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053316797 | claims | 1. A fuel spacer assembly for a fuel assembly comprising: (a) a plurality of tubular ferrules each forming a fuel rod insertion passage in which a fuel rod is inserted; (b) a support means in the shape of a belt for supporting a periphery of the tubular ferrules bundled in a lattice arrangement; and (c) a spring means for axially supporting the fuel rods disposed in the ferrules, wherein (i) each of said ferrules has a cylindrical wall to which an inward projection is formed to support the fuel rod; (ii) adjoining ferrules are joined together horizontally; (iii) each of said ferrules has at least one end to which a plurality of cutouts and petals are formed around the end portion by cutting out parts of the end portion, said ferrules being reversely arranged in their axial attitudes; and (iv) at least one flat portion is formed between adjoining petal portions, and the adjoining ferrules are spot welded to each other at said flat portions thereof. (a) a plurality of tubular ferrules each forming a fuel rod insertion passage in which a fuel rod is inserted; (b) a support means in the shape of a belt for supporting a periphery of the tubular ferrules bundled in a lattice arrangement; and (c) a spring means for axially supporting the fuel rods disposed in the ferrules, wherein (i) each of said ferrules has a cylindrical wall to which an inward projection is formed to support the fuel rod; (ii) adjoining ferrules are joined together horizontally; (iii) each of said ferrules has at least one end to which a plurality of cutouts and petals are formed around the end portion by cutting out parts of the end portion, said ferrules being reversely arranged in their axial attitudes and said petals having a shape selected from the group consisting of triangular, trapezoidal, V and M; and (iv) at least four flat portions are formed between adjoining petal portions, and the adjoining ferrules are spot welded to each other at said flat portions thereof. 2. A fuel spacer assembly according to claim 1, wherein four petal portions are formed to at least one end of the ferrule. 3. A fuel spacer assembly according to claim 2, wherein each of said petal portions has a rectangular shape. 4. A fuel spacer assembly according to claim 2, wherein each of said petal portions has a trapezoidal shape. 5. A fuel spacer assembly according to claim 2, wherein each of said petal portions has a triangular shape. 6. A fuel spacer assembly according to claim 2, wherein said petal portions have V or M shape. 7. A fuel spacer assembly according to claim 1, wherein said cutout portions and petal portions are formed to both axial ends of each of said ferrules, said ferrules being arranged in the same direction. 8. A fuel spacer assembly according to claim 7, wherein said cutout portions and petal portions are formed on both axial ends of the ferrule have same shape. 9. A fuel spacer assembly according to claim 7, wherein said cutout portions and petal portions formed on both axial ends of the ferrule have shapes different from each other. 10. A fuel spacer assembly according to claim 7, wherein the petal portions formed to an end portion of the ferrule on a downstream side are twisted outward with respect to a coolant flow between fuel rods to provide revolutional flow. 11. A fuel spacer assembly according to claim 1, wherein the adjoining ones of said ferrules are joined together such that an end portion of one ferrule to which the cutout portions are formed is spot welded to an end portion of another ferrule to which any cutout portion is not formed. 12. A fuel spacer assembly according to claim 11, wherein the cutout portions formed to an end portion of the ferrule on a downstream side are twisted outward with respect to a coolant flow between fuel rods to provide revolutional flow. 13. A fuel spacer assembly according to claim 1, further comprising bridging pieces for bridging ferrules arranged centrally in the lattice arrangement of the ferrules and supporting a water rod disposed centrally in the lattice arrangement. 14. A fuel spacer assembly according to claim 1, wherein said support means is provide with lobes projected outward for keeping constant a distance between a channel box of the fuel assembly. 15. A fuel spacer assembly according to claim 1, wherein each of said tubular ferrules has substantially a circular cross section. 16. A fuel spacer assembly according to claim 1, wherein each of said tubular ferrules has substantially an octagonal cross section. 17. A fuel spacer assembly for a fuel assembly comprising: 18. A fuel spacer as claimed in claim 17, wherein each of said petal portions has a trapezoidal shape. 19. A fuel spacer as claimed in claim 17, wherein each of said petal portions has a triangular shape. 20. A fuel spacer as claimed in claim 17, wherein said petal portions have a V or M shape. |
summary | ||
048896632 | abstract | For manufacturing uranium oxide based nuclear fuel pellets, a fine and reactive U.sub.3 O.sub.8 powder is mixed with a fine UO.sub.2 powder obtained by dry conversion. The U.sub.3 O.sub.8 is obtained by oxidation in air of UO.sub.2 obtained by a dry process, at a temperture less than 800.degree. C. |
claims | 1. A modular cathode assembly, comprising:a basket including a permeable surface permitting a fluid electrolyte to pass through the basket, the basket being electrically conductive;a first assembly support joined to a rim of the basket; anda cathode plate extending through the first assembly support and into the basket, the cathode plate being electrically insulated from the basket, the cathode plate being electrically conductive. 2. The modular cathode assembly of claim 1, wherein the basket includes an upper portion and a lower portion, the upper portion and the lower portion being electrically connected and defining at least one gap in the basket through which material may be placed in the basket. 3. The modular cathode assembly of claim 2, wherein the basket has a planar shape and wherein the lower portion includes the permeable surface on at least two sides with a largest area of the lower portion. 4. The modular cathode assembly of claim 2, wherein the lower portion is divided into a plurality of sections each configured to retain solid material and prevent the solid material from moving between the sections. 5. The modular cathode assembly of claim 1, wherein the cathode plate extends a substantially full length of the basket and a substantially full width of the basket. 6. The modular cathode assembly of claim 1, whereinthe first assembly support is configured to support the cathode plate. 7. The modular cathode assembly of claim 6, further comprising:at least one plate electrical connector extending through the first assembly support, the plate electrical connector configured to provide electric power to the cathode plate and being insulated from the first assembly support; andat least one basket electrical connector extending from the first assembly support, the basket electrical connector configured to provide electric power to the basket through the first assembly support. 8. The modular cathode assembly of claim 7, wherein the basket electrical connector and the plate electrical connector have a same knife-edge shape and are arranged in a line. 9. The modular cathode assembly of claim 6, wherein the first assembly support has a length so as to support the modular cathode assembly within a frame, and the basket is aligned at a center portion of the first assembly support so as to provide a substantially even reducing potential through the modular cathode assembly. 10. The modular cathode assembly of claim 1, wherein the cathode plate is fabricated of a material chosen from the group of stainless steel, tungsten, tantalum, and molybdenum. 11. The modular cathode assembly of claim 1, further comprising:at least one insulating band on a surface of the cathode plate, the insulating band having a thickness and length to seat between the cathode plate and basket. 12. The modular cathode assembly of claim 1, wherein the first assembly support has a lateral dimension that is greater than a lateral dimension of the basket. 13. The modular cathode assembly of claim 1, wherein the first assembly support is configured to facilitate a lifting of an entirety of the modular cathode assembly. 14. The modular cathode assembly of claim 1, further comprising:a second assembly support joined to the cathode plate, the second assembly support disposed above the first assembly support. 15. The modular cathode assembly of claim 14, further comprising:an insulating pad disposed between the first assembly support and the second assembly support. 16. The modular cathode assembly of claim 1, further comprising:a pair of lift posts on opposite ends of the first assembly support, the pair of lift posts being positioned above the basket and the cathode plate. |
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044787847 | summary | BACKGROUND OF THE INVENTION Generation of electrical power by means of nuclear energy has long been proven feasible; but even so, opposition against such activity is consistent because of varying safety considerations. One issue that opponents of nuclear energy raise is the possible release to atmosphere of radioactivity, such as might occur in an overheating malfunction situation incidental to a coolant blockage, a power excursion, an electrical power failure, or the like. To counteract this opposition, reactor development has established redundant cooling systems to dissipate any build-up of heat in the reactor core. One reactor design would use a primary reactor coolant, such as high pressure water or molten sodium that flows through the core; and a secondary or isolated coolant of water-steam that cools the primary coolant remote from the core. Since only the secondary coolant is expanded through the electrical power generating apparatus, it is relatively free of radioactive contaminants. Redundant cooling systems mean that the reactor operation can continue or be stopped safely even in the event of a complete failure of one of the cooling systems. However, one limiting factor to a redundant design is its dependence on electrical power, including standby or emergency power; whereupon even a redundant cooling system could fail or become severely degraded if it were the "active" type and required electrical input power. Another problem associated with reactor design is excessive thermal expansion incurred upon the reactor components being subjected to wide variations of temperatures. In this regard, the reactor might include an open-top tank perhaps 50-80 feet in diameter and within which the reactor core and primary reactor coolant (sodium) would be confined; and a heavy deck to close and seal the open top of the reactor tank. The deck is structural in nature and suspends from it reactor components such as heat exchangers, primary coolant flow pumps, control and safety instruments, and fuel rod control and loading and unloading mechanism. These components are specifically positioned and cooperate with one another within the reactor tank, so that excessive differential thermal expansion of the deck structure can be amplified significantly to cause misalignment of these components or separation of the seals and/or conduits isolating cooling flow between these components. The deck commonly has been fabricated of vertically-separated upper and lower horizontal deck plates and interconnecting vertical walls between the deck plates. The lower deck plate overlies the primary reactor coolant liquid confined in the vessel at temperatures as high as 600.degree.-1000.degree. F., and is thereby subjected to a significant heat input. The upper deck plate is exposed to ambient air of a reactor containment building; and consequently has a capacity to dissipate heat. Although radiation shielding and thermal insulating materials are supported proximate the underside of the lower deck plate, nonetheless a large temperature difference would exist between the upper and lower deck plates if adequate cooling were not provided. Conventional deck design attempts to establish and maintain a generally small temperature differential between the upper and lower deck plates. One system provides for circulating coolant through appropriate coolant passages formed in the deck structure. The coolant has been either a gas such as air or nitrogen, or a liquid such as water. This approach, however, requires an active source, typically electric pump means, to force the coolant through the passages. Consequently, under an electric power failure design comparison, the cooling capacity drops off dramatically to produce excessive temperature differences between the upper and lower plates. Inasmuch as the upper and lower deck plates are normally separated from one another by, for example 10 or 12 feet, any temperature differentials beyond a designed amount can cause significant thermal movement between the deck plates and misalignment of the components supported by the deck. A passive dual concept design variation provides for convective flow of coolant through the deck structure. This is not totally satisfactory since this design generally has required draft chimneys to assure adequate cooling and moreover, the hollow deck design must be open to the atmosphere. This is contrary to a preferred design concept that confines the deck coolant within a sealed hollow deck structure. SUMMARY OF THE INVENTION This invention relates to an improved passive arrangement maintaining adjacent or related components of a nuclear reactor within specified temperature differences even without the use of electrical power. This invention specifically provides for passive cooling means that are interconnected operatively between related components of a power reactor in order to maintain these components within design temperature differences by cooling one component while heating the other component, the cooling means being operative solely with thermal transfer and without electrical power. A specific object of this invention is to provide for use in a reactor improved passive cooling means in the form of heat pipes located about the reactor, each heat pipe having a vaporizing section operatively associated with one reactor component that is to be cooled and a primary condensing section operatively associated with a second reactor component that is to be heated, thereby providing for thermal transfer and temperature equalization between these components. A more specific object of this invention is to provide passive cooling means in the form of heat pipes, each heat pipe further having a secondary condensing section that is located outwardly beyond the reactor confinement tank and that projects into a secondary heat sink, such as ambient air formed within a containment building for the reactor itself, so as to provide for additional cooling capacity of the reactor components during overheat or emergency conditions, including operation without electrical power where all other modes of cooling might be inoperative. |
059303212 | abstract | An integrated head assembly for a nuclear reactor pressure vessel includes a closure head with CRDM assemblies extending upwardly from the head. A CRDM seismic support disposed above the closure head provides lateral support for the CRDM assemblies. The seismic support also has air flow holes which communicate with the interior of a shroud enclosing the CRDMs and extending upwardly from the closure head to the seismic support. The shroud has an air port in direct air flow communication with the surrounding atmosphere so that the closure head, shroud and seismic support define an air flow passageway directly communicating with the surrounding atmosphere via the air port and without the extensive ductwork and, therefore, with substantially less power. A missile shield disposed above and in air flow communication with the seismic support provides a lightweight, compact physical barrier for removing energy from dislocated objects such as CRDM drive rods. |
046510095 | abstract | An apparatus wherein a first thin member and a second thin member, the first thin member bearing a pattern, and the second thin member is exposed to the pattern of the first thin member. It includes a vacuum line for discharging a gas existing between the first thin member and the second thin member without close-contact therebetween, and a device for bringing the first and second members into proximity close-contact with each other after said discharging means discharges the gas from between the first thin member and the second thin member. |
claims | The ornamental design for a syringe holding device, as shown and described. |
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052563383 | claims | 1. A solidifying material for disposal of radioactive wastes in solidified waste form which comprises a mixture of a cement type hydraulic solidifying material and a fibrous material having a property to adsorb radioactive nuclides in the radioactive waste in the form of ion and/or molecule onto its surface, and to increase retention of the radioactive wastes within said waste form; the fibrous material also having a property to increase the tensile strength of the waste form, thereby increasing the waste loading within said waste form. 2. A structure for disposal of radioactive wastes at least a part of which is made of a cement type hydraulic solidifying material wherein said cement type hydraulic solidifying material contains a fibrous material having a property to adsorb radioactive nuclides in the radioactive wastes in the form of ion and/or molecule onto its surface, and to increase retention of the radioactive wastes in said structure; said fibrous material also having property to increase the tensile strength of said structure, thereby increasing the waste loading in said structure. 3. A structure according to claim 2, wherein the structure is a waste container for radioactive wastes at least a part of which is composed of the cement type hydraulic solidifying material. 4. A structure according to claim 2, wherein said structure is a structure in a disposal site for radioactive wastes at least a part of which is composed of the cement type hydraulic solidifying material. 5. A solidifying material according to claim 1, wherein the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is at least one member selected from the group consisting of fibrous active carbon, ion exchange fibers, and alkali metal titanate fibers. 6. A structure according to claim 2, wherein the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is at least one member selected from the group consisting of fibrous active carbon, ion exchange fibers, and alkali metal titanate fibers. 7. A solidifying material according to claim 1, wherein the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is fibrous active carbon and has an aspect ratio of 200-300. 8. A structure according to claim 2, wherein the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is fibrous active carbon and has an aspect ratio of 200-300. 9. A solidifying material according to claim 1, wherein the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is fibrous active carbon having micropores on its surface. 10. A structure according to claim 2, wherein the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is fibrous active carbon having micropores on its surface. 11. A solidifying material according to claim 9, wherein the micropores have an average pore diameter of 10-25 .ANG.. 12. A structure according to claim 10, wherein the micropores have an average pore diameter of 10-25 .ANG.. 13. A solidifying material according to claim 1, wherein the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is fibrous active carbon having a diameter on the order of about 10 to 15 .mu.m and a fiber length of about 3 mm. 14. A structure according to claim 2, wherein the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is fibrous active carbon having a diameter on the order of about 10 to 15 .mu.m and a fiber length of about 3 mm. 15. A solidifying material according to claim 1, wherein an amount of the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is about 5% by weight or less of said solidifying material. 16. A structure according to claim 2, wherein an amount of the fibrous material having a property to adsorb radioactive nuclides in the form of ion and/or molecule onto its surface is about 5% by weight or less of said structure. 17. A solidifying material for disposal of radioactive wastes in solidified waste form which comprises an admixture of a cement type hydraulic solidifying material and fibrous active carbon having micropores on its surface. 18. A structure for disposal of radioactive wastes at least a part of which structure is composed of a cement type hydraulic solidifying material wherein said cement type hydraulic solidifying material contains fibrous active carbon having micropores on its surface. 19. A process for solidifying radioactive wastes which comprises a step of feeding the waste into a kneading tank, a step of pouring a cement type hydraulic solidifying material into the kneading tank, a step of adding to the kneading tank a fibrous material having a property to adsorb radioactive nuclides in the radioactive wastes in the form of ion and/or molecule onto its surface, a step of adding water to the kneading tank, a step of kneading the wastes, the hydraulic solidifying material, the fibrous material and water in the kneading tank, and a step of pouring the kneading product obtained at the kneading step into a waste container to solidify the kneaded product; the fibrous material also having properties to increase retention of the radioactive wastes in the solidified kneaded product and to increase the tensile strength of the solidified kneaded product thereby increasing the waste loading therein. 20. A process for solidifying radioactive wastes which comprise a step of feeding the wastes into a waste container, a step of kneading a cement type hydraulic solidifying material, a fibrous material having a property to adsorb radioactive nuclides in the wastes in the form of ion and/or molecule onto its surface and water in a kneading tank, a step of pouring the kneaded product obtained in the kneading step into said waste container to solidify the product within said waste container, the fibrous material also having properties to increase retention of the radioactive wastes within the waste form and to increase the tensile strength of the product, thereby increasing the waste loading therein. 21. A process for solidifying radioactive wastes which comprises a step of feeding the wastes into a waste container, a step of pouring a cement type hydraulic solidifying material into the waste container, a step of pouring into the waste container a fibrous material having a property to adsorb radioactive nuclides in the wastes in the form of ion and/or molecule onto its surface, a step of adding water to the waste container, and a step of kneading and curing the wastes, the hydraulic solidifying material, the fibrous material and water in the waste container thereby to set the kneaded and cured product; the fibrous material also having properties to increase retention of the radioactive wastes within the waste form and to increase the tensile strength of the product, thereby increasing the waste loading therein. 22. A solidifying material for disposal of radioactive wastes and for making a solidified waste form which comprises an admixture of a cement type hydraulic solidifying material and fibrous material exhibiting the ability to increase the distribution coefficient of the radioactive wastes in the waste form, and the ability to increase the tensile strength of the waste form, thereby increasing the waste loading in the waste form. 23. A solidifying material according to claim 22, wherein the fibrous material comprises ion exchange fibers having functional groups, said fibers adsorbing at least anion of radioactive nuclides dissolved in liquid by ion exchange reaction with said functional groups. 24. A solidifying material according to claim 23, wherein said fibrous material comprises fibrous active carbon, having a property to adsorb nuclides in the form of at least anion or molecule onto its surface and having micropores on its surface. 25. A solidifying material according to claim 22, wherein said fibrous material is at least one member selected from the group consisting of fibrous active carbon, at least anion exchange fibers and alkali metal titanate fibers. 26. A solidified waste form, which comprises radioactive wastes and a mixture of a cement type hydraulic solidifying material and a fibrous active carbon, said waste form containing the radioactive wastes in an amount of 25-60 wt. %. 27. A solidified waste form according to claim 26, wherein said waste form also has a distribution coefficient of carbon-14 which increases with addition of the fibrous active carbon. 28. A solidified waste form comprising radioactive wastes admixed with a solidifying cement material and a fibrous material, said fibrous material having a property to increase both the distribution coefficient of said radioactive wastes in said waste form and the packing rate of the wastes within said waste form, the radioactive wastes constituting at least 25% by weight of the waste form and the fibrous material constituting no more than 10% by weight of the solidifying cement material. 29. A solidified waste form containing radioactive wastes, solidifying cement material and fibrous material, said fibrous material having a property to adsorb radioactive nuclides in the radioactive wastes in the form at least anion and/or molecule onto its surface and an average micropore diameter of 10-25 .ANG. on its surface, or a property to adsorb at least anion of said radioactive nuclides dissolved in liquid by ion exchange reaction with functional groups contained in the fibrous material; said fibrous material also having the properties to increase the distribution coefficient of the radioactive waste within said waste form, the tensile strength of the waste form and the packing rate of the wastes within said waste form. 30. A solidifying material according to claim 1, wherein the waste form exhibits a compressive strength of at least 30 kg/cm.sup.2 after the waste form is cured for one month and is dipped in water for one month. 31. A solidifying material according to claim 22, wherein the waste form exhibits a compressive strength of at least 30 kg/cm.sup.2 after the waste form is cured for one month and is dipped in water for one month. 32. A solidifying waste form according to claim 26, wherein the waste form exhibits a compressive strength of at least 30 kg/cm.sup.2 after the waste form is cured for one month and is dipped in water for one month. 33. A solidified waste form comprising radioactive wastes admixed with a solidifying cement material and a fibrous material, the fibrous material having a property to increase both the distribution coefficient of the radioactie wastes in the waste form and a packing rate of the wastes within said waste form. 34. A process for solidifying radioactive wastes which comprises a step of feeding the wastes into a kneading tank, a step of pouring a cement type hydraulic solidifying material into the kneading tank, a step of adding to the kneading tank a fibrous material having a property to adsorb radioactive nuclides in the wastes in the form of ion and/or molecule onto its surface, a step of adding water to the kneading tank, a step of kneading the wastes, the hydraulic solidifying material, the fibrous material and water in the kneading tank, and a step of pouring the kneading product obtained at the kneading step into a waste container to solidify the kneaded product; the fibrous material both increasing the tensile strength of the product and increasing the distribution coefficient of the radioactive nuclides in said product, thereby increasing the waste loading in the product. 35. A process for solidifying radioactive wastes which comprises a step of feeding the wastes into a waste container, a step of kneading a cement type hydraulic solidifying material, a fibrous material having a property to adsorb radioactive nuclides in the wastes in the form of ion and/or molecule onto its surface and water in a kneading tank, a step of pouring the kneaded product obtained in the kneading step into said waste container to solidify the product within said waste container, the fibrous material both increasing the tensile strength of the product, and increasing the distribution coefficient of the radioactive nuclides in said product, thereby increasing the waste loading in said product. 36. A process for solidifying radioactive wastes which comprises a step of feeding the wastes into a waste container, a step of pouring a cement type hydraulic solidifying material into the waste container, a step of pouring into the waste container a fibrous material having a property to adsorb radioactive nuclides in the wastes in the form of ion and/or molecule onto its surface, a step of adding water to the waste container, and a step of kneading and curing the wastes, the hydraulic solidifying material, the fibrous material and water in the waste container thereby to set the kneaded and cured product; the fibrous material both increasing the tensile strength of the product and increasing the distribution coefficient of the radioactive nuclides in said product, thereby increasing the waste loading in said product. 37. A process for producing a structure for disposal of radioactive wastes which comprises the steps of mixing a fibrous material having a property to adsorb radioactive nuclides in the wastes in the form of ion and/or molecule onto its surface, a cement-type hydraulic solidifying material and water and solidifying the resultant admixture to form said structure. |
051475960 | abstract | A method and apparatus for plasma relaxation under magnetic global topological constraint produces a hot magnetically confined toroidal Z-pinch plasma with a plurality of straight and toroidal relaxing plasma discharges so as to generate at least one open-ended poloidal null separatrix in the magnetic field with one poloidal null within the plasma space situated in the small major radius side of the toroidal discharge, forming thereby a magnetic configuration (called DAG) with non-zero homotopic invariant, including a toroidal reversed-field pinch with inner poloidal divertor, in a region of open plasma magnetic surfaces surrounding the toroidal discharges, when toroidal magnetic field component is also made to be substantially different from zero at the poloidal null. The topologically constrained relaxation invention, called topomak, may be operated in equilibria with regions of nested closed magnetic surfaces of high magnetic shear with safety factor Q radially varying from negative, but greater than -1, values to +infinity, and with high plasma/magnetic pressures ratio, closed to known theoretical stability conditions, the topological invariant opposing plasma relaxation to less favorable lower-energy states without reversal. The toroidally reversed poloidal divertor is effectively produced in the topomak by replacing the solid conducting inner core of prior art reversed-field-pinch relaxation devices by straight-pinch-like current discharge of plasma along the major axis under conditions where the topological constraint holds. The DAG plasma configuration has cylindrical topology. |
043205283 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to the drawings of the invention in detail and more particularly to FIG. 1, there is shown at 10 a steam generator or heat exchanger. The external shell or envelope 12 of said heat exchanger is a pressure vessel. Inside this external shell 12 are a large number of tubes 14 which are the tubes that carry the primary fluid within the primary system of said heat exchanger. Said tubes 14 pass through support plates 16 which are located along the length of said tubes 14 and which encircle each tube 14 so as to form a means for separating one tube from the next and allowing each tube to remain in a fixed position within the tube bundle. Said support plates 16 are in turn contained within a cylindrical iron wrapper 18. The tubes 14 are typically made of a nickel alloy such as inconel, and number on the order of 10,000, although the configuration of the heat exchanger and corresponding number of tubes will vary from manufacturer to manufacturer. The tubes 14 usually range from 5/8 inch to 7/8 inch in outer diameter and are approximately 50 mils in thickness. The support plates 16, in most current heat exchangers, are made of carbon steel and are approximately 3/4 inch to 1 inch thick. The tubes 14 are connected at their bottom end to an apertured plate or tube sheet 20. In normal operation, the primary fluid 2 comes from a heat source such as a nuclear reactor and enters said heat exchanger 10 through a primary entrance nozzle 24. The fluid enters into the area between the bottom of the pressure vessel external shell 12 and the tube sheet 20. A separating wall 22 separates the inlet side 25 of the heat exchanger 10 from the outlet side 27. The primary fluid 2 which comes from a heat source such as a nuclear reactor carries heat with it as it is forced through the various tubes 14 and up through the heat exchanger 10. The heat exchanger 10 illustrated in FIG. 1 is of the U-bend type, where the tubes 14 run most of the length of the heat exchanger 10 and are bent at the top to form a U-shaped configuration. The U-shaped tubes 14 are attached at their bottom to the tube sheet 20 which is mounted to the back of the external shell 12 of the heat exchanger 10, and thereby define the primary system of the heat exchanger 10. Upon reaching the uppermost portion of the tubes 14, the primary fluid 2 starts back down the opposite side of the tubes 14 and exits the heat exchanger 10 through the primary outlet nozzle 26 on the outlet side 27 of the heat exchanger 10. Heat which is carried by the primary fluid 2 is transferred to the secondary fluid 4 while the primary fluid 2 is circulating through tubes 14. Said secondary fluid 4 enters the heat exchanger 10 through secondary inlets 42 and 44 located in the external shell 12 and is located in the area surrounding said tubes 14 and within the external shell 12. Sufficient heat is transferred to the secondary fluid 4 so that the primary fluid 2 exiting the primary outlet nozzle 26 is at a substantially lower temperature than it was when it entered the heat exchanger through primary inlet nozzle 24. The secondary fluid 4 absorbs heat carried by the primary fluid 2 and said secondary fluid 4 becomes steam during the heat absorption process. Said steam passes through separators 30 which remove excess moisture from said steam, and then exits through the steam outlet 32 at the top of the heat exchanger 10. The high pressure steam can then be used to drive a turbine. The secondary fluid 4, secondary inlets 42 and 44, separators 30, and steam outlet 32 define the secondary system of the heat exchanger 10. The primary fluid 2 can be water. A gas such as helium or another liquid such as liquid sodium can also be used for the primary fluid. The secondary fluid 4 is usually water. Referring to FIG. 2, said support plates 16 contain apertures or crevices 38 through which said tubes 14 run. It is at the site of the apertures or crevices 38 that one of the problems which the present invention is intended to solve first occurs. In those heat exchangers in which the support plates 16 are made of steel, the elevated temperatures and water environment promote the oxidation of the support plates 16 and magnetite is formed from the steel on the exposed surfaces. As previously described, magnetite, which is a ceramic material and is relatively "spongy", occupies a greater spatial volume than the steel which has been oxidized to form the magnetite. As shown in FIG. 3, as the steel support plate 16 is oxidized to magnetite 40, and the magnetite 40 builds up at the area where the tubing 14 is surrounded by the support plate 16, the crevice or aperture 38 between the support plate 16 and tubing 14 is reduced, and magnetite 40 eventually fills the aperture 38 between the support plate 16 and the tubing 14. As further shown in FIG. 3, the phenomena known as "denting" or "pinching" takes place. The tubing 14 is constricted by the increasing volume of the magnetite 40, and can be damaged and/or cracked. The movement of fluid through the tubing 14 can be substantially impeded at the site of this restriction. Although magnetite 40 will also be created on other surfaces of support plate 16, conventional cleaning methods, such as those described by M. F. Obrecht, et al in his paper, Supra might be satisfactory to handle the problems at these other areas on the support plates 16. The magnetite 40 within the aperture 38, which causes the denting and deformation of tube 14, is not easily susceptible to the cleaning methods disclosed in the prior art. The chemical solvents cannot easily reach into this area. Conventional chemical cleaning methods utilizing more or less accepted chemical cleaning formulations are so slow as to endanger the integrity of the heat exchanger system. If these chemicals are left long enough to be effective against the magnetite, they will also attack the basic structural elements of the heat exchanger as well. Conventional chemical methods known in the prior art are also ineffective in removing the magnetite 40 at the aperture 38 because the cleaning fluid cannot be adequately circulated or agitated to continually bring a fresh supply of cleaning fluid to the site to be cleaned. The present invention involves the process of and apparatus for removing the buildup of products of corrosion, oxidation, sedimentation, and comparable chemical reactions from various portions of heat exchanger systems such as the location wherein the primary heat exchanger tubes come in contact with support plates for those tubes. The process involves immersing the surfaces to be cleaned in a chemical solvent capable of attacking said buildup of products of corrosion, oxidation, sedimentation and comparable chemical reactions at a relatively slow rate. The solvent is then heated to desired temperatures adjacent said surfaces to be cleaned. Finally, the process involves generating a source of sonic energy to be used in conjunction with said chemical solvent and directing said sonic energy through said chemical solvent and to said surfaces to be cleaned at specific frequencies whereby cavitation of said sonic energy is combined with said chemical solvent so as to enhance and accelerate the removal of said buildup of products of corrosion, oxidation, sedimentation and comparable chemical reactions. The present invention solves the problem of removing the magnetite 40 from the apertures or crevices 38 between said support plates 16 and said tubes 14. Referring to FIG. 4, a chemical solvent 80 is placed inside the heat exchanger 10 and within the exterior shell 12. Sufficient chemical solvent is put into the heat exchanger to cover said tubes 14 and said support plates 16, as shown in FIG. 4. One chemical solvent which can be used is the combination of 8% solution of sodium salt of ethylenediaminetetracetic acid (EDTA), plus 4% solution of citric acid plus an effective amount of a standard corrosion inhibitor (such as 0.6% of OSI-1 corrosion inhibitor sold by Halliburton Services). Said chemical solvent 80 can be heated to a desired temperature, which is between 120.degree. F. and 220.degree. F. A preferred heating method would be the utilization of the primary circulating system to circulate a heated fluid through the tubes 14 until the solvent has reached its desired temperature. Once achieved, that temperature can be maintained by adding heat through the primary system. Alternatively, the chemical solvent 80 can be heated externally and then the heated solvent 80 can be added to the secondary system inside the heat exchanger 10. This method is less desirable than the preferred method because it requires the heating and circulating of a potentially hazardous and corrosive substance. Further, utilizing a benign heating fluid through the tubes 14 in the primary system provides the additional benefit of inducing a convection flow of the chemical solvent 80 at the interfaces of the tubes 14 and the support plates 16. Care should be taken that the temperatures at the interfaces of the tubes 14 and the support plates 16 during the cleaning process does not exceed the desired levels since undue heating adversely affects the efficiency of the sonic cleaning process. Sonic energy is generated from transducers 50 which contain a face 51 and a rear portion 53. Referring to FIGS. 4 and 5, the preferred placement of the sonic transducers 50 is shown in the form of a ring 52 of such transducers encircling the wrapper 18 which in turn encircles the support plates 16 and tubes 14. The wrapper 18 significantly reduces the effectiveness of sonic energy generated by the sonic transducers 50. Further, a problem is created because the thin fluid layer of chemical solvent 80 which is trapped between the transducer face 51 and the wrapper 18 cavitates or boils due to the heat generated by the transducer 50 and this is turn decouples the transducer 50 from the wrapper 18. This problem is solved by either of the following means. The first and preferred method shown in FIG. 5b, involves placing a thin layer of high boiling point fluid 90 between the transducer face 51 and the wrapper 18. The fluid 90, such as oil, can be placed in a container 92 such as a flexible plastic bag which is approximately 1/8 inch thick, and will remain in place by pressure between the face of the transducer 50 and the wrapper 18. The combination of this coupling fluid 90 and the container 92 for the fluid 90 should have the same acoustic impedance as the metal wrapper 18 in order to have good sonic transmission. The transducers 50 are held firmly against the fluid filled container 92 or metal wrapper 18 by mechanical means such as a support wedge 99 placed between the rear portion of the transducer 53 and the internal vertical portion of the shell 12, or by direct mechanical or magnetic attachment to the metal wrapper 18. In the second method, shown in FIG. 5a, windows 94 whose dimensions are approximately the size of the transducer face 50 are cut in the wrapper 18 portion in front of each transducer 50. After the cleaning process has been completed, these windows 94 are sealed by replacing the metal removed on cutting the window 94 in the wrapper 18 and welding the piece of metal back in place. When the windows 94 are cut slightly smaller than the face of the transducer 51, the transducer can be held in place against the metal wrapper 18 by direct mechanical or magnetic attachment to the metal wrapper 18, or by mechanical means such as a support wedge 99 placed between the rear portion of the transducer 53 and the internal vertical portion of the shell 12. When the window 94 is cut slightly larger than the face of the transducer 51, part of the transducer 50 can be placed through the metal wrapper and will remain in place in this fashion. The ring 52 of transducers 50 is energized to radiate sonic energy in the frequency spectrum between 2 KHZ and 200 KHZ. The choice of these frequencies permits improved coupling of the sonic energy into the chemical solvent 80 and to the sites of interest such as the aperture 38 between the support plates 16 and tubes 14. The optimum cleaning interval for any heat exchanger can be experimentally determined, but it is believed that approximately 24 hours of sonic irradiation should be adequate to clean the first or uppermost plate. Sonic irradiation can be extended for longer periods as necessary. Results of experimental tests have shown that over a 24 hour cleaning period negligible adverse effects from the chemical solvent 80 are experienced by the other components. Some experiments suggest that the cleaning process may be accomplished in somewhat less time and, in any given heat exchanger, it may be possible to visually observe the progress of the cleaning, at least insofar as the uppermost support plate is concerned, since it might be subject to visual monitoring. As each plate 16 is cleaned, the fluid level is dropped as is the ring 52 of transducers 50 and the process is repeated. This procedure, has, however, the effect of exposing at least the lower portions of the vessel to the chemical solvent for longer periods of time. In view of the longer, but "passive" exposure to the solvent, as one proceeds toward the bottom of the tank the period of time during which the sonic transducers are operated at each fluid level is progressively reduced. It has been experimentally determined that using the chemical solvent 80 alone without sonic energy irradiation would require approximately 8 days to achieve a similar cleaning effect as is achieved by the present invention in only one day. Therefore, the adverse affects of the solvent 80 on the components of the heat exchanger are substantially reduced due to the significant decrease in time that the solvent 80 must remain inside the heat exchanger. The embodiment of the present invention described above requires the use of a ring of sonic transducers around the outer circumference of the metal wrapper 18 of the heat exchanger 10. As each support plate and tube is cleaned, the cleaning solvent level 80 is lowered to a few inches above the next support plate and the ring 52 of sonic transducers 50 is lowered to be in alignment with the next support plate to be cleaned, as shown in FIG. 5. A key point in this process is that the level of chemical solvent must be only a few inches above the surface area to be cleaned. If the level is much higher, the effectiveness of the sonic energy in creating the cavitation at the site to be cleaned is significantly reduced. In order to create cavitation at the site to be cleaned, the transducers must be able to generate a power output greater than about 0.2 watts per square centimeter at room temperature. This power density limitation on the transducers is demonstrated in the textbook "Sonics--Techniques For The Use Of Sound And Ultrasound In Engineering And Science, by Theodor F. Huetter and Richard H. Bolt, Fourth Edition published in 1965," pages 228 to 232. Referring specifically to FIG. 6.13 on page 230 of said textbook, in order to produce cavitation in degassed water at room temperature, the transducer must generate approximately 0.2 watts per cubic centimeter. As shown by the chart, if the transducer has a power output greater than about 0.2 watts per square centimeter, cavitation will be produced over a broad frequency range. An alternative embodiment of the present invention is shown in FIG. 6 wherein the ring 52" of transducers 50" is wholly exterior to the heat exchanger 10 and is placed around the outer circumference of the external shell 12 of the heat exchanger 10. In this embodiment, the actual cleaning procedure would be substantially similar to that of the preferred embodiment described above except that the ring 52" of transducers 50" is mounted on the outside and must be "coupled" to the interior of the vessel. The heat exchanger 10 is filled with the chemical solvent 80 which is heated to the desired temperature. The ring 52" of transducers 50" is placed at the height of the uppermost support plate 16 and is energized. The sonic energy is transmitted to the interior through a sonic coupler 58 which may include a fluid held in place by seals 60. As each support plate and tube is cleaned, the cleaning solvent level 80 is lowered to just above the next support plate and the ring 52" of sonic transducers 50" is lowered to be in alignment with the next support plate to be cleaned. The patent to Ostrofsky, U.S. Pat. No. 3,295,596 illustrates a particular coupler apparatus which would be employed. The embodiment of the present invention is designed to be used with those heat exchangers where interior access is either severely limited or is considered too hazardous. The rings 52, 52" of transducers 50, 50" can be successively repositioned in the vertical direction during the cleaning process. At each repositioning, the fluid level is lowered to a height above the transducer ring sufficient to support and maintain the efficient transmission of sonic radiation to the surfaces to be cleaned. As shown, the tubes and plates are cleaned in increments. It may be sufficient that each increment includes one of the support plates and that a suitable interval of time is employed to irradiate the plate. The time required for each of the plates can, of course, be experimentally determined. However, it is believed that although the sonic energy is primarily directed at a particular plate and its tube intersections, the adjacent plates will also benefit from the sonic energy and the cleaning of those plates will proceed, as well. The time required for the later increments may be progressively less, so that by the time the lowermost plate is reached, the required cleaning time for this plate will be substantially less than for the others. The total time during which the lowermost portions of the heat exchanger have been immersed in the solvent bath will, nevertheless, be substantially less than required through the use of solvents alone. Because the cleaning action of the solvent 80 is intensified, it is possible to use a chemical solvent at greater concentrations for shorter cleaning time. Depending upon the construction of the heat exchanger and the materials used in its fabrication, some optimum combination of solvent strength and cleaning time can be devised to minimize the unwanted effects of the solvents on the structural components. Many of the special fluid properties necessary to maximize the efficiency of the sonic cleaning process, can be achieved in the compounding of the chemical solvent. The solvent should be active at relatively low temperatures (below 200.degree. F.) and be substantially immune to the effects of sonic cavitation. Further, the solvent should optimize those properties which support high cavitation energy levels such as high surface tension, low vapor pressure and low viscosity. The utilization of sonic energy in the cleaning process not only has a direct effect on the scale, corrosion products and magnetite, but also enhances the effect of the chemical solvent by agitating and circulating the solvent in the regions being cleaned. This agitation tends to carry away "saturated solvent" and waste products, and brings fresh solvent to the region so that the solvent does not lose its effectiveness. While the process of cleaning the particular surfaces of the heat exchanger has been described, the presence of the sludge pile, and its effect on the cleaning process has not been considered heretofore. Because the sludge pile does contain a large quantity of loose sediment, magnetite, copper and other corrosion products, the fluid agitation caused by the sonic cavitation may stir up the sludge and its presence may actually interfere with the cleaning action of the solvent upon the structural parts. It may therefore be desirable to initiate a preliminary cleaning process in an attempt to remove the sludge pile before any other cleaning is attempted. For this operation, it may be preferable to have transducers mounted to the exterior shell 12 of the heat exchanger 10 and to use a fairly concentrated and relatively strong chemical solvent which just covers the sludge pile only and is not brought in contact with the remaining structural elements. Is is also possible that through the application of sonic energy alone, the sludge pile can be "stirred up" sufficiently to enable a flushing operation to carry away a substantial portion of the sludge pile, without the need for chemical solvent action. If the removal of the sludge pile is not to be undertaken, it may be necessary to provide some physical isolation of the sludge pile from the cleaning solvent so as not to contaminate and/or neutralize the chemical solvent before it has had a change to work on the structures to be cleaned. In this event, it may be necessary to provide a blanketing layer of an appropriate liquid which will effectively isolate the sludge pile from the chemical solvent bath. Another alternative embodiment of the present invention is shown in FIG. 7 wherein the ring 52' of transducers 50' are placed inside the heat exchanger 10 and inside the metal wrapper 18, and over the bundle of and substantially parallel to the tubes 14. The effectiveness of this placement may be limited if the vessel is quite deep. Very deep vessels might not be optimally served. However, for those heat exchangers in which the embodiment can be successfully employed, it offers the advantages of both easier installation and removal. Turning next to FIG. 8 and FIG. 9, there is shown an additional alternative embodiment of the present invention. As shown, individual sonic transducers 70 are placed within selected tubes 14 of the primary system. Energizing these transducers 70 can concentrate the sonic energy in the immediate vicinity of the tubes 14. By appropriate positioning of a transducer 70, along the axis of the tube, the energy can be successively directed to the deposits at each of the support plates 16, in turn. This application of the present invention can also be used to clean tubes which are badly corroded internally or which are dented. The cleaning of these tubes would prevent further tube damage and would eliminate the need to remove tubes from service by plugging them at the tube sheet 20. Access to the interior of the tubes can be achieved either from the manifold area at the primary inlet 24 and primary outlet 26, or, selected tubes can be cut and later repaired when the cleaning process has been concluded. These transducers 70 mounted interior to the tubes 14 could be employed in conjunction with other transducers which could be either mounted on the exterior wall 12 of the heat exchanger 10 or mounted on the metal wrapper 18 to operate in a cooperating and coordinated fashion. Alternatively, if relatively unrestricted access can be gained to the interior of the heat exchanger, some transducer elements can be attached directly to support plates 16. As shown in FIG. 8, it is also possible to utilize pressure sensitive transducers 72 at various locations within the vessel to determine the magnitude of sonic energy at selected locations. This monitoring capability can increase the efficiency of the cleaning process since the sonic transducers 70 can then be selectively or differentially driven to maximize the cleaning action at desired locations. Other variations and modifications will appear to those skilled in the art in terms of instrumentation, directing the sonic energy and using measurements of water pressure and frequency to determine the energy level at any given point within the heat exchanger system. Where time is a critical factor, as in the cleaning of the heat exchanger portion of a nuclear reactor, the present invention provides time savings that are appreciable and significant. Of course, the present invention is not intended to be restricted to any particular form or arrangement, or any specific embodiment disclosed herein, or any specific use, since the same may be modified in various particulars or relations without departing from the spirit or scope of the claimed invention hereinabove shown and described of which the methods shown are intended only for illustration and for disclosure of an operative embodiment and not to show all of the various forms of modification in which the invention might be embodied. The invention has been described in considerable detail in order to comply with the patent laws by providing a full public disclosure of at least one of its forms. However, such detailed description is not intended in any way to limit the broad features or principles of the invention, or the scope of patent monopoly to be granted. |
summary | ||
046876251 | summary | BACKGROUND OF THE INVENTION This invention relates to improvements of piping passing through a nuclear reactor containment vessel. Generally, in a nuclear power plant, high temperature and high pressure steam generated through thermal energy produced in a nuclear reactor is led from the containment vessel of the reactor to the outside to rotate turbines to generate electricity. After rotating the turbines, steam is condensed into water which is returned to the nuclear reactor in the containment vessel via a feedwater pipe. Besides the main steam pipe for feeding steam to the turbines and the feedwater pipe for returning water to the reactor, pipes for transporting steam and water, for example, a main steam drain line for releasing drain of main steam, nuclear core spray pipes for cooling the reactor core, pipes of system for removing residual heat for cooling the reactor are passed through the containment vessel. Moreover, pipes for transporting gas, such as drywell ventilating pipes for performing ventilation of the containment vessel and pipes of an off-gas system for treating gases are also passed through. As aforesaid, a multiplicity of pipes through which steam, water and gas are transported are passed through the containment vessel, and each of these pipes is formed with shut-off valves mounted on inside and outside of the wall of the containment vessel. For example, Japanese Patent Application Laid-Open No. 36490/79 discloses the piping passing through the containment vessel and the valves in a nuclear reactor. The main steam pipe of a boiling-water reactor (BWR) shown in FIG. 1 will now be described. Water changes into high temperature and high pressure steam due to heat produced by nuclear reactions taking place in a pressure vessel 1 of the nuclear reactor. Steam thus generated usually has a temperature of about 270.degree. C. and a pressure of about 70 kg/cm.sup.2. Steam generated within the pressure vessel 1 is led from a containment vessel 3 of the nuclear reactor via a main steam pipe 2 extending through a wall of the containment vessel 3 to the outside thereof and then to a turbine shed, not shown, where steam rotates turbines to actuate a generator to generate electricity. After being released from the turbines, steam changes back to water which is returned to the pressure vessel 1 in the containment vessel 3. The containment vessel 3 is formed of steel and of a substantially truncated conical configuration. It has a diameter of about 25-29 m at the bottom and is enclosed by a concrete shell 6 at the outside. The pressure in the containment vessel 3 is usually at the atmospheric pressure level. However, the containment vessel 3 is designed such that its shell is capable of withstanding an internal pressure equivalent to several atmospheric pressure supposing that an accident happens involving a guillotine rupture of pipes within the containment vessel and high temperature and high pressure steam gushes out of the pipes. In the case of an advanced boiling-water reactor (ABWR), the containment vessel 3 of the reactor is formed of concrete as shown in FIG. 2 and designed such that an internal pressure is borne by its concrete wall. The concrete wall has a lining of steel plates. In both the BWR and ABWR, the containment vessel 3 has a function to confine the radioactive materials and to prevent them from being scattered in atmosphere when accidents such as breakage of pressure vessel or piping rupture occur. Thus, the pipes passing through the containment vessel are each provided with valves mounted on the inside and the outside of the containment vessel. Such valves are provided to the main steam pipe as well, which will be described by referring to FIG. 1. The main steam pipe 2 is usually made of carbon steel and has a diameter in the range between 400 and 700 mm and a wall thickness in the range between 20 and 40 mm. One nuclear power plant generally has four systems of main steam pipe. Each system of main steam piping 2 is provided with an inner main steam shut-off valve 4 and an outer main steam shut-off valve 5 mounted near an inner wall surface and an outer wall surface of the containment vessel 3 respectively as double safety means. The main steam shut-off valves 4 and 5 are closed when steam leaks or other trouble occurs during the operation of the reactor. When steam leaks occur in the main steam pipe between steam nozzles of the pressure vessel 1 and the inner main steam shut-off valve 4, for example, the inner main steam shut-off valve 4 is closed to cut off the supply of steam to the turbine system while allowing steam to spread within the containment vessel 3. The closure of the inner main steam shut-off valve 4 results in the radioactive steam being confined within the containment vessel 3. Also, when steam leaks occur in the main steam pipe between the outer main steam shut-off valve 5 and the turbines, the outer main steam shut-off valve 5 is closed and the supply of steam to the turbines is interrupted, thereby minimizing the leaks of steam. When steam leaks occur in the main steam pipe between the inner main steam shut-off valve 4 and outer main steam shut-off valve 5, the two shut-off valves 4 and 5 are closed to minimize the steam leaks. Between the two shut-off valves 4 and 5, the main steam pipe 2 extends through an aperture formed in the wall of the containment vessel 3 and is secured to the wall. The containment vessel 3 being used at room temperature, loads are applied by thermal stresses to the portion of the main steam pipe that is secured to the wall of the containment vessel 3, so that the main steam pipe 2 is mounted to the wall of the containment vessel 3 by utilizing highly advanced technology. Yet, it is inevitable that crack formation might occur in the main steam pipe 2 in a portion thereof between the outer wall surface of the containment vessel and a portion of the main steam pipe 2 including the outer main steam shutoff valve 5, thereby causing steam to leak. It is for the purpose of preventing this steam leak that the inner main steam shut-off valve 4 is provided. In the containment vessel of the prior art described hereinabove, the main steam pipe 2 has the problem that in the event of steam leaks occuring between the outer wall surface of the containment vessel 3 and the portion of the main steam pipe 2 including the outer main steam shut-off valve 5, steam would be released into the atmosphere outside the containment vessel 3 during the period of time from the occurrence of the accident to the closure of the inner main steam shut-off valve 4 and the area of radioactive contamination is enlarged. SUMMARY OF THE INVENTION An object of this invention is to provide piping of a nuclear reactor containment vessel which can prevent the radioactive materials from being scattered in atmosphere in case of leaks occuring at a pipe between an outer wall surface of the containment vessel and a portion of the pipe including an outer shut-off valve provided at the outside of the containment vessel and omit an inner shut-off valve provided in the containment vessel as a means of a double safety means. The piping of a nuclear reactor containment vessel of this invention comprises pipes passing through the containment vessel and extending to the outside of the containment vessel, outer shut-off valves each provided at a portion of the pipe which is located at the outside of the containment vessel and isolating vessels for covering at least outer surfaces of welded portions of the pipes each being located between an outer wall surface of the containment vessel and portion including the outer shut-off valve and for isolating the covered portions of the pipes from atomsphere. Preferably, the isolating vessels include bellows constructions and steam detectable transducers. |
description | To gain the technical result, mentioned above, proper in the suggested lens for radiation transforming, representing the neutral or charged particle flux, this lens contains the radiation transporting channels, adjoining by the walls, with total external reflection, oriented by input ends so that to capture a radiation of the source in use. Unlike known lenses, the lens according to the present invention is made as a package of sublenses of various degree of integration. As this takes place, a sublens of the least degree of integration represents a package of radiation transporting channels, which is growing out of the joint drawing and forming of capillaries, packed in the beam, at the pressure of gaseous medium in the space between them less than the pressure inside channels of capillaries, and the temperature of softening of the material and splicing the walls of the adjoining capillaries. A sublens of every higher degree of integration represents a package of sublenses of the previous degree of integration, growing out of their joint drawing and forming at the pressure of the gaseous medium in the space between them less than the pressure inside the channels of sublenses, and the temperature of softening of the material and splicing the adjoining sublenses. The ends of this unified structure are cut and form an input and output ends of the lens. The unified structure and the lenses of each degree of integration can have an envelope, made of the same material, as capillaries, or very close to it on value of the coefficient of thermal expansion. The envelopes increase the rigidity of the structure and the lens strength. However, a lens, in which the sublenses do not have envelopes, is more transparent. The inventive lens is named an integral lens because of combination a great amount radiation transporting channels (106 and more) in it (therefore with reference to sublenses the concept of a degree of integration is used), has channels with smaller cross-section, than the prior art monolithic lens, or miniature lenses, as the channels diameter diminishes on the every stage of drawing. Correspondingly the degree of radiation focusing increases, i.e. a size of the focal spot decreases. All sublenses of the highest degree of integration can be packed in a common envelope. The latter in this case is an external envelope of a lens. In some applications a presence of coating of one or more layers, made of one and the same or different chemical elements, on the inner side of walls of the channels is useful. Before producing an integral lens the coatings are applied on the inner side of a tube, the capillaries are resulting from. Thus it is important, that the coefficient of heat expansion of the material, coatings are made of, should be close to the coefficient of heat expansion of the material, the capillaries are produced from. In this case the process proceeds without complications. Multilayer periodical coatings allow to implement advantages, caused by interference phenomena, incipient at reflection from the surfaces, having such coatings. In particular, radiation monochromation, transported through the channels with the walls, having such coatings, is possible. The application of rough coating gives an appearance of diffusion component at reflection and can develops the conditions for radiation transporting at the angle of incidence, exceeding the critical angle of the total external reflection. The full integral lens, as well as known lenses of the previous generations, is made with a capability of a divergent radiation focusing; for this purpose input and output ends of the radiation transporting channels are oriented, accordingly, to the first and second focal points. In first of them the radiation source is placed, when using the lens; in the second point the focal spot of the lens is forming. An integral half-lens is used for transforming the divergent radiation to quasi-parallel, as well as at use of lenses of previous generations. In an integral half-lens some ends are oriented to the first focal spot, and other ends are parallel to each other. It is not always appropriate to make full integral lenses for the divergent radiation focusing symmetrical. If a size of an X-ray source is large enough, it is worthwhile to make the focal distance from the input end of the lens large, and the focal distance from the output end of the lens lesser in order to obtain small focal spot. For this purpose the radius of curvature of channels of a half of lens, adjoining to an input end, must be larger, than the radius of curvature of channels of a half of lens, adjoining to the output end, i.e. the lens must be asymmetrical with respect to the cross-section medial on its length. An integral lens can be made as an axi-symmetric body, as well, with the generatrix, having a knee, and different diameters on the part of an input and output, in particular for changing the size of cross section of the transported beam. In this case the lens is xe2x80x9cbottlexe2x80x9d shaped. It is a traditional demand in the process of creating lenses: all transporting channels of lenses must be filled with radiation completely. For this purpose it is necessary that the filling factor xcex3=R(xcex8c)2/2d was more or equal to 1 (here R is the radius of curvature of the channel, d is the diameter of the channel, xcex8c is the critical angle of total external reflection). However, the executing of this requirement is not always appropriate. In a case, when xcex3xe2x89xa71, the size of the focal spot of the lens is equal to d+2foutput xcex8c where foutput is the size of the focal spot of the lens on the part of an output. It means that it is impossible to make the size of the focal spot of the lens less than d. If xcex3xe2x89xa71 fails, that will take place only partial filling of the channels with a radiation. Thus X-ray photons or neutrons xe2x80x9cforcexe2x80x9d against the side of walls of transporting channels, peripheral with respect to an optical axis of the lens. If the factor xcex3 less than less than 1 takes place, the effective size of the channels can be much less, than the size of channels d. Thus the total transmission of the lens decreases. But the size of the focal spot decreases proportionally also, and the area of the focal spot decreases even more sharply, due to what radiation density in the focal spot grows. Lenses of viewed purpose have aberrations, consisting that the position of the focal spot in lengthwise direction is rather spread. The characteristic size of spreading, as a rule, exceeds in tens and more times the size of the focal spot in the crosswise direction. The radiation transporting channels, adjoining to the optical axis of the lens, give the very major contribution to the spreading. The participation of these channels in the forming of the focal spot gives as well a magnification of the crosswise sizes of the spot, as these channels have less curvature (down to zero), and it is impossible to execute the requirement xcex3 less than less than 1, and even xcex3 less than 1 for them. In one of special cases of embodiment of the suggested lens it is possible to except the influence of these channels on the spreading of the focal spot in lengthwise direction and magnification of its crosswise sizes by closing the part of lens, adjoining to the optical axis, on the part of the input or output by screens, or by making this part impermeable for the radiation by the other method. For example, it would be possible to make continuous (without channels) that part of the lens, where sublenses could be, and for their channels xcex3xe2x89xa71. The specific of the other special cases of embodiment of the suggested lens is that the channels of one or more sublenses, placed near the lengthwise axis of the lens, are made with a capability of radiation transporting at a single total external reflection or without it. For this purpose they can be made, for example, of smaller length, than the channels of sublenses, which are more distanced from the lengthwise axis of the lens. Owing to this fact, losses of a radiation in the channels of the sublenses reduce, and the overall transmission coefficient of the lens increases. The same result is obtained (but in combination with the increase of spreading of the focal spot) when the central channels are made of a major diameter. The operations, being carried out on the different stages of the technological process of producing of the suggested integral lens, are of the same tape and do not depend on the degree of integration of the sublenses, used at every stage. The most suitable material for producing integral lenses is glass; it is possible to use other materials, for example, ceramics, metals, alloys. The suggested method of producing the integral lenses, includes two or more stages of embodiment of stocks, placed in a tubular envelope. Thus the capillaries are used at the first stage as stocks, and at every next stage the stocks, which are growing out of the realization of the previous stage, are used. As against the previous one, in the suggested method the tubular envelope with the stocks, filling it, is drawn in the furnace. Thus the feed speed must be kept lower, than the product withdrawal speed, at the constant relation between these speeds. After that the stocks, resulting from this stage, are gained by cutting lengthwise the product, emerging from the oven. After completion of the last stage, the tubular envelope is filled with the stocks, which are growing out of this stage. Then the tubular envelope with the stocks, filling it, is drawn in the furnace, keeping the feed speed in the furnace lower, than the product withdrawal speed from the furnace, changing periodically the relation between these two speeds to form barrel-shaped thickenings on the finite product. Then the lenses, in the form of parts of the product, are made by cutting lengthwise the finite product. Each lens has only one barrel-shaped thickening. At all stages of realization of the method the tubular envelopes are used. These envelopes are made of the same material as the capillaries, or very close to this material on the thermal expansion coefficient. The process of drawing of tubular envelopes with stocks, filling the envelopes, is realized at the pressure of the gaseous medium in the space between the stocks less than the pressure inside the channels of the stocks, and the temperature of softening of the material and splicing the walls of the neighboring channels. In dependence of how the cutting is made (in sections disposed symmetrically or asymmetrically on each end of a maximum of the barrel-shaped thickenings, or in section relevant to a maximum of thickening and on each end of it), symmetrical or asymmetrical full or half-lenses are made. The regime of drawing speed (relation between the feed speed of the tubular envelope with the stocks in the furnace and the product withdrawal speed from the furnace) defines the lens form. In particular, when this relation (in the process of barrel-shaped thickening forming) changes, the lens with various curvature radius of the channels on different sides of the maximum of barrel-shaped thickening is produced. The lens as an axi-symmetric body with generatrix, having a knee, and the ends of the channels, being parallel to the lengthwise axis of the lens (a xe2x80x9cbottlexe2x80x9d shaped lens) is produced by cutting the part of the product, outgoing from the furnace. This part of the product is enclosed between the maximum of the barrel-shaped swelling and the cross-section, being on the other side of the inflection point of the generatrix on the part of the product, where its diameter is constant. To produce lenses without envelopes, which cover sublenses, each stage of producing the stocks should be finished with etching the envelopes. Similarly, if it is necessary to produce lenses without external envelope, it should be etched. The suggested analytical device, as well as the known one, more close to it, includes a radiation source (representing neutral or charged particle beam), a means for positioning the subject under study (the means is placed with a capability of a radiation of the source acting on the subject under study), one or more radiation detectors (placed with a capability of a radiation passed through the object under study or excited in it acts on the detectors), one or more lenses for transforming a radiation of the source or radiation, excited in the object under study. These lenses are placed on the radiation way from the source to the object under study and/or on the way from the last one to one or more said radiation detectors. These detectors contain the radiation transporting channels, adjoining by their walls, with total external reflection, and the channels are oriented with their input ends so as to capture the radiation, being transported. As against known, at least one of the lenses is made as a package of sublenses of a various degree of integration. Thus the sublens of the least degree of integration represents a package of radiation transporting channels, which is growing out of joint drawing and forming the capillaries bundle at the pressure of the gaseous medium in the space between the capillaries, being less than pressure inside the channels of capillaries, and at the temperature of a softening of the material and splicing the walls of the neighboring capillaries. The sublens of each higher degree of integration represents a package of sublenses of the previous degree of integration, which is growing out of their joint drawing and forming at the pressure of the gaseous medium in the space between the sublenses, being less than pressure inside the channels of sublenses, and at the temperature of a softening of the material and splicing the walls of neighboring sublenses. All sublenses of the highest degree of integration are combined in a unified structure, which is growing out of their joint drawing and forming at the pressure of the gaseous medium in the space between the sublenses, being less than the pressure inside the channels of sublenses, and at the temperature of a softening of the material and splicing the neighboring sublenses. The ends of the unified structure are cut, and they form the input and output ends of the lens. A lot of characteristic geometries of the integral lenses placing in the analytical device together with some other constructive peculiarities of the device. So, an analytical device can be made with a capability of scanning the surface or volume of the object under study by means of the aligned focuses of the lenses, placed on the way from the source to the object under study and from the last one to the detector. At such geometry three-dimensional local analysis can take place, if the object is scanned in three dimensions. The sensitivity of the method is high enough, as the detector receives the radiation significantly from the area, where both lenses have common focus. In this geometry a specific case can take place, when an integral lens, placed on the radiation way from the object under study to the detector, forms a quasi-parallel beam, and between the lens and the detector a crystal-monochromator or multilayer diffraction structure are placed with a capability of varying their placement and the angle of incidence of the quasi-parallel beam on them to fulfill the Bragg condition for different lengths of radiation waves, excited in the object under study. The usage of the lens significantly decreases the losses in comparison with the collimation method of producing of a parallel beam, falling on the monochromator. In the other geometry synchrotron or other source is used as the source, forming a parallel beam, and a lens, placed on the radiation way from the source to the object under study, is made with a capability of such beam focusing. One more geometry is characterized by the fact, that a source of a broadband X-rays is used in an analytical device. The X-rays is transported simultaneously by two lenses, made with a capability of forming a quasi-parallel beam. Two crystal-monochromators are placed between an output of each of the lenses and the means for positioning the object under study. Thus one of the crystals is placed with capability of selecting a radiation, having a wavelength lower, and the other crystal is placed with a capability of selecting a radiation, having a wavelength higher, than the absorption line of the element, which presence is checked in the object under study. The device comprises two detectors, each of them being placed after the means for positioning of the object under study so that to receive the radiation, passed through the object under study, and formed by one of crystal-monochromators. The difference of the output signals of the detectors is proportional to the concentration of the element under checking. Two other geometries, described below, have similar coefficients. In one of them an analytical device includes, besides the source, one more X-ray sources. Thus the radiation of one source has a wavelength lower, and the other one higher, than the absorption line of the element, which presence is checked in the object under study. Only one lens, which can form a quasi-parallel beam, is placed between each source and a means for positioning the object under study. The device includes two detectors, each of them is placed after the means for positioning the object under study so that to receive the radiation, passed through the object under study from only one source. The difference of the output signals of the detectors, as in the previous case, is proportional to the concentration of the element under checking. In the other geometry the source is made as an X-ray source with an anode with a capability of receiving the radiation with two characteristic wavelengthsxe2x80x94lower and higher than the absorption line of the element, which presence is checked in the object under study. One lens is placed between the source and the means for positioning the object under study. The lens is made with a capability of forming a quasi-parallel beam. A rotating screen with cycling windows, closed by filters, is placed in front of or behind the lens; these windows are transparent for one and opaque for the other said wavelength. The difference of output signals of the detectors, conforming two neighboring windows, is proportional to the concentration of the element under checking. One more type of geometry is characterized by usage of the radiation of the secondary target, placed behind the lens on the radiation way from the source to the object under study. Thus the lens is made with a capability of focusing the source radiation on the secondary target. It allows to irradiate the object under study by a monochromatic radiation of the secondary target, what increases the sensitivity of analysis in cases, when the elements, being checked for presence in the object, have absorption lines, close to the radiation line of the secondary target. The presence of the lens, which concentrates the source radiation on the target, makes possible to compensate the disadvantage of this method (the disadvantage is caused by low intensity of the secondary radiation). The sensitivity of the method increases in addition in the geometry with the secondary target, which is characterized by the presence of the second lens between the secondary target and the means for positioning the object under study. The advantages of usage the polarized radiation for irradiation of the object under study, in this case, are the same as in the geometry, described below. In this geometry a lens and a crystal-monochromator, or a multi-layer diffraction structure are placed in succession on the radiation way from the source to the object under study. Thus the lens is made and oriented with a capability of forming a quasi-parallel beam, falling at an angle of 45xc2x0 on the crystal-monochromator or the multi-layer diffraction structure for forming the polarized radiation by them, and the detector is placed at an angle of 90xc2x0 to the direction of propagation of the polarized radiation. In this geometry, owing to the polarized selection, the background, caused by the Compton scattered radiation drops out. The next geometry realizes the method of a phase contrast. In this geometry a lens and a crystal-monochromator are placed in succession on the radiation away from the source to the object under study in the analytical device. Thus the lens is made and oriented with a capability of forming a quasi-parallel beam, falling on the crystal-monochromator at the Bragg angle. The crystal is placed in parallel or with slight deflection on the radiation away from the object under study to the detector. It provides a capability of fixing the phase contrast of areas of the object under study by means of the detector (the areas have different densities and cause different refraction of the radiation, falling on them). The geometry, typical for medical applications, provides the usage of an X-ray source and embodiment of the means for positioning the object under study with a capability of examining the parts or the organs of a human body. In particular, when using the analytical device for mammography purposes, an X-ray source has a molybdenum (Mo) anode, and the means for positioning the object under study is made to provide a capability of examining the mammary gland. Thus the integral lens is placed on the radiation away from an X-ray source with the molybdenum anode to the object under study, the lens is made with a capability of forming a quasi-parallel beam with the cross-section, being enough for simultaneous action on the whole area under study; and the detector is placed to provide the distance, not less than 30 cm, between it and the object under study. The usage of the parallel beam and the choice of the distance provide fine contrast of a gained image without usage of the special means for decreasing the influence of the scattered radiation, excited in the object under study. One more possible field of application of the suggested analytical device in medical diagnostics is computer tomography. In the described geometry, providing the usage of an X-ray source and the embodiment of the means for positioning the object under study with a capability of examining the parts or organs of a human body, it is stipulated the opportunity of rotational movement rather each other of the means for positioning, from one hand, the lens, placed between the means and the means for positioning the object under study, from the other hand, and the detector, which output is connected to computer means for processing the results of detection. Thus the integral lens is made with a capability of focusing the radiation, formed by the source, inside the object under study. The focusing point here represents a virtual radiation source, placed inside the object under study, that causes the principal difference from a common scanning computer tomograph, in which the detector absorbs the radiation, passed through the object under study from the source, placed outside the object under study. Due to this the procedure of an image formation of small areas of the object under study can be simplified. In the suggested invention, related to the device for radiotherapy, the irradiation doze on the tissues, surrounding the tumor, can be decreased by means of focusing the radiation on the tumor, due to what the radiation concentration in healthy tissues, namely on the patient""s skin, considerably decreases at the same doze of irradiation on the tumor. To obtain the result the suggested device, as well as the known one, includes one or more radiation sources, representing the neutral or charged particle flux, as well as the means for positioning the patient""s body or its part for irradiation. As against the known one, the suggested device for radiotherapy includes the lens, placed between each of the sources and the means for positioning, for radiation focusing on the patient""s tumor. The lens includes the radiation transporting channels, adjoining by their walls, with total external reflection; the channels are oriented by their input ends with a capability of capturing the transported radiation. The given lens is made as a package of sublenses of different degree of integration. Thus the sublens of the least degree of integration is made as a package of channels for transporting the radiation, which is growing out of the joint drawing and forming of channels bundle at the pressure of the gaseous medium in the space between the channels, being less than the pressure inside the channel of the capillaries, and at the temperature of a softening of the material and splicing the neighboring capillaries. Each sublens of the higher degree of integration is made as a package of sublenses of the previous degree of integration, which is growing out of their joint drawing and forming at the pressure of the gaseous medium in the space between the of sublenses, being less than the pressure inside the channels of sublenses, and at the temperature of a softening of the material and splicing the neighboring sublenses. All sublenses of the highest degree of integration are combined in a unified structure, growing out of their joint drawing (i.e., pulling or stretching) and forming at the pressure of the gaseous medium in the space between the sublenses, being less than the pressure inside the channels of sublenses, and at the temperature of a softening of the material and splicing the neighboring sublenses. The ends of the unified structure are cut and form an input and output ends of the lens. A nuclear reactor or accelerator may be used as the sources. Quasi-parallel beams of thermal or epithermal neutrons are formed on the outputs of the said nuclear reactor or accelerator. Thus the used integral lens can contain the curved longitudinal axis for the neutron beam turning. As it was already mentioned at discussion above, neither with the assembled lenses (lenses of the first generation), nor with the monolithic lenses (lenses of the second generation) it is impossible to realize the channel size of about 1 xcexcm on the input and of about 0.1 xcexcm on the output at the exit aperture of 10 cm2 and more, what is necessary for lithography in microelectronics. The parameters can be realized with an integral lens. The suggested device for contact X-ray lithography contains the soft X-rays source, the lens for transformation the divergent radiation of the source to quasi-parallel (this lens contains the radiation transporting channels, adjoining by their walls, with total external reflection), and the means for positioning the mask and the substrate with the resist, applied on it. As against the known one, the lens of the suggested device is made as a package of sublenses of different degrees of integration. Thus the lens of the least degree of integration represents a package of radiation transporting channels, which is formed by joint drawing the bundle of capillaries at the pressure of the gaseous medium in the space between the channels of capillaries, being less than the pressure inside the channels of capillaries, and at the temperature of softening of the material and splicing the neighboring capillaries. The sublens of each higher degree of integration is made as a package of sublenses of the previous degree of integration, which is growing out of their joint drawing and forming of at the pressure of the gaseous medium in the space between the sublenses, being less than the pressure inside the channels of the sublenses, and at the temperature of softening a material and splicing of the neighboring sublenses. All sublenses of the highest degree of integration are combined in an unified structure, which is growing out of their joint drawing and forming at pressure of the gaseous medium in the space between the sublenses, being less than the pressure inside the channels of sublenses, and at the temperature of softening a material and splicing the neighboring sublenses. The ends of the unified structure are cut and form the input and output ends of the lens. It is possible to increase the accuracy of mask imaging on the resist up to the level, being enough for projection lithography in microelectronics owing to the usage of the suggested integral lenses in the device. The suggested device for projection X-ray lithography, as well as the known one, contains the soft X-ray source, the lens for transforming the divergent radiation of the source to quasi-parallel, intended for irradiating the mask, the means for mask positioning, the lens for X-ray image transmission of the mask on the resist with diminution of the image size, the means for placing the substrate with the resist, applied on it. Thus both said lenses contain the radiation transporting channels, adjoining by their walls, with total external reflection. As against the known device, at least second of the lenses in the suggested device for the projection lithography is made as a package of sublenses of various degree of integration. Thus the sublens of the least degree of integration is made as a package of radiation transporting channels, which is growing out of the joint drawing and forming of the bundle of capillaries at the pressure of the gaseous medium in the space between them, being less than the pressure inside the channels of the capillaries, and at the temperature of a softening of the material and splicing the neighboring capillaries. The sublens of each higher degree of integration is made as a package of sublenses of the previous degree of integration, which is growing out of their joint drawing and forming at the pressure of the gaseous medium in the space between them, being less than the pressure inside the channels of sublenses, and at the temperature of a softening of the material and splicing the neighboring sublenses. All sublenses of the highest degree of integration are combined in a unified structure, which is growing out of their joint drawing and forming at the pressure of the gaseous medium in the space between them, being less than the pressure inside the channels of sublenses, and at the temperature of a softening of the material and splicing of the neighboring sublenses. The ends of the unified structure are cut and form the input and output ends of the lens. To decrease the image size, transmitted on the resist, the second of the lenses, used in the device, is made as an axi-symmetric body with a geneatrix, having a knee, and with the input and output ends of channels, being parallel to the longitudinal axis of the lens, and the input diameter of the lens is smaller than the output one. The same relation takes place between the diameters of separate channels for radiation transportation on the input and output of the lens. The relation of the diameters, which must be considerably more than 1, determines a degree of diminution of the mask image at its transmission on the resist, and, therefore, the degree of miniaturization of the products of microelectronics. Referring to FIG. 1, the full integral lens 1 has an input 2 and output 3 focuses, placed on its optical axis 4 in the point of the intersection of the continuations of the axial lines of the radiation transporting channels. FIG. 2 depicts one of these channels. A particle, captured by the input end of the channel, moves in the channels along the trajectory 6, being reflected from the walls 7 of the channel at angles, less than the critical value xcex8c of the angle of the total external reflection. xcex8c is of several mrad. The cross-section of the channels is of micron fractions size order, and their quantity, as it was mentioned, is about 1 million. Therefore the given images are conditional and the scale of the figures is far from the real one. FIG. 3, illustrating the forming of the focal spot by the radiation, exited from the channels 5, depicts the focal spot, which is spread in the lengthwise direction and can have the size 9, considerably exceeding the size 8 in the cross direction. This phenomenon refers to one of the types of aberrations in the optical systems. To decrease this aberration it can be recommended to follow not the traditional requirement of filling the whole cross-section of the transporting channel with the radiation (xcex3xe2x89xa71), but visa versa (xcex3 less than 1), or even (xcex3 less than less than 1), when producing the integral lens. In this case FIG. 4 depicts the character of trajectory 6 of the particle, captured by the channel. Thus the radiation is reflected each time from one and the same wall 7 of the channel 5, and the radiation, as though, xe2x80x9cpressesxe2x80x9d to the wall, filling a small part of the cross-section of the channel. As a result the size of the focal spot is determined by the size of this part of the cross-section of the channel, and the same effect is achieved, as well as at diminution of the section. As to decrease the degree of filling the cross-section of the channel by radiation, with other conditions being equal, it is necessary to decrease the radius of channels curvature, the continuation of the output ends of the channels converge in the focus area at major angels. Owing to this fact the spread of the focal spot in the lengthwise direction decreases, that promotes eliminating the aberration mentioned above. FIG. 5 depicts the described phenomena, where the parts 10, participating in radiation transporting, of the channels 5 are black colored. It is visible, that the sizes of the focal spot 11 are smaller in both directions, than on the FIG. 3. It can be impossible to follow the requirement (xcex3 less than less than 1) or (xcex3 less than 1) for the central channels (adjoining the optical axis of the lens), having smaller curvature than peripheral ones. The central part of the lens can be made without the radiation transporting channels (see FIG. 6, where the continuous central part 12 is shaded) or it can be closed with the screen from the source side to except the negative influence of the central channels. Each channel of the symmetrical (with respect to the middle cross-section lengthwise the lens) full lens has the constant curvature radius, the smaller it is (i.e. the channel curvature is larger), the more distanced is the channel from the optical axis 4 of the lens (see FIGS. 1 and 6). The full lens can be made asymmetrical with respect to the section, as it is shown in FIG. 7. The curvature of each channel of the asymmetrical lens is inconstant along its lengthwise. Thus the curvature is larger for the ends of all channels, adjacent to one of the faces, and it is smaller for the opposite ends of the same channels, adjacent to the other face. FIG. 7 depicts the channels, adjoining to the left face and having smaller curvature (larger radius of curvature). The center of curvature can occupy different positions (FIG. 7, positions 13 and 14) for different parts of the channels of the ends. The integral half-lens 14 (FIG. 8a) has only one focus 2 from the side of the smaller face (left one in FIG. 8a). The ends of the channels, adjoining this face, are oriented toward the focus 2. The ends of the channels, adjoining the larger face (right one in FIG. 8b), are parallel to the optical axis 4 of the half-lens 14. If the focus 2 is combined with the point source, the radiation 15 on the output of the half-lens 14 is quasi-parallel. If such radiation 16 is delivered from the major face (FIG. 8b), the ends of the channels, adjoining the smaller face (right one in FIG. 8b), become output ones. In this case the radiation, yielding from the half-lens 14, concentrates in the focus. The faces of the full lens 1 and the half-lens 14, facing the focuses, can be made sphere-shaped with the center in the corresponding focus, as it is shown in FIG. 1, FIG. 7 and FIG. 8a, b. In this case equal requirements of radiation capture of the point source for all channels are provided. The bottle-shaped lens 17 (FIG. 9) has the ends of the channels, being parallel to the optical axis of the lens, from both faces. Such lens has the form of an axi-symmetric body with the knee of the generatrix. The input quasi-parallel beam 16, falling on the smaller (left one in FIG. 9) is transformed by the lens to the output quasi-parallel beam 16xe2x80x2 with the larger section. The cross-section of the output beam, vice versa, decreases as against the input one, when the input radiation is submitted to the larger face (right one in FIG. 9). If the input beam is an image carrier, for instance X-ray image, and the distribution of the radiation intensity in the cross-section of the beam is of character, corresponding the image, so the image scale on the output of the lens changes in appropriate way. The change of the image scale in the integral lens may be as much as two orders. Thus the small diameter of the channels in combination with the absence of the shadowing influence of the envelopes of sublenses (in case, when the lenses are etched in the process of their producing) provides the good quality of reproduction of image details. FIG. 10 depicts the common picture of the cross-section for all types of integral lenses (in view of the note, made above, regarding the convention and scale of the image). This figure depicts the specific case, in which the full lens, as a whole, and the sublens as well have the envelopes. The channels 5 for radiation transporting are inside the envelope 18 of the sublenses of the least (first) degree of integration. Groups of such sublenses, forming the sublenses of the next (second) degree of integration, are placed in the envelopes 19. The package of such sublenses forms the lens as a whole with the envelope 20. FIG. 11 depicts the form of one of peripheral sublenses 18, 19 (distant from the optical axis of the lens). It is necessary to pay attention, that the construction of the suggested integral lens is not simply the result of assembling in a direct sequence of the channels-capillaries in the lenses of the first degree of integration, first of all, then grouping the last ones in the lenses of the second degree of integration, etc. This construction is connected directly with the suggested method of producing, what explains the presence of elements of this method in the characteristic of the construction. Sublenses of any degree of integration and the integral lens do not appear as they are assembled, they result from the realization of the method as a whole after finalizing the forming, which several stages of drawing precede. Neither the lens as a whole, nor the sublenses, being a part of the lens, are not present before the realizing of forming, there are only stocks with straight channels. xe2x80x9cFormingxe2x80x9d, being presented in the characteristic of the integral lens as the feature of the sublenses of different degrees of integration and the lens as a whole, is precisely the above forming, achieved at the final stage of the method. Only after such forming the parts of the integral lens, called the sublenses of the highest degree of integration, and the parts of these sublenses, called the sublenses of the lower degrees of integration, get the features of the lenses. The features differ them from the package of parallel channels. At the same time the produced lens can not be disassembled into sublenses and separate channels. Therefore the sublens, shown in FIG. 11, does not exist off the integral lens as a whole (similarly, the separate electronic components can not be allocated from the integral microchips). The prefix xe2x80x9csubxe2x80x9d of the term xe2x80x9csublensxe2x80x9d shows that each sublens, not existing independently, carries out the subordinate role in the composition of the lens as a whole. This reason causes the term xe2x80x9ca sublensxe2x80x9d (but not xe2x80x9ca lensxe2x80x9d) usage to indicate the components of the integral lens. Thus not only plenty of channels in the lens as a whole and in each of its sublenses, but the circumstances are the basis for the term xe2x80x9cintegralxe2x80x9d usage in the head of the suggested invention, regarding to the lens, and the concept xe2x80x9cthe degree (level) of integrationxe2x80x9d for the sublenses characteristic. Only separate capillaries are integrated (combined) in the sublens of the first degree (level) of integration, the elements, being the lenses themselves in the functional relation (the sublenses of the first, second, etc. degrees of integration), are integrated in the sublenses of the second degree of integration and higher. As it was said above in the characteristic of the suggested invention, relating to the integral lens, the envelopes of the sublenses, which presence is determined by the technology of producing, and which eliminating demands to amplify the method of producing with the operations of etching of these envelopes, play the positive role, as well, increasing the structure stiffness. It is necessary to use for the envelopes the same material, as well as for capillaries, or close to it in value of the thermal expansion coefficient. The removal of the envelopes makes the technological process more difficult, however they deteriorate the lens transparence moderately. Their negative influence on the uniformity of transportation of the radiation intensity along the cross-section of the beam is more essential. Therefore the usage of the lenses free of envelopes, covering the sublenses, is necessary not so much for increasing the transparence of the lens, as much as for eliminating the cause of nonuniformity of intensity transportation along the cross-section of the beam, what can be important in a series of applications. To produce the lenses, described in the suggested method, the tubular envelope 21 (FIG. 12), for instance glass one, is filled with the stocks, received at the previous stage of the method, and then it is delivered to the furnace 22 vertically by means of the upper drive 23, and it is drawing from the furnace at a speed, exceeding the feed speed, by means of the bottom drive 24. The product 25 with significantly smaller diameter than the diameter of the envelope 21 at the entrance of the furnace is a result of drawing. The temperature in the furnace must be enough to soften the material and splice the neighboring stocks, filling the tubular envelope 21. At the first stage as the stocks, which the tubular envelope is filled by, the capillaries are used, in particular, glass ones, produced from the glass of the same sort, as it was used for producing the envelope. The glass capillaries can be produced with the use of the similar technology by means of drawing of glass tubes with the further cutting them on the capillaries of desired length. In the process of drawing the axisymmetric temperature field should be formed (FIG. 12 depicts the distribution of temperature T along the furnace height L, having narrow maximum 27). The transition region 26 of the initial diameter of the tubular envelope 21, filled with the stocks, in the smaller diameter is placed in the zone of narrow peak 27 of the temperature distribution along the furnace height. The pressure between the capillaries should be kept lower than inside the channels of the stocks to prevent the collapse of the capillaries in the process of drawing, accompanying by compression of the stocks, placed in the tubular envelope (eventually, it is important to maintain the higher, than in the space, pressure in the channels of capillaries of the sublenses of the least degree of integration). For this purpose the upper ends of the channels of the stocks should be closed before placing in the envelope (for instance, the upper ends of the stocks should be spliced), and in the process of drawing the gas should be drawn off from the upper end of the envelope filled with the stocks (the draw off is diagrammatically shown in position 28, FIG. 12). It is not necessary to seal the bottom ends of the channels of the stocks, and the envelope, filled with the stocks, because the result, close to the sealing, is obtained by essential diminution of the diameter of the product, emerging from the furnace, in comparison with the initial diameter of the envelope with the stocks, delivered to the furnace from above. The product, growing out of the drawing, is cut after cooling, and one gets the stocks for the next stage. The tubular envelope is filled with the stocks, and the envelope is drawing similarly the previous stage. Stocks, obtained at every stage, are acid etchable to remove the material of the envelopes before the tubular shell is filled with the stocks, if it is necessary to produce the lens with the envelope free sublenses. The described stages should be realized several times (usually 3-5), after what the final stage should be realized. At this stage (FIG. 13) the drawing of the product from the furnace is slowed down and then is accelerated again periodically, therefore thickenings 28 are made, connected with tapers 29. The parts of the thickenings, directly adjoining the maximum, are barrel-shaped. The desired curvature of barrel-shaped generatrixes, in which the channels are placed, is obtained by regulation of the variable speed of drawing (i.e. the relation between the speeds of the upper and bottom drives 23, 24), and it is possible to obtain the thickenings, asymmetrical to the maximum as well. At this stage, as well as at the previous stage of producing the stocks, the closing of upper ends of the channels of the stocks before placing them in the tubular envelope and the drawing off the gas from the upper end of the envelope (with the stocks placed in it) is carried out (the drawing off is not shown in FIG. 13). The product with periodic thickenings, obtained at the given stage, (FIG. 14) is cut lengthwise to produce the lenses of the desired type. The positions 30, 31, 32 in FIG. 14 depict the parts of the product, which, after being cut, present correspondingly a full lens, a half-lens or a xe2x80x9cbottle-shapedxe2x80x9d lens. When using the integral lenses in the analytical devices for flaw detection, elemental analysis, analysis of the internal structure of the objects, and diagnostics in technology and medicine, huge number of geometries of relative position of radiation sources, analysis object, means for radiation detection, lenses, and other elements is possible. Only some of them in combination with some constructive peculiarities of the analytical device, associated with corresponding geometries, are considered below. The means for positioning of the object under study (hereinafter it is sometimes called a sample) is one of the constructive elements of the analytical device. As the radiation interacts with the sample by operation of the analytical device, further as a rule precisely the object under study (a sample) is mentioned, and not the means for positioning, though it (and not the sample) is a constructive element of the analytical device. High efficiency of analysis, owing to focusing of the source radiation in one point on the surface of the object under study in combination with the radiation capture, scattered by the sample, in some bodily angle with the following radiation concentration on the detector, is obtained owing to the geometry, showed in FIG. 15. Here the full lenses 1 and 1xe2x80x2 have combined focus 34, which can scan the surface or interior areas of the sample 33. The detector 35 absorbs the radiation, focused by the second lens 1xe2x80x2. The analysis, using the low-power source 2, can be realized by means of the lens 1xe2x80x2, focusing the radiation of the point source 2 on the object of analysis, and the lens 1. Similar geometry (without the second lens 1xe2x80x2) is used in energy dispersion method, when the semi-conductor detector is used. Thus the lens 1 focuses the radiation on the object (sample), the detector 35 is placed close to the sample, and the detector registers both a fluorescent radiation and a radiation, scattered by the sample. In such geometry the integral lens 1 increases the photon flow on the sample, and the detector vicinity to the sample makes it possible to collect more quantity of photons. The lens 1 removes high-energy photons, which create the high background of the scattered radiation, from the source spectrum. The analysis localization is obtained by means of radiation focusing on the small area of the sample 33. The important specific case of the embodiment of the analytic device is the use of X-ray tubes with a through anode. If the lens with very small focal distance is used (for instance, the lens, in which, at the factor xcex3 less than less than 1, the effect of xe2x80x9cpressingxe2x80x9d to the exterior side of the transporting channels arises), so such lens can be placed closely to the through anode. Thus the lens can be made small-sized, conserving the wide capture angle simultaneously. Such combination is especially effective (the tube with through anode plus the integral lens), when the anode is microfocal (0.1-100 microns). As the solid angle of the radiation of the through anode is wide (it is close to a hemisphere), the tube with the through anode can be effectively used simultaneously with some lenses, and each lens gathers the radiation from the part of the solid angle. It is necessary to mention, concerning both the described schemes, and those, which will be described below, that these schemes contain minimum elements, being enough to realize the analysis by means of the device (i.e. to get some information about the object under study). To provide the receiving the information, handy for immediate use, to improve the receiving the clear information operatively, etc., the analytical devices are supplemented with the means for processing and presenting the information, which are connected to the detector output. The means realize transformation of the output signals of the detector, visualization of the signals synchronously with the mechanical movements of the elements of the analytical device, etc. The synchronization demands the connection of the means for processing and presenting the information with the means for realizing the movements. The means for processing and presenting the information, used with the analytical devices, are known. And their functions and structure do not depend on the way, which the signals, carrying the information about the object under study, were received by. For this reason the detector output is accepted to view as the output of the analytical device (the detector output is sensitive to the radiation, which is growing out from the source radiation and the object under study interaction, therefore the detector output carries the information about the features of the object under study). In the next considered geometry (FIG. 16) a means for monochromating the radiation, excited in the sample 33, is used (crystal-monochromator 36). The radiation is monochromated owing to the conditions of reflecting of the parallel beam from the crystal-monochromator are met in the very narrow interval of particle energies. To form a parallel beam and, simultaneously, to gather a radiation, scattered by the object under study, the half-lens 14 is used. Its focus is combined with the focus of the full lens 1, focusing the radiation of the point source 2 in the point 34 of the object under analysis. Varying the particle energy, falling on the detector 35, makes possible to study in more details the features of the sample by means of change of angular position of the crystal-monochromator, in particular to study the sample on presence of definite chemical elements. The geometry in FIG. 17 differs from the previous one in that a source of quasi-parallel radiation 17 (for example, a synchrotron source) is meant to be used instead of a point source. The half-lens 14xe2x80x2 focuses the radiation of this source in the point 34, being at the same time a focus of the half-lens 1, which forms a quasi-parallel beam for the monochromator 36. A common peculiarity of the following two geometries (FIG. 18 and FIG. 19) is the fact, that radiation, passing through the sample, and the radiation, excited in the sample by acting of monochromatic radiations of two close wavelengths, are studied simultaneously. In the geometry in FIG. 18 such radiations are obtained from one broadband point source 2 by means of two crystal-monochromators 36 and 36xe2x80x2, irradiating them with parallel beams, formed by half-lenses 14 and 14xe2x80x2, which common focus coincides with the source 2. To prevent the direct hit of the radiation of the source 2 on the sample 33 an absorbing screen (it is not shown in the drawing) must be set between them. The output signals of the detectors 35 and 35xe2x80x2 differ in that degree, in what the reaction of the object under study is different, when the object is irradiated with particle fluxes of different, but close energies. Difference of these signals gives the information only about such difference. Therefore if one of the energies is higher, and the other is lower than the absorption line of the element, which presence it is necessary to detect in the sample, the sensitivity of the device is very high owing to the exclusion of all other factors influence on the difference of output signals of the detectors 35 and 35xe2x80x2. The given geometry can by used, for example, in angiography, when iodine is injected in a patient""s blood, and it allows to increment the sensitivity of the method approximately on two orders in comparison with the case, when the lenses, which form a parallel radiation, falling on the monochromators, are absent, and the distance between the monochromators and the source must be increased. In the geometry in FIG. 19, realizing the same principle, two different point sources 2 and 2xe2x80x2 are used to obtain particles with different, but close energies. The radiation of these sources has clearly defined characteristic lines: higher and lower than the absorption line of the element, to be detected. The radiation of both sources is transformed, by means of the half-lenses 14 and 14xe2x80x2, to quasi-parallel one, acting directly on the sample 33. FIG. 20 depicts one more variant of realizing of the same principle. In this geometry radiations with two energies, acting on the sample 33, are formed alternately as a result of radiation transmission of the same source 2 through the alternating filter-windows of the rotating screen 37. These windows alternate in such a way, that they are transparent for one wavelength and opaque for the other wavelength of the radiation, which must act on the object under analysis. The rotating screen 37 with windows can be placed both after the half-lens 14, which transforms a divergent radiation of the source to quasi-parallel (FIG. 20 depicts this case), and before the half-lens 14. The difference of the output signals of the detector 35, corresponding to two adjacent positions of the rotating screen 37, can be used in the same way as in the geometries in FIG. 18 and FIG. 19. In the geometry in FIG. 21 the usage of the secondary target 38 is provided for obtaining a monochromatic radiation with the wavelength, defined by the features of the target. A weakness of the known devices with a secondary target is rather low intensity of a secondary radiation. The influence of the weakness is removed due to the usage of the lens 1 in the described geometry. The lens 1 concentrates the source radiation on the target in a small area 34 of the focal spot. The radiation of the secondary target 38 falls on the object under study 33, where fluorescence radiation, which falls on the detector 35, arises. This geometry makes possible to irradiate the object under study with rather intensive monochromatic radiation of the secondary target. In the geometry in FIG. 22 the sample 35 is irradiated with a monochromatic radiation as well, but in this case the crystal-monochromator 36 is the radiation source, not the secondary target. A parallel beam, required for a monochromatic radiation forming, is formed of the divergent radiation of the broadband source 2 by the half-lens 14. A wavelength (particle energy) of the radiation, acting on the object under study, can be changed by varying an angular position of the crystal-monochromator. In the geometry in FIG. 23 the crystal-monochromator 36, irradiated by an quasi-parallel beam, formed by the half-lens 14, is used as well. A feature of the crystal-monochromator to form a polarized radiation is used in this geometry. For this purpose the quasi-parallel beam is directed to the crystal-monochromator 36 at xcex8=45xc2x0 angle. A diffracted radiation from the crystal-monochromator 36 falls on the sample under study 33, and the radiation from the sample under study 33 falls on the detector 35, positioned at a 90xc2x0 angle to the direction of propagation of the polarized radiation of the crystal-monochromator 36. Due to this polarized selection takes place, and the detector 35 is free of the background influence, produced by the divergent Compton radiation, arising in the sample under study when the radiation from the crystal-monochromator 36 acts on it. In this geometry a target made of light metal (for example, beryllium (Be)) can be used instead of the crystal-monochromator. The geometry in FIG. 24 is used to realize the method of a phase contrast. In this method a sample is irradiated with a monochromatic radiation, formed by the first crystal-monochromator 36, and a parallel beam for this purpose is formed of the divergent radiation of the source 2 by the half-lens 14. The radiation falls on the crystal-monochromator 36 at a Bragg angle xcex8Br. The second crystal-monochromator 36xe2x80x2, identical to the first one, is positioned after the sample with a capability of varying its angular position in small limits with respect to the position, parallel to the first one. When there are some irregularities in the sample, which differ in density from the neighboring areas, a radiation refracts in such irregularities, passing through them, differently than in the neighboring areas. It can be fixed when a signal appears on the output of the detector 35 at a definite position of the second crystal-monochromator. The sensitivity of the method of the phase contrast is much higher in comparison with the immediate fixation of differences of planes (for example, differences of radiation intensities, passed through the neighboring areas of the object with different, but close densities). The usage of lenses makes possible, without increasing the source power, to work at increased magnitude of intensity of the quasi-parallel radiation, falling on the crystal-monochromator, and the radiation, falling on the detector. It was already mentioned above (see the usage of the analytical device in angiography) that the analytical device can be used in medical diagnostics. FIG. 25 depicts the usage of an integral half-lens in the analytical device, solving problems of medical diagnostics. The object under study 39 (a part or an organ of a human body) is irradiated with a quasi-parallel radiation, formed by the half-lens 14 from the divergent radiation of the source 2, being placed in the focus of this lens. The detector 35 receives two-dimensional density distribution of the radiation, passed through the object 39 (this two-dimensional density distribution of the radiation is interpreted as density distribution of the object in the corresponding projection). A distinction of the given geometry is that the detector must be placed far enough from the object (for a distance of not less than 30 cm). Due to the fact, that the object is irradiated with a quasi-parallel beam, the distance of the detector practically has not an effect for a desired signal level of densities distribution of the object. However in this case the influence of the divergent radiation, arising in the object, sufficiently attenuates, due to what an image contrast range increases. In this case an integral lens is made with a capability of forming a radiation field of 20xc3x9720 cm2 order size. If the detector is placed at the mentioned distance from the object, so it is no need to use any means for suppressing the divergent radiation in this geometry. Thus both problems are solved: spatial resolution and doze problems. Let, for example, the detector is at the distance of 50 cm from the object. If the resolution is equal to 10xe2x88x924xc3x9750=50xc3x9710xe2x88x923 cm =50 xcexcm the beam divergence will be equal to 10xe2x88x924 rad. At the same time an omnidirectional radiation, diverged in the object, reaches the detector with significant (in more than 30 times) attenuation at the distance of 50 cm from the object. Therefore it is possible to do without antiscattering rasters, which usage in order to increase the image contrast range mates with the increase of the radiation dose. Use of integral lenses makes possible to solve the problems of early diagnostics of oncologic diseases due to the obtainable resolution of 50-100 xcexcm order. It is appropriate to use an X-ray tube with a molybdenum (Mo) anode (E=17.5 keV) as a source in mammography researches. Scanning computer tomography is one more promising field of usage of analytical devices with integral lenses in medicine. Modern tomographes provides the image of the density distribution of tissues of a human organism by registration of the radiation intensity, passed from the source to the radiation detector. To calculate the density distribution with the high resolution in one other section it is necessary to irradiate this section many times (usually, more than one hundred) at different angles. Thus the dose is usually high, of 1 R order. The usage of an integral lens with the high level of the radiation focusing provides to change the situation efficiently. As it is shown in FIG. 26, a full lens 1 is placed between a source 2 and a patient 39 so that a second focus is placed inside the area under study. The detector 35, as usual, is on the other side of the patient and it is directed to the radiation yield. The point, the radiation is focused in, acts as a virtual radiation source, placed inside the object under study. Due to this and small sizes of such source, geometric blurriness of the radiation from the source decreases sufficiently. The blurriness is expressed by the formula: U=bd/1, where bxe2x80x94source size, dxe2x80x94a distance from the object to the source, lxe2x80x94a distance from the object to the detector. When the source is outside the object, d and l are of same order, and blurriness U is of same order with b, i.e. with the source size. If the source is inside the object and placed close to the defect to be detected (here it is a tumor), so d less than less than 1, what explains decreasing of the blurriness of the source. Due to the small size of a focal spot of an integral lens the blurriness decreases more, what allows to make less irradiations to obtain the sufficient accuracy of the image reconstruction. Due to the possibility of alignment of a focus with any desired point inside the area under study a procedure of the image formation when examining a small object can be simplified. For example, if it is necessary to examine an area of 1 cm2 size order of lungs, an output focus of a lens can be placed directly close to this selected area. The focus can be displaced in this area with an accuracy, being equal to the focal spot of the lens. If, for example, a focal distance is 20 cm, so this focal spot is of 0.1 mm size order at the energy 50 keV, when xcex8cr≈510xe2x88x924 rad. FIG. 26 depicts the geometry where an element 40 conventionally represents a presence of rigid connection between a source 2, a full integral lens 2 and a detector 35. At tomography examination these three objects must rotate respectively to a means for patient positioning 39 as an integral part (a variant of rotating of the means for positioning together with a patient, when the source 2, the lens 1 and the detector 35 are fixed, is possible as well). FIG. 27 and FIG. 28 depict the usage of integral lenses in radiotherapy, when obtained result is provided by their higher indexes, such as a size of a focal spot and a focal distance, which defines a size of a focal spot with other things being equal. FIG. 27 depicts a device for radiotherapy, a point source 2 is used in, and FIG. 28 depicts a source of parallel radiation 16, for example an output of a nuclear reactor or accelerator, forming quasi-parallel beams of thermal or epithermal neutrons. The radiation is directed to the patient 39 and it is focused inside the tumor 41. A neutron beam extracts from the reactor, and to direct the beam for usage in the device for radiotherapy it is necessary to turn it by means of a lens (not only integral one) with a curved longitudinal axis. Providing a high intensity irradiation on a tumor in combination with a low irradiation of surrounding tissues and skin is a serious problem in radiotherapy. It is necessary for this purpose to cross the beams on the tumor at wide angles. The wider are these angles, the larger area of the skin surface and tissues, surrounding the tumor, is covered by the radiation before it reaches the tumor. An integral lens as a means for focusing the radiation, in particular, the lens, described above, where an effect of radiation xe2x80x9cpressingxe2x80x9d against the external sides of the channels walls takes place, has precisely those features, which are necessary to solve these problems: it can provide high quality of focusing at a considerable ratio of an output aperture to a focal distance (the latter feature contributes to wider angles of crossing of the beams, which converge at focusing). The suggested device can comprise some lenses, irradiating the tumor from different positions, to create the large doze gradients on the tumor. A system of lenses can be made with a capability of being displaced with maintenance of the cross of the beams, formed by lenses, on the tumor. Experiments, carried out, show that even at small energies of 25-30 keV order on depth of 30 cm a doze on the tumor can exceed a doze on the surface. Water phantom of 1-5 cm thickness were used in the experiment. FIG. 29 and FIG. 30 depict schematically the devices for a lithography, the suggested integral lens can be used in as well. The first one, intended for a contact lithography, comprises a means 43 for a resist and substrate placing. This means is placed close to a means 42 for a mask placing. The latter is placed opposite an output face of the integral half-lens 14, which forms a quasi-parallel beam from the divergent beam of the source 2. In this case a homogeneity of a quasi-parallel beam, i.e. a steadiness of the radiation density along its cross section, is very important. Therefore X-ray lithography is a field, where it is necessary to use integral lenses, comprising sublenses without envelopes. A device for projection lithography differs from the considered one, that a xe2x80x9cbottle shapedxe2x80x9d lens 16, faced its smaller face to the means 43 for a resist and substrate placing, is placed between the means 42 for a mask placing and the means for a substrate with a resist placing. The size of the larger face of the lens approximates that of the output end of the half-lens 14. A presence of the xe2x80x9cbottle shapedxe2x80x9d lens 16, oriented in the manner, provides image transmission of the mask to the resist with decreasing. The degree of decreasing of the image scale is defined by a relationship of the input and output diameters of the lens. A relationship of diameter of the separate channels (capillaries) on the input and output of the lens is the same. As this relationship can be much more than 1, the elements of microelectronics of small sizes can be obtained when using a device for projection lithography. Usage of sublenses without envelopes in the xe2x80x9cbottle shapedxe2x80x9d lens 16, used in the device for the projection lithography, is important in a greater extent than in the half-lens 14. In summary, it should be further emphasized that going from the monolithic lenses and the lenses, made as an assembly of microlenses to the integral lenses as a new generation of means for high energies radiation controlling not only provides the increase of indexes accuracy of means, including such lenses, according to the indexes of lenses. In some cases this going makes possible to produce devices, acceptable for practical use (being transportable, suitable for hermetization when used in corrosive medium, and having acceptable cost). In the past the sizes, cost, etc. of the lenses, as well as the impossibility of usage of simple and cheap radiation sources prevent from producing the devices. While the invention has been described in terms of a single preferred embodiment, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the appended claims. |
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abstract | A method of separating material, such as foam, sludge, oil or grease, at a fluid's surface, by applying acoustic pressure shock waves to the material and the fluid's surface such that acoustic pressure shock waves are propagated in liquid medium of the fluid and in gas medium above the fluid surface. |
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abstract | A method of providing an end-capped tubular ceramic composite for containing nuclear fuel (34) in a nuclear reactor involves the steps of providing a tubular ceramic composite (40), providing at least one end plug (14, 46, 48), applying (42) the at least one end plug material to the ends of the tubular ceramic composite, applying electrodes to the end plug and tubular ceramic composite and applying current in a plasma sintering means (10, 50) to provide a hermetically sealed tube (52). The invention also provides a sealed tube made by this method. |
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052176827 | claims | 1. A nuclear reactor system comprising: a reactor core and a main heat transport path containing a main heat removal component; at least one main coolant pump and a first coolant wherein, during normal operation, the first coolant is pumped by the main coolant pump through the reactor core to the main heat removal component and back to the reactor core to transport heat generated in the reactor core to the main heat removal component; the main heat transport path including a heat exchanger located in that path after the main heat removal component's outlet with the secondary side of the heat exchanger being included in a decay heat removal loop containing a second liquid coolant and having a vapor separator connected to an outlet of the secondary side of the heat exchanger; the separator's outlet being connected to an inlet of a further heat exchanger located in a reservoir containing a third liquid coolant which forms a heat sink; the further heat exchanger's outlet being connected to an inlet to the secondary side of the heat exchanger; and wherein the further heat exchanger is located at a higher elevation than the heat exchanger whereby a natural convection flow can occur in the decay heat removal path, the vapor/liquid interface in the loop normally being at a higher elevation than the heat sink which restricts any natural convection flow until boiling of the second liquid coolant occurs in the heat exchanger. 2. A nuclear reactor system as defined in claim 1, wherein the second liquid coolant is water. 3. A nuclear reactor system as defined in claim 2, wherein the first coolant is heavy water. 4. A nuclear reactor system as defined in claim 3, wherein the primary heat removal component is a steam generator. 5. A nuclear reactor system as defined in claim 4, wherein the steam generator's input is connected to a higher temperature outlet header for the reactor and an outlet of the heat exchanger is connected to a low temperature inlet header for the reactor. 6. A nuclear reactor system as defined in claim 2, wherein the decay heat removal path is pressurized. |
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claims | 1. A method for irradiating product packages, comprising the steps of: pre-defining a threshold of maximum effective dimension; measuring the maximum effective dimension of a product package; comparing said maximum effective dimension to said threshold; directing said product package either into a first processing unit or into a second processing unit for sterilising said product package, depending on the effective dimension of the product package, said product package being directed into the first processing unit wherein the product package is sterilised with an electron-beam if the maximum effective dimension of said product package is under the threshold, or said product package being directed into the second processing unit wherein the product package is sterilised with alternative sterilisation means, if the product package has at least an area with an effective dimension above the threshold. 2. The method according to claim 1 , wherein the alternative sterilisation means are a gas sterilisation process. claim 1 3. The method according to claim 1 , wherein processing a package with an e-beam source is performed by an e-beam directed along the shortest dimension of the package. claim 1 4. The method according to claim 1 , wherein the alternative sterilisation means arc an X-ray or gamma irradiation process. claim 1 5. The method according to claim 4 , wherein product packages having at least an area with an effective dimension above said threshold are grouped in arrays, a number of arrays are stacked, and said stack is irradiated from the side by an X-ray or gamma source. claim 4 6. The method according to claim 5 , wherein said stack is rotated in front of the X-ray or gamma source during irradiation. claim 5 7. An apparatus for irradiating product packages, comprising an irradiation source, a shielding, comprising an entry maze, an exit maze, and a conveyor device comprises: a detection device for detecting product packages having everywhere an effective dimension below some threshold; means for directing product packages having everywhere an effective dimension below said threshold to an e-beam source; means for directing other product packages having at least an area with an effective dimension above said threshold to alternative means. 8. The apparatus according to claim 7 wherein said alternative means are a gas sterilant device. claim 7 9. A method or apparatus according to claim 7 wherein said threshold is comprised between 1 and 6 g/cm 2 . claim 7 10. The apparatus according to claim 7 wherein said alternative means are an X-ray or gamma irradiation device. claim 7 11. The apparatus according to claim 10 further comprising a means for grouping packages having at least an area with an effective dimension above said threshold in arrays, for stacking a number of said arrays, and for irradiating said stack from the side by an X-ray or gamma source. claim 10 12. The apparatus according to claim 11 further comprising a turntable for rotating said stack during irradiation. claim 11 |
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059784318 | summary | The present invention relates to the production of nuclear fuel pellets. In particular, it relates to the production of mixed oxide (MOX) nuclear fuel pellets. The use of MOX nuclear fuel pellets in pins or rods in fuel assemblies for light water reactors (LWR), eg pressurised water reactors (PWR) and boiling water reactors (BWR) is known, eg as described in Applicants' EP 627,743A. Incorporation of burnable neutron poisons in MOX fuel is unknown. Such poisons have been included as separate fuel rods or incorporated in the fuel pellets of non MOX fuels. Such poisons allow thermal hot spots to be controlled, especially in mixed reactor cores containing both uranium oxide and mixed oxide fuels. They also allow higher initial fissile isotope enrichments to be used (providing longer fuel cycles and a higher quantity of electricity from the fuel element before discharge from reactor) due to suppression of the initial reactivity. However, such poisons when added directly to the fuel have a deleterious effect on the size of the grains making up the fuel pellets, adversely affecting fission gas retention in the pellets. Various methods have been described in the prior art for producing fuel pellets in which steps are provided to counteract the effect on grain size of neutron poisons. However, the fuel pellets produced by these known methods do not show ideal properties. The mechanical and physical properties of such pellets may be inadequate, causing for example the pellets to be damaged easily by chips or cracks. The density of the pellet material may vary across the pellet giving a variation in burn up. Such pellets may contain large inhomogeneously dispersed plutonium agglomerates which may lead to several disadvantages including decreased solubility in nitric acid. Consequently treating spent fuel by conventional reprocessing processes is made more difficult. Addition of the neutron fuel poison directly to the fuel, as opposed to the incorporation of separate rods within the reactor, mean for example that there would no longer be the need for extra production lines for the production of neutron poison rods, it would increase the even fuel burn up and would not require any special assembly design, thus providing a more economic system. It is an object of the present invention to provide a method for the production of thermal MOX fuel pellets incorporating burnable poison(s) in which the aforementioned problems are reduced or eliminated. According to the present invention there is provided a method of producing mixed oxide fuel pellets for use in a nuclear reactor, the mixed oxide comprising oxides of at least two fissile elements, the method including the steps of: (i) providing the mixed oxide with a neutron poison to form a fuel; PA1 (ii) milling the fuel to form a fuel powder; PA1 (iii) treating the milled fuel with a spheroidising step; and PA1 (iv) pressing and sintering the fuel resulting from the spheroidising step (iii) to produce a fuel pellet. Suitable milling, pressing and sintering steps are known per se and are described for example in Applicants' EP 277,708B. Preferably, the method includes one or more steps to counteract the grain size limiting effect of the neutron poison. Such steps may be known per se. The method may include addition of one or more additives, prior to the pressing step or these additives may be added at the milling step. The additives are introduced to reduce grain size limitation. Such additives which are known per se include one or more of Ti, Al, Nb, Cr and Mg, eg in a maximum total concentration of typically in the range 0.01 to 1% by weight. Alternatively, or in addition, the method may include control of heating and/or cooling rate at the beginning or end of sintering or a part of the sintering step, and/or the introduction of a small quantity (eg up to 8 percent by volume) of an oxidising gas (eg moisture or carbon dioxide). This oxidising gas is introduced into the gaseous atmosphere employed during the sintering step (normally a reducing atmosphere), eg at specific selected parts of the sintering step when the sintering temperature has been reduced and additionally, for the adoption of sintering temperatures (eg 2000.degree. C.) which are higher than those conventionally used (eg 1600 to 1700.degree. C.) in at least part of the sintering step. Alternatively, or in addition, grain growth may be promoted by addition of seed crystals to the powder prior to the pressing and sintering steps. This optional step is described in Applicants' EP 416,778A and corresponding U.S. Pat. No. 5,061,434. The seed crystals may be UO.sub.2. The seed content may comprise from 1 to 8 percent by weight of the pressed material. The present invention allows thermal MOX nuclear fuel pellets for use in LWR to be produced having a combination of properties not available in the prior art. Thus, such pellets can incorporate neutron poisons thereby providing longer fuel cycles and higher burn up whilst maintaining satisfactory grain sizes, eg a mean size greater than 10 to 15 .mu.m. Such fuel pellets also provide enhanced fission product gas retention during fuel irradiation thereby extending fuel burn up. Furthermore, in contrast to the pellets containing neutron poisons made by prior art methods, such pellets can have a uniform density in turn giving uniform and predictable burn up, thus increasing the amount of electricity generated from the fuel element before discharge from the reactor is necessary; good mechanical properties, whereby the possibility of damage during remote handling is significantly reduced; and can be soluble in nitric acid and therefore suitable for treatment by reprocessing (after a suitable time) following irradiation. By control of the sintering process MOX pellets incorporating a neutron poison may be produced having a satisfactory pellet quality, friability, chip resistance, grain size, high and consistent density whilst incorporating the neutron poison. Preferably, however, approximately 1-3% poison is added which is sufficient to benefit from the above-mentioned advantages. Most preferably, therefore the sintering is carried out at approximately 1650.degree. C. and there being no requirement for two rate ramping to occur in the sintering process. The pellet density may be controlled by the addition of a pore forming additive, eg the product CONPOR (RTM) supplied by Applicants and described in Applicants' GB 1461263 and corresponding U.S. Pat. No. 3,953,286. In the method of the present invention, the fissile elements employed to produce the MOX fuel pellets may include uranium and plutonium. Normally, each of these elements will comprise a mixture of isotopes one of which is fissile. The pellets produced may thus comprise a mixed oxide system comprising uranium oxide and plutonium oxide, the latter comprising for example up to ten percent by weight, and most especially from two percent to six percent by weight, of the mixed system. The neutron poison included in the mixed oxide system may include any one or more of the known additives, eg one or more of boron and oxides of lanthanides, eg oxides of gadolinium, erbium and other rare earths. Preferably, the total poison additive concentration is in the range 0.5 to 10 percent by weight, particularly 2 to 6 percent by weight, of the overall mixed oxide system. Preferably additives are introduced into the fuel to minimise the reduction in grain size which commonly occurs as a result of the addition of neutron poisons. Problems from bloating and micro-cracking may be overcome by adjusting sintering conditions and/or the introduction of additives. In the method according to the present invention the milling step is preferably carried out in an attritor mill typically at 100 revolutions per minute for 40 minutes with a ball/charge ratio of 3.5 to 7.5. As in the prior art, a small amount, eg 0.1 by weight, of a solid lubricant such as zinc stearate may be added to the mill before the charge to be milled is added. In the method according to the present invention, the spheroidising step is preferably carried out using a spheroidiser as claimed in Applicants' EP 331, 311 and corresponding U.S. Pat. No. 4,936,766. In the method according to the present invention, the pressing step is preferably carried out using a pressure of typically 20 to 30 tons per square inch for a period of 1 to 5 seconds. According to a further aspect of the present invention there is provided a method of producing for use in fuel for a nuclear reactor pellets comprising a mixed oxide system comprising oxides of at least two fissile elements and an additive which acts as a neutron poison, which method comprises producing a free flowing powder by a binderless process which includes a step of milling a powder comprising a mixture of the oxides of the fissile elements, treating the product of the milling step without any pre-compaction and/or granulation in a spheroidising step, mixing, in an additive mixing the step and sintering the product of the pre-sintering product of the pre-sintering pressing step. |
abstract | This invention discloses a method for the co-solidification of low-level radioactive wet wastes of BWR nuclear power plants, including concentrate waste, spent ion exchange resins and sludge wastes etc., with very high volume efficiency. In this invention, for promoting the stability of the solidified waste, sodium sulfate in the concentrate solution is converted to sodium hydroxide and barium sulfate by reacting with barium hydroxide. The conversion product barium sulfate possessing high density and stability is insoluble and used as a fine aggregate material in the solidified waste. Sodium hydroxide is used to stabilize ion exchange resins and to form a highly water-durable solidified waste form with silicates and phosphates in the solidification agent mixture. The solidification agent used in this invention is a formulated powder mixture completely made from inorganic materials. Therefore, there is no aging problem of the solidified waste. In this invention, the waste loading of the solidified waste is highly increased due to the conversion of sodium sulfate and the co-solidification of wastes. Thus, the solidification volume efficiency of the present invention is about three times of the solidification of the waste separately. |
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claims | 1. A radiation-monitoring diagnostic hodoscope system for producing an approximate image of radiation-producing components within and below a pressure vessel of shutdown nuclear plant, said system comprising:A) at least one gamma-radiation-monitoring hodoscope unit adapted to detect gamma radiation in a limited substantially-straight narrow radiation beam of less than 50 degrees and in at least one specific gamma-energy range, said at least one hodoscope unit comprising:1) a collimating means adapted to produce said narrow radiation beam and2) at least one radiation detector adapted to produce electrical signals corresponding to intensities of gamma radiation in said at least one specific gamma energy range;B) a positioning means for positioning said at least one hodoscope unit so as to accumulate sufficient radiation data representing radiation intensity and gamma energies in a sufficiently large number of narrow radiation beams to create said approximate image of said gamma radiation-producing sources within and below said pressure vessel; andC) a computer processor programmed with an algorithm adapted to associate said gamma or neutron radiation data so as to produce said approximate image of said radiation-producing components. 2. The system as in claim 1 wherein the at least one specific gamma energy range is at least two specific gamma energy ranges. 3. The system as in claim 1 wherein the processor is programmed to produce an approximate one-dimensional image. 4. The system as in claim 1 wherein the processor is programmed to produce an approximate two-dimensional image. 5. The system as in claim 1 wherein the processor is programmed to produce an approximate three-dimensional reconstructed image. 6. The system as in claim 1 wherein said system also comprises at least one neutron-radiation monitoring hodoscope. 7. The system as in claim 1 wherein said systems comprises at least one neutron- and gamma-radiation-monitoring hodoscope. 8. The system as in claim 1 wherein the nuclear plant is a boiling-water nuclear plant. 9. The system as in claim 1 wherein the nuclear plant is a pressurized-water-cooled nuclear plant. 10. The system as in claim 1 wherein the nuclear plant is a single nuclear plant of a group of nuclear plants consisting of: gas-cooled nuclear plants, liquid-metal-cooled nuclear plants, and heavy-water-cooled nuclear plants. 11. The system as in claim 1 wherein the at least one radiation detector is at least one scintillator detector. 12. The system as in claim 11 wherein the at least one scintillator detector is a sodium-iodide detector comprising a NaI scintillator. 13. The system as in claim 11 wherein each of the at least one scintillator detector includes a photomultiplier tube and a preamplifier. 14. The system as in claim 11 wherein each of the at least one scintillator detector includes a single photomultiplier for detecting light photons. 15. The system as in claim 1 wherein the at least one radiation detector is a bismuth-germanate-oxide (BGO) detector. 16. The system as in claim 1 wherein the at least one radiation-monitoring hodoscope unit is a plurality of such hodoscope units mounted external to the pressure vessel and adapted to function as plant-operation-monitoring instruments, as well as a real-time monitoring function of a shutdown nuclear plant, as well as monitoring such a plant while undergoing damaging or potentially damaging transients. 17. The system as in claim 16, wherein the damaging or potentially damaging transient includes one of a group of transients consisting of an accidental or uncontrolled loss-of-coolant condition, including melting of the reactor fuel, and melt-through of nuclear fuel through the bottom of the pressure vessel. 18. The system as in claim 16 wherein a biological shield surrounds the pressure vessel and at least a portion of the plurality of hodoscope units are mounted in or within the biological shield and pointed toward the pressure vessel so as to monitor gamma radiation produced within the pressure vessel. 19. The system as in claim 18 wherein the at least one hodoscope unit mounted within the biological shield is pointed to a region below the pressure vessel so as to monitor radiation originating in the region below the pressure vessel. 20. The system as in claim 18 wherein the at least one hodoscope unit is pointed to the region below the pressure vessel. 21. The system as in claim 16 wherein data obtained from at least some of the hodoscopes units is stored for later analysis. |
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abstract | Disclosed is an appearance processing method comprising: designing a reference appearance for designing a set shape as a theoretical value; producing a specimen; comparing the reference appearance with the specimen and thus setting a deviation region; performing ion beam milling for milling the deviation region of the specimen by ion beam; and comparing the milling-processed specimen with the reference appearance after the ion beam milling thus to obtain a deviation and milling the deviation region repeatedly thus to make the specimen consist with the reference appearance. Accordingly, an arbitrary shape, a minute spherical surface, or an aspheric shape can be precisely processed, and a large quantity of fabrication by a uniform processing precision is possible. |
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043938990 | claims | 1. Apparatus for plugging a plurality of cylindrical holes provided through an inner peripheral wall of a cylindrical container, said apparatus comprising a plurality of plugs to be inserted into said plurality of holes for plugging the same, a supporting ring assembly having an outer diameter smaller than an inner diameter of said container, a beam assembly detachably connected to said ring assembly, means provided on said beam assembly for supporting said plurality of plugs and simultaneously forcing said plugs radially outwardly into said cylindrical holes of said cylindrical container, and means for preventing said plugs from being driven radially inwardly out of said cylindrical holes. 2. Apparatus as set forth in claim 1 wherein said supporting ring assembly is divided into circumferential pieces. 3. Apparatus as set forth in claim 1 which further comprises means for accurately positioning said supporting ring assembly so as to align said plugs supported by said supporting means with said cylindrical holes. 4. Apparatus as set forth in claim 3 wherein said positioning means comprises a plurality of brackets secured on the inner peripheral wall of the container in a circumferentially spaced apart relation, and a corresponding number of supporting pieces secured on the radially outer surface of said ring assembly so that said pieces are engageable with said brackets when said ring assembly is positioned correctly. 5. Apparatus as set forth in claim 1 wherein said means for supporting and forcing said plugs into said holes comprises carriages which are simultaneously driven radially outwardly along said beam assembly by a hydraulic device. 6. Apparatus as set forth in claim 1 wherein said means for preventing said plugs from being driven out of said cylindrical holes comprises means for bringing said ring assembly to a position where a rod projectable from said ring assembly is aligned with each said plug, and a hydraulic device for driving said rod radially outwardly into a tight contact with said plug. |
abstract | Examples of advanced fuel cycles for fusion reactors are described. Examples include fuel cycles for use in field reverse configuration (FRC) plasma reactors. In some examples, reaction gases may be removed from a fusion reactor between pulses (e.g. plasmoid collisions). In some examples, a D-3He reaction is performed, with the 3He provided from decay of byproducts of previous reactions (e.g. tritium). |
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abstract | A process for co-producing synthesis gas and power includes producing a synthesis gas comprising at least CO and H2 by reacting a hydrocarbonaceous feedstock with oxygen, the synthesis gas being at a first temperature, separating air from a compressed air stream by means of at least one ion transport membrane unit thereby producing a permeate stream consisting predominantly of oxygen and a reject stream of oxygen-depleted air at a second temperature which is lower than the first temperature, indirectly heating the reject stream of oxygen-depleted air with the synthesis gas and at least partially expanding, the heated reject stream of oxygen-depleted air through at least one turbine to generate power, producing an at least partially expanded reject stream of oxygen-depleted air, and feeding at least a portion of the permeate stream consisting predominantly of oxygen to the synthesis gas generation stage to provide oxygen for production of synthesis gas. |
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050842285 | summary | FIELD OF THE INVENTION The invention relates to a sealing device for an instrumentation column and, in particular, for a thermocouple column penetrating the head of a vessel of a pressurized-water nuclear reactor. BACKGROUND OF THE INVENTION In pressurized-water nuclear reactors, the vessel enclosing the core of the reactor has a head with a substantially hemispherical shape having openings in which followers are fastened enabling the passage of the control rods of the reactor and of instrumentation columns such as thermocouple columns; a set of thermocouples enabling the temperature of the cooling fluid to be measured at the outlet of the assemblies of the core of the reactor is arranged in each of the thermocouple columns. Each of the followers has a part projecting beneath the head ensuring the guidance of the thermocouple column and a part projecting above the head having means for connecting a tubular bearing and sealing unit of the thermocouple column which may be fastened in the extension of the follower. Inside the bearing unit fastened to the follower, a shoulder is provided against which part of the thermocouple column may bear, a sealing strip being placed therebetween. The thermocouple column which traverses the bores of the bearing unit and of the follower, situated in each other's extension, has an end which engages with a pulling device resting on the end of the bearing unit. By virtue of the pulling device, the thermocouple column may be displaced between a low position where its sealing surface is at a distance from the shoulder of the corresponding bearing unit and a high position where the sealing surface of the thermocouple column is applied against the shoulder with a degree of contact pressure which ensures sealing. The bearing unit of the thermocouple column generally has two parts placed in each other's extension which are assembled, a sealing strip being placed therebetween, and held in place in their assembled position by a clamping bracket engaged on corresponding tapered areas of the two parts of the bearing unit. The lower part of the bearing unit is connected to the follower by its joining means which generally consists of a threaded part onto which is engaged a corresponding tapped bore of the lower part of the bearing unit. The joint between the follower and the lower part of the bearing unit is completed by welding two circular seams placed to coincide in order to ensure the sealing of the screwed joint. The upper end part of the bearing unit including the sealing area of the thermocouple column has an upper end surface against which the pulling device of the instrumentation column bears. When it is desired to raise the vessel head, after having performed the depressurization, the tensile force exerted on the thermocouple column is relaxed and the two parts are separated from the bearing unit by disassembling the clamping brackets. The pulling device on the thermocouple column may be separated from the latter, enabling the upper part of the bearing unit to slide in order to separate it from the thermocouple column. The thermocouple column may then be removed completely from the follower and from the lower part of the bearing unit. This procedure is also necessary when it is desired to change the sealing strip of a thermocouple column. These various operations take a relatively long time to perform and may even prove impossible when the clamping pieces seize up. SUMMARY OF THE INVENTION The object of the invention is therefore to provide a sealing device for an instrumentation column and, in particular, for a thermocouple column penetrating the head of a pressurized-water nuclear reactor vessel, inside a tubular follower fastened in a penetration opening of the vessel head and projecting inwardly and outwardly from the head, having a tubular bearing unit fastened to the end of the follower situated outside the head and in its extension, in which a leaktight bearing area is provided for the instrumentation column traversing the bore of the tubular bearing unit and of the follower, as well as a means for pulling on one end of the instrumentation column projecting outwardly from the bearing unit and resting on the end of this bearing unit, this sealing device enabling the thermocouple column to be extracted quickly and easily, even when the clamping and bracketing parts of the bearing unit have seized up. To this end, the bearing unit has an end part in which is provided the bearing area of the thermocouple column and on which the means for pulling the instrumentation column rests, consisting of two successive sections in the axial direction: a first section being fastened to the outer end of the follower and having an outer, peripheral annular throat and at least three openings traversing the first section in an axial direction so as to open into the peripheral throat, a second section being superposed on the first and having openings in the extension of the openings of the first section and the bearing area of the instrumentation column, a mounting piece consisting of two half-rings being introduced into the peripheral throat of the first section and having tapped openings in the extension of the openings of the first and second sections in an assembled position where screws are introduced into the coinciding openings of the first and of the second sections and screwed into the tapped openings of the mounting piece so as to assemble the first and the second sections, a sealing strip being placed therebetween. |
062228986 | abstract | A method of jacketing a uranium slug to an aluminum container comprising applying a coating to the exterior of the container, the coating consisting of colloidal graphite in water, permitting the coating to dry, applying an alloy of aluminum and silicon to the interior surface of the container at a temperature between 588.degree. C. and 594.degree. C., inserting the slug into the container in complete contact with the alloy, and quenching the assembly. |
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abstract | A method for preparing alpha sources of polonium. A sample of polonium is provided in a solution. A controlled amount of sulfide and a controlled amount of a metal capable of forming an insoluble sulfide salt in the solution are introduced into the solution, in order to co-precipitate polonium from the solution. The precipitates are filtered out. |
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claims | 1. A method for measuring a demagnification of a charged particle beam exposure apparatus, the method comprising:measuring a first stage position of a mask stage of the charged particle beam exposure apparatus in accordance with a mask stage coordinate system having a measurement accuracy of an order of 1 nm with an opening portion of a mask placed on the mask stage being situated in a first opening position;irradiating a first charged particle beam to a first irradiation position on a surface of a specimen through the opening portion of the mask, the first charged particle beam being shaped through the opening portion and then passing through an objective lens system;measuring the first irradiation position in accordance with a specimen stage coordinate system having a measurement accuracy of 1 nm;moving the mask stage to a second stage position to situate the opening portion of the mask in a second opening position different from the first opening position by a distance of an order of several hundred μm;measuring the second stage position of the mask stage in accordance with the mask stage coordinate system;irradiating a second charged particle beam to a second irradiation position on the surface of the specimen through the opening portion of the mask moved together with the mask stage, the second charged particle beam being shaped through the opening portion situated in the second opening position and then passing through an objective lens system;measuring the second irradiation position in accordance with the specimen stage coordinate system; andcalculating a demagnification η of the charged particle beam exposure apparatus from a distance L between the first and second stage positions and a distance 1 between the first and second irradiation positions using an equation η=1/L. 2. A method according to claim 1, further comprising: adjusting the demagnification of the charged particle beam exposure apparatus corresponding to the demagnification obtained by the calculating. |
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062947915 | summary | BACKGROUND OF THE INVENTION This invention relates to irradiation systems which utilize a conveyor system for transporting articles in a chamber through a target region scanned by radiation from a radiation source. The invention is particularly related (1) to a system for synchronizing the movements of queues providing for the movements of the articles into the chamber, past the radiation source for irradiation of the articles and then from the chamber after the irradiation of the articles and (2) to the disposition of a shield in the chamber for inhibiting radiation from reaching the queues and the walls of the invention. Co-pending application Ser. No. 09/102,942 by John Thomas Allen et al. on Jun. 23, 1998, and assigned of record to the assignee of record of this application discloses and claims an article irradiation system which includes (1) a radiation source for scanning a target region with radiation, (2) a conveyor system including a process conveyor positioned for transporting articles in a given direction through the target region and (3) radiation shielding material defining the walls of a chamber containing the radiation source, the target region and a portion of the conveyor system. The radiation source is disposed inside a loop defined by a portion of the conveyor system and is adapted to scan the articles in the chamber in a plane transverse to the given direction of transport by the process conveyor. A shield (e.g., an intermediate wall) of radiation shielding materials positioned within the loop supports a radiation shielding ceiling of the chamber, inhibits photons emitted from a beam stop in one of the chamber walls from impinging on other walls of the chamber and restricts flow in the chamber of ozone derived in the target region from the radiation source. BRIEF DESCRIPTION OF THE INVENTION In one embodiment of the invention, an article irradiation system includes (1) a radiation source for scanning a target region with radiation, (2) a conveyor system including a process conveyor positioned for transporting articles in a given direction through the target region, and (3) radiation shielding material defining the walls of a chamber containing the radiation source, the target region and a position of the conveyor system. The radiation source is disposed inside a loop defined by a portion of the conveyor system and is adapted to scan the articles in the chamber in a plane transverse to the given direction of the transport by the process conveyor. A shield (e.g., an intermediate wall) of radiation shielding material positioned within the loop supports a radiation shielding ceiling of the chamber, inhibits photons emitted from a beam stop in one of the chamber walls from impinging on the outer walls of the chamber and restricts flow in the chamber of ozone derived in the target region from the radiation source. A first queue is disposed outside of the chamber for transferring into the chamber articles from a loading area; a second queue is disposed in the chamber for moving the articles past the radiation source for irradiation by the source; and a third queue is disposed in the chamber for transferring articles from the chamber, after irradiation, for movement to an unloading area. The operations of the first, second and third queues are synchronized. The shield inhibits radiation from the source from reaching the queues. |
claims | 1. A molecular imaging method for imaging a breast of a patient, the method comprising:administering a radiopharmaceutical to the patient;positioning a molecular imaging system, the system comprising:a stand;a gantry connected to and movable in relation to the stand;a first support arm articulated to the gantry;a first gamma camera connected to the first support arm;a second support arm articulated to the gantry;a second gamma camera connected to the second support arm;a third support arm articulated to the gantry;a first compression paddle connected to the third support arm;a fourth support arm articulated to the gantry;a second compression paddle connected to the fourth support arm;wherein the first support arm, the second support arm, the third support arm, and the fourth support arm are each mechanically independent and configured to be articulated independently relative to the gantry;wherein the first gamma camera, the second gamma camera, the first compression paddle, and the second compression paddle are each mechanically independent;at least one pixel-registered collimator with slant holes; anda controller connected to the gantry to control movements of the gantry, movements of the support arms, and an acquisition of an image by at least one of the cameras;positioning and compressing the breast utilizing the first compression paddle and the second compression paddle;positioning the slant holes of the at least one pixel-registered collimator towards a chest wall tissue;acquiring a molecular image; anddecompressing the breast. 2. The method of claim 1, wherein at least one of the first compression paddle andthe second compression paddle comprises an aperture and the method further comprises a step comprising at least one of a biopsy and a surgical procedure. 3. The method of claim 1, wherein the molecular imaging system further comprises an ultrasound probe. 4. The method of claim 1, wherein at least one of the first compression paddle and the second compression paddle comprises a concave curved surface. 5. The method of claim 1, wherein the at least one pixel-registered collimator with slant holes comprises a variable-angle slant-hole collimator comprising a plurality of slidable stacked plates and one or more slantable alignment pins, the plates comprising an array of pixel registered holes. 6. The method of claim 1, wherein at least one of the first gamma camera and the second gamma camera comprises the at least one pixel-registered collimator and a detector assembly. 7. The method of claim 6, wherein the other of the first gamma camera and the second gamma camera comprises at least one of a parallel-hole collimator, a slant-hole collimator, a focusing collimator, and a multiple-pinhole collimator. 8. The method of claim 6, wherein the gantry has an axis and at least one of the support arms is at least one of translatable parallel to the axis, rotatable to the axis, translatable radially to the axis, and tiltable with respect to the axis. 9. The method of claim 6, wherein the detector assembly comprises a scintillator and an array of photodetectors. 10. The method of claim 6, wherein the detector assembly comprises an array of solid-state detectors. |
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description | The present invention relates to a scanning probe microscope for high-accuracy measurement of a sample shape, and a surface shape measuring method of the sample using the same. With the miniaturizing trend of circuit patterns in progress associated with high integration of the semiconductor circuit, inspection measurement technique and failure analysis technique for the semiconductor manufacturing process has been increasingly recognized as important. Increase in the recording density of the hard disk device has placed more importance on the miniature structure or planarity of the pole part of the record/reproduction head, surface roughness of the recording medium, and measurement of a three-dimensional shape of stripe-like or dot-like structure of magnetism for further improving the recording density. The scanning probe microscope (hereinafter referred to as SPM: Scanning Probe Microscope) optimal for such usage has been widely known as an approach to measurement of the shape of the sample surface in the atomic order by scanning with the probe while having a fine probe tip brought proximal to or in contact with the sample surface. Under the surface shape measurement using the SPM, the inspection region is restricted to a narrow region, for example, within several hundreds of micrometers square or less. Meanwhile, when measuring the very small area in the atomic order, the field of view ranging from several tens to several hundreds of nanometers is required to be measured with the accuracy in the atomic order or less. In this case, the mechanism for scanning with the probe is required to exhibit high positioning accuracy. Meanwhile, the broad range of approximately several tens of micrometers is required to be observed at high speeds in order to identify the measurement region. Furthermore, the local difference in height of the sample surface in the broad range of several hundreds of micrometers needs to be measured at high speeds. Use of the SPM provides an advantage to ensure measurement of the three-dimensional shape of the sample surface with high resolution of approximately 0.1 nanometers. However, a certain amount of time is required to position the measurement point, and to measure at the point on the sample surface, thus failing to provide sufficient measurement throughput. In the manufacturing line for the device such as the semiconductor and the hard disk device, it is not used in-line (in the manufacturing process), and accordingly, it is mainly used off-line for the failure analysis. If measurement results of the SPM allow immediate detection of abnormality of the respective process devices, and feedback to the processing conditions of the respective process devices, manufacturing of the failure products may be minimized to improve the production yield on the manufacturing line. Therefore, implementation of the in-line SPM is highly expected. Upon implementation of the in-line SPM, it is essential to perform the processing (measurement) of the measurement points as large as possible for a unit time. The manufacturing line at present requires the processing time of 20 seconds or shorter, which may be converted into the measurement throughput corresponding to 30 WPH (wafer per hour) or more. Generally, a piezoelectric device is used as an actuator of a mechanism for positioning the probe of the SPM on the sample with high-accuracy. For example, Patent Literature 1 discloses that the highly accurate SPM is realized by three axes X, Y and Z as parallel flat plates, which are individually driven by piezoelectric devices, and simultaneously, the probe position is controlled through measurement by means of a displacement gauge. A three-dimensional miniature scan mechanism as disclosed in Patent Literature 2 serves as another probe drive mechanism for improving positioning accuracy of the probe. This mechanism is configured to use three voice coil motors for driving three-axis stage provided with a Y-stage connected to an outer frame with an elastic member, and an XZ-stage (serving as both X-stage and Z-stage) connected to the Y-stage therein with the elastic member. All the stages each consisted of the same member are integrally formed. The driving force of the voice coil motor is applied to each of those stages via a spindle. The respective spindles are configured to be always pressed in the operation direction of each of the stages in parallel regardless of displacement of the respective stages. For example, when only the Y-stage is operated, the elastic members for connecting the outer frame and the Y-stage are all elastically deformed uniformly. Therefore, there is no chance of application of the unnecessary force to the operation axis other than the Y-axis. This makes it possible to realize the probe scanning mechanism capable of controlling the probe positioning with respect to the three axes of the probe individually with high-accuracy. Patent Document 3 discloses the method of improving the stage positioning resolution using the piezoelectric device that is formed by connecting two types of those for fine and rough movements. Patent Literature 4 discloses the SPM configured to improve the measurement throughput. Specifically, the sample surface position is detected by an approach sensor formed of an objective lens placed just above the probe, a laser diode, and a photodiode. The sample surface is brought into proximal to the tip position of the probe at high speeds to shorten the time taken for the SPM to start the measuring operation so as to improve the measurement throughput of the SPM. The SPM as disclosed in Patent Literature 3 has the objective lens just above the probe contact position on the sample. As the objective lens is placed just above the probe contact position on the sample, the measurement positioning on the sample is performed using an observation optical system, and then the measurement may be performed without moving the sample position. This makes it possible to improve the SPM measurement throughput. Patent Literature 1: Japanese Patent Laid-Open Publication No. 2004-303991 Patent Literature 2: Japanese Patent No. 3544453 Patent Literature 3: Japanese Patent Laid-Open Publication No. 2005-347484 Patent Literature 4: Japanese Patent Laid-Open Publication No, 2004-125540 Since the generally employed SPM has an unintentional displacement in Z-direction as the probe scanning mechanism of the probe scans in the XY-direction, planarity in the nm-order cannot be expected. There has been an example of measuring displacement of a probe attachment portion of the high-accuracy probe scanning mechanism. In this case, however, it is difficult to implement both the high-accuracy probe scanning mechanism and the scanning over the broad range. Although the scanning mechanism that covers the broad range is operated for scanning in the XY-direction at the sample side instead of the probe side, and for driving in the Z-direction at the probe side, the vertical movement in the Z-direction occurs in association with the scanning in the XY-direction on the sample stage. In the aforementioned case, the planarity in the nm-order cannot be expected. It is an object of the present invention to provide a scanning probe microscope capable of scanning with the probe in the broad range quickly and scanning with the probe in the small range accurately with high resolution by solving the aforementioned problem of the related art, and a sample surface shape measuring method using the scanning probe microscope. In order to address the aforementioned problem, the present invention is configured to allow the high-accuracy displacement system to measure the displacement in the Z-direction as the non drive direction of the XY-stage at the sample side, and to correct the measurement value of the scanning probe microscope based on the measured value, or execute feedback to the probe displacement mechanism so as to ensure high-accuracy profile measurement under no influence of fluctuation of the position of the XY-stage in the non drive direction during the sample scanning. For the purpose of addressing the problem, the present invention provides a scanning probe microscope which measures a surface shape of a sample by bringing a probe into proximal to or contact with the surface of the sample, comprising: a probe, a probe holder that holds the probe, probe drive unit that drives the probe holder at least in a vertical direction, first measurement unit which measures a position of the probe drive unit in the vertical direction, sample stage unit movable in a plane, on which the sample is mounted, second measurement unit which measures a position of the sample stage unit in a direction orthogonal to the plane, vertical rough stage unit configured to change a vertical relative position between the probe held by the probe holder and the sample stage unit, horizontal rough stage unit configured to change a horizontal relative position between the probe held by the probe holder and the sample stage unit, detection unit which detects a contact state between the sample and the probe held by the probe holder, and image generation unit that generates an image of the sample surface using information obtained through measurement performed by the first measurement unit, information obtained through measurement performed by the second measurement unit, and information obtained through detection performed by the detection unit. For the purpose of attaining the problem, the present invention provides a sample surface shape measuring method using a scanning probe microscope, which includes the steps of driving a probe in a vertical direction with respect to a surface of a sample mounted on a sample stage that is movable in a plane using a probe drive system, bringing the probe into proximal to or contact with the surface of the sample by changing a relative position between the probe and the sample stage in the vertical direction using vertical rough stage unit, measuring a position of the probe drive system in the vertical direction, measuring a position of the sample stage in a direction orthogonal to the plane, and correcting a displacement component of the sample stage in the direction orthogonal to the plane upon movement of the sample stage therein using information derived from measurement of the position of the probe drive system in the vertical direction, and information derived from measurement of the position of the sample stage in the direction orthogonal to the plane for measurement of the surface shape of the sample. The present invention allows the high-accuracy profile measurement under no influence of fluctuation in the position in the non drive direction of the XY-stage during the sample scanning. Application of the SPM according to the invention to the manufacturing process of the semiconductor and hard disk ensures optimization of conditions for processing the manufacturing apparatus based on the measurement results of the SPM, thus improving yield of the device manufacturing process. As a first embodiment of the present invention, a structure of the SPM as a base of the invention will be described referring to FIGS. 1 to 3. Referring to FIG. 1, a reference numeral 103 denotes a measuring sample, 104 denotes a sample stage which holds the sample 103 through vacuum suction so as to be moved in X-, Y-, and Z-directions, and a rotating direction in an XY-plane. Operations of the sample stage are controlled by a stage control unit 111. A probe 102 is held by a probe drive mechanism 101 via a probe holder 115. The probe drive mechanism 101 accurately positions the probe 102 above the sample 103 in the X-, Y- and Z-directions. The probe 102 is formed of a silicon material, and has a tip processed through etching or focused ion beams to have a diameter of 10 nanometers or less. Alternatively, it may have the tip provided with a carbon nanotube with the diameter of approximately 10 nm. The probe 102 includes a cantilever and the probe formed on the distal end thereof. In the specification, the cantilever and the probe altogether will be simply referred to as the probe. An observation optical system lens barrel 105 provided with an objective lens 106 is placed above the probe drive mechanism 101. The observation optical system 105 has a built-in image pickup camera. An optical image of a surface of the sample 103 that has been magnified by the objective lens 106 is displayed on a TV camera (TV monitor) 107 via an optical image processing unit 108. Each of the observation optical system 105 and the objective lens 106 has a focus axis that is vertically moved in Z-direction by a moving mechanism (not shown). A small piezoelectric device may be combined with the probe holder 115 so as to ensure oscillation of the retained probe 102 at the amplitude in the order ranging from several to several tens of nanometers. FIGS. 2A to 2C are explanatory views showing a structure of the probe drive mechanism 101 shown in FIG. 1. FIG. 2A is an XY-plan view of the probe drive mechanism 101, FIG. 2B is a sectional view of the probe drive mechanism 101 taken along line A-A′, and FIG. 2C is a YZ-plan view of the probe drive mechanism 101. The probe drive mechanism 101 is formed by integrating holders 201 and 202, and a Y-stage 203 in the same plane via elastic deformation portions 204a, 204b, 204c, 204d, and further integrating an X-stage 207 in the same plane as the Y-stage 203 via elastic deformation portions 208a, 208b, 208c, 208d so that the X-stage 207 is orthogonal to the Y-stage 203. The X-stage 207 has a through hole 211 through which the objective lens 106 penetrates. Multilayer piezoelectric devices (in this embodiment, it will be simply referred to as a piezoelectric device) 205, 206 are bonded between the holders 201, 202 and the Y-stage 203. As the piezoelectric devices 205 and 206 equally expand/contract at the same time, the Y-stage 203 is driven in the Y-axis direction. A drive mechanism formed of the piezoelectric device 205 and the elastic deformation portions 204a, 204b, and another drive mechanism formed of the piezoelectric device 206 and the elastic deformation portions 204c, 204d, which are paired are symmetrically arranged with respect to a field of view center position 212 of the objective lens (tip position of the probe 102) as the center. A general piezoelectric device (piezo-ceramic element) has its length varied by application of direct current voltage. In order to obtain a large displacement at low voltage, the multilayer piezoelectric device with stack of a thin piezoelectric device and the electrode has been often used. For example, the multilayer piezoelectric device with its length of 40 mm will extend by 20 micrometers by applying the voltage of 100V. In this case of the piezoelectric device, assuming that the voltage noise is approximately 5 mV, the resolution is obtained by multiplying the movable distance by a ratio between the noise and the maximum applied voltage, that is, 1 nanometer. The structure that establishes the resolution in the order of subnanometer will be described later. Piezoelectric devices 209 and 210 are bonded between the Y-stage 203 and the X-stage 207. The X-stage 207 is driven in X-axis direction by equal expansion/contraction of the piezoelectric devices 209 and 210 at the same time. The drive mechanism formed of the piezoelectric device 209 and the elastic deformation portions 208a, 208b, and the drive mechanism formed of the piezoelectric device 210 and the elastic deformation portions 208c, 208d, which are paired are symmetrically arranged with respect to the field of view center position 212 of the objective lens (tip position of the probe 102) as the center. Each of the piezoelectric devices 209 and 210 has its maximum movable distance set to 20 micrometers, and movable resolution set to 1 nanometer. A Z-axis mechanism 213 is attached to a bottom surface of the X-stage 207 orthogonal to the movable plane of the Y-stage 203 and the X-stage 207. The Z-axis mechanism 213 is configured by integrating fixed portions 218, 219 with a Z-stage 214 in the same plane via elastic deformation portions 215a, 215b, 215c, and 215d. Piezoelectric devices 216 and 217 are bonded between the fixed portions 218, 219 and the Z-stage 214. The Z-stage 214 is driven in the Z-axis direction by equal amount of expansion/contraction of the piezoelectric devices 216 and 217 at the same time. A drive mechanism formed of the piezoelectric device 216 and the elastic deformation portions 215a, 215b, and another drive mechanism formed of the piezoelectric device 217 and the elastic deformation portions 215c, 215d, which are paired are symmetrically arranged with respect to an optical axis 212′ of the objective lens in an XZ-plane. Each of the piezoelectric devices 216 and 217 has the maximum variable distance set to 10 micrometers, and the movable resolution set to 1 nanometer. The probe 102 is attached to the Z-stage 214 via the probe holder 115 so that the tip position of the probe 102 is aligned with the field of view center position 212 of the objective lens. As described above, the probe drive mechanism 101 according to the present invention allows the X-stage 207, Y-stage 203, and Z-stage 214 for driving the probe 102 three-dimensionally to be independently operated without being interfered with one another. At left and right sides of the Y-stage 203, for example, the stage drive mechanism formed of the two elastic deformation portions 204a, 204b arranged on an extended line of an expanding/contracting axis of the interposed piezoelectric device 205, and another stage drive mechanism (piezoelectric device 206, elastic deformation portions 204c, 204d), which are paired are arranged. As each of the piezoelectric devices 205 and 206 expands and contracts by equal amount, the elastic deformation portions 204a, 204b, 204c and 204d may be uniformly deformed. This may eliminate Abbe error of the Y-stage 203, resulting in improved straightness of the Y-stage 203 far better than ever before. It is clear that the principle of the operation applies to the X-stage 207 and the Z-stage 214. Operations of the X-stage 207, Y-stage 203 and Z-stage 214 of the probe drive mechanism 101 are controlled by a probe drive control unit 110. The multilayer piezoelectric devices may individually cause difference in the expanding/contracting displacement upon application of the voltage. Hysteresis characteristics exist between the applied potential and the displacement irrespective of use of the same piezoelectric device. In this case, the hysteresis characteristic which differs for the individual piezoelectric device is preliminarily measured so that the applied voltage is adjusted for the respective piezoelectric devices to establish the desired displacement. In the embodiment, the piezoelectric devices are used for operating the X-stage 207, Y-stage 203, and Z-stage 214 of the probe drive mechanism 101. However, the power source for the respective stages is not limited to the piezoelectric device, but may be a linear actuator so long as it provides accuracy and power sufficient to have positioning of the probe 102. As the material for forming the probe drive mechanism 101, the material with a large ratio between rigidity and specific gravity such as aluminum alloy and titanium, and the material with low thermal expansion coefficient (linear expansion coefficient) such as a nickel-iron alloy may be used. The observation optical system lens barrel 105 and the objective lens 106 provided above the probe drive mechanism 101 are allowed to be vertically moved in the Z-axis direction by a moving mechanism (not shown). They are inserted into the through hole 211 formed in the X-stage 207 so as not to bring the objective lens 106 into contact with the probe drive mechanism 101. As the probe drive mechanism 101 according to the present invention has no mechanism above the probe 102 for scanning, the objective lens 106 allows direct observation of the probe 102, and at the same time, observation of the surface of the sample 103 with high resolution. For example, if the aperture ratio of the objective lens 106 is specified to 0.7, and the operation distance is specified to 6 mm, the pattern on the sample 103 may be clearly observed in the condition where the resolution is 1 micrometer or less. As the objective lens 106 and the sample stage 104 are moved downward by equal amount (for example, by 1 mm) so that the objective lens 106 is not brought into contact with the probe 102 while having its position fixed, the pattern on the sample 103 just below the probe 102 can be observed without being influenced by the presence of the probe 102 placed within the field of view of the objective lens 106. The aforementioned process may be realized using the optical phenomenon that occurs under the condition where the objective lens 106 has high aperture ratio, and the probe 102 occupies only a part of the field of view of the objective lens 106. FIG. 3 is an explanatory view with respect to the XZ-plane of the probe drive mechanism 101, showing a structure of the probe deflection detection unit for detecting contact between the probe 102 and the surface of the sample 103. A reference numeral 301 denotes a laser diode with oscillation wavelength set to 600 nanometers, and oscillation output set to 0.1 milliwatts. The laser light oscillated from the laser diode 301 is shaped by a collimator lens 302 into parallel light, and is turned back on a mirror 303 (not shown) attached to the holder 202 in the Y-axis direction. It is further reflected on a mirror 304 (not shown) attached to the Y-stage 203 in the X-axis direction again, and is applied to the back surface of the probe 102 via mirrors 305 and 306. The laser light reflected on the back surface of the probe 102 is reflected by mirrors 307 and 308, and is turned back on a mirror 309 (not shown) attached to the Y-stage 203 in the Y-axis direction. It is further reflected in the X-axis direction again by a mirror 310 (not shown) attached to the holder 202 so as to be received by a photodetector 311. The laser diode 301 is fixed to the holder 201 of the probe drive mechanism 101, the photodetector 311 is fixed onto the holder 202, and the mirrors 305, 306, 307 and 308 are fixed to the Z-stage 214 using a jig (not shown) so as to allow detection of deflection amount of the probe as the change in the laser irradiation position of the photodetector 311 on the laser beam receiving surface irrespective of position of the probe 102. As the photodetector 311, a PSD (position sensitive device), an image sensor, a bisecting or quad-cell photodiode may be employed. When deflection is generated in the probe 102 as a result of contact between the probe 102 and the sample 103, the laser irradiation position on the light receiving surface of the photodetector 311 will move in the Y-axis direction. The photodetector 311 converts the change in the laser irradiation position into a voltage signal, and allows a probe deflection detection unit 109 to detect the contact between the probe 102 and the surface of the sample 103. The probe deflection detection unit may be configured to detect amplitude and phase of the oscillation of a probe deflection signal, which is caused by deflection of the probe 102 when it is oscillated by the probe holder 115 and the like so as to detect the force acting between the probe 102 and the sample 103. In other words, when the tip of the oscillating probe is brought into closer to the sample, the force acting between the probe tip and the sample changes oscillation states, for example, the oscillation amplitude, phase of the oscillation with respect to the oscillation signal, and the oscillation frequency. The force may be measured by detecting those oscillation states. The structure of the high speed SPM that covers broad range with high-accuracy, which is provided with the rough movement mechanism, a responsive switching mechanism, and a displacement gauge will be described referring to FIGS. 4A and 4B. Measurement of the probe position in the Z-direction will be described. The probe holder 115 is configured to have its part opposite a Z-axis capacitive sensor 224 fixed to the bottom surface of at least any one of holders 201′ and 202′, or the bottom surface of an X-stage 207′ with a mechanism (not shown). The interval between opposite surfaces of the probe holder 115 and the capacitive sensor 224 is set to 20 micrometers. The Z-axis capacitive sensor 224 is capable of measuring the distance from the probe holder 115 with the resolution of 0.1 nanometers, so as to measure the moving distance of a Z-stage 214′. The probe holder 115 and the Z-axis capacitive sensor 224 are provided on the Z-axis overlapped with the optical axis 212′ of the objective lens in the XZ-plane. This arrangement allows measurement of the stage displacement (displacement of the tip position of the probe 102) at the field of view center position 212 of the objective lens. This structure hardly causes the Abbe error in spite of yawing error in the operation of the Z-stage 214′. The probe holder 115 is formed of the metal material having electrical conduction with the metal material for forming the Z-stage 214′, and has the surface opposite the Z-axis capacitive sensor 224 subjected to the precision grinding process. Use of the displacement sensor with higher accuracy, for example, the laser interference displacement gauge to be described later with the resolution of approximately 10 picometers in place of the capacitive sensor ensures implementation of the SPM measurement with higher accuracy and resolution. According to the embodiment shown in FIGS. 4A and 4B, a rough Z-stage 403 is mounted on an air slider 404. A sample stage 401, on which the sample 103 is mounted, is mounted on the rough Z-stage 403. The air slider 404 and the rough Z-stage 403 are joined with a rough XY-stage 402 and an elastic plate 406 so that the slider 404 is placed on a surface plate 405. The rough XY-stage 402 is fixed to the surface plate 405 with a structure (not shown). The observation position on the sample 103 may be selected by moving the air slider 404 in the XY-plane by means of the rough XY-stage 402 via the elastic plate 406. The aforementioned structure is made because its height is smaller than that of the general structure formed by stacking the X-stage, Y-stage and Z-stage so as to keep high rigidity at static state. This makes it possible to eliminate the oscillation of the sample 103 almost completely, which is optimal to the scanning probe microscope. Upon movement of the rough XY-stage 402, air may be blown between the air slider 404 and the surface plate 405 so as to make the friction force small. Alternatively, the air slider 404 is made slidably movable with respect to the surface plate 405 without blowing the air. The latter process is effective for measurement of the broad area on the sample ranging from several hundreds of micrometers to several tens of millimeters, especially when measuring the surface shape of the sample 103 using the probe 102 while sliding the air slider 404 on the surface plate 405 especially with planarity because no gap is generated by air. When measuring the intermediate region on the sample 103 ranging from several tens to several hundreds of micrometers using the probe 102, the sample stage 401 is driven. This stage has the similar structure of the one at the probe side, which is driven by the piezoelectric device and uses the elastic guide. However, it is not provided with the part with the function corresponding to that of the Z-axis 214′ of the stage at the probe side. The structure allows the design by focusing on the movable range rather than rigidity required for the high-speed scanning of the probe, resulting in the broader stage with the movable range of several hundreds of micrometers. As it is difficult to scan over a broad range while ensuring high planarity, a displacement sensor 410 such as the capacitive sensor or the laser interference displacement gauge is used to measure positional change in the non scan direction upon scanning on the sample stage 401, that is, vertical movement, and the measurement results of the scanning probe microscope at the respective points are corrected with respect to height data. This makes it possible to realize the measurement with higher planarity. Specifically, a flat target 411 is provided at the rear side of the sample stage 401 as shown in FIG. 4B so that the vertical movement of the target 411 during scanning is measured by the displacement sensor 410. For example, assuming that the planarity of the stage 401 during scanning is 10 nanometers, if accuracy of the displacement sensor 401 is 0.1 nanometers, the aforementioned correction ensures improvement of measurement accuracy with respect to the planarity as the measurement result of the scanning probe microscope from 10 to 0.1 nanometers. In the aforementioned explanation, the measurement results are corrected by the displacement gauge 410. However, height of the probe 102 may be corrected through direct feedback to the Z-stage 214 to follow up the vertical movement of the upper surface of the sample 103 caused by scanning of the sample stage 401. The aforementioned correction will be described referring to FIG. 24. It is assumed that the actual surface profile of the sample 103 corresponds to an actual profile 451 (plotting by taking the x-axis as the position in the horizontal direction (X- or Y-direction), and the y-axis as the position in the Z-direction). There is a very small step-like configuration at a right end of the profile 451, which is often required to be quantitatively measured. While scanning the sample stage 401 on which the sample 103 is mounted in the XY-direction, vertical movement in the Z-direction as the non drive direction occurs owing to the characteristic of the guide mechanism of the scanning mechanism as indicated by the vertical movement of the stage 452 shown in FIG. 24. It is possible to suppress the vertical movement to be kept small by using the elastic guide. However, the vertical movement normally of several tens of nms will occur. The vertical movement of approximately 5 nm still occurs in spite of the well-made stage. For this, the profile to be measured is obtained by adding the actual profile 451 to the vertical movement 452 of the stage as indicated by the measured profile 453 shown in FIG. 24. Therefore, it is impossible to measure the subtle step-like configuration of the actual profile 451. If the vertical movement of the stage is allowed to be measured through another method, a corrected profile 454 may be obtained by subtracting the vertical movement 452 of the stage from the measured profile 453, thus ensuring correction. The method of measuring the vertical movement of the stage may be realized by measuring the sample with secured planarity. However, it is difficult to secure the planarity of the sample. Furthermore, foreign substance or stain on the sample may lead to the error in the vertical movement profile 452 of the stage. Difference in the scanning characteristic of the stage between the time for measurement of the sample to be calibrated and the time for measuring the actual sample is influential. The vertical movement caused by the oscillation upon scanning of the stage may vary for each cycle. It is therefore difficult to conduct the complete correction. The displacement sensor 410 is used as shown in FIG. 4B to measure the vertical movement of the sample 103 during the sample measurement from the side opposite the probe (that is, the rear side of the sample stage 401). Besides the smooth vertical movement as indicated by the vertical movement profile 452 of the stage as shown in FIG. 24 owing to deviation of the sample stage 401 from the flat surface for scanning, the dynamic vertical movement of the sample stage 401, that is, the error caused by the oscillation may also be corrected. When the target 411 is placed just below a measuring portion of the probe 102, the method shown in FIG. 4B ensures the accuracy. If the rough movement stage 403 moves to measure the part of the sample 103 other than the center with the probe 102, the error may occur in response to not only the vertical movement of the sample stage 401 but also movement that results in inclination change such as pitching and rolling simultaneously. In other words, if the measuring part of the vertical movement of the sample stage 401, which is measured by the displacement gauge 410 is out of alignment with the measuring part of the sample 103, which is measured by the probe 102 in the horizontal direction, the change in the height of the sample 103 at the position scanned by the probe 102 is out of alignment with the change in the height of the sample stage 401, which is measured by the displacement gauge 410 by the amount corresponding to the product of the misalignment and the inclination of the sample stage 401. Another embodiment will be described referring to FIG. 22 for the purpose of coping with the aforementioned situation. As FIGS. 22(a) and 22(b) show, a plurality of displacement gauges 410-1 and 410-2 are used to measure the target 411 attached to the rear surface of the sample stage 401. The vertical movement at the scanning position with the probe 102 will be obtained through the following process. It is assumed that measurement values of height measured by the two displacement gauges 401-1 and 410-2 are set to Z1 and Z2, respectively, and the distance of the measurement position of the probe 102 from the displacement gauge 410-1 is set to x1, and the distance of the measurement position of the probe 102 from the displacement gauge 410-2 is set to x2. A fluctuation Z in the height of the sample stage 401 at the measurement position of the probe 102 may be calculated using the formula of Z=(Z1*x2+Z2*x1)/(x2+x1). The aforementioned process for obtaining the vertical movement data of the stage is employed when the sample 103 is laterally long, and misalignment of the measurement position with the probe 102 occurs only in the lateral direction. If the sample 103 extends in the depth direction with respect to the drawing of FIG. 22, and the measurement position of the probe 102 is required to be moved in the depth direction, an additional displacement gauge 410-3 (not shown in FIGS. 22(a) and 22(b)) is provided as shown in FIG. 22(c). Assuming that the distance of the scanning position with the probe 102 from the line formed by connecting the displacement gauges 410-1 and 410-2 is set to y1, and the distance from the displacement gauge 410-3 is set to y2, a fluctuation Z′ in the height of the sample stage 401 at the measurement position with the probe 102 may be calculated through the formula of Z′=(Z*y2+Z2*y1)/(y2+y1) using the calculated value Z and a height Z3 measured by the added displacement gauge 410-3. Another embodiment will be shown referring to FIG. 23. If the displacement gauge 410 may be kept substantially below the probe 102 at all the time irrespective of movement of the rough movement stage 403, use of only the single displacement gauge 410 allows accurate measurement of the vertical movement data 452 of the stage even if the sample stage 401 changes the inclination owing to pitching and rolling caused by the scanning. For this, the structure shown in FIG. 23(a) is employed by fixing a retainer member 412 to the holder 202 of the probe drive mechanism 101 using the both-end support beam structure, and further fixing the displacement gauge 410 to the retainer member 412. In this formation, the retainer member 412 and the displacement gauge 410 are kept from being in contact with the sample stage 401. This allows the position of the displacement gauge 410 to be kept substantially below the probe 102 all the time irrespective of movement of the sample 103 and the sample stage 401 caused by the rough movement stage 402. Besides the vertical movement during the sample measurement as indicated by the vertical movement profile 45 of the stage shown in FIG. 24, which is caused by misalignment from the flat surface of the sample stage 401 for scanning, the dynamic vertical movement of the sample stage 401, that is, error owing to oscillation may also be corrected. It is possible to correct various types of changes between sides of the sample stage 402 and the upper probe scanning mechanism 101, specifically, time drift of the relative distance between the probe and the sample owing to the temperature change, and influence by the oscillation by measuring such change using the displacement gauge 410. In this case, it is necessary to configure the retainer member 412 to be unlikely to cause oscillation. The material selected to have the thermal expansion coefficient substantially the same as that of the probe drive mechanism 101 may improve correction accuracy of the drift caused by the temperature change. According to another embodiment as shown in FIG. 23(b), the displacement sensor 410 is gently retained by a retainer member 412′ by means of the cantilever structure. A horizontal position of the displacement sensor 410 is always kept at the position substantially below the probe 102 by the retainer member 412′. As the displacement sensor 410 is pressed against a lower base portion 4011 of the sample stage 401 in the vertical direction, the distance between the lower base portion 4011 of the sample stage 401 and the target 411 attached to the operating portion of the stage 401 may be measured. The structure shown in FIG. 23(a) allows the correction with respect to the temperature drift, but has a problem of deteriorated correction accuracy upon oscillation of the displacement gauge 410 owing to low rigidity of the retainer member 412. On the contrary, the structure shown in FIG. 23(b) keeps high rigidity against the lower base portion 4011 of the sample stage 401 at the vertical position of the displacement gauge 410 in spite of low rigidity of the retainer member 412′. This provides the effect of preventing the risk of deteriorated correction accuracy caused by the oscillation. In all the structures shown in FIGS. 4B, 22A, 23A and 23B, the X- and Y-scanning mechanisms are provided at the side of the sample stage 401. Accordingly, provision of at least the Z-axis drive function at the side of the probe drive mechanism 101 is sufficient. The XY-axis scanning function will be necessary as the component when the scanning with high resolution is required in the narrower range. Measurement of the probe position in the X- and Y-directions will be described. An X-axis capacitive sensor 223 and a Y-axis capacitive sensor 222 are fixed to at least one of holders 201′ and 202′ by a mechanism (not shown), and are opposite the tip end of the Z-stage 214′. An opposite surface on the Z-stage is subjected to the precision grinding process. The X-axis capacitive sensor 223 and the Y-axis capacitive sensor 222 are provided on the X-axis and Y-axis which contain the field of view center position 212 (tip end position of the probe 102) of the objective lens in the XY-plane. This arrangement allows measurement of the stage displacement (displacement of the tip end position of the probe 102) at the field of view center position 212 of the objective lens. The structure hardly causes the Abbe error caused by the error in the yawing and pitching contained in the operation of the X- and Y-stages on which the Z-stage 214′ is mounted. Feedback control using the outputs of the displacement gauges allows scanning by accurately controlling the tip end position of the probe, and measurement of the shape and dimension by the high-accuracy SPM. Instead of the capacitive sensor, the displacement sensor with higher accuracy with the resolution of approximately 10 picometers such as the laser interference displacement gauge to be described later may be employed for realizing the SPM measurement with higher accuracy and resolution. The following structure is provided in order to realize the high-speed measurement in the broad range and the high-accuracy measurement in the narrow range. Specifically, instead of the piezoelectric device 205 that has been described referring to FIGS. 2A to 2C, the fine/rough movement drive mechanism formed of elements 205a, 205b and 205c shown in FIGS. 4A and 4B is employed. Each of the piezoelectric devices 206, 209 and 210 may be replaced with the piezoelectric device 205, and accordingly, the piezoelectric device 205 will only be described (with respect to the piezoelectric devices 209 and 210, the Y-stage 203 may be replaced with the X-stage 207, and the Y displacement sensor 222 may be replaced with the X displacement sensor 223). A reference numeral 205a denotes the piezoelectric device that constitutes the rough movement mechanism, and is bonded to the displacement expansion mechanism 205b. The reference numeral 205b constitutes leverage, having one end fixed to the holder 201, intermediate portion pressed by the piezoelectric device 205a, and the other end bonded to the fine movement piezoelectric device 205c. The displacement of the piezoelectric device 205a is expanded and transmitted to the piezoelectric device 205c by an amount corresponding to a ratio of the distance between the fixed portion of the displacement expansion mechanism 205b and the bonded portion with the 205c to the distance between the fixed portion and the bonded portion with the 205a (leverage magnification factor). For example, assuming that the leverage magnification factor is set to 5, and the expansion of the piezoelectric device 205a is set to 20 micrometers, one end of the piezoelectric device 205c will have a displacement of 100 micrometers. Furthermore, the piezoelectric device 205c transmits the displacement to the Y-stage 204 so as to be displaced. At this time, the displacement expansion system formed of the piezoelectric devices 206a, 206b and 206c also transmits the displacement to the Y-stage 204. As described above, if the displacement resolution of each of the piezoelectric devices 205a and 206a is 1 nanometer, the displacement noise transmitted to the stage 204 will be magnified by 5 times, that is, 5 nanometers. The piezoelectric device 205c (see FIG. 4A) is the fine movement piezoelectric devices, which is configured to expand by approximately 1 micrometer upon application of the voltage at 100V. Then the displacement of the fine movement piezoelectric device is added to displace the Y-stage. Assuming that the voltage noise is set to 5 mV, the noise of the fine movement piezoelectric device will be 50 picometers. At this time, if the response of the fine movement piezoelectric devices 205c is faster than the rough movement piezoelectric devices 205a, the displacement sensor 222 detects the position of the Y-stage 203′ in the Y-direction to conduct feedback to allow the Y-stage 203′ to control the Y-stage 203′ with the resolution in substantially the same order as that of the displacement sensor. As described later referring to FIG. 15, the feedback control is realized by allowing a probe scanning control unit 112 to process the stage displacement data detected by a stage displacement detection unit 128, and driving the piezoelectric device via the probe drive control unit 110. A rough movement piezoelectric device driver 500 and a fine movement piezoelectric device driver 510 are provided for the respective axes in the probe drive control unit 110. The fine movement piezoelectric device may fail to cancel the noise unless the response at the rough movement side is sufficiently small. In case that the piezoelectric device serves as the load with the capacity C electrically. Assuming that it is driven by the driver amplifier with the output resistance R, when the capacity of the driver amplifier is large, and the output resistance R may be made small, the time constant RC becomes short as shown in FIG. 5A, resulting in quick response to the order position input through the amplifier. However, the noise after reaching the ordered position is large, which cannot be sufficiently cancelled by the fine movement piezoelectric device. If the output resistance is set to be large as indicated by FIG. 5B, the noise may be reduced, but the time constant RC is increased. This may cause the problem of considerably retarding the response upon long distance positioning that cannot be covered by the fine movement piezoelectric device. As the structure of the rough movement piezoelectric device driver 500 shown in FIGS. 6A to 6F indicates, the response of the rough movement piezoelectric device is accelerated by the responsive switching mechanism upon the long distance positioning, and the response is retarded in the static state to allow the fine movement piezoelectric device to conduct the positioning. Referring to FIG. 6A, the rough movement piezoelectric device is shown as a capacitor 550 with the capacity C. A driver amplifier 501 is connected to the rough movement piezoelectric device 550 via an output resistance R (502). A high speed driving output resistance Rs (505) is connected to the output resistance 502 in parallel via a switcher 506r. If Rs<<R, the output resistance becomes RsR/(Rs≈Rs upon turning of the responsive switching signal ON so as to respond at high speeds with the time constant RsC. When the switcher 506r is in OFF state, the response is performed at low speeds with the time constant RC in the low noise mode. When performing the long distance positioning, the switcher 506r is turned ON, and then OFF upon approach to the target. This may allow both the high speed positioning and stabilization in the static state. In the embodiment referring to FIG. 6A, the switching is explicitly performed. However, it is possible to perform the switching automatically. Referring to FIG. 6B, instead of the responsive switcher 506r, a structure 506 formed by connecting oppositely directed diodes in parallel is inserted. Assuming that the voltage drop of the diode in the forward direction is set to Vd, and the current flowing through the output resistance 502 exceeds the Vd/R, the diode is turned ON. This may apply the current to the high speed response resistance Rs to accelerate the response. If the voltage at both ends of the piezoelectric device 550 is brought into close to the target value, the current becomes low. Then the switcher 506 is turned OFF to deteriorate the response, and accordingly, reduce the noise. Alternatively, the structure as shown in FIG. 6C may provide the same effect. A resistance 502′ as R-Rs is connected to the resistance Rs (505) in series to form the output resistance, and the switcher 506 formed of the diode is connected to the resistance 502′ in parallel. If the current flowing through the resistance 502′ exceeds the Vd/(R-Rs), the diode is turned ON, and the current flows to the high speed response resistance Rs to accelerate the response. Referring to FIG. 6D, a fine movement piezoelectric device driver 510 is connected to a piezoelectric device 551 with capacity Op via an output resistance Rp (512) from a driver amplifier 511. The Rp may be set to the value so as to realize the response required by the time constant RpCp. Change in the displacement with respect to the step-like input position will be shown in FIGS. 6E and 6F. As FIG. 6E shows, a rough movement displacement X initially responds at high speeds with the time constant RsC. As the difference between the order position and the displacement X becomes smaller, the time constant at the response is reduced to the RC through the switcher 506 or 506r so that the position X slowly changes while having the small displacement noise. The fine movement displacement Xp displaces at high speeds with the time constant RpCp as shown in FIG. 6F. Since the movable range is small, the order position displaces within the movable range although it exceeds the range thereof, while keeping the displacement noise small. Referring to FIG. 7, if the capacitor is inserted between the fine movement piezoelectric device and the driver circuit in series, the voltage is divided into partial pressures at a ratio inverse to that of the capacity between the piezoelectric device and the capacitor. This may improve noise, that is, the displacement resolution of the fine movement piezoelectric device. As the drawing shows, the driver amplifier 511 drives the piezoelectric device 551 via the output resistance 512 (resistance value Rp), and further a capacitor 560 with capacity 1/α of the capacitance Op of the piezoelectric device 551. This may divide the voltage of the capacitors 560 and 551 at both ends into partial pressures at the ratio of α to 1, thus reducing the noise to 1/(1+α). Each resistance of αRb and Rb inserted in parallel with the capacitors serves to prevent gradual displacement of the partial pressure ratio owing to leak of electrical charge of the capacitor with the high resistance in the MO order, which sufficiently makes the time constant RbCp large. For example, assuming that the α is set to 4, in the example of the aforementioned fine movement piezoelectric device, the displacement resolution becomes 10 picometers that is ⅕ of 50 picometers. In return for this, the movable range of the fine movement piezoelectric device becomes 0.2 micrometers as ⅕ of 1 micrometer. Operations of the probe scanning control unit 112 according to the present invention will be described referring to FIGS. 8A to 8C. Referring to FIG. 8A, a rough movement target position 802 is given under an open control where feedback of the measurement results of the displacement gauge is not performed. A responsive switching signal 801 keeps the response of a responsive switching amplifier 806 at high speeds from change in the rough movement target position 802 until the response is stabilized. Thereafter, the response is switched to the low speed (low noise). The structure for automatically switching the response without using the responsive switching signal 801 from outside may be available. The position of the stage is detected by a displacement gauge 811, and is appropriately filtered by a filter 812 to reduce the noise, which is compared with a target position 803 by the comparator 813. The resultant error is transmitted to an amplifier 807 via a control unit 805 so as to conduct the feedback control of a fine movement piezoelectric device 809. The control unit herein denotes the device that outputs the value obtained by multiplying the appropriately filtered input by the gain. This is generally used in the control theory. For example, the control unit called PID controller provides three kinds of values each formed by multiplying the input value, the integrated value thereof, and the derivative value by different gains individually, and outputs the value summed up of those three values. The aforementioned structure allows both high speed response in the broad range and the high-accuracy positioning. FIG. 8B illustrates another possible structure that filters a detection position 831 of the stage through a filter 832 to reduce the noise, and the resultant value is compared with a target position 822 in 833. The resultant positional error is passed to respective control units 823 and 825 for rough movement and fine movement, respectively to drive a rough movement piezoelectric device 827 via the responsive switching amplifier 826, and to drive a fine movement piezoelectric device 829 via a normal amplifier 828. An input to the fine movement amplifier 828 is added to a control amount to the rough movement piezoelectric device 827 via another control unit 824. The operation of the control unit increases the integrating operation. If the state where the fine movement piezoelectric device 829 is expanded on average is prolonged, the resultant amount is added to the control amount to the rough movement piezoelectric device 827 to expand the rough movement piezoelectric device 827. Then the fine movement piezoelectric device 829 in turn is contracted. This applies to the case where the expansion and contraction are inverted. This makes it possible to automatically adjust the displacement of the rough movement piezoelectric device so that the fine piezoelectric device is usable at the center of the operation range on average. The embodiment shown in the drawing allows the responsive switching amplifier to fix the output value in accordance with the rough movement fixed signal. This makes it possible to explicitly stop operations of the rough movement piezoelectric device to realize positioning with low noise when using the SPM in the scanning range that can be covered by the fine movement piezoelectric device. The displacement in the aforementioned case will be described referring to FIGS. 9A to 9C. When the order position is largely changed stepwise, the positional error is transmitted to the rough movement piezoelectric device amplifier and the fine movement piezoelectric device amplifier via the respective control units, and the rough movement displacement and the fine movement displacement are changed as shown in FIGS. 9A and 9B, respectively. If the change in the order position is large, the rough movement displacement shown in FIG. 9A responds at high speeds and changes with the time constant RsC. Meanwhile, the fine movement displacement Xp shown in FIG. 9B changes at high speeds but the displacement gradually shifts toward the rough movement displacement X as this state is added to the input of the rough movement piezoelectric device amplifier via the control unit. As the total displacement X+Xp shown in FIG. 9C approaches the ordered position, the fine movement displacement returns to zero (intermediate position) again. The total displacement at this time changes as indicated by the solid line as the fine movement displacement is added compared with the displacement only of the rough movement piezoelectric device as indicated by the dashed line. Therefore, the time constant changes at high speed in accordance with the time constant RpCp of the fine movement displacement. Another possible structure shown in FIG. 8C provides the improved displacement noise effect by completely stopping the operation of the rough movement piezoelectric device in the static state without controlling the rough movement fixed signal as described referring to FIG. 8B. This structure is different from the one shown in FIG. 8B in a dead-zone. A dead-zone A842 is intended not to drive a rough movement piezoelectric device 848 when the positional error is within a certain range. Assuming that the input is set to X, the output is set to Y, and the dead-zone is set to +/−W, the values expressed as Y=X+W (X<−W), Y=0(−W<x<W), and Y=X−W(W<X) are output. The dead-zone is set to the range slightly smaller than the movable range of a fine movement piezoelectric device 850 so as to allow the rough movement piezoelectric device 848 to be driven automatically only when the fine movement piezoelectric device 850 cannot perform positioning. Another dead-zone 3846 may also be provided to allow the rough movement piezoelectric device to be driven only when the state where the fine movement piezoelectric device 850 has been deviated from the center of the drive range is continued in response to turning of the output from the dead-zone B ON owing to increase in the integrated output of the control unit 845 just to the front of the dead-zone B846. The aforementioned displacement state will be described referring to FIGS. 10A to 10C. Referring to FIG. 10A, when the step-like change in the ordered position is small, and it is smaller than the dead-zone W set within the movable range of the fine movement, or the rough movement fixed signal is explicitly turned ON, the rough movement displacement X does not change. In this case, the positional error is transmitted to the fine movement piezoelectric device amplifier with the dead-zones A and B out of the signal path. The fine movement displacement Xp responds with the time constant RpCp as indicated by FIG. 10B so as to follow up the order position as the total displacement as indicated by FIG. 10C. Another structure that allows a single amplifier to drive the rough movement piezoelectric device 550 and the fine movement piezoelectric device 551 will be described referring to FIG. 11A. The driver amplifier 501 drives the fine movement piezoelectric device (551) with capacity Op via the output resistance Rp (512). The driver amplifier 501 is connected to the rough movement piezoelectric device 550 via the output resistance R (502). The high-speed driving output resistance Rs (505) is connected to the output resistance 502 in parallel via the switcher 506r. If Rs<<R, the output resistance becomes RsR/(Rs+R)≈Rs upon turning of the responsive switching signal ON so as to respond at high speeds with the time constant RsC. When the switcher 506r is in OFF state, the response is performed at low speeds with the time constant RC in the low noise mode. When performing the long distance positioning, the switcher 506r is turned ON, and then OFF upon approach to the target. This may allow both the high speed positioning and stabilization in the static state. In the embodiment referring to FIG. 11A, the switching is explicitly performed. However, it is possible to perform the switching automatically. Referring to FIG. 11B, instead of the responsive switcher 506r, oppositely directed diodes are inserted in parallel. Assuming that the voltage drop of the diode in the forward direction is set to Vd, and the current flowing through the output resistance 502 exceeds the Vd/R, the diode is turned ON. This may apply the current to the high speed response resistance Rs to allow the response at higher speeds. If the voltage at both ends of the piezoelectric device 550 is brought into close to the target value, the current becomes low. Then the switcher 506 is turned OFF again to retard the response while reducing the noise in turn. The difference in the response between the rough movement amplifier and the fine movement amplifier allows the fine movement piezoelectric device to respond with respect to positioning at the small stroke automatically. The rough movement piezoelectric device and the fine movement piezoelectric device simultaneously respond with respect to the positioning at large stroke. As the position is brought into close to the target position, the response of the rough movement amplifier is retarded so as to allow the fine movement piezoelectric device to respond. Another structure that allows the probe 102 as described referring to FIGS. 4A and 4B to perform both high speed scanning in the broad range and accurate scanning in the narrow range will be described referring to FIGS. 12A and 12B. As the structure shown in FIGS. 12A and 12B is substantially the same as the one described referring to FIGS. 2A to 2C, only the different structure will be described. Two kinds of rough movement piezoelectric devices 205a′, 206a′ connected with each other, and fine movement piezoelectric devices 205c′, 206c′ connected with each other correspond to the piezoelectric devices 205 and 206 of the Y-axis, respectively. The structure described referring to FIGS. 4A and 4B realizes the rough movement by expanding the displacement of the piezoelectric device. Meanwhile, the structure shown in FIGS. 12A and 12B realizes the rough movement by increasing the length of the piezoelectric device. This applies to those of the X-axis. Two kinds of rough movement piezoelectric devices 209a′, 210a′ connected with each other, and fine movement piezoelectric devices 209c′, 210c′ connected with each other correspond to the piezoelectric devices 209 and 210 of the X-axis, respectively. This may also apply to those of Z-axis. Two kinds of rough movement piezoelectric devices 216a, 217a connected with each other, and fine movement piezoelectric devices 216c, 217c connected with each other correspond to the piezoelectric devices 216 and 217 of the Z-axis, respectively. They are driven by the circuit similar to the one as described referring to FIGS. 4A and 4B so as to allow both the high speed scanning in the broad range and the high-accuracy scanning in the narrow range. In this embodiment, the sample stage 104 is formed using general XYZ-stage. However, use of the stage as described referring to FIG. 4B may further improve the accuracy. Another structure that allows the probe 102 as described referring to FIGS. 4A and 4B to perform both high speed scanning in the broad range and accurate scanning in the narrow range will be described referring to FIG. 13. A Y-axis rough movement piezoelectric device 205a″ is fixed to a holder 201′″, which drives a Y-stage 203′″ via a displacement expansion mechanism 205b″ using the principle of leverage. The Y-stage 203″ is supported at the holder 201′″ so as to smoothly move only in the Y-direction via elastic deformation portions 204a′,204b′, 204c′ and 204d′. An X rough movement piezoelectric device 210a″ is fixed to the Y-stage 203′″, which drives an X-stage 207″ via a displacement expansion mechanism 210b″ using the principle of leverage. An X-stage 207″ is supported so as to smoothly move with respect to the Y-stage 203′″ only in the X-direction via elastic deformation portions 208a′, 208b′, 208c′ and 208d′. A fine movement stage 204′ is supported inside the X-stage 207″ so as to smoothly move only in the XY-direction via elastic deformation portions 230a, 230b, 230c and 230d. The elastic deformation portions 230a, 230b, 230c and 230d are arranged to form an L-like shape so as to have smooth elastic deformations both in the X- and Y-directions. The fine movement stage 240′ is driven in the X- and Y-directions by the fine movement X piezoelectric device 210c″ and a fine movement Y piezoelectric device 205c″, respectively. The fine movement piezoelectric devices 210c″ and 205c″ are bonded to the X-stage 207″ and the fine movement stage 240′, respectively using an elastic hinge so as to transmit the force only in the expanding/contracting direction of the piezoelectric device. The displacement of the probe 102 in the XY-direction is measured by the X displacement gauge 223 and Y displacement gauge 222. They are driven by the circuit similar to the one as described referring to FIGS. 4A and 4B to allow both the high speed scanning in the broad range and the high-accuracy scanning in the narrow range. Another structure that allows the probe 102 as described referring to FIGS. 4A and 4B to perform both high speed scanning in the broad range and accurate scanning in the narrow range will be described referring to FIG. 14. A rough movement stage 241 is in a holder 201″″ so as to smoothly move only in the XY-direction via elastic deformation portions 231a, 231b, 231c and 231d. The rough movement stage 241 is driven by an externally provided X rough movement actuator 210a′″ and a Y rough movement actuator 205a′″ in the X- and Y-directions, respectively. Each of those actuators may be formed as a large-sized piezoelectric device, and a rotation-linear motion converting mechanism formed of a rotary motor such as a voice coil motor, servo motor and a step motor, and a ball screw. A fine movement stage 240″ is supported inside the rough movement stage 241 via elastic deformation portions 230a′, 230b′, 230c′ and 230d′ so as to smoothly move only in the XY-direction. The elastic deformation portions 230a′, 230b′, 230c′ and 230d′ are arranged to form an L-like shape so as to have smooth elastic deformations both in the X- and Y-directions. The fine movement stage 204″ is driven by a fine movement X piezoelectric device 210c′″ and a fine movement Y piezoelectric device 205c′″ in the X- and Y-directions, respectively. The fine movement X piezoelectric device 210c′″ and fine movement Y piezoelectric device 205c′″ are bonded to the rough movement stage 241 and the fine movement stage 240″, respectively using the elastic hinge so as to transmit the force only in the expanding/contracting direction of the piezoelectric device. The displacement of the probe 102 in the XY-direction is measured by the X displacement gauge 223 and the Y displacement gauge 222. They are driven by the circuit similar to the one as described referring to FIGS. 4A and 4B to allow both the high speed scanning in the broad range and the high-accuracy scanning in the narrow range. However, the appropriate responsive switching or rough movement fixation are required in accordance with each type of the actuators 210a′″ and 205a′″. For example, a brake shoe (not shown) is pressed against a rod that presses the rough movement stage 241 using an electromagnetic brake for fixing under the frictional force. Alternatively, the rod that presses the rough movement stage 241 is provided with a fluid damper (not shown) to reduce the flow channel of the orifice of the damper to retard the response. As another example, external coils are inserted in series between the coil of the voice coil motor and the driver amplifier. If short circuit occurs between both ends of the external coil by the relay, the high speed response is realized. If the relay is released, the current flowing through the coil, that is, the time constant upon response of the force generated by the voice coil motor is increased in proportion to the rate of increase in the coil inductance. This may reduce the displacement noise. Operations of the SPM according to the present invention will be described referring to FIGS. 1, 15A and 15B. FIG. 15A represents a part of the semiconductor manufacturing process using the SPM according to the present invention for explanation of functions of the in-line SPM. The following explanation will be made on the assumption of the semiconductor manufacturing process. However, the description may be made by taking the manufacturing process of the hard disk as an example instead of the semiconductor. In this case, the wafer may be replaced with the recording medium, the wafer, the rover obtained by cutting the wafer into rectangles, and the head obtained by cutting the rover into pieces each for a unit of the head of the hard disk. The wafer that has been processed by manufacturing devices A1501 and B1502 sequentially is separated into those subjected to the process of a manufacturing device C1504 per unit of lot, and those subjected to the manufacturing device C1504 after it is measured by an SPM 1503. Ratio between the separated wafers is preliminarily instructed to the host computer by an operator in consideration of the throughput (the number of the processed wafers per unit of time) of the SPM 1503, All the manufacturing devices 1501, 1502, 1504, and the SPM 1503 are connected to a host computer 1505 of the semiconductor manufacturing line via a data network. The host computer 1505 manages records and process steps of all the wafers in production. The wafers are carried among those devices by a carrier device (not shown). For example, the manufacturing device A1501 is a dry etching device, the manufacturing device B1502 is a resist peeling device, and the manufacturing device C1504 is a film formation device. The wafers having the process by the manufacturing device B1502 completed is carried to the SPM 1503 at a predetermined rate based on the process management information of the wafer managed by the host computer 1505. The SPM 1503 sends the inquiry with respect to the process management information about the carried wafer to the host computer 1505 to obtain the coordinate information of the measurement point on the wafer for performing the measurement. The SPM 1503 outputs the measurement results of the respective measurement points on the wafer to the host computer 1505 after the measurement so that the wafer is carried to the manufacturing device C1504 by the carrier device. The host computer 1505 analyzes the measurement results obtained from the SPM 1503, and changes (optimizes) the processing conditions of the respective manufacturing devices 1501, 1502 and 1504 as necessary. For example, the SPM 1503 measures the difference in the height of the etching at a plurality of positions on the wafer, and changes the etching condition of the manufacturing device A1501 (dry etching device) based on variation in the measurement values. Alternatively, there may be the case where after analysis of the SPM 1503 with respect to the measurement results, the wafer is returned to the manufacturing device B1502 so as to be processed again. The processing conditions in the cases as described above, which are different from those normally employed for the respective manufacturing devices are determined and managed appropriately by the host computer 1505 based on the measurement results of the SPM 1503. In a certain case, the operator may involve the aforementioned feedback operation (depending on the situation, feedforward may be performed for determining the processing conditions of the manufacturing process from the process performed by the SPM 1503 onward based on the SPM measurement results). When determining (optimizing) the process conditions of the respective manufacturing devices based on the measurement results of the SPM 1503 in the process as described above, as the measurement accuracy of the SPM 1503 becomes higher, the process conditions of the respective manufacturing devices may be set in more detail. It is ideal to allow the SPM 1503 to complete measurement of the wafer with the process performed by the manufacturing device upstream of the SPM 1503 completed until it is processed by the next processing device without going through the SPM 1503 for the purpose of using the SPM 1503 as the in-line device in the semiconductor manufacturing process. Accordingly, it is an essential task to improve the throughput of the in-line SPM. FIG. 15B is an explanatory view of a series of operations of the SPM 1503 according to the present invention. The specific operations of the SPM 1503 will be described referring to FIG. 1. The wafers with the process performed by the manufacturing devices 1501 and 1502 in the process upstream of the SPM 1503 completed are stored in a wafer case per unit of lot, and loaded in a wafer cassette of the SPM 1503 by the carrier device (S1501). The SPM 1503 reads the barcode of the wafer case, and obtains the corresponding process information and the inspection condition from the host computer of the semiconductor manufacturing line (S1502). Thereafter, a loader of the SPM 1503 picks up the single wafer from the wafer cassette, and mounts it on the sample stage 104 so that the orientation flat of the wafer is aligned in the fixed direction (S1503). The wafer alignment is performed in the following process steps (S1504). First, the wafer 103 is held by the sample stage 104 with vacuum suction, and a wafer number drawn on the surface of the wafer 103 is read by a detector (not shown). Then it is moved to the position just below the probe drive mechanism 101 while being kept on the sample stage 104. The sample stage 104 in the Z-axis direction is positioned at the bottom dead center. Until this time, the observation optical system 105 moves upward to the top dead center to rotate a revolver (not shown) so that the objective lens 106 is replaced with, for example, an alignment objective lens (not shown) with low magnification of approximately 50. The parfocal distance for the objective lens 106 is the same as that of the alignment objective lens. Then the observation optical system 105 is moved downward to adjust the focus position so that the focal position is set to the back surface (upper surface) of the probe 102. The focusing operation is automatically performed by image recognition performed by the optical image processing unit 108. Then the observation optical system 105 is further moved downward by a fixed amount (for example, 1 mm) so as to move the focal position of the observation optical system 105 to the position lower than the one at which the SPM image is taken. The sample stage 104 is moved in the XY-direction to the position where an alignment mark position on the wafer 103 comes within the field of view of the alignment objective lens (not shown). Then it is gradually moved upward in the Z-direction so as to bring the surface of the wafer 103 in line with the focal position of the observation optical system 105. The alignment mark is then recognized as the image by the optical image processing unit 108. At this time, under the condition where the aperture ratio of the alignment objective lens is low, the probe 102 may be observed simultaneously with the optical image obtained by the observation optical system 105. It is therefore preferable to perform the image recognition of the alignment mark at the position where the alignment mark is not overlapped with the probe 102 in the field of view of the observation optical system 105. The alignment mark on the wafer 103 is recognized as the image at least at two positions so that the correlation between the pattern on the wafer 103 and the XY-coordinate axes of the sample stage 104 is obtained, and stored in an overall control unit 114. During the alignment operation of the wafer 103, the observation optical system 105 is moved downward by the fixed amount so that the focal position is moved to the position lower than the one for picking up of the SPM image. Accordingly, the surface of the wafer 103 is not brought into contact with the tip of the probe 102. After completion of the alignment operation, the observation optical system 105 is moved upward again to the top dead center to rotate the revolver (not shown) so that the lens is replaced with the objective lens 106 with high power (for example, 100 magnifications). The observation optical system 105 is moved downward, and the focus position is adjusted so that the focal position is brought in line with the rear surface (upper surface) of the probe 102. The focusing operation is automatically performed by the image recognition performed by the optical image processing unit 108. The observation optical system 105 is further moved downward by the fixed amount (for example, 1 mm) to move the focal position to the position lower than the one for picking up of the SPM image. In this case, the objective lens is replaced upon alignment of the wafer 103. However, the observation optical system 105 may have the function of zooming the optical image for changing the observation magnification without replacing the objective lens. The overall control unit moves the sample stage 104 in the XY-direction to the position where the first measurement point comes into the field of view of the observation optical system 105 based on the inspection information (coordinate information) obtained from the host computer (S1505). The optical image processing unit recognizes the measurement point (or peripheral pattern of the measurement point) contained in the field of view (display region on the TV monitor 107) of the observation optical system 105 as the image. The XY-axis of the sample stage 104 is adjusted minutely to perform positioning of the measurement point. The objective lens 106 has the power of 100 magnifications, and moves the observation optical system 105 downward by the fixed amount (for example, 1 mm). The focal position is moved to the position lower than the one for picking up of the SPM image to observe the surface of the wafer 103. This makes it possible to observe the surface of the wafer 103 with high resolution without being influenced by the existence of the probe 102 provided in the field of view of the objective lens 106. For example, if the aperture ratio of the objective lens 106 is specified as 0.7, the pattern on the wafer 103 may be clearly observed under the condition of the resolution of 1 micrometer or less. It is possible to observe the pattern on the wafer 103 just below the probe 102. This is established by using the optical phenomenon obtained under the condition where the objective lens has a large aperture ratio, and the probe 102 occupies only a part of the field of view of the objective lens 106. The positioning of the measurement points may be performed by the operator who observes the TV monitor 107 so as to directly designate the coordinate from the overall control unit. Thereafter, the observation optical system 105 is moved upward by the fixed amount to adjust the focus position so that the focal position is located on the rear surface (upper surface) of the probe 102. The SPM according to the present embodiment is not required to move the sample stage 104 for the period from determination of the measurement point in the field of view of the observation optical system 105 to the end of the subsequent measurement operation. A conventional SPM is provided with the probe drive mechanism just above the probe, and accordingly, the field of view position of the observation optical system is overlapped with the SPM image measurement position. It is therefore necessary to secure the time for operating the stage so as to move the measurement point to the SPM image measurement position, and perform accurate positioning again. However, if it is provided with the function for observing the measurement point and the probe without moving the sample stage 104, the probe drive mechanism of the conventional SPM is installed just above the probe and it may prevent increase in the aperture ratio of the observation optical system, thus failing to allow observation of the pattern on the wafer surface with sufficient resolution. The SPM according to the present embodiment is configured to have the through hole 211 in the probe drive mechanism 101, which allows observation of the measurement point and the probe using the objective lens with high aperture ratio just above the probe 102 without moving the sample stage 104. The operation for contacting the tip of the probe 102 with the surface of the wafer 103 (S1506) will be described. The probe drive mechanism 101 is a three-dimensional (X, Y, Z) probe scanning mechanism as a structure for driving the stage with the elastic deformation portion using the piezoelectric device, and provided with the probe 102 held at the probe holder 115 on the bottom. The probe drive mechanism 101 has the through hole that allows insertion of the objective lens 106 in the contactless manner. A focus axis (not shown) of the observation optical system 105 is adjusted to allow observation of both the probe 102 and the surface of the wafer 103 without moving the sample stage 104. The movable region of the probe drive mechanism 101 is set to 20 micrometers in the X-axis direction, 20 micrometers in the Y-axis direction, and 10 micrometers in the Z-axis direction. The detailed structure is illustrated in FIGS. 2A to 2C. The contact between the tip of the probe 102 and the surface of the wafer 103 will be described referring to FIGS. 16A and 16B. It is established by repeating a series of operations of (1) moving the probe drive mechanism 101 upward along the Z-axis to the top dead center, (2) moving the sample stage 104 upward along the Z-axis by 10 micrometers, and (3) moving the probe drive mechanism 101 downward along the Z-axis to the bottom dead center while monitoring the detection signal of the probe deflection detection unit 109. That is, if the tip of the probe 102 is brought into contact with the surface of the wafer 103 in the aforementioned step (3), the detection signal of the probe deflection detection unit 109 is changed. The probe scanning control unit 112 detects the aforementioned contact by capturing the change. The detailed operation principle has been described referring to FIG. 3. FIG. 16B indicates that the probe 102 is brought into contact with the sample 103 in the third cycle of step (3) for moving the probe downward. Thereafter, the probe 102 is moved upward to the top dead center, and the sample stage 104 is moved upward along the Z-axis by the amount calculated so that the height of the sample surface comes into a target height 912 set around the center of the movable range 911 in the Z-direction of the probe 102. The probe 102 is then moved downward again until the contact between the probe tip and the surface of the wafer 103 is detected (S1507). With the aforementioned method, only the probe 102 that can be controlled more accurately is driven in contacting the probe tip with the sample. This may provide the effect of preventing the damage to the fine probe tip, which may be caused by application of excessive force to the probe owing to the contact between the probe 102 and the sample 103 while driving the Z-axis at the sample side. Another method of making the probe 102 and the sample 103 proximal with each other will be described referring to FIGS. 17A and 17B. In this case, the sample 103 is moved upward by a sample Z-stage while having the probe 102 moved downward to the bottom dead center. Upon detection of the contact between the sample 103 and the probe 102, the probe 102 is immediately evacuated to the top dead center at high speeds so as to prevent the damage to the tip of the probe 102 while restraining the state where the driven and oscillated surface of the sample 103 is in contact with the probe 102 as least as possible. The surface of the sample 103 is moved upward by the amount calculated so that the height of the sample surface comes into the target height 912 set around the center of the movable range 911 of the probe 102, and then stopped. Thereafter, the probe 102 is moved downward again until the contact between the tip of the probe and the surface of the wafer 103 is detected. After detecting the contact between the tip of the probe 102 and the surface of the wafer 103, the probe drive mechanism 101 is driven to scan with the probe 102 for picking up of the SPM image. For example, the region with 1 micrometer square on the wafer 103 is divided into 256 sections in the X-direction, and into 10 sections in the Y-direction, and the probe 102 is moved upward by 1 micrometer, for example. The contact position is sequentially moved toward the X-direction (Y-direction) so that the contact between the probe 102 and the wafer 103 is repeatedly detected. The contact detection is performed by operating only the probe 102 within the movable range of the probe drive mechanism 101 without moving the sample stage 104. The operation of the probe drive mechanism 101 is controlled by the probe scanning control unit 112 via the probe drive control unit 110. Each of the movement axes (X-, Y-, Z-stages) of the probe drive mechanism 101 is provided with the capacitive sensor as shown in FIGS. 11A and 11B. The displacement of the respective capacitive sensors is detected by the stage displacement detection unit 128, and stored in an SPM image generation unit 113 via the probe scanning control unit 112. The SPM image generation unit 113 generates an XY-plane distribution image with respect to the displacement of the probe 102 measured in the state where the probe 102 is in contact with the respective contact points on the wafer 103 (displacement of the probe drive mechanism 101 on the Z-stage). The piezoelectric device used in the probe drive mechanism 101 is capable of operating at the response speed from 2 to 3 kHz. The aforementioned measurement operation ends within several seconds. The obtained SPM images (data) are stored in the overall control unit. The measurement coordinate and the number of measurement points on the wafer 103 are preliminarily set. If there are measurement points left on the wafer 103, the observation optical system 105 and the sample stage 104 are moved downward by the equal amount so that the XY-coordinate of the stage 104 is moved to the coordinate of the next measurement point. The process then proceeds to the measurement operation again (S1508). If the measurement points no longer exist on the wafer 103, the observation optical system 105 and the sample stage 104 are moved downward by the equal amount to unload the wafer 103 from the sample stage 104 (S1509). If the next wafer to be measured exists in the wafer case, it is loaded on the sample stage 104 and performs the measurement repeatedly (S1510). When measurement of all the wafers in the wafer case is finished, the data stored in the overall control unit 114 are output to the host computer (S1511). The wafer case is carried to the next processing device by the carrier device (not shown) (S1512). The conventional SPM is required to recognize the measurement position by the observation optical system for performing the measurement positioning, and to move the sample stage to the probe scanning mechanism (position of the probe 102). If the distance between the position of the observation optical system and the probe scanning mechanism (position of the probe 102) is 150 mm, 2 to 3 seconds may be required for operating the sample stage. However, when 10 measurement points exist on the single wafer, the total time taken for operation of the sample stage for the measurement positioning may be 20 to 30 seconds which may result in the cause of large deterioration in the measurement throughput of the SPM. The SPM according to the present embodiment is operated to allow observation of both the probe 102 and the surface of the wafer 103 by adjusting the focus of the observation optical system 105 without moving the sample stage 104, thus saving the time taken for performing the measurement positioning. As a result, the time taken for a series of operating the device for each of the wafers to be measured (loading the wafer, for example, measuring the etching unevenness at 9 measurement positions, and thereafter, unloading the wafer) may be 2 minutes or shorter (30 WPH). This makes it possible to implement the in-line SPM with improved throughput. The operation of the present invention will be described referring to FIGS. 18A and 18B, which is intended to designate the measurement position accurately based on the SPM measurement results rather than designation based on the coordinate of the sample XY-stage 410 and the observation results of the observation optical system 105. A reference numeral 901 denotes a region that can be scanned by the probe 102 through the rough movement piezoelectric device. A range 910 that is considered to contain the pattern required to be measured is scanned with the probe 102 to obtain the measurement results 910. The pattern required to be measured is found from the results, and the area that contains only the pattern is accurately measured by the probe 102. At this time, if the area is smaller than a measurable size (area that can be scanned by the fine movement element) 902 of the fine movement piezoelectric device, the rough movement piezoelectric device is fixed so as to allow the high-accuracy measurement by the scanning only with the fine movement piezoelectric device. If the two types of actuators for the rough movement and the fine movement along the Z axis are installed, the position of the rough movement piezoelectric device is adjusted so that the height of the area required to be measured comes into the height control width 912 of the fine movement piezoelectric device. This makes it possible to perform high-accuracy measurement with respect to the height. The measurement sequence will be described referring to FIG. 19. Firstly, the sample stage is moved to bring the probe 102 to the position above the sample 103 required to be measured (S1901). If the response of the Z rough movement amplifier is required to be explicitly switched, it is switched at high speeds (S1902). The sample proximal process as described referring to FIGS. 16 and 17 is executed (S1903). If the response of the XY rough movement amplifier is required to be explicitly switched, it is switched at high speeds (S1904). The rough movement scanning with the probe 102 is performed for measurement (S1905) (The aforementioned control is executed by the probe scanning control unit 112 shown in FIG. 15). Based on this, the position of the measured pattern is automatically obtained through image processing by the overall control unit 114 from those obtained measurement images (in the SPM image generation unit 113), or designated on the screen by the user (S1906). If the response of the XY rough movement amplifier is required to be explicitly switched after moving the XY-axis to the center of the measured region (S1907), it is switched at low speeds (S1908). Alternatively, rough movement fixation is performed (S1909). If the rough and fine movement mechanisms along the Z axis are installed, the similar process will be performed. Thereafter, the scanning with the probe 102 through the fine movement piezoelectric device is performed to implement the high-accuracy measurement with higher power (S1910). IN case the measurement is finished (S1911), the response of the Z rough movement amplifier is switched at high speeds in response to the need of explicit switching of the Z rough amplifier (S1912), and the sample 103 is evacuated (S1913). In case the zooming or minor measurement of the measurement position is required again in the field of view of the same fine movement scanning, the fine movement scanning is performed again. If the measurement is required to be performed in another field of view (S1920), the process is started again from obtaining the position through the image processing or designation by the user. If there is no pattern required to be measured in the range of the same rough movement scanning, the response of the XY rough movement amplifier is explicitly switched again at high speeds if needed (S1921). The process is started over from the operation for changing the rough movement scanning range for scanning again (S1922). The aforementioned sequence allows high speed and high-accuracy measurement by switching between the high speed scanning in the broad range and the high-accuracy scanning in the narrow range according to the present invention. An embodiment of another laser interference displacement gauge different from the capacitive sensor will be described as the displacement gauge used for the present invention referring to FIGS. 20, and 21A to 21C. The capacitive sensor detects the interval from the flat metal electrode as the target as a value converted into the change in the electrostatic capacity. Meanwhile, the laser interference displacement gauge detects the interval from the flat mirror as a value converted into the phase of the interference pattern. As FIG. 20 shows, an optical interference displacement sensor of the embodiment includes a light source unit (not shown), a sensor unit 100 and a displacement output unit 70. The light source unit guides a linear polarized laser beam with the wavelength of 632.8 nm which is emitted from a frequency stabilizing He—Ne laser light source to the sensor unit 100 in a polarizing direction at 45° with a polarization-preserving fiber 2. The sensor unit 100 includes an interferometer 600 and a displacement computing unit 50. The interferometer 600 allows the collimator 3 to form the polarized light at 45° projected from the polarization-preserving fiber 2 into a parallel light 4, and further allows transmission of a polarizer 5 such as Glan-Thompson prism so as to reflect the transmitted light 6 at a prism mirror 7 and an unpolarized beam splitter 8. It is further allowed to have incidence to a reference mirror 9. As shown in FIG. 21B, the reference mirror 9 is structured by forming a diffraction grating 9b made of metal such as aluminum on a synthetic quarts substrate 9a. The incident polarized beam 6 directed at 45° to the diffraction grating is formed of two orthogonal polarization components resulting from vector resolution. An S polarization component 25s parallel to the longitudinal direction of the diffraction grating reflects thereon, and an orthogonal P polarization component 25p transmits the diffraction grating. That is, this diffraction grating shows the nature of so-called diffraction polarizer (Wire Grid Polarizer). In this embodiment, the pitch, stroke width, and height of the diffraction grating 9b are set to 144 nm, 65 nm, and 165 nm, respectively. An S polarized beam 6r reflected from the reference mirror 9 is used as the reference beam. A transmitted P polarized beam 6m is used as the measurement light. The P polarized beam 6m transmits a quarterwave plate 10, and then becomes a circular polarized light. It is reflected from a target mirror 12 mounted on a measuring object 31 to transmit the quarterwave plate 10 again, and becomes the S polarized light. It is reflected on the reference mirror 9, transmits the quarterwave plate 10, and becomes a circular polarized light. It is reflected on the target mirror 12 to transmit the quarterwave plate 10, and becomes a P polarized light. It then transmits the reference mirror 9. In other words, the measurement light 6m reciprocates on the optical path between the reference mirror 9 and the target mirror 12 twice. A moving distance 31d of the measuring object 31 is detected as the value magnified twice. The S polarized beam 6r reflected from the reference mirror 9, and the transmitted P polarized beam 6m are synthesized as an orthogonal polarized beam 14 which transmits the unpolarized beam splitter 8. The orthogonal polarized beam 14 passes through an opening 13 for removing the stray light, and is divided into four orthogonal polarized beams 17 using two oppositely arranged quadrangular pyramidal prisms 15a and 15b. The method of dividing the beam is not limited to the use of the prism as described above. The diffraction optical device may also be applied. The four orthogonal polarized beams 17 transmit phase shift elements 18 and 19, which cause polarization interference between the orthogonal polarized components in the state where the phase shifts of 0, π/2, π, 3π/2 are given so as to generate four phase shift interference lights 20. The phase shift element 18 is divided into two sections as shown in FIG. 21A. The lower half section is formed of a synthetic silica 18d, and the upper half section is formed of a photonic crystal 18c. Referring to an enlarged view, the photonic crystal 18c forms horizontal line-and-space-like diffraction grating at the pitch smaller than the wavelength of the incident light to a synthetic silica substrate 18c1, on which dielectric thin films 18c2 and 18c3 each having a different refractive index are stacked. The cross section of the thin film layers stacked on the diffraction grating retains the jagged shape like a triangular waveform in the film thickness direction by means of the concavo-convex structure of the diffraction grating. As the material for forming the thin film, Si, SiO2, TiO2, Ta2O5, Nb2O5 may be employed. The multilayer thin film structure based on the diffraction grating becomes the photonic crystal having the diffraction grating directed toward the crystal axis. It presents the double refraction characteristic resulting from diffraction and interference among a plurality of thin films. This makes it possible to control characteristics of polarization, transmission and reflection of the incident light (Reference: Product catalog of Photonic Lattice, Inc.) The diffraction grating pitch, depth and thickness of each of the thin films are controlled in consideration of the wavelength of the incident light and the desired characteristic. As an important characteristic, use of the film forming technique such as the photolithography technique and spattering employed for the semiconductor device manufacturing allows polarized elements and wavelength elements each having the crystal axis directed differently to be formed in array on a single substrate. The photonic crystal 18c has a function as the quarterwave plate, and the crystal axis direction is indicated by a bold arrow. As illustrated in FIG. 19, among four orthogonal polarized beams 17, two orthogonal polarized beams that transmit the photonic crystal 18c have the phase difference of π/2 therebetween. Meanwhile, the rest of two orthogonal polarized beams transmit the synthetic silica 18d without causing the phase difference. The phase shift element 19 is divided into two sections as shown in FIG. 21C. The left half section is formed of a photonic crystal 19a with a crystal axis directed at 45°, and the right half section is formed of a photonic crystal 19b with a crystal axis inversely directed at 45°. Likewise the photonic crystal 18c, the photonic crystal 19a has the line-and-space-like diffraction grating directed at 45° at a pitch smaller than the wavelength of the incident beam on a synthetic silica substrate 19a1, on which dielectric thin films 19a2 and 19a3 each having the different refractive index are stacked. The photonic crystal 19b has the same structure. The photonic crystals 19a and 19b serve as polarizers, and the respective crystal-axis directions are indicated by bold arrows. Referring to FIG. 20, among four orthogonal polarized beams 17, two polarized components that constitute the two orthogonal polarized beams which transmit the photonic crystal 19a, and two polarized components that constitute the two orthogonal polarized beams which transmit the photonic crystal 19b interfere with one another in the state where the phase difference of π is relatively given. The polarized interference occurs among the respective orthogonal polarized components of the four orthogonal polarized beams 17 that have transmitted the phase shift elements 18 and 19 in the presence of the phase shifts of 0, π/2, π, 3π/2 so that four phase shift interference lights 20 are generated. The four phase shift interference lights 20 transmit an interference filter 21 with the transmission center wavelength of 632.8 nm, and are received by four photoelectric transducers 22 such as photodiodes for the purpose of avoiding the influence of the ambient light. They are amplified by an amplifier 23 so as to be output as four phase shift interference signals 41a, 41b, 41c, and 41d. The four phase shift interference signals 41a, 41b, 41c, and 41d are expressed as the following formulae (1) to (4), respectively. Ia = Im + Ir + 2 ( Im · Ir ) ( 1 / 2 ) cos ( 4 π nD / λ ) ( formula 1 ) Ib = Im + Ir + 2 ( Im · Ir ) ( 1 / 2 ) cos ( 4 π nD / λ + π ) = Im + Ir - 2 ( Im · Ir ) ( 1 / 2 ) cos ( 4 π nD / λ ) ( formula 2 ) Ic = Im + Ir + 2 ( Im · Ir ) ( 1 / 2 ) cos ( 4 π nD / λ + π / 2 ) = Im + Ir + 2 ( Im · Ir ) ( 1 / 2 ) sin ( 4 π nD / λ ) ( formula 3 ) Id = Im + Ir + 2 ( Im · Ir ) ( 1 / 2 ) cos ( 4 π nD / λ + 3 π / 2 ) = Im + Ir - 2 ( Im · Ir ) ( 1 / 2 ) sin ( 4 π nD / λ ) ( formula 4 ) where Im denotes a detection intensity of the probe light, Ir denotes a detection intensity of the reference light, n denotes the diffraction index of air, D denotes a moving distance 31d of the measuring object 31, and λ, denotes the wavelength of the laser light 4. The displacement computing unit 50 calculates the moving distance D of the measuring object 31 based on the formula (5), which is displayed on a displacement output unit 70 as a moving distance signal 61.D=(λ/4πn)tan−1{(Ic−Id)/(Ia−Ib)} (formula 5) In the embodiment, the diffraction polarized element (Wire Grid Polarizer) is employed as the reference mirror 9. As has been clearly described above, it is possible to employ the photonic crystal 9c having the horizontal crystal axis direction as indicated by FIG. 21C. The quarterwave plate 10 is allowed to employ a photonic crystal 10c having the crystal axis directed at 45°. In order to further simplify the interferometer 600, the phase shift element 19 shown in FIG. 21C is formed only of the photonic crystal 19a. The phase shift interference signals 41a and 41c expressed by the formulae (1) and (3) are calculated, based on which the moving distance D of the measuring object 31 may be obtained. As FIG. 20 clearly shows, two beams directed to the target mirror 12, that is, the measurement light 6m and the reference light 6r are emitted from the light source unit to the sensor unit 100. They pass a completely identical optical path until they reach the reference mirror 9, and further from the reference mirror 9 to the four photoelectric transducers 22. In other words, the common path interferometer is structured. If air fluctuation causes the temperature distribution or refractive index distribution in the optical path, or mechanical oscillation occurs, such disturbance may equally influence both beams. Therefore, as both beams interfere with each other, the influence caused by the disturbance is completely offset. As a result, the interference light is not influenced by the disturbance. The measurement light 6m only exists on the optical path between the reference mirror 9 and the target mirror 12. As the stroke of the scanning probe microscope is several hundreds of microns at most, the interval between the reference mirror 9 and the target mirror 12 may be set to 1 mm or smaller. The influence of the disturbance in such a small interval is negligible. Fluctuation in the intensity of the laser beam by itself is expressed as fluctuation of the probe light detection intensity Im and the reference light detection intensity Ir, respectively in the formulae (1) to (4). They may be offset by subtraction and division in the formula (5) executed by the displacement computing unit 50. The optical interference displacement sensor of the present embodiment is simply configured to generate four orthogonal polarized beams, and allow the arrayed phase shift elements to generate four phase shift interference beams spatially in parallel so as to be received. Compared to the conventional phase shift interferometer, it largely reduces the optical components to provide a merit of significantly reducing the size of the displacement sensor. Specifically, the dimension of the interferometer 600 may be reduced approximately to 20×15×50 mm or smaller. As four phase shift interference lights pass the adjacent optical paths, it is possible to minimize the influence of the disturbance caused by such as the temperature distribution, humidity distribution, atmospheric pressure distribution, and airflow change owing to the air fluctuation between the optical paths, even if those disturbance are superimposed. The optical interference displacement sensor according to the present embodiment is capable of stably measuring the moving distance and a position of the measuring object with accuracy from sub-nanometers to 10 picometers or less without controlling the environmental factors such as the temperature, humidity, atmospheric pressure, density, and acoustic oscillation with high-accuracy. The SPM scanning mechanism is feedback controlled using such sensor to ensure stable control of the position of the probe tip of the SPM with the accuracy from sub-nanometers to 10 picometers or less, resulting in the high-accuracy SPM device. The present invention is applied to the scanning probe microscope used for inspection measurement and failure analysis in the semiconductor manufacturing process, and measurement of the sample shape with high-accuracy, for example, three-dimensional shape of the magnetic medium with stripe-like or dot-like structure of the hard disk device. 1 . . . light source unit 2 . . . polarization-preserving fiber 3 . . . collimator 5 . . . polarizer 7 . . . prism mirror 8 . . . unpolarized beam splitter 9 . . . reference mirror 10 . . . quarterwave plate 12,12x,12y,12z . . . target mirror 14,17,81,218 . . . orthogonal polarized beam 13 . . . opening 15a,15b . . . quadrangular pyramidal prism 18,19,82,83,84,219,220 . . . phase shift element 9c,10c,18c,19a,19b,82c,82d,83c,83d, 84a,84b . . . photonic crystal 20,85,221 . . . phase shift interference light 21,86 . . . interference filter 22 . . . photoelectric transducer 23,88,223 . . . amplifier 31 . . . measuring object 50,51,52 . . . displacement computing unit 70 . . . displacement output unit 101 . . . probe drive mechanism 102 . . . probe 103 . . . wafer 104 . . . sample stage 105 . . . observation optical system 106 objective lens 201,202 . . . holder 203 . . . Y-stage 204a,204b,204c,204d . . . elastic deformation portion 205,206,209,210,216,217 . . . piezoelectric device 205a,206a,209a,210a,216a,217a . . . rough movement piezoelectric device 205b,206b,209b,210b . . . displacement expansion mechanism 205c,206c,209c,210c,216c,217c . . . fine movement piezoelectric device 205a′,210a . . . rough movement actuator 207 . . . X-stage 211 . . . through hole 214 . . . Z-stage 240 . . . fine movement stage 230a,230b,230c,230d . . . elastic deformation portion 231a,231b,231c,231d . . . elastic deformation guide 241 . . . rough movement stage 220,221 . . . target 222,223,224,301 . . . laser diode 311 . . . photodetector 401 . . . sample stage 410 . . . displacement sensor 402 . . . rough XY-stage 404 . . . air slider 403 . . . rough Z-stage 405 . . . surface plate 406 . . . elastic plate 410 . . . sample XY-stage 500 . . . flutter piezoelectric device driver 501 . . . driver amplifier 506 . . . switcher 506r . . . switcher r 510 . . . rough movement piezoelectric device driver 511 . . . driver amplifier 512 . . . output resistance |
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052215156 | description | DETAILED DESCRIPTION OF A PREFERRED EMBODIMENT The installation which will now be described can be used particularly for mutually welding the components of a grid 1 of the kind shown in FIG. 1, which may have the construction described in detail in EP-A-0 159 228 or FR-A-2 474 229. Grid 1 comprises two intersecting sets of mutually interlocked elementary plates 2. A securing weld 3, called "type A", the detail of which is shown in FIG. 1A, secures the plates together at each intersection, on each of the two major faces of grid 1. The edges of plates 2 form, with peripheral plates 5 forming the belt, a T-shaped intersection which receives, on each face, a weld 4 called "type B", shown in FIG. 1B. Plates 2 comprise at their ends, lugs which are engaged in slots formed in the plates 5 of the belt. Each end may in particular comprise two or three lugs 7 engaging in respective slots 8 (FIG. 1C). The lugs, some of which may be deformed so as to provide mechanical locking, are fixed by edge welds called "type C". Finally, welding beads 9 secure the elements of the belt by connecting flanged edges 10 formed at the ends of the peripheral plates 5. These welds, shown in FIG. 1D, are said to be "of type D". The "type D" welds may be replaced by edge-to-edge welds, as shown in FIG. 1DD. In some cases, the plates forming the grid are not fixed by lab welding, but by edge-to-edge welding at location confronting internal plate 2 (FIG. 1E). This type of weld is generally formed at the second internal plate from a corner of the grid, for making it possible to shape the plate defining the pocket situated at the corner of the grid. The installation shown in FIG. 2 and the succeeding figures is suitable for satisfactorily carrying out the numerous spot welds required for forming a grid of the kind shown in FIG. 1. In order to hold all components of grid 1 in a mutually correct position, each assembled grid is first of all placed in a frame for holding the components of the grid in a well-defined position and for building a unit which can be handled and brought into all the orientations required for welding. The frame may be as described in document EP-A-0 159 228, to which reference may be made. The installation, whose general construction is shown in FIG. 2, is contained in a cell 11 whose front face is equipped with movable transparent panels giving access to the enclosure for loading/unloading. The installation comprises a support structure having a beam 12 which supports cabinets containing the electric supply means and the circuits for regulating and controlling the welding operations in accordance with a prerecorded program and a framework 14 which carries the different movable components. On framework 14 are fixed slides 15 (FIGS. 2 to 4), disposed horizontally in a direction X, on which a main carriage 21 and an auxiliary carriage 22 placed underneath can move. The carriages are connected together by an arm 24. The main carriage 21 carries two welding chambers 16 and 17 fixed side-by-side, each having a front door for introducing and removing grids. The auxiliary carriage 22 carries means for conditioning the atmosphere of the chambers and particular the vacuum pump. Carriages 21 and 22 are movable among axis X. They are driven by a thruster and are precisely positioned by stops having dampers. The ceiling of each of chambers 16 and 17 comprises a window which is transparent for the welding radiation. The radiation is delivered by a laser source carried by a table with crossed movements and along direction X and along the horizontal direction Y orthogonal to X. The laser generator may be regarded as comprising a laser properly speaking 20 and an optical system 18 for reflecting along the vertical direction Z and for focussing at an adjustable distance. The laser may be carried by a cradle 26 fixed to the upper plate 25 of the crossed movement table 19. For welding zirconium alloy grids, a 400 W pulse YAG may be used. A range of movement of 400 mm along X and along Y is sufficient to effect all the welds of a fuel assembly grid for a pressurized water reactor of the kind used at the present time. An example of a focussing optical system 18 for adjusting the focal point so that it is exactly at the position of the weld to be executed will be described hereinbelow. Chamber 16 is provided with a device 27 for angular control about an axis parallel to direction Y, whose purpose is to receive a grid contained in its frame for carrying out type C and type D (or DD or E) welds. That chamber is shown in FIG. 4 in a position where its entrance window is situated under the zone scanned by the movement of the laser beam, for effecting the welds on the grid contained in the chamber. The plate 35 of device 27 which holds in position a grid contained in its frame and gives it the eight orientations required for carrying out type C (and possibly E) welds, as well as type D or DD welds, when they exist at the four corners of the grid, passes through the rear wall of chamber 16. In other words, the purpose of device 27 is to bring the grid into the four angular positions required for carrying out welds C, possibly E, on the four faces of the belt and, in other cases, the four additional angular positions required for making welds at the corners of the grid. In all cases, the major faces of the grid will be parallel to direction Z, i.e., to the path of the laser beam during welding. By adjusting the working distance, not only type C spot welds, but also welding beads of type D or DD, can be carried out, when the latter are to be made. The orientation device 27 comprises a circular plate 29 equipped with cams 30 for fixing the frame template 32 containing, the grid, whose periphery is shown schematically in broken lines in FIGS. 4, 5 and 5A. The two cams 30 apply the frame against positioning pins 31 and against the plate. The pivoting parts of the frames pivot in crescent shaped grooves 33 formed in the frame. Plate 29 is fixed to a disk 35, which is secured by the output shaft to a drive motor (not shown) equipped with an encoder giving an indication as to the angular position to cabinets 13. Chamber 17 is also equipped with an orientation device 28, shown in FIGS. 6 and 6A. This device again comprises a plate 29a fixed to a disk 35a for angular control about an axis parallel to direction Y. But plate 29a receives the frame in a position in which the major faces of the grid and two of the sides are parallel to the orientation axis. To that end, plate 29a is fixed directly to disk 35 and a base 36 carrying cams 30a and pins 31a, which is orthogonal to the plate. In base 36 is formed an opening 37 of sufficient size to allow access to all spot welds to be carried out on the major face of the grid which is turned towards the base. The laser source may have the construction shown schematically in FIG. 7. The beam delivered by the laser 20 is reflected by a dichroic mirror 38 towards the focussing optical system 18 formed of several lenses. The set of lenses is mounted in a motor-driven mount and movable along axis Z by a distance of 200 mm, so that the working distance may be adjusted to an optimum whatever the welds to be carried out. For such adjustments, the image of the position to be welded, taken up by the optical system 18 and passing through the dichroic mirror 38, is picked up by a CCD camera which transmits this image to a monitor forming part of the control panel. The operator may then focus by means of a mechanism (not shown) until a clean image in visible light is obtained, indicating a correct working distance. Since the movements of the optical system 18 along axis Z are controlled by the control electronics, adjustment of the working distance is in fact automatic. The optical system 18 may have the construction shown in FIG. 8. This optical system 18 comprises a mount supporting three lenses 40, 42 and 44. The lenses 40 (divergent) and 42 (collimating) form a x2 focal telescope for reducing the divergence of the beam. Lens 44 focusses the beam on the spot to be welded. In addition, lens 44 is mounted on a slide causing it to oscillate in direction X by an amount corresponding to the desired distance between the spots to be welded, so as to form weldings of type C, D or E. The amplitude of movement may, for example, be adjustable from 0 to 2 mm, and the oscillating movement may be given by electro-magnets moving the slide between adjustable stops. The case shown in FIG. 8 further comprises means for illuminating the position where firing is to take place, formed by lens 46 focussing the output beam of two optical fibers 48 fed with light by a generator (not shown). In a modification of the invention, the two chambers 16 and 17 are fixed and the compound movement table is mounted on means for bringing the laser generator successively above chambers 16 and above chambers 17. To reduce the consumption of inert gas, the installation is advantageously adapted to replace the air by gas, not by scavenging, but by evacuating and then filling. Evacuation seems at first glance infeasible, for glass windows probably could fail under the pressure forces applied during evacuation. This problem is solved, in the embodiment shown in FIGS. 4, 4A, 9 and 10, by mounting, on the frame of the installation, lids to be applied around the windows during evacuation and balancing the pressure which prevails on the opposite faces of the windows. Lids 50 and 52 are used alternately, and are applied against the window of that chamber which is not in alignment with the optical system of the laser. To that end lids 50 and 52 are connected to a support frame 54 by respective control mechanisms. The mechanism shown schematically in FIGS. 3, 4 and 9 comprises inflatable cushions 56 inserted between a bearing plate 57 fast with the frame and a shoe 58 fixed to the lids. The shoes are guided by rods 60 sliding in the bearing plate 57 and urged towards an upper position by springs 62. Downward movement of shoes 58 and of the covers is limited by abutment of nuts 64, screwed onto a threaded end portion of rods 60, against plates 57. Each window is provided with several balancing valves occupying, for example, the positions shown at 66 in FIG. 4A, for one of the windows. Each valve comprises a passage formed in the wall of the chamber, a portion of which is defined by a seat 68. The seat is arranged for receiving a closure member 70, urged by a spring 72 to its closed position. In closed position, the closure member 70 has a portion projecting above the wall of the chamber. This wall carries an annular seal 74 encircling all valves. When lid 50 is applied against seal 74, it forces down the closure members and connects the inside of the chamber with the space between the window and the lid. The communication is closed as soon as the lid is removed. The method may be carried out as follows in the apparatus shown in FIGS. 2 to 8. The assembled plates of a grid are placed in a frame which forms a template holding the plates in a well-defined position relative to each other. A first sequence of operations is provided for welding the belt. To that end, frame 32 containing the grid is placed on plate 29 in chamber 16 and locked by means of cams 30. Chamber 16 is closed. The lid protecting the window of chamber 16 is applied against the wall of the chamber for balancing the pressures on each side of the window. The inside of the chamber is evacuated to a primary vacuum by means of the pump of the conditioning device 23, and is then filled with argon. Two pumping and filling sequences are sufficient to obtain a sufficiently pure atmosphere, whose oxygen content is less than 50 vpm and whose content is less than 150 vpm. The lid may then be raised. The overpressure in the chamber may be 40 mbars and is maintained with an argon flow of 20 to 60 l/mn for removing the welding flues appearing in the chamber. Advantageously the installation comprises means for analyizing the argon which exits through a vent, for checking that the oxygen and humidity contents do not exceed the above-mentioned thresholds. Chamber 16 being held fixed on its slides under the optical system 18 type C and D (or E) welds may be carried out automatically. The laser is directed to each welding position by means of the cross-movement table 19. Advantageously, type D or E welds are carried out first type D welds requiring a working distance different from type E welds. Each weld may be formed with energy between 14 and 22 Joules per pulse, at a rate of 7 to 16 Hz, the pulse time duration being about 5 ms. Type C welds may be achieved with parameters of the same order of magnitude as those required for the D and E beam welds. While welding takes place automatically, without movement of chambers 16 and 17, the operator may introduce in chamber 17 a second grid, on which type A and B welds remain to be executed. The time required for loading chamber 17 and for conditioning the atmosphere thereof is less than that for welding in chamber 16. When the welds to be executed in chamber 16 are completed, carriages 21 and 22 are moved over their slides automatically, under the control of the electronics contained in cabinets 13. Following such movement, the window of chamber 17 is under the optical system of 18. Chamber 16 is then opened and the grid which occupied it is removed and replaced by a new grid, while type A and B welds are effected. The latter welds require movements of the laser generator by means of table 19 in the two directions X and Y. Each weld may generally be provided by one or two pulses of a duration of about 5 ms, at a frequency of 5 to 10 Hz and with a total energy of 14 to 24 Joules per pulse. The welds are first of all made on a major face, then on the other, after plate 29a has been pivoted through 180.degree.. |
claims | 1. An apparatus comprising:a nuclear reactor including a pressure vessel and a nuclear reactor core comprising fissile material disposed in the pressure vessel;an internal control rod drive mechanism (CRDM) including an electric motor disposed in the pressure vessel and a support surface including sealed electrical connectors electrically connected with the electric motor to deliver electrical power to the electrical motor; anda support element secured entirely within the pressure vessel which abuts the support surface of the internal CRDM and supports the internal CRDM in the pressure vessel, the support element being configured to be submerged in primary coolant and including sealed electrical connectors mating with the sealed electrical connectors on the support surface of the internal CRDM to deliver electrical power to the electric motor of the internal CRDM. 2. The apparatus of claim 1 wherein the internal CRDM further comprises:mineral insulated cables (MI cables) electrically connecting the electric motor to the sealed electrical connectors on the support surface, wherein each MI cable is connected to one of the sealed electrical connectors and the sealed electrical connectors are sealed glass connectors, sealed ceramic connectors, or sealed glass ceramic connectors. 3. The apparatus of claim 1 wherein the internal CRDM further comprises:mineral insulated cables (MI cables) electrically connecting the electric motor to the sealed electrical connectors on the support surface, wherein each MI cable is connected to one of the sealed electrical connectors and the sealed electrical connectors are welded onto the ends of the MI cables. 4. The apparatus of claim 1 further comprising:springs disposed between the sealed electrical connectors of the support element and the mating sealed electrical connectors on the support surface of the internal CRDM. 5. The apparatus of claim 4 wherein the springs are wave springs. 6. The apparatus of claim 1 further comprising:a purge line integrated with each mated connection of a sealed electrical connector of the support element and the mated sealed electrical connector on the support surface of the internal CRDM, wherein the purge line defines a conduit from the exterior of the sealed electrical connector on the support surface to an area between the sealed electrical connector on the support surface and the sealed electrical connector of the support element in the mated connection. 7. The apparatus of claim 1 wherein the internal CRDM includes a standoff mechanically secured with the internal CRDM, the support surface of the internal CRDM being a surface of the standoff. 8. The apparatus of claim 1 wherein the support element comprises:a distribution plate including mineral insulated cables (MI cables) disposed on or in the distribution plate and terminating at the sealed electrical connectors of the distribution plate. 9. The apparatus of claim 1, where the sealed electrical connectors of the support surface of the internal CRDM are female electrical connectors, and the electrical connectors of the support element are male electrical connectors. 10. The apparatus of claim 1, where the sealed electrical connectors of the support surface of the internal CRDM are male electrical connectors, and the electrical connectors of the support element are female electrical connectors. |
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050200844 | abstract | A method for the rapid and sensitive analysis of heavy metal ores, especially those of gold and uranium, uses high-engery X-ray fluorescence spectroscopy. The invention is of particular interest for the measurement of samples from gold or bodies which typically have concentrations up to 10 ppm by mass. Preferred features include the use of an X-ray tube as a source, the counting of emitted fluorescence photons in energy bands selected to correlate with the characteristic x-ray fluorescence emissions of elements of interest, the excitement of the ore sample by irradiation with high energy bremsstrahlung radiation filtered through tin, the exploitation of polarization in analysis for uranium, the interposition of a platinum-group metal filter between the sample and the detector, and the use of high-purity germanium detectors. Techniques are described for the detection and elimination of inaccuracies due to the presence of certain interfering metals and correction for variations in sample density. Apparatus for use in the method of the invention is also disclosed and claimed. |
claims | 1. A radiation attenuation system, comprising:a first shield panel formed of a first radiation attenuating material;a second shield panel formed of a second radiation attenuating material; anda frame disposed below the first shield panel and the second shield panel, the frame comprising:a first end portion defining a first array of slots; anda second end portion defining a second array of slots; andwherein the first array of slots and the second array of slots are configured to receive an end portion of the first shield panel and an end portion of the second shield panel such that the second shield panel is spaced apart from the first shield panel to form a first trough sized to fit a limb of a patient. 2. The radiation attenuation system of claim 1, wherein the first radiation attenuating material and the second radiation attenuating material both comprise at least one of acrylic lead or leaded glass. 3. The radiation attenuation system of claim 2, wherein the first shield panel and the second shield panel each have a thickness of between 4 mm and 18 mm. 4. The radiation attenuation system of claim 1, further comprising a connecting portion extending between the first end portion and the second end portion. 5. The radiation attenuation system of claim 4, wherein the frame comprises an I-shaped structure configured to receive both legs of the patient. 6. The radiation attenuation system of claim 1, further comprising:a third shield panel;wherein the first array of slots and the second array of slots are configured to receive an end portion of the third shield panel such that the third shield panel is spaced apart from the first shield panel to form a second trough sized to fit a limb of the patient. 7. The radiation attenuation system of claim 6, further comprising a connecting portion extending between the first end portion and the second end portion;wherein the connecting portion defines a longitudinal slot extending between the first array of slots and the second array of slots; the first shield panel being received in the longitudinal slot. 8. The radiation attenuation system of claim 1, wherein the first end portion comprises a first hinged outer portion; the first hinged outer portion defining a first slot; and wherein the second end portion comprises a second hinged outer portion; the second hinged outer portion defining a second slot. 9. The radiation attenuation system of claim 1, wherein the frame holds the first shield panel and the second shield panel upright by receiving the end portion of the first shield panel and the end portion of the second shield panel. 10. A radiation attenuation system for the scanning of a leg of a patient, comprising:a first shield panel;a second shield panel;a third shield panel; anda frame disposed below the first shield panel, the second shield panel, and the third shield panel, the frame comprising:a connecting portion extending from a first end to a second end;at least one first arm defining a first array of slots and extending outward from the connecting portion between the first end and the second end; andat least one second arm defining a second array of slots and extending outward from the connecting portion between the at least one first arm and the second end;wherein the first array of slots and the second array of slots are configured to receive an end portion of the first shield panel, an end portion of the second shield panel, and an end portion of the third shield panel such that the second shield panel and the third shield panel are spaced apart from the first shield panel to form a pair of troughs sized to fit the legs of the patient. 11. The radiation attenuation system of claim 10, wherein the first shield panel and the second shield panel comprise at least one of acrylic lead or leaded glass. 12. The radiation attenuation system of claim 10, wherein the connecting portion extends substantially parallel to the leg of the patient and defines a longitudinal slot extending between the first array of slots and the second array of slots; the first shield panel being received in the longitudinal slot. 13. The radiation attenuation system of claim 10, wherein the frame comprises high density polypropylene foam. 14. The radiation attenuation system of claim 10, wherein the at least one first arm comprises an inner portion and an outer portion coupled to the inner portion by a hinged member and defining a space between the inner portion and the outer portion, the space between the inner portion and the outer portion defining a first slot of the first array of slots. 15. An apparatus for attenuating radiation scattered from a patient undergoing radiological examination on a table, comprising:a frame configured to be supported by the table; anda first shield panel formed of a radiation attenuating material and supported by a first portion of the frame on an end portion of the first shield panel;wherein the first shield panel at least partly defines a trough configured to receive a limb of the patient and attenuates radiation scattered from the patient. 16. The apparatus of claim 15, comprising a second shield panel formed of the radiation attenuating material and supported by a second portion of the frame on an end portion of the second shield panel;wherein the first shield panel, the second shield panel, and the frame at least partly define the trough. 17. The apparatus of claim 16, wherein the frame comprises a third portion located between the first portion and the second portion, the third portion including a cutout configured to comfortably receive the limb of the patient. 18. The apparatus of claim 15, wherein the radiation attenuating material comprises a medium having an attenuating material suspended therein. 19. The apparatus of claim 18, wherein the radiation attenuating material comprises at least one of acrylic lead or leaded glass. 20. The apparatus of claim 18, wherein the frame comprises a semi-rigid, radiotranslucent material. |
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description | 1. Field of the Invention The invention relates to ion traps and systems and methods that use ion traps. 2. Discussion of the Related Art FIG. 1A illustrates a conventional design for a planar ion trap 8. The ion trap 8 includes central electrode 10, inner surrounding electrodes 12, and outer surrounding electrodes 14. The electrodes 10, 12, 14 have rectangular shapes, and the outer electrodes 14 are segmented. The electrodes 10, 12, 14 are flat metal layers that are located on a planar top surface of a quartz or alumina substrate 16. Thus, the electrodes 10, 12, 14 of the ion trap 8 have a planar structure. Operating the planar ion trap 8 involves applying a high frequency voltage between the inner surrounding electrodes 12 and the central and outer surrounding electrodes 10, 14, and applying a static or quasi-static voltage between the segments of outer surrounding electrodes 14. The high-frequency voltage produces a pattern of electric fields, E, with a small quadruple component in a cylindrical free-space region 18 that is located above and between the paired inner surrounding electrodes 12 as illustrated is FIG. 1B. In the free-space region 18, the high-frequency electric fields can traps ions vertically and laterally. The static or quasi-static voltage produces an electric field pattern that can trap the ions along the axis of the ion trap 8. Thus, the combination of high frequency and static or quasi-static voltages traps ions in the planar ion trap 8. The ion trap 8 also includes a number of metallic electrical leads (not shown) that run along the top surface of the substrate 16. The electrical leads connect the electrodes 10, 12, 14 to high-frequency and static or quasi-static voltage drivers (not shown). These drivers are located off the edges of the substrate 16. Various embodiments provide structures for planar ion traps and arrays of ion traps in which electrical connections are conveniently disposed. The structures include special electrical connections that traverse the substrates on which the ion traps are located rather than running out to lateral edges of the substrates. In particular, the special electrical connections are located in vias that traverse the thickness of the substrates. Thus, control voltage sources can connect to the ion traps through surfaces of the substrates that are opposite to the surfaces on which the ion traps themselves are located. Such backside connection configurations enable shielding control circuitry from high intensity radio frequency (RF) fields of the ion traps and also provide simple connection layouts for control voltage sources. Due to the simple connection layouts, arrays of the ion traps can have patterns that would be unavailable in the absence of such backside connections. These special via-based connections also permit designs for high-density arrays of ion trap electrodes in which electrical crosstalk is low. In one aspect, the invention features an apparatus for an ion trap. The apparatus includes an electrically conductive substrate having top and bottom surfaces and one or more vias that cross from the top surface to the bottom surface. The apparatus includes a pair of planar first electrodes supported over the top surface and second electrodes. The second electrodes have planar surfaces that are also located over the top surface. Portions of the planar surfaces are located laterally adjacent to the planar first electrodes. One of the second electrodes includes a portion that is located in one of the vias and traverses the substrate. In another aspect, the invention features an apparatus. The apparatus includes an electrically conductive substrate having top and bottom surfaces and having a plurality of ion traps. Each ion trap has first and second electrodes and is configured to trap ions over the top surface of the substrate. Each second electrode includes a portion that crosses through the substrate. Herein, like reference numbers indicate functionally similar structures and/or features. Herein, some figures may exaggerate dimensions of certain elements to better illustrate the embodiments. While illustrative embodiments are described by the Figures and detailed description, the inventions may be embodied in various forms and are not limited to embodiments described in the Figures and detailed description. FIGS. 2a and 3 show an embodiment of a planar ion trap 20 that is configured to be driven by a radio frequency (RF) driver with a frequency of about 100 MHz and a maximum voltage of about 100 volts. Other embodiments of planar ion traps may operate at other high frequencies and voltages. Herein, RF's are in the range of 10 mega Hertz (MHz) to 300 MHz and preferably are between about 50 MHz to about 200 MHz. The planar ion trap 20 is integrated into a conducting substrate 22. The substrate 22 is either a metal substrate or a heavily doped semiconductor wafer. An exemplary doped semiconductor substrate is a silicon wafer that has been doped to have a resistivity of about 5×10−3 to 5×10−2 Ohm-centimeters (Ω-cm). Such silicon wafers may be up to about 8 inches in diameter and have a thickness of 725 micrometers (μm) or less. The planar ion trap 20 also includes a pair of raised RF electrodes 24, an outer pair of slowly varying of static voltage (SVSV) electrodes 26, and a central SVSV electrode 28. Herein, slowly varying or static voltages vary over times of about 10−6 second to about 1 second, and SVSV electrodes are configured to apply such SVSV voltages. The RF electrodes 24 are metal films of about 1 μm thick or less, e.g., films of gold, chrome, titanium, or a combination thereof. The outer and central SVSV electrodes 26, 28 are polysilicon, which has been doped to have a low resistivity, e.g., about 10−3 Ω-cm, thereby reducing RF losses therein. The SVSV electrodes 26, 28 have planar portions 40 that are located over the top surface of the conductive substrate 22 and through-substrate portions 38 that fill vias crossing the conductive substrate 22. To reduce RF losses, the planar portions 40 should have a thickness of about 20 μm or more, and the through-substrate portions 38 should have a diameter of about 50 μm or more. The SVSV electrodes 26, 28 are insulated from the conductive substrate 22 by a thin dielectric layer 32, e.g., a 0.2 μm thick or thinner layer of silicon dioxide, e.g., 0.1 μm of silicon dioxide. The ion trap 20 occupies a rectangular area over the free top surface of the semiconductor substrate 22. The RF, outer SVSV, and central SVSV electrodes 24, 26, 28 are also rectangular. The central SVSV electrode 28 is separated by silicon dioxide spacers 36 into axial segments, e.g., 50–200 μm long segments, which enable controlling the axial position of ions in the ion trap 20. The various electrodes 24, 26, 28 have lengths of up to about 30 centimeters along the axis of the ion trap 20 In the ion trap 20, the RF, outer SVSV, and central SVSV electrodes 24, 26, 28 have flat top surfaces that are located over and parallel to the top surface of the conductive substrate 22. Dielectric pedestals 30 support the RF electrodes 24 above the SVSV electrodes 26, 28. Exemplary dielectric pedestals 30 are formed of silicon dioxide and have heights of about 5–20 μm, e.g., a height of about 10 μm. Near the ion trap 20, the two SVSV electrodes 26, 28 preferably are designed to cover substantially all of dielectric layer 32, because uncovered dielectric can produce stray electric fields that affect the ions. For that reason, vias 34, which separate the outer and central SVSV electrodes 26, 28 and vias 36, which, separate segments of the central SVSV electrode 28, are preferably thin. Exemplary vias 34, 36 are covered with silicon dioxide and have small widths of about 0.3 μm or less to limit the amount of uncovered dielectric. In the ion trap 20, the center-to-center distance between a pair of RF electrodes 24 determines the trapping height and is typically fixed by the form of the optical beams that will be used to address the ions. For example, the trapping height may be selected so that a laser beam can address ions in parallel. Light propagating parallel to the top surface of the conductive substrate 22 can address many ions in parallel if the light does not undergo substantial scattering from topographic features on the top surface. For a Gaussian laser beam with a diameter of about 10–40 μm, such features will not cause significant scattering if the trapping height is about 50 μm above the RF electrodes 24. To produce such a trapping height, the RF electrodes 24 typically would have a center-to-center separation of 50 μm or more, e.g., about 100 μm or more. During operation, the ion trap 20 laterally and vertically traps ions with a RF electric field and longitudinally traps and moves the ions with a SVSV electric field whose frequency is much lower than that of the RF electric field. A RF voltage driver (not shown) produces the RF electric fields by driving the RF electrodes 24. The RF voltage driver connects between the RF electrodes 24 and the conductive substrate 22. SVSV voltage drivers (not shown) produce the SVSV electric field by driving adjacent segments of the SVSV electrode 28 differently. The SVSV voltage drivers connect to the segments of the SVSV electrode 28 at the bottom of the conductive substrate via the through-substrate portions 38 of the SVSV electrodes 26, 28. FIG. 4 shows an expected pattern of electric field magnitudes, E1–E5, produced when an RF voltage is applied between the RF electrodes 24 and the conductive substrate 22. The pattern includes a cylindrical-shaped region 42 where the magnitude of the electric field typically has a local minimum. The cylindrical-shaped region 42 is located above and between the paired RF electrodes 24. Due to the local minimum of the magnitude of the electric field, the region 42 is able to vertically and laterally trap ions when a strong RF voltage drives the RF electrodes 24. FIG. 2b shows an alternate embodiment for an ion trap 20′, which is based on silicon-on-insulator (SOI) technology. In the ion trap 20′, the planar portions 40 of the SVSV electrodes 26, 28 of FIG. 2a are replaced by doped crystalline silicon portions 40′. The SVSV electrodes 26, 28 still include through-substrate portions 38 fabricated with heavily doped polysilicon. FIG. 5 shows a lumped circuit that simulates the RF behavior of the ion traps 20 and 20′ of FIGS. 2a and 2b, respectively. At RF frequencies, the ion traps 20, 20′ function as capacitive bridge divider circuits that include capacitors C1 and C2 and resistors R1 and R2. In the lumped circuit, each C1 capacitor has an upper plate that is formed by one of the RF electrodes 24 and a lower plate that is formed by the planar portions, i.e., element 40 or 40′, of the SVSV electrodes 26, 28. In the lumped circuit, each capacitor C2 has an upper plate that is formed by the SVSV electrodes 26, 28 and a lower plate that is formed by the doped semiconductor substrate 22. In the lumped circuit, the resistors R1 and R2 represent the resistances of the paths between exposed surfaces of the SVSV electrodes 26, 28 and surfaces of said electrodes 26, 28 that face the conductive substrate 22. The values of resistors R1 and R2 are substantially determined by the properties of planar portions 40, 40′ of the SVSV electrodes 26, 28. In the lumped circuit, the current's return path is between the lower plate of capacitor C2 and the upper plate of capacitor C1 and thus, passes through the conductive substrate 22. The ion trap 20 has two geometrical features that cause the capacitance of capacitor C2 to be much greater than that of capacitor C1. First, while the plate separation for the capacitor C1 is of the order of the height of dielectric spacers 30, the plate separation for the capacitor C2 is of order of the much smaller thickness of the dielectric layer 32. Second, while the plate area of the capacitor C1 is of order of the area of the RF electrodes 24, the plate area of the capacitor C2 is of order of the much larger area of the portion of the dielectric layer 32 disposed between the conductive substrate 22 and the SVSV electrodes 26, 28. Due to these geometric features, the ratio C2/C1 can be in the range of about 300 to 3,000 and may often be, at least, as large as about 1,000. The large value of C2/C1 ensures that RF voltage driver produces a much larger voltage drop across capacitor C1 than across capacitor C2. That is, even though the RF voltage difference between the RF electrode 24 and the SVSV electrodes 26, 28 may be about 100 volts, RF voltage differences between the SVSV electrodes 26, 28 and the doped semiconductor substrate 22 are much smaller. The large value of C2/C1 causes the bottom side of the semiconductor substrate 22 to be shielded from the strong RF electric fields that exist in the ion trap 20. The RF shielding or shunting enables the placement of sensitive electrode control circuitry near the bottom surface of the semiconductor substrate 22 and/or electrical connection to the SVSV electrodes 26, 28 from the bottom of the conductive substrate 22. Embodiments of the ion trap 20, 20′ of FIGS. 2a and 2b may be incorporated into complex spatially multiplexed arrays of the ion traps 10, 10′. Such arrays may find useful applications in a device, which is known as a quantum computer. FIG. 6 shows an exemplary array 44 of spatially multiplexed ion traps 20A, 20B, 20C that are located on a single conductive substrate 22. The ion trap 20A connects via ion coupler 46 to both the ion trap 20B and the ion trap 20C. Varying voltages applied to different segments of the SVSV electrode 28 would displace ions from the ion trap 20A to the ion traps 20B, 20C and/or vice versa. The array 44 also, supports complex electrode configurations. For example, SVSV electrode 26′ can be on an island over the substrate 22, because electrical connections to the SVSV electrodes 26′ pass through the substrate 22 rather than running on the top surface of the substrate 22. The exemplary array 44 also illustrates that center-to-center distances between RF electrodes 24 may vary in a complex pattern of spatially multiplexed ion traps 20. For example, the RF electrodes 24 are closer together in ion coupler 46 to ensure that the ions are not liberated therein. Similarly, the RF electrodes 24 are farther apart in ion traps 20A, 20B, 20C so that the trapping height is higher above the conductive substrate 22. Then, trapped ion will less affected by stray fields produced by surface charge distributions and will be more accessible to laser beams directed parallel to the top surface of the substrate 22. In other embodiments, the distance between pairs of RF electrodes varies from ion trap 20 to ion trap 20 so that the ion traps of an array trap ions at different trapping heights. The backside connections for the SVSV electrodes 26, 28 enable the design of denser and more complex patterns of ion traps 20 over the conducting substrate 22. In particular, the backside connections enable high densities of said ion traps 20. FIG. 7 shows a multi-chip module 50 that has an array of ion traps 20 thereon. The multi-chip ion trap module 50 includes a stack that is formed by first, second, and third semiconductor wafers 52, 54, 56 and solder balls 42 that electrically connect adjacent wafers 52, 54, 56. In particular, the multi-chip module 50 couples SVSV voltage drivers and control circuitry to the ion traps 20 via the bottom surface of the doped first semiconductor substrate 52 in which the ion traps 20 are fabricated. The first semiconductor wafer 52 has a top surface that supports an array of planar ion traps 20 and a bottom surface that is adjacent the second semiconductor substrate 54. The ion traps 20 are driven by an RF voltage driver that connects between the traps' RF electrodes 24 and the doped first semiconductor wafer 52. The second semiconductor wafer 54 is substantially shielded from the intense RF voltages used to operate the ion traps 20 by capacitive bridge circuits in the doped first semiconductor wafer 52 as already described. The second semiconductor wafer includes an array of transmission gates 60 that control SVSV voltages applied to the ion traps 20 of the doped first semiconductor wafer 52. Each transmission gate 60 includes back-to-back p-type and n-type FET's 62 that connect an external digital-to-analog converter (DAC) to an associated one of the SVSV electrodes 26, 28 as shown in FIG. 8. Each transmission gate 60 also includes cascaded inverters 64 that control the gates of the p-type and n-type FET's 62 in response to logic control signals. Thus, the transmission gates 60 control application of SVSV control voltages from one or more external DAC's to the ion traps 20 on the first semiconductor wafer 22. The one or more DAC's electrically connect to the transmission gates 60 via one edge of the second semiconductor wafer 54. The second semiconductor wafer 54 may also include an array of integrated resistor or RC and LC filters for each via connection. The third semiconductor wafer 56 includes digital circuitry for controlling multi-chip module 50. The digital circuitry may perform operations that control the transmission gates 60, receive optical measurements for use in quantum error correction, and perform quantum computing instructions. The digital circuitry may include logic circuitry and storage for a machine executable program of instructions for one of the above-described operations. The digital circuitry may, e.g., be CMOS circuitry. Such circuitry is protected from strong electric fields of the ion traps by the above-described RF screening. FIG. 9 shows a vacuum setup 70 for maintaining an operating environment for the ion traps 20 of the multi-chip module 50 of FIG. 7. The vacuum setup 70 includes first and second chambers 72, 74. The first chamber 72 is either kept at atmospheric pressure or at a low pressure of about 10−3 or less Torr. The second chamber 74 is maintained at a high vacuum of about 10−11 Torr by a separate pump 76. The multi-chip module 50 is positioned so that the first semiconductor wafer 22 and a high vacuum seal 78 close a port between the first and second chambers 72, 74. Such a configure seals the second chamber 74 without to individual seal control lines in the high vacuum environment. The ion traps 20 of the first substrate 52 are subjected to the high vacuum of the second chamber 74 and can also be externally illuminated by laser light transmitted through a window 80 in the second vacuum chamber 74. The operation of the ion traps 20 of the multi-chip module 50 also involves conventional optical cooling and excitation methods. These conventional methods include the Doppler cooling method and Raman sideband cooling. In either case, the optical cooling setup includes one or more lasers and associated collimation optics. In the Doppler cooling method, a laser should typically be tuned to produce light whose frequency is associated with an energy slightly lower than that of the lowest excitation energy in the ion traps 20. For such frequencies, laser light stimulates absorptions and emissions by ions having higher energies. Then, said ions undergo de-excitation, which causes them to fall into lower states of the ion traps 20. Multiple lasers may be used to de-excite vibrational modes that are associated with independent degrees of freedom in the ion traps 20, or one laser beam may be obliquely oriented with respect to the normal modes of the ion trap 20 so that said single laser can de-excite all orthogonal vibrational modes in the ion trap 20. Various setups for optical cooling use optical elements such as fiber arrays, MEMS mirrors, and/or photonic crystals. For example, such cooling methods may use a grating to enable light of a single laser beam to pass through several ion traps 20 thereby cooling ions in each of the separate ion traps 20. Typically, such optical cooling should be arranged so that ions in different ion traps 20 are illuminated with equal light intensities. FIG. 10 illustrates a method 100 for fabricating one embodiment of the ion trap 20 of FIG. 2a. The method 100 involves performing a first sequence of front-side processes, performing a sequence of backside processes, and then, performing a second sequence of front side processes. The processes produce the intermediate structures 126, 130, 134, 138, 142, 144, 146 shown in FIG. 11. The first sequence of front side processes includes the following steps. First, a plasma enhanced chemical vapor deposition (PECVD) at about 400° C.–500° C. forms a silicon dioxide layer 120 with a thickness of about 300 nanometers (nm) on a top surface of heavily doped silicon wafer 122 (step 102). Next, a low pressure chemical vapor deposition (LPCVD) at 600° C.–700° C. forms a thick layer 124 of about 15 to 30 μm of polysilicon on the silicon dioxide layer 122 as shown in intermediate structure 126 (step 103). During the LPCVD step, the polysilicon is also doped with phosphorous. After the LPCVD, a rapid thermal anneal at about 1040° C. is performed for about 60 seconds to activate the phosphorus thereby causing the doped polysilicon layer 124 to have a low final resistivity of 0.5 to 5 mΩ-cm. Next, a chemical mechanical polish (CMP) of the free surface of the layer 124 of n-doped polysilicon produces a surface where height roughness is of the order of tens of nanometers or less (step 104). The CMP ensures that the final SVSV electrodes 26, 28 will have smooth top surfaces thereby reducing the magnitude of stray electric fields that could otherwise interfere with subsequent ion trapping. The article of K. Miller, D. Fong, D. Dawson, and B. Todd, “Die-scale wafer flatness: 3-dimensional imaging across 20 mm with nanometer-scale resolution”, SPIE Proceedings, Vol. 3050 (1997) page 266, which is incorporated by reference herein in its entirety, describes a CMP process that is suitable for making such a smooth surface on a polysilicon layer. Next, a mask-controlled dry etch forms vias 128 through the layer 124 of n-doped polysilicon as shown in intermediate structure 130 (step 105). The vias 128 pattern the layer 124 of n-type polysilicon into the SVSV electrode 26 and the SVSV electrode 28. Next, another LPCVD deposits a thick silicon dioxide layer 132 of about 10–20 μm on the n-doped polysilicon as shown in intermediate structure 134 (step 106). Then, the thick silicon dioxide layer 132 is annealed at 1050° C. for about 4 to 10 hours to release stress and cause densification therein. The sequence of backside processes includes the following steps. First, a mechanical grinding of the backside of the doped semiconductor wafer 122 reduces the wafer's thickness to about 280 μm (step 107). Then, contact lithography and a deep reactive ion etch (DRIE) produces through-wafer vias 136 as shown in intermediate structure 138 (step 108). A suitable DRIE is described in U.S. Pat. No. 5,501,893, issued Mar. 26, 1996 to F. Laermer et al (Herein, referred to as the '893 patent) and in U.S. patent application Ser. No. 10/656,432, filed Sep. 5, 2003, by C. S. Pai and S. Pau (Herein, referred to as the '432 application). The '893 patent and '432 patent application are incorporated by reference herein in their entirety. Next, a thermal process at about 1,000° C. grows a thin layer 140 of about 0.1 to 0.2 μm of silicon dioxide on the exposed surfaces of the through-wafer vias 136 and on the backside of the doped silicon wafer 122 as shown in intermediate structure 142 (step 109). Next, a series of LPCVD's alternated with CMP's fills the through-wafer vias 136 with n-doped polysilicon as shown in intermediate structure 144 (step 110). The LPCVD process for depositing doped polysilicon has already been described with respect to above-step 103. The CMP's are selected to stop on the silicon dioxide layers 120, 140. The fill step completes fabrication of the SVSV electrodes 26, 28. The second sequence of front side processes includes the following steps. First, a sputtering process deposits a layer of about 300 nm of metal, e.g., gold, on the top surface of the silicon dioxide layer 132 (step 111). Then, a mask-controlled wet etch patterns the layer of metal to produce the RF electrodes 24 as shown in intermediate structure 146 (step 112). Alternatively, the metal can be patterned using a liftoff process in which, a layer of sacrificial material such as photoresist is deposited, patterned and developed. Then, the metal is deposited on top of the sacrificial material, and the sacrificial material is removed to pattern the metal. After the metal has been patterned, a timed wet etch that is based on an aqueous solution of HF patterns the silicon dioxide layer 132 to produce the insulating dielectric pedestals 30 of final structure 148 (step 113). Alternately, in method 100, the intermediate structure 126 can be replaced by a structure fabricated by a silicon-on-insulator (SOI) process. In such a structure, the doped semiconductor layer 124 is replaced by a doped crystalline semiconductor layer. Such SOI structures are sold commercially, for example, by Soitec Inc. of Peabody, Mass. 01960, USA. FIG. 12 illustrates an alternate method 150 for fabricating the ion trap 20 shown in FIG. 2a. The method 150 involves performing a sequence of front-side processes and then, performing a sequence of backside processes on a doped silicon wafer 122. The processes produce intermediate structures 176, 180, 184, 190, 192, 198 as shown in FIG. 13. The sequence of front side processes includes the following steps. First, a PECVD forms a layer 172 of about 0.5 μm or less of silicon dioxide on the top surface of the doped silicon wafer 122 (step 152). Next, a dry etch forms windows by removing the silicon dioxide from portions of the top surface and then, etches deep vias 174 through the windows as shown in intermediate structure 176 (step 153). The series includes a conventional dry etch of silicon dioxide and a DRIE as already described with respect to above step 108. Both dry etches are controlled by a contact mask. Next, a thermal process grows a layer 178 of about 0.2–0.1 μm or less of silicon dioxide on the exposed surface of the deep vias 176 as shown in intermediate structure 180 (step 154). Next, a LPCVD deposits a thick layer 182 of doped polysilicon on the intermediate structure 180 (step 155). The LPCVD uses the same process described with respect to above step 103. After the LPCVD, the doped polysilicon fills the deep via 174 and also covers the silicon dioxide layer 172. Next, a CMP of the layer 182 of doped polysilicon produces a free surface whose height roughness is of the order of tens of nanometers or less (step 156). A suitable process for the CMP was described with respect to above step 104. Next, a dry etch that stops on silicon dioxide is performed to form through-vias 186 in the layer 182 of doped polysilicon (step 157). The dry etch produces the SVSV electrodes 26, 28 as shown in intermediate structure 184. Next, another LPCVD deposits a silicon dioxide layer 188 with a thickness of about 10–20 μm on the n-doped polysilicon (step 158). Then, the thick silicon dioxide layer 188 is annealed at 1050° C. for about 4 to 10 hours to release stress and cause densification therein. Next, a mask-controlled deposition of gold produces the RF electrodes 24 on the silicon dioxide layer 188 as shown in intermediate structure 190 (step 159). Next, a timed wet-etch with an aqueous solution of HF patterns the silicon dioxide layer 188 to produce insulating dielectric pedestals 30 as shown in intermediate structure 192 (step 160). Finally, a thick layer 194 of resist is deposited over the top surface of intermediate structure 192 and hardened to provide protection during the backside processes (step 161). The sequence of backside processes includes the following steps. First, a mechanical grind of the backside reduces the thickness of the doped semiconductor wafer 122 to about 280 μm (step 162). Next, a CMP of the backside of the doped semiconductor wafer 122 exposes the polysilicon in the deep vias 174 (step 163). Next, a PECVD forms a thin layer 196 of about 0.5 μm or less of silicon dioxide on the bottom surface of the doped silicon wafer 122 (step 164). Next, a dry etch patterns the layer 196 of silicon dioxide to selectively expose the polysilicon of the through-portions of the SVSV electrodes 26, 28 as shown in intermediate structure 198 (step 165). Finally, a standard stripping step removes the protective layer of resist from the front side of the intermediate structure 196 thereby producing the ion trap 20 (step 166). From the disclosure, drawings, and claims, other embodiments of the invention will be apparent to those skilled in the art. |
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abstract | A method for producing a reaction product containing 99mTC may include providing 100Mo-metal targets to be irradiated, irradiating the 100Mo-metal target with a proton stream having an energy for the induction of a 100Mo(p, 2n)99mTC core reaction, heating the 100Mo-metal target to over 300° C., recovering incurred 99mTc in a sublimation-extraction process with the aid of oxygen gas which is conducted over the 100 Mo-metal target forming 99mTc-Technetium oxide. Further, a device for producing the reaction product containing 99mTc may include a 100Mo metal target, an acceleration unit for providing a proton stream, which can be directed to the 100Mo-Metal target, such that a 100Mo(p, 2n)99mTC core reaction is induced upon irradiation of the 100Mo-metal target by the proton stream, a gas supply line for conducting oxygen gas onto the irradiated 100Mo-metal target to form 99mTC-Technetium oxide, and a gas discharge line to discharge the sublimated 99mTC-Technetium oxide. |
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060312378 | summary | FIELD OF THE INVENTION The present invention relates to a radiation image storage panel using a stimulable phosphor. BACKGROUND OF THE INVENTION A radiation image recording and reproducing method utilizing a stimulable phosphor described, for instance, in U.S. Pat. No. 4,239,968, is now practically employed. In the method, a radiation image storage panel comprising a stimulable phosphor (i.e., stimulable phosphor sheet) is employed, and the method comprises the steps of causing the stimulable phosphor of the panel to absorb radiation energy having passed through an object or having radiated from an object; sequentially exciting the stimulable phosphor with an electromagnetic wave such as visible light or infrared rays (hereinafter referred to as "stimulating rays") to release the radiation energy stored in the phosphor as light emission (i.e., stimulated emission); photoelectrically detecting the emitted light to obtain electric signals; and reproducing the radiation image of the object as a visible image from the electric signals. In the radiation image recording and reproducing method, a radiation image is obtainable with a sufficient amount of information by applying a radiation to the object at a considerably smaller dose, as compared with a conventional radiography using a combination of a radiographic film and radiographic intensifying screen. Further, the radiation image recording and reproducing method using a stimulable phosphor is of great value especially when the method is employed for medical diagnosis. The radiation image storage panel employed in the above-described method has a basic structure comprising a support and a stimulable phosphor layer provided on one surface of the support. However, if the phosphor layer is self-supporting, the support may be omitted. Further, a transparent film of polymer material is generally placed on the free surface (i.e., surface not facing the support) of the phosphor layer to keep the phosphor layer from chemical deterioration or physical shock. The phosphor layer generally comprises a binder and a stimulable phosphor dispersed therein. The stimulable phosphor emits stimulated emission when excited with a stimulating ray after having been exposed to a radiation such as X-ray. Accordingly, the radiation having passed through an object or radiated from an object is absorbed by the phosphor layer of the panel in proportion to the applied radiation dose, and a radiation image of the object is produced in the panel in the from of a radiation energy-stored image. The radiation energy-stored image can be released as stimulated emission by sequentially irradiating the panel with stimulating rays. The stimulated emission is then photoelectrically detected to give electric signals, so as to reproduce a visible image from the electric signals. The radiation image recording and reproducing method is very useful for obtaining a radiation image as a visible image as described hereinbefore. It is desired for the radiation image storage panel employed in the method to have a high sensitivity and provide an image of high quality (high sharpness, high graininess, etc.). The sensitivity of the radiation image storage panel is essentially determined by the total amount of stimulated emission given by the stimulable phosphor contained therein, and the total emission amount varies depending upon not only the emission luminance of the phosphor but also the content (i.e., amount) of the phosphor in the phosphor layer. The large content of the phosphor also results in increase of absorption of a radiation such as X-rays, so that the panel shows an increased high sensitivity and provides an image of improved quality, especially an image of improved graininess. On the other hand, assuming that the content of the phosphor in the phosphor layer is kept at the same level, if the phosphor layer is densely packed with the phosphor, a panel using such phosphor layer provides an image of high sharpness, because such phosphor layer can be made thinner to reduce spread of stimulating rays caused by scattering in the phosphor layer. U.S. Pat. No. 4,910,407 discloses a radiation image storage panel having a compressed phosphor layer provided on the support. Since the compressed phosphor layer is packed with the phosphor more densely than conventional phosphor layers, the panel disclosed in the publication gives an image of improved sharpness. However, in contrast, the obtained image is often rendered poor in view of graininess because the compression treatment destroys a part of the phosphor in the layer. In order to solve this problem, Japanese Patent Provisional Publication No. H2-278197 proposes a radiation image storage panel having a compressed phosphor layer containing a particular binder. In more detail, a thermoplastic elastomer having softening point or melting point of 30 to 150.degree. C. is used as a binder of the phosphor layer, and the compression treatment is carried out at the temperature above the softening point or melting point. Since this compression treatment makes the phosphor densely packed in the phosphor layer without destroying, the panel gives an image of both high sharpness and high graininess. Further, Japanese Patent Provisional Publication No. H7-287098 proposes a radiation image storage panel having two phosphor layers comprising different binders of thermoplastic resin (for example, thermoplastic elastomers having different softening points). In the radiation image recording and reproducing method, the radiation image storage panel is repeatedly used in the cyclic procedure comprising the steps of exposing to a radiation (for recording of a radiation image), irradiating with stimulating rays (for reading of the recorded image) and exposing to an erasing light (for erasing the remaining image). In an apparatus for this method, the panel is repeatedly transferred from one step to another step by means of conveying means such as belt and rolls. Such repeated conveying, however, is liable to cause some cracks in the phosphor layer especially when the panel has the above-described phosphor layer compressed under heating. Since the cracks are apt to scatter the radiation and/or stimulating rays, the panel having a cracked phosphor layer gives an image of poor quality. In order to solve this problem, U.S. Pat. No. 5,641,968 proposes a further improved radiation image storage panel. In the proposed panel, the binder of the phosphor layer comprises a thermoplastic elastomer (e.g., polyurethane elastomer) having an elastic modules of not more than 0.3 kgf/mm.sup.2, as well as a softening point or melting point of 30 to 150.degree. C. As described above, thermoplastic polyurethane elastomer is known to have excellent properties as a material for the binder resin of the phosphor layer of the radiation image storage panel, especially for that of the phosphor layer compressed (after having been formed) under heating so as to be densely packed with the phosphor. SUMMARY OF THE INVENTION The inventors, however, have found that the above radiation image storage panel (namely, the panel having a phosphor layer comprising thermoplastic polyurethane elastomer, especially aromatic polyurethane elastomer, as a binder resin) has a relatively low light-resistance (i.e., durability against light). Therefore, the phosphor layer of the radiation image storage panel is liable to deteriorate after repeated uses, and consequently the quality of the reproduced image is apt to gradually lowers. Accordingly, it is an object of the present invention to provide a radiation image storage panel having excellent durability. Particularly, it is an object of the invention to provide a radiation image storage panel having excellent durability (against both repeated conveying and light) enough to give an image of high quality even after the panel is repeatedly used for a long time in the cyclic procedure comprising the steps of exposing to a radiation, irradiating with stimulating rays so as to reproduce the image, exposing to an erasing light, and transferring among the steps in the apparatus. The present invention resides in a radiation image storage panel having a phosphor layer comprising a stimulable phosphor and a binder, wherein said binder comprises a resin containing a thermoplastic polyurethane elastomer as a main component, and said phosphor layer contains a radical scavenger. The radical scavenger preferably is a hindered phenol compound or a hindered amine compound. The amount of the radical scavenger preferably is in the range of 0.05 to 10 weight parts per 100 weight parts of the polyurethane resin. In the case that the thermoplastic polyurethane elastomer is an aromatic polyurethane elastomer, the effect of the invention is more effectively observed. Further, if the molecular structure of the aromatic polyurethane elastomer contains a repeating unit derived from diphenylmethane diisocyanate, the invention is particularly advantageous. The thermoplastic polyurethane elastomer preferably employed in the invention has an elastic modules of not more than 0.3 kgf/mm.sup.2 (more preferably, not more than 0.1 kgf/mm.sup.2) and softening point of 30 to 150.degree. C. (more preferably, 50 to 120.degree. C.). The softening point in this specification means Vicat softening point, which is determined by measuring the temperature when a standard indenter (diameter: 1 mm) loaded with 1 kg weight penetrates into the sample to reach the depth of 1 mm from the surface. The amount of the thermoplastic polyurethane elastomer preferably is in the range of 30 to 100 weight % (more preferably 60 to 100 weight %) of the binder resin. The invention is particularly suitable for the radiation image storage panel having the phosphor layer which was prepared by subjecting a formed (coated and dried) phosphor layer to compression treatment. DETAILED DESCRIPTION OF THE INVENTION The radiation image storage panel of the invention is now described in detail. First, an explanation about the stimulable phosphor employable for the invention is given below. The stimulable phosphor gives a stimulated emission when it is irradiated with stimulating rays after it is exposed to radiation. In the preferred radiation image storage panel, a stimulable phosphor giving a stimulated emission of a wavelength in the range of 300 to 500 nm when it is irradiated with stimulating rays of a wavelength in the range of 400 to 900 nm is employed. Examples of the preferred stimulable phosphors include divalent europium activated alkaline earth metal halide phosphors, cerium activated alkaline earth metal halide phosphors and cerium activated oxyhalide phosphors. Each of those stimulable phosphors favorably gives the stimulated emission of high luminance. However, the stimulable phosphors employable in the radiation image storage panel of the invention are not limited to the above-mentioned preferred stimulable phosphors. Any other phosphors can be also employed, provided that the phosphor gives stimulated emission when excited with stimulating rays after exposure to a radiation. A coating dispersion for forming the phosphor layer is prepared in the following manner. The stimulable phosphor and a binder are well mixed in an appropriate solvent to give a coating dispersion in which the phosphor particles are uniformly dispersed in the binder solution. The binder used for the invention comprises a resin containing a thermoplastic polyurethane elastomer as a main component in combination with a radical scavenger. The binder resin may comprise only a single thermoplastic polyurethane elastomer or a combination of plural thermoplastic polyurethane elastomers. An aromatic polyurethane elastomer is preferably used as the thermoplastic polyurethane elastomer of the invention, and it is particularly preferred that the molecular structure of the aromatic polyurethane elastomer contain a repeating unit derived from diphenylmethane diisocyanate. The thermoplastic polyurethane elastomer may be used in combination with other polymers (e.g., epoxy resin, acrylic resin and polyimide resin), under the condition that the amount of the thermoplastic polyurethane elastomer is in an amount of not less than 30 weight % of the total binder resin. The phosphor layer of the invention is characterized by containing a radical scavenger (a radical trap agent) as well as the thermoplastic polyurethane elastomer. The radical scavenger is generally used in an amount of 0.05 to 10 weight parts (preferably 0.1 to 1 weight parts) per 100 weight parts of the thermoplastic polyurethane elastomer. As the radical scavengers, hindered phenol compounds or hindered amine compounds are preferably employed for the invention. Various hindered phenol compounds and hindered amine compounds employable as the radical scavenger are commercially available. Examples of such radical scavengers of hindered phenol compounds include ADK STAB A0-20, A0-30, A0-40, A0-50, A0-60, A0-70, A0-75, A0-80 and A0-330 (trade names; available from Adeka Argas Chemical CO., Ltd.). Examples of the radical scavenger of hindered amine compounds include Sanol LS-744, LS-770, LS-765 and LS-2626 (trade names; available from Sankyo CO., Ltd.); Mark LA-77, LA-57, LA-67, LA-62, LA-68 and LA-63 (trade names; available from Adeka Argas Chemical CO., Ltd.); Tinuvin 144, Tinuvin 622LD and Chimassorb 944FL (or LD) (trade names; available from Ciba-Geigy); Cyasorb UV3346 (trade names; available from American Cyanamid); and Spinuvex A-36 (trade names; available from Montedison). Examples of the solvents employable for preparing the coating dispersion include lower alcohols such as methanol, ethanol, n-propanol and n-butanol; chlorinated hydrocarbons such as methylene chloride and ethylene chloride; ketones such as acetone, methyl ethyl ketone and methyl isobutyl ketone; esters of lower alcohols with lower aliphatic acids such as methyl acetate, ethyl acetate and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, ethylene glycol monomethyl ether and tetrahydrofuran; and mixtures of the above-mentioned compounds. In the coating dispersion, the binder polymer and the stimulable phosphor are introduced generally at a ratio of 1:1 to 1:100 (binder:phosphor, by weight), preferably 1:8 to 1:40 (by weight). The ratio can be varied depending on the desired characteristics of the storage panel and natures of the binder polymers and phosphors. The coating dispersion may contain a dispersing agent to assist the dispersibility of the phosphor particles therein, and also contain a variety of additives such as a plasticizer for increasing the bonding between the binder and the phosphor particles in the phosphor layer. Examples of the dispersing agents include phthalic acid, stearic acid, caproic acid and a hydrophobic surface active agent. Examples of the plasticizers include phosphates such as triphenyl phosphate, tricresyl phosphate and diphenyl phosphate; phthalates such as diethyl phthalate and dimethoxyethyl phthalate; glycolates such as ethylphthalyl ethyl glycolate and butylphthalyl butyl glycolate; and polyesters of polyethylene glycols with aliphatic dicarboxylic acids such as polyester of triethylene glycol with adipic acid and polyester of diethylene glycol with succinic acid. The prepared coating dispersion containing the phosphor and the binder is coated uniformly on a temporary support to form a coated layer film. The coating can be performed by known coating means such as doctor blade, roll coater, and knife coater. The temporary support can be optionally selected from the known sheet materials such as a glass plate, a metal plate and sheet materials employed for the support of conventional radiographic intensifying screen or radiation image storage panel. Examples of such known materials include films of plastic materials such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, cellulose triacetate, and polycarbonate; metal sheets such as aluminum foil and aluminum alloy foil; ordinary papers; baryta paper; resin-coated papers; pigment papers containing titanium dioxide or the like; papers sizes with polyvinyl alcohol or the like; and ceramic sheets such as sheets of alumina, zirconia, magnesia and titania. After the dispersion is evenly coated on the temporary support and then dried to form a coated layer film (i.e., a phosphor sheet for the phosphor layer), the formed phosphor sheet is then peeled off from the temporary support. Preferably, the surface of the temporary support is beforehand coated with a releasing agent so that the phosphor sheet may be easily peeled off. Thus prepared phosphor sheet is superposed on a permanent support. The permanent support can be optionally selected from the same sheet materials as those for the temporary support above-described. Some of the known radiation image storage panels have various auxiliary layers: for instance, an adhesive layer which is formed of a polymer material such as gelatin or an acrylic resin on the support and which enhances strength between the support and the phosphor layer or increases sensitivity or image quality (e.g., sharpness and graininess) of the obtainable radiation image; a light-reflecting layer of a light reflecting material such as titanium dioxide; and a light-absorbing layer of a light-absorbing material such as carbon black. The radiation image storage panel of the invention may have one or more of such auxiliary layers. Further, the support of the radiation image storage panel of the invention may have a great number of very small convexes or concaves on its surface. If the support is coated with one or more auxiliary layers, the convexes or concaves may be formed on these layers. The great number of very small convexes or concaves can improve sharpness of the radiation image reproduced by the use of the storage panel. The prepared phosphor sheet is placed on the permanent support and then compressed at the temperature above the softening point (or melting point) of the polymer, so as to be fixed on the support. Examples of the compressing apparatus for the compression treatment employable in the invention include known apparatus such as a calendar roll and a hot press. For instance, a compression treatment using a calendar roll is carried out by moving the phosphor sheet at a certain speed to pass through between two rollers heated at the temperature above the softening point (or melting point) of the polymer. The compressing apparatus employable for the invention is not restricted to them. Any other apparatus can be employed as far as it can compress the phosphor sheet under heating in the manner described above. The pressure in the compression treatment is generally not less than 50 kgw/cm.sup.2, and preferably in the range of 200 to 700 kgw/cm.sup.2. The temperature is preferably set to be 10 to 50.degree. C. higher than the softening point (or melting point) of the polymer. In the case that a calendar roll is used, the temperatures of two rollers are preferably set at the same. The moving speed is preferably in the range of 0.1 to 5.0 m/min. As described above, a transparent protective film is generally provided on the free surface (surface not facing the support) of the phosphor layer to keep the phosphor layer from chemical deterioration or physical shock. In the radiation image storage panel of the invention, it is preferred to provide such transparent protective film for the same purpose. The transparent protective film can be provided by coating the surface of the phosphor layer with a solution of a transparent polymer such as a cellulose derivatives (e.g., cellulose acetate or nitrocellulose), a synthetic polymer (e.g., polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl acetate or vinyl chloride/vinyl acetate copolymer) and fluororesin (e.g., fluoroolefin-vinyl ether copolymer). Optionally, a crosslinking agent such as an isocyanate is employable. Alternatively, the transparent protective film can be provided by beforehand preparing a transparent sheet such as a glass sheet or a sheet of polymer (e.g., polyethylene terephthalate, polyethylene naphthalate, polyethylene, polyvinylidene chloride and polyamide), followed by placing and fixing it onto the phosphor layer with an appropriate adhesive agent. The transparent protective film generally has a thickness in the range of 0.1 to 20 .mu.m. One or more layers of constituting the radiation image storage panel can be so colored as to well absorb the stimulating rays and not to absorb the stimulated emission. Such coloring is effective to increase sharpness of the image obtained by the use of the storage panel. Otherwise, an independent colored layer can be placed in an appropriate position of the storage panel for the same purpose. |
043814620 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The preferred example of the exergy transformer system is based on utilization of solar energy; the solar exergy is released by nuclear reactions on the sun, and stored in the form of free enthalpy of two metastable liquid compounds (NH.sub.2).sub.2 and (OH).sub.2, bearing in mind that (OH).sub.2 is generated only as a by-product of the generation of H.sub.2 which is needed for the (NH.sub.2).sub.2 synthesis. Both, the process of exergy transformation as well as the design of the transformer system are determined by the physical quantities at the entrance or input and the exit or output of the transformer. Quantities at the entrance are the specific exergy of solar radiation spectrally distributed as well as the flux density of radition; quantities at exit are the specific free enthalpies of the two compounds synthesized in the transformer and the ratio of both mass flows, respectively of exergy stored. The transformer yields additionally electrical energy over and above the energy needed to maintain operation of the transformer system. The specific process envisioned here particularly as far as the hydrazine synthesis is concerned, is to be seen in that hydrazine is formed by an electrolytic process specifically by forming (NH.sub.2).sub.2 out of LiNH.sub.2. The energy needed to sustain that process is taken ultimately from the sun. The solar energy is used to obtain the production of that electrical energy needed to sustain the electrolysis using lithium as or as part of a circulating fluid system. The electrolysis will be produced within an MHD conversion process in which kinetic energy of a fluid is converted into electrical energy, including the energy to obtain the electrolysis. The kinetic energy is the result of a two-phase process in which solar exergy absorbed by a liquid phase is transferred to an isothermally expanding gas as it accelerates the liquid phase, and the electrolysis is carried out in that liquid phase, while the movement of the liquid phase is used to generate the magnetic field causing the electric field in the liquid phase to sustain electrolysis therein. Liquid and gaseous phases complete separate but temporarily linked circulations, whereby the liquid phase absorbs the solar energy, heats the expanding gaseous phase while being accelerated by it, serves as carrier for the electrolysis and returns. The gaseous phase of the two-phase flow is alternated between low temperature compression and high temperature expansion with recuperative heat exchange inbetween. Turning now to details of certain aspects of this basic process, the specific exergy of radiation depends on its wave length; it is continuously distributed over the spectrum between the limits of about .lambda.=0.8.multidot.10.sup.-6 m in the infrared and of about .lambda.=0.3.multidot.10.sup.-6 m in the ultraviolet. The specific exergy e.sub.s of radiation, therefore, covers the range of EQU 150<e.sub.s <400 kWs/mol if related to the unit mol of particle quantities. This quantity is calculated from the equation EQU e.sub.s =N.sub.A .multidot.hc/.lambda. with N.sub.A =6.02.multidot.10.sup.23 1/mol (Avogadro's constant), h=6.63.multidot.10.sup.-34 Ws.sup.2 (Planck's constant), c=3.multidot.10.sup.8 m/s (speed of light). The fluxdensity q.sub.s of radiation is defined to be the exergy, which passes through a surface unit, in normal direction within unit time, and is approximately, without taking into consideration any additional absorption in the atmosphere; EQU q.sub.s =1,4 kW/m.sup.2 The process of synthesizing (NH.sub.2).sub.2 and (OH).sub.2 can be explained, in principle, as being subdivided into the following step: ##STR1## The steps 1.1 and 2.1 are similar and O.sub.2 appears to be a rest product of synthesis 1 (though not to be produced directly), while H.sub.2 is a rest product of synthesis 2, which both can be combined according to step 2.2 to hydrogen-peroxide. The two synthesis can be coupled in an overall exergy transformer system performing the following steps: ##STR2## Herein, steps (1) and (2) are only listed separately, in reality free oxygen is not produced. The FIGS. 2 and 3 present the change of free enthalpy g of formation of (NH.sub.2).sub.2 and H.sub.2 +(OH).sub.2. Generally speaking, if the difference in enthalpie after and before the reaction is positive, the step is endergonic, because the reaction can take place only by supply of exergy; exergy can be stored by this reaction, if the reaction can be reversed. If the enthalpie difference is negative, however, the step is exergonic, due to the release of exergy, and reaction takes place spontaneously. A brief estimate will clarify the principles of operation of the exergy transformation: the formation of H.sub.2 according to step 1 of the coupled processes 1+2 needs the supply of specific exergy of at least 56.5 kcal/mol=235 kWs/mol; the formation of hydrazine requires at least a specific exergy of 630 kWs/mol. If the exergy of solar radiation were used directly for a photosynthesis of these compounds, only the ultraviolet radiation could be employed, while the remainder of solar spectrum could not be used; in addition, the different reactions needed in that case will be multiquanta processes. The exergy conversion and transformation system as per this invention absorbs actually the total exergy of solar radiation it receives and transfers it as heat to an inert gas (N.sub.2). This gas is the thermo-fluid-dynamic working fluid, or tfd for short, of the MHD process and synthesis and is used thermodynamically to drive a liquid phase whose resulting kinetic energy can be used in an MHD conversion process and which can sustain an electrolytic process due to interaction with the magnetic field it generates. In order to capture sufficient exergy by absorption, it is deemed necessary to increase the flux-density of solar radiation by a factor of about 1000, cooperating directly with an exergy absorbing surface at the entrance of the exergy transformer for the transfer of heat into the transformer. Therefore, the input portion of the exergy transformer will include a focussing reflector, described by way of example with reference to FIGS. 40 and 41, see also FIG. 8. I now proceed to describe certains aspects of the thermodynamics involved here. The tfd-working fluid of the exergy transformer expands isothermally to accelerate the liquid phase and imparts upon it the expansion work as kinetic energy; by this the tfd working fluid performs work to overcome internal forces, and ultimately that work is used in the electrolytic process, conceivably even for both electrolytic processes. Conversely the radiation as absorbed by the liquid phase itself, prior to that acceleration will replenish continuously the enthalpy of the gas that was converted into work in the transformer. As a result, the enthalpy available (i.e. exergy of enthalpy) will not change during the expansion and will be constant even at the end of expansion. This enthalpic exergy must be withdrawn from the gas (tfd fluid), which has expanded, before the gas will be recompressed for circulation within the transformer system, and transferred to the gas which is recompressed already. Therefore, this exergy transfer will be performed by a recuperative heat exchange between the decompressed gas and entering the heat exchanger at the lower pressure p=p.sub.low, but at the upper temperature T=T.sub.upper of process, and the gas that has already been compressed again, and entering the heat exchanger (again) now at the higher upper pressure p=p.sub.upper, but at the lower temperature T=T.sub.low. The process of the thermo-fluid-dynamic working fluid is determined by these two conditions for isenthalpic expansion as well as for the introduction of recuperative heat exchange. FIG. 4 shows the exergy flux diagram of this process. The specific work of expansion-a.sub.exp, performed by the tfd gas with a mass flow rate m.sub.tfd, must be balance by the heat flux supplied ##EQU1## The specific work is given by: ##EQU2## .pi.=p.sub.upper /p.sub.low (pressure ratio of process), R=8.3 Ws/mol K (gas constant of N.sub.2). The specific work of compression is given by: ##EQU3## Compression should, therefore, take place at as low temperature T.sub.low <T.sub.upper as possible, in order to limit the work to be supplied, for the difference of expansion- and compression work is the net useful work provided by the process: ##EQU4## The requirement of recuperative heat exchange results in a limiting condition for the maximum of pressure ratio, because the available energy of gas which has to be transferred within the heat exchanger, cannot exceed the net work of process: ##EQU5## c.sub.p "=39.1 Ws/mol K (specific heat at constant pressure of N.sub.2), .kappa.=1.4 (adiabatic exponent of N.sub.2) As a result, the maximum pressure ratio .pi..sub.max is: ##EQU6## The efficiency .eta..sub.th of this process is given by the Carnot-factor .eta..sub.C (if internal and external exergy losses are not considered), the latter depending on the temperature ratio T.sub.low /T.sub.upper exclusively: ##EQU7## To give an example: for T.sub.upper =750 K and for T.sub.low =250 K is according to equation (8) .eta..sub.th =.eta..sub.c =0.666. The maximum specific net work is in this case according to (4) about 14 kWs/mol and is, therefore, lower by a factor of about 50 than that required for the different steps of synthesis. The net work of the thermo-fluid-dynamic working fluid will be converted ultimately into electrical energy, which is obtained by the introduction of a second working fluid, namely the liquid phase being accelerated by the expansion of the tfd gas and serving also as a fluid dynamic medium (mfd #1) that performs mechanical work in that an MHD conversion process converts the kinetic energy of that mfd #1 fluid into the electrical energy needed for the electrosynthesis. Moreover, the substance to be electrolytically decomposed must become a part of the liquidous phase of the MHD working fluid, as will be discussed shortly. The hydrazine (and peroxide) electrolysis requires a voltage of a few volts. Details of this MHD conversion process and the generation of the necessary electrical energy will also be described below. Presently it should be discussed what energy is actually needed for the electrolytic synthesis of hydrazine and peroxide and what electrochemical reactions are involved. The specific work expended on an electric charge, after having traversed a voltage difference of n-volts is: ##EQU8## or, if one uses mols to define particle quantities, that value a.sub.el. is given by n.multidot.N.sub.A .multidot.e.multidot.v=100 kWs/mol. The work a is the one needed to obtain the electrolytic process; n is the voltage that will in fact produce that work. The MHD process is designed to furnish that value n; it is but a few volts. The electrosynthesis of (NH).sub.2 and (OH).sub.2 by means of the above mentioned four steps depends on the fact that there is a similarity in structure in these two components, namely two groups or radicals are interconnected, OH and NH.sub.2 respectively. Moreover, the groups are chemically rather similar. In order to develop the desired reactions and the means of obtaining them, the follow step by step analysis is helpful. The OH groups and the NH.sub.2 groups both can be generated as negatively charged ions in that specifically H.sub.2 O as well as NH.sub.3 molecules can appear as hydrogen donors as well as hydrogen acceptors in accordance with the following two reactions, occurring of course in different carriers for solutions. ##EQU9## Since the hydrogen transfer in both reactions is strongly endergonic, they are quite improbable. On the other hand, if a one-valued metal is present, e.g. K or Li these reactions become exergonic and appear spontaneous (with a probability of almost unity). ##EQU10## In both cases, an electron transfers from the negative ion to the positive ions i.e. from OH.sup.- to K.sup.+ and from NH.sub.2.sup.- to Li.sup.+ ; respective two groups will in fact combine into hydrogen peroxide (di-hydroxide) and hydrazine (di-amid) resp. This is possible because the OH.sup.- groups as well as the NH.sub.2.sup.- groups have a completed electron shell of eight electrons. It is, therefore, merely necessary to provide for an electric field by means of which this electron transfer can in fact be enforced. It can thus be seen that only the combination of two neutral OH and NH.sub.2 groups leads again to a complete electron shell in either case due to a co-valent combination by means of an electron pair that is common to both groups in a molecule. ##EQU11## Both compounds are metastabil, thus exhibiting the tendency of giving off H-atoms to revert to double compounds ##EQU12## Since H.sub.2 O is a raw material for the storage of exergy in the exergy transformer, the first two steps of the synthesis require the electrolysis of H.sub.2 O but without the usual decay of (OH).sub.2 by means of catalytic effect of impurities ##EQU13## Both steps furnish the H.sub.2 for the hydrazine synthesis (step 3+4 in the above mentioned combined method). Very significantly, the exergy transformer as per this invention avoids the step of using NH.sub.3 as per relation 12b because LiNH.sub.2 is used as an intermediate product which on the one hand can be decomposed electrolytically and, on the other hand it can be synthesized directly from the elements Li, N.sub.2 and H.sub.2 as the reaction is exergonic. This is significant, as Li is used as mfd #1 fluid, and LiNH.sub.2 can readily become a part thereof. FIG. 5 shows the step 1 to generate catalytically Li-amid as an intermediate product. The exergy which is generated by the reaction if carried out at 300 K is quite high and that reaction cannot really be used successfully for and as the last step in an electrosynthesis running at such a low temperature. However, as shown in FIG. 6, the free enthalpie approaches zero for high temperatures at about 900.degree. Kelvin. Thus, the electrosynthesis of Li-amid should be carried out at these temperatures. The solar energy capturing process, therefore, should heat the components for that process to that temperature which in turn becomes the upper temperature for the isenthalpic production of the necessary kinetic energy for the MHD process. FIG. 7 shows a diagram for the entire process as far as the energy consumption is concerned. The solar conversion and MHD conversion process run on solar energy produces a certain amount of electrical energy. About 75% of that electrical exergy is stored by means of the electrosynthesis of (OH).sub.2 and H.sub.2, the remainder of the electrical exergy (25%) are used for the electrolysis in which (NH.sub.2).sub.2 is made out of Li-amid. The solar exergy transformer system depicted in FIG. 8 has the following primary objectives: 1. Solar exergy is to be absorbed covering a continuous spectrum as wide as possible and amplifying the radiation flux density by a factor of, say, 1000. 2. Electrical energy is to be produced at two descrete voltages, each in the order of a few volts, which actually increases the specific exergy of the radiation received. 3. H.sub.2 O and N.sub.2 is to be separated from air, essentially the cooling air, for use as primary raw material for the exergy storage on a material exergy carrier. 4. (OH).sub.2 is to be synthesized electrically for both, storage of exergy and producing H.sub.2 as a raw material for the hydrazine synthesis. 5. Electrosynthesis of (NH.sub.2).sub.2 as solar exergy storing fuel, preceded by the formation of Li-amid, using N.sub.2 and H.sub.2 as per process steps 3 and 4 and using Li as an intermediary circulating carrier. The flow diagram of FIG. 8 depicts and explains these functions of the exergy transformer and as a complete system. However, the main portion is contained in block 208 and provides for the synthesis of hydrazine as principle output with solar energy serving as input. Block 209 depicts the formation of hydrogen peroxide as the preferred but not exclusively usable oxidizer for hydrazine. Moreover, auxiliary fluids are needed for and consumed in the process of forming hydrazine, namely nitrogen and hydrogen which can be produced as by-products in the formation of hydrogen peroxide. Accordingly, block 209 depicts the auxiliary process for providing for these additional materials, and the entire process needs only air as material input (without the oxygen). The block 208 contains basically three circulations, a first circulation for a thermo fluid-dynamic work fluid or tfd fluid established basically by nitrogen. The second circulation is provided by the magneto fluid-dynamic work fluid or mfd fluid #1 which is established by lithium, mixed with LiNH.sub.2 and always mixed with finely dispersed electrically conductive substances such as iron. The third circulation can be provided by a second mfd fluid, i.e., mfd fluid #2 which is a solution of Li and NH.sub.3. Mfd fluid #2 provides primarily for cooling and can be replaced. Details of block 208 will be described shortly. Reference numeral 210 may denote intermediate storage of products wherein 202 refers specifically to storage for hydrazine made as per process block 208. 188 denotes the storage for hydrogen peroxide made in block 209. Block 179 denotes water storage. I now turn to the production of the raw products needed in the hydrazine synthesis, namely H.sub.2 and N.sub.2. Block 209 denotes this process. It is assumed that the only "true" raw material to be used is air 175. The air is sucked into the process at 176, whereby excess electrical energy generated at 199 pursuant to the hydrazine synthesis can be used to run the blower. Nitrogen is separated from air at 177 by known process (such as the Ericson process) and passes to a nitrogen injection at 192 for the Li-amid generation. Moisture is separated from the air at 178 by precipitation and injected at 181 in a flow of a mfd fluid #3 circulating along a path 180 for an H.sub.2 producing electrolytic process. Excess water as separated may be stored and/or discharged at 179. Hydrogen is separated from circulation 180 at 182 i.e. it sucked out of the system for injection at a point 192 into the flow of mfd fluid #1 of the hydrazine synthesis process 208. An MHD conversion process with hydrogen peroxide synthesis takes place at 184 whereby electrical energy for the electrolytic process is furnished by the solar MHD conversion system 208 via line 206. The process 184 therefore, runs as MHD motor under electrolytic generation of H.sub.2 and (OH).sub.2. The peroxide is extracted from the circulation at 185 by evaporation (using e.g. excess heat from unit 208) and after condensation of the (OH).sub.2 will pass for storage to 186. FIG. 8 is actually drawn for illustrating functional separation; the physical H.sub.2 separation i.e. the outflow of hydrogen as a gas from the mfd #3 fluid occurs right in and from the converter 184, so that 182 should actually be superimposed upon 184. The situation is different, however, as to (OH).sub.2. This peroxide is flushed out of the converter 184 and rapid physical separation from the H.sub.2 is essential, because otherwise (OH).sub.2 will separate again into H.sub.2 O and O.sub.2. The (OH).sub.2 separation from the mfd #3 liquid at point 185 is carried out by evaporation. The mfd fluid #3 with hydrogen passes through a prime mover 187 for sustaining the circulation (that may be a MHD pump) to complete the circulation. The fluid circulating through path 180 is a watery solution of potassium hydroxide. The MHD motor 184 sets up a circular electric field in that solution. Specifically, the coil system in the converter 184 is excited by electrical energy extracted from the hydrazine generator and solar energy converter 208. The watery solution of KOH with finely dispersed iron interacts with the field generated with a slip S>O as between phase and liquid velocity to originate toroidal current which are ultimately instrumental in the generation of the electrolysis. The Reynolds number (see definition below) is low due to the low electrical conductivity of H.sub.2 O and the interaction is rather weak. The negative OH ions and positive potassium ions sustain the current flow through the mfd liquid as a result of the electric field set up in KOH+H.sub.2 O liquid as pumped through unit 184. Electron transfer results in the generation of electrically neutral potassium as well as in the formation of (OH).sub.2. The metallic potassium combines with the water to form (i.e. to restore) KOH with the result of formation of H.sub.2. It should be noted, that the finely divided iron particles serve as principle electron conductors within the circular electric field set up in the liquidous mfd #3, so that throughout current conduction is carried out predominantly by electron flow within the iron particles and through ion flow inbetween the particles bearing in mind that the external energization is an alternating field and the passing solution of KOH, water and (OH).sub.2 will not undergo electron exchange with the electrodes so that (OH).sub.2 will not separate again into H.sub.2 and O.sub.2. The primary function of the exergy transformer 208 is to convert specific exergy of the thermo fluid dynamic working medium (tfd) into electrical energy under utilization of the liquidous magneto-fluid-dynamic work medium (mfd #1) which is basically a liquidous metal and which includes finely divided iron so as to assume a certain electric conductivity and ferromagnetic characteristics. This second medium when moved in an external magnetic field interacts therewith electromagnetically by means of the so called Lorentz-force. These two media can additionally interact fluid mechanically by operation of their viscosity, for one fluid drags the other. Together they constitute the two phase MHD-work fluid wherein the tfd fluid is the gaseous phase and the mfd #1 fluid is the non-gaseous (predominantly liquidous) phase. An MHD process operates as follows: the tfd work fluid (gas) performs work when expanding, that work is not expended against external forces but on the mfd #1 work medium. Rather than moving turbine blades, pistons or the like, work is expended on the basis of local imbalances, and specifically for the case of viscous interaction work is performed by one medium on the other by operation of speed differentials and by the tendency to equalize such speed differentials as between the two media. The mfd work fluid works against external forces, but not mechanical ones with varying system boundaries; rather the accelerated mfd #1 liquid works against a retarding, outer magnetic field (across rigid mechanical boundaries) which field in turn results from the movement of the electrically conductive liquid adjacent energizing coils. There is a certain lack in consistency in the known MHD processes, namely that the compressing work performed on the tfd gas is carried out by means of compressors having mechanically movable parts and system boundaries. The novel process avoids this approach. Proceeding now to details of the hydrazine synthesis as outlined in FIG. 8, solar radiation 188 is collected by a reflector 189 and focussed for absorption and heating at 191 of the mfd fluid #1 which is lithium mixed with finely divided Fe and moves in a circulation flow path 190. The heating process 191 may be carried out via a separate circulation of sodium, the latter absorbing thermal energy more readily and heating the lithium to a temperature in excess of about 750.degree. Kelvin. Nitrogen and hydrogen are injected into the mfd #1 fluid at 192 to obtain LiNH.sub.2 in 193 by catalytic reaction, the Fe particles serving as catalyst and at a sufficiently high temperature. The functions 191, 192, and 193 are carried out in compartments A to D of FIG. 24. The tfd working fluid (gas--N.sub.2) is mixed with the mfd #1 fluid at 195. The tfd gas circulates along a separate path 194, but the mfd fluid #1 circulation as well as the tfd fluid circulation are temporarily combined at that point 195. The tfd fluid is pressurized at that point and upon mixing with the mfd fluid assumes its temperature, (compartment G in FIG. 27). The combined fluids constitute a two phase flow, whereby the mfd fluid #1 is predominantly the liquid phase and the tfd fluid is the gaseous phase. The gaseous phase is decompressed isothermally at 196 so that a portion of its enthalpie is converted into kinetic energy which in turn is imparted upon the droplets of the liquid mfd phase. The decompressed tfd fluid is separated from the mfd #1 fluid at 197, and the mfd #1 fluid is focussed at 198. In reality, the focussing of the liquid phase is part of the separation from the gaseous phase--tfd fluid, N.sub.2 (compartment J of FIG. 27). The focussed liquid continues as a free flowing liquid jet riding on a gaseous cushion and being subjected to an MHD conversion process 199. In particular, the jet passes through a self-exciting coil-capacitor system, connected electrically analogous to an asynchronous motor with capacitor load for self-excitation. The interaction of the fast moving conductive-ferromagnetic jet with coils produces a travelling magnetic field and interaction of the latter with the jet on the basis of the Maxwell equation curl E+B=0 produces an electric field so that the LiNH.sub.2 in the jet is subjected to electrolysis. The iron particles serve as bipolar electrodes in the electrolytic process which sustain a current flow in the liquidous jet as a whole. Any electrical energy not consumed in the electrolysis is externally available at 206, 207, driving, for example, the MHD converter 184 in which the water electrolysis takes place as outlined above. Following the electrolysis the mfd #1 fluid is passed through an emergency jet spoiler 200 (jet shut off) and block 201 represents the hydrazine separation from the lithium, the residual LiNH.sub.2 and the iron particles. The liquid jet is captured and recompressed at 203 (diffusor action), so that it can be returned via circulation 190 to the zone of heating (191) completing the path for Li and Fe, including residual LiNH.sub.2. Please note also here, that the functionally separated steps 200, 201, 203 are realized in a combined structure (compartment M--FIG. 32). The decompressed gaseous tfd fluid was separated from the two phase flow at 197 and passes through a recuperative heat exchanger 204 in which it gives off thermal exergy to the tfd gas as leaving an isothermal compression stage 205. A recuperative heat exchanger is shown in FIG. 32, Compartment O. The cooled tfd fluid enters 205 and is mixed with a second mfd (or mfd #2) fluid at 211, to undergo heat exchange so that the subsequent compression of the tfd fluid, box 212, is carried out under isenthalpic conditions (compartment Q in FIG. 32). The mfd #2 fluid is condensed at 213 and separated from the tfd fluid (N.sub.2) at 214 from which it is returned to the recuperative heat exchanger to receive thermal energy from the tfd fluid before the latter is recompressed. The pressurized and reheated tfd fluid is now returned to point 195 for mixing with the mfd fluid. About 10% of the pressure is needed to sustain the return flow of the tfd gas to the mixing point 195. The mfd #2 fluid following separation from the tfd fluid is returned to mixing point 211. The condensation of the mfd #2 fluid as per function box 213 is actually part of the separation of function box 214 as far as implementation is concerned (compartment R in FIG. 36). The condensation is the result of heat exchange with a fluid in function box 213 circulating along path 217. That heat exchange fluid is cooled by ambient air (box 215), whose flow is indicated by 216. FIG. 8 demonstrates the central position of the tfd work fluid and the interaction of it with the two fluids mfd #1 and mfd #2. These interactions are limited in time and space and concern exclusively isothermic and isenthalpic processes. One is the isothermic decompression of the tfd fluid in 196 under acceleration of the mfd #1 liquid and carried out at the upper working temperature T=T.sub.u, the other process is the isothermic compression in 212 at the lower working temperature, T=T.sub.low, with mfd #2 serving as coolant, while being at least in parts caused to circulate by the decelerating tfd gas as it is being compressed. The gaseous tfd work medium circulates through the system without receiving or expending any work via movable system boundaries. Both liquidous media, mfd #1 and mfd #2 are driven by means of dragging forces exerted by the tfd gas upon the two liquids whenever being mixed or combined therewith. The tfd gas does not have any access to any heat exchange with the environment, except through the mfd #1 and #2 fluids. The interaction between the tfd gas and the two mfd fluids (liquids) is predominantly but not exclusively based on viscosity. Rather, a generalized thermodynamic force is effective being in the nature of a temperature difference between the tfd gas and either of the mfd liquids. This temperature differential enforces the heat flow needed respectively for isenthalpic decompression and compression. In particular, the mfd fluids both serve additionally as heat transfer and storage media. The mfd #1 liquid stores solar energy and heats the tfd gas upon mixing and during decompression thereof. The mfd #2 fluid ensures low temperature isothermic recompression of the tfd gas. This function dominates as to mfd #2, a MHD pump keeps only the circulation going for that liquid. The mass flow is lower by about a factor of 50 as compared with mfd #1 due to evaporative cooling of that mfd #2 fluid. As a consequence, the technical system does not only have rigid system boundary but the size of the system boundaries have no influence on the process and work performed by the tfd work medium. In either case, tfd and mfd fluids mix almost homogenially so that very large surface areas are available for the heat transfer, and the average depth of heat penetration is very very small, so that this transfer occurs almost instantaneously on contact and mixing of the fluids. As stated above, mfd #1 is a solution of Li and LiNH.sub.2, the latter being in effect an intermediate product for the synthesis of (NH.sub.2).sub.2 from N.sub.2 and H.sub.2. The heat capacity and thermal conductivity of this solution (which includes some iron particles), permits full utilization of the concentration of solar flux density by means of reflector 189 up to 125 W/cm.sup.2. The mfd #2 fluid is fully analogous thereto and tuned to a lower operating temperature of, in cases, T.sub.v =250 K. It is a solution of Li and HNH.sub.2 having a high electric conductivity even at such low temperatures. Moreover, an LiNH.sub.2 residue (from mfd 190 1) that may have been carried over by the tfd gas to the mfd 190 2 liquid, can go into solution to permit chemical regeneration, recovery and return to the mfd #1 fluid. Mg and Ca are suitable reactants to separate the LiNH.sub.2 from the mfd #2 fluid. Before describing construction and layout of the MHD system 208 in greater detail, I refer to an important feature of this system, namely the reflector which is used for focussing the solar radiation. The radiation density must be increased by about a factor of 1000. A rigid reflector may prove to be impractical and expensive. Moreover, it is advisable to provide a reflector which is in fact buyontly supported. Such a feature facilitates the orientation of the mirror including following the sun and a buyont construction may even permit the mirror with centrally disposed MHD transformation unit to be positioned at some distance from ground. FIG. 40 shows a modular MHD system (=208), shown as an elongated tube 27. One of the units shown in detail in FIGS. 24 through 39 may be contained in or constitute module 27, or a cluster thereof will be arranged as shown in FIG. 21 and may be contained in unit 27. The front portion of each such module (compartments A to D of FIG. 24, or portion 191 of FIG. 1) is contained in the focus 127 established either by the exposed outer skins 15 of the modules or by a "black" absorber covering that skin. The modules or tube 27 is held via tube 126 for support and protection. Reference numeral 128 refers to the air gaps through which air can enter into heat exchange at the low temperature side of the modules (see compartments S through Y, FIG. 38). The reflector is established by a reflecting foil 115 which constitutes the inner surface of the concave mirror as well as the top foil of a buoyoncy support structure. The periphery of the reflector is established by a hollow toroidal bead, hose or tube 108 with a diameter of 200 meter of the annulus and 30 m diameter of the circular cross-section of the toroid. Tube 108 is filled with hydrogen 109 for establishing the main buoyoncy. Tube 108 is strengthened on the inside by a chamber 110 filled with H.sub.2 under higher pressure. Welding seam 113, between the wall of chamber 110 and tube 108 serves as anchoring points or line for the outer ends of support arms 114. A seam 112 is the boundary and connect point between mirror foil 115 and hose or bead 108. Support arms 114 are pivotally mounted on a central support tube 117 by means of pivot joints 116. A second joint 118 of each arm is provided in about the middle thereof and is connected to a bottom foil 124 which connects also to joint 113. Arms 114 center the bead and are tensioned by cable 119. A welding seam or connecting line 120 fastens the coil 115 to an annulus, ring or sleeve 122, a foil 121 is also fastened thereat. Annulus 122 is slidable positioned on tube 117 and can be moved up and down e.g. by means of a suitable drive and positioner for adjusting the reflector 115 in relation to the outer tube 108. In order to compell reflector foil 115 to assume the desired contour (parabolic), foils 115, 121 and 124 together constitute a cushion and pneumatically elastic backing 123 for the reflector foil. The connections 116, 118 and 113 support this cushion 123. Relatively low pressure therein sucks the foil 115 towards the inside. Points 120, 116, 118, 113 and 112 are all fixed position points in relation to which the foils curve inwardly. As stated, central pipe 117 holds the MHD system 27 in a holder 126. The air exit and thermodynamic low temperature of the MHD system is established through air conduction through slots 128 of central pipe 117. Pipe 117 is placed into a pipe 129 to which one can connect the several inlet and outlet ducts for the fluids needed to operate the generator, e.g. water and/or hydrogen, while hydrazine is discharged therethrough. The connection between 117 and 129 is a releasible one, so that the mirror can be collapsed and for example replaced by a different one, in case of damage and for repair or replacement. Bolts 130 permit the release. In order to orient the reflector towards the sun, tube 129 has a bellow like section 131 interposed. Spindles 132 bias the bellows axially but to a different extent thereby causing the entire assembly to tilt. The reflector assembly including annulus 122 will be placed in position over the pipe 129, but central pipe 117 (to which the joint 116 and lower foil 114 is fastened) is inserted into and secured to pipe 129 by means of the bolts 130. Next, tube 108 is inflated by introducing H.sub.2 whereby the arms 114 are unfolded and the cushion 123 is deployed. The final contour of reflector foil 115 is established by means of adjusting ring 122. FIG. 41 shows another version of the reflector construction which is actually preferred. Features common to both assemblies have been omitted. The difference arises from utilizing a smaller tube or hose 133 while a tensioning cushion 135 rather than the cable 119 of FIG. 40 are provided. Thus, one does not need mechanical operation of such cable. The cushion 123 is deployed by inflating cushion 135 through injection of hydrogen 111. Since that cushion adds buyoncy, bead-hose 133 can be made smaller indeed. The tensioning cushion 135 is established on its upper side by lower foil 124 of the reflector cushion, while a tensioned foil 137 forms the lower side of cushion 135. Foil 137 is connected to tube 133 along a joint-seam 136. Cushion 135 is stabilized additionally by a compartment 134, and as to central pipe 117 the connection to foils 124 and 121 is made thereat. Pivot joints 118 are still needed in arms 114; the latter run through the inside of cushion 135 and are protected by the H.sub.2 therein. After having described the reflector in which the MHD unit or units as mounted, I proceed to the description of construction details of the MHD modules. A unit 208 as per the system and method diagram of FIG. 8 is designed to be for elongated construction. Such an MHD unit should be amenable to mass production and easy to transport; light weight construction is preferred. Thus, the essential structure parts of a MHD unit constitutes similar pipes, tubes, and preshaped and punched sheets of about 3.0 mm gauge or less to be interconnected by welding. An MHD unit has uniformly hexagonal cross-section throughout its extension (see FIGS. 22 et seq, particularly the several cross-sections). This way, they can be clustered in honeycomb fashion (FIG. 20) to permit parallel operation of many units. Each MHD unit is, as far as construction is concerned, comprised of a supporting frame; the specific components for the MHD generator proper not being part of that frame; and an outer skin structure with as small a leakage rate as possible. If the MHD unit is not run on solar energy, nuclear fission and breeder materials must be included. The frame is the basic support structure into which are reacted all forces that are not transmitted to the outside or act from the outside onto the unit. The support frame is set up by six parallel tubes 8 and by partitioning and stiffening sheets traversed by and secured to these tubes. A central, but sectionalized tubing 7 traverses these sheets and constitutes also a part of the support frame. The skin structure is secured to the partitions. FIG. 12 shows a first partition 1 which is more in the nature of a subframe having a central sleeve 1x (opening 4) surrounded by six small sleeves 1y (opening 3) and held by struts 1z, while bars 1w provide for an outer hexagonal frame. This construction is provided primarily for transmission of forces. The length (transverse to the plane of the drawing) can be variable. This subframe 1 provides for maximum free cross-section of flow in axial direction. FIGS. 13 and 14 show a transverse partition 2 with a central opening 4, peripheral openings 3, and, optional, openings 5. The openings 3 receive tubes 8 (FIG. 15) and opening 4 may receive sections of the central tubing 7. If such tubings are inserted, a partition 2 provides for a true dividing partition as to the space outside of tubing 17 and around inserted tubes 8. The edges 6 of sheet-partition 2 are flanged and the openings may be beaded to obtain stiffening and to serve as welding flange. FIG. 15 shows by way of example a plurality of partitions 2 and central tubing 7 while being also traversed by the tubes 8. In addition, this Figure shows a small pipe or tube 9 (traversing an opening 5) serving as auxiliary fluid duct without, however, constituting a portion of the basic support frame. For this, partitions 2 are either seated on and welded to tubing 7 or partitions 2 receive and hold the light tubes 8, or both as shown in the central portion of the Figure. The Figure shows also that a partition sheet 2 when not on a tube 7 permits flow of the same medium in the central area or zone (not occupied by tube 7) as well as in the zone around the pipes 8. Reference numeral 10 denotes welding seams. FIGS. 16 and 17 show a modification of the partitions to be used in those cases where the MHD unit is to be partitioned beyond the inner skin so that the radial dimensions of this end wall 11 are enlarged. FIG. 18 shows a plug element 12 for closing any of the openings that receive tubes 8, or the tubes themselves, are to be closed and partitioned. These plugs are also welded and their cap like configuration permits placement of sensors and/or adjustment and actuating equipment. FIG. 19 shows by way of example placement of such plugs as well as the enveloping of the frame by a double skin. The inner skin 13 is made of sheet metal which is corrosion-proof as regards contact with the several materials e.g. lithium, particularly for the quite elevated temperatures that will occur. This inner skin is stiffened by means of welded-on corrugated sheet material 14 which transmits also any forces to the outer skin 15 seated thereon. The gap between skins 13 and 15 is denoted 20 and performs important functions to be described shortly. The inner skin 13 is, so to speak, continued at the one ends by a partition 2 and also inwardly, wherever compartmentalization of the interior space, outside of tubes 8 is desired; the partitions are welded to the skin at flanges 6. The welding seam will be removed if the inner skin has to be removed for access to the interior thereof. The same or other skin material is welded on, following e.g. repair, replacement or the like. The caps 12 close out openings 3. The other partitions 2, not serving as true space dividers for compartmentalization need not to be welded to the skin 13. The outer skin 15 is loosely seated on the corrugated sheathing 14, the latter being welded only to skin 13. The outer skin is axially terminated by connection to a (larger) partition or axial end wall 11. The respective welding seam 17 is also removable and restorable for access and its openings 3 are also plugged by caps 12. The central tubing 17 can be closed e.g. by means of a cylindrical plug 18. This plug 18 carries a ball 19 at its end, serving e.g. as suspension element, for adjustment particularly when the unit is combined with others, and as storage space. A module as such is identified by numeral 27. FIG. 20 shows a plurality of such units in honeycomb assembly. One of them is shown in cross-section next to a partition 2. One can see inner and outer skins 13, 15 as well as the corrugated stiffening 14. Specifically, each of the skins is made from three segments such as 22, 23 which are welded together. The welding flange 24 of the inner skin 13 projects into the axial gap 20. Flange 24 is intrumental in adjusting the disposition of outer skin 15 as well as for mounting control and sensor lines or heating cable 26. These lines and cable run to the several caps 12. The welding flange 25 of outer skin 15 is shown in inward extension but could project outwardly. In the case of butt welding, no such flange is needed. The gap 20 between the two skins as well as the space 21 at one front end serve for enhancing reliability of the system. For example, space 21 may be held under low pressure which can be monitored and supervised to detect any leakage. Space 21 communicates with gap 20. In parts the gap will serve as duct for circulating a heat exchange medium, such as liguidous metal. If the unit is run on nuclear energy with fission and breeding sustained inside of the unit, gap 20 serves as thermal insulator. As stated, the basic elements for the construction of the supporting frame are sheets, used for its transversal stabilization, and tubes. In detail, there are sheets, extended in longitudinal direction, thus forming longitudinal partitions or subframes 1 as well as sheets extended in vertical direction, thus forming vertical or transverse partitions 2; there are, in addition, the central tube 7, the tubes 8 of smaller diameter located outside of the central tube as well as the small tubes 9 of lowest diameter used for internal connecting piping. All these elements are also used to construct the main components of the MHD-module, enclosed the various compartments F, G, H . . . S and T, U, V . . . X, Y, infra, and connected with the supporting frame and construction as described. As a rule for supporting frame, it is a rule also for the components, that only punched, deformed (shaped) and flanged sheets are used but major lathe work is not required; the aim is to permit the one-line production of MHD-modules with a very high output capacity. The MHD-converter, however, is the one exception from this rule; for this component coils have to be wound, stator blocks to be assembled and coils must be insulated as well as inserted into the stator blocks. The MHD-converter, however, is installed as a single unit in a central tube (7) section and can thus be removed or replaced easily in case of module replacement, which might be necessary when the permissible number of operations hours was reached (due to corrosion, for example). This central, MDH converter can be reused in the same way nuclear fuel pins or the MHD-working fluid, composed from both the tfd- and mfd-working fluids, can be reused in another module. The first step of production is the construction of the supporting frame, while the second step consists in the leak detection of the skeleton; in the third step, therefore, the various components have to be fixed and are connected with the supporting frame. It is a useful approach to assemble the modules on turntable which in turn is mounted on a carriage. Normally the module is positioned horizontally on that carriage; in the fourth step, however, when the module is jacketed by means of the inner skin, the module on the turntable should be shifted into an upright position. This upright position is needed also for the fifth step of production including leak detection of inner skin, fixing of sensors, cables and heaters. During the sixth step, when the outer skin has to be attached, the horizontal position is preferred. (This car for module assembling is not shown in any drawing). FIGS. 21, 22 and 23 show the entrance section (in regard to the exergy) for an MHD-module with an internal nuclear power reactor as heat source. The space between any two adjacent partitions of the supporting frame of the skeleton construction, is named a compartment, and these compartments are respectively identified by A, B, C . . . . Nuclear fuel elements 28 as provided in the form of the well known fuel pins or rods are located inside of a central tube 7 of the skeleton and supported therein in the usual way by means of a grid 29. The breeding material 30 is located outside of the central tubing 7 within the compartments A, B, C and D thus forming the blanket, fixed at the partitions 2. The coolant, which is at the same time the mfd-working fluid, passes first through the blanket 30 and will be reversed in its flow direction while entering slots 32 in the central tube 7 and flows along the fuel pins 28 thus passing through the grid 29. For radiation shielding in axial direction a neutron absorber 33 forming layers of small pebbles and preferably being flooded by the coolant, is located within a large plug 18 as well as in the central tube 7 and in the free space between the external tubes 8 in compartments E and F. The gap 20 and the cavity 21 covering over the entire length of compartments, are filled with a protective gas of low pressure for thermal insulation. The outer skin 15 is discontinued within the compartment E and substituted by a relatively short segment 42 of the inner skin. Both of the welding seams 43 can be removed easily in order to facilitate any partial dismanteling of the module, especially for purposes of replacement of the nuclear material. The compartment E is, for this reason, subdivided in a nuclear and a non-nuclear half-compartment by the additional partition 2, serving for a distinct reliability control. Details concerning the circulation of the mfd fluid will be discussed shortly when explaining the preferred embodiment. FIGS. 24, 25 and 26 shows the, in the alternative, input part of an MHD-module wherein energy input is provided from an external heat source, such as, in this preferred example, from the sun. The gap 20 between outer skin 15 and inner skin 13 is, therefore, used in daytime for the transmission of heat from the outer skin. Skin 15 is directly exposed to solar radiation 35 over the entire length of compartments A, B, C and D, and absorbs the radiation. The gap 20 adjacent compartments A to D is filled by a circulating heat exchange medium such as a liquidous alkali metal, e.g. sodium which is heated through direct contact with the outer skin and heats the inner skin 13, which in turn is in direct contact with the non-gaseous phase of the mfd-working fluid composed from Li, Li(NH.sub.2) and Fe-particles. At nighttime, gap 20 has to provide the thermal insulation. In the daytime, the circulation of the mfd-working fluid for purposes of heat exchange and receiving solar energy is as follows. The non-gaseous phase of the mfd-working fluid 31 returns from its magnetohydrodynamic work functions and arrives at compartment D through tubes 8a, 8c and 8e, after having traversed compartments M, L, K etc. The fluid leaves the three tubes 8a, c and e at compartment D and enters the free space between the central tube 7 and the axial, inner skin 13 in order to undergo heat exchange with an alkali metal such as sodium which circulates in gap 20 between skins 13, 15. The circulating sodium absorbs solar energy, or, more accurately is heated by the outer skin which has absorbed the solar radiation 35 adjacent to compartments D, C, B and A. The mfd-fluid coolant then enters the central tube 7 via the slots 32, and the central tubes guide the fluid through tube 7 towards compartment G and to further components of the MHD-module located in the compartments G, H . . . . At night, the central tube 7 is the main heat reservoir of the module as far as the mfd-fluid is concerned. As one can see from compartment D in FIG. 25, the space outside of tube 7 is closed by one of the partitions 2, and that space receives mfd fluid through the exits of tubes 8a, c, e as stated. The chamber to the right of the partition 2 separating compartments D and E is filled with sodium 16. The same is true with regard to the space or chamber around central tube 7 in compartment F, denoted 39 and being separated on both sides (i.e. from compartments E and G) by means of partitions 2. Tubes 8b, d, f transport the sodium between these chambers in compartments E and F outside of central tube 7. The sodium enters the gap 20 of compartments A through D through slots 40 in tubes 8b, d, f in compartment E and through an annular slot 20a in skin 13 in the same compartment. The sodium advances all the way to the left of the lefthand partition 2 of compartment A to fill space 21. This way, sodium surrounds the mfd fluid in compartments A through D for transferring absorbed solar energy to that mfd fluid. It should be mentioned that chamber 39 (space around 7) is filled predominantly with pressurized N.sub.2 during daytime to force the sodium in the chamber in compartments E and F into the gap 20 of compartments A to D. During daytime operation, the righthand portion of compartment E i.e. the chamber around tube 7 and to the right of the central partition 2 of that compartment as well as to the left of the partition 2 separating compartments E and F is under vacuum (or low pressure N.sub.2). The same is true always with regard to the portion of gap 20 adjacent to compartments F, G, H etc., for purposes of thermal insulation of these compartments. The purpose thereof will be described shortly. As can be seen from FIGS. 24 and 25, a helical tube 34 loops around tube 7, traversing the space occupied in the other compartments by tubes 8 (the latter terminate adjacent the dividing line between compartments D and E). This tube 34 has small lateral openings to disperse a mixture of N.sub.2 and H.sub.2 into the mfd-fluid within the annular space between skin 13 and tubing 7. As stated above, this liquid is composed of Fe, Li and Li(NH.sub.2). The Li(NH.sub.2) content thereof has been lowered (and the Li content has been increased) by process to be described as that fluid returns to compartments A to D via tubes 8a, c, e. The solar-heated lithium reacts with the N.sub.2 and H.sub.2 as supplied via tube 34 and as dispersed into the fluid to form Li(NH.sub.2) under catalytic reaction, using the dispersed Fe particles as catalyst. The chemical process has been described above, presently I describe the physical set up as to how to obtain that reaction. Tube 34 actually ends in compartment A, it enters compartment E as straight tube of small dimensions and is run to that point as straight tube from compartment S, traversing all the compartments inbetween. The connection of tube 34 to external supply for N.sub.2 and H.sub.2 (see FIG. 8) is made at that compartment S. At night, due to the lack of solar radiation, the gap 20 at compartments A to D has to be emptied from the liquid metal (sodium) for obtaining thermal insulation of these compartments. In this preferred example given here, flooding of the gap 20 with a liquid metal and emptying takes place automatically by making use of the ball-shaped reservoir 19. During daytime, ball 19 is also exposed to solar radiation pressurizing the protective gas 37 (N.sub.2) therein. The reservoir 19 is connected by a thin pipe 38 with the reservoir 39 for the heat exchange liquid metal 36 (sodium) located at compartment F. In case the gas pressure in reservoir 19 decreases due to lack of radiation heating, the gas contracts and sucks the liquid metal 36 out of gap 20, through the slots 40 within the three tubes 8 b, d, f of compartments E, F and will enter the reservoir in compartment F. Both, the three tubes 8 as well as the space 39 of compartment F are hermetically separated from the other compartments and from the corresponding parts of tube 8, respectively, by welding the partitions to the inner skin 13. Additionally, plugs 41 are inserted into the three tubes 8 d, d, f in the level of the righthand partition 2, separating compartment F from compartment G. These plugs permit utilization of pipes 8b, d, f to the right as conduits for other fluid (namely, high pressure N.sub.2). It should be mentioned, that upon emptying space 21 and gap 20 adjacent to compartments A to D from sodium, an insulative gas may be used as replacement. Also, some of the openings 40, either those in E or those in F may be closed by means of valves to confine the sodium to chamber 39 in compartment F. The gap 20 surrounding compartments F, G, etc. is always used for thermal insulation, and, therefore, filled with a very low pressure protective gas; this section of gap 20 is separated from the gap 20 at compartments A through D by the additional (central) partition 2 in compartment E. The respective subcompartments around tube 7 communicate separately with these gap 20 portions respectively, to the left and to the right of compartment E. The outer skin 15 is interrupted here but there still is present a short segment 42 of the inner skin isolating the annular gap 20a and 20b from the two chambers of compartment E into the portions of gap 20 to the left and to the right. The welding seams thereat can be removed easily to permit partial dismanteling of the module when needed. The FIGS. 27, 28, 29 and 30 show the compartments F through L as continuing compartments A, B . . . F. Compartments F and G, shown again in FIG. 27 and to be taken in conjunction with FIG. 28, depicts the connection, so to speak of two major components. The one major component is the solar energy absorber, mfd fluid heater and Li(NH.sub.2) synthesizer as established by compartments A through F and as described in the preceding paragraphs. The other major component is the two phase fluid portion of the system as continued in the MHD device. The linkage between these major components is as follows: The partition 2 separating the space around tube 7 and of compartment F from the analogous space of compartment G, separates therewith the sodium reservoir 39 from space occupied by low pressure N.sub.2 (compartment G). That N.sub.2 is separated from the N.sub.2 supply through tube 34 and is also separated from gas 37 of reservoir 19. In fact, the N.sub.2 in chamber G is the decompressed gaseous phase of the MHD working fluid. FIG. 25 shows only the continuation of tubes 8 in compartment G; plugs 41 in pipes 8b, d, f prevent flow of sodium into compartment G; the same pipes will receive high pressure N.sub.2 (tfd) arriving in compartment G from chamber R. Pipes 8a, c, e continue to pass mfd fluid (Li, Fe and some Li(NH.sub.2)) towards compartments D just traversing compartments F, G, H etc. on their return path from compartment M. Compartment G in FIG. 25 shows these pipes only, additional equipment for that compartment is shown in FIG. 27. Central tube 7 feeds hot mfd fluid, enriched with Li(NH.sub.2) into the end of compartment F. Tube 7 is interrupted in compartments G and F, and particularly closed off by an axial end partition 7a traversed only by three inlet pipes 44a for three mixing chambers 44 being provided for mixing the tfd- and mfd-working fluids. Specifically, chambers 44 combine hot, Li(NH.sub.2) enriched mfd fluid from tube 7 with pressurized tfd fluid N.sub.2 arriving in tubes 8b, 8d and 8f (to the right of plugs 41 in the dividing plane between compartments F and G). The mixing chambers intercept these tubes; the sodium flow in these tubes is blocked off by these plugs 41. Each chamber 44 has two nozzles, there being six nozzles 45 accordingly; only one of the nozzles 45 is shown in FIGS. 27 and 29 for the sake of clarity; the others are disposed in corresponding positions. The nozzles 45 are provided inbetween respective adjacent tube 8; the mixing chambers intercept them as stated above. These mixing chambers are of course respectively connected to tubes 8b, d, f to receive high pressure tfd gas N.sub.2. They are partitioned and the partition runs right in the plane of the section view of FIG. 28. Pressurized tfd gas (N.sub.2) enters the portion of the mixing chambers to the right of that partition while hot mfd #1 liquid is to the left of that partition. Small tubes traverse the partition as well as the chamber portion to the right thereof and run the hot mfd #1 liquid right to the entrance of nozzles 45 (two per mixing chamber). The pressurized tfd gas flows directly to the nozzle entrances. The tubes 8a, c, e just pass through the chambers 44 without connection as return of the mfd liquid towards compartment D. The nozzles 45 provide for the acceleration of both of the two working fluids as they mix in the entrance of the nozzles and beyond. As outlined above, the pressurized tfd fluid (gas) is heated upon being mixed with enriched mfd fluid and expands isenthalpic in nozzles 45 thereby accelerating the mfd fluid (see equations (1) and (2), supra). The mfd liquid is broken up into droplets, being hurled towards and through compartment H, in which two working fluids are decoupled. As a consequence, the entire space of compartments G, H and I inside of skin 13, but with the exceptions of tubes 8, is filled with depressurized N.sub.2. This depressurized N.sub.2 follows then generally (arrow 47) a flow path along tubes 8 and on the outside of the continuation of tube 7 which contains the MHD generator in compartments J, K, L and M. The liquid phase of the mfd fluid is ejected by the nozzles 45 towards the entrance for the MHD generator in compartment J for being focussed therein to establish a free flowing jet. The kinetic energy of that jet has, of course, resulted from acceleration by the isothermally decompressing tfd fluid in nozzles 45. In the MHD generator the kinetic energy of the mfd fluid jet is converted into electrical energy causing the jet to decelerate. As already mentioned, the MHD-converter proper is installed in a segment of central tube 7. This segment is connected to a longitudinal partition 1, being a part of the supporting skeleton so as to transmit the large forces from the free jet, due to its deceleration, to the tubes 8 of the system. The central tubing 7 is also used to separate the MHD-converter proper in regard to the tfd-working fluid 47, which flows along the central tube 7, on its outside, after expansion and upon separation from the mfd-working fluid 31. It should be mentioned, that the magnetic focussing affects the liquid phase only (Li--Li(NH.sub.2)--Fe) and is appropriately effective in front of the entrance to the MHD generator. The gaseous phase (N.sub.2) upon leaving nozzles 45 experiences a sudden enlargement in cross-section and looses momentum. Sheets (not shown) in compartment N could provide for diffusor effect to slow the flow of tfd-gas. Moreover, this N.sub.2 is not affected by the focussing. Hence, the N.sub.2 will be separated from the liquid phase in compartments H and J by the dynamics of the process generally, and by focussing of the liquid phase in particular. The nozzles 45 direct generally the flow of fluid towards a focal point 52, but the gaseous phase separates while the liquid droplets are guided towards that focal point. For this, a separator 57 and Coanda lip 58 is disposed ahead of the MHD entrance enhancing fluid-mechanically the coagulation of the liquid droplets as well as focussing thereof; the gaseous phase flows along a different path. Specifically, liquid droplets in the two phase stream hitting separator 57 on the inside form a film on the inner surface. The six jets are in fact combined and the common film continues along the outside of Coanda lip 58 with a radial inward component for leaving the lip as a hollow jet lamina which becomes a "solid" core jet on focussing by the magnetic coils in the MHD device. The hollow core and converging film collects liquid droplets still inside while the residual gaseous phase is squeezed out. The segment of central tube 7 housing the MHD-converter proper, is deformed conically in compartment J to establish the converter entrance. The MHD-converter includes stator blocks 48, and ring-shaped or annular coils 49 are disposed for magnetizing this stator core. Specifically, the stator blocks are of comb construction being arranged along the center axis, around that axis whereby the teeth of the combs point radially inwardly. The coils 49 are annular coils arranged in the gaps between the teeth, looping around the center axis. The coils are for example interconnected analogous to a three phase asynchronous machine, the connection pattern being repeated along the axis so that upon energization a travelling wave is produced with a flux vector dB/dt in and along the center axis, coinciding with the axis of the jet of mfd-1 fluid. The inner diameter of the comb-coil structure increases in the axial direction jet flow and the axial spacing between comb teeth decrease in that direction. The arrangement operates at constant frequency, but the jet looses kinetic energy and widens to some extent. As stated above, the stator coils are connected to capacitors to obtain a self-exciting oscillating system tuned to the desired frequency of the travelling wave produced (e.g. 2.5 Khz). Since the machine operates as generator, electrical energy can be taken from the coils e.g. to run the H.sub.2 electrolysis (see FIG. 8). Additionally, the jet functions analogous to a short circuited rotor and consumes electrical exergy in the electrolysis for splitting Li(NH.sub.2) into Li and NH.sub.2. A particular coil 50 is disposed right at the entrance and is separately energized. Coil 50 energizes particularly pole-shoes 51 for magnetically focussing the the liquid phase in the focus 52 on the central axis of the module. The magnetic field at the entrance and as set up by the coil 50 and pole shoes 51 is strongly inhomogenous but of radial symmetry to cause the droplets to converge towards the center axis. The magnetic field is that of a magnetic lens and induction causes a magnetic field to be set up in the droplets forcing them in direction of decreasing field strength to obtain a compact jet. Any residual gas is forced out of the jet. It should be noted that magnetic focussing and Coanda lip mutually reinforce the focussing. Actually, either device may suffice by itself in principle. A central, axial duct 53 is formed by the annular arrangement of stator blocks which duct is enlarged in diameter downstream; the duct is sealed hermetically and physically established by a thin walled tube 54, which should have very low electrical conductivity. Tube 54 thus separates the jet from the stator blocks 48, and coils 49 and 50. The free space 55 between stator blocks and coils or, to put it differently, the annular space between tube 7 of the MHD generator and tube 54 is filled with a coolant, preferably N.sub.2, bypassed from the tfd-working fluid after its isothermal compression; the piping necessary is not shown here. This particular coolant leaves the coil space of the MHD-converter at elevated temperature through the slots 56 and pours into the duct 53, along the inner wall of tube 54, between it and the free jet of mfd liquid. Thus, the free compact jet of the mfd-working fluid is guided and held apart from the wall of tube 54 by a residual fraction of the tfd-working fluid to serve as bearing or cushion. The free jet is not directly shown in the Figures, but can be understood to coincide with the axial center line in compartments K and L. By operation of the movement of a free flowing conductive jet (liquidous Li, Li(NH.sub.2) and, primarily the iron particles therein) through the coils 49, the coils are inductively energized. The coils are connected with capacitors as stated above and the interaction with the moving conductive jet acts as stimulus for causing the coil-capacitor system to oscillate and its resonance frequency is e.g. 2.5 Khz. As a consequence of the oscillation, and due to the three phase and periodically repeated connection and disposition of the coils 49 along the jet path a travelling magnetic wave is produced by these coils. Since there is a relative movement between jet and travelling magnetic field, i.e. there is a finite slip s, the oscillation is not attenuated but amplified. The work for this amplification is taken from the kinetic energy of the jet and the latter is retarded. As a consequence of this magnetic field set up by the coils 49 and interacting with the mfd fluid, a circular electric field vector (looping around the central axis) is established therein, and the resulting voltage in the jet causes electrolytic decompositioning of the Li(NH.sub.2), separating the lithium from NH.sub.2, whereby the dispersed Fe particles serve as bipolar electrodes. The iron particles should have dimensions of about 10.sup.-2 to 10.sup.-4 cm. Nevertheless these particles readily float and move with the jet. The electric field vector being closed around the axis of the jet is of course an oscillating one, and the iron particles serving as electrodes move within the jet. Hence, the electrolysis performed is not carried out in relation to fixed electrodes establishing surfaces of constant electro potential vis a vis a potential difference relative to the electrolyte. Rather, the electric field strength is constant along a closed field line and is not a gradient of a potential field. The oscillatory, closed loop field when sufficiently strong causes a displacement of electrons i.e. from the NH.sub.2.sup.- ions to the Li.sup.+ ions, everywhere along a field line and per se independently from the existence of these electrode--iron particles. The Maxwell equation, curl E+B=0, yields a voltage by integration along a closed field line, provided of course B.noteq.0 which is true due to the oscillatory energization by the resonating exciter coils which produce the time variable inductance B. That voltage is not taken in relation to the electrodes, but is the effective voltage acting on an electron that finds itself on a closed loop field line. The electrodes have a different function. They provide for electric conductivity in the mfd #1 liquid as a whole which per se is a poor conductor except for the iron particles. The chemically produced electrons (as split off the NH.sub.2.sup.- ions) are moved as far as electron conduction and current flow is concerned, primarily through the metal of these electrode particles. Since the metal of the electrode particles dominates in the electronic conduction, a strong (instantaneous) current will flow indeed in the jet, in effect transporting electrons from NH.sub.2.sup.- to Li.sup.+ in the otherwise poorly conductive mfd #1 liquid. That current is of course an oscillating one and is representative of the electron transfer in the liquid from the NH.sub.2.sup.- ions to the Li.sup.+ ions. The oscillating nature of that electrolysis producing current does not cause alternation between electrolysis and decompositioning, because the jet flows rapidly as a liquid stream and the NH.sub.2 will combine into (NH.sub.2).sub.2 which is an exergonic reaction and occurs spontaneously. There is the possibility of re-separation of the hydrazine into NH.sub.2 ions, however, hydrazine is a gas at the operating temperature (800.degree. K.) and will tend to leave the liquidous mfd fluid. Thus, the newly formed hydrazine will separate from the liquid jet and interposes itself as a gas cushion between the jet and the tube 54. The metallic lithium that remains just enriches the lithium content of the mfd #1 fluid. As we leave FIG. 24, a somewhat expanded Li-Li(NH.sub.2)--Fe liquid jet leaves along the axis. The lithium content was increased and the Li(NH.sub.2) content has been depleted. That jet is surrounded by a cushion formed by a mixture of N.sub.2 and hydrazine (gaseous), but still flowing in the diverging tube 54. It should be noted, that the field induced in the jet is actually carried out of the MHD coil systems and decays relatively slowly thereby sustaining further electrolysis which is particularly conductive at this point to prevent recompositioning of Li and NH.sub.2 in the hot fluid, bearing in mind that catalytically effective Fe particles are still present. Outside of tube 7 decompressed N.sub.2 (tfd) flows parallelly thereto, also to the right. The six tubes 8 of course transport separately returning mfd fluid and pressurized tfd fluid to the left for use as outlined above. The FIGS. 32, 33 and 34 present the compartment M, which contains the exit of the MHD-converter combined with structure for the jet capture. At this place, a further separation takes place. The residual gaseous phase, which accompanied and cushioned the liquid jet, is at the same time (chemically inert --N.sub.2) the protective gas for the hydrazine formed within the jet. The portion of tube 7 in compartment M does not contain any coils. At some point in compartment L a partition between tubes 7 and 54 confines the pressurized N.sub.2 gas in the annular space between these two tubes, right at the end of the coil arrangement of the MHD generator in compartment L. That also is the end of tube 54, and tube 7 is now filled with a mixture of N.sub.2 and gaseous hydrazine, still surrounding the liquidous but significantly slowed down jet. The jet is captured in a venturi pipe, jet capture tube 62. This tube is held inside of tube 7 by means of two partitions 63, defining a chamber into which the captured liquid phase--mfd flows, through lateral pots 62a in tube 62. This particular chamber has three outlet pipes 65a, c, e respectively connected to radial connections 67a, c, e which run the liquidous phase, i.e. Li--Fe with residual Li(NH.sub.2) into the three pipes 8a, 8c, 8e (compartment M) which return this exhausted mfd liquid to the compartment D. The jet capturing tube 62 is subjected to very large forces which have to be reacted into the skeleton; this will be done by the central tube 7, which supports the capturing tube 62 by the two sheets 63. The free space between the tubes 7 and 62 defines the chamber in which the liquid mfd is collected and has the same internal static pressure as the end of the capturing tube has, which is equivalent to the jet stagnation pressure. In order to approach as much as possible the theoretically maximum stagnation pressure, which results from the residual kinetic energy of the free jet when leaving the magnetic field, the capturing tube 62 is contoured by an insert to reach optimal diffusor function. Accordingly, diffusor tube 62 repressurizes the mfd fluid for its return to the heat absorption chambers of compartments A to D. The three pipes 8a, c, e returning the pressurized mfd fluid to compartment D are provided with plugs, i.e. internal portions 41 right in the dividing plane for compartments M and N (actually establishing this division). These same three tubes or pipes, 8a, 8c, 8e, receive the mixture of hydrazine and N.sub.2 from the interiolr of tube 7 as surrounding the jet, but not having entered capture tube 6. The N.sub.2 -hydrazine mixture is evacuated from the interior of MHD tube 7 via the suction type tubes 59 which connect to tubes 8a, c, e via tubes 66a, c, e. The slots 60 in the suction tubes can be closed by movement of (internal) pistons operated by servo-mechanism 61. The suction closing device is powered by an internal pressurized gas system and rendered operational if the non-gaseous phase in form of the free jet does not meet completely the jet capture tube 62 or fills the MHD-duct 54 to such a degree, that liquid overflow could cause mfd liquid to enter the ducts 49. This may occur, for example, during exergy transformer start up procedure. It should be mentioned that valves are provided in the connection between tubes 8b, d, f and chambers 44, which can be closed whenever the two phase-operation is to be interrupted. This may occur in an emergency when, for example, power is not extracted (for reasons of output failure) from the liquid jet in the MHD converter so that the jet would hit with its full impact the baffle 7a. That would produce a dangerous shock. However, upon interrupting the flow of pressurized tdf gas into the chambers 44, the acceleration of the liquid phase is interrupted. Please note that this emergency equipment was termed jet spoiler 200 in the block diagram of FIG. 8. Closing of slots 60 by mechanism 61 takes also place in this case and the latter equipment is part of the jet spoiler 200. As stated, the tubes 59 lead through the jet capturing chamber (in sealed relation) established by partitions 63 and into compartment N. Radially extending connecting tubes 66a, 66c, 66e discharge tubes 59 into pipes 8a, 8c, 8e as they extend to the right from the partititions 41 in these pipes along the M/N dividing line to run the hydrazine--N.sub.2 mixture out of the MHD generator portion. The low pressure N.sub.2 --tfd which separated in compartments H and J from the mfd liquid and flows along the outside of tube 7 containing the MHD generator, around tubes 8 and enters compartments N, surrounding here all of the pipe and tube sections 66 and 67. The high pressure tfd gas passes through pipes 8b, 8d, 8f and through and along the MHD generator without participation until reaching the mixing chambers 44 in compartment G as described, except that a small portion may be tapped to feed the annular space between tubes 54 and 7 in the MHD generator chambers J, K, L. The pressurizing of the decompressed tfd fluiding arriving in N so as to close the circulation of the gaseous phase of the MHD system is carried out in the compartments to the right of N. It should be noted that the jet capturing function is actually reinforced by the tubes 59 for the hydrazine and residual tfd-working fluid suction as well as by the tubes 65 for the mfd-working fluid leaving the capturing device. The radial fluid transfer means 66, 67, which are used in mixing chambers 44 are, in principle, the same as used here to conduct the exhausted mfd and tfd fluids to the tubes 8 of the supporting frame of skeleton construction. The transfer means 66 and 67 for both fluids are arranged in two's and are designed to compensate, in addition, the jet's thrust. The compartment N could best be described as the transition connection and isolation zone between the MHD generator (and hydrazine synthesizer), and the equipment for recuperative heat exchange and repressurization of the tfd fluid. The recuperative heat exchange is contained basically in compartment O with input/output sections in compartments N and P. The repressurization of the tfd gas--N.sub.2 occurs in compartment Q. The heat exchange in heat exchanger O occurs between the low pressure tfd gas before compression, and the same but compressed gas (N.sub.2). The heat exchanger serves additionally to serve as hydrazine condenser. The heat exchange chamber 70 proper is established inside of skin 13 with a particular internal jacket 68 and between two partitions 2. These partitions run, of course, the tubes 8 through the chamber, whereby particularly, tubes 8b, 8d, 8f have a certain section plugged by plugs 41a, b while ahead and behind of the plugs, but still inside chamber 70 openings discharge the pressurized tfd gas, N.sub.2, into chamber 70 and collect it again. The high pressure tfd gas arrives in pipes or tubes 8b, 8d, 8f in compartment P, enters chamber 70 and circulates therein as indicated by the helical line, while leaving chamber 70 into pipes 8b, 8d, 8f through the lefthand openings to the left of the lefthand plug 41a. While circulating in chamber 70 the high pressure tfd gas N.sub.2 undergoes heat exchange, i.e. is being heated by the low pressure tfd gas N.sub.2 which has arrived in compartment N and is run through heat exchange chamber 70 by a multitude of thin tubes 69, only one being shown in FIG. 32, the multitude is denoted by dotting in FIG. 34. That low pressure tfd was separated from the liquid phase ahead of the MHD generator and flowed around tube 7 thereof until reaching the compartment N. The high pressure tfd gas N.sub.2 thus flows around tubes 69 in chamber 70 to receive thermal energy from the low pressure tfd gas before the latter is compressed. The three tubes 8a, 8c, 8e are normally used to conduct the mfd-working fluid, but not in the compartments upstream of the compartment M. A plug 41 to the left of compartment N closes these tubes; so that these tubes, 8a, c, e, can be used downstream of compartment M for other purposes, the one of which is to conduct the hydrazine and residual tfd-working fluid as already described. That residual tfd fluid served initially as cushion between the liquid jet and the tube 54 in the MHD generator. By passing through the heat exchanger section 70 in tubes 8a, c, e, both gases will also be cooled. These three tubes are, therefore, to be understood to serve as hydrazine condensers and are, therefore, covered at the inner surface with a wick-like structure 72 for sucking the hydrazine already condensed as well as for enlarging the condenser surface. The heat exchanger will be fixed on the supporting frame by welding. The liquidous hydrazine as caught by the wick-like layer 72 is thereby prevented from following the flow of the residual N.sub.2 in tubes 8a, c, e and is collected in reservoirs 78 at the righthand border of compartment P. From there it can be withdrawn via tube 79 for flowing into a collection tank (not shown). The residual tfd gas N.sub.2 which also arrived in pipes 8a, c, e in compartment P is passed through connectors 77 into the central portion of compartment P in which end also the tubes 69 following heat withdrawal in chamber 70. Compartment P is, therefore, provided for (a) hydrazine collection and withdrawal and (b) collection of the cooled low pressure tfd gas N.sub.2. The additional function, namely feeding the high pressure tfd gas into the heat exchange chamber 70 from tubes 8b, d, f was described earlier. Before continuing with the functional description and particularly the pressurization of the tfd fluid, it should be mentioned, that FIGS. 32, 33, 34 show further examples for the application of the three standard tubes 7, 8 and 9 as well as of the two standard partitions 1 and 2 within the compartments N, O, etc. Both, the recuperative heat exchanger as well as the MHD-converter are units, have been integrated into the supporting skeleton which includes tubes 8; the outer jacket 68 of the heat exchanger is made by using two vertical partitions 2 for the front sides, which are welded with a longitudinal partition 1 thus forming a hexagonal prismatic embodiment. Before inserting the six tubes 8 of the supporting skeleton in this embodiment, the numerous small diameter tubes 69 have to be fixed in the vertical partitions 2 thus completing the heat exchanger; the small diameter tubes are the standard tubes 9 normally used for internal connecting piping, and are here used to conduct the low pressure tfd-working fluid through the heat exchanger. The vertical partitions 2, and the bottom plate covering the large middle-opening of the transition are perforated by holes with beaded edges necessary to affixed the small diameter tubes 69 by welding. In FIG. 35 the construction of module components from punched and deformed sheets is demonstrated in detail at the transfer portions 66 and 67. The same principle is used for the nozzles transfer mains 44, which are, in addition, mixing chambers for both the working fluids. The transverse sheets 73 and 74 are beaded at edges in the same manner the partitions 2 are made, and they will be welded first on those edges which touch the tubes entering and leaving the transfer mains; in a second step the sheet 75, which plays the same role the longitudinal transition 1 does on other place, will be stripped over and connected by weldings. Continuing now with the system description, compartment P contains also the entrance to the compressor, provided as a nozzle downstream and formed by sheets 76 (shown only in one case). It should be mentioned at this point, that the low pressure tfd fluid when flowing from compartment M to compartment N is subjected to a diffusor action because of sudden enlargement in cross-section. In M, gas N.sub.2 flowed around the MHD converter containing tube 7 which ends at the dividing line between compartments M and N. Some sheets, similar to 76 could be provided here to provide a more gradual transition to the larger flow area and cross-section in compartment N. The nozzle is formed by reducing the cross-section for tfd-working fluid flow in compartment P until the entrance cross-section of the isothermal diffusor 80 of compartment Q is reached. As stated above, the residual tfd-working fluid having accompanied the hydrazine, flows via the discharge outlets 77 into the main flow of the low pressure tfd gas in compartment P. The hydrazine, already liquified, is protected from being carried further by means of the wick-like structure, and as stated, will flow into the reservoir 78 to be emptied through the tube 79. The diffusor 80 for obtaining at least approximately isothermal compression of the tfd-working fluid N.sub.2 is located in compartment Q. In order to obtain isothermal compression of the tfd gas N.sub.2, it is caused to undergo heat exchange inside of and while passing through the diffusor. Before however describing that heat exchange, the completion of the circulation of the tfd gas N.sub.2 (closing of the loop of the gaseous working fluid) shall be described first. The low pressure tfd gas N.sub.2 as entering nozzle 76 of the diffusor is compressed in diffusor 80 and leaves it for compartment R, inside of a continuation section of central tubing 7. Three suction tubes 88 (FIGS. 36, 37) suck the pressuized tfd gas out of that chamber and transfer pipes 89 connect these three suction tubes to the three tubes or pipes 8b, d, f. These tubes transport the pressurized tfd gas N.sub.2 to the heat exchanger where it leaves these pipes temporarily for circulation in chamber 70 around tubes 69, and returns to tubes 8b, d, f for transport to the mixing chambers 44! This then completes the circulation of the tfd fluid--gas N.sub.2. The particular portion of the tubes 8b, d, f used otherwise for N.sub.2 gas recirculation, are closed with a plug 41 in regard to the compartments S, T, . . . ; this section houses the valves and their servo-mechanisms, not shown here, for shutdown of recirculation. This way these particular tubes 8, reserved otherwise for gas recirculation, can be used at night as reservoir for already pressurized tfd-working fluid. Appropriate valves are installed within the transfer ducts for the gas, coupled in action with the valves of the duct for the mfd-working fluid 1, which is the central tube 7. The FIG. 28 shows bellows 91 of the valve drive mechanism. The internal pressurized gas servo system is not shown here, as this is optional equipment not needed in principle. The tfd fluid N.sub.2 while being subjected to compression in diffusor 80 is additionally chilled through intimate contact with a fluid termed in the following mfd-2. The reason for referring to this fluid as a magneto-fluid-dynamic fluid is to be seen in that it is or at least could be pumped as a coolant by means of a MHD type pump. The mfd-2 fluid is preferably Li(NH.sub.3) and enters the flow of compressing tfd-N.sub.2 in diffusor 80 of compartment Q. In particular, the walls of diffusor 80 are porous in order to permit the mfd-working fluid 2 to leak from its reservoir 81 in the back and around the diffusor 80 into the flow of N.sub.2, for intimate mixing therewith. Droplets of mfd #2 are actually carried along by the flow of gas, thereby causing this mfd #2 liquid to be accelerated and moved. The inner surface of the diffusor is actually enlarged by a wick-like structure 82 made from wire gauze, and the mfd-2 liquid discharges therefrom into the diffusor interior for evaporative cooling of the compressed tfd gas N.sub.2 while intimately mixing therewith. This cooling of the tfd fluid establishes its low temperature so that the compression work is minimized (see equation 3--supra). This cooling process leads to the lowest temperature of the tfd fluid, but involves comparatively little heat transfer in the steady state, as the low pressure tfd fluid has lost recuperatively heat exergy to the high pressure tfd fluid in heat exchanger 0. The mfd-2 fluid arrives at compartment Q from compartment R via tubes 8a, 8d, and 8e. Please note that these tubes are not used otherwise in compartments Q and R, plugs 41 in the dividing plane between compartments Q and P retain the hydrazine--N.sub.2 flow in these pipes 8a, d, e in compartment P (arriving there from N and O). The mfd-2 coolant will be pumped either by MHD-pumps, not shown here, or moves by capillary forces into these pipes 8a, d, e and in compartment R. It will be recalled, that the pressurized tfd gas N.sub.2 is collected in the central chamber of compartment R. Actually, the compressed gas N.sub.2 is subjected to strong baffle action when entering compartment R and hitting cold wall 85 so that liquidous or condensing components (including e.g. carried along (NH.sub.3)) drops off and is not returned. The mfd-2 fluid arrive in the same chamber. This coolant mfd-2 precipitates on the surface of cold fingers 86 and is caught by the wick-like gauze layer 82 and seeps through ducts 87 into the space, outside of tube section 7 around tubes 8 in compartment R. From there, the mfd-2 fluid is pumped, as stated above, by means of MHD pumps or by capillary forces into tubes 8a, d, e for return to compartment Q. This then completes the circulation of the mfd-2 fluid. The primary function of the mfd-2 fluid (Li(NH.sub.3)) is to provide for isothermic conditions for the compression of N.sub.2 in diffusor 80--compartment Q. The mfd-2 fluid receives heat in this process which is to be removed from that fluid in a manner described shortly. Presently however, it should be described that mfd-2, i.e. the Li(NH.sub.3) performs an additional function. The tfd-gas N.sub.2 following its separation from mfd-1 fluid in compartment I and also in compartment M will carry certain portions of the mfd-1 fluid as non-gaseous component, and here particularly, Li(NH.sub.2). That component is carried along, enters even diffusor 80 and will go into solution in the dispersed mfd 2 fluid. Other substances, e.g. may have been removed from the tfd flow by baffle action in compartment R, as the pressurized tfd gas N.sub.2 was being returned and any precipitation was collected and removed in the lining 82 in compartment R along the wall of tubing 7 and discharged therefrom through openings 87. All accumulated liquid is then pumped from compartment R back to compartment Q, through tubes 8a, 8c, 8e. These particular portions of tubes 8a, 8c, 8e in compartment Q are used also to house a regeneration device 83, in which the carry over of mfd-working fluid 1 in form of Li(NH.sub.2) should be eliminated. This device 83 is made from sheets or sintered components of the elements Ca or Mg and absorbs by chemical reaction the NH.sub.2 -groups dissolved within the mfd #2 coolant Li(NH.sub.3). By the action of this regeneration device the Li-content of the mfd-2 liquid increases continuously. Preferably at night, when the exergy transformer is not in operation due to lack of exergy supply, the trapping material of regenerator 83 has to be regenerated; for example, by thermal dissociation of the metal-amides formed during the daytime operation, into NH.sub.3 and N.sub.2. In addition, the deposited lithium has to be flushed out. The regeneration device 83 is connected for this reason not only with the reservoir 81 for mfd-2 (=Li-NH.sub.3) but connection is to be made also to feed the excess lithium back into the reservoir for mfd 1 fluid. For this, one can use the tube 34 which passes N.sub.2 and H.sub.2 into the system but is not used in the night time. Thus, tube 34 will be connected with regenerator 83 during the night to feed the Li into compartments A, B, C, D. The regeneration device 83 has to provide both, the recirculation of NH.sub.3 formed in excess as well the recirculation of Li accumulated in the coolant mfd-2 liquid (Li-NH.sub.3), back into the mfd-working fluid 1 as resting at night. Both components are dissolved at low temperature and will be transported in liquid phase via the line 34 into the mfd-1 reservoir; the reaction of the NH.sub.3 -component with Li to form Li-amide and H.sub.2 takes place at higher temperature, in the morning. This double use of line 34 does not interfere with the injection of N.sub.2 and H.sub.2 along the same line 34 for the synthesis of hydrazine, for these processes take place only at daytime. FIGS. 36 and 37 show the separation-chamber and heat exchange chamber between primary and secondary coolant and contained predominantly within the compartment R; this component, again, is composed from the standard tubes and partitions. The primary coolant is the fluid mfd-2 and the secondary coolant is provided for external heat exchange, for example, with air. The reason for this separation is to be seen in the necessity of removing spurious components of mfd 1 fluid from the tfd-gas as outlined above and the mixing of the latter with the coolant (mfd-2) necessitates provisions for the cleaning process. This particular circulation of mfd-2 fluid should be held as short as possible to prevent the mfd-1 residue from clogging the circulation ducts. This is the reason for not using mfd-2 also in direct heat exchange with ambient air (requiring large areas and zones for flow). Basically, however, the cooling process undertaken by mfd-2 is the primary one and determinative of the low point in temperature for the tfd gas N.sub.2 ; the other coolant is merely provided as heat transport and decoupling agent due to the aforesaid additional function of the mfd-2 circulation (mfd-1 residue capture). The recompressed tfd-working fluid N.sub.2 (leaving the isothermal diffusor) is reversed in flow direction in the central tube 7 inside of compartment R and distributed into the three tubes 8b, d, f of the main frame. The chamber wall 84 is made of a section of the central tubing 7, and is welded into two vertical partitions 2, constituting therefore a part of the support frame. In addition, the coolant fluid, called mfd-2 and providing for the isothermic compression of the tfd-gas, is separated from the compressed tfd gas N.sub.2 as was outlined above and pumped back through the regenerator 83. Still in addition now, the mfd-2 coolant is to be cooled itself by means of the secondary coolant, circulating through compartments R through Y. In order to obtain immediate heat exchange between mfd-2 (primary coolant) and secondary coolant--hollow fingers 86 are inserted into the chamber defined inside tube section 7 of compartment R. These fingers extend from a bottom plate 85. Fingers 86 are also made from the thin standard tube 9, which were also used in the recuperative heat exchanger (69). The hollow fingers 86 thus penetrate the interior of the said separating chamber in compartment R and are cooled from the inside by evaporation of the secondary coolant flowing therein. The secondary coolant can also be Li(NH.sub.3) or any other suitable coolant which will evaporate on heat exchange with the mfd-2 fluid but can be condensed by heat exchange with ambient air. It was mentioned above that all surfaces of the separation chamber are covered with a wire gauze 82 of wick-like structure; the primary coolant, when condensed at the cold fingers, leaks within the capillaries of wick to pass through the suction slots 87, and then to MHD-pumps, not shown here, which pump the now liquidous mfd-2 coolant through the regeneration device 83 into the reservoir 83. The central tube 7, forming the separation and heat exchange chamber in compartment R, is extended into the compartment S and has a cylindrical, hollow insert 92, serving as recipient chamber for the evaporated secondary coolant. This insert 92 is closed by the bottom sheet 85, which in turn is penetrated by the hollow cooling fingers 86 communicating with the interior of insert 92. These fingers are welded onto beaded edges of holes in the bottom plate 85. Insert 92 constitutes a structural unit and will be shifted into and welded to the central tube 7 at their respective righthand ends. The secondary liquid coolant Li(NH.sub.3) is supplied via the pipe 83 from the compartments T, U . . . and distributed to the various hollow fingers 86 for evaporation therein. As shown for one finger, but is valid for all, an inner coaxial tube 94 in each finger leads the coolant to the tip of the finger 86, where it leaves the respective tube 94 in order to wet the internal surface of the finger for evaporation. The vaporized coolant is collected in the gas chamber of insert 92 and is passed by means of three radial ducts 95 into three of the six tubes 8 in chambers S, T, etc. and running through an air cooler therein. It should be mentioned at this point that all of the six tubes 8a through f are plugged by means of plugs 41 along the dividing line between compartments R and S. The tubes 8a, c, e hold primary cooling fluid (mfd-2=Li(NH.sub.3)) to the left of these plugs, and tubes 8b, d, f pass pressurized tdf fluid --N.sub.2. All tubes 8 to the right of these plugs in the dividing plane between compartments R and S are available for passage of gaseous secondary cooling fluid (evaporated Li(NH.sub.3)). Only three of the tubes 8 are actually used for feeding the evaporated secondary cooling fluid into the cooler (compartments U et seq); the other three tubes 8 are used as store for liquified secondary coolant, and pipes 93 return the liquified secondary coolant to the fingers 86. The free space 21 between insert 92 and the vertical partition 11, holding the righthand axial end of outer skin 15 communicates with the gap 20 in axial direction. Due to the fact that the outer skin 15 will not be thermally extended and contracted to the same extent the inner skin 13 will probably be, the vertical partition 11 is not directly welded to the tubes 8, but indirectly through interposed, length compensating bellows 96. The bellows, however, are placed between compartments S and U, and the righthand end of bellows are fixed to the tubes 8 at the end of compartment T by means of welding seams 99. The gap 20 (filled with protective gas at very low pressure) is continued within the bellows. All parts, including the tubes 8 of compartments T, U . . . are not covered by skin and are, therefore, exposed to ambient air. The central opening of a particular vertical partition 11 is normally used for receiving the central tube 7, but that opening is closed in compartment S by means of spherical deformed sheet 97, positioned for exposure to the surrounding coolant air flow. In this half-sphere, the ion-getter-pump 98 is installed, which has to provide the very low pressure for the gas circulating in gap 20 between the inner and outer skins 13, 15 respectively. The heat exchanger in FIGS. 38 and 39, operating as between the secondary coolant Li(NH.sub.3) and ambient air occupies all of compartments U, V, W, X and Y, as well as the air flow outlet in compartment T. The heat exchanger is likewise made from the standard parts employed throughout and will be installed as a unit and connected to the main portion of the MHD-module by the welding 99. The heat exchange unit is composed from the six standard tubes 8, the central tube 7 and from modified longitudinal frame parts 1. Three of the tubes 8 are used for the transfer of the gaseous secondary coolant; slots 100 permit the gas to pass through and to touch the inner surfaces of the heat exchanger for condensation. The other three tubes 8 are used as a reservoir for the liquified secondary coolant, pumped into by a MHD-pump 101. The tubes 93 take the liquidous secondary cooling from these tubes. The longitudinal transition 1 is shown slightly modified. It is composed from the segments 102 and 103, which serve here as outer and inner skin, respectively, of heat exchanger; both these segments are deformed in a way resulting in channels 104 and 105 offering a maximum surface area to the coolant air. The segments are, for this reason, as well as for stabilization, corrugated (in the same manner as the corrugated sheet 14 for the reinforcement of inner skin 13). Both segments are joined at lips 106 by weldings. The segments will be covered before assembling on their inner surfaces with a wire gauze 107 with wick-like structure providing enlargement and also wetting of the surface. The coolant air is supplied from the compartment Z (not shown here), which is coupled to the air duct. The air leaves the MHD-module at compartment T. The hoods 12 house the sensors for control of continuous air flow. One condition for the exergy transformers operation is to focus solar radiation on the entrance heat exchanger of MHD-module resulting in an increase in flux density by a factor of 1000. A second condition is to supply the MHD-modules with cold air in large quantities for removal of the waste heat of MHD-process; a third condition is to separate both N.sub.2 and H.sub.2 O from the coolant air (in cases where no water is available at ground level) to be the ducts for exergy storage. There are two solutions to the problem, depending upon the location of the exergy transformation: if the transformer is to be used in the arid or tropical hot zones between, say 30.degree. and the equator, then the problem is to a lesser degree the availability of solar radiation, due to the climate, but the availability of water if the transformer is to be used in the moderated zones between say 30.degree. and 60.degree. latitude, then the availability of solar energy is the more dominant problem due to frequent clod covers. In either case, the solar exergy must be focussed. After having described the equipment by means of which to use solar (or other nuclear) exergy for obtaining the synthesis of hydrazine, several of the critical aspects of the operation and of the process as a whole shall be discussed and here particularly the interaction of the fluids and of the magnetic fields as well as the overall MHD conversion process. It will be recalled from the description of FIG. 8, that the gaseous medium tfd-fluid, N.sub.2 has a central position. From the description above it can readily be deduced how the gaseous phase and medium called tfd actually drives the two liquids, mfd #1 and 2. In one case (mfd #1) the liquid is accelerated out of the mixing chambers 44 by means of the nozzles 45, in the other case, the tfd gas actually causes the mfd #2 liquid to evaporate and to otherwise mingle with the gas in the diffusor 80 thereby actually driving the liquid (mfd #2) as part of and within its circulation. In both instances there is a generalized thermodynamic force as a result of a temperature difference between the tfd gas and the respective mfd liquid; in both cases there is isenthalpic pressure change, expansion in one instance, compression in the other. The three essential properties of the interaction between tfd and mfd fluids, particularly the tfd gas and the mfd liquid are depicted in FIG. 9. There is a close analogy with the electromagnetic interaction between the magnetic field as set up by the coils 49 and the self-consist or eigen field of the mfd #1 liquid jet. These interactions are interactions via forces resulting from local non-equilibrium. These forces require certain energy which is lost otherwise. The interactions can be weak or strong which depends on the ratio of transferred exergy by operation of the interaction in relation to the total exergy content of the media (or fields). The strength of the respective interaction is adjustable by means of adjustment of some of the parameters that determine the process. The work ability a.sub.exp (exergy content) of the tfd gas is transferred by means of the viscous interaction with the mfd #1 liquid in mixing chambers and nozzles (44, 45) as follows: kinetic energy as imparted upon the mfd #1 droplets: kinetic energy of the tfd; internal losses to sustain the interaction. The forces X; of the interaction result from local imbalances or non-equilibrium such as the velocity differences of the two fluids. As a consequence, a momentum I is produced by operation of thermodynamically irreversible processes. The products of forces and flux (of momenta) is the loss of exergy needed to sustain the interaction. ##EQU14## The exergetic efficiency of the viscous interaction in the two phase nozzles 45 as the sum of the respective efficiencies for either fluid results in ##EQU15## wherein the single (') refers to the mfd #1 liquid and the double (") refers to the tfd gas. The viscous interaction in the exergy transformer as described is adjusted to be strong (in contradistinction to known MHD process) operating with a plasma or a liquid metal-gas emulsion as MHD work fluid. Specifically, the exergy transferred from the (expanding) tfd gas to the mfd #1 liquid is so large that both media assume comparable specific kinetic energy following interaction in the nozzles 45. The decisive parameter in FIG. 9 is the relative proportion X of the tfd fluid in relation to the total mass flow. ##EQU16## for 0.2<.times.<0.3, i.e. to the right of the maximum of the specific kinetic energy e".sub.kin of the mfd #1 fluid, one obtains the strongest interaction. For X.fwdarw.0 (gas-metal emulsion) as well as for X.fwdarw.1 (plasma process) the interaction approaches zero. The two fluids employed here are predominantly Li and N.sub.2. They interact in a temperature range between 750.degree. K. and 850.degree. K. One can in fact obtain a ratio of .phi.'=e'.sub.kin /x.multidot.a.sub.exp =0.5 and .phi."=e".sub.kin /x:a.sub.exp =0.3 with a total nozzle efficiency .phi..sub.nozzles =0.8. Using e'.sub.kin and e".sub.kin separately is the logical result of a strong viscous interaction. Since the tfd gas (N.sub.2) has transferred in nozzles 45 the maximum possible exergy and is "exhausted" in this respect, it would not serve any purpose to run both fluids through the MHD converter process. This is quite different from MHD processes with weak viscous interaction. It is for this reason that one separates the fluids in compartment J. This in turn permits the utilization of e".sub.kin of the tfd gas for obtaining the isothermic compression in compartment Q, at low temperature. The specific kinetic energy e'.sub.kin of the mfd-working fluid 1 is extracted in form of electrical energy in the course of the electro-dynamic interaction in compartments K and L. FIG. 10 shows the transfer of compression work. In analogy to the viscous non-equilibrium interaction between the tfd and mfd #1 fluids; I now proceed to the description of the electromagnetic interaction in the MHD generator. The working fluids of the exergy transformer are separated in compartment I by means of two steps. In the first step the homogenous distribution of both fluids--as can be found within the two-phase nozzles--will be disturbed downstream of the nozzle. This has been achieved by the parallel operation of the several nozzles 45 all oriented towards an axis and to point of convergence 152, common to all nozzles. The non-gaseous phase has a much higher density and, therefore, higher inertia than the gaseous phase; it tends to maintain the initial direction concentrating itself in the neighborhood of the axis common to the nozzle system upstream of the point of convergence, while the gaseous phase expands to fill the empty space of compartments H and J around the free jet being formed. Within the area of jet formation X.fwdarw.0, outside of the free jet in being X.fwdarw.1; in both these regions the strength of viscous interaction decreases continuously. Due to the components of velocity of the converging stream normal to its (desired) flight direction, and due to some residual weak viscous interaction a compact liquid mfd-free jet will not be formed spontaneously; the gaseous phase, at the other hand, will be expanded further as caused by the increase of cross section (compartment N) for flow towards to the suction channels. The second step of separation results by electro-magnetic interaction. Kinetic energy of the mfd #1 working fluid is extracted and re-supplied in form of electrical energy; by this, forces are exerted on the different droplets performing work to stop motion normal to the bulk (axial) flight direction, causing them to coagulate. The MHD-converter proper can be defined as that area of the exergy transformer, in which the electrodynamic interaction takes place in order to extract kinetic energy from the mfd-working fluid #1 and to transfer it (via the systems boundary) in form of electrical energy. The MHD-converter is composed from numerous annular coils 49, which surround the mfd-working fluid #1 flowing free, concentric to the center axis of the system. The entrance of the coil system is located near the point 53 of convergence, upstream thereof and in a region, in which the free flowing mfd-working fluid is not yet a compact jet. As stated above, the distance between the different coils 49 decreases in flow direction while their diameter increases. The coils are inserted into statorblocks 48 formed of comb like construction so that, on the one hand, the magnetic field is guided for travelling along but outside of the free jet, and on the other hand forces are transferred from the free jet to the exergy transformer coils. The coil system is a three-phase system, in general excited with the same constant frequency f, and is coupled with a capacitor bank to be able to oscillate self-excitedly. Electro-magnetic energy is shifted periodically between the coils and the capacitors; the magnetic field generated by the coils forms in total a magnetic wave or travelling field with a phase velocity decreasing in direction of motion: ##EQU17## .lambda. is proportional to the distance of coils, .omega.=2.pi.f, k=2.pi./.lambda. (wave-number). The electro-dynamic interaction caused by this device, is essentially an interaction between two magnetic fields, which are the field B.sub.extern of the coils and the field B.sub.eigen carried along with the mfd-working fluid 1 at the velocity of fluid v.sub.fluid. The exergy transferred during interaction is energy of the electro-magnetic field. The reason for including coils as well as the mfd #1 liquid in the interaction is to be seen in that both of them are the conductors for electric currents which in turn generate the magnetic fields. The mfd-working fluid, in addition, supplies the exergy to be transferred during interaction at the expense of its kinetic energy. The interaction is based--in the same way as does the viscous and thermal interaction--on a local non-equilibrium, given by the relative velocity (v.sub.fluid -v.sub.phase) between both magnetic fields. At the origin of the second field, within the mfd-working fluid #1, an electrical field E is generated (due to the transformation of the homogenous Maxwell-equations for an inertial system in motion): ##EQU18## The electrical field exerts a force on the electrical charges within the fluid, and it is this force, which is the generalized force of interaction--not the Lorentz-force. The resulting (generalized) flux is the electric current, given by the electrical conductivity .sigma. of the mfd #1 working fluid; the specific current density j is (due to the fact, that the velocity vectors are parallel in this interaction): ##EQU19## s is the slip defined by--s=(v.sub.fluid -v.sub.phase)/v.sub.phase. The specific internal consumption for sustaining the interaction, eigenconsumption of interaction, is given by: ##EQU20## Exergy for extraction is transferred during interaction by the field B.sub.eigen. That field B.sub.eigen can be calculated from the inhomogenous Maxwell-equation with j to be the source-term. B.sub.eigen is shifted in phase in regard to B.sub.extern by a phase angle of .pi./2. This is the reason, one can calculate the amplitude .vertline.B.sub.eigen .vertline. from the other amplitude .vertline.B.sub.extern .vertline. without considering the total field B.sub.total : ##EQU21## (j.sup.2 =-1) The ratio of both amplitudes is: ##EQU22## with R.sub.m =.sigma..multidot..mu..multidot..mu..sub.o .multidot.v.sub.phase /k being defined as magnetic Reynolds-number. .mu..sub.o =.pi.4.multidot.10.sup.-7 Vs/Am, .mu.=relative permeability of the liquid. The stability of interaction leads to the condition: ##EQU23## .+-.s.multidot.R.sub.m =1 is the condition for maximal strength of interaction; in this case is .vertline.B.sub.eigen.vertline. =.vertline.B.sub.extern .vertline., and the energy of the field is proportional to: ##EQU24## The power factor of interaction is given for .+-.s.multidot.R.sub.m .ltoreq.1: ##EQU25## The maximum value is (in this first order approximation) cos .phi.=1/.sqroot.2=0.705. The exergy for this interaction is used both for internal, i.e. eigenconsumption and, to a much larger extent to maintain the local non-equilibrium which means the continued generation of the field B.sub.eigen from the current-density j within the mfd #1 working fluid. This second part can be calculated from the specific force exerted by the external field via the currents j upon the liquid: ##EQU26## To shift the mfd #1 working fluid at the velocity v.sub.fluid under the (retarding) influence of this force, the specific work ##EQU27## has to be performed, and will be taken from the kinetic energy of the fluid. Inertia force of fluid and Lorentz-force have, therefore, to compensate each other. The net exergy transferred during interaction is: ##EQU28## The exergetic efficiency of interaction is given by (the well known formula): ##EQU29## This electro-magnetic interaction as described thus far does not include the stabilization of the free jet--focussing of mfd #1 working fluid to obtain a compact jet, guidance and focussing when flowing within the coil system--nor does it include the electro-synthesis of hydrazine. All these different processes consume exergy for the work to be expended on and in the jet; this work must be performed also by making use of the above discussed interaction, because the jet flows freely and is not in contact with any wall! For this purpose, additional generalized forces according to equation (18) have to be generated by local variation of the slip -s and of the external B.sub.extern. The exergetic efficiency .phi..sub.converter of the non-idealized interaction is always lower than .phi..sub.MHD, for this number is related to an infinitively extended undisturbed field and a constant slip. It should be noted, that the slip -s of the MHD-converter is not constant (locally) even without stabilization of jet for the following reason. If all the coils 49 were to be excited with the same frequency f, then the phase angle between voltage and current should be the same for all coils. This, however, means that .vertline.B.sub.extern .vertline.=.vertline.B.sub.eigen .vertline. and, hence, -s.multidot.R.sub.m =1. Because R.sub.m is proportional to v.sup.2.sub.phase /.omega. and must decrease along the fluid path, the condition of a constant phase angle, .phi.=const. can be met only by increasing the slip in flow direction! The focussing of flow at the entrance of MHD-converter is achieved by changing the sign of the slip s as well as by proper adjustment of field B.sub.extern at the entrance section J (which can be supported by a surface separator upstream). The jet as formed thereat runs over a distance of a few wavelengths under-synchronously, not over-synchronously, exergy is supplied to the jet at that point; the distortion of the magnetic field lines at the entrance to the converter results in focussing forces k.sub.Lorentz acting on the fluid particles in which a current can flow. For this purpose the first coil or the first few coils, adjacent the entrance (compartment J) are not excited together with the other coils; the phase velocity of the magnetic wave and its harmonics can, therefore, be controlled independently. A similar method can be used for augmenting the synthesis of hydrazine; it is possible, as an example, the last part of the coil system of MHD-converter to operate in the brake-mode by reversing the phase velocity. This method also might be based on a separate excitation of that part of coil system. After having described viscous and electromagnetic interactions, I now turn to an overview as well as details of the principles of the MHD-process within the exergy transformer and regarding MHD-converter, two-phase nozzles 45, recuperative heat exchanger (compartment O) and the diffusor 80 for recompressing the tfd gas. It is the advantage of the free jet MHD-converter operating with a radial field, that the jet will be stabilized in the direction of axis of coil system. The currents induced are annular currents and flow anti-parallel to those in the coil for excitation. The problems resulting from the use of side bars and of finite width as known from flat channel type MHD-converter have been avoided. A real problem is posed by the condition that the external magnetic field must be closed by means of and through the jet; the flux density being necessarily very high. This is a reason for limiting the wavelength; this length should not exceed in average 0.1 m. The high velocity of the fluid has as a consequence that the MHD-converter will be operated at a frequency in the kHz-range. Due to the skin effect in Cu, the currents will penetrate no more than 0.5 mm; the coils 49 are actually made from small tubes with a thin wall, cooled inside by a coolant. For .lambda..sub.average =0.1 m, v.sub.phase average =250 m/s follows f=2.5 kHz. The electrical conductivity of Li is at 750 K about .sigma.=10.sup.7 1/.OMEGA.m; for the Li-LiNH.sub.2 solution .sigma.=10.sup.6 1/.OMEGA.m is a good estimate. The magnetic Reynolds-number is: ##EQU30## wherein .mu. is the permeability of the mfd #1 liquid. That liquid is made to assume a permeability by adding modest quantities of iron to serve as the catalyst for the Li-NH.sub.2 -synthesis as well as the bipolar electrodes for the Li-NH.sub.2 -electrolysis. The use of iron can also solve the problem of a strong electro-magnetic interaction even within the free jet MHD-converter of the exergy transformer. The specific work a.sub.MHD performed during interaction (27) is related to unit volume while the specific kinetic energy of the fluid v.sup.2.sub.fluid /2 is related to unit massflow. Therefore, in the steady state of operation, the specific work of interaction, integrated over the volume of the free jet, must be the same as the difference in total kinetic energy of the jet and before and after the interaction: The first basic condition for the exergy transformer is: ##EQU31## The condition (30) can be met under the following assumptions: ##EQU32## then: ##EQU33## the only free parameter is .mu., which is the permeability of the liquid to which iron particles have been added. Under the stated conditions, the parameter is .mu.=4.9. Since iron has a permeability roughly between 100 and 1000, rather small quantities of iron particles suffice to obtain that low permeability for the liquid as a whole. Under these assumptions the power density of electro-magnetic interaction within the free jet converter amounts to 2.56 kW/cm.sup.3, the average magnetic Reynolds-number R.sub.m .apprxeq.25, the average slip -s=0.04, the average slip frequency -s.multidot.f=100 Hz, the average loss density (in form of heat) is about 100 W/cm.sup.3 (equivalent to the power density within the blanket of a fast breeder reactor). The specific kinetic energy of working fluid at entrance is v'.sub.in.sup.2 /2=61.5 Ws/g. A free jet with an entrance diameter of d.sub.in =3 cm has a fluid power of about 15 MW if increased in diameter to d.sub.ex =6.7 cm. Due to -s<<1 is .phi..sub.MHD .apprxeq.1.0. Under the assumption of a more realistic exergetic efficiency of MHD-converter of .phi..sub.converter =0.75 the net electrical power extraction is N.sub.electrical =11.2 MW. The induced electrical field E.sub.average is given by equation (18) and for the brake-mode with s.gtoreq.1, .vertline.E.sub.average .vertline..ltoreq.2.5 V/cm, which is sufficiently high for the LiNH.sub.2 electrolysis with its specific exergy consumption of about 2.2 (electron) volts. S.gtoreq.1 results from phase inverted connection of the coils more downstream, but excited with and by the same frequency and preferably included in the oscillator coil-capacitor system as a whole. The residual kinetic energy of both the tfd- as well as the mfd #1 working fluid will be needed for the recirculation of these fluids using diffusors realizing the ram-jet principle. However, about 90% of the recompression is used to bring the tfd gas back up to the operating pressure for isenthalpic expansion in the nozzles 45. The total kinetic energy of both fluids, at the end of viscous interaction (15) amounts to: ##EQU34## Kinetic energy will be extracted from the mfd #1 working fluid within the MHD-converter according to equation (30): ##EQU35## The tfd-working fluid is, of course, not affected by the processes within the converter. The residual kinetic energies are: ##EQU36## The principle of ram-jet operation demands, that the residual energy of the respective working fluid covers both the theoretical compression work, the internal, eigenconsumption as well as work for recirculation within the loop. The second basic condition for the exergy transformer is: ##EQU37## The condition (34a) for the mfd #1 working fluid (which is the basis for the project MHD-staustrahlrohr*) with an one-component mfd-working fluid) has been met without any major difficulties. The compression work is calculated to be a'.sub.comp =(p.sub.upper -p.sub.low)/.rho.'.sub.mfd due to the incompressible fluid. The theoretical stagnation pressure is for the assumptions made before about 28 bar, which is sufficiently high to tolerate high exergy losses by the jet capture in compartment M; the residual energy is 0.04 times the kinetic energy of the working fluid before entering the MHD-converter. FNT *ram jet tube The condition (34b) for the tfd-working fluid, however, is the critical one and is decisive for the realization of the exergy transformer. In the case of isothermal compression in diffusor 80 according to (2) and (3) one obtains compression work to be equal to: ##EQU38## The residual kinetic energy at the termination of viscous interaction is characterized by .phi.".sub.nozzle following (15); one can describe the exergy necessary for eigenconsumption during compression in diffusor 80 and recirculation--including friction losses within the recuperative heat exchanger--by introducing the exergetic efficiency: ##EQU39## using (35), the condition (34b) reads: ##EQU40## In case of this exergy transformer the condition (36) has to be fulfilled by controlling the strength of viscous interaction varying the ratio x/(1-x)=m.sub.tfd /m.sub.mfd of both fluids as well as by choosing proper the ratio of densities .rho.'/.rho." (at beginning of expansion). If 0.4.gtoreq..phi.".sub.nozzle <0.45 (see FIG. 9) the parameter x can vary between 0.2 and 0.3. The permissible range, in which .phi.".sub.ram jet may change is for T.sub.upper =750 K and T.sub.low =250 K: ##EQU41## For a temperature of 300 K, the figures vary only by about 20%. These numbers can be reached by an adequate design. Due to the following relations: ##EQU42## the specific expansion work can be calculated; using x=0.3; .phi.'.sub.nozzle =0.4; .phi.".sub.nozzle =0.43 the expansion work is a.sub.exp =360 Ws/g; from this the exit velocity of the tfd-working fluid follows to be v".sub.ex =557 m/s according to the specific kinetic energy v.sub.ex ".sup.2 /2=155 Ws/g. After separation the tfd-working fluid approaches the velocity of sound ##EQU43## In order to reduce the friction losses during recuperation according to the limits given by the second condition (34b) or (36) respectively, the velocity of the tfd-working fluid has to be decreased by adiabatic deceleration within diffusor (compartment N). The eigenconsumption of exergy for the recuperation can be approximated applying the Reynolds-analogy between the specific heat flux and the shear-tension: ##EQU44## v" is the velocity during recuperation, .DELTA.T" is the temperature difference between hot and cold fluids, .xi. is a factor describing shape of heater tubes. (37) is the second term of the right side of equation (35) for .phi.".sub.ram jet ; this term should not exceed 0.1. For .xi.=0.81, .DELTA.T"=50 K must be, therefore, v"=35 m/s. FIG. 11 is an temperature-entropy diagram for both the tfd-working fluid N.sub.2 and the mfd #1 working fluid Li-LiNH.sub.2 -Fe. The tfd-working fluid is decelerated and adiabatically after separation from the mfd 4/ working fluid, before recuperation (compartment N); when leaving the recuperative heat exchanger (compartment P) it will be accelerated again. The rise in temperature caused by deceleration is used for heat exchange in compartment Q. The pressure ratio .pi. can be calculated from the ratio of the expansion work utilized a.sub.exp =360 Ws/g to the maximum possible expansion work R.multidot.T.sub.upper .multidot.ln.sub.max =750 Ws/g: ##EQU45## It is .pi.=5.35. The specific compression work is a".sub.comp =120 Ws/g. The tfd-working fluid entering the diffusor 80 (after loosing thermal energy in the recuperator) has to be cooled, which is achieved by evaporation of the NH.sub.3 component of the mfd #2 working fluid and at high velocity in the frontal portion of diffusor 80. In this case the viscous interaction is, however, weak, due to both the low densities and low fraction of NH.sub.3. It will be recalled, that the mfd #2 working fluid is basically a coolant. The process in the diffusor 80 is comparable to that within a heat pipe. The range of parameters of this process has to be selected in such a manner, that the local vapor pressure of NH.sub.3 and the pressure of N.sub.2 equalize only after the tfd fluid velocity has been decreased substantially. Thereafter, cooling by evaporation will be replaced by cooling on wetted surfaces. The variation of thermodynamic states of the mfd #1 fluid results from its function to be a heat storage medium; it follows: ##EQU46## c.sub.p '=4 Ws/gK (specific heat at constant pressure of Li-LiNH.sub.2); .DELTA.T' (temperature range of heat storage). Under the assumptions made before .DELTA.T'=38.5 K follows. The total efficiency of the process in the exergy transformer should be related to the conversion of the solar radiation absorbed to the electrical energy at exit of the coil system; it is defined, using (8) and with N.sub.el being the net electrical energy of the MHD-converter: ##EQU47## If the efficiency .phi..sub.MHD of interaction will be supplemented by considering total eigenconsumption, and if the slip s is understood to be the local slip, then the effective efficiency .phi..sub.converter can be defined by using the first basic condition (30) as follows: ##EQU48## The total efficiency .eta..sub.th can be decuded directly from (32), provided the second basic condition (34a+b) is actually met: ##EQU49## From the data mentioned before one finds .eta..sub.th =0.288; from this, the exergetic efficiency of the process is determined to be .phi..sub.process =0.432 due to .eta..sub.c =0.666. It is well known that processes in MHD-systems running both on lines of constant enthalpy and on isobares, will have a total efficiency, which is--in theory--comparable to those in nuclear power stations. MHD-systems of this kind, however, have been based on a weak viscous interaction maintained within the MHD-converter proper parallel to the electro-magnetic interaction which is, therefore, also a weak one (extraction from d.c. power at R.sub.m <1). These systems can hardly be operated without movable boundaries (turbines as well as compressors). To summarize and conclude: The substantial improvement of the present MHD-process within the exergy transformer expressed by the high total efficiency if compared to the well known MHD-processes with condensation of the tfd-working fluid and recirculation by the ram jet principle, is achieved by utilizing the residual kinetic energy of both fluids. In addition, recuperation takes place independent from the expansion in the nozzles. It is important to note, that the electro-magnetic interaction includes separation of the two working fluids, and that this interaction takes place at high velocities and with high frequencies based on a free flying jet. The increase of the magnetic Reynolds-number R.sub.m up to 25 by ferromagnetic components of the mfd-working fluid #1 helps to solve the (old) problem of adapting the thermodynamic acceleration of the tfd-working fluid to the energy extraction in the MHD-converter, which was solved in all known liquid-metal-MHD-systems only by tolerating very large losses of exergy. It should be noted at last, that the exergy transformer will be operated in a technical most feasible relatively low range of temperatures which so far as not attainable to the systems mentioned before with both a strong viscous and electromagnetic interaction. .eta..sub.th according to (41) is not the total efficiency of the exergy transformer, or, in other words, is not the efficiency of the storage of solar exergy in form of free enthalpy of the chemical compounds (OH).sub.2 and (NH.sub.2).sub.2. Rather, .eta..sub.th is a very good approximation due to the fact, that the (exergetic) efficiency of chemical reactions is quite high in general; the internal, eigenconsumption of exergy is low. It seems to be not of major importance, that this eigenconsumption of the chemical reactions is not included in .eta..sub.th. The (OH).sub.2 -synthesis was found to reach technical efficiencies up to 90%; the last step of (NH.sub.2).sub.2 -synthesis (electrolysis of Li-NH.sub.2), however, needs only about 25% of the total electrical energy; even if the efficiency of this process (not known so far) is much lower, its influence on the total efficiency is softened due to the low weight. A compensation of losses seems to be possible utilizing by parts energy of the field B.sub.eigen carried along with the free jet for the Li-amide-electrolysis; normally this energy is lost. On the basis of the foregoing detailed explanation it will readily be understood that the peroxide synthesis can be carried out quite analogously and is run on a simplified basis because the coil-core-liquid system does not have to operate on the basis of thermo-fluid dynamic acceleration of the working fluid (though it could) but a pump (187--FIG. 8) is used instead. Also, the electrical energy is applied externally, namely from the MHD converter of the hydrazine and solar exergy exploiting system. The a.c. electrolysis is, therefore, used by interaction between coils and a watery solution of KOH used as circulating working fluid here, with metallic particles, preferably iron, but possibly Cu or Al being interspersed for the same reason, namely to establish conductivity in the otherwise poorly conductive electrolyte. The voltage needed here for electrolysis is also the result of the effect as expressed Maxwell (vector) equation B+curl E=0, and integration of E along a closed electric field line, looping around the axis of fluid flow, yields the voltage U (not a potential difference in a potential field, there is none) which is directly effective on electrons to move them from OH.sup.- to K.sup.+. In the following, it shall be described how the hydrazine and the generation of H.sub.2 (needed for the hydrazine synthesis) with concurring production of (OH.sub.2).sub.2 can be carried out by one basic fluid circulating system. For this I turn to FIG. 42. In toto, this system is more economical (fewer parts, no H.sub.2 storage, no electric transmission). The system is based on the (justified) assumption that as intermediate products M-NH.sub.2 and M-OH can be used with M standing for the same metal, particularly the same alkalimetal. The system, furthermore is based on the "compromise" that only one of these intermediate products is synthesized electrolytically, the other one chemically. The box 308 in FIG. 42 depicts the flow chart of this combination synthesis. Reflector 289 is the same as before and the same is true for the accumulation and extraction facilities 302, 286, and 279. A circulation 290 in unit 308 is now a circulation of M and M-OH, M being for example Li or K. Block 291 denotes the heating of that fluid by solar energy and block 292 denotes the adding of hydrogen and nitrogen to that liquid so that functionally M-NH.sub.2 is generated in block 293. This will be a catalytic reaction with iron for example serving as catalyst. Please note, that this amid-formation is not linked to the use of lithium but works with other alkali-metals as well. Thus far the situation is very similar to the function and steps as was explained above with reference to FIG. 8. However, the liquid now continuing to circulate is M, MOH and M-NH.sub.2. At point 295 and 281, water is added to the circulation. This is actually the entrance to the accelerator nozzles such as 45, supra. Thus, water is used here as the tfd fluid. The water evaporates and expands along 296 and accelerates the working liquid as before. However additionally, the water reacts with the M-NH.sub.2 and forms MOH+(NH.sub.2).sub.2 +H.sub.2. In other words, the hydrazine is the product of a chemical reaction of metal-amid and water under formation of H.sub.2 and hydrazine. Additionally, the residual metal is also converted into MOH+H.sub.2. Following the acceleration, the liquid phase consists essentially of MOH and M while hydrazine and hydrogen accompany the tfd gas (namely H.sub.2 O) in the liquid gas separation process. Please note, that more water is added at 295 than can react with the M-NH.sub.2 and the metal so that all of the M-NH.sub.2 decomposes under formation of hydrazine while excess water (steam) serves as the tfd gas performing the acceleration producing work on the liquid phase. The steam and H.sub.2 are separated at 297 analogous to the gas--liquid separation as described above. The gas includes also hydrazine which is precipitated by cooling in 301 because hydrazine has a higher boiling point than water. The water--H.sub.2 mixture (gaseous) is extracted as tfd fluid and subjected to recuperative heat exchange in 304 with isothermic compression (and condensation of the water) in 305 which is simplified in FIG. 42 but may well be constructed analogous to the detailed arrangement of FIG. 8. However, a mere recompression under cooling by air may suffice. The cooled and recompressed H.sub.2 and water is recirculated and heated in the recuperative heat exchanger. In view of the high pressure, the water remains in liquidous form so that the H.sub.2 can readily be separated therefrom in 282 for separate injection into the liquid fluid circulation respectively at 292 and 295. As far as the metal-hydroxide is concerned, it is subjected to mechanical and/or electromagnetic focussing at 298 (please note that iron particles are dispersed in this liquid), and in 284 the MHD conversion process takes place whereby substantially all electrical energy is consumed to obtain electrolysis M-(OH).sub.2. The (OH).sub.2 is flushed out at 285 and the tfd cushioning gas is also separated from the liquid phase at that point. Please note that the (OH).sub.2 is produced as a vapor that separates readily from the MOH--M jet and will be condensated for extraction. The block 303 denotes jet capture and to kinetic energy-to-pressure conversion for obtaining a return flow of the mixture of metal and metal--OH to the solar heat exchange and collector 291. The righthand portion of the drawing shows basically a flow path for air, 275, sucked into the system for cooling (heat exchange 305), separation of water 278 and extraction of nitrogen, 277. Reference numeral 276 refers to a blower which sucks the air. That blowr may have to be run by electrical energy from converter 284. That, however, is a very small load and will not interfere with the operation of the MHD generator. It can thus be seen that the MHD conversion process is used only for (OH).sub.2 generation. As far as the hydrazine generation is concerned, the essential functions performed by the MHD process is the reconstitution of the metal so that the solar energy can generate M-NH.sub.2 which subsequently reacts with water to obtain MOH and (NH.sub.2).sub.2 as well as H.sub.2 to be used in the synthesis of M-NH.sub.2. |
abstract | A radiation treatment delivery system, includes a linear accelerator (LINAC) and a multileaf collimator (MLC), coupled with the distal end of the LINAC, wherein the MLC has two banks of leaves, organized into a plurality of opposing leaf pairs. The system further includes a processing device, operatively coupled to the LINAC and the MLC, to control the plurality of leaf pairs of the MLC such that for each of a plurality of radiation beam delivery positional sections corresponds to a range of radiation beam positions over a discrete time interval that constrains an overall treatment time and wherein each leaf pair of the plurality of opposing leaf pairs is open to a fixed opening for a fraction of time in the discrete time interval and closed for the remaining fraction of time in the discrete time interval, while a radiation beam of the radiation treatment system is active. |
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abstract | An electron microscope capable of producing EELS (electron energy-loss spectroscopy) has a spectral position correcting signal supply circuit for supplying a spectral position correcting signal H to a first driver amplifier to project spectra at the center of a CCD camera. This correcting signal H corresponds to a beam deflection signal A′ supplied from a scan generator to a second driver amplifier, an excitation signal B′ supplied from an intermediate lens excitation signal supply circuit to a third driver amplifier, and another excitation signal supplied from a projector lens excitation signal supply circuit to a fourth driver amplifier. |
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claims | 1. A polymer composite for extracting active and non-active Cesium from high level acidic radioactive nuclear waste and/or other inorganic wastes/solutions comprising 10-40% by weight of a polymer and 60-90% by weight of Ammonium molybdophosphate (AMP) based on the weight of the polymer composite,wherein the polymer comprises polysulfone, derivatives of polysulfone, or a combination thereof,wherein the polymer composite comprises an inner porous structure and an outer structured layer having surface pores,wherein the polymer composite has a void volume of 15 to 70% and a skeleton density of 1.1 to 1.6 gm/cc adapted for equilibrium time of 30-100 minutes and a Cesium ion exchange capacity of 0.4-1.0 meq/gm. 2. A polymer composite as claimed in claim 1, wherein the outer structured layer has a thickness ranging from 20 to 25 μm with the surface pores in the range of 100-300 nm,wherein the polymer composite has a void volume of 45 to 50% and a density of 1.2 gm/cc adapted for equilibrium time of 35-40 minutes and a Cesium ion exchange capacity of 0.75-0.8 meq/gm. 3. A polymer composite as claimed in claim 1, wherein the polymer comprises polyether sulfone or its derivatives. 4. A polymer composite as claimed in claim 1, wherein said derivatives of polysulfone comprise derivatives in the form of different substituents attached to the benzene ring of the unit. 5. A polymer composite as claimed in claim 1, comprising a polymer to AMP weight ratio between 1:2 to 1:6, and a void volume of 15 to 60%. 6. A polymer composite as claimed in claim 1, wherein said composite is in the form of a film, a bead or a fiber. 7. A polymer composite as claimed in claim 1, wherein said polymer comprises a molecular weight between 60,000 to 200,000 and a Glass Transition Temperature (Tg) between 170 to 250° C. 8. A polymer composite as claimed in claim 7, wherein the polymer comprises a first polymer and a second polymer wherein the first polymer comprises a molecular weight of 150,000 and a Glass Transition Temperature (Tg) of 210° C. and wherein the second polymer comprises a molecular weight of 60,000 and a Glass Transition Temperature (Tg) of 180° C. 9. A polymer composite as claimed in claim 1, comprising a void volume of 20-22%, a density of 1.6 gm/cc adapted for equilibrium time of 90-100 minutes and a cesium ion exchange capacity of 0.7 meq/gm. 10. A polymer composite as claimed in claim 1, comprising improved granulometric properties which is thermally stable up to 200° C., radiation resistant and stable in acidic and alkaline medium without any significant change in ion exchange capacity of AMP. 11. A process for the preparation of the polymer composite as claimed in claim 1 comprising of the following steps:(a) dissolving the polymer in a solvent to form a solution,(b) dispersing the AMP in the solution at a temperature ranging of from 20 to 50° C., and(c) obtaining therefrom the said polymer composite. 12. A method of using the polymer composite as claimed in claim 1 for the extraction of active and non-active Cesium from high level acidic radioactive nuclear waste and/or other inorganic wastes/solutions by following the steps of:a) providing said polymer compositeb) bringing said polymer composite in contact with high level acidic radioactive nuclear waste and/or other inorganic wastes/solutions for Cs+ ion removal/extraction from said wastes/solutions and obtaining a cesium bound composite therefrom;c) treating the cesium bound composite in alkaline medium to download the Cs-bound AMP for further separation and reuse of Cesium. |
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abstract | A module for storing high level radioactive waste includes an outer shell, having a hermetically closed bottom end, and an inner shell forming a cavity and being positioned inside the outer shell to form a space therebetween. At least one divider extends from the top to the bottom of the inner shell to create a plurality of inlet passageways through the space, each inlet passageway connecting to a bottom portion of the cavity. A plurality of inlet ducts each connect at least one of the inlet passageways and ambient atmosphere, and each includes an inlet duct cover affixed atop a surrounding inlet wall, the inlet wall being peripherally perforated. A removable lid is positioned atop the inner shell and has at least one outlet passageway connecting the cavity and the ambient atmosphere, the lid and the top of the inner shell being configured to form a hermetic seal therebetween. |
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abstract | A standoff supporting a control rod drive mechanism (CRDM) in a nuclear reactor is connected to a distribution plate which provides electrical power and hydraulics. The standoff has connectors that require no action to effectuate the electrical connection to the distribution plate other than placement of the standoff onto the distribution plate. This facilitates replacement of the CRDM. In addition to the connectors, the standoff has alignment features to ensure the CRDM is connected in the correct orientation. After placement, the standoff may be secured to the distribution plate by bolts or other fasteners. The distribution plate may be a single plate that contains the electrical and hydraulic lines and also is strong enough to provide support to the CRDMs or may comprise a stack of two or more plates. |
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047479981 | summary | The invention relates to temperature activated switches, particularly to thermionic switches, and more particularly to a thermally actuated thermionic switch. Temperature responsive switches which involve a change of state condition or expansion of an operative material when temperature is applied thereto are well known in the art. These prior switches are exemplified by U.S. Pat. Nos. 3,791,298 issued Feb. 12, 1974 to P. Amberny, and 3,815,816 issued June 11, 1974 to D. Scarelli. Thermionic devices have been in use for many years as lights, vacuum tubes, power converters, and as electrically driven switches. These prior thermionic devices use control grids, temperature difference between the emitter and collector, or voltage changes to cause their actions. More recently, thermionic devices have been utilized in nuclear reactor control systems, particularly in self-actuated control systems responsive to low-flow, high temperature, or over-power conditions of the reactor. In such control systems, the control rods are rapidly inserted into the reactor core for quick shut down of the reactor. Such self-actuated reactor control systems are, for example, described and claimed in copending U.S. Patent Application Ser. Nos. 270,672 and 270,682, each filed June 4, 1981 in the name of D. M. Barrus et al, and assigned to the assignee of this application. While various thermionic switches have been developed, a need has existed for a simple, yet effective thermionic switch responsive to temperature particularly in the field of reactor control systems. Such an improved switch would find use in numerous applications for temperature control and limiting functions, aside from their use in reactor systems. SUMMARY OF THE INVENTION The instant invention satisfies the above-mentioned need by providing a simply constructed, yet effective thermally actuated thermionic switch. The thermally actuated thermionic switch of this invention is a diode differing from those mentioned above in that it operates in an isothermal condition (not depending on temperature differences between the electrodes as in a power converter), nor does it use a control grid as in a vacuum tube. Therefore, it is an object of this invention to provide a thermionic switch. A further object of the invention is to provide a thermally actuated thermionic switch. Another object of the invention is to provide a thermionic switch which responds electrically to an increase in temperature by changing from a high impedance to a low impedance at a predictable temperature set point. Another object of this invention is to provide a thermally actuated thermionic switch which is particularly suitable for use in nuclear reactor control systems. Another object of the invention is to provide a thermally actuated thermionic switch which can be utilized for temperature control and limiting functions. Other objects of the invention will become readily apparent to those skilled in the art from the following description and accompanying drawings. The above objects are accomplished by a thermally actuated thermionic switch which operates in an isothermal condition, and is responsive to temperatures above a pre-set minimum. The thermionic switch of this invention responds to an increase of temperature by changing from a high impedance to a low impedance. Such thermionic switches are particularly useful in reactor control or shutdown systems, wherein the switch is responsive to the temperature of the coolant flowing through the reactor core. More specifically, the thermally actuated thermionic switch of this invention comprises two electrodes, an emitter and a collector, which are separated mechanically and electrically isolated from one another, and provided with a quantity of thermionic material in matrix in a graphite block reservoir, and an electrical circuit connected to said electrodes, such that heating of said thermionic material causes the switch to trigger for activating a desired mechanism, such as an associated electromagnetic apparatus of a reactor control system. |
053389417 | description | SPECIFIC DESCRIPTION Referring first to FIG. 3, it can be seen that a radiation shielding container for receiving spent fuel elements of a nuclear reactor, especially for transport, but also for storage and adapted to be filled in a water basin as previously described, is represented at 10 and comprises a spherulitic cast iron body 11 whose outer surface is provided with a sealing coating 18 of a powder melt and consisting of nickel or a nickel-based alloy, including chromium/nickel 18-8 austenitic alloy. A similar coating, referred to as a powder melt coating can be provided at 19 at the interior of the container defining the space 20 receiving the irradiated fuel elements. The coating can be applied to the seats 13 in which the stepped shoulders 14 of the spherulitic cast iron cover 12 can be received. The entire container can be closed by a lid 15 which is attached by bolts 16 to the cover 12 and bolts 17 to the container body. FIG. 1 shows a cast body 1 having a surface 2 provided with open pores 3. On this surface a sealing layer 4 is applied to nickel or nickel-based alloy. As can be seen in FIG. 1, the coating 4 is applied galvanically, i.e. by electroplating techniques. It must be applied in a multiplicity of layers a, b, c, d and e in order to bridge the open pores 3. Not only is the open pore 3 not filled, but because of the potential characteristics in the region of the pore during the electrodeposition process, the coating 4 contains a cavity in the region of the pore which is only closed by a thin layer of the coating although the overall thickness of the layer is considerable. As a consequence, the coating is sensitive to mechanical disruption which can cause breakthrough to that cavity and expose the open pore to the action of water. The effectiveness of this type of coating in preventing the container from forming a galvanic element in a water basin during filling with the irradiated fuel elements, therefore, is limited. By contrast, as can be seen in FIG. 2, when the sealing layer 4 has a texture 5 of a layer solidified from a particle melt in which the particles have diameters substantially smaller than the diameters of the pores, the layer fills the pore 3 and the overall layer thickness can be substantially smaller. The layer thickness for example, may be of the order of 100 micrometers and the particle size can be of the order of 1 to 10 micrometers. The system has been found to be highly advantageous for spherulitic cast irons having the following compositions: 3.2 to 3.8% by weight carbon, 1.6 to 2.6% by weight silicon, 0.1 to 0.3% manganese, 0.025 to 0.06% by weight magnesium, the balance being iron and the usual elements unavoidably present in spherulitic cast irons. The preferred composition of the powder is 99 or more percent by weight nickel and phosphorous and other elements commonly present with nickel, and high purity nickel can be present here as well. As can be seen from FIG. 4, the spherulitic cast iron substrate 21 can be coated with powder 22 from a powder spray nozzle and a laser beam played back and forth across the powder coated surface as represented by the laser 24 to fuse the particles together and to the substrate. In principle, therefore, following casting of the body in an initial step at 30, represented in FIG. 5, the body of the container can be subjected to an abrasive surface treatment at 31 by shot peening or the like and can then be coated with the powder or droplets by plasma spray 32 or coated with the powder as described in connection with FIG. 4 in a separate application 33 followed by a laser fusion in a successive step 34. FIG. 6 shows the path of the laser beam 36 on the powder coated surface 35 of the substrate 37, i.e. the back and forth or reciprocating path previously mentioned. |
046408118 | claims | 1. A linear motion device comprising: (a) an axially movable vertical drive shaft provided with a plurality of circumferential grooves equally spaced in the vertical direction, said drive shaft being arranged for connection with a nuclear reactor control rod at the lower end thereof, and (b) two gripping devices axially spaced relative to said drive shaft, each of said devices having: (c) wherein each of said pawls comprises an upper tooth and a lower tooth separated by a vertical distance equal to the distance between two successive grooves of said drive shaft and wherein said lower axis is located at a vertical distance below the tip of said upper tooth which is between one sixth and one fourth of the vertical distance separating the tips of said upper tooth and said lower tooth on one of said pawls. 2. Linear motion device according to claim 1 wherein said lower axis of said pawl is centered at a location situated below said upper tooth at a vertical distance of about 1/5 of the vertical distance separating the two tips of said engaging teeth on said pawl. |
description | 1. Field of Invention The present invention relates to a light source device incorporated into an exposure device utilized in a manufacturing process for a semiconductor or a liquid crystal substrate, for a color filter, and the like. 2. Description of Related Art In a manufacturing process for a semiconductor, a liquid crystal substrate or a color filter, shortening of treatment time and batch exposure of articles to be treated having a large surface area are in demand. In response to this demand, a high-pressure discharge lamp with greater ultraviolet light emission intensity into which a large input power can be entered is proposed. However, when the input power into the high-pressure discharge lamp is increased, the load on the electrodes is increased and the problem results that the high-pressure discharge lamp is blackened due to materials evaporating from the electrodes so that a short lifespan results. FIG. 13 shows a light source device as described in JP-A-61-193358. As shown in FIG. 13, this light source device 100 is a device where an electrodeless discharge lamp 104 is arranged within an ellipsoidal reflector 101; a laser beam is radiated into the discharge vessel of the discharge lamp 104 via a hole 102 in the side surface of the ellipsoidal reflector 101; and the discharge gas enclosed within the discharge vessel is excited and produces light. In this light source device 100, because there is no electrode in the discharge lamp 104, the problem mentioned above can be solved. However, the light source device 100 described in JP-A-61-193358 has the light entrance hole 102 and a light exit hole 103 for the laser beam in the side surface of the ellipsoidal reflector 101, and when ultraviolet radiation generated from the electrodeless discharge lamp 104 is focused by the ellipsoidal reflector 101, because of the holes 102, 103 on the reflecting surface, there is the problem that the ultraviolet radiation cannot be efficiently utilized. Further, the laser beam enters into the electrodeless discharge lamp 104 from a direction intersecting the optical axis X of the ellipsoidal reflector 101, and the discharge extends in a lateral direction (direction intersecting with the optical axis X), and the discharge occurs even in a region shifted from the focal point of the ellipsoidal reflector 101. This causes the problem that the ultraviolet radiation cannot be efficiently utilized because the ultraviolet radiation is not accurately reflected. FIG. 14 shows a light source device as is described in US 2007/0228300 A1. As shown in FIG. 14, this light source device 200 is a device where an electrodeless discharge lamp is arranged within a reflector 201 and a laser beam enters into the discharge vessel 203 of the discharge lamp via an opening 202 at the apex of the reflector 201, and discharge gas enclosed in the discharge vessel 203 is excited and produces light. In this light source device 200, because there is no electrode in the discharge lamp, the above mentioned problem can be solved. In the light source device 200 described in US 2007/0228300 A1, the laser beam entering into the reflector 201 from the opening 202 at the apex of the reflector 201 is reflected by the discharge vessel 203 and the discharge 204 is generated. However, a portion of the laser beam passes through the discharge 204 and passes through the discharge vessel 203, as well, and the laser beam is radiated onto the irradiation surface along with the radiant light generated by the discharge. Consequently, the problem results that the article to be treated on the irradiation surface is damaged due to this undesired effect by the laser beam. FIGS. 15 &16 show configurations for the purpose of solving the problem of the light source device 200 shown in US 2007/0228300 A1. In the configuration shown in FIG. 15, a laser beam entering from the opening side for emitting light from the reflector 205 is reflected by the reflector 206; is radiated into the reflector 205; discharge gas filled in the discharge vessel is excited and discharge is generated; and the light generated by the discharge is reflected by the reflector 208 and is emitted. In the configurations shown in FIGS. 15 & 16, the problem in the light source device shown in FIG. 14 can be solved. However, in the configurations shown in FIGS. 15 & 16, the reflectors 206, 208 require wavelength selectivity and manufacturing is difficult, and there are cases where the cutting of the wavelengths cannot be accurately done. In addition, a part of the radiant light is absorbed by the reflector 206 and a part of the radiant light is absorbed by the reflector 208; therefore, there is the problem that the radiant light cannot be efficiently utilized. Taking the above mentioned problems into consideration, a primary object of the present invention is to provide a light source device that radiates a laser beam into a discharge vessel so as to cause radiant light to be emitted from the discharge vessel, wherein the light emitted from the discharge vessel is reflected by an ellipsoidal reflecting surface and the reflected light can be efficiently utilized, by introducing the laser beam by utilizing a region which is not irradiated with light due to reflected light from the ellipsoidal reflector being blocked by the discharge vessel. In the present invention, for the purpose of solving the previously mentioned problems, the means mentioned below have been adopted. The first aspect of the invention relates to a light source device, comprising an ellipsoidal reflector, a discharge vessel having an emission substance enclosed therein, the discharge vessel being arranged at a focal point of the ellipsoidal reflector, a laser for generating a laser beam, means for converging the laser beam toward an opening side of the ellipsoidal reflector for irradiating and exciting the emission substance for causing light to be emitted from the discharge vessel; and a planar mirror positioned to receive emitted light reflected by the ellipsoidal reflector and for changing the direction of the reflected light, wherein the planar mirror comprises a window in an area in a region not irradiated with reflected light where the reflected light from the ellipsoidal reflector is blocked by the discharge vessel; and wherein the laser is arranged to cause the laser beam to pass through said window. In a preferred embodiment of the invention, the light source device of the first aspect, comprises a collecting lens for focusing the laser beam arranged between the planar mirror and the discharge vessel. In another preferred embodiment of the invention, the light source device of the first aspect has a collecting lens for focusing the laser beam arranged at the opposite side from the discharge vessel for the window. In another preferred embodiment of the invention, the light source device of the first means has a collecting reflector for collecting and reflecting the laser beam arranged at the opposite side from the discharge vessel for the window. In yet another preferred embodiment of the invention, the light source device of the first means has a collecting lens part for focusing the laser beam formed in a portion of the discharge vessel. In still another preferred embodiment of the invention, the light source device comprises a discharge vessel which is an electrodeless discharge vessel not having any electrodes within the discharge vessel. In an alternative embodiment of the invention, the light source device comprises a discharge vessel having a pair of electrodes inside. In another preferred embodiment of the invention, in the light source device having an electrodeless discharge vessel, the laser beam introduced into the discharge vessel is a laser beam from a pulsed laser for initiating discharge start-up or a laser beam from a pulsed laser or a CW laser for discharge maintenance. In the case of a discharge vessel having electrodes arranged therein, the light source device of another preferred embodiment comprises a pulsed laser or a CW laser for introducing a laser beam into the discharge vessel for discharge maintenance. In another preferred embodiment of the invention, the discharge vessel has heating means. Further, the heating means preferably is a heating element that absorbs the laser beam introduced into the discharge vessel and generates heat. According to the present invention, since the laser beam to be introduced into the discharge vessel is introduced from a window placed in a region which is not irradiated by the reflected light, where the reflected light from the ellipsoidal reflector is blocked by the discharge vessel and to which the reflected light will not be radiated, and there is a planar mirror for changing the direction of the reflected light from the ellipsoidal reflector, the radiant light emitted from the discharge vessel is reflected by the ellipsoidal reflector and the reflected light can be efficiently utilized. In addition, since the laser beam is irradiated toward the discharge vessel from the opening side of the ellipsoidal reflector, the laser beam will never be directly radiated to the article to be treated on the irradiation surface, and the article to be treated will not be damaged by the laser beam. A first embodiment of the present invention is explained using FIG. 1. FIG. 1 shows the configuration of a light source device relating to the invention of this embodiment. As shown in FIG. 1, the discharge vessel 1 is made of quartz glass and comprised of a light-emitting part 11 and a sealing part 12, and for example, 4.5 mg/cm3 of mercury and xenon at 2 atm are enclosed in the light-emitting part 11 as emission substances. The discharge vessel 1 is an electrodeless discharge vessel with no electrodes inside. An ellipsoidal reflector 2 has an apex opening 21; the sealing part 12 of the discharge vessel 21 is inserted into the apex opening 21; the sealing part 12 is retained behind the ellipsoidal reflector 2. The discharge vessel 1 is arranged at a focal point F1 of the ellipsoidal reflector 2. A laser beam generator 3 is placed outside the ellipsoidal reflector 2, and a laser beam is introduced into the discharge vessel 1 from the laser beam generator 3, for example, comprised of a 20 kHz pulsed laser or a continuous wave (CW) laser. In the reflected light reflected by the ellipsoidal reflector 2, a region L1-L2 formed between the discharge vessel 1 and a planar mirror 4 facing the other focal point F2 of the ellipsoidal reflector 2 is a reflected light blocking region L1-L2. L1 and L2 are lines connecting the planar mirror 4 and points on the external surface of the discharge vessel 1 where its diameter is at maximum. The surface area where the reflected light blocking region L1-L2 hit the planar mirror 4 is a reflected light unirradiated region L3-L4 where the reflected light from the ellipsoidal reflector 2 is blocked by the discharge vessel 1 and which the reflected light will not reach. A window 41 is formed in the planar mirror 4 in the reflected light unirradiated region L3-L4. The laser beam emitted from the laser beam generator 3 is introduced via the window 41, and focused by a collecting lens 5 arranged between the window 41 and the discharge vessel 1 and radiated into the discharge vessel 1. Focusing of the laser beam enables the energy density to be increased at the focal point, to excite the emission substance and to generate radiant light. The radiant light is reflected by the ellipsoidal reflector 2 and the reflected light changes its direction at the reflection surface of the planar mirror 4 except for at the window 41 and is reflected sideway onto the article to be irradiated. Furthermore, the window 41 is a through-hole formed in the planar mirror 4, and except for the through-hole, the planar mirror 4 is made of a substrate through which the laser beam will transmit, and where a reflecting film can be formed on the substrate except for at the window 41. According to the invention of this embodiment, since the window 41 of the planar mirror 4 and the collecting lens 5 are placed in the reflected light blocking region L1-L2, a region where no reflected light from the ellipsoidal reflector 2 exists is used so that the reflected light from the ellipsoidal reflector 2 can be efficiently utilized. Further, since the laser beam is introduced into the discharge vessel 1 from the opening side of the ellipsoidal reflector 2 via the window 41, the laser beam will not be directly irradiated to the article to be treated on the irradiation surface, and the article to be treated will not be damaged by the laser beam. Further, the laser beam is designed to travel along the optical axis X of the ellipsoidal reflector 2, the discharge generated within the discharge vessel 1 extends toward the optical axis X, and the radiant light capture ratio of the ellipsoidal reflector 2 becomes higher and the radiant light can be efficiently utilized. A second embodiment of the present invention is explained with reference to FIG. 2. FIG. 2 shows a configuration of this embodiment of a light source device relating to the invention. As shown in FIG. 2, a laser beam emitted from the laser beam generator 3 is focused by a collecting lens 5 arranged between the laser beam generator 3 and the window 41 of the planar mirror 4, is introduced via the window, and radiated into the discharge vessel 1. Focusing of the laser beam enables increased energy density at the focal point, to excite the emission substance and to generate radiant light. The radiant light is reflected by the ellipsoidal reflector 2 and the reflected light changes its direction at the reflection surface of the planar mirror 4 except for at the window 41 and is reflected sideways toward an article to be irradiated. Furthermore, other elements in FIG. 2 correspond to those of the same reference numbers shown in FIG. 1. According to the invention of this embodiment, since the window 41 of the planar mirror 4 is placed in the reflected light blocking region L1-L2, a region where no reflected light from the ellipsoidal reflector 2 exists is used, and the reflected light from the ellipsoidal reflector 2 can be efficiently utilized. Further, since the laser beam is introduced into the discharge vessel 1 from the opening side of the ellipsoidal reflector 2, the laser beam will not be directly irradiated to the article to be treated on the irradiation surface, and the article to be treated will not be damaged by the laser beam. Also, since the laser beam is designed to travel along the optical axis X of the ellipsoidal reflector 2, the discharge to be generated within the discharge vessel 1 extends toward the optical axis X, and the radiant light capture ratio of the ellipsoidal reflector 2 is high so that the radiant light can be efficiently utilized. A third embodiment of the present invention is explained with reference to FIG. 3. FIG. 3 shows a configuration of a light source device relating to this embodiment of the invention. As shown in FIG. 3, a laser beam emitted from the laser beam generator 3 is focused and reflected by a collecting reflector lens 6 arranged between the laser beam generator 3 and the window 41 of the planar mirror 4, and the reflected light is introduced via the window 41 and radiated to the discharge vessel 1. Focusing of the laser beam enables the energy density at the focal point to be increased, to excite the emission substance, and to generate radiant light. The radiant light is reflected by the ellipsoidal reflector 2, and the reflected light changes its direction on the reflecting surface except for at the window 41 and is reflected sideways toward an article to be irradiated. Other elements correspond to those with the same reference numbers shown in FIG. 1. According to the invention of this embodiment, since the window 41 of the planar mirror 4 is placed in the reflected light blocking region L1-L2, this utilizes a region where reflected light from the ellipsoidal mirror 2 does not exist, and the reflected light from the ellipsoidal reflector 2 can be efficiently utilized. Further, since the laser beam is introduced into the discharge vessel 1 from the opening side of the ellipsoidal reflecting via the window 41, the laser beam will not be directly radiated onto the article to be treated on the irradiation surface, and the article to be treated will not be damaged by the laser beam. Further, since the laser beam is designed to travel along the optical axis X of the ellipsoidal reflector 2, the discharge to be generated within the discharge vessel 1 extends toward the optical axis X and the radiant light capture ratio by the ellipsoidal reflector 2 is high so that the radiant light can be efficiently utilized. A fourth embodiment of the present invention is explained with reference to FIG. 4. FIG. 4 shows a configuration of a light source device relating to this embodiment. As shown in FIG. 4, a laser beam emitted from the laser beam generator 3 is introduced via the window 41 of the planar mirror 4, and is focused by a collecting lens part 19 formed in a portion of the discharge vessel 1 and radiated into the discharge vessel 1. Focusing of the laser beam enables the energy density at the focal point to be increased; to excite the emission substance; and to generate radiant light. The radiant light is reflected by the ellipsoidal reflector 2, and the reflected light changes its direction on the reflecting surface except for at the window 41 and is reflected sideways toward an article to be irradiated. Other elements correspond to those with the same reference numbers shown in FIG. 1. According to the invention of this embodiment, since the window 41 of the planar mirror 4 is placed in the reflected light blocking region L1-L2, this utilizes a region where reflected light from the ellipsoidal mirror 2 does not exist, and the reflected light from the ellipsoidal reflector 2 can be efficiently utilized. Further, since the laser beam is introduced into the discharge vessel 1 from the opening side of the ellipsoidal reflector 2 via the window 41, the laser beam will not be directly radiated toward an article to be treated on the irradiation surface, so that the article to be treated will not be damaged by the laser beam. Further, since the laser beam is designed to travel along the optical axis X of the ellipsoidal reflector 2, the discharge generated within the discharge vessel 1 extends toward the optical axis X and the radiant light capture ratio of the ellipsoidal reflector 2 is high so that the radiant light is efficiently utilized. A fifth embodiment of the present invention is explained with reference to FIG. 5. FIG. 5 shows a configuration of a light source device relating to this embodiment. As shown in FIG. 5, a laser beam A that is generated by a laser beam generator 3A is transmitted through a reflector 7 and a laser beam B that is generated by a laser beam generator 3B and is reflected by the reflector 7 are focused by the collecting lens 5 arranged between the window 41 of the planar mirror 4 and the discharge vessel 1, and are radiated into the discharge vessel 1. The laser beam A is a laser beam for maintaining the discharge emitted by a CW laser, and the laser B is a laser beam for starting the discharge emitted, for example, by a 20 kHz pulsed laser. Superimposition of the laser beam B onto the laser beam A enables acceleration of the excitation of the emission substance within the discharge vessel 1, and to generate the discharge with certainty as compared to the case of irradiating only the laser beam A. Furthermore, after the discharge is stabilized, the laser beam B is stopped. Further, the operation timing of the laser beam A and the laser beam B may be either simultaneous or one after the other. Further, other than the combination mentioned above, for the laser beam A and the laser beam B, both can be beams from pulsed lasers. Furthermore, since other elements and effects of this embodiment are similar to those in the first embodiment, further explanation is omitted. A sixth embodiment of the present invention is explained with reference to FIG. 6. FIG. 6 shows a configuration of a light source device relating to this embodiment. As shown in FIG. 6, both the laser beam A generated by a laser beam generator 3A and transmitted through the reflector 7 and the laser beam B generated by the laser beam generator 3B and reflected by the reflector 7 are focused by the collecting lens 5 arranged between the reflector 7 and the window 41 of the planar mirror 4, and are radiated to the discharge vessel 1 via the window 41. The laser beam A is a laser beam for discharge maintenance generated by a CW laser, and the laser B is a laser beam for discharge start-up generated by, for example, a 20 kHz pulsed laser. Superimposition of the laser beam B onto the laser beam A enables excitation of the emission substance within the discharge vessel 1 to be accelerated, and assures that discharge is securely generated as compared to the case of irradiating with only the laser beam A. Furthermore, after the discharge is stabilized, the laser beam B is stopped. Further, the timing of the laser beam A and of the laser beam B may be simultaneous or one may be applied after the other. Further, for the laser beam A and the laser beam B, other than the combination mentioned above, both laser beam A and the laser beam B can be generated by a pulsed laser. Furthermore, since other aspects and effects of this embodiment are similar to those in the first embodiment, further explanation is omitted. A seventh embodiment of the present invention is explained with reference to FIG. 7. As shown in FIG. 7, a laser beam A is generated by laser beam generator 3A and transmitted through the reflector 7 and a laser beam B is generated by the laser beam generator 3B and reflected by the reflector 7, and both are focused by the light collecting reflector 6, and are radiated to the discharge vessel 1 via the window 41. The laser beam A is a laser beam for discharge maintenance generated by a CW laser, and the laser B is a laser beam for discharge start-up generated by, for example, a 20 kHz pulsed laser. Superimposition of the laser beam B onto the laser beam A enables the excitation of the emission substance within the discharge vessel 1 to be accelerated, and assures that discharge is securely generated as compared to the case of irradiating with only the laser beam A. Furthermore, after the discharge is stabilized, the laser beam B is stopped. Further, the application timing of the laser beam A and of the laser beam B may be simultaneous or one may be applied after the other. Also, for the laser beam A and the laser beam B, other than the combination mentioned above, both the laser beam A and the laser beam B can be generated by pulsed lasers. Furthermore, since other aspects and effects of this embodiment are similar to those in the first embodiment, further explanation is omitted. An eighth embodiment of the present invention is explained with reference to FIG. 8. As shown in FIG. 8, the laser beam A is generated by a laser beam generator 3A and is transmitted through the reflector 7 and the laser beam B is generated by the laser beam generator 3B and reflected by the reflector 7, and both are passed through the window 41 of the planar mirror 4, and are collected by the collecting lens part 19 formed in a portion of the discharge vessel 1, and radiated into the discharge vessel 1. The laser beam A is a laser beam for discharge maintenance generated by a CW laser, and the laser B is a laser beam for discharge start-up generated by, for example, a 20 kHz pulsed laser. Superimposition of the laser beam B onto the laser beam A enables excitation of the emission substance within the discharge vessel 1 to be accelerated, and assures generation of discharge as compared to the case of irradiating with only the laser beam A. Furthermore, after the discharge is stabilized, the laser beam B is stopped. Also, the timing of the laser beam A and the laser beam B may be simultaneous or one may be applied after the other. Further, for the laser beam A and the laser beam B, other than the combination mentioned above, both laser beam A and the laser beam B can be generated by pulsed lasers. Furthermore, since other aspects and effects of this embodiment are similar to those in the first embodiment, further explanation is omitted. FIG. 9 is an enlarged sectional view of the discharge vessel 1 shown in the first to third embodiments and the fifth to seventh embodiments. As shown in FIG. 9, the discharge vessel 1 is an electrodeless discharge vessel having no electrodes within it. A heater 13 and a heating element 14 for absorbing the laser beam and generating heat are arranged on the sealing part 12 of the discharge vessel 1. The heating element 14 is formed of ferric oxide (Fe2O3) applied on pure carbon or a carbon mixture, aluminum, metal or ceramics. Further, either the heater 13 or the heating element 14 can also be placed in the discharge vessel 1. Placement of the heating means in the discharge vessel 1 enables to increase the temperature of the discharge vessel 1 and to accelerate the excitation of the emission substance. FIG. 10 shows a detailed configuration of the discharge vessel 1 shown in the fourth and eighth embodiments. As shown in FIG. 10, the discharge vessel 1 is an electrodeless discharge vessel having no electrodes inside, and the collecting lens part 19 is formed in a portion of the discharge vessel 1 for focusing the laser beam. Since the other configuration and effects are similar to those in the discharge vessel 1 explained relative to FIG. 9, further explanation is omitted. FIG. 11 shows a configuration of the discharge vessel 1 in the case of a discharge vessel having electrodes as shown in the first to third embodiments and the fifth to seventh embodiments, instead of the electrodeless discharge vessel shown in FIG. 9. As shown in FIG. 11, the discharge vessel 1 is a discharge vessel having a pair of electrodes 15, 16 within the discharge vessel 1, the electrodes 15, 16 being connected to metal foils 17 embedded in the sealing part 12, and external leads 18 connected to the metal foils 17 and projecting from the sealing part 12. In the case of the first to third embodiments, when voltage for discharge start-up is supplied from a power source (not shown) to the external leads 18 and the voltage is applied between the electrodes 15, 16, the excitation of the emission substance within the discharge vessel 1 is accelerated and the discharge can be generated with certainty as compared to the case of only irradiating with a laser beam. Furthermore, after the discharge is stabilized, the power supplied to the electrodes 15, 16 is stopped. In the case of the fifth to seventh embodiments, the laser beam B generated by a pulsed laser is emitted for discharge start-up; concurrently, the voltage for discharge start-up is applied to the electrodes 15, 16 and then stopped, and the laser beam A for maintaining the discharge generated by the pulsed laser or a CW laser continues to be emitted. Alternatively, the laser beam B generated by the pulsed laser is radiated for starting the discharge, and the voltage for discharge start-up is applied to the electrodes 15, 16; concurrently, irradiation by the laser beam A for discharge maintenance generated by a pulsed laser or a CW laser may occur. FIG. 12 shows a configuration of the discharge vessel 1 in the case of a discharge vessel having electrodes inside shown in the fifth and eleventh embodiments, instead of the electrodeless discharge vessel shown in FIG. 10. As shown in FIG. 12, the collecting lens part 19 is formed in a portion of the discharge vessel 1 for focusing the laser beam. Other aspects and effects are similar to those in the discharge vessel 1 explained with reference to FIG. 11 so that further explanation is omitted. |
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051805413 | summary | FIELD OF THE INVENTION The invention relates to a device for the displacement of a load along a vertical axis of a well, and particularly to a lifting device associated with a fuel-assembly handling flask. BACKGROUND OF THE INVENTION Fast-neutron nuclear reactors cooled by a liquid metal, such as sodium, comprise a core consisting of assemblies of elongate prism-shaped form immersed in liquid sodium contained in the reactor vessel. It may be necessary to extract fuel assemblies from the reactor core within the vessel, for example in order to replace spent or defective assemblies by new assemblies. The assemblies which are taken out of the reactor vessel are in the irradiated state and generate radioactive radiation and an emission of heat. The fuel assemblies taken out of the vessel of the nuclear reactor must therefore be arranged in containers affording biological protection of the environment in which the assemblies are displaced or stored temporarily. In carrying out the transfer of the fuel assemblies of fast-neutron nuclear reactors, it is customary to use handling flasks comprising a solid body which is made of a material absorbing nuclear radiation and in which is formed a channel passing through the body of the flask in its longitudinal direction and in a central position and serving as a receptacle for a fuel assembly introduced into the handling flask. The channel opens out via a sealingly closable orifice at one of the ends of the body of the flask to make it possible to introduce an assembly into the flask and to extract it. During operations of introducing a fuel assembly into the flask and extracting it therefrom, the flask is arranged in such a way that the channel receiving the fuel assembly is in vertical position. The operations of introducing and extracting a fuel assembly are executed by means of a lifting set comprising winches associated with the flask and making it possible for the assembly fastened to a grab at its upper end to be displaced within the channel passing through the flask and in its axial extension. The well shut-off device arranged in the lower part of the flask is generally connected to a corresponding device associated, for example, with a fuel-assembly passage well passing through the closing slab of the vessel of the nuclear reactor. It is obvious that the operations of transferring the fuel assemblies between the reactor vessel and a handling flask must be conducted with a very high degree of safety, since incidents, such as the fall of a fuel assembly during its transfer, a failure of the lifting means of the assembly during transfer or a lack of cooling of the assembly, can cause damage to the fuel assembly or to some components of the reactor, a considerable delay in the handling operations or other harmful consequences resulting in an increase in the operating costs of the nuclear reactor. It may also be necessary to employ emergency procedures which involve an extremely high outlay and which can require the intervention of operators in zones subjected to irradiation. The lifting means associated with a fuel-assembly handling flask are therefore designed so as to include some redundancy in terms of their capabilities of holding and displacing the load consisting of the fuel assembly fastened to the grab being displaced in the channel of the flask. Such lifting devices generally comprise a double winch installed in the upper part of the flask and consisting of two motor shafts carrying a cable-winding drum at each of their ends. Two cables are each wound on two drums driven by different motor shafts and ensure the suspension and displacement of a grab comprising load attachment means. The grab has a support, on which are mounted pulleys which interact with the cables in order to ensure the suspension and displacement of the load. This device, which affords great operating safety in that it has redundancy making it possible to limit the consequences of a cable break or of a motor failure, has the disadvantage of considerably increasing the bulk of the flask, the upper part of which carries the set of lifting means. The mass of these lifting means therefore means that the center of gravity of the flask as a whole is located at an appreciable height, this having an effect on the anti-seismic devices to be provided. To make it easier to handle the flask during the transfer of a fuel assembly and to store flask during the periods when it is not being used, it is entirely desirable to reduce the volume of the flask as much as possible and to lower the position of the center of gravity. SUMMARY OF THE INVENTION The object of the invention is to provide a device for the displacement of a load in the vertical direction along the axis of a channel formed in the central part of a hollow body, comprising at least two sets of two drums which are driven by two motor devices and on which are wound two cables for the suspension and displacement of a grab movable in the channel and in its axial extension and comprising load attachment means and a support equipped with pulleys over which the cable passes, this displacement device making it possible to lower the position of the center of gravity and to reduce the bulk of the unit consisting of the hollow body, in which the load displacement channel is formed, and of the displacement device itself, while at the same time permitting operation with a very high degree of safety, especially in the event of a cable break or of a failure of a motor device. To this end, each of the sets of two drums driven by a motor means and constituting a winch is fastened to the outer surface of the hollow body, in such a way that the drums of each of the winches are each located opposite one of the drums of the other winch in relation to the vertical axis of the channel, the cable associated with each of the drums of a first winch being common to the drum of the second winch located opposite in relation to the axis of the channel and interacting with a set of deflecting pulleys and at least one grab-supporting pulley on its run between the two drums on which it is wound at its ends. |
054004993 | description | DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 4A, the internal bushing removal tool in accordance with the preferred embodiment is shown during insertion into the piston coupling 24c. The tool comprises a ram arm 104 having a bore 104e (see FIG. 5A) for receiving the shaft of a swivel pin 105 (see FIG. 5B). A swivel arm 103 (see FIG. 5C) has a swivel block 103f with a bore 103e for receiving swivel pin 105. Block 103f resides inside a cavity 104f in ram arm 104. Swivel arm 103 is held in place on swivel pin 105 (with two machined wrench flats) by a hex nut 106 with a lock washer 107 therebetween (see FIG. 6). The swivel arm and ram arm have opposing surfaces separated by gap 111a and 111b that allow a small angle of rotation of swivel arm 103 about the axis of swivel pin 105 and relative to ram arm 104. The arms 103 and 104 have opposing seats 103b, 104b and 103c, 104c for receiving respective ends of concentrically arranged inner (109) and outer (110) springs (see FIG. 4A). A guide pin 108 mounted on ram arm 104 projects inside inner spring 109 along its axis to guide the windings during compression of the spring, thereby restraining non-axial flexing of the spring. The inner and outer springs are compression springs which urge the ram and swivel arms apart, until full open stop is achieved by contact of adjacent surfaces of 103f and 104f. The ram arm 104 has an arcuate shoulder with a radial arcuate contact surface 104a (see FIG. 7). Similarly, the swivel arm 103 has an arcuate shoulder with a radial arcuate contact surface 103a. Inclined rigid members 103g and 104g connect the contact surfaces to the bored members that mount on swivel pin 105. At the position shown in FIG. 4A, the inclined portions 103g and 104g bear against the near inner peripheral edge of the internal bushing 63 to be removed. In a conventional CRD, the bore of each internal bushing 63 has a radius less than the radius of the bore of piston coupling 24c. As the removal tool is forced leftward from that position, the inner peripheral edge of the bushing will exert radially inwardly directed forces which overcome the spring forces urging ram and swivel arms 103, 104 apart. As a result, the contact surfaces 103a and 104a travel through the bore and past the far inner peripheral edge of the bushing. When the contact surfaces clear the far inner peripheral edge of bushing 63, the arms are urged apart by springs 109 and 110. The outer peripheral edge of each contact surface is pushed radially outward to a locus beyond the radius of the bore of bushing 63 (as shown in FIG. 4C), thereby latching the removal tool to the internal bushing. In the latched position, contact surface 103a abuts the internal bushing along a first arc and contact surface 104a abuts the internal bushing along a second arc diametrally opposed to the first arc. In these positions, the arcuate contact surfaces will bear against diametrally opposed portions of the end face of the internal bushing. Thus, swivel arm 103, ram arm 104, swivel pin 105, inner spring 109 and outer spring 110 form a springloaded collet having a pair of arc-shaped contact surfaces which can be latched behind the far inner peripheral edge of the internal bushing to be removed. These contact surfaces are then forced against the bushing end face to push bushing 63 out of the corresponding recess in piston coupling 24c. The respective ends of arms 103 and 104 are provided with cylindrical concavities 103d and 104d, respectively, to reduce the mass of the arms. These ends serve as handles by which the arms can be manually pressed together during the insertion step of FIG. 4A. The removal tool in accordance with the invention further comprises a ram 102 which screws into an end portion of ram arm 104. Ram 102 is preferably a solid cylinder having a flat end. During removal of the internal bushings, ram 102 and piston coupling 24c are held in horizontal or vertical positions by means of a stand 120 (see FIG. 8). Stand 120 is a cylindrical tube with a chamfered inlet 124 and an annular shoulder 122 which separates bores 128 and 130 of different diameter. Bore 128 receives the end of the piston coupling 24c, with the annular end face 121 of piston coupling 24c sitting on and supported by shoulder 122. A hammer or mallet is impacted against the flat end of ram 102 to drive the tool along the longitudinal axis and out of the piston coupling 24c. The force of the impact is transferred via contact surfaces 103a and 104a to the opposing radial end face of the internal bushing, thereby pushing the bushing axially out of the annular recess in which it is seated (see FIG. 4C), without damage to the piston coupling. A window 126 allows the operator to view the progressive downward displacement of bushing 63. The diameter of bore 130 is such that the removed bushing 63 passes through. The preferred embodiment of the internal bushing removal tool has been disclosed for the purpose of illustration. Variations and modifications of the disclosed structure which do not depart from the concept of this invention will be readily apparent to mechanical engineers skilled in the art of tooling. All such variations and modifications are intended to be encompassed by the claims set forth hereinafter. |
056087675 | abstract | A device for generating direct current by neutron activation of a plurality of series-connected beta-emitter (nuclear decay electron) cells, located in the out-of-core region of a light water nuclear reactor. The device can be used as either a current source, or preferably configured as a DC voltage source, capable of powering low-power, radiation-hardened, high-temperature integrated circuitry contained in the reactor vessel. As such, the device acts like a DC battery that is activated by (n, .gamma.) reactions, both thermal and epithermal (by resonance capture). The device is not operable until exposed to a substantial neutron flux, so it has unlimited shelf-life and is not radioactive during manufacture In the preferred embodiment, an isotope of the metallic rare-earth element dysprosium is configured in a "sandwich" geometry to generate sufficient current that a useful steady voltage can be generated by means of a simple voltage regulation circuit. |
abstract | Embodiments disclose a radiotherapy apparatus comprising a source of radiation configured to emit a beam of radiation and a collimator structure configured to limit a lateral extent of the beam, the collimator structure including a primary collimator configured to shape the beam, a first collimator comprising a plurality of adjacent elongate leaves, the leaves being extendable into the beam in a first direction transverse to the beam, and a block collimator including an aperture configured to permit the beam to pass through, the block collimator being extendable into the beam in a second direction transverse to the beam and transverse to the first direction. In some embodiments, the aperture may be cone-shaped or a through-hole, which may be empty or filled with a radiotransparent material. In some embodiments, the block collimator may include a plurality of apertures, which may be of varying dimensions. |
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abstract | An administration device that includes a hermetic container closed by a cap, containing a radiopharmaceutical medicament, and provided with a protective shield made of a radiopaque material. The device includes a support provided with attachment structure. The container is removably attached to the support in a position allowing access to the cap. The support includes a baseplate provided with an opening allowing access to the cap. A cover and rods connect the baseplate and the cover. |
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description | 1. Field of the Invention Embodiments of the present invention relate to a drawing apparatus configured to perform drawing on a substrate with a plurality of charged particle beams. 2. Description of the Related Art As one example of the drawing apparatuses, a multi-column drawing apparatus is known in which a projection unit is provided for each of the charged particle beams (see Japanese Patent Application Laid-Open No. 09-007538). Since projection units are provided independently, such a drawing apparatus does not have a crossover on which all of the charged particle beams converge. Thus, the influence of a coulomb effect is small, and such a drawing apparatus may effectively increase the number of charged particle beams. However, in order to increase the number of charged particle beams in the multi-column drawing apparatus, it is generally necessary to increase the divergence angle (divergence half angle) of a charged particle beam from a charged particle source in an irradiation optical system which is located on the front side of the plurality of projection units. When the divergence angle of a charged particle beam from the charged particle source increases, the charged particle beams irradiated on the plurality of projection units are not easily made parallel sufficiently due to the aberration of the irradiation optical system. As a result, the irradiation angle (incidence angle) becomes non-uniform. Eventually, the non-uniformity of the irradiation angle causes non-uniformity of properties between the charged particle beams. However, there is an issue associated with the aberration of the irradiation optical system. One disclosed aspect of the embodiments is directed to, for example, a drawing apparatus advantageous in terms of uniformity in a property with respect to a plurality of charged particle beams although the drawing apparatus includes an irradiation optical system of which irradiation angles are not uniform. According to an aspect of the embodiments, a drawing apparatus configured to perform drawing on a substrate with a plurality of charged particle beams includes an irradiation optical system including a collimator lens on which a diverging charged particle beam is incident; an aperture array configured to split the charged particle beam from the irradiation optical system into a plurality of charged particle beams; a converging lens array configured to form a plurality of crossovers of the plurality of charged particle beams from the aperture array; and a projection optical system including an element in which a plurality of apertures corresponding to the plurality of crossovers are formed, and a plurality of projection lenses corresponding to the plurality of apertures and configured to project charged particle beams from the plurality of apertures onto the substrate, wherein the converging lens array includes converging lenses disposed such that each of the plurality of crossovers, which are formed by the converging lenses from the charged particle beam incident on the aperture array at incidence angles associated with aberration of the irradiation optical system, is aligned with corresponding one of the plurality of apertures in the element. According to an exemplary embodiment, it is possible to provide, for example, a drawing apparatus advantageous in terms of uniformity in a property with respect to a plurality of charged particle beams although the drawing apparatus includes an irradiation optical system of which irradiation angles are not uniform. Further features and aspects of the embodiments will become apparent from the following detailed description of exemplary embodiments with reference to the attached drawings. Various exemplary embodiments, features, and aspects of the embodiments will be described in detail below with reference to the drawings. FIG. 1 is a diagram illustrating a configuration of a drawing apparatus (a drawing apparatus configured to perform drawing on a substrate with a plurality of charged particle beams) according to a first exemplary embodiment of the present invention. The drawing apparatus of the present exemplary embodiment is a multi-column drawing apparatus in which a projection unit is provided for each charged particle beam. Although an example in which an electron beam is used as the charged particle beam is described, the charged particle beam is not limited to that, but another charged particle beam such as an ion beam may be used. In FIG. 1, electron beams emitted by an anode electrode 110 from an electron source 108 through the adjustment by a Wehnelt electrode 109 form a crossover 112 (irradiation system crossover) through a crossover adjustment optical system 111 (crossover adjustment system). In the present exemplary embodiment, the electron source 108 may be a thermionic electron source in which LaB6 or BaO/W (dispenser cathode) is included in an electron emitter. The crossover adjustment optical system 111 includes two stages of electrostatic lenses, and each electrostatic lens may be an Einzel electrostatic lens which includes three electrodes, and in which a negative potential is applied to an intermediate electrode, and the upper and lower electrodes are grounded. The electron beams radiated with a wide angle from the crossover 112 become parallel beams by the collimator lens 115 and irradiate the aperture array 117. The parallel beams irradiating the aperture array 117 are split by the aperture array 117 to become multi-electron beams 118 (plural electron beams). The multi-electron beams 118 are converged by a (first) converging lens array 119 and are focused on a blanker array 122. In the present exemplary embodiment, the converging lens array 119 may be an Einzel electrostatic lens array which includes three porous electrodes, and in which a negative potential is applied to an intermediate electrode of the three electrodes, and the upper and lower electrodes are grounded. The aperture array 117 is placed at the position (the position of a front-side focal plane of the converging lens array 119) of a pupil plane of the converging lens array 119 so that the aperture array 117 has a function of defining the area of electron beams passing through the pupil plane of the converging lens array 119. The blanker array 122 is a device including deflection electrodes (more exactly, a deflection electrode pair) which may be controlled individually. The blanker array 122 performs blanking by deflecting the multi-electron beams 118 individually based on a blanking signal generated by a drawing pattern generating circuit 102, a bitmap conversion circuit 103, and a blanking instruction circuit 106. No voltage may be applied to the deflection electrodes of the blanker array 122 when electron beams are not blanked, whereas a voltage may be applied to the deflection electrodes of the blanker array 122 when electron beams are blanked. In the present exemplary embodiment, the electron beams deflected by the blanker array 122 are blocked by a stop aperture array 123 located on the rear side, whereby a blanking state is realized. In the present exemplary embodiment, the blanker array and the stop aperture array include two stages. More specifically, a (second) blanker array 127 and a (second) stop aperture array 128 having the similar structure as the (first) blanker array 122 and the (first) stop aperture array 123 are disposed on the rear side. The multi-electron beams 118 having passed through the blanker array 122 are focused on the second blanker array 127 by the second converging lens array 126. In addition, the multi-electron beams 118 are converged by third and fourth converging lenses 130 and 132 and are focused on a wafer 133 (substrate). In the present exemplary embodiment, the second, third, and fourth converging lens arrays 126, 130, and 132 may be an Einzel electrostatic lens array similarly to the first converging lens array 119. In the present exemplary embodiment, the fourth converging lens array 132 is an objective lens array, and the projection magnification thereof is set to about 1/100, for example. As a result, a spot diameter (which is 2 μm by full width at half maximum (FWHM)) of an electron beam 121 on an intermediate image forming surface on the blanker array 122 is reduced on the wafer 133 by about 1/100 to become a spot diameter of about 20 nm by FWHM. Scanning (sweeping) of the multi-electron beams 118 on the wafer 133 may be performed using a deflector 131. The deflector 131 is formed by counter electrode pairs, and for example, may be configured by four stages of counter electrode pair to perform two stages of deflection with respect to each of X and Y directions (in FIG. 1, for the sake of simplicity, two stages of deflector is illustrated as one unit). The deflector 131 is driven according to a signal generated by a deflection signal generating circuit 104. During drawing of patterns, a stage 134 holding the wafer 133 is continuously moved in the X direction. In parallel with this, the electron beam 135 on the wafer is deflected in the Y direction by the deflector 131 based on the real-time measurement results of the position of the stage 134 by a position measuring equipment (for example, one using a laser distance measuring machine). In parallel with them, blanking of an electron beam is performed according to a drawing pattern by the first and second blanker arrays 122 and 127. With such an operation, patterns may be drawn on the wafer 133 at high speed. An electron (charged particle) optical system described above may be roughly split into the following three parts. The first part is an irradiation optical system 140 (also referred to as an irradiation system), which includes the elements from the electron source 108 to the collimator lens 115. The second part is a multi-beam forming optical system 150, which includes the aperture array 117 splitting the electron beam exiting the irradiation optical system 140 into multi-electron beams and the converging lens array 119 forming a plurality of crossovers from the multi-electron beams. The multi-beam forming optical system 150 is also simply referred to as a multi-beam forming system. The third part is a projection optical system 160, which includes an element in which a plurality of apertures corresponding to the plurality of crossovers is provided and a plurality of projection optical units provided to the plurality of apertures and configured to project an electron beam (crossover) onto the wafer (substrate). In the present exemplary embodiment, the element is the blanker array 122, for example. The projection optical unit is also simply referred to as a projection unit, and the projection optical system is simply referred to as a projection system. The present exemplary embodiment is characterized in the configuration of the multi-beam forming optical system 150. FIG. 2 is a diagram illustrating electron beams passing through an aperture array and a converging lens array when the present invention is not applied. FIG. 2 illustrates a portion including the multi-beam forming optical system 150 in FIG. 1. In FIG. 2, electron beams radiated with a wide angle from the crossover 112 are incident on the collimator lens 115 and are collimated (made approximately parallel) by the collimator lens 115. However, when the divergence angle (divergence half angle) of electron beams is large, the electron beams are not made exactly parallel due to an aberration of the irradiation optical system 140, but such a non-uniformity occurs that the irradiation angles (incidence angles) thereof are different depending on the position in an electron beam receiving surface. In the present exemplary embodiment, the aberration of the irradiation optical system includes spherical aberration of the crossover adjustment optical system 111, spherical aberration of the collimator lens 115, and aberration (this aberration may correspond to a spherical aberration of a concave lens) due to a space-charge effect between the electron source and the aperture array 117. For example, when spherical aberration of the collimator lens 115 is dominant among the aberrations of the irradiation optical system 140, electron beams 204 incident on the aperture array 117 are inclined more inside as the electron beams are located more outside due to spherical aberration (positive spherical aberration) of a convex lens. Therefore, principal rays 205 of the multi-electron beams having passed through the aperture array are also inclined more inside as the principal beams are located more outside. As a result, the electron beams having passed through the converging lens array 119 deviate closer to the inner side from desired positions on the blanker array 122 as the electron beams are located closer to the outer side. In this way, the beam arrangement of the multi-electron beams becomes non-uniform, and the electron beams on the outer side do not pass through the centers of the apertures 203 of the blanker array 122. As a result, the deflection properties of the blanker array 122 become non-uniform. Conversely, when the effect of the aberration due to the space-charge effect is dominant, the electron beams 204 incident on the aperture array 117 may be inclined more outside as the electron beams are located more outside due to spherical aberration (negative spherical aberration) of the concave lens. Therefore, the sum of spherical aberrations, respectively formed by the crossover adjustment optical system 111, the collimator lens 115 and the space-charge effect, determines an angular distribution of electron beams. More specifically, whether the electron beams located more outside will be inclined more inside or more outside is determined by the sum. In the exemplary embodiment of the present specification, a case where the aberrations of the irradiation optical system have non-uniformity such that spherical aberration of the collimator lens 115 is dominant and the electron beams incident on the aperture array are inclined more inside as the electron beams are located more outside will be described. FIGS. 3A and 3B are diagrams illustrating an aperture arrangement of an aperture array and a converging lens array and an arrangement of electron beams on an image forming surface, respectively, in the configuration of FIG. 2. An aperture arrangement 201 of the aperture array and an aperture arrangement 202 of the converging lens array in FIG. 3A are made identical to an aperture arrangement 203 of the blanker array in FIG. 3B. Although a case where the apertures 203 of the blanker array have a square lattice-shaped arrangement is illustrated as an example, the present invention is not limited to that. For example, another arrangement having periodicity such as a checkerboard lattice-shaped arrangement may be used. As illustrated in FIG. 3B, as described above, the positions of the electron beams 121 on the image forming surface (or the blanker array) are closer to the inner side in relation to the positions of the apertures 203 of the blanker array as the electron beams are located closer to the outer side due to the aberrations of the irradiation optical system. More specifically, the beam arrangement 121 on the blanker array (the image forming surface) deviates in relation to the arrangement of the apertures 203 of the blanker array. Therefore, assuming that aberrations of the irradiation optical system are present, it is not desirable to make the arrangement of the apertures 201 of the aperture array and the arrangement of the apertures 202 of the converging lens array identical to the arrangement of the aperture array 203 of the blanker array. In contrast, FIG. 4 is a diagram illustrating electron beams passing through the aperture array and the converging lens array in the first exemplary embodiment. In FIG. 4, the positions of the respective apertures of the aperture array 117 and the converging lens array 119 deviate by the same amount in relation to the positions (the positions of desired electron beams) of the corresponding apertures on the blanker array 122 (or the image forming surface). In the present exemplary embodiment, the same amount means not only a case where the amounts are exactly identical but also a case where the amounts are not identical, due to a manufacturing error or a layout error, within an allowable range set from the precision required for a drawing apparatus. The amount of displacement (eccentricity) of the aperture position may be set based on the incidence angle of an electron beam corresponding to the aberration of the irradiation optical system. The incidence angle may be set by a function of a distance, for example, a third-order polynomial (described below), from a blanker center (the center of the blanker array 122) at the position on the blanker array 122. Trajectories 401 of the multi-electron beams when the positions of the apertures of the aperture array 117 and the converging lens array 119 deviate by taking the incidence angles of the electron beams into consideration are as illustrated in FIG. 4. More specifically, such trajectories are obtained that the arrangement of electron beams on the blanker array 121 (or the image forming surface) is identical to the arrangement of the centers of the apertures 203 of the blanker array 122. By correcting the non-uniformity of the beam arrangement of the multi-electron beams in such a manner, the electron beams on the outer side also pass through the centers of the apertures 203 of the blanker array 122, whereby the deflection properties of the blanker array 122 are improved. In FIG. 4, for the sake of comparison, the trajectories 402 of the multi-electron beams in the configuration of FIG. 2 are depicted by dotted lines. FIGS. 5A and 5B are diagrams illustrating an aperture arrangement of an aperture array and a converging lens array and the arrangement of electron beams on the image forming surface (or the blanker array 122) in the first exemplary embodiment. FIG. 5A illustrates the aperture arrangement of an aperture array and a converging lens array, obtained by displacing the positions of the respective apertures 201 of the aperture array and the positions of the respective apertures 202 of the converging lens array by the same amount in relation to the positions of the corresponding apertures 203 of the blanker array. FIG. 5B illustrates the arrangement of electron beams on the image forming surface, and the arrangement of electron beams matches a desired arrangement of electron beam as a result of correction. In the present exemplary embodiment, matching means that a deviation of the positions of respective electron beams in relation to target positions is within a tolerance range. In the present exemplary embodiment, the aperture array 117 may be placed on the pupil plane (front-side focal plane) of the converging lens array 119. In a state where the aperture array 117 is placed on the pupil plane of the converging lens array 119, when the aperture arrangement 201 of the aperture array and the aperture arrangement 202 of the converging lens array deviate by the same amount, the area of electron beams passing through the pupil plane of the converging lens array 119 does not change. Thus, even when the aperture positions of the aperture array and the converging lens array are displaced by the same amount while maintaining a state where the aperture centers thereof are on the same axis, the angles of the principal rays of the multi-electron beams incident on the image forming surface may be maintained to be uniform. More specifically, by performing the correction described above by disposing the aperture array 117 on the front-side focal plane of the converging lens array 119, the non-uniformity of the beam arrangement of the multi-electron beams on the image forming surface may be corrected. In addition, the uniformity of the incidence angles on the image forming surface may be maintained. When there is a parallel eccentricity between the aperture array 117 and the converging lens array 119, the area of electron beams passing through the pupil plane of the converging lens array 119 changes uniformly over all of the multi-electron beams. Thus, all of the multi-electron beams on the image forming surface are inclined uniformly. Such a uniform inclination may be easily corrected in a lump by an aligner deflector 120. In the present exemplary embodiment, the issue is the non-uniformity occurring due to the individual inclination of multi-electron beams, and the present invention is directed to suppressing the non-uniformity occurring due to aberration of the irradiation optical system. In the first exemplary embodiment, the amount of deviation of the aperture arrangement 201 of the aperture array and the aperture arrangement 202 of the converging lens array is specifically determined by three parameters in addition to the distance (image height) Y from the center of the blanker array to an electron beam on the blanker array. The three parameters include a spherical aberration coefficient Cs of the irradiation optical system, and the focal length f and the defocus adjustment amount Δf the collimator lens. In the present exemplary embodiment, although the defocus adjustment amount Δf may be adjusted by the crossover adjustment optical system 111, the present invention is not limited to that, and the defocus adjustment amount may be adjusted by changing the power of the collimator lens, for example. In the present exemplary embodiment, the spherical aberration coefficient Cs of the irradiation optical system may be expressed by an expression, Cs=Cs(CO_adjust)+Cs(CL)+Cs(Coulomb). Cs(CO_adjust) is the spherical aberration coefficient of the crossover adjustment optical system, Cs(CL) is the spherical aberration coefficient of the collimator lens, and Cs(Coulomb) is the spherical aberration coefficient due to a space-charge effect. The amount of angular deviation Δθ of electron beam due to aberration of the irradiation optical system may be approximately expressed by Δθ=Cs(Y/f)3+Δf(Y/f) using the above parameters. This expression is a third-order polynomial in terms of the distance Y. FIGS. 6A, 6B, and 6C are diagrams illustrating a difference in aperture arrangement of an aperture array and a converging lens array depending on the presence of a defocus of an irradiation optical system in the first exemplary embodiment. FIG. 6A illustrates the aperture arrangement 201 of the aperture array and the aperture arrangement 202 of the converging lens array when the defocus adjustment amount Δf is 0 (defocus amount is zero). FIG. 6B illustrates the aperture arrangement 201 of the aperture array and the aperture arrangement 202 of the converging lens array when defocus adjustment is performed (defocusing is performed). FIG. 6C is a graph in which the distance (image height) Y is on the horizontal axis, and the amount of angular deviation of an electron beam due to aberration of the irradiation optical system is on the vertical axis (illustrating a case where Cs=5000 mm, f=500 mm, and Δf=1.5 mm). In the graph, the amount of angular deviation is positive when an electron beam is inclined inside. In FIG. 6C, the amount of angular deviation of an electron beam when defocus adjustment is not present is proportional to the cube of the distance Y. Therefore, the aperture arrangement of the aperture array and the converging lens array is corrected to become an aperture arrangement having an amount of deviation proportional to the cube of the distance Y as illustrated in FIG. 6A. On the other hand, in FIG. 6C, as for the amount of angular deviation of an electron beam when defocus adjustment is performed, a defocus term proportional to the distance Y is added in addition to the term proportional to the cube of the distance Y. Thus, as may be understood from FIG. 6C, as for the electron beam when defocus adjustment is performed, an electron beam in an area where the distance Y is small is inclined outside, whereas an electron beam in an area where the distance Y is large is inclined inside. Taking that into consideration, the aperture arrangement of the aperture array and the converging lens array is corrected in a manner such that an aperture 601 in an area where the distance Y is small deviates toward the inner side in relation to a desired beam arrangement on the image forming surface whereas an aperture 602 in an area where the distance Y is large deviates toward the outer side as illustrated in FIG. 6B. As described above, when defocus adjustment is performed, an aperture arrangement pattern becomes somewhat complex. However, as apparent from the graph of FIG. 6C, the range of absolute values of the amount of angular deviation becomes smaller when defocus adjustment is performed. Thus, defocus adjustment provides an advantage in that the amount of deviation of the aperture arrangement of the aperture array and the converging lens array may be decreased. This may be easily understood when FIGS. 6A and 6B are compared with each other. As described above, defocus adjustment has advantages and disadvantages. It should be understood that in all exemplary embodiments of the present invention, an aperture arrangement pattern of the aperture array and the converging lens array may be changed by defocus adjustment. Moreover, the aperture arrangement pattern illustrated in the exemplary embodiments is exemplary only, and an arrangement pattern configured to correct the non-uniformity of the angles of electron beams occurring due to aberration of the irradiation optical system also falls within the scope of the present invention. FIG. 7 is a diagram illustrating electron beams passing through the aperture array 117 and the converging lens array 119 in a second exemplary embodiment of the present invention. FIG. 7 illustrates a portion corresponding to the multi-beam forming optical system 150 of FIG. 1, and the other constituent elements of the present exemplary embodiment are similar to those of the first exemplary embodiment. In FIG. 7, the aperture positions 202 of the converging lens array deviate according to a third-order polynomial in terms of the distance (image height) Y to correct the non-uniformity of the arrangement of electron beams on the image forming surface due to aberration of the irradiation optical system similarly to the first exemplary embodiment. Moreover, the position of the aperture array 117 is disposed at a position deviating from a front-side focal plane 701 of the converging lens array 119. Ideally, the position of the aperture array 117 may be placed on the front-side focal plane 701 of the converging lens array 119. However, there may be a case where an ideal layout is not possible, such as a case where it is difficult to secure amounting space or a case where the focal length of the converging lens array 119 is very long. In such a case, as long as it is possible to accurately recognize an angular deviation of electron beams due to aberration of the irradiation optical system, multi-electron beams may be made incident with a uniform angle of principal ray in relation to the blanker array 122 (or the image forming surface) similarly to the first exemplary embodiment. In order to realize that, in FIG. 7, it is necessary to determine the aperture arrangement of the aperture array 117 so that a convergent angular distribution of electron beams due to the converging lens array 119 becomes uniform over all of the multi-electron beams. More specifically, the convergent angular distribution of multi-electron beams is determined by a distribution of electron beams passing through the front-side focal plane 701 of the converging lens array 119. Thus, when it is possible to exactly recognize an angular deviation (angular distribution) of electron beams due to the aberration of the irradiation optical system, it is possible to define a distribution of electron beams passing through the front-side focal plane 701. Specifically, a configuration as illustrated in FIG. 7 may be adopted. More specifically, similarly to the first exemplary embodiment, the aperture positions of the aperture array 117 may be determined so that the center of an (imaginary) electron beam distribution 703 on the front-side focal plane 701 of the converging lens array is on an optical axis 704 of the converging lens array. For example, in FIG. 7, the position of the aperture array 117 is disposed approximately at the center between the converging lens array 119 and the front-side focal plane 701 of the converging lens array. In this case, the amount of deviation of the apertures 201 of the aperture array is approximately half the amount of deviation of the apertures 202 of the converging lens array. By doing so, the center of the (imaginary) electron beam distribution 703 on the front-side focal plane 701 of the converging lens array is located on the optical axis 704 of the converging lens array. More generally, the amount of deviation of the apertures 201 of the aperture array may be proportional to the distance 710 between the front-side focal plane of the converging lens array and the aperture array. FIGS. 8A, 8B, and 8C are diagrams illustrating the aperture arrangement of an aperture array and a converging lens array and the arrangement of electron beams on the image forming surface in the second exemplary embodiment. FIG. 8A illustrates the arrangement of the apertures 202 of the converging lens array, FIG. 8B illustrates the arrangement of the apertures 201 of the aperture array, and FIG. 8C illustrates the arrangement of electron beams on the image forming surface. Circular dotted lines in FIGS. 8A and 8B illustrate the apertures 203 of the blanker array. In FIG. 8B, the amount of deviation of the apertures of the aperture array is set to be approximately half the amount of deviation of the apertures of the converging lens array to define the electron beam distribution 703 on the front-side focal plane 701 of the converging lens array as described above. As described above, even when the aperture array 117 is not disposed on the front-side focal plane 701 of the converging lens array, by adopting the configuration of the present exemplary embodiment, the same advantages as the first exemplary embodiments may be obtained. However, as will be described with reference to FIGS. 9A, 9B, 10A, and 10B, it is useful to dispose the aperture array 117 on the front-side focal plane 701 of the converging lens array as close as possible similarly to the first exemplary embodiment. FIGS. 9A and 9B are diagrams illustrating electron beams reaching respective portions within a spot beam. FIG. 9A is a diagram illustrating electron beams reaching the respective portions within a spot beam according to the first exemplary embodiment, in which the aperture array 117 is placed on the front-side focal plane 701 of the converging lens array. Thus, on-axis and off-axis principal rays including a principal ray 901 of an off-axis beam advancing toward an outer-side portion of a spot beam image are parallel to the optical axis. FIG. 9B is a diagram illustrating electron beams reaching the respective portions within a spot beam according to the second exemplary embodiment, in which the aperture array 117 is not placed on the front-side focal plane 701. In this case, as may be understood from FIG. 9B, an angular distribution of off-axis electron beams on the front-side focal plane 701 of the converging lens array is different from that of on-axis electron beams. More specifically, the principal ray 901 of an off-axis beam advancing toward the outer-side portion of a spot beam image is not parallel to the optical axis but is inclined. As a result, when a focus deviates, the beam spot tends to become blurred. More specifically, in the configuration of the second exemplary embodiment, it is not possible to make both the on-axis and off-axis principal rays parallel to the optical axis. However, this influence is small when the diameter of a beam spot on the image forming surface is small. Thus, in the configuration of the second exemplary embodiment, it is useful to decrease the diameter of a beam spot on the image forming surface to an extent such that the influence of an inclination of off-axis light beams is allowable. FIGS. 10A and 10B are diagrams illustrating electron beams when an estimate of an angular deviation of an electron beam has an error. FIG. 10A illustrates a case where an estimate of an angular deviation of an electron beam has an error in the first exemplary embodiment, in which an actual electron beam is denoted by a solid line, and an estimate electron beam is denoted by a dotted line. Since there is an estimation error, although an image forming position 121 of an electron beam deviates in relation to an estimated image forming position 1002, a principal ray 205 of the electron beam is parallel to the optical axis. This is because, even when there is an estimation error, the apertures 201 of the aperture array are on the front-side focal plane of the converging lens array. FIG. 10B illustrates a case where an estimate of an angular deviation of an electron beam has an error in the second exemplary embodiment, in which an actual electron beam is denoted by a solid line, and an estimate electron beam is denoted by a dotted line. Since there is an estimation error, the image forming position 121 of an electron beam deviates in relation to the estimated image forming position 1002, and in the case of the second exemplary embodiment, the angle of the principal ray 205 of the electron beam also deviates. This is because the aperture array 117 is not on the front-side focal plane 701 of the converging lens array. As a result, as may be understood from FIG. 10B, the electron beam distribution on the front-side focal plane 701 of the converging lens array further deviates in relation to the estimate. More specifically, in the configuration of the second exemplary embodiment, when the estimate of the angular deviation of the electron beam has an error, it is necessary to pay attention to the fact that the angle of the principal ray 205 as well as the image forming positions 121 of the multi-electron beams deviate. As described above, when employing the configuration of the second exemplary embodiment, it is necessary to decrease the diameter of a beam spot on the image forming surface to an extent such that the influence of an inclination of an off-axis beam is allowable and to pay attention to the influence on the angle of a principal ray, of an estimation error of the angular deviation of the electron beam. FIG. 11 is a diagram illustrating the configuration of a drawing apparatus according to a third exemplary embodiment of the present invention. The irradiation optical system 140 and the multi-beam forming optical system 150 having different configurations from those of FIG. 1 will be described. An electron source array 1110 is one in which a plurality of thermal field emission (TFE) electron sources is arranged. The thermal field emission electron source includes a thermal field emission emitter 1101, a suppressor electrode 1102, a first anode electrode 1103, and a second anode electrode 1104. The thermal field emission emitter 1101 corresponds to a cathode. The suppressor electrode 1102 has a function of restricting electron emission from portions other than a tip end of the cathode. The first and second anode electrodes 1103 and 1104 form an electric field for allowing electrons to be emitted from the thermal field emission emitter 1101. The thermal field emission emitter 1101 emits electrons by a combination of a thermionic emission effect by heating and a Shottky effect under a strong electric field by an anode electrode. A group of electron beams emitted from the thermal field emission emitters 1101 arranged in an array shape form (irradiation optical system) crossovers 112 arranged in an array shape by the crossover adjustment optical systems 111 arranged similarly in an array shape. In the present exemplary embodiment, a thermal field emission cathode material such as ZrO/W is used for the thermal field emission emitter 1101. Electron beams 114 radiated from the crossovers 112 arranged in an array shape are made parallel by a collimator lens array 1105 and form a plurality of electron beams which do not overlap each other. The plurality of electron beams irradiates a plurality of subarray areas (each including a plurality of apertures) on the aperture array 117. As may be understood from FIG. 11, with regard to one array among the plurality of electron source arrays 1110, the configuration of the optical system thereof is equivalent to that of FIG. 1. Thus, the configuration of the above-described exemplary embodiment may be applied to the optical systems corresponding to the respective electron sources (respective subarray areas) in parallel. FIGS. 12A and 12B are diagrams illustrating the aperture arrangement of an aperture array and a converging lens array and the arrangement of electron beams on the image forming surface in the third exemplary embodiment. FIG. 12A illustrates the aperture arrangement of an aperture array and a converging lens array in a 3×3 subarray area in the present exemplary embodiment, and FIG. 12B illustrates the arrangement 121 of electron beams on the image forming surface in the 3×3 subarray area. As illustrated in FIG. 12A, in the respective subarray areas, the apertures 201 of the aperture array and the apertures 202 of the converging lens array deviate in relation to the apertures 203 of the blanker array to correct the non-uniformity of the angles of electron beams due to aberration of the irradiation optical system. Since a plurality of irradiation optical systems having the similar configuration is arranged in parallel, the aperture arrangement of the aperture array and the converging lens array is similar in any subarray area. In FIG. 12A, the aperture array 117 is placed on the front-side focal plane 701 of the converging lens array, and the apertures 201 of the aperture array and the apertures 202 of the converging lens array deviate by the similar amount. By applying the configuration of the first exemplary embodiment to each subarray area as illustrated in FIG. 12A, the non-uniformity of multi-electron beams is corrected as illustrated in FIG. 12B. As described above, when the irradiation optical systems are provided in parallel, the present invention may be applied to the plurality of irradiation optical systems in parallel. Thus, even when the above-described defocus adjustment of the irradiation optical system is performed, as for the aperture arrangement of the aperture array and the converging lens array, the arrangement illustrated in FIGS. 6A to 6C may be applied to each irradiation optical system (subarray area). Moreover, even when the aperture array 117 is disposed to deviate from the front-side focal plane 701 of the converging lens array, it is apparent that as for the aperture arrangement of the aperture array and the converging lens array, the arrangement illustrated in FIG. 8 may be applied to each irradiation optical system (subarray area). FIG. 13 is a diagram illustrating the configuration of a drawing apparatus according to a fourth exemplary embodiment of the present invention. In FIG. 13, since the configuration from the electron source 108 to the aperture array 117 is similar to that of FIG. 1, the description thereof is not repeated, and the constituent elements located closer to the rear side than the aperture array 117 will be described. The multi-electron beams formed by the aperture array 117 are converged by the converging lens array 119. In the fourth exemplary embodiment, the powers of the respective lenses of the converging lens array 119 are set so that the multi-electron beams converge on a stop aperture array 1303 on the rear side. Immediately after passing through the converging lens array 119, the multi-electron beams are further split into submulti-electron beams by a projecting aperture array 1301. FIG. 13 illustrates a state where one multi-electron beam is split into 3×3 submulti-electron beams. Since the powers of the respective lenses of the converging lens array 119 are set as described above, the submulti-electron beams converge on the stop aperture array 1303. In the present exemplary embodiment, in the stop aperture array 1303, an aperture is provided for each submulti-electron beam. The arrangement of the apertures 1304 of the stop aperture array 1303 is configured to be identical to the arrangement of the apertures at the center of the 3×3 sub-aperture arrays of the projecting aperture array 1301. The blanker array 122 is provided right below the projecting aperture array 1301, so that similarly to the configuration of FIG. 1, an operation of blanking respective electron beams may be performed by individual deflection. When it is desired to blank (block) an electron beam, a voltage is applied to the corresponding electrode pair of the blanker array 122, whereby the electron beam is blocked by the stop aperture array 1303. FIG. 13 illustrates an electron beam 125 deflected (blocked) by the blanker array 122. The submulti-electron beams having passed through the stop aperture array 1303 are converged by the second converging lens array 132 and are focused on the surface of the wafer 133. The projecting aperture array 1301 is disposed on the image plane of the second converging lens array 132, and a 3×3 aperture pattern of the projecting aperture array 1301 is reduced and projected onto the surface of the wafer 133 by the respective lenses of the second converging lens array 132. For example, the aperture diameter of the projecting aperture array 1301 is set to 2.5 μm, and the projection magnification of the second converging lens array 132 is set to 1/100. As a result, an image having a diameter of 25 nm is formed on the surface of the wafer 133. In addition, the stop aperture array 1303 is disposed on the front-side focal plane of the second converging lens array 132 to define an area of electron beams passing through the pupil plane of the second converging lens array 132. A deflector array 1302 is disposed near the stop aperture array 1303, so that similarly to the configuration of FIG. 1, deflection (scanning) of submulti-electron beams may be performed. More simply, the deflector array 1302 may be driven by a common application voltage, and the electrode structure thereof may be formed of a comb tooth-shaped confronting electrode. FIGS. 14A, 14B, and 14C are diagrams illustrating electron beams passing through an aperture array and a converging lens array and the arrangement of electron beams on a stop aperture array in the configuration (in a case where the present invention is not applied) of FIG. 13. When the angular distribution of electron beams becomes non-uniform due to aberration of an irradiation optical system, the arrangement of electron beams (crossovers) formed on the stop aperture array 1303 by the converging lens array 119 becomes non-uniform. More specifically, the arrangement of spots of submulti-electron beams of the stop aperture array 1303 becomes non-uniform due to aberration of the irradiation optical system. FIG. 14C illustrates the arrangement thereof, in which such a non-uniformity occurs that electron beams converge closer to the inside in relation to a desired position (the position of an aperture 1304 of the stop aperture array) as the electron beams are located closer to the outside (as the image height increases) as illustrated in FIG. 3B. In the present exemplary embodiment, since the multi-electron beams are further split into submulti-electron beams by the projecting aperture array 1301, the influence of shifting of electron beams radiated on the projecting aperture array 1301 needs to be taken into consideration. As may be understood from FIG. 14A, electron beams radiated on the projecting aperture array 1301 are shifted closer to the inside as the electron beams are located closer to the outside due to aberration of the irradiation optical system. As a result, the respective principal rays of the submulti-electron beam are inclined more inside as the principal rays are located more outside due to aberration of the irradiation optical system (this may be understood by comparing a group of electron beams at the center of FIG. 14A with a group of electron beams on the left and right side). Therefore, the angular distribution of electron beams defined by the stop aperture array 1303 is different depending on the subarray area. As a result, the arrangement and the intensity (current intensity) of electron beams on the surface of the wafer 133 become non-uniform. FIGS. 15A, 15B, and 15C are diagrams illustrating electron beams passing through an aperture array and a converging lens array and the arrangement of electron beams on a stop aperture array when the present invention is applied to the configuration of FIG. 13. In the present exemplary embodiment, the non-uniformity is corrected by arranging the apertures 201 of the aperture array and the apertures 202 of the converging lens array to deviate according to a third-order polynomial in terms of the distance (image height) as illustrated in FIG. 15B similarly to the first exemplary embodiment. All of the configurations used in the first and second exemplary embodiments are applicable to the present exemplary embodiment, and these configurations also fall within the scope of the embodiments. According to the present exemplary embodiment as illustrated in FIGS. 15A to 15C, the non-uniformity may be corrected so that the respective principal rays of the submulti-electron beam are not inclined due to aberration of the irradiation optical system and converge on the centers of the apertures 1304 of the stop aperture array. In the above exemplary embodiments, the arrangement of the apertures 201 of the aperture array and the apertures 202 of the converging lens array is determined according to the spherical aberration of the irradiation optical system. In practice, since spherical aberration of the irradiation optical system is estimated by simulation or actual measurement, this estimation may incur errors. Thus, when the estimation error exceeds an allowable value, the correction based on the arrangement of the apertures 201 of the aperture array and the apertures 202 of the converging lens array has non-allowable correction residues (errors). In such a case, it is undesirable to manufacture the aperture array and the converging lens array again from the perspective of manufacturing costs. In this respect, the following exemplary embodiments including a fifth exemplary embodiment are directed to a configuration advantageous when correction residues occur due to an estimation error of spherical aberration of the irradiation optical system. The configuration includes an adjustment unit that adjusts the aberration of the irradiation optical system. The adjustment unit adjusts the aberration so that the position of each of a plurality of crossovers which are incident on the aperture array at an incidence angle associated with the aberration and are formed by the converging lens array matches the corresponding aperture. The corresponding aperture is a corresponding aperture of an element such as the blanker array or the stop aperture array as described above. FIG. 16 is a diagram illustrating a configuration of a drawing apparatus according to the fifth exemplary embodiment. Since the configuration of the present exemplary embodiment is characterized in the configuration of the collimator lens 115, the configuration thereof will be described. In the present exemplary embodiment, the collimator lens 115 includes three stages of lens (charged particle lens), in which diverging charged particle beams are collimated by a main collimator lens 1701 on the middle stage, a first adjustment lens 1702 on the upper stage, and a second adjustment lens 1703 on the lower stage. By configuring the collimator lens to have multiple stages (a plurality of charged particle lenses), it is possible to adjust spherical aberration of the irradiation optical system while maintaining the focal length of the collimator lens to be constant. In the present exemplary embodiment, the focal length of the collimator lens means the focal length (combined focal length) when multiple stages of collimator lens are regarded as one lens. The above-described spherical aberration may be adjusted while maintaining the front-side focal point position (object plane-side focal point position) and the front-side principal plane position (object plane-side principal plane position) by individually controlling (adjusting) the powers of the first adjustment lens 1702, the main collimator lens 1701, and the second adjustment lens 1703, for example. In the present exemplary embodiment, the front-side focal point position and the front-side principal plane position mean the front-side focal point position and the front-side principal plane position when multiple stages of collimator lens are regarded as one lens. FIG. 16 illustrates a trajectory 1706 of an electron beam when the collimator lens includes one stage of electron lens. Moreover, the adjustment of the spherical aberration may be performed by moving the respective lenses in the multiple stages of collimator lens. In this case, a mechanism for driving the main collimator lens 1701, the first adjustment lens 1702, and the second adjustment lens 1703 may be provided as a unit associated with the movement of each of them (that is, three electrodes constituting the respective lenses form one unit). In addition, the spherical aberration may be adjusted by a combination of the adjustment of the powers of the respective electron lenses and the adjustment of the positions thereof. Although a collimator lens including three stages of electron lens has been illustrated, the configuration of the collimator lens is not limited to one which includes three stages of electron lenses but may include one which includes two or four or more stages of electron lens. Such adjustment involves changing spherical aberration of the irradiation optical system by changing the path of an electron beam while fixing the front-side focal point position and the front-side principal plane position. More specifically, one kind of optical property is varied while fixing two kinds of optical properties. Thus, such adjustment may be realized with at least three control parameters in principle (mathematically). For example, in the above configuration example, three control parameters are used by varying the potentials applied to the three stages of electron lens. Moreover, when the collimator lens includes two stages of electron lens, for example, at least three control parameters may be used by adding the adjustment (movement) of at least one electron lens to the adjustment of the potentials applied thereto. Furthermore, when four or more stages of electron lens are included, the above adjustment may be realized by using at least three control parameters. The above adjustment may be performed based on an estimation error amount of the spherical aberration of the irradiation optical system. The estimation error amount may be obtained by measuring a positional deviation of electron beams on the wafer 133, for example. More specifically, the positions of electron beams are measured in relation to a plurality of different image heights, for example, and it may be examined whether the amount of positional deviation of electron beams (the amount of deviation from a target position) has a correlation expressed by the above cubic function. If the amount of positional deviation of electron beams has a correlation, the adjustment may be performed using the coefficients of the cubic function as the estimation errors. By configuring the collimator lens to have multiple stages as in the case of the present exemplary embodiment, the aberration (spherical aberration) may be adjusted while maintaining the optical properties other than the aberration (spherical aberration). In this way, the issue associated with the above correction residues may be solved. This will be described with reference to FIGS. 17A, 17B, 17C, and 17D. FIGS. 17A, 17B, 17C, and 17D are diagrams illustrating the configuration and the function of a multi-stage collimator lens. FIG. 17A is a graph illustrating a relation between a change of spherical aberration of a multi-stage collimator lens and a change of the amount of deviation of irradiation angle. FIG. 17B is a diagram illustrating the arrangement of the apertures 201 of the aperture array and the apertures 202 of the converging lens array determined in advance according to estimated spherical aberration of the irradiation optical system. As illustrated in FIG. 17A, the amount of deviation of the irradiation angle of electron beams due to the irradiation optical system may be adjusted by adjusting spherical aberration of a multi-stage collimator lens. Thus, even when the estimated spherical aberration of the irradiation optical system has an error in relation to the actual spherical aberration, the correction residues resulting from the estimation error of the spherical aberration may be suppressed (corrected) by adjusting spherical aberration of the irradiation optical system. In the present exemplary embodiment, since the aperture pattern of FIG. 17B is formed according to the value of the spherical aberration estimated in advance, the correction residues thereof are generally small. Therefore, such correction residues may be generally corrected by finely adjusting spherical aberration of the irradiation optical system. FIGS. 17C and 17D illustrate an adjustment example of the spherical aberration due to a multi-stage collimator lens. In the adjustment in FIGS. 17C and 17D, it may be understood that the positions of a (combined) front-side focal plane 1704 and a (combined) front-side principal plane 1705 when a 3-stage collimator lens is regarded as one lens are maintained to be constant. As a result, the optical properties other than the aberration (spherical aberration) of the irradiation optical system, for example, the parallelism and the irradiation angle of an electron beam near the optical axis are maintained. As described above, it is possible to adjust the aberration (spherical aberration) of the irradiation optical system while maintaining the optical properties other than the aberration (spherical aberration) as illustrated in FIGS. 17C and 17D. The concept of suppressing the residues of the correction of the deviation of irradiation angle due to a change in the aperture arrangement of the aperture array and the converging lens array through the adjustment of the spherical aberration of the irradiation optical system due to a multi-stage collimator lens is not limited to the configuration of the fifth exemplary embodiment. A sixth exemplary embodiment is directed to a configuration example in which a multi-stage collimator lens is applied to the configuration of the fourth exemplary embodiment. FIG. 18 is a diagram illustrating a configuration of a drawing apparatus according to the sixth exemplary embodiment. In the present exemplary embodiment, spherical aberration of the irradiation optical system is varied by replacing the collimator lens 115 according to the fourth exemplary embodiment with the multi-stage collimator lens 115 as described in the fifth exemplary embodiment. Thus, the difference between the present exemplary embodiment and the fourth exemplary embodiment lies in the configuration of the collimator lens 115. In the present exemplary embodiment, the configuration and the function of the multi-stage collimator lens 115 are similar to those of the fifth exemplary embodiment. More specifically, by configuring the collimator lens to have multiple stages, the correction residues resulting from an estimation error of the aberration (spherical aberration) of the irradiation optical system may be suppressed (corrected) by adjusting the aberration (spherical aberration) while maintaining the optical properties other than the aberration (spherical aberration). In the present exemplary embodiment, the estimation error of the spherical aberration of the irradiation optical system appears as the positional deviation of electron beams on the stop aperture array 1303. Thus, the amount of estimation error may be obtained by measuring the amount of positional deviation (deviation from a target position) of electron beams on the stop aperture array 1303 in relation to a plurality of different image heights, for example. More specifically, a sensor configured to detect an electron beam (incident current) may be disposed on the stage 134, for example. More specifically, electron beams are scanned on the stop aperture array using the aligner 120, and electron beams having passed through the apertures of the stop aperture array are detected by the sensor, whereby the positional deviation may be measured. Moreover, by performing this measurement on a plurality of electron beams corresponding to a plurality of different image heights, it may be examined whether the amount of positional deviation of electron beams has a correlation with the above cubic function. In the fifth and sixth exemplary embodiments, spherical aberration of the irradiation optical system has been adjusted so that other optical properties are not changed by configuring the collimator lens to have multiple stages of lens. In a seventh exemplary embodiment, spherical aberration of the irradiation optical system is adjusted while suppressing the amount of change in other optical properties within an allowable range although the change is greater than that of the fifth and sixth exemplary embodiments. The configuration of the seventh exemplary embodiment is similar to that of the first, third, and fourth exemplary embodiments except the following respects. The seventh exemplary embodiment is characterized in that spherical aberration of the irradiation optical system is adjusted by adjusting the focal length (or the power) of the collimator lens 115 and adjusting the positions of the crossovers 112 formed on the front side of the collimator lens 115. In the present exemplary embodiment, by adjusting the power of the collimator lens 115, the dependency on the image height of spherical aberration of the irradiation optical system may be adjusted. This may be understood from the cubic function representing Δθ described above. The amount of angular deviation Δθ of electron beams due to spherical aberration of the irradiation optical system may be approximately expressed by a cubic function, Δθ=Cs(Y/f)3+Δf(Y/f), as described above. Thus, by adjusting the focal length f (or the power) of the collimator lens 115, the dependency on the image height Y of Δθ may be adjusted. For example, when an electron emission surface of a cathode is planar, depending on the configuration of an electron source, no crossover (true crossover) at which electrons actually converge or diverge may be provided on the front side of the collimator lens 115, but imaginary or virtual crossovers (virtual crossovers) may be formed on the front side of the collimator lens 115. In this case, electrons on the rear side of the collimator lens take such a trajectory that the electrons diverge from the virtual crossovers to be made parallel by the collimator lens. Thus, optical systems disposed closer to the rear side than the collimator lens may be configured using the virtual crossovers as virtual object points. Therefore, in systems in which no true crossover is provided on the front side of the collimator lens 115, the positions of the virtual crossovers may be employed as the positions of the crossovers 112 when performing the adjustment. In the present exemplary embodiment, it is assumed that the crossovers (irradiation system crossovers) which are formed on the front side of the collimator lens by the irradiation optical system include both the real crossovers and the virtual crossovers. As an adjustment unit for adjusting the positions of the crossovers 112, a driving unit for moving the part (also referred to as a charged particle source) extending from a cathode electrode to the crossover adjustment optical system and an adjustment unit for adjusting the potentials of the electrodes constituting the crossover adjustment optical system may be employed. FIGS. 19A, 19B, and 19C are diagrams illustrating these two units. FIG. 19A illustrates a state before adjustment. FIG. 19B illustrates a state in which the position of a crossover is adjusted by the driving unit for moving the electron source part (a part surrounded by a dotted line in the figure). FIG. 19C illustrates a state in which the position of the crossover is adjusted by the adjustment unit for adjusting the potentials of the electrodes constituting the crossover adjustment optical system. It may be understood from FIGS. 19A, 19B, and 19C that adjustment may be performed by any one of the driving unit and the adjustment unit so that the position of the crossover matches a target position (the crossover position is located on a target crossover plane 1901). In the present exemplary embodiment, the position of the crossover 112 may be naturally adjusted by a combination of these two units. When the configuration of the present exemplary embodiment is employed, the influence on optical systems on the subsequent stage needs to be taken into consideration. One example of the influence is a change of the magnification of the rear-side optical system due to a change of the focal length of the collimator lens. The ratio of a magnification change is expressed by f′/f, where f is a focal length before change and f′ is a focal length after change. Thus, when the configuration of the present exemplary embodiment is employed, it is useful to include a unit configured to correct a magnification change of the rear-side optical system or to perform the above adjustment within a range such that the magnification change of the rear-side optical system is allowable. In the present exemplary embodiment, one example of the unit correcting the magnification change involves adjusting the diameter of a crossover using the crossover adjustment optical system, for example. However, when the adjustment by the crossover adjustment optical system is performed, since spherical aberration of the crossover adjustment optical system may also be changed, adjustment needs to be performed by taking the change of the spherical aberration into consideration. Moreover, when a configuration in which the crossover adjustment optical system is not included in the charged particle source is employed, the correction of the magnification change is not performed by the crossover adjustment optical system as a matter of course. Since the coulomb effect is great in crossovers in a high current-density area, the configuration without the crossover adjustment optical system may be employed to obviate the effect. In this case, the above adjustment may be performed within such a range that the magnification change of the rear-side optical system is allowable. A method of manufacturing an article according to an exemplary embodiment is suitable for manufacturing micro-devices such as a semiconductor device and articles such as elements having a microscopic structure, for example. The manufacturing method includes an operation or a step (a step of performing drawing on a substrate) of forming a latent image pattern on a photosensitive material applied on a substrate using the drawing apparatus and a step of developing the substrate on which the latent image pattern is formed by the above step. The manufacturing method may include other known steps (oxidation, film formation, deposition, doping, planarization, etching, resist removal, dicing, bonding, packaging, and the like). The article manufacturing method of the present exemplary embodiment is advantageous in terms of at least one of performance, quality, productivity, and production cost of articles as compared to the conventional method. While exemplary embodiments have been described, the present invention is not limited to these exemplary embodiments but may be modified and changed in various ways within the scope of the spirit thereof. For example, the apertures of the converging lens array may be deviated rather than deviating the apertures of the aperture array so that the positions of the crossovers formed by the converging lens array match the apertures (the centers thereof) of a rear-side element such as the blanker array or the stop aperture array. However, this configuration requires attention to the fact that the principal rays of electron beams incident on the apertures of the element are not parallel to the optical axis. This configuration may be used, for example, when such an angular deviation of principal rays is allowable and when an optical element for correcting the angular deviation is additionally included. While the embodiments have been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all modifications, equivalent structures, and functions. This application claims priority from Japanese Patent Applications No. 2011-068014 filed Mar. 25, 2011 and No. 2011-122742 filed May 31, 2011, which are hereby incorporated by reference herein in their entirety. |
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039649695 | description | DESCRIPTION OF THE INVENTION Broadly, the invention is directed to an internal core tightener for fuel elements of a nuclear reactor and is a linear actuated expanding device which uses a minimum of moving parts to perform the lateral tightening function. The key features include: (1) large contact areas to transmit loads during reactor operation, (2) actuation cam surfaces loaded only during clamping and unclamping operations, and (3) preloaded pads with compliant travel at each face of the hexagonal assembly at each clamping plane to accommodate thermal expansion and irradiation induced swelling. This last feature enables use of a "fixed" outer core boundary, and thus eliminates the uncertainty in gross core dimensions, and potential for rapid core reactivity changes as a result of core dimensional change. Referring now to the embodiment of the invention, illustrated in the drawings, FIGS. 1-6 are shown at approximately one-half the scale of FIGS. 7-12. The upper half of FIGS. 7-9 are illustrated in the clamped position while the lower half is illustrated in the unclamped position, whereby certain components in the lower half are shown as being located a distance to the left of the location of the same component in the upper half of each of FIG. 7 and having different cross-sections when viewed in FIGS. 8 and 9. As shown in FIG. 1, an element 10 for a nuclear reactor, such as used in a liquid metal fast breeder reactor, either as a fuel assembly or control assembly, incorporates load pad assemblies indicated generally at 11 and 12 at two spaced clamping planes along the length of element 10, as will be described in greater detail hereinafter. Element 10 includes an outer casing or wrapper 13, hexagonal in configuration, the corners of which are machined out in the vicinity of the load pad assemblies 11 and 12 as indicated at 14, leaving only the relatively flexible flat sides 15 of casing 13 as support members for the load pad assemblies. Load pad assemblies 11 and 12 are moved radially outward during the clamping operation, for example, from an unclamped cross-section distance indicated at A in FIG. 2 of 3.959 inches to be clamped cross-section distance indicated at B in FIG. 3 is 4.134 inches. FIG. 3 illustrates at C the cross-section distance of 4.074 inches, for example, across the load pad assemblies 11 and 12 after compliance travel (the inward movement due to thermal expansion and irradiation induced swelling of the adjacent similar elements positioned about element 10). Thus, the radial outward distance from unclamped to clamped and with compliance travel may vary from about 0.088 to 0.058 inches, the average being about 0.073 inches in the embodiment illustrated. The length of element 10, for example, is 60 inches. FIGS. 4-6 show an actuation sleeve guidance and latch arrangement located in the central portion of element 10 which functions to latch or secure an actuation sleeve 16 to external casing 13. As shown a guide member 17, having a U-shaped grooved portion with one leg of the U substantially longer than the other leg, is fixedly attached to sleeve 16 and a latch member 18 is attached to casing 13 adjacent an opening 19 therein. Movement of actuation sleeve 16 with respect to casing 13 causes latch member 18 to travel along the long leg of the groove of guide member 17 to the bottom of the U whereupon a turning motion of actuation sleeve 16 moves latch member 18 through the bottom of the U whereby a reverse motion of the sleeve 16 locks the latch member 18 in the short leg of the U shaped groove of guide 17. Element 10 and load pad assemblies 11 and 12 are illustrated in detail in FIGS. 7-10. Inasmuch as load pad assemblies 11 and 12 are substantially identical, only assembly 11 will be described in detail with similar components of assembly 12 being given corresponding reference numerals. As noted above, the central section of element 10 has been omitted in FIG. 7 for clarity. Again, it is pointed out that the lower half of each of FIGS. 7-9 as illustrated in the unclamped position with the upper half shown in the clamped position, thus accounting for the different locations of certain of the components in the upper and lower halves of each Figure. As seen in FIG. 7, element 10 is provided with a longitudinally extending support tube 20 which extends outwardly from the right hand end of casing 13 and into a lower tube fitting 21, load pad assembly 12 being positioned intermediate the right terminal end of casing 13 and lower tube fitting 21. Actuation sleeve 16 is positioned about support tube 20 and is provided with two operating sections, one of which is constructed to cooperate with load pad assembly 11 and the other with load pad assembly 12. Actuation sleeve is provided in the area of load pad assembly 11 with a cam-like section or member 22 located in spaced relation with a shoulder-forming member or section 23 having an enlarged end section 24, with another cam-like section 22' and shoulder-forming member 23' positioned to cooperate with load pad assembly 12. Load pad assembly 11 is located in an upper clamping plane indicated at 25, positioned in this embodiment at 127.5 inches above the core support top, not shown, while load pad assembly 12 is located in a lower clamping plane indicated at 26, positioned at 85 inches above the core support top, there being a difference, in this embodiment, of 42.5 inches between planes 25 and 26 which pass through the center of assemblies 211 and 12. Positioned about actuation sleeve 16 intermediate cam-like section 22 and shoulder-forming member 23 is a load collar 27 which is moved by sleeve 16 from the unclamped position to the clamped position where collar 27 is located intermediate load pad assembly 11 and sleeve 16 holding load pad assembly 11 outwardly into the clamped position as shown in the upper half of FIGS. 7 and 8, as discussed in more detail hereafter. Load pad assembly 11 is composed of six identical subassemblies positioned about hexagonal outer casing 13 on the relatively flexible flat sides 15 as described above with respect to FIG. 1. Each sub-assembly is composed of a load pad 28, a load pad support 29, a pair of resilient members 30, such as belleville spring washers, and a pair of threaded members 31 which are threaded into threaded apertures in load pad 28 with heads thereof abutting against flanges on load pad support 29, and function to adjustably retain resilient members 30 intermediate load pad 28 and load pad support 19. Load pad support 29 is provided on the external side thereof with shoulder forming sections which abut against the ends of casing sides 15, as indicated at 32, portions of casing sides 15 having been cut-away to accommodate load pad assembly 11. The inner end portions of each load pad support 29 are provided with tapered surfaces 33 and 34 which cooperate with cam 22 of actuation sleeve 16 for moving load pad assembly 11 from the unclamped to clamped position and return to the unclamped position, as will be described in greater detail hereinafter. As pointed out above, load pad assembly 12 is generally similar to assembly 11, the difference being in the external configuration of load pad supports 29' which are constructed to extend into an annular space 35 provided in the lower tube fitting 21. A load collar positioning pin 36 is threaded through each of load pad support 29 and serves as a stop for load collar 27 when it is moved toward the right hand side as shown in the upper half of FIG. 7 by actuation sleeve 16. To allow movement of cam 22 past pins 36, the cam is provided with a plurality of grooves 37, see FIG. 9, through which pins 36 pass as actuation sleeve 16 is moved. The internal support tube 20 in addition to serving as a locating structure for the other components and as a guide for actuation sleeve 16, serves as a control rod guide tube in the case where the element 10 is affixed to a control assembly. An upper end fitting 38 secured to support tube 20 serves as a handle for the entire assembly. A final fabrication operation joins the upper ends (left hand ends) of the support tube 20 and outer wrapper of casing 13 by the installation of support lugs 39, three such lugs being used in this embodiment as shown in FIG. 11. This action also captures or retains actuation sleeve 26 and load collar 27 between casing 13 and support tube 20. As shown in FIGS. 11 and 12, enlarged end section 24 of actuation sleeve 16, is provided with actuator tool engagement receptacles 40 (three shown in this embodiment), whereby an actuation tool can be inserted for movement of actuation sleeve 16 from the unclamped position to the clamped position which moves load pad assemblies 11 and 12 outwardly with respect to casing 13. The dual objective of having a "rigid" component for clamping alignment purposes and a "flexible" component for accommodating expansion is met by the preloaded load pad assemblies 11 and 12. Preload force (.about. 1000 pounds in this case) is provided by the belleville spring washers 30 in each of the sub-assemblies of load pad assemblies 11 and 12. This force is significantly greater than that necessary to constrain adjacent bowed fuel assemblies and therefore enables accurate "rigid element" positioning during clamping and unclamping operations. For example, due to the radial outward movement of load pad assemblies 11 and 12 by actuation sleeve 16, the assemblies are moved outwardly 0.088 inch. Forces due to thermal expansion and irradiation induced swelling during reactor operation overcome the preload force of spring washers 30. This enables localized accommodation for these dimensional changes (0.030 inch compliant or spring travel, as indicated at E in FIG. 7, for each load pad 28, for example) within a predictable load range (from 1000 pounds to 1300 pounds, for example) and yet does not involve overall radial core growth. The remaining 0.058 inch, indicated at F in FIG. 7, of the outward 0.088 inch movement of load pad assemblies 11 and 12 is maintained by actuation sleeve 16 and load collar 27. The clamping operation of the above-described internal core tightener is accomplished by moving actuation sleeve 16 axially from its position shown in the lower half to the position shown in the upper half of FIG. 7 causing cam 22 to engage the tapered ends 33 of load pad supports 29 moving load pad assembly 11 outward as cam 22 passes along in inner surface of load pad supports 29. Cam 22, being a few mils larger in diameter than load collar 27, forces the load pad assembly 11 outwardly sufficient distance to allow for relatively easy movement of the load collar 27, being moved by shoulder-forming member 23 of actuation sleeve, to the position beneath load pad supports 29, further movement of load collar 27 being stopped by load collar positioning pins 36. Thus, during clamping operation, the load collar 27 moves into position between member 23 and pins 36 to take the reaction loads of the load pad assembly 11 as the cam 22 is moved past load pad supports 29 to an unloaded condition as shown in the upper half of FIG. 7. While the above description has been directed to load pad assembly 11, load pad assembly 12 is simultaneously actuated in the same manner. Unclamping operation is accomplished by reverse movement of actuation sleeve 16 causing load collars 27 and 27' to be withdrawn by cams 22 and 22' to the position shown in the lower half of FIG. 7. Actuation forces are minimized since the cam action surfaces (cam 22 and load pad support inner surfaces) are in contact only during actuation. This reduces the frictional drag problem to sliding friction rather than static friction which would be significantly greater. Generous clearances are provided between all moving parts except the cam-to-load pad support surface during actuation and load collar-to-load pad support surface during reactor operation. Furthermore, the actuating cams 22, being slightly larger in diameter than the load collars 27, separate to the contacting surfaces (which have sustained high loads at operating conditions) before the load collars are retracted. This provides a "pry-apart" action before the load collars are moved. Large contact area is provided between the load collars and inner load pad support surfaces. The resultant low contact stress minimizes the break-away forces for unclamping since the potential is diminished for occurrence of the phenomen known as "self-welding" (brought about in the reactor environment by high bearing loads and high temperature). Load bearing components are relatively small. This allows great freedom in material and/or special surface coating selection to minimize friction and self-welding. The provision of internal compliance via the spring load pad assemblies enables use of a rigid core boundary during reactor operation. Any rapid changes related to the internal compliance restraint system can only cause localized movement of core components and thus has negligible effect on gross core neutronics. The primary function for the preloaded load pad assemblies is to accommodate expansion during reactor operation. An optional application for this apparatus could be to use the compliant load pads as load limiting devices under other operating conditions such as the clamping operation. It could also provide a "staged" compliant travel by building in more than one threshold spring force such that part of the compliant travel occurs under one set of load conditions and another part of the compliant travel occurs under greatly differing load conditions. A further variation of the compliant travel behavior would be to use variable spring characteristics (and thus applied force variation) as a function of temperature, i.e., lower load limits at elevated temperature. Another option for the above-described apparatus is to use any part thereof to fulfill a more limited requirement. Some examples of this are: (1) non-compliant load pad assemblies if rigid clamping were the requirement, (2) compliant load pad assemblies only if expanding action were not a requirement, and (3) different quantity of clamp pads or different location of clamping action. It has thus been shown the the present invention provides an internal core tightener which uses a minimum of moving parts to perform the lateral tightening function, thus substantially advancing the start-of-the-art. While a particular embodiment of the invention has been illustrated and described, modifications will become apparent to those skilled in the art, and it is intended to cover in the appended claims all such modifications as come within the spirit and scope of the invention. |
047117540 | claims | 1. A method of impacting a surface with a desired kinetic impact energy comprising the steps of: (a) providing an impacting device which can apply a variable impact energy corresponding to the magnitude of an input control signal; (b) placing said impact device adjacent the surface to be impacted; (c) thereafter applying an input control signal of a preset magnitude to said impact device to initiate an impact; (d) determining the kinetic energy of the impact; (e) comparing the value of the determined kinetic energy with a value corresponding to the desired kinetic impact energy; (f) indicating the results of the comparison; (g) adjusting the preset magnitude of the signal used for said control signal to reduce any difference as a result of comparison; and (h) thereafter repeating steps (c) to (g) until a repeatable impact of the desired impact energy is determined and indicated. detecting the movement of said plunger and producing an output signal whose magnitude is proportional to the distance moved by said plunger after application of said input voltage; sampling the magnitude of said output signal at uniform time increments; subtracting the sampled values from successive sampling times to provide difference values; and, upon detecting a zero difference value, indicating that impact has occurred, utilizing the immediately previously provided difference value as a measure of the velocity of the plunger just prior to impact, and thus of the kinetic impact energy. first means for applying a controllable impact force, corresponding to the magnitude of an input signal, to an adjacent surface; second means, responsive to an input control signal, for supplying an input signal of a preset magnitude to said first means to produce said impact force; third means for determining the kinetic energy of the impact; fourth means for comparing the kinetic energy of the impact with a desired kinetic energy value and for producing an output signal corresponding to any difference; fifth means for indicating the results of such comparison; sixth means, responsive to said output signal from said fourth means for adjusting said preset magnitude of said input control signal to reduce any error; and seventh means for supplying said input control signal at desired times to initiate an impact. a solenoid having a coil and a plunger of known mass; means, responsive to an input control signal, for applying an input voltage of a preset magnitude across said coil for a given time period; means for detecting the position of said plunger and for producing an output signal corresponding to the instantaneous said position; means for sampling said output signal at uniform time intervals, and for storing at least the last three sampled values; first comparing means for comparing successive sampled values and for stopping the sampling when no difference between two successive sampled values is detected; second comparing means for comparing the difference between the last two different sampled values and a constant value corresponding to the desired impact energy, and for producing an output signal indicative of any difference; means for indicating the results of the comparison by said second comparing means; means, responsive to the output signal from said second comparing means, for adjusting said preset magnitude of said input voltage to reduce any error; and means for thereafter supplying a further control signal to said means for applying to cause same to apply an input voltage of the adjusted preset magnitude to said coil. 2. A method as defined in claim 1 wherein said impacting device is a solenoid whose plunger provides the impact; wherein said input control signal is an input voltage applied across the solenoid coil; and wherein said step of determining includes; measuring the velocity of the plunger just prior to impact. 3. A method as defined in claim 2 further comprising: prior to each said step (c), slowly increasing the magnitude, starting from zero, of a voltage signal supplied to said solenoid coil until initial movement of said plunger is detected; and carrying out said step (c) upon said detection of initial movement of said plunger. 4. A method as defined in claim 2 wherein said step of measuring includes: 5. A method as defined in claim 4 further comprising: prior to each said step (c), slowly increasing the magnitude, starting from zero, of a voltage signal applied to said solenoid coil, and sensing the position of said plunger; and carrying out said step (c) upon sensing of an initial change in the position of said plunger. 6. A method of testing the sensitivity of an impact detector mounted on a surface of a nuclear reactor coolant surface comprising: impacting a surface of the nuclear reactor adjacent the detector according to the method defined in claim 1 and selecting said desired kinetic impact energy to correspond to the desired sensitivity of the impact detector. 7. Apparatus for impacting a surface with a desired kinetic impact energy comprising, in combination: 8. Apparatus as defined in claim 7 wherein said seventh means supplies said input control signal upon initial energizing of said apparatus and thereafter following each adjustment of said preset magnitude by said sixth means. 9. Apparatus as defined in claim 8 wherein: said first means comprises a solenoid having a plunger of known mass and a coil across which said input signal of preset magnitude is supplied; and said third means comprises means for determining the final velocity of said plunger. 10. Apparatus as defined in claim 9 wherein said means for determining the final velocity includes: means for detecting the position of said plunger and for producing an output signal corresponding to same; means for sampling said output signal from said means for detecting at uniform time intervals; and means for determining the absence of a difference between successive sampled values and for utilizing the immediately proceeding difference between sampled values as a measure of the final velocity, and thus of the kinetic energy of impact. 11. Apparatus as defined in claim 9 wherein said seventh means includes means for initially slowly increasing the magnitude of a voltage supplied to said solenoid coil; means for detecting any movement of said plunger while said voltage is being increased; and means responsive to the detection of initial movement of said plunger for causing said input signal of a preset magnitude to be supplied to said first means. 12. Apparatus for impacting a surface with desired kinetic impact energy comprising in combination: 13. Apparatus as defined in claim 12 wherein said means for applying an input voltage further includes: means, responsive to the receipt of said control signal, for initially applying a voltage across said coil in increasing increments until said means for detecting the position of said plunger produces an output signal indicating a change of position from the initial rest position of said plunger; and for thereafter causing said input voltage of a preset magnitude to be applied across said coil. 14. Apparatus as defined in claim 12 wherein said means for detecting the position of said plunger includes: a linear variable differential transformer having a primary winding, a pair of secondary windings connected in series opposition and a linearly moveable core; a nonmetallic rod mechanically connecting said core to said plunger for movement therewith; a voltage source for applying a voltage across said primary winding; and means connected across said series connected secondary windings for producing an output voltage whose magnitude corresponds to the instantaneous position of said core, and hence of said plunger. 15. Apparatus as defined in claim 14 wherein: said voltage source comprises a high frequency signal generator; and said means connected across said series connected secondary windings comprises passive demodulator means for demodulating the output signal from said secondary windings and a voltage amplifier connected to the output of said demodulator for providing a liner d.c. output signal whose magnitude corresponds to the position of said core. 16. Apparatus as defined in claim 12 wherein said means for indicating includes first, second and third indicator lamps, and means for energizing said first indicator lamp when said output signal from said second means for comparing indicates no difference and for energizing a respective said second and third of said indicator lamps when said output signal from said second comparing means indicates that said difference between the last two different sampled values and said constant value is respectively greater or less than the desired said constant value. |
summary | ||
claims | 1. A non-transitory computer-readable storage medium storing a resonance calculation program, wherein the resonance calculation program configured to instruct a computer to execute a resonance calculation of calculating an effective cross section serving as an input value for neutron transport calculation on hardware at a time of calculating a neutron flux in a fuel assembly storing a fuel rod, whereina cross section of the fuel assembly taken along an orthogonal plane orthogonal to an axial direction of the fuel rod is defined as an analysis target region in the resonance calculation, the analysis target region being divided into a plurality of detailed regions, a part of the detailed regions being a resonance region where a resonance phenomenon occurs,a neutron escape probability in the resonance region is expressed by a polynomial rational expression representing a gray range from a black body in which the resonance region absorbs all of neutrons to a white body in which the resonance region does not absorb all of the neutrons at all, the polynomial rational expression including a first rational coefficient and a second rational coefficient,the resonance calculation program uses:a fitting equation for calculating the first rational coefficient and the second rational coefficient, with the first rational coefficient and the second rational coefficient used as factors;a first calculation equation for calculating a background cross section for calculating the effective cross section, with the first rational coefficient used as a factor;a second calculation equation for calculating the neutron flux, with the background cross section used as a factor; anda third calculation equation for calculating the effective cross section, with the second rational coefficient and the neutron flux obtained by the second calculation equation used as factors, and whereinthe resonance calculation program instructs the computer to perform the following steps:a calculation point setting step of setting a macroscopic cross section in the gray range, to the resonance region as a calculation point;a first neutron flux calculation step of calculating the neutron flux set at the calculation point and corresponding to the macroscopic cross section based on Method of Characteristics;a coefficient calculation step of fitting the fitting equation to the macroscopic cross section and the neutron flux so as to provide a function representing the macroscopic cross section and the neutron flux at the calculation point, and calculating the first rational coefficient and the second rational coefficient;a background cross section calculation step of assigning the calculated first rational coefficient to the first calculation expression, and calculating the background cross section;an effective cross section interpolation step of interpolating the effective cross section from a cross section storage unit storing the effective cross section made to correspond to the background cross section, with the calculated background cross section used as an argument;a second neutron flux calculation step of assigning the background cross section to the second calculation equation, and calculating the neutron flux; andan effective cross section calculation step of assigning the effective cross section obtained at the effective cross section interpolation step, the neutron flux obtained at the second neutron flux calculation step, and the second rational coefficient obtained at the coefficient calculation step to the third calculation equation, and calculating the effective cross section. 2. The non-transitory computer-readable storage medium storing the resonance calculation program of claim 1, whereina neutron escape probability in the resonance region is expressed by following calculation equation (1): [ Equation 1 ] P f → m ( E ) = ∑ n = 1 N β n α n Σ t f ( E ) l f + α n ( 1 ) Pf→m(E) . . . Neutron escape probabilityE . . . Neutron energyN . . . Number of termαn . . . First rational coefficientβn . . . Second rational coefficientΣtf . . . Macroscopic total cross section in a resonance region flf . . . Average chord length in the resonance region f;the fitting equation is expressed by following calculation equation (2): [ Equation 2 ] ϕ f ( Σ t f ) = ∑ n = 1 N - 1 β n Σ p f l f + α n Σ t f l f + α n + ( 1 - ∑ n = 1 N - 1 β n ) · Σ p f l f + α N Σ t f l f + α N ( 2 ) φf . . . Neutron flux in the resonance region fΣpf . . . Macroscopic potential scattering cross section in the resonance region f;the first calculation equation is expressed by following calculation equation (3): [ Equation 3 ] σ 0 nr = ∑ k ≠ r λ k N k f σ p k + α n / l f N r f ( 3 ) σ0nr . . . Background cross section of a resonance nuclide r at an n-th termλk . . . IR parameter of the nuclide kNkf . . . Atomic number density of a nuclide k in the resonance region fNrf . . . Atomic number density of the resonance nuclide r in the resonance region fσpk . . . Microscopic potential scattering cross section of the nuclide k;the second calculation equation is expressed by following calculation equation (4): [ Equation 4 ] φ g r ( σ 0 nr ) = σ p r + σ 0 nr σ a , g r ( σ 0 nr ) + σ p r + σ 0 nr ( 4 ) φgr . . . Neutron flux of the resonance nuclide r in a group gσrp . . . Microscopic potential scattering cross section of the resonance nuclide r σa,gr . . . Microscopic absorption cross section of the resonance nuclide r in the group g; andthe third calculation equation is expressed by following calculation equation (5): [ Equation 5 ] σ x , g r , f = ∑ n = 1 N β n σ x , g ( σ 0 nr ) φ g r ( σ 0 nr ) ∑ n = 1 N β n φ g r ( σ 0 nr ) ( 5 ) σx,gr . . . Effective microscopic cross section of the resonance nuclide r in the group g for reaction xσx,gr,f . . . Effective microscopic cross section of the resonance nuclide r in the group g for the reaction x in the resonance region f. 3. The non-transitory computer-readable storage medium storing the resonance calculation program of claim 2, wherein at the calculation point setting step, number of calculation points is set to equal to or greater than 2N−1. |
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description | This application is based upon and claims the benefit of priority from the prior Japanese Patent Application No. 2013-025579, filed on Feb. 13, 2013, the entire contents of which are incorporated herein by reference. Embodiments described herein relate to a sample processing method. When a sample for an electron microscope is processed by a focused ion beam (FIB) apparatus, the sample is processed with a focused ion beam to fabricate an observation slice. In this case, if plural slices are individually fabricated, final thicknesses of these slices are varied because it is difficult to uniform conditions for processing the slices. Embodiments will now be explained with reference to the accompanying drawings. In one embodiment, a sample processing method includes placing a sample on a sample placing module. The method further includes setting first processing boxes on one side of slice formation scheduled regions of the sample, and setting second processing boxes on the other side of the slice formation scheduled regions of the sample. The method further includes processing the sample by performing a primary scan which sequentially scans the first processing boxes with a continuously generated ion beam, and a secondary scan which sequentially scans the second processing boxes with a continuously generated ion beam, to form a plurality of slices of the sample. The primary and secondary scans are performed so that a first scanning condition for scanning first regions within the first and second processing boxes is set different from a second scanning condition for scanning second regions between the first processing boxes and between the second processing boxes, to allow frame portions of the sample to remain in the second regions after the slices are formed. FIGS. 1A to 1D are perspective views and a top view for explaining a sample processing method of a first embodiment. FIG. 1A is a perspective view showing a sample 1 before slices are formed. The sample 1 of FIG. 1A is a block cut away from a semiconductor wafer. The sample 1 is placed on a sample placing module 21 and is processed with a focused ion beam 22 as shown in FIG. 10. FIG. 10 is a cross-sectional view schematically showing the sample 1 of the first embodiment irradiated with the focused ion beam 22. The X and Y directions respectively represent directions parallel to an upper surface of the sample 1 and vertical to each other. The Z direction represents a direction vertical to the upper surface of the sample 1. Examples of the sample placing module 21 include a holder, a stage and a shuttle. FIG. 1B is a perspective view showing the sample 1 in which plural slices 4a to 4c are formed. In this method, first openings 2a to 2c and second openings 3a to 3c are formed in the sample 1 by the focused ion beam 22, so that the slices 4a to 4c are formed between the first openings 2a to 2c and the second openings 3a to 3c. Reference characters “da” to “dc” in FIG. 1B designate thicknesses of the slices 4a to 4c, respectively. Reference numeral 5 designates frame portions remaining on both ends of the slices 4a to 4c, the first openings 2a to 2c and the second openings 3a to 3c after the slices 4a to 4c are completed. The frame portions 5 have a function of reinforcing the strength of the slices 4a to 4c. Although the first and second openings 2a to 3c do not penetrate the sample 1 in FIG. 1B, they may penetrate the sample 1 as shown in FIG. 1C. Although the positions of the slices 4a to 4c are shifted from each other in the Y direction in FIGS. 1B and 1C, it is not necessarily needed to shift these positions from each other in the Y direction. FIG. 1D is a top view showing a method of forming the slices 4a to 4c. This method forms the sample 1 of FIG. 1B or 1C from the sample 1 of FIG. 1A. First, first processing boxes 12a to 12c are set on one side of slice formation scheduled regions 14a to 14c of the sample 1, and second processing boxes 13a to 13c are set on the other side of the slice formation scheduled regions 14a to 14c of the sample 1. The slice formation scheduled regions 14a to 14c are regions scheduled to form the slices 4a to 4c in the sample 1. The first and second processing boxes 12a to 13c are virtual boxes which are set in regions scheduled to form the first and second openings 2a to 3c in the sample 1 by software which controls an FIB apparatus. Reference characters “d1” and “d2” respectively designate widths of the first and second processing boxes 12a to 13c in the Y direction (thickness direction of the slices 4a to 4c). Reference numeral 15 designates frame formation scheduled regions of the sample 1, which are regions to form the frames 5 in the sample 1. Next, regions within the first and second processing boxes 12a to 13c are scanned by the focused ion beam and are sputter-etched to form the first and second openings 2a to 3c. As a result, the slices 4a to 4c are formed in the slice formation scheduled regions 14a to 14c. In the frame formation scheduled regions 15, the frame portions 5 are made to remain. Hereinafter, a detailed description is given of the sample processing method of FIG. 1D with reference to FIGS. 2A to 2C. FIGS. 2A to 2C are top views for explaining the sample processing method of the first embodiment in detail. First, as shown in FIG. 2A, primary scans are performed a plurality of times, where each primary scan sequentially scans the first processing boxes 12a to 12c with a continuously generated focused ion beam once. As a result, the first openings 2a to 2c are formed in the sample 1 (FIG. 2B). Next, as shown in FIG. 2B, secondary scans are performed a plurality of times, where each secondary scan sequentially scans the second processing boxes 13a to 13c with a continuously generated focused ion beam once. As a result, the second openings 3a to 3c are formed in the sample 1 (FIG. 2C). In this way, the slices 4a to 4c are formed in the sample 1 as shown in FIG. 2C. Reference character “W1” designates a length of the first and second processing boxes 12a to 13c in the X direction. In the present embodiment, the length “W1” takes the same value in these processing boxes 12a to 13c. Reference character “W2” designates a length of the frame formation scheduled regions 15 between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c in the X direction. In the present embodiment, the length “W2” takes almost the same value in these frame formation scheduled regions 15. For example, the length “W2” is about 1 μm. In the present embodiment, the length “W1” and the length “W2” are set at almost the same length. In the present embodiment, the width “d1” (see FIG. 1) of the first processing boxes 12a to 12c in the Y direction takes the same value in these processing boxes 12a to 12c, and the width “d2” of the second processing boxes 13a to 13c in the Y direction also takes the same value in these processing boxes 13a to 13c. In the present embodiment, the widths “d1” and “d2” are set at almost the same width. Hereinafter, regions within the first and second processing boxes 12a to 13c are referred to as “first regions” and regions between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c are referred to as “second regions.” Reference character “t1” designates first dwell time for scanning each first region within the first and second processing boxes 12a to 13c. In the present embodiment, the first dwell time “t1” takes the same value in the first regions of the sample 1. Reference character “t2” designates second dwell time for scanning each second region between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c. In the present embodiment, the second dwell time “t2” takes the same value in the second regions of the sample 1. Hereinafter, a detailed description is given of the primary scans which scan the first processing boxes 12a to 12c with reference to FIG. 2A. Since the secondary scans which scan the second processing boxes 13a to 13c are performed in a similar manner to the primary scans, a detailed description about the secondary scans is omitted. In a first primary scan, a first region within the first processing box 12a is scanned in the first dwell time “tr” as shown with arrow “A1”. Next, as shown with arrow “X1”, a second region between the first processing boxes 12a and 12b is scanned in the second dwell time “t2”. Next, as shown with arrow “B1”, a first region within the first processing box 12b is scanned in the first dwell time “t1”. Next, as shown with arrow “Y1”, a second region between the first processing boxes 12b and 12c is scanned in the second dwell time “t2”. Next, as shown with arrow “C1”, a first region within the first processing box 12c is scanned in the first dwell time “t1”. In this way, the first primary scan is finished. The second and subsequent primary scans are executed in a similar manner to the first primary scan. The second primary scan is performed in order of arrows “A2”, “X2”, “B2”, “Y2” and “C2”. The n-th (n is an integer of 3 or larger) primary scan is performed in order of arrow “An”, “Xn”, “Bn”, “Yn”, and “Cn”. In this way, the first openings 2a to 2c are formed. In the present embodiment, each primary scan is performed with a continuously generated ion beam. For example, the first primary scan is performed while an ion beam is generated from arrow “A1” to arrow “C1”. This makes it possible to execute a scan from arrow “A1” to arrow “C1” without changing parameters such as intensity, an acceleration voltage, and beam current of the ion beam. Similarly, the n-th primary scan is performed while an ion beam is generated from arrow “An” to arrow “Cn”. As described above, each primary scan of the present embodiment is performed so that the first processing boxes 12a to 12c are sequentially scanned with a continuously generated ion beam. Similarly, each secondary scan of the present embodiment is performed so that the second processing boxes 13a to 13c are sequentially scanned with a continuously generated ion beam. Therefore, in the present embodiment, it is possible to execute each of the primary and secondary scans without changing parameters such as intensity, an acceleration voltage, and beam current of the ion beam, so that occurrence of variations in thicknesses “da” to “dc” of the slices 4a to 4c can be suppressed. Making the thicknesses “da” to “dc” of the slices 4a to 4c to be uniform brings about such an advantage as facilitating quantitative comparison between observation results of the slices 4a to 4c. However, in the present embodiment, since the first and second processing boxes 12a to 13c are sequentially scanned with a continuously generated ion beam, not only the first regions within the first and second processing boxes 12a to 13c but also the second regions between the processing boxes 12a to 12c and between the second processing boxes 13a to 13c are etched. In this case, if the frame portions 5 between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c disappears, the slices 4a to 4c may be twisted, which may hinder appropriate observation. Accordingly, in the present embodiment, to cope with the disappearance of the frame portions 5, a first scanning condition for scanning the first regions within the first and second processing boxes 12a to 13c are set different from a second scanning condition for scanning the second regions between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c. More specifically, the second dwell time “t2” is set shorter than the first dwell time “t1” (t2<t1) in the primary and secondary scans. In other words, the first regions within the first and second processing boxes 12a to 13c are slowly scanned, while the second regions between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c are quickly scanned in the present embodiment. As a result, an etching amount in the second regions between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c becomes smaller than an etching amount in the first regions within the first and second processing boxes 12a to 13c. Therefore, according to the present embodiment, it is possible to allow the frame portions 5 to remain in the second regions between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c after the slices 4a to 4c are formed. In the present embodiment, it is preferable to set the second dwell time “t2” to be 1/1000 or less of the first dwell time “t1” (t2≦t1/1000). For example, when the first dwell time “t1” is 10μ second, the second dwell time “t2” is preferably set to 0.01μ, second or less. The reason why such setting is preferable will be described in detail with reference to FIGS. 3A to 5C. (1) Explanation of FIGS. 3A to 5C FIGS. 3A to 5C are cross-sectional views regarding the sample processing method of the first embodiment in the cases of t2=t1/10, t2=t1/100, and t2=t1/1000, respectively. Reference character “H” designates a height of the slices 4a to 4c (=a depth of the openings 2a to 3c). FIG. 3A shows a cross-section of the sample 1 at the time when the first primary scan has been finished in the case of t2=t1/10. As shown in FIG. 3A, holes with a depth “H” are formed in the first regions within the first processing boxes 12a to 12c which were scanned by an ion beam. These holes are to be formed into the openings 2a to 2c in the end. The height of the frame formation scheduled regions 15 is reduced to 0.9H. This value is approximately estimated on the basis that “t2” is 1/10 of “t1” and therefore an etching rate of the frame formation scheduled regions 15 is 1/10 of an etching rate of the processing boxes 12a to 12c. FIGS. 3B and 3C respectively show cross-sections of the sample 1 at the time when the second and tenth primary scans have been finished in the case of t2=t1/10. As shown in FIG. 3C, in the case of t2=t1/10, the height of the frame formation scheduled regions 15 disappears after execution of ten scans. In this case, the slices 4a to 4c may be twisted. FIGS. 4A and 4C respectively show cross-sections of the sample 1 at the time when the first, tenth, and fiftieth primary scans have been finished in the case of t2=t1/100. In the case of t2=t1/100, the etching rate of the frame formation scheduled regions 15 is slowed as compared with the case of t2=t1/10. However, the height of the frame formation scheduled regions 15 is reduced up to 0.5H at the time when 50 scans have been performed as shown in FIG. 4C. Generally, the processing boxes 12a to 12c are scanned with an ion beam about a few dozen times to a few hundred times until the slices 4a to 4c are completed. In order to sufficiently reinforce the strength of the slices 4a to 4c, the height of the frame portions is preferably equal to or more than half of the height “H” of the slices 4a to 4c. However, in the case of t2=t1/100, the height of the frame formation scheduled regions 15 is reduced up to 0.5H by execution of 50 scans, and therefore there is a possibility that the strength of the slices 4a to 4c cannot sufficiently be reinforced. FIGS. 5A and 5C respectively show cross-sections of the sample 1 at the time when the first, tenth, and hundredth primary scans have been finished in the case of t2=t1/1000. As shown in FIG. 5A, in the case of t2=t1/1000, the height of the frame formation scheduled regions 15 is kept at 0.9 H even after execution of 100 scans. Therefore, in the case of t2=t1/1000, it can be considered that the height of the frame portions 5 is sufficiently secured even after execution of about several hundred scans and the strength of the slices 4a to 4c can sufficiently be reinforced. Therefore, it is preferable to set the second dwell time “t2” to be 1/1000 or less of the first dwell time “t1” in the present embodiment. Reference character “E” in FIGS. 4C and 5C designates edge portions of the frame formation scheduled regions 15. Since the etching rate in the edge portions “E” is larger than that in other portions, repeated scanning with an ion beam causes the edge portions “E” to be rounded. As a consequence, an effective height of the frame formation scheduled regions 15 is lowered, which may possibly hinder sufficient reinforcement of the strength of the slices 4a to 4c. Accordingly, the first and second dwell time “t1” and “t2” are preferably set in consideration of the rounding of the edge portions “E”. Moreover, since increasing the length “W2” in the X direction of the frame formation scheduled regions 15 weakens an influence of rounding of the edge portions “E”, it is preferable to set the length “W2” to be long enough to successfully avoid the influence of rounding of the edge portions “E”. (2) Modification of First Embodiment A modification of the first embodiment will be described with reference to FIGS. 2A to 2C again. In FIGS. 2A and 2B, after all the primary scans are finished and the first openings 2a to 2c are completed, the secondary scans are started to fabricate the second openings 3a to 3c. However, in the present embodiment, the primary and secondary scans may be performed alternately in the order of, for example, the first primary scan, the first secondary scan, the second primary scan, and the second secondary scan. In this case, the primary and second scans may be performed alternately in the order of a primary scan, a secondary scan, a primary scan, and a secondary scan as described above, or may be performed alternately in the order of primary scans, secondary scans, primary scans, and secondary scans. In FIGS. 2A and 2B, the primary and secondary scans are both performed so as to proceed in +X direction only. However, in the present embodiment, at least in one of the primary and secondary scans, both a +X directional scan which proceeds in +X direction and a −X directional scan which proceeds in −X direction may be performed. For example, odd-numbered scans such as scans “A1” to “C1” may be performed so as to proceed in +X direction, while even-numbered scans such as scans “A2” to “C2” may be performed so as to proceed in −X direction. Moreover, the primary and secondary scans in the present embodiment are performed so that the second dwell time “t2” is set shorter than the first dwell time “t1”. In other words, the first regions within the first and second processing boxes 12a to 13c are slowly scanned, while the second regions between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c are quickly scanned in the primary and secondary scans in the present embodiment. The second dwell time “t2” is preferably set to 1/1000 or less of the first dwell time “t1”. As described in the explanation of FIGS. 3A to 5C, a ratio between the etching rate in the first regions and the etching rate in the second regions generally coincides with a ratio between the first dwell time “t1” and the second dwell time “t2”. However, the ratio between these etching rates also depends on a ratio between a first ion beam scanning distance (=length “W1”) in the first dwell time “t1” and a second ion beam scanning distance (=length “W2”) in the second dwell time “t2”. This is because a longer scanning distance in a fixed time tends to shorten a period of time for irradiating the same portion with an ion beam and to slower the etching rate. Accordingly, a relationship between the scans of the first regions and the scans of the second regions may be defined with a scanning speed instead of dwell time in the present embodiment. The scanning speed is obtained by dividing an ion beam scanning distance by dwell time. More specifically, the relationship can be defined by using a first scanning speed “V1” for scanning each first region within the first and second processing boxes 12a to 13c, and a second scanning speed “V2” for scanning each second region between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c. For example, the primary and secondary scans of the present embodiment may be performed so that the second scanning speed “V2” is set faster than the first scanning speed “V1.” (V2>V1). The reason of this setting is similar to the reason why t2<t1 is set. The second scanning speed “V2” is preferably set to be 1000 times or more of the first scanning speed “V1” (V2≧V1×1000). The reason of this setting is also similar to the reason why t2≦t1/1000 is preferable. As described above, each of the primary and secondary scans of the present embodiment is performed so that the first or second processing boxes 12a to 13c are sequentially scanned with a continuously generated ion beam. Therefore, according to the present embodiment, it is possible to suppress occurrence of variations in thicknesses of the slices 4a to 4c. Moreover, in the present embodiment, the first scanning condition for scanning the first regions within the first and second processing boxes 12a to 13c are made different from the second scanning condition for scanning the second regions between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c, to allow the frame portions 5 to remain in the second regions after the slices 4a to 4c are formed. Therefore, according to the present embodiment, it is possible to suppress occurrence of variations in thicknesses of the slices 4a to 4c while reinforcing the strength of the slices 4a to 4c with the presence of the frame portions 5. FIGS. 6A to 6D are perspective views and a top view for explaining a sample processing method of a second embodiment. FIG. 6A is a perspective view showing plural samples la to is before slices are formed. These samples is to is are picked up by a lift-out technique and then are placed in alignment on a grid which is fixed to the sample placing module 21 (see FIG. 10). The samples is to is have almost the same height and are placed in the vicinity of each other in the same visual field. The samples is to is are processed with the focused ion beam 22 (see FIG. 10). The samples 1a to 1c are preferably placed in alignment as much as possible by using device structure inside the samples is to 1c, crystal planes of the samples 1a to 1c or the like. FIGS. 11A and 11B are a perspective view and a top view showing an example of the placed samples 1a to is of the second embodiment. FIGS. 11A and 11B show the samples is to 1c placed with a slight inclination with respect to each other due to an error at the time of placement. It is preferable that inclination of these samples 1a to is be corrected by using their device structure or crystal planes so that the samples is to is are aligned as much as possible according to purposes. FIGS. 6B and 6C are perspective views showing the samples 1a to 1c after the slices 4a to 4c are formed. In this method, the first openings 2a to 2c and the second openings 3a to 3c are respectively formed in the samples 1a to is to form the slices 4a to 4c. Reference characters 5a to 5c designate frame portions remaining on both ends of the slices 4a to 4c, the first openings 2a to 2c, and the second openings 3a to 3c after the slices 4a to 4c are completed. FIG. 6D is a top view showing a method for forming the slices 4a to 4c. This method forms the samples 1a to is of FIG. 6B or 6C from the samples 1a to 1c of FIG. 6A. First, first processing boxes 12a to 12c are set on one side of slice formation scheduled regions 14a to 14c of the samples 1a to 1c, and second processing boxes 13a to 13c are set on the other side of the slice formation scheduled regions 14a to 14c of the samples is to 1c, respectively. Reference characters 15a to 15c designate frame formation scheduled regions of the samples is to 1c, respectively. Next, regions within the first and second processing boxes 12a to 13c are scanned by a focused ion beam and are sputter-etched to form the first and second openings 2a to 3c. As a result, the slices 4a to 4c are formed in the slice formation scheduled regions 14a to 14c. In the frame formation scheduled regions 15a to 15c, frame portions 5a to 5c are made to remain. Hereinafter, a detailed description is given of the sample processing method of FIG. 6D with reference to FIGS. 7A to 7C. FIGS. 7A to 7C are top views for explaining the sample processing method of the second embodiment in detail. First, as shown in FIG. 7A, primary scans are performed a plurality of times, where each primary scan sequentially scans the first processing boxes 12a to 12c of the samples 1a to 1c with a continuously generated focused ion beam. As a result, the first openings 2a to 2c are formed in the samples is to 1c (FIG. 7B). Next, as shown in FIG. 7B, secondary scans are performed a plurality of times, each secondary scan sequentially scans the second processing boxes 13a to 13c of the samples 1a to 1c with a continuously generated focused ion beam. As a result, the second openings 3a to 3c are formed in the samples 1a to is (FIG. 7C). In this way, the slices 4a to 4c are formed on the samples is to 1c as shown in FIG. 7C. Each primary scan of the present embodiment is performed so that the first processing boxes 12a to 12c are sequentially scanned with a continuously generated ion beam as in the first embodiment. Similarly, each secondary scan of the present embodiment is performed so that the second processing boxes 13a to 13c are sequentially scanned with a continuously generated ion beam. Therefore, according to the present embodiment, it is possible to suppress occurrence of variations in thicknesses of the slices 4a to 4c as in the first embodiment. Moreover, in the present embodiment, the first scanning condition for scanning the first regions within the first and second processing boxes 12a to 13c are made different from the second scanning condition for scanning the second regions between the first processing boxes 12a to 12c and the second processing boxes 13a to 13c, to allow the frame portions 5a to 5c to remain in the regions after the slices 4a to 4c are formed as in the first embodiment. Therefore, according to the present embodiment, it is possible to suppress occurrence of variations in thicknesses of the slices 4a to 4c while reinforcing the strength of the slices 4a to 4c with the presence of the frame portions 5a to 5c on both the sides of the slices 4a to 4c as in the first embodiment. FIGS. 8A to 8D are perspective views and a top view for explaining a sample processing method of a third embodiment. In the present embodiment, as shown in FIGS. 8B and 8C, the frame portions 5a to 5c are left on one side of the slices 4a to 4c, the first openings 2a to 2c, and the second openings 3a to 3c. The structure of the present embodiment is employed when, for example, the strength of the slices 4a to 4c can sufficiently be reinforced only with the frame portions 5a to 5c on one side of the slices 4a to 4c. FIGS. 9A to 9C are top views for explaining the sample processing method of the third embodiment in detail. In the present embodiment, the first scanning condition for scanning the first regions within the first and second processing boxes 12a to 13c are made different from the second scanning condition for scanning the second regions between the first processing boxes 12a to 12c and between the second processing boxes 13a to 13c, to allow the frame portions 5a to 5c to remain in the second regions between the first and second processing boxes 12a to 13c after the slices 4a to 4c are formed as in the first and second embodiments. Therefore, according to the present embodiment, it is possible to suppress occurrence of variations in thicknesses of the slices 4a to 4c while reinforcing the strength of the slices 4a to 4c with the presence of the frame portions 5a to 5c on one side of the slices 4a to 4c as in the first and second embodiments. While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the methods 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. |
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description | This application claims priority from U.S. Provisional Application No. 61/190,435 filed Aug. 28, 2008 for Electron Enhanced Multi Frequency Pumping of Fusion Reactions by Curtis A. Bimbach and also claims priority from U.S. Provisional Patent Application No. 61/211,449 filed Mar. 30, 2009 for Method of Reduction of Hydrodynamic Instabilities in Fusion Reactions by Curtis A. Bimbach, the contents of each of which is herein incorporated by reference. This invention relates to various techniques of enhancing preignition conditions of thermonuclear fusion reactions. More particularly, the invention relates to concepts including (a) injecting electrons of predetermined energy, and quantity or fluence, into a fusion fuel plasma, and (b) temporally-staged pumping of a fusion reaction, which may be practiced alone or in combination with each other. Thermonuclear fusion reactions occur when two light atomic nuclei fuse together to form a heavier nucleus. In doing so, the fusion reaction releases a large amount of energy. This specification describes three techniques for enhancing preignition conditions of fusion reactions. The first technique for enhancing preignition conditions of fusion reactions relates to achieving the correct ion and electron temperature ratio to facilitate the ignition of a thermonuclear fusion reaction. As is known in the art, there is an apparent contradiction in the pumping requirements for pumping fusion fuel to create conditions suitable for igniting the fuel to produce a plasma. On one hand, in order to achieve proper compression, the X-ray pumping energy cannot be too high or the X-rays will pass through the target with minimal interaction. On the other hand, it is desirable to pump the plasma to a very high temperature, which, for example, is around 100 KeV for a proton-11Boron reaction (p-11B), to facilitate ignition of a fusion plasma. Further, it is useful to control the specific ratio between the ion temperature and the electron temperature. Plasma temperature of ions or electrons is commonly measured in degrees Kelvin (° K) or electron Volts (eV), and is a measure of the thermal kinetic energy per particle. An important consideration is whether the fusion fuel plasma is degenerate or not. In physics, degeneracy refers to the density of particles at the same energy level (i.e., ions, electrons, nuclei and neutrons). A plasma above a certain density is referred to as being degenerate; a plasma below a lower density is referred to as non-degenerate; and a plasma between those two densities is referred to as partially degenerate. Classical analysis has shown that if the temperature difference between the ions and electrons in a fusion fuel plasma is too great, then the energy from the ions drains to the electrons potentially quenching the reactions. However, Son, S. and Fisch, N.J., Aneutronic fusion in a degenerate plasma (2004), Physics Letters, Section A: General, Atomic and Solid State Physics, 329 (1-2) (2004), pp. 80-81 (hereinafter, “Son et al.”) teaches a different point of view. The following discussion is derived from Son et al. If the electrons are completely degenerate, then the drag on an ion comes mainly from the electrons. The force from electrons does not cancel in contrast to the classical limit. This is because, due to the lack of the asymmetry of the electron-hole transition probability, the drag force of electrons on an ion is not exactly an inverse-square law force. The drag force depends on the direction relative to the ion-velocity. The cancellation, however, occurs only for inverse-square forces. Completely degenerate electrons do not drag the ion because these electrons do not collide with the ion due to the lack of available holes. In the p-11B fusion reaction, a large reduction of the stopping frequency for an appropriate electron temperature is anticipated. The Bremsstrahlung is also reduced by this process. Bremsstrahlung is a form of high-energy ionizing radiation that occurs as a result of the deceleration of electrons. The literal translation from German is “Braking Radiation”. As taught by Yamaguchi, Kawata et al., Bremsstrahlung Energy Loss of Degenerate Plasma, National Institute for Fusion Science (Japan), NII Electronic Library Service, six pages, an electron with a velocity ve at infinity collides with an ion located at the origin. The radiation energy (so-called effective radiation) dqv emitted from the electron in the frequency interval dv is given by: dq v = 32 π 2 Z 2 e 6 3 3 m e 2 c 3 v c 2 dv ,where Z is the atomic number of ion, −e the electron charge, me the electron mass and c the speed of light. Referring again to Son et al., when the ion temperature, a measure of ion energy, is significantly greater than electron temperature, a measure of electron energy, not all electrons collide with the ions, since many of the electron-hole transitions are forbidden. The estimate, using the classical derivation of the Bremsstrahlung, shows that the total loss will be reduced by O((T/EF)3/2) from the classical formula. If the Bremsstrahlung is reduced to a level where the electrons begin to heat up, it is then desirable to add small amounts of a high-Z impurity (doping) into the fuel so as to fine tune the Bremsstrahlung to balance with the ion-electron energy transfer at the optimal electron temperature. As further taught by Son et al., at such a high density as 1029 cm−3, a significant fraction of the energy radiated will be reabsorbed, given the fact that the electron temperature is a few tens of KeV. The Compton heating of the electrons also turns out to be significant. It is clear to the extent that these effects tend to reduce the coupling of the electrons, and it will be even easier to maintain disparate ion and electron temperature and hence greater activity. There is a possible ignition regime for p-11B where:ρ>105 g/cm,Ti≅100 KeV, and Te=30 KeV. Son et al. also teaches that the degeneracy of the electrons reduces the stopping power and the Bremsstrahlung losses, which, in turn, facilitates self-sustained burning. It is mainly the reduction in the stopping power of the electrons that enables such a large differential between ion and electron temperature to be maintained to achieve a favorable result. In summary, the foregoing discussion teaches that control of the ion-to-electron temperature ratio of fusion fuel plasma enhances preignition conditions of a fusion reaction. On the basis of the foregoing discussion, the present inventor has surmised that for achieving a desired ratio, it would be desirable to have control over the energy, and the quantity or fluence, of the electrons injected into the reaction. The second technique for enhancing preignition conditions of a fusion reaction relates to reduction of hydrodynamic instabilities in inertial confinement fusion reactions. Hydrodynamic instability has been the bane of researchers in nuclear and thermonuclear physics since the inception of nuclear technology during the Second World War in the Manhattan Project in the U.S.A. It is a phenomenon where the symmetry of a reaction is reduced by any of a variety of degrading processes. Small perturbations to a plasma in hydrodynamic equilibrium release free energy in a manner which allows these perturbations to grow. This leads to non-uniform heating and, in the case of fusion reactions, a collapse of the reaction before it reaches maximum energy. It, would, therefore, be desirable to provide techniques for driving a fusion reaction to minimize the potential for the formation of hydrodynamic instabilities and to reduce those that may occur. The third technique for enhancing preignition conditions of a fusion reaction combines the first and second techniques mentioned above. This provides a variety of techniques to exercise control of the preignition stage of a thermonuclear reaction. Six discrete combinations of steps are described below, but other techniques may be used in any of the combinations. One form of the invention concerns a system for enhancing preignition conditions of a fusion reaction. The system includes a target chamber for receiving a fusion fuel, and energy driving means oriented to direct plasma confinement means onto the fusion fuel to facilitate ignition of a controlled fusion reaction of said fusion fuel. An improvement comprises a plurality of electron sources providing electron beams of a predetermined energy and one of fluence and quantity, directed onto and illuminating, a fusion fuel-derived plasma for controlling the ratio of ion temperature and electron temperature of said plasma. By controlling the ratio of ion temperature to electron temperature of the plasma, the preignition conditions for a fusion reaction are beneficially enhanced. A second form of the invention concerns a system for enhancing other preignition conditions of a fusion reaction. The system comprises a central target chamber for receiving a spherical pellet of fusion target material and at least first and second pluralities of energy drivers oriented to supply X ray pulses to the fusion target material in a 3-dimensionally symmetric manner about said pellet. The first and second pluralities of energy drivers supply to the fusion target material first and second temporally-spaced groups of X-ray pulses. The second group is supplied after an interval of time from when the first group is supplied, as a preignition condition of said fusion target material. Supplying temporally-spaced energy pulses to the plasma serves to reduce hydrodynamic instability of the plasma. A third form of the invention combines the electron enhancement feature of the first form of the invention with one or more elements of the temporally-staged energy pulses of the second form of the invention. Combinations of the first and second forms of the invention further enhance preignition conditions of a fusion reaction. Some embodiments of the present invention combine different technologies respectively described in the two different, above-cited provisional patent applications to produce enhanced control of preignition conditions of thermonuclear fusion reactions. A first technology relates to injecting electrons of predetermined energy, and quantity or fluence, into a fusion fuel plasma for controlling the ratio of ion temperature to electron temperature, to achieve better control of the reaction and to reduce hydrodynamic instability. A second technology relates to temporally-staged pumping of fusion reactions, with one object being to further reduce hydrodynamic instabilities of fusion fuel plasma. However, each technology stands on its own as a valid technique for enhancing preignition conditions of fusion reactions. As a third technology, both technologies combined yield an enhanced level of control of preignition conditions of a fusion reaction. The first through third technologies of the invention are described as follows: The first technology, relating to electron enhancement of a fusion plasma, is a useful means of providing fine control of small-scale thermonuclear reactions. It allows one to adjust the ion temperature to electron temperature ratio, thus altering the burn characteristics of the reaction. Electron enhancement is useful no matter what state of degeneracy the plasma is in, “degeneracy” being defined in the Background of the Invention above. However, the necessary level of electron enhancement varies with the degree of degeneracy of the plasma. FIG. 1 illustrates electrons 10 being injected into a fusion fuel plasma 12 (hereinafter “plasma”). By providing electron enhancement structures in a fusion reactor design, operation in different degeneracy regimes can be economically achieved. It is taught in the prior art that there is a critical balance between ion temperature and electron temperature. With electron enhancement (injection) at the correct temperature (KeV), optimal conditions for burning fusion fuel can be achieved more readily. This process can be further fine-tuned by controlled doping of the fuel with selected amounts of high-Z materials. FIG. 2 shows a preferred electron gun 14, including a cathode 16 that emits electrons 10. The electrons 10 are accelerated by a series of electrodes 18, 20 and 22 through an aperture 24 towards the plasma 12 (FIG. 1). The electron gun 14 is mounted in a housing 26 of non-magnetic, vacuum-tight construction. The cathode 16 is mounted on a cathode support 28, which penetrates the rear wall of the enclosure 26 through a vacuum-tight, electrically insulated feedthrough 30. The left-shown end of the cathode support 28 emerges from the feedthrough 30 and serves as an electrical connection point for receiving power. The grid 18 and accelerator electrodes 20 and 22 serve to control and extract the beam of electrons 10 and focus it on the plasma 12. Vacuum-tight, electrically insulated feedthroughs 32, 34 and 36 mechanically support and provide electrical connection to the grid 18 and accelerator electrodes 20 and 22, respectively. A chemical getter pump 38 helps maintain the vacuum in housing 26. A vacuum-tight, electrically insulated feedthrough 40 provides mechanical support and electrical connection to the getter pump 38. The prior art teaches that while electron enhancement is desirable for plasmas in any state of degeneracy, (i.e., degenerate, non-degenerate or partially degenerate), maximum efficiency can be achieved by implementation with degenerate plasmas. It has been shown by Son et al., described in the Background of the Invention, above, that if the temperature difference between the ions and electrons in a plasma resulting from burning of a fusion fuel is too great, then the energy from the ions drains to the electrons, potentially quenching the reactions. According to the present invention, the electron sources permeate the targeted fuel plasma with high energy electrons. To allow for slight deviations in the trajectory of each individual fuel pellet, it is preferred to permeate, not only the targeted fuel plasma, but also an additional volume beyond the boundary of the targeted fuel, wherein the additional volume represents, for example, 1 percent of the maximum dimension of the targeted fuel plasma, as measured along a line passing through the geometric center of the targeted fuel plasma. The energy level of the electrons is adjustable to achieve the correct electron temperature in the plasma of the targeted fuel by injection of electrons at the desired temperature. This is done by changing the voltage on the power supply attached to the electron sources. The trajectories of the electrons are controlled by either electromagnetic or electrostatic focusing means such as accelerator electrodes 20 and 22 in FIG. 4, as described below. It is necessary to introduce the electrons separately from the energy driving means. This arrangement has the advantage of allowing fine tuning of the electron energy to meet specific requirements of the reaction without compromising the RF heating capabilities disclosed in U.S. Patent Application Publication US 2008/0063132 A1 dated Mar. 13, 2008, also by the present inventor C. A. Birnbach. The foregoing publication is referred to hereinafter as the “'132 publication”. Thus, FIG. 3 shows a preferred fusion reactor 42 comprising a central, spherical vacuum vessel 44. A plurality of X-ray lasers 46 and a plurality of electron guns 14 are symmetrically arranged on the surface of the vessel 44 about the center of vessel 44. The fuel pellet injector 48 connected to the vacuum vessel 44 is shown. In order to properly illuminate the fusion fuel, a plurality of electron guns 14 is disposed through 4π steradians and focused on the plasma 12 (FIG. 1), preferably symmetrically about the plasma. Focusing of beams of electrons 10 (FIG. 1) may be accomplished as shown in FIG. 4. In that figure, electrodes 20 and 22 (also shown in FIG. 2) focus the beam of electrons 10 onto the centroid of the plasma 12. The grid 18 serves to control and modulate the flow of electrons to the aperture 24 and allows synchronization of the timing of the pulses. Preferably, all electron sources have the same energy (electron Volts [eV]) and fluence (Amps). In order to assure that all electron sources have the desired energy and fluence, an electron gun controller 50 as shown in FIG. 5 is provided. The electron gun controller 50 comprises a high voltage power supply 52 having a user-controlled voltage input 54 and a user-controlled current input 56. User-controlled inputs 54 and 56 are one variety of controlled input that may be used. A host computer 58 is connected to the electron gun controller 50 to provide system level control. The high voltage power supply 52 provides all necessary voltages and control signals for the electron gun 14 under the control of the host computer 58. As one possible example, a plurality of six orthogonally disposed electron sources arranged symmetrically around the fusion fuel target may be used to achieve the desired degree of uniformity, where each source illuminates approximately ⅙th of the surface area of the fusion fuel target. Other numbers of electron sources will be apparent to persons of ordinary skill in the art based on the present specification. The electron sources may comprise any type of electron gun as long as they meet the requirements of energy, quantity or fluence, and ability to synchronize, set forth herein. It is desirable for the electron sources to permeate the targeted fusion fuel plasma region with a predetermined number of electrons at a predetermined energy, specific to the fusion fuel system in use. The grid 18 allows synchronization and control of the quantity of electrons. The resulting confluence of electrons serves the purpose of providing the correct number of electrons relative to the number of ions present to achieve a desired ratio of ions to electrons. The ion temperature can be determined from the composition of the fusion fuel and the energy of the pumping X-ray beams. From the ion temperature, the required voltage setting for the electron source power supply to achieve the desired ion temperature to electron temperature ratio can be determined. The quantity of electrons is determined by the number of atoms in the supplied fusion fuel as regulated by the action of the grid 18. Son et al. teaches that, to avoid Bremsstrahlung losses, the electron temperature (Te) must be much lower than the ion temperature (Ti). The electron temperature Te cannot be too low because the fusion byproducts would then be preferentially stopped by the ions. In view of this consideration, the electron temperature must be in a narrow range to preserve the possibility of self burning. The electron temperature Te is determined from the balance between the energy input from the ions and the losses from the Bremsstrahlung. The ratio of Ti to Te varies with the fusion fuel used. For instance, for the typical fusion fuels such as Deuterium-Deuterium, Deuterium-Tritium, Deuterium-3Helium, Proton-6Lithium, Proton-11Boron, the ratio typically varies between 2:1 and 20:1. Preferably, a plurality of electron sources provide electron beams of a predetermined energy, and fluence or quantity, are directed onto and illuminating, the fusion fuel plasma. Preferably, all the electron sources have their respective voltage within one tenth of a percent of each other, and all have their respective current within a one-fourth of a percent of each other, assuming that the electron sources are disposed so that their electron beams are symmetrically oriented about the fusion fuel target plasma. Preferably, the number of electron sources used results in a specified number of electrons per unit volume of the fusion fuel plasma that is within 10 percent of any other unit volume within the plasma. There are a large number of possible configurations of electron sources and orientation of those sources about target fusion material that will achieve the required conditions defined above. The foregoing discloses active optimization of controlled fusion reactions relative to the degree of degeneracy of the fusion plasma. This is accomplished by changing the electron temperature to alter the ratio of ion temperature (Ti) to electron temperature (Te), and selective introduction of specified amounts of electrons in the reaction. These modifications allow enhancements of the preignition conditions of fusion reactions to be optimized for operation in various degenerate, partially degenerate, and non-degenerate states of plasma. The second technology, relating to temporally-staged pumping of fusion reactions, may be used with the system described in the '132 publication. The principle of the temporally-staged pumping is also applicable to other inertial confinement fusion systems. In the '132 publication, the reactor has a plurality of X-ray laser drivers. While the drawings of the '132 publication only show 6 symmetrically arranged drivers, the text contemplates higher numbers, the next logical number of drivers being 14 as shown in present FIG. 6 as temporally-pumped fusion reactor 70. The present embodiment of the invention employs a temporally-staged pulse train to drive the fusion reaction. The primary set of X-ray lasers 46a (i.e., the 6 lasers located on 3 orthogonal axes as shown in the '132 publication) fire first. The second set 46b (the remaining 8) fire a short, predetermined period of time later. For clarity of illustration, the second set 46b is shown with a thicker line than the first set 46a. The period of time between the groups of pulses is a critical value. If the second pulse group arrives too soon, it merges with the first pulse group and there is no opportunity to remediate hydrodynamic instability. It is possible to operate the reactor with all pulse groups simultaneous (zero delay between pulses), which is the condition contemplated by the '132 publication. In contrast, the present embodiment contemplates an adjustable system which allows temporally separating the pulses into symmetrical sets slightly separated in time. If the separation is too great, the second pulse will arrive after the reaction has either: (1) collapsed, (2) passed a “point of no return” after which it is impossible to correct instabilities, or (3) the full fusion reaction has occurred and the second pulse is unnecessary or detrimental To quantify the foregoing timing concerns, the total time of the reaction is defined by the time the first symmetrical X-ray compression pulse group first hits the fuel pellet to the time when thermonuclear fusion occurs. If, for example, the total time of the reaction is 3 nanoseconds, the second pulse group would, for example, arrive approximately 500 picoseconds after the first pulse group. If the second pulse group arrives more than about 1.5 nanoseconds after the first pulse group, it may be too late. If it arrives 10 nanoseconds after the first pulse, it is definitely too late to be of use. The values given here are relative and are intended merely to express a principle, not to define actual values for conducting a fusion reaction. FIGS. 7A-7D show relative time lines of temporally-staged pulses of energy for establishing preignition conditions for a fusion reaction. FIG. 7A: This figure depicts first 72 and second 74 X-ray pulses. Double-headed arrow 75 indicates that the second pulse 74 can occur over a variable period of time. FIG. 7B: This figure depicts first 72 and second 74 X-ray pulses, with an RF heating pulse 76 following the first X-ray pulse 72 by a fixed period of time. Double-headed arrow 75 indicates that the second pulse 74 can occur over a variable period of time. FIG. 7C: This figure depicts first X-ray pulse 72 followed by an electron pulse 78 and second X-ray pulse 74. Double-headed arrow 75 indicates that the second pulse 74 can occur over a variable period of time. Double-headed arrow 79 indicates that the electron pulse 78 can occur over a variable period of time to allow adjustment of the timing and synchronization. FIG. 7D: This figure depicts first X-ray pulse 72 followed by an electron pulse 78. Double-headed arrow 79 indicates that the electron pulse 78 can occur over a variable period of time. The foregoing description teaches relative relationships between various pulse combinations, providing a sense of the proportions involved. Such description indicates that it is desirable to be able to provide drive signals that can be broken into two or more groups. This advantageously allows the variable timings indicated by double-headed arrows 75 and 79 in FIGS. 7A-7D (and also in FIGS. 10A-10B described below) to be accurately adjusted with a fine (e.g., picosecond or smaller) resolution. As shown in FIG. 8, this can be accomplished by creating a timing network 90 using commercially available timing delay generators such as those manufactured by Highland Technologies Inc. of San Francisco, Calif. The timing network 90 comprises three sections: a clock section 92, a timing section 94, and cable & jitter compensation section 96. The clock section 92 comprises a master clock 98, such as a high precision low-jitter oscillator. The master clock generates the timing pulses for the entire system. The master clock 98 is typically a temperature-controlled crystal oscillator, but could also be an atomic clock. It is connected to the timing section 94 by an array of preferably equal-length cables 100a, 100b and 100c. The length of these cables is preferably controlled to 0.001 inch (25.4 microns) overall, including connectors. The timing section 94 comprises three timing delay generators 102a, 102b and 102c. Timing delay generator 102a establishes the firing time of the first X-ray pulse. Timing delay generator 102b establishes the firing time of the electron pulse, if present in the system. The timing of the electron pulses is predetermined by the system operator, as shown in FIG. 7C at 79. Timing delay generator 102c establishes the delay of the second X-ray pulse relative to the first X-ray pulse, as shown in FIGS. 7A-7C, and also in FIG. 10A, to be described below. The flow and quantity of electrons 10 are regulated by the control of the grid 18 (FIG. 2) under control of the host computer 58. The timing delay generators of section 94 are connected to an array of cable and jitter compensation delay generators in section 96. Cable compensation, as used herein, provides a means for correcting for the differences in length of cables 104a-104f, 106a-106n (where n is the number of electron guns 14 used) and 108a-108h to assure that pulses arrive synchronously at the first set 46a of X-ray lasers, electron guns 14, or the second set 46b of X-rays lasers, respectively. Jitter compensation, as used herein, provides a means for correcting for small differences when manufacturing lasers 46 (FIG. 3), or sets 46a and 46b (FIG. 9) of lasers or electron guns 14 (FIGS. 2, 3 and 9. Each device has its own jitter value, which does not change with time, and is treated similarly to an offset for cable-length compensation. In use, the delays for cable compensation and jitter section 96 delays are set first. Then, the timing adjustments of timing section 94 are set to provide the desired operating sequence as shown in FIGS. 7A-7D and 10A-10B. The timing delay generators 102a-102c, 110a-110f, 112a-112n (where n is the number of electron guns 14 used) and 114a-114h, and the master clock 98, each of which is connected to the host computer 58, are controlled by the host computer 58. This allows for rapid optimization of the timing conditions by a series of iterative measurements during the start-up of the system. The system design allows for multiple-input means to the timing network 90 and electron gun controller 50, which can include direct manually controlled inputs by an operator or programmed controlled inputs by the host computer 58. Beneficially, the present technique of temporally-staged pumping of fusion reactions is anticipated to allow a reduction in the accuracy of the fabrication of the fuel pellets. Currently, it is necessary to limit surface discontinuities to less than 1% of the total surface to reduce the formation of “jets” of plasma that surge outwardly from the main body of the plasma and locally cool the plasma. Such jets of plasma are characteristic of hydrodynamic instability. The 2nd temporally-staged X-ray pulse 74 of FIGS. 7A-7C and FIG. 10A (and additional temporally-stage pulse(s) if employed) of the current embodiment of the invention act to contain the jets characteristic of hydrodynamic instability as they form. Therefore, greater surface discontinuities of fuel pellets can be tolerated. It will be obvious to those skilled in the art from the present specification that each set of lasers should be capable of delivering the full drive energy required to achieve fusion. This is not absolutely necessary, but if each set only has a portion of the required energy, this places further restrictions on the timing tolerances of the system, since, in this condition, both pulses must arrive within a specified time window. The object of the current embodiment of the invention is to reduce the sensitivity of the overall fusion reaction to hydrodynamic instabilities, so providing each group of symmetrical pulses with the full drive energy capacity is desirable and preferred. It is possible that more than two temporally-staged groups of drive pulses may be required to mitigate the effects of hydrodynamic instability and the system architecture can provide for this. It will be obvious to those skilled in the art from the present specification that there are a number of possible variations of this technique which can act to favorably reduce the negative effects or amount of hydrodynamic instability in inertial confinement fusion reactions. Maximum utility and synergy is obtained by combining the two previously described technologies, as shown in FIG. 10A. While each individual process has its own unique attributes, when combined, a synergistic methodology emerges. The combined processes allow the following sequence of events as a means for triggering and controlling fusion reactions, with reference to FIG. 10A: 1. A first X-ray pulse 72 illuminates the fusion fuel. This totally ionizes the fuel, creating the plasma 12 (FIG. 1) and begins the compression and heating processes. An RF heating pulse 76 can optionally be applied to the fusion fuel plasma 12 a fixed time after the first X-ray pulse 72 is applied, as disclosed in the '132 publication. 2. An electron pulse 78 illuminates the fusion fuel region and introduces a specific number of electrons 10 (FIG. 1) of a specific energy into the plasma 12 (FIG. 1) produced by the foregoing Step 1. This has the effect of altering the ratio of ion temperature to electron temperature and minimizing deleterious effects as previously described, thus enhancing the probability of a desirable reaction occurring. The flow and quantity of electrons 10 are regulated by the control of the grid 18 (FIG. 2) under control of the host computer 58. 3. A second X-ray pulse 74 further compresses and heats the plasma 12 (FIG. 1). This second X-ray pulse 74 is composed of beams that arrive from different directions than the beams that form the first X-ray pulse 72. The effect of this is to contain and mitigate any hydrodynamic instability that may have formed during the preceding steps. 4. The timing and sequence of these three sets of pulses (i.e., 72 plus 76, 78, and 74) are important and must be adjusted carefully to achieve best system performance. This is accomplished by adjusting the delay generator 102b (FIG. 8) to control the timing of the generation of each set of pulses. The timing of the electron pulse 78 is adjusted as indicated by double-headed arrow 79, and the timing of the second X-ray pulse 74 is adjusted as indicated by double-headed arrow 75. The simplest method to optimize system performance is to use iterative optimization routines under the control of the host computer 58 (FIG. 8) to provide controlled input(s) to the timing network 90. The programming of such optimization routines will be apparent to those skilled in the art based on the present specification. Such optimization routines test individual delay setting combinations 75 and 79 of FIGS. 7A-7D and of FIGS. 10A-10B, described below, and are thus able to determine the combination of delay settings that yields the best system performance. Use of such computer routines to provide controlled inputs may be preferable to employing user-controlled inputs, such as 54 and 56 in FIG. 5 and 75 and 79 of FIGS. 7A-7D and of FIGS. 10A-10B. Variations on the foregoing sequence of steps illustrated in FIG. 10A are shown in FIGS. 7A-7D, as previously described, and in FIG. 10B. FIG. 10B depicts first X-ray pulse 72 followed by an RF heating pulse 76, which follows the first X-ray pulse 72 by a fixed period of time, which, in turn is, followed by an electron pulse 78. Double-headed arrow 79 indicates that the electron pulse 78 can occur over a variable period of time. All of the enhancements of this specification can be combined with the technology of the '132 publication to achieve improved control of the preignition conditions of a thermonuclear fusion reaction. While the techniques discussed above are applicable to many different types of fusion processes, either singly or in combination, they were originally conceived as adjuncts to the invention described in the '132 publication. As such, they are particularly preferred techniques, which are now described in more detail as follows, with reference to the present drawings of the current invention. The '132 publication describes a unique system for controlling some preignition conditions of fusion reactions. It is classed as a Direct X-ray Drive Inertial Confinement fusion system. It utilizes X-ray lasers 46 (FIG. 3) as the primary means of pumping the reaction. The current invention describes system-level enhancements which further promote the ability to exercise control of preignition conditions of a fusion reaction. The system of the '132 publication includes a central target chamber 44 (FIG. 3) for receiving fusion target material. A plurality of X-ray lasers 46 (FIG. 3) are arranged around the target chamber 44 so as to supply energy to fusion target material in the chamber to initiate a controlled fusion reaction of the material, releasing energy in the forms of fusion plasma 12 (FIG. 1) and heat. In more detail, FIG. 3 shows a reactor for generation of energy by controlled nuclear fusion. The system includes a central target chamber 44. A series six or more X-ray lasers 46 are arranged in symmetrical pairs around the central target chamber 44. The symmetrical X-ray lasers 46 are arranged in symmetrical manner about a target pellet location at the center of chamber 44, so as to collectively create a preferably highly spherical wavefront that impinges on the target fusion pellet (not shown) at the center of chamber 44. The X-ray lasers 46 produce X-ray beams 72 (FIGS. 7A-7D and FIGS. 10A-10B) at high fluency, which symmetrically compress the target to initiate and sustain a fusion reaction. The X-ray lasers 46 are preferably Stimulated X-ray Emitters (SXE) as first described by the inventor of this current invention in U.S. Pat. No. 4,723,263. In the preferred embodiment, the mentioned SXE X-ray lasers 46 are fitted with an RF producing means (not shown) which provides a simultaneous pulse of RF energy 76 (FIGS. 7B, 10A and 10B) to provide additional heat to the reaction. This is described further in the '132 publication in its discussion of FIGS. 10-13 of that publication. Optimal performance of any fusion system depends on creating a perfectly symmetrical compression of the fuel target pellet. The X-ray lasers 46 (FIG. 3) of the current invention provide a means of symmetrically illuminating the target. If the wavefronts (not shown) that impinge on the target are given a concave geometry whose radius matches the radius of the target pellet, then it is possible to create an almost perfectly symmetrical compression wavefront on the fuel target pellet. The reason that this is necessary is to minimize hydrodynamic instability which, if severe enough, can cause the fuel pellet to heat in a non-uniform fashion and thus not ignite in a fusion reaction. An aspect of the current invention advantageously utilizes the concave geometry of the wavefronts in a temporally-staged manner to further minimize the negative effects of hydrodynamic instability. This is accomplished by use of a second X-ray pulse 74 slightly delayed in time with reference to the first X-ray pulse 72 (FIGS. 7A-7C and FIG. 10A). The combined, temporally-staged wavefronts 72 and 74 of the energy beams approximate two collapsing spherical shells. The implosion process of a typical direct-drive ICF target is roughly divided into three phases: (1) initial phase, (2) acceleration phase, and (3) deceleration phase. In the initial phase, a first shock wave travels in a fuel pellet and the pellet is accelerated mainly by the shock wave. The initial phase has a second requirement: total ionization of the fuel. This promotes the fusion reaction by increasing the ease with which the fusion fuel ions are combined in the subsequent phases. This is accomplished by the high energy impinging X-rays knocking the electrons out of their orbits and leaving a bare nucleus, which is the preferred state for fusing to other nuclei. The outer (or ablative) shell is ablatively accelerated inward in the second phase. Then, fuel is compressed heavily in the deceleration phase. In the initial phase, perturbations on the target surface are seeded by initial imprint due to laser irradiation nonuniformity, along with the original target surface roughness. The perturbations grown on the outer surface due primarily to the hydrodynamic instability in the second (acceleration) phase are then fed through on the inner surface. In the current embodiment of the invention, with reference to FIG. 7C, the use of temporally-staged pulses is preferably sequenced to the three stages described above. The initial X-ray pulse 72 starts the process in the initial phase. It is preferably closely followed by the electron pulse 78 at the beginning of the acceleration phase. Synchronization of the electron pulse 78 is achieved by use of the grid 18 (FIG. 2). The second X-ray pulse 74 preferably closely follows the electron pulse during the early portion of the acceleration phase. This sequence allows the electrons to optimally interact with the plasma created by the initial impact of the first X-ray pulse 72. This action prepares the plasma 12 (FIG. 1) for optimal compression and ultimately, a fusion implosion. The second X-ray pulse 74 also acts to minimize any hydrodynamic instabilities that may occur during the initial and acceleration phases. In an alternate embodiment of the current invention, the system of the '132 publication may include an RF heating means integral to the X-ray lasers 46 (FIG. 3) to produce an RF pulse 76 (FIGS. 7B, 10A and 10B). One consequence of this is that an RF heating pulse 76 of over 200 MegaJoules at a specified frequency in excess of 150 GHz is synchronously produced and travels along with the X-ray pulse 72. This RF pulse 76 is useful in providing additional heat to the plasma 12 (FIG. 1) at essentially no additional cost or energy consumption. This is because it is generated using the excess energy of the SXE X-ray lasers 46 X-ray production process. This RF pulse 76 is slightly delayed behind the X-ray pulse 72 by a fixed period of time. By having the RF pulse 76 occur just behind the first X-ray pulse 72, it arrives more or less synchronously with the electron pulse 78. Preferably, a controlled input to timing network 90 (FIG. 8) via the host computer 58 (FIG. 8) allows the timing of these events to be fine tuned to optimize this effect (FIG. 10A). This produces a four-part pulse train as shown in FIG. 10A, which increases the degree of control over preignition conditions of the fusion fuel for creating optimal conditions for igniting the fusion fuel. The present specification discloses six separate enhancement scenarios for inertial confinement fusion (ICF) systems: 1. Temporally-Staged X-ray pulses (FIG. 7A). 2. Combined Temporally-Staged X-ray Pulses and RF Enhanced plasma (FIG. 7B). 3. Combined Temporally-Staged X-ray Pulses and Electron Enhanced plasma (FIG. 7C). 4. Electron Enhanced plasma (FIG. 7D). 5. RF and Electron Enhanced plasma (FIG. 10B). 6. Combined Temporally-Staged X-ray Pulses and RF and Electron Enhanced plasma (FIG. 10A), the preferred embodiment. Individually, each technique has merit. In the various combinations, they offer successively increasing degrees of enhancement and control over the preignition conditions of a fusion reaction. While the invention has been described with respect to specific embodiments by way of illustration, many modifications and changes will occur to those skilled in the art. In this connection, the word “means” used herein connotes singular or plural instrumentalities, regardless of whether the verb used with the term “means” is normally of singular or plural tense. The second set of X-ray sources for producing a second X-ray pulse would not be present in some systems. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true scope and spirit of the invention. |
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abstract | A method of raster scanning a sample on a continuously moving stage for charged-particle beam imaging said sample is disclosed. The method includes line scanning a charged-particle beam across a surface of the sample repeatedly to form on the surface at least one 2-dimensional line array composed of scan lines lying adjacent to each other. When each line scan is to be performed, the charged-particle beam is shifted, along the stage-moving direction, by an extra predefined distance at least equal to a distance the stage has traveled during a time period from the beginning of the first line scan of the first formed line array to the beginning of the current line scan (to be performed) of the current line array (to be formed). |
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claims | 1. A method of consolidating a calcined material comprising radioactive material, said method comprising:mixing a radionuclide containing calcine with at least one additive to form a pre-HIP powder;loading the pre-HIP powder into a can;sealing the can;loading the sealed can through a bottom of a HIP vessel;closing said HIP vessel; andhot-isostatic pressing the sealed can within the HIP vessel at a temperature ranging from 1000° C. to 1250° C. and a pressure ranging from 30 to 100 MPa for a time ranging from 10-14 hours. 2. The method of claim 1, further comprising preheating the pre-HIP powder prior to loading it in the sealed can into the HIP vessel. 3. The method of claim 2, wherein said preheating comprises heating the pre-HIP powder to a temperature sufficient to remove excess moisture from said pre-HIP powder. 4. The method of claim 3, wherein said temperature sufficient to remove excess moisture ranges from 100° C. to 400° C. 5. The method of claim 2, wherein said preheating comprises heating the pre-HIP powder to a temperature sufficient to drive off unwanted constituents without volatilizing any radionuclides present in said powder. 6. The method of claim 5, wherein said temperature sufficient to drive off unwanted constituents without volatilizing any radionuclides present in said powder ranges from 400° C. to 900° C. 7. The method of claim 1, further comprising preheating the pre-HIP powder prior to loading the pre-HIP powder in said HIP can. 8. The method of claim 7, further comprising loading said pre-heated powder and can into the HIP vessel while at temperatures up to 600° C. 9. The method of claim 1, wherein loading the can through the bottom of the HIP vessel includes using at least one robot of an automated loading system. 10. The method of claim 1, further comprising evacuating and sealing said can prior to loading it in said HIP vessel. 11. The method of claim 1, wherein said pre-HIP powder comprises 60-80% radioactive calcine. 12. The method of claim 11, wherein the ratio of radioactive calcine to additive is about 80:20 by weight. 13. The method of claim 1, wherein the additive comprises at least one oxide chosen from BaO, CaO, Al2O3, TiO2, and SiO2, which, when combined with the calcine, form a ceramic mineral or glass/ceramic material after said hot isostatic pressing. 14. The method of claim 13, wherein said ceramic mineral or glass/ceramic comprises hollandite (BaAl2Ti6O16), zirconolite (CaZrThO7), and perovskite (CaTiO3). 15. The method of claim 1, wherein said can comprises Stainless Steel. 16. The method of claim 1, further comprising encapsulating said can inside a containment vessel prior to loading through the bottom of the HIP vessel. 17. The method of claim 16, further comprising positioning the containment vessel with said can contained therein on a bottom closure of said HIP vessel, and subsequently raising and securing the bottom closure to seal the HIP vessel. 18. The method of claim 1, wherein sealing said can includes welding said can. 19. The method of claim 1, further comprising cooling the can in said HIP vessel after hot isostatic pressing. 20. The method of claim 1, further comprising removing said can from said HIP vessel after hot isostatic pressing and prior to cooling said can. |
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description | This application is based upon and claims the benefit of priority from prior Japanese Patent Application No. 2005-137422, filed May 10, 2005, the entire contents of which are incorporated herein by reference. 1. Field of the Invention The present invention relates to an electron beam lithography apparatus, lithography method, and lithography program for drawing a circuit pattern of a semiconductor integrated circuit and a manufacturing method of a semiconductor device. 2. Description of the Related Art In the manufacture of semiconductor elements, CMP (Chemical Mechanical Polishing), etching, and the like are used. These processes result in different processing shapes depending on the presence/absence of a surrounding pattern. On the other hand, each semiconductor chip generally has a rectangular shape, and a silicon wafer has a circular shape. For this reason, when chips are to be laid out on the entire surface of a wafer, deficient chips are formed near the periphery of the wafer. Since these deficient chips do not function as chips, it is wasteful to expose them on the wafer. However, under the present situation, in order to suppress variations of the processing shapes upon CMP or etching described above, these deficient chips are also drawn. This deficient chip drawing causes the following two problems in electron beam lithography. First, a waste in time required to draw deficient chips is a serious problem in electron beam lithography which originally has a low throughput. Second, upon drawing deficient chips, a stage which mounts the wafer is irradiated with an electron beam. As a result, contaminations are accumulated on the stage. Note that Jpn. Pat. Appln. KOKAI Publication No. 2000-269126 discloses the following technique. That is, upon drawing an invalid chip region as a region which suffers deficiency or insufficient chips to be drawn near the periphery of the wafer, a plurality of dummy patterns are exposed to have the same area density as a valid chip area, and a rectangle of a maximum shot size is set by a variable shaped electron beam. According to an aspect of the invention, there is provided an electron beam lithography apparatus comprising: a first setting unit configured to set a drawing position on a semiconductor substrate based on layout information of the semiconductor substrate; a second setting unit configured to set a valid range on the semiconductor substrate based on shape information of the semiconductor substrate; a determination unit configured to determine whether or not the drawing position falls within the valid range; and an irradiation unit configured to irradiate the semiconductor substrate with an electron beam when the determination unit determines that the drawing position falls within the valid range. According to another aspect of the invention, there is provided an electron beam lithography method comprising: setting a drawing position on a semiconductor substrate based on layout information of the semiconductor substrate; setting a valid range on the semiconductor substrate based on shape information of the semiconductor substrate; determining whether or not the drawing position falls within the valid range; and irradiating the semiconductor substrate with an electron beam when it is determined that the drawing position falls within the valid range. According to another aspect of the invention, there is provided an electron beam lithography program which is stored in a storage medium readable by a computer, the program making the computer: set a drawing position on a semiconductor substrate based on layout information of the semiconductor substrate; set a valid range on the semiconductor substrate based on shape information of the semiconductor substrate; determine whether or not the drawing position falls within the valid range; and irradiate the semiconductor substrate with an electron beam when it is determined that the drawing position falls within the valid range. According to another aspect of the invention, there is provided a manufacturing method of a semiconductor device which manufactures a semiconductor device by use of a semiconductor substrate on which a lithography process is performed, the lithography process comprising: setting a drawing position on a semiconductor substrate based on layout information of the semiconductor substrate; setting a valid range on the semiconductor substrate based on shape information of the semiconductor substrate; determining whether or not the drawing position falls within the valid range; and irradiating the semiconductor substrate with an electron beam when it is determined that the drawing position falls within the valid range. Embodiments of the present invention will be described hereinafter with reference to the accompanying drawings. An electron beam lithography apparatus used in the first embodiment of the invention uses a continuous stage movement system and a main-sub 2-step deflection system. FIG. 1 is a schematic view of an electron beam lithography apparatus according to the first embodiment. A sample chamber 1 houses an X-Y stage 101 which mounts a wafer (sample, semiconductor substrate) S. This stage 101 is driven by a stage driving circuit 11, and the moving position of the stage 101 is measured by a laser meter 12. Secondary electrons and reflected electrons from the wafer S are detected by an electron detector 13. An electron optical system 2 is arranged in a lens barrel 200 above the sample chamber 1. The electron optical system 2 includes an electron gun 201, various lenses (condenser lens 202, projection lens 203, reducing lens 204, and objective lens 205), various deflectors (CP deflectors 205a to 205d, main deflector 206a, sub deflector 206b, and blanking deflector 207), a beam shaping aperture 208, and a CP aperture 209. In FIG. 1, a beam adjustment electrode, coil, and the like which are equipped in the conventional electron beam lithography apparatus are not shown. A control circuit 3 controls, via a blanking amplifier 401, the blanking deflector 207, which turns on and off a beam. The control circuit 3 controls, via a beam shaping amplifier 402, the CP deflectors 205a to 205d, which shape a beam. Furthermore, the control circuit 3 controls the main deflector 206a via a main deflection amplifier 403, and the sub deflector 206bvia a sub deflection amplifier 404. With this control, a beam is scanned on the wafer S. Note that an acceleration voltage is 5 keV, and the sizes of the deflection regions of the main deflector 206a and the sub deflector 206b are respectively 1.5 mm and 50 μm. FIG. 2 is a view for explaining a lithography method according to the first embodiment. The continuous stage movement system used in the first embodiment is a system in which a plurality of chips on the wafer S are divided into stripe-shaped main deflection regions called stripes, and patterns are drawn while continuously driving the stage 101, as shown in FIG. 2. This system can expect a high throughput since the number of times of step movement of the stage 101 is small. Note that the stripes are divided in the vertical direction in FIG. 2, but they may be divided in the horizontal direction. FIG. 7A and subsequent figures show an example in which stripes are divided in the horizontal direction. The main-sub 2-step deflection system is a system in which the main deflector 206a aligns the sub deflection region within the range as broad as several mm, and the sub deflector 206b aligns a shot within a range of several ten μm at high speed, thus drawing a drawing range at high speed. In this system, chip data (drawing data) is divided into stripe-shaped main deflection regions called frames. The sub deflection region position in the main deflection region is aligned by the main deflector 206a, and the shot position in the sub deflection region is aligned by the sub deflector 206b. These series of control operations are executed by a control program stored in a storage device (storage medium) 40 in a control computer (computer) 4 shown in FIG. 1. This control program controls respective units such as the control circuit 3 to operate in accordance with EB drawing data and layout data, thus executing drawing. FIG. 3 is a schematic view of the electron beam lithography apparatus according to the first embodiment. The functions of respective units will be described below based on FIG. 3. The same reference numerals in FIG. 3 denote the same parts as in FIG. 1. Also, a description of sequence items done in the conventional electron beam lithography apparatus such as a parameter transfer sequence to a deflection control circuit 301 and the like will be omitted. The storage device 40 in the control computer 4 stores drawing data 401a, wafer layout data 401b, and wafer shape data 401c. The control circuit 3 comprises a deflection control circuit 301, data mapping circuit 302, and position correction circuit 303. The deflection control circuit 301 comprises arithmetic units 301a, 301b, and 301c. The control computer 4 writes the drawing data 401a, wafer layout data 401b (including procedure data, chip position data, frame position data, and stripe position data), and wafer shape data 401c in the data mapping circuit 302. FIGS. 4A and 4B show the structure of the drawing data 401a. FIG. 4A shows the data format of the drawing data 401a, and FIG. 4B is a view for explaining respective data in FIG. 4A. As shown in FIG. 4A, the drawing data 401a includes main deflection data required to control the main deflector 206a, and sub deflection data (shot data) required to control the sub deflector 206b. The main deflection data describes the positions (Xm, Ym) of sub deflection regions in the main deflection region, addresses indicating the data start positions of shots included in each sub deflection region, and control codes including the number of shots in each sub deflection region. The position (Xm, Ym) of each sub deflection region in the main deflection region is described as that of the center of each sub deflection region from a frame origin, and indicates the drawing position of each sub deflection region on a frame coordinate system (from the frame origin). The sub deflection data is written with the positions (Xs, Ys) of shots in the sub deflection region, CP aperture positions required to control the CP deflectors 205a to 205d, irradiation times, shot sizes, and the like. Note that the shot position (Xs, Ys) is described as a shot lower left position to have the center of the sub deflection region as an origin. Each CP aperture position is an aperture position from a CP aperture origin. Each shot size is described as the width and height when the shot lower left position is defined as an origin. FIGS. 5A to 8 are views for explaining details of the wafer layout data 401b. The wafer layout data 401bincludes chip position data, frame position data, stripe position data, and procedure data, as described above. In this apparatus, the sizes of the deflection regions of the main deflector 206a and sub deflector 206b are respectively 1.5 mm and 50 μm, as described above. However, in FIGS. 5A to 7, FIG. 9, FIG. 20, and FIG. 21, the wafer size is 200 mm (diameter), the chip size is 25 mm2, and the frame width is 6.25 mm for the sake of descriptive convenience. FIG. 5A shows a chip layout, and FIG. 5B shows chip position data. The chip position data gives chip numbers (X, Y) and describes respective chip positions (Xchip, Ychip) on a wafer coordinate system (the wafer center is an origin), as shown in FIG. 5B, in correspondence with respective chips laid out on the wafer S shown in FIG. 5A. FIG. 6A shows chip data, and FIG. 6B shows frame position data generated based on the chip data. The frame position data describes frame origin positions (Xf, Yf) corresponding to frame numbers on a chip coordinate system (the chip center is an origin), as shown in FIG. 6B, in correspondence with respective frames of the chip data shown in FIG. 6A. FIG. 7A shows a stripe layout, and FIG. 7B shows stripe position data generated based on the chip layout data and frame position data. The drawing region on the wafer S is divided into stripes, as shown in FIG. 7A, and the stripe position data describes stripe origin positions (Xstr, Ystr) corresponding to respective stripe numbers, as shown in FIG. 7B. In this case, by adding the origin position of each frame shown in FIG. 6B to each chip origin position shown in FIG. 5B, the stripe origin position (Xstr, Ystr) shown in FIG. 7B can be calculated. FIG. 8 shows procedure data. As shown in FIG. 8, the procedure data describes chip numbers, frame numbers, and stripe numbers. FIG. 9 is a view for explaining generation of the wafer shape data 401c, and FIG. 10 shows the wafer shape data. In order to generate the wafer shape data, Y (X axis direction) positions (one-dashed chain lines) are set for respective stripes on the chip layout on the wafer S. In FIG. 9, this Y position is set at the center (b in FIG. 9) of each stripe in the Y direction. Next, intersections (Xmin, Xmax, c in FIG. 9) between a wafer valid range (dotted line, a in FIG. 9) and the Y positions of the respective stripes are calculated. Note that the operator designates the wafer valid range (broken line, a in FIG. 9), and inputs it to the control computer. For example, when the wafer size is 200 mm (diameter), the operator inputs the wafer valid range (broken line, a in FIG. 9) as a range of a radius of 95 mm. As the setting of the valid range, a range of a diameter of 190 mm may be input. In this way, the Y positions (b in FIG. 9) and valid ranges Xmin and Xmax (c in FIG. 9) are calculated for all the stripes, and the wafer shape data shown in FIG. 10 is generated. In this embodiment, the control computer 4 generates the wafer shape data 401c based on the wafer layout data 401b (including procedure data, chip position data, frame position data, and stripe position data) and the wafer valid range (broken line, a in FIG. 9) designated by the operator, and writes the generated data in the data mapping circuit 302. FIG. 11 is a block diagram showing the arrangement of the data mapping circuit 302 according to the first embodiment. The data mapping circuit 302 comprises a bus adapter 311, main deflection data circuit 312, shot data circuit 313, and mapping circuit 314, which are connected to a data bus 315. The control computer 4 writes the chip data in the data mapping circuit 302 via a bus adapter 41. Main deflection data is stored in a memory in the main deflection data circuit 312, and shot data is stored in a memory in the shot data circuit 313. The procedure data shown in FIG. 8 is stored in a first memory 3142 connected to a first arithmetic circuit 3141 in the mapping circuit 314. The chip position data shown in FIG. 5B, the frame position data shown in FIG. 6B, and the stripe position data shown in FIG. 7B are stored in a second memory 3144 connected to a second arithmetic circuit 3143 in the mapping circuit 314. The wafer shape data shown in FIG. 10 is stored in the second memory 3144 in the mapping circuit 314. In FIG. 3, after the wafer S is placed on the stage 101 and a drawing preparation is completed, the control computer 4 issues a data output instruction to the data mapping circuit 302. The drawing preparation means a state in which a moving start point and end point of the stage 101 are calculated, and the stage 101 is located at the moving start point. The moving start point and end point of the stage 101 are calculated from a drawing start point and end point (Xstart, Xend) of each stripe. A runup distance and deceleration distance (X runup, X deceleration) are determined based on the drawing start point and end point (Xstart, Xend) of each stripe in correspondence with the stage speed of each stripe. That is, a stage moving start point and end point (Xstgs, Xstge) are determined as follows: In case of forward movement,stage moving start point (Xstgs)=drawing start point (Xstart)−runup distance (X runup)stage moving end point (Xstge)=drawing end point (Xend)+deceleration distance (X deceleration) In case of reverse movement,stage moving start point (Xstgs)=drawing start point (Xstart)+runup distance (X runup)stage moving end point (Xstge)=drawing end point (Xend)−deceleration distance (X deceleration) More specifically, when the transfer start address, the number of words, and the number of transfer repetition times are instructed to the main deflection data circuit 312 shown in FIG. 11, transfer of the main deflection data starts from the memory in the main deflection data circuit 312 to the first arithmetic circuit 3141 in the mapping circuit 314. The main deflection data circuit 312 determines to output data or pause data transfer by detecting a half-full (HF) flag of a FIFO in the mapping circuit 314. After the data output instruction is issued to the data mapping circuit 302, the control computer 4 issues a moving instruction to the stage 101. The control computer 4 moves the stage 101 to the stage moving start point via the stage driving circuit 11, and designates the moving end position and speed. The first arithmetic circuit 3141 in the mapping circuit 314 receives the main deflection data from the main deflection data circuit 312 by its FIFO, and loads one set of main deflection data from the FIFO. Then, the circuit 3141 appends chip numbers, frame numbers, and stripe numbers to the main deflection data received from the main deflection data circuit 312 in accordance with the procedure data stored in the first memory 3142. The last sub deflection position data of each frame is appended with a control code indicating the end of the frame, and the first arithmetic circuit 3141 detects this control code to advance the procedure of the procedure data by one. Furthermore, the first arithmetic circuit 3141 gives a control code indicating the end of a stripe to the last sub deflection position data of that stripe in accordance with the procedure data. After the first arithmetic circuit 3141 gives this control code, it advances the procedure of the procedure data by one, and returns to an instruction waiting state from the control computer 4. The second arithmetic circuit 3143 converts the main deflection data including the chip numbers and frame numbers sent from the first arithmetic circuit 3141 into the wafer coordinate system to check whether or not the data fall within the valid range. First, the second arithmetic circuit 3143 calls out chip position data stored in the second memory 3144 based on the chip number and reads out a chip position (Xchip, Ychip) described using the wafer coordinate system (the wafer center is an origin). Next, the second arithmetic circuit 3143 calls out frame position data stored in the second memory 3144 based on the frame number, and reads out a frame origin position (Xf, Yf) described using the chip coordinate system (the chip center is an origin). Then, the second arithmetic circuit 3143 adds the chip position (Xchip, Ychip), frame position (Xf, Yf), and main deflection position (Xm, Ym) to calculate a main deflection position (Xmwf, Ymwf) on the wafer coordinate system.Xmwf=Xm+Xf+XchipYmwf=Ym+Yf+YchipNote that the main deflection position (Xmwf, Ymwf) indicates the drawing position of each sub deflection region on the wafer coordinate system (from the wafer origin). The second arithmetic circuit 3143 determines if data is valid with respect to the main deflection position (Xmwf, Ymwf). The second arithmetic circuit 3143 calls out the wafer shape data shown in FIG. 10 from the second memory 3144, calls out the wafer valid range (Xmin, Xmax) from the second memory 3144 based on the main deflection position Ymwf, and compares the main deflection position Xmwf with the wafer valid range (Xmin, Xmax). In this comparison, if the main deflection position Xmwf falls within the valid range which is defined by:wafer valid range Xmin<main deflection position Xmwf<wafer valid range Xmaxthe second arithmetic circuit 3143 calls out shot data from the shot data circuit 313; otherwise, it discards the data and loads the next main deflection data from the FIFO. If the second arithmetic circuit 3143 determines that the main deflection position Xmwf falls within the valid range, it reads out shot data from the shot data circuit 313. More specifically, the second arithmetic circuit 3143 activates the shot data circuit 313 by designating the start address of shot data and the number of shots included in the main deflection data shown in FIG. 4A. The shot data circuit 313 outputs shot data described at the address designated from the second arithmetic circuit 3143 as many as the designated number of shots to the second arithmetic circuit 3143. The second arithmetic circuit 3143 appends the shot data sent from the shot data circuit 313 to the main deflection data, and outputs that data to the subsequent position correction circuit 303 in a format shown in FIG. 12. FIG. 12 shows output data from the data mapping circuit 302. Referring to FIG. 12, Xsub indicates a SUB_X position (32 bits); Ysub, a SUB_Y position (32 bits); Nf, a FIG read count designation (28 bits); Cnx, a chip X position (5 bits); Cny, a chip Y position (5 bits); stn, a stripe number (10 bits); Cx, a CP_X position (5 bits); Cy, a CP_Y position (5 bits); t, an irradiation time period (14 bits); L1, a shot size (14 bits); L2, a shot size (14 bits); Xs, a shot position (16 bits); and Ys, a shot position (16 bits). The position correction circuit 303 divides the received data into the main scan data and shot data. Furthermore, the position correction circuit 303 applies position correction of a wafer distortion and chip distortion to the main deflection data, converts the main deflection data from the wafer coordinate system into the stage coordinate system, and outputs the converted data to the subsequent deflection control circuit 301. The position correction circuit 303 outputs the shot data to the arithmetic unit 301c in the deflection control circuit 301. The deflection control circuit 301 processes the received main deflection data and shot data. The arithmetic unit 301a determines based on the output (current stage coordinates (Xstg, Ystg), wafer height) from the position circuit 12 whether or not the main deflection data converted into the stage coordinate system falls within the drawing range. If the main deflection data falls within the drawing range, the arithmetic unit 301a determines the main deflection position, and applies position correction due to a lens distortion. Furthermore, the main deflection data is output to the main deflection amplifier 403 via the arithmetic unit 301b, thus controlling the main deflector 206a to generate a desired voltage. The arithmetic unit 301b always measures the output from the position circuit 12, and corrects the output from the main deflection amplifier 403 so that the electron beam position traces the stage position. The shot data undergoes a position correction arithmetic operation by the arithmetic unit 301c, and is then output to the sub deflection amplifier 404, thus controlling the sub deflector 206b to generate a desired voltage. When the main deflector 206a and the sub deflector 206b have reached the desired voltages, a blanking signal generation circuit (not shown) releases a blanking signal, and the wafer S is irradiated with an electron beam b. In the description of the above embodiment, the control computer 4 generates the wafer shape data 401c based on the wafer layout data 401b (including procedure data, chip position data, frame position data, and stripe position data) and the wafer valid range (broken line, a in FIG. 9), and writes it in the data mapping circuit 302. However, another method may be used. For example, the control computer 4 may write the wafer valid range in the data mapping circuit 302, which may generate the wafer shape data shown in FIG. 10 in advance. According to the first embodiment of the invention, since it is determined based on the wafer shape information if each deficient chip part is located on the wafer, and beam irradiation is done based on the determination result, the chip yield can be improved. Also, no contaminations are generated on the stage. Furthermore, no drawing data is prepared for deficient chip drawing, and the wasteful time can be reduced. Therefore, the productivity in electron beam exposure can be greatly improved. In the first embodiment, the second arithmetic circuit 3143 determines if data is valid with respect to the main deflection position (Xmwf, Ymwf). If the main deflection position Xmwf falls within the valid range, the second arithmetic circuit 3143 calls out shot data from the shot data circuit 313, and outputs it to the subsequent position correction circuit 303 in the format shown in FIG. 12. However, another method may be used. In the second embodiment, a method of appending a beam on-off flag to data to be output to the subsequent position correction circuit 303 will be described. In the second embodiment, the second arithmetic circuit 3143 determines if data is valid with respect to the main deflection position (Xmwf, Ymwf). The second arithmetic circuit 3143 calls out the wafer shape data shown in FIG. 10 from the second memory 3144, calls out the wafer valid range (Xmin, Xmax) from the second memory 3144 based on the main deflection position Ymwf, and compares the main deflection position Xmwf with the wafer valid range (Xmin, Xmax). In this comparison, if the main deflection position Xmwf falls within the valid range which is defined by:wafer valid range Xmin<main deflection position Xmwf<wafer valid range Xmaxthe second arithmetic circuit 3143 calls out shot data from the shot data circuit 313. More specifically, the second arithmetic circuit 3143 activates the shot data circuit 313 by designating the start address of shot data and the number of shots included in the main deflection data shown in FIG. 4A. The shot data circuit 313 outputs shot data described at the address designated from the second arithmetic circuit 3143 as many as the designated number of shots. The second arithmetic circuit 3143 appends the shot data sent from the shot data circuit 313 to the main deflection data, and outputs that data to the subsequent position correction circuit 303 in the format shown in FIG. 12. On the other hand, if the main deflection position Xmwf falls outside the valid range as a result of comparison with the wafer valid range (Xmin, Xmax), a control flag that instructs to turn off a beam is appended to the data to be output to the subsequent position correction circuit 303. More specifically, as shown in FIG. 13, a control flag (2001) that instructs to turn off a beam is appended to the data to be output to the subsequent position correction circuit 303. The deflection control circuit 301 performs beam on-off control of the shot data in the sub deflection region output from the position correction circuit 303 based on this control flag that instructs to turn off a beam. That is, if the control flag (2001) is “1”, the deflection control circuit 301 controls to turn off a beam for the corresponding shot data in the sub deflection region. According to the second embodiment, since it is determined based on the wafer shape information if each deficient chip part is located on the wafer, and beam irradiation is done based on the determination result, the chip yield can be improved. Also, no contaminations are generated. Furthermore, no drawing data is prepared for deficient chip drawing, and the wasteful time can be reduced. Therefore, the productivity in electron beam exposure can be greatly improved. In the third embodiment, the position control circuit determines the valid range in place of the data mapping circuit unlike in the first and second embodiments. The schematic views of the electron beam lithography apparatus according to the third embodiment are the same as those shown in FIGS. 1 and 3 in the first embodiment. A description redundant to the first embodiment in that of the electron beam lithography apparatus according to the third embodiment will be omitted. FIG. 14 is a block diagram showing the arrangement of the data mapping circuit 302 according to the third embodiment. The data mapping circuit 302 comprises a bus adapter 311, main deflection data circuit 312, shot data circuit 313, and mapping circuit 314′, which are connected to a data bus 315. The control computer 4 writes the chip data in the data mapping circuit 302 via a bus adapter 41. Main deflection data is stored in a memory in the main deflection data circuit 312, and shot data is stored in that in the shot data circuit 313. The procedure data shown in FIG. 8 is stored in a first memory 3142 connected to a first arithmetic circuit 3141 in the mapping circuit 314′. FIG. 15 is a block diagram showing the arrangement of the position correction circuit 303 according to the third embodiment. The control computer 4 writes the drawing data 401a in the data mapping circuit 302, and the wafer layout data 401b (including chip position data, frame position data, and stripe position data) and the wafer shape data 401c in the position correction circuit 303. The chip position data shown in FIG. 5B, the frame position data shown in FIG. 6B, and the stripe position data shown in FIG. 7B are stored in a second memory 3033 connected to a second arithmetic circuit 3032 in the position correction circuit 303. The wafer shape data shown in FIG. 10 is stored in a third memory 3035 connected to a third arithmetic circuit 3034. In FIG. 3, after the wafer S is placed on the stage 101 and a drawing preparation is completed, the control computer 4 issues a data output instruction to the data mapping circuit 302. The drawing preparation means a state in which a moving start point and end point of the stage 101 are calculated, and the stage 101 is located at the moving start point. The moving start point and end point of the stage 101 are calculated from a drawing start point and end point (Xstart, Xend) of each stripe. A runup distance and deceleration distance (X runup, X deceleration) are determined based on the drawing start point and end point (Xstart, Xend) of each stripe in correspondence with the stage speed of each stripe. That is, a stage moving start point and end point (Xstgs, Xstge) are determined as follows: In case of forward movement,stage moving start point (Xstgs)=drawing start point (Xstart)−runup distance (X runup)stage moving end point (Xstge)=drawing end point (Xend)+deceleration distance (X deceleration) In case of reverse movement,stage moving start point (Xstgs)=drawing start point (Xstart)+runup distance (X runup)stage moving end point (Xstge)=drawing end point (Xend)−deceleration distance (X deceleration) More specifically, when the transfer start address, the number of words, and the number of transfer repetition times are instructed to the main deflection data circuit 312 shown in FIG. 14, transfer of the main deflection data starts from the memory in the main deflection data circuit 312 to the first arithmetic circuit 3141 in the mapping circuit 314′. The main deflection data circuit 312 determines to output data or pause data transfer by detecting a half-full (HF) flag of a FIFO in the mapping circuit 314′. After the data output instruction is issued to the data mapping circuit 302, the control computer 4 issues a moving instruction to the stage 101. The control computer 4 moves the stage 101 to the stage moving start point via the stage driving circuit 11, and designates the moving end position and speed. When the first arithmetic circuit 3141 in the mapping circuit 314′ receives the main deflection data from the main deflection data circuit 312 by its FIFO, and loads one set of main deflection data from the FIFO, it reads out shot data from the shot data circuit 313. More specifically, the first arithmetic circuit 3141 activates the shot data circuit 313 by designating the start address of shot data and the number of shots included in the main deflection data shown in FIG. 4A. The shot data circuit 313 outputs shot data described at the address designated from the first arithmetic circuit 3141 as many as the designated number of shots. The first arithmetic circuit 3141 appends the shot data sent from the shot data circuit 313 to the main deflection data, and outputs that data to the subsequent position correction circuit 303 in the format shown in FIG. 12. In this case, the first arithmetic circuit 3141 appends chip numbers, frame numbers, and stripe numbers to the main deflection data received from the main deflection data circuit 312 in accordance with the procedure data stored in the first memory 3142. The last sub deflection position data of each frame is appended with a control code indicating the end of the frame, and the first arithmetic circuit 3141 detects this control code to advance the procedure of the procedure data by one. The position correction circuit 303 divides the received data into the main scan data and shot data. Initially, a first arithmetic circuit 3031 divides the received data into main deflection data and shot data. The main deflection data is output to the second arithmetic circuit 3032, and the shot data is output to the arithmetic unit 301c of the deflection control circuit 301. The second arithmetic circuit 3032 of the position correction circuit 303 converts the main deflection data which are sent from the data mapping circuit 302 and includes the chip numbers and frame numbers onto the wafer coordinate system to determine whether or not the data fall within the valid range. First, the second arithmetic circuit 3032 calls out chip position data stored in the second memory 3033 based on the chip number and reads out a chip position (Xchip, Ychip) described using the wafer coordinate system (the wafer center is an origin). Next, the second arithmetic circuit 3032 calls out frame position data stored in the second memory 3033 based on the frame number, and reads out a frame origin position (Xf, Yf) described using the chip coordinate system (the chip center is an origin). Then, the second arithmetic circuit 3032 adds the chip position (Xchip, Ychip), frame position (Xf, Yf), and main deflection position (Xm, Ym) to calculate a main deflection position (Xmwf, Ymwf) on the wafer coordinate system.Xmwf=Xm+Xf+XchipYmwf=Ym+Yf+YchipNote that the main deflection position (Xmwf, Ymwf) indicates the drawing position of each sub deflection region on the wafer coordinate system (from the wafer origin). The third arithmetic circuit 3034 of the position correction circuit 303 determines if data is valid with respect to the main deflection position (Xmwf, Ymwf). The third arithmetic circuit 3034 calls out the wafer shape data shown in FIG. 10 from the third memory 3035, calls out the wafer valid range (Xmin, Xmax) from the third memory 3035 based on the main deflection position Ymwf, and compares the main deflection position Xmwf with the wafer valid range (Xmin, Xmax). In this comparison, if the main deflection position Xmwf falls outside the valid range which is defined by:wafer valid range Xmin<main deflection position Xmwf<wafer valid range Xmaxthe third arithmetic circuit 3034 sets a control flag that instructs the deflection control circuit 301 to forcibly turn off a beam. More specifically, a register as a control flag that instructs to turn off a beam is assured in the deflection control circuit 301, and the third arithmetic circuit 3034 sets the flag of this register. The deflection control circuit 301 controls to turn on or off a beam in correspondence with the shot data in the sub deflection region output from the position correction circuit 303 based on the control flag that instructs to turn off a beam. In this way, drawing is done in the deflection control circuit 301, but the sample S is not irradiated with any beam. On the other hand, if the main deflection position Xmwf falls within the valid range in the above comparison, the third arithmetic circuit 3034 sets a control flag that instructs the deflection control circuit 301 to perform normal drawing. In this case, drawing is done according to the drawing time period described in the shot data. Furthermore, a fourth arithmetic circuit 3036 applies position correction of a wafer distortion and chip distortion to the main deflection data, converts the main deflection data from the wafer coordinate system into the stage coordinate system, and outputs the converted data to the subsequent deflection control circuit 301. Note that the fourth arithmetic circuit 3036 comprises a memory (not shown), which stores coefficients required for position correction. The deflection control circuit 301 processes the received main deflection data and shot data. As for the main deflection data converted into the stage coordinate system, the arithmetic unit 301a determines a main deflection position (Xmdef, Ymdef) based on the output (current stage coordinates (Xstg, Ystg), wafer height) from the position circuit 12, and applies position correction due to a lens distortion. Note that the main deflection position (Xmdef, Ymdef) is the drawing position of the sub deflection region on a main deflection region coordinate system (from a main deflection region origin), and is obtained by adding a chip distortion correction amount and wafer distortion correction amount.Xmdef=Xmstg−Xstg Ymdef=Ymstg−Ystg Furthermore, the main deflection data is output to the main deflection amplifier 403 via the arithmetic unit 301b, thus controlling the main deflector 206a to generate a desired voltage. The arithmetic unit 301b always measures the output from the position circuit 12, and corrects the output from the main deflection amplifier 403 so that the electron beam position traces the stage position. The shot data undergoes a position correction arithmetic operation by the arithmetic unit 301c, and is then output to the sub deflection amplifier 404, thus controlling the sub deflector 206b to generate a desired voltage. When the main deflector 206a and the sub deflector 206b have reached the desired voltages, a blanking signal generation circuit (not shown) releases a blanking signal, and the wafer S is irradiated with an electron beam b. According to the third embodiment, since it is determined based on the wafer shape information if each deficient chip part is located on the wafer, and beam irradiation is done based on the determination result, the chip yield can be improved. Also, no contaminations are generated. Furthermore, no drawing data is prepared for deficient chip drawing, and the wasteful time can be reduced. Therefore, the productivity in electron beam exposure can be greatly improved. The fourth embodiment will be described below. The schematic views of the electron beam lithography apparatus according to the fourth embodiment are the same as those shown in FIGS. 1 and 3 in the first embodiment, and the data mapping circuit is the same as that shown in FIG. 14 in the third embodiment. A description redundant to that of the electron beam lithography apparatus of the first to third embodiments will be omitted. FIG. 16 is a block diagram showing the arrangement of the position correction circuit 303 according to the fourth embodiment. A difference of the fourth embodiment from the third embodiment is that the second to fourth arithmetic circuits (3032, 3034, and 3036) in the third embodiment are configured using a DSP (Digital Signal Processor). Accordingly, the second and third memories (3033 and 3035) are replaced by an internal or external memory (second memory 30311 in FIG. 16) connected to the DSP via a bus. In the fourth embodiment, after it is determined whether or not data is valid with respect to the main deflection position (Xmwf, Ymwf), position correction of a wafer distortion and chip distortion is applied. However, the order of these processes may be reversed. A description of the fourth embodiment of the invention will be given according to the processing flow which applies position correction of a wafer distortion and chip distortion to the main deflection position (Xmwf, Ymwf) and then determines whether or not data is valid. The control computer 4 shown in FIG. 16 writes the drawing data 401a in the data mapping circuit 302, and the wafer layout data 401b (including chip position data, frame position data, and stripe position data) and the wafer shape data 401c in the position correction circuit 303. As in the third embodiment, after the data output instruction is issued to the data mapping circuit 302, the control computer 4 issues a moving instruction to the stage 101. The control computer 4 moves the stage 101 to the stage moving start point via the stage driving circuit 11, and designates the moving end position and speed. When the first arithmetic circuit 3141 in the mapping circuit 314′ receives the main deflection data from the main deflection data circuit 312 by its FIFO, and loads one set of main deflection data from the FIFO, it reads out shot data from the shot data circuit 313. More specifically, the first arithmetic circuit 3141 activates the shot data circuit 313 by designating the start address of shot data and the number of shots included in the main deflection data shown in FIG. 4A. The shot data circuit 313 outputs shot data described at the address designated from the first arithmetic circuit 3141 as many as the designated number of shots. The first arithmetic circuit 3141 appends the shot data sent from the shot data circuit 313 to the main deflection data, and outputs that data to the subsequent position correction circuit 303 in the format shown in FIG. 12. In this case, the first arithmetic circuit 3141 appends chip numbers, frame numbers, and stripe numbers to the main deflection data received from the main deflection data circuit 312 in accordance with the procedure data stored in the first memory 3142. The last sub deflection position data of each frame is appended with a control code indicating the end of the frame, and the first arithmetic circuit 3141 detects this control code to advance the procedure of the procedure data by one. The position correction circuit 303 divides the received data into the main scan data and shot data. Initially, a first arithmetic circuit 3031 divides the received data into main deflection data and shot data. The main deflection data is output to a second arithmetic circuit 30310, and the shot data is output to the arithmetic unit 301c of the deflection control circuit 301. The second arithmetic circuit 30310 of the position correction circuit 303 converts the main deflection data which is received from the data mapping circuit 302 and includes the chip numbers and frame numbers into the wafer coordinate system, and determines whether or not to fall within the valid range. Note that the second arithmetic circuit comprises a DSP (Digital Signal Processor), and it will be referred to as a DSP hereinafter. In the DSP 30310, an execution program is sent from the control computer 4, and is written in an internal memory of the DSP 30310 and a second memory 30311 connected to the DSP 30310 via the bus adapter 311 and data bus 315. When the position correction circuit includes a ROM (Read Only Memory) connected to the DSP 30310, the execution program may be loaded from that ROM. FIG. 17 shows the processing flow (S1 to S7) in the DSP 30310. Step S1) The DSP 30310 reads out main deflection data (SF information in FIG. 17) which is output from the first arithmetic circuit 3031 and includes the chip numbers, frame numbers, and the like. Step S2) The DSP 30310 calls out frame position data stored in the second memory 30311 based on the frame number assigned to the main deflection data (SF information in FIG. 17), and reads out a frame origin position (Xf, Yf) described using the chip coordinate system (the chip center is an origin). Furthermore, the DSP 30310 adds the frame position (Xf, Yf) and main deflection position (Xm, Ym) to calculate a main deflection position (Xmchip, Ymchip) on the chip coordinate system. Note that the main deflection position (Xmchip, Ymchip) indicates the drawing position of the sub deflection region on the chip coordinate system (from the chip origin).Xmchip=Xm+Xf Ymchip=Ym+Yf Step S2′) The DSP 30310 calculates chip distortion correction amounts for the main deflection position (Xmchip, Ymchip) on the chip coordinate system. Chip distortion coefficients are stored in advance in the second memory 30311 in correspondence with chip numbers as ternary coefficients for Xmchip and Ymchip. The DSP 30310 calls out chip distortion coefficients based on the chip number assigned to the main deflection data (SF information in FIG. 17), and calculates chip distortion correction amounts Cchipx and Cchipy for the main deflection position (Xmchip, Ymchip). Step S3) The DSP 30310 then calls out chip position data stored in the second memory 30311 based on the chip number assigned to the main deflection data (SF information in FIG. 17), and reads out a chip position (Xchip, Ychip) described using the wafer coordinate system (the wafer center is an origin). Furthermore, the DSP 30310 calculates a main deflection position (Xmwf, Ymwf) on the wafer coordinate system based on the main deflection position (Xmchip, Ymchip) on the chip coordinate system. Note that the main deflection position (Xmwf, Ymwf) indicates the drawing position of each sub deflection region on the wafer coordinate system (from the wafer origin).Xmwf=Xmchip+XchipYmwf=Ymchip+Ychip Step S3′) The DSP 30310 calculates wafer distortion correction amounts for the main deflection position (Xmwf, Ymwf) on the wafer coordinate system. Wafer distortion coefficients are stored in advance in the second memory 30311 as ternary coefficients for Xmwf and Ymwf. The DSP 30310 calls out wafer distortion coefficients, and calculates wafer distortion correction amounts Cwfx and Cwfy for the main deflection position (Xmwf, Ymwf). Step S4) Furthermore, the DSP 30310 applies position correction of a wafer distortion and chip distortion to the main deflection data. In this case, the chip distortion correction amounts Cchipx and Cchipy and the wafer distortion correction amounts Cwfx and Cwfy are added to the main deflection position (Xmwf, Ymwf) on the wafer coordinate system to calculate a main deflection position (Xmwf′, Ymwf′) on the wafer coordinate system. Note that the main deflection position (Xmwf′, Ymwf′) is the drawing position of the sub deflection region on the wafer coordinate system (from the wafer origin), and is obtained by adding the chip distortion correction amounts and wafer distortion correction amounts.Xmwf′=Xmwf+Cchipx+Cwfx Ymwf′=Ymwf+Cchipy+Cwfy Step S5) The DSP 30310 determines whether or not data is valid with respect to the main deflection position (Xmwf′, Ymwf′). The DSP 30310 calls out the wafer shape data shown in FIG. 10 from the second memory 30311, calls out the wafer valid range (Xmin, Xmax) from the second memory 30311 based on the main deflection position Ymwf′, and compares the main deflection position Xmwf′ with the wafer valid range (Xmin, Xmax). Step S6′) In this comparison, if the main deflection position Xmwf′ falls outside the valid range which is defined by:wafer valid range Xmin<main deflection position Xmwf′<wafer valid range Xmaxthe DSP 30310 sets a control flag that instructs the deflection control circuit 301 to forcibly turn off a beam. In this way, drawing is done in the deflection control circuit 301, but the sample S is not irradiated with any beam. Step S6) On the other hand, if the main deflection position Xmwf′ falls within the valid range in the comparison in step S5, the DSP 30310 sets a control flag that instructs the deflection control circuit 301 to perform normal drawing. In this case, drawing is done according to the drawing time period described in the shot data. Step S7) The DSP 30310 adds a wafer origin (Xwf, Ywf) described using the stage coordinate system to the main deflection position (Xmwf′, Ymwf′) described using the wafer coordinate system to calculate a main deflection position (Xmstg, Ymstg) converted into the stage coordinate system. Note that the main deflection position (Xmstg, Ymstg) is the drawing position of the sub deflection region on the stage coordinate system (from the stage origin), and is obtained by adding the chip distortion correction amounts and wafer distortion correction amounts.Xmstg=Xmwf′+Xwf Ymstg=Ymwf′+Ywf Step S8) Finally, the DSP 30310 outputs the calculated main deflection position (Xmstg, Ymstg) to the subsequent deflection control circuit 301. The deflection control circuit 301 processes the received main deflection data and shot data. As for the main deflection data converted into the stage coordinate system, the arithmetic unit 301a determines a main deflection position (Xmdef, Ymdef) based on the output (current stage coordinates (Xstg, Ystg), wafer height) from the position circuit 12, and applies position correction due to a lens distortion. Note that the main deflection position (Xmdef, Ymdef) is the drawing position of the sub deflection region on a main deflection region coordinate system (from a main deflection region origin), and is obtained by adding the chip distortion correction amounts and wafer distortion correction amounts.Xmdef=Xmstg−Xstg Ymdef=Ymstg−Ystg Furthermore, the main deflection data is output to the main deflection amplifier 403 via the arithmetic unit 301b, thus controlling the main deflector 206a to generate a desired voltage. The arithmetic unit 301b always measures the output from the position circuit 12, and corrects the output from the main deflection amplifier 403 so that the electron beam position traces the stage position. The shot data undergoes a position correction arithmetic operation by the arithmetic unit 301c, and is then output to the sub deflection amplifier 404, thus controlling the sub deflector 206b to generate a desired voltage. When the main deflector 206a and the sub deflector 206b have reached the desired voltages, a blanking signal generation circuit (not shown) releases a blanking signal, and the wafer S is irradiated with an electron beam b. In the description of the above embodiment, the control computer 4 generates the wafer shape data 401c based on the wafer layout data 401b (including procedure data, chip position data, frame position data, and stripe position data) and the wafer valid range (broken line, a in FIG. 9), and writes it in the data mapping circuit 302. However, another method may be used. For example, the control computer 4 may write the wafer valid range in the position correction circuit 303, which may generate the wafer shape data shown in FIG. 10. For example, as shown in FIG. 19, a value (e.g., 95 mm (radius)) indicating the wafer valid range is written in advance in the DSP 30310, and the valid range (Xmin, Xmax) for each stripe can be calculated based on the main deflection position Xmwf′ (S5′ in FIG. 18). Also, the value (e.g., 95 mm (radius)) indicating the wafer valid range is written in advance in the DSP 30310, and the DSP 30310 can generate the wafer shape data shown in FIG. 10 in advance. In the third and fourth embodiments, a register as a control flag that instructs to turn off a beam is assured in the deflection control circuit 301, and the deflection control circuit 301 controls to turn on or off a beam in correspondence with the shot data in the sub deflection region output from the position correction circuit 303 based on the control flag that instructs to turn off a beam. However, another method may be used. For example, a control flag that instructs to turn off a beam may be set in an empty bit of the drawing data shown in FIG. 12. More specifically, as shown in FIG. 19, an empty bit (2101) in the shot data is used as a control flag that instructs to turn off a beam, and the deflection control circuit 301 may read this bit (2101) to control to turn on or off a beam in correspondence with the shot data in the sub deflection region. According to this modification, since it is determined based on the wafer shape information if each deficient chip part is located on the wafer, and beam irradiation is done based on the determination result, the chip yield can be improved. Also, no contaminations are generated. Furthermore, no drawing data is prepared for deficient chip drawing, and the wasteful time can be reduced. Therefore, the productivity in electron beam exposure can be greatly improved. In the fifth embodiment, a stage runup position and drawing range are calculated based on wafer shape data unlike in the first to fourth embodiments. The schematic views of the electron beam lithography apparatus according to the fifth embodiment are the same as those shown in FIGS. 1 and 3 in the first embodiment. In the fifth embodiment, the moving start point and end point (Xstgs, Xstge) of the stage 101 are calculated using the wafer shape data shown in FIG. 10. Initially, a drawing start point and end point (Xstart, Xend) of each stripe are calculated from the chip layout. The drawing start point and end point (Xstart, Xend) of each stripe are compared with the wafer valid range (Xmin, Xmax) described in the wafer shape data. If the drawing start point and end point (Xstart, Xend) are broader than the wafer valid range (Xmin, Xmax), the wafer valid range (Xmin, Xmax) is replaced by the drawing start point and end point. Upon completion of updating of the drawing start point and end point (Xstart, Xend) of each stripe, a runup distance and deceleration distance (X runup, X deceleration) are determined in correspondence with the stage speed of each stripe. That is, the stage moving start point and end point (Xstgs, Xstge) are determined as follows: In case of forward movement,stage moving start point (Xstgs)=drawing start point (Xstart)−runup distance (X runup)stage moving end point (Xstge)=drawing end point (Xend)+deceleration distance (X deceleration) In case of reverse movement,stage moving start point (Xstgs)=drawing start point (Xstart)+runup distance (X runup)stage moving end point (Xstge)=drawing end point (Xend)−deceleration distance (X deceleration) Subsequently, based on the chip number in the procedure data shown in FIG. 8, a chip position range (Xmin, Xmax) of that procedure is calculated. The chip position range (Xmin, Xmax) of that procedure is compared with the drawing start point and end point (Xstart, Xend) of the corresponding stripe. If the chip completely falls outside the range of the drawing start point and end point (Xstart, Xend) of the corresponding stripe, that procedure is deleted. This processing is applied to all the procedures to update the procedure data. FIG. 20 is a view for explaining the drawing range based on the conventional method. FIG. 21 is a view for explaining the drawing range indicated by the procedure data generated according to the fifth embodiment. As can be seen from FIG. 21, the drawing area of the drawing range shown in FIG. 21 is smaller than that based on the conventional method shown in FIG. 20. Upon drawing, the procedure data generated in this way is transferred to the electron beam lithography apparatus of each of the first to fourth embodiments to execute drawing. According to the fifth embodiment, since it is determined based on the wafer shape information if each deficient chip part is located on the wafer, and beam irradiation is done based on the determination result, the chip yield can be improved. Also, no contaminations are generated on the stage. Furthermore, no drawing data is prepared for deficient chip drawing, and the wasteful time can be reduced. Furthermore, the wasteful time associated with stage movement can be reduced. Therefore, the productivity in electron beam exposure can be greatly improved. Finally, a semiconductor device is manufactured by using the wafer on which the electron beam lithography process described in any of the first to fifth embodiments is performed. Note that the invention is not limited to the above embodiments, and modifications may be made as needed without departing from the scope of the invention. For example, in each of the above embodiments, the operator designates the wafer valid range (broken line, a in FIG. 9), and inputs it to the control computer. Alternatively, the wafer valid range may be designated by another method. For example, a valid range may be registered in advance in the computer as a system parameter. When the electron beam lithography apparatus is controlled by a production control computer, the production control computer may generate the drawing data 401a, wafer layout data 401b, and wafer shape data 401c and may store them in the computer 4. According to the embodiments of the invention, an electron beam lithography apparatus, lithography method, and lithography program which efficiently make deficient chip drawing, and a manufacturing method of a semiconductor device can be provided. Additional advantages and modifications will readily occur to those skilled in the art. Therefore, the invention in its broader aspects is not limited to the specific details and representative embodiments shown and described herein. Accordingly, various modifications may be made without departing from the spirit or scope of the general inventive concept as defined by the appended claims and their equivalents. |
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050154222 | description | DETAILED DESCRIPTION A process for fabricating UO.sub.2 pellets, according to the invention, will specifically be described below. The process is characterized in that when ADU is precipitated, the U concentration in UO.sub.2 F.sub.2 aqueous solution is brought to a value within the range from 50 to 500 g/l, that the reaction of the UO.sub.2 F.sub.2 aqueous solution with NH.sub.3 is divided into two stages, and that the NH.sub.3 /U molar ratio is set in the first step to a value within the range from 3 to 6, and in the second stage to a value within the range from 6 to 12. According to the above-described process, the properties of the ADU formed are substantially determined by the precipitating reaction in the first stage. In this connection, if conditions are such that the NH.sub.3 /U molar ratio is equal to or less than 6, it is possible to form ADU as primary particles which are relatively large in size, even if the U concentration in the UO.sub.2 F.sub.2 aqueous solution is equal to or less than 500 g/l. It is considered that the reason for this is that in the case where the NH.sub.3 /U molar ratio is equal to or less than 6, as the NH.sub.4 F concentration increases on the basis of the reaction represented by the following chemical equation (3) in which the ADU is precipitated out of the UO.sub.2 F.sub.2 aqueous solution, the NH.sub.4 F causes a reaction to occur whereby the ADU is formed by way of ammonium uranyl fluoride (AUF), as represented by the equations (4) and (5): EQU UO.sub.2 F+3NH.sub.4 OH.fwdarw.(1/2)(NH.sub.4).sub.2 U.sub.2 O.sub.7 +2NH.sub.4 F+(3/2)H.sub.2 O (3) EQU UO.sub.2 F.sub.2 +3NH.sub.4 F.fwdarw.(NH.sub.4).sub.3 UO.sub.2 F.sub.5 (4) EQU (NH.sub.4).sub.3 UO.sub.2 F.sub.5 +3NH.sub.4 OH.fwdarw.(1/2)(NH.sub.4).sub.2 U.sub.2 O.sub.7 +5NH.sub.4 F+(3/2)H.sub.2 O (5) Since the AUF is a crystalline material inert under normal conditions, the ADU formed by way of the AUF is also inert and has relatively large primary particles. The lower the NH.sub.3 /U molar ratio set in the first stage reaction, the greater the tendency for the ADU to be formed by way of the AUF, so that ADU which is inert and has larger primary particles is obtained. It is not desirable for the NH.sub.3 /U molar ratio to be lower than 3 in the first stage precipitating reaction, because this will lower the ratio at which the U is precipitated. On the other hand, if the NH.sub.3 /U molar ratio is equal to or higher than 6, the conventional problems cannot be solved. In this connection, although the U remains in the aqueous solution even if the NH.sub.3 /U molar ratio is within the range of from 3 to 6, it is possible to react the U sufficiently if the NH.sub.3 /U molar ratio in the second stage reaction is brought to a value within the range of from 6 to 12. Further, if the NH.sub.3 /U molar ratio is lower than 6 in the second stage reaction, the U is not sufficiently precipitated. On the other hand, there is no value in having a NH.sub.3 /U molar ratio above 12, because this merely increases the amount of water used and an amount of waste liquid. Also in the case where the NH.sub.3 /U molar ratio is brought to a value within the range from 6 to 12 in the second stage in order to precipitate the ADU sufficiently in the manner mentioned above, the properties of the resulting ADU are no different than those of the ADU formed in the standard method equation (2). Thus, according to the process of this invention, it is possible to easily fabricate pellets with an optimal particle size within the range from 10 to 100 um and which are homogeneous in properties, without wasting the U even under for the condition where the U concentration in the UO.sub.2 F.sub.2 aqueous solution is equal to or less than 500 g/l. The advantages of the invention will next be expounded with reference to an embodiment. The UO.sub.2 F.sub.2 powder was dissolved in demineralized water to form an aqueous solution whose U concentration within the range from 40 to 600 g/l. The aqueous solution and NH.sub.3 water were first fed continuously to a first-stage settling chamber, with a 2.5 to 6.5 NH.sub.3 /U molar ratio, to carry out the first stage ADU precipitation. Subsequently, the ADU slurry formed in the first-stage settling chamber, and the aqueous NH.sub.3 were fed continuously to a second stage settling chamber, and the NH.sub.3 /U molar ratio brought to a value within the range from 5 to 15. The resulting second-stage ADU slurry was filtered and dried and, thereafter, calcined and reduced at 650.degree. C. under a H.sub.2 atmosphere, to transform the slurry into UO.sub.2 powder. The UO.sub.2 powder was compacted at a pressure of 5 t/cm.sup.2, and then sintered for four hours at 1750.degree. C. in an H.sub.2 atmosphere, to form pellets. The following table indicates the relationship between the pellet grain size and the ADU precipitating conditions at each of the first-stage and second-stage settling chambers. TABLE ______________________________________ U CONCENTRATION FIRST SECOND PELLET UO.sub.2 F.sub.2 STAGE STAGE GRAIN AQUEOUS SOLUTION NH.sub.3 /U NH.sub.3 /U SIZE (g/l) RATIO RATIO (.mu.m) ______________________________________ 50 2.5 9.0 7 50 3.0 9.0 10 50 4.3 9.0 46 50 6.0 9.0 98 50 6.5 9.0 110 40 6.0 9.0 105 50 6.0 9.0 96 300 6.0 9.0 42 500 6.0 9.0 23 600 6.0 9.0 9 100 5.0 5.0 34 100 5.0 6.0 36 100 5.0 9.0 33 100 5.0 12.0 35 100 5.0 15.0 34 ______________________________________ As will be clear from the above table, in case where the U concentration in the UO.sub.2 F.sub.2 aqueous solution was 50 g/l, pellets having a grain size within the range from 10 to 100 .mu.m were obtained when the NH.sub.3 /U molar ratio in the first stage was within the range from 3 to 6. Further, if the NH.sub.3 /U molar ratio in the first stage was brought to 6, pellets having a grain size within the range from 10 to 100 .mu.m were obtained when the U concentration in the UO.sub.2 F.sub.2 aqueous solution was within the range from 50 to 500 g/l. Moreover, if the U concentration was 100 g/l and the NH.sub.3 /U molar ratio in the first stage was brought to 5, the grain size of the pellets remained practically unchanged, even if the NH.sub.3 /U molar ratio in the second stage varied within the range from 5 to 15. If, however, the NH.sub.3 /U molar ratio in the second stage was 5, the loss of the U was so great that approximately 20% of the U remained in the waste liquid. On the other hand, even if the NH.sub.3 /U molar ratio in the second stage was 15, the U loss remained the same as for when the ratio ranged from 6 to 12, and a sufficiently high collecting ratio was obtained even if the NH.sub.3 /U molar ratio in the second stage was within the range from 6 to 12. As described above, according to the UO.sub.2 pellet fabrication process of the invention, it is possible to easily fabricate pellets which have their optional grain size within the range from 10 to 100 .mu.m and which are homogeneous in properties, without wasting the U even under conditions where the U concentration in the UO.sub.2 F.sub.2 is equal to or less than 500 g/l. Thus, the amount of the pellets restrict the rate of release of fission product gas can be set to a desired value, making it possible to enhance the combustion stability of the pellets. |
summary | ||
claims | 1. A method for inspecting a plurality of target features arrayed in spaced arrangement on a surface of a target object, comprising the steps of:providing a fixture for holding the target object;providing a high speed camera;selectively positioning at least one of the holding fixture and the high speed camera relative to the other in a continuous relative motion along a three-dimensional path over a plurality of selected target features without pause; andeach time the high speed camera orientates to a selected target feature, capturing an image and determining a location of the selected target feature during an exposure duration using the high speed camera while in relative motion, the high speed camera enabling inspecting of the plurality of selected target features without pause, movement of the selected target feature relative to the high speed camera over a duration of a frame capture being less than a predetermined fraction of a true position tolerance of the selected target feature. 2. The method as recited in claim 1 further comprising the step of providing a position manipulator in operative association with the holding fixture for selectively positioning the holding fixture to orient a feature to be imaged on the target object to a desired orientation relative to the high speed camera at each selected target feature along the three dimensional path. 3. The method as recited in claim 1 further comprising the step of storing the captured image in a data archive and processing the captured image in parallel with relative movement of the high speed camera and the holding fixture from the imaged target feature to a next to be imaged target feature. 4. The method as recited in claim 1 further comprising the steps of:providing a light array in operative association with the high speed camera; andeach time the high speed camera orientates to a selected target feature, powering the light array to illuminate the selected target feature during the exposure duration. 5. The method as recited in claim 4 wherein the step of providing a light array in operative association with the high speed camera comprises providing an array of a plurality of light emitting diodes in operative association with the high speed camera; and the step of powering the light array optionally includes selectively overpowering the light emitting diodes during the exposure duration. 6. The method as recited in claim 1 wherein the high speed camera has an exposure duration of less than about 3 milliseconds. 7. An inspection system for inspecting a plurality of target features arrayed in spaced arrangement on a surface of a target object, comprising:a position manipulator having a fixture for holding the target object;a high speed camera, the high speed camera having an exposure duration of less than 3 milliseconds and configured to at least in part capture an image and determine a location of the target features, the high speed camera enabling inspecting of the plurality of selected target features without pause, movement of the selected target feature relative to the high speed camera over a duration of a frame capture being less than a predetermined fraction of a true position tolerance of the selected target feature;a light array in operative association with the high speed camera;a controller operatively associated with the high speed camera and with the position manipulator; anda processor operatively associated with the high speed camera for processing an image of a target feature received from the high speed camera. 8. The inspection system as recited in claim 7 wherein the high speed camera comprises a video camera having a frame rate capability of at least about 300 frames per second. 9. The inspection system as recited in claim 8 wherein the video camera has a frame rate capability of at least about 1000 frames per second. 10. The inspection system as recited in claim 7 wherein the light array includes a plurality of light emitting diodes. 11. The inspection apparatus as recited in claim 10 further comprising a LED driver operatively associated with the light emitting diodes for selectively switching the light emitting diodes from zero to full rated power in less than about 1 microsecond. 12. The inspection apparatus as recited in claim 10 wherein the LED driver has the capability of selectively switching the light emitting diodes from zero to a power level in excess of full rated power in less than about 1 microsecond. 13. A method for inspecting a turbine airfoil for measuring the location of at least of a plurality of selected holes of a multiplicity of holes arrayed in spaced arrangement in a surface of the turbine airfoil, comprising the steps of:providing a position manipulator having a fixture for holding the turbine airfoil during inspection, the position manipulator having a 5-degree of freedom positioning system for selectively positioning the holding fixture to orientate the turbine airfoil;providing a high speed camera having an exposure duration;providing a plurality of light emitting diodes in operative association with the high speed camera;selectively positioning at least one of the holding fixture and the high speed camera relative to the other in a continuous relative motion along a three-dimensional path over the plurality of selected holes without pause; andeach time the high speed camera orientates to a selected one of the plurality of selected holes, powering at least selected light emitting diodes of the plurality of the lighting emitting diodes to illuminate the selected hole at least for the exposure duration and capturing an image and determining a location of the selected hole during the exposure duration using the high speed camera while in relative motion with respect to the selected hole, the high speed camera enabling on-the-fly inspecting of the plurality of selected holes without pause, movement of the selected hole relative to the high speed camera over a duration of a frame capture being less than a predetermined fraction of a true position tolerance of the selected hole. 14. The method as recited in claim 13 wherein the high speed camera has an exposure duration of less than about 3 milliseconds. 15. The method as recited in claim 14 wherein the step of selectively positioning at least one of the holding fixture and the high speed camera relative to the other includes the step of simultaneously moving the high speed camera and repositioning the holding fixture in relative motion. 16. The method as recited in claim 14 wherein the high speed camera comprises a video camera having a frame rate of at least 300 frames per second and in relative motion with respect to a selected hole to be imaged at a relative speed of at least about 50 inches per minute. 17. The method as recited in claim 13 further comprising the step of storing the captured hole image in a data archive and processing the captured image in parallel with movement of the video camera from the imaged hole to a next selected hole to be imaged. 18. The method as recited in claim 13 wherein the step of powering at least selected light emitting diodes of the plurality of light emitting diodes comprises powering the selected light emitting diodes from zero power to at least full power in less than about 1 millisecond. 19. The method as recited in claim 13 further comprising the step of triggering the high speed camera to image a target feature when the high-speed camera and the target feature are aligned in gun barrel shot relationship. 20. The method as recited in claim 13 further comprising the step of probing the position of the turbine airfoil within the fixture, the step of probing including the steps of:setting a nominal location and orientation of a turbine airfoil loaded into the CNC machine to what was found as an actual location and orientation of a most previous turbine airfoil inspected; andinitially probing a selected single point on the turbine airfoil to establish an estimate of the turbine airfoil location along the part Z-axis. |
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description | The present application claims priority from Japanese application serial no. 2007-049190, filed on Feb. 28, 2007, the content of which is hereby incorporated by reference into this application. The present invention relates to a light water reactor, a core of the light water reactor and fuel assembly, and more particularly, to a light water reactor, a core of the light water reactor and fuel assembly preferably applied to a boiling water reactor. When actinide nuclide, which has many isotopes and is included in a nuclear fuel material in a fuel assembly loaded in a core of a light water reactor, burns in a core, the actinide nuclide to transfers among isotopes in succession by nuclear transmutation such as nuclear fission and neutron absorption. Since odd-numbered nucleus that has a large nuclear fission cross section with respect to a resonance and thermal neutrons, and even-numbered nucleus that undergoes fission only for fast neutrons are present as the actinide nuclide, in general, present ratios of the isotopes present in the actinide nuclides included in the fuel assembly largely change as the actinide nuclides burn. It is known that this present ratio change depends on the neutron energy spectrum at the position at which the fuel assembly is loaded in the core. Current light water rectors use slightly enriched uranium as nuclear fuel. However, since the natural uranium resource is finite, it is necessary to successively replace fuel assemblies used in the light water reactor with recycled fuel assemblies including a nuclear fuel material which is formed by enriching depleted uranium, which is a residual after uranium enrichment, with the transuranic nuclide (TRU) extracted from spent fuel assemblies in the light water reactor. TRU needs to be recycled as a useful resource over a very long period predicted to be necessary for commercial reactors, and during this period, the amount of TRU needs to always increase or to be maintained nearly constant. JP 3428150 B describes technology to implement a breeder reactor in which the amount of fissionable Pu is increased or maintained nearly constant in light water reactors that occupy most of the current commercial reactors. In a light water reactor in which the breeder reactor described in JP 3428150 B and R. TAKEDA et al., “General Features of Resource-Renewable BWR (RBWR) and Scenario of Long-term Energy Supply”, Proc. of International Conference on Evaluation of Emerging Nuclear Fuel Cycle Systems. GLOBAL '95 Versailles, France, September, 1995, P. 938 is became a reality, a plurality of fuel assemblies, each of which has a hexagonal transverse cross section, are disposed in the core, each fuel assembly being formed by closely arranging a plurality of fuel rods in a triangular grid. In the core of this light water reactor, the amount of water around the fuel rods is lessened due to the close arrangement of the fuel rods, and thereby the ratios of resonant energy neutrons and fast energy neutrons are increased. In addition, the height of a mixed oxide fuel section of the TRU is reduced and blanket zones loaded with depleted uranium are disposed above and below the mixed oxide burning part so as to maintain a negative void coefficient, which is a safety criterion. The core is formed in two stacked stages by applying the concept of a parfait-type core described in G. A. Ducat et al., Evaluation of the Parfait Blanket Concept for Fast Breeder Reactors, MITNE-157, ABSTRACT, January, 1974, thereby a breeding ratio of 1 or more is ensure, keeping the economy. To recycle TRU, the reprocessing of spent fuel is indispensable. Due to a fear that consumer TRU is diverted to weapons of mass destruction, there has been an increasing demand for nuclear non-proliferation and thereby restrictions on TRU recycling have been severe. It is certain that an electric power generating system superior to a fission reactor is put into practical use on some day in the future. At that time, the value of TRU is lowered from a very useful fuel equivalent to enriched uranium to a cumbersome long-lived waste material. Accordingly, the most important object in nuclear power development is to establish a TRU disposal method. At present, there is a result that only Pu out of TRU included in spent fuel of a light water reactor was burnt only once, but multi-recycling of Pu and TRU is considered to be impossible. Since a fast neutron field is considered to be effective in TRU burning, development is proceeding in two ways, that is, one method for stopping a beam from an accelerator even in a system having a positive reactivity coefficient so as to ensure safety by an accelerator driven system (ADS) obtained by combining a sub-critical system and a large accelerator, and another method for using a fast breeder reactor (FBR). However, the development in these methods remains in a scenario in which the weight of TRU is partially reduced. The light water reactors described in JP 3428150 B and R. TAKEDA et al., “General Features of Resource-Renewable BWR (RBWR) and Scenario of Long-term Energy Supply” Proc. of International Conference on Evaluation of Emerging Nuclear Fuel Cycle Systems. GLOBAL '95 Versailles, France, September, 1995, P. 938, in which TRU is recycled, are thermally restricted by a maximum linear heat generating rate (MLHGR), which stipulates the temperature at the center of each fuel pellet, and a minimum critical power ratio (MCPR), which prevents a cladding tube of the fuel rod from being burnt out. The limitation by the MCPR has prevented the improvement of the core performance. During a transition to the recycling age, TRU elements with different ratios of isotopes are supplied from the core, which is loaded with uranium fuel, in the light water reactor. Accordingly, various reactivity coefficients, which are important restrictive conditions from the viewpoint of safety, are worsened and a margin for the restrictive conditions is lessened. This forces the recycling to stop and thereby the multi-recycling may not be realized. Recently, nuclear non-proliferation has attracted much attention on a worldwide scale, making it difficult to use TRU, which may be diverted to weapons of mass destruction, in consumer applications. Accordingly, a system that can recycle TRU with a high nuclear proliferation resistance, in which the ratio of Pu-239 is small, is demanded. If recycling is repeated to have TRU disappear, only fissionable odd-numbered nuclides disappear first and the ratio of the even-numbered nuclides, in which only fast energy neutrons undergo nuclear fission, increases. Accordingly, criticality cannot be maintained and thus nuclear fission chain reaction cannot be continued, or reactivity coefficients, which are provided as restrictive conditions for safety, become positive, so the TRU disappearance work has to be canceled in an incomplete state. These problems are examples to be solved to realize multi-recycling. light water reactor, a core of the light water reactor and fuel assembly that has a large nuclear proliferation resistance while satisfying restrictive conditions for safety, can increase a burnup, and can perform multi-recycling. The present invention for achieving the above object is characterized in that the ratio of Pu-239 in all transuranic nuclides included in a fuel assembly, which is loaded in a core, with a burnup of 0 is within the range from 3% to 45%, and that the fuel assembly having a channel box and a plurality of fuel rods disposed in the channel box, is such that the transverse cross section of fuel pellets in the fuel rods occupies 30% to 55% of the transverse cross section of a unit fuel rod lattice in the channel box. Another aspect of the present invention that can attain the above object provides a light water reactor characterized in that there are a core loaded with a plurality of fuel assemblies including transuranic nuclides, a coolant supplying apparatus for supplying a coolant to the core, and a coolant flow rate control apparatus for adjusting a flow rate of the coolant supplied to the core by controlling the coolant supplying apparatus, wherein the coolant flow rate control apparatus sets a coolant flow rate in an operation cycle to a set coolant flow rate, which is determined from a ratio of Pu-239 in transuranic nuclides included in a fuel assembly with a burnup of 0, which is loaded in the core before an operation starts in the operation cycle, so that the ratios of a plurality of isotopes of transuranic nuclides present in the core upon the completion of the operation in the operation cycle are substantially the same as the ratios of the plurality of isotopes in a state in which the operation in the operation cycle can be started. According to the present invention, a nuclear proliferation resistance can be increased while restrictive conditions for safety are satisfied, a burnup can be increased, and multi-recycling can be performed. A Na-cooled fast nuclear reactor with the aim of breeding TRU is designed so that neutron flux, in a fast neutron field having a high ν value, which indicates the number of neutrons generated in a single nuclear fission, is increased as much as possible in order to increase a breeding ratio. The design of the fast core focuses only on fissionable Pu that is important to maintain criticality, that is, Pu-239 and Pu-241. A light water breeder reactor also applies this design idea, and is reduced the amount of water used to moderate neutrons to a minimum amount necessary to cool fuel rods so as to increase the neutron energy in the field. Light water used as a coolant in a light water reactor classified as a thermal neutron reactor has two major features, as compared with heavy water, graphite, Na, Pb, and the like as coolants used in other type of reactors. First, many neutrons can be supplied to the resonance and thermal regions, which occupy a major part in a neutron capturing cross section used by the even-numbered nuclides to transfer to the odd-numbered nuclides because a hydrogen atom in light water used to moderate neutrons has almost the same mass as the neutron and has a high slowing down power. Second, a fast neutron flux at 0.1 MeV or higher is higher than in other systems and thus many neutrons can be supplied even to a high energy region that contributes to fast nuclear fission of the even-numbered nuclides because a scattering cross section of the hydrogen atom is as large as about 20 barns in a range from thermal energy to about 10 keV, and the scatting cross section rapidly starts to decrease around 10 keV, and falls to 10 barns at 200 keV, to 2 barns or less at 4 MeV or higher, and to 1 barn at 10 MeV which is smaller than the entire cross section of Na. The inventors noted not only fissionable Pu but also all TRU nuclides with the above two features sufficiently taken into consideration, and newly found that because reactor cooling water, which is a feature of a boiling water reactor (BWR), which is one type of light water reactor, is separated in a channel box in each fuel assembly, fuel assemblies having different internal fuel assembly structures can be loaded in a single core. Another new finding of the inventors is that when fuel assemblies having different isotope ratios need to be loaded in a core, if the ratio of Pu-239 present in TRU is maintained at a fixed value or less, a light water reactor that can cause TRU to be increased, maintained at a fixed level, or immediately reduced with a sufficient thermal margin while maintaining a negative void coefficient can be provided; to maintain the ratio of Pu-239 at the fixed value or less, the fuel assembly is used while its isotope ratio is being changed to a desired value by changing water-to-fuel volume ratio of the fuel assembly to change the neutron energy spectrum, a function for changing the neutron energy spectrum is used to adjust the ratio of isotopes by core flow rate control, and recycling is performed under a condition that the TRU isotope ratio is substantially fixed between each of cycles. The present invention aims to expand functions of a recycling type of light water reactor and improve its performance. In a case where the performance of a breeder reactor may need to be improved in the light water reactor described in JP 3428150 B, and in a case where TRU that is considered to be discarded as a long-lived radioactive waste when the TRU becomes unnecessary may be used as a nuclear fuel and all TRU elements other than TRU elements for one core may be finally undergo nuclear fission, such present invention was devised to increase the burnup of a fuel assembly including TRU and enable TRU multi-recycling by the inventors. An overview of a parfait-type core will be now described. The parfait-type core has fuel assemblies, which are new fuel assemblies with a burnup of 0, including a lower blanket zone, a lower fissile zone, an internal blanket zone, an upper fissile zone, and an upper blanket zone disposed in that order from bottom to top. Therefore, in a parfait-type core as well, a lower blanket zone, a lower fissile zone, an internal blanket zone, an upper fissile zone, and an upper blanket zone are formed from bottom to top. The lower fissile zone and upper fissile zone include TRU oxide fuel (or mixed oxide fuel of a TRU oxide and uranium oxide). A core that lacks the internal blanket zone between the upper blanket zone and the lower blanket zone and includes only a single fissile zone is referred to as a one fissile zone core. The fissile zone in the one fissile zone core also includes TRU oxide fuel (or mixed oxide fuel of a TRU oxide and uranium oxide). The present invention is intended for the above recycling type of light water reactor and the core of the light water reactor. Study results obtained by the inventors will be described below, in which a BWR core with an electric power of 1350 MW is used as an example; 720 fuel assemblies, each of which includes 271 fuel rods, are loaded in the core, and the breeding ratio is 1.01. Suppose that this BWR core has conventional fuel assemblies in which a burnup of a core zone including the upper and lower fissile zones and the internal blanket zone and excluding the upper and lower blanket zones described in JP 3428150 B and R. TAKEDA et al., “General Features of Resource-Renewable BWR (RBWR) and Scenario of Long-term Energy Supply” Proc. of International Conference on Evaluation of Emerging Nuclear Fuel Cycle Systems. GLOBAL '95 Versailles, France, September, 1995, P. 938, is 45 GWd/t. If the burnup of these conventional fuel assemblies is further increased without alternation, a problem arises in the BWR core. This problem is caused due to a void coefficient insufficient to maintain criticality, a reduced Pu isotope ratio, a lowered breeding ratio, a change of the void coefficient, which is a safety index, to a positive value, and the like. TRU recycling then has to be stopped in midstream. That is, multi-recycling becomes impossible. To continue TRU recycling while a BWR having the above BWR core is safely operated, the void coefficient must be maintained within a predetermined range. As a result of the study by the inventors, the inventors found that when a core flow rate, which is a parameter specific to the BWR, is set to a predetermined value to adjust the void fraction of the core and thereby to adjust the neutron energy spectrum, the burnup of the fuel assembly can be increased and the TRU multi-recycling can be achieved. According to the finding by the inventors, when the core flow rate is set, as found by the inventors, the ratios of a plurality of TRU isotopes present in the BWR core upon the completion of a BWR operation in an operation cycle can be made substantially the same as the ratios of the plurality of TRU isotopes present in the BWR core in a state in which the BWR is ready for operation in that operation cycle, for example, in a state immediately before an operation starts in that operation cycle. The void coefficient can also be maintained within a predetermined range (substantially fixed) in that operation cycle. Immediately before the above operation starts, the BWR core includes new fuel assemblies (fuel assemblies having a burnup of 0) and fuel assemblies that have been present in the BWR core for at least one operation cycle. When a certain fuel assembly loaded in the BWR core is noted, the fuel assembly undergoes an operation in, for example, four operation cycles in the BWR core until the fuel assembly is taken out of the BWR core as a spent fuel. When the core flow rate is adjusted, as found by the inventors, the ratios of a plurality of TRU isotopes included in the fuel assembly when the fuel assembly is taken out of the BWR core as a spent fuel can be made substantially the same as the ratios of the plurality of TRU isotopes included in a new fuel assembly to be loaded in the BWR core. The new fuel assembly is yet to undergo an operation in the nuclear reactor and thus its burnup is 0. For convenience, it is called TRU isotope ratio conservation that, as described above, the ratios of a plurality of TRU isotopes present in the BWR core upon the completion of a BWR operation in an operation cycle can be made substantially the same as the ratios of the plurality of TRU isotopes present in the BWR core in a state in which the BWR is ready for operation in that operation cycle. The ratios of a plurality of TRU isotopes included in the fuel assembly when the fuel assembly is taken out of the BWR core as a spent fuel can also be made substantially the same as the ratios of the plurality of TRU isotopes included in a new fuel assembly to be loaded in the BWR core. This is another aspect of the TRU isotope ratio conservation. The reactor core flow adjustment as described above in the above BWR is performed so that a relative core flow rate determined according to the characteristics shown in FIG. 2 is obtained. FIG. 2 shows the relation between the relative core flow rate and the ratio of Pu-239 in TRU included in a new fuel assembly to be loaded in the core. A core flow rate at which the ratios of TRU isotopes having different ratios of Pu-239 in TRU included in a new fuel assembly can be maintained is determined from FIG. 2. The inventors investigated the composition of the TRU isotopes included in a spent fuel assembly in a light water reactor, and newly found that if a core flow rate is set with the ratio of Pu-239 in TRU taken into consideration, the TRU isotope ratio conservation can be achieved. The above core flow rate is set so that the void coefficient in each operation cycle keeps within a predetermined range. The setting of the core flow rate is performed on the basis of a relative core flow rate (referred to as a set core flow rate), which is determined from FIG. 2 according to the ratio of Pu-239 in TRU included in the new fuel assembly to be loaded in the core. In each operation cycle, when the reactor power reaches at least its rated power, at least the core flow rate has been adjusted and has been set to the above set core flow rate. The core flow rate is maintained at the set core flow rate until the operation cycle is completed. Accordingly, control rods are used in reactor power control. Another solution to an insufficient reactivity may be to increase the ratio of Pu-239 in TRU in each fuel rod. In the other solution, the ratios of the TRU isotopes in the core upon the completion of an operation cycle cannot be made substantially the same as the ratios at the start of the operation cycle. To make these ratios substantially the same, the core flow rate must be reduced from the set core flow rate, preventing the MCPR standard, which is a thermal restrictive condition, from being satisfied. As a result of a study by the inventors, as shown in FIG. 2, when the ratio of Pu-239 in all TRU elements included in a new fuel assembly was lowered to 45% or less, all restrictive conditions were satisfied, core performance including a high burnup and the like of the fuel assembly could be improved while the 1.01 breeding ratio was maintained, and TRU multi-recycling could be achieved. To further increase the burnup of the fuel assembly and efficiently use TRU by achieving TRU multi-recycling, the ratio of Pu-239 in all TRU elements included in the new fuel assembly is preferably set within a range from 40% to 45%. When the ratio is included in the range, the amount of TRU in the BWR core can be fixed until the operation cycle ends, without being reduced from the amount at the start of the operation cycle. In some cases, the amount of TRU can be increased upon the completion of the operation cycle. In the description that follows, another BWR core is used as an example. In this BWR core, its electric power is 1350 MW, and 720 fuel assemblies, each of which includes 331 fuel rods, are loaded. The BWR core has a function for making TRU disappear. When a TRU cycle is repeated to have TRU disappear, only odd-numbered nuclides usually burn first and subcriticality is brought in midstream, leaving non-burnt TRU. This problem can be solved when the ratios of the TRU isotopes are substantially fixed by the above TRU isotope ratio conservation found by the inventors and TRU is burnt. Accordingly, the burnup of the fuel assembly can be further increased and TRU multi-recycling can be achieved. However, to reduce TRU, the ratio of Pu-239 to all TRU elements in TRU must be lowered and the amount of Pu-239 supplied from U-238 for each recycle must be reduced. FIG. 3 indicates a relation between the ratio of Pu-239 in TRU included in a new fuel assembly to be loaded and atomic ratio of hydrogen to heavy metal in a parfait-type core and a one fissile zone core. This relation indicated in FIG. 3 was determined by the inventors, assuming that the TRU isotope ratio conservation can be achieved in each core. Characteristic 41 is concerned with the parfait-type core, and characteristic 42 is concerned with the one fissile zone core. As seen from FIG. 3, when the diameter of the fuel rod in the new fuel assembly is reduced, the ratio of water to TRU is increased (atomic ratio of hydrogen to heavy metal is increased), so the number of each of neutrons in the resonance and thermal region increases. This increase in neutrons promotes the capturing of neutrons of the even-numbered nuclides, increasing the efficiency of nuclear conversion from the even-numbered nuclides to the odd-numbered nuclides and thereby increasing the TRU fission efficiency. Accordingly, TRU can be reduced faster. The TRU fission efficiency is defined as a net amount by which TRU is reduced with respect to a total amount of nuclear fission during the lifetime of the fuel assembly. FIG. 4 indicates a relation between the fission efficiency and the ratio of Pu-239 in TRU included in a new fuel assembly to be loaded in the parfait-type core and a one fissile zone core and a relation between the void coefficient and the ratio of Pu-239 in TRU. The relation between the ratio of Pu-239 in TRU and the fission efficiency is represented by characteristic 10 for the parfait-type core and characteristic 43 for the one fissile zone core. The relation between the ratio of Pu-239 in TRU and the void coefficient is represented by characteristic 11 for the parfait-type core with a core discharge burnup of 47 GWd/t, characteristic 12 for the parfait-type core with a core discharge burnup of 65 GWd/t, and characteristic 44 for the one fissile zone core with a core discharge burnup of 75 GWd/t. As shown in FIG. 4, as long as the ratios of the TRU isotopes are substantially fixed during burn-up, as the ratio of Pu-239 is reduced, the fast energy component having a positive void reactivity component is reduced relative to a core with a breeding ratio of 1. Therefore, the void coefficient in a system in which the ratio of Pu-239 is reduced is maintained negative. The amount of water in the core is larger than the amount of water in a core with a breeding ratio of 1, so there is no problem with MCPR. When the ratio of Pu-239 in all TRU elements falls to less than 8% in the parfait-type core, the ratio of the even-numbered nuclides, which can undergo nuclear fission only in the fast energy region, is increased. Thus, since, to maintain criticality, the height of the core must be increased and thereby the void coefficient becomes positive, the parfait-type core can no longer satisfy the safety standard for light water rectors. In the one fissile zone core as well, which is lower in height more negative in void coefficient than the parfait-type core, when the ratio of Pu-239 in all TRU elements falls to less than 3%, the void coefficient becomes positive, in which case, the one fissile zone core can also no longer satisfy the safety standard for light water rectors. To satisfy the safety standard for light water rectors, the ratio of Pu-239 in all TRU elements must be 8% or more for the parfait-type core and 3% or more for the one fissile zone core. To reduce TRU in the core, the ratio of Pu-239 in all TRU elements must be 8% or more but less than 40% for the parfait-type core and 3% or more but less than 40% for the one fissile zone core. In the one fissile zone core, however, when the ratio of Pu-239 in all TRU elements is 8% or more, even if the TRU fission efficiency is slightly increased, the net amount by which TRU is reduced is lowered because the reactor power of the one fissile zone core is small. When the ratio is 3% or more but 8% or less, the TRU fission efficiency can be further increased and the net amount by which TRU is reduced can also be increased. When the ratio of Pu-239 in all TRU elements falls to 15% or less within the range from 3% or more to less than 40%, the TRU fission efficiency is greatly increased, so TRU can be abruptly reduced. For both cores, when the ratio by which the transverse cross section of fuel pellet occupies the transverse cross section of a unit fuel rod lattice in a channel box exceeds 55%, the gap between fuel rods is less than 1 mm, making fuel assemblies extremely difficult to assemble. Accordingly, the ratio by which the transverse cross section of fuel pellet to the transverse cross section of a unit fuel rod lattice needs to be 55% or less. When the cross section ratio falls to less than 30%, the fuel rod becomes too thin, reducing the amount of the nuclear fuel material on the transverse cross section is lessened. To compensate for the reduction, the fuel rod must be elongated, making the void coefficient positive. Accordingly, the cross section ratio must be 30% or more. It is also possible to load a core such as a parfait-type core with a new fuel assembly produced by the use of a nuclear fuel material from which minor actinide has been removed by TRU reprocessing. In this type of core as well, when the core flow rate is adjusted so that it becomes the set core flow rate determined based on the ratio of Pu-239 in all Pu elements included in a new fuel assembly to be loaded in the core, the TRU isotope ratio conservation described above can be achieved. To increase the burnup of a fuel assembly and achieve TRU multi-recycling when a nuclear fuel material from which minor actinide has been removed is used, the ratio of Pu-239 in all Pu elements included in the new fuel assembly must be 3% or more but 50% or less and the ratio of Pu-240 in all Pu elements included in the new fuel assembly must be 35% or more but 45% or less. When the ratio of Pu-239 exceeds 50%, the heat removal capacity is reduced, so the reactor power must be reduced to a value lower than its rated power. This prevents the electric power generation capacity of the BWR from being fully used. From these reasons, the ratio of Pu-239 must be 50% or less. When the ratio of Pu-239 in all Pu elements fall to less than 3%, the void coefficient becomes positive, so the ratio of Pu-239 must be 3% or more. When the ratio of Pu-240 in all Pu elements exceeds 45%, the void coefficient becomes positive, so the ratio of Pu-240 must be 45% or less. When the ratio of Pu-240 in all Pu elements falls to less than 35%, the heat removal capacity is lowered, the electric power generation capacity of the BWR cannot be fully used. Accordingly, the ratio of Pu-240 must be 35% or more. Embodiments of the present invention will be described below in detail with reference to the drawings. A light water reactor according to a first embodiment, which is a preferred embodiment of the present invention, will be described below in detail with reference to FIGS. 1 and 5 to 11 as well as Table 1. The light water reactor of the present embodiment has a core intended to generate 1350-MW electric power. TABLE 1NuclideComposition (wt %)Np-2370.5Pu-2383.0Pu-23944.0Pu-24036.1Pu-2415.0Pu-2424.9Am-2413.7Am-242M0.1Am-2431.3Cm-2441.0Cm-2450.3Cm-2460.1 However, the power scale is not limited to this value. It is possible to implement a light water reactor having another power scale to which the present embodiment can be applied by changing the number of fuel assemblies loaded in the core. The light water reactor in the present embodiment, which is a BWR intended to generate 1350-MW electric power, will be outlined with reference to FIG. 5. The BWR 19 disposes a core 20, a steam separator 21, and a steam dryer 22 in a reactor pressure vessel 27. The core 20 is a parfait-type core, which is surrounded by a core shroud 25 in the reactor pressure vessel 27. The steam separator 21 is disposed above the core 20, and the steam dryer 22 is disposed above the steam separator 21. A plurality of internal pumps 26 are provided at the bottom of the reactor pressure vessel 27. Impellers of each internal pump 26 are disposed in a downcorner formed between the reactor pressure vessel 27 and the core shroud 25. A main steam pipe 23 and feed water pipe 24 are connected to the reactor pressure vessel 27. The core 20 includes 720 fuel assemblies 1 as shown in FIG. 6. A Y-shaped control rod 2 is provided for each three fuel assemblies 1. A total of 223 control rods 2 are insertably disposed in the core 20. Each control rod 2 is linked individually to control rod drive mechanisms 29 disposed at the bottom of the reactor pressure vessel 27. The control rod drive mechanism 29, which is driven by a motor, can fine adjust the motion of the control rod 2 in its axial direction. The control rod drive mechanism 29 performs operation for withdrawing the control rod 2 from the core 20 and inserting the control rod 2 into the core 20. A plurality of local power range monitors (LPRMs) 32, each of which is a neutron detector, are disposed in the core 20. These LPRMs 32 are connected to an average power range monitor (APRM) 31, which is connected to a control rod drive control apparatus 30. FIG. 7 is a transverse cross sectional view of a fuel assembly lattice. The fuel assembly 1 has 271 fuel rods 3 with a diameter of 10.1 mm in a regular triangle lattice in a channel box 4 being a hexagonal tube. The transverse cross section of the fuel assembly 1 is hexagonal, and the gap between fuel rods 3 is 1.3 mm. A plurality of fuel pellets (not shown) made of a nuclear fuel substance are disposed in a cladding tube (not shown) of the fuel rod 3 so that they are arranged in the axial direction. The fuel rod row in the outermost peripheral layer includes nine fuel rods 3. The transverse cross section of the fuel pellets occupies 54% of the transverse cross section of a unit fuel rod lattice in the channel box 4. The Y-shaped control rod 2 has three blades, which externally extends from a tie rod disposed at the center. These blades, each of which has a plurality of neutron absorbing rods loaded with B4C, are disposed around the tie rod at intervals of 120 degrees. The control rod 2 has a follower made of carbon, which has a smaller slowing down power than light water, in an insertion end, which is first inserted into the core 20. While the BWR 19 is in operation, the coolant in the downcorner is pressurized by the rotation of the internal pump (coolant supplying apparatus) 26 and then supplied into the core 20. The coolant supplied into the core 20 is introduced to the fuel assemblies 1, and heated by heat generated by nuclear fission of the nuclear fission material, causing part of the coolant to turn into steam. The coolant in a gas-liquid two-phase flow state is introduced from the core 20 to the steam separator 21, where the steam is separated. Moisture including in the separated steam is further removed by the steam dryer 22. The steam from which moisture has been removed is supplied through the main steam pipe 23 to a turbine (not shown), rotating the turbine. A power generator (not shown) linked to the turbine rotates and generates electric power. The steam is exhausted from the turbine and then condensed in a condenser (not shown), turning into condensed water. The condensed water (feed water) is introduced through the feed water pipe 24 to the reactor pressure vessel 27. The liquid coolant separated by the steam dryer 22 is mixed with the feed water and the mixture is pressurized again by the internal pump 26. The arrangement of the fuel assemblies 1 in the core 20 in a state of an equilibrium core state will be described with reference to FIG. 8. Fuel assemblies 1D in the operation cycle of which is the fourth cycle and staying in the core for the longest time in the in-core fuel dwelling time, are disposed in the outermost peripheral region of the core having a low neutron impedance. A core outer region internally adjacent to the outermost peripheral region includes fuel assemblies 1A, which have the highest neutron infinite multiplication factor and stay in the core in a first cycle in the in-core fuel dwelling time, flattening the power distribution in radial directions of the core. In a core inner region, fuel assemblies 1B, 1C, and 1D, the operation cycles of which are respectively second cycle, third cycle, and fourth cycle in the in-core fuel dwelling time, are dispersed, as shown in FIG. 8. This dispersion flattens the power distribution in the core inner region. Each of the fuel assemblies 1A, 1B, 1C, and 1D is the fuel assembly 1 shown in FIG. 7 and FIGS. 10 and 11 given later. Lower tie plates (not shown) of the fuel assemblies are supported individually by a plurality of fuel supports (not shown) attached to a core plate disposed at the bottom of the core 20. A coolant passage through which the coolant is fed to the fuel assembly is formed in the fuel support. An orifice (not shown) attached in the fuel support is disposed at the inlet of the coolant passage. The core 20 forms two areas in its radial directions, the outer reactor core region 6 and inner reactor core region 7 (see FIG. 9). The orifice disposed in the outermost peripheral region 6, where the power of the fuel assembly 1 is small, has a smaller bore diameter than the orifice disposed in the internal area 7. The fuel assembly 1 has five zones, which are an upper blanket zone 5, an upper fissile zone 6, an internal blanket zone 7, a lower fissile zone 8, and a lower blanket zone 9, in succession from an upper end of an active fuel length to a lower end of the active fuel length in that order, as shown in FIG. 10. The upper blanket zone 5 is 120 mm high, the upper fissile zone 6 is 227 mm high, the internal blanket zone 7 is 450 mm high, the lower fissile zone 8 is 225 mm high, and the lower blanket zone 9 is 180 mm high. When the fuel assembly 1 is a new fuel assembly with a burnup of 0, each fuel rod 3 of the fuel assembly 1 is loaded with depleted uranium in the three blanket zones and with mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8, the mixed oxide fuel including 172 parts by weight of depleted uranium per 100 parts by weight of TRU. The enrichment of fissionable Pu in the mixed oxide fuel is 18 wt %. The blanket zones are not loaded with the mixed oxide fuel. In the blanket zones, natural uranium or depleted uranium recovered from spent fuel assemblies may be used instead of the depleted uranium. The fuel assembly 1 includes five types of fuel rods 3 shown in FIG. 11. These fuel rods 3 are fuel rods 3A to 3E. The fuel rods 3A to 3E are disposed in the fuel assembly 1, as shown in FIG. 11. In a state the new fuel assembly, the enrichment of fissionable Pu in mixed oxide fuel loaded in the upper fissile zone 6 and lower fissile zone 8 of each of the fuel rods 3A to 3E is 10.7 wt % in the fuel rod 3A, 13.5 wt % in the fuel rod 3B, 16.8 wt % in the fuel rod 3C, 18.2 wt % in the fuel rod 3D, and 19.5 wt % in the fuel rod 3E. The blanket zones in each fuel rod 3 do not include TRU, but the mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8 in the each fuel rod 3 includes TRU with the composition shown in Table 1. When the fuel assembly 1 is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 44 wt %. The composition in Table 1 is also a TRU composition of a fuel assembly 1 that is taken out of the core 20, stays in a fuel storage pool and fuel reprocessing facility for two years and in a fuel manufacturing facility for one year, totaling three years, and then loaded again in the core as new fuel. After the operation of the BWR 19 is stopped in one operation cycle, one-fourth, for example, of the fuel assemblies 1 disposed in the core 20, which is an equilibrium core, is replaced with fuel assemblies (new fuel assemblies) 1 having a burnup of 0. After the new fuel assemblies 1 have been loaded in the core 20, the operation of the BWR 19 in the next operation cycle starts. In the next operation cycle, the new fuel assemblies 1 are used as fuel assemblies in the first operation cycle. When the internal pumps 26 are driven, the coolant is supplied to the core 20, as described above. The flow rate of the coolant supplied to the core 20 (core flow rate) is set to a minimum flow rate. The rotational speed of the internal pump 26 is controlled by a core flow rate control apparatus (coolant flow rate control apparatus) 33. The control rod drive mechanism 29 is driven according to a control signal from the control rod driving control apparatus 30, and the control rod 2 is withdrawn from the core 20. After the BWR 19 reaches the critical state and heatup mode of BWR is completed, another control rod 2 is further withdrawn, increasing the reactor power. The increasing of the reactor power caused by withdrawing control rods 2 is tentatively stopped. A storage apparatus (not shown) in the core flow rate control apparatus 33 stores the characteristics in FIG. 2. An operator enters, from an input apparatus (not shown), information about the ratio of Pu-239 in all TRU elements included in the new fuel assembly 1 loaded in the core 20 at the time of the above fuel replacement (this information is referred to as ratio information), that is, 44 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined based on the entered ratio information and the characteristics in FIG. 2. From the characteristic in FIG. 2, it is found that the set core flow rate at 44 wt %, which is the ratio information, is a relative core flow rate 1.00. The core flow rate control apparatus 33 increases the rotational speed of the internal pump 26 until the core flow rate reaches the set core flow rate. When the core flow rate reaches the set core flow rate, the core flow rate control apparatus 33 stops the rotational speed of the internal pump 26 from increasing to stop the core flow rate from increasing. After that, the core flow rate is maintained by the core flow rate control apparatus 33 at the set core flow rate until the operation of the BWR 19 is stopped in the operation cycle. As the core flow rate increases up to the set core flow rate, the reactor power also increases. After the increasing of the core flow rate has been stopped, the withdrawal of the control rod 2 is resumed and the reactor power is increased up to 100%, which is the rated power. Upon the completion of the operation cycle, the control rod 2 is inserted into the core 20 and the operation of the BWR 19 is stopped. FIG. 12 illustrates an axial relative power distribution and void fraction distribution of the core 20 when the BWR 19 is operating at a reactor power of 100%. The average void fraction of the core is 67%, and the steam weight percent at the outlet of the core is 41 wt %. When the BWR 19 is operating at the rated power, each LPRM 32 outputs a detection signal according to the detection of a neutron generated in nuclear fission. The APRM 31 inputs and averages these detection signals to obtain reactor power. This reactor power obtained by APRM 31 is input to the control rod drive control apparatus 30. The control rod drive control apparatus 30 operates the control rod drive mechanism 29 to have it withdraw the control rod 2 out of the core 20 so that the input reactor power becomes the rated power. The reactor power is maintained at the rated power during the operation cycle, in this way. In the present embodiment in which the ratio of Pu-239 in all TRU elements included in the new fuel assembly 1 is 44 wt % and the set core flow rate, that is, the relative core flow rate, is 1.00, the reason why the TRU isotope ratio conservation can be achieved will be specifically described below by using the generation and decay chain of actinide nuclides shown in FIG. 1. The absolute amount of each of a plurality of TRU isotopes, shown in Table 1, included in the new fuel assembly 1 decreases in a in-core fuel dwelling time (four operation cycles) during which the new fuel assembly 1 stays in the core 20 until it is taken out of the core 20 as a spent fuel assembly. Since nuclear fission occurs as indicated by the generation and decay chain of the actinide nuclide, when the fuel assembly 1 is taken out of the core 20 as a spent fuel assembly and loaded again in the core 20 as a new fuel assembly, however, the ratios of the TRU isotopes in the fuel assembly 1 are substantially the same as their ratios in the above new fuel assembly 1. In the description that follows, Pu-239, Pu-240, Pu-241, and Am-243 shown in Table 1, which are typical TRU isotopes, are used as examples. When the new fuel assembly 1 is taken out from the core 20 as a spent fuel assembly, the amount of Pu-239 included in the upper fissile zone 6 and lower fissile zone 8 of the new fuel assembly 1 has been reduced. During the four operation cycles, however, U-238 present in each blanket zone is converted into Pu-239 due to the neutron capturing reaction and subsequent β decay, generating new Pu-239. The amount of Pu-240 included in the upper fissile zone 6 and lower fissile zone 8 has been also reduced when the fuel assembly 1 is taken out from the core 20, but new Pu-240 is generated from U-238 in each blanket zone. The ratio of Am-243 newly generated from other TRU isotopes present in the upper fissile zone 6 and lower fissile zone 8 is the same as the ratio of Am-243 decreased due to neutron capturing. The amount of Pu-241 increased in each blanket zone is greater than the amount of Pu-241 reduced in the upper fissile zone 6 and lower fissile zone 8 due to nuclear fission, so the amount of Pu-241 in the spent fuel assembly is about 20% more than the amount of Pu-241 in the new fuel assembly. Since the half-life of Pu-241 is 14.4 years, which is relatively short, however, its amount is reduced due to decay while the fuel assembly is taken out of the core 20 as a spent fuel assembly and loaded again in the core as the new fuel assembly. Accordingly, when the fuel assembly is taken as a spent fuel assembly and loaded again in the core as a new fuel assembly, the ratios of the TRU isotopes included in the fuel assembly are substantially the same as their ratios in new fuel assembly 1. The ratios of a plurality of TRU isotopes present in the BWR core upon the completion of the BWR operation in an operation cycle are also substantially the same as the ratios of the plurality of TRU isotopes present in the BWR core in a state in which the BWR is ready for an operation in that operation cycle. According to the present embodiment, the core flow rate control apparatus 33 adjusts the core flow rate so that it reaches the set core flow rate determined based on the ratio of Pu-239 in TRU included in the new fuel assembly 1, which is 44 wt %. As a result of this adjustment, the neutron energy spectrum is also adjusted. The TRU isotope ratio conservation can be achieved by the decrease of the amount of a relevant TRU isotope included in the upper fissile zone 6 and lower fissile zone 8 and the generation of the relevant isotope in each blanket zone, and further, for a TRU isotope that is hardly generated in each blanket zone, by disappearance of the amount of this isotope lost and the generation of this isotope from other TRU isotopes included in the upper fissile zone 6 and lower fissile zone 8, as described above. The TRU isotope ratio conservation can be achieved in this way. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, a nuclear proliferation resistance can be increased while restrictive conditions for safety are satisfied. In addition, since the ratio of Pu-239 in TRU is 44 wt %, the fuel assembly 1 taken out of the core 20 can have much more TRU than the new fuel assembly 1. Specifically, according to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using the reactor pressure vessel 27 having almost the same size as the ABWR can achieve a discharge burnup of 45 GWd/t in the core zone including the upper and lower fissile zones and the internal blanket zone excluding the upper and lower blanket zones, a discharge burnup of 54 GWd/t in the core zone, which is larger than in the breeder reactor in the light water reactor described in JP 3428150 B, and a discharge burnup of 47 GWd/t in the core 20 including the upper and lower blanket zones. In the present embodiment, the void coefficient is −2×10−6 Δk/k/% void, MCPR is 1.3, and when the ratios of the TRU isotopes are substantially fixed as described above, a breeding ratio of 1.01 can be attained. In the present embodiment, when the reactor power is lowered from a set reactor power (the rated power, for example), the reactor power is controlled by operating (withdrawing) the control rod 2 by the control rod drive mechanism 29 which is controlled by the control rod drive control apparatus 30, rather than the core flow rate control apparatus 33. Accordingly, the present embodiment can achieve both the TRU isotope ratio conservation and reactor power control. A light water reactor according to a second embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 13 and 14 as well as Table 2. The light water reactor of the present embodiment has a structure in which the core 20 and the fuel assembly 1 in the first embodiment are respectively replaced with a core 20A shown in FIG. 13 and a fuel assembly 1H shown in FIG. 14. Other structures of TABLE 2NuclideComposition (wt %)Pu-2381.0Pu-23948.6Pu-24039.7Pu-2416.0Pu-2424.4Am-2410.3the core 20A are the same as in the first embodiment. In the present embodiment, only structures different from the first embodiment will be described, and the explanation of the same structures as in the first embodiment will be omitted. The core 20A is a parfait-type core. The fuel assembly 1H disposed in the core 20A has the same structure as the fuel assembly 1 used in the first embodiment, except the dimensions shown in FIG. 14 and the TRU composition indicated in Table 2. In the fuel assembly 1H as well, the transverse cross section of the fuel pellet occupies 54% of the transverse cross section of a unit fuel rod lattice, as in the first embodiment. In state of an equilibrium core, the core 20A includes fuel assemblies 1A to 1E as shown in FIG. 13. The fuel assemblies 1E, the operation cycle of which is the fifth cycle, staying in the core for the longest time of the in-core fuel dwelling time, are disposed in an outermost peripheral region of the core. A core outer region internally adjacent to the outermost peripheral region includes the fuel assemblies 1A, the operation cycle of which is the first cycle. In a core inner region, the fuel assemblies 1B, 1C, and 1D, the operation cycles of which are respectively the second cycle, third cycle, and fourth cycle, are dispersed. Three fuel assemblies 1D are included in the outermost peripheral region. This arrangement of the fuel assemblies enables the power distribution in the radial directions of the core 20A to be flattened. Each of the fuel assemblies 1A to 1E used in the present embodiment is the fuel assembly 1H. A high burnup can be achieved by using mixed oxide fuel of depleted uranium, and plutonium and Am-241 from which minor actinide has been removed by TRU reprocessing. Am-241 included in new fuel is generated due to decay of Pu-241 in the plutonium from which minor actinide has been removed by TRU reprocessing before the plutonium is loaded in the core 20A as the new fuel. As with the fuel assembly 1, the fuel assembly 1H has five zones within its active fuel length. As shown in FIG. 14, the upper blanket zone 5 is 200 mm high, the upper fissile zone 6 is 211 mm high, the internal blanket zone 7 is 310 mm high, the lower fissile zone 8 is 207 mm high, and the lower blanket zone 9 is 220 mm high. When the fuel assembly 1H is a new fuel assembly with a burnup of 0, each fuel rod 3 of the fuel assembly 1H is loaded with depleted uranium in the three blanket zones and with mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8, the mixed oxide fuel including 198 parts by weight of depleted uranium per 100 parts by weight of plutonium from which minor actinide has been removed by TRU reprocessing and Am-241 generated due to decay of Pu-241. The enrichment of fissionable Pu in the mixed oxide fuel is 18 wt %. The blanket zones are not loaded with the mixed oxide fuel. The fuel assembly 1H also includes fuel rods 3A to 3E, as in the first embodiment. Each of the fuel rods 3A to 3E is the fuel rod 3. The mixed oxide fuel present in the upper fissile zone 6 and lower fissile zone 8 has the composition indicated in Table 2. When the fuel assembly 1H is a new fuel assembly, the ratio of Pu-239 in all Pu elements and Am-241 is 48.6 wt % and the ratio of Pu-240 in all Pu elements and Am-241 is 39.7 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined based on ratio information (indicating that a ratio of Pu-239 in all Pu elements and Am-241 is 48.6 wt %) entered from the input apparatus and the same characteristics as shown in FIG. 2. This characteristics are obtained, in a core that uses Pu and Am-241 from which minor actinide has been removed by TRU reprocessing as a new fuel assembly, by determining a core flow rate at which the ratios of all Pu elements and Am-241 isotopes can be maintained in each of a plurality of cores having different ratios of Pu-239 in all Pu elements and Am-241 isotopes in the new fuel assembly. The core flow rate control apparatus 33 increases the rotational speed of the internal pump 26 until the core flow rate reaches the set core flow rate, as in the first embodiment. When the core flow rate reaches the core flow rate setting, the core flow rate control apparatus 33 stops the increase of the rotational speed of the internal pump 26. After that, the core flow rate is maintained at the set core flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in all Pu elements in the new fuel assembly 1H loaded in the core 20A, which is 48.6 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment as well, the fuel assembly 1H taken out of the core 20A can have much more TRU than the new fuel assembly 1H. Specifically, according to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using the reactor pressure vessel 27 having almost the same size as the ABWR can achieve a discharge burnup of 51 GWd/t for the core 20A, which is higher than the burnup in the first embodiment, and 68 GWd/t for the core zone excluding the upper and lower blanket zones. In the present embodiment, the void coefficient is −3×10−5 Δk/k/% void, MCPR is 1.3, and when the ratios of the Pu and Am-241 isotopes are substantially fixed as described in the first embodiment, a breeding ratio of 1.01 can be attained. A light water reactor according to a third embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 15 to 17 as well as Table 3. The light water reactor of the present embodiment has a structure in which the core 20 and the fuel assembly 1 in the first embodiment are respectively replaced with a core 20B shown in FIG. 16 and a fuel assembly 1J shown in FIGS. 15 and 17. Other TABLE 3NuclideComposition (wt %)Np-2370.6Pu-2383.3Pu-23940.1Pu-24037.1Pu-2415.4Pu-2426.0Am-2413.7Am-242M0.2Am-2431.6Cm-2441.4Cm-2450.5Cm-2460.2structures of the core 20B are the same as in the first embodiment. In the present embodiment, only structures different from the first embodiment will be described, and the explanation of the same structures as in the first embodiment will be omitted. The core 20B is a parfait-type core. The fuel assembly 1J disposed in the core 20B will be described with reference to FIG. 15. The fuel assembly 1J, the transverse cross section of which is hexagonal, has 331 fuel rods 3J with a diameter of 9.2 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3J is 1.1 mm. The transverse cross section of the fuel pellet occupies 53% of the transverse cross section of a unit fuel rod lattice. In state of an equilibrium core, the core 20B includes fuel assemblies 1A to 1D as shown in FIG. 16. As with the core 20, the fuel assemblies 1D, the operation cycle of which is the fourth cycle, staying in the core for the longest time of the in-core fuel dwelling time, are disposed in an outermost peripheral region of the core. A core outer region internally adjacent to the outermost peripheral region includes the fuel assemblies 1A, the operation cycle of which the first cycle. In an inner core zone, the fuel assemblies 1B, 1C, and 1D, the operation cycles of which are respectively the second cycle, third cycle, and fourth cycle, are dispersed. There is an intermediate region, in which a plurality of fuel assemblies 1D are disposed in a loop, between the core inner region and the core outer region. In the core 20B, the power distribution in its radial directions is flattened. Each of the fuel assemblies 1A to 1E shown in FIG. 16 is the fuel assembly 1J. As with the fuel assembly 1, the fuel assembly 1J has five zones within its active fuel length (see FIG. 17). The upper blanket zone 5 is 90 mm high, the upper fissile zone 6 is 241 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 241 mm high, and the lower blanket zone 9 is 90 mm high. When the fuel assembly 1J is a new fuel assembly with a burnup of 0, each fuel rod 3J of the fuel assembly 1J is loaded with depleted uranium in the three blanket zones and with mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8, the mixed oxide fuel including 153 parts by weight of depleted uranium per 100 parts by weight of TRU. The enrichment of fissionable Pu in the mixed oxide fuel is 18 wt %. The blanket zones are not loaded with the mixed oxide fuel. The fuel assembly 1J also includes fuel rods 3A to 3E, as in the first embodiment. Each of the fuel rods 3A to 3E is the fuel rod 3J. The mixed oxide fuel present in the upper fissile zone 6 and lower fissile zone 8 includes TRU having the composition indicated in Table 3. When the fuel assembly 1J is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 40.1 wt %. The blanket zones are not loaded with the mixed oxide fuel. The core flow rate control apparatus 33 sets a set core flow rate, which is determined based on ratio information (40.1 wt %) entered from the input apparatus and the same characteristics shown in FIG. 2. The core flow rate control apparatus 33 increases the rotational speed of the internal pump 26 until the core flow rate reaches the set core flow rate, as in the first embodiment. When the core flow rate reaches the set core flow rate, the core flow rate control apparatus 33 stops the rotational speed of the internal pump 26 from increasing. After that, the core flow rate is maintained at the set core flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1J loaded in the core 20B, which is 40.1 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment as well, the fuel assembly 1J taken out of the core 20B can have much more TRU than the new fuel assembly 1J. Specifically, according to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can achieve a discharge burnup of 53 GWd/t for the core 20B and a void coefficient of −3×10−6 Δk/k/% void. In the present embodiment, MCPR is 1.3, and the TRU isotope ratio conservation and a breeding ratio of 1.01 can be achieved as described above. A light water reactor according to a fourth embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 18 to 20 as well as Table 4. The light water reactor in the present embodiment has a structure in which the core 20 and the fuel assembly 1 in the first embodiment are respectively replaced with a core 20C shown in FIG. 19 and a fuel assembly 1K shown in FIGS. 18 and 20. Other TABLE 4NuclideComposition (wt %)Np-2370.2Pu-2385.1Pu-23914.4Pu-24040.2Pu-2414.8Pu-24220.5Am-2414.7Am-242M0.2Am-2434.0Cm-2443.6Cm-2451.1Cm-2460.8Cm-2470.2Cm-2480.2structures of the core 20c are the same as in the first embodiment. In the present embodiment, only structures different from the first embodiment will be described, and the explanation of the same structures as in the first embodiment will be omitted. The core 20C is also a parfait-type core. The fuel assembly 1K (see FIG. 18) disposed in the core 20C has 331 fuel rods 3K with a diameter of 7.7 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3K is 2.6 mm. The fuel rod row in the outermost peripheral layer includes 10 fuel rods 3K. The transverse cross section of the fuel pellet occupies 36% of the transverse cross section of a unit fuel rod lattice. The core 20C includes fuel assemblies 1A to 1D that have experienced a different number of operation cycles, as shown in FIG. 19, in state of an equilibrium core. The fuel assemblies 1D, the operation cycle of which is the fourth cycle, are disposed in an outermost peripheral region. A core outer region includes the fuel assemblies 1A, the operation cycle of which is the first cycle. In a core inner region, the fuel assemblies 1B, 1C, and 1D, the operation cycles of which are respectively the second cycle, third cycle, and fourth cycle, are dispersed. There is an intermediate region, in which plurality of fuel assemblies 1B are disposed in a loop, between the core inner region and the core outer region. In this type of core 20C, the power distribution in its radial directions is more flattened. Each of the fuel assemblies 1A to 1E shown in FIG. 19 is the fuel assembly 1K. As with the fuel assembly 1, the fuel assembly 1K has five zones within its active fuel length (see FIG. 20). The upper blanket zone 5 is 30 mm high, the upper fissile zone 6 is 194 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 194 mm high, and the lower blanket zone 9 is 30 mm high. When the fuel assembly 1K is a new fuel assembly with a burnup of 0, each fuel rod 3K of the fuel assembly 1K is loaded with depleted uranium in the three blanket zones and with mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8, the mixed oxide fuel including 7 parts by weight of depleted uranium per 100 parts by weight of TRU. The enrichment of fissionable Pu in the mixed oxide fuel is 18 wt %. The blanket zones are not loaded with the mixed oxide fuel. The fuel assembly 1K also includes fuel rods 3A to 3E, each of which is the fuel rod 3K. The mixed oxide fuel present in the upper fissile zone 6 and lower fissile zone 8 includes TRU having the composition indicated in Table 4. When the fuel assembly 1K is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 14.4 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (14.4 wt %) and the characteristics shown in FIG. 2, as in the first embodiment. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. When the core flow rate reaches the set core flow rate, the core flow rate control apparatus 33 stops the increase of the rotation of the internal pump 26. After that, the core flow rate is maintained at the set core flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1K loaded in the core 20C, which is 14.4 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1K taken out of the core 20C can have less TRU than the new fuel assembly 1K. Specifically, according to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can achieve a discharge burnup of 65 GWd/t for the core 20C. In the present embodiment, the fission efficiency of TRU is 44%, the void coefficient is −2×10−4 Δk/k/% void, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to a fifth embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 21 and 22 as well as Table 5. The light water reactor of the present embodiment has a structure in which the fuel assembly 1K disposed in the core 20C in the fourth embodiment is replaced with a fuel assembly 1L shown in FIGS. 21 and 22. Other structures of the core of the TABLE 5NuclideComposition (wt %)Np-2370.2Pu-2385.2Pu-2398.5Pu-24038.9Pu-2414.8Pu-24225.4Am-2414.3Am-242M0.2Am-2434.7Cm-2444.8Cm-2451.4Cm-2461.2Cm-2470.2Cm-2480.2present embodiment are the same as in the fourth embodiment. In the present embodiment, only structures different from the fourth embodiment will be described. The core used in this embodiment is also a parfait-type core. The structure of the fuel assembly 1L will be described with reference with FIGS. 21 and 22. The fuel assembly 1L has 331 fuel rods 3L with a diameter of 7.4 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3L is 2.9 mm. The fuel rod row in the outermost peripheral layer includes 10 fuel rods 3L. The transverse cross section of the fuel pellet occupies 31% of the transverse cross section of a unit fuel rod lattice. The arrangement of the fuel assemblies 1L in the radial directions of the core in the present embodiment is the same as the arrangement shown in FIG. 19. As with the fuel assembly 1K, the fuel assembly 1L has five zones within its active fuel length (see FIG. 22). The upper blanket zone 5 is 20 mm high, the upper fissile zone 6 is 237 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 237 mm high, and the lower blanket zone 9 is 20 mm high. When the fuel assembly 1L is a new fuel assembly with a burnup of 0, each fuel rod 3L in the fuel assembly 1L is loaded with depleted uranium in the three blanket zones and with TRU oxide fuel in the upper fissile zone 6 and lower fissile zone 8. The enrichment of fissionable Pu in the TRU fuel is 13.3 wt %. The upper fissile zone 6 and lower fissile zone 8 are not loaded with mixed oxide fuel of TRU and depleted uranium. The blanket zones are not loaded with the TRU oxide fuel The fuel assembly 1L also includes fuel rods 3A to 3E, each of which is the fuel rod 3L. The TRU fuel present in the upper fissile zone 6 and lower fissile zone 8 includes TRU having the composition indicated in Table 5. When the fuel assembly 1L is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 8.5 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (8.5 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. When the core flow rate reaches the set core flow rate, the core flow rate control apparatus 33 stops the increase of the rotation of the internal pump 26. After that, the core flow rate is maintained at the set core flow rate until the operation of the BWR 19 is stopped in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1L loaded in the core, which is 8.5 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1L taken out of the core can have less TRU than the new fuel assembly 1L. Specifically, according to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can achieve a discharge burnup of 65 GWd/t for the core. In the present embodiment, the fission efficiency of TRU is 55%, the void coefficient is −3×10−5 Δk/k/% void, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to a sixth embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 23 to 25 as well as Table 6. The light water reactor of the present embodiment has a structure in which the core 20 and the fuel assembly 1 in the first embodiment are respectively replaced with a core 20D shown in FIG. 24 and a fuel assembly 1M shown in FIGS. 23 and 25. Other TABLE 6NuclideComposition (wt %)Np-2370.2Pu-2384.2Pu-2394.0Pu-24037.7Pu-2413.4Pu-24233.0Am-2414.3Am-242M0.2Am-2435.7Cm-2444.4Cm-2451.3Cm-2461.1Cm-2470.2Cm-2480.3structures of the core 20D are the same as in the first embodiment. In the present embodiment, only structures different from the first embodiment will be described. The light water reactor of the present embodiment produces an electric power of 450 MW, and the core 20D is a one fissile zone core. The fuel assembly 1M (see FIG. 23) disposed in the core 20D has 331 fuel rods 3M with a diameter of 8.7 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3M is 1.6 mm. The fuel rod row in the outermost peripheral layer includes 10 fuel rods 3M. The transverse cross section of the fuel pellet occupies 46% of the transverse cross section of a unit fuel rod lattice. FIG. 24 shows the core 20D in state of an equilibrium core. The fuel assemblies 1D, the operation cycle of which is the fourth cycle, are disposed in an outermost peripheral region of the core. A core outer region includes the fuel assemblies 1A, the operation cycle of which is the first cycle. In a core inner region, the fuel assemblies 1B, 1C, and 1D, the operation cycles of which are respectively the second cycle, third cycle, and fourth cycle, are dispersed. There is an intermediate region, in which a plurality of fuel assemblies 1B are disposed in a loop, between the core inner region and the core outer region. In this type of core 20D, the power distribution in its radial directions is more flattened. Each of the fuel assemblies 1A to 1E shown in FIG. 24 is the fuel assembly 1M. The fuel assembly 1M has three zones within its active fuel length (see FIG. 25). The upper blanket zone 5 is 20 mm high, the lower blanket zone 9 is 20 mm high, and the fissile zone 15 formed between these blanket zones is 201 mm high. When the fuel assembly 1M is a new fuel assembly with a burnup of 0, each fuel rod 3M is loaded with depleted uranium in the two blanket zones and with TRU oxide fuel in the fissile zone 15. The enrichment of fissionable Pu in the TRU oxide fuel is 7.4 wt %. The blanket zones are not loaded with TRU. The fuel assembly 1M also includes fuel rods 3A to 3E, each of which is the fuel rod 3M. The TRU oxide fuel present in the fissile zone 15 includes TRU having the composition indicated in Table 6. When the fuel assembly 1M is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 4.0 wt %. The core flow rate control apparatus 33 sets a core flow rate setting, which is determined from ratio information (4.0 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. When the core flow rate reaches the set core flow rate, the core flow rate control apparatus 33 stops the increase of the rotation of the internal pump 26. After that, the core flow rate is maintained at the set flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1M loaded in the core 20D, which is 4.0 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1M taken out of the core 20D can have less TRU than the new fuel assembly 1M. Specifically, according to the present embodiment, the BWR 19 generating a 450 MW electric power by using a reactor pressure vessel having almost the same size as the ABWR can achieve a discharge burnup of 75 GWd/t for the core 20D. In the present embodiment, fission efficiency of TRU is 80%, the void coefficient is −4×10−5 Δk/k/% void, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to a seventh embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 26 to 29 as well as Table 7. The light water reactor of the present embodiment has a structure in which the core 20 and the fuel assembly 1 in the first embodiment are respectively replaced with a core 20E shown in FIGS. 26 and 28 and a fuel assembly 1N shown in FIGS. 27 and 29. Other TABLE 7NuclideComposition (wt %)Np-2370.2Pu-2385.4Pu-23912.9Pu-24040.5Pu-2414.9Pu-24220.9Am-2414.8Am-242M0.2Am-2434.0Cm-2443.8Cm-2451.1Cm-2460.9Cm-2470.2Cm-2480.2structures of the core 20E are the same as in the first embodiment. In the present embodiment, only structures different from the first embodiment will be described. The electric power of the core in the present embodiment is 830 MW, which is lower than the electric power in the first embodiment. The core 20E is a parfait-type core. The fuel assembly 1N having a square transverse cross section, which is loaded in the core 20E, has 196 fuel rods 3N with a diameter of 8.1 mm in a square grid in a channel box 4A. The pitch between fuel rods 3N is 9.4 mm. Fourteen fuel rods 3M are disposed in a fuel rod row in the outermost peripheral layer. The transverse cross section of the fuel pellet occupies 41% of the transverse cross section of a unit fuel rod lattice. In the core 20E, 872 fuel assemblies 1N are disposed. A cross-shaped control rod 2A is provided for each four fuel assemblies 1N. A water exclusion plate (not shown) is suspended from an upper lattice plate disposed at the top of the core 20E on a side on which no cross-shaped control rods 2A are inserted in a gap area outside the channel box 4A shown in FIG. 27. The water drain plate has a function for excluding water from the gap area outside the channel box 4A. FIG. 28 shows the core 20E in state of an equilibrium core. The fuel assemblies 1d, the operation cycle of which is the fourth cycle, and fuel assemblies 1e, the operation cycle of which is the fifth cycle, are disposed in an outermost peripheral region of the core. A core outer region includes the fuel assemblies 1a, the operation cycle of which is the first cycle. In a core inner region, the fuel assemblies 1b, 1c, and 1d, the operation cycles which are respectively the second cycle, third cycle, and fourth cycle, are dispersed. There is an intermediate region, in which a plurality of fuel assemblies 1b are disposed in a loop, between the core inner region and the core outer region. In this type of core 20E, the power distribution in its radial directions is more flattened. The fuel assembly 1N has five zones within its active fuel length (see FIG. 29). The upper blanket zone 5 is 40 mm high, the upper fissile zone 6 is 180 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 174 mm high, and the lower blanket zone 9 is 90 mm high. When the fuel assembly 1N is a new fuel assembly with a burnup of 0, each fuel rod 3N of the fuel assembly 1N is loaded with depleted uranium in the three blanket zones and with TRU oxide fuel in the upper fissile zone 6 and lower fissile zone 8. The enrichment of fissionable Pu in the TRU fuel is 17.8 wt %. The blanket zones are not loaded with TRU. The TRU oxide fuel present in the upper fissile zone 6 and lower fissile zone 8 includes TRU having the composition indicated in Table 7. When the fuel assembly 1N is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 12.9 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (12.9 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. When the core flow rate reaches the set core flow rate, the core flow rate control apparatus 33 stops the increase of the rotation of the internal pump 26. After that, the core flow rate is maintained at the set flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1N loaded in the core, which is 12.9 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1N taken out of the core can have less TRU than the new fuel assembly 1N. Specifically, according to the present embodiment, a current ABWR generating an 848 MW electric power can be used to achieve a discharge burnup of 45 GWd/t for the core 20E. In the present embodiment, the fission efficiency of TRU is 43%, the void coefficient is −2×10−5 Δk/k/% void, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to an eighth embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 30 to 32 as well as Table 8. The light water reactor of the present embodiment has a structure in which the core 20 and the fuel assembly 1 in the first embodiment are respectively replaced with a core 20F shown in FIG. 31 and a fuel assembly 1P shown in FIGS. 30 and 32. Other TABLE 8NuclideComposition (wt %)Np-2370.5Pu-2384.2Pu-23931.6Pu-24038.7Pu-2415.8Pu-2428.9Am-2414.2Am-242M0.2Am-2432.3Cm-2442.3Cm-2450.7Cm-2460.4Cm-2470.1Cm-2480.1structures of the core 20F are the same as in the first embodiment. In the present embodiment, only structures different from the first embodiment will be described. The electric power of the core in the present embodiment is 1350 MW. The core 20F is a parfait-type core. The fuel assembly 1P disposed in the core 20F has 331 fuel rods 3P with a diameter of 8.7 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3P is 1.6 mm. The fuel rod row in the outermost peripheral layer includes 10 fuel rods 3P. The transverse cross section of the fuel pellet occupies 47% of the transverse cross section of a unit fuel rod lattice. In a state of an equilibrium core, the core 20F disposes the fuel assemblies 1D, the operation cycle of which is the fourth cycle, in the outermost peripheral region and the fuel assemblies 1A, the operation cycle of which is the first cycle, in a core outer region. In a core inner region, the fuel assemblies 1B, 1C, and 1D, the operation cycles of which are respectively the second cycle, third cycle, and fourth cycle, are dispersed. There is an intermediate region, in which a plurality of fuel assemblies 1B are disposed in a loop, between the core inner region and the core outer region. In this type of core 20F, the power distribution in its radial directions is more flattened. Each of the fuel assemblies 1A to 1E shown in FIG. 31 is the fuel assembly 1P. The fuel assembly 1P has five zones within its active fuel length (see FIG. 32). The upper blanket zone 5 is 90 mm high, the upper fissile zone 6 is 240 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 240 mm high, and the lower blanket zone 9 is 90 mm high. When the fuel assembly 1P is a new fuel assembly with a burnup of 0, each fuel rod 3P of the fuel assembly 1P is loaded with depleted uranium in the three blanket zones and with mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8, the mixed oxide fuel including 108 parts by weight of depleted uranium per 100 parts by weight of TRU. The enrichment of fissionable Pu in the mixed oxide fuel is 18 wt %. The blanket zones are not loaded with TRU. The fuel assembly 1P also includes fuel rods 3A to 3E, each of which is the fuel rod 3P. The mixed oxide fuel includes TRU having the composition indicated in Table 8. When the fuel assembly 1P is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 31.6 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (31.6 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. The core flow rate is maintained at the set flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1P loaded in the core, which is 31.6 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1P taken out of the core can have less TRU than the new fuel assembly 1P. According to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can increase the discharger burnup of 57 GWd/t for the core 20F. In the present embodiment, the void coefficient is −2×10−5 Δk/k/% void, the fission efficiency of TRU is 15%, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to a ninth embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 33 to 35 as well as Table 9. The light water reactor of the present embodiment has a structure in which the core 20 and the fuel assembly 1 in the first embodiment are respectively replaced with a core 20G shown in FIG. 34 and a fuel assembly 1Q shown in FIGS. 33 and 35. Other TABLE 9NuclideComposition (wt %)Np-2370.4Pu-2384.6Pu-23926.4Pu-24039.9Pu-2415.8Pu-24211.2Am-2414.4Am-242M0.2Am-2432.7Cm-2442.8Cm-2450.9Cm-2460.5Cm-2470.1Cm-2480.1structures of the core 20G are the same as in the first embodiment. In the present embodiment, only structures different from the first embodiment will be described. The core 20G is a parfait-type core. The fuel assembly 1Q disposed in the core 20G has 331 fuel rods 3Q with a diameter of 8.5 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3Q is 1.8 mm. The fuel rod row in the outermost peripheral layer includes 10 fuel rods 3Q. The transverse cross section of the fuel pellet occupies 45% of the transverse cross section of a unit fuel rod lattice. In a state of an equilibrium core, the core 20F disposes the fuel assemblies 1D, the operation cycle of which is the fourth cycle, in the outermost peripheral region and the fuel assemblies 1A, the operation cycle of which is the first cycle, in a core outer region. In a core inner region, the fuel assemblies 1B, 1C, and 1D, the operation cycles of which are respectively the second cycle, third cycle, and fourth cycle, are dispersed. There is an intermediate region, in which a plurality of fuel assemblies 1B are disposed in a loop, between the core inner region and the core outer region. In this type of core 20G, the power distribution in its radial directions is more flattened. Each of the fuel assemblies 1A to 1E shown in FIG. 34 is the fuel assembly 1Q. The fuel assembly 1Q has five zones within its active fuel length (see FIG. 35). The upper blanket zone 5 is 90 mm high, the upper fissile zone 6 is 224 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 224 mm high, and the lower blanket zone 9 is 90 mm high. When the fuel assembly 1Q is a new fuel assembly with a burnup of 0, each fuel rod 3Q of the fuel assembly 1Q is loaded with depleted uranium in the three blanket zones and with mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8, the mixed oxide fuel including 79 parts by weight of depleted uranium per 100 parts by weight of TRU. The enrichment of fissionable Pu in the mixed oxide fuel is 18 wt %. The blanket zones are not loaded with TRU. The fuel assembly 1Q also includes fuel rods 3A to 3E, each of which is the fuel rod 3Q. The mixed oxide fuel includes TRU having the composition indicated in Table 9. When the fuel assembly 1Q is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 26.4 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (26.4 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. The core flow rate is maintained at the set flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1Q loaded in the core, which is 26.4 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1Q taken out of the core can have less TRU than the new fuel assembly 1Q. According to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can increase the discharge burnup of 58 GWd/t for the core 20G. In the present embodiment, the void coefficient is −3×10−5 Δk/k/% void, the fission efficiency of TRU is 22%, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to a tenth embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 36 and 37 as well as Table 10. The light water reactor of the present embodiment has a structure in which the fuel assembly 1Q disposed in the core 20G in the ninth embodiment is replaced with a fuel assembly 1R shown in FIGS. 36 and 37. Other structures of the core 20G are the TABLE 10NuclideComposition (wt %)Np-2370.3Pu-2385.1Pu-23919.7Pu-24040.6Pu-2415.3Pu-24215.3Am-2414.7Am-242M0.2Am-2433.4Cm-2443.4Cm-2451.1Cm-2460.7Cm-2470.1Cm-2480.1same as in the ninth embodiment. In the present embodiment, only structures different from the ninth embodiment will be described. The core used in this embodiment is also a parfait-type core. As shown in FIGS. 36 and 37, the fuel assembly 1R has 331 fuel rods 3R with a diameter of 8.1 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3R is 2.2 mm. The fuel rod row in the outermost peripheral layer includes 10 fuel rods 3R. The transverse cross section of the fuel pellet occupies 40% of the transverse cross section of a unit fuel rod lattice. The fuel assemblies 1R in the present embodiment are disposed in its radial directions in the same arrangement as in FIG. 34. As with the fuel assembly 1Q, the fuel assembly 1R has five zones within its active fuel length (see FIG. 37). The upper blanket zone 5 is 40 mm high, the upper fissile zone 6 is 212 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 212 mm high, and the lower blanket zone 9 is 40 mm high. When the fuel assembly 1R is a new fuel assembly with a burnup of 0, each fuel rod 3R of the fuel assembly 1R is loaded with depleted uranium in the three blanket zones and with mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8, the mixed oxide fuel including 39 parts by weight of depleted uranium per 100 parts by weight of TRU. The enrichment of fissionable Pu in the mixed oxide fuel is 18 wt %. The blanket zones are not loaded with TRU. The fuel assembly 1R also includes fuel rods 3A to 3E, each of which is the fuel rod 3R. The mixed oxide fuel present in the upper fissile zone 6 and lower fissile zone 8 includes TRU having the composition indicated in Table 10. When the fuel assembly 1R is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 19.7 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (19.7 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. The core flow rate is maintained at the set core flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1R loaded in the core, which is 19.7 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1R taken out of the core can have less TRU than the new fuel assembly 1R. According to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can increase the discharge burnup of 59 GWd/t for the core. In the embodiment, the void coefficient is −4×10−5 Δk/k/% void, the fission efficiency of TRU is 34%, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to an eleventh embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 38 and 39 as well as Table 11. The light water reactor of the present embodiment has a structure in which the fuel assembly 1K disposed in the core 20C in the fourth embodiment is replaced with a fuel assembly 1S shown in FIGS. 38 and 39. Other structures of the core are the same TABLE 11NuclideComposition (wt %)Np-2370.2Pu-2385.1Pu-23912.9Pu-24040.8Pu-2414.7Pu-24221.2Am-2414.7Am-242M0.2Am-2434.1Cm-2443.7Cm-2451.1Cm-2460.9Cm-2470.2Cm-2480.2as in the fourth embodiment. In the present embodiment, only structures different from the fourth embodiment will be described. The core used in the present embodiment is also a parfait-type core. As shown in FIGS. 38 and 39, the fuel assembly 1S has 331 fuel rods 3S with a diameter of 7.6 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3S is 2.7 mm. The fuel rod row in the outermost peripheral layer includes 10 fuel rods 3S. The transverse cross section of the fuel pellet occupies 35% of the transverse cross section of a unit fuel rod lattice. The fuel assemblies 1S in the present embodiment are disposed in its radial directions in the same arrangement as in FIG. 19. As with the fuel assembly 1K, the fuel assembly 1S has five zones within its active fuel length (see FIG. 39). The upper blanket zone 5 is 35 mm high, the upper fissile zone 6 is 189 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 189 mm high, and the lower blanket zone 9 is 35 mm high. When the fuel assembly 1S is a new fuel assembly with a burnup of 0, each fuel rod 3S of the fuel assembly 1S is loaded with depleted uranium in the three blanket zones and with TRU oxide fuel in the upper fissile zone 6 and lower fissile zone 8. The enrichment of fissionable Pu in the TRU oxide fuel is 18 wt %. The blanket zones are not loaded with TRU. The fuel assembly 1S also includes fuel rods 3A to 3E, each of which is the fuel rod 3S. The TRU oxide fuel present in the upper fissile zone 6 and lower fissile zone 8 includes TRU having the composition indicated in Table 10. When the fuel assembly 1S is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 12.9 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (12.9 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. The core flow rate is maintained at the set core flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate setting determined by the ratio of Pu-239 in TRU in the new fuel assembly 1S loaded in the core, which is 12.9 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1S taken out of the core can have less TRU than the new fuel assembly 1S. According to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can attain a discharge burnup of 65 GWd/t for the core. In the embodiment, the fission efficiency of TRU is 47%, the void coefficient is −3×10−4 Δk/k/% void, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to a twelfth embodiment which is another embodiment of the present invention will be described below in detail with reference to FIGS. 40 and 41 as well as Table 12. The light water reactor of the present embodiment has a structure in which the fuel assembly 1K disposed in the core 20C in the fourth embodiment is replaced with a fuel assembly 1T shown in FIGS. 40 and 41. Other structures of the core of the TABLE 12NuclideComposition (wt %)Np-2370.2Pu-2385.2Pu-23911.0Pu-24040.5Pu-2414.8Pu-24222.6Am-2414.6Am-242M0.2Am-2434.3Cm-2444.1Cm-2451.2Cm-2460.9Cm-2470.2Cm-2480.2present embodiment are the same as in the fourth embodiment. In the present embodiment, only structures different from the fourth embodiment will be described. The core used in this embodiment is also a parfait-type core. The fuel assembly 1T has 331 fuel rods 3T with a diameter of 7.5 mm in a regular triangle lattice in the channel box 4. The gap between fuel rods 3T is 2.8 mm. The fuel rod row in the outermost peripheral layer includes 10 fuel rods 3T. The transverse cross section of the fuel pellet occupies 34% of the transverse cross section of a unit fuel rod lattice. The fuel assemblies 1T of the present embodiment are disposed in its radial directions in the same arrangement as in FIG. 19. As with the fuel assembly 1K, the fuel assembly 1T has five zones within its active fuel length (see FIG. 41). The upper blanket zone 5 is 30 mm high, the upper fissile zone 6 is 204 mm high, the internal blanket zone 7 is 560 mm high, the lower fissile zone 8 is 204 mm high, and the lower blanket zone 9 is 30 mm high. When the fuel assembly 1T is a new fuel assembly with a burnup of 0, each fuel rod 3T of the fuel assembly 1T is loaded with depleted uranium in the three blanket zones and with TRU oxide fuel in the upper fissile zone 6 and lower fissile zone 8. The enrichment of fissionable Pu in the TRU oxide fuel is 16 wt %. The blanket zones are not loaded with TRU. The fuel assembly 1T also includes fuel rods 3A to 3E, each of which is the fuel rod 3T. The TRU oxide fuel present in the upper fissile zone 6 and lower fissile zone 8 includes TRU having the composition indicated in Table 12. When the fuel assembly 1T is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 11.0 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (11.0 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. The core flow rate is maintained at the set flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1T loaded in the core, which is 11.0 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1T taken out of the core can have less TRU than the new fuel assembly 1T. According to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can attain a discharge burnup of 65 GWd/t for the core. In the present embodiment, the fission efficiency of TRU is 50%, the void coefficient is −2×10−4 Δk/k/% void, MCPR is 1.3, the TRU isotope ratio conservation can be achieved, and the amount of TRU can be reduced. A light water reactor according to a thirteenth embodiment which is another embodiment of the present invention will be described below in detail with reference to FIG. 42 as well as Table 1. The light water reactor of the present embodiment has a structure in which the fuel assembly 1 disposed in the core 20 in the first embodiment is replaced with a fuel assembly 1U shown in FIG. 42. Other structures of the core of the present embodiment are the same as in the first embodiment. In the present embodiment, only structures different from the first embodiment will be described. The core used in the present embodiment is also a parfait-type core. The fuel assembly 1U is formed by arranging the five zones in the fuel assembly 1 as shown in FIG. 42. The fuel assembly 1U has the same structure as the fuel assembly 1. In the fuel assembly 1U, the upper blanket zone 5 is 120 mm high, the upper fissile zone 6 is 226 mm high, the internal blanket zone 7 is 450 mm high, the lower fissile zone 8 is 224 mm high, and the lower blanket zone 9 is 180 mm high. When the fuel assembly 1U is a new fuel assembly with a burnup of 0, each fuel rod of the fuel assembly 1U is loaded with depleted uranium in the three blanket zones and with mixed oxide fuel in the upper fissile zone 6 and lower fissile zone 8, the mixed oxide fuel including 172 parts by weight of depleted uranium per 100 parts by weight of TRU. The enrichment of fissionable Pu in the TRU oxide fuel is 18 wt %. The blanket zones are not loaded with TRU. The fuel assembly 1U also includes fuel rods 3A to 3E. The mixed oxide fuel present in the upper fissile zone 6 and lower fissile zone 8 includes TRU having the composition indicated in Table 1. When the fuel assembly 1U is a new fuel assembly, the ratio of Pu-239 in all TRU elements is 44 wt %. The core flow rate control apparatus 33 sets a set core flow rate, which is determined from ratio information (44 wt %) and the characteristics shown in FIG. 2. The core flow rate control apparatus 33 controls the internal pump 26 and increases the core flow rate until it reaches the set core flow rate. The core flow rate is maintained at the set core flow rate until the BWR 19 is shut down in the operation cycle. In the present embodiment as well, adjustment is performed so that the set core flow rate determined by the ratio of Pu-239 in TRU in the new fuel assembly 1U loaded in the core, which is 44 wt %, is reached, so the TRU isotope ratio conservation can be implemented as in the first embodiment. In the present embodiment, therefore, the burnup can be further increased and TRU multi-recycling becomes feasible. In the present embodiment, the fuel assembly 1U taken out of the core can have less TRU than the new fuel assembly 1U. According to the present embodiment, the BWR 19 generating a 1350 MW electric power, which is the same as the electric power of a current ABWR, by using a reactor pressure vessel having almost the same size as the ABWR can achieve a discharge burnup of 45 GWd/t in a core zone including the upper and lower fissile zones and the internal blanket zone excluding the upper and lower blanket zones, a discharge burnup of 52 GWd/t in the core zone, which is larger than the burnup in the breeder reactor in the light water reactor described in JP 3428150 B, and a burnup of 45 GWd/t in the core including the upper and lower blanket zones. In the present embodiment, MCPR is 1.3, the void coefficient is −2×10−5 Δk/k/% void, the TRU isotope ratio conservation can be achieved while the absolute value of the negative void coefficient value is greater than in the first embodiment, and a breeding ratio of 1.01 can be attained. |
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description | 1. Field of the Invention The present invention relates to a method and apparatus for detecting degradation in a remote storage device. 2. Related Art Enterprise computer systems often include a large number of hard disk drives. For example, a single server system can sometimes have as many as 15,000 hard disk drives. Losing data stored on these disk drives can have a devastating effect on an organization. For example, airlines rely on the integrity of data stored in their reservation systems for most of their day-to-day operations, and would essentially cease to function if this data became lost or corrupted. If fault-prone hard disk drives can be identified before they fail, preventative measures can be taken to avoid such failures. Present techniques that are used to identify hard disk drives that are likely to fail have many shortcomings. One technique analyzes internal counter-type variables, such as read retries, write retries, seek errors, dwell time (time between reads/writes) to determine whether a disk drive is likely to fail. Unfortunately, in practice, this technique suffers from a high missed-alarm probability (MAP) of 50%, and a false-alarm probability (FAP) of 1%. This high MAP increases the probability of massive data loss, and the FAP causes a large number of No-Trouble-Found (NTF) drives to be returned, resulting in increased warranty costs. Another technique monitors internal discrete performance metrics within disk drives, for example, by monitoring internal diagnostic counter-type variables called “SMART variables.” However, hard disk drive manufacturers are reluctant to add extra diagnostics to monitor these variables, because doing so increases the cost of the commodity hard disk drives. Furthermore, in practice, this technique fails to identify approximately 50% of imminent hard disk drive failures. To prevent catastrophic data loss due to hard disk failures, systems often use redundant arrays of inexpensive disks (RAID). Unfortunately, because the capacity of hard disk drives have increased dramatically in recent years, the time needed to rebuild a RAID disk after a failure of one of the disks has also increased dramatically. Consequently, the rebuild process can take many hours to several days, during which time the system is susceptible to a second hard disk drive failure which would cause massive data loss. Furthermore, data loss can occur if a second disk fails before a first disk is replaced. Hence, even the most advanced redundancy-based solutions are susceptible to data loss. Moreover, some computer systems store data to remote storage devices. Typically, information about the health of the remote storage device is not available to the computer system. Hence, the computer system cannot determine whether the remote storage device is at the onset of degradation. Hence, what is needed is a method and an apparatus for detecting degradation of a remote storage device without the problems described above. One embodiment of the present invention provides a system that monitors telemetry from a host computer system to detect degradation in a remote storage device. During operation, the system monitors performance parameters from a host computer system which accesses the remote storage device, wherein the performance parameters relate to the interactions between the host computer system and the remote storage device. The system then determines whether the monitored performance parameters have deviated from predicted values for the performance parameters. If so, the system generates a signal indicating that the remote storage device has degraded. In a variation on this embodiment, prior to determining whether the performance parameters have deviated from predicted values, the system uses a non-linear non-parametric regression technique to generate the predicted values for the monitored performance parameters based on a model of the host computer system which was generated while the remote storage device was operating in a non-degraded state. In a further variation, the non-linear non-parametric regression technique is a multivariate state estimation technique (MSET). In a further variation, prior to using the non-linear non-parametric regression technique to generate predicted values for the monitored performance parameters, the system preprocesses the monitored performance parameters to remove outlying and flat data. In a further variation, prior to monitoring the performance parameters, the system generates the model during a training phase by: (1) monitoring the performance parameters from the host computer system while the remote storage device is operating in a non-degraded state; (2) preprocessing the monitored performance parameters to remove outlying and flat data; and (3) using the non-linear non-parametric regression technique to build the model. In a variation on this embodiment, while determining whether the performance parameters have deviated from predicted values, the system determines whether the monitored performance parameters have deviated a specified amount from the predicted values. In a variation on this embodiment, while determining whether the performance parameters have deviated from predicted values, the system uses a sequential probability ratio test (SPRT). In a variation on this embodiment, the remote storage device can include: a hard disk drive or a storage array. In a variation on this embodiment, the performance parameters can include disk-related metrics, which can include: average service time; average response time; number of kilobytes (kB) read per second; number of kB written per second; number of read requests per second; number of write requests per second; and number of soft errors per second. In a variation on this embodiment, the performance parameters can include software variables, which can include: load metrics; CPU utilization; idle time; memory utilization; transaction latencies; and other performance metrics reported by the operating system. In a variation on this embodiment, the performance parameters can include hardware variables, which can include: temperature; voltage; current; and fan speed. The following description is presented to enable any person skilled in the art to make and use the invention, and is provided in the context of a particular application and its requirements. Various modifications to the disclosed embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the present invention. Thus, the present invention is not limited to the embodiments shown, but is to be accorded the widest scope consistent with the principles and features disclosed herein. The data structures and code described in this detailed description are typically stored on a computer-readable storage medium, which may be any device or medium that can store code and/or data for use by a computer system. This includes, but is not limited to, volatile memory, non-volatile memory, magnetic and optical storage devices such as disk drives, magnetic tape, CDs (compact discs), DVDs (digital versatile discs or digital video discs), or other media capable of storing computer readable media now known or later developed. Overview One embodiment of the present invention monitors telemetry data from a host computer system, which accesses a remote storage device, to determine whether the remote storage device has degraded. The telemetry data can include performance parameters collected from physical and software sensors for the host computer system. In one embodiment of the present invention, performance parameters from the remote storage device are not directly monitored and the determination of whether the remote storage device has degraded is based only on the performance parameters monitored from the host computer system. In one embodiment of the present invention, the performance parameters from the host computer system are processed by a pattern recognition tool to detect degradation in the remote storage device. In one embodiment of the present invention, if the pattern recognition tool identifies that the remote storage device is at the onset of degradation, preemptive actions can be taken to prevent a catastrophic failure of the remote storage device. For example, the preemptive actions can include: replacing a degraded storage device; or failing-over to a redundant storage device. Typically, the time-to-failure that is predicted is sufficiently long to allow for these preemptive actions. In one embodiment of the present invention, a non-linear non-parametric (NLNP) regression technique is used to analyze the performance parameters. In one embodiment of the present invention, during a training phase, the NLNP regression technique builds a model of the host computer system based on performance parameters monitored from the host computer system while the host computer system accesses a remote storage device which is operating in a non-degraded state. The model of the host computer system is then used during the monitoring phase to generate predicted values of the performance parameters for the host computer system. In one embodiment of the present invention, a discrepancy between a predicted value for a performance parameter and a monitored value for the performance parameter results in an alarm being generated. In one embodiment of the present invention, a sequential probability ratio test (SPRT) is used to determine whether the discrepancy in the values of the performance parameters warrants an alarm being generated. Note that although this specification describes the present invention as applied to monitoring disk drives, the present invention can generally be applied to any storage device, including but not limited to, magnetic, optical, and magneto-optical storage devices, as well as storage devices based on flash memory and/or battery-backed up memory, or any other type of non-volatile storage device. Computer System FIG. 1 presents a block diagram illustrating a host computer system 102 and a remote storage device 116 in accordance with an embodiment of the present invention. Host computer system 102 includes processor 104, memory 106, storage device 108, real-time telemetry system 110, and network interface 112. Processor 104 can generally include any type of processor, including, but not limited to, a microprocessor, a mainframe computer, a digital signal processor, a personal organizer, a device controller and a computational engine within an appliance. Memory 106 can include any type of memory, including but not limited to, dynamic random access memory (DRAM), static random access memory (SRAM), flash memory, and read only memory (ROM). Storage device 108 can include any type of non-volatile storage device that can be coupled to a computer system. This includes, but is not limited to, magnetic, optical, and magneto-optical storage devices, as well as storage devices based on flash memory and/or battery-backed up memory. Network interface 112 can include any type of interface that provides connectivity between a computer system and a network, including, but not limited to, a wireless network interface, an Ethernet interface, and a phone network interface. In one embodiment of the present invention, real-time telemetry system 110 is separate from host computer system 102. Note that real-time telemetry system 110 is described in more detail below with reference to FIG. 2. Host computer system 102 uses network interface 112 to interact with remote storage device 116 through network 114. Note that network 114 can generally include any type of wired or wireless communication channel capable of coupling together computing nodes. This includes, but is not limited to, a local area network, a wide area network, or a combination of networks. In one embodiment of the present invention, network 114 includes the Internet. As illustrated in FIG. 1, remote storage device 116 is a storage array which includes storage devices 118-133, such as hard disk drives. In another embodiment of the present invention, remote storage device 116 contains a single storage device. Real-Time Telemetry System FIG. 2 illustrates real-time telemetry system 110 in accordance with an embodiment of the present invention. Referring to FIG. 2, host computer system 102 can generally include any computational node including a mechanism for servicing requests from a client for computational and/or data storage resources. In the present embodiment, host computer system 102 is a high-end uniprocessor or multiprocessor server that is being monitored by real-time telemetry system 110. Real-time telemetry system 110 contains telemetry device 204, analytical re-sampling program 206, sensitivity analysis tool 208, and non-linear non-parametric (NLNP) regression device 210. In one embodiment of the present invention, NLNP regression device 210 uses a multi-variate state estimation technique (MSET) device. Telemetry device 204 gathers information from the various sensors and monitoring tools within server 202, and directs the signals to a remote location that contains analytical re-sampling program 206, sensitivity analysis tool 208, and NLNP regression device 210. Note that NLNP regression device 210 is described in more detail below. The term “MSET” as used in this specification refers to a multivariate state estimation technique, which loosely represents a class of pattern recognition algorithms. For example, see [Gribok] “Use of Kernel Based Techniques for Sensor Validation in Nuclear Power Plants,” by Andrei V. Gribok, J. Wesley Hines, and Robert E. Uhrig, The Third American Nuclear Society International Topical Meeting on Nuclear Plant Instrumentation and Control and Human-Machine Interface Technologies, Washington D.C., Nov. 13-17, 2000. This paper outlines several different pattern recognition approaches. Hence, the term “MSET” as used in this specification can refer to (among other things) any technique outlined in [Gribok], including Ordinary Least Squares (OLS), Support Vector Machines (SVM), Artificial Neural Networks (ANNs), MSET, or Regularized MSET (RMSET). Analytical re-sampling program 206 ensures that the monitored signals have a uniform sampling rate. In doing so, analytical re-sampling program 206 uses interpolation techniques, if necessary, to fill in missing data points, or to equalize the sampling intervals when the raw data is non-uniformly sampled. After the signals pass through analytical re-sampling program 206, they are aligned and correlated by sensitivity analysis tool 108. For example, in one embodiment of the present invention sensitivity analysis tool 208 incorporates a novel moving window technique that “slides” through the signals with systematically varying window widths. The system systematically varies the alignment between sliding windows for different signals to optimize the degree of association between the signals, as quantified by an “F-statistic,” which is computed and ranked for all signal windows by sensitivity analysis tool 108. While statistically comparing the quality of two fits, F-statistics reveal the measure of regression. The higher the value of the F-statistic, the better the correlation is between two signals. The lead/lag value for the sliding window that results in the F-statistic with the highest value is chosen, and the candidate signal is aligned to maximize this value. This process is repeated for each signal by sensitivity analysis tool 208. Signals that have an F-statistic very close to 1 are “completely correlated” and can be discarded. This can result when two signals are measuring the same metric, but are expressing them in different engineering units. For example, a signal can convey a temperature in degrees Fahrenheit, while a second signal conveys the same temperature in degrees Centigrade. Since these two signals are perfectly correlated, one does not contain any additional information over the other, and therefore, one may be discarded. Some signals may exhibit little correlation, or no correlation whatsoever. In this case, these signals may be dropped because they add little predictive information. Once a highly correlated subset of the signals has been determined, they are combined into one group or cluster for processing by the NLNP regression device 210. Nonlinear, Nonparametric Regression The present invention introduces a novel approach for detecting degradation in a remote storage device. To this end, one embodiment of the present invention uses an advanced pattern recognition approach, which produces predicted values of performance parameters for host computer system 102 based on: (1) software variables reported by the operating system on host computer system 102, (2) hardware variables generated by the sensors on host computer system 102, and (3) a model of host computer system 102 which was generated during a training phase. One embodiment of the present invention continuously monitors a variety of instrumentation signals in real time during operation of the server. (Note that although we refer to a single computer system in this disclosure, the present invention can also apply to a collection of computer systems). These instrumentation signals can also include signals associated with internal performance parameters maintained by software within the computer system. For example, these internal performance parameters can include, but are not limited to, system throughput, transaction latencies, queue lengths, central processing unit (CPU) utilization, load on CPU, idle time, memory utilization, load on the memory, load on the cache, I/O traffic, bus saturation metrics, FIFO overflow statistics, and various operational profiles gathered through “virtual sensors” located within the operating system. These instrumentation signals can also include signals associated with canary performance parameters for synthetic user transactions, which are periodically generated for the purpose of measuring quality of service from the end user's perspective. These instrumentation signals can additionally include hardware variables, including, but not limited to, internal temperatures, voltages, currents, and fan speeds. Furthermore, these instrumentation signals can include disk-related metrics for a remote storage device, including, but not limited to, average service time, average response time, number of kilobytes (kB) read per second, number of kB written per second, number of read requests per second, number of write requests per second, and number of soft errors per second. The foregoing instrumentation parameters are monitored continuously with an advanced statistical pattern recognition technique. One embodiment of the present invention uses a class of techniques known as nonlinear, nonparametric (NLNP) regression techniques. One such regression technique is the Multivariate State Estimation Technique (MSET). Alternatively, the present invention can use other pattern recognition techniques, such as neural networks or other types of NLNP regression. Another embodiment of the present invention uses a linear regression technique. In each case, the pattern recognition module learns how the behavior of host computer system 102 relates to the health of remote storage device 116. The pattern recognition module then generates a model of host computer system 102 that is used to determine whether remote storage device has degraded. This determination is made without directly monitoring performance parameters from remote storage device 116. In one embodiment of the present invention, the components from which the instrumentation signals originate are field replaceable units (FRUs), which can be independently monitored. Note that all major system components, including both hardware and software components, can be decomposed into FRUs. (For example, a software FRU can include: an operating system, a middleware component, a database, or an application.) Also note that the present invention is not meant to be limited to server computer systems. In general, the present invention can be applied to any type of computer system. This includes, but is not limited to, a computer system based on a microprocessor, a mainframe computer, a digital signal processor, a portable computing device, a personal organizer, a device controller, and a computational engine within an appliance. Detecting Degradation on a Remote Storage Device FIG. 3 presents a flowchart illustrating the process of generating a model of the host computer system during a training phase in accordance with an embodiment of the present invention. The process begins when the system monitors the performance parameters from the host computer system while the remote storage device is operating in a non-degraded state (step 302). Next, the system preprocesses the monitored performance parameters to remove outlying and flat data (step 304). The system then uses the non-linear non-parametric regression technique to build the model (step 306). FIG. 4 presents a flowchart illustrating the process of monitoring telemetry from a host computer system during a subsequent monitoring phase to detect degradation in a remote storage device in accordance with an embodiment of the present invention. The process begins when the system monitors performance parameters from a host computer system which accesses the remote storage device, wherein the performance parameters relate to the interactions between the host computer system and the remote storage device (step 402). Next, the system preprocesses the monitored performance parameters to remove outlying and flat data (step 404). The system then uses a non-linear non-parametric regression technique to generate the predicted values for the monitored performance parameters based on a model of the host computer system which was generated while the remote storage device was operating in a non-degraded state (step 406). Next, the system determines whether the monitored performance parameters have deviated from predicted values for the performance parameters (step 408). In one embodiment of the present invention, while determining whether the performance parameters have deviated from predicted values, the system determines whether the monitored performance parameters have deviated a specified amount from the predicted values. In another embodiment of the present invention, the system uses a sequential probability ration test (SPRT) to determine whether the performance parameters have deviated from predicted values. If the monitored performance parameters have deviated from predicted values for the performance parameters (step 410—yes), the system generates a signal indicating that the remote storage device has degraded (step 412). Otherwise (step 410—no), the system continues monitoring performance parameters (step 402). The foregoing descriptions of embodiments of the present invention have been presented only for purposes of illustration and description. They are not intended to be exhaustive or to limit the present invention to the forms disclosed. Accordingly, many modifications and variations will be apparent to practitioners skilled in the art. Additionally, the above disclosure is not intended to limit the present invention. The scope of the present invention is defined by the appended claims. |
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052710530 | summary | FIELD OF THE INVENTION This invention relates to nuclear rector fuel assemblies and in particular those assemblies which include spaced fuel rod support grids mounted in a reactor core as a unit. The fuel rods are held between an upper end fitting or top nozzle and a lower end fitting by means of spacer grids. The reactor coolant flows upwardly from holes in the lower end fitting along the fuel rods, and upwardly through holes in the upper end fitting. When the fuel assembly is loaded in a reactor core, an upper core plate over the fuel assembly reacts against fuel assembly holddown spring assemblies attached by fasteners to the upper end fitting to provide a downward force. This force combines with the fuel assembly weight to prevent fuel assembly liftoff from hydraulic forces during operation of the reactor pumps. BACKGROUND OF THE INVENTION Debris in the circulating coolant which collects or is trapped in fuel rod spacer grids is believed responsible for as many as 70% of known fuel rod failures. Laboratory and in-reactor experience indicate that fuel rod cladding failures can be caused by debris trapped in a grid region which reacts against the fuel rod cladding in a vibratory fashion resulting in rapid wear of the cladding. The size and shape of the debris capable of causing severe damage is quite variable and may include broken fuel assembly fasteners or other holddown spring assembly broken parts. Accordingly, it is desirable to be able to operate safely without reconstitution even if a part of the assembly breaks. This can be accomplished by retention of any potential debris. U.S. Pat. No. 5,053,191 describes an improved fuel assembly holddown cantilevered spring and it and U.S. Pat. No. 4,792,429 show how the spring ends were designed to provide spring capture and retention in the unlikely event that a cantilever spring broke during operation. However, machining of these patents' leaves and capturing mechanisms are expensive and time consuming. SUMMARY OF THE INVENTION It is, accordingly, an object of the present invention to modify the typical holddown spring assembly to eliminate the likelihood of debris from broken parts. This is accomplished by the use of a fuel assembly holddown leaf spring assembly instead of the typical cantilever spring of some commercial reactor designs. The holddown leaf spring assembly of the invention improves or duplicates the cantilever holddown spring characteristics while capturing both ends of the spring without elaborate capturing and retention mechanisms. In addition, the number of springs may be cut in half and machining costs reduced. The novel fuel assembly holddown leaf spring assembly is constructed with similar materials as the prior art cantilever springs. The location of the top of the spring is in the opposite corner as compared to the cantilever design. This is due to the fact that the length of the leaf spring has to be longer than the cantilever and must be fit onto the top nozzle. The additional length requires the leaf spring to extend from near the top nozzle corner which accepts the upper core plate's fuel assembly aligning pins to the opposite aligning pin corner. The leaves themselves require only one hole being drilled at each end. The holes are used to secure the leaves to the upper end fitting. The use of welding plugs as described in Swedish patent application No. 9002638-6, filed Aug. 14, 1990, is more amenable to the design. However, the leaf spring could be designed to be held by spring screws, as in the prior art cantilevered spring design of U.S. Pat. Nos. 5,053,191 and 4,792,429. The structure of the holddown leaf spring assembly with spring retention means of the invention for use on an upper end fitting of a nuclear fuel assembly includes a unitary elongated metal bar having two substantially tapered width leg portions joined by an arcuate transition portion therebetween adjacent the reduced width end of each of the tapered width leg portions. The wider and opposite end of each of the tapered width leg portions from the reduced width end and adjacent transition portion are adapted to be mounted to the fuel assembly end fitting by spring retention means. The spring retention means are pins welded within openings in the wider opposite ends of the leg portions and these wider opposite ends are adapted to be received and retained by the pins in spring retaining slots in the upper end fitting. The opposite ends are straight in order to facilitate their insertion into spring retaining slots in the upper end fitting. Alternatively, the spring retention means are screws within openings in the opposite ends and caps as shown in U.S. Pat. No. 4,792,429 and U.S. Pat. No. 5,053,191. The novel structure of the instant invention prevents spring breakage and resultant debris by having an even stress distribution. This is created by the tapered width or cross-section. Moreover, with both ends of the leaf spring attached by retaining structure, in the event a spring breaks, there are no unrestrained loose parts to create debris. The attachment of the leaf ends within slots in the upper end fitting also avoids bends at the leaf spring ends and permits use of only welded or staked spring holddown pins in spring leg end openings without caps and the complicated and expensive machining they require. Accordingly, the holddown leaf spring assembly of the invention is easier to manufacture and requires fewer parts than the prior art. An added advantage is derived from the narrowing of the legs and the transition portion by the taper and elimination of retaining caps in that this structure opens the flow path of reactor coolant when coupled with a narrowing of the lower end fitting marginal lip or rim. The effect of a linearly changing spring force by the tapering of the width in the illustrated embodiment is to distribute and reduce localized stresses in the metal bars as compared to an untapered bar. It is also possible to reduce localized stresses by tapering the bar thicknesses. The word "width", as used in the claims, applies both to horizontal width and vertical width or thickness, although, it is generally more expensive to taper the vertical "width" or thickness. The bars are of an INCONEL material typically used in prior art cantilevered springs. |
056129823 | claims | 1. A nuclear power plant comprising: a reactor vessel; a containment structure enclosing the reactor vessel, the containment structure having a sidewall and a domed top end; an out-of-containment heat sink; and a containment cooling system piped with the out-of-containment heat sink, the cooling system including an in-containment heat exchanger vertically extending adjacent the sidewall of the containment structure and into the domed top end of the containment structure for transferring heat from atmosphere within the containment structure, the heat exchanger having a plurality of substantially parallel pipes with cooling fins vertically extending therefrom, the finned pipes having inlets elevated above the reactor vessel for inducing natural circulation of atmosphere in the containment. 2. The nuclear power plant of claim 1, wherein the reactor vessel is enclosed within a double containment structure. 3. The nuclear power plant of claim 1, wherein the in-containment heat exchanger has a vertically extending backing plate adjoining the vertically extending fins. 4. The nuclear power plant of claim 1, wherein the in-containment heat exchanger has baffles spaced from the substantially parallel pipes and extending horizontally of the vertically extending fins. 5. The nuclear power plant of claim 1, wherein the substantially parallel pipes are between a vertically extending backing plate adjoining the vertically extending fins and baffles extending horizontally of the vertically extending fins. 6. The nuclear power plant of claim 1 further comprising a steam generator hydraulically connected with the reactor vessel and an operating floor adjacent the steam generator, wherein the in-containment heat exchanger extends from the operating floor into the domed top of the containment structure. 7. The nuclear power plant of claim 1, wherein the substantially parallel pipes of the in-containment heat exchanger are within about three feet of the sidewall of the containment structure for inducing air circulation along the sidewall of the containment structure. 8. The nuclear power plant of claim 1 further including a condensate collection gutter disposed below and spaced from the in-containment heat exchanger for collecting condensate therefrom. 9. The nuclear power plant of claim 8, wherein the condensate collection gutter extends from the sidewall of the containment structure. 10. The nuclear power plant of claim 1, wherein the containment cooling system is adapted to passively transfer heat from the atmosphere within the containment structure to the out-of-containment heat sink. |
description | A basic embodiment of the photocathode electron projector is shown in FIGS. 1 and 2, where FIG. 1 shows an exploded view of the parts that form the projector, and FIG. 2 shows the assembled and operating device. Electrons are used to transfer a pattern from a photocathode to an electron resist-coated sample, e.g. a wafer 100. In this system, an anode 115 is attached to the sample 100. Cathode 150 is coupled to the patterned portion 120. The anode and cathode 150 are arranged spaced from one another in a simple diode configuration. A patterned mask is used as photoemitter 120, i.e., a device that emits electrons when irradiated by ultraviolet light. Photoemitter 120 is formed with the features which are to be transferred to the resist-coated wafer or xe2x80x9csamplexe2x80x9d 100. As shown in FIG. 2, a 3 Kev acceleration voltage is applied to cathode 150, and conducted to patterned surface 124. The patterned surface is electrically connected to the bias voltage, and hence effectively becomes the cathode surface. A glass spacer 150 has a gold coated surface 152 to stand off the electron acceleration voltage, typically 2-5 KeV field, most preferably approximately a 3 KeV field, shown applied at 152 to the cathode 150. The patterned masks are preferably formed from gold-palladium (Auxe2x80x94Pd ). Au/Pd requires lower wavelength UV sources than pure Au and therefore can produce smaller features. The photoemitter 120 is formed by a quartz mask that includes an irradiation receiving surface 122, and a coated and patterned front surface 124. The actual substrate 99 can be quartz or any other ultraviolet-transmissive material. The front surface 124 is preferably coated with a Cr/Au pattern covered with Au/Pd forming features to be transferred. The irradiation receiving surface 122 is illuminated by filtered ultraviolet light 134 from an ultraviolet light source 130 which is filtered through a filter 132. The ultraviolet light source can be the same type used in UV lithography. The filtered ultraviolet light 134 passes through the photoemitter 120 under an acceleration field from the electrostatic field generated between the anode and cathode. Electrons 200 are emitted at the patterned surface 124. Those electrons are accelerated by the electrostatic fields, and are used to selectively expose the resist on the sample 100. This operation is a lithography in the sense that the electrons form a pattern based on the pattern that is formed on patterned surface 124. The accelerated ultraviolet photons preferably have energies that are at least slightly higher than the work function of the metal coating 126 on the surface 124. The electrons 200 preferably have large enough energies to penetrate the resist layer on the sample 100 when reaching the sample. The emitted electrons are also focused by a magnetic field B that is parallel to the electric field. This focusing can be helpful to avoid edge effects from the finite tangential velocities of the emitted electrons. Hence parallel magnetic fields B and electric fields E accelerate the electrons 200. This causes the electrons to undergo a circular harmonic motion. For example, this may result in a cyclotronic orbit in a perpendicular direction to the fields. The strength of the fields are preferably set such that the electrons 200 have an integer number of cyclotronic orbits between the cathode surface 124 and the anode, preferably one cyclotronic orbit. In this way, the electron lands on the surface at substantially the same location as it was emitting from the mask. FIG. 2 shows the electron emissions 200 and their cyclotronic orbits. Ideally the electrons that are emitted from a point on the cathode surface 124 are imaged to a corresponding point on the sample 100 on the anode, preferably in the sensitive resist portion coupled to the anode. After the sample is exposed, it can be developed, and the resist pattern can then be transferred to a more robust sample or used directly as a mask. Higher energy photons are more likely to generate an electron when hitting the photoemitter material. However, more energetic electrons will have varying energies which can cause chromatic aberrations. Feature resolution in this system is directly affected by chromatic aberration caused by variation of emission energies of the photoelectrons. The present system trades off the brightness obtained from more energetic electrons for uniformity. The preferred embodiment uses substantially a single photoelectron emission energy. By doing so, the present system obtains substantially monochromatic electrons, e.g. within 5-10% of one another, more preferably within 1-2% of one another. A preferred mode filters the ultraviolet radiation to obtain the monochromatic electrons. These electrons have energies which are just above the work function frequency of the photoemitting substance. The work function is the lowest energy at which an electron will be emitted from the photoemitter. Hence, this obtains substantially only a single photoelectron emission energy, or at least emission energies within 5-10%, more preferably within 2% or 1%, of the work function of the metal in the pattern. The results may also be improved by minimizing the distance between the source and the sample. A typical distance between source and sample could be one cyclotron orbit. At 3 KeV, and a magnetic field of 1.46 Tesla, a cyclotron orbit is about 1.27 mm. A 1.4 Tesla magnet or greater is preferred. A higher strength magnet reduces the radius of the cyclotronic orbit. A smaller radius cyclotronic orbit has less movement as a function of height. In effect, this creates a longer depth-of-field. The inventors also found that pattern resolution is deleteriously affected by poor mechanical stability within the source/sample exposure system during exposure. Resolution is also decreased by non-uniformity of the magnetic field. Preferably, a highly uniform modern superconducting magnetic is used for this purpose, e.g. the kind of magnet now used for medical NMR. The basic system uses a number of additional features which are described herein. The electron emitter mask 124 has special properties. The preferred formation process of this mask is shown in FIGS. 3A-3E. FIG. 3A represents the initial step. A quartz mask substrate 300 is first covered with a 950 nm thick layer of Au/Cr, which is used as a mask layer on the substrate using standard chromium mask formation techniques. This is covered with a 70 nm resist overlayer of polymethylmethacrylate xe2x80x9cPMMAxe2x80x9d forming the mask 304. In FIG. 3B, the PMMA mask 304 is exposed to form features 310. The underlying Au layer is ion milled in FIG. 3C, forming gold features 312. Using techniques of standard electron beam lithography, the residual PMMA is then removed as shown in FIG. 3C to leave features of Au (gold) on the surface. A 20 nm thick sputter-deposited gold-palladium (Auxe2x80x94Pd ) electron emitting layer 320 is finally formed on the surface. It is contemplated that deterioration of the electron emission efficiency could eventually be observed on the gold is palladium emitter coating. If so, then low voltage oxygen plasma etching of this surface can be used for cleaning. The system shown in FIGS. 1 and 2 has so far demonstrated patterns of approximately 100 nm for lines, and 300 nm for spaced gratings. The material used was a PMMA resist at 3 keV. One disadvantage of using low acceleration voltages is the associated need to use thin resist coated on the sample 100. This often limits the usefulness of the resist as an etch mask or lift-off mask for further processing, since the film itself is relatively thin. Mask amplification techniques can be used to transfer the high resolution pattern from the resist layer on to a robust mask. A multilayer mask arrangement has been used for this purpose. The mask amplification is carried out by depositing layers of more robust materials on the wafer. These robust materials can include Au, SiO2, and Ni. After the materials are supplied, a thin layer of high resolution positive resist, such as PMMA, is deposited on the wafer. The positive resist is exposed and developed, and then used as a mask to selectively etch the underlying layers of robust materials using a sequence of ion milling and reactive ion etching. Similar multilevel resist schemes can be carried out using polyimide and germanium layers as is known in the art. An alternative technique, originally developed at IBM for planar DUV lithography, uses surface silation of novolac-based resists. In this technique, surface bonding of the resist is altered by electron beam irradiation. This changes the rate of diffusion of the silicon-containing compounds into the surface of the resist. The sample is subsequently oxygen ion etched, and the silicon-diffused areas are effectively masked by a thin silicon dioxide layer. The device of FIG. 4 is a locked-transfer system which can be used to effect pattern transfer as described above. The electron exposure shown in FIG. 2 is preferably carried out under vacuum. The vacuum permits larger mean-free paths for the photoemitted electrons, and also minimizes mask contamination and prevents electrostatic arcing. Electron emission intensity and exposure doses are made more reproducible if the gold surface is kept clean. First, the xe2x80x9csandwichxe2x80x9d 199 including the structure of FIG. 2 is positioned into the bore 408 of a magnet 410. The magnet can be, for example a niobium alloy superconducting magnet used in NMR. A mercury light source 402 is used to produce ultraviolet irradiation via a sapphire window 404. The light is directed through the bore 408 of the superconducting magnet 410. A magnetically-coupled feed-through 422 is used for positioning the sample 199 in the bore 408, and for removing and re-locating a new sample in the bore. Vacumn is maintained by pumps 428, 430 and can be selectively interrupted via valves. Alignment between the positions of the photoemitter mask 120 and the sample wafer 100 can be extremely important. An alignment technique is illustrated in FIG. 5. This system uses detection indicia. Micromachined 250 xcexcm via-holes are formed through the silicon wafer 100 that is to be exposed. Alignment marks are also formed in the mask 120. The alignment marks in the mask can be, for example, in the shape of a cross xe2x80x9c+xe2x80x9d. This shape is optimized to cause high signal gradients when scanning is aligned. A p-n diode 500 can be placed below the sample surface. The diode produces current when illuminated by the [illumination] electrons passing through both indicia in the mask and in the sample. Alignment is achieved by scanning the alignment marks over the holes, analyzing the alignment response, and then determining signal levels on both sides of the peak signal. A cross can produce high levels when aligned and lower levels when not aligned. The system has been found to have +/xe2x88x920.2 xcexcm alignment with about a 3"sgr" deviation. An alternate system puts the P-N junction directly on the sample surface so that the position of the P-N junction becomes the position of alignment. An alternate system uses excitation of characteristic x-rays from the sample surface. Evaporated or sputter-deposited layers are used which form characteristic x-rays when irradiated by electrons. The x-ray signals are filtered, and then measured with a dispersive x-ray detector. The signal strength is then maximized to optimize the sample-to-source alignment. Other detector elements on the sample can alternately be used. FIG. 6 shows an alternative mask which includes an integral ultraviolet filter element. The quartz substrate 99 is covered at the illumination receiving surface 602 by dielectric layer 604, which forms a Fabry-Perot filter that filters the ultraviolet radiation 134 from the ultraviolet source 130. Use of the ultraviolet filter on the bottom surface of the mask 600 enjoys certain advantages. A first advantage is since the filter can be over the entire surface of the mask, the filter is actually larger than the filter used in the first embodiment. Hence better filtering characteristics and better resolution can often be obtained. The filter on the sample can also provide better intensity emission since there is one fewer air-to-element boundary. Moreover, since the mask 600 is already complicated and expensive, the additional structure needed for the mask can be minimal. This mask also includes additional optical elements thereon. For example, diffractive optical element 610 can include an element such as a lens or a zone plate. The element 610 can have focal length F which can be tuned to a desired length. The voltage applied via 152 to the cathode can also be variable as shown by variable source 151. Any change in the wavelength of the light can change characteristics of the cyclotronically-orbiting electrons. Adjustment of the electrostatic value by adjusting the variable source 151 can be used to compensate for the optimum desired distance from the mask to the sample. Although only a few embodiments have been described in detail above, other embodiments are contemplated by the inventor and are intended to be encompassed within the following claims. In addition, other modifications are contemplated and are also intended to be covered. |
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abstract | Disclosed are methods, systems, and computer-product programs for increasing accuracy in cone-beam computed tomography (CBCT) by obscuring portions of the radiation source so that the radiation only passes through the specific areas of the patient related to the regions-of-interest to the doctor. The obscuring action causes less radiation scattering to occur in the patient's body, thereby reducing a major source of error in the image accuracy caused by scattered radiation. Scattered radiation received by detector pixels that are obscured by direct-line of sight radiation may be used to estimate the scattered radiation in the un-obscured portion, which can be used to further increase the accuracy of the image. |
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041750047 | summary | BACKGROUND OF THE INVENTION This invention relates to fuel assemblies for nuclear reactors and, more particularly, to a guide tube arrangement which restrains spacer grid movement and which offers secondary alternative means for supporting a fuel assembly during handling operations. In water cooled heterogenous nuclear reactors, the reactor core in which the fission chain is sustained generally contains an array of fuel assemblies which are identical in mechanical construction and mechanically interchangeable in any core location. The fuel assemblies are designed to maintain structural adequacy and reliability during core operation, handling, and shipping. Fuel assembly design for core operation typically considers the combined effects of flow induced vibration, temperature gradients, and seismic disturbances under both steady state and transient conditions. Each fuel assembly contains thin elongated fuel elements, a number of spacer grids, guide tubes, an instrumentation tube, and end fittings. The fuel elements, typically known as fuel rods or pins, house the nuclear fuel. The ends of the fuel elements are sealed with end caps. The fuel elements, guide tubes and instrument tube are supported in a square array at intervals along their lengths by spacer grids which maintain the lateral spacing between these components. The guide tubes are rigidly attached at their extremities to the end fittings. Use of similar material in the guide tubes and fuel elements results in minimum differential thermal expansion. The spacer grids are constructed from rectangular strips or plates which are slotted and fitted together in an "egg crate" fashion. The walls of the square cells, formed by the interlaced strips, contain integrally punched projections which provide lateral support for the fuel elements. Spacer grid to fuel assembly component contact loads are established to minimize fretting, but to allow axial relative motion resulting from fuel element irradiation growth and differential thermal expansion. Depending upon the position of the assembly within the reactor core, the guide tubes are used to provide continuous sheath guidance for control rods, axial power shaping rods, burnable poison rods, or orifice rods. Clearance is provided within the guide tubes to permit coolant flow therethrough to limit the operating temperature of the absorber materials. In addition, this clearance is designed to permit rod motion within the guide tubes as required during reactor operation under all conditions including seismic disturbances. Joined to each end of the guide tubes are flanged and threaded sleeves which secure the guide tubes to each end fitting by lock welded nuts. Each fuel assembly is typically installed vertically, in a reactor pressure vessel, on and supported by a core grid assembly support plate. The lower end fitting positions the fuel assembly relative to the core grid plate. The lower ends of the fuel elements rest on the grid of the lower end fitting. Penetrations in the lower end fitting are provided for attaching the lower ends of the guide tubes thereto. The upper end fitting provides means for coupling fuel assembly handling equipment and positioning the fuel assembly within the reactor core. In operation, the fuel elements in the reactor core become depleted at different rates, those in the center usually being subjected to a higher neutron flux and thus becoming depleted before those near the outside of the core where a lower neutron flux prevails. Consequently, all of the fuel assemblies are not normally replaced at one time but rather in stages. Furthermore, at each refueling, partially depleted elements may be relocated in order to optimize core performance and extend the time between refueling outages. Generally, spent and new fuel assemblies are transferred from and to the core, respectively, and partially spent fuel assemblies are relocated within the core, by hoists equipped with fuel assembly grapple mechanisms which mechanically engage the upper end fitting. During handling of a fuel assembly, the assembly load, which normally bears on the grid of the lower end fitting, is transferred to the guide tubes. Should a failure of all the giide tubes occur, the fuel assembly's integrity will be destroyed and it will separate into its component parts which may result in damage to the fuel elements and the development of hazardous conditions. Reactor coolant, under operating conditions, flows relatively parallel to the longitudinal axes of the fuel elements thereby subjecting the leading lengthwise edge of the spacer grid plates to hydraulic forces. Hence, the spacer grid may be subjected to vertical movements or perturbations under steady state or transient conditions or both. In the past, in order to restrain spacer grid movement, sleeves have been attached to the spacer grids and mechanically engaged to protrusions formed on the guide tubes. Alternatively, it has been proposed to engage tab extensions formed on the spacer grid plates with clips attached to the guide tubes in order to restrain spacer grid movement. The use of sleeves, tabs and clips, however, results in the addition of material within the reactor core which is capable of parasitically absorbing neutrons, thereby decreasing reactor efficiency. Moreover, the prior art arrangement required the forming of the protrusions after the guide tube was inserted into the spacer grid complicating both assembly and disassembly procedures. Additionally, use of guide tube clips adds the additional step of welding extraneous material to the guide tube which is capable of disengaging from the tube and being carried through the reactor coolant systems. SUMMARY OF THE INVENTION According to the present invention, in a fuel assembly of the type described above, a guide tube arrangement is presented which restrains spacer grid movement without the introduction of additional material capable of parasitic absorption, which readily permits assembly and disassembly of the fuel assembly, and which offers a secondary means of support during fuel assembly handling operations in the event that the guide tubes become disengaged from the lower end fitting. The foregoing is achieved by forming protuberancies, located in a preferred embodiment, at ninety degree intervals about the guide tube, longitudinally spaced such that they can be disposed adjacent either side of a spacer grid plate within the fuel assembly or centrally between saddle projections formed on the grid plates. The fuel assembly is completed by inserting the tube into a longitudinally aligned group of spacer grid cells such that the guide protuberancies project into the corners of the cell. When the guide tube has traversed the desired insertion length, it is rotated forty-five degrees thereby bringing the protuberancies into longitudinal alignment with the lengthwise edges or the saddles of the adjacent spacer grid plates that form the cells. Hence, longitudinal movements of the grid plates are restricted by the protuberancies. During handling of the fuel assembly, the assembly load which bears on the lower end fitting is transferred to the guide tubes. Should a failure of all the guide tubes occur, the fuel elements will slip until the upper end cap which is formed with a diametrical section greater than the width of a spacer grid cell is stopped by the upper edges of the upper spacer grid assembly. The upper spacer grid assembly, in turn, will slip until it is restricted by the guide tube protuberancies. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming a part of this specification. For a better understanding of the invention, its operating advantages and specific objects attained by its use, reference should be had to the accompanying drawings and descriptive matter in which there is illustrated and described a preferred embodiment of the invention . |
description | FIG. 5 is a perspective view of a duct-type spacer grid for nuclear fuel assemblies in accordance with the primary embodiment of this invention. As shown in the drawing, the duct-type spacer grid 2 of this invention comprises a plurality of duct-shaped grid elements 11, individually provided with both a fuel rod support spring 12 of FIG. 8 and a swirl flow vane of FIG. 9. The above spacer grid 2 is fabricated by horizontally and arranging in parallel the grid elements 11, each of which has an octagonal cross-section. In such a case, the grid elements 11 are welded together at the upper and lower area of the wall thereof. In the present invention, each of the grid elements 11 may be produced using a tube having an octagonal cross-section. Alternatively, each of the grid elements 11 may be made of a thin and narrow strip by forming the strip into a hollow single structure having an octagonal cross-section. When the grid element 11 is made of an octagonal tube, the tube is machined through a pressing process so as to form a plurality of spring windows 13, 14, line contact springs 12, and swirl flow vanes 30 on the tube. On the other hand, when the grid element 11 is produced using a thin and narrow strip, the strip is primarily formed into a tube structure having an octagonal cross-section, thus forming a tube having a desired size. The tube is, thereafter, machined through a pressing process wherein a plurality of spring windows 13, 14, surface contact springs 12, and swirl flow vanes 30 are formed on the tube in the same manner as that described for the case of using an octagonal tube. After the pressing process, the tube is subjected to a welding process wherein the edges are welded and seamed together. A desired grid element 11 is thus completely produced. The duct-type spacer grid 2, having a plurality of independent octagonal cells 8 within the grid elements 11, has an agreeable structure capable of more effectively resisting against a lateral impact in comparison with a conventional grid structure formed using the inner strips that intersect each other at right angles at the center of a subchannel 107. The reason why the duct-type grid 2 has such a structural advantage is as follows. That is, when the spacer grid 2 is geometrically designed to have a plurality of independent octagonal cells 8 as described above, the grid 2 more quickly and effectively transfers the lateral impact in every direction than in the case of a conventional strip-type spacer grid. Therefore, when the same lateral impact is applied to both types of spacer grids, the allowable impact load of the duct-type grid of this invention is remarkably greater than that of the conventional strip-type grid. As shown in FIGS. 6 and 7, a plurality of longitudinal spring windows, or left- and right-side windows 13 and 14 are formed on the sidewall of each of the grid elements 11 through a pressing process, with a strip-shaped line contact spring 12 being left within each of the windows 13 and 14 while extending at the center of the window. The central portion of each spring 12 is bent toward the center of the grid element 11. The spring 12 thus elastically supports an elongated fuel rod 6 at the bulged portion when the fuel rod 6 is inserted into the cell 8 of the grid element 11. Within each grid element 11, four line contact springs 12 are formed on diametrically opposite four of eight sidewalls. Therefore, the four springs 12 uniformly apply the same spring force to the external surface of a fuel rod 6, inserted into the cell 8, while accomplishing a balance. The spring windows 13 and 14 are used as openings for allowing coolant to pass through so as to more effectively cool the fuel rods 6 within the spacer grid 2. A collateral objective of the windows 13 and 14 is to give additional flexibility to the springs 12. FIG. 8 is a view, showing the operation of the springs 12 when they elastically support a fuel rod 6 within a grid element 11 of the spacer grid 2. When the springs 12 support the fuel rod 6 within the grid element 11, the springs 12 are brought into line contact with the external surface of the fuel rod 6. Therefore, the spring 12 is so-called a line contact spring. Since the springs 12 come into line contact with the fuel rod 6 as described above, the surface contact area of each spring 6 is increased, while contact pressure is applied from the spring 12 to the fuel rod 6. Therefore, it is possible for the spacer grid 2 of this invention to minimize surface damage of the fuel rods 6 due to fretting wear. FIG. 9 is a perspective view, showing the top portion of an octagonal grid element 11 included in the spacer grid of this invention, with two integral type swirl flow vanes 30 being provided at the top of the grid element 11. As shown in the drawing, each of the two vanes 30 comprises two blade parts: a main blade 31 and a sub-blade 32. Within each of the grid elements 11, the two vanes 30 are positioned to have different heights. In order to form each swirl flow vane 30 within a grid element 11, an extension part, integrally and axially extending from one sidewall of a grid element 11, is primarily bent toward the center of the main flow path 7, thus forming a sub-blade 32. Thereafter, the extension part is secondarily bent at the top of the sub-blade 32 toward the center of the main flow path 7, thus forming a main blade 31. In the swirl flow vanes 30, each sub-blade 32 provides an inclined surface, at which the main blade 31 starts to extend. The sub-blade 32 maximizes the size of the main blade 31. The different heights of the flow vanes 30 within each grid element 11 are accomplished by the different heights of the sub-blades 32. As the sub-blades 32 have such different heights, the cross-sectioned area of the flow path gradually varies, thus reducing the pressure loss caused by the swirl flow vanes 30. FIG. 10 is a plan view, showing an arrangement of integral type swirl flow vanes provided at the top of the duct-type spacer grid 2 of this invention. As shown in the drawing, two swirl flow vanes 30 are provided within each main flow path 7 of the spacer grid 2. Since each of the vanes 30 is bent outwardly, the vanes 30 are almost completely free from being undesirably brought into contact with the fuel rods 6. In addition, the swirling directions of the vanes 30 provided at the main flow paths 7 of the grid 2 are designed as follows. That is, the swirl flow vanes 30, provided at the main flow paths 7 on a perpendicular arrangement, are designed in that their swirling directions are opposite to each other. However, the vanes 30, provided at the main flow paths 7 on a diagonal arrangement, are designed to have the same swirling direction. FIG. 11 is a perspective view, showing the two swirl flow vanes 30 before they are bent to a desired configuration. As shown in the drawing, each of the vanes 30 extends from a unit grid element 11 while forming a triangular plate shape having a specifically curved profile and/or a specifically bent linear profile at both edges. Of course, it should be understood that each of the vanes 30 may have another shape in place of the above-mentioned triangular shape and/or another edge profile in place of the above-mentioned profiles in accordance with a desired swirl flow. The above duct-type spacer grid 2 has the following operational effect. That is, the grid element 11 of the spacer grid 2 comprises a duct having an octagonal cross-section, and so the grid element 11 does not pass across the center of the subchannel 107, through which coolant flows at a high speed. Therefore, the spacer grid 2 reduces pressure loss caused by the grid elements 11. Each of the grid elements 11 is formed as an independent cell 8 for placing and supporting an elongated fuel rod 6, thus having an improved resistance against a lateral impact applied to the sidewall of the grid 2. Within each of the main flow paths 7 of the spacer grid 2, four swirl flow vanes 30 are axially positioned to have different heights, thus reducing pressure loss at the main blades 32 of the vanes 30. Since each of the main blades 32 of the swirl flow vanes 30 is bent outwardly from the cells 8, the main blades 32 are almost completely free from being undesirably brought into contact with the fuel rods 6 when the fuel rods 6 are inserted into the cells 8. FIG. 12 is a perspective view of a duct-type spacer grid 2a for nuclear fuel assemblies in accordance with the second embodiment of this invention. In the spacer grid 2a of the second embodiment, the construction of both the duct-shaped grid elements 11 and the swirl flow vanes 30 remains the same as that described for the primary embodiment. But, the line contact springs 12a of the spacer grid 2a are positioned on the sidewalls around the main flow paths 7 different from the springs 12 of the primary embodiment. Therefore, the spring windows 13 and 14 are positioned on said sidewalls around the main flow paths 7 in the second embodiment. This structure finally increases the amount of coolant flowing through the windows 13 and 14 since a large amount of coolant passes through the main flow paths 7. Therefore, the spacer grid 2a of this embodiment improves the cooling effect for the fuel rods 6 within the grid elements 11. FIG. 13 is a perspective view of a duct-type spacer grid 2b for nuclear fuel assemblies in accordance with the third embodiment of this invention. In the spacer grid 2b of this embodiment, the construction of both the duct-shaped grid elements 11 and the swirl flow vanes 30 remains the same as that described for the primary embodiment. However, the arrangement of the line contact springs 12b of this embodiment is altered as follows. That is, the arrangement of the springs 12b of the neighboring grid elements 11 is rotated at an angle of 45xc2x0 one by one. In other words, the arrangement of the springs 12b in the third embodiment is accomplished by alternately using the arrangements of the springs 12 and 12a of the primary and second embodiments. FIG. 14 is a perspective view of a duct-type spacer grid 2c for nuclear fuel assemblies in accordance with the fourth embodiment of this invention. In the spacer grid 2c of this embodiment, the construction of the duct-shaped grid elements 11, the swirl flow vanes 30, the line contact springs 12 and the spring windows 13 and 14 remains the same as that described for the primary embodiment. However, the spacer grid 2c of this embodiment further comprises a plurality of additional coolant flow windows 15. The additional windows 15 are formed on the sidewalls between the spring-provided sidewalls of each grid element 11. This structure increases the amount of coolant flow between the cells 8, thus improving the cooling effect for the fuel rods 6 within the grid elements 11. As described above, the present invention provides a duct-type spacer grid for nuclear fuel assemblies. The spacer grid of this invention consists of a plurality of duct-shaped grid elements individually having an octagonal cross-section. The grid elements are closely arranged in parallel into a matrix structure prior to being welded together. In the spacer grid, the duct-shaped grid elements do not pass across the center of the subchannel 107, through which coolant flows at a high speed. Therefore, the spacer grid of this invention effectively reduces pressure loss caused by the grid elements. Each of the grid elements is formed as an independent cell effectively resisting against a lateral impact applied to the sidewall of the grid. In the duct-type spacer grid of this invention, two swirl flow vanes are axially positioned to have different heights within each subchannel 107. The swirl flow vanes thus reduce pressure loss at their main blades. In addition, since each of the main blades of the swirl flow vanes is bent outwardly from the cells, the main blades are almost completely free from being undesirably brought into contact with fuel rods when the fuel rods are inserted into the cells. Another advantage of this invention resides in that each elongated fuel rod is supported within a cell by line contact springs without using any dimple, with the surface contact springs being positioned at the same height. The spacer grid of this invention thus uniformly distributes its spring force on the spring contact area of each fuel rod, and so it almost completely prevents damage of the fuel rod due to fretting wear. 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. |
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050200844 | claims | 1. A method for analyzing a sample of ore for at least one heavy metal, said method comprising the steps of: exciting the ore with high energy x-rays to produce a fluorescence emission spectrum, and measuring the intensity of the K-emission bands of the metal or metals in the spectrum, said method further including: wherein photons are counted in each of two background energy bands lying to either side of a K.alpha..sub.1 peak and in each of two signal energy bands lying between the background bands to either side of a peak maximum, total counts of photons in the background and in the signal bands being compared, the two background bands being substantially equal in energy width and the two signal bands being substantially equal in energy width. (1) a gold K.alpha..sub.2 peak on both sides of a maximum, (2) a trough between the gold K.alpha.2 peak and a gold K.alpha.1 peak, (3) a slope of the gold K.alpha..sub.1 peak on the low energy side of its maximum, (4) a slope of the gold K.alpha..sub.1 peak on the high-energy side of its maximum, (5) a trough between the gold K.alpha..sub.1 peak and a mercury K.alpha..sub.1 peak, and (6) the mercury K.alpha..sub.1 peak on both sides of its maximum. (a) producing the X-rays by an X-ray tube with one of a plutonium or uranium anode and a secondary target, (b) exciting the ore sample with characteristic K X-rays of the material of the anode or secondary target, and (c) passing the fluorescence photons emitted by the same through an iridium filter. exciting the ore with high energy x-rays to produce a fluorescence emission spectrum, and measuring the intensity of the K-emission bands of the metal or metals in the spectrum, said method further including: wherein a sample of ore containing thorium is analyzed for uranium and optionally also for gold, the method further including counting the photons in each of six adjacent energy bands embracing respectively: (a) exciting the sample with high-energy bremsstrahlung X-rays having maximum energy at about 115 keV and produced by an X-ray tube with a tungsten anode and filtered through a metallic tin filter, (b) passing an X-ray fluorescence spectrum emitted by the sample at right angles to the exciting X-rays through a metallic iridium or platinum filter, (c) detecting fluorescence photons by a germanium detector, and (d) measuring intensity of K-emission bands of gold content of the sample. (a) a source of high-energy X-rays, (b) means to hold the sample in a path of the X-rays, (c) detector means to count fluorescence photons emitted by the sample, (d) means to compare counts of emitted photons in selected energy bands, an X-ray tube with a tungsten anode, a metallic tin filter, means to hold and retain a sample of ore in a path of the X-rays emitted from the tube and passed through the filter, an X-ray detector and means to detect the emission of photons of various energies from the sample, wherein one of a metallic platinum and an iridium filter is interposed between the sample and the detectors, and germanium detectors are used. 2. The method of claim 1, including using tungsten as an anode material of the x-ray tube. 3. The method of claim 1, wherein the ore is powdered gold ore having a gold content of below 10,000 parts per million. 4. The method of claim 2, wherein a gold content in 90% of the ore samples analyzed is up to 10 parts per million. 5. The method of claim 1, 2 or 3, wherein the ore contains and is analyzed for gold and uranium. 6. The method of any of claims 1-4, wherein the filter is tin metal. 7. The method of any of claims 1-4, wherein passing the fluorescence photons emitted by the sample through a heavy metal filter reduces the bremsstrahlung energy peak and thereby enhances a relative number of counts in the K-bands of the at least one heavy metal under analysis. 8. The method of claim 7 in which the filter is of iridium of platinum and the ore contains gold. 9. The method of claim 7 wherein the filter is of osmium and the ore contains platinum. 10. The method of any of claims 1-4, wherein the emitted photons are counted by at least one detector of high purity germanium. 11. The method of claim 10 in which the detector is a disc of active thickness 2-4 mm. 12. The method of any of claims 1-4, wherein the fluorescence spectrum is analyzed at a scattering angle of 80.degree.-100.degree.. 13. A method according to claim 1, wherein said eliminating step includes using a tin metallic filter. 14. The method of claim 1, wherein the ore is analyzed for gold, and wherein the K-emission peak is a gold K.alpha..sub.1 peak. 15. The method of claim 1 wherein a sample of ore containing at least one of mercury and tungsten is analyzed for gold, the method further including counting the photons in each of six adjacent energy bands embracing respectively: 16. The method of claim 1 for analyzing gold in an ore, the method further comprising: 17. A method for analyzing a sample of ore for at least one heavy metal, said method comprising the steps of: 18. A method of analyzing a sample of ore, said method comprising the steps of: 19. Apparatus for analyzing a heavy metal content of an ore sample, comprising: 20. The apparatus of claim 29 in which an anode is of tungsten. 21. The apparatus of claim 19 or 20 further comprising a heavy metal filter interposed between the sample and the detector means. 22. The apparatus of claim 19 or 20, wherein the detector means is at least one body of high purity germanium. 23. The apparatus of claim 22, wherein the detector means comprises a plurality of high purity germanium discs each 2-4 mm thick. 24. The apparatus of claim 19 or 20, wherein the fluorescence spectrum is viewed at a scattering angle in the range from 80.degree.-100.degree. to the exciting radiation. 25. The apparatus of claim 19 wherein the X-ray source is a tube with one of a plutonium or uranium anode and secondary target, and an iridium filter is interposed between the sample and the detecting means. 26. An apparatus for analyzing at least one of gold and uranium content of a sample of ore by X-ray fluorescence, comprising: 27. A method according to claim 1 or 14, wherein said method further includes passing fluorescence photons emitted by the sample through a metallic osmium filter before counting them. |
claims | 1. An exposure method, comprising: a first exposure step, using a first mask pattern, for transferring an image of the first mask pattern onto a first region upon a substrate, the transferred image including a fine pattern, wherein the first region is exposed with an exposure amount less than an exposure threshold value; and a second exposure step, using a second mask pattern, for transferring an image of the second mask pattern onto a second region upon the substrate, the transferred image including a rough pattern, wherein at least a portion of the second region is exposed with an exposure amount less than 3 the exposure threshold value, wherein exposures by said first and second exposure steps are carried out superposedly, prior to a development process, wherein a portion of a region in which the first region and the portion of the second region are superposed one upon another has an exposure amount greater than the exposure threshold value, wherein in said first and second exposure steps the first mask pattern and the second mask pattern are illuminated with light from a light source having passed through an illumination optical system having a curved surface mirror for changing a cross-sectional shape of the light, and wherein said first and second exposure steps use light having a wavelength not less than 0.5 nm and not greater than 20 nm. 2. A method according to claim 1 , wherein the first mask pattern is used to form a fine pattern in a predetermined portion of the workpiece, the second mask pattern is used to form a rough pattern in the predetermined region of the workpiece, and a smallest linewidth of the rough pattern is larger than that of the first mask pattern. claim 1 3. A method according to claim 1 , wherein each of the first mask pattern and the fine pattern has a periodic structure. claim 1 4. A method according to claim 1 , wherein the first mask pattern comprises one of a line-and-space pattern, a checkered pattern and a grid-like pattern. claim 1 5. A method according to claim 1 , wherein at least a portion of the first mask pattern and at least a portion of the fine pattern include a periodic pattern, and the period of the periodic pattern portion of the first mask pattern is substantially equal to the period of the periodic pattern portion of the fine pattern. claim 1 6. A method according to claim 1 , wherein at least a portion of the first mask pattern and at least a portion of the fine pattern include a periodic pattern, and the period of the fine pattern is substantially equal to 1/n times the period of the periodic pattern portion of the first mask pattern, wherein n is an integer not less than 2. claim 1 7. A method according to claim 1 , wherein said first exposure step is performed while placing the first mask pattern at a first position and at a second position shifted from the first position by an amount corresponding to a half of the period of the first mask pattern. claim 1 8. A method according to claim 1 , wherein the fine pattern is based on a Fresnel diffraction image of the first mask pattern. claim 1 9. A method according to claim 1 , wherein the rough pattern is based on a Fresnel diffraction image, and exposures in said first and second exposure steps are performed so that a peak position of an exposure intensity of the rough pattern and a peak position of an exposure intensity of the fine pattern are registered with each other. claim 1 10. A method according to claim 1 , wherein at least a portion of the fine pattern includes a periodic pattern, and a smallest linewidth of the second mask pattern is not less than a smallest period of the fine pattern. claim 1 11. A method according to claim 1 , wherein at least a portion of the fine pattern includes a periodic pattern, and a smallest linewidth of the second mask pattern is substantially equal to xc2xd times a smallest period of the fine pattern. claim 1 12. A method according to claim 1 , wherein the first and second exposure steps are performed with different spacings, respectively, held between the mask and the workpiece. claim 1 13. A method according to claim 1 , wherein the first and second mask patterns have absorbing material patterns, respectively, which are different in thickness from each other. claim 1 14. A method according to claim 1 , wherein at least one of said first and second exposure steps is performed by use of X-rays. claim 1 15. An exposure apparatus for performing exposure in accordance with a method as recited in claim 1 . claim 1 16. An exposure apparatus, comprising a shutter for adjusting an exposure amount with light from a light source, which reaches a workpiece, wherein said exposure apparatus performs the exposure of the workpiece in accordance with a method as recited in claim 1 . claim 1 17. A device manufacturing method, comprising: performing an exposure process to a workpiece, the exposure processing including (i) a first exposure step, using a first mask pattern, for transferring an image of the first mask pattern onto a first region upon a substrate, the transferred image including a fine pattern, wherein the first region is exposed with an exposure amount less than an exposure threshold value, and (ii) a second exposure step, using a second mask pattern including a rough pattern, for transferring an image of the second mask pattern onto a second region upon the substrate, the transferred image including a rough pattern, wherein at least a portion of the second region is exposed with an exposure amount less than the exposure threshold value, wherein exposures by said first and second exposure steps are carried out superposedly, prior to a development process, wherein a portion of a region in which the first region and the portion of the second region are superposed one upon another has an exposure amount greater than the exposure threshold value, wherein in said first and second exposure steps the first mask pattern and the second mask pattern are illuminated with light from a light source, having passed through an illumination optical system having a curved surface mirror for changing a cross-sectional shape of the light and wherein said first and second exposure steps use light having a wavelength not less than 0.5 nm and not greater than 20 nm; and developing the exposed workpiece, whereby a circuit pattern is formed on the workpiece. 18. A device, comprising: a substrate; and a circuit pattern formed on the substrate through an exposure process, the exposure process including performing an exposure process to a workpiece, the exposure process including (i) a first exposure step using a first mask pattern, for transferring an image of the first mask pattern onto a first region upon a substrate, the transferred image including a fine pattern, wherein the first region is exposed with an exposure amount less than an exposure threshold value, and (ii) a second exposure step, using a second mask pattern, for transferring an image of the second mask pattern onto a second region upon the substrate, the transferred image including a rough pattern, wherein at least a portion of the second region is exposed with an exposure amount less than the exposure threshold value, wherein exposure by the first and second exposure steps are carried out superposedly, prior to a development process, wherein a portion of a region in which the first region and the portion of the second region are superposed one upon another has an exposure amount greater than the exposure threshold value, wherein in the first and second exposure steps the first mask pattern and the second mask pattern are illuminated with light from a light source, having passed through an illumination optical system having a curved surface mirror for changing a cross-sectional shape of the light, and wherein the first and second exposure steps use light having a wavelength not less than 0.5 nm and not greater than 20 nm. 19. An exposure method, comprising: a first exposure step, using a first mask pattern, for transferring an image of the first mask pattern onto a first region upon a substrate, the transferred image including a fine pattern, wherein the fine pattern has a period which is substantially equal to 1/n times a product of a projection magnification and a period of a periodic structure of the first mask pattern, where n is an integer not less than 2; and a second exposure step, using a second mask pattern, for transferring an image of the second mask pattern onto a second region upon the substrate, the transferred image including a rough pattern, wherein exposures by said first and second mask exposure steps are carried out superposedly, prior to a development process, wherein in said first and second exposure steps the first mask pattern and the second mask pattern are illuminated with light from a light source, having passed through an illumination optical system having a curved surface mirror for changing a cross-sectional shape of light, and wherein said first and second exposure steps use light having a wavelength not less than 0.5 nm and not greater than 20 nm. 20. A method according to claim 19 , wherein a first region having an exposure amount less than an exposure threshold value is produced by the first exposure step, a second region having an exposure amount less than the exposure threshold value is produced by the second exposure step, and at least a portion of a third region in which the first and second regions are superposed one upon another has an exposure amount greater than the exposure threshold value. claim 19 21. A method according to claim 19 , wherein at least a portion of the fine pattern includes a periodic pattern, and a smallest linewidth of the second mask pattern is not less than a smallest period of the fine pattern. claim 19 22. A method according to claim 19 , wherein at least a portion of the fine pattern includes a periodic pattern, and a smallest linewidth of the second mask pattern is substantially equal to xc2xd times a smallest period of the fine pattern. claim 19 23. A device manufacturing method, comprising the steps of: performing an exposure process to a workpiece in accordance with an exposure method as recited in claim 19 ; and claim 19 developing the exposed workpiece, whereby a circuit pattern is formed on the workpiece. 24. A device comprising: a substrate; and a circuit pattern formed on the substrate through an exposure process made to a workpiece in accordance with an exposure method as recited in claim 19 , and a development process for developing the exposed workpiece. claim 19 25. An exposure apparatus for performing exposure in accordance with a method as recited in claim 19 . claim 19 26. An exposure apparatus, comprising a shutter for adjusting an exposure amount with light from a light source, which reaches a workpiece, wherein said exposure apparatus performs the exposure of the workpiece in accordance with a method as recited in claim 19 . claim 19 27. An exposure method, comprising: a first exposure step, using a first mask pattern, for transferring an image of the first mask pattern onto a first region upon a substrate, the transferred image including a fine pattern; and a second exposure step, using a second mask pattern, for transferring an image of the second mask pattern onto a second region upon the substrate, the transferred image including a rough pattern, wherein a smallest linewidth of the rough pattern is not less than twice a smallest linewidth of the fine pattern, wherein exposures by said first and second exposure steps are carried out superposedly, prior to a development process, wherein, in said first and second exposure steps, the first mask pattern and the second mask pattern are illuminated with light from a light source, having passed through an illumination optical system having a curved surface mirror for changing a cross-sectional shape of the light, and wherein said first and second exposure steps use light having a wavelength not less than 0.5 nm and not greater than 20 nm. 28. A method according to claim 27 , wherein a first region having an exposure amount less than an exposure threshold value is produced by the first exposure step, a second region having an exposure amount less than the exposure threshold value is produced by the second exposure step, and at least a portion of a third region in which the first and second regions are superposed one upon another has an exposure amount grater than the exposure threshold value. claim 27 29. A method according to claim 27 , wherein at least a portion of the first mask pattern includes a periodic pattern, and the period of the periodic pattern of the fine pattern is substantially equal to the period of the periodic pattern of the first mask pattern. claim 27 30. A method according to claim 27 , wherein at least a portion of the first mask pattern includes a periodic pattern, and the period of the periodic pattern portion of the fine pattern is substantially equal to 1/n times the period of the periodic pattern portion of the first mask pattern, wherein n is an integer not less than 2. claim 27 31. A device manufacturing method, comprising the steps of: performing an exposure process to a workpiece in accordance with an exposure method as recited in claim 27 ; and claim 27 developing the exposed workpiece, whereby a circuit pattern is formed on the workpiece. 32. A device comprising: a substrate; and a circuit pattern formed on the substrate through an exposure process made to a workpiece in accordance with an exposure method as recited in claim 27 , and a development process for developing the exposed workpiece. claim 27 33. An exposure apparatus for performing exposure in accordance with a method as recited in claim 27 . claim 27 34. An exposure apparatus, comprising a shutter for adjusting an exposure amount with light from a light source, which reaches a workpiece, wherein said exposure apparatus performs the exposure of the workpiece in accordance with a method as recited in claim 27 . claim 27 35. An exposure method, comprising: a first exposure step, using a first mask pattern, for transferring an image of the first mask pattern onto a first region upon a substrate, the transferred image including a fine pattern, wherein the first region is exposed with an exposure amount less than an exposure threshold value, and wherein the fine pattern has a period which is substantially equal to 1/n times a product of a projection magnification and a period of a periodic structure of the first mask pattern, where n is an integer not less than 2; and a second exposure step, using a second mask pattern, for transferring an image of the second mask pattern onto a second region upon the substrate, the transferred image including a rough pattern, wherein a smallest linewidth of the rough pattern is not less than twice a smallest linewidth of the fine pattern, wherein exposures by said first and second exposure steps are carried out superposedly, prior to a development process, wherein a portion of a region in which the first region and the portion of the second region are superposed one upon another has an exposure amount greater than the exposure threshold value, wherein in said first and second exposure steps the first mask pattern and the second mask pattern are illuminated with light from a light source, having passed through an illumination optical system having a curved surface mirror for changing a cross-sectional shape of the light, and wherein said first and second exposure steps use light having a wavelength not less than 0.5 nm and not greater than 20 nm. 36. A method according to claim 35 , wherein at least a portion of the fine pattern includes a periodic pattern, and a smallest linewidth of the second mask pattern is not less than a smallest period of the fine pattern. claim 35 37. A device manufacturing method, comprising the steps of; performing an exposure process to a workpiece in accordance with an exposure method as recited in claim 35 ; and claim 35 developing the exposed workpiece, whereby a circuit pattern is formed on the workpiece. 38. A device comprising: a substrate; and a circuit pattern formed on the substrate through an exposure process made to a workpiece in accordance with an exposure method as recited in claim 35 , and a development process for developing the exposed workpiece. claim 35 39. An exposure apparatus for performing exposure in accordance with a method as recited in claim 35 . claim 35 40. An exposure apparatus, comprising a shutter for adjusting an exposure amount from a light source, which reaches a workpiece, wherein said exposure apparatus performs the exposure of the workpiece in accordance with a method as recited in claim 35 . claim 35 |
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039649687 | description | DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the drawings, a fuel assembly 1 in accordance with the invention (FIG. 1) is installed in a nuclear reactor 2 (FIG. 2), in a core 3 of the reactor 2. In the embodiment in question, the nuclear reactor 2 is a fast reactor with a liquid-metal heat transfer fluid. The core 3 of the reactor 2 is surrounded by axial blankets 4, with a lateral blanket 5 and a neutron shielding 6. The fuel assemblies 1 (FIG. 1) are secured in a plenum chamber 8 (FIG. 2) of the reactor 2 by way of stems 7. The stem 7 (FIG. 1) has openings 9 formed therein, wherethrough the heat transfer medium is delivered into the assembly 1 from the chamber 8 (FIG. 2). In the upper portion of the assembly 1 (FIG. 1) parts 10 are formed wherethrough the heat transfer medium is drained from the assembly 1. Inside the assembly 1 there are housed fuel elements 11 secured in a support grid 12 installed in the lower portion of a housing 13 of the assembly 1. The fuel elements 11 are spatially fixed within the assembly 1 by means of spacer members 14 (FIG. 3), each formed as a bunch of wires disposed on the lateral surface of the fuel element 11 (FIG. 4) and arranged in a helical line. The bunch comprises three wires 15, 16 and 17, each of which adjoins the other two along the entire length thereof. The wires 15 and 16 (FIG. 5) constitute the base of the bunch adjoining the jacket of the fuel element 11 whereon they are disposed, whereas the third wire 17 is disposed externally in the space defined by the wires 15 and 16, and adjoins the adjacent fuel elements 11. In the embodiment being described, the wires 15, 16 and 17 are rigidly interconnected by welding between planes 18 (FIG. 4) of contact with the fuel elements 11 adjacent the fuel element 11 whereon said wires 15, 16 and 17 are disposed. The pitch of the helical line in which the spacer member is arranged is selected in each case so to provide the specified number of bearing points along the length of the fuel element. As has been earlier noted, the wires 15, 16 and 17 are interconnected only between the planes 18 of contact with the adjacent fuel elements 11, so that the wire 17 may be driven by transverse stresses to separate the wires 15 and 16 in the planes 18, enter the space thereby defined by the wires 15 and 16, and move therebetween as far as making contact with the surface of the fuel element 11 whereon said spacer member is disposed. The rigidity of the spacer member, which underlies its ability to undergo deformation under the effects of a certain transverse stress, may be varied by varying the distance from the junction of the bunch wires to the nearest plane of contact. The fuel element spacing in the assembly is selected so as to provide for normal cooling of the fuel elements throughout the entire service life of the assembly in the reactor, which is determined by the bunch wire diameter and may be varied within broad limits. On the other hand, the lateral compressibility, or travel of the spacer member depends only on the diameter of the external wire which may differ from the diameter of the other wires in the bunch. An alternative embodiment of the proposed nuclear reactor fuel assembly is possible which is similar to the one described hereabove and which comprises increasing the number of wires in the bunch. In this latter embodiment, a spacer member 19 (FIG. 6) is formed as a bunch of six wires, which makes it possible to additionally increase the lateral compressibility of this spacer member 19 by reducing the diameter of its wires required to provide for the predetermined spacing of the fuel elements in the assembly. With the spacer membe arranged in a helical line, there is no need to fit each and every fuel element therewith, for the spacer member of one fuel element is in contact with the adjacent fuel elements, providing support therefor. The latter consideration logically leads to yet another embodiment of the proposed nuclear reactor fuel assembly, similar to the first embodiment described hereabove. The distinguishing feature of the third embodiment resides in that the spacer members 14 (FIG. 7) are disposed on only some of the fuel elements, and provide support for all the fuel elements at least at three points along the perimeter thereof. In the embodiment being described, one out of every three fuel elements 11 is provided with a spacer member 14, with the pitch of the helical line in which the spacer member 14 being arranged is smaller than that selected for the first embodiment described hereabove. The proposed nuclear reactor fuel assembly operates as follows: In the course of operation of the fuel assembly 1 (FIG. 1) in the core 3 (FIG. 2) of the nuclear reactor 2, the fuel and the jackets of the fuel elements 11 (FIG. 59) undergo swelling, and hence increase in diameter. The resultant transverse stresses cause the spacer members 14 to be deformed. The external wire 17 of each spacer member 14 separates the wires 15 and 16, (FIG. 8) and enters into the space thus defined, thereby causing a considerable reduction in the contact stresses in the jackets of the fuel elements induced by the spacer members 14 acting thereupon. In their turn, the wires 15 and 16 tend to eject the wire 17, thereby imparting elasticity to the proposed spacer member 14 as a whole, so that the spacer member 14 continues to exert an effort on the adjacent fuel elements 11 required to keep the fuel elements uniformly spaced along the entire length of the assembly 1 (FIG. 1), thereby preventing local distortions of the geometry of the passage sections of the cells of the fuel elements 11 and maintaining constancy in the cooling conditions. The second and third embodiments of the proposed fuel assembly operate in a similar manner. With the proposed fuel assembly comprising spacer members formed as bunches of wires, the additional space can be provided between the fuel elements to take up the deformation of the fuel elements in the course of operation, with the size of the additional space being determined by the deforming capacity, or travel, of the spacer members. The nuclear reactor fuel assembly of this invention affords the possibility, which being comparatively easy to realize, of obviating any geometrical distortions of the individual cells of the fuel elements, whatever the initial spacing thereof is provided, to make up for the swelling of the fuel elements as the fuel burns up. The proposed arrangement likewise prevents considerable contact stresses from arising in the fuel element cans any deformation, and bars transmitted by the fuel element to the housing of the fuel assembly in the course of its operation. Also local distortions of the passage section geometry is eliminated which otherwise cause local temperature increases in the jackets of the fuel elements. All the above-mentioned advantages of the proposed fuel assembly are conducing to a longer service life of the fuel elements, and to improved economics of the fuel cycle of fast neutron power reactors employing the proposed fuel assembly. Furthermore, the design of the proposed fuel assembly is such tht it needs no appreciable changes in manufacturing procedures; also it requires small costs for its design and in testing purposes. |
abstract | A system and method for predicting acoustic loads expected on a boiling water reactor (BWR) may include a BWR scale model, a test fixture for generating air flow in the scale model, and one or measurement devices for monitoring system behavior to predict how acoustic loads may affect plant operation for the BWR being evaluated. |
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055442110 | claims | 1. A fresh fuel assembly for loading in a nuclear reactor, charged with uranium and no plutonium and having a plurality of fuel rods and at least one water rod surrounded by said fuel rods, said fuel assembly comprising: a fuel-charged zone including axially upper and lower end regions charged with natural uranium and an enriched uranium region between said upper and lower end regions, said enriched uranium region having three sections of an upper section, a middle section and a lower section of different levels of enrichment; said middle section having an average enrichment of a level higher than an average enrichment level of said upper and lower sections; a difference in the average enrichment level between said middle section and said lower section being smaller than a difference in the average enrichment level between said middle section and said upper section; wherein the fuel assembly comprises said fuel rods arranged in nine columns and nine rows; wherein a pair of water rods are disposed adjacent to each other in a central portion of the cross-section of said fuel assembly so as to occupy an area substantially equal to an area to be occupied by seven fuel rods; wherein a part of said plurality of fuel rods comprises burnable-poison-containing fuel rods containing uranium and a burnable poison and the rest of said plurality of fuel rods comprises uranium fuel rods containing uranium and no burnable poison; wherein a part of said uranium fuel rods have axially upper and lower end regions charged with natural uranium, and an enriched uranium region between said upper and lower end regions, said enriched uranium region having three sections of an upper section, a middle section and a lower section of different levels of enrichment, said middle section having an enrichment of a level higher than an enrichment level of said upper and lower sections, a difference in enrichment level between said middle section and said lower section being smaller than a difference in enrichment level between said middle section and said upper section; and wherein a burnable poison content per unit axial length in the upper section of each burnable-poison-containing fuel rod is smaller than a burnable poison content per unit axial length in other sections of said enriched uranium region of the burnable-poison-containing fuel rod. said first fuel rods including a plurality of kinds of uranium fuel rods each having upper and lower end regions charged with natural uranium and an intermediated enriched uranium region of a uniform axial enrichment distribution, and one kind of uranium fuel rods each having upper and lower end regions charged with natural uranium and an intermediate enriched uranium region composed of three sections of different levels of enrichment, the uranium fuel rods having said three sections of different enrichment levels being disposed in the outermost layer of fuel rods at portions between adjacent corners of the fuel assembly, as viewed in the cross-section of the fuel assembly, and other portions of the outermost layer of fuel rods, as viewed in the fuel assembly cross-section, being constituted by the first fuel rods having the uniform axial enrichment distributions in said enriched uranium regions. a first fuel assembly having a plurality of fuel rods charged with a nuclear fuel material and arranged in nine columns and nine rows and a pair of water rods which are arranged adjacent to each other at the central portion of the cross-section of said first fuel assembly and occupying an area which can accommodate seven fuel rods, said first fuel assembly containing a burnable poison; and a second fuel assembly having a plurality of fuel rods charged with a nuclear fuel and arranged in nine columns and nine rows and a pair of water rods which are arranged adjacent to each other at the central portion of the cross-section of said second fuel assembly and occupying an area which can accommodate seven fuel rods, said second fuel assembly containing a burnable poison of an amount greater than an amount of said burnable poison contained in said first fuel assembly; wherein a part of said plurality of fuel rods of said first and second fuel assemblies comprises burnable-poison-containing fuel rods containing uranium and a burnable poison and the rest of said plurality of fuel rods comprises uranium fuel rods containing uranium and no burnable poison; wherein each of said first and second fuel assemblies before loading in the nuclear reactor is charged with uranium and no plutonium and comprises a fuel-charged zone including axially upper and lower end regions charged with natural uranium, and an enriched uranium region between said upper and lower end regions, said enriched uranium having an upper section, a middle section and a lower section of different enrichment; said middle section having average enrichment of a level higher than an average enrichment level of said upper and lower sections; a difference in the average enrichment level between said middle section and said lower section being smaller than a difference in the average enrichment level between said middle section and said upper section; wherein a part of said uranium fuel rods has axially upper and lower end regions charged with natural uranium, and an enriched uranium region between said upper and lower end regions, said enriched uranium region having an upper section, a middle section and a lower section of different levels of enrichment, said middle section having an enrichment of a level higher than an enrichment level of said upper and lower sections, a difference in the enrichment level between said middle section and said lower section being smaller than a difference in the enrichment level between said middle section and said lower section; and wherein a burnable poison content per unit axial length in the upper section of each burnable-poison-containing fuel rod is smaller than a burnable poison content per unit axial length in other sections of said enriched uranium region of the burnable-poison-containing fuel rod. 2. A fresh fuel assembly according to claim 1, wherein said uranium fuel rods include first fuel rods, second fuel rods having an axial length shorter than an axial length said first fuel rods, the uranium fuel rods having said three sections, in said uranium region, of different levels of enrichment are included in said first fuel rods and not in said second fuel rods, the upper end of the nuclear-fuel-charged zone in each said second fuel rod being located within said middle section, the average enrichment, as viewed in the cross-section of the fuel assembly, of the portion of said middle section above said upper end of the fuel-charged zone in each second fuel rod being smaller than the average enrichment of the portion of said middle section below said upper end of the fuel-charged zone of said second fuel rods. 3. A fresh fuel assembly according to claim 2, wherein the difference in the average enrichment, said viewed in the cross-section of the fuel assembly, between the portion of said middle section below the upper end of said fuel-charged zone of said second fuel rod and said lower section thereof is lower than the difference in the average enrichment between the portion of said middle section above said upper end of the fuel-charged zone of said second fuel rod and said upper section thereof. 4. A fresh fuel assembly according to claim 2, wherein the enrichment of said enriched uranium region of said second fuel rod is higher than the average enrichment of the whole fuel assembly. 5. A fresh fuel assembly according to claim 4 wherein the content of the burnable poison per unit axial length is smallest in said upper section, medium in said middle section and greatest in said lower section. 6. A fresh fuel assembly according to claim 1, wherein said uranium fuel rods include first fuel rods, second fuel rods having axial lengths shorter than an axial length of said first fuel rods, 7. A fresh fuel assembly according to claim 1, wherein the axial length of the natural uranium regions ranges from 1/24 to 1/12 of the axial length of the whole fuel-charged zone. 8. A fresh fuel assembly according to claim 1, wherein the axial length of said upper section of said enriched uranium region ranges from 1/12 to 1/8 of the axial length of the whole fuel-charged zone. 9. A fresh fuel assembly according to claim 1, wherein the boundary between said lower section and said middle section is positioned within the range between 1/3 and 7/12 of the axial length of the whole fuel-charged zone as measured from the lower end of said fuel-charged zone. 10. A fresh fuel assembly according to claim 1, wherein fuel rods having higher enrichment than the average enrichment over the whole fuel assembly are disposed to form the outermost layer of fuel rods in the cross-section of the fuel assembly. 11. A fresh fuel assembly according to claim 1, wherein the rest of said uranium fuel rods includes at least one uranium fuel rod having axially upper and lower end regions charged with natural uranium and an enriched uranium region of an enrichment level substantially uniform axially thereof. 12. A nuclear reactor having a reactor core, said reactor core comprising: 13. A nuclear reactor according to claim 12, wherein said uranium fuel rods include first fuel rods and second fuel rods having axial lengths shorter than an axial length of said first fuel rods. 14. A nuclear reactor according to claim 12, wherein the content of the burnable poison per unit axial length is the smallest in said upper section, medium in said middle-section and the greatest in said lower section. 15. A nuclear reactor according to claim 12, wherein the average concentration of said burnable poison in said first fuel assembly is greater than in said second fuel assembly. 16. A nuclear reactor according to claim 12, wherein the first and second fuel assemblies which have stayed in the reactor core and burnt are disposed at four positions surrounding each of control rods which are disposed at the outermost portion and central portion of the cross-section of said reactor core. |
claims | 1. A collimator for a radiotherapy apparatus, comprising:a block of radiation-attenuating material for moving into and out of a beam of therapeutic radiation during delivery of the therapeutic radiation, the block having:a top face and a bottom face, each transverse to a propagation direction of the beam and defining a depth direction extending from the top face to the bottom face; anda front face, at least one main rear face, and at least two side faces, each face extending from the top face to the bottom face, the side faces extending from the front face to the at least one main rear face,wherein the front face forms a leading edge when the block is moved into the beam, andwherein the at least one main rear face is substantially planar in the depth direction of the block and non-parallel to the front face. 2. The collimator according to claim 1, wherein the at least one main rear face comprises a single main rear face extending between the two side faces. 3. The collimator according to claim 1, wherein the at least one main rear face comprises two main rear faces forming a concave V-shape transverse to the propagation direction of the beam, in which each face of the V-shape rear face is non-parallel to the front face. 4. The collimator according to claim 1, wherein the at least one main rear face is at an angle to the front face of between 10° and 80°. 5. The collimator according to claim 1, wherein the at least one main rear face is at an angle to the front face of between 30° and 60°. 6. The collimator according to claim 1, wherein the two side faces are substantially planar or parallel to each other. 7. The collimator according to claim 1, wherein at least one of the top face and bottom face are substantially planar. 8. The collimator according to claim 7, wherein the top face and bottom face are parallel and planar to each other. 9. The collimator according to claim 1, wherein the collimator is arranged to be mountable in a radiotherapy apparatus so as to be moveable back and forth in a direction transverse to the front face. 10. The collimator according to claim 1, wherein the block further includes a web material disposed against the at least one rear main face. 11. The collimator according to claim 1, wherein the block has a uniform thickness in the depth direction. 12. The collimator of claim 1, whereinthe block has a minimum thickness in a direction defined from the front face tothe at least one main rear face, the minimum thickness being determined based on a speed of movement of leaves of a multi-leaf collimator. 13. A radiotherapy apparatus comprising:a beam source and an associated primary collimator defining a rectangular aperture for a radiation beam emitted by the beam source, the aperture having a long dimension and a short dimension;a multi-leaf collimator with leaves moveable across the short dimension, and having a range of movement adequate to transport a tip of each leaf from one side of the aperture to the other side; anda block collimator having a depth in a propagation direction of a beam emanating from the beam source, the block collimator further having:a front face defining leading edge of the block when the block moves into the beam;at least one main rear face defining a trailing edge when the block moves into the beam, wherein the at least one main rear face is substantially planar in the direction of the depth of the block and non-parallel to the front face,wherein the block collimator is moveable in a direction aligned with the long dimension. 14. A method of operation of a radiotherapy apparatus according to claim 13, wherein the movement of the leaves and the collimator block are controlled so as to match the profile of a rear face of the collimator block extending in the direction of the radiation beam. 15. The method according to claim 14, wherein movement of the leaves and/or the collimator block is controlled so as to account for acceleration and/or deceleration of the moving leaves and/or collimator block. |
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051241137 | summary | BACKGROUND OF THE INVENTION The invention relates to a nuclear reactor with improved efficiency capable of better utilization of the fuel material of the core arrays. Nuclear reactors cooled and moderated by pressurized light water comprise a vessel containing the reactor core immersed in pressurized water filling the vessel. The core of the reactor comprises tall arrays relative to their cross-section arranged vertically and side by side. The arrays themselves consist of bundles of fissile fuel rods in contact by their external surface with the cooling water of the reactor. For the operation of the reactor, an assembly of control rods associated with certain arrays of the core is used. These control rods consist of parallel bars of strongly neutron-absorbing material which can be moved vertically within guide tubes replacing some fuel rods in the arrays forming the core. One of the major problems involved in the operation of nuclear reactors is to obtain high efficiency as regards the use of the nuclear fuel of the arrays. This fuel generally consists of uranium in the form of uranium oxide containing fertile uranium 238 preponderantly and a quantity of fissile uranium 235 which varies as a function of the enrichment of the fuel. During the operation of the reactor, the fissile fuel is consumed so that it is necessary to replace at least a part of the core arrays of the reactor after a certain period of operation. The cost of the operations to enrich, recharge, replace the used fuel and withdraw it is very high, so that it is desirable to make the best possible use of the fuel introduced into the reactor core in order to improve the economic operating conditions of the reactor. It is particularly attempted to effect the most complete possible combustion of the uranium contained in the material of the arrays. By improving the combustion of the uranium, it is possible either to prolong the useful life of the core for a given initial charge of fissile uranium, or to reduce the initial charge of fissile uranium in the core for a given useful life. In the former case, the operating costs of the nuclear reactor are reduced by effecting recharges at longer intervals of time. In the latter case, it will be possible, for example, either to reduce the volume and the total mass of the fuel rods of the core, or again to use a fuel with a lower degree of enrichment. In this way the cost of the fuel charge will be reduced. In order to operate the reactor, that is to say in order to regulate the reactivity of the core, neutron-absorbing materials are used either in the form of control rods which are inserted into the core of the reactor, or in the form of elements dissolved in the cooling and moderating water of the reactor. After the core is charged, its reactivity is high, so that it is necessary to use absorbing materials in increased quantity for the operation of the reactor. For example, clusters of rods containing consumable poisons are introduced into the guide tubes of some arrays of the core, or again neutron-absorbing poisons are introduced in considerable quantity into the cooling water. When the excess reactivity decreases due to the exhaustion of the fuel, the concentration of the neutron-absorbing poisons which are dissolved is decreased correspondingly. These neutron-absorbing poisons, which are necessary for the operation of the reactor in its initial state, are expensive in themselves and reduce the energetic efficiency of the fissile fuel contained in the core. It has been proposed to utilize the excess reactivity of the core in its initial state to produce a fissile fuel (plutonium 239) from the uranium 238 contained in the fuel of the arrays. To do this, the neutron energy spectrum in the core is shifted towards the high energies, by reducing the ratio of the volume of moderator to the volume of fuel in the core, during the first part of the fuel cycle. When the excess reactivity of the fuel becomes virtually zero, the ratio of volume of moderator to volume of fuel is restored to a value permitting the neutron spectrum to be restored to its customary zone for pressurized water nuclear reactors. The neutrons are then said to be "thermal" or "slow". This has the effect of producing a fresh excess of reactivity, which permits the period of use of the fuel to be prolonged. The ratio of moderator volume to fuel volume is influenced by introducing into the first part of the fuel cycle, bars of neutron-transparent material within some guide tubes of the core arrays. In this way the water contained by these guide tubes is expelled and the volume of moderator in the core is reduced by this amount. To obtain an appreciable effect, it is necessary to displace approximately 20% of the cooling water during almost 60% of the useful life of the core. To do this, it is necessary to use a very large number of neutron-transparent rods introduced into all the guide tubes of the core arrays, with the exception of those used for the guidance of the absorbing control rods of the reactor. This considerably complicates the conception and the design of the reactor. In fact, all the equipments containing the core of the reactor must be dimensioned so as to be able to perform the guidance above the core and the control in translation of the spectrum variation rods. This conception therefore dictates the insertion of a large number of guide tubes in that part of the internal equipments through which the heat-laden water normally escapes, to the detriment of the water balance of the reactor. It is therefore necessary to adopt a fresh conception of the circulating of the coolant in the reactor vessel. Moreover, the control in translation of these clusters necessitates the location on the cover of the vessel of a very large number of control mechanisms which must be interposed with the existing mechanisms of the control clusters permitting the running of the reactor. All these demands lead particularly, for equal power, to an increase in the dimensions of the reactor vessel compared to a conventional reactor. Moreover, a shift of the neutron spectrum towards the high energies involves an increased loss of neutrons outside the reactor and greater "embrittlement" of the steel of the reactor vessel. SUMMARY OF THE INVENTION The invention therefore aims to propose a nuclear reactor with improved efficiency comprising a vessel containing a core consisting of arrays of fissile fuel arranged side by side and vertically, immersed in pressurized light water forming the moderator and cooling fluid of the reactor and control rods of neutron-absorbing material movable vertically in the core to regulate the power of the reactor, this nuclear reactor permitting improved utilization of the fuel of the arrays and a reduction of the neutron flow, hence of the embrittlement effect of the steel of the reactor vessel, whilst being simple in design and conception. To this end, the nuclear reactor according to the invention further comprises: a massive metal partition of material reflecting high energy neutrons arranged at the circumference of the core and over its entire height, two layers of material absorbing low energy neutrons and containing fertile material arranged one at the lower part of the core and the other at its upper part, throughout its cross-section, an assembly of neutron energy spectrum variation rods of a material absorbing low energy neutrons associated with vertical movement devices permitting their total insertion into at least a part of the arrays of the core or their total extraction so as to vary the ratio of the volume of the moderator to the volume of fissile material in the core and to shift the neutron energy spectrum, these rods being distributed regularly throughout the cross-section of the core. According to a preferred embodiment, the spectrum variation rods are associated with one fuel array in two in the core, according to a checkerboard arrangement. |
045267138 | abstract | In a treatment system of radioactive waste solution including sodium sulfate generated from a boiling water type nuclear reactor, waste solution is fed into a thin film evaporator where the waste solution is evaporated and made into powder while precipitating in a peripheral surface of the evaporator vessel. The surface of the precipitated solid is wiped by rotating wiper blades and removed off as radioactive solid powder. The rotational speed of a rotor to which the wiper blades are secured is controlled at a minimum and necessary rotational speed which contributes to make the waste solution into the powder so that the rate of worn out of the wiper blade is decreased. |
description | This patent application claims the benefit of priority to U.S. Provisional Application No. 62/513,497, filed on Jun. 1, 2017, the contents of which are hereby incorporated by reference in their entirety for any purpose whatsoever. The invention described herein was made in the performance of work under a NASA contract and by an employee of the United States Government and is subject to the provisions of Public Law 96-517 (35 U.S.C. § 202) and may be manufactured and used by or for the Government for governmental purposes without the payment of any royalties thereon or therefore. In accordance with 35 U.S.C. § 202, the contractor elected not to retain title. Portable electronic devices require a power supply to function. The power supply may be internal to a device, such as a battery including electrochemical cells, or external to the tool, such as a battery pack coupled to the device. Radioisotope thermoelectric generators (RTGs) may be used as a power supply for large devices, such as deep space probes. RTGs are large, bulky, heavy, and costly and do not generate significant power, rendering RTGs unsuitable power supplies for smaller and/or portable electronic devices. A thermionic (TI) power cell includes a layer of radioactive material that generates heat due to radioactive decay, a layer of electron emitting material disposed on the layer of radioactive material, and a layer of electron collecting material. The layer of electron emitting material is physically separated from the layer of electron collecting material to define a chamber between the layer of electron collecting material and the layer of electron emitting material. The chamber is substantially evacuated, or evaluated as much as reasonably practicable, to permit electrons to traverse the chamber from the layer of electron emitting material to the layer of electron collecting material. Heat generated over time by the layer of radioactive material causes a substantially constant flow of electrons to be emitted by the layer of electron emitting material to induce an electric current to flow through the layer of electron collecting material when the layer of electron collecting material is connected to an electrical load. A method for generating an electric current includes heating a layer of electron emitting material disposed on a layer of radioactive material by radioactive decay of the layer of radioactive material. The method includes emitting electrons from the layer of electron emitting material to a layer of electron collecting material by thermionic emission. The layer of electron emitting material is physically separated from the layer of electron collecting material to define a chamber between the layer of electron collecting material and the layer of electron emitting material. The chamber is substantially evacuated to permit electrons to traverse the chamber from the layer of electron emitting material to the layer of electron collecting material. The method includes inducing an electric current to flow through the layer of electron collecting material connected to an electrical load. Heat generated over time by the layer of radioactive material causes a substantially constant flow of electrons to be emitted by the layer of electron emitting material. The disclosure further provides implementations of a thermionic (TI) power cell that includes a heat source, a heat conductive layer that provides heat from the heat source, a layer of electron emitting material disposed on the heat conductive layer, and a layer of electron collecting material. The layer of electron emitting material is physically separated from the layer of electron collecting material to define a chamber between the layer of electron collecting material and the layer of electron emitting material. The chamber is substantially evacuated to permit electrons to traverse the chamber from the layer of electron emitting material to the layer of electron collecting material. Heat generated over time by the heat source causes a substantially constant flow of electrons to be emitted by the layer of electron emitting material to induce an electric current to flow through the layer of electron collecting material when the layer of electron collecting material is connected to an electrical load. The heat source can include any suitable heat source, such as an exhaust manifold and the like. These and other features, advantages, and objects of the present invention will be further understood and appreciated by those skilled in the art by reference to the following specification, claims, and appended drawings. For purposes of description herein, the terms “upper,” “lower,” “right,” “left,” “rear,” “front,” “vertical,” “horizontal,” and derivatives thereof shall relate to the structure as oriented in FIG. 3. However, it is to be understood that the embodiments may assume various alternative orientations and step sequences, except where expressly specified to the contrary. It is also to be understood that the specific devices and processes illustrated in the attached drawings, and described in the following specification, are simply exemplary embodiments of the inventive concepts defined in the appended claims. Hence, specific dimensions and other physical characteristics relating to the embodiments disclosed herein are not to be considered as limiting, unless the claims expressly state otherwise. FIG. 1 is a block diagram schematic of an illustrative thermoelectric generator (TEG) 100 as known in the prior art. The illustrated TEG is a solid state device that converts heat flux directly into electrical energy. The TEG 100 includes a heat source 102. In a RTG, which is a type of TEG, the heat source 102 is a heat-generating radioactive material, such as plutonium-238 (Pu-238). The heat source 102 is coupled to an n-type semiconductor material 106 and a p-type semiconductor material 108 via contact 104. A heat sink 114 is coupled to the n-type semiconductor material 106 via contact 110 and the p-type semiconductor material 108 via contact 112. The heat generated by the heat source 102 drives electrons and hole carriers in the n-type and p-type semiconductor materials 106 and 108, respectively, toward the heat sink 114, which results in a continuous current flow. An electrical load 116 can be coupled to the contacts 110 and 112 to supply an electric current flow to the electrical load 116. However, the amount of current generated by TEGs is limited by multiple factors. Carrier concentrations of semiconductor materials used in TEGs are less than carrier concentrations of metals (about two to three orders of magnitude less) that are used in other types of power supplies. Moreover, the figure of merit (FoM) of the TEG 100 is limited. A high FoM requires high electrical conductivity and low thermal conductivity but this is a severe obstacle. The motion of electrons is measured as an electrical current and the kinetic energy of electrons is regarded as thermal energy at the same time. Although electrical and thermal conductivities are regarded as intrinsic properties of material, they are defined from Boltzmann statistical means. Moreover, because the FoM is inversely related to the thermal conductivity, an “ideal” TEG would have a thermal conductivity of zero. But if the thermal conductivity was zero, then no heat would flow in the TEG and, therefore, no thermal power could be converted to electrical power. To overcome these limitations, the size of the TEG 100 may be increased. For example, increasing the size of the n-type and p-type semiconductor materials 106 and 108 increases the number of carriers that can be driven by the heat source 102. However, the size of the heat source 102 must also be increased to generate sufficient heat to the larger n-type and p-type semiconductor materials 106 and 108. Consequently, TEGs are large, bulky, heavy, and costly, and not suitable power supplies for small electronic devices. RTGs require kilograms of radioactive material, which is difficult and expensive to produce in large quantities. Even though the output current generated by an RTG can be improved by increasing the size of the RTG, the current density still suffers from the limitations of TEGs described above. Furthermore, increasing the size of the RTG may not be a viable option because as the size of devices decrease, such as the size of space probes, the large sizes and weights of RTGs increase launch costs significantly for low earth orbit and even more for higher orbits. In contrast, the output current density of a TEG does not vary with a change in the size of the TEG. Therefore, the size of a TEG is scalable without affecting the output current density. FIG. 2 is a block diagram illustration of an exemplary thermionic generator (TIG) 220 in accordance with one or more embodiments of the present disclosure. In contrast to the prior art TEG 100 shown in FIG. 1, the TIG 220 uses thermionic emission to generate an electrical current. Thermionic emission is the thermally induced flow of charge carriers (e.g., electrons, ions) from a surface. Thermionic emission occurs when the thermal energy (heat) given to a charge carrier overcomes the work function of the material so that the charge carrier is emitted from the material. As used herein, “work function” refers to the minimum thermodynamic work (i.e., the amount of energy) necessary to remove a charge carrier from a solid material to a point in a vacuum immediately outside the surface of the solid material. The TIG 220 includes a heat source 228 coupled to an electron emitter 226. The heat source 228 provides heat to the electron emitter 226 to generate an electric potential in the electron emitter 226. As shown in FIG. 2, the electron emitter 226 can include a spike 224 to focus the electric potential generated in the electron emitter 226 at the tip of the spike 224. Focusing the electric potential aids in energizing electrons of the electron emitter 226 so that the electrons escape the electron emitter 226 entirely, via the spike 224, and into the vacuum chamber 230. The TIG 220 includes an electron collector 222 to collect the electrons emitted from the electron emitter 226. An electrical load 216 can be coupled to the electron collector 222 and the electron emitter 226 to supply an electric current flow to the electrical load 216. The current density generated by thermionic emission is quantified by the Richardson-Dushman equation. Heating the electron emitter 226 to approximately 800 to 1000 degrees Celsius (° C.) generates a measureable current density by thermionic emission. Shortening the gap 232 between the electron emitter 226 and the electron collector 222, or the gap 232 between the tip of the spike 224 and the electron collector 222 as shown in FIG. 2, increases the electric current flow generated by the TIG 220. The distance of the gap 232 can range between approximately 100 micrometers (μm) to 1 millimeter (mm). In contrast to the TEG 100 that requires semiconductor materials to operate, the illustrated TIG 220 uses conductive materials with low work functions for the electron emitter 226 and the electron collector 222. A material that has a low work function and a high availability of electrons for emission provides effective electron emission. Non-limiting examples of such electron emitting materials include metals such as copper (Cu) The electron emitter 226 can include a semiconductor material; however, semiconductor materials have lower electron densities than other electron emitting materials (e.g., metals). Thus, a large quantity of a semiconductor material is necessary to have sufficient electrons available to generate an electric current capable of powering an electric device. Further suitable emitter materials are described below. The TIG 220 includes fewer components than the TEG 100. While the current flow generated by the TEG 100 increases with an increase in the size of the components of the TEG 100, the current flow generated by the TIG 220 increases with an increase in the sharpness of the emitter spikes (e.g., 224) and the topological arrangement of the spikes (e.g., number of spikes per area (spike density)) on the surface of the electron emitter 226 of the TIG 220 (e.g., a smaller vacuum gap 232). Changing the distance of the gap 232 between the spike 224 and the electron collector 222 has a significant impact of the current flow generated by the TIG 220. If the gap 232 is too small, then the electrical field distribution breaks down so that electrons flow from the electron collector 222 to the electron emitter 226 via the spike 224, which can cause wear and damage to the electron collector 222, the spike 224, and/or the electron emitter 226 over time. If the gap 232 is too large, then stationary electrons, also referred to as a dark current, form on the surface of the electron emitter 226. Optimizing the distance of the gap 232 and/or the size of the spikes (e.g., 224) without reducing the number of electrons available for thermionic emission is preferable. The spikes can be uniform in size and shape to maintain a uniform gap 232. Thermionic emission increases dramatically as the distance of the gap 232 decreases. But, as explained above, there may be a risk of dielectric breakdown so that arcs of electrons travel from the electron collector 222 to the spike 224. If the gap 232 was small enough to cause quantum tunneling, then power generation capability of the TIG 220 increases even more because quantum tunneling permits far more electrons to reach the electron collector 222. However, the electron emitter 226, spike 224, and electron collector 222 would have to comprise the same material so that the electrons maintain the same energy after quantum tunneling. The disclosed thermionic (TI) power cells in accordance with one or more embodiments provide approaches for a scalable, portable power supply. Such TI power cells can be used in multiple applications including, but not limited to, space exploration and terrestrial uses (e.g., robots, rovers, beacons, remote sensors, and/or drones). The disclosed TI power cells can serve as a power supply for micro-satellites, thereby making micro-satellites more feasible for deep space exploration that would otherwise be too costly with a full-size probe. As explained above, TIGs are simpler and more efficient than TEGs. The efficiency of a TIG can be expected to be approximately 10-20% whereas the efficiency of a TEG can be expected to be approximately 7%. The disclosed TI power cells can be manufactured using semiconductor manufacturing techniques. Thus, the manufacturing costs associated with the TI power cells are less than the manufacturing costs associated with TEGs and RTGs. The disclosed TI power cell can supply power to multiple devices over a significant amount of time by removing a TI power cell from one device and coupling the TI power cell to another device. For example, implementations including plutonium-238 (Pu-238) as a heat source have long use lives because the half-life of Pu-238 is 87.7 years. However, the heat source is not limited to Pu-238 and other radioactive isotopes can be used. Implementations of the present disclosure can use any source of heat, such as engine exhaust manifolds, that generates sufficient heat for thermionic emission to occur. Unlike batteries and other electrochemical cells, the disclosed TI power cells are not susceptible to chemical decay within a TI power cell itself over time. Whereas the active regions of solar cells are directly exposed to the harsh environment of space, but the disclosed TI power cells can be enclosed, for example, by an outer shell, to provide protection against high energy particles, such as galactic cosmic rays (GCRs). The disclosed TI power cells can continue to operate even if the enclosure is damaged. The disclosed TI power cells operate continuously, simplifying use of the TI power cells as compared to batteries. The TI power cells can be a drop-in replacement power supply for devices previously using batteries and/or solar cells as a power supply. FIG. 3 is an open view of an exemplary TI power cell 340. The TI power cell 340 includes a layer of radioactive material 342. The layer of radioactive material 342 generates heat due to radioactive decay of the radioactive material. A non-limiting example of radioactive material is plutonium-238 (Pu-238). A layer of insulating material 344-1 is disposed on an upper surface of the layer of radioactive material 342 and a layer of insulating material 344-2 is disposed on a lower surface of the layer of radioactive material 342. At least one of the layers of insulating material 344-1 and 344-2 can be a thin-film insulator. The layers of insulating material 344-1 and 344-2 protect the electron emitting material and the electron collecting material of the TI power cell 340 from overheating and/or the radioactive material. The TI power cell 340 includes a layer of electron emitting material 346-1 disposed on the layer of insulating material 344-1 and a layer of electron emitting material 346-2 disposed on the layer of insulating material 344-2. Non-limiting examples of electron emitting material include copper (Cu), silicon (Si), silicon germanium (SiGe), diamond, tungsten (W), lanthanum hexaboride (LaB6), carbon nanotubes (CNTs) and diamond. The layers of electron emitting material 346-1 and 346-2 have a low work function. Such layers of electron emitting material may be formed or supplemented with a high-density array of protrusions such as spikes, bumps, ridges, and the like. The TI power cell 340 includes a layer of electron collecting material 348-1 above the layer of electron emitting material 346-1 and a layer of electron collecting material 348-2 below the layer of electron emitting material 346-2. A non-limiting example of electron collecting material is Cu. The layer of electron collecting material 348-1 is separated from the layer of electron emitting material 346-1 by an evacuated chamber, referred to herein as a vacuum gap 350-1 and the layer of electron collecting material 348-2 is separated from the layer of electron emitting material 346-2 by a similar vacuum gap 350-2. The TI power cell 340 can include a first terminal coupled to the layer of electron emitting material 346-1 or 346-2 and a second terminal coupled to the layer of electron collecting material 348-1 or 348-2. An electrical load 316 can be coupled to the first and second terminals so that an electric current is induced to flow through the layer of electron collecting material 348-1 or 348-2 when connected to the electrical load 316. FIG. 4 is a cross-sectional view of the exemplary TI power cell 340 of FIG. 3. The layer of radioactive material 342 can be a thin plate of radioactive material. In one implementation, the layer of radioactive material 342 includes up to five grams of Pu-238. Such small quantities of Pu-238 are readily producible, and can be reused for recycling if the TI power cell 340 is dismantled. The small quantity of radioactive material enables the size of the TI power cell 340 to be scalable. At least one implementation of the TI power cell 340 has dimension of 5 centimeters (cm) long, 3 cm, and 0.5 cm thick (approximately the size of a battery for a cellular phone) for use as a power supply of portable electric devices. The layer of radioactive material 342 can be encapsulated by the insulating material so that the layers of insulating material 344-1 and 344-2 shown separately in FIG. 3 are part of the layer of insulating material 344 shown in FIG. 4. Similarly, the layers of electron emitting material 346-1 and 346-2 shown separately in FIG. 3 can be part of the layer of electron emitting material 346 shown in FIG. 4. The layer of electron emitting material 346 can encapsulate the layer of insulating material 344. The layers of electron collecting material 348-1 and 348-2 shown separately in FIG. 3 can be part of the layer of electron collecting material 348 shown in FIG. 4. The layer of electron collecting material 348 is separated from the layer of electron emitting material 346 by the vacuum gap 350. The vacuum gaps 350-1 and 350-2 shown separately in FIG. 3 form a chamber that surrounds the layer of electron emitting material 346, the layer of insulating material 344, and the layer of radioactive material 342. Although not shown in FIG. 4, the TI power cell 340 can include vacuum insulation cladding that encompasses the layer of electron collecting material 348. Preferably, the vacuum insulation cladding can withstand a continuous temperature gradient of at least 500° C. per millimeter. FIG. 5 is a cross-sectional view of an exemplary layer of electron emitting material 346 including an array of spikes 524. As explained above, the spikes 524 focus the electrical potential generated in the layer of electron emitting material 346 at the tip of the spikes 524 so that the electrons escape the spikes 524 entirely. In one implementation, each spike 524 can be on the order of 100s of micrometers (μm) tall. The spikes are tall enough so that the voltage concentration at the tips of the spikes 524 does not get absorbed into the layer of electron emitting material 346 on which the spikes 524 rest. The array of the spikes 524 emits thermalized electrons effectively because the strength of an electric field generated by a collected charge density at the tip of one or more of the spikes 524 is sufficient to repel electrons into the vacuum gap 350. The surface of the layer of electron emitting material 346 (e.g., upper and/or lower surfaces and/or sides) can be modified topologically to include an array of the spikes 524. For example, the array of the spikes 524 can be formed using semiconductor microfabrication technology. Fin field-effect transistor (FinFET) semiconductor processing can achieve device sizes of twenty nanometers or less, for example, with electron emitting materials including Cu, Si, and SiGe. Such semiconductor microfabrication technology can be used to manufacture the layer of electron emitting material 346. Because well-established semiconductor manufacturing techniques can be used, costs associated with manufacturing the TI power cell 340 are reduced. Decreasing the size of the tips of the spikes 524, increases the voltage concentration at the tips. In at least one implementation, the spikes 524 are formed such that the tips of the spikes are spaced away from one another by approximately 100 μm. Decreasing the spacing between tips of the spikes 524 increases the electrical power generated by the TI power cell 340. However, if lateral spacing of the spikes 524 is less than the height of the spikes 524, then the electric fields from each spike will overlap, mimicking a flat surface and thereby decreasing the thermionic emission from the layer of electron emitting material 346 to the layer of electron collecting material 348, possibly causing electrons to jump from one of the spikes 524 to another. The lateral spacing can range between approximately 100 μm to 1 mm. The efficiency of the TI power cell 340 can be limited by the number of spikes 524 in an array formed on the layer of electron emitting material 346. Thus, increasing the number of the spikes 524 improves the utilization of heat generated by the layer of radioactive material 342, but increasing the number of the spikes 524 is limited by the height and lateral spacing of the spikes 524 as explained above. Implementations of the disclosed TI power cells can include an array of emitters on the layer of electron emitting material 346 other than the array of spikes 524. The surface of the layer of electron emitting material 346 can include various geometric formations (e.g., protrusions) to focus the electric potential in the layer of electron emitting material 346. For example, the layer of electron emitting material 346 includes an array of one-dimensional (1-D) ridges. FIG. 6 is a cross-sectional view of an exemplary layer of spacer material 652 between a layer of electron emitting material 346 and the layer of electron collecting material 348. Non-limiting examples of spacer material include oxides and nitrides. The layer of spacer material 652 can be deposited on the layer of electron emitting material 346 including an array of the spikes 524. The layer of spacer material 652 advantageously reduces the size of the vacuum gap 656 surrounding the tips 654 of the spikes 524 so that the layer of electron collecting material 348 is positioned a few micrometers or less from the tips 654 of the spikes 524. An exemplary method of depositing the layer of spacer material 652 as shown in FIG. 6 includes depositing spacer material on a layer of electron material 346 including an array of the spikes 524. The deposited spacer material is polished flat (e.g., by chemical mechanical polishing) so that thickness of the deposited spacer material above the tips 654 of the spikes 524 is a few micrometers. The spacer material above the tips 654 of the spikes 524 is selectively patterned and removed (e.g., chemically removed). The voids above the tips 654 of the spikes 524 are filled with a temporary spacer material that is removable with an etchant that does not affect the previously deposited spacer material. The layer of electron collecting material 348 is deposited on the deposited spacer material and the temporary spacer material. Vias (e.g., holes) are etched in the layer of electron collecting material 348 on or near the tips 654 of the spikes 524. The temporary spacer material is removed using an etchant inserted into the vias in the layer of electron collecting material 348. This exemplary method results in a few micrometer gap 656 between the tips 654 of the spikes 524 and the layer of electron collecting material 348. A vacuum can be applied to the vias in the layer of electron collecting material to evacuate the gaps 656. FIG. 7 is a graph 770 of the emission current density vs temperature of various compositions of an exemplary layer of electron emitting material including an array of spikes. Samples of copper (Cu), stainless steel 316 (SS316), tungsten (W) wire, n-doped silicon (Si), silicon germanium (SiGe)/aluminum oxide (Al2O3) film, and tantalum wire were heated to approximately 700° C. The tips of the spikes were 1 mm away from the layer of electron collecting material. The emission current shown in the graph 770 is normalized by the emission area for comparison between samples of different sizes. The emission current was measured with a picoammeter. The sample of Cu showed the best performance at approximately 1E-5 amperes per millimeter (A/mm). FIG. 8 is a graph 880 of the emission current density vs temperature of various compositions of an exemplary flat layer of electron emitting material. Samples of copper (Cu), stainless steel 316 (SS316), tungsten (W) wire, n-doped silicon (Si), silicon germanium (SiGe)/aluminum oxide (Al2O3) film, and tantalum wire were heated to approximately 700° C. The layer of electron emitting material was 3 mm away from the layer of electron collecting material. The emission current shown in the graph 880 is normalized by the emission area for comparison between samples of different sizes. The sample of n-doped Si and SiGe/Al2O3 films showed the highest current density at 3E-5 A/mm. Though aspects and features may in some cases be described in individual figures, it will be appreciated that features from one figure can be combined with features of another figure even though the combination is not explicitly shown or explicitly described as a combination. It is intended that the specification and drawings be considered as examples only, with a true scope of the invention being indicated by the following claims. |
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046541713 | summary | BACKGROUND OF THE INVENTION The present invention relates to a process for confining and limiting pollution of an isostatic pressing enclosure in the case of the processing therein of dangerous or radioactive products and when attempts are made, at the end of the pressing operation, to establish whether or not contamination has taken place. Isostatic pressing is widely used at present for all applications where a product has to be subject to an identical pressure action in all directions. This process can more particularly be used for producing mechanical parts by compaction of a powder, for the compaction of carbon-carbon composite materials, the compaction of tungsten carbide parts, the elimination of defects in certains parts or for compacting radioactive waste before the transportation thereof to a storage location. The principle of isostatic pressing or compression consists of depositing the material to be processed within an enclosure, into which is introduced a fluid under a high pressure, which can in certain cases be up to 6000 bars. In the case where the operation is performed hot, a furnace is installed within the enclosure and the temperature and pressure are simultaneously raised. The fluids used can be a liquid such as oil, or a neutral gas such as helium or argon or, possibly, nitrogen. The installation generally incorporates a compressor for raising the gas or liquid to the appropriate pressure. The isostatic pressing enclosure is generally shaped like a cylinder, closed at one of its ends by a fast handling plug, the different supply energies of the enclosure entering via a plug located at the other end. As the pressure prevailing in the enclosure is very high, it is necessary to protect it against radial forces which occur. For this purpose, it is possible to reinforce the enclosure wall with a coiled wire and place the same within a "mesh" shaped like a double horseshoe, within which is placed the enclosure, the shape and dimensions of the mesh being such that an accidental expulsion of the plugs is prevented. When the pressing operation is ended, simultaneously with allowing the temperature to return to the ambient temperature, the fluid contained in the enclosure is discharged through a decompression circuit, in order to bring the pressure within the enclosure to a value equal to atmospheric pressure before extracting the processed products. A special problem arises when the isostatic pressing enclosure is used for the compacting of nuclear waste or, in general terms, toxic or dangerous products. The latter are placed within a flexible material sheath, which is itself enclosed in a container placed within the enclosure. However, during the operation, leaks or a fracture of the container can occur and the gas which has become radioactive can possibly contaminate the different parts of the enclosure, particularly the furnace and the inner walls of the latter. Moreover, the discharge of the gas through the decompression circuit can cause the contamination thereof and the pollution of the atmosphere. At present, in order to obviate these disadvantages, the users of presses working on polluting, toxic or radioactive products, use a confinement means constituted be a very large glove box, within which is located the enclosure, the compressor or compressors supplying the same, together with the means maintaining the enclosure plug in place during the pressing operation, such as the aforementioned mesh. However, this procedure suffers from the disadvantage that, in the case of contamination, all the members within the glove box are contaminated. It is not always possible to carry out decontamination and all the means risk becoming unusable, which is very costly. SUMMARY OF THE INVENTION The problem of the present invention is to obviate this disadvantage by using a process and an apparatus making it possible to carry out inspections and controls by limiting contamination to a small part of the complete installation. According to the main feature of the process according to the invention, the isostatic pressing enclosure is positioned vertically and sealed in its upper part by a plug or cover and the pressing operation takes place with the aid of a fluid introduced into the enclosure which is raised to high pressure, wherein the following stages are performed: following an isostatic pressing operation, the fluid contained in the enclosure is discharged through a special decompression circuit; PA0 a glove box is placed above the enclosure and has at least one face to which is fixed a flexible membrane equipped with a glove; PA0 the glove box is sealingly fixed to a support plate integral with the enclosure, the plug being located within the glove box; PA0 the plug is removed and it is deposited within the glove box; PA0 the sampling and inspection operations necessary for detecting any contamination are performed. If the operation is carried out hot, the enclosure contains a furnace and the latter is advantageously protected by an insulating sleeve. In this case, once the glove box is sealingly fixed above the enclosure and the plug has been removed, the furnace insulating sleeve is removed and deposited within the glove box before carrying out the sampling and inspection operations. The invention also relates to an apparatus for performing this process. According to the main feature of this apparatus, it comprises: a decompression circuit incorporating at least one pipe connected to the enclosure, said pipe being equipped with at least one decompression valve and at least one filter, as well as a glove box having at least one face to which is fixed a flexible membrane equipped with a glove, the glove box also comprising means for sealingly fixing it to a support plate integral with the enclosure and means for removing the plug and depositing it within the glove box. If the enclosure is equipped with a furnace protected by an insulating sleeve, the glove box also has means for removing the sleeve from the enclosure and depositing it within the glove box. Finally, it can be advantageous to provide on the decompression circuit a system of taking samples for analyses and which is fitted to a pipe connected in parallel to the main decompression pipe. |
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