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041860497	abstract	Heat exchanger integrated into the main vessel of a molten combustible salt reactor comprising a reactor skirt containing the active core, a main vessel surrounding the reactor skirt, pumps and primary exchangers, an outer vessel which doubles the main vessel, a thermostatic coolant between the main and outer vessels maintaining the main vessel wall at a temperature below the melting temperature of a crust of salt which is inactive from a nuclear standpoint and which forms a coating of solid salt protecting the inner surface of said main vessel, wherein the calories are extracted from the core by means of autonomous heat transfer modules each comprising a primary exchanger and a pump, whereby each module is suspended in the intermediate space between the main vessel and the reactor skirt and supported by a bearing surface whose base is located on a cooperating bearing surface provided around an opening made in the wall of a supporting ferrule fixed close to the bottom of the reactor skirt and over the entire circumference of the latter, said ferrule extending from the skirt to the vicinity of the main vessel in the solid protective salt crust.
040381382	claims	1. In a liquid metal cooled fast reactor, a sub-assembly comprising a bundle of spaced fuel elements surrounded by a wrapper, said fuel elements each comprising an elongate cylindrical sheath at least a portion of which is of constant diameter cross section and containing nuclear fuel and having at least one spacing member for spacing the fuel element from neighboring elements in a bundle, said spacing member comprising a wire member helically wrapped around the sheath in the form of a helix over said portion of said fuel element sheath of constant diameter, the improvement wherein all of said wire members are identical and each of said wire members comprises a wire of constant diameter wound about its longitudinal axis in the manner of an open coil spring and wrapped around said fuel element as said helix such that said wire member contacts the fuel element at a series of regularly spaced intermittent points such that, in use, coolant can flow between said wire member and the fuel element and between the points of contact. 2. In a liquid metal cooled fast reactor, a sub-assembly comprising a bundle of spaced fuel elements surrounded by a wrapper, said fuel elements each comprising an elongate cylindrical sheath at least a portion of which is a constant diameter cross section and containing nuclear fuel and having at least one spacing member for spacing the fuel element from neighboring elements in a bundle, said spacing member comprising a wire member helically wrapped around the sheath in the form of a helix over said portions of said fuel element sheath of constant diameter, the improvement wherein all of said wire members are identical and each of said wire members comprises two wires of constant and equal diameter interwound with each other and wrapped around said fuel element as said helix such that said wire member contacts the fuel element at a series of regularly spaced intermittent points such that, in use, coolant can flow between said wire member and the fuel element and between the points of contact.
	claims	1. A contour collimator or adaptive filter for adjusting a contour of a ray path of x-ray radiation, the contour collimator comprising:a fluid impermeable for x-ray radiation; andelectroactive polymer elements actively connected to the fluid, the electroactive polymer elements being disposed and configured such that, by application of an electrical voltage to at least one of the electroactive polymer elements, the fluid is partly displaceable, an aperture forming the contour in the fluid being formed through the fluid. 2. The contour collimator or adaptive filter as claimed in claim 1, wherein the fluid is an eutectic alloy that includes gallium, indium and tin. 3. The contour collimator or adaptive filter as claimed in claim 1, further comprising a first layered unit with the fluid. 4. The contour collimator or adaptive filter as claimed in claim 3, further comprising a second layered unit with the electroactive polymer elements and electrical leads to supply the electrical voltage. 5. The contour collimator or adaptive filter as claimed in claim 4, further comprising a third layered unit permeable for x-ray radiation with a plurality of indentations disposed in the shape of a grid. 6. The contour collimator or adaptive filter as claimed in claim 5, wherein the first layered unit is disposed between the second layered unit and the third layered unit such that, on application of the electrical voltage, the electroactive polymer elements are pressable into the indentations of the third layered unit, andwherein the fluid is displaced from areas below the indentations so that the aperture is produced in the first layered unit. 7. The contour collimator or adaptive filter as claimed in claim 1, further comprising:at least one voltage source; andswitching elements that connect the electroactive polymer elements electrically to the at least one voltage source. 8. The contour collimator or adaptive filter as claimed in claim 7, further comprising an electrical control unit operable to switch on the switching elements such that the aperture is formable. 9. The contour collimator or adaptive filter as claimed in claim 6, wherein a plurality of layered units of the first layered unit, the second layered unit, and the third layered unit are stacked. 10. The contour collimator or adaptive filter as claimed in claim 2, further comprising a first layered unit with the fluid. 11. The contour collimator or adaptive filter as claimed in claim 10, further comprising a second layered unit with the electroactive polymer elements and electrical leads to supply the electrical voltage. 12. The contour collimator or adaptive filter as claimed in claim 11, further comprising a third layered unit permeable for x-ray radiation with a plurality of indentations disposed in the shape of a grid. 13. The contour collimator or adaptive filter as claimed in claim 12, wherein the first layered unit is disposed between the second layered unit and the third layered unit such that, on application of the electrical voltage, the electroactive polymer elements are pressable into the indentations of the third layered unit, andwherein the fluid is displaced from areas below the indentations so that the aperture is produced in the first layered unit. 14. The contour collimator or adaptive filter as claimed in claim 2, further comprising:at least one voltage source; andswitching elements that connect the electroactive polymer elements electrically to the at least one voltage source. 15. The contour collimator or adaptive filter as claimed in claim 3, further comprising:at least one voltage source; andswitching elements that connect the electroactive polymer elements electrically to the at least one voltage source. 16. The contour collimator or adaptive filter as claimed in claim 6, further comprising:at least one voltage source; andswitching elements that connect the electroactive polymer elements electrically to the at least one voltage source. 17. The contour collimator or adaptive filter as claimed in claim 16, further comprising an electrical control unit operable to switch on the switching elements such that the aperture is formable. 18. The contour collimator or adaptive filter as claimed in claim 17, wherein a plurality of layered units of the first layered unit, the second layered unit, and the third layered unit are stacked. 19. A method for adjusting a contour of a ray path of x-ray radiation with a contour collimator or adaptive filter, the method comprising:applying an electrical voltage to a number of electroactive polymer elements;forming an aperture of the contour in a fluid impermeable for x-ray radiation by performing the applying, the forming comprising partly displacing the fluid by the electroactive polymer elements activated by the electrical voltage. 20. The method as claimed in claim 19, further comprising activating and deactivating the electroactive polymer elements by switching elements conducting the electrical voltage.
	claims	1. A neutron generator, comprising:a pre-moderator block of moderating material having an upper surface, a lower surface, a first and a second end, first and second side surfaces, a first length, a first width less than the first length, and a first thickness;a cylindrical acceleration chamber having a first diameter the first width of the pre-moderator block, sealed at one end to the upper surface of the pre-moderator block adjacent the first end of the pre-moderator block, with a vertical axis perpendicular to the upper surface, the acceleration chamber having a height and a top cover at a second end away from the pre-moderator block;a vacuum pump engaging the acceleration chamber, evacuating the acceleration chamber to a high vacuum;a plasma ion chamber opening into the acceleration chamber through an ion extraction iris through the top cover of the acceleration chamber on the vertical axis of the acceleration chamber;a gas source providing deuterium gas to the plasma ion chamber;a microwave energy source ionizing the gas in the plasma ion chamber;a cylindrical primary isolation well extending a distance into the pre-moderator block from the upper surface, centered on the vertical axis of the acceleration chamber;a secondary isolation well in a shape of a hollow cylinder surrounding the primary isolation well, to a depth somewhat less than the distance of the primary isolation well, within the first diameter of the acceleration chamber;a water-cooled titanium target disk having a target surface orthogonal to the axis of the acceleration chamber, the target disk having a diameter smaller than a diameter of the isolation well, positioned at a lower extremity of the isolation well, the target disk biased to a negative DC voltage; and electrically grounded metal cladding covering all otherwise exposed surfaces of the pre-moderator block;wherein ions extracted through the ion extraction iris are accelerated to bombard the titanium target at the lower extremity of the primary isolation well, producing energetic neutrons that pass through and are moderated by the pre-moderator block, and wherein any path along a surface from the titanium target to an electrically grounded element is necessarily maximized by the primary and secondary isolation wells. 2. The neutron generator of claim 1 wherein the material of the pre-moderator block is Ultra-High-Molecular-Weight Polyethylene (UHMWPE), or High-Density Polyethylene (HDPE), or polytetrafluoroethene (PTFE). 3. The neutron generator of claim 2 wherein surfaces of the primary and secondary isolation wells are formed in continuous curves and are roughened to enhance resistance to high-voltage flashover. 4. The neutron generator of claim 1 further comprising supply and return water channels lengthwise through the pre-moderator block from the second end of the pre-moderator block to the titanium target, providing cooling water cooling the target. 5. The neutron generator of claim 1 further comprising a female socket for a high-voltage male connector at the second end of the pre-moderator block, coupled to a high-voltage bus bar implemented lengthwise through the pre-moderator block, to the target, for biasing the target to a negative DC voltage. 6. The neutron generator of claim 1 wherein both the first and second side surfaces of the pre-moderator block are angled inward from vertical by thirty degrees for at least a portion of the height, enabling six neutron generators to be placed with the angled side surfaces fully adjacent, forming a closed ring about a center point. 7. The neutron generator of claim 1 wherein both the first and second side surfaces of the pre-moderator block are angled inward from vertical by forty-five degrees for at least a portion of the height, enabling eight neutron generators to be placed with the angled side surfaces fully adjacent, forming a closed ring about a center point.
	description	This application is a divisional application claiming priority under 35 U.S.C. § 120 to U.S. patent application Ser. No. 16/260,889, entitled GRAIN BOUNDARY ENHANCED UN AND U3Si2 PELLETS WITH IMPROVED OXIDATION RESISTANCE, which claims benefit under 35 U.S.C. § 119 (e) to U.S. Provisional Application Nos. 62/655,421, filed Apr. 10, 2018 and 62/623,621, filed Jan. 30, 2018, the entire disclosures of which are hereby incorporated by reference herein. This invention was made with government support under Contract No. DE-NE0008222 awarded by the Department of Energy. The U.S. Government has certain rights in this invention. The invention relates to fuels for nuclear reactors, and more particularly to methods of improving corrosion resistance of nuclear fuels. Enhancing the safety and performance of light water reactors is an ongoing subject of research. Uranium Nitride (UN) and Uranium Silicide (U3Si2) fuels have been selected as the leading candidates for advanced light water reactor fuel due to their high thermal conductivity and density. One of the major weaknesses for UN fuel, however, is its interaction with water and steam at normal operating conditions and high temperatures. The reaction of U3Si2 with water and steam is less severe than UN but any improvement is beneficial. It has been reported in the literature that the grain boundaries of UN and U3Si2 are preferentially attacked when exposed to water or steam and appear to be the major cause for rapid reaction and disintegration of these fissile materials. UN and U3Si2 are fuels with much improved thermal conductivity and density compared to most fuel types. If the water and steam corrosion resistance problem can be solved for UN and U3Si2, it will become a much more attractive accident tolerant fuel pellet. A method for adding additives or dopants to Uranium Nitride (UN) and Uranium Silicide (U3Si2) pellets to improve their water corrosion resistance in nuclear reactor coolant during operation and in high temperature steam in loss of coolant accidents conditions is described. It is found that UN pellets have minimal oxidation resistance in water and steam even at 200° C. U3Si2 has better oxidation resistance than UN but still reacts with air, water, or steam at temperatures higher than 360° C. See E. Sooby Wood, et.al, “Oxidation behavior of U—Si compounds in air from 25 to 1000° C.”, Journal of Nuclear Materials, 484 (2016) pp. 245-b 257. A method for improving corrosion resistance of nuclear fuels is described herein which includes mixing a powdered fissile material selected from the group consisting of UN and U3Si2 with an additive selected from oxidation resistant materials wherein the powdered fissile material comprises grains having grain boundaries, pressing the mixed fissile and additive materials into a pellet, and sintering the pellet to a temperature greater than the melting point of the additive, sufficient for melting the additive for coating the grain boundaries of the fissile material and densifying the pellet. The additive selected may also have a median particle size distribution significantly lower than the median particle size distribution of the UN or U3Si2 while having a melting point greater than the UN or U3Si2. In various aspects, the oxidation resistant additive may have a melting point lower than the sintering temperature of the fissile material. In various aspects, when the melting point of the oxidation resistant additive is greater than the sintering temperature of UN or U3Si2, the oxidation resistant particles can have a median particle size distribution less than 10% than that of the UN or U3Si2. By the method described herein, small amounts of oxidation resistant compound(s) (less than 20 wt %) are incorporated into the fissile material, (i.e., UN and U3Si2) at the grain boundaries of the material and thus achieve improved oxidation resistance. The additives may be in powder form and may be added or mixed with U3Si2 or UN powders before pressing into pellets and sintering. The additives may be coated to the U3Si2 or UN powders to form protective layers before pressing into pellets and sintering. The oxidation resistant particles may also be applied through vapor deposition (such as physical vapor deposition, chemical vapor deposition, and atomic layer deposition) to green (unsintered) pellets of UN or U3Si2 to coat the outside of the pellet and penetrate into the green pellet as the green pellet has a lot of open pores/channel through the pellet. Upon sintering, the oxidation resistant material will be incorporated into the outside grain structure (grain boundary) of the UN or U3Si2. In certain aspects, the additives include one or a mixture of molybdenum, titanium, aluminum, chromium, thorium, copper, nickel, manganese, tungsten, niobium, zirconium, yttrium, cerium, magnesium, alloys containing at least 50 atomic % of at least one of molybdenum, titanium, aluminum, chromium, thorium, copper, nickel, manganese, tungsten, niobium, zirconium, yttrium, cerium, and magnesium, magnesium nitride, ZrSi2, ZrSiO4, CrSi2, BeO, and UO2 and glassy materials, such as a borosilicate glass. Either the additive or mixture of additives to be mixed with the fissile material has a lower melting point than UN or U3Si2 or, the additive or mixture of additives and the nuclear fuel form low melting point eutectics. In various aspects, densification is achieved via liquid phase sintering or co-sintering. Pellets can be sintered, for example, by using sintering methods selected from the group consisting of pressureless sintering, hot pressing, hot isostatic pressing, spark plasma sintering, field assisted sintering, or flash sintering. Those skilled in the art will recognize that any suitable known sintering method may be used. Also described herein is a nuclear fuel comprising a pellet comprised of compressed and densified grains of a fissile material selected from the group consisting of UN and U3Si2, and an oxidation resistant additive, preferably present in amounts less than about 20% by weight of the fissile material, that coats at least a portion of the grain boundaries of the fissile material. In certain aspects, the additives include one or a mixture of molybdenum, titanium, aluminum, chromium, thorium, copper, nickel, manganese, tungsten, niobium, zirconium, yttrium, cerium, magnesium, alloys containing at least 50 atomic % of at least one of molybdenum, titanium, aluminum, chromium, thorium, copper, nickel, manganese, tungsten, niobium, zirconium, yttrium, cerium, and magnesium, magnesium nitride, ZrSi2, ZrSiO4, CrSi2, BeO, and UO2 and glassy materials, such as a borosilicate glass. As used herein, the singular form of “a”, “an”, and “the” include the plural references unless the context clearly dictates otherwise. Thus, the articles “a” and “an” are used herein to refer to one or to more than one (i.e., to at least one) of the grammatical object of the article. By way of example, “an element” means one element or more than one element. In the present application, including the claims, other than where otherwise indicated, all numbers expressing quantities, values or characteristics are to be understood as being modified in all instances by the term “about.” Thus, numbers may be read as if preceded by the word “about” even though the term “about” may not expressly appear with the number. Accordingly, unless indicated to the contrary, any numerical parameters set forth in the following description may vary depending on the desired properties one seeks to obtain in the compositions and methods according to the present disclosure. At the very least, and not as an attempt to limit the application of the doctrine of equivalents to the scope of the claims, each numerical parameter described in the present description should at least be construed in light of the number of reported significant digits and by applying ordinary rounding techniques. Further, any numerical range recited herein is intended to include all sub-ranges subsumed therein. For example, a range of “1 to 10” is intended to include any and all sub-ranges between (and including) the recited minimum value of 1 and the recited maximum value of 10, that is, having a minimum value equal to or greater than 1 and a maximum value of equal to or less than 10. Methods are described herein for increasing the oxidation resistance of the grain boundaries of fissile materials, such as UN and U3Si2 nuclear fuels, so that interactions with water or steam can be suppressed and the washout of fuel pellets can be minimized should a leak in the fuel rod occur. Improving the oxidation resistance of the grain boundaries will improve the resistance to the oxidation reaction and the resulting fragmentation as the less dense UO2 is formed, which is the key degradation mechanism when U3Si2 and UN are exposed to water or steam at higher temperatures. The grain boundary modification could be the most effective method to improve the corrosion and oxidation resistance of high density fuels like U3Si2 and UN. A method for improving the oxidation resistance of the grain boundaries and improving the corrosion resistance of nuclear fuels is described herein. The method includes mixing a powdered fissile material selected from the group consisting of UN and U3Si2 with an additive selected from oxidation resistant materials. In various aspects, the additives may have a melting point lower than the sintering temperature of the fissile material. The mixture is pressed into a pellet, then sintered to a temperature greater than the melting point of the additive. As the additive melts, it flows around the still solid grains of the fissile material, coating the grain boundaries of the fissile material and densifying the pellet. In various aspects, when the melting point of the oxidation resistant particles is greater than the sintering temperature of UN or U3Si2, the oxidation resistant particles can have a median particle size distribution less than 10% than that of the UN or U3Si2. In certain aspects, the additives may be coated to the U3Si2 or UN powders to form protective layers before pressing into pellets and sintering. The oxidation resistant particles may also be applied through vapor deposition (such as physical vapor deposition, chemical vapor deposition, and atomic layer deposition) to green (unsintered) pellets of UN or U3Si2 to coat the outside of the pellet and penetrate into the green pellet as the green pellet has a lot of open pores/channels through the pellet. Upon sintering, the oxidation resistant material will be incorporated into the outside grain structure (grain boundary) of the UN or U3Si2 pellets. The additives distributed along grain boundaries may stop fission gas releases from the U3Si2 grains such as Xe and Kr, as well as volatile fission products like Iodine. This will result in lower rod internal pressure which improves operating margins and the dry storage. In addition to oxidation resistance, the corrosion resistance phase will also prevent U3Si2 from interacting with cladding, plenum spring, and other rod internal components such as spacers which separate U3Si2 from end plug and plenum springs. The additives may be in powder form and may be added or mixed with U3Si2 or UN powders before pressing into pellets and sintering. The additives may be coated to the U3Si2 or UN powders to form protective layers before pressing into pellets and sintering. The desired characteristics of the additive are that it is an oxidation resistant material and that it has a melting point lower than the melting point of the fissile material, either UN or U3Si2, with which it is mixed; and in various aspects, at least 200° C., and in certain aspects, from 200 to 300° C. lower than the sintering temperature of the fissile material. Alternatively, if the melting point of the oxidation resistant particles is greater than the sintering point of UN or U3Si2, then the oxidation resistant particles can have a median particle size distribution less than 10% than that of the UN or U3Si2, and in certain aspects, a median particle size distribution less than 1% than that of the UN or U3Si2. In certain aspects, exemplary additives include one or a mixture of molybdenum, titanium, aluminum, chromium, thorium, copper, nickel, manganese, tungsten, niobium, zirconium, yttrium, cerium, magnesium, alloys containing at least 50 atomic % of at least one of molybdenum, titanium, aluminum, chromium, thorium, copper, nickel, manganese, tungsten, niobium, zirconium, yttrium, cerium, and magnesium, magnesium nitride, ZrSi2, ZrSiO4, CrSi2, BeO, and UO2 and glassy materials, such as a borosilicate glass. Either (1) the additive or the mixture of additives have lower melting points than the fissile material (UN or U3Si2) with which it is mixed or (2) the additive or the mixture of additives and the nuclear fuel form low melting point eutectics. For example, the fissile material may be UN and may be mixed with BeO as the additive. BeO has a melting point lower than the sintering temperature of UN. Those skilled in the art will be able to determine the melting points or sintering temperatures of the fissile material and the melting points of the oxidative resistant additives, or determine the melting point eutectics of the selected fissile material and additive, and select, according to the method described herein, the appropriate additive or mixture of additives for mixing with either UN or U3Si2. The fuel and additive mixture may be formed into pellets by compressing the mixture of particles in suitable commercially available mechanical or hydraulic presses to achieve the desired “green” density and strength. A basic press may incorporate a die platen with single action capability while the most complex styles have multiple moving platens to form “multi-level” parts. Presses are available in a wide range of tonnage capability. The tonnage required to press powder into the desired compact pellet shape is determined by multiplying the projected surface area of the part by a load factor determined by the compressibility characteristics of the powder. To begin the process, the mixture of particles is filled into a die. The rate of die filling is based largely on the flowability of the particles. Once the die is filled, a punch moves towards the particles. The punch applies pressure to the particles, compacting them to the geometry of the die. In certain pelleting processes, the particles may be fed into a die and pressed biaxially into cylindrical pellets using a load of several hundred MPa. Following compression, the oxidation resistant particles may also be applied through vapor deposition (such as physical vapor deposition, chemical vapor deposition, and atomic layer deposition) to the green (unsintered) pellets of UN or U3Si2 to coat the outside of the pellet and penetrate into the green pellet as the green pellet has a lot of open pores/channel through the pellet. The pellets are sintered by heating in a furnace at temperatures varying with the material being sintered under a controlled atmosphere, usually comprised of argon. Sintering is a thermal process that consolidates the green pellets by converting the mechanical bonds of the particles formed during compression into stronger bonds and greatly strengthened pellets. Upon sintering, the oxidation resistant material will be incorporated into the outside grain structure (grain boundary) of the UN or U3Si2 pellets. The compressed and sintered pellets are then cooled and machined to the desired dimensions. Exemplary pellets may be about one centimeter, or slightly less, in diameter, and one centimeter, or slightly more, in length. Referring to the FIGURE, the hexagons in Part A represent grains of UN or U3Si2 fuel 12 with grains of an additive 14 mixed with the UN or U3Si2 fuel grains 12. As sintering proceeds and the temperature reaches and, in various aspects, surpasses the melting or softening point of the additive, the additive 14 melts or softens, and as shown in Part B of the FIGURE, flows about the mixture, coating all or at least a portion of the UN or U3Si2 fuel grains 12 on the grain boundaries. If the additive has a higher melting point than the sintering temperature of U3Si2 or UN, the fine particles are sintered into the grain boundaries of the larger U3Si2 or UN grains. The fuel 12 grain boundary coverage by the additive 14 in the FIGURE is an ideal case, and the actual coverage may be lower. It is preferred that the additive phase is interconnected. In various aspects, densification is achieved via liquid phase sintering or co-sintering. Pellets can be sintered, for example, by using sintering methods selected from the group consisting of liquid phase sintering, pressureless sintering, hot pressing, hot isostatic pressing, spark plasma sintering, sometimes referred to as field assisted sintering or pulsed electric current sintering. Those skilled in the art will recognize that any suitable known sintering method may be used. In a typical sintering process for producing nuclear fuel pellets, the pressed powder pellets are heated so that adjacent grains fuse together, producing a solid fuel pellet with improved mechanical strength compared to the pressed powder pellet. This “fusing” of grains results in an increase in the density of the pellet. Therefore, the process is sometimes called densification. In hot isostatic pressing, the compaction and sintering processes are combined into a single step. In various aspects, the sintering may be done by a liquid phase sintering and co-sintering processes, both advanced processing technologies which have not heretofore been used in nuclear fuel manufacturing. In liquid phase sintering, the solid grains are insoluble in the liquid so the liquid phase can wet on the solid phase. This insolubility causes the liquid phase to wet the solid, providing a capillary force that pulls the grains together. At the same time, the high temperature softens the solid, further assisting densification. During heating, the particles sinter. The solid grains rearrange when a melt forms and spreads. Subsequent densification is accompanied by coarsening. The liquid wets and penetrates between the solid grains. See German, R. M., Sun, P. & Park, S. J., J Mater Sci (2009) 44:1. https://doi.org/10.1007/s10853-008-3008-0. In various aspects, the sintering process may be done using spark plasma sintering, wherein external pressure and an electric field are applied simultaneously to enhance the densification of the pressed powder pellets. A pulsed DC current directly passes through the die, as well as the powder compact. The electric field driven densification supplements sintering with a form of hot pressing, to enable lower temperatures and shorter amount of time than typical sintering. The heat generation is internal, in contrast to the conventional hot pressing, where the heat is provided by external heating elements. Pressureless sintering is a well-known sintering method involving the sintering of a powder compact (sometimes at very high temperatures, depending on the powder) without applied pressure. This avoids density variations in the final pellet, which occurs with more traditional hot pressing methods. In another aspect, the sintering may be done by hot isostatic pressing. In this techniques, powders are usually encapsulated in a metallic or glass container. The container is evacuated, the powder out-gassed to avoid contamination of the materials by any residual gas during the consolidation stage and sealed-off It is then heated and subjected to isostatic pressure sufficient to plastically deform both the container and the powder. The rate of densification of the powder depends upon the yield strength of the powder at the temperatures and pressures chosen. At moderate temperature the yield strength of the powder can still be high and require high pressure to produce densification in an economic time. The method produces a nuclear fuel comprising a pellet comprised of compressed and densified grains of a fissile material selected from the group consisting of UN and U3Si2, and an oxidation resistant additive, preferably present in amounts less than about 20% by weight of the fissile material, that coats at least a portion of the grain boundaries of the fissile material. In certain aspects, the additives include one or a mixture of molybdenum, titanium, aluminum, chromium, thorium, copper, nickel, manganese, tungsten, niobium, zirconium, yttrium, cerium, magnesium, alloys containing at least 50 atomic % of at least one of molybdenum, titanium, aluminum, chromium, thorium, copper, nickel, manganese, tungsten, niobium, zirconium, yttrium, cerium, and magnesium, magnesium nitride, ZrSi2, ZrSiO4, CrSi2, BeO, and UO2 and glassy materials, such as a borosilicate glass. The present invention has been described in accordance with several examples, which are intended to be illustrative in all aspects rather than restrictive. Thus, the present invention is capable of many variations in detailed implementation, which may be derived from the description contained herein by a person of ordinary skill in the art. All patents, patent applications, publications, or other disclosure material mentioned herein, are hereby incorporated by reference in their entirety as if each individual reference was expressly incorporated by reference respectively. All references, and any material, or portion thereof, that are said to be incorporated by reference herein are incorporated herein only to the extent that the incorporated material does not conflict with existing definitions, statements, or other disclosure material set forth in this disclosure. As such, and to the extent necessary, the disclosure as set forth herein supersedes any conflicting material incorporated herein by reference and the disclosure expressly set forth in the present application controls. The present invention has been described with reference to various exemplary and illustrative embodiments. The embodiments described herein are understood as providing illustrative features of varying detail of various embodiments of the disclosed invention; and therefore, unless otherwise specified, it is to be understood that, to the extent possible, one or more features, elements, components, constituents, ingredients, structures, modules, and/or aspects of the disclosed embodiments may be combined, separated, interchanged, and/or rearranged with or relative to one or more other features, elements, components, constituents, ingredients, structures, modules, and/or aspects of the disclosed embodiments without departing from the scope of the disclosed invention. Accordingly, it will be recognized by persons having ordinary skill in the art that various substitutions, modifications or combinations of any of the exemplary embodiments may be made without departing from the scope of the invention. In addition, persons skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the various embodiments of the invention described herein upon review of this specification. Thus, the invention is not limited by the description of the various embodiments, but rather by the claims.
	description	The present invention pertains to X-ray imaging systems. It particularly pertains to interventional X-ray imaging systems. X-ray imaging procedures have not only become the standard for many diagnostic applications in the medical field but have also seen increasing use across a variety of surgical or interventional applications. Interventional procedures are less invasive alternatives to open surgery wherein implements are inserted through relatively small incisions or natural orifices. Interventional procedures can be performed under X-ray guidance by using X-ray fluoroscopy systems that provide real-time projection images. Increasingly interventional specialists are relying on 3-D images for intraoperative guidance and verification, such as images acquired by computed tomography (CT). In contrast to clinical CT scanners these images are acquired at relatively slow rotation speeds and typically have lower image quality than clinical CT scans. In some cases interventional specialists may use bi-planar fluoroscopy systems. In these systems two single-plane fluoroscopic systems can image the patient from two different angular positions. Advantages of using such systems include the ability to provide the interventional specialist with additional spatial information and to reduce the amount of contrast agent that needs to be injected into the patient in order to view a contrast-highlighted internal feature from multiple angles. Radiation exposure can be a concern with all X-ray imaging techniques. Concern has grown for fluoroscopy and CT in particular due to their relatively high levels of radiation exposure. While the benefits of these techniques can outweigh the risks of radiation exposure, provide imaging equipment that performs the imaging task at lower dose. A drawback of some low-dose systems is a relatively small field of view, limiting use to cardiac applications. What is needed is an X-ray imaging system that can address the need for 3-D images during interventional procedures and is flexible enough for multiple interventional imaging applications. What is further needed is a low dose imaging system for interventional imaging applications. The present invention pertains to a method of medical imaging comprising forming a computed tomography dataset by acquiring image data from two source-detector pairs while rotating the pairs simultaneously through non-overlapping sets of angles around an axis of rotation. The sets of angles can be at least 90 degrees each, and the rotations may be completed in less than 3 seconds by a motor or other element. Additional image data can also be acquired from the source-detector pairs while stationary and positioned at a predetermined angle relative to one another, and the computed tomography dataset can be used for registration of this image data. The predetermined angle may space the source-detector pairs between 80 and 100 degrees apart around an imaging volume. Sources of the source-detector pairs may be configured to emit radiation from a plurality of discrete locations on their faces or may be point sources. In the former case, the computed tomography dataset may also be used as a prior, e.g. a Bayesian prior, for reconstruction of a three-dimensional image from the additional image data and for correction of image artifacts. A three-dimensional reconstruction from the image data acquired with the source-detector pairs in static positions may be completed with a maximum-likelihood maximization in voxel space, in and ordered-subset maximization framework, or with a maximum likelihood algorithm for transmission tomography. The sources of source-detector pairs may be configured such that less than 10 cm exists between the pluralities of discrete emissive locations when the sources are positioned as near as possible. This configuration may allow a relatively large field of view. The source-detector pairs may also be configured to image a region of interest with higher exposure relative to other regions of the imaging volume. These and other objects and advantages of the various embodiments of the present invention will be recognized by those of ordinary skill in the art after reading the following detailed description of the embodiments that are illustrated in the various drawing figures. Reference will now be made in detail to embodiments of the present invention, examples of which are illustrated in the accompanying drawings. While the invention will be described in conjunction with these embodiments, it will be understood that they are not intended to limit the invention to these embodiments. On the contrary, the invention is intended to cover alternatives, modifications and equivalents, which may be included within the spirit and scope of the invention as defined by the appended claims. Furthermore, in the following detailed description of embodiments of the present invention, numerous specific details are set forth in order to provide a thorough understanding of the present invention. However, it will be recognized by one of ordinary skill in the art that the present invention may be practiced without these specific details. In other instances, well-known methods, procedures, components, and circuits have not been described in detail as not to unnecessarily obscure aspects of the embodiments of the present invention. FIG. 1 is a diagram representing two source-detector pairs of an embodiment of the present invention. Embodiments of the present invention may feature two or three X-ray sources and two or three X-ray detectors. In FIG. 1 a first source 14 and a first detector 16 are positioned such that the face of first source 14 and the face of first detector 16 may be parallel and separated by a distance long enough to accommodate a patient or subject for imaging. A second source 15 and a second detector 17 may be similarly positioned relative to one another; the face of second source 15 may be parallel to the face of second detector 17 with a distance long enough to accommodate imaging subjects maintained between them. A first axis 11 has been drawn connecting the centers of the faces of first source 14 and first detector 16, and a second axis 12 has been drawn connecting the centers of the faces of second source 15 and second detector 17. These axes may be physical, e.g. beams or other supports, or non-physical, e.g. maintained by maintaining the spatial relationship of a source and detector relative to one another. For example, in embodiments of the present invention medical C-arms, U-shaped arms, O-arms, physical axes of other shapes, tracks along which source and detector motion can be confined, closed gantries, or any other mechanical structure may be used to maintain the fixed distances between, orientations of, and rotations about an isocenter by two source-detector pairs. In some embodiments of the present invention, the distance maintained between source and detector in source-detector pairs can be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 inches, or any non-integer number of inches between these enumerated values. These embodiments of the present invention may be particularly useful for the imaging of extremities, including but not limited to podiatric, dental, and similar imaging applications. In some embodiments of the present invention, the distance maintained between source and detector in source-detector pairs can be between 20 inches and 120 inches, 30 inches and 100 inches, or 40 inches and 70 inches, inclusive, and any other integer or non-integer number of inches within the enumerated ranges. For example, the distance may be 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 46, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, or 56 inches, or any non-integer number of inches between the enumerated values. A point of overlap 18 between first axis 11 and second axis 12 may correspond to an isocenter of the system, e.g. a point at which an X-ray beam traveling from the center of the face of first source 14 to the center of the face of first detector 16 would intersect an X-ray beam traveling from the center of the face of second source 15 to the center of the face of second detector 17. While angle 13 between first axis 11 and second axis 12, relating to the separation between the two sources or between the two detectors, may change, the isocenter of the system can remain fixed in space at point of overlap 18. In one embodiment of the present invention, first source 14 and second source 15 may be point sources, wherein X-rays are emitted from a single discrete point on the face of the source. A point source may be an X-ray tube or any other means of emitting X-ray radiation from a small discrete point. In this embodiment, first detector 16 and second detector 17 may be any type of X-ray detecting sensors, including but not limited to flat-panel detectors or image intensifier systems. In another embodiment of the present invention, first source 14 and second source 15 may be multi-focal spot sources, wherein X-rays can be emitted from a plurality of discrete locations of the face of the source. A multi-focal spot source may be array of carbon nanotubes, a scanning beam source, a scanning laser source, an array of single cathode emitters, or any other source capable of emitting radiation from a plurality of discrete locations on its face. First detector 16 and second detector 17 may be any type of X-ray detecting sensor including but not limited to fast photon-counting detectors. One example of a multi-focal spot source and photon-counting detector combination that may be utilized in this embodiment of the present invention is disclosed in U.S. Pat. No. 5,729,584 entitled “Scanning Beam X-ray Imaging System” and hereby incorporated by reference. The faces of sources and detectors in embodiments of the present invention may also be circular, square, polygonal, rectangular, trapezoidal, triangular, or any other shape. Embodiments of the present invention utilizing multi-focal spot sources may comprise source faces of diameters or widths ranging from 1″ to 5″, 5″ to 10″, 10″ to 15″, or 15″ to 20″, inclusive, or any other integer or non-integer number of inches within the enumerated ranges. Embodiments of the present invention utilizing pixelated detectors in conjunction with multi-focal spot sources may comprise detectors of diameters or widths ranging from 1 to 2 cm, 2 to 3 cm, 3 to 4 cm, 4 to 5 cm, 5 to 6 cm, 6 to 7 cm, 7 to 8 cm, 8 to 9 cm, 9 to 10 cm, 10 to 11 cm, 11 to 12 cm, 12 to 13 cm, 13 to 14 cm, 14 to 15 cm, 15 to 16 cm, 16 to 17 cm, 17 to 18 cm, 18 to 19 cm, or 19 to 20 cm, inclusive, or any non-integer number of centimeters between the enumerated values. Embodiments of the present invention utilizing point X-ray sources may emit X-rays from an emissive point or spot having a diameter or width of 0.1 mm to 5 mm, inclusive. Emissive points or spots may further have a width, diameter, or full-width at half maximum between 0.1 mm and 0.5 mm, 0.5 mm and 1.0 mm, 1.0 mm and 2.0 mm, 2.0 mm and 3.0 mm, 3.0 mm and 5.0 mm, or any other integer or non-integer number of millimeters within the enumerated ranges. Diameters or widths may also be larger than 5.0 mm, though image resolution may degrade with increasing focal spot size. Embodiments of the present invention utilizing point sources may comprise detectors of widths or diameters of 0 to 10 cm, 10 to 20 cm, 20 to 30 cm, 30 to 40 cm, 40 to 50 cm, or 50 to 60 cm, inclusive, or any other integer or non-integer number of centimeters within the enumerated ranges. For example, detectors may have widths or diameters of 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, or 35 cm, inclusive, or any non-integer number of centimeters between the enumerated values. It is possible that detector widths or diameters may be greater than 60 cm for some applications. In embodiments of the present invention comprising multi-focal spot source, each source-detector pair may provide tomosynthetic image data due to the plurality of focal spots on the source face; a specific plane or multiple planes within the field of view of a given source-detector pair may be reconstructed. System comprising multi-focal spot sources can also demonstrate superior contrast-to-noise and lower patient exposure at a given level of image quality compared to point-source, or shadowgraph, systems, as detectors can be smaller and collect less scattered radiation. FIG. 2 is a diagram illustrating a source-detector pair comprising a multi-focal spot source and small detector of one embodiment of the present invention. Source 31 can project beams of radiation from a plurality of discrete locations towards a detector. For example, a beam 34 can be emitted from a discrete focal spot 33 and configured to illuminate detector 35. In one embodiment of the present invention, the distances and orientations of two X-ray source-detector pairs may be maintained by the sources and detectors being mounted on two medical C-arms. FIG. 3 is a diagram showing an X-ray source and X-ray detector mounted on opposing ends of a medical C-arm in one embodiment of the present invention. A second C-arm holding a second source-detector pair may also be affixed at joint 22. Rotation of the C-arm 21 may occur around a rotation axis through a joint 22 and an isocenter 19 of the system; in the view of FIG. 3, first source 14 and first detector 16 may be rotated into or out of the page. Both C-arms can rotate around a common axis of rotation through a shared isocenter. An isocenter may or may not be located at the midpoint between a source and detector in a source-detector pair. It may be desirable that a human patient can be positioned at the isocenter of the system so that rotations occur around the patient and the targeted patient volume remains in focus even if the angle between the source-detector pairs changes. In point-source systems imaging performance may be optimized by positioning a patient nearer to the detector than to the source. Therefore, in an embodiment of the present invention comprising point-source systems, source-detector pairs may be connected to one another in a manner that creates a system isocenter closer to the detectors than to the sources. For example, with reference again to FIG. 1, the system may be configures such that point of overlap 18 is nearer to first detector 16 and second detector 17 than first source 14 and second source 15 along first axis 11 and second axis 12, respectively. In tomosynthetic imaging systems, imaging performance may be optimized by positioning a patient nearer to the source than the detector. An embodiment of the present invention comprising tomosynthetic systems may be configured such that a system isocenter is closer to the sources than the detectors of two source-detector pairs. A visualization of an offset or non-centered isocenter may be a pair of scissors. A pair of scissors is made up of two pieces, each piece typically being a blade with a handle. The handle is typically shorter than the blade, but a joint is usually placed between the handle and the blade, not at the actual midpoint of a piece. Blades and handles rotate around the joint, or isocenter, of the scissors despite differing lengths on either side of the joint. The curved geometry of C-arms may permit the placement of an area or volume of a patient to be imaged at the isocenter of two source-detector pairs in embodiments of the present invention. A patient may be positioned on a bed or table or otherwise secured within the crook or “C” of the C-arms while imaging occurs. Furthermore, an apparatus to which the two C-arms are affixed may rotate the C-arms around other axes to widen the range of possible patient positions. For example, with reference to FIG. 3, joint 22 may be moved vertically or along a curved track. The rotation of source-detector pairs around an isocenter, e.g. the change in an angle between the source-detector pairs, may be electronically controllable. For example, an embodiment of the present invention may include an electronically controlled mechanical motor, set of motors, actuators, or other means of rotating the source-detector pairs. The means of rotation may be coupled to an electronic input unit allowing a user to select rotation parameters to be implemented during imaging. Optional input values may also include frame rate, e.g. the frequency at which images are captured, total number of degrees to be rotated, or other imaging-related parameters. Alternatively, an embodiment may be configured to convert a user-selected end-result, e.g. a number of images of a given level of quality taken at specific angular intervals, into appropriate operating parameters, e.g. angular speed, frame rate, etc., required to achieve said end-result. The calculation of operating parameters may account for system-specific capabilities; information regarding the speed at which the imaging system can collect sufficient data for image reconstruction at a given level of quality, the speeds to which axes can be safely accelerated or decelerated, the angles through which axes can rotate without contact between sources and detectors, and so forth may be included in the determination of operating parameters. Embodiments of the present invention may be used for at least three different imaging procedures: computed tomography (CT), bi-planar imaging, and fluoroscopy. Physicians within an operating room, catheterization lab (“cath lab”), or other facility may wish to perform one, two, or three of these imaging procedures for pre-operative diagnosis, intraoperative guidance, post-operative verification, and other purposes. Embodiments of the present invention with these three different modalities can prove space- and cost-efficient and may also incur speed and image quality benefits compared to single-modality systems. In a computed axial tomography (CAT) scan a patient may be positioned on a table and slid through an enclosed, circular gantry. An X-ray source and arc of X-ray detectors may be positioned opposite one another inside the gantry and rotated at a high speed to acquire images from a series of different angles or views. A comprehensive three-dimensional image of the imaging volume can be formed by reconstructing the series of views and can be used for identification of cancers, tumors, infarctions, fractures, and other internal conditions. This type of three-dimensional image may be desirable during a medical procedure, for example to accurately position an implement that has been inserted into the patient, e.g. an ablative device or catheter, or to ensure that a medical condition has been sufficiently corrected, e.g. cancer removed or infarction cleared, before completing the surgery and closing incisions. However, during an interventional or surgical procedure positioning a patient for a conventional CAT scan may be difficult or impossible. A CT dataset or image may instead be acquired by rotating a C-arm on opposing ends of which are mounted an X-ray source and an X-ray detector such that the X-ray source and detector can rotate around the patient, sliding an O-arm around the patient within which source and detector rotate, or by similarly lower-profile methods. To accurately reconstruct a three-dimensional representation of a targeted volume, images may be taken through at least 180 degrees, plus some number of degrees that account for beam properties, around the imaging volume. An intraoperative CT imaging system may be designed to acquire images through the 180 plus degrees as quickly as possible because patient motion between frames, even from a patient's breathing or heartbeat, can introduce motion blurring into individual frames or the final three-dimensional reconstruction. Imaging speed may also be important as patients may be involved in a time-sensitive medical procedure or otherwise ill or injured. The maximum rotational speed safely achievable in intraoperative CT may be significantly lower than in a CAT scan. In one embodiment of the present invention, two X-ray source-detector pairs may be rotated in a manner such that one source-detector pair can sweep out a number of degrees while the other source-detector pair sweeps out the rest of the degrees necessary to construct a three-dimensional CT image. In this embodiment, the number of views required for the CT reconstruction can be collected in half the time it would have taken a single axis rotating at the same speed to collect the views. Source-detector pairs may be rotated through any total number of degrees possibly ranging from one to 360 degrees. Reconstructed CT image quality may be enhanced for numbers of degrees greater than 180. Some embodiments of the present invention may rotate source-detector pairs through a total number of degrees between 180 and 185, 185 and 190, 190 and 200, 200 and 205, 205 and 210, or 210 and 215 degrees, inclusive. Some embodiments of the present invention may rotate source-detector pairs through a total number of degrees between 215 and 230, 230 and 245, 245 and 260, 260 and 275, 275 and 290, 290 and 305, or 305 and 320 inclusive. Some embodiments of the present invention may rotate source-detector pairs through a total number of degrees between 320 and 325, 325 and 330, 330 and 335, 335 and 340, 345 and 350, or 355 and 360, inclusive. Source-detector pairs may be initially positioned with any angle between them allowing the predetermined amount of rotation to occur and may be rotated in the same direction or in opposing directions. The time taken for a single axis carrying a source and detector to rotate through and obtain images at a given set of degrees can be limited by patient safety concerns. Currently, fast C-arm CT scans may take approximately four to six seconds. This speed may increase in the future. Embodiments of the present invention can cut the minimum time required to complete an intraoperative CT in half. For example, if four to six seconds is assumed as a reference time for intraoperative CT with a single source-detector pair, then an intraoperative CT scan using two source-detector pairs may take only 2 to 3 seconds, or less than 3 seconds. In one embodiment of the present invention, source-detector pairs comprising point-source imaging systems are used to acquire a CT dataset in less than 3 seconds, or half the time that would be required to acquire the dataset with a single source-detector pair. Image data can be acquired at a predetermined number of angles, e.g. views, as the source-detector pairs are rotated, and reconstruction of a three-dimensional image may be accomplished using standard cone-beam reconstruction, multiplanar reconstruction, standard filtered back projection, maximum-likelihood algorithm for transmission tomography, ordered subset expectation maximization, or any other iterative or non-iterative CT reconstruction method or combination of methods. In another embodiment of the present invention, source-detector pairs comprising multi-focal spot sources are used for acquisition of a CT dataset. The low-dose advantages of multi-focal spot source, e.g. tomosynthetic, systems may be particularly desirable in CT applications as concerns exist regarding the amount of radiation incurred by patients while undergoing CT, a large number of high-quality images providing the most accurate three-dimensional reconstruction, and its effect on the probability of cancer development. Image data collected as the source-detector pairs rotate may be used to generate image planes using shift-and-add reconstruction or other techniques as described in U.S. Pat. No. 6,178,223 entitled “Image reconstruction method and apparatus,” hereby incorporated by reference. Reconstruction of a three-dimensional image may be accomplished using maximum likelihood expectation maximization (MLEM); Fourier re-binning with John's equation (FORE-J), which can re-sort image data acquired with a multi-focal spot source to resemble data acquired with a point source; maximum-likelihood algorithm for transmission tomography (ML-TR); ordered subset expectation maximization (OSEM); or any other iterative or non-iterative three-dimensional reconstruction algorithms or combinations thereof. In one embodiment of the present invention, datasets acquired during a fast C-arm CT scan are reconstructed using an iterative algorithm utilizing the maximum-likelihood algorithm for transmission tomography (ML-TR) as described by De Man et. al. [cite] ML-TR seeks to find a set of linear attenuation coefficients {μi}j=1J that maximizes the log-likelihood for a set of measurements {yi}i=1I,L=Σi=1I(yi·ln(ŷi)−ŷi)where i denotes a given projection line, j a given pixel, and ŷ the expected number of photons detected along projection line i given the current reconstruction {μi}. It can be shown that μ j n + 1 = μ j n + ∑ i = 1 I ⁢ ⁢ l ij · ( y ^ i - y i ⁢ ) ∑ i = 1 I ⁢ ⁢ l ij · [ ∑ h = 1 J ⁢ ⁢ l ih ] · y ^ i maximizes this log-likelihood. The expected number of photons ŷ along a given projection line can be calculated as y ^ i = b i · exp ( - ∑ j = 1 J ⁢ ⁢ l ij ⁢ μ j ) where the factor bi can be determined by acquiring images from the source-detector pairs with no imaging volume present. In a further embodiment, the ML-TR algorithm can be implemented in an ordered-subset maximization (OSEM) framework. This embodiment may improve the computational speed of reconstruction. A principle of OSEM is to perform iterations only for a small subset of angular samples, which may be widely spaced over the angular range. Subsequent iterations can then be performed on different subsets until all angles have been used and one complete iteration has been performed. In this embodiment of the present invention, the number of subsets utilized may range from one to the number of views acquired, e.g. the number of angles at which an image dataset is acquired, inclusive. The number of subsets utilized may also be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, or 25. The number of views within a subset may be any number of views between two views and the number of views acquired, inclusive. The number of views in a subset may also be 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, or any other number of views. For example, in one embodiment of the present invention, each of two source-detector pairs can be rotated through 180 degrees and acquire image data, e.g. a view, every 4 degrees such that a total of 90 views over 360 degrees are acquired. A reconstruction algorithm implementing ML-TR in an OSEM framework could then utilize, for example, fifteen subsets, each subset comprising six views, and possibly be run for ten complete iterations. Embodiments of the present invention may also be used for imaging without rotation of the source-detector pairs, in which case connective axes of the pairs may be fixed at a given angle relative to one another during the imaging process. For bi-planar imaging, the angle between the two source-detector pairs of an embodiment of the present invention may be fixed at any integer or non-integer number of degrees between zero and 180. A near-zero minimum angle and near-180 maximum angle between source-detector pairs in embodiments of the present invention may be determined by the angles at which adjacent edges of the two sources or two detectors come into contact. For example, if the source-detector pairs are multi-focal spot, tomosynthetic systems, angles may be constrained by the edges of the two source faces coming into contact with one another, the sources being the relatively larger elements of source-detector pairs. If the source-detector pairs are point X-ray source imaging system, angles may be constrained by the edges of the two detector faces coming into contact. The angle between the two source-detector pairs of embodiments of the present invention may be a number of degrees between 0 and 10, 10 and 20, 20 and 30, 30 and 40, 40 and 50, 50 and 60, 60 and 70, 70 and 80, 80 and 90, 90 and 100, 100 and 110, 110 and 120, 120 and 130, 130 and 140, 140 and 150, 150 and 160, 160 and 170, or 170 and 180, inclusive, or any other integer or non-integer number of degrees between the enumerated values. Bi-planar X-ray imaging may be particularly useful for procedures in which a contrast agent may be inserted into a patient to highlight veins or other features that are not intrinsically opaque to X-ray radiation. It may be desirable to limit the amount of contrast agent injected into a patient as contrast agents have been known in some cases to cause allergic reactions and even kidney failure. When more than one perspective of a feature highlighted by a contrast agent may be useful to a physician, two X-ray imaging systems positioned at different angles around the patient may be utilized for bi-planar image acquisition after a single dose of contrast agent has been administered. Acquiring two views simultaneously can spare the additional dose of contrast agent which may be administered if time were taken to move an X-ray system from one angle to another. In one embodiment of the present invention, a novel bi-planar imaging system may comprise two multi-focal spot, tomosynthetic imaging systems. Multiple planes between a source and detector can be reconstructed from the data acquired by a single system, and a three-dimensional image or video may be constructed using the data acquired by both systems. Acquisition of a three-dimensional image in this fashion may provide significantly less radiation exposure to the patient compared to collecting projection images through 180 degrees or more around the patient, e.g. compared to computed tomography; this embodiment may allow a surgeon to acquire three-dimensional images frequently during a procedure without concern of excessive radiation dose. Furthermore, this embodiment may enable real-time, e.g. video, imaging, whereas even CAT scans may not acquire data fast enough to generate real-time three-dimensional images. Reconstruction of a three-dimensional image from two tomosynthetic images in embodiments of the present invention may be accomplished using MLEM, ML-TR, or any other reconstruction algorithm in voxel space. A voxel may be considered the three-dimensional equivalent of a pixel; if a pixel is considered a square area in two-dimensional space, a voxel would be a cubic volume in three-dimensional space. In one embodiment of the present invention, an ML-TR algorithm in an OSEM framework may be utilized to reconstruct a three-dimensional image from two bi-planar images. For example, one subset comprising two views may be utilized. Three-dimensional reconstruction from two tomosynthetic images may be optimized when the images are acquired with source-detector pairs positioned when the angle between source-detector pairs is between 60 and 120 degrees, 70 and 110 degrees, or 80 and 100 degrees, inclusive, e.g. nearly perpendicular to one another. However, three-dimensional reconstruction from two tomosynthetic images in this embodiment of the present invention may also be accomplished for other angles of separation. For example, angles less than 60 degrees may be optimal if the spatial frequency of an imaging volume is significantly higher in one dimension than in another, e.g. if details of an imaging volume viewable from one direction are much finer than those in a perpendicular view. In embodiments of the present invention, the axes of two source-detector pairs may also be fixed at the smallest angle possible given the geometry of the system, e.g. at a near-zero minimum number of degrees as previously discussed. FIG. 4 is a diagram illustrating an embodiment of the present invention with two source-detector pairs positioned at the minimum number of degrees given the source and detector geometry. Faces of two multi-focal spot sources of tomosynthetic source-detector pairs may be in an angled configuration 63. Reconstruction algorithms can account for the imaging geometry created by angled configuration 63 and produce images similar to those that would have been acquired by a single, extended flat detector. This correction can be accomplished using a mask or any other method of correcting for known image distortions. For example, an appropriate assignment of the signals from pixels of detectors 61 into an image plane can be determined analytically or experimentally and can account for the sampling effects of angled configuration 63. Flat configuration 64 may represent the area that would be subtended by the two multi-focal spot sources shown in angled configuration 63 if they were instead positioned adjacently in the same plane. Outermost X-ray paths 62 between detectors 61 and angled configuration 63 are also shown. X-ray paths 62 are extended past angled configuration 63 into the plane of flat configuration 64 to represent the boundaries of the flat source that is “simulated” by two sources in angled configuration 63. It can be seen that a simulated flat detector can actually be wider than the source area created by flat configuration 64. The size of a multi-focal spot source may be related to the field of view available from an imaging system; the angled configuration that may be created when two source-detector pairs are positioned at a smallest possible angle in embodiments of the present invention may achieve a larger field of view than if a flat source of equivalent surface area were used. The field of view (FOV) of an imaging system may refer to the dimensions of the region that can be imaged by the system. The FOV of an imaging system may in large part be determined by imaging geometry of the system, including but not limited to the size of one or more of its components, e.g. source or detector, and the distances maintained between the source, detector, and subject during imaging. Despite low-dose and other advantages, tomosynthetic imaging systems utilizing a multi-focal spot source have seen somewhat limited application, primarily being used for cardiac procedure and related imaging, due to their relatively small fields of view. One embodiment of the present invention comprises two tomosynthetic imaging systems, positioned at a near-zero minimum number of degrees. This embodiment may provide a field-of-view large enough for a wider range of applications, including fluoroscopy and interventional procedures on larger tissues and organs of the human body, e.g. cranial, gastrointestinal, or other procedures. FIG. 5 is a diagram illustrating a field of view of a multi-focal spot, tomosynthetic imaging system. A possible imaging volume 159 is indicated between large source 59 and small detector 151. It can be seen that the widest field of view 158 may be on the source side of the imaging volume. FIG. 6 is a diagram illustrating a field of view of an embodiment of the present invention comprising two multi-focal spot source-detector pairs. First small detector 51 and second small detector 52 can be illuminated by first large source 53 and second large source 54, respectively. A possible imaging volume 150 of this embodiment may be larger than imaging volume 159 available from a single source-detector pair. Particularly, a maximum field of view 149 may be significantly wider than field of view 158 available from the single source-detector pair. This embodiment may provide a field of view suitable for a broader range of clinical applications than existing tomosynthetic imaging systems. It can also be seen in FIG. 6 that imaging volume 150 may have regional variations in X-ray flux. A central region of imaging volume 150 may be imaged by both source-detector pairs, whereas outer regions of the imaging volume may be imaged by a single source-detector pair. As the central region may receive twice the amount of X-ray flux relative to outer regions of the imaging volume, reconstructed images may display higher contrast-to-noise ratios and less out-of-plane blurring in the area imaged near the center of the imaging volume relative to the outer edges of the imaging volume. Differing degrees of image quality within a single X-ray image can be desirable as a physician may wish to view a small region of interest (ROI), such as a heart during a cardiac procedure, with very high-quality images, e.g. good contrast-to-noise, while generally monitoring the surrounding area. Since prolonged X-ray exposure can have adverse health effects, it can be beneficial to use a lower amount of X-ray flux to image areas outside of the ROI. Source-to-detector distance, source size, detector size, or other parameters of imaging geometry may be configured to create a central region, e.g. region imaged by both source-detector pairs, that is the size of a probable region of interest for a given application or range of applications. Alternatively, a system may be designed such that the region receiving flux from both X-ray sources is large enough to encompass the full width of a human body. In this embodiment, a patient may be positioned such that an entire plane or planes of interest can be imaged with high contrast-to-noise and low out-of-plane blurring. Fields of view of embodiments of the present invention may be circular, square, polygonal, rectangular, trapezoidal, triangular, or any other shape, e.g. as determined by source and detector geometry. A field of view may have a maximum diameter or width of 5 to 10 cm, 10 to 15 cm, 15 to 20 cm, 20 to 25 cm, 25 to 30 cm, 30 to 35 cm, 35 to 40 cm, 40 to 45 cm, or 45 to 50 cm, inclusive, or any integer or non-integer number of centimeters within these enumerated values. For example, a field of view may have a diameter of 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, or 40 cm, inclusive, or any non-integer between these enumerated values. For some applications, a field of view may have a diameter or width of less than 5 cm or greater than 40 cm. For example, one embodiment of the present invention comprises two tomosynthetic source-detector pairs each having an individual field of view with a diameter of approximately 20 cm and a total field of view when positioned at a minimum possible angle of approximately 35 cm. Source faces in this embodiment may be circular and may have a diameter of 10″. Detector faces may be rectangular and may be 10 cm by 5 cm. Since each multi-focal spot source in embodiments of the present invention may have an amount of non-emissive, e.g. dead, space along the edges of its face due to source housing, connections to the target material, or other support structures, a gap in emissive locations may exist between the two source faces when positioned in the configuration of FIG. 6. This gap may affect the size or shape of the imaging volume or maximum field of view. Depending on the positioning of a patient relative to the source for a give application, the effect on the imaging volume may or may not be detrimental. FIG. 7 is a diagram illustrating two multi-focal spot sources of one embodiment of the present invention configured to minimize the distance from emissive locations on one source to those on the other when the sources are positioned adjacently, e.g. with a minimum angle between source-detector pairs. The focal spot pattern across the faces of two sources in this embodiment may resemble the pattern of focal spots on a single, large-area multi-focal spot when they are placed in contact adjacently. For example, two scanning-beam sources may be fabricated with emissive target screens extending very close to edges of the source faces, reducing dead area along edges at which two source faces meet. Other types of source pairs may be configured to minimize a gap in the emissive surface, including a pair of nanotube arrays or any other pair of sources with little to no dead space along two adjacent edges. In these embodiments, a gap may be 2 cm, 3 cm, 4 cm, 5 cm, 6 cm, 7 cm, 8 cm, 9 cm, 10 cm, or a non-integer number of centimeters between these enumerated values. A gap may also be between 10 and 15 cm, 15 and 20 cm, 25 and 30 cm, 30 and 35 cm, 35 and 40 cm, 40 and 45 cm, or 45 and 50 cm, inclusive. In one embodiment of the present invention, two scanning beam sources configured with minimal non-emissive area along adjacent edges and two photon-counting element-array detectors may be attached to two C-arms, e.g. such that each C-arm has a source on one end and a photon-counting detector on the opposing end. The two C-arms may be connected to one another by a joint aligned with an isocenter of the two source-detector pairs. Either the joint or another point on either C-arm may be connected to a support structure. FIG. 8 is a diagram illustrating a relationship between aspects of three modalities of an embodiment of the present invention. In the embodiment of FIG. 8, an apparatus modality may be selected, as indicated by decision block 91. The modality may be for example a computed tomography modality 92, an extended-FOV fluoroscopy modality 93, or a bi-planar imaging modality 94. In one embodiment, in computed tomography modality 92 the apparatus may allow election in a decision block 95 to either set operating parameters, e.g. rotation speed, frame rate, etc. in option 97, or image specifications, e.g. final image resolution, in option 96. Operating parameters may be calculated in step 98 if a user selects option 96. Alternatively, a system may only provide option 96 or only provide option 97 under computed tomography modality 95. The system can implement the operating parameters from option 97 or step 98, acquiring images while rotating two or more source-detector pairs around an isocenter, as in step 99. Any type of CT reconstruction method can be utilized to generate a three-dimensional image in step 100. For extended-FOV fluoroscopy modality 93 source-detector pairs of the system may be aligned at a near-zero minimum angle, e.g. with sources or detectors in contact adjacently. In step 101 a single set of image data may be acquired in this configuration or image data may be continuously acquired. If predetermined artifacts of system geometry are present in acquired images, they may be corrected in step 102 prior to displaying an image or video in step 103. Alternatively, a single source-detector pair may be utilized in extended-FOV fluoroscopy modality 93 if the field of view provided by the single source-detector pair is sufficient for a given application. For bi-planar imaging modality 94 source-detector pairs may be positioned at any angle relative to one another in step 105. An image, images, or video can be displayed in step 106. If the apparatus comprises tomosynthetic source-detector pairs, then a three-dimensional image or video may also be reconstructed from two bi-planar data sets in step 107. Other embodiments of the present invention utilize multiple modalities of an imaging system capable of at least three different imaging procedures in conjunction with one another, potentially to optimize the accuracy or registration of one or more of these modalities. Registration may refer to the determination of a spatial relationship between multiple views, e.g. image data sets, of the same object or imaging volume, for example by selecting a reference data set and transforming coordinates of any other data sets into the coordinates of the reference data set. Accurate image registration can properly combine or overlay multiple data sets. Registration can be achieved by feature recognition, intensity mapping, or other methods relating data sets to the reference data set. In one embodiment of the present invention, a three-dimensional image can be reconstructed from two bi-planar images acquired with multi-focal spot sources. In this embodiment, a CT data set can also be acquired with the same source-detector pairs used for bi-planar imaging. A lack of relative motion between the patient and imaging system can be achieved between the CT scan and bi-planar image acquisition. The CT data set can be used as a reference data set for registration of the two bi-planar images. A CT scan may also be utilized for registration of images acquired via other modalities of the imaging system, e.g. fluoroscopy, and with an imaging system comprising point sources rather than multi-focal spot sources. In other embodiments of the present invention, imaging artifacts from insufficient data can be alleviated with a CT scan taken with little or no motion between the patient and imaging system during the transition from a CT to another imaging modality. Data from a preliminary or secondary CT scan can be used as a prior, e.g. a Bayesian prior, for reconstruction. Alternatively, another method of improving reconstructions with an additional data set may be used. In one such embodiment, two bi-planar tomosynthetic data sets can be reconstructed to form a three-dimensional image using MLEM, ML-TR, OSEM, ML-TR in an OSEM framework, or any other iterative or non-iterative reconstruction algorithm. The value of a given pixel or voxel from the preliminary CT dataset can be incorporated as a constraint, factor, or other term when determining probable pixel or voxel values via likelihood maximization or another method of the reconstruction algorithm. Interventional procedures can often be planned based on an image or series from a preliminary CAT scan, which, for example, shows a tumor or other malignancy and surrounding internal features. This preliminary CAT scan may have been completed relatively long before, e.g. days, weeks, or months before, the interventional procedure. Internal features of a patient can change between the time at which the CAT scan completed and the time of the procedure, e.g. from weight loss or malignancy growth. In one embodiment of the present invention, a CT modality of an imaging system comprising a set of source-detector pairs may be utilized directly before an interventional procedure. The interventional procedure may be guided by a fluoroscopy modality of the same imaging system. This embodiment allows a CT scan to be quickly completed before an interventional procedure without moving the patient or imaging system. A lack of relative motion between the patient and apparatus can result in this preliminary CT scan providing absolute locations or coordinates of internal features within the patient where they may be during the procedure. In another embodiment of the present invention, an interventional procedure requiring some amount of three-dimensional information in a localized region, e.g. in the cardiac region for placement of an ablative device, can be completed using bi-planar imaging. A fast CT scan can be taken prior to bi-planar imaging, and the third-dimension coordinate of features seen in the two bi-planar two-dimensional images can be determined by comparison to the three-dimensional CT image or map. Embodiments of the present invention may also be useful for verification or validation following an interventional procedure. For example, in one embodiment of the present invention, an interventional procedure may be completed under fluoroscopic guidance, e.g. with two source-detector pairs positioned at a minimum possible angle. A CT image may then be acquired by rotating the two source-detector pairs outward in opposite directions from the minimum angle configuration. If the three-dimensional image validates the success of the procedure, a physician may proceed to remove any implements within the patient and close incisions. If the three-dimensional image shows remaining malignancy or other issues, the source-detector pairs may be re-positioned for real-time image guidance and the procedure continued. FIG. 9 is a flowchart illustrating a number of manners in which modalities of an imaging apparatus may be utilized in a number of embodiments of the present invention. As previously described, two source-detector pairs can be utilized to acquire a CT data set. The same source-detector pairs can then be positioned for fluoroscopy, e.g. at a minimum possible angle, or bi-planar imaging. If fluoroscopy is being used as guidance for an interventional or surgical procedure, it may be valuable to determine or confirm the locations and conditions of internal features being targeted by the procedure. The CT data set may be utilized to determine absolute locations of internal features seen in fluoroscopic images, including third-dimension locations. It may also be used for registration of fluoroscopic images, e.g. to combine the views taken by two source-detector pairs in this embodiment. Similarly, a CT data set can be used for registration of bi-planar images or as a prior for reconstruction of a three-dimensional image, if the bi-planar images are tomosynthetic. Embodiments of the present invention may utilize other combinations of the modalities of an apparatus comprising two source-detector pairs that can improve imaging speed, registration, or quality. Bi-planar imaging may be performed before or after extended-FOV fluoroscopy, extended-FOV fluoroscopy before or after CT, CT before or after bi-planar imaging, and so forth, where acquisition of each type of image by a single apparatus can allow for there to be little to no intermediate motion between a patient and the imaging. The foregoing descriptions of specific embodiments of the present invention have been presented for purposes of illustration and description. They are not intended to be exhaustive or to limit the invention to the precise forms disclosed, and many modifications and variations are possible in light of the above teaching. The embodiments were chosen and described in order to best explain the principles of the invention and its practical application, to thereby enable others skilled in the art to best utilize the invention and various embodiments with various modifications as are suited to the particular use contemplated. It is intended that the scope of the invention be defined by the claims appended hereto and their equivalents.
055815863	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of this invention will now be described with reference to the drawings. Structural items which are the same as in the prior art described above are given the same reference numerals and further detailed description is omitted. As shown by the block diagram of FIG. 2, the 205 control rod drive mechanisms 1 that drive the 205 control rods, not shown, are combined in groups of four mechanisms apiece, a single inverter power source 20 being provided for each group of four control rod drive mechanisms 1. In more detail, the arrangement is constituted by 52 control rod changeover devices 22 that select the control rod drive mechanisms 1 to be driven, from the 205 control rod drive mechanisms 1, coupled to the 205 control rods, not shown; 52 inverter power sources 20 constituting drive power sources of the electric motors in control rod drive mechanisms 1; and 52 inverter controllers 24 that control the inverter power sources 20; as well as a control unit 26 and man-machine device 28 which serves as an interface with a human operator. Each inverter power source 20 is coupled to receive power from a conventional plant power source or a standby power source. Also, the current control rod position is input from each control rod drive mechanism 1 to control unit 26 as a control rod position signal S1, and drive information S2 is output from man-machine device 28. Furthermore, control unit 26 outputs to inverter controller 24 an inverter control signal S3 and, to control rod changeover device 22, a selected control rod signal S6. The changeover timing information of the switching elements in the output unit of the inverter power sources 20 is output from inverter controller 24 as inverter drive signal S4. Inverter power unit 20 outputs its inverter output S7 to control rod changeover device 22. Control rod changeover device 22 is constructed such that the control rods, not shown, are driven by the control rod mechanisms 1 in response to output of a selected control rod drive mechanism drive signal S8 to the selected control rod drive mechanism 1 in response to changing over of the inverter output S7 through an electrical switching device included in changeover device 22 in accordance with the selected control rod signal S6. For example, control rod changeover device 22 can comprise a plurality of separately controllable electrical switches, such as mechanical or solid-state switching devices, for selectively coupling the inverter output S7 to one of the control rod drive mechanism associated therewith. Operation of the above construction will now be described. As shown in FIG. 2, control unit 26 receives from man-machine device 28 (1) control rod selection mode, (2) control rod drive mode, or (3) control rod insertion/withdrawal mode, and drive information S2 of the target position calculated from these three modes. It also continually receives from the 205 control rod drive mechanisms 1 control rod position signals S1 that indicate where the control rod drive mechanisms S1 are stopped, i.e., at what part of the reactor core the control rod is stopped. As shown by the block diagram of FIG. 3, control unit 26 includes: a drive control rod selection unit 30, an inverter power source selection unit 32, and a control rod drive mechanism drive information evaluation unit 34, and executes the following control in response to control rod position signal S1 from the control rod drive mechanism 1 and drive information S2 from man-machine device 28. A selected mode signal (single mode or ganged mode) S9 included in drive information S2 is input to drive control rod selection unit 30. When this identifies the number of the control rod changeover device 22 that drives the selected control rod drive mechanism 1, it outputs this information, as selected control rod signal S6, to the control rod changeover device 22 corresponding to the selected control rod drive mechanism 1. Control rod changeover device 22 switches to the selected control rod drive mechanism 1. Simultaneously, drive control rod selection unit 30 outputs to inverter power source selection unit 32 a control rod changeover device signal S10 that controls the appropriate inverter controller 24 to control the associated inverter power source 20 to provide power for the control rod drive mechanism 1 that is driven. Also, drive mode signal S11 (step, notch or continuous) included in drive information S2, insertion/withdrawal command signal S12, and target position signal S13 are input to control rod drive mechanism drive information evaluation unit 34. This control rod drive mechanism drive information evaluation unit 34 generates an inverter operating signal S14, which continues output of the control rod drive mode (step, notch or continuous), and insertion/withdrawal command (control rod drive mechanism rotation direction) of inverter power source 20 to inverter power source selection unit 32 until the control rod position signal S1 of the control rod drive mechanism 1 in question has reached the target position. Inverter power source selection unit 32 selects an inverter power source 20 to be driven in accordance with the number of the control rod changeover device 22 of the control rod drive mechanism 1 to be driven, which is received in the form of control rod changeover device signal S10 from the drive control rod selection unit 30. Unit 32 also outputs the input inverter operating signal S14 received from control rod drive mechanism drive information evaluation unit 34, in the form of an inverter control signal S3, to the inverter controller 24 of the corresponding inverter power source 20. Continuing the description of the various signals that are output by control unit 26 with reference to FIG. 2, the inverter controllers 24 are driven to output inverter drive signals S4 to inverter power units 20 by means of inverter control signal S3, which is output from control unit 26. The inverter output S7 that is output from the inverter power source 20 that is driven is supplied to the corresponding control rod changeover device 22. With reference to control rod changeover device 22, a switch within control rod changeover device 22 corresponding to the control rod drive mechanism 1 that is to be driven is selected and closed in response to the selected control rod signal S6 that is output from control unit 26. Inverter output S7 that is output from the inverter power source 20 is thereby supplied, as selected control rod drive mechanism drive signal S8, only to the control rod drive mechanism 1 that is selected by man-machine device 28, thereby driving this control rod drive mechanism 1. It should be noted that, in this invention, when the control rods are operated in a ganged group, the load capacity of a single inverter power source 20 is that of a single control rod drive mechanism 1. Even if 26 control rods, which is the maximum in a ganged group in the present embodiment, are operated simultaneously, there is no possibility of two or more of the four control rod drive mechanisms 1 which constitute the load of the same inverter power source 20 being driven simultaneously. This is achieved by the 52 inverter power units 20 being assembled with the 205 control rod drive mechanisms 1 being constituted with four mechanisms in each group. An example of the apportionment of the 205 mechanisms to the 52 inverter power sources is: 4 mechanisms.times.50; 3 mechanisms.times.1; and 2 mechanisms.times.1. When, in reactor scram, ere, an "all control rods to be fully inserted" command is output from the reactor emergency shutdown system, the control rods are temporarily separated from the electric motors of the control rod drive mechanisms 1, and are all inserted at high speed by water pressure from a separate water pressure source, not shown. Furthermore, as shown by the logic diagram of FIG. 4, control unit 26 outputs an "all control rods to be fully inserted" command signal S15, included in drive information S2, to drive control rod selection unit 30 and inverter power source selection unit 32. Inverter power source selection unit 32 receives "all control rods to be fully inserted" command signal S15, and outputs an all-inverter drive command signal S16 to all 52 of inverter power sources 20. Also, drive control rod selection unit 30 receives "all control rods to be fully inserted" command signal S15 and closes an arbitrary one of the switches for control rod drive mechanisms 1 in control rod changeover device 22. Thereby, 52 control rod drive mechanisms are inserted at once. After the 52 control rod drive mechanisms 1 whose switches have been closed have reached the fully inserted position, the switches of other control rod drive mechanisms 1 that have not yet been fully inserted are closed. By carrying out this operation a total of 4 times sequentially, all of the 205 control rod drive mechanisms 1 are put into the fully inserted position. Thus, the control rods are maintained in fully inserted position as a backup system of the control rods which were previously fully inserted by water pressure. It should be noted that although an arrangement was described in which four control rod drive mechanisms 1 were driven by a single inverter power source 20 in the above embodiment, with this invention, it is possible to drive an arbitrary number N of control rod drive mechanisms with a single inverter power source 20. Thus, the number of inverter power sources 20 can be further reduced by determining the number N of control rod drive mechanisms 1 that is permitted from the relationship with the ganged mode operation of control rod drive mechanisms 1 in accordance with the operational requirements of the plant. With this invention, in an atomic power plant equipped with control rod drive mechanisms operated by electric motor drive, the number of inverter power sources, constituting the drive power sources, that need to be provided can be greatly reduced without affecting the control rod operating performance. Thus, the noise generated by the inverter power sources can be reduced and the control equipment can be simplified, thereby also facilitating maintenance. Numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that, within the scope of the appended claims, the present invention can be practiced in a manner other than as specifically described herein.
063242583	claims	1. An apparatus for making combined transmission and emission recordings of an object using radiation, the apparatus comprising: a radiation source; a camera sensitive to radiation from the radiation source and to emitted radiation from the object, the radiation and the emitted radiation having different energy levels; a collimator arranged between the radiation source and the camera; radiation-directing means which ensure that the radiation of the radiation source is radiated in a planar radiation beam so that the camera is illuminated according to a substantially line-shaped irradiation pattern; and means for moving the line-shaped irradiation pattern over the camera in a direction substantially perpendicular to the longitudinal direction thereof; wherein the collimator is fixed relative to the camera; and wherein the collimator is a focused fan beam collimator. wherein the radiation source is a line-shaped radiation source, whose longitudinal direction is directed parallel to the convergence line of the collimator; wherein said plane in which the radiation is radiated contains the convergence line of the collimator; and wherein the collimator is a focused cone beam collimator. wherein the shielding extends around the radiation source; and wherein the shielding is rotatable with regard to the convergence line of the collimator. wherein the shielding extends around the radiation source; and wherein the combination of the radiation source and the shielding is rotatable with respect to the convergence line of the collimator. wherein the radiation source is a point-shaped radiation source, which is arranged adjacent the convergence line of the collimator; wherein said plane in which the radiation is radiated is substantially perpendicular to the convergence line of the collimator; and wherein means are present for moving said plane in a direction parallel to the convergence line of the collimator. wherein the shielding extends around the radiation source; and wherein the combination of the radiation source and the shielding is movable along the convergence line of the collimator. wherein the first camera is provided with a first fan beam collimator, whose focal line is located on the side of the first fan beam collimator directed to the second camera; wherein the second camera is provided with a second fan beam collimator, whose focal line is located on the side of the second fan beam collimator directed to the first camera; wherein the focal line of the first fan beam collimator and the focal line of the second fan beam collimator are mutually parallel; and wherein a first point source is movable along the focal line of the first fan beam collimator and wherein a second point source is movable along the focal line of the second fan beam collimator. wherein the first camera is provided with a first cone beam collimator, whose focal point is located on the side of the first cone beam collimator directed to the second camera; wherein the second camera is provided with a second cone beam collimator, whose focal point is located on the side of the second cone beam collimator directed to the first camera; wherein adjacent the focal point of the first cone beam collimator a first point source is arranged, which is associated with a first shielding element with a first movable passage slit; and wherein adjacent the focal point of the second cone beam collimator a second point source is arranged, which is associated with a second shielding element with a second movable passage slit; wherein the first passage slit and the second passage slit are mutually parallel; and wherein the first passage slit is movable in a direction perpendicular to the first passage slit, and wherein the second passage slit is movable in a direction perpendicular to the second passage slit. a control device for computing whether sensed radiation is emitted radiation or source radiation. a radiation source; a camera sensitive to radiation from the radiation source and to emitted radiation from the object, the radiation and the emitted radiation having different energy levels; a collimator arranged between the radiation source and the camera; radiation-directing means which ensure that the radiation of the radiation source is radiated in a planar radiation beam so that the camera is illuminated according to a substantially line-shaped irradiation pattern; and means for moving the line-shaped irradiation pattern over the camera in a direction substantially perpendicular to the longitudinal direction thereof; wherein the collimator is fixed relative to the camera; and wherein the collimator is a focused fan beam collimator. a control device for computing whether sensed radiation is emitted radiation or source radiation according to energy level. a radiation source; a camera sensitive to radiation from the radiation source and to emitted radiation from the object, the radiation and the emitted radiation having different energy levels; a collimator arranged between the radiation source and the camera; radiation-directing means which ensure that the radiation of the radiation source is radiated in a planar radiation beam so that the camera is illuminated according to a substantially line-shaped irradiation pattern; and means for moving the line-shaped irradiation pattern over the camera in a direction substantially perpendicular to the longitudinal direction thereof; wherein the collimator is fixed relative to the camera; and wherein the collimator is a focused cone beam collimator. wherein the radiation source is a point=shaped radiation source, which is arranged adjacent to the convergence point of the collimator; and wherein said plane in which the radiation is radiated contains the convergence point of the collimator; and which means are present for rotating said plane about an axis of rotation lying in that plane, which axis of rotation intersects the convergence point of the collimator. a shielding which is provided with a movable passage slit. wherein the shielding extends around the radiation source; and wherein the shielding is rotatable about the axis of rotation. wherein the radiation source is associated with a shielding element provided with a passage slit, the passage slit of said shielding element being movable with respect to the radiation source. wherein the first camera is provided with a first cone beam collimator, whose focal point is located on the side of the first cone beam collimator directed to the second camera; wherein the second camera is provided with a second cone beam collimator, whose focal point is located on the side of the second cone beam collimator directed to the first camera; wherein adjacent the focal point of the first cone beam collimator a first point source is arranged, which is associated with a first shielding element with a first movable passage slit; and wherein adjacent the focal point for the second cone beam collimator a second point source is arranged, which is associated with a second shielding element with a second movable passage slit; wherein the first passage slit and the second passage slit are mutually parallel; and wherein the first passage slit is movable in a direction perpendicular to the fist passage slit, and wherein the second passage slit is movable in a direction perpendicular to the second passage slit. a radiation source; a camera sensitive to radiation from the radiation source and to emitted radiation from the object, the radiation and the emitted radiation having different energy levels; a collimator arranged between the radiation source and the camera; radiation-directing means which ensure that the radiation of the radiation source is radiated in a planar radiation beam so that the camera is illuminated according to a substantially line-shaped irradiation pattern; and means for moving the line-shaped irradiation pattern over the camera in a direction substantially perpendicular to the longitudinal direction thereof; wherein the collimator is fixed relative to the camera; and wherein the collimator is a focused cone beam collimator. 2. The apparatus according to claim 1, wherein the collimator has at least one convergence line; 3. The apparatus according to claim 2, wherein the radiation-directing means comprises a shielding, which is provided with a movable passage slit. 4. The apparatus according to claim 2, wherein the line-shaped radiation source substantially coincides with the convergence line of the collimator; 5. The apparatus according to claim 2, wherein the line-shaped radiation source is spaced from the convergence line of the collimator; 6. The apparatus according to claim 1, wherein the collimator has at least one convergence line; 7. The apparatus according to claim 6, wherein the radiation-directing means comprises a shielding which is provided with a movable passage slit. 8. The apparatus according to claim 7, wherein the point-shaped radiation source lies substantially on the convergence line of the collimator; 9. The apparatus according to claim 1, wherein a first camera and a second camera are arranged at an angle with respect to each other, which angle is about 90.degree.; 10. The apparatus according to claim 1, wherein a first camera and a second camera are arranged at an angle with respect to each other, which angle is about 90.degree.; 11. The apparatus according to claim 1, the apparatus further comprising: 12. An apparatus for making transmission and/or emission recordings of an object using radiation, the apparatus comprising: 13. The apparatus according to claim 12, the apparatus further comprising: 14. An apparatus for making combined transmission and emission recordings of an object using radiation, the apparatus comprising: 15. The apparatus according to claim 14, wherein the collimator is a cone beam collimator with a single convergence point; 16. The apparatus according to claim 15, wherein the radiation-directing means comprises: 17. The apparatus according to claim 16, wherein the point-shaped radiation source is located substantially at the convergence point of the collimator; 18. The apparatus according to claim 14, wherein the radiation source is stationarily arranged adjacent the focal point of the cone beam collimator; and 19. The apparatus according to claim 18, wherein the shielding element is a plate-shaped shielding element that is linearly movable in a direction perpendicular to said passage slit. 20. The apparatus according to claim 19, wherein the shielding element is a shielding element extending around the radiation source, which shielding element is rotatable about an axis of rotation extending through the radiation source, which axis of rotation is parallel to said passage slit. 21. The apparatus according to claim 14, wherein a first camera and a second camera are arranged at an angle with respect to each other, which angle is about 90.degree.; 22. The apparatus according to claim 18, wherein the shielding element is arranged before the radiation source, which shielding element is provided with a substantially point-shaped passage opening, and wherein said point-shaped passage opening is located adjacent the focal point of a cone beam collimator. 23. An apparatus for making transmission and/or emission recordings of an object using radiation, the apparatus comprising:
056617682	claims	1. An apparatus for the transfer of nuclear fuel assemblies comprising; a plurality of loading stand support columns that extend vertically from the bottom of a fuel pool floor to the top of said fuel pool; a basket, supported for vertical travel within said support columns, for receiving a plurality of fuel assemblies from fuel storage racks in said pool; and an elevator for raising and lowering said basket; and further including a transfer container for receiving said plurality of fuel assemblies from said basket, and wherein said basket includes means for mating with said transfer container to ensure proper alignment between said transfer container and said basket. a plurality of grapples connected to said hoist cable for latching onto a corresponding plurality of fuel assemblies supported in said basket in a raised position, whereby said grapple assembly and hoist cable are operable to raise said latched fuel assemblies from said basket and into said sleeve without immersion of said grapple assembly and cable into water contained in said fuel pool. placing a loading stand assembly including a plurality of loading stand support columns into a fuel pool containing water such that said support columns extend vertically from a floor of said fuel pool to the top of said fuel pool; supporting a basket within said support columns; receiving a plurality of fuel assemblies in said basket; raising said basket with said plurality of fuel assemblies received therein; positioning a transfer container over said loading stand assembly; and raising a plurality of fuel assemblies from said basket into said transfer container. lowering a sliding sleeve from said body to a position directly over said basket; raising a plurality of compartments included in said sliding sleeve; and raising said sliding sleeve with said fuel assemblies completely within said transfer container body. 2. An apparatus as in claim 1 further including a transition shield mounted within said support columes and extending vertically such that a portion of said shield extends above the level of water in said pool and a portion extends below water in said pool. 3. An apparatus as in claim 2 further including a loading stand adapter plate mounted on top of said support columns for supporting said elevator. 4. An apparatus as in claim 3 wherein said adapter plate includes a hole for receiving said transition shield and including a support lip around said hole for engaging a corresponding lip on said transition shield to partially support said shield. 5. An apparatus as in claim 3 wherein each said support column includes a pin at the top of each column and said adapter plate includes a plurality of holes for receiving said column pins. 6. An apparatus as in claim 5 including at least one shim mounted on at least one said column pin and beneath said adapter plate for levelling said adapter plate. 7. An apparatus as in claim 3 further including a plurality of vertical guides mounted to said loading stand adapter plate for guiding the vertical travel of said basket. 8. An apparatus as in claim 3 further including means for vertically locating said basket in its uppermost position within said support columns and relative to said adapter plate. 9. An apparatus as in claim 8 wherein said locating means includes an outer flange connected to said basket, said flange limiting upper vertical travel of said basket by contact of said flange with a bottom surface of said transition shield. 10. An apparatus as in claim 9 wherein said flange includes vertical extension members and said transition shield includes openings for receiving said extensions. 11. An apparatus as in claim 10 wherein said extensions are pins. 12. An apparatus as in claim 1 wherein said transfer container comprises an elongated hollow body and a sleeve for sliding vertically within said body, said sleeve including a plurality of compartments, each of said compartments for receiving a fuel assembly from said basket, and wherein said means for mating ensures proper alignment between said sleeve and said basket. 13. An apparatus as in claim 1 further including a transfer container comprising an elongated hollow body and a sleeve for sliding vertically within said body, said sleeve including a plurality of compartments, each of said compartments for receiving a fuel assembly from said basket, and wherein said basket includes means for mating with said sleeve to ensure proper alignment between said sleeve and said basket. 14. An apparatus as in claim 13 further including a loading stand adapter plate mounted on top of said support columns for supporting said elevator and wherein said loading stand adapter plate includes means for aligning said transfer container with said basket. 15. An apparatus as in claim 14 wherein said means for aligning includes pins on said adapter plate and corresponding holes in said transfer container. 16. An apparatus as in claim 13 wherein said mating means includes a flanged lip on said basket for receiving a corresponding flange on said sleeve. 17. An apparatus as in claim 13 further including a hoist cable and a hoist connected to said hoist cable for lowering and raising said cable vertically within said transfer container; 18. An apparatus as in claim 1 wherein each of said loading stand support columns comprises at least one removable vertical section, whereby said columns are adjustable in height to accommodate varying fuel pool depths. 19. An apparatus as in claim 1 wherein said basket comprises a plurality of compartments configured to provide a separation distance between fuel assemblies received in said compartments, whereby said separation distance aids in maintaining subcriticality of said fuel assemblies in said compartments. 20. An apparatus as in claim 19 wherein said basket compartments are constructed of a material containing a neutron absorbing material as a component to further aid in maintaining subcriticality of said fuel assemblies. 21. An apparatus as in claim 20 wherein said neutron absorbing material is boron. 22. An apparatus as in claim 1 wherein said basket is removable from said elevator to allow interchange of said basket with another basket to accommodate varying size and numbers of fuel assemblies. 23. An apparatus as in claim 1 further including anchored supports connected to said columns for securing said columns to withstand earth vibrations. 24. A method for transferring nuclear fuel assemblies comprising: 25. A method as in claim 24 further including the step of mounting a transition shield within said support columns such that a portion of said shield extends above the level of water in said pool and a portion extends below water in said pool. 26. A method as in claim 25 wherein said step of raising said basket includes raising said basket into said transition shield and partially out of said water in said pool. 27. A method as in claim 26 wherein said step of raising said basket into said transition shield includes the step of aligning said basket with said transition shield. 28. A method as in claim 24 further including the step of mounting an adapter plate on top of said support columns. 29. A method as in claim 28 further including the step of placing at least one shim beneath said adapter plate to level said adapter plate. 30. A method as in claim 28 wherein said step of raising said basket includes the step of vertically locating said basket in an uppermost position within said support columns and relative to said adapter plate. 31. A method as in claim 24 wherein said transfer container has an elongated hollow body and further including the steps of: 32. A method as in claim 31 wherein said steps of lowering and raising said sliding sleeve includes the steps of lowering and raising, respectively, a grapple assembly in engagement with said sliding sleeve. 33. A method as in claim 32 further including the step of latching a plurality of grapples onto a corresponding plurality of fuel assemblies in said basket prior to said step of raising a plurality of fuel assemblies from said basket and into said sliding sleeve. 34. A method as in claim 33 wherein said step of latching includes actuating grapples independently whereby selected fuel assemblies can be latched. 35. A method as in claim 31 further including the step of mating said sleeve with said basket to ensure proper alignment therebetween. 36. A method as in claim 24 further including the step of adjusting the height of said loading stand support columns to accommodate varying fuel pool depths. 37. A method as in claim 36 wherein said height adjusting step includes the step of removing at least one vertical section from each of said loading stand support columns. 38. A method as in claim 36 wherein said height adjusting step includes the step of adding at least one vertical section to each of said loading stand support columns. 39. A method as in claim 24 further including the step of constructing said basket with a plurality of compartments configured to provide a separation distance between fuel assemblies received in said compartments, whereby said separation distance aids in maintaining subcriticality of said fuel assemblies in said compartments. 40. A method as in claim 39 further including the step of constructing said basket compartments of a material containing a neutron absorbing material as a component to further aid in maintaining subcriticality of said fuel assemblies in said compartments. 41. A method as in claim 40 further including the step of constructing said basket compartments of a material containing boron as a component to further aid in maintaining subcriticality of said fuel assemblies in said compartments. 42. A method as in claim 24 further including the step of interchanging said basket with another basket to accommodate varying size and numbers of fuel assemblies. 43. A method as in claim 24 further including the step of connecting said loading stand support columns to anchored supports for securing said columns to withstand earth vibrations.
059303212	summary	BACKGROUND OF THE INVENTION The invention relates to a head assembly for a nuclear reactor pressure vessel and more particularly to a simplified integrated head assembly including a missile shield disposed above control rod drive mechanisms operatively extending through the closure head of the pressure vessel. Pressure vessels containing fuel assemblies in commercial pressurized water nuclear reactor facilities have control rods which are operated by control rod drive mechanism assemblies (CRDMs). The CRDMs are mechanically supported on a removable closure head bolted to the pressure vessel and laterally supported by a seismic support platform and vertically restrained by a missile shield. Missile shields are generally relatively large heavy concrete or metal structures designed to absorb kinetic energy from dislocated CRDMs or other objects originally attached to the reactor pressure vessel. In addition, the closure head must also mechanically support a complex ventilation system located above the closure head for providing a substantial, continuous flow of ambient containment air through the CRDM coil region. See, in this regard, FIG. 1 of U.S. Pat. No. 4,678,623 which shows a head arrangement found in many commercial facilities. Briefly, FIG. 1 shows a design wherein the surrounding ambient air below the seismic support platform 28 is drawn across the unbaffled upper portion of the CRDMs, downwardly along the baffled electromagnetic coils of the CRDMs, into a lower plenum 20, upwardly through ducts 22 into an upper plenum 24 and then exhausted by fans 26 into the surrounding atmosphere above the fans. By exhausting the air upwardly in this manner, the hot exhaust air from the CRDMs can be blown into the general containment atmosphere so that the walls of the refueling canal near the head of the reactor vessel are not be substantially heated. Concrete walls should not be exposed to temperatures of about 150.degree. F. and are preferably not exposed to temperatures of more than 120.degree. F. In addition to the ventilation system, and as is shown in FIG. 1 of U.S. Pat. No. 4,828,789, a closure head may also support a shield surrounding the CRDM assemblies for protecting maintenance workers from radioactive CRDM assemblies. During refueling operations, the closure head, CRDM assemblies and their supporting subsystems, missile shield and other devices located over the closure head must be disassembled, lifted and removed so that the closure head can be removed and the spent fuel assemblies in the core of the pressure vessel below can be rearranged or replaced with fresh fuel assemblies. To reduce the time required to remove a closure head in order to refuel a nuclear reactor, an integrated head assembly was developed in the 1980s as a backfit for the design discussed above. As is shown in FIG. 2 of U.S. Pat. No. 4,678,623, the integrated head assembly replaced the ducts 22 extending from the lower plenum to the upper plenum with a duct arrangement 136, 138 and 140 which partially encircled the CRDMs. In this type of arrangement, the surrounding ambient air below the seismic support 128 was drawn along the exposed upper portion of the CRDMs, downwardly past the baffled electromagnetic coils and into the lower plenum 120, upwardly through the ducts 136-140 into the upper plena 162, and then exhausted into the atmosphere by fans 126. Advantageously, this and other equipment was supported by the closure head during power operations and could be lifted as a unit from the closure head during refueling operations. See, also, U.S. Pat. No. 4,830,814 and UK Patent Application No. 2,100,496 which show another integrated head assembly design. While the integrated head assembly design introduced in the 1980s successfully provided its intended advantages quite well, it has proven to be difficult to backfit all of the associated assemblies and subassemblies in a radioactive, operating nuclear facility. A natural convection ventilation design which could be more readily backfitted in an operating facility such as the reactor shown in FIG. 1 of U.S. Pat. No. 4,678,623 previously was proposed for cooling the CRDM coils without the need for any ventilation fans. It was determined in developing a natural convection ventilation design that the closure head arrangements employing the above described forced circulation type of ventilation systems utilized most of the fan power to draw the cooling air through the air ducts and utilized relatively little power to circulate the cooling air through the CRDM electromagnetic coil region. This natural circulation design included a redesigned, taller cooling shroud to increase the natural draft and other features for reducing the air flow resistance through the head region. However, a finite element analysis of the natural circulation design indicated that natural convection could achieve only about one-fourth of the 48,000 cubic feet per minute (CFM) air flow required by the design. Calculations showed that such an arrangement could result in a peak coil surface temperatures of up to about 380.degree. F. based upon a continuous stepping heat load estimate of 12 kw/CRDM. Although such conditions may be considered acceptable based on the peak specified allowable temperature of 392.degree. F. at the coils, this design provides an assured temperature margin of only 32.degree. F., which might require more frequent replacement of the coils after many years of operation at the increased temperatures. Thus, the nuclear industry has not developed an entirely satisfactory integrated head assembly design which will substantially cool the CRDM assemblies, reduce refueling time and radiation exposure. SUMMARY OF THE INVENTION It is an object of the present invention to provide a practical head assembly design including a missile shield, which provides substantial cooling for the CRDM assemblies, including their electromagnetic coils, and reduced refueling time and radiation exposure. It is a further object to provide a design which can be backfit into commercial nuclear reactor facilities as well as employed in new construction. With these objects in view, the present invention resides in an integrated head assembly which includes a pressure vessel closure head. A CRDM seismic support having air flow holes is disposed above the closure head with CRDMs extending upwardly from the closure head through the CRDM seismic support and between the air flow holes of the CRDM seismic support. A shroud enclosing the CRDMs extends upwardly from the closure head to the seismic support and is in air flow communication with the seismic support air flow holes. The shroud also has an air port, and preferably more than one air port, in direct air flow communication with the surrounding atmosphere. At least one ventilation fan (and preferably three or four fans) is disposed above the closure head and in air flow communication with the air flow passageway defined by the closure head, shroud and seismic support for circulating the air between the ambient atmosphere and the air flow passageway in order to cool the CRDMs in the head assembly. Also, a missile shield having air flow holes is disposed between the CRDM seismic support and the ventilation fan. Advantageously, large quantities of cooling air ventilate the head assembly to cool the CRDMs without unnecessarily wasting most of the fan power in air ducts during power operation. In addition, the entire head assembly can be lifted as a unit and transferred during refueling operations. Also, it has been estimated that this head assembly with its CRDM-encircling shroud can be installed in about one third the time required to install the head assembly shown in FIG. 2 of U.S. Pat. No. 4,678,623 so that there will be reduced exposure to radiation during installation and later during maintenance operations. Further, the integrated head assembly can be employed in new construction or readily backfitted in existing commercial facilities, including those facilities having integrated head assemblies from the 1980s, and may be used with existing lift devices. In a preferred embodiment of the present invention the integrated head assembly includes a downdraft ventilating fan supported on a missile shield superjacent the CRDM seismic support for blowing atmospheric air downwardly over the CRDMs and then out through one or more air ports into the ambient atmosphere around the head assembly in a refueling canal. Advantageously, natural air circulation in the refueling canals of commercial facilities will circulate the air from the head assembly (at a temperature which could be up to about 160.degree. F.) upwardly out of the refueling canals.
046413367	abstract	The invention relates to a soft tissue filter arrangement in X-ray imaging of a patient's skull by means of a chefalostat, wherein a patient (P) is by means of ear plugs (5) or the like supports preferably fixed relative to imaging coordinates as well as by means of a nasion and/or forehead support (6) set in a determined position and location between an X-ray source (1) and a film (4) or the like imaging medium and wherein the X-ray source is provided with diaphragm (2) for directing X-rays to the patient and restricting them to a proper sized beam (3) for imaging. The arrangement comprises preferably V-shaped filter means (7) whose position relative to the soft tissues of a patient's face in a cross-sectional plane perpendicular to the X-ray beam is adapted to be set on the basis of a distance (D) between said ear plugs (5) or the like supports and said nasion and/or forehead support (6) or on the basis of a patient's skull dimension correlating sufficiently well therewith. The nasion and/or forehead support (6 ) can be preferably provided with control elements and a scale by means of which the control elements (8) of said filter means (7) can be adapted to be controlled for producing an image having optimum patientwise exposure.
043137920	summary	RELATED APPLICATIONS The moveable gamma thermometer of this application is adapted to be used, during the steady state high flux operation of the nuclear reactor, to calibrate the multiple gamma thermometers of the fixed gamma thermometer array of a prior application, Ser. No. 888,881 PA1 Filed: Mar. 21, 1978 PA1 By: Erik Rolstad et al. PA1 For: Apparatus for determining the local power generation in a nuclear reactor fuel assembly. BRIEF SUMMARY AND BACKGROUND OF INVENTION This invention relates to the measurement of a quantity, linear heat generation rate, often abbreviated LHGR. The word linear is used because the quantity is a measure of the heat generated within one unit length of the fuel pin of a nuclear reactor. The LHGR of a fuel pin will be different at different locations along its length since fission depends, in part, on proximity of other sources of radioactivity. The quantity is important since, if the quantity goes too high, the cladding of the fuel pins is in danger of melting. Thus, the linear heat generation rate is as important to safe nuclear reactor operation as is reliability of coolant flow. The gamma thermometer array of the above-identified Rolstad et al. application contains a plurality of thermocouples which operate at individual temperatures which are multivariable functions of the local heat generation rate and the individual thermal resistance between the thermocouples and their respective heat sinks, cooled by the circulating reactor coolant. The said individual thermal resistance to the respective heat sink, whether the reactor be boiling or pressurized, is accurately known, and thus the local heat generating rates can be calculated from the readings of the plural thermocouples. The calculation of local heat generating rate from the data furnished by the gamma thermometer array of Rolstad et al. is fairly straightforward and simple compared to the corresponding calculation required to determine the same quantity using data furnished by the more common miniature fission chambers and self-powered neutron detectors, which respond almost entirely to thermal neutrons. The latter calculations must take into account the variability among the individual sensors, and must also be corrected for the continuous depletion of emitter material in the sensor. Furthermore, the local thermal neutron flux, as calculated from the corrected output of miniature fission chambers and self-powered neutron detectors, must be converted into local heat generation rate by a complex calculation which takes into account the fact that, as the U.sup.235 of the reactor is being depleted by the fission process, the local heat generating rate goes down, but the local thermal neutron flux goes up. Thus, the quantity being directly measured and the calculated quantity of interest are inversely and very complexly related. The situation often arises that the magnitude of the corrections to the basic signal is three times larger than that of the basic signal itself. A problem with neutron sensors is that they cannot be manufactured identically. Furthermore, they cannot be calibrated reliably before being placed in service, because there is no source of sufficient neutron flux, outside of a reactor, to calibrate them. In the event such source were available, the radioactivity induced by calibration would render further handling economically impracticable. In contrast, and uniquely for such instruments, gamma thermometers can be manufactured nearly identically, and can be tested at the point of manufacture to prove the relationship of each signal output to the heat generated in the sensors. Their signals can thus be relied upon to reflect accurately the heat being generated within the sensors and data, available in the open literature, establish that the heat to signal relationship is constant for many years. There does remain, however, the problem of relating the measured heat generation rate in the sensor to the unknown LHGR of adjacent fuel pins which the sensors purport to measure. The single available truly independent measurement against which this property can be tested in any light water reactor is the average fuel LHGR, which is determined by calorimetry. To determine average fuel LHGR the total heat being generated in the core is calculated by combining measurements of total mass flow and temperature rise of the coolant and small corrections made for heat not being generated in the fuel pins themselves. By dividing the total heat rate so obtained by the total length of fuel in the core an average value of LHGR is obtained. The distributed in-core sensors, however, purport to measure local LHGR, not average heat rate. If a reactor contained a large number of such sensors uniformly distributed, their signals could be averaged and compared to, and uniformly corrected if necessary, for changes in the ratio of average signal to average LHGR, which changes might take place over the several year lifetime of the fuel assemblies. In accordance with the instant invention, a traveling miniature gamma thermometer is provided, and is caused to travel through bores which are distributed in an array through the reactor core. In some cases the traveling gamma thermometer would have to be on a miniature scale, compared to gamma thermometers of the prior art, in order to be able to fit, for example, in a dry bore located in the inner rod of the gamma thermometer of the Rolstad application. In other cases diameters up to 1/4 or 3/8 inch might be allowable when used in the in-core instrument thimbles employed in many reactors. The traveling gamma thermometer need not be precisely calibrated during manufacture, since its inherent stability permits it to correctly reflect differing relative levels of activity as it is traversed through the nuclear reactor core, unless extremely poor thermal contact between the traveling gamma thermometer and the associated bore should cause the unit to be many degrees hotter; on the order of 100.degree. C., than its nominal value. This stability, during the core scanning, permits the construction of an accurate three dimensional relative gamma flux activity level plot of the reactor core. With the use of calorimetry, the relative gamma levels are readily changed to LHGR levels by determining the ratio between average gamma ray activity and average LHGR and correcting local readings by this ratio. Thus, the minature traveling gamma thermometer of this invention is adapted to scan the cross sections of a reactor core to determine the levels of activity at different locations in the core, and the results of such scanning can be used to determine LHGRs within the core and, if the reactor is so equipped, to verify theoretical calibrations of the in-place gamma thermometers of a full or partial gamma thermometer array of the Rolstad et al type, using methods of calorimetry. If a full and symmetrically related system of gamma thermometers of the Rolstad type were in place in the reactor core then the average of all of the measurements could be related to the calorimetrically determined average LHGR of the fuel and an experimental ratio determined between LHGR and gamma thermometer signal to verify the theoretical value of this ratio. In this case the system would gain little or nothing in calibration precision through use of the traveling gamma thermometer of the instant application. For partial, non-symmetric or sparse systems of the Rolstad type of gamma thermometers, however, a calibration of average LHGR indicated against average LHGR from calorimetry can be insufficiently precise and calibration precision could be greatly increased by use of a traveling gamma thermometer of the instant application. The traveling gamma thermometer of the instant application finds an important application in precision calibration of full systems of older types of unstable neutron measuring instruments such as fission chambers or self-powered neutron detectors which have not yet been or cannot easily be replaced by fixed gamma thermometer systems of the Rolstad type. In fact, traveling probe systems employing either fission chambers or self-powered neutron detectors have been found necessary in pressurized water reactors of two major types after the stability of these fixed neutron instruments proved unsuitable and have always been necessary to frequently recalibrate the very unstable fixed instruments used in boiling water reactors. For reactors employing such unstable fixed systems and for reactors using only traveling probes the traveling gamma thermometer of the instant application provides a superior method of local LHGR determination. The traveling gamma thermometer described herein is useful in a proof-of-precision application to demonstrate the precision of the Rolstad type of gamma thermometer before a full system is in place. For example, if only three or four Rolstad units were in place in a reactor whose full, symmetrical compliment was 50 units from each containing 7 sensors, then the LHGR's calculated from these could be shown to be identical over a long period of time with LHGRs from a traveling gamma thermometer which had traversed the entire core and had been repreatedly consistent against overall calorimetric calibration as described above.
	description	The present invention claims priority from Japanese patent applications JP 2006-128962 filed on May 8, 2006, and JP 2005-325559 filed on Nov. 10, 2005, the contents of which are hereby incorporated by reference into this application. The present invention relates to charged particle beam apparatuses such as electron microscopes and focused ion beam systems. A conventional scanning electron microscope (SEM) creates an image as follows: an electron beam emitted from an electron gun consisting of a field emitter or thermal field emitter electron source is accelerated and made a thin electron beam by an electron lens; this beam as a primary electron beam is scanned over a sample through a scanning deflector and generated secondary electrons or backscattered electrons are detected. The material of the electron source for a general-purpose SEM is tungsten. The material of the electron source for semiconductor observation may be tungsten which contains zirconia. To ensure that the electron source emits a good quality electron beam for a long time, the area around the electron source must be maintained in a high vacuum condition (10−7 to 10−8 Pa). For this purpose, as shown in FIG. 8, conventionally a plurality of ion pumps (three pumps IP-1, IP-2, IP-3 in the figure) has been used to evacuate the column by differential pumping. This method is disclosed in Japanese Patent Application Laid-Open No. 2002-358920. Although an ion pump has an advantageous that it has no movable part and can maintain the pressure 10−8 Pa or less simply by supplying power to it, its size is several dozen centimeters square or more and a magnetic shield is needed for the column (because it generates a magnetic field) and therefore its space requirement and weight are considerable. One approach to a compact apparatus without ion pumps is disclosed in U.S. Pat. No. 4,833,362 and Japanese Patent Application Laid-Open No. 6-111745 where a non-evaporable getter pump is incorporated. As another approach, Japanese Patent Application Laid-Open No. 2000-149850 describes an electron gun which incorporates a getter ion pump, eliminating the need for conventional ion pumps. A further approach described in Japanese Patent Application Laid-Open No. 2004-202309 is a non-evaporable getter pump in which non-evaporable getter alloy is placed in a space enclosed by a mesh in order to prevent generation of foreign particles and the mesh is finer than microparticles which are generated. As mentioned above, when a field emitter electron gun is used, in order to achieve the required high vacuum level of 10−7 to 10−8 Pa, a differential pumping structure is adopted to evacuate each chamber by a pump dedicated to it. A non-evaporable getter pump is advantageous in terms of size reduction because it does not require an installation space like an ion pump and can be built in the column. Here the non-evaporable getter pump means a vacuum pump which uses a getter alloy which absorbs gas simply by heating getter without evaporating it (for example, zirconium-vanadium alloy). For gas absorption, the gas should have a very low electric potential or be likely to have a chemical bond with getter alloy particles. This implies a problem that electrochemically stable gases such as rare gases and fluorocarbon are hardly removed because they are completely in equilibrium. Furthermore, for an apparatus which uses a non-evaporable getter pump, in many cases getter alloy particles of 100 microns or less are made into porous pellets by sintering or deposited on a metal sheet (for example nichrome) in order to increase the pumping speed. Consequently there is a problem that getter alloy particles exposed on the surface might come off and become foreign particles, clogging an opening in an electron optics or they might be charged, causing an electric discharge. An object of the present invention is to provide a compact charged particle beam apparatus with a non-evaporable getter pump in which high vacuum is maintained even during electron beam emission without generating foreign particles. To achieve the above object, according to the present invention, a charged particle beam apparatus has an electron optics with a differential pumping structure in which a non-evaporable getter pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber and a minimum required vacuum pump is placed in a downstream vacuum chamber under the conditions described below. Preferably the vacuum pump should be a sputter ion pump with a high efficiency in rare gas removal or a noble ion pump. A remarkable effect of the use of such a pump is a substantial increase in the time for which high vacuum is maintained. A turbo-molecular pump may be used instead of an ion pump. In placing a non-evaporable getter pump in the apparatus, the first point to note is that means to support the sheet getter pump should be designed to avoid contact of non-evaporable getter alloy with other parts (or hold it in a way not to contact anything). The second point is that if a pellet made by sintering fine particles of non-evaporable getter alloy is used, a small chamber should be provided on a column side wall and used as an auxiliary pump. Instead of fine particles of non-evaporable getter alloy, relatively large particles of about 3 mm square (bulk alloy) may be used. The use of such bulk alloy particles considerably reduces the possibility of generation of foreign particles upon contact. However, in this case, since surface area of the non-evaporable getter alloy is smaller, the pumping speed is lower. Taking the above advantage and disadvantage into consideration, grained getter alloy is held in a container partitioned by a mesh and placed in the vicinity of a typical built-in heater for a charged particle beam. Furthermore, the space between the most downstream electron gun chamber and the sample chamber is sealed except an opening through which an electron beam passes. However, if an adequate level of conductance exists between the chambers, the need for an ion pump or turbo-molecular pump is completely able to eliminate. Next, charged particle beam apparatuses according to preferred embodiments of the invention will be outlined. According to one aspect of the invention, a charged particle beam apparatus comprises: a charged particle source; a charged particle optics which focuses a charged particle beam emitted from the charged particle source on a sample and performs scanning; and means of vacuum pumping which evacuates the charged particle optics. The means of vacuum pumping has a differential pumping structure with two or more vacuum chambers connected through an opening in series; a pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber with a high degree of vacuum; and a gas absorbing surface of the non-evaporable getter alloy is fixed without contact with other parts. According to a second aspect of the invention, in the above charged particle beam apparatus, the non-evaporable getter pump has a deposited non-evaporable getter alloy on one side of a metal sheet. According to a third aspect of the invention, in the above charged particle beam apparatus, the non-evaporable getter pump is placed in the upstream vacuum chamber. The pump surface on which the non-evaporable getter alloy is deposited is on the vacuum side and the pump surface on which the non-evaporable getter alloy is not deposited is fixed in contact with an inner wall surface of the vacuum chamber with a high degree of vacuum. According to a fourth aspect of the invention, in the above charged particle beam apparatus, the side of the non-evaporable getter pump on which non-evaporable getter alloy is deposited has some areas without non-evaporable getter alloy and means for fixations is provided on the area to be out of contact with non-evaporable getter alloy, and the pump is fixed in the upstream vacuum chamber. According to a fifth aspect of the invention, in the above charged particle beam apparatus, an additional chamber for the upstream vacuum chamber is provided and pellets made by binding non-evaporable getter alloy particles are placed in the additional chamber. According to a sixth aspect of the invention, in the above charged particle beam apparatus, a porous mesh is placed between the upstream vacuum chamber and the additional chamber. According to a seventh aspect of the invention, in the above charged particle beam apparatus, a heater is located on the lower surface of the additional chamber. According to an eighth aspect of the invention, in the above charged particle beam apparatus, a vacuum gauge is provided in the additional chamber. According to a ninth aspect of the invention, in the above charged particle beam apparatus, an opening between the additional chamber and the upstream vacuum chamber is in a position higher than the pellets. According to a tenth aspect of the invention, in the above charged particle beam apparatus, the means of vacuum pumping has a differential pumping structure which consists of three or more vacuum chambers connected through an opening in series; a pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber with a high degree of vacuum; a vacuum chamber which lies downstream of the upstream vacuum chamber and has a lower degree of vacuum than the upstream vacuum chamber is connected with a vacuum chamber which lies downstream of the downstream vacuum chamber and has a lower degree of vacuum than the downstream vacuum chamber through a valve which is able to adjust flow rate; and a turbo-molecular pump is provided to evacuate the vacuum chamber which has the lowest degree of vacuum. According to an eleventh aspect of the invention, a charged particle beam apparatus comprises: a charged particle source; a charged particle optics which focuses a charged particle beam emitted from the charged particle source on a sample and performs scanning; and means of vacuum pumping which evacuates the charged particle optics. The means of vacuum pumping has a differential pumping structure with two or more vacuum chambers connected through an opening in series; and a second pump made of grained non-evaporable getter alloy with particles on the order of less than 10 millimeters is placed in an upstream vacuum chamber with a high degree of vacuum. According to a twelfth aspect of the invention, in the above charged particle beam apparatus, a first pump made of non-evaporable getter alloy with finer particles than the grained non-evaporable getter alloy is placed in a first vacuum chamber with a high degree of vacuum located most upstream, and a second pump made of the grained non-evaporable getter alloy is placed in a second vacuum chamber which is located downstream of the first vacuum chamber and has a lower degree of vacuum than the first vacuum chamber. According to a thirteenth aspect of the invention, in the above charged particle beam apparatus, a gas absorbing surface of the non-evaporable getter alloy of the first pump is fixed without contact with other parts, and the non-evaporable getter alloy particles of the second pump are held around a heater by mesh texture metal. According to a fourteenth aspect of the invention, in the above charged particle beam apparatus, the non-evaporable getter alloy of the second pump consists of particles of about 3 mm square. According to a fifteenth aspect of the invention, in the above charged particle beam apparatus, the means of vacuum pumping has a differential pumping structure which consists of three or more vacuum chambers connected through an opening in series, and the vacuum chambers are connected by a rough pumping port and vacuum is controlled by a assigned valve for each chamber. According to a sixteenth aspect of the invention, a charged particle beam apparatus comprises: an ion source; an ion illumination optics which focuses an ion beam emitted from the ion source on a sample and performs scanning; and means of vacuum pumping which evacuates the ion illumination optics, and in the apparatus, a surface of the sample is processed by irradiation with the ion beam. The means of vacuum pumping has a differential pumping structure with two or more vacuum chambers connected through an opening in series; a pump made of non-evaporable getter alloy is placed in an upstream vacuum chamber with a high degree of vacuum; and a gas absorbing surface of the non-evaporable getter alloy is fixed without contact with other parts. According to the invention, it is possible to realize a compact charged particle beam apparatus with non-evaporable getter pumps which can maintain high degree of vacuum even during emission of an electron beam without generating foreign particles. Next, preferred embodiments of the present invention will be described in detail referring to the accompanying drawings. FIG. 1 shows the structure of a charged particle beam apparatus according to the first embodiment of the invention. This embodiment employs a thermal field emitter electron gun (TFE) as an electron source. This electron source 1 is fitted to a flange with a diameter of 152 mm and connected with a feedthrough to electrodes (suppressor, extractor, tip) (not shown). The electron source 1 is inserted and fixed in an electron gun column 2. The electron gun column 2 consists of a first vacuum chamber 85 and a second vacuum chamber 86 with an opening between them. This leads to a differential pumping effect of a non-evaporable getter pump which increases the achieved degree of vacuum of the first vacuum chamber 85 (decreases the pressure). Another possible design for more compactness is that the first vacuum chamber 85 and the second vacuum chamber 86 are integrated into one vacuum chamber to omit part of the pipe including a valve 16 in a rough pumping port 14. The rough pumping port 14 in the charged particle beam apparatus according to the first embodiment can be detached along the two-dot chain line in FIG. 1, namely outside valves 15 and 16. For this reason, a part for vacuum seal such as a flange is provided in the portion corresponding to the two-dot chain line in FIG. 1. The electron gun column 2 has a sheet non-evaporable getter pump 3 along its inner circumference. When heated, the non-evaporable getter pump 3 is activated to be able to absorb gas molecules. Therefore, a heater (not shown) is provided outside the electron gun column 2. In this embodiment, a sheath heater is wound around it. A non-evaporable getter pump 5 is wound around an electrode heater 4 which is used to bake the electrode before emission to prevent gas generation with electron beam emission. Since the non-evaporable getter pump 3 is in the form of a sheet, it can have larger surface area inside a small vacuum vessel 2 than a pump in the form of a block of several centimeters square and therefore a higher pumping speed and a longer lifetime are assured. Moreover, as shown in FIG. 2, the non-evaporable getter pump 3 consists of a sheet 3-1 and non-evaporable getter alloy 3-2 where the non-evaporable getter alloy 3-2 is deposited on only one side of the sheet 3-1 and this side is on the vacuum side. This is desirable because the brittle non-evaporable getter alloy 3-2 is prevented from coming off due to avoiding contacting the inner wall of the column 301. In case that non-evaporable getter alloy should be deposited on both sides of the sheet; contact with the column is unavoidable. In order to decrease coming off, the non-evaporable getter alloy 3-2 deposited on a surface of the sheet 3-1 is partially stripped to expose part of the sheet surface to make an area free of non-evaporable getter alloy for a means of fixation 302, as shown in FIG. 3. This arrangement is desirable because generation of foreign particles cannot occur due to contact between sheets or contact of the means for fixation 302 with the non-evaporable getter alloy. Also, the means for fixation 302 fixes the non-evaporable getter 3 more securely. Besides, not only generation of foreign particles can be prevented but also thermal conductivity can be increased, because the sheet 3-1 is in contact with the column 301 in this way and heated by a heater wound around the outside of the column 301. If a sheet 5-1 is wound around a cylindrical heater 4 as shown in FIG. 4, the sheet should be in contact with the cylinder and non-evaporable getter alloy 5-2 should not be in contact with it. The means for fixing the sheet should be fitted to an exposed area of the sheet 5-1 as mentioned above to avoid contact with the non-evaporable getter alloy 5-2. An exposed area may be made by stripping part of the deposited non-evaporable getter alloy or using a mask during the deposition process to leave an alloy-free area in the deposited non-evaporable getter alloy in advance. Although the sheet non-evaporable getter pump is used here, instead a non-evaporable getter material can be deposited on the heater surface too. This increases packaging density and reduces the risk of the material coming off. On the other hand, special care must be taken not to allow the non-evaporable getter alloy deposited on the heater surface to touch other components. If there were loose foreign particles, an electric discharge due to shorting would be likely to occur because the non-evaporable getter material is an alloy and electrically conductive. Therefore, this arrangement seems particularly advantageous when an electron gun which includes a high voltage component is used. FIG. 12 shows the result of a test on the frequency of generation of loose foreign particles. In this test, three samples were prepared: (1) a sample with non-evaporable getter (NEG) alloy film formed at both sides of the sheet, (2) a sample with non-evaporable getter alloy film formed at both sides of the sheet and a NEG-free area clamped by fixation means, and (3) a sample with non-evaporable getter alloy film formed at one side of the sheet placed in a vacuum vessel. The test method was as follows: the sheet was inserted along the inner wall of a vacuum vessel with an inside diameter of 37 mm, the vessel was fixed above a silicon wafer with no foreign matter, the vessel outer wall was hit with a hammer 20 times, then foreign particles which had fallen on the silicon wafer were counted. The test is considered an acceleration test on foreign particles. An optical microscope was used to count foreign particles. Foreign particles with a diameter of 5 microns or more were detected by visual inspection and recorded. The test result indicates that the number of foreign particles is as many as over 3000 for the sample with non-evaporable getter alloy film formed at both sides. For the sample with non-evaporable getter alloy film formed at both sides and clamped by fixation means, the number is incomparably small or 6. This is probably because the fixation means decreases the frequency of contact between the vacuum vessel inner wall and the non-evaporable getter alloy during hitting and reduces the force of contact. For the sample with non-evaporable getter alloy film formed at one side, it was confirmed that the number of foreign particles is minimum or 1. If the sheet with non-evaporable getter alloy film formed at one side is clamped by fixation means, it is considered to generate less foreign particles due to disturbance. In addition to the above type of non-evaporable getter pump, there is a porous type which is made by pulverized non-evaporable getter alloy into fine particles of 100 mesh or so and forming them into pellets of several centimeters square. Since this type has a large effective surface area, it is advantageous in that the pumping speed can be higher than the sheet type or deposition type but disadvantageous in that foreign particles are easily generated upon contact. In this embodiment, as shown in FIG. 1, an additional chamber 17 is provided beside the electron gun column 2 and some pellets 20 are inserted therein. Beneath the additional chamber 17 is a heater 19 which is used to activate the non-evaporable getter pellets 20. It is desirable to provide a vacuum gauge 18 in the additional chamber 17 to check the achieved degree of vacuum. Also, as shown in FIG. 5, if the boundaries with the electron gun column 2 and the additional chamber 17 are partitioned by meshes 304 and 305, foreign particles are prevented from entering the electron gun column 2. As shown in FIG. 14, when the pellets are placed in the additional chamber 17 downward from the opening for connection with the electron gun column 2 by a distance as indicated by arrow 401, loose particles of non-evaporable getter alloy hardly enter the column under the gravitational influence. A thermocouple on the side face of the electron gun column 2 monitors the temperature of heating the non-evaporable getter pump 3. In this embodiment, the sheet non-evaporable getter pump 3 placed along the inner circumference of the electron gun column 2 is designed to be activated at 400° C. for ten minutes. The non-evaporable getter pump 5 around the electrode heater 4 is designed to be activated at 550-600° C. The reason for this is that when baking by the electrode heater takes place for about 8 hours as described later, it is important to prevent the non-evaporable getter pump 5 around the heater from being activated and absorbing a lot of gas, resulting in a shorter lifetime. Since downstream of the electron gun column 2 there is an electro-optics column 6 which includes a coil 38 and electric wiring, usually the column temperature cannot be increased to more than 100° C. Hence, because of insufficient baking, it is estimated that a considerable amount of gas which the non-evaporable getter pump hardly removes is released from the wall surface on the vacuum side. Besides, inflow of rare gases such as argon gas from the sample chamber 7 with the lowest degree of vacuum might lower the degree of vacuum in the electron gun column 2. Since the atmosphere contains about 1% argon, particular attention must be paid to this point. Typically the sample chamber is evacuated by a turbo-molecular pump 9 and the degree of vacuum in the chamber is about 10−3 Pa. In order to solve this problem, the conventional apparatus as shown in FIG. 8 uses special ion pumps (IP-1, -2, -3) to evacuate the chambers separated through small-radius openings. As can be understood from FIG. 6, this embodiment (indicated by solid line) is remarkably different from the conventional apparatus (indicated by broken line). As shown in FIG. 8, the ion pumps (equivalent to IP-1, -2, and -3 in FIG. 8) are fixed somewhat away from the column in order to avoid the influence of a magnetic field from the getter pump, which also limits the possibility of size reduction. Next, details of this embodiment will be described referring to FIG. 1. As mentioned above, since a high degree of vacuum cannot be maintained only by the non-evaporable getter pump 3, this embodiment combines it with an ion pump. This apparatus includes a series of three vacuum chambers: an electron gun chamber as the electron source 1 located most upstream (first vacuum chamber 85), an intermediate chamber (second vacuum chamber 86) connected with the chamber 85 through an opening, and the electro-optics column 6 (third vacuum chamber 87) connected with the chamber 86 thorough an opening. Further, the third vacuum chamber 87 is connected with the sample chamber 7 through an opening, constituting a differential pumping structure. The upstream electron gun chamber and intermediate chamber incorporate non-evaporable getter pumps 3 and 5 respectively and the additional chamber 17, located beside the intermediate chamber, incorporates pellet type non-evaporable getter pumps 20 and the ion pump 13 is provided for the downstream electro-optics column 6 to evacuate it. The partial pressure of gas hardly evacuated by the non-evaporable getter pump is very low, so it has been demonstrated by an experiment that a single small ion pump with a pumping speed of 20 liters/second or less is enough to remove such gas. Especially it is more advantageous to use a sputter ion pump or noble ion pump since it removes rare gases efficiently at a lower pumping speed. As FIG. 6 suggests, space requirement can be remarkably reduced in comparison with the conventional apparatus with three ion pumps (indicated by dotted line), contributing to apparatus compactness. Another advantage is that when the weighty ion pump is located in as low a position as possible, the position of centroid is low and the vibration characteristic is substantially improved. The largest advantageous effect is that generation of foreign particles by the sheet non-evaporable getter pump is prevented and the pellet type non-evaporable getter pump 20 with a high pumping speed is operated without generating foreign particles. Next, the process of attaining a prescribed vacuum condition according to this embodiment will be explained. After all components which are to face the vacuum in the electron gun column 2 are cleaned and dried, they are assembled. While the assembled electron gun column 2 is evacuated, it is attached to another apparatus in which the baking temperature is not limited to 100° C. or less unlike this embodiment and baking is performed at 300° C. for about 8 hours using the sheath heater (not shown) wound around the electron gun column 2 to degas the inside. Then, after breaking the vacuum of the chamber, the electron gun column 2 is removed and mounted on the electro-optics column 6 of the scanning electron microscope and vacuum pumping is started by the turbo-molecular pump 9. The valves 15, 16 and 21 fitted to the rough pumping port 14 are opened to remove gas from the electron gun column 2 efficiently. In this condition, the heater (not shown) wound around the outside of the electron gun column 2 is turned on to start baking. During baking, the temperature of the interface between the electron gun column 2 and the electro-optics column 6 is monitored and when the temperature reaches about 80° C., the heater is turned off. Baking is performed for about 10 hours under the above mentioned temperature control. After that, voltage is supplied to the electrode heater 4 to bake it and, at the same time, activate the non-evaporable getter pump 5 around it. Here, a target temperature of the heater 4 of about 550° C. is held for about one hour. To activate the pellet type non-evaporable getter pump 20 in the additional chamber 17, the heater 19 is turned on and maintained at 350° C. for one hour. After the temperature goes down to room temperature naturally, the valves 15, 16 and 21 fitted to the rough pumping port 14 are closed and the ion pump 13 is turned on for evacuation. With the above procedure, vacuum pumping is performed without foreign particles from the non-evaporable getter pump and the achieved degree of vacuum in the electron gun column 2 becomes 10−8 Pa. It has been confirmed that even when in this condition a gun valve 8 driven by an air cylinder is opened to open the sample chamber through the opening, the degree of vacuum in the electron gun column 2 is maintained at the level of 10−8 Pa. The degree of vacuum of the ion pump 13 is about 5×10−6 Pa. It can be said from this that as a result of differential pumping, the achieved degree of vacuum is higher as the chamber lies more upstream. Next, control means of the apparatus according to this embodiment will be described. The various components of the apparatus including the turbo-molecular pump 9, ion pump 13, electron source 1, gun valve 8, electron optics 38, vacuum gauge 18 and heater 19 are connected with the control means 501 so that the control means 501 can receive and transmit operation and detection signals and a processor in the control means 501 performs sequence control. A display 500 is used for user interfacing and display of an SEM image. It has been confirmed that through the control means, 2 kV is supplied to the electron source to let it emit electrons and the electron gun emits an electron beam without any abnormal discharge and any substantial change in the degree of vacuum while keeping the degree of vacuum in the electron gun column 2 at the level of 10−8 Pa. In addition, although the non-evaporable getter pump tends to decrease its pumping speed as it absorbs more gas, a high degree of vacuum can be achieved continuously for as long as 3-4 years thanks to: (1) adoption of the differential pumping structure, (2) combination with the sputter ion pump, and (3) increased pumping speed by the use of the sheet non-evaporable getter pump and pellet type non-evaporable getter pump. Although this embodiment adopts an ion pump as a pump combined with the non-evaporable getter pump, a turbo-molecular pump may be used instead of an ion pump. However, in the case of a turbo-molecular pump, since its blade, which turns for vacuum pumping, is structurally destined to vibrate during turning, if it is located-near the electron gun, the SEM image may vibrate. Hence, it is more desirable to use an ion pump or a vacuum pumping device which vibrates less, as the pump combined with the non-evaporable getter pump. So far the first embodiment as exemplified by a charged particle beam apparatus using electron beams, particularly a scanning electron microscope, has been described. However, obviously the invention can be applied to many types of charged particle beam apparatus such as transmission electron microscopes, electron beam writing systems and focused ion beam systems using ion particles. While the first embodiment concerns an apparatus which uses an auxiliary pump, the second embodiment concerns an apparatus in which a column does not requires any type of auxiliary pump such as an ion pump or turbo-molecular pump. Referring to FIG. 7, the basic structure of the apparatus is almost the same as the first embodiment except the following points. First, in the second embodiment, the ion pump 13 for the electro-optics column 6 is eliminated and instead a valve 300 is connected with the sample chamber 7. Carbon contaminants on parts with low heat resistance which cannot withstand the baking temperature of 200° C. or so are cleaned in advance. It is particularly important to remove all oily residues on machined surfaces of metallic parts. This reduces generation of hydrocarbon gases which a non-evaporable getter pump hardly removes. Although generation of hydrocarbon gases is reduced, all such gases are not removed. Therefore, the second difference from the first embodiment is to use the evacuation function of the turbo-molecular pump 9 which evacuates the sample chamber 7 connected with the valve 300. Since the turbo-molecular pump mechanically absorbs gas molecules, it can remove rare gases such as hydrocarbon and argon. The conductance can be controlled by adjusting the opening degree of the valve 300; while monitoring the vacuum gauge 18, the opening degree of the valve 300 should be adjusted and when the most desirable degree of vacuum is attained, the valve position should be fixed. The other structural parts and the control method and means may be almost the same as in the first embodiment. However, it should be noted here that there is no longer information on vacuum which would be obtained from the ion pump. To compensate for lack of such information, a signal from the vacuum gauge 18 in the additional chamber 17 may be used or a vacuum gauge (not shown in FIG. 7) may be newly installed for the electro-optics column 6. As detailed so far, according to the present invention, it is possible to realize a compact charged particle beam apparatus, such as a scanning electron microscope, focused ion beam system or charged particle beam apparatus with a plurality of columns, in which the degree of vacuum in the column including the electron source is maintained at the level of 10−8 Pa with less generation of foreign particles. This embodiment concerns non-evaporable getter alloy in a form other than a sheet or pellet. Specifically, the getter alloy size should be on the millimeter order (less than 10 mm) and typically, grained non-evaporable getter alloy of approx. 3 mm square is easy to handle. The alloy is a bulk alloy of the above size and generates no foreign particles upon contact. However, since the effective surface area of the bulk alloy is smaller, the pumping speed tends to be lower. By contrast, the pellet type is porous because it is made by sintering fine particles of several microns to several hundreds of microns and therefore in case of the pellet type, the surface area is larger but fine particles easily come off upon contact. In order to increase the surface area of grained non-evaporable getter alloy, its surface should have a convexo-concave shape. The surface of the grained non-evaporable getter alloy used in this embodiment has a convexo-concave pattern which is repeated in cycles of several microns to several dozen microns. As a result of comparison in pumping speed between the grained non-evaporable getter pump and the pellet type one, it has been found that under the same test conditions, the pumping speed of the pellet is 3 or 4 times higher and the pumping speed difference between them may be considered to be not so significant. In other words, since the grained getter alloy generates less foreign particles upon contact, it is suitable to be located in the vicinity of the electron source. An embodiment as a scanning electron microscope which uses such grained non-evaporable getter alloy will be detailed below. FIG. 9 illustrates the basic structure of the scanning electron microscope according to this embodiment. Like the first embodiment, this embodiment employs a thermal field emitter electron gun (TFE) as an electron source. This electron source 1 is fitted to a flange with a diameter of 152 mm and connected with a feed through to an electrode (suppressor, extractor, tip) (not shown). The electron source 1 is inserted and fixed in an electron gun column 2. The electron gun column 2 consists of a first vacuum chamber 85 and a second vacuum chamber 86 with an opening between them. This leads to a differential pumping effect of a non-evaporable getter pump which increases the achieved degree of vacuum of the first vacuum chamber 85 (decreases the pressure). The primary characteristic of this embodiment is to provide a pump 25 in which grained non-evaporable getter alloys is held by metal mesh in the second vacuum chamber 86. In this arrangement, contact between the alloys and the mesh is unavoidable. Therefore, generation of foreign particles upon contact between the mesh and the grained non-evaporable getter alloy was examined by a test. The mesh used in the test is made of stainless steel and its open-area-ratio is 70-80%. The test was conducted as follows: five particles (grains) of alloy are placed on the mesh and the mesh is reciprocated horizontally over a silicon wafer five times; then falled foreign particles on the wafer are counted. For the purpose of comparison, pellet alloy was tested similarly. Since actually the alloy is just held and there is virtually no relative movement, this may be an acceleration test under severe conditions. The test result is shown in FIG. 11. It has been found that 29 foreign particles came from the pellet and only one particle from the grained alloy. This result reveals that the number of foreign particles from the grained alloy is incomparably small. The use of grained alloy makes it possible that the non-evaporable getter pump is located in the immediate vicinity of the electron gun without generation of foreign particles. Consequently a high degree of vacuum can be maintained in the area around the electron source which requires the highest level of vacuum. Next, a concrete structure which uses grained non-evaporable getter alloy will be detailed. FIG. 10 shows the vacuum pump 25 which holds grained non-evaporable getter alloy 26. The grained non-evaporable getter alloy 26 used here has a total weight of 75 grams and is housed in the space surrounded by the outer wall of an anode electrode heater (ceramic heater in this case) 4 and a stainless steel mesh (open-area-ratio 70%) 27. This structure is efficient in the sense that the grained non-evaporable getter alloy can be easily heated in the vacuum and baking of the anode electrode can be done simultaneously. Although the getter alloy is placed outside the heater in this embodiment, it may be placed inside the cylindrical heater or both inside and outside the heater. In the figure, 4-1 denotes an electrode which supplies electricity to the heater 4. As described above, the pump 25 which uses grained non-evaporable getter alloy is placed in the second vacuum chamber 86 in the scanning electron microscope as shown in FIG. 9; however, the present invention is not limited thereto. Needless to say it may be placed in any other vacuum chamber including the most upstream vacuum chamber. For example, if it is located in the immediate vicinity of the electron source which requires the highest level of vacuum, vacuum pumping without generation of foreign particles is possible. As a result of a test in which actual vacuum pumping was done using a non-evaporable getter pump, a superhigh degree of vacuum, 5.0×10−8 Pa, was achieved for the electron source. The fourth embodiment does not include a vacuum gauge like the vacuum gauge 18 for the auxiliary pump in the additional chamber 17 which the first embodiment includes. The absence of such a vacuum gauge reduces the apparatus cost. Next, the fourth embodiment will be detailed referring to FIG. 13. The basic structure is the same as that of the first embodiment. This embodiment employs a thermal field emitter electron gun (TFE) as an electron source. This electron source 1 is fitted to a flange with a diameter of 152 mm and connected with a feedthrough to an electrodes (suppressor, extractor, tip) (not shown). The electron source 1 is inserted and fixed in an electron gun column 2. The electron gun column 2 consists of a first vacuum chamber 85 and a second vacuum chamber 86 with an opening between them. This leads to a differential pumping effect of a non-evaporable getter pump which increases the achieved degree of vacuum of the first vacuum chamber 85 (decreases the pressure). The electron gun column 2 has a sheet non-evaporable getter pump 3 along its inner circumference. When heated, the non-evaporable getter pump 3 is activated to absorb gas. Therefore, a heater (not shown) is provided outside the electron gun column 2. In this embodiment, a sheath heater is wound around it. Also a non-evaporable getter pump is wound in the first vacuum chamber 85 facing the inner circumference of an electrode heater 4. Since the non-evaporable getter pump 3 is in the form of a sheet, it can have a larger surface area inside a small vacuum vessel 2 than a pump in the form of a block of several centimeters square and therefore a higher pumping speed and a longer lifetime are assured. In this embodiment, pellet non-evaporable getter alloy 20 is placed in the additional chamber 17 connected with the second vacuum chamber 86 and a heater 19 is attached to the outside (atmosphere side) of the additional chamber. The difference from the first embodiment is absence of a vacuum gauge which is intended to check the degree of vacuum achieved by the non-evaporable getter pump in the additional chamber 17. In this embodiment, the same function is provided without a vacuum gauge. The first vacuum chamber 85 and the electro-optics column 6 located downstream of the second vacuum chamber 86 are connected through a rough pumping port 24 and the chambers can be connected or disconnected through corresponding valves 16 and 22. The vacuum chamber and sample chamber 7 which are on the downstream are connected through a rough pumping port 23. The electro-optics column 6 is evacuated by an ion pump 13. Regarding the ion pump 13, the output current value depends on the degree of vacuum and thus the degree of vacuum can be measured without an additional vacuum gauge. The pumping effect on the upstream can be checked taking advantage of this feature. The procedure is as follows. First, gas is roughly pumped out of the whole apparatus until the degree of vacuum in the sample chamber 7 reaches about 1×10−3 Pa. The degree of vacuum in the sample chamber 7 is measured using a vacuum gauge (not shown). During this process, the valves 16, 21 and 22 remain open. By doing so, the whole column is efficiently evacuated. After rough pumping is finished, baking of the ion pump 13, rough pumping ports 23, 24, additional chamber 17 and electron gun chamber 3 is done preferably at 200° C. for about 10 hours to reduce gas from the inner wall surface. Then, the ion pump 13 is turned on to start vacuum pumping and the degree of vacuum is recorded on a chart sheet. Then, the non-evaporable getter alloy 3 is heated and activated. A sheath heater (not shown) is used to activate it. At the same time, the ceramic heater 4 is turned on to activate grained non-evaporable getter alloy 26 (FIG. 10). In this embodiment, 400° C. is maintained for one hour for activation. Next, the degree of vacuum of the ion pump 13 in this condition is measured. Let's take the degree of vacuum measured here as A. Then, the valve 21 is closed. At this time, it is necessary to confirm that the degree of vacuum of the ion pump increases. Let's take this degree of vacuum as B. Then, the valve 16 is closed and it should be confirmed that the degree of vacuum decreases. This confirmation is made to make sure that the non-evaporable getter alloy in the electron gun chamber 3 is active and performs vacuum pumping. Let's take this degree of vacuum as C. Then, the valve 22 is closed and it should be confirmed that the degree of vacuum decreases. Let's take this degree of vacuum as D. Lastly, whether the relation B>C>D>A exists or not is checked. If so, the air tightness of the chambers constituting the differential pumping system, operation of the ion pump, activation of the non-evaporable getter alloy are normal, which means that the system works normally without a vacuum gauge in the additional chamber 17. Needless to say, there is no problem with the provision of a vacuum gauge in the additional chamber 17. Referring to FIG. 15, a focused ion beam (FIB) system according to an embodiment of the present invention will be described below. The FIB system is a system which focuses ion particles heavier than electrons on a sample 49 to process the sample surface or detects electrons emitted from an area irradiated with an ion beam in the same manner as the SEM to create an image to be observed. The conventional FIB system uses two or more ion pumps. As shown in FIG. 15, if the present invention is applied, the FIB column in the system and its surroundings can be smaller, as in the first embodiment. The optics which focuses an ion beam 50 is a static electron optics consisting of a plurality of electrodes 40, 41, 42, 43 and 44 and does not have an electromagnetic lens which uses a coil, as seen in the SEM. Therefore, the heat resistance is higher than in the SEM and the FIB system can introduce non-evaporable getter pumps 45 and 46 more easily. The ion source 39 in the FIB system must be located most upstream and the degree of vacuum must be maintained at the level of 10−7 Pa or so. For this reason, the system adopts a differential pumping structure like the SEM according to the first embodiment. The system shown in FIG. 15 has a two-step differential pumping structure. A sample chamber 54 and a vacuum chamber 53 located upstream of it are evacuated by a turbo-molecular pump 47. A non-evaporable getter pump 45 in an ion source chamber 52 is in the form of a sheet and obviously means to avoid contact with the non-evaporable getter alloy as used in the first embodiment is also useful in this embodiment in order to prevent generation of foreign particles. As mentioned above, since an ion beam is focused by the static electron optics, a non-evaporable getter pump 46 may also be placed in the vacuum chamber 53. Hence, the pumping speed can be increased. Furthermore, as shown in FIG. 15, an additional chamber 17 is provided as means to evacuate the ion source chamber 52 with pellets non-evaporable getter alloy 20 and thus a high vacuum is maintained at high pumping speed without generation of foreign particles, as in the first embodiment. The structure and operation of the evacuation pump in the additional chamber are the same as in the first embodiment. It is desirable to provide an ion pump 51 for vacuum pumping of the ion source chamber 52 because it removes rare gases which a non-evaporable getter pump hardly removes and methane. By using measurement data on the degree of vacuum of the ion pump 51, the vacuum gauge 18 in the additional chamber 17 may be eliminated, which is desirable from the viewpoint of apparatus cost reduction. The above components are connected with control means 504 through signal lines so that the control means 504 can receive and transmit control signals and image data and control operation sequences for the whole apparatus. A display 505 can be used for user interfacing and display of an image. The other structural components are the same as in the conventional FIB system and detailed description thereof is omitted here. This embodiment is also applicable to a system which does not use an electron beam. A microsampling apparatus according to the sixth embodiment of the invention will be described below, referring to FIG. 16. A microsampling apparatus is designed for inspection and analysis of semiconductor devices, etc. whereby part of a semiconductor device is cut and its cross section is observed and analyzed. The apparatus has an FIB column 77 for cutting a sample and an SEM column 78 for observing the cutting position and cut cross section simultaneously where the two columns are angled to each other. The columns are also inclined by a given angle to an axis 81 vertical to the surface of a sample 60 placed in a horizontal plane. Hence the two columns are inclined adjacently to each other. This structure has a problem that a plurality of ion pumps which are conventionally attached to each column may interfere with each other or because of the weight of the ion pumps, the position of centroid is high and the columns easily vibrate. In the microsampling apparatus according to this embodiment, the FIB and SEM columns each use only one ion pump. Therefore, the overall weight of the apparatus is far lighter than that of the conventional apparatus in which each column uses two or three ion pumps. In addition, if the ion pump is a sputter ion pump or noble ion pump, the efficiency in removal of rare gases which a non-evaporable getter pump hardly removes is improved, contributing to further size reduction. In this embodiment, the FIB column and the SEM column each use one separate ion pump but one ion pump may be shared by both the columns. An ion source 61 is located in the most upstream vacuum chamber of the FIB column 77 in which a non-evaporable getter pump 79 is placed. Also a non-evaporable getter pump 80 is placed in a downstream vacuum chamber on the other side of an opening in a static electron optics 63 and a vacuum chamber on the other side of an opening in a static electron optics 64 is evacuated by an ion pump 69. An ion beam emitted from the ion source 61 goes through the static electron optics 63, 64 and 65 and is focused on a target area of the sample surface to perform a given cutting process. The present invention is applied to the SEM column 78 like the FIB column. An electron source 62 is located in the most upstream vacuum chamber in which a non-evaporable getter pump 81 is placed. Also a non-evaporable getter pump 82 is placed in a downstream vacuum chamber on the other side of an opening 66 and a vacuum chamber located more downstream is evacuated by an ion pump 70. Since the latter vacuum chamber incorporates an electromagnetic optics 67 which has a coil and is low in heat resistance, a non-evaporable getter pump cannot be placed in it. This structure is the same as the SEM column in the first embodiment. An electron beam emitted from the electron source 62 is focused on the surface of the sample 60 where secondary electrons are generated; the secondary electrons are detected by a secondary electron detector 76 to form an SEM image whether it is during or before/after ion beam processing. Since the ion source chamber of the FIB column 78 and the electron source chamber of the SEM column 77 require a high degree of vacuum as mentioned above, an auxiliary pump with pellets non-evaporable getter alloy 20 in the additional chamber 17 as shown in FIG. 16 is useful. This pump is far smaller and far lighter than an ion pump and when heated at a given temperature for a given time, at room temperature it achieves a pumping speed equivalent to or higher than the pumping speed which an ion pump would achieve. The FIB column 77 is fixed in an inclined position where the angle θ of its central axis 84 to the vertical axis 81 is 30 degrees. The central axis 80 of the SEM column 78 is inclined by 45 degrees with respect to the vertical axis 81. The relative angle between the FIB column and the SEM column is 90 degrees. Under the two columns is a sample chamber which is evacuated by a turbo-molecular pump 83. There are also a stage 71 which holds the sample 60 and moves and positions it, arms 72 and 73 for microsampling, and drive means 74 and 75 which drive them. These microsampling means are intended to handle a micro chip processed with an ion beam. The above components are connected with control means 506 through signal lines so that the control means can receive and transmit control signals and image data. A display 507 may be used for user interfacing and display of an image. As discussed so far, according to the present invention, it is possible to realize a compact charged particle beam apparatus, for example a compact scanning electron microscope, focused ion beam system or charged particle beam apparatus with plural columns, which maintains the degree of vacuum in a column incorporating an electron source at a high level of 10−8 Pa and generates few foreign particles.
	claims	1. A system comprising:a beam filter positioning device comprising a plate configured to support one or more beam filters, and one or more axes operable to move the plate relative to a beam line, said one or more axes comprising one or more servo motors and one or more feedback devices; anda control mechanism coupled to the one or more servo motors and the one or more feedback devices, said control mechanism being configured to adjust a position of at least one of the one or more beam filters relative to the beam line based on at least signals from the one or more feedback devices. 2. The system of claim 1 wherein said one or more axes comprises a linear axis operable to translate the plate and a rotation axis operable to rotate the plate. 3. The system of claim 2 wherein said linear axis is operable to move the rotation axis. 4. The system of claim 1 wherein said one or more beam filters comprises one or more photon flattening filters. 5. The system of claim 1 wherein said one or more beam filters comprises one or more photon flattening filters and one or more electron scattering foils. 6. The system of claim 5 wherein the one or more photon flattening filters are arranges in an arc or a circular configuration having a first radius, and the one or more eletron scattering foils are arranged in an arc or circular configuration having a second radius that is different from the first radius. 7. The system of claim 1 further comprising an ion chamber and an axis operable to move the ion chamber, said ion chamber being coupled to said control mechanism for providing signals indicative of the parameters of a beam, and said ion chamber axis being coupled to the control mechanism configured to automatically adjust a position of the ion chamber relative to the beam line. 8. The system of claim 7 further comprising a field light assembly comprising one or more light sources and a mirror member reflecting light from one of the light sources to provide a light field that would illuminate from a virtual light source when in use, said mirror member being supported by the plate supporting the one or more beam filters, and said one or more light sources being movable by the ion chamber axis, thereby a position of the virtual light source is automatically adjusted by the control mechanism. 9. A beam filter positioning device comprising:a plate configured to support one or more beam filters; andtwo or more axes operable to move the plate. 10. The beam filter positioning device of claim 9 wherein said two or more axes comprise a first linear axis operable to translate the plate and a rotation axis operable to rotate the plate. 11. The beam filter positioning device of claim 10, wherein said first linear axis is operable to translate the rotation axis. 12. The beam filter positioning device of claim 9 wherein said one or more beam filters comprise one or more photon flattening filters and one or more electron scattering foils. 13. The beam filter positioning device of claim 12 wherein said one or more photon flattening filters are positioned in a circular or partial circular configuration having a first radius, said one or more electron scattering foils are positioned in a circular or partial circular configuration having a second radius different from the first radius. 14. The beam filter positioning device of claim 9 further comprising an ion chamber and an axis operable to move the ion chamber. 15. The beam filter positioning device of claim 14 further comprising a field light assembly comprising a mirror member and one or more light sources, said mirror member being supported by the plate supporting the one or more beam filters, and said one or more light sources being movable by said ion chamber axis. 16. The beam filter positioning device of claim 9 further comprising a target assembly, said target assembly including one or more targets and an axis operable to move the target assembly. 17. The beam filter positioning device of claim 9 further comprising a backscatter filter operable to be moved by one of the two or more axes moving the plate. 18. The beam filter positioning device of claim 9 wherein said two or more axes comprise one or more servo motors and one or more feedback devices. 19. A method of adjusting a beam filter position in a radiation system comprising the steps of:providing a plate and one or more beam filters supported by the plate; andmoving the plate using one or more motion axes to position a beam filter relative to a beam line, said one or more axes comprising one or more servo motors and one or more feedback devices;wherein said step of moving is controlled by a control mechanism that is coupled to the one or more servo motors and the one or more feedback devices and operable by a computer software in an non-transitory computer readable medium to adjust the position of the beam filter. 20. A method of adjusting field light in a radiation system comprising the steps ofproviding a field light assembly including a mirror and a light source; andmoving the mirror using at least one first motion axis and/or moving the light source using a second motion axis to provide a light field that would illuminate from a virtual light source, said first and second motion axes each comprising a servo motor and one or more feedback devices;wherein said step of moving the mirror and/or moving the light source are controlled by a control mechanism that is coupled to the servo motors and feedback devices and operable by a computer software in a non-transitory computer readable medium to adjust a position of the virtual light source in three degrees of freedom. 21. A beam filter device comprising:a body;a plurality of photon flattening filters supported by the body and arranged in an arc or circular configuration having a first radius; anda plurality of eletron scattering foils supported by the body and arranged in an arc or a circular configuration having a second radius that is different from the first radius. 22. The beam filter device of claim 21 wherein the second radius is greater than the first radius. 23. The beam filter device of claim 21 further comprising a mirror supported by the body and configured to reflect light from a source. 24. The beam filter device of claim 21 wherein the body is provided with a plurality of ports adapted to receive and support the plurality of photon flattening filters. 25. The beam filter device of claim 21 wherein the plurality of electron scattering foils comprise primary scattering foils and secondary scattering foils arranged a different elevations. 26. The beam filter device of claim 21 further comprising a member coupled to the body and adapted to aid in moving the body by one or more motion axes.
	description	This application is a continuation of U.S. patent application Ser. No. 10/306,468, filed Nov. 27, 2002 now U.S. Pat. No. 6,898,263, which is hereby incorporated by reference in its entirety. This invention relates generally to medical imaging systems, and more specifically to a method and apparatus for soft-tissue volume visualization using a medical imaging system. In spite of recent advancements in computed tomography (CT) technology, such as faster scanning speed, larger coverage with multiple detector rows, and thinner slices, energy resolution is still a missing piece, namely, a wide x-ray photon energy spectrum from the x-ray source and a lack of energy resolution from CT detection systems preclude energy discrimination CT. X-ray attenuation through a given object is not a constant. Rather, x-ray attenuation is strongly dependent on the x-ray photon energy. This physical phenomenon manifests itself in an image as a beam-hardening artifact, such as non-uniformity, shading, and streaks. Some beam-hardening artifacts can be easily corrected, but others may be more difficult to correct. In general, known methods to correct beam hardening artifacts include water calibration, which includes calibrating each CT machine to remove beam hardening from materials similar to water, and iterative bone correction, wherein bones are separated in the first-pass image then correcting for beam hardening from bones in the second-pass. However, beam hardening from materials other than water and bone, such as metals and contrast agents, may be difficult to correct. In addition, even with the above described correction methods, conventional CT does not provide quantitative image values. Rather, the same material at different locations often shows different CT numbers. Another drawback of conventional CT is a lack of material characterization. For example, a highly attenuating material with a low density can result in the same CT number in the image as a less attenuating material with a high density. Thus, there is little or no information about the material composition of a scanned object based solely on the CT number. Additionally, similar to traditional x-ray methods, at least some known soft-tissue volume visualization methods project rays through an object. However, without segmenting out bone from other material within the object, visualization of subtle, yet possibly diagnostically important, structures may be difficult. Traditionally, bone segmentation of CT images is based on image characteristics and Hounsfield numbers. Dual-energy decomposition lends itself nicely for the soft-tissue and bone separation. However, the methods and systems described below can also remove calcification, which contains diagnostic information in CT. In one aspect, a method for obtaining data is provided. The method includes scanning an object using a multi-energy computed tomography (MECT) system to obtain data to generate an anatomical image, and decomposing the obtained data to generate a first density image representative of bone material and a second density image representative of soft-tissue. The method further includes segmenting at least one of the first density image and the second density image, and volume rendering the second density image. In another aspect, a multi-energy computed tomography (MECT) system is provided. The MECT includes at least one radiation source, at least one radiation detector, and a computer operationally coupled to the radiation source and the radiation detector. The computer is configured to receive data regarding a first energy spectrum of a scan of an object, receive data regarding a second energy spectrum of the scan of the object, decompose the received data to generate a first density image representative of bone material and a second density image representative of soft-tissue, identify within the first density image areas smaller than a predetermined size, and import data into the second density image from the data regarding the first energy spectrum according to the identified areas of the first density image. In a further aspect, a multi-energy computed tomography (MECT) system is provided. The CT system includes at least one radiation source, at least one radiation detector, and a computer operationally coupled to the radiation source and the radiation detector. The computer is configured to receive image data for an object, decompose the received image data into a first density image representative of bone material and a second density image representative of soft-tissue, identify within the first density image areas smaller than a predetermined size, and extract the identified areas within the first density image using an algorithm configured to use the connectivity of binary pixels. In an additional aspect, a computer readable medium embedded with a program is provided. The computer readable medium is configured to instruct a computer to receive data regarding a first energy spectrum of a scan of an object, receive data regarding a second energy spectrum of the scan of the object, decompose the received data to generate a first density image representative of bone material and a second density image representative of soft-tissue, threshold the first density image to produce a first binary mask image representing bone and calcification, extract areas identified as smaller than a predetermined size from the first binary mask image to produce a second binary mask image substantially representing calcification, and import data into the second density image from the received data according to the extracted areas of the first binary mask image. In yet another aspect, a method is provided for obtaining data. The method includes scanning an object using a multi-energy computed tomography (MECT) system to obtain data to generate an anatomical image, decomposing the obtained data to generate a first density image and a second density image, and volume rendering at least one of the first and second density image. The methods and apparatus described herein facilitate augmenting segmentation capabilities of multi-energy imaging with a method for image-based segmentation. The methods and systems described herein facilitate real-time volume buildup and visualization of soft-tissue. More specifically, the methods and systems described herein facilitate segmenting bone material from an image while retaining calcification within the image, and facilitate augmenting segmentation capabilities of multi-energy imaging to guide surgical navigation and radiation therapy. In some known CT imaging system configurations, an x-ray source projects a fan-shaped beam which is collimated to lie within an x-y plane of a Cartesian coordinate system and generally referred to as an “imaging plane”. The x-ray beam passes through an object being imaged, such as a patient. The beam, after being attenuated by the object, impinges upon an array of radiation detectors. The intensity of the attenuated radiation beam received at the detector array is dependent upon the attenuation of an x-ray beam by the object. Each detector element of the array produces a separate electrical signal that is a measurement of the beam intensity at the detector location. The intensity measurements from all the detectors are acquired separately to produce a transmission profile. In third generation CT systems, the x-ray source and the detector array are rotated with a gantry within the imaging plane and around the object to be imaged such that the angle at which the x-ray beam intersects the object constantly changes. A group of x-ray attenuation measurements, i.e., projection data, from the detector array at one gantry angle is referred to as a “view”. A “scan” of the object comprises a set of views made at different gantry angles, or view angles, during one revolution of the x-ray source and detector. In an axial scan, the projection data is processed to construct an image that corresponds to a two-dimensional slice taken through the object. One method for reconstructing an image from a set of projection data is referred to in the art as the filtered backprojection technique. This process converts the attenuation measurements from a scan into integers called “CT numbers” or “Hounsfield units” (HU), which are used to control the brightness of a corresponding pixel on a cathode ray tube display. To reduce the total scan time, a “helical” scan may be performed, wherein the patient is moved while the data for the prescribed number of slices is acquired. Such a system generates a single helix from a fan beam helical scan. The helix mapped out by the fan beam yields projection data from which images in each prescribed slice may be reconstructed. Reconstruction algorithms for helical scanning typically use helical weighing algorithms that weight the collected data as a function of view angle and detector channel index. Specifically, prior to a filtered backprojection process, the data is weighted according to a helical weighing factor, which is a function of both the gantry angle and detector angle. The weighted data is then processed to generate CT numbers and to construct an image that corresponds to a two-dimensional slice taken through the object. To further reduce the total acquisition time, multi-slice CT has been introduced. In multi-slice CT, multiple rows of projection data are acquired simultaneously at any time instant. When combined with helical scan mode, the system generates a single helix of cone beam projection data Similar to the single slice helical, weighting scheme, a method can be derived to multiply the weight with the projection data prior to the filtered backprojection algorithm. As used herein, an element or step recited in the singular and proceeded with the word “a” or “an” should be understood as not excluding plural said elements or steps, unless such exclusion is explicitly recited. Furthermore, references to “one embodiment” of the methods and systems described herein are not intended to be interpreted as excluding the existence of additional embodiments that also incorporate the recited features. Also as used herein, the phrase “reconstructing an image” is not intended to exclude embodiments of the methods and systems described herein in which data representing an image is generated but a viewable image is not. However, many embodiments generate (or are configured to generate) at least one viewable image. Herein are described methods and apparatus for tissue characterization and soft-tissue volume visualization using an energy-discriminating (also known as multi-energy) computed tomography (MECT) system. First described is MECT system 10 and followed by applications using MECT system 10. Referring to FIGS. 1 and 2, a multi-energy scanning imaging system, for example, a multi-energy multi-slice computed tomography (MECT) imaging system 10, is shown as including a gantry 12 representative of a “third generation” CT imaging system. Gantry 12 has an x-ray source 14 that projects a beam of x-rays 16 toward a detector array 18 on the opposite side of gantry 12. Detector array 18 is formed by a plurality of detector rows (not shown) including a plurality of detector elements 20 which together sense the projected x-rays that pass through an object, such as a medical patient 22. Each detector element 20 produces an electrical signal that represents the intensity of an impinging x-ray beam and hence can be used to estimate the attenuation of the beam as it passes through object or patient 22. During a scan to acquire x-ray projection data, gantry 12 and the components mounted therein rotate about a center of rotation 24. FIG. 2 shows only a single row of detector elements 20 (i.e., a detector row). However, multi-slice detector array 18 includes a plurality of parallel detector rows of detector elements 20 such that projection data corresponding to a plurality of quasi-parallel or parallel slices can be acquired simultaneously during a scan. Rotation of components on gantry 12 and the operation of x-ray source 14 are governed by a control mechanism 26 of MECT system 10. Control mechanism 26 includes an x-ray controller 28 that provides power and timing signals to x-ray source 14 and a gantry motor controller 30 that controls the rotational speed and position of components on gantry 12. A data acquisition system (DAS) 32 in control mechanism 26 samples analog data from detector elements 20 and converts the data to digital signals for subsequent processing. An image reconstructor 34 receives sampled and digitized x-ray data from DAS 32 and performs high-speed image reconstruction. The reconstructed image is applied as an input to a computer 36, which stores the image in a storage device 38. Image reconstructor 34 can be specialized hardware or computer programs executing on computer 36. Computer 36 also receives commands and scanning parameters from an operator via console 40 that has a keyboard. An associated cathode ray tube display 42 allows the operator to observe the reconstructed image and other data from computer 36. The operator supplied commands and parameters are used by computer 36 to provide control signals and information to DAS 32, x-ray controller 28, and gantry motor controller 30. In addition, computer 36 operates a table motor controller 44, which controls a motorized table 46 to position patient 22 in gantry 12. Particularly, table 46 moves portions of patient 22 through gantry opening 48. In one embodiment, computer 36 includes a device 50, for example, a floppy disk drive, CD-ROM drive, DVD drive, magnetic optical disk (MOD) device, or any other digital device including a network connecting device such as an Ethernet device for reading instructions and/or data from a computer-readable medium 52, such as a floppy disk, a CD-ROM, a DVD or an other digital source such as a network or the Internet, as well as yet to be developed digital devices. In another embodiment, computer 36 executes instructions stored in firmware (not shown). Computer 36 is programmed to perform functions described herein, and as used herein, the term computer is not limited to just those integrated circuits referred to in the art as computers, but broadly refers to computers, processors, microcontrollers, microcomputers, programmable logic controllers, application specific integrated circuits, and other programmable circuits, and these terms are used interchangeably herein. CT imaging system 10 is an energy-discriminating (also known as multi-energy) computed tomography (MECT) system in that system 10 is configured to be responsive to different x-ray spectra. This can be accomplished with a conventional third generation CT system to acquire projections sequentially at different x-ray tube potentials. For example, two scans are acquired either back to back or interleaved in which the tube operates at 80 kVp and 160 kVp potentials, for example. Alternatively, special filters are placed between the x-ray source and the detector such that different detector rows collect projections of different x-ray energy spectrum. Alternatively, the special filters that shape the x-ray spectrum can be used for two scans that are acquired either back to back or interleaved. Yet another embodiment is to use energy sensitive detectors such that each x-ray photon reaching the detector is recorded with its photon energy. Although the specific embodiment mentioned above refers to a third generation CT system, the methods described herein equally apply to fourth generation CT systems (stationary detector—rotating x-ray source) and fifth generation CT systems (stationary detector and x-ray source). There are different methods to obtain multi-energy measurements: (1) scan with two distinctive energy spectra, (2) detect photon energy according to energy deposition in the detector, and (3) photon counting. Photon counting provides clean spectra separation and an adjustable energy separation point for balancing photon statistics. MECT facilitates reducing or eliminating a plurality of problems associated with conventional CT, such as, but not limited to, a lack of energy discrimination and material characterization. In the absence of object scatter, one only need system 10 to separately detect two regions of photon energy spectrum, the low-energy and the high-energy portions of the incident x-ray spectrum. The behavior at any other energy can be derived based on the signal from the two energy regions. This phenomenon is driven by the fundamental fact that in the energy region where medical CT is interested, two physical processes dominate the x-ray attenuation, (1) Compton scatter and the (2) photoelectric effect. Thus, detected signals from two energy regions provide sufficient information to resolve the energy dependence of the material being imaged. Furthermore, detected signals from two energy regions provide sufficient information to determine the relative composition of an object composed of two materials. In an exemplary embodiment, MECT decomposes a high-energy image and a low-energy image using a decomposition method, such as through a CT number difference decomposition, a Compton and photoelectric decomposition, a basis material decomposition (BMD), or a logarithm subtraction decomposition (LSD). The CT number difference algorithm includes calculating a difference value in a CT or a Hounsfield number between two images obtained at different tube potentials. In one embodiment, the difference values are calculated on a pixel-by-pixel basis. In another embodiment, average CT number differences are calculated over a region of interest. The Compton and photoelectric decomposition includes acquiring a pair of images using MECT 10, and separately representing the attenuations from Compton and photoelectric processes. The BMD includes acquiring two CT images, wherein each image represents the equivalent density of one of the basis materials. Since a material density is independent of x-ray photon energy, these images are approximately free of beam-hardening artifacts. Additionally, an operator can choose the basis material to target a certain material of interest, thus enhancing the image contrast. In use, the BMD algorithm is based on the concept that the x-ray attenuation (in the energy region for medical CT) of any given material can be represented by proper density mix of other two given materials, accordingly, these two materials are called the basis materials. In one embodiment, using the LSD, the images are acquired with quasi-monoenergetic x-ray spectra, and the imaged object can be characterized by an effective attenuation coefficient for each of the two materials, therefore the LSD does not incorporate beam-hardening corrections. Additionally, the LSD is not calibrated, but uses a determination of the tissue cancellation parameters, which are the ratio of the effective attenuation coefficient of a given material at the average energy of each exposure. In an exemplary embodiment, the tissue cancellation parameter is primarily dependent upon the spectra used to acquire the images, and on any additional factors that change the measured signal intensity from that which would be expected for a pair of ideal, mono-energetic exposures. It should be noted that in order to optimize a multi-energy CT system, the larger the spectra separation, the better the image quality. Also, the photon statistics in these two energy regions should be similar, otherwise, the poorer statistical region will dominate the image noise. The methods and systems described herein apply the above principle to tissue characterization and soft-tissue volume visualization. In specific, ME CT system 10 is utilized to produce CT images as herein described. Pre-reconstruction analysis, post-reconstruction analysis and scout image analysis are three techniques that can be used with MECT system 10 to provide tissue characterization. FIG. 3 is a flow chart representing a pre-reconstruction analysis 54 wherein a decomposition 56 is accomplished prior to a reconstruction 58. Computer 36 collects the acquired projection data generated by detector array 18 (shown in FIG. 1) at discrete angular positions of the rotating gantry 12 (shown in FIG. 1), and passes the signals to a preprocessor 60. Preprocessor 60 re-sorts the projection data received from computer 36 to optimize the sequence for the subsequent mathematical processing. Preprocessor 60 also corrects the projection data from computer 36 for detector temperature, intensity of the primary beam, gain and offset, and other deterministic error factors. Preprocessor 60 then extracts data corresponding to a high-energy view 62 and routes it to a high-energy channel path 64, and routes the data corresponding to a low-energy views 66 to a low-energy path 68. Using the high-energy data and low-energy data, a decomposition algorithm is used to produce two streams of projection data, which are then reconstructed to obtain two individual images pertaining to two different materials. FIG. 4 is a flow chart representing a post-reconstruction analysis wherein decomposition 56 is accomplished after reconstruction 58. Computer 36 collects the acquired projection data generated by detector array 18 (shown in FIG. 1) at discrete angular positions of rotating gantry 12 (shown in FIG. 1), and routes the data corresponding to high-energy views 62 to high-energy path 64 and routes the data corresponding to low-energy views 66 to low-energy path 68. A first CT image 70 corresponding to the high-energy series of projections 62 and a second CT image 72 corresponding to low-energy series of projections 66 are reconstructed 58. Decomposition 56 is then performed to obtain two individual images respectively, pertaining to two different materials. In scout image analysis, the signal flow can be similar to FIG. 3 or FIG. 4. However, the table is moved relative to the non-rotating gantry to acquire the data. The use of dual energy techniques in projection x-ray imaging may facilitate diagnosing and monitoring osteoporosis, and determining an average fat-tissue to lean-tissue ratio (fat/lean ratio). Dual energy techniques may also facilitate cross-sectional or tomographic x-ray imaging for osteoporosis detection in human subjects, and may facilitate non-destructive testing applications, for example explosive and/or contraband detection. The methods and systems described herein apply multi-energy imaging to volume visualization. Techniques that allow visualization of three-dimensional data are referred to as volume rendering. More specifically, volume rendering is a technique used for visualizing sampled functions of three: spatial dimensions by computing 2-D projections of a semitransparent volume. Volume rendering is applied to medical imaging, wherein volume data is available from X-ray CT scanners. CT scanners produce three-dimensional stacks of parallel plane images, or slices, each of which consist of an array of X-ray absorption coefficients. Typical X-ray CT images have a resolution of 512×512×12 bits, and include up to 500 slices in a stack. In the two-dimensional domain, slices can be viewed one at a time. An advantage of CT images over conventional X-ray images is that each slice only contains information from one plane. A conventional X-ray image, on the other hand, contains information from all planes, and the result is an accumulation of shadows that are a function of the density of anything that absorbs X-rays, for example tissue, bone, organs, etc. The availability of the stacks of parallel data produced by CT scanners prompted the development of techniques for viewing the data as a three-dimensional field, rather than as individual slices. Therefore, the CT image data can now be viewed from any viewpoint. A number of different methods are used for viewing CT image data as a three-dimensional field, for example, including rendering voxels in a binary partitioned space, marching cubes, and ray casting. When rendering voxels in a binary partitioned space, choices are made for the entire voxel. This may produce a “blocky” image. In addition, rendering voxels in a binary partitioned space may result in a lack of dynamic range in the computed surface normals, which will produce images with relatively poor shading. Using marching cubes for viewing CT image data in a three-dimensional field solves some of the problems associated with rendering voxels in a binary partitioned space. However, using marching cubes requires that a binary decision be made as to the position of the intermediate surface that is extracted and rendered. Furthermore, extracting an intermediate structure may cause false positives (artifacts that do not exist) and false negatives (discarding small or poorly defined features). Using ray casting for viewing CT image data in a three-dimensional field facilitates use of the three-dimensional data without attempting to impose any geometric structure on it. Ray casting solves one of the most important limitations of surface extraction techniques, namely the way in which surface extraction techniques display a projection of a thin shell in the acquisition space. More specifically, surface extraction techniques fail to take into account that, particularly in medical imaging, data may originate from fluid and other materials, which may be partially transparent and should be modeled as such. Ray casting, however, does take into account that data may originate from fluid and other materials, and can model materials that are partially transparent. FIG. 5 is a schematic illustration of a method 80 for soft-tissue volume visualization using MECT system 10 (shown in FIGS. 1 and 2). Method 80 describes 3D visualization using a combination of physics-based segmentation (multi-energy decomposition data) and image-based segmentation. More specifically, method 80 includes acquiring 82 MECT anatomic image data for an object (not shown), wherein the anatomic image data includes a high-energy image (H) and a low-energy image (L). The anatomic image data is then decomposed 84 to obtain a density image representing soft-tissue within the object and a density image representing bone material within the object. The high-energy image, low-energy image, soft-tissue density image, and bone-material density image are then segmented 86 using image-based segmentation to determine a region of interest within the object. In one embodiment, high-energy image, low-energy image, the soft-tissue density image, and the bone-material density image are segmented 86 individually using image-based segmentation. In another embodiment, high-energy image, low-energy image, the soft-tissue density image, and the bone-material density image are segmented 86 in combination using image-based segmentation. Several segmentation techniques can be used for image-based segmentation to determine a region of interest within the object, including, but not limited to, Hounsfield or CT number (threshold) techniques, iterative thresholding, k-means segmentation, edge detection, edge linking, curve fitting, curve smoothing, 2D/3D morphological filtering, region growing, fuzzy clustering, image/volume measurements, heuristics, knowledge-based rules, decision trees, and neural networks. Segmentation of a region of interest can be performed manually and/or automatically. In one embodiment, the high-energy image, the low-energy image, the soft-tissue density image, and the bone-material density image are segmented manually to determine a region of interest within the object by displaying the data and a user delineating the region of interest using a mouse or any other suitable interface, for example, a touch screen, eye-tracking, and/or voice commands. In addition, in one embodiment, the high-energy image, the low-energy image, the soft-tissue density image, and the bone-material density image are automatically segmented to determine a region of interest with the object by using an algorithm that utilizes prior knowledge, such as the shape and size of a mass, to automatically delineate the area of interest. In yet another embodiment, the high-energy image, the low-energy image, the soft-tissue density image, and the bone-material density image are segmented to determine a region of interest within the object semi-automatically by combining manual and automatic segmentation. The image-based segmented high-energy anatomical image data, the image-based segmented soft-tissue density image, and the image-based segmented bone density image are then used 88 to obtain a soft-tissue image including bone material for the region of interest within the object. The soft-tissue image including bone material is then used to build a three-dimensional image, which in turn is used for rendering 90 to provide high-contrast rendered images. In an alternative embodiment, the high-energy image, the low-energy image, the soft-tissue density image, and the bone-material density image are not segmented 86, but rather, at least one of the high-energy image, the low-energy image, the soft-tissue density image, and the bone-material density image are used to build a three-dimensional image, which is used for rendering 90 to provide high-contrast rendered images. Rendering 90 is performed using conventional rendering techniques, such as, for example, techniques describe in The Visualization Toolkit, An Object-Orientated Approach to 3D Graphics, Will Shroeder, Ken Martin, and Bill Lorensen, Prentice-Hall 1996. In one embodiment, volume rendering is used to provide high-contrast rendered images. In another embodiment, surface rendering is used to provide high-contrast rendered images. FIG. 6 is a schematic illustration of a method 100 for soft-tissue volume visualization using MECT system 10 (shown in FIGS. 1 and 2). More specifically, method 100 is a specific example of one embodiment of method 80. In use, method 100 includes acquiring 102 MECT anatomic image data for a region of interest within an object (not shown) or, alternatively, the object in its entirety, wherein the anatomic image data includes a high-energy image and a low-energy image. The anatomic image data is then decomposed 104 to obtain a density image representing soft-tissue within the region of interest (Is) and a density image representing bone-material within the region of interest (Ib). In one embodiment, the density image representing soft-tissue is obtained using the following decomposition equation: I s = H L w s ,where 0<ws<wb<1. Additionally, and in one embodiment, the density image representing bone-material is obtained using the following decomposition equation: I b = H L wb ,where 0<ws<wb<1. The density image representing soft-tissue is then contrast matched 106 with a standard CT image of the region of interest. For example, in the exemplary embodiment, the contrast of structures within the soft-tissue density image are matched with the corresponding structures in the high-energy anatomical image data H. In one embodiment, the soft-tissue density image is contrast matched 106 with the high-energy anatomical image data H by solving the above decomposition equations for H in terms of Is, Ib, wb, and ws, to obtain the following relationship: H = I s w b w b - w s ⁢ I b - w s w b - w s . By differentiation of the logarithm of the above equation, the following contrast equation is derived: C ⁡ ( H ) = w b ⁢ w b - w s ⁢ C ⁡ ( I s ) - w s ⁢ w b - w s ⁢ C ⁡ ( I b ) ,wherein C(.) represents the contrast in the image. From the above C(H) equation, it may be evident that while matching the contrast in the soft-tissue density image and the corresponding structures in the high-energy anatomical image data, the contrast [C(Ib)] resulting from the bone-material density image may need to be suppressed. In one embodiment, to reduce the fine-detail contrast while preserving the scaling, the bone-material density image is low-pass filtered such that all structural information is eliminated. Accordingly, a contrast matched soft-tissue image (IHS) is obtained from the following equation: I HS = I s w b w b - w s ⁢ LPF ( I b - w s w b - w s ) ,wherein the function LPF(.) performs the low-pass filtering of the bone-material density image. In one embodiment, a boxcar filter is used as LPF(.) to perform low-pass filtering of the image, wherein the boxcar filter smoothes an image by the average of a given neighborhood. Using boxcar filtering, each point in an image requires only four arithmetic operations, irrespective of kernel size. In addition, and in one embodiment, the length of the separable kernel is variable. In an alternative embodiment, a bone mask is derived by segmenting the bone image. The bone mask is inverted to obtain the soft-tissue mask. The inverted bone mask is superimposed on the soft-tissue image and the soft-tissue regions are contrast-matched to the soft-tissue regions of the standard image. Special care is taken at the borders of the mask to alleviate problems resulting from the bone-soft-tissue transition region. In one embodiment, the border regions can be rank-order filtered, for example, using median criterion to suppress high intensity transition rings in 3D. The resulting image is a contrast-matched soft-tissue image. The bone-material density image is then thresholded 108 to produce a first binary mask image containing bone and calcification. More specifically, because the bone-material density image includes both calcium and bone, the bone-material density image is thresholded 108 to separate out high-contrast bone regions and the high-contrast calcification regions from the low-contrast regions. Islands smaller than a pre-specified size are then extracted 110 from the first binary mask image to produce a second binary mask image corresponding substantially to calcification. In one embodiment, an algorithm using the connectivity of binary pixels is used to extract 110 small islands from the first binary mask image to produce the second binary mask image. For example, in one embodiment four-connectivity is used to determine the size of connected components and extract 110 islands smaller than the pre-specified limit to produce the second binary mask image. In another embodiment, eight-connectivity is used to determine the size of connected components and extract 110 islands smaller than the pre-specified limit to produce the second binary mask image. The original pixel values from the high-energy anatomical image data that correspond to the second binary mask image are then merged 112 with the contrast-matched soft-tissue image to obtain a soft-tissue image including calcification. More specifically, the regions within the high-energy anatomical image data that correspond to the second binary mask image are extracted from the high-energy anatomical image and merged with the contrast-matched soft-tissue image to produce a soft-tissue image including calcification. The soft-tissue image including calcification is then used to build a three-dimensional image, which in turn is used for rendering 114 to provide high-contrast rendered images. Rendering 114 is performed using conventional rendering techniques, such as, for example, techniques describe in The Visualization Toolkit, An Object-Orientated Approach to 3D Graphics, Will Shroeder, Ken Martin, and Bill Lorensen, Prentice-Hall 1996. In one embodiment, volume rendering is used to provide high-contrast rendered images. In another embodiment, surface rendering is used to provide high-contrast rendered images. In an alternative embodiment wherein calcification identification is not desired for visualization, normalized soft-tissue image data is used to produce three-dimensional renderings of soft-tissue. FIG. 7 is a schematic illustration of a known surgical navigation system 130. System 130 includes a surgical patient 132, image data 134 for patient 132, a reference means 136 having a reference point on a reference coordinate system that is external to patient 132, a position and orientation determination means 138 coupled to patient 132 for determining the position and orientation of patient 132, a surgical instrument 140, a surgical instrument position determination means 142 coupled to instrument 140 for determining the position of surgical instrument 140, and a display 144 coupled to a computer 146. Computer 146 converts patient display data to objective display data, converts instrument location and orientation data for display on display 144, and provides a known relationship between patient 132 and the reference point. Computer 146 displays patient image data 134 and instrument 140 on display 144 substantially simultaneously. FIG. 8 is a schematic illustration of a surgical navigation system 150 for use with method 80 (shown in FIG. 5) to provide surgical instrument mapping for two volumes simultaneously and assist in identification of subtle soft-tissue structures and their spatial relationship to bone. System 150 includes a surgical patient 152, image data 154 for patient 152 including multi-energy CT data, a reference means 156 having a reference point on a reference coordinate system that is external to patient 152, a position and orientation determination means 158 coupled to patient 152 for determining the position and orientation of patient 152, a surgical instrument 160, a surgical instrument position determination means 162 coupled to instrument 160 for determining the position of surgical instrument 160, and a display 164 coupled to a computer 166. Computer 166 converts patient display data to objective display data, converts instrument location and orientation data for display on display 164, and provides a known relationship between patient 152 and the reference point. Computer 166 displays patient image data 154 and instrument 160 on display 164 substantially simultaneously. In addition, computer 166 displays a standard image of patient image data 154 on display 164, displays a soft-tissue only image of patient image data 154 on display 164, and displays a bone-only image of patient image data 154 on display 164. In one embodiment, computer 166 displays the standard image, the soft-tissue only image, and the bone-only image substantially simultaneously. In another embodiment, computer 166 includes a toggling capability for toggling between display of the standard image, the soft-tissue only image, and the bone-only image on display 164. FIG. 9 is a schematic illustration of a known radiation system 180. System 180 includes a radiation therapy patient 182, image data 184 for patient 182, a reference means 186 having a reference point on a reference coordinate system that is external to patient 182, a position and orientation determination means 188 coupled to patient 182 for determining the position and orientation of patient 182, a radiation therapy sub-system 190, a simulation and modeling means 192 for planning paths and dosage, and a display 194 coupled to a computer 196. Computer 146 converts patient display data to objective display data, converts radiation localization for display on display 194, and provides a known relationship between patient 182 and the reference point. Computer 196 displays patient image data 184 and the radiation localization on display 194 substantially simultaneously. FIG. 10 is a schematic illustration of a radiation system 210 for use with method 80 (shown in FIG. 5) to provide radiation therapy planning and simulation calculations. System 210 includes a radiation therapy patient 212, image data 214 for patient 212 including multi-energy CT image data, a reference means 216 having a reference point on a reference coordinate system that is external to patient 212, a position and orientation determination means 218 coupled to patient 212 for determining the position and orientation of patient 212, a radiation therapy sub-system 220, a simulation and modeling means 222 for planning paths and dosage, and a display 224 coupled to a computer 226. Computer 226 converts patient display data to objective display data, converts radiation localization for display on display 224, and provides a known relationship between patient 212 and the reference point. Computer 226 displays patient image data 184 and the radiation localization on display 194 substantially simultaneously. In addition, computer 226 displays a standard image of patient image data 214 on display 224, displays a soft-tissue only image of patient image data 214 on display 224, and displays a bone-only image of patient image data 214 on display 224. In one embodiment, computer 226 displays the standard image, the soft-tissue only image, and the bone-only image substantially simultaneously. In another embodiment, computer 226 includes a toggling capability for toggling between display of the standard image, the soft-tissue only image, and the bone-only image on display 224. The above-described methods and systems facilitate augmenting segmentation capabilities of multi-energy imaging with a method for image-based segmentation, and may facilitate real-time volume buildup and visualization of soft-tissue. More specifically, the above-described methods and systems facilitate segmenting bone material from an image while retaining calcification within the image, facilitate providing traditional surgical instrument mapping for two volumes simultaneously, facilitate identification of subtle soft-tissue structures and their spatial relationship to bone, facilitate computer simulation of dosage and paths for radiation therapy, and facilitate improving radiation therapy planning and simulation calculations. Exemplary embodiments of MECT methods and systems are described above in detail. The methods and systems are not limited to the specific embodiments described herein, but rather, components of each method and system may be utilized independently and separately from other components described herein. In addition, each method and system component can also be used in combination with other components described herein. While the invention has been described in terms of various specific embodiments, those skilled in the art will recognize that the invention can be practiced with modification within the spirit and scope of the claims.
039473180	summary	The present invention relates to nuclear engineering, and more particularly to a liquid-metal-cooled reactor. Known in the art are liquid-metal-cooled reactors comprising two rotatable plugs, the first plug having at least one hole and being arranged internally of the second, a recharging mechanism with a guide tube adapted to move through the hole of the first plug with the aid of a drive and accommodating a rod provided with means for gripping a fuel element stack and removing it from the reactor core into the guide tube. These reactors are also provided with a device for detecting stacks with leaky fuel elements, comprising a sampler to withdraw coolant samples from each individual fuel element stack, with an inert carrier gas being fed under pressure to the sampler, and having an inner space wherein a coolant sample is degassed and which communicates with a device for measuring the radioactivity of the inert carrier gas and of the gases evolved from the coolant sample, evacuated from the sampler. A disadvantage inherent in such a liquid-metal-cooled reactor, comprising a device for detecting stacks with leaky fuel elements resides in the complexity of the design of the sampler of the device for detecting stacks with leaky fuel elements, which sampler is made in the form of a collector with intricate piping arranged inside the reactor. This complicates the recharging of the fuel element stacks, which involves dismantling of the whole installation. The reactor is thus rendered difficult to operate, with additional time required to check faulty fuel element stacks, and the risk of exposure to radioactive matter contaminating the equipment inside the reactor involved. It is an object of the invention to provide a liquid-metal-cooled reactor allowing consecutive checks of all fuel element stacks without removing them from the reactor core, upon stopping the reactor, and, at the same time, to remove faulty stacks from the core. With this and other objects in view, the present invention relates to a liquid-metal-cooled reactor comprising two rotatable plugs, one plug having at least one hole and being arranged internally of the other, a recharging mechanism with a guide tube for moving through the hole of the first plug and accommodating a rod with means for gripping a fuel element stack and removing it from the core into the guide tube, and a device for detecting stacks with leaky fuel elements, provided with a sampler to withdraw coolant samples from individual fuel elements, which sampler is adapted to receive inert carrier gas fed thereto under pressure and to degas a coolant sample, the inner space of the sampler communicating with means for measuring the radioactivity of the inert carrier gas and of the gases evolved from the coolant sample, both evacuated from the sampler. According to the invention, the guide tube of the recharging mechanism is used as the sampler, together with means for introducing the inert carrier gas, and means for evacuating the inert carrier gas together with the gases evolved from the coolant sample. It is recommended that the wall of the guide tube of the recharging mechanism be provided with a duct for removing the inert carrier gas together with the gases evolved from the coolant sample, which duct communicates with the inner space of the guide tube through a hole made in the guide tube wall, above the coolant level, and a duct for feeding the inert carrier gas into the tube, which duct also communicates with the inner space of the guide tube through a hole made in the that wall, level with the bottom end of the fuel element stack, transferred from the core to the tube. It is alternatively also suggested that a duct be provided in the wall of the rod with the gripper for feeding the inert carrier gas into the tube, which duct communicates with the inner space of the rod through a hole in the proximity to the end face of the rod, fitted on the bottom end whereof is a sealing member intended to shut off the coolant flow from the fuel element stack, as well as at least one hole made in the rod above the coolant level in the guide tube to evacuate the inert carrier gas together with the gases evolved from the coolant sample.
	abstract	A radioisotope production gas target for producing gas isotopes such as C-11. The radioisotope production gas target includes a target chamber that is in the shape of a hollow cylinder and has a plurality of inner fins protruding from an inner surface thereof along a length thereof, and a body that is shaped of a hollow cylinder enclosing the target chamber, and has a target gas inlet for feeding target gas to a hollow region of the target chamber, a target gas outlet for collecting the target gas after a nuclear reaction occurs, and a first coolant inlet and a first coolant outlet respectively feeding and discharging a coolant flowing along an outer surface of the target chamber, and includes a thin metal sheet in front thereof through which a beam of protons passes.
	claims	1. A container for storing or transporting spent nuclear fuel, the container comprising:a plurality of tubes that receive spent nuclear fuel assemblies, each tube having four sidewalls and four corners defining a rectangular cross section, the four sidewalls forming a continuous inner sidewall;an attachment means for attaching respective pairs of a plurality of corners of the tubes to each other, at least one corner of a first one of the tubes engaging another corner of a second one of the tubes, the attachment means comprising a plurality of recesses in respective ones of the corners and a plurality of rods that are positioned in the recesses between respective engaged ones of the corners, wherein each of the rods is a cylinder having a single cylindrical wall, the cylindrical wall of each of the rods contacting at least two recesses associated with at least two of the tubes;each engaged corner of the first and second ones of the tubes being formed from an intersection of a first sidewall and a second sidewall, the first and second side wails being normal to each other;the first sidewall of the first one of the tubes and the first sidewall of the second one of the tubes being in substantial alignment; andthe second sidewall of the first one of the tubes and the second sidewall of the second one of the tubes being in substantial alignment. 2. The container of claim 1, wherein each of the first rods has an opening and the attachment means further comprises at least one pin, wherein the openings of at least one respective pair of the first rods mounted in respective ones of the recesses of the first and second ones of the tubes are axially aligned, wherein the at least one pin is inserted through the openings of the at least one respective pair of the first rods. 3. The container of claim 1, wherein the rods further comprise at least one first rod and at least one second rod, the at least one first rod being mounted in a corresponding at least one of the recesses of the first one of the tubes and the at least one second rod being mounted in a corresponding at least one of the recesses of the second one of the tubes, the at least one first rod engaging a respective one of the recesses of the second one of the tubes and the at least one second rod engaging a respective one of the recesses of the first one of the tubes when the first side wall of the first one of the tubes and the first side wall of the second one of the tubes are in substantial alignment, and the second side wall of the first one of the tubes and the second side wall of the second one of the tubes are in substantial alignment. 4. The container of claim 3, further comprising a first and a second set of the tubes, wherein the second rods are mounted on the tubes within the first set, wherein each of the second rods of the first set of tubes engages a respective one of the tubes in the second set of tubes. 5. The container of claim 1, wherein the plurality of tubes is arranged in the alternating pattern such that the placement of a four-tube array linked at the corners of the tubes creates a developed cell. 6. A container for storing or transporting spent nuclear fuel, the container comprising:a plurality of tubes that receive spent nuclear fuel, each of the plurality of tubes having a continuous inner sidewall;a plurality of first rods being mounted at a point where each respective one of the tubes abuts against another one of the tubes, each of said first rods having an opening, wherein each respective one of the first rods is mounted in a recess of both a first one of the tubes and a second one of the tubes, wherein each of the rods comprises at least one outer wail, the at least one outer wall of each of the rods contacting the recesses of both the first and second ones of the tubes;at least one pin;wherein the openings of respective ones of the first rods mounted on the first one of the tubes are substantially aligned with the openings of respective ones of the first rods mounted on the second one of the tubes;the at least one pin extends through the aligned ones of the openings of the first rods, thereby linking respective ones of the tubes together; andwherein each one of the respective ones of the first rods mate with a corresponding recess in the second one of the tubes when the openings of the respective ones of the first rods mounted in the recesses in the first one of the tubes are substantially aligned with the openings of the respective ones of the first rods mounted on the second one of the tubes. 7. The container of claim 6, wherein the at least one pin is captured by one of the first rods. 8. The container of claim 6, wherein the at least one pin comprises a head portion and a body portion, the body portion extending through the openings of the aligned ones of the first rods and the head portion resting against one of the first rods. 9. The container of claim 6, further comprising a first set of tubes upon which the second rods are mounted, and a second set of tubes without second rods mounted thereon, the second rods of the first set of tubes engaging the second set of tubes when the tubes are linked together. 10. The container of claim 6, wherein each of the tubes has four sidewalls and four corners defining a rectangular cross section, the plurality of recesses being formed at the corners of the tubes. 11. The container of claim 10, wherein:the tubes are arranged in an alternating pattern; andthe tubes are linked together at the corners, wherein a sidewall of a first one of the tubes is in substantial alignment with a sidewall of a second one of the tubes. 12. The container of claim 11, wherein the tubes are arranged in the alternating pattern such that the placement of a four-tube array linked at the corners of the tubes creates a developed cell. 13. A container for storing spent nuclear nucerfue, the container comprising:a plurality of tubes that receive spent nuclear fuel assemblies, each of the tubes having a plurality of recesses and a continuous inner sidewall;a plurality of first rods being mounted in respective ones of the recesses; andwherein at least one first rod mounted on a respective one of the tubes is attached to at least one of the first rods mounted on at least one second one of the tubes, thereby linking the respective one of the tubes and the at least one second one of the tubes together, wherein each of the first rods is seated in both a first one of the recesses of the respective one of the tubes and a second one of the recesses of the at least one second one of the tubes, and each of the rods comprises at least one outer wall, the at least one outer wall of each of the rods contacting both the first and second ones of the recesses. 14. The container of claim 13, wherein each of the first rods has an opening and respective pairs of the first rods are attached to each other by axially aligning the openings of the respective pairs of the first rods and extending a pin through the openings of each of the respective pairs of the first rods. 15. The container of claim 14, wherein the pin comprises a head portion and a body portion, the body portion extending through the openings of each of the respective pairs of the first rods and the head portion abutting against one of the first rods. 16. The container of claim 14, wherein the pin is captured by one of the first rods. 17. The container of claim 13, wherein each of the tubes has four sidewalls and four corners defining a rectangular cross section, the recesses being formed along at least one of the corners of the tubes and the first rods being mounted in the plurality of recesses along the at least one of the corners of the tubes. 18. The container of claim 17, wherein the tubes are arranged in an alternating pattern and the tubes are linked together at the corners, wherein a first one of the side walls of the first one of the tubes is substantially aligned with a first one of the side walls of the second one of the tubes, and a second one of the side wails of the first one of the tubes is substantially aligned with a second one of the side walls of the second one of the tubes. 19. The container of claim 13, further comprising at least one second rod being mounted in the recesses of respective ones of the tubes, he at least one second rod mounted in the recess of a respective one of the tubes engaging the recess of a remaining one of tubes when the tubes are linked together. 20. The container of claim 19, wherein the plurality of tubes comprises a first set of tubes and a second set of tubes, wherein the second rods are mounted in each one of the tubes in the second set of tubes. 21. The container of claim 18, wherein the plurality of tubes is arranged in the alternating pattern such that the placement of a four-tube array linked at the corners of the tubes creates a developed cell. 22. An apparatus for the storage and transport of spent nuclear fuel, comprising:an array of tubes having a continuous inner sidewall;a container, wherein the array of tubes are disposed in the container and the array of tubes contacts at least one side wall of the container;a plurality of couplings between adjacent pairs of the tubes, wherein each of the couplings comprises:a first rod disposed on a first one of the tubes;a second rod attached to a second one of the tubes;the first rod being disposed in recesses formed in the outer surfaces of both the first and second ones of the tubes, and the second rod being disposed in the recesses formed in the outer surfaces of both the first and second ones of the tubes, wherein each of the first and second rods comprises at least one outer wall, the at least one outer wall of each of the first and second rods contacting the recesses formed in the outer surfaces of both the first and second ones of the tubes;the first and second rods each having an opening along a length of the first and second rods; anda pin extending through the openings of the first and second rods; andwherein a horizontal bearing load applied to the array of tubes is transferred through the tubes and the couplings to the at least one side wall of the container. 23. The apparatus of c aim 22, wherein each of the tubes further comprises a plurality of side walls, wherein at least one of the side walls of a respective one of the tubes and a side wall of a second one of the tubes are in substantial alignment. 24. The apparatus of claim 22, wherein the recesses are formed in a plurality of corners in the outer surfaces of the tubes. 25. The apparatus of claim 22, wherein a cross sectional shape of the tubes is selected from the group consisting of a square, a rectangle, a circle, a triangle, a hexagon, a heptagon, and an octagon. 26. The apparatus of claim 22, wherein the array of tubes forms a cell, wherein the tubes are arranged in an alternating pattern in the cell.
042726824	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawings, there is shown an ion milling machine, generally designated by the reference numeral 10, having a main working chamber 12, a specimen positioning cylinder 14 and a small upper chamber 16. A piston 18 is disposed for vertical movement in cylinder 14 and extends into working chamber 12. Positioning cylinder 14, having a neck portion 15, is secured to the bottom of working chamber 12. An O-ring seal 20 is provided around neck 15 which extends from cylinder 14 into the lower portion of working chamber 12. A vacuum tight seal is thus provided between neck 15 and work chamber 12. Elongated piston 18 extends through the neck 15 of positioning cylinder 14 and into working chamber 12. An O-ring seal 22 provides a seal between piston 18 and the neck 15 of positioning cylinder 14. A sealing plate 24 is slidably disposed within cylinder 14 around piston 18. Sealing plate 24 includes an O-ring seal 26 which provides a pressure seal between sealing plate 24 and the inner wall of cylinder 14. Another O-ring seal 28 provides a seal between sealing plate 24 and piston 18. Bearing 38 is provided between sealing plate 24 and piston 18 to facilitate rotation of piston 18 during ion milling operations. A port 30 is provided for communicating with the inside of cylinder 14. Piston 12 is held in its lowered operating position as shown in FIG. 1 by admitting pressurized gas into cylinder 14 through port 30. The pressurized gas entering cylinder 14 through port 30 forces sealing plate 24 downwardly and this in turn moves piston 18 toward its lowered position. A stop plate 40 is provided on the bottom of cylinder 14. As sealing plate 24 is forced downwardly, it engages and is stopped by stop plate 40. Atmospheric pressure tends to bias piston 18 upwardly because working chamber 12 is evacuated. However, the pressurized gas admitted through port 30 and acting upon sealing price 24 overcomes this upward bias and moves piston 18 to its lowered position. In its lowered position, piston 18 is rotated about its vertical axis by a drive motor 32 acting through meshed nylon bevel gears 34 and 36, the latter being secured to the bottom of piston 18. Stop plate 40 has an opening 42 formed therethrough which is larger in diameter than bevel gear 36. Bevel gear 36 can thus pass through opening 42 and move into cylinder 14 when piston 18 moves upwardly. A specimen 50 to be thinned by ion milling machine 10 is mounted on the horizontal top surface of specimen holder 52 which is screwed onto the top of piston 18. Ion guns 54 are movably mounted within work chamber 12. Ion guns 54 direct beams of ions along paths 56 and 56' to the upper and lower surfaces, respectively, of specimen 50 as it slowly rotates with the rotation of piston 18. To raise the specimen 50 for easy viewing, the pressurized gas in positioning cylinder 14 is released and atmospheric pressure acting on piston 18 forces piston 18 to rise until it is stopped by the sealing plate 24 engaging the top of cylinder 14. A limit switch (not shown) senses the upward movement of piston 18 and stops drive motor 32; this facilitates re-engagement of bevel gears 34 and 36 when piston 18 is lowered to resume ion milling operations. A sealing O-ring 58 is disposed in the top opening of working chamber 12 to provide an air tight seal between working chamber 12 and piston 18 as piston 18 raises specimen holder 52 into smaller chamber 16. When piston 18 is in the raised position, a vacuum tight seal is thereby provided between small upper chamber 16 and working chamber 12. A phantom view of specimen holder 52 in its fully raised position within upper chamber 16 is shown in FIG. 1. In this position, specimen 50 can be inspected at close quarters through transparent viewing window 60. If desired, small upper chamber 16 can be removed from the work chamber 12 by admitting air into the inside of the upper chamber by depressing valve 62. When the pressure inside of upper chamber 16 is raised to atmospheric, chamber 16 can be lifted away, thereby exposing specimen 50. Specimen holder 52 can then be unscrewed from the top of piston 18 to remove the specimen. The specimen 50 on holder 52 is returned to working chamber 12 by first screwing holder 52 onto the top of piston 18. The small upper chamber 16 is then repositioned over specimen holder 52 and the air inside of upper chamber 16 is evacuated by depressing vacuum valve 64 which provides communication between upper chamber 16 and a vacuum source line 66. When chamber 16 is evacuated, pressurized gas is admitted to cylinder 14 to force sealing plate 24 downwardly and move the specimen into its normal working position in the evacuated working chamber 12. As piston 18 reaches its lowered position, the limit switch described above is actuated as bevel gears 34 and 36 engage. Motor 32 is thereby re-started to rotate piston 18 at a relatively slow speed, such as 1 rpm, to resume ion milling operations. Electrical isolation of piston 18 during ion milling operations is provided by nylon gears 34 and 36, the various rubber O-rings described above, plastic screws and washings which attach stop plate 40 to cylinder 14, and a plastic bushing within neck 15. A micro-ammeter (not shown) connected between stop plate 40 and work chamber 12 gives a continual indicaton of the ion and electron currents flowing between the ion guns 54 and the specimen 50 and specimen holder 52.
041845145	abstract	A valve system incorporating single failure protective logic. The system consists of a valve combination or composite valve which allows actuation or de-actuation of a device such as a hydraulic cylinder or other mechanism, integral with or separate from the valve assembly, by means of three independent input signals combined in a function commonly known as two-out-of-three logic. Using the input signals as independent and redundant actuation/de-actuation signals, a single signal failure, or failure of the corresponding valve or valve set, will neither prevent the desired action, nor cause the undesired action of the mechanism.
	description	1. Field The present application relates to methods for the production of brachytherapy and radiography targets. 2. Description of Related Art Conventional methods for producing brachytherapy seeds involve non-irradiated wires (e.g., non-irradiated iridium wires) that are subsequently provided with the desired activity. The desired activity may be provided thereto through neutron absorption in a nuclear reactor. Brachytherapy seeds have also been produced from irradiated wires. With regard to the production of the seeds, the irradiation of long wires has been suggested, wherein the irradiated wires are subsequently cut into individual seeds. However, because of flux variations in a reactor, the attainment of seeds with uniform activity is difficult. A method for producing uniform activity targets according to an embodiment of the invention may include arranging a plurality of targets in a holding device having an array of compartments. Each target is assigned to a compartment based on a known flux of a reactor core so as to facilitate an appropriate exposure of the targets to the flux based on target placement within the array of compartments. The holding device is positioned within the reactor core to irradiate the targets. The targets may be formed of the same or different materials and may be placed individually or in groups in the compartments. The targets may be radially arranged such that more targets are grouped together in compartments that are at a greater radial distance from a center of the holding device. The targets may also be axially arranged such that more targets are grouped together in compartments in axial portions of the holding device that are subjected to higher flux during irradiation. Furthermore, more targets may be grouped together in compartments that are in closer proximity to the flux during irradiation. The targets may also be arranged based on their self-shielding properties. For instance, targets with lower self-shielding properties may be grouped together in one or more compartments, while targets with higher self-shielding properties may be separated from each other so as to be grouped in different compartments. The targets may also be arranged based on their different cross sections. For instance, targets having lower cross sections may be arranged in one or more compartments that are in closer proximity to the flux during irradiation. The number of targets in a compartment may be increased so as to decrease a resulting activity of each target in the compartment after irradiation. The method for producing uniform activity targets may further include waiting a predetermined period of time for impurities to decay after irradiation prior to collecting the irradiated targets. A method for producing uniform activity targets according to another embodiment of the invention may include positioning targets within a holding device according to a predetermined or subsequently determined target loading configuration. The determined target loading configuration is based on a required flux for each target in conjunction with a known environment of a reactor core that is used to irradiate the targets. The determined target loading configuration may be in a form of a ring pattern and/or correspond to a shape of a target plate of the holding device. As a result of the determined target loading configuration, a target may be subjected to uniform or non-uniform flux. A method for producing uniform activity targets according to another embodiment of the invention may include arranging a plurality of targets in a holding device having an array of compartments, each target being assigned to a compartment based on a known flux of a reactor core so as to facilitate an appropriate exposure of the targets to the flux based on target placement within the array of compartments. The holding device is positioned within the reactor core to irradiate the targets. The targets may be formed of different natural or enriched neutron-absorption isotopes and may be arranged by isotope type, cross section, and self-shielding properties. It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. For example, an implanted region illustrated as a rectangle will, typically, have rounded or curved features and/or a gradient of implant concentration at its edges rather than a binary change from implanted to non-implanted region. Likewise, a buried region formed by implantation may result in some implantation in the region between the buried region and the surface through which the implantation takes place. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. A method according to the present invention enables the production of brachytherapy and/or radiography targets (e.g., seeds, wafers) in a reactor core such that the targets have relatively uniform activity. The targets may be used in the treatment of cancer (e.g., breast cancer, prostate cancer). For example, during cancer treatment, multiple targets (e.g., seeds) may be placed in a tumor. As a result, targets having relatively uniform activity will provide the intended amount of radiation so as to destroy the tumor without damaging surrounding tissues. The device of producing such targets is described in further detail in “BRACHYTHERAPY AND RADIOGRAPHY TARGET HOLDING DEVICE” (HDP Ref.: 8564-000184/US; GE Ref.: 24IG237430), filed concurrently herewith, the entire contents of which are incorporated herein by reference. FIG. 1 is a perspective view of a target holding device according to an embodiment of the invention. FIG. 2 is a partially exploded view of a target holding device according to an embodiment of the invention. Referring to FIGS. 1-2, the target holding device 100 includes a plurality of target plates 102 and a plurality of separator plates 104, wherein the plurality of target plates 102 and the plurality of separator plates 104 are alternately arranged. The thickness of each of the target plates 102 may be varied as needed to accommodate for the size of the intended targets to be contained therein. Thus, although the lower target plates 102 are shown as being thicker than the upper target plates 102, the opposite may be true or the target plates 102 may all be of the same thickness. Furthermore, although the target plates 102 are shown as having the same diameter, the target plates 102 may have different diameters (e.g., tapering arrangement) based on reactor conditions and/or intended targets. The alternately arranged target plates 102 and separator plates 104 are sandwiched between a pair of end plates 106. A shaft 108 passes through the end plates 106 and the alternately arranged target plates 102 and separator plates 104 to facilitate the alignment and joinder of the plates. The joinder of the end plates 106 and the alternately arranged target plates 102 and separator plates 104 may be secured with a nut and washer arrangement although other suitable fastening mechanisms may be used. Furthermore, although the target holding device 100 is shown as having a single shaft 108, it should be understood that a plurality of shafts 108 may be employed. As shown in FIG. 2, each target plate 102 has a plurality of holes/compartments 202 in addition to the central hole for the shaft 108. The plurality of holes 202 may be provided in various sizes and configurations depending on production requirements. Although the upper and lower target plates 102 are shown as having holes 202 of different sizes and configurations, it should be understood that all the target plates 102 may have holes 202 of the same size and/or configuration. The plurality of holes 202 may extend partially or completely through each target plate 102. When the holes 202 are provided such that they only extend partially through each target plate 102, the separator plates 104 may be omitted. In such a case, an upper surface of a target plate 102 would directly contact a lower surface of an adjacent target plate 102. On the other hand, when the holes 202 are provided such that they extend completely through the target plates 102, the separator plates 104 are placed between the target plates 102 so as to separate the holes 202 of each target plates 102, thereby defining a plurality of individual compartments within each target plate 102 for holding one or more targets (e.g., seeds, wafers) therein. FIG. 3 is a perspective view of a target plate according to an embodiment of the invention. Referring to FIG. 3, the target plate 102 has a plurality of holes 202 for holding one or more targets (e.g., seeds, wafers) therein during production. The target plate 102 may be formed of a relatively low cross-section material (e.g., aluminum, molybdenum, graphite, zirconium) to allow a higher amount of flux to reach the targets contained therein. For instance, the material may have a cross-section of about 10 barns or less. Alternatively, the target plate 102 may be formed of a neutron moderator material (e.g., beryllium, graphite). Furthermore, the use of materials of relatively high purity may confer the added benefit of lower radiation exposure to personnel as a result of less impurities being irradiated during target production. The upper and lower surfaces of the target plate 102 may be polished so as to be relatively smooth and flat. The thickness of the target plate 102 may be varied to accommodate the targets to be contained therein. Although the target plate 102 is illustrated as being disc-shaped, it should be understood that the target plate 102 may have a triangular shape, a square shape, or other suitable shape. Additionally, it should be understood that the size and/or configuration of the holes 202 may be varied based on production requirements. Furthermore, although not shown, the target plate 102 may include one or more alignment markings on the side surface to assist with the orientation of the target plate 102 during the stacking step of assembling the target holding device 100. FIG. 4 is a plan view of a target plate according to an embodiment of the invention. Referring to FIG. 4, in addition to having a plurality of holes 202, the target plate 102 may also have sectional markings 402 to assist in the identification of each hole 202, thereby also facilitating the placement of one or more targets within the holes 202. Although the holes 202 are illustrated as extending completely through the target plate 102, it should be understood, as discussed above, that the holes may only extend partially through the target plate 102. Additionally, although the sectional markings 402 are illustrated as dividing the target plate 102 into quadrants, it should be understood that the sectional markings 402 may be alternatively provided so as to divide the target plate 102 into more or less sections. Furthermore, it should be understood that the sectional markings 402 may be linear, curved, or otherwise provided to accommodate the configuration of the holes 202 in the target plate 102. FIG. 5 is a diagram illustrating a system for mapping the holes of a target plate according to an embodiment of the invention. Referring to FIG. 5, the plurality of holes in a target plate may be divided into four quadrants Q1-Q4. The plurality of holes in the target plate may also be associated with rows/rings R1-R5. The holes in each of quadrants Q1-Q4 may be further associated with holes H1-H6. With such a coordinate system based on quadrants Q1-Q4, rows R1-R5, and holes H1-H6, each hole in the target plate may be properly identified so as to facilitate the strategic placement of one or more targets therein. For instance, the hole identified as Q2, R3, H2 is expressly labeled in FIG. 5 for purposes of illustration. It should be understood that a suitable coordinate system may differ from that shown in FIG. 5 depending on the size of the holes, the configuration of the holes, the shape of the target plate, etc. For example, an alternate coordinate system may have more or less quadrants, rows, and/or holes than as shown in FIG. 5. Furthermore, other grouping methodologies may also be suitable and need not be limited to the methodology exemplified by the quadrants, rows, and holes shown in FIG. 5. FIG. 6 is a perspective view of a target plate that has been loaded with targets according to an embodiment of the invention. Referring to FIG. 6, the holes 202 of a target plate 102 may be loaded with one or more targets 600. The targets 600 may be formed of the same material or different materials. The targets 600 may also be formed of natural isotopes or enriched isotopes. For example, suitable targets may be formed of chromium (Cr), copper (Cu), erbium (Er), germanium (Ge), gold (Au), holmium (Ho), iridium (Ir), lutetium (Lu), palladium (Pd), samarium (Sm), thulium (Tm), ytterbium (Yb), and/or yttrium (Y), although other suitable materials may also be used. The size of the targets 600 may be adjusted as appropriate for their intended use (e.g., radiography targets). For instance, a target 600 may have a length of about 3 mm and a diameter of about 0.5 mm. It should be understood that the size of the holes 202 and/or the thickness of the target plates 102 may be adjusted as needed to accommodate the targets 600. The targets 600 are strategically loaded in the appropriate holes 202 based on various factors (including the characteristics of each target material, known flux conditions of a reactor core, the desired activity of the resulting targets, etc.) so as to attain targets 600 having relatively uniform activity. As shown in FIG. 6, the targets may be radially arranged such that more targets are grouped together in the outer holes 202 than the inner holes 202. For instance, each of the outermost holes 202 are illustrated as containing seven targets 600, while each of the innermost holes are illustrated as containing one target 600. However, it should be understood that each hole 202 does not need to be occupied with a target 600, and the placement of a target 600 as well as the number of targets 600 in a hole 202 may vary depending on various factors, including the characteristics of the target material, known flux conditions of a reactor core, the desired activity of the resulting target, etc. Because the outer holes 202 will be closer to the flux when the target holding device 100 is placed in a reactor core, a greater number of targets 600 may be placed in each of the outer holes 202, thereby resulting in more equal activity amongst the targets 600 in the outer holes 202. On the other hand, fewer targets 600 may be placed in each of the inner holes 202 to offset the fact that these targets 600 will be farther from the flux, thereby allowing the targets 600 in the inner holes 202 to attain activity levels comparable to the targets 600 in the outer holes 202. Thus, the number of targets 600 in each hole 202 may be increased so as to decrease the resulting activity of each target in the hole 202. Conversely, the number of targets 600 in each hole 202 may be decreased so as to increase the resulting activity of each target in the hole 202. It should be understood that FIG. 6 assumes that all the targets 600 are formed of the same isotope to simplify the radial target placement illustration (although the targets 600 may be formed of different isotopes). Different isotopes may have different characteristics, including different neutron absorption rates and different decay rates. These characteristics will affect the overall placement as well as the grouping of the targets 600 when different isotopes are involved in the production process. For instance, if the targets 600 in the outermost holes 202 are formed of different isotopes having higher self-shielding properties than the targets 600 in the inner holes 202, then fewer such targets 600 may be needed in each of the outermost holes 202 to create the desired self-shielding effect. In another example, iridium (Ir) and gold (Au) seeds were loaded in a target plate 102 having holes 202 corresponding to the coordinate system illustrated in FIG. 5. Iridium has a much higher neutron absorption rate, but gold has a higher decay rate and initially has higher activities. A single iridium seed was loaded in a hole 202 corresponding to Q 1, R5, H5, while two gold seeds were loaded in a hole 202 corresponding to Q 1, R4, H4. Based only on the radial placement and the number of seeds per hole, it would seem that the single iridium seed in the outermost ring would have the highest activity after irradiation. However, because of gold's high decay rate, the two gold seeds actually had the higher activities of 57.38 μCi and 58.61 μCi, respectively, compared to the 49.75 μCi for the iridium seed. Thus, characteristics of the target material (e.g., neutron absorption rate, decay rate, etc.) should be taken into account when deciding where to place and/or how to group the targets so as to attain more uniform activities. The targets 600 may also be arranged based on cross-section, wherein cross-section (σ) is the probability that an interaction will occur and is measured in barns. For instance, targets 600 formed of materials having lower cross-sections will have a lower probability that an interaction will occur compared to targets 600 formed of materials having higher cross-sections. As a result, targets 600 formed of materials having lower cross-sections may be arranged in holes 202 that will be in closer proximity to the flux during irradiation. With regard to FIG. 6, such lower cross-section targets 600 may be placed in the outer holes 202 of the target plate 102. FIG. 7 is a cross-sectional view of a loaded target holding device, taken along its longitudinal axis, according to an embodiment of the invention. In addition to the determination of where to place a target 600 in a target plate 102, there is also the consideration of which target plate 102 of the target holding device 100 to place the target 600. As shown in FIG. 7, the targets 600 may be axially arranged such that more targets 600 are grouped together in an axial portion of the target holding device 100 that is subjected to higher flux during irradiation in a reactor core. FIG. 7 illustrates an example where the mid-axial portion of the target holding device 100 is subjected to higher flux during irradiation in a reactor core. Furthermore, the targets 600 may be arranged so as to be more concentrated on a particular side of the target holding device 100 that will be subjected to a higher flux during irradiation. It should be understood that when a plurality of targets 600 of different materials are to be placed in the target holding device 100 for irradiation, the individual characteristics (e.g., neutron absorption rate) of each target 600 will be considered in conjunction with external factors (e.g., known flux conditions of the reactor core) when determining the proper arrangement within the target holding device 100. For instance, not only is the proper target plate 102 and hole 202 determined for a target 600 but also whether grouping is appropriate, and if so, the target(s) 600 that should be grouped together so as to attain targets 600 in the target holding device 100 having relative uniform activity. FIG. 8 is a perspective view of a target holder assembly according to an embodiment of the invention. Referring to FIG. 8, the target holder assembly 800 includes a target holding device 100 connected to a cable 802. The cable 802 may be formed of any material having sufficient rigidity to facilitate the introduction of the target holding device 100 into a reactor core, sufficient strength to facilitate the retrieval of the target holding device 100 from the reactor core, and sufficient flexibility to maneuver the target holding device 100 through piping turns. For instance, the cable 802 may be a braided steel cable or a flexible electrical conduit cable. To assist with the introduction of the target holding device 100 into a reactor core, the cable 802 may be marked at a predefined length, wherein the predefined length corresponds to a distance from a reference point, to a predetermined location within the reactor core. After the target holding device 100 has been irradiated in the reactor core, a predetermined period of time may be allowed to pass before disassembling the target holding device 100 and collecting the targets 600. This waiting period may be beneficial by permitting any impurities in the target holding device 100 (as well as the targets 600 themselves) to sufficiently decay, thereby reducing or preventing the risk of harmful radiation exposure to personnel. While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
058928057	summary	BACKGROUND OF THE INVENTION This invention is related to a method of operation of a nuclear power plant, and particularly to a method suitable for operation of a boiling water reactor power plant. Generally, corrosion products, such as metallic ion components and insoluble components (clad) and the like, are dissolved little by little into water from structural materials, such as piping, pumps, heat exchangers, etc., of a boiling water reactor power plant (hereinafter referred to as BWR power plant). Most of the corrosion products formed in a turbine system on an upper side of a clean-up system for condensate water are removed by the clean-up system. But, the corrosion products formed in a feed water system at a downstream side of the clean-up system for condensate water are not removed. These corrosion products enter into the nuclear reactor together with the feed water. Most of the corrosion products which enter into the nuclear reactor deposit on the surface of the fuel rods. The corrosion products which are deposited on the surface of the fuel rods are transformed into radioactive nuclides by irradiation with neutrons. For example, Ni and Co contained in the corrosion products are transformed into .sup.58 Co and .sup.60 Co, which have a long half life, respectively, by neutron irradiation. A part of the corrosion products, being a radioactive substance, dissolves from the surface of the fuel rods into the reactor water, or exfoliates from the surfaces of the fuel rods. The dissolved or the exfoliated corrosion products deposit on the inner surfaces of equipment and pipings of a primary loop recirculation system or the clean-up system for the reactor water. Therefore, the dosage rate of the equipment and the pipings of the primary loop recirculation system, or of the reactor water cleanup system, increases. In the case where NiFe.sub.2 O.sub.4 and CoFe.sub.2 O.sub.4 are composite oxides of the corrosion products of Ni and Co that deposit on the surfaces of the fuel rods, the speed of re-dissolution of the composite oxides into the reactor water, or the speed of their exfoliation from the surfaces of the fuel rods, becomes very slow. The composite oxides stay on the surfaces of the fuel rods for a long time after they have deposited. As a result, re-deposition of the corrosion products, which are radioactive substances, on the equipment and pipings is suppressed. Ni and Co in the reactor water form stable composite oxides by setting a weight ratio of Fe/Ni in the feed water to 2 or more (actually, about 3). In order to obtain the Fe/Ni weight ratio, a technique for controlling the iron concentration in the feed water has already been adopted in the BWR. However, even when the Fe concentration is controlled, as mentioned above, a new phenomenon was observed wherein the concentration of the radioactive substances, such as .sup.60 Co, in the reactor water changes. The reason is that the concentration of the radioactive substances in the reactor water does not stabilize due to an increase of the quantity of Cr dissolving from stainless steel pipes used for heat transfer pipes of the feed water heater. The increase in the dissolution quantity of Cr accelerates re-dissolution of clad deposited on the fuel rods. Several measures are described in Japanese patent Laid-open Print No. 5-288893. These measures suppress a fluctuation in the concentration of radioactive substances in the reactor water, to control the Cr quantity in the deposit on the fuel rods in addition to controlling the Fe quantity. The Laid-open Print describes a method for reducing the Cr content in clad deposited on the fuel rods by methods such as a method for properly managing the concentration of an oxidizing agent in the feed water, a method for substituting a material having a high Cr content for a low Cr content material, a method for making alkali ions coexistent with Cr ions in the reactor water, and a method for efficiently operating the clean-up equipment for cleaning the reactor water. Japanese Patent Publication No. 68914 describes a technique that controls the pH of the reactor water to a weak alkali state. This is the technique that suppresses an uptake of radiation to the main pipe and is applied only at the time of the starting operation of the nuclear reactor when the uptake speed is fast. But, Japanese Patent Laid-open Print No. 5-288893 does not pay attention to the injection time of an alkali metal. The technique disclosed in Japanese Patent Publication No. 6-8914 is applied only to controlling the weak alkali state at the time of starting, but this technique cannot suppress Cr loading on the fuel rods in new fuel assemblies to be loaded during every operating cycle. SUMMARY OF THE INVENTION An object of this invention is to provide a method of operating a BWR power plant that can reduce Cr loading on fuel rod surfaces over all operating cycles. A first feature of this invention for achieving the above object is to inject an alkali metal or alkaline earth metal into the reactor water during the term from a starting operation of a preoperating test or of each fuel of the cycle of the nuclear reactor to the 2000 EFPH, and to stop the injection of the alkali metal or the alkaline earth metal during the period between the 2000 EFPH and the stopping of the BWR power plant. EFPH stands for an effective full power hour, which represents a percentage of an integral value of the actual thermal output per a rated thermal output within a time period of the actual thermal output. Cr deposited on the surfaces of the fuel rods dissolves into the reactor water thereby to locally acidify the reactor water on the surfaces of the fuel rods. This accelerates the dissolution of the deposit into the reactor water. As will be described later, the deposit of Cr on the surfaces of the fuel rods occurs by taking Cr into an oxide film during the term of forming the oxide film on the fuel rod surfaces. The above term is from the starting operation of the preoperating test or of each fuel cycle of the nuclear reactor to the 2000 EFPH. By the injection of the alkali metal or the alkaline earth metal into the reactor water during the above term, Cr easily exists in the reactor water as Cr oxide ions. Therefore, the amount of Cr that deposits on the surfaces of the fuel rods as a Cr oxide decreases. This phenomenon lowers the local acidification of the reactor water, which is caused by dissolution of Cr deposited on the fuel rod surfaces so that the dissolution of the radioactive substances into the reactor water is suppressed. The concentration of the radioactive substances contained in the reactor water decreases, resulting in a decrease in the surface dose rate of the pipes and the devices for the primary loop recirculation system, the clean-up system of reactor water and so on. A second feature of this invention is to provide a method for operating a BWR power plant comprising pipings of a clean-up system, both ends of which are connected to a nuclear reactor, wherein the clean-up system for the reactor water comprises the pipings of the clean-up system, a first clean-up unit having ion exchange resin to which an alkali metal or alkaline earth metal is added, the first clean-up unit being installed in the pipings of the clean-up system, and a second clean-up unit having an ion exchange resin to which no alkali metal or the alkaline earth metal is added and which is connected in parallel with the first clean-up unit, the improvement of which comprises the following steps: supplying the reactor water in the nuclear reactor to the piping of the clean-up system, returning the reactor water to the nuclear reactor after the reactor water is purified by the first clean-up unit during the term from the starting test of said nuclear reactor or the starting operation of each fuel cycle to the 2000 EFPH, and returning the reactor water to said reactor after purifying it using the second clean-up unit during the period between the 2000 EFPH and the stopping of the nuclear reactor. By the second feature, the same effect as in the first feature is achieved. According to the second feature, the alkali metal or the alkaline earth metal can be easily shifted from the ion exchange resin in the first clean-up unit to the reactor water during the above term, thereby cleaning the reactor water with the first clean-up unit. A third feature of this invention is to inject a material, which changes the pH of the feed water to the acid side, into the feed water from the feed water system or the condensate system during the period between the starting operation and the 2000 EFPH and to stop the injection of the material after the above period lapses. By injecting the material for changing the pH of the feed water to the acid side into the feed water from the feed water system or the condensate system during the above term, nonradioactive Cr which exists in the interior of the structure of the feed water system or the condensate system becomes a stable Cr oxide. Therefore, the dissolution of the Cr into the cooling water of the primary system is suppressed, and the Cr quantity included in the reactor water is decreased more than in the case of the first feature. A fourth feature of this invention is to inject hydrogen of a molar concentration which is 2.about.3 times the molar concentration of dissolved oxygen into the feed water during the above term. The injection of the hydrogen at the above concentration reduces the corrosion potential of the feed water in the above term. Therefore, the Cr on the interior of the structure of the feed water system or of the condensate system becomes a stable Cr oxide, and the dissolution of Cr into the feed water is suppressed. A fifth feature of this invention is to use cladding tubes which have no oxide film on the surfaces thereof for fuel rods of fuel assemblies of 0(zero) GW.multidot.day/t burn-up loaded in the nuclear reactor. Because of the amount of Cr which is taken into an oxide film from the reactor water in forming the oxide film on the surfaces of the cladding tubes in the nuclear reactor, there is little dissolution of the Cr on the surfaces of the cladding tubes. Therefore, even when the fuel assemblies of 0(zero) GW.multidot.day/t burn-up comprising fuel rods containing cladding tubes not formed with an oxide film on the surfaces are loaded in the nuclear reactor, the concentration of the radioactive substances contained in the reactor water is small. A sixth feature of this invention is to control the quantity of oxygen which is injected into feed water from a condensate system or a feed water system so as to obtain a dissolved oxygen concentration of 10 ppb to 30 ppb in the feed water during the above term, whereby corrosion of the condensate system or of the feed water system in the term is remarkably decreased. Consequently, the quantity of the Cr brought into the nuclear reactor together with the feed water remarkably decreases. The quantity of the Cr taken into the surfaces of fuel rods decreases, and the concentration of the radioactive substances contained in the reactor water decreases. A seventh feature of this invention is to increase the quantity of reactor water supplied to a clean-up system for the reactor water for purifying the reactor water during the above term. In the term, the amount of reactor water to be supplied to the reactor clean-up system is increased so that the quantity of the radioactive substances in the reactor water can be decreased. An eighth feature of this invention is to use a material of low Cr dissolution for at least one part of the primary system pipings, which are connected to the nuclear reactor, in which cooling water flows, so that the dissolution quantity of the Cr from the low Cr dissolution material absolutely decreases. Therefore, the cr quantity itself which is taken into the nuclear reactor is reduced, and the Cr quantity deposited on the fuel rods is reduced.
054596750	description	DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS In a method of the invention signals from industrial process sensors can be used to modify or terminate degrading or anomalous processes. The sensor signals are manipulated to provide input data to a statistical analysis technique, such as a process entitled Spectrum Transformed Sequential Testing ("SPRT"). Details of this process and the invention therein are disclosed in U.S. patent application 07/827,776, now U.S. Pat. No. 5,223,207, which is incorporated by reference herein in its entirety. A further illustration of the use of SPRT for analysis of data bases is set forth in the copending application filed contemporaneously, entitled "Processing Data Base Information Having Nonwhite Noise," also incorporated by reference herein in its entirety (Ser. No. 08/068,712). The procedures followed in a preferred method are shown generally in FIG. 8. In performing such a preferred analysis of the sensor signals, a dual transformation method is performed, insofar as it entails both a frequency-domain transformation of the original time-series data and a subsequent time-domain transformation of the resultant data. The data stream that passes through the dual frequency-domain, time-domain transformation is then processed with the SPRT procedure, which uses a log-likelihood ratio test. A computer software appendix is also attached procedure and its implementation in the context of, and modified by, the instant invention. In the preferred embodiment, successive data observations are performed on a discrete process Y, which represents a comparison of the stochastic components of physical processes monitored by a sensor, and most preferably pairs of sensors. In practice, the Y function is obtained by simply differencing the digitized signals from two respective sensors. Let y.sub.k represent a sample from the process Y at time t.sub.k. During normal operation with an undegraded physical system and with sensors that are functioning within specifications the y.sub.k should be normally distributed with mean of zero. Note that if the two signals being compared do not have the same nominal mean values (due, for example, to differences in calibration), then the input signals will be pre-normalized to the same nominal mean values during initial operation. In performing the monitoring of industrial processes, the system's purpose is to declare a first system or a second system degraded if the drift in Y is sufficiently large that the sequence of observations appears to be distributed about a mean +M or -M, where M is our pre-assigned system-disturbance magnitude. We would like to devise a quantitative framework that enables us to decide between two hypotheses, namely: H.sub.1 : Y is drawn from a Gaussian probability distribution function ("PDF") with mean M and variance of .sigma..sup.2. PA1 H.sub.2 : Y is drawn from a Gaussian PDF with mean 0 and variance .sigma..sup.2. We will suppose that if H.sub.1 or H.sub.2 is true, we wish to decide for H.sub.1 or H.sub.2 with probability (1-.beta.) or (1-.alpha.), respectively, where .alpha. and .beta. represent the error (misidentification) probabilities. From the conventional, well known theory of Wald, the test depends on the likelihood ratio 1.sub.n, where ##EQU1## After "n" observations have been made, the sequential probability ratio is just the product of the probability ratios for each step: ##EQU2## where f(y.vertline.H) is the distribution of the random variable y. Wald's theory operates as follows: Continue sampling as long as A<1.sub.n <B. Stop sampling and decide H.sub.1 as soon as 1.sub.n .gtoreq.B, and stop sampling and decide H.sub.2 as soon as 1.sub.n .ltoreq.A. The acceptance thresholds are related to the error (misidentification) probabilities by the following expressions: ##EQU3## The (user specified) value of .alpha. is the probability of accepting H.sub.1 when H.sub.2 is true (false alarm probability). .beta. is the probability of accepting H.sub.2 when H.sub.1 is true (missed alarm probability). If we can assume that the random variable y.sub.k is normally distributed, then the likelihood that H.sub.1 is true (i.e., mean M, variance .sigma..sup.2) is given by: ##EQU4## Similarly for H.sub.2 (mean 0, variance .sigma..sup.2): ##EQU5## The ratio of (5) and (6) gives the likelihood ratio 1.sub.n ##EQU6## Combining (4) and (7), and taking natural logs gives ##EQU7## Our sequential sampling and decision strategy can be concisely represented as: ##EQU8## Following Wald's sequential analysis, it is conventional that a decision test based on the log likelihood ratio has an optimal property; that is, for given probabilities .alpha. and .beta. there is no other procedure with at least as low error probabilities or expected risk and with shorter length average sampling time. A primary limitation that has heretofore precluded the applicability of Wald-type binary hypothesis tests for sensor and equipment surveillance strategies lies in the primary assumption upon which Wald's theory is predicated; i.e., that the original process Y is strictly "white" noise, independently-distributed random data. White noise is thus well known to be a signal which is uncorrelated. Such white noise can, for example, include Gaussian noise. It is, however, very rare to find physical process variables associated with operating machinery that are not contaminated with serially-correlated, deterministic noise components. Serially-correlated noise components are conventionally known to be signal data whose successive time point values are dependent on one another. Noise components includes, for example, auto-correlated (also known as serially correlated) noise and Markov dependent noise. Auto-correlated noise is a known form of noise wherein pairs of correlation coefficients describe the time series correlation of various data signal values along the time series of data. That is, the data U.sub.1, U.sub.2, . . . , U.sub.n have correlation coefficients (U.sub.1, U.sub.2), (U.sub.2, U.sub.3), . . . , (U.sub.n-1, U.sub.n) and likewise have correlation coefficients (U.sub.1, U.sub.3), (U.sub.2, U.sub.4) etc. If these data are auto-correlated, at least some of the coefficients are non-zero. Markov dependent noise on the other hand is a very special form of correlation between past and future data signals. Rather, given the value of U.sub.k, the values of U.sub.n, n>k, do not depend on the values of U.sub.j where j<k. This implies the correlation pairs (U.sub.j, U.sub.n) given the value U.sub.k, are all zero. If, however, the present value is imprecise, then the correlation coefficients may be nonzero. This invention can overcome this limitation to conventional surveillance strategies by integrating the Wald sequential-test approach with a new dual transformation technique. This symbiotic combination of frequency-domain transformations and time-domain transformations produces a tractable solution to a particularly difficult problem that has plagued signal-processing specialists for many years. In the preferred embodiment of the method shown in detail in FIG. 8, serially-correlated data signals from an industrial process can be rendered amenable to the SPRT testing methodology described hereinbefore. This is preferably done by performing a frequency-domain transformation of the original difference function Y. A particularly preferred method of such a frequency transformation is accomplished by generating a Fourier series using a set of highest "1" number of modes. Other procedures for rendering the data amenable to SPRT methods includes, for example, auto regressive techniques, which can accomplish substantially similar results described herein for Fourier analysis. In the preferred approach of Fourier analysis to determine the "1" highest modes (see FIG. 8A): ##EQU9## where a.sub.0 /2 is the mean value of the series, a.sub.m and b.sub.m are the Fourier coefficients corresponding to the Fourier frequency .omega..sub.m, and N is the total number of observations. Using the Fourier coefficients, we next generate a composite function, X.sub.t, using the values of the largest harmonics identified in the Fourier transformation of Y.sub.t. The following numerical approximation to the Fourier transform is useful in determining the Fourier coefficients a.sub.m and b.sub.m. Let x.sub.j be the value of X.sub.t at the jth time increment. Then assuming 2.pi. periodicity and letting .omega..sub.m =2.pi.m/N, the approximation to the Fourier transform yields: ##EQU10## for 0<m<N/2. Furthermore, the power spectral density ("PSD") function for the signal is given by 1.sub.m where ##EQU11## To keep the signal bandwidth as narrow as possible without distorting the PSD, no spectral windows or smoothing are used in our implementation of the frequency-domain transformation. In analysis of a pumping system of the EBR-II reactor of Argonne National Laboratory, the Fourier modes corresponding to the eight highest 1.sub.m provide the amplitudes and frequencies contained in X.sub.t. In our investigations for the particular pumping system data taken, the highest eight 1.sub.m modes were found to give an accurate reconstruction of X.sub.t while reducing most of the serial correlation for the physical variables we have studied. In other industrial processes, the analysis could result in more or fewer modes being needed to accurately construct the functional behavior of a composite curve. Therefore, the number of modes used is a variable which is iterated to minimize the degree of nonwhite noise for any given application. As noted in FIG. 8A a variety of noise tests are applied in order to remove serially correlated noise. The reconstruction of X.sub.t uses the general form of Eqn. (12), where the coefficients and frequencies employed are those associated with the eight highest PSD values. This yields a Fourier composite curve (see end of flowchart in FIG. 8A) with essentially the same correlation structure and the same mean as Y.sub.t. Finally, we generate a discrete residual function R.sub.t by differencing corresponding values of Y.sub.t and X.sub.t. This residual function, which is substantially devoid of serially correlated contamination, is then processed with the SPRT technique described hereinbefore. In a specific example application of the above referenced methodology, certain variables were monitored from the Argonne National Laboratory reactor EBR-II. In particular, EBR-II reactor coolant pumps (RCPs) and delayed neutron (DN) monitoring systems were tested continuously to demonstrate the power and utility of the invention. The RCP and DN systems were chosen for initial application of the approach because SPRT-based techniques have already been under development for both the systems. All data used in this investigation were recorded during full-power, steady state operation at EBR-II. The data have been digitized at a 2-per-second sampling rate using 2.sup.14 (16,384) observations for each signal of interest. FIGS. 1-3 illustrate data associated with the preferred spectral filtering approach as applied to the EBR-II primary pump power signal, which measures the power (in kW) needed to operate the pump. The basic procedure of FIG. 8 was then followed in the analysis. FIG. 1 shows 136 minutes of the original signal as it was digitized at the 2-Hz sampling rate. FIG. 2 shows a Fourier composite constructed from the eight most prominent harmonics identified in the original signal. The residual function, obtained by subtracting the Fourier composite curve from the raw data, is shown in FIG. 3. Periodograms of the raw signal and the residual function have been computed and are plotted in FIG. 4. Note the presence of eight depressions in the periodogram of the residual function in FIG. 4B, corresponding to the most prominent periodicities in the original, unfiltered data. Histograms computed from the raw signal and the residual function are plotted in FIG. 5. For each histogram shown we have superimposed a Gaussian curve (solid line) computed from a purely Gaussian distribution having the same mean and variance. Comparison of FIG. 5A and 5B provide a clear demonstration of the effectiveness of the spectral filtering in reducing asymmetry in the histogram. Quantitatively, this decreased asymmetry is reflected in a decrease in the skewness (or third moment of the noise) from 0.15 (raw signal) to 0.10 (residual function). It should be noted here that selective spectral filtering, which we have designed to reduce the consequences of serial correlation in our sequential testing scheme, does not require that the degree of nonnormality in the data will also be reduced. For many of the signals we have investigated at EBR-II, the reduction in serial correlation is, however, accompanied by a reduction in the absolute value of the skewness for the residual function. To quantitatively evaluate the improvement in whiteness effected by the spectral filtering method, we employ the conventional Fisher Kappa white noise test. For each time series we compute the Fisher Kappa statistic from the defining equation ##EQU12## where 1(.omega..sub.k) is the PSD function (see Eq. 14) at discrete frequencies .omega..sub.k, and 1(L) signifies the largest PSD ordinate identified in the stationary time series. The Kappa statistic is the ratio of the largest PSD ordinate for the signal to the average ordinate for a PSD computed from a signal contaminated with pure white noise. For EBR-II the power signal for the pump used in the present example has a .kappa. of 1940 and 68.7 for the raw signal and the residual function, respectively. Thus, we can say that the spectral filtering procedure has reduced the degree of nonwhiteness in the signal by a factor of 28. Strictly speaking, the residual function is still not a pure white noise process. The 95% critical value for Kappa for a time series with 2.sup.14 observations is 12.6. This means that only for computed Kappa statistics lower than 12.6 could we accept the null hypothesis that the signal is contaminated by pure white noise. The fact that our residual function is not purely white is reasonable on a physical basis because the complex interplay of mechanisms that influence the stochastic components of a physical process would not be expected to have a purely white correlation structure. The important point, however, is that the reduction in nonwhiteness effected by the spectral filtering procedure using only the highest eight harmonics in the raw signal has been found to preserve the pre-specified false alarm and missed alarm probabilities in the SPRT sequential testing procedure (see below). Table I summarizes the computed Fisher Kappa statistics for thirteen EBR-II plant signals that are used in the subject surveillance systems. In every case the table shows a substantial improvement in signal whiteness. The complete SPRT technique integrates the spectral decomposition and filtering process steps described hereinbefore with the known SPRT binary hypothesis procedure. The process can be illustratively demonstrated by application of the SPRT technique to two redundant delayed neutron detectors (designated AND A and DND B) whose signals were archived during long-term normal (i.e., undegraded) operation with a steady DN source in EBR-II. For demonstration purposes a SPRT was designed with a false alarm rate, .alpha., of 0.01. Although this value is higher than we would designate for a production surveillance system, it gives a reasonable frequency of false alarms so that asymptotic values of .alpha. can be obtained with only tens of thousands of discrete observations. According to the theory of the SPRT technique, it can be easily proved that for pure white noise (such as Gaussian), independently distributed processes, .alpha. provides an upper bound to the probability (per observation interval) of obtaining a false alarm--i.e., obtaining a "data disturbance" annunciation when, in fact, the signals under surveillance are undegraded. FIGS. 6 and 7 illustrate sequences of SPRT results for raw DND signals and for spectrally-whitened DND signals, respectively. In FIGS. 6A and 6B, and 7A and 7B, respectively, are shown the DN signals from detectors DND-A and DND-B. The steady-state values of the signals have been normalized to zero. TABLE I ______________________________________ Effectiveness of Spectral Filtering for Measured Plant Signals Fisher Kappa Test Statistic (N = 16,384) Plant Variable I.D. Raw Signal Residual Function ______________________________________ Pump 1 Power 1940 68.7 Pump 2 Power 366 52.2 Pump 1 Speed 181 25.6 Pump 2 Speed 299 30.9 Pump 1 Radial Vibr (top) 123 67.7 Pump 2 Radial Vibr (top) 155 65.4 Pump 1 Radial Vibr (bottom) 1520 290.0 Pump 2 Radial Vibr (bottom) 1694 80.1 DN Monitor A 96 39.4 DN Monitor B 81 44.9 DN Detector 1 86 36.0 DN Detector 2 149 44.1 DN Detector 3 13 8.2 ______________________________________ Normalization to adjust for differences in calibration factor or viewing geometry for redundant sensors does not affect the operability of the SPRT. FIGS. 6C and 7C in each figure show point wise differences of signals DND-A and DND-B. It is this difference function that is input to the SPRT technique. Output from the SPRT method is shown for a 250-second segment in FIGS. 6D and 7D. Interpretation of the SPRT output in FIGS. 6D and 7D is as follows: When the SPRT index reaches a lower threshold, A, one can conclude with a 99% confidence factor that there is no degradation in the sensors. For this demonstration A is equal to 4.60, which corresponds to false-alarm and missed-alarm probabilities of 0.01. As FIGS. 6D and 7D illustrate, each time the SPRT output data reaches A, it is reset to zero and the surveillance continues. If the SPRT index drifts in the positive direction and exceeds a positive threshold, B, of +4.60, then it can be concluded with a 99% confidence factor that there is degradation in at least one of tile sensors. Any triggers of the positive threshold are signified with diamond symbols in FIGS. 6D and 7D. In this case, since we can certify that tile detectors were functioning properly during the time period our signals were being archived, any triggers of the positive threshold are false alarms. If we extend sufficiently the surveillance experiment illustrated in FIG. 6D, we can get an asymptotic estimate of the false alarm probability .alpha.. We have performed this exercise using 1000-observation windows, tracking the frequency of false alarm trips in each window, then repeating the procedure for a total of sixteen independent windows to get an estimate of the variance on this procedure for evaluating .alpha.. The resulting false-alarm frequency for the raw, unfiltered, signals is .alpha.=0.07330 with a variance of 0.000075. The very small variance shows that there would be only a negligible improvement in our estimate by extending the experiment to longer data streams. This value of .alpha. is significantly higher than the design value of .alpha.=0.01, and illustrates the danger of blindly applying a SPRT test technique to signals that may be contaminated by excessive serial correlation. The data output shown in FIG. 7D employs the complete SPRT technique shown schematically in FIG. 8. When we repeat the foregoing exercise using 16 independent 1000-observation windows, we obtain an asymptotic cumulative false-alarm frequency of 0.009142 with a variance of 0.000036. This is less than (i.e., more conservative than) the design value of .alpha.=0.01, as desired. It will be recalled from the description hereinbefore regarding one preferred embodiment, we have used the eight most prominent harmonics in the spectral filtration stage of the SPRT technique. By repeating the foregoing empirical procedure for evaluating the asymptotic values of .alpha., we have found that eight modes are sufficient for the input variables shown in Table I. Furthermore, by simulating subtle degradation in individual signals, we have found that the presence of serial correlation in raw signals gives rise to excessive missed-alarm probabilities as well. In this case spectral whitening is equally effective in ensuring that pre-specified missed-alarm probabilities are not exceeded using the SPRT technique. In another different form of the invention, it is not necessary to have two sensor signals to form a difference function. One sensor can provide a real signal characteristic of an ongoing process and a record artificial signal can be generated to allow formation of a difference function. Techniques such as an auto regressive moving average (ARMA) methodology can be used to provide the appropriate signal, such as a DC level signal, a cyclic signal or other predictable signal. Such an ARMA method is a well-known procedure for generating artificial signal values, and this method can even be used to learn the particular cyclic nature of a process being monitored enabling construction of the artificial signal. The two signals, one a real sensor signal and the other an artificial signal, can thus be used in the same manner as described hereinbefore for two real sensor signals. The difference function Y is then formed, transformations performed and a residual function is determined which is free of serially correlated noise. Fourier techniques are very effective in achieving a whitened signal for analysis, but there are other means to achieve substantially the same results using a different analytical methodology. For example, filtration of serial correlation can be accomplished by using the autoregressive moving average (ARMA) method. This ARMA technique estimates the specific correlation structure existing between sensor points of an industrial process and utilizes this correlation estimate to effectively filter the data sample being evaluated. A technique has therefore been devised which integrates frequency-domain filtering with sequential testing methodology to provide a solution to a problem that is endemic to industrial signal surveillance. The subject invention particularly allows sensing slow degradation that evolves over a long time period (gradual decalibration bias in a sensor, appearance of a new radiation source in the presence of a noisy background signal, wear out or buildup of a radial rub in rotating machinery, etc. ). The system thus can alert the operator of the incipience or onset of the disturbance long before it would be apparent to visual inspection of strip chart or CRT signal traces, and well before conventional threshold limit checks would be tripped. This permits the operator to terminate, modify or avoid events that might otherwise challenge technical specification guidelines or availability goals. Thus, in many cases the operator can schedule corrective actions (sensor replacement or recalibration; component adjustment, alignment, or rebalancing; etc.) to be performed during a scheduled system outage. Another important feature of the technique which distinguishes it from conventional methods is the built-in quantitative false-alarm and missed-alarm probabilities. This is quite important in the context of high-risk industrial processes and applications. The invention makes it possible to apply formal reliability analysis methods to an overall system comprising a network of interacting SPRT modules that are simultaneously monitoring a variety of plan variables. This amenability to formal reliability analysis methodology will, for example, greatly enhance the process of granting approval for nuclear-plant applications of the invention, a system that can potentially save a utility millions of dollars per year per reactor. While preferred embodiments of the invention have been shown and described, it will be clear to those skilled in the art that various changes and modifications can be made without departing from the invention in its broader aspects as set forth in the claims provided hereinafter.
045129495	summary	BACKGROUND OF THE INVENTION This invention relates to anaylsis of fuel rod performance in a nuclear power plant reactor and more particularly to the monitoring of power density in a nuclear power reactor for analysis of fuel rod performance. Fuel rod failure is a costly factor in nuclear power plant operation and has created a need for the development of an on-line, fuel failure avoidance system through which (a) the state of all fuel rods is continuously monitored, (b) the data obtained by monitoring is analyzed, and (c) fuel rod failure forecasts are generated as a result of such analysis. The foregoing anaylsis function of such failure avoidance systems has involved the creation of a failure model from which to calculate the expected frequency of fuel failure in commercial nuclear power plant reactors. One such failure model developed is based on the concept of fuel rod failure resulting primarily from pellet-clad interaction. Experiments have shown that pellet-clad interaction failures occur either during rapid increases in power, referred to as "power shocks", or within a few hours thereafter. The power shocks produce thermal expansion, fission gas release, and shape distortion of the fuel pellets causing clad strain and longitudinal cracks in the fuel rod cladding. Pellet deformation also results in axial localization of strain at pellet joints. Other factors associated with pellet clad interaction are also believed to be responsible for fuel rod failure, but all such factors are consequences of power shocks. Accurate and continuous monitoring of fuel rod power density is therefore essential in order to enable detection of power shocks and through a failure model as aforementioned to furnish a power utility operator with the information necessary to control power distribution by control rod movement and/or coolant flow rate control in a boiling water reactor or by control rod movement and/or boron concentration control in the moderator of a pressure water reactor. The power density of the reactor has been monitored through sensors located in the fuel rod assembly. One type of sensor heretofore utilized for such purpose has been of the thermal neutron flux type. Although such neutron flux sensors provide power measurement signals that exhibit a rapid response to changes in local power density, they are unsatisfactory from two other important standpoints. First, the power measurement signal of a neutron flux sensor is not directly related to the linear heat generation rate of the fuel rod so that various calibration and correction factors must be introduced in order to approximate the rather complex relationship involved. Second, the neutron flux sensor has an emitter subject to burn-out. According to prior copending application Ser. No. 888,881, filed Mar. 21, 1978 now U.S. Pat. No. 4,298,430, issued Nov. 3, 1981 owned in common with the present application, a local power density sensor is disclosed, which provides a signal output which is directly related to the linear heat generation rate for the fuel rods to enable more accurate determination of this parameter as compared to measurement by neutron flux sensors. Further, the sensor disclosed in the aforementioned prior patent is of the gamma radiation heat generating type which has no emitter subject to burn-out. However, the gamma ray sensor does not have a rapid signal response to changes in power as in the case of a neutron flux sensor which is in conflict with the requirement for real time local fuel power measurements in a fuel failure avoidance system. It is therefore an important object of the present invention to provide a method of furnishing a nuclear power utility operator with real time, yet accurate, knowledge of local fuel power rate in the reactor core to enable operation of the power plant within adequate margins with respect to those operational parameters determined from local power measurements. An additional object is to provide a power monitoring system for the fuel rods of the nuclear power reactor which benefits from the use of a gamma ray type of sensor. SUMMARY OF THE INVENTION In accordance with the present invention, a plurality of gamma ray sensors of the type disclosed in the aforementioned prior patent, provide input analog signals processed through two parallel paths to produce two separate power shape readouts that may be compared. One of the signal processing lines, generally known in the art, is of the precision type including a process computer into which various model parameters and correction factors are introduced from data storage to supply precision information to the utility operator from which fuel failure avoidance decisions may be made in the operation of the power plant. The other signal processing line directly converts the analog signals into a power readout as a function of local fuel power rates of fuel rods adjacent to the sensors by calibration of the analog signals. According to certain embodiments, both of the signal processing lines include a dynamic filter assembly through which a signal deconvolution process is performed in order to modify the readouts so as to compensate for delays caused by slow signal response of the sensors to changes in power. A continuous readout from the direct signal processing line may be compared with the precision readout of the signal processing line in parallel therewith to provide updated corrective calibration of the continuous readout. The continuous readout will provide the utility operator with information necessary to avoid plant shutdown during interruptions in the precision readout arising from computer downtime caused by updating of its data storage or other causes.
	summary
	claims	1. A method of inspecting a pipe comprising the steps of:transporting a scanning assembly to the pipe;remotely wedging the scanning assembly between the pipe and an opposing surface to support the scanning assembly in a desired position;supporting the entire weight of the scanning assembly employing at least one hydraulically operated wedge extending from a first side of the scanning assembly and an arm extending from a second side of the scanning assembly; andscanning a surface of the pipe. 2. The method of claim 1 further comprising the steps of:positioning the scanning assembly at a desired location along the pipe; andextending the at least one hydraulically operated wedge and the arm to contact both the pipe and the opposing surface. 3. The method of claim 2 including the steps of:operating the at least one hydraulically operated wedge hydraulically; andoperating the arm pneumatically. 4. A method of inspecting a pipe, comprising:transporting a scanning assembly to the pipe;positioning the scanning assembly between the pipe and an opposing surface;supporting the entire weight of the scanning assembly employing a hydraulically-operated wedge extending from a first side of the scanning assembly and an arm extending from a second side of the scanning assembly; andscanning a surface of the pipe. 5. The method of claim 4, further comprising:hydraulically extending the hydraulically-operated wedge; andpneumatically extending the arm. 6. The method of claim 5, further comprising:engaging the pipe with the hydraulically-operated wedge; andengaging the opposing surface with the arm. 7. The method of claim 5, further comprising:engaging the opposing surface with the hydraulically-operated wedge; andengaging the pipe with the arm.
046559914	abstract	A probe is disclosed for detecting the absence of helical springs from an array of mutually spaced springs, each mounted on a separate shank. The probe includes an elongate arm having a pair of pawls mounted in an aperture at one end of the arm, biased to extend from the aperture. During probing, the helical springs normally prevent the pawls from assuming their extended positions outside the aperture, which is urged by the applied biasing force. If a helical spring is missing from the array, the appropriate pawl pivots outward into its extended position and becomes lodged against the springless shank to lock the probe in position. Its location in the array then indicates where a spring must be replaced.
043280714	abstract	Tubes or cables designated as ducts and extending through a movable component which is capable of rotational motion about a vertical axis are supported between a fixed point located externally of the movable component and a second point which is located on the vertical axis of rotation of the component and constitutes the extremity of the supporting means. The portions of ducts located between the extremity of the supporting means and the center of rotation of the movable component are guided and maintained in uniformly spaced relation on a ruled surface of revolution about the axis of said movable component so that the duct portions thus form a bundle-type assembly. Means are further provided for securing the lower extremity of the guiding means to the movable component at the center of rotation of this latter.
052606210	abstract	An electric battery comprises a semiconductor junction incorporating an inorganic crystalline compound of Group III and Group V elements of the Periodic Table characterized by a predetermined annealing temperature for defects therein; a nuclear source of relatively high energy radiation and concomitant heat, which radiation causes generation of such defects in the semiconductor junction; and a thermal impedance enclosure for the nuclear source and the semiconductor-junction for retaining therewithin a sufficient quantity of heat to maintain a functional relationship between the generation of defects and the predetermined annealing temperature during operation.
040627268	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS OF THE INVENTION For a more complete appreciation of the invention, attention is invited to the following description of an illustrative embodiment of the invention, as shown in the attached drawings. In FIG. 1 there is illustrated a nuclear reactor pressure vessel 10 which has a longitudinally disposed cylindrical envelope closed at each end by a convex base and a domed roof. Reactor coolant inlet and outlet nozzles 12 and 14 respectively, protrude from the pressure vessel 10 near the domed roof. These nozzles are generally all disposed in the same plane, that is, transverse to the longitudinal axis of the cylindrical vessel and are separated from each other with an angular displacement. An annular flange 16 formed on the inner surface of the vessel 10 serves as a means for supporting a distribution hoop 18. The hoop 18 has an opening 20, for reactor coolant discharge, which is aligned with the outlet nozzle 14 in the vessel 10. The distribution hoop 18 is extended by means of a skirt 22 and a thermal shield 24 which serve as a hydraulic guide for the incoming fluid coolant entering the annulus 26 formed between the hoop-skirt assembly and the pressure vessel wall from the inlet nozzle 12. Furthermore, the skirt 22 supports the fuel elements in the reactor core (not shown). In operation, the coolant enters the pressure vessel 10 through the inlet nozzle 12 and flows downwardly through the annulus 26, rises through the reactor core (not shown) to the distribution hoop 18, whereupon the heated coolant is discharged from the vessel 10 through the opening 20 and the outlet nozzle 14. As shown in FIG. 2, the outlet nozzle 14 for the vessel 10 is in alignment with the opening 20 in the distribution hoop 18. An outlet nozzle seal 28 in accordance with this invention joins the hoop 18 to the vessel 10 or, more specifically, joins the hoop discharge opening 20 to the reactor pressure vessel outlet nozzle 14. As shown, the seal 28 is disposed within a recess 29 located circumferentially about the opening 20. The seal is comprised of an expansion bellows 30 attached at one end to seal ring 32 and at the other end to a compression ring 34 or the hoop 18. The seal 28 or, more specifically, the expansion bellows 30 is designed such that, in its assembled relationship with respect to the hoop opening 20 and the vessel nozzle 14, it forces the seal ring 32 into sealing engagement with the reactor pressure vessel. Furthermore, this sealing engagement is not dependent on reactor operation or thermal expansion. The seal ring 32 presents a broad surface 33 to engage the pressure vessel and prevent flow leakage therebetween. As shown, the pressure vessel may be cladded with a wear surface 36 to aid in the leak prevention between the seal ring and the vessel and to resist wear due to movement of the hoop-seal assembly with respect to the vessel. The expansion bellows 30 is an impervious hollow cylindrical or annular member having a plurality of flexible convolutions circumferentially disposed about the cylindrically shaped member in order to provide the necessary resiliency so as to prevent the structural coupling of the hoop to the vessel, and also, to provide the necessary force to hold the seal ring 32 in a leak tight relationship about, for example, the vessel nozzle 14. The impervious expansion bellows wall or boundary, moreover, prevents fluid communication across the bellows as is found in other spring seal systems. Furthermore, leakage across the bellows is prevented by seal welding or circumferentially attaching, in a leak-proof manner, the bellows to both the seal ring, at one end, and the compression ring or hoop at the other end. In accordance with this invention, therefore, a leak-proof sealing means is provided for fluid communication from the hoop opening to the outlet nozzle. In the embodiment of the invention shown in FIG. 2 the bellows seal is welded to a compression ring 34 disposed within the recess 29. The compression ring 34 is a cylindrical ring member having an elbow shape cross section. One arm 38 of the compression ring forms an outer protection wall for the expansion bellows spring 30, and the other arm 40 forms a support ring to which the expansion bellows is attached. Further, in this embodiment of the invention, a channel liner 42, connected to the compression ring 34, and, in particular, connected to the ring 40 forms an inner protection wall for the bellows. The compression ring 34 and the channel liner 42 form a cylindrical annular cavity as in the previous spring seal systems. However, in this system, the close tolerance machining of the sealing ring and the cavity are not required, since the bellows wall prevents flow leakage. In addition to forming an inner protection wall which prevents excessive lateral movement of the bellows, the channel liner 42 also serves as a smooth wall flow path from the opening 20 to the nozzle 14 to reduce the flow resistance through the sealing means to the outlet nozzle. In accordance with this invention, flow leakage between the incoming and outgoing coolant in the vicinity of the outlet nozzle 14 is prevented by the seal ring pressure vessel contact established by the self-actuating bellows, and, in addition, fluid communication across the bellows is precluded since the bellows wall provides an impervious cylindrically or annularly shaped boundary across which fluid flow is precluded.
	claims	1. A boiling water reactor core of a burner type, wherein a ratio of a number of fuel assemblies loaded on the core to a number of control rod drive mechanisms for driving control rods is at least 3, wherein a fuel of fuel rods of the fuel assemblies comprises at least one of (a) a first fuel of uranium which is an oxide of a low enriched uranium having an average enrichment for the fuel rods of the fuel assemblies of 3 to 8 wt %, (b) a second fuel of uranium and plutonium which has an average enrichment concentration of fissile plutonium for the fuel rods of the fuel assemblies of 2 to less than 6 wt %, and (c) a third fuel of uranium, plutonium and minor actinides for the fuel rods of the fuel assemblies, and wherein the fuel assemblies further include at least one water rod, characterized in that a heavy metal density is a weight of the at least one of (a) the first fuel, (b) the second fuel, and (c) the third fuel of the fuel rods of the fuel assemblies having the at least one water rod contained in a unit volume of a core area of the boiling water reactor core is 2.1 to 3.4 kg/L at a time of fuel loading of the fuel assemblies in the boiling water reactor core. 2. The BWR core according to claim 1, wherein a ratio of volume of a region of two phase flow cooling water including sub-cooled water for cooling fuel rods to a unit volume of the core is 18 to 39%, the two flow cooling phase water being present in a channel box, except for gaps between channel boxes outside of the channel boxes of the fuel assemblies, in guide members into which the control rods are inserted, and the inside of the at least one water rod. 3. The BWR core according to claim 1, wherein a ratio of volume of a region of subcooled water and saturated water to a unit volume of the core is 26 to 38%, the subcooled water and saturated water being present in gaps between channel boxes outside of the channel boxes of the fuel assemblies, in guide members into which the control rods are inserted, and the inside of the at least one water rod. 4. The BWR core according to claim 1, wherein a ratio of volume of a region of subcooled water and saturated water to a unit volume of the core is 6 to 9%, the subcooled water and saturated water being present in guide members into which control rods are inserted, and the inside of water rods. 5. The BWR core according to claim 1, wherein a ratio of volume of a region of a fuel substance to a unit volume of the core is 23 to 37%. 6. The BWR core according to claim 1, wherein a volume ratio of a volume of subcooled water and saturated water for cooling fuel rods, except for water in gaps between channel boxes outside of the channel boxes of the fuel assemblies, in guide members into which the control rods are inserted, and the inside of the at least one water rod to a volume of a fuel substance area is 0.5 to 1.8 in the reactor core area. 7. The BWR core according to claim 1, wherein a power density is 63 to 140 kW/I. 8. The BWR core according to claim 1, wherein an average of distance between channel boxes of adjoining fuel assemblies, the channel boxes facing each other, is 17 to 40 mm. 9. The BWR core according to claim 1, wherein a distance between fuel rods is 0.7 to 2.6 mm in case of a square lattice configuration or 0.7 to 3.6 mm in case of triangular lattice configuration. 10. The BWR core according to claims 1, wherein a ratio of a channel box outer width of a fuel assembly to an average fuel bundle pitch is 0.80 to 0.89. 11. The BWR core according to claim 1, wherein an active fuel length is 1.0 to 3.0 m. 12. The BWR core according to claim 1, wherein the core is configured such that the control rods are inserted into gaps between fuel assembly channel boxes, and wherein an average gap distance of the channel boxes where the control rods are inserted is larger than that where the control rods are not inserted. 13. The BWR core according to claim 1, wherein the core is constructed by fuel assemblies which have the at least one water rod whose sectional area is larger than the sectional area of a unit cell of the fuel rod lattice. 14. The boiling water reactor core according to claim 1, wherein the core is constituted by square fuel assemblies and cross-shaped control rods inserted between the fuel assemblies at a rate of one control rod per 4 fuel assemblies. 15. The boiling water reactor core according to claim 1, wherein the core is constituted by square fuel assemblies and round-shaped control rods inserted into the fuel assemblies at a rate of at least one control rod per 1 fuel assembly. 16. The boiling water reactor core according to claim 1, wherein the core is constituted by hexagonal shape fuel assemblies and Y-type control rods inserted between the fuel assemblies. 17. The boiling water reactor core according to claim 1, wherein the core is constituted by hexagonal shape fuel assemblies and round or hexagonal shaped control rods inserted into the fuel assemblies at a rate of at least one control rod per 1 fuel assembly. 18. The boiling water reactor core according to claim 14, wherein at least one of a water removal plate and a water removal rod is disposed in gaps between the channel boxes or in the at least one water rod, at least one of the removal plate and removal rod being able to be withdrawn during operation of the core. 19. The boiling water reactor core according to claim 14, wherein a water removal plate is disposed adjacent the control rods, the water removal plate being detachable and being withdrawable from the core during operation of the core. 20. The boiling water reactor core according to claim 15, wherein a water removal rod of round or hexagonal shape is disposed adjacent the control rods, the water removal rod being withdrawable from the core during operation of the core. 21. A boiling water reactor core of a burner type, wherein a ratio of a number of fuel assemblies loaded on the core to a number of control rod drive mechanisms for driving control rods is at least 3, and an effective water-to-fuel volume ratio of at least 1 at the time the reactor is operated at at least 50% of rated power, the fuel assemblies including at least one water rod and at least one of (a) a first fuel of uranium of fuel rods of the fuel assemblies, (b) a second fuel of uranium and plutonium of the fuel rods of the fuel assemblies, and (c) a third fuel of uranium, plutonium and minor actinides of the fuel rods of the fuel assemblies, characterized in that a heavy metal density is a weight of the at least one of (a) the first fuel, (b) the second fuel, and (c) the third fuel of the fuel rods of the fuel assemblies having the at least one water rod contained in a unit volume of a core area of the boiling water reactor core is 2.1 to 3.4 kg/L at a time of fuel loading of the fuel assemblies in the boiling water reactor core. 22. The BWR core according to claim 21, wherein a ratio of volume of a region of two phase flow cooling water including subcooled water for cooling fuel rods to a unit volume of the core is 18 to 39%, the two phase flow cooling water being present in a channel box, except for water in gaps between channel boxes outside of the channel boxes of the fuel assemblies, in guide members for inserting control rods thereinto, and the inside of the at least one water rod. 23. The BWR core according to claim 21, wherein a ratio of volume of a region of subcooled water and saturated water to a unit volume of the core is 26 to 38%, the subcooled water and saturated water being present in gaps between channel boxes outside of the channel boxes of the fuel assemblies, in guide members for inserting control rods thereinto, and the inside of the at least one water rod. 24. The BWR core according to claim 21, wherein a ratio of volume of a region of subcooled water and saturated water to a unit volume of the core is 6 to 9%, the subcooled water and saturated water being present in guide members into which control rods are inserted in channel boxes, and the inside of the at least one water rod. 25. The BWR core according to claim 21, wherein a ratio of volume of a region of a fuel substance to a unit volume of the core is 23 to 37%. 26. The BWR core according to claim 21, wherein a ratio of a volume of the two phase flow cooling water including sub-cooled water for cooling the fuel rods, except for water in gaps between channel boxes outside of the channel boxes of the fuel assemblies, in guide members into which the control rods are inserted, and the inside of the at least one water rod, to a volume of a fuel substance area is 0.5 to 1.8. 27. The BWR core according to claim 21, wherein a power density is 63 to 140 kW/I. 28. The BWR core according to claim 21, wherein an average of distance between channel boxes of adjoining fuel assemblies, the channel boxes facing each other, is 17 to 40 mm. 29. The BWR core according to claim 21, wherein a distance between fuel rods is 0.7 to 2.6 mm in case of a square lattice configuration or 0.7 to 3.6 mm in case of triangular lattice configuration. 30. The BWR core according to claim 21, wherein a ratio of a channel box outer width of a fuel assembly to an average fuel bundle pitch is 0.80 to 0.89. 31. The BWR core according to claim 21, wherein an active fuel length of fuel is 1.0 to 3.0 m. 32. The BWR core according to claim 21, wherein the core is configured such that the control rods are inserted into gaps between fuel assembly channel boxes, and wherein an average gap distance of the channel boxes where the control rods are inserted is larger than that where the control rods are not inserted. 33. The BWR core according to claim 21, wherein the core is constructed by fuel assemblies which have the at least one water rod whose sectional area is larger than the sectional area of a unit cell of the fuel rod lattice. 34. The boiling water reactor core according to claim 21, wherein the core is constituted by square fuel assemblies and cross-shaped control rods inserted between the fuel assemblies at a rate of one control rod per 4 fuel assemblies. 35. The boiling water reactor core according to claim 21, wherein the core is constituted by square fuel assemblies and round-shaped control rods inserted into the fuel assemblies at a rate of at least one control rod per one fuel assembly. 36. The boiling water reactor core according to claim 21, wherein the core is constituted by hexagonal shape fuel assemblies and Y-type control rods inserted between the fuel assemblies. 37. The boiling water reactor core according to claim 21, wherein the core is constituted by hexagonal shape fuel assemblies and round or hexagonal shaped control rods inserted into the fuel assemblies at a rate of at least one control rod per 1 fuel assembly. 38. The boiling water reactor core according to claim 34, wherein at least one of a water removal plate and a water removal rod is disposed in gaps between channel boxes or in the at least one water rod, the at least one of the removal plate and removal rod being withdrawable during operation of the core. 39. The boiling water reactor core according to claim 34, wherein a water removal plate is disposed adjacent the control rods, the water removal plate being detachable. 40. The boiling water reactor core according to claim 35, wherein a water removal plate is disposed adjacent the control rods, the water removal plate being detachable.
	claims	1. A nuclear steam supply system with natural gravity-driven coolant circulation, the system comprising:a vertically-oriented reactor vessel comprising an elongated cylindrical shell forming an internal cavity configured for containing primary coolant and a nuclear reactor fuel core;a vertically-oriented steam generating vessel comprising a top, a bottom, an elongated cylindrical shell extending between the top and bottom defining an internal cavity, a top tubesheet, and a bottom tubesheet;a vertical riser pipe extending vertically between the top and bottom tubesheets, the riser pipe fluidly connected to the reactor vessel;a plurality of heat transfer tubes extending vertically between the top and bottom tubesheets; anda flange-less 90 degree primary coolant fluid coupling forming a flow conduit for exchanging primary coolant between the steam generating vessel and reactor vessel;the fluid coupling comprising a reactor vessel outer inlet nozzle and a reactor vessel inner outlet nozzle inside the outer inlet nozzle and arranged concentrically thereto;the inner outlet nozzle having an inlet end directly coupled to the reactor vessel, and an outlet end directly coupled to the riser pipe in the steam generating vessel;the outer inlet nozzle external to the steam generating vessel and having an inlet end directly coupled to a bottom outlet nozzle of the steam generating vessel, and an outlet end directly coupled to the shell of the reactor vessel;the outer inlet nozzle comprising a vertically-extending upper eccentric cone section defining the inlet end of the outer inlet nozzle which is directly coupled to the bottom outlet nozzle of the steam generating vessel, and an adjoining horizontally-extending stub pipe section defining the outlet end of the outer inlet nozzle which is directly coupled to the shell of the reactor vessel;wherein the eccentric cone section comprises a vertically straight inner wall and a straight opposing inclined outer wall obliquely angled to the inner wall;wherein a closed primary coolant loop is formed in which primary coolant flows from the reactor vessel through the eccentric cone into the steam generator vessel and returns from the steam generating vessel to the reactor vessel through the eccentric cone. 2. The system according to claim 1, wherein the riser pipe extends through the eccentric cone and is fluidly coupled to the reactor vessel. 3. The system according to claim 1, wherein the primary coolant flows from the reactor vessel upwards through the riser pipe of the steam generator vessel at a first temperature, reverses direction, and flows downward through the tubes into the fluid coupling at a second temperature lower than the first temperature. 4. The system according to claim 1, further comprising an annular bottom collection plenum formed between the riser pipe and the eccentric cone section, the bottom collection plenum being in fluid communication with a tube side of the steam generating vessel to collect primary coolant flowing outwards from the heat transfer tubes through the bottom tubesheet. 5. The system according to claim 1, wherein the eccentric cone section is fluidly coupled to the bottom tubesheet and the heat transfer tubes. 6. The system according to claim 1, wherein the eccentric cone section is physically located externally to the shell of the steam generating vessel. 7. The system according to claim 1, wherein the stub pipe section is oriented 90 degrees to the eccentric cone section and joined to the eccentric cone section via an angled miter joint. 8. The system according to claim 7, wherein the eccentric cone section has a top end coupled to the bottom tubesheet and a narrower bottom end coupled to the stub pipe section. 9. The system according to claim 1, further comprising a reactor primary coolant outlet nozzle having a first end welded to a reactor shroud internal to the reactor vessel shell and a second end welded to an inlet nozzle of the steam generating vessel at the bottom of riser pipe, the reactor primary coolant outlet nozzle being disposed inside the eccentric cone section of the fluid coupling. 10. The system according to claim 1, wherein a total horizontal length of the fluid coupling between the reactor vessel and steam generating vessel is less than or equal to the diameter of the steam generating vessel. 11. The system according to claim 1, wherein no portion of a primary coolant pump resides inside the outer inlet nozzle. 12. The system according to claim 1, wherein the inner outlet nozzle inside the outer inlet nozzle of the fluid coupling includes a straight section of pipe oriented parallel to the inclined outer wall of the eccentric cone section.
06326627&	summary	FIELD OF THE INVENTION The present invention pertains generally to devices and methods for generating ions and for separating ions of different mass charge ratios from each other. More particularly, the present invention pertains to devices and methods that are capable of effectively separating ions of different mass charge ratios after the ions have been generated by plasma sputtering. The present invention is particularly, but not exclusively, useful as a device and method for plasma sputtering a multi-metallic substrate, wherein previously-sputtered heavier ions are redirected into contact with the substrate for additional sputtering, and previously-sputtered lighter ions are prevented from doing so and, instead, are separately collected. BACKGROUND OF THE INVENTION For applications wherein the purpose is to separate a constituent element from a chemical compound, from a metallic alloy or from some other mixture of elements, there are several possible ways to proceed. In some instances, mechanical separation may be possible. In others, chemical separation may be more appropriate. Further, when mechanical or chemical processes are not feasible, it may happen that procedures and processes involving plasma physics may be necessary. If so, it is necessary to first generate a multi-species plasma that contains the target constituent. Then, it is necessary to separate the target constituent from the rest of the multi-species plasma. There are many known ways in the pertinent art by which plasmas, including multi-species plasmas, can be generated. For example, the evaporation of a substrate by an electron beam or by laser ablation is often used in plasma processing applications. Another method involves sputtering. With sputtering, atoms are removed from an electrode by positive ion bombardment of a source material. Insofar as sputtering is concerned, a relatively recent development in this field is provided in an article entitled "Universal Metal Ion Source" authored by Churkin et al. of the Budker Institute of Nuclear Physics, Novosibirsk Russia, and presented in the American Institute of Physics, 1998. In particular, this article discloses an electrode that is used as a metal ion source and sputtered in a magnetic trap. As disclosed in the Churkin article, this is done with crossed electrical and magnetic fields. As implied above, once the multi-species plasma has been generated, it is still necessary to separate the target constituent from the plasma. Again, such a separation can be accomplished in several ways known in the pertinent art. For example, plasma centrifuges and their methods of operation are well known. On the other hand, and not yet so well known, plasma filters and their methods of operation are also useful for this purposes. For example, the invention as disclosed by Ohkawa in U.S. application Ser. No. 09/192,945, filed on Nov. 16, 1998, for an invention entitled "Plasma Mass Filter" and assigned to the same assignee as the present invention is useful for separating ions of different mass charge ratios. Due to the fact that the phenomena involved with plasma filter procedures are quite different from those involved with a plasma centrifuge, it is helpful to mathematically consider these phenomena as they will apply to the situation wherein a multi-species plasma is generated using a sputtered ion source. In a vacuum chamber, when an inwardly oriented, radial electric field (E) is crossed with an axial magnetic field (B), charged particles will have orbits that are described by the following equation: EQU md.sup.2 r/dt.sup.2 =eE+e[VB] In the equation above, "m" is the mass of the charged particle (e.g. ion), "e" is the ion charge, and "V" is particle velocity. For a conservation of energy, it can be shown from the above equation that: EQU m(V.sub.r.sup.2 +V.sub..theta..sup.2 +V.sub.z.sup.2)/2+e.phi.+(r)=.epsilon. EQU mV.sub..theta. r+eBr.sup.2 /2=M where ".theta." is electrode potential, ".epsilon." is the total energy of a particle, "M" is the angular momentum of the particle, "V.sub.r " is the radial component of particle velocity, "V.sub..theta. " is the angular component of particle velocity, and "V.sub.z " is the axial component of particle velocity. In a cylindrical-shaped vacuum chamber, immediately after a charged particle has been ionized at a distance r.sub.max from the central axis, it will have a very small kinetic energy and the total energy .epsilon. will be: EQU .epsilon.=e.phi.(r.sub.max) and its angular momentum will be: EQU M=eB(r.sub.max).sup.2 /2 Once ionized, the particle will then be influenced by the radial electric field (E) in the chamber that will accelerate it toward the axis. Acting against this acceleration of the charged particle toward the axis will be a Lorentz force that deflects the charged particle away from the axis and back to its original distance from the axis, i.e. r.sub.max. At the point when the charged particle (ion) is closest to the axis, i.e. at r.sub.min, its radial velocity will be equal to zero (V.sub.r =0). For this condition: EQU U=.phi.(r.sub.max)-.phi.(r.sub.min)=(eB((r.sub.max).sup.2 -(r.sub.min).sup.2 /r.sub.min).sup.2 /8m At this point, consider that the electric field (E) is, at least in part, generated by a central electrode that is oriented along the central axis. Further, consider that the central electrode is generally rod-shaped and has a radius that is equal to "a" (i.e. r.sub.min =a). Thus, if r.sub.min is less than "a" (i.e. r.sub.min <a), when the charged particle is accelerated toward the electrode it will be lost to the electrode. If, as indicated, the above-described conditions are established in a generally cylindrical shaped chamber that has a wall at a radius "b" from the central axis, there is a critical electrical potential in the chamber that can be expressed as: EQU U(r)=e.sup.2 B.sup.2 (r.sup.2 -a.sup.2).sup.2 /8a.sup.2 m=U.sub.o (r.sup.2 -a.sup.2).sup.2 /(b.sup.2 -a.sup.2).sup.2 (Eq. 1) The total voltage applied between the central electrode and the wall of the chamber can then be expressed as: EQU U.sub.o =e.sup.2 B.sup.2 (b.sup.2 -a.sup.2).sup.2 /8a.sup.2 m The consequence of all this is that when U.sub.o is established inside the chamber with radial profile U(r), described by Eq. 1, ions with a mass greater than "m" (i.e. m.sub.2 >m) will fall onto the central electrode. On the other hand, ions with a mass less than "m" (i.e. m.sub.1 <m) will not fall onto the central electrode but, instead, will be confined inside the chamber for subsequent separation from the plasma. In light of the above, it is an object of the present invention to provide a device for separating ions from each other which uses relatively heavier mass ions in a multi-species plasma to sputter a metallic electrode and, thereby, generate more of the multi-species plasma. Another object of the present invention is to provide a device for separating ions from each other that effectively confines relatively lighter mass ions to a predetermined volume in a chamber for subsequent removal therefrom. Yet another object of the present invention is to provide a device for separating ions from each other that is effective for separating metal ions from a metal alloy. Still another object of the present invention is to provide a device for separating ions from each other that is easy to use, relatively simple to manufacture and comparatively cost effective. SUMMARY OF THE PREFERRED EMBODIMENTS A device for separating ions of different mass charge ratios from each other includes an elongated chamber that defines a longitudinally aligned central axis and has a first end and a second end. In its configuration, the elongated chamber is preferably cylindrical shaped and has a wall that is positioned at a distance "b" from the central axis. A central electrode is positioned in the chamber and is aligned along the axis. Preferably, the electrode is rod-shaped, has a radius "a," and is made of at least two elements. For example, one of the elements is preferably a light metal that has a mass "m.sub.1." The other element is relatively heavy, such as a heavy impurity, and it has a mass "m.sub.2." An axially oriented magnetic field, B, is generated in the chamber by magnetic coils that are specifically configured to create so-called "magnetic mirrors" at the opposite ends of the chamber. More specifically, the magnetic mirror at one end of the chamber exists over the full plasma cross section. At the opposite end of the chamber, however, the magnetic mirror exists only at the plasma periphery and thus, an annular-shaped mirror establishes an effective exit opening near the axis of the chamber. In addition to the magnetic field, B, a radially oriented electric field, E, is also generated inside the chamber. Accordingly, there are crossed electric and magnetic fields (E.times.B) in the chamber that will exert forces on charged particles in a predictable manner. The consequence of these forces for a charged particle (ion) having a mass, m, will depend on the particular configurations of both the electric field, E, and the magnetic field, B. Recall, the configuration of the magnetic field, B, requires the establishment of magnetic mirrors at opposite ends of the chamber. To interact with this particular magnetic field configuration, the present invention requires that the electric field, E, be configured with a critical electric potential U.sub.o =e.sup.2 B.sup.2 (b.sup.2 -a.sup.2).sup.2 /8a.sup.2 m, wherein "e" is the ion charge. This critical potential is established between the central electrode and the wall of the chamber. Additional electrodes, positioned at the ends of the chamber, can be used together with the central electrode to control the electric field radial profile. In operation, the magnetic coils are activated to create a steady state magnetic field (B) in the substantially cylindrical-shaped chamber. As indicated above, a full magnetic mirror is created at one end of the chamber and an annular-shaped magnetic mirror is created at the other end. The chamber is then initially pre-filled with a gas such as Hydrogen (H.sub.2) or Argon (Ar). The initial gas pressure in the chamber will be established at approximately 10.sup.-4 Torr. Next, a voltage, in the range of about one to three thousand electron volts (U.apprxeq.1-3 keV), is applied to interact with gas in the chamber and, thereby, generate a plasma discharge. Positive ions from this plasma discharge are then accelerated by the electric field, E, toward the central electrode. Collisions between the ions and the central electrode cause metal ions and neutral atoms to sputter from the central electrode. In turn, the sputtered neutral atoms are ionized by the electric field (E). Thus, the process is continued in a sustained operation as some of these new ions are accelerated back toward the electrode for subsequent sputtering. As caused by the present invention, it will happen that some of the newly ionized charged particles will have insufficient mass to be accelerated into collision with the electrode. Due to the establishment of a critical electric potential U.sub.o =e.sup.2 B.sup.2 (b.sup.2 -a.sup.2).sup.2 /8a.sup.2 m in the chamber (recall "e" is the ion charge, "m" is the ion mass, "b" is the radius of the chamber, and "a" is the radius of the central electrode), the ions will react to U.sub.o differently, according to their mass. Specifically, when U.sub.o is established inside the chamber, ions with a mass greater than "m" (i.e. m.sub.2 >m) will fall onto the central electrode. Thus, it is the relatively heavier ions that will continue sputtering the electrode to sustain the generation of a plasma in the chamber. On the other hand, ions with a mass less than "m" (i.e. m.sub.1 <m) will not fall onto the central electrode. Instead, these lighter ions will be confined inside the chamber for subsequent removal from the plasma. Specifically, the removal of the lighter ions will be accomplished through the exit opening of the annular-shaped magnetic mirror.
051280680	abstract	Particulate material such as for example soil contaminated with heavy metals, radioactive species and organics, singly or in combination, is treated by first washing the contaminated material with a contaminant mobilizing solution comprising a leaching agent, a surfactant or a mixture thereof. Large particles, typically greater than 5 mm are mechanically separated, washed with water and returned to the site as recovered soil. Fines, along with contaminants dissolved or dispersed in the contaminant mobilizing solution are separated from intermediate sized particles by a countercurrent flow of the contaminant mobilizing solution, preferably in a mineral jig. The intermediate sized particles are then abraded in an attrition scrubber to dislodge attached mineral slimes or fines. These additional fines are separated from the intermediate sized particles with a countercurrent flow of wash water in a second mineral jig. For some applications, the intermediate sized particles can also be abraded in an attrition scrubber prior to size separation in the first mineral jig. The slurry of intermediate sized particles and wash water discharged from the second mineral jig is dewatered to produce additional recovered soil. If the contamination includes insoluble heavy metal particles, they are separated from the effluent discharged from the second mineral jig by density separation preferably in a cross-current flow jig, prior to dewatering. Various techniques can be used to separate the fines and the contaminants dissolved and dispersed in the waste slurries discharged by the two mineral jigs used for countercurrent flow size separation from the contaminant mobilizing solution which is recycled.
052934110	description	DETAILED DESCRIPTION OF THE INVENTION A nuclear reactor power control device of one preferred embodiment according to the present invention, which is applied to a boiling type nuclear reactor, is explained in reference to FIG. 1. First of all, an outline of the boiling water type nuclear reactor plant to which the present invention is applied is explained. The steam generated at core 2 in a nuclear reactor pressure vessel 1 is supplied to a turbine 5 through a main steam pipe 3. This steam, drives the turbine 5 and then is condensed into water at a condenser 6. This water is returned as feed water to the nuclear reactor pressure vessel through a feed water pipe 10. This feed water is pressurized by feed water pumps 11A and 11B (or a feed water pump 15). The feed water pumps 11A and 11B are turbine driven types and each has a supply capacity corresponding to a cooling water flow of 55% (feed water flow). A bleeder tube 12A introduces the steam bled from the turbine 5 to the turbine of the feed water pump 11A. A steam governor valve 13A and a steam stop valve 14A are provided in the bleeder tube 12A. A bleeder tube 12B introduces the steam bled from the turbine 5 to the turbine of the feed water pump 11B. A steam governor valve 13B and a steam stop valve 14B are provided in the bleeder tube 12B. The feed water pump 15 is a motor driven type and has a supply capacity corresponding to a feed water flow of 27.5%. A feed water governor valve 16 is provided in the feed water pipe 10 down stream of the feed water pump 15. A generator 9 is disengageably connected to the turbine 5. A steam governor valve 4 is provided in the main steam tube 3. A bypass pipe 7 with a bypass valve 8 is directly connected between the main steam tube 3 and the condenser 6. Through the drive of a reactor internal pump (RIP) 17, cooling water is supplied to the core 2. The cooling water flow supplied to the core, that is core flow, is controlled by adjusting the speed of RIP 17. The nuclear reactor power of the boiling water type nuclear reactor is controlled by the control of the core flow, as well by the control rods 18. The control rods are connected to a control rod driving device 19. Both hydraulic driven and motor driven type may be used for the control rod driving device 19. A water level gauge 20 is provided at the nuclear reactor pressure vessel 1. The water level gauge 20 detects the water level H in the nuclear reactor pressure vessel 1. A flow meter 21 that detects the steam flow Qs discharged from the nuclear reactor pressure vessel 1 is provided in the main steam tube 3. A flow meter 22 that detects the feed water flow Qw supplied to the nuclear reactor pressure vessel 1 is provided at the feed water pipe 10. A feed water controller 23 receives as input the detected water level H, steam flow Qs and feed water flow Qw, and controls the feed water flow based upon these inputs, through the well known three element control. The feed water controller 23 outputs a control signal for controlling opening degrees of the steam governor valves 13A and 13B and the feed water governor valve 16. In a normal operation of the nuclear reactor (for example, in the power operation of 100%) the feed water pumps 11A and 11B are driven and the feed water pump 15 is standing by as a back-up. A trip detection device 24 receives inputs of measured values, such as speed of the feed water pumps 11A, 11B, discharge pressure of the feed water pumps 11A, 11B, bled steam flow supplied to the pump driving turbines, current flowing to the motor of the feed water pump 15 and conditions relating to the feed water pump, such as the voltage applied thereto, and thereby detects the trip of the feed water pumps 11A, 11B. When the trip detection device 24 detects the trip of a certain feed water pump, the device outputs a trip signal St to the steam stop valve (14A or 14B) of the corresponding feed water pump and a circuit breaker 25. The steam stop valve is full-closed by the trip signal St. The circuit breaker 25 is opened by the trip signal St. The present embodiment further includes four detectors as indicate below. A generator output detector 26 detects an electric power W that is the output of the generator. A neutron detector 27, which detects nuclear reactor power P.sub.R, is provided in the core 2. A flow meter 28 provided in the nuclear reactor measures core flow Qr. A position detector 29 measures the insertion depth (position of the control rod in axial direction) of the control rod 18 into the core. An output control device 30 controls the nuclear reactor power P.sub.R both in normal and abnormal conditions. The output control device 30 includes abnormal feed water control system 31, output pattern setting device 46, nuclear reactor power setting device 47, a low value priority circuit 48 and nuclear reactor power setting device 49, as shown in FIG. 2. The abnormal feed water control system 31 has allowable nuclear reactor power setting device 32 and operating mode switch 40. The allowable nuclear reactor power setting device 32 includes target power generating device 33, run-out, that is overspeed, preventing device 34 and adders 35, 36, 37 and switches 38, 39. The overspeed preventing device 34 has a signal generator 34A connected to the adder 36 through the switch 34B and a signal generator 34C connected to the adder 36 through the switch 34D. The signal generator 34A outputs signal S.sub.2 that corresponds to 20%. The signal generator 34C outputs signal S.sub.2 that corresponds to 110%. The adder 35 is connected to the flow meters 21 and 22 and outputs the difference S.sub.1 =Qs-Qw, the output signals of the respective flow meters. The switches 34B, 38, 39 are closed (ON) when the operation mode switch 40 outputs a speed reduction signal RB. The switch 34D is opened (OFF) when the speed reduction signal RB is output. The adder 36 is connected to the adder 35 through the switch 38. The adder 36 outputs a signal S.sub.3 obtained by adding the difference S.sub.1 to the signal S.sub.2. The adder 37 is connected to the target power generating device 33 through the switch 39 and also to the adder 36. The adder 37 outputs difference S.sub.5 =S.sub.4 -S.sub.3. The signal S.sub.4 is a target output that is output from the target power generating device 33 and is the allowable nuclear reactor power at the moment of trip of the feed water pump 11A (or 11B). In the example of the present embodiment, the signal S.sub.4 is a signal corresponding to the nuclear reactor power of 75%. The operation mode switch 40 includes TD-RFP (turbine driver type reactor feed water pump) trip confirming device 41, flow difference determining device 42, water level determining device 43, an AND circuit 44 and an OR circuit 45. The TD-RFP trip confirming device 41 outputs a signal of logic "1" when the trip signal St is output. The flow difference determining device 42 outputs a signal of logic "1" when the difference S.sub.1 =Qs-Qw becomes larger than a fixed value. The water level determining device 43 outputs a signal of logic "1" when the water level "H" goes down to a fixed value. The fixed value of the water level "H" is a level set at a comparatively higher level than the low nuclear reactor water level that causes the nuclear reactor scram, and further is set at a lower level than the normal water level. The outputs of the flow difference determining device 42 and the water level determining device 43 are input to the AND circuit 44. The outputs of the TD-RFP trip confirmation device 41 and the AND circuit 44 are input to the OR circuit 45. The OR circuit 45 outputs a speed reduction signal RB when either the TD-RFP trip confirmation device 41 or the AND circuit 44 outputs a signal of logic "1". The output pattern setting device 46 is connected to a general supervisory computer not shown. The output pattern setting device 46 prepares an output pattern of the generator based upon data output from the general supervisory computer. The nuclear reactor power setting device 47 is connected to the output pattern setting device 46. The nuclear reactor power setting device 47 determines a fixed nuclear reactor power corresponding to the output pattern of the generator prepared by the output pattern setting device 46 and the measured electric power W. The input side of the low value priority circuit 48 is connected to the adder 37 of the allowable nuclear reactor power setting device 32 and the nuclear reactor power setting device 47, and the output side thereof is connected to the nuclear reactor power control device 49. The low value priority circuit 48 selects a lower output among those of the adder 37 and the nuclear reactor power setting device 47 and outputs the same as a signal Pr. The nuclear reactor power control device 49 is shown in FIG. 3 and has output S.sub.6. The nuclear reactor power control device 49 is provided with adders 50, 58, switches 51, 55, 59, a limiter 52, hysteresis switches 53, 56, 60, a PI controller 54, and a target core flow setting device 57. Each of these hysteresis switches has a dead zone. The adder 50 is connected to the neutron detector 27 and the low value priority circuit 48. The adder 50 outputs the difference .DELTA.P.sub.R =P.sub.R -Pr. The switches 51 and 59 are opened (OFF) based on the power (or speed) reduction signal RB, and the switch 55 is closed (ON) based on the power reduction signal RB. The limiter 52 is connected to the adder 50 through the switch 51, and connected to the hysteresis switch 53 and the PI controller 54. The target core flow setting device 57 determines a corresponding fixed core flow Q.sub.RO based on the output pattern of the generator prepared by the output pattern setting device 46. The adder 58 is connected to the flow meter 28 and the target core flow setting device 57 and determines the difference .DELTA.Q.sub.R =Q.sub.RO -Q.sub.R. The hysteresis switch 60 is connected to the adder through the switch 59. The PI controller 54 is connected to a recirculation flow control device 61. The recirculation flow control device 61 is also called a core flow control device. The hysteresis switches 56 and 60 have outputs S.sub.7 and S.sub.8 connected to a control rod driving control device 62. The recirculation flow control device 61 receives as inputs the output signals S.sub.6, S.sub.3, RB of the output control device 30, carries out the processing sequence shown in FIG. 4, and controls the core flow .DELTA.Q.sub.R. The recirculation flow control device 61 outputs a control signal R.sub.1 to the driving motor for the RIP 17. The control rod drive control device 62 shown in FIGS. 2 and 5, outputs a control signal C.sub.R to the control rod driving device 19. The control rod driving control device 62 has a control device 63 and a control rod worth minimizer 64. The control device 63 inputs the output signals from the output control device 30 and the control rod worth minimizer 64, and then it carries out the processing sequence shown in FIG. 6. In the control rod worth minimizer 64, a control rod insertion and withdrawal sequence is set that defines the manipulation order of the control rods in normal operation. The signal from the position detector 29 is transmitted to the control rod worth minimizer 64. An example of the control rod insertion and withdrawal sequence is illustrated in FIG. 7. In FIG. 7, the column F.sub.1 shows the group number of the control rod. The column F.sub.2 shows the relative value of lapsed time and the column F.sub.3 shows the position of the control rod in the axial direction. One group includes a plurality (usually 4) of control rods 18. The column F.sub.3 indicates the notch number determined by equally dividing the core in its axial direction into forty-eight parts, for indicating the position of the control rod. The notch number of "48" corresponds to the full withdrawal of the control rods 18. Further the notch number of "0" corresponds to the full insertion of the control rods. The control rods included in the group 27 are withdrawn to the position of notch "6" at the lapsed time of 12 and to the position of notch "12" at the lapsed time 13. At the lapsed time 12 the control rods 18 in groups 22 and 23 are withdrawn to the position of notch "12" and the control rods 18 in groups 26 to 30 are withdrawn to the position of notch "6". The operation of the nuclear reactor power control device according to the present embodiment is explained below. First of all, the case where the two feed water pumps 11A and 11B are in a normal operating condition is explained, with reference to FIG. 2. Since the trip detection device 24 detects no trips of the feed water pumps 11A and 11B, no trip signal St is output. Therefore the OR circuit 45 outputs no power reduction signal RB, and the switches 34B, 38, 39 of the allowable nuclear reactor power setting device 32 are opened (OFF). Further, the switch 34D is closed (ON). The switches 51 and 59 of the nuclear reactor power control device 49 in FIG. 3 are closed (ON) and the switch 55 thereof is opened (OFF). Among the signals output from the signal generator 34C and the fixed value of the nuclear reactor power output from the nuclear reactor power setting device 47, the low value priority circuit 48 selects the later fixed value as a signal Pr. The signal Pr is output to the nuclear reactor power control device 49. The output .DELTA.P.sub.R from the adder 50 of FIG. 3 is input to the limiter 52 through switch 51. The output of the limiter 52 is transmitted to the hysteresis switch 53. The PI controller 54 inputs the output of the hysteresis switch 53 and outputs a signal S.sub.6. The hysteresis switch 60 inputs the difference .DELTA.Q.sub.R from adder 58 through switch 59 and outputs a corresponding signal S.sub.8. The signal S.sub.6 is transmitted to the recirculation flow control device 61. Further the signal S.sub.8 is input to the control rod driving control device 62. Since no power reduction signal is input to the recirculation flow control device 61, step 61A of FIG. 4 becomes "NO". Therefore, the process of the next step 61G is performed, and the recirculation flow control device 61 outputs a control signal R.sub.1. The control signal R.sub.1 is a signal for generating a pump speed corresponding to the signal S.sub.6. The speed of the RIP 17 is controlled based on the control signal R.sub.1. Accordingly, the core flow is controlled by the recirculation flow control device 61 to obtain a nuclear reactor power determined at the nuclear reactor power setting device 47. The control of the nuclear reactor power by the manipulation of the control rods is carried out by inputting the signal S.sub.8 to the control rod driving control device 62. Namely, the determination in step 62A of FIG. 6 becomes "YES", and the processing of the step 62G is executed. The step 62G outputs the control signal C.sub.R to the control rod driving device 19 for manipulating the corresponding control rod in order to manipulate control rods in a fixed group defined in the control rod worth minimizer 64. The fixed value Q.sub.RO of the core flow is determined based on the output pattern of the generator prepared at the output pattern setting device 46. Further the control signal C.sub.R is generated based on the difference .DELTA.Q.sub.R. Accordingly, the control of the nuclear reactor power by the control rods functions to obtain a fixed nuclear reactor power together with the control of the nuclear reactor power by the adjustment of core recirculation flow, which supplement each other. For the start and stop of the nuclear reactor and the nuclear reactor power control such as in the power operation (nuclear reactor power of 100%), a load following operation and an AFC operation are carried out through the above explained core flow control and control rod control. Assuming that the boiling water type nuclear reactor reaches an operating condition (point A in FIG. 14) of a nuclear reactor power of 100% and a core flow of 85% through the above explained nuclear reactor power control. The core flow of 85% is the minimum core flow at the nuclear reactor power of 100%, in the expanded operation range. The operation of the present embodiment is explained when an abnormality happens under these conditions, wherein the feed water pump 11A trips and the feed water pump 15 that stands by does not start. One feed water pump 11B is now running. In this first case, the trip signal St output from the trip detector 24 because of the trip of the feed water pump 11A fully closes the steam stop valve 14A. The TD-RFP trip confirming device 41 of the operation mode switch 40 receiving this trip signal, outputs a signal of logic "1". The OR circuit 45 outputs a power reduction signal RB in response to this signal. Therefore, the switches 34B, 38, 49, 55 are closed and the switches 34D, 51, 59 are opened. The operation mode switch 40 works also as a power reduction signal generating device. The power reduction signal RB is input to the recirculation flow control device 61. Therefore, the step 61A of FIG. 4 determines "YES". Next the step 61B is executed. The step 61B runs back, that is rapidly reduces the speed of the RIP 17, that is, performs pump run-back. Namely, the speed R.sub.2 of the RIP 17 is obtained, which determines the corresponding core flow Q.sub.R1 to the nuclear reactor power of 75% and the control signal R.sub.1 corresponding to the speed R.sub.2 is output. Through the control signal R.sub.1, the RIP 17 is reduced in speed to the speed R.sub.2. Further, the core flow Q.sub.R1, when the nuclear reactor power decreases to 75% through the speed reduction of the RIP 17, varies depending upon the nuclear reactor operating conditions (in particular, nuclear reactor power and the core flow) at the moment of the speed reduction of the RIP 17. Thereforem it is necessary to obtain a core flow corresponding to the nuclear reactor operating condition when the RIP 17 is reduced in speed by using many core flow-nuclear reactor power characteristic curves (for example, the characteristic curves C.sub.1, C.sub.2, C.sub.3, C.sub.4 of FIG. 14) illustrating the decreasing process of the nuclear reactor power due to the speed reduction of the RIP 17. The recirculation flow control device 61 of the present embodiment stores these core flow-nuclear reactor power characteristic curves and determines the core flow Q.sub.R1 by using these characteristic curves. In the present case, since the normal operating condition of a nuclear power of 100% and a core flow of 85% is assumed, the core flow Q.sub.R1 is obtained by using the characteristic curve C.sub.1. The core flow corresponding to point B of FIG. 14 on the minimum speed curve K of FIG. 14 is used to produce the signal to control the RIP 17. Since only the feed water pump 11B is operating, the feed water flow Qw is less than the steam flow so that there is a mismatch between the steam flow Qs and the feed water flow Qw. Therefore the adder 35 of the allowable nuclear reactor power setting device 32 outputs the difference S.sub.1 used to make the mismatch amount zero. The adder 36 outputs the signal S.sub.3 that is obtained by adding the signal S.sub.2, which corresponds to 20% of the output from the signal generator 34A, to the signal S.sub.1. The adder 37 outputs the difference S.sub.5. The signal S.sub.3 is transmitted to the recirculation flow control device 61 and the control rod drive control device 62. The signal S.sub.5 is transmitted to the lower value selection or priority circuit 48. The reasons why the signal S.sub.2 that corresponds to 20% of the output of the signal generator 34A is added in the adder 36 for obtaining the signal S.sub.3 are as follows. The rated capacity of the turbine driven type feed water pump is 55%, but the operation at 68% for a short period is possible. However, when the feed water pump 11B is operated for a long time (for example, over one minute) under the feed water capacity of 68%, the feed water pump 11B itself is tripped for preventing over speed. Under this condition, the nuclear reactor scram is reached. The overspeed preventing device 34 has a function of reducing the nuclear reactor power to a level to prevent overspeed of the turbine driven type feed water pump. When such an overspeed preventing device is not provided, the feed water pump 11B possibly runs too fast and trips even if the nuclear reactor power runs back, that is rapidly reduces the to the state where the abovementioned difference becomes zero. The signal S.sub.2 output from the overspeed preventing device 34 has a value to ensure reducing the nuclear reactor power to a level that should prevent overspeed of the turbine driven type feed water pump. The reasons why the signal S.sub.4 corresponding to 75% of the nuclear reactor power is defined for the target output generating device 33 are as follows. In a case that one turbine driven type feed water pump and one motor driven type feed water pump are in an operating condition, an obtainable nuclear reactor power is 75%. The nuclear reactor power of 75% also corresponds to the nuclear reactor power at point B; from the operating condition of a nuclear reactor power of 100% and the core flow of 85% all of the RIPs 17 are speed reduced so that the core flow is reduced to a value on the minimum revolution speed curve K of FIG. 4 for the RIP 17. The target output generating device 33 changes a fixed value of the nuclear reactor power to 75%, which is lower than a fixed value of the nuclear reactor power setting device 47. By thus lowering the fixed value, the control of reducing the nuclear reactor power is facilitated after the speed reduction of the RIP. In the present embodiment, wherein one turbine driven type feed water pump and one motor driven type feed water pump are operated, the nuclear reactor scram is avoided by reducing the nuclear reactor power to 75%. The recirculation flow control device 61 executes the processing of the step 61C after the step 61B, in FIG. 4. With the input of the signal S.sub.3, the determination in the step 61C becomes "YES". Next the step 61D is executed, which is not shown in FIG. 4. The step 61D determines whether the speed of the RIP 17 is the fixed minimum speed (a speed for obtaining the minimum speed curve K of FIG. 14) and generates "YES". For carrying out this determination, a tachometer (not shown) for detecting the speed of the RIP 17 is provided, the output of this tachometer is input to the recirculation flow control device 61. For the determination of the step 61D as "YES", the speed of the RIP 17 is maintained at a fixed minimum revolution speed. It is not possible to reduce the speed of the RIP 17 below a fixed minimum speed. When the determination of the step 61D is "NO", the processing in steps 61E and 61F are performed, as discussed below. The lower value priority circuit 48 selects the signal S.sub.5 as the signal Pr. The difference .DELTA.P.sub.R is output from the adder 50 (in FIG. 3) of the nuclear reactor power control device 49, which receives the signals Pr and P.sub.R, and .DELTA.P.sub.R =P.sub.R -S.sub.5, the difference between the nuclear reactor power P.sub.R measured at the neutron detector 27 and the signal S.sub.5. The hysteresis switch 56 outputs a signal S.sub.7 based upon the difference .DELTA.P.sub.R. The control rod driving control device 62 receives signals S.sub.3 and S.sub.7. Therefore, in FIG. 6, the step 62A becomes "NO", and the next step 62B becomes "YES". The step 62C thereafter also becomes "YES" and the processing is shifted to the step 62D. When the determination in steps 62B or 62C is "NO" the manipulation of the control rods is stopped by the step 62F. In the step 62D, the groups of control rods that are used as selected control rods are defined in response to the magnitude of the signal S3. The plurality of control rods 18 included in the defined control rod groups become the selected control rods. In the present case, the forty-four control rods 18 positioned in encircled boxes of the grid in FIG. 8 are defined as the selected control rods. FIG. 8 shows a cross sectional view of the core 2 and one box surrounded by the grid represents one cell. One cell includes four fuel rod assemblies and between these one control rod is inserted. Incidentally the selected control rods shown in FIG. 8 correspond to SR.sub.1 in the characteristic curve diagram of the step 62D in FIG. 6. Further the selected control rods corresponding to SR.sub.2 in the characteristic curve diagram are positioned in the encircled boxes in FIG. 9, and the control rods corresponding to SR.sub.3 are positioned in the encircled boxes in FIG. 10. The numerals indicated in the circles in FIG. 9 and FIG. 10 are the group number of the control rods. Within the values of the signal S.sub.3 indicated by RA.sub.1 in the characteristic curve diagram of the step 62D in FIG. 6, the selected control rods of SR.sub.1 are determined. In the same manner, within the values of signal S.sub.3 indicated by RA.sub.2, the selected control rods of SR.sub.2 are determined and within the values of signal S3 indicated by RA.sub.3 the selected control rods of SR3 are determined. The selected control rods once determined never change until the nuclear reactor power decreases to the nuclear reactor power of the point C in FIG. 14 even if the signal S.sub.3 changes greatly. Step 62E outputs a control signal C.sub.R that causes insertion into the core of a plurality of the control rods included in the control rod groups determined as above as the selected control rods. The control signal C.sub.R is transmitted to the control rod driving device 19 that manipulates the respective control rods determined as the selected control rods. The control rod driving device 19, receiving the control signal C.sub.R, inserts the corresponding control rods into the core 2. Through the runback (that is, speed reduction) of the RIP 17 and the insertion of the selected control rods, the nuclear reactor power decreases from the point A to the point C of FIG. 14. The nuclear reactor power at point C (55%) is a nuclear reactor power wherein the operation of one turbine driven feed water pump avoids the nuclear reactor scram and moreover the overspeed of the feed water pump is surely prevented. The insertion of the selected control rods of the present case functions to reduce the nuclear reactor power corresponding to the difference between point B and point C in FIG. 14. When only the avoidance of the nuclear reactor scram is required, it is enough to decrease the nuclear reactor power to about 65%. However, in such a case, the overspeed of the feed water pump 11B under operation possibly happens. The changes of the steam flow Qs, the feed water flow Qw and the water level H are shown in FIG. 11, when the above described abnormality of the feed water pump happened under the operating condition of point A in FIG. 14. The feed water flow Qw suddenly decreases due to the trip of the feed water pump 11A. Further the steam flow Qs also suddenly decreases because of the decrease of the nuclear reactor power due to the speed reduction of the RIP that occurs substantially simultaneously with the trip of the feed water pump 11A. The initiation of decrease of the steam flow Qs, which is much earlier than the case in FIG. 15, begins substantially simultaneously with the initiation of decrease of the feed water flow; this is because the generation of the power reduction signal RB occurs substantially simultaneously with the generation of the trip signal St from the trip detection device 24. The point M.sub.1 matches the point B of FIG. 14. By the operation of the control rod driving control device 62 based upon the mismatched amount difference S.sub.1 between the steam flow Qs and the feed water flow Qw output from the adder 35, the nuclear reactor power is decreased through the insertion of the selected control rods into the core so that the steam flow below the point M.sub.1 gradually decreases. Soon the steam flow Qs becomes less than the feed water flow Qw. This mismatch is canceled through the operation of the feed water controller 23, and the feed water flow Qw and the steam flow Qs become the same. On the other hand, the water level H once decreased due to the trip of the feed water pump 11A, rises in response to the power reduction of the nuclear reactor power with the insertion of the selected control rods. The water level H does not reduce to the fixed level of the nuclear reactor scram and the nuclear reactor scram is avoided. Namely the conventional problems shown in FIG. 15 are eliminated. In the present embodiment, the insertion initiation time of the selected control rods into the core has been hastened, as compared to the prior art. This is because the preparation of the control signal C.sub.R utilizing the difference S.sub.1 in the control rod driving control device 62 is allowed by the use of the power reduction signal RB. The second case is explained wherein the operating condition of the nuclear reactor is at the point D.sub.1 on the characteristic curve C.sub.2 of FIG. 14. Like the first case, it is assumed that an abnormality happened, for example an abnormality of the feed water system, including the feed water pump and the feed water lines, e.g., breakage of a pressurized feed water line. The operation of the output control device 30 at this moment is the same as that described above. The recirculation flow control device 61 executes processing in steps 61A, 61B, 61C, 61D of FIG. 4 in their order. The nuclear reactor power decreases to 75% along the characteristic curve C.sub.2 through the speed reduction operation by the step 61B. Such nuclear reactor power reduction is achieved by speed reduction of the RIP 17 to a point D.sub.2 on the characteristic curve C.sub.2 where the core flow becomes Q.sub.R1. Since the step 61D becomes "No", the processing is shifted to the step 61E. The step 61E determines the speed R.sub.3 of the RIP 17 to further reduce the nuclear reactor power to point D.sub.2. The speed R.sub.3 is determined based upon the magnitude of the signal S.sub.3. In the characteristic curve diagram in step 61E, K.sub.1 shows a fixed minimum speed of the RIP 17 The step 61F outputs a control signal R.sub.1 based upon the speed R.sub.3. The speed of the RIP 17 reduces to R.sub.3 and the nuclear reactor power reaches a value at the point D.sub.3 in FIG. 14. The power reduction of the nuclear reactor power corresponding to the difference between point D.sub.3 and point C is carried out by executing the steps 62A to 62E in FIG. 6 of the control rod driving control device 62. Further, when the initial operating condition (the operating condition when an abnormality occurs, e.g., the feed water pump 11A trips and the feed water pump 15 never starts) is on the characteristic curve C.sub.2, the selected control rods determined by the step 62D are for SR.sub.2. Incidentally, when an initial operating condition is on the characteristic curve C.sub.3, the selected control rods determined by the step 62D are SR.sub.3. The third case is explained wherein the initial operating condition is at point E.sub.1 on the characteristic curve C.sub.4 of FIG. 14. The operation of the output control device 30 is the same as that described above. In the present case, only by the execution of steps 61A to 61F of FIG. 4 by the recirculation flow control device 61, the nuclear reactor power decreases to the point C. Namely no insertion of the selected control rods is performed. Further, with the step 61B, the RIP 17 is reduced in speed so that the core flow Q.sub.R on the characteristic curve C.sub.4 reaches point E.sub.2. In the cases explained above, the insertion of the selected control rods is continued until the signal S.sub.3 reaches zero and at the moment thereof the insertion is stopped. There is a case wherein all of the selected control rods are not completely inserted into the core, but the inserting operation is stopped, so that a part thereof in the axial direction is inserted into the core. For carrying out such operation of the selected control rods, it is preferable to use a motor driven type control rod driving device 19, which makes possible a short length drive of the control rods. Accordingly the nuclear reactor power is reduced to a necessary minimum amount that avoids both the nuclear reactor scram and the overspeed of the feed water pump 11B. This leads to a shortening of time required to raise the nuclear reactor power to the rated output after the elimination of the abnormal condition. The power reduction of the nuclear reactor power to the necessary minimum amount allows for the determination of the number of the selected control rods in response to signal S.sub.3, as shown in step 62D of FIG. 6, so that a fine control is effected. Even if the decrease of the nuclear reactor power due to reduction of the core flow is effected after a fixed power reduction (output of 75%) of the nuclear reactor power based upon the speed reduction of the RIP 17, the speed of the RIP 17 is determined in response to the signal S.sub.3, as shown in step 61E of FIG. 4. The reduction of the nuclear reactor power by the RIP 17 after such fixed power reduction of the nuclear reactor power is also determined to be the necessary minimum amount. The present embodiment is also obtainable with the characteristic curve shown in FIG. 12. FIG. 12 shows a characteristic curve when the above described abnormality of the feed water pump occurs during nuclear reactor operation at point G.sub.1 in FIG. 14, through the load following operation. In this case, the same output control as the third case is carried out. Like FIG. 11, the feed water flow Qw and the steam flow Qs suddenly decrease by the trip of the feed water pump 11A and the speed reduction of the RIP 17. The point M.sub.2 corresponds to the point G.sub.2 in FIG. 14, and to the position of nuclear reactor power of 75%. Below the point M.sub.2, the nuclear reactor power decreases in response to the difference S.sub.1, with the recirculation flow control device 61, and the steam flow Qs gradually decreases. The water level H decreases below the normal water level but does not decrease to the nuclear reactor scram water level, needless to say in this case also no nuclear reactor scram happens. The second reduction of the feed water flow in FIG. 12 is effected by the feed water controller 23. The features in the characteristic curve of FIG. 12 will become apparent when compared with the characteristic curve of FIG. 16. FIG. 16 shows characteristic curves when the abnormality of the feed water pump occurred in the conventional device having the characteristic curve shown in FIG. 15 and during an operating condition at the point G.sub.1 of FIG. 14. In the conventional device, when one turbine driven type feed water pump is tripped, as described above, the reduction of the nuclear reactor power is effected based upon the nuclear reactor water level and the mismatched amount between the feed water flow and the steam flow. Therefore, like the characteristic curve in FIG. 15, the initiation of the decrease of the steam flow is delayed and the nuclear reactor power reduces unnecessarily to the point G.sub.3 of FIG. 14. Accordingly the steam flow in the characteristic curve of FIG. 15 decreases in comparison with the characteristic curve of FIG. 12. The nuclear reactor water level as shown in FIG. 16(B) decreases in comparison with FIG. 12, and further it takes a longer time to stabilize at a normal water level state. In the present embodiment, since the reduction of the core flow by the speed reduction of the RIP 17 during the above described abnormality of the feed water pump is limited to the core flow Q.sub.R1 that corresponds to the fixed nuclear reactor power (output of 75%), the problems shown in FIG. 16 are eliminated. In all the cases of the present embodiment, the nuclear reactor power reduced by the RIP speed reduction corresponds to the difference between the nuclear reactor power at the moment of abnormality occurrence and the nuclear reactor power of 75%. All the nuclear reactor powers at points B, D.sub.2, E.sub.2 and G.sub.2 are that of 75%. The operating mode switch 40 has a function of the flow difference determining device 42 and the function of the water level determining device 43. Even with the AND terms, of these functions a speed reduction signal is generated, by an abnormality other than the trip of the feed water pump, for example, the abnormality disclosed in Japanese Patent Application Laid-Open No. 49-37094 (1974), which is a broken pipe. This abnormality of the feed water flow may occur for many reasons and the RIP speed reduction occurs. Without providing the operation mode switch 40, it may be possible to use the trip signal St as the speed reduction signal RB. In this case, for causes other than the trip of the feed water pump (for example, based upon the output from the AND circuit of FIG. 2), the power reduction signal RB for speed reduction of the RIP 17 is generated such that the construction of the nuclear reactor power control device becomes complex. The output pattern setting device 46, the nuclear reactor power setting device 47, and the nuclear reactor power control device 49 constitute the power control device of the nuclear reactor in a normal condition. In the present embodiment, since the signal from the allowable nuclear reactor power setting device 32 included in the abnormal feed water control device 31 is transmitted to the nuclear reactor power control device 49, it may be said that a part of the power control device during normal condition is commonly used as a part of the abnormal feed water control device 31. For this reason, the structure of the nuclear reactor control device according to the present embodiment is simplified. The power reduction signal RB is also a switching signal for switching the first nuclear reactor power control function, which is included in the nuclear reactor control device of the present embodiment and used during normal condition of the feed water pump, to and from the second nuclear reactor power control function used during abnormal condition of the feed water pump. In case the power reduction signal RB is generated based upon the trip signal St, the trip signal can be the above switching signal. FIG. 13 shows a change of the negative reaction degree (converted output %) when the four control rods "a", as shown in FIG. 8, are moved from the full withdrawal condition to the full insertion condition into the core 2. Herein 0 on the abscissa indicates that the control rods are in a condition of full withdrawal. 200 on the abscissa device indicates that the control rods are in a condition of full insertion. The negative reaction degree changes in an S shape. Accordingly, when the control rods are in a condition near to the full withdrawal, change of the negative reaction degree is small even if the control rods are moved. For obtaining a large change of the negative reaction degree, it preferable to determine the control rods that are partially inserted into the core 2 and perform power control in a normal operating condition with the control rods that are fully withdrawn from the core. Among the selected control rods shown in FIG. 9 and FIG. 10, control rods in group numbers 22 and 24 are included that are used for the output control in a normal operation. Among the selected control rods of FIG. 8 the control rods of group number 22 are included. The number of selected control rods can be reduced by using the control rods used in the output control during a normal nuclear reactor operation as the selected control rods. The output pattern setting device 46 shown in FIG. 2 and the nuclear reactor power setting device 47 may be provided in the general supervisory computer as explained above. Another embodiment of the operation mode switch 40 of FIG. 2 is shown in FIGS. 17-19. In the operation mode switch 40A of the embodiment of FIG. 17, a delay circuit 84 is added to the constitution of the operation mode switch 40. The delay circuit 84 is connected to the output side of the OR circuit 45. In the embodiment of FIGS. 1 and 2, when the operation mode switch 40A is used in place of the operation mode switch 40, the delay circuit 84 outputs power reduction signals, which are the outputs of the OR circuit 45, to the respective switch of the allowable nuclear reactor power setting device 32 and the nuclear reactor power control device 49. The power reduction signals output from the OR circuit 45 are directly input to the recirculation flow control device 61 without passing through the delay circuit 84. The delay circuit outputs the power reduction signals that were input, but with a fixed delay (for example 2 or 3 seconds). In the above embodiment of FIG. 1, the speed reduction of the RIP 17 and the insertion of the selected control rods are substantially simultaneously effected. However, in the embodiment of FIG. 17, after the initiation of the reduction of the nuclear reactor power by the speed reduction of the RIP 17 by recirculation flow control device 61 without delay, the insertion of the selected control rods is effected after the delay of the delay circuit 84. Namely, the insertion of the selected control rods, after the reduction of nuclear reactor power due to the speed reduction of the RIP 17, decreases the distortion of the output distribution of the core in its axial direction that is affected by the insertion of the selected control rods. This is preferable in view of the practical use of the nuclear reactor. A nuclear reactor power control device of another embodiment according to the present invention is explained based upon FIG. 18. In the nuclear reactor power control device of FIG. 18, a turbine control device 67 is provided in place of the output pattern setting device 46 and the nuclear reactor power setting device 47 of the embodiment in FIG. 1. The output of the turbine control device 67 is input to the low value priority circuit 48 of the output control device 30A. The output control device 30A does not include the output pattern setting device 46 and the nuclear reactor power setting device 47, but includes the operation mode switch 40A. The pressure gauge 65 that detects the steam pressure P supplied to the turbine 5 is disposed in the main steam pipe 3. A tachometer 66 detects the speed R of the turbine 5. The turbine control device 67, as seen in FIG. 20, includes a pressure controller 68, a speed controller 69, a lower value selection circuit 70 and a load setter 71. The load setter 71 sets a load setting value L.sub.0 based upon the instruction of the general supervisory computer. The pressure signal P output from the pressure gauge 65 is input to the adder 72. The adder 72 calculates the difference .DELTA.P between the pressure setting value P.sub.0 and the pressure signal P. The pressure controller 68 outputs a steam flow demand signal S.sub.11 that is obtained based upon the difference .DELTA.P. The turbine speed R that is obtained at the tachometer 66 is input to an adder 73. The adder 73 determines the difference .DELTA.R between the speed R and the speed setting value R.sub.0. The speed controller 69 outputs a signal S.sub.12 in response to the difference .DELTA.R. An adder 74 obtains the speed adjusting signal S.sub.13 by adding the signal S.sub.12 to the load setting value L.sub.0. The lower value selection circuit 70 selects a signal having a lower value among the steam flow demand signal S.sub.11 and the speed adjusting signal S.sub.13 as a governor valve opening degree demand signal S.sub.14. Since the signal S.sub.12 is large because of its added bias, usually the steam flow demand signal S.sub.11 is selected. The steam governor valve 4 is controlled by the steam flow demand signal S.sub.11. An adder 76 outputs a bypass valve opening degree demand signal S.sub.15 by adding the steam flow demand signal S.sub.11, the governor valve opening degree demand signal S.sub.14 and a bias B.sub.1. The bypass valve 8 is controlled based upon the bypass valve opening degree demand signal S.sub.15. An adder 75 inputs the steam flow demand signal S.sub.11, the speed adjusting signal S.sub.13 and a bias signal B.sub.2 and it outputs a signal S.sub.16. The signal S.sub.16 corresponds to the nuclear reactor power setting value prepared at the nuclear reactor power setting device 47. The signal S.sub.16 is transmitted to the low value priority circuit 48 of the output control device 30A. The output control device 30A of FIGS. 17-19 functions substantially the same as the output control device 30 shown in FIGS. 1 and 2. In more detail, the function obtained by the operation mode switch 40A is added. With the operation mode switch 40A, the effects produced by the embodiment of FIG. 1 are obtained. The present invention is applicable to a boiling water type nuclear reactor having a recirculation piping system other than the RIP. Namely, by controlling a recirculation pump disposed in the recirculation piping system with the control signal R.sub.1, by step 61F processing signal S.sub.3 of FIG. 4, output from the recirculation flow control device 61, the same functions as the above embodiments are obtained. Since the second pump is reduced in speed based upon a trip signal that is generated when the first pump is tripped, the decrease of the steam flow at the moment of the feed water pump trip is hastened and the possibility of the nuclear reactor scram is decreased. Since the first operation for decreasing the nuclear reactor power to a first fixed value by speed reduction of the second pump and the second operation for reducing the nuclear reactor power to a second fixed value that is lower than the first fixed value are performed, the decrease degree of the steam flow at the moment of the feed water pump trip is suppressed without unnecessarily increasing. Since the nuclear reactor power is decreased to a level that prevents overspeed of the other first pumps under operation, the overspeed of the first pumps under operation is prevented. Since the set value of the nuclear reactor power is switched to a second fixed value that is lower than a first fixed value used at the moment of the first pump trip, the nuclear reactor power reduction control after the speed reduction of the second pump is facilitated. While a preferred embodiment has been described with variations, further embodiments, variations and modifications are contemplated within the spirit and scope of the following claims.
	claims	1. A method of containing a nuclear reactor pressure vessel for transportation and storage, the method comprising: removing at least one external fitting from a nuclear pressure vessel to an extent that a non-removed portion of said fitting is substantially flush with an external surface of said pressure vessel; disposing a body of said pressure vessel within a canister; substantially filling a gap between an interior of said canister and said pressure vessel with a stabilizer; disposing said removed external fitting within said pressure vessel body; and closing said canister. 2. A method of containing a nuclear reactor pressure vessel for transportation and storage, the method comprising: removing a portion of said pressure vessel which is of low radioactivity; removing at least one external fitting from said nuclear pressure vessel to an extent that a non-removed portion of said fitting is substantially flush with an external surface of said pressure vessel; disposing a body of said pressure vessel within a canister; substantially filling a gap between an interior of said canister and said pressure vessel with a stabilizer; closing said canister; and attaching said portion which is of low radioactivity to an exterior of said canister. 3. A method of containing a nuclear reactor pressure vessel for transportation and storage, the method comprising: removing at least one external fitting from a nuclear reactor pressure vessel; disposing a body of said pressure vessel within a canister; substantially filling a gap between an interior of said canister and said pressure vessel with a stabilizer; disposing said removed external fitting within said pressure vessel body; and closing said canister. 4. The method of claim 3 , comprising coating interior and exterior surfaces of said pressure vessel with sealant. claim 3 5. The method of claim 3 , wherein said filling said gap with stabilizer comprises substantially filling said gap with low density cellular concrete. claim 3 6. The method of claim 3 , comprising sealing said canister with a metalizing spray. claim 3 7. The method of claim 3 , comprising: claim 3 removing a portion of said pressure vessel which is of low radioactivity; and attaching said portion to an exterior of said canister. 8. The method of claim 3 , comprising filling at least a portion of said pressure vessel body with a stabilizer. claim 3 9. The method of claim 3 , wherein substantially filling said gap with stabilizer comprises completely filling said gap with stabilizer. claim 3 10. A method of containing a nuclear reactor pressure vessel for transportation and storage, the method comprising: removing from a nuclear reactor pressure vessel a portion of said pressure vessel which is of low radioactivity; disposing a body of said pressure vessel within a canister; and attaching said removed portion to an exterior of said canister. 11. The method of claim 10 , comprising coating interior and exterior surfaces of said pressure vessel body with sealant. claim 10 12. The method of claim 10 , comprising substantially filling a gap between an interior of said canister and said pressure vessel body with a stabilizer. claim 10 13. The method of claim 12 , wherein substantially filling said gap with stabilizer comprises completely filling said gap with stabilizer. claim 12 14. The method of claim 12 , wherein filling said gap with stabilizer comprises substantially filling said gap with low density cellular concrete. claim 12 15. The method of claim 10 , comprising filling at least a portion of said pressure vessel body with a stabilizer. claim 10 16. The method of claim 10 , comprising sealing said canister with a metalizing spray. claim 10 17. A method of containing a nuclear reactor pressure vessel for transportation and storage, the method comprising: removing a head, at least a substantial portion of all protruding external fittings, and at least a substantial portion of external insulation from a nuclear reactor pressure vessel; removing a portion of reactor internals from an interior of said pressure vessel; relocating at least some of said removed external fittings, insulation, and internals within said interior of said pressure vessel; sealing penetrations in said pressure vessel; disposing a body of said pressure vessel within a container; closing said container; sealing said container; and attaching said head to an exterior of said container. 18. The method of claim 17 , comprising coating an interior surface of said pressure vessel with sealant. claim 17 19. The method of claim 17 , comprising substantially filling a gap between an interior of said container and said pressure vessel with a stabilizer. claim 17 20. The method of claim 19 , wherein said filling said gap with stabilizer comprises substantially filling said gap with low density cellular concrete. claim 19 21. The method of claim 19 , wherein substantially filling said gap with stabilizer comprises completely filling said gap with stabilizser. claim 19 22. The method of claim 17 , wherein removing at least a substantial portion of said protruding external fittings comprises removing said external fittings to the extent that any unremoved portions of said fittings protrude no further from said pressure vessel body than an outer perimeter of a head-to-body joint flange on said pressure vessel body. claim 17 23. The method of claim 17 , comprising filling at least a portion of said pressure vessel body with a stabilizer. claim 17 24. The method of claim 17 , comprising removing at least a portion of an internals set of said pressure vessel and replacing said removed internals portion with a radiation shield before at relocating at least a portion of said removed external fittings, insulation, and internals set within said interior of said pressure vessel. claim 17 25. The method of claim 17 , comprising sealing said container with a metalizing spray. claim 17 26. The method of claim 17 , comprising removing said portion of reactor internals while said reactor pressure vessel is partially filled with liquid. claim 17
	description	The present disclosure relates to nuclear reactors and, more specifically, control rod guide tubes for supporting control rods extracted from the reactor core and for channeling coolant flow to fuel supports and fuel assemblies in a reactor core. The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. A nuclear reactor pressure vessel (RPV) has a generally cylindrical shape and is closed at both ends, e.g., by a bottom head and a removable top head. A top guide is spaced above a core plate within the RPV. A core shroud, or shroud, surrounds the core plate and is supported by a shroud support structure. Particularly, the shroud has a generally cylindrical shape and surrounds both the core plate and the top guide. The top guide includes several openings, and fuel assemblies are inserted through the openings and are supported by the core plate. The core plate includes a flat plate supported by a plurality of beams. A nuclear reactor core includes a plurality of individual fuel assemblies that have different characteristics that affect the strategy for operation of the core. For example, a nuclear reactor core typically has several hundred individual fuel assemblies that have different characteristics; each fuel assembly includes a plurality of fuel rods. The fuel assemblies are arranged within the reactor core so that the interaction between the fuel assemblies satisfies regulatory and reactor design guidelines and constraints. In addition the core arrangement determines the cycle energy, which is the amount of energy that the reactor core generates before the core needs to be refreshed with new fuel elements, the core loading arrangement preferably optimizes the core cycle energy. A core cycle is determined from one periodic reactor core refueling to a second reactor core refueling. During the course of the cycle of operation, the excess reactivity, which defines the energy capability of the core, is controlled in two ways. Specifically, a burnable poison, e.g., gadolinia, is incorporated in the fresh fuel. The quantity of initial burnable poison is determined by design constraints typically set by the utility and by the National Regulatory Commission (NRC). The burnable poison controls most, but not all, of the excess reactivity. A second way is through the manipulation of control rods within the core. Control rods control the excess reactivity. Specifically, the reactor core contains control rods which assure safe shutdown and provide the primary mechanism for controlling the maximum power peaking factor. The total number of control rods available varies with core size and geometry, and is typically between 50 and 269. The position of the control rods, i.e., fully inserted, fully withdrawn, or somewhere between, is based on the need to control the excess reactivity and to meet other operational constraints, such as the maximum core power peaking factor. Coolant is introduced in the core to cool the core and to be transitioned into steam as a working fluid for energy generation. Normal coolant flow enters the fuel assemblies as a single phased flow with slightly sub-cooled coolant from the fuel support. The flow goes vertically upward around the control rod guide tubes, and then turns horizontally as the flow enters a side inlet to a fuel support supporting a fuel assembly. The flow then turns ninety degree within the fuel support and upward until it passes through an orifice of the fuel support to provide a pressure drop to assist coolant distribution to the fuel assemblies. The flow then turns vertical and enters a lumen on the lower tie plate of the fuel assembly and is distributed around the individual fuel rods of the fuel assembly. Known reactors have included fuel support orifice regions within the core, one around the peripheral and one near the center. The peripheral region includes all fuel locations around the periphery of the core, and the center region includes the remainder of the locations. The fuel support orifices are designed to limit the fluid flow to the fuel assemblies in the peripheral region to about half of the fluid flow per fuel element of the center region. Limiting the peripheral flow by this magnitude has permitted the very low power peripheral fuel elements to saturate the coolant flow, but with maintaining the exit quality and average voids that are still much lower than for the other higher power region. This uneven exit quality and average void can produce inefficient steam separation and nuclear moderation. It is also known that the coolant flow can be adjusted through varying the design of the fuel assembly. For example, it is known that each fuel assembly can include a main coolant flow channel and inlet that has a substantial constant flow. However, the fuel assemblies can also include one or more secondary coolant flow channels that can vary to adjust the coolant flow in the particular fuel assemblies. In some cases, three types of fuel assemblies can provide three different secondary coolant flows. Each such fuel assembly can be positioned in the core to provide for a desired coolant flow. For example, the three different fuel assemblies can be arranged into three or more core regions. The flow of coolant through each fuel assembly in each region can be different from the coolant flow through a fuel assembly in each other region based on the position of the three different fuel assemblies. However, this requires the manufacture of three different fuel assemblies and/or tie plates. In the known reactor arrangements, the fluid flow into the fuel support and then into the lower tie plate of the fuel assemblies is asymmetrical and unstable. The inventors hereof have succeeded at designing control rod guide tubes that can enable an improved symmetrical and/or stable fluid flow into the fuel support and then into the fuel assembly. Additionally, the inventors hereof have designed a reactor core fluid flow assembly and methods for providing coolant into fuel assemblies having a reduced pressure drop associated with the providing of the fluid flow to the fuel support and, therefore, to fuel assemblies. According to one aspect, a control rod guide tube for a nuclear reactor includes a body having an axial length defining a lower end portion and an upper end portion and a cavity within a substantial length of the body including orifices at the upper and lower end portions of the body. A control rod chamber located within the cavity is configured for receiving a control rod. A plurality of ports is coupled to the cavity and is positioned at a substantial length from the upper end portion of the body. Also included are at least two flow channels within the cavity extending a substantial portion of the axial length of the body. Each flow channel is fluidly coupled to one or more of the ports for receiving fluid flow from outside the body and an outlet proximate to the upper end portion of the body for providing the received fluid flow. According to another aspect, a control rod guide tube for a nuclear reactor includes a body having a cylindrical wall defining an upper end portion, a lower end portion, a cavity defined by an interior surface of the wall and extending from the upper end portion to the lower end portion, and a plurality of ports positioned axially along the wall between the upper end portion and the lower end portion for providing fluid flow into the body cavity. Also included is an insert dimensioned for positioning within the body cavity and having an upper end portion and a lower end portion and including a control rod chamber adapted for receiving a control rod and a plurality of channel fixtures that, at least partially, define one or more flow channels within the cavity of the body. The flow channels are configured for receiving a fluid flow through one or more of the body ports, channeling the received fluid flow within the body cavity between the lower end portion and the upper end portion, and providing the fluid flow to the upper end portion of the body. According to yet another aspect, a control rod guide tube for a nuclear reactor includes means for receiving a control rod, and means for channeling a substantially symmetrical fluid flow into a lower orifice of a fuel assembly cavity of a fuel support. According to still another aspect, a method of stabilizing fluid flows to fuel assemblies within a nuclear reactor includes enclosing a control rod chamber within a cavity of a body of a control rod guide tube. The control rod chamber is adapted for receiving a control rod. A plurality of axial flow channels are positioned within the body cavity of the control rod guide tube. The method also includes coupling the body to a fuel support that has a plurality of fuel assembly cavities adapted for providing the fluid flows to the fuel assemblies. The coupling includes fluidly mating each of the axial flow channels to a corresponding fuel assembly cavity. According to another aspect, a method of flow control management in a nuclear reactor includes receiving a fluid flow into a flow channel of a control rod guide tube through one or more ports defined by the control rod guide tube, providing the received fluid flow from the flow channel to a cavity of a fuel support, providing the fluid flow from the fuel support cavity to a lumen on a lower tie plate of a fuel assembly. Further aspects of the present invention will be in part apparent and in part pointed out below. It should be understood that various aspects of the disclosure may be implemented individually or in combination with one another. It should also be understood that the detailed description and drawings, while indicating certain exemplary embodiments, are intended for purposes of illustration only and should not be construed as limiting the scope of the disclosure. It should be understood that throughout the drawings, corresponding reference numerals indicate like or corresponding parts and features. The following description is merely exemplary in nature and is not intended to limit the present disclosure or the disclosure's applications or uses. In some embodiments, a control rod guide tube for a nuclear reactor includes a body having an axial length defining a lower end portion and an upper end portion and a cavity within a substantial length of the body including orifices at the upper and lower end portions of the body. A control rod chamber located within the cavity is configured for receiving a control rod. A plurality of ports is coupled to the cavity and is positioned at a substantial length from the upper end portion of the body. Also included are at least two flow channels within the cavity extending a substantial portion of the axial length of the body. Each flow channel is fluidly coupled to one or more of the ports for receiving fluid flow from outside the body and an outlet proximate to the upper end portion of the body for providing the received fluid flow. This can be better understood with reference to the figures. As seen by way of the exemplary operating environment of FIG. 1, a conventional boiling water reactor (BWR) has a reactor pressure vessel 10 and a core shroud 12 arranged concentrically in the reactor pressure vessel 10 with an annular region, namely, the downcomer annulus 14, therebetween. The core shroud 12 is a stainless steel cylinder surrounding the nuclear fuel core 13. In particular, the core shroud 12 comprises a shroud head flange 12a for supporting the shroud head (not shown); a circular cylindrical upper shroud wall 12b having a top end welded to shroud head flange 12a; an annular top guide support ring 12c welded to the bottom end of upper shroud wall 12b; a circular cylindrical middle shroud wall 12d that is a welded assembly welded to the top guide support ring 12c; and an annular core plate support ring 12e welded to the bottom of the middle shroud wall 12d and to the top of a lower shroud wall 12f. As seen in FIG. 1, the shroud 12 is vertically supported by a plurality of shroud support legs 16, each of the latter being welded to the bottom head 17 of the reactor pressure vessel 10. The core shroud 12 is laterally supported by an annular shroud support plate 18, which is welded at its inner diameter to the core shroud 12 and at its outer diameter to the reactor pressure vessel 10. The shroud support plate 18 has a plurality of circular apertures 20 in flow communication with diffusers of a plurality of jet pump assemblies (not shown), The fuel core 13 of a BWR consists of a multiplicity of upright and parallel fuel assemblies 22 (also referred to as fuel bundles) arranged in arrays, each fuel assembly 22 includes an array of fuel rods inside a fuel channel made of zirconium-based alloy. Each array of fuel bundle assemblies is supported at the top by a top guide 24 and at the bottom by a core plate 26 and its underlying support structure 27. The core plate 26 subdivides the reactor into the fuel core 13 and a lower plenum 15. The core top guide 24 provides lateral support for the top of the fuel assemblies 22 and the core plate 26 provides lateral support for the bottom of the fuel assemblies 22. This lateral support maintains the correct fuel channel spacing in each array to permit vertical travel of a control rod 28 including a plurality of control rod blades 29 between the fuel assemblies 22. The power level of the reactor is maintained or adjusted by positioning the control rods 28 up and down within the core 13 while the fuel assemblies 22 are held stationary. Each control rod 28 has a cruciform cross-section consisting of four wings or control rod blades 29 at right angles. Each control rod blade 29 consists of a multiplicity of parallel tubes welded in a row with each tube containing stacked capsules filled with neutron-absorbing material. Each control rod 28 is raised or lowered with the support of a control rod guide tube 30 by an associated control rod drive (33) which can be releasably coupled by a spud at its top to a socket in the bottom of the control rod 28. The control rod drives 33 are used to position control rods 28 in a BWR to control the fission rate and fission density, and to provide adequate excess negative reactivity to shutdown the reactor from any normal operating or accident condition at the most reactive time in core life. Each control rod drive 33 is mounted vertically in a control rod drive housing 32 which is welded to a stub tube 34, which in turn is welded to the bottom head 17 of the reactor pressure vessel 10. The control rod drive 33 is a double-acting, mechanically latched hydraulic cylinder. The control rod drive 33 is capable of inserting or withdrawing a control rod (28) at a slow controlled rate for normal reactor operation and of providing rapid control rod 28 insertion (scram) in the event of an emergency requiring rapid shutdown of the reactor. The control rod drive housing 32 has an upper flange that bolts to a lower flange of the control rod guide tube 30. Each control rod guide tube 30 sits on top of and is vertically supported by its associated control rod drive housing 32. The uppermost portion of the control rod guide tube 30 penetrates a corresponding circular aperture in the core plate 26. There can be more than 140 control rod guide tubes 30 penetrating an equal number of circular apertures 35 in the core plate 26, each aperture 35 has a diameter slightly greater than the outer diameter of the control rod guide tube 30. The control rod drive housings 32 and control rod guide tubes 30 have two functions: (1) to house the control rod drive 33 mechanisms and the control rods 28, respectively, and (2) to support the weight of the fuel in the fuel assemblies 22. The fuel weight is reacted at an orifice of a fuel support 36 that is positioned on the top of the control rod guide tube 30. The control rod guide tubes 30 and housings 32 act as columns carrying the weight of the fuel. During operation of the reactor, water in the lower plenum 15 enters ports 38 of the control rod guide tube 30. The water is channeled within the control rod guide tube 30 to the orifice of the fuel support 36 and into a lumen of a lower tie plate of the fuel assemblies 22. The water continues to rise in the fuel assemblies 22 and in the fuel core 13, with a substantial amount turning to steam, which is used in the production of electrical energy. As illustrated by the exemplary embodiments if FIGS. 2-5, the control rod guide tube 30 has a body 40 with an axial length defining an upper end portion 42 and a lower end portion 44 and a cavity 46 within a substantial length of the body 40. An orifice 48 at the upper end portion 42 and orifice 50 at the lower end portion 44 of the body 40. The upper end portion 42 can be adapted for coupling to a bottom of a fuel support 36 for fluidly coupling a flow channel to a bottom orifice of the fuel support 36 and to a fuel assembly 22 engaged with or positioned on top of the fuel support 36. The lower end portion 44 can be adapted for coupling to a control rod drive housing 32 for supporting the control rod guide tube 30 within the lower plenum 15 and in alignment with the control rod drive 33. This can include a coupling fixture (shown in FIG. 6) that can be attached to the lower end portion of the body 40 for releasably coupling the control rod guide tube 30. A control rod chamber 52 (as shown in FIGS. 3, 4, and 5, by way of examples) is located within the cavity 46. The control rod chamber 52 is adapted, configured and/or dimensioned for receiving the control rod 28. As the control rod 28 generally has a cruciform shape, the control rod chamber 52 can also have a corresponding cruciform shape. The control rod chamber 52 can be defined, at least in part, within the cavity 46 by one or more structures, referred herein generally as an insert 54. The insert can be have monolithic body or can be a grouping of one or more insert components that together form the insert 54 and that define, at least in part, the control rod chamber 52 within the cavity 46. One example of a multiple component insert 54A is illustrated, by way of example, in FIG. 3. In this embodiment, the insert 54A includes four insert flow fixtures 56 each having a curved-shaped that when assembled with their convex portions back-to-back define a cruciform-shaped control rod chamber 52. Additionally, each insert flow fixture 56 defines a portion of a flow channel 58 by its convex shape. In some embodiments, each pair of insert flow fixtures 56 (also referred herein as channel fixtures) are coupled at an outer periphery forming a hollow arm 61 defining a portion of the control rod chamber 52 configured for receiving a control rod blade 29 of the control rod 30. An example embodiment of a monolithic body for an insert 54B is illustrated in FIG. 4. In this embodiment, the cruciform-shaped control rod chamber 52 is fully enclosed at the ends of each blade 29. Flow channels 58 are also provided along an external convex surface of this embodiment of insert 54B. Optionally, one or more control rod inlets 60 can provide for a flow of coolant into the control rod chamber 52 and therefore about the control rod 28 and its control rod blades 29 contained with the control rod chamber 52. The ports 38 are coupled to the cavity 46 and are positioned at a substantial length from the upper end portion 42 of the body 40. Generally, a substantial length as described herein includes a length of the total substantial body length such that the flow from the ports 38 to the upper end portion 42 within the cavity 46 becomes stable or is otherwise generally symmetrical, or lacking significant amounts of asymmetries or turbulence. The substantial length can be proximate to the lower end portion 44 as illustrated in FIG. 2, or can be at any distance greater than near or proximate to the upper end portion 42. As such, a substantial length can include any length greater than a minor length and is not intended to be indicated of requiring a majority or more of the total length of the body 40. Additionally, while FIGS. 2 and 5 illustrate five ports 38 positioned along four sides of the body 40, more or less ports are possible and still within the scope of this disclosure. Additionally, the cross-sectional area of the ports 38 can vary, as well as the number of ports axially aligned along the body 40. As noted, the control rod guide tube 30 includes at least two flow channels 58 within the cavity 46. In some embodiments, the flow channels 58 are defined in part by the insert 54 and in part by an interior surface of the body 40. Generally, in some embodiments, the flow channels 58 extend a substantial portion of the axial length of the body 40. Each flow channel 58 is fluidly coupled to one or more ports 38 for receiving fluid flow from the lower plenum 15 and an outlet 62 proximate to and/or defined by the upper end portion 42 of the body 40. The outlet 62 provides the fluid flow to an orifice of a coupled fuel support 36. Generally, in some embodiments, the cross-sectional area of each flow channel 58 is about equal to or less than a cross-sectional area of the coupled fuel assembly orifice (not shown). In one embodiment, a plurality of ports 38 are coupled to a flow channel 58 and the combined cross-sectional area of the coupled ports 38 is greater than a cross-sectional area of the coupled flow channel 58. In this manner, flow from the lower plenum 15 into the flow channel 58 is not restricted at the ports 38 and turbulence can be reduced. It should be noted that in some embodiments, the insert 54 can be fixed in position relative to the body 40. For example, the insert flow fixture 56 of insert 54A can be welded or otherwise affixed within the cavity 46 such as to an inner surface defining the cavity 46. This can include fixedly attaching the insert 54 to an inner surface such that each flow channel 58 is substantially enclosed by a portion of the inner surface and the insert 54, to reduce any turbulence that can be caused or related to a non-enclosed or open or unattached portion of the insert 54 and the inner surface. Additionally, the monolithic insert 54B can also be affixed within the cavity 46 of the body 40. In other embodiments, the insert 54 can be rotatable within the cavity 46. Having a rotatable insert 54 can provide for, among others, for rotating a control rod 38 within the control rod guide tube 30 during a refueling operation without having to remove the control rod 38 and/or the control rod guide tube 30. Referring now to FIG. 6, one embodiment of a fuel support 36 is illustrated from a bottom perspective. As shown, generally the fuel support 36 also includes a cruciform chamber for allowing passage of the control rod 28 into the fuel core 13. The fuel support 36 includes a plurality of orifices 66 for receiving the flow from the flow channels 38 of the control rod guide tube 30. The lower end portion 68 of the fuel support 36 is adapted for coupling to the upper end portion 42 of the body 40. This can include by welding or any other suitable method of attachment. As shown in FIG. 7, the fuel support 36 and the control rod guide tube 30 are coupled to align the flow channel 58 with the orifices 66. As shown, the insert flow fixtures 56 are aligned to define a flow channel 58 that provides a fluid flow into each orifice 66. As noted above, the cross-sectional area of the flow channels 58 can be about equal to or less than the cross-sectional area of the coupled orifice 66. In such embodiments, little to no pressure increase occurs at the point of interface between the flow channel 58 and the orifice 66. In some embodiments, the comparative cross-sectional areas can provide for a pressure drop at this interface. FIG. 8 illustrates one embodiment of a control rod guide tube 30 assembled with a fuel support 36 affixed to the upper end portion 42 and a coupling fixture 70 affixed to the lower end portion 44. According to other embodiments, a method of stabilizing fluid flows to fuel assemblies within a nuclear reactor includes enclosing a control rod chamber within a cavity of a body of a control rod guide tube wherein the control rod chamber is adapted for receiving a control rod. The method also includes defining a plurality of axial flow channels within the body cavity of the control rod guide tube. The method further includes coupling the body to a fuel support having a plurality of fuel assembly cavities adapted for providing the fluid flows to the fuel assemblies. The coupling includes fluidly mating each of the axial flow channels to a corresponding fuel assembly cavity. This can include providing one or more ports on the body for each axial flow channel and/or defining axial flow channels to have a cross-sectional area less than or equal to a fluidly-mated fuel assembly cavity. In another operational embodiment, a method of flow control management in a nuclear reactor includes receiving a fluid flow into a flow channel of a control rod guide tube through one or more ports defined by the control rod guide tube. The method also includes providing the received fluid flow from the flow channel to a cavity of a fuel support, providing the fluid flow from the fuel support cavity to a lumen on a lower tie plate of a fuel assembly. Generally, this can include receiving the fluid flow from one or more of the ports for reducing flow asymmetries within the flow channel and flow asymmetries as provided from the flow channels to an orifice of the fuel assembly coupled thereto. In some embodiments, the method can also include providing a fluid flow from a flow channel to the fuel support orifice or cavity such that the provided fluid flow does not experience or result in an increase (and in some embodiments within a substantial increase) in fluid pressure as provided by control rod guide tube. This can be an improvement from fluid flows provided by the traditional inlets on the sides of the fuel support. In this exemplary manner, a fuel support or other fluid handling portions of the reactor can be modified to take advantage of the reduction in the fluid pressure provided by the control rod guide tube as described by the various embodiments of this disclosure. This can include, in some embodiments, reducing a pressure drop of the fluid flow across the control rod guide tube as provided herein and increasing a pressure drop of the fluid flow across the fuel support and the lower tie plate as a result of the reduction in the inlet fluid flow as provided by the control rod guide tube as compared to the side inlet of the fuel support. Further operational benefits for a reactor can be provided by configuring or modifying the fuel support or an orifice or cavity thereof to further modify the fluid flow to the fuel assembly. When describing elements or features and/or embodiments thereof, the articles “a”, “an”, “the”, and “said” are intended to mean that there are one or more of the elements or features. The terms “comprising”, “including”, and “having” are intended to be inclusive and mean that there may be additional elements or features beyond those specifically described. Those skilled in the art will recognize that various changes can be made to the exemplary embodiments and implementations described above without departing from the scope of the disclosure. Accordingly, all matter contained in the above description or shown in the accompanying drawings should be interpreted as illustrative and not in a limiting sense. It is further to be understood that the processes or steps described herein are not to be construed as necessarily requiring their performance in the particular order discussed or illustrated. It is also to be understood that additional or alternative processes or steps may be employed.
047708409	summary	FIELD OF THE INVENTION The invention relates to light water nuclear reactors and, more particularly, to a method for operating such a reactor for operation with different neutron energy spectra. BACKGROUND OF THE INVENTION The light water nuclear reactors typically comprise a pressure containment vessel containing a core constituted of vertical fuel assemblies located in side-by-side relation, each having fuel elements distributed at the nodes of a regular network, each fuel element containing fissile material and possibly fertile material. The fuel elements are substituted at some of the nodes of the network with guide tubes slidably receiving movable rods of control clusters. The fuel assemblies are at least partially substituted with other fuel assemblies after each burn-up cycle of the reactor. In each fuel assembly, the fuel elements are separated by a gap which flows cooling and moderating water. A moderation ratio VM/VU is defined as a ratio of a moderator module VM to the fissile material volume VU in the core. Conventional light water reactors now in operation have a moderation ratio such that the energy spectrum of the neutrons is thermal. Two directions have been explored for improving the light water reactors and for a better use of the fuel material. Both directions imply that the moderation ratio is at least temporarily decreased. The first approach consists of varying the neutron energy spectrum as the fuel burns up during a cycle. The natural uranium consumption and the initial degree of enrichment may be decreased for a predetermined burn-up rate. A spectral shift reactor which appears of particular interest is described in French Patent Application No. 82 18011 (FR-A-2,535,509). That reactor is comparable in structure to the conventional PWRs but includes a mechanical device for shifting the neutron spectrum, comprising clusters of rods containing fertile material, such as natural or depleted uranium oxide. The clusters are movable for insertion into the core or removal from the core during operation of the reactor. When fertile rods are introduced in guide tubes of the assemblies, they force moderating water out of the guide tubes and decrease the moderator volume VM in the core. As a consequence, during an operating cycle of the core, the neutron energy spectrum may be shifted. During a first part of the cycle, the clusters of fertile rods are maintained in the core. They shift the energy spectrum toward higher energies and increase the conversion rate of fertile material (uranium 238) into fissile material (plutonium). During a second part of the cycle, the clusters dedicated to spectral shift are progressively removed. The fissile material formed during the first part of the cycle is then partially burnt. The conversion rate is increased by about 10% with respect to a conventional thermal neutron PWR due to conversion rate increase. The other approach consists of under-moderating the reactor at all times. Then it is possible to use a mixed fuel comprising natural uranium and plutonium with a "breeding" rate of plutonium of about 1. However, the necessary decrease of the moderation rate VM/VU typically requires that the fuel elements be located in the fuel assemblies in a triangular rather than square array. Most under-moderated reactors comprise two types of fuel assemblies. Some, called fissile assemblies, contain principally fissile material; the others, called fertile assemblies, contain a material capable of being converted to fissile material under the effect of neutron bombardment. The fertile assemblies are generally disposed at the periphery of the core where they collect neutrons produced by the fissile assemblies. Proposals have been made for combining the advantages of spectral shift (particularly the gain on uranium consumption) and of under-moderation (plutonium breeding rate possibly greater than 1, possible use of depleted uranium, increased cycle duration). French Patent Application No. 83 15591 discloses a reactor having a heterogeneous core in which fuel assemblies of a type suitable for use in under-moderated reactors and fuel asssemblies for spectral shift reactors are associated for best utilization of plutonium previously produced in the fuel assemblies of conventional thermal neutron PWRs. That plutonium is recovered during reprocessing of spent fuel assemblies. However, that approach requires that a utility which has a plurality of nuclear power plants should dedicate at least one power plant to use of recovered plutonium. A first consideration suggests that the difficulty cannot be overcome since that type of fuel assembly which is required for under-moderated reactors does not lend to use in association with the internals and the control system of a reactor for operation with thermal neutrons, and conversely. SUMMARY OF THE INVENTION It is an object of the invention to provide an improved method of operation of a spectral shift reactor. It is a more specific object to overcome the drawback consisting of the need for operation of a plurality of different types of reactors each of specific design. It is still an other object to provide a flexible process of operation of a PWR having a core consisting of fuel elements all having the same geometry. For that purpose, there is provided a method of operating a light water nuclear reactor wherein the internals of the reactor are so designed that it may receive either fuel assemblies of a first type for under-moderated operation with a high breeding rate or fuel assemblies of a second type having guide tubes authorizing spectral shift from the thermal range to the intermediary range. Part at least of the assemblies of one type are substituted with the assemblies of the other type after an operating cycle of the core. If the assemblies for under-moderated operation are so designed that they also authorize spectral shift and if the guide tubes for fertile rods are located at the same places in all fuel assemblies, it will be possible, without any modification of the higher internals of the reactor and of the cluster control mechanisms, to operate the reactor within a very broad moderation range, from thermal neutron reactors up to plutonium producing under-moderated reactors, during operating cycles. For achieving the required compatibility of the different fuel assemblies, all fuel assemblies will include fuel elements distributed according to the same, typically triangular, array. The reactor will typically be operated during the first cycle with regular spectral shift, the fuel assemblies including U235 enriched uranium as fissile material. During the second, under-moderated, operating cycle, the fissile material will be natural or depleted uranium with plutonium, as oxides UO.sub.2 -PUO.sub.2. As an example only, the moderation ratio ranges may be as follows: ______________________________________ SSR UMR ______________________________________ VM/VU Lifted fertile clusters 2 1,4 Inserted fertile clusters 1,5 1,1 ______________________________________ The abbreviations SS and UM respectively correspond to operation with spectral shift and under-moderation. The present day PWRs generally operate with a moderation rate of about 1.9. For carrying out the invention, it will typically be necessary to provide the pressure vessel with a control rod operating mechanism for each fuel assembly location. About two thirds of the mechanisms will be for spectral shift (fertile clusters) while one third will be for the usual fine control regulation and safety purposes (absorbing clusters). The actuating mechanisms may be conventional. The absorbing clusters will typically be associated with ratchet type electromechanical mechanisms, while the fertile clusters will be associated with hydraulic mechanisms. According to an other aspect of the invention, there is provided a reactor comprising, in a pressure containment vessel, a core consisting of adjacent vertical fuel assemblies each comprising fuel elements and guide tubes distributed at the nodes of a triangular array. The vessel is provided with mechanisms for vertical movement of control clusters. Upper internals in the vessel are used for guiding the clusters. Some of the clusters consist of fertile rods for shifting the neutron spectrum during a cycle. The other control clusters include absorbing material. The reactor has an actuating mechanism above each fuel assembly location and the fuel element array in each assembly is such that the core is under-moderated when all nodes are occupied by a rod or fuel element. Some at least of the assemblies comprise water filled tubes at some of the nodes of the network. The number and the distribution of such tubes are such that they authorize thermal operation of the reactor. The invention will be better understood from the following description of a particular embodiment, given by way of example only. The description refers to the accompanying drawings.
	abstract	An electrical power system for a nuclear power facility includes an active alternating current (AC) power bus configured to be electrically coupled to a plurality of engineered safety feature (ESF) loads of a plurality of nuclear power systems, each of the ESF loads configured to fail to a safe position upon loss of primary AC power; a critical battery system electrically coupled to the active AC bus, the critical battery system comprising a plurality of valve regulated lead acid (VRLA) batteries; and a primary AC power source electrically coupled to the active AC bus.
048866350	summary	The invention relates to a gripping tool for a device for the remote-controlled removal of samples or specimens from a container, especially a pressure vessel of a reactor, including a guide bar disposed on a mast, and at least two catches in the form of a two-armed-lever disposed on the mast in pivots for surrounding a head of the sample housing like a clamp when activated. A conduit is provided on the outside wall of the core vessel of a reactor pressure vessel in which a radiation sample column disposed in a capsule is inserted after the first fuel assembly cycle. Following the second fuel assembly cycle, the capsule containing the sample is-removed from the reactor pressure vessel and is suspended under water at the edge of the fuel assembly reservoir. Removal of the sample takes place from the fuel assembly reservoir. Then a fresh radiation sample is inserted into the reactor pressure vessel. It is known to use a gripping tool for the removal of samples having a guide bar disposed on a mast, in which catches are each fixed on a pivot point in such way that they grasp a head of the housing like a clamp when activated. The gripping tool is suspended from a crane and lowered towards the reactor pressure vessel until it is seated on the head of the sample retainer, where the catches engage the sample head and grasp it like a clamp. It is possible for buckling or damage to the radiation sample to occur during the course of setting down the gripping tool, which must be done by remote control from a considerable height. It is accordingly an object of the invention to provide a gripping tool for a device for the remote-controlled removal of samples from a container, in particular from a pressure vessel of a reactor, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which avoids a deformation of the housing and thus damage to the sample. With the foregoing and other objects in view there is provided, in accordance with the invention, a gripping tool for a device for the remote-controlled removal of samples in housings with heads from a container, in particular a pressure vessel of a reactor, comprising a mast having a first coupling part or connecting element, a second coupling part or connecting element opposite and associated with the first coupling part, a guide bar elastically bearing or being disposed on the second coupling part in a telescoping manner, pivots disposed on the guide bar, at least two catches of a two-armed lever being disposed on the pivots and having guide grooves formed therein, a bushing or sleeve surrounding the guide bar having guide pins each engaging a respective one of the guide grooves, and at least one remotely controlled linear drive moving the bushing in the direction of the longitudinal axis of the bushing for surrounding the head of the sample housing with the catches like tongs or a clamp. In this way the gripping tool can be placed on the head of the housing for the sample with the catches open. The forces acting on the head of the housing for the sample during placement are kept small due to the elastic mounting of the guide bar on the mast and damage to the radiation column is prevented. In accordance with another feature of the invention, the at least one remotely controlled linear drive is a pressure medium drive including at least one cylinder disposed on the guide bar having a piston with a piston rod connected to the bushing. In accordance with a further feature of the invention, there are provided control lines connected to the cylinder, and a return spring disposed in the cylinder for maintaining the catches in a closed position in case of pressure reduction in the control lines. In accordance with a concomitant feature of the invention, the first coupling part is an existing element provided for pulling fuel assemblies, and the second coupling part is adapted to and connected with the first coupling part. Due to this feature, the mast for pulling fuel assemblies which is provided in a nuclear power plant in any event, can be used for the gripping tool so that a separate mast for the gripping tool is not necessary. This results in a considerable simplification as compared to the prior art structure, since only the head need to be exchanged. Other features which are considered as characteristic for the invention are set forth in the appended claims. Although the invention is illustrated and described herein as embodied in a gripping tool for a device for the remote-controlled removal of samples from a container, in particular from a pressure vessel of a reactor, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims.
	abstract	Described herein are embodiments of a method to control energy dose output from a laser-produced plasma extreme ultraviolet light system by adjusting timing of fired laser beam pulses. During stroboscopic firing, pulses are timed to lase droplets until a dose target of EUV has been achieved. Once accumulated EUV reaches the dose target, pulses are timed so as to not lase droplets during the remainder of the packet, and thereby prevent additional EUV light generation during those portions of the packet. In a continuous burst mode, pulses are timed to irradiate droplets until accumulated burst error meets or exceeds a threshold burst error. If accumulated burst error meets or exceeds the threshold burst error, a next pulse is timed to not irradiate a next droplet. Thus, the embodiments described herein manipulate pulse timing to obtain a constant desired dose target that can more precisely match downstream dosing requirements.
	abstract	A conductive transparent probe used in a probe control apparatus for adjusting a distance between the apex of the probe and a sample by vibrating the probe with an vibrator in a direction perpendicular to the axis of the probe is provided. The conductive transparent probe includes: an optical fiber having a taper part at one end; a conductive transparent film formed on the surface of the taper part; a first metal film formed on the surface of the optical fiber other than the taper part; wherein the conductive transparent film and the first metal film are electrically connected, and length and thickness of the first metal film are determined such that the conductive transparent probe vibrates while contacting with the vibrator.
	abstract	A safety vial system has a vial adapter subsystem irreversibly mountable to the top of a vial containing a hazardous medicament and a vial base subsystem sealingly engaging a lower portion of the vial adapter subsystem and telescopically movable therein from a first position providing a path for gas sterilization around the vial to a second position wherein the path is closed to form a sterilized expandable, neutral pressure bellows chamber around and below the vial. The device has a removable top cap, a pierceable barrier film, a normally closed needleless valve in fluid communication with a dual lumen spike initially disposed above the film and a frangible product integrity ring holding the activation housing in place for sealed telescopic movement on a main body that surrounds the vial. The user pulls the product integrity ring and removes it, and then pushes the activation housing axially downward until it clicks to lock the device in the activated position wherein both lumens of the spike are in communication with the inside of the vial. The user removes the top cap on the activation housing assembly, and then uses a needleless syringe with an adapter thereon to add diluent and mixes if needed and withdraw drug from the vial via the valve.
	summary
054085098	claims	1. An elongation measuring system for tensioned studs comprising: a housing in a fixed position on and disposed about a stud and a nut; a piston means and cylinder means disposed in the upper portion of the housing; a puller bar nut connected to the top of the puller bar, the puller bar nut adapted to be urged upward by the piston means to tension the stud when said stud is attached to the puller bar through the puller bar socket; hydraulic control means mounted on the tensioner, said control means coacting with said hydraulic pumping means, said piston means and said nut drive motor means and said puller bar drive motor means to control the puller by said tensioner; piston sensor means comprising puller bar socket sensor means and nut sensor means disposed in said housing to sense the position of said pistons, said puller socket, and said nut and to coact with said hydraulic pumping system; elongation measuring system means comprising a centering disk disposed at the bottom of said puller bar and a datum disk disposed above said centering disk; pin means extended from said datum disk through said centering means adapted to contact the end of a stud to be tensioned; resilient means connected to said pin means to urge said pin means into the extended position; indicating rod means extending from and through said datum disk to a linear variable differential transmitter; a datum sleeve connected to said datum disk; said datum sleeve and said indicator rod coacting with said linear variable differential transmitter to indicate the position of said tensioner. lower housing means adapted to be positioned on and disposed about a stud and a nut; upper housing means having a plurality of units; cylinder means positioned between each of the plurality of units for separating the units to elongate the upper housing means; puller bar means extending from the upper housing means for engaging a stud; puller bar nut means for supporting the puller bar means at an upper unit of one of the plurality of units of the upper housing; puller bar socket means extending from the puller bar means for engaging a stud; puller bar socket drive means on the upper housing means for driving the puller bar socket means to threadibly engage a stud; hydraulic pressure means on the upper housing for pressurizing the cylinders in the upper housing to exert a force on the puller bar to elongate a stud; nut drive means on the lower housing for driving a nut on a stud to tighten or loosen the nut; nut sensor means on the lower housing for sensing the position of the nut; puller bar sensor means on the lower housing for sensing the position of the puller bar; and stud elongation mounted within the puller bar means measuring means for measuring the elongation of the stud. a bore extending within a stud; a relaxed rod fixed in the bore at one end; a locating annulus positioned within a stud for receiving and positioning the relaxed rod; an indicator rod extending from within the puller bar means contacting the relaxed rod and moveable with the relaxed rod; and a variable differential transmitter fixedly positioned within the housing for receiving the indicator rod for measuring movement of the indicator rod, and the elongation of a stud. a housing extending about a stud and nut; positioning means for positioning the housing about a stud and a nut; puller bar means extending from the housing for engaging a stud; drive means on the housing for driving the puller bar means to attach the puller bar to a stud; hydraulic means on the housing for exerting a force on the puller bar to elongate a stud; and stud elongation measuring means interconnected with the puller bar means for measuring the elongation of the stud. a bore extending within a stud; a relaxed rod fixed in the bore at one end; a locating annulus positioned within a stud for receiving and positioning the relaxed rod; an indicator rod extending from within the puller bar means contacting the relaxed rod and moveable with the relaxed rod; and a variable differential transmitter fixedly positioned within the housing for receiving the indicator rod for measuring movement of the indicator rod, and the elongation of a stud. a stud; a bore extending within the stud; a relaxed rod fixed in the bore at one end; locating means for the relaxed rod to coact with an indicator rod; a variable differential transmitter fixedly positioned in relation to the top of the stud; a datum disk positioned at the top of said stud in the end of said bore; a datum sleeve fixedly connecting said datum disk to said variable differential transmitter; an indicator rod extending from the variable differential transmitter through said datum sleeve and said datum disk and coacting with the relaxed rod to measure the elongation of the stud. 2. The apparatus of claim 1 wherein the stud nut drive gearing includes a pinion gear driven by the stud nut drive motor, the pinion gear coacting with the nut socket to rotate the nut. 3. An automated stud tensioner comprising: 4. The apparatus of claim 3 wherein the nut drive means includes a pinion gear driven by a nut drive motor. 5. The apparatus of claim 4 wherein the stud elongation measuring means comprises: 6. An automated stud tensioner comprising: 7. The apparatus of claim 6 wherein the upper housing includes a plurality units separated by cylinders to permit elongation of the upper housing. 8. The apparatus of claim 7 wherein the nut drive means includes a pinion gear driven by a nut drive motor. 9. The apparatus of claim 8 wherein the stud elongation measuring means comprises: 10. A stud elongation measuring apparatus comprising:
051620979	abstract	In accordance with the present invention, a nuclear reactor with a recirculating heat transfer fluid has a bi-level core which provides enhanced flexibility in fuel arrangement. The bi-level core includes two sets of fuel units, one set arranged on a first level, the other set arranged on a second level. Preferably, fuel units of the second level are arranged in vertical alignment with fuel units of the first level. This permits a fuel unit of the first level to be accessed by removing only the adjacent fuel unit of the second level. During refueling operations, fuel units can be shifted from one level to the other, providing additional flexibility in arranging units at various stages of burnup. Preferably, fuel units of the first level are inverted relative to the fuel units of the second level. The inversion provides for placing plenum sections of fuel rods in different levels away from each other so that the plenums do not introduce a discontinuity in neutron generation, and allows for more uniform axial fuel burnup. The bi-level core allows fuel to be initially positioned in the second level for conversion of fertile fuel to fissile fuel, and then repositioned to the first level for more complete axial burnup. In a preferred embodiment the first level boils water to generate saturated steam, and the second level is cooled by the saturated steam and generates superheated steam.
	description	The present invention relates to transport of a fuel assembly used in a nuclear reactor. An assembly of nuclear fuel used in a nuclear power plant or the like is referred to as “fuel assembly”. A fuel assembly loaded in a nuclear reactor, burned for a predetermined period, and taken out from the nuclear reactor contains fission products (FP). Therefore, the fuel assembly is normally cooled in a cooling pit of a nuclear power plant or the like for a predetermined period. Thereafter, the fuel assembly is housed in a fuel assembly housing container having a radiation shielding function, transported to processing facilities or interim storage facilities by a vehicle or a ship, and stored at the facilities until reprocessing is performed. Patent Literature 1 discloses a buffer member positioned in a radial direction gap between a radioactive material assembly and a basket, and a spacer positioned in an axial direction gap between the radioactive material assembly and a lid. Patent Literature 1: Japanese Patent No. 3600551 (paragraph 0006, FIG. 8, and FIG. 11) A fuel assembly includes a nozzle having a plurality of legs (normally, four) at opposite ends of a plurality of fuel rods. However, when a transporting cask that houses the fuel assembly drops vertically, that is, the fuel assembly drops with its longitudinal direction being a vertical direction, the nozzle may be bent and deformed. In this case, there is a risk that the fuel assembly is deformed due to the deformation of the nozzle. Therefore, an object of the present invention is to suppress deformation of a fuel assembly at the time of dropping. According to an aspect of the present invention, a shock-absorbing device for a fuel assembly that suppresses a shock given to a fuel assembly constituted by combining a plurality of fuel rods and arranging a first nozzle and a second nozzle at opposite ends of the fuel rods includes: a nozzle support fitted to a depression of the first nozzle; and a buffer combined with the nozzle support, with stiffness of the fuel rods in a longitudinal direction being equal to or less than that of the nozzle support. The shock-absorbing device for a fuel assembly supports the first nozzle of the fuel assembly by the nozzle support to suppress flexure of the first nozzle resulting from an impact force due to dropping. Further, the impact force acting on the fuel assembly is absorbed by the buffer. With this configuration, deformation of the first nozzle due to dropping can be suppressed, thereby suppressing deformation of the fuel rods caused by the deformation of the first nozzle. Further, because the impact force acting on the fuel assembly is weakened, deformation of the fuel assembly is suppressed. Due to these effects, the present invention can suppress deformation of the fuel assembly at the time of dropping. In the nozzle support fitted to the depression, and the buffer combined with the nozzle support and having a stiffness of the fuel rod in a longitudinal direction equal to or less than that of the nozzle support, it can be selected whether the second nozzle is not combined with any of these, is combined only with the buffer, or is combined with the nozzle support and the buffer. According to an aspect of the present invention, a shock-absorbing device for a fuel assembly that suppresses a shock given to a fuel assembly constituted by combining a plurality of fuel rods and arranging a first nozzle and a second nozzle at opposite ends of the fuel rods includes: a nozzle support fitted to a depression of the first nozzle; and a buffer combined with the nozzle support, with stiffness of the fuel rods combined with the first nozzle and the second nozzle in a longitudinal direction being equal to or less than that of the nozzle support. The shock-absorbing device for a fuel assembly supports the first nozzle of the fuel assembly by the nozzle support to suppress flexure of the first nozzle resulting from an impact force due to dropping. Further, the impact force acting on the fuel assembly is absorbed by the buffer. With this configuration, deformation of the first nozzle or second nozzle caused by dropping can be suppressed, thereby suppressing deformation of the fuel rods resulting from the deformation. Further, because the impact force acting on the fuel assembly is weakened by the buffer, deformation of the fuel assembly can be suppressed. Due to these effects, the present invention can suppress deformation of the fuel assembly at the time of dropping. According to an aspect of the present invention, a shock-absorbing device for a fuel assembly that suppresses a shock given to a fuel assembly constituted by combining a plurality of fuel rods and arranging a first nozzle and a second nozzle at opposite ends of the fuel rods includes: a nozzle support fitted to a depression of the first nozzle and a depression of the second nozzle; and a buffer combined with the nozzle support, with stiffness of the fuel rods in a longitudinal direction being equal to or less than that of the nozzle support. The shock-absorbing device for a fuel assembly supports the first and second nozzles of the fuel assembly by the nozzle support to suppress flexure of the first and second nozzles resulting from an impact force due to dropping. Further, the impact force acting on the fuel assembly is absorbed by the buffer. With this configuration, deformation of the first and second nozzles caused by dropping can be suppressed, thereby suppressing deformation of the fuel rods resulting from the deformation. Further, because the impact force acting on the fuel assembly is weakened by the buffer, deformation of the fuel assembly can be suppressed. Due to these effects, the present invention can suppress deformation of the fuel assembly at the time of dropping. As a desirable mode of the present invention, in the shock-absorbing device for a fuel assembly, it is preferable that the buffer is constituted by enclosing at least one of resin, wood, and honeycomb by a casing. The configuration of the buffer is formed of a board, a honeycomb structure, a laminated structure, foam, or wool, and a plurality of these can be combined. For example, a wood laminated material is covered with a metal plate to form the buffer. Accordingly, the buffer can be formed relatively easily. As a desirable mode of the present invention, in the shock-absorbing device for a fuel assembly, it is preferable that the buffer includes a plurality of plate materials, and board surfaces of the plate materials are parallel to a longitudinal direction of the fuel rods. With this configuration, stiffness of the buffer can be adjusted relatively easily by adjusting the number, height and the like of the plate materials. As a desirable mode of the present invention, in the shock-absorbing device for a fuel assembly, it is preferable that the buffer includes a plurality of rod-like members, and an axial direction of the rod-like members is parallel to a longitudinal direction of the fuel rods. With this configuration, stiffness of the buffer can be adjusted relatively easily by adjusting the number, height and the like of the rod-like members. As a desirable mode of the present invention, in the shock-absorbing device for a fuel assembly, it is preferable that the first nozzle is arranged on a side of a bottom of a fuel assembly housing container for transporting the fuel assembly, and the buffer on the side of the first nozzle is arranged on the bottom of the fuel assembly housing container. With this configuration, the shock-absorbing device for a fuel assembly does not need to be fitted to the fuel assembly before housing the fuel assembly in the fuel assembly housing container. Therefore, the work efficiency for loading the fuel assembly in the fuel assembly housing container is improved. As a desirable mode of the present invention, in the shock-absorbing device for a fuel assembly, it is preferable that the first nozzle is arranged on the bottom side of the fuel assembly housing container for transporting the fuel assembly, and the buffer on the first nozzle side is combined with a basket arranged inside the fuel assembly housing container to house the fuel assembly and arranged on the bottom side of the fuel assembly housing container. With this configuration, the shock-absorbing device for a fuel assembly does not need to be fitted to the fuel assembly before housing the fuel assembly in the fuel assembly housing container. Therefore, the work efficiency for loading the fuel assembly in the fuel assembly housing container is improved. Further, the shock-absorbing device for a fuel assembly can be fitted to the basket at the time of assembling the basket and the basket can be incorporated in the fuel assembly housing container. Therefore, the shock-absorbing device for a fuel assembly does not need to be laid on the bottom inside the fuel assembly housing container. Accordingly, a work for incorporating the shock-absorbing device for a fuel assembly in the fuel assembly housing container is facilitated. As a desirable mode of the present invention, in the shock-absorbing device for a fuel assembly, it is preferable that the second nozzle is arranged at the opening of the fuel assembly housing container for transporting the fuel assembly, and the buffer on the second nozzle side is arranged on the lid of the fuel assembly housing container for transporting the fuel assembly. With this configuration, the shock-absorbing device can be combined with the second nozzle of the fuel assembly only by fitting the lid after the fuel assembly has been loaded in the fuel assembly housing container. In the present invention, it is preferable in a shock absorber for a fuel assembly that the shock absorber optimizes nozzle-deformation suppression capabilities by the nozzle support and shock absorbing capacity by the buffer. For example, buffering capacity of the buffer coming into contact with the nozzle support is optimized more than that of the buffer coming into contact with nozzle legs by selecting the thickness, material, laminated constitution, dividing arrangement and the like of the buffer. Accordingly, the nozzle-deformation suppression capabilities and shock buffering capacity can be balanced by setting an amount of compression of the buffer that absorbs shock and deforms due to a load of the nozzle legs on the buffer and a load of a nozzle plane on the buffer through the nozzle support substantially equal. With this configuration, it can be prevented that the nozzle deforms in a convex shape, if the amount of compression of the buffer by the nozzle legs is larger than that of the buffer by the nozzle support, and the nozzle deforms in a concave shape, if the amount of compression of the buffer by the nozzle legs is smaller than that of the buffer by the nozzle support. To solve the above problems and achieve an object of the invention, a fuel assembly housing container according to the present invention includes a body that is a container with a bottom and houses a fuel assembly in an internal space thereof; and a shock-absorbing device for a fuel assembly arranged at least on the bottom of the body. Because the fuel assembly housing container includes the shock-absorbing device for a fuel assembly according to the present invention, deformation of the fuel assembly at the time of dropping can be suppressed. As a desirable mode of the present invention, it is preferable that the shock-absorbing device for a fuel assembly is arranged on a lid fitted to an opening of the internal space. In this manner, the fuel assembly is housed in the fuel assembly housing container, and in the fuel assembly housing container, the buffer of the shock-absorbing device for a fuel assembly according to the present invention is installed, respectively, in contact with the first and second nozzles of the fuel assembly. With this configuration, deformation of the fuel assembly at the time of dropping can be suppressed more effectively. The present invention can suppress deformation of a fuel assembly at the time of dropping. The present invention will be explained below in detail with reference to the accompanying drawings. The present invention is not limited to the following explanations. In addition, constituent elements in the following explanations include those that can be easily assumed by persons skilled in the art or that are substantially equivalent. A shock-absorbing device for a fuel assembly according to the present invention is suitable for a fuel assembly of a PWR (Pressurized Water Reactor). However, application of the present invention to a BWR (Boiling Water Reactor) is not excluded. The shock-absorbing device for a fuel assembly according to the present invention is particularly suitable at the time of transporting the fuel assembly; however, application thereof at the time of storing the fuel assembly is not excluded. The shock-absorbing device for a fuel assembly according to the present invention can be applied not only to transport of the fuel assembly taken out from a nuclear reactor, but also to transport of a fuel assembly newly manufactured and loaded in a nuclear reactor. FIG. 1 is a schematic diagram of an overall configuration of a fuel assembly housing container that houses a fuel assembly. A fuel assembly housing container 1 houses a fuel assembly taken out from the nuclear reactor, and is used for transport and storage of the fuel assembly. The fuel assembly housing container 1 includes a body 2, which is a container with a bottom, a neutron shield 3 fitted to outside of the body 2, a primary lid 4, and a secondary lid 5. The body 2 includes a cylindrical barrel, a bottom provided at one end of the barrel, and a space (also referred to as “internal space of the body”, or “cavity”) 2I formed by the body and the bottom becomes a space for housing the fuel assembly. The fuel assembly is stored in cells 30C of a basket 30 having a plurality of grid cells 30C. The basket 30 housing the fuel assembly is housed in the internal space 2I of the body 2 (the internal space of the body). In the present embodiment, the basket 30 is constituted by combining a plurality of square pipes 31 with an external shape and an inner shape in cross section being substantially regular tetragon, and the inside of the square pipe 31 becomes the cell 30C. The body 2 has a function of shielding gamma rays from the fuel assembly housed in the internal space 2I of the body. The neutron shield 3 is provided therein with a neutron shielding material for shielding neutrons. A spacer 38 is arranged between the internal space 2I of the body and the basket 30. The spacer 38 transmits decay heat from the fuel assembly housed in the basket 30 to the body 2. The decay heat is released to the atmosphere via the body 2 and the neutron shield 3. After the fuel assembly is housed in the basket 30 (that is, after the fuel assembly is housed in the internal space 2I of the body), the primary lid (the lid) 4 is fitted to an opening of the internal space 2I of the body, and then the secondary lid 5 is fitted thereto to seal the internal space 2I of the body. A tertiary lid can be provided according to specifications. When the primary lid 4 and the secondary lid 5 are not distinguished from each other, these are referred to as “lid”. FIG. 2 is an explanatory diagram of a fuel assembly and the shock-absorbing device for a fuel assembly according to the present embodiment. A fuel assembly 20 is constituted by bundling a plurality of fuel rods 21 by a plurality of support grids 22. A lower nozzle (first nozzle) 24 and an upper nozzle (second nozzle) 23 are respectively arranged at opposite ends of the fuel rods 21. In a state where the fuel assembly 20 is housed inside of the fuel assembly housing container 1 shown in FIG. 1, the lower nozzle 24 is on a side of a bottom 2B of the body 2, and the upper nozzle 23 is on the primary lid 4 side (on an opening side of the fuel assembly housing container 1, that is, an opening side of the internal space 2I of the body). When the fuel assembly 20 is arranged in the nuclear reactor, the lower nozzle 24 is arranged on a vertical direction side, and the upper nozzle 23 is arranged on the opposite side in the vertical direction. FIG. 3A depicts a state where the fuel assembly housing container vertically drops. FIG. 3B is a schematic diagram of a shape of the lower nozzle at normal times. FIG. 3C is a schematic diagram of a shape of the lower nozzle when the fuel assembly housing container vertically drops. As shown in FIG. 3A, a state where the lid or bottom of the fuel assembly housing container 1 drops on the ground GL in the vertical direction (a direction shown by an arrow G in FIG. 3A) is referred to as “vertical drop”. In the case of vertical drop, an impact load of the fuel assembly 20 in a direction substantially parallel to a longitudinal direction (a direction shown by an arrow S in FIG. 2) acts on the fuel assembly 20. The lower nozzle 24 is normally in a non-deformation state as shown in FIG. 3B. The lower nozzle 24 (same as the upper nozzle 23) is substantially in a shape of regular tetragon as viewed in a plan view, and supports the fuel assembly 20 by a plurality of (specifically, four) legs 24F (23F) respectively provided at four corners. Accordingly, a depression 24U (23U) is formed in a portion surrounded by the four legs. Therefore, if the fuel assembly housing container 1 vertically drops and an impact force in a substantially parallel direction to the longitudinal direction of the fuel assembly 20 acts on the fuel assembly 20, as shown in FIG. 3C, the center of the lower nozzle 24 (the upper nozzle 23) may be bent. If the lower nozzle 24 (the upper nozzle 23) is bent, the fuel rod 21 shown in FIG. 2 may be deformed accompanying this. Therefore, in the present embodiment, the shock-absorbing device for a fuel assembly (hereinafter, “shock-absorbing device”) 10 is fitted to the lower nozzle 24 (the upper nozzle 23) to suppress flexure (deformation) of the lower nozzle 24 (the upper nozzle 23) and suppress an impact force generated due to dropping and acting on the fuel assembly 20. FIG. 4 is a perspective view of the shock-absorbing device according to the present embodiment. As shown in FIGS. 4 and 1, the shock-absorbing device 10 includes a nozzle support 12, and a buffer 11. The nozzle support 12 is fitted to the depression 24U of the lower nozzle 24 and the depression 23U of the upper nozzle 23. The buffer 11 is combined with the nozzle support 12, and stiffness thereof in the longitudinal direction of the fuel rods 21 constituting the fuel assembly 20 is equal to or lower than that of the nozzle support 12. The stiffness here is compression stiffness as the entire buffer 11 and nozzle support 12. That is, when the buffer 11 and the nozzle support 12 receive a compression force parallel to the longitudinal direction of the fuel rods 21, if the compression force is the same, the buffer 11 deforms similarly to the nozzle support 12, or deforms greater than the nozzle support 12. According to such a configuration, the shock-absorbing device 10 supports the lower nozzle 24 (the upper nozzle 23) by the nozzle support 12, and suppresses flexure of the lower nozzle 24 (the upper nozzle 23) resulting from the impact force due to dropping. The impact force acting on the fuel assembly 20 is absorbed by the buffer 11. With this configuration, because deformation of the lower nozzle 24 (the upper nozzle 23) due to dropping can be suppressed, deformation of the fuel rods 21 due to the deformation of the lower nozzle 24 (the upper nozzle 23) can be suppressed. The impact force acting on the fuel assembly 20 is weakened by the buffer 11. As a result, because the deformation of the fuel assembly 20 is further suppressed, its safety is improved. In the present embodiment, the shock-absorbing device 10 is provided respectively in both of the lower nozzle 24 and the upper nozzle 23. With this configuration, a clearance between the fuel assembly 20 housed in the fuel assembly housing container 1 and the fuel assembly housing container 1 in the longitudinal direction can be decreased. As a result, because a movement of the fuel assembly 20 in the longitudinal direction is suppressed, when the fuel assembly housing container 1 is grounded at the time of dropping, a movement of the fuel assembly 20 toward the ground can be suppressed. With this configuration, the impact force acting on the fuel assembly 20 can be further weakened. The upper nozzle 23 is positioned on the side of the primary and secondary lids 4 and 5. When the fuel assembly housing container 1 drops with the primary lid 4 and the secondary lid 5 being downward, the impact force due to the dropping is transmitted from the upper nozzle 23 to the primary lid 4. In the present embodiment, because the shock-absorbing device 10 is provided in the upper nozzle 23, the impact force transmitted from the upper nozzle 23 is weakened by the shock-absorbing device 10, thereby enabling to maintain sealing by the primary lid 4. In view of further weakening the impact force transmitted from the upper nozzle 23 to the primary lid 4, it is preferable that the buffer 11 of the shock-absorbing device 10 provided in the upper nozzle 23 can absorb larger impact energy than the buffer 11 provided in the lower nozzle 24. FIG. 5A is a perspective view of the nozzle support constituting the shock-absorbing device according to the present embodiment. As shown in FIG. 5A, the nozzle support 12 constituting the shock-absorbing device 10 is placed on the buffer 11. The nozzle support 12 is a plate like member with four corners of a regular tetragon being removed as viewed in a plan view. With this configuration, as shown in FIG. 4, when the nozzle support 12 is fitted to the lower nozzle 24 (the upper nozzle 23), the four legs of the lower nozzle 24 (the upper nozzle 23) and the nozzle support 12 do not interference with each other. It is preferable that the nozzle support 12 has compression stiffness as high as possible in a direction where a load due to vertical drop is input (a direction orthogonal to a plate surface of the nozzle support 12). Therefore, the nozzle support 12 is constituted by using a material strong against compression or a structure strong against compression, or by combining the both. For example, stainless steel, iron, aluminum, aluminum alloy, lead, or concrete are used for the nozzle support 12. When using these materials, it is preferable that the nozzle support 12 is solid. With this configuration, the nozzle support 12 can ensure higher compression stiffness. When a material having a radiation shielding function such as iron, aluminum alloy containing boron (B10), stainless steel, lead, or concrete is used, gamma rays and neutrons discharged from the fuel assembly 20 can be shielded, which is more preferable. FIGS. 5B to 5D are perspective views of other configuration examples of the nozzle support according to the present embodiment. As in a shock-absorbing device 10a shown in FIG. 5B, a disk-like nozzle support 12a can be used, or as in a shock-absorbing device 10b shown in FIG. 5C, a nozzle support 12b having a cruciform shape as viewed in a plan view can be used. As in a shock-absorbing device 10c shown in FIG. 5D, ribs 12cr combined to have a cruciform shape as viewed in a plan view are clamped by using two flat plates 12cp so that the ribs 12cr and the flat plates 12cp are orthogonal to each other, to constitute the nozzle support 12c. Because the nozzle support 12c improves the compression stiffness by the structure thereof, the material constituting the nozzle support 12c can be less. As a result, reduction of material cost and weight saving can be realized. FIG. 6A is a perspective view of the buffer constituting the shock-absorbing device according to the present embodiment. In the present embodiment, the buffer 11 has a square shape as viewed in a plan view, and compression stiffness thereof in a direction where the load due to vertical drop is input (a direction orthogonal to the plate surface of the nozzle support 12) is equal to or lower than the nozzle support 12. The shape of the buffer 11 is not limited to the square shape. The buffer 11 is formed by a plate member, a honeycomb structure, a laminated structure, foam, or wool, and a plurality of these can be combined. The buffer 11 is constituted by surrounding a buffer member 11I, for example, by a casing 11E, which is a holding member. Note that the casing 11E is not always necessary. The buffer member 11I is constituted, for example, by using any one of resin, wood, and metal, or combining at least two of these materials. The casing 11E is constituted by combining an iron board or a stainless steel board, for example. When resin is used for the buffer member 11I, it is preferable to use hydrogen-containing resin, for example. This is because a neutron shielding function can be demonstrated by using such resin. When a honeycomb is used for the buffer member 11I, it is preferable that a penetrating direction of holes is parallel to a direction where the load due to vertical drop is input. With this configuration, the compression stiffness of the buffer 11 can be adjusted to be appropriate. In the present embodiment, the honeycomb includes one obtained by combining a plurality of polygonal holes such as hexagonal holes, pentagonal holes, or quadrangular holes, other than one obtained by combining a plurality of regular hexagonal holes. When wood is used for the buffer member 11I, it is preferable that a fiber direction of wood is parallel to a direction where the load due to vertical drop is input. With this configuration, the compression stiffness of the buffer 11 can be adjusted to be appropriate. The compression stiffness of the buffer 11 can be adjusted by differentiating the fiber direction of wood. FIGS. 6B and 6C are perspective views of other configuration examples of the buffer according to the present embodiment. A buffer 11a shown in FIG. 6B includes a plurality of plate materials 11P, and the plate materials 11P are arranged such that plate surfaces thereof are parallel to a direction where the load due to vertical drop is input, that is, parallel to the longitudinal direction of the fuel rods 21. In this example, a plurality of plate materials 11P are fitted to a bottom plate 11B orthogonally thereto. The compression stiffness of the buffer 11a can be adjusted according to the number, thickness, and height of the plate materials 11P. The plate material 11P is not limited to the one with the plate surface being parallel to the longitudinal direction of the fuel rods 21, and for example, the plate surface can be inclined with respect to the longitudinal direction of the fuel rods 21, or the plate material 11P can have a curved portion (for example, a cross section of the plate material 11P is in a dog-leg shape). A buffer 11b shown in FIG. 6C includes a plurality of rod-like members 11N and the rod-like members 11N are arranged with an axial direction being parallel to the longitudinal direction of the fuel rods. In this example, a plurality of rod-like members 11N are fitted to the bottom plate 11B orthogonally thereto. The compression stiffness of the buffer 11b can be adjusted according to the number, diameter, and height of the rod-like members 11N. The configuration of the buffer is not limited to the configuration described above, and for example, an elastic body such as a disc spring, a plate spring, or a helical spring can be used. FIGS. 7A and 7B are schematic diagrams of examples in which the shock-absorbing device according to the present embodiment is fitted to the fuel assembly housing container. In the example shown in FIG. 7A, the buffer 11 constituting the shock-absorbing device 10 on the lower nozzle 24 side is arranged on the bottom 2B of the fuel assembly housing container 1 for transporting the fuel assembly 20. In this case, before the basket 30 shown in FIG. 1 is arranged in the internal space 2I of the body, the shock-absorbing device 10 is laid on the bottom 2B beforehand. The position where the shock-absorbing device 10 is arranged is matched with the position of the cells 30C constituting the basket 30. With this configuration, the shock-absorbing device 10 can be fitted together with the lower nozzle 24 of the fuel assembly 20 only by loading the fuel assembly 20 in the basket 30. In the example shown in FIG. 7B, the buffer 11 constituting the shock-absorbing device 10 on the upper nozzle 23 side is arranged on the lid, more specifically, the primary lid 4 of the fuel assembly housing container 1 for transporting the fuel assembly 20. In this case, the position where the shock-absorbing device 10 is arranged is matched with the position of the cells 30C constituting the basket 30. With this configuration, the shock-absorbing device 10 can be fitted together with the upper nozzle 23 of the fuel assembly 20 only by fitting the primary lid 4 to the body 2. FIGS. 7C and 7D are examples in which a plurality of buffers are arranged on a buffer support member. FIG. 7C is a plan view and FIG. 7D is a side view. Thus, a plurality of buffers 11 can be fitted to a disk 14, which is a buffer support member. The disk 14 fitted with the buffers 11 is arranged on the bottom of the body 2 of the fuel assembly housing container 1 shown in FIG. 1 or fitted to the primary lid 4. With this configuration, because the buffers 11 can be handled collectively, installation work of the buffers 11 is facilitated. The nozzle support 12 can be fitted to the buffers 11 and then fitted to the disk 14. FIGS. 8A and 8B are schematic diagrams of examples in which the shock-absorbing device according to the present embodiment is fitted to a basket. In the example shown in FIG. 8A, the shock-absorbing device 10 is fitted to the basket 30 shown in FIG. 1. More specifically, the shock-absorbing device 10 is fitted to an end of the square pipe 31 constituting the basket 30 (an end on the bottom 2B side of the fuel assembly housing container 1). In this case, the buffer 11 and the square pipe 31 are connected via a coupling member 32, thereby fitting the shock-absorbing device 10 to the square pipe 31. The coupling member 32, the buffer 11, and the square pipe 31 are coupled with one another by a bolt, welding or the like. In the configuration shown in FIG. 8A, the buffer 11 projects from the square pipe 31. However, if a certain distance is required between respective square pipes 31, a projected portion of the buffer can be used as a spacer, and thus assembly of the basket 30 is facilitated. As an example in which a certain distance is required between respective square pipes 31, for example, when a neutron shield or a structure for shielding neutrons is arranged. The example shown in FIG. 8B is identical to the example shown in FIG. 8A in that the shock-absorbing device 10 is fitted to an end of the square pipe 31 constituting the basket 30 (an end on the bottom 2B side of the fuel assembly housing container 1). However, an external shape and size of the buffer 11 of the shock-absorbing device 10 are set to be approximately the same as those of the square pipe 31, preferably, the same as those of the square pipe 31, or set to be smaller than those of the square pipe 31. The buffer 11 and the square pipe 31 are coupled with each other via a coupling member 33, and the shock-absorbing device 10 is fitted to the square pipe 31. In the example shown in FIG. 8B, because the buffer 11 does not project from the square pipe 31, this example is advantageous when it is desired that the square pipes 31 are arranged closely to each other. As described above, by fitting the shock-absorbing device 10 to the basket 30 that houses the fuel assembly, the shock-absorbing device 10 can be fitted together with the upper nozzle 23 of the fuel assembly 20 only by loading the fuel assembly 20 in the basket 30. With this configuration, the shock-absorbing device 10 does not need to be fitted to the fuel assembly 20 before loading the fuel assembly 20 in the basket 30, thereby facilitating a loading work of the fuel assembly 20 in the basket 30. According to a mode of operations, the fuel assembly 20 can be loaded in the basket 30 after the shock-absorbing device 10 is fitted to the fuel assembly 20. FIGS. 9A to 9D depict modifications of the shock-absorbing device according to the present embodiment. As an arrangement at the time of joining the nozzles (the lower nozzle and the upper nozzle) to the shock-absorbing device, it can be considered to design so that nozzle legs actually come into contact with the buffer. When the fuel assembly housing container drops in this state, if material characteristics of the buffer show a deformation behavior of an elastic body, deformation of the buffer becomes uniform over the entire range of the buffer, and the nozzle and the nozzle support do not come into contact with each other, and thus deformation of the nozzle may not be suppressed sufficiently. Therefore, as shown in FIGS. 9A to 9D, the configuration of the buffer is changed or an inside structure of the buffer or a material thereof is devised, so that absorption of impact energy and the deformation of the nozzle become appropriate. In a shock-absorbing device 10d shown in FIG. 9A, a buffer 11d includes a first buffer 11A and the second buffer 11B. In this case, a depression is formed in the first buffer 11A, and the second buffer 11B is arranged in the depression. The first buffer 11A and the lower nozzle 24 (or the upper nozzle 23) are brought into contact with each other, and the second buffer 11B and the nozzle support 12 are brought into contact with each other. With this configuration, a timing of deformation of the first buffer 11A that comes into contact with the legs 24F (23F) of the lower nozzle 24 (or the upper nozzle 23) is made different from that of deformation of the second buffer 11B that comes into contact with the nozzle support 12. That is, the first buffer 11A that comes into contact with the legs 24F (23F) deforms until a gap between the lower nozzle 24 (or the upper nozzle 23) and the nozzle support 12 is filled, and at the timing when the gap is filled, the buffer 11d, that is both of the first buffer 11A and the second buffer 11B start to deform. A shock-absorbing device 10e shown in FIG. 9B has approximately the same configuration as that of the shock-absorbing device 10d, and a buffer 11e includes a first buffer 11C and a second buffer 11D. In this case, a gap is provided between the first buffer 11C and the second buffer 11D. According to this configuration, a timing of deformation of the first buffer 11C that comes into contact with the legs 24F (23F) of the lower nozzle 24 (or the upper nozzle 23) is made different from that of deformation of the second buffer 11D that comes into contact with the nozzle support 12. That is, the first buffer 11A that comes into contact with the legs 24F (23F) deforms until the gap between the lower nozzle 24 (or the upper nozzle 23) and the nozzle support 12 is filled, and at the timing when the gap is filled, the buffer 11d, that is, both of the first buffer 11A and the second buffer 11B start to deform. In a shock-absorbing device 10f shown in FIG. 9C, the buffer 11d includes a first buffer 11E and a second buffer 11F. In this case, stiffness of the first buffer 11E in a compression direction is set lower than that of the second buffer 11F in the compression direction, and the first buffer 11A and the lower nozzle 24 (or the upper nozzle 23) are brought into contact with each other, and the second buffer 11B and the nozzle support 12 are brought into contact with each other. At this time, a salient is formed in the second buffer 11F, and the first buffer 11E is arranged around the salient and brought into contact with the lower nozzle 24 (or the upper nozzle 23). With this configuration, a timing of deformation of the first buffer 11E that comes into contact with the legs 24F (23F) of the lower nozzle 24 (or the upper nozzle 23) is made different from that of deformation of the second buffer 11F that comes into contact with the nozzle support 12. That is, the first buffer 11E that comes into contact with the legs 24F (23F) deforms until the gap between the lower nozzle 24 (or the upper nozzle 23) and the nozzle support 12 is filled, and at the timing when the gap is filled, the buffer 11e, that is, both of the first buffer 11E and the second buffer 11F start to deform. When a contact surface between the nozzle support and the buffer is formed of a flat surface, a change occurs in a load distribution to the buffer coming into contact with the nozzle legs and a load distribution to the buffer coming into contact with the nozzle support. Therefore, even if buffering capacity can be maintained, nozzle-deformation suppression capabilities may not be demonstrated sufficiently. Therefore, as in a shock-absorbing device 10g shown in FIG. 9D, the buffering capacity and the nozzle-deformation suppression capabilities are balanced by optimizing a thickness of a buffer 11g, or optimizing the buffering capacity between a portion of the buffer 11g coming into contact with the legs 24F (23F) of the lower nozzle 24 (or the upper nozzle 23) and a portion of the buffer 11g coming into contact with the nozzle support 12 (for example, by using different materials for these portions). In the present embodiment, the lower nozzle or the upper nozzle of the fuel assembly is supported by the nozzle support, so as to suppress flexure (deformation) of the lower nozzle or the upper nozzle resulting from an impact force due to dropping. Further, the impact force acting on the fuel assembly is absorbed by the buffer. With this configuration, the deformation of the lower nozzle or the upper nozzle due to dropping can be suppressed. Furthermore, because the impact force acting on the fuel assembly is weakened by the buffer, it is possible to suppress the deformation of the fuel assembly. As described above, the shock-absorbing device for a fuel assembly according to the present invention is useful for transporting of a fuel assembly, and is particularly suitable to suppress deformation of a fuel assembly at the time of dropping. 1 fuel assembly housing container 2 body 2B bottom 2I internal space of body 3 neutron shield 4 primary lid 5 secondary lid 10, 10a, 10b, 10c, 10d, 10e, 10f, 10g shock-absorbing device 11, 11a, 11b, 11c, 11d, 11e, 11f, 11g buffer 11B bottom plate 11E casing 11I buffer member 11N rod-like member 11P plate material 12, 12a, 12b, 12c, 12d, 12e, 12f, 12g nozzle support 12cp flat plate 12cr rib 20 fuel assembly 21 fuel rod 22 support grid 23 upper nozzle 23F leg 23U depression 24 lower nozzle 24F leg 24U depression 30 basket 30C cell 31 square pipe 32, 33 coupling member 38 spacer
	description	The present disclosure relates to an extreme ultraviolet light generation device. In recent years, as semiconductor processes become finer, transfer patterns for use in photolithographies of semiconductor processes have rapidly become finer. In the next generation, microfabrication at 70 nm to 45 nm, and further, microfabrication at 32 nm or less will be demanded. In order to meet the demand for microfabrication at 32 nm or less, for example, the development of an exposure apparatus in which a system for generating EUV (extreme ultraviolet) light at a wavelength of approximately 13 nm is combined with a reduced projection reflective optics is expected. Three types of EUV light generation systems have been proposed, which include an LPP (laser produced plasma) type system using plasma generated by irradiating a target material with a laser beam, a DPP (discharge produced plasma) type system using plasma generated by electric discharge, and an SR (synchrotron radiation) type system using orbital radiation. An extreme ultraviolet light generation device according to an aspect of the present disclosure may be an extreme ultraviolet light generation device for generating extreme ultraviolet light by irradiating a target with a pulse laser beam and thereby turning the target into plasma, and may include: a chamber; a magnet configured to form a magnetic field in the chamber; and an ion catcher including a collision unit disposed so that ions guided by the magnetic field collide with the collision unit. Contents 1. Overview 2. Terms 3. Overview of EUV Light Generation System 3.1 Configuration 3.2 Operation 4. EUV Light Generation Device Including Ion Catcher 4.1 Overall Configuration 4.2 Laser Beam Direction Control Unit 4.3 Focusing Optical System 4.4 Magnets 4.5 Ion Catcher 5. EUV Light Generation Device Including Tubular Ion Catcher 6. EUV Light Generation Device Whose Ion Catcher Includes Exhaust Pump 6.1 Gas Supply System 6.2 Ion Catcher 7. EUV Light Generation Device Whose Ion Catcher Includes Gate Valves 8. EUV Light Generation Device Whose Ion Catcher Includes Powder Pump 9. EUV Light Generation Device Including Ion Catcher Constituted by Tubular Member 10. EUV Light Generation Device Including Ion Catcher Disposed in Obscuration Area 11. Shapes of Tubular Members Selected embodiments of the present disclosure will be described in detail below with reference to the accompanying drawings. The embodiments to be described below are merely illustrative in nature and do not limit the scope of the present disclosure. Further, the configuration(s) and operation(s) described in each embodiment are not all essential in implementing the present disclosure. Corresponding elements may be referenced by corresponding reference numerals and characters, and duplicate descriptions thereof may be omitted. 1. Overview In an LPP-type EUV light generation device, a target supply unit may output a target so that the target reaches a plasma generation region. A laser apparatus may irradiate the target with a pulse laser beam at the point in time when the target reaches the plasma generation region. This may cause the target to be turned into plasma, and EUV light may be emitted from the plasma. The EUV light thus emitted may be reflected and concentrated by an EUV collector mirror. The plasma may contain high-energy ions. The ions contained in the plasma may be caught by an ion catcher. However, a collision of the high-energy ions against the ion catcher may cause the ions to rebound and scatter or may cause a surface of the ion catcher to be sputtered so that sputtered particles scatter. The ions or sputtered particles having scattered may adhere to an optical element in a chamber, such as the EUV collector mirror, to deteriorate the characteristics of the optical element. A collision of electrically neutral particles, as well as the ions, against the ion catcher may deliver a similar result. Such electrically neutral particles are hereinafter referred to as “neutral particles”. Note here that the ion catcher may be one configured to catch the ions and/or the neutral particles. According to an aspect of the present disclosure, the EUV light generation device may include: a magnet configured to form a magnetic field in the chamber; and an ion catcher including a collision unit disposed so that ions guided by the magnetic field collide with the collision unit. The ion catcher may include a plurality of collision surfaces disposed to be inclined with respect to the magnetic field. 2. Terms Several terms used in the present disclosure will be described below. A “plasma generation region” may refer to a predetermined region where generation of the plasma for generating the EUV light begins. A “Y direction” may substantially coincide with a direction of movement of a target 27. A “Z direction” may be a direction perpendicular to the Y direction. The Z direction may substantially coincide with a traveling direction of a pulse laser beam 33. The Z direction may also substantially coincide with a travelling direction of reflected light 252 reflected by an EUV collector mirror 23. An “X direction” may be a direction perpendicular to both the Y direction and the Z direction. The X direction may substantially coincide with a direction of a central axis of a magnetic field that is formed by magnets 6a and 6b. 3. Overview of EUV Light Generation System 3.1 Configuration FIG. 1 schematically illustrates an exemplary configuration of an LPP type EUV light generation system. An EUV light generation device 1 may be used with at least one laser apparatus 3. Hereinafter, a system that includes the EUV light generation device 1 and the laser apparatus 3 may be referred to as an EUV light generation system 11. As shown in FIG. 1 and described in detail below, the EUV light generation device 1 may include a chamber 2 and a target supply unit 26. The chamber 2 may be sealed airtight. The target supply unit 26 may be mounted onto the chamber 2, for example, to penetrate a wall of the chamber 2. A target material to be supplied by the target supply unit 26 may include, but is not limited to, tin, terbium, gadolinium, lithium, xenon, or a combination of any two or more of them. The chamber 2 may have at least one through-hole formed in its wall. A window 21 may be located at the through-hole. A pulse laser beam 32 that is outputted from the laser apparatus 3 may travel through the window 21. In the chamber 2, the EUV collector mirror 23 having a spheroidal reflective surface may be provided. The EUV collector mirror 23 may have a first focusing point and a second focusing point. The reflective surface of the EUV collector mirror 23 may have a multi-layered reflective film in which molybdenum and silicon are alternately laminated, for example. The EUV collector mirror 23 may be preferably positioned such that the first focusing point is positioned in a plasma generation region 25 and the second focusing point is positioned in an intermediate focus (IF) region 292. The EUV collector mirror 23 may have a through-hole 24, formed at the center thereof, through which the pulse laser beam 33 travels. The EUV light generation device 1 may further include an EUV light generation controller 5 and a target sensor 4. The target sensor 4 may have an imaging function and detect the presence, actual path, position, speed, and the like of the target 27. Further, the EUV light generation device 1 may include a connection part 29 for allowing the inside of the chamber 2 to be in communication with the inside of an exposure apparatus 6. A wall 291 having an aperture may be provided in the connection part 29. The wall 291 may be positioned such that the second focusing point of the EUV collector mirror 23 lies in the aperture formed in the wall 291. The EUV light generation device 1 may also include a laser beam direction control unit 34, a laser beam focusing mirror 22, and a target collector 28 for collecting targets 27. The laser beam direction control unit 34 may include an optical element for defining the direction in which the laser beam travels and an actuator for adjusting the position or the posture of the optical element. 3.2 Operation With reference to FIG. 1, a pulse laser beam 31 outputted from the laser apparatus 3 may pass through the laser beam direction control unit 34 and be outputted therefrom as the pulse laser beam 32. The pulse laser beam 32 may travel through the window 21 and enter the chamber 2. The pulse laser beam 32 may travel through the inside of the chamber 2 along at least one laser beam path, be reflected by the laser beam focusing mirror 22, and strike at least one target 27 as the pulse laser beam 33. The target supply unit 26 may be configured to output the target(s) 27 toward the plasma generation region 25 in the chamber 2. The target 27 may be irradiated with at least one pulse of the pulse laser beam 33. Upon being irradiated with the pulse laser beam, the target 27 may be turned into plasma, and emitted light 251 may be emitted from the plasma. The EUV light included in the emitted light 251 may be reflected at a higher reflectance than light at other wavelength regions by the EUV collector mirror 23. The reflected light 252, which includes the EUV light reflected by the EUV collector mirror 23, may be concentrated to the intermediate focus region 292 and be outputted to the exposure apparatus 6. Here, one target 27 may be irradiated with multiple pulses included in the pulse laser beam 33. The EUV light generation controller 5 may be configured to integrally control the entire EUV light generation system 11. The EUV light generation controller 5 may be configured to process image data and the like of the target 27 captured by the target sensor 4. Further, the EUV light generation controller 5 may be configured to control at least one of the timing when the target 27 is outputted and the direction in which the target 27 is outputted. Furthermore, the EUV light generation controller 5 may be configured to control at least one of the timing when the laser apparatus 3 oscillates, the direction in which the pulse laser beam 32 travels, and the position at which the pulse laser beam 33 is focused. The various controls mentioned above are merely examples, and other controls may be added as necessary. 4. EUV Light Generation Device Including Ion Catcher 4.1 Overall Configuration FIG. 2 is a partial cross-sectional view illustrating a configuration of an EUV light generation system 11 according to a first embodiment. FIG. 2 illustrates a cross-section taken along a plane perpendicular to a trajectory of the target 27. The plane perpendicular to the trajectory of the target 27 may be a plane substantially parallel to the ZX plane. As shown in FIG. 2, a focusing optical system 22a, the EUV collector mirror 23, an EUV collector mirror holder 81, plates 82 and 83, and ion catchers 5a and 5a may be provided inside the chamber 2. The laser apparatus 3 and a laser beam direction control unit 34a may be provided outside the chamber 2. The laser apparatus 3 may include a CO2 laser device. The laser apparatus 3 may output a pulse laser beam. 4.2 Laser Beam Direction Control Unit The laser beam direction control unit 34a may include high-reflecting mirrors 341 and 342. The high-reflecting mirror 341 may be supported by a holder 343. The high-reflecting mirror 342 may be supported by a holder 344. The high-reflecting mirror 341 may be provided in an optical path of the pulse laser beam 31 outputted by the laser apparatus 3. The high-reflecting mirror 341 may reflect the pulse laser beam 31 at a high reflectance. The high-reflecting mirror 342 may be provided in an optical path of the pulse laser beam reflected by the high-reflecting mirror 341. The high-reflecting mirror 342 may reflect the pulse laser beam at a high reflectance to guide this beam as the pulse laser beam 32 into the focusing optical system 22a. 4.3 Focusing Optical System The focusing optical system 22a may include an off-axis paraboloidal mirror 221 and a flat mirror 222. The off-axis paraboloidal mirror 221 may be supported by a holder 223. The flat mirror 222 may be supported by a holder 224. The holders 223 and 224 may be fixed to the plate 83. The EUV collector mirror 23 may be fixed to the plate 82 via the EUV collector mirror holder 81. The plates 82 and 83 may be fixed to the chamber 2. The off-axis paraboloidal mirror 221 may be provided in an optical path of the pulse laser beam 32. The off-axis paraboloidal mirror 221 may reflect the pulse laser beam 32 toward the flat mirror 222. The flat mirror 222 may reflect the pulse laser beam, which has been reflected by the off-axis paraboloidal mirror 221, as the pulse laser beam 33 toward the plasma generation region 25 or the vicinity thereof. The pulse laser beam 33 may be concentrated to the plasma generation region 25 or the vicinity thereof according to the shape of the reflective surface of the off-axis paraboloidal mirror 221. In the plasma generation region 25 or the vicinity thereof, the target 27 in a form of a single droplet may be irradiated with the pulse laser beam 33. Irradiation of the target 27 with the pulse laser beam 33 may cause the target 27 to turn into plasma to generate EUV light. 4.4 Magnets Each of the magnets 6a and 6b may be an electromagnet including a coil. The magnets 6a and 6b may be disposed in opposed positions across the chamber 2 so that the central axes of their coils coincide with each other. The magnets 6a and 6b may be configured to be able to form a magnetic field in the chamber. A magnetic field that is formed by the magnets 6a and 6b may be strongest near the centers of the bores of the respective coils and be slightly weaker between the magnet 6a and the magnet 6b. The ions contained in the plasma may receive Lorentz force perpendicular to both the direction of the magnetic field and the direction of movement of the ions when dispersing from the plasma generation region 25. The Lorentz force may cause an actual path of movement of the ions to be in a substantially circular shape as seen from a direction parallel to the magnetic field. That is, the ions may move in a spiral manner along the magnetic field. 4.5 Ion Catcher The ion catchers 5a and 5a may be attached to an inner side of the chamber 2. The ion catchers 5a and 5a may be provided on the central axis of the magnetic field that is formed by the magnets 6a and 6b. FIGS. 3A to 3C illustrate an exemplary configuration of one ion catcher 5a of the ion catchers illustrated in FIG. 2. FIG. 3A is a view of the ion catcher 5a as seen from the direction parallel to the magnetic field. FIG. 3B is a side view of the ion catcher 5a illustrated in FIG. 3A. FIG. 3C is a partially-enlarged view of the ion catcher 5a illustrated in FIG. 3B. As shown in FIGS. 3A and 3B, the ion catcher 5a may include a circular plate 51 and a plurality of deep grooves 52 formed in the circular plate 51. The deep grooves 52 may be triangular in cross-section. As shown in FIG. 3C, these deep grooves 52 may constitute a plurality of collision surfaces 53 and 54. The plurality of collision surfaces 53 may not be parallel to the XY plane but be inclined. The plurality of collision surfaces 53 may not be provided perpendicularly to the circular plate 51 but be inclined toward an upstream side of the optical path of the reflected light 252 reflected by the EUV collector mirror 23. The upstream side of the optical path of the reflected light 252 reflected by the EUV collector mirror 23 may be oriented to a direction from the intermediate focus region 292 toward the center of a reflective surface of the EUV collector mirror 23. Even when the ions or the neutral particles collide with and are reflected by the collision surfaces 53 as indicated by an arrow P in FIG. 3C, the ions or the neutral particles thus reflected may hit the other collision surfaces 54 and adhere to the collision surfaces 54. The ions or the neutral particles thus reflected are hereinafter referred to as “reflected particles”. Alternatively, even when the ions or the neutral particles collide with the collision surfaces 53 as indicated by the arrow P in FIG. 3C to cause the collision surfaces 53 to be sputtered, sputtered particles having jumped out of the collision surfaces 53 may hit the other collision surfaces 54 and adhere to the collision surfaces 54. This makes it possible to prevent the reflected particles or the sputtered particles from scattering into the chamber 2. FIGS. 4A to 4C illustrate an exemplary configuration of another ion catcher 5b. FIG. 4A is a view of the ion catcher 5b as seen from the direction parallel to the magnetic field. FIG. 4B is a side view of the ion catcher 5b illustrated in FIG. 4A. FIG. 4C is a partially-enlarged view of the ion catcher 5b illustrated in FIG. 4B. As shown in FIGS. 4A and 4B, the ion catcher 5b may include a circular plate 55 and a plurality of plates 56 fixed to the circular plate 55. As shown in FIG. 4C, these plates 56 may constitute a plurality of collision surfaces 57 and 58. The plurality of collision surfaces 57 and 58 may be parallel to the XY plane. The plurality of collision surfaces 57 and 58 may be provided perpendicularly to the circular plate 55. Even when the ions or the neutral particles collide with and are reflected by the collision surfaces 57 as indicated by an arrow P in FIG. 4C, the reflected particles may hit the other collision surfaces 58 and adhere to the collision surfaces 58. Alternatively, even when the ions or the neutral particles collide with the collision surfaces 57 as indicated by the arrow P in FIG. 4C to cause the collision surfaces 57 to be sputtered, sputtered particles may hit the other collision surfaces 58 and adhere to the collision surfaces 58. This makes it possible to prevent the reflected particles or the sputtered particles from scattering into the chamber 2. FIG. 5 illustrates an exemplary configuration of still another ion catcher 5c. FIG. 5 also illustrates a positional relationship between the ion catcher 5c and the EUV collector mirror 23. Since the reflective surface of the EUV collector mirror 23 faces upward in FIG. 5, a lower side of FIG. 5 may correspond to the upstream side of the reflected light 252 reflected by the EUV collector mirror 23. The ion catcher 5c may include a plate 51 and a plurality of deep grooves 52 formed in the plate 51. The deep grooves 52 may be triangular in cross-section. These deep grooves 52 may constitute a plurality of collision surfaces 53 and 54. As shown in FIG. 5, the plurality of collision surfaces 53 and 34 may be more inclined than the plurality of collision surfaces 53 and 54 illustrated in FIG. 3. The plurality of collision surfaces 54, as well as the plurality of collision surfaces 53, may not be parallel to the XY plane but be inclined. FIG. 6 illustrates an exemplary configuration of still another ion catcher 5d. A lower side of FIG. 6 may correspond to the upstream side of the reflected light 252 reflected by the EUV collector mirror 23. The ion catcher 5d may include an inclined plate 55 and a plurality of plates 56 fixed to the inclined plate 55. These plates 56 may constitute a plurality of collision surfaces 57 and 58. As shown in FIG. 6, the plurality of collision surfaces 57 and 58 may not be parallel to the XY plane but be inclined. The plurality of collision surfaces 57 and 58 may be provided perpendicularly to the circular plate 55. Thus, even when the plurality of collision surfaces 57 and 58 are not inclined with respect to the plate 55, the inclination of the plate 55 may allow the collision surfaces to be preferably inclined. FIG. 7 illustrates an exemplary configuration of still another ion catcher 5e. A lower side of FIG. 7 may correspond to the upstream side of the reflected light 252 reflected by the EUV collector mirror 23. The ion catcher 5e may include an inclined plate 55 and a plurality of plates 56 fixed to the inclined plate 55. These plates 56 may constitute a plurality of collision surfaces 57 and 58. As shown in FIG. 7, the plurality of collision surfaces 57 and 58 may not be parallel to the XY plane but be inclined. The plurality of collision surfaces 57 and 58 may not be provided perpendicularly to the circular plate 55 but be inclined toward the upstream side of the optical path of the reflected light 252 reflected by the EUV collector mirror 23. FIG. 8 illustrates an exemplary configuration of still another ion catcher 5f. A lower side of FIG. 8 may correspond to the upstream side of the reflected light 252 reflected by the EUV collector mirror 23. The ion catcher 5f may include an inclined plate 55 and a plurality of curved plates 56 fixed to the inclined plate 55. These plates 56 may constitute a plurality of collision surfaces 57 and 58. As shown in FIG. 8, the plurality of collision surfaces 57 and 58 may not be parallel to the XY plane but be inclined. The plurality of plates 56 may be curved toward the upstream side of the optical path of the reflected light 252 reflected by the EUV collector mirror 23. 5. EUV Light Generation Device Including Tubular Ion Catcher FIG. 9 is a partial cross-sectional view illustrating a configuration of an EUV light generation system 11 according to a second embodiment. Each of ion catchers 5g and 5g may include a tubular member 40, a first collision unit 41 provided at a first end of the tubular member 40, and a second collision unit 42 provided at a second end of the tubular member 40. In the following description, the first end of the tubular member 40 may be an end of the tubular member 40 that is closer to the plasma generation region 25. The first end of the tubular member 40 may have an opening in a direction along the magnetic field. The second end of the tubular member 40 may be an end of the tubular member 40 that is farther away from the plasma generation region 25. FIGS. 10A to 10C are enlarged views of the first collision unit 41 illustrated in FIG. 9. FIG. 10A is a view of the first collision unit 41 as seen from the direction parallel to the magnetic field. FIG. 10B is a side view of the first collision unit 41 illustrated in FIG. 10A. FIG. 10C is a partially-enlarged view of the first collision unit 41 illustrated in FIG. 10B. The first collision unit 41 may be constituted by a plurality of plate members 43 obliquely arranged at intervals. Each of the plate members 43 may have collision surfaces with which the ions or the neutral particles collide. The first collision unit 41 does not have to have a plate 55 (see FIGS. 4A to 4C). Referring back to FIG. 9, the second collision unit 42 may have conical or polygonally-pyramidal surfaces. The tubular members 40 may be positioned through the bores of the coils constituting the respective magnets 6a and 6b. This may cause a strong magnetic field to be formed inside the tubular member 40. When the ions or the neutral particles collide with and are reflected by any of the collision surfaces of the first collision unit 41, the first collision unit 41 may not be able to completely catch the ions or the neutral particles, with the result that the ions or the neutral particles may enter the tubular member 40. Here, the ions may be decelerated, since a strong magnetic field is formed inside the tubular member 40. The neutral particles may also be decelerated when being reflected by the first collision unit 41. Therefore, the ions or the neutral particles may easily adhere to the second collision unit 42 without being reflected by the second collision unit 42. If reflected by the second collision unit 42, the ions or the neutral particles are further decelerated. This reduces the possibility of the ions or the neutral particles passing through the first collision unit 41 again and returning to the inside of the chamber 2. That is, the inside of the tubular member 40 serves as a relaxation space in which the ions or the neutral particles are decelerated, thus making it possible to efficiently catch the ions or the neutral particles. 6. EUV Light Generation Device Whose Ion Catcher Includes Exhaust Pump 6.1 Gas Supply System FIG. 11 is a partial cross-sectional view illustrating a configuration of an EUV light generation system 11 according to a third embodiment. As shown in FIG. 11, a sub-chamber 20 may be provided inside the chamber 2. Pipes 61 and 63 may be attached to the chamber 2. Control valves 62 and 64 and a gas supply source 65 may be provided outside the chamber 2. The plate 83 and the focusing optical system 22a may be housed within the sub-chamber 20. The sub-chamber 20 may include a hollow conical portion 70 penetrating the EUV collector mirror 23. The conical portion 70 may have openings at its base and at its tip, respectively. The pulse laser beam 33 may pass through the conical portion 70 from a base opening 71 to a tip opening 72 to reach the plasma generation region 25. That is, the sub-chamber 20, which includes the conical portion 70, may surround an optical path of the pulse laser beam 33 between the focusing optical system 22a and the plasma generation region 25. An outer conical portion 73 may be located around the conical portion 70. There may be a space between the conical portion 70 and the outer conical portion 73. The outer conical portion 73 may also penetrate the EUV collector mirror 23. The outer conical portion 73 may include a return portion 74 spreading outward at an end near the reflective surface of the EUV collector mirror 23. Another return portion 75 may be fixed to an outer surface of the conical portion 70. There may be a space between the return portion 74 and the return portion 75. The space between the outer conical portion 73 and the conical portion 70 and the space between the return portions 74 and 75 may communicate with each other to form a gas passageway. The gas supply source 65 may be connected to the inside of the sub-chamber 20 via the control valve 62 and the pipe 61. The control valve 62 may be configured to be able to change the flow rate of hydrogen gas that is supplied to the pipe 61. The pipe 61 may have an opening inside the sub-chamber 20 and supply hydrogen gas to the vicinity of the window 21. The supply of hydrogen gas into the sub-chamber 20 may cause the pressure inside the sub-chamber 20 to be higher than the pressure inside the chamber 2 and outside the sub-chamber 20. The hydrogen gas supplied into the sub-chamber 20 may flow out from the tip opening 72 of the conical portion 70 toward an area around the plasma generation region 25. Since the pressure inside the sub-chamber 20 is made higher than the pressure inside the chamber 2 by supplying the hydrogen gas into the sub-chamber 20, debris of the target material may be prevented from entering into the sub-chamber 20. If the debris of the target material adheres to the focusing optical system 22a and/or the window 21 inside the sub-chamber 20, the debris can be removed by etching with the hydrogen gas. The gas supply source 65 may also be connected to the gas passageway in the space between the conical portion 70 and the outer conical portion 73 via the control valve 64 and the pipe 63. The control valve 64 may be configured to be able to change the flow rate of hydrogen gas that is supplied to the pipe 63. The pipe 63 may be connected to the gas passageway formed in the space between the conical portion 70 and the outer conical portion 73 and supply hydrogen gas to the gas passageway. The hydrogen gas may flow out of the space between the return portions 74 and 75 radially from a central part of the EUV collector mirror 23 toward an outer circumferential side of the EUV collector mirror 23 along the reflective surface of the EUV collector mirror 23. The flow of the hydrogen gas along the reflective surface of the EUV collector mirror 23 may prevent debris of the target material from reaching the reflective surface of the EUV collector mirror 23. If the debris of the target material adheres to the reflective surface of the EUV collector mirror 23, the debris can be removed by etching with the hydrogen gas. 6.2 Ion Catcher Each of ion catchers 5h and 5h may include a tubular member 40, a first collision unit 41 provided at a first end of the tubular member 40, and a second collision unit 42 provided at a second end of the tubular member 40. The first collision unit 41 and the second collision unit 42 may be identical in configuration to those illustrated in FIG. 9. An exhaust pump 45 may be connected to the tubular member 40 via an exhaust flow passage 44. Further, the possibility of the ions or the neutral particles being decelerated by colliding with an inner wall of the tubular member 40 may be increased by making the tubular member 40 comparatively long. The exhaust pump 45 may exhaust the gas from the tubular member 40 to cause a difference in pressure between the inside of the chamber 2 and the inside of the tubular member 40 so that the ions or the neutral particles may be efficiently flown into the tubular member 40. Further, the exhaust pump 45 may exhaust the gas from the tubular member 40 to allow the ions or the neutral particles to be efficiently removed from the tubular member 40 by the exhaust pump 45. The exhaust pump 45 may be connected to a part of the tubular member 40 between a portion that is close to the second collision unit 42 and a middle portion of the tubular member 40. This allows the ions to be decelerated in the process of moving through the inside of the tubular member 40 or deactivated by being exposed to a gas flow, so that the ions may be efficiently removed by the exhaust pump 45. 7. EUV Light Generation Device Whose Ion Catcher Includes Gate Valves FIG. 12 is a partial cross-sectional view illustrating a configuration of an EUV light generation system 11 according to a fourth embodiment. A tubular member 40 constituting each of ion catchers 5i and 5i may include a first member 40a having a first end and a second member 40b having a second end. The second member 40b may be separable from the first member 40a. The first member 40a and the second member 40b may be fastened to each other by a bolt (not illustrated) so as to be hermetically fixed. No collision unit may be provided at the first end of the tubular member 40. Although no collision unit is provided at the first end of the tubular member 40, the ions may be decelerated while moving through the inside of the tubular member 40 or deactivated by being exposed to a gas flow. A collision unit 42a may be provided at the second end of the tubular member 40. The collision unit 42a may be provided with a plurality of deep grooves that are triangular in cross-section, and may be identical in configuration to the ion catcher 5a illustrated in FIG. 2 and FIGS. 3A to 3C. A gate valve 46 may be provided near the middle of the tubular member 40. Further, a gate valve 47 may be provided in the exhaust flow passage 44, via which the exhaust pump 45 and the tubular member 40 are connected to each other. In the event of a replacement of the collision unit 42a, the gate valve 46 may be closed. In the event of maintenance of the exhaust pump 45, the gate valve 47 may be closed. This may suppress fluctuation in pressure inside the chamber 2 during the maintenance. 8. EUV Light Generation Device Whose Ion Catcher Includes Powder Pump FIG. 13 is a partial cross-sectional view illustrating a configuration of an EUV light generation system 11 according to a fifth embodiment. A second member 40b of a tubular member 40 constituting each of ion catchers 5j and 5j may be provided with a powder pump 49. The powder pump 49 may be an apparatus that ejects a powder dispersed in gas. A collision unit 42b may be provided near a connection part connecting the powder pump 49 and the tubular member 40. The collision unit 42b may be an oblique arrangement of plate members, and may be identical in configuration to the first collision unit 41 illustrated in FIGS. 10A to 10C. Such a configuration of the collision unit 42b may allow the powder pump 49 to eject the powder. Further, a powder filter 48 may be provided near a connection part connecting the tubular member 40 and the exhaust flow passage 44. This may prevent the powder from flowing into the exhaust pump 45, and an extension of the life of the exhaust pump 45 may be expected. 9. EUV Light Generation Device Including Ion Catcher Constituted by Tubular Member FIG. 14 is a partial cross-sectional view illustrating a configuration of an EUV light generation system 11 according to a sixth embodiment. In the sixth embodiment, each of ion catchers 5k and 5k may have a tubular member 40 provided with no exhaust pump. Further, no oblique collision surfaces may be provided inside the tubular member 40. Even without oblique collision surfaces, the tubular member 40 being sufficiently long may prevent the ions or the neutral particles from returning to the inside of the chamber 2. Assuming that φ is maximum diameter of the opening at the first end of the tubular member 40, convergent ion beam diameter by the magnetic field may preferably be equal to or smaller than φ. In this case, the convergent ion beam diameter may be defined as the diameter of a region where a cross-sectional number density distribution of the ions at the first end is equal to or greater than 1/e2 of a peak value. It may be assumed that L is the length of the tubular member 40 from the first end to the second end. It may further be assumed that the ions entering the tubular member 40 through the first end may reach the second end of the tubular member 40 and reflected particles or sputtered particles may isotropically disperse from the second end. Furthermore, out of the particles having isotropically dispersed from the second end, particles having dispersed into a range of a solid angle Ω may return to the inside of the chamber 2 through the first end of the tubular member 40. It may be assumed that particles having dispersed out of the range of the solid angle Ω from the second end are decelerated by colliding with the inner wall of the tubular member 40 at least once and adhere to the inner wall of the tubular member 40. In this case, in order that particles returning to the inside of the chamber 2 account for less than 1% of the particles having isotropically dispersed from the second end, Eq. 1 may hold as follows:Ω/2π<0.01 (Eq. 1) Ω may be expressed by Eq. 2 as follows:Ω=2π(1−cos α) (Eq. 2) cos α may be expressed by Eq. 3 as follows:cos α=L/√(L2+φ2/4) (Eq. 3) It should be noted that √(X) may be the positive square root of X. Eq. 4 may be given from Eq. 1, Eq. 2, and Eq. 3 as follows:L/φ>3.55 (Eq. 4) According to Eq. 4, the conditions to be satisfied by L and φ may be defined in order that particles returning to the inside of the chamber 2 account for less than 1% of the particles having isotropically dispersed from the second end. Further, in order that particles returning to the inside of the chamber 2 account for less than 0.3% of the particles having isotropically dispersed from the second end, Eq. 5 may be given in a manner similar to that described above:L/φ>6.46 (Eq. 5) As explained above, preferably, the size of the tubular member may satisfy Eq. 4. More preferably, the size of the tubular member may satisfy Eq. 5. For example, if φ=81 mm and L=541.5 mm, Eq. 5 may be satisfied since L/φ=6.69. 10. EUV Light Generation Device Including Ion Catcher Disposed in Obscuration Area FIGS. 15A and 15B are partial cross-sectional views illustrating a configuration of an EUV light generation system 11 according to a seventh embodiment. FIG. 15A illustrates a cross-section that is parallel to the ZX plane and passes through the plasma generation region 25. FIG. 15B illustrates a cross-section that is parallel to the XY plane and passes through the plasma generation region 25. According to a design of the exposure apparatus, the EUV light generation system 11 may have an obscuration area OA. The obscuration area OA may be a part of a beam region of EUV light that is not used for exposure. In this case, even in an optical path of the EUV light, ion catchers 5m and 5m may be provided in the obscuration area OA. As shown in FIGS. 15A and 15B, a part of the tubular member 40 may be located inside the chamber 2. The part of the tubular member 40 may further be located in the obscuration area OA. This allows the first end of the tubular member 40 to be located near the plasma generation region 25. This allows the tubular member 40 to efficiently collect the ions contained in the plasma generated in the plasma generation region 25. FIGS. 16A and 16B are partial cross-sectional views illustrating a configuration of an EUV light generation system 11 according to an eighth embodiment. FIG. 16A illustrates a cross-section that is parallel to the ZX plane and passes through the plasma generation region 25. FIG. 16B illustrates a cross-section that is parallel to the XY plane and passes through the plasma generation region 25. In the eighth embodiment, too, ion catchers 5n and 5n may be provided in an obscuration area. As shown in FIGS. 16A and 16B, the tubular member 40 may be located inside the chamber 2. A part of the tubular member 40 may be located in the obscuration area OA. This allows the first end of the tubular member 40 to be located near the plasma generation region 25. This allows the tubular member 40 to efficiently collect the ions contained in the plasma generated in the plasma generation region 25. A collision unit 42a may be provided at the second end of the tubular member 40. The collision unit 42a may be provided with a plurality of deep grooves that are triangular in cross-section, and may be identical in configuration to the ion catcher 5a illustrated in FIG. 2 and FIGS. 3A to 3C. This allows the tubular member 40 to efficiently collect the ions even when the tubular member 40 has such a length as to fall within the chamber 2. According to the eighth embodiment, the tubular member 40 does not need to be disposed in the bores of the magnets 6a and 6b. This may prevent the tubular member 40 from becoming an obstacle, for example, to moving and replacing the chamber 2 with respect to the magnets 6a and 6b. 11. Shapes of Tubular Members FIGS. 17A to 17I illustrate variations in the shapes of the tubular members 40 that are used in the embodiments described above. In each of the embodiments described above, a case has been described where the shape of the tubular member 40 is a cylindrical shape. However, the present disclosure is not limited to this case. In each of FIGS. 17A to 17I, the first end of the tubular member 40 may be shown on the upper side of the drawing, and the second end of the tubular member 40 may be shown on the lower side of the drawing. Instead of having a cylindrical shape such as that shown in FIG. 17A, the tubular member 40 may have a tapered shape such as that shown in FIG. 17B. Alternatively, as shown in FIG. 17e, the first end of the tubular member 40 may be partially closed except for a small opening 40c. As shown in FIG. 17D, the tubular member 40 may be bent. As shown in FIGS. 17E and 17F, the tubular member 40 may include conical surfaces. In FIG. 17E, the tubular member 40 may have its second end depressed in a conical shape. In FIG. 17F, the tubular member 40 may have its second end projecting in a conical shape. As shown in FIG. 17G, the shape of the tubular member 40 may be a polygonally-columnar shape. Alternatively, as shown in FIG. 17H, the tubular member 40 may include polygonally-pyramidal surfaces. Alternatively, as shown in FIG. 17I, the tubular member 40 may have a polygonally-pyramidal shape. The above-described embodiments and the modifications thereof are merely examples for implementing the present disclosure, and the present disclosure is not limited thereto. It will be clear to those skilled in the art that making various modifications according to the specifications or the like is within the scope of the present disclosure, and other various embodiments are possible within the scope of the present disclosure. The terms used in this specification and the appended claims should be interpreted as “non-limiting.” For example, the terms “include” and “be included” should be interpreted as “including the stated elements but not limited to the stated elements.” The term “have” should be interpreted as “having the stated elements but not limited to the stated elements.” Further, the modifier “one (a/an)” should be interpreted as “at least one” or “one or more.”
054616476	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to the drawings, it is seen in FIG. 1 that the invention is generally indicated by the numeral 10. The invention is a drive tool for engaging and driving the reusable locking arrangement between the guide tubes and the upper end fitting illustrated in FIG. 6. Drive tool 10 is generally comprised of driver 12, wrench 14, and positioner 16. Driver 12 is formed from a shaft with a first end that has a larger diameter than the remainder of the shaft. Drive head 17 is received on the first end of driver 12 to provide an attachment point for tool extensions. The transition to the smaller diameter forms a shoulder that accommodates a thrust washer 18 that is received on the shaft from the second end. Thrust washer 18 serves to help maintain spring 20 in its installed position over the narrower diameter of the shaft. A radial notch and axial slots in communication with the radial notch are provided a selected distance from the tapered end. Radial notch 22, best seen in FIGS. 4 and 5, is formed by a reduced diameter section. Four axial slots 24 are provided that begin at radial notch 22 and extend toward the second tapered end of the shaft. Axial slots 24 are spaced ninety degrees apart around the circumference of the shaft. Wrench 14, seen in FIGS. 1 and 2, is attached to the shaft in a suitable manner such as by a roll pin 26 that is inserted through the shaft and wrench 14. This will result in corresponding rotation of wrench 14 with driver 12. Wrench 14 is provided with slots at its lower end, four in the preferred embodiment, that are equally spaced apart around the circumference. Slots 28 are sized to cooperate with the collar of the locking arrangement on the guide tubes and upper end fitting illustrated in FIG. 6 and will be further explained below. Positioner 16, seen in FIG. 1, is attached to driver 12 at radial notch 22 and axial slots 24 for positioning wrench 14 and for allowing selected axial and rotational movement of driver 12 relative to positioner 16 when in position on the upper end fitting. The upper end of positioner 16 is provided with a circular bore sized to slidably and rotatably receive the shaft of driver 12. Bushing 30 is received on the shaft between positioner 16 and spring 20. The lower end of positioner 16, seen in FIG. 3, is provided with slot 32, the purpose of which will be explained below. Set screw 34 is threaded through positioner 16 so as to be slidably received in radial notch 22 and any of axial slots 24 depending upon the position of driver 12, as seen in FIGS. 4 and 5. This provides for movement of driver 12 relative to said positioner 16 between a first normal position where set screw 34 is located at the end of one of the axial slots 24 distant from the radial 22 notch and a second operational position where set screw 34 is located in the radial notch 22 for rotation of driver 12. In operation, the tapered end of driver 12 is inserted into the quick disconnect collar 36 seen in FIG. 6 with upper end fitting 38. Drive tool 10 is lowered until slot 32 on positioner 16 is seated on one of the grillages 40 and aligns slots 28 in wrench 14 with projections 42 on quick disconnect collar 36. Driver 12 is in its first normal position at this time. Downward pressure against spring 20 causes driver 12 to move to its second operation position and causes engagement of wrench 14 with projections 42. FIGS. 4 and 5 illustrate the operation of set screw 34 during downward movement of driver 12. Axial slots 24 interact with set screw 34 to prevent rotation of driver 12 until it has moved downwardly enough such that set screw 34 is received in radial notch 22, which then allows rotation of driver 12. Driver 12 is then rotated ninety degrees to unlock the quick disconnect collar 36 from upper end fitting 38. Spring 20 forces driver 12 back to its first normal position after ninety degrees of rotation unless downward pressure is maintained. This provides a means of positive indication to the operator that drive tool has been used properly to unlock or lock the quick disconnect collar 36 from the upper end fitting 38. It should be noted that FIG. 6 illustrates all quick disconnect collars 36 in the locked position and that drive tool 10 may be selectively used to rotate quick disconnect collars 36 between either their locked or unlocked positions on upper end fitting 38. This eliminates the need for separate tools for locking and unlocking the upper end fitting 38 in place as in the past. Interaction between set screw 34, slots 24, and notch 22 serve to prevent unwanted rotation of driver 12 when in the first normal position and to help provide positive ninety degree rotation during operation.
	description	This application claims the benefit of U.S. provisional application entitled POLYCAPILLARY OPTIC, application No. 61/515,853 filed on Aug. 6, 2011, and of U.S. patent application entitled X-RAY GENERATOR WITH POLYCAPILLARY OPTIC, application Ser. No. 13/051,708 filed on Mar. 18, 2012, which is a continuation of U.S. patent application entitled X-RAY GENERATOR WITH POLYCAPILLARY OPTIC, application Ser. No. 12/421,907 filed on Apr. 10, 2009, which claims priority to U.S. provisional application entitled X-RAY GENERATOR WITH POLYCAPILLARY OPTIC, application No. 61/044,148 filed on Apr. 11, 2008, the entirety of all mentioned applications being hereby incorporated by reference. The present invention relates systems for generating and controlling the beam direction of x-ray radiation for analytical instruments including x-ray diffractometry, x-ray spectrometry or other x-ray analysis applications using polycapillary optics. X-rays and neutrons are an effective probe medium for evaluation of many features of materials. X-ray diffraction, spectrometry and microscopy are widely used for materials structure and composition measurements. Many applications require an x-ray beam having controlled beam characteristics in its interaction with the target, and some of them need an x-ray optic for an analysis of the beam after its interaction with the material sample. A variety of x-ray optics is in use in analytical instruments. One of the x-ray optics that is in quite wide use is a glass polycapillary optic. The glass polycapillary optic comprises a bundle of hollow glass fibers arranged in some specific way. These hollow fibers guide x-rays entering them, and by total external reflection, the x-ray beam is transmitted along the fiber. Various polycapillary optic designs exist for focusing an x-ray beam, collimation, and the like. A polycapillary optic can be used in a wide range of x-ray photon energies, but in the range of laboratory photon energies (5 to 25 keV) it has various benefits. It can provide a uniquely large geometrical solid collection angle up to several tens of steradians, which provides an efficient use of the x-ray energy emanating from the source. Further, the polycapillary optic can shape the beam in three dimensions. These two features make polycapillary optics a preferred component of x-ray optics. An alternative arrangement can be provided with a crystal bent in two planes, but its capturing capabilities are lower due to limitations of angular acceptance in the diffraction plane of a Johann crystal. A polycapillary focusing optic is preferably used in applications that do not require a high beam monochromaticity and can utilize a beam with a high convergence. Similarly, polycapillary collimating optics can provide a beam of large size and flux when requirements for the beam divergence are not too high. Many analytical applications are suitable for polycapillary optics, and polycapillary optics are in wide use in micro x-ray fluorescence analyzers, x-ray diffractometers for stress and texture analysis, and many other applications. The technology of glass polycapillary optic fabrication progressed significantly since their first use. A variety of optical arrangements and shapes can be produced. An opening lumen of a single capillary and the wall thickness can vary in a wide range, down to a micrometer-scale capillary diameter. On the other hand, a glass polycapillary optic is not free from some principal and technological limitations. Capillary technology is currently limited to glass material formed in a high-temperature process. Currently, there is no technology available for a good control of mid and high spatial frequency roughness of the internal wall surface during this process. Absent a metrology for measuring the roughness directly, representative results of the roughness are currently obtained through modeling the optic with the different roughness parameters and comparing the results with experimental data. These results show that the internal capillary structure is not perfect. Further technology refinements may improve these parameters, but the internal surface roughness may affect optical efficiency well into the future. A single capillary optic may be used as well, although not as universally as a glass polycapillary optic. Several typical shapes of single capillary optics are particularly common. A straight single glass capillary is commonly used to form an x-ray beam with a predefined beam cross section and divergence. One advantage of a single straight capillary over a system with two pinholes is that the part of the beam that passes the first pinhole, but would miss the second pinhole, is retained in the optical path of the single capillary by total external reflection from the capillary walls. The mechanism of radiation penetration through the straight capillary is the same as for polycapillary systems, utilizing multiple total external reflections. Similarly, conical single glass capillary can be used to concentrate x-ray radiation. A single total external reflection can be utilized in a capillary with a more sophisticated internal shape, for instance an ellipsoidal configuration. These kinds of optics are typically not made exclusively of glass, but include other materials. One more specific device that provides x-ray beam with a width on a nanometer scale in one dimension is an x-ray waveguide. The coupling and propagation of radiation through this device is described in the terms of wave theory. The design condition could, however, be formulated in physical-geometrical terms for a three-layer symmetric structure: θCc>θCg, where θCc and θCg are critical total external reflection angles of outside cladding (θCc) and of guiding layers (θCg). Similarly to the polycapillary glass optic, single capillary optics will benefit from a better surface precision and smoothness. It is thus desirable to find novel alternatives to glass capillaries for further improvement of the optical efficiency of x-ray photon and neutron guides. According to a first aspect of the present invention, a device for guiding a beam originating a beam source comprises at least one nanotube with a shape that changes at least the beam shape or the direction of a beam propagating through the nanotube. According to a further aspect of the present invention, the at least one nanotube may be partly or wholly made of carbon. The dimensions may be chosen for guiding x-rays or a neutron beam. According to a further aspect of the present invention, the at least one nanotube is preferably oriented in a way that the optical entrance points toward the beam source. For shaping the beam, the at least one nanotube may, for example, have a section with a decreasing inner diameter or a conical interior surface proximate the optical exit. The interior diameter may decrease from the optical entrance toward the optical exit for enhancing the beam density. According to a further aspect of the present invention, a multilayer nanotube having a plurality of coaxial cylindrical walls decreases photon losses compared to a single-wall nanotube. The material of the multilayer nanotube can be chosen to provide layers of the same material or of different materials. One or more of the walls may consist of carbon. Where the walls consist of different materials, the materials may be arranged in an order in which a critical total external reflection angle of successive walls increases in a radially outward direction from the central axial line. According to a further aspect of the present invention, the internal diameter of a multiwall nanotube may be altered by adding or removing inner walls. According to a further aspect of the present invention, colossal nanotubes are suitable for photon wavelengths with a larger critical total external reflection angle than hard x-rays. According to a further aspect of the present invention, the device according to the invention may comprise a bundle of self-assembled nanotubes. At least a portion of the nanotubes of the bundle may be multilayer nanotubes having a wall thickness that varies along the length of the nanotube due to a change in the number of coaxial walls. According to a further aspect of the present invention, a smaller outer diameter and a smaller number of coaxial walls at the optical entrance than remote from the optical entrance increases the clear aperture of the nanotube bundle at the optical entrance. According to a further aspect of the present invention, the nanotube bundle can be grown by simultaneous propagation from a growth plate, particularly from a spherical growth plate for receiving a beam from a point-shaped beam source. Further details and benefits of the present invention become apparent from the subsequent description of several preferred embodiments illustrated in the attached drawing figures. Entirely new tubular structures developed during last two decades are called nanotubes. The name nanotube refers to the thickness of these tubes that is typically in a sub-micrometer range. Several properties specific to the nanostructure of these tubes have contributed to a variety of new product applications: as light and electron emitters, as reinforcement for industrial and construction materials, as thermoconducting medium for heat transfer, and many others. C (carbon) is the most common element of these structures, but nanotubes from other materials such as boron nitride, silicon oxide, and rare earth fluoride have been fabricated, as well. This variety suggests that a relatively wide selection of materials of varying effective atomic numbers may be available. As illustrated in FIGS. 1 through 3, a carbon nanotube can be described as rolled graphene sheets with seamlessly connected edges. As graphene is a single layer of carbon atoms arranged in a honeycomb pattern 16, a nanotube possesses a so-called chirality that is determined by the direction in which the graphene sheet is rolled up and that characterizes the orientation of the hexagons 12, 12′, and 12″ forming the honeycomb pattern 16. FIG. 1 illustrates a so-called “armchair” structure of a carbon nanotube 10, in which the hexagons 12 each have a pair of opposing sides 14 that extend in the circumferential direction of the nanotube. FIG. 2 is an example of a nanotube 10′ with a so-called “zigzag” structure, in which the hexagons 12′ each have a pair of opposing sides 14′ extending in the axial direction of the nanotube 10′. FIG. 3 depicts a nanotube 10″ with an intermediate chirality, in which the hexagons 12″ have neither purely axial nor purely circumferential sides. Nanotubes can be grown by self-assembly. Methods of growing nanotube from a growth plate include chemical vapor deposition on coated silicon substrates using various catalyst films. The growth of nanotube by self-assembly creates nanotubes with walls including interior wall surfaces that are smooth to the atomic level, similar to an atomic plane of a perfect crystal. As will be explained in more detail below, the use of self-assembled carbon nanotubes in polycapillary systems for x-ray optics can be sufficiently described with macroscopical considerations. Therefore, polycapillary structures for x-ray optics can utilize nanotubes of any chirality. In the following, single-wall nanotubes will be designated with reference numeral 10, regardless of individual chiralities. Furthermore, in the subsequent figures, a specific chirality may be depicted for purely illustrative purposes. Any shown chirality can be replaced with any other chirality without leaving the scope of the present invention. For producing a polycapillary optic, individual carbon nanotubes 10 can be arranged in bundles as illustrated in FIG. 4. The most compact arrangement of cylindrical nanotubes 10 is obtained in a hexagonal structure as illustrated. This arrangement also minimizes gaps 18 between the nanotubes 10 that lead to a photon loss of an incoming x-ray beam. Nanotubes can be produced as single-layer or single-wall nanotubes or as multi-layer or multi-wall nanotubes. A single-wall nanotube 10 has one layer of carbon atoms as shown in FIGS. 1-4. A multi-wall nanotube 20 has a plurality of concentric nanotubes 22, 24, and 26 arranged inside each other. FIG. 5 illustrates such a multi-wall nanotube 20 consisting of the three single-wall nanotubes 22, 24, and 26. In an ideal multi-wall nanotube 20, the individual layers 22, 24, and 26 of carbon atoms do not share any covalent bonds with each other so that the carbon atoms are connected by much higher forces within one layer than with carbon atoms occupying a different layer. Multilayer carbon nanotubes, for example, have been successfully grown via vapor deposition on a tungsten-coated silicon substrate with a sputtered nickel catalyst film. In an atmosphere of nitrogen and acetylene gases, temperatures ranged between 630 and 790° C. Diameters of the multiwall nanotubes are adjustable by varying the substrate temperature. As illustrated in FIG. 6, colossal nanotubes 30 resemble multiwall nanotubes 20 with large diameters D ranging between about 40 μm and about 100 μm, in which the individual concentric layers 32 and 34 of the colossal nanotube are interconnected with radial webs 36 of graphene extending along the length of the colossal nanotube 30. These webs 36 stabilize the nanotube structure and are usually arranged at a distance from each other that approximately corresponds to a typical distance of graphene layers in graphite so that longitudinal channels 38 are formed between the concentric graphene layers 32 and 34 of the colossal nanotube 30. The channels 38 have an approximately rectangular or trapezoid cross-section. Colossal nanotubes 30 as shown in FIG. 6 could be used as a basic optical element for relatively low energy photons that have a larger critical angle of total external reflection than high-energy photons. Colossal nanotubes 30 are relatively stable and thus are suitable for use in a single capillary optic. Alternatively, colossal nanotubes 30 could be a part of a polycapillary optic for soft x-rays because their diameter is typically larger than what is considered optimal for x-rays of a shorter wavelength that undergo total external reflection only at small incident angles. The following considerations are applicable to conventional polycapillary optics and polycapillary nanotube structures alike. Polycapillary optics are primarily used for focusing or for collimating an x-ray beam. FIGS. 7A and 7B show focusing optics 40 and 50 utilizing a polycapillary arrangement. The arrangement of FIG. 7A is configured for a point-shaped beam source 42, while the arrangement of FIG. 7B is configured to focus a parallel light beam 52. FIG. 7C illustrates a collimating optic 60 that transforms light originating from a point-shaped beam source 42 into a parallel light beam 52. Notably, the collimating polycapillary optic 60 of FIG. 7C is in principle an inverted focusing optic 50 for a parallel light bundle as illustrated in FIG. 7B. While in the following, the description may refer to a light source or a light wave, it should be understood that the term “light” is used in a broad sense to include beams of particles that behave in a similar way as photons or neutrons and should not be viewed as a limitation to electromagnetic waves. Likewise, any description referencing photons or x-rays is also applicable to other particles exhibiting similar behavior. A total external reflection inside a capillary occurs in that an incident light wave penetrates an interior capillary wall from inside lumen of the capillary and is redirected back to the interior surface. Total external reflection is a phenomenon observed with x-ray-like radiation because for x-ray-like wavelengths, many materials have a real component of the refractive index that is smaller than 1. After total external reflection, the light wave leaves the medium at an angle identical to the incident angle of the light wave. The wave intensity distribution inside the medium is described in an exponential function of the distance from the surface of the medium. The penetration depth Z0 describes the depth under the geometrical medium surface where the wave intensity is reduced to 1/e. “e” is the dimensionless Euler Number, which approximately equals 2.7182. A so-called multi-bounce polycapillary optic, referring to multiple reflections inside a capillary, works most effectively under the condition that the entire range of incident angles of incoming photons remains below the so-called critical angle θC of the medium material. In this context, the critical angle θC is the threshold angle for total reflection measured from a plane tangential to the reflecting surface. This definition for capillary systems differs from the typical definition of the term “incident angle” when used in classic optics dealing with total internal reflections on a plane. The mentioned penetration depth Z0 in this range of incident angles does not depend on any x-ray photon energy and is entirely defined by the medium material, mostly its mass density. The penetration depth Z0 decreases from 4.1 nm for carbon, through 3.2 nm for glass to 1.2 nm for heavy metals. FIGS. 8A and 8B illustrate different propagation modes inside a multi-bounce capillary 70. Each single capillary 70 of a polycapillary optic can be bent to deflect an x-ray photon 72 or 74 from its initial incident direction to the direction desirable at the optical exit of the capillary 70. For a clarity and simplicity, the following considerations apply to the principle of a collimated optic 60 depicted in FIG. 7C. The capillary ends proximate the beam source 42 are preferably aligned to point toward the point-shaped beam source 42, and the opposite ends of the capillary are parallel for collimation. This means that each capillary 70 is bent to a specific curvature that depends on its radial distance from the center axis X of the optic 60, in the following called the optical axis X. The following condition that restricts the radius R of the capillary curvature to ensure that all reflections occur at angles below the critical angle:R≧2d/θC2 (1)where d is the capillary diameter, θC is the critical angle of total external reflection measured from a plane tangential to the reflecting surface. This expression is a base for a capillary optic design for avoiding a significant photon loss during photon propagation. Another consideration is that two different modes of photon propagation occur in a multi-bounce optic, depending on the radius of the capillary curvature shown in FIGS. 8A and 8B. FIG. 8A illustrates a straight or “slightly” bent capillary 70. The multiple reflections occur in an alternating manner on opposite sides of the capillary wall in a so-called double-wall reflection mode. As shown in FIG. 8B, in a capillary 70 bent with a smaller radius R, reflections occur repeatedly on the same side of the capillary wall in a so-called garland reflection. Depending on the prevailing conditions, the total number of reflections and thus the photon loss during transmission varies. Accordingly, any quantitative description of polycapillary lens performances depends of the mode of propagation. A simple geometrical analysis suggests that the condition of the transition from one mode to the other is:θtr=(2d/R)1/2 (2) where θtr is the incident angle of a photon entering a capillary with the opening diameter d and a curvature with a bending radius R, at which a transition from the double-wall mode of FIG. 8A to the garland mode of FIG. 8B occurs. This observation applies to incident angles θ measured from a plane tangential to the reflecting capillary wall. If the incident angle θ of a photon hitting the outer wall of the capillary with radius R is greater than θtr, the double-wall reflection mode of FIG. 8A applies, while the garland reflection of FIG. 8B occurs if θ is smaller than θtr. This means that both modes are typically present in the polycapillary optic because capillaries located at a larger radial distance from the optical axis X have a locally smaller bending radius R than those close to the optical axis X. While the bending radius R may change over the length of a capillary 70, a useful simplification for approximate calculations assumes a constant bending radius R over the length L of the capillary 70. Because in a circularly bent capillary 70, the photon incident angle θ does not change, the mode of propagation remains the same during propagation. For calculating a capillary transmission, the number of reflections and the reflectivity should be known as functions of the incident angle θ. A simple geometrical analysis suggests that the number of reflections N in the garland reflection mode of FIG. 8B is defined by the expression:N=L/(R2θ) (3)where L is the length of the capillary. The quantity of reflections N in double-wall reflection mode is defined by the expression:N=L/(R(θo−θi)) (4),where θo and θi are incident angles on outside (concave) and inside (convex) walls of the capillary. The outside and inside incident angles θo and θi are related to each other according to the equation:θo2=θi2+2d/R (5) Two notable observations result from the expressions (3)-(5). First, the expression (4) results in N=L/(Rθ) when the inside angle θi approaches zero and the outside angle is represented by the angle θ. This expression coincides with the quantity of reflections in a straight capillary. Second, the expressions (3) and (4) suggest that the quantity of reflections change with a step at θtr: if one considers a transition from smaller θ (garland reflection) to larger θ (double-wall reflection), the number N of reflections doubles from L/(R2θ) to L/(Rθ). Notably, however, the reflectivity as a function of the incident angle θ changes smoothly because the incident angle θ on the convex interior wall is equal to zero at the point of transition and the reflectivity is 100% at an incident angle θ equal to zero, independent of the material of the reflecting wall. Single reflection reflectivity as a function of the incident angle θ other than zero can be calculated using Fresnel formulas through physical constancies of the materials. The considerations above are sufficient for calculations of a collimating capillary lens transmission with the following simplifying assumptions: Only rays propagating in a two-dimensional axial plane containing the optical axis are considered; and the size of the point-shaped beam source in the focal spot is negligible. A single-wall nanotube 10 provides a limited reflectivity at total reflection angles because it includes only one atomic layer of carbon atoms arranged in a honeycomb pattern 16. The single layer does not provide the penetration depth Z0 of 4.1 nm given above for carbon. Also, the value of 4.1 nm for the penetration depth Z0 does not mean that a nanotube wall of such thickness reflects all incident light. According to the definition of the penetration depth Z0 above, a layer with the thickness of Z0 reflects only a portion of 1-1/e (or 63%) of the photons compared to an infinitely thick layer. This level of reflectivity is dissatisfactory for optics involving multiple reflections. To avoid a significant loss of efficiency due to a finite wall thickness, the loss of reflectivity is preferably very small. If for a given incident angle θ and for a given energy, the reflectivity of a medium of infinite thickness is ρ, then a photon flux loss attributed to a single reflection on the infinitely thick wall is (1−ρ). To obtain a finitely thick wall for which the additional loss of reflectivity due to the finite thickness is smaller than that value (1−ρ), the following approximate qualitative assessment can be made. The minimal thickness T of the walls could be calculated as:T=Z0In(1/(1−ρ)) (6),where Z0 is the penetration depth. A wide range of incident angles, from zero to the critical angle are typically present when a beam propagates through a multi-capillary optic. The number of reflections inside the capillary depends on the initial incident angle, capillary bending and the mechanism of propagation. Some criterion for the choice of the wall thickness will be given below. As an example, to limit the reflectivity loss due to the finite wall thickness to an amount equal to the photon loss at a single reflection with the incident angle of θC/2 from a wall with infinite wall thickness, the wall thickness T should be 30 nm for silicon oxide nanotubes and 37 nm for carbon nanotubes. This means that for obtaining high reflectivity and transmission, nanotubes can be configured to have multiple walls, possibly hundreds. The number of concentric walls may vary. In the following, the contemplations on polycapillary optics are applied to nanotubes arranged in a collimating optic as illustrated in FIG. 7C. For the following calculations, three approximations are made: The distance from the source to the optical entrance is 4 mm; the nanotube bending radius R is constant and the internal diameter d is constant along the nanotube length L. The resulting lens design parameters and transmission are given in Table 1 below. TABLE 1Lens design parameters and performances summaryNanotube MaterialSilicon oxideCarbonRadiationCuMoCuMoWavelength rangenm0.1520.710.1520.71Tube openingnm144148176191Tube wallnm28.829.735.238.2thicknessLens entrancemm2.92.92.92.9diameterLens exitmm7.927.112.049.7diameterLens lengthmm7.244.815.389.0Transmission0.2880.4250.6690.713Transmissionmm−25.92E−037.37E−045.87E−033.68E−04area density For a rough assessment under even unfavorable conditions, a calculation was carried out for lenses with an extremely large capture angle of 1 radian in each plane (a capture angle significantly larger than typically considered for casual glass lenses). The results show that the lens transmission reaches a useful value, even under these extreme conditions. A high-yield transmission and a compact design of nanotube-based polycapillary optics is possible by using very small capillary diameters d, preferably less than 200 nm. It is further evident from the calculation that carbon nanotubes promise a higher transmission in the considered range of photon energies as a result of a higher reflectivity of material with a lower effective atomic number. The parameter denoted in the table as transmission area density is the ratio of the lens transmission and the area of the beam at the lens exit. A higher value of this parameter represents a higher flux density at the lens exit, which may be desirable for some applications. Silicon oxide nanotubes promise a higher value of this parameter with Molybdenum (Mo) radiation. This means that the lens design parameters and material can be matched for optimal performance for a given application. It is possible to compare these results with the predictions for a traditional glass polycapillary lens. Applying the above-described model to an ideal glass capillary lens having an ideal wall surface without waviness or misalignment of capillaries and with an generous capillary diameter of 1.5 μm, about ten times larger than that of the nanotube lens for Cu radiation, and a wall thickness of 0.1 μm, the calculated transmission area flux density is about 50 times lower than for the nanotube lens. With these parameters, the improvement of a nanotube optic over any real glass polycapillary optic with imperfections on internal walls will likely be more than two orders of magnitude. In all examples, the photon wavelength is at least 1000 times smaller than the capillary diameter. These proportions suggest that a simple geometrical assessment should provide reasonable predictions. A bundle of multiwall nanotubes can be used to form a lens that shapes an x-ray beam. FIG. 9. shows a partial schematic cross-section through such a nanotube bundle. The transmission calculation above counts the photons that hit an internal wall 82 of one of the bundled nanotubes 30 once the photons have entered the nanotube 30. But the entrance of a nanotube bundle has areas of photon loss caused by two factors. First, the nanotubes have a finite wall thickness T, and the ratio between the open nanotube cross-section A (the lumen) and the wall cross-section W, indicated by hatching in the drawing, defines the clear nanotube aperture. For this example, it is assumed in the calculations that the ratio K of the inner nanotube diameter d and its wall thickness T is five. The clear nanotube aperture is about 51% in this case. With larger K value, for example with K=10, the clear nanotube aperture can be increased to about 69%, but this will approximately double the lens dimensions and will reduce the flux density of the collimated beam. Second, there is empty space 18 between the tubes. The packing coefficient for a hexagonal circular tube arrangement is about 91%. So, to find a lens efficiency the value of transmission given in the table above has to be multiplied with the clear aperture factor of about 0.46, corresponding to the product of 51% and 91%. Still, even an efficiency in the range of about 0.1-0.3 (equal to about 10-30%) is attractive for the large solid capture angle of about 1 steradian on which the calculations above were based. Nanotube technology made a tremendous progress since the discovery of nanotubes. Because of numerous promising applications of nanotubes, especially carbon nanotubes, multiple growth mechanisms and specific technological steps have been developed and implemented. Some of them are relevant for nanotube x-ray optics and are described below. Nanotubes from a variety of materials as carbon, polystyrene, boron nitride, silicon oxide, fluoride of rare earth elements, can be produced in large quantities. Nanotubes can be grown in a consistent structure and in compact bundles. The combination of several technological approaches allow to design and build a nanotube based device for guiding x-ray photons and neutrons with features and performances not achievable with traditional glass capillary technology. A preferred device for guiding x-ray photons and neutrons utilizes self-assembled nanotubes for total external reflection of photons or neutrons. One major advantage of self-assembled nanotubes as a photon-guiding element is their smooth surface on an atomic level. Further, the possibility to control their growth in a predictable manner allows a precision that exceeds the quality of traditional glass capillary technology. Multiwall nanotubes 90 as shown in FIG. 10 can be grown with a controllable inner diameter d and wall thickness T. Of particular interest may be a configuration of multiwall nanotubes 90 with specific adjusted positions of subsequent outer layers wi as shown in FIG. 11. The multiwall nanotubes can be grown with a specified spacing from each other and in a direction normal, i.e. perpendicular, to a growth plate. For assembling a photon-guiding nanotube the axes of nanotubes will be aligned precisely along the propagation directions of an incoming beam. As previously illustrated in FIGS. 7A through 7C, two cases occur most often: a parallel incoming beam and a point source. For a parallel incoming beam, parallel nanotubes can be grown from a planar growth plate. The axes of the self-assembling nanotubes are all perpendicular to the growth plate surface and can be distributed evenly across the growth plate. The nanotube growth perpendicular to the growth plate provides that their axes are parallel, at least in the vicinity of the growth plate. For obtaining a divergent bundle of nanotubes 90, the nanotubes 90 can be grown from a spherical growth plate 92 as shown in FIGS. 10 and 11. This setup allows proper positioning of the entrance side of the nanotube assembly intended to capture radiation from a point-shaped x-ray source 42. To initiate nanotube self-assembly intended for coupling with a point-shaped beam source, the base growth plate shape can be spherical as it is shown in FIGS. 10 and 11. The area adjacent to the growth plate is shown in FIGS. 10 and 11 as zone 1. All tube axes x1, x2, and x3 converge to the spherical center of the growth plate 92. Remote from the growth plate, the nanotubes 90 may have a bent shape so that the central axes xi form bent central axial lines. After removal of the growth plate 92, a point-shaped beam source 42 is placed preferably in the location of the spherical center with respect to the nanotubes 90. The point-shaped beam source 42 is thus located in the point at which the central axial lines projecting from the nanotubes intersect. For any other angular distribution of an incoming beam, the growth plate can be shaped to form a growth surface normal to the respective ray direction at each surface point. Without limitation, the following example refers to a nanotube assembly design intended for guiding a diverging beam originating from a point-shaped beam source 42. The description below applies in analogy to any other diverging beam. The minimal internal nanotube diameter that can be grown in this manner ranges in the order of magnitude of about 1-2 nm. The internal nanotube diameter d for an x-ray photon guide is preferably about a hundred times larger than the minimal nanotube diameter. The reason for such dimension is that the suitable wall thickness T providing a sufficient total reflection is in the order of tens of nm. Thus, for obtaining a favorable clear nanotube aperture, the internal nanotube diameter d is preferably chosen to be five to ten times larger than the wall thickness T. Implementing a larger tube diameter d leads to a larger bending radius R, larger device dimensions and a reduced flux density. To improve the flux density, a procedure can be used that allows improving the clear aperture of the lens without increasing overall lens dimensions. The resulting structure is shown in FIG. 11, designated as zone 2. The ends of the external layers wi of each multiwall nanotube 90 are displaced relative to each other. In zone 1, the nanotube growth starts with an initial thickness T1 and layer w1 forming the outermost layer of the nanotube 90. With increasing distance from the growth plate 92, outer layers w2, w3, w4, w5, and so on, are added to each nanotube 90, increasing the wall thickness T from T1 to T2, to T3, T4, T5, etc., until the individual wall thickness T of each nanotube 90 is sufficient for reducing photon losses to an acceptable level. This procedure allows a gradual increase of the nanotube wall thickness T while keeping the internal nanotube diameter d small. The initially small wall thickness T1 is advantageous at the entrance of a multiwall nanotube 90 because the percentage of the open aperture relative to the occupied growth plate surface is increased compared to nanotube bundles with a constant wall thickness T. The thinner nanotube wall thickness T1 at the very entrance in zone 1 and zone 2 has a negligible effect on the intensity of the overall transmission because very few reflections occur in this area. At greater distances from the growth plate 92, an optimal nanotube wall thickness T can be chosen to support a high reflectivity for thousands of reflections. Accordingly, the nanotube wall thickness T can, for example, start at about four to five times the above described penetration depth Z0 (about 4 Z0 to 5 Z0) at the growth plate in zone 1 and gradually increase to about 10 Z0 or 20 Z0 in zone 2 without reducing the clear nanotube aperture. The increasing number of layers wi in zone 2 of FIG. 11 is not representative of the actual number of layers wi of each nanotube 90, which is much greater when the wall thickness T corresponds to multiple penetration depths Z0. In a preferred embodiment, the wall thickness T increases at a rate that compensates the increasing distances between the nanotubes 90 as the nanotubes progress from the growth plate 92 along radially extending central axial lines x1, x2, and x3. In this manner, the neighboring nanotubes 90 touch each other with their outer layers wi at each added layer wi of wall thickness T. Due to the contact among the nanotubes 90, zone 2 of the assembly near the growth plate is rigid and well defined. The rigidity of nanotube assembly facilitates a removal of the assembly from the growth plate 92. Once the desired wall thickness T has been reached, the individual nanotubes 90 can separate from each other and progress along separate paths. as indicated in FIG. 10. This feature combined with the self-assembling growth mechanism allows a precise positioning of all nanotubes 90 in the assembly. A similar precision is likely not achievable with technology for manufacturing polycapillary optics made of glass. Another preferred configuration of a nanotube assembly concerns an improvement to the flux density of the outgoing beam and a reduction of the beam divergence at the assembly exit where a quasi-parallel outgoing beam is desirable. To reduce the beam divergence, a capillary system commonly includes a conically expanded part, often forming the exit portion of each capillary. It is known that a photon, after incurring multiple reflections on such conical surface, propagates at a reduced angle relative to the central axis of the cone. In glass polycapillary designs, this conical capillary expansion is often combined with capillary bending. This is not always an optimal approach for reducing the beam divergence in a nanotube assembly. As described above, two mechanisms of photon propagation are present in a polycapillary optic such as a nanotube assembly. The most frequently occurring mechanism in optics with a high capture angle is the garland reflection. Expanding the nanotube diameter will not reduce the incident angle for photons propagating in the garland mode because these photons are not affected by any angle between opposite walls of the nanotube. It is thus preferable for a nanotube assembly intended for collimating an x-ray beam to have two distinguished areas: one area of nanotube bending, designated as zone 3, where photons might propagate in the garland mode, and another substantially straight area of expanding nanotube diameter, designated as zone 4, as shown in FIG. 12. One technology that is feasible for expanding a nanotube diameter is shown in FIG. 13. An insertion of a heptagon 96 in the honeycomb pattern 16 in the place of one of the hexagons 12 of an otherwise cylindrical nanotube wall leads to a conical expansion of the nanotube 94. A subsequent insertion of a pentagon 98 returns the nanotube 98 to a cylindrical shape of a larger diameter. An effective opening angle α of a sequence of conical expansions, shown in zone 4 of FIG. 12, can be controlled by the arrangement of heptagons 96 and pentagons 98. The number of heptagons 96 inserted around the circumference of the nanotube 94 determines an incremental opening angle of each individual conical expansion. The axial distance from the heptagons 96 to an identical number of pentagons 98 determines the length of the conical expansion, and the axial distance of the pentagons 98 to the next group of heptagons 96 determines the length of an intermediate cylindrical section between two conical expansions. A sequential use of nanotube diameter transitions with defined steps of incremental conical expansions along the nanotube length will create a quasi-conical overall surface with an overall opening angle α composed of incremental opening angles and intermediate cylindrical portions. Each step of the diameter change is smaller than the typical distance between atoms. For an x-ray beam having a wavelength much greater than the distances between atoms, the quasi-conical surface is smooth for the total external reflection mechanism. While FIG. 13 shows a single-layer nanotube 110 with only one expansion step for clarity, the insertion of irregularities can be performed in each one of the coaxial walls of a multi-layer nanotube at predetermined axial distances. Several features are intended for improving nanotubes positioning and arrangement contributing to an improvement in performances of the nanotube assembly. Preferably, an area with constant nanotube diameters is located at the exit of a collimating optic assembly as shown in FIG. 12, zone 5. This feature allows aligning the nanotubes 94 parallel with a high precision by compressing the assembly so that the outer layers of the individual nanotubes 94 touch each other. This allows a proper alignment of the low-divergence beam exiting the conical portion of the tubes in zone 4. An alternative preferred aspect of the present invention is a gradual increase of the nanotube wall thickness T in the bent area, designated as zone 6 in FIG. 14. The configuration of zone 6 is interchangeable with zone 3 shown in FIG. 12. As illustrated in FIG. 14, the wall thickness T of the individual nanotubes 100 in the assembly may be increased by adding outer layers to the extent that the respective outside layers of adjacent nanotubes touch each other before exiting zone 6. This contact provides stability to the precise arrangement of the nanotubes 100 and increases the rigidity of the assembly. The increase of wall thickness T in zone 6, is an extension of the technology described for zone 2, with the modification that the steps of adding layers wi are adapted to the bent state of the nanotubes 100. Where an increased wall thickness is provided in the bent section of zone 6, a different technology can be applied to create the subsequent quasi-conically expanded part, designated as zone 7 in FIG. 14. Zone 7 represents an alternative to zone 4 of FIG. 12. FIG. 14 illustrates zone 7, in which, for an expansion of the interior diameter d of each individual nanotube 100, the respective interior layers of the nanotube can be successively discontinued so that each time an inner layer ends, a previously intermediate layer becomes the inner layer. FIG. 15 illustrates such a successive removal of inner layers wi. Each layer wi retains its constant diameter. The innermost layer w5 of the multiwall nanotube 100 emerging from zone 6 has an inner diameter d5 and ends in a first step at a defined distance from zone 5. Then the next layer w4 with inner diameter d4 ends at the next step in a defined distance from the first step, providing a quasi-conically expanding interior surface designated as zone 7. These steps are repeated with w3 having diameter d3, w2 having diameter d2, and so on, until the wall thickness T and inner diameter d of zone 5 are attained. The reduction in wall thickness T resulting from a single step corresponds to the distance between the layers wi. Each of these steps is larger the previously described steps caused by the insertion of heptagons 96 and pentagons 94 into the honeycomb pattern 16, but the resulting quasi-conical surface can still be considered as smooth for total external reflection for most x-ray wavelengths. The described nanotube-based collimating device can be reversed in a beam path to become a focusing optic for a parallel beam. The above-described zones can be selectively combined in a polycapillary nanotube assembly. For example, for directing radiation from one focal point at the point-shaped beam source to the other focal point may include zones 1 and 2 and zone 6. The outer diameter of the nanotubes may then decrease subsequent to zone 6 in a reversal of zone 2 after the nanotubes have reached a parallel alignment relative to each other. The proper positions and directions of the nanotubes at the exit of the polycapillary optic can be ensured by precise control of the outer diameter of the nanotubes and tight assembly during manufacturing. The inner nanotube diameter could be reduced for a smaller focus with a reverse technology described for zone 4 or zone 7. An alternative way of providing a focusing optic for a point-shaped beam source involves coupling of two collimating nanotube devices with the second device being reversed for focusing the beam that has been collimated by the first device. Different types of couplings can be implemented. A tight coupling with a precise alignment of the two assembles provides that the axes of the nanotubes of both assembles coincide. An alternative way of coupling can occur at a distance equal to or larger than the ratio between the exit internal nanotube diameter of the first device and the beam divergence. At such a distance, the beam distribution has become uniform so that an efficiency loss that may occur due to the clear aperture of the second device is fairly low because the nanotubes have a larger inner diameter at this cross section of the second assembly. Nanotubes with a non-circular cross section could be preferable for forming a beam with a specific shape, for instance “fan” beam. It is known that nanotubes have a much lower strength in the radial direction compared to the axial direction. This feature could be used to change the nanotube shape from circular to oval, for instance by applying radial compression forces to the nanotubes assembly. Another way of achieving non-circular cross sections is using non-circular “seeds” for nanotubes growth on the growth plate. By aligning the nanotubes in a tight nanotube bundle along their length the nanotubes retain their shape obtained at the growth plate. Even a nanotube comprising only a single nanotube positioned at the optical axis or in some bent position can incorporate some of the advanced features described above. As mentioned earlier, multiple versions of single glass capillary designs are used for multiple applications. The nanotube may be able provide a better performance in many situations due to its smooth interior wall and higher reflectivity. Accordingly, applications requiring the beam to have a limited cross section and divergence and that currently use a straight glass capillary can benefit from a straight nanotube. Both multiwall and colossal nanotubes could be used for this application. A nanotube with an ellipsoidal internal surface for a single reflection focusing could be produced with the technology described for manufacturing conical nanotubes with adequate control of internal diameter steps at selected positions and in the desired direction. These nanotube devices may outperform the focusing capability of an ellipsoidal glass capillary due to the enhanced smoothness of their reflecting surfaces. One preferred embodiment of the invention is a waveguide built by implementing nanotube technology. A straight nanotube could function as a waveguide and be effectively coupled via resonant beam coupling or via front coupling modes with a beam having a central symmetry and adequate convergence. Also, two or more nanotubes can be assembled in the manner that a nanotube with a smaller θC is inserted inside a nanotube with a larger θC. This arrangement allows utilizing an incoming beam with a larger angular convergence. The exit end of the device may have a narrowing conical shape with a decreasing diameter for a further beam cross section reduction, both in single-layer and multilayer nanotubes. Various radiation guiding devices based on nanotubes and multiple technological procedures for their implementation were described above. The described useful and implementable details of optical systems based on suitable self-assembling nanostructures serve to design, optimize, and build x-ray and neutron guiding devices. New self-assembling procedures and structures may lead to modifications of the described examples that are evident to a person of ordinary skill in the art. Notably, the term “x-ray photons and neutrons” should not be interpreted in a narrow way. The invention is applicable to all types of charged or charge-less particles, which exhibit the total external reflection mechanism similar to the reflection of x-rays and neutrons. The foregoing description of various embodiments of the invention has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise embodiments disclosed. Numerous modifications or variations are possible in light of the above teachings. The embodiments discussed were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
	summary
	claims	1. A nuclear steam supply system with shutdown cooling system, the nuclear steam supply system comprising:a reactor vessel having an internal cavity;a reactor core comprising nuclear fuel disposed within the internal cavity and operable to heat a primary coolant;a steam generating vessel fluidly coupled to the reactor vessel;a riser pipe positioned within the steam generating vessel and fluidly coupled to the reactor vessel;a primary coolant loop formed within the reactor vessel and the steam generating vessel, the primary coolant loop being configured for circulating primary coolant through the reactor vessel and steam generating vessel; anda primary coolant cooling system comprising:an intake conduit having an inlet fluidly coupled to the primary coolant loop;a pump fluidly coupled to the intake conduit, the pump configured and operable to extract and pressurize primary coolant from the primary coolant loop and discharge the pressurized primary coolant through an injection conduit;a Venturi injection nozzle having an inlet fluidly coupled to the injection conduit and an outlet positioned within the riser pipe to inject pressurized primary coolant into the riser pipe from the pump; anda heat exchanger configured and operable to cool the extracted primary coolant. 2. The nuclear steam supply system according to claim 1, wherein the inlet of the intake conduit is located at a bottom of the reactor vessel. 3. The nuclear steam supply system according claim 1, wherein the inlet of the intake conduit is located at a bottom of the steam generating vessel. 4. The nuclear steam supply system according to claim 1, wherein the inlet of the intake conduit is located at a bottom of the riser pipe. 5. The nuclear steam supply system according to claim 1, wherein the steam generating vessel comprises a steam generating section and a superheater section disposed above the steam generating section in vertically stacked relationship, the superheater section being operable to heat a secondary coolant to superheated steam conditions. 6. The nuclear steam supply system according to claim 5, further comprising:the steam generating section and the superheater section including a pair of vertically spaced apart tubesheets and a tube bundle comprising a plurality of vertically-oriented tubes extending between the tubesheets; andwherein the injection nozzle is positioned so as to inject the pressurized primary coolant into the riser pipe of the steam generating section at or near an elevation of a bottom one of the tubesheets. 7. The nuclear steam supply system according to claim 1, wherein the injection conduit is a pipe having a diameter of approximately 6 inches and wherein the injection nozzle has a diameter of approximately 3 inches. 8. The nuclear steam supply system according to claim 1, wherein injecting the pressurized primary coolant into the riser pipe through the injection nozzle creates a low pressure Venturi effect that causes the primary coolant to flow through the primary coolant loop. 9. The nuclear steam supply system according to claim 1, further comprising:the steam generating vessel including a plurality of stacked heat exchangers fluidly connected in a vertically stacked relationship;the stacked heat exchangers each including a pair of vertically spaced apart tubesheets and a tube bundle comprising a plurality of vertically oriented tubes extending between the tubesheets;wherein upon injecting the pressurized primary coolant into the riser pipe, the primary coolant flows vertically upwards through the riser pipe to a top of the steam generating vessel, vertically downwards from the top of the steam generating vessel through the tubes of the stacked heat exchangers, vertically downwards through a downcomer in the reactor vessel to the bottom of the reactor vessel, vertically upwards within a riser column in the reactor vessel, and from the riser column in the reactor vessel back into the riser pipe in the steam generating vessel; andwherein a secondary coolant flows upwards between the tubes on a shell side of each of the stacked heat exchangers. 10. The nuclear steam supply system according to claim 1, wherein the reactor vessel, the steam generating vessel, and the primary coolant cooling system are positioned within a containment vessel. 11. The nuclear steam supply system according to claim 1, wherein at least a portion of the primary coolant cooling system is positioned external to the reactor vessel and the steam generating vessel. 12. The nuclear steam supply system according to claim 1, wherein the primary coolant cooling system is a one-way fluid flow circuit in which the primary coolant flows from the primary coolant loop through the intake conduit, through the pump, into the injection conduit, through the heat exchanger, further through the injection conduit, and into the riser pipe of the steam generating vessel via the injection nozzle. 13. The nuclear steam supply system according to claim 1, wherein the primary coolant cooling system further comprises a valve that is welded at one end to a forging in the form of an integral piping nozzle of the reactor vessel and at another end to an inner pipe fluidly coupled to the valve and arranged inside an outer pipe that concentrically surrounds the inner pipe, the inner and outer pipes collectively forming the intake conduit. 14. The nuclear steam supply system according to claim 13, further comprising a pressure vessel enclosing the valve, a valve stem of the valve protruding from the pressure vessel, and wherein a connection between the inner pipe and the valve and a connection between the valve and the integral piping nozzle of the reactor vessel are located within the pressure vessel. 15. The nuclear steam supply system according to claim 1, wherein the primary coolant cooling system extracts a portion of the total volume of the primary coolant from the primary coolant loop, the remainder of the primary coolant remaining in the primary coolant loop. 16. The nuclear steam supply system according to claim 1, wherein the pressurized primary coolant from the injection nozzle mixes with the primary coolant drawn into the riser pipe from the reactor vessel by a Venturi flow effect to form a mixed primary coolant flow through the riser pipe. 17. The nuclear steam supply system according claim 1, wherein the primary coolant is cooled in the heat exchanger by water from a component cooling system. 18. The nuclear steam supply system according to claim 1, wherein the heat exchanger is a shell and tube type. 19. A nuclear steam supply system with shutdown cooling system, the nuclear steam supply system comprising:a reactor vessel having an internal cavity;a reactor core comprising nuclear fuel disposed within the internal cavity and operable to heat a primary coolant;a steam generating vessel fluidly coupled to the reactor vessel and containing a secondary coolant for producing steam to operate a steam turbine, the steam generating vessel including a superheater section and a steam generator section;a riser pipe positioned inside the steam generating vessel and fluidly coupled to the reactor vessel;a primary coolant flow loop formed within the reactor vessel and the steam generating vessel, the primary coolant flow loop being configured and operable for circulating primary coolant through the reactor vessel and steam generating vessel;a primary coolant cooling system comprising:a first pump having an inlet fluidly coupled to the primary coolant flow loop, the first pump configured and operable to extract and pressurize a portion of the primary coolant from the primary coolant loop;a Venturi injection nozzle having an inlet fluidly coupled to a discharge of the first pump and an outlet positioned inside the riser pipe in the steam generating vessel, the injection nozzle receiving and injecting the pressurized portion of the primary coolant into the riser pipe from the pump; anda first heat exchanger configured and operable to cool the extracted primary coolant prior to injecting the pressurized portion of the primary coolant;a secondary coolant cooling system comprising:a steam bypass condenser having an inlet fluidly coupled to the superheater section of the steam generator vessel for receiving and cooling secondary coolant in a steam phase;a second heat exchanger having an inlet fluidly coupled to the steam generator section of the steam generating vessel for receiving and cooling secondary coolant in a liquid phase;a second pump having an inlet fluidly coupled to the steam bypass condenser and the second heat exchanger, the second pump configured and operable to pressurize and circulate secondary coolant through the steam generator in a secondary coolant flow loop;wherein the secondary coolant cooling system is configured to cool secondary coolant in either the steam or liquid phase. 20. The nuclear steam supply system according to claim 19, wherein the second heat exchanger is disposed in the secondary coolant flow loop between a discharge outlet of the second pump and the steam generating vessel. 21. The nuclear steam supply system according to claim 19, wherein the second heat exchanger is disposed in the secondary coolant flow loop between the inlet of the second pump and the steam generating vessel. 22. The nuclear steam supply system according to claim 19, wherein the steam bypass condenser is disposed in the secondary coolant flow loop between the second pump and the steam generating vessel. 23. The nuclear steam supply system according to claim 19, wherein the secondary coolant flow loop is external to the steam generating vessel. 24. The nuclear steam supply system according to claim 19, wherein the steam generating vessel and reactor vessel are vertically elongated. 25. The nuclear steam supply system according to claim 24, wherein the superheater section and steam generating section of steam generating vessel are disposed in vertically stacked relationship. 26. The nuclear steam supply system according to claim 25, wherein the superheater section is positioned above the steam generating section. 27. The nuclear steam supply system according to claim 19, wherein the portion of the primary coolant extracted by the pump is less than 50% of the total volume of primary coolant contained in the primary coolant flow loop. 28. The nuclear steam supply system according to claim 19, wherein the portion of the primary coolant extracted by the pump is about 10% of the total volume of primary coolant contained in the primary coolant flow loop. 29. A nuclear steam supply system with shutdown cooling system, the nuclear steam supply system comprising:a reactor vessel having an internal cavity;a vertically elongated reactor core comprising nuclear fuel disposed within the internal cavity and operable to heat a primary coolant;a vertically elongated steam generating vessel fluidly coupled to the reactor vessel and containing a secondary coolant for producing steam to operate a steam turbine, the steam generating vessel including a superheater section and a steam generator section;a vertically elongated riser pipe positioned inside the steam generating vessel and fluidly coupled to the reactor vessel;a primary coolant flow loop formed within the reactor vessel and the steam generating vessel, the primary coolant flow loop being configured and operable for circulating primary coolant through the reactor vessel and steam generating vessel;a secondary coolant flow loop formed outside of the reactor vessel and steam generating vessel, the secondary coolant flow loop being configured and operable for circulating secondary coolant through the steam generating vessel; anda Venturi jet pump disposed inside the riser pipe of the steam generating vessel, the jet pump including an injection nozzle fluidly coupled to the primary coolant flow loop by a pump fluidly coupled to the primary coolant flow loop which extracts and pressurizes the portion of the primary coolant from the primary coolant flow loop and discharges the pressurized portion of the primary coolant to the injection nozzle;wherein the jet pump receives and injects a portion of the primary coolant into the riser pipe which draws and mixes primary coolant from the reactor vessel with the injected portion of the primary coolant in the jet pump to circulate primary coolant through the primary coolant flow loop. 30. The nuclear steam supply system according to claim 29, further comprising a first heat exchanger disposed upstream of the jet pump and configured to cool the portion of the primary coolant received by the jet pump before injection into the riser pipe. 31. The nuclear steam supply system according to claim 29, wherein the injection nozzle discharges primary coolant in an upwards directions inside the riser pipe. 32. The nuclear steam supply system according to claim 29, further comprising a second pump fluidly coupled to the secondary coolant flow loop which receives secondary coolant extracted at a first elevation from the steam generating vessel, pressurizes the secondary coolant, and returns the pressurized secondary coolant at a second elevation to the steam generating vessel which is different than the first elevation. 33. The nuclear steam supply system according to claim 32, further comprising:a bypass condenser fluidly coupled to the secondary coolant flow loop, the bypass condenser configured to receive and condense secondary coolant in a steam phase extracted from the superheater section of the steam generating vessel;wherein the second pump takes suction from and receives liquid phase secondary coolant from the bypass condenser. 34. The nuclear steam supply system according to claim 32, further comprising:a heat exchanger fluidly coupled to the secondary coolant flow loop, the heat exchanger configured to receive secondary coolant in a liquid phase extracted from the steam generating section of the steam generating vessel;wherein the second pump takes suction from and receives liquid phase secondary coolant from the heat exchanger. 35. The nuclear steam supply system according to claim 32, wherein the superheater section is vertically stacked above the steam generating section in the steam generating vessel.
	description	This application claims priority to the provisional patent application entitled “Handling Beam Glitches During Solar Cell Implantation,” filed Jun. 29, 2010 and assigned U.S. application Ser. No. 61/359,649, the disclosure of which is hereby incorporated by reference. This invention relates to ion implantation of workpieces and, more particularly, to forming solar cells using ion implantation. Ion implantation is a standard technique for introducing conductivity-altering impurities into a workpiece. A desired impurity material is ionized in an ion source, the ions are accelerated to form an ion beam of prescribed energy, and the ion beam is directed at the surface of the workpiece. The energetic ions in the beam penetrate into the bulk of the workpiece material and are embedded into the crystalline lattice of the workpiece material to form a region of desired conductivity. Solar cells are one example of a device that uses silicon workpieces. Any reduced cost to the manufacture or production of high-performance solar cells or any efficiency improvement to high-performance solar cells would have a positive impact on the implementation of solar cells worldwide. This will enable the wider availability of a clean energy technology. There are many different solar cell architectures. Two specific designs are the selective emitter (SE) and the interdigitated backside contact (IBC). A SE solar cell has high-dose regions across the lightly doped surface to enable better current generation in the lightly doped regions while enabling low-resistance contacts for current collection in the high-dose regions. An IBC solar cell has alternating p-type and n-type regions across the surface not impinged by sunlight. Both a SE and IBC solar cell may be implanted to dope the various n-type or p-type regions. “Glitches” may occur during implantation. A glitch is when the beam quality is suddenly degraded in the middle of an implantation operation, potentially rendering the workpiece unusable. Such a glitch can be caused at various locations along the beam path. Ion implanters generally employ several electrodes along the beam path, which accelerate the beam, decelerate the beam, or suppress spurious streams of electrons that are generated during operation. Generally, glitches occur across acceleration gaps, deceleration gaps, or suppression gaps, although glitches may occur elsewhere. These glitches may be detected as a sharp change in the current from one of the power supply units for the electrodes. This causes a change in the delivered ion dose to the workpiece surface. Due to the threat of potential impact to the performance of the workpiece being implanted, glitches can be quite costly. Thus, steps are usually taken to both minimize the occurrence of such glitches and to recover from the glitches if possible. When a glitch is detected, one solution is to immediately reduce the ion beam current to zero, thus terminating the implantation at a defined location on the workpiece. Once the glitch condition has been removed, implantation ideally resumes at exactly the same location on the workpiece with ideally the same beam characteristics that existed when the glitch was detected. The goal is to achieve a uniform doping profile, and this can be achieved by controlling the beam current, the workpiece scan speed, or the workpiece exposure time. Repairing the dose loss caused by the glitch in such a manner may take over 30 seconds, which may be too time-consuming for the throughput demands of certain workpiece manufacturing industries, such as the solar cell industry. Therefore, there is a need in the art for an improved method of glitch recovery for the implantation of workpieces such as solar cells. According to a first aspect of the invention, a method of ion implantation is provided. The method comprises implanting a first workpiece during a first pass at a first speed. The first pass results in a region of uneven dose in the first workpiece. The first workpiece is implanted during a second pass at a second speed. The second speed is different from the first speed. According to a second aspect of the invention, a method of workpiece fabrication is provided. The method comprises implanting a workpiece. The implanting results in a region of uneven dose in the workpiece. Metal contacts are applied to the workpiece orthogonal to the region of uneven dose. According to a third aspect of the invention, a method of ion implantation is provided. The method comprises implanting at least one workpiece. A region of uneven dose in the workpiece caused by the implanting is detected. Additional implantation into the workpiece is performed whereby an entirety of the workpiece has a larger dose after the additional implantation than after the implanting. The embodiments of this method are described herein in connection with an ion implanter. Beamline ion implanters, plasma doping ion implanters, or flood ion implanters may be used. Any n-type or p-type dopants may be used, but the embodiments herein are not limited solely to dopants. Furthermore, embodiments of this process may be applied to many solar cell architectures or even other workpieces such as semiconductor wafers, light-emitting diodes (LEDs), or flat panels. While various passes or speeds are referred to “first” or “second,” this nomenclature is used for simplicity. The “first” pass when the glitch occurs may actually be, for example, the fourth overall pass during implantation of a workpiece. Thus, the invention is not limited to the specific embodiments described below. FIG. 1 is a simplified block diagram of a beam-line ion implanter. Those skilled in the art will recognize that the beam-line ion implanter 500 is only one of many examples of differing beam-line ion implanters. In general, the beam-line ion implanter 500 includes an ion source 501 to generate ions that are extracted to form an ion beam 502, which may be, for example, a ribbon beam or a spot beam. The ion beam 502 of FIG. 1 may correspond to the ions used for implanting in the embodiments disclosed herein. The ion beam 502 may be mass analyzed and converted from a diverging ion beam to a ribbon ion beam with substantially parallel ion trajectories in one instance. The ion beam 502 may not be mass analyzed prior to implantation in another instance. The beam-line ion implanter 500 may further include an acceleration or deceleration unit 503 in some embodiments. An end station 504 supports one or more workpieces, such as the workpiece 506, in the path of the ion beam 502 such that ions of the desired species are implanted into workpiece 506. The end station 504 may include workpiece holder, such as platen 505, to support the workpiece 506. The workpiece holder also may be other mechanisms such as a conveyor belt. This particular end station 504 also may include a scanner (not illustrated) for moving the workpiece 506 perpendicular to the long dimension of the ion beam 502 cross-section, thereby distributing ions over the entire surface of workpiece 506. The beam-line ion implanter 500 may include additional components known to those skilled in the art such as automated workpiece handling equipment, Faraday sensors, or an electron flood gun. It will be understood to those skilled in the art that the entire path traversed by the ion beam 502 is evacuated during ion implantation. The beam-line ion implanter 500 may incorporate hot or cold implantation of ions in some embodiments. Glitches may occur within an ion implanter, such as the beam-line ion implanter 500. If this glitch is sufficiently short and the number of passes over a workpiece sufficiently large, it may be possible to ignore the glitch because there will likely be no effect to the workpiece. However, at some point the glitch is large enough or the glitch recovery time may be long enough that the glitch cannot be ignored because a significant dose loss will result and, if the workpiece is a solar cell, the solar cell efficiency may be affected. If a glitch with such significant dose loss occurs, then the damage caused by the glitch may be repaired to avoid yield loss. FIG. 2 is a chart comparing dose versus workpiece y-position. This illustrates a single glitch on the dose uniformity for a workpiece, which in this instance is a solar cell. This example is based on an implant with eight scans or passes. The total dose may be between approximately 1E15 cm−2 and 1E16 cm−2 in one instance. The line scans are illustrated for various glitch durations. The impact on the dose is reported as a local dose loss and whole workpiece dose non-uniformity. As seen, the effect on dose of a 50 ms glitch is larger than that of a 10 ms glitch. It was been experimentally determined that the field region for an SE solar cell is not as sensitive as a semiconductor wafer to the absolute dose. Other solar cell architectures or workpieces may have similar sensitivities with respect to a semiconductor wafer. Thus, while a semiconductor wafer may need near-perfect repair of the dose, a solar cell or other workpiece may need far less precise repair. Short circuit current density, Jsc, and open circuit voltage, Voc, do not change rapidly as a function of dose. For some implants with a ±15% change in dose, approximately no change for Jsc or Voc may occur. Additionally, the dose needed for contacting or adding metal contacts to the solar cell may only require a certain dose to properly function. An increase in dose may be beneficial for forming improved metal contacts. Fill factor, FF, and series resistance, Rseries, can be used as a proxy for contact quality. It has been shown that FF increases and Rseries decreases as a function of increasing dose. Glitch detection may be performed multiple ways. For example, a faraday cup or other detection device can monitor beam current in the implanter. In another example, the power supply units are monitored. Drops in current from one of the power supply units may indicate that a glitch occurred or is occurring. Other measurements to the beam current in the implanter also can detect glitches. A controller, which may be a computer or other processor, can receive signals and compensate for any detected glitches. This controller can determine where on the workpiece or workpieces the glitch occurred and use this information to compensate for the glitch. Glitches may have a varying duration. Some glitches may be more than 50 ms, though other lengths are of course possible. In one instance using a ribbon beam, the glitch is a line across an entire surface of a workpiece. In another instance using a spot beam, the glitch may be a dot on the surface of the workpiece. It is assumed in these embodiments that the solar cells or other workpieces are disposed on a platen in a 2×3 arrangement with multiple passes or scans during implant. Such an arrangement is illustrated in FIG. 10. A total of six workpieces 506 are arranged on the platen 505. These workpieces 506 are disposed in a first workpiece pair 103, second workpiece pair 104, and third workpiece pair 105, which refer to the workpieces 506 in the horizontal direction. The workpieces 506 scan in the direction 507. Of course, other configurations or implant methods are possible. For example, a single workpiece, two workpiece, three workpieces in a 1×3 arrangement, or four workpieces in a 2×2 arrangement may be implanted. All may benefit from the embodiments disclosed herein. While scanning the workpiece is specifically mentioned, scanning the ion beam or a combination of scanning the ion beam and workpiece also may be performed. If a glitch occurs during a blanket implant of a workpiece, or a uniform implant over an entire surface of a workpiece, there are at least five responses. The pass following a glitch may be intentionally slowed compared to the previous pass to over-dose all six workpieces in the 2×3 configuration. FIG. 3 is a chart comparing scan speeds versus platen position in a first embodiment. The x-axis position includes three workpieces in a 2×3 arrangement broken into a first workpiece pair 103, second workpiece pair 104, and third workpiece pair 105. The glitch occurs at position 102 of the first workpiece pair 103 during the first implant pass 100, which occurs at a first speed. Thus, only the first workpiece pair 103 is affected by the glitch and a region of uneven dose occurs in this first workpiece pair 103. A second implant pass 101 is performed or added to increase the dose on every workpiece. This second implant pass 101 occurs at a second speed and is slowed compared to the first speed of first implant pass 100. Thus, most or all of the workpieces will be over-dosed and the position 102 will have an implant dose at least equal to the desired value, if not higher. FIG. 4 is a chart illustrating dose versus platen position corresponding to the embodiment of FIG. 3. In FIG. 4, the first workpiece pair 103, second workpiece pair 104, and third workpiece pair 105 are illustrated and correspond to FIG. 3. The position 102 where the glitch occurs also corresponds to FIG. 3. A desired dose level 600 is illustrated (represented by the horizontal dashed line). Since the second implant pass from FIG. 3 was slowed compared to the first implant pass, the actual dose level 601 is larger than the desired dose level 600 for all workpieces. Even the region around the position 102 where the glitch occurs has a higher dose than the desired dose level 600. The pass following a glitch may be slowed for the row or pair of workpieces affected by the glitch to intentionally over-dose those workpieces. FIG. 5 is a chart comparing scan speeds versus platen position in a second embodiment. As with the embodiment of FIG. 3, in FIG. 5 a glitch occurs at position 102 of the first workpiece pair 103 during the first implant pass 100, which occurs at a first speed. Thus, only the first workpiece pair 103 is affected by the glitch and a region of uneven dose occurs in this first workpiece pair 103. A second implant pass 200 is performed or added. The second implant pass 200 is at a second speed, slower than the first speed, for the first workpiece pair 103 affected by the glitch, and a third speed, faster than the second speed, for the other workpieces that were not affected by the glitch. This third speed during the second implant pass 200 may be faster than, slower than, or approximately equal to the first speed of the first implant pass 100 in one instance. FIG. 5 merely illustrates the speed of the first implant pass 100 as different from the speed of the second implant pass 200 for simplicity. This will increase the dose primarily on the workpiece affected by the glitch and may increase throughput with respect to the embodiment of FIG. 3. FIG. 6 is a chart illustrating dose versus platen position corresponding to the embodiment of FIG. 5. In FIG. 6, the first workpiece pair 103, second workpiece pair 104, and third workpiece pair 105 are illustrated and correspond to FIG. 5. The position 102 where the glitch occurs also corresponds to FIG. 5. A desired dose level 600 is illustrated. Since the second implant pass from FIG. 5 was slowed compared to the first implant pass for the first workpiece pair 103, the actual dose level 601 is larger than the desired dose level 600 for the first workpiece pair 103. With the second workpiece pair 104 and third workpiece pair 105, the actual dose level 601 may be approximately the same as the desired dose level 600. The pass following a glitch may be slowed only over the specific area of the workpiece where the glitch occurred to refill the lost dose on the workpieces. This may minimize the effect on any workpieces not affected by the glitch. FIG. 7 is a chart comparing scan speeds versus platen position in a third embodiment. As with the embodiments of FIGS. 3 and 5, in FIG. 7 a glitch occurs at position 102 of the first workpiece pair 103 during the first implant pass 100 at a first speed. Thus, only the first workpiece pair 103 is affected by the glitch and a region of uneven dose occurs in this first workpiece pair 103. A second implant pass 300 is added or performed. The second implant pass 300 slows only for the region around the glitch at position 102. Thus, in the region around the glitch at the position 102, a second speed, slower than the first speed, occurs. For the rest of the areas of the workpieces, the second implant pass 300 occurs at a third speed, which is faster than the second speed. This third speed of the second implant pass 300 may be at a speed slower than, faster than, or approximately equal to that of the first speed of the first implant pass 100 in one instance. FIG. 7 merely illustrates the speed of the first implant pass 100 as different from the speed of the second implant pass 300 for simplicity. This will increase the dose only on the area of the workpiece affected by the glitch and may reduce throughput loss compared to the embodiments of FIGS. 3 and 5. FIG. 8 is a chart illustrating dose versus platen position corresponding to the embodiment of FIG. 7. In FIG. 8, the first workpiece pair 103, second workpiece pair 104, and third workpiece pair 105 are illustrated and correspond to FIG. 7. The position 102 where the glitch occurs also corresponds to FIG. 7. A desired dose level 600 is illustrated. Since the second implant pass from FIG. 7 was slowed compared to the first implant pass for the region around the glitch at position 102, the actual dose level 601 is larger than the desired dose level 600 for this region around the position 102. With the remainder of the first workpiece pair 103 and all of the second workpiece pair 104 and third workpiece pair 105, the actual dose level 601 may be approximately the same as the desired dose level 600. While slowing the second implant passes is disclosed in FIGS. 3, 5, and 7, these second implant passes also may be faster or equal in speed to the first implant pass. In such an instance, higher throughput may be desired or only a small additional dose is needed to compensate for the glitch. For example, for a small glitch, the second implant; pass may be faster than the first implant pass to compensate. In this example, the combined dose from the first implant pass and second implant pass is approximately equal to or greater than the desired dose level. One or more additional pass also may be added to over-dose all workpieces. The additional pass or passes may be performed at the same speed or different speeds as the standard implant passes. For example, the additional passes may be at a faster speed than the initial implant passes. While one additional pass may be added, two or more additional passes may be added. In one specific instance, an odd number of passes is added and the to return pass is “blanked” such that no beam implants the workpieces. For example, during blanking the arc may be quenched, the ion beam directed away from the workpiece, the beam may be blocked, or the platen is rotated to shadow the workpieces from the beam. Adding an even number of passes may be simpler for workpiece handling purposes. For example, two passes at a faster speed than the initial implant passes are added. This may be combined with the embodiments of FIG. 3, 5, or 7 in one instance or may be a method of glitch compensation separate from the embodiments of FIG. 3, 5, or 7. While the embodiments of FIGS. 3, 5, and 7 illustrated a single glitch at position 102 in the first workpiece pair 103, multiple glitches may occur. These multiple glitches can occur on the same workpiece or workpiece pair. These multiple glitches also can occur in multiple workpieces or different workpiece pairs. The embodiments of FIGS. 3, 5, and 7 can be applied if multiple glitches occur. For example, an implant pass may be slowed for multiple workpiece passes or around multiple positions where a glitch occurred. The workpiece affected by the glitch also may be rotated by 90° prior to printing the metal contacts on its surface. This will allow the metal lines to be orthogonal to the missing dose region. This may be better than the alternative of having a few metal lines miss a correctly doped region. FIGS. 9A-B are a top perspective view of rotating a workpiece to reduce the effects of glitching. As illustrated in FIG. 9A, the workpiece 400 includes a region 401 with a different dose due to a glitch that occurred during implantation. In FIG. 9B, the workpiece 400 has been rotated 90°. The metal lines 402 are disposed on the workpiece 400 perpendicular to the region 401 to reduce the negative effects of the lower dose in the region 401. Of course, the pattern of the metal lines 402 also may skip the region 401 and run parallel to the region 401, but this may limit or reduce the energy collected from the workpiece 400. In one instance, workpiece handling systems may rotate the workpiece 400 prior to the metallization steps that create the metal lines 402. In one particular embodiment, the workpiece 400 with the region 401 or others with a region 401 are rotated prior to metallization while other workpieces are not rotated prior to metallization. In another particular embodiment, all workpieces including the workpiece 400 are rotated prior to metallization. Glitches may be more complicated with selective implants. A selective implant only implants a portion of the workpiece. For example, a series of higher dose lines may be implanted during a selective implant. Photoresist, an oxide, a stencil mask, or a shadow mask may be used to enable selective implants. If a glitch occurs during a selective implant, any of the embodiments listed for blanket implants may be used except the embodiment of FIG. 9 where the workpiece is rotated 90° prior to printing the metal contacts. Then the metal contacts would be misaligned or not aligned to any heavily doped region. For the embodiments of FIG. 3, 5, or 7 or the use of additional passes, the mask can remain in place during the implants that: include different speeds or for the additional passes. This will result in additional dose for all or some of the selective implant. Slowing the scan speed for the least amount of time has the least impact on throughput, which may be desirable for solar cells or other workpieces that require high throughput. All solutions, however, improve the yield for solar cell implants. To use the embodiments herein, the implanter may use a measurement system to monitor potential glitches and a controller connected to the scan system for the ion beam or platen. This controller may modify the scan or implant to compensate for glitches. Such modification may take into account the overall throughput impact and may select the best solution to the glitch. Factors such as the position of the glitch on the workpiece, the size of the glitch on the workpiece, the duration of the glitch, the number of passes for the desired dose level, the particular layer or region of the workpiece being implanted, or the type of workpiece or solar cell architecture being implanted may be considered to determine the best glitch solution. This best solution may be based on a desired throughput or solar cell architecture, for example. And while the embodiments disclosed herein are all related to fixing glitches, the solution in some instances may be to ignore a glitch altogether. For example, if glitches occur on multiple different workpieces, one solution may be to ignore a glitch on one workpiece while repairing a glitch on another workpiece. This ignored glitch may not have enough of an impact on the workpiece to justify the lower throughput caused by fixing this particular glitch. This controller also may add passes or otherwise select the best solution to the glitch taking into account a minimum dose needed on the workpiece, such as, for example, the desired dose level 600. Uniformity across the workpieces or individual workpieces may be ignored as long as the minimum dose is implanted. Such a minimum dose may be calculated based on the needs for contact formation or emitter formation, for example. The number of passes or speed of the individual passes is configured to implant this minimum dose in one embodiment. The present disclosure is not to be limited in scope by the specific embodiments described herein. Indeed, other various embodiments of and modifications to the present disclosure, in addition to those described herein, will be apparent to those of ordinary skill in the art from the foregoing description and accompanying drawings. Thus, such other embodiments and modifications are intended to fall within the scope of the present disclosure. Furthermore, although the present disclosure has been described herein in the context of a particular implementation in a particular environment for a particular purpose, those of ordinary skill in the art will recognize that its usefulness is not limited thereto and that the present disclosure may be beneficially implemented in any number of environments for any number of purposes. Accordingly, the claims set forth below should be construed in view of the full breadth and spirit of the present disclosure as described herein.
	abstract	Disclosed herein is a joint structure between a top nozzle and a guide thimble. The joint structure includes an outer guide post, an inner-extension tube head, an inner-extension tube body, a wedge and the guide thimble. The outer guide post is provided with an external thread formed on a lower end thereof. The inner-extension tube head includes an annular retaining part formed on an upper end thereof. An internal thread is formed on a medial portion of the inner-extension tube head. An external thread is formed on each of upper and lower ends of the inner-extension tube body. A stop protrusion is provided under a lower end of the wedge. The wedge is welded to the inner-extension tube body after the top nozzle has been joined with the guide thimble. A stop protrusion receiving depression is formed in the guide thimble.
	summary
046612904	abstract	An apparatus for compacting a solid waste material includes a hollow cylindrical body having a charging inlet for charging the solid waste material therethrough into the hollow cylindrical body, a heating portion for heating the solid waste material in the hollow cylindrical body, and a discharging outlet for discharging the solid waste material from the hollow cylindrical body; a rotatable shaft disposed in the hollow cylindrical body and having a helical screw blade thereon, the screw blade and an inner wall surface of the hollow cylindrical body being spaced from each other with a clearance provided therebetween for allowing the solid waste material in the hollow cylindrical body to form a bridge therein; a support for radially movably supporting an end of the rotatable shaft; a prime mover coupled to the end of the rotatable shaft through the support; and an outlet nozzle coupled to the discharging outlet for compressing the solid waste material discharged from the discharging outlet. The compacting apparatus can compact various solid waste materials including plastics discharged from homes, factories, nuclear power plants, and other facilities, and compacted solid waste materials can be solidified into solid masses or pelletized.
055132294	summary	FIELD OF THE INVENTION This invention relates generally to maintenance of a control rod drive of a boiling water reactor. Specifically, the invention relates to tools for removal of a control rod drive during the exchange process. BACKGROUND OF THE INVENTION Control rod drives (CRDs) are used to position control rods in boiling water reactors (BWRs) to control the fission rate and fission density, and to provide adequate excess negative reactivity to shutdown the reactor from any normal operating or accident condition at the most reactive time in core life. Referring to FIG. 1, each CRD is mounted vertically in a CRD housing 10 which is welded to a stub tube 8, which in turn is welded to the bottom head of the reactor pressure vessel 4. The CRD flange 6 is bolted and sealed to the flange 10a of the CRD housing 10, which contains ports for attaching the CRD hydraulic system lines 80, 81. Demineralized water supplied by the CRD hydraulic system serves as the hydraulic fluid for CRD operation. As shown schematically in FIG. 1, the CRD is a double-acting, mechanically latched hydraulic cylinder. The CRD is capable of inserting or withdrawing a control rod (not shown) at a slow controlled rate for normal reactor operation and of providing rapid control rod insertion (scram) in the event of an emergency requiring rapid shutdown of the reactor. A locking mechanism in the CRD permits the control rod to be positioned at 6-inch (152.4-mm) increments of stroke and to be held in these latched positions until the CRD is actuated for movement to a new position. A spud 46 at the top of the index tube 26 (the moving element) engages and locks into a socket at the bottom of the control rod. Once coupled, the CRD and control rod form an integral unit which must be manually uncoupled by specific procedures before a CRD or control rod may be removed from the reactor. When installed in the reactor, the CRD is wholly contained in housing 10. The CRD flange 6 contains an insert port 66, a withdraw port 70 and an integral two-way check valve (with a ball 20). For normal drive operation, drive water is supplied via an associated hydraulic control unit (HCU) to the insert port 66 for drive insertion and/or to withdraw port 70 for drive withdrawal. For rapid shutdown, reactor pressure is admitted to the two-way check valve from the annular space between the CRD and a thermal sleeve (not shown) through passages in the CRD flange, called scram vessel ports. The check valve directs reactor pressure or external hydraulic pressure to the underside of drive piston 24. Referring to FIGS. 2A and 2B, the CRD further comprises an inner cylinder 57 and an outer tube 56, which form an annulus through which water is applied to a collet piston 29b to unlock index tube 26. The internal diameter of inner cylinder 57 is honed to provide the surface required for expanding seals 65 on the drive piston 24. A collet housing 51 (which is part of outer tube 56) is provided with ports 73 to permit free passage of water from the clearance space between the outer diameter of index tube 26 and the inner diameter of inner cylinder 57 and the inner diameter of collet housing 51. The bottom of collet piston 29b normally rests against a spacer 52 in the upper portion of the annular space. Grooves in the spacer permit the passage of water between the bottom of the collet piston 29b and the passage area within the cylinder, tube and flange. Welded pipes 80 and 81, installed in the CRD housing, port water to the insert port 66 and the withdraw port 70 respectively. A port 69 below outer tube 56 connects to withdraw port 70 in CRD flange 6 so that water is applied through the annulus to collet piston 29b when a withdraw signal is given. The CRD is secured to the CRD housing flange 10a by eight mounting bolts (not shown). A pressure-tight seal is effected between the mated flanges by O-ring gaskets (not shown) mounted in a spacer 7 secured to the CRD flange face. Insert port 66 contains a ball check valve which consists of check-valve ball 20, ball retainer 21, and retainer O-ring 22. This valve directs HCU accumulator pressure or reactor pressure to the underside of drive piston 24 during scram operation. Port 66 is connected internally to the annulus and the bottom of drive piston 24 and serves as the inlet for water during normal insertion or scram. Water enters this port for a brief period in response to a withdraw signal to move the index tube 26 upward so that collet fingers 29a are cammed out. Following this brief unlocking period, water from below drive piston 24 is discharged through port 66 and through the under-piston hydraulic line for the duration of the withdraw signal. During the time the CRD remains stationary, cooling water passes through an annulus internal to flange 6 to the area between outer tube 56 and the inside of the thermal sleeve to cool the CRD. The withdraw port 70 serves as the inlet port for water during control rod withdrawal and as the outlet port for water during normal or scram insertion. It connects with internal porting and annuli to the area above drive piston 24. During a withdraw operation, water is supplied from port 70 through a small connecting port in CRD flange 6 to the annular space between outer tube 56 and inner cylinder 57 for application to the bottom of collet piston 29b. The locking mechanism consists of collet fingers 29a, collet piston 29b, barrel 35, guide cap 39, and collet spring 31. The mechanism is contained in the collet housing 51 portion of outer tube 56 and is the means by which index tube 26 is locked to hold the control rod at a selected position. The collet assembly consists of a collet piston 29b fitted with four expansion piston seal rings 28, six fingers 29a and a retainer (not shown) and is set into a bore in the collet housing 51. In addition, a spring 31, barrel 35 and guide cap 39 complete the components installed in the collet housing 51. Guide cap 39 is held in place above the collet by three plugs 37 which penetrate the upper end of collet housing 51, and which are held in place by fillister-head screws. It provides a fixed camming surface to guide collet fingers 29a upward and away from index tube 26 when unlocking pressure is applied to collet piston 29b. Barrel 35 is installed below guide cap 39 and serves as fixed seat for collet spring 31. The collet mechanism requires a hydraulic pressure greater than reactor pressure to unlock for CRD-withdraw movement. A preload is placed on collet spring 31 at assembly and must be overcome before the collet can be moved toward the unlocked position. For control rod withdrawal, a brief insert signal is applied to move index tube 26 upward to relieve the axial load on collet fingers 29a, camming them outward against the sloping lower surface of index tube locking notch 55. Immediately thereafter, withdraw pressure is applied. In addition to moving index tube 26 downward, this pressure is at the same time applied to the bottom of collet piston 29b to overcome the spring pressure and cam the fingers 29a outward against guide cap 39. When the withdraw signal ceases, the spring pressure forces the collet downward so that fingers 29a slip off guide cap 39. As index tube 26 settles downward, collet fingers 29a snap into the next higher notch and lock. When collet fingers 29a engage a locking notch 55, collet piston 29b transfers the control rod weight from index tube 26 to the outer tube 56. Unlocking is not required for CRD insertion. The collet fingers are cammed out of the locking notch as index tube 26 moves upward. The fingers 29a grip the outside wall of index tube 26 and snap into the next lower locking notch for single-notch insertion to hold index tube 26 in position. For scram insertion, index tube 26 moves continuously to its limit of travel during which the fingers snap into and cam out of each locking notch as index tube 26 moves upward. When the insert, withdraw or scram pressures are removed, index tube 26 settles back, from the limit of travel, and locks to hold the control rod in the required position. The drive piston 24 and index tube 26 are the primary subassembly in the CRD, providing the driving link with the control rod as well as the notches for the locking mechanism collet fingers. Drive piston 24 operates between positive end stops, with a hydraulic cushion provided at the upper end only. Index tube 26 is a nitrided stainless-steel tube threaded internally at both ends. The spud 46 is threaded to its upper end, while the head of the drive piston 24 is threaded to its lower end. Both connections are secured in place by means of lock bands 25, 44. There are 25 notches machined into the wall of index tube 26, all but one of which are locking notches 55 spaced at 6-inch intervals. The uppermost surfaces of these notches engage collet fingers 29b, providing 24 increments at which a control rod may be positioned and preventing inadvertent withdrawal of the rod from the core. The lower surfaces of the locking notches slope gradually so that the collet fingers cam outward for control rod insertion. Drive piston 24 is provided with internal (62, 71, 72) and external seal rings (65), and is operated in the annular space between piston tube 15 and inner cylinder 57. Internal (63) and external (64) bushings prevent metal-to-metal contact between drive piston 24 and the surface of piston tube 15 and the wall of inner cylinder 57 respectively. When a control rod is driven upward to its fully inserted position during normal operation or scram, the upper end of the piston head contacts the spring washers 30 which are installed below the stop piston 33. Washers 30 and stop piston 33 provide the upper limit of travel for drive piston 24. The spring washers, together with the series of buffer orifices 53 in the upper portion of piston tube 15, effectively cushion the moving drive piston 24 and reduce the shock of impact when the piston head contacts the stop piston. The magnet housing, which comprises the lower end of drive piston 24, contains a ring magnet 67 which actuates the switches inside a position indicator probe 12a to provide remote electrical signals indicating control rod position. The piston tube assembly forms the innermost cylindrical wall of the CRD. It is a welded unit consisting of piston tube 15 and a position indicator tube 61. The piston tube assembly provides three basic functions for CRD operation: (a) position indicator tube 61 is a pressure-containing part which forms a drywell housing for position indicator probe 12a (see FIG. 2A); (b) piston tube 15 provides for the porting of water to or from the upper end of the piston head portion of drive piston 24 during rod movement; and (c) during control rod scram insertion, buffer orifices 53 in piston tube 15 progressively shut off water flow to provide gradual deceleration of drive piston 24 and index tube 26. A stud 59 is welded to the upper end of tube piston 15. Stud 59 is threaded for mounting the stop piston 33. A shoulder on the stud, just below the threaded section, is machined to provide a recess for the spring washers 30 that cushion the upward movement of drive piston 24. The tube section 15a and head section 15b of piston tube 15 provide space for position indicator tube 61, which is welded to the inner diameter of the threaded end of head section 15b and extends upward through the length of tube section 15a, terminating in a watertight cap near the upper end of the tube section. Piston tube 15 is secured by a nut 16 at the lower end of the CRD. Two horizontal ports are provided in the head section 15b, 180.degree. apart, to transmit water between the withdraw porting in the CRD flange and the annulus between indicator tube 61 and tube section 15a of piston tube 15 for application to the top of drive piston 24. Three O-ring seals 18 are installed around head section 15b. Two seal the bottom of the CRD against water leakage and one seals the drive piston 24 under-piston pressure from the drive piston over-piston pressure. A position indicator probe 12a is slidably inserted into indicator tube 61. As shown in FIGS. 2A and 4, probe 12a is welded to a plate 12b, which plate is in turn bolted to housing 12. Housing 12 is secured to the CRD ring flange 17 by screws 13. A cable clamp 11, located at the bottom of a plug 106, secures a connecting electrical cable (not shown) to plug 106. Ring flange 17 is in turn secured to the CRD housing by screws 9. Thus, probe 12a, housing 12 and cable clamp 11 (with the cables passing therethrough) can be removed as a unit. Probe 12a includes a switch support 103 with 53 reed switches and a thermocouple for transmitting electrical signals to provide remote indications of control rod position and CRD operating temperature. Only switches S48, S49 and S50 are shown in FIG. 4. The reed switches are connected by electrical wires 105 to a receptacle 14, which receives plug 106. The plug and receptacle are standard electrical components with 27 pins and sockets respectively. Housing 12 serves as a protective covering for the electrical wires 104. The switch support assembly consists of a switch support 103 and a flange (not shown). The switch support 103 has two channels extending its full length which provide for mounting of the position switches on two sides of the support. A thin-walled protective tube 107 is installed over the length of the switch support. Tube 107 is held in place by a split rivet (not shown) which penetrates the switch support at the upper end. The 53 reed switches are identical and are attached to switch support 103 by spring clips 109. Each switch is encased in a silicone-impregnated fiberglass sleeve for insulation. The switches are normally open and are closed individually during CRD operation by ring magnet 67 installed in the bottom of drive piston 24. The stop piston 33 threads onto the stud 59 at the upper end of piston tube 15. This piston provides the seal between reactor pressure and the area above the drive piston. It also functions as a positive-end stop at the upper limit of drive piston travel. Six spring washers 30 below the stop piston help absorb the final mechanical shock at the end of travel. Seals 34 include an upper pair used to maintain pressure above the drive piston during CRD withdrawal and a lower pair used only during the cushioning of the drive piston at the upper end of the stroke. Two external bushings 32 prevent metal-to-metal contact between stop piston 33 and index tube 26. As seen in FIG. 3, spud 46, which connects the control rod 90 and the CRD, is threaded onto the upper end of index tube 26 and held in place by locking band 44. The coupling arrangement will accommodate a small amount of angular misalignment between the CRD and the control rod. Six spring fingers permit the spud to enter the mating socket 92 on the control rod. A lock plug 94 then enters spud 46 from socket 92 and prevents uncoupling. Two uncoupling mechanisms are provided. The lock plug 94 may be raised against the return force of a spring 95 by an actuating shaft 96 which extends through the center of the control rod velocity limiter to an unlocking handle (not shown). The control rod, with lock plug 94 raised, may then be lifted from the CRD. The lock plug may also be raised from below to uncouple the CRD from below the reactor vessel. To accomplish this, a special tool is attached to the bottom of the CRD and used to raise the piston tube 15 (see FIG. 2B). This raises an uncoupling rod, lifting lock plug 94 so that spud 46 disengages from the control rod coupling socket 92. The uncoupling rod consists of a rod 48 and a tube 43, supported in the base of the spud at the upper end of the CRD. The rod 48 is welded to the flared end of tube 43 such that a dimension of 1.125 inch exists between the top of rod 48 and the top end of spud 46. This is a critical dimension and must be maintained to ensure proper CRD and control-rod coupling. For this reason, uncoupling rods cannot be interchanged unless the critical dimension is verified. In addition to its function in uncoupling, rod 48 positions the control rod lock plug 92 such that it supports (i.e., opposes radially inward deflection of) the spud fingers when the control rod and CRD are coupled. In order to perform maintenance on a CRD, the CRD must be removed from the CRD housing. To accomplish this, the CRD must first be uncoupled from the control rod. Conventional practice is to remove the position indicator probe from the CRD prior to drive removal. The purpose is to allow access by an uncoupling tool in the space occupied by the probe. The uncoupling tool is used for final determination that the CRD is uncoupled from the control rod prior to lowering the drive out of its housing. The uncoupling tool is also used to uncouple the drive from the control rod from beneath the RPV, but often this function is performed from the refueling floor. All work performed under vessel is in a high-radiation area and reduction of any time or tasks in the under vessel area results in a reduction in the overall radiation exposure accrued by the utility during an outage. The removal of the position indicator probe under vessel contributes approximately one man-rem to the total radiation exposure received by the crew performing the CRD exchange. SUMMARY OF THE INVENTION The present invention is a method for removing a CRD with the position indicator probe in place. This allows probe removal to be performed in a low-dose area, thereby effectively reducing the exposure received by the crew removing the probe to nearly zero. A further feature of the invention is an electronic tool for continuous CRD uncoupled monitoring during drive removal. The tool uses the position indicator probe to verify that the drive is uncoupled. The electronic monitoring tool is mounted on the CRD removal equipment. The monitoring circuit is connected to selected position switches inside the position indicator probe, which is installed in the stationary CRD piston tube. These selected switches are normally open and are closed when a ring magnet on the movable drive piston is in proximity to the respective switch. Accordingly, the position of the index tube/drive piston assembly, and the control rod coupled thereto via the spud, can be determined from the state of the position switches. The detected state of the switches can be used to determine whether the index tube/drive piston assembly is being extended relative to the piston tube, as the CRD is lowered during the initial stage of removal. Indicator lights are activated in dependence on the position of the ring magnet on the drive piston relative to selected position switches. These lights annunciate a coupled condition wherein the index tube is displacing relative to the piston tube, due to coupling with the control rod, as the unbolted CRD flange is lowered. In response to this annunciation, removal will be discontinued until the drive has been uncoupled.
	summary
047088435	summary	The invention relates to a control unit for a nuclear reactor used for the production of electricity or for naval propulsion, including a plurality of sealed vessels in communication with the inside of the tank of the reactor, each enclosing a mechanism for moving a cluster of neutron-absorbing material in the core of the reactor. BACKGROUND OF THE INVENTION For controlling nuclear reactors, in particular pressurized water nuclear reactors, clusters of materials highly absorbent to neutrons are used, these being moved vertically in the core of the reactor between the fuel elements, so as to adjust the power supplied by the reactor according to the power program required. On the other hand, these clusters of absorbent material also serve for producing the emergency shut-off of the reactor, when all the units are caused to fall into maximum insertion position of the core of the reactor. To achieve the movement or the falling back of these clusters of absorbent material extended upwards by an operating rod of great length, displacement mechanisms cooperating with the operating rod are used, and these are arranged inside sealed vessels communicating with the inside of the tank of the reactor within which the core is located. These sealed vessels must permit a displacement of the operating rod corresponding to a movement of the absorbent unit between its positions of maximum and minimum insertion. The amplitude of these movements corresponds substantially to the height of the fuel assemblies, i.e., in the case of currently constructed pressurized water nuclear reactors, about 4.20 m. The displacement mechanisms, for example pawls, are driven by a driving device which is generally arranged at the lower part of the sealed vessels which extend the tank of the reactor upwards from the cover of this tank. Consequently, the height of the sealed vessels above the pawl mechanism, cooperating with the operating rod, including notches also distributed over the length of the rod, must be at least equal to the height of the fuel assemblies. The sealed vessels of very great height must be held at their upper part by means of an anti-earthquake device constituted by a plate itself held in position by means of tie-rods arranged on the walls of the pool of the reactor. It is extremely important, in fact, to limit stresses and distortions in the mechanisms in case of earthquakes to permit the emergency shut-down of the reactor by falling back of the clusters of absorbent material in the case where the reactor undergoes seismic shocks. This plate holding the upper part of the sealed vessels also plays the role of anti-missile plate since it is designed to stop the sealed vessels in the case when the latter would be ejected, so as to prevent any deterioration of the adjacent equipment. It is necessary on the other hand to create, at the level of the drive devices of the mechanisms, ventilation preventing too considerable a rise in temperature under the effect of the primary fluid filling the tank of the reactor and the sealed vessels, and to cool the drive devices to enable them to operate under good conditions. Finally, it is also necessary to heat-insulate the cover of the tank from the outer medium, in order to avoid any loss which could lower the yield of the boiler and oblige the conditioning device, for the building which encloses the reactor, to be reinforced. The control assemblies such as described above have drawbacks due to the fact that their considerable height above the cover of the tank substantially increases the height and bulk of the latter, and that the presence of anti-earthquake devices fixed to the walls of the pool of the reactor complicates operations of opening and closing the cover of the tank. The presence of the anti-earthquake plate above the motors and at the upper part of the sealed vessels is moreover troublesome when it becomes necessary to change a faulty motor or a part of the mechanism situated in the sealed vessel, which operation must be carried out in the presence of ionizing radiation. On the other hand, it is necessary to use a complex and bulky heat extraction device at the level of the drive devices at the lower part of the vessels. Another drawback is that only the cover of the tank is heat-insulated, so that there is produced a considerable heat loss at the level of the sealed vessels. SUMMARY OF THE INVENTION It is an object of the invention to provide a control unit for a nuclear reactor including a plurality of sealed vessels, communicating with the inside of the tank of the reactor, extending this tank above its cover in the vertical direction, and each enclosing a displacement mechanism for a cluster of neutron absorbent material into the core of the reactor, driven by a drive device, this control unit being of reduced height above the cover of the tank and enabling effective protection of the sealed vessels and of the mechanisms in the case of earthquake shocks, easier dismounting and remounting of the cover of the tank, good ventilation of the drive devices for the mechanisms without the use of a complex ventilation device, effective heat-insulation of the group of sealed vessels, as well as easier access to the motors and to the mechanism placed in the sealed vessel to carry out maintenance and possible repair operations. To this end, the drive devices are positioned at the upper part of the sealed vessels, within vertical aeration ducts, and the control unit includes a supporting and insulating device for the sealed vessels constituted by a strong vertical structure fast with the cover of the tank, occupying the whole height of the sealed vessels up to a level below the level of the drive device, a horizontal plate fixed to the upper part of the vertical structure having openings for the passage of the sealed vessels, and an envelope thermally insulating the sealed vessels from the external medium to a level below the level of the drive device. In order that the invention may be more clearly understood, an embodiment of a control unit according to the invention will now be described with reference to the accompanying drawings, purely by way of illustrative example, in comparison with a control unit according to the prior art.
	description	The present invention relates to an X-ray generator that generates the X-ray and extreme ultraviolet (“EUV”) light, and an exposure apparatus having the same. In manufacturing such a fine semiconductor device as a semiconductor memory and a logic circuit in photolithography technology, a reduction projection exposure apparatus has been conventionally employed which uses a projection optical system to project a circuit pattern formed on a mask (reticle) onto a wafer, etc. to transfer the circuit pattern. It is also important for the fine processing to use the exposure light having a shorter wavelength, to make uniform the light intensity that Koehler-illuminates the reticle, and to make uniform the effective light source distribution as an angular distribution of the exposure light that illuminates the reticle and the wafer. The minimum critical dimension to be transferred by the projection exposure apparatus or resolution is proportionate to a wavelength of light used for exposure. Thus, a projection optical apparatus using the EUV light with a wavelength of about 10 nm to about 15 nm much shorter than that of the UV light (referred to as “EUV exposure apparatus” hereinafter) has been developed. The EUV exposure apparatus typically uses a laser plasma light source. It irradiates a laser beam to a target material to generate plasma for use as the EUV light. The EUV exposure apparatus also typically uses a discharge plasma light source that generates the plasma and generates the EUV light by introducing gas to the electrode for discharging. For example, prior art include Japanese Patent Publications, Application Nos. 2002-174700 and 2004-226244. However, the laser plasma light source generates not only the EUV light but also flying particles called debris from the target material. In addition, the debris is emitted from the supply mechanism that supplies the target material. The debris also spreads from the electrode material in the discharge plasma light source. The debris causes contaminations, damages, and lowered reflectivity of optical elements, making uneven the light intensity and deteriorating the throughput. Accordingly, U.S. Pat. No. 6,359,969 arranges a debris mitigation system between a light emitting point and a mirror so as to remove the debris. The debris mitigation system is designed to remove the debris and transmit the EUV light, but actually it shields part of the EUV light and lowers the light intensity and throughput. In addition, the debris mitigation system shields the EUV light of a certain angle range, makes uneven the angular distribution and lowers the imaging performance. For example, FIG. 3 schematically shows a relationship between the light intensity per unit solid angle and the angle from the optical axis near the light source outlet. E1 is energy taken in by the optical system. The minimum angle θ1 is determined, as shown in FIG. 4, by an area shielded by the debris mitigation system, and the maximum angle θ2 is determined by the downstream optical system. Without the debris mitigation system, the minimum angle θ1 is smaller, and the angular uniformity and the light intensity that depends upon a product between the angle and the light intensity improves, but the mirror would get damaged by the debris. Accordingly, it is an exemplary object of the present invention to provide an X-ray generator and an exposure apparatus, which improve the uniformity of each of the light intensity and the angular distribution of the exposure light. An X-ray generator according to one aspect of the present invention for generating plasma and X-ray emitted from the plasma includes a unit for generating the plasma, and plural reflection optical systems for introducing the X-ray through different optical paths. An exposure apparatus according to another aspect of the present invention includes the above X-ray generator, an illumination optical system for illuminating a reticle having a pattern with X-ray generated by said X-ray generator, and a projection optical system for projecting the pattern of the reticle illuminated by said illumination optical system, onto an object to be exposed. A device manufacturing method according to still another aspect of the present invention includes the steps of exposing an object using the above exposure apparatus, and developing the object exposed. Other objects and further features of the present invention will become readily apparent from the following description of the preferred embodiments with reference to accompanying drawings. Referring now to the accompanying drawings, a description will be given of an X-ray generator (EUV light source) 10 according to this embodiment. Here, FIG. 1 is a partial section of the EUV light source 10. The EUV light source 10 includes, in a vacuum chamber 12, a plasma generating means that is not shown in FIG. 1 and will be described later, a debris mitigation system 14, and first and second optical systems 20 and 30 that introduce the EUV light through different optical paths. Thus, the EUV light source 10 has plural optical systems, makes uniform the angular distribution, and increases the light intensity of the light source. The first optical system 20 is a condenser optical system that includes a spheroid mirror and condenses the X-ray (or EUV light) generated from the plasma generating point PL. One of the focal points of the first optical system 20 is the plasma generating point PL, and the other is the light source outlet O. A light that connects a center of the plasma generating point PL to a center of the light source outlet O corresponds to the optical axis OA. The acceptable solid angle is determined by the debris mitigation system 14 and the downstream optical system. The second optical system 30 is an optical system that enhances the light intensity of the light source outlet O and the angular distribution uniformity. More specifically, the second optical system 30 supplements the light intensity and the angular distribution of the EUV light at the light source outlet O corresponding to the angular range shielded by the debris mitigation system 14. The second optical system 30 includes a spheroid mirror 32 and a hyperboloid mirror 34. The number of reflections is once in the first optical system 20, whereas the number of reflections is twice in the second optical system 30. Therefore, the number of reflections is different between these optical systems. One of the focal points of the second optical system 30 is also the plasma generating point PL, and the other is also the light source outlet O. More specifically, the spheroid mirror 32 has one focal point at the plasma emitting point PL, and the other focal point F on the optical axis. The hyperboloid mirror 34 has the focus points at both the plasma emitting point PL and the light source outlet O. Thus, the first and second optical systems 20 and 30 have approximately the same condensing point, where a phrase “approximately the same” intends to cover tolerance. The second optical system 30 is arranged at a position that does not shield the first optical system 20. This embodiment assumes that the plasma emitting point PL uniformly distributes on the focal plane, and the EUV light emits isotropically from each location. It also assumes that the first optical system 20 ideally images, at an image point or the light source outlet O, the plasma emitting point PL of the object point. Therefore, the image uniformly circularly distributes at the image position, and the angular distribution of the EUV light does not depend upon the location. The reflectance of the first optical system 20 is set to R. From the above assumptions, the brightness at the light source outlet O is expressed by IR [W/mm2/sr/nm] irrespective of the capturing optical system, where I [W/mm2/sr/nm] is the brightness of the emission at the plasma emitting point PL. Since an image has a fixed size S at the light source outlet O captured by the optical system downstream from the light source, the light intensity per solid angle at the light source outlet O is IRS [W/sr/nm]. Therefore, a difference of the light intensity per solid angle at the light source outlet O is only the reflectance. If there is only the first optical system 20, the debris mitigation system 14 shields the light and forms an area A that does not include the reflected light, for example, as shown in FIG. 2. FIG. 3 is an angular distribution of the EUV light emitted from the light source. E1 is the energy captured by the first optical system 20. However, when the second optical system 30 is properly designed and its reflectance is set to R′, the angular distribution can be corrected as shown in FIG. 4. In FIG. 4, E1 is the energy captured by the first optical system 20, and E2 is the energy captured by the second optical system 30. In FIG. 4, E1 denotes the light intensity distribution similar to that in FIG. 3, and the light intensity distribution E2 is extended by an angular zone from θ0 to θ1. Thereby, the light intensity increases, the throughput increases, and the more uniform angular distribution in the range from θ0 to θ2 improves the imaging characteristic. The capturing amount of the EUV light is expressed by a product (or etendue) between the solid angle and the size. The etendue [mm2·sr] is defined as (solid angle captured by the optical system)×size. The etendue of 1 or smaller is preferable for exposure of a size of 100 nm or smaller. A description will now be given of the concrete structure of FIG. 1. First, as shown in FIG. 5, in the state where only the first optical system 20 exists, the plasma emitting point PL uniformly distributes in a circle with Φ0.5 mm on the focal plane, and the plasma brightness of 50 [W/mm2/sr/nm]. For example, it is assumed by taking the debris removing capability into account the debris mitigation system 14 disclosed in U.S. Pat. No. 6,359,969 has a size of Φ100 mm. The image has a size of 10 mm2 and a solid angle of 0.1 sr (etendue=1[mm2·sr]) as a result of capture by the optical system downstream from the light source. Table 1 shows parameters of the first optical system 20 determined in terms of the size of the plasma emitting point, the size of the debris mitigation system 14, and the etendue: TABLE 1FIRST OPTICAL SYSTEM (SPHEROID MIRROR) 20DISTANCE BETWEEN FOCAL1000 mmPOINTSLENGTH OF MAJOR AXIS1200 mmLENGTH OF MINOR AXIS 660 mmANGLE BETWEEN OPTICAL 90°-144°AXIS AND LIGHT INCIDENTUPON MIRRORSOLID ANGLE 5 srANGLE BETWEEN OPTICAL3.4°-10°AXIS AND REFLECTED LIGHTSOLID ANGLE0.1 sr As shown in FIG. 6, the angular distribution at the light source outlet has IRS=300 [W/sr/nm], θ1=3.4° and θ2=10° in FIG. 3. Therefore, no light exists due to shielding by the debris mitigation system 14 from 0° to 3.4° from the optical axis OA, and the light exists from 3.4° to 10°. The image at the light source outlet O has a size of about 10 mm2, and a solid angle of 0.1 sr, and thus the etendue of about 1 [mm2·sr]. The energy per unit solid angle of the EUV light emitted from the light source becomes 300 [W/sr/nm], where the reflectance of the mirror is 0.6. The total energy captured by the first optical system 20 and emitted from the light source is 300 [W/sr/nm]×0.1 [sr]=30 [W/nm]. Accordingly, the second optical system 30 is configured as shown in FIG. 1 by combining the spheroid mirror 32 and the hyperboloid mirror 34 so as to supplement the angular range between 0° and 3.4°. The EUV light emitted from the plasma emitting point PL is captured by the second optical system 30, and forms a light source image at the light source outlet. Table 2 shows one example of parameters of the second optical system 30. TABLE 2SECOND OPTICAL SYSTEM 30SPHEROIDHYPERBOLOIDMIRROR 32MIRROR 34DISTANCE BETWEEN FOCAL370 mm 630 mmPOINTSLENGTH OF MAJOR AXIS700 mmLENGTH OF MINOR AXIS660 mmDISTANCE BETWEEN APEXES 440 mmANGLE BETWEEN OPTICAL7°-21°AXIS AND LIGHT INCIDENTUPON MIRRORANGLE BETWEEN OPTICAL0.75°-3.4°AXIS AND REFLECTED LIGHTSOLID ANGLE 0.6 sr0.01 sr Due to the second optical system 30, the light exists in the range between 0.75° and 3.4°, as shown in FIG. 7. The image at the light source outlet O by the second optical system 30 has a size of about 10 mm2 and a solid angle of 0.01 sr. Thus, the energy per unit solid angle of the EUV light emitted from the light source becomes 180 [W/sr/nm], where the reflectance of each of the spheroid and hyperboloid mirrors 32 and 34 is 0.6. The total energy captured by the second optical system and emitted from the light source is 180 [W/sr/nm]×0.01 [sr]=1.8 [W/nm]. This corresponds to θ0=0.75 and IR'S=180 in FIG. 4. As a result of that the first and second optical systems 20 and 30 are simultaneously used, the angular distribution of the energy per unit solid angle is as shown in FIG. 7, and the uneven angular distribution is corrected. The increasing rate of the total energy is 1.8 [W/nm]/30 [W/nm]=0.06, and the light intensity increases by about 6%. While the illustrative parameters of the second optical system 30 are shown in the table, the number of configurations of the second optical system 30 is not one even if it combines the spheroid mirror 32 and the hyperboloid 34. The image to be captured by the downstream illumination optical system has a size of 10 mm2 and a solid angle of 0.01 sr from 0° to 3.4°. Therefore, the maximum etendue that can be captured by the second optical system 30 and fed to the following optical system is 100 [mm2]×0.01 sr=0.1 [mm2·sr]. The second optical system may have an arbitrary configuration as long as it captures the etendue of 0.1 [mm2·sr] or greater from the plasma, and supplements the angular distribution between 0° and 3.4°. For example, the EUV light source 10A having a second optical system 30A having a configuration shown in FIG. 8 has the same effect. Table 3 shows parameters of the second optical system 30A. TABLE 3SECOND OPTICAL SYSTEM 30ASPHEROIDHYPERBOLOIDMIRROR 32AMIRROR 34ADISTANCE BETWEEN FOCAL100 mm 630 mmPOINTSLENGTH OF MAJOR AXIS700 mmLENGTH OF MINOR AXIS690 mmDISTANCE BETWEEN APEXES 440 mmANGLE BETWEEN OPTICAL24°-24°AXIS AND LIGHT INCIDENTUPON MIRRORANGLE BETWEEN OPTICAL0.75°-3.4°AXIS AND REFLECTED LIGHTSOLID ANGLE 3 sr0.01 sr Alternatively, an EUV light source 10B having a second optical system 30B that includes a plane mirror 32B and a mirror 34B having a curvature may be used. The focal point of the second optical system 30B accords with two focal points of the first optical system 20, i.e., the plasma emitting point PL and the light source outlet O. The mirrors 32B and 34B in the second optical system 30 do not have a revolving body, but preferably have a rotational symmetry with respect to the optical axis. The number of reflections of the second optical system 30B is not limited to twice, but the smaller number of reflections is preferable when the energy attenuation due to the reflection is considered. This embodiment is similar to the first embodiment in that the second optical system 30B does not shield the optical path of the first optical system 20. The second optical system 30 may include plural mirrors each having a curvature. The focal points of the second optical system 30 accord with the two focal points of the first optical system 20, i.e., the plasma emitting point PL and the light source outlet O. The number of reflections of the second optical system is not limited to twice, but the smaller number of reflections is preferable when the energy attenuation due to the reflection is considered. This embodiment is similar to the first embodiment in that the second optical system 30 does not shield the optical path of the first optical system 20. Referring now to FIG. 10, a description will be given of the X-ray generator that has a debris mitigation system of this embodiment and the exposure apparatus 100 having the same. Here, FIG. 10 is a schematic block diagram of a structure of the exposure apparatus 100. The inventive exposure apparatus 100 is a projection exposure apparatus that exposes a circuit pattern of a reticle 120 onto an object 140 using the EUV light with a wavelength of 13.4 nm as exposure light in a step-and-scan or step-and-repeat manner. This exposure apparatus is suitable for a lithography process less than submicron or quarter micron, and the present embodiment uses the step-and-scan exposure apparatus (also referred to as a “scanner”) as an example. The “step-and-scan”, as used herein, is an exposure method that exposes a reticle pattern onto a wafer by continuously scanning the wafer relative to the reticle, and by moving, after a shot of exposure, the wafer stepwise to the next exposure area to be shot. The “step-and-repeat” is another mode of exposure method that moves a wafer stepwise to an exposure area for the next shot every shot of cell projection onto the wafer. The exposure apparatus 100 includes an illumination apparatus 110, a reticle stage 125 that supports and mounts the reticle 120, a projection optical system 130, a wafer stage 145 that supports and mounts the object 140 to be exposed, an alignment detecting mechanism 150, and a focus position detecting mechanism 160. The illumination apparatus 110 uses arc-shaped EUV light, for example, with a wavelength of 13.4 nm corresponding to an arc-shaped field of the projection optical system 130 to illuminate the reticle 120, and includes an EUV light source 112 and illumination optical system 114. The EUV light source 112 according to this embodiment is a laser plasma light source that irradiates a laser beam LL to a target T, and generates plasma and the EUV light EL radiated from the plasma. The EUV light source 112 may apply any one of the above EUV light sources 10 to 10B. The EUV light source 112 includes a laser light source part 40 that irradiates the laser beam LL, an optical system 50 that introduces the laser beam LL to the target T, and a target supply unit 60, in addition to the above structure of the EUV light source 10. FIG. 10 omits a detailed configuration of the EUV light source 10 for illustration purposes. The laser beam LL emitted from the laser light source part is condensed by the optical system 50, and irradiated onto the target T. The target T may include copper, tin, aluminum and other metal materials, or Xe gas, droplets and cluster. For example, the target T is intermittently supplied as Xe droplets from the target supply unit 60 in synchronization with the emissions of the laser beam LL of the laser light source part 40. The energy from the laser beam LL generates the high-temperature and high-density plasma from the target T, and emits the EUV light from the plasma 1. The EUV light is collected by the first optical system 10, and supplied to the following illumination optical system 114. The optical system 50 includes a lens, a mirror, a plane-parallel plate glass, etc., and serves as part of the vacuum diaphragm of the vacuum chamber 12. A laser introduction window 54 that transmits the laser beam LL to the vacuum chamber 12 is part of the optical system 50. The optical system 50 adjusts the laser beam LL for efficient acquisitions of the EUV light so that its spot size and energy density on the target T is necessary and sufficient to generate the plasma. The plasma also generates the debris in addition to the EUV light, which originates from the target T, copper, and target supply unit 60. The generated debris gradually adheres to and deposits on the first optical system 10, lowering the light intensity. Accordingly, the debris mitigation system 14 is arranged between the plasma emitting point PL and the first optical system 10. In addition, the second optical system 30 omitted in FIG. 10 supplements the EUV light shielded by the debris mitigation system 14. The illumination optical system 114 includes condenser mirrors 114a, and an optical integrator 114b. The condenser mirror 114a serves to collect the EUV light that is isotropically irradiated from the laser plasma. The optical integrator 114b serves to uniformly illuminate the reticle 120 with a predetermined numerical aperture (“NA”). An aperture to limit the illumination area to an arc shape is also provided. The illumination optical system 114 may use a multilayer mirror and an grazing angle total reflection mirror. The reticle 120 is a reflection reticle that has a circuit pattern or image to be transferred, and supported and driven by the reticle stage 125. The diffracted light from the reticle 120 is reflected by the projection optical system 130 and projected onto the object 140. The reticle 120 and the object 140 are arranged in an optically conjugate relationship. The exposure apparatus 100 is a scanner, and projects a reduced size of the pattern of the reticle 120 onto the object 140 by scanning the reticle 120 and the object 140. The reticle stage 125 supports the reticle 120 and is connected to a moving mechanism (not shown). The reticle stage 125 may use any structure known in the art. A moving mechanism (not shown) may include a linear motor etc., and drives the reticle stage 125 at least in a direction X and moves the reticle 120. The exposure apparatus 100 synchronously scans the reticle 120 and the object 140. The projection optical system 130 uses plural multilayer mirrors 130a to project a reduced size of a pattern of the reticle 120 onto the object 140. The number of mirrors 130a is about four to six. For wide exposure area with the small number of mirrors, the reticle 120 and object 140 are simultaneously scanned to transfer a wide area that is an arc-shaped area or ring field apart from the optical axis by a predetermined distance. The projection optical system 130 has a NA of about 0.2 to 0.3. The instant embodiment uses a wafer for the object 140, but it may include a spherical semiconductor and liquid crystal plate and a wide range of other objects to be exposed. Photoresist is applied onto the object 140. The object 140 is held onto the wafer stage 145 by a wafer chuck 145a. The wafer stage 145 moves the object 140, for example, using a linear motor in XYZ directions. The reticle 120 and the object 140 are synchronously scanned. The positions of the reticle stage 125 and wafer stage 145 are monitored, for example, by a laser interferometer, and driven at a constant speed ratio. The aligment detection system 150 measures a positional relationship between the position of the reticle 120 and the optical axis of the projection optical system 130, and a positional relationship between the position of the object 140 and the optical axis of the projection optical system 130, and sets positions and angles of the reticle stage 125 and the wafer stage 145 so that a projected image of the reticle 120 may be positioned in place on the object 140. A focus detection optical system 160 measures a focus position on the object 140 surface, and control over a position and angle of the wafer stage 145 may always maintain the object 140 surface at an imaging position of the projection optical system 130 during exposure. In exposure, the EUV light emitted from the illumination apparatus 110 illuminates the reticle 120, and images a pattern of the reticle 120 onto the object 140 surface. The instant embodiment uses an arc or ring shaped image plane, scans the reticle 120 and object 140 at a speed ratio corresponding to a reduction ratio to expose the entire surface of the reticle 120. The EUV light source 112 in the illumination apparatus 110 used for the exposure apparatus 100 improves the light intensity and the angular distribution of the exposure light, sufficiently removes the debris, and stably generates the EUV light. Thus, the exposure apparatus 100 may manufacture devices (such as a semiconductor device, a LCD device, an image-taking device (such as a CCD), and a thin-film magnetic head) with good economical efficiency and throughput. Referring now to FIGS. 11 and 12, a description will be given of an embodiment of a device manufacturing method using the above exposure apparatus 100. FIG. 11 is a flowchart for explaining manufacture of devices (i.e., semiconductor chips such as IC and LSI, LCDs, CCDs, etc.). Here, a description will be given of a fabrication of a semiconductor chip as an example. Step 1 (circuit design) designs a semiconductor device circuit. Step 2 (reticle fabrication) forms a reticle having a designed circuit pattern. Step 3 (wafer preparation) manufactures a wafer using materials such as silicon. Step 4 (wafer process), which is referred to as a pretreatment, forms actual circuitry on the wafer through photolithography using the mask and wafer. Step 5 (assembly), which is also referred to as a posttreatment, forms into a semiconductor chip the wafer formed in Step 4 and includes an assembly step (e.g., dicing, bonding), a packaging step (chip sealing), and the like. Step 6 (inspection) performs various tests for the semiconductor device made in Step 5, such as a validity test and a durability test. Through these steps, a semiconductor device is finished and shipped (Step 7). FIG. 12 is a detailed flowchart of the wafer process in Step 4. Step 11 (oxidation) oxidizes the wafer's surface. Step 12 (CVD) forms an insulating film on the wafer's surface. Step 13 (electrode formation) forms electrodes on the wafer by vapor disposition and the like. Step 14 (ion implantation) implants ions into the wafer. Step 15 (resist process) applies a photosensitive material onto the wafer. Step 16 (exposure) uses the exposure apparatus 100 to expose a circuit pattern of the reticle onto the wafer. Step 17 (development) develops the exposed wafer. Step 18 (etching) etches parts other than a developed resist image. Step 19 (resist stripping) removes the disused resist after etching. These steps are repeated, and multilayer circuit patterns are formed on the wafer. The device manufacturing method of this embodiment may manufacture a higher quality device than the conventional method. The device fabrication method that uses the exposure apparatus 100 and the resultant devices also constitute one aspect of the present invention. Further, the present invention is not limited to these preferred embodiments, and various variations and modifications may be made without departing from the scope of the present invention. This application claims a benefit of priority based on Japanese Patent Application No. 2004-295625, filed on Oct. 8, 2004, which is hereby incorporated by reference herein in its entirety as if fully set forth herein.
048658049	claims	1. An end plug for welded disposition within the end of a tube, comprising: a circumferentially extending, axially oriented land surface, having a radial extent defined by means of a first predetermined dimension, for disposition within said end of said tube; a circumferentially extending, axially oriented land surface, having a radial extent defined by means of a second predetermined dimension which is greater than said first predetermined dimension, for disposition outside of said end of said tube, said second land surface being disposed upstream of said first land surface; an annularly extending, radially oriented shoulder portion, defined at the downstream end of said second land surface and having a radially inward depth which is greater than the difference defined between said first and second radial dimensions of said first and second land surfaces, for engaging said end of said tube in a butt contact fashion; and annular groove means defined between the upstream end of said first land surface and said shoulder portion of said end plug, for eliminating porosity defects normally developed within a weldment defined between said tube end and said end plug when said end plug is welded within said tube end, and including a conical surface which extends radially outwardly from the innermost radial depth extent of said shoulder portion to said upstream end of said first land surface. said conical surface is disposed at an angle of 45.degree. with respect to said shoulder portion of said end plug. said end plug is a nuclear reactor fuel rod end plug for disposition within the end of a nuclear reactor fuel rod cladding tube. said groove is defined to a radially inwardly extending depth of 0.100 inches. means for forming said weldment defined between said tube and said end plug by laser beam welding. TIG welding means for forming said weldment defined between said tube and said end plug. said end plug is fabricated from stainless steel. said end plug is fabricated from a zirconium alloy. said weldment is an annular girth weld defined about the outer periphery of said juncture defined between said end plug and said tube. a first circumferentially extending, axially oriented land surface, having a radial extend defined by means of a first predetermined dimension, for disposition within said end of said tube; a second circumferentially extending, axially oriented land surface, having a radial extent defined by means of a second predetermined dimension which is greater than said first predetermined dimension, for disposition outside of said end of said tube, said second land surface being disposed upstream of said first land surface; an annularly extending, radially oriented shoulder portion, defined at the downstream end of said second land surface and having a radially inward depth which is greater than the difference defined between said first and second radial dimensions of said first and second land surfaces, for engaging said end of said tube in a butt contact fashion; and annular groove means defined between the upstream end of said first land surface and said shoulder portion of said end plug, for eliminating porosity defects normally developed within a weldment defined between said tube end and said end plug when said end plug is welded within said tube end under said laser beam welding conditions, and including a conical surface which extends radially outwardly from the innermost radial depth extent of said shoulder portion to said upstream end of said first land surface. said end plug is a nuclear reactor fuel rod end plug for disposition within the end of a nuclear reactor fuel rod cladding tube. a first circumferentially extending, axially oriented land surface, having a radial extent defined by means of a first predetermined dimension, for disposition within said end of said tube; a second circumferentially extending, axially oriented land surface, disposed upstream of said first land surface and having a radial extent defined by means of a second predetermined dimension which is greater than said first predetermined dimension, for disposition outside of said end of said tube; an annularly extending, radially oriented shoulder portion, defined at the downstream end of said second land surface and having a radially inward depth which is greater than the difference defined between said first and second radial dimensions of said first and second land surfaces, for engaging said end of said tube in a butt contact fashion; and annular groove means defined between the upstream end of said first land surface and said shoulder portion of said end plug, for eliminating porosity defects normally developed within a weldment defined between said end plug and said tube end when said end plug is welded within said tube end by means of said welding process, and including a conical surface which extends radially outwardly from the innermost radial depth extent of said shoulder portion to said upstream end of said first land surface. means for forming said weldment defined between said tube and said end plug by laser beam welding. a generally right circular cylindrical smaller diameter portion and a coaxially joined generally right circular cylindrical larger diameter portion, the juncture of said smaller and larger diameter portions having a generally radially inwardly extending circumferential groove as defined by means of a radially oriented shoulder surface for engaging said each end of said cladding tube and a conical surface extending radially outwardly from the radially innermost portion of said shoulder surface, with said smaller diameter portion frictionally longitudinally engageable with the interior surface of said tube and with said larger diameter portion having a chamfered free end and having a generally constant diameter from said juncture to said chamfered free end. (a) a cladding tube; (b) a plurality of nuclear fuel pellets disposed in said tube; and (c) an end plug welded to each end of said tube, said end plug including a generally right circular cylindrical smaller diameter portion and a coaxially joined generally right circular cylindrical larger diameter portion, the juncture of said smaller and larger diameter portions having a generally radially inwardly extending circumferential groove as defined by means of a radially oriented shoulder surface for engaging said each end of said cladding tube and a conical surface extending radially outwardly from the radially innermost portion of said shoulder surface, with said smaller diameter portion frictionally longitudinally engaged with the interior surface of said tube and with said larger diameter portion having a chamfered free end and having a generally constant diameter from said juncture to said chamfered free end. said conical surface is disposed at an angle of 45.degree. with respect to said shoulder portion of said end plug. said radially inward depth of said shoulder portion is 0.100 inches. said end plug is fabricated from a zirconium alloy. said conical surface is disposed at an angle of 45.degree. with respect to said shoulder portion of said end plug. said radially inward depth of said shoulder portion is 0.100 inches. said welding process comprises laser beam welding techniques. said end plug is fabricated from a zirconium alloy. 2. An end plug as set forth in claim 1, wherein: 3. An end plug as set forth in claim 1, wherein: 4. An end plug as set forth in claim 1, wherein: 5. An end plug as set forth in claim 1, further comprising: 6. An end plug as set forth in claim 1, further comprising: 7. An end plug as set forth in claim 1, wherein: 8. An end plug as set forth in claim 1, wherein: 9. An end plug as set forth in claim 1, wherein: 10. An end plug for welded disposition within the end of a tube by means of laser beam welding techniques, comprising: 11. An end plug as set forth in claim 10, wherein: 12. A nuclear reactor fuel rod end plug for fixation within the end of a nuclear reactor fuel rod cladding tube by means of a welding process, comprising: 13. A nuclear reactor fuel rod end plug as set forth in claim 12, wherein: 14. An end plug for welding to each end of a nuclear reactor fuel rod cladding tube, said end plug comprising: 15. A nuclear reactor fuel rod, comprising: 16. An end plug as set forth in claim 10, wherein: 17. An end plug as set forth in claim 10, wherein: 18. An end plug as set forth in claim 10, wherein: 19. An end plug as set forth in claim 12, wherein: 20. An end plug as set forth in claim 12, wherein: 21. An end plug as set forth in claim 12, wherein: 22. An end plug as set forth in claim 12, wherein:
047529474	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS A primary radiation diaphragm 3 is shown in FIG. 1 for use in gating an X-ray beam 2 generated at an X-ray focus, schematically indicated at 1. The primary diaphragm 3 includes a rectangular diaphragm system 4 having a pair of diaphragm plates 5 and 6 disposed in a plane and adjustable in opposite directions relative to each other, and another pair of diaphragm plates 5a and 6a disposed in a plane spaced from the plane containing the plates 5 and 6, the plates 5a and 6a also being mounted for adjustable movement in opposite directions relative to each other. The upper diaphragm plates 5a and 6a are synchronously moved in combination to a slightly greater extent then are the plates 5 and 6 with respect to a central ray 7 of the X-ray beam 2 so as to permit, if needed, diverging of the beam 2 as indicated in FIG. 1. Two further pairs of diaphragm plates are also included within the diaphragm system 4 movable in opposite directions which are perpendicular to the directions of movement of the diaphragm pairs 5a and 6 a and the diaphragm pair 5 and 6. One plate 8 and one plate 8a of these additional pairs of plates are shown in FIG. 1. The plates 8 and 8a, and the corresponding plates in each pair (not shown) limit the extent of the X-ray beam 2 in a direction perpendicular to the plane of FIG. 1. The primary diaphragm 3 also includes an iris diaphragm 9 disposed in front of the rectangular diaphragm system 4 in the direction of beam propagation. The iris diaphragm 9 adapts the shape of the X-ray beam 2 to the shape of the input luminescent screen of an X-ray image intensifier (not shown) by inserting wedges at the corners of the rectangular diaphragm system 4, as needed. Two diaphragm plates 10 and 20 are shown in FIG. 3 with the surrounding parts and mountings omitted for clarity. Those details are shown in FIGS. 2 and 3 discussed below. The diaphragm plates 10 and 20 are adjustable in opposite directions relative to the central ray 7 in two different parallel planes so that the plates 10 and 20 can be moved past each other over each other. The path of adjustment of the diaphragm plates 10 and 20 is thus large enough so that each diaphragm plate 10 and 20 can selectively limit the X-ray beam 2 with one of its two edges, those two edges being disposed perpendicular to the path of adjustment of the plates. For example, diaphragm plate 10 has a left edge 15 which may be selectively contoured, and a right edge 14, which may be straight. The primary radiation diaphragm 3 also has a light sight including a light source 12 and a mirror 13 which is transmissive for x-radiation. The mirror 13 generates a visible light field which is coextensive with the X-ray field so that the extent of the gated X-ray field can be seen on the examination subject. The gating of the X-ray beam 2 by the diaphragm plates 10 and 20 is achieved as more clearly seen in FIGS. 2 and 3. In FIG. 2, more clarity only the left diaphragm plate 10 is shown. The plate 10 is shown at a left extreme position in dashed lines and at a right extreme position in dot and dashed lines in FIG. 2. A diaphragm plate 10 is mounted on an annular disc 11 and is displaceable along a slot 12 in the disc 11. The plate 10 is guided in the slot 12 by two pegs 13. The slot 12 is of a length such that the X-ray beam 2 can be optionally limited by the straight right edge 14 of the plate 10, or by the curved left edge 15 of the diaphragm plate 10. The maximum diaphragm aperture is defined by a rectangular opening 16 in the disc 11. As can be seen in FIGS. 2 and 3, the diaphragm plate 10 can be moved from the left extreme position to the right extreme position, in which case the curved edge 15 limits the X-ray beam 2. The different shapes of edges and 14 permit the gated field to similarly exhibit a different shape, dependent upon the position of the diaphragm plate 10. The edge 15 functions to gate the beam to a shape corresponding to the heart contour, and as stated above, is curved for this purpose. The edge 14 is a straight line. In a known manner, the diaphragm plate 10 is bevelled at its regions close to the edge, and is thus partially transparent to x-radiation. The diaphragm plate 20 (not shown in FIG. 2) is a mirror image of the plate 10. Adjustment of the diaphragm plate 10 (as well as the plate 20 by a similar mechanism) is undertaken by a pin 17 mounted to the plate 10 which is moved in an oblong opening of a disc 19 disposed beneath the disc 11. The disc 19, as well as a disc 22 disposed above the disc 11, has a central opening for defining the maximum field size. The disc 22 has not been shown in FIG. 2. The disc 22 also has a radial slot, in which a pin 23 of the diaphragm 20 is displaceably guided. For adjusting the diaphragm plates 10 and 20, a relative rotation of the discs 19 and 22 relative to the disc 11 is undertaken. When all three discs 11, 19 and 22 are rotated congruently and synchronously, the position of the gated slot is also rotated. The discs 11, 19 and 22 are provided with outside denticulation, schematically indicated by the dashed line inside the circumference of the disc 11 in FIG. 2, so as to be individually or synchronously rotated. The pins 17 and 23 are mounted to shoulders of the diaphragm plates 10 and 20. The shoulders are bent downwardly or upwardly at right angles to the remainder of the plates. The diaphragm plates 10 and 20 can be moved completely past one another so as to selectively limit the X-ray beam 2 with one of the two edges of the plates. These are the two edges referenced 14 and 15 for the diaphragm plate 10. As stated above, the diaphragm plate 20 is a mirror image of the diaphragm plate 10, that is, the straight edge is at the left in the position shown in FIG. 3, and the edge matched to the heart contour is at the right as shown in FIG. 3. Although modifications and changes may be suggested by those skilled in the art it is the intention of the inventor to embody within the patent warranted hereon all changes and modificatons as reasonably and properly come within the scope of their contribution to the art.
	claims	1. An ion implantation system comprising:an ion implanter configured to produce a ribbon-like ion beam;an AEF system configured to filter an energy of the ribbon-like ion beam by bending the beam at a final energy bend; an AEF dose cup associated with the AEF system, and configured to measure ion beam current substantially immediately following the final energy bend; andan end station downstream of the AEF system, the end station defined by a chamber wherein a workpiece is secured in place for movement relative to the ribbon-like ion beam for implantation of ions therein;wherein the AEF dose cup is located external to the end station chamber. 2. The system of claim 1, wherein the AEF system comprises:a pair of deflection plates to deflect the ion beam by a target angle of deflection, thereby defining a final energy level of the ion beam corresponding to the angle of deflection from an original path;a set of suppression electrodes downstream of the deflection plates, the electrodes configured to terminate a positive potential imparted to the ion beam by the deflection plates and a beam dump plate to absorb energy of neutral particles in the beam not deflected by the deflection plates; andthe AEF dose cup immediately following the final energy bend in the ion beam for measuring the ion current in the beam before a substantial portion of the ion beam can become neutralized. 3. The system of claim 1, wherein the final energy level of the ion beam corresponds to an angle of deflection of about 15 degrees from the original path. 4. The system of claim 1, wherein the AEF dose cup is located in an overscan region in relationship to the area of the workpiece scanned by the ribbon-like ion beam. 5. The system of claim 1, wherein the plane of the final energy bend in the ion beam is orthogonal to the plane of the ribbon-like ion beam. 6. The system of claim 1, wherein the AEF dose cup is located within the AEF system located in an AEF chamber region, wherein a pressure is reduced by a pump below a pressure of the end station downstream from the AEF chamber. 7. The system of claim 1, further comprising a dose compensation control system, wherein the AEF dose cup measurement is used to control the scan velocity of the workpiece across the ion beam. 8. The system of claim 7, further comprising pressure compensation to correct the AEF dose cup measurements, the pressure compensation comprising:a pressure sensor operable to measure a pressure associated with the implantation system in the AEF system located external to the end station chamber, the sensor having an output connected to the compensation control system to correct the scan velocity based on the pressure measured;one of a compensation circuit, and a compensation software routine adapted to determine a pressure compensation factor as a function of the measured pressure and the measured ion beam current; anda scan motion control system operable to control a scan velocity of the workpiece across the ion beam based on the pressure measured and the pressure compensation factor. 9. The system of claim 8, wherein the AEF system is located in an AEF chamber region external to the end station chamber, and wherein the pressure within the AEF chamber is further reduced by a pump below the pressure of the end station chamber downstream from the AEF chamber to further reduce the effect of outgassing and pressure on the AEF cup. 10. The system of claim 1, wherein readings from a dose cup near the workpiece are compared to those of the AEF cup during an implant to deduce the charge exchange rate difference between the two positions, thereby enabling a determination of the number of neutral particles produced over the corresponding path length. 11. The system of claim 1, wherein the ion current measured at the AEF dose cup is proportional to the current going to the workpiece. 12. The system of claim 1, wherein the ion current implanted at the workpiece is determined to be proportional to the current measured in the AEF dose cup by a scaling factor Cp according to the relationship:Iimplanted=IAEFCp. 13. The system of claim 12, wherein Cp is calculated based on readings of the AEF cup and an End Station cup to determine the fraction of charge exchange affecting the AEF cup and to compensate the readings for pressure changes. 14. The system of claim 1, wherein the ribbon-like ion beam is a scanned ion beam. 15. The system of claim 1, wherein the ribbon-like ion beam is a continuous ion beam. 16. The system of claim 1, wherein the AEF dose cup measures the ion current associated with final energy of the beam at a location before the beam traverses a greater portion of the distance of the beam path toward the workpiece. 17. The system of claim 16, wherein the AEF dose cup is located nearer to the final energy bend in the ion beam than to the workpiece. 18. The system of claim 1, wherein the AEF dose cup is located nearer to the final energy bend in the ion beam than to the workpiece. 19. The system of claim 16, wherein the AEF dose cup is located at a position wherein measurements of the ion current associated with final energy of the beam are made before the beam has subsequently exchanged a greater portion of the ions of the beam on the path toward the workpiece. 20. The system of claim 1, wherein the AEF dose cup is located at a position wherein measurements of the ion current associated with final energy of the beam are made before the beam has subsequently exchanged a significant portion of the ions of the beam on the path toward the workpiece. 21. An ion implantation system comprising:an ion implanter configured to produce one of a scanned or ribbon-like ion beam;an AEF system configured to filter an energy of the ion beam by bending the beam at a final energy bend; an AEF dose cup associated with the AEF system, and configured to measure ion beam current, the AEF dose cup located following the final energy bend nearer to the final energy bend than to a workpiece; andan end station downstream of the AEF system, the end station defined by a chamber wherein the workpiece is secured in place and provides movement relative to the ribbon-like ion beam for implantation of ions therein;wherein the AEF dose cup is located external to the end station chamber. 22. The system of claim 21, wherein the AEF system comprises:a pair of deflection plates to deflect the ion beam by a target angle of deflection, thereby defining a final energy level of the ion beam corresponding to the angle of deflection from an original path;a set of suppression electrodes downstream of the deflection plates, the electrodes-configured to terminate a positive potential imparted to the ion beam by the deflection plates; andthe AEF dose cup immediately following the final energy bend in the ion beam for measuring the ion current in the beam before a substantial portion of the ion beam can become neutralized. 23. The system of claim 21, wherein the final energy level of the ion beam corresponds to an angle of deflection of about 15 degrees from the original path. 24. The system of claim 21, wherein the AEF dose cup is located in an overscan region in relationship to the area of the workpiece scanned by the ribbon-like ion beam. 25. The system of claim 21, wherein the plane of the final energy bend in the ion beam is orthogonal to the plane of the ribbon-like ion beam. 26. The system of claim 21, wherein the AEF dose cup is located within the AEF system that is located in a chamber region upstream of the end station, wherein a pressure is reduced by a pump below a pressure of the end station. 27. The system of claim 21, further comprising a dose compensation control system, wherein the AEF dose cup measurement is used to control the scan velocity of the workpiece across the ion beam. 28. The system of claim 27, further comprising pressure compensation to correct the AEF dose cup measurements, the pressure compensation comprising:a pressure sensor operable to measure a pressure associated with the implantation system in the AEF system located external to the end station chamber, the sensor having an output connected to the compensation control system to correct the scan velocity based on the pressure measured;one of a compensation circuit, and a compensation software routine adapted to determine a pressure compensation factor as a function of the measured pressure and the measured ion beam current; anda scan motion control system operable to control a scan velocity of the workpiece across the ion beam based on the pressure measured and the pressure compensation factor. 29. The system of claim 27, wherein an AEF system is located in an AEF chamber region external to the end station chamber, and wherein the pressure within the AEF chamber is further reduced by a pump below the pressure of the end station chamber downstream from the AEF chamber to further reduce the effect of outgassing and pressure on the AEF cup. 30. The system of claim 21, wherein readings from a dose cup near the workpiece are compared to those of the AEF cup during an implant to deduce the charge exchange rate difference between the two positions, thereby enabling a determination of the number of neutral particles produced over the corresponding path length. 31. The system of claim 21, wherein the ion current measured at the AEF dose cup is proportional to the current going to the workpiece. 32. The system of claim 21, wherein the ion current implanted at the workpiece is determined during implant to be proportional to the current measured in the AEF dose cup by a scaling factor Cp according to the relationship:Iimplanted=IAEFCp. 33. The system of claim 32, wherein Cp is calculated based on readings of the AEF cup and an End Station cup to determine the fraction of charge exchange affecting the AEF cup and to compensate the readings for pressure changes. 34. The system of claim 21, wherein the ion beam is a scanned ion beam. 35. The system of claim 21, wherein the ion beam is a continuous ribbon-like ion beam. 36. The system of claim 21, wherein the AEF dose cup is located at a position wherein measurements of the ion current associated with final energy of the beam may be made before the beam has subsequently exchanged a greater portion of the ions of the beam on the path toward the workpiece. 37. The system of claim 21, wherein the AEF dose cup is located at a position wherein measurements of the ion current associated with final energy of the beam may be made before the beam has subsequently exchanged a significant portion of the ions of the beam on the path toward the workpiece. 38. A method of dynamically compensating for pressure and ion source variations using an AEF dose cup located near a final energy bend upstream of an end station, the AEF dose cup located external to an end station chamber in an ion implantation system, comprising:providing a workpiece within the end station chamber having a profiler cup at therein near the plane of a workpiece of the ion implantation system;calibrating the AEF dose cup during an implant set-up process to establish an ion current proportionality constant relative to the profile cup;assuming an initial scan velocity of the workpiece past the ion beam;implanting a region of the workpiece with an ion beam using the ion implantation system and the established ion current proportionality constant while measuring ion beam current at the AEF dose cup in the ion implantation system;measuring the ion current associated with the implanted workpiece; anddetermining a scan velocity compensation according to the initial scan velocity, the measured ion beam current at the AEF dose cup, the ion current proportionality constant, and a desired dose level.
052672743	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method of determining the chemical composition of apatite grains contained within rock samples taken from the bore of a well being drilled or from the surface of the Earth. 2. Description of the Prior Art Numerous methods of analyzing the chemical composition of minerals have been used including the currently used method of using a microprobe to focus a beam of electrons onto the surface of a material and causing X-rays to be generated. By carefully monitoring the X-rays emitted during the bombardment of a surface by the electron beam, it is possible to determine the chemical composition of the material being bombarded. Presently, in the oil exploration field, it is desirous to identify apatite grains contained within rocks which are rich in fluorine in order to perform analyses on them for purposes of determining the thermal history of the rock. This is most often accomplished by grinding or crushing the rock sample to obtain sand-sized grains and then separating the grains containing apatite crystals from the surrounding grains of minerals and rock in a multiple stage process using the density and magnetic characteristics of the surrounding minerals. After a multiple step process, the remaining grains of the rock sample consist of a sufficiently high percentage of apatite for purposes of analysis. A representative portion of the remaining apatite grains is then incorporated into an epoxy wafer attached to a petrographic slide, polished to expose internal surfaces, and etched with acid. The epoxy wafer is covered with a muscovite mica detector in the form of a mask and placed adjacent to the core of a nuclear reactor along with a uranium-doped glass covered with a second muscovite mica detector where both are irradiated with thermal neutrons. The epoxy wafer, uranium-doped glass, and their attached muscovite mica detectors are then removed from the reactor and the muscovite mica detectors are immersed in hydrofluoric acid to etch the induced fission tracks caused by the induced fission of uranium in the apatite grains and the uranium-doped glass. The concentration of .sup.238 U and the fission track density per unit volume are determined for a volume of an apatite grain beneath a selected area of the apatite grain and the fission track age for each grain is determined. In the methods currently practiced within the industry, the chemical composition of the apatite grains is then determined by a process known as microprobe analysis. This process consists of placing the apatite grains under an electron beam thereby inducing each affected apatite grain to produce X-rays. Through the careful monitoring and detection of these emitted X-rays, it is possible to determine whether the apatite grain being subjected to the electron beam is fluorine-rich, chlorine-rich, or water-rich, or some combination of these types. The currently practiced process of determining the chemical composition of the apatite grains is an extremely costly, time consuming, and labor intensive process, and, as such, it is rarely done with sufficient completeness. Additionally, the level of expertise required of the person performing the actual steps of the analyses currently used is greater than in that of the present invention. The method of the present invention demands a high level of expertise only during the interpretation phase rather than during the actual performance of the analyses, consumes less time for a given number of samples, and results in greatly increased capital savings. Read, U.S. Pat. No. 1,799,604 discloses a method and apparatus for identifying precious gems and crystals which operates upon the principle of an initial ray or beam of light striking a diamond and being reflected or refracted into secondary rays of light whose intensity and direction are dependent upon the angles, faces and imperfections in the diamond. This apparatus allows the recording of the secondary rays so that the diamond or crystal can be identified thereby under identical conditions. Grayson, U.S. Pat. No. 4,093,420 discloses a method of prospecting for accumulations of minerals based upon organic material present in the rock samples taken at differing locations and depths. This method is based upon the amount of light emitted or absorbed by the specific organic particles within the rocks and the gradients between samples taken at the same location but at different depths are plotted on a map. By repeating this procedure for numerous locations, the contours which will appear on the map will encircle the mineral deposit. Trossarelli, U.S. Pat. No. 4,906,093 discloses an illuminator device for the spectroscopic observation of samples wherein the substance under examination is illuminated by a source of white light and possesses optical fibers for transmitting the residual illumination light passed through the substance observed to an observation spectroscope. Dobrilla, U.S. Pat. No. 4,925,298 discloses a method for measuring and plotting the etch pit density on the surface of an etched test wafer. In this method, a beam of light is focused onto an etched wafer and the intensity of the light reflected is compared with the intensity of a reference wafer to calculate the etch pit density of the etched wafer. This procedure is repeated for different areas of the etched wafer so that any variances within each wafer may be detected. In the method of the present invention, the chemical composition of the apatite grains is determined by taking measurements of etch figures formed by the intersection of etched naturally occurring fission tracks or other crystallographic imperfections, such as other charged-particle tracks, defects, dislocations, fluid inclusions, mineral inclusions, polishing scratches, and fractures, with the planar surface of the apatite grain being observed. The purpose of the measurements is to determine if the apatite is of a fluorine-rich, chlorine-rich, or water-rich nature. Apatite grains which are fluorine-rich are identified by the characteristic dimensions of the etch figures within their etched planar surfaces. The dimensions of the etch figures in fluorine-rich apatite and relatively non-fluorine-rich apatite are taken and, together with other information gathered by methods of analysis already used within the geological sector of the scientific community, the pooled fission track ages and the pooled distributions of perceived track lengths pertaining to the fluorine-rich apatite grains and the relatively non-fluorine-rich apatite grains, respectively, are determined. While the prior art discloses methods and apparatus with which to observe mineral or rock samples and even calculate the density of etch pits on the surface of a wafer containing crystals which has been etched, the actual use of the dimensions of the resulting etch pits and the etch figures they form has not been practiced to determine chemical composition of the crystalline structure which has been etched. SUMMARY OF THE INVENTION It is an objective of this invention to provide a method for utilizing measurements of two-dimensional etch figures formed by the intersection of etched, naturally occurring fission tracks and other crystallographic imperfections with the surface of the apatite grain in which they exist to determine the chemical characteristics and composition of the apatite. Apatite grains are obtained from rock samples from the bore of a well or from the surface of the Earth for the purpose of determining the geological evolution of the rock samples. By observing and measuring the etch pits and the etch figures they form after exposing naturally occurring fission tracks and other crystallographic imperfections to acid, it may be determined whether the apatite grains being analyzed are predominantly fluorine-rich (or fluorapatite), chlorine-rich (or chlorapatite), or water-rich (or hydroxyapatite), and, using already existing methods, it will allow the pooled fission track ages and the pooled distributions of perceived track lengths to be determined for the predominantly fluorine-rich apatite grains and for the predominantly non-fluorine-rich apatite grains. The present method utilizes the shape and dimensions of two-dimensional etch figures on etched planar surfaces of apatite grains in order to determine the chemical composition of apatite grains obtained from rock samples. Over time, fission tracks accumulate in the apatite grains due to the self-destruction of the nuclei of the trace element .sup.238 U. The fission that occurs when one of these nuclei spontaneously destructs causes damage to the surrounding crystalline structure of the host apatite grain. The resulting damage is an elongated path known as a fission track. While these fission tracks cannot be seen optically, they may be enlarged or etched, sufficiently to be viewed using either an optical microscope or a scanning-electron microscope, by exposing the planar surface of the apatite grain to an acidic solution and preferentially dissolving the crystallographic damage that constitutes the naturally occurring fission tracks. The etching process transforms fission tracks that intersect the etched planar surface of an apatite grain into etch pits. An etch pit is a polyhedral (or three-dimensional) recess issuing from the etched planar surface of the apatite grain; prior to becoming an etch pit, the space within the polyhedral recess was initially composed of apatite material that ultimately was preferentially dissolved by the acidic solution. An etch figure is the polygonal (or two-dimensional) cross-section of the etch pit where it intersects the etched planar surface of an apatite grain. Other crystallographic imperfections are etched in a similar manner to that of naturally occurring fission tracks, and these include other charged-particle tracks, defects, dislocations, fluid inclusions, mineral inclusions, polishing scratches, and fractures. Additionally, naturally occurring fission tracks which do not intersect the etched planar surface of an apatite grain may still be etched if they intersect another fission track or a crack in the crystal structure of the apatite grain that does intersect the etched planar surface. In this manner, some subsurface fission tracks can be etched and viewed. The intersection of the etch pits with the etched planar surface of an apatite grain causes polygonal apertures or etch figures to be formed on that surface. If the crystallographic c-axis of an apatite grain is parallel to the etched planar surface, one of the two orthogonal axes of each etch figure will be parallel to the c-axis of the apatite grain. One of the measurements taken is the maximum diameter of the etch figure taken along a line segment which is parallel to the crystallographic c-axis of the apatite grain. Another measurement taken is the maximum diameter of the etch figure taken along a line segment which is perpendicular to the crystallographic c-axis of the apatite grain. Arithmetic mean maximum etch figure diameters parallel and perpendicular to the crystallographic c-axis are calculated for each apatite grain studied by taking the average of the respective diameters for a series of etch figures measured for each apatite grain. The mineral apatite is categorized as being fluorine-rich, chlorine-rich, or water-rich apatite, or some combination of these types. By measuring the arithmetic mean maximum diameter parallel to the crystallographic c-axis and the arithmetic mean maximum diameter perpendicular to the c-axis of the etch figures, it is possible to identify the fluorine-rich apatite grains. Etch figures in fluorine-rich apatite tend to be relatively small in size and exhibit a shape characterized as short and narrow. Chlorine-rich apatite tends to exhibit etch figures that are longer and proportionately wider while water-rich apatite etch figures exhibit dimensions which are approximately equal in length to those of chlorine-rich apatite while having a proportionately narrower diameter perpendicular to the crystallographic c-axis. The crystallographic defects within the apatite crystal or grain that make up a naturally occurring fission track exhibit a natural tendency to convert back to pristine (undamaged) crystalline material. This process is referred to as fission track annealing or annealing and occurs at all temperatures near the Earth's surface. Annealing is the process by which fission tracks are eliminated wholly or partially from their host apatite grain. The annealing process is most rapid at temperatures between 70.degree. C. and 130.degree. C. over geologic time. Annealing occurs more rapidly in fluorine-rich apatite in comparison to the annealing rate in chlorine-rich apatite. Fluorine-rich apatite is most useful for the study of oil formation whereas chlorine-rich apatite is useful for the study of natural gas formation. Because fluorine-rich apatite occurs most commonly in nature and also because the dimensions and characteristic shape of etch figures formed in fluorine-rich apatite are most easily identified and measured it is desirable to perform analyses on apatite that is predominantly fluorine-rich. However, analyses are also performed on relatively non-fluorine-rich apatite, when such apatite is present, as the present invention provides a method to distinguish between these apatite types. Non-fluorine-rich apatite is apatite that is not categorized as fluorine-rich. In addition to the measurements of the arithmetic mean maximum etch figure diameters parallel and perpendicular to the crystallographic c-axis for each apatite grain studied, the fission track ages and the perceived track length distributions of fluorine-rich and non-fluorine-rich apatite grains are also measured using presently practiced methods. The etch figure measurements provide a means to group the apatite grains into fluorine-rich apatite and relatively non-fluorine-rich apatite and enable the calculation of a pooled fission track age and a pooled distribution of perceived track lengths corresponding to each apatite type. Furthermore, the etch figure measurements eliminate the need to perform expensive microprobe analyses to determine the chemical composition of the apatite grains. Fission track age measurements for apatite grains require that the etched apatite grains be masked by a thin sheet of muscovite mica detector and then be placed in close proximity to the core of a nuclear reactor along with a uranium-doped glass covered by a second muscovite mica detector to be irradiated with thermal neutrons in order to determine the amount of .sup.238 U in the apatite grains. It is presently common practice to irradiate the apatite grains and the muscovite mica detectors prior to measuring the chemical composition of the apatite grains by microprobe analysis. This approach necessarily exposes the analyst to radioactive material but it is practiced because of the high cost of the microprobe analyses and the requirement that all other measurements be completed for the apatite grains prior to microprobe analysis in order to most efficiently employ this method of chemical composition measurement. The method of the present invention eliminates the requirement of prolonged exposure and handling of the radioactive apatite grains after irradiation by permitting a thorough analysis of the chemical composition of the apatite grains to be performed prior to irradiation of the apatite grains in the nuclear reactor. Following irradiation of the apatite grains, it is only necessary to examine the relatively less radioactive muscovite mica detectors that were irradiated in contact with the apatite grains and the uranium-doped glass. The method of the present invention for performing fission track analysis utilizing the dimensions of etch figures in apatite eliminates the requirement of performing costly microprobe analyses to determine the chemical composition of the apatite grains and in doing so allows more rapid analysis, eliminates the requirement for a high level of expertise at all levels of analyses, and eliminates the need to be exposed to radioactive material for extended periods of time while performing the analyses. Further features and advantages of the invention will become more readily apparent from the following detailed description when taken in conjunction with the accompanying drawings.
049833537	abstract	In a steam generator utilized with a liquid sodium cooled nuclear reactor, provision is made to vent the violent sodium water reaction emanating from a tube rupture casualty. The steam generator includes a sodium plenum at the bottom thereof containing a conventional rupture disk for venting sodium, steam, and reaction products including hydrogen immediately upon a tube rupture casualty. The invention includes providing an alternate concentric flow path interior to the steam generator and parallel to the tube bundle. This alternate concentric flow path extends from the upper portion of the steam generator down into the lower head or plenum adjacent to the pressure relief diaphragm. This alternate path is partially filled with sodium during normal reactor operation. In the event of a tube bundle break, the alternate flow path dumps its sodium through the conventional rupture disk and then provides an immediate alternate pressure release path in parallel with the tube bundle for steam and water flow from the tube rupture site to the rupture disk. This parallel flow path reduces the pressure differential from the water/steam flow through the tube bundle such that water/steam does not flow back through the intermediate heat transport system to the intermediate heat exchanger (IHX) where it would react with residual sodium and potentially damage the IHX tube bundle which is part of the reactor primary containment barrier.
	abstract	A flow limiter may include a head and a fin extending from a bottom of the head. The head may include a side surface having at least one first hole and the side surface may be symmetric about a first axis. The fin may include at least one second hole and the at least one second hole may have an axis substantially perpendicular to the first axis. The flow limiter may be inserted into a support casting that may interface with a nuclear fuel bundle to reduce the flow of water to the nuclear fuel bundle thereby reducing a moisture carry over (MCO) level at an exit of a fuel bundle of a nuclear reactor.
	abstract	Currently, the known method of shortening the scintillation response of scintillation material is to suppress the amplitude-minor slower components of the scintillation response, whereas the possibilities of significant shortening of the amplitude-dominant component of the scintillation response in this method are limited. The invention concerns the method of shortening the scintillation response of scintillator luminescence centres which uses co-doping with Ce or Pr together with co-doping with ions from the lanthanoids, 3d transition metals, 4d transition metals or 5s2 or 6s2 ions group. Having had the luminescence centres electrons excited as a result of absorbed electromagnetic radiation, the scintillator created in this method is capable of taking away a part of the energy from the excited luminescence centres via a non-radiative energy transfer, which results in a significant shortening of the time of duration of the amplitude-dominant component of the scintillation response.
	claims	1. A method for making a neutron generating target, the method comprising:disposing a neutron source layer on a surface of a target substrate, the neutron source layer comprising a first surface facing the target substrate and a second surface facing away from the target substrate; andmodifying the second surface of the neutron source layer to generate a plurality of surface features to form a roughened second surface, the plurality of surface features comprising a plurality of different heights, wherein the modifying a surface of the neutron source layer comprises a material removal process or a material addition process. 2. The method of claim 1, wherein the material removal process comprises abrasive blasting, etching, or polishing. 3. The method of claim 1, wherein the material addition process comprises vacuum deposition, plating, or printing. 4. The method of claim 1, wherein the disposing a neutron source layer on a surface of the target substrate comprises pressing the neutron source layer on the surface of the target substrate, or depositing the neutron source layer on the surface of the target substrate by evaporation. 5. The method of claim 1, further comprising heating the neutron source layer and the target substrate to an elevated temperature for a duration of time to form a bond between the neutron source layer and the target substrate. 6. The method of claim 5, wherein the elevated temperature is between about 100 degrees Celsius and about 500 degrees Celsius. 7. The method of claim 5, wherein the duration of time is between about 0.1 hours and about 10 hours. 8. The method of claim 1, wherein the target substrate comprises at least one of copper, aluminum, titanium, molybdenum, and stainless steel. 9. The method of claim 1, wherein the neutron source layer comprises at least one of lithium, beryllium, and carbon. 10. A method for making a neutron generating target, the method comprising:disposing a neutron source layer on a surface of a target substrate, the neutron source layer comprising a first surface facing the target substrate and a second surface facing away from the target substrate;modifying the second surface of the neutron source layer to generate a plurality of surface features to form a roughened second surface, the plurality of surface features comprising a plurality of different heights; andheating the neutron source layer and the target substrate to an elevated temperature for a duration of time to form a bond between the neutron source layer and the target substrate. 11. A neutron generating target made by the method of claim 1, the target comprising:a target substrate; anda neutron source layer disposed on a surface of the target substrate and bonded to the target substrate, the neutron source layer comprising a first surface facing the target substrate and a roughened second surface facing away from the target substrate, wherein the second surface comprises a plurality of surface features, the plurality of surface features comprising a plurality of different heights. 12. The target of claim 11, wherein the one or more surface features are recessed into the neutron source layer. 13. The target of claim 12, wherein the one or more surface features have a depth of between about 1 micron and about 50 microns. 14. The target of claim 11, wherein the one or more surface features have a height of between about 1 micron and about 50 microns. 15. The target of claim 11, wherein the one or more surface features comprise a plurality of surface features with an average pitch of between about 1 micron and about 50 microns. 16. The target of claim 11, wherein the target substrate comprises at least one of copper, aluminum, titanium, molybdenum, and stainless steel. 17. The target of claim 11, wherein the neutron source layer comprises at least one of lithium, beryllium, and carbon. 18. The target of claim 11, wherein the neutron source layer has a thickness of between about 10 microns and about 500 microns.
	claims	1. A lithographic projection apparatus comprising:a programmable patterning structure configured to pattern a radiation beam generated by a radiation system according to a desired pattern and generate a patterned radiation beam;a projection system configured to project the patterned radiation beam onto a target portion of a substrate;a positioning structure configured to move the substrate relative to the projection system during exposure by the patterned radiation beam;a single-faceted oscillatingly pivotable mirror configured to move the patterned radiation beam relative to the projection system during at least one pulse of the radiation beam; andan actuator configured to oscillatingly pivot the mirror according to an oscillation timing that substantially corresponds to a pulse frequency of the radiation system, whereby the patterned radiation beam is scanned in synchronism with the movement of the substrate during the at least one pulse. 2. The apparatus of claim 1, wherein the actuator is controlled by a controller and wherein the controller, actuator and radiation system are interconnected in a control loop arrangement and wherein the control loop is configured to maintain synchronism between oscillation of the mirror and pulses of the radiation system. 3. The apparatus of claim 1, wherein the pivotable mirror is supported by a support assembly, and a frequency of the oscillation timing substantially corresponds to a resonance frequency of the mirror and its support assembly. 4. The apparatus of claim 3, wherein the support assembly further comprises the actuator. 5. The apparatus of claim 4, wherein the support assembly further comprises at least one counter-mass, constructed and arranged to isolate forces produced by the actuator from a remaining part of the apparatus. 6. The apparatus of claim 1, wherein the actuator comprises a plurality of motors, constructed and arranged to impart rotational forces on the mirror. 7. The apparatus of claim 1, wherein, when in use, the mirror oscillates with a sinusoidal motion. 8. The apparatus of claim 7, wherein, when in use, the pulses of the radiation system substantially correspond in timing to a zero crossing of the sinusoidal motion of the mirror oscillation. 9. The apparatus of claim 1, wherein the mirror is substantially planar. 10. The apparatus of claim 1, wherein the mirror is located proximate a pupil plane of the projection system, or a conjugate plane thereof. 11. The apparatus of claim 1, wherein the mirror is located at a conjugate plane of a pupil plane of the projection system. 12. The apparatus of claim 1, wherein the positioning structure is configured to move the substrate at a substantially constant velocity relative to the projection system during a plurality of pulses of the radiation beam and during intervals therebetween, and wherein the patterned radiation beam is moved in synchronism with the movement of the substrate for a duration of at least one pulse of the radiation beam. 13. The apparatus of claim 1, wherein the patterned radiation beam is scanned in synchronism with the movement of the substrate during a plurality of pulses of the radiation beam, such that a pattern of the programmable patterning structure is projected onto substantially a same place on the substrate a plurality of times. 14. The apparatus of claim 1, wherein a configuration of the programmable patterning structure is changed between the plurality of projections that are directed onto substantially the same place on the substrate. 15. The lithographic projection apparatus according to claim 13, wherein (i) an intensity of the patterned radiation beam, (ii) an illumination of the programmable patterning structure, (iii) a pupil filtering, or any combination of (i) to (iii), are changed for at least one of the plurality of projections that are directed onto substantially the same place on the substrate. 16. A device manufacturing method, comprising:providing a pulsed beam of radiation;patterning the pulsed beam according to a desired pattern to generate a patterned radiation beam;projecting the patterned radiation beam onto a target portion of a layer of radiation-sensitive material that at least partially covers a substrate;moving the substrate relative to a projection system that projects the patterned radiation beam onto the substrate during exposure; andoscillatingly pivoting a single-faceted pivotable mirror according to an oscillation timing that substantially corresponds to a pulse frequency of the radiation beam, thereby altering a path of the patterned radiation beam relative to the projection system during at least one pulse of the radiation beam, wherein the path is altered in synchronism with the movement of the substrate during the at least one pulse and wherein a cross-section of the patterned radiation beam is projected onto a plane parallel to a surface of the target portion of the substrate. 17. The method of claim 16, wherein moving the substrate includes moving the substrate at a substantially constant velocity relative to the projection system during a plurality of pulses of the radiation beam and during intervals therebetween, and wherein the path is altered in synchronism with the movement of the substrate for a duration of at least one pulse of the radiation beam. 18. The method of claim 16, further comprising altering the path of the patterned radiation beam in synchronism with the movement of the substrate during a plurality of pulses of the radiation beam, such that a pattern of the programmable patterning structure is projected onto substantially a same place on the substrate a plurality of times. 19. The method of claim 18, further comprising changing a configuration of the programmable patterning structure between the plurality of projections that are directed onto substantially the same place on the substrate. 20. The method of claim 18, further comprising changing (i) an intensity of the patterned radiation beam, (ii) an illumination of the programmable patterning structure, (iii) a pupil filtering, or any combination of (i) to (iii), for at least one of the plurality of projections that are directed onto substantially the same place on the substrate. 21. The method of claim 16, wherein the mirror oscillates with a sinusoidal motion. 22. The method of claim 21, wherein pulses of the pulsed beam substantially correspond in timing to zero crossings of the sinusoidal motion of the mirror oscillation. 23. An apparatus comprising a projection system, said projection system having:a single-faceted oscillatingly pivotable mirror, andan actuator functionally connected to said pivotable mirror, said actuator being configured to oscillatingly pivot the mirror. 24. The apparatus of claim 23, wherein said pivotable mirror is positioned in the pupil plane of an optical system. 25. The apparatus of claim 23, wherein said actuator is configured to oscillate the mirror at a frequency in the range of 1-10 kHz. 26. The apparatus of claim 23, further comprisinga radiation source, anda patterning device constructed and arranged to receive a radiation beam provided by said radiation source and to pattern the radiation beam. 27. The apparatus of claim 26, wherein said patterning device is a programmable patterning device.
	summary
	claims	1. A method for correcting an optical mask pattern comprising:providing a test optical mask having a plurality of original patterns configured according to original drawing data;transferring the original patterns to a first photo-resistant layer corresponding to forming of a plurality of first post-development patterns, and measuring first dimensions of all of each of the first post-development patterns;conducting a pattern shrink process to the first post-development patterns corresponding to forming of a plurality of first post-shrinkage pattern, and measuring second dimensions of all of each of the first post-shrinkage patterns;calculating a bias value between the first dimensions and the second dimensions, and collecting data of the original patterns, the first dimensions, the second dimensions and the bias value for obtaining a database;building an optical proximity effect correction (OPC) module in accordance with the database; andcorrecting the original drawing data according to the OPC module so as to obtain a corrected drawing data. 2. The method for correcting an optical mask pattern according to claim 1, further comprising:performing a first verifying step for the OPC module after the OPC module is built. 3. The method for correcting an optical mask pattern according to claim 2, wherein the first verifying step comprises:building a verifying fitting curve module with the original drawing data and the first dimensions; andcomparing the OPC module to the verifying fitting curve module to judge whether a plurality of second post-development patterns preformed on a second photo-resistant layer are correct or not, and if it is incorrect, the step of building the OPC module repeats. 4. The method for correcting an optical mask pattern according to claim 2, further comprising:performing a second verifying step for the OPC module after the first verifying step. 5. The method for correcting an optical mask pattern according to claim 4, wherein the second verifying step further comprises:comparing the OPC module and the original drawing data to determine whether a plurality of second post-shrinkage patterns preformed on a second photo-resistant layer are correct or not, and if it is incorrect, the step of building the OPC module repeats. 6. The method for correcting an optical mask pattern according to claim 1, wherein the pattern shrink process comprises a chemical shrink process, a thermal flow process, a chemical amplification of resist line process or a double exposure with Levnson-type phase shift masks process. 7. The method for correcting an optical mask pattern according to claim 1, wherein the original drawing data comprises critical dimensions (CDs), pattern density, and duty ratio. 8. A method for configuring an optical mask pattern comprising:performing a plurality of original patterns on a test optical mask according to original drawing data;transferring the original patterns to a first photo-resistant layer corresponding to forming of a plurality of first post-development patterns, and measuring first dimensions of all of the first post-development patterns, respectively;performing a pattern shrink process to the first post-development patterns corresponding to forming of a plurality of first post-shrinkage pattern, and measuring second dimensions of all the first post-shrinkage patterns, respectively;calculating a bias value between the first dimensions and the second dimensions, and collecting data of the original patterns, the first dimensions, the second dimensions and the bias value for obtaining information for a database;building an optical proximity effect correction (OPC) module in accordance with the database;correcting the original drawing data according to the OPC module so as to obtain a corrected drawing data;a writing step performed to write the corrected drawing data onto an optical mask and to configure a pattern on the optical mask. 9. The method for configuring an optical mask pattern according to claim 8, further comprising: performing a first verifying step for the OPC module after the OPC module is built. 10. The method for configuring an optical mask pattern according to claim 9, wherein the first verifying step comprises:building a verifying fitting curve module with the original drawing data and the first dimensions; andcomparing the OPC module to the verifying fitting curve module to determine whether a plurality of second post-development patterns preformed on a second photo-resistant layer are correct or not, and if it is incorrect, the step of building the OPC module repeats. 11. The method for configuring an optical mask pattern according to claim 9, further comprising:performing a second verifying step for the OPC module after the first verifying step. 12. The method for configuring an optical mask pattern according to claim 11, wherein the second verifying step further comprises:comparing the OPC module and the original drawing data to determine whether a plurality of second post-shrinkage patterns preformed on a second photo-resistant layer are correct or not, and if it is incorrect, the step of building the OPC module repeats. 13. The method for configuring an optical mask pattern according to claim 8, wherein the pattern shrink process includes a chemical shrink process, a thermal flow process, a chemical amplification of resist line process or a double exposure with Levnson-type phase shift masks process. 14. The method for configuring an optical mask pattern according to claim 8, wherein the original drawing data comprises critical dimensions (CDs), pattern density, and duty ratio. 15. The method for configuring an optical mask pattern according to claim 8, wherein the wiring step is performed with an electron beam or a laser beam.
	description	This patent application is a continuation of U.S. patent application Ser. No. 16/518,944, filed Jul. 22, 2019, issued as U.S. Pat. No. 10,893,737 on Jan. 19, 2021, which is a continuation of U.S. patent application Ser. No. 15/659,545, filed Jul. 25, 2017, issued as U.S. Pat. No. 10,357,094 on Jul. 23, 2019, which is a continuation of U.S. patent application Ser. No. 14/848,256, filed Sep. 8, 2015, issued as U.S. Pat. No. 9,713,371 on Jul. 25, 2017, which claims the benefit of U.S. patent application 62/046,453, filed Sep. 5, 2014. These applications and U.S. patent application 62/002,763, filed May 23, 2014, are incorporated by reference along with all other references cited in this application. The present invention relates generally to providing a portable ultraviolet (UV) light source for curing UV-curable gel nail polish. More particularly, the present invention relates to a portable UV nail lamp with a light emitting diode light source and rechargeable battery. The present invention also relates to a UV nail lamp with a light emitting diode (LED) light source and a platform for a user's hand. UV nail lamps are available for the salon and home to cure UV-curable nail polish. These nail lamps typically have UV fluorescent tubes or bulbs that use alternating current (AC) power. So, these nail lamps have an AC cord that needs to be plugged into the wall, which restricts their placement, since they need to be close to a wall socket. This can be problematic. In a salon, for example, this can restrict the number of lamps in use, the location of nail lamp stations, and thus, the number of customers that can use the lamps at a given time. The tubes or bulbs of these nail lamps consume rather significant amounts of power and generate heat, which makes these nail lamps typically large and bulky to accommodate the bulb size and to allow for heat dissipation. This makes these nail lamps somewhat difficult to move, and certainly very difficult to travel with and use in a location without a wall socket, such as while on an airplane. Further, the light from the bulbs of these lamps tends be uneven, so a person's nails are exposed to difference intensities of light output, which causes the nails to dry at different times or to cure unevenly. Further, traditional nail lamps use light bulbs that tend to produce uneven light, so a person's nails are exposed to difference intensities of light output, which causes the nails to dry at different times or to cure unevenly. These bulbs also tend to be bulky which causes the nail lamps to be large and cumbersome. Conventional bulbs can also consume much electrical energy while operating. These lamps often have a flat platform on an inside of the lamp for a user to place their hand during drying. With long drying times, the user's hand can become uncomfortable or cramp up with the fingers in a strained, stretched out position within the lamp. There is a risk that the nails can smudge before setting as the user's nails brush up against other fingers or inside the lamp. As can be appreciated, an improved nail lamp is needed. What is also needed is a method and an apparatus which can accommodate a user's five fingers in a comfortable and ergonomic resting position within a nail lamp. What is also desired is an efficient way to evenly cure UV-curable nail polish on each of the user's nails. A nail lamp for curing UV-curable nail gel uses light emitting diodes (LEDs) that emit ultraviolet light and are relatively lower power. The nail lamp is powered from an exterior power source, such as a wall socket, or by a rechargeable battery pack. A battery compartment of the nail lamp holds the battery pack, which is removable without disassembling the nail lamp. The nail lamp is easily transportable to different locations and can be used even when a wall socket is unavailable. A curing time of the nail lamp is user-selectable. The nail lamp can also include detection sensors to detect a person's hand or foot in a treatment chamber and automatically turn on or off the LEDs. A nail lamp for curing UV-curable nail gel is powered by direct current (DC) and can be battery operated. The nail lamp uses surface-mounted light emitting diodes (SMD LEDs) which are relatively lower power. The nail lamp is easily transportable and can be used even when a wall socket is unavailable, such as while traveling on an airplane or in a car. The nail lamp has a cavity or treatment chamber that can accept a user's five fingers. So, the nail lamp can evenly cure nail polish on up to five fingers at once. A compact portable LED nail curing lamp has surface-mounted light emitting diode (SMD LED) lights. The lamp provides fast and consistent results producing high gloss finish and even curing of nail polish (e.g., UV-curable gel polish). The nail lamp has a micro-USB port, which can be used to power the lamp using a wall adapter, car charger, laptop USB port, or mobile power bank for ultimate portability. In an implementation, a system includes a compact LED nail curing lamp and a mobile power battery pack. The system also includes a cable to connect the nail lamp and the mobile power battery pack. The battery pack provides portable power to the nail lamp so that the nail lamp can be used portably, such as during travel or on an airplane when a wall outlet is unavailable. A compact LED nail curing lamp has a sleek design with advanced technology, highly efficient surface-mounted light emitting diode (SMD LED) lights. The lamp provides excellent results producing high gloss finish and even curing of nail polish (e.g., UV-curable gel polish). A specific implementation of a compact LED nail curing lamp is the SMD LED Lamp S2 product by LeChat Nail Care Products of Hercules, Calif. The compact LED nail curing lamp has a micro USB port, which is convenient to use. The user can power this SMD LED lamp (e.g., LeChat's LED Lamp S2 product) using a wall adapter (included), car charger (optional), laptop USB port, or mobile power bank for ultimate portability. In an implementation, a mobile power bank battery that can be used with the SMD LED Lamp S2 product is the LeChat Mobile Power™ battery pack by LeChat Nail Care Products. This product is approved by the Underwriters Laboratories. The packaging of the product can include the certification “UL Approved.” The product is also compliant with U.S. and international standards of the Restriction of Hazardous Substances Directive (RoHS) for environmental friendly products. In an implementation, a system includes a compact LED nail curing lamp (e.g., LeChat S2 product) and a mobile power battery pack (e.g., LeChat Mobile Power product). The system also includes a cable to connect the nail lamp and the mobile power battery pack. In an implementation, the nail lamp has a micro-B USB connector input and the mobile power battery pack has a type A USB receptacle, and the cable connects these together. The battery pack provides portable power to the nail lamp so that the nail lamp can be used portably, such as during travel or on an airplane when a wall outlet is unavailable. The lamp has a large, illuminated single-button that turns the lamp on for a preset cure time of 30 seconds for efficient, rapid LED/UV gel curing. The compact design saves space and allows for portability that is convenient for travel and pedicure applications. The lamp is lightweight and designed for carrying from place to place. The nail lamp includes professional durable materials that are long lasting and reliable. In an implementation, the nail lamp is a 6-watt LED lamp that includes forty-two SMD LED lights that provide evenly distributed light that allows for an efficient cure in about 30 seconds. In an implementation, a system includes: a upper housing having a button and a power input; and a lower housing, connected to the upper housing, the cavity or treatment chamber including openings through which surface-mounted light emitting diodes can emit light through. The cavity is sufficiently wide (e.g., about 4.25 inches or 10.6 centimeters) to accommodate five fingers of a human hand placed on a flat surface. In an enclosure formed between the upper and lower, there is circuitry. The circuitry includes at least one printed circuit board with the surface-mounted light emitting diodes; a button; a multiplexer, connected to the power input; a control circuit, connected to button and the multiplexer; a timer, connected to the control circuit and the multiplexer; a recharging circuit, connected and the multiplexer. The system includes a rechargeable battery comprising a battery output coupled to the multiplexer. The recharging circuit is connected to the rechargeable battery, so it can be recharged from, for example a wall outlet, that is connected to the power input. The multiplexer switches between the power input and the rechargeable battery to supply power circuitry. The housing can include a USB power output, which can be used to power or charge other devices. The power input can be a micro USB power input, which is readily available. A nail lamp includes a housing including a base and an outer cover. On a front side of the housing, there is an opening to a cavity within the housing. Inside the housing are inner surfaces of the housing including a platform, an inner side wall, and an inner roof of the housing. The opening is shaped and sized to allow a user's hand or foot to pass through the opening into the space within the housing. A finger plate is positioned on an inside of a housing of a nail lamp. The finger plate includes five side by side depressions that are adapted to support a user's fingers when the user places a hand inside the housing on the plate. In an implementation, the finger plate is removable from the housing. Different finger plates (or foot plates) can be used for users with different size hands or feet. An arrangement of light sources is positioned on sidewalls and inner roof of an inside of a housing. The light sources can be LEDs using surface mount technology (SMT), or surface mount devices (SMD) LEDs. In an implementation, a SMD LED can produce UV light in a range of about 340 nanometers to about 410 nanometers. Other objects, features, and advantages of the present invention will become apparent upon consideration of the following detailed description and the accompanying drawings, in which like reference designations represent like features throughout the figures. FIGS. 1-8 show views of a nail lamp 100. FIG. 1 shows a perspective view, FIG. 2 shows a top view, FIG. 3 shows a front side view, FIG. 4 shows an upside down view, FIG. 5 shows a right side view, FIG. 6 shows a back side view, FIG. 7 shows a bottom or underside view, and FIG. 8 shows the nail lamp as part of a kit 800. The nail lamp device has an exterior surface 102 and at one side, an opening 104 through which a user can place their hand into an interior space 106 of the nail lamp. There is a control button on the exterior that is used to turn on an interior lighting source 108 of the device, which exposes the interior space to light from the interior lighting source. As an example, a user can insert their fingers into the interior space, turn on the cure interior lighting source, and cure their UV-curable nail polish or UV-curable nail gel coated nails with the interior light. In an implementation, there is also an exterior lighting source (e.g., an LED) of the device, which also turns on in response to the control button and is on when the interior lighting source is on. Light from the exterior lighting source is visible through a translucent material (e.g., translucent plastic) of the control button. When the interior lighting source is off, the light from the exterior lighting source will also be off. The exterior lighting source is used as an indicator that the device is on—that the interior lighting source is on. In an implementation, the interior lighting source emits light of a different wavelength from the exterior lighting source. The interior lighting source can emit UV light (wavelengths ranging approximately from 100 nanometers to 400 nanometers) to cure UV-curable gel polish. And the exterior lighting source emits wavelengths of light within the visible light spectrum (wavelengths ranging approximately from 390 nanometers to 700 nanometers). In specific implementations, the exterior lighting source emits red, green, blue, or any combination of red, green, or blue colors. The red colors include wavelengths ranging approximately from 620-740 nanometers. The green colors include wavelengths ranging approximately from 495-570 nanometers. The blue colors include wavelengths ranging approximately from 450-495 nanometers. More specifically, the nail lamp includes a housing. The housing includes an outer cover (also be referred to as an exterior surface) and inner walls. In an implementation the outer cover is made a plastic material that has a glossy sheen finish (e.g., metallic finish). On a side of the housing, there is an opening to a space (or cavity or interior space or treatment chamber) within the housing. The space within the housing is defined by inner walls of the housing. The inner walls can be made of a reflective material. This material can direct emitted light from SMD LEDs into the cavity toward the user's nails. In an implementation, the interior of the lamp includes six inner walls. One of the walls forms a ceiling of the cavity. The other walls are angled with respect to this wall. In another implementation, shown in FIG. 4, the interior of the lamp includes seven inner walls, 110, 112, 114, 116, 118, 120, and 122. In an implementation, the opening is shaped and sized to allow a user's hand to pass through the opening into the cavity. In another implementation, the opening is adapted to allow a foot to pass through the opening. In another implementation, the nail lamp is adapted to be used for both a hand and foot. FIG. 6 shows a specific implementation of a nail lamp that includes a port 124 for a micro-USB connector cable. A power source can be coupled to the port to provide the nail lamp with operating power. In other implementations, the port can be a USB port, or plug, or other types of ports for electrical power transfer. As shown in FIG. 7, on a bottom of the housing, there are grip members 126 that prevent the housing from sliding on a work surface. The grip member is one or more rubber pads which provide friction against the surface. The grip members can help stabilize the nail lamp during curing to prevent nudging the nails during use or on uneven or unlevel surfaces (e.g., table on a train or airplane). FIG. 8 shows a specific implementation of a nail lamp that is part of kit 800. The kit includes a packaging (e.g., a box) that includes the nail lamp 100, a power adaptor 128, and a USB/micro-USB cable 130. Below is a table of operational modes of the SMD LED lamp. TABLE AModeOperational Mode1. No power to power inputUV light is not operational2. Power to power inputPower UV light components and operational3. Press button when UV UV light turns on and turns off automaticallylight offafter 30 seconds (or other preset time)4. Press button while UV UV light immediately turns offlight on FIG. 9 shows a block diagram of a cross-section of a nail lamp 900. There are five inner walls of the cavity that are visible. There is a first wall 902 that forms a ceiling of the cavity. There are two walls 904 and 906 next to the right and left of the first wall that are angled with respect to the first wall. The first, second, and third walls have SMD LEDs 907 that are attached to printed circuit boards arranged between these inner walls and the outer cover. The cavity also includes a fourth wall 908 adjacent the second wall and a fifth wall 910 adjacent the third wall. These walls have a reflective material 912 (e.g., iron, steel, aluminum, aluminum alloy, other metal or metal alloy, or other sheet metal) to direct 913 light into the cavity, and do not include SMD LEDs. A button 914 is coupled to an exterior 916 of the nail lamp. FIG. 10 shows a block diagram of a specific implementation of a first printed circuit board 1000 (PCB1). A power input 1002 (e.g., a universal serial bus (or USB) power connector input) provides power to a timer 1004, a control circuit 1006, and an LED driver 1008 of PCB1. A button 1010 is connected to the control circuit that is connected to the timer. The button can activate the control circuit that controls the timer which activates the LED driver to activate one or more SMD LEDs 1012 of PCB1. The LED driver can also control an LED 1014 that connects to the button. For example, the LED will turn on behind the button to cause the button to light up. FIG. 11 shows a block diagram of a cross section of a double-sided printed circuit board PCB1 1100 with SMD LED lights 1102 and 1104 attached to opposite sides of PCB1. There are two SMD LEDs 1102 on one side of PCB1 that emit light in a first direction away from PCB1 toward a button 1106 of the nail lamp (e.g., a back-lit control button). On an opposite side of PCB1, there is a group of SMD LEDs 1104 that emit light in a second direction away from PCB1 into a cavity of the lamp housing. FIGS. 12A-12B shows a comparison between a standard LED 1202 and a SMD LED 1204. Light from a standard LED is emitted at a smaller beam angle (angle A) compared to the SMD LED which has a greater beam angle (angle B) and beam spread. At a given distance away from a surface, the SMD LED and standard LED will each emit light in the shape of a cone. The SMD LED has a greater beam spread and will emit a greater area of illumination than the standard LED. So, a base of the cone of light (e.g., circle) for the SMD LED will have a greater area (e.g., greater diameter, B is greater than A) than that of a standard LED. Thus, fewer SMD LEDs are needed to light an area, allowing for less power used and greater energy savings. FIG. 13 shows a block diagram of a specific implementation of a nail lamp 1300 with four internal printed circuit boards. PCB1 1302 is connected to a second printed circuit board PCB2 1304 and a third printed circuit board PCB3 1306. PCB2 and PCB3 each includes at least one SMD LED light. PCB1 is also connected to a fourth printed circuit board PCB4 1308, which includes a USB connector input 1310. PCBs 1-3 provide the SMD LEDs that light the UV light cavity of the nail lamp housing. The cavity has a top horizontal section (light provided by PCB1) and two angled sections (light provided by PCBs 2 and 3) relative to the top horizontal section. And a micro USB connector (provided by PCB4) is positioned at a back of the nail lamp housing. In a specific implementation, PCBs 1-3 provide 42 LEDs, of which 24 are on PCB1, 9 are on PCB2, and 9 are on PCB3. In a specific implementation, a compact LED nail curing lamp has a sleek design with advanced technology, highly efficient surface-mounted light emitting diode (SMD LED) lights. The lamp provides excellent results producing high gloss finish and even curing of nail polish (e.g., UV-curable gel polish). A specific implementation of a compact LED nail curing lamp is the SMD LED Lamp S2 product by LeChat Nail Care Products of Hercules, Calif. The compact LED nail curing lamp has a micro USB port, which is convenient to use. The user can power this SMD LED lamp (e.g., LeChat's LED Lamp S2 product) using a wall adapter (included), car charger (optional), laptop USB port, or mobile power bank for ultimate portability. In an implementation, a mobile power bank battery that can be used with the SMD LED Lamp S2 product is the LeChat Mobile Power™ battery pack by LeChat Nail Care Products. This product is approved by the Underwriters Laboratories. The packaging of the product can include the certification “UL Approved.” The product is also compliant with U.S. and international standards of the Restriction of Hazardous Substances Directive (RoHS) for environmental friendly products. In a specific implementation, the lamp has a large, illuminated single-button that turns the lamp on for a preset cure time of 30 seconds for efficient, rapid LED/UV gel curing. The compact design saves space and allows for portability that is convenient for travel and pedicure applications. The lamp is lightweight and designed for carrying from place to place. The nail lamp includes professional durable materials that are long lasting and reliable. In a specific implementation, the nail lamp is a 6-Watt LED lamp that includes forty-two SMD LED lights that provide evenly distributed light that allows for an efficient cure in about 30 seconds. An SMD LED is mounted and soldered into a circuit board. Compared to a standard LED, an SMD LED is small in size since it has no leads or surrounding packaging that a standard LED has. A SMD LED does not have the standard LED epoxy enclosure, and thus, SMD LED lights emit a much wider viewing angle instead of the focused, narrow light of the standard LED. SMD LEDs provide advantages over standard LEDs. The SMD LED has lower voltage and current requirements which allows it to give off very little heat. SMD LEDs emit a higher level of brightness while consuming less power than standard LEDs. With standard LEDs, the UV light produced to cure UV gels over time breaks down the epoxy surrounding the standard LED causing the epoxy to crack. Once cracked, the standard LED no longer flows evenly, which disrupts the transmission of light, resulting in an uneven cure. In contrast, SMD LEDs have no epoxy that surrounds it, and thus, will not crack. The resulting emission of light will be even throughout the lifetime of the light. Further, standard LEDs use a higher voltage and therefore, produce more heat. The heat produced by the higher voltage LED lights can shorten the life of the standard LED, which causes them to go out faster compared to SMD LEDs. In a specific implementation, the SMD LED Lamp S2 product is a nail lamp having a 6-Watt LED lamp with an output voltage of 5 volts and 1.2 amps. The lamp includes 42 SMD LED lights. A width of the lamp is about 103.5 millimeters. A length of the lamp is about 146.5 millimeters. A height of the lamp is about 56 millimeters. In an implementation, the nail lamp product is part of a kit which includes a universal AC adapter. The adapter has an input power of about 100 volts to about 200 volts at 50 or 60 hertz. The adaptor has an output power of about 12 volts at 1.2 amps. The kit also includes a user guide or manual which includes operating instructions, safety warranty, product specifications, a certificate of warranty, and a warranty registration card. To use the SMD LED Lamp S2 product, a user can follow the following instructions (which are included on the user manual): 1. Plug the power adaptor into the back of the SMD LED lamp and then plug the other end into a wall outlet, a car outlet, a computer, or a mobile power bank. 2. To turn the SMD LED lamp “on,” press the power button that is located on top of the lamp to the “on” position, where the LED light of the button lights up. The lamp will automatically shut off after 30 seconds. 3. The SMD LED lamp can be used with both fingernails and toenails. For toenails, the user can place the lamp over toes and perform steps 1 and 2 above. The user should follow the following safety precautions when using the SMD LED lamp product. These precautions are included on the user guide as part of the kit. 1. Never look directly into the LED/UV lights when machine is ON. 2. Do not overexpose the nails or skin under light. 3. Do not use the LED light in or around water. 4. Unplug the LED light when not being used. 5. Certain cosmetics or prescriptive lotions can cause sensitivity to LED light. Do not use lamp if using any. 6. Do not pull the cord to unplug. Instead, grab plug firmly and pull to unplug. 7. Do not use any corrosive sanitizer, solvents, thinners, or scrubbing to clean the machine. 8. Do not stack anything on top of the LED Lamp. 9. Do not disassemble the LED Lamp. This will void the Warranty. 10. Do not try to repair the machine. Please contact the distributor for service. 11. The plastic bag in packaging is a choking hazard. Do not place over head. Keep away from children and pets. 12. The electric power system is labeled on the box. Please pay attention to the voltage and frequency. FIG. 14 shows a block diagram of a specific implementation of a nail lamp that is adapted to be used with a rechargeable battery pack 1402 that is external 1404 to the housing 1406 of the nail lamp. The rechargeable battery is a unit that is separate from the nail lamp. Circuitry to recharge this rechargeable battery pack is contained within (or internal 1408 to) a housing of the rechargeable battery pack. There battery pack (or the nail lamp) may have a battery gauge or charge level indicator that indicates a charge level remaining in the battery. For example, the battery gauge can indicate there 75 percent charge remaining in the battery pack. For example, in an implementation, the display of the nail lamp can display the battery charge level of the battery pack (such as by the user pressing a battery charge level button). For example, the rechargeable battery is a portable power pack with a USB plug output (e.g., type A USB receptacle). The nail lamp has a USB power connector 1410 (e.g., micro-B USB receptacle) that can connect to the rechargeable battery using a cable. The micro-B USB receptacle of the nail lamp is connected to the type A USB receptacle of the rechargeable battery via a micro USB cable. Then, the battery pack supplies power to the nail lamp (which consumes 6 watts maximum). In an implementation, the nail lamp consumes 6 watts or less of power. Through the USB, the power adapter or batter can provide about 5 volts and 1.2 amps. In other implementations, the nail lamp consumes 5 watts or less of power (e.g., 5 volts and 1 amp), 4.5 watts or less (e.g., 5 volts and 900 milliamps), or 2.5 watts or less of power (500 milliamps). In another implementation, the nail lamp consumer more than 6 watts, such as 10 watts (e.g., 5.1 volts and 2.1 amps) or 12 watts (5.1 volts and 2.4 amps). With more power, the cavity of the nail lamp can be made larger (allow for more comfort or larger hands), or there can be more LEDs (for more even light coverage), or higher intensity LEDs (possibly for better nail curing), or any combination of these. Thus the nail lamp and rechargeable battery are a nail lamp system that allow for cordless (e.g., not connected to a wall outlet) and portable use. Users and customers need not rely on being within proximal distance to a wall outlet. In a salon, this can restrict the number of lamps in use, the location of nail lamp stations, and thus, the number of customers that can use the lamps at a given time. With a portable rechargeable nail lamp, salon customers can dry their nails anywhere in the salon, which allows for more customers that can be serviced at a given time, and reduced wait times for customers. Further, a portable rechargeable nail lamp is convenient to use during travel (e.g., on a train or airplane), and in places where there is limited or no access to wall outlets. Users can also save time by drying their nails while doing other tasks that would otherwise had to have been done at other times. For example, while working on a laptop or making phone calls at work, a person can concurrently cure their nails while the nail lamp is running on batteries or connected to their laptop. Although this application specifically describes the nail lamp as having a micro-B USB receptacle and the battery pack as having a type A USB receptacle, one having ordinary skill in the art understands that other connector types can be used to provide power. For example, some other connectors may be used such as mini-USB connector (e.g., USB mini-B), mini-A, micro-AB, or Apple's lightning connector. In a specific implementation, a portable external battery pack is the LeChat Mobile Power™. The Mobile Power pack product includes a battery housing having a USB output port, a micro USB input port, an LED power indicator, a power or flashlight button, and an LED light. The Mobile Pack product also includes a cable for connecting the battery housing with a nail lamp (e.g., the SMD LED Lamp S2 product). The cable includes a USB cable, a micro USB connector on one end of the cable, and a USB connector on an opposite end of the cable. To charge the Mobile Power product, a user can connect the micro USB connector of the cable to the micro USB input port of the external battery housing, and the other USB connector end of the cable to a USB port of a power source including a wall adapter (to a wall outlet), a laptop USB port, a desktop USB port, or a DC 5-volt USB charger. The LED power indicator of the battery pack will flicker to indicate that the external battery has started charging. When all LED power indicator lights are lit, this indicates that the battery is fully charged. In an implementation, there are four battery indicator lights arranged in a row on an external surface of the battery pack. When the Mobile Power battery pack is fully charged and ready to be used to power an electronic device, the user should first check whether the charging voltage of the digital or electronic device is matched with an output voltage (DC 5 volts) of the external battery. The user can connect the USB connector of the cable to the USB port of the battery pack, and the other micro USB connector end of the cable to a micro USB port of an electronic device such as the SMD LED nail lamp. The can be used as a general mobile power pack, and can be used to power other electronic devices such as a smart phone, tablet device, or any electronic device with a DC 5-volt USB input. A number of the battery LED power indicator lights will light according to the remaining charge capacity of the battery pack. In a specific implementation, there are four indicator lights (L1-L4) in a row with L1 on a left end, L2 to the right of L1, L3 to the right of L2, and L4 to the right of L3, and on the right end. When L1 is flashing, this indicates that there is about 0 to about 25 percent charge capacity level in the battery. When L1 and L2 are flashing, this indicates that there is about 25 to about 50 percent charge capacity level in the battery. When L1, L2, and L3 are flashing, this indicates that there is about 50 to about 75 percent charge capacity level in the battery. And when L1, L2, L3, and L4 are flashing, this indicates that there is about 75 to about 100 percent charge capacity level in the battery. When the capacity remaining in the battery is less than about 5 percent, the first light (L1) will blink to remind the user to recharge the external battery. In a specific implementation, the external battery includes a flashlight button for a flashlight function. To activate the flashlight option, the user can double click the flashlight (or power) button on the battery. Brightness of the light will cycle between 10 percent, 50 percent, and 100 percent brightness. The flashlight should not be turned on under hot temperature environments for long periods of time. In a specific implementation, when the power button is pressed, the LED indicator lights will turn on. These lights will automatically turn off in about 10 seconds for power saving. When needing to charge or power digital or electronic products, the user can simply plug the cable into the external battery device, and it will start charging when it detects the load. The user should follow the following safety precautions when using the Mobile Power product. These instructions are included in a kit containing the Mobile Power product. 1. Charge fully before using the mobile power device. 2. Do not place or use mobile device at high temperature or in humid environment. Do not expose to excessive sunlight. (Operating temperature range: charging: 0 degrees Celsius to 45 degrees Celsius; discharging: −10 degrees Celsius to about 60 degrees Celsius; and storage environment: about −20 degrees Celsius to about 60 degrees Celsius). 3. The user should not throw the mobile power device in fire or water so as to avoid fire, explosion, or both. 4. Keep the mobile power device out of reach of children. 5. Do not disassemble the device arbitrarily, since in some of the products, there are no removable or maintainable parts that are installed in the product. 6. Do not vigorously shake, hit or impact the mobile power device. 7. If the mobile power device has exposed liquid or other abnormalities, discontinue use, and contact customer service. 8. If the mobile power device has liquid leakage and splashes into the user's eyes, do not rub the eyes, wash with clean water immediately, and go to the hospital for medical treatment. 9. It is normal for the temperature of the mobile power device to rise during use; do not operate in a confined environment. 10. The transmission lines and connectors of the mobile power device must be provided by the original manufacturer. The use of transmission lines or connectors of nonoriginal manufacturer may result in severe or fatal injuries and property losses. 11. Do not cover or block the mobile power device with paper or other objects, to avoid blocking the heat dissipation and cold cutting. 12. Do not use the mobile power device if nobody is watching it in the car or anywhere. 13. Before using mobile power device, check its voltage demand. 14. If the mobile power device is not used for a long period of time, please charge or discharge it once every three months to ensure service life. 15. Remove power supply and power cord when the mobile power device is not in use. 16. Fully charge the mobile power device after the mobile power device is fully discharged. FIG. 15 shows a block diagram of a specific implementation of a nail lamp 1500 having a PCB5 1502 that can receive power from a USB power connector 1504 (e.g., micro-B USB receptacle) or rechargeable battery pack 1506. Unlike the FIG. 14 system, the rechargeable battery pack is specifically adapted to connect directly to the nail lamp circuitry (powering the nail lamp) without using the USB power connector. Specifically, power is not provided from the battery pack through the USB power connector, but rather directly from the battery. Further, the rechargeable battery pack can integrate with the housing of the nail lamp. In an example, the rechargeable battery pack snaps into place into a bottom of the nail lamp via a latching mechanism. And the rechargeable battery pack can be unlatched to be removed and replaced with a new pack, which may be desirable when the pack is spent or no longer holding charge (e.g., at the end of life of the pack). In an implementation, compared to the FIG. 14 system, circuitry to recharge this rechargeable battery pack is contained within a housing of the nail lamp (e.g., PCB5 of the nail lamp). Referring to FIG. 16, PCB5 is similar to PCB1 as described previously, but includes a recharging circuit 1602 and other circuitry to multiplex 1604 (mux), switch, or other switching mechanism to switch between taking power from the USB power connector or the rechargeable battery pack. Power from the USB power connector (such as connected to a wall adapter or other power source) can be used to power the nail lamp and also recharge (via the recharging circuit) the rechargeable battery too. FIG. 17 shows an implementation where the nail lamp of FIG. 16 includes one or more USB power output connectors 1701. These connectors can be used to charge a user's or customer's device, such as a phone or tablet. The user or customer will connect their device (e.g., phone) via a cable to one power output connectors. The device will be charged from the power from the USB power connector input 1702 or the battery 1703 through a mux 1704 or switch. Typically when the USB power input is connected to power, this power is used to charge the user's device (and also the rechargeable battery pack of the nail lamp). When the USB power input is not connected to power, the user's device is charged by the nail lamp battery. FIG. 18 shows an example of a rechargeable battery pack 1802 that can be connected 1803 to the housing of nail lamp 1804. In this implementation, the battery is contained within a base plate 1806 of the nail lamp. When the nail lamp is used, the user or customer places their fingers (that will be exposed to the UV light) onto the battery pack base plate. The battery pack base plate snaps or latches into place in the housing of the nail lamp. FIG. 19 shows an outline of a plan view of the battery pack base plate. More specifically, referring to FIG. 18, the rechargeable battery pack connects to the nail lamp at one or more connection points via connectors. For example, the nail lamp has a connector for connecting to the external rechargeable battery pack which the nail lamp is designed for. In a specific implementation, the nail lamp has a female connector while the external rechargeable battery pack has a corresponding male connector that fits into the nail lamp's connector. In another specific implementation, the nail lamp includes a male connector that fits into the external rechargeable battery pack's female connector. In other implementations, however, the nail lamp's connector can have any number or combination of pins and shapes in order to interface with the external rechargeable battery pack that the nail lamp is designed for. In a specific implementation, the nail lamp can include a fastening member that fastens to the external rechargeable battery pack to ensure a tight fit. As an example, the nail lamp can include a latch to secure the lamp to the battery. In another specific implementation, when the external rechargeable battery pack is connected to the nail lamp, the nail lamp looks for an authentication or handshaking signal (e.g., sending of an authentication code). If the lamp does not receive the proper authentication, the lamp may display a signal (e.g., flashing lights) that the battery is not an authorized peripheral for the lamp or the lamp can simply not allow the lamp circuitry to interface with the battery (e.g., not allow charging). An authentication circuit can be included in the circuitry of the lamp to provide proper authentication to the nail lamp. FIG. 19 shows a specific implementation an outline of a plan view of the battery pack base plate 1806 that is designed for a nail lamp. In an implementation, the nail lamp is the SMD LED Lamp S2 product by LeChat Nail Care Products. The shape of the external rechargeable battery pack corresponds to the shape of a base of the nail lamp, which connects to the external rechargeable battery pack. The shape of the external rechargeable battery pack allows a user to align the battery with the shape of the nail lamp base for connecting the two portions together. When connected, where the lamp and battery portions meet, the exterior surfaces become flush with each other. There will be a seam that is between the nail lamp and the battery pack. At the seam, the surfaces of the lamp and battery are relatively flush with each other. The seam line remains visible and can be felt tactilely. The battery pack base plate can have a finger plate integrated with the plate. In an implementation, the finger plate is removable from the base plate to allow for replacement or cleaning between uses. More discussion on a finger plate is in U.S. patent application 62/002,763, which is incorporated by reference. FIG. 20 shows a block diagram of a specific implementation of a kit 2000 for a nail lamp. The kit includes a UV light unit 2002, a battery pack 2004, a USB charger 2006, a USB charging cable 2008, and a user guide 2010 or instructions on use. These components can be arranged in a packaging of the kit which can include a box. In an implementation, the box can have compartments or trays for holding the components in place within the box. For example, one kit implementation is the system described in connection with FIG. 14 above. This kit has the battery pack connecting to the lamp with the USB connector input, and also the recharging circuitry is contained within the battery pack housing. Another kit implementation is the system described in connection with FIGS. 15-19 above. This kit has the battery pack directly connecting to the lamp, rather than through the USB connector input. The recharging circuitry is contained within the nail lamp housing. FIG. 21-23 show views of another implementation of a nail lamp 2100. FIG. 21 shows a perspective view, FIG. 22 shows a top view, and FIG. 23 shows a right side view. The nail lamp device has an exterior surface and at one side, an opening through which a user can place their hand into an interior space of the nail lamp. There are controls on the exterior that are used to turn on an interior lighting source of the device, which exposes the interior space to light from the interior lighting source. As an example, a user can insert their fingers into the interior space, turn on the cure interior lighting source, and cure their UV nail polish or UV nail gel coated nails with the interior light. In an implementation, the device includes sensors that detect when a hand is present inside the unit. This turns on both the interior curing lights as well as the exterior glowing lights for an allotted time (e.g., turning off after 15, 30, or 60 seconds). The light can also be manually turned on or off with, for example, button controls as an additional convenience. In an implementation, there is also an exterior lighting source of the device, which also turns on in response to the controls and is on when the interior lighting source is on. Light from the exterior lighting source is visible through a translucent shell (e.g., translucent plastic) of the exterior of the device. The translucent shell can be clear material or a light-diffusing material. When the interior lighting source is off, the light from the exterior lighting source will also be off. The exterior lighting source is used as an indicator that the device is on—that the interior lighting source is on. The entire exterior surface of the device can be lighted when on. This exterior lighting feature will make it easier for the user to know that the light is on and the curing cycle is continuing. The user will be able to see the exterior light is on from many positions and many angles, especially compared to attempting to peek into the opening (which will be partially blocked by a hand) and trying to see whether the interior lighting source is on. And the interior lighting source may not be visible light. In an implementation, on the exterior, there is a digital display. The display shows a length time in digits that the light will be turned on for. Further, the display can be a count down (or count up) timer that shows the time remaining for the light to be on. The digital display is optional and can be omitted in some implementations. More specifically, the nail lamp includes a housing 2102. The housing includes a base 2103 and an outer cover 2105. On a front side of the housing, there is an opening 2107 to a space (or cavity) within the housing. The space within the housing is defined by inner surfaces of the housing including a platform 2109, an inner side wall 2111, and an inner roof (not visible). The inner surfaces of the inside of the housing can be made of metal, plastic, or a combination of these. In an implementation, the opening is shaped and sized to allow a user's hand to pass through the opening into the space within the housing. The user's hand can be positioned within a cavity formed by the space, surrounded by the inner surfaces of the housing. In another implementation, the opening is adapted to allow a foot to pass through the opening. In another implementation, the nail lamp is adapted to be used for both a hand and foot. The outer cover of the housing includes a screen or display 2120 and controls, which in an implementation, are button features 2122a, 2122b, and 2122c. The screen may be an LED-backlit liquid crystal display (LCD) to display to a user a status or parameter of the nail lamp such as a time elapsed or a time remaining for a particular cure setting of the lamp. The display can also indicate other parameters of the lamp such as a power setting (e.g., “ON,” “OFF,” “LOW,” “HIGH,” or other messages). The screen can display images such as words, digits, 7-segment displays, meters, and others. The button features can indicate various cure settings of the nail lamp. Each button can be associated with a certain time of curing. For example, a first button can indicate a first timer setting for a first interval of time (e.g., 15 seconds). When a user selects the first timer setting by pushing the first button, an LED light source of the lamp will turn on for a time of 15 seconds of curing. A second button can indicate a second timer setting for a second interval of time (e.g., 30 seconds), and a third button can indicate a third timer setting for a third interval of time (e.g., 60 seconds). In other implementations, there can be fewer buttons (e.g., 1 or 2 buttons) or more than 3 buttons (e.g., 4, 5, or 6, or greater). FIG. 24 shows a view of an inside of a housing of a nail lamp, as viewed from a lower surface of the interior space looking toward the upper surface (e.g., inner roof). Side surfaces or side surfaces are angled with respect to the lower surface. The upper surface and side surfaces include a number of light source structures as shown. In an implementation, the light source structures are surface mounted light emitting diodes (LEDs). The LEDs can be referred to a surface mounted devices or SMDs. The LEDs are surface mounted to one or more printed circuit boards that housed within the device's enclosure, between surfaces of the interior space and exterior shell of the device. In other implementation, light sources can include other types of LEDs (other than SMDs), laser diodes, light bulbs, or other lighting. Some light source structures can be different from other light source structures. For example, first light structures 2421, 2423, 2425, 2427, 2429, 2431, 2433, 2435, 2437, 2439, 2441, 2443, 2445, and 2447 are different from the other light structures, which can be referred to as second light structures. In an implementation, the first light structures have higher energy output than the first light structures. For example, the first light structures can be 2-watt LEDs, while the second light structures are 1-watt LEDs. The light sources can include lights of the same or different output power and wavelength. In the specific arrangement of lights in FIG. 24, LED lights are positioned on the side walls and roof of the inside of the housing. There are seven side walls connected to the roof. The shaded LED lights (2421, 2423, 2425, 2427, 2429, 2431, 2433, 2435, 2437, 2439, 2441, 2443, 2445, and 2447) indicate 2-Watt output LEDs, while the remaining unshaded LED lights are 1-Watt output LEDs. Generally, on side walls of the housing, each 2-Watt LED is positioned between two 1-Watt LEDs. This distribution of LEDs can provide each nail of a user's hand (or foot) with an even exposure of light since a 2-Watt LED is positioned near each nail, as shown in FIG. 18. In other implementations, the LEDs can be arranged in another arrangement, such as an alternating pattern. On the inner roof of the housing, there is a combination of 2-Watt and 1-Watt LED lights. The 2-Watt LEDs can be arranged to correspond to a user's nails, so that a 2-Watt LED is near each nail. For example, when the user's left hand is inserted into a cavity of the housing, as shown in FIG. 18, each nail of the hand is irradiated by at least two nearby 2-Watt LEDs. Referring to FIG. 24, with the user's hand placed in the cavity, each nail is irradiated by at least one nearby sidewall LED and one nearby inner roof LED. Table B below shows how each nail is irradiated for both right and left hands of the user. TABLE BRight HandLeft HandSidewallSidewallFingerLEDRoof LEDFingerLEDRoof LEDThumb nail24212435Thumb nail24332447Index nail24252439Index nail24292443Middle nail24272441Middle nail24272441Ring nail24292443Ring nail24252439Little nail24312445Little nail24232437 Each nail is also irradiated by at least two 1-Watt LEDs. For example, when the left hand is placed in the cavity, the thumbnail is irradiated by 2-Watt LEDs 2421 and 2437, and by the two 1-Watt LEDs surrounding LED 2421. The index fingernail is irradiated by 2-Watt LEDs 2425 and 2439, and by two 1-Watt LEDs between LEDs 2425 and 2427, and between LEDs 2439 and 2441. FIG. 25 shows an inside view of a housing of a nail lamp in relief. Light sources are positioned along sidewalls and inner roof of the housing. The side walls and roof include openings or apertures to expose a light source, which can be positioned in or behind the opening. Light from the light source radiates through the opening and into the space provided by the housing. By using surface mounted LEDs, the LEDs are recessed in openings of the enclosure. This is in comparison to other not-surface-mounted types of LEDs that have a bulb-portion that extend through the openings. Also in some implementations, the LEDs can be flush with the enclosure surface. FIG. 26 shows specific arrangement of LED lights on sidewalls and inner roof of a housing. The LEDs that are circled are 2-Watt LEDs using surface mount technology (SMT). These LEDs are referred to as surface mount devices (SMD) LEDs. The LEDs that are not circled, that are positioned between the 2-Watt LEDs, are 1-Watt SMD LEDs. In an implementation, a SMD LED can produce UV light in a range of about 340 nanometers to about 410 nanometers. In a specific implementation, the SMD LEDs can produce UV light at about 395 nanometers peak irradiance. In another specific implementation, the SMD LEDs can produce UV light at about 350 nanometers. In another specific implementation, the SMD LEDs can produce UV light at about 365 nanometers. FIG. 27 shows a specific arrangement of LED lights on sidewalls and inner roof of a housing with five inner sidewalls of the housing. The configuration of LED lights in FIG. 27 is slightly different from that shown in FIGS. 24, 25, and 26. There are two fewer LEDs than the other configurations. The circled LEDs indicate 2-Watt SMD LEDs, and the uncircled LEDs indicate 1-Watt SMD LEDs. For each sidewall, one 2-Watt LED is positioned between two 1-Watt LEDs. FIG. 28 shows a specific arrangement of SMD LED lights on sidewalls and inner roof of a housing with seven inner sidewalls of the housing. Compared to the arrangement in FIG. 7, this housing includes 2 additional sidewalls, each with a 2-Watt LED 2806 and 2808. So, the arrangement in FIG. 7 has five 2-Watt LEDs on sidewalls, while this arrangement includes seven 2-Watt LEDs positioned on sidewalls. The arrangement with two additional LEDs can increase the cost of the device, but provides the irradiation for curing, which can reduce curing time and improve a uniformity of the curing. FIG. 29 shows a top view of a finger plate 2901. The finger plate is placed onto the lower surface of the interior space of a nail lamp. The finger plate is a guide for the fingers, so the fingers will be properly positioned inside the nail lamp. The user places the fingers on the finger plate, and the nails are held in position for exposure to the curing light. The finger plate can be removable (e.g., sliding out from a bottom of the lamp), such as for cleaning or so other finger plates can be used for different sized fingers. The finger plate is designed for the right or left hand, but in other implementations, there may be a specific finger plate design for each hand. The finger plate includes five side by side depressions or grooves that are adapted to support a user's fingers when the user places a hand inside the housing on the plate. A first depression 2902 can be a sloped surface (or indentation, groove, or recess) for supporting the user's thumb or little finger. A second depression 2903 can be a groove (or indentation or recess) for supporting the user's index or ring finger. A third depression 2904 can be a groove (or indentation or recess) for supporting the user's middle finger. A fourth depression 2905 can be a groove (or indentation or recess) for supporting the user's index or ring finger. A fifth depression 2906 can be a sloped surface (or groove, indentation, or recess) for supporting the user's thumb or little finger. The finger plate can include thumb guides 2910 and 2911 that include circular grooves in the finger plate. The circular groove can provide a tactile guide for the user to place the thumb when the user inserts the hand into the housing. The thumb guide allows the user to keep the hand in the same position through the curing so that the nails cure evenly and without smudging. In an implementation, the finger plate is removable from the housing. Different finger plates can be used for users with different size hands. The finger plate can also be removed to facilitate cleaning of the plate and of the inside of the housing. In salons, the plate can be removed between uses to sterilize the plate for a new user. The finger plate can also be replaced with a foot plate for curing polish on a person's foot for a pedicure. FIG. 30 shows an outline of the finger plate overlaid on a bottom up view of an inside of a housing of a nail lamp. This figure shows the positioning of the light structures in relation to the finger plate grooves. Light sources are arranged along an inner roof of the housing. The roof includes openings or apertures to expose a light source (e.g., LED, or SMD LED, or others), which can be positioned in or behind the opening. Light from the light source radiates through the opening and into the space provided by the housing. FIG. 30 shows a specific arrangement of light sources relative to a finger plate of the housing. The finger plate includes finger grooves, with spacers (e.g., raised regions or ridges) between adjacent finger grooves. There is at least one light source positioned over each finger groove. Over a first finger groove 3002, there are two openings with a light source at each opening. There is a light source positioned over a second finger groove 3003, third finger groove 3004, and fourth finger groove 3005. A light source is positioned between and over the second and third finger grooves, and the third and fourth finger grooves. There are two light sources positioned over a fifth finger groove 3006. FIG. 31 shows a specific implementation of a finger plate 3101 with extended grooves for fingers of a user's hand. There can be spacers 3105 between adjacent grooves. The finger plate includes stops 3107 in some grooves to prevent the user's fingers from sliding in the grooves (e.g., away from or toward the light sources). The stops can provide a tactile gauge for the user to indicate where to place the fingers during curing. In a specific implementation, a height of the stops is about 3 millimeters from a surface of the groove. In other implementations, the height is less than 3 millimeters (e.g., 0.5, 1, 1.5, 2, or 2.5 millimeters or greater). In other implementations, the height is greater than 3 millimeters (e.g., about 3.1, 3.2, 3.3, 3.4, 3.5, 3.6, 3.7, 3.8, 3.9, or 4 millimeters or more). In an implementation, a finger plate can have shorter or longer grooves than that of FIG. 31. FIG. 32 shows an implementation of a finger plate with grooves that are shorter compared to the finger plate in FIG. 31. An edge 3202 of the finger plate provides a stop for a user's fingers. The edge can have raised regions or stops to provide the user with a tactile guide for placement of the fingers or fingertips. In a specific implementation, a height of the stops is about 1.5 millimeters from a surface of the groove. In other implementations, the height is less than 1.5 millimeters (e.g., 0.5, 1, 1.1, 1.2, 1.3, or 1.4 millimeters). In other implementations, the height is greater than 1.5 millimeters (e.g., about 1.6, 1.7, 1.8, 1.9, or 2 millimeters or more). In other implementations, the edge does not have a raised rim, and the user can place the fingertips at the edge itself. FIG. 33 shows the positioning of a user's hand (e.g., left hand) in the finger plate of FIG. 31, against the finger stops. FIG. 34 shows the positioning of a user's hand (e.g., left hand) in the finger plate of FIG. 32, against the finger stops. FIG. 35 shows a rear perspective view of a finger plate. A top view of the finger plate is in FIG. 29. As discussed, the plate can include five depressed regions (e.g., finger grooves) with adjacent regions separated by a raised region 3505 (or ridge). Three of the finger grooves, in the middle, are elevated compared to the other two finger grooves, on either side of the middle three. The depressed regions can be contoured or curved to provide comfort to a user's fingers when resting in the depressed regions. The depressed regions and raised regions can also prevent the fingers from moving while curing which can cause uneven curing or smudging. FIG. 36 shows a front perspective view of a finger plate. A first groove 3602 and a fifth groove 3603 are less raised from a base of the housing than second, third, and fourth grooves 3604, 3605, and 3606. The first and fifth grooves are slightly angled away from the second, third, and fourth grooves. A surface of the fingerplate between a front edge of the grooves and a base of the finger plate can be sloped. By elevating the second, third, and fourth finger grooves, the fingers will be positioned closer to the upper surface and the light structures. This will increase the radiation to the fingers which improve curing of the polish or gel. Curing time will be reduced and the uniformity of the curing will improve. Further, this structure reflects a natural positioning of a person's fingers at rest. So, when a user places fingers into the grooves of the finger plate, the fingers can rest in a natural position that ergonomic and comfortable than if the grooves were positioned at the same height from the base of the housing. FIG. 37 shows an irradiation pattern for light structures for the arrangement of FIG. 27. This specific arrangement of lights (e.g., LEDs) has sidewalls and inner roof of a housing with five inner sidewalls of the housing. A user's hand is positioned in the housing and each nail is irradiated by nearby light sources. A thumbnail is irradiated by three nearby light sources while a little finger nail 3705 is irradiated by two nearby light sources. In a specific implementation, for each sidewall of the housing, there is one 2-Watt LED that is surrounded by two 1-Watt LEDs. The thumbnail is irradiated by all three LEDs, while the little finger nail is irradiated by two 1-Watt LEDs. FIG. 38 shows an irradiation pattern for light structures for the arrangement of FIGS. 24, 25, 26, and 28. This specific arrangement of lights (e.g., LEDs) has sidewalls and inner roof of a housing with seven inner sidewalls of the housing. Compared to the arrangement in FIG. 37, there are two additional sidewalls 3803 and 3805, each sidewall with a light source 3806 and 3808. In this arrangement, the user's nails (right hand or left hand) can be evenly irradiated. The thumbnail and little finger nail of each hand can be each irradiated by at least three light sources. In a specific implementation, for each sidewall of the housing with three light sources, there is one 2-Watt LED that is surrounded by two 1-Watt LEDs. On each sidewall 3803 and 3805, there is one 2-Watt LED. The thumbnail and little finger nail is each irradiated by one 2-Watt LED and two 1-Watt LEDs. FIG. 39 shows a finger plate for an inside space having five inner sidewalls, such as used in connection with the light structure arrangement of FIG. 27. FIG. 40 shows a finger plate for an inside space having seven inner sidewalls, such as used in connection with the light structure arrangement of FIG. 28. The finger plates described in this application can be adapted or modified to be used with the configuration of FIG. 27 or 28, or both. For example, the finger plate in FIG. 40 can be used with the FIG. 27 configuration. And the finger plate in FIG. 39 can be used with the FIG. 28 configuration. Compared to the configuration in FIG. 39, two additional side walls 4006 and 4008 can be added at corners 3906 and 3908. The finger plate also includes indicator members 4010 (finger points) positioned in the grooves of the finger plate. In an implementation, the indicator members are raised dots or bumps analogous to Braille dots that provide the user a tactile guide that the fingertips are positioned properly. Note that for the first and fifth grooves, these include two indicator dots. This is because there grooves, depending on which hand, are for the thumb or pinkie, which are a different length. In other implementation, the indicator members can be other raised regions (e.g., bump, projection, or ridge, or others) or recessed regions that can provide the user tactile feedback. When the user inserts the hand into grooves of the finger plate, the user cannot see how far to extend the fingers into housing. With the indicator members, the user can feel where to position the hand during curing. FIG. 41 shows a front view of an inside of a housing of a nail lamp with an outer cover of the housing removed. The side walls and roof include openings 4105. Light source structures 4110 can be located in or behind the openings and are exposed through the openings. Light sources can be connected to circuit boards 4115. In a specific implementation, light sources are SMD LEDs that are mounted onto circuit boards. Circuit boards 4115 may be printed circuit boards upon which the surface mounted LEDs are soldered. There can also be heat sinks or heat fins to which the LEDs are attached to dissipate heat. There can be LEDs mounted on both sides of a printed circuit board. One side will include the LEDs facing the inside of the interior space, while the other side will include the LEDs for lighting the exterior of the device. There can be multiple printed circuit boards, with boards for the sidewalls and upper surface of the interior space. FIG. 42 shows a front view of an inside of a housing of a nail lamp with five inside side walls. Side walls are angled with respect to a vertical y-axis to allow the light sources to be angled toward a finger plate of the housing. In a specific implementation, an angle 4209 at which a side wall is angled with respect to the vertical axis is about 30 degrees. In other implementations, the angle is less than 30 degrees (e.g., about 20, 21, 22, 23, 24, 25, 26, 27, 28, or 29 degrees). In other implementations, the angle is greater than 30 degrees (e.g., about 31, 32, 33, 34, 35, 36, 37, 88, or 39 degrees, or more). FIG. 43 shows a front view of an inside of a housing of a nail lamp with seven inside side walls. Compared to the configuration in FIG. 42, the side walls can be less angled with respect to the vertical y-axis. In a specific implementation, an angle 4309 at which a side wall is angled with respect to the vertical axis is about 26 degrees. In other implementations, the angle is less than 26 degrees (e.g., about 18, 19, 20, 21, 22, 23, 24, or 25 degrees). In other implementations, the angle is greater than 26 degrees (e.g., about 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 88, or 39 degrees, or more). FIG. 44 shows a top view of an exterior of a nail lamp. There are preset settings for a user to select for curing. In an implementation, the user can select a preset curing time (e.g., 15 seconds, 30 seconds, or 60 seconds). The UV nail lamp in FIG. 44 is set to a setting of 60 seconds curing time. When the user presses the button for the selected setting, the button can light up and remain lit during the curing. A display can indicate to the user how much time has elapsed or is remaining on the curing time. The display shows 20 seconds (or 2 seconds) has elapsed or is remaining of the selected 60 seconds. Once the time expires, the UV lights, along with the lights of the housing, will turn off. In an implementation, when the user selects the desired cure time by pressing the button, the display will display the selected time. In an implementation, an exterior lighting source of the device does not turn on until a person's hand is inserted inside of the nail lamp. When the hand is inside, a sensor of the device detects when a hand is present inside the unit. This turns on both the interior curing lights as well as the exterior glowing lights for duration of the selected curing. When curing begins, exterior light source of the device will turn on, causing the exterior surface of the lamp to glow a soft and steady light for the duration of the curing time. The exterior lights can be positioned within the device, between interior curing lights and an outer translucent cover of the device. The translucent cover can be a translucent plastic material. The translucent plastic material can be a diffusing material or a diffuser, or the translucent plastic material can be combined with another diffusing material or diffuser, such as a composite material including both a translucent plastic layer and a light diffusing layer. In an implementation, the translucent plastic material of the lamp shell includes a light diffusing property. When light irradiated from the exterior light source hits an inside surface of and is transmitted through the translucent plastic material, the plastic material diffuses or spreads out (i.e., scatters) the light to give a softer light relative to the more concentrated light initially radiated from the exterior lighting source (e.g., diode on the circuit board). The scattered light can be across the entire exterior shell and cause the device to have a soft and steady glow of light. For example, in FIG. 44, about six exterior lights sources are used to illuminate and cause the lamp's exterior surface to glow. The light diffuser material spreads and homogenizes the nonuniform or uneven illumination of six light sources into a more uniform illumination. In an implementation, light diffusing property is present across an entire exterior surface area of the shell. When light from an exterior lighting source (located inside the nail lamp housing) enters an inside surface of the lamp shell, the light diffusing material scatters the light across the entire exterior surface area of the shell. This causes a more even glow across the entire lamp shell. In an implementation, the lamp shell has a light diffusing property when the lamp shell is made of a translucent material and a light diffuser film is coupled to an interior surface, or exterior surface, or both interior and exterior surfaces of the translucent lamp shell material. Examples of light diffusing films includes mylar or acetate, or similar films. Other examples of light diffusing film include films that have varying degrees of opacity. In another implementation, the lamp shell has a light diffusing property when the lamp shell includes a roughened surface, which scatters light. In a specific implementation, the lamp shell includes randomly sized and randomly placed particles on a surface of the lamp shell. In another specific implementation, particles can be of sizes large enough to be visible to the eye. In another specific implementation, the lamp shell includes a matting agent. The matting agent can blur spots of relatively more intense light produced by individual light sources. Examples of a matting agent can include silica powder, calcium carbonate powder, alumina powder, or the like. In a further implementation, the matting agents can have a particle size of approximately 1 to 5 microns. In an implementation, the light diffusing material is positioned over all of the exterior lighting sources so that all of the light from the exterior lighting sources will enter the light diffusing material and exit as an even glow that is spread across the entire surface of the shell. In a specific implementation, the light diffusing material is applied over an entire inner surface of the shell. In another implementation, the light diffusing material is applied over an outer surface of the shell. In another implementation, the light diffusing material is positioned over a portion of the exterior lighting sources. A portion of the light will enter and exit the light diffusing material and a portion of the light will not enter the light diffusing layer. This can result in various glow patterns across the shell the nail lamp. Each glow pattern can have a functional purpose, such as using a certain glow pattern to show when customers are close to finishing curing their gel nail polishes. In an implementation, a greater portion of the lamp shell's exterior surface area includes light diffusing property (or light diffusing material) than a portion that does not have light diffusing property. In another implementation, the lamp shell's exterior surface includes a portion with light diffusing property and an opaque portion, which does not let light travel through. In a specific implementation, the portion of the lamp shell's exterior surface that includes light diffusing property ranges from 10 percent to 100 percent. The remaining portion of the lamp shell's exterior surface is opaque. In another implementation, the lamp shell's exterior surface includes a portion with light diffusing property, a transparent portion, and an opaque portion. In an implementation, the nail lamp housing includes a first layer with light diffusing properties that is coupled to a second layer of material, which blocks out light. In a specific implementation, the light blocking material can block out specific wavelengths of light, such as UV light. Some of the interior light sources can emit UV light. Though the interior light sources are directed into the cavity (or interior space), some light rays may reflect off the inner walls of the cavity and be emitted through the shell of the nail lamp. To prevent the UV light from emitting through the shell, a layer of UV light blocking material can be added to the housing. Examples of materials that block out UV light are polycarbonate, acrylic, acrylic glass, and the like. In an implementation, the exterior light sources are positioned in regions of rather than the entire device. For example, the exterior lights can be positioned along an outer perimeter of the device. When the light is transmitted through and scattered by the translucent outer cover, the regions closest to the light sources will glow brighter than the regions farther away from the light sources (e.g., a top region of the outer cover). Typically, the LEDs for the exterior lighting are not the same wavelength as the interior lighting. In an implementation, the exterior lights are non-UV lights. In an implementation, these lights can produce visible colored light, all the same color, such as in blue. Other colors can include pink, orange, yellow, red, green, or purple or others. In other implementations, there can be different colors of exterior light (such as blue and yellow, or red and green). In other implementations, the lights are LEDs such as RGB LEDs that can produce changing colors of light during curing. FIG. 45 shows a perspective view of an exterior of a nail lamp. The display shows 44 seconds has elapsed or is remaining of the selected 60 seconds. Once the time expires, the UV lights, along with the lights of the housing, will turn off. FIG. 46 shows a top perspective view of an exterior of a nail lamp that is turned on (i.e., curing mode). A timer displays 20 seconds (or 2 seconds) has elapsed or is remaining of the selected 60 seconds. UV lights on an inside of the housing are turned on, and glow from an opening of the housing of the lamp. A specific process flow for operating a UV nail lamp is presented in table C below. It should be understood that the invention is not limited to the specific flows and steps presented. A flow of the invention may have additional steps (not necessarily described in this application), different steps which replace some of the steps presented, fewer steps or a subset of the steps presented, or steps in a different order than presented, or any combination of these. Further, the steps in other implementations of the invention may not be exactly the same as the steps presented and may be modified or altered as appropriate for a particular application. TABLE CStepFlow1Power on UV lamp.2Select curing mode. This can include a user selecting a cursing time, or a level of curing, or other parameters from a preset options (e.g., menu or buttons). The use can also manually input a desired curing time or level of curing (e.g., buttons, dial, knob, or menu). In an implementation, the user presses one of a plurality of buttons to select a predetermined curing time (e.g., 15 seconds, 30, seconds, and 60 seconds). A display can display the selected curing time or setting. Lights between an insde of the housing and an outer cover of the housing will light up, causing the housing to light up or glow during curing.3A user inserts a hand (or foot) into the housing. The user's hand can rest on a finger plate. The finger plate can have finger indicator members that allow the user to feel where to rest the fingertips4Timer starts when the user's hand is inside the housing. As the timer starts, UV light sources within the housing turn on toirradiate the user's nails.5Timer stops after the selected time expires. When the timer stops, the UV light sources turn off. Lights between the inside of the housing and the other cover of the housing will turn off, causingthe housing to dim.6User removes hand from the housing.7Power off UV lamp. FIG. 47 shows a block diagram of a specific implementation a nail lamp that is adapted to be used with a power source that is external to the nail lamp. The nail lamp includes a shell 4702 (also referred to as an exterior surface) and an enclosure 4704 (also referred to as a cavity or interior space), which is defined by an upper surface 4706 (also referred to as inner wall of a nail lamp's housing) of the enclosure. A user can place a hand inside the enclosure. A removable finger plate 4708 can optionally attach to the nail lamp and further define the enclosure. A power circuit 4710, inside the lamp, is coupled to an external battery 4712 or an adapter 4714, both of which are outside of the nail lamp. The external battery can be connected to a charger 4716. The adapter can be connected to an external power supply (e.g., a wall outlet). The external battery or external power supply provides power to a power circuit. The power circuit provides power to sensors 4718, one or more interior LEDs 4720, a control circuit 4722 that includes a control unit 4724 and a timer display 4726, and one or more LED units 4728 that include exterior LEDs 4730 and interior LEDs 4720. The interior LED can also be referred to as an interior lighting source, discussed above, and used to cure the gel polish. The exterior LED can also be referred to as an exterior lighting source, discussed above, and produces light to indicate that the interior LED is activated. A button 4732, located outside of the shell, is connected to the control circuit. When pressed, the button activates the control circuit that controls the timer display and activates one or more SMD interior LEDs 4720 or LED units 4728. Heat sinks can be coupled to the interior LEDs within the shell. The heat sink can absorb heat given off by an activated LED so that a user's hand will not feel hot and uncomfortable inside the nail lamp. The power circuit can optionally include an internal battery 4734. The internal battery can be charged by connecting to an external battery or an adapter that is connected to an external power source such as a wall outlet. After the internal battery has been charged by the external battery or external power supply, the nail lamp can operate without being connected to an external battery or adapter. The power circuit can also include a switch between the internal battery and external power connections (e.g., such as connection to an external battery or wall outlet) to allow the nail lamp to switch between internal and external power sources. FIGS. 48-50 show an implementation of a nail lamp 4802 that includes a battery input port 4804 (also referred to as a power input) so that the nail lamp can be used with a rechargeable battery pack that is external to the housing of the nail lamp. The rechargeable external battery 4806 can provide power to the nail lamp. The external battery can be removably coupled to a cable 4808, which is removably coupled to the battery input port. FIG. 48 shows a block diagram of nail lamp 4802. FIG. 49 shows a side view of the nail lamp including the external battery attached to the nail lamp via the cable. FIG. 50A shows a first short side of the external battery. FIG. 50B shows a second short side of the external battery. FIG. 50C shows a first long side of the external battery. FIG. 50D shows a top face of the external battery. The external battery supplies power to the nail lamp. With an external battery coupled to the nail lamp and providing power, the nail lamp does not have to be coupled to a wall outlet or laptop for power supply, the nail lamp can be moved around a room to any location. To charge the external battery, the external battery can be connected to an adapter, which can be connected to a wall outlet. The external battery can also be charged by being connected to a charging dock. After the external battery is charged, it can be disconnected from the adapter or dock and coupled to the nail lamp. FIG. 51 shows a block diagram of a charging dock 5102 and an external battery 5104. The charging dock includes a battery dock 5106 for the external battery, and optionally a latch 5108 to prevent the battery from falling out of position in the battery dock. Once the external battery is inserted into the battery dock, the charging dock starts charging it. The charging dock stops charging the external battery after the battery is removed. The charging dock can be connected to a power supply via a cable 5110 that can be connected to an adapter 5112, which can be connected to the power supply (e.g., a wall outlet). FIGS. 52-54 show an implementation of a nail lamp 5202 including a battery dock attachment 5204 that can be removably coupled to an exterior of the nail lamp. FIG. 52 shows a block diagram of the nail lamp and the battery dock attachment. FIG. 53 shows a side view of the nail lamp and the battery dock attachment attached to the nail lamp. FIG. 54 shows a side view of the nail lamp with the battery dock attachment detached from the nail lamp. The battery dock includes a slot for a battery 5208 and a latch 5210 to hold the battery firmly to the battery dock. The latch can be, for example, a spring loaded release latch. The battery can be inserted into the slot. The battery dock attachment provides for easy removal of the battery when the battery needs to be recharged. FIGS. 55-57 show an implementation of a nail lamp 5502 that includes an internal battery dock 5504 where a rechargeable battery pack 5506 can integrate with the housing of the nail lamp. The internal battery dock is removably coupled to a battery 5506 to be removably coupled within the housing of the nail lamp. FIG. 55 shows a block diagram of the nail lamp including the internal battery dock. FIG. 56 shows a specific implementation of nail lamp 5502 in which the internal battery dock is located at a bottom 5606 of the nail lamp. The battery can be inserted into the bottom of the nail lamp. In other implementations, the battery dock can be located elsewhere, such as the top or side of the nail lamp, for easy access to the battery dock. The internal battery dock optionally includes a latch 5508 to hold the battery firmly to the battery dock. The latch can be, for example, a spring loaded release latch. The battery can be inserted into the slot. FIG. 57 shows a perspective view of the battery. The battery can include leads (e.g., copper strips) or pins that interface with the battery dock. FIG. 58 shows a specific implementation of an interior lighting source unit 5801. The interior lighting source unit includes at least one UV wavelength (which is approximately 100-400 nanometers) light source and at least one LED. The LED can produce light of a wavelength that is same or different from that produced by a UV wavelength light source. In a specific implementation (shown in FIG. 59), four UV light sources and one LED can be arranged such that the one LED lighting source 5803 is in the middle and the UV light sources 5805 surround the LED lighting source on four sides, like a rectangle, or square, or diamond shape. FIG. 59 shows another arrangement 5901 where three UV lighting sources surround one LED lighting source in a triangle shape. In a specific implementation, the LED produces light of 405 nanometers and can be 1-3 Watt LEDs. In another specific implementation, the UV lighting source produces light of 365 nanometers. FIG. 60 shows a strip 6001 of interior lighting source units 6002 and a magnification (indicated by broken line 6003) of one of the interior lighting source unit. An LED 6004 is adjacent to another LED 6006. The LEDs produce light of different wavelengths from each other. In a specific implementation, LED 6004 produces light of 405 nanometers, which can be used to cure LED gel. And LED 6006 produces light of 365 nanometers, which can be used to cure UV curable gel or extension gel. This arrangement of UV and LED light sources allow for universal usage of the nail lamp because the nail lamp can be used to cure both LED and UV-curable gel polish. In a further implementation, the nail lamp can be an inductive nail lamp, which the power required to generate light is transferred from outside the nail lamp to the gas inside via an electric or magnetic field. A benefit to an inductive nail lamp is extended lamp life. This description of the invention has been presented for the purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise form described, and many modifications and variations are possible in light of the teaching above. The embodiments were chosen and described in order to best explain the principles of the invention and its practical applications. This description will enable others skilled in the art to best utilize and practice the invention in various embodiments and with various modifications as are suited to a particular use. The scope of the invention is defined by the following claims.
047626682	claims	1. An ultrasonic cleaning device for a venturi flow nozzle mounted in a pipe in a fluid system comprising: a transducer positioned adjacent and abutting said nozzle in said pipe for producing and transmitting sound waves to said nozzle; and a mounting and sealing assembly mounted in an opening in said pipe for maintaining said transducer in position adjacent said nozzle and for sealing said opening. a transducer positioned adjacent said nozzle in said pipe for producing and transmitting sound waves to said nozzle; a mounting and sealing assembly mounted in an opening in said pipe for maintaining said transducer in position adjacent said nozzle and for sealing said opening, said mounting and sealing assembly including a fitting threadably mounted in said opening and spring means for biasing said transducer towards said nozzle; and wherein said transducer includes a threaded portion at one end for connection to said nozzle. a plurality of transducers positioned adjacent said nozzle in said pipe for producing and transmitting sound waves to said nozzle; a mounting and sealing assembly mounted in an opening in said pipe for each said transducer for maintaining each said transducer in position adjacent said nozzle and for sealing said opening, each said mounting and sealing assembly including a fitting threadably mounted in said opening and spring means for biasing said transducer towards said nozzle; and wherein each said transducer includes a threaded portion at one end for connection to said nozzle. a transducer mounted adjacent said pipe for producing sound waves; a rod connected at one end to said transducer and extending through an opening into said pipe so that the other end of said rod contacts said nozzle to transmit said sound waves thereto; and a guiding and sealing assembly for said rod attached to said pipe around said pipe opening. a transducer mounted adjacent said pipe for producing sound waves; a horn attached to said transducer for concentrating said sound waves; a rod connected at one end to said horn and extending through an opening into said pipe so that the other end of said rod contacts said nozzle to transmit said sound waves thereto; and a guiding and sealing assembly for said rod attached to said pipe around said pipe opening, said assembly comprising a base member and a cover member, each having a central opening therein through which said rod passes, and sealing means surrounding said rod. a plurality of transducer assemblies mounted around said pipe for producing and transmitting sound waves to said nozzle; each said transducer assembly including a transducer for producing sound waves, a horn attached to said transducer for concentrating said sound waves and a rod connected at one end to said horn and extending through an opening into said pipe so that the other end of said rod contacts said nozzle to transmit said sound waves thereto; and a guiding and sealing assembly for each said rod attached to said pipe around each said pipe opening, each said assembly comprising a base member and a cover member, each having a central opening therein through which said rod passes, and sealing means surrounding said rod. 2. The device of claim 1 which includes a plurality of said transducers and said mounting and sealing assemblies mounted around said pipe. 3. The device of claim 1 wherein said transducer includes a threaded portion at one end for connection to said nozzle. 4. The device of claim 1 wherein said mounting and sealing assembly includes a fitting mounted in said opening and spring means for biasing said transducer towards said nozzle. 5. The device of claim 4 wherein said fitting is threadably engaged with at least a portion of said opening. 6. The device of claim 4 wherein said mounting and sealing assembly includes a base member attached to said pipe, said base member having a central opening therein in alignment with said opening in said pipe and wherein at least a portion of said fitting is threadably engaged with said base member. 7. An ultrasonic cleaning device for a venturi flow nozzle mounted in a pipe in a fluid system comprising: 8. The device of claim 7 which includes a plurality of said transducers and said mounting and sealing assemblies mounted around said pipe. 9. The device of claim 7 wherein said mounting and sealing assembly includes a base member attached to said pipe, said base member having a central opening therein in alignment with said opening in said pipe and wherein at least a portion of said fitting is threadably engaged with said base member. 10. In a nuclear reactor system having a pipe with a venturi flow nozzle mounted therein, an ultrasonic cleaning device for said nozzle comprising: 11. The device of claim 10 wherein each said mounting and sealing assembly includes a base member attached to said pipe, said base member having a central opening therein in alignment with said opening in said pipe and wherein at least a portion of said fitting is threadably engaged with said base member. 12. An ultrasonic cleaning device for a venturi flow nozzle mounted in a pipe in a fluid system comprising: 13. The device of claim 12 which includes a horn between said transducer and said one end of said rod to concentrate said sound waves to said rod. 14. The device of claim 12 which includes a cover around said transducer. 15. The device of claim 12 which includes a plurality of said transducers and rods mounted around said pipe for producing and transmitting said sound waves to said nozzle. 16. The device of claim 12 wherein said rod includes a threaded portion at said other end for connection to said nozzle. 17. The device of claim 12 which includes a plate mounted around said pipe for supporting said transducer. 18. The device of claim 12 wherein said guiding and sealing assembly comprises a base member and a cover member, each having a central opening therein through which said rod passes, and sealing means surrounding said rod. 19. The device of claim 18 wherein said guiding and sealing assembly further includes spring means for biasing said rod towards said nozzle. 20. The device of claim 18 wherein said sealing means includes at least one packing ring around said rod in at least one of said central openings. 21. The device of claim 18 wherein said sealing means includes a bellows surrounding said rod. 22. An ultrasonic cleaning device for a venturi flow nozzle mounted in a pipe in a fluid system comprising: 23. The device of claim 22 which includes a cover around said transducer. 24. The device of claim 22 which includes a plurality of said transducers, horns and rods mounted around said pipe for producing and transmitting said sound waves to said nozzle. 25. The device of claim 22 wherein said rod includes a threaded portion at said other end for connection to said nozzle. 26. The device of claim 22 which includes a plate mounted around said pipe for supporting said transducers, horns and rods. 27. The device of claim 22 wherein said guiding and sealing assembly further includes spring means for biasing said rod towards said nozzle. 28. The device of claim 22 wherein said sealing means includes at least one packing ring around said rod in at least one of said central openings. 29. The device of claim 22 wherein said sealing means includes a bellows surrounding said rod. 30. In a nuclear reactor system having a pipe with a venturi flow nozzle mounted therein, an ultrasonic cleaning device for said nozzle comprising: 31. The device of claim 30 wherein each said guiding and sealing assembly further includes spring means for biasing said rod towards said nozzle. 32. The device of claim 30 wherein each transducer assembly further includes a cover around each transducer.
052271242	abstract	An ICM housing welded to a wall of a reactor pressure vessel in operation is provided with a molten metal layer containing 4 wt. % or more .delta. ferrite at a portion of an inner peripheral surface thereof which corresponds to a weld. A sleeve made of stainless steel is located at the competent portion of the inner peripheral surface of the ICM housing stainless steel so as to be molten by means of a TIG welding machine to form the molten metal layer. The molten metal layer prevents stress corrosion cracking of the ICM housing.
	summary
	summary
051065746	claims	1. A gas cooled nuclear reactor suitable for use in space comprising: a lightweight structure comprising a plurality of at least three sections, each sector comprising a container for a reactor core separate and distinct from the reactor cores of the other sectors, each sector being capable of operating on its own and in cooperation with one or more of the other sectors and each sector having a common juncture with every other sector; and means associated with each sector for independently introducing gas coolant into and extracting coolant from each sector to cool the core therein, wherein in event of failure of the cooling system of a core in a sector, one or more of the other sectors comprise means for conducting heat away from the failed sector core and means for convecting the heat away, and wherein operation of said one or more other sectors is maintained. 2. The invention of claim 1 further comprising means associated with each sector for independently fueling, emptying and refueling each sector. 3. The invention of claim 2 wherein fuel provided to the sector cores comprises microspheres suspended in a solid medium to form pellets. 4. The invention of claim 2 wherein said fueling, emptying and refueling means comprises means for using the vacuum of space in accomplishing fueling, emptying and refueling. 5. The invention of claim 1 wherein said sectors are made from at least one group consisting of Mo, Mo-Re alloy, Mo alloy, Re alloy, and W-Re alloys.
	description	This application claims priority to and the benefit of U.S. Provisional Application No. 62/455,408, filed Feb. 6, 2017 and titled “FABRICATION OF URANIUM NITRIDE”, the entire content of which is incorporated herein by reference. The United States government has certain rights in this invention pursuant to Contract No. DE-AC52-06NA25396 between the United States Department of Energy and Los Alamos National Security, LLC for the operation of Los Alamos National Laboratory. Uranium mononitride (uranium nitride, UN) is an attractive nuclear fuel that is being considered as an alternative to conventional UO2 nuclear fuels due to its higher thermal conductivity and melting point (e.g., temperature tolerance). However, the industrial use of uranium nitride has been limited by a lack of methods for the production of suitably large quantities. Carbothermic reduction to nitridation (CTR-N) is presently the most commonly used process for producing uranium nitride. However, this process has historically been limited to batch processing techniques due to its use of a breathing furnace, which alternatingly exposes the uranium material to vacuum and various process gases. Such batch processing techniques are typically incompatible with nuclear fuel production facilities. Thus, the use of this process to produce uranium nitride has been limited. According to embodiments of the present disclosure, a method of producing uranium nitride (UN) includes reacting a reaction mixture including uranium carbide with a gas including hydrogen and nitrogen, cooling the reaction mixture to a temperature suitable to produce a phase including U2N3, and heating the reaction mixture to a temperature suitable to convert the phase including U2N3 to a phase including UN. In some embodiments, the method may further include reacting UO2 with at least three molar equivalents of carbon to form the reaction mixture including uranium carbide. In some embodiments, the at least three molar equivalents of carbon may be an excess of three molar equivalents of carbon. For example, the reaction mixture including uranium carbide may be formed by reacting UO2 with at least three molar equivalents of carbon, and in some embodiments, an excess of three molar equivalents of carbon. In some embodiments, reacting UO2 with at least three equivalents of carbon may be accomplished under an active vacuum. In some embodiments, reacting UO2 with at least three molar equivalents of carbon may be accomplished under an inert atmosphere including N2, Ar, He, H2, or a mixture thereof. In some embodiments, the method may further include granulating the reaction mixture including uranium carbide prior to reaction with the gas including hydrogen and nitrogen. In some embodiments, the method may further include repeating the processes of cooling the reaction mixture and heating the reaction mixture to purify the UN. In some embodiments, the method may be a continuous process, in which the reaction mixture including uranium carbide is continuously moved through a series of at least first, second, and third reaction zones arranged in a sequence, wherein the first reaction zone has a temperature corresponding to reacting the reaction mixture including uranium carbide with the gas including hydrogen and nitrogen; the second reaction zone has a temperature corresponding to the cooling the reaction mixture to the temperature suitable to produce the phase including U2N3; and the third reaction zone has a temperature corresponding to the heating the reaction mixture to the temperature suitable to convert the phase including U2N3 to the phase including UN. In some embodiments, cooling the reaction mixture to a temperature suitable to produce the phase including U2N3 may include cooling the reaction mixture below a phase transition temperature between the phase including U2N3 and the phase including UN. In some embodiments, the temperature suitable to produce the phase including U2N3 may be about 1352° C. to about 1132° C. In some embodiments, heating the reaction mixture to the temperature suitable to convert the phase including U2N3 to the phase including UN may include heating the reaction mixture above a phase transition temperature between the phase including U2N3 and the phase including UN. In some embodiments, the phase transition temperature between the phase including U2N3 and the phase including UN may be greater than about 1352° C. Aspects of example embodiments of the present disclosure are directed toward a method of producing uranium nitride (e.g., uranium mononitride), and/or uranium-containing intermediates that can be used to further produce uranium nitride and other nuclear fuels. The method can be easily integrated into existing uranium production facilities as part of a continuous process. Conventional methods of producing uranium nitride typically rely on a two-part process called carbothermic reduction to nitridation (CTR-N), also known as carbothermal reduction-nitridation. According to this process, carbon is used to reduce a metal oxide (e.g., uranium oxide), and the carbon atoms in the resulting metal carbide are subsequently replaced by nitrogen. The chemical reactions involved in an example conventional CTR-N process as applied to uranium compounds may be described by the equations listed in Scheme 1. In Scheme 1, Equation 1, uranium (IV) oxide (e.g., uranium dioxide, UO2) is reacted with a carbon source (e.g., carbon) at a temperature greater than about 1450° C. in an inert atmosphere to produce uranium carbide (UC) and carbon monoxide (CO). In Scheme 1, Equations 2A and 2B, the uranium carbide and any excess carbon, respectively, are subsequently reacted with H2 and N2 gas to produce UN and to remove the carbon as HCN gas. The equilibria of both reactions can be driven forward by removing the gaseous products, for example, under vacuum or by selective absorption. Scheme 1UO2+3CUC+2CO(g) (1)UC+N2(g)+0.5H2(g)UN+HCN(g) (2A)C+0.5N2(g)+0.5H2(g)HCN(g) (2B) FIG. 1 is a block diagram 1 depicting the above-described method of converting UO2 to UN in the related art. According to FIG. 1 and in accordance with Scheme 1, Equation 1, UO2 (2) and C(5) (4) are mixed and reacted (block 6) to produce UC (8) and CO(g) (10), the latter of which (i.e., CO(g)) is subsequently removed from the reaction (block 12). The mixture 18 of UC (8) and any excess C (4) is reacted with H2(g) (14) and N2(g) (16). In accordance with Scheme 2, Equation 2B, the excess C (4) in the reaction mixture is converted to HCN(g) (20), which is subsequently removed from the reaction (block 22). The rate of conversion is proportional to the concentration of C (4) in the mixture, and accordingly decreases over time. In accordance with Scheme 2, Equation 2A, the UC (8) in the reaction mixture is converted to UN (24) (block 26) with concomitant production of HCN(g) (20). The method is complete once enough UC (8) has been converted to UN (24) and enough C (4) has been removed to yield UN (24) as a final product having a desired level of purity. The above-described CTR-N method has several limiting drawbacks. For example, the amount of carbon must be carefully controlled in the first part of the process (Scheme 1, Equation 1). An insufficient amount of carbon results in incomplete reaction of the UO2, and thereby the presence of oxygen impurities in the final product. However, an excess amount of carbon results in the retention of carbon impurities. Therefore, the purity and utility of the final product depend on the addition of an exact, stoichiometric amount of carbon, which can be difficult to attain in practice. Although the excess carbon can be converted over time into HCN via reaction with H2 and N2, the rate of that reaction (described in Scheme 1, Equation 2B) decreases as the concentration of C approaches 0 (e.g., because the rate is proportional to [C]); this additionally limits the purity that can be obtained within an industrially relevant timescale. In addition, the use of a breathing furnace to alternatingly remove the CO and HCN byproducts (e.g., by applying a vacuum) and introduce the H2 and N2 reactants (e.g., by atmospheric backfilling) is necessarily tied to batch processing, which is incompatible with many presently existing nuclear fuel processing plants. Aspects of embodiments of the present disclosure provide a method of producing uranium nitride (e.g., processing uranium oxide to uranium nitride) that is less sensitive to an excess amount of carbon, and is therefore able to produce uranium nitride of higher purity compared to related art methods of producing uranium nitride. In addition, the method is amenable to continuous processing, thereby enabling process scaling. According to some embodiments, a method of producing uranium nitride includes reacting a reaction mixture including uranium carbide with a gas including hydrogen and nitrogen, cooling the reaction mixture to a temperature suitable to produce a phase including U2N3, and heating the reaction mixture to a temperature suitable to convert the phase including U2N3 to a phase including UN. In some embodiments, a method of producing uranium nitride includes reacting UO2 with at least three molar equivalents of carbon to form a reaction mixture including uranium carbide, granulating the reaction mixture including uranium carbide prior to reaction with a gas including hydrogen and nitrogen, reacting the reaction mixture including uranium carbide with the gas including hydrogen and nitrogen, cooling the reaction mixture to a temperature suitable to produce a phase including U2N3, and heating the reaction mixture to a temperature suitable to convert the phase including U2N3 to a phase including UN. In addition, example embodiments of the present disclosure provide one or more methods of producing each intermediate product described in the above processes, e.g., methods including combinations of two or more of each of the processes described above. Throughout this disclosure, when a process or reaction is described as being represented by, approximated by, generally, and/or substantially similar to a specific chemical equation or equilibrium, the equation and/or equilibrium is presented only to illustrate example embodiments of the present disclosure, and is not meant to limit the embodiment to any particular mechanism or theory, or otherwise limit the scope of embodiments of the present disclosure. For example, the process or reaction may be suitably described by another equation or equilibrium different from that presented herein. Furthermore, additional reactants, reagents, products, and/or other species that are not described in the equation or equilibrium may be present in the reaction or process, and the equation or equilibrium may not necessarily provide a full description of the chemistry involved therein. In addition, it will be understood that the reactions and reagents described herein may be modified or substituted by a person of ordinary skill in the art in various ways. Examples of such modifications that are expressly described herein are included as embodiments of the present disclosure, but are not intended to be limiting. Any suitable method of producing or obtaining uranium carbide may be used. In some embodiments, the method for producing UN includes reacting UO2 with at least three molar equivalents of carbon to form the reaction mixture including uranium carbide. As used herein, the term “at least three molar equivalents” may refer to any amount greater than or equal to about three times the number of moles of UO2. In some embodiments, the UO2 reactant may be converted to a uranium carbide (UC) product in a 1:1 stoichiometric ratio. In some embodiments, the reaction may further produce carbon monoxide gas (CO) as a byproduct, and when the oxygen content of the UO2 reactant is released in the form of CO, the stoichiometry of the UO2 reactant to the CO product may be 1:2. In some embodiments, for example, the method for producing UN may include a process generally following the equilibrium described in Scheme 2, Equation 1: Scheme 2, Equation 1UO2+3CUC+2CO(g) (1) Typically, a slight excess of three equivalents of carbon (e.g., about 3.05 to about 3.1 equivalents) may be used to encourage complete or substantially complete conversion of UO2 to UC. As used to describe this reaction, the term “substantially complete” may refer to a situation in which most of the UO2 reactant has been converted to UC, and only minimal or trace amounts of UO2 remain in the reaction mixture. In some embodiments, “substantially complete” may refer to greater than or equal to 99 wt % conversion of UO2 to one or more products, for example, greater than or equal to 99.5 wt % conversion, or greater than or equal to 99.9 wt % conversion. In some embodiments, “substantially complete” may refer to the point in time at which the percentage yield of the reaction is greater than or equal to 99% based on the actual vs. theoretical yield, for example, greater than or equal to 99.5%, or 99.9% based on the actual vs. theoretical yield. While larger excesses of carbon can also be used according to embodiments of this disclosure, larger excesses of carbon would increase the amount of carbon that would need to be removed as a waste product in subsequent production steps. Therefore, in order to reduce the time, energy, and material costs needed for purification of the final UN product, the number of moles of carbon may be, for example, about 3.0 times to about 4.0 times the number of moles of UO2, and in some embodiments, about 3.0 times to about 3.5 times, about 3.01 times to about 3.2 times, or about 3.05 times to about 3.1 times the number of moles of UO2. The carbon may be derived from any suitable carbon source as long as it is capable of being co-milled with the UO2. The carbon source may include, for example, graphite, graphene, carbon black, acetylene black, crystalline carbon, amorphous carbon, activated carbon, coke, pitch, or a mixture thereof. The carbon source may have any suitable density or surface area. Although a carbon source with oxygen-containing impurities (e.g., surface functional groups including oxygen, such as carbonate, carboxylate, carbonyl, lactone, and hydroxide) may be used, because some of the carbon atoms will be lost to reduction of those impurities (e.g., as CO2 or CO), a larger amount of the carbon source may be necessary to compensate for that loss. Accordingly, the number (e.g., moles) of carbon atoms in the reaction mixture may be at least about 1.5 times the total number (e.g., moles) of oxygen atoms in the reaction mixture. In some embodiments, for example, the number of carbon atoms may be about 1.5 times to about 1.8 times the total number of oxygen atoms, or about 1.5 times to about 1.6 times the total number of oxygen atoms. However, it will be understood that a person of ordinary skill in the art is capable of selecting other suitable kinds and amounts of the carbon source based on the principles described herein. In some embodiments, the carbon source and the UO2 are co-milled and pressed into slugs or pellets in order to increase the interfacial surface area between the two reactants, thereby increasing their rate of solid-state diffusion, as well as the overall reaction rate. The co-milling may be achieved using any suitable method, such as ball-milling, wet milling, jet milling, roller milling, cutter milling, etc. In some embodiments, the average particle size of the carbon source and the UO2 after milling may be less than about 500 μm. For example, the average particle size may be less than about 100 μm, less than about 1 μm, or less than about 100 nm. The size and shape of the slugs or pellets are not particularly limited. For example, the slugs may have an average outer diameter (OD) of about 1 mm to about 5 cm (50 mm), or about 10 mm to about 40 mm. The slugs may have an average length of about 1 mm to about 2 cm (20 mm), or about 5 mm to about 10 mm. The pressing may be achieved using any suitable method or device, and a person of ordinary skill in the art is capable of selecting a method, density, and pressure according to the desired physical characteristics of the pellets. The reaction between the carbon source and the UO2 may be carried out at a high temperature in order to activate and accelerate solid state diffusion and reduction. As used in the context of this reaction, the term “high temperature” may refer to any temperature at which the reaction is able to proceed to at least 99% conversion, and in some embodiments 99.5% conversion, within an industrially relevant time scale (e.g., within about 24 hours, and in some embodiments within about 12 hours). The conversion ratio may be measured using any suitable method capable of monitoring the concentrations of reactant and product, for example, by X-ray diffraction (XRD) analysis or elemental analysis. In some embodiments, the “high temperature” may be the same temperature used in subsequent parts of the production process requiring an elevated temperature. For example, the reaction may be carried out at greater than about 1352° C., or about 1375° C. to about 2000° C., or about 1400° C. to about 1800° C. The reaction temperature of this process and of other processes described herein may be held substantially constant (e.g., within a range of ±5° C., or for example ±10° C.), or may vary within the described ranges, unless expressly stated otherwise. In addition, the reaction between the carbon source and the UO2 may be carried out under an atmosphere that does not include oxygen or an oxygen source, e.g., an inert or reducing atmosphere. For example, the reaction may be carried out under argon (Ar), hydrogen (H2), nitrogen (N2), helium (He), or a mixture thereof. In some embodiments, the reaction may be carried out under a static or active vacuum or partial vacuum. Furthermore, the gases included in the atmosphere may be static, or may be flowing. The total pressure or partial pressure of the gas or gases is not particularly limited. In some embodiments, for example, the starting pressure may be about 1 atm or less. Typically, however, the use of a pressure equal to or less than about 1 atm and/or a configuration that continuously removes CO (e.g., vacuum or flowing gases) may favor completion of the CO gas-producing reaction, according to Le Chatelier's principle. After production of the uranium carbide and carbon monoxide as described herein with respect to Scheme 2, Equation 1, the uranium carbide may be reacted with hydrogen and nitrogen to produce uranium mononitride. In some embodiments, reacting a reaction mixture including uranium carbide with a gas including hydrogen and nitrogen may include a process generally following the equilibrium described in Scheme 2, Equation 2A: Scheme 2, Equation 2AUC+N2(g)+0.5H2(g)UN+HCN(g) (2A) While the uranium carbide used in this reaction process may be the product of the reaction described herein in connection with Equation 1, any suitable uranium carbide source may be used. Furthermore, although the gas including hydrogen and nitrogen is represented in Equation 2A as a mixture of N2, and/or H2, other suitable forms of such gas may be used according to the example embodiments described herein. In some embodiments, the method for producing UN includes granulating a reaction mixture including uranium carbide prior to reaction with the gas including hydrogen and nitrogen. As described above, the reaction mixture including uranium carbide may be obtained according to the previously described process, or by any suitable process. The granulation may be used to increase the surface area of the UC-containing particles that may be exposed to the gas, thereby increasing the rate of this process and allowing for scale-up and processing of large amounts of the reaction mixture. The granulating may be achieved using any suitable method, such as crushing, ball-milling, wet milling, jet milling, roller milling, cutter milling, etc. The granulating may be carried out under any suitable temperature, atmosphere, and pressure as long as the conditions do not result in unwanted oxidation or introduction of other impurities. For example, the granulating may be carried out under a dry, inert atmosphere (e.g., an oxygen-free atmosphere). As used herein, the term “oxygen-free atmosphere” is used in its art-recognized sense to refer to an atmosphere including less than about 1 ppm to about 20 ppm O2 and about 1 ppm to 10 ppm H2O, and in some embodiments less than about 1 ppm to 3 ppm O2, less than about 1 ppm O2, and/or less than about 0.5 ppm to 1 μm H2O. In some embodiments, the granulating may be carried out under a temperature, atmosphere, and/or pressure substantially similar to that used for the preceding process of reacting UO2 with at least three molar equivalents of carbon to form the reaction mixture including uranium carbide, or the following process of reacting a reaction mixture including uranium carbide with a gas including hydrogen and nitrogen. The size of the reaction mixture particles after granulating is not particularly limited, and in some embodiments, the average particle size of the UC after granulating may be less than about 500 μm. For example, the average particle size may be less than about 2,000 μm, less than about 100 μm, or less than about 10 μm. In some embodiments, a method for producing UN includes reacting a reaction mixture including uranium carbide with a gas including hydrogen and nitrogen (e.g., hydrogen atoms and nitrogen atoms). The reaction mixture including uranium carbide may be produced using the processes described herein, including reacting UO2 with at least three molar equivalents of carbon; and/or granulating the reaction mixture including uranium carbide prior to reaction with the gas including hydrogen and nitrogen. However, the uranium carbide may be obtained using any other suitable process. The stoichiometry of the reaction between uranium carbide, hydrogen atoms, and nitrogen atoms may be 1:2:1. The gas including hydrogen and nitrogen may include any suitable ratio of hydrogen to nitrogen as long as the number of moles of hydrogen and nitrogen provided by the gaseous reactant are both sufficient to react with the uranium carbide according to the 1:2:1 stoichiometry described above, as well as any carbon-containing impurities, as described below. In some embodiments, when the hydrogen atoms are present as hydrogen gas (H2) and the nitrogen atoms are present as nitrogen gas (N2), the stoichiometry of the reaction between uranium carbide, hydrogen gas, and nitrogen gas may be 1:0.5:1 (e.g., 2:1:2). In some embodiments, the gas including hydrogen and nitrogen may include a molar excess of one or both elements relative to the uranium carbide. The gas including hydrogen and nitrogen may be a single gas or a mixture of gases. In some embodiments, the gas including hydrogen and nitrogen may have a composition including hydrogen atoms and nitrogen atoms. In some embodiments, for example, the gas including hydrogen and nitrogen may include a mixture of hydrogen gas (H2) and nitrogen gas (N2), as discussed above and in connection with Scheme 2, Equation 2A. In some embodiments, the gas including hydrogen and nitrogen may include or be ammonia (NH3) or hydrazine (N2H4). In some embodiments, the gas including hydrogen and nitrogen may include a mixture of NH3, hydrazine, N2, and/or H2. Additionally, although some example embodiments are described as including a mixture of H2 and N2, it is understood that any suitable gas (such as the gases described herein) may be used in its place. The total pressure of the gas including hydrogen and nitrogen is not particularly limited, and may change during the course of the reaction or process as gases are consumed and produced. In some embodiments, for example, the starting total pressure of gas (e.g., the starting pressure of the gas including hydrogen and nitrogen) may be about 1 atm. In some embodiments, the starting pressure of the gas including hydrogen and nitrogen may be greater than about 1 atm, for example about 1 atm to about 2 atm, in order to increase the concentration of the reactants and thereby increase the rate of the reaction. When the gas is a mixture of two of more gases, the partial pressure (e.g., ratio) of each gas is not particularly limited. In some embodiments, the gases may be continuously flowed to remove HCN and to favor completion of the HCN gas-producing reaction. The reaction between the reaction mixture including uranium carbide and a gas including hydrogen and nitrogen may be initiated at any temperature suitable for nitridating the uranium carbide (e.g., converting the uranium carbide to uranium nitride with concomitant production of HCN gas). For example, the reaction may be carried out at a temperature greater than about 500° C., or greater than about 700° C., or greater than about 1000° C. In some embodiments, the reaction may be carried out at greater than about 1350° C., or about 1350° C. to about 2000° C., or about 1400° C. to about 1800° C. In some embodiments, the reaction may be carried out at a temperature that enables the reaction to proceed to at least 99% conversion, and in some embodiments at least 99.5% conversion at an industrially relevant time scale (e.g., within about 24 hours, and in some embodiments within about 12 hours), as described above. In some embodiments, the reaction mixture including uranium carbide may further include carbon, for example, when the uranium carbide is produced from UO2 using the processes described herein. The amount of carbon is not particularly limited, but should be as low as practically attainable from the uranium carbide production process, as described herein in connection with the process of reacting UO2 with at least three molar equivalents of carbon to produce the uranium carbide. The carbon remaining in the reaction mixture after production of the uranium carbide may react with the gas including hydrogen and nitrogen to produce HCN gas. In some embodiments, for example, reacting a reaction mixture including uranium carbide with a gas including hydrogen and nitrogen may include a process generally following the equilibrium described in Scheme 2, Equation 2B: Scheme 2, Equation 2BC+0.5N2(g)+0.5H2(g)HCN(g) (2B) The reaction of carbon with the gas including hydrogen and nitrogen may occur concurrently with (e.g., under the same temperature, pressure, and reaction conditions as) the reaction of UC with the gas including hydrogen and nitrogen (e.g., as described herein in connection with Scheme 2, Equation 2A). The reactions between UC, C, and the gas including hydrogen and nitrogen may be carried out under an atmosphere that does not include oxygen or an oxygen source, e.g., an inert or reducing atmosphere. In some embodiments, the reaction may be carried out under an atmosphere composed only of the gas including hydrogen and nitrogen. In some embodiments, the atmosphere may further include a noble gas such as argon (Ar), helium (He), or a mixture thereof. The gases included in the atmosphere may be static, or may be flowing. The gaseous HCN product may be removed using any suitable strategy in order to favor completion of Equations 2A and 2B, according to Le Chatelier's principle. The removal strategy may be continuous or may be carried out in batches. In some embodiments, the HCN may be removed by selective chemisorption. In some embodiments, the HCN may be removed under an intermittent partial vacuum (e.g., a pressure equal to or less than about 1 atm) or may be removed under a continuous or intermittent flow of gas that does not include HCN. The total pressure or partial pressure of the gas or gases is not particularly limited. In some embodiments, for example, the starting pressure may be about 1 atm. However, Le Chatelier's principle and rate law theory also suggests that in some embodiments, the use of a higher partial pressure of the gas including hydrogen and nitrogen (e.g., at a pressure equal to or higher than about 1 atm) may favor completion of the HCN gas-producing reaction by increasing the concentration of reactants. Therefore, in some embodiments, the reactions of Equation 2A and 2B may be carried out under an atmosphere composed only of the gas including hydrogen and nitrogen at a pressure equal to or higher than about 1 atm, and the HCN gas may be removed in batches or by chemisorption (e.g., when the pressure is above 1 atm), or removed under a flow of gas (e.g., at a pressure of about 1 atm). As the reaction mixture including uranium carbide and/or carbon reacts with the gas including hydrogen and nitrogen, the reaction mixture may include a mixture of uranium carbide, uranium nitride, and/or carbon. When the reaction is held at a temperature greater than about 1350° C., or about 1350° C. to about 2000° C., or about 1400° C. to about 1800° C., as described above, the components of the reaction mixture may diffuse and be intermixed as a solid solution (e.g., the atoms of both may be intermixed in a single crystal lattice or phase), and may therefore be equivalently described or referred to as U(NxCy). This intermixing and stoichiometric equivalency may be generally described by the relationship in Scheme 2, Equation 3: Scheme 2, Equation 3UC+UN+C≈U(NxCy) (3) Here, the values of x and y describe the relative numbers of nitrogen and carbon atoms, respectively, compared to the number of uranium atoms, and may each be any real number greater than or equal to 0. In Equation 3, U(NxCy) is understood to be stoichiometrically and compositionally equivalent to a reaction mixture including uranium carbide, uranium nitride, and/or carbon, but specific reference to U(NxCy) may imply mixing of the reaction mixture including uranium carbide, uranium nitride, and/or carbon under high temperatures to thereby attain a more homogenous (evenly mixed) structure. As such, references to the two may be used interchangeably and should be considered in context, i.e., in terms of the ambient temperature and mixing conditions. In some embodiments, for example, the reaction mixture may be held at or above the intermixing temperature for about 24 hours, or about 12 hours to thereby obtain higher degrees of mixing In some embodiments, a method of producing uranium nitride includes cooling a reaction mixture, for example, a reaction mixture including uranium carbide, uranium nitride, and/or carbon and/or a reaction mixture including U(NxCy) to a temperature suitable to produce a phase including uranium sesquinitride (U2N3). The production of U2N3 may be accompanied by formation of a separate phase including UC. The reaction mixture may be produced by reacting a reaction mixture including uranium carbide with a gas including hydrogen and nitrogen, as described above, or may be any suitable reaction mixture including U(NxCy). In some embodiments, cooling the reaction mixture to a temperature suitable to produce a phase including uranium sesquinitride (U2N3) may include a process generally described by Scheme 2, Equation 4: Scheme 2, Equation 4U(NxCy)→U2N3+UC (4) In some embodiments, the reaction mixture may be cooled to a temperature suitable for precipitation of or decomposition to U2N3, for example, below the phase transition temperature for UN/U2N3. As used herein, the term “phase transition temperature” is used in its art-recognized sense to refer to a temperature at which a substance undergoes a physical rearrangement in its atomic structure in order to achieve a lower energy state. As used in the context of this reaction, for example, the term “phase transition temperature” refers to the temperature at which an equilibrium (e.g., chemical equilibrium) can be observed between a phase including UN in the presence of a gas including nitrogen (e.g., N2), and a phase including U2N3. As recognized in the art, movement in either direction away from the equilibrium condition results in selective and substantially complete formation of an appropriate phase. Moreover, as used herein, the term “phase” refers to a substance or a portion of a substance having uniform physical properties. In some embodiments, for example, the physical rearrangement may entail a transition between solid, liquid, gas, or plasma. In some embodiments, the physical rearrangement may entail a transition between crystal lattices or unit cells having different crystal geometries and packing. In some embodiments, a substance including two or more components may partition into two separate phases or substances. However, embodiments of the present disclosure are not limited thereto, and it will be understood that other kinds of phase transitions known in the art are possible. FIG. 2 is a phase change diagram 30 for uranium and nitrogen, showing various phase transition temperatures for the mixture (e.g., the temperature dependence of transformations between various phases of a material including a mixture of uranium and/or nitrogen), as originally published by ASM International, 2006, Diagram No. 1600412 and modified herein for clarity, the entire content of which is incorporated herein by reference. The phase transition temperature corresponding to the transition boundary between a phase containing UN (“UN+G”, 32) and phases containing U2N3 (“U2N3 ht+G”, 34) and (“U2N3 ht”, 36) for mixtures of uranium and nitrogen between about 35 at. % to about 50 at. % of U can be seen in the leftmost region of the phase change diagram 30. At a temperature higher than the phase transition temperature, formation of the phase including UN in the presence of gaseous nitrogen (“UN+G”, 32) is energetically favored; conversely, at a temperature lower than the phase transition temperature, formation of the phases including U2N3 (e.g., “U2N3 ht+G”, 34 and “U2N3 ht”, 36) is energetically favored. The phase transition temperature for this equilibrium reaction is about 1352° C., as shown in the drawing. Accordingly, in some embodiments, the reaction mixture including U(NxCy) may be cooled to a temperature lower than about 1352° C. In some embodiments, when at least part of the UN portion of U(NxCy) undergoes a phase transition to U2N3, the remaining portion of U(NxCy) is enriched in carbon (e.g., UC and/or C). The two phases are mutually insoluble (or poorly soluble), and may therefore precipitate or partition into separate regions or domains. Without being limited to any particular mechanism or theory, it is believed that the mutual insolubility of the two phases is due to their differing crystal structures. Specifically, the crystal structure of the phase including U(NxCy) has a face-centered cubic (fcc) unit cell, while the crystal structure of the phase including U2N3 has a hexagonal unit cell. These unit cells cannot be packed into the same lattice, and therefore precipitate in separate lattices (domains). Accordingly, the fcc domains may be enriched in carbon. The local increase in concentration of the carbon reactant may increase the rate of its conversion to HCN gas, thereby decreasing the overall amount of carbon impurities in the reaction mixture. In some embodiments, as can be seen in FIG. 2, when the reaction mixture including U(NxCy) and/or U2N3 is further cooled below a second phase transition temperature corresponding to an equilibrium between “U2N3 ht” (high temperature) (36) and “UN1.6 rt+G” (room temperature) (38) at about 1132° C., the phase including U2N3 may further decompose or be converted to a phase including UN1.6. The phase including UN1.6 has an fcc unit cell, which is similar to and therefore miscible with U(NxCy). Accordingly, cooling the reaction mixture below this second phase transition temperature corresponding to U2N3/UN1.6 may result in production of a phase including UN1.6 that does not precipitate in a separate domain, such that the nitrogen and carbon content in the reaction mixture does not segregate and the rate of carbon conversion to HCN is not increased. Therefore, in some embodiments, the reaction mixture including U(NxCy) is cooled to a temperature greater than about 1132° C. and lower than about 1352° C. (e.g., about 1132° C. to about 1352° C.) for example, about 1150° C. to about 1340° C., or about 1200° C. to about 1300° C. The amount of time that the reaction mixture is held at a temperature suitable to produce a phase including U2N3 is not particularly limited, and may be any suitable length of time. In some embodiments, for example, the length of time may be selected to be longer than the timescale of the phase transition in order to encourage substantially complete precipitation of U2N3 and to allow ample time for reaction of any carbon impurities, for example, 5 times or 10 times longer. In some embodiments, the length of time may be selected to correspond to the time after which the rate of HCN production falls below a threshold value, for example, as determined by monitoring of the partial pressure of HCN (PHCN). In some embodiments, the length of time may be about 12 to 24 hours, or about 12 hours. However, embodiments of the present disclosure are not limited thereto, and a person of skill in the art is capable of selecting an appropriate reaction time according to the principles described herein. In some embodiments, a method for producing UN includes heating a reaction mixture to a temperature suitable to convert the phase including U2N3 to a phase including UN. The starting reaction mixture may be produced by cooling a reaction mixture including U(NxCy) to a temperature suitable to produce a phase including uranium sesquinitride (U2N3), as described above, or may be any suitable reaction mixture including U2N3. In some embodiments, heating the reaction mixture to a temperature suitable to convert the phase including U2N3 to a phase including UN may include a process generally described by Scheme 2, Equation 5: Scheme 2, Equation 5U2N3+UC→U(NxCz);z<y (5) In some embodiments, for example, when the reaction mixture is produced according to the process described in Scheme 2, Equation 4, the phase including U2N3 may form a shell on the outer surface of particles of the reaction mixture, which may block or partially block physical contact between the phase including U(NxCy) and the gas including hydrogen and nitrogen, thus slowing the conversion of precipitated carbon to HCN. Accordingly, in some embodiments, the reaction mixture may be heated to re-dissolve the shell. For example, the reaction mixture may be heated to a temperature suitable for conversion of U2N3 to UN, or for example, above the phase transition temperature for UN/U2N3, as defined herein. Accordingly, in some embodiments, the reaction mixture including U2N3 is heated to a temperature higher than about 1352° C. For example, the reaction may be heated to about 1375° C. to about 2000° C., or about 1400° C. to about 1800° C. The phase including U2N3 is thus converted to a phase including UN, which redissolves (e.g., solutionizes) into the U(NxCz) (where z<y, denoting a lower concentration of carbon than before due to removal of carbon during the cooling of the reaction mixture). Accordingly, when the starting reaction mixture of Equation 5 is a product of Scheme 2, Equation 4, the process described in Equation 5 may be viewed as a return to the conditions and reaction products of Scheme 2, Equation 4 with a decreased concentration of carbon. The atmosphere and pressure of the reaction mixture during this process may be similar to that used during the process of reacting a reaction mixture including uranium carbide with a gas including hydrogen and nitrogen. In some embodiments, for example, the total pressure may be about 1 atm or greater. In some embodiments, the gases may be continuously flowed. The amount of time that the reaction mixture is held at a temperature suitable to convert the phase including U2N3 to a phase including UN is not particularly limited, and may be any suitable length of time. In some embodiments, for example, the length of time may be selected to be longer than the timescale of the phase transition in order to encourage substantially complete conversion to UN and to allow ample time for mixing and equilibration of UN and U(NxCz), for example, 10 times or 20 times longer. In some embodiments, the length of time may be selected to correspond to the time after which the nitrogen and carbon anions are uniformly distributed within the reaction particles. In some embodiments, the length of time may be about 12 hrs to about 24 hrs, or about 12 hrs to about 18 hrs. However, embodiments of the present disclosure are not limited thereto, and a person of skill in the art is capable of selecting an appropriate reaction time according to the principles described herein. One or more example embodiments including each of the processes described above may be represented as a whole by the equations of Scheme 2 (Equations 1 to 5). In Equations 1 to 5, the numbered reactions may not proceed to completion in a stepwise fashion. Instead, two or more reactions may proceed simultaneously as part of an ongoing, complex equilibrium. As such, it will be understood that the species present in the reaction or reactor at any point in time are not necessarily limited to the species listed on one side of any single chemical equation, and that a reaction or reaction mixture described as including or comprising one or more species may include or comprise additional species. Scheme 2UO2+3CUC+2CO(g) (1)UC+N2(g)+0.5H2(g)UN+HCN(g) (2A)C+0.5N2(g)+0.5H2(g)HCN(g) (2B)UC+UN+C≈U(NxCy) (3)U(NxCy)→U2N3+UC (4)U2N3+UC→U(NxCz);z<y (5) In some embodiments, the method for producing UN includes repeating the processes of cooling the reaction mixture and heating the reaction mixture until UN having a desired purity is obtained (e.g., z in U(NxCz) is decreased to a desired value). For example, the processes may be repeated until a concentration of about 100 ppm C and/or about 100 ppm O is obtained, compared to a concentration of about 1000 ppm C and/or about 1000 ppm O obtained using conventional UN production methods. Once a desired purity has been attained, the process of cooling the reaction mixture can be repeated a final time in the absence of N2 (e.g., after removing the N2) to thereby precipitate the UN having the desired purity as the final product. FIG. 3 is a block diagram 50 depicting the above-described method of converting UO2 to UN according to embodiments of the present disclosure. According to FIG. 3 and in accordance with Scheme 2, Equation 1, UO2 (52) and C(s) (54) are mixed and reacted (block 56) to produce UC (58) and CO(g) (60), the latter of which (i.e., CO(g)) is subsequently removed from the reaction (block 62). The mixture 68 of UC (58) and any excess C (54) is reacted with H2(g) (64) and N2(g) (66). In accordance with Scheme 2, Equation 2B, the excess C (54) in the reaction mixture is converted to HCN(g) (70), which is subsequently removed from the reaction (block 72). The rate of conversion is proportional to the concentration of C (54) in the mixture. Next, in accordance with Scheme 2, Equation 2A, the UC (58) in the reaction mixture is converted to UN (74) (block 76). Meanwhile, in accordance with Scheme 2, Equation 3, the UN (74) and any remaining UC (58) and C (54) are mixed at high temperature to form U(NxCy) (78) (block 80). The temperature of the reaction is subsequently lowered, and in accordance with Scheme 2, Equation 4, the U(NxCy) (78) undergoes a phase transition and separates into U2N3 (82) and UC (58), which precipitate in separate crystal domains (block 84). The high local concentrations of UC and C in these crystal domains increase the rate of conversion to HCN(g) (70) according to blocks 72 and 76. The process can be repeatedly cycled between blocks 80 and 84 until enough UC (58) has been converted and enough C (54) has been removed to yield UN (74) or U2N3 (82) having a desired level of purity (e.g., so that y→0 in U(NxCy) (78)). Finally, the temperature is lowered to convert any U2N3 (82) into UN (88) as a final product (block 86). In some embodiments, the method for producing UN may be a batch process. For example, the reaction mixture may be held within a single vessel or chamber throughout the entire UN production process, which is heated or cooled and filled or evacuated with suitable gases in a sequence corresponding to the processes included in one or more example embodiments of the present disclosure. In some embodiments, the method for producing UN may be a continuous process. For example, the reaction mixture may be continuously moved through a series of reaction zones via a belt, a mixer blade, gravity, etc., where each zone is arranged in a suitable sequence and has a temperature corresponding to a process included in one or more example embodiments of the present disclosure. In some embodiments, the reaction mixture comprising uranium carbide may be continuously moved one or more times through a series of at least first, second, and third reaction zones arranged in that sequence, wherein the first reaction zone has a temperature corresponding to the reacting the reaction mixture comprising uranium carbide with the gas comprising hydrogen and nitrogen; the second reaction zone has a temperature corresponding to the cooling the reaction mixture to the temperature suitable to produce the phase comprising U2N3; and the third reaction zone has a temperature corresponding to the heating the reaction mixture to the temperature suitable to convert the phase comprising U2N3 to the phase comprising UN (which may be redissolved into the reaction mixture as U(NxCz) as described herein). As the reaction mixture is progressively moved between and exposed to the at least the first, second, and third reaction zones, the reaction mixture may undergo a series of reactions such as those described in Scheme 2, Equations 2 to 5. In some embodiments, the reaction mixture may be cycled through one or more of the reaction zones in the same sequence to thereby repeat the heating and cooling cycles and their associated reactions. For example, the reaction mixture may be subsequently cycled multiple times between the second reaction zone and the third reaction zone, (corresponding to Scheme 2, Equations 4 and 5, and blocks 80 and 84 in FIG. 3). When the method for producing UN is a continuous process, the process may be carried out under a single atmospheric composition, e.g., a reducing atmosphere and/or a gas including hydrogen and nitrogen, such as a mixture of H2 and N2, as described above. The following examples and experimental data are provided for illustrative purposes only, and do not limit the scope of the embodiments of the present disclosure. Uranium oxide powder (processed in-house) and graphite powder (200 mesh, 99.9995% metals basis, Alfa Aesar, Ward Hill, Mass.) were co-milled using a high energy zirconia ball mill (Spex SamplePrep, Metuchen, N.J.) for 100 minutes before being pressed at 370 MPa into 40 gram compacts with a 10 mm nominal thickness using a 40 mm outer diameter punch and die. Each compact was then placed into a tungsten carrier, with a tungsten foil serving as a diffusion barrier between the sample and the tungsten carrier. The compact was heated to 1730° C. under vacuum and held at temperature for 24 hours. The oxygen content of the reaction mixture following this uranium carbide formation process was measured to be 950 wppm using an oxygen/nitrogen analyzer (EMGA-820, Horiba Instruments, Irvine, Calif.). The reaction mixture including UC was screened through a #12 (e.g., 12 mesh) sieve, producing granules having an average diameter of about 1.5 mm. This material was again loaded onto a tungsten carrier with a fresh tungsten foil. The reaction mixture was heated to 1730° C. under a flowing atmosphere of 95% N2/5% H2 for twelve hours. The temperature was then decreased to 1330° C., and the material was again held for twelve hours, completing one heating/cooling cycle. The heating/cooling cycle was repeated two more times, resulting in three total heating/cooling cycles. The oxygen and carbon content of the material after three cycles was measured to be 180 wppm and 580 wppm, respectively, using an oxygen/nitrogen analyzer (EMGA-820, Horiba Instruments, Irvine, Calif.) and a carbon/sulfur analyzer (EMIA-8100, Horiba Instruments, Irvine, Calif.). The tungsten foil in the carrier was freshly replaced, and three more heating/cooling cycles were repeated. The oxygen and carbon content was found to be 140 and 290 wppm following this second treatment, respectively, demonstrating that the phase transitions associated with repeated temperature cycling are effective in quickly decreasing the concentration of carbon-containing impurities (e.g., UC and C), and to a lesser extent, oxygen-containing impurities (e.g., UO2) during production of UN according to embodiments of the present disclosure. As described herein, example embodiments of the present disclosure may enable production of uranium nitride having improved purity. In addition, the methods according to embodiments of the present disclosure, as described herein, may be compatible with continuous chemical processing methods and plants. For example, existing plants for nuclear fuels processing (such as those for producing UO2 nuclear fuel) using continuous chemical processing facilities may be readily retrofitted or adapted to produce UN according to embodiments of the present disclosure. Furthermore, the methods according to embodiments of the present disclosure, as described herein, may be robust to processing deviations (e.g., excess carbon, temperature, and time fluctuations) during processing. In contrast, conventional processes for producing UN are more sensitive to the amount of carbon reactant, as described above, and may be subject to oxidation and subsequent loss of product if the breathing furnace is inadvertently halted during a shutdown. While certain exemplary embodiments of the present disclosure have been illustrated and described, those of ordinary skill in the art will recognize that various changes and modifications can be made to the described embodiments without departing from the spirit and scope of the present invention, and equivalents thereof, as defined in the claims that follow this description. For example, although certain components may have been described in the singular, i.e., “an” inert gas, “a” reaction mixture, and the like, one or more of these components in any combination can be used according to the present disclosure. Also, although certain embodiments have been described as “comprising” or “including” the specified components, embodiments “consisting essentially of” or “consisting of” the listed components are also within the scope of this disclosure. For example, while embodiments of the present invention are described as comprising reacting a reaction mixture; cooling the reaction mixture; and heating the reaction mixture, embodiments consisting essentially of or consisting of these items are also within the scope of this disclosure. Accordingly, a method of producing uranium nitride may consist essentially of reacting a reaction mixture, cooling the reaction mixture, and heating the reaction mixture. In this context, “consisting essentially of” means that any additional components or process actions will not materially affect the products and byproducts produced by the reaction. As used herein, unless otherwise expressly specified, all numbers such as those expressing values, ranges, amounts or percentages may be read as if prefaced by the word “about,” even if the term does not expressly appear. Further, the word “about” is used as a term of approximation, and not as a term of degree, and reflects the penumbra of variation associated with measurement, significant figures, and interchangeability, all as understood by a person having ordinary skill in the art to which this disclosure pertains. Any numerical range recited herein is intended to include all sub-ranges subsumed therein. Plural encompasses singular and vice versa. For example, while the present disclosure may describe “an” inert gas or “a” reaction mixture, a mixture of such inert gases or reaction mixtures can be used. When ranges are given, any endpoints of those ranges and/or numbers within those ranges can be combined within the scope of the present disclosure. The terms “including” and like terms mean “including but not limited to,” unless specified to the contrary. Notwithstanding that the numerical ranges and parameters set forth herein may be approximations, numerical values set forth in the Examples are reported as precisely as is practical. Any numerical value, however, inherently contains certain errors necessarily resulting from the standard variation found in their respective testing measurements. The word “comprising” and variations thereof as used in this description and in the claims do not limit the disclosure to exclude any variants or additions.
063242591	claims	1. In a scattered-ray grid having a carrier on which a plurality of radiation absorption elements are disposed in a plurality of rows, said grid having a grid center and each of said rows having an origin and radiating spoke-like away from said grid center, the improvement comprising: at least one of said rows having an origin at said grid center; and the respective origins of rows, other than said at least one row originating at said grid center, being disposed at intersections of respective radial lines with at least an arc of respective circles of predetermined radii relative to said grid center, each of said radial lines dividing an angle section between two adjacent rows by a predetermined ratio. said grid being divided into a plurality of identical grid sectors; in each of said grid sectors, at least one of said rows having an origin at said grid center; and in each of said grid sectors, the respective origins of rows, other than said at least one row originating at said grid center, being disposed at intersections of respective radial lines with at least an arc of respective circles of predetermined radii relative to said grid center, each of said radial lines dividing an angle section between two adjacent rows by a predetermined ratio. originating at least one of said rows at said grid center; and placing the respective origins of rows, other than said at least one row originating at said grid center, at intersections of respective radial lines with at least an arc of respective circles of predetermined radii relative to said grid center, each of said radial lines dividing an angle section between two adjacent rows by a predetermined ratio. (a) starting with a single row originating at said grid center and dividing an angle of 360.degree. defined by said single row originating at said grid center by a radial line at said predetermined ratio, and placing the origin of a next row at an intersection between said radial line and a circle having said predetermined origin radius; (b) identifying a largest angle section between said next row and said radial line and dividing said largest angle section with a new radial line at said predetermined ratio and incrementing a radius of said circle having said predetermined origin radius by said increment to obtain a new circle and placing the origin of a next row at an intersection of said new line and said new circle; and (c) repeating step (b) a selected number of times for successive new radial lines and with successive increments of said new circle by said equal increments. (a) starting with a circle of a predetermined origin radius and originating two of said rows at said grid center, said two rows intersecting said circle having said predetermined origin radius respectively at two points and defining an angle section therebetween; (b) dividing said angle section with a line at said predetermined ratio and originating a next row at an intersection of said line and said circle having said predetermined origin radius, and thereby defining a largest remaining angle section between adjacent rows; (c) incrementing said circle having said predetermined origin radius by an increment to obtain a new circle and dividing said largest angle section with a new line at said predetermined ratio and originating a next row at an intersection of said new line and said new circle, and thereby defining a new largest angle section between adjacent rows; and (d) repeating step (c) for successive equal increments of said new circle by said increment. identifying said new angle section as an angle section having a largest sum of said angle section plus an additional angle value, and determining said additional angle value by weighting, with a predetermined weighting factor or, angular spacings from the adjacent rows of said angle section respectively to adjacent rows on opposite sides of said angle section. dividing said grid into a plurality of identical grid sectors in each of said grid sectors, originating at least one of said rows at said grid center; and in each of said grid sectors, placing the respective origins of rows, other than said at least one row originating at said grid center, intersections of respective radial lines with at least an arc of respective circles of predetermined radii relative to said grid center, each of said lines dividing an angle section between two adjacent rows by a predetermined ratio. (a) starting with a single row originating at said grid center and dividing an angle of 360.degree. defined by said single row originating at said grid center by a radial line at said predetermined ratio, and placing the origin of a next row at an intersection between said radial line and a circle having said predetermined origin radius; (b) identifying a largest angle section between said next row and said radial line and dividing said largest angle section with a new radial line at said predetermined ratio and incrementing a radius of said circle having said predetermined origin radius by said increment to obtain a new circle and placing the origin of a next row at an intersection of said new line and said new circle; and (c) repeating step (b) a selected number of times for successive new radial lines and with successive increments of said new circle by said equal increments. (a) starting with a circle of a predetermined origin radius and originating two of said rows at said grid center, said two rows intersecting said circle having said predetermined origin radius respectively at two points and defining an angle section therebetween; (b) dividing said angle section with a line at said predetermined ratio and originating a next row at an intersection of said line and said circle having said predetermined origin radius, and thereby defining a largest remaining angle section between adjacent rows; (c) incrementing said circle having said predetermined origin radius by an increment to obtain a new circle and dividing said largest angle section with a new line at said predetermined ratio and originating a next row at an intersection of said new line and said new circle, and thereby defining a new largest angle section between adjacent rows; and (d) repeating step (c) for successive equal increments of said new circle by said increment. identifying said new angle section as an angle section having a largest sum of said angle section plus an additional angle value, and determining said additional angle value by weighting, with a predetermined weighting factor, angular spacings from the adjacent rows of said angle section respectively to adjacent rows on opposite sides of said angle section. 2. The improvement of claim 1 wherein only one of said rows originates at said grid center, and all other rows in said plurality of rows have respective origins at different radii relative to said grid center. 3. The improvement of claim 1 wherein each of said radial lines divides an angle section between two adjacent rows by a predetermined ratio p:q, with p.noteq.q. 4. In a scattered-ray grid having a carrier on which a plurality of radiation absorption elements are disposed in a plurality of rows, said grid having a grid center and each of said rows having an origin and radiating spoke-like away from said grid center, the improvement comprising: 5. The improvement of claim 4 wherein, in each of said grid sectors, only one of said rows originates at said grid center, and all other rows in each of said sectors have respective origins at different radii relative to said grid center. 6. The improvement of claim 4 wherein each of said radial lines divides an angle section between two adjacent rows by a predetermined ratio p:q, with p.noteq.q. 7. In a scattered-ray grid having a carrier on which a plurality of radiation absorption elements are disposed in a plurality of rows, said grid having a grid center and each of said rows having an origin and radiating spoke-like away from said grid center, a method for determining placement of the respective origins of said rows on said carrier comprising the steps of: 8. A method as claimed in claim 7 comprising originating only one of said rows at said grid center, and placing the respective origins of all rows, other than said one row originating at said grid center, at different radii relative to said grid center. 9. A method as claimed in claim 8 comprising determining said different radii by starting with a predetermined origin radius and incrementing said predetermined origin radius in successive equal increments. 10. A method as claimed in claim 9 comprising: 11. A method as claimed in claim 7 comprising: 12. A method as claimed in claim 11, comprising determining each new angle section by the steps of: 13. A method as claimed in claim 12 comprising using a value for said weighting factor which is less than 1. 14. A method as claimed in claim 7 comprising using a ratio p:q as said predetermined ratio, with p.noteq.q. 15. In a scattered-ray grid having a carrier on which a plurality of radiation absorption elements are disposed in a plurality of rows, said grid having a grid center and each of said rows having an origin and radiating spoke-like away from said grid center, a method for determining placement of the respective origins of said rows on said carrier comprising the steps of: 16. A method as claimed in claim 15 comprising in each of said grid sectors, originating only one of said rows at said grid center, and placing the respective origins of all rows in each of said grid sectors, other than said one row originating at said grid center, at different radii relative to said grid center. 17. A method as claimed in claim 16 comprising determining said different radii by starting with a predetermined origin radius and incrementing said predetermined origin radius in successive equal increments. 18. A method as claimed in claim 17 comprising: 19. A method as claimed in claim 15 comprising: 20. A method as claimed in claim 19, comprising determining each new angle section by the steps of: 21. A method as claimed in claim 20 comprising using a value for said weighting factor which is less than 1. 22. A method as claimed in claim 15 comprising using a ratio p:q as said predetermined ratio, with p.noteq.q.
	claims	1. A method comprising attenuating, while involved in a human adversarial situation, one's own emanated electromagnetic field at frequencies less than about 1 gigahertz by wearing one or more articles of apparel that include an electromagnetically shielding fabric, which shielding fabric comprises a substantially continuous system of conductive fibers combined with a non-conductive fabric and attenuates the emanated electromagnetic field at frequencies less than about 1 gigahertz, wherein said attenuating one's own emanated electromagnetic field at frequencies less than about 1 gigahertz decreases the likelihood of one's own emanated electromagnetic field alerting or cueing a human adversary and thereby decreases the likelihood of that emanated electromagnetic field affecting progress or an outcome of the human adversarial situation. 2. The method of claim 1 wherein the electromagnetically shielding fabric attenuates the emanated electromagnetic field at frequencies less than about 1 megahertz, and said attenuating of one's own emanated electromagnetic field at frequencies less than about 1 megahertz decreases the likelihood of one's own emanated electromagnetic field alerting or cueing a human adversary and thereby decreases the likelihood of that emanated electromagnetic field affecting the progress or the outcome of the human adversarial situation. 3. The method of claim 2 wherein the electromagnetically shielding fabric attenuates the emanated electromagnetic field at frequencies less than about 1 kilohertz, and said attenuating of one's own emanated electromagnetic field at frequencies less than about 1 kilohertz decreases the likelihood of one's own emanated electromagnetic field alerting or cueing a human adversary and thereby decreases the likelihood of that emanated electromagnetic field affecting the progress or the outcome of the human adversarial situation. 4. The method of claim 1 wherein the conductive fibers are intermingled with non-conductive fibers that form the non-conducting fabric. 5. The method of claim 1 wherein the conductive fibers are applied to a surface of the non-conducting fabric. 6. The method of claim 1 wherein at least one of the articles of apparel comprises an article of clothing, footwear, headwear, or eyewear. 7. The method of claim 1 wherein the shielding fabric includes between about 2% and about 35% by weight of the conductive fibers. 8. The method of claim 1 wherein the conductive fibers comprise stainless steel, copper, silver, conductive ceramic, carbon fiber or nanotubes, carbon monofilament or multifilament yarn, conductive polymer, or conductive nanotubes. 9. The method of claim 1 wherein at least one of the articles of apparel includes an odor absorber, suppressant, attenuator, or blocker. 10. The method of claim 9 wherein the conductive fibers act as the odor absorber, suppressant, attenuator, or blocker. 11. The method of claim 10 wherein the conductive fibers at least partly absorb the scent or odor and comprise carbon fibers, carbon monofilament yarn, or carbon multifilament yarn. 12. The method of claim 1 wherein the human adversarial situation includes one or more of: (i) a team or individual athletic contest; (ii) a mental or verbal contest; (iii) board or card games; (iv) an interview, debriefing, or interrogation; (v) a law enforcement situation; (vi) a military, combat, or tactical situation; or (vii) a covert operation. 13. A method comprising:providing to a user one or more articles of apparel that include an electromagnetically shielding fabric, which shielding fabric comprises a substantially continuous system of conductive fibers combined with a non-conductive fabric and attenuates the user's emanated electromagnetic field at frequencies less than about 1 gigahertz; andinstructing the user to wear, while involved in a human adversarial situation, at least one of the articles of apparel,wherein said attenuating of the user's emanated electromagnetic field at frequencies less than about 1 gigahertz decreases the likelihood of the user's emanated electromagnetic field alerting or cueing a human adversary and thereby decreases the likelihood of that emanated electromagnetic field affecting progress or an outcome of the human adversarial situation. 14. The method of claim 13 wherein the electromagnetically shielding fabric attenuates the emanated electromagnetic field at frequencies less than about 1 megahertz, and said attenuating of the user's emanated electromagnetic field at frequencies less than about 1 megahertz decreases the likelihood of the user's emanated electromagnetic field alerting or cueing a human adversary and thereby decreases the likelihood of that emanated electromagnetic field affecting progress or an outcome of the human adversarial situation. 15. The method of claim 14 wherein the electromagnetically shielding fabric attenuates the emanated electromagnetic field at frequencies less than about 1 kilohertz, and said attenuating of the user's emanated electromagnetic field at frequencies less than about 1 kilohertz decreases the likelihood of the user's emanated electromagnetic field alerting or cueing a human adversary and thereby decreases the likelihood of that emanated electromagnetic field affecting progress or an outcome of the human adversarial situation. 16. The method of claim 13 further comprising constructing at least one of the articles of apparel prior to providing it to the user. 17. The method of claim 13 wherein the conductive fibers are intermingled with non-conductive fibers that form the non-conducting fabric. 18. The method of claim 13 wherein the conductive fibers are applied to a surface of the non-conducting fabric. 19. The method of claim 13 wherein at least one of the articles of apparel comprises an article of clothing, footwear, headwear, or eyewear. 20. The method of claim 13 wherein the shielding fabric includes between about 2% and about 35% by weight of the conductive fibers. 21. The method of claim 13 wherein the conductive fibers comprise stainless steel, copper, silver, conductive ceramic, carbon fiber or nanotubes, carbon monofilament or multifilament yarn, conductive polymer, or conductive nanotubes. 22. The method of claim 13 wherein at least one of the articles of apparel includes an odor absorber, suppressant, attenuator, or blocker. 23. The method of claim 22 wherein the conductive fibers act as the odor absorber, suppressant, attenuator, or blocker. 24. The method of claim 23 wherein the conductive fibers at least partly absorb the scent or odor and comprise carbon fibers, carbon monofilament yarn, or carbon multifilament yarn. 25. The method of claim 13 wherein the human adversarial situation includes one or more of: (i) a team or individual athletic contest; (ii) a mental or verbal contest; (iii) board or card games; (iv) an interview, debriefing, or interrogation; (v) a law enforcement situation; (vi) a military, combat, or tactical situation; or (vii) a covert operation.
	abstract	Systems, methods, and devices of the various embodiments enable a Nuclear Thermionic Avalanche Cell (NTAC) to capture gamma ray photons emitted during a fission process, such as a fission process of Uranium-235 (U-235), and to breed and use a new gamma ray source to increase an overall emission flux of gamma ray photons. Various embodiments combine a fission process with the production of Co-60, thereby boosting the output flux of gamma ray photons for use by a NTAC in generating power. Various embodiments combine a fission process with the production of Co-60, a NTAC generating avalanche cell power, and a thermoelectric generator generating thermoelectric power.
048266477	summary	CROSS REFERENCES TO RELATED APPLICATIONS This application is related to copending application Ser. Nos. 217,060 entitled "Mechanical Spectral Shift Reactor" by W. J. Dollard et al.; 217,056 entitled "Latching Mechanism" by L. Veronesi now U.S. Pat. No. 4,439,054, dated Mar. 27, 1984; 217,054 entitled "Spectral Shift Reactor Control Method" by A. J. Impink, Jr.; 217,052 entitled "Displacer Rod For Use In A Mechanical Spectral Shift Reactor" by R. K. Gjertsen et al., now U.S. Pat. No. 4,432,934, dated Feb. 21, 1984; 217,053 entitled "Mechanical Spectral Shift Reactor" by D. G. Sherwood et al.; 217,275 entitled "Mechanical Spectral Shift Reactor" by J. F. Wilson et al.; 217,055 entitled "Hydraulic Drive Mechanism" by L. Veronesi et al., now U.S. Pat. No. 4,550,941, dated Nov. 5, 1985; 217,059 entitled "Fuel Assembly For A Nuclear Reactor" by R. K. Gjertsen; and 217,051 entitled "Fuel Assembly For A Nuclear Reactor" by R. K. Gjertsen et al., now U.S. Pat. No. 4,418,036, dated Nov. 29, 1983 all of which are filed Dec. 16, 1980 and to 228,007 entitled "Self-Rupturing Gas Moderator Rod For A Nuclear Reactor" by G. R. Marlatt, filed, now U.S. Pat. No. 4,371,495, dated Feb. 1, 1983 all of which are assigned to the Westinghouse Electric Corporation BACKGROUND OF THE INVENTION The invention relates to spectral shift reactor control and more particularly to mechanical means for spectral shift reactor control. In typical nuclear reactors, reactivity control is accomplished by varying the amount of neutron absorbing material (poisons) in the reactor core. Generally, neutron absorbing control rods are utilized to perform this function by varying the number and location of the control rods with respect to the reactor core. In addition to control rods, burnable poisons and poisons dissolved in the reactor coolant can be used to control reactivity. In the conventional designs of pressurized water reactors, an excessive amount of reactivity is designed into the reactor core at start-up so that as the reactivity is depleted over the life of the core the excess reactivity may be employed to lengthen the core life. Since an excessive amount of reactivity is designed into the reactor core at the beginning of core life, neutron absorbing material such as soluble boron must be placed in the core at that time in order to properly control the excess reactivity. Over the core life, as reactivity is consumed, the neutron absorbing material is gradually removed from the reactor core so that the original excess reactivity may be used. While this arrangement provides one means of controlling a nuclear reactor over an extended core life, the neutron absorbing material used during core life absorbs neutrons and removes reactivity from the reactor core that could otherwise be used in a more productive manner such as in plutonium fuel production. The consumption of reactivity in this manner without producing a useful product results in a less efficient depletion of uranium and greater fuel costs than could otherwise be achieved. Therefore, it would be advantageous to be able to extend the life of the reactor core without suppressing excess reactivity with neutron absorbing material thereby providing an extended core life with a significantly lower fuel cost. One such method of producing an extended core life while reducing the amount of neutron absorbing material in the reactor core is by the use of "Spectral Shift Control". As is well understood in the art, in one such method the reduction of excess reactivity (and thus neutron absorbing material) is achieved by replacing a large portion of the ordinary reactor coolant water with heavy water. This retards the chain reaction by shifting the neutron spectrum to higher energies and permits the reactor to operate at full power with reduced neutron absorbing material. This shift in the neutron spectrum to a "hardened" spectrum also causes more of the U.sup.238 to be converted to plutonium that is eventually used to produce heat. Thus, the shift from a "soft" to a "hard" spectrum results in more neutrons being consumed by U.sup.238 in a useful manner rather than by poisons. As reactivity is consumed, the heavy water is gradually replaced with ordinary water so that the reactor core reactivity is maintained at a proper level. By the end of core life, essentially all the heavy water has been replaced by ordinary water while the core reactivity has been maintained. Thus, the reactor can be controlled without the use of neutron absorbing material and without the use of excess reactivity at start-up which results in a significant uranium fuel cost savings. The additional plutonium production also reduces the U.sup.235 enrichment requirements. While the use of heavy water as a substitute for ordinary water can be used to effect the "spectral shift", the use of heavy water can be an expensive and complicated technology. Another well known phenomenon related to reactor control is referred to as xenon transient behavior. Xenon-135 is a fission product of uranium fuel some of which is a direct fission product of uranium-235 but most of which originates from the radioactive decay of tellurium-135 and iodine-135 which are produced from the fissioning of uranium-235. The major portion of the xenon thus produced is produced in a delayed manner due to the intermediate isotope production. This results in a time delay of several hours between the fissioning of fissile or fertile material and the production of large quantities of xenon-135. On the other side of the xenon transient phenomenon is the fact that since xenon-135 has a large neutron absorbing cross-section, xenon-135 tends to absorb neutrons and be destroyed thereby. Thus, xenon acts as a neutron poison in a reactor core robbing the core of neutrons that could be used to sustain the chain reaction. The transient usually associated with the xenon phenomenon arises because as power is reduced due to load follow reasons, neutron population in the core decreases which results in less destruction of xenon and in temporary xenon accumulation. This temporary accumulation of xenon further reduces reactor power by xenon absorption of neutrons. However, the reduction in reactor power lowers the core temperature which increases core reactivity due to the negative moderator temperature coefficient of the reactor. Thus, a minor oscillation in reactor power, xenon population, and core temperature can result from transient xenon production. Likewise, a similar result may occur from an attempt to increase reactor power in response to load follow requirements. This may occur since an increase in reactor power requires an increase in neutron population and fuel depletion which increases xenon production in the fuel. But since the xenon production is delayed in time, the poisonous effect of the xenon is temporarily delayed which again produces the transient oscillations between core temperature, xenon population, and reactor power. As is well understood in the art, the effects of these xenon transients can be effectively controlled by the addition or subtraction of boron in the reactor coolant by a feed-and-bleed process. The change in boron concentration in the reactor coolant can be timed to correspond to the changes in core reactivity due to the xenon transient thereby negating such transient. This can be accomplished as long as the boron concentration in the reactor coolant is sufficiently high to make a feed-and-bleed process possible in a timely manner. However, when the boron concentration falls below a given level, for example below 100 ppm. as is necessary near the end of core life, boron cannot be removed from the reactor coolant fast enough to compensate for xenon accumulation. Therefore, as the boron concentration in the reactor coolant nears a low level such as at the end of core life, boron compensation of xenon becomes very difficult which effectively prevents load follow maneuvering of reactor power so as to avoid xenon transients. Therefore, what is needed is apparatus to extend core life and provide for load follow capabilities at low reactor coolant boron concentrations. SUMMARY OF THE INVENTION A mechanical spectral shift reactor comprises apparatus for inserting and withdrawing water displacer elements having differing neutron absorbing capabilities for selectively changing the water-moderator volume in the core thereby changing the reactivity of the core. The displacer elements may comprise substantially hollow cylindrical low neutron absorbing rods and substantially hollow cylindrical thick walled stainless rods. Since the stainless steel displacer rods have greater neutron absorbing capability; they can effect greater reactivity change per rod. However, by arranging fewer stainless steel displacer rods in a cluster, the reactivity worth of the stainless steel displacer rod cluster can be less than a low neutron absorbing displacer rod cluster.
	summary
	abstract	Systems and methods are used to increase the penetration and reduce the exclusion zone of radiographic systems. An X-ray detection method irradiates an object with X-ray fanlets including vertically moving fan beams, each fanlet having an angular range smaller than the angular coverage of the object. The fanlets are produced by modulating an X-ray beam, synchronizing the X-ray beam and the fanlets, detecting the fanlets irradiating the object, collecting image slices from the detector array corresponding to a complete scan cycle of the fanlets, and processing the image slices collected for combining into a composite image.
	claims	1. A radiation photographing apparatus comprising: a radiation image receiving portion receiving radiation emitted from a radiation generating portion and transmitted through an object and obtaining a radiation image; a first portion including a scattered ray removing member for removing radiation scattered by the object or a radiation detector for use in controlling an exposure to the radiation of said radiation image receiving portion; a supporting portion for supporting said first portion so that said first portion is movable between a position on a radiation generating portion side of said radiation image receiving portion and a position on a side opposite to the radiation generating portion side of said radiation image receiving portion substantially without being separated from said radiation image receiving portion. 2. The apparatus of claim 1 , further comprising a housing or a frame member covering said radiation image receiving portion and wherein said first portion is held on said housing or said frame member by said supporting portion. claim 1 3. The apparatus of claim 1 , wherein said supporting portion comprises a connecting mechanism and said first portion is connected to said radiation image receiving portion through said connecting mechanism. claim 1 4. The apparatus of claim 3 , wherein said first portion comprises a guide portion having a predetermined route, and said connecting mechanism comprises an engagement member engaged with said guide portion and movable on said guide portion. claim 3 5. The apparatus of claim 4 , wherein said guide portion has a U-shaped route as the predetermined route. claim 4 6. The apparatus of claim 3 , wherein said connecting mechanism comprises at least two members rotatably coupled together. claim 3 7. The apparatus of claim 1 , wherein said radiation image receiving portion comprises a radiation image detector in which a plurality of detecting elements for converting the radiation into charges are two-dimensionally arranged, and a signal reading circuit for reading an output signal from said radiation image detector. claim 1 8. The apparatus of claim 1 , comprising a plurality of said first portions, each of which includes a scattered ray removing member, and each said scattered ray removing member differing in kind from others, and one of said first portions can be selectively disposed at the position on the radiation generating portion side. claim 1 9. The apparatus of claim 8 , wherein said supporting portion comprises a guide portion for selectively disposing one of said first portions at the position on the radiation generating portion side, and wherein each of said first portions comprises an engagement portion engaged with said guide portion. claim 8 10. The apparatus of claim 8 , further comprising detecting means for detecting a scattered ray removing member included in said first portion, and lock means for fixing said first portion at the position on the radiation generating portion side on the basis of a result of the detection by said detecting means. claim 8 11. The apparatus of claim 1 , further comprising lock means for imparting a limitation to movement of said first portion from the position on the radiation generating portion side. claim 1 12. The apparatus of claim 11 , wherein said lock means is operated by detecting disposition of said first portion at a position on the radiation generating portion side. claim 11 13. The apparatus of claim 11 , wherein said lock means is operated on the basis of information regarding a region to be photographed and information regarding a scattered ray removing member included in said first portion. claim 11 14. The apparatus of claim 1 , wherein said supporting portion guides said first portion to move between the position on the radiation generating portion side during the use of said first portion and the position on the side opposite to said radiation generating portion side during the non-use of said first portion. claim 1 15. The apparatus of claim 14 , wherein said supporting portion comprises a guide groove, and an engagement portion for engagement with said guide groove. claim 14 16. The apparatus of claim 1 , wherein said supporting portion comprises an arm mechanism holding said first portion and capable of displacing said first portion between the position on the radiation generating portion side during the use of said first portion and the position on the side opposite to the radiation generating portion side during the non-use of said first portion. claim 1 17. The apparatus of claim 16 , wherein said arm mechanism comprises a plurality of connecting members rotatable relative to one another. claim 16 18. A radiation photographing apparatus having: a radiation image receiving portion for receiving radiation emitted from a radiation generating portion and transmitted through an object and obtaining a radiation image; a first portion including a scattered ray removing member or a radiation detector for use in controlling an exposure to the radiation of said radiation image receiving portion; and guide means designed to guide said first portion to move between a position on a radiation generating portion side of said radiation image receiving portion during the use of said first portion and a position on a side opposite to said radiation generating portion side of the radiation image receiving portion during the non-use of said first portion. 19. The apparatus of claim 18 , wherein said guide means comprises a guide groove and an engagement portion for engagement with said guide groove provided on said first portion. claim 18 20. A radiation photographing apparatus having: a radiation image receiving portion for receiving radiation emitted from a radiation generating portion and transmitted through an object and obtaining a radiation image; a first portion including a scattered ray removing member or a radiation detector for use in controlling an exposure to the radiation of said radiation image receiving portion; and an arm mechanism holding said first portion and capable of displacing said first portion between a position on a radiation generating portion side of said radiation image receiving portion during the use of said first portion and a position on a side opposite to the radiation generating portion side of said radiation image receiving portion during the non-use of said first portion. 21. The apparatus of claim 20 , wherein said arm mechanism comprises a plurality of connecting rotatable relative to one another. claim 20
061577030	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS This application is related to U.S. patent application Ser. Nos. 09/167,399, and 09/167,638, filed on the same day herewith, and U.S. Pat. No. 5,859,893, all of which are incorporated herein by reference in their entirety. FIG. 1 depicts a top view of a x-ray beam hardening filter 100 according to an embodiment of the present invention. (As used herein, "top" and "bottom" are used only for purposes of illustration.) The x-ray beam hardening filter 100 preferably comprises a support member 110, a beam hardening sheet 120, and an actuator. The support member 110 is preferably a stainless steel structure that has a washer-like shape. The support member 110 comprises one or more direction guides 170. According to one embodiment, two direction guides 170 are carved or etched into support member 110 at opposing sides. Preferably, the direction guides 170 facilitate alignment of the x-ray beam hardening filter 100 over a collimator, as well as directing the movement of x-ray beam hardening filter 100 in a straight path. However, according to an alternative embodiment, the direction guides 170 can be replaced by a single pin from which the x-ray support member 110 can pivot as it is moved at an opposing end. The beam hardening sheet 120 is attached to the support member 110. The beam hardening sheet 120 is preferably composed of copper (Cu) and beryllium (Be). The copper is configured to absorb lower energy x-ray radiation, whereas the beryllium is added to increase the structural rigidity of the x-ray beam hardening filter 100. The actual ratio of the elements of the beam hardening sheet 120 can vary between x-ray imaging applications and objects to be imaged. The beam hardening sheet 120 contains a plurality of coterminously arranged areas of varying x-ray absorption. The areas of varying x-ray absorption are disposed about an active area of the beam hardening sheet, that is, they are arranged in the areas where an x-ray beam is likely to be dwelled. Some of the plurality of coterminously arranged areas are configured to absorb a significant energy level from a polychromatic x-ray beam, such as 10 keV, whereas others are configured to absorb little to no x-ray energy from the polychromatic x-ray beam. These higher and lower levels of x-ray absorption are arranged in regular intervals about a surface area of the beam hardening sheet 120. According to a preferred embodiment, an arrangement of varying levels of x-ray radiation is accomplished via a multidimensional array of apertures 130 which are disposed about the surface area of the beam hardening sheet 120. The array of apertures 130 are chemically etched into the surface of the beam hardening sheet 120 at regularly spaced intervals with a hole pitch of A.sub.p. Each aperture 130 has a diameter A.sub.d. Each aperture 130 is preferably no closer than to any other aperture than a distance approximately equal to diameter A.sub.d. The apertures 130 are configured to allow x-ray photons to freely pass through them, whereas other areas of the beam hardening sheet 120 (that is, without apertures 130) are configured to absorb some of the x-ray photons incident thereon. The beam hardening sheet 120 is bonded to the support member 110 with a brazing paste after aligning the apertures 130 within the support member 110, the movement of the actuator, and the collimator. The support member 110 comprises a receiver. According to one embodiment, the receiver is a rectangular aperture 160. Within rectangular aperture 160, a cam 140, having a diameter C.sub.d, is at least partially enclosed. The cam 140 rotates within rectangular aperture 160 based upon external control of a motor (not shown). The cam 140 is mounted to a cam shaft (not shown) at a rotation location 150. The rotation location 150 is offset from a center point of the rectangular aperture 160 a distance approximately equal to one-quarter of the aperture 130 pitch A.sub.p. The rectangular aperture 160, it may be noted, has a major axis with a length of approximately twice the distance between the rotation location 150 and an outer most point on cam 140, and a minor axis approximately equal to the cam 140 diameter C.sub.d. As engagement mechanism is moved by the actuator (cam 140 is rotated by the motor), pressure is applied to the edge of the receiver (e.g., rectangular aperture 160). As pressure is applied, the support member 110 moves, in a path defined by direction guides 170, in a straight line. Since the beam hardening sheet 120 is attached to the support member, it also moves, thereby causing the apertures 130 to be placed either into or out of the path of x-ray beams which are passing through collimator apertures. (described in further detail with reference to FIG. 6.) When the apertures 130 are aligned with collimator apertures, the x-ray beams pass through beam hardening filter 100 with little to no x-ray absorption. However, when the apertures are not in the path of the polychromatic x-ray beam, for example, when the areas between adjacent apertures 130 are aligned with the collimator apertures, then x-ray radiation is absorbed by the beam hardening sheet 120. FIG. 2A depicts a side view of an electrical motor 200 employed as a part of the actuator. Preferably, the motor comprises a winding (not shown), housed in a motor block 210, the winding centered about a cam shaft 220. Terminals 230 receive two power cables. FIG. 2B depicts a bottom view of the motor 200, which also shows the terminals 230. According to one embodiment, the motor 200 has the following electrical and mechanical characteristics: 4.5 V, 170 mA, 205 mW, rated torque 500 g cm, 40 rpm, and a gear ratio of 1:298. A suitable motor meeting these characteristics is Copal Corporation model no. LA12G-344, which can be obtained through distributor PEI Sales Assoc. of Cupertino, Calif. FIGS. 3A-C depict an actuator 300. Referring to FIG. 3A, mounting block 360 supports the motor housing 210 and is used to attach the motor housing 210 to the collimator. Furthermore, a position plate 310 rests at a base portion of cam shaft 220 (described in further detail with reference to FIGS. 4A-B). The position plate 310 will be described in further detail below and with reference to FIGS. 5A-C. Power cables 320 are shown attached to electrical terminals 230. Attached at an end of power cables 320 is a two prong male connector 330. FIG. 3B depicts a top view of the actuator 300. Rivets 350 are used to connect the mounting block 360 to the collimator. Also shown in FIG. 3B and 3C are position sensors 340. The sensors 340 are preferably electro-optical sensors. As the cam shaft 220 rotates, so too does the position plate 310. According to a preferred embodiment, the position plate 310 is configured to alternatively cover the two sensors 340. Because of the shape of the sense plate and the rotation of the cam shaft 220, the approximate position of the apertures 130 relative to the collimator apertures can be known. For example, when a the position plate 310 covers only a first sensor, the x-ray beam hardening filter 100 is set in absorption mode, however, when only a second sensor is covered by the position plate 310, then the x-ray beam hardening filter 100 is set in a non-absorption mode (or a less absorbing mode). When both sensors 340 are simultaneously covered or uncovered, then the x-ray beam hardening filter 100 is in an intermediate phase between an absorbing and a non-absorbing mode. FIG. 4A depicts a top view of a cam bearing 400. The cam bearing 400 has an outer diameter (CBO.sub.d) 402 and an inner diameter (CBI.sub.d) 404. According to one embodiment, the outer diameter 402 is larger than the minor axis of the rectangular aperture 160, whereas the inner diameter 404 is smaller than the minor axis of the rectangular aperture 160. FIG. 4B depicts a side view of the cam bearing 400. Viewed from the side, cam bearing 400 essentially comprises three washer-shaped body parts 410, 420 and 430. Part 410 has is relatively thin (e.g., 0.010 inches), whereas parts 420 and 430 are relatively thick (e.g., 0.040 inches). Part 420 is configured to be at least thick enough such that support member 110 can slide between parts 410 and 430. In such an embodiment, the rectangular aperture 160 is modified to have not only the rectangular aperture 160 described above, but also a bulbous end extending from one side, the bulbous end creating an opening at least sufficiently large to pass the outer diameter (CBO.sub.d) 402 through it. The rectangular aperture 160 has a minor axis approximately equal to the diameter of part 420, but smaller than the diameter (CBO.sub.d) 402. Accordingly, the support member 110 is capable of dropping over the cam bearing 400 so that the bulbous end surrounds the cam bearing 400. The support member 110 is then slid from the bulbous end and toward the rectangular aperture 160 until it comes to rest within the cavity created by parts 410, 420 and 430. Alignment of the support member 110 is finalized with direction guides 170. FIGS. 5A-C depict a cam-filter control 500. The cam-filter control 500 comprises a cam 530 and a position plate 510. An inner diameter 520 of the cam-filter control 500 is configured to slide over the cam shaft 220. Furthermore, the cam 530 and the position plate 510 are attached together such that the outermost point 532 (relative to rotation location 150) on the cam 530 is aligned to a point approximately 10.degree. clockwise of the midpoint of the outer diameter of the position plate 510. The position plate 510 is substantially similar to the position plate 310, described above, the primary difference being it is secured to the cam 530 to form the cam-filter control 500. As the cam shaft 220 rotates, the cam-filter control 500 does too. As the cam-filter control 500 rotates, the position plate 510 rotates over sensors 340. Additionally, the cam 530, through cam bearing 400, applies a force to the support member 110, which in turn moves the x-ray beam hardening filter 100 such that the apertures 130 are moved into or out of the path of the polychromatic x-ray beam. FIG. 6 depicts a cross-sectional view of the x-ray beam hardening filter 600, together with a collimator 660 and a cover 650. The collimator 660 and the cover 650 are tied together with posts 680. The cover 650 preferably comprises an x-ray transmissive material. The collimator 660 comprises of a material that is not x-ray transmissive. The collimator 660 further comprises an array of collimator apertures 662 through which x-rays (e.g., 604) can pass. Areas of the collimator through which incident x-rays can pass are said to be illumination areas, whereas areas where an incident x-ray beam cannot pass are called non-illumination areas. In the broader spirit of the invention, the collimator and x-ray beam hardening filter are part of an x-ray target assembly. Mounted to collimator 660 are motors 631 and 632. The motors 631 and 632 are attached to the collimator 660 via mounting blocks (e.g., mounting blocks 360). The cam bearings 641 and 642 slip over the cam-filter controls 646 and 647, respectively, and lock into place (e.g., with locking pins or rings). In one embodiment, the cover 650 comprises a cooling element. The x-ray beam hardening filter 600 comprises two independent beam hardening sheets 610 and 620. However, according to another embodiment, the x-ray beam hardening filter 600 comprises multiple filters substantially similar to the x-ray beam hardening filter 100 as depicted in FIG. 1. The cam bearing 641 engages first beam hardening sheet 610. The cam bearing 641 is rotated by the motor 631. The cam bearing 642 engages second beam hardening sheet 620. The cam bearing 642 is rotated by the motor 632. Together, the motor, the cam shaft, the cam-filter control, the cam and, the cam bearing form an actuator. However, in other embodiments, more or less parts can comprise the actuator, so long as the actuator is still configured to move a portion of the x-ray beam hardening filter 600. If n beam hardening sheets are used in the x-ray beam hardening filter 600, then one or more actuators are preferably capable of moving the beam hardening sheets (e.g., 610 and 620) in 2.sup.n different positions. For example, if four beam hardening sheets are employed, as many as four actuators can be used and 2.sup.4 (16) different positions of the four beam hardening sheets are possible. Different configurations of the actuators can accomplish such a positioning either by varying the cam shape or, simply by individually controlling each motor and cam. Depending on the actuator configuration, as well as the collimator 660 configuration, notches and additional apertures may be cut into each successive layer of the x-ray beam hardening filter 600 so that movement of any layer is not physically constricted by another layer, or some other physical obstruction (e.g., a head of a rivet or bolt protruding through the top surface of collimator 660.) Note that in FIG. 6, that beam hardening sheet 620 is slightly askew; that is, beam hardening sheet 620 is shifted to left in the figure relative to a fixed location, for example the collimator 660. When polychromatic x-ray beam 602 is incident upon beam hardening area 672, then a portion of the polychromatic x-ray beam 602 is absorbed by the beam hardening filter 620. The polychromatic x-ray beam passes through beam hardening sheet 620, then it passes through aperture 674 of beam hardening sheet 610, and finally it passes through the collimator aperture 662--as filtered polychromatic x-ray beam 604. If beam hardening sheet 620 is shift right and beam hardening sheet 610 is shifted left, then polychromatic x-ray beam 602 is instead received at aperture 670. As the x-ray beam 602 passes through beam hardening sheet 620, it is received by beam hardening sheet 610, which is operating in absorption mode, at beam hardening area 676. Beam hardening area 676 absorbs a portion of the polychromatic x-ray beam 602 and the resulting beam is passed through collimator aperture 662 and exits collimator 660 as filtered polychromatic x-ray beam 604. Based upon the mode of the beam hardening sheets 610 and 620 (e.g., absorbing or non-absorbing) the x-ray beam hardening filter 600 can absorb varying amounts of x-ray radiation from the incident x-ray beam 602. Accordingly, the apertures 130 are configured to have a low x-ray transmissivity such that most, if not all of the x-ray photons incident on the aperture 130 pass through it. According to a preferred embodiment, beam hardening sheet 610 absorbs twice the x-ray energy of beam hardening sheet 620. Doubling the absorption quality of each successive beam hardening sheet added to the filter, while employing actuators capable of 2.sup.n positioning gives a high degree of control and selectivity of the x-ray beam hardening filter 600. Alternatively, multiple beam hardening sheets employed in the x-ray beam filter can have the same x-ray absorption quality, which provides fewer distinct amounts of x-ray absorption of the overall x-ray beam hardening filter 600. FIG. 7 depicts a cross-sectional view of a collimator assembly incorporating an x-ray beam hardening filter 600. FIG. 7 depicts many of the same elements as FIG. 6, with like numerals referring to like elements. Added in FIG. 7 is detail pertaining to the collimator 660 and overall assembly of the x-ray beam hardening filter 600 with the collimator 660. Collimator 660 comprises a plurality of collimator sheets 740 stacked one on top of the other. The collimator sheets 740 build up to a divider sheet 745, which provides structural support for the plurality of collimator sheets 740. On top of the divider sheet 745 are a plurality of trimmed collimator sheets 730, which simply create a void for the actuator components (e.g., motor 631 and cam-filter control 646). A support pin 700 ties the collimator 660 and the collimator cover 650 together. The support pin 700 is located outside of the outer edge of the support member (e.g., support member 110) so that it will not obstruct movement of the beam hardening sheets. According to one embodiment, the outer edge of the support member comprises notches which prevent the beam hardening filter and the support pin 700 from colliding. In a preferred embodiment of the present invention, the collimator utilizes more than one support pin 700. The support pin 700 further comprises a spacer 710, which allows pressure to be applied to the outer surfaces of the collimator assembly without increasing the friction on the beam hardening sheets (e.g., beam hardening sheets 610 and 620). A unique feature of the present invention is that a minimum amount of movement is required to cause the x-ray beam hardening filter to intercept a polychromatic x-ray beam. In an x-ray system having a large area x-ray source (e.g., 25 cm), the x-ray beam hardening filters disclosed in the description and accompanying drawings is highly advantageous; it minimizes space compared to traditional beam hardening filters while providing a high degree of flexibility in the amount of x-ray radiation the beam hardening filter absorbs. The x-ray beam hardening filter does not need to be moved a distance as great as the diameter of the x-ray source to fully enable the x-ray beam hardening filter. Rather, the x-ray beam hardening filter can be moved a distance substantially less than the diameter of the x-ray source and accomplish the same end. In the foregoing specification, the invention has been described with reference to specific embodiments thereof. It will be evident, however, that various modifications and changes may be made thereto without departing from the broader spirit and scope of the invention. The specification and drawings are, accordingly, to be regarded in an illustrative, rather than a restrictive sense.
	summary
	summary
	claims	1. A method for filtering gas effluents from an industrial installation comprising the following steps:providing from an industrial installation a gas effluent comprising a mixture of gases;filtering harmful elements from the gas effluent by sifting, sorption and/or diffusion membrane separation through a plurality of membranes each with a tubular geometry, an inner wall, an outer wall, pores varying in dimension radially and axially, and dimensions of the pores decreasing in the direction of effluent gas flow, with each membrane filtering a specific harmful element of the harmful elements to obtain filtered specific harmful elements and processed gas effluent with a purification coefficient greater than 100;sorting the filtered specific harmful elements and storing the filtered specific harmful elements in separate storage reservoirs; anddischarging the processed gas effluent. 2. The method according to claim 1, wherein the gas effluent provided comprises fumes from an industrial installation. 3. The method according to claim 1, wherein the gas effluent provided comprises fumes from an industrial installation during operation. 4. The method according to claim 1, wherein the gas effluent provided is extracted from a ventilation system. 5. The method according to claim 1, wherein the gas effluent provided comprises fumes from a fire. 6. The method according to claim 1, wherein the gas effluent provided comprises components from fission products. 7. The method according to claim 1, wherein the gas effluent provided has a temperature greater than 40° C. 8. The method according to claim 1, wherein the gas effluent provided has a processing flow rate greater than 1 kg/s. 9. The method according to claim 1, wherein the gas effluent provided has a pressure of more than 1 bar. 10. The method according to claim 1, wherein said storage reservoirs are gas storage reservoirs containing zeolites. 11. The method according to claim 1, wherein the membranes are formed of ceramic, aramid fiber and/or a polymer. 12. The method according to claim 1, wherein the method is operable at a pressure of 1.5 bars or greater, without use of energy external from that of the industrial installation.
	claims	1. A method of shielding surroundings from radiation emitted by an X-ray system externally positioned around the periphery of a region of interest located inside an object, the method comprising:providing at least one radiation shield assembly connectable to the X-ray system, said radiation shield assembly includes a support base operatively connectable to a radiation source or a radiation detector of the X-ray system, and a plurality of individually controllable radiation shield segments sequentially positioned relative to said support base and extendable towards the object;determining a chosen proximity of a free end of at least one of said radiation shield segments to an opposing portion of the object; andindividually actuating and extending or retracting one or more of said at least one radiation shield segments relative to said support base, until said free end is at said chosen proximity to said opposing portion of the object. 2. The method according to claim 1, further comprising:repeating determining and individually actuating said at least one of said radiation shield segments, or/and said at least one or more others of said radiation shield segments, until collectively forming a contiguous radiopaque screen spanning at least partially around the periphery of the region of interest with an edge contoured correlatively with a surface curvature of the object. 3. The method according to claim 1, wherein determining is performed by using at least one positioning sensor configured for detecting positioning of at least one of said radiation shield segments relative to the object. 4. The method according to claim 3, wherein individually actuating is performed by using a drive mechanism configured for extending or/and retracting a selected number of said radiation shield segments in correlation to said position detecting. 5. The method according to claim 4, wherein determining and actuating are performed by at least one control unit. 6. The method according to claim 3, wherein said positioning sensor is coupled to at least one of said radiation shield segments and senses and reacts to positioning or proximity of said at least one free end relative to said opposing portion of the object, or to a contact therebetween. 7. The method according to claim 6, wherein said positioning sensor detects a portion of the radiation emitted by said radiation source and leaking through said plurality of radiation shield segments. 8. The method according to claim 1, wherein the control unit individually extends or retracts a plurality of radiation shield segments relative to a support base or/and to one or more other radiation shield segments. 9. The method according to claim 8, wherein one or more radiation shield segments and/or groups of radiation shield segments are controlled by a plurality of controllers, wherein each of said controllers is configured for controlling a single separate unit or group of said units. 10. The method according to claim 8, comprising retracting a single separate unit or group of said radiation shield segments with an individual driver.
050227874	claims	1. A method of returning geothermal noncondensable gas including H.sub.2 S gas together with geothermal waste water into an underground statum through a waste water return well under the two-phase gas-and-liquid flow conditions of froth or slug flow at the gas returning point around the wellhead, characterized in that the introduction of the geothermal gas at the gas returning point around the wellhead is regulated to satisfy the following equation; EQU V.sub.go <1.33V.sub.eo -0.41, 2. The method of claim 1, wherein the gas is introduced into the waste water above the ground level of the stratum.
	description	The present invention relates to a nozzle repair method for repairing a nozzle provided in a nuclear reactor vessel and a nuclear reactor vessel provided with a nozzle. For example, a nuclear power plant that includes a pressurized water reactor (PWR) uses light water as a nuclear reactor coolant and a neutron moderator while keeping the light water as high-temperature and high-pressure water which is not boiled throughout a reactor core, sends the high-temperature and high-pressure water to a vapor generator so as to generate a vapor by a heat exchange operation, and sends the vapor to a turbine generator so as to generate electric power. In such a nuclear power plant, there is a need to periodically inspect various structures of the pressurized water reactor in order to ensure sufficient safety or reliability. Then, when a problem is found after various inspections, a necessary portion involved with the problem is repaired. For example, in the pressurized water reactor, a nuclear reactor vessel body is provided with a plurality of instrumentation nozzles penetrating a lower end plate. Further, each of the instrumentation nozzles is formed so that an in-core instrumentation guide pipe is fixed to the upper end thereof inside the reactor and a conduit tube is connected to the lower end thereof outside the reactor. Then, a neutron flux detector capable of measuring a neutron flux is insertable from the instrumentation nozzle to a reactor core (a fuel assembly) through the in-core instrumentation guide pipe by using the conduit tube. The instrumentation nozzle is formed in a manner such that an in-core instrumentation cylinder formed of nickel base alloy is fitted into an attachment hole of a nuclear reactor vessel body formed of low-alloy steel and is welded by a material of nickel base alloy. For that reason, there is a possibility that a stress corrosion crack may occur in the in-core instrumentation cylinder due to the long-term use. Thus, when the stress corrosion crack occurs, there is a need to repair the instrumentation nozzle. A nozzle repair method of the related art is disclosed in, for example, Patent Literature 1 below. A method of repairing an elongated housing disclosed in Patent Literature 1 includes cutting an elongated housing such as a neutron flux monitor housing fixed to a lower end plate of a nuclear reactor vessel by welding at a welding portion in the vertical direction, removing the cut housing, removing a groove-welding portion for a nozzle of the nuclear reactor vessel along with the remaining housing, restoring a grooving portion to a head portion of the nozzle, fixing a housing inserted from a penetration hole of the nuclear reactor pressure vessel through a groove-welding portion for the nozzle, and fixing an inserted front end to the housing by welding. Patent Literature 1: Japanese Patent Application Laid-open No. 2-102493 In the above-described nozzle repair method of the related art, when the grooving portion is restored by removing the groove-welding portion for the nozzle of the nuclear reactor vessel along with the remaining housing, the inner surface of the penetration hole is machined, a new housing is inserted into the processed penetration hole, and the new housing is fixed by welding the groove-welding portion for the nozzle. For that reason, the inner diameter of the penetration hole into which the housing is inserted after the repair becomes larger than that of the penetration hole before the repair. Meanwhile, the inner diameter of the new housing is uniform, but the outer diameter needs to be large so as to match the inner diameter of the penetration hole after the repair. In a technical standard for nuclear power generation equipment, the depth or the width of the welding joint with respect to the plate thickness of the pipe is set. Thus, when the plate thickness of the housing increases, the depth or the width of the welding joint increases. The instrumentation nozzle of the nuclear reactor vessel body is formed so that the circumferential inner surface is provided with a buttered-welding layer formed of stainless steel. Since the buttered-welding layer does not form the reinforced member of the nuclear reactor vessel body, the welding joint needs to be located within a range not reaching the buttered-welding layer. However, when the depth or the width of the welding joint increases, there is a possibility that the welding portion reaches the buttered-welding layer. Accordingly, there is a concern that the repair is difficult. The invention is made to solve the above-described problems, and an object of the invention is to provide a nozzle repair method and a nuclear reactor vessel that improve the workability of a repair by suppressing a nozzle welding area to a predetermined range. According to an aspect of the present invention, a nozzle repair method for a nozzle in which an in-core instrumentation cylinder is inserted into an attachment hole formed in a semi-spherical portion of a nuclear reactor vessel and the inner surface side of the semi-spherical portion is groove-welded so as to fix the in-core instrumentation cylinder, comprises: removing a connection portion with respect to the in-core instrumentation cylinder in a groove-welding portion; removing the in-core instrumentation cylinder from the semi-spherical portion; forming a surface buttered-welding portion by buttered-welding the surface of the groove-welding portion; forming a welding groove by grooving the surface buttered-welding portion; inserting a new in-core instrumentation cylinder provided with a circumferential groove portion outside an instrumentation equipment guide passage into the attachment hole; and fixing the new in-core instrumentation cylinder by groove-welding the welding groove. Accordingly, a welding groove is formed by buttered welding the surface of the groove-welding portion in which the in-core instrumentation cylinder is removed, a new in-core instrumentation cylinder provided with a circumferential groove portion outside the instrumentation equipment guide passage is inserted into the attachment hole, and the in-core instrumentation cylinder is fixed by groove-welding the welding groove. Since the new in-core instrumentation cylinder is provided with the circumferential groove portion, the thickness of the portion fixed to the attachment hole by groove-welding is thinned toward the outside of the groove portion. Accordingly, the depth or the width of each of the welding groove and the groove-welding portion for the welding groove may be suppressed within a predetermined range, and hence the workability of the repair may be improved. Advantageously, in the nozzle repair method, when the surface buttered-welding portion is formed on the surface of the groove-welding portion, buttered-welding is performed on an area extending to the inner surface of the semi-spherical portion and buttered-welding is performed on an area extending to the attachment hole. Accordingly, since the surface of the remaining existing groove-welding portion is coated by a new surface buttered-welding portion without any gap, the stress corrosion cracking resistance may be improved. Advantageously, in the nozzle repair method, the surface buttered-welding portion is formed on the surface of the groove-welding portion and the inner surface of the attachment hole is machined. Accordingly, since the inner surface of the attachment hole is machined and a new in-core instrumentation cylinder is inserted into the attachment hole, the attachment precision may be improved. Advantageously, in the nozzle repair method, the welding groove is formed within an area of the groove-welding portion. Accordingly, the in-core instrumentation cylinder may be appropriately fixed to the attachment hole, and hence the durability of the nozzle welding portion may be improved. Advantageously, in the nozzle repair method, the new in-core instrumentation cylinder includes a main body portion which is inserted into the attachment hole, a support portion which is continuous to the upper end of the main body portion and has a diameter smaller than the main body portion, the instrumentation equipment guide passage which penetrates the main body portion and the support portion, and the groove portion of which the end is opened to a stepped portion between the main body portion and the support portion. Accordingly, since the new in-core instrumentation cylinder is provided with the groove portion which is opened to the stepped portion between the main body portion and the support portion, the instrumentation nozzle may be simplified, and the depth or the width of each of the welding groove and the groove-welding portion for the welding groove in the in-core instrumentation cylinder may be suppressed within a predetermined range. Advantageously, in the nozzle repair method, a welding material used to fix the new in-core instrumentation cylinder to the semi-spherical portion is a material having higher stress corrosion cracking resistance than the welding material of the groove-welding portion. Accordingly, the stress corrosion cracking resistance may be improved compared to the nozzle of the related art. According to another aspect of the present invention, a nuclear reactor vessel comprises: a nuclear reactor vessel body of which a lower portion is formed in a semi-spherical shape; a nuclear reactor vessel head which is formed in a semi-spherical shape and is attached to an upper portion of the nuclear reactor vessel body; an inlet nozzle and an outlet nozzle which are provided at the side portion of the nuclear reactor vessel body; a reactor core which is disposed inside the nuclear reactor vessel body and is formed by a plurality of fuel assemblies; a plurality of control rods which is insertable into the fuel assemblies; a control rod driving mechanism which moves the control rods in the vertical direction; and a plurality of instrumentation nozzles which is provided at the lower portion of the nuclear reactor vessel body and into which a neutron flux detector is insertable. Any one of the plurality of instrumentation nozzles includes a main body portion which is fixed to the lower portion of the nuclear reactor vessel body, a support portion which is continuous to the upper end of the main body portion and has a diameter smaller than the main body portion, an instrumentation equipment guide passage which penetrates the main body portion and the support portion, and a groove portion of which the end is opened to a stepped portion between the main body portion and the support portion and which is formed in the circumferential direction. Accordingly, since the new in-core instrumentation cylinder is provided with the circumferential groove portion, the thickness of the portion fixed to the attachment hole by groove-welding is thinned toward the outside of the groove portion. Accordingly, the depth or the width of each of the welding groove and the groove-welding portion for the welding groove may be suppressed within a predetermined range. As a result, the workability of the repair may be improved, and the structure of the repaired instrumentation nozzle may be simplified. According to the nozzle repair method and the nuclear reactor vessel of the invention, since the new in-core instrumentation cylinder is provided with the circumferential groove portion outside the instrumentation equipment guide passage, the thickness of the portion fixed to the attachment hole by groove-welding is thinned toward the outside of the groove portion. Accordingly, the depth or the width of each of the welding groove and the groove-welding portion for the welding groove may be suppressed within a predetermined range, and hence the workability of the repair may be improved. Hereinafter, a preferred embodiment of a nozzle repair method and a nuclear reactor vessel according to the invention will be described in detail with reference to the accompanying drawings. Furthermore, the invention is not limited to the embodiment. FIG. 2 is a schematic configuration diagram of a nuclear power plant, and FIG. 3 is a longitudinal sectional view illustrating a pressurized water reactor. A nuclear reactor of the embodiment is a pressurized water reactor (PWR) that uses light water as a nuclear reactor coolant and a neutron moderator while keeping the light water as high-temperature and high-pressure water which is not boiled throughout a reactor core, sends the high-temperature and high-pressure water to a vapor generator so as to generate a vapor by a heat exchange operation, and sends the vapor to a turbine generator so as to generate electric power. In a nuclear power plant that includes the pressurized water reactor of the embodiment, as illustrated in FIG. 2, a containment 11 accommodates a pressurized water reactor 12 and a vapor generator 13 therein. Here, the pressurized water reactor 12 and the vapor generator 13 are connected to a high-temperature-side supply pipe 14 through a low-temperature-side supply pipe 15, the high-temperature-side supply pipe 14 is provided with a pressurizer 16, and the low-temperature-side supply pipe 15 is provided with a primary cooling water pump 17. In this case, light water is used as a moderator and primary cooling water (coolant), and a primary cooling system is controlled at a high-pressure state of about 150 to 160 atm by the pressurizer 16 in order to prevent the primary cooling water from being boiled in the reactor core portion. Accordingly, in the pressurized water reactor 12, the light water as the primary cooling water is heated by low-enriched uranium or MOX as a fuel (an atomic fuel), and the high-temperature primary cooling water is sent to the vapor generator 13 through the high-temperature-side supply pipe 14 while being maintained at a predetermined high pressure by the pressurizer 16. In the vapor generator 13, the primary cooling water which is cooled by a heat exchange operation between the high-temperature and high-pressure primary cooling water and the secondary cooling water is returned to the pressurized water reactor 12 through the low-temperature-side supply pipe 15. The vapor generator 13 is connected to a vapor turbine 32 through a pipe 31 that supplies the heated secondary cooling water, that is, vapor, and the pipe 31 is provided with a main vapor isolation valve 33. The vapor turbine 32 includes a high-pressure turbine 34 and a low-pressure turbine 35, and is connected to a generator (a generation device) 36. Further, a moisture separation heater 37 is provided between the high-pressure turbine 34 and the low-pressure turbine 35. Here, a cooling water branch pipe 38 which is branched from the pipe 31 is connected to the moisture separation heater 37, the high-pressure turbine 34 and the moisture separation heater 37 are connected to each other by a low-temperature reheating pipe 39, and the moisture separation heater 37 and the low-pressure turbine 35 are connected to each other by a high-temperature reheating pipe 40. Further, the low-pressure turbine 35 of the vapor turbine 32 includes a condenser 41. Here, the condenser 41 is connected to a turbine bypass pipe 43 which extends from the pipe 31 and includes a bypass valve 42, and is connected to a water intake pipe 44 and a drainage pipe 45 which supply and discharge the cooling water (for example, sea water). The water intake pipe 44 includes a circulation water pump 46, and the other end thereof is disposed under the sea along with the drainage pipe 45. Then, the condenser 41 is connected to a pipe 47, a condensate pump 48, a grand condenser 49, a condensed water desalting device 50, a condensate booster pump 51, and a low-pressure feed water heater 52. Further, the pipe 47 is connected to a deaerator 53, and is provided with a water feeding pump 54, a high-pressure feed water heater 55, and a water feeding control valve 56. Accordingly, in the vapor generator 13, the vapor which is generated by the heat exchange operation with respect to the high-pressure and high-temperature primary cooling water is sent to the vapor turbine 32 (from the high-pressure turbine 34 to the low-pressure turbine 35) through the pipe 31. Then, the vapor turbine 32 is driven by the vapor so that the generator 36 generates electric power. At this time, the vapor which is sent from the vapor generator 13 is used to drive the high-pressure turbine 34, passes through the moisture separation heater 37 so that the vapor is heated while a moisture contained in the vapor is removed, and is used to drive the low-pressure turbine 35. Then, the vapor having been used to drive the vapor turbine 32 is cooled into condensed water by the sea water in the condenser 41, and is returned to the vapor generator 13 through the grand condenser 49, the condensed water desalting device 50, the low-pressure feed water heater 52, the deaerator 53, the high-pressure feed water heater 55, and the like. In the pressurized water reactor 12 of the nuclear power plant with such a configuration, as illustrated in FIG. 3, a nuclear reactor vessel 61 includes a nuclear reactor vessel body 62 and a nuclear reactor vessel head (an upper end plate) 63 attached to the upper portion thereof so that an in-core structure is inserted thereinto, and the nuclear reactor vessel head 63 is fixed to the nuclear reactor vessel body 62 by a plurality of stud bolts 64 and a plurality of nuts 65 so as to be opened and closed. The nuclear reactor vessel body 62 has a cylindrical shape of which the upper portion is opened by the separation of the nuclear reactor vessel head 63 and the lower portion is formed in a semi-spherical shape while being closed by a lower end plate 66. Then, the upper portion of the nuclear reactor vessel body 62 is provided with an inlet nozzle (an entrance nozzle) 67 which supplies the light water (coolant) as the primary cooling water and an outlet nozzle (an exist nozzle) 68 which discharges the light water. Further, the nuclear reactor vessel body 62 is provided with a water injection nozzle (a water injection nozzle) (not illustrated) separately from the inlet nozzle 67 and the outlet nozzle 68. In the inside of the nuclear reactor vessel body 62, an upper core support 69 is fixed to a portion above the inlet nozzle 67 and the outlet nozzle 68 and a lower core support 70 is fixed so as to be located in the vicinity of the lower end plate 66. The upper core support 69 and the lower core support 70 are formed in a disk shape and are provided with a plurality of flow holes (not illustrated). Then, the upper core support 69 is connected to an upper core plate 72 provided with a plurality of flow holes (not illustrated) at a lower portion thereof through a plurality of reactor core support rods 71. A core barrel 73 which has a cylindrical shape is disposed inside the nuclear reactor vessel body 62 with a predetermined gap with respect to the inner wall surface. Further, the upper portion of the core barrel 73 is connected to the upper core plate 72, and the lower portion thereof is connected to a lower core support plate 74 having a disk shape and a plurality of flow holes (not illustrated) formed therein. Then, the lower core support plate 74 is supported by the lower core support 70. That is, the core barrel 73 is suspended on the lower core support 70 of the nuclear reactor vessel body 62. The reactor core 75 is formed by the upper core plate 72, the core barrel 73, and the lower core support plate 74, and the reactor core 75 has a plurality of fuel assemblies 76 disposed therein. Although not illustrated in the drawings, each of the fuel assemblies 76 is formed by binding a plurality of fuel rods in a grid shape by a support grid. Here, the upper nozzle is fixed to the upper end, and the lower nozzle is fixed to the lower end. Further, the reactor core 75 has a plurality of control rods 77 disposed therein. The plurality of control rods 77 is formed as a control rod cluster 78 while the upper ends are evenly arranged, and is insertable into the fuel assembly 76. In the upper core support 69, a plurality of control rod cluster guide pipes 79 is fixed while penetrating the upper core support 69, and each control rod cluster guide pipe 79 is formed so that the lower end thereof extends to the control rod cluster 78 inside the fuel assembly 76. The upper portion of the nuclear reactor vessel head 63 that constitutes the nuclear reactor vessel 61 is formed in a semi-spherical shape, and a magnetic jack type control rod driving mechanism 80 is accommodated in a housing 81 which is integrated with the nuclear reactor vessel head 63. The plurality of control rod cluster guide pipes 79 is formed so that the upper ends thereof extend to the control rod driving mechanism 80, and control rod cluster driving shafts 82 which extend from the control rod driving mechanism 80 extend to the fuel assemblies 76 while passing through the inside of the control rod cluster guide pipes 79, thereby gripping the control rod cluster 78. The control rod driving mechanism 80 extends in the vertical direction so as to be connected to the control rod cluster 78, and a control rod cluster driving shaft 82 of which the surface is provided with a plurality of circumferential grooves formed in the longitudinal direction is moved in the vertical direction by the magnetic jack, thereby controlling the output of the nuclear reactor. Further, the nuclear reactor vessel body 62 is provided with a plurality of instrumentation nozzles 83 which penetrates the lower end plate 66, and each of the instrumentation nozzles 83 is formed so that the upper end inside the reactor is connected to the in-core instrumentation guide pipe 84 and the lower end outside the reactor is connected to a conduit tube 85. In each of the in-core instrumentation guide pipes 84, the upper end is connected to the lower core support 70 and upper and lower connection plates 86 and 87 for suppressing a vibration are connected to the in-core instrumentation guide pipes. A thimble pipe 88 is provided with a neutron flux detector (not illustrated) capable of measuring a neutron flux, and is insertable to the fuel assembly 76 while penetrating the lower core support plate 74 from the conduit tube 85 along the instrumentation nozzle 83 and the in-core instrumentation guide pipe 84. Accordingly, the nuclear fission inside the reactor core 75 is controlled in a manner such that the control rod cluster driving shaft 82 is moved by the control rod driving mechanism 80 so as to extract the control rod 77 from the fuel assembly 76 by a predetermined amount. Then, the light water charged into the nuclear reactor vessel 61 is heated by the generated thermal energy, and the high-temperature light water is discharged from the outlet nozzle 68 so as to be sent to the vapor generator 13 as described above. That is, neutrons are discharged by the nuclear fission of the atomic fuel forming the fuel assembly 76, and the light water as the moderator and the primary cooling water decreases the movement energy of the discharged high-speed neutrons so as to form thermal neutrons. Accordingly, new nuclear fission may easily occur, and the generated heat is stolen and cooled. Meanwhile, when the control rod 77 is inserted into the fuel assembly 76, the number of neutrons generated inside the reactor core 75 may be adjusted. Further, when the entire control rod 77 is inserted into the fuel assembly 76, the nuclear reactor may be emergently stopped. Further, the nuclear reactor vessel 61 is formed so that an upper plenum 89 communicating with the outlet nozzle 68 is provided above the reactor core 75 and a lower plenum 90 is provided therebelow. Then, a down corner portion 91 which communicates with the inlet nozzle 67 and the lower plenum 90 is formed between the nuclear reactor vessel 61 and the core barrel 73. Accordingly, the light water flows from the inlet nozzle 67 into the nuclear reactor vessel body 62, flows downward to the down corner portion 91, reaches the lower plenum 90, rises while being guided upward by the spherical inner surface of the lower plenum 90, passes through the lower core support 70 and the lower core support plate 74, and flows into the reactor core 75. The light water which flows into the reactor core 75 increases in temperature while cooling the fuel assembly 76 by absorbing the thermal energy generated from the fuel assembly 76 constituting the reactor core 75, passes through the upper core plate 72, rises to the upper plenum 89, and is discharged through the outlet nozzle 68. In the nuclear reactor vessel 61 with such a configuration, the instrumentation nozzle 83 is formed in a manner such that the in-core instrumentation cylinder is fitted into an attachment hole formed in the lower end plate 66 of the nuclear reactor vessel body 62 and the upper end of the in-core instrumentation cylinder is fixed to the inner surface of the lower end plate 66 by groove-welding. The nuclear reactor vessel body 62 is formed by buttered-welding a stainless steel to the inner surface of low-alloy steel as a base material, and the in-core instrumentation cylinder of the nickel base alloy is welded to the nuclear reactor vessel body 62 by the material of the nickel base alloy while being fitted into the attachment hole of the nuclear reactor vessel body 62. For that reason, there is a possibility that a stress corrosion crack may occur in the in-core instrumentation cylinder due to the long-term use. Thus, when the stress corrosion crack occurs, there is a need to repair the instrumentation nozzle 83. In a case where the instrumentation nozzle 83 is repaired, the groove-welding portion of the instrumentation nozzle 83 is trepanned so as to remove the in-core instrumentation cylinder, the inner surface of the attachment hole is machined, and a new in-core instrumentation cylinder is inserted into the processed attachment hole and is fixed by groove-welding. For that reason, the inner diameter of the repaired attachment hole becomes larger than that of the unrepaired attachment hole, and hence the outer diameter of the new in-core instrumentation cylinder is large although the inner diameter thereof is uniform. In a technical standard for nuclear power generation equipment, the depth or the width of the welding joint is set with respect to the plate thickness of the pipe. Thus, when the plate thickness of the in-core instrumentation cylinder increases, the depth or the width of the welding joint increases. Then, the welding joint extends to not the reinforced member of the nuclear reactor vessel body 62, but the buttered-welding layer. Accordingly, there is a concern that the repair is difficult. Therefore, the nozzle repair method of the embodiment includes removing the connection portion with respect to the in-core instrumentation cylinder in the existing groove-welding portion, removing the in-core instrumentation cylinder from the lower end plate (the semi-spherical portion) 66, forming a surface buttered-welding portion on the surface of the groove-welding portion by buttered-welding, forming a welding groove by grooving the surface buttered-welding portion, inserting a new in-core instrumentation cylinder provided with a circumferential groove portion outside the instrumentation equipment guide passage into the attachment hole, and fixing the new in-core instrumentation cylinder by groove-welding the welding groove. In this case, since the new in-core instrumentation cylinder is provided with the groove portion in the circumferential direction, the thickness of the portion fixed to the attachment hole by groove-welding is thinned toward the outside of the groove portion. Accordingly, the depth or the width of each of the welding groove and the groove-welding portion for the welding groove may be suppressed within a predetermined range, and hence the workability of the repair may be improved. FIG. 1 is a cross-sectional view illustrating an instrumentation nozzle of a nuclear reactor vessel that is repaired by a nozzle repair method according to an embodiment of the invention, FIG. 4 is a flowchart illustrating the nozzle repair method of the embodiment, FIG. 5-1 is a schematic diagram of the nuclear reactor vessel illustrating a water stopping operation for an in-core instrumentation cylinder in the instrumentation nozzle, FIG. 5-2 is a schematic diagram illustrating the water stopping operation for the in-core instrumentation cylinder, FIG. 6 is a schematic diagram illustrating a conduit tube cutting operation, FIG. 7 is a schematic diagram illustrating a water stopping cap attachment operation, FIG. 8 is a schematic diagram illustrating an operation of mounting a guide device and a support trestle to the nuclear reactor vessel, FIG. 9 is a schematic diagram illustrating a water removing operation in the nuclear reactor vessel, FIG. 10 is a schematic diagram illustrating a cutting operation for the in-core instrumentation cylinder, FIG. 11-1 is a schematic diagram illustrating a trepanning operation for the in-core instrumentation cylinder, FIG. 11-2 is a cross-sectional view illustrating the trepanned in-core instrumentation cylinder, FIG. 12 is a cross-sectional view illustrating a drawing operation in the in-core instrumentation cylinder, FIG. 13-1 is a schematic diagram illustrating a thickness measurement operation for a stainless steel overlaid portion in the instrumentation nozzle, FIG. 13-2 is a main enlarged diagram illustrating a thickness measurement operation for the stainless steel overlaid portion in the instrumentation nozzle, FIG. 14-1 is a schematic diagram illustrating a welding portion area measurement operation in the instrumentation nozzle, FIG. 14-2 is a main enlarged diagram illustrating the welding portion area measurement operation in the instrumentation nozzle, FIG. 15-1 is a schematic diagram illustrating a buttered-welding operation in the instrumentation nozzle, FIG. 15-2 is a cross-sectional view illustrating the instrumentation nozzle subjected to a buttered-welding operation, FIG. 16 is a cross-sectional view illustrating a buttered-welding portion subjected to a shaping operation in the instrumentation nozzle, FIG. 17 is a schematic diagram illustrating a measurement operation for a welding portion in the instrumentation nozzle, FIG. 18-1 is a schematic diagram illustrating a grooving operation for the welding portion in the instrumentation nozzle, FIG. 18-2 is a cross-sectional view illustrating a welding portion subjected to a grooving operation in the instrumentation nozzle, FIG. 19-1 is a schematic diagram illustrating an operation of inserting an in-core instrumentation cylinder into the instrumentation nozzle, FIG. 19-2 is a cross-sectional view illustrating the in-core instrumentation cylinder inserted into the instrumentation nozzle, FIG. 20-1 is a schematic diagram illustrating a welding operation and an inspection operation for the in-core instrumentation cylinder in the instrumentation nozzle, FIG. 20-2 is a cross-sectional view illustrating the in-core instrumentation cylinder welded to the instrumentation nozzle, and FIG. 21 is a schematic diagram illustrating an inspection operation for a welding portion of the in-core instrumentation cylinder in the instrumentation nozzle. Hereinafter, a nozzle repair method of the embodiment will be described in detail with reference to the cross-sectional view of FIG. 1, the flowchart of FIG. 4, and the schematic diagrams from FIGS. 5-1 to 21. As illustrated in FIGS. 4 and 5-1, in step S11, the nuclear reactor vessel head 63 is separated from the nuclear reactor vessel body 62 constituting the nuclear reactor vessel 61 in the pressurized water reactor 12, and an in-core structure (an upper in-core structure 12A and a lower in-core structure 12B) provided therein is removed. In this case, a nuclear reactor building 101 is provided with a cavity 102 capable of storing the cooling water, and an appliance temporary placement pool 104 is provided near a nuclear reactor pool 103 where the pressurized water reactor 12 is suspended. For that reason, the upper in-core structure 12A and the lower in-core structure 12B are temporarily placed while being immersed into the cooling water of the appliance temporary placement pool 104. As illustrated in FIG. 5-2, in the nuclear reactor vessel body 62, an inner surface of a base material 201 formed of low-alloy steel is provided with a buttered-welding layer 202 formed of stainless steel. Then, the instrumentation nozzle 83 has a configuration in which an in-core instrumentation cylinder 204 formed of a nickel base alloy (for example, Inconel 600/trademark) is inserted and positioned into an attachment hole 203 formed in the lower end plate 66 of the nuclear reactor vessel body 62 in the vertical direction and a groove-welding portion 206 (a lower welding portion 206a and a main welding portion 206b) formed of a nickel base alloy (for example, Inconel 600) is provided in a grooving portion 205 formed in the inner surface of the lower end plate 66. As illustrated in FIGS. 4, 5-1, and 5-2, in step S12, a water stopping plug handling device 105 is provided above the cavity 102 and a water stopping plug attachment device 106 gripping a water stopping plug 107 moves downward inside the cooling water of the cavity 102. Then, the water stopping plug 107 is fitted to the upper end of the in-core instrumentation cylinder 204 constituting the instrumentation nozzle 83 of the nuclear reactor vessel body 62 so as to plug the upper end. Further, as illustrated in FIGS. 4 and 6, in step S13, the conduit tube 85 connected to the lower end of the in-core instrumentation cylinder 204 is cut. Then, as illustrated in FIGS. 4 and 7, in step S14, a water stopping cap 108 is fixed to the lower portion of the instrumentation nozzle 83. In this case, the water stopping cap 108 includes a casing 108a of which an upper end is opened and a lower end is closed, a pipe 108b which is connected to the lower portion of the casing 108a, and an opening/closing valve 108c which is provided in the pipe 108b. Meanwhile, the outer surface of the lower end plate 66 is provided with a buttered-welding layer 207 formed of stainless steel in advance. For that reason, the water stopping cap 108 has a configuration in which the upper end of the casing 108a is welded and fixed to the buttered-welding layer 207 of the lower end plate 66 so as to cover the lower portion of the in-core instrumentation cylinder 204. When the water is stopped at the upper and lower ends of the existing in-core instrumentation cylinder 204 of the instrumentation nozzle 83, an aerial space for performing a water removing process in the nuclear reactor vessel body 62 is formed. That is, as illustrated in FIGS. 4 and 8, in step S15, a support trestle 110 equipped with a guide device 109 moves downward inside the cooling water from the upside of the cavity 102, and the guide device 109 is adjusted to a predetermined height position. Then, as illustrated in FIGS. 4 and 9, in step S16, when the guide device 109 is provided inside the nuclear reactor vessel body 62, the water is stopped at the upper end of the nuclear reactor vessel body 62 by a seal plate 111, and a guide pipe 112 is connected to the seal plate. In this state, a drying facility (not illustrated) is provided above the cavity 102, and the cooling water inside the nuclear reactor vessel body 62 is discharged through the guide pipe 112 by using a submersible pump, so that an aerial space (the diagonal line part of FIG. 9) is formed in the reactor. In this case, the water is also stopped at the inlet nozzle 67 and the outlet nozzle 68 of the nuclear reactor vessel body 62. Then, when an aerial space is formed inside the nuclear reactor vessel body 62, the water stopping plug 107 is separated from the upper end of the in-core instrumentation cylinder 204 of the instrumentation nozzle 83. Furthermore, here, a configuration is employed in which the water is stopped at the upper end of the nuclear reactor vessel body 62 by the seal plate 111 and the entire water therein is discharged. However, a configuration may be employed in which the instrumentation nozzle 83 is surrounded by a casing (not illustrated) and the cooling water inside the casing is discharged so as to form an aerial space. When an aerial space is formed inside the nuclear reactor vessel body 62, various operations are performed inside the nuclear reactor vessel body 62. However, various devices are carried into the nuclear reactor vessel body 62 through the guide pipe 112, and are used while being supported by the guide device 109. As illustrated in FIGS. 4 and 10, in step S17, the upper portion of the in-core instrumentation cylinder 204 in the instrumentation nozzle 83 is cut (machined) by a cutting device (not illustrated) and the upper portion of the cut in-core instrumentation cylinder 204 is collected. As illustrated in FIGS. 4 and 11-1, in step S18, the groove-welding portion 206 of the in-core instrumentation cylinder 204 fixed to the lower end plate 66 is trepanned (as a trepanning portion 208) by using a cutting device (not illustrated), and as illustrated in FIG. 11-2, an opening gap 209 is formed between the in-core instrumentation cylinder 204 and the groove-welding portion 206. That is, the trepanning portion 208 as the connection portion with respect to the in-core instrumentation cylinder 204 in the groove-welding portion 206 is removed. At this time, the trepanning process is performed from the upper end of the groove-welding portion 206, that is, the inner surface of the lower end plate 66 to the downside of the groove-welding portion 206, that is, the base material 201 of the lower end plate 66. Furthermore, even when the groove-welding portion 206 of the in-core instrumentation cylinder 204 is trepanned by a cutting device, produced chips are collected by a suction device (not illustrated). As illustrated in FIGS. 4 and 12, in step S19, the in-core instrumentation cylinder 204 is extracted and collected upward from the attachment hole 203 of the lower end plate 66 by using an extraction device (not illustrated). As illustrated in FIG. 4, in step S20, the groove-welding portion 206 is inspected. First, as illustrated in FIGS. 13-1 and 13-2, the thickness of the buttered-welding layer 202 is measured in a manner such that a thickness measurement device (an ultrasonic inspection device) 122 attached to a processing head 121 moves along the surface of the buttered-welding layer 202 in the periphery of the groove-welding portion 206, and hence it is checked whether the thickness of the buttered-welding layer 202 is equal to or larger than a predetermined thickness. Next, as illustrated in FIGS. 14-1 and 14-2, the range of the groove-welding portion 206 is measured in a manner such that an area measurement device (an eddy current inspection device) 124 attached to a processing head 123 moves along the surface of the groove-welding portion 206, and hence it is checked whether the range of the groove-welding portion 206 is equal to or larger than a predetermined range. As illustrated in FIGS. 4 and 15-1, in step S21, the surface of the groove-welding portion 206 is buttered-welded by the buttered-welding device 125. That is, as illustrated in FIGS. 15-1 and 15-2, first, a tab plate 127 having a plug shape is positioned to the inside of the groove-welding portion 206, that is, the upper end of the attachment hole 203 by using a support rod 126. Next, a welding head 128 moves along the surface of the groove-welding portion 206 so as to form a surface buttered-welding portion 210 by buttered-welding the surface of the groove-welding portion 206. Furthermore, the tab plate 127 is not limited to a plug shape, but may be formed in a donut shape or the like. At this time, when the welding head 128 moves to the inner surface (the surface) of the lower end plate 66 (the buttered-welding layer 202) and the surface of the tab plate 127 beyond the surface of the groove-welding portion 206 while monitoring the processing state using a camera 129, the surface buttered-welding portion 210 extends to the lower end plate 66 and extends to the attachment hole 203. In this case, two layers or more of buttered-welding are performed on the surface of the groove-welding portion 206 so as to form the surface buttered-welding portion 210 thicker than at least the thickness of the groove-welding portion 206. Subsequently, the thickness of the surface buttered-welding portion 210 is measured in a manner such that a thickness measurement device (a penetration flaw inspection device), which is not illustrated, moves along the surface of the surface buttered-welding portion 210, and hence it is checked whether the thickness of the surface buttered-welding portion 210 is equal to or larger than a predetermined thickness. Then, as illustrated in FIG. 16, the tab plate 127 is removed by a cutting device 141. Further, the surface buttered-welding portion 210 extending to the attachment hole 203 is removed and shaped by the cutting device 141, and the inner surface of the attachment hole 203 is machined so as to shape the inner surface. Then, as illustrated in FIG. 17, the thickness (the depth) of the groove-welding portion 206 of the attachment hole 203 is measured by using an overlaid thickness measurement device (an eddy current inspection device) 130, and hence it is checked whether the thickness of the groove-welding portion 206 is equal to or larger than a predetermined thickness. As illustrated in FIGS. 4 and 18-1, in step S22, the groove-welding portion 206 (the main welding portion 206b) is grooved by a grooving device 132 attached to the processing head 131. That is, as illustrated in FIGS. 18-1 and 18-2, a welding groove 212 having a predetermined width W in the surface direction of the lower end plate 66 and a predetermined depth D in the thickness direction of the lower end plate 66 is formed by grooving the upper end near the attachment hole 203 in the inner surface of the lower end plate 66 and the surface buttered-welding portion 210 provided in the periphery of the attachment hole 203. In this case, the periphery of the attachment hole 203 has a curved shape, but the welding groove 212 has the same shape in the entire periphery. Further, the welding groove 212 is provided in the surface buttered-welding portion 210, and remains while not being grooved to the existing groove-welding portion 206. At this time, the welding groove 212 is inspected in a manner such that a penetration flaw inspection device (not illustrated) moves along the surface of the welding groove 212. As illustrated in FIGS. 4 and 19-1, in step S23, a new in-core instrumentation cylinder 204A formed of a nickel base alloy (for example, Inconel 690) is prepared, the upper end of the new in-core instrumentation cylinder 204A is restrained by a restraining device 134 provided in a processing head 133, and the in-core instrumentation cylinder 204A is inserted from the upside into the attachment hole 203 of the lower end plate 66. In this case, the new in-core instrumentation cylinder 204A includes, as illustrated in FIG. 1, a main body portion 204a which is inserted into the attachment hole 203 of the lower end plate 66, a lower body 204b which is continuous to the lower end of the main body portion 204a and has an outer diameter slightly smaller than the outer diameter of the main body portion 204a, a support portion 204c which is continuous to the upper end of the main body portion 204a and has an outer diameter smaller than the outer diameter of the main body portion 204a, an instrumentation equipment guide passage 204d which penetrates the main body portion 204a and the support portion 204c, and a groove portion 204f of which an end is opened to a stepped portion 204e between the main body portion 204a and the support portion 204c. The outer diameter R of the main body portion 204a is set to correspond to the inner diameter of the shaped attachment hole 203. Further, the groove portion 204f is continuous in the circumferential direction, and has a predetermined depth. For that reason, in the new in-core instrumentation cylinder 204A, an outer peripheral wall portion 204g located at the outside of the groove portion 204f has a thickness T smaller than the thickness of the main body portion 204a due to the groove portion 204f. Accordingly, when the in-core instrumentation cylinder 204A is inserted into the attachment hole 203 of the lower end plate 66, the outer peripheral wall portion 204g is disposed inside at least the surface buttered-welding portion 210. When the new in-core instrumentation cylinder 204A is fixed by welding, as illustrated in FIGS. 19-1 and 19-2, the new in-core instrumentation cylinder 204A is positioned to the lower end plate 66 so that the outer peripheral wall portion 204g is disposed inside the surface buttered-welding portion 210. Subsequently, the in-core instrumentation cylinder 204A is temporarily welded by a welding head 136 of the welding device 135 provided in the processing head 133. As illustrated in FIGS. 4 and 20-1, in step S24, the new in-core instrumentation cylinder 204A which is temporarily welded to the attachment hole 203 of the lower end plate 66 is fixed by groove-welding. That is, as illustrated in FIGS. 20-1 and 20-2, a new groove welding portion 213 is formed and fixed by groove-welding the outer peripheral portion of the in-core instrumentation cylinder 204A in a manner such that the welding head 136 of the welding device 135 moves along the welding groove 212 while monitoring the welding groove 212 using the camera 137. In this case, it is desirable that the material of the new in-core instrumentation cylinder 204A fixed to the lower end plate 66, the welding material of the surface buttered-welding portion 210, and the welding material used to fix the in-core instrumentation cylinder 204A be prepared as a nickel base alloy (for example, Inconel 690) as a welding material having higher stress corrosion cracking resistance than the nickel base alloy (for example, Inconel 600) as the welding material of the existing in-core instrumentation cylinder 204 or the groove-welding portion 206. However, the material of the new in-core instrumentation cylinder 204A and the welding material of the new groove welding portion 213 may be the same as that of the existing in-core instrumentation cylinder 204 or the groove-welding portion 206. For example, both may be stainless steel. Further, it is desirable that the welding material of the surface buttered-welding portion 210 be also the nickel base alloy (for example, Inconel 690) as the welding material having high stress corrosion cracking resistance. However, the same material may be used or stainless steel may be used. As illustrated in FIGS. 4 and 21, in step S25, the new groove welding portion 213 is inspected. That is, it is checked whether the inclination degree (the erection angle) of the in-core instrumentation cylinder 204A is within a predetermined range by an inclinometer (not illustrated) while the in-core instrumentation cylinder 204A is supported by a support portion 139 of a processing head 138. Further, it is checked whether a crack occurs by inspecting the new groove welding portion 213 in a manner such that the penetration flaw inspection device 140 moves along the surface of the new groove welding portion 213. Then, as illustrated in FIG. 4, in step S26, the cooling water is supplied into the nuclear reactor vessel body 62 after the conduit tube 85 is connected to the repaired instrumentation nozzle 83. Then, the in-core structure (the upper in-core structure 12A and the lower in-core structure 12B) is returned into the nuclear reactor vessel body 62 after various devices such as the seal plate 111 are removed, and then the nuclear reactor vessel head 63 is attached to restore the in-core structure. As illustrated in FIG. 1, in the repaired instrumentation nozzle 83, the existing groove-welding portion 206 having a semi-spherical shape at the inner surface side is provided in the attachment hole 203 of the nuclear reactor vessel body 62 having the buttered-welding layer 202 formed of stainless steel as the inner surface of the base material 201 formed of low-alloy steel, the surface buttered-welding portion 210 is provided in the surface of the groove-welding portion 206, the in-core instrumentation cylinder 204A formed of a nickel base alloy is inserted and positioned to the attachment hole 203, the new groove welding portion 213 formed of a nickel base alloy and having higher stress corrosion cracking resistance than the groove-welding portion 206 is provided in the welding groove 212 formed in the surface buttered-welding portion 210, and the in-core instrumentation cylinder 204A is fixed by the new groove welding portion 213. In this way, the nozzle repair method of the embodiment includes removing the connection portion (the trepanning portion) 208 with respect to the in-core instrumentation cylinder 204 in the groove-welding portion 206, removing the in-core instrumentation cylinder 204 from the lower end plate (the semi-spherical portion) 66, forming the surface buttered-welding portion 210 by buttered-welding the surface of the groove-welding portion 206, forming the welding groove 212 by grooving the surface buttered-welding portion 210, inserting the new in-core instrumentation cylinder 204A provided with the circumferential groove portion 204f outside the instrumentation equipment guide passage 204d into the attachment hole 203, and fixing the new in-core instrumentation cylinder 204A by groove-welding the welding groove 212. Accordingly, the welding groove 212 is formed by buttered-welding the surface of the groove-welding portion 206 in which the in-core instrumentation cylinder 204 is removed, the new in-core instrumentation cylinder 204A provided with the groove portion 204f is inserted into the attachment hole 203, and the in-core instrumentation cylinder 204A is fixed by groove-welding the welding groove 212. Since the new in-core instrumentation cylinder 204A is provided with the circumferential groove portion 204f, the thickness T of the outer peripheral wall portion 204g outside the groove portion 204f is smaller than the thickness of the main body portion 204a. In a technical standards for nuclear power generation equipment, the depth or the width of the welding joint is set to 0.75 times or more the plate thickness of the pipe. For that reason, the depth or the width of the new groove welding portion 213 (the welding groove 212) may be decreased in accordance with a decrease in the thickness T of the outer peripheral wall portion 204g of the in-core instrumentation cylinder 204A. In the nuclear reactor vessel body 62, the inner surface of the base material 201 formed of low-alloy steel is provided with the buttered-welding layer 202 formed of stainless steel. Since the buttered-welding layer 202 does not constitute the reinforced member of the nuclear reactor vessel body 62, the new groove welding portion 213 needs to be set within a range not reaching the buttered-welding layer 202. In the embodiment, since the new groove welding portion 213 exists within the area A of the existing groove-welding portion 206 while the width W and the depth D are set to be small, the repair may be easily performed, and the workability may be improved. In the nozzle repair method of the embodiment, when the surface buttered-welding portion 210 is formed on the surface of the groove-welding portion 206, buttered-welding is performed to the inner surface of the lower end plate 66, and buttered-welding is performed to the attachment hole 203. Accordingly, since the surface of the existing groove-welding portion 206 is coated by the new surface buttered-welding portion 210 without any gap, the stress corrosion cracking resistance may be improved. In the nozzle repair method of the embodiment, the inner surface of the attachment hole 203 is machined after the surface buttered-welding portion 210 is formed on the surface of the groove-welding portion 206. Accordingly, since the new in-core instrumentation cylinder 204A is inserted into the attachment hole 203 after the inner surface of the attachment hole 203 is machined, the attachment precision may be improved. In the nozzle repair method of the embodiment, the welding groove 212 is formed within the area of the groove-welding portion 206. Accordingly, since the new in-core instrumentation cylinder 204A may be appropriately fixed to the attachment hole 203, the durability of the instrumentation nozzle 83 may be improved. In the nozzle repair method of the embodiment, the new in-core instrumentation cylinder 204A includes the main body portion 204a which is inserted into the attachment hole 203, the small-diameter support portion 204c which is continuous to the upper end of the main body portion 204a, the instrumentation equipment guide passage 204d which penetrates the main body portion 204a and the support portion 204c, and the circumferential groove portion 204f of which the end is opened to the stepped portion 204e between the main body portion 204a and the support portion 204c. Accordingly, in the new in-core instrumentation cylinder 204a, since the groove portion 204f is opened to the stepped portion 204e, the groove portion 204f may be easily formed. Also, it is possible to simplify the in-core instrumentation cylinder 204A and to suppress the depth or the width of each of the welding groove 212 and the new groove welding portion 213 for the welding groove 212 in the in-core instrumentation cylinder 204A within a predetermined range. In the nozzle repair method of the embodiment, the welding material (the surface buttered-welding portion 210 and the new groove welding portion 213) used to fix the new in-core instrumentation cylinder 204A to the lower end plate 66 is prepared as a material having higher stress corrosion cracking resistance than the welding material of the groove-welding portion 206. Accordingly, it is possible to improve the stress corrosion cracking resistance compared to the existing instrumentation nozzle 83. Further, in the nuclear reactor vessel of the embodiment, the surface buttered-welding portion 210 is provided on the surface of the buttered-welding layer 202 in the attachment hole 203 of the nuclear reactor vessel body 62 having the buttered-welding layer 202 formed of stainless steel and formed on the inner surface of the base material 201 formed of low-alloy steel after the repair of the instrumentation nozzle 83, the welding groove 212 is formed on the surface buttered-welding portion 210, the in-core instrumentation cylinder 204A formed of a nickel base alloy is inserted and positioned to the attachment hole 203, the new groove welding portion 213 formed of a nickel base alloy and having higher stress corrosion cracking resistance than the groove-welding portion 206 is provided in the welding groove 212, and the in-core instrumentation cylinder 204A is fixed by the new groove welding portion 213. Accordingly, since the new in-core instrumentation cylinder 204A is fixed to the lower end plate 66 of the nuclear reactor vessel body 62 by the new groove welding portion 213 having high stress corrosion cracking resistance, the stress corrosion cracking resistance of the instrumentation nozzle 83 may be improved. In the nuclear reactor vessel of the embodiment, the circumferential groove portion 204f is formed by the opening of the end to the stepped portion 204e with respect to the main body portion 204a in the in-core instrumentation cylinder 204A. Accordingly, since the thickness of the outer peripheral wall portion 204g of the in-core instrumentation cylinder 204A is decreased by the groove portion 204f, the depth or the width of the new groove welding portion 213 (the welding groove 212) may be decreased. Accordingly, the workability of the repair of the instrumentation nozzle 83 may be improved, and the structure of the repaired instrumentation nozzle 83 may be simplified. Furthermore, in the above-described embodiment, the groove portion 204f which is formed in the in-core instrumentation cylinder 204A has a configuration in which the radial width is uniform in the depth direction, but the width may be tapered in the depth direction. However, the thickness of the outer peripheral wall portion 204g needs to be uniform. Further, in the above-described embodiment, a method of repairing the instrumentation nozzle 83 provided in the lower end plate 66 of the nuclear reactor vessel body 62 has been described, but the method may be also used to repair the instrumentation nozzle provided in the upper end plate of the nuclear reactor vessel head 63. Further, a case has been described in which the nozzle repair method of the invention is applied to the pressurized water reactor, but the nozzle repair method may be also applied to a boiling-water nuclear reactor. 61 NUCLEAR REACTOR VESSEL 62 NUCLEAR REACTOR VESSEL BODY 63 NUCLEAR REACTOR VESSEL HEAD 66 LOWER END PLATE (SEMI-SPHERICAL PORTION) 83 INSTRUMENTATION NOZZLE 84 IN-CORE INSTRUMENTATION GUIDE PIPE 85 CONDUIT TUBE 88 THIMBLE PIPE 201 BASE MATERIAL 202 BUTTERED-WELDING LAYER 203 ATTACHMENT HOLE 204 IN-CORE INSTRUMENTATION CYLINDER 204A IN-CORE INSTRUMENTATION CYLINDER 204a MAIN BODY PORTION 204c SUPPORT PORTION 204d INSTRUMENTATION EQUIPMENT GUIDE PASSAGE 204f GROOVE PORTION 204g OUTER PERIPHERAL WALL PORTION 205 GROOVING PORTION 206 GROOVE-WELDING PORTION 208 TREPANNING PORTION (CONNECTION PORTION) 210 SURFACE BUTTERED-WELDING PORTION 212 WELDING GROOVE 213 NEW GROOVE WELDING PORTION
052727394	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT With reference to FIGS. 4 and 5, a preferred embodiment of the apparatus and method in accordance with the present invention will be described relative to its use in a heat exchanger of the type found in a Westinghouse-type nuclear reactor system as described relative to FIGS. 1 and 2, above. However, as will also be made clear, the present invention is by no means limited to the specific environment used as an illustrative example. Furthermore, since, except for the specific zone illustrated in FIGS. 4 and 5, a heat exchanger in accordance with the present invention will be identical in every other respect to any conventional heat exchanger with which it is implemented, the detailed description will be limited to only those aspects which are novel to the present invention. Still further, it should be appreciated that while only a few of the tube openings 33 of the support plates 25 and one cold leg 19 of the bundle of heat exchanger tubes 16 is illustrated in FIGS. 4 and 5, for simplicity, the number and placement of such openings and heat exchanger tubes will conform with conventional practice. FIG. 4 shows the zone of the heat exchanger 15 which is in the area of feed nozzle 36. In this area, the nonradioactive water circulating through the heat exchanger 15 will have a flow path which, at least in part, has a crosswise directional flow component relative to the cold legs 19 of the heat exchanger tubes 16 which are extending axially through the steam generator vessel formed by wrapper 29 and shell 31. Since, as shown in FIGS. 3A, 3B, the parallel heat exchanger tubes extend through the openings 33 of the support plates 25 with a tube-to-plate clearance gap 35 to facilitate manufacture of the heat exchanger, the cross flow components of the nonradioactive water flow can cause the leg 19 of the heat exchanger tubes to vibrate within the oversized openings 33 if no corrective action is taken. However, in accordance with the present invention, in any such zones where cross flow components can act on a portion of the heat exchanger tubes extending axially through the support plates, the conventional manner of constructing and mounting the support plates 25 is replaced with that in accordance with the present invention. While in a typical Westinghouse-type nuclear steam generator the only such zone will be in the area of the feed nozzle 36, extending above and below it to an extent that will depend on the specific design, and the support plates in the remaining area of the heat exchanger will be conventionally constructed and mounted, the construction and mounting techniques in accordance with the present invention may be applied to any point in any type of heat exchanger where cross flows will occur, by design or circumstance, and would result in undesirable vibration and wear. More specifically, the present invention provides a means for applying a loading of the portion of the heat exchanger tubes that are subject to crosswise directional flow components which prevents them from vibrating. This loading is applied by causing alternate support plates to shift in opposite directions, transversely relative to the heat exchanger tubes, as the heat exchanger is brought up to operational temperatures and pressures when the steam generator is put into operation. As can be seen in FIGS. 4 and 5, alternate support plates 25a, 25b have one end secured and one end free. In the case of the alternate plates 25a, the support plates are connected to the wall of the wrapper 29 while the end adjacent the central divider 27 is free of connection to the central divider plate. On the other hand, the alternate support plates 25b are connected to the central divider plate 27 with there being no connection between the wrapper 29 and the adjacent edge portion of the support plates 25b. In this regard, while an expansion gap 54, of approximately 0.5" (12.7 mm) is shown as existing between the free ends of the support plates 25a, 25b and the central divider plate 27 or the wrapper 29, including its preheater distribution box 37, respectively, the provision of such an expansion gap 54 is not essential to the practice of the present invention. The connection of the support plates 25a, 25b to the central divider 27 or the wrapper 29 is preferably a bracket-type connection comprised of a plurality of hook-shaped mounting brackets 50, the free ends of which are received in elongated mounting slots 52. In the illustrated embodiment, the mounting brackets are shown attached to the central divider plate and the wrapper with the mounting slots being formed in the support plates 25a, 25b. However, this relationship can be reversed or other forms of attachment utilized so long as the form of the connection selected is capable of exerting a pulling force upon the support plates which will shift them toward the central divider plate or the wrapper. In this regard, it is noted that the connection between the support plates 25a, 25b and the respective one of the central divider plate and wrapper with which the connection is formed is not intended to replace the usual vertical support provided, for example, via stay rods and spacer pipes, and merely serves to produce a relative displacement that is derived from thermal motions of the support plates and thermal and pressure motion of the wrapper and distribution box. Once the magnitude of the relative displacement derived from these motions exceeds the magnitude of the tube-to-plate clearance gap 35, preloading forces are developed in the tubes. Since every other plate imposes an oppositely directed preloading force, a passive, positive tube support is generated when the unit is brought up to its operating temperatures and pressures. The magnitude of the preload forces can be adjusted through selection of the stiffness of the central divider plate, the diameter of the heat exchanger tubing and the tube support span within the range of such values that are standard in the industry. As can be seen most clearly in FIG. 5, each of the elongated slots 52 has a length that is greater than the lateral width of the respective hook that is received in it. This permits lateral movement of the end of each mounting bracket 50 within the respective slot 52 so as not to affect other thermal expansions. Furthermore, while the width of the slots 52 can be set to produce a snug fitting of the mounting brackets 50, these slots can have a width that is greater than the thickness of the mounting brackets 50 so long as the slots are positioned so that the facing sides of the slot and bracket which must engage to produce a pulling effect on the plates. In FIG. 4, this means that the surface of the end of the brackets 50 that faces the central divider plate 27 would engage with the facing wall of the slots of plates 25b, and the side of the mounting brackets facing the wrapper 29 would engage the facing surface of the slots in plates 25a at ambient temperatures and pressures. Additionally, as shown in FIG. 5, the central divider plate can be keyed to shell 31 through the wrapper 29 and together with the selection of the points of attachment can serve to "tune" the motion connection for the support plates so as to obtain the desired stiffness for producing the above-noted relative displacement from the thermal motions of the support plates and thermal/pressure motion of the vessel walls and feed nozzle. Since the secondary of a nuclear steam generator is typically built from the bottom up, the illustrated arrangement in which the hook-shaped mounting brackets 50 engage within the slots 52 from above makes it easier to add the brackets 50 after mounting of the plates 25 without influencing the positioning of the plates due to the provision of these mounting brackets. However, if other assembly techniques were to be used for construction of the heat exchanger, the hook-shaped brackets 50 could engage the slots 52 of the support plates 25 from below. Likewise, while the support plates 25 have been shown as being solid plates within which openings have been formed, they could be open flow supports of a grid-like construction or any other known support plate type. Similarly, the circulation path can be a vertical or axial flow through openings in the plates or can be a forced back-and-forth motion along the plates and through cut-out openings in them. Thus, the concepts of the present invention are generically applicable to any and all types of heat exchanger flow paths used in heat exchangers of the general type composed of a plurality of parallel heat exchanger tubes mounted extending through a plurality of support plates within a vessel. In view of the foregoing, it should now be apparent that the present invention is susceptible to numerous permutations, modifications and embodiments beyond that disclosed herein so that the present invention should not be viewed as limited to the specific embodiment disclosed herein, and, instead, it is intended to encompass the full scope of the appended claims.
	claims	1. A process of producing essentially copper 64 -free copper 64 comprising: irradiating an enriched zinc 70 target with protons of an energy from about 10 MeV to about 25 MeV to produce copper 67 ; and, separating copper 67 from the irradiated target to yield an essentially copper 64 -free copper 67 product having a copper 64 to copper 67 ratio of less than 0.1 to 1. 2. The process of claim 1 further including separating enriched zinc 70 from the irradiated target and recycling the separated enriched zinc 70 into an enriched zinc 70 target for subsequent irradiation. claim 1 3. The process of claim 1 wherein said enriched zinc 70 target contains at least about 70 percent zinc 70 . claim 1 4. The process of claim 1 wherein said enriched zinc 70 target contains about 99 percent zinc 70 . claim 1
	abstract	A Thorium molten salt energy system is disclosed that includes a proton beam source for producing a proton beam, that can vary between a first energy level and a second energy level of, where the generated proton bean can be directed into a main assembly containing both Thorium-containing molten salt and Thorium fuel rods, each containing an inner Beryllium element and an outer solid Thorium element. The generated proton beam can be shaped and directed to impinge upon Lithium within the molten salt to promote the generation of thermal neutrons and the fission of Uranium within the molten salt. The generated proton beam can also be shaped and directed to impinge upon the Beryllium within the Thorium fuel rods to promote the generation of high energy neutrons.
	summary
059149957	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a nuclear reactor fuel assembly having a fuel assembly base 2 and a fuel assembly head 3, between which fuel rods 4 are disposed parallel to each other. These fuel rods 4 contain nuclear fuel in a jacket tube which is closed in gas-tight fashion at both ends. Each fuel rod 4 has one end extending loosely through a lead-through in the fuel assembly head 3 and another end resting loosely on the fuel assembly base 2. Each fuel rod 4 is fed through a respective opening in a plurality of grid-shaped spacers 5, which are also spaced apart from and located next to each other, as viewed in the longitudinal direction of the nuclear reactor fuel assembly. The fuel assembly base 2 and the fuel assembly head 3 each have a square profile, and a water tube 6 having a square cross section is disposed in the center of this square profile. Each of the two mutually parallel sides of this square cross section are parallel to two mutually parallel sides of the square profile of the fuel assembly base 2 and the fuel assembly head 3. The water tube 6 has a first open lower end 7 with which the water tube is screwed into a lead-through 8 in the fuel assembly base 2. As is shown particularly clearly in FIG. 2, an end cap 9 has been inserted into a second upper end of the water tube 6 and is welded to the water tube 6. This end cap 9 has a lead-through 10 which is coaxial with the water tube 6. One partial body 12 and another partial body 11 are also seen in FIG. 2. The other partial body 11 which has outlet conduits for water from the water tube 6, has a lower first end that is screwed into the lead-through 10. The other partial body 11 forms an elongated extension body at the upper end of the water tube 6, together with the one partial body 12 which is coaxial with the other partial body 11 and the water tube 6. The one partial body 12, which is coaxial with the other partial body 11, has a lower second end 13 which is screwed into an upper second end of the other partial body 11, and an upper second end of the one partial body 12 engages a lower end of a sleeve 14 in the fuel assembly head 3. Seen as a whole, the first or lower end of the elongated extension body 11, 12 is screwed into the second end of the water tube 6 or the second end of the water tube 6 is screwed into the first or lower end of the elongated extension body 11, 12. The second or upper end of the elongated extension body 11, 12 grips and is held at the fuel assembly head 3. On the exterior of the jacket, the upper second end of the one partial body 12 has three pairs of radially directed tongues 15, which are spaced apart from each other in the longitudinal direction of the one partial body 12. As is seen in the cross section according to FIG. 3 along with FIG. 2, the two tongues 15 of each pair are formed by legs of two vertical and opposite angles a with respect to a penetration point S of a longitudinal axis L of the one partial body 12. The vertical and opposite angles .alpha. have the same value for all of the pairs of tongues 15 and are less than 90.degree.. All three of the pairs of tongues 15 are furthermore in alignment with each other, so that these tongues 15 are rotationally oriented in relation to the longitudinal axis L of the one partial body 12. A retaining sleeve 16 is inserted into the upper end of the sleeve 14 and is coaxial with the one partial body 12 and rotatable around its longitudinal axis inside the sleeve 14 to form a bayonet connection between the one partial body 12 and the fuel assembly head 3. In addition, the retaining sleeve 16 has a shoulder 24 on its exterior on the jacket, with which this retaining sleeve 16 is supported on an edge of the upper end of the sleeve 14. On the inside of the jacket, the retaining sleeve 16 has three pairs of tongues 17 which are spaced apart from each other in the direction of the longitudinal axis of the retaining sleeve 16 and thus of the one partial body 12. These pairs of tongues 17 are also defined by the legs of the two vertical and opposite angles .alpha. which are of the same size as the vertical and opposite angles .alpha. limiting the tongues 15. The pairs of tongues 17 in the retaining sleeve 16 are also in alignment, when viewed in the direction of the longitudinal axis of the retaining sleeve 16. Furthermore, these tongues 17 of the retaining sleeve 16 grip the tongues 15 on the one partial body 12 from behind, if two protrusions 18, which are disposed on the exterior of the jacket of the retaining sleeve 16 in a diameter of this retaining sleeve 16, have each engaged a groove 19 in the edge on the upper end of the sleeve 14. Both grooves 19 are also located on a diameter of the sleeve 14. A thread is located on the end of the one partial body 12 that is screwed into the other partial body 11. An optional check or counter nut 20 is seated on the thread and braced against the other partial body 11. The optional check nut 20 may be welded to the one partial body 12 by a hollow weld 21 in order to secure it against rotation, and a thread in the check nut 20 and the associated thread on the one partial body 12 are disposed at a distance from the weld 21. The check nut 20 is welded to the other partial body 11 by a lip weld or V-weld 22. Furthermore, a helical spring 23, which is coaxial with the one partial body 12 and is placed under pressure, is seated on the outside of the one partial body 12 and is supported at one end on the check nut 20 and at the other end on the fuel assembly head 3 and in this way presses the protrusions 18 on the outside of the retaining sleeve 16 into the grooves 19 at the edge of the upper end of the sleeve 14. The one partial body 12, which is screwed into the other partial body 11 and on which the helical spring 23 and the check nut 20 are already seated, is aligned with respect to the water tube 6 which has a square cross section. Then the check nut 20 is braced against the other partial body 11 and is welded to the one partial body 12 and the other partial body 11. Following this, the fuel assembly head 3 is pushed on the one partial body 12 so that one end of the fuel rods 4 engage the inside of the fuel assembly head 3. The retaining sleeve 16 is then placed on the upper end of the one partial body 12. Since the tongues 15 on the exterior of the upper end of the one partial body 12 are rotationally oriented, the tongues 17 on the interior of the jacket of the retaining sleeve 16 fit exactly between the tongues 15 on the exterior of the jacket of the one partial body 12. When turning the retaining sleeve 16 by 90 .degree. about its longitudinal axis, the protrusions 18 on the exterior of the retaining sleeve 16 are locked into the two grooves 19 at the upper end of the sleeve 14, so that the fuel assembly head 3 is fixed on the one partial body 12. In briefly summarizing the structure of FIG. 3, the tongues 17 are attached at the inner jacket surface of the retaining sleeve 16. The retaining sleeve 16 is rotatable about its longitudinal axis while it is inserted into the sleeve 14 of the fuel assembly head 3 and it has projections formed at the outer jacket surface arranged along a diameter of the retaining sleeve 16. The projections 18 are locked in the groove 19 formed at the upper edge of the sleeve 14. Referring now to FIGS. 4a-4f, which depict a series of assembly steps with the aid of a model of a preferred exemplary embodiment of the invention, there is shown a fuel assembly head with the sleeve 14 and a groove 19 formed at the edge at the upper end at the sleeve 14. The retaining sleeve 16 sits in the sleeve 14. The inside surface of the retaining sleeve 16 is provided with tongues 17 and on the outside jacket there is formed a protrusion 18. That protrusion 18 lies on the upper edge of the sleeve 14, outside of the groove 19. FIG. 4b illustrates the end of the partial body 12 of the extension body, which partial body is to engage in the fuel assembly head 3. The tongues 15 are clearly shown. Also, the upper ends of four fuel rods are shown. FIG. 4c illustrates how the fuel assembly head of FIG. 1 is placed onto the partial body 12 of the extension body and onto the four upper ends of the fuel rods. FIG. 4d illustrates how the fuel assembly head placed on the upper end of the partial body 12 of the extension body and onto the fuel rods is pressed against the helical spring shown in FIG. 3. The helical spring is thereby pretensioned. FIG. 4e shows a situation in which the retaining sleeve 16 has been rotated from the position of FIG. 4d. The tongues 17 on the inside of the jacket of the retaining sleeve 16 engage exactly between the tongues 15 on the outer jacket of the partial body 12. Also, the retaining sleeve 16 is positioned such that the projection 18 may engage in the groove 19. FIG. 4f, finally, shows how the retaining sleeve 16 is locked in the groove 19 of the sleeve 14. In this position, the sleeve 14 is pressed against the retaining sleeve 16 by the biased helical spring. Accordingly, the retaining sleeve 16 can no longer be loosened, unless the fuel assembly head with the sleeve 14 is pressed downwardly against the helical spring (FIG. 3), such that it assumes the position shown in FIG. 4d. The term "bayonet closure" as recited in the claims may be understood as follows: The fuel assembly head 3 in FIG. 2 is pushed on the partial body 12 against the helical spring 23 as far as possible in the direction of the water tube 6. Then the retaining sleeve 16 can easily be placed on the end of the partial body 12 with the tongues 15, so that the tongues 17 on the inside of the rotating sleeve 16 fit exactly between the tongues 15 on the outside of the partial body 12. The retaining sleeve 16 is then rotated about its axis by 90.degree., so that the tongues 17 engage between the tongues 15. At this point, the projections 18 of the retaining sleeve are placed exactly above the grooves 19. If, at that point, the helical spring 23 is allowed to push the partial body 12 away from the water tube 6, the projections 18 engage in the grooves 19 and the step 24 on the outside of the retaining sleeve 16 sits on the upper edge of the sleeve 14. Now the bayonet closure is tightly closed.
	claims	1. A movable carriage for moving an article support member in a lithographic apparatus, said article support member constructed and arranged to move and support an article to be placed in a beam path of said lithographic apparatus, said carriage comprising a compartmented composite structure. 2. A movable carriage according to claim 1, wherein said carriage is constructed and arranged to provide an interface between a long stroke and a short stroke actuator in the lithographic apparatus, and wherein said carriage further comprises a first sensor for driving said long stroke actuator and a second sensor, positioned at a distance from said first sensor, for driving said short stroke actuator so as to arrange said article to be placed on a predetermined location. 3. A movable carriage according to claim 1, further comprising a non-composite mounting interface and/or cooling interface for mounting and/or cooling a short stroke actuator. 4. A movable carriage according to claim 3, wherein said carriage is uncooled. 5. A movable carriage according to claim 3, wherein said non-composite mounting interface comprises a metal and/or ceramic material glued to said composite material. 6. A movable carriage according to claim 3, wherein said cooling interface comprises a metal cooling surface. 7. A movable carriage according to claim 6, wherein said metal cooling surface is coupled to a duct for ducting coolant. 8. A movable carriage according to claim 7, wherein said duct comprises a composite material. 9. A movable carriage according to claim 1, wherein said composite is chosen from a group of low coefficient of thermal expansion (CTE) materials. 10. A movable carriage according to claim 9, wherein said composite comprises carbon fiber. 11. A movable carriage according to claim 1, wherein said composite structure comprises at least one composite box structure. 12. A movable carriage according to claim 11, wherein said box structure comprises a base plate and upstanding contours. 13. A movable carriage according to claim 12, wherein the upstanding contours are integral with the base plate. 14. A movable carriage according to claim 12, wherein the upstanding contours comprise an L-form extremal mounting profile for gluing to a cover plate. 15. A movable carriage according to claim 11, wherein said composite box structure comprises a rectangular outer box and a triangular inner box provided in said outer box. 16. A movable carriage according to claim 11, wherein said composite box structure comprises a composite rib structure. 17. A movable carriage according to claim 16, wherein said rib structure is glued to the box structure. 18. A movable carriage according to claim 17, wherein said rib structure comprises an L-form extremal mounting profile for gluing to a cover plate. 19. A movable carriage according to claim 1, wherein said composite structure comprises a plurality of boxed compartments glued together.
	claims	1. A method for fabricating precision x-ray collimators including precision focusing x-ray collimators comprising the steps of: providing an electrically conductive substrate; coating said substrate with a layer of x-ray resist; utilizing an intense collimated radiation source for exposing said layer of x-ray resist with a pattern of x-ray; said pattern delineating a grid of apertures to collimate the x-rays defined by a grating mask disposed proximate to said substrate; said pattern defined by first scanning said substrate vertically in a z-direction while varying an angle of inclination of said substrate as a function of a vertical position during the first scan; rotating the substrate by 90 degrees in an X-Z plane while keeping said grating mask fixed; and second scanning said rotated substrate vertically in said z-direction while varying said angle of inclination of said substrate as a function of a vertical position during the second scan for fabricating x-ray collimators having precision focusing in two directions; removing exposed parts of said x-ray resist; and electroplating regions of said removed x-ray resist. 2. A method for fabricating precision x-ray collimators as recited in claim 1 wherein the step of providing an electrically conductive substrate includes the step of coating a substrate with a layer of electrically conductive material. claim 1 3. A method for fabricating precision x-ray collimators as recited in claim 2 wherein the step of coating a substrate with a layer of electrically conductive material includes the steps of coating a substrate with a layer of metal. claim 2 4. A method for fabricating focusing x-ray collimators as recited in claim 1 wherein the step of utilizing an intense collimated radiation source for exposing said layer of x-ray resist with a pattern of x-ray includes the steps of utilizing a synchrotron radiation source for exposing said layer of x-ray resist with a pattern of x-ray. claim 1 5. A method for fabricating precision x-ray collimators as recited in claim 1 wherein said first and second scanning steps produce x-ray collimators having different focus distance relative to the X direction versus the Z direction. claim 1 6. A method for fabricating precision x-ray collimators as recited in claim 1 wherein said first and second scanning steps produce x-ray collimators having different focus distance as a function of the distance from the center of the collimator. claim 1 7. A method for fabricating precision focusing x-ray collimators as recited in claim 1 wherein the step of utilizing an intense collimated radiation source for exposing said layer of x-ray resist with said pattern of x-ray includes the steps of utilizing a two stage scanner, a first stage of said two stage scanner for moving said substrate in a first direction and a second stage of said two stage scanner mounted on said first stage for rotating said substrate in a plane about the first direction. claim 1 8. A method for fabricating precision x-ray collimators as recited in claim 1 further includes the step of removing remaining resist from said substrate after electroplating regions of said removed x-ray resist. claim 1 9. A method for fabricating precision x-ray collimators as recited in claim 1 wherein the step of coating said substrate with said layer of x-ray resist includes the steps of coating said sub strate with a positive x-ray resist polymethylmethacrylate (PMMA) or a negative x-ray resist epoxy. claim 1 10. A method for fabricating precision x-ray collimators as recited in claim 1 wherein the step of removing exposed parts of said x-ray resist includes the steps of removing exposed parts of said x-ray resist polymethylmethacrylate (PMMA) or said negative x-ray resist epoxy. claim 1 11. A method for fabricating precision x-ray collimators as recited in claim 1 wherein the step of electroplating regions of said removed x-ray resist includes the step of electroplating regions of said removed x-ray resist with a metal capable of absorbing x-rays. claim 1 12. A method for fabricating precision x-ray collimators as recited in claim 11 wherein the step of electroplating regions of said removed x-ray resist with said metal capable of absorbing x-rays includes the steps of electroplating one of gold, nickel, copper, platinum, zinc, lead, tin and alloys thereof, or another galvanic metal into regions of said removed x-ray resist. claim 11

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