed from the plasma center 20 and automatically purifies the plasma core of spent fuel. Further, since the amount and energy of the energetic ions in the plasma 11 is reduced, there is less energy available which can create unwanted instabilities in the plasma 11. Yet another advantage of the invention is that the removal of energy from the energetic ions will reduce the ion pressure and allow the magnetic field required to contain the plasma to be smaller and thus be cheaper to generate. Likewise, if the extracted ion energy is channeled to the fuel ions without heating the electrons, the total electron pressure will naturally be reduced, bringing a corresponding reduction in the magnetic field required to contain the plasma. A limitation of the power that may be extracted by this invention is the fact that only 20% of the total fusion power from a D-T reaction is available in the form of energetic ions. Nonetheless, advanced fuel reactors utilizing deuterium-deuterium (D-D) and D-.sup.3 He reactions should be able to utilize the method of this invention with even greater effect since energetic ions dominate the total fusion power of such advanced reactors. The foregoing description of a preferred embodiment of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form disclosed. For example, waves used to diffuse the energetic ions need not be limited to the lower hybrid wave. There may be other more efficient and suitable waves for extracting energy from the energetic ions. The embodiment described herein explains the principles of the invention so that others skilled in the art may practice the invention in various embodiments and with various modifications as suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto.
054019753	claims	1. A method for constructing a toroidal molecule, comprising the steps of: forming a toroidal molecule such that a plurality of sixfold rings each including six atoms are arranged in a torus form, while changing external physical force to be applied to the atoms; changing the atoms arrangement of said toroidal molecule such that first ones of said sixfold rings arranged on an outer wall surface of said toroidal molecule are replaced by first fivefold rings each including five atoms, said first sixfold rings being apart from each other; and changing the atoms arrangement of said toroidal molecule such that second ones of said sixfold rings arranged on an inner wall surface of said toroidal molecule are replaced by second fivefold rings each including five atoms and sevenfold rings each including seven atoms, said second sixfold rings being apart from each other, wherein each of said first and second fivefold rings and said sevenfold rings is surrounded by said sixfold rings. arranging a plurality of toroidal molecules on a substrate material one-, two- or three-dimensionally to form a crystal of said toroidal molecules; and changing sizes of said toroidal molecules spatially to construct a cluster of carbon molecules. making a hole of said toroidal molecule to adsorb another atom/molecule; and identifying an atom/molecule having a size fitted to the hole of said toroidal molecule. making a hole of said toroidal molecule to adsorb another atom/molecule; and detecting a pressure from change of electric characteristics of said toroidal molecule. making a hole of said toroidal molecule to adsorb another atom; and taking said other atom from a part of the torus into said toroidal molecule. making a hole of said toroidal molecule to adsorb another atom; and taking said other atom from a gap between the atoms of the torus into said toroidal molecule. making a hole of said toroidal molecule to absorb another slender molecule; and passing said another slender molecule through said hole of said toroidal molecule. making holes of a plurality of toroidal molecules, each said toroidal molecule having one hole, to adsorb other molecules; and passing said other molecules through said holes of said plurality of said toroidal molecules, respectively; and engaging concave portions of said outer wall surfaces of said toroidal molecules with convex portions thereof. changing the number of atoms constituting said toroidal molecule; and changing energy band structure of electrons/holes of said atoms in said toroidal molecule to respond to specific light. making a hole of said toroidal molecule to adsorb another molecule; and making said another molecule to block said hole of said toroidal molecule; and radiating a neutron beam or gamma ray onto a portion of said hole for a chemical reaction or nuclear reaction to give to said hole-blocking molecule kinetic energy for elutriation of the hole-blocking molecule from said toroidal molecule. providing a lead wire in a vicinity of said toroidal molecule; and supplying electric field from said lead wire to said toroidal molecule to change electron distribution in said toroidal molecule. bringing a probe of a scanning tunneling microscope close to a vicinity of said toroidal molecule; and supplying electric field from said probe to said toroidal molecule to change electron distribution in said toroidal molecule. making a hole of said toroidal molecule to adsorb another molecule; and heating said toroidal molecule to change a size of said hole of said toroidal molecule; passing said another molecule through said hole; and quenching said toroidal molecule to reduce the size of said hole to chop said other molecule. combining a plurality of said toroidal molecules; and adding impurities to said toroidal molecules to give magnetization thereto. making a hole of said toroidal molecule to adsorb another molecule; and passing said another slender molecule through said hole of said toroidal molecule; and spinning said toroidal molecule around said slender molecule. combining a plurality of toroidal molecules while changing bondings of the atoms by locally applying said external physical force to said plurality of said toroidal molecules to form a cluster of carbon molecules. forming a molecular machine by using the cluster. catching by a probe of a scanning tunneling microscope, a specific fivefold ring of a spheroidal carbon molecule having a surface constituted by sixfold, fivefold and sevenfold rings each including a plurality of carbon atoms, the fivefold rings including the specific fivefold ring; and pressing by said probe, said specific fivefold ring down to another fivefold ring in a position symmetrical with said specific fivefold ring with respect to a center of said spheroidal carbon molecule to form said toroidal molecule. arranging said atoms one by one by using a scanning tunneling microscope to form said toroidal molecule. forming a toroidal molecule such that a plurality of first sixfold rings each including six atoms are arranged in a torus form, while changing external physical force to be applied to the atoms; changing the atoms arrangement of said toroidal molecule such that some of said first sixfold rings arranged on an outer wall surface of said toroidal molecule are replaced by second sixfold rings each including six atoms and having a size larger than that of each of said first sixfold rings; and changing the atoms arrangement of said toroidal molecule such that some of said first sixfold rings arranged on an inner wall surface of said toroidal molecule are replaced by said second sixfold rings and third sixfold rings each including six atoms and having a size smaller than the size of each of said first sixfold rings, and wherein each of said second and third sixfold rings is surrounded by said first sixfold rings. (a) forming a helically-coiled molecule such that a plurality of sixfold rings each including six atoms are cylindrically arranged and connected to one after another, while changing external physical force to be applied to the atoms; (b) changing the arrangement of the atoms of said helically-coiled molecule such that first ones of said sixfold rings arranged on an outer wall surface of said helically-coiled molecule are replaced by first fivefold rings each including five atoms; and (c) changing the arrangement of the atoms of said helically-coiled molecule such that second ones of said sixfold rings arranged on an inner wall surface of said helically-coiled molecule are replaced by second fivefold rings each including five atoms and sevenfold rings each including seven atoms, and wherein each of said first and second fivefold rings and said sevenfold rings is surrounded by said sixfold rings. forming a spring of a molecular machine by using said helically-coiled molecule. forming a twist, in accordance with information to be written, to a first helically-coiled molecule by using a second helically-coiled molecule; and reading a state of twist of said first helically-coiled molecule written in accordance with said information, by using said second helically-coiled molecule. combining a plurality of helically-coiled molecules and a plurality of other molecules to form a molecular machine. supplying an electric current to said helically-coiled molecule to form a solenoid coil. forming a molecular machine by using said helically-coiled molecule. reducing helical and cylindrical diameters of said helically-coiled molecule with approach of a helical tip thereof to form a molecular spring. adding atoms such as nitrogen atoms or boron atoms to said helically-coiled molecule. 2. A method according to claim 1, further comprising the steps of: 3. A method according to claim 1, further comprising the steps of: 4. A method according to claim 1, further comprising the steps of: 5. A method according to claim 1, further comprising the steps of: 6. A method according to claim 1, further comprising the steps of: 7. A method according to claim 1, further comprising the steps of: 8. A method according to claim 1, further comprising the steps of: 9. A method according to claim 1, further comprising the steps of: 10. A method according to claim 1, further comprising the steps of: 11. A method according to claim 1, further comprising the steps of: 12. A method according to claim 1, further comprising the steps of: 13. A method according to claim 1, further comprising the steps of: 14. A method according to claim 1, further comprising the steps of: 15. A method according to claim 1, further comprising the steps of: 16. A method according to claim 1, further comprising the step of: 17. A method according to claim 16, further comprising the step of: 18. A method according to claim 1, further comprising the steps of: 19. A method according to claim 1, further comprising the step of: 20. A method for constructing a toroidal molecule, comprising the steps of: 21. A method for constructing a helically-coiled molecule, comprising the steps of: 22. A method according to claim 21, further comprising the step of: 23. A method according to claim 21, further comprising the steps of: 24. A method according to claim 21, further comprising the step of: 25. A method according to claim 21, further comprising the step of: 26. A method according to claim 25, further comprising the step of: 27. A method according to claim 21, further comprising the step of: 28. A method according to claim 21, further comprising the step of:
	abstract	An HTS assembly for use in a toroidal field coil having a central column is described. The HTS assembly comprises a plurality of parallel arrays of HTS tapes arranged to pass through the central column, each array comprising a plurality of HTS tapes arranged such that c-axes of all tapes in an array are parallel to each other, and such that planes of the HTS layers of the HTS tapes are perpendicular to a first radius of the central column. 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 tape. The plurality of arrays comprises first and second sets of arrays. Each array within the first set of arrays comprises HTS tapes of a first type having a first c-angle, and each array within the second set of arrays comprises HTS tapes of a second type having a second c-angle which is greater than the first c-angle. The first set of arrays are arranged closer to the first radius than the second set of arrays.
	abstract	A charged particle beam apparatus comprising a preparatory evacuation chamber (15 in FIG. 1A) into which a sample (12) is conveyed and which is preliminarily evacuated, an ultraviolet irradiation unit (21) which is disposed in the preparatory evacuation chamber (15) and which irradiates the surface of the sample (12) conveyed into the preparatory evacuation chamber (15), with ultraviolet rays for a predetermined time period, and a sample chamber (16) into which the sample (12) is conveyed in the preliminarily evacuated state of the preparatory evacuation chamber (15) or from which the sample (12) is conveyed into the preparatory evacuation chamber (15), wherein the ultraviolet irradiation of the sample (12) by the ultraviolet irradiation unit (21) is performed before the conveyance of the sample (12) into the sample chamber (16), or/and after the conveyance thereof from the sample chamber (16), thereby to remove contamination on the surface of the sample (12).
	summary
	claims	1. A composite material, comprising a polymer, a plurality of metal nanoparticles, and a surface-modifying agent, wherein:the polymer is selected from the group consisting of polydimethylsiloxane (PDMS), polyamide, polyacrylonitrile, polyethylene, polypropylene, polyvinyl chloride, epoxy resin, polyimide, polyurethane, polyurethane polyvinylidene fluoride, and polyvinylidene difluoride;the surface-modifying agent is nanocellulose;the surface-modifying agent and the polymer form an interpenetrating network; andthe plurality of metal nanoparticles comprises metal nanoparticles selected from the group consisting of lead nanoparticles, tungsten nanoparticles, bismuth nanoparticles, and uranium nanoparticles. 2. The composite material of claim 1, wherein the polymer is PDMS. 3. The composite material of claim 1, wherein the plurality of metal nanoparticles comprises bismuth nanoparticles. 4. The composite material of claim 1, wherein the average size of the plurality of metal nanoparticles is from 1 nm to 40,000 nm. 5. The composite material of claim 1, wherein the average size of the plurality of metal nanoparticles is 5 nm. 6. The composite material of claim 1, wherein the amount of the plurality of metal nanoparticles in the composite material is from 0.5 wt. % to 40 wt. %. 7. The composite material of claim 1, wherein the amount of the plurality of metal nanoparticles in the composite is 2 wt. %. 8. The composite material of claim 1, wherein nanocellulose comprises cellulose nanofibers. 9. The composite material of claim 1, wherein nanocellulose comprises cellulose nanocrystals. 10. The composite material of claim 1, wherein the amount of nanocellulose in the composite material is from 0.5 wt. % to 40 wt. %. 11. A film comprising at least one composite material of claim 1. 12. A method for shielding a subject from electromagnetic radiation, comprising placing at least one composite material of claim 1 between the subject and a source of electromagnetic radiation, thereby reducing a dose of electromagnetic radiation received by the subject. 13. The method of claim 12, wherein the dose of electromagnetic radiation received by the subject is reduced by an amount from 95% to 99%. 14. The method of claim 12, wherein the dose of electromagnetic radiation received by the subject is reduced by at least 96%. 15. The method of claim 12, wherein the electromagnetic radiation is X-ray radiation.
050154370	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS The Figure illustrates a graphite core block 2 which may be assembled with a plurality of identical graphite core blocks, in the manner described above, to form a reactor core. In such a core, horizontally adjacent blocks will normally be separated by a small gap. Block 2 is shown broken away in several layers to illustrate the various flow channels therein. In accordance with the prior art, block 2 is provided with a plurality of vertical channels 4 extending throughout the height of block 2. Each channel 4 can be spaced inwardly from the edges of its associated blocks or can be formed of mating half cylinder recesses at the edges of horizontally adjacent blocks. The various core blocks are stacked atop one another so that continuous vertical channels 4 are formed to communicate with the region above and below the core. Under normal conditions, the flow of coolant, typically helium, vertically through channels 4 will provide adequate cooling of the core. However, if a blockage should develop in a channel 4, the flow of coolant through that channel will be prevented and substantial local heating can occur in the region where coolant flow no longer occurs. According to the invention, the effect of such a blockage is alleviated by the provision of a plurality of transverse channels 6 each interconnecting a row of vertical channels 4. Channels 6 extend entirely across the width of block 2 so that each channel 6 communicates with regions adjacent at opposite lateral sides of block 2 and with corresponding transverse channels in adjacent blocks. According to a further feature of the invention, each end of each channel 6 is flared, as shown in the Figure, to assure communication with corresponding channels in adjacent blocks in the event of slight misalignments between blocks. Channels 6 may be horizontal or may be inclined to the horizontal. The inclination can vary over a substantial range. If channels 6 are inclined to the horizontal, it is preferred that the inclination be small enough to assure that each channel 6 will extend between vertical sides of block 2. However, a horizontal orientation is preferred because this will simplify the task of aligning the channels in one block with those in each adjacent block. Preferably, as illustrated, transverse channels 6 are arranged in a plurality of layers, with the channels of each layer interconnecting alternate rows of vertical channels 4 and extending between two opposite faces of block 2. Each row of channels 6 extends in a direction which is transverse to the direction of the vertically adjacent layers of channels. The diameters which the channels should have to provide sufficient coolant flow can be determined according to established principles in the art. For a typical core having dimensions in the range indicated earlier herein, the vertical coolant flow channels 4, and the nonvertical channels 6 in each layer of such channels may have a center-to-center spacing of the order of 10 cm. In the illustrated embodiment, the channels 6 in each layer interconnect every other row of vertical channels 4 and the channels 6 in each layer are arranged so that each vertical channel 4 communicates with spaced layers of the nonvertical channels 6. The nonvertical channels 6 extending between two vertical sides of block 2 may be offset, from one layer of channels 6 to the next, by the spacing, perpendicular to those channels, between adjacent rows of vertical channels 4, to assure that all vertical channels 4 communicate with at least some vertically spaced nonvertical channels 6. According to one alternative embodiment of the invention, each layer of channels 6 can include a sufficient number of channels to interconnect all rows of vertical channels 4, rather than every other row as shown in the Figure. In addition, each layer of channels 6 can be oriented to extend between two side walls of block 2 other than diametrically opposed side walls. Thus, some or all of channels 6 can extend between two side walls which are separated by a single intervening side wall or can extend between two adjacent side walls. According to a further alternative, the arrangement of channels 6 illustrated in the Figure can be supplemented by auxiliary channels interconnecting any vertical channels 4 which are not interconnected by the arrangement shown. Further, if desired, two or more groups of intersecting channels 6 can be disposed in a single plane, or layer. In addition, when a core is built up from a plurality of small blocks 2, some of the channels 6 can be formed by molding semicircular recesses in the upper and lower walls of each block such that the recesses formed in vertically adjacent blocks of the core are located in registry to form channels 6 of circular cross section. The Figure further shows one large diameter vertical passage 8 which may be provided to receive a control rod or instrumentation, as is conventional in the art. While the description above refers to particular embodiments of the present invention, it will be understood that many modifications may be made without departing from the spirit thereof. The accompanying claims are intended to cover such modifications as would fall within the true scope and spirit of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being indicated by the appended claims, rather than the foregoing description, and all changes which come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
040574660	summary	BACKGROUND In well-known commercial nuclear power reactors, the reactor core is of the heterogeneous type, that is, the nuclear fuel is in the form of elongated, cladded rods. These rods or elements are grouped together and supported between upper and lower tie plates to form separately removable fuel assemblies or bundles. A sufficient number of such fuel assemblies are arranged in a matrix, approximately a right circular cylinder, to form the nuclear reactor core capable of self-sustained fission reaction. The core is submersed in a fluid, such as light water, which serves both as a coolant and as a neutron moderator. A plurality of control rods, containing neutron absorbing material, are selectively insertable among the fuel assemblies to control the reactivity, and hence the power level of operation, of the core. In some reactors, for example, the boiling water type, the power level also can be adjusted by changing the rate of coolant flow through the nuclear core. Typically, the above-mentioned fuel rods or elements comprise a sealed tube, formed of a suitable metal such as a zirconium alloy, containing a plurality of sintered pellets of an oxide of a suitable fuel, such as uranium oxide, as shown, for example, by J. L. Lass et al in U.S. Pat. No. 3,365,371. The tube, sealed by end plugs, thus serves as a cladding to isolate the nuclear fuel from the moderator-coolant and to prevent the release of fission products. The tubular fuel rod cladding, which may be of the order of 0.032 inches in thickness, is subjected to severe service because of the high pressure, high temperature and nuclear radiation in the environment of the nuclear reactor core. Fuel elements of the type under discussion, in general, have given reliable performance. However, some fuel elements failures have occurred for several reasons. (The term "failure" is herein meant to indicate that the fuel rod cladding has developed one or more openings, cracks or holes which permit escape of fission products from the fuel element into the surrounding coolant.) One type of failure that has been observed is characterized by longitudinal, brittle splits or cracks in the cladding generally occurring adjacent fuel pellet interfaces or adjacent cracks in the pellets. It is presently believed that such failures are primarily caused by mechanical interaction between the fuel pellets and the cladding during certain conditions of fuel operation!. Thus, this type of failure is designated pellet-cladding interaction failure. More specifically and as presently understood, the circumstances of likely pellet-cladding interaction failure are briefly as follows: During exposure (burnup) in the fuel, the fuel pellets expand or swell. The pellets also become distorted in shape. In particular the pellets tend to take on an "hour-glass" shape as opposed to their original cylindrical shape. In other words, the pellet tend to expand more at their ends than at their centers. Additionally the end surfaces of the pellets tend to become convex with the result that adjacent pellet edges move away from one another. Irradiation also lowers the ductility of the cladding. Thus a sudden large change in the power level of irradiated fuel can cause relatively rapid swelling of the fuel pellets against the cladding. If the expanding, separating edges of adjacent pellets (or adjacent sides of a pellet crack) lock against the cladding, the resulting localized strain may exceed the ultimate strain of the embrittled cladding with resulting cracking to produce the pellet-cladding interaction failure. It is obviously highly desirable to eliminate or at least to minimize the incidence of such pellet-cladding interaction failures. SUMMARY An object of the present invention is to provide a method of conditioning the fuel in a reactor core to a predetermined maximum power level of operation so that subsequent relatively rapid changes in power level (particularly power increases) below and up to this maximum power level can be made with minimum risk of pellet-cladding interaction fuel rod failures. This and other objectives are accomplished by taking advantage of the discovery that reactor fuel can be conditioned for subsequent high power operating level changes by a method of systematically increasing the local power of the fuel in the high power range (that is, within the power range of fuel pellet-cladding interaction) at or below a discovered critical rate. It is found that such power increase, at or below the discovered critical rate, provides a gradual, long-term, accommodation between the cladding and the fuel pellets, in response to the stresses created by expanding fuel pellets, without cladding failure. By "long-term" is meant that the accommodation persists for a significant period of time, perhaps not indefinitely-depending on operating conditions, but for at least a period of time sufficient for practical application of the conditioning method in commercial nuclear reactor core operation.
	description	The present invention relates to the field of storing and/or transporting PWR (Pressurised Water Reactor) type nuclear fuel assemblies which can be either irradiated (case of UO2 or MOX fuel), or not irradiated when this is MOX fuel. Such a device, also called a storage “basket” or “rack”, comprises a plurality of adjacent housings each able to receive a nuclear fuel assembly. This storage device, intended to be housed in a cavity of a package, is designed so as to be capable of simultaneously fulfiling three essential functions, which will be briefly set out below. These is first the thermal transfer function of the heat released by the fuel assemblies. Generally, aluminium or an alloy thereof is used, because of its proper heat conductivity. The second function relates to the neutron absorption, and the worry of maintaining the sub-criticality of the storage device when this is loaded with the fuel assemblies. This is made by using neutron absorbing materials, such as boron. Additionally, the sub-criticality can also be ensured by providing spaces likely to be filled with water, for example just inside the partitions forming the housings of the storage device. Finally, the third essential function relates to the mechanical strength of the device, which is mainly ensured by the presence of structural elements, most frequently made of steel. It is noted that the overall mechanical strength of the device has to be compatible with regulatory safety requirements for transporting/temporarily storing nuclear materials, in particular as regards the so-called “free fall” tests. In documents FR 2 872 955 and FR 2 650 113, storage baskets are disclosed in which some of the functions are separately ensured, with dissociated elements. In the solutions suggested by these documents, for each partition, the thickness of the aluminium based external walls is set so as to achieve satisfactory heat conductivity performance. This thickness of both external walls depends on the total thickness of the partition, determined beforehand to fulfil package compactness objectives, aiming at housing as many fuel assemblies as possible in a given volume of the cavity of this package. Then, in the case of a design as described in document FR 2 650 113, the thickness of the walls of neutron absorbing material located between the aluminium walls, as well as the content of these walls of neutron absorbing elements are determined. The purpose is to check the sub-criticality of the pack formed by the package in which the basket as well as the fuel assemblies are located. The criterion search for is usually a criticality factor Keff+3σ lower than or equal to 0.95. For determining these thicknesses, calculations take the case where the package is in a configuration of loading under water into account. The water which is present in the housings of the basket increases the reactivity within the pack. But when water is introduced between the walls of neutron absorbing material equipping the partitions, this enables the efficiency of the neutron absorbing elements to be improved and thus neutron interactions to be reduced between assemblies. Thereby, the partitions play the role of neutron insulation between the housings. However, with the existing solutions, it turns out to be complicated to find a dimensioning resulting in a satisfactory compromise in terms of overall mass and costs. Indeed, an increase in the thickness of the walls of neutron absorbing material appears as the solution to decrease the content of neutron absorbing elements in these walls, and thus to reduce costs thereof. However, this is strongly detrimental to the overall mass of the basket, without substantially decreasing the necessary content of neutron absorbing elements to fulfil the sub-criticality criterion. To achieve satisfactory contents of neutron absorbing elements, largely overdimensioned wall thicknesses should be provided, which are incompatible with package operating requirements. Thus, the invention has the purpose to at least partially overcome the abovementioned drawbacks, relating to the embodiments of prior art. To do this, the invention has the object to provide a storage device for temporarily storing and/or transporting PWR type nuclear fuel assemblies, said device being intended to be housed in the cavity of a package and including a plurality of adjacent housings each intended to receive a nuclear fuel assembly, the housings being delimited by separating partitions at least one of which delimits on either side of the same a first housing and a second housing of the fuel assembly. According to the invention, said partition comprises: two first walls each partly delimiting, respectively with its external surface, said first and second housings, both first walls being made of a first material of aluminium alloy free of neutron absorbing elements, both first walls delimiting a first inter-wall space therebetween; two second walls arranged in the first inter-wall space and made of a second material comprising neutron absorbing elements and distinct from the first material, each second wall having an external surface facing one of both first walls, as well as an internal surface arranged such that both internal surfaces of both second walls are facing each other and delimit a second inter-wall space therebetween, the distance between the internal and external surfaces of each second wall defining a thickness e2, whereas a distance E is defined between the external surface of each second wall and a median partition plane parallel to the first and second walls, the thickness e2 and the distance E meeting the following condition:0.1≤e2/E≤0.43. Surprisingly, this particular dimensioning enables a satisfactory sub-criticality function to be ensured while limiting: the volume/mass of the second walls, which turns out to be beneficial to fulfil operating requirements; the volume content of neutron absorbing elements in the second material, thus limiting purchase cost/production costs of the second walls; the total amount of neutron absorbing elements, for a substantial financial saving; a difficulty in qualifying the constituent elements, which also results in a financial saving; the costs of the first walls, which are elements that are conventional, common in industry; difficulties in achieving proper heat transfer characteristics for the first walls, because they are free of neutron absorbing elements. In other words, the invention shows the existence of a restricted partition dimensioning range, enabling all the above-mentioned advantages to be achieved. In this regard, it is noted that it is known the existence of a strong interaction between the amount of hydrogen atoms located in the water gap intended to be introduced in the second inter-wall space under loading/unloading conditions (these atoms directly contributing to neutron moderation), and the amount of neutron absorbing elements in the second walls, for the purpose of absorbing neutrons after they have been moderated by the water gap. However, no element of prior art would make it possible to predict the existence of such a narrow dimensioning range, fulfiling all the imposed criteria satisfactorily. On the other hand, the invention has at least any of the following optional characteristics, taken alone or in combination. To obtain an even more efficient compromise, the thickness e2 and the distance E meet the following condition:0.15≤e2/E≤0.32. The distance E is between 20 and 30 mm. The second material comprises neutron absorbing elements chosen from boron and cadmium, even if other neutron absorbing elements can be contemplated, without departing from the scope of the invention. Each second wall is pressed against the first associated wall, taking for example the form of a coating deposited onto the internal surface of the first wall. Alternatively, a clearance J is present between each second wall and the first associated wall, the clearance J being between 1 and 5 mm. This range of values provides an efficiency for the drying between the two walls, once the package is drained off. The storage device has a number of housings between four and twenty-four housings, each housing being intended to receive a nuclear fuel assembly. At least one of the housings has a quadrilateral shaped cross-section. At least some of said partitions are made using notched structural assemblies, the structural assemblies being interlaced and stacked along a stacking direction parallel to the axes of the housings. Alternatively, at least some of said partitions are partly made using tubular elements each internally defining one of said housings, the walls of these tubular elements making up said first walls of the partitions. In this alternative, the second walls are externally secured to the tubular elements. The invention has also the object to provide a package for temporarily storing and/or transporting PWR type nuclear fuel assemblies, the package comprising a cavity in which a storage device as described above is housed. Finally, the invention has the object to provide a pack comprising such a package as well as fuel assemblies arranged in the housings of the storage device of this package. Further advantages and characteristics of the invention will appear in the non-limiting detailed description below. In reference to FIGS. 1 and 2, a storage device 1 is represented, provided to be placed in the cavity of a package (not represented) for transporting and/or temporarily storing PWR type irradiated nuclear fuel assemblies (not represented). Conventionally, when the package receives the storage device 1 and that this is loaded with irradiated fuel assemblies, all of these elements form a pack, which is also an object of the invention. As is visible in FIGS. 1 and 2, the storage device 1 comprises a plurality of adjacent housings 2 disposed in parallel, the latter each extending along a longitudinal axis 4. The housings 2 are each capable of receiving at least one square cross-section fuel assembly, and preferably a single one. The housings are provided in a number between four and twenty-four, for example twelve housings as in FIG. 1. The housings 2 are thus provided so as to be juxtaposed to each other. They are made through a plurality of separating partitions 9, 11 parallel to the axes 4, and also parallel to a longitudinal axis of the package passing through its bottom and its lid. The partitions 9, 11 are formed using notched structural assemblies 6a, 6b, stacked along a stacking direction 8 which is preferably parallel to the longitudinal axes 4 of the housings 2. By convention, in the following of the description, it is assumed that the notion of “height” is to be associated with the stacking direction 8. The partitions 9, 11 are arranged parallel and perpendicular to each other, such that the assemblies 6a are located parallel to each other, whereas the assemblies 6b are also located parallel to each other, but perpendicular to the assemblies 6a. When the structural assemblies 6a, 6b are stacked along the stacking direction 8, the partitions 9, 11 resulting therefrom delimit together the housings 2, each having a substantially square shaped transverse cross-section. Of course, the housings 2 could have any other shape allowing a differently shaped fuel assembly to be held, such as a hexagonal shape. In the storage device 1 represented in FIGS. 1 and 2 where the housings 2 are of a square cross-section, the structural assemblies 6a form separating partitions 9 parallel to a direction 10, whereas the structural assemblies 6b form separating partitions 11 parallel to a direction 12, the directions 8, 10 and 12 being perpendicular to each other. Preferably, each of the assemblies 6a, 6b extends between two peripheral partitions 14 to which it is secured, these peripheral partitions 14 enabling the storage device 1 to be closed sideways. By way of indicating example and as represented, these peripheral partitions 14 can be provided four in number, each extending on the entire height of the device 1, and partly delimiting the peripheral housings 2 of this device 1. On the other hand, as is clearly apparent from the above, the partitions 9, 11 participate in delimiting several housings 2 on either side of the same. In this regard, FIG. 3 shows a part of one of the separating partitions 9, delimiting on either side of the same a first housing 2 as well as a second housing 2, their two axes 4 being located in a dummy plane orthogonal to that of the partition 9. Only two housings 2 are represented in FIG. 3, but as previously mentioned, it is to be understood that this partition 9 is preferably provided to delimit one or more other housings 2 on either side of the same. The partition 9 of FIG. 3 will now be described in more detail, and it is to be considered that the other partitions 9, as well as the abovementioned partitions 11, have an identical or similar design. The partition 9 has a symmetry along a median plane 20 orthogonal to the transverse plane P of FIG. 1. On each side of this plane 20, the partition 9 includes a first wall 22 parallel to the median plane 20, and comprising an external surface 24 as well as an internal surface 26. The external surface 24 partly delimits the associated housing 2, whereas the two internal surfaces 26 of both walls 22 delimit a first inter-wall space 28 therebetween. The first walls 22 are made of an aluminium alloy free of neutron absorbing elements. It is indicated that by neutron absorbing elements, it is meant elements which have an effective cross-section higher than 100 barns for the thermal neutrons. By way of indicating examples, this is an aluminium alloy free of boron, gadolinium, hafnium, cadmium, indium, etc. In the case of a design with stacked and interlaced notched assemblies, each first wall 22 is thus segmented along the height direction of the device 1. The thickness e1 of each first wall 22 is for example between 5 and 25 mm, whereas the distance “a” separating both external surfaces 24 is in the order of 40 to 100 mm, whereas the distance “d” separating both internal surfaces 26 is in the order of 30 to 60 mm. In the first inter-wall space 28, with each first wall 22, a second wall 30 parallel to the median plane 20 is associated. Each wall 30 comprises an external surface 34 as well as an internal surface 36. The external surface 34 faces the internal surface 26 of its first associative wall, whereas both internal surfaces 36 face each other and delimit a second inter-wall space 38 therebetween. The second walls 30 are made of a second material comprising neutron absorbing elements, for example an alloy comprising boron carbide (B4C), preferably an aluminium based alloy. In the case of a design with stacked and interlaced notched assemblies, each second wall 22 is also segmented along the height direction of the device 1. In the embodiment exhibited in FIG. 3, a clearance J is provided between the internal surface 26 and the external surface 34 facing it. This clearance J is for example between 1 and 5 mm, so as to provide a proper drying efficiency between both walls 22, 30, once the package is drained off. Alternatively, the second wall 30 can be pressed against the internal surface 26 of its first associated wall, so as to limit water infiltrations. To do this, a technique of depositing the second wall 30 onto the first wall 22 can be implemented, for example such that the latter takes the form of a coating deposited onto the internal surface 26. For example, this can be a composite comprising a particle loaded metal matrix comprising neutron absorbing elements. The thickness e2 of each first wall 22 is for example between 2 and 10 mm, whereas the distance “E” separating the external surface 34 from the median plane 20 is for example between 15 and 40 mm, and further preferentially between 20 and 30 mm. One the features of the invention lies in the choice of the dimensions for the thickness e2 and the distance E, such that they satisfy the condition 0.1≤e2/E≤0.43, and more preferentially 0.15≤e2/E≤0.32, corresponding to the case where E is 23.5 mm and e2 values for which Keff+3σ is satisfied with a maximum content of boron carbide (B4C) of 25%. Indeed, it has been noticed that these ranges of dimension ratios advantageously result in partitions satisfying cost, mass and sub-criticality criteria. In reference to FIG. 4 now, it is shown a graph in which the curves (a) and (b) and (c) represent, as a function of the ratio e2/E, the volume content of boron carbide in an aluminium alloy required for achieving a criticality factor Keff+3σ of a 0.95 value. For curve (a), the distance E is set to 23.5 mm, whereas for curve (b), the distance E is set to 20 mm, and for curve (c), the distance E is set to 30 mm. Surprisingly, these curves show that for e2/E ratios between 0.1 and 0.43, the volume content of boron carbide sufficient to satisfy the sub-criticality criterion does not exceed 26%, which enables the second walls 30 to be manufactured at a reasonable cost. Further surprisingly, these curves show that the minimum content to satisfy the sub-criticality criterion corresponds to an identical e2/E ratio regardless of the E value, this optimum ratio Rop being substantially equal to 0.23. The three curves are thus axially offset, along the ordinate axis corresponding to the content of boron carbide. The higher is the E value, the lower is the required volume content of boron carbide, and reversely. This content is even reduced to around 25% when the e2/E ratio is 0.23, and E values higher than 20. For E values higher than or equal to 23.5 mm, this content is further reduced to less than 23% when the e2/E ratio is set between 0.2 and 0.25. In reference now to FIGS. 5a and 5b, the assemblies 6a, 6b for forming the partitions 9, 11 are shown, in two distinct configurations upon assembling. These assemblies 6a, 6b each have spacers 40 separating the two second walls 30. They are equipped with notches 42 made at the first walls 22, so as to allow assembling by stacking and interlacing, in the way described in document FR 2 872 922. In addition, it is indicated that the second walls 22 do not extend at the interlaced portions, such that they are interrupted along each assembly 6a, 6b. This enables a financial saving to be generated, without embrittling the sub-criticality criterion insofar as the interlaced zones have only a low on the criticality factor. According to another embodiment shown in FIG. 6, square transverse cross-section tubular elements 50 are provided, each defining one of the housings 2. All or only some of the four walls of a tubular element 50 form the first walls 22, which are externally coated with a second wall 30. The partition 9 is thereby formed by the facing parts of two adjacent tubes 50. Of course, various modifications could be provided by those skilled in the art to the storage devices 1 just described, only by way of non-limiting examples.
047541474	claims	1. A collimator apparatus for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: (a) support plate means having a central opening around a beam axis through which the beam of radiation can pass; (b) a bundle of nested rods mounted on the support plate means each rod being movable into the beam at an angle to the beam axis to interfere with the beam, the rods having first ends which together define a first surface for shaping the beam around the beam axis and opposite ends from the first ends of the rods wherein the rods are nested so that the beam can not pass between the rods; (c) a holder means mounting the rods so that the first surface is defined and the beam is shaped by the first ends of the rods; and (d) releasable clamping means mounted on the support plate means and engaging the rods between the first and second ends to secure the rods together in the shape defined by the first ends of the rods. (a) support plate means having a central opening around a beam axis through which the beam of radiation can pass; (b) a bundle of nested metal rods mounted on the support plate means each rod having a longitudinal axis perpendicular to the beam axis and having first ends which together define a first surface for shaping the beam around the beam axis and opposite ends from the first ends wherein the rods are nested so that the beam can not pass between the rods; (c) a holder means mounting the rods including shaping means adjacent the opposite ends of the rods, wherein the rod shaping means has a second surface corresponding to the first surface which defines varying positions of the first ends of the rods so that the first surface is defined and the beam is shaped by the first ends of the rods; and (d) clamping means mounted on the support plate means for securing the rods together in the shape defined by the shaping means. (a) providing a collimator apparatus for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: support plate means having a central opening around a beam axis through which the beam of radiation can pass; a bundle of nested rods mounted on the support plate means each rod being movable into the beam at an angle to the beam axis to interfere with the beam, the rods having first ends which together define a first surface for shaping the beam around the beam axis and opposite ends from the first ends of the rods a holder means mounting the rods so that the first surface is defined and the beam is shaped by the first ends of the rods wherein the rods are nested so that the beam can not pass between the rods; and releasable clamping means mounted on the support plate means and engaging the rods between the first and second ends to secure the rods together in the shape defined by the first ends of the rods; (b) moving the rods in the holder means to thereby define the first surface for shaping the beam in the collimator; (c) clamping the rods with the clamping means; and (d) irradiating the defined area of an object with the shaped beam defined by the rods. (a) providing support plate means mounted on the radiation source having a central opening around a beam axis through which the beam of radiation can pass; a bundle of nested metal rods mounted on the support plate means each rod having a longitudinal axis perpendicular to the beam axis and having first ends which together define a first surface for shaping the beam around the beam axis and opposite ends from the first ends wherein the rods are nested so that the beam can not pass between the rods; a holder means mounting the rods including shaping means adjacent the opposite ends of the rods, wherein the rod shaping means has a second surface corresponding to the first surface which defines varying positions of the first ends of the rods so that the first surface is defined and the beam is shaped by the first ends of the rods; and clamping means mounted on the support plate means for securing the rods together in the shape defined by the shaping means; (b) providng the rod shaping means by shaping a material to conform to an outline of an x-ray image of defined area to the body to be irradiated and thereby providing the second surface of the rod shaping means; (c) mounting the rod shaping means in the holder means with the opposite ends of the rods engaging the rod shaping means second surface to thereby define the first surface for shaping the beam in the collimator corresponding to the x-ray image; (d) clamping the rods with the clamping means; and (e) irradiating the defined area of an object with the shaped beam defined by the rods. 2. The collimator apparatus of claim 1 wherein there are two opposed bundles of rods mounted on the support plate means with the first ends opposite each other. 3. The collimator apparatus of claim 1 wherein the rods are circular in cross-section and have a diameter of between about 1 mm and 3 mm. 4. The collimator apparatus of claim 1 wherein rods have a composition for interfering with a neutron beam. 5. The collimator apparatus of claim 1 wherein the rods have a composition for interference with a photon beam. 6. A collimator apparatus for producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: 7. The collimator apparatus of claim 6 wherein there are two opposed bundles of rods mounted on the support plate means with the first ends opposite each other and with the opposed rods having parallel longitudinal axis. 8. The collimator apparatus of claim 6 wherein the rods are circular in cross-section and have a diameter of between about 1 mm and 3 mm. 9. The collimator apparatus of claim 6 wherein the metal composition of the rods is selected from the group consisting of tungsten and stainless steel. 10. The collimator apparatus of claim 6 wherein the rod shaping means is composed of polystyrene foam which is mounted on the holder. 11. The collimator apparatus of claim 6 wherein the rods have a composition for interference with a neutron or photon beam. 12. The collimator apparatus of claim 6 wherein the rods have a polygonal cross-section. 13. The collimator apparatus of claim 6 wherein the support plate means is rotatable around the beam axis by a drive means. 14. The collimator apparatus of claim 6 wherein the support plate means is circular and has a ring gear mounted around the central opening, wherein a worm gear driven by a drive means engages the ring gear to rotate the support plate means. 15. A method of producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: 16. A method of producing a cross-sectionally shaped beam of radiation from a radiation source which comprises: 17. The method of claim 16 wherein there are two opposed bundles of rods mounted on the support plate means as mirror images of each other with the first ends opposite each other and with the rods in each bundle having parallel longitudinal axis and wherein each of the bundles of rods is mounted on one of two opposed second surfaces of two opposed rod shaping means. 18. The method of claim 16 wherein the rod shaping means is composed of polystyrene foam which is cut to the shape of the beam. 19. The method of claim 16 wherein the beam is a neutron beam and wherein the rods are made from the metal selected from tungsten and stainless steel. 20. The method of claim 16 wherein the support plate means is rotated around the beam axis by a drive means. 21. The method of claim 20 wherein the support plate means has a ring gear mounted around the central opening and wherein a drive means with a worm gear meshed to the ring gear rotates the worm gear, ring gear and support plate. 22. The method of claim 16 wherein a beam selected from neutrons and photons is produced by the radiation source. 23. The method of claim 22 wherein the beam is of neutrons produced from a target irradiated with an accelerated beam of charged particles which impinge upon the target releasing the neutrons which then pass through the opening in the support plate. 24. The method of claim 16 wherein the rods each have a circular cross-section and a diameter of between about 1 and 3 mm. 25. The method of claim 16 wherein the rods have a polygonal cross-section. 26. The method of claim 16 wherein a patient is irradiated.
	description	This application is related to application Ser. No. 10/932,908, filed Sep. 2, 2004. 1. Field of the Invention The present invention relates generally to nuclear reactor fuel assemblies, and more particularly, is concerned with a debris filter bottom grid for a nuclear fuel assembly. 2. Description of Related Art During manufacture, subsequent installation and repair of components of the nuclear reactor coolant circulation system, diligent effort is made to help assure the removal of all debris from the reactor vessel and its associated systems, which circulate coolant throughout the primary reactor coolant loop under various operating conditions. Although elaborate procedures are carried out to help assure debris removal, experience shows that in spite of the safeguards used to effect such removal, some chips and metal particles still remain hidden in the system. Most of the debris consists of metal turnings, which were probably left in the primary system after steam generator repair or replacement. In particular, fuel assembly damage due to debris trapped at the lower most grid has been noted in several reactors in recent years. Debris enters through the fuel assembly bottom nozzle flow holes from the coolant flow openings in the lower core support plate when the plant is started up. The debris tends to be engaged in the lower most support grid of the fuel assembly within the spaces between the “egg-crate” shaped cell walls of the grid and the lower end portions of the fuel rod tubes. The damage consists of fuel rod tube perforations caused by fretting of the debris in contact with the exterior of the cladding tubes which sealably enclose the fissile material. Debris also becomes entangled in the lower nozzle plate holes and the flowing coolant causes the debris to gyrate, which tends to cut through the cladding of the fuel rods. Several different approaches have been proposed and tried for carrying out the removal of debris from the nuclear reactors. Many of these approaches are discussed in U.S. Pat. No. 4,096,032 to Mayers et al. Others are illustrated and described in the various patents cross referenced in U.S. Pat. No. 4,900,507, assigned to the instant Assignee. While all of the approaches described in the cited patent and cross references operate reasonably well and generally achieve their objective under the range of operating conditions for which they were designed, a need still exists for a further improved approach to the problem of debris filtering in nuclear reactors, to address an improved reduction in pressure drop across the bottom nozzle that is required for more advanced fuel designs currently going under development and to address a stress corrosion cracking problem that has been experienced in some of the operating debris filtering grids; mainly those known as P-grids. That improvement is addressed in part in co-pending application Ser. No. 10/932,908, filed Sep. 2, 2004, and Ser. No. 10/51,349, filed Jan. 5, 2004. A further need exists to trap even smaller debris without substantially increasing the pressure drop across the fuel assembly while overcoming the fatigue problems experienced by the current P-grids due to flow induced vibrations and stress corrosion cracking due to the high stresses that are induced during manufacture. The present invention provides a debris filter lower most grid in a fuel assembly designed to satisfy the aforementioned needs. The debris filter lower most grid of this invention is positioned just above the fuel assembly bottom nozzle and is generally formed from a spaced array of two sets of orthogonally arranged, parallel, spaced, elongated straps connected in an egg-crate lattice pattern. The lattice defines a number of cells, most of which support the fuel rods of the fuel assembly. Each of the cells that support fuel rods has walls with a cell height along the axial dimension of the fuel assembly equal to the width of one of the orthogonal arrangement of straps and a cell width along the elongated dimension of the straps equal to the distance between intersections of the straps. At least one wall of at least some of the cells that support fuel rods has at least two distinct protrusions that separately extend from the cell wall inwardly into the fuel rod cell on either side of the width of the wall near a corner of the fuel rod cell approximately at the same elevation along the cell height and spaced from the fuel rod that extends through the cell, at least at the beginning of life of the fuel assembly. A spring extends inwardly into the cell from the one wall above the protrusions and a dimple extends inwardly into the cell substantially centered along the width of the wall at an elevation between the two distinct protrusions and the spring. The spring is sized to contact the fuel rod that passes through the cell and the dimple is sized to be spaced from the fuel rod at least at the beginning of life of the fuel assembly. Preferably, the lower most grid of this invention is positioned substantially adjacent the bottom nozzle which cooperates with the lower most grid as a debris filter. Additionally, the elevations of the protrusions preferably coincide to oppose the fuel rod end plug so that any fretting due to trapped debris will not impact the fuel rod cladding which is above the end plug. In one embodiment, the protrusions are horizontally oriented with the dimple and/or spring vertically oriented. In still another embodiment, a second protrusion is located vertically adjacent each of the protrusions and extends in an opposite direction into an adjacent cell that supports a fuel rod. Similarly, a second dimple is positioned vertically adjacent the dimple and extends in the opposite direction into the adjacent cell that supports a fuel rod. Preferably, a third dimple extends in the opposite direction at a position vertically above the spring into the adjacent cell that supports a fuel rod and is gauged to provide contact support for the fuel rod in that adjacent cell. Preferably, the third dimple is oriented vertically and the second dimple is oriented horizontally. Thus, the arrangement of dimples and protrusions provides improved debris trapping and the arrangement of dimples and springs provides improved support that will reduce damage due to vibration. Furthermore, the grid straps will be made from 0.0105 inch (0.0267 cm) thick nickel-plated alloy 718 straps that are brazed together and are heat treated with a “low temperature” anneal that will eliminate the stress corrosion cracking problem. In the following description, like reference characters designate like or corresponding parts throughout the several views of the drawings. Also, in the following description, it is to be understood that such terms as “forward”, “rearward”, “left”, “upwardly”, “downwardly” and the like are words of convenience and are not to be construed as limiting terms. Referring now to the drawings and particularly to FIG. 1, there is shown an elevational view of a fuel assembly, represented in vertically shortened form and being generally designated by reference character 10. The fuel assembly 10 is the type used in a pressurized water reactor and has a structural skeleton which, at its lower end, includes the debris filter bottom nozzle 12, which is described more fully in co-pending application Ser. No. 10/751,349. The bottom nozzle 12 supports the fuel assembly 10 on a lower core support plate 14 in the core region of the nuclear reactor (not shown). In addition to the bottom nozzle 12, the structural skeleton of the fuel assembly 10 also includes a top nozzle 16 at its upper end and a number of guide tubes or thimbles 18, which extend longitudinally between the bottom and top nozzles 12 and 16 and at opposite ends are rigidly attached thereto. The fuel assembly 10 further includes a plurality of transverse grids 20 axially spaced along, and mounted to, the guide thimbles 18 and an organized array of elongated fuel rods 22 transversely spaced and supported by the grids 20. Also, the assembly 10 has an instrumentation tube 24 located in the center thereof and extending between and either captured by or mounted to the bottom and top nozzles 12 and 16. With such an arrangement of parts, fuel assembly 10 forms an integral unit capable of being conveniently handled without damaging the assembly of parts. As mentioned above, the fuel rods 22 in the array thereof in the assembly 10 are held in spaced relationship with one another by the grids 20 spaced along the fuel assembly length. Each fuel rod 22 includes nuclear fuel pellets 26 and is closed at its opposite ends by upper and lower end plugs 28 and 30. The pellets 26 are maintained in a stack by a plenum spring 32 disposed between the upper end plug 28 and the top of the pellet stack. The fuel pellets 26, composed of fissile material, are responsible for creating the reactive power of the reactor. A liquid moderator/coolant such as water or water containing boron, is pumped upwardly through a plurality of flow openings in the lower core plate 14 to the fuel assembly. The bottom nozzle 12 of the fuel assembly 10 passes the coolant upwardly through the guide tubes 18 and along the fuel rods 22 of the assembly in order to extract heat generated therein for the production of useful work. To control the fission process, a number of control rods 34 are reciprocally movable in the guide thimbles 18 located at predetermined positions in the fuel assembly 10. Specifically, a rod cluster control mechanism 36 positioned above the top nozzle 16 supports the control rods 34. The control mechanism has an internally threaded cylindrical member 37 with a plurality of radially extending flukes or arms 38. Each arm 38 is interconnected to a control rod 34 such that the control rod mechanism 36 is operable to move the control rods vertically in the guide thimbles 18 to thereby control the fission process in the fuel assembly 10, all in a well-known manner. As mentioned above, fuel assembly damage due to debris trapped at or below the lower most one of the grids 20 supporting the fuel bearing regions of the fuel rods has been found to be a problem. Therefore, to prevent the occurrence of such damage, it is highly desirable to minimize the debris that passes through the bottom nozzle flow holes or the interfaces between the outlets of the bottom nozzle flow holes and the adjoining structures. The invention described in U.S. patent Ser. No. 10/751,349, relates to a bottom nozzle 12 which, in addition to supporting the fuel assembly 10 on the lower core support plate 14, also contains features which function to filter out potentially damaging sized debris from the coolant flow passed upwardly through the bottom nozzle, with a reduction in pressure drop over previous designs. The bottom nozzle 12 includes support means, for example, the skirt 40 shown in FIG. 1. The support means, skirt 40 in this embodiment, includes a plurality of corner legs 42 for supporting the fuel assembly 10 on the lower core support plate 14. A generally rectangular planar plate 46 commonly referred to as the bottom nozzle adapter plate is suitable attached, such as by welding, to the upper surface 44 of the support skirt 40. In the nozzle adapter plate 46 of the debris filter bottom nozzle 12, a large number of small holes (not shown) are concentrated in the area of the flow holes through the lower core support plate 14 and are sized to filter out damaging sized debris without adversely affecting flow or the pressure drop through the bottom nozzle adapter plate 46 and across the fuel assembly 10, which substantially covers every portion of the plate 46 across its length and breadth. The diameter of the flow holes through the bottom nozzle adapter plate 46 does not allow passage of most of the debris that is of the size typically caught in the lower most support grid 20. If the debris is small enough to pass through these plate flow holes, it will in most case also pass through the grids 20 since the diameter of flow holes are small enough to catch most of the debris having a cross section larger than that of unoccupied spaces through a fuel bearing cell of the support grid 20. By ensuring that most of the debris is small enough to pass through the grids unoccupied spaces, the debris filter bottom nozzle 12 significantly reduces the potential for debris induced fuel rod failures. It should be appreciated that the improvement of co-pending U.S. application Ser. Nos. 10/751,349 and 10/932,908 do not require that the narrowest cross section of the flow through holes in the bottom nozzle adapter plate 46 be equal to or smaller than the largest cross sectional dimension of the unoccupied spacers through a fuel bearing cell of the support grid 20, especially when the outlet of the flow through the holes in the adapter plate effectively operate in junction with adjoining structures, such as this invention, to further constrict the flow path. For example, when protective grids such as that of this invention, are employed, which typically are located approximately 0.025 to 0.125 inches (0.064 to 0.318 cm) above the nozzle plate 46, the grid straps and protrusions further delimit the flow and trap debris in the area within and between the protective grid and the nozzle adapter plate 46. The improved debris catching system of this invention provides an integrated spacer grid design to be used in a nuclear fuel assembly to support fuel rods and filter entrained debris in the coolant without substantially changing the overall height of the grid over conventional designs, which is approximately 1.522 inches (3.866 cm.) for the inner strap design. The spacer grid design has multi-level debris catching features which provide the debris filtering function. The filtering features include debris filtering arches, which may be similar to the dimples which support the fuel rods under the pressure of opposing grid springs, except that the debris filtering arches do not contact the fuel rods, but reduce the fretting wear by trapping debris at fuel rod solid end plug elevations. Three debris catching systems, working with the debris filter bottom nozzle described above, provide an improved integrated design. Like many conventional spacer grids, the lower most spacer grid 48 of this invention is comprised of straight grid straps 50 and 52 that are interleaved together to form an egg-crate configuration having a plurality of roughly square cells 54 and 56 as shown in FIG. 2. A spaced, parallel array of a plurality of grid straps 50 of equal length are positioned orthogonal to a second plurality of spaced, parallel grid straps 52 of equal length and are encircled by a border strap 58, with each of the straps being welded together at their intersections. The cells 54 support fuel rods while the cells 56 support guide tubes and an instrumentation tube which passes through the center cell. Because the fuel rods must maintain a spacing or pitch between each other, these straight straps 50 and 52 at the locations that border the cells 54 that support the fuel rods have springs 60 and/or dimples 62 that are stamped in the sides of the straps 50, 52 and 58 to protrude into the cells 54 to contact the fuel rods and hold them firmly in position. The stamped features on the grid straps 50 and 52, i.e., the springs 60 and the dimples 62, require careful design and precise manufacturing to assure adequate forces are maintained to secure the fuel rods when considered in combination with the other grids 20 in the tandem array of grids along the fuel assembly. The grid 48 of this invention, as can better be appreciated from FIGS. 3 and 4 also includes on each wall of the cells 54 that support fuel rods, a laterally oriented arch at each lower corner with an additional laterally oriented dimple 66 approximately centered laterally on the wall and spaced above the arches 64. The additional dimples 66 substantially covers the lateral distance between the arches 64 though it should be appreciated that the width of the arches 64 could be increased and the width of the dimples 66 decreased so long as the combined width of the arches 64 and the dimple 66 substantially cover the width of the wall of the cell. The arches 64 and the dimple 66 extend approximately the same distance into the cell and are sized so that they do not contact the fuel elements. The sole function of the arches 64 and the dimple 66 is to catch debris. Similarly, a second pair of arches 64′ and a dimple 66′ are formed just above the arches 64 and dimples 66, just described, but the latter arches and dimple extend in the opposite direction into the adjacent cell to perform the same function in the adjacent cell. An additional dimple 70 and 70′, oriented in the vertical direction, protrudes into the adjacent cells and is designed to contact the fuel rods which are pressured against the dimples 70 and 70′ respectively by springs 68 and 68′ protruding into the adjacent cells from the opposite cell walls. A vertically oriented spring 68 is substantially centered on the wall between the dimple 66 and the dimple 70 and protrudes into the cell to contact and pressure the fuel rod against a corresponding dimple 70 on the opposite cell wall. The springs and dimples on adjacent cell walls on a given strap 50, 52 protrude in opposite directions as shown in FIG. 4. Of the two vertically adjacent dimples 66 and 66′ the upper dimple 66′ is always the one that contacts and supports the fuel rod while the lower one is spaced from the fuel rod and performs the debris catching function in conjunction with the arches 64. The lower arches 64 on a given strap are always stamped in the same direction with the upper arches 64′ stamped in the opposite direction so that all of the corresponding arches have the same elevation, from cell to cell and extend in the same direction, for ease of manufacture. The springs 68 bias the fuel rods against the dimples 66′ and 70 on the opposite walls of the cell while the arches 64 and dimples 66 cooperate to trap debris. The straps 50, 52 are preferably made from a 0.0105 inch (0.0267 cm) nickel plated alloy-718, are brazed together and are heat treated using a “low temperature” anneal. The “low temperature” anneal avoids the excessive grain growth experienced by the prior art using a “high temperature” anneal. The “low temperature” anneal temperature range is 950˜1000° C. and the “high temperature” anneal temperature range is 1030˜1070° C. The excessive grain growth is believed to have caused the stress corrosion cracking experienced by the prior art. The fatigue issues which are currently observed in the prior art grids will be overcome because the new grid design of this invention will be a stiffer structure that will not have the same vibration characteristics as the prior art lower most grid. While the grid is stiffer, its height, approximately 2.025 inch (5.141 cm.) for the inner strap, is not increased over that of the prior art so it will not adversely affect the stiffness of the fuel assembly. It should be noted that the straps illustrated in FIGS. 3 and 4 are straps that correspond to one or the rows within the fuel assembly of FIG. 2 that does not interface with the cell that is attached to a control rod guide thimble. The walls of the cells that interface with the guide thimbles have neither arches, dimples or springs which extend into those cells 56. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalents thereof.
	abstract	A cooling system (10) for an extreme ultraviolet (EUV) grazing incidence collector (GIC) mirror assembly (240) having at least one shell (20) with a back surface (22) is disclosed. The cooling system has a plurality of spaced apart circularly configured cooling lines (30) arranged in parallel planes (PL) that are perpendicular to the shell central axis (AC) and that are in thermal contact with and that run around the back surface. Input and output secondary cooling-fluid manifolds (44, 46) are respectively fluidly connected to the plurality of cooling lines to flow a cooling fluid from the input secondary cooling-fluid manifold to the output cooling secondary fluid manifold over two semicircular paths for each cooling line. Separating the cooling fluid input and output locations reduces thermal gradients that can cause local surface deformations in the shell that can lead to degraded focusing performance.
054085080	claims	1. A system for simultaneously testing at least any two control rod clusters contained within a reactor vessel, the system comprising: a) a control rod drive mechanism attached to said control rod clusters for retracting said control rod clusters from within the reactor vessel to a position suitable for testing; b) electrical power means connected to said control rod drive mechanism for supplying electrical power to said control rod drive mechanism and for terminating the power to said control rod drive mechanism and, when terminated, causing all said control rod clusters to fall into the reactor vessel; c) a rod position indicator attached to said control rod drive mechanism for monitoring the position of said control rod clusters; and d) computing means operatively connected to said rod position indicator and receiving a signal representing a fall time of each control rod cluster for substantially simultaneously generating an elapsed time profile of all said control rod clusters falling into the reactor vessel. (a) withdrawing at least the two control rod clusters to a position suitable for testing; (b) causing at least the two control rod clusters to simultaneously fall into the reactor vessel; (c) transmitting a signal to a computing means representing a fall time of each tested control rod cluster; and (d) substantially simultaneously generating an elapsed time profile for each control rod cluster by the computing means. 2. The system as in claim 1, wherein said computing means includes means for determining a dashpot entry time and a turnaround time. 3. The system as in claim 2, wherein said computing means includes means for displaying the elapsed time profile of a control rod cluster in increments of one millisecond. 4. The system as in claim 3, wherein said computing means includes means for storing each control rod profile. 5. The system as in claim 4, wherein said computing means includes means for converting an analog signal to a digital signal. 6. The system as in claim 5, wherein said computing means is located outside a containment building for minimizing exposure to any radiation. 7. A method for simultaneously testing at least any two control rod clusters contained within a reactor vessel, comprising the steps of: 8. The method as in claim 7 further comprising the step of computing a dashpot entry time and a turnaround time by the computing means. 9. The method as in claim 8 further comprising the step of displaying the elapsed time profile of each control rod cluster in one millisecond increments for analysis of any problems.
	summary
042591546	description	DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, the reference numeral 1 designates the overall structure of the nuclear reactor containment which includes a closure casing 2. The closure casing 2 is divided by a diaphragm floor 3 into a conical drywell 4 and a cylindrical pressure suppression chamber 5, and a plurality of bent downcomer tubes 6 extends through the diaphragm floor 3. As shown in FIG. 2, the diaphragm floor 3 is, as in a conventional manner, arranged such that radial beams 7 are supported at their inner ends by a pressure vessel pedestal 8 and are radially positioned from the pedestal 8 to shear keys 9, and a plurality of lateral beams 10 is provided between the radial beams 7 for connection thereof. It is preferable that there are provided auxiliary radial beams 11 between the lateral beams 10 for reinforcement thereof. In this embodiment, each of the beams 7, 10 and 11 is made of a H-shaped structural steel, and as shown in FIGS. 4 and 7 the connection of these beams adjacent to each other is made by cutting away the upper and lower flange portions of one H-shaped structural steel by an appropriate length and then welding the end of the web portion thereof to the side of the web portion of the other H-shaped structural steel. The lower surface of the respective radial beam 7 is coated a steel plate layer 12 secured thereto by welding or bolts, and the radial beam 7 at its portion near the outer end is supported in the vertical direction by a vertical column 13 extending from a bottom portion of the pressure suppression chamber 5. The outer end of the respective radial beam 7 is, as in a conventional manner, supported by the shear key 9 provided on the inner surface of the closure casing, and the shear key 9 has an ordinal arrangement adapted to permit the vertical and radial deformations of the associated radial beam, but restrain the deformation in the circumferential direction of the diaphragm floor. Embedded and provided between the radial beams 7 and on the steel plate layer 8 is a concrete layer 14 which comprises as shown in FIGS. 3 and 5 a central layer 15 including reinforcing steels (not shown), and upper and lower layers 16 and 17 for insulating heat and which are not provided with any reinforcing steel. The connection between the diaphragm floor 3 and the pedestal 8 is made by means that a plurality of anchor bolts 19 extending through a steel plate 18 provided circumferentially of the pedestal to serve as a mold is embedded in the central and upper concrete layers 15 and 16. The reference numeral 20 designates an annular sealing bellows provided around the outer periphery of the diaphragm floor 3. With the arrangement described above, the first embodiment of the present invention is advantageous in that since the concrete layer 14 which is a main member for providing the diaphragm floor 3 with rigidity, it is possible to substantially align the axis of the rigidity of the diaphragm floor 3 with the level of the shear keys 9, and the horizontal load at an earthquake is directly transmitted from the pedestal 8 to the shear keys 9 such that there will be caused no bending moment on the shear keys 9 and no such torsion in the closure casing 2 and diaphragm floor 3 as is often caused in the conventional structure. Since the concrete is embedded between the structural steels, furthermore, it is possible to greatly decrease or omit the amount of the reinforcing steels and there is no need to provide the stud bolts in the connection of the steel plate layer 12 and the concrete layer 14 thereby to expect the simplification of the concrete placing and the increase in the strength of the construction. Moreover, the overall thickness of the diaphragm floor 3 may be equal to the thickness of the structural steels such that the thickness of the diaphragm floor itself can be reduced to provide a space larger than the drywell of the containment. FIGS. 6 and 7 show another embodiment of the connecting means between the diaphragm floor 3 and the pedestal 8. There is provided a steel plate 21 wound around the outer periphery of the pedestal 8, and a plurality of fin-like anchor plates 22 is welded on the steel plate 21 to extend radially of the nuclear reactor containment, the anchor plates 22 is also welded or bolted to the radial beams 7. The other parts of this embodiment are similar to those of the first-mentioned embodiment. Although the embodiments described above are arranged such that the steel plate layer 12 is coated on the lower surface of the radial beams 7, it is also possible to arrange that the steel plate layer is formed by bridging the steel plates across the lower flanges of the H-shaped steel radial beams with the ends of the steel plate riding on the upper side of the lower flanges. In this case, the disposition of the steel plates becomes more easy. In case of using a mold to form the bottom surface of the concrete layer 14, furthermore, it is possible to form the steel plate layer 12 on the upper side of the radial beams 7, and the layer may be omitted therefrom. It is, moreover, appreciated that the radial beams and the other beams can be made of other structural steels than the H-shaped steels.
	summary
	summary
051209730	claims	1. A device for inserting and withdrawing radioactive radiation sources into and from applicators, comprising at least one shielded loading and/or storage station for the radiation sources and a flexible thrust wire that is guided in a channel and has a coupling that releases said radiation sources in the radiation position, said device also comprising: two drives connected respectively with a thrust and a traction wire each guided in a channel, said channels being combined in a fork, said traction wire cooperating with a radiation source in a releasable coupling effective in the direction of traction and said thrust wire cooperating with a radiation source in a releasable coupling effective only in the direction of thrust; a switch located between the channels leading to the applicators and those leading to the loading and/or storage station on the one side and the fork on the other side; and a release means for the coupling effective in the direction of traction located between the switch and the fork. 2. A device according to claim 1 wherein the radiation sources consist of needle-shaped holders that are filled with radioactive material and have at one end a sleeve having inwardly-facing spring elements which, together with a pin that can be inserted in the sleeve and has a diameter such that it cooperates with the ends of the springs, forms the releasable coupling effective in the direction of traction. 3. A device according to claim 2, wherein the release means for the coupling effective in the direction of traction comprises a stop that cooperates with an end face of the sleeve. 4. A device according to claim 3, wherein the greatest diameter of the end of the traction wire with the pin is smaller than the diameter of the sleeve and the stop consists of a duct for the wire having an internal diameter greater than the diameter of the end of the traction wire with the pin but smaller than the diameter of the sleeve. 5. A device according to claim 1, wherein the radiation sources consist of needle-shaped holders that are filled with radioactive material and have on one end a sleeve having resilient, inwardly-directed hooks which, together with a pin located at one end of the traction wire and having a locking groove to engage the hooks, forms the releasable coupling effective in the direction of traction. 6. A device according to claim 5 wherein the release means for the coupling effective in the direction of traction comprises wedge faces that engage under oblique faces on the hooks, the greatest diameter of the end of the traction wire with the pin is smaller than the diameter of the sleeve, and the internal diameter of a wire duct through the release means is greater than the diameter of the end of the traction cable with the faces but smaller than the sleeve diameter. 7. A device according to claim 1, wherein the radiation sources consist of needle-shaped holders that are filled with radioactive materials and of which one end consists of a magnetic material that, together with an extension made of magnetic material on one end of the traction wire, forms the releasable coupling effective in the direction of traction. 8. A device according to claim 7, wherein the release means for the coupling effective in the direction of fraction consists of a stop that cooperates with an end face of the end of the holder. 9. A device for inserting and removing radioactive radiation sources into and from applicators wherein said sources can be transported between a loading and/or storage station by means of flexible wires coupled to said sources and guided through channels, said device comprising first and second drives respectively for a traction and a thrust wire, channels for said traction and thrust wires leading from said drives and combining in a fork into a common channel switchably connectable by a switching means to channels leading respectively to at least one shielded loading and/or storage container and to said applicators, said traction wire cooperating with a radiation source in a releasable coupling effective in the direction of traction and said thrust wire cooperating with a radiation source in a releasable coupling effective only in the direction of thrust, and means for releasing said coupling effective in the direction of traction located between said switching means and said fork.
	description	1. Field of the Invention The present invention relates, in general, to removal of core decay heat in a pool type liquid metal reactor which uses liquid sodium as a coolant when a normal heat removal system breaks down and, more particularly, to a direct pool cooling type passive safety grade decay heat removal method and system for a liquid metal reactor, which is capable of providing a large heat removal capacity suitable in design of a large thermal rated liquid metal reactor, and for minimizing heat loss during the normal plant operation while improving operational reliability. 2. Description of the Related Art A general liquid metal reactor (LMR) is provided with a residual heat removal system (RHRS) for removing core decay heat arising due to urgent shutdown of the reactor when a normal heat removal system, which is formed through a reactor core, primary heat transport system (PHTS), an intermediate heat exchanger (IHX), intermediate heat transport system (IHTS) and a steam generator system (SGS), breaks down. A conventional residual heat removal system for a pool type liquid metal reactor is designed to effectively remove core decay heat using thermal inertia of a hot pool disposed above a core outlet. The conventional residual heat removal systems are generally classified into the passive vessel cooling system (PVCS) and the direct reactor cooling system (DRCS) according to a residual heat removal capacity on the basis of thermal output of the core of a liquid metal reactor. FIG. 9 shows the passive vessel cooling system (PVCS). When a normal heat removal system breaks down, sodium in a hot pool 150 is heated, and accordingly expanded. The expansion of the sodium raises its liquid level X1 above an overflow slot on a reactor baffle 130. As hot sodium heated in a core 110 flows over the overflow slot, it makes direct contact with a reactor vessel 100 so that convection and conduction heat transfer is performed between the hot sodium and the reactor vessel 100. In this way, core decay heat is removed. The passive vessel cooling system is a system applicable to small and medium thermal rated pool type liquid metal reactors with relatively low core heat output of 1,000 MWth or less. Specifically, the heat absorbed into the reactor vessel 100 by means of the convection and the conduction is transmitted to a containment vessel 230 disposed outside the reactor vessel 100 by means of thermal radiation. The heat of the containment vessel 230 is absorbed by air flowing through an air channel radially divided by an air separator 220 disposed between the containment vessel 230 and a reactor support wall made of concrete and surrounding the containment vessel 230. Finally, the air heated in the air channel inside the air separator 220 is continuously discharged into the atmosphere, and external cold air is continuously introduced along the air channel outside the air separator. Through natural circulation of air as described above, the core decay heat is passively and continuously removed. The passive vessel cooling system requires neither operator action nor any active component actuation when the normal heat removal system breaks down. Consequently, this system has an advantage in that it adopts a completely passive concept, by which operational reliability is guaranteed. However, the passive vessel cooling system is not applicable to a large thermal rated reactor since it can only be suitably used in a liquid metal reactor with relatively low core heat output of 1,000 MWth or less, as mentioned above, considering economical efficiency based on heat transfer surface area determined by the diameter of the reactor vessel and the related requirement for accommodating components in the pool. FIG. 10 shows the direct reactor cooling system (DRCS). As shown in FIG. 10, the direct reactor cooling system comprises a sodium-sodium heat exchanger 20′ disposed in a hot pool 150 in such a manner that it is below the liquid level X2 of hot sodium in the hot pool 150, a sodium-air heat exchanger 40′ disposed on a reactor building, and a heat removing sodium loop 30′ connected between the sodium-sodium heat exchanger 20′ and the sodium-air heat exchanger 40′. The direct reactor cooling system is a system for discharging heat into a final heat sink, i.e., the atmosphere through natural circulation of sodium using density difference in the heat removing sodium loop 30′ formed by elevation difference between a heat inflow part and a heat sink part. The direct reactor cooling system has advantages in that it is not restricted by heat output of the core unlike the aforesaid passive vessel cooling system, and in that it provides a sufficient decay heat removal capacity required according to the goal of design. In the direct reactor cooling system (DRCS), however, heat must be continuously supplied even in the normal plant operation in order to prevent solidification of liquid sodium in the heat removing sodium loop 30′ when the heat is transmitted from the hot pool 150 to the sodium-air heat exchanger 40′ via the heat removing sodium loop 30′. Such heat supplied during the normal plant operation is considered as a heat loss of a pool type liquid metal reactor system. Consequently, the direct reactor cooling system is designed to have the following components to minimize the heat loss during the normal steady-state conditions. In an air flow inlet 43′, through which air is introduced into the sodium-air heat exchanger 40′, and an air flow outlet 47′, through which air is discharged from the sodium-air heat exchanger 40′, are disposed dampers 170, respectively. In addition, isolation valves 180 are mounted in the heat removing sodium loop 30′. The flow rate of sodium and air is controlled by proper manipulations for the opening fraction of the dampers 170 and the isolation valves 180 so that the minimum amount of heat necessary to prevent solidification of the liquid sodium is supplied to the heat removing sodium loop 30′ during the normal plant operation. Consequently, the heat loss is minimized during the normal plant operation of the hot pool. When the normal heat removal system breaks down, the dampers 170 and the isolation valves 180 are opened to the maximum extent so that the core decay heat is effectively removed. As described above, the isolation valves 180 are disposed in the heat removing sodium loop 30′, and the dampers 170 are disposed in the air flow inlet 43′ and the air flow outlet 47′, so that the opening fraction of the isolation valves 180 and the dampers is controlled to supply proper amount of heat necessary both for minimizing a heat loss in the normal plant operation and for preventing solidification of sodium in the heat removing sodium loop 30′. To increase operational reliability of the decay heat removal system during system transient conditions, the isolation valves 180 and the dampers 170 are designed with a specific safety grade so that the direct reactor cooling system has a passive concept. In the direct reactor cooling system, however, mechanical driving requirements of the isolation valves 180 and the dampers 170 must be satisfied, which means that decay heat removal function on the basis of the completely passive concept is impossible. Furthermore, the direct reactor cooling system (DRCS) is inferior to the passive vessel cooling system (PVCS) in terms of operational safety related to operational reliability of the decay heat removal system. Therefore, the present invention has been made in view of the above problems, and it is an object of the present invention to provide a direct pool cooling type passive safety grade decay heat removal method and system for a liquid metal reactor, which are capable of providing a large heat removal capacity required by a large thermal rated pool type liquid metal reactor, having a completely passive concept so that core decay heat is always effectively removed without operator action or any active component actuation, and minimizing heat loss during the normal plant operation while improving operational reliability. In accordance with one aspect of the present invention, the above and other objects can be accomplished by the provision of a direct pool cooling type passive safety grade decay heat removal method for a liquid metal reactor, wherein liquid level difference between a hot pool defined above the reactor core and inside a reactor baffle and a cold pool defined between the reactor baffle and the inner wall of a reactor vessel is maintained by a primary pumping head under normal steady-state conditions, the interior of the reactor vessel being partitioned into the hot pool and the cold pool by the reactor baffle, wherein a sodium-sodium heat exchanger connected to a sodium-air heat exchanger mounted above a reactor building via a heat removing sodium loop is disposed at the position higher than a liquid level of the sodium in the cold pool under the normal steady-state conditions, and wherein the liquid level of the sodium in the cold pool rises so that the liquid level difference between the hot pool and the cold pool is eliminated when the primary pump trip occurs due to a breakdown of a normal heat removal system, and the sodium in the hot pool is expanded due to a continuously generated core decay heat so that the sodium in the hot pool overflows into the cold pool to form natural circulation between the hot pool and the cold pool, whereby the sodium-sodium heat exchanger makes direct contact with the hot sodium so that the core decay heat is discharged into a final heat sink, the atmosphere. Preferably, the outer circumference of the reactor vessel is also cooled with external air by using a passive vessel cooling system. Preferably, at least one circular vertical tube is disposed in the hot pool inside the reactor baffle, the circular vertical tube has the lower end communicating with the cold pool so that the sodium in the circular vertical tube has the same liquid level as the liquid level of the sodium in the cold pool, and the upper end extended upward to the extent that it is placed at the position higher than a liquid level of the sodium in the hot pool under the normal steady-state conditions, the sodium-sodium heat exchanger is disposed in the circular vertical tube while it is placed at the position higher than the liquid level of the sodium in the cold pool under the normal steady-state conditions, and heat transfer by thermal radiation is performed between the inner circumference of the circular vertical tube and the sodium-sodium heat exchanger under the normal steady-state conditions so that solidification of the sodium in the heat removing sodium loop is prevented. Preferably, the core decay heat is removed by the combination of the heat removing sodium loop and the sodium-air heat exchanger on the basis of a completely passive concept without the provision of dampers disposed in an air inlet and an air outlet of the sodium-air heat exchanger and isolation valves mounted in the heat removing sodium loop. Preferably, the heat transfer by thermal radiation is quantitatively controlled by manipulating surface emissivity of the sodium-sodium heat exchanger and the circular vertical tube to minimize heat loss under the normal steady-state conditions so that the minimum amount of heat necessary to prevent solidification of the sodium is supplied to the heat removing sodium loop. In accordance with another aspect of the present invention, there is provided a direct pool cooling type passive safety grade decay heat removal system for a liquid metal reactor comprising a reactor vessel having the interior partitioned into a hot pool and a cold pool by a cylindrical reactor baffle, the hot pool being defined above a core and inside the reactor baffle, the cold pool being defined between the reactor baffle and the inner wall of the reactor vessel, liquid level difference between the hot pool and the cold pool being maintained by a primary pumping head under normal steady-state conditions, wherein the decay heat removal system for removing core decay heat when a normal heat removal system breaks down comprises, at least one sodium-sodium heat exchanger disposed in the cold pool while being placed at the position higher than a liquid level of the sodium in the cold pool under the normal steady-state conditions so that only heat transfer by thermal radiation is performed under the normal steady-state conditions, at least one sodium-air heat exchanger mounted above a reactor building, and a heat removing sodium loop connected between the sodium-sodium heat exchanger and the sodium-air heat exchanger. Preferably, the direct pool cooling type passive safety grade decay heat removal system of the present invention further comprises at least one circular vertical tube disposed at the edge of the hot pool inside the reactor baffle, the circular vertical tube having the lower end communicating with the cold pool so that the sodium in the circular vertical tube is maintained with the same liquid level as the liquid level of the sodium in the cold pool, and the upper end disposed at the position higher than a liquid level of the sodium in the hot pool, wherein the sodium-sodium heat exchanger is disposed in the circular vertical tube while it is placed at the position higher than the liquid level of the sodium in the cold pool under the normal steady-state conditions. Preferably, the sodium-air heat exchanger is not provided at an air inlet and an air outlet thereof with dampers, and the heat removing sodium loop is not provided with isolation valves. Preferably, the sodium-sodium heat exchanger comprises, a U-shaped heat transmitting unit consisting of a cold sodium downcomer vertically arranged in the sodium-sodium heat exchanger while being disposed along the center of the sodium-sodium heat exchanger, the upper end of which is connected to a cold leg of the heat removing sodium loop, and a plurality of heat transmitting tubes surrounding the outer circumference of the cold sodium downcomer, the heat transmitting tubes being concentrically arranged while they are uniformly spaced apart from each other in the radial direction, and a heated sodium collector provided at the upper part of the U-shaped heat transmitting unit, the heated sodium collector communicating with the heat transmitting tubes and connected to a hot leg of the heat removing sodium loop. Preferably, the sodium-sodium heat exchanger is disposed in such a manner that the lower end of the heated sodium collector is placed at the position higher than a liquid level of the sodium rising by pool sodium expansion under transient conditions. Now, a preferred embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following, the decay heat removal method and system of the present invention will be specifically described on the basis of a liquid metal reactor to which the decay heat removal system of the present invention is applied. As shown in FIGS. 1 and 2, a liquid metal reactor, to which the decay heat removal system according to the preferred embodiment of the present invention is applied, comprises a reactor vessel 100, a reactor core 110 concentrically disposed in the lower part of the reactor vessel 100, and a cylindrical core support barrel 120 surrounding the reactor core 110 and extended upward to a predetermined height above the reactor core 110. To the cylindrical core support barrel 120 is attached a ring-shaped separating plate 125, which is vertically extended from the outer circumference of the core support barrel 120 and horizontally disposed. To the edge of the separating plate 125 is attached a cylindrical reactor baffle 130, which is vertically upwardly extended from the edge of the separating plate 125 and disposed between the inner wall of the reactor vessel 100 and the outer circumference of the core support barrel 120. The interior of the reactor vessel 100 is partitioned into a hot pool 150 and a cold pool 200. The hot pool 150 is defined above the reactor core 110 and the separating plate 125 and inside the reactor baffle 130, and the cold pool 200 is defined below the separating plate 125 and between the outer circumference of the reactor baffle 130 and the inner wall of the reactor vessel 100. The height of the reactor baffle 130 is higher than the liquid level X of sodium in the hot pool 150 during the normal plant operation so that overflow of hot sodium into the cold pool 200 is prevented. The height of the core support barrel 120 is lower than the liquid level X of sodium in the hot pool 150 so that the hot sodium is always filled in the space outside the core support barrel 120 in the hot pool 150. Between the outer circumference of the core support barrel 120 and the inner circumference of the reactor baffle 130 are disposed a plurality of intermediate heat exchangers (IHX) 140, which are components constituting a normal heat removal system. The intermediate heat exchangers 140 are preferably arranged in a predetermined array pattern. Between the outer circumference of the core support barrel 120 and the inner circumference of the reactor baffle 130 are also disposed a plurality of primary pumps 145 for pumping liquid sodium in the cold pool 200 into the hot pool 150 via the reactor core 110 so that a predetermined liquid level difference Z is maintained between the hot pool 150 and the cold pool 200 during the normal plant operation. The primary pumps 145 are also preferably arranged in a predetermined array pattern. The intermediate heat exchangers 140 are disposed in pairs, and each pair of intermediate heat exchangers 140 are connected to steam generators (not shown) disposed outside the reactor boundary so that heat generated from the reactor core 110 is removed during the normal plant operation. In piping connected between the intermediate heat exchangers 140 and the steam generators are mounted intermediate isolation valves 190 for stopping flow of internal sodium under transient conditions, i.e., when a severe accident including radioactive sodium leak from the intermediate heat exchanger 140 to the secondary system occurs. At the edge of the hot pool 150, which is close to the inside of the reactor baffle 130, are disposed three circular vertical tubes 10. Each circular vertical tube 10 has the lower end communicating with the cold pool 200 so that the sodium in each circular vertical tube 10 is maintained with the same liquid level as the liquid level Y of the sodium in the cold pool 200 by pumping head of the primary pumps 145. The upper end of each circular vertical tube 10 is disposed in such a manner that it is higher than the liquid level X of the sodium in the hot pool 150 during the normal plant operation like the reactor baffle 130. More specifically, the circular vertical tubes 10 are disposed between the inner wall of the reactor baffle 130 and the outer wall of the core support barrel 120 in such a manner that they are spaced uniformly apart from each other while they do not overlap with the intermediate heat exchangers 140 and the primary pumps 145, as shown in FIG. 2. The lower end of each circular vertical tube 10 penetrates through the separating plate 125 to communicate with the cold pool 200. The upper end of each circular vertical tube 10 is vertically extended in such a manner that the height of the upper end is identical to that of the reactor baffle 130. Consequently, the circular vertical tubes 10 do not communicate with the hot pool 150 but with the cold pool 200 so that the sodium in each circular vertical tube 10 has the same liquid level as the liquid level Y of the sodium in the cold pool 200 by pumping of the primary pumps 145. The outer circumference of each circular vertical tube 10 is in contact with the sodium in the hot pool 150. In the empty space above the hot pool 150 and the cold pool 200 including inside the circular vertical tubes 10 is filled an inert gas, such as helium, nitrogen, argon, etc. The filled inert gas absorbs small pressure fluctuation arising when the pressure is excessive in the hot and cold pools 150 and 200 so that relatively rapid over-pressurization of the entire system is prevented. In addition, the filled inert gas serves as a thermal insulation for decreasing the amount of heat transmitted from the hot pool 150 to the reactor head 160. As shown in FIG. 3, a sodium-sodium heat exchanger 20 is disposed in the circular vertical tube 10 in such a manner that the sodium-sodium heat exchanger 20 is placed at the position higher than the liquid level Y of the sodium in the cold pool 200 during the normal plant operation. Consequently, the sodium-sodium heat exchanger 20 is not in direct contact with the sodium in the cold pool 200, and thus only heat transfer by thermal radiation is performed between the sodium-sodium heat exchanger 20 and the inner circumference of the circular vertical tube 10. To the sodium-sodium heat exchanger 20 is connected a sodium-air heat exchanger 40, which is mounted above the reactor building, via a heat removing sodium loop 30 penetrating through the reactor head 160, so that the heat absorbed from the reactor pool is discharged from the sodium-air heat exchanger 40 to the atmosphere. In the sodium-air heat exchanger 40, direct heat exchange is performed between the heat transmitted from the hot pool 150 via the heat removing sodium loop 30 and an air introduced into the sodium-air heat exchanger 40 through an air inlet 43 formed at the lower part of the sodium-air heat exchanger 40 and discharged from the sodium-air heat exchanger 40 through an air outlet 47 formed at the upper part of the sodium-air heat exchanger 40 after the heat exchange between the heat transfer tube surface of the sodium-air heat exchanger and an air. The decay heat removal system for a liquid metal reactor of the present invention with the above-stated construction can minimize heat loss during the normal plant operation and supply the minimum amount of heat necessary to prevent solidification of the sodium in the heat removing sodium loop 30 during the normal plant operation without the provision of the dampers 170 disposed in the air flow inlet 43′ and the air flow outlet 47′ of the sodium-air heat exchanger 40′ and the isolation valves 180 mounted in the heat removing sodium loop 30′ as in the conventional direct reactor cooling system of FIG. 10. Consequently, the decay heat removal system for a liquid metal reactor of the present invention is operated on the basis of a completely passive concept. More specifically, the decay heat removal system of the present invention does not control the amount of heat removed from the decay heat removal system by controlling flow rate of the air through the dampers 170 during the normal plant operation and by controlling flow rate of the sodium through the isolation valves 180 during the normal plant operation, which is realized by complicated components including a mechanical driving unit. The decay heat removal system of the present invention quantitatively controls heat transfer rate by thermal radiation between the circular vertical tubes 10 and the sodium-sodium heat exchanger 20 through determination of the optimum surface emissivity of a heat transmitting surface so that the minimum amount of heat necessary to prevent solidification of the sodium is supplied to the heat removing sodium loop 30 during the normal plant operation. To efficiently remove decay heat and supply the minimum amount of heat necessary to prevent solidification of sodium, the sodium-sodium heat exchanger 20 includes a U-shaped heat transmitting unit 25, which is suitable to perform heat exchange between sodium and sodium by natural circulation, as shown in FIGS. 5 and 6, so that the decay heat removal system of the present invention provides more efficient heat removal performance under transient conditions as well as under normal steady-state conditions. The U-shaped heat transmitting unit 25 comprises a cold sodium downcomer 23 vertically arranged in the sodium-sodium heat exchanger 20 while being disposed along the center of the sodium-sodium heat exchanger 20, the upper end of which is connected to a cold leg 33 of the heat removing sodium loop 30, and a plurality of heat transmitting tubes 27 surrounding the outer circumference of the cold sodium downcomer 23. The heat transmitting tubes 27 are concentrically arranged while they are uniformly spaced apart from each other in the radial direction. Consequently, cold sodium moving downward through the cold sodium downcomer 23 efficiently absorbs the external heat as it moves upward through the heat transmitting tubes 27. Also, the sodium-sodium heat exchanger 20 is provided at the upper part thereof with a heated sodium collector 29 for collecting the sodium in the sodium-sodium heat exchanger 20 absorbing the heat from the hot sodium as it moves upward through the heat transmitting tubes 27. The heated sodium collected by the heated sodium collector 29 is supplied into the sodium-air heat exchanger 40 mounted above the reactor building via a hot leg 37 of the heat removing sodium loop 30 by natural circulation in the heat removing sodium loop 30 arising from density difference. The heat transmitting tubes 27 of the sodium-sodium heat exchanger 20 are uniformly arranged in the radial direction so that heat is properly transmitted into the heat removing sodium loop 30 through heat transfer by thermal radiation during the normal plant operation. Furthermore, the lower end of the heated sodium collector 29, which is disposed in the upper part of the sodium-sodium heat exchanger 20, is placed at the position higher than the liquid level X′ of the sodium rising by expansion of the sodium under transient conditions so that problems caused by direct contact of the heated sodium collector 29 and the hot sodium are eliminated and flow interference is minimized even when the hot sodium overflows into the circular vertical tube 10. The surface emissivity of the heat transmitting tubes 27 of the sodium-sodium heat exchanger 20 and the circular vertical tubes 10 may be controlled by various kinds of surface treatment, which changes surface roughness or degree of oxidization, so that the minimum amount of heat necessary to prevent solidification of the sodium is supplied to the heat removing sodium loop 30. Consequently, heat loss is minimized during the normal plant operation. The operation of the decay heat removal system of the present invention with the above-stated construction will now be described. Under normal steady-state conditions, the sodium is not filled in the upper part of the circular vertical tube 10 by liquid level difference Z generated from pumping head of the primary pump 145, as shown in FIG. 3. Consequently, heat transfer only by thermal radiation is performed between the inner circumference of the circular vertical tube 10 and the surfaces of the heat transmitting tubes 27 of the sodium-sodium heat exchanger 20 so that the heat from the hot pool 150 is absorbed by the sodium-sodium heat exchanger 20, and then the absorbed heat is supplied into the heat removing sodium loop 30. The heat supplied into the heat removing sodium loop 30 is used to prevent solidification of sodium in the heat removing sodium loop 30. Since such supply of the heat into the heat removing sodium loop 30 is heat loss from the point of view of efficiency of the entire liquid metal reactor system during the normal steady-state conditions, surface emissivity of the heat transmitting tubes 27 of the sodium-sodium heat exchanger 20 and the circular vertical tube 10 is properly controlled so that the minimum amount of heat transfer rate is permitted. Under transient conditions, for example, when the normal heat removal system through the intermediate heat exchanger (IHX) 140 breaks down, the primary pump 145 is automatically tripped, and accordingly the liquid level Y of the cold pool 200 rises with the result that the liquid level difference Z between the hot pool 150 and the cold pool 200 is eliminated, as shown in FIG. 4. Also, the sodium in the hot pool 150 is expanded due to the decay heat of the core 110 so that the liquid level X of the sodium in the hot pool 150 rises up to the liquid level X′ above the top elevation of the reactor baffle 130 and the circular vertical tube 10. Consequently, the hot sodium flows over the overflow slot on the reactor baffle 130 and the circular vertical tube 10, and flows into the annular space between the reactor vessel 100 and the reactor baffle 130 and into the circular vertical tube 10, in which the sodium-sodium heat exchanger 20 is mounted. At this time, the sodium-sodium heat exchanger 20 mounted in the circular vertical tube 10 makes direct contact with the hot sodium so that heat is transmitted from the hot sodium to the heat removing sodium loop 30 via the sodium-sodium heat exchanger 20. As a result of heat removal at the sodium-sodium heat exchanger, the density of the sodium inside the circular vertical tube 10 increases so that the density of the sodium inside the circular vertical tube 10 is higher than that of the sodium outside the circular vertical tube 10. Such density difference induces natural circulation of the sodium from the hot pool 150 to the cold pool 200. As the hot sodium flows through the annular space between the circular vertical tube 10 and the heat transmitting tubes 27 of the sodium-sodium heat exchanger 20, the heat exchange mechanism between the hot pool 150 and the sodium-sodium heat exchanger 20, which performs heat transfer only by thermal radiation during the normal steady-state conditions, converted into the heat exchange mechanism performing heat transfer by convection due to the flow of the hot sodium in the circular vertical tube 10. Consequently, rapid heat transfer is accomplished from the hot pool 150 and the sodium-sodium heat exchanger 20 so that the heat of the hot pool 150 is effectively removed. The operation of the sodium-sodium heat exchanger 20 under normal steady-state conditions and under transient conditions will be described in more detail. Under the normal steady-state conditions as shown in FIG. 5, sodium in the heat removing sodium loop 30, which has been cooled in the sodium-air heat exchanger 40, is introduced into the upper center part of the sodium-sodium heat exchanger 20, and moves downward along the cold sodium downcomer 23. After turning 180 degrees at the lower end of the cold sodium downcomer 23, the sodium moves upward along the heat transmitting tubes 27 surrounding the outer circumference of the cold sodium downcomer 23. At this time, the sodium moving upward along the heat transmitting tubes 27 absorbs heat necessary for preventing solidification of the sodium in the heat removing sodium loop 30 by means of a radiation heat transfer mechanism performing heat transfer by thermal radiation between the inner circumference of the circular vertical tube 10 and the heat transmitting tubes 27 of the sodium-sodium heat exchanger 20. The sodium absorbing the heat continuously moves upward by the density difference so that the sodium is collected in the heated sodium collector 29 above the heat transmitting tubes 27. The collected sodium is introduced into the sodium-air heat exchanger 40 via the hot leg 37 of the heat removing sodium loop 30. The sodium introduced into the sodium-air heat exchanger 40 is cooled by heat transfer between the sodium and the external air introduced into the sodium-air heat exchanger 40 via the air inlet 43. Thereafter, the cold sodium is supplied again into the sodium-sodium heat exchanger 20 via the cold leg 33 of the heat removing sodium loop 30. Under the transient conditions as shown in FIG. 6, sodium in the heat removing sodium loop 30, which has been cooled in the sodium-air heat exchanger 40, is introduced into the upper center part of the sodium-sodium heat exchanger 20, and moves downward along the cold sodium downcomer 23. After turning 180 degrees at the lower end of the cold sodium downcomer 23, the sodium moves upward along the heat transmitting tubes 27 surrounding the outer circumference of the cold sodium downcomer 23. At this time, the sodium moving upward along the heat transmitting tubes 27 rapidly absorbs heat by means of direct contact between the hot sodium introduced into the circular vertical tube 10 and the outer circumference of the sodium-sodium heat exchanger 20 and the convection heat transfer mechanism based on the natural circulation of the sodium from the hot pool 150 to the cold pool 200. The sodium absorbing the heat continuously moves upward so that the sodium is collected in the heated sodium collector 29 above the heat transmitting tubes 27. The collected sodium is introduced into the sodium-air heat exchanger 40 via the hot leg 37 of the heat removing sodium loop 30. The sodium introduced into the sodium-air heat exchanger 40 is cooled by a convection heat transfer between the sodium and the external air introduced into the sodium-air heat exchanger 40 via the air inlet 43. The aforesaid circulation of the heat removing sodium is continuously accomplished by means of the natural circulation caused by the density difference. Consequently, the core decay heat can be continuously discharged into the final heat sink, i.e., the atmosphere, without operator action or any active component actuation. The decay heat removal system of the present invention is capable of simultaneously performing the decay heat removal accomplished by the conventional passive vessel cooling system (PVCS), whereby the decay heat removal system of the present invention can be easily applied to a large thermal rated liquid metal reactor. In the liquid metal reactor equipped with the decay heat removal system of the present invention, the liquid level Y is low in the circular vertical tube 10, in which the sodium-sodium heat exchanger 20 is mounted, and in the annular space between the reactor baffle 130 and the reactor vessel 100, by the liquid level difference Z between the hot pool 150 and the cold pool 200 generated from pumping head of the primary pump 145 under the normal steady-state conditions as shown in FIG. 7. Consequently, the sodium-sodium heat exchanger 20 is enclosed by cover gas, which is filled in the upper part of the hot pool 150 and in the upper part of the cold pool 200, while it does not come into direct contact with the sodium. The cover gas filled in the annular space between the reactor vessel 100 and the reactor baffle 130 serves as a thermal cover as in the passive vessel cooling system (PVCS) so that only the minimum heat loss by a radiation heat transfer from the outer circumference of the reactor vessel 100 is incurred during the normal plant operation. The heat removal through the sodium-sodium heat exchanger 20 is accomplished only by a radiation heat transfer between the inner circumference of the circular vertical tube 10 and the heat transmitting tubes 27 of the sodium-sodium heat exchanger 20. In other words, the heat is transmitted to the heat removing sodium loop 30 only by a radiation heat transfer between the inner circumference of the circular vertical tube 10 and the heat transmitting tubes 27 of the sodium-sodium heat exchanger 20. Consequently, the amount of the heat transmitted to the heat removing sodium loop 30 is decreased as compared to the amount of the heat removed due to the heat transfer by direct contact with the sodium, and thus heat loss is minimized under the normal steady-state conditions. In the liquid metal reactor equipped with the decay heat removal system of the present invention, the primary pump 145 is not operated, and accordingly the liquid level Y of the sodium in the cold pool 200 rises with the result that the liquid level difference Z between the hot pool 150 and the cold pool 200 is eliminated, under transient conditions, for example, when the normal heat removal system breaks down, as shown in FIG. 8. The sodium in the hot pool 150 is expanded due to continuous generation of the core decay heat. Consequently, the hot sodium flows over the overflow slot on the reactor baffle 130 and the circular vertical tube 10, in which the sodium-sodium heat exchanger 20 is mounted, so that heat removal by direct contact of the inner circumference of the reactor vessel 100 and the hot sodium as in the passive vessel cooling system (PVCS) is performed, and simultaneously heat removal by direct contact of the sodium-sodium heat exchanger 20 in the circular vertical tube 10 and the hot sodium as in the direct reactor cooling system (DRCS) is also performed. In this way, the core decay heat is effectively discharged into the final heat sink, i.e., the atmosphere under the transient conditions. The direct pool cooling type decay heat removal system of the present invention is operated on the basis of the completely passive concept as in the passive vessel cooling system while it provides a large heat removal capacity, whereby the decay heat removal system of the present invention can be easily applied to a large thermal rated liquid metal reactor. As apparent from the above description, the present invention provides a direct pool cooling type passive safety grade decay heat removal method and system for a liquid metal reactor which are capable of effectively removing decay heat on the basis of a completely passive concept without the provision of dampers disposed in an inlet and an outlet of a sodium-air heat exchanger and isolation valves mounted in a heat removing sodium loop as in the conventional direct reactor cooling system and therefore without operational problems caused due to malfunction of active components for actuating the dampers and the isolation valves. In addition, the minimum amount of heat necessary to prevent solidification of the sodium is supplied to the heat removing sodium loop during the normal plant operation, whereby heat loss incurred by the decay heat removal system is minimized, and thus economical efficiency of the decay heat removal system according to the present invention is increased. With the heat removal system of the present invention, it is possible to design a large thermal rated liquid metal reactor capable of removing core decay heat while having high operational reliability without operator action or any active component actuation under transient conditions, as in the passive vessel cooling system (PVCS), which is applied to small and medium-sized liquid metal reactors. Furthermore, the decay heat removal system of the present invention is capable of performing decay heat removal accomplished by a direct reactor cooling system as well as decay heat removal accomplished by the passive vessel cooling system (PVCS), which are operated on the basis of a completely passive concept, whereby a large heat removal capacity suitable to design a large thermal rated liquid metal reactor is provided. The decay heat removal system of the present invention is also provided with a plurality of decay heat removal channels, whereby maximum safety is guaranteed with the improved operational reliability. In conclusion, the decay heat removal system of the present invention is operated on the basis of a completely passive concept with improved operational reliability. Heat loss incurred by the decay heat removal system is minimized under normal steady-state conditions, whereby economical efficiency is maximized. The decay heat removal system of the present invention can effectively remove core decay heat under transient conditions. Moreover, the decay heat removal system of the present invention provides an additional heat removal capacity obtained by the passive vessel cooling system, whereby the decay heat removal system of the present invention can be easily applied to a large thermal rated liquid metal reactor. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
	claims	1. A digital protection system having at least two channels and at least two trains, the system comprising:a reactor trip switchgear system (RTSS) including at least one reactor trip breaker (RTB) for each train to control a supply of power to a control element drive mechanism (CEDM), each RTB disposed between the supply of power and the CDEM;a process protection system having, in one channel, first and second comparative logic controllers of different types that are mutually independent of each other, the first and second comparative logic controllers each receiving process variables as inputs and each outputting comparison logic results;a reactor protection system having, in one train, first and second concurrent logic controllers of different types that are mutually independent from each other, the first and second concurrent controllers each receiving the comparison logic results as inputs and each outputting concurrent logic results, the reactor protection system comprising a first initiation circuit including a first pair of coils and a second initiation circuit including a second pair of coils, each of the first and second initiation circuits further including a series circuit in which a plurality of relays are connected in series and a parallel circuit in which a plurality of relays are connected in parallel,wherein one of the series circuit relays is controlled by receiving one of the concurrent logic results as an input and one of the parallel circuit relays is controlled by receiving the other of the concurrent logic results as an input, andwherein, according to the concurrent logic results, the first initiation circuit transmits a control signal to the RTSS via the first pair of coils and the second initiation circuit transmits a control signal to the RTSS via the second pair of coils. 2. The digital protection system of claim 1, wherein the at least two channels include a first channel, a second channel, a third channel, and a fourth channel. 3. The digital protection system of claim 1, wherein the at least two trains include a first train and a second train. 4. The digital protection system of claim 1, wherein the different types of comparative logic controllers include a field programmable gate array (FPGA) type and a programmable logic controller (PLC) type. 5. The digital protection system of claim 1, wherein the comparative logic controllers each transmit the comparison logic results only to concurrent logic controllers of one type. 6. The digital protection system of claim 1, wherein the process variables include information indicative of at least one of a reactor coolant hot-tube temperature, a reactor coolant cold-tube temperature, a reactor coolant flow rate, a pressurizer pressure, a pressurizer water level, a neutron flux value, a containment building pressure, a steam generator water level, a steam pipe pressure, and a refueling water tank level. 7. The digital protection system of claim 1,wherein the comparison logic results include one of a normal signal and an abnormal signal,wherein the first concurrent logic controller outputs the concurrent logic results based on the number of the comparison logic results and the number of the abnormal signals received from the first comparative logic controllers included in each channel, the outputted concurrent logic results of the first concurrent logic controller including a first output signal being input to one relay included in the series circuit and a second output signal being input to one relay included in the parallel circuit, the first and second output signals having opposite logic values, andwherein the second concurrent logic controller outputs the concurrent logic results based on the number of the comparison logic results and the number of the abnormal signals received from the second comparative logic controllers included in each channel, the outputted concurrent logic results of the second comparative logic controllers including a third output signal being input to one relay included in the series circuit and a fourth output signal being input to one relay included in the parallel circuit, the third and fourth output signals having opposite logic values. 8. The digital protection system of claim 7,wherein the first concurrent logic controller outputs the concurrent logic results when the received comparison logic results includes at least one abnormal signal, by outputting a first logic value to the series circuit and a second logic value to the parallel circuit, andwherein the second concurrent logic controller outputs the concurrent logic results when the received comparison logic results include at least one abnormal signal, by outputting the first logic value to the series circuit and the second logic value to the parallel circuit. 9. The digital protection system of claim 7,wherein the first concurrent logic controller outputs the concurrent logic results when the received comparison logic results includes at least one normal signal, by outputting a first logic value to the series circuit and a second logic value to the parallel circuit, andwherein the second concurrent logic controller outputs the concurrent logic results when the received comparison logic results include at least one normal signal, by outputting the first logic value to the series circuit and the second logic value to the parallel circuit. 10. The digital protection system of claim 1,wherein the supply of power is generated by a motor-generator (MG) set,wherein each RTB of the RTSS includes a normally open (NO) contact, andwherein the NO contacts of the RTBs includefirst and second NO contacts respectively connected between the MG set and a central node, andthird and fourth NO contacts respectively connected between the central node and the CDEM. 11. The digital protection system of claim 10, wherein, when at least one of the first NO contact and the second NO contact is closed and at least one of the third NO contact and the fourth NO contact is closed, power is supplied from the MG set to the CEDM. 12. The digital protection system of claim 10, wherein, when both the first NO contact and the second NO contact are open or both the third NO contact and the fourth NO contact are open, power supplied from the MG set to the CEDM is interrupted. 13. The digital protection system of claim 10,wherein the first initiation circuit further includes:a first series circuit for controlling the first NO contact according to an output signal from the concurrent logic controller; anda first parallel circuit for controlling the second NO contact according to the output signal from the concurrent logic controller, andwherein the second initiation circuit further includes:a second parallel circuit for controlling the third NO contact according to the output signal from the concurrent logic controller; anda second series circuit for controlling the fourth NO contact according to the output signal from the concurrent logic controller. 14. The digital protection system of claim 13, wherein the first series circuit and the first parallel circuit receive the output signals from the first concurrent logic controller and the second concurrent logic controller included in a first train of the at least two trains as inputs. 15. The digital protection system of claim 14, wherein the second series circuit and the second parallel circuit receive the output signals from the first concurrent logic controller and the second concurrent logic controller included in a second train of the at least two trains as inputs. 16. The digital protection system of claim 13,wherein the first initiation circuit further includes a third circuit including a relay for controlling the second NO contact, the relay for controlling the second NO contact being controlled by the first parallel circuit, andwherein the second initiation circuit further includes a fourth circuit including a relay for controlling the third NO contact, the relay for controlling the third NO contact being controlled by the first parallel circuit. 17. The digital protection system of claim 16, wherein the relays included in the third circuit and the fourth circuit are normally closed (NC) contacts. 18. The digital protection system of claim 13,wherein the first series circuit or the second series circuit includes two relays connected in series, the two series relays being respectively turned on/off according to the output signal from the concurrent logic controller, andwherein the first NO contact or the fourth NO contact is closed when the two relays are both on, and the first NO contact or the fourth NO contact is open when at least one of the two relays is off. 19. The digital protection system of claim 16,wherein the first parallel circuit or the second parallel circuit includes two relays connected in parallel, the two parallel relays being turned on/off according to the output signal from the concurrent logic controller,wherein the relay included in the third circuit or the fourth circuit is turned on when the relays included in the first parallel circuit or the second parallel circuit are all off, andwherein the relays included in the third circuit or the fourth circuit are turned off when at least one of the relays included in the first parallel circuit or the second parallel circuit is on. 20. The digital protection system of claim 1,wherein the at least one RTB of the RTSS includes a first pair of RTBs controlled by the first initiation circuit and a second pair of RTBs controlled by the second initiation circuit, andwherein the first pair of RTBs is disposed between the supply of power and a central node of the RTSS, and the second pair of RTBs is disposed between the central node of the RTSS and the CEDM.
046363360	description	The invention may be better understood by reference to the following examples which are intended to be illustrative of the process of the present invention and not in any way limitative thereof. EXAMPLE 1 The apparatus utilized comprised a commercially available spray dryer constructed of stainless steel. From the spray dryer exhaust, gases with their entrained solids were ducted directly to a fabric filter (commercially available baghouse filter). Sampling locations for gas analysis were, among other places, at the spray dryer inlet before any liquid waste enters the spray dryer and the spray dryer outlet. NO.sub.x measurements were made with a chemiluminescence analyzer. Temperatures also were monitored with the output recorded on a chart recorder. The gas flow rates through the spray dryer were determined by standard pitot tube transfer flow measurements and pressure also was monitored. The average residence time of liquid waste and hot gas in the spray dryer was calculated using the known volume of the spray dryer and flow rates of the waste and gas. A chelate-containing liquid waste was formulated comprising 90 wt. % water and 10 wt. % EDTA in complex with sodium. The waste was introduced into the spray dryer at ambient temperature where it was contacted with a hot gas having an average temperature of approximately 370.degree. C. to produce in a time of about 1.6 seconds an outlet gas having an average temperature of about 173.degree. C. and containing the dried chelating agent. The solid product was collected in the bag filter and recovered as a dry, flowable powder having a density of about 0.39 grams/cc. In contrast, utilizing the same waste and time it was found that if the outlet temperature was allowed to go below 150.degree. that a sticky residue formed on the walls of the spray dryer in such thickness as to necessitate terminating the test. EXAMPLE 2 A simulated copper-containing decontamination liquid waste was formulated. The liquid waste comprised 83.7 wt. % water, 2.5 wt. % EDTA, 5.3 wt. % tetrasodium EDTA, 5.2 wt. % ammonium hydroxide, 2.6 wt. % copper sulfate, and about 0.7 wt. % powdered anion and cation exchange resins. The exchange resins were added to act as abrasives to remove dried residue from the walls of the spray dryer. A finely atomized spray of the waste was introduced into the spray dryer where it was contacted with a hot gas stream having an initial or inlet temperature of 313.degree. C. In a time of about 1.8 seconds the gas temperature (as measured at the outlet of the spray dryer) was about 185.degree. C. The solid product was collected from the filter and found to be a dry, flowable powder having a density of about 0.25 grams/cc. During this test no increase in NO.sub.x was detected, thus demonstrating that the amine chelating agent had not undergone any decomposition. EXAMPLE 3 A simulated iron decontamination liquid waste was formulated. The liquid waste comprised 76.5 wt. % water, 15.4 wt. % EDTA, 1.05 wt. % FE.sub.2 O.sub.3 and 7.05 wt. % NH.sub.4 OH. The liquid waste was introduced into the spray dryer where it was contacted with a hot gas stream having an initial temperature of 313.degree. C. In a time of about 2.1 seconds the gas temperature (as measured at the spray dryer outlet) was reduced to about 172.degree. C. A solid product was recovered from the fabric filter in the form of a dry flowable powder which had a density of about 0.87 grams/cc. Further, throughout the test there was no increase in the NO.sub.x emissions which would have been indicative of any decomposition of the amine chelating agent. It is believed that the foregoing examples clearly demonstrate the efficacy of the present invention to treat a liquid waste containing an organic amine chelating agent to produce a dry, flowable powder of the agent. To demonstrate the benefits obtained from treating an organic amine chelating agent in accordance with the present invention, the following comparison is offered. When an EDTA liquid waste such as is described in Examples 2 and 3 is treated in accordance with the current required practice for such a low-level radioactive liquid waste containing an organic amine chelating agent, one cubic meter of the waste mixed with cement would produce a mixture which upon solidification, would have a volume of 1.7 cubic meters. In contrast, when that same waste from Example 3 is treated in accordance with the present invention it would produce a dry powder product having a volume of only 0.22 cubic meter and when blended with cement would have a volume of 0.56 cubic meter. Further, 1 cubic meter of the EDTA-copper liquid waste from Example 2, while producing a less dense powder, would still only have a volume of 0.48 cubic meter. When wetted and mixed with cement the resulting product would shrink to a volume of 0.21 cubic meter. Thus when the powder product from the present invention is processed in accordance with the current practice, the end product provides substantial reduction in volume and associated disposal cost. Similar benefits are obtainable when the powder product is solidified in other materials, for example, polymers currently used for such purpose. Thus, it is seen that the present invention makes possible what was heretofore believed to be unobtainable; namely, the rapid conversion of a waste containing an organic amine chelating agent into a dry, flowable powder. Further, the practice of the present invention provides a substantial economic benefit. The process of the present invention is capable of substantially reducing the volume of low-level radioactive wastes while producing a dry, flowable radioactive solid product and a gaseous product which contains substantially no NO.sub.x and also retains volatile radionuclides in the solid product. In addition, greater volume reductions can be realized by compression of the spray-dried powder obtained in the process of this invention. It will, of course, be realized that various modifications can be made to the design and operation of the process of this invention without departing from the spirit thereof. For example, waste materials other than those specifically exemplified herein can be spray dried according to the process of this invention. The material to be treated can be introduced into the spray dryer using various single or multiple fluid spray nozzles or other forms of atomizers. Multiple nozzles or atomizers can be used, if desired. In addition, other gas-solid separation means can be used to separate the gaseous and solid products of the process. For example, electrostatic or metal filters or cyclones may be used. Other ways of treating the gaseous and solid products following separation can be used, if desired. Thus, while the principle, preferred design and mode of operation of the invention have been explained and what is now considered to represent its best embodiment has been illustrated and described, it should be understood that, within the scope of the appended claims, the invention can be practiced otherwise than as specifically illustrated and described.
063079178	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a soller slit for collimating diverging X-rays to parallel X-rays. Also, the present invention relates to an X-ray apparatus constructed with the same soller slit. 2. Description of the Related Art There has been known an X-ray apparatus that is an apparatus for analyzing a specimen with using X-rays. Further, there has been known an X-ray apparatus having a structure in which a soller slit for collimating X-rays incident to a specimen or X-rays diffracted by the specimen to parallel X-ray beams by limiting divergence of the X-rays. FIG. 12 shows an example of a conventional X-ray apparatus using such soller slit. In the X-ray apparatus, a specimen `S` performs the so-called .theta. rotation in which the specimen `s` continuously or intermittently rotates about an axis line Xs of the specimen `s` at a predetermined angular speed, and simultaneously, an X-ray counter 51 performs the so-called 2.theta. rotation in which the X-ray counter 51 rotates about the axis line Xs in the same direction at an angular speed twice the predetermined angular speed. X-rays emitted from an X-ray focal point `F` are directed through a monochromator slit 52, monochromator 53, a soller slit 54 and a divergence limiting slit 56 to the specimen `S`, while the .theta. rotation and the 2.theta. rotation being performed. The conventional soller slit 54 is constructed by piling up a plurality of thin metal foils 61 with using a spacer between adjacent metal foils, as shown in FIG. 13. A front and rear portions of this soller slit 54 in a propagating direction of an X-ray `R` are opened to allow the X-ray to pass through and side portions thereof are closed by spacers 59 and side walls 62. In FIG. 12, the soller slit 54 limits divergence of X-rays generated from the X-ray focal point `F` and then reflected or diffracted by the monochromator 53, to form parallel X-ray beams incident on the specimen. In some case, the soller slit is arranged between a divergence limiting slit 57 and a light receiving slit 58 to direct X-rays to an X-ray counter 51 by limiting divergence of X-rays diffracted by the specimen `S`. In FIG. 12, when Bragg's diffraction condition is satisfied between X-ray incident on the specimen `S` under the .theta. rotation and crystal lattice face of the same specimen `S`, X-ray diffraction occurs at the specimen `S`. Thus diffracted X-rays are detected by the X-ray counter 51 through the scattering ray limiting slit 57 and the light receiving slit 58, which perform 2.theta. rotations, respectively. On the basis of this detection, both the diffraction angle 2.theta. and the X-ray intensity regarding X-rays diffracted at the specimen `S` are measured. In the X-ray apparatus mentioned above, the soller slit 54 is located in a position remote from other X-ray optical elements such as the monochromator 53 and the specimen `S` as shown in FIG. 12. Therefore, a space dedicated to the soller slit 54 is required, causing the size of the X-ray apparatus to be large. SUMMARY OF THE INVENTION The present invention was made in view of the above mentioned state of art and has an object to remove, in an X-ray apparatus, the necessity of providing a space for arranging a soller slit to thereby increase an X-ray intensity received by the X-ray counter. (1) In order to achieve the above object, a soller slit according to the present invention, which includes a plurality of metal foils stacked with a constant interval provided by spacers each between adjacent foils, is featured by that the end portion of the metal foils opposite to the spacers are opened. The metal foil can be formed of any metal material, provided that the metal material is impermeable with respect to X-rays. For example, stainless steal may be used therefor. PA1 (2) In the X-ray apparatus mentioned above, each spacer can have a configuration having a forwardly peaked center portion of a front end and both end portions thereof behind. In general, the metal foil is very thin and has low rigidity, so that it is easily deformed, for example, warped. On the contrary, when spacers having a configuration mentioned above being used, it is possible to support the metal foils so as to be hardly deformed. Therefore, spacers having a configuration mentioned above are preferable in the case where the metal foils are supported on one sides with the other sides thereof being opened, that is, the metal foils are supported in the form of a cantilever, as in the present invention. PA1 (3) In the case where the metal foils are supported in the form of a cantilever by the spacers as mentioned above, it is preferable to form each spacer having a delta configuration, namely, a form of a mountain equipped with a forward apex. With such configuration of the spacer, it is possible to form the spacer easily while holding the propagation passage of X-rays passing along the metal foils. PA1 (4) An X-ray apparatus according to the present invention comprises an X-ray source for generating X-rays, an X-ray detector for detecting X-rays diffracted by the specimen after being generated by the X-ray source, and a soller slit. In this X-ray apparatus, the soller slit includes a plurality of metal foils stacked with a constant interval between adjacent foils by spacers. End portions of the stacked metal foils on the side opposite to the spacers constitute an opened end portion. The soller slit is arranged in opposing relation to the specimen with the opened end portion of the metal foils being in contact with or in the vicinity of a surface of the specimen. PA1 (5) Another X-ray apparatus according to the present invention comprises an X-ray source for generating X-rays, an X-ray detector for detecting X-rays diffracted by the specimen after being generated by the X-ray source, a monochromator for making X-rays generated by the X-ray source or X-rays diffracted by the specimen monochromatic, and a soller slit. In this X-ray apparatus, the soller slit includes a plurality of metal foils stacked with a constant interval between adjacent foils by spacers. End portions of the stacked metal foils on the side opposite to the spacers constitute an opened end portion. Further, the soller slit is arranged in opposing relation to the monochromator with the opened end portion of the metal foils being in contact with or in the vicinity of the monochromator. In the soller slit mentioned above, since one end portion of the metal foils are opened to be a free end, other X-ray optical components such as a monochromator, a specimen, etc., can be arranged in facing relation to the opened portion. Therefore, there is no need of separately providing a space dedicated to the soller slit, causing the size of the X-ray apparatus to be reduced. Further, since reduction of the X-ray apparatus in size makes possible to shorten an X-ray passage, it is possible to increase intensity of X-rays to be detected by an X-ray detector. Further, the soller slit can be mounted directly on and preferably integrally with the optical component such as the monochromator, so that the optical component and the soller slit are necessarily determined in position relative to each other. As a result, there is no need of separately regulating positions of the soller slit and the optical components opposing to the soller slit in regulating an optical axis regulation related to various X-ray optical components constituting the X-ray apparatus. Therefore, it becomes possible to easily perform an optical axis regulation work related to the X-ray apparatus. When such spacers are arranged in a manner that the forward apexes thereof are positioned extremely close to the specimen or the monochromator, the forward apexes make possible to effectively exclude unnecessary X-rays such as scattered X-rays, which may cause a noise in a result of measurement. Thus, a high signal-to-noise ratio is obtained in a result of measurement, resulting in a reliable result of measurement. According to the aforesaid X-ray apparatus including the soller slit having one end portion opened, the specimen can be arranged in opposing relation to the opened end portion. With this constitution , it is possible to collimate X-rays to parallel X-ray beams by the soller slit, while irradiating the specimen with X-rays and deriving diffracted X-rays from the specimen. Since the soller slit is arranged in a position opposing to the specimen and preferably integrally with the same specimen as well, there is no need of providing a space dedicated to only the soller slit, so that the size of the whole X-ray apparatus can be reduced. As a result, it becomes possible to increase the intensity of X-rays to be received by the X-ray counter. According to this X-ray apparatus including the soller slit having one end portion opened, the monochromator can be arranged in opposing relation to the opened end portion. With this constitution, it is possible to collimate X-rays to parallel X-ray beam by the soller slit, while irradiating the monochromator with X-rays and deriving diffracted X-rays from the monochromator. Since the soller slit is arranged in a position opposing to the monochromator and preferably integrally with the same monochromator, there is no need of providing a space dedicated to only the soller slit, so that the size of the whole X-ray apparatus can be reduced. As a result, it becomes possible to increase the intensity of X-rays to be received by the X-ray counter.
	description	The present application is a continuation of U.S. patent application Ser. No. 12/212,874 filed on Sep. 18, 2008, which claims foreign priority benefits under Title 35 U.S.C. § 119 of European Patent Application No. EP 07116749.8 filed on 19 Sep. 2007, each of which is incorporated herein by reference in its entirety. The invention relates to a marking method for marking defective test elements and to a production method for producing test elements, which involves a marking method according to the invention. The invention furthermore relates to a marking device, in particular for carrying out a marking method according to the invention, and to a production device for producing test elements, which comprises a marking device according to the invention. The invention furthermore relates to an analytical test instrument which uses a test element produced by the production method according to the invention. Such marking and production methods, marking and production devices and analytical test instruments are used particularly in chemical analysis and in medical technology. By means of the test elements, for example analytes such as e.g. metabolites in samples, particularly in liquid samples such as e.g. in blood, urine, in interstitial fluid or other bodily fluids, can be detected qualitatively and/or quantitatively. An essential application example of the present invention lies in the field of blood sugar diagnosis In many fields of technology, natural science and medicine, analytes in samples must reliably be detected qualitatively and/or quantitatively. This is done in many cases with test elements, which react sensitively to one or more analytes. In particular, it is possible to use test elements which comprise at least one test material that changes at least one measurable property when the analyte is present in the sample, or upon contact with the analyte. These properties may for example, as mentioned in more detail below, be electrical and/or optical properties. An essential application field of the present invention, albeit one to which the invention is not restricted, is medical diagnosis. For example, the monitoring of blood glucose concentrations is an essential part of daily life for diabetics. In this case the blood glucose concentration must rapidly and simply be determined generally several times per day, so that corresponding medical measures can be implemented if appropriate. In order not to restrict the daily life of a diabetic more than necessary, corresponding mobile instruments are often used which should be simple to transport and handle, so that the blood glucose concentration can be measured rapidly and simply but nevertheless reliably, for example in the workplace or in leisure time. Static instruments may however also be used, for example instruments which are designed for hospitals, medical practices or care institutions. Various analysis instruments are currently on the market, which sometimes function according to different measurement methods. Various diagnostic methods are employed for this, for example optical or electrochemical measurement methods. The aforementioned test elements, which are usually provided in the form of test strips, are often an essential element of these measurement methods. For example, they may be electrochemical and/or optical test strips. Examples of electrochemical test strips are described, for example, in U.S. Pat. No. 5,286,362. Optical test elements are described, for example in CA 2,050,677. Other types of test elements are also known and may be used in the scope of the present invention, for example implantable test elements (see for example EP 0 678 308 B1). Instead of individual test elements, for example test strips or test tubes, test elements are also known which are held in a magazine or in another type of storage device. For example, a plurality of test elements may be rigidly connected together, for example in the scope of a test disc on which there are a plurality of test fields. Other types of multiple test elements are known, for example in the scope of band cassettes in which a multiplicity of test elements or test fields are arranged on a common band so that they may for example be used in succession. Other embodiments of magazines are drum magazines, in which a plurality of test elements are accommodated in a magazine drum. Other embodiments are also known. The reliability of the analyte detection plays a crucial role in particular for quantitative detection methods in medical diagnosis. Thus, a range of further decisions generally depend on the result of the detection, for example a decision about insulin medication or a decision about another kind of medical treatment. To this extent efficient quality management is required in the production of the test elements, which reliably prevents defective test elements from being put into circulation or, if they are in circulation, from being used there. This quality management may involve a multiplicity of test methods which can subject the test elements to particular function tests already during the production process, or after production. For example, tests may be carried out which (for example by means of image recognition, electronic measurements, optical measurements or combinations of measurements) check particular functionalities of the test elements and thereby identify defective test elements with a certain probability. The production of such test elements is generally a mass process, in which a multiplicity of test elements are produced on a large technical scale with a high throughput. When a defective test element is identified, it is therefore generally not possible to reject this test element directly. Methods are therefore known from the prior art in which test elements identified as defective are marked as being defective during or after the production method. Examples of such marking methods are disclosed in US 2004/0048359 A1, where defective regions are marked with a pen or marker. Another method known from the prior art is described in EP 0132790 A2. Here, a multiplicity of test elements are produced on a common band and, after a defect is found, a suitable marking in the form of a color point or a magnetic marking is applied so that the defective test element can subsequently be rejected simply and reliably. In practice, however, the marking and production methods known from the prior art have numerous disadvantages. For instance, the known marking methods generally employ additional working substances and auxiliary substances, for example inks for the color points, paints, magnetic materials or similar materials. These additional working and auxiliary substances may however interact with the functionality of the test elements, and may for example influence the functionality of a test material (for example a test chemical for the detection of blood glucose or another metabolite). Thus, in general, safety of the working and auxiliary substances used for the marking must extensively be checked and confirmed, for example in order to obtain corresponding statutory approvals. Another disadvantage of known methods is that many of the known application methods for the working and auxiliary substances, which are used for the marking, are complex and susceptible to error. For example, paints or inks for the marking may be applied by means of a printing method which, however, is per se error-prone in many cases. Another disadvantage is that in many cases the applied working and auxiliary substances, which are generally used for the marking in the prior art, are applied in liquid form so that a drying time is required after application. In many cases, these drying times of the marking limit the manufacturing speed of the production processes and therefore increase the production costs considerably. It is therefore an object of the present invention to provide a marking method which at least substantially avoids the above-described disadvantages of known marking methods. The marking method should allow simple, rapid and reliable marking of defective test elements, and this is intended to be done without significantly increasing the production costs. The invention provides a marking method for marking defective test elements, a production method which involves this marking method, a marking device for marking defective test elements, a production device for producing test elements while employing a marking device, and an analytical test instrument which uses test elements produced by the method according to the invention. Advantageous refinements of the invention are presented in the dependent claims. These refinements may be implemented individually or in combination with one another. The test elements are adapted to detect at least one analyte in a sample. They may for example be test elements of the above-described types known from the prior art, for example test elements for the detection of metabolites in liquid samples, particularly in blood, urine, interstitial fat tissue or other bodily fluids. Test elements may however also be used for other types of analytes and samples. The test elements may for example be configured in strip form, in leaflet form, in disc form, in the form of bands or in similar configurations, in each case individually or several combined together. The test elements may be suitable for one or more tests, and they may in particular have one or more test fields onto which the sample can be applied, or into contact with which the sample can be brought. Like known methods from the prior art, the marking method is configured so that at least some of the test elements are provided with a defect marking which contains information about defectiveness of the test elements. For example, a test element identified as defective may be provided with a corresponding marking. In contrast to the prior art, in which for example colored marking is carried out, the test elements comprise at least one radiation-sensitive material. In order to be marked, the test elements are exposed to at least one radiation which is adapted and/or selected to induce marking in the form of at least one optically detectable change in the radiation-sensitive material. In contrast to the prior art, application of an additional marking substance onto the test element is thus not necessary; rather, preferably radiation-sensitive properties of the test element itself are used in order to mark the test element. As an alternative or in addition, markings independent of the functionality of the test elements, in particular a test chemical in test fields of the test elements, may also be applied onto the test elements, for example onto a support band of the test elements or onto separate marking fields independent of the test fields. The marking may be carried out contactlessly so that it does not affect production of the test elements (for example in the form of mechanical contact). It is thus possible to avoid affecting essential machine parameters, for example tension forces on a test element band, as may occur for example when liquid marking means are being applied. Furthermore, the application of a reject marking by means of radiation is virtually independent of the manufacturing speed, so that this is an extremely robust marking process. The marking is generally only a question of the irradiation dose. Furthermore, besides the material costs for additional marking substances, the marking method according to the invention also obviates the costs of their provision, storage and release. Also, it is generally not necessary to determine by elaborate confirmation tests whether there is an interaction of the marking substances with unmarked test elements. It likewise obviates a strategic dependency on the delivery reliability of particular marking substances. The said advantages become clear in particular when radiation-sensitive properties of a test material of the test element itself are used. As described above, many types of test elements contain such test materials, which are often also referred to as a “detection chemical” or “test chemical” and which are selected and adapted to change at least one measurable property when the at least one analyte is present in the sample, in particular a measurable electrical and/or optical property. In this regard, reference may be made to the test elements known from the prior art and the test chemical used therein, which is for example applied onto test fields of the test elements. This detection chemical, or this test material, itself generally has radiation-sensitive properties. This is the case in particular when using optical test elements in which the at least one analyte is detected for example in the form of a color change or a fluorescence change. Detectable, long-term changes in the test materials may however also be induced with other types of test materials by suitable selection of the radiation. It is particularly preferred for the detectable changes to be configured so that they are irreversible. At least, however, the detectable change should have a stability in the range of a few minutes, preferably from a few hours up to a few days. If the marking remains on the test elements, for example for subsequent readout by a correspondingly adapted analysis instrument, even longer stabilization is necessary, for example an optically detectable change which is stable over a period of from several months to years. In the case in which the test material of the test elements is itself used as a radiation-sensitive material and therefore to store information about possible defects, application of additional substances onto the test elements for marking can be entirely obviated. This makes the advantages explained above (avoiding the need to check compatibility, cost reductions etc.) particularly clearly beneficial. As described above, for marking the test elements, as an alternative or in addition to using the test materials or the test chemical which defines the analytical functionality of the test fields of the test elements, a marking may also be applied outside the test fields onto the test elements. To this end, for example, a support material (for example a support band) of the test elements may itself contain a radiation-sensitive material which can be used for the marking. As an alternative or in addition, a separate marking material independent of the test materials or the test chemical and with radiation-sensitive properties may also be applied onto the test elements. For example, separate marking fields may be provided which contain a radiation-sensitive material and which can therefore be marked. Any desired combinations may also be envisaged, for example marking on the test field (in which case the test field has a first radiation-sensitive material) and marking on a separate marking field (which has a second radiation-sensitive material). Accordingly, the invention also provides a test element which is suitable for use in such a marking method and which has at least one such marking field separate from the test field or fields and with a radiation-sensitive material. Here, “separate” is intended to mean a functional separation but not necessarily a strict spatial separation. For example marking fields may be adjacent to test fields, partially overlap with them or even be stacked in a layer structure (for example below the test fields) so that overall the functionality of the test fields is not affected by the marking fields. The at least one optically detectable change in the radiation-sensitive material, whether pertaining only to the test fields themselves or to separate marking fields, can subsequently be recorded by a suitable sensor and interpreted as a reject marking. Possible configurations of this recording will be discussed in more detail below. It should be pointed out that it is not categorically necessary to mark the defective test elements with radiation; rather, “inverse” marking by means of the described optically detectable change is also possible. For example, each test element which is identified as defect-free may be marked by means of the radiation whereas each test element identified as defective remains unmarked. Intermediate stages or other types of defect marking are also possible, for example by “writing” information about a quality level of the test element into the radiation-sensitive material using the at least one radiation, for example in the form of a bit value. The information content of the defect marking may thus be configured differently and may in various ways contain information about defectiveness (which may also include freedom from defects) of the respective marked test element (and/or even the test elements, i.e. for example other test elements from a batch). As described above, this may for example involve the information “defective”, “not defective”, a quality level or similar information. This information about the defectiveness of the respective marked test element is introduced into the radiation-sensitive material by means of the at least one radiation. It is particularly preferred for the radiation being used, which could in principle also be particle radiation, for example neutron radiation, to comprise electromagnetic radiation. The use of ultraviolet radiation has in particular been found to be expedient, i.e. radiation in the wavelength range between 1 nm and 400 nm. The wavelength range of from 250 nm to 400 nm is particularly preferred, in particular the wavelength range between 350 nm and 380 nm, since this wavelength range not only coincides well with the sensitivity of conventional test materials but is also readily achievable technically. The preferred use of UV light, particularly in the said preferred wavelength range, is therefore advantageous especially in conjunction with the use of a wet chemical as an information medium for the defect information, since many of these test materials or wet chemicals react sensitively to UV radiation, in particular for optical analyte detection. For example, multiple bonds in organic constituents of the test materials may be permanently broken by UV radiation, which may in turn be recognizable for example by a color transformation or another optically detectable change. Incandescent lamps, gas discharge lamps, lasers, light-emitting diodes, flash lamps or a combination of such light sources, which preferably in turn emit at least partially in the ultraviolet spectral range, may preferably be used in order to generate the at least one radiation. The optically detectable change, according to the description above, may for example comprise a color change, a change of luminescence (for example fluorescence and/or phosphorescence), a change of reflectivity or a combination of these changes and/or further changes. The proposed marking method may for example be used as a “stand-alone” method to mark test elements which have already been fully produced. It is particularly preferred, however, to integrate the proposed marking method in one of the proposed embodiments in the scope of a production method for producing test elements of the described type. A multiplicity of the test elements are produced in this production method, and at least one of the test elements (preferably all the test elements and/or random samples of the test elements being produced) is subjected to a defect check. For example, as explained above, this defect check may involve an optical check (for example a color and/or fluorescence measurement), a visual check (for example in the scope of pattern recognition, in particular by means of a digital image processing program), a fluorescence check or similar types of defect checks or combinations of defect checks. In this way, for example, it is possible to identify whether the test elements themselves (for example a support band of the test elements) are deformed, or whether a detection chemical has been applied correctly (for example whether a test field has been applied and/or whether this test field has been deformed during the application) or the like. Another example of a test criterion for the defect check is represented by the homogeneity of the test fields. For example, it is possible to check whether a test chemical is contained homogeneously and/or with a constant layer thickness on the test field. This homogeneity may for example be checked by means of optical inspection in the visible, infrared or ultraviolet spectral range. As an alternative or in addition, a layer thickness and/or homogeneity inspection may also be carried out for example by means of ellipsometric methods, transmission methods, mechanical sampling methods or other customary layer thickness measurement methods, which can preferably sample or simultaneously record a surface. Thus, for example, defects in the production of the test fields may be found (for example defects in a printing method). Tolerance thresholds for the homogeneity may be specified in this case (for example “allowed” ranges for the layer thickness values inside a test field) in order to qualify the test fields or test elements as defect-free or defective. Another example of a test criterion for the defect inspection is a distance inspection in which (for example optically, for example by means of pattern recognition) spacings of particular elements on and/or in the test elements are compared with threshold values. For example, it is possible to check whether test fields have a predetermined distance from one another and/or a predetermined distance from particular markings. Two- or three-dimensional distance monitoring is also possible. Furthermore tolerance ranges may also be specified, inside which the distance measurements are still tolerable and outside which the test elements are identified as defective. Furthermore, as an alternative or in addition, electrical or electrochemical measurement methods may also be used, for example resistance measurements, impedance measurements or similar types of measurements. A combination of the said defect check types and/or other types of defect check may be used and are known to the person skilled in the art. The defect check may already be carried out during production of the test elements, so that it may for example be integrated into a manufacturing line. As an alternative or in addition, the defect check may also be done after production. Conventional methods known to the person skilled in the art may be used for producing the test elements, for example thick film methods, semiconductor technology methods, printing methods or a combination of these/or other customary method steps. The production of the test elements is known to the person skilled in the art. In particular, a band method may be used, as mentioned in more detail below. Furthermore, the test material may preferably be produced separately and subsequently applied onto the band or another type of support (for example in a laminating process). During or after the defect check, a decision is made as to whether the test element is defective. Similarly as in the description above of the term “defect information” or “defect marking”, the term “defective” is to be interpreted in the broad sense. For example, it may involve “digital” defectiveness, for example in the form of defectiveness or freedom from defects (in which case tolerance thresholds may also respectively be specified, for example thresholds for tolerable defects), or a number of intermediate information items. This intermediate information may for example in turn comprise quality grades of the respectively checked test element, which may for example again be expressed in a bit value. Subsequent to the defect checks or already during the defect check, the test element may in turn be provided with a defect marking which contains information about defectiveness of the respective test element. With respect to this information about the defectiveness, reference may be made to the description above. For this marking of the at least one of the test elements, a marking method according to the above description is used in one of the embodiments presented. For example, as described above, at least one test material (test chemical) of the test element may in turn be used as an information medium for the marking. For example, as likewise explained above, the marking method may be configured so that the detection chemical or test chemical becomes colored accordingly. In this way, in particular, a test element or a part of the test element (for example a particular test field) may be rendered unusable so that a false measurement value can be excluded from the analyte detection. This at least one information item, which is contained in the defect marking, may subsequently be used further. In particular, test elements marked in a rejection step may be rejected. This is naturally advantageous particularly for production methods in which test elements are divided up during or after production, so that test elements marked as being defective (i.e. depending on the type of defect information applied, marked or unmarked test elements or test elements which indicate defect information with an insufficient quality level) can be rejected and for example disposed of. For example, a plurality of test elements may be produced as bandware on a common support band, in which case the bandware may for example subsequently be held in a band cassette. Test elements identified as defective may for example be cut out before reception in the band cassette, and the remaining defect-free band may subsequently be reassembled in a splicing step. In this way, defective test elements can be avoided even in bandware. As an alternative or in addition, the bandware may also subsequently be divided up, so that defective test elements can be rejected. In this way, it is respectively possible to ensure that substantially all test elements entering the market are defect-free. The bandware may also be configured so that (as explained in the introduction for the description of the prior art) it is held in a band cassette. The test band may in this case contain a multiplicity of test elements which, for example, can be used in succession. For example, defective elements may be specially marked so that either they cannot be used, they are identified as defective by an analysis instrument or they are otherwise restricted in their use. As an alternative or in addition, however, it is preferred to assemble the band so that it does not comprise any defective test elements, for example by the above-described cutting process with subsequent rejection and splicing of the remaining band. The production method may furthermore preferably be configured so that it optionally comprises an inspection step after the at least one method step in which the at least one defect marking is applied. In this inspection step, it is possible to check whether the defect marking has been applied correctly. For example, this may be done by monitoring the at least one optically detectable change in the radiation-sensitive material and comparing it with a setpoint value. For example, this setpoint value may be stored in a data memory, for example a data memory (for example a shift register) which is also used for the defect marking itself. In this way, it is possible to check directly whether the defect marking has been carried out correctly. If it found that this is not the case, then for example a warning may be sent to a technician and/or the defectively marked test element may be marked again and/or rejected. Various other possibilities may be envisaged. Corresponding to the marking method presented above and the production method respectively in one of the described embodiments, the invention furthermore provides a marking device for marking defective test elements. The marking device may in particular be adapted to carry out a marking method of the described type in one of the alternative embodiments. Accordingly, the marking device has at least one radiation source for exposing the test elements to at least one radiation. For the effect of this radiation and the possible types of marking in the marking device, reference may be made to the description above. The marking device may furthermore comprise at least one test device, which is adapted to subject at least one of the test elements to a defect test. Preferably all the test elements or random samples of the test elements are subjected to this defect check. With respect to the possible configuration of the defect check, reference may likewise be made to the description above. The marking method is adapted to identify and/or decide whether the test element is defective. With respect to the term “defective” and its possible meanings, reference may likewise be made to the description above. According to the above description of the possible marking methods, the radiation source may in turn have for example incandescent lamps, gas discharge lamps, lasers, light-emitting diodes, flash lamps or combinations of these and/or other radiation sources, in particular for generating ultraviolet radiation according to the description above and in the preferred wavelength range described above. It is particularly preferred to achieve high parallelity and therefore a high throughput of the marking method, when the marking device has a multiplicity of modularly constructed light sources. In particular, these may be a multiplicity of modularly constructed light generator units for generating ultraviolet light. These modularly constructed light generator units may for example comprise a multiplicity of identical light generator units, which may be arranged for example in a circuitry compartment of the marking device. For example, the circuitry compartment may receive these light generator units in the form of identical slot-in racks. The marking device may comprise at least one application position where some or all of the test elements are provided with the defect marking. In order to achieve a high level of parallelization and therefore a high throughput, a plurality of application positions may also be provided. For example, a test material (test chemical, detection chemical) in the form of one or more test fields may be applied respectively onto a test element, in which case a separate application position may be provided for each test field. It is particularly preferred for the marking device to furthermore have at least one waveguide, which is adapted to conduct the radiation from the at least one radiation source to the application position. Depending on the type of radiation being used, this at least one waveguide may in particular be a light waveguide. If ultraviolet light is used as the radiation, which is particularly preferred, then this light waveguide should be matched to the wavelength respectively being used. Rigid or flexible waveguides may be used, for example waveguides with a plastic and/or glass material. Such waveguides may for example be produced as rigid plastic waveguides. It is particularly preferred, however, for the waveguide to comprise at least one fiber light guide i.e. a flexible light guide. Glass fibers and/or, as is particularly preferred, plastic fiber light guides may be used. Respectively, depending on the desired properties of the radiation, multimode or single-mode fibers may be used. For example a plurality of fiber light guides, for example plastic fiber light guides, may be combined to form fiber bundles. For example, the preferred UV light generator units described above, which are preferably located in a circuitry compartment of the marking device, may be connected to the at least one application position via one or more fiber bundles. If fiber bundles are used, then it is in particular preferred for the marking device to comprise at least one cross-section converter. This cross-section converter is adapted to hold a multiplicity of fiber light guides of at least one of the fiber bundles so that the fiber ends of the fiber light guides are arranged in a predetermined pattern in the application position. In this way, for example by corresponding arrangement of the fiber ends to form a pattern, the throughput of the test elements can be increased since a plurality of test elements can be exposed in parallel, intensities and radiation doses can be increased (by simultaneous exposure using a plurality of fibers and/or exposure using a plurality of fibers in succession), and a plurality of defect markings could even be written simultaneously onto an individual test element. This configuration of the marking device becomes clearly advantageous in particular when, as is likewise preferred, the test elements are produced in a continuous process. For example, the test elements could be produced in the form of a continuous test element band which, as described above, is subsequently divided up or which may be held as a whole or in sections in a band cassette. The pattern of the fiber ends which is generated by the cross-section converter may in this case permit simultaneous irradiation in the application position both, for example, parallel to a running direction of the band and, as an alternative or in addition, perpendicularly to the running direction of the band. A plurality of bands may also be processed simultaneously, for example by a plurality of bands with test elements being generated in parallel. For example, when producing bandware, a wide band may initially be produced with a plurality of test elements respectively arranged in parallel, which is then cut up into a plurality of sub-bands (for example in a cutting process). The marking device may have a guide table in the application position, in which at least two, preferably at least five test elements can be exposed simultaneously to the radiation i.e. marked. For example, five bands or sub-bands with test elements may be passed simultaneously through the guide table. For the predetermined pattern which is produced by the cross-section converter, in particular a line pattern (for example with a line parallel and/or perpendicular to the movement direction of the band), a matrix pattern or a rectangular pattern is preferred. Other patterns are of course also possible. It is also possible to arrange a plurality of cross-section converters in parallel with one another, for example a plurality of cross-section converters with fiber ends respectively arranged linearly. This is advantageous particularly in the above-described alternative embodiment in which a plurality of test bands with test elements are produced in parallel, since in this way for example a cross-section converter with a fiber end pattern can be assigned to each band or sub-band. As an alternative or in addition, the marking device may furthermore have at least one set of beam shaping optics for beam shaping of the radiation. For example, lens systems may be provided in order to bring the markings or the shape of the markings on the test elements into a desired shape, for example a linear or rectangle shape. Besides the marking device, the invention furthermore provides a production device for producing test elements which may in particular be adapted to produce test elements according to the above-described production method in one of the described method variants. The production device has a fabrication device for producing a multiplicity of test elements. As described above, production devices known from the prior art may for example be used for this fabrication device, for example production devices which operate with semiconductor and/or thick film processes and/or printing methods and/or adhesive bonding methods. In particular, the production device may be adapted to produce a multiplicity of test elements continuously, for example in the form of a band process, a multiplicity of test elements being held on a band. These test elements may subsequently be divided up, or the band may be used per se, for example in a band cassette. The production device furthermore has at least one marking device according to one of the embodiments described above. Besides this, the production device may furthermore have at least one sorting device for rejecting test elements marked as being defective. When producing bandware, for example for a band cassette with test elements, it is preferred for the production device furthermore to have a cutting and splicing device i.e. a device which can cut defective test elements out from a band in order subsequently to adhesively bond this band back together or reassemble it in another way, for example by lamination. In this way, an endless band with defect-free test elements can be produced. Again, the terms “defective” and “defect-free” are to be interpreted in the broad sense, for which reference may be made to the description above. For example, tolerance thresholds may again be specified. Depending on whether the test elements are divided up during or after production, instead of being rejected defective elements may also for example stay on a band and merely remain unused subsequently, for example by readout of the marking (see also below). The production device may in particular furthermore have at least one test device. This test device is adapted to subject the test elements to a defect check. The defect check methods already described above may be used for this, i.e. for example electrical, electrochemical or optical measurements or a combination of these defect check methods. For example, the test device may comprise a camera by which the test elements are recorded. As an alternative or in addition, for example, an image recognition system may also be provided which is for example adapted to detect deviations of a test field and/or a shape of the test elements from a predetermined standard (for example by more than a predetermined tolerance threshold). As an alternative or in addition, one or more test light sources may also be used, for example in order to check fluorescence properties and/or color properties and/or reflection properties of the test element, for example properties of the test chemical and/or of one or more test fields. Furthermore, as an alternative or in addition as likewise explained above, one or more resistance measurement devices may for example also be provided and/or one or more impedance measurement devices and/or similar devices for electrical or electrochemical defect checking. The production device, in particular the test device, may as an alternative or in addition furthermore comprise one or more data memories, which may be volatile and/or nonvolatile data memories. In the scope of mass production, it is particularly preferred for this at least one data memory to comprise at least one shift register. For example, a continuous or stepwise production process may in turn be used, in which the defect check takes place at one site by means of the defect checking device, in which case the results of this defect check may be entered into the data memory, in particular the shift register. In this way, a multiplicity of test elements can be tested in succession so that a test element currently located in the marking device (for example one or more test elements in an application position) can respectively be assigned to the information item or items by corresponding readout of the shift register, for example of the marking device. In this way, the test elements can be marked by means of the marking device. Similarly, the information may also be used subsequently for rejection of the test elements. Similarly as the description above of a preferred method in which an inspection step is carried out, the production device may furthermore comprise at least one inspection device which is adapted to check whether marking has been carried out correctly in the marking device. For example, the inspection device may in turn receive data from a data memory, for example a shift register, preferably using the same data as that which the marking device can access and on the basis of which the defect markings of the test elements have been applied. In this way, by cross-referencing, it is possible to ensure at least substantially that the marking device is operating correctly and for example failures in individual light sources or other types of malfunctions can be identified. If such a malfunction is identified, then for example the production device may be configured so that it rejects the defectively marked test elements and/or sends a warning to a technician or carries out similar actions. The inspection device may for example comprise one or more photodiodes and/or other types of photodetectors, in order to monitor the at least one optically detectable change in the radiation-sensitive material. One or more light sources may also be provided, for example in order to assist function of the photodetectors by corresponding exposure of the radiation-sensitive material. The invention furthermore provides an analytical test instrument for detecting at least one analyte in a sample, which comprises at least one test element that is produced by the production method described above in one of the method variants presented. As a counterpart to the defect marking which may be present on the test element, the analytical test instrument has an interrogation device which is configured to identify whether the test element is marked. To this end, the interrogation device is adapted to identify the at least one optically detectable change in the radiation-sensitive material of the test element. For example, this analytical test instrument may furthermore comprise a drive and evaluation device for carrying out a quantitative and/or qualitative detection of the at least one analyte in the sample by means of the at least one test element. It is particularly preferred for the analytical test instrument to be adapted to determine a blood sugar concentration. In this case, it is possible to use individual test elements, a plurality of test elements which are held in a magazine (in which case for example a test element is respectively taken from the magazine), or test elements which are held in a band cassette. Other types of test elements are also possible, for example implantable test elements. The interrogation device is therefore configured to interrogate the defect marking of the at least one test element, preferably the at least one test element which is currently being used or intended to be used. If, according to the information contained in the defect marking, it is found that the test element is defective, then various actions may be carried out. Inter alia, a warning may be sent to a user of the analytical test instrument, for example via a display, optical indicator elements (for example warning lights), via acoustical signals or via a combination of these options. As an alternative or in addition, a test with the marked test element may also be prevented. Furthermore, as an alternative or in addition, it may be required that a new test element should be taken from a multiplicity of test elements held in a magazine. For example, as explained above, said test elements in said magazine may be individual test elements or flexibly or rigidly connected test elements. A band cassette may for example also be used, so that it is possible for example to wind forward to a subsequent test field in the event that a test field is identified as defective. Further details and features of the invention may be found in the following description of preferred exemplary embodiments in conjunction with the dependent claims. The respective features may be implemented on their own, or several may be implemented in combination with one another. The invention is not restricted to the exemplary embodiments. The exemplary embodiments are represented schematically in the figures. Reference numerals which are the same in the figures denote elements which are identical or functionally equivalent, or which correspond to one another in respect of their function. For purposes of promoting an understanding of the principles of the invention, reference will now be made to the embodiments illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated device, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates. FIG. 1 represents an exemplary embodiment of a production device 110 for the production of the test elements for detecting at least one analyte in a sample. The test elements are denoted by the reference numerals 112, 114 and 116 in FIG. 1, depending on the production state or stage which these test elements occupy inside the production device 110, or depending on the configuration of these test elements. The individual elements of the production device 110 are arranged merely symbolically in FIG. 1. A continuous production process is represented, in which the test elements are initially produced as a bandware 116 on an endless band 118. For example, this endless band 118 may be a paper band, in particular a multilayered coated paper band. Other support materials may also be used as an alternative or in addition, for example plastic bands, ceramic bands, composite materials and similar support materials. For example a polyethylene sheet, a PET sheet or another sheet material may be used as a support material. The production direction from the starting material to the finished test elements 112, 114 passes from left to right in FIG. 1, which is symbolically represented by the arrow 120 in FIG. 1. As an alternative to continuous production processes as represented in FIG. 1, discontinuous processes are also possible, for example batch processes, in which test elements are produced individually or in batches. This may also be done in the case of band-type products, for example by winding sections of bandware onto support rolls in order to be temporarily stored and/or transferred to other method sections. The production process may also be interrupted so that, for example, the test elements can be manufactured at different sites (for example at different stations) in various manufacturing stages. Furthermore, the sequence of the individual process steps of the production process of the production device 110 as represented is not categorically necessary, i.e. for example testing and marking of semifinished test elements may also be carried out so that for example further production steps may follow testing and marking. The production device 110 has a fabrication device 122, which is indicated merely symbolically in FIG. 1. Here, for example, the endless band 118 may be provided with test fields where a test material (also referred to below as a test chemical or detection chemical) may respectively be applied onto the endless band 118. The application may for example be carried out by adhesive bonding, which is indicated symbolically by an adhesive bonding station 123 in FIG. 1. Here, for example by an adhesive bonding or a laminating process, test fields with the test material (test chemical, detection chemical) may respectively be bonded adhesively onto the support material. Besides the test material, markings which are used for subsequent positioning of the test elements 116 in an analytical test instrument may furthermore be applied, for example printed, onto the support band 118 as well. The fabrication device 122 may comprise various individual devices for producing the test elements 116, for example coating nozzles, printers (for example screen, template, pad, inkjet or flexographic printers) or other types of fabrication apparatus or combinations of fabrication apparatus. A plurality of bands may also be combined as support materials. It is also possible to subdivide the fabrication partially into separate methods, so that for example semifinished products such as a printed support band may be delivered to the fabrication device 122. The apparatus of the fabrication apparatus 122, which are known to the person skilled in the art from the production of test elements, need not be discussed in further detail. It is particularly preferred for the fabrication apparatus 122 to be adapted so that it produces a wide support band 118 on which a plurality of test elements 116 are arranged in parallel with one another. For example, the band 118 may initially be configured so that five such test element tracks are arranged next to one another. These may then be cut into individual test element bands, for example by longitudinal cuts in a cutting device (symbolically denoted by 125 in FIG. 1). This cutting may be carried out at various stages of the production process shown in FIG. 1. A different configuration is nevertheless also possible, i.e. for example a configuration with merely one support band 118. The production device 110 in this exemplary embodiment furthermore has a central control unit 124. Likewise, as an alternative, this control unit 124 may also be constructed decentrally so that the production device 110 may for example comprise a plurality of controllers. These controllers may be connected to one another, or they may also operate autonomously. In this exemplary embodiment, the central control unit 124 comprises at least one processor 126 and at least one data memory 128. This at least one data memory 128 may in particular comprise a shift register. The central control unit 124 may for example be configured in program technology in order to control a production method, for example a production method according to one of the exemplary embodiments described above. The production device 110 furthermore comprises one or more test devices 130. This test device 130 is also represented merely symbolically in FIG. 1. For example, this test device 130 may comprise one or more cameras 132. These cameras may for example be configured to observe the test fields on the test elements 116, which are for example still configured as bandware at this production stage. The test device 130 may furthermore comprise an image recognition system 134, which may for example be designed decentrally or (as symbolically represented in FIG. 1) as a component of the central control unit 124. The image recognition system 134 may in particular comprise one or more image recognition software modules, which may for example run on the at least one processor 126. The image recognition system 134 may be adapted to evaluate image data, which are generated by the camera 132. In this way, for example, it is possible to identify when test fields of the test elements 116 deviate from a predetermined form, for example in respect of their shape and/or color. In this way, for example, defects which have occurred in the fabrication device 122 can be identified. Other types of defects may in principle also be detected, as well as other types of test devices 130, for example transmission measurements, reflection measurements, fluorescence measurements, resistance measurements, impedance measurements or combinations of these and/or other measurements. The test device 130 and/or the central control unit 124 may for example be configured so that information is assigned to each individual test field of the test elements 116. In the simplest case, this information may be a 1-bit value which is for example entered for each individual test field into a shift register of the data memory 128. In this way, the information travels virtually with the test elements in the throughput direction 120. Other types of information allocation may nevertheless also be envisaged. It will be assumed below that a 1-bit defect information value is stored, in which for example “0” stands for “defect-free” and “1” stands for “defective”. As described in detail above, other configurations of the defect information are nevertheless also possible. After the test device 130 in FIG. 1, the test elements 116 pass through a marking device 136 which is likewise represented merely symbolically in FIG. 1. According to the result of the defect check in the test device 130 as described above and the defect information for example correspondingly stored in the data memory 128 for each test element 116 and/or for each test field of the test elements 116, the test elements 116 are marked in this marking device 136. The marking is configured in particular so that the defect information can be reconstructed from it. For example, it is possible to mark each test element 116 as a whole and/or each test field of the test elements 116 individually. It will be assumed below that the marking is carried out so that defective test fields are marked whereas defect-free test fields and/or defect-free test elements 116 remained unmarked. In the present exemplary embodiment, it is assumed that the test materials of the test elements (i.e. the test chemical of the individual test fields of the test elements) is itself used as an information medium, i.e. as a radiation-sensitive material. This will be explained in more detail below. The marking device 136 has a radiation source 138 in the form of a light generator unit 140. This light generator unit 140 is constructed modularly and has for example a circuitry compartment 142 with a power supply in the form of an electrical supply unit 168 and a multiplicity of modular individual light sources 144. These individual light sources 144 are represented symbolically as light-emitting diodes in FIG. 1, UV light-emitting diodes preferably being used. The radiation source 138 in this exemplary embodiment is preferably connected via a fiber bundle 146 with a multiplicity of plastic fiber light guides 148 to at least one cross-section converter 150. This at least one cross-section converter 150, which will be explained in more detail below with the aid of FIG. 2, is arranged in an application position 152 preferably above the test elements 116. The test elements 116 are preferably guided in this application position in a guide table 154, in which case a plurality of bands (for example five bands after cutting in the cutting device 125) may be guided in parallel through the application position 152. The guide table 154 may in particular ensure that the bands of the test elements 116 are positioned exactly, in particular exactly with respect to the cross-section converter 150. In this way, according to the intended marking of the test elements 116 in the marking device 136, the test elements 116 may be exposed to radiation 156 (which is indicated merely symbolically in FIG. 1). This radiation exposure may in particular be controlled in turn by the central control unit 124, for example according to the information stored in the shift register of the data memory 128 for each individual test element 116 and/or for each individual test field of the test elements 116. After passing through the application position 152, the test elements 116 may in principle be used. An inspection device 157 is optionally provided in FIG. 1, which inspects whether the markings have been applied correctly in the marking device 136. For example, this inspection device 157 may comprise a separate photodiode or other detector for each band, which checks the markings. This information may for example be evaluated in the central control unit, where for example the identified markings are compared with setpoint information stored in the data memory 128, particularly in the shift register. If a defect marking is found in this case, then for example a warning may be sent or the respective test element 116 may be rejected. Furthermore, the test elements 116 may optionally also be subjected to other processing steps, for example further at least partial coating, application of protective materials or the like. As described above, to this end for example further fabrication devices 122 may follow downstream of the application position 152 in the throughput direction 120. As described in the introduction, there are many different embodiments of test elements. In FIG. 1, therefore, two possibilities in the form of a “branch” are represented symbolically and merely generically for the numerous different possibilities for the configuration of test elements which may be used in the scope of the present invention. Thus the bandware of the test elements 116 as a “precursor” may be divided up into individual test elements 112 for example in a dividing device 158 which is likewise represented merely symbolically in FIG. 1. This dividing device may be followed by a sorting device 160, in which the divided test elements 112 can be separated into defect-free and defective elements according to their marking applied in the application position 152. As described above, however, sorting into a plurality of classes may also be carried out instead of purely digital sorting. The sorting device 160 may then be followed by a packaging device 162 in which the test elements 112 are for example cassetted, magazined and/or provided with repackaging and/or blister packaging. As represented symbolically in FIG. 1, this results in the finished test element containers 164. As an alternative to dividing and producing individual test elements 112, the test elements may also be configured as band-like test elements 114. To this end, for example, sections of the bandware-type test elements 116 may be cut and processed in a cassetting device 166 to form band cassettes (indicated symbolically in FIG. 1). In order to be able to reject defective test elements (i.e. individual test elements suitable for a single test or test elements suitable for a plurality of tests) from test elements 114 in bandware form as well, the cassetting device 166 may in turn be preceded by a sorting device 160. In this sorting device 160, defect information may in turn be read out from the markings of the individual test elements or test element sections (i.e. sections which are respectively suitable for a single test). If it is found that a test element 114 or a section of this test element 114 is defective, then this section may for example be cut out. So that a continuous band can nevertheless subsequently be cassetted, the sorting device 160 may correspondingly be assigned a cutting and splicing device 167, which is arranged downstream of the sorting device 160 in FIG. 1. Other arrangements are however also possible, for example arrangements in which the cutting and splicing device 167 is a component of the sorting device 160. In the cutting and splicing device 167, band sections which are marked as being defective are cut out, removed and the ends of the remaining band are reconnected (“splicing”), for example by adhesive bonding. This technique is known for example from traditional cinema film technology. In this context, in view of the many different possibilities for the technical configuration of test elements, it should be pointed out that the term “test element” is to be interpreted in the broad sense in the scope of the entire invention. They may be elements which have at least one test field that is suitable for the qualitative or quantitative detection of the at least one analyte. For example, a single strip-shaped test element 112 with a single test field or a plurality of test fields may be used as the test element. For example, a plurality of test elements may respectively be provided for a particular analyte. As an alternative, as likewise explained above, bandware may also be used as test elements so that in this case band-like test elements 114 are provided. In this case, the entire test element bands of the band-like test elements 114 may be referred to as a test element, or individual test sections on these band-like test elements 114, for example test elements respectively with a test field, may be referred to as a test element. Without restriction of the possible other meanings and different nomenclature, the latter will be assumed below so that an individual test section for a test will be referred to as the test element 114 in the case of bandware. The light generator units 140 of the marking device 136, or the modularly constructed individual light sources 144, may in particular be configured so that a plurality of individual light sources 144 are combined in a circuitry compartment 142, one electrical supply unit 168 respectively being assigned five individual light sources 144 in a row in this exemplary embodiment. The individual light sources 144 are for example respectively enclosed by a slot-in housing which allows insertion into the circuitry compartment 142. A plug connector, via which the modular individual light sources 144 can be supplied with energy, may respectively be provided on the rear side of the slot-in housing. Data interchange may furthermore take place via these plug connectors, so that for example the individual light sources 144 (or individual radiation sources contained in these individual light sources 144) can be driven appropriately in order to control the marking in the marking device 136 expediently. For example, this control may in turn be carried out via a central control unit 124. The individual light sources 144 may respectively contain electronics boards which, for example, may comprise one or more printed circuit boards fitted with components. A multiplicity of light-emitting diodes, in particular UV light-emitting diodes 176, which can preferably be driven individually, may respectively be contained on these electronics boards. These UV light-emitting diodes 176 may preferably be light-emitting diodes with a wavelength in the range of about 250 nm to 400 nm, particularly in the range between 350 and 380 nm, which preferably have a power of from 50 mW to 500 mW, particularly preferably in the range of 100 mW to 200 mW. To this extent, the expression “individual light source” 144 is not to be understood as meaning that these individual light sources 144 respectively comprise only a single radiation source; rather, a plurality of radiation sources may be provided in the form of UV light-emitting diodes 176, as in this exemplary embodiment. A number of UV light-emitting diodes 176 equal to five may for example be provided per electronics board. For light guiding, for example, a coupling plate in which individual plastic fiber light guides 148 are fixed with their input ends, may be arranged above the UV light-emitting diodes 176. This fixing may for example be carried out by adhesive bonding, by clamping or by a combination of fixing techniques. Other techniques are also possible. The fixing is carried out such that one input end of the plastic fiber light guides 148 is respectively arranged above one UV light-emitting diode 176, so that the light of this UV light-emitting diode 176 is respectively input into one plastic fiber light guide 148. This simple allocation is generally sufficient for the input, although more complex input optics may also be provided, for example lens systems, in particular microlens systems, or similar input devices. The plastic fiber light guides 148 are subsequently combined to form fiber bundles 146, which may for example be fed out from the slot-in housing of the individual light sources 144 via strain relief devices. A plurality of the fiber bundles 146 may subsequently be assembled to form higher-level fiber bundles 146, for example in order to be guided as a common fiber bundle 146 to the application position 152 in FIG. 1 (in which case a plurality of application positions 152 may also be provided as appropriate). FIG. 2 shows a possible exemplary embodiment of a cross-section converter 150 in perspective representation. The cross-section converter 150 comprises a frame 182, in which for example a multiplicity of openings 184 may be provided, which may in particular allow pinning, screwing or other fixing of the cross-section converter 150. These openings 184, which may for example be configured as pinning bores or pin bores, are represented merely schematically in FIG. 2 and may also be adapted to the respective pinning situation or other assembly techniques and configured differently. In this way, a plurality of cross-section converters 150 can be combined to form cross-section converter modules, for example by pinning or screwing, and fixed in the application position 152. The frames 182 may for example be made of aluminium, stainless steel, plastic and/or other materials. The cross-section converters 150 are configured so that they split an incoming fiber bundle 146 (at the bottom in FIG. 2) into individual plastic fiber light guides 148. The output fiber ends of the individual plastic fiber light guides 148 (at the top in FIG. 2) are arranged to form a desired pattern 188 and fixed in this way. Again, this fixing may be carried out by clamping, adhesive bonding or by a type of fixing. In the preferred exemplary embodiment represented in FIG. 2, the pattern 188 has a line pattern in which, in this exemplary embodiment, fifteen fiber ends 186 are arranged preferably at least approximately equidistantly to form a line. Since preferably two or more such cross-section converters 150 are respectively arranged successively in the throughput direction 120 in a module, this respectively gives in total a line pattern with thirty or more fiber ends 186 arranged in a row. Each fiber end 186 may for example have a diameter of about 1 mm to 3 mm. Such a line emits for example in total a UV light power of about 500 mW to 1500 mW, for example about 1000 mW. As described above other types of patterns 188 may nevertheless also be used, for example matrix patterns with for example a rectangular matrix. Other configurations are also possible. In particular other types of fibers instead of plastic fiber light guides 148 may also be used, for example glass fibers. Also, instead of the simple output from the fiber ends 186 as represented in FIG. 2, additional beam shaping optics may be provided, for example with one or more common lenses for all the fiber ends 186, or with individual lenses for the fiber ends 186. In this way, the beam cross sections can be adapted further. In the arrangement according to FIG. 1, for example, a plurality of cross-section converters 150 in the application position 152 may be combined to form an application module 190. In this case a plurality of cross-section converters 150 are preferably pinned with pins and/or screwed through the openings 184 represented in FIG. 2. The openings 184 may for example be configured as bores and/or pin bores and/or threaded bores. In particular a clamping frame may be provided in order to receive the individual modules of the cross-section converters 150. In the representation according to FIG. 1, each of the cross-section converters 150 may for example correspond to the exemplary embodiment according to FIG. 2, although the cross-section converters 150 are rotated in comparison with FIG. 2 so that the fiber ends 186 (not visible in FIG. 1) point downwards in FIG. 1. Preferably (not represented in FIG. 1) two such cross-section converters 150 are arranged successively in series in the throughput direction 120, and preferably five such cross-section converter pairs are arranged next to one another perpendicularly to the throughput direction 120. The guide table 154 represented schematically in FIG. 1 comprises for example five rectangular guide grooves, which are respectively matched in respect of their dimensioning to the bandware of the test elements 116. This dimensioning may for example be configured so that these guide grooves correspond in their width to the individual strips which are obtained after the cutting device 125 (in which wide test strips are for example cut longitudinally into three, five or another number of narrower strips) and are respectively delivered to the guide grooves. Overall positioning of uncut test elements 116 by the guide table 154 is however also possible in principle. In this way the band-like test elements 116 are guided precisely by the guide table 154 and its guide grooves, so that the test elements 116 or test fields arranged thereon and/or other types of radiation-sensitive materials (for example marking fields) can be positioned exactly with respect to the fiber ends 186. Since for example the shift register of the data memory 128 in FIG. 1 contains information as to which test elements or test fields or marking fields are currently located in the application position 152, the individual light sources 144 or light-emitting diodes 176 contained in them can thereby be switched appropriately in order to mark particular test elements 116 expediently, particular test fields and/or particular marking fields. As an alternative or in addition, here as in other possible embodiments of the invention, positioning marks may also be provided on the test elements 116, which additionally facilitate positioning and/or identification of the test elements 116 for marking. FIG. 3 represents an exemplary embodiment of the test element 116. The test element 116 is configured as bandware in this example, merely one test section of the band being shown. The band of the test element 116 in this exemplary embodiment is provided with a multiplicity of positioning marks 195, which are printed onto the endless band 118 for example by a screen printing method. These positioning marks 195 may be used for positioning the bandware during production of the test elements 116, and/or they may be used to position the test elements correctly for sample application and/or evaluation of the test subsequently during use of the test elements 116 in an analysis instrument. The exemplary embodiment in FIG. 3 shows a test element 116 before it passes through a cutting device 125 (see FIG. 1). This means that in the case represented it is still a wide uncut raw band, in which three individual (in this case rectangular) test fields 196, 198 and 200 are respectively arranged parallel to one another on the endless band 118 and in this state still form an overall test field 204. This uncut band may subsequently also be cut in the cutting device 125, for example along the cutting lines 201 indicated in FIG. 3, so as to finally obtain the actual band-like test elements 116 in which only one of the test fields 196, 198, 200 is respectively arranged adjacently. The edge strips without test fields may be discarded. As an alternative, however, the band represented in FIG. 3 may also be used uncut so that a test element 116 has three test fields 196, 198, 200 next to one another. These could for example be used for averaging. The test fields 196, 198 and 200 comprise for example a detection chemical which experiences a color transformation when a liquid sample is applied, for example a blood sample, according to the presence of an analyte, for example blood glucose. This detection chemical is employed as a radiation-sensitive material 202 in the present exemplary embodiment, which is used as an information medium for the defect information. As explained above, however, in this or other exemplary embodiments it would also be possible to use separate marking fields which have radiation-sensitive materials independently of the test chemical. The exemplary embodiment of a test element 116 as represented in FIG. 3 has already passed through the application position 152. The upper test field 196 in FIG. 3 has deliberately been exposed by means of the radiation source 138, which results in a visible color change of this test field 196 relative to the unexposed test fields 198, 200. In this way, for example, the upper test field 196 can deliberately be made unusable for an analysis. The color change may for example be identified photometrically (for example by a reflection, transmission or color measurement or other types of measurements). It should be pointed out that the test element 116 represented in FIG. 3 was therefore not produced in the fabrication device 110 shown in FIG. 1, since the test elements 116 in FIG. 1 are already cut in the cutting device 125 before they reach the marking device 136, in contrast to the uncut and still marked test element 116 in FIG. 3. The example in FIG. 3 serves however merely to illustrate the principle of the invention. Marking after cutting is also possible, similarly as in FIG. 1. FIG. 4 symbolically represents an exemplary embodiment of an analytical test instrument 206 according to the invention, which operates with test elements 114 marked according to the invention. Furthermore, FIG. 5 represents a possible method for detecting at least one analyte in a sample, which may be carried out particularly in conjunction with the analytical test instrument represented in FIG. 4 but which may however also be used independently of it. It should be pointed out that in the ideal case, which also constitutes the normal case, the test elements 114 are produced so that no test elements 114 marked as being defective enter circulation. To this extent the analytical test instrument 206 described below, or an analytical test instrument 206 according to the invention in another embodiment of the invention, merely provides additional security that if despite rejection of defective test elements 114 during production, such test elements marked 114 as being defective should enter into circulation, they are not used for tests. As an alternative, although this is less preferred, selection could be carried out only at the time of testing by means of the analytical test instrument 206, so that test elements 114 marked as being defective are not rejected until during the testing, i.e. they are not used. This would have the disadvantage that under certain circumstances a smaller number of test elements 114 would be available, although this could be possibly be compensated for by a surplus of test elements 114 (i.e. an extra number in addition to the nominal number of individual test elements 114), particularly in the case of a multiplicity of test elements 114. In this exemplary embodiment, the analytical test instrument 206 has for example a band-like test element 114, for example a test element 114 held in a band cassette. Other types of test elements could nevertheless also be provided as an alternative or in addition, for example strip-like test elements, for example in a linear magazine, a drum magazine, a disc magazine or another type of magazine. In this exemplary embodiment, the analytical test instrument 206 has an optical excitation device 208 and an optical detection device 210, which are indicated merely symbolically in FIG. 4. By means of this excitation device 208 which may for example comprise one or more light sources, and the detection device 210 which may for example comprise one or more photodiodes, one or more test fields 212 on the test element may for example be examined for analyte-introduced color changes in a test position 214. The analytical test instrument 206 in this example preferably has a cover 216 in a housing 218 of the analytical test instrument 206. This cover 216 releases the test position 214 or a test field 212 located in this test position 214 for the application of a sample 220, which is preferably a liquid sample in this exemplary embodiment. The analytical test instrument 206 furthermore has a drive and evaluation unit 222. This drive and evaluation unit 222 may for example comprise one or more microcomputers and be adapted to drive the excitation device 208 and/or the detection device 210. Transport of the band-like test element 114 may furthermore be controlled, so that delivery of a test field 212 into the test position 214 can be controlled. These controls, and data interchange in the other direction, are symbolically indicated by the double arrow 224 in FIG. 4. The analytical test instrument 206 furthermore preferably has indicator means, for example a display 226, and user interface elements 228. In this way, the functions of the analytical test instrument 206 can be controlled and measurement information can be output. In normal operation i.e. operation known to the prior art, under the control of the drive and evaluation unit 222 a particular test field 212 is moved into the test position 214, the cover 216 is released and application of the sample 220 is enabled. An optical evaluation of the test field 212 is subsequently carried out by the excitation device 208 and the detection device 210, so that for example an analyte concentration can be determined, in particular a blood sugar concentration. This may for example be output on the display 226. According to the invention, however, the analytical test instrument 206 in the exemplary embodiment represented in FIG. 4 furthermore has an interrogation device 230 which is adapted to identify and evaluate markings which, for example, have been applied onto the test element 114 and/or the test field 212 according to the method described above. In this exemplary embodiment represented in FIG. 4, this interrogation device 230 uses the excitation device 208 and the detection device 210 as well as a corresponding interrogation algorithm, for example implemented as software technology in the drive and evaluation unit 222. As an alternative, however, the interrogation device 230 could also be implemented as a separate device distinct from the excitation device 208 and the detection device 210, for example by means of a separate interrogation excitation device and/or a separate interrogation detection device (not represented in FIG. 4). Marked test elements 114 and/or marked test fields 212 may be identified in this way, for example by detecting a coloration of the test fields 212. In the proposed method, a particular test element 114 and/or a particular test field 212 is initially provided in the test position 214. This is denoted symbolically by the reference 232 in FIG. 5. The interrogation device 230 is subsequently used to interrogate whether the test field 212 and/or the test element 114 is provided with a marking, and/or the defect information contained in the marking is read out (step 234). This information may for example be evaluated in the drive and evaluation unit 222. A decision step 236 may subsequently be carried out, in which a decision is made as to whether the test field 212 and/or the test element 114 is defective according to the defect information read out (branch 238) or defect-free (branch 240 in FIG. 5). If the test field 212 and/or the test element 114 is identified as defective, a warning may optionally be sent to the user, for example in the form of a visual warning (for example on the display 226) and/or an acoustic warning. As an alternative or in addition, as represented in FIG. 5, step 232 may be repeated, a new test field 212 and/or test element 114 being provided. In the arrangement according to FIG. 4, for example a fresh previously unused test field 212 may be moved into the test position 214. For example, with the arrangement in FIG. 4, the method steps described so far may be carried out such that the cover 216 is closed while these method steps are being carried out, so that application of the sample 220 is not yet possible. If however it is found in step 236 that the test field is defect-free, then a measurement 242 may subsequently take place, the detection of at least one analyte in the sample 220 being carried out. For example, in the scope of this measurement in FIG. 4 the cover 216 may be released and/or the excitation device 208 and the detection device 210 may be put into operation, for example in order to carry out an analyte-induced color change. FIG. 6 represents an exemplary embodiment of a possible band cassette 244, which may for example be used in the analytical test instrument 206 represented in FIG. 4 and which makes it possible for example to carry out a multiplicity of glucose analyses on liquid samples 220 (for example blood samples) obtained in situ by the patient himself. To this end, the band cassette 244 comprises a test element 114 in the form of an analytical test band 246. The analytical test band 246 can be drawn from a storage spool 248 and wound via a band guide 250 onto a winding spool 252. A test band section 254 of the analytical test band 246 is in this case stretched flat over a plane bearing frame 258 at a measurement site 256, in order to allow application of the liquid sample 220 on the front side, for example in the form of bodily fluid (for example blood or tissue fluid) and precise reflectometric measurement on the rear side. The test band 246 has a transparent support band 260 which, for example, may correspond to the endless band 118 in FIG. 3 (in cut form). On the front side of this support band 260, for example similarly as at the top of FIG. 3, test fields are applied like labels, which may for example correspond to the test fields 196, 198 and 200 in FIG. 3. These test fields 262 may for example comprise dry chemicals, which respond to the analyte (for example glucose) in the applied liquid sample 220 (for example blood fluid) and lead to a measurable variation in the back-scattering of light when illuminated from the rear side. For example, the support band 260 may have a 5 mm wide and about 10 μm thick sheet, on the front side of which a detection film with a thickness of 50 μm is locally applied (for example labelled on). For a measurement, measurement light is shone through a measurement opening 264 bordered by the bearing frame 258 and reflected, without optical elements such as lenses, filters or physically filled windows needing to be present inside the aperture region. The measurement opening 264 may however if necessary be surrounded by a shutter (not represented in FIG. 6). This allows defined rear-side focusing or alignment of an optical measurement unit (not contained in the band cassette 244) of the analytical test instrument 206 onto the test band section 254, which is exposed flatly through the measurement opening 264. In order to transport the test fields 262 successively to the measurement site 256, a band drive of the analytical test instrument 206, engaging in a hub 266 of the winding spool 252, makes it possible to wind the test band 246 forward. Retaining forces of about 2 newtons are in this case generated by friction on the storage spool 248 and in the region of the band guide 250 (in particular on a push-through seal 268 there), so that the test band 246 is tensioned sufficiently to ensure that it bears flatly on the bearing frame 258. The band guide 250 may for example be formed by an injection-moulded polypropylene part, which may likewise form a support body for the spools 248, 252. In order to cover the band guide 250 on the outside, a lid part 270 is provided which has a hole on a tapered narrow side wall for readily accessible of release of the bearing frame 258. As explained above, either the test element 114, which is provided in cassetted form here, may be understood as the entire analytical test band 246 or individual test band sections 254 (for example test band sections respectively with one test field 262) may also be considered as such test elements 114. The test band 246 as a whole may respectively be marked or, as an alternative or in addition, marking of individual test band sections 254 may also be carried out by means of the method proposed above. If a separate device is used in order to read out defect markings, this may for example be integrated into the said optical measurement unit of the analytical test instrument 206. As an alternative, as described above, the excitation device 208 and the detection device 210 of the analytical test instrument 206 may also fulfill the function of reading out the defect markings in addition to the analysis function. Combinations of these two possibilities may also be envisaged, for example in the scope of a separate light source for reading out the defect markings, although with the detection device 210 simultaneously performing the defect readout task. In this way, by using the band cassette 244 represented in FIG. 6, the analytical test instrument 206 may for example be adapted to interrogate whether the test band section 254 currently located in the measurement site 256 is defective, before carrying out the measurement. If it is, then for example the next test band section 254 is wound forward by corresponding actuation of the spools 248, 252, and the procedure is repeated for example by using the method described above with reference to FIG. 5. While the invention has been illustrated and described in detail in the drawings and foregoing description, the same is to be considered as illustrative and not restrictive in character, it being understood that only the preferred embodiments have been shown and described and that all changes and modifications that come within the spirit of the inventions are desired to be protected. It should be understood that while the use of words such as preferable, preferably, preferred or more preferred utilized in the description above indicate that the feature so described may be more desirable, it nonetheless may not be necessary and embodiments lacking the same may be contemplated as within the scope of the invention, the scope being defined by the claims that follow. In reading the claims, it is intended that when words such as “a,” “an,” “at least one,” or “at least one portion” are used there is no intention to limit the claim to only one item unless specifically stated to the contrary in the claim. When the language “at least a portion” and/or “a portion” is used the item can include a portion and/or the entire item unless specifically stated to the contrary. Furthermore, all patents, patent applications, and publications cited herein are hereby incorporated by reference. 110 production device 112 test elements, divided up 114 test elements, cassetted 116 test elements, bandware 118 endless band 120 throughput direction 122 production device 123 bonding station for adhesive bonding of the test materials 124 central control unit 125 cutting device 126 processor 128 data memory 130 test device 132 camera 134 image recognition system 136 marking device 138 radiation source 140 light generator unit 142 circuitry compartment 144 individual light sources 146 fiber bundle 148 plastic fiber light guide 150 cross-section converter 152 application position 154 guide table 156 radiation 157 control device 158 dividing device 160 sorting device 162 packaging device 164 finished test element container 166 cassetting device 167 cutting and splicing device 168 electrical supply unit 176 UV light-emitting diodes 182 frame 184 openings 186 fiber ends 188 pattern 190 application module 195 positioning marks 196 test field 198 test field 200 test field 201 cutting lines 202 radiation-sensitive material 204 overall test field 206 analytical test instrument 208 excitation device 210 detection device 212 test field 214 test position 216 cover 218 housing 220 sample 222 drive and evaluation unit 224 control 226 display 228 user interface elements 230 interrogation device 232 provision of a new test field/test element 234 interrogate marking 236 test field/test element defective? 238 test field/test element defective 240 test field/test element defect-free 242 measurement 244 band cassette 246 analytical test band 248 storage spool 250 band guide 252 winding spool 254 test band section 256 measurement site 258 bearing frame 260 support band 262 test fields 264 measurement opening 266 hub 268 push-through seal 270 lid part
	claims	1. A phase plate for use in a particle-optical apparatus, said phase plate to be irradiated by a beam of particles, said phase plate comprising:a central structure that is non-transparent to particles,said central structure surrounded by an area transparent to particles;said central structure surrounding a foil transparent to particles, said foil surrounding a central through-hole for passing a part of the beam, said foil equipped to cause a phase shift between the part of the beam passing through the through-hole and the part of the beam passing through the foil; andsaid central structure equipped to cause a phase shift between the part of the beam passing through the foil and the through-hole and the part of the beam passing outside the central structure. 2. The phase plate of claim 1 in which the foil is a carbon foil. 3. The phase plate of claim 1 in which for at least one line in the plane of the phase plate and passing through the centre of the through-hole, said line thus intersecting the central structure at two opposite sides, the at least one line intersects the central structure from a distance R1 to a distance of R2 from the through-hole in one direction, and a distance from R3 to a distance of R4 from the through-hole in the other direction, and in which R3≧R2. 4. The phase plate of claim 3 in which the central structure is formed from two half-annuli, one half-annulus with inner radius R1 and outer radius R2, and the other half-annulus with an inner radius of R3 and an outer radius of R4, and in which R3≧R2, and the through-hole is located at the centre points of the two annuli from which the two half-annuli are formed. 5. Particle-optical apparatus equipped with a phase plate and equipped with an objective lens, said particle-optical apparatus illuminating a sample with a beam of particles the phase plate placed substantially in a plane where the beam illuminating the sample is focused, in which the phase plate is the phase plate according to claim 1. 6. The particle-optical apparatus of claim 5 in which, in working, the combined phase shift caused by the foil and the electric potential in the central structure results in a phase shift θ of substantially θ=n·π for the particles transmitted through the foil, with n an integer. 7. The particle-optical apparatus of claim 6 in which, in working, the combined phase shift caused by the foil and the electric potential in the central structure results in a phase shift θ of substantially θ=0. 8. The particle-optical apparatus according to claim 5 in which the apparatus is equipped to image the back-focal plane of the objective lens on the phase plate with a variable magnification. 9. Method of forming an image using a particle-optical apparatus equipped with an objective lens for illuminating a sample and a phase plate, the particle-optical apparatus equipped to image the plane where the objective lens forms a focus onto the phase plate, characterized in that:the particle-optical apparatus is equipped with the phase plate according to claim 1, andthe particle-optical apparatus is equipped to image the plane where the objective lens forms a focus onto the phase plate with a variable magnification,and the method comprises;determining a desired lower spatial frequency range of the image, said lower spatial frequency range caused by the interference of particles transmitted through the foil with particles passing through the through-hole;determining a desired higher spatial frequency range of the image, said higher spatial frequency range caused by the interference of particles transmitted around the central structure with particles passing through the through-hole; andadjusting the magnification with which the back-focal plane is imaged on the phase plate so that particles corresponding with said lower and the higher spatial frequency range are not intercepted by the central structure. 10. The method of claim 9 in which determining a lower spatial frequency range and determining a higher spatial frequency range takes the form of determining a central spatial frequency around which said lower spatial frequency range and said higher spatial frequency range are centred. 11. A particle-optical apparatus for forming an image of a sample comprising:an objective lens for illuminating a sample with charged particles; anda phase plate defining a first region in which the phase of the charged particles passing through the first region is shiftable by an adjustable amount;a second region within the first region, in which the phase of the charged particles passing through the second region is shifted by a fixed amount in addition to the adjustable amount; anda third region, outside of the first region, through which pass charged particles that did not pass though the first region, the charged particles passing through the three regions combining to form an image of a sample. 12. The particle-optical apparatus of claim 11 in which the phase plate include electrodes to provide in the first region an electric field that is adjustable to adjust the phase shift of charged particles passing through the first region and in which the second region includes a film that shifts the phase of the charged particles passing through the second region. 13. The particle-optical apparatus of claim 11 in which the phase of the charged particles passing through the third region is not shifted. 14. The particle-optical apparatus of claim 11 in which the sum of the fixed amount of phase shift in the second region and the adjustable phase shift in the first region results in a phase shift such that particles passing through the second region differ in phase from particles passing though the third region by n·π radians, with n being an integer. 15. The particle-optical apparatus of claim 11 in which the fixed amount of phase shift in the second region is equal in magnitude and opposite in sign to the adjustable phase shift in the first region. 16. The particle-optical apparatus of claim 11 in which the second region is defined by a film through which the charged particles pass and in which the portion of the first region that is not included in the second region is a hole in the film defining second region. 17. A particle-optical apparatus for forming an image of a sample comprising:an objective lens for illuminating a sample; anda phase plate for shifting the phase of some particles in a beam relative to other particles in the beam, the phase plate defining three regions through which charged particles pass:a foil region defined by a foil that shifts the phase of charged particles passing through the foil by a fixed amount;a through-hole region defined by a hole in the foil; andan exterior region outside the outer diameter of the foil,the charged particles passing through the fixed shift region, the through-hole region, and the exterior region combining to form an image of the sample. 18. The particle-optical apparatus of claim 17 in which the phase plate comprises two partial annuluses having different inner diameters so that if a particle scattered at an angle of α impacts one of the annuluses, a second particle scattered at an angle −α will not impact the second annulus, except at the areas at which the annuluses connect. 19. The particle-optical apparatus of claim 18 further comprising electrode to provide an electric field to shift the phase of the charged particles passes through the foil region and the through-hole region. 20. The particle-optical apparatus of claim 18 in which the shape of the foil region is defined by two partial annuluses having different inner diameters such that if a particle scattered at an angle of α impacts one of the annuluses, a second particle scattered at an angle −α will not impact the second annulus, except at the areas at which the annuluses connect. 21. Method of forming an image using a particle-optical apparatus equipped with an objective lens for illuminating a sample and a phase plate, the particle-optical apparatus equipped to image the plane where the objective lens forms a focus onto the phase plate, comprising:passing a first set of charged particles through a first region in which the phase of the charged particles is shifted by a first amount;passing a subset of the first set of charged particles through a second region, which is a subset of the first region and in which the charged particles in the subset are phase shifted by second amount;passing a second set of charged particles though a third region in which the charged particles are phase shifted by a third amount;combining the charged particles in the first and second sets of charged particles to form an image. 22. The particle-optical apparatus of claim 21 in which the second amount and the third amount differ by n·π, n being an integer.
055531075	summary	BACKGROUND OF THE INVENTION The invention relates to a pressurized water nuclear reactor vessel having support columns supporting an upper support plate above an upper core support plate in its upper plenum and, more particularly, to a pressure vessel having slotted support columns for guiding reactor coolant flowing from the upper core support plate into the upper plenum. In the power operation of a pressurized water nuclear reactor facility, reactor coolant absorbs heat from fission reactions of pelletized fuel contained within thousands of one inch or smaller diameter fuel rods arranged in about 120 to about 190 fuel assemblies supported in the core of a reactor vessel by a lower core support plate and an upper core support plate. Hot coolant streams then flow from the core region upwardly through various passageways in the upper core support plate into an upper plenum where the several coolant streams mix together and then flow from the upper plenum through a hot leg to a steam generator. In commercial facilities, fuel assemblies having different enrichments are loaded into the core in patterns which provide a uniform power distribution throughout the core. In low leakage fuel assembly loading patterns, the most highly enriched fuel assemblies are generally located between peripherally located lower enrichment fuel assemblies (which advantageously reduces the neutron fluence and improves the core efficiency) and the lowest enriched fuel assemblies in the central core region. However, calculations have shown that the temperatures of the coolant streams flowing through the passageways above the various regions of a core having a low leakage pattern may vary up to about thirty to fifty degrees Fahrenheit or more. The inventors have determined that these coolant streams may not sufficiently thermally mix together in the upper plenum above the upper core support plate and that this thermal condition may cause hot leg streaming of the coolant flowing through the hot leg with significant temperature deviations from the bulk coolant temperature. Hot leg streaming may result in inaccurate readings by hot leg resistance temperature detectors and uncertain heat balances around the reactor. SUMMARY OF THE INVENTION Thus, it is an object of the present invention to thermally mix the streams of hot coolant in the upper plenum before the coolant flows into the hot leg. It is a further object of the present invention to mitigate hot leg streaming. With these objects in view, the present invention resides in a pressurized water nuclear reactor pressure vessel having an upper plenum defined by core support plate and an upper support plate. Support columns extend upwardly through the plenum for supporting the upper support plate above the upper core support plate. The core support plate has passageways for the passage of coolant into the upper plenum and peripheral hollow support columns extending upwardly above the peripheral passageways. These columns have unslotted lower sections and peripherally slotted upper portions for guiding the coolant flowing from the underlying passageways into the upper regions of the plenum. Advantageously, relatively cold coolant streams flowing from the peripheral columns will substantially mix with the bulk of the coolant in the plenum before flowing into the hot leg.
	summary
046631097	claims	1. A closed, curved, planar toroidal field coil for use on a stellarator having a helical axis, said coil having a radius r.sub.o, pitch kr.sub.o and period m, the curve of said coil being defined in .rho., .theta. coordinates by the relationship: EQU .rho.=a.sub.c +.delta..sub.2 cos 2.theta.+.delta..sub.3 cos 3.theta. where a.sub.c, .delta..sub.2, and .delta..sub.3 are constants and at least one of .sub.2 and .sub.3 is not equal to zero and wherein a.sub.c, .delta..sub.2, and .delta..sub.3 satisfy the relationship: ##EQU6## and .delta..sub.2 .noteq.0 and .delta..sub.3 .noteq.0. 2. The coil of claim 1 wherein the curve of said coil is substantially "D" shaped. 3. The coil of claim 1 wherein the curve of said coil is substantially "bean" shaped. 4. The coil of claim 1 wherein kr.sub.o =1, .delta..sub.2 /a.sub.c =-0.3, and .delta..sub.3 /a.sub.c =-0.1. 5. Apparatus for confining a plasma comprising: a closed endless tube; and a plurality of closed, curved, planar coils spaced about said tube, the centers of said coils defining a helical axis, said helical axis having a radius r.sub.o, pitch kr.sub.o and period m and being substantially parallel to the axis of said tube, the plane of each coil being substantially perpendicular to said helical axis, the curve of each coil being defined in .rho., .theta. coordinates by the relationship: EQU .rho.=a.sub.c +.delta..sub.2 cos 2.theta.+.delta..sub.3 cos 3.theta., 6. The apparatus of claim 5 wherein the axis of said tube is coaxial with the helical axis of said coils. 7. The apparatus of claim 6 wherein kr.sub.o =1, .delta..sub.2 /a.sub.c =-0.3, and .delta..sub.3 /a.sub.c =-0.1.
	summary
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	claims	1. A fuel bundle for a liquid metal cooled reactor, comprising:a channel;a nose assembly secured to a lower end of the channel;a plurality of fuel rods disposed within the channel, at least one of the fuel rods having at least one guard ring surrounding the fuel rod and spacing the fuel rod from adjacent fuel rods,wherein the at least one guard ring is only rigidly affixed to the fuel rodthe plurality of fuel rods including a first set of fuel rods and a second set of fuel rods, each of the fuel rods in the first set of fuel rods having a first pattern of one or more guard rings longitudinally arranged thereon, each of the fuel rods in the second set of fuel rods having a second pattern of one or more guard rings longitudinally arranged thereon, the first pattern being different than the second pattern. 2. The fuel bundle of claim 1, wherein the fuel rod includes more than one guard ring disposed along a longitudinal length of the fuel rod. 3. The fuel bundle of claim 1, wherein at least a first fuel rod and a second fuel rod in the plurality of fuel rods each have at least one guard ring, the guard ring of the first fuel rod being at a different longitudinal position than the guard ring of the second fuel rod. 4. The fuel bundle of claim 1, wherein at least one fuel rod of the plurality of fuel rods does not have a guard ring. 5. The fuel bundle of claim 1, further comprising:tabs extending from walls of the channel to space fuel rods in the plurality of fuel rods away from the walls of the channel. 6. The fuel bundle of claim 1, wherein the first pattern of one or more guard rings includes a first repeating pattern of more than one guard ring longitudinally arranged along each of the fuel rods in the first set of fuel rods, and the second pattern of one or more guard rings includes a second repeating pattern of more than one guard ring longitudinally arranged along each of the fuel rods in the second set of fuel rods, the first repeating pattern and the second repeating pattern being different. 7. The fuel bundle of claim 6, wherein the first repeating pattern and the second repeating pattern are different because the more than one guard ring longitudinally arranged along each of the fuel rods in the first set of fuel rods is positioned at a different axial elevation within the fuel bundle as compared to the more than one guard ring longitudinally arranged along each of the fuel rods in the second set of fuel rods. 8. The fuel bundle of claim 6, wherein,the more than one guard ring longitudinally arranged along each of the fuel rods of the first set of fuel rods includes a first plurality of guard ring subsets, the first plurality of guard ring subsets including more than two groupings of guard rings where each grouping shares a common axial elevation within the fuel bundle,the more than one guard ring longitudinally arranged along each of the fuel rods of the second set of fuel rods includes a second plurality of guard ring subsets, the second plurality of guard ring subsets including more than two groupings of guard rings where each grouping shares a common axial elevation within the fuel bundle. 9. A fuel bundle for a liquid metal cooled reactor, comprising:a channel;a nose assembly secured to a lower end of the channel;a plurality of fuel rods disposed within the channel, at least one of the fuel rods having at least one guard ring surrounding the fuel rod and spacing the fuel rod from adjacent fuel rods,wherein the plurality of fuel rods include a first set of fuel rods and a second set of fuel rods, each of the fuel rods in the first set of fuel rods has a first pattern of the one or more guard rings longitudinally arranged thereon, each of the fuel rods in the second set of fuel rods has a second pattern of the one or more guard rings longitudinally arranged thereon, the first pattern being different than the second pattern. 10. The fuel bundle of claim 9, wherein the first pattern of the one or more guard rings includes a first repeating pattern of more than one guard ring longitudinally arranged along each of the fuel rods in the first set of fuel rods, and the second pattern of the one or more guard rings includes a second repeating pattern of more than one guard ring longitudinally arranged along each of the fuel rods in the second set of fuel rods, the first repeating pattern and the second repeating pattern being different. 11. The fuel bundle of claim 10, wherein the first repeating pattern and the second repeating pattern are different because the more than one guard ring longitudinally arranged along each of the fuel rods in the first set of fuel rods is positioned at a different axial elevation within the fuel bundle as compared to the more than one guard ring longitudinally arranged along each of the fuel rods in the second set of fuel rods. 12. The fuel bundle of claim 10, wherein,the more than one guard ring longitudinally arranged along each of the fuel rods of the first set of fuel rods includes a first plurality of guard ring subsets, the first plurality of guard ring subsets including more than two groupings of guard rings where each grouping shares a common axial elevation within the fuel bundle,the more than one guard ring longitudinally arranged along each of the fuel rods of the second set of fuel rods includes a second plurality of guard ring subsets, the second plurality of guard ring subsets including more than two groupings of guard rings where each grouping shares a common axial elevation within the fuel bundle. 13. The fuel bundle of claim 1, wherein the at least one guard ring is circular. 14. The fuel bundle of claim 9, wherein the at least one guard ring is circular.
044407181	abstract	A dismountable and movable device for the transfer of fuel assemblies for a breeder nuclear reactor, comprising a platform (11) mounted for rotation on a support (12) resting on the structure of the reactor. The platform is provided with apertures (19, 20) and carries a hopper (23) which can contain a fuel assembly (5) in vertical position, at the level of one of the apertures (19). The apertures can be brought into correspondence with vertical shafts (14, 15) permitting access to storage (5a) and evacuation (5b) positions for the assemblies (5). The hopper (23) contains a winch (37) for the vertical displacement of the assemblies in the hopper and the shafts when they are in correspondence. The shafts and the platform comprise complementary connecting and sealing devices to assure the connection between the hopper and the shafts. The device is particularly useful for reactors grouped on one and the same site where transport of the assemblies is effected by modules displaced on the site.
	summary
	claims	1. A nuclear steam supply system comprising:a containment enclosing a primary loop of the nuclear steam supply system within an interior thereof;a reactor vessel supported within a reactor well within a lower interior of the containment, the reactor well having walls that substantially surround a lower portion of the reactor vessel;a vertical shield wall that extends up from an upper portion of the reactor well walls and substantially encircles an upper portion of the reactor vessel and extends vertically above the reactor well substantially to an elevation of an operating deck;a missile shield capping a top of the vertical shield wall; andwherein the shield wall includes at least one air inlet door located along at least a portion of a lower section of the shield wall, the inlet door being configured to be normally closed during reactor operation, but is configured to be opened during an outage to enable cooling air flow along an interior of the shield wall, and an outlet door located along at least a portion of an upper section of the shield wail, below the operating deck, the outlet door being configured to be normally closed during, reactor operation, but is configured to be opened during an outage to enable cooling air flow along the interior of the shield wall. 2. The nuclear steam supply system of claim 1 including a plurality of the outlet doors spaced circumferentially around. the upper section of the shield wall. 3. A nuclear steam supply system comprising:a containment enclosing a primary loop of the nuclear steam supply system within an interior thereof;a reactor vessel supported within a reactor well within a lower interior of the containment the reactor well having walls that substantially surround a lower portion of the reactor vessel;a vertical shield wall that extends up from an upper portion of the reactor well walls and substantially encircles an upper portion of the reactor vessel and extends vertically above the reactor well substantially to an elevation of an operating deck;a missile shield capping a top of the vertical shield wall; andwherein the shield wall includes at least one air inlet door located along at least a portion of a lower section of the shield wall, the inlet door being configured to be normally closed during reactor operation, but is configured to be opened during an outage to enable cooling air flow along an interior of the shield wall and wherein the inlet door has a neutron absorbent panel. 4. The nuclear steam supply system of claim 3 wherein the neutron absorbent panel is removeably attached to the inlet door with fasteners. 5. The nuclear steam supply system of claim 3 wherein the neutron absorbent panel is formed from a metal can filled with boro-silicate concrete. 6. A nuclear steam supply system comprising:a containment enclosing primary loop of the nuclear steam supply system within an interior thereof:a reactor vessel supported within a reactor well within a lower interior of the containment, the reactor well having walls that substantially surround a lower portion of the reactor vessel:a vertical shield wall that extends up from an upper portion of the reactor well walls and substantially encircles an upper portion of the reactor vessel and extends vertically above the reactor well substantially to an elevation of an operating deck;a missile shield capping a top of the vertical shield walk; andwherein the shield wall includes at least one air inlet door located along at least a portion of a lower section of the shield wall, the inlet door being configured to be normally closed during reactor operation, but is configured to he opened during an outage to enable cooling air flow along an interior of the shield wall and wherein the containment has a polar crane with an main and auxiliary hook and the shield wall is constructed in sections with substantially each section having a weight that is no heavier than can be lifted by the auxiliary hook.
	summary
053373375	summary	BACKGROUND OF THE INVENTION The present invention relates to a fuel assembly and more particularly to a fuel assembly suitable for application to a water cooling-type nuclear reactor, which can be attain a higher burnup, improve fuel economy and contribute to a desired thermal allowance. A fuel assembly for a boiling water-type nuclear reactor generally comprises bundles of fuel rods each comprising a cladding and fuel pellets containing a fissile material, filled in the cladding, and a channel box having a square cross-section, which covers the fuel rods, as disclosed by a book "Light water reactor" written by Mamoru Akiyama and published by Dobun Shoin Publishing Co., Tokyo, Japan. Reactor core is charged with a plurality of the fuel assemblies. As fuel material, enriched uranium or mixed material of plutonium and uranium is used in an oxide form. The reactivity of reactor core decreases with burning of the fissile material contained in the fuel material, and thus more fissile material than the critical mass is charged in the reactor core in the initial period of an operation cycle of a nuclear reactor so as to keep the nuclear reactor in a critical state even at the final stage of the operating cycle. The resulting excess reactivity is controlled by inserting a control rod of cross type cross-section containing boron carbide or hafnium between a plurality of the adjacent fuel assemblies and adding a burnable poison such as gadolinia, etc. to the fuel material, thereby adjusting the neutron absorption. Recently, higher burnup is keenly desired from the viewpoint of prolongation of continuous operation period of a nuclear reactor and reduction in generation of spent fuel assemblies. In order to attain the higher burnup, it is necessary to increase the fuel enrichment, but the excess reactivity is inevitably increased thereby. In the assemblies of the prior art, gadolinia (oxide of gadolinium) is used as a burnable poison. Gadolinium is characterized in that the excess reactivity can be controlled with a small amount of added gadolinium, because the thermal neutron absorption cross-section of odd nuclei (.sup.155 Gd and .sup.157 Gd) is considerably large, as shown in FIG. 3. However, gadolinium has a (n, .gamma.) nuclear reaction chain and a large resonance integrate of converted even nuclei (.sup.156 Gd and .sup.158 Gd) (see FIG. 3), and thus is a cause for neutron parasitic absorption. That is, when the excess reactivity increased by higher burnup is controlled only by gadolinia (strong neutron-absorbing substance), the reactivity of the reactor core is decreased by about 2% .DELTA.k/kk' due to the neutron parasitic absorption by gadolinia. Thus, it is necessary to charge the fissile material in excess correspondingly, and the fuel economy is deteriorated (first problem). Furthermore, addition of gadolinia reduces the heat conductivity of pellets, and thus the enrichment of fissile material (.sup.235 U, etc.) in gadolinia-containing fuel rods is made lower than the maximum enrichment in a fuel assembly from the viewpoint of maintaining the soundness of fuel rods, thereby suppressing the power after burning-out of gadolinia. However, when the applicable uranium enrichment is limited, the average enrichment of a fuel assembly will be lower than the maximum uranium enrichment, and a higher burnup cannot be obtained (second problem). FIG. 2 shows distribution of thermal neutron flux in the horizontal cross-sectional direction of a fuel assembly, where there is a difference in the thermal neutron flux at least by twice between the fuel rods at the respective corners of a channel box with softest neutron spectrum and the fuel rods at the second and third positions from the respective corners with hardest neutron spectrum. Such a structure gives excessively a large power from the fuel rods positioned in the peripheral region of a fuel assembly having a high thermal neutron flux, and thus the fuel rod power distribution in the fuel assembly is flattered by making the enrichment of fissile material (.sup.235 uranium, etc.) in the peripheral region than that of the center region. However, when the applicable uranium enrichment is limited even in that case, an average enrichment of a fuel assembly will be lower than the maximum uranium enrichment and no higher burnup can be obtained (third problem). Technique of adding gadolinia to the fuel rods positioned in the peripheral region of a fuel assembly to flatten the fuel rod power distribution is disclosed in Japanese Patent Application Kokai (Laid-open) No. 62-32386. Even if the fuel rod power distribution could be flattened at the initial period of lifetime of the fuel assembly, the power of gadolinia-containing fuel rods will be increased with the progress of gadolinia burning, because gadolinia has a large thermal neutron absorption cross-section. Thus, it is difficult to flatten the fuel rod power distribution throughout the lifetime of a fuel assembly, and the above-mentioned problems 1 and 3 can never be solved thereby. Technique of adding boron, a weak burnable absorber, to the fuel rods in the peripheral region of a fuel assembly to solve the above-mentioned problem 3 is disclosed in Japanese Patent Application Kokai (Laid-open) No. 57-196189. However, when the excess reactivity is controlled only with .sup.10 B having a thermal neutron absorption cross-section by about 1/100 smaller than that of .sup.157 Gd, a large number of fuel rods must be such burnable absorber-containing fuel rods. When all the fuel rods positioned in the peripheral region of a fuel assembly are such burnable absorber-containing fuel rods, the control rod worth will be decreased, if the fuel assembly is to be used in boiling water-type nuclear reactors. Technique of adding boron to the peripheral region of a fuel pellet and gadolinia to the center region to solve the above-mentioned problems 1 and 2 is disclosed in Japanese Patent Application Kokai (Laid-open) No. 57-196189. In that case the number of burnable absorber-containing fuel rods can be reduced, but the problem 3 is not solved. SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems 1, 2 and 3 and provide a fuel assembly suitable for higher burnup. Another object of the present invention is to provide a nuclear reactor core suitable for an increase in the availability factor and the lifetime of nuclear fuel, using the present fuel assemblies. According to the present fuel assembly, a plurality of burnable absorbers having different neutron absorption cross-section are used. That is, burnable poison elements having a relatively small neutron absorption cross-section such as boron, etc. are more provided, in regions having a relatively large ratio by volume of moderator to fuel, a soft neutron energy spectrum and a large thermal neutron flux such as the peripheral region and the lower level region of a fuel assembly than in other regions, i.e. regions having an average neutron energy spectrum, and burnable poison elements having a relatively large neutron absorption cross-section such as gadolinium, etc. is more provided in regions having an average neutron energy spectrum than in other regions, i.e. regions having a soft neutron energy spectrum. The plurality of these burnable absorbers are added to fuel rods separately according to the difference in the neutron absorption cross-section. It is also possible to add the plurality of these burnable absorbers into the upper level section and the lower level section of one fuel rod discretely. The present nuclear reactor core is charged by at least one of the above-mentioned fuel assemblies. The present fuel assembly functions as follows in contrast to the conventional fuel assembly using only one kind of burnable poison element. From the viewpoint of reactivity and power distribution, the weak absorber must have a concentration capable of burning for a period equal to that of the strong absorber. In order to make the fuel rod power after the burning of the weak absorber equal to the conventional one, it is not preferable to excessively suppress the power in the initial period of burning (0 GWd/t). Characteristics of boron as a weak absorber is a smaller self-shielding effect than that of gadolinia and the reactivity control can be changed only by adjusting its concentration. On the basis of the above-mentioned characteristics, burnable poison elements having a relatively small neutron absorption cross-section such as boron, etc. are provided in fuel rods in the fuel assembly peripheral regions having a relatively large ratio by volume of moderator to fuel and a large thermal neutron flux. Furthermore, the thermal neutron can be properly absorbed by setting the boron concentration to an appropriate value, and the thermal neutron flux distribution and the fuel rod power distribution can be flattened even if the fissile material enrichment distribution of fuel is kept uniform. On the other hand, control of excess reactivity can be made mainly by burning the burnable poison elements having a relatively large neutron absorption cross-section provided in the center region of the fuel assembly. In the fuel assembly having the above-mentioned structure, part of excess reactivity and local power peaking can be controlled by boron, and thus the amount of gadolinia to be added (i.e. number of fuel rods which gadolinia is to be added to and total amount of gadolia to be added) can be reduced to increase the reactivity. Even in case that the uranium enrichment is limited, higher burnup can be obtained.
	abstract	A structure includes a silicon substrate having a plurality of recessed portions, each recessed portion having a bottom and a side wall, silicide layers, each silicide layer in contact with the bottoms of the plurality of recessed portions, and a metal structure including metal portions, each metal portion disposed in the plurality of recessed portions and in contact with the silicide layers. The silicide layers are electrically connected to each other through the silicon substrate.
061309273	abstract	A grid with coolant deflecting channels for used in nuclear fuel assemblies is disclosed. In the grid, two sets of intersecting grid strips are arranged in sets at right angles to each other prior to being encircled by four perimeter strips, thus forming a plurality of four-walled cells individually placing and supporting an elongated fuel rod therein. Each of the grid strips is made up of two narrow sheets which are deformed at a plurality of regularly spaced portions to provide nozzle-type coolant deflecting channels. The channels individually have an upright Y-shaped or reversed Y-shaped configuration capable of so deflecting coolant as to mix low temperature coolant with high temperature coolant. The channels thus form a uniform temperature distribution within a fuel assembly. The channels are so inclined with respect to the axes of the fuel rods as to form wide and linear positioning springs at middle portions thereof. The middle portions of the channels thus individually have a dual function of a deflecting channel for coolant and a positioning spring for the fuel rods.
	claims	1. A neutron-capture therapy apparatus comprising:a cylindrical moderator structure composed primarily of a moderator material, having a length, an outside diameter, a cylindrical outer surface, an inside diameter, and a cylindrical inner surface, the inside diameter and length defining a treatment zone;a plurality of fusion neutron generators arranged in an array surrounding the cylindrical outer surface of the cylindrical moderator structure, each fusion neutron generator comprising an ion source emitting ions toward target material positioned at the cylindrical outside surface of the cylindrical moderator structure, the ions accelerated toward the target material by a DC voltage imposed between the target material and the ion source, impingement of the ions at the target material producing fast neutrons by a fusion reaction in the target material; anda cylindrical fast neutron reflector surrounding the cylindrical moderator structure and the fusion neutron generators;wherein fast neutrons are emitted isotropically from the target material at a plurality of different positions around the cylindrical outer surface of the moderator structure as a result of ion bombardment, neutrons emitted in a direction toward the cylindrical fast neutron reflector are reflected back into the cylindrical moderator structure, and moderated epithermal neutrons enter the treatment zone across the entire cylindrical inner surface of the moderator structure. 2. The neutron-capture therapy apparatus of claim 1 wherein the ion sources are equally spaced apart in a circular array. 3. The neutron-capture therapy apparatus of claim 1 wherein the target material is titanium, and is provided at the cylindrical outside surface of the moderator structure as a plurality of targets, one target corresponding to each fusion neutron generator. 4. The neutron-capture therapy apparatus of claim 1 wherein the ion sources are embedded in the cylindrical fast neutron reflector. 5. The neutron-capture therapy apparatus of claim 1 wherein fast-neutron generators are embedded in the cylindrical moderator structure. 6. The neutron-capture therapy apparatus of claim 1 wherein the target material is contiguous around the cylindrical outside surface of the cylindrical moderator structure. 7. The neutron-capture therapy apparatus of claim 1 wherein the cylindrical moderator structure comprises a plurality of wedge-shaped elements, equal in number to the plurality of fast-neutron generators, and each fast-neutron generator is embedded in one wedge shaped moderator element. 8. The neutron-capture therapy apparatus of claim 7 wherein the wedge-shaped elements are adjustable in position, changing flux density at different positions in the treatment zone.
044366922	summary	TECHNICAL FIELD This invention relates to the nuclear reactor field. More particularly, it pertains to method and apparatus for plugging a relatively large underwater nozzle in the sidewall of a reactor pressure vessel. BACKGROUND ART A boiling water reactor vessel is constructed in such a manner that it has a relatively large underwater nozzle extending through its sidewall which is used to recirculate water in the core shroud. This nozzle is relatively large--conventionally, for example, 28" in diameter. Quite often the piping and valving associated with the line leaving this nozzle require servicing, or even replacement. When such service is required, it would be desirable to be able to perform it without having to drain the reactor pressure vessel. In this manner, the necessity for removing the reactor fuel to a storage pool could be avoided. A smaller sized nozzle can often be plugged by means of a "freeze seal". This is a technique wherein liquid nitrogen is circulated around the nozzle to freeze the water within to effectuate a seal. However, the usual recirculating nozzle is too large to employ such a technique. In the past, it has been possible to plug the recirculation nozzle of a boiling water reactor vessel by lowering into the vessel a disk shaped plug which is curved to fit against the vessel sidewall and includes a relatively deep, conical extension which serves to position the plug in the nozzle opening. A hydraulic cylinder on the rear of the plug pushes against the core shroud to seat the plug in the nozzle opening. A circular pneumatic sealing member on the edge of the plug disk is then inflated to seal off the plug. The foregoing technique has been successfully applied in older-type reactor vessels. However, the plug which is used in that technique is relatively thick, approximately 61/2 inches. Nevertheless, it could be lowered straight down in the annular space between the core shroud and the reactor wall. In the newer reactors, however, there have been added a number of elements which form obstructions, thereby preventing the relatively thick prior art plugs from being employed. The primary obstructions are jet pumps which are positioned in the space between the reactor wall and the core shroud. Prior art plugs are too thick to pass between the jet pumps and the sidewall. Even if they could, they would be prevented from doing so because of intervening plumbing, such as core spray inlet pipes and feedwater spargers, and also by the reactor pressure vessel guide rod. Accordingly, it is a primary object of the present invention to provide improved method and apparatus for plugging the recirculation nozzle of a water-filled boiling water reactor pressure vessel. Other objects, features, and advantages will be apparent from the following description and appended claims. DISCLOSURE OF INVENTION There is disclosed herein a method of plugging an underwater nozzle in the sidewall of a cylindrical nuclear reactor pressure vessel which contains a core shroud radially displaced from the sidewall to form an annular space. The annular space contains jet pumps which are spaced from the sidewall. In accordance with the method, a substantially disk shaped plug is provided which has a diameter sufficient to cover the nozzle opening. The plug is curved to match the curve of the reactor sidewall. Means are provided on one surface of the plug for sealing against the sidewall around the nozzle opening. Cylinder/piston means are carried by the other side of the plug. The plug is lowered by means of a first cable into the annular space above the jet pumps. The cable is then pushed toward the sidewall until the plug is vertically aligned with the space between the sidewall and the jet pumps. The plug is lowered on the first cable until it enters the space between the sidewall and the jet pumps. The plug is then laterally shifted into vertical alignment with the nozzle to be plugged and the weight of the plug is simultaneously shifted to a second cable. The plug is then lowered by the second cable into alignment with the nozzle opening. The cylinder/piston means is then actuated to force the plug away from the core shroud and into sealing engagement over the nozzle opening.
	summary
063174839	abstract	An optically curved device is presented for use in focusing or imaging x-rays from a divergent source. The device includes a plurality of curved atomic reflection planes, at least some of which are separated by a spacing d which varies in at least one direction across the optically curved device. A doubly curved optical surface is disposed over the plurality of curved reflection planes. The spacing d varies continuously in the at least one direction for enhanced matching of incident angles of x-rays from a divergent source impinging on the optical surface with the Bragg angles on at least some points of the optical surface. The doubly curved optical surface can have an elliptic, parabolic, spheric or aspheric profile.
	summary
	abstract	A nuclear waste cask with impact protection includes impact limiters detachably coupled to opposite ends of the cask. Each impact limiter may comprise a deformable energy-absorbing perforated sleeve of cylindrical shape comprising an array of closely-spaced longitudinally elongated perforations. The perforations may comprise longitudinal passages having a circular cross-sectional shape in certain embodiments. The perforated sleeve may have an annular metallic body of monolithic unitary structure in which the perforations are formed and a central opening to receive the ends of the cask therein. When exposed to external impact forces such as created by dropping the cask, the perforations collapse inwards in the impact or crush zone to absorb the energy of fall while preventing or minimizing any forces transmitted to the cask to maintain the integrity of waste containment barrier.
046541837	summary	BACKGROUND OF THE INVENTION The invention relates to processes for photo detaching negative ions in a magnetic field and, more particularly, relates to a process for achieving selective neutralization of a given population of negative hydrogen ions in a magnetic field in order to produce an intense negative hydrogen ion beam with spin polarized protons. There has been an increasing demand in the last several years for spin polarized protons that are useful in a number of different applications for high energy research. The development of fusion reactors may also create the need for intense "high" energy neutral deuterium beams that have polarized nuclei. A number of different processes presently exist for producing such spin polarized protons and high energy neutral deuterium beams; however, all such present prior art methods known to the applicant are initiated by either polarizing an electron of the hydrogen atom, or by producing nuclear and electron spin polarized atomic gas. In such prior art processes, a necessary subsequent step is to either polarize the nuclear spin in one case, or to eject a particular spin state from a gas in an alternative case. Finally, the nuclear polarized atomic beam thus produced needs to be converted to either a positive or negative ion beam before it is entered into a suitable accelerator. All of these known prior art methods have certain major drawbacks. One such drawback is that considerable difficulty is encountered in attempting to produce a proper polarized atomic beam which has both high density and high velocity, as is necessary in order to avoid space charge effects and collisional destruction. A further significant disadvantage of such prior art methods is that the efficiency of converting polarized H to polarized H.sup.-, or even to H.sup.+, is rather poor in currently available processes. One known process for achieving neutralization of accelerated ions by photo-induced charge detachment involves the employment of a laser beam that is directed across the path of a negative ion beam to effect photodetachment of electrons from the beam of ions. An example of that type of prior art process is disclosed in U.S. Pat. No. 4,140,577, which issued Feb. 20, 1979. A related U.S. Pat. No. 4,140,576, which also issued Feb. 20, 1979, discloses a cavity that is useful with a relatively efficient strip diode laser that emits monochromatically at an approximate wavelength equal to 8,000 .ANG. for H.sup.- ions, in order to strip excess electrons by photodetachment with increased efficiency and reduced illumination required to obtain approximately 85 percent neutralization. Such prior art processes do not use selective neutralization of H.sup.- ions in a magnetic field as is done in the process of the invention as disclosed in the present application. Accordingly, no polarized ions or even neutrals result from such prior art processes. Other types of processes are known in the prior art wherein isotope separation is achieved by selectively ionizing given isotopes with polarized laser light. For example, U.S. Pat. No. 3,959,649, which issued May 25, 1976, and U.S. Pat. No. 4,020,350, which issued Apr. 26, 1977, disclose methods in which polarized laser light is used in laser isotope separation processes that are employed to selectively ionize given isotopes. Although such prior art methods employ polarized laser light, they do not result in the production of any spin polarized nuclei. Accordingly, except insofar as such prior art processes provide an awareness and understanding of the uses of polarized laser light, they appear to be of minimal relevance with respect to the process of the present invention disclosed herein. A somewhat more relevant prior art photodetachment method is described by W. A. M. Blumberg, W. M. Atano and D. J. Larson in an article entitled "Theory of the Photodetachment of Negative Ions in a Magnetic Field", which appeared at pp. 139-148 of Vol. 19, (No. 2) of the Jan. 15, 1979 issue of Physical Review. That paper presents a theory of a process for achieving photodetachment of atomic negative sulfer ions in a magnetic field. A basic element of the theory considered in that paper involves the confinement of the motion of the detached electron in the directions transverse to an applied magnetic field. Such confinement leads to the quantization of the transverse kinetic energy into the familar cyclotron, or Landau levels. As a result of the theoretical and experimental work reported by those authors, the theory discussed in the paper was said to predict the dependence of the photodetachment cross section upon magnetic field strength and upon light frequency. The experiments to confirm the theories discussed, were performed on ions that were confined in a trap of the Penning type, in which a uniform magnetic field and a quadrupolar static electric potential are present. The authors concluded that their theory, which was developed for S.sup.- atomic photodetachment, should also be equally valid for photodetachment of O.sup.-. In light of the shortcomings and disadvantages of all known prior art methods, as explained above, it remains desirable to provide a simple, essentially one-step photodetachment process that is operable to produce a multi-ampere beam of H.sup.- ions and to achieve laser neutralization of the H.sup.- ion beam with essentially 100 percent efficiency. OBJECTS OF THE INVENTION Accordingly, it is a primary object of the invention to provide a process for economically and efficiently producing a multi-ampere H.sup.- ion beam of either pulsed or steady state. Another object of the invention is to provide a process for selective neutralization of H.sup.- beams in a magnetic field thereby to produce an intense negative hydrogen ion beam with spin polarized protons, while avoiding the disadvantages of prior art methods. A further object of the invention is to provide a process that utilizes a beam of laser light in the range of 1135 .ANG. to 32,000 .ANG. to selectivly neutralize a majority of H.sup.- ions in a spin polarized beam of such ions, thereby to produce photodetachment products comprising free electrons and H.sup.o atoms. Further objects and advantages of the invention will become apparent from the description of it that follows considered in conjunction with the accompanying drawings. SUMMARY OF THE INVENTION In one preferred arrangement of the invention, a multi-ampere beam of H.sup.- ions is passed through a uniform solenoid magnetic field that spin polarizes the H.sup.- ions to separate them into first and second groups, or populations, of ions, which groups have their respective protons either spin aligned with, or spin aligned in opposition to, the magnetic field. A beam of laser light is directed through the spin polarized beam of H.sup.- ions to selectively neutralize a majority (preferably substantially 100 percent) of the ions in one of the polarized groups or populations; consequently, that group can be readily separated from the intense beam of H.sup.- ions in the other group of spin polarized ions, by subjecting the H.sup.- ions to magnetic curvature.
042382904	description	DETAILED DESCRIPTION OF THE INVENTION To explain the invention in further detail, an embodiment example will be described in the following, referring to the drawing. In FIG. 1 is shown schematically part of a nuclear reactor installation with a pressurized-water power reactor of, say, 1000 MWe. Of this installation can be seen in the figure a steam generator 1, which feeds a live-steam line 2. The steam generator is arranged in a containment 3, which encloses all the components of the primary loop. Among them, although not shown, are, in addition to the indicated steam generator 1, a reactor pressure vessel with the reactor core and three other steam generators, which are connected to the reactor pressure vessel in the same manner as the steam generator 1. The live-steam line 2, from the output of the generator 1, is brought through the containment 3 by means of a feed-through 4. A similar feed-through can be provided in the area of the secondary shield, not specifically shown. Outside the containment is mounted a shut-off valve 6, from which the outer line part 7 of the live-steam line 2 leads to a steam turbine, not specifically shown. Inside the containment, there is installed in the train of the live-steam line 2, a fast-acting valve 8 according to the invention. Its drive mechanism is designated as a whole with 9. The new valve 8, which is designed as a corner valve, can become effective also as a safety valve, as indicated by the spring 10. By the term "safety valve" is meant a normally-closed valve which opens automatically in response to excessive pressure in the pipe line with which the valve is associated. A branch 12 of the line 2 ahead of the fast-acting valve 8 leads to an inner safety valve 13. The safety valve 13 may advantageously have a response pressure which is a few bar higher than the response pressure of the valve 8. Its blow-off line 14 may also lead to a blow-down tank. Outside the containment 3, a line 16 is connected to the live-steam line 2 ahead of the shut-down valve 6; it leads, on the one hand, to an exhaust 18 via a safety valve 17. The exhaust 18 may also be equipped with a sound absorber. Parallel to the safety valve 17 are arranged two series-connected so-called blowdown control valves 20, which may optionally be of the same design, and which make possible the controlled blow-down of live steam, for instance, for shutting down the nuclear reactor in case of an accident. The fast-acting valve 8 is shown in FIG. 2 in a cross section. Its valve disk 22 is matched to the cross section of the live-steam line 2. For a diameter of the line 2 of 700 mm, for instance, the diameter of the valve disk 22 has the same size. The valve disk 22 may be armored throughout its outer rim 23, so that a particularly high strength is obtained. The same applies to the valve seat 24. The angles of inclination of the rim 23 of the valve disk, which is conical, and the valve seat 24 with, for instance, 60.degree. and 90.degree., are chosen so that for an aperture cross section of about 15% of the line cross section, an expanding Venturi tube results in the region 25. The valve disk 22 is provided with a stem 32 which is brought through the cover 34 of the valve 8 by means of sealing rings 33. The stem 32 leads to the pressure-medium actuator 9. The latter comprises a piston 35 and a cylinder 37, which can be operated, for instance, with pressurized oil as the pressure medium. At the stem 32 is provided a dog 40, with which two stops are associated. The one stop, 41, is provided for the opening direction. It includes a pawl 42 which is attached to a slide 43, which is adjustable by means of a screw-threaded spindle 44. The spindle 44 can be rotated, for instance, by a motor 45, in such a way that the stop 41 can be adjusted in the range between 15 and 30% of the maximum aperture cross section of the valve. Another stop 47, which acts in the closing direction of the valve disk 22, can likewise be adjusted by means of the slide 43. It limits the closing movement to an opening cross section between 0 and 15%. Thus, the opening and the closing limiters, 41, 47 are dependent on each other. However, disengaging the pawl 42 makes possible a complete opening for normal operation, regardless of the position of the slide 43; the clearance cross section of the valve is then the same as the aperture cross section of the live-steam line 2. In normal operation, the fast acting valve 8 is open and its aperture cross section coincides with the line cross section, so that the flow of the live steam is practically not impeded. Should a break of the live-steam line 2 occur or another defect happen which represents a leak in the live-steam line 2, then the fast-acting valve 8 is closed under the action of pressure medium due to a stimulus initiated by probes, not shown in FIG. 2, in the event of a leak. For this purpose, the cylinder 37 is acted upon by a pressure medium source of redundant design, e.g., a pressurized-oil tank 50, in a controlled manner via a valve 51. The closing time is as short as possible; it is, for instance, 2 seconds. If the closing of the fast-acting valve 8, to which the simultaneous closing of corresponding valves at the other steam generators of the plant corresponds, leads to a pressure increase, perhaps because a fast shutdown of the reactor (scramming) it not possible quickly enough, the valve disk 22 is lifted up at a pressure of, for instance, 1.2 the nominal pressure of the installation, because the counterforce that acts in the closing direction is overcome. The closing force may stem here from the pressure on the piston 36, which is controlled in a suitable manner. However, also other forces are conceivable as holding forces in the closed position, e.g., spring support which furnishes a defined closing force. For an opening movement of the valve disk 22 triggered by the steam pressure in the line 2, the travel is limited by the pawl 42 and the slide 43. The limited opening travel takes care that no more than half the aperture cross section of the valve is released. The opening travel of the valve disk 22 is preferably so small that 30% or less is available for blowing-off the overpressure in the line 2. It is thereby prevented that the flowout rate leads to disturbances in the steam generator 1, particularly to breaks of the heat exchanger tube bundle, which constitutes the wall separating the primary and the secondary loop of the pressurized-water reactor installation. In the description above of the operation, it was initially assumed as a simplification for ease of understanding that in the event of a closing command, the fast-acting valve 2 shuts off the live-steam line 2 completely. Through the closing limiter with the stop 47, provision can be made, however, that the fast-acting valve 8 can be closed, in the event of a fast-closing not belonging to normal operation, during operational live-steam production of more than 30% of the nominal output, only to a gap of about 10% for a short time of, say, 20 seconds. For this reason, overpressure cannot build up immediately and the output control can usually throttle the steam production during the 20 seconds mentioned to the extent that also after the complete closing, no further lifting of the valve disk 22 is to be expected. In any case, so-called fluttering of the valve disk 22 is hereby prevented. The gap 25, which is set by the closure limiter, can be adapted to the operational steam production as it can be expected that the steam production is reduced in the event of a shutdown the faster as was the smaller the original power output. However, it is also possible to run the closure limiter 47 closed, starting from the maximum value, in a time-dependent and proportional manner after a fast shut-off, for instance, by means of a clock mechanism (not shown). A further possibility is a control as a function of the steam pressure (not shown). The objective is here always to close the fast-acting valve 8 so fast and completely as is possible without an impermissible pressure rise in the generator that no radioactivity can get out of the containment with the steam due to damage to the generator. In FIG. 3 is shown by a schematic presentation similar to FIG. 1 that the fast-acting valve 8 with the pressure-medium actuator 9 can also be equipped with pressure-dependent servo control. To this end, the pressure in the live-steam line 2 between the steam generator 1 and the fast-acting valve 8 is ascertained by a probe in the form of a manometer 55. Depending on the magnitude of this pressure, the opening mechanism, indicated by the spring 10, of the fast-acting valve acting as a safety valve, and among other things, also the position of the stop 42, can be adjusted so, as indicated by the functional line 56, that sufficient blow-off is possible without excessive flow velocities. In parallel to the fast-acting valve 8, a bypass line 58 is provided which includes a valve 59, which can be closed by motor power, with a nominal diameter of 400 mm. In series with the valve 59 is disposed a choke 60 for limiting the flow which takes care that the maximally permissible outflow rate of the steam generator 1 cannot be exceeded even if the valve 59 is completely open. The bypass line 58 merely serves to increase the safety for the case that the fast-acting valve 8 does not open properly in the event of a pressure increase. In the embodiment example according to FIG. 3, the line 16 with the safety valve 17 and the blowdown control valves 20 outside the containment 3 is bypassed by a further safety valve 61, which is provided for reasons of redundancy. In the embodiment example according to FIG. 4, in which the fast-acting valve 8 is again provided with the bypass line 58, its valve 59' is controlled as a function of pressure. The manometer 55 therefore acts not only on the opening mechanism 10 of the safety valve 8, but also on the motor drive of the valve 59', indicated by the spring 63. In the embodiment example according to FIG. 4, the closing mechanism 9 of the fast-acting valve 8 is operated, as indicated by the functional line 64, as a function of the pressure in a valve chamber 65, which is provided outside of the containment 3 as an addition to a secondary shield 68 which consists of concrete and encloses the containment. As the valve chamber 65 contains the shut-off valve 6 for the live-steam outlet 7, the part of the live-steam line 2 between the feed-through 4 through the containment 3 and the shut-off valve 6, which cannot be shut off by the valve 6, and which is in part enclosed by a double tube 69, can be monitored by the manometer 66. The closing of the fast-acting valve 8 can thus be initiated by a pressure increase in the valve chamber 65 if, for instance, due to a leak 70 increased pressure is produced, which is determined by the manometer 66. The valve chamber 65 also contains the safety valve 17 and the blowdown control valves 20. Care must therefore be taken that the outlet 18 is in connection with the free atmosphere at least to the extent that the opening of the safety valve 17 or of the blowdown valves 20 does not lead to a pressure increase at the manometer 66 which triggers the closing of the fast-acting valve 8. In the embodiment examples, only one steam generator with a live-steam line was shown. In the nuclear reactor installations with two to four steam generators common for large power ratings, a fast-acting valve 8 according to the invention will be assigned to each live-steam line 2.
	description	This application claims the benefit of U.S. Provisional Application No. 60/866,134, filed Nov. 16, 2006. This Provisional Application is hereby incorporated herein by reference in its entirety. This invention relates in general to x-ray optics, and in particular to an improved x-ray focusing crystal optic having multiple layers, each layer having a predetermined crystalline orientation. In x-ray analysis systems, high x-ray beam intensity and small beam spot sizes are important to reduce sample exposure times, increase spatial resolution, and consequently, improve the signal-to-background ratio and overall quality of x-ray analysis measurements. In the past, expensive and powerful x-ray sources, such as rotating anode x-ray tubes or synchrotrons, were the only options available to produce high-intensity x-ray beams. Recently, the development of x-ray optic devices has made it possible to collect the diverging radiation from an x-ray source by focusing the x-rays. A combination of x-ray focusing optics and small, low-power x-ray sources can produce x-ray beams with intensities comparable to those achieved with more expensive devices. As a result, systems based on a combination of small, inexpensive x-ray sources, excitation optics, and collection optics have greatly expanded the availability and capabilities of x-ray analysis equipment in, for example, small laboratories and in the field. Monochromatization of x-ray beams in the excitation and/or detection paths is also useful, as discussed above. One existing x-ray monochromatization technology is based on diffraction of x-rays on optical crystals, for example, germanium (Ge) or silicon (Si) crystals. Curved crystals can provide deflection of diverging radiation from an x-ray source onto a target, as well as providing monochromatization of photons reaching the target. Two common types of curved crystals are known as singly-curved crystals and doubly-curved crystals (DCCs). Using what is known in the art as Rowland circle geometry, singly-curved crystals provide focusing in two dimensions, leaving x-ray radiation unfocused in the third or orthogonal plane. Doubly-curved crystals provide focusing of x-rays from the source to a point target in all three dimensions. This three-dimensional focusing is referred to in the art as “point-to-point” focusing. Commonly-assigned U.S. Pat. Nos. 6,285,506 and 7,035,374 disclose various configurations of curved x-ray optics for x-ray focusing and monochromatization. In general, these patents disclose a flexible layer of material (e.g., Si) formed into curved optic elements. The monochromating function, and the transmission efficiency of the optic are determined by the crystal structure of the optic. The present invention provides certain improvements in the formation of curved crystal optics, offering important performance advantages. The shortcomings of the prior art are overcome and additional advantages are provided by the present invention, which in one aspect is an optic for accepting and redirecting x-rays, the optic having at least two layers, the layers having a similar or differing material composition and similar or differing crystalline orientation. Each of the layers exhibits a diffractive effect, and their collective effect provides a diffractive effect on the received x-rays. In one embodiment, the layers are silicon, and are bonded together using a silicon-on-insulator bonding technique. In another embodiment, an adhesive bonding technique may be used. The optic may be a curved, monochromating optic. In another aspect, the present invention is a method for forming an x-ray optic, using a material-on-insulator bonding technique to bond at least two material layers together, each of the at least two layers having a pre-determined crystalline orientation. In one embodiment, the two layers may be formed into a curved, monochromating optic. Further additional features and advantages are realized through the techniques of the present invention. Other embodiments and aspects of the invention are described in detail herein and are considered a part of the claimed invention. An x-ray optic structure and exemplary technique for its formation are disclosed with reference to FIGS. 1a-i. (The dimensions in these drawings are exaggerated, and not necessarily in proportion, for illustrative purposes only.) As discussed further below, the optic formed according to the present invention includes multiple layers of, e.g., silicon, each layer having a different, pre-determined crystalline orientation, and bonded together using, e.g., a silicon-on-insulator bonding technique. Silicon-on-insulator (SOI) bonding techniques are known in the art, as described in Celler et al, “Frontiers of Silicon-on-Insulator,” Journal of Applied Physics, Volume 93, Number 9, 1 May 2003, the entirety of which is incorporated by reference. In general, SOI techniques involve molecular bonding at the atomic/molecular level using, e.g., Van der Walls forces, and possibly chemically assisted bonding. The term “material-on-insulator” is used broadly herein to connote this family of techniques, without limiting the material to silicon. The present invention leverages the maturity of the SOI process to fabricate, in one embodiment, a curved monochromating x-ray optic having multiple layers, each with a potentially different crystal orientation. A first substrate 10 (e.g., silicon or germanium) is provided having a first crystalline orientation (represented by the direction of the hash pattern). An oxide layer 20 is formed over the substrate 10 using known processes such as thermal growth (see Celler). A second layer 30 (e.g., silicon), having a second crystalline orientation, is bonded to layer 10 using the above-described SOI bonding techniques. The second layer is then polished 100 (using a standard planar polishing process, e.g., chem-mech polishing), leaving layer 30′. In one embodiment the resultant layer thicknesses are 1-5 um for the silicon layers, and about 0.1-0.5 um for the intervening oxide layers. This process is repeated using another oxide layer 40, and another layer 50 (again, having its own customized orientation). Layer 50 is then polished 100 leaving layer 50′. This process can be repeated again, using another oxide layer 60, and another layer 70 (again, having its own customized orientation). Layer 70 is then polished 100 leaving layer 70′. FIG. 2 shows the resulting thin (about 20-50 um), layered structure 110 having four finished layers, each with its own, predetermined crystalline orientation. Though four layers are shown in this example, the present invention can encompass any plurality of layers, depending on design parameters. And, not all the orientations need to be different. By pre-determining the crystalline orientation of each layer, the diffraction properties of the structure as a whole can be optimized. According to the present invention, each individual crystalline layer provides an individual diffractive effect. These diffractive effects can be separately modeled, and their collective effect in the final optic can then be predicted and implemented according to final design criteria. This stands in contrast to known “multi-layer” optics, having many layers of angstrom/nanometer thicknesses, each without an individual diffractive effect, but wherein the interactions between the layers result in an overall diffractive effect. In another aspect of the present invention, layers of differing material composition can be employed in the same optic, with either the same or differing crystalline orientations between the layers (or mixes thereof); and layers of similar (or the same) material composition can be employed, again with either the same or differing crystalline orientations between the layers (or mixes thereof). In any of these aspects of the present invention, especially where the above-described methods of material-on-insulator may be unsuitable, adhesive (e.g., epoxy) layers can be used to bind adjacent crystalline layers in accordance with the sequence of steps discussed above for the material-on-insulator bonding technique. Structure 110 can then be formed into a curved, monochromating optic, including a doubly-curved crystal (DCC) optic. One embodiment of such a doubly-curved optical device is depicted in FIGS. 3 and 3A, and is described in detail in U.S. Pat. No. 6,285,506 B1, issued Sep. 4, 2001, the entirety of which is hereby incorporated herein by reference. In the embodiment of FIG. 3, a doubly-curved optical device includes the flexible layer 110, a thick epoxy layer 112 and a backing plate 114. The structure of the device is shown further in the cross-sectional elevational view in FIG. 3A. In this device, the epoxy layer 112 holds and constrains the flexible layer 110 to a selected geometry having a curvature. Preferably, the thickness of the epoxy layer is greater than 20 μm and the thickness of the flexible layer is greater than 5 μm. Further, the thickness of the epoxy layer is typically thicker than the thickness of the flexible layer. The flexible layer can be one of a large variety of materials, including: mica, Si, Ge, quartz, plastic, glass etc. The epoxy layer 112 can be a paste type with viscosity in the order of 103 to 104 poise and 30 to 60 minutes pot life. The backing plate 114 can be a solid object that bonds well with the epoxy. The surface 118 of the backing plate can be flat (FIG. 3A) or curved, and its exact shape and surface finish are not critical to the shape and surface finish of the flexible layer. In the device of FIGS. 3 & 3A, a specially prepared backing plate is not required. Surrounding the flexible layer may be a thin sheet of protection material 116, such as a thin plastic, which is used around the flexible layer edge (see FIG. 3A). The protection material protects the fabrication mold so that the mold is reusable, and would not be necessary for a mold that is the exact size or smaller than the flexible layer, or for a sacrificial mold. Doubly-curved optical devices, such as doubly-curved crystal (DCC) optics, are now used in material analysis to collect and focus x-rays from a large solid angle and increase the usable flux from an x-ray source. Three-dimensional focusing of characteristic x-rays can be achieved by diffraction from a toroidal crystal used with a small x-ray source. This point-to-point Johan geometry is illustrated in FIG. 4. The diffracting planes of each crystal optic element 200 can be parallel to the crystal surface. If the focal circle 210 containing a point source and the focal point has radius R0, then the crystal surface has, for example, a radius R of curvature of 2R0 in the plane of the focal circle and a radius of curvature of r=2R0 sin 2θBrag in the perpendicular plane, with the radius centered on a line segment drawn between the source and the focal point. X-rays diverging from the source, and incident on the crystal surface at angles within the rocking curve of the crystal will be reflected efficiently to the focal or image point. The monochromatic flux density at the focal point for a DCC-based system is several orders of magnitude greater than that of conventional systems with higher power sources and similar source to object distances. This increase yields a very high sensitivity for use in many different applications, including (as described herein) x-ray fluorescence and diffraction. As a further enhancement, FIG. 4 illustrates that the optical device may comprise multiple doubly-curved crystal optic elements 200 arranged in a grid pattern about the Rowland circle, each element formed from a flexible structure 110 as discussed above (either with similar or different element-to-element layer structures). Such a structure may be arranged to optimize the capture and redirection of divergent radiation via Bragg diffraction. In one aspect, a plurality of optic crystals having varying atomic diffraction plane orientations can be used to capture and focus divergent x-rays towards a focal point. In another aspect, a two or three dimensional matrix of crystals can be positioned relative to an x-ray source to capture and focus divergent x-rays in three dimensions. Further details of such a structure are presented in the above-incorporated U.S. Pat. No. 7,035,374 B1, issued Apr. 25, 2006. The layered optic structure of the present invention offers the following advantages: The optic's mosaicity and rocking curves are controlled by layer orientation design. The efficiency of the optic is increased—each layer (with its own custom orientation) can have its own field of view, resulting in a composite field of view which increases efficiency and allows the optic to accommodate a larger source spot size. And, by accommodating a larger source spot size, system implementation is easier. The bandwidth (i.e., monochromatization) of the optic can be controlled, and, advantageously, increased in certain monochromating applications. The process steps depicted herein are just examples. There may be many variations to these diagrams or the steps (or operations) described therein without departing from the spirit of the invention. For instance, the steps may be performed in a differing order, or steps may be added, deleted or modified. All of these variations are considered a part of the claimed invention. Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.
	abstract	A single-leaf X-ray collimator comprises at least one collimating leaf member having at least one collimating aperture. The collimating leaf member is adapted to be configured to rotate about at least one of a vertical or horizontal plane. The collimator provides elliptical collimation and hence improved dosage efficiency.
	claims	1. A system for generating an X-ray pulse, comprising: an electron beam source configured to direct a pulse of electrons at a beam interaction zone; and a laser beam source configured to direct an optical pulse of photons at the beam interaction zone, the system configured such that when operational, the electrons in the electron pulse collide with the photons in the optical pulse at the beam interaction zone, the collision producing a pulse of approximately monochromatic X-ray photons, at least one characteristics of the pulse of approximately monochromatic X-ray photons being individually controllable. 2. The system of claim 1 , wherein the pulse of approximately monochromatic X-ray photons is utilized to perform an imaging application. claim 1 3. The system of claim 2 , wherein the imaging application is three-dimensional, volumetric mammography without use of breast compression. claim 2 4. The system of claim 2 , wherein the pulse of X-ray photons is the only pulse of approximately monochromatic X-ray photons used to perform the imaging application. claim 2 5. The system of claim 2 , wherein a drug is administered to a patient that collects on a portion of the patient to be imaged, the pulse of approximately monochromatic X-ray photons is tuned to a predetermined energy level sufficient to dislodge valence electrons from the drug, and imaging photons are produced at the portion of the patient being imaged. claim 2 6. A system for generating an X-ray pulse, comprising: an electron beam source configured to direct a pulse of electrons at a beam interaction zone, the pulse of electrons having a predetermined electron pulse charge of at least one nanocoulomb and a predetermined electron pulse length less than approximately ten picoseconds; and a laser beam source configured to direct an optical pulse of photons at the beam interaction zone the optical pulse having a predetermined optical pulse length of less than approximately ten picoseconds and a predetermined optical pulse energy level of less than approximately ten joules, the system configured such that when operational, the electrons in the electron pulse collide with the photons in the optical pulse at the beam interaction zone, the collision producing a pulse of approximately monochromatic X-ray photons, the pulse of approximately monochromatic X-ray photons having a predetermined pulse length of less than approximately ten picoseconds and a predetermined flux of at least approximately 10 9 photons per pulse. 7. The system of claim 6 , wherein the pulse of approximately monochromatic X-ray photons is utilized to perform an imaging application. claim 6 8. The system of claim 7 , wherein the imaging application is three-dimensional, volumetric mammography without use of breast compression. claim 7 9. The system of claim 7 , wherein the pulse of X-ray photons is the only pulse of approximately monochromatic X-ray photons used to perform the imaging application. claim 7 10. The system of claim 7 , wherein a drug is administered to a patient that collects on a portion of the patient to be imaged, pulse of approximately monochromatic X-ray photons is tuned to a predetermined energy level sufficient to dislodge valence electrons from the drug, and imaging photons are produced at the portion of the patient being imaged. claim 7 11. A method of generating an X-ray pulse comprising: generating an individually-configured optical pulse; generating an individually-configured electron pulse synchronously with generation of the optical pulse; and colliding the optical pulse and the electron pulse at a beam interaction zone, the collision of electrons in the electron pulse with photons in the optical pulse producing an individually-configured pulse of approximately monochromatic X-ray photons. 12. The method of claim 11 , further comprising claim 11 imaging a target object with the individually-configured pulse of approximately monochromatic X-ray photons. 13. The method of claim 12 , wherein the individually-configured pulse of approximately monochromatic X-ray photons is the only source of X-ray photons used in performing the imaging. claim 12 14. The method of claim 11 , further comprising performing three-dimensional volumetric mammography with the individually-configured pulse of approximately monochromatic X-ray photons. claim 11 15. The method of claim 11 , further comprising: administering to a patient a drug having K shell electrons having a predetermined binding energy, the drug collecting at a portion of the patient to be imaged; claim 11 tuning the individually-configured pulse of X-ray photons to the predetermined binding energy of the K shell electrons; focusing the individually-configured pulse of X-ray photons at the portion of the patient; and observing imaging photons produced at the portion of the patient by the interaction of the individually-configured pulse of approximately monochromatic X-ray photons with the K shell electrons of the drug. 16. A system for generating an X-ray pulse, comprising: an electron source configured to direct a pulse of electrons at an interaction zone; and a photon source configured to direct a pulse of photons at the interaction zone, the system configured such that when operational, the election source is sufficiently synchronized in time and duration with the photon source to cause a collision of the pulse of electrons and the pulse of photons in the interaction zone, the collision producing the X-ray pulse. 17. The system of claim 16 , wherein the X-ray pulse produced when the system is operational is an approximately monochromatic pulse of X-ray photons. claim 16
	description	The present invention relates to limiting pressurized water stress corrosion cracking (PWSCC) in pressurized water reactors. More specifically, the present invention provides an apparatus and method for limiting stress corrosion cracking in a pressurized water reactor (PWR) through the addition of low-level concentrations of zinc compounds into a reactor coolant system (RCS). The current invention also provides a method for evaluating the effect of and applying zinc acetate to the RCS of PWRs at a target zinc concentration of 5 ppb (operating range of 3 to 8 ppb) in order to reduce the initiation rate of PWSCC. The developed methodology provides for the steps of quantitatively assessing the PWSCC initiation rate of a candidate system through evaluating operational Eddy Current Testing (ET) data and PWSCC failure history using empirical and mathematical relationships, determining the extent of damage to the candidate system, approximating the point in plant life where zinc addition is needed for PWSCC mitigation, quantitatively assessing the PWSCC initiation benefit for various high-concentration (≧10 ppb) and low-concentration (<10 ppb) zinc programs, demonstrating a PWSCC initiation benefit from zinc at low concentrations (<10 ppb) in the RCS and applying zinc acetate to the RCS at concentrations of 1 to 10 ppb for PWSCC mitigation. Stress corrosion cracking occurs in a material due to a combination of a corrosive environment and tensile forces placed on the material. Cracking can be induced in materials in different ways including cold forming, welding, grinding, machining, and heat treatment as well as other physical stresses placed on the material. Stress corrosion cracking in nuclear reactor environments is a significant phenomenon that must be carefully monitored for successful operation of a nuclear power plant facility. Without careful monitoring for PWSCC, material defects may begin and may ultimately damage the material. If cracking continues, the materials may be damaged to such an extent that the materials must be removed from service and replaced. In the nuclear reactor environment, such replacement of components is extremely undesirable due to radiological concerns related to worker and facility safety, as well as overall plant economic concerns. In Boiling Water Reactors (BWRs), different methodologies are used to limit corrosion on reactor water systems. Some methodologies include application of hydrogen water chemistry to limit the overall nuclear reactor environment of these water systems to a more reducing state. The application of hydrogen water chemistry has significant drawbacks, however, in that radiation levels in systems connected to the reactor often increase dramatically, posing a significant risk for workers and equipment. Other methodologies relate to placement of noble metals on the reactor water systems in order to limit the amount of voltage difference between differing reactor water system areas as defined in the standard hydrogen electrode scale. Through experimentation it has been found that values above approximately −0.230 to −0.300 V result in stress corrosion cracking. The placement of noble metals such as iridium, platinum, palladium and rhodium in key corrosion-prone positions has been found to help in limiting damage to reactor water systems by decreasing these harmful values. In new construction, the components may be coated with these metals, thereby providing protection. For nuclear power plants already in operation this alternative is not practical as the components in question must be removed from service and replaced with new components. In an effort to increase the corrosion resistance of existing nuclear power plant facilities, injection of noble metals into the reactor coolant water stream itself has been found to help improve resistance to stress corrosion cracking. The noble metals are passed into the reactor coolant water stream where these metals coat the insides of various components in the nuclear power plant environment. The noble metals further deposit on an outside layer of the system to be protected. The noble metals decrease the electrochemical corrosion potential of the systems and therefore help to protect the overall system integrity. Zinc, in the form of zinc oxide, zinc acetate, or zinc borate, has been used in the commercial nuclear industry for a number of years in order to reduce radiation dose rates of system components in both PWRs and BWRs. In order to achieve these dose reduction benefits, zinc has been applied at concentrations of between 5 to 10 ppb in BWRs and 3 to 8 ppb in PWRs. Laboratory testing has demonstrated that applying high concentrations of zinc (≧10 ppb) may be beneficial in reducing the initiation of PWSCC in PWRs. Some operating United States PWRs currently use zinc at concentrations of 20 to 40 ppb in the reactor coolant, which is believed by the industry, including the Electric Power Research Institute (EPRI), to achieve PWSCC protection; however, no definitive evidence of the magnitude of benefit, if any, has been available to the industry. Analysis of laboratory test data in open literature indicates that certain types of addition of zinc to the primary water systems in nuclear facilities may be expected to provide a reduction in the initiation rate of PWSCC in Alloy 600 components. A combined project conducted by Airey et al. in 1996 and Angell et al. in 1999 was performed in two test phases. The Phase 1 test consisted of exposing reverse U-bends (RUBs), bent beams (6% and 12% plastic strain) and pre-cracked compact wedge open loading (WOL) samples from various heats of Alloy 600 and Alloy 690 materials. During Phase 1, the specimens were exposed to simulated PWR conditions for a 12-month fuel cycle (1,200 ppm B, 2.2 ppm Li, and 25-50 cc/kg H2). The specimens were exposed in two autoclaves for up to 7,500 hours at 350° C. (662° F.). Zinc was injected into one of the autoclaves, with a target concentration of approximately 40 ppb in the effluent. In order to achieve this target concentration, an initial dose of 100 ppm was used to condition the system. After 7,500 hours of exposure in the autoclave the RUB specimens exhibited a low incidence of cracking wherein only two zinc specimens and one control specimen cracked. This number of cracked specimens was below an anticipated number of cracked specimens, however the test results did not allow the researchers to draw any meaningful conclusions. An additional result of the testing was that the bent beam specimens tended to exhibit surface crazing, rather than defined cracking. The crazing was attributed to a cold worked surface layer present on the original material. The testing results of the WOL specimens indicated that zinc addition had no effect on crack growth rate. The above experimental results indicated that zinc injection had little impact on cracking of metal specimens undergoing test conditions. The researchers also observed that the oxide film thickness on specimens exposed to zinc were thinner, 35 nm versus 230 nm on the control specimens. This led the researchers to question whether the stress was too high on the WOL specimens (loaded to 40 MPa√m) to identify an effect of adding zinc. Researchers, however, planned a second set of tests, Phase 2. Under the Phase 2 testing, the same types of specimens and material heats were used. WOL specimens loaded to 25 MPa√m and 40 MPa√m were included in the test matrix. Additionally, the chemistry environment was modified to reflect an 18-month fuel cycle (1,800 ppm B, 3.5 ppm Li, and 25-50 cc/kg H2). The result of the Phase 2 tests showed a benefit in the reduction of crack initiation for the Alloy 600 materials from the addition of zinc at high dose concentrations. The RUB samples (results provided in Table 1) showed fewer specimens cracked (up to 67% fewer) in the autoclave containing 40 ppb zinc. Additionally, it was noted that none of the 16 bent beam specimens exposed to zinc cracked, while 6 of the 16 control specimens cracked. These results are provided in Table 2. These results led the researchers to conclude that high levels of zinc addition had a definite impact on PWSCC initiation. Researchers did not, however, explore the effects of low levels of zinc addition. TABLE 1RUB Test Conditions and Results (662° F.) by Angell et al.Phase 1, simulating beginning of cyclePhase 2, simulating beginning ofwater for a 12-month fuel cyclecycle water for an 18-month fuel cycleWithout zincWith zincWithout zincWith zincZinc—40 ppb—40 ppbTemperature350° C. (662° F.)350° C. (662° F.)Hydrogen25-50 cc H2/kg H2O or 0.1 MPa25-50 cc H2/kg H2O or 0.1 MPaB1200 mg/kg B as H3BO31800 mg/kg B as H3BO3Li2.2 mg/kg Li as LiOH3.5 mg/kg Li as LIOHpH6.75 at 292° C. and 7.10 at 350° C.6.75 at 292° C. and 7.10 at 350° C.Phase 1Phase 2Without zincWith zincWithout zincWith zincSpecimen I.D.Heat7500 hours7500 hours5500 hours7500 hours5500 hours7500 hoursAlloy 60096834, (c)1/62/63/6 (a)3/6 (a)1/6 (a)1/6 (a)StudsvikAlloy600MAAlloy 690752245, (c)0/60/60/4 (a)0/4 (a)0/4 (a)0/4 (a)StudsvikAlloy690TTAlloy 600Not——1/4 3/4 0/4 2/4 Westing houselisted(a) Include two uncracked specimens carried forward from Phase 1. However, for Alloy 600, it was not mentioned if the cracked ones in Phase 2 included the ones from Phase 1. For Alloy 690, the maximum specimen exposure time without failure was 15,000 hours.(b) x/y—x is the accumulated number of specimens cracked; y is the total number of RUB specimens tested.(c) The descriptions on the RUB specimen I.D. were vague and could not be associated directly with the chemical composition of the Alloy 600 and Alloy 690 SG tubes listed. Hence, the specimen heat number was an educated guess. TABLE 2Alloy 600 Phase 2 Bent Beam ResultsSPECIMENSPLASTICCRACKED/EXPOSEDZINCSTRAINSUR-27505500ADDITIONHEAT(%)FACEHOURSHOURSYESA6AM0/40/4YESB6AM0/40/4YESA12EP0/40/4YESB12EP0/40/4NOA6AM0/41/4NOB6AM0/40/4NOA12EP1/44/4NOB12EP0/41/4AM—as machined; EP—electropolished The results of the WOL crack propagation specimens, however, were consistent with Phase 1 in that no benefit from zinc injection was found, as shown in FIG. 1. Analysis of the fracture surfaces of the control and zinc-exposed specimens revealed no discernable differences in the oxides. These results led the researchers to conclude that zinc most likely was not being transported to the crack tip and therefore had no impact on crack propagation. Tests were also performed by Kawamura et al. in 1998 and 2000 using mill annealed Alloy 600 tubing and plate in order to evaluate zinc effects on both PWSCC initiation and propagation. Initiation was studied using slow strain rate tests (SSRT) of tubing material at 360° C. (680° F.) in water containing 50 ppm B, 2.2 ppm Li, 25 cc H2/kg H2O, and (for zinc tests) 10 ppb Zn. Propagation was studied using double cantilevered beam (DCB) specimens wedge loaded from <10 to >70 MPa√m. In many cases, the test specimens were pre-filmed by exposing them to water containing 50 ppm B, 2.2 ppm Li, and 25 cc/kg H2 (both with and without 10 ppb Zn) for up to 2,000 hours prior to testing. Later testing revealed little difference between specimens that were pre-filmed and those that were not. The SSRT results were reported in terms of “fracture ratios” (i.e., fraction of specimen that showed PWSCC failure). The testing showed a sharp decrease in fracture ratios as a function of zinc concentration between 0 and 10 ppb zinc (see FIG. 2) and a decrease by a factor of two for specimens exposed to zinc; 10-15% versus 20-30% in the control specimens (see FIG. 3). The crack propagation tests were monitored by periodically removing and fracturing some of the specimens and measuring crack advancement. The results of these tests indicated that crack rates (most likely also including the initiation times into the calculation) were approximately 10 times lower for the zinc environments as provided in FIG. 4. It should be noted that in all cases, the crack growth rates were low. It should also be noted that, contrary to previous studies the researchers found chromite spinel oxides, which can incorporate zinc, in the crack tip. Research reports have been provided to the Electric Power Research Institute by the Nuclear Power Engineering Corporation (NUPEC) in which the effect of zinc additions on PWSCC have been evaluated. Some of the project details have been published in the open literature. A materials integrity test was performed in a large loop specifically designed and constructed in generating these reports. The types of testing included SSRT, constant load RUB tests, and constant strain RUB tests. Slow Strain Rate Tests Slow strain rate testing was performed at 370° C. (698° F.) with a strain rate of 0.5 μm/minute. Three SSRT environmental conditions were used, as shown in Table 3. TABLE 3Slow Strain Rate Test ConditionsTEST NO.BORON (PPM)LITHIUM (PPM)ZINC (PPB)12802.010218003.510318003.50 Four specimens were included in each SSRT environment. All specimens were prefilmed in primary water conditions containing 10 ppm zinc. The reported fracture ratios were all approximately 10% as shown in FIG. 5, indicating that the presence of 10 ppb zinc had no effect on the PWSCC susceptibility in these B and Li environments. Constant load testing of Alloy 600 MA and Alloy 600 TT tubing was performed at 340° C. (644° F.). Alloy 690 TT tubing was also included and tested at 360° C. (680° F.). All specimens were strain hardened prior to testing at 60 kg/mm2 and the applied testing load was equivalent to a tensile stress of 588 MPa. The Alloy 690 TT material was not prefilmed; the Alloy 600 TT material was prefilmed in primary water with the addition of 10 ppb zinc; and the Alloy 600 MA material was prepared in three conditions: a) without prefilming, b) prefilmed in primary water only, and c) prefilmed in primary water with the addition of 10 ppb zinc. The prefilming was performed after the strain hardening treatment. The Alloy 600 MA material results are the only ones reported in the literature and are provided in Table 4. The use of prefilming made little to no difference in the test results. Also, the testing performed in the 10 ppb zinc environment (Environment B) appears to show only marginal improvement in the failure times. Constant strain tests were performed using RUB specimens made from both Alloy 600 MA and Alloy 600 TT materials. Alloy 690, Alloy X-750, Type 316, and Type 304 materials were also included, but the data were not presented in the references. A matrix of environmental test conditions, strain levels and prefilming was employed as shown in Table 5. The test results indicate that for Alloy 600 MA materials, prefilmed specimens tend to crack more than non-prefilmed specimens, particularly under 5% strain. Higher strain conditions showed no beneficial effect of zinc addition. The test results for Alloy 600 TT material appeared to show a small improvement in PWSCC resistance in the zinc environments. The authors concluded from these test results that PWSCC susceptibility of Alloy 600 MA and TT materials was essentially the same or somewhat lower in a 10 ppb zinc environment compared to a water environment of a typical primary water system in a nuclear power plant. TABLE 4Constant Load Test Results for Alloy 600 MA MaterialENVIRONMENT AENVIRONMENT BPREFILMSPECIMENRUPTURESPECIMENRUPTURECONDITIONNO.TIME, HRNO.TIME, HRNO ZINC6M-30189876M-31183896M-30288626M-31257256M-30384396M-313>92286M-30486896M-31473676M-305>92286M-315>92286M-30657986M-316>92286M-30778856M-317>92286M-308>92286M-31891296M-309>92286M-319>92286M-31050966M-320921410 PPB6M-32192026M-331>9228ZINC6M-32289176M-33271916M-32369856M-33368366M-32449386M-334>92286M-32543376M-335>92286M-32667046M-33647196M-32764196M-33747896M-32880766M-33889346M-32976666M-33982066M-33048506M-3407650Environment A: 280 ppm boron and 2.0 ppm lithium*Environment B: 280 ppm boron, 2.0 ppm lithium, and 10 ppb zinc TABLE 5Constant Strain RUB Testing of Alloy 600 MaterialsENVIRONMENT A+ENVIRONMENT B+ENVIRONMENT C+PREFILMPRE-STRAIN LEVELPRE-STRAIN LEVELPRE-STRAIN LEVELMATERIALCONDITION5%10%15%5%10%15%5%10%15%ALLOYNONE1/1010/1010/101/1010/109/103/108/10 8/10600 MAPW4/1010/10ALL #4/1010/10ALL #8/1010/10 10/10PW + 107/1010/10ALL #5/1010/10ALL #———PPB ZNPW + 50——————9/109/1010/10PPB ZNALLOYPW—————————600 TTPW + 100/10 0/10 5/100/10 0/103/10———PPBZNPW + 50——————0/101/10 4/10PPB ZNNote:Results for 0 and 10 ppb zinc are after 9228 hours; results for 50 ppb zinc are after 5005 hours; and “All #” indicates all specimens cracked at 5010 hoursPrefilmed 2000 hours in primary water (PW) environment with or without zinc+Environment A: 280 ppm boron, 2.0 ppm lithium at 320° C.; Environment B: A + 10 ppb zinc; and Environment C: A + 50 ppb zinc Zinc addition has been applied to a number of PWRs in the United States and abroad for the purposes of radiation source term reduction (5 ppb Zn in the reactor water) and PWSCC initiation reduction (20 to 40 ppb Zn in the reactor water). Several studies of these programs, including the results of the field applications, can be found in various EPRI topical reports. None of these reports, however, identified any relationship between the addition of zinc and reduction in pressurized water reactor stress corrosion cracking. Limitations of Background References The laboratory data recited above on the effect of low-concentration zinc addition (≦10 ppb in the reactor coolant) regarding the initiation of PWSCC is not comprehensive. Because of the large costs and schedule requirements of zinc addition studies, the various testing programs contain fragmentary information about zinc and its effects on water systems of a nuclear reactor water system. The field application studies of zinc addition, furthermore, have focused on two “known” applications of zinc. First, zinc has been applied at concentrations of approximately 5 ppb in the reactor coolant, and the resulting effects on the plant radiation fields (generally secondary systems) have been studied. Secondly, zinc has been applied at a concentration of 20 to 40 ppb, and the effect on the initiation rate of PWSCC has been studied, although a definitive quantification of the measure of improvement has not been determined. There are two major shortcomings of the current knowledge base: 1) the quantitative prediction of the benefit of zinc on PWSCC at candidate plants and 2) the application of zinc at low-concentrations (<10 ppb) for the purpose of PWSCC initiation mitigation. There is therefore a need to provide an apparatus and method to protect a pressurized water reactor from stress corrosion cracking wherein the application of materials to limit the stress corrosion cracking must be at low zinc concentration levels of less than 10 ppb. There is an additional need to provide an apparatus and method to protect currently operating pressurized water reactors from stress corrosion cracking without unduly increasing radiation levels for workers and equipment associated with reactor water coolant systems. There is also a need to provide an apparatus and method to protect currently operating pressurized water reactors from stress corrosion cracking in an economical and non-damaging way for the nuclear fuel present in the reactor. It is therefore an objective of the present invention to provide an apparatus and method to protect a pressurized water reactor from stress corrosion cracking wherein the application of materials to limit the stress corrosion cracking must be at low zinc concentration levels of less than 10 ppb. It is also an objective of the present invention to provide an apparatus and method to protect operational pressurized water reactors from stress corrosion cracking without unduly increasing radiation levels for workers and equipment associated with reactor water coolant systems. It is a further objective of the present invention to provide an apparatus and method to protect operational pressurized water reactors from stress corrosion cracking in an economical and non-damaging way for the nuclear fuel present in the reactor. The objectives of the present invention are achieved as illustrated and described. The present invention provides a method to evaluate the effect of applying a zinc compound to a reactor coolant system of a pressurized water reactor, the method disclosing the steps of quantitatively assessing a pressurized water reactor stress corrosion cracking initiation rate of a candidate system through analysis of operational eddy current testing data and pressurized water stress corrosion cracking failure history using empirical relationships, determining an extent of damage to the candidate system, approximating when zinc addition to the system will mitigate pressurized water stress corrosion cracking, quantitatively assessing pressurized water stress corrosion cracking initiation benefit for high-concentration (≧10 ppb) and low-concentration (<10 ppb) zinc addition programs, and calculating a pressurized water reactor stress corrosion cracking initiation benefit from zinc addition at low concentrations (<10 ppb) in the reactor coolant system. The current invention uses a combination of empirical data and numerical analysis to quantitatively evaluate the effect of zinc addition on the initiation rate of PWSCC. The invention also provides for applying zinc acetate to the RCS of PWRs at a target zinc concentration of ≧10 ppb (versus the current range of 20 to 40 ppb), wherein the application reduces the initiation rate of PWSCC. The developed methodology comprises the steps of quantitatively assessing the PWSCC initiation rate of the candidate plant through operational ET data and PWSCC failure history, using empirical and mathematical relationships, determining the extent of damage to the plant systems and approximating the point in plant life where zinc addition is needed for PWSCC mitigation. The methodology also provides for quantitatively assessing the PWSCC initiation benefit for various high-concentration (≧10 ppb) and low-concentration (<10 ppb) zinc programs, demonstrating a PWSCC initiation benefit from zinc at low concentrations (<10 ppb) in the RCS and applying zinc acetate to the RCS at concentrations of 1-10 ppb for PWSCC mitigation—concentrations that have proven to be safe for RCS materials of construction, including the nuclear fuel. The invention and analysis techniques indicate that low concentration additions of zinc compounds, above the solubility of zinc chromite, in reactor coolant will result in PWSCC mitigation, in contravention of teachings of others in the art which require high concentration additions of zinc. A further aspect of the invention is that with the current zinc injection equipment and methods, PWSCC can be delayed in any of the pressurized water reactor plant currently injecting zinc. An exemplary embodiment of the invention involves the combination of empirical field data, including eddy current test data and plant component PWSCC failure histories, with laboratory data as inputs to statistical analyses in order to prove the quantitative benefit of zinc addition on PWSCC initiation. The statistical analyses used to aggregate the data includes probabilistic analysis, e.g., Weibull analysis. Eddy current data is obtained from a nuclear plant system that is to be evaluated for PWSCC. A non-limiting example of the data to be obtained and used in analysis is eddy current data based on information from a database recording analysis results, such as the EPRI Steam Generator Degradation Database. To successfully trend PWSCC, a normalized degradation rate is calculated, wherein the normalized degradation rate is defined as the number of tubes (or components) with new PWSCC indications divided by the number of rotating coil examinations in the examination region (TSP examinations or tubesheet examinations). As PWSCC initiation has been shown to be very sensitive to temperature, a temperature scaling factor adjustment is made to the eddy current data, for example, the temperature scaling factor documented in reference EPRI NP-7493 can be applied to the PWSCC indication data. A database of degradation rates is then developed for nuclear plant systems by adjusting the degradation data in the degradation database to a common reference temperature. Several temperatures are used to establish the reference temperature, including the reactor hot-leg temperature and the pressurizer temperature as non-limiting examples. The temperature correction is then applied to the degradation data as an adjustment in the Effective Full Power Years (EFPY) of plant operation. Table 6 provides a cumulative PWSCC degradation rate as a function of EFPY adjusted for temperature for two example nuclear plants. The ratio column is obtained by taking the PWSCC Indications and dividing this number by the number of exams. The “cumulative” column adds the individual ratios provided up until that time. The final column in the table indicates the start of zinc addition as a binary value. TABLE 6PWSCC Summary for Zinc PlantsPWSCCCumu-ZincPlantEFPYIndicationsExamsRatiolativeAdditionA1.2504310.00000.00000A2.2704300.00000.00000A4.49027400.00000.00000A5.86030200.00000.00000A7.143325460.01300.01300A8.467958210.01360.02650A9.75131155720.00840.03491A11.476200860.00380.03871A12.8759193590.00300.04181A14.323158210.00150.04321B2.0502290.00000.00000B3.1604200.00000.00000B4.43027300.00000.00000B5.744361010.00700.00700B7.081646530.00340.01050B8.41123107110.01150.02200B10.0366166310.00400.02591B11.545149500.00300.02891B12.9328141050.00200.03091B14.540190590.00210.03301 A probabilistic predictive tool is then developed and used to correlate EFPY and the normalized degradation rate (the Ratio column in Table 6) in order to provide trending and predicting information. One such predictive tool to correlate EFPY and the normalized degradation rate is obtained by the Weibull analysis method. When the data in Table 6 is analyzed to determine the Weibull slope for PWSCC initiation before and after the zinc addition, the results are those provided in Table 7. TABLE 7Weibull Analysis for PWSCC Initiation at Units A and BAllslope1.751intercept−7.723scale82.221Pre Zincslope2.844intercept−9.932scale32.878Post Zincslope0.463intercept−4.496scale16607 Finally, FIG. 6 gives a graphical depiction of the Weibull analysis of PWSCC initiation rate based on the normalized degradation data. FIG. 6 illustrates that applying this method allows for the quantification of the change in the degradation rate following zinc injection. The data in FIG. 6 illustrates that the PWSCC initiation rate (based on new indications normalized by the number of rotating coil examinations) had a Weibull slope of 2.844 for examinations prior to the start of zinc addition and a Weibull slope of 0.463 after beginning zinc addition. As a result, the Weibull slope indicates the effect of zinc addition on PWSCC at a nuclear power plant. Low-Concentration Zinc Injection for PWSCC Mitigation Evaluation Literature (EPRI Document 1003389, November 2003) suggests that there is a direct relationship between radiation dose rates on reactor coolant system components and the amount of zinc injected into the system. The present invention, however, involves the inventors discovery that the magnitude of PWSCC mitigation due to zinc injection at nuclear power plants is a function of the mass of zinc incorporated into the surface oxides of the reactor coolant system. Furthermore, the inventors have determined that the magnitude of PWSCC mitigation is not directly a function of zinc concentration in the reactor coolant because zinc uptake into the surface oxides is not significantly affected by coolant zinc concentration, as shown below. Three different zinc injection programs were evaluated for zinc uptake by the reactor coolant oxides, and the data is presented in Table 8. TABLE 8Zinc Injection Summary of Plants L, M, and GCYCLENO. OFAVG. ZNZINCZINCNET ZNPLANTNUMBERCYCLESCONC.INJECTEDREMOVEDIN RCSA91315.853.052.80A102214.082.551.53A113154.042.691.35B91213.481.621.86B102163.562.870.69B113154.913.341.57C14152.870.472.40C1524.51.49——C16351.430.341.09 Table 8 indicates that test Plants A and B injected significantly more zinc in each of their cycles than did Plant C. Much of this zinc, however, was removed by the letdown demineralizers at Plants A and B and was therefore not incorporated into the surface oxide films (where it is effective in mitigating PWSCC). In contrast, Plant C had much lower zinc removal by the demineralizers. As a result, the actual amount of zinc remaining in the RCS at all three plants was similar for the first and third cycles of zinc injection (Cycle 15 data was not reported for Plant C). On average, Plants A and B had only 10% more zinc in the system than did Plant C. Additionally, Plant C is a smaller reactor than Plants A and B, so the zinc uptake would be expected to be proportionately smaller. In evaluating the data, however, plants B and C had almost equal zinc uptakes in their first and third cycles of zinc injection. When the data is corrected for the relative surface area of the units, Plant C actually incorporated more zinc per unit area than did Plants A and B (average of the two units). Based on this data, the steady-state uptake rate of zinc into the RCS oxides is fairly independent of the RCS zinc concentration within the 5 to 30 ppb band, as long as the concentration is above the ZnCr2O4 solubility, contrary to expected results provided in other literature. The significance of this evaluation is that zinc concentration in the reactor coolant (<10 ppb as Zn) that was originally thought to be too low for PWSCC mitigation is actually able to incorporate as much zinc into the RCS surface oxides (where Zn is effective) as a high-concentration program, provided that the reactor coolant zinc concentration is maintained above the solubility of zinc chromite. As a result, any amount of zinc in the reactor coolant in excess of the zinc chromite solubility limit will lead to an amount of PWSCC mitigation protection. Low-concentration zinc programs (5 to 10 ppb Zn in the reactor coolant) can produce the same magnitude of PWSCC mitigation as high-concentration zinc programs (shown in FIG. 6). Operating a nuclear power plant with a low-concentration zinc program provides significant advantages over high-concentration programs, including the following: lower zinc costs, less tramp oxide (CRUD) deposited on the nuclear fuel rods, lower risk of CRUD-induced fuel damage, and lower risk of Axial Offset Anomaly (which results from boron uptake into CRUD. The invention also provides a quantitative assessment of the potential benefits of zinc addition. To aid in this quantitative assessment, the Temperature Scaling Factor, as provided in the EPRI statistical analysis guidelines, is applicable for quantification of zinc addition benefits. The apparent activation energy is estimated at 50 kcal/mole. The adjustment for stress is the ratio of the stress levels to the fourth power. When Weibull analysis is used for different temperatures or stress conditions, correction factors are provided in the EPRI statistical analysis guidelines. Other factors such as material susceptibility and chemical environment may also be considered. ERPI NP 7493 and the U.S. Department of Commerce document ADA 143 100, Weibull Analysis Handbook, Nov 83, each provide some discussion about methods for extrapolation of Weibull analysis results from one case to another and are applicable herein. The invention methodology applies the correction factors, as needed for each individual case, as adjustments in the service life of the components. Based on this methodology, the invention uses an actual EFPY for plotting data whereas an effective EFPY, adjusted for temperature and/or stress, is used to calculate a Weibull cumulative distribution. Based on the Weibull distribution and zinc improvement factors obtained from literature and/or field inspection data, the invention methodology calculates component degradation curves for zinc and no-zinc environments. Example Calculation An example calculation for the estimation of zinc improvement curves described above is performed for steam generator tubing of a PWR based on degradation data obtained from field inspections of an operating PWR using zinc addition. The Thot for these data from the individual nuclear power plants was the same, so no Temperature Scaling Factor (TSF) was applied to the data. The reference data was based on 0.875 inch OD mill annealed tubing with a wall of 0.050 inch. The evaluation tubing is 0.625 inch OD sensitized tubing with a wall thickness of 0.037 inch. The respective yield strength values taken from the EPRI Steam Generator Degradation specific Management Flaw Handbook provides a stress correction factor of 0.90. The plant under evaluation has documented six (6) tubes removed from service due to PWSCC (data from steam generator degradation database—excluding the explosive expansion region) with a rotating inspection program of approximately 2,249 from FDMS. This places the plant's degradation rate at about 0.0027 at 17.4 EFPY. Application of the stress factor places the effective plant life at 17.40.9 or 15.7 EFPY. Calculation of the actual lifetime associated with the 0.0027 degradation rate indicates an effective lifetime of 4.5 EFPY. This correlation to the actual plant degradation rate accounts for other factors such as plant chemistry and stress relief. For the purpose of data review, a range of values is used for evaluating the relative potential benefit of zinc addition. These values, ranging from “Low Benefit” to “High Benefit” are based on laboratory data and field inspection data. When applied to the Weibull PWSCC slope and the corrected EFPY of the evaluation plant, the data provides an estimate of the range of PWSCC initiation benefit that can be expected from zinc addition. As an example, FIG. 7 shows the range of expected degradation using the evaluation plant EFPY corrected only by the stress ratio. The zinc addition effect is calculated from 19 EFPY. As an alternative example of applying the invention methodology, available industry data on PWSCC failures can be used to construct these plots for components that do not have a large body of field inspection data (e.g., pressurizer nozzles). As part of the invention methodology development, various PWSCC failures from approximately 50 US and international PWRs were collected and used to build a database for the Weibull analyses. In order to evaluate the industry data, the invention methodology groups the failures by component (e.g., CRDM, pressurizer nozzle, heater diaphragm). Once the data was compiled, the Weibull characteristics for each component were calculated, and those with similar slopes were grouped together for ease of analysis. Once these groupings were established, degradation curves were constructed for each group of components in a similar manner as previously discussed for the SG tubes. A sample curve for pressurized nozzles at the evaluation plant is presented in FIG. 8. In the foregoing specification, the invention has been described with reference to specific exemplary embodiments thereof. It will, however, be evident that various modifications and changes may be made thereunto without departing from the broader spirit and scope of the invention as set forth in the appended claims. The specification and drawings are accordingly to be regarded in an illustrative rather than in a restrictive sense.
	abstract	In the particle beam therapy system, a beam transport system includes a beam-path changer for changing a beam path so as to transport a charged particle beam to any one of the plurality of particle beam irradiation apparatuses; and a treatment management device includes a beam-path controller that generates an emitter control signal for controlling an emitter of an accelerator and a beam-path changer control signal for controlling the beam-path changer so that, with respect to the plurality of particle beam irradiation apparatuses in which treatment is performed at the same treatment period of time, the charged particle beam is transported to each one of the plurality of particle beam irradiation apparatuses for each time period allocated thereto.
	claims	1. A method for creating a pattern with improved virtual grid on a workpiece sensitive to electromagnetic radiation comprising the actions of:emitting electromagnetic radiation onto a computer controlled reticle having a multitude of modulating elements (pixels),arranging the pixels in said computer controlled reticle according to a digital description,creating an image of said computer controlled reticle on said workpiece, wherein said pixels in said computer controlled reticle are arranged in alternate grayscale states along at least a part of one feature edge in order to create a smaller address grid. 2. The method according to claim 1, wherein said pixels in said computer controlled reticle along at least one feature edge belong to a one-dimensional line of pixels. 3. The method according to claim 1, wherein said image is created in one writing pass. 4. The method according to claim 1, wherein said image is created by means of a plurality of writing passes. 5. The method according to claim 4, wherein said pixels in said computer controlled reticle along at least one feature edge are arranged differently in said plurality of writing passes. 6. The method according to claim 5, wherein, in a first writing pass, at least a first pixel along at least one feature edge is set to a first grayscale value and surrounded with pixels set to at least one other gray scale value, and in at least one other writing pass at least a second pixel along said at least one feature edge is set to said first grayscale value with surrounding pixels set to at least one other gray scale value. 7. The method according to claim 6, wherein the pattern is created by four writing passes. 8. The method according to claim 6, wherein said at least one pixel in the different writing passes set to said first grayscale value are non overlapping. 9. The method according to claim 6, wherein said surrounding pixels are set to the same grayscale value. 10. The method according to claim 6, wherein said surrounding pixels are set to the different grayscale values. 11. The method according to claim 1, wherein said pixels in said computer controlled reticle along at least one feature edge belong to at least two lines of pixels. 12. The method according to claim 11, wherein said pixels in said at least two lines are weighted differently when forming said virtual grid. 13. The method according to claim 1, wherein said pixels are micromirrors in an SLM. 14. The method according to claim 1, wherein said pixels are transmissive. 15. An apparatus for creating a pattern on a workpiece sensitive to electromagnetic radiation comprising:a source to emit electromagnetic radiation onto a computer controlled reticle having a multitude of modulating elements (pixels),a projection system to create an image of said computer controlled reticle on said workpiece, wherein said pixels in said computer controlled reticle are arranged in alternate grayscale states along at least a part of a boundary of at least one element to be patterned, in order to fine-adjust the position of an edge of said element in said image to be created on the workpiece. 16. The apparatus according to claim 15, wherein said pixels in said computer controlled reticle along at least one feature edge belong to a one-dimensional line of pixels. 17. The apparatus according to claim 15, wherein said image is created in one writing pass. 18. The apparatus according to claim 15, wherein said image is created by means of a plurality of writing passes. 19. The apparatus according to claim 18, wherein said pixels in said computer controlled reticle along at least one feature edge are arranged differently in said plurality of writing passes. 20. The apparatus according to claim 19, wherein, in a first writing pass, at least a first pixel along at least a part of one feature edge is set to a first grayscale value and surrounded with pixels set to at least a second gray scale value, and in at least a second writing pass at least a second pixel along said part of said feature edge is set to said first grayscale value with surrounding pixels set to at least said second gray scale value. 21. The apparatus according to claim 20, wherein the pattern is created by four writing passes. 22. The apparatus according to claim 20, wherein said pixels set to said first grayscale value in the different writing passes are non overlapping. 23. The apparatus according to claim 22, wherein said pixels set to said first grayscale value in the different writing passes are spaced apart with at least one pixel. 24. The apparatus according to claim 20, wherein said surrounding pixels are set to the same grayscale value. 25. The apparatus according to claim 20, wherein said surrounding pixels are set to the different grayscale values. 26. The apparatus according to claim 15, wherein said pixels in said computer controlled reticle along at least a part of one feature edge belong to a line with a width of two pixels. 27. The apparatus according to claim 15, wherein said pixels in said computer controlled reticle along at least one feature edge belong to a line with a width of three pixels. 28. The apparatus according to claim 15, wherein said pixels are micromirrors in an SLM. 29. The apparatus according to claim 15, wherein said computer controlled reticle is a transmissive SLM.
	summary
	description	Now, the present invention will be described by way of examples. FIG. 2 is a schematic block diagram of the signal detection apparatus according to the invention in Example 1. In FIG. 2, reference numeral 201 denotes a cantilever type displacement detection probe unit provided with a piezo resistance as a strain gauge. FIG. 3 is a schematic illustration of the piezo resistance lever used in the detection apparatus. Referring to FIG. 3, an electroconductive probe 301 is held electrically in contact with a piezo resistor 304 arranged at-the front end of the lever. In FIG. 3, reference numeral 303 denotes a silicon substrate and reference numeral 302 denotes a wiring pattern, while reference numeral 305 denotes a silicon oxide film for electrically isolating the substrate and the wiring patterns from each other. As for the dimensions of the probe unit, the cantilever has a width W of 20 xcexcm, a length L of 100 xcexcm and a height H of 2 xcexcm. The resonance frequency of the lever is about 15 kHz. Firstly, the operation of the probe unit as an AFM will be described below. As the lever type probe unit 201 and the specimen 202 to be observed are moved close to each other by an access controller 209, they exert force on each other, which is typically atomic force. When they are brought close to each other to such a distance that the interacting force gets to a predetermined level, a scan signal generator 207 generates a scan signal, which is applied to the XY drive mechanism of a stage 203 carrying the specimen by way of an amplifier 208 to drive the stage and the specimen intra-planarly. Then, the probe scans the surface of the specimen and obtains information of the change in the interacting force that it is expressed as a change in the deflection of the lever, thereby giving the output in the form of a change in the piezo resistance. During the operation, a certain bias is applied to the specimen 202 by a bias-applying circuit 211. The change in the piezo resistance is measured by a signal measurement section 204 to transmit the obtained signal to a controller 210. The controller 210 mainly controls the access controller 209 and the bias-applying circuit 211 according to the values input by the operator by way of a setting section 206. Additionally, it generates an image signal for visualizing the signal from the signal measurement section 204 to a monitor 205. Now, the operation of the probe unit as an STM (for measuring the electric current) will be described also by referring to FIG. 2. A tunnelling current flows between the lever type probe unit 201 and the specimen 202 to be observed when a predetermined voltage is applied to the specimen 202 by the bias-applying circuit 211, and then the probe unit 201 and the specimen 202 are brought closer to each other than a certain distance. The electric current reflects the electrical state of the surface of the specimen so that the local electrical state of the specimen can be observed by measuring the electric current. As in the case of the AFM, the stage is driven to observe electric current flowing through the probe unit by the signal measurement section 204, thereby obtaining the two-dimensional information of the electric state of the surface of the specimen 202. The obtained information is visualized by the controller 210 so that the operator can observe the visible image on the display screen of a monitor 205. Now, the signal measurement section 204 that is characteristic to the present invention will be described in detail. The signal measurement section 204 has a configuration as schematically illustrated in FIGS. 1A and 1B. Note that the piezo resistance of the lever and the resistance between the specimen and the probe are shown in addition to the signal measurement section 204. Firstly, the operation of the AFM of the apparatus will be described by referring to FIG. 1A. For an apparatus operating as an AFM, the deflection of the piezo resistance lever has to be detected. According to the invention, the piezo resistance (Rs) or the change in the piezo resistance (xcex94Rs) is measured by measuring the electric current flowing through the piezo resistor when a predetermined bias Vs is applied thereto. Through the lever, therefrom is a constant current xe2x80x98isxe2x80x99 with respect to the resistance Rs, a variable current xcex94is with respect to the resistance xcex94Rs which changes in response to the deflection of the lever and a current iT flowing from the specimen by way of the probe. The current iT flowing from the specimen by way of the probe is not necessary for measuring the piezo resistance. However, the current iT can be reduced to substantially nil by applying VT of a half of the bias of the piezo resistance, or VT=Vs/2, to the specimen so as to reduce the voltage between the specimen and the probe to substantially nil, because the lever is prepared by way of a semiconductor process as described above so that the piezo resistance between one of the two bases of the probe unit and the tip of the probe is equal to the piezo resistance between the other base and the tip, or a half of the overall piezo resistance of the probe unit. Note that Rs is about 10 kxcexa9 while the resistance between the specimen and the probe is generally greater than 100 Mxcexa9 (in the case of a tunnelling current). Additionally, Rs is generally about several kilo-ohms (kxcexa9) and xcex94Rs/Rs=10xe2x88x926 to 10xe2x88x928 (per deflection of 1 nm). Thus, there is normally a dimensional difference of about 10xe2x88x926 to 10xe2x88x928 between xe2x80x98isxe2x80x99 and xcex94is. Therefore, it is vitally important to eliminate xe2x80x98isxe2x80x99 in order to reliably detect xcex94is. Resistance RL in FIGS. 1A and 1B is introduced for this purpose. By adjusting RL with a switch SW set on, it is possible to select an appropriate value for xe2x80x98isxe2x80x99 by means of the bias applied by the power source xe2x88x92Vs to take away xe2x80x98isxe2x80x99 from the signal. Then, only xcex94is flows through feedback resistance Rf and appears as an output Vo. With the above described arrangement, the AFM effectively and efficiently detects the change in the piezo resistance. In this example, a probe having a piezo resistance Rs of 10 kxcexa9 and a sensitivity of xcex94Rs/Rs=10xe2x88x928 was used with an applied voltage of Vs=1V and a resistance of Rf=1Mxcexa9 to successfully obtain a clear AFM image. While intra-planar resolution was dependent on the diameter of the tip of the probe, which was as large as about 10 nm in this example, the apparatus showed a high sensitivity in the direction perpendicular to the surface of the spectral with a resolution of 0.1 nm. Now, the operation of the STM (for measuring the electric current) will be discussed by referring to FIG. 1B. Electric current xcex94iT flowing through the resistance RT between the-specimen and the probe is measured by the STM. The electric current to be detected will be greater than 10 nA because the resistance RT exceeds 100Mxcexa9. Therefore, it will be difficult to detect xcex94iT effectively when electric current flows due to the applied voltage Vs. Taking this into consideration, it is so arranged for the STM to make Vs equal to zero so that no voltage may be applied to the piezo resistance. Then, a voltage VT is applied to the specimen to cause electric current xcex94iT to flow. Under this condition, xcex94iT flows to both the Vs side and the amplifier side on a half and half basis because Vs is equal to zero. In other words, the current flowing to the amplifier is equal to xcex94iT/2. Additionally, if the lever carrying the piezo resistance is deflected to change the resistance during the operation of measuring the electric current, xcex94iT is very small because the piezo resistance which is about 10 kxcexa9 is very small and negligible relative to the resistance between specimen and the probe that is as large as 100Mxcexa9. Thus, the influence of the change in the piezo resistance on the xcex94iT is further small and hence much more negligible. Then, it is necessary to open SW for separating the system of RL and xe2x88x92Vs provided to xe2x80x9cabsorbxe2x80x9d the electric current. With this arrangement, xcex94iT/2 is totally transformed to output Vo through the feedback resistance Rf. With the above operation, the electric current is measured effectively and efficiently. In this example, a specimen obtained by causing Au to epitaxially grow on a cleaved mica substrate was observed. The Au was biased by VT=2V and the same probe unit used as an AFM was used for an STM observation to successfully obtain an excellent current image showing grains specific to epitaxially grown Au that are as large as several hundreds of nanometers. When an AFM observation and an STM observation were conducted sequentially for the same micro-region, it was proved by the profiles of the observed grains that the image obtained by the AFM completely agreed with the one obtained by measuring the electric current. Thus, this example proves that both the undulations on the surface of a micro-region of a specimen and the electric properties of the region can be observed by means of the same probe unit according to the invention. In this example, a multi-probe AFM/STM apparatus was prepared by using a plurality of probe units, each of which was the same as the one prepared in Example 1. The overall system configuration is identical with the one illustrated in FIG. 2 except that the system comprises a plurality of probes 201 and signal measurement sections 204. Since each of the probes is prepared by way of a semiconductor process as in Example 1, it is easy to arrange a plurality of probes having identical characteristics. FIG. 4 is a schematic circuit diagram of the signal measurement system of the embodiment of a detection apparatus according to the invention in Example 2. The probes has respective piezo resistances of the lever portions P1 through PN, N representing the number of probes. VT represents the potential of the specimen observed when a bias is applied by a bias-applying circuit 211 as shown in FIG. 2. Both an AFM observation and an STM observation (for measuring the electric current) were conducted by operating the apparatus as in Example 1. More specifically, the SW is turned on for an AFM observation and a predetermined voltage was applied as Vs. Then, VT is made equal to Vs/2 and the variable resistances RT were set to respective values selected depending on the variances of the piezo resistances. During the operation of the STM observation, on the other hand, Vs is made equal to zero and a predetermined voltage is used for VT, while SW is turned off so that no electric current is absorbed. The outputs of the amplifiers U are selectively used by a multiplexer 401 that is arranged downstream to provide an output of Vo, which is then input to the controller 210 shown in FIG. 2 and demultiplexed for each of the probes to obtain its output that may then typically be sent to the monitor 205. In this example, a specimen obtained by causing Au to epitaxially grow on a cleaved mica substrate was observed as in Example 1. A total of ten probes were used. The piezo resistance Rs of each of the probes was 10 kxcexa9 and the sensitivity xcex94Rs/Rs was 10xe2x88x928, while Rf was made equal to 1Mxcexa9 and Vs=1V was used for the AFM observation whereas VT=2V was used for the STM observation, showing that the apparatus could observe the specimen with a high sensitivity in the direction perpendicular to the surface of the specimen. The AFM resolution was 0.1 nm as in Example 1. When an AFM observation and an STM observation were conducted sequentially for the same micro-region, it was proved by the profiles of the observed grains that the image obtained by the AFM completely agreed with the one obtained by measuring the electric current. Thus, this example also proves that both the undulations on the surface of a micro-region of a specimen and the electric properties of the region can be observed by means of the same probe unit according to the invention. In this example, an observation system was prepared by using a detection apparatus according to the invention. It will be described below. FIG. 5 shows the overall configuration of the multi-probe AFM/STM observation system used in this example. A probe array unit 501 of the system has a configuration as will be described hereinafter by referring to FIG. 7. A measurement output VO is sent to a probe unit control circuit 503. This probe unit control circuit 503 outputs various output values (as will be described hereinafter) selected to control the probe array unit 501 and the data obtained by measurement to a data bus 504 in response to a request from a central processing unit (CPU) 505. The data sent to the data bus 504 may be processed by the central control unit (CPU) 505 and/or read directly by an output device 506 according to the command from the central control unit (CPU) 505. The output device 506 may be a monitor typically comprising a CRT, a printer and/or a network. Thus, the output device 506 may refer to one or more than one devices that receive the same data simultaneously. Although not shown, the central control unit 505 receives command signals from the operator and sends the parameters specified by the command signals to the probe unit control circuit by way of the bus. The parameters may include the scope of observation, the observation start point, the observation speed, the bias to be applied to the specimen for observing the electric current flowing therethrough and the characteristics values of each of the probes that are obtained in advance (including the piezo resistance value, the gauging ratio, etc.). The probe unit control circuit 503 controls the probe array unit 501 and the stage 502 according to the parameters it receives. Now, the probe array unit 501 will be described in greater detail by referring to FIG. 7. The probe array unit 501 is provided with a plurality of AFM/STM probes having piezo resistances (P1, P2 and so on). Each of the probes has the same profile as the one described above in Example 1 and a structure as shown in FIGS. 1A and 1B. A voltage VSH is applied to an end of each of the probes to observe the piezo resistance, while a control voltage VSL is applied to the other end of the probe by way of a MOSFET (such as R1 or R2 in FIG. 7). These voltage values are selected by the probe unit control circuit 503 shown in FIG. 5 and the contact of the MOSFET and the lever is input to an I/V conversion circuit (such as T1 or T2 FIG. 7). The electric current flowing to the I/V conversion circuit is converted into a voltage signal, which is then sent to a double switch (such as S1 or S2 in FIG. 7). After passing through the switch, the signal is output as the measurement output signal VO. Resistance-setting bias VR is applied to the gate of the MOSFET by way of the switch (such as S1 or S2) so that the MOSFET operates like the variable resistance RL shown in FIGS. 1A and 1B by controlling the VR. A probe selector 701 outputs a switch control signal (such as C1 or C2 in FIG. 7) that controls the switching operation of each of the double switches (such as S1 or S2) connected to the corresponding probe. The probe array unit 501 operates in a manner as described below. To begin with, the AFM operation of the unit will be discussed. When a probe selection signal PS is input to a probe selector 701, it closes only the switch (to be assumed as switch Sn) of the probe specified by the selection signal PS and keeps all the remaining switches open. As a result, the output of the corresponding I/V conversion circuit (Tn) is linked to the measurement output signal VO, at the same time and the corresponding resistance-setting bias VR is applied to the gate of the MOSFET (Rn) to make the latter have a predetermined resistance. The electric current produced by the voltage VSH passes through the piezo resistance lever (Pn) and is partly absorbed by the MOSFET (Rn), and the remaining current flows into the I/V conversion circuit (Tn). The electric current contains the signal component representing the deflection of the lever and therefore represents the undulations of the surface of the specimen being observed as described above by referring to Example 1. As described above, the output of the I/V conversion circuit (Tn) is linked to the measurement output signal VO, the measured value from the probe (Pn) is output as VO. When measuring the electric current, the MOSFET is made completely open by lowering the resistance-setting bias VR to a level lower than the VSL. The VSH is set to 0V. The operation of the probe selector and that of the switches are identical with those described above for the AFM. Now, the probe unit control circuit 503 will be described in detail. As described above, the probe unit control circuit 503 controls the probe array unit and collects data. It contains therein an A/D converter 603 for digitizing data, a memory 602 for storing the obtained digital data, an interface section 601 for sending some of the data stored in the memory 602 to the bus and obtaining parameters from the bus, a probe-setting section 604 for selecting the probe to be used for measurement, a bias generator 605 for outputting various voltages to be applied for the purpose of measurement and a scan controller 606 for controlling the operation of driving the stage for scanning, placing it in position and addressing various data. The probe unit control circuit 503 operates in a manner as described below in detail. Upon receiving a measurement start signal from the bus, the interface section 601 defines the area to be measured and selects various scan parameters (including the measurement mode that may be the AFM mode, the STM mode or the AFM/STM mode, the measurement position, the scope of measurement and the scanning rate) for the scan controller 606. Additionally, it triggers the start of the measurement operation by means of a measurement control signal. Still additionally, it outputs some of the measurement data stored in the memory in response to a request from the central control unit (CPU) 505 or some other component. The scan controller 606 that holds the selected parameters selects signals for the respective actuators, rests the addresses for data and starts the scanning operation. The scan controller 606 outputs an address signal in addition to an XY-scan signal for driving the stage for the scanning operation. The address signal is used to address various measurement data in order to store them in the memory 602. The memory 602 has a logical structure as shown in FIGS. 8A and 8B. The memory is divided into an S-matrix domain for storing data obtained by the STM measurement and an A-matrix domain for storing data obtained by the AFM measurement. Each of the domains contains matrix regions that are laid one on the other and the number of which is equal to that of probes (or n in the case of FIG. 8A). The inside of each of the matrix region reflects the physical positions of the corresponding probe taken for the observation. Referring to FIG. 8B, the area scanned by the probe contains horizontally p dots and vertically q dots, or a total of pxc3x97q dots. In other words, these dots are sampled by the probe. It should be noted, however, that FIGS. 8A and 8B are schematic illustrations of the memory 602 and do not accurately show the physical structure of the inside of the memory device. Thus, the scan controller 606 defines the correspondence of the physical positions on the surface of the specimen with the obtained data by way of addressing as described above and also that of the probes and the mode of measurement with the obtained data. In other words, it outputs the address of the memory where the obtained data is currently being stored. Then, the address signal is received by the memory 602, the probe-setting section 604 and the bias generator 605. The probe-setting section 604 computationally determines the probe to be used for measurement from the address signal it receives and transmits a probe selection signal specifying the probe to be used to the probe array unit 501. Then, the signal of the probe specified by the probe selection signal is received as VO as described above by referring to FIG. 7. The bias generator 605 recognizes the measurement to be conducted is an AFM measurement or an STM measurement on the basis of the address signal it receives and determines the voltages to be used for the measurement. Now, the operation of the bias generator 605 will be described by way of an example. If it is recognized from the address signal that the measurement to be conducted is an AFM measurement using the probe Pn, the bias generator 605 outputs the VSH and the VSL that are predetermined along with the VT that is equal to VSH/2. It also determines the value of the VR by using the piezo resistance of the probe that is measured and stored in advance and outputs the VR. The value of the VR may alternatively be determined by using the value defined in advance as a bias parameter and obtained from the interface or by using a filter designed to make the DC component of the output signal VO detected on a real time basis equal to zero. If, on the other hand, it is recognized from the address signal that the measurement to be conducted is an STM measurement also using the probe Pn. the bias generator 605 outputs 0V for VSH and there are applied, a predetermined value for VSL, the value of VSL for VR and a predetermined sampling bias for VT. As a result, the electric current flowing between the specimen and the probe can be measured as described above in Example 1. In this example, a specimen obtained by causing Au to epitaxially grow on a cleaved mica substrate was observed as in Example 1. A total of one hundred probes were used. The probes are arranged longitudinally and transversally to show a matrix of 10xc3x9710, where any two adjacently located probes were separated by a distance of 100 xcexcm. The piezo resistance Rs of each of the probes was about 10 kxcexa9 and the sensitivity xcex94Rs/Rs was 10xe2x88x928. The measurement operation was carried out by causing the stage to raster-scan the specimen. More specifically, the specimen was scanned along lines in the main-scanning direction simultaneously, while moving the stage in either of the sub-scanning directions at a low rate. Each of the probes was made to cover an area of 100 xcexcm-square which was sampled for 512 times per raster and a total of 512 rasters were conducted. By referring to FIGS. 8A and 8B, it will be seen that the number of probes is n=100, the number of elements was p=512 per row as well as q=512 per column. A number of different sequences may be conceivable for the actual sampling operation. For instance, each of the probes may be used for AFM sampling per raster and then for STM sampling per raster. In other words, the probe may be used twice per raster, once for AFM sampling and once for STM sampling. Alternatively, all the probes may be used for AFM sampling for a frame and then they may be returned to the starting positions to carry out an STM sampling operation for the frame. Still alternatively, two samplings of an AFM sampling operation and an STM sampling operation may be carried out before moving the probes to the next respective positions. Any of such alternative sequences may selectively be used by taking the type of the specimen to be observed and the time allowed to observe the specimen into consideration along with other factors. In this example, each of the probes was used twice per raster, once for AFM sampling and once for STM sampling, in order to obtain desired data. A value of 106V/A was selected for the gain of the I/V conversion. Additionally, VSH=1V and VSL=xe2x88x921V were used for AFM sampling. As for the VR, it was measured in advance and stored in the memory for each of the probes as a value that makes the output of the probe equal to zero when the deflection of the lever is nil. In other words, the VR was measured for each of the probes and stored in the bias generator 605 in advance. VT=2V was used for STM sampling, indicating that the apparatus could observe the specimen with a high sensitivity in the direction perpendicular to the surface of the specimen exactly as in the case of Example 1. The AFM resolution was 0.1 nm as in Example 1. When an AFM observation and an STM observation were conducted sequentially for the same micro-region, it was proved by the profiles of the observed grains that the image obtained by the AFM completely agreed with the one obtained by measuring the electric current. Additionally, because any two adjacently located probes were separated from each other by 100 xcexcm, the coverage of each probe bordered on those of the neighboring probes so that a surface area of 1 mm2 could be observed completely with an enhanced level of resolution. As described above, according to the invention, a common electric path is used for both the electric current flowing to the piezo resistance of a probe in order to detect the surface profile of a specimen (recording medium) in an AFM observation and the electric flowing between the specimen and the electroconductive probe in order to detect the electric properties of the specimen in an STM observation. As a result it is possible to greatly simplify the configuration of the probe, the wiring arrangement of the detection system and the detection circuit for detecting both the surface profile and the electric properties of the specimen. It is also possible to realize a multi-probe observation system adapted to both AFM and STM observations.
	abstract	A method for precipitating uranium from an aqueous solution and/or sediment comprising uranium and/or vanadium is presented. The method includes precipitating uranium as a uranyl vanadate through mixing an aqueous solution and/or sediment comprising uranium and/or vanadium and a solution comprising a monovalent or divalent cation to form the corresponding cation uranyl vanadate precipitate. The method also provides a pathway for extraction of uranium and vanadium from an aqueous solution and/or sediment.
	description	This application is based on and claims the benefit of priority from Japanese Patent Application No. 2009-166071, filed on Jul. 14, 2009, the entire contents of which are expressly incorporated herein by reference. A. Field Embodiments described herein relate generally to an X-ray diagnosis apparatus and a method for controlling an X-ray irradiation region, and more particularly, to an X-ray diagnosis apparatus and a method for controlling an X-ray irradiation region that can appropriately narrow down an X-ray radiation aperture so as to fit a configuration of a region of interest during acquisition of X-ray projection data for reconstructing tomography images of an object. B. Background In recent years, medical image diagnosis by using an X-ray diagnosis apparatus, an X-ray computer tomography (CT) apparatus or a magnetic resonance instrument (MRI) apparatus, has been widely applied for cardiovascular diagnosis and following observation of cardiology in accompany with a development of catheter techniques. Usually, for performing angiography, two dimensional (2D) or three dimensional (3D) image data is generated by reconstructing X-ray image data acquired through X-ray irradiations over the diagnosis target region along directions more than 180 degrees around the target region. In this case, when some region would have been dropped out from the acquired image, the reconstructed image appears artifacts. To avoid this, for acquiring 2D or 3D images, X-ray irradiations have performed in a wide viewing field so as to sufficiently cover the imaging portion in 180 degrees. As a result, a serious problem of exposure dose on an object has been increased since X-rays are irradiated on an unnecessary portion other than a region of interest in a diagnosis target region. Generally, an X-ray diagnosis apparatus includes an X-ray generator and an X-ray detector so as to face each other by holding them on a C-arm holder. Further, a collimator is provided between the X-ray generator and the X-ray detector. The collimator includes a plurality of aperture blades for setting up a size and a position of an aperture so that X-rays emitted from the X-ray generator selectively irradiate onto an examination target portion of an object. A conventional method has been proposed to reduce X-ray exposure dose to an object by moving the aperture blades in an approaching or a seceding direction to or from a center axis of X-ray beams so as to irradiate X-rays onto the diagnosis target region. The aperture blades in the conventional collimator can be moved merely in an approaching or a seceding directions to or from a center axis of X-ray beams. Accordingly, when a diagnosis target region has a spherical shape, such as a skull bone, having almost equal expanses in every direction, unnecessary X-ray irradiations can be effectively eliminated. However, as illustrated in FIG. 5A, when X-ray irradiations are performed to a diagnosis target region having a strong directionality, such as blood vessels, in the cardiovascular diagnosis, X-rays irradiated onto unnecessary regions of the diagnosis. This causes a serious problem of unnecessary X-ray exposure doses. The exemplary embodiments consistent with the present invention addresses these and other problems and drawbacks and provides an X-ray diagnosis apparatus and a method for controlling X-ray exposure dose that can eliminate unnecessary X-ray irradiations onto periphery of a target region and can reduce X-ray exposure dose to the object by sliding and/or turning a plurality of aperture blades in an X-ray collimator based on a figure of the target region having a strong directionality. According to certain exemplary embodiments, an X-ray diagnosis apparatus object includes an X-ray tube configured to generate X-rays to an examination target portion of an object, an X-ray detecting unit configured to detect X-rays penetrated through the object, an X-ray collimating unit including a plurality of aperture blades for setting an irradiation region of the X-rays generated from the X-ray tube and a driving unit configured to rotationally move the X-ray tube and the X-ray detecting unit. The X-ray diagnosis apparatus object further includes an image data generating unit configured to generate image data by performing a reconstruction process based on projection data detected in accompany with the rotationally movements along a plurality of different imaging directions by the X-ray detecting unit, a region of interest setting unit configured to set up a region of interest on the examination target portion, and an X-ray aperture controlling unit configured to control the X-ray collimating unit so as to slide and turn the aperture blades in accompany with the rotationally movements, based on the set up data of the region of interest and the imaging direction. According to another exemplary embodiment, a method is provided for controlling X-ray exposure dose includes generating X-rays from an X-ray tube to an examination target region of an object; detecting X-rays penetrated through the object by an X-ray detecting unit; setting up an X-ray irradiation region a plurality of aperture blades through an X-ray collimating unit; and rotationally moving the X-ray tube and the X-ray detecting unit. The controlling method further includes generating image data by performing a reconstruction process of a plurality of different imaging directions based on projection data of a plurality of different imaging directions detected by the X-ray detecting unit in accordance with the rotationally movements; setting up a region of interest to the examination target region; and controlling the X-ray collimating unit so as to slide and move the aperture blades in accordance with the rotationally movement based on the set up data of the region of interest and the imaging directions. According to one exemplary embodiment, when image data is generated based on projection data acquired through X-ray irradiations to a region of interest of an object, unnecessary X-ray irradiations to the periphery of the region of interest can be inhibited by sliding and/or turning aperture blades of a movable collimator based on a figure of the region of interest having a strong directionality in a prescribed direction. Consequently, X-ray exposure dose in the X-ray imaging to the object can be reduced. In the following exemplary embodiment consistent with the present invention, X-ray diagnosis apparatus initially sets up a 3D region of interest on an examination target portion (blood vessel site) having a strong directionality, based on a plurality of 2D image data acquired through X-ray imaging in a preliminary imaging mode to an object. The imaging direction is successively renewed by turning the imaging system at a periphery of the object. Then, X-ray imaging in an actual imaging mode is performed to the examination target portion before and after administrating a contrast agent by sliding and/or turning the aperture blades in the movable collimator based on a projected figure of the 3D region of interest to each of the imaging directions. A volume data is generated by performing a reconstruction process of a difference projection data generated through a subtraction process between a mask projection data acquired through the X-ray imaging before administrating the contrast agent and a contrast projection data acquired through the X-ray imaging after administrating the contrast agent. 3D image data of the examination target portion is generated by performing a rendering process of the volume data. FIG. 1 is a block diagram illustrating a construction of the X-ray diagnosis apparatus. The X-ray diagnosis apparatus 100 includes an X-ray imaging unit 1, an X-ray generating unit 2, an X-ray detecting unit 3, an image data generating unit 6, a holding unit 7, a bed unit 8 and a moving mechanism drive unit 9. Both in a preliminary imaging mode for setting a region of interest of an examination target site (blood vessel site) in an object 150 on devices placed in a blood vessel, such as a stent or coils, and in an actual imaging mode for observing the placed blood vessel devices in the examination target site, the X-ray imaging unit 1 generates projection data by irradiating X-rays on the examination target portion and by detecting the X-rays penetrated through the target portion. The image data generating unit 6 generates 2D image data of a wide range based on the projection data acquired in the preliminary imaging mode. The image data generating unit 6 further generates 3D image data of a narrow range based on the projection data acquired in the actual imaging mode. The holding unit 7 supports the X-ray generating unit 2 and the X-ray detecting unit 3 for moving in prescribed directions around a periphery of an object 150. Hereinafter these units are collectively referred to as an “imaging system”. The bed unit 8 moves a top plate placing an object 150 in a prescribed direction. The moving mechanism drive unit 9 supplies drive signals to various moving mechanisms provided in the holding unit 7 and the bed unit 8. The moving mechanism drive unit 9 further detects position data of the imaging system and the top plate based on these drive signals. The X-ray diagnosis apparatus 100 further includes a display unit 10, a region of interest setting unit 11, an input unit 12 and a system control unit 13. The display unit 10 displays 2D image data in a preliminary imaging mode and a 3D image data in an actual imaging mode generated through the image data generating unit 6. Based on an interest point indicated by the input unit 12, the region of interest setting unit 11 sets up a 3D region of interest to the examination target portion indicated in the 2D image data. The input unit 12 inputs object data and various command signals, and sets up X-ray imaging conditions including an X-ray irradiation condition, imaging directions in a preliminary imaging mode and an actual imaging mode and image data generating conditions, and designates interest points on 2D image data in the preliminary imaging mode. The system control unit 13 totally controls each of the units. The X-ray imaging unit 1 includes, as illustrated in FIG. 1, an X-ray generating unit 2, an X-ray detecting unit 3, a projection data generating unit 4 and a high voltage generating unit 5. The X-ray imaging unit 1 generates projection data based on X-rays penetrated through an object 150 by performing X-ray irradiations both in a preliminary imaging mode and in an actual imaging mode. In the preliminary imaging mode, X-ray irradiation is performed in a wide range by sliding and turning aperture blades of a movable collimator provided in the X-ray generating unit 2. In the actual imaging mode, X-ray irradiation is performed in a narrow range by sliding and turning the aperture blades of the movable collimator. FIG. 2 illustrates a construction in the X-ray imaging unit 1, the X-ray generating unit 2 and the high voltage generating unit 5. The X-ray generating unit 2 includes an X-ray tube 21 for irradiating X-rays onto an examination target region and a movable collimator 22 for forming X-ray cone beams irradiated from the X-ray tube 21. The X-ray tube 21 generates X-rays by accelerating electrons emitted from a filament in a high voltage and by bombarding to a tungsten anode plate. The movable collimator 22 is used both for reducing an exposure dose over an object 150 and for increasing a quality of image data. FIG. 3 illustrates a construction of the movable collimator 22. The movable collimator 22 includes a plurality aperture blades (upper blades) 221, a plurality of lower blades 222 and a plurality of compensation filters 223. The plurality of upper blades 221 narrows the X-rays emitted from the X-ray tube 21 down to an irradiation region in a preliminary imaging mode and in an actual imaging mode. The plurality of lower blades 222 reduces scattered rays and leakage dose by moving in connection with the upper blades 221. The compensation filter 223 prevents halation by selectively reducing X-rays penetrated through penetrated through media having a low dosage. The movable collimator 22 further includes an aperture blade moving mechanism 224. The aperture blade moving mechanism 224 moves and turns the plurality of aperture blades 221, the plurality of lower blades 222 and the plurality of compensation filter 223 in prescribed positions through wire ropes and pulleys. FIG. 4 depicts a construction and function of the plurality of aperture blades (upper blades) 221 provided in the movable collimator 22. To avoid redundant explanations, the construction and function of the plurality of lower blades 222 and the compensation filters 223 that are moved in conjunction with the plurality of upper blades 221 are omitted. As illustrated in FIG. 4, the X-ray tube 21 and the plane detector 31 of the X-ray detecting unit 3 are provided so as to face the object 150 each other. A plurality of aperture blades (upper blades) 221 of the movable collimator 22 is provided between the X-ray tube 21 and the object 150. The upper blades 221 are constructed by a set of four aperture blades 221a through 221d that can move in an approaching or a seceding direction (A direction) to or from a center axis Cr of X-ray beams and can rotate around a periphery of the center axis Cr in a prescribed direction (B direction). Each of the four aperture blades 221a through 221d is coupled to the pulley (not shown) of the aperture blade moving mechanism 224 (FIG. 3) through wire ropes (not shown). Thus, the aperture blade moving mechanism 224 shown in FIG. 3 can voluntarily set up a size, a position and a direction of an X-ray irradiation region to an object 150 by moving each of the aperture blades 221a through 221d in the A direction and also by turning them in the B direction. FIG. 5A illustrates an X-ray irradiation region set up by the conventional movable collimator. FIG. 5B illustrates an X-ray irradiation region set up by the movable collimator 22 having a rotating function of the aperture blades 221 consistent with the present invention. In these examples show X-ray irradiation regions for performing an X-ray imaging to follow by observation of an examination target site (a blood vessel site) in which a coil b1 is put in an aneurysm a1 and a stent b2 is put in a peripheral normal blood vessel a2. Such an examination target site has a strong directionality in a particular direction. Since the aperture blades in the conventional movable collimator can be moved merely in an approaching or a seceding to and from the center axis Cr of X-ray beams (FIG. 4), X-ray irradiation is performed on a relatively wider region including unnecessary regions for the examination as shown in FIG. 5A. On the contrary, the movable collimator 22 consistent with the embodiment of the present invention can move the aperture blades 221a-221d so as to approach and secede to and from the center axis Cr of X-ray beams, and also can turn the aperture blades 221a-221d around the center axis. Consequently, as illustrated in FIG. 5B, despite a directionality of the examination target portion, unnecessary X-ray irradiations onto non-examination region can be significantly reduced. As a result, effective X-ray irradiations can be performed merely on the examination target region. Accordingly, it becomes possible to reduce exposure dose during an X-ray imaging in an actual imaging mode. When a size of a viewing field of the X-ray irradiations is varied to reduce X-ray exposure dose to an object 150 by rotating the movable collimator 22, since an X-ray shielding characteristic of the aperture blade is uniformly fixed, significant intensity differences of contrast density would occur between a center portion and peripheral portions of projection image data. When image data is generated by reconstructing such projection image data having significant intensity differences of contrast density, the quality of the generated image data is deteriorated by the artifact generated due to non-continuity of the projection image data. Thus, when the thickness of the aperture blade is uniform, the appearance of artifact increases at the outer edge portion of the blade. To avoid this problem, the aperture blade according to the present embodiment has a varied thickness that increases with going outside, as illustrated in FIG. 5B. This thickness configuration can reduce the contrast near the edge portions. Accordingly, the quality of the generated image data is improved by restraining the artifact. Further, according to the embodiment consistent with the present invention, as illustrated in FIGS. 6A and 6B, the aperture blade can vary the X-ray shielding characteristics. For instance, as illustrated in FIG. 6A, each of four aperture blades 221a-221d is constructed by piling up a plurality N (e.g., N=4) of X-ray shielding plates 226a-226d that can slide in the A direction. Each of the X-ray shielding plates 226a-226d is connected to a pulley of the aperture blade moving mechanism 224 through a wire rope. The aperture blade moving mechanism 224 can arbitrarily set up an intensity distribution of projection data at periphery regions of the examination target region. For instance, depending on the degree of the non-continuity of the intensity distribution in the projection data, a moving amount of the respective X-ray shielding plates 226a-226d in the A direction is controlled. FIG. 6A depicts a configuration of the aperture blades 221 having an edge angle αa formed by the aperture blade moving mechanism 224 when the variation of the projection data at peripheral regions of the examination target region is relatively small. FIG. 6B illustrates a configuration of the aperture blades 221 having an edge angle αb (αb<αa) formed by the aperture blade moving mechanism 224 when the projection data largely varies at peripheral regions of the examination target region. The edge angle is automatically set up in accordance with a size of the examination target region or a size of 3D region of interest set up in the examination target region. Thus it becomes possible to uniformly perform X-ray irradiation to the target region by changing the inclination of aperture edge of the blades which are piled up like stairs in accordance with the thickness of the target region. This configuration has an effect not only in the 3D angiography but in the usual X ray photography. Turning back to FIG. 2, there are two kinds of methods for the X-ray detector 3 to detect cone beams irradiated from the X-ray generator 2. One is a method for using a plane detector and the other is a method for using an image intensifier (I.I.) or an X-ray television. As the X-ray detecting unit 3 in this embodiment, a plane detector is used for directly converting X-rays into charges. Of course, another type of the plane detector also can be used. The plane detector 31 in the X-ray detecting unit 3 is constructed by two dimensionally arranging small detection elements in a column direction and a line direction. Each detection element includes a photoelectric film for generating charges depending on the irradiated X-rays, a condenser for accumulating the charges and a thin film transistor (TFT). To easy understanding, the plane detector 31 includes two detection elements arranged in a column direction (up and down direction of drawing) and a line direction (right and left direction of drawing). As illustrated in FIG. 7, in the plane detector 31, a first terminal of the photoelectric films 312-11, 312-12, 312-21 and 312-22 is connected to a first terminal of the capacitors 313-11, 313-12, 313-21 and 313-22. Further, each connecting point is connected to a source terminal of the TFTs 314-11, 314-12, 314-21 and 314-22. Each of photoelectric films 312-11, 312-12, 312-21 and 312-22 is connected to a bias source (not shown), and a second terminal of the capacitors 313-11, 313-12, 313-21 and 313-22 is grounded. Further, each gate of the TFTs 314-11 and 314-21 along the line direction is commonly connected to an output terminal 32-1 of the gate driver 32, and each gate of the TFT 314-12 and TFT 314-22 is commonly connected to an output terminal 32-2 of the gate driver 32. In the column direction, drain terminals of TFT 314-11 and 314-12 are commonly connected to a signal output line 319-1 and drain terminals of TFT 314-21 and 314-22 are commonly connected to a signal output line 319-2. The signal output lines 319-1 and 319-2 are connected to the projection data generating unit 4. A gate driver 32 supplies driving pulses to the gate terminal of TFT 315 for reading out signal charges accumulated in the capacitor 313 by the X-ray irradiation Referring FIG. 2, the projection data generating unit 4 includes a charge/voltage converter 41, an A/D converter 42 and a parallel/serial converter 43. The charge/voltage converter 41 converts charges read out from the plane detector 31 to voltages. The charges are readout in a parallel by a line or a column. The A/D converter 42 converts outputs from the charge/voltage converter 41 to digital signals. The parallel/serial converter 43 converts the digitalized parallel signals to time serial signals (projection data). The high voltage generating unit 5 includes an X-ray control unit 51 and a high voltage generator 52. The high voltage generator 52 generates a high voltage for supplying between an anode and a cathode to accelerate thermal electrons generate from the cathode of the X-ray tube 21. The X-ray control unit 51 controls X-ray irradiation conditions, such as a tube current and a tube voltage in the high voltage generator 52, an irradiation time, and an irradiation timing, in accordance with instruction signals supplied from the system control unit 13 Referring again FIG. 1, the image data generating unit 6 includes a projection data memory 61, an image processing unit 62, a subtraction process unit 63, a reconstruction processing unit 64 and a rendering process unit 65. The projection data memory 61 generates two dimensional (2D) projection data by successively storing projection data supplied from the projection data generating unit 4 in the X-ray detecting unit 3 into a self memory circuit. For instance, in a preliminary imaging mode, two of 2D projection data are generated through X-ray irradiations along the orthogonally crossed imaging directions θa and θb set up to the object 150, and the 2D projection data are stored into the memory circuit in the projection data memory 61. In an actual imaging mode, before administrating a contrast agent into an object 150, a plurality M of 2D projection data (hereinafter referred to as “mask projection data”) is generated through X-ray irradiations along the imaging direction θ1 through θM imaging direction θ1 through θM by continuously turning around the imaging system around a periphery of the object 150. And the mask projection data is stored with attaching the respective imaging directions as collateral data. Similarly, after administrating a contrast agent into the object 150, X-ray irradiation is performed to generate a plurality M of 2D projection data (hereinafter referred to as “contrast projection data”) along the imaging direction θ1 through θM by continuously turning around the imaging system around the periphery of the object 150. And the contrast projection data is stored with attaching the respective imaging directions as collateral data. The imaging directions θ1 through θM in the actual imaging mode will be explained later in detail. The image processing unit 62 includes an arithmetic circuit and a memory circuit (both are not shown). The arithmetic circuit reads out 2D projection data acquired along the imaging directions θa and θb in the preliminary imaging mode, and generates 2D image data (radiographic image data) for setting a region of interest by performing imaging processes, such as an interpolation process and a filtering process, to the 2D projection data. The acquired 2D image data is stored in the memory circuit. The subtraction process unit 63 reads out mask projection data before administrating a contrast agent and projection data after administrating the contrast agent that region acquired along the imaging directions θ1 through θM in an actual imaging mode together their collateral imaging direction data from the memory circuit in the projection data memory 61. And the subtraction process unit 63 generates a plurality M of 2D difference projection data corresponded to the imaging directions θ1 through θM by applying the rotational digital subtraction angiography (DSA) method that performs a subtraction process between mask projection data and contrast projection data acquired along the same imaging direction. The acquired plurality M of difference projection data is stored in the memory circuit of the reconstruction processing unit 64 by adding data of imaging directions θ1 through θM. The reconstruction processing unit 64 includes an arithmetic circuit and a memory circuit (both are not shown). The arithmetic circuit reads out the plurality M of difference projection data generated and stored in the subtraction process unit 63. And the reconstruction processing unit 64 generates 3D projection data by performing a reconstruction process of the difference projection data based on the collateral imaging direction data. Further, the reconstruction processing unit 64 generates volume data by processing a voxel interpolation of the 3D projection data. The rendering process unit 65 sets up opacity and a color tone based on the voxel value of the volume data generated by the reconstruction processing unit 64. The reconstruction processing unit 64 generates 3D image data (volume rendering image data) by performing a rendering process of the volume data based on the opacity and color tone, and an observing point and a line of sight supplied from the input unit 12. FIG. 8 illustrates a practical construction of the holding unit 7 and the bed unit 8. The holding unit 7 has a C-arm 71 for supporting the X-ray generating unit 2 and the X-ray detecting unit 3 at each of the edges portions, respectively. The bed unit 8 has a top plate 81 for placing an object 150. To easily understand, a body axis direction of the object 150, e.g., a longitudinal direction of the top plate 81 is referred to as y-direction, a vertical direction to a floor surface 160 for providing the holding unit 7 and the bed unit 8 is referred to as z-direction, and an orthogonal direction to the y-direction and z-direction, e.g., a traversing direction of the top plate 81, is referred to as x-direction. The holding unit 7 includes a C-arm 71, an arm holder 72, an arm brace member 73 and a floor circling arm 74. One edge portion of the floor circling arm 74 is rotatably mounted so as to rotate around a floor rotation axis z1 vertical to the floor surface 160 in the arrow direction d. At the other edge portion of the floor circling arm 74, an arm support 73 having an arm support rotation axis z2 parallel to the z-direction is rotatably mounted in the arrow direction c. Further, on a side surface of the arm brace member 73, an arm holder 72 is rotatably mounted so as to rotate around an arm main rotation axis z3 parallel to the y-direction in the arrow b direction. On the side surface of the arm holder 72, the C arm 71 is mounted so as to freely slide in the direction of the arrow a around the arm slide center axis z4. Each edge of the C arm 71, an X-ray generating unit 2 and an X-ray detecting unit 3 are mounted so as to face each other. The X-ray detecting unit 3 mounted at one edge portion of the C arm 71 can be moved in the arrow e direction. Further, the X-ray detecting unit 3 can be freely rotated around the imaging system rotation axis z5 in the arrow f direction in conjunction with the movable collimator 22 provided in the X-ray generating unit 2. Each of the units constructing the holding unit 7 includes a C arm slide mechanism for sliding the C arm 71 in the a-direction around the arm slide center axis z4, a holder rotation mechanism for rotating the arm holder 72 in the b-direction around the arm main rotation axis z3, a support rotation mechanism for rotating the arm support 73 around the arm support rotation axis z2 in the c-direction and a floor circling arm rotation mechanism for rotating the floor circling arm 74 around the floor rotation axis z1 in the d-direction (all are not shown). Further, each of the units in the holding unit 7 includes an imaging system moving mechanism for moving the X-ray detecting unit 3 in the e-direction and an imaging system rotating mechanism for rotating the X-ray detecting unit 3 around the imaging system rotation axis z5 in the f-direction (both are not shown). The bed unit 8 includes a vertical direction moving mechanism for moving up and down the top plate 81 for placing the object 150 in the h-direction (z-direction), and a horizontal direction moving mechanism for sliding the top plate 81 in a longitudinal direction ga (y-direction) or a traversing direction gb (x-direction) (both are not shown). By rotating or moving both the holding unit 7 and each unit provided in the bed unit 8 in a prescribed direction, the imaging system provided at edge portions of the C arm 71 can locate at an appropriate position or a direction for X-ray imaging of an object 150 placed on the top plate 81. Thus, a desired imaging direction can be set up. The moving mechanism drive unit 9 (FIG. 1) includes a mechanism drive unit 91, a mechanism drive control unit 92 and a position detecting unit 93. FIG. 9 illustrates a practical embodiment of the moving mechanism drive unit 9 for supplying drive signals to the movable collimator 22 in the X-ray generating unit 2 and various moving mechanisms provided in the holding unit 7 and the bed unit 8. The aperture blade moving mechanism 224 provided in the movable collimator 22 includes an aperture blade sliding mechanism 22a and an aperture blade turning mechanism 22b. The aperture blade sliding mechanism 22a slides the aperture blade 221 in the A-direction so as to approach or secede to or from a center axis Cr of X-ray beams. The aperture blade turning mechanism 22b rotates the aperture blade 221 in the B-direction at a periphery of the center axis Cr. The holding unit 7 includes a C-arm sliding mechanism 71a, a holder turning mechanism 72a, a support post rotating mechanism 73a, floor circling arm rotating mechanism 74a, an imaging system moving mechanism 75a and an imaging system rotating mechanism 75b. The C-arm sliding mechanism 71a is provided at a connecting portion of the C-arm 71 and the arm holder 72. The C-arm sliding mechanism 71a slides the C-arm 71 in the a-direction. The holder turning mechanism 72a is provided at a connecting portion of the arm holder 72 and the arm support post 73, and rotates the arm holder 72 in the b-direction. The support post rotating mechanism 73a is provided at a connecting portion of the arm support post 73 and the floor circling arm 74, and rotates the arm support post 73 in the c-direction. The floor circling arm rotating mechanism 74a is provided at a connection portion of the floor circling arm 74 and a floor surface 160, and rotates the floor circling arm 74 in the d-direction. Further, an imaging system moving mechanism 75a and an imaging system rotating mechanism 75b are provided at a connecting portion of the edge of the C-arm 71 and the X-ray detecting unit 3. The imaging system moving mechanism 75a moves the X-ray detecting unit 3 in the e-direction. The imaging system rotating mechanism 75b rotates the X-ray detecting unit 3 in the f-direction. A vertically moving mechanism 81a and a horizontally moving mechanism 81b are provided in the bed unit 8. The vertically moving mechanism 81a lifts the top plate 81 for placing an object 150 up and down in the h-direction. The horizontally moving mechanism 81b slides the top plate 81 in the ga-direction and the gb-direction. Drive signals generated by the mechanism drive unit 91 based on the control signals supplied from the mechanism drive control unit 92 in the moving mechanism drive unit 9 are supplied to the aperture blade sliding mechanism 22a and the aperture blade rotating mechanism 22b in the aperture blade moving mechanism 224, C-arm sliding mechanism 71a in the holding unit 7, the holder turning mechanism 72a, the support post rotating mechanism 73a, the floor circling arm rotating mechanism 74a, the imaging system moving mechanism 75a and the imaging system rotating mechanism 75b, and the vertically moving mechanism 81a and the horizontally moving mechanism 81b in the bed unit 8. Thus, by controlling the above-described moving mechanisms based on the control signals generated in the mechanism drive control unit 92, as illustrated in FIG. 5B, aperture blades 221a-221d can be moved at appropriate positions so as that an opening formed by the aperture blades 221 almost coincide with a size of the examination target region. Further, the imaging system provided at the edges of the C-arm 71 can be placed at a desired position to an object 150 placed on the top plate 81. The position detecting unit 93 in the moving mechanism drive unit 9 detects position data of the imaging system provided on the C-arm 71 and position data of the top plate 81 based on the drive signals generated by the mechanism drive unit 91. The position detecting unit 93 further calculates imaging directions to the object 150 by using these position data. The acquired imaging direction data is supplied to the projection data memory 61 in the image data generating unit 6 through the system control unit 13. The imaging direction data is stored together with 2D projection data acquired in the imaging directions θa and θb during a preliminary imaging mode or 2D projection data acquired in the imaging directions θ1 trough θM during an actual imaging mode as collateral data for the projection data. FIG. 10 illustrates the imaging directions and the imaging scopes during an actual imaging mode in the embodiment consistent with the present invention. The imaging system is continuously rotated around a periphery an object 150 both before administrating a contrast agent and after administrating the contrast agent. Then, X-ray imaging along the imaging directions θ1 through θM are performed by sliding and rotating the aperture blade 221a-221ds in the movable collimator 22 in a prescribed direction. Based on the acquired mask projection data and the contrast projection data, 3D image data is generated by reconstructing difference projection data in the imaging direction θ1 through θM. FIG. 10 depicts an imaging scope θ0 for acquiring the minimally required difference projection data for performing the reconstruction process. For the reconstruction process, it is needed to acquire a plurality of difference projection data at a prescribed angular interval in the scope of 180 degrees plus a fun angle θf. In this case, the imaging system is rotated by the C-arm sliding mechanism 71a provided in the holding unit 7 or by the holder turning mechanism 72a (FIG. 9). The sliding and rotating movements of the aperture blades 221a through 221d are executed by the aperture blade sliding mechanism 22a and the aperture blade rotating mechanism 22b constructing the aperture blade moving mechanism 224 in the movable collimator 22. The fan angle θf shown in FIG. 10 is determined based on the X-ray irradiation angle emitted from the X-ray generating unit 2. The display unit 10 (FIG. 1) includes a display data generator, a data converter and a monitor (all are not shown). The display data generator composes (provides in parallel) 2D image data in the imaging directions θa and θb supplied from the image processing unit 62 in the image data generating unit in a preliminary imaging mode. Further, when an interest point is designated by the input unit 12 for indicating an edge portion of a device (stent) placed in a blood vessel in the examination target site, the display data generator generates a first display data by overlapping the 3D region of interest data set up on the examination target portion by the region of interest setting unit 11 based on the interest point data supplied from the input unit 12 and this interest point over the 2D image data. The display data generator further generates a second display data by adding collateral data, such as object data and X-ray imaging conditions to the 3D image data supplied from the rendering process unit 65 in the image data generating unit 6 in an actual imaging mode. The data converter converts the first and second display data into a prescribed displaying format. The converted display data is displayed on a monitor by performing D/A conversion and the television format conversion. FIG. 11 illustrates the first display data displayed on a monitor in the display unit 10 in the preliminary imaging mode, interest points designated by the input unit 12 on the examination target region of the first display data and 3D region of interest set up by the region of interest setting unit 11 based on the position data of the interest points. As illustrated in FIG. 11, 2D image data Da (θa) and Db (θb) acquired along the imaging directions θa and θb in the preliminary imaging mode are displayed on the monitor in the display unit 10 as the first display data. Through the input unit 12, interest points Pa and Pb are designated at the edge portions of the stent b2 put in the blood vessel a2 displayed in the first display data at the examination target region. By receiving the position data of the interest point, the region of interest setting unit 11 (FIG. 1) sets up a 3D region of interest surrounding the examination target region Ri. Thus, in the preliminary imaging mode, the first display data displayed on the monitor in the display unit 10 is constructed by arranging 2D image data Da (θa) acquired in the imaging direction θa and 2D image data Db (θb) acquired in the imaging direction θb orthogonally crossing the imaging direction θa in parallel. As shown in FIG. 11, in each of 2D image data Da (θa) and Db (θb), a coil b1 placed in aneurysm a1 and a stent b2 put in the blood vessel a2 are displayed as the examination target region. When such a first display data is displayed in the display unit 10, an operator designates the interest points Pa and Pb for indicating edges of the stent b2 in each of 2D image data Da (θa) and Db (θb) by using an input device, such as a mouse, provided in the input unit 12. The position data of interest points Pa and Pb are supplied to the system control unit 13 through the input unit 12. By receiving the position data, the region of interest setting unit 11 sets up a 3D region of interest Ri of a length determined based on a line segment connecting the interest points Pa and Pb and a width determined outside edges of the blood vessel a2 and the aneurysm a1. By designating the interest points Pa and Pb in each of 2D image data Da (θa) and Db (θb), it becomes possible to identify the position coordinate of the edge portions of the stent in a 3D space. Accordingly, the region of interest setting unit 11 can sets up a 3D region of interest in the examination region based on the interest points Pa and Pb. The input unit 12 (FIG. 1) includes an imaging mode selection unit 121 for selecting an imaging mode, an imaging condition setting unit 122 for setting up X-ray imaging conditions including X-ray irradiation conditions and an interest point designating unit 123 for designating an interest point to the 2D image data in the preliminary imaging mode. The input unit 12 inputs object data and various command signals through input devices, such as a display panel, a keyboard, a mouse, etc. The input unit 12 further sets up lengths and widths of 3D region of interest, and designates imaging directions both in the preliminary imaging mode and the actual imaging mode and image data generating conditions. The system control unit 13 includes a CPU and a memory circuit (both not shown). The system control unit 13 stores the input data and the set up data supplied from the input unit 12 into the memory circuit. Then, based on these data, the system control unit 13 totally controls each unit in the X-ray diagnosis apparatus to generate and display 2D image data in the preliminary imaging mode and 3D image data in the actual imaging mode. FIG. 12 is a flowchart illustrating a setting up process of 3D region of interest in the preliminary imaging mode according to the present embodiment. Prior to perform X-ray imaging to an object 150 in the preliminary imaging mode, an operator of an X-ray diagnosis apparatus 100 performs an initial set up the apparatus through the input unit 12 (FIG. 12, step S1). Thus, after inputting the object data, X-ray imaging conditions including X-ray irradiation conditions, the imaging directions θa and θb in the preliminary imaging mode, imaging directions θ1 through θM in the actual imaging mode, image data generating conditions and lengths and widths of 3D region of interest are set up. These input and set up data are stored in the memory circuit of the system control unit 13. When the apparatus has been initially set up, the operator selects the preliminary imaging mode through the input unit 12 (FIG. 12, step S2) after moving the top plate 81 placing an object 150 to a prescribed position, and inputs a start command for the preliminary imaging mode (FIG. 12, step S3). By supplying this command signal to the system control unit 13, an X-ray imaging in the preliminary imaging mode is started. Thus, by receiving the start command signal of the preliminary imaging mode, the system control unit 13 reads out the set up data of the imaging directions θa and θb from the self memory circuit, and supplies them to the mechanism drive control unit 92 in the moving mechanism unit 9. By receiving the set up data, the mechanism drive control unit 92 supplies a mechanism drive control signal generated based on the set up data in the imaging direction θa to the mechanism drive unit 91. The mechanism drive unit 91 generates a drive signal based on the mechanism drive control signal, and supplies to the holder turning mechanism 72a in the holding unit 7 to set up the imaging system in the imaging direction θa by rotating the C arm 71 (FIG. 12, step S4). Then, the system control unit 13 supplies X-ray irradiation conditions read out from the memory circuit and the X-ray generating command signal to the X-ray control unit 51 in the high voltage generating unit 5. The X-ray control unit 51 controls the high voltage generator 52 based on the X-ray irradiation conditions to supply a high voltage to the X-ray tube 21 in the X-ray generating unit 2. The X-ray tube 21 irradiates X-rays for the preliminary imaging mode onto the object 150 in a prescribed period through the movable collimator 22. The X-rays penetrated through the object 150 are detected by the plane detector 31 in the X-ray detecting unit 3. In the plane detector 31, each photoelectric film 312 arranged in each detection elements 311 accumulates a signal charge proportioned to the X-rays penetrated through the object 150 to the capacitor 313. When the X-ray irradiation has finished, the gate driver 32 receives clock pulses from the system control unit 13 and successively reads out the accumulated signal charge from the capacitor 313 y supplying drive pulses to TFT 314 in the plane detector 31. The read out signal charge is converted into a voltage in the charge/voltage converter 41 of the projection data generating unit 4. Further, the A/D converter 42 converts the voltage to digital signal and stores in the buffer memory in the parallel/serial converter 43 as projection data of a one line. The parallel/serial converter 43 reads out the projection data from the buffer memory in serial by a line, and successively stores into the projection data memory 61 in the image data generating unit 6 to generate 2D projection data. The image processing unit 62 generates 2D image data along the imaging direction θa by performing imaging processes to 2D projection data generated in the projection data memory 61. The generated 2D image data is stored in the memory circuit of the image processing unit 62 (FIG. 12, step S5). When the storing of 2D image data along the imaging direction θa has finished, the system control unit 13 controls the moving mechanism drive unit 9 to set up the imaging system in the imaging direction θb substantially orthogonal to the imaging direction θa (FIG. 12, step S6). Further, the system control unit 13 controls to generate and store 2D image data along the imaging direction θb as described the step S5. When 2D image data in the imaging directions θa and θb have been generated and stored, the display unit 10 displays the 2D image data along the imaging directions θa and θb read out from the memory circuit in the image processing unit 62 by arranging in parallel on the monitor (FIG. 12, step S7). By observing the two 2D image data displayed on the monitor, the operator designates the interest point at each edge portion of the stent put in the blood vessel displayed in the examination target region of 2D image data input unit 12 by using an input device (FIG. 12, step S8). The position data of the interest point is supplied to the region of interest setting unit 11 through the system control unit 13. The region of interest setting unit 11 sets up a 3D region of interest surrounding the examination target region based on the position data (FIG. 12, step S9). FIG. 13 is a flowchart illustrating generating and displaying steps of 3D image data in an actual imaging mode consistent with the present embodiment. When the setting of a 3D region of interest to the examination target region has finished at the step S9 in FIG. 12, the operator selects an actual imaging mode through the input unit 12 (FIG. 13, step S11). Further, a start command for acquiring mask projection data is input by using the input unit 12 (FIG. 13, step S12). By supplying the acquisition start command signal to the system control unit 13, an acquisition of the mask projection data of the object 150 in the actual imaging mode is started. Thus, by receiving the acquisition start command signal, the system control unit 13 reads out the set up data on the imaging directions θ1 through θM in the actual imaging mode from the self memory circuit and supplies them to the mechanism drive control unit 92 in the moving mechanism drive unit 9. By receiving these set up data, the mechanism drive control unit 92 mechanism initially supplies a mechanism drive control signal generated based on the set up data along the imaging direction θ1 to the mechanism drive unit 91. The mechanism drive unit 91 supplies a drive signal generated based on the mechanism drive control signal and supplies to the holder turning mechanism 72a in the holding unit 7 for setting up the imaging system supported on an edge portion of the C-arm 71 in the first imaging direction θ1. Further, the system control unit 13 supplies a 3D region of interest data set up in the region of interest setting unit 11 to the mechanism drive control unit 92 in the moving mechanism drive unit 9. By receiving the set up data, the mechanism drive control unit 92 supplies a mechanism drive control signal generated based on a projected figure of the 3D region of interest in the first imaging direction θ1 to the mechanism drive unit 91. The mechanism drive unit 91 generates a drive signal based on the mechanism drive control signal and supplies it to the aperture blade moving mechanism 224 in the movable collimator 22 so as to locate the aperture blades 221a-221d by sliding and turning at an appropriate position for an X ray irradiation to the examination target region (FIG. 13, step S13). Then, the system control unit 13 supplies X-ray irradiation conditions read out from the memory circuit and the X-ray generating command signal to the X-ray control unit 51 in the high voltage generating unit 5. Based on the X-ray irradiation conditions, the high voltage control unit 41 supplies a high voltage to the X-ray tube 21 by controlling the X-ray generating unit 2. The X-ray tube 21 irradiates X-rays to the object 150 through the movable collimator 22 in a prescribed period. The X-rays penetrated through the object 150 are detected by the X-ray detecting unit 3. The projection data generating unit 4 generates projection data by performing processes of the detected signals in the X-ray detecting unit 3. By successively storing the acquired projection data in the projection data memory 61, mask projection data in the imaging direction θ1 is generated (FIG. 13, step S14). When the acquisition of mask projection data along the imaging direction θ1 has finished, the system control unit 13 successively rotates the imaging system in each of the imaging directions θ2 through θM by controlling each unit. Further, by sliding and rotating the aperture blades 221a-221d in the movable collimator 22 based on the projected figure of 3D region of interest in these imaging directions, X-ray imaging is performed onto the object 150. The projection data supplied in time series from the X-ray imaging unit 1 is successively stored in the projection data memory 61 for generating mask projection data along each of the imaging directions θ2 through θM. Thus, by repeating the steps S13 and S14, the mask projection data generated along each of the imaging directions θ1 through θM is stored in the projection data memory 61 together the imaging direction as collateral data. Then, the operator administrates a contrast agent into the object 150 (FIG. 13, step S15). At a time when the contrast agent reaches to the examination target region, a contrast projection data acquisition start command is input through the input unit 12 (FIG. 13, step S16). By receiving the contrast projection data acquisition start command, the system control unit 13 moves the imaging system and the aperture blades by totally controlling each of units in the X-ray diagnosis apparatus 100 (FIG. 13, step S17). Further, the system control unit 13 performs X-ray imaging in the actual imaging mode along the imaging direction θ1 through θM for generating and storing the contrast projection data (FIG. 13, step S18). Acquisition of the mask projection data and the contrast projection data along the imaging direction θ1 through θM have finished, the subtraction process unit 63 reads out the mask projection data before administrating the contrast agent and the contrast projection data after administrating the contrast agent acquired in these imaging directions together the collateral data, i.e., the imaging direction data from the memory circuit in the projection data memory 61, and generates a plurality M of difference projection data corresponding to the imaging directions θ1 through θM by performing a subtraction process between the mask projection data and the contrast projection data that are acquired along the same imaging direction. The difference projection data is stored in the memory circuit in the reconstruction processing unit 64 by adding the direction data of the imaging directions θ1 through θM (FIG. 13, step S19). The reconstruction processing unit 64 reads out and performs reconstruction processes of the difference projection data based on the collateral data of the imaging directions θ1 through θM to generate volume data (FIG. 13, step S20). Then, the rendering process unit 65 sets up an opacity degree and a color tone based on voxel value of the volume data generated by the reconstruction processing unit 64. By performing a rendering process of the volume data based on the set up opacity degree and the color tone and a viewing point and a visual line direction supplied from the input unit 12, the rendering process unit 65 generates 3D image data (FIG. 13, step S21). According to the above-mentioned rendering process, for generating image data based on projection data acquired through X-ray irradiations to a region of interest of an object, unnecessary X-ray irradiations to the periphery of the region of interest can be inhibited by sliding and rotating the aperture blades in the collimator based on a figure of the region of interest having a strong directionality. As a result, exposure dose to the object during the X-ray imaging can be reduced. Particularly, since the sliding amount and the rotation angle are optimized by each of imaging directions, appropriate and sufficient projection data for a reconstruction process can be acquired, image data of good quality can be generated through an X-ray imaging of a low exposure dose. According to the embodiment consistent with the present invention, the aperture blades provided in the movable collimator are constructed so as that a shielding amount becomes gradually smaller into a center portion. Accordingly, even when an X-ray irradiation is performed to a relatively narrow region through the aperture blades, the intensity distribution near the periphery of projection data does not significantly change. Consequently, high quality image data can be generated by reducing artifacts due to non-continuity of projection data. Since the above-described aperture blades are constructed by a plurality of X-ray shielding plates that can independently slide to the center direction of the X-ray beam, it becomes possible to form the intensity distribution of the projection data in accordance with the examination target region so as to restrain occurrence of artifacts. The embodiments of the present invention can be modified. For instance, while the stent is put in the normal blood vessel running a periphery of the aneurysm for preventing the coil slipping off from the neck portion of the aneurysm in the embodiments, it is possible to put a stent in the blood vessel to prevent a resteonis of a blood vessel that is treated by a balloon catheter. Further, it is possible to perform the X-ray imaging to a blood vessel in which a device does not put in. The examination target region having a strong directionality may include lumen other than a blood vessel. In the exemplary embodiments, a plurality of interest points is designated to 2D image data acquired along two orthogonal imaging directions. Then, 3D region of interest surrounding an examination target region is set up based on these interest points. Of course, in the preliminary imaging mode, it needs not to use such two orthogonal imaging directions. For instance, 3D region of interest can be set up based on 2D image data acquired along more than three imaging directions. While the interest points are designated to a plurality of 2D image data acquired by the usual X-ray imaging in the above-described embodiments, it is also possible to designate the interest point on 3D image data acquired by using the digital subtraction angiography (DSA) method or the usual X-ray imaging. Further, the designation of the interest points is not limited to the edge portion of the medical treatment devices put in a blood vessel displayed on the image data, but can voluntarily be designate to the blood vessel or the devices put in the blood vessel. In the above-described exemplary embodiments, a running direction of a blood vessel is detected based on the interest points and 3D region of interest having a prescribed length and a width is set up along the running direction. It is also possible to designate the length and the width region of interest can be set based on an outline data of the blood vessel and the devices put in the blood vessel by automatically extracting from the image data in a preliminary imaging mode. Further, X-ray imaging in an actual imaging mode can be performed based on the 3D region of interest data of the examination target portion preliminarily measured by the X-ray diagnosis apparatus or another image diagnosis apparatus. In the exemplary embodiments, the setting of an imaging direction is performed by rotating the imaging system. It is also possible to perform by sliding the C arm having the imaging system. In the above-described exemplary embodiments, the plurality of aperture blades are turned so as that an effective X-ray irradiation is performed on an examination target portion having a particular directionality. It is also possible to rotate the collimator itself by stead of rotating the aperture blades. While certain embodiments, the X-ray imaging in an actual imaging mode generates the volume data based on the difference projection data generated by using the DSA and 3D image data is generated based on the volume data, the volume data can be generated based on 2D projection data acquired through a normal X-ray imaging. The image data generated based on the volume data does not limit to 3D image data. For instance, the image data generated based on the volume data may includes multi-planar reconstruction (MPR) image data generated at a prescribed slice plane of the volume data and maximum intensity projection (MIP) image data projected the volume data in a prescribed direction. While certain embodiments have been described, these embodiments are presented by way of example only, and are not intended to limit the scope of the invention. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms; furthermore, various omissions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
050230433	summary	BACKGROUND OF THE INVENTION The present invention relates to an actively cooled device including bodies of heat resistant (i.e. refractory) material which are each surface brazed to at least one coolant conduit. Many purposes require highly thermally stressable shields, the so-called "heat shields". Typical examples are the diverters and limiters of a fusion reactor. Since heat shields are a preferred field of application for the invention, it will hereinafter be described for the example of heat shields. However, the invention is not limited to them; it can also be used for other actively cooled devices, such as cooled drawing dies for the production of profiled rods, cooled electrodes for fusion electrolysis and the like. If it meets certain quality requirements, graphite, due to its characteristics, is a good heat shield material for plasma physical systems, such as fusion reactors, and other vacuum systems. Low atomic weight, high sublimation temperature, good heat conduction, and low atomization rate are some of these characteristics. On the other hand, graphite also has various drawbacks, such as porosity, low mechanical strength and low ductility. The porosity of graphite generally forbids, already for density reasons, direct contact of the graphite with a cooling fluid. Its poor mechanical strength and ductility make the joining of graphite parts more difficult and limit the maximum temperature under which it can be used. In the past, therefore, graphite elements serving as heat shields could be cooled only by radiation or by thermal contact with a heat dissipating fastening structure. The graphite elements of such a known heat shield in an experimental fusion reactor, such as a Tokamak, are therefore adiabatically heated during a plasma discharge which lasts up to about 10 seconds and then require at least about 10 minutes to cool sufficiently. Longer plasma discharges or stationary operation is therefore impossible if the prior art graphite heat shields are used. Similar problems exist with the so-called first wall of fusion reactors. In this connection, the JAERI-M82-174 (1982) report discloses the soldering of silicon carbide plates to a planar frontal face of strip-like projections formed in a base plate by cooling channels having a trapezoidal cross section. The Journal of Nuclear Materials 103 & 104 (1981) pages 31-40, further discloses a limiter which contains water cooled copper plates to whose surface graphite tiles are brazed. However, the strength of these planar brazed connections leaves something to be desired under the unavoidable alternating temperature and pressure stresses, and cracks frequently develop at the solder locations which greatly impede heat transfer. Consequently, the present invention is based on the problem of assuring, in a device, e.g. a heat shield, employing elements made of a heat resistant material which are actively cooled by a coolant, the durability of the brazed connections and thus reliable dissipation of heat from the heat resistant elements to the coolant so that greater stressability and/or longer service life result. SUMMARY OF THE INVENTION In the present invention, the above-mentioned problems are thus solved in that the bodies or elements of the device are each provided with at least one recess having an at least part circular cross section, into which a member having a corresponding cross section and being part of a metallic cooling pipe is brazed directly and with surface contact. The geometry is preferably and advantageously selected so that the heat transfer surface between the element and the cooling pipe is approximately equal to the thermally stressed surface of the element. An element may also be brazed directly to a plurality of cooling pipes. Embodiments of the invention will now be described in greater detail with reference to the drawing for the example of heat shields for fusion reactors.
	claims	1. A method of determining the nearness to criticality of a nuclear reactor having a control rod configuration in a core region of a nuclear reactor vessel and a coolant moderator circulating therethrough, comprising the steps of:Monitoring a first source range detector signal (CMC) during a transient portion of the detector signal to obtain a neutron radiation level of the core when the coolant moderator is at a density corresponding to a first temperature;Raising the temperature of the core to a second temperature;Monitoring a second source range detector signal (CMH) during a transient portion of the detector signal to obtain a neutron radiation level of the core when the coolant moderator is at a density corresponding to the second temperature, the monitored first source range detector signal and the monitored second source range detector signal each having a background non-neutron signal component (N);Determining the background non-neutron signal component based upon the monitored first and second source range detector signals in accordance with the relationship N = { K eff H - K eff C 1 - K eff H + R ⁡ ( T H ) R ⁡ ( T C ) + F H F C - 1 } ⁢ C MC - C MH { K eff H - K eff C 1 - K eff H + R ⁡ ( T H ) R ⁡ ( T C ) + F H F C - 1 } - 1 Removing the background non-neutron signal component from the monitored neutron radiation level obtained at the second temperature to obtain background adjusted neutron radiation level; andDetermining the nearness to criticality based upon the background adjusted neutron radiation level. 2. The method of claim 1 wherein the nuclear reactor is a pressurized light water reactor. 3. The method of claim 2 wherein the moderator is borated water. 4. The method of claim 1 wherein the control rod configuration and a concentration of the moderator remain unchanged between the monitoring of the first source range detector signal and the monitoring of the second source range detector signal. 5. The method of claim 4 wherein in the step of determining the background non-neutron signal component a term 1/ICRREH is approximated from a ratio of the monitored values of CMH and CMC to arrive at an initial value of N. 6. The method of claim 5 including the step of subtracting the initial value of N from the values of CMH and CMC and calculating the residual value of N. 7. The method of claim 6 including the steps of:Raising the temperature of the core to a third temperature;Monitoring a third source range detector signal during a transient portion of the detector signal to obtain a neutron radiation level of the core when the coolant moderator is at a density corresponding to the third temperature;Determining N from the second source range detector signal and the third source range detector signal using an approximation for 1/ICRREH;Calculating a new residual value of N;Iterating the foregoing process until a final residual value of N is determined which is less than the resolution limit of a measurement of the source range signal; andDetermining a final value of N from the sum of all the values of N used to produce the final residual value of N.
	abstract	A radiotherapy apparatus comprises a first collimator and a second collimator, the first collimator being a multi-leaf collimator, the second collimator comprising a plurality of slits having a width which is a fraction of the width of the leaves of the first collimator, the first and second collimators being aligned such that each slit of the second collimator is associated with a leaf of the first collimator. A first irradiation is made, during which the first collimator will define the outer edge of the irradiation pattern, and the second collimator will serve to narrow the effective width of each leaf of the first collimator. This narrowing is a simple function of the relative widths of the slits of the second collimator and the leaves of the first. This will leave gaps in between the slits of the second collimator, which can then be filled by moving one or more of the patient, first and second collimators, so as to irradiate an area omitted in the first irradiation. In this second irradiation, the positions of the leaves of the first collimator are adjusted as necessary. This process is then repeated until the entire target area has been irradiated. Suitable values for the fraction are {fraction (1/2, 1/3, 1/4)}, or ⅕.
052746860	abstract	A method for enhancing the wear and corrosion resistance of a tubular nuclear fuel assembly component (40), comprising the step of coating the component with a corrosion and wear resistant material by an anodic arc plasma deposition process (70). The coating is preferably a nitride reactively formed during the plasma deposition process. The component is preferably a nuclear fuel rod cladding tube and the coating material is one of ZrN or TiN.
046997571	abstract	A nuclear fuel rod has a sheath closed by end plugs and a stack of fuel pellets in the sheath. The stack is retained in abutment against one of the end plugs during handling of the fuel rod by a radially expandable element having a cross-sectional area in rest condition such as it frictionally engages an internal surface of said sheath. When the fuel rod is brought to the reactor operating temperature, the radially expandable element is contracted clear of frictional contact by temperature responsive means of a shape memory alloy operatively associated with said radially expandable element and having a transformation temperature above atmospheric temperature.
	abstract	An apparatus (10, 10″) for producing an alignment surface on an associated substrate (12, 12″) of a liquid crystal display. An electron source (40) produces a collimated electron beam (50). A substrate support (20, 20″) supports the associated substrate (12, 12″) with a surface normal (80) of the substrate arranged at a preselected angle (α) relative to the collimated electron beam (50). The collimated electron beam (50) is rastered across the associated substrate (12, 12″) at the preselected angle (α) while the substrate moves through the electron beam.
056129831	description	DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1, the reference sign 1 generally designates the cylindrical wall forming the containment of a reactor (not shown) in a nuclear power plant. However, the wall 1 is in FIG. 1 indicated in the form of a simple arcuate line. In actual practice, the wall is composed of a very thick reinforced concrete wall and a leak-proof lining of non-corrosive sheet-metal applied on the inside of the wall. A number of columns 2, 2', which form part of the loadbearing structure of the containment, are arranged inwardly of the cylindrical wall at a distance therefrom. In practice, such columns, which may be made of concrete, are evenly distributed along the periphery of the cylindrical wall, e.g. at a pitch of 12.5.degree.. The columns may have a diameter of 0.8-1.0 m. Adjacent to the cylindrical wall, there is arranged a back-flushable strainer 3, which might be of conventional design. In a particular aspect of the invention, it is, however, preferred that a strainer of the type shown in detail in FIGS. 3-7 be used. The strainer 3 is connected to a first conduit 4 running through the wall 1 and, on the outside thereof, connected to a suction pump (not shown). The strainer is kept in place by means of brackets 5 (see FIG. 2) which are connected to attachments 6 anchored in the wall 1. A washwater conduit 7 is connected to the strainer and serves to supply either clean water from outside or filtered water to the interior of the strainer in order to flush the strainer wall. It should be pointed out that the strainers in the power plant are arranged in the vicinity of the bottom 8 of the containment 1 at a considerable distance below the normal water level 9 in the condensation pool formed by the bottom part of the containment. Reference is now made to FIGS. 3-7, which illustrate the construction of the preferred back-flushable strainer in more detail. As is seen most clearly in FIGS. 3 and 4, the strainer 3 substantially consists of a cylindrical strainer wall 10 in the form of a perforated metal sheet. In practice, the cylindrical strainer wall or tube 10 may have a length in the range of 0.7-1.5 m, suitably a length of about 1.0 m, and a diameter in the range of 0.4-0.6 m, suitably a diameter of about 0.5 m. The perforations may have a diameter in the range of 2-4 mm, the strainer wall having a total perforation area in the range of 25%-40%, suitably 30%-35%. Such dimensions enable a flow in the range of 100-250 kg/s through the strainer wall. In the embodiment illustrated, the strainer wall is vertically oriented and closed at the upper end. To be more specific, the strainer wall 10 merges, via a frustoconical portion 11, into a comparatively narrow throat 12 which ends with a frustoconical metal sheet 13 whose diameter much exceeds that of the strainer wall or tube 10. A clamp 14 (see FIG. 2), kept in place by the brackets 5, can be connected to the throat 12. The lower end of the strainer wall or tube 10 is open and connected to the first conduit 4 connected to the suction pump. The conduit 7 for supplying wash water to the interior of the strainer has a smaller diameter than the conduit 4, in which it is inserted through a hole 15 in a curved portion thereof, the portion 7' of the conduit 7 located inside the conduit 4 and the straight portion 4' of the conduit 4 connecting to the strainer being concentric. The diameter of the portion 4' is somewhat smaller than that of the strainer wall or tube 10, a conically tapering collar 16 being arranged at the transition therebetween. According to a characteristic feature of the strainer illustrated in FIGS. 3 and 4, the strainer wall or tube 10 is on the outside provided with a number of longitudinal, peripherally spaced-apart and radially projecting wings or wing-like elements 17. In the embodiment illustrated, the strainer has four wings 17 arranged at a pitch of 900 and extending along the entire length of the strainer wall or tube 10 and all the way up to the frustoconical metal sheet 13, which serves as an attachment for the wings. Advantageously, the width of the wings is in the range of 25%-75% of the diameter of the strainer wall or tube 10, conveniently about 50% thereof. In conventional strainers without wings, the fibres deposite in the form of a continuous circumferential mat, in which the fibres are fairly closely intertwined. Such a continuous fibre mat offers a considerable resistance to removal from the strainer wall by back-flushing. The inventive strainer being provided with the wings 17, the fibre mat is divided into a number of separate sections (here four) which, individually, are much more easily released from the strainer wall. Compared with conventional strainers, the inventive strainer has the considerable advantage of a rotation-generating means, generally designated 18, being arranged adjacent to the opening of the wash-water conduit 7 close to the strainer. As appears from FIG. 3 combined with FIGS. 5-7, the rotation-generating means consists of a conical body 19 centrally arranged in the conduit 7, and a plurality of curved blades 20 arranged on the outside of the body 19. The conduit 7, or more precisely the straight portion 7' thereof, ends with a conically tapering collar or tubular element 21, like the portion 4' of the conduit 4. The blades 20 extend between the inside of the collar 21 and the outside of the centrally-arranged body 19. The conicity of the centrally-arranged body 19 is so adjusted to the conicity of the collar 21 that the flow-through area of any optional horizontal cross-section taken along the vertical central axis is approximately of the same size. As appears from FIG. 5, the upper portions of the blades 20 adjacent to the annular opening passage are inclined in relation to the radial direction, and the blades have a curved shape, as appears from FIG. 6. Jointly, these features result in that the water supplied to the strainer by the rotation-generating means 18 is caused to rotate or circle such that, under the action of the centripetal force, it will be pressed outwards against the strainer wall 10 rather than move in an axial, vertical flow. In this manner, the wash water will be pressed out through the holes in the strainer wall with much greater force than in conventional strainers. Furthermore, it may be mentioned that the collar 21 is maintained in concentric position with respect to the collar 16 by means of a suitable number of radially projecting flanges 22, as shown in FIG. 5. Reference is now made to FIGS. 8 and 9 which, in combination with FIGS. 1 and 2, illustrate how a number of secondary strainers 24 are connected, by a third conduit 23, to the first conduit 4 connected to the suction pump. In the embodiment illustrated, five secondary strainers 24 are connected to each suction pump and the associated back-flushable strainer. Each secondary strainer consists of an elongate, apertured tube which is substantially vertically mounted and which has a diameter or maximum cross-sectional dimension in the range of 200-400 mm, suitably 250-350 mm, and a length which is at least five times, suitably at least ten times, larger than the diameter. In the embodiment shown in FIGS. 8 and 9, the strainer tubes 24 have a diameter of about 300 mm and a length of about 4 m. However, the length of the strainer tubes may vary within fairly wide limits, e.g. in the range of 2-6 m. As in the strainer 3, the holes in each strainer tube may have a diameter in the range of 2-4 mm, in which case the total hole area should be in the range of 25%-40%. The strainer tubes may either be continuous throughout their entire length or be composed of shorter tubular sections. In a preferred embodiment, the secondary strainers 24 are mounted on one of the columns 2 forming part of the loadbearing structure of the containment. In this way, the mounting of the strainers 24 does not involve any engagement whatsoever with the lining of the wall 1 and thus does not cause any sealing problems with respect to the lining. As appears most clearly from FIG. 8, the strainers are mounted with the aid of a number of clamp sets which are vertically spaced apart along the upright or column 2 and which each comprise a main clamp 25 consisting of two first part-circular hoop elements 25', 25" enclosing the column 2 and interconnected by bolted joints 26, 26' or the like. The hoop element 25' is provided with four radially projecting support means 27 which at a free end each support one of two second part-circular hoop elements 28', 28" which jointly enclose each strainer 24 and are interconnected by bolted joints 29, 29'. In analogous manner, the hoop element 25" is provided with a radially projecting support means 27 and an associated additional clamp set 28 which supports one of the strainers 24 (five in all). Thus, the clamp means 25, 28 enable simple and expedient mounting of the individual elongate strainers, each easily introduced down into the containment also through extremely narrow passages. At the lower ends, the strainers 24 are each connected to an arcuate tubular portion 23' by flanged joints. The tubular portion 23' constitutes one end of the conduit 23, whose opposite end is connected to the first conduit 4 passing from the back-flushable strainer 3. To be more precise, the two conduits 4 and 23 are interconnected at a point 30 (see FIG. 2) located between the back-flushable strainer 3 and the suction pump disposed on the outside of the containment. Function and Advantages of the Invention This invention is based on the insight that the pressure drop across the strainers is a function of the coverage degree as well as the surface load (flow). Tests have shown that the pressure drop is roughly proportional to the thickness of the fibre mat or cake and to the speed squared. Thus, a doubled strainer area permits a fibre mat four times as thick for a given pressure drop, which means that eight times the amount of fibres can be retrieved (unless the thickness becomes so considerable as to prevent collection). In the inventive device described above, the back-flushable strainer 3 has about the same area as conventional strainers, whereas the additional, secondary strainers 24 have a total area which is about 10-20 times larger. As a result, the inventive device is capable of handling about 500-1000 times larger amounts of fibres at a given pressure drop, while at the same time involving a considerable improvement of the cleaning effect of the strainers. The provision of the secondary strainers 24 by the side of each back-flushable strainer 3 ensures that also large amounts of fibres can be intercepted without there being any need of back-flushing soon after a reactor trip. The advantages of the invention are obvious. Owing to their elongate and slender shape, the strainers 24 can be introduced through extremely narrow passages, while at the same time being easily mounted inside the containment without any need of complicated equipment or without the leak-proof lining on the inside of the containment being any way affected. The combination of the elongate, slender shape and the vertical arrangement of the strainers further ensures that these are not acted upon by excessive mechanical forces when the water in the condensation pool is heaving. Moreover, the back-flushable strainer designed in accordance with FIGS. 3-7, ensures a considerably improved effect in back-flushing, since the wings 17 facilitate the release of the fibres from the outside of the strainer wall as well as the rotation-generating means 18 improving the flushing effect. Conceivable Modifications of the Invention It goes without saying that the invention is not restricted to the embodiment described above and shown in the drawings. Thus, the collecting conduit 23 from the additional strainers 24 may be connected directly to the back-flushable strainer 3 (whether a conventional strainer or the preferred inventive strainer illustrated in FIGS. 3-7), the conduit 4 to the suction pump being connected to an opposite end of the back-flushable strainer (the latter being thus open at both ends). Furthermore, the strainer 24 can be modified in various ways. For instance, a folded fine strainer, e.g. consisting of straining cloth, may be provided in each perforated strainer. If so, the external, cylindrical and perforated strainer wall serves as a prestrainer for the internal straining cloth or fine strainer, which is then protected by the external perforated strainer wall or tube, which of course is much stronger. Also the back-flushable strainer shown in FIGS. 3-7 can be modified in various ways. For instance, means other than radially projecting wings or metal sheets can be used for dividing the external fibre mat into several separate sections. Thus, the strainer wall need not be perforated in axial separate zones of suitable width.
	summary
045286850	abstract	A device for linearly oscillating one or more of a plurality of X-ray filter elements singly or in combination in and out of an X-ray beam at television frame rates. First and second substantially coplanar filter elements are adjacent each other and formed as a unitary member that is transverse to the X-ray beam. It is slidable bidirectionally on parallel guide tracks in one plane. A servo motor drives a closed loop belt which attaches to said member. A third planar filter element runs on tracks in a plane parallel to that of the unitary member. There are lug means on the third element spaced apart in the direction of its travel member that project up and are between the lug means on the third element to enable pushing or pulling it. Thus, the first and second filter elements can be oscillated alternately in and out of the X-ray beam by moving said unitary member without engaging the third element so it stays out of the beam. The member can be driven to one travel limit to pull the third element into the beam and let it stay there while the first element is oscillated beneath it so the beam passes through two filters. And the member can be driven to one travel limit and not be oscillated so the third filter element stays in the beam.
	abstract	Quadrupole-octupole aberration corrector for application in a TEM, STEM or SEM. A known corrector for correcting third-order and fifth-order aberrations of the objective is embodied with eight quadrupoles and three octupoles. The corrector according to the invention has at least the same aberration-correcting power, but, according to the invention, is embodied with six quadrupoles and three octupoles. By adding octupoles with a relatively weak excitation to a portion of the quadrupoles, correction of the anisotropic coma of the objective lens is also attained. By embodying all quadrupoles, or a portion thereof, to be electromagnetic, chromatic aberrations can also be corrected for.
046876316	abstract	A reusable fastener device includes an attachment nut and a retainer housing mounted to the adapter plate of the fuel assembly top nozzle and removable with the top nozzle upon reconstitution of the fuel assembly. The attachment nut has a central tubular stem and upper and lower flanges connected to and extending radially outwardly from opposite ends of the stem. The stem is internally threaded for mating with the threaded upper end plug extension of the strucutural member. The upper flange of the nut has a conical-shaped lower surface and a periphery adapted for engagement in order to rotate the nut for threading onto and unthreading from the structural member extension between fastened and unfastened positions. The lower flange of the nut is in the form of a plurality of radial segments extending outwardly from the stem and angularly spaced from one another so as to define a plurality of cutouts therebetween which alternate with the segments. The retainer housing has a tubular hollow body and a plurality of upper sectors and lower tabs connected to and extending respectively radially inwardly and outwardly from opposite ends of the tubular body. The upper sectors are angularly spaced from one another so as to define a plurality of openings sized to receive the radial segments of the nut therethrough. Also, the upper sectors extend radially inwardly from the tubular body so as to define a central opening sized to receive the central stem of the nut and to define an interrupted conical-shaped upper surface surrounding the central opening which matches the conical-shaped lower surface on the upper flange of the nut. The lower tabs rest upon and are rigidly connected to the top nozzle adapter plate so as to align the central opening of the retainer housing with the hole through the adapter plate and dispose the upper sectors in a location spaced from the adapter plate at which their interrupted conical-shaped upper surface will be contacted by the conical-shaped lower surface of the upper flange of the nut when the central stem thereof is threaded onto the upper end extension of the structural member to the fastened position. The upper sectors are yieldably deflectible upon being contacted by the upper flange of the nut such that inner edges of the upper sectors engage the central stem of the nut so as to rotationally lock the lower flange of the nut to the adapter plate when the nut is rotated to its fastened position. Finally, the retainer housing also includes auxiliary tabs attached to the upper sectors and being bendable between open and closed positions for respectively allowing and preventing passage of the lower segments of the nut through the openings defined between the upper sectors of the retainer housing.
	description	This application is a continuation of U.S. application Ser. No. 10/706,707 filed Nov. 12, 2003, now U.S. Pat. No. 7,107,187, entitled METHOD FOR MODELING SYSTEM PERFORMANCE. None The present invention relates to the modeling of systems comprising computer software operating on computer hardware. More particularly, the present invention relates to real-time collection of system metrics and the systems and methods for the modeling of system performance parameters as non-linear functions for use in predicting system performance, identifying circumstances at which system performance will become unacceptable, and issuing alarms when system performance is near or beyond unacceptable conditions. Computing systems have become an integral part of business, government, and most other aspects of modern life. Most people are likely regrettably familiar with poor performing computer systems. A poor performing computer system may be simply poorly designed and, therefore, fundamentality incapable of performing well. Even well-designed systems will perform poorly, however, if adequate resources to meet the demands placed upon the system are not available. Properly matching the resources available to a system with the demand placed upon the system requires both accurate capacity planning and adequate system testing to predict the resources that will be necessary for the system to function properly at the loads expected for the system. Predicting the load that will be placed upon a system may involve a number of issues, and this prediction may be performed in a variety of ways. For example, future load on a system may be predicted using data describing the historical change in the demand for the system. Such data may be collected by monitoring a system or its predecessor, although such historical data may not always be available, particularly for an entirely new system. Other methods, such as incorporating planned marketing efforts or other future events known to be likely to occur, may also be used. The way in which system load is predicted is immaterial to the present invention. Regardless how a prediction of future system load is made, a system must have adequate resources to meet that demand if the system is to perform properly. Determining what amount of resources are required to meet a given system demand may also be a complex problem. Those skilled in the art will realize that system testing may be performed, often before a system is deployed, to determine how the system will perform under a variety of loads. System testing may allow system managers to identify the load at which system performance becomes unacceptable, which may coincide with a load at which system performance becomes highly nonlinear. One skilled in the art will also appreciate that such testing can be an enormously complex and expensive proposition, and will further realize that such testing often does not provide accurate information as to at what load a system's performance will deteriorate. One reason for the expense and difficulty of testing is the large number of tests necessary to obtain a reasonably accurate model of system performance. One skilled in the art will likely be familiar with the modeling of a system's performance as a linear function of load. One skilled in the art will further realize, however, that a linear model of system performance as a function of load is often a sufficiently accurate depiction of system performance within only a certain range of loads, with the range of loads within which system performance is substantially linear varying for different systems. System performance often becomes non-linear at some point as the load on the system increases. The point at which system performance becomes nonlinear may be referred to as the point at which the linear model breaks down. The load at which a system's performance begins to degrade in a non-linear fashion may be referred to as the knee. At the knee, system throughput increases more slowly while response time increases more quickly. At this point system performance suffers severely, but identifying the knee in testing can be difficult. Accordingly, while a basic linear model theoretically can be obtained with as little as two data points, additional data points are necessary to determine when a linear model of system performance will break down. Obtaining sufficient data points to determine when a linear model of system performance breaks down often requires extensive testing. At the same time, such testing may not yield an accurate model of system performance, particularly as the system moves beyond a load range in which its performance is substantially linear. The collection of system metrics in a production environment may be used to monitor system performance. System metrics collected in a production environment may also be used to model system performance. However, linear modeling of system performance using system metrics collected in a production environment will not be likely to yield a better prediction of the system's knee unless the system operates at or beyond that point. Of course, one skilled in the art will appreciate that the purpose of system testing and system modeling is to avoid system operation at and beyond the knee, meaning that if such data is available the modeling and monitoring has already substantially failed. A further challenge to using system metrics collected in a production environment is the burden of collecting the metrics. Simply put, collecting system metrics consumes resources. The system to be monitored, and/or associated systems operating with it, must measure, record, and process metrics. Particularly when a system is already facing a shortage of resources, the increased cost of monitoring the system's metrics must occur in an efficient fashion and provide significant benefit to be justified. The present invention provides systems and methods to collect metrics from a system operating in a production environment. The collected metrics may be used as a plurality of data points to model system performance by fitting a non-linear curve to the data points. The use of a non-linear curve may better identify the load at which a system's operation will become unacceptable. Systems and methods in accordance with the present invention may also identify correlations between measured system metrics, which may be used to develop further models of system performance. The present invention may also be utilized to identify a point of interest in system performance for use in monitoring a system in a production environment so that an alarm may issue if system performance exceeds predetermined parameters around the point of interest. The present invention provides systems and methods for monitoring system performance, identifying correlations between system metrics, modeling system performance, identifying acceptable operating parameters, and issuing alarms if acceptable operating parameters are exceeded, wherein a system comprises computer software operating on computer hardware. The present invention may be used in conjunction with a system comprising any computer software operating on any computer hardware. One example of such a system is an order processing system that receives orders input into a user interface, processes that information, and then provides pertinent information to persons or systems responsible for filling the orders. However, any system comprising software operating on hardware may be monitored and/or modeled using systems and methods in accordance with the present invention. In systems and methods in accordance with the present invention, system metrics may be measured and used to model system performance. For example, data points for system throughput may be obtained at a plurality of loads, and system performance may then be modeled by fitting a non-linear curve to the data points to obtain a non-linear model of system throughput as a function of load. One skilled in the art will appreciate that the data points used in accordance with the present invention to model system performance may be obtained in a variety of ways. By way of example, data points may be obtained through system testing or through monitoring system performance while the system is in use. A system that is in use may be described as being in a production environment. One skilled in the art will appreciate that numerous methods, procedures, techniques, and protocols exist or may be developed for system testing, and that any of these may be used in system testing to obtain data points for use in accordance with the present invention. Likewise, one skilled in the art will appreciate that a variety of methods, procedures, techniques, and protocols exist or may be developed for system monitoring in addition to those described herein, and that any of these may be used to monitor a system operating in its production environment to obtain data points for use in accordance with the system modeling aspects of the present invention. In the examples described herein for FIG. 1 through FIG. 6B, the system performance parameters measured and modeled are response time and throughput as a function of load. One skilled in the art will appreciate that other network performance parameters may also be modeled using methods in accordance with the present invention. Response time may be measured as the time required for a system request to be processed, throughput may be measured as the number of system requests processed in a given period of time, and load may be defined as the total number of system users, although one skilled in the art will realize that these parameters may be defined in a number of other ways. FIG. 1 illustrates a graph depicting system performance data points at a variety of loads. FIG. 1 illustrates system response time and system throughput as a function of load on a single graph. As can be seen in FIG. 1, twelve data points were collected through testing for both response time and throughput. Solid lines connect collected data points, although no attempt has been made to fit a curve, either linear or nonlinear, to the data points in FIG. 1. In FIG. 1, response time is illustrated on the left vertical axis in units of seconds, throughput is illustrated on the right vertical axis in units of requests processed, and system load is illustrated on the horizontal axis in units of total users. As illustrated in FIG. 1, twelve data points were required to illustrate where system performance became extremely non-linear. As can be seen in FIG. 1, this knee occurs at a load of 1,100 users. It should be realized that FIG. 1 illustrates only a comparatively small set of data points. In actual practice, considerably more data points, and correspondingly more testing, may be required to satisfactorily forecast system performance and to identify the load at which system performance becomes non-linear and the load at which system performance will become unacceptable. Referring now to FIG. 2, non-linear curves are illustrated that have been fit to data points for response time and throughput as a function of load. The system modeled in FIG. 2 is the same as the system for which system performance is illustrated in FIG. 1. As can be seen in FIG. 2, only five response time data points and five throughput data points were used to model the non-linear curves. In FIG. 2, response time was modeled by fitting an exponential curve to the response time data points, while the throughput behavior was modeled by fitting a logarithmic curve to the throughput data points. As illustrated in FIG. 2, throughput was modeled as y=180013Ln(x)+348238 and response time was modeled as y=0.6772e0.1783x, where x denotes system load. The numerical values in these equations may be determined using curve fitting techniques well known in the art that regressively fit a curve to data points by adjusting the constants of the equation until an optimal fit to the available data points is obtained. As illustrated in FIG. 2, the R2 value, which is a measure of the quality of the fit of the curve to the data points, is reasonably high for each curve, being R2=0.888 for response time and R2=0.8757 for throughput. One skilled in the art will appreciate that any method for fitting a curve to collected data points may be used in this process. One skilled in the art will further realize that non-linear curves other than exponential and logarithmic curves may be used if the performance parameter being modeled performs in a manner that lends itself to a different mathematical model. A range in which the distance between the throughput and response time curves is maximized is illustrated by shading in FIG. 2. This range extends from a load of 800 users to a load of 1,050 users. As a load exceeds the optimal range, system performance may be compromised. The optimal range illustrated in FIG. 2 is obtained by identifying the load at which the distance between the response time and throughput curves is greatest. A range of loads may be defined around this identified optimal load in a variety of ways. For example, the optimal range may be defined as the range of loads at which the distance between the curves remains at a predetermined percentage of the maximum distance. Alternatively, the optimal range may be defined as a specific load range around the optimal load, however, such a definition may prove problematic in a rapidly changing system. In comparing FIG. 1 and FIG. 2, it should be noted that FIG. 2 utilizes less than half the data points utilized in FIG. 1. It should be further realized that while the non-linear curves modeled in FIG. 2 do not exactly match the lines connecting data points in FIG. 1, the optimal range identified using the curves in FIG. 2 identifies a maximum load very close to the load at which system response time and system throughput begins to behave in a highly non-linear fashion in FIG. 1. One skilled in the art will further realize that if considerably more data points were obtained in addition to those illustrated in FIG. 1, the resulting graph may likely even more closely resemble the models illustrated in FIG. 2. Referring now to FIG. 3 a model of system performance based upon seven data points is illustrated. The system whose performance was modeled in FIG. 2. The curves fit to the data points in FIG. 3 are, for system throughput, y=261828Ln(x)+297982, which provides an R2 value of R2=0.855, and for system response time, y=0.7234e0.1512x, with an R2 value of R2=0.9188. As in FIG. 2, the optimal range determined in FIG. 3 is illustrated using a shaded rectangle. The optimal range determined in the model illustrated in FIG. 3 is a load of 950 users to 1,150 users. It should be noted that the optimal range determined in FIG. 3 using additional data points to fit the curves resembles the optimal range obtained in FIG. 2. Referring now to FIG. 4 a model of system performance based upon ten data points is illustrated. The system modeled in FIG. 4 is the same system that was modeled in FIG. 2 and FIG. 3 is illustrated as modeled using ten data points. In modeling system throughput using a curve fit to the data points, the curve fit to the system throughput data points in FIG. 4 is y=389262Ln(x)+194342, which has a R2 value of R2=0.837. In fitting an exponential curve to the system response data points, the equation fit to the data points in FIG. 4 is y=0.6732e0.1725x, with R2 value of R2=0.9652. The optimal range determined using the model illustrated in FIG. 4 is illustrated with a shaded rectangle. The optimal range determined based upon the model illustrated in FIG. 4 is from a load of 900 users to a load of 1,050 users. Once again, it should be noted that the optimal range determined in FIG. 4 corresponds well with the optimal range in FIG. 1, FIG. 2 and FIG. 3. One skilled in the art will appreciate that a relationship between units of response time and units of throughput were defined to enable response time and throughput to be illustrated on a single graph in FIGS. 1-4, as well as to allow a distance between the curves to be defined. One skilled in the art will appreciate that the precise relationship between throughput and response time vary depending upon the system in question and the units used to measure throughput and response time, or whatever other network operation parameters are measured and modeled. Graphs such as the graph illustrated in FIG. 2 may be particularly useful in accordance with the present invention to visually represent a model of system behavior to a user. The relationship between response time and throughput may also be defined mathematically, for example based upon the distance between the two curves. In this case, the distance may be defined as the value of the throughput curve at a given load minus the value of the response time curve at the same load. The load at which this distance is maximized may be thought of as the optimal system load. It should be noted, however, that an optimal system load may be defined in a variety of ways, some of which are described below in connection with examples of methods in accordance with the present invention. A range around such an optimal system load may be identified as the optimal operating range for a system. This range may be determined, for example, as the range of loads over which the distance between the curves is a given portion, such as ninety percent, of the maximum distance. A system may be monitored and, if its load or the other measured system operating parameters exceed the optimal range, an alarm may be issued so that system operators may take appropriate steps to bring additional resources to the system or to otherwise improve system performance before system performance. Alternatively, the methods in accordance herein may be used to identify a load at which a particular parameter, such as system response time, will cease to be acceptable, and then issue an alarm when that load is reached. Likewise, in some systems other parameters, such as throughput or response time, rather than load, may be monitored with alarms being issued whenever certain threshold values are reached. Referring now to FIG. 5, a method 500 for modeling system performance is illustrated. While method 500 illustrates a method in accordance with the present invention for modeling system response time and throughput, methods in accordance with the present invention may be used to model other network parameters. In step 512 the system's throughput may be tested using a plurality of loads to obtain a plurality of throughput data points. Any testing procedure may be used in step 512. The throughput data points obtained in step 512 are utilized in step 516 to model the system's throughput as a function of load by fitting a non-linear curve to the plurality of throughput data points. It should be appreciated that the type of non-linear curve fit to the throughput data points may vary, but may appropriately comprise a logarithmic curve. It should further be appreciated that a variety of methods may be used to fit a non-linear curve to the throughput data points. Furthermore, the number of throughput data points used to fit a curve may vary. For example, a very small number of data points, such as three, may be used in fitting a non-linear curve. Alternatively, a larger number, such as ten as illustrated in FIG. 4, or more may be used to fit a non-linear curve. One skilled in the art will realize that as the number of throughput data points increases the resulting curve will likely better model actual system performance and that a compromise between accuracy of modeling and expense of testing must sometimes be reached. However, methods in accordance with the present invention permit a more favorable compromise to be reached, in that an acceptably accurate model may be achieved using relatively few data points. In step 514 the system's response time may be tested using a plurality of loads to obtain a plurality of response time data points. Any testing procedure may be used in step 514. Step 514 may be performed in conjunction with step 512, although these steps may also be performed separately. The response time data points obtained in step 514 are utilized in step 518 to model the system's response time as a function of load by fitting a non-linear curve to the plurality of response time data points. It should be appreciated that the type of non-linear curve fit to the response time data points may vary, but may appropriately comprise an exponential curve. It should be further appreciated that a variety of methods may be used to fit a non-linear curve to the response time data points. Alternatively, a larger number of data points, such as five, or seven as illustrated in FIG. 2, or more may also be used to fit a non-linear curve. One skilled in the art will realize that as the number of response time data points increases the resulting curve will likely better model actual system performance and that a compromise between accuracy of modeling and expense of testing must sometimes be reached. However, methods in accordance with the present invention permit a more favorable compromise to be reached, in that an acceptably accurate model may be achieved using relatively few data points. In step 520 a maximum acceptable response time may be defined. For example, users of the system may determine that a response time greater than a given predetermined amount, such as five seconds, is unacceptable. Thus, in this example, the maximum acceptable response time would be five seconds. Using the non-linear curve modeling the system's response time as a function of load, step 522 may determine the maximum system load as the load at which the maximum acceptable response time is reached. Step 524 may then determine the maximum system throughput using the model of the system's throughput to determine the throughput for the system at the maximum load. Step 520, step 322, and step 524 allow a system's operator to obtain information regarding the maximum capabilities of the system in operation. However, one or more of step 520, step 522, and step 524 may be omitted from methods in accordance with the present invention. In step 530 a linear relationship may be defined between response time and throughput. This definition in step 530 may be used in step 532 of displaying a graph of the throughput model curve and the response time model curve in a single graph. If step 530 is omitted, step 532, if performed may display multiple graphs. Step 530 may further permit step 534 of calculating the distance between the throughput model curve and the response time model curve. This distance may be monitored in system operation and an alarm may be issued if the distance falls below a threshold amount. The distance calculated in step 534 may be used in step 536 to determine the optimal load for the system. For example, the optimal load may be the load at which the distance between the curves is maximized. Optimal load may be defined in other ways, as well, such as the load at which a desired throughput or response time is attained or the load of which system utilization is reached. An optimal range may be defined around the optimal load for use in monitoring system performance and issuing an alarm should system performance exceed the optimal range. Referring now to FIG. 6, an alternative method 600 in accordance with the present invention is illustrated. While method 600 illustrates a method in accordance with the present invention for modeling system response time and throughput, methods in accordance with the present invention may be used to model other network parameters. Method 600 may be particularly suitable for modeling the performance of a system already functioning in a production environment. In step 612 the system's throughput is measured at predetermined times to obtain throughput data points at the loads existing at the measurement times. The predetermined times at which measurements are taken according to step 612 may appropriately vary from system to system. For example, measurements could be made on a daily, hourly, weekly, or other basis. Measurements could also be made after a predetermined number of system processes. In step 613 the throughput data points may be stored. Step 613 may store the throughput data points to a hard drive, in computer memory, or in any other fashion. In step 616 the throughput data points may be used to model the system's throughput as a function of load by fitting a non-linear curve to the stored system throughput data points. It should be noted that a variety of non-linear curves may be used, such as a logarithmic curve. One skilled in the art will realize that a variety of curve-fitting methodologies may be used. It should be further noted that step 616 may be performed at a variety of times. For example, step 616 may be performed at predetermined times, such as on a daily or weekly basis. Alternatively, step 616 may be performed every time a predetermined number of new throughput data points have been stored in step 613. For example, step 616 may be performed one, ten, on hundred, or some other number of new data points have been stored in step 613. Whatever timing is used to perform step 616, it may be expected that as additional throughput data points are added the curve modeled in step 616 will increasingly and accurately reflect system throughput as a function of load. Step 616 may use every stored throughput data point, or it may use a subset of stored throughput data points, such as the data points for the last week of operation. In step 614 the system's response time is measured at predetermined times to obtain response time at the loads existing at the measurement times. As with step 612, step 614 may be performed at a variety of times, such as on a daily, hourly, weekly, or other basis as appropriate for the system in question. In step 615 the response time data points may be stored. Step 615 may store the response time data points to a hard drive, in computer memory, or in any other fashion. In step 618 the response time data points may be used to model the system's response time as a function of load by fitting a non-linear curve to the stored system response data points. It should be noted that a variety of non-linear curves may be used, such as an exponential curve. One skilled in the art will realize that a variety of curve fitting methodologies may be used. It should be further noted that step 618 may be performed at a variety of times. For example, step 618 may be performed at predetermined times, such as on a daily or weekly basis. Alternatively, step 618 may be performed every time a predetermined number of new response time data points have been stored in step 615. Fore example, step 618 may be performed when one, ten, one hundred, or some other number of new data points have been stored in step 615. Whatever timing is used to perform step 616, it may be expected that as additional response time data points are added the curve modeled in step 618 will increasingly and accurately reflect system response time as a function of load. Step 618 may use every stored response time data point, or it may use a subset of stored response time data points, such as the data points for the last week of operation. In step 620 a maximum acceptable response time may be defined. The maximum acceptable response time may be a predetermined amount of time within which a response must be made by the system for system performance to be deemed acceptable. For example, a maximum acceptable response time of five seconds may be used. If system response time is being monitored step 621 may issue an alarm if the maximum acceptable response time is reached or exceeded. Such an alarm may indicate that the system requires additional resources or adjustments to function properly. Alternatively, step 621 may issue an alarm when response time reaches a predetermined percentage of the maximum acceptable response time, such as, for example, eighty percent. Based upon the maximum acceptable response time defined in step 620 and the model of the system's response time as a function of load created in step 618, step 622 may determine the maximum system load as the load at which the maximum acceptable response time is reached. In step 623 an alarm may be issued if the maximum system load is reached. Alternatively, step 623 may issue an alarm if a predetermined percentage of the maximum system load is reached, such as, for example, eighty percent. In step 624 the maximum system load determined in step 622 and the model of the system's throughput as a function load created in step 616 may be used to determine the maximum system throughput as the throughput at the maximum system load. In step 625 an alarm may be issued if the maximum acceptable response time is reached. Alternatively, step 625 may issue an alarm if a predetermined percentage of the maximum throughput is reached, for example eighty percent. In step 630 a relationship may be defined between response time and throughput. The relationship defined in step 630 may be a linear relationship. In step 632 a graph may be displayed of the throughput model curve and the response time model curve. Step 632 may display both curves in a single graph through a graphical user interface. If step 630 is omitted, step 432 may display the curves in multiple graphs. The relationship between throughput and response time defined in step 630 may also be used to calculate a distance between the throughput model curve and the response time model curve in step 634. Using distance as calculated in step 634, step 636 may determine an optimal load as the load at which the distance between the curves is maximized. Optimal load may be defined in other ways, as well, such as the load at which a desired throughput or response time is attained or the load at which a given system utilization is reached. Step 640 may define an optimal load range around the optimal load. In step 641 an alarm may be issued if the optimal load range defined in step 640 is exceeded. Of course, methods in accordance with the present invention, such as method 500 and method 600, may be used to model network parameters other than system throughput and system response time. Methods in accordance with the present invention may be used to measure a first network parameter, model the first network parameter as a non-linear curve, measure a second network parameter, and model the second network parameter as a non-linear curve. Measuring the first network parameter and the second network parameter may comprise testing the system, measuring the network parameters during system operation, or a combination thereof. A relationship may be defined between the first network parameter and the second network parameter. Such a relationship may allow a distance to be determined between the curve modeling the first network parameter and the curve modeling the second network parameter. Such a relationship may also allow the display of the curve modeling the first network parameter and the curve modeling the second network parameter on a single graph. It should be appreciated that example method 300 and example method 400 are exemplary methods in accordance with the present invention, and that many steps discussed therein may be omitted, while additional steps may be added. The methods in accordance with the present invention are not limited to any particular way of obtaining data points, whether through testing or monitoring a system in a production environment, nor are they limited to any particular method for fitting a non-linear curve to the data points obtained. Referring now to FIG. 7, a plurality of systems are illustrated showing them connected together in a network 700. System 710 can be a computer, server, order processor, or any other device contained within the network. The present invention, depicted in FIG. 7, shows a number of systems connected together in the network. The present invention applies to any network size. As depicted by servers 720, 730, and 740, the network size can vary depending on the desired need. One skilled in the art can appreciate the magnitude of having a plurality of systems in a network spread across a large distance and needing the manpower and labor to monitor those systems or to service those systems on a continual basis. Within the network, alarms and metrics can be triggered and logged so that proper performance of the system can be maintained or proper performance of a particular application can be maintained. A plurality of devices such as monitors 750, servers 760, telephones 770, audible devices 780 or any other personal notification mechanism 790 can receive notifications of any alarming condition to allow one to correct the alarming condition. Such notification can be used to make improvements to the applications, systems, or network. An alarming condition can be triggered by exceeding the response time, exceeding the maximum throughput, or exceeding the maximum load on the system. Although the systems can come from different vendors, this invention allows for those systems to be integrated together in a network for the opportunity of collecting metrics. The metrics are collected on the systems and are kept on the systems until such time processes transport those metrics to a database 795. Once in the database 795, the metrics are used to model the system's performance as depicted in FIGS. 1, 2, 3, and 4. Referring now to FIG. 8, several processes are illustrated to show the components involved in collecting metrics. FIG. 8 depicts processes that allow for alarms and metrics to be triggered and logged so that proper performance of the system can be maintained or the proper performance of an application can be maintained. FIG. 8 illustrates how data points (also referred to as metrics) are captured to enable the creation of the graphs depicted in FIGS. 1, 2, 3 and 4. The inventor developed computer software programs to operate on a plurality of systems. FIG. 8 shows only one system 810 as a representation of the plurality of systems containing at least one of the same processes. The first step in the invention is to build a logadaptor process 820. The logadaptor process 820 creates a set of files to reside on the plurality of systems. These files are used to collect metrics and hold threshold data. The logadaptor process 820 may be built through a set of initialization steps and may run on the system 710. Subsequently, it is replicated onto the rest of the systems throughout the network where it runs independently on those systems. Essentially, one can have one logadapter process 820 running on each system 710 in the network. The logadaptor process 820 can run on all of the systems or can run on a select number of systems. The logadaptor process 820 can be replicated onto other systems via such devices such as a chron process or a daemon process. The logadaptor process 820 takes inputs 830 from a user to set up the initial conditions for the types of applications or systems to be monitored and the types of metrics to be collected. As the logadaptor process 820 begins to run on the plurality of systems, it will automatically generate configuration files 840 pertaining to threshold data and alarm data to run on a particular system. The logadaptor process 820 may perform this function in two ways: It can monitor applications on the system on which it is running, or it can monitor applications on remote systems. Once the configuration files 840 are generated automatically, the configuration files 840 initiate the function for collecting metrics data. The logadapter process 820 stores the metric data in files 850 which subsequently get transferred to a database 880 (same as 795). Referring to FIG. 10, a method in accordance with the present invention for collecting and alarming metrics in either a testing or production environment is illustrated. To start the method, a user or system may provide initial inputs 1010 to establish the initialization sequences needed for the software. With the initial inputs 1010, the software program builds a logadapter process 1015 running on the system 710. The logadapter process 820 gets distributed to at least one of the systems 820. As a software program, the logadapter process 820 runs on the system 710 but is susceptible to external faults that may prevent it from running successfully. The method of the primary invention monitors the logadapter process running on systems 1025 and checks to determine if the logadapter process is running 1030. If the logadapter process 820 is not running, it is restarted 1035. If the logadapter process 820 is running then the method generates configuration files for metric data 1040. The method of the primary invention defines the metrics to be collected 1045 based on the received initial inputs 1010 and the configuration files 840. With this information a set of thresholds for data collection 1050 and thresholds for triggering alarms 1055 are enabled. Upon the happening of an event, metric data may simultaneously trigger an alarm and get collected. A plurality of alarms as depicted in 1090, 1091, 1092, and 1093 can occur. The software program executes in a manner for the method to continue executing in a loop. The method takes all of the previously mentioned information and monitors applications running on the systems 1060. It collects metrics on the applications 1065 and places the data in files 1070. The method checks the logadapter process 1075 to determine if it is running and the procedure starts again on a continuous basis. It should be further realized that a variety of actions may be taken if an alarm is issued in accordance with the present invention for a system in a production environment. Additional computing resources may be added, such as additional servers or additional system memory, the software of the system may be improved and modified to enhance efficiency, or some combination of the two may be taken. Alternatively, steps may be taken to reduce load on the system to facilitate better system performance. The steps taken by a system operator due to information obtained in practicing methods in accordance with the present invention are immaterial. Referring now to FIG. 7, a method 700 for monitoring and modeling system performance in a production environment is illustrated. System metrics are defined in step 705. Any measurable system metric may be defined in step 705, and one skilled in the art will appreciate that different system metrics may be appropriate for different systems. Defining step 705 may be performed automatically using, for example, system monitoring software, or may be performed by one or more personnel entering metric definitions to be received by system monitoring software. In step 710 system metrics are measured and recorded. Step 710 may be performed in a variety of ways. For example, a system to be monitored may periodically measure and record metrics associated with that system and maintain it on storage media associated with that system for later collection and/or analysis. One skilled in the art will be familiar with the use of monitoring software that operates on a functioning system to periodically record system metrics. Step 710 may also be performed external to the system to be monitored. In step 715 system metrics are collected. Collecting step 715 and step 710 may be combined, particularly if recording step 710 occurs external to the system to be monitored. If step 710 occurs on the storage media of the system to be monitored, collecting step 715 may occur less frequently than recording step 710. For example, recording step 710 may occur hourly, while collection step 715 may occur once daily. Collection step 715 may serve to transport metric data to an external system for analysis and modeling. One skilled in the art will appreciate that collection step 715 may be advantageously scheduled to occur during times, such as overnight, when system and bandwidth resources are not in high demand. Collected metric data may be stored in a database for subsequent processing at a central processing hub. A central processing hub may be any computing device, such as a server, that receives measured system metrics and performs an analysis upon those metrics. The system metric data may be analyzed to identify correlations between the system metrics in identification step 720. Step 720 may be performed at a central processing hub. Identification step 720 may be particularly advantageous when a large number of metrics are measured, not all of which have known correlations between them. In identification step 720 various metrics data may be analyzed over a given period of time to determine whether a mathematical relationship exists between a pair of metrics, such as system load and processor utilization. The identification of correlations between system metrics may then be used to provide more accurate models of system performance. Step 720 may identify pairs of metrics having an identified correlation between them. For example, a primary pair of system metrics may comprise a first system metric and a second metric having a correlation between them. By way of further example, a secondary pair of system metrics may comprise a third system metric and a fourth system metric. There may be metrics common between, for example, a primary pair of system metrics and a secondary pair of system metrics, such that the primary pair of system metrics comprises a first system metric and a second system metric and the secondary pair of system metrics comprises a third system metric and the second system metric. Also, a correlation may be identified, for example, between the first system metric and the third system metric in this example. One skilled in the art will appreciate that any number of pairs of any number of system metrics having correlation between them and that the designation of a pair as primary, secondary, tertiary, etc. and that the designation of a metric as first, second, third etc. are immaterial to the present invention. Step 720 may alternatively identify system metrics having a correlation with a predetermined system metric. In many uses, a system metric such as system load may be the predetermined system metric with which other system metrics are analyzed for correlations, although system metrics are analyzed for correlations, although any system metric maybe used for this purpose. In step 725 system performance is modeled as a non-linear relationship between system metrics. The model constructed in modeling step 725 may utilize correlations identified in identification step 720 or may use predetermined metrics identified by a system administrator or others through prior experience. In step 730 unacceptable system operation ranges may be identified. For example, a model constructed in modeling step 725 may indicate that a certain monitored system metric, such as system response time, may reach an unacceptable range when another system metric, such as system load, reaches a given point. Step 730 may identify a variety of unacceptable system operation ranges for each pair of metrics modeled, and may further identify unacceptable operation ranges for more than one pair of metrics. For example, varying degrees of unacceptable system response time may be identified. The degree to which each identified range is unacceptable may increase, from a moderately unacceptable level that requires prompt attention to correct to a fully unacceptable response time which requires immediate corrective action. In step 735 an optimal system operation range may be identified using the model constructed in modeling step 725. Methods such as those described above that maximize the distance between curved modeling to different metrics to as a function of load may be used to identify an optimal system operation range in step 735. Alarm thresholds may be defined in step 740. The alarm thresholds defined in step 740 may be based upon one or more unacceptable system operation ranges identified in step 730 and/or an optimal system operation range identified in step 735. The alarms defined in step 740 may constitute varying degrees and may be based upon different metrics. For example, an alarm may be defined to trigger if system metrics leave the optimal system operation range defined in step 735. Such an alarm may be of a low level, given that the performance of the monitored system may be non-optimal but may remain entirely acceptable to users. A higher level of alarm may then issue if one or more system metric enters into an unacceptable system operation range. If varying degrees of unacceptable system operation ranges were identified in step 730, correspondingly differing alarms may be defined in step 740. In step 745 alarms may be issued if alarm thresholds are met. Step 745 may operate based upon the alarm thresholds defined in step 740 and the system metrics collected in step 715. Alternatively, a system may periodically receive alarm thresholds defined in step 740 and may issue an alarm if the systems recorded metrics recorded in step 710 meet or exceed an alarm threshold. Referring now to FIG. 8, an environment in which systems and methods in accordance with the present invention for monitoring and modeling system operation in a production environment is illustrated. A server 810 or other appropriate computing equipment may operate software implementing methods in accordance with the present invention. Any number of systems may be monitored and modeled in accordance with the present invention, including computer software operating on a first server 820, computer software operating on a second server 830 and computer software operating on a third server 840. Monitored systems in accordance with the present invention may be related, but need not be related. Monitored systems may include multiple systems that utilize a single server. Server 810 performing monitoring and modeling functions may connect to the servers for systems to be monitored and modeled through any networking means, such as through a local area network. Collected metrics from the monitored systems may be stored in databases 895. Databases 895 may comprise a single database or may comprise multiple databases. Databases 895 may be maintained upon server 810 or may be maintained external to server 810. Server 810 and the software implementing systems and methods in accordance with the present invention for monitoring and modeling systems may be accessed through client 815. Client 815 may be any device through which a system operator may access and/or manipulate the software in accordance with the present invention operating upon server 810 and/or the system metrics collected in accordance with the present invention. Client 815 may be a computer workstation, a desktop computer, a lap top personal computer, a PDA, mobile telephone, table personal computer, or any other computing device. Server 810 may also connect through any appropriate networking media to devices for use in issuing system performance alarms. For example, an alarm may be sent to a system administrator's computer 850 through e-mail, instant messaging, or other means. By way of further example, an alarm may be sent to a monitoring server 860 and placed in a queue for access by a system administrator. As a yet further example, an alarm may be transmitted to mobile phone 870 belonging to a system administrator by use of a recorded message, a short text message, or other means. As a further example, an audible alarm 880 may be used to audibly notify a system administrator or other personnel of the status of a monitored system. Referring now to FIG. 9, a system 900 for collecting system metrics is illustrated. While systems in accordance with the present invention, such as system 900, may operate with any commercially available system monitoring software, or may further operation with specially developed system monitoring software, the example of system 900 illustrated in FIG. 9 is particularly adapted for use with commercially available monitoring software sold under the trademark MeasureWare. One skilled in the art will appreciate the modifications that could be made to system 900 to allow operation with other monitoring software. System 900 includes component 910. Component 910 includes a log adaptor 912. Log adaptor 912 may operate on a server on other computing device and may execute process in accordance with software implementing the methods of the present invention. Log adapter 912 may relay upon manually created configuration files 915 in operation. Manually generated files 915 may include a DSI configuration file 916. The DSI configuration file 916 may comprise lines describing the type-delimited metrics to collect, the type-delimited metric format, the path to the log set, the value at which to trigger an alarm or a metric (which may be left blank to turn of alarming), the application name, the application designation, the open view OPC message group, to indicate whether DSI logging is on or off, and settings for specific files such as the maximum indexes per record per hour per summarization or per retention. Manually generated files 915 may further comprise an IDS configuration file 916 to set to initial type-delimited values, the first being the starting transaction ID number and the second being the starting metric ID number to use when generating new specification files. Manually generated files may further include the OBCA client configuration file 918. Automatically generated files 920 may also be part of system 910. Automatically generated files 920 may include a class configuration file 921 that contains one line per transaction with the short transaction name from the transaction configuration file 922. Transaction configuration file 922 may be a translation file to accommodate the 18-character limit in MeasureWare log file set names. Each line of the translation configuration file 922 may contain one line per transaction that has two values that are type-delimited. The first value may be a potentially shortened value of the full transaction name that is within the 18-character maximum followed by the full transaction name. The long name of a transaction may be the name actually used for a log file, with the short name being used in the class configuration file 921 for use by MeasureWare. The time threshold configuration file 923 may hold the average service time threshold violation values per transaction for levels of warnings such as minor, major, critical, or other levels desired by a user. An error threshold configuration file 924 may also be used, but may be omitted. A percent threshold configuration file 925 also may be optionally included. A previous alarm configuration file 926 may be included to maintain historical alarm information. Log adapter 912 may receive manually generated files 915 and may operate in the generation of automatically generated files 920. One skilled in the art will appreciate that methods in accordance with the present invention may be implemented using computer software. Such software may take the form of computer readable code embodied on one or more computer readable media. Software implementing the present invention may operate independently, but may also be incorporated with system testing software or system monitoring software. Any software language may be used to implement methods in accordance with the present invention.
	description	This invention was made with government support under Contract Number DE-AC07-05-ID14517 awarded by the United States Department of Energy. The government has certain rights in the invention. Embodiments of the disclosure relate generally to structures comprising fuel elements integral with heat pipes, to modular nuclear reactors, and methods of forming such modular nuclear reactors and structures. More particularly, embodiments of the disclosure relate to modular nuclear reactors including a plurality of the structures, modular nuclear reactors comprising a plurality of reactor sections, and related methods of forming the modular nuclear reactors with preassembled components. Power production in areas remote from conventional power sources is often desired. In addition, mobile power production is often desired during power outages, natural disasters, or in areas that are remote from conventional power and fuel sources. One option of mobile power production includes diesel-powered or gas-powered electricity generators. However, transportation of fuels for such generators may be unduly burdensome and costly when the generators are located at substantial distances from heavily traveled areas or at times immediately following a natural disaster when normal transportation routes are compromised. One alternative to such diesel-powered or gas-powered generators includes nuclear reactors. Mobile nuclear reactors may include a monolithic reactor core or may suffer from one or more design flaws. For example, some mobile nuclear reactors comprise a monolithic reactor core that serves as cladding for fuel elements and heat pipe evaporator sections of the reactor core. However, the monolithic reactor core requires a plurality of holes formed therein to house fuel elements of the reactor core. FIG. 1A is a simplified plan view of a portion of a reactor core 100 including a monolithic structure 102. The monolithic structure 102 may be defined by a webbed structure defining a plurality of holes therein for housing fuel elements 104 and heat, pipes 106. The monolithic structure 102 may have a length greater than about 100 cm (such as about 150 cm). Due to the length of the holes and the shape of the monolithic structure, the holes are difficult to fabricate (e.g., machine). FIG. 1B and FIG. 1C are simplified plan views of the reactor core 100 illustrating a fuel element 104 and a heat pipe 106, respectively. The fuel element 104 and the heat pipe 106 may be substantially surrounded by the monolithic structure 102. For example, the heat pipe 106 may include a heat transfer fluid directly filling and in contact with the monolithic structure 102. In other words, the heat pipe 106 may not include a pipe wall and the heat transfer fluid may be contained within the holes of the monolithic structure 102. Portions of the monolithic structure 102 between the fuel element 104 and the heat pipe 106 and between adjacent fuel elements 104 may exhibit a relatively thin wall. For example, referring to FIG. 1B, a distance D1 between the fuel elements 104 and the heat pipes 106 may be as small as about 1.0 mm and a distance D2 between adjacent fuel elements 104 may be as small as about 1.75 mm. During use and operation, the thin area may be susceptible to deformation and breaking. For example, at the operating temperatures of the reactor core, the material of the monolithic structure 102 may be susceptible to deformation or breaking. In addition, the heat pipes 106 may be welded to an upper reflector at a boundary between the heat pipes 106 and the upper reflector. However, welding each heat pipe 106 of the reactor core may require welding hundreds to thousands of heat pipes 106 to form a seal between the heat pipes 106 and the upper reflector. A failed weld between a single heat pipe 106 and the upper reflector may result in a leak between the reactor core and the external environment, compromising the safety of the nuclear reactor. Embodiments disclosed herein include structures including a heat pipe integral with a fuel element, modular nuclear reactors, and related methods. For example, in accordance with one embodiment, a modular nuclear reactor comprises a central portion comprising a plurality of structures. Each structure comprises a fuel material surrounded by an outer cladding material, the fuel material defining an annular space at a center portion of the fuel material, a heat pipe disposed in the annular space, and an inner cladding between the fuel material and the heat pipe. The modular nuclear reactor further comprises a side reflector disposed around the central portion. In additional embodiments, a modular nuclear reactor comprises a plurality of sections, each section comprising an inner tank comprising a front plate, a back plate, side plate, a top plate, and a bottom plate, a plurality of grid plates, each grid plate of the plurality of grid plates comprising a plurality of apertures and vertically separated from an adjacent grid plate, a plurality of fuel elements extending through each grid plate of the plurality of grid plates, and a plurality of heat pipes extending through each grid plate of the plurality of grid plates, the top plate, and an upper reflector. The modular nuclear reactor further comprises a side reflector material surrounding the plurality of sections. In further embodiments, a method of forming a modular nuclear reactor comprises assembling one or more fuel element structures on a grid plate, each fuel element structure comprising a fuel material surrounded by an outer cladding material, the fuel material defining an annular space at a center portion of the fuel material, a heat pipe disposed in the annular space, and an inner cladding between the fuel material and the heat pipe. The method further comprises disposing an upper reflector over the one or more fuel element structures. In yet additional embodiments, a method of forming a modular nuclear reactor comprises assembling one or more prefabricated fuel elements on a bottom plate of an inner tank and through apertures in a plurality of grid plates, assembling one or more prefabricated heat pipes on the bottom plate of the inner tank and through the apertures in the plurality of grid plates, forming a seal between the one or more prefabricated heat pipes and a top plate of the inner tank, forming an outer tank substantially surrounding the inner tank, and filling the inner tank with a heat transfer fluid. Illustrations presented herein are not meant to be actual views of any particular material, component, or system, but are merely idealized representations that are employed to describe embodiments of the disclosure. The following description provides specific details, such as material types, dimensions, and processing conditions in order to provide a thorough description of embodiments of the disclosure. However, a person of ordinary skill in the art will understand that the embodiments of the disclosure may be practiced without employing these specific details. Indeed, the embodiments of the disclosure may be practiced in conjunction with conventional fabrication techniques employed in the industry. In addition, the description provided below does not form a complete process flow, apparatus, or system for forming a structure comprising a heat pipe integral with a fuel element, a nuclear reactor core, or a related system including the structure or the nuclear reactor core. Only those process acts and structures necessary to understand the embodiments of the disclosure are described in detail below. Additional acts to form structures comprising a heat pipe integral with a fuel element, and a nuclear reactor core may be performed by conventional techniques. Also note, any drawings accompanying the present application are for illustrative purposes only, and are thus not drawn to scale. Additionally, elements common between figures may retain the same numerical designation. According to embodiments described herein, a structure comprising a fuel element and a heat pipe integral with the fuel element may comprise a polygonal (e.g., hexagonal) shape configured to be closely packed together with other like structures to form a nuclear reactor core comprising a plurality of the structures. The structure may comprise an outer cladding having a polygonal shape, such as a hexagonal shape. A fuel material may be disposed within the outer cladding and may directly contact inner walls of the outer cladding. In some embodiments, the fuel material may exhibit a polygonal shape, such as a hexagonal shape, substantially corresponding to the shape of the outer cladding. The fuel material may include an annular opening through a central portion thereof. A heat pipe may extend through the annular opening in the central portion of the fuel material. An inner cladding material may be disposed between the fuel material and the heat pipe. The outer cladding, the fuel material, and the heat pipe may form the structure. A plurality of structures may be grouped together to form a nuclear reactor core. In some embodiments, the structures comprise a hexagonal shape and a majority of the structures may be surrounded by about six other structures. The structures may be prefabricated and may be used to assemble a nuclear reactor core. In some embodiments, the structures may be transported to a remote location for assembly of the nuclear reactor core. The nuclear reactor core including the structures may exhibit an improved packing density of fuel elements and heat pipes relative to other nuclear reactor cores. In other words, the nuclear reactor core may comprise a reduced footprint relative to other nuclear reactor cores. In some embodiments, the nuclear reactor core may be configured to produce an increased power output relative to other nuclear reactor cores having the same weight or size. In other embodiments, a nuclear reactor core includes a plurality of sections comprising the nuclear reactor core. Each section of the plurality of sections may be isolated and operate substantially independently of the other sections. Each section may include an inner tank housing a plurality of heat pipes and a plurality of fuel elements, each heat pipe surrounded by a plurality of fuel elements. The inner tank may be filled with a heat transfer fluid, such as, for example, sodium. The inner tank may comprise walls (e.g., a front plate, a back plate, side plates, a top plate, and a bottom plate), each comprising a material compatible with the nuclear reactor core, such as, for example, stainless steel (e.g., 316 stainless steel (about 12 atomic percent Ni, about 17 atomic percent Cr, about 2.5 atomic percent Mo, about 1.00 atomic percent silicon, about 2.00 atomic percent manganese, about 0.080 atomic percent carbon, about 0.045 atomic percent phosphorus, about 0.030 atomic percent sulfur, and a balance of iron)). The inner tank may include a plurality of grid plates disposed therein. Each grid play may comprise a plurality of apertures arranged in a predetermined pattern. Each of the heat pipes and the fuel elements may pass through an aperture of each grid plate. An outer tank, comprising an upper reflector and a lower reflector may be disposed around the inner tank and configured to contain any materials that may leak from the inner tank. Each heat pipe may extend through holes of the upper reflector and may be welded to the upper reflector to form a seal between the heat pipes and the upper reflector. The outer tank and the inner tank may comprise a section of the reactor core. A plurality of sections may be arranged in a circular pattern to form the reactor core. In some embodiments, failure of one section of the reactor core may not affect the other sections of the reactor core such that the reactor core may continue to operate despite failure of one or more of the sections. FIG. 2A is a cross-sectional view of a reactor core 200 according to embodiments of the disclosure. The reactor core 200 may include a plurality of structures 250 each comprising a heat pipe integral with a fuel element. The structures 250 may be disposed within a central portion 252 of the reactor core 200. The central portion 252 may exhibit a polygonal shape, a square shape, a rectangular shape, a triangular shape, a hexagonal shape, a circular shape, or another shape. In some embodiments, the central portion 252 has a hexagonal shape. A side reflector material 254 may surround the central portion 252. The side reflector material 254 may comprise a material formulated and configured to reflect neutrons and reduce or substantially prevent stray neutrons from traveling outside the reactor core 200. The side reflector material 254 comprise alumina (Al2O3), graphite, beryllium, or another reflector material. In some embodiments, the side reflector material 254 comprises alumina. The reactor core 200 may include a plurality of control drums 256 disposed around a periphery thereof. The control drums 256 may be disposed within the side reflector material 254. The control drums 256 may each include a section comprising a reactor poison material 258 formulated and configured to stop a reaction within the reactor core 200. In some embodiments, the reactor poison material 258 comprises boron carbide (B4C). The reactor poison material 258 may extend along a portion of a circumference of the control drums 256. In some embodiments, the reactor poison material 258 extends along about 120° of the circumference of the control drums 256. In use and operation, the control drums 256 may be rotated to control a reaction rate of the reactor core 200. The reactor core 200 may further include a casing 260 disposed around the side reflector material 254. In some embodiments, the casing 260 comprises a stainless steel material. A neutron shield 262 may surround the casing 260. In some embodiments, the neutron shield 262 comprises boron carbide. The reactor core 200 may further comprise a lead gamma shield 264 disposed around the neutron shield 262. In some embodiments, an air gap may be disposed between the lead gamma shield 264 and the neutron shield 262. In some embodiments, an outer wall or casing may be disposed around the lead gamma shield 264. The reactor core 200 may include an opening 266 defined at least by outer walls of some of the structures 250. The opening 266 may be located at a center of the central portion 252. In some embodiments, the opening 266 may be hexagonally-shaped. In other embodiments, the opening 266 may have another shape, such as a circular shape, a square shape, a rectangular shape, a polygonal shape, or another shape. The opening 266 may be configured to receive one or more control rods that may be configured to be received by the opening 266. In some embodiments, the control rods may be configured to shut down the reactor core 200, such as in an emergency situation. Referring to FIG. 2B through FIG. 2I, the structures 250 and the components thereof are illustrated. FIG. 2B is a cross-sectional view of an outer cladding material 202 that may be used to form a structure for use in the reactor core 200 (FIG. 2A), according to embodiments of the disclosure. The outer cladding 202 may have a polygonal shape, a square shape, a rectangular shape, a triangular shape, a circular shape, a hexagonal shape, or another shape. In some embodiments, the outer cladding 202 has a hexagonal shape. A thickness T1 of the outer cladding 202 may be between about 0.5 mm and about 3.0 mm, such as between about 0.5 mm and about 1.0 mm, between about 1.0 mm and about 2.0 mm, or between about 2.0 mm and about 3.0 mm. In some embodiments, the thickness T1 may be equal to about 1.0 mm. An inner portion 203 of the outer cladding 202 may be defined by inner walls of the outer cladding 202. A distance P (e.g., a pitch) between opposing sides of the outer cladding 202 may be between about 1.5 cm and about 4.0 cm, such as between about 1.5 cm and about 2.0 cm, between about 2.0 cm and about 2.5 cm, between about 2.5 cm and about 3.0 cm, or between about 3.0 cm and about 4.0 cm. In some embodiments, the distance P may be equal to about 2.7 cm or about 2.8 cm. The outer cladding 202 may comprise a suitable material configured to contain a fuel material and any fission products thereof. The outer cladding 202 may be configured to exhibit one or more of a neutron absorption cross section, a neutron radiation resistance, a thermal expansion, a thermal conductivity, and a compatibility with a fuel material (e.g., radiation tolerant materials) and other materials of the reactor core 200 (FIG. 2A). The outer cladding 202 may comprise stainless steel (e.g., 316 stainless steel), a zirconium-based material (e.g., Zircaloy-2, Zircaloy-3, Zircaloy-4, ZrSn, ZIRLO®, etc.), silicon carbide, FeCrAl alloys, or another material. In some embodiments, the outer cladding 202 comprises 316 stainless steel. In some such embodiments, the outer cladding 202 may comprise a 316 stainless steel tube having a hexagonal shape. FIG. 2C is a cross-sectional view of a fuel material 204 that may be used in the reactor core 200 (FIG. 2A). Fuel material 204 may have a shape substantially similar to a shape of the outer cladding 202. In some such embodiments, the fuel material 204 may be sized and shaped to be disposed within the outer cladding 202. In some embodiments, the fuel material 204 may be sized and shaped such that outer surfaces thereof directly contact inner surfaces of the outer cladding 202. The fuel material 204 may comprise any suitable nuclear fuel. By way of nonlimiting example, the fuel material 204 may comprise low-enriched uranium dioxide (UO2), uranium-zirconium (U—Zr), uranium silicide (U3Si2), uranium carbide (UC), uranium-molybdenum fuels (U—Mo), uranium nitride (UN), uranium niobium (U—Nb), uranium-beryllium (UBex) and oxides thereof (e.g., BeO—UO2), alloys thereof, other fissile fuels and enrichments, and combinations thereof. The fuel material 204 may exhibit a maximum thickness D3 at locations corresponding to points of the hexagonal shape of the fuel material 204. The fuel material 204 may exhibit a minimum thickness D4 at locations between points of the hexagonal shape. The maximum thickness D3 may be between about 40 mm and about 70 mm, such as between about 40 mm and about 50 mm, between about 50 mm and about 60 mm, or between about 60 mm and about 70 mm. In some embodiments, the maximum thickness D3 is about 54 mm. The minimum thickness D4 may be between about 25 mm and about 45 mm, such as between about 25 mm and about 30 mm, between about 30 mm and about 35 mm, between about 35 mm and about 40 mm, or between about 40 mm and about 45 mm. In some embodiments, the minimum thickness D4 may be about 34 mm. The fuel material 204 may include an annular portion 205 at a center thereof. The annular portion 205 may be configured to receive a heat pipe and an inner cladding material. FIG. 2D is a cross-sectional view of an inner cladding 206 configured to surround inner portions of the fuel material 204 (FIG. 2C). A thickness T2 of the inner cladding 206 may be between about 0.2 mm and about 1.0 mm, such as between about 0.2 mm and about 0.4 mm, between about 0.4 mm and about 0.6 mm, or between about 0.6 mm and about 1.0 mm. In some embodiments, the thickness T2 is equal to about 0.4 mm. The inner cladding 206 may be configured to exhibit one or more of a desired neutron absorption cross section, a neutron radiation resistance, a thermal expansion, a thermal conductivity, and a compatibility with a fuel material (e.g., radiation tolerant materials) and other materials of the reactor core 200 (FIG. 2A). The inner cladding 206 may comprise stainless steel (e.g., 316 stainless steel), a zirconium-based material (e.g., Zircaloy-2, Zircaloy-3, Zircaloy-4, ZrSn, ZIRLO®, etc.), silicon carbide, FeCrAl alloys, or another material. In some embodiments, the inner cladding 206 comprises 316 stainless steel. In some embodiments, the inner cladding 206 comprises the same material as the outer cladding 202 (FIG. 2B). FIG. 2E is a cross-sectional view of a heat pipe 208. The heat pipe 208 may be sized and shaped to be disposed within the inner cladding 206 (FIG. 2D). The heat pipe 208 may comprise an outer wall 212 configured to house a heat transfer fluid 210 within the heat pipe 208. The heat transfer fluid 210 may comprise sodium, potassium, another heat transfer fluid, or mixtures thereof. The heat pipe 208 may be configured to transfer heat from the fuel material 204 to another fluid, such as in a heat exchanger of a power generation system comprising the reactor core 200 (FIG. 2A). FIG. 2F is a longitudinal cross-sectional view of the heat pipe 208. The heat pipe 208 may comprise a first end 220 and a second end 222. The first end 220 may be exposed to thermal energy to form a vapor 224 in the first end 220. The vapor 224 may travel through the heat pipe 208 to the second end 222, which may exhibit a similar or relatively lower temperature than the first end 220. The vapor 224 may condense at the second end 222 to form a liquid 226. The liquid 226 may be absorbed by a wick 228, which may extend around a central portion of the heat pipe 208. The liquid 226 may travel back to the first end 220 via capillary forces in the wick 228. The outer wall 212 may surround the wick 228. The outer wall 212 may comprise a suitable material for use in the reactor core 200 (FIG. 2A). In some embodiments, the outer wall 212 comprises stainless steel, such as 316 stainless steel. FIG. 2G is a cross-sectional view of the structure 250 in an assembled configuration. The structure 250 may include the heat pipe 208, the outer wall 212 of the heat pipe 208, the inner cladding 206 surrounding the fuel material 204 surrounding the inner cladding 206, and the outer cladding 202 surrounding the fuel material 204. In some embodiments, a volume between the outer wall 212 and the inner cladding 206 may be filled with sodium. In some embodiments, a volume of the fuel material 204 between the inner cladding 206 and the outer cladding 202 may be pressurized with helium gas. A shape of the structure 250 may be defined by a shape of the outer cladding 202. The shape of the structure 250 may be such that a plurality of structures 250 may be grouped together without a substantial space between adjacent structures 250, as illustrated in FIG. 2H, a cluster 270 of the structures 250 may be grouped together. The shape of the structure 250 may facilitate an increased packing density of fuel elements (e.g., fuel rods, fuel pins, etc.) within the reactor core 200 (FIG. 2A). In some embodiments, the structure 250 may exhibit a hexagonal shape. In some embodiments, adjacent structures 250 may be separated by a gap 272. In other embodiments, adjacent structures 250 may directly contact each other. FIG. 2I is a longitudinal cross-sectional view of the structure 250 (FIG. 2A). The structure 250 includes the heat pipe 208 at a central portion thereof. The fuel material 204, the outer cladding 202, and the inner cladding 206 may extend only a portion of a length of the structure 250. The heat pipe 208 may extend beyond each of the fuel material 204, the outer cladding 202, and the inner cladding 206. By way of nonlimiting example, the first end 220 of the heat pipe 208 may be surrounded by the fuel material 204, the inner cladding 206, and the outer cladding 202. The second end 222 of the heat pipe 208 may not be surrounded by the fuel material 204, the inner cladding 206, and the outer cladding 202. In some embodiments, the heat pipe 208 extends about 2.5 meters beyond the fuel material 204, the inner cladding 206, and the outer cladding 202. In some embodiments, the second end 222 may be located proximate one or more structures for transferring heat from the second end 222 to another material or fluid, such as in a heat exchanger, as will be described herein. In some embodiments, the second end 222 of the heat pipe 208 may extend through one or more of an upper reflector, a fission gas plenum, a shield, and one or more heat exchangers. In some embodiments, the reactor core 200 may comprise a plurality of the structures 250. By way of nonlimiting example, the reactor core 200 may comprise about 1,224 of the structures 250, although the reactor core 200 is not so limited and may include any number of the structures 250. For example, in some embodiments, the reactor core 200 may comprise at least about 500 structures 250, at least about 750 structures 250, at least about 1,000 structures 250, at least about 1,500 structures 250, or at least about 2,000 structures 250. In some embodiments, the structures 250 may be prefabricated prior to assembly of the reactor core 200 (FIG. 2A). Each structure 250 may comprise a heat pipe 208 that is integral with a fuel material 204. The fuel material 204 may be surrounded by a cladding material (e.g., outer cladding 202 and inner cladding 206). The heat pipe 208 may be configured to transfer heat from the fuel material 204 to another medium to produce power, as will be described herein. The reactor core 200 including the structures 250 may exhibit a higher effective k value (effective neutron multiplication factor and hence, a greater reactivity) than conventional reactor cores comprising separate fuel elements and heat pipes (i.e., reactor cores wherein the heat pipes are not integral with the fuel elements). Without wishing to be bound by any particular theory, it is believed that the higher effective k value is due to a greater packing density of the structures 250 including the fuel material 204 and integral heat pipes 208 compared to a packing density of relatively isolated heat pipes and fuel elements in conventional reactor cores. In some embodiments, the reactor core 200 may be configured to provide between about 2 MW and about 8 MW of power, such as about 5 MW of power. The structures 250 may facilitate relatively simple assembly of a reactor core 200. FIG. 3 is a flowchart illustrating a method 300 of assembling a reactor core, according to embodiments of the disclosure. The method 300 includes act 302 including assembling one or more fuel element structures on a grid plate; act 304 including disposing an upper reflector over the fuel element structures; and act 306 including coupling a portion of the heat pipes to a heat exchanger. Act 302 includes assembling one or more fuel element structures on a grid plate. The fuel element structures may be substantially the same as the structures 250 described above with reference to FIG. 2G. Accordingly, the structures may each comprise a heat pipe integral with a fuel element. The grid plate may comprise a plurality of openings or cavities for receiving the structures. In some embodiments, the grid plate comprises a pattern of openings or cavities substantially similar to the pattern of the central portion 252 in FIG. 2A. In some embodiments, the grid plate comprises a plurality of hexagonally-shaped openings or cavities for receiving each of the structures. The structures may be closely spaced, as illustrated in FIG. 2A and FIG. 2H. Act 304 includes disposing an upper reflector over the fuel element structures. The upper reflector may comprise a suitable reflector material for use in a nuclear reactor core. By way of nonlimiting example, the upper reflector may comprise stainless steel, beryllium oxide (BeO), or another material. In some embodiments, a portion of the heat pipes of the fuel element structures may extend beyond the upper reflector. In some such embodiments, the heat pipes may pass through apertures in the upper reflector. Act 306 includes coupling a portion of the heat pipes to a heat exchanger. The heat exchanger may be configured to transfer heat from the heat pipes to another fluid. Thermal energy in the another fluid may be used for power generation, such as in, for example, a turbine, as may be understood by one of ordinary skill in the art. FIG. 4A is a cross-sectional view of a reactor core 400, according to other embodiments of the disclosure. The reactor core 400 may be similar to the reactor core 200 (FIG. 2A), but the reactor core 400 may include a different central portion 452. The reactor core 400 may include a side reflector material 454 surrounding the central portion 452. The side reflector material 454 may be substantially the same as the side reflector material 254 described above with reference to FIG. 2A. The reactor core 400 may further include a plurality of control drums 456 including a reactor poison material 458, a casing 460, a neutron shield 462, a lead gamma shield 464, and an outer wall, each of which may be substantially similar to like structures described above with reference to FIG. 2A. The central portion 452 of the reactor core 400 may include a plurality of sections 490. The central portion 452 may exhibit a hexagonal shape, a circular shape, a polygonal shape, a square shape, a rectangular shape, a triangular shape, or another shape. In some embodiments, the central portion 452 may be arranged in a hexagonal shape. In some such embodiments, each section 490 of the plurality of sections 490 may comprise a portion of a hexagon. The sections 490 may be arranged in a hexagonal pattern. In some embodiments, a center of the reactor core 400 may comprise an opening 402. The opening 402 may have a circular shape, a hexagonal shape, or another shape. In some embodiments, the opening 402 has a circular shape. The opening 402 may be sized and shaped to receive one or more control rods and may be used for reactor control. The reactor core 400 may include between about two sections and about twelve sections 490, such as about six sections. Angle θ may determine a number of sections 490 in the reactor core 400. By way of nonlimiting example, where θ comprise about 60°, the reactor core 400 may comprise six sections 490. Each section 490 may include a plurality of heat pipes 408 and a plurality of fuel elements 404. Although FIG. 4A illustrates each section 490 as including a certain number and pattern of heat pipes 408 and fuel elements 404, the disclosure is not so limited. In some embodiments, each section 490 may include between about 100 and about 300 heat pipes 408, such as between about 125 and about 275, between about 150 and about 250, or between about 175 and about 225 heat pipes 408. In some embodiments, each section 490 may include about 204 heat pipes 408. Each section 490 may include between about 200 and about 500 fuel elements 404, such as between about 250 and about 450, or between about 300 and about 400 fuel elements 404. In some embodiments, each section comprises about 352 fuel elements 404. In some embodiments, the central portion 452 is configured such that reactor control blades may be disposed between adjacent sections 490 to control the reactor core 400. FIG. 4B through FIG. 4D are perspective views of a section 490 of the reactor core 400 of FIG. 4A. FIG. 4B is a perspective view of a partially assembled section 490. The section 490 may include a plurality of heat pipes 408 and a plurality of fuel elements 404 (e.g., fuel pins, fuel rods, etc.), only a few of which are illustrated for clarity. The section 490 may include a bottom plate 410 and a top plate 412. The plurality of heat pipes 408 and the plurality of fuel elements 404 may extend from a top of the bottom plate 410 to a bottom of the top plate 412. A bottom of each of the fuel elements 404 and each of the heat pipes 408 may be received in respective cavities in the bottom plate 410. The bottom plate 410 may be configured to orient and position each of the fuel elements 404 and each of the heat pipes 408 in the section 490 relative to one another. For example, the bottom plate 410 may be configured to orient the heat pipes 408 such that a majority of the heat pipes 408 are surrounded by about six fuel elements 404, similar to the pattern of heat pipes 106 and fuel elements 104 described above with reference to FIG. 1A. The section 490 may include a plurality of grid plates 470 interspersed between the bottom plate 410 and the top plate 412. The grid plates 470 may be configured to align the heat pipes 408 and the fuel elements 404 with respect to each other. In other words, the grid plates 470 may be configured to orient the heat pipes 408 and the fuel elements 404 in a desired pattern. In some embodiments, the heat pipes 408 may be arranged such that substantially all of the heat pipes 408 are closer to fuel elements 404 than to other heat pipes 408. In some embodiments, each heat pipe 408 may be surrounded by a plurality of fuel elements 404. The section 490 may include between about two grid plates 470 and about fifteen grid plates 470, such as between about three grid plates 470 and about twelve grid plates 470, between about four grid plates 470 and about ten grid plates 470, or between about five grid plates 470 and about eight grid plates 470. In some embodiments, the section 490 comprises about four grid plates 470. The grid plates 470 may each include a plurality of apertures 472 formed therein. The apertures 472 may be configured to receive the heat pipes 408 and the fuel elements 404. In some embodiments, the apertures 472 may include a sufficient tolerance (e.g., about 0.010 inch) to allow the heat pipes 408 and fuel elements 404 to pass therethrough. Each grid plate 470 may include a same number of total apertures 472 as a total number of heat pipes 408 and fuel elements 404 in the section of the reactor core 400 (FIG. 4A). In some embodiments, apertures 472 configured to receive the heat pipes 408 may be sized differently than apertures 472 configured to receive the fuel elements 404, facilitating simple fabrication of the reactor core 400. In some embodiments, each of the grid plates 470 includes a same number of apertures 472 and in a same pattern as the other grid plates 470. The heat pipes 408 may extend through the top plate 412 to a location where heat may be transferred from the heat pipes 408 to another fluid. The heat pipes 408 may be substantially similar to the heat pipe 208 described above with reference to FIG. 2E and FIG. 2F. In some embodiments, the heat pipes 408 comprise an outer portion comprising the same material as the top plate 412 (e.g., stainless steel, such as 316 stainless steel). The heat pipes 408 may be filled with sodium, potassium, or a combination thereof. In some embodiments, the heat pipes 408 are filled with sodium. The heat pipes 408 may extend from a top of the bottom plate 410, through the apertures 472 in the grid plates 470, and through an aperture 414 in the top plate 412. Each of the heat pipes 408 may be welded at regions 416 at an interface between the heat pipe 408 and a top of the top plate 412. The fuel elements 404 may comprise any suitable fuel for use in a nuclear reactor. By way of nonlimiting example, the fuel elements 404 may comprise low-enriched uranium dioxide (UO2), uranium-zirconium (U—Zr), uranium silicide (U3Si2), uranium carbide (UC), uranium-molybdenum fuels (U—Mo), uranium nitride (UN), uranium niobium (U—Nb), uranium-beryllium (UBex) and oxides thereof (e.g., BeO—UO2), alloys thereof, other fissile fuels and enrichments, and combinations thereof. In some embodiments, the fuel elements 404 may comprise fuel rods, filled with pellets of the nuclear fuel. In some embodiments, the fuel elements 404 are surrounded with a cladding material. FIG. 4C is a perspective view of an inner tank 480 of a section 490 (FIG. 4A). Each section 490 may comprise an inner tank 480. For clarity, the grid plates 470 and the fuel elements 404 are not illustrated in FIG. 4C, but it will be understood that the inner tank 480 includes the grid plates 470, the heat pipes 408, and the fuel elements 404 extending therethrough. The inner tank 480 may enclose a volume 430 defined by the bottom plate 410, a front plate 418, a back plate 420, the top plate 412, and a pair of opposing side plates 422 (one of which is not shown to show the volume 430). Each of the bottom plate 410, the front plate 418, the back plate 420, the top plate 412, and the side plates 422 may comprise a stainless steel material, such as 316 stainless steel. Each of the bottom plate 410, the front plate 418, the back plate 420, the top plate 412, and the side plates 422 may have a thickness T3 equal to between about 0.25 cm and about 1.0 cm, such as between about 0.4 cm and about 0.8 cm, or between about 0.5 cm and about 0.7 cm. In some embodiments, each of the bottom plate 410, the front plate 418, the back plate 420, the top plate 412, and the side plates 422 has a thickness T3 of about 0.5 cm. However, the disclosure is not so limited and the thickness of each of the bottom plate 410, the front plate 418, the back plate 420, the top plate 412, and the side plates 422 may be different. A height H1 of the inner tank 480 (e.g., a height of the front plate 418 and the back plate 420) may be between about 100 cm and about 200 cm, such as between about 120 cm and about 180 cm, or between about 140 cm and about 160 cm. In some embodiments, the height H1 is equal to about 150 cm. In some embodiments, each of the plates may be welded to adjacent plates. By way of nonlimiting example, the bottom plate 410 may be welded to each of the front plate 418, the back plate 420, and the side plates 422, the front plate 418 may be welded to the bottom plate 410, the side plates 422, and the top plate 412, the back plate 420 may be welded to the bottom plate 410, the side plates 422, and the top plate 412, the side plates 422 may be welded to the bottom plate 410, the front plate 418, the back plate 420, and the top plate 412, and the top plate 412 may be welded to the front plate 418, the back plate 420, and the side plates 422. In some embodiments, each of the bottom plate 410, the front plate 418, the back plate 420, the side plates 422, and the top plate 412 comprise the same material (e.g., stainless steel, such as 316 stainless steel), facilitating welding of similar metals together. A fill tube 424 may extend through an opening in the top plate 412 into the volume 430. The fill tube 424 may facilitate filling the volume 430 with one or more materials. In some embodiments, the volume 430 is filled with a heat transfer fluid. The heat transfer fluid may facilitate improved heat transfer between the fuel elements 404 and the heat pipes 408. Accordingly, the inner tank 480 may be filled with a heat transfer fluid, which may substantially fill the volume 430 in the inner tank 480 and contact each of the heat pipes 408 and each of the fuel elements 404. In some embodiments, the heat transfer fluid may form a thermal bond with the heat pipes 408 and the fuel elements 404. With reference again to FIG. 4B, it will be understood that the volume 430 between adjacent grid plates 470 may be substantially filled with the heat transfer fluid such that there are substantially no air or voids in the volume 430. The heat transfer fluid may comprise sodium, potassium, or a combination thereof. In some embodiments, the heat transfer fluid comprises sodium. In some such embodiments, the heat transfer fluid may be compatible with a fluid in the heat pipes 408. By way of nonlimiting example, a fluid in the heat pipes 408 may comprise potassium and the heat transfer fluid may comprise sodium. In some embodiments, the heat transfer fluid may be configured to boil at a temperature higher than about 880° C., such as where the heat transfer fluid comprises sodium. By way of comparison, conventional reactor cores may have maximum operating temperatures of about 700° C. FIG. 4D is a perspective view of a section 490 of a reactor core 400 (FIG. 4A). The section 490 includes an outer tank 495 in which the inner tank 480 is contained. The outer tank 495 may include a lower reflector 492, an upper reflector 494, a front wall 496, a back wall 498, and side walls 497 (one of which is not shown so that the volume 430 may be seen). In some embodiments, each of the lower reflector 492, the upper reflector 494, the front wall 496, the back wall 498, and the side walls 497 may comprise a neutron reflector (i.e., a material configured to reflect neutrons). In some embodiments, the lower reflector 492, the upper reflector 494, the front wall 496, the back wall 498, and the side walls 497 may comprise a stainless steel material (e.g., 316 stainless steel). In other embodiments, each of the lower reflector 492, the upper reflector 494, the front wall 496, the back wall 498, and the side walls 497 may comprise graphite, beryllium, tungsten, or other reflector material. In some embodiments, each of the lower reflector 492, the upper reflector 494, the front wall 496, the back wall 498, and the side walls 497 may comprise the same material. In some embodiments, each of the lower reflector 492, the upper reflector 494, the front wall 496, the back wall 498, and the side walls 497 may comprise the same material as each of the bottom plate 410, the front plate 418, the back plate 420, the top plate 412, and the side plates 422. In some such embodiments, each of the lower reflector 492, the upper reflector 494, the front wall 496, the back wall 498, and the side walls 497 may comprise 316 stainless steel. As illustrated in FIG. 4D, each of the heat pipes 408 may extend from the top of the bottom plate 410 through the top plate 412 and through the upper reflector 494. Each heat pipe 408 may be welded to the upper reflector 494 at regions 416 at an interface between the heat pipes 408 and the upper surface of the upper reflector 494. As described above, the volume 430 may be filled with a heat transfer fluid. The heat transfer fluid may form an effective and ideal thermal bond between the fuel elements 404 and the heat pipes 408. The heat transfer fluid may distribute heat uniformly throughout the volume 430 through conductive and convective fluid heat transfer mechanisms. In some embodiments, the heat transfer fluid in the volume 430 may facilitate uniform heating of the heat pipes 408 in the reactor core 400, reducing a potential for cascade heat pipe failures and reducing localized fuel element and heat pipe “hot spots” (i.e., regions of the fuel elements 404 and the heat pipes 408 that exhibit a relatively higher temperature than other portions of the fuel elements 404 and the heat pipes 408). The heat transfer fluid may not be subject to thermal stresses as a monolithic structure may be. Due to the relatively small size of the sections 490 and the reactor core 400, a relatively small volume of the heat transfer fluid may be required compared to conventional reactor cores. In use and operation, the material in the volume 430 may be sealed from an outside of the section 490 by at least the inner tank 480 and the outer tank 495. Since the heat pipes 408 are sealed at the regions 416 and the plates are welded together, the inner tank 480 may comprise a pressure sealed vessel. Similarly, since the heat pipes 408 are sealed at the regions 416 between the heat pipes 408 and the upper reflector 494, any material that may have leaked from the inner tank 480 may be confined within the outer tank 495. In some embodiments, loss of any of the heat transfer fluid from one of the sections 490 may provide an indication a loss of reactivity. In other words, a reactivity of the reactor core 400 may decrease as the heat transfer fluid leaks from the inner tank 480. In addition, the loss of any heat transfer fluid may be isolated to only one section 490 of the reactor core 400 rather than the entirety of the reactor core 400. Accordingly, the reactor core 400 (FIG. 4A) may be configured to be assembled in remote locations with prefabricated materials. The reactor core 400 may be assembled with prefabricated fuel elements and prefabricated heat pipes. The grid plates may be relatively easy to manufacture compared to a monolithic structure or other structure of conventional reactor cores. Since the reactor core 400 does not include a monolithic structure, a weight of the reactor core 400 may be reduced compared to prior art reactor cores. Grid plates 470 with predrilled apertures 472 patterned in a desired configuration may be used to align the heat pipes 408 and the fuel elements 404 in each section 490. Forming the reactor core 400 in a plurality of sections 490 may facilitate relatively easy reactor assembly relative to assembly of other reactor cores. In addition, the plurality of sections 490 may reduce or prevent criticality mishaps during transport, assembly, and operation of the reactor core 400. In some embodiments, if one of the sections 490 of the reactor core 400 fails during operation, the other sections 490 may continue to retain structural integrity and operate without failure of the entirety of the reactor core 400. FIG. 5 is a simplified flowchart illustrating a method 500 of forming the reactor core 400 (FIG. 4A), according to embodiments of the disclosure. The method 500 comprises act 502 including assembling one or more prefabricated fuel elements on a bottom plate of an inner tank and through one or more grid plates and a top plate; act 504 including assembling one or more prefabricated heat pipes on the bottom plate and through the one or more grid plates and the top plate; act 506 including forming a seal between the one or more heat pipes and the top plate; act 508 including attaching the bottom plate to a front plate, a back plate, and side plates and attaching the top plate to the front plate, the back plate, and the side plates to form the inner tank; act 510 including attaching a lower reflector of an outer tank to the bottom plate and forming an outer front wall, an outer back wall, and outer side walls around the inner tank; act 512 including passing apertures in an upper reflector through the one or more prefabricated heat pipes and attaching the upper reflector to the outer front wall, the outer back wall, and the outer side walls to form the outer tank; act 514 including forming a seal between the one or more heat pipes and the upper reflector; and act 516 including filling the inner tank with a heat transfer fluid. Act 502 includes assembling one or more prefabricated fuel elements on a bottom plate of an inner tank and through one or more grid plates and a top plate. The prefabricated fuel elements may be substantially the same as the fuel element 404 described above with reference to FIG. 4A through FIG. 4D. In some embodiments, it is contemplated that the one or more grid plates may be temporarily attached (e.g., tack welded) to one or more of a front plate (e.g., front plate 418 (FIG. 4C)), a back plate (e.g., back plate 420 (FIG. 4C)), or a side plate (e.g., side plates 422 (FIG. 4C)) prior to assembling the one or more fuel elements through the top plate and the one or more grid plates. The bottom plate may be configured to receive a lower portion of each of the fuel elements. The bottom plate may be configured such that a lower portion of each fuel element is coplanar with the lower portion of the other fuel elements. Act 504 includes assembling one or more prefabricated heat pipes on the bottom plate and through the one or more grid plates and the top plate. The heat pipes may be substantially the same as the heat pipes 408 described above with reference to FIG. 4A through FIG. 4D. The bottom plate may be configured to receive a lower portion of each of the heat pipes. For example, the bottom plate may be configured such that a lower portion of each heat pipe is coplanar with a lower portion of the other heat pipes. In some embodiments, the lower portion of the heat pipes may be coplanar with the lower portion of the fuel elements. Act 506 includes forming a seal between the one or more heat pipes and the top plate. The one or more heat pipes may be sealed to the top plate at, for example, a location proximate a top surface of the top plate. The one or more heat pipes may be welded to the top plate to form the seal between each heat pipe and the top plate. In some embodiments, the one or more heat pipes may comprise a same material as the top plate. In some embodiments, each heat pipe may be welded to the top plate prior to passing another heat pipe through the top plate, the grid plates, and to the bottom plate. Act 508 includes attaching the bottom plate to a front plate, a back plate, and side plates and attaching the top plate to the front plate, the back plate, and the side plates to form an inner tank. The front plate, the back plate, and the side plates may be substantially similar to the front plate 418, the back plate 420, and the side plates 422 described above with reference to FIG. 4C. In some embodiments, the plates are attached to each other by welding. Act 510 includes attaching a lower reflector of an outer tank to the bottom plate and forming an outer front wall, an outer back wall, and outer side walls around the inner tank. Attaching the lower reflector to the bottom plate may comprise welding the lower reflector to the bottom plate. The front wall, the back wall, and the side walls of the outer tank may be welded to a respective front wall, back wall, and side walls of the inner tank. In addition, one or more of the front wall, back wall, and side walls of the outer tank may be welded to the lower reflector. In some embodiments, each of the walls may comprise the same material (e.g., 316 stainless steel). Act 512 includes passing apertures in an upper reflector through the one or more prefabricated heat pipes and attaching the upper reflector to the outer front wall and outer back wall, and the outer side walls to form the outer tank. The upper reflector may be welded to the outer front wall, the outer back wall, and the outer side walls. In some embodiments, a volume between the top plate and the upper reflector may be filled with a liquid, such as, for example, sodium, or a gas, such as, for example, argon. Act 514 includes forming a seal between the one or more heat pipes and the upper reflector. The one or more heat pipes may be sealed to the upper reflector at, for example, a location proximate a top of the upper reflector. The one or more heat pipes may be welded to the upper reflector to form the seal between each heat pipe and the upper reflector. In some embodiments, the one or more heat pipes may comprise a same material as the upper reflector. Act 516 includes filling the inner tank with a heat transfer fluid. The inner tank may be filled from a fill tube (e.g., fill tube 424 (FIG. 4C, FIG. 4D)) extending through the upper reflector and the top plate into the inner tank. After filling the inner tank with the heat transfer fluid, the fill tube may be plugged or otherwise sealed. FIG. 6 is a simplified cut-away perspective view of a reactor core 600 operably coupled to a heat exchanger 602. The reactor core 600 may be substantially similar to the reactor core 200 or the reactor core 400 described above with reference to FIG. 2A and FIG. 4A, respectively. In some embodiments, the reactor core 600 may have a diameter of about 1 meter and a length of about 1.5 meters. The reactor core 600 may include a plurality of heat pipes 604 extending therethrough. The heat pipes 604 may extend from the reactor core 600 to the heat exchanger 602. A material within the heat pipes 604 may be heated in the reactor core 600 by fuel elements 606 in the reactor core 600. The heated material in the heat pipes 604 may be cooled in the heat exchanger 602. The heat exchanger 602 may comprise inlet connections 608 for operably coupling the heat exchanger 602 to a heat transfer fluid and outlet connections 610 for discharging a heated heat transfer fluid from the heat exchanger 602. The heat transfer fluid may be heated by the heat pipes 604 in the heat exchanger 602. The heated heat transfer fluid may be used to produce power, as will be understood by those of ordinary skill in the art. The reactor core 600 may be surrounded by a plurality of rotating control drums 612 configured to control a reaction rate of the reactor core 600. A side reflector 614 may surround the reactor core 600. The side reflector 614 may comprise any neutron reflector material such as, for example, beryllium oxide (BeO), stainless steel (e.g., 316 stainless steel), or alumina (Al2O3). The plurality of rotating control drums 612 may be disposed within the side reflector 614. FIG. 7 is a simplified schematic illustrating a system 700 for power generation, according to some embodiments of the disclosure. The system 700 may include a nuclear reactor core 702 configured to generate heat. The reactor core 702 may comprise a plurality of heat pipes 703 configured to transfer heat from fuel elements of the reactor core 702 to a fluid outside of the reactor core 702. The reactor core 702 may be coupled to a heat exchanger 704 through the heat pipes 703, which may extend from the reactor core 702 to the heat exchanger 704. The reactor core 702 and the heat exchanger 704 may be substantially similar to the reactor core 600 and the heat exchanger 602 described with reference to FIG. 6. A fluid 706 may be compressed in a compressor 708 to form a compressed fluid 710. The compressed fluid 710 may pass through a recuperator 712 wherein the compressed fluid 710 is partially preheated to form a preheated fluid 714. The preheated fluid 714 may be passed across the heat pipes 703 extending into the heat exchanger 704 to heat the preheated fluid 714 and form a heated fluid 716. Energy from the heated fluid 716 may be recovered in a turbine 718, which may be coupled to a power generator 720 to produce power. In some embodiments, the power generator 720 may be operably coupled to the compressor 708 to drive the compressor 708. In some embodiments, the fluid 706 may comprise air. In other embodiments, the fluid 706 may comprise carbon dioxide, nitrogen, or other fluid through which heat may be exchanged. Although FIG. 7 illustrates that the system 700 as comprising an open cycle, the disclosure is not so limited and the system 700 may comprise any system for heat recovery, such as, for example, a Brayton cycle system. One of ordinary skill in the art will understand that the reactor core 702 may be used in any type of system for power generation. In some embodiments, the reactor core 702 may be configured to provide between about 2 MW and about 8 MW of power, such as between about 2 MW and about 4 MW, between about 4 MW and about 6 MW, or between about 6 MW and about 8 MW of power. In some embodiments, the reactor core 702 is configured to provide about 5 MW of power. While embodiments of the disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it should be understood that the disclosure is not limited to the particular forms disclosed. Rather, the disclosure encompasses all modifications, variations, combinations, and alternatives falling within the scope of the disclosure as defined by the following appended claims and their legal equivalents.
	claims	1. A grid strap for a spacer grid, comprising:an upper plate (11a) having a dimple (12a) protruding in one direction from one side of the upper plate (11a) and an upper base (15a) extending downwardly from a center of the upper plate (11a);a pair of symmetrically opposed upper left-hand and upper right-hand supports (16a and 16b) branching off downwardly from the upper base (15a);a lower plate (11b) having a dimple (12b) protruding in the one direction and a lower base (15b) extending upwardly from a center of the lower plate (11b);a pair of symmetrically opposed lower left-hand and lower right-hand supports (16a and 16b) branching off upwardly from the lower base (15b);a pair of symmetrically opposed bridges (18a and 18b) connected to the pair of symmetrically opposed upper left-hand and upper right-hand supports (16a and 16b) on one end of each bridge (18a and 18b) and the pair of symmetrically opposed lower left-hand and lower right-hand supports (16a and 16b) on an opposing end of each bridge (18a and 18b); anda conformal curvature (17) extending from one bridge (18a) through a center region to the other bridge (18b), the conformal curvature (17) having top and bottom edges (21a and 21b) defining a distance therebetween,wherein the center region is the midpoint between the bridges (18a and 18b) and the distance between the top and bottom edges (21a and 21b) being lesser at the midpoint than at the bridges (18a and 18b),wherein the conformal curvature (17) is curved to be concave in the direction opposite to the one direction in which the dimples (12a and 12b) protrude,wherein the upper and lower bases (15a and 15b), upper left-hand and right-hand supports (16a and 16b), lower left-hand and right-hand supports (16a and 16b), bridges (18a and 18b) and conformal curvature (17) combine to form a spacer grid spring (14) protruding in the direction opposite to the one direction in which the dimples (12a and 12b) protrude,wherein all the area of the conformal curvature (17) including top and bottom edges (21a and 21b) are configured to contact a fuel rod (3),wherein the bridges (18a and 18b) are curved to be concave in the direction opposite to the one direction in which the dimples (12a and 12b) protrude,wherein each bridge (18a and 18b) is curved around a lateral axis of the grid strap and configured to be spaced from and parallel to a longitudinal axis of a fuel rod (3), andwherein the top and bottom edges (21a and 21b) are curved to be tapered toward the center region. 2. The grid strap of claim 1, wherein each of the pair of symmetrically opposed upper left-hand and right-hand supports and each of the pair of symmetrically opposed lower lefthand and right-hand supports comprise a wedge-shape. 3. The grid strap of claim 1, wherein the rigidity of the left-hand supports and right-hand supports (16a and 16b) is lower than the rigidity of the conformal curvature (17).
	claims	1. A method comprising:preparing a solvent composition which consists essentially of: hydrofluorocarbon as a vehicle for transporting the radioactive substance, wherein said hydrofluorocarbon is C5H2F10, C4H5F5, c-C5H3F7, or C7HF15, and wherein the solvent composition further comprises 3 to 15% by weight of ethanol based on the total weight of the solvent composition; andremoving a radioactive substance using the solvent composition. 2. A method comprising:preparing a solvent composition which consists essentially of: hydrofluorocarbon as a vehicle for transporting the radioactive substance, wherein said hydrofluorocarbon is C5H2F10, C4H5F5, c-C5H3F7, or C7HF15, and wherein the solvent composition further comprises 3 to 15% by weight of alcohol based on the total weight of the solvent composition, the alcohol being selected from the group consisting of: methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, and t-butanol, and any mixtures thereof; andremoving a radioactive substances using the solvent composition.
	claims	1. An apparatus, comprising:a first electron beam source configured to provide a first electron beam to a surface region of a sample;a second electron beam source configured to provide a second electron beam to pass through the sample, the second electron beam having an initial energy level less than an initial energy level of the first electron beam; anda receiving unit configured to analyze the first electron beam and the second electron beam to obtain information about the sample. 2. The apparatus of claim 1, wherein the initial energy level of the second electron beam is at least one order of magnitude less than the initial energy level of the first electron beam. 3. The apparatus of claim 1, wherein the first electron beam is configured to interact with the surface region of the sample. 4. The apparatus of claim 1, wherein the first electron beam has an initial energy in a range from about 10 keV to about 100 keV, and the second electron beam has an initial energy in a range from about 1 eV to about 100 eV. 5. The apparatus of claim 1, further comprising first optics configured to direct the first electron beam to the sample, to receive the first electron beam and the second electron beam from the sample, and to direct the first electron beam and the second electron beam toward the receiving unit. 6. The apparatus of claim 5, wherein the first optics includes one or more lenses and a first magnetic element configured to redirect the first electron beam from a first path to a second path toward the sample and to redirect the first electron beam and the second electron beam from a third path from the sample to a fourth path toward the receiving unit. 7. The apparatus of claim 6, further comprising second optics located between the first optics and the receiving unit, the second optics including a second magnetic element and a mirror, the second magnetic element configured to redirect the first electron beam and the second electron beams from the fourth path to a fifth path toward the mirror, and from a sixth path from the mirror to a seventh path toward the receiving unit. 8. The apparatus of claim 5, further comprising a cathode objective lens between the first optics and the sample, the cathode objective lens configured to accelerate the first and second electron beams away from the sample. 9. A system, comprising:an electron microscopy assembly configured to provide a first electron beam to a surface region of a sample and to pass a second electron beam through the sample, the second electron beam having an initial energy level less than an initial energy level of the first electron beam; andan analysis unit configured to analyze the sample based on the first electron beam and the second electron beam. 10. The system of claim 9, wherein the electron microscopy assembly comprises:a first electron beam source configured to generate the first electron beam;a second electron beam source configured to generate the second electron beam; anda receiving unit configured to receive the first and second electron beams and transmit corresponding signals to the analysis unit. 11. The system of claim 10, wherein the initial energy level of the second electron beam is at least one order of magnitude less than the initial energy level of the first electron beam. 12. The system of claim 10, wherein the first electron beam has an initial voltage in a range from about 10 keV to about 100 keV, and the second electron beam has an initial voltage in a range from about 1 eV to about 100 eV. 13. The system of claim 9, wherein the electron microscopy assembly comprises:first optics including one or more lenses and a first magnetic element configured to redirect the first electron beam from a first path to a second path toward the sample and to redirect the first electron beam and the second electron beam from a third path from the sample to a fourth path toward the receiving unit. 14. The system of claim 13, wherein the electron microscopy assembly further comprises:second optics located between the first optics and a receiving unit configured to receive the first and second electron beams and transmit corresponding data to the analysis unit, the second optics including a second magnetic element and a mirror, the second magnetic element configured to redirect the first electron beam and the second electron beams from the fourth path to a fifth path toward the mirror, and from a sixth path from the mirror to a seventh path toward the receiving unit. 15. The system of claim 13, wherein the electron microscopy assembly further comprises:a cathode objective lens between the first optics and the sample, the cathode objective lens configured to accelerate the first and second electron beams away from the sample. 16. An electron microscopy assembly, comprising:a first electron beam source configured to generate a first electron beam to travel in a first direction to contact a surface region of the sample and to scatter from the surface region of the sample and travel in a second direction opposite the first direction;a second electron beam source configured to generate a second electron beam to pass through the sample and travel in the second direction co-linearly with the first electron beam; anda receiving unit configured to receive the first and second electron beams to generate data corresponding to the sample. 17. The electron microscopy assembly of claim 16, wherein an initial energy level of the second electron beam is at least one order of magnitude less than an initial energy level of the first electron beam. 18. The electron microscopy assembly of claim 16, wherein the first electron beam has an initial voltage in a range from about 10 keV to about 100 keV, and the second electron beam has an initial voltage in a range from about 1 eV to about 100 eV. 19. The electron microscopy assembly of claim 16, further comprising:first optics including one or more lenses and a first magnetic element configured to redirect the first electron beam from a first path to a second path toward the sample and to redirect the first electron beam and the second electron beam from a third path from the sample to a fourth path toward the receiving unit. 20. The electron microscopy assembly of claim 19, further comprising:second optics located between the first optics and the receiving unit, the second optics including a second magnetic element and a mirror, the second magnetic element configured to redirect the first electron beam and the second electron beams from the fourth path to a fifth path toward the mirror, and from a sixth path from the mirror to a seventh path toward the receiving unit.
	abstract	Provide a nuclear reactor power monitoring technology for enhancing the monitoring accuracy and reliability in nuclear thermal hydraulic stability.
042467837	description	Referring now to the figures of the drawing and first, particularly to FIG. 1 thereof, it is seen that a spacer mesh of a spacer includes walls 1, 2, 3 and 4, which represent sections of crossed, upright webs. In these mesh walls are disposed resilient contact projections 5 as well as rigid contact projections 6. There is further shown the position of a fuel rod 20, which rests against the rigid contact projections 6 and slightly deforms the resilient contact projections 5, elastically. To ensure operationally secure clamping of the fuel rods 20 in the spacer meshes, the resilient contact projections 5 must supply definite contact pressures. In the conventional devices used up to now, the spring forces have been checked by indirect measurement and the clearance between the springs and the rigid contact projections (inscribed mesh diameter) was determined by limit or go-no go plug gages. The permissible range of this clearance was determined empirically. It was found, however, that this testing method is too inaccurate and is inherently full of uncertainties. Thus, the spread of the spring forces is not determined, the measurement of the clearance depends on the inspector and the spring force actually present cannot be determined; only its range of force can be given. The measuring device according to the invention, which is shown in the embodiment examples of FIGS. 2 and 3, serves for measuring these spring forces and thereby, the spring characteristic as well. The embodiment of FIG. 2 has no friction-dependent, mechanically movable parts. In addition, it is small and handy and can be handled separately from the indicating device. This device therefore also has little weight, so that from this aspect as well, interference with the measurement results is avoided. An added advantage is that this device can be placed into the spacer grid in any position, i.e., in the vertical position as well, so that canting the meauring device in the spacer mesh due to its own weight is therefore impossible. In FIG. 2, two rigid contact projections 6 are attached to the mesh wall 2 and a resilient contact projection 5 is attached to the mesh wall 1. For measuring the spring force of the projection 5, the measuring device includes a ground plug 11, the diameter of which corresponds exactly to that of the fuel rods 20 which are to be inserted into the spacer meshed. This plug is further provided with a slot 12 as in FIG. 2, for instance, by electron-beam machining or spark erosion, so that a flexible beam 13 remains. At the transition to the solid part of the plug 11, this flexible beam 13 is provided with at least one wire strain gage 17 which is connected through an amplifier 15 to a suitable indicating device 16. This, however, is within the state of the art, so that details are not shown for the sake of clarity. The plug 11 is fastened to a heat-insulating handle 14 which serves simultaneously, as shown, as a stop against the spacer grid, so that the point of contact between the spring or resilient contact projection 5 and the flexible beam 13 is thereby always accurately fixed. The slotting 12 of this flexible beam 13 is formed so that the contact point 18 of a resilient contact projection 5, not shown, which is shifted 90.degree. in the spacer mesh, comes to lie on the solid part of the plug 11 and therefore cannot falsify the indication. The measurement principle of this device is based on the fact that due to the contact of the resilient projections 5 with the flexible beam 13, the latter is slightly bent, This bend is in turn picked up electrically by the wire strain gage 17 and is made visible at the indicating device 16 through the amplifier 15 and an interposed conventional measuring bridge, not shown. The calibration of this device is very simple, since only the flexible beam 13 needs to be loaded with known forces at the contact point with the resilient contact projection 5. It has been found that this measuring device permits very reliable operation, and the measuring of the individual springs in the spacer meshes is accomplished very quickly. Since the handle 14 of the plug 11, through which the measuring leads are also brought out, is constructed as heat insulation, no falsification of the measured values through heat transfer from the operator to the measuring device proper is possible either. Since the plug 11 must always have the same diameter as the fuel rods 20 being used, it is necessary to have plugs 11 with the proper dimensions available for measuring different spacer geometries. These plugs can be made so that they are exchangeable in the handle 14 and with respect to the electronic evaluator by means of a mechanical coupling. Contrary to FIG. 2, the embodiment example according to FIG. 3 shows a hollow plug 21, in the interior of which the flexible beam 22 is fastened at one end. Wire strain gages 17 are again attached in the vicinity of this fastening point and the measuring lines are brought out through the non-illustrated handle which is similar to the handle 14 shown in FIG. 2. A radial pin 23 which protrudes to the outside through a hole 24 in the plug 21 is attached to the free end of this flexible beam 22 for making contact with the resilient projection 5. This embodiment is better protected against external influences than that according to FIG. 2. It can also be sealed, for instance, by means of an elastic rubber substance, so that it can also be used, for instance, under water. To further illustrate this device, it should be mentioned that the plug 11 or 21, respectively, has a diameter in the order of 10 mm, corresponding to the diameter of the fuel rods. The flexure of the flexible beam 13 or 22, respectively, at the point where the spring makes contact is in the order of 16 .mu.m. Instead of the wire strain gages, other force transducers can, of course, also be used, such as the piezoelectric type, for example. In conclusion, it should be mentioned that a measuring device of this kind can be used in all spacer types in which springs serve for centering fuel rods. The plugs 11 and 21, respectively, then only need to be adapted to the respective spacer geometry. Such measuring devices of course, can logically also be used for measuring the spring force in other equipment outside the field of nuclear power plant engineering, where a simple and reliable control of resilient parts is likewise required.
051014220	summary	BACKGROUND OF THE INVENTION This invention was made with Government support under Grant No. R01 GM 39803, awarded by the National Institute of Health. The Government has certain rights in the invention. The present invention relates to apparatus for guiding X-rays along the hollow bore of a tapered glass capillary, and more particularly to a method and apparatus for securing such a capillary so that it is sufficiently straight to propagate X-rays. Edward A. Stern et al, in an article entitled "Simple Method for Focusing X-Rays Using Tapered Capillaries", Applied Optics, Vol. 27, No. 24, Dec. 15, 1988, pages 5135 to 5139, provided a thorough analysis of the method of focusing X-rays through the use of tapered capillaries. As pointed out by Stern et al, for many uses of X-rays it is necessary or desirable to focus them into a very small spatial region. The standard methods for doing this require very precise dimensions in the focusing elements, on the order of microns or less, and consequently such focusing typically has been difficult and expensive. As described in the Applied Optics article, however, X-rays can be focused by the use of a capillary which has an entrance opening having the dimension of the incident X-ray beam and having an exit opening which has the dimension which is desired for the focused beam. The X-ray beam which is to be focused is directed into a capillary so that the rays impinge on the inner surface of the capillary wall at angles below the critical glancing angle and reflect from that inner surface due to total external reflection so that the capillary acts as a waveguide. By appropriately narrowing the capillary along its length, the X-rays are concentrated over a broad band of energies so that the X-rays which pass through the central aperture of the capillary are, in effect, focused when they pass out the small end of the capillary, since the cross-sectional dimension of the beam is reduced and its intensity is increased. Very short, rapidly tapering glass capillaries may be formed, as by drawing, to produce elongated glass tubes having an internal surfaces which taper inwardly from their inlet ends to their outlet ends for use in aperture visible light, as described in U.S. Pat. No. 4,917,462 to Isaacson et al. Because of critical angle limitations for X-rays, however, capiillaries fabricated for X-ray focusing must be very different than those used for aperturing visible light. In the Applied Optics article, an untapered glass capillary is used to provide intensity enhancement of X-rays, and this capillary rested on a coextensive support, such as a V-groove formed in a metal plate. According to that article, a tapered capillary needs to be several meters long in order to concentrate a 500 micrometer diameter beam to a spot 10 micrometers in diameter. It has been found that the provision of a tapered glass tube of this length creates problems in handling, and that resting such a capillary on a metal plate does not maintain its linearity within necessary tolerances to maximize the output of X-rays. Although capillaries are inexpensive and simple to fabricate, and do not require the extreme precision of dimensions or shape necessary with the methods of focusing utilizing mirrors and zone plates currently in use, nevertheless it has been found that it is necessary to maintain such a capillary linear within a fraction of a milliradian of resolution to prevent absorption of the X-rays by the glass wall as they propagate along the capillary bore. Furthermore, because the glass tube is fragile, it is desirable to provide a coating on the exterior surface of the tube to give it strength and flexibility. However, such a coating can interfere with the ability to maintain the linearity of the capillary. SUMMARY OF THE INVENTION In accordance with the present invention, a glass capillary is formed, as by heating a glass tube and drawing it slowly to extend its length, to produce the desired taper to both the exterior surface and to the interior bore. The capillary is then provided with a plastic coating which is applied to the exterior surface of the glass to give it improved strength and flexibility. The linearity of the interior bore is obtained, in accordance with the invention, by gripping the two ends of the capillary, and pulling the capillary taut. It has been found that the tensile strength of glass is sufficiently high to permit application of tensile forces sufficiently great to remove sag from the capillary. However, shear forces can easily break the glass at its securing points, and accordingly the gripping mechanism must be carefully constructed. A securing mechanism for gripping the glass, in accordance with the invention, includes a vertical metal support at each end of the tube, each support having a central aperture into which the corresponding end of the tube is inserted. The tube is then secured to the support by a suitable adhesive such as an epoxy. However, since the plastic coating can break loose from the glass and cause slippage when a large tension is applied, in accordance with the invention the plastic coating is stripped partially away from the glass in the region of the two end supports so that the supports are secured in part to the glass and in part to the plastic coating. The adhesive bond between the glass and the metal support is very strong and can withstand the necessary tension to enable the capillary to be pulled taut. Furthermore, the bond between the plastic coating and the metal support has been found to serve as a strain relief on the glass tube to prevent shear forces due to the weight of the capillary from breaking the glass at its junction with the support. In order to propagate X-rays through the tapered capillary, it is necessary to ensure that the ends of the capillary, where they are connected to the supports, are aligned with the axis of the capillary between the supports. In order to do this, the vertical metal supports are secured in gimbal mountings which are adjustable around two axes to permit the end portions of the capillaries to be adjusted and aligned with the axis of the capillary. The gimbals have motorized controls so that alignment can be done remotely, allowing the device to be used, for example, in a radiation area without exposing the operator to radiation while the capillary as being aligned with the X-rays. It has also been found that air in a capillary tends to absorb X-rays, and a capillary 1.6 meters long, for example, contains enough air to reduce the flux density of 8 keV X-rays by a factor of 5. However, helium is transparent to X-rays, and by supplying helium under pressure to the large end of the tapered capillary, a very small flow of helium will occur through the capillary. The flow from the large end to the small end is made sufficient to push all of the air out of the capillary bore to thereby improve the flux density at the output of the capillary. Thus, the present invention provides a tapered, helium-filled, cladded glass X-ray optical capillary, or fiber, that will concentrate a beam of X-rays to a high intensity spot to effectively focus the X-ray beam.
	abstract	A device for UV curing a coating or printed ink on a workpiece such as an optical fiber comprises dual elliptical reflectors arranged to have a co-located focus. The workpiece is centered at the co-located focus such that the dual elliptical reflectors are disposed on opposing sides of the workpiece. Two separate light sources are positioned at a second focus of each elliptical reflector, wherein light irradiated from the light sources is substantially concentrated onto the surface of the workpiece at the co-located focus.
	claims	1. A method for state sensing of a technical system, the technical system being an energy store, the method comprising: measuring at least one performance quantity; supplying the at least one measured performance quantity to a state estimation routine for determining at least one state variable characterizing a current system state using a model based on at least one system-dependent model parameter and the at least one measured performance quantity; and supplying the at least one measured performance quantity to a parameter estimation routine to determine the at least one system-dependent model parameter depending on a use to improve a state estimation; wherein a selection of at least one of the at least one state variable characterizing the current system state and the at least one system-dependent model parameter determined by estimation depends on a dynamic response of the at least one measured performance quantity. 2. The method of claim 1 , wherein at least one of the at least one state variable and ones of the at least one system-dependent model parameter not selected is one of unchanged and set again by fixed predetermined models. claim 1 3. The method of claim 1 , wherein: claim 1 at a high dynamic response of the at least one measured performance quantity, ones of the at least one state variable having small time constants and ones of the at least one system-dependent model parameter having small time constants are selected for estimation; and at a low dynamic response, ones of the at least one state variable having large time constants and ones of the at least one system-dependent model parameter having large time constants are selected for estimation. 4. The method of claim 1 , further comprising: claim 1 determining before an estimation determination whether the technical system is in a limit state at one of a beginning and an end of a service life of the technical system, wherein at least one of the at least one state variable state and the at least one system-dependent model parameter is not selected if the technical system is in the limit state. 5. The method of claim 1 , wherein a quality of an estimation is checked based on a covariance matrix. claim 1 6. The method of claim 1 , wherein at least one of the at least one state variable and the at least one system-dependent model parameter is used only if associated covariances of the covariance matrix converge. claim 1 7. A device for state sensing of a technical system, the technical system being an energy store, the device comprising: a measuring arrangement to measure at least one performance quantity of the energy store; a supplying arrangement to supply the at least one measured performance quantity to a state estimator to determine at least one state variable characterizing a current system state using a model based on at least one system-dependent model parameter and the at least one measured performance quantity; a parameter estimator to determine the at least one system-dependent model parameter depending on a use to improve a state estimation, the at least one measured performance quantity being supplied to the parameter estimator; a detecting arrangement to detect a dynamic response of the at least one measured performance quantity; and a selection unit connected to the detecting arrangement to select at least one of ones of the at least one state variable and ones of the at least one system-dependent model parameter determined in at least one of the state estimator and the parameter estimator depending on the dynamic response. 8. The device of claim 7 , further comprising: claim 7 a calculating arrangement to calculate a covariance matrix for at least one of the at least one state variable and the at least one system-dependent model parameter; and an evaluating arrangement to evaluate the covariance matrix. 9. A computer program for being executed on at least one of a computer, a state estimator and a parameter estimator, the computer program comprising: program code operable to perform a process for state sensing of a technical system, the technical system being an energy store, the process including: measuring at least one performance quantity; supplying the at least one measured performance quantity to a state estimation routine for determining at least one state variable characterizing a current system state using a model based on at least one system-dependent model parameter and the at least one measured performance quantity; and supplying the at least one measured performance quantity to a parameter estimation routine to determine the at least one system-dependent model parameter depending on a use to improve a state estimation; wherein a selection of at least one of the at least one state variable characterizing the current system state and the at least one system-dependent model parameter determined by estimation depends on a dynamic response of the at least one measured performance quantity. 10. A computer program product for being executed on at least one of a computer, a state estimator and a parameter estimator, the computer program comprising: a computer-readable data carrier storing program code that is operable to perform a process for state sensing of a technical system, the technical system being an energy store, the process including: measuring at least one performance quantity; supplying the at least one measured performance quantity to a state estimation routine for determining at least one state variable characterizing a current system state using a model based on at least one system-dependent model parameter and the at least one measured performance quantity; and supplying the at least one measured performance quantity to a parameter estimation routine to determine the at least one system-dependent model parameter depending on a use to improve a state estimation; wherein a selection of at least one of the at least one state variable characterizing the current system state and the at least one system-dependent model parameter determined by estimation depends on a dynamic response of the at least one measured performance quantity. 11. The method of claim 1 , wherein the at least one state variable is supplied to the parameter estimation routine. claim 1 12. The device of claim 7 , wherein the at least one state variable is supplied to the parameter estimator. claim 7
	summary
	abstract	A device attenuates an electromagnetic pulse generated in an installation in which a high-power laser beam is sent to a target mounted on a target support. The device includes an electrically conductive plate, electrically connected to an electric earth of the installation and to which the target support is fixed, a plate of material which absorbs electromagnetic waves fixed to one face of the electrically conductive plate located on the target support side and a device for passing a discharge current, which is the result of an interaction of the laser beam with the target, between the target and the electrically conductive plate, where the device for passing the discharge current is equipped with a device for attenuating the current.
048448605	summary	FIELD OF THE INVENTION The present invention relates to nuclear reactors and more particularly to supporting spaced fuel elements in bundles or assemblies in the reactor by means of a welded fuel element support grid with integral flow directing vanes which direct fluid flow for increased heat transfer. BACKGROUND OF THE INVENTION Fuel assemblies for nuclear reactors are generally provided in the form of fuel element or rod arrays maintained by a structure which includes a plurality of welded spacer grids, a lower end fitting and an upper end fitting. Guide thimbles provide the structural integrity between the lower end fitting, the upper end fitting and the spacer grids intermediate the ends of the fuel assembly. The spacer grids define an array of fuel rods which, typically, may be rows and columns of up to 20 rods each. One such spacer and support grid is disclosed in U.S. Pat. No. 3,481,832. The typical fuel element support grid for supporting a spaced array of nuclear fuel elements or rods intermediate their ends includes a generally quadrangular or other polygonal perimeter. A plurality of fuel element compartments or cells within the perimeter are defined by first and second grid-forming members or strips welded to the perimeter and joined to each other at their lines of intersection. The grid-forming members of the fuel element support grid are slotted for part of their width along lines of intersection with the other grid-forming members of the array such that they may be assembled and interlocked at their lines of intersection in what is termed "egg-crate" fashion. The grid-forming members of one embodiment of the present invention are also bent at points corresponding to intermediate points of the compartments for reasons discussed in U.S. Pat. No. 3,423,287. The wavy-strip structure of this embodiment has been utilized because it provides a good strength-to-weight ratio without severely affecting the flow of cooling or moderating fluid through the grid of the nuclear reactor. The grid strip bends typically act as internal arches and act with integral projecting springs for engaging and supporting the fuel elements within the compartments. Thus, at each fuel rod grid position in the fuel assembly, axial, lateral and rotational restraint is provided against fuel rod motion due to coolant flow, seismic disturbance or external impact. The spacer grids also act as lateral guides during insertion and withdrawal of the fuel assembly from the reactor. All of the elements of the fuel lattice, including the springs and the arch forming bends within the compartments, are arranged with respect to the fuel coolant flow in order to minimize pressure drop across the grid. Since separate arches out of the plane of the grid-forming members are not necessary, a minimum pressure drop is accomplished. In U.S. Pat. No. 3,764,470, a flow twister, mixing vane, or fluid flow directing vane was disclosed for redirecting the cooling fluid in the channels between the spaced parallel nuclear fuel elements. Those twisters where U-shaped metal sheets which straddled one grid member at an intersection with the free ends of the "U" folded on themselves to form two pairs of oppositely directed spirals and a pair of slots receiving the other grid member. The purpose of the twisters was to direct cooling fluid inwardly toward and spirally around the adjacent fuel rods. The desirability and theory of their use is described in the "Background of the Invention" of U.S. Pat. No. 3,764,470. The same background is applicable to the invention described herein. This patent also shows bent or "wavy" grid-forming members which define integral arches. SUMMARY OF THE INVENTION Fluid flow directing vanes or "mixing vanes" provided according to the principals of the invention are integral to the strips and provide improved strength for the grid and improved hydraulic performance of the type previously provided by the separate "twisters" of U.S. Pat. No. 3,764.470. A major advantage of the fluid flow directing vanes being integral is that there is little chance of them becoming loose parts or debris within the flow stream circulating in the reactor in a manner which would damage the internals of the reactor. Moreover, the particular design of the integral fluid flow directing vanes of the instant invention where present provide the grid with increased strength over conventional grids with or without integral fluid flow directing vanes because the vanes themselves are "contained" and provide a strong means of attaching the strips of an intersecting pair to each other. The advantages provided by the invention are accomplished in a spacer grid assembly of typical egg-crate assembly but with strips intersecting at additional points for some or all intersections formed by two strips. Individual strips of only four different types are required to produce the interior area of the grid using wavy strips but additional types to produce special fuel rod support features or special cells to accommodate guide thimbles or guide tubes can be made compatible with the four basic strips. The attachment welds at any such reinforced pair of intersecting strips in the region of the flow directing vanes can be, optionally, made at either one, two, or three locations in a manner that will be described hereinafter. A grid constructed according to the principles of the invention, with its novel integral flow directing vanes and bends provides superior performance over other designs of grids during seismic events and other off-normal conditions and during normal reactor operation. During fabrication, the strip shape is stamped and bent into wavy shape. No manual or other post assembly bending requirements to form and position the vanes is required. Because of the particular shape of the integral flow directing vanes, they pass the fuel rod support springs and arches or bends more readily during assembly than do bent mixing vanes of a conventional design as for example seen in U.S. Pat. No. 4,576,786. Moreover, because of the particular design of the grid and "contained" integral fluid flow directing vanes, there is easier access to the welds and less criticality in the least accessible or intermediate weld, if it is chosen to use one, in the area adjacent the integral attachment of the vanes to the strips. Since the vanes are integral and "contained" within the normal width of the strips without projecting beyond the strip edges, the flow directing vanes are less likely to be damaged during use and during fuel assembly fabrication than are the projecting types of integral vanes previously utilized. If desired, fluid flow directing vanes according to the invention can be provided on both the upstream and downstream side of the grid structure. The novel flow directing vanes' performance during seismic events or other off normal conditions provides resistance to lateral loading because they are "contained" and not projecting. The grid reinforcement is in part due to the fact that span lengths of the thin cross-sections are reduced at some corners by means of the shape of the fluid flow directing vanes. Accordingly, a reduced strip cross-section will provide a resistance to lateral loading that is equivalent to that achieved with a conventional design. The benefits of the reduced cross-section can be utilized elsewhere. For example, the thinner cross-section will effect a lower pressure drop for a given strength or given resistance to damage from seismic events or it will permit the use of larger diameter fuel elements with no net effect on pressure drop. Alternately, a change could be made from a conventional grid design of a given material to the current invention with an inherently weaker, but more economical material, while maintaining the cross-section of the strips. The structural improvement afforded by the design would offset the inferior material properties. During normal operation, the fluid flow directing vanes provide a good mix from the open or corner areas of the fuel element cells to the tight areas. This mix affords better heat transfer and a better "thermal margin" for reasons discussed in U.S. Pat. No. 3,764,470. This is accomplished with an acceptable pressure drop because of the reduced cross-section of the strips for a given required grid strength. The "contained" integral flow directing vanes also reduce pressure drop from conventional grids by permitting smaller than conventional weld nugget sizes. Moreover, the weld geometry at the intersection of two strips in a conventional grid structure provides greater flow restriction and undesirable turbulence than welds required at the vane's intersections of the present invention. This is true whether the strips are straight or bent. Also, without the abrupt flow control surface bends which integral flow control vanes have exhibited in the past, a lower pressure drop across the grid than would otherwise be the case is produced by the "contained" vanes of the invention. During fuel assembly reconstitution, individual fuel elements may be removed from and reinserted into the assembly. Individual mixing vanes which project beyond the strip edges, as in a conventional design, can become bent during the reinsertion process as the tip of the fuel element first approaches the grid. This bending can lead to blockage of further insertion, or to contact with the reinserted element or adjacent elements during subsequent operation. Such contact can initiate local wear and possibly breaching of the fuel element cladding tube. Also, if the bending of a conventional vane is severe enough, the vane could fracture and become debris within the circulating fluid of the nuclear reactor. Such debris is a common source of fuel element breaching in operating reactors. The "contained" vanes of the instant invention provide a geometry which is impervious to damage by fuel elements during reconstitution, thereby eliminating concerns of contact or debris during subsequent operation. The spacer grid embodiment utilizing wavy strips represents an advantage over designs which use straight strips. The hydraulic performance of the wavy grid is such that a grid with straight strips which has both a compatible pressure drop and an equivalent strength has not been found. The embodiment of wavy strips described in this continuation-in-part application provides a potential means to further improve this hydraulic advantage, and at the same time to improve the corrosion behavior and DNB performance of the fuel.
047524405	claims	1. In a control rod for nuclear reactors which comprises a number of elongated absorber plates, each absorber plate including a plurality of channels which extend substantially perpendicularly to the longitudinal direction of the absorber plate, some of said channels containing a powdered neutron-asborber material composed of grains and which gives off gas and swells upon irradiation, said channels which contain a powdered neutron-absorber material which gives off gas and swells upon irradiation having a circular cross section, each absorber plate including an edge portion which extends in the longitudinal direction of the absorber plate and comprises a gas-tight edge and a longitudinal space located inside said gas-tight edge, said longitudinal space being in open communication with and permitting a gas flow between said channels in the absorber plate, the improvement wherein a separate elongated body of metallic neutron-absorber material is located between the powdered neutron-absorber material and the edge portion in a plurality of said channels which contain powdered neutron-absorber material which gives off gas and swells upon irradiation, each said elongated body having a circular cross section and a predetermined diameter which is less than the diameter of the channel in which it is positioned, thereby providing a predetermined gap between said elongated body and the inner wall of the channel in which it is positioned, said predetermined gap being smaller than the size of at least 50% of the grains of said powdered neutron-absorber material, thus allowing gas to flow therethrough but counteracting simultaneous movement of the grains of said powdered neutron-absorber material therethrough. 2. A control rod according to claim 1, wherein each said separate body of metallic neutron-absorber material has a circular-cylindrical shape. 3. A control rod according to claim 1, wherein each said edge portion comprises an outwardly sealed slot which contains said longitudinal space. 4. A control rod according to claim 3, wherein a longitudinal bar is located in said slot between the longitudinal space and the channels, said longitudinal bar covering a portion of the cross sections of the orifices of all of said channels. 5. A control rod according to claim 4, wherein said bar consists of a metallic neutron-absorber material along at least a part of its length. 6. A control rod according to claim 1, wherein said edge portion of each absorber plate constitutes an edge facing outwardly, as seen from the centre of the control rod. 7. A control rod according to claim 1, wherein said powdered neutron-absorber material consists of boron carbide. 8. A control rod according to claim 1, wherein said metallic neutron-absorber material consists of hafnium.
	claims	1. A power module assembly comprising:a reactor housing;a reactor core located in a lower portion of the reactor housing;a heat exchanger proximately located about an upper portion of the reactor housing, the upper portion comprising a fluid exit for a primary coolant from the reactor housing, the lower portion comprising a fluid entry for the primary coolant to the reactor housing; anda passageway provided in the reactor housing intermediate the lower portion and the upper portion, the passageway comprising a flow path for an auxiliary flow of the primary coolant to the fluid entry, the flow path adjustable based, at least in part, on a mode of operation of the power module assembly. 2. The power module assembly according to claim 1, wherein the flow path is in fluid communication with the fluid entry of the reactor housing without passing through the upper portion of the reactor housing. 3. The power module assembly according to claim 1, wherein during a loss of coolant accident, the flow of primary coolant out of the upper portion of the reactor housing comprises steam, and wherein the auxiliary flow of primary coolant comprises a mixture of two-phase coolant. 4. The power module assembly according to claim 1, wherein the flow path is closed or reduced based, at least in part, on a full power operation of the power module assembly. 5. The power module assembly according to claim 4, wherein the flow path is open based, at least in part, on a shut-down operation. 6. The power module assembly according to claim 5, wherein the shut-down operation comprises a loss of coolant accident or an over-pressurization event. 7. The power module assembly according to claim 1, wherein a level of the primary coolant is above an outlet of the upper portion of the reactor housing during full power operation, and wherein the level of primary coolant is below the outlet during a shutdown operation. 8. The power module assembly according to claim 7, wherein the level of the primary coolant remains above the passageway during the shut-down operation. 9. A nuclear reactor module comprising:a reactor vessel;a reactor housing mounted inside the reactor vessel, wherein the reactor housing comprises a shroud and a riser located above the shroud;a heat exchanger proximately located about the riser;a reactor core located in the shroud; anda steam generator flow by-pass system configured to provide an auxiliary flow path, between the shroud and the riser, of primary coolant to the reactor core to augment a primary flow path of the primary coolant out of the riser and into the shroud, wherein the auxiliary flow path of primary coolant exits the reactor housing without passing by the heat exchanger, and the steam generator flow by-pass system comprises one or more baffles that adjustably control an opening area of the auxiliary flow path of the primary coolant. 10. The nuclear reactor module according to claim 9, wherein the auxiliary flow path of primary coolant exits the reactor housing due to a difference in hydrostatic forces on either side of the auxiliary flow path. 11. The nuclear reactor module according to claim 10, wherein the primary coolant exits the reactor housing as a result of a decrease in rate of the primary flow path of the primary coolant out of the riser. 12. The nuclear reactor module according to claim 9, wherein the one or more baffles are controllable to rotate about a pivot to open or close. 13. The nuclear reactor module according to claim 9, wherein the steam generator flow by-pass system comprises a unidirectional valve. 14. The nuclear reactor module according to claim 9, wherein the steam generator flow by-pass system forms a passageway for coolant to exit the reactor housing during a loss of coolant accident or a depressurization event. 15. The nuclear reactor module according to claim 14, wherein the passageway opens due to a change in temperature within the reactor vessel. 16. The nuclear reactor module according to claim 15, wherein the steam generator flow by-pass system comprises a bi-metallic cover located over the passageway, and wherein the bi-metallic cover comprises materials having different thermal expansion properties. 17. The nuclear reactor module according to claim 14, wherein a difference in rate of thermal expansion between the shroud and the riser causes the passageway to open. 18. The nuclear reactor module according to claim 17, wherein the riser and the shroud are separately attached to the reactor vessel. 19. A method of cooling a nuclear reactor comprising:circulating a primary coolant through a reactor housing comprising an upper riser and a lower shroud, wherein a primary flow path of the primary coolant passes by a heat exchanger proximately located about the riser, and wherein the primary coolant enters the lower shroud;detecting a loss of coolant accident or a depressurization event;decreasing a fluid level of the primary coolant below the top of the riser, wherein the primary coolant exits the riser as steam;adjustably controlling an auxiliary passageway provided in the reactor housing to form a fluid pathway through the reactor housing between the upper riser and the lower shroud;circulating an auxiliary flow path of the primary coolant from the auxiliary passageway and through the fluid pathway; andcombining the primary coolant from the auxiliary flow path with the primary coolant from the primary flow path that enters the lower shroud. 20. The method according to claim 19, wherein the primary coolant that exits the riser as steam condenses as liquid coolant before being combined with the primary coolant of the auxiliary flow path. 21. The method according to claim 20, wherein the primary coolant of the auxiliary flow path circulates through the auxiliary passageway due to a difference in hydrostatic forces on either side of the passageway. 22. The method according to claim 19, wherein circulating the auxiliary flow path of the primary coolant through the auxiliary passageway reduces a concentration of nonvolatile additives in the primary coolant within the reactor housing. 23. A power module assembly comprising:a reactor housing;a reactor core located in a lower portion of the reactor housing;a heat exchanger proximately located about an upper portion of the reactor housing, wherein primary coolant flows out of the reactor housing via the upper portion, and wherein the primary coolant flows into the reactor housing via the lower portion; anda passageway provided in the reactor housing intermediate the lower portion and the upper portion, the passageway configured to provide an auxiliary flow of primary coolant to the reactor core to augment the flow of the primary coolant out of the upper portion of the reactor housing and into the lower portion, and during a loss of coolant accident, the flow of primary coolant out of the upper portion of the reactor housing comprises steam and the auxiliary flow of primary coolant comprises a mixture of two-phase coolant. 24. A power module assembly comprising:a reactor housing;a reactor core located in a lower portion of the reactor housing;a heat exchanger proximately located about an upper portion of the reactor housing, wherein primary coolant flows out of the reactor housing via the upper portion, and wherein the primary coolant flows into the reactor housing via the lower portion; anda passageway provided in the reactor housing intermediate the lower portion and the upper portion, the passageway configured to provide an auxiliary flow of primary coolant to the reactor core to augment the flow of the primary coolant out of the upper portion of the reactor housing and into the lower portion, the passageway closed or reduced during a full power operation of the power module assembly. 25. A nuclear reactor module comprising:a reactor vessel;a reactor housing mounted inside the reactor vessel, wherein the reactor housing comprises a shroud and a riser located above the shroud;a heat exchanger proximately located about the riser;a reactor core located in the shroud; anda steam generator flow by-pass system configured to provide an auxiliary flow path of primary coolant to the reactor core to augment a primary flow path of the primary coolant out of the riser and into the shroud, wherein the auxiliary flow path of primary coolant exits the reactor housing without passing by the heat exchanger,wherein the steam generator flow by-pass system forms a passageway for coolant to exit the reactor housing during a loss of coolant accident or a depressurization event, and the passageway opens due to a change in temperature within the reactor vessel. 26. A nuclear reactor module comprising:a reactor vessel;a reactor housing mounted inside the reactor vessel, wherein the reactor housing comprises a shroud and a riser located above the shroud;a heat exchanger proximately located about the riser;a reactor core located in the shroud; anda steam generator flow by-pass system configured to provide an auxiliary flow path of primary coolant to the reactor core to augment a primary flow path of the primary coolant out of the riser and into the shroud, wherein the auxiliary flow path of primary coolant exits the reactor housing without passing by the heat exchanger,wherein the steam generator flow by-pass system forms a passageway for coolant to exit the reactor housing during a loss of coolant accident or a depressurization event, and a difference in rate of thermal expansion between the shroud and the riser causes the passageway to open. 27. A method of cooling a nuclear reactor comprising:circulating a primary coolant through a reactor housing comprising an upper riser and a lower shroud, wherein a primary flow path of the primary coolant passes by a heat exchanger proximately located about the riser, and wherein the primary coolant enters the lower shroud;detecting a loss of coolant accident or a depressurization event;decreasing a fluid level of the primary coolant below the top of the riser, wherein the primary coolant exits the riser as steam;circulating an auxiliary flow path of the primary coolant through an auxiliary passageway provided in the reactor housing, wherein the auxiliary flow path of the primary coolant exits the reactor housing without passing by the heat exchanger; andcombining the primary coolant from the auxiliary flow path with the primary coolant from the primary flow path that enters the lower shroud,wherein circulating the auxiliary flow path of the primary coolant through the auxiliary passageway reduces a concentration of nonvolatile additives in the primary coolant within the reactor housing.
048141364	abstract	This is a process for producing material for lining reactor fuel element claddings. Rather than using unalloyed zirconium, this invention provides for an alloy liner for the cladding. The process uses electron beam melting of zirconium, to give very low metallic impurities to reduce solid solution strengthening and second phase formation and property variability from lot to lot, while using alloying to reduce the susceptibility to steam corrosion. Preferably, oxygen is controlled to a low level as well, to provide a low, but fabricable, hardness in the alloyed liner material.
	abstract	The present invention relates to a lower end fitting for reducing flow resistance due to an in-core instrument in a nuclear fuel assembly, that is, a lower end fitting (100) having a plurality of flow holes for a nuclear fuel assembly, in which the flow holes (121) are formed under an assembly groove in which an instrumentation tube (131) for a nuclear fuel assembly is inserted, and at least two or more flow holes (121) are formed at a predetermined distance from the central axis (C) of the instrumentation tube (131).
	description	This patent application claims the benefit of priority under 35 U.S.C. § 119 from Korean Patent Application No. 10-2014-0023605 filed Feb. 27, 2014, the contents of which are incorporated herein by reference. 1. Field of the Invention The present disclosure relates to a water-air combined passive feed water cooling apparatus and system, and more particularly, to a water-air combined passive feed water cooling apparatus and system for effective cooling, condensing steam of cooling water generated by water cooling through air cooling and refilling the same as cooling water for a heat exchanger of a passive feed water cooling system. 2. Description of the Related Art After an accident of a light water reactor including a security system configured as an active pump driven using electricity, when a feed water system does not operate, residual heat of a nuclear reactor is removed by driving an auxiliary feed water pump through a steam generator. On the other hand, there is a passive auxiliary feed water cooling system does not need electricity and removes residual heat of a nuclear reactor through a steam generator as a passive apparatus for natural circulation force. Referring to FIG. 1, since a design of a general passive auxiliary feed water system has a structure, in which when cooling water in a heat exchange cooling tank (PCCT: Passive Containment Cooling Tank) 1 located outside a reactor containment building boils, generated steam 2 is discharged into the air, the cooling ability of the general passive auxiliary feed water system is lost after all the cooling water of the heat exchange cooling tank (PCCT) 1 is evaporated. A cooling time of the passive auxiliary feed water system is designed generally to have 8 hour cooling ability as a reference. However, after Fukushima nuclear accidents, it is necessary for a nuclear reactor cooling system to have about 72 hour cooling ability. To greatly extend the cooling time of a general passive feed water system from 8 hours to 72 hours or more, it is necessary to design a volume of a cooling tank of the passive feed water system to be greater several times. Accordingly, it is necessary not only to increase a volume of a water tank but also to strongly design supporting structures for the water tank to be resistant to earthquakes. Also, an auxiliary feed water system using a pump has a possibility of a failure caused by an error of an operator, power failure, the malfunction of the pump. To overcome such limitations, there is provided a passive auxiliary feed water cooling system capable of increasing security and economic feasibility by passively cooling down residual heat of a nuclear reactor through condensing steam generated from a secondary side of a steam generator when a nuclear reactor accident occurs. For example, there are Korean Patent Registration No. 10-0261752 and Korean Patent Publication No. 2001-0076565, including a vertical isolation condenser of a boiling water reactor, an isolation condenser tank including cooling water and heat-exchangeable with the isolation condenser, a pipe connecting a steam generator to the isolation condenser, and a makeup water tank. However, general passive auxiliary feed water cooling systems for a light-water nuclear reactor have limitations such as refilling a cooling water tank of a passive auxiliary feed water system with cooling water after all cooling water of the heat exchange cooling tank (PCCT) 1 is evaporated or designing a cooling water tank to be greater several times. Due to the limitations, it is necessary to provide a water-air combined feed water cooling system extending a cooling water exhaustion time by refilling a cooling tank of a passive feed water system with steam evaporated from the cooling tank and discharged into the air. Cited invention 1: Korean Patent Registration No. 10-0261752 Cited invention 2: Korean Patent Publication No. 2001-0076565 Embodiments of the present invention are directed to provide a water-air combined passive feed water cooling apparatus and system extending a cooling water exhaustion time by cooling down steam of cooling water evaporated from a cooling tank of a general passive feed water system into the air through an air cooling heat exchanger and recirculating the steam to the cooling tank. According to an aspect of the present invention, there is provided a water-air combined passive feed water cooling apparatus including a water cooling heat exchanger connected to the inside of a containment building to cool down heat of a steam generator using a water cooling method, a cooling tank including the water cooling heat exchanger therein and storing cooling water condensing main steam generated by the steam generator, an evaporative steam pipe connected to the cooling tank, the evaporative steam pipe, into which steam of the cooling water generated by the water cooling heat exchanger in the cooling tank flows, an air cooling heat exchanger connected to the evaporative steam pipe and cooling down and liquefying the steam flowing into the evaporative steam pipe, and a condensed water collecting pipe for refilling the cooling tank with the steam liquefied by the air cooling heat exchanger. The cooling tank may be formed of a pressure vessel. The air cooling heat exchanger may include a radiator receiving steam of cooling water generated in the cooling tank through the evaporative steam pipe and emitting heat outwards. The air cooling heat exchanger may be formed of a horizontal heat exchange condensing tube. The apparatus of claim 4, wherein the horizontal heat exchange condensing tube is formed of a heat exchange tube including a cooling fin to increase heat emission efficiency. The air cooling heat exchanger may be formed with a pipe for emitting a non-condensed gas. The pipe for emitting the non-condensed gas may be exposed outwards at a top pipe of the radiator. The radiator may be formed of at least two vertical pipes and at least two horizontal pipes intersecting with one another. The horizontal pipes may have an incline to allow the condensed steam to flow toward the condensed water collecting pipe. The condensed cooling water may be allowed to flow into the vertical pipes extended from the condensed water collecting pipe due to the incline. The condensed water collecting pipe, to prevent a backflow toward the condensed water collecting pipe, may have an outlet located below an uppermost location of the water cooling heat exchanger. According to another aspect of the present invention, there is provided a passive feed water cooling system including a water cooling heat exchanger located outside a containment building and connected to the inside of the containment building to cool down heat of a steam generator using a water cooling method, a cooling tank located outside the containment building, including the water cooling heat exchanger therein and storing cooling water condensing main steam generated by the steam generator, an evaporative steam pipe connected to the cooling tank, the evaporative steam pipe, into which steam of the cooling water generated by the water cooling heat exchanger in the cooling tank flows, an air cooling heat exchanger connected to the evaporative steam pipe and cooling down and liquefying the steam flowing into the evaporative steam pipe, a condensed water collecting pipe for refilling the cooling tank with the steam liquefied by the air cooling heat exchanger, an air induction duct formed outside the air cooling heat exchanger and formed of a hollow pipe including one air inlet and one air outlet to induce an air flow outside the air cooling heat exchanger, and a cooling air blower installed inside the air induction duct and forcibly generating an air flow, in which the passive feed water cooling systems are formed on four sides of the containment building, respectively. The cooling water blower may be located on a top end inside the air induction duct. The cooling air blower may be located on a bottom end inside the air induction duct. The cooling air blower may be located in a middle inside the air induction duct. The cooling air blower may be selectively formed in at least two selected from the top end, the bottom end, and the middle inside the air induction duct. The air induction duct may be extended in a direction horizontal to a ground surface. The air induction duct may include an electric-powered fan generating an air flow and a driving unit for driving the electric-powered fan. The electric-powered fan may include at least three rotors. Also, to naturally circulate the air when the driving unit does not operate, the electric-powered fan may have a total projected cross-sectional area of the rotors less than about ⅓ of a cross-sectional area of the air induction duct. The driving unit may be formed of a motor. Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the attached drawings. Herein, configurations and operations illustrated in the drawings and described with reference thereto are just at least one embodiment. However, the technical scope and essential configurations and operations of the present invention are not limited thereto. Generic terms widely used for functions in present are selected as the terms used herein. However, they may vary with the intension of those skilled in the art, practice, or the appearance of novel technology. Also, particularly, there are present terms selected arbitrarily by applicant(s). In this case, meanings thereof will be described in detail. Accordingly, the terms used herein are not determined simple designations but will be defined based on meanings thereof and the contents throughout the present specification. The present invention provides a passive feed water cooling system including a water cooling heat exchanger located outside a containment building to be connected to the inside of the containment building and cooling down heat of a steam generator using a water cooling method, a cooling tank located outside the containment building, including the water cooling heat exchanger therein, and storing cooling water for condensing main steam generated by the steam generator, an evaporative steam pipe connected to the cooling tank to allow steam of cooling water generated by the water cooling heat exchanger to flow therein, an air cooling heat exchanger for cooling down the steam flowing into the evaporative steam pipe to liquefy the steam, a condensed water collecting pipe for refilling the cooling tank with the steam liquefied by the air cooling heat exchanger, an air induction duct formed outside the air cooling heat exchanger, which is a hollow pipe including one air inlet and one air outlet, to induce an air flow outside the air cooling heat exchanger, and a cooling air blower installed in the air induction duct to forcibly generate an air flow. The passive feed water cooling system provides water-air combined passive feed water cooling systems formed on four sides of the containment building, respectively. Hereinafter, it will be described in detail with reference to the attached drawings. FIG. 2 is a vertical cross-sectional view of a water-air combined passive feed water cooling apparatus according to an embodiment of the present invention. Referring to FIG. 2, the water-air combined passive feed water cooling apparatus may include a water cooling heat exchanger 210, a cooling tank 220, an evaporative steam pipe 230, an air cooling heat exchanger 240, a condensed water collecting pipe 250, an air induction duct 260, and a cooling air blower 270. A containment building 10 protects a nuclear reactor causing a high indoor temperature and prevents radioactive materials from being discharged into the air. A steam generator 20 is formed inside the containment building 10. Main steam is condensed by the water cooling heat exchanger 210 in the cooling tank 220 and flows into the steam generator 20 through a feed water pipe 30. The evaporated main steam is discharged through a steam pipe 40. The main steam may be a coolant circulating through the steam generator 20, the steam pipe 40, the water cooling heat exchanger 210, and the feed water pipe 30. The cooling water heat exchanger 210 is connected between the feed water pipe 30 and the steam pipe 40 to condense the main steam flowing through the steam pipe 40. The main steam is condensed by the cooling water in the cooling tank 220. The main steam condensed by the water cooling heat exchanger 210 may flow again into the steam generator through the feed water pipe 30. A method of condensing the steam using the cooling water is a water cooling method, which rapidly cools down but is impossible to cool down when cooling water in a cooling tank is exhausted. The cooling tank 220 may be a container storing cooling water. The cooling tank 220 cools down heat generated by the water cooling heat exchanger 210 using cooling water stored therein. Due thereto, the cooling water may be evaporated. The cooling tank 220 may be formed with a cover on a top thereof to prevent steam generated from the cooling tank 220 from being discharged outwards. The cooling tank 220 may be a pressure vessel available at more than constant pressure. Due to a structure described above, the steam generated from the cooling tank 220 is not discharged outwards and may mostly flow into the evaporative steam pipe 230. The evaporative steam pipe 230 may be inserted with the steam generated from the cooling tank 220. The evaporative steam pipe 230 is installed on a top of the cooling tank 220 and is connected to the air cooling heat exchanger 240. Cooling steam generated from the cooling tank 220 may flow into the air cooling heat exchanger 240 due to the pressure of the cooling steam. The air cooling heat exchanger 240 may be a radiator for emitting outwards heat of the cooling steam flowing from the evaporative steam pipe 230. The radiator is an apparatus for emitting outwards heat. To efficiently perform emission, the radiator may have a structure formed with a large surface area. Steam may flow from the evaporative steam pipe 230 to the air cooling heat exchanger 240. However, when a large amount of steam flows from the evaporative steam pipe 230, it is necessary to design the pressure of the air cooling heat exchanger 240 is necessary to be high. In this case, there are limitations in stability and manufacturing costs. Accordingly, to prevent a significant increase in pressure in the air cooling heat exchanger 240 caused by the steam flowing from the evaporative steam pipe 230, a part of an upper pipe of the air cooling heat exchanger 240 (hereinafter, referred to as an opening portion 247) may be exposed outwards to the air. Due to a configuration of the air cooling heat exchanger 240 as described above, steam with excessive pressure and some of a non-condensed gas not condensed may be discharged outwards through the opening portion 247. An orifice is formed on the opening portion 247 of the air cooling heat exchanger 240 to form an air-exposed area to be controllable. Hereinafter, it will be described in detail with reference to FIG. 3. The air cooling heat exchanger 240 is formed with a plurality of vertical pipes 243 and a plurality of horizontal pipes 245 intersecting one another. The plurality of horizontal pipes 245 may have an incline to allow steam of cooling water liquefied in the air cooling heat exchanger 240, which is condensed to water, to flow through the horizontal pipes 245 to refill the cooling tank 220 through the condensed water collecting pipe 250. The incline may be at an angle of about −3 degrees to be appropriate for allowing the steam of cooling water liquefied in the air cooling heat exchanger 240 to flow through the horizontal pipes 245 and to flow into the condensed water collecting pipe 250. The plurality of horizontal pipes 245 may include a plurality of fins to enlarge a contact area exposed outwards. One of the vertical pipes 243 may be extended to be connected to the condensed water collecting pipe 250. The condensed water may flow into the extended one of the vertical pipes 243, connected to the condensed water collecting pipe 250, due to the incline of the plurality of horizontal pipes 245. The condensed water collecting pipe 250 is extended from the air cooling heat exchanger 240 to the cooling tank 220. The condensed water collecting pipe 250 is configured not to allow steam generated from the cooling tank 220 to flow into the air cooling heat exchanger 240 through the condensed water collecting pipe 250 when the steam generated from the cooling tank 220 flows into the air cooling heat exchanger 240 through the evaporative steam pipe 230. To prevent a backflow, an outlet of the condensed water collecting pipe 250 may be located below a lowest free water surface of the cooling water in the cooling tank 220. Herein, a head of cooling water located in the condensed water collecting pipe 250 is formed to be greater than the resistance of the evaporative steam pipe 230 that is a connection point between the cooling tank 220 and the air cooling heat exchanger 240, thereby preventing the steam of cooling water from flowing back to the air cooling heat exchanger 240 through the condensed water collecting pipe 250. In the configuration described above, the outlet of the condensed water collecting pipe 250 may be located below the lowest free water surface of the cooling water in the cooling tank 220. When the outlet of the condensed water collecting pipe 250 is located above the lowest free water surface of the cooling water in the cooling tank 220, the steam of cooling water generated by the water cooling heat exchanger 210 may flow backward to the air cooling heat exchanger 240 through the condensed water collecting pipe 250. The air induction duct 260 may increase the efficiency of natural circulating air cooling when cooling down the air cooling heat exchanger 240. The air cooling heat exchanger 240 is located in the air induction duct 260. The air induction duct 260 may have a hollow pipe shape formed with an air inlet and an air outlet on top and bottom thereof, respectively, and may be in accordance with an outer wall of the containment building 10. Due to the configuration of a chimney described above and heat of the air cooling heat exchanger 240, a chimney effect may occur in the air induction duct 260, which forms an air flow from a bottom to a top of the air induction duct 260. Due to an ascending current generated by the chimney effect, the natural circulation cooling of the air cooling heat exchanger 240 may be rapidly performed. The cooling air blower 270 includes a driving unit 273 and an electric-powered fan 275. It is possible to forcibly generate the ascending current in the air induction duct 260 by the electric-powered fan 275 installed in a path of the air induction duct 260. This allows a larger amount of air of a naturally generated ascending current to flow, thereby increasing the cooling efficiency of the air cooling heat exchanger 240. The electric-powered fan 275 may be driven by the driving unit 273. The driving unit 273 may be a motor. Hereinafter, the electric-powered fan 275 will be described in detail with reference to FIG. 6. FIG. 4 is a vertical cross-sectional view of a water-air combined passive feed water cooling system according to an embodiment of the present invention. Referring to FIG. 4, the air induction duct 260 of the water-air combined passive feed water cooling system includes one air inlet and one air outlet. The air inlet is formed on a bottom of the air induction duct 260 as a hollow pipe formed vertically to a ground surface. The outlet is formed on a top of the air induction duct 260. The cooling air blower 270 may be formed at least one in the air induction duct 260. Herein, the air inlet may be formed on the bottom of the air induction duct 260 in a direction horizontal to the ground surface. The cooling air blower 270 may be formed in the air inlet in the horizontal direction. The cooling air blower 270 may be installed in any one of a top end, a bottom end, and a middle of the air induction duct 260. Preferably, the cooling air blower 270 may be installed on the bottom end of the air induction duct 260 but is not limited thereto. When the cooling air blower 270 is installed on the bottom end of the air induction duct 260, it becomes easy to replace, maintain, and repair the cooling air blower 270. FIG. 5 is a horizontal cross-sectional view of the water-air combined passive feed water cooling system of FIG. 4. Referring to FIG. 5, the water-air combined passive feed water cooling system may be formed four on the outside the containment building 10. A plurality of water-air combined passive feed water cooling systems may increase the efficiency of cooling through a plurality of coolers. When some of the coolers do not operate, it is possible to maintain cooling. To have ability of about 100% cooling down residual heat when one of the four coolers breaks down, each of the four water-air combined passive feed water cooling systems may have a heat removal capacity of cooling down more than about 33% of residual heat emitted from a nuclear reactor in the containment building 10 but is not limited thereto. FIGS. 6A and 6B illustrate operations of the cooling air blower 270 of the water-air combined passive feed water cooling system. Referring to FIG. 6A, the cooling air blower 270 may include the electric-powered fan 275 and the driving unit 273. The cooling air blower 270 is formed in the path of the air induction duct 260 but is not limited. The electric-powered fan 275 is driven by the driving unit 273. The driving unit 273 generates rotational motion and may be a motor. Due to rotations of the electric-powered fan 275, an ascending current generated in the air induction duct 260 may increase. However, when power is not supplied due to an accident occurring in the nuclear reactor, the electric-powered fan 275 does not rotate. Herein, when the electric-powered fan 275 has a large area, the occurrence of the ascending current may be limited. To overcome a limitation described above, the area of the electric-powered fan 275 may be reduced. Referring to FIG. 6B, the area of the electric-powered fan 275, to increase the pass of a natural ascending current k2 occurring in the air induction duct 260, may be less than about ⅓ of a cross-sectional area of the air induction duct 260 but is not limited thereto. Due to the configuration described above, the water-air combined passive feed water cooling system may allow forcible circulation by driving the electric-powered fan 275 when power is supplied, and may allow natural circulation when the power is not supplied and the electric-powered fan 275 is not driven. FIG. 7 is a vertical cross-sectional view illustrating a state, in which the cooling air blower 270 of the water-air combined passive feed water cooling system is installed on the bottom of the air induction duct 260 to be vertical to the ground surface. Referring to FIG. 7, the air cooling heat exchanger 240 is located in the air induction duct 260. The air induction duct 260 may have a hollow pipe shape formed with an air inlet and an air outlet on top and bottom thereof, respectively, and may be in accordance with an outer wall of the containment building 10. The air induction duct 260 may be extended to allow the air inlet to be in accordance with a shape of the cooling tank 220. The air inlet may be installed to be vertical to the ground surface. Also, the cooling air blower 270 may be installed in the air inlet and may be installed to be vertical to the ground surface according to a shape of the air inlet. FIG. 8 is a vertical cross-sectional view illustrating a state, in which the cooling air blower 270 is installed on the bottom of the air induction duct 260 to be horizontal to the ground surface. Referring to FIG. 8, the air cooling heat exchanger 240 is located in the air induction duct 260. The air induction duct 260 may have a hollow pipe shape formed with an air inlet and an air outlet on top and bottom thereof, respectively, and may be in accordance with an outer wall of the containment building 10. The air induction duct 260 may be formed with the air inlet on a top of the cooling tank 220 to be extended in a direction horizontal to the ground surface. Also, the cooling air blower 270 may be installed in the air inlet and may be installed to be horizontal to the ground surface according to a shape of the air inlet. FIG. 9 is a graph illustrating a thermal load on the nuclear reactor according to an operation time of the water-air combined passive feed water cooling system. Referring to FIG. 9, in an initial stage of an accident, heat at a high temperature is generated in the nuclear reactor and a lot of thermal loads are generated due to the heat of the high temperature. Initially, the thermal loads may be rapidly cooled down by a water cooling system having a great heat removal capacity. In advanced stages of the accident, in which heat emission diminishes, the thermal loads may be cooled down by an air cooling system having a smaller heat removal capacity than the water cooling system but capable of cooling down infinitely without a limitation of cooling water exhaustion, thereby preventing an excessive increase in volume of a heat exchanger and simultaneously providing desired cooling ability. FIG. 10 is a graph illustrating an operation time and a cooling water level according to a heat removal capacity of the air cooling heat exchanger of the water-air combined passive feed water cooling system. Referring to FIG. 10, when heat of a steam generator is cooled down by a water cooling heat exchanger of a cooling tank in a general passive auxiliary feed water cooling system, when the evaporation of cooling water in the cooling tank starts at a time point of XI after an accident occurs and is performed for about 8 hours, all the cooling water is evaporated and the cooling tank lacks water. However, the water-air combined passive feed water cooling system according to the embodiment condenses evaporated cooling water through an air cooling process to refill a cooling tank, thereby extending an exhaustion time of the cooling water. According to an increase in a steam condensing capacity of an air cooling heat exchanger of the water-air combined passive feed water cooling system, the exhaustion time of the cooling water may be more increase, thereby having an at least more than about 72 hours of the exhaustion time. When condensing all 100% steam discharged outwards from a cooling tank into the air in a general passive auxiliary feed water cooling system to recirculate through the cooling tank, it means a water level of cooling water is absolutely not reduced. To have a cooling time capacity of more than about 72 hours, the water-air combined passive feed water cooling system may be configured while an air cooling heat exchanger is having an appropriate level of a steam condensing capacity. As described above, according to the embodiment, steam of cooling discharged from a cooling tank of a general passive feed water system into the air is condensed by an air cooling heat exchanger to refill the cooling tank, thereby greatly increasing a cooling time of about 8 hours of the general passive feed water system to be more than about 72 hours. That is, without designing a volume of the cooling tank of the general passive feed water system to be greater several times, the cooling time may be greatly increased to be more than about 72 hours. Accordingly, it is possible to simultaneously overcome limitations such as an increase in a volume of a cooling tank of a passive feed water system and an increase in a thickness of a wall of an auxiliary building for a nuclear reactor according to the increase in the volume of the cooling tank. In addition, according to the embodiment, since a high pressure boundary of the general passive feed water system is perfectly separated from a pressure boundary of an air cooling heat exchanger system, there is no increase in damageable portions of the high pressure boundary of the general feed water system according to an increase in a heat transfer area of the air cooling heat exchanger system. Additionally, according to the embodiment, since it is unnecessary to include a controller such as a valve or a pump necessary to activate or deactivate an air cooling heat exchanger, there is no possibility of a failure of a corresponding device. When a forcible circulating air cooling fan operating in a state of supplying power indoors or outdoors of a nuclear power plant is deactivated because the power is not supplied, since having a structure for allowing cooling air to naturally circulate through an open area between rotors of the fan, an active/passive conversion controller is unnecessary. Also, due to cooling systems installed on four sides of a containment building, water-air combined passive feed water cooling systems operate independently from one another. Although one of air outlets is closed and one of the cooling systems does not operate, other cooling systems may independently operate. According to the above-described present invention, steam of cooling evaporated into the air is condensed by a natural circulating air cooling heat exchanger to refill a cooling tank, thereby extending a cooling water exhaustion time of the cooling tank, for example, to be more than about 72 hours. Accordingly, it is possible to increase a cooling time without an increase in a cooling water capacity of the cooling tank. Since it is unnecessary to increase the cooling water capacity, improved effects may be provided using small facilities, thereby reducing costs and processes. Regardless of supplying power indoors and outdoors of a nuclear power plant, air cooling is continuously performed by a natural circulating air cooling heat exchanger. Although a loss of power occurs and an electric-powered fan is deactivated, since it is possible to convert from forcible circulating air cooing through the electric-powered fan to natural circulation air cooling without operating an additional converter, cooling may be continuously performed when an accident of a nuclear reactor occurs. An air induction duct for cooling down an air cooling heat exchanger includes respective air outlets. When one of the air outlets is closed, others may be independently driven from one another. Although the preferred embodiments of the present invention have been disclosed for illustrative purposes, those skilled in the art will appreciate that various modifications, additions and substitutions are possible, without departing from the scope and spirit of the invention as disclosed in the accompanying claims.
	description	FIG. 1 is a schematic and perspective view for explaining reflection of parallel light impinging on a reflection type integrator having convex cylindrical surfaces. FIG. 2 is a schematic and sectional view of the reflection type integrator having cylindrical surfaces. FIG. 3 is a schematic view for explaining reflection of X-rays at a cylindrical surface of a reflection type integrator having convex cylindrical surfaces. FIG. 4 is a schematic view for explaining an angular distribution of X-rays reflected by a cylindrical surface of a reflection type integrator having cylindrical surfaces. In these drawings, denoted at 5 is a reflection type integrator having convex cylindrical surfaces. An X-ray beam of substantially parallel light emitted from an X-ray light source is projected on the reflection type integrator 5 having a plurality of cylindrical surfaces, and secondary light sources are defined by this integrator. The X-rays emitted from these secondary light sources have an angular distribution of a conical surface shape. A reflector having a focal point placed at the secondary light source position reflects the X-rays to illuminate a mask. For explanation of the function of such a reflection type integrator having cylindrical surfaces, first the action of reflection light in a case where parallel light impinges on one cylindrical surface reflector will be described with reference to FIG. 3. As shown, parallel light is incident on one cylindrical surface at an angle xcex8 with respect to a plane perpendicular to the central axis thereof. If the light ray vector of the projected parallel light is R1=(0, xe2x88x92cos xcex8, sin xcex8) and the vector of a normal to the reflection surface of the cylindrical surface shape is n=(xe2x88x92sin xcex1, cos xcex1, 0), then the light ray vector of the reflection light is R2=(cos xcex8xc3x97sin 2xcex1, cos xcex8xc3x97cos 2xcex1, sin xcex8). Here, if the light ray vector of the reflection light is plotted in a phase space, the result is a circle of a radius cos xcex8 on an X-Y plane as shown in FIG. 4. That is, the reflection light is formed into divergent light of a conical surface shape, and the secondary light source is located at the position of apex of this conical surface. If the cylindrical surface comprises a concave surface, the secondary light source is placed outside the reflection surface. If the cylindrical surface comprises a convex surface, the secondary light source is placed inside the reflection surface. Also, if the reflection surface is limitedly provided by a portion of a cylindrical surface and the central angle thereof is 2xc3x8, then as shown in FIG. 4 the light ray vector of reflection light is arcuate with a central angle 4xc3x8 upon the X-Y plane. Next, a case wherein parallel light is projected on a reflection mirror provided by a portion of a cylindrical surface, wherein a reflection mirror having a focal length f and a focal point placed at the position of this secondary light source, and wherein a mask is placed at the position away from this reflection mirror by a distance f, will be considered. The light emitted from the secondary light source is divergent light and, after it is reflected by the reflection mirror of a focal length f, it is transformed into parallel light. The reflection light here is formed into a sheet beam of an arcuate sectional shape with a central angle 4xc3x8, at a radius fxc3x97cos xcex8. Thus, only an arcuate region upon the mask, having a radius fxc3x97cos xcex8 and a central angle 4xc3x8 can be illuminated. While one cylindrical surface reflection mirror has been explained above, a cylindrical surface integrator such as shown in FIG. 1 will now be considered. That is, as shown, parallel light of a diameter D is projected on a reflection mirror of a wider area, having a number of cylindrical surfaces arrayed in parallel in a one-dimensional direction. If the reflection mirror and the mask are disposed in the same manner as in the foregoing example, the angular distribution of light reflected by the reflection mirror, with a number of cylindrical surfaces arrayed in parallel, is essentially the same as in the preceding case. Thus, an arcuate region on the mask with a radius fxc3x97cos xcex8 and a central angle 4xc3x8 is illuminated. Since the light which impinges on a single point on the mask comes from the whole illumination region on the reflection mirror provided by cylindrical surfaces arrayed in parallel, the angular extension of it is D/f. That is, the numerical aperture of the illumination optical system is D/(2f). If the mask-side numerical aperture of the projection optical system is NAp1, the coherence factor is "sgr"=D/(2fNAp1). Therefore, in accordance with the thickness (size) of the parallel light, an optimum coherence factor "sgr" can be set. Next, embodiments of the present invention which use a reflection type integrator with plural cylindrical surfaces will be explained with reference to some drawings. [Embodiment 1] FIG. 5 is a schematic view of an X-ray reduction projection exposure apparatus according to a first embodiment of the present invention. FIG. 6 is a schematic and perspective view of a reflection type integrator with convex cylindrical surfaces, usable in the first embodiment of the present invention. FIG. 7 is a schematic view for explaining an illumination region on the surface of a mask, in the first embodiment of the present invention. Denoted in these drawings at 1 is a light emission point for X-rays, and denoted at 2 is an X-ray beam. Denoted at 3 is a filter, and denoted at 4 is a first rotational parabolic surface mirror. Denotod at 5 is a reflection type convex cylindrical surface integrator, and denoted at 6 is a second rotatational parabolic surface mirror. Denoted at 7 is a mask, and denoted at 8 is a projection optical system. Denoted at 9 is a wafer, and denoted at 10 is a mask stage. Denoted at 11 is a wafer stage, and denoted at 12 is an arcuate aperture. Denoted at 13 is a laser plasma X-ray light source, and denoted at 14 is a laser collecting optical system. Denoted at 15 is an illumination region on the mask surface, and denoted at 16 is an arcuate region through which the exposure is to be performed. Denoted at 17 is a vacuum chamber. The X-ray reduction projection exposure apparatus of the first embodiment of the preset invention comprises a laser plasma X-ray light source 13, an illumination optical system, a mask 7, a projection optical system 8, a wafer 9, stages 10 and 11 on which the mask or wafer is placed, an alignment mechanism for precisely aligning the positions of the mask and wafer, a vacuum chamber 17 for keeping the optical arrangement as a whole in a vacuum to prevent X-ray attenuation, and an evacuation device, for example. The illumination optical system comprises a first rotational parabolic surface mirror 4, a reflection type convex cylindrical surface integrator 5, and a second rotational parabolic surface mirror 6. The mask 7 comprises a multilayered film reflection mirror on which a transfer pattern is defined by a non-reflective portion, provided by an X-ray absorptive material. The X-ray beam as reflected by the mask 7 is imaged by the projection optical system 8 upon the wafer 9 surface. The protection optical system 7 is so designed that good imaging performance is provided within a narrow arcuate region off the axis. For example, with a reduction magnification of 1:5, good imaging performance is assured with respect to a region on the mask 7 surface at 200 mm off the axis, and to a region on the wafer 9 surface at 40 mm off the axis, with a width of 1 mm. In order that the exposure process is performed only by use of this narrow arcuate region, an aperture 12 having an arcuate opening is disposed just before the wafer 9. For transfer of the pattern on the whole surface of the mask 7 having a rectangular shape, the mask 7 and the wafer 9 are scanningly moved simultaneously, at a predetermined speed ratio. The projection optical system 8 has two multilayered film reflection mirrors, and it serves to project the pattern of the mask 7 onto the wafer 9 in a reduced scale. The reduction magnification corresponds to the scan speed ratio between the mask and the wafer. The projection optical system 8 comprises a telecentric system. The X-ray beam 2 emitted from the light emission point 1 of the laser plasma X-ray source 13 passes a shield filter 3 of the target, for prevention of particle scattering, and it is reflected by the first rotational parabolic surface mirror 4, whereby it is transformed into a parallel beam. This beam is then reflected by the reflection type integrator 5 with convex cylindrical surfaces, whereby a number of secondary light sources are produced. The X-rays from these secondary light sources are reflected by the second rotational parabolic surface mirror 6, and they illuminate the mask 7. Both of the distance from the secondary light source to the second rotational parabolic surface mirror 6 and the distance from the second parabolic surface mirror 6 to the mask 7 are equal to the focal length of the second rotational parabolic surface mirror. Thus, the conditions for Koehler illumination are satisfied. The reflection type convex cylindrical surface integrator 5 comprises a total reflection mirror having a shape that a number of small convex cylindrical surfaces are arrayed one-dimensionally such as shown in FIG. 6. In the sectional shape of the integrator 5, each arcuate portion has a radius of 0.5 mm and a central angle of 30 deg. When parallel light impinges on it, on a plane inside the reflection surface at a distance of 0.25 mm, there is formed a virtual image of linear secondary light sources, arrayed in parallel, that is, of the laser plasma X-ray light source 13. In this embodiment, the parallel X-ray beam has a thickness of 20 mm, and the incidence angle of the parallel X-ray beam upon-the integrator 5 is 85 deg. The second rotational parabolic surface mirror 6, having a focal length f=2300 mm, has its focal point disposed at the position of the secondary light sources, as the linear secondary light sources arrayed in parallel are defined on a plane spaced by 0.25 mm from the reflection surface when parallel light is projected on the integrator 5. Also, the mask 7 is disposed at a distance 2300 mm from the second rotational parabolic surface mirror 6. Light emitted from one point on the secondary light source is divergent light having an angular distribution like a conical surface. It is reflected by the second rotational parabolic surface mirror 6 having a focal length f=2300 mm, and it is transformed into parallel light. Then, as shown in FIG. 7, an arcuate region 16 on the mask 7 having a radius 2300 mmxc3x97cos 85(deg)=200 mm and a central angle 30 deg.xc3x972=60 deg. is illuminated. Here, the numerical aperture of the illumination optical system is 20/(2xc3x972300)=0.0043. If the numerical aperture of the projection optical system is 0.01 on the mask side and 0.05 on the wafer side, the coherence factor is 0.43. On the mask 7 surface, an arcuate region 16 of a radius 200 mm and a central angle 60 deg. is illuminated, and the pattern within this region is projected in a reduced scale onto the resist surface of the wafer 9. If the reduction magnification is 1:5, an arcuate region on the wafer 9 having a radius 40 mm and central angle 60 deg. is illuminated at once. With the scan of the mask 7 and the wafer 9, a square region of 40 mm square, for example, can be exposed with good precision. As described, this embodiment uses a reflection type convex cylindrical surface integrator 5 having a reflection surface provided by a number of small convex cylindrical surfaces arrayed one-dimensionally, by which the region on the mask 7 to be illuminated can be defined with an arcuate shape and, simultaneously, an optimum value for a coherence factor of the illumination optical system can be set. Also, the shape of the illumination region 15 on the mask 7 surface is restricted to the vicinity of the arcuate region 16 with which the exposure process is performed actually. Wasteful illumination of X-rays to a wide area outside the exposure region, such as shown in FIG. 14, is prevented. Thus, the loss of light quantity is reduced, the exposure time can be shortened and throughput can be improved. [Embodiment 2] FIG. 8 is a schematic view of an X-ray reduction projection exposure apparatus according to a second embodiment of the present Invention. FIG. 9 is a schematic and perspective view of a reflection type integrator with concave cylindrical surfaces, usable in the second embodiment of the present invention. Denoted in these drawings at 801 is an undulator X-ray light source, and denoted at 802 is an X-ray beam. Denoted at 803 is a convex surface mirror, and denoted at 804 is a first concave surface mirror. Denoted at 805 is a reflection type integrator with concave cylindrical surfaces, and denoted at 806 is a second concave surface mirror Denoted at 807 is a mask, and denoted at 808 is a projection optical system. Denoted at 809 is a wafer. Denoted at 810 is a mask stage, and denoted at 811 is a wafer stage. Denoted at 812 is an arcuate aperture, and denoted at 817 is a vacuum chamber. The X-ray reduction projection exposure apparatus according to the second embodiment of the present invention comprises an undulator X-ray light source 801, an illumination optical system, a mask 807, a projection optical system 808, a wafer 809, stages 810 and 811 having the mask or wafer placed thereon, an alignment mechanism for precisely aligning the positions of the mask and wafer, a vacuum chamber for keeping the optical arrangement as a whole in a vacuum for prevention of X-ray attenuation, and an evacuation device, for example. The illumination optical system of this embodiment comprises an undulator X-ray light source 801, a convex surface mirror 803, a first concave surface mirror 804, a reflection type concave cylindrical surface integrator 805, and a second concave surface mirror 806. The mask 807 comprises a multilayered film reflection mirror on which a transfer pattern is defined by a non-reflective portion, provided by an X-ray absorptive material. The X-ray beam as reflected by the mask 807 is imaged by the projection optical system 808 upon the wafer 809 surface. The projection optical system 808 is so designed that good imaging performance is provided in a narrow arcuate region off the axis. In order that the exposure process is performed only by use of this narrow arcuate region, an aperture 812 having an arcuate opening is disposed just before the wafer 809. For transfer of the pattern on the whole surface of the mask 807 having a rectangular shape, the mask 807 and the wafer 809 are scanningly moved simultaneously. The projection optical system 808 has three multilayered film reflection mirrors, and it serves to project the pattern of the mask 807 onto the wafer 809 in a reduced scale. The X-ray beam 802 emitted from the light emission point of the undulator X-ray light source 801 is a narrow and substantially parallel beam. It is reflected by the convex surface mirror 803 and the first concave surface mirror 804, whereby it is transformed into a thick parallel beam. This beam is reflected by the reflection type concave cylindrical surface integrator 805 of the structure that concave cylindrical surfaces with multilayered films for increased X-ray reflectivity are arrayed in parallel. By this, a number of secondary light sources are produced. Light emitted from a single point on the secondary light source is divergent light of a conical surface shape and, after being reflected by the second concave surface mirror 806, it is transformed into parallel light. Then, an arcuate region on the mask 807 is illuminated. As described above, this embodiment uses a reflection type concave cylindrical surface integrator 805 having a number of small concave cylindrical surfaces arrayed one-dimensionally, by which the region on the mask 807 to be illuminated can be made arcuate and, additionally, an optimum value for the coherence factor of the illumination optical system can be set. Also, the shape of the illumination region on the mask 807 surface is restricted to an arcuate region with which the exposure is to be done actually. Wasteful X-ray illumination to those areas outside the exposure region is prevented. Thus, the loss of light quantity is reduced, the exposure time can be shortened and the throughput can be improved. The X-ray illumination optical system and X-ray reduction exposure apparatus described above assure, with use of a reflection type integrator having a reflection mirror of a wide area provided by a number of cylindrical surfaces arrayed in parallel, illumination of only an arcuate region on a mask. Also, it enables setting the numerical aperture of the illumination system to provide an optimum coherent factor "sgr". The shape of the illumination region on the mask is restricted to an arcuate region with which the exposure is to be done actually, and wasteful X-ray illumination to those areas other than the exposure region is prevented. Thus, loss of light quantity is reduced, the exposure time can be shortened and the throughput can be enhanced. The reflection surface of the reflection type integrator may be provided with a multilayered film, to provide higher X-ray reflectivity. [Embodiment of a Device Manufacturing Method] Next, an embodiment of a device manufacturing method for producing semiconductor devices, for example, which uses an exposure apparatus such as described above, will be explained. FIG. 10 is a flow chart of a procedure for the manufacture of microdevices such as semiconductor chips (e.g., ICs or LSIs), liquid crystal panels, and CCDs, for example. Step 1 is a design process for designing a circuit of a semiconductor device. Step 2 is a process for making a mask on the basis of the circuit pattern design. Step 3 is a process for preparing a wafer by using a material such as silicon. Step 4 is a wafer process which is called a pre-process wherein, by using the so prepared mask and wafer, circuits are practically formed on the wafer through lithography. Step 5 subsequent to this is an assembling step which is called a post-process wherein the wafer having been processed by step 4 is formed into semiconductor chips. This step includes an assembling (dicing and bonding) process and a packaging (chip sealing) process. Step 6 is an inspection step wherein an operation check, a durability check and so on for the semiconductor devices provided by step 5, are carried out. With these processes, semiconductor devices are completed and they are shipped (step 7). FIG. 11 is a flow chart showing details of the wafer process. Step 11 is an oxidation process for oxidizing the surface of a wafer. Step 12 is a CVD process for forming an insulating film on the wafer surface. Step 13 is an electrode forming process for forming electrodes upon the wafer by vapor deposition. Step 14 is an ion implanting process for implanting ions to the wafer. Step 15 is a resist process for applying a resist (photosensitive material) to the wafer. Step 16 is an exposure process for printing, by exposure, the circuit pattern of the mask on the wafer through the exposure apparatus described above. Step 17 is a developing process for developing the exposed wafer. Step 18 is an etching process for removing portions other than the developed resist image. Step 19 is a resist separation process for separating the resist material remaining on the wafer after being subjected to the etching process. By repeating these processes, circuit patterns are superposedly formed on the wafer. With these processes, high density microdevices can be manufactured. While the invention has been described with reference to the structures disclosed herein, it is not confined to the details set forth and this application is intended to cover such modifications or changes as may come within the purposes of the improvements or the scope of the following claims.
	summary
	abstract	A method and system for external alternate suppression pool cooling for a Boiling Water Nuclear Reactor (BWR) that does not breach the Mark I primary containment. The external cooling system may include a heat sink fluidly coupled to cooling coils surrounding the suppression pool. Cool water may be pumped through the cooling coils without the need for normal plant electrical power, which is ideal during a plant emergency. The cooling system may also be operated and controlled from a remote location to protect the safety of plant personnel.
	abstract	In an X-ray detection device having an X-ray detection element array of photo diodes for multi channels arranged with a predetermined pitch on a substrate, a plurality of scintillators adhered onto respective photo diodes, and isolation walls disposed between neighboring scintillators for respective channels an isolation band for isolating the respective channels is provided between respective light receiving portions of the photo diode array for the multi channels, and the surface of the isolation band is covered by a material having light absorbing property, and the width of the region which is covered by the material having light absorbing property is equal to a region occupied by the width of the isolation wall provided between neighboring scintillators for the respective channels. Thereby, light leakage between the neighboring elements in a multi element X-ray detection device of scintillators and a silicon photo diode array is prevented to provide an X-ray detection device suitable for a multi slice type X-ray CT apparatus, in which the S/N ratio and spatial resolution of the device are enhanced by effectively guiding the light induced in the scintillators into the silicon photo diode array. An X-ray CT apparatus using such X-ray detection device can be provided.
045444994	description	The following examples are presented. Unless otherwise specified all solutions are aqueous solutions, the "aqueous ammonium hydroxide" or "NH.sub.4 OH" wherever used in the Examples contains about 28% NH.sub.3, ppm means parts per million parts of solution, ppb means parts per billion parts of solution, ppt mean parts per trillion parts of solution, all parts and percentages are on a weight bases, all temperatures are given in degrees Centigrade, and anion exchange tests were carried out at room temperature and at a pH of 6 unless otherwise indicated. EXAMPLE 1 This example illustrates the preparation of the porous glass that is used in the subsequent examples. In the subsequent examples, unless otherwise specified, the porous glass that is used is in the form of cylinders or rods 6 to 9 mm in diameter and one to several centimeters in length. The porous glass is formed by the method disclosed hereinabove; that is, a mixture of powders of silica, boric acid, sodium carbonate and potassium carbonate is prepared in such proportions that yield a glass nominally comprising 3.5 mol percent Na.sub.2 O, 3.5 mol percent K.sub.2 O, 33 mol percent B.sub.2 O.sub.3 and 60 mol percent SiO.sub.2. The mixture is heated in a Pt crucible up to 1400.degree. C. in an electric furnace and thus is melted into a molten glass which is pulled into rods about 8 mm in diameter and cut to about 2.5 cm long. After cooling, the glass is phase-separated by heat treating at 550.degree. C. for 2 hours and then is leached in a 3N HCl bath at 95.degree. C. for three days. Phase-separation results in two phases; one, a high silica phase and a low silica phase comprising the remaining silica, boron trioxide and alkali metal oxide. Leaching removes the boron-rich phase leaving behind a porous glass comprising about 95 mol percent SiO.sub.2 and about 5 mol percent B.sub.2 O.sub.3 and having interconnected pores and at least about 3 mol percent silicon-bonded hydroxyl groups. Subsequent rinsing in water yields a porous glass preform ready for use in the following examples. EXAMPLE 2 In this example, there is described the use of an organofunctionalsilane possessing a single-NH.sub.2 functional group, namely, the gamma-aminopropyltriethoxysilane to alter the surface characteristics of the porous glass so as to give it anion exchange capability when hydrated. Six 1" porous glass rods prepared as described in Example 1 were soaked in an aqueous solution containing 2% gamma-aminopropyltriethoxysilane by weight of the solution at 5.degree. C. for 5 hours. This aqueous solution was prepared by first forming a dilute aqueous ammonium hydroxide solution having a pH of about 9, cooling it to a temperature of about 5.degree. C. and then introducing the above-mentioned silane. The treated porous glass rods were then dried under vacuum at 5.degree. C. for 18 hours, allowed to warm to room temperature, and finally were heated from room temperature to 200.degree. C. in order to react the silicon-bonded ethoxy groups of the silane with the silicon-bonded hydroxy groups of the glass to form .tbd.SiOSi.tbd. bonds between the glass and the silane, thus bonding the silane to the glass surface. Two anion-containing test media were prepared comprising 100 ml of an aqueous solution containing 56.0 ppm CrO.sub.4.sup.-2 and a 100 ml of an aqueous solution containing 41.8 ppm MoO.sub.4.sup.-2. Three glass rods treated as described above were immersed in the chromate solution and three were immersed in the molybdate solution. The decreases of CrO.sub.4.sup.-2 and MoO.sub.4.sup.-2 anions in the respective solutions due to anion-exchange into the glass rods were measured against soaking time. The results are shown in Table 3 below. TABLE 3 ______________________________________ Soaking Time CrO.sub.4.sup.= MoO.sub.4.sup.= (hrs) Concentration (ppm) Concentration (ppm) ______________________________________ 0 56 41.8 1 54.5 35 2 53 28 3 52 21 11 44.5 11 24 44 6 ______________________________________ These results illustrate the effectiveness of the treated porous glass rods in removing anions from highly dilute aqueous solutions and illustrates the special effectiveness with respect to the molybdate solution. The anion exchange capacity of the treated porous glass rods for the chromate anion would be capable of removing radioactive chromate anions from very large volumes of radioactive coolants (typically containing 4.times.10.sup.-9 ppm of Cr as CrO.sub.4). For example, it would be capable of removing chromate anions from 7.times.10.sup.8 cc of coolant per cc of treated porous glass on a calculated basis. EXAMPLE 3 The procedure of Example 2 was repeated except that: (i) the organofunctionalsilane had one --NH.sub.2 group and one .dbd.NH group; specifically, N-beta-aminoethyl-gamma-aminopropyltrimethoxysilane was used here to change the surface characteristics of the porous glass; (ii) the silane concentration in the glass rod treatment step was 4% instead of 2%; and (iii) the anion concentrations of the anion-containing media were initially 52.4 ppm CrO.sub.4.sup.-2 and 45.4 ppm MoO.sub.4.sup.-2, respectively. The results of the anion exchange test are given in Table 4 below. TABLE 4 ______________________________________ Soaking Time CrO.sub.4.sup.= MoO.sub.4.sup.= (hrs) Concentration (ppm) Concentration (ppm) ______________________________________ 0 52.4 45.4 1 43 19 2 41 10 4 34.5 4 24 36 4.5 ______________________________________ These results illustrate the effectiveness of the treated porous glass rods in removing anions from highly dilute aqueous solutions and illustrate the special effectiveness of the treated porous glass rods in respect to the molybdate solution. EXAMPLE 4 This example illustrates the treatment of porous glass which is provided with anion exchange capability by hydrous zirconium bonded through oxy groups to silicon of the glass. Two 3" porous glass rods prepared as described in Example 1 were immersed in an 11.7% Zr(NO.sub.3).sub.4.5H.sub.2 O aqueous solution at room temperature for 17 hours thus allowing the Zr(NO.sub.3).sub.4 to diffuse inside the pores of the glass. The stuffed rods were then transfered to an oven at 100.degree. C. for 11/2 hours to evoke precipitation of the Zr salt by evaporation of the water. Finally the rods were heated to 200.degree. C. under vacuum to decompose the nitrate within the glass pores into zirconium oxide which hydrates in the presence of water to impart anionic exchange capability. It is believed that the hydrated zirconium atoms bonded to each other in the form of crystals and that some of the zirconium atoms are bonded to silicon of the glass rod through divalent oxygen linkages. Two anion-containing test media were prepared comprising 100 ml of an aqueous solution of 56.0 ppm CrO.sub.4.sup.-2 and 100 ml of an aqueous solution of 41.8 ppm MoO.sub.4.sup.-2. One treated rod was immersed in the chromate solution to remove CrO.sub.4.sup.-2 therefrom and the other rod was immersed in the molybdate solution to remove MoO.sub.4.sup.-2 ions therefrom. The results are given in Table 5 below. TABLE 5 ______________________________________ Soaking Time CrO.sub.4.sup.= MoO.sub.4.sup.= (hrs) Concentration (ppm) Concentration (ppm) ______________________________________ 0 56 41.8 1 48.5 40 2 42.5 33.5 4 26 27 11 15 16 24 8 10 ______________________________________ These results show that the hydrated zirconium oxide treated porous glass rods are highly efficient in removing chromate and molybdate anions from very dilute solutions containing same. These rods were heated to 850.degree. C. to collapse the pores thus permanently fixating the exchanged anions (CrO.sub.4.sup.= and MoO.sub.4.sup.=) into the glass structure. EXAMPLE 5 The procedure of Example 4 was repeated except that: Hydrous oxides of lead instead of zirconium were impregnated into the porous glass by molecular stuffing with Pb(NO.sub.3).sub.2, then precipitating the salt at 100.degree. C., and finally decomposing the nitrate at 500.degree. C. and then hydrating. The concentration of the aqueous stuffing solution was 45% Pb(NO.sub.3).sub.2 at 95.degree. C. The results of removal by anion exchange of the anions from the anion-containing test media are given in Table 6 below. TABLE 6 ______________________________________ Soaking Time CrO.sub.4.sup.= MoO.sub.4.sup.= (hrs) Concentration (ppm) Concentration (ppm) ______________________________________ 0 56 42 1 48.5 39 2 47 36 4 46 36 11 43.5 33.5 24 41 31 ______________________________________ These results show that hydrated lead oxide treated porous glass rods are effective in removing chromate and molybdate anions from dilute solutions containing same. EXAMPLE 6 This example illustrates the anchoring of an insoluble salt moiety, namely --OZr(OH).sub.3 to silicon of porous glass and then making use of the zirconium-bonded OH groups to ion exchange with other anions. A 2" porous glass rod prepared as described in Example 1 was immersed in a solution containing 14 g NaNO.sub.3, 12 ml NH.sub.4 OH and 38 ml H.sub.2 O at room temperature for 17 hours to exchange the protons of the silicon-bond hydroxyl groups on the glass surface for Na ions in the ammonia base solution. The rod was washed afterwards to remove any excess Na.sup.+. The washed rod was then soaked in a 17% Zr(NO.sub.3).sub.4.5H.sub.2 O aqueous solution for 24 hours at room temperature to exchange Zr.sup.+4 for Na.sup.+. Finally, the Zr(NO.sub.3)-exchanged rod was immersed in a 24% NH.sub.4 OH solution at room temperature for 17 hours to replace the NO.sub.3 groups with the OH groups of the ammonia solution. Subsequently, the rod was washed free of excess ammonia and was immersed in a chromate anion exchange medium initially containing 13.1 ppm CrO.sub.4.sup.-2. The decrease of CrO.sub.4.sup.-2 ions in the solution due to ion-exchange vs. soaking time is shown in Table 7 below. TABLE 7 ______________________________________ Soaking Time CrO.sub.4.sup.= (hrs) Concentration (ppm) ______________________________________ 0 13.1 4 12 24 11 ______________________________________ These results show the anionic porous glass rods of this Example to be effective in removing anions from dilute solutions containing same and are capable of treating very large volumes of dilute radioactive coolants to remove radioactive anions therefrom. EXAMPLES 7-11 The procedures described for Examples 2 through 6 are respectively carried out in Examples 7 through 11 except that the chromate and molybdate anions used in the test media are radioactive; otherwise all steps, proportions, materials and conditions are the same. The concentrations of radioactive anions chemically bound in the final glass product are essentially the same as those concentrations correspondingly given in Tables 3-7. EXAMPLE 12 This example illustrates a method for treating primary coolant from a pressurized water nuclear reactor plant. A mixture of powders of silica, boric acid, sodium carbonate and potassium carbonate is prepared in such proportions that yield a glass comprising 3.5 mol percent Na.sub.2 O, 3.5 mol percent K.sub.2 O, 33 mol percent B.sub.2 O.sub.3 and 60 mol percent SiO.sub.2. The mixture is heated in a platinum crucible up to 1400.degree. C. in an electric furnace to produce a molten glass which is pulled into rods about 8 mm in diameter. The glass rods are cooled and the glass is phase-separated by heat treating at about 550.degree. C. for about 110 minutes. The rods are then crushed to form a powder which is sieved through a 32 mesh screen onto a 150 mesh screen. The glass particles collected on the 150 mesh screen are leached in 3NHCl at about 80.degree. C. for about 6 hours to remove the boron-rich phase and leave behind a porous glass comprising about 95 mol percent SiO.sub.2 and about 5 mol percent B.sub.2 O.sub.3. The porous glass has interconnected pores and contains at least about 5 mol percent silicon-bonded hydroxyl groups. The glass particles are then rinsed in deionized water until the rinse water reaches a pH of about 7. The porous glass powder is then immersed in an approximate 3.2 molar lithium nitrate-ammonium hydroxide aqueous solution (1 part ammonium hydroxide to 3 parts water) for three days and then is rinsed in water until the pH of the rinse water is reduced to about 8. The resulting powder is then placed into a Vycor glass* tube plugged with a filter at the bottom to prevent the powder from escaping, thus forming an ion exchange column. A radioactive primary coolant from a pressurized water nuclear reactor plant utilizing UO.sub.2 fuel clad in stainless steel (containing 4.9 weight percent .sup.235 U) is passed through the column. The primary coolant has the composition of 100 ppm boron, 1 ppm lithium, about 100 ppb silica and the radionucleides listed in Table 8 below which lists the radionuclide, the probable source, the probable form and the average concentration in microcuries per milliliter. FNT *Vycor brand silica glass No. 7913 made by Corning Glass Works and containing 96 wt. % silica and 4 wt. % B.sub. 2 O.sub.3. TABLE 8 ______________________________________ Average Average Radio- Probable Probable Concentra- Concentra- nuclide Source.sup.a Form.sup.b tion (uCi/ml) tion (ppb) ______________________________________ 3.sub.H (1),(2) Water, gas 2.4 0.249 14.sub.C 1.2 .times. 10.sup.-5 2.69 .times. 10.sup.-3 24.sub.Na (1) Cation 1.9 .times. 10.sup.-2 2.18 .times. 10.sup.-6 32.sub.p 3.3 .times. 10.sup.-5 1.16 .times. 10.sup.-8 35.sub.S 3 .times. 10.sup.-6 7.08 .times. 10.sup.-8 51.sub.Cr (1) Anion 3.7 .times. 10.sup.-4 4.02 .times. 10.sup.-6 54.sub.Mn (1) Cation, s 2.7 .times. 10.sup.-4 3.38 .times. 10.sup.-5 55.sub.Fe (1) Cation, s 1.9 .times. 10.sup.-4 7.6 .times. 10.sup.-5 59.sub.Fe (1) Cation, s 1.0 .times. 10.sup.-5 2.03 .times. 10.sup.-7 57.sub.Co (1) Cation, s 1.2 .times. 10.sup.-6 1.42 .times. 10.sup.-7 58.sub.Co (1) Cation, s 4.7 .times. 10.sup.-4 1.48 .times. 10.sup.-5 60.sub.Co (1) Cation, s 7.7 .times. 10.sup.-5 6.81 .times. 10.sup.-5 63.sub.Ni (1) Cation, s 8.0 .times. 10.sup.-6 1.30 .times. 10.sup.-4 64.sub.Cu (1) Cation, anion, s 5.4 .times. 10.sup.-4 1.41 .times. 10.sup.-7 89.sub.Sr (2) Cation 2.8 .times. 10.sup.-6 9.93 .times. 10.sup.-8 90.sub.Sr (2) Cation 4 .times. 10.sup.-7 2.84 .times. 10.sup.-6 91.sub.Sr (2) Cation 9.8 .times. 10.sup.-5 2.76 .times. 10.sup.-8 90.sub.Y (2) s 91.sub.Y (2) s 92.sub.Y (2) s 95.sub.Zr (1),(2) s 1.7 .times. 10.sup.-5 8.06 .times. 10.sup.-7 95.sub.Nb (1),(2) s 1.9 .times. 10.sup.-5 4.83 .times. 10.sup.-7 99.sub.Mo (1),(2) Anion 1.2 .times. 10.sup.-4 2.54 .times. 10.sup.-7 103.sub.Ru (2) s 0 106.sub.Ru (2) s 0 122.sub.Sb (1) s 1.0 .times. 10.sup.-4 2.62 .times. 10.sup.-7 124.sub.Sb (1) s 2.0 .times. 10.sup.-5 1.16 .times. 10.sup.-6 132.sub.Te (2) Anion, s 131.sub.I (2) Anion 4.6 .times. 10.sup.-5 3.71 .times. 10.sup.-6 132.sub.I (2) Anion 133.sub.I (2) Anion 6.2 .times. 10.sup.-4 5.5 .times. 10.sup.-7 135.sub.I (2) Anion 9 .times. 10.sup.-4 2.60 .times. 10.sup.-7 134.sub.Cs (2) Cation 4.7 .times. 10.sup.-7 3.62 .times. 10.sup.-7 136.sub.Cs (2) Cation 0 137.sub.Cs (2) Cation 1.1 .times. 10.sup.-6 1.26 .times. 10.sup.-5 140.sub.Ba (2) Cation 4.7 .times. 10.sup.-6 6.45 .times. 10.sup.-8 141.sub.Ce (2) Anion, s 0 143.sub.Ce (2) Anion, s 0 144.sub.Ce (2) Anion, s 0 143.sub.Pr (2) Anion, s 110m.sub.Ag (1) s 1.2 .times. 10.sup.-5 2.52 .times. 10.sup.-6 181.sub.Hf (1) s 6 .times. 10.sup.-6 3.70 .times. 10.sup.-7 182.sub.Ta (1) s 2.5 .times. 10.sup.-5 4.01 .times. 10.sup.-6 183.sub.Ta (1) s 6.2 .times. 10.sup.-5 4.34 .times. 10.sup.-7 185.sub.W (1) s 1.2 .times. 10.sup.-5 1.28 .times. 10.sup.-6 187.sub.W (1) s 3.7 .times. 10.sup.-4 5.30 .times. 10.sup.-7 85m.sub.Kr (2) Gas 85.sub.Kr (2) Gas 88.sub.Kr (2) Gas 133.sub.Xe (2) Gas 8.9 .times. 10.sup.-5 4.78 .times. 10.sup.-8 135.sub.Xe (2) Gas 9 .times. 10.sup.-5 3.54 .times. 10.sup.-8 ______________________________________ .sup.a (1) Neutron activation products of nuclides from fuel cladding, construction material, and water. (2) Leakage from fuel. Mostly fission products. .sup.b Gas: presumably as dissolved gas. s: insoluble solids. The radioactive cations listed in Table 8 cation-exchange with lithium cations bonded to silicon through oxy groups in the porous glass thereby binding the radionuclides to the porous glass through said silicon-bonded oxy groups and releasing lithium cations to the coolant solution. The insoluble radioactive solids in the coolant also filter out on the external surfaces of the porous glass particles. Additional porous glass particles can be added to increase the filtering capacity of the ion exchange column as the insoluble solids build-up in the column. Under some conditions, mainly dependent on existing governmental regulations, the porous silicage glass containing bound cationic radionuclides may be disposed and/or buried or suitably containerized often times in steel and/or concrete or mixed with cement powder or urea-formaldehyde formulations and "set" therein and thereafter disposed and/or buried. The particulate porous glass can be heated to collapse the pores thereof as described herein. The anionic radionuclides are not substantially removed in the above-mentioned column and pass with the coolant through the column. The anionic radionuclides are subsequently removed by passing the coolant through a glass column packed with any one of the porous glass anion exchangers described in Examples 2-6. The glass column is prepared as follows: An open porous tube is prepared by pulling a glass tube of the same composition as described in Example 1 and phase-separated and leached as in Example 1, and having an outside diameter of 10 mm and a wall thickness of .about.1 mm. The porous tube is then soaked in a solution saturated with CsNO.sub.3 with enough NH.sub.4 OH to give a pH of 10 for 18 hrs, and washed in room temperature water until a pH of 7 is obtained. The Cs exchanged tube is subsequently dried under vacuum and is heated from room temperature to 600.degree. C. at 15.degree. C./hr and from 600.degree. C. to 870.degree. C. at 50.degree. C./hr to collapse the pores. When the porous anion exchange glass becomes loaded with anionic radionuclides, the entire column containing the loaded porous anion exchange glass is removed from the system and a fresh column is substituted. The loaded column is held in a safe location for three months to allow the I.sup.131 to completely decay, a precaution taken to avoid evaporation of I.sub.131 during subsequent heat treatments. Thereafter, the porous glass particles can be heated to collapse the pores thereof and, if desired, the column can be heated to collapse the glass tube around the particles thereby enveloping the filtered solids and the glass particles containing the cationic and anionic radio-nuclides within the glass column. While the glass column may crack because of differential thermal contraction, it still contains and further immobilizes the radioactive materials and forms a product that is many times more durable than cement or metal drums heretofore used. There is thus provided a durable package of concentrated radionuclides which is highly resistant to leaching by water or other fluids. As illustrated in Example 12, liquid radwaste that must be satisfactorily treated and disposed of can be highly dilute. The volume of dilute radwaste treated with a given amount of ion exchange porous glass or silica gel pursuant to this invention can be practically unlimited before all the available exchange sites (i.e. silicon-bonded alkali metal oxy, Group Ib, metal oxy, ammonium oxy, hydroxy ammonium organosiloxy, hydrous polyvalent metal oxy and carboxyorganosiloxy groups) in the porous silicate glass or silica gel are filled by radioactive cations. For Example, the weight of the dilute liquid radwaste described in Example 12 that could be expected to be treated before exhausting all exchange sites would be of the order of 10.sup.9 or more times the weight of the ion exchange porous glass or silica gel employed. Futhermore, it could be expected that other parts of the system would require overhaul, e.g., repair or replacement of pumps or piping or other equipment, before the ion exchange silicate glass or silica gel becomes exhausted. Consequently, it is quite possible, if not probable, that the radioactivity of the resulting porous glass or silica gel when disposed of may never reach 1 millicurie or even 1 microcurie per cc. of the glass or silica gel. In the absence of malfunction requiring overhaul of the other parts of the radwaste treatment system, 100 or less to 10.sup.9 or more, preferably 100 to 10.sup.6, weight parts of radwaste can be treated for each weight part of porous silicate glass or silica gel having silicon-bonded anion and/or cation exchange groups pursuant to this invention. For reasons of safety all simulated radwaste solutions used in the Examples were actually non-radioactive; however, radioactive solutions of the same kind can be substituted and concentrated and encapsulated in accordance with the foregoing Examples. EXAMPLE 13 In this example, there is described the use of particles of cation-exchange porous glass possessing a carboxyl functional group, namely ##STR14## groups, bonded to silicon of porous silicate glass on the internal surfaces of the pores thereof. Porous glass of this type is purchased from the Pierce Chemical Company, POB 117, Rockford, Ill. 61105. The glass particles containing the above-mentioned functional groups are immersed in an aqueous solution containing 10 ppm radioactive strontium cations (2.35 mg strontium per 100 ml H.sub.2 O) at about 25.degree. for about three days while occasionally stirring the solution. After this period of soaking the particles are removed and dried at room temperature. After the soaking period the solution is analyzed by atomic absorption for strontium and has a lower concentration of strontium illustrating the effectiveness of the carboxy organosiloxy group containing glass in removing radioactive cations from aqueous solutions containing same. EXAMPLE 14 This example illustrates the treatment of porous glass which is provided with anion exchange capability by hydrous titanium bonded through oxy groups to silicon of the glass as well as hydrous titanium oxides which are molecular stuffed in the pores of a glass matrix. Six 2" long porous glass rods prepared as described in Example 1 were immersed in a solution of 18 g TiO.sub.2 and 100 ml of 3N HNO.sub.3 at room temperature for about 65 hours thus allowing the TiO.sub.2 to become Ti(NO.sub.3).sub.4 and to diffuse inside the pores of the glass. Four of the resulting six stuffed rods were then transferred to an oven at 200.degree. C. for 2 hours under vacuum to dry the rods by evaporation of the water as well as to decompose the titanium nitrates residing in the pores of the glass. Two other rods were put into NH.sub.4 OH for 2 hours at room temperature and then evacuated for 2 hours at room temperature to dry them and subsequently were heated gradually from 200.degree. C. to 400.degree. C. to decompose the nitrates and precipitate Ti in the oxide form. All six rods were black indicating the presence of some reduced Ti.sup.+3 (e.g. Ti.sub. 2 O.sub.3). The titanium oxides within the pores hydrate upon contact with water (e.g., from the atmosphere or from the aqueous radwaste solution or otherwise) to impart anion exchange capability. It is believed that some of the hydrated titanium atoms are bonded to each other in the form of crystals and that some of the titanium atoms are bonded to silicon of the glass rods through oxy linkages. Two anion-containing test media were prepared comprising 35 ml of an aqueous solution of 5.5 ppm CrO.sub.4.sup.-2 and 35 ml of an aqueous solution of 31.7 ppm MoO.sub.4.sup.-2. Two treated rods from the first group were immersed in the chromate solution to remove CrO.sub.4.sup.-2 therefrom and the other two rods from the first group were immersed in the molybdate solution to remove MoO.sub.4.sup.-2 ions therefrom. The results are given in Table 9 below. TABLE 9 ______________________________________ Soaking Time CrO.sub.4.sup.= MoO.sub.4.sup.= (hrs.) Concentration (ppm) Concentration (ppm) ______________________________________ 0 5.5 31.7 1 4.6 14.8 2 3.7 7.2 6 2.2 2.7 19 0.8 1.4 ______________________________________ Similarly, one treated rod from the second group (of two rods) was immersed in an identical chromate solution to remove CrO.sub.4.sup.-2 therefrom and the other rod from the second group was immersed in an identical molybdate solution to remove MoO.sub.4.sup.-2 therefrom. The results are given in Table 10 below. TABLE 10 ______________________________________ Soaking Time CrO.sub.4.sup.= MoO.sub.4.sup.= (hrs.) Concentration (ppm) Concentration (ppm) ______________________________________ 0 5.5 31.7 1 5.3 29.9 2 4.6 27.3 6 3.7 21.4 19 1.7 11.2 ______________________________________
042954010	summary	BACKGROUND OF THE INVENTION The invention relates generally to the field of disposal of highly radioactive materials, and, more particularly, to a method and apparatus for reducing the volume of radioactive rectangular tubular fuel channels stored under water. In one type of boiling water nuclear reactor (BWR), there is a fuel assembly consisting of fuel rods surrounded by a fuel channel. The channel is a 5.278 inch square tube, approximately fourteen feet long, with open ends and made of zircalloy. The channels typically have a wall thickness of 0.080, 0.100 or 0.120 inch. There are a large number of these fuel assemblies in a BWR reactor, and one-third of these assemblies are normally replaced each year. Even though the fuel channels are normally reused after the fuel rods are removed, for various reasons it has been determined that in some cases, they cannot be resued, but must be replaced, thereby requiring these highly radioactive fuel channels to be disposed of in a safe and economical manner. These used fuel channels are highly radioactive for two reasons. First, the zircalloy metal itself has become somewhat radioactive during operation of the nuclear reactor, and second, there is formed on the outside of the channel a crust or crud which itself is also highly radioactive. The present method of disposing of such radioactive fuel channels is to place them in a special heavy metal shipping cask, and transport them to one of the five federal disposal grounds in the country where they are then buried. However, the rental for these casks is quite expensive, and it would be highly desirable to reduce the effective volume of these tubular fuel channels thereby to increase the number of channels which can be shipped in each cask. There are presently hundreds of these fuel channels stored in water-filled fuel pools at numerous BWR-nuclear power plants. Due to the radiation levels of these fuel channels, they must be handled under water, thus posing one problem. Another problem is that the handling operation must result in as little debris as possible, since such debris is radioactive and will contaminate the pool water. One suggestion has been to crush the fuel channels in order to reduce their volume, but this procedure would result in a great deal of debris in the form of flaked-off radioactive crust dislodged from the channel during the crushing operation. In addition, the volume reduction would not be optimum using this method of compaction. SUMMARY OF THE INVENTION Therefore, the broad object of this invention is to provide a method and apparatus for disposing of these fuel channels, which are stored under water, by minimizing the effective volume of each fuel channel, with a minimum of radioactive debris, such that each shipping cask can accommodate a much larger number of fuel channels than would otherwise be possible. A more specific object of this invention is to cut under water a radioactive rectangular tube into four side plates which are then nested or stacked as they are placed in a shipping cask which is also under water. Another object of the invention is to provide an apparatus into which a rectangular fuel channel may be placed under water, such apparatus being provided with four roller cutters which travel along the four longitudinal edges or corners of the fuel channel to cut the fuel channel simultaneously and efficiently into four side plates which are then placed in a shipping cask, thereby greatly increasing the total number of fuel channels which may be accommodated by each shipping cask.
	claims	1. An electrical distribution system for a nuclear power plant, comprising:at least one primary alternating current (AC) power source;a first plurality of AC loads of a plurality of nuclear reactor systems of the nuclear power plant, each of the first plurality of AC loads comprising a critical electrical load of the plurality of nuclear reactor systems that fails to a safety position based on a loss of electrical power from the primary AC power source;a first AC power bus that is electrically coupled to the at least one primary AC power source, the first plurality of AC loads, and a first critical battery system that comprises one or more non-qualified battery sources;a second plurality of AC loads of the plurality of nuclear reactor systems, each of the second plurality of AC loads comprising a non-critical electrical load of the plurality of nuclear reactor systems; anda second AC power bus that is electrically coupled to the at least one primary AC power source, the second plurality of AC loads, and a non-critical battery system that comprises one or more qualified battery sources. 2. The electrical distribution system of claim 1, wherein the first plurality of AC loads comprise engineered safety feature (ESF) electrical loads, and the one or more non-qualified battery sources of the first critical battery system comprise valve regulated lead acid (VRLA) batteries. 3. The electrical distribution system of claim 1, wherein the second plurality of AC loads comprise active post-accident monitoring (PAM) electrical loads and common electrical loads, and the one or more qualified battery sources comprise vented lead acid (V LA) batteries. 4. The electrical distribution system of claim 3, wherein the non-critical battery system comprises:a first battery train electrically coupled to a first channel of the second AC power bus; anda second battery train electrically coupled to a second channel of the second AC power bus, each of the first and second battery trains comprising one or more qualified battery sources that comprise VLA batteries. 5. The electrical distribution system of claim 4, further comprising a third battery train electrically coupled to both of the first and second channels of the second AC power bus, the third battery train comprising one or more qualified battery sources that comprise VLA batteries. 6. The electrical distribution system of claim 1, wherein the first critical battery system is sized to supply AC power to the first plurality of AC loads for about 24 hours based on a loss of electrical power from the primary AC power source. 7. The electrical distribution system of claim 1, wherein the non-critical battery systems is sized to supply AC power to the second plurality of AC loads for about 72 hours based on a loss of electrical power from the primary AC power source. 8. The electrical distribution system of claim 1, further comprising:a third AC power bus that is electrically coupled to the primary AC power source, the first plurality of AC loads, and a second critical battery system that comprises one or more non-qualified battery sources. 9. The electrical distribution system of claim 1, wherein each of the nuclear power systems comprises a passively cooled modular nuclear reactor. 10. A method for providing power to a nuclear power plant, comprising:providing at least one primary alternating current (AC) power source;providing a first plurality of AC loads of a plurality of nuclear reactor systems of the nuclear power plant, each of the first plurality of AC loads comprising a critical electrical load of the plurality of nuclear reactor systems that fails to a safety position based on a loss of electrical power from the primary AC power source;electrically coupling a first AC power bus to the primary AC power source, the first plurality of AC loads, and a first critical battery system that comprises one or more non-qualified battery sources;providing a second plurality of AC loads of the plurality of nuclear reactor systems, each of the second plurality of AC loads comprising a non-critical electrical load of the plurality of nuclear reactor systems; andelectrically coupling a second AC power bus to the second plurality of AC loads and a non-critical battery system that comprises one or more qualified battery sources. 11. The method of claim 10, wherein the first plurality of AC loads comprise engineered safety feature (ESF) electrical loads, and the one or more non-qualified battery sources of the first critical battery system comprise valve regulated lead acid (VRLA) batteries. 12. The method of claim 10, wherein the second plurality of AC loads comprise active post-accident monitoring (PAM) electrical loads and common electrical loads, and the one or more qualified battery sources comprise vented lead acid (VLA) batteries. 13. The method of claim 12, further comprising:electrically coupling a first battery train of the non-critical battery system to a first channel of the second AC power bus; andelectrically coupling a second battery train of the non-critical battery system to a second channel of the second AC power bus, each of the first and second battery trains comprising one or more qualified battery sources that comprise VLA batteries. 14. The method of claim 13, further comprising:electrically coupling a third battery train of the non-critical battery system to both of the first and second channels of the second AC power bus, the third battery train comprising one or more qualified battery sources that comprise VLA batteries. 15. The method of claim 10, further comprising:sizing the first critical battery system to supply AC power to the first plurality of AC loads for about 24 hours based on a loss of electrical power from the primary AC power source. 16. The method of claim 10, further comprising:sizing the non-critical battery systems to supply AC power to the second plurality of AC loads for about 72 hours based on a loss of electrical power from the primary AC power source. 17. The method of claim 10, further comprising:electrically coupling a third AC power bus to the primary AC power source, the first plurality of AC loads, and a second critical battery system that comprises one or more non-qualified battery sources. 18. The method of claim 10, further comprising:detecting a loss of primary AC power from the at least one primary AC power source;adjusting at least a portion of the first plurality of AC loads to their respective safety positions;supplying AC power to the portion of the first plurality of AC loads from the one or more non-qualified battery sources through the first AC power bus; andsupplying AC power to the second plurality of AC loads from the one or more qualified battery sources through the second AC power bus. 19. The method of claim 18, further comprising:detecting a restoration of primary AC power from the at least one primary AC power source;supplying AC power to the portion of the first plurality of AC loads from the at least one primary AC power source through the first AC power bus; andsupplying AC power to the second plurality of AC loads from the at least one primary AC power source through the second AC power bus.
050229737	description	Referring now to FIG. 1 and FIG. 2, part of a solvent extraction column 10 of hollow cylindrical form is shown, and it is assumed that a heavier phase (usually aqueous) is dispersed and therefore moves down the column 10. In the column 10 a shallow receptacle 12 is surrounded by a funnel-shaped collector 14. In a typical operation, the receptacle 12 is charged to a high potential by means of a DC generator (not shown) and the collector 14 is at earth potential. The receptacle 12 dimensions are not critical but the receptacle 12 is made as small as possible in order to reduce the static hold-up of dispersed phase in the column 10. To this end, the underside 16 of the receptacle 12 may be inwardly dished as shown in order to reduce static hold-up still further. The receptacle 12 has an outer wall 13 supplied with six symmetrically disposed discharge ports in the form of nozzles 18 mounted as close to the bottom of the receptacle 12 as practicable. The receptacle 12 is supported in the column by means of one or more rods of non-conducting material (not shown) and is electrically insulated from all other components of the column 10. The collector 14 is similarly supported unless the column 10 is operated with the collector 14 at earth potential. Referring now to FIG. 1 and FIG. 3, the collector 14 has a vertical cylindrical wall 20 and a conical base 22 with a central outlet 24 through which the dispersed phase passes to the next receptacle 12 below. The base 22 has four symmetrically disposed radially displaced riser ports 26 through which the (lighter) continuous phase passes upwards through the column 10, the riser ports 26 having conical caps 28 defining gaps 29 in order to inhibit dispersed phase passing downwards through the riser ports 26 and thereby bypassing the receptacle 12 beneath. The diameter of the collector wall 20 is made such that it fits snugly within the column 10. As shown in FIG. 4, the column 10 may be constructed by stacking a series arrangement of receptacles 12 and collectors 14. In one method of operation receptacles 12 identified as (1), (3) and (5) are positively charged whilst receptacles 12 (2), (4) and (6) are negatively charged with respect to earth potential. All the collectors 14 identified as (1)-(6) are earthed. This arrangement has the advantage that since all the collectors 14 are earthed they need not be electrically insulated from the column 10. Furthermore the heavy phase leaving the bottom of the column 10 is electrically neutral. It is however possible to operate with alternative circuits and, as an example, all receptacles 12 may be positively charged whilst all collectors 14 are negatively charged. In FIG. 4, the conducting heavy phase (usually aqueous in practice) is fed to the top of the column 10 and enters receptacle 12 (1). The heavy phase flows through the charged nozzles 18 and issues as a charged spray of very small droplets of heavy phase. These droplets are attracted to the earthed collector 14 where they coalesce on the wall 20 and then flow by gravity down through the outlet 24 to the next receptacle 12 below where the entire process is repeated. Finally, the heavy coalesced phase leaves the collector 14 (6) and forms an interface 32 at the bottom of the column 10 from where it is withdrawn. The heavy coalesced phase could, in principle, be withdrawn directly from collector 14 (6) but by allowing it to flow to the bottom of the column 10 a small volume of column 10 is created for the introduction and distribution of the light continuous phase. The latter then rises up the column 10, passing through the riser ports 26 in each collector 14 on the way, and is withdrawn at the top of the column 10. Contact between the two phases is effected in two different ways. Thus the rising continuous phase encounters the fine spray of dispersed phase droplets leaving each nozzle 18 and at the same time contacts the falling film of dispersed phase on the wall 20 of each collector 14. The overall mechanism of mass transfer is therefore a combination of cross-flow and countercurrent transfer. By far the more important mode of transfer is that involving the droplet spray since in this case not only are the droplets oscillating because of the electrical charge that they carry but their interfacial area is also very high. The characteristics of the droplets, including their mean size, is controlled not by the nozzle 18 diameter but by the voltage applied to the nozzles 18. The important parameter is the electrical field strength between the tip of each nozzle 18 and the wall 20 of the collector 14. Referring again to FIG. 1, the distance between the tip of each nozzle 18 and the wall 20 is denoted by L. If V volts are applied to the nozzles 18, the field strength E is given by V/L. When E is less than 1 kV/cm, droplets form separately at the nozzles 18 although they are smaller than would be the case if no field were applied. When E is equal to 1.5 kV/cm or greater, myriads of very small droplets issue from the nozzles 18 and it is in this "spray" regime that the column 10 should operate. Although relatively high DC voltages may be called for, the current required is very small and only a few watts would be consumed by each receptacle 12. The invention is thus very economical in terms of energy utilisation. It should also be noted that the droplet size is independent of the nozzle 18 diameter in the spray regime. This is an important feature when extraction of liquors containing suspended solids is contemplated, such as biological broths which may contain cell fragments or other lysis products. In such situations, the nozzle 18 diameter may be made sufficiently large to avoid blocking without impairing the very small droplet size range needed to maintain a high interfacial area of contact. In principle the invention may be used in co-current as well as in counter-current flows through a solvent extraction column. The number of nozzles 18 may be selected to provide a required discharge of charged droplets towards the wall 20. There may be fewer or more than the six shown in FIG. 2. Although the nozzles 18 have been shown as aligned normal to the longitudinal axis of the column 10, if desired the nozzles 18 may be aligned at alternative angles. The number of riser ports 26 is selected to provide the required flow of the continuous phase, and may be fewer or more than the four shown in FIG. 3. The use of a relatively high wall 20 for the collector 14 has advantages, but if necessary the electric field could be applied between the nozzles 18 and the column 10.
062636650	claims	1. A microthruster comprising, a housing having a) a fuel section and b) a discharge section, a) said fuel section having, b) said discharge section being mounted over said plenum and having means for opening said valve and means for heating said tank to drive expanding propellant vapors through said valve, into said plenum, through said apertures in said heating unit to heat and further expand such gas which then is driven through said ducts to discharge to provide thrust for said housing. a) said fuel section having, b) said mid section being mounted on said plenum and having, c) said discharge section being mounted on said mid section and having 2. A microthruster comprising, a housing having a) a fuel section, b) a mid section and c) a discharge section in series, 3. The microthruster of claim 2 having means for driving said vapors through said passages and into said stagnation chamber, to deflect off the walls thereof, including said floor and discharge out of said opening to provide thrust for said housing. 4. The microthruster of claim 2 having a heating element mounted on said floor below said discharge opening. 5. The microthruster of claim 2 having a pedestal mounted on said floor below said discharge opening and means for heating said tank to drive expanding propellant vapors through said valve, into said plenum, through said passages and into said stagnation chamber, to deflect off the walls thereof, including off said pedestal and discharge out through said opening to provide thrust for said housing. 6. The microthruster of claim 2 wherein a heating element is mounted on said pedestal. 7. The microthruster of claim 6 wherein said heating element and pedestal are indented on the top surface thereof. 8. The microthruster of claim 2 wherein a heating element is mounted in said discharge opening. 9. The microthruster of claim 8 wherein said discharge opening is bent to turn or baffle the vapor stream discharging therethrough. 10. The microthruster of claim 2 having an exterior belt means for heating said tank. 11. The microthruster of claim 2 wherein said mid-section has a lower insulative portion surmounted by an upper thermally conductive portion. 12. The microthruster of claim 2 having a gas filter mounted between said valve and said plenum. 13. The microthruster of claim 2 having at least one heating element mounted in one or more of said sections and passing said vapors into proximity or into contact with said heating element as they flow from said valve to exit said discharge opening. 14. The microthruster of claim 13 wherein said heating element is mounted in a location selected from the group of, in one or more of said passages, in said stagnation chamber and in said discharge opening. 15. The microthruster of claim 13 wherein said heating element is in a film. 16. The microthruster of claim 2 wherein said discharge opening is an expansion slot or orifice. 17. The microthruster of claim 16 wherein a plurality of said discharge openings are mounted in a discharge plate. 18. The microthruster of claim 17 wherein said discharge plate has an insulative coating on the top side thereof.
	abstract	A device for granulating powders by cryogenic atomisation, characterised in that it comprises: a device for mixing powders by cryogenic fluid, comprising at least one chamber for mixing powders, comprising a cryogenic fluid; and a device for atomising a suspension of powders mixed by the device for mixing powders in order to allow a granulation of the powders, comprising a way of fractionating the suspension of powders making it possible to adjust the size of the droplets of powders to be atomised, and a method for adjusting the moisture of the mixed powders and/or the moisture of the atomisation atmosphere.
	summary
052389758	claims	1. A non-conductive microwave radiation absorbing adhesive comprising dissipative particles dispersed in a polymeric dielectric material chosen from the group consisting of thermosetting adhesives and thermoplastic adhesives, in which the dissipative particles range in largest dimension from 0.1 to 150 microns, and are chosen from the group consisting of solid microspheres made from a dissipative material, hollow microbubbles made from a dissipative material, solid microspheres coated with a dissipative material, hollow microbubbles coated with a dissipative material, filaments made from a dissipative material, and flakes made from a dissipative material, and in which at least one dissipative material is chosen from the group consisting of tungsten, chromium, aluminum, copper, titanium, titanium nitride, molybdenum disilicide, iron, and nickel. 2. The absorbing adhesive of claim 1 in which the polymeric dielectric material is chosen from the group consisting of polyamides, polyethylenes, polypropylenes, polymethylmethacrylates, urethanes, cellulose acetates, vinyl acetates, epoxies, and silicones. 3. The absorbing adhesive of claim 1 in which the volume loading of the dissipative particles is between 1 and 60 percent. 4. The absorbing adhesive of claim 3 in which the volume loading of the dissipative particles is between 10 and 50 percent.
	abstract	An elution tool for a radiopharmaceutical elution system includes an elution tool. The tool has a vial chamber sized and shaped for receiving an elution vial. An access opening is aligned with a septum of the elution vial when the elution vial is received in the vial chamber. An elution tool lid is secured to the elution tool body by a hinged connection. The elution tool lid is rotatable at the hinged connection and movable relative to the elution tool body between an occluded position and an exposed position. The tool also includes a latching mechanism for selectively and releasably locking the lid in the occluded position.
	abstract	A device and method for removing radioactive crud material deposited on surfaces of a nuclear fuel assembly in a nuclear plant is provided. The device comprises a container arranged to accommodate the nuclear fuel assembly, a first pumping means to pump a fluid, composed of water and ice, through the container in order to release the deposit from the nuclear fuel assembly by abrasion and to transport the released radioactive material out from the container. The first pump means also enables the feeding of a gas or steam or both to the fluid that is fed into and through the container in order to create a turbulence in the fluid. The device further comprises means, arranged in a xcex3-radiation-dampening medium, disposed to receive the radioactive deposit transported out of the container by the fluid.

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