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044302908	summary	BACKGROUND AND SUMMARY OF THE INVENTION This invention relates to plasma confining devices intended to generate a thermonuclear reaction, and more particularly to a plasma confining device which is additionally applied to a cusp magnetic field and a mirror magnetic field with linear open ends which are used in plasma confinement system with magnetic field. An object of this invention is to provide a plasma confining device in which, with respect to a plasma confinement system of open end type in which the particle loss is great essentially, the particle loss and accordingly the energy loss are reduced, whereby the plasma confining performance is remarkably improved. The foregoing object and other objects of the invention will become more apparent from the following description and the appended claim when read in conjunction with the accompanying drawings.
	abstract	Microlithography apparatus and methods are disclosed for achieving high-resolution pattern transfer of a pattern onto a substrate, such as a semiconductor wafer, using extreme ultraviolet (EUV, also termed soft X-ray) radiation. The apparatus include an imaging-optical system (projection-optical system) capable of receiving pattern-encoding EUV light from a mask and forming an image of the pattern on the substrate. The desired wavelength of the EUV light is 20 nm to 50 nm, and the imaging-optical system includes multiple reflective mirrors having aspherical surficial profiles and multilayer-film reflective surfaces. The apparatus are configured especially to achieve a pattern-element resolution, of the projected image, of 70 nm or finer.
	claims	1. A spacer for holding a number of elongated fuel rods intended to be located in a nuclear plantthe spacer enclosing a number of cells, each cell having a longitudinal axis and arranged to receive a fuel rod in such a way that the fuel rod extends substantially in parallel with the longitudinal axis,each cell being formed by a sleeve, having an upper edge and a lower edge,the sleeve including a number of elongated abutment surfaces, which project inwardly towards the longitudinal axis and extend substantially in parallel with the longitudinal axis for abutment to the fuel rod to be received in the cell, andthe lower edge, seen transversely to the longitudinal axis, having a wave shape with wave peaks, which are aligned with a respective one of said elongated abutment surfaces, and wave valleys located between two adjacent ones of said elongated abutment surfaces;wherein the upper edge, seen transversely to the longitudinal axis, has a wave shape with wave peaks, which are aligned with a respective one of said elongated abutment surfaces, and with wave valleys located between two adjacent ones of said elongated abutment surfaces,each of said elongated abutment surfaces extending from a respective one of said wave peaks of the upper edge to a respective one of said wave peaks of the lower edge, andthe sleeves abut each other in the spacer along respective connection areas, each extending substantially parallel to the longitudinal axis between one of said wave valleys of the upper edge and one of said wave valleys of the lower edge; andsaid connection area having a length and said sleeve having a thickness, said thickness being less than 0.24 mm, said length of said connection area and said thickness of said sleeve being configured to make said elongated abutment surfaces rotatable with respect to a center point of said connection area to permit a certain inclination of the fuel rod. 2. A spacer according to claim 1, wherein each sleeve includes at least four of said abutment surfaces. 3. A spacer according to claim 1, wherein each of said abutment surfaces is formed by a respective ridge projecting inwardly towards the longitudinal axis. 4. A spacer according to claim 1, wherein the sleeves are permanently connected to each other by means of weld joints. 5. A spacer according to claim 1, wherein said sleeves are permanently connected to each other by means of weld joints, wherein said weld joints include an edge weld at said connection area at least one of the upper edge and the lower edge. 6. A spacer according claim 1, wherein substantially each sleeve is manufactured of a sheet-shaped material that is bent to the sleeve shape. 7. A spacer according to claim 6, wherein the sheet-shaped material before said bending has a first connection portion in the proximity of the first end of the sheet-shaped material and a second connection portion in the proximity of a second end of the sheet-shaped material, wherein the first end overlaps the second end of the sleeve after said bending. 8. A spacer according to claim 7, wherein the first connection portion and the second connection portion are permanently connected to each other by means of at least one weld joint. 9. A spacer according to claim 8, wherein said weld joint includes a spot weld. 10. A spacer according to claim 1, wherein substantially each sleeve is manufactured from a tubular material which is worked to the wave shape of the upper edge and the lower edge. 11. A spacer according to claim 1, wherein the sleeve seen in the direction of the longitudinal axis has four substantially orthogonal long sides, wherein each long side includes one of said abutment surfaces. 12. A spacer according to claim 11, wherein each long side includes one of said wave peaks of the upper edge and one of said wave peaks of the lower edge. 13. A spacer according to any claim 11, wherein the sleeve, seen in the direction of the longitudinal axis, has four substantially orthogonal short sides, wherein each short side connects two of said long sides and includes a portion of one of said wave valleys of the upper edge and a portion of one said wave valleys of the lower edge. 14. A spacer according to claim 6, wherein the sleeve has a thickness of the material, which is less than or equal to 0.20 mm. 15. A spacer according to claim 6, wherein the sleeve has a thickness of the material, which is less than or equal to 0.18 mm. 16. A spacer according to claim 1, wherein the nuclear plant is arranged to permit re-circulation of a coolant flow and wherein the spacer is arranged to be located in the coolant flow, the spacer including at least one vane for influencing the coolant flow. 17. A spacer according to claim 7, wherein the nuclear plant is arranged to permit re-circulation of a coolant flow, wherein the spacer is arranged to be located in the coolant flow, and wherein the spacer includes at least one vane for influencing the coolant flow, said vane being formed by a portion of the material, which extends from the first connection portion. 18. A spacer according to claim 16, wherein the sleeve includes a slit, which extends from at least one of the upper edge and lower edge and which permits outward bending of a part of the sleeve for forming said vane. 19. A spacer according to claim 17, wherein said vane is inclined in relation to the longitudinal axis. 20. A spacer according to claim 16, wherein the sleeve seen in the direction of the longitudinal axis has four substantially orthogonal long sides, wherein said vane extends outwardly from one of said long sides. 21. A spacer according to claim 1, wherein the spacer, seen in the direction of the longitudinal axis, has a substantially rectangular shape and includes at least two separate outer edge elements which extend along a respective side of the spacer. 22. A spacer according to claim 21, wherein one of the four corners of the rectangular shape is reduced through the lack of outer sleeve, and that the spacer includes a separate inner edge element, which extends along two of said sides and along said reduced corner. 23. A spacer according to claim 22, wherein the inner edge element includes a vane, which is located at said reduced corner and which is inclined upwardly and inwardly towards a centre of the spacer. 24. A fuel unit for a nuclear plant including a number of elongated fuel rods and a number of spacers for holding the fuel rods, whereineach of the spacers enclose a number of cells, which each have a longitudinal axis and is arranged to receive one of said fuel rods in such a way that the fuel rod extends in parallel to the longitudinal axis,each cell is formed by a sleeve, which has an upper edge and a lower edge,the sleeve includes a number of elongated abutment surfaces, which project inwardly towards the longitudinal axis and extend substantially in parallel with the longitudinal axis for abutment to the fuel rod to be received in the cell;the lower edge, seen transversely to the longitudinal axis, has a wave shape with wave peaks, which are aligned with a respective one of said abutment surfaces, and wave valleys located between two adjacent ones of said abutment surfaces;wherein the upper edge, seen transversely to the longitudinal axis, has a wave shape with wave peaks, which are aligned with a respective one of said abutment surfaces, and with wave valleys located between two adjacent ones of said abutment surfaces,each of said elongated abutment surfaces extending from a respective one of said wave peaks of the upper edge to a respective one of said wave peaks of the lower edge, andthe sleeves abut each other in the spacer along respective connection areas, each extending substantially parallel to the longitudinal axis between one of said wave valleys of the upper edge and one of said wave valleys of the lower edge;said connection areas having a length and said sleeve having a thickness, said thickness being less than 0.24 mm, said length of said connection area and said thickness of said sleeve being configured to make said elongated abutment surfaces rotatable with respect to a center point of said connection areas to permit a certain inclination of the fuel rod.
	summary
050154354	summary	FIELD OF THE INVENTION The invention relates to a device for demountable fastening of a guide tube into an end fitting of a fuel assembly of a nuclear reactor cooled with light water and in particular of a reactor cooled by pressurized water. BACKGROUND OF THE INVENTION Water-cooled nuclear reactors and, in particular, pressurized-water nuclear reactors comprise assemblies consisting of a bundle of fuel rods of great length arranged parallel to each other and held in a framework consisting of guide tubes, spacers and two end fittings. The guide tubes are arranged in the longitudinal direction of the assembly and are connected to transverse spacers arranged at regular intervals along the length of the assembly. At each of their ends, the guide tubes are also connected to either of the two end fittings constituting the stiffening and closure parts of the assembly. The fuel rods of the assembly form a bundle in which the rods are parallel to each other and arranged, in the transverse sections of the assembly, according to a uniform lattice determined by the spacers. Certain positions in the lattice are occupied by guide tubes which are generally connected rigidly to the spacers. The guide tubes have a length which is greater than the length of the fuel rods and are placed in the bundle so as to have a part which projects relative to the bundle of fuel rods at each of their ends. The end fittings are fastened to these projecting parts of the guide tube so as to ensure the closure of the assembly at each of its ends. The fuel rods consist of sintered pellets of nuclear fuel material stacked inside a metal sheath isolating the pellets from the fluid surrounding the fuel assembly. In the case of a sheath rupture in a fuel assembly rod, it is necessary to replace this rod very quickly to avoid leakages of radioactive product into the reactor coolant fluid. To gain access to the fuel rods and to perform their replacement, it is necessary to dismantle one of the end fittings of the assembly, and this involves removing the connections between the corresponding ends of the guide tubes and the end fitting. The end fittings comprise passage holes reproducing the lattice of the guide tubes in each of which a guide tube is engaged and fastened. In order to make it possible to replace defective rods in fuel assemblies, new fuel assemblies have been designed and developed, comprising guide tubes whose connection to at least one of the end fittings is demountable. To perform the replacement of the defective fuel rods, the assembly is placed under water in a vertical position, in a pool such as a storage pool; the assembly rests on the bottom of the pool by means of its lower end fittings. The other, upper end fitting is accessible under a certain depth of water from above the pool. In a known type of demountable fuel assembly, the parts of the guide tubes engaged in the upper end fitting of the assembly comprise a radially expandable part which can be, for example, attached to the end of the guide tube. This expandable part can consist of a split ring having a part which projects radially outwards and which is intended to be housed in a cavity of corresponding shape machined inside the end fitting, in the passage hole for the guide tube. A locking sleeve introduced inside the guide tube produces the radial expansion of the split ring and the interlocking of the guide tube by its radially projecting part which fits inside the cavity machined in the end fitting. The guide tube is engaged in the hole passing through the adapter plate of the end fitting only over a certain length, the remaining part of the hole, above the guide tube, opening out onto the upper face of the adapter plate of the end fitting. There is a known demountable connection for a guide tube of a fuel assembly of the type described above, comprising a locking sleeve having a ring ensuring the expansion of the guide tube and extended axially by a fastening shell which, when the locking sleeve is fitted into the guide tube, is housed in the part of the hole situated above the guide tube and opening onto the upper face of the adapter plate. Radial cavities are provided in this part of the hole of the adapter plate and, after the locking sleeve has been fitted into the guide tube, the fastening shell is distorted so that the distorted parts of this fastening shell enter inside the cavities to produce the axial and rotational locking of locking sleeve. Efficient fastening of the guide tube is thus obtained by means of operations which can be performed without difficulty from above the assembly. However, the dismantling of the guide tube makes it necessary, as a first step, to perform the extraction of the locking sleeve, which is held in the end fitting by the fastening shell. This operation can be performed by a tool which is introduced into the sleeve and which comprises radially moveable parts which can be placed under the lower end of the sleeve. Traction is applied to the tool to allow the fastening shell to be unlocked and the sleeve to be extracted from the guide tube. This operation of extracting the locking sleeve before dismantling the end fitting of the assembly requires the use of complex tooling whose positioning, in the axial direction, inside the opening of the end fitting and of the sleeve, must be adjusted with great accuracy, so that the movable parts come to bear on the lower end of the sleeve when traction is applied to the tool. In addition, it is very difficult to check that the tool has been correctly fitted inside the sleeve, from the upper level of the pool. Furthermore, the extraction of the sleeve is produced by a thrust on its lower end, with the result that this sleeve is liable to undergo some buckling, which makes the extraction more difficult. Finally, the distorted regions of the fastening shell entering the cavities of the end fitting are extracted from the cavities only with difficulty when a thrust is applied to the lower end of the sleeve. There has also been disclosed in EP-A-0.098.774 a locking sleeve comprising an annular groove machined in the inner part of the sleeve, in an upper radially widened part of the locking sleeve also comprising the deformable shell. Such a locking sleeve has some advantages, as the extraction of the sleeve may be effected by introducing a tool in the annular groove and by exerting traction on the sleeve through a part of its inner bore. However, such a sleeve, having a radially widened upper part and a radially extending outer rim separating the upper part from the lower locking part of the sleeve, requires the end fitting of the assembly to be specially machined, at the level of the opening receiving the guide tube. Additionally, the shape of the sleeve requires more complicated and expensive forming or machining operations. SUMMARY OF THE INVENTION The purpose of the invention is therefore to provide a device for demountable fastening of a guide tube into an end fitting of a fuel assembly of a nuclear reactor cooled by light water, comprising a bundle of parallel fuel rods held in a framework consisting of guide tubes, spacers and end fittings fastened to the ends of the guide tubes. At least one of the end fittings is fastened demountably to one of the ends of each of the guide tubes by means of an end part of the guide tube which can be distorted radially and which has an interlocking part projecting radially outwards, engaged inside and over a part of the length of an opening passing through the end fitting and comprising, in its part receiving the guide tube, an annular widening intended to receive the interlocking parts of the guide tube. Radial expansion of the end of the guide tube and the holding of its interlocking parts in the annular widening of the opening of the end fitting are provided by a locking sleeve comprising a ring for expanding the guide tube and a shell for fastening in the end fitting, remaining projecting at the end of the guide tube in the locking position of the sleeve inside a part of the opening of the end fitting which does not receive the guide tube. This part of the opening of the end fitting comprises at least one radial cavity inside which a part of the locking shell is distorted radially to ensure the fastening of the locking sleeve; this device has a simple shape and can be placed and extracted from a guide tube in a simple and efficient manner. For this purpose: (1) the outer surface of the locking sleeve has successively in the axial direction a cylindrical part and a frusto-conical part without any radially protruding part; PA1 (2) the fastening shell constituting the upper cylindrical part of the sleeve is integral with the lower frusto-conical part constituting the ring for expanding the tube and is substantially less thick than the upper part of the frusto-conical ring for expanding the tube; and PA1 (3) an interlocking annular groove is machined in the upper part of the internal surface of the ring for expanding the tube.
	summary
051184613	abstract	In an apparatus including a fluid circulation unit for allowing a fluid in a container to be circulated along a passage in the container, a flow rate measuring apparatus includes a rotational speed transducer for detecting the rotational speed of a motor for driving the fluid circulation unit and a pipe network model calculator for receiving a rotational speed signal from the rotational speed transducer. The model calculator has an initially programmed pipe network model corresponding to flows in the container and calculates the flow rate at a corresponding location of the model with the rotational speed of the circulation unit replaced by constants of the model and hence calculates a flow rate of the fluid at that location in a real passage.
	claims	1. An anti-scatter grid, comprising:a substrate comprising a first face, and a second face, the first face comprising a plurality of grooves opening onto the first face of the substrate and not opening onto the second face of the substrate, wherein the second face does not comprise grooves,wherein the first face is arranged opposite the second face, the second face facing a radiation source, and the first face facing an image receptor configured to receive radiation emitted by the radiation source,wherein the substrate has low X-ray absorption properties, andwherein the grooves are filled with a material having high X-ray absorption properties and each having an orientation such that the planes of all the grooves are convergent and intersect along a line situated on the side of the second face where the grooves do not open. 2. An anti-scatter grid according to claim 1, wherein the substrate is a material selected from the group consisting of polyetherimides, polyimides and polycarbonates. 3. An anti-scatter grid according to claim 1, wherein the substrate consists of carbon, preferably in the form of graphite. 4. An anti-scatter grid according to claim 1, wherein the absorbent material comprises a metallic lead alloy. 5. An anti-scatter grid according to claim 1, further comprising:a protective layer on at least one face, the protective layer comprising a material having the property of attenuating X-rays slightly. 6. An anti-scatter grid according to claim 1, wherein the grid ratio is between 2 and 16, and wherein the number of grooves per centimeter is between 30 and 300. 7. A medical imaging system, comprising:a radiation source;an image receptor configured to receive radiation emitted by the source via an object of a patient to undergo imaging; andan anti-scatter grid comprising a substrate comprising a first face, and a second face, the first face comprising a plurality of grooves opening onto the first face of the substrate and not opening onto the second face of the substrate, wherein the second face does not comprise grooves,wherein the first face is arranged opposite the second face,wherein the substrate has low X-ray absorption properties,wherein the grooves are filled with a material having high X-ray absorption properties and each having an orientation such that the planes of all the grooves are convergent and intersect along a line situated on the side of the second face where the grooves do not open, andwherein the medical imaging system is arranged such that the second face where the grooves do not open is positioned on the side of the radiation source and the first face where the groove open is positioned on the image receptor, or a predetermined distance from the image receptor. 8. The medical imaging system according to claim 7, wherein the substrate is a material selected from the group consisting of polyetherimides, polyimides and polycarbonates. 9. The medical imaging system according to claim 7, wherein the substrate consists of carbon, preferably in the form of graphite. 10. The medical imaging system according to claim 7, wherein the absorbent material comprises a metallic lead alloy. 11. The medical imaging system according to claim 7, wherein the anti-scatter grid further comprises a protective layer on at least one face, the protective layer comprising a material having the property of attenuating X-rays slightly. 12. The medical imaging system according to claim 7, wherein the grid ratio of the anti-scatter grid is between 2 and 16, and wherein the number of grooves per centimeter is between 30 and 300.
061005347	abstract	A microscopic area scanning apparatus is provided with at least three hollow cylindrical piezoelectric elements each driven in three XYZ directions by one of divided electrodes. Three or more hollow cylindrical piezoelectric elements are arranged on a circumference of a common plane. Balls are each axially provided at a free end of the hollow cylindrical piezoelectric element. Ball retainers rotatably and slidably support a respective ball in contact therewith. A sample stage is fixed to the ball retainers. A table fixes the hollow cylindrical piezoelectric elements on the circumference of the common plane. Thus, the microscopic area scanning apparatus can realize both a wide X-Y scanning range and a high Z-direction resonant frequency without utilizing an elastic hinge.
	claims	1. A method for extracting a minute sample from a sample substrate, comprising:applying a focused ion beam to the sample substrate in a condition where an optical axis of an electron beam optical system is located in a portion of the sample substrate to be the minute sample to cut out the minute sample; andsupporting the minute sample and lowering the sample substrate in a condition where the optical axis of the electron beam optical system is located on the minute sample. 2. A method according to claim 1, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 3. A method according to claim 1, wherein said sample substrate comprises a wafer. 4. A method for extracting a minute sample from a sample substrate, comprising:cutting out the minute sample from the sample substrate by applying a focused ion beam to the sample substrate with confirmation by an electron microscope; andlowering the sample substrate while supporting the minute sample by a manipulator with confirmation by the electron microscope. 5. A method according to claim 4, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 6. A method according to claim 4, wherein said sample substrate comprises a wafer. 7. A method for extracting a minute sample from a sample substrate, comprising:applying a focused ion beam to the sample substrate in a condition where an optical axis of an electron beam optical system is located in a portion of the sample substrate to be the minute sample to cut out the minute sample; andsupporting the minute sample and moving the sample substrate in a condition where the optical axis of the electron beam optical system is located on the minute sample so that the minute sample is consequently separated from the sample substrate. 8. A method according to claim 7, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 9. A method according to claim 7, wherein said sample substrate comprises a wafer. 10. A method for extracting a minute sample from a sample substrate, comprising:cutting out the minute sample from the sample substrate by applying a focused ion beam to the sample substrate with confirmation by an electron microscope; andmoving the sample substrate while supporting the minute sample by a manipulator with confirmation by an electron microscope so that the minute sample is consequently lifted from the sample substrate. 11. A method according to claim 10, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 12. A method according to claim 10, wherein said sample substrate comprises a wafer. 13. A method for extracting a minute sample from a sample substrate, comprising:cutting out the minute sample from the sample substrate by applying a focused ion beam to the sample substrate with confirmation by an electron microscope; andsupporting the minute sample and lowering the sample substrate in a condition where an optical axis of an electron beam optical system is located on the minute sample. 14. A method according to claim 13, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 15. A method according to claim 13, wherein said sample substrate comprises a wafer. 16. A method for extracting a minute sample from a sample substrate, comprising:cutting out the minute sample from the sample substrate by applying a focused ion beam to the sample substrate with confirmation by an electron microscope; andsupporting the minute sample and moving the sample substrate in a condition where an optical axis of the electron beam optical system is located on the minute sample so that the minute sample is consequently lifted. 17. A method according to claim 16, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 18. A method according to claim 16, wherein said sample substrate comprises a wafer. 19. A method for extracting a sample from a sample substrate, comprising:applying a focused ion beam to the sample substrate in a condition where an optical axis of an electron beam optical system is located in a portion of the sample substrate to be the minute sample to cut out the minute sample; andlowering the sample substrate while supporting the minute sample by a manipulator with confirmation by an electron microscope. 20. A method according to claim 19, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 21. A method according to claim 19, wherein said sample substrate comprises a wafer. 22. A method for extracting a sample from a sample substrate, comprising:applying a focused ion beam to the sample substrate in a condition where an optical axis of an electron beam optical system is located in a portion of the sample substrate to be the minute sample to cut out the minute sample; andmoving the sample substrate while supporting the minute sample by a manipulator with confirmation by an electron microscope so that the minute sample is consequently lifted. 23. A method according to claim 22, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 24. A method according to claim 22, wherein said sample substrate comprises a wafer. 25. A method for extracting a sample from a sample substrate, comprising:applying a focused ion beam to the sample substrate in a condition where an optical axis of an electron beam optical system is located in a portion of the sample substrate to be the minute sample to cut out the sample; andlowering the sample substrate while supporting the minute sample by a manipulator. 26. A method according to claim 25, further comprising joining the minute sample and a probe of the manipulator by depositing deposition gas on a contact area between the minute sample and the probe. 27. A method according to claim 25, wherein said sample substrate comprises a wafer.
	claims	1. A dry storage canister for storing spent nuclear fuel rods, the canister comprising:an elongated outer housing having a first end and a second end; andan elongated internal basket provided within the outer housing, the elongated internal basket extending in a region between the first end and the second end of the elongated outer housing, the internal basket having a plurality of separate elongated storage cells, each of the cells comprising a plurality of the spent nuclear fuel rods that have been separated from their respective fuel rod assemblies, the plurality of the spent nuclear fuel rods having a rod packing density of approximately 4 to 6 of the spent nuclear fuel rods per square inch. 2. The canister of claim 1, wherein the spent nuclear fuel rods are contiguous within each of the cells. 3. The canister of claim 1, wherein the outer housing is an elongated cylindrical housing. 4. The canister of claim 1, wherein the internal basket is made of a metal material having a high thermal conductivity. 5. The canister of claim 1, wherein the internal basket is made of one or more of carbon steel, aluminum, or copper. 6. The canister of claim 1, wherein the internal basket comprises multiple tubes that define the storage cells. 7. The canister of claim 1, further comprising a cask in which the canister is placed. 8. The canister of claim 1, wherein does not include any neutron absorbing material. 9. A dry storage canister for storing spent nuclear fuel rods that have been separated from their fuel rod assemblies, the canister comprising:the spent nuclear fuel rods that have been separated from their fuel rod assemblies and that have been packed together with a rod packing density of approximately 4 to 6 of the spent nuclear fuel rods per square inch; andmeans for housing the spent nuclear fuel rods, wherein the means for housing does not include any neutron absorbing material. 10. The canister of claim 9, wherein the canister further comprises multiple tubes. 11. The canister of claim 9, wherein the spent nuclear fuel rods that have been separated from their fuel rod assemblies are contiguous within each of the cells. 12. The canister of claim 9, further comprising a central tube. 13. The canister of claim 9, further comprising a central tube that provides a space for a drain tube to drain the canister of a neutron moderator. 14. The canister of claim 1, wherein the elongated internal basket comprises a central tube. 15. The canister of claim 1, wherein the elongated internal basket comprises a central tube that provides space for a drain tube to drain the canister of a neutron moderator.
040173585	claims	1. A process for reversibly changing the boric acid concentration in coolant circulated through a nuclear reactor coolant system comprising the steps of: removing coolant having a first concentration of boron therein from the reactor coolant system; reducing the temperature of the removed coolant to a first lower level; conveying the reduced temperature coolant in a forward direction through a tank charged with ion exchange resins to remove boron from the resins and thereby increase the concentration of boron in said removed coolant; returning said removed coolant having increased boron concentration to the reactor coolant system; and thereafter; again removing and reducing the temperature of coolant from the reactor coolant system to a second level lower than said first level; conveying the second temperature level coolant in a reverse flow direction through said tank to deposit boron on said resins and thereby decrease the concentration of boron in the second temperature level coolant; and returning said second temperature level coolant having a decreased concentration of boron therein to the reactor coolant system; continuing the circulation of said reduced temperature coolant and the second temperature level coolant respectively through the tank until an equilibrium is established between the concentration of boron and the temperature of said coolants. the second temperature level coolant always flows in the reverse direction through said tank for depositing boron on said resins. removing coolant having a first concentration of boron therein from the reactor coolant system; reducing the temperature of the removed coolant to a first lower level; conveying the reduced temperature coolant in a forward direction through a tank charged with ion exchange resins to remove boron from the resins and thereby increase the concentration of boron in said removed coolant; discharging said removed coolant having increased boron concentration to a first coolant container; and thereafter; again removing and reducing the temperature of coolant from the reactor coolant system to a second level conveying the second temperature level coolant in a reverse flow direction through said tank to deposit boron on said resins and thereby decrease the concentration of boron in the second temperature level coolant; and discharging said second temperature level coolant having a decreased concentration of boron therein to a second coolant container; continuing the circulation of said reduced temperature coolant at said reduced temperature level and the second temperature level coolant at said second level temperature respectively, back and forth repeatedly through the ion exchange tank and between said containers to provide coolant having a high concentration of boron in the first coolant container, and coolant having a low concentration of boron in the second coolant container. 2. The process according to claim 1 wherein the reduced temperature coolant always flows into one end of said tank and upwardly over a baffle therein and then down the other side thereof to the outlet on the same side of the tank, thereby removing boron from the resins therein; and 3. A process for reversibly changing the boric acid concentration in coolant circulated through a nuclear reactor coolant system comprising the steps of:
	summary
	description	The present application claims priority from Japanese Patent Application No. 2008-236624 filed on Sep. 16, 2008, the contents of which are incorporated herein by reference in their entirety. 1. Field of the Invention The present invention relates to an extreme ultraviolet (EUV) light source apparatus for generating ultraviolet light by applying a laser beam to a target material to turn the target material into plasma. 2. Description of a Related Art In recent years, as semiconductor processes become finer, photolithography has been making rapid progress toward finer fabrication. In the next generation, micro-fabrication at 60 nm to 45 nm, further, micro-fabrication at 32 nm and beyond will be required. Accordingly, for example, exposure equipment is expected to be developed by combining an EUV light source for generating EUV light having a wavelength of about 13 nm and reduced projection reflective optics. As the EUV light source, there is an LPP (laser produced plasma) light source using plasma generated by applying a laser beam to a target (hereinafter, also referred to as “LPP type EUV light source apparatus”). The LPP light source has advantages that extremely high intensity close to black body radiation can be obtained because plasma density can be considerably made larger, that the light emission of only the necessary waveband can be performed by selecting the target material, and that an extremely large collection solid angle of 2π to 4π steradian can be ensured because it is a point light source having substantially isotropic angle distribution and there is no structure such as electrodes surrounding the light source. Therefore, the LPP light source is considered to be predominant as a light source for EUV lithography, which requires power of more than several tens of watts to one hundred of watts. In the LPP type EUV light source apparatus, by injecting a target material from a nozzle and applying a laser beam to the target material, the target material is excited and turned into plasma. Various wavelength components including extreme ultraviolet (EUV) light are radiated from the plasma. Then, a desired wavelength component of them is selectively reflected and collected by using a collector mirror (an EUV collector mirror), and outputted to a unit using EUV light (e.g., exposure unit). For example, in order to collect EUV light having a wavelength near 13.5 nm, an EUV collector mirror having a reflecting surface, on which a multilayer coating of alternately stacked molybdenum and silicon (Mo/Si multilayer coating) is formed, is used. In the LPP type EUV light source apparatus, the influence of neutral particles and ions having various velocities emitted from plasma on the EUV collector mirror is problematic. Since the EUV collector mirror is located near the plasma, the neutral particles and low-velocity ions emitted from the plasma adhere to the reflecting surface of the EUV collector mirror and reduce the reflectance of the EUV collector mirror. On the other hand, the fast ions emitted from the plasma damage the multilayer coating formed on the reflecting surface of the EUV collector mirror (in this application, this is referred to as “sputtering”). It is considered that neutral particles can be suppressed by optimizing the process of generating fully-ionized plasma according to various methods such as a double-pulse application method and a minimum mass target method that is described in International Publication WO 02/46839 A2. However, ion generation is inevitable as long as the plasma is generated. Accordingly, measures for ions are absolutely necessary. The low-velocity ions adhere to the EUV collector mirror and reduce the reflectance thereof. Since the ions only adhere to the EUV collector mirror, in principle, the adhesions can be removed by a cleaning technology using a reactive gas or the like. After cleaning, the reflectance of the EUV collector mirror is recovered and the EUV collector mirror can continuously be used. However, in order to fulfill the requirement for an EUV light source apparatus for exposure (a period in which the reflectance decreases by 10% is one year or more), an amount of adherence (thickness) of a metal film on the reflecting surface of the EUV collector mirror is acceptable as a very small value of about 0.75 nm for tin (Sn). Accordingly, it is necessary to perform high-speed cleaning at a high frequency. On the other hand, fast ions sputter the surface of the EUV collector mirror, and damage the reflecting coating to reduce the reflectance. When the EUV collector mirror is damaged and its reflectance becomes lower, replacement of the EUV collector mirror is required. A technology of reproducing the reflecting coating within the EUV light source apparatus is also available, however, it is necessary to add a high-accuracy coating formation apparatus for providing high surface flatness of about 0.2 nm (rms), for example, and that increases cost. Further, due to the damage distribution, it is substantially impossible to obtain a uniform reflectance distribution even when the reflecting coating is reproduced. Therefore, generally, several hundreds of layers of reflecting coatings have been deposited for extending the lifetime of the EUV collector mirror until replacement. Further, as a method of reducing the damage density of fast ions, there is a method of separating the distance between the EUV collector mirror and a plasma generation point (light emission point). In this case, there has been a problem that the catching solid angle of the EUV light becomes smaller and the output of available EUV light becomes lower. In order to solve the problem, for example, a method of using an EUV collector mirror having a large diameter equal to or more than φ500 mm is conceivable. However, there are problems that it is difficult to generate several hundreds of layers of reflecting coatings while maintaining the surface roughness and form accuracy, and such an EUV collector mirror is expensive even if it can be fabricated. In order to solve the problems, Japanese Patent Application Publication JP-P2005-197456A discloses an EUV light source apparatus including a magnetic field generating unit for generating a magnetic field within a collective optics when current is supplied, and trapping charged particles emitted from plasma by using the magnetic field to prevent adherence of the target material to the EUV collector mirror and sputtering of the EUV collector mirror. FIG. 21 schematically shows a configuration of the EUV light source apparatus according to JP-P2005-197456A. The EUV light source apparatus includes a target supply unit, a driver laser for applying a laser beam to a target, and an EUV collector mirror for collecting EUV light to output the EUV light. As shown in FIG. 22, a pair of electromagnetic coils having magnetic poles directed toward the same direction are provided with a part, where the laser beam is applied to the target, in between. The pair of electromagnetic coils form a mirror magnetic field around the laser application part and capture the charged particles flying from the target within the magnetic field to prevent the charged particles from reaching the EUV collector mirror. However, in order to deflect fast ions having energy up to 10 keV not to reach the EUV collector mirror, a strong magnetic field is necessary. In order to form a strong magnetic field in a space around the EUV collector mirror as shown in FIG. 21, Helmholtz coils having a gap equal to or more than the diameter (e.g., φ300 mm) of the EUV collector mirror should be prepared. Such electromagnetic coils are very large and not only cause constraints on design but also cause upsizing of the apparatus and increase in the apparatus cost. Further, since a strong magnetic field is generated within and around the EUV light source apparatus, materials that can be used inside and outside of the EUV apparatus are limited. This is because it should be avoided that the magnetic field acts on the structure or the servo motor and causes deformation of the structure or malfunction of the motor. Furthermore, there are problems of generating secondary cost in such a case where it is necessary to provide a magnetic field shield to cover the EUV light source apparatus and prevent malfunction of other apparatuses due to the strong magnetic field. The present invention has been achieved in view of the above-mentioned problems. A purpose of the present invention is to provide an extreme ultraviolet light source apparatus including magnetic field forming means having sufficient capability of protection against ions radiated from plasma while using a relatively small magnetic source. In order to accomplish the above-mentioned purpose, an extreme ultraviolet light source apparatus according to one aspect of the present invention is an extreme ultraviolet light source apparatus for generating extreme ultraviolet light by applying a laser beam to a target material to turn the target material into plasma, and the apparatus includes: a chamber in which extreme ultraviolet light is generated; a target nozzle for injecting a target material toward a predetermined plasma emission point within the chamber; a driver laser for applying a laser beam to the target material at the plasma emission point to generate plasma; a collector mirror for collecting the extreme ultraviolet light radiated from the plasma; and magnetic field forming means including at least one magnetic source and at least one magnetic material to be magnetized by the at least one magnetic source, the at least one magnetic material having two leading end parts projecting from the at least one magnetic source to face each other with the plasma emission point in between, and forming a magnetic field between a trajectory of the target material and the collector mirror. According to the one aspect of the present invention, since the two leading end parts of the at least one magnetic material to be magnetized by the at least one magnetic source are provided to project from the at least one magnetic source with the plasma emission point in between, the magnetic flux is concentrated on the gap sandwiching the plasma emission point. Therefore, high-density lines of magnetic force can be formed without using a large magnetic source, and charged particles radiated from the plasma can be prevented from colliding with the EUV collector mirror. As a result, the degree of freedom of design can be improved, the entire apparatus can be downsized, and the apparatus cost can be reduced. Further, the strong magnetic field becomes local and the magnetic field is rapidly attenuated at a slight distance, and therefore, the constrains on materials within the extreme ultraviolet light source apparatus are relaxed, the magnetic field shield is simple also serving as an apparatus cover, and the apparatus cost is reduced. Hereinafter, preferred embodiments of the present invention will be explained in detail by referring to the drawings. The same reference numerals are assigned to the same component elements and the description thereof will be omitted. FIG. 1 is a side view showing a configuration of an extreme ultraviolet light source apparatus according to the first embodiment of the present invention. The extreme ultraviolet (EUV) light source apparatus according to the embodiment employs a laser produced plasma (LPP) system for generating EUV light by applying a laser beam to a target material for excitation. As shown in FIG. 1, the EUV light source apparatus includes an EUV chamber 10 in which EUV light is generated, a target supply unit 12 having a target nozzle 13 for injecting a target material on the leading end thereof, a target collecting unit (target collecting tube) 14, a driver laser 23 for generating a laser beam 24, a focusing lens 25, and an EUV collector mirror 16. To the EUV chamber 10, a laser beam entrance window 20 for introducing the laser beam 24 into the EUV chamber 10 and an exposure unit interface 18 for guiding the collected EUV light to an external exposure unit are provided. Further, in the EUV collector mirror 16, an entrance hole for passing the laser beam 24 is formed. Furthermore, the EUV light source apparatus includes an upper electromagnetic coil 30 and a lower electromagnetic coil 32 as magnetic sources, a power supply 33 for supplying current to the upper electromagnetic coil 30 and the lower electromagnetic coil 32, an upper magnetic core (magnetic material) 34 to be magnetized by the upper electromagnetic coil 30, and a lower magnetic core (magnetic material) 36 to be magnetized by the lower electromagnetic coil 32. The upper magnetic core 34 forming a cylinder is provided along the inner wall of the upper electromagnetic coil 30 to surround a pipe of the target supply unit 12. Further, the lower magnetic core 36 forming a cylinder is provided along the inner wall of the lower electromagnetic coil 32 to surround a target collecting tube of the target collecting unit 14. A refrigerant path 40 connected to a refrigerator 42 is formed within the upper magnetic core 34, and a refrigerant path 44 connected to a refrigerator 46 is formed within the lower magnetic core 36. In the EUV light source apparatus, a target 22 is injected from the target nozzle 13 of the target supply unit 12. The state of the target material introduced into the target supply unit 12 may be gas, liquid, or solid. For example, when a target material in a gas state at the normal temperature such as xenon is used as a liquid target, the xenon gas is pressurized and cooled in the target supply unit 12 and the liquefied xenon is supplied to the target nozzle 13. On the other hand, for example, when a target material in a solid state at the normal temperature such as tin is used as a liquid target, the tin is heated in the target supply unit 12 and the liquefied tin is supplied to the target nozzle 13. In the embodiment, tin (Sn) droplets are used as the target 22. The target nozzle 13 injects the target material supplied from the target supply unit 12 to supply the droplet target 22 to a predetermined position (plasma emission point) within the EUV chamber 10. The target nozzle 13 includes a vibration mechanism having a piezoelectric element or the like, and produces droplets of the target material according to the Rayleigh's stability theory of minute disturbance. The driver laser 23 is a laser beam source that can perform pulse oscillation at a high-repetition frequency (e.g., pulse width of about several nanoseconds to several tens of nanoseconds and repetition frequency of about 10 kHz to 100 kHz), and outputs the laser beam 24 to be applied to the target 22 to turn the target 22 into plasma. Further, the focusing lens 25 collects the laser beam 24 outputted from the driver laser 23 and applies it to the plasma emission point (also referred to as “laser application position”). In place of the focusing lens 25, a collective optics including an optical component such as a mirror or a combination of plural optical components may be used. The laser beam 24 is applied from the driver laser 23 through the focusing lens 25 and the laser beam entrance window 20 to the target 22. The laser entrance hole for passing the laser beam 24 is formed in the EUV collector mirror 16, and the laser beam 24 passes through the laser entrance hole and is applied to the target 22. Thereby, the target 22 is excited and plasma 26 is generated, and various lights including EUV light having a wavelength of 13.5 nm are radiated from the plasma 26. The EUV collector mirror 16 is a collective optics for collecting a specific wavelength component (e.g., EUV light near 13.5 nm) from the various wavelength components radiated from the plasma 26. The EUV collector mirror 16 has a concave reflecting surface on which a molybdenum (Mo)/silicon (Si) multilayer coating for selectively reflecting the EUV light near 13.5 nm, for example, is formed. By the EUV collector mirror 16, the EUV light is reflected and collected in a predetermined direction along an EUV catching optical path 28 and outputted through the exposure unit interface 18 to the exposure unit. The collective optics of the EUV light is not limited to the EUV collector mirror 16 as shown in FIG. 1, but may be formed by using plural optical components, and it is necessary to form a reflection optics for suppressing absorption of EUV light. The exposure unit interface 18 has a positioning mechanism relative to the exposure unit for preventing contamination from entering the exposure unit to improve purity of the EUV light. Further, since the EUV light is attenuated in the atmosphere, the plasma 26 is generated within the EUV chamber 10 isolated from the atmosphere. The pressure within the EUV chamber 10 is held at about 0.1 Pa, for example, by an evacuation apparatus. The target collecting unit 14 is provided in a location facing the target nozzle 13 with the plasma emission point in between. The target collecting unit 14 collects the target material that has been injected from the target nozzle 13 but not turned into plasma without laser beam application and a residue of the target material to which the laser beam has been applied. Thereby, the unwanted target material is prevented from flying and contaminating the EUV collector mirror 16 and so on, and the degree of vacuum within the EUV chamber 10 is prevented from lowering. The upper electromagnetic coil 30 and the lower electromagnetic coil 32 are provided outside of the EUV chamber 10. The leading end part of the upper magnetic core 34 projects from the end surface of the upper electromagnetic coil 30, and extends into the EUV chamber 10. Further, the leading end part of the lower magnetic core 36 projects from the end surface of the lower electromagnetic coil 32, and extends into the EUV chamber 10. Within the EUV chamber 10, the leading end part of the upper magnetic core 34 and the leading end part of the lower magnetic core 36 are located to face each other with the plasma generation point in between. The upper magnetic core 34 and the lower magnetic core 36 have hollow structures, and the target supply unit 12 is provided within the upper magnetic core 34 and the target collecting unit 14 is provided within the lower magnetic core 36. The leading end part of the upper magnetic core 34 extends near the leading end of the target supply unit 12, and the leading end part of the lower magnetic core 36 extends near the leading end of the target collecting unit 14. The upper magnetic core 34 and the lower magnetic core 36 are formed of a material having high saturation magnetic flux density such as a ferromagnetic material for downsizing. Prior to plasma generation, the power supply 33 supplies current to the upper electromagnetic coil 30 and the lower electromagnetic coil 32 to magnetize the upper magnetic core 34 and the lower magnetic core 36, and thereby, a mirror-shaped magnetic field 38 is formed along the trajectory of the target material at least between the trajectory of the target material and the EUV collector mirror. By the upper magnetic core 34 and the lower magnetic core 36 facing each other with the plasma emission point in between, a magnetic field is locally generated only near the plasma with a small gap, and thus, a magnetic field having a strength comparable with that in a conventional technology can be generated around the plasma by smaller electromagnetic coils compared to those of the related technology. Further, by the upper magnetic core 34 and the lower magnetic core 36 extending into the EUV chamber 10, the magnetic field 38 can be generated in a location apart from the upper electromagnetic coil 30 and the lower electromagnetic coil 32, and therefore, the upper electromagnetic coil 30 and the lower electromagnetic coil 32 can be provided outside of the EUV chamber 10. Fast ions are generated substantially simultaneously with the plasma generation, and the fast ions are caught by the magnetic field around the plasma and ejected in the vertical directions in FIG. 1. Then, the fast ions collide with the upper magnetic core 34 and the lower magnetic core 36 as emission points of the lines of magnetic force, or caught by the target collecting unit 14. Since the upper magnetic core 34 and the lower magnetic core 36 are hit by the ions as described above, the refrigerant paths 40 and 44 for circulating a refrigerant for cooling are formed within the upper magnetic core 34 and the lower magnetic core 36, respectively. The refrigerant paths 40 and 44 are coupled to the refrigerators 42 and 46, respectively, and cool the upper magnetic core 34 and the lower magnetic core 36 because the refrigerators 42 and 46 cool the refrigerant. Further, it is desirable that the surfaces of the upper magnetic core 34 and the lower magnetic core 36 are coated with a material that is hard to be damaged by ion collision. Materials having high hardness and resistance properties against the sputtering such as TiN, Si3N4, BN, Al2O3, TiO2, MgAl2O4, carbon (C), and titanium (Ti) are suitable for the coating material. Especially, in the case where tin (Sn) is used as the target material, it is preferable that titanium (Ti) having a high wettability for liquid tin and relatively high resistance properties against the sputtering is used as the coating material. Further, in the case where porous titanium is coated on the magnetic cores, even if tin ions reach the magnetic cores and tin adheres to the magnetic cores, tin leaks into pores of the porous titanium, and therefore, it is possible to prevent tin from being sputtered again by fast ions colliding with the magnetic cores. FIGS. 2A and 2B show a partial configuration of an extreme ultraviolet light source apparatus according to the second embodiment of the present invention. FIG. 2A is a side view, and FIG. 2B is a bottom view. The magnetic field 38 generated for deflecting fast ions may have a distribution in which the magnetic field is stronger between the trajectory of the target material and the EUV collector mirror 16. Accordingly, in the second embodiment, the upper magnetic core 34 and the lower magnetic core 36 are provided only at the EUV collector mirror side of the target supply unit 12 and the target collecting unit 14, and thereby, a strong magnetic field is formed between the trajectory of the target material and the EUV collector mirror 16. The other points are the same as those in the first embodiment. In the second embodiment, since the strong magnetic field is generated at the EUV collector mirror side of the trajectory of the target material, ions generated from plasma can be prevented from colliding with the EUV collector mirror 16. In addition, the sectional area in which the upper magnetic core 34 and the lower magnetic core 36 block the EUV catching optical path 28 is small, and therefore, there is an advantage that the amount of caught EUV light is larger than that in the first embodiment. FIGS. 3A-3D show a partial configuration of an extreme ultraviolet light source apparatus according to the third embodiment of the present invention. FIG. 3A is a side view, FIGS. 3B and 3C are bottom views, and FIG. 3D is a plan view. In the third embodiment, the upper electromagnetic coil 30 and the upper magnetic core 34 are separated from the target supply unit 12, and the lower electromagnetic coil 32 and the lower magnetic core 36 are separated from the target collecting unit 14. The other points are the same as those in the second embodiment. In the third embodiment, as is in the case of the second embodiment, a strong magnetic field can be formed between the trajectory of the target material and the EUV collector mirror 16. Further, in the third embodiment, the shapes of the magnetic cores can be formed relatively freely. For example, as shown in FIG. 3C, when the upper magnetic core 34 and the lower magnetic core 36 are formed in flat plates, protection against ions can be realized across a wide area. The shapes of the upper magnetic core 34 and the lower magnetic core 36 are not limited to flat plates, but may be curved to form circular arcs. Since the shapes of the magnetic cores can be formed relatively freely as described above, the magnetic field can be formed according to the size of the EUV collector mirror 16 and the location of the structures within the EUV chamber 10. For example, as shown in FIG. 3D, not only the EUV collector mirror 16 but also optical components such as an EUV light amount sensor 47, a laser beam focusing optics 48, and a target location monitor unit 49 may be targets of protection, and the magnetic field 38 may be formed to shield them from plasma. FIGS. 4A and 4B show a partial configuration of an extreme ultraviolet light source apparatus according to the fourth embodiment of the present invention. FIG. 4A is a side view, and FIG. 4B is a bottom view. In the fourth embodiment, auxiliary rings 35 and 37 are added to the upper magnetic core 34 and the lower magnetic core 36, respectively, and the magnetic field 38 covering the plasma 26 is formed. The auxiliary rings 35 and 37 are formed of a magnetic material. The other points are the same as those in the second embodiment. In this case, in the same manner as that in the first embodiment, ions generated from the plasma 26 can be caught over substantially all directions and the shadows of the magnetic cores formed in the EUV light path can be minimized. Since the shapes of the magnetic cores can be formed relatively freely as described above, the magnetic field 38 can be allowed to effectively act according to the location of the structures within the EUV chamber 10. The magnetic field 38 is local and any large electromagnetic coils like those in the conventional case are not necessary. Further, as is in the case of the first embodiment, the upper magnetic core 34 and the lower magnetic core 36 may be cooled or the upper magnetic core 34 and the lower magnetic core 36 may be coated. FIG. 5 is a side view showing a partial configuration of an extreme ultraviolet light source apparatus according to the fifth embodiment of the present invention. The fifth embodiment is a modification of the first embodiment. In the fifth embodiment, the magnetic field 38 generated for deflecting fast ions has a distribution in which the magnetic field is stronger at the target supply unit side in the trajectory of the target material. The first to fourth embodiments generate a magnetic field substantially symmetric in the vertical direction. That is, the substantially symmetric magnetic field is generated at the target supply unit side and the target collecting unit side. However, by the magnetic field substantially symmetric in vertical direction, ions captured by the magnetic field are converged homogeneously to the target supply unit side and the target collecting unit side. When a long-period operation is performed under the condition, a problem arises that the target nozzle 13 of the target supply unit 12 deforms due to collision of ions and therefore the trajectory of the target material changes. Durability may be improved by applying an ion-resistant coating or the like on the front surface of the target nozzle 13. However, ions are easily ejected into the space in which lines of magnetic force are sparse, and in the case where the strong magnetic field is formed at the target supply unit side, the amount of ion collision against the target nozzle 13 can be relatively reduced. Accordingly, in the fifth embodiment, the lower magnetic core 36 at the target collecting unit side is made thicker for reducing magnetic flux density on the end surface of the lower magnetic core 36. Relatively, on the upper magnetic core 34 at the target supply unit side, the magnetic flux density becomes higher and ions hardly reach there. FIG. 6 is a side view showing a partial configuration of an extreme ultraviolet light source apparatus according to the sixth embodiment of the present invention. The sixth embodiment is a modified example of the fifth embodiment. In the sixth embodiment, the lower magnetic core 36 at the target collecting unit side is apart from the trajectory of the target material as a center axis of the target supply unit 12 and the target collecting unit 14 so that the magnetic field 38 has a gradient. At the target supply unit side, the magnetic field is close to the target supply unit 12 and ions hardly reach there. FIG. 7 is a side view showing a partial configuration of an extreme ultraviolet light source apparatus according to the seventh embodiment of the present invention. The seventh embodiment is a modified example of the sixth embodiment. In the seventh embodiment, the lower magnetic core 36 at the target collecting unit side is apart from the target collecting unit 14 together with the lower electromagnetic coil 32, and thereby, the magnetic field at the target collecting unit side is made weaker. FIGS. 8A and 8B show a partial configuration of an extreme ultraviolet light source apparatus according to the eighth embodiment of the present invention. FIG. 8A is a side view, and FIG. 8B is a plan view. Further, FIGS. 9A and 9B show a partial configuration of an extreme ultraviolet light source apparatus according to a modified example of the eighth embodiment of the present invention. FIG. 9A is a side view, and FIG. 9B is a plan view. In the eighth embodiment and the modified example thereof, the upper and lower magnetic cores are magnetically coupled by using yokes made of a magnetic material. When the upper magnetic core 34 and the lower magnetic core 36 are coupled by yokes 52, 54, 56, substantially all of the lines of magnetic force pass through magnetic materials except for the gap sandwiching the plasma 26. Thereby, a configuration with little leakage magnetic field to the outside of the magnetic materials can be realized. According to the configuration, it is not necessary to carefully select materials of other structures within the EUV chamber 10, and the magnetic shield is not necessary. Further, in some cases, the number of electromagnetic coils can be reduced. In addition, an electromagnetic coil 50 may be attached to an arbitrary location in the magnetic circuit as shown in FIGS. 8A and 8B or FIGS. 9A and 98, and the degree of freedom of design can be improved. Further, the surface of at least one of the yokes 52, 54, 56 may be coated with a material that is hard to be damaged by ion collision. Materials having high hardness and resistance properties against the sputtering such as TiN, Si3N4, BN, Al2O3, TiO2, MgAl2O4, carbon (C), and titanium (Ti) are suitable for the coating material. Especially, in the case where tin (Sn) is used as the target material, it is preferable that porous titanium is used as the coating material. FIG. 10 is a plan view showing a partial configuration of an extreme ultraviolet light source apparatus according to the ninth embodiment of the present invention. In the ninth embodiment, the leading end parts of the upper magnetic core 34 and the lower magnetic core 36 are formed in conical shapes and shadows of the upper magnetic core 34 and the lower magnetic core 36 formed in the EUV catching optical path 28 are made smaller. The part blocking the EUV catching optical path 28 is only the periphery of the leading end of the target nozzle 13 and the leading end of the target collecting unit 14, and therefore, the acquisition efficiency of the EUV light can be improved. Further, in FIG. 10, the target supply unit 12 and the target collecting unit 14 are horizontally provided and the target material is horizontally outputted, and thereby, the trajectory of the target material is set in the horizontal direction. In this way, even when the direction of the trajectory of the target material changes, the target motion and the ion removal function are not so different as long as the target injection capability can be ensured. FIGS. 11-13 are side vies showing a partial configuration of an extreme ultraviolet light source apparatus according to the tenth embodiment of the present invention. In the tenth embodiment, the magnetic circuit is configured by a magnetic core 58 passing through the axis part of the electromagnetic coil 50 and formed with a gap in the plasma emission point. The magnetic core 58 may penetrate the EUV collector mirror 16. When the magnetic core 58 formed with a gap in the plasma emission point is used, ions radiated from the plasma 26 are caught and collide with the magnetic core 58, and thus, the target nozzle 13 is protected. In addition, since the magnetic field is formed to surround the plasma 26, ions moving toward the EUV collector mirror 16 are reduced and the EUV collector mirror 16 is also protected. Further, most of the lines of magnetic force pass through the magnetic core 58, and the leakage magnetic field to the outside is very scarce. FIGS. 11 and 12 show variations of the positional relationship between the incident direction of the laser beam 24 and the magnetic core 58. As shown in FIG. 11, the magnetic core 58 may be allowed to penetrate the center axis of the EUV collector mirror 16 so that the shadow of the magnetic core 58 in the EUV catching optical path 28 is minimized. Alternatively, as shown in FIG. 12, with the emphasis on the ease of alignment, the laser beam 24 may be allowed to enter the center axis of the EUV collector mirror 16, and the magnetic core 58 may be provided to avoid the center axis of the EUV collector mirror 16. Further, as shown in FIG. 13, a cavity may be formed in a part of the magnetic core 58 sandwiching the plasma emission point, and the cavity may be used as an incident path of the laser beam 24. According to the arrangement as shown in FIG. 13, the shadow of the magnetic core 58 formed in the EUV catching optical path 28 can be minimized and alignment of the laser incident axis is easy. However, ions are ejected to the laser incident axis, and therefore, the ions may collide with the laser beam focusing optics and damage it. In order to avoid this, it is desirable to provide a bias electrode 62 for catching ions, a direct-current power supply 64 for supplying a direct-current voltage to the bias electrode 62, or the like. FIGS. 14-16 are side views showing a partial configuration of an extreme ultraviolet light source apparatus according to the eleventh embodiment of the present invention. Since ions are affected not only by a magnetic field but also by an electric field, the electric field may be also used by utilizing the influence. In the eleventh embodiment, the action of the electric field is also used and the ion protection effect of the EUV collector mirror can be increased. The other points are the same as those in the first embodiment. FIG. 14 shows a partial configuration of an EUV light source apparatus with further improved ion protection effect by forming an electrode 66, which repulses the ions, on the rear surface of the EUV collector mirror 16. The electrode 66 is provided on the rear surface of the EUV collector mirror 16, and a direct-current power supply 68 supplies a voltage having the same polarity as that of the ions to the electrode 66. Thereby, the electric field that repulsively acts on the ions is formed on the front surface of the EUV collector mirror 16, and therefore, the ions with high energy passing through the magnetic field 38 can be prevented to reach the EUV collector mirror 16. FIG. 15 shows a partial configuration of an EUV light source apparatus using the upper magnetic core 34 and the lower magnetic core 36 as electrodes. A direct-current power supply 70 supplies a voltage having a different polarity from that of ions to the upper magnetic core 34 and the lower magnetic core 36. Thereby, the EUV collector mirror 16 can be protected by allowing the ions to aggressively collide with the upper magnetic core 34 and the lower magnetic core 36, but not to collide with the EUV collector mirror 16. In this case, it is desirable to take measures for ion protection of coating or the like on the upper magnetic core 34 and the lower magnetic core 36. FIG. 16 shows a partial configuration of an EUV light source apparatus using both the configuration as shown in FIG. 14 and the configuration as shown in FIG. 15. The direct-current power supply 68 supplies a voltage having the same polarity as that of ions to the electrode 66 formed on the rear surface of the EUV collector mirror 16 to repulse the ions, and the direct-current power supply 70 applies a voltage having a different polarity from that of ions to the upper magnetic core 34 and the lower magnetic core 36 to absorb the ions. Therefore, according to the configuration as shown in FIG. 16, the probability that the ions collide with the EUV collector mirror 16 becomes lower. FIG. 17 is a side view showing a partial configuration of an extreme ultraviolet light source apparatus according to the twelfth embodiment of the present invention. In the twelfth embodiment, the ion protection effect of the EUV collector mirror is increased also by using the action of the electric field. The EUV light source apparatus has a function of forming the mirror magnetic field 38 around the plasma emission point to prevent sputtering of the EUV collector mirror 16 due to ions radiated from the plasma 26, and a function of forming an electric field in the plasma emission point to prevent the ions from moving to the EUV collector mirror 16. The other points are the same as those in the first embodiment. As shown in FIG. 17, an electrode rod 76 having a hollow structure is provided in the optical path of the laser beam 24 and an opposite electrode rod 74 is provided with the plasma emission point in between, and a direct-current power supply 72 supplies a direct-current voltage between the electrode rod 76 and the electrode rod 74. Thereby, the ions not caught by the magnetic field 38 but emitted to the EUV collector mirror side are caught by the electrode rod 76 having a potential with opposite polarity to that of ions. In this case, the inner surface of the tubular electrode rod 76 is also the ion collision surface, and therefore, the amount of ion collision per unit area decreases, and the damage on the upper magnetic core 34 and the lower magnetic core 36 can be reduced. The amount of ions passing through the hole of the electrode rod 76 is extremely small, and the possibility that the laser beam focusing optics is subjected to ion collision is low. In the embodiment, the potential of the electrode rod 76 also serving as the laser optical path has opposite polarity to that of ions. Alternatively, the potential of the electrode rod 76 may have the same polarity as that of ions and the potential of the opposed electrode rod 74 may have opposite polarity to that of ions, so that the ions are allowed to collide with the opposed electrode rod 74. FIG. 18 is a side view showing a partial configuration of an extreme ultraviolet light source apparatus according to the thirteenth embodiment of the present invention. In the thirteenth embodiment, particles radiated from plasma are aggressively charged and removed by using the action of the magnetic field and/or electric field, and thereby, the ion protection effect of the EUV collector mirror is increased. The other points are the same as those in the first embodiment. The EUV light source apparatus includes the direct-current power supply 68 for supplying a direct-current voltage to the electrode 66 formed on the rear surface of the EUV collector mirror 16, a direct-current power supply 70 for supplying a direct-current voltage to the upper magnetic core 34 and the lower magnetic core 36, a charging unit 78 such as an electron gun or a microwave source for charging particles radiated from the plasma, and a power supply 80 for supplying a voltage to the charging unit 78. Depending on conditions of the target material, laser beam, and so on, there is a case where the ionization rate of the particles radiated from the plasma is low. In such a case, the charging unit 78 aggressively charges the particles radiated from the plasma. If the particles can be charged, the charged particles can be caught by utilizing the action of the mirror magnetic field generated by the upper electromagnetic coil 30 and the lower electromagnetic coil 32 and/or the electric field generated by the electrode 66, the upper magnetic core 34 and the lower magnetic core 36. Therefore, even when the ionization rate is low, the particles radiated from the plasma can be effectively caught and the EUV collector mirror 16 can be protected. FIGS. 19A and 19B show a partial configuration of an extreme ultraviolet light source apparatus according to the fourteenth embodiment of the present invention. FIG. 19A is a plan view seen from the above, and FIG. 19B is a side view. In the fourteenth embodiment, each component is arranged such that a trajectory of the target material and a direction of the magnetic field are substantially orthogonal to each other. Further, as the magnetic sources, magnets are employed in place of the electromagnetic coils. The other points are the same as those in the first embodiment. As shown in FIG. 19A, the EUV light source apparatus includes a magnet 30a, a magnet 32a, a magnetic core (magnetic material) 34a to be magnetized by the magnet 30a, and a magnetic core (magnetic material) 36a to be magnetized by the magnet 32a. The magnetic core 34a forming a cylinder is provided along the inner wall of the magnet 30a, and the magnetic core 36a forming a cylinder is provided along the inner wall of the magnet 32a. An ion collecting unit 81 is provided inside of the cylinder formed of the magnetic core 34a, and an ion collecting unit 82 is provided inside of the cylinder formed of the magnetic core 36a. The ion collecting units 81 and 82 collects the ions that are captured by the magnetic field and ejected in the horizontal directions. As shown in FIG. 19B, in the EUV light source apparatus, a target 22 is injected from the target nozzle 13 of the target supply unit 12. The target nozzle 13 injects a target material supplied from the target supply unit 12 to supply the droplet target 22 to a predetermined position (plasma emission point) within the EUV chamber 10. The driver laser 23 outputs the laser beam 24 to be applied to the target 22 to turn the target 22 into plasma. Further, the focusing lens 25 focuses the laser beam 24 outputted from the driver laser 23 and applies it to the plasma emission point. The laser beam 24 is applied from the driver laser 23 through the focusing lens 25 and the laser beam entrance window 20 to the target 22. Thereby, the target 22 is excited and plasma 26 is generated, and various lights including EUV light having a wavelength of 13.5 nm are radiated from the plasma 26. The EUV collector mirror 16 collects a predetermined wavelength component (e.g., EUV light near 13.5 nm) from the various wavelength components radiated from the plasma 26. By the EUV collector mirror 16, the EUV light is reflected and collected in a predetermined direction along the EUV catching optical path 28 and outputted through the exposure unit interface 18 to the exposure unit. The target collecting unit 14 is provided in a location facing the target nozzle 13 with the plasma emission point in between. The target collecting unit 14 collects the target material that has been injected from the target nozzle 13 but not turned into plasma without laser beam application and a residue of the target material to which the laser beam has been applied. Referring to FIG. 19A again, the magnets 30a and 32a are provided outside of the EUV chamber 10. The leading end part of the magnetic core 34a projects from the end surface of the magnet 30a, and extends into the EUV chamber 10. Further, the leading end part of the magnetic core 36a projects from the end surface of the magnet 32a, and extends into the EUV chamber 10. Within the EUV chamber 10, the leading end part of the magnetic core 34a and the leading end part of the magnetic core 36a are located to face each other with the plasma generation point in between. The magnetic cores 34a and 36a are respectively magnetized by magnets 30a and 32a, and thereby, a mirror-shaped magnetic field 38 is formed along the trajectory of the target material at least between the trajectory of the target material and the EUV collector mirror. By the magnetic cores 34a and 36a facing each other with the plasma emission point in between, a magnetic field is locally generated only near the plasma with a small gap, and thus, a magnetic field having a certain strength can be generated around the plasma by smaller magnets. Further, by the magnetic cores 34a and 36a extending into the EUV chamber 10, the magnetic field 38 can be generated in a location apart from the magnets 30a and 32a, and therefore, the magnets 30a and 32a can be provided outside of the EUV chamber 10. Fast ions are generated substantially simultaneously with the plasma generation, and the fast ions are caught by the magnetic field around the plasma and ejected in the horizontal directions. Then, the fast ions collide with the magnetic cores 34a and 36a as emission points of the lines of magnetic force, or caught by the ion collecting units 81 and 82. According to the fourteenth embodiment, since ions are apt to not collide with the target nozzle 13, the target nozzle 13 is not sputtered and it is possible to supply the target 22 stably. Further, the lifetime of the target nozzle 13 can be improved. Since the target material that has not been applied with the laser beam is also collected in the target collecting unit 14, a large amount of the target material is accumulated. When the fast ions are incident upon the target material accumulated in the target collecting unit 14, the target material is sputtered to spout. The EUV light source apparatus according to the fourteenth embodiment can prevent this phenomenon. Although the magnets are arranged outside of the EUV chamber 10 in the fourteenth embodiment, the present invention is not limited to the embodiment, but the magnets 30a and 32a or the ion collecting units 81 and 82 may be arranged inside of the EUV chamber 10. FIG. 20 is a plan view showing a partial configuration of an extreme ultraviolet light source apparatus according to the fifteenth embodiment of the present invention. The fifteenth embodiment is a modification of the fourteenth embodiment. In the fifteenth embodiment, the surfaces of the magnetic cores and/or the ion collecting units are coated with a material for preventing the sputtering. In order to increase the strength of the magnetic field around the plasma 26, it is necessary that the magnetic cores 34a and 36a extend to as near positions as possible to the plasma 26. However, the fast ions radiated from the plasma 26 collide with the magnetic cores 34a and 36a to sputter the material of the magnetic cores. The sputtered material of the magnetic cores adheres to optical elements (for example, the laser beam entrance window 20 and the EUV collector mirror 16), and reduces the collecting efficiency of the laser beam and the collecting efficiency of the EUV light, respectively. Accordingly, in order to prevent the sputtering, it is desirable that the surfaces of the magnetic cores 34a and 36a are coated with a material that is hard to be damaged by ion collision so as to form a coating layer 91. Materials having high hardness and resistance properties against the sputtering such as TiN, Si3N4, BN, Al2O3, TiO2, MgAl2O4, carbon (C), and titanium (Ti) are suitable for the coating material. Especially, in the case where tin (Sn) is used as the target material, it is preferable that titanium (Ti) having a high wettability for liquid tin and relatively high resistance properties against the sputtering is used as the coating material. Further, in the case where porous titanium is coated on the magnetic cores, even if tin ions reach the magnetic cores and tin adheres to the magnetic cores, tin leaks into pores of the porous titanium, and therefore, it is possible to prevent tin from being sputtered again by fast ions colliding with the magnetic cores. Further, the surfaces of the ion collecting units 81 and 82 may be coated with the coating material as mentioned above so as to form a coating layer 92. Thereby, even if the fast ions radiated from the plasma 26 collide with the surfaces of the ion collecting units 81 and 82, the surfaces of the ion collecting units 81 and 82 become hardly sputtered. Furthermore, in the case where the magnets 30a and 32a are arranged inside of the EUV chamber 10, the surfaces of the magnets 30a and 32a may be coated with the coating material as mentioned above. In the first to thirteenth embodiments as described above, as the magnetic sources, magnets may be employed in place of the electromagnetic coils. Further, in the fourteenth to fifteenth embodiments, as the magnetic sources, electromagnetic coils may be employed in place of the magnets.
	claims	1. An electron beam measurement apparatus, which measures, based on information on an image, a pattern formed on a sample, comprising an electron optical system that has a lens and a deflector and scans a predetermined observation region on the sample with an electron beam emitted from an electron source, a detector for detecting a charged particle secondarily generated from the sample by irradiation with the electron beam, and means for forming an image based on the detected charged particle, the patterns being delineated in a single layer present on a substrate by a multi-exposure method, the electron beam measurement apparatus including:means for classifying patterns, which are included in an image acquired by the irradiation with the electron beam on the patterns on the sample, into groups according to an exposure history record, the exposure history record being acquired based on brightness of the patterns included in the image and a difference between shapes of white bands of the patterns. 2. The electron beam measurement apparatus according to claim 1, whereinthe patterns are classified into the groups based on an image formed based on a secondary electron of the charged particle and an image formed based on a reflective electron of the charged particle. 3. The electron beam measurement apparatus according to claim 1, whereinthe patterns are classified into the groups according to the exposure history record by comparing the acquired image with a design database. 4. The electron beam measurement apparatus according to claim 1, whereinthe patterns are classified into the groups such that a pattern having portion arranged alternately is included in one of the groups that is different from the other group including the other pattern. 5. The electron beam measurement apparatus according to claim 1, whereinan image processing parameter or an waveform processing parameter is used for each of the classified groups to obtain the size of a portion of the pattern included in the group or the position of the contour of the portion of the pattern, the used parameter varying depending on the group. 6. The electron beam measurement apparatus according to claim 1, whereina reference image or a reference waveform is used for each of the classified groups to obtain the size of a portion of the pattern included in the group or the position of the contour of the portion of the pattern, the used reference image or the used reference waveform varying depending on the group. 7. The electron beam measurement apparatus according to claim 1, whereininformation on a relative positional relationship between the classified groups is obtained. 8. An electron beam measurement apparatus, which measures, based on information on an image, a pattern formed on a sample, comprising an electron optical system that has a lens and a deflector and scans a predetermined observation region on a sample with an electron beam emitted from an electron source, a detector for detecting a charged particle secondarily generated from the sample by irradiation with the electron beam, and means for forming an image based on the detected charged particle, the patterns being delineated in a single layer present on a substrate by a multi-exposure method, the electron beam measurement apparatus including:means for classifying the patterns in the plurality of images into a plurality of groups according to an exposure history record by irradiating patterns with the electron beam to acquire a plurality of images respectively indicating regions that mostly overlap each other under respective image acquisition conditions different from each other, whereinany of the images that is acquired under any of the image acquisition conditions is used for any of the groups to obtain the size of a portion of the pattern included in the group or the position of the contour of the portion of the pattern, the image acquisition condition varying depending on the group. 9. The electron beam measurement apparatus according to claim 1, whereinthe patterns are delineated on the sample by a double patterning technique. 10. The electron beam measurement apparatus according to claim 1, whereinthe image formed based on the detected charged particle is a scanning electron microscope image. 11. The electron beam measurement apparatus according to claim 8, whereinthe patterns are delineated on the sample by a double patterning technique. 12. The electron beam measurement apparatus according to claim 8, whereinthe image formed based on the detected charged particle is a scanning electron microscope image.
	description	The sample cell 10 illustrated in FIG. 1 is an integral self-contained unit of generally three dimensional rectangular configuration. The cell includes structure 11 defining an enclosed sample chamber 12, and, mounted by being applied to structure 11, a body or target layer 20 of a substance excitable by an appropriate incident beam 5 to generate x-ray radiation 6. Cell 10 is arranged so that at least a portion of the radiation 6 traverses chamber 12 and thereby irradiates sample 7 in the chamber, and thereafter exits the structure for detection by x-ray detector 35. Structure 11 includes a relatively thicker substrate/spacer layer 22 and a relatively thinner window layer 24. These are spaced apart to define chamber 12, which is closed laterally by a peripheral side wall 26. Target layer 20 is applied by vapor deposition techniques, such as magnetron sputtering, thermal or electron beam evaporation, or chemical vapor deposition (CVD), to the major face 23 of substrate 22 which is the outer face relative to chamber 12. In an alternative arrangement, the chamber 12 may be open, but, especially for use with biological sample materials studied in vivo or in vitro, is preferably sealed with a gasket or other suitable arrangement such as bonded mylar or epoxy resin. In the present embodiment, the target layer 20 of excitable substance is an excitation layer which is typically formed of a substance of sufficiently high atomic number (Z) to provide, in response to excitation by an electron beam, medium to hard x-rays ( greater than xcx9c1 keV) capable of readily penetrating the excitation layer and the remainder of the cell. Examples of suitable materials include gold, platinum, copper, aluminium, nickel, molybdenum and tungsten. The thickness of the target layer 20 might typically be in the range 10 nm to 1000 nm. The layer thickness is selected according to the desired effective source size which is affected, inter alia, by the desired field of view and the geometry of the exciting beam, since a take-off angle of the x-rays produced by the x-ray source excited in the excitation layer is involved. In the case of electron excitation of target layer 20, the layer may need to be electrically connected to earth to prevent charging up if the excitation layer is a conductor. Some enhancement of cooling of the target layer via thermal conduction through the substrate may also be advantageous. The incident particle or radiation beam, an electron beam in the preferred arrangement, is preferably of sufficient energy to excite the desired characteristic energy x-rays or range of Bremstrahlung required for imaging. In the case of excitation by an electron beam, the electron energy is desirably such as to have sufficient over-voltage relative to the characteristic x-ray energy of the principal lines proposed for use in the imaging, to yield sufficient x-ray intensity. This might be in the range 1 kV to 150 kV for the accelerating voltage of the electrons. The substrate or spacer layer 22 may act in several ways including: (i) as a physical support for the relatively thin target layer 20; (ii) as a spacer layer to provide a controlled separation of the sample from the source; and (iii) as an energy bandpass filter for the transmitted radiation. (iv) as an aid to cooling of the target layer. Thickness here might be in the range 1 xcexcm to 500 xcexcm. This thickness is the prime determinant in controlling the desired magnification. A further function of this layer is to reduce the thickness over which relatively hard x-rays are produced and so this layer will typically consist of a lower atomic number and/or density material than the target layer 20. Suitable materials would include: polished Si (wafers which are commercially available), float or polished glass, and thin layers of Be, B, mica, sapphire, diamond and other semiconductor materials used as substrates. These can be produced with very smooth surfaces at close to the atomic level. When acting as a substrate, this layer should preferably be such as to provide a physical support for thin films of the excitation material (layer 20), and will preferably: (i) be highly homogeneous, i.e. uniform in density and thickness at the atomic level; and (ii) have very smooth surfaces, in order not to significantly degrade the spatial coherence of the x-ray wavefield induced in the excitation layer, i.e. preserve high spatial coherence of the incident beam in the radiation that irradiates the sample. In this way, contrast is optimised in the image, on the basis of the concept described in international parent publication WO96/31098. A further function of layer 22 is to truncate the splash or spreading of the electon beam in the excitation layer and thereby the effective size of the x-ray source. In certain cases layer 22 may not be required if the target material is sufficiently stable mechanically and if broadening of the effective x-ray source size is not exacerbated by the target thickness. A possible modification of the basic design of the cell is to hollow out the substrate/spacer layer to reduce the effect of absorption (especially in the case of the excitation of lower energy x-rays such as Al Kxcex1). A modified cell 10xe2x80x2 of this general type is illustrated in FIG. 2, in which like primed numerals indicate like components. The cavity formed in layer 22xe2x80x2 is indicated at 30xe2x80x2. A residual thin partition 22a is left between cavity 30xe2x80x2 and sample chamber 12xe2x80x2. This residual thin partition may be coated on the sample side with a further thin layer of material 25 in a similar manner to target layer 20xe2x80x2 but with a view to acting as a low x-ray energy absorption filter. Exit or window layer 24,24xe2x80x2 may act to contain the sample and also to filter any undesired x-ray radiation coming from excitation of the substrate/spacer layer 22,22xe2x80x2 which would have a larger effective source size than that of the excitation layer and so lead to loss of resolution. Suitable materials might include Kapton, Al, mylar, Si and Ge. Layer 24 should preferably be smooth and of uniform density so as not to lead to additional structure in the image due to phase-contrast effects. The thickness is that appropriate to achieve sufficient energy filtration or physical support for the enclosed sample. This exit window might also be coated with a suitable selective x-ray absorber. A further modification of the cell is shown at 10xe2x80x3 in FIG. 3 and enables substantial variation of the magnification in the image over a range, say, from xc3x97100 to xc3x97100,000. In FIG. 3, like components are indicated by like double-primed reference numerals. The variation of the magnification is achieved by providing excitable target layer 20xe2x80x3 and substrate 22xe2x80x3, as a unit 40 translatable towards and away from partition 22a within a peripheral wall 42. Alternatively, the peripheral structure 42 may be translated towards and away from the target layer 20xe2x80x3. In another modification, target layer 20 may be divided or patterned on a continuous substrate 22. FIG. 4 diagrammatically illustrates an exemplary arrangement in which gold spots 20a comprising target layer 20 are spaced on a substrate 22 of silicon. The advantage of this arrangement is that an x-ray beam 6 of accurately predictable xe2x80x9csourcexe2x80x9d size can be generated by a wider, less sharply forcussed electron beam 5. The illustrated cells would typically be manufactured by either micromachining or conventional techniques to dimensions selected so that the cell may be inserted as an integral self-contained unit, with pre-inserted sample 7 in chamber 12, into the sample stage of one or more types of commercially available electron microscopes or microprobes. FIG. 5 diagrammatically illustrates just such an assembly in a scanning electron microscope (SEM), for the embodiment of FIG. 1. Sample cell 10, once charged with a sample, is placed within a holder 50 in turn suspended from the upper wall 61 of a sample stage 60. Holder 50 includes a pair of fixed side walls 52, 53 with inturned lower flanges 52a, 53a, depending from wall 61, and adjustable rails 54, 55 that rest on flanges 52a, 53a. Respective piezo-actuators 56 provide for fine accurate adjustment of rails 54, 55 horizontally with respect to side walls 52, 53, and of cell 10 vertically with respect to rails 54, 55. Cell 10 is centred under an irradiation aperture 62 in upper stage wall 61 through which an electron beam is directed at target layer 20 from shielded pipe 70 retained in scanning coils 72. The beam originates from a suitable electron beam source (not shown) and is surrounded by a focussing magnet 75 for focussing the electron beam onto target layer 20. For very high spatial resolution x-ray imaging, the electron beam source may advantageously be a field emission tip, in order to minimise spot size and thereby enhance lateral spatial coherence as earlier discussed. Sample stage 60 serves as a shield against stray radiation and, as is conventional, is held on a mount 64 that allows significant vertical adjustment. The whole assembly is retained within an evacuable chamber 77 formed by an outer housing 76. A secondary electron detector 78 is provided at the side to help facilitate alignment and focussing. Sample stage 60 further includes an annular partition 66 with a central aperture 67 controlled by a shutter 68 with driver 69. The base 63 of sample stage 60 supports an x-ray recording medium as detector 35, which in this case is in vacuum. It should be noted however that, in many cases, the detector system may be outside the vacuum chamber, in which case a suitable x-ray window means would be incorporated in the outer housing 76. Moreover, in further adaptations of the invention, the sample cell may itself constitute the vacuum window for the outer housing 76. With the illustrated adaptation, the microscope may be used for x-ray absorption or phase-contrast imaging, and x-ray radiation 6 detected, after it passes out of window layer 24, at x-ray recording medium 35. x-ray imaging systems utilising CCD detectors or photostimulable phosphor image plates, are suitable for use as recording medium 35. Scanners are available for processing image plates. A further advantageous embodiment of the invention involves using 2-dimensional energy resolving detectors such as those based on CdMnTe or superconducting Josephson junctions, in order to simultaneously derive one or more effective x-ray images each corresponding to a narrow x-ray energy bandpass. This is data well-suited for use in phase retrieval methods described in our co-pending international patent application PCT/AU97/00882, especially for the high spatial resolution required in the present micro-imaging context. The configuration depicted in FIG. 4 is suitable for ultra high spatial resolution imaging of microscopic objects and features, including small biological systems such as viruses and cells, and possibly large biological molecules. The configuration makes possible a very small effective source size so that high spatial resolution or useful magnification can be obtained by making the source-to-object distance very small (down to the order of a few tens of microns or less) while the object-to-image plane distance can be macroscopic, say around 10 to 100 mm. The incident electron beam 5 is preferably focussed to a width in the range 10 to 1000 nm at the target. As earlier foreshadowed, for optimum performance in phase contrast imaging, and as taught by our co-pending international patent publication WO96/31098, all components except the sample should be such as to preserve as much as possible the high lateral spatial coherence of the x-ray beam and in practice this means that they have extremely smooth surfaces down virtually to the atomic level and also should best be of highly uniform density, ie. highly homogenous and free from micro defects and impurities. The x-ray radiation may be substantially either polychromatic or monochromatic, according to application and method of derivation of the image. In the latter case, it may be advantageous to enhance the degree of monochromaticity, eg by judicious choice of materials and/or of the excitation voltage of the electrons striking the target layer. In the former case, it may be advantageous to invoke the use of energy sensitive detectors. FIG. 6 depicts an alternative embodiment in which a sample cell 110 is assembled within the irradiation aperture 162 of a sample stage upper wall 161. Aperture 162 includes a generally cylindrical cavity 200 with a divergent or conical upper opening 202 and a reduced diameter lower opening 204. Cavity 200 is divided into a lower portion and an upper portion by a fixed peripheral ring 126 akin to side wall 26 of the embodiment of FIG. 1. A window platform 124 for sample 127 is adjustably retained on lipped ring rail 154: piezo-actuators 156, 157 allow lateral and axial adjustment of sample position as before. An integral plate comprising target layer 120 and substrate/spacer layer 122 is placed on ring 126 and, if necessary, a stabilising ring 95 placed on top to complete the assembled cell. It will be seen that sample chamber 112 is defined in part by each of substrate/spacer layer 122, ring 126 and window platform 124, and that the target layer-sample separation is adjustable in axial extent by piezo-actuators 156, 157. Generally, of course, the target layer or sample stage may be adjustable to vary magnification in the microscope. FIG. 7 is a modified form of embodiment of FIG. 6, in which like parts are indicated by like primed reference numerals. Here, the components are retained as a self-contained unit 150 defined by side wall 152, that seats snugly in cavity 200xe2x80x2 on the rim 203 of opening 204xe2x80x2 Dividing spacer ring 126xe2x80x2 is fixed to this side wall, which has an inturned lower flange 152a, for slidably supporting lipped ring 154xe2x80x2. In each of the embodiments described above, there is a single sample chamber 12. For particular applications, a self-contained cell structure may define multiple sub-cells having discrete sample chambers. Some discussion will now be provided in relation to significant parameters in an x-ray imaging arrangement utilising a cell of the illustrated form in a scanning electron microscope. For the purpose of this discussion, the following values of the parameters indicated in FIG. 1 may be referred to:these are typical or representative values suitable for use in the practice of an embodiment of the invention. t1 thickness of target layer 20 10 nm (and 100 nm) t2 thickness of support/spacer layer 22 10 microns t3 thickness of sample chamber 12 a few microns (generally t3xe2x89xa6t2) t4 thickness of window layer 24 a few tens of microns but this is not a critical parameter xcex1 convergence angle of incident electron 2xc2x0 beam 5 xcex2 angular width of x-ray beam 6 10xc2x0 1Di window to detector distance 100 mm Blurring at the image plane due to finite size of the source will occur on a spatial scale of order: xcx9c\|t1 sin (xcex2/2)\|+\|t1 tan (xcex1/2)\| allowing only for purely geometrical effects. For the numbers chosen above for these parameters this would give a value of the order of 1 nm, and is therefore negligible in the case of the present parameter values. The main geometrical parameters affecting magnification, M, are indicated in the diagram of FIG. 8. With this approximation, the magnification of the image is given by: M≈(1Di+t2+t4)/t2xcx9c1Di/t2 for 1Dixcx9c100 mm, t2xcx9c10 xcexcm: M=100 /0.01=104. Therefore, a 2.5 nm feature in the object will appear as a 0.025 mm (25 xcexcm) feature in the image. Such a feature is comparable with the typical spatial resolutions available with high-resolution digital x-ray imaging systems based on charge-coupled devices and photostimulable phosphor imaging plates. It is desirable that xcex2 and t2 be large in order to produce a large field of view of the sample (object), ie: =2 t2 tan(P/2)≈2t2xcex2/2 and for the particular parameter values chosen above xcx9c2xc3x9710xc3x97tan (5xc2x0)≈2 xcexcm at the object plane. With an electronic imaging system one could record many images from the same sample by scanning (or rastering) the probe beam. A 2 micron field of view on the sample would correspond to (2xc3x97104)xc3x97(2xc3x97104)(xcexcm2)=20xc3x9720 (mm2) on the imaging plane. This is also well suited to the field of view of high resolution electronic imaging systems such as CCD""s etc. A detailed analysis of the dependence of contrast and resolution on the key physical parameters involved in x-ray imaging with a microfocus source involves the following key quantities: s source size R1 source to object plane distance R2 object plane to image plane distance xcex x-ray wavelength u=1/d where u is the spatial frequency in an object corresponding to a spatial period d D spatial resolution at the imaging plane xcex1 angular divergence in the quasi-plane wave case. The present inventors, together with others, have undertaken a classical optics treatment of contrast and resolution for partially coherent illumination of a thin object, published (after the priority date of this application) in Rev. Sci. Instrums. 68 (7) July 1997. The results may be presented in terms of optical transfer functions for both absorptionxe2x80x94and phase-contrast contributions to the image. A summary of the critical conditions governing contrast and resolution in x-ray microscopy are presented in Table 1 appended hereto. More specifically, it may be shown that optimum phase contrast in the spherical-wave (present) case is given by: u=(2xcexR1)xe2x88x92xc2xd and taking R1=10 xcexcm xcex=0.1 nm one obtains u=1/dxcx9c40 nm. The coherence limit on resolution, dlow, due to finite source size (say, s=10 nm) is u=1/s=108 mxe2x88x921 or dlow=10 nm. The visibility upper u limit, 11/s, occurs with optimum phase contrast when R1=S2/2xcex=(10xc3x9710xe2x88x929)2/(2xc3x9710xe2x88x9210)=0.5 xcexcm in the above case. These results give some feeling for the dimensions of key parameters required to give optimum contrast for a given x-ray wavelength. Analysis of image intensity data and extraction of effective pure phase and absorption-contrast images, or mixtures, may advantageously be based on Maxwell""s equations or an appropriate variant, e.g. utilising the Fourier optics or appropriate Transport of Intensity Equations (TIE), as set out e.g. in our earlier patent applications in this area, especially co-pending international patent application PCT/AU97/00882. In order to help illustrate the nature of expected contrast and resolution in the case of x-ray microscopy of very small objects using the present invention, some illustrative calculated intensity profiles (sections of images) are presented in FIGS. 9 to 12. These calculations are for a simple cylindrical sample (object)xe2x80x94a polystyrene fibrexe2x80x94of different sizes and under different imaging conditions, for 1 keV x-rays and variable R1 (source-object distance) but constant R1+R2 (R2 being object-image distance). The main observable features are the levels of contrast and resolution achievable with 1 keV x-rays. To a first approximation the maximum contrast condition may be gained from the results given in Table I. The calculations from which FIGS. 9 to 12 were derived were carried out using wave optics based on the Kirchhoff formula for propagation of electromagnetic radiation. These involve fairly intensive numerical integration. Both absorption and phase effects are considered. As can be seen, the curves are of intensity in the image plane, but referred back to distance on the object. The four figures are for different diameter fibres and all are for 1 keV x-rays and R1+R2 fixed at 10 cm. Each figure shows curves for different values of R1 (and therefore R2). The vertical dashed lines mark the edges of the associated fibre. Even for the smallest fibre (0.05 xcexcm) there is around 4% contrast for suitable R1, which is useful. An intensity value of unity corresponds to what would be obtained in the absence of an object. The projected structure of a sample (object) can be reconstructed from one or more digitised images in several ways, depending on the nature of the object, and the accuracy and degree of sophistication desired. Reconstruction in this context means determining the distribution of both real (refractive) and imaginary (absorptive) parts of the projected refractive index of the object along the optic axis. In many cases, especially for thin objects typically examined in a microscope, the most useful starting point is perhaps the linearized diffraction equation (in 1 dimension): I(u)/ID≅xcex4(u)xe2x88x922 sin (xcfx80xcexz u2) xcfx86(u)xe2x88x922 cos (xcfx80xcexz u2)xcexc(u)xe2x80x83xe2x80x83(1) where xcex is the x-ray wavelength, z the object-image distance, and I, xcfx86 and xcexc are the Fourier representations of the image intensity and object phase and absorption transmission functions respectively. The variable u represents spatial frequency. An incident monochromatic plane wave propagating in the z direction is assumed. The present discussion is in terms of the plane wave case, although the spherical-wave case is really more appropriate for microscopy and can be deduced from the plane wave case by suitable algebraic transformations. In general xcfx86(u) and xcexc(u) cannot both be determined from a single measurement of I(u); at least two independent measurements, using different values of z or xcex are needed. However, for the case of a pure phase object, for which the last term in equation (1) vanishes, a single measurement of I(u), i.e. measuring a single image, is in principle sufficient to determine xcfx86(u), the spatial distribution of phase shift due to the object. Even here, however, there are advantages in performing several measurements, to reduce the effects of noise and of the zeroes of the xe2x80x9ctransfer functionxe2x80x9d sin (xcfx80xcexz u2), which cause loss of information for specific values of the spatial frequency u. This is one reason why the variability of xe2x80x9cfocal lengthxe2x80x9d z and/or wavelength xcex is considered to be a useful feature of the present instrument. For sufficiently small values of xcexzu2 a further simplification may be made to equation (1), viz the sin and cos terms may be expanded to first order, giving: I(u)xe2x88x92ID(u)≈xe2x88x922xcfx80xcexzu2xcfx86(u)xe2x80x83xe2x80x83(2) which is similar to a form of the Transport of Intensity Equation (M. R. Teague J.Opt.Soc.Am., A73, 1434-41, (1983); T. E. Gureyev, A. Roberts, and K. A. Nugent, J.Opt.Soc.Am., A12 1932-41, 1942-46 (1995); Gureyev and Wilkins, J.Opt.Soc.Am. A15, 579-585 (1998). It describes the differential phase-contrast regime (Pogany, Gao, and Wilkins, Rev. Sci. Instrum. 68,2774-82 (1997) which has already been demonstrated (see Wilkins et al, Nature (1996)). If the linear theory is inadequate, one may revert to the basic Fresnel-Kirchoff diffraction formula (in Fourier space): F(u)=exp (xe2x88x92ikz) Q(u) exp (ixcfx80xcexzu2)xe2x80x83xe2x80x83(3) and attempt to find the object transmission function Q which best reproduces the observed intensity(ies) I(x)=\|F(x)\|2. This may be carried out iteratively, in a similar manner to that used in numerical forms of reconstruction (retrieval) of optical holograms and electron microscope images, and several schemes have been described (J. R. Fienup, xe2x80x9cPhase Retrieval Algorithms:A Comparisonxe2x80x9d, Appl. Opt 21 2758 (1982); R. W. Gerchberg and W. O. Saxton, Optik (Stuttgart) 35 237, (1972)). Convergence, however, is often very slow, and there is much scope for improved algorithms. The above all refer to one- or two-dimensional projections of object structure. For three-dimensional object reconstruction at least two projections are generally required (stereoscopy) or many (for tomography). The former might be achieved in the present instrument by use of beam deflection; the latter would require a means of accurately rotating the specimen, which could be done by conventional mechanical means but would require further modifications beyond the standard microscope configuration described in this application. Advantages of the illustrated sample cells and related method for high resolution hard x-ray imaging (especially phase-contrast imaging) include the following: Very high spatial resolution (ie. useful magnification). Can be used in conjunction with high resolution scanning electron microscopes as a special sample cell. Can be used to study biological samples in vivo or in vitro in an electron microscope without requiring the biological sample itself to be in vacuo, although the sample cell is in vacuo (but appropriately sealed with a gasket or epoxy, say) Reduced radiation damage to the sample as result of the ability to obtain image contrast at higher x-ray energies than conventional soft x-ray microscopy of biological material. Can vary the characteristic x-ray energy by using different excitation target materials and/or electron accelerating voltage. High mechanical stability due to integrated structure Exit window of cell can be used to act as a rejection filter of low energy x-rays and so remove (clean up) unwanted background radiation (especially from the substrate/spacer layer) which might degrade overall resolution due to having a large effective source size. The volume of the cell may be made quite small. This might even be made adjustable in situ by use of an appropriate gasket and applied pressure, with possibility of adjustment to improve the visibility of certain features of interest in the sample. Cells are in principle reusable. Cells could be maintained at, say, room temperature by appropriate heating stage in microscope. Can study large area of sample by shifting e-beam or translating sample cell, and recording different exposures. Focusing of the electron beam on the excitation target can be conveniently monitored by use of the secondary electron detector, or by the use of electronic imaging detectors. Can be used to implement limited field computerised tomography (CT) either by scanning the exciting beam on the target or by rotating the whole cell.
048903124	description	FIG. 1 shows a rectangular plate 1 of piezoelectric material. The plate is slit from one of the sides 2 by a number of parallel saw cuts which extend in the direction of the opposite side 3, but which terminate at some distance from the side 3. The saw cuts each lie at an equal distance from each other or from the long sides 4, 5 of the plate 1. There is thus formed from the rectangular plate 1 a number (in the embodiment shown 19) of tongues 6 which extend in parallel from a common base which is formed by the unslit part 7 of the rectangular plate. The free ends of the tongues 6 can move in a direction transverse to the surface of the plate 1 with respect to each other. FIG. 2 shows a similar assembly of attenuation tongues formed from a single plate 1' of piezoelectric material. In this embodiment the side 3' is, however, longer than the side 2' and the saw cuts converge when viewed from the longest side 3' in the direction of the shortest side 2', while the long sides 4', 5', corresponding to the long sides 4, 5 of FIG. 1, also converge so that wedge-shaped tongues 6' are obtained which again terminate at some distance from the longest side 3' while leaving free a base 7'. It is pointed out that in FIG. 2 the tongues are not equally long, as a result of which they have a different dynamic behaviour. This possible drawback can be eliminated by, for example, constructing the side 2' of the plate 1' as a circular arc as indicated by broken lines at 2" and making the slits equally long so that the ends of the slits also lie on a circular arc 8. The assemblies of attenuation tongues shown in FIGS. 1 and 2 therefore have the form of a comb. Because the tongues have been formed from a single plate of material and, in addition, continue to form a single whole with the base of the comb (the unslit section 7 or 7') the tongues do not have to be separately mounted and adjusted during assembly in slit radiography equipment. It is possible to make do with mounting and aligning the comb as a whole, which is relatively simple. The replacement of such a tongue assembly can also be performed very simply and rapidly. Because the separation between two tongues is in each case formed by a single saw cut or a slit made in another manner, the gap between two adjacent tongues is automatically equally large over the whole length of the slit. The slits required to form the tongues can be made with a fine small saw. However, it is also possible to make the slits by means of a laser or by means of ultrasonic techniques known per se. In practice, it has proved possible to make very narrow slits with a width in the order of 50 .mu.m by means of ultrasonic techniques. Such a small gap between adjacent tongues cannot, or virtually cannot, be achieved if "loose" tongues are used. FIG. 3 shows in plan view the assembly of FIG. 1 in the assembled state, and FIG. 4 shows a section along the line IV--IV in FIG. 3. The tongue plate 1 provided with slits is mounted in a box-shaped casing 30 with an upper wall 31, a lower wall 32, side walls 33 and 34 and a front wall 35. A back wall is not drawn since it is not necessary. If desired, however, a back wall could indeed be present, which would then have to be provided with a slit. In the front wall 35 a slit 36 has been made. The slit 36, which acts as a slit diaphragm, of the casing faces an x-ray source, the focus of which is indicated by 37. The maximum width and thickness of the fanshaped x-ray beam 38 transmitted through the casing is therefore determined by the dimensions of the slit. Preferably, however, separate adjustment means are further provided in the casing in order to limit the x-ray beam accurately as will be described in further detail below. It is pointed out that hereinbefore and hereinafter the descriptions "upper" and "lower" are used in relation to the orientation of the figure. In reality, the position of the casing depends on the manner in which the slit radiograpjhy equipment is installed. In practical equipment, for example, the wall 34 may be the lower wall and the wall 33 the upper wall, or the wall 31 may be the lower wall and the wall 32 the upper wall. The x-ray source might also be situated on the other side of the casing (i.e. on the right-hand side in FIGS. 3 and 4). In the embodiment shown the non-slit section, the base 7, of the tongue plate 1 is mounted on the lower wall 32 of the casing and its tongues are directed obliquely upwards towards the slit in the front wall. Above the base 7 there is disposed a clamping bracket 39 which is attached by means of bolts 40 or the like to the lower wall of the casing on either side of the tongue plate and thus clamps the tongue plate against a spacer 41 of insulating material. In order to be able to control the piezoelectric tongues separately, the tongues have to be electrically separated from each other at least on one side of the tongue plate. For this purpose, in the exemplary embodiment shown the slits in the plate 1 are continued on the lower side across the base 7 to a depth of about half the thickness of the plate, as is indicated by broken lines 42 in FIG. 3. Since such slits to a depth of half the thickness weaken the tongue plate, the base 7 is preferably provided with a glued reinforcing strip 43 of a suitable material on the non-slit upper surface. Moreover, the ridge 7 is provided with a common electrical connecting point 44 on the upper side. In the spacer 41 there is disposed a cutout in which connector element 45 is placed which brings about separate electrical connections with each tongue 6. For this purpose, the connecting points of the connector element in the exemplary embodiment shown are connected to electrically conducting tracks (not shown) disposed on an insulating plate 46 placed on the lower wall of the casing. One conducting track is provided for each tongue and preferably an additional track is also present which is connected to the common connecting point 44. The conducting tracks are connected to diagrammatically indicated connector pins 47, two of which are visible, which reach through a cutout in the lower wall. The ends of the tongues 6 situated near the slit 36 reach, during operation, to a greater or lesser extent into the x-ray beam 38 and in the quiescent state are situated just outside the x-ray beam or in the x-ray beam, depending on the chosen manner of controlling the position of the tongues. Although the piezoelectric material of the tongues themselves in most cases already attenuates x-ray radiation to an extent which is adequate to influence the x-ray beam in the required manner, if desired, elements 48 of an x-ray radiation-absorbing material, for example lead or tungsten, can be provided on the ends of the tongues. Said elements may advantageously be formed from a strip of material which is provided, for example, by gluing along the edge 2, or 2' of the plate 1, 1' which has not yet been slit. As a result of the slitting the separate absorption elements are then produced simultaneously with the tongues. The use of absorption elements on the free ends of the tongues has the additional advantage that the influencing of the x-ray beam can be made proportional to the angular position of the tongues in a simple manner. In addition, the risk is reduced that unattenuated x-ray radiation is transmitted between two adjacent tongues which have a different angular position, i.e. whose ends reach to a different extent into the x-ray beam. Admittedly, said risk is nevertheless already very small in a tongue assembly according to the invention as a consequence of the very narrow slits between the tongues. In the tongue assembly shown, the risk of transmission of x-ray radiation which cannot be influenced via the slits between the tongues virtually only exists in the case of the slits on either side of the centre tongue (s) because said slits are most in line with the x-ray radiation at that point. This is dependent on the distance between the tongues and the x-ray focus, the dimensions of the x-ray focus and the width of the ends of the tongus. All this can, if desired, be prevented by providing at least the centre tongue(s) with two small elements or horns of absorbing material which reach forward, i.e. in the direction of the x-ray source and which precisely shield slits on either side of the tongue. Such small elements are indicated at 63, 64 for the centre tongue in FIG. 5 which shows the centre tongue 60 and two adjacent tongues 61, 62. If elements 48 are also used, the horns 63, 64 may form a single whole with the element 48 concerned. As an alternative it is possible to provide all the tongues apart from the centre one with absorption elements 48 and to provide the centre tongue with an element 48' (FIG. 6) which reaches forward and which is equally as wide as the tongue itself plus the two slits on either side of the tongue. Depending on the distance between the x-ray focus and the tongues, the width of the ends of the tongues and the dimensions of the x-ray focus, it may be desirable to provide the tongues, at least in the central region, alternately with elements 48 and 48'. The difference in dynamic behaviour of the tongues produced by this can be compensated for by constructing the ends of the tongues provided with elements 48' in a wedge-shaped manner as is indicated by broken lines at 65 in FIG. 6 for the centre tongue. A similar method could in principle be used also in the case of tongue 60 of FIG. 5. It is pointed out that use of additional absorption elements reduces the mechanical resonant frequency of the tongues, as a result of which the response of the tongues becomes slower. This effect can be compensated for by constructing all the tongues with a wedge-shaped end. By choosing the length and/or tapering of the wedgeshaped sections differently for tongues which are provided with an absorption element projecting forwards such s 48' from those chosen for tongues which are provided with an element which does not project forward such as 48, the same resonant frequency can be obtained for every tongue. In general it is of importance in slit radiography equipment provided with attenuation tongues to be able to set the dimensions of the scanning x-ray beam, i.e. the thickness and the width, or rather the angles .rho. (FIG. 3) and .alpha. (FIG. 4) as accurately as possible in order to be certain that the whole of the scanning x-ray beam, or at least a fixed section thereof can also in fact be influenced by the tongues. If a tongue plate according to the invention is used, this is still more important because the maximum deflection of the tongues has preferably to be as small as possible in order to prevent the base 7 from cracking at the position of the junction with the tongues. A relatively small maximum deflection of the tongues requires a relatively large setting accuracy for the dimensions of the x-ray beam. For this purpose, according to the invention, there are disposed on either side of the x-ray beam strongly absorbing, for example lead, elements 49 and 50 respectively which are attached to the side walls 33, 34 of the casing in the exemplary embodiment shown and whose distance from the side walls is adjustable, as is indicated diagrammatically by arrows 51. For the setting, an adjustment screw may, for example, be provided such as is indicated by 52 for the element 50. The thickness of the x-ray beam can be set in a similar manner by an adjustable strip of absorbing material disposed on the upper side of the x-ray beam. The lower side of the x-ray beam is defined in this exemplary embodiment by the lower edge of the slit 36 in the casing 30 which is also manufactured from a material which absorbs x-ray radiation. FIG. 4 shows such a strip of absorbing material 53 which is joined to the upper wall via a spring plate or strip 54 and whose distance from the upper wall can be set by means of one or more adjustment screws 55. It is pointed out that only a few exemplary embodiments of the invention have been described above. In addition to the above various modifications are obvious to those skilled in the art. Thus, for example, the risk of spark flashover between adjacent tongues can be reduced by providing the tongues with a layer of lacquer. Such modifications are considered to fall within the scope of the invention.
	abstract	In order to carry out a radioactivated reactor pressure vessel from a nuclear reactor building of a nuclear power plant, a first opening portion for carrying out the reactor pressure vessel is provided in a roof of the nuclear reactor building. A radiation shield for covering the reactor pressure vessel and shielding radiations is carried into the reactor building through the first opening portion, and installed on a reactor shield wall. A hanger is lowered through the first opening portion and a slit provided on an upper lid of the radiation shield. A portion of a lid of the reactor pressure vessel and a portion of the upper lid of the radiation shield are abutted by hanging up the reactor pressure vessel by the hanger. The reactor pressure vessel and the radiation shield integrated therewith are raised and carried out of the reactor building, whereby the shield can be easily mounted on the large-sized apparatus in a short time and a dose of radiation exposed to a worker when the shield is mounted can be reduced.
	claims	1. An elongated composite container having a hollow central bore, the container comprised of an outer metallic tubular portion and an inner metallic barrier metallurgically bonded to the outer metallic tubular portion, the inner metallic barrier having a combination of crack resistance and corrosion resistance consisting essentially of commercially pure zirconium microalloyed with iron in the range of from about 850-1500 ppm, and the balance incidental impurities. 2. The composite container of claim 1 wherein the zirconium base alloy is Zircaloy-2. claim 1 3. The elongated composite container of claim 1 wherein the inner metallic barrier comprises about 10 to about 20% of the total composite container thickness. claim 1 4. An elongated composite container having a hollow central bore, the container having an outer metallic tubular portion and an inner metallic barrier metallurgically bonded to the outer metallic tubular portion, the inner metallic barrier comprising commercially pure zirconium microalloyed with iron in the range of above about 1500 ppm and below 2000 ppm., the composite container characterized by improved corrosion resistance and stress corrosion cracking resistance of the inner metallic barrier. 5. The container of claim 1 wherein the inner metallic barrier has a composition of iron in the range of 1000xc2x1150 ppm microalloyed with commercially pure Zirconium. claim 1 6. The composite container of claim 1 wherein the outer metallic tubular portion is comprised of a zirconium base alloy. claim 1 7. The composite container of claim 1 in which the inner metallic barrier includes iron in the range of from about 1000-1500 ppm, which is alloyed with zirconium. claim 1 8. An elongated composite container having a hollow central bore, the container having an outer metallic tubular portion and an inner metallic barrier metallurgically bonded to the outer metallic tubular portion, the inner metallic barrier consisting essentially of commercially pure zirconium microalloyed with iron in a range from about 1000-1500 ppm, the composite container characterized by improved corrosion resistance and stress corrosion cracking resistance of the inner metallic barrier. 9. The composite container of claim 4 wherein the outer metallic tubular portion is comprised of a zirconium base alloy. claim 4 10. The composite container of claim 8 wherein the outer metallic tubular portion is comprised of a zirconium base alloy. claim 8
	description	The present invention concerns a method of making a nuclear fuel pellet for a nuclear power reactor. Different manners of producing nuclear fuel pellets are known by a person skilled in the art. It is normal to make the nuclear fuel pellet from a nuclear fuel material in powder form. The nuclear fuel material may for example be UO2, where U is enriched with regard to 235U. The powder material may also include additives, such as U3O8 and binder material. The powder is pressed in order to form a so-called green pellet. The concept “green pellet” in this technical field means the pressed pellet before it is sintered. The green pellet is thus thereafter sintered in a furnace. The sintered pellets are thereafter ground in order to obtain the correct diameter and surface finish. It is also known to include some additives in the powder in order to increase the grain size in the sintered pellet. For example WO 00/49621 A1 gives some examples of such additives and describes how the nuclear fuel pellet may be produced. Other examples of how to increase the grain size in the nuclear fuel are described in GB 2177249 A, GB 2020641 A, GB 2107691 A and DE 3235944 A1. WO 2005/041208 A2 describes that a porous uranium dioxide arrangement is infiltrated with a precursor liquid in the form of allylhydridopolycarbosilane in order to enhance the thermal conductivity in the nuclear fuel. Another phenomenon that occurs when using nuclear fuel in a nuclear reactor is a structure in the used nuclear fuel pellets called high burn-up structure (HBS) or rim structure. When the nuclear fuel has been used for a longer time in a nuclear reactor (i.e. a high burn-up) a new restructured configuration appears at the outer thin region of the fuel pellet. This phenomenon is described for example in the article “The high burn-up structure in nuclear fuel” by V. V. Rondinella et al. in Materials Today, December 2010, Volume 13, No. 12, pages 24-32. The HBS means that the grains in the outer region of the nuclear fuel pellet subdivide into very small grains. The outer region in which the HBS appears may for example be less than 100 μm thick. Different problems caused by the HBS are mentioned in this document. WO 97/13252 A1 and JP 9-127279 A describe different ways of reducing problems of the rim structure. When in this document a certain percentage of a material is mentioned, this concerns weight percent, if nothing else is said. When in this document a certain grain size is mentioned, this refers to the so-called two dimensional (2D) grain size, i.e. the grain size measured in a plane, if nothing else is said. As mentioned above, the HBS may have negative effects. For example, HBS may have a detrimental effect on thermal conductivity, fission gas release, and behavior during a loss-of-coolant event. There is therefore regulations stating that nuclear fuel may only be used up to a certain burn-up level. An object of the present invention is to provide a method of making a nuclear fuel pellet, with which method improved nuclear fuel can be produced. A particular object is thereby to make a nuclear fuel with which the formation of the HBS is prevented or delayed. A further object is to provide such a method which can be carried out in a relatively simple manner. The above objects are achieved by a method of making a nuclear fuel pellet for a nuclear power reactor, the method comprising the following steps: providing a nuclear fuel material in powder form, providing an additive, pressing the powder such that a so-called green pellet is ob-tained, wherein said additive is added either to said nuclear fuel mate-rial in powder form or to the green pellet, sintering the so obtained green pellet, wherein said additive is such that larger grains in the nuclear fuel material are present in the pellet after the sintering step as com-pared with the grain size obtained if a pellet, which is produced ac-cording to the above manner but without the addition of the additive, is sintered in the same manner, wherein said additive is made of or includes a substance which causes said larger grains in the sintered pellet, wherein said sub-stance is selected and the method is performed such that at least to 90% of the substance, leaves at least an outer portion of the pellet before and/or during the sintering step. The inventors of the present invention have realized that the occurrence of the above described HBS may be prevented, or delayed, if the nuclear fuel pellet has larger grains at least in the outer portion of the nuclear fuel pellet (where the HBS occurs). Furthermore, the inventors have realized that it may be an advantage if additives do not remain in the sintered pellet, or at least not in an outer portion of the pellet. For example, the presence of additives may affect the neutron economy; i.e. the additives may absorb neutrons. On the other hand, as explained above, large grains, at least in the outer portion of the nuclear fuel pellet, are advantageous in order to prevent the HBS. It is therefore an advantage to use a substance that leaves at least an outer portion of the pellet before or during the sintering step. The mentioned substance may also, to the same extents as mentioned in claim 1, leave the whole nuclear fuel pellet before and/or during the sintering step. With a nuclear fuel pellet made in accordance with the present invention, the formation of HBS can thus be prevented or delayed when using the nuclear fuel pellet in a nuclear reactor. The nuclear fuel produced in accordance with the present invention can therefore be used for a longer time in the nuclear reactor, i.e. to a higher burn-up. The substance may be included in a compound, such that the additive is a compound which includes the substance which causes the larger grains. The rest of the compound may act primarily as a carrier of the substance which causes the larger grains. For example, the additive may be UB4. In this case the B will cause the larger grains, but the U as such in the compound UB4 will not substantially contribute the larger grains. This is thus the reason why it is stated in the claim that the substance causes the larger grains. The substance is preferably a chemical element, for example B or Cr. The additive may include more than one such substance. The nuclear fuel material in the powder is preferably based on UO2 as the actual nuclear fuel material. The nuclear fuel material in powder form may to at least 60%, preferably to at least 70%, more preferred to at least 80% or at least 90%, consist of UO2. As is known to a person skilled in the art, the powder may also comprise other matters, such as binders, U3O8, burnable neutron absorbers, pore formers and sintering aid, for example Al2O3. When it is said that larger grains are obtained with the additive (as compared with the grain size obtained if a pellet that has been produced in the same manner, but without the addition of the additive, is sintered in the same manner), this means that substantially larger grains are obtained, for example the average grain size (at least in the part of the pellet, where the additive is added) may be at least 50% larger, preferable at least 100% larger, most preferred at least 200% larger. The average grain size obtained with the help of the additive may for example be at least 20 μm, preferably at least 30 μm. According to one manner of carrying out the method of the invention, the produced nuclear fuel pellet has a substantially cylindrical shape with a radius r, wherein said outer portion is the part of the nuclear fuel pellet that is located between 0.8 r and r, or between 0.9 r and r, or between 0.95 r and r. According to a further manner of carrying out the method of the invention, said substance is made of, or comprises, B and/or Cr. These substances are advantageous substances that will increase the grain size. According to a further manner of carrying out the method of the invention, said additive to at least 60%, preferably to at least 80%, most preferred to 100%, is selected from the group consisting of B, UB4, B4C, ZrB2, Cr, CrO, CrO2 and Cr2O3 or combinations thereof. These additives have been found to be particularly advantageous in order to obtain the larger grain size, without the mentioned substance remaining in at least an outer portion of the produced pellet. According to a further manner of carrying out the method of the invention, said additive comprises B and at least 90% of said B is 11B. B in the form of the isotope 10B acts as a neutron absorber. However, if the purpose of the added B is to increase the grain size, but not to act as a neutron absorber, then it is preferable to use the isotope 11B, since if some B would remain in the sintered pellet, this B will in this case not act as a neutron absorber. The B may, for example, be selected such that it in said additive to at least 98% is present in the form of the isotope 11B. According to a further manner of carrying out the method of the invention, the method comprises arranging said additive such that an outer portion of the green pellet contains substantially more additive than an inner portion of the green pellet, such that the sintered pellet has a larger grain size in the outer portion than in the inner portion. If the additive is only present in an outer portion, it is easier to make the additive leave the pellet, for example during a heating step, such as the sintering step. Furthermore, as explained above, the HBS occurs at the outer portion of the nuclear fuel pellet. It is therefore sufficient to have larger grains in the outer portion of the nuclear fuel pellet in order to prevent or delay the formation of the HBS. The outer and inner portions may be defined in different manners. For example, if we consider a cylindrical nuclear fuel pellet with a radius r, the inner portion may for example be the part of the nuclear fuel pellet from the centre of the pellet outwards up to for example 0.6 r and the outer portion may for example be the part of the nuclear fuel pellet that is located between 0.8 r and r or between 0.9 r and r, or between 0.95 r and r (depending on where it is desired that the grains are larger). When it is stated that the grain size is larger in the outer portion, also this may be defined in different manners. For example, if we consider the average 2D grain size in the outer portion and the average 2D grain size in the inner portion, the average grain size in the outer portion may be at least 50%, preferably at least 100%, larger than the average grain size in the inner portion. According to a further manner of carrying out the method of the invention, said additive is provided in the form of particles. Such particles may be mixed with the nuclear fuel material in powder form before pressing this powder into the green pellet. Alternatively, the particles may be added to the green pellet. According to a further manner of carrying out the method of the invention, the method comprises providing a liquid and arranging the additive in the liquid such that said additive is in the form of particles dispersed in said liquid, wherein the liquid with the additive is added either to said nuclear fuel material in powder form or to the green pellet. It is advantageous to use a liquid as a carrier of such particles. Since the particles are dispersed in the liquid, the particles do not dissolve in the liquid. According to a further manner of carrying out the method of the invention, the method comprises adding said liquid with the additive to the green pellet by contacting the green pellet with the liquid such that the liquid, with the additive, penetrates into the green pellet and controlling the penetration depth of the liquid, and thereby of the additive, into the green pellet. According to this alternative, the additive which increases the grain size is thus added after the green pellet has been formed. It is therefore not necessary to add the additive to the powder before pressing the green pellet. Since the additive is provided in a liquid, it can be controlled to which extent the additive enters into the green pellet. An improved control of the addition of the additive which increases the grain size is therefore achieved. Furthermore, it is quite easy to apply the liquid, with additive, to the green pellet. By controlling the penetration depth, it is possible to control in which region in the pellet the liquid, with the additive, is present. It is thereby possible to control where the additive is present in the pellet. According to a further manner of carrying out the method of the invention, said step of controlling the penetration depth is done by selecting one or both of the following: the viscosity of the liquid with included additive, the amount of the liquid, with the additive, which is added to the green pellet when contacting the green pellet with the liquid, with the additive. By selecting a liquid with a certain viscosity it is possible to control the penetration depth of the liquid. The penetration depth may also be controlled by controlling how much liquid is added to the green pellet. The amount of the liquid, with the additive, which is added to the green pellet can be controlled for example by spraying a certain amount of the liquid, with additive, onto the green pellet, or by exposing the green pellet to the liquid, with additive (for example by dipping the green pellet in the liquid, with additive) during a predetermined time. The penetration depth of the liquid, with the additive, into the green pellet can be controlled such that an outer portion of the green pellet contains substantially more liquid, and thereby more additive, than an inner portion of the green pellet, such that the sintered pellet has a larger grain size in the outer portion than in the inner portion. Said liquid with additive can be selected and said method can be performed such that the liquid with additive will penetrate into the pores which exist between the grains in the green pellet. The green pellet will have pores both between the grains in the green pellet and inside the grains in the green pellet. The pores inside the grains are normally smaller than the pores which exist between the grains. Consequently, it can be controlled (for example by selecting a certain viscosity) that the liquid will penetrate into the pores which exist between the grains. Said liquid with additive can be selected and said method can be performed such that the liquid with additive will not, at least not to any substantial degree, penetrate into the pores which exist in the grains in the green pellet. According to this alternative, the additive will not to any substantial degree enter into the grains, but the additive will be added into the pores which exist between the grains. Alternatively, said liquid with additive can be selected and said method can be performed such that the liquid with additive will penetrate also into the pores which exist in the grains in the green pellet. According to this alternative, the additive will thus enter also into the pores in the grains. With the present invention it is thus possible to control where in the green pellet the additive is added. According to a further manner of carrying out the method of the invention, said liquid is selected and said method is performed such that the liquid will completely, or at least to 99%, leave the pellet before or during the sintering step. Since the liquid will leave the pellet, the liquid (and the material which constitutes the liquid) will not be present in the sintered pellet. Consequently, the liquid acts as a carrier of the additive and will not influence the properties of the produced pellet. Preferably, the liquid leaves the pellet during a step of heating the pellet. This can either be a separate heating step before the sintering step or the heating that is performed during the sintering step. The latter alternative has the advantage that no separate heating step is necessary. Said liquid can be selected such that the additive does not dissolve in the liquid, and such that the nuclear fuel material in the green pellet is not dissolved by the liquid. According to a further manner of carrying out the method of the invention, said liquid is an oil, preferably a mineral oil. Such liquids have advantageous properties for acting as a carrier for the additive. Furthermore, by selecting a suitable mineral oil, a suitable viscosity is achieved. The invention also concerns a method of making and using nuclear fuel. This method comprises: making a plurality of nuclear fuel pellets according to any one of the preceding manners, arranging the nuclear fuel pellets in cladding tubes, arranging the cladding tubes, with the nuclear fuel pellets, in the core of a nuclear power reactor in a nuclear power plant, such that at least 20%, preferably at least 50%, most preferred 100%, of the nuclear fuel material in said core are made of pellets made in accordance with any one of the preceding manners, operating the nuclear reactor to produce energy. By using the advantageous nuclear fuel pellets obtained with the method according to the present invention in a real nuclear power reactor, the advantages of the produced nuclear fuel are thus achieved in a nuclear power reactor plant for producing energy. The nuclear power reactor preferably comprises several thousand cladding tubes comprising nuclear fuel pellets produced with the method according to the present invention. By using the nuclear fuel pellets produced in accordance with the present invention in a nuclear reactor, the nuclear fuel may be used for a longer time, since the formation of HBS is prevented or delayed with the present invention. Since a person skilled in the art knows how to produce nuclear fuel pellets from a powder, all the details of such a method will not be described herein. However, the main steps which are relevant to the present invention are described. FIG. 1 shows schematically the main steps of a manner of carrying out a method according to the present invention. A nuclear fuel material in powder form is provided. The nuclear fuel material may be based on UO2, which is enriched concerning 235U. The powder may also comprise other materials, for example binder materials and U3O8. An additive is provided. The additive constitutes or includes a substance that will increase the grain size of the sintered pellet. Furthermore, the substance is such that it will leave at least an outer portion of the pellet before and/or during a sintering step. The additive may for example comprise B, for example in the form of UB4. According to one embodiment, the B is in the form of 11B. B has the property of increasing the grain size when the green pellet is sintered. However, B will also to a large extent leave the pellet when it is heated during the sintering process, or before the sintering if a heating step is performed before the actual sintering. According to another alternative, the additive may be for example Cr2O3. Also Cr has the property of increasing the grain size. Furthermore, also Cr will to a substantial degree leave at least an outer portion of the pellet if sufficient temperature and time are used for heating the pellet, before or during the sintering step. The additive is preferably in the form of particles, i.e. a powder. The additive powder is mixed with the nuclear fuel material in powder form. The mixed powder is pressed such that a green pellet is formed. The additive may be mixed with the whole nuclear fuel material in powder form. Alternatively, it is possible to mix the additive with only a part of the nuclear fuel material in powder form. According to the first mentioned alternative, the additive may thus be distributed in the whole green pellet. According to the second alternative, it is possible to arrange the nuclear fuel material in powder form without the additive in an inner portion and to add the mixture of the additive and the nuclear fuel material in powder form to an outer portion before the green pellet is pressed. According to the second alternative, the additive will thus be present only in an outer portion of the green pellet. The green pellet is then sintered. This can be done for example in a furnace which contains different zones where the pellet is heated up to a final temperature of about 1 800° C. The temperature and the time is selected such that the substance in the additive which causes the larger grains in the sintered pellet will substantially leave (evaporate) at least an outer portion of the pellet during the sintering step. Alternatively, a separate heating step may be performed before the actual sintering in order to achieve this. The sintered pellet is ground in order to obtain the correct diameter and surface finish. The nuclear fuel pellet has a substantially cylindrical shape with a radius r. The outer portion of the pellet may for example be the part of the produced nuclear fuel pellet that is located between 0.9 r and r. When a plurality of nuclear fuel pellets have been made in accordance with the present invention, the nuclear fuel pellets are arranged in cladding tubes. The cladding tubes are then positioned in nuclear fuel assemblies which are arranged in a nuclear reactor. The nuclear reactor is then operated in order to produce energy. FIG. 2 shows a flow chart of another manner of carrying out a method according to the invention. The main difference in the method according to FIG. 2, as compared with the method according to FIG. 1, is that the additive is added after the green pellet has been formed. According to FIG. 2, a nuclear fuel material in powder form is provided. The same nuclear fuel material as mentioned in connection with FIG. 1 may be used. The powder is pressed such that a “green” pellet is formed. The green pellet will be porous. For example 50% of the pressed pellet may consist of pores. An additive is provided. The additive is made of or includes a substance which will increase the grain size of the sintered pellet. Furthermore, the substance, which causes the larger grains, is such that it will leave at least an outer portion of the pellet before and/or during a following sintering step. The additive may for example comprise B, for example in the form of UB4. According to one embodiment, the B is in the form of 11B. According to another example, the additive may be Cr2O3. The additive is preferably in the form of particles, i.e. a powder. The size of the particles should be small enough so that the particles can penetrate into the pores in the green pellet, into which it is intended that the particles should penetrate. The particle size may for example be about 1 μm. A liquid is provided. The liquid may be a mineral oil. The mineral oil may be selected to have a desired viscosity, for example a kinematic viscosity of 320 centistokes. The additive is mixed with the liquid. Preferably, the additive particles are dispersed in the liquid, i.e. the liquid is selected such that the additive particles do not dissolve in the liquid, and also such that the nuclear fuel material in the green pellet is not dissolved by the liquid. The green pellet is brought into contact with the liquid with the additive. The green pellet may for example be dipped into the liquid with additive or the liquid with additive may be sprayed onto the green pellet. The penetration depth of the liquid, and thereby of the additive, into the green pellet is controlled. This can be done by selecting a suitable viscosity of the liquid or by controlling the amount of liquid, with the additive, which is added to the green pellet. This can be done for example by spraying a certain amount of the liquid onto the pellet or by dipping the green pellet in the liquid, with additive, during a predetermined time. The penetration depth can be controlled such that the additive is added only to an outer portion of the green pellet. By controlling for example the viscosity of the liquid, with the additive, or the size of the additive particles, it is also possible to control into which pores in the green pellet that the additive will enter. For example, it may be controlled that the additive will substantially only enter into the pores which exist between the grains in the green pellet. Alternatively, it may be controlled that the additive will enter also into the pores which exist in the grains in the green pellet. The so treated green pellet is then sintered. This can be done for example by a sintering process in a furnace which contains different zones where the pellet is heated up to a final temperature of about 1 800° C. The liquid is preferably selected such that it will evaporate during the heating process. There may be a separate heating step before the actual sintering in order to evaporate the liquid. However, no such separate heating step may be necessary, since the liquid will evaporate during the sintering process. The time and temperature for the heating/sintering process are selected such that also (at least) the substance which causes the larger grains will substantially leave at least an outer portion of the pellet before and/or during the sintering step. The outer portion of the pellet may, as explained above, for example be the part of the produced nuclear fuel pellet that is located between 0.9 r and r. When it is desired to increase the grain size in the whole nuclear fuel pellet, the additive, and the viscosity of the liquid, may be selected such that the whole pellet is infiltrated with the liquid with the additive. However, as explained above, it is possible to control the penetration depth of the liquid with the additive. According to a preferred manner of carrying out the present invention, the penetration depth is controlled such that the additive will substantially enter only into an outer peripheral portion of the green pellet. When the green pellet is then sintered, larger grains will be obtained mainly in an outer portion of the pellet. FIG. 3 illustrates schematically how the grain size may vary in a pellet produced in this manner or in the manner described in connection with FIG. 1 (if the additive is added in an outer portion of the pellet). The x-axis shows the radius of the sintered pellet. The radius r 1.0 is thus the outer periphery of the pellet. The radius of the pellet may for example be about 4.6 mm. The y-axis in FIG. 3 shows the average 2D grain size. The curve in FIG. 3 thus shows how the average 2D grain size varies with the radius. FIG. 3 thus illustrates that according to this embodiment of the invention, a substantially larger grain size is obtained in the outer portion of the sintered pellet. This has in particular the advantage that the formation of the above described HBS can be prevented or delayed. In the same manner as described in connection with FIG. 1, a plurality of nuclear fuel pellets are produced according to the method of the present invention. The produced pellets are arranged in cladding tubes. The cladding tubes are arranged in the core of a nuclear power reactor, such that the core includes several thousand cladding tubes with pellets produced in accordance with the present invention. The nuclear reactor is operated in order to produce energy. The present invention is not limited to the examples described herein, but can be varied and modified within the scope of the following claims.
041526023	claims	1. A nuclear fuel rack disposed within an enclosure having substantially vertical walls, said rack including a plurality of cells each sized to receive a nuclear fuel assembly, said rack positioned so as to have a side substantially parallel to and spaced from one of said walls, said rack additionally having a seismic restraint comprising: a. a cylinder; b. a piston cooperatively associated with said cylinder for sliding motion with respect thereto; c. means for allowing a controlled flow of fluid into said cylinder so as to restrain motion of said piston; d. a support surface joined to one of said piston and cylinder and positionable substantially perpendicular thereto; e. means for affixing the other of said piston and cylinder to said rack in a substantially horizontal orientation; and f. an elastic structure substantially stationary at one end with respect to said rack and acting at the other end upon the one of said piston and cylinder joined to said surface. a. a cylinder; b. a piston cooperatively associated with said cylinder for sliding motion with respect thereto; c. means for allowing a controlled flow of fluid into said cylinder so as to restrain motion of said piston; d. a support pad joined to one of said piston and cylinder and positionable so as to contact said wall; e. means for affixing the other of said piston and cylinder to said rack in a substantially horizontal orientation; and f. an elastic structure cooperatively associated with the one of said piston and cylinder joined to said pad so as to continuously apply a lateral positioning force thereto. 2. The nuclear fuel rack of claim 1 additionally comprising means for selectively retaining said piston fixed with respect to said cylinder. 3. The nuclear fuel rack of claim 2 wherein said cylinder includes a wall having an opening therethrough, said piston includes an aperture alignable with said opening, and said selective retaining means comprise a pin removably insertable into said aligned opening and aperture. 4. The nuclear fuel rack of claim 1 wherein said fluid flow controlling means comprise a preselected clearnance between said piston and cylinder. 5. A lateral restraint for a nuclear fuel rack having a plurality of cells each sized to receive a nuclear fuel assembly disposed within a walled fuel storage pit, said restraint affixed to said rack so as to extend laterally therefrom and comprising:
040244059	summary	BACKGROUND OF THE INVENTION This invention relates to a dental X-ray eye shield and more particularly to a glasses-type of shield having a radiolucent frame and radiopaque, shielding lens cups. The public is exposed daily to possible radiation from the following sources: medical and dental X-rays, the sun, color television, microwave ovens, etc. According to the U.S. Public Health Service, the two greatest sources of exposure are medical and dental X-rays. In the field of dentistry, radiographs have become a standard diagnostic procedure. However, this is of concern to many since unnecessary exposure to radiation is thought to be harmful. Not only is radiation of concern during routine dental X-rays, but it is especially important when a series of radiographs are required, e.g., in the diagnosis and evaluation of so many potential young orthodontic patients. For these reasons, Medwedeff in U.S. Pats. Re. Nos. 25,773; 3,092,721, and 3,304,423 addresses the problem. Disclosed in the Medwedeff patents is a dental X-ray shield and aiming means. The Medwedeff devide is an attempt to prevent any unnecessary radiation exposure. While this is certainly a laudable objective, the system of Medwedeff is cumbersome, difficult to use, and has found little acceptance in the profession. Therefore, the problem remains. At present, the only readily accepted solution is use of blanket or garment type shields containing lead impregnated plastic materials. These are conventionally draped over the patent's chest during dental radiography. They do not protect the eyes. One thought is that the eyes alone might be protected easily and economically without resorting to a Medwedeff-type device. This is an area of particular concern since the tissues of the eye are very susceptible to radiation. Cataracts and tumors of the eye may result from accumulated excessive radiation. Of course, eye radiation shields are known, but to my knowledge none have been used as a protection against dental X-rays. In fact, the eye radiation shields with which I am familiar could not be used effectively for that purpose. That is, Crosson (U.S. Pat. No. 3,030,628 ) and Christianson (U.S. Pat. No. 3,325,825 ) shown eye radiation shields, but neither would effectively block out X-ray radiation from all angles. Christianson is an RF radiation shield in the form of goggles. It has a conductive frame and a light transparent lens. The conductive frame would also make it unacceptable for dental use. It would be impossible to position the X-ray machine cone for quality radiographs on a patient wearing such an eye shield because important anatomical landmarks vital to an accurate diagnosis would be blocked or distorted by the conductive frame. Besides an RF radiation shield which permits vision through the lenses, would not effectively protect the eyes themselves against X-ray radiation. The mask of Crosson is similar. The louvers 21 of Crosson protect against radioactive radiation, but at the same time allow vision through the lens. Accordingly, the need remains for an eye shield which may be used during dental radiography without interference of the frame in making the radiographs while at the same time preventing radiation exposure of the eye tissue. SUMMARY OF THE INVENTION The present invention fulfills that need by providing an X-ray eye shield which will effectively protect the patient's eye tissue without interfering in any manner with the work of the dentist, hygienist, or dental assistant. It will protect against excess radiation during routine diagnostic radiographs, as well as provide a safety shield to protect the eyes from any radiation leaks which might occur. Perhaps more significantly, it will help allay the fear and apprehension of so many radiophobic patients who are concerned about the potential dangers of radiation. The eye shield of the instant invention is basically a glasses-type device which fits the head of the patient. A radiolucent frame (plastic) conforms to the contour of the head. Spring-loaded hinges may be used to hold the frame tightly in place on the patient. The bridge of the frame is lower than on a normal spectacle frame. This permits positioning of the nose guide of certain common X-ray machines on the bridge of the nose. Attached to the frame are two radiopaque lens cups. These are hinged passively so that they may be adjusted, as desired, into close conformity with the eye socket. The lens cups contain a material which will prevent passage of X-ray radiation. In this case the material is preferably 0.030 to 0.040 inch thick lead encased in plastic. A suitable thin metal support or frame may be used for support of the lens cups, although, this is not necessary. The lens cups are coextensive with the metal hinges on the frame so that the only areas from which radiation is occluded is the area inside the eye socket. All other surrounding areas of the oral cavity are exposed so that the important anatomical landmarks necessary to accurate diagnosis may be X-rayed without distortion. Accordingly, it is a object of the present invention to provide an X-ray eye shield which may be used during dental radiography. Other objects and advantages of the invention will be apparent from the following descripton, the accompanying drawing and the appendedd claims.
	description	This application claims priority based on International Patent Application No. PCT/FR2005/050204 filed on Mar. 31, 2005, entitled “Sealed Docking Device for Mobile Containers of Various Diameters” by Luc Tumolo and Pascal Le Chevalier, which claims priority of French Application No. 04 50657, filed on Apr. 2, 2004, and which was not published in English. This invention relates to a device that enables mobile containers equipped with docking systems of the same design but of various diameters to be docked in a sealed manner on a containment box. In particular, a device such as this can be used to equip a containment box intended for remote servicing of mobile containers, such as containers used to provide for transport of contaminated nuclear equipment to an unloading unit in which this equipment can be repaired or conditioned as waste. In nuclear facilities, mobile containers are used to carry out the replacement of contaminated equipment. More precisely, the contaminated equipment is placed inside mobile containers by means of which it is transported to unloading units. The contaminated equipment can be conditioned in these units as waste or undergo appropriate repairs. The mobile containers are equipped with a sealed docking system that makes it possible to ensure leak tightness during replacement and disposal of a piece of equipment. This sealed docking system is closed with a plug during transport of the contaminated equipment to the unloading unit. The upper portion of this plug is very highly contaminated by this equipment. In existing facilities, servicing of the mobile containers is ensured by placing them inside a protective vinyl bag and by inserting them through an airlock into a decontamination cell. The plugs of the mobile containers are decontaminated inside said cell by operators that are outfitted with sealed suits and whose holding time is monitored. The object of the invention is a device that enables mobile containers equipped with docking systems of the same design but of various diameters to be docked in a sealed manner on a containment box, so as to be able to carry out the cleaning operations of the plug remotely, inside the containment box, the latter likewise ensuring the protection of the operators against radiation. According to the invention, this problem is solved by means of a device for the sealed docking of mobile containers equipped with plugs of various diameters on a containment box having a counter flange through which a circular access opening passes, characterized in that it includes: at least one docking flange and one center disk, concentric to each other, capable of being placed one inside the other inside the access opening of the counter flange, the outside diameters of the center disk and of each docking flange corresponding to those of the plugs; locking/unlocking means for successively unlocking the center disk and each docking flange, by moving outwardly, and for successively locking each docking flange and the center disk, by moving inwardly, in relation to said access opening. This arrangement makes it possible to dock mobile containers of various sizes on the containment box. As a matter of fact, the particular design of the locking/unlocking means makes it possible to remove only the center disk, in the case of a container equipped with a small-diameter plug, or to additionally remove one or more docking flanges when the containers are closed with larger-diameter plugs. According to a preferred embodiment of the invention, the device also includes as many centering caps of various diameters as there are plug diameters, a cap having a diameter corresponding to that of the plug of the mobile container to be docked being fastened onto the containment box. In this case, a cap having dimensions suited to the diameter of the plug is fastened to the counter flange before docking the mobile container on the containment box. This cap makes it possible to ensure that the mobile container is correctly centered in relation to the opening in the counter flange. In the preferred embodiment of the invention, each centering cap advantageously includes unlocking limitation means, prohibiting the locking/unlocking means from unlocking each docking flange having an inside diameter larger than the diameter of the plug of the mobile container. Owing to this arrangement, the unlocking operation concerns only the disk and, possibly, the docking flange or flanges whose inside diameter corresponds to the diameter of the plug. According to another feature of the invention, the locking/unlocking means include a plate capable of rotating on the counter flange, as many pairs of cams being formed on said plate as there are plug diameters, a strike plate being engaged with each of the cams so as to move between a locking position and an unlocking position when the plate is rotated. The unlocking limitation means advantageously include a pin, associated with the rotating plate and lodged inside of a notch of limited circumferential length, formed in the centering cap. In the latter case, the locking/unlocking means more preferably include a spindle which passes through the counter flange and means of controlling the rotation of said spindle, the latter being engaged with a first sector gear formed on the plate and with a second sector gear formed on a cap holding the pin. Additionally, a floating bearing ring is preferably mounted inside of each of the centering caps. In the preferred embodiment of the invention, the counter flange is mounted on an upper wall of the containment box and the latter contains a platform on which the docking flange and the center disk rest, control means making it possible to move the platform between a high position for holding the docking flange and the center disk inside of said opening, irrespective of the status of the locking/unlocking means, and a low position allowing the plug to be cleaned. In a preferred application of the invention, the containment box thus contains means for cleaning the plug remotely. FIG. 1 is a schematic representation of a containment box 10 servicing a nuclear facility. The containment box 10 is equipped with a sealed docking device 14 made in accordance with the invention. In the embodiment shown for non-limiting illustrative purposes, the sealed docking device 14 is built into the upper horizontal wall 12 of the containment box. Alternatively, this same device could be built into any other wall of the containment box, without exceeding the scope of the invention. The sealed docking device 14, which will be described in detail below, is designed to enable a leak-proof connection of mobile containers 42 of various sizes with the containment box 10. More precisely, the sealed docking device 14 is designed to enable the docking of mobile containers 42 having the same design, but equipped with plugs 44 of different diameters. When the docking operation is completed, the facility shown in FIG. 1 may in particular make it possible to clean the upper surface 44a (FIG. 2) and the peripheral surfaces of the plug 44, which closes the mobile container 42, thanks to remote cleaning means 15 located inside the containment box 10. It is likewise possible to ensure the cleaning, servicing or monitoring of the equipment situated inside the container, or else the cleaning of the container itself. The containment box 10 thus ensures the protection of the operators against radiation. As shown more precisely in FIGS. 2 to 4, the sealed docking device 14 according to the invention includes a counter flange 16. In the embodiment shown, this counter flange 16 is fastened in a leak-proof manner to the upper horizontal wall 12 of the containment box 10. It delimits a circular access opening 18. In accordance with the invention, the sealed docking device 14 first and foremost includes at least one docking flange (three, in the embodiment shown, designated by the reference numbers 20a, 20b and 20c) and one center disk 22, which are concentric to each other. The docking flanges 20a, 20b and 20c are ring-shaped and are capable of being mounted one inside the other, along with the center disk 22, inside the circular access opening 18 formed in the counter flange 16. They then seal said access opening in a leak-proof manner, in the horizontal plane of the counter flange 16. It is to be noted that the peripheral edges of the inside of the access opening 18, the outside of the center disk 22 and the inside and outside of the docking flanges 20a, 20b and 20c have complementary shapes such that each docking flange as well as the center disk can be freely moved towards the interior of the containment box, i.e., downwardly, in relation to the docking flange or to the counter flange that surrounds it contiguously. On the other hand, any movement in the opposite direction, i.e., outward or upward, is impossible. As will be better understood below, the number of docking flanges 20a, 20b and 20c that surround the center disk 22 depends on the number of different types of mobile containers 42 that one wishes to be able to dock on the containment box 10. More precisely, if one wishes to be able to dock on the containment box 10 mobile containers 42 whose plugs 44 have n different diameters, a sealed docking device 14 including n−1 docking flanges will be used. In the embodiment shown, where the sealed docking device 14 includes three docking flanges 20a, 20b and 20c, mobile containers 42 equipped with plugs 44 having four different diameters can thus be docked. The sealed docking device 14 according to the invention additionally includes locking/unlocking means 24. By moving outwardly, these locking/unlocking means 24 have the primary function of successively unlocking the center disk 22 and each of the docking flanges 20a, 20b and 20c. This characteristic makes it possible to unlock only the center disk 22, when the plug of the mobile container previously docked on the containment box has the smallest possible diameter, or to unlock only the center disk 22 and the docking flange or flanges 20a, 20b and 20c which overlap the bottom surface 44b of the plug of the mobile container docked on the containment box. The locking/unlocking means 24 are mounted on the counter flange 16 so as to be capable of being operated from the outside of the containment box 10. In the embodiment shown in FIGS. 2 to 4, the locking/unlocking means 24 include a flat horizontal plate 26, supported by the counter flange 16 so as to be able to rotate freely about the vertical axis of the circular access opening 18. More precisely, the plate 26 is rotatably mounted on a tubular center portion 16a of the counter flange 16, which protrudes downwardly inside the containment box 10. The plate 26 comprises as many pairs of cams 28a, 28b, 28c and 28d as there are different plug 44 diameters on the mobile containers 42 that one wishes to be able to dock on the containment box 10. In other words, if the plugs of the mobile containers to be docked have n different diameters, the plate 26 comprises n pairs of cams. In the embodiment shown, as already mentioned, the number n is equal to four. The cams of each pair of cams 28a, 28b, 28c and 28d are situated at diametrically opposed locations in relation to the vertical axis of the circular access opening 18. In the embodiment shown in FIGS. 2 to 4, the cams 28a, 28b, 28c and 28d consist of slots that run through the entire thickness of the plate 26. The cams 28d closest to the axis of the opening 18 successively include, in a clockwise direction, an end portion slanted towards said axis and a main arc of circle-shaped portion centered on said axis. The cams 28c immediately adjacent to cams 28d successively include, in a clockwise direction, a first arc of circle-shaped portion centered on the axis of the opening 18, an intermediate portion slanted towards said axis and a third arc of circle-shaped portion centered on said axis and having a smaller diameter than the first portion. The cams 28b immediately adjacent to cams 28c successively include, in a clockwise direction, a first arc of circle-shaped portion centered on the axis of the opening 18, an intermediate portion slanted towards said axis and a third arc of circle-shaped portion centered on said axis and having a smaller diameter than the first part. Finally, the cams 28a most distant from the axis of the opening 18 successively include, in a clockwise direction, a main arc of circle-shaped portion centered on the axis of the opening 18 and an end portion slanted towards said axis. The cams 28d, 28c, 28b and 28a are angularly offset, in a clockwise direction, moving away from the axis of the opening 18, as shown in FIG. 3. The locking/unlocking means 24 additionally include as many pairs of strike plates 30a, 30b, 30c and 30d as there are cams 28a, 28b, 28c and 28d. More precisely, one strike plate 30a, 30b, 30c and 30d is engaged with each of the cams 28a, 28b, 28c and 28d, so as to be able to move between a locking position and an unlocking position, when the plate 26 is rotated about the axis of the opening 18. In the embodiment shown in the figures, each of the strike plates 30a, 30b, 30c and 30d has a substantially L-shape comprising a small arm oriented parallel to the axis of the opening 18 and a large arm oriented in a direction perpendicular and secant to said axis. The small arm of each of the strike plates 30a, 30b, 30c and 30d passes through the slot consisting of the cam 28a, 28b, 28c and 28d which corresponds to it, with the result being that each of the strike plates is engaged with one of the cams. The large arm of each of the strike plates 30a, 30b, 30c and 30d is slidably mounted in a hole provided for this purpose in the tubular center portion 16a of the counter flange 16. The holes in which the strike plates 30a, 30b, 30c and 30d are lodged are angularly offset in the same way as the cams 28a, 28b, 28c and 28d supported by the plate 26. Consequently, all of the small arms of the strike plates 30a, 30b, 30c and 30d are simultaneously placed at the front end, the center portion or rear end of the corresponding cams, in a clockwise manner, according to the angular position of the plate 26. In the angular position of the plate 26 shown in FIG. 3, the small arms of the strike plates 30a, 30b, 30c and 30d are all placed at the rear end of the corresponding cams 28a, 28b, 28c and 28d, in a clockwise manner. All of the strike plates 30a, 30b, 30c and 30d are then situated in their unlocking position. As a matter of fact, the ends of the large arms of the strike plates 30a, 30b, 30c and 30d are completely retracted into the holes formed in the tubular center portion 16a of the counter flange 16. In the opposite angular position (not shown) of the plate 26, the small arms of the strike plates 30a, 30b, 30c and 30d are all placed at the front end of the corresponding cams 28a, 28b, 28c and 28d, in a clockwise manner. All of the strike plates 30a, 30b, 30c and 30d are then situated in their locking position. As a matter of fact, the ends of the large arms of the strike plates 30a, 30b, 30c and 30d protrude inside of the center portion of the counter flange 16. The arrangement just described makes it possible to control a successive movement of each of the strike plates 30d, 30c, 30b and 30a towards the axis of the opening 18 when the plate 26 is rotated in a counter clockwise direction, starting at the completely locked position shown in FIG. 3. This direction of rotation of the plate 26 thus has the effect of moving one or more of the strike plates 30d, 30c, 30b and 30a from their initial unlocked position into their locking position, according to the angle of rotation of the plate 26. Conversely, this arrangement makes it possible to control a successive movement of each of the pairs of strike plates 30a, 30b, 30c and 30d while moving away from the axis of the opening 18, when the plate 26 is rotated in a clockwise direction, starting at the completely locked position opposite the one shown in FIG. 3. This direction of rotation of the plate 26 thus has the effect of moving one or more of the pairs of strike plates 30a, 30b, 30c and 30d from their initial locked position into their unlocking position, according to the angle of rotation of the plate 26. As shown more precisely in FIGS. 2 and 3, each of the docking flanges 20a, 20b and 20c as well as the center disk 22 include a pair of diametrically opposed protrusions on their bottom face turned towards the interior of the containment box 10. More precisely, the protrusions formed on each of these parts are shaped such that they extend away from the axis of the opening 18, at locations that are offset angularly from one part to another. These protrusions formed on the docking flanges 20a, 20b and 20c and on the center disk 22 are therefore flush with the inside surface of the tubular center portion 16a of the counter flange 16, immediately above one of the corresponding pairs of strike plates 30a, 30b, 30c and 30d. When the docking flanges 20a, 20b and 20c and the center disk 22 are placed inside the opening 18, the bottom faces of the aforesaid protrusions are situated at the same level as the top faces of the large arms of the strike plates 30a, 30b, 30c and 30d. As a result, it becomes impossible for the center disk 22, the docking flange 20a adjacent to said disk, the docking flange 20b adjacent to the latter and the outside docking flange 20c to slip towards the interior of the containment box 10, in as much as the strike plates 30a, 30b, 30c and 30d are in locked position. The protrusions formed on each of the parts consisting of the docking flanges 20a, 20b and 20c and the center disk 22 also have the effect of making it impossible to open any of the docking flanges 20a, 20b and 20c when the center disk 22 is in place, impossible to open any of the docking flanges 20b and 20c when the inside docking flange 20a is in place, and impossible to open the outside docking flange 20c when the intermediate docking flange 20b is in place. In the embodiment shown for illustrative purposes in FIGS. 3 and 4, the locking/unlocking means 14 additionally include a vertical control pin 32 which passes through the counter flange 16 in a leak-proof manner, while at the same time being able to freely rotate thereabout. In its portion situated inside the containment box 10, beneath the counter flange 16, the control pin 32 holds a pinion 34 which is engaged with a sector gear 36 formed on a peripheral edge of the plate 26. In its portion situated outside the containment box 10, above the counter flange 16, the control pin 32 is engaged with control means. In the embodiment shown for illustrative purposes, these control means consist of a crank 38 capable of being operated manually. The crank 38 is mechanically connected to the pin 32 by a bell crankcase 39. Alternatively, other control means, such as a motor or the like, may also be used, without exceeding the scope of the invention. In the preferred embodiment of the invention shown in the figures, the sealed docking device 14 likewise includes centering caps 40. More precisely, the device includes as many centering caps 40 of different diameters as there are plug 44 diameters among the mobile containers 42 capable of being docked on the containment box 10. As illustrated more particularly in FIGS. 2 and 4, the centering cap 40, whose diameter corresponds to that of the plug 44 of the mobile container 42 being docked, is fastened onto the face of the counter flange 16 turned towards the exterior of the containment box 10, i.e., upwardly. This attachment is produced by any appropriate means (screws, bolts, etc.), so that the centering cap 40 is centered on the axis of the circular opening 18 formed in the counter flange 16. As seen, in particular, in FIGS. 2 and 4, the centering cap 40 is chosen so that its inside diameter is equal to the outside diameter of the mobile container 42 being docked, in the area of the latter that surrounds its plug 44. In the preferred embodiment of the invention shown in the figures, each centering cap 40 incorporates unlocking limitation means. These unlocking limitation means have the function of prohibiting the locking/unlocking means 24 from unlocking the docking flange or flanges 20a, 20b and 20c which have an inside diameter larger than the diameter of the plug 44 of the mobile container 42 being docked. Any risk is thereby eliminated that the docking flanges having diameters larger than that of the plug might be accidentally removed. As shown, in particular, in FIG. 4, the unlocking limitation means may, in particular, include a pin 46, connected to the rotating plate 26, and a notch 48 formed in the centering cap 40 and in which the pin 46 is lodged. More precisely, the pin 46 is integral with a ring 50 supported by the counter flange 16 so as to be able to rotate freely about the axis of the circular opening 18. The ring 50 is mounted on the outside of the counter flange 16, around the centering cap 40, and the pin 46 protrudes into the ring 50. Furthermore, the notch 48 is formed on the outside peripheral surface of the centering cap 40 and has a limited circumferential length. Thus, the angular displacement of the ring 50 is limited by the circumferential length of the notch 48 in which the pin is lodged 46. On its outside periphery, the ring 50 comprises a gear sector 52. A second pinion 54 fastened to the control pin 32 is engaged with the sector gear 52. Activation of the control means consisting of the crank 38 thus has the effect of simultaneously rotating the plate 26 and the ring 50 in the same direction. The angle of rotation of the plate 26 is thus limited by the abutment of the pin 46 against one or the other of the ends of the notch 48, depending on the direction of said rotation. Consequently, when the control pin 32 is operated in the unlocking direction, only the center disk 22 and the docking flange or flanges 20a, 20b and 20c, whose strike plates 30a, 30b, 30c and 30d are moved away from the axis of the circular access opening 18 as a result of the thus limited rotation of the plate 26, are unlocked. When the control pin 32 is then operated in the locking direction, the center disk 22 and the previously unlocked docking flange or flanges 20a, 20b and 20c are once again locked as a result of the movement of the corresponding strike plates 30a, 30b, 30c and 30d towards the axis of the circular access opening 18. In the preferred embodiment shown in the figures, the sealed docking device 14 additionally includes as many floating bearing rings of various diameters as there are plug 44 diameters. More precisely, a floating bearing ring 55, whose diameter corresponds to that of the plug 44 of the mobile container 42 being docked, is mounted inside each of the centering caps 40, on the exterior of the containment box 10. When the counter flange 16 is mounted on the upper horizontal wall of the containment box 10, as illustrated, in particular, in FIG. 1, a horizontal platform 56 is advantageously placed inside the containment box, under the circular access opening 18. This platform 56 is mounted at the end of an arm 58 whose opposite end is capable of sliding along a vertical guide rail 60, as a result of the action of a motor 62. Another motor 64 makes it possible to rotate the rail 60 about its vertical axis. The motors 62 and 64 are placed outside of the containment box 10. The arrangement just described consists of an elevator capable of moving the platform 56 between a high position and a low position. In its high position, the platform 56 is flush with the center disk 22 and the docking flanges 20a, 20b and 20c. It thus holds these parts in their positions for closing off the circular access opening 18, even if one or more of them are unlocked. When the platform 56 is lowered, it takes with it the center disk 22 and the docking flange or flanges 20a, 20b and 20c, when one or more of these parts are unlocked. It is thereby possible to release the bottom face of the plug 44 from the mobile container 42 previously docked on the containment box 10, over a diameter corresponding exactly to the diameter of said plug. As a matter of fact, the sealed docking device 14 according to the invention makes it possible to only unlock the center disk 22 alone, the center disk 22 and the immediately adjacent docking flange 20a, the center disk 22 and the two closest docking flanges 20a and 20b, or else the center disk 22 and the three docking flanges 20a, 20b and 20c, depending on the diameter of the plug 44 of the mobile container 42 previously docked on the containment box 10. When the sealed docking device 14 includes unlocking limitation means built into the centering cap 40 fastened onto the counter flange 16 as described above, unlocking of the docking flanges 20a, 20b and 20c is automatically prevented or limited to the flange or flanges the opening of which is indispensable in order to release the bottom face of the plug 44 from the mobile container docked on the containment box. When the bottom face of the plug 44 is thus released, the means 15 for cleaning said plug remotely are actuated. These remote cleaning means may, in particular, consist of conventional nuclear decontamination means known by those skilled in the art. Of course, the invention is not limited to the embodiment just described for illustrative purposes, but encompasses all variants thereof. Thus, it shall be understood, in particular, that the sealed docking device according to the invention may be used for applications other than the cleaning of the plug of the mobile container docked on the containment box. Furthermore, the use of centering caps and floating bearing rings is not indispensable to the implementation of the invention, in its broadest definition.
060884207	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS A reactor core according to preferred embodiments of the present invention will be described hereunder with reference to the accompanying drawings. As mentioned above, FIG. 1 is a longitudinally sectional view theoretically showing a first embodiment of a reactor core according to the present invention, and FIG. 2 is a top plan view of the reactor core shown in FIG. 1. FIG. 1 and FIG. 2 each show an example in which a reactor core is applied to a water cooling reactor such as a light water reactor, for example, to a boiling water reactor. In the boiling water reactor, a reactor core 10 is formed in a reactor pressure vessel, not shown. In this reactor core 10, rectangular cylindrical fuel assemblies 11 are charged in a manner of being arranged at an regular pitch in a longitudinal and crosswise direction, for example, at a pitch interval of 300 mm or more. The fuel assembly 11 charged in the reactor core 10 is supported on a core support plate 12 as shown in FIG. 3. Further, the fuel assembly 11 is composed of at least two kinds, that is, a normal fuel assembly 13 having a normal fuel effective (exothermic portion) length LM and a partial fuel assembly 14 having a shorter fuel effective length LP. A plural kinds of the partial fuel assemblies 14 may be prepared in accordance with the fuel effective length LP. As shown in FIG. 1, shaft brackets 15, each having a length of about 20 to 30 cm, are provided on upper and lower portions of the normal fuel assemblies 13 and on a lower potion of the partial fuel assembly 14. The upper portion of the partial fuel assembly 14 is formed with a streaming path 16 and the shaft bracket is not provided thereon. In the reactor core 10 of the boiling water reactor, the normal fuel assemblies 13 and the partial fuel assemblies 14 are dispersively arranged alternately in a diametrical direction thereof at a predetermined arrangement pattern. These normal fuel assemblies 13 and partial fuel assemblies 14 may be also dispersively arranged alternately in the diametrical direction and the circumferential direction. Therefore, various arrangement patterns may be considered. However, it is desirable that four fuel assemblies 11, which should be arranged on the central portion of the reactor core 10, are composed of the partial fuel assemblies 14, and it is desirable that the fuel assemblies which should be arranged on the outermost circumference are the normal fuel assemblies 13. In the reactor core 10 of the boiling water reactor, the normal fuel assemblies 13 and the partial fuel assemblies 14 are charged in a state of being properly combined with each other. A control rod 18 having a cross-shaped traverse section is provided between four fuel assemblies 11 adjacent to each other so as to be taken in and out. Moreover, as shown in FIG. 4, the fuel assemblies 11 are arranged in a substantially square space defined by four control rods 18 adjacent to each other. A blade 18a constituting the control rod 18 is taken in and out so as to surround the fuel assembly 11. In the fuel assembly 11, the normal fuel assembly 13 and the partial fuel assembly 14 have the same plane structure as shown in FIG. 4. FIG. 4 is a view showing an upper surface of the fuel assembly 11. The fuel assembly 11 has an area size of several times, for example, four times, as much as the existing fuel assembly. Thus, the arrangement pitch of the fuel assembly 11 is wide, and for example, the fuel assembly having the four-times area size has an arrangement pitch of about 300 mm or more. The fuel assembly 11 itself is made larger than the existing fuel assembly, and thereby, the coolant in a gap between fuel assemblies 11 is reduced so as to lower a ratio of water serving as a coolant, with respect to the overall volume. Further, a ratio of water to fuel is lowered so that a breeding ratio is set to at least about 1, for example, to 1.0 to 1.1. As shown in FIG. 4, in the fuel assembly 11, a fuel bundle 21 is housed in a cylindrical channel box 20 as a rectangular outer housing. The fuel bundle 21 is a fuel element bundle which has, as a whole, a rectangular, e.g., square transverse section. A seal alloy or stainless steel material is used as a material for the channel box 20. In the fuel bundle 21, a number of fuel rods (fuel pins) 22 are closely arranged with a predetermined regularity, and is made into a bundle by means of a fuel spacer, e.g., a grid spacer 23 as shown in FIG. 5 so that an interval between fuel rods 22 is retained. A plurality of the grid spacers 23 are provided at a predetermined interval in a longitudinal direction of the fuel bundle 21. If the channel box 20 is formed of stainless steel, the channel box 20 has mechanical and physical strength larger than the channel box made of seal alloy used in the existing light water reactor. For this reason, the channel box 20 has high rigidity, so that the channel box 20 can be made thin. The thickness of the channel box made of stainless steel is set to about 3 mm to 5 mm, preferably, to about 3 mm. As described above, the channel box 20 is made thin, and a fuel volumetric ratio can be hence increased, and a ratio of water to the fuel can be lowered. The fuel bundle 21 housed in the channel box 20 is constructed in a manner that a number of fuel rods 22 are made into bundle. The grid spacer 23 bundling up the fuel rods 22 includes a thin hexagonal cylinder having a thickness of about 0.2 mm, or a honeycomb type grid lattice 25 which is constructed in a manner that many rectangular and cylindrical sleeves 24 as pipe-like grid structure are fixed and integrated in a state of being closely arranged in its plane. The rectangular cylindrical sleeve 24 is formed of stainless steel or inconell having high rigidity and high mechanical and physical strength. Moreover, the grid spacer 23 may be constructed in a manner of surrounding the outer peripheral side of the honeycomb type grid lattice 25 by a rectangular outer frame 26 which functions as a reinforcing frame 26, or the grid spacer 23 may be constructed by the honeycomb type grid lattice 25 having no outer frame. One corner portion of the rectangular cylindrical sleeve 24 of the honeycomb type grid lattice 25 is provided with a vibration preventive spring 27. The vibration preventive spring 27 comprises a spring member such as a flat spring or a rod spring, which is bent into a V-letter or arc shape and has the entire length of about 15 mm. Upper and lower ends of the vibration preventive spring 27 are welded to an inner wall surface of the corner portion of the rectangular cylindrical sleeve 24, and an intermediate portion of the spring elastically projects into the cylindrical sleeve 24. Further, the cylindrical sleeve 24 of the honeycomb type grid lattice 25 is provided with a pair of protrusions (projections) 28 on a symmetrical position separated from the vibration preventive spring 27 at an angle of 120.degree.. The protrusion 28 bulges like an arc from the corner portion of the rectangular cylindrical sleeve 24 to the inside thereof. Moreover, the protrusion 28 may be formed as a dimple which is recessed on a side face of the corner portion of the cylindrical sleeve 24 and projects into the sleeve. Further, the protrusion 28 may be formed in the following manner. Specifically, cut portions extending to the circumferential direction are formed to upper and lower portions of the corner portion of the rectangular cylindrical sleeve 24, and then, the cut portion having a up-and-down predetermined width is inwardly pressed and deformed so as to be bulged. The fuel rod 22, which is nuclear fuel element, is successively guided into each sleeve 24 of the honeycomb type grid lattice 25 constituting the grid spacer 23, and then, inserted fuel rod 22 is supported at three points by means of the paired protrusions 28 and the vibration preventive spring 27 so as to prevent fuel rods 22 from contacting with each other, thus constituting the fuel bundle 21. In the fuel bundle 21 thus constructed, each fuel rod 22 is held at a predetermined interval by means of the paired protrusions 28 and the vibration preventive spring 27, and a coolant channel is secured therein, whereby each fuel rod 22 is restricted from vibrating and a fuel can be previously and securely prevented from being broken down. As shown in FIG. 5 to FIG. 7, the honeycomb type grid lattice 25 has been constructed by integrally combining the cylindrical sleeve 24 and the vibration preventive spring 27. In place of the honeycomb type grid lattice 25, a grid spacer 23A as shown in FIG. 8 may be used. The grid spacer 23A comprises a spring-integral type grid lattice 30 which integrally combines a ring-like or tours-like upper and lower circular guide 31 constituting a grid and a vibration preventive spring 32. The circular guide 31 constitutes a grid of the grid spacer 23A. Further, a reference numeral 33 denotes a protrusion which is formed at the circular guide 31 of the spring-integral type grid lattice 30. It is desirable that the paired protrusions 33 and the vibration preventive spring 32 are provided at a 120.degree. angular interval. However, these paired protrusions 33 and vibration preventive spring 32 are not necessarily provided at the 120.degree. angular interval, and a degree of freedom of angle is given when providing them. In a number of fuel rods (fuel pin) 22 constituting the fuel bundle 21, as shown in FIG. 9, a fuel cladding tube 35 is filled with a nuclear fuel material 36 (fissionable material) which is a pellet or particle size fuel material. Plutonium and recovery uranium are used as the fuel material which is the nuclear fuel material. Further, as conventionally made, natural uranium or depleted uranium may be mixed with plutonium. However, in the case where the aforesaid plutonium and recovery uranium are used as the fuel material, the number of neutrons generated from materials other than plutonium is increased, so that a breeding ratio can be made high. The fuel rods of the fuel bundle 21 is formed into a triangular arrangement so as to improve a filling density of fuel rods 22. For example, the fuel rods 22 are arranged by relatively shifting them by a fuel rod single pitch in a column direction in a manner such that that an even-column fuel rod 22 is positioned between odd-column fuel rods. In this manner, three fuel rods adjacent to each other are closely arranged so as to form an equilateral triangle. In this fuel bundle 21, the even-column fuel rod 22 is relatively shifted by only half pitch in the column direction with respect to the odd-column fuel rod 22. The relative shift serves to make small a fuel rod pitch in a line direction, further improving the arrangement density of the fuel rods 22. The odd-column fuel rod 22 has been relatively shifted by the half pitch with respect to the even-column fuel rod 22. In place of doing so, even if the odd-column fuel rod 22 is relatively shifted by only half pitch in the line direction with respect to the odd-column fuel rod 22, substantially the same effect as that described above will be obtainable. Since the fuel rods 22 constituting the fuel bundle 21 has a triangular arrangement structure, these fuel rods 22 can be closely arranged and the filling density of fuel can be improved as compared with a square arrangement structure in which fuel rods 22 are arranged in a lined-up form in longitudinal and traverse directions, i.e. column and line directions. The existing zirconium alloy (zircaloy) material or stainless steel material is used as the material for the fuel cladding tube 35 of the fuel rod 22. In the case where the stainless steel having high mechanical and physical strength is used in place of the existing zirconium alloy (zircaloy) material, a wall thickness of the fuel cladding tube 35 can be made thin. In the case of using the fuel cladding tube 35 made of stainless steel, when a fuel rod diameter is 10 mm.phi., the wall thickness of the fuel cladding tube is set to 0.25 mm to 0.4 mm, preferably, to a degree of 0.3 mm. Therefore, the wall thickness can be made thinner as compared with about 0.5 mm in the case of using zirconium alloy. As described above, the wall thickness of the fuel cladding tube 35 is made thin, which serves to increase the fuel volume ratio and the ratio of water to the fuel is lowered, and the ratio, thus being applicable to the reactor core 10 whose breeding ratio is at least about 1. The reactor core 10 is one applicable for a fast spectral reactor. Therefore, even if the stainless steel is used, the neutron absorption by the structural material is small like the case of zirconium alloy used in the existing light water reactor. The fuel assemblies 11 are composed of the normal fuel assemblies 13 and the partial fuel assemblies 14 as shown in FIG. 1 to FIG. 3. The control rod 18 having a cross-shaped traverse section is provided between the four fuel assemblies 11 adjacent to each other so as to be freely taken in and out. As shown in FIG. 4, a protrusion 38 is provided on the central portion at which the blade 18a of the control rod 18 does not reach in the gap defined between the fuel assemblies 11. The protrusion 38 is provided on the central portion of the outer side of the channel box 20 along the longitudinal direction thereof. Further, the protrusion 38 constitutes a water removal space to lower the ratio of water to fuel. The interior of the protrusion 38 may be formed into a hollow, and as described above, since the protrusion 38 is provided, or the interior of the protrusion 38 is formed so as to provide a hollow structure, the breeding ratio can be increased and a void reactivity can be reduced. The channel box 20 of the fuel assembly 11 is provided with a support pad 39 at an outer side on the upper portion thereof. The support pads 39 are provided at four portions on the outer side of the channel box 20. These support pads 39 serve to dispense an upper lattice plate which functions as a fuel assembly fixing frame used in the existing light water reactor and also serve to make small a gap defined between fuel assemblies 11. Therefore, it is possible to increase a fuel volume ratio and to lower the ratio of water to fuel. In FIG. 3, a reference numeral 40 denotes an orifice for guiding the coolant into the fuel assembly 11. Further, in the reactor core 10, the partial fuel assemblies 14 and the normal fuel assemblies 13 are arranged in combination with each other. According to this arrangement, if a reactor power output rises up and the void reactivity increases, neutrons generated in the reactor core 10 leak out at an upper portion of the reactor core through the streaming path 16 of the partial fuel assembly 14. In this manner, the neutron leakage effect is obtained in the core axial direction, and thereby, the void reactivity can be made negative. The partial fuel assembly 14 is a fuel assembly which has a fuel effective length LP of an exothermic portion shorter than the height of core. The normal fuel assembly 13 is an ordinary fuel assembly which has a predetermined fuel effective length LM and is substantially equal to a fuel effective height of core. In the case where the entire length of the fuel assembly 11 is approximately 4 m, the maximum length (fuel effective length) LM of the exothermic portion of the normal fuel assembly 13 is set to, for example, 2 m or less. On the other hand, the maximum length (fuel effective length) LP of the exothermic portion of the partial fuel assembly 14 is set to, for example, 1 m or less. According to this arrangement, the core diametrical direction size is made the same as the conventional light water reactor while the void reactivity being made negative. The control rod 18, which is inserted between the fuel assemblies in four groups so as to be freely taken in and out, is constructed as shown in FIG. 10. The control rod 18 has the entire length equal to the entire length of the fuel assembly 11 of, for example, about 4 m. A neutron absorption substance such as B.sub.4 C, hafnium or the like is stored in a lower half portion of the control rod 18. The lower half portion of the control rod 18 is constructed as a control rod absorber 43. A follower 45 is formed on the upper portion of the control rod absorber 43 through an intermediate partition plate 44 having a hollow structure. The intermediate partition plate 44 is formed of stainless steel, for example. A reference numeral 46 denotes a supporting portion of the control rod 18. The follower 45 is formed of a thin-walled steel plate and is formed with a flat hermetic (sealed) space 47 having an interior which is filled with by an inert gas such as helium or the like. This hermetic space 47 forms a water removal space. When the control rod 18 is withdrawn, as shown in FIG. 3, the follower 45 is positioned correspondingly to the fuel effective length portion (exothermic portion) LM of the fuel assembly 11 so as to prevent the coolant from flowing therein, while forming a coolant removal space. Thus, the ratio of water in the gap between the fuel assemblies 11 to the overall volume is lowered, and also, the ratio of water to fuel is lowered. The control rod absorber 43 of the control rod 18 has a length in the axial direction equivalent to the fuel effective portion (exothermic portion) LM of the normal fuel assembly 13. Moreover, in the reactor core 10 of the boiling water reactor, the shaft brackets 15 are provided at the upper and lower portions of the normal fuel assembly 13 and at the lower portion of the partial fuel assembly 14 so as to absorb the neutrons leaking from the reactor core 10. For example, stainless steel having a neutron absorbing ability is used as the material for the shaft bracket 15. Further, the shaft bracket 15 is not provided on the upper portion of the partial fuel assembly 14. According to such arrangement provided with no shaft bracket, a neutron leakage to the upper portion of the partial fuel assembly 14 is increased in the void increase, and the void reactivity is made negative even if the breeding ratio is at least about 1. Therefore, an inherent stability of the reactor core 10 can be ensured. Next, the operation of the reactor core 10 of the boiling water reactor of this embodiment will be described hereunder. The reactor core 10 has a volume ratio of water to fuel, which is less than 1, preferably, about 0.5 or less, and is remarkably smaller than the conventional reactor core of a light water reactor having a volume ratio of water to fuel, which is about 2.0 to 2.5. A ratio of coolant channel cross section to the fuel cross section of the reactor core 10 is set preferably to about 0.5 or less. Accordingly, in the reactor core 10, a fissionable material such as plutonium or the like in the fuel is subjected to a fissile reaction by a neutron, and the heat and neutrons are generated. A part of high energy neutrons (fast neutron) produced through the fissile reaction leaks outside the reactor core 10. However, most of high energy neutrons is moderated and scattered by the water as a coolant flowing between fuel rods 22, between these fuel rods 22 and the channel box 20, and between the channel box 20 and the control rod 18, and then, are again incident upon the fuel rod 22, thus contributing to the fissile reaction or the neutron absorption reaction. In the case where the volume ratio of water to fuel is about 0.5, a moderation (slow-down) effect by water is small, and an average neutron energy is an energy for a water cooling reactor close to sodium fast breeder reactor. For this reason, the ratio of neutron capture reaction by fissionable material is small like the existing light water reactor, and the neutron per neutron absorption is much generated, for example, two or more. Thus, the neutron absorbed in a parent material (element) such as uranium 238 (U-238) or the like is much increased, and it is possible to set the breeding ratio to about 1, preferably, to a range from 1.0 to 1.1. In the reactor core structure mentioned above, it is possible to set the breeding ratio to at least about 1, so that a utilization (capacity) factor of uranium resource can be greatly improved. More specifically, the utilization factor is about 100 times as much as in a case of the conventional utilization factor. Thus, even in the reactor core having the same dimension as the core diametrical direction size of the conventional boiling water reactor, the void reactivity can be made negative in the overall operating range. Therefore, it is possible to obtain negative reaction feedback characteristic and to secure inherent stability. Further, effective utilization of the fuel can be achieved, and also, environmental protection and economy can be simultaneously satisfied. FIG. 11 shows a second embodiment of a reactor core according to the present invention. The reactor core shown in this second embodiment is constructed in a manner that a rectangular and cylindrical hermetic container 50 is provided on an upper portion of the partial fuel assembly 14 charged in a reactor core 10A. The entire reactor core structure and the supporting structure of the fuel assembly 11 are substantially the same as those shown in FIG. 2 and FIG. 3. Therefore, like reference numerals are used to designate the same components as these of the first embodiment and their details are omitted. The reactor core shown in FIG. 11 is applied to a water cooling reactor such as light water reactor, for example, to a boiling water reactor. In the reactor core 10A, a number of rectangular cylindrical fuel assemblies 11 are charged in a state of being arranged at an equal pitch in longitudinal and traverse direction. The fuel assemblies 11 charged in the reactor core 10A are composed of at least two kinds, that is, normal fuel assemblies 13 each having a normal fuel effective (exothermic portion) length LM and partial fuel assemblies 14 each having a shorter fuel effective length LP as shown in FIG. 3. The upper portion of the partial fuel assembly 14 is formed with a streaming path 16. The streaming path 16 is formed by providing the cylindrical hermetic container 50 used as an empty can on the upper portion of the partial fuel assembly 14. The cylindrical hermetic container 50 is made of zirconium, zircaloy or aluminum material having a small neutron absorption cross section, and an inert gas such as helium, argon or the like is encapsulated or sealed as a seal gas in the interior thereof. As described above, the hermetic container 50 is made of zirconium, zircaloy or aluminum material, and it is therefore possible to make small a neutron collisional reaction of a neutron and the structural material of the hermetic container (hermetic container itself). Further, the hermetic container 50 is housed in the upper portion of the cylindrical channel box 20 of the partial fuel assembly 14 so as to form a water removal space. FIG. 12 and FIG. 13 are top plan views showing the normal fuel assembly 13 and the partial fuel assembly 14 charged in the reactor core of the water cooling reactor, respectively. The normal fuel assembly 13 and the partial fuel assembly 14 of the fuel assembly 11 are housed in the channel box 20 forming as rectangular cylindrical outer housing so as to form the fuel bundle 21 as a fuel element bundle therein. In the fuel bundle 21, a large number of fuel rods 22 is formed into a bundle by means of the fuel spacer, for example, the grid spacer 25 as shown in FIG. 5 to FIG. 7 so as to form a substantially square shape in its plane and are closely arranged in the channel box 20. The fuel bundle 21 is constructed in a manner that three fuel rods (fuel pin) adjacent to each other are arranged so as to provide an equilateral triangular shape, and then, is formed into a square bundle shape (rectangular shape), as a whole. A plurality of protrusions 51 for engagement are provided on an inner side of the channel box 20. These protrusions 51 are provided so as to correspond to unevenness on the outer side of the fuel bundle 21 and attains a function as a guide. Further, the protrusions 51 extend along the axial direction of the channel box 20 and form water removal space. Moreover, the protrusions 38 shown in FIG. 4 may be provided on the outer sides of the channel box 20, and if the protrusions 38 are provided, the ratio of water to fuel can be made smaller. The inner side of the channel box 20 is provided with the protrusions 51, each facing recess portion of the outer side of the fuel bundle 21. According to this arrangement, it is possible to make small a gap defined between the fuel bundle 21 and the channel box 20. Further, the protrusions 51 are provided so as to correspond to unevenness formed on the outer sides of the fuel bundle 21, and it is therefore possible to lower the ratio of water to nuclear fuel and to increase the breeding ratio of the nuclear fuel, while the void reactivity can be reduced. The fuel bundle 21 housed in the channel box 20 is constructed as shown in FIG. 14. More specifically, a coolant removal rod 52 is arranged on the center in each gap between three fuel rods 22 which have a triangular arrangement structure in its fuel rod arrangement. The coolant (water) removal rod 52 is made of zirconium, zircaloy or aluminum material having a small neutron absorption cross section. Preferably, the coolant removal rod 52 is formed into a shape of a hollow tube so as to restrict a neutron absorbing moderation by the structural material of the coolant removal rod 52. The coolant removal rod 52, which does not contain a nuclear fuel, is provided in each gap between fuel rods 22 to reduce the amount of coolant, and a change in the coolant amount after and before the void becomes small. In a water cooling reactor of a fast spectral system, a positive void reactivity occurs. The principal factor is as follows. More specifically, a moderation of neutron is reduced due to void effect of coolant, and the neutron spectrum is hardened, and thus, a neutron per absorption reaction of fissionable material (nuclear fuel material) is much generated and increase in its number. In the cooling water reactor, a factor of the positive void reactivity is eliminated by decreasing an amount of the coolant existing in the reactor core 10A, and the neutron leakage effect which is a factor of negative void reactivity, is unchanged, so that the void reactivity can be reduced as a whole. Next, the operation of the reactor core of the second embodiment will be described hereunder. The reactor core 10A is applied to a water cooling reactor, and during normal operation, in the reactor core 10A, a nuclear fissionable material (a nuclear fuel) such as plutonium or the like is mainly subjected to the fission reaction by means of neutrons so that heat and neutrons (mainly, fast neutrons) are generated. A part of generated neutrons leaks outside the reactor core 10A. However, most neutrons are moderated and scattered by water serving as a coolant flowing between the fuel rod 22 and the channel box 20 or between the channel boxes 20, and then, are again incident upon the fuel rod 22 so as to cause a fission reaction or neutron absorption reaction. If the ratio of water to fuel is small, the neutron moderation effect by water is small, and an average neutron energy is close to a sodium water cooling type fast breeder reactor. In the reactor core 10A, the hermetic container 50, which is filled with a sealed gas, is provided on the upper portion of the partial fuel assembly 14. Thus, the hermetic container 50 serves to remove the water as the coolant, and the ratio of water to fuel is small, and further, the number of generated neutrons per neutron absorption is two or more. Therefore, the number of neutrons absorbed in the parent material such as U-238 is much, and as a result, the breeding ratio can be increased. An empty space in the hermetic container 50 is filled with a gas, and for this reason, an atomic abundance density is lower than a state that water is boiled, and scattering reaction of neutrons is hard to occur. Therefore, the neutrons are easy to pass through the hermetic container 50, so that the neutrons can easily leak from the reactor core 10A in the core axial direction. For this reason, the coolant of the core fuel portion or the coolant of the streaming channel portion constituting the streaming path 16 can facilitate a leakage of voided neutron in the core axial direction, and it is possible to lower the void reactivity and to make it negative value. In this case, aluminum, zirconium or zirconium alloy (zircaloy) is used as the material of the hermetic container 50 having an empty space, and it is therefore possible to make small neutron collision reaction of the neutron and the structural material of the hermetic container 50. On the other hand, if the hermetic container 50 is made of a high strength material such as stainless steel or the like, iron or nickel (Ni) is contained in the stainless steel. Thus, a neutron absorption cross section of iron or the like is relatively large, and an exothermic reaction will be caused by the neutron absorption. However, aluminum has a neutron absorption cross section smaller about one place in figure than that of iron. Further, zirconium or zircaloy has a neutron absorption cross section which is about a half of the neutron absorption cross section of nickel, and the exothermic reaction caused by neutron absorption is decreased. If aluminum, zirconium or zirconium alloy (zircaloy) is used as the material of the hermetic container 50, neutron absorption by the hermetic container 50 is reduced. On the other hand, neutron absorption by the parent material (U-238) in nuclear fuel material is relatively increased. The U-238 is made into .sup.239 Pu (Pu-239) by neutron absorption, and is used as a nuclear fuel, thus increasing the breeding ratio. Moreover, a scattering cross section of neutron is substantially the same as that of an element such as aluminum or zirconium. However, aluminum or zirconium has a metallic atomic density smaller than that of stainless steel, and therefore, a neutron scattering is hard to be caused. Thus, the neutron is easy to pass through the hermetic container 50 in the axial direction, that is, streaming is easy to be made, so that the void reactivity can be further lowered. In the fuel assembly 11, the coolant removal rod 52 is provided between fuel rods 22 which form a triangular arrangement, and the protrusion 51 is provided in the channel box 22. According to this arrangement, an amount of water which is a coolant is reduced, so that the void reactivity can be further lowered. At this time, the protrusions 38 as shown in FIG. 4 are additionally provided on the central portions of the outer sides of the channel box 20, thus an amount of coolant being further reduced. Therefore, the protrusion 38 performs a function of lowering the void reactivity. In the fuel assembly 11 shown in FIG. 12 and FIG. 13, although there is shown an example in which the protrusion 51 has been provided in the channel box along the longitudinal direction of the channel box 20, the protrusion 51 may be constructed as shown in FIG. 15. The protrusion 51 shown in FIG. 15 is formed so as to have an inner hollow structure. Therefore, the structural material (protrusion itself) reacting with a neutron is reduced in its amount so as to further increase the breeding ratio. The neutron leakage to the core axial direction is easy to be caused, so that the void reactivity can be lowered. Next, a third embodiment of a reactor core according to the present invention will be described hereunder with reference to FIG. 16 and FIG. 17. In the reactor core of this third embodiment, the fuel assembly 11 charged in a reactor core 10B is improved. The entire construction of the reactor core of this embodiment substantially the same as that of FIG. 1 and FIG. 2, and therefore, the details are omitted. In the reactor core 10B, the fuel assemblies 11 are provided with support pads 55 at upper portions on the outer peripheries thereof. The support pad 55 serves to dispense an upper plate lattice which functions as a fuel assembly fixing frame used in the existing light water reactor. The support pad 55 has an L- or V-letter shape in plane as shown in FIG. 17 and is provided at each of four corners on the upper portion of the channel box 20 of the fuel assembly 11. The support pads 55 are provided at the corner portions of the upper side on the outer periphery of the fuel assembly 11 so as to make it possible to dispense or eliminate a fuel assembly fixing frame for supporting the top portion of the fuel assembly 11 in the horizontal direction. Thus, a gap between fuel assemblies 11 is made narrow, and the fuel assembly is much charged in the reactor core, so that the breeding ratio can be increased. The L-shaped support pad 55 is attached so as to ride on each corner portion of the cylindrical channel box 20 of the fuel assembly 11 from the side portion. Thus, the fuel assemblies 11 adjacent to each other are stably supported by means of two support pads 55 which contact with each other at two places on both sides in the widthwise direction of the channel box 20. Therefore, it is possible to surely prevent the fuel assemblies 11 from directly contacting to each other and to ensure a gap for inserting the control rod 18 between adjacent fuel assemblies 11 so that the control rod 18 can be stably withdrawal. FIG. 18 shows a fourth embodiment of a reactor core according to the present invention. In the reactor core of in this fourth embodiment, a fuel assembly 56 charged in the reactor core has an improved structure. The fuel assembly 56 of this embodiment is not constructed in a manner that the normal fuel assembly 13 and the partial fuel assembly 14 are combined. The fuel assembly 56 of this embodiment includes a normal fuel element region 57 and a partial fuel element region 58. The normal fuel element region 57 and the partial fuel element region 58 are formed through a coolant channel partition wall 59 and are housed in the rectangular cylindrical channel box 20. In FIG. 18, there is shown an arrangement example such that the partial fuel element region 58 is formed on the central portion of the fuel assembly 56, and the normal fuel element region 57 is formed at the peripheral portion of the partial fuel element region 58. The normal fuel element region 57 is formed in a manner that a normal fuel element having an ordinary fuel effective (exothermic portion) length LM is arranged, and on the other hand, the partial fuel element region 58 is formed in a manner that a short-dimension fuel element having a short fuel effective length LP is arranged. Both the normal and short-dimension fuel elements comprises a fuel rod, for example. Flow rates of the coolant guided into the normal fuel element region 57 of the fuel assembly 56 and the partial fuel element region 58 thereof are suitably distributed by means of an orifice 60, which is provided on the upper portion of the fuel assembly 56. According to this structure, the upper portion of the partial fuel element region 58 is voided and a neutron streaming path 61 is formed on the voided portion. At this time, the partial fuel element region 58 facilitates the leakage of neutron in the core direction, so that the void reactivity can be lowered. An empty can-like hermetic container as shown in FIG. 11 and FIG. 13 may be provided on the upper portion of the partial fuel element region 58. In the above fourth embodiment of the arrangement mentioned above, the partial fuel element region 58 is formed on the central portion of the fuel assembly 56, and the normal fuel element region is formed at the periphery of the partial fuel element region 58. In this fourth embodiment, the normal fuel element region 58 and the partial fuel element region 57 may be arranged in the manner reverse to the above arrangement, or various modifications may be made. Further, it may be possible to divide the region into three or more regions other than two regions, and each region may be properly selected as a normal fuel element region or as a partial fuel element region. Each of the above embodiments shows the example of the reactor core in which fuel rods as fuel elements are arranged in the fuel assembly 11 so as to form a triangular structure. These fuel rods 22 may be arranged so as to form a square, like the existing fuel assembly as shown in FIG. 19. In this case, in order to decrease the volume ratio of water to nuclear fuel of the fuel assembly charged in the reactor core, the coolant removal rod 52 is provided at the central portion between four adjacent fuel rods 22 which are mutually arranged so as to provide a square shape. Preferably, the coolant removal rod 52 is formed with an inner hollow structure so as to restrict moderation of neutrons. The coolant removal rod 52 is provided at the central portion between fuel rods 22 which are arranged so as to form a square, and the coolant having a large neutron moderation is removed. The coolant removal rod 52 is formed with the inner hollow structure, and the moderation of neutrons by the structural material (coolant removal rod) is restricted. Therefore, the breeding ratio can be increased. In this case, it is possible to facilitate a leakage of neutron in the axial direction of the coolant removal rod 52, and neutron leakage effect is enhanced. Therefore, the void reactivity lowering effect is slightly caused, thus contributing to lowering of the void reactivity. FIG. 20 shows a modified example of FIG. 19, in which the coolant removal rod 52, which is provided at the central portion between fuel rods 22 arranged so as to provide a square shape, is made of aluminum, zirconium or zircaloy having a low neutron absorption cross section. As described above, since the coolant removal rod 52 is made of a material having a low neutron absorption, the neutron absorption is restricted and the breeding ratio can be increased. In the embodiments of the present invention described above, although the reactor core is applied to the boiling water reactor, the arrangements or structures of the normal fuel assembly and the partial fuel assembly are applicable to a reactor core of a pressurized water reactor. In the case of being applied to the pressurized water reactor, a position where the fuel effective portion of the partial fuel assembly is formed is not specially limited, and the fuel effective portion may be in line with the upper side of the fuel effective portion of the normal fuel assembly. Further, a cluster type control rod is used as the control rod. According to the cluster type control rod, the control rod is taken in and out of the fuel assembly from the upper portion thereof. For this reason, in the cluster type control rod, a follower forming a water removal space is provided on the lower portion of the control rod absorber. In this manner, the present invention is applicable to a water cooling reactor which uses water as a coolant. As is evident from the above explanation, in the reactor core according to the present invention, the fuel volume ratio is increased so as to lower the ratio of water to fuel, and it is therefore possible to increase a breeding ratio and to improve the utilization factor of uranium resource. Thus, the uranium resource can be effectively utilized, and environmental protective, stability and economy can be greatly improved. It is to be noted that the present invention is not limited to the described embodiments and many other changes and modifications may be made without departing from the scopes of the appended claims.
	claims	1. A process for the excitation, extraction, capture and isolation of electrons of particles from medium sources, comprising:a. providing a means for the capture of electrons of particles from a medium of ground or other sources,b. providing a means for the capture of electrons of particles from a medium of water or other sources,c. providing a means for the capture and isolation of electrons through the attraction of said electrons to positive electric charges induced onto a section of electron isolation components,d. providing a means to produce positive electric charges by an induced negative electric charge placed onto another section of said electron isolation components,e. providing a means to induce positive and negative electric charges onto sections of said electron isolation components by exposing said components to positive electric fields,f. providing a means to excite, extract and capture electrons of said mediums by the attraction of said electrons to positively charged holes,g. providing a means to produce positively charged holes by exposing components to positive and negative electric fields,h. providing a means to produce said positive and negative electric fields through the application of charge segregation and storage assemblies,i. providing a means of charge segregation and storage by the application of an electric potential difference,j. providing a means for the production of said electric fields through any combination selected from the group consisting of electric, magnetic or electromagnetic sources,k. enabling the control or distribution of said captured or isolated electrons as electric energy.
046648712	abstract	Disclosed is a nuclear power plant comprising a high-temperature pebble bed reactor contained in a cylindrical steel pressure vessel in which an upper part of the cylindrical steel pressure vessel, which contains a heat utilization system, is retracted and equipped with a cover upon which circulating blowers are placed. The heat utilization system comprises, in a known manner, a single steam generator. The steam generator comprises at least two sub-systems independent of one another, with their own distributors and collectors, and with their own inlet and outlet lines. A first shut-down arrangement comprises a plurality of absorber rods insertable into bores of the side reflector from above and comprises rod drives arranged outside the steel pressure vessel in the area of its retracted upper part. A second shut-down arrangement comprises small absorber spheres for introducing into the core of the reactor, and several storage containers and annular conduits for said spheres. The storage containers are also arranged outside the steel pressure vessel in the area of its retracted upper part. Annular conduits for the introduction of the small absorber sphere are, however, disposed inside the steel pressure vessel and connected with channels provided in projections of the side reflector protruding into the core.
	summary
050892215	description	Referring to FIG. 15, an exemplary fuel bundle F is disclosed in which spacers are utilized. Specifically, a lower tie plate N and an upper tie plate U are illustrated. Lower tie plate N supports the fuel rods 9. Upper tie plate U braces the rods in the vertical upstanding side-by-side relation to maintain the fuel rods vertically parallel to one another. A channel 8 surrounds the fuel rods between the tie plates and continues fluid flow from the lower tie plate N to the upper tie plate U. Spacers S1 and S2 are located between the tie plates and around the fuel rods. These spacers function to maintain the sid-by-side alignment of the fuel rods 9 between the tie plates as well as to provide improved fluid flow, especially from the inside of the channel 8 to the outer fuel rods in the fuel bundle. Having set forth the generic construction of an exemplary fuel bundle F, the construction of a spacer grid of the prior art will be set forth. Thereafter, the improvements of the present invention to the spacer grid will be set forth. Finally, various spacer constructions which can be utilized in fuel bundles will be illustrated. Referring to FIG. 1A, an illustration of a discrete cell C' of the prior art is set forth. The cell includes two spring legs, 14, 16. These respective spring legs are spaced apart one from another and are connected at the top by rod encircling arms 18 and at the bottom by rod encircling arms 20. Each of the respective spring legs 14, 16 is deflected inwardly and defines at a central portion thereof respective rod contacting portions 15,17. The respective arms 18,20 when surrounding a fuel rod must form stops onto which the fuel rod is urged. Therefore, the arms in their encirclement of a fuel rod are bent inwardly at respective stop portions. These stop portions include arcuate portions 21, 23 in upward arms 18 and arcuate portions 25, 27 in lower arms 20. Typically, a fuel rod R (shown in broken lines) passes medially through each cell unit. As can be seen, the fuel rod is urged at the rod contacting springs portions 15, 17 onto the respective stops 21, 23 in upper arms 18 and 25, 27 in lower arms 20. Referring the FIG. 1C, the method of fastening together the cells of the prior art can be seen and understood. Specifically, the spring legs 14, 16 of each cell units adjoin the cantilevered arms 18, 20 of each adjacent cell unit. It will hereafter be emphasized that in the construction of the cell units of this invention the spring legs of pair cell units are remote from one another. This remote placement enables the rod encircling bands to extend across the center of the cell pair while the respective spring legs are at remote extremes of each cell pair. (See FIG. 2B and the position of the respective spring legs 24, 26.) Having set forth the prior art cell construction with respect to FIGS. 1A, 1B and 1C, the preferred embodiment of this invention will now be set forth. Referring to FIG. 2A, a front elevation is shown of a blank of spring material precut to form a cell C utilized with this invention. As will be set forth, cell C is similar to cell C' illustrated in FIG. 1A. Specifically the spring metal is preferably an alloy sold under the trademark of Inconel by the International Nickel Company. The metal is 0.008" to 0.012" thick and die cut in the shape of FIG. 2A. Specifically, there is a first spring leg 24, a second spring leg 26 with an upper rod encircling arm 28 and a lower encircling arm 30. Observing the upper portion of the metal to be formed into the cell, it can be seen that an axis 33 is utilized to divide at a medial location the metal blank between the respective spring legs 24, 26. At the upper arm 28, leg 31 is slightly shorter than leg 32. Similarly, the lower arm 30 has legs which differ slightly in length. This difference in the lengths of the legs is a departure from the prior art. The use of these respective long and short legs will be illustrated with respect to FIG. 2B to show the attachment of the two formed cell structures C into a convenient self-bracing structural unit for fabrication of the spacer set forth herein. Additionally, and over the prior art, an upper spring stop 34 and a lower spring stop 35 are formed in the respective arms 28, 30 overlying the spring leg 24. As will be set forth with respect to FIG. 2C, these respective stops prevent bending of the spring leg 24 beyond the elastic limit. Similarly, a spring stop 36 and a spring stop 37 is formed overlying spring leg 26. These respective stops function identically to stops 34, 35 in preventing bending of the spring leg 26 beyond the elastic limit. The reader will understand that during shipment of fuel bundles the spacers frequently become dynamically loaded with the weight of the fuel rods. The respective stops function to prevent overloading of the spring legs during fuel bundle assembly and during transport. Those understanding the construction of the prior art spacers will realize that bending is typically formed by passing the material of FIG. 2A through a series of bending dies. Respective bends are made at each of the dies until the full structure of one of the discrete cells C1 or C2 FIG. 2B is formed. Since the construction of such a series of dies is well within ordinary skill in the art, such construction will not be set forth herein. It will suffice to say that the cells C1 and C2 are individually fabricated as shown in FIG. 2B. Referring to FIG. 2B, two cells C1 and C2 are illustrated in a cell unit P. Each cell includes spring legs 24, 26 with an upper arm portion 28 and a lower arm portion 30. Each of the spring legs 24, 26 has a rod contacting portion 25, 27. Rod contacting portion 25, 27 biases a contained rod into the rod stops 45, 46, 47, 48. It will be understood that bands 45, 46, 47, 48 are given a compound curvature. This curvature is inward toward the contained fuel rod in each cell so that the fuel rod bears against the bands 45, 46, 47 and 48. It will further be seen that bands 45, 46, 47, 48 are convex as exposed to the fuel rods. This convex curvature enables the fuel rods to be inserted within each cell without the end of the fuel rod hanging up on the end of the cell. It can be seen that upper arms 28 and lower arms 30 are bent into encirclement so that the respective arm ends at 50, 51 on cell unit C2 are off-center with respect to the arm ends 50, 51 from cell unit C1. In the construction of the cell unit pair P of cell units C1, C2, the two cell units are preferably confronted one to another. Thereafter and in the confronted position at the respective upper arms 28 and lower arms 30, the units are spot welded. It can be seen that there is formed a structurally rigid unit. The respective spring legs 24, 26 of cell unit C2 and 24, 26 of cell unit C1 form rigid spaced apart vertical legs members to the paired cell units. At the same time, the joined together upper arms 28 and lower arms 30 form horizontal spanning units. As will hereinafter be illustrated, this cell unit pair can be conveniently manipulated to construct varying configurations of a spacer. An aspect of the prevention of spring leg movement beyond the elastic limit may be illustrated with respect to FIG. 2C. Referring to FIG. 2C, it can be seen that it is a vertical side elevation of spring member 26 taken along lines 2C--2C of FIG. 2B. The spring leg 26 is shown in two positions. The solid lines show the spring in its normal position, where it biases the fuel rod against the stops. As can be understood, the rod when so biased will be well away from the respective spring stops 36, adjacent upper arm 28 and stop 36 adjacent lower arm 30. If, however, the fuel rod is biased to fully deflect spring member 26, the rod contacting portion will move to the position shown at 27'. In this position, the rod R will be biased against the respective stops 36. A three point stance will result with no further deflection of the spring member 26. This being the case, it will be understood that by selecting the dimension of the respective spring 26 and of the rod contacting portion 27 and of the upper and lower stops 36, flexure of the spring can be limited so that yielding and permanent deflection of the spring does not occur. Having set forth the cell pair here illustrated, brief reference may be made to FIGS. 3A, 3B, 4A, 4B, 5, and 6 for the disclosure of the varying patterns into which the cell pair may be constructed. Referring to FIG. 3A, there is shown a schematic in which 4 lattice positions are occupied. In this 4 lattice position unit, cell pairs designated P1-P2 are arrayed in side-by-side parallel relation. Referring to FIG. 3B, the side elevation illustrates the minimal structure of the Inconel sections of the disclosed spacer construction. Specifically, arms 28 extend in a plane at the top of the spacer. Further, arms 30 extend in a plane at the bottom of the spacer. The spatial interval there between is spanned by the spring legs 24, 26. Thus, the spring legs 24, 26 act not only for the bias of the contained fuel rods in the cells but additionally form the vertical interconnecting members between the upper grid (formed by arms 28) and the lower grid (formed by arms 30). Thereafter, welding at the abutted interfaces of the cell arms 28, 30 (see FIG. 2B) occurs. Such welding is typically by a fusion weld such as that provided by an inert tungsten gas weld or alternately a laser weld depending upon production preferences. At this juncture, a solid and interlocking grid structure is formed. (See FIG. 3B.) Referring to FIG. 4, a grid having an aperture for a large water rod R shown. The disclosed aperture includes the omission of designated but omitted cell pairs P1, P2, P3, P4, P5 and P6. As can be seen, it is required that the included cell pairs be aligned so that omitted cell pairs P1, P2, P3, and P4 be oriented in one direction while designated but omitted cell pairs P5 and P6 are oriented in an orthogonal direction. Referring to FIG. 5, an embodiment is illustrated having two types of required apertures. A first aperture constructed precisely analogous to that already illustrated with respect to FIG. 4 is for a water rod R. A second set of apertures are for overlying partial length rods. Such partial length rods are disclosed in United States patent application Ser. No. 176,975, filed Apr. 4, 1988 entitled Two-Phase Pressure Drop Reduction BWR Assembly Design. Referring to FIG. 5, the array shown can be best illustrated by observing cell pairs P1, P2, P3 and P4. Specifically, cell pairs P1 and P3 are across the pictorial representation of FIG. 5. Cell pairs P2 and P4 are oriented orthogonally. The four cell pairs each define a place for two rods. A total of eight rods occupies nine lattice positions. In the center of the cell pairs P1, P2, P3 and P4 is an omitted portion of the grid which omitted portion of the grid is for the overlying of a partial length rod. It will be realized that this omission is not trivial. Specifically, and during operation at full steaming rates of such a reactor, the locations overlying partial length rods are known to be volumes of high steam venting. These volumes of high steam venting can experience back pressure even when passing the relatively low profiles of the cell pairs here illustrated. By the expedient of aligning four cell pairs around nine lattice positions with the central position vacant, a preferred lattice structure with improved venting is provided. Those skilled in the art will understand that the remaining pair alignments illustrated at P5-P13 are logical extensions of the pattern illustrated with respect to cell pairs P1-P4. Specifically, it can be seen that in the ten wide lattice array, lattice positions L2,2, L2,4, L2,7, and L2,9 are vacant. These vacancies continue in a similar pattern throughout the ten by ten array here illustrated. It can thus be seen that the cell pairs here illustrated can be uniquely arrayed for the construction of any desired full length fuel rod, partial length fuel rod, or water rod disposition. Referring to FIG. 6, two large water rods R1 and R2 are shown positioned in apertures similar to the aperture previously described with respect to FIGS. 4 and 5. In FIG. 6 the arrangement of cells is slightly different from that of FIGS. 4 and 5. Each corner cell is a single cell, and is not paired with another cell. These cells are oriented so that the springs are oriented away from the corners. The remainder of cells are pairs. Referring to FIG. 6, a construction of the spacer of this invention is illustrated having two large water rods R1 and R2 in parallel, side-by-side relation. It can be seen that each one of the water rods R1, R2 occupies four lattice positions. The remainder of the cell pairs are arrayed to form a complete grid. Referring to FIG. 7, a detail of FIG. 6 at the aperture for water rod R1 is illustrated. Two band members 60 form a lining into which the water rod R1 is braced. The construction of these aligning members are illustrated with respect to FIGS. 8A and 8B. Referring to FIGS. 8A and 8B, it can be seen that the inner band members 60 are formed in two equal segments, which segments have their respective ends at 63, 64. Referring to FIG. 8B, there is an upper member 72 and a lower member 74. These members form the upper and lower portions of the inner band, and encircle a water rod. Referring to FIG. 7, the upper members 72 are welded to the grid cells at locations 66. These respective bands are connected by spring numbers 65, 67 in a manner that is analogous to each of the cell members. Two features of the band members are noteworthy. First, the band members define respective spring legs 65, 66 each having a spring medial spring portion 68 for bearing on the water rod R1. These respective spring members securely brace the water rod in place and maintain such bracing in the absence of appreciable vibration. Secondly, deflecting tabs 70 overlie each of the spring leg members 65, 67 at the upper portion of the band members. These deflecting members serve to deflect water passing upwardly to the adjacent fuel rods braced by the spacer. Referring back to FIG. 7, the attachment of the spacer band 60 interior of the array can be easily understood. Specifically, band ends 63, 64 are identified. It can be seen that by placing two members 60 in the disposition illustrated in FIG. 7 bracing of the respective water rods R1, R2 securely at the spacer can occur. Having set forth the Inconel cellular arrays and their varied constructions, it will be observed that the construction set forth gives a relatively minimum possible amount of spring material in an array for the spacing of fuel rods. In the typical fuel bundle assembly there are on the order of 7 or 8 such spacer arrays. It is necessary that such spacer arrays be surrounded by a continuous band. This continuous band locates the spacer within the channel. It also reduces the coolant flow between the grid and the channel wall, and causes water intermixture into the rising liquid and vapor water coolant flowing on the outside of the fuel rods. Referring to FIG. 9, the grid of FIG. 6 is shown together with the preferred embodiment of the band. The interior cells and water rods are not shown. The band is shown partially exploded away from the sides of the grid. Specifically, band sides B1, B2, are shown spaced apart from the grid G. Bands B3 and B4 are shown in their final position next to the grid. It will be observed that the bands are broken at respective gap 101 (between bands B1 and B2), gap 102 (between bands B2 and B3), and Gap 104 (between band B4, B1). Gap 103 (between bands B3 and B4) has been welded. Each band includes a plurality of inwardly deflecting tabs 110, which tabs have the function of deflecting water flowing near the sidewall of the fuel channel inwardly to and toward the rod array. Referring to FIG. 10, a band segment B3 of the preferred embodiment is illustrated. Band segment B3 terminates along a first side at end 101 and along a second side at an end 102. Band segment B3 defines a plurality of flow deflecting tabs 110. It is the function of these tabs to deflect water flowing along the channel sides to and toward the array of contained fuel rods. The band also includes respective raised portions 120. These respective raised portions enable the band to standoff from the sidewalls of the channels. The respective raised portions 120 additionally can have two alternate functions. First, the respective raised portions can themselves deflect water flowing along the sides of the channel. Such deflection causes a turbulence which ensures mixture of any water layer flowing along the inside of the channel to and towards the fuel rod array. Secondly, the raised portions 120 are oriented to provide stiffness to the band. With a flexible band, flow induced vibration of the band can occur. In the natural mode of vibration the band deflects away from the grid and the maximum deflection occurs halfway between the corners at each side of the spacer. Referring to FIG. 9, the location of maximum deflection on the left side of the spacer is at 103. FIG. 11A shows a side elevation view of the preferred embodiment of the band. The raised portion of the band 120 extends over most of the band width and over slightly more than half of the band height. FIG. 11B shows a section at B--B of FIG. 11A and illustrates the shape of the raised portion 120. This shape is similar to a corrugation, and gives the band side a stiffness several times that of a band with no raised portion. This increased stiffness prevents flow induced vibration of the band. FIG. 11C shows an enlarged top view of the corner region of the spacer, together with the corner region of a channel 130. The distance 132 between the inside of the band and the channel 130 should be small, in order to provide good thermal performance for the outer fuel rods. Unfortunately, as the gap 132 is reduced, the gap between the corner fuel rod and the channel corner is also reduced. For a given gap 132 along the sides, the corner gap becomes smaller as the fuel rod array is changed from an 8.times.8 array to a 9.times.9 and to a 10.times.10 array. As the number of fuel rods in each row and column is increased, the corner rod moves closer to the channel. The channel corner radius cannot be decreased, because the channel corners would then interfere with other reactor components. FIG. 11C has been drawn approximately to scale for a 10.times.10 array. If the corner portion 136 of the Zircaloy band were to lie entirely outside the corner Inconel cell, there would be insufficient clearance between the band and the channel corner, and insertion of the space into the channel would be difficult or impossible. Referring to FIG. 11A, slots 138 have been cut into the corner of the band. The upper and lower arms of the corner cell project into these slots. As can be seen in FIG. 11C, the band corner 136 can then be moved away from the channel corner, toward the corner fuel rod. At the same time, the grid is captured by the band since part of the grid projects into the corner slots. It will thus be understood that the band members at their respective corners accommodate the decreasing diameter of the fuel rod R1. At the same time, these corner sections key firmly the band members B1-B4 around the spacer to the Inconel spacer grid. FIGS. 12A, 12B, 13A, 13B, 13C, 14A and 14B illustrate an alternate embodiment of the Zircaloy spacer band. In this embodiment, the band stiffness is not increased. Instead, Inconel straps are used to tie the band to the Inconel grid. FIG. 12A shows a top view of a segment of this band. As in the prior art, bath tub type indentations 140 are used to space the band away from the channel. FIG. 12B shows a side elevation view of this band. A change from the configuration of FIGS. 11A and 11B is that cutouts 142 are made at the top and bottom of the band. These cutouts are used in conjunction with Inconel straps, which will be described later. Additional cutouts 144 are used at the band corners. These cutouts perform the same function as the corner slots in the preferred embodiment. The upper and lower arms of the corner cell project into the cutouts, allowing the band corner to be spaced away from the channel corner. FIGS. 13A, B, and C show the Inconel strap. FIG. 13A is a side elevation view of an Inconel strap. The length l of the strap is slightly less than the width of the spacer and the width w is equal to the width of the spacer arms. FIG. 13B shows a top view of the strap. The bends 150 project into the cutouts 142 of FIG. 12B. FIG. 13C shows an enlarged top view of the strap. A projection 152 is used to bear against the band, halfway between the bend regions 150. FIG. 14A shows a top view of a portion of the spacer, illustrating how the strap locks the band securely to the spacer grid. The strap acts as a series of springs, bearing against the band at the points 152. The strap is shown prior to welding to the grid. In this position there are gaps 154 between the strap and grid. To attach the strap to the grid, the gaps 154 are closed, bending the strap and applying loads to the band at the contact points 152. The Inconel strap is then welded to the Inconel grid at locations 154. FIG. 14B shows a side elevation view of the strap and part of the band.
046541705	abstract	Disclosed is an oxidizing composition of water, about 0.1 to saturation of an alkali metal hypohalite, and sufficient alkali metal hydroxide to raise the pH of the solution to at least about 12. A method of decontaminating metal surfaces having a coating thereon which contains radioactive substances is also disclosed. The composition is passed over the coating at a temperature of about 50.degree. to about 120.degree. C. followed by passing a decontamination solution over the coating.
	summary
043808557	abstract	Hollow shell laser fusion targets, such as glass microballoons, are filled with gases of the type which do not permeate through the wall of the balloon. A hole is laser-drilled in the balloon, a plug is placed over the hole and gas is introduced into the balloon through the loosely plugged hole. Thereafter the plug is melted to form a seal over the hole, entrapping the gas within the target. The plug is, for example, a polymer such as highly crystalline polystyrene, or glass.
	summary
048760560	summary	This invention relates to a method and an apparatus for measuring the flow of a fluid in a duct, and particularly though not exclusively for measuring the flow of liquid in a sub-sea pipeline. According to the present invention there is provided a method for measuring the flow of a fluid in a duct having at least a length thereof immersed in a saline sea, the method comprising locating a container adjacent to the duct, with the container having an inlet communicating with the sea to allow ingress, as a test fluid, of sea water from the sea, causing the test fluid to enter the container, storing the test fluid in the container, irradiating the test fluid in the container with neutrons so as to generate atoms of a predetermined radioactive nuclide in the test fluid, injecting at spaced time intervals a sample of the irradiated test fluid from the container into the duct, detecting, at a location spaced apart along the duct from the location at which the injection takes place, radiation emitted by the predetermined radioactive atoms, and determining, from the elapsed time between the injection of the test fluid and the detection of the radiation, the flow rate of the fluid. An advantage accruing from use of sea water as a test fluid obtained from the environment of the duct is that the apparatus can operate for a long period of time without any need for servicing; the period of operation is not limited by the storage capacity of the container. It is therefore suited to use in remote or hostile locations such as on the sea bed. The invention is especially suited to measuring flow in under-sea pipelines carrying oil, for example from an oil well. Sea water typically contains sodium ions at a concentration of about 10 g/liter. As a consequence of neutron irradiation, sodium-24 nuclides are created. These decay with emission of beta and gamma radiation and with a half-life of 14.8 hours.
	claims	1. A semiconductor processing apparatus comprising:a stage configured to receive mounted thereon a substrate having a semiconductor film to be processed is;a supply section that includes at least (a) a beam shaper that shapes a laser beam into a top-hat laser beam with a top-hat beam profile and (b) a diffraction grating that modulates the top-hat type laser beam into a plurality of energy beams in which adjacent energy beams have a tangent line therebetween, the supply section being configured to supply the plurality of energy beams onto the semiconductor film mounted on the stage in such a way that irradiation points of the energy beams are linearly aligned on the semiconductor film at given intervals; anda control section that (a) moves the plurality of energy beams and the substrate relative to each other in a scan direction that is tilted at an angle relative to the linear alignment of the irradiation points on the semiconductor film, and (b) affects scanning of the semiconductor film with the irradiation points of the plurality of energy beams in parallel to thereby control a heat treatment on the semiconductor film,wherein,the tangent line is tangential to both footprints of the adjacent energy beams,the angle between the linear alignment of energy beams and the scan direction is set such that the scan direction is parallel to the tangent line,the angle is such that there is no gap between the footprints of the adjacent energy beams along a direction perpendicular to the scan direction, andthe semiconductor processing apparatus being effective to form crescent-shaped crystal grains on the semiconductor film that are aligned along the tangent line. 2. The semiconductor processing apparatus according to claim 1, wherein the control section is configured to tilt a direction of the linear alignment of the irradiation points of the plurality of energy beams with respect to the scan direction of the irradiation points thereof. 3. The semiconductor processing apparatus according to claim 1, wherein when performing a heat treatment on the semiconductor film to be a channel portion of a semiconductor device, the control section is configured to control the intervals of the plurality of energy beams, a scan speed thereof, and an amount of energy thereof in such a way that grain boundaries of the semiconductor film which are formed by irradiation of the plurality of energy beams are provided periodically in a lengthwise direction of the channel portion. 4. The semiconductor processing apparatus according to claim 1, wherein the supply section is configured to supply a laser beam with a wavelength of 350 nm to 470 nm as the energy beam. 5. The semiconductor processing apparatus according to claim 1, wherein the supply section is configured to supply a laser beam generated from a semiconductor laser oscillator of a GaN compound as the energy beam. 6. A semiconductor processing method comprising the steps of:shaping, using a beam shaper, a laser beam into a top-hat laser beam with a top-hat beam profile;modulating, using a diffraction grating, the top-hat type laser beam into a plurality of energy beams in which adjacent energy beams have a tangent line therebetween;supplying the plurality of energy beams onto a semiconductor film provided on a substrate to be processed in such a way that irradiation points of the energy beams are linearly aligned on the semiconductor film at given intervals; andmoving the plurality of energy beams supplied and the substrate relative to each other in a scan direction that is tilted at an angle relative to the linear alignment of the irradiation points on the semiconductor film, and affects scanning the semiconductor film with the irradiation points of the plurality of energy beams in parallel to thereby control a heat treatment on the semiconductor film,wherein,the tangent line is tangential to both footprints of the adjacent energy beams,the angle between the linear alignment of energy beams and the scan direction is set such that the scan direction is parallel to the tangent line,the angle is such that there is no gap between the footprints of the adjacent energy beams along a direction perpendicular to the scan direction, andthe semiconductor processing method being effective to form crescent-shaped crystal grains on the semiconductor film that are aligned along the tangent line. 7. The semiconductor processing method according to claim 6, wherein in controlling the heat treatment on the semiconductor film, a direction of the linear alignment of the irradiation points of the plurality of energy beams is tilted with respect to the scan direction of the irradiation points thereof. 8. The semiconductor processing method according to claim 6, wherein when performing a heat treatment on the semiconductor film to be a channel portion of a semiconductor device, the intervals of the plurality of energy beams, a scan speed thereof, and an amount of energy thereof are controlled in such a way that grain boundaries of the semiconductor film which are formed by irradiation of the plurality of energy beams are provided periodically in a lengthwise direction of the channel portion. 9. The semiconductor processing method according to claim 6, wherein the scan direction of the plurality of energy beams is turned back in an opposite direction for each stage of a scan area.
	claims	1. A treatment process for a zirconium alloy for use in a nuclear reactor, comprising:preparing a zirconium alloy ingot, the zirconium alloy ingot having a composition of which is in weight % or weight ppm:0.40%≤Nb≤1.05%;traces ≤Sn≤2%;(0.5 Nb−0.25) %≤Fe≤0.50%;traces ≤Ni≤0.10%;traces <(Cr+V) %<0.50%;traces ≤S≤35 ppm;600 ppm≤O≤2000 ppm;traces ≤Si≤120 ppm;traces ≤C≤150 ppm;If 0.50%≤Nb≤1.05%, then (Cr+V) %≤(0.2 +3/4Fe−1/4Nb) %; andthe remaining being Zr and unavoidable impurities;at least one step of reheating and hot shaping the zirconium alloy ingot;at least one cycle of cold rolling-annealing steps on the zirconium alloy ingot after the at least one step of reheating and hot shaping, a last annealing of the at least one cycle of cold rolling-annealing steps being a final annealing step which gives a product formed therefrom a final stress-relieved, partially recrystallized or completely recrystallized condition,the annealing of at least one of the cold rolling-annealing steps being performed at a temperature comprised between 650° C. and the lowest of either 700° C. or (710−20×Nb %)° C., and the annealings of the other cold rolling-annealing steps, if any, being performed at a temperature not higher than 600° C. 2. The treatment process as recited in claim 1 wherein the at least one step of reheating and hot shaping the zirconium alloy ingot includes a reheating and quenching step following a hot shaping step. 3. The treatment process as recited in claim 1 further comprising an annealing the ingot after the at least one step of reheating and hot shaping the zirconium alloy ingot. 4. The treatment process as recited in claim 1 wherein (0.02+1/3Fe) %≤(Cr+V) %. 5. The treatment process as recited in claim 1 wherein 0.50%≤Nb≤1.05%, and (0.02+1/3Fe)%≤(Cr+V)%≤(0.2 +3/4Fe−1/4Nb)%. 6. The treatment process as recited in claim 1 wherein the at least one cycle of cold rolling-annealing steps is at least two cycles of cold rolling-annealing. 7. The treatment process as recited in claim 1 wherein the temperatures and durations of the reheating and annealing steps are chosen so that arithmetic mean sizes of the precipitates is between 50 and 250 nm. 8. The treatment process as recited in claim 1 wherein the composition of the prepared zirconium alloy ingot is: 1200 ppm≤O≤1600 ppm. 9. A zirconium alloy having a composition in weight% or weight ppm comprising:0. 40%≤Nb≤1.05%;traces≤Sn≤2%;(0.5 Nb−0.25)%≤Fe≤0.50%;traces ≤Ni≤0.10%;traces ≤(Cr+V)%≤0.50%;traces ≤S≤35 ppm;600 ppm≤O≤2000 ppm;traces ≤Si≤120 ppm;traces ≤C≤150 ppm;if 0.50%≤Nb≤1.05%, then (Cr+V)%≤(0.2 +3/4Fe−1/4Nb) %;(0.02+1/3Fe)%≤(Cr+V)%; andthe remaining being Zr and unavoidable impurities;wherein the zirconium alloy has undergone treatments comprising at least one hot shaping step and at least one cycle of cold rolling-annealing steps, the annealing of at least one of the cold rolling-annealing steps having been performed at a temperature comprised between 650° C. and the lowest of either 700° C. or (710−20×Nb%)° C., and wherein the annealings of the other cold rolling-annealing steps, if any, having been performed at a temperature not higher than 600° C., and in that its microstructure is deprived of β-Zr phase. 10. The zirconium alloy as recited in claim 9 wherein 1200 ppm ≤O≤1600 ppm. 11. A fuel cladding tube for a fuel assembly for a light water nuclear reactor, the fuel cladding made of the zirconium alloy as recited in claim 9. 12. A guide thimble for a fuel assembly for a pressurized water nuclear reactor, the guide thimble made of the zirconium alloy as recited in claim 9. 13. A fuel channel for a fuel assembly for a boiling water nuclear reactor, the fuel channel made of the zirconium alloy as recited in claim 9. 14. A grid for a fuel assembly for a light water nuclear reactor, wherein the grid made of the zirconium alloy as recited in claim 9. 15. A water channel for a fuel assembly for a boiling water nuclear reactor, wherein the water channel made of the zirconium alloy as recited in claim 9. 16. The treatment process as recited in claim 1 wherein the partially recrystallized or completely recrystallized condition is formed by more than 10% of recrystallized grains.
	description	1. Field This invention pertains generally to nuclear reactor fuel assemblies and more particularly to nuclear reactor fuel assemblies that employ a spacer or mixer or support grid constructed of a high temperature strength, corrosion resistant, accident tolerant composition, and methods of making the spacer or mixer or support grid. 2. Description of Related Art In most pressurized water nuclear reactors (PWRs), boiling water reactors (BWRs) and heavy water reactors (HWRs), collectively referred to herein as water reactors, the reactor core is comprised of a large number of elongated fuel assemblies that generate the reactive power of the reactor. These fuel assemblies typically include a plurality of fuel rods held in an organized, array by a plurality of grids spaced axially along the fuel assembly length and attached to a plurality of elongated thimble tubes or other support structure of the fuel assembly. A description of a PWR structure is particularly provided, however, it is understood that the invention is applicable to water reactors in general. The thimble tubes typically receive control rods or instrumentation therein. Top and bottom nozzles are on opposite ends of the fuel assembly and are secured to the ends of the thimble tubes that extend slightly above and below the ends of the fuel rods. The grids, as is known in the relevant art, are used to precisely maintain the spacing and support between the fuel rods in the reactor core, provide lateral support for the fuel rods, and induce mixing of the coolant. One type of conventional grid design includes a plurality of interleaved straps that together form an egg-crate configuration having a plurality of roughly square cells which individually accept the fuel rods therein. Depending upon the configuration of the thimble tubes, the thimble tubes can either be received in cells that are sized the same as those that receive fuel rods therein, or in relatively larger thimble cells defined in the interleaved straps. The interleaved straps provide attachment points to the thimble tubes, thus enabling positioning of the grids at spaced locations along the length of the fuel assembly. The straps are configured such that the cells through which the fuel rods pass each include one or more relatively compliant springs and a plurality of relatively rigid dimples which cooperate to form the fuel rod support feature of the grid. Outer straps of the grid are attached together and peripherally enclose the inner straps of the grid to impart strength and rigidity to the grid and define individual fuel rod cells around the perimeter of the grid. The inner straps are typically welded or braised at each intersection and the inner straps are also welded or braised to the peripheral or outer straps defining the outer perimeter of the assembly. At the individual cell level, the fuel rods support is normally provided by the combination of rigid support dimples and flexible springs as mentioned above. There are many variations to the spring-dimple support geometry that have been used or are currently in use, including diagonal springs, “I” shaped springs, cantilevered springs, horizontal and vertical dimples, etc. The number of springs per cell also varies. The typical arrangement is two springs and four dimples per cell. The geometry of the dimples and springs needs to be carefully determined to provide adequate rod support through the life of the assembly. During irradiation, the initial spring force relaxes more or less rapidly, depending on the spring material and irradiation environment. The cladding diameter also changes as a result of the very high coolant pressure and operating temperatures and the fuel pellets inside the rod also change their diameter by densification and swelling. The outside cladding diameter also increases, due to the formation of an oxide layer. As a result of these dimensional and material property changes, maintaining adequate rod support through the life of the fuel assembly is very challenging. Under the effect of axial flow and cross flow induced by thermal and pressure gradients within the reactor and other flow disturbances, such as standing waves and eddies, the fuel rods, which are slender bodies, are continuously vibrating with relatively small amplitudes. If the rod is not properly supported, this very small vibration amplitude may lead to relative motion between the support points and the cladding. If the pressure exerted by the sliding rod on the relatively small dimple and grid support surfaces is high enough, the small corrosion layer on the surface of the cladding can be removed by abrasion, exposing the base metal to the coolant. As a new corrosion layer is formed on the exposed fresh cladding surface, it is also removed by abrasion until ultimately the wall of the rod is perforated. This phenomenon is known as corrosion fretting and in 2006 it was the leading cause of fuel failures in PWR reactors. Support grids also provide another important function in the fuel assembly, that of coolant mixing to decrease the maximum coolant temperature. Since the heat generated by each fuel rod is not uniform, there are thermal gradients in the coolant. One important parameter in the design of the fuel assemblies is to maintain the efficient heat transfer from the fuel rods to the coolant. The higher the amount of heat removed per unit time, the higher the power being generated. At high enough coolant temperatures, the rate of heat that can be removed per unit of cladding area in a given time decreases abruptly in a significant way. This phenomenon is known as deviation from nucleate boiling or DNB. If within the parameters of reactor operation, the coolant temperature would reach the point of DNB, the cladding surface temperature would increase rapidly in order to evacuate the heat generated inside the fuel rod and rapid cladding oxidation would lead to cladding failure. It is clear that DNB needs to be avoided to prevent fuel rod failures. Since DNB, if it occurs, takes place at the point where the coolant is at its maximum temperature, it follows that decreasing the maximum coolant temperature by coolant mixing within the assembly permits the generation of larger amounts of power without reaching DNB conditions. Normally, the improved mixing is achieved by using mixing vanes in the down flow side of the grid structure. The effectiveness of mixing is dependent upon the shape, size and location of the mixing vanes relative to the fuel rod. Other important functions of the grid include the ability to sustain handling and normal operation at anticipated accident loads without losing function and to avoid “hot spots” on the fuel rods due to the formation of steam pockets between the fuel rods and the support points, which may result when not enough coolant is locally available to evacuate the heat generated in the fuel rod. Steam pockets cause overheating of the fuel rod to the point of failure by rapid localized corrosion of the cladding. The grids, grid straps and integral flow mixers, e.g., mixing vanes, typically have been constructed of zirconium alloy because these materials exhibit low neutron adsorption cross-section and adequate mechanical and chemical properties. Similarly, fuel cladding materials also have been constructed of zirconium alloy. However, alternative fuel cladding materials are being considered for future nuclear reactor design and operation. Such new and different materials include silicon carbide (SiC) ceramic matrix composites which demonstrate properties that can provide for better safety margin and accident tolerance. However, the benefits of implementing new fuel cladding materials, such as SiC, can be offset because the grids, straps and/or mixing vanes inside the core contain a significant amount of zirconium. Thus, it is desirable to replace the zirconium-containing grids, straps and mixing vanes with other materials which have better structure stability, strength, and oxidation resistance at temperatures beyond normal operation and design basis accidents of a nuclear reactor. It is thus desired to provide an improved material (e.g., containing little to no zirconium) that exhibits high temperature strength, corrosion resistance and accident tolerance for use in constructing grids for nuclear reactor fuel assemblies. The foregoing objectives are achieved employing a nuclear reactor fuel assembly having a parallel, spaced array of a plurality of elongated nuclear fuel rods supported between a lower nozzle and an upper nozzle and a plurality of spaced grids arranged in tandem along the axial length of the fuel rods between the upper nozzle and the lower nozzle. The plurality of spaced grids or portions or parts thereof are constructed of a composition including one or more ternary compounds of the general formula I:Mn+1AXn (I) wherein M is a transition metal, A is an element selected from the group A elements in the Chemical Periodic Table, X is selected from the group consisting of carbon and nitrogen, and n is an integer from 1 to 3. In certain embodiments, M is selected from the group consisting of titanium, zirconium and niobium. Further, A can be selected from the group consisting of aluminum, silicon and tin. In certain embodiments, the one or more ternary compounds of the general formula I are selected from the group consisting of Ti2AlC, Ti3AlC2, Ti4AlN3, Ti2SiC, Ti3SiC2, Ti3SnC2, Zr2AlC, Zr2TiC, Zr2SnC, Nb2SnC, Nb3SiC2, (ZrxNb1-x)2AlC wherein x is greater than zero and less than 1. The molar ratio of the M component to the A component to the X component of the one or more ternary compounds of the general formula I can be selected from the group consisting of 2:1:1, 3:1:2 and 4:1:3. The ternary compounds of the general formula I can each have a density of greater than 85% of its theoretical density, and preferably greater than 95% of its theoretical density. In certain embodiments, one or more of the plurality of spaced grids has a pattern stamped on the surface of the material. Further, one or more of the plurality of spaced grids can include grid straps, integral flow mixers and combinations thereof. The fuel assembly can be employed in a water reactor selected from the group consisting of a pressurized water reactor, boiling water reactor and heavy water reactor. In another aspect, the invention provides a method of preparing an article selected from the group consisting of a support grid, a grid strap and an integral flow mixer for a nuclear reactor fuel assembly which includes obtaining in powder form a composition including one or more ternary compounds of the general formula I:Mn+1AXn (I) wherein M is a transition metal, A is an element selected from the group A elements in the Chemical Periodic Table, X is selected from the group consisting of carbon and nitrogen, and n is an integer from 1 to 3, and subjecting the composition to a process selected from the group consisting of uni-axial or isostatic hot pressing, additive manufacturing techniques, electric field assisted sintering and cold press followed by conventional sintering. In certain embodiments, the article is prepared by obtaining a first powder composition including a ternary compound of the formula I and a second powder composition including a different second ternary compound of the formula I, depositing a first portion of the first powder composition onto a target area, scanning directed energy source which emits a beam over a surface of the target area, sintering a first layer of the first powder composition portion corresponding to a first cross-sectional region of the article, depositing a second portion of the second powder composition onto the first sintered layer, scanning the directed energy source over the first sintered layer, sintering a second layer of the second powder composition portion corresponding to a second cross-sectional region of the article, joining the first and second layers during the sintering of the second layer, and depositing successive alternating portions of the first and second powder compositions onto the previous sintered layers and sintering each successive portion to produce successive sintered layers joined at a previous sintered layer and the article including a plurality of sintered layers. The method can further include employing a three-dimensional CAD file which is mathematically sliced into two-dimensional cross-sections. In certain embodiments, the article includes one or more grid straps which are joined together by a process selected from the group consisting of welding, brazing and fusing. The fusing can be conducted using a laser or an electron beam and materials for brazing are selected from the group consisting of copper, copper-zinc, copper-zinc-nickel, nickel-chromium-phosphorus, nickel-silver, and silver alloy. The invention relates to sintered ternary compounds for use in constructing articles, such as grids or portions or parts of the grids, such as grid straps and integral flow mixers, for nuclear reactor fuel assemblies. Historically, grids, grid straps and integral flow mixers are constructed of zirconium and/or zirconium alloy. It is an object of this invention to replace these conventional materials with compositions including one or more sintered ternary compounds having one or more properties of improved structure stability, strength, and oxidation resistance at temperatures which exceed normal operation. It is contemplated that the compositions in accordance with the invention are substantially composed of the one or more ternary compounds, however, the compositions may include material(s) other than the one or more ternary compounds. For ease of description, the disclosure provided herein is directed to a pressurized nuclear reactor (PWR) design, however, it is understood that the invention is equally applicable to various water reactor designs including boiling water reactors (BWRs) and heavy water reactors (HWRs). When Loss of Coolant Accidents (LOCAs) occur the fuel cladding temperature can be as high as 2200° F., and the temperature of the grids, grid straps and integral flow mixers which are in contact with the fuel rods can be the same high temperature. For beyond design basis accidents, the cladding and grid temperature may be well beyond 2200° F. for an extended period of time. It has been shown that grids, grid straps and integral flow mixers made of conventional material, such as zirconium alloy, may have “run-away” oxidation when exposed to steam at temperatures at or above 2200° F. and as a result, lose strength and structure integrity, and produce hydrogen gas. Failures of grids, grid straps and integral flow mixers may lead to more significant consequences such as loss of coolable geometry or even core meltdown. It is thus, an objective of the invention to develop articles, such as grids, grid straps and integral flow mixers, e.g., mixing vanes, for nuclear reactor fuel assemblies which are constructed of ternary compound-containing compositions which demonstrate excellent oxidation resistance and can avoid “run-away” oxidation at LOCA temperatures. FIG. 1A is an elevational view, represented in vertically shortened form, of a fuel assembly being generally designated by reference character 110. The fuel assembly 110 is the type used in a pressurized water reactor and has a structural skeleton which, at its lower end includes a bottom nozzle 112. The bottom nozzle 112 supports the fuel assembly 110 on a lower core plate 114 in a core region of the nuclear reactor. In addition to the bottom nozzle 112, the structural skeleton of the fuel assembly 110 also includes a top nozzle 116 at its upper end and a number of guide tubes or thimbles 118 which align with guide tubes in the upper internals of the reactor. The guide tubes or thimbles 118 extend longitudinally between the bottom and top nozzles 112 and 116 and at opposite ends are rigidly attached thereto. The fuel assembly 110 further includes a plurality of transverse grids 120 axially spaced along and mounted to the guide thimbles 118 and an organized array of elongated fuel rods 122 transversely spaced and supported by the grids 120. A plan view of a conventional grid 120 without the guide thimbles 118 and fuel rods 122 is shown in FIG. 2. The guide thimbles 118 pass through the cells labeled 124 and the fuel rods 122 occupy the remaining cells 126 except for the center cell which is reserved for an instrument thimble 138 (shown in FIG. 1A). As can be seen from FIG. 2, the grids 120 are conventionally formed from an array of orthogonal straps 128 and 130 that are interleaved in an egg-crate pattern with the adjacent interface of four straps defining approximately square support cells through which the fuel rods 122 are supported in the cells 126 in transverse, spaced relationship with each other. In many designs, springs 132 and dimples 134 are stamped into opposite walls of the straps 128 and 130 that form the support cells 126. The springs and dimples extend radially into the support cells and capture the fuel rods 122 therebetween; exerting pressure on the fuel rod cladding to hold the rods in position. The orthogonal array of straps 128 and 130 is welded at each strap end to a bordering strap 136 to complete the grid structure 120. In the prior art embodiment shown in FIG. 2, the bordering strap 136 is formed from four separate straps welded together at the corners. Also, as previously mentioned the assembly 110, as shown in FIG. 1A, has an instrumentation tube 138 located in the center thereof that extends between and is captured by the bottom and top nozzles 112 and 116. With such an arrangement of parts, fuel assembly 110 forms and integral unit capable of being conveniently handled without damaging the assembly of parts. As mentioned above, the fuel rods 122 in the array thereof in the assembly 110 are held in spaced relationship with one another by the grids 120 spaced along the fuel assembly length. As shown in FIG. 1A each fuel rod 122 includes the plurality of nuclear fuel pellets 140 and is closed at its opposite ends by upper and lower end plugs 142 and 144. Commonly, a plenum spring 150 is disposed between the upper end plug 142 and the pellets 140 to maintain the pellets in a tight stacked relationship within the rod 122. The fuel pellets 140, composed of fissile material, are responsible for creating the reactive power of the nuclear reactor. A liquid moderator/coolant, such as water or water containing boron and other coolant additives, is pumped upwardly through the fuel assemblies of the core in order to extract heat generated therein for the production of useful work. The cladding 146 which surrounds the pellets 140 functions as a barrier to prevent the fission byproducts from entering the coolant and further contaminating the reactor system. To control the fission process, a number of control rods 148 are reciprocally moveable in the guide thimbles 118 located at predetermined positions in the fuel assembly 110. The guide thimble cell locations 124 can be specifically seen in FIG. 2, except for the center location which is occupied by the instrumentation tube 138. Specifically, a rod cluster control mechanism 152, positioned above the top nozzle 116, supports a plurality of the control rods 148. The control mechanism has an internally threaded cylindrical hub member 154 with a plurality of radially extending flukes or arms 156 that form a configuration commonly known as a spider. Each arm 156 is interconnected to a control rod 148 such that the control rod mechanism 152 is operable to move the control rods vertically in the guide thimbles 118 to thereby control the fission process in the fuel assembly 110, under the motive power of a control rod drive shaft which is coupled to the control rod hub 154, all in a well known manner. FIG. 1B shows a portion of the fuel assembly 110 in FIG. 1A wherein the fuel rods 122 are held in spaced relationship with one another by the grids 120. As shown in FIG. 1B, mixing vanes 89 are installed on an upper surface of one of the plurality of grids 120. The mixing vanes 89 create turbulence, for example, in the region 91. Various designs of support grids, spacers and mixers are known in the art. The invention is not limited by these particular designs and therefore, the invention is equally applicable to the various designs. For example, an alternative support grid design is illustrated in FIGS. 3 through 17. As shown in FIGS. 3 and 5, the support grid 26 includes a frame assembly 40 and at least one generally cylindrical tubular member 50. The frame assembly 40 includes a plurality of cells 42 defined by cell walls 43. Each cell 42 has a width as indicated by the letter “w”. In one embodiment, the cells 42 and cell walls 43 are formed from a plurality of substantially flat, elongated strap members 44 disposed in two interlocked sets, a vertical set 46 and a horizontal set 48. The strap members 44 in the vertical and horizontal sets 48 of strap members 44 are generally perpendicular to each other. Additionally, the strap members 44 in each set are generally evenly spaced. In this configuration, the strap members 44 form generally squire cells 42A. Thus, each cell 42A has two diagonal axes “d1” and “d2,” which are perpendicular to each other and extend through the corners of the cell 42A, as well as two normal axes “n1” and “n2,” which are perpendicular to each other and extend through the center of the cell 42A and which intersect perpendicularly with the cell walls 43. The points on the cell wall 43 that the two normal axes pass through are the closest point, “cp”, between the cell wall 43 and the center of the cell 42. As shown in FIG. 4, the frame assembly 40 also has a height, indicated by the letter “h”, wherein the height is substantially less that the width or length of the frame assembly 40. Further, the frame assembly 40 has a top side 47 and a bottom side 49. It is notable that the strap members 44 of the present invention do not include protuberances, such as springs and dimples. The lack of additional support structures makes the construction of the frame assembly 40 very easy. The tubular member 50 of the support grid 26 is shown in FIGS. 5 and 6. The tubular member 50 includes at least one helical fluted portion or fuel rod contact portion 52, a cell contact portion 54, and a transition portion 56 disposed therebetween. As shown in FIGS. 5-7, the tubular member 50 has four fuel rod contact portions 52, which is the preferred embodiment. Other configurations are discussed below. The cell contact portion 54 has a greater diameter being generally equivalent to said cell width and is structured to snugly engage the cell 46. The fuel rod contact portion 52 has a lesser diameter, being generally equivalent to said fuel rod 28 diameter. Thus, the tubular member 50 may be disposed in a cell 42 and a fuel rod 28 may be disposed in the tubular member 50. In a preferred embodiment, the tubular member 50 is made from a material having a uniform thickness. Thus, the helical fuel rod contact portion 52 defines an outer passage 60 between the outer side of the tubular member 50 and the cell wall 43. Additionally, the cell contact portion 54, which is spaced from the fuel rod 28, defines an inner passage 62. Water which flows through either the outer or inner passages 60, 62 is influenced by the shape of the helical fuel rod contact portion 52 resulting in the water being mixed. The tubular member 50 may be constructed with any number of helical fuel rod contact portions 52 which may have any degree of pitch. For example, as shown in FIG. 8, a tubular member 50 has a single helical fuel rod contact portion 52 that extends 360 degrees about the tubular member 50. As shown in FIG. 9, a tubular member 50 has a two helical fuel rod contact portions 52 that each extend 180 degrees about the tubular member 50. As shown in FIG. 10, a tubular member 50 has a two helical fuel rod contact portions 52 that each extend 360 degrees about the tubular member 50. As noted above, FIG. 6 shows a tubular member 50 having a four helical fuel rod contact portions 52 that each extend 90 degrees about the tubular member 50. Preferably, the helical fuel rod contact portions 52 are spaced evenly about the tubular member 50, but this is not required. These examples have used a number (N) of helical fuel rod contact portions 52 and an angular displacement (A) that equals 360 degrees or a multiple of 360 degrees. This configuration is especially adapted for use in a square cell 42A. That is, the cell contact portion 54 will only contact the cell wall 43 at the closest point on the cell wall 43. At other points, e.g., the corner of the cell 42A, the tubular member 50 greater diameter, that is the cell contact portion 54, will not contact a cell wall 43. Thus, as shown best in FIG. 7, where there are four evenly spaced, helical fuel rod contact portions 52 that each extend 90 degrees about the tubular member 50, there are four corresponding cell contact portions 54, each disposed between a helical fuel rod contact portions 52. To ensure the greatest amount of surface area contact between the tubular member 50 and the cell wall 43, the tubular member 50 is disposed with each helical fuel rod contact portion 52 generally aligned with a diagonal axis at the top side 47 of the cell and aligned with a different diagonal axis at the bottom side 49 of the cell. In this orientation, the cell contact portion 54 is aligned with a cell wall 43 closest point at the top side 47 and at the bottom side 49. A similar configuration may be made with cells 42 of any shape. That is, the number (N) of helical fuel rod contact portions 52 is preferably equal to the number of sides (S) to the cell 42, and the angular displacement (A) is preferably 360 degrees/S. Thus, the tubular member may be positioned with each helical fuel rod contact portion 52 generally aligned with an axis passing through the corner of the cell 42 at the top side 47 of the cell and aligned with a different axis passing through the corner of the cell 42 at the bottom side 49 of the cell. Thus, the cell contact portion 54 is aligned with the cell wall 43 closest point at the top side 47 and at the bottom side 49. In another embodiment, the frame assembly 40 includes a plurality of cylindrical cells 42B defined by a plurality of connected tubular frame members 70. As shown in FIG. 11, the frame assembly 40 may have a plurality of densely packed tubular frame members 70, however, as shown in FIG. 12, a pattern of aligned tubular frame members 70 is preferred. That is, the tubular frame members 70 are coupled to each other at 90 degree intervals about the perimeter of each tubular frame member 70. The tubular member 50 is disposed within the cylindrical cells 42B. As shown in FIG. 13, the combination of the tubular member 50 and the cylindrical cell 42B again creates an inner passage 62 between the fuel rod 28 and the tubular member 50 and an outer passage 60 between the tubular member 50 and the tubular frame member 70. The cylindrical cell 42B of the tubular frame member 70 has the additional advantage that the entire cell contact portion 54 abuts the cell wall 43. That is, the diameter of the cylindrical cell 42B is the same as the cell width, which is also the same as the closest point, and, as such, the cell contact portion 54 will engage the cell wall 43 along the entire height of the cell wall 43. This is unlike a square cell 42A wherein the cell contact portion 54 does not contact the cell wall 43 at the corners. In another embodiment, shown in FIG. 14, the functions of the tubular member 50 and the tubular frame member 70 have been combined in a helical frame member 80. That is, the frame assembly 40 includes a plurality of helical frame members 81 disposed in a matrix pattern. The helical frame member 80, like the tubular member 50, includes at least one helical fuel rod contact portion 52, however, instead of a cell contact portion 54, the outer side of the helical frame member 80 is a contact portion 55 structured to be directly coupled to the contact portion 55 of an adjacent helical frame member 80. As with the tubular frame member 70 embodiment of the frame assembly 40, the helical frame members 80 are coupled to each other at 90 degree intervals about the perimeter of each helical frame member 80. Additionally, in this embodiment the frame assembly 40 preferably includes a plurality of outer straps 82 structured to extend about the perimeter of the plurality of helical frame members 81. The outer straps 82 are coupled to the contact portion 55 of the helical frame members 80 disposed at the outer edge of the plurality of helical frame members 81. A fuel rod 28 is disposed through at least one helical frame member 80. As shown best in FIG. 13, as viewed as a cross-section, the tubular member 50 components, i.e., the helical fuel rod contact portion 52, the cell contact portion 54, and the transition portion 56, preferably, are shaped as smooth curves. This configuration gives the tubular member 50 a compressible, spring-like quality. However, as shown in FIG. 15, the cell contact portion 54 may include an extended planar length or platform 90. The platform 90 is structured to provide a greater surface area which engages the cell wall 43. The greater length of the platform 90 will necessitate the transition portion 56 having a sharp curve. Similarly, as shown in FIG. 16, the helical fuel rod contact portion 52 may include a concave platform 92 adapted to extend radially about the fuel rod 28. As before, greater length of the concave platform 92 will necessitate the transition portion 56 having a sharp curve. A tubular member 50 may also include both a platform 90 at the cell contact portion 54 and a concave platform 92 at the helical fuel rod contact portion 52. Finally, the tubular member 50 may also be constructed with a generally flat transition portion 56 with angled ends 94. As shown in FIG. 17, in this embodiment the transition portion 56 is generally planar in a cross-sectional top view. It is understood that, due to the helical nature of the fuel rod contact portion 52, the transition portion 56 is not flat in the direction of the height of the frame assembly 40. The compositions of the invention include one or more ternary compounds of the general formula I:Mn+1AXn (I) wherein M is a transition metal, A is an element selected from the group A elements in the Chemical Periodic Table, X is carbon (C) or nitrogen (N), and n is an integer from 1 to 3. These ternary compounds are referred to as MAX phase compounds. In certain embodiments, M includes titanium (Ti), zirconium (Zr), niobium (Nb) and, mixtures and combinations thereof. Further, in certain embodiments, A includes aluminum (Al), silicon (Si), tin (Sn) and, mixtures and combinations thereof. Thus, in certain embodiments, the ternary compounds in accordance with the invention include Ti2AlC, Ti3AlC2, Ti4AlN3, Ti2SiC, Ti3SiC2, Ti3SnC2, Zr2AlC, Zr2TiC, Zr2SnC, Nb2SnC, Nb3SiC2, (ZrxNb1−x)2AlC wherein x is greater than zero and less than 1 and, mixtures and combinations thereof. Suitable compounds of the general formula I for use in the invention have a density of greater than 85% of their theoretical density, and preferably a density of greater than 95% of their theoretical density. Furthermore, in certain embodiments the stoichiometry of the ternary compounds is such that the molar ratio of the M component to the A component to the X component (M:A:X) is 2:1:1 or 2:1:2 or 4:1:3. That is, n equals 1, 2 or 3. In certain embodiments, the compositions of the invention can include carbide (wherein X is carbon), nitride (wherein X is nitrogen) or a mixture or combination of carbide and nitride (wherein X is a mixture of combination of carbon and nitrogen). The ternary compounds according to general formula I exhibit material strength (e.g., Young's modules) similar to the material strength of zirconium alloys and they can maintain the strength at elevated temperatures. For example, the yield strength of Ti2AlC is about 700 MPa, which is about half of the yield strength of Inconel 718 but twice the yield strength of typical zirconium alloys with 1% Sn and 0.7% Nb. Further, suitable ternary compounds according to the invention demonstrate at least one of the following properties: adequate ductility, elasticity and low neutron adsorption cross-section. In addition, use of the ternary compounds according to the invention result in less hydrogen being produced and therefore, the ternary compounds and the articles constructed therefrom are not as susceptible to hydrogen induced embrittlement as is zirconium alloy. Furthermore, it is contemplated that the maximum strain or elongation of the ternary compounds is increased due to the presence of elements M and A in general formula I, which form intermetallics in the matrix. In a nuclear reactor core, a combination of cladding which is constructed of SiC and articles, e.g., grids, grid straps and integral flow mixers, which are constructed of MAX phase compounds allows at least substantial, and in some instances complete, removal of zirconium from of the core thereby further increasing the accident tolerance of the nuclear fuel. Articles for nuclear reactor fuel assemblies, such as grids, grid straps and mixing vanes, constructed of ternary compound-containing compositions in accordance with the invention can be manufactured using conventional techniques known in the art. Non-limiting examples of such techniques include uniaxial or isostatic hot pressing, additive manufacturing techniques, electric field assisted sintering and cold press followed by conventional sintering. In certain embodiments, for example, the articles can be made using conventional pressure-less sintering employing an apparatus including a laser or other directed energy source which is selectable for emitting a beam in a target area, a powder dispenser system for depositing powder into the target area and, a laser control mechanism to move the aim of the laser beam and modulate the laser to selectively sinter a layer of powder dispensed into the target area. The control mechanism operates to selectively sinter only the powder disposed within defined boundaries to produce the desired layer of the article. The control mechanism operates the laser to selectively sinter sequential layers of powder, producing a completed article including a plurality of layers sintered together. The ternary compound(s) can be powdered in a conventional manner, for example, by mechanical crushing. Preferably, the control mechanism includes a computer, e.g., a CAD/CAM system, to determine the defined boundaries for each layer. That is, given the overall dimensions and configuration of the article, e.g., grid, grid strap or integral flow mixer, the computer determines the defined boundaries for each layer and operates the laser control mechanism in accordance with the defined boundaries. Alternatively, the computer can be initially programmed with the defined boundaries of each layer. Sintering apparatus and methods are generally known in the art. A suitable apparatus and method for use in the invention is disclosed in U.S. Pat. No. 4,863,538, which is incorporated herein by reference in its entirety. In accordance with certain embodiments of the invention, one or more ternary compounds of the general formula I is used (e.g., layered) in a sintering process to produce an article, e.g., grid, grid strap or integral flow mixer. The one or more ternary compounds are in the form of a powder and deposited into the target area as above-described. The process is controlled such that the laser selectively sinters a layer consisting of a first ternary compound powder (of the general formula I) and the laser then selectively sinters sequential layers of powder, producing a completed article comprising a plurality of layers sintered together. Each of the sequential layers can include the first ternary compound powder or alternatively, each of the sequential layers can include alternating layers of a first ternary compound powder and a different second ternary compound powder (of the general formula I). Additional materials or powders can be mixed or combined with the one or more ternary compounds to form compositions in accordance with the invention. In one embodiment, a grid can be made by the use of laser or electron beams for sintering wherein the process is initiated with a 3D CAD file which is mathematically sliced into 2D cross-sections and the grid is built a layer at a time until completed. Thus, the grid can be the build-up of a layer-by-layer process. That is, the grid can be considered a plurality of discrete cross-sectional regions which cumulatively conclude the three-dimensional configuration of the grid. Each discrete cross-sectional region has defined two-dimensional boundaries. FIG. 18 broadly illustrates a sintering apparatus 210 which includes a laser 212, powder dispenser 214, and laser control means 216. In more detail, the powder dispenser 214 includes a hopper 220 for receiving the powder 222 and having an outlet 224. The outlet 224 is oriented for dispensing the powder to a target area 226, which in FIG. 18 is generally defined by the confinement structure 228. It is contemplated and understood that many alternatives exist for dispensing the powder 222. In accordance with the invention, powder 222 includes a combination of one, two or more carbides and/or nitrides of the general formula I. The components of the laser 212 are shown somewhat schematically in FIG. 18 and include a laser head 230, a safety shutter 232, and a front mirror assembly 234. The type of laser used is dependent upon many factors, and in particular upon the type of powder 222 that is to be sintered. Generally, the laser beam output of the laser 212 has a wavelength near infrared. In either a pulsed or continuous mode, the laser 212 can be modulated on or off to selectively produce a laser beam which travels generally along the path shown by the arrows in FIG. 18. To focus the laser beam, a diverging lens 236 and converging lens 238 are disposed along the path of travel of the laser beam as shown in FIG. 18. The diverging lens 236 placed between the laser 212 and convening lens 238 creates a virtual focal point between the diverging lens 236 and the laser 212. Varying the distance between the converging lens 238 and the virtual focal point, allows control of the true focal point along the laser beam path of travel on the side of the converging lens 238 remote from the laser 212. There have been many advances in the field of optics, and it is recognized that many alternatives are available to efficiently focus the laser beam at a known location. The laser control means 216 includes computer 240 and scanning system 242. In a preferred embodiment, the computer 240 includes a microprocessor for controlling the laser 212 and a CAD/CAM system for generating the data. In the embodiment illustrated in FIG. 18, a personal computer is used. As shown in FIG. 18, the scanning system 242 includes a prism 244 for redirecting the path of travel of the laser beam. The scanning system 242 also includes a pair of mirrors 246, 247 driven by respective galvonometers 248,249. A function generator driver 250 controls the movement of the galvonometer 248 so that the aim of the laser beam (represented by the arrows in FIG. 18) can be controlled in the target area 226. The driver 250 is operatively coupled to the computer 240 as shown in FIG. 18. It will be appreciated that alternative scanning methods are available for use as the scanning system 242, including acusto-optic scanners, rotating polygon mirrors, and resonant mirror scanners. In FIG. 19, a portion of 252 is schematically illustrated and shows four layers 254-257. The aim of the laser beam 212 is directed in a raster scan pattern as at 266. As used herein, “aim” is used as a neutral term indication direction, but does not imply the modulation state of the laser 212. In accordance with the invention, layer 254 can include a first ternary compound powder (of the general formula I), layer 255 can include a different second ternary compound powder (of the general formula I), layer 256 can include the first compound powder and layer 257 can include the different second ternary compound powder. A first portion of powder 222 is deposited in the target area 226 and selectively sintered by the laser beam 212 to produce a first sintered layer 254 (FIG. 19). The first sintered layer 254 corresponds to a first cross-section region of the desired grid. The laser beam selectively sinters only the deposited powder 222 within the confines of the defined boundaries. This process is repeated layer-by-layer with the individual layers sintered together to produce a cohesive grid, e.g., part 252 of FIG. 19. The dimensions of the article can generally vary. In certain embodiments, the thickness (e.g., the successive layers in the sintering process) of the grid or grid strap can be between about 0.015 inch and about 0.035 inches. The height can be between about 0.45 inches and about 2.25 inches. The width can be between about 7 inches and about 15 inches. In certain embodiments, the grids or grid straps manufactured according to the invention can be stamped using customized dies to create patterns which can be used to assemble fuel grids. The stamping can be accomplished using conventional apparatus, techniques and methods known in the art. Further, the grid straps produced in accordance with the invention can be joined together by welding or brazing using convention apparatus, techniques and methods known to one having ordinary skill. The brazing materials include but are not limited to copper, copper-zinc, copper-zinc-nickel, nickel-chromium-phosphorus, nickel-silver, and silver alloy. Furthermore, a laser or electron beams can be used to fuse together the grid straps. While specific embodiments of the invention have been described in detail, it will be appreciated by those skilled in the art that various modifications and alternatives to those details could be developed in light of the overall teachings of the disclosure. Accordingly, the particular embodiments disclosed are meant to be illustrative only and not limiting as to the scope of the invention which is to be given the full breadth of the appended claims and any and all equivalents thereof.
	abstract	The present invention relates to a method for creating a pattern on a workpiece sensitive to electromagnetic radiation. Electromagnetic radiation is emitted onto a computer controlled reticle having a multitude of modulating elements (pixels). The pixels are arranged in said computer controlled reticle according to a digital description. An image of said computer controlled reticle is created on said workpiece, wherein said pixels in said computer controlled reticle are arranged in alternate states along at least a part of one feature edge in order to create a smaller address grid. The invention also relates to an apparatus for creating a pattern on a workpiece. The invention also relates to a semiconducting wafer and a mask.
044328923	claims	1. In a process for the safe intermediate and final storage of tritium after reaction of tritium or a tritium containing gas with a hydride forming metal in comminuted form, the improvement comprising pressing to a molded body at room temperature a mirton of the tritium containing metal particles and a metal which has a low permeability for tritium. 2. A process according to claim 1 wherein for the pressing there is used aluminum powder. 3. A process according to claim 2 wherein the pressing process is carried out in a jacket of a metal which has a low permeability for tritium. 4. A process according to claim 1 wherein the pressing process is carried out in a jacket of a metal which has a low permeability for tritium. 5. A process according to claim 4 wherein the molded body is inserted in a metal containment. 6. A process according to claim 3 wherein the molded body is inserted in a metal containment. 7. A process according to claim 2 wherein the molded body is inserted in a metal containment. 8. A process according to claim 1 wherein the molded body is inserted in a metal containment. 9. A process according to claim 5 wherein the containment is in the form of a tube or U-profile. 10. A process according to claim 5 wherein the containment is made of steel. 11. A process according to claim 5, including the steps of filling the containment with molded bodies, then closing the containment and rolling or pressing the containment flat. 12. A process according to claim 11 comprising inserting the shaped containment in a final storage container and casting it in concrete. 13. A process according to claim 8 comprising inserting the shaped containment in a final storage container and casting it in concrete. 14. A process according to claim 7 comprising inserting the shaped containment in a final storage container and casting it in concrete. 15. A process according to claim 6 comprising inserting the shaped containment in a final storage container and casting it in concrete. 16. A process according to claim 5 comprising inserting the shaped containment in a final storage container and casting it in concrete.
	claims	1. A lower end plug for an internally and externally-cooled annular nuclear fuel rod comprising:a support with a slenderness ratio in the range of 1 to 20;a coolant inflow part with an inner inflow space and a plurality of inflow holes in a wall thereof, so as to interact with the inflow space, coupled to a lower end of the internally and externally-cooled annular nuclear fuel rod at an upper end thereof, and extending from an upper end of the support in a reverse conical shape such that the inflow space interacts with an inner channel of the internally and externally-cooled annular nuclear fuel rod; anda coupler extending from a lower end of the support and coupled with a handling tool of the internally and externally-cooled annular nuclear fuel rod,wherein each of the inflow holes is inclined in such a manner that an outer end thereof, exposed outwards, is located lower than an inner end thereof, exposed inwards. 2. The lower end plug as set forth in claim 1, wherein each of the normal lines of faces that the outer end and the inner end of inflow holes form is formed perpendicular to the wall of the coolant inflow part.
	summary
	description	The invention relates to structure of an X-ray converter based on at least two such optoelectronic converters as television camera (hereinafter, TV camera), photodiode matrix, etc. These converters are used in X-ray apparatus: for diagnostic angiographic examinations using X-ray contrast substances, in particular, for determining of vessels' passability and efficiency of blood supply of organs and tissues, for locating of probes, catheters, and other diagnostic or surgical instruments introduced into the body through blood vessels, trachea and bronchial tubes, esophagus, anus, and other tubular organs, for a repeated roentgenography of lungs, heart, stomach, and other (in particular, movable) organs, for a filmless roentgenography in traumatology, for a filmless photofluorography at mass-scale examinations of population, for roentgenography in urology and other departments of clinics, where periodic observation of slow propagation of an X-ray contrast agent in the body is needed, and, optionally, for X-ray defectoscopy of arbitrary devices or for frontier and customs inspection of the luggage of passengers and cargoes. WO 98/11722 (PCT/UA96/00016, priority date of 10 Sep. 1996) discloses an X-ray diagnostic system equipped with an X-ray converter based on at least two TV cameras rigidly fastened to a common base in such a way that their separate fields of view partly overlap each other and the joint field view of theirs overlaps the area of said converter. In this system: optical inputs of all TV cameras are oriented towards the converter of X-radiation into visible light (this converter is made from such suitable material as cesium iodide or salts of rare-earth elements and the like and hereinafter designated as the “X ray-to-optical converter”), and electrical outputs of all TV cameras are connected through an ADC-unit to a multichannel corrector of geometric distortions, which provides synthesis of integral output video signal from fragmentary video signals. The resolution of this integral output video signal is the higher, the more TV cameras are used in said converter. Moreover, this signal, after adjustment of said corrector, contains practically no distortions caused by unavoidable differences in the geometric shape and dimensions of individual TV cameras and their parts, and by inevitable errors in their mounting. X-ray diagnostic systems equipped with said X-ray converters are convenient in manufacturing and servicing and are of a reasonable price, and the experience in their many years' practical application confirmed that: first, an integral output video signal can be obtained with a frequency of not less than 25 frames per second, which is sufficient for angiographic examinations, second, the radiation dose absorbed by patient during one X-ray examination is reduced as a rule by a factor of 20 and more in comparison with the ordinary photofluorography, third, the protection of the medical or other operating staff is facilitated, because any display for the demonstration of images based on integral output video signals can be located at a safe distance from X-ray source, fourth, said images are convenient for recording and storing on high-capacity modern data carriers for the keeping of case histories and repeated reviews, and fifth, digital video records can be easily converted into usual images on the X-ray film by exposing it in front of a display suitable in the screen size. In fact, “Apparatus for printing multiform images . . . ” has been designed for this purpose (see RU 22249 U1 and UA 1282 U). It is available at the CIS market now. However, the same practical experience demonstrated that the quality of images based on integral output video signals is substantially dependent on: first, optical disturbances which arise, in particular: over illumination from external light sources, under action of parasitic light fluxes between TV cameras and the X-ray-to-optical converter and between adjacent TV cameras, and over distortion of light fluxes in optical channels of TV cameras, and second, the action on TV cameras of such X-radiation that isn't converted into the visible light, whose power can reach 70% (and at best is not less than 30%) of the initial power of this radiation. Some of said disadvantages have been relatively easily eliminated or at least appreciably attenuated. Thus, the converter according to U.S. Pat. No. 6,002,743 was equipped with: a housing made of X-ray-transparent material opaque for the visible light (in order to eliminate the illumination from external light sources), and a one-piece plate of X-ray-opaque lead glass installed between the X-ray-to-optical converter and optical inputs of TV cameras (in order to absorb the residual X-radiation). Such plate protects TV cameras from said residual X-radiation the more efficiently, the greater its thickness. Accordingly, the reliability of the converter as a whole is markedly enhanced. However, this obvious improvement call out undesirable side effects, namely: intensification of parasitic light fluxes between TV cameras and the X-ray-to-optical converter and between adjacent TV cameras and, as a result, additional distortions of light fluxes in optical channels of TV cameras. Indeed, the brightness of that part of the total X-radiation flux which passed through the patient or another obstacle is inhomogeneous by itself and, what is particularly important, substantially differs from the brightness of the remaining part of said flux. Accordingly, the visible image on the X-ray-to-optical converter as well has parts differing in the brightness. The brightest parts give rise to an intense Lambert's radiation of light in broad solid angles. Corresponding light fluxes freely propagate in random directions in the lead glass plate and therefore only partly get to optical inputs of TV cameras, which are located exactly opposite said bright sections. Other parts of the light fluxes give rise to the parasitic illumination of adjacent TV cameras and, reflecting many times from converter parts (in particular from objective lenses of TV cameras) and propagating within the lead glass plate or passing through it, can get: to optical inputs of random TV cameras of the converter, creating a random set of optical interferences in every diagnostic session, and to relatively dark zones of the X-ray-to-optical converter, creating a random illumination commensurable with the brightness of said zones. These undesirable effects are especially pronounced when the angle of incidence of light rays from the X-ray-to-optical converter on surfaces of objective lenses of corresponding TV cameras exceeds the angle of total internal reflection in the lead glass. Moreover, in such cases the secondary reflection results in polarization of light. U.S. Pat. No. 6,370,225 discloses a more perfect X-ray converter, which is most similar to the proposed below converter in subject matter. This known converter comprises of: a light-proof housing, one of whose walls is X-ray-transparent, and the following units fastened one after another behind the wall: an X-ray-to-optical converter, a polarizing filter, a filter of residual X-radiation in the form of a lead-glass plate, an unit of photodetector's objective lenses, where the number and placement of the objective lenses correspond to the number and placement of optoelectronic converters (in particular, TV cameras) in the photodetector, and said photodetector containing at least two optoelectronic converters having partly overlapping fields of view and separated electrical outputs for connecting to a system for processing of fragmentary video signals and their “sewing together” into an integral output video signal. Along with above-indicated attributes, the following specific features characterize the known converter: said lead-glass plate is on the side facing said objective lenses divided by blind slots intersecting at right angles into sections whose number is equal to the optoelectronic converters' number of the photodetector, the depth of said slots is of about 0.25 to 0.35 of the thickness of the lead-glass plate and the slots are filled with an opaque material, and each said objective lens has one input lens which abuts upon the lead-glass plate surface, three intermediate lenses separated by air gaps, and one output lens which abuts upon the photodetector surface. One skilled in the art will appreciate that known X-ray converter solves the problem of improving the image quality by parts only and not efficiently enough, and the problem of enhancing the reliability is practically not solved. In fact: the polarizing filter attenuates the polarized component of light reflected from the lead glass, but does not affect the remaining light flux, multi-lens optical systems of said objective lenses, where lenses are separated by air gaps, give rise to irregular reflections of practically unpolarized light onto said X-ray-to-optical converter, and darkened slots only reduce (but not exclude) a parasitic illumination of adjacent optoelectronic converters because of free motion of light beams in the not slotted part of the lead-glass plate. Due to this, integral video signals can contain artifacts in the diagnostic picture. Moreover, said slots reduce down to unacceptable level not only the mechanical strength of the brittle lead-glass plate, but also the reliability of the converter as a whole. The invention is based on the problem of creation, by improving the form, positional relationship and relative dimensions of parts, such X-ray converter that would secure effective suppression of internal interferences within optical channels and operating reliability at once. This problem is solved in that in an X-ray converter having: a light-proof housing, one of whose walls is X-ray-transparent, and following units fastened one after another behind this wall: an X-ray-to-optical converter, a filter of residual X-radiation, an unit of objective lenses, each of which contains at least two one by one installed lenses for focusing a part of the light flux on the corresponding optoelectronic converter, and a photodetector containing at least two optoelectronic converters having partly overlapping fields of view and separated electrical outputs for connecting to a system for processing of fragmentary video signals and their “sewing together” into an integral output video signal, according to the invention, the light-proof housing is equipped with an additional light-opaque and X-ray-opaque partition that has through-holes, whose number and placement correspond to the number and placement of objective lenses and optoelectronic converters, and is rigidly fastened within said housing practically parallel to the X-ray-to-optical converter, the filter of residual X-radiation is formed as washers that are made from an X-ray-opaque light-transparent material and rigidly fastened within said through-holes of the additional partition, said additional partition is equipped with blinds, whose number and placement correspond to the number and placement of objective lenses and optoelectronic converters; these blinds are installed on such side of this partition that is opposite to said X-ray-to-optical converter, and length A of each said blind and distance D from the front (in the pass of X-rays) surface of said X-ray-to-optical converter to the plane of front (in the pass of light) end faces of the objective lenses are related by the ratio A/D=(0.50 . . . 0.95). An X-ray converter equipped with above-mentioned additional and perfected parts allows at once: first, to reduce the parasitic illumination of adjacent optoelectronic converters considerably, because lead-glass washers serving as the filter of residual X-radiation are optically insulated from one another in said partition, while the light reflected from parts of optical channels to the surface of the X-ray-to-optical converter and back mostly returns via the blinds into initial channels, and second, to enhance the operating reliability of the converter, because the X-ray load on optoelectronic converters is limited to only that insignificant part of the X-radiation, not converted into light, which can pass through washers of said filter, and the danger of a mechanical break-down of the filter is excluded practically. It is preferable to select the A/D ratio within (0.55-0.90). This warrants the overlap of fields of view of the optoelectronic converters. Further distinction consists in that said additional partition comprises of a lead plate and a supporting plate made from suitable rigid material. This warrants practically full absorption of such residual X-radiation, which does not get into said blinds, and sufficient strength and stability of the housing and fastened therein parts of optical channels. Next distinctions consist in that each objective lens is equipped with at least one diaphragm for restriction of the light flux, and preferably, with three diaphragms installed respectively ahead of the input lens, between lenses, and after the output lens. These diaphragms additionally protect optoelectronic converters from light interferences that can arise because of repeated light reflections within optical channels. And, finally, additional distinctions consist in that interior of the side housing walls, blinds on the inside, and diaphragms on both sides have black mat coatings, and surfaces of said washers of the filter of residual X-radiation and the lenses of said objective lenses have antireflecting coatings. Such coatings— serve as additional means for the suppression of random light interferences caused by light reflections within optical channels, and practically prevent decrease of the image brightness at field of view edges of each optoelectronic converters, which can occur under the diaphragms' action. The X-ray converter in the simplest embodiment (see FIG. 1) contains at least: a light-proof housing 1, one of whose end walls 2 is made from such X-ray transparent material as Getinaks or coal fiber-reinforced plastic etc., and following units fastened one after another behind said wall 2— an X-ray-to-optical converter 3 that is made from salts of rare-earth elements or cesium iodide usually and abuts upon the end wall 2 of the housing 1, blinds 4, whose number and placement correspond to the number and placement of indicated below objective lenses and optoelectronic converters; the blinds 4 are installed within the housing 1 so that “fields of view” of said optoelectronic converters partly overlap one another, an additional light-opaque and X-ray-opaque partition 5 that is rigidly fastened in housing 1 and serves as a support for said blinds 4 and other indicated below elements of optical channels; the partition 5 has through-holes closed by rigidly fastened (usually calked) washers 6 produced usually from such X-ray-opaque light-transparent material as lead glass (these washers 6 serve, in aggregate, as filter of residual X-radiation at the inputs into optical channels), objective lenses 7, whose number and placement correspond to the number and placement of indicated below optoelectronic converters; each such objective lens 7 has at least two separated by an air gap lenses 8 that are intended for the focusing of parts of the image on optoelectronic converters, and, as a rule, three (input, intermediate, and output) diaphragms 9 that are intended for limiting the light flux, optoelectronic converters 10, each of which is fastened on an own support in adjusting device 11 for installation on the optical axis of corresponding objective lens 7; these converters 10 are formed usually as commercially available TV cameras. Electrical outputs of the optoelectronic converters 10 are formed as plug-and-socket connectors 12. They are through a flexible multiple-conductor cable 13 connected: first, to an (not shown) electric power source, and second, to electronic unit 14 for correction of geometric distortions and “sewing together” of fragmentary video signals into output integral video signals for demonstration of images by a video monitor of suitable personal computer 15 and/or their recording on suitable digital image carrier. Partition 5 has, as a rule, two (not especially designated) parts, namely: an formed usually as a leaden plate absorber of such residual X-radiation that goes past the optical channels, and a supporting plate formed from such fast rigid material as duraluminum, steel, or any reinforced polymer etc. As a rule, interior of side walls of the housing 1, all blinds 4 on the inside and all diaphragms 9 on both sides have black mat coating 16; and surfaces of the all said washers 6 and lenses 8 have antireflecting coatings 17. It is clear for any person skilled in the art that blinds 4 must warrant partial overlap of fields of view of the adjacent optoelectronic converters 10 on X-ray-to-optical converter 3 (it is shown on FIG. 1 as intersection of light beams emitted from X-ray-to-optical converter 3 into objective lenses 7). Along with this condition, said blinds 4 are for: minimization of decreasing of image brightness at edges of field of view of each optoelectronic converter 10 (even when objective lenses 7 have diaphragms 9), and substantial reducing of parasitic illumination of adjacent TV cameras by light repeatedly reflected from lenses 8 to X-ray-to-optical converter 3 and back. Thereto, length A of blinds 4 is selected with account of distance D from the front (in the pass of X-rays) surface of X-ray-to-optical converter 3 to the plane of front (in the pass of light) end faces of objective lenses 7 in accordance with the ratio A/D=(0.50-0.95) and preferably (0.50-0.90). Said ratios have been determined experimentally on a prototype X-ray converter, which had: X ray-to-optical converter 3, based on gadolinium oxysulfide, a set of changeable blinds 4 of various heights A with black mat coatings 16 on their inside surfaces, light-opaque and X-ray-opaque partition 5 formed as fast joined 2.5 mm thick leaden plate and 8.0 mm thick duraluminum plate; this partition 5 had 36 through-holes 27 mm in diameter and such calked in said through-holes lead-glass washers 6 a 10.0 mm thick that are provided with antireflecting coatings 17 on both sides, objective lenses 7 each of which formed as set of glued-together lenses with antireflecting coatings 17 on their free surfaces, a photodetector formed as an lattice of 6×6=36 optoelectronic converters 10 (in particular, photodiode matrices produced by Japanese company “Sony”) served for brightness measurements during experiments, electronic unit 14 for correction of geometric distortions and “sewing together” of fragmentary video signals into integral video signals; said unit 14 was produced by “Teleoptic” company (Kiev, Ukraine) and driven by software “Alpha-Teleoptic” of the same firm, and usual PC 15 equipped with a liquid-crystal video monitor. In addition, the following devices has been used in experiments: X-ray tube (model 2.5-50BD150) produced by Research-and-Production Association “Svetlana” (Sankt-Peterburg, Russia), produced by “MosRentgen” (Moscow, Russia) pulsed power source for feeding said tube; this source had anode voltage of 40-125 kV and operating current of 40-400 ma, collimator (i.e. leaden blinds) installed at the output of said X-ray tube to provide for uniform illumination of the whole receiving surface of the X-ray-to-optical converter 3, movable screen (not shown in drawings) formed as an X-ray-opaque leaden plate whose dimensions correspond to the maximum field of view of each optoelectronic converter 10 (in particular, 44×33 mm for each said photodiode matrix). This screen was intended for blocking of X-ray inputs into individual optical channels. Dimension D was of 75 mm and remained unchanged in all experiments. 1. The measurement procedure has been carried out with account of two basic prerequisites established experimentally in the course of a long practical operation of several series of X-ray converters. 2. The first prerequisite consists in that the overlap of fields of view of adjacent optoelectronic converters 10 must be, as a rule— 3. no less than 3% in order to avoid an accidental loss of some part of diagnostic information, but 4. no more than 10% in order to avoid excessive losses of the resolution of the photodetector as a whole. 5. From the above it follows that length A of blinds 4 cannot be equal to dimension D (in order to exclude full insulation of optical channels). 6. Accordingly, the second prerequisite consists in that the blocking of X-ray input to each selected individual optical channel by said movable screen does not exclude the illumination of the photodiode matrix in such channel through adjacent optical channels. Due to this, the detection of light by the photodiode matrix under any optical channel that is screened from the X-radiation and the distribution of brightness within this matrix can serve as a criterion of efficiency of selection of A/D ratio. The procedure of determination of acceptable limits of said ratio, based on these prerequisites, included: (1) determination of the initial brightness of light in optically insulated channels at the use of a free X-ray-to-optical converter, (2) serial determination of brightness of light directly by each regularly scheduled photodiode matrix and its distribution with respect to the such matrix central zone (using software “Alpha-Teleoptic”) in each optical channel, the X-ray input to which was temporarily closed by the movable leaden screen; this determination was executed: (2.1.) first, at absence of the blinds 4, and, (2.2) further, using the blinds 4 of various length (and, accordingly, with various A/D ratios) down to complete overlap of the gap between X-ray-to-optical converter 3 and partition 5 and full insulation of optical channels. Results of measurements are presented in the table below. DEPENDENCY OF ILLUMINATION OF OPTICAL CHANNELS,CLOSED WITH RE MOVABLE LEADEN SCREEN, THROUGHADJACENT OPTICAL CHANNELS ACCORDING TO A/D RATIOBrightness, % ofinitial valueat left-at right-handhandatbound-bound-nosA/DcenteraryaryRemarks106.48.810.0Blinds absent20.224.05.66.2Blinds not effective30.422.03.03.240.501.62.22.5Blinds reduce parasitic illu-mination to acceptable level50.551.21.82.0Blinds effectively reduce para-40.620.81.61.8sitic illumination of adjacent60.750.40.81.0optical channels and flatten70.830.30.60.7brightness on working surfaceof optoelectronic converters80.900.20.40.5Blinds slightly restrict fieldof view of photodiode matrices90.950.10.20.3Sewing of fragments togetherinto integral image is feasible101.0000Blinds insulate optical channelsand divide image into separatefragments As is shown in the table, appreciable decrease of the parasitic illumination of adjacent optical channels and flattening of the brightness on the working surface of optoelectronic converters take place at the ratio A/D=0.50 and reach a practically possible maximum at A/D=0.95, when the overlap of fields of view of adjacent optoelectronic converters 10 approaches 2%. Already in this range, A/D=(0.50-0.95), the software for identification and elimination of such random optical interferences which can affect the quality of the sewing together fragmentary video signals into integral video signals (and images of objects being diagnosed or checked, corresponding to them) becomes needless. In practice, however, it is preferable to set the A/D ratio at between 0.55 and 0.90 when random optical interferences are negligible and cannot affect the quality of the medical diagnosis and all the more of the quality of the X-ray flaw detection or of the border and customs inspection of the luggage of passengers and cargoes. The above-described X-ray converter operates as follows: At the assembling or before the start of operation, optoelectronic converters 10 are with the aid of adjusting devices 11 (see FIG. 1) installed in output planes of objective lenses 7 in such a manner that centers of light-sensitive surfaces of converters 10 correspond to foci of objective lenses 7, each of which is placed opposite to certain part of the surface of X-ray-to-optical converter 3 (see FIG. 2). To facilitate the adjustment, known calibrating test objects (spatial phantoms) can be used, as indicated, e.g., in WO 98/11722. The adjusted converter is installed into the device for the X-ray diagnostics (or flaw detection, or inspection) so that the object of investigation can be in the gap between the output of the X-ray tube and the X-ray-transparent wall 2 of lightproof housing 1. Then, at each tube activation the X-ray flux will act on X-ray-to-optical converter 3, which serves as a Lambert's light source and generates a light flux differentiated in the brightness because of interaction with the object of diagnostics (or flaw detection, or inspection). Blinds 4 divide this light flux into separate beams, which through washers 8 made of lead glass that filters off the residual X-radiation and objective lenses 7 get onto light-sensitive surfaces of optoelectronic converters 10. They generate analog electric signals which correspond to partly overlapping fragments of the image formed on X-ray-to-optical converter 3. Said signals, via plug-and-socket connectors 12 and flexible multiple-conductor cable 13, arrive to electronic unit 14, which converts them into a digital form, corrects geometric distortions, and “sews together” fragmentary digital video signals into integral digital video signals for a subsequent demonstration of images on the video monitor of PC 15 and/or recording on suitable digital storage devices. Specific features of operation of the described X-ray converter are as follows. Light- and X-ray-opaque partition 5 practically fully absorbs that part of the residual X-radiation, which does not get onto lead-glass washers 6 and fully excludes leakages of light between said washers 6. Blinds 4 drastically reduce the parasitic illumination of adjacent optical channels with light reflected from objective lenses 7 and/or optoelectronic converters 10 to X-ray-to-optical converter 3 and back. Diaphragms 9 additionally suppress random optical interferences (particularly in the form of light reflected from surfaces of optoelectronic converters 10). Black mat coatings 16 of side walls of housing 1, of blinds 4 on the inside, and of diaphragms 9 on both sides serve for the same purpose (but for any light interferences). And, finally, anti-reflection coatings 17 reduce the reflectivity of surfaces of washers 6 and lenses 8 practically by an order of magnitude. The industrial applicability of the X-ray converter is due to: first, possibility of its production with the use of modern components in various configurations, and second, possibility of its use for the synthesis of integral (with no visible joints) images of objects being diagnosed with a high resolution.
052710521	abstract	A nuclear reactor plant is provided in which the reactor coolant system contains a dissolved solution of enriched boric acid. The boron-10 to boron-11 atomic isotope ratio of the enriched boric acid solution is greater than 30:70 at the start of the reactor core cycle. The nuclear reactor plant design provides for minimal mixing between the reactor coolant solution containing the enriched boric acid solution and the natural boric acid solution used during refueling operations.
060524359	summary	BACKGROUND OF THE INVENTION The present invention relates to a radiation emitting device, and more particularly, to a system and method for efficiently delivering radiation treatment. DESCRIPTION OF THE RELATED ART Radiation emitting devices are generally known and used, for instance, as radiation therapy devices for the treatment of patients. A radiation therapy device generally includes a gantry which can be swiveled around a horizontal axis of rotation in the course of a therapeutic treatment. A linear accelerator is located in the gantry for generating a high energy radiation beam for therapy. This high energy radiation beam can be an electron beam or photon (X-ray) beam. During treatment, this radiation beam is trained on one zone of a patient lying in the isocenter of the gantry rotation. In the case of an electron beam, for example, the electron accelerator typically includes an electron gun, accelerating cavities, an exit window, and a radio frequency input. A trigger system generates modulator and injector signals and supplies them to an injector and a high voltage modulator. The modulator generates the radio frequency pulses and the injector generates the injector pulses. The injector pulses control the quantity of the electrons that will be emitted by the electron gun. The radio frequency creates an electromagnetic field in the accelerator which accelerates the electron beam toward the exit window. The injector and the radio frequency pulses must be synchronized; otherwise, beam acceleration will not occur. To control the radiation emitted toward an object, a beam shielding device, such as a plate arrangement or a collimator, is typically provided in the trajectory of the radiation beam between the radiation source and the object. An example of a plate arrangement is a set of four plates that can be used to define an opening for the radiation beam. A collimator is a beam shielding device which could include multiple leaves, for example, a plurality of relatively thin plates or rods, typically arranged as opposing leaf pairs. The plates themselves are formed of a relatively dense and radiation impervious material and are generally independently positionable to delimit the radiation beam. The beam shielding device defines a field on the object to which a prescribed amount of radiation is to be delivered. The usual treatment field shape results in a three-dimensional treatment volume which includes segments of normal tissue, thereby limiting the dose that can be given to the tumor. The dose delivered to the tumor can be increased if the amount of normal tissue being irradiated is decreased and the dose delivered to the normal tissue is decreased. Avoidance of delivery of radiation to the organs surrounding and overlying the tumor determines the dosage that can be delivered to the tumor. The delivery of radiation by a radiation therapy device is prescribed and approved by an oncologist. The prescription is a definition of, for example, a particular volume and the level of radiation permitted to be delivered to that volume. Actual operation of the radiation equipment, however, is normally done by a therapist. When the therapist administers the actual delivery of the radiation treatment as prescribed by the oncologist, the radiation-emitting device is programmed to deliver that specific treatment. When programming the treatment, the therapist has to take into account the actual radiation output and has to adjust the dose delivery based on the plate arrangement opening to achieve the prescribed radiation treatment at the desired depth in the target. The oncologist's challenge is to determine the best number of fields and delivered intensity levels to optimize the dose volume histograms, which define a cumulative level of radiation which is to be delivered to a specified volume. To optimize dose volume histograms to the prescriptions, the three-dimensional volume is broken into cells, each cell defining a particular level of radiation to be administered. The outputs of the optimization engines are intensity maps, which are determined by varying the intensity at each "cell" in the map. The intensity maps specify a number of fields defining desired (optimized) intensity levels at each cell. The fields may be statically or dynamically modulated, such that a different accumulated dosage is received at different points in the field. Once radiation has been delivered according to the intensity map, the accumulated dosage at each cell, or dose volume histogram, should correspond to the prescription as closely as possible. One technique used in conjunction with intensity modulation is auto-sequencing. In an auto-sequencing technique, the segments are delivered via a verify and record system in a rapid and fully automated manner. An important component of auto-sequencing is the ability to cycle the radiation beam on and off quickly during an intensity modulation radiation treatment. As it is known in the art, the radio-frequency (RF) system must be stabilized prior to activating the radiation beam. An unstable RF system can cause undesirable injector pulses and hence, dosimetry errors. Several methods are available for controlling the beam on a pulse-by-pulse basis. For example, the RF trigger may be disabled, thus de-enabling RF power to the injector. Alternatively, the injector trigger itself may be disabled so as to eliminate injector pulses resulting from unstable RF inputs. Finally, the accelerator electron gun's grid may be biased negatively enough to eliminate stray injector pulses. However, each of these techniques introduces treatment delays and dosimetry errors generated by RF or injection instabilities thereby rendering them unsuitable for use with intensity modulation radiation treatments. Accordingly, there is a need for an improved method for stabilizing the RF system in a radiation treatment device. In particular, there is a need for a method for precise and rapid disabling and enabling of the treatment beam between intensity modulation radiation treatment fields. SUMMARY OF THE INVENTION These problems in the prior art are overcome in large part by a system and method for control of radiation therapy delivery according to the present invention. In particular, prior to the delivery of the actual treatment, a run up is executed in order to stabilize the RF system. The run up is accomplished by initiating the triggers with the injector and RF pulses out of phase so that the electrons, for example, in the accelerating waveguide do not get accelerated even though the RF system is being pulsed. The RF warm up period during which the injector and RF pulses are out of phase, ends at RAD ON (Radiation On) with the injector pulse being phase-shifted to coincide in time with the RF pulse thereby resulting in the production of electron beam pulses. Following the application of the run up period, precise and rapid disabling and enabling of the treatment beam between IMRT fields can be accomplished. The electron injection is phase-shifted in and out without affecting either the injector or the RF pulse amplitudes, thereby allowing transitions between a stable RAD ON beam and no beam between one pulse and the next.
053923243	abstract	The nuclear reactor includes a fuel core (5) inside a vessel (2) and a system (1) for cooling the core (5), in which a liquid metal circulates and on which is placed at least one steam generator (15). The steam generator includes a casing (15a) in which the liquid metal circulates, water-feed means (16) and means for heat exchange between the liquid metal and the feed water. The liquid metal is caused to circulate in the cooling system (1), the steam generator (15) not being fed with water and the liquid metal circulating in the steam generator (15) is cooled by the flow of a gas in contact with the casing (15a) of the steam generator (15). The cooling device includes a tubular element (25) placed around the casing (15a) of the steam generator and defining an annular space for a cooling gas to flow around the casing (15a).
	summary
055330754	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to spent fuel shipping containers for nuclear fuel removed from a reactor and, more particularly, to device and method loading such containers with spent fuel. 2. The Prior Art A spent fuel shipping container is a large steel cylinder or drum, typically 8 ft. in diameter and 15 ft. in height, and weighing 300,000 lbs. The container is used for the shipment of multiple pieces of spent nuclear fuel. Referring to FIG. 1, a representative container, which is generally denoted 10, includes a top or lid 12 that can be rotated on a bearing (not shown) such that an access opening 14 in the top of the container, i.e., in the cover 12, can be rotated to a position wherein the opening 14 is positioned precisely over the center of one of a plurality of fuel pockets 16 provided within container 10. Thus, spent fuel is inserted through access opening 14 into container 10 and thence into the selected fuel pocket 16. An index ring (not shown in FIG. 1), graduated in degrees, is affixed to the top 12 of the container 10 so that the correct indexed location of the access opening 14 over each of the respective pockets 16 can be identified for recording. Prior to placing fuel inside the container 10, the precise index location of each pocket 16 is determined by the use of a mechanical alignment device (not shown). Typically, this alignment device is shaped like a cylindrical "plug" with a rod extending vertically upwardly through the top of the plug. The plug is inserted through the access opening 14 of the cover 12 into the corresponding container pocket 16. The diameter of the plug is such that the plug forms what is effectively a piston--cylinder fit with the pocket 16. Once the plug is installed, the rod associated with the plug, which extends upwardly above the top of container 10, is used, along with suitable mechanical adapters, to establish that the center of the access opening 14 is precisely aligned with the center of the corresponding fuel pocket 16. The reading of the index ring (in degrees of rotation) is then recorded and this reading is used subsequently to align the opening 14 in the cover 12 in the appropriate position above each of the other fuel pockets 16 as fuel is put into the container. It will be appreciated that the mechanical alignment device described above suffers a number of disadvantages and limitations. Some disadvantages of the prior art mechanical device and the method of using the same include those resulting from the fact that the mechanical device must be installed into, and in contact with, the "internals" of the spent fuel container which are highly radioactively contaminated. Thus, during the alignment operation, the radioactive contamination is transferred to the alignment device itself. After alignment of each fuel pocket, the alignment device is removed and must be partially decontaminated prior to the installation thereof into the next pocket. After the completion of all alignments, the device is completely decontaminated for subsequent packaging and storage until the next container is prepared for use. It will be appreciated that this radioactive decontamination presents a risk to operators due to the high levels of contamination normally encountered. Considering other limitations and disadvantages thereof, the mechanical alignment device must be installed into and subsequently removed from, each pocket being aligned. Further, the device requires the repeated use of containments in order to be able to operate the device in a radioactive environment, i.e., so as to separate the operator from the contamination within in the container. Moreover, the required decontamination of the mechanical device subjects operating personnel to radiation exposure. Historically, the time required to accomplish the alignment of each fuel pocket using the prior art mechanical device ranges from two to eight hours. Moreover, significant amount of time and resources are devoted to preparation of the mechanical device for use, including the performance of load testing and non-destructive testing of lifting attachments. Further, the mechanical device requires the use of an auxiliary crane for installation and removal and the device itself is inherently large and awkward to handle. SUMMARY OF THE INVENTION In accordance with the invention, an alignment device for a spent fuel container is provided which significantly reduces the effect of or totally eliminates, each of the disadvantages of the prior art mechanical device discussed above. The alignment device of the invention includes a laser device which is affixed to a lightweight support plate that is installed over the access opening of the cover or lid of the spent fuel container. A pre-established mark on the periphery of, or otherwise associated with, each pocket acts as a laser target. When the device is installed, the container cover is rotated over each pocket and when aligned with the laser target, the rotational position of the cover, and hence of the access opening therein, is observed and recorded. Briefly considering some of the important advantages of the invention, the laser device of the invention is not installed into or in contact with the internals of the spent fuel container. As a consequence, there is little chance that the high levels of contamination contained within the container will be transferred to the device. Therefore, the risks associated with such transferred contamination are essentially eliminated. Further, the laser device is not installed into each pocket. As will be described, the device is installed once, on top of the container, and remains there until all pockets have been aligned. In addition, the laser device does not require the repeated use of containments, because the device itself acts as a contaminant barrier. The radiation exposure encountered during decontamination of the prior art mechanical device is virtually eliminated. Other advantages include a substantial reduction in the alignment time required. It is estimated that the two to eight hour alignment time referred to above which is required in using the prior art mechanical device will be reduced to about 10 minutes with the laser device of the invention, thereby resulting in substantial cost savings. Further, no load testing or non-destructive testing of the laser device is required, no crane is necessary and the laser device can be installed manually. The laser device is significantly less expensive than its prior art mechanical counterpart, considering manufacturing and operating costs. Moreover, the laser device provides more accurate alignment, is less likely to develop time-consuming repair problems, and is self-contained. In accordance with a preferred embodiment of a first aspect of the invention, an alignment device is provided for use with a spent fuel shipping container including a plurality of fuel pockets for spent fuel arranged in an annular array and having a rotatable cover including an access opening therein, the alignment device comprising: a plate for installation over the access opening in the container and including a laser admittance window therein; a laser device mounted on the plate for directing a laser beam through the laser admittance window into the container; and indexing means on the container for providing an indication of the angular position of the rotatable cover when the laser beam produced by the laser is brought into alignment with a fuel pocket in the container. In one embodiment, the plate further comprises a viewing window therein for enabling viewing of the laser beam within the container. In another embodiment, the laser admittance window is sized so as to permit viewing of the laser beam within the container. Preferably the device further comprises fixing means for fixing the orientation of the plate, and the laser mounted thereon, on the cover of the container. In one embodiment, the fixing means comprises a pair of pin members on the plate and a corresponding pair of pin openings formed in the cover. In another embodiment, the fixing means comprises a pair of pin members on the cover and a corresponding pair of pin openings formed in the plate. The plate further advantageously comprises at least one handle for facilitating installation and removal of the plate. Preferably, the device further comprises sealing means for providing a seal between the plate and the cover of the container. Advantageously, the plate is circular in shape and the sealing means comprises a sealing O-ring disposed around the periphery of the plate. The laser device preferably comprises a low power laser and a laser mount comprising a cage in which the laser is supported and a bracket securing the cage to the plate. In accordance with a preferred embodiment of the invention, a method is provided for determining the alignment position of an access opening of a cover for a spent fuel container with respect to each of a plurality of annularly arranged fuel pockets within the spent fuel container so that spent fuel can be placed into each of said fuel pockets through the access opening, the method comprising: pre-establishing an alignment target for each of the fuel pockets; mounting a support plate including a laser admittance window therein over the access opening of the cover of the spent fuel container; affixing a laser to the support plate in alignment with said laser admittance window in an orientation wherein, when the laser is energized, laser beam is directed into the container through the window; energizing the laser and rotating the cover until the laser beam directed by the laser into said container is in alignment with the target of a first fuel pocket; using an index ring arrangement at the top of the container to determine the angular position of the cover, and hence the relative angular alignment position of the first fuel pocket, when the laser beam is in alignment with the target of the first fuel pocket; and repeating the process for each of the other fuel pockets. Preferably each of the targets is established by providing a target groove at the site of the respective fuel pocket which produces enhanced reflection of a laser beam in alignment with the groove. Advantageously, the groove is provided on a slanted shoulder at the top of the fuel pocket. The method preferably further comprises viewing the laser beam within the container so as to determine when the laser beam is in alignment with the target. Affixing of the laser to the support plate preferably comprises mounting the laser in a fixture (mount) on the plate. The support plate is preferably mounted on said cover in a predetermined orientation determined by a mounting assembly for the plate. The mounting assembly advantageously comprises a pair of pin members and a corresponding pair of openings for receiving the pin members. Other features and advantages of the invention will be set forth in, or apparent from, the following detailed description of preferred embodiments of the invention.
053012143	description	PREFERRED EMBODIMENT OF THE INVENTION A first embodiment will be explained with reference to FIGS. 1 and 2. In the following explanation, the component sections which are common to the conventional fuel assembly are given the same reference numbers, and their explanations are omitted. In the following descriptions, the direction is referenced with respect to the travel direction of the fuel rods which travel longitudinally from the right to the left of the illustration in FIG. 1. Therefore, the right side of a component or an apparatus is referred to as the entry-side and the left side thereof as the exit-side. The assembling apparatus of the first embodiment comprises, from the fuel rod entry-side of the assembling apparatus: (a) a fuel rod magazine 30, which houses a plurality of longitudinally extending parallel fuel rods 6, disposed at the entry-end of the assembling apparatus (right in FIG. 1); (b) seven grid support frames 20 (termed support frames 20) which support the grids 4 so that the grid cells 5 face in the direction of the longitudinal fuel rods 6; and (c) a plurality of pull-in rods 40, housed in a pull-in loader 50, disposed on the exit-end of the apparatus with the support frames 20 in between, for gripping the tips of the fuel rods 6 at their exit-side (left end in FIG. 1). Each of the grids 4 is divided, as shown in FIG. 5, into four square quadrants, 4a, 4b, 4c, and 4d, formed by the two orthogonal lines 1 and m which pass through the central axis O of the assembling apparatus coaxial with the central axis O of the grids 4. Four grid cells for guide pipes 5a (termed pipe-cells 5a, i.e. those grid cells 5 for inserting guide pipes 3) are distributed symmetrically in each of the quadrants in such a way that the locations of the pipe-cells 5a in one quadrant coincide exactly with all the other quadrants when any one quadrant is rotated in 90 degree steps about the central axis O. In other words, the pipe-cells 5a are disposed symmetrically about the central axis O. The pull-in rods 40 are positioned so that they correspond with the locations of the fuel rods 6 in the fuel rod magazine 30, and with the fuel-rod-cells 5b (i.e. those grid cells 5 which are assigned to hold fuel rods 6) in each of the four quadrants. In other words, the fuel rods 6 are placed in specific fuel-rod-cells 5b of the quadrant avoiding duplication with the pipe-cells 5a. The group of pull-in rods 40 disposed within one quadrant is rotatable as a unit about the central axis O by means of a rotating device disposed on the pull-in loader 50 which supports all the pull-in rods 40 as shown in FIG. 1. The length of the pull-in rods 40 is such that they can reach the fuel rods 6 housed in the fuel rod magazine 30 through the grid cells 5 by translating freely along the longitudinal direction via a longitudinal base 57. The support frames 20 are disposed at a given spacing on a rotating base 21 which extends in the fuel rod direction. The rotating base 21 can be raised, by power means, to a vertical position when the fuel rod loading operation is completed. The tips of the pull-in rods 40 (at the entry-end) are provided with a gripper 41 to grip the fuel rods 6, and are further provided with a number of holding plates 42 for maintaining the fuel rods in specific alignment. The pull-in loader 50 comprises: (a) an extended L-shaped base 51, whose cross section is shown in FIG. 2, disposed in the longitudinal direction, which support the pull-in rods 40 via support plates 42; (b) guide rails 52 disposed on both edge sections of the L-shaped extended base 51 extending in the longitudinal direction; (c) guide parts 53 which protrude from the two side surfaces of the support plates 42 facing the extended base 51, and slidingly engages with the guide rails 52; (d) a motor 55 which is disposed at the exit-end of the extended base 51 (left end in FIG. 1) for rotating the base 51 via gearing 54 about the central axis O coaxial with the central axis O of the grids 4; (e) a transfer base 56, shown in FIG. 1, which is disposed near the exit-end of the pull-in rods 40, housing a linear motor which moves the entire pull-in rods 40 toward the grids 4; (f) a longitudinal base 57 which extends on the extended base 51 longitudinally between the transfer base 56 and the extended base 51; (g) a ring-shaped rotatable rail 58 which rotates in the peripheral direction, disposed near each end of the pull-in rods 40, for guiding the rotating motions of extended base 51 and the pull-in rods 40 rotating about the central axis O by means of the motor 55 and gearing 54; (h) peripheral rotation guide (not shown), disposed between the rotatable rails 58 and both the longitudinal base 57 and the support plate 42, detachably attached to the longitudinal base 57 and the support plate 42 so as not to interfere with the movement of the pull-in rods 40 with the rotatable rails 58; and (i) rail supports 59 providing support to the rotatable rails 58. The operation of the assembling apparatus of the embodiment will be explained in the following. First, by operating the linear motor attached to the transfer base 56, the pull-in rods 40 are translated toward the grids 4 along the longitudinal base 57 (i.e. along the extended base 51), and after passing through the grid cells 5 of the grids 4 to reach the tip ends at the exit-side end of the fuel rods 6 housed in the fuel rod magazine 30. Then, the grippers 41 contact and grip the tip ends of the fuel rods 6. The pull-in rods 40 are able to pass through the grid cells 5 of the grids 4 without any interference from any of the guide pipes 3, because all the pull-in rods 40 in a particular quadrant correspond with the assigned fuel-rod-cells 5b for the fuel rods 6 disposed within the particular quadrant of the grids 4. Next, the linear motor is again operated to retract the pull-in rods 40 so as to pull the fuel rods 6 gripped by the pull-in rods 40 into the fuel-rod cells 5b of the grids 4. Thus, it is possible to load a quarter of all the fuel rods 6 in one operation simply by retracting the pull-in rods 40. After the fuel rods 6 are positioned properly in the fuel-rod cells 5b of the grids 4, the grippers 41 release the fuel rods 6, and the pull-in rods 40 are retracted slightly toward the exit-side to return them to their original position. Then, by means of the motor 55 of the pull-in loader 50 (via the gear 54, the extended base 51 and the support plate 42), the pull-in rods 40 are rotated about the central axis O (refer to FIG. 1) through 90 degrees. By this procedure, the pull-in rods 40 in the nearest neighbor quadrant are made to move to the loading locations (refer to FIG. 5) so as to enable loading of the fuel rods 6 disposed in the quadrant of the fuel rod magazine 30 into the corresponding quadrant of the grids 4 of the fuel assembly. In the present embodiment, the grid cells 5 of the grids 4 are divided into four quadrants, 4a, 4b, 4c and 4d, and the grid cells 5 in each quadrant are assigned in such a way that, when the pull-in rods 40 are rotated through a 90 degree angle, the locations of the pipe-cells 5a in one quadrant always correspond with the pipe cell 5a in the next quadrant. Because of this arrangement, when the pull-in rods 40 in a quadrant are rotated through 90 degrees for loading, the locations of the pull-in rods 40 always correspond with the fuel-rod-cells 5b, thus enabling the pull-in rods 40 to avoid aligning with the pipe-cells 5a. The pull-in rods 40 can then be operated to load the fuel rods 6 in the next quadrant into the fuel-rod-cells 5b of the grids 4. By repeating the above process steps for other quadrants, all the fuel rods 6 in the fuel rod magazine 30 can be loaded into the grids 4 of a fuel assembly. According to the present embodiment, only two main operational steps, pulling-in of the fuel rods 6 by the pull-in rods 40 and rotating of the pull-in rods 40, are required to load all the fuel rods 6 into the fuel assembly. The assembling apparatus is simplified because the loading apparatus does not depend on such complex device as a pull-in rod selector. The assembling operation is carried out quickly and efficiently because all the fuel rods 6 are loaded into the fuel assembly in four rotation steps, enabling to shorten the assembling time. It should be noted that the present invention is not limited by the particular embodiment presented, and other variations of the invention are possible within the limitations disclosed in the following claims.
053612833	abstract	An integral, reusable locking arrangement between the guide tube assembly and upper end fitting of a reconstitutable fuel assembly that eliminates all loose fastener components at the reactor site. A retainer sleeve is fabricated to cooperate with the upper end sleeve of the guide tube assembly. Slots adjacent to the upper end of the sleeve receive rigid tabs on the upper end sleeve to hold the retainer sleeve and upper end sleeve together. The retainer sleeve is formed from a cylindrical tube that has a plurality of flexible curved tabs spaced around the circumference of the tube substantially at the mid section of the tube. Optional lower tabs serve to center the guide tube assembly in the upper end fitting and provide a more rigid connection. The mid section tabs are received against the shoulders of slots provided along the walls of the hole in the upper end fitting and serve to retain the guide tube assembly and upper end fitting in the installed position. Removal of the upper end fitting is accomplished by rotation of the retainer sleeve to force the tabs inboard and then sliding the upper end fitting upward.
	description	This application is related to U.S. patent application Ser. No. 11/060,275 and filed Feb. 17, 2005, owned by a common assignee as the instant invention. This patent application claims priority to the U.S. Provisional Patent Application 60/557,892 filed on Mar. 31, 2004, which is herein incorporated by reference in its entirety. This patent application is a Continuation-in-Part of U.S. patent application Ser. No. 10/877,092, filed on Jun. 25, 2004, which is a Continuation of U.S. patent application Ser. No. 10/309,429, filed on Dec. 4, 2002, issued as U.S. 6,870,516, also incorporated by reference in its entirety, which is a Continuation-in-Part application of U.S. patent application Ser. No. 10/075,778, filed on Feb. 14, 2002, now issued as U.S. Pat. No. 6,741,221, which claimed priority to U.S. Provisional Patent Applications Ser. No. 60/317,808, filed on Sep. 7, 2001, Ser. No. 60/269,414, filed on Feb. 16, 2001, and Ser. No. 60/268,822, filed on Feb. 15, 2001. (1) Field of the Invention This invention relates to roofing materials and, more particularly, to conductive roofing materials molded of conductive loaded resin-based materials comprising micron conductive powders, micron conductive fibers, or a combination thereof, substantially homogenized within a base resin when molded. This manufacturing process yields a conductive part or material usable within the EMF or electronic spectrum(s). (2) Description of the Prior Art Buildings of any kind require a roof, or roofing system, to protect building contents from the environment. The roof, itself, requires a covering material capable of shedding water. Residential roofing systems generally include three-tab shingles as one of the primary roof protection materials and are the roofing industry's current standard. Three-tab shingles consist of two layers of asphalt around a felt or fiberglass mat core covered with ceramic mineral granules. The shingles are typically notched into three integrated pieces, or tabs. On shallow pitched, or flat, roofs an asphalted felt or a fiberglass rolled roofing is the common protection material. Alternately, a synthetic rubber or a special Polyvinyl Chloride (PVC) plastic sheet is becoming more common for the flat or shallow pitched roof. In commercial structures, in particular metal buildings, a standing seam metal roof is frequently used. A standing seam metal roof is constructed of interlocking metal panels that run vertically from the roof's ridge (the top of the roof) to the eave. The interlocking seam where two panels join together is raised above the roof's flat surface, allowing water to run off without seeping between metal panels. Other common types of roofing materials are ceramic or concrete tiles. These tiles are assembled to provide a waterproof and fireproof roof. Shedding of water, or precipitation, is not the only consideration in roofing material applications. Other considerations include dealing with lighting, electromagnetic energy, heat build-up, and corrosion. Buildings that are in locations that are subject to lighting strikes, may need to provide lighting arrestors to allow any charge accumulated during a thunderstorm to be dissipated from the vicinity of the building without damaging the building. Most roofing materials, such as prior art shingles and roofing tiles, are good insulators. Therefore, these materials do not typically provide a path for dissipation of electrical charge as it accumulates. Metal roofs are inherently conductive. However, due to the desire to prevent corrosion, most metal roofing materials are coated or painted as a rust inhibitor. These coatings are typically insulating and thus reduce the ability to dissipate electrical charge or to prevent a lightening strike. Several prior art inventions relate to roofing materials. U.S. Patent Publication U.S. 2002/0043044 A1 to Foster et al teaches a method of shingle composition that utilizes a rubber component in the range from about 5–95% by weight and a polyolefin component in the range of about 5–50% by weight. This invention teaches that the weight of this shingle to be less than 150 pounds per roofing square for ⅛ inch thickness as compared to typical asphalt shingles weighing 185 pounds per roofing square of the same thickness. U.S. Patent Publication U.S. 2002/0095901 A1 to Tremblay teaches a metal roofing shingle comprising a flat rectangular panel made of metallic sheet material. U.S. Patent Publication U.S. 2004/0241476 A1 to Friedman et al teaches a synthetic roofing shingle or tile that utilizes a core of recycled inexpensive materials with an outer skin material of greater quality and weather resistance. U.S. Patent Publication U.S. 2003/0054148 A1 to Jolitz teaches a composite roofing shingle that comprises about 35–65% polyethylene and 50–70% crushed limestone filler. U.S. Patent Publication U.S. 2002/0189188 A1 to Iole et al teaches a roofing system for buildings with synthetic resin molded components formed of entirely recyclable material. U.S. Patent Publication U.S. 2002/0152697 A1 to Hokkirigawa et al teaches a roofing tile and snow-melting, tiled roof using the same. This invention utilizes a fire resistant ceramic tile with an embedded nichrome wire for a resistive heat element. U.S. Patent Publication U.S. 2004/0074164 A1 to Behrens teaches a high frequency reducing green roofing that utilizes a layer of textile fibers, a vegetation layer, and a flat or three-dimensional structure of electrically conductive filaments. U.S. Patent Publication U.S. 2002/0180077 A1 to Glatkowski et al teaches a carbon nanotube fiber-reinforced composite structure for electromagnetic and lightning strike protection. This invention utilizes electrically conductive carbon nanotubes to act as the conductive filler. A principal object of the present invention is to provide effective conductive roofing materials. A further object of the present invention is to provide a method to form conductive roofing materials. A further object of the present invention is to provide conductive roofing materials molded of conductive loaded resin-based materials. A yet further object of the present invention is to provide methods to fabricate conductive roofing materials from a conductive loaded resin-based material incorporating various forms of the material. A yet further object of the present invention is to provide a method to fabricate conductive roofing materials from a conductive loaded resin-based material where the material is in the form of a fabric. In accordance with the objects of this invention, a conductive roofing device is achieved. The device comprises a conductive loaded, resin-based material comprising conductive materials in a base resin host. Also in accordance with the objects of this invention, a conductive roofing device is achieved. The device comprises a conductive loaded, resin-based material comprising conductive materials in a base resin host. The weight of the conductive materials is between 20% and 50% of the total weight of the conductive loaded resin-based material. Also in accordance with the objects of this invention, a conductive roofing device is achieved. The device comprises a conductive loaded, resin-based material comprising micron conductive fiber in a base resin host. The weight of the micron conductive fiber is between 20% and 50% of the total weight of the conductive loaded resin-based material. A plurality of conical surface appendages on the conductive roofing device are of the conductive loaded resin-based material. Also in accordance with the objects of this invention, a method to form a conductor roofing device is achieved. The method comprises providing a conductive loaded, resin-based material comprising conductive materials in a resin-based host. The conductive loaded, resin-based material is molded into a conductive roofing device. Also in accordance with the objects of this invention, a method to form a conductive roofing device is achieved. The method comprises providing a conductive loaded, resin-based material comprising conductive materials in a resin-based host. The percent by weight of the conductive materials is between 20% and 40% of the total weight of the conductive loaded resin-based material. The conductive loaded, resin-based material is molded into a conductive roofing device. Also in accordance with the objects of this invention, a method to form a conductive roofing device is achieved. The method comprises providing a conductive loaded, resin-based material comprising micron conductive fiber in a resin-based host. The percent by weight of the micron conductive fiber is between 25% and 35% of the total weight of the conductive loaded resin-based material. The conductive loaded, resin-based material is molded into a conductive roofing device. Conical surface appendages are formed of the conductive loaded resin-based material on the top surfaces of the conductive roofing device. This invention relates to conductive roofing materials molded of conductive loaded resin-based materials comprising micron conductive powders, micron conductive fibers, or a combination thereof, substantially homogenized within a base resin when molded. The conductive loaded resin-based materials of the invention are base resins loaded with conductive materials, which then makes any base resin a conductor rather than an insulator. The resins provide the structural integrity to the molded part. The micron conductive fibers, micron conductive powders, or a combination thereof, are substantially homogenized within the resin during the molding process, providing the electrical continuity. The conductive loaded resin-based materials can be molded, extruded or the like to provide almost any desired shape or size. The molded conductive loaded resin-based materials can also be cut, stamped, or vacuumed formed from an injection molded or extruded sheet or bar stock, over-molded, laminated, milled or the like to provide the desired shape and size. The thermal or electrical conductivity characteristics of conductive roofing materials fabricated using conductive loaded resin-based materials depend on the composition of the conductive loaded resin-based materials, of which the loading or doping parameters can be adjusted, to aid in achieving the desired structural, electrical or other physical characteristics of the material. The selected materials used to fabricate the conductive roofing materials are substantially homogenized together using molding techniques and or methods such as injection molding, over-molding, insert molding, thermo-set, protrusion, extrusion or the like. Characteristics related to 2D, 3D, 4D, and 5D designs, molding and electrical characteristics, include the physical and electrical advantages that can be achieved during the molding process of the actual parts and the polymer physics associated within the conductive networks within the molded part(s) or formed material(s). In the conductive loaded resin-based material, electrons travel from point to point when under stress, following the path of least resistance. Most resin-based materials are insulators and represent a high resistance to electron passage. The doping of the conductive loading into the resin-based material alters the inherent resistance of the polymers. At a threshold concentration of conductive loading, the resistance through the combined mass is lowered enough to allow electron movement. Speed of electron movement depends on conductive loading concentration, that is, the separation between the conductive loading particles. Increasing conductive loading content reduces interparticle separation distance, and, at a critical distance known as the percolation point, resistance decreases dramatically and electrons move rapidly. The use of conductive loaded resin-based materials in the fabrication of conductive roofing materials significantly lowers the cost of materials and the design and manufacturing processes used to hold ease of close tolerances, by forming these materials into desired shapes and sizes. The conductive roofing materials can be manufactured into infinite shapes and sizes using conventional forming methods such as injection molding, over-molding, or extrusion or the like. The conductive loaded resin-based materials, when molded, typically but not exclusively produce a desirable usable range of resistivity from between about 5 and 25 ohms per square, but other resistivities can be achieved by varying the doping parameters and/or resin selection(s). The conductive loaded resin-based materials comprise micron conductive powders, micron conductive fibers, or any combination thereof, which are substantially homogenized together within the base resin, during the molding process, yielding an easy to produce low cost, electrically conductive, close tolerance manufactured part or circuit. The resulting molded article comprises a three dimensional, continuous network of conductive loading and polymer matrix. The micron conductive powders can be of carbons, graphites, amines or the like, and/or of metal powders such as nickel, copper, silver, aluminum, or plated or the like. The use of carbons or other forms of powders such as graphite(s) etc. can create additional low level electron exchange and, when used in combination with micron conductive fibers, creates a micron filler element within the micron conductive network of fiber(s) producing further electrical conductivity as well as acting as a lubricant for the molding equipment. The micron conductive fibers can be nickel plated carbon fiber, stainless steel fiber, copper fiber, silver fiber, aluminum fiber, or the like, or combinations thereof. The structural material is a material such as any polymer resin. Structural material can be, here given as examples and not as an exhaustive list, polymer resins produced by GE PLASTICS, Pittsfield, Mass., a range of other plastics produced by GE PLASTICS, Pittsfield, Mass., a range of other plastics produced by other manufacturers, silicones produced by GE SILICONES, Waterford, N.Y., or other flexible resin-based rubber compounds produced by other manufacturers. The resin-based structural material loaded with micron conductive powders, micron conductive fibers, or in combination thereof can be molded, using conventional molding methods such as injection molding or over-molding, or extrusion to create desired shapes and sizes. The molded conductive loaded resin-based materials can also be stamped, cut or milled as desired to form create the desired shape form factor(s) of the conductive roofing materials. The doping composition and directionality associated with the micron conductors within the loaded base resins can affect the electrical and structural characteristics of the conductive roofing materials and can be precisely controlled by mold designs, gating and or protrusion design(s) and or during the molding process itself. In addition, the resin base can be selected to obtain the desired thermal characteristics such as very high melting point or specific thermal conductivity. A resin-based sandwich laminate could also be fabricated with random or continuous webbed micron stainless steel fibers or other conductive fibers, forming a cloth like material. The webbed conductive fiber can be laminated or the like to materials such as Teflon, Polyesters, or any resin-based flexible or solid material(s), which when discretely designed in fiber content(s), orientation(s) and shape(s), will produce a very highly conductive flexible cloth-like material. Such a cloth-like material could also be used in forming conductive roofing materials that could be embedded in a person's clothing as well as other resin materials such as rubber(s) or plastic(s). When using conductive fibers as a webbed conductor as part of a laminate or cloth-like material, the fibers may have diameters of between about 3 and 12 microns, typically between about 8 and 12 microns or in the range of about 10 microns, with length(s) that can be seamless or overlapping. The conductive loaded resin-based material of the present invention can be made resistant to corrosion and/or metal electrolysis by selecting micron conductive fiber and/or micron conductive powder and base resin that are resistant to corrosion and/or metal electrolysis. For example, if a corrosion/electrolysis resistant base resin is combined with stainless steel fiber and carbon fiber/powder, then a corrosion and/or metal electrolysis resistant conductive loaded resin-based material is achieved. Another additional and important feature of the present invention is that the conductive loaded resin-based material of the present invention may be made flame retardant. Selection of a flame-retardant (FR) base resin material allows the resulting product to exhibit flame retardant capability. This is especially important in conductive roofing material applications as described herein. The substantially homogeneous mixing of micron conductive fiber and/or micron conductive powder and base resin described in the present invention may also be described as doping. That is, the substantially homogeneous mixing converts the typically non-conductive base resin material into a conductive material. This process is analogous to the doping process whereby a semiconductor material, such as silicon, can be converted into a conductive material through the introduction of donor/acceptor ions as is well known in the art of semiconductor devices. Therefore, the present invention uses the term doping to mean converting a typically non-conductive base resin material into a conductive material through the substantially homogeneous mixing of micron conductive fiber and/or micron conductive powder into a base resin. As an additional and important feature of the present invention, the molded conductor loaded resin-based material exhibits excellent thermal dissipation characteristics. Therefore, conductive roofing materials manufactured from the molded conductor loaded resin-based material can provide added thermal dissipation capabilities to the application. For example, heat can be dissipated from electrical devices physically and/or electrically connected to conductive roofing materials of the present invention. As a significant advantage of the present invention, conductive roofing materials constructed of the conductive loaded resin-based material can be easily interfaced to an electrical circuit or grounded. In one embodiment, a wire can be attached to a conductive loaded resin-based conductive roofing material via a screw that is fastened to the material. For example, a simple sheet-metal type, self-tapping screw, when fastened to the material, can achieve excellent electrical connectivity via the conductive matrix of the conductive loaded resin-based material. To facilitate this approach a boss may be molded into the conductive loaded resin-based material to accommodate such a screw. Alternatively, if a solderable screw material, such as copper, is used, then a wire can be soldered to the screw that is embedded into the conductive loaded resin-based material. In another embodiment, the conductive loaded resin-based material is partly or completely plated with a metal layer. The metal layer forms excellent electrical conductivity with the conductive matrix. A connection of this metal layer to another circuit or to ground is then made. For example, if the metal layer is solderable, then a soldered connection may be made between the conductive roofing material and a grounding wire. A typical metal deposition process for forming a metal layer onto the conductive loaded resin-based material is vacuum metallization. Vacuum metallization is the process where a metal layer, such as aluminum, is deposited on the conductive loaded resin-based material inside a vacuum chamber. In a metallic painting process, metal particles, such as silver, copper, or nickel, or the like, are dispersed in an acrylic, vinyl, epoxy, or urethane binder. Most resin-based materials accept and hold paint well, and automatic spraying systems apply coating with consistency. In addition, the excellent conductivity of the conductive loaded resin-based material of the present invention facilitates the use of extremely efficient, electrostatic painting techniques. The conductive loaded resin-based material can be contacted in any of several ways. In one embodiment, a pin is embedded into the conductive loaded resin-based material by insert molding, ultrasonic welding, pressing, or other means. A connection with a metal wire can easily be made to this pin and results in excellent contact to the conductive loaded resin-based material. In another embodiment, a hole is formed in to the conductive loaded resin-based material either during the molding process or by a subsequent process step such as drilling, punching, or the like. A pin is then placed into the hole and is then ultrasonically welded to form a permanent mechanical and electrical contact. In yet another embodiment, a pin or a wire is soldered to the conductive loaded resin-based material. In this case, a hole is formed in the conductive loaded resin-based material either during the molding operation or by drilling, stamping, punching, or the like. A solderable layer is then formed in the hole. The solderable layer is preferably formed by metal plating. A conductor is placed into the hole and then mechanically and electrically bonded by point, wave, or reflow soldering. Another method to provide connectivity to the conductive loaded resin-based material is through the application of a solderable ink film to the surface. One exemplary solderable ink is a combination of copper and solder particles in an epoxy resin binder. The resulting mixture is an active, screen-printable and dispensable material. During curing, the solder reflows to coat and to connect the copper particles and to thereby form a cured surface that is directly solderable without the need for additional plating or other processing steps. Any solderable material may then be mechanically and/or electrically attached, via soldering, to the conductive loaded resin-based material at the location of the applied solderable ink. Many other types of solderable inks can be used to provide this solderable surface onto the conductive loaded resin-based material of the present invention. Another exemplary embodiment of a solderable ink is a mixture of one or more metal powder systems with a reactive organic medium. This type of ink material is converted to solderable pure metal during a low temperature cure without any organic binders or alloying elements. Referring now to FIGS. 1a and 1b, a first preferred embodiment of the present invention is illustrated. A conductive roofing shingle 5 and a protective roofing system 15 are shown. The conductive roofing shingle 5 and protective roofing system 15 are formed of conductive loaded resin-based materials. The conductive roofing shingle 5 and protective roofing system 15 are structured to provide both environmental protection for a roof a path for dissipating electrical charge generated in an electrical storm. A very low cost, flexible, roofing shingle 5 is formed from conductive loaded resin-based materials. Several important features of the present invention are shown and discussed below. Referring particularly to FIG. 1a, a very low cost roofing shingle is shown comprising conductive loaded resin-based materials. A conductive three-tab shingle 5, as is commonly used in the art of residential construction, is shown. Referring particularly to FIG. 1b, a plurality of the conductive roofing shingles 5 is placed at the upper area of a building to form a protective roofing system 15. The roofing shingles 5 provide for dissipation of electrical charge to lessen the probability of a lightening strike. The conductive loaded resin-based materials 10 of the roofing shingles 5 are connected together directly with appropriate conductors or indirectly with the fasteners that attach the shingles 5 to the roof of the building. The shingles are then connected with an appropriate conductor to provide a conductive path 12 to the electrical earth ground. The roofing shingle 5 as described is manufactured of conductive loaded resin-based materials 10 comprising micron conductive powders, micron conductive fibers, or a combination thereof, substantially homogenized within a base resin. In one preferred embodiment, the conductive shingles 5 are formed by calendaring the conductive loaded resin-based material into a thin sheet. The sheet of conductive loaded resin-based material is then cut or stamped into the desired shape. In another preferred embodiment, the conductive loaded resin-based material is extruded into a thin sheet and then cut or stamped into the desired shape. In another embodiment, the conductive loaded resin-based material is vacuumed formed to the desired conductive shingle shape. In another embodiment, the conductive loaded resin-based material is injection molded to form the conductive shingle 5. In another embodiment, the conductive loaded resin-based material is calendered or is extruded and then stacked into a laminate prior to cutting or stamping into the desired shape. The roofing shingle 5 of FIGS. 1a and 1b are exemplary. The roofing shingle 5 may be shaped into any form necessary for an application. In another embodiment, the conductive loaded resin-based material is over-molded onto an inner layer, such as asphalted felt, fiberglass, or another structural material. Referring now to FIG. 11, a cross section of a roofing device 200 comprising the conductive loaded resin-based material 204 and an inner structural layer 208 is shown. The conductive roofing devices of the present invention provide a conductive path to discharge electrical energy. The conductivity of the conductive loaded resin-based material can be optimized to achieve the needed conductive/resistive characteristics for a given application. The doping level of the conductive loading is controlled by the percent, by weight, of the conductive loading and is controlled by the type of loading that is selected. Further, the conductive roofing devices can be made non-corrosive by selecting a non-corrosive conductive loading material, such as stainless steal, and combining this with a non-corrosive resin-based material. Referring now to FIG. 7, a second preferred embodiment of the present invention is illustrated. A conductive standing seam roofing panel 105 comprising the conductive loaded resin-based material of the present invention is shown. In one preferred embodiment, the conductive standing seam roofing panel 105 is formed by calendaring the conductive loaded resin-based material into a thin sheet. The sheet of conductive loaded resin-based material is then cut or stamped into the desired shape. In another preferred embodiment, the conductive loaded resin-based material is extruded into the desired shape. In another embodiment, the conductive loaded resin-based material is vacuumed formed to the desired conductive standing seam roofing panel 105 shape. In another embodiment, the conductive loaded resin-based material is injection molded to form the conductive standing seam roofing panel 105. In another embodiment, the conductive loaded resin-based material is over-molded onto an inner layer, such as asphalted felt, fiberglass, or another structural material. In another embodiment, the conductive loaded resin-based material is calendered or is extruded into thin sheets which are then stacked into a laminate prior to cutting or stamping into the desired shape. A metal roofing panel of the prior art is subject to oxidation and corrosion. This is a serious concern that reduces the lifetime, the electrical contact and the performance of prior art roofing panel. The conductive loaded resin-based material is easily formulated to prevent oxidation and corrosion and to provide the electrical conductivity of the roofing panel 20. Referring now to FIG. 8, a third preferred embodiment of the present invention is illustrated. A conductive roofing tile 125 formed of the conductive loaded resin-based materials of the present invention is shown. In one preferred embodiment, the conductive roofing tile 125 is formed by calendaring the conductive loaded resin-based material into a thin sheet. The sheet of conductive loaded resin-based material is then stamped and/or cut into the desired shape. In another preferred embodiment, the conductive loaded resin-based material is extruded into the desired shape. In another embodiment, the conductive loaded resin-based material is vacuumed formed to the desired conductive roofing tile 125 shape. In another embodiment, the conductive loaded resin-based material is injection molded to form the conductive roofing tile 125. In another embodiment, the conductive loaded resin-based material is over-molded onto an inner layer, such as asphalted felt, fiberglass, or another structural material. In another embodiment, the conductive loaded resin-based material is calendered or is extruded into thin sheets which are then stacked into a laminate prior to cutting or stamping into the desired shape. Referring now to FIG. 9, a fourth preferred embodiment of the present invention is illustrated. A conductive roll roofing material 145 formed of the conductive loaded resin-based materials of the present invention is shown. Roll roofing is particularly useful for covering flat roofs and is frequently used in commercial buildings. In one preferred embodiment, the conductive roll roofing material 145 is formed by calendaring the conductive loaded resin-based material into a thin sheet. The sheet of conductive loaded resin-based material is then cut to the desired length. In another preferred embodiment, the conductive loaded resin-based material is extruded into a thin sheet and then cut to the desired length. In another embodiment, the conductive loaded resin-based material is co-extruded onto an inner layer, such as asphalted felt, fiberglass, or another structural material. In another embodiment, the conductive loaded resin-based material is calendered or is extruded into thin sheets which are then stacked into a laminate prior to cutting to the desired length. The roofing materials of the preferred embodiments, including the conductive roofing shingle 5 of FIGS. 1a and 1b, the conductive standing seam roof panel 105, of FIG. 7, the conductive roofing tile 125 of FIG. 8, and the conductive roll roofing material 145 of FIG. 9, may be provided with appendages for the dissipation of the electrical charge build up during an electrical storm that can lead to a lightening strike. Referring now to FIG. 10, fifth preferred embodiment 170 of the present invention is illustrated. In this embodiment 170, appendages 180 are molded into the surface of the conductive loaded resin-based roofing material 175. The appendages 180 are useful in any of the above-described roofing materials and/or systems. In the preferred embodiment, these appendages 180 are conical shapes. The conical shapes 180 are sized to allow for electrical charge to dissipate from the roofing system to thereby protect the building structure from a lighting strike. The conductive loaded resin-based materials employed in the roofing shingles, roofing panels, roofing tiles, or roll roofing material described above are also thermally conductive. Thus these roofing materials may be used to transmit heat energy that is generated by sunlight falling on the roofing system of the building. In one preferred embodiment, roofing materials and systems comprising the conductive loaded resin-based material of the present invention are used as radiators for cooling the building structure. In another embodiment, the roofing materials and systems include piping for carrying fluid which is heated and stored for a solar heating device. In a preferred embodiment, the conductive roofing shingles, roofing panels, roofing tiles, and roll roofing material as described herein are formed entirely of the conductive loaded resin-based materials. In another embodiment, the conductive loaded resin-based materials are laminated to a substrate such as asphalted felt, fiberglass, or other structural materials. The conductive loaded resin-based material of the present invention typically comprises a micron powder(s) of conductor particles and/or in combination of micron fiber(s) substantially homogenized within a base resin host. FIG. 2 shows cross section view of an example of conductor loaded resin-based material 32 having powder of conductor particles 34 in a base resin host 30. In this example the diameter D of the conductor particles 34 in the powder is between about 3 and 12 microns. FIG. 3 shows a cross section view of an example of conductor loaded resin-based material 36 having conductor fibers 38 in a base resin host 30. The conductor fibers 38 have a diameter of between about 3 and 12 microns, typically in the range of 10 microns or between about 8 and 12 microns, and a length of between about 2 and 14 millimeters. The conductors used for these conductor particles 34 or conductor fibers 38 can be stainless steel, nickel, copper, silver, aluminum, or other suitable metals or conductive fibers, or combinations thereof. These conductor particles and or fibers are substantially homogenized within a base resin. As previously mentioned, the conductive loaded resin-based materials have a sheet resistance between about 5 and 25 ohms per square, though other values can be achieved by varying the doping parameters and/or resin selection. To realize this sheet resistance the weight of the conductor material comprises between about 20% and about 50% of the total weight of the conductive loaded resin-based material. More preferably, the weight of the conductive material comprises between about 20% and about 40% of the total weight of the conductive loaded resin-based material. More preferably yet, the weight of the conductive material comprises between about 25% and about 35% of the total weight of the conductive loaded resin-based material. Still more preferably yet, the weight of the conductive material comprises about 30% of the total weight of the conductive loaded resin-based material. Stainless Steel Fiber of 6–12 micron in diameter and lengths of 4–6 mm and comprising, by weight, about 30% of the total weight of the conductive loaded resin-based material will produce a very highly conductive parameter, efficient within any EMF spectrum. Referring now to FIG. 4, another preferred embodiment of the present invention is illustrated where the conductive materials comprise a combination of both conductive powders 34 and micron conductive fibers 38 substantially homogenized together within the resin base 30 during a molding process. Referring now to FIGS. 5a and 5b, a preferred composition of the conductive loaded, resin-based material is illustrated. The conductive loaded resin-based material can be formed into fibers or textiles that are then woven or webbed into a conductive fabric. The conductive loaded resin-based material is formed in strands that can be woven as shown. FIG. 5a shows a conductive fabric 42 where the fibers are woven together in a two-dimensional weave 46 and 50 of fibers or textiles. FIG. 5b shows a conductive fabric 42′ where the fibers are formed in a webbed arrangement. In the webbed arrangement, one or more continuous strands of the conductive fiber are nested in a random fashion. The resulting conductive fabrics or textiles 42, see FIG. 5a, and 42′, see FIG. 5b, can be made very thin, thick, rigid, flexible or in solid form(s). Similarly, a conductive, but cloth-like, material can be formed using woven or webbed micron stainless steel fibers, or other micron conductive fibers. These woven or webbed conductive cloths could also be sandwich laminated to one or more layers of materials such as Polyester(s), Teflon(s), Kevlar(s) or any other desired resin-based material(s). This conductive fabric may then be cut into desired shapes and sizes. Conductive roofing materials formed from conductive loaded resin-based materials can be formed or molded in a number of different ways including injection molding, extrusion or chemically induced molding or forming. FIG. 6a shows a simplified schematic diagram of an injection mold showing a lower portion 54 and upper portion 58 of the mold 50. Conductive loaded blended resin-based material is injected into the mold cavity 64 through an injection opening 60 and then the substantially homogenized conductive material cures by thermal reaction. The upper portion 58 and lower portion 54 of the mold are then separated or parted and the conductive roofing materials are removed. FIG. 6b shows a simplified schematic diagram of an extruder 70 for forming conductive roofing materials using extrusion. Conductive loaded resin-based material(s) is placed in the hopper 80 of the extrusion unit 74. A piston, screw, press or other means 78 is then used to force the thermally molten or a chemically induced curing conductive loaded resin-based material through an extrusion opening 82 which shapes the thermally molten curing or chemically induced cured conductive loaded resin-based material to the desired shape. The conductive loaded resin-based material is then fully cured by chemical reaction or thermal reaction to a hardened or pliable state and is ready for use. Thermoplastic or thermosetting resin-based materials and associated processes may be used in molding the conductive loaded resin-based articles of the present invention. The advantages of the present invention may now be summarized. Effective conductive roofing materials are achieved. Methods to form conductive roofing materials are achieved. Methods to fabricate conductive roofing materials from a conductive loaded resin-based material incorporating various forms of the material are achieved. As shown in the preferred embodiments, the novel methods and devices of the present invention provide an effective and manufacturable alternative to the prior art. While the invention has been particularly shown and described with reference to the preferred embodiments thereof, it will be understood by those skilled in the art that various changes in form and details may be made without departing from the spirit and scope of the invention.
	summary
051046105	abstract	The divergence of the magnetic field for confining the ionized gas (9) in a sealed high-flux neutron tube comprising a Penning-type ion source (1) is increased in the direction of the ion emission zone by influencing the magnet assembly (8) of the ion source. The ion beam extracted from the plasma is accelerated (2) and projected onto a target (4). The geometry and the position of the anode (13) inside the ion source are adapted to the topography of the lines of force in order to ensure minimum interception of the ionizing electrons moving in the structure, which adaptation is achieved notably by using a truncated anode whose generatrices take the shape of the lines of force.
047298677	claims	1. For use with a fuel assembly having at least one grid formed of interleaved straps defining a plurality of hollow cells for respectively receiving a plurality of fuel rods, at least some of said straps being disposed in pairs thereof so as to form springs in pairs thereof being positioned in back-to-back relationships between adjacent ones of said cells, said springs in each pair thereof being configured to normally assume expanded positions in which they are displaced away from one another to engage fuel rods received in said respective cells and being deflectible to retracted positions in which they are displaced toward one another to allow loading of the fuel rods in said respective cells without engaging said springs, a spring retainer apparatus for facilitating the loading of said fuel rods into said cells of said fuel assembly grid, comprising: (a) a plurality of elongated holder bars, each holder bar being alignable with one of said pairs of said straps of said grid which defines said pairs of springs and extendible along, and in spaced relation from, said one strap pair and between and spaced from positions occupied by fuel rods when received in said cells of said grid; and (b) a plurality of members supported by each of said holder bars corresponding to said pairs of springs defined by said pair of straps aligned with said holder bar; (c) each of said members having a terminal end configured to engage and retain said springs of one of said pairs thereof in their retracted positions when said respective holder bar supporting said member is aligned with and moved toward said pair of straps aligned with said holder bar; (d) each of said members being an elongated post with said terminal end of said member being a bifurcated end on said post defining at least one pair of spaced apart fingers adapted to receive said pair of springs therebetween for retaining said springs in their retracted positions. (a) first and second spring retainer assemblies, each of said spring retainer assemblies including (b) said holder bars of said respective first and second spring retainer assemblies having mating means permitting said assemblies to be superimposed one on top of the other in criss-cross fashion and interconnected in alignment with all of said pairs of springs defined by said straps of said grid. (a) aligning a plurality of elongated holder bars with pairs of said straps of said grid which defines said pairs of springs such that said holder bars extend along, and in spaced relation from, said strap pairs and between and spaced from positions occupied by fuel rods when received in said cells of said grid; and (b) moving said holder bars toward said pairs of said straps to insert bifurcated terminal ends of members supported by each of said holder bars about and in engagement with said springs to retain said springs in their retracted positions within the bifurcated terminal ends of the members. 2. The spring retainer apparatus as recited in claim 1, wherein said bifurcated end on each of said posts define two spaced pairs of spaced apart fingers adapted to receive said pair of springs therebetween and engage said pair at two displaced locations therealong for retaining them in their retracted positions. 3. The spring retainer apparatus as recited in claim 1, wherein each member in said plurality thereof supported by a respective one holder bar is rigidly connected to and extends from said bar in a generally parallel relationship with respect to the other members of said plurality thereof supported by said bar. 4. The spring retainer apparatus as recited in claim 1, wherein said bifurcated terminal end of each member defines a pocket adapted to receive said pair of springs therein and retain said springs in their retracted positions and a convergently-tapered entrance to said pocket for facilitating insertion of said springs when in their retracted positions into said pocket. 5. The spring retainer apparatus as recited in claim 1, wherein said bifurcated terminal end of each member defines a pocket adapted to receive said pair of springs therein and retain said springs in their retracted positions and a convergently-tapered entrance to said pocket for causing deflection of said springs from their normal expanded positions to their retracted positions and facilitating insertion of said retracted springs into said pocket. 6. For use with a fuel assembly having at least one grid formed of interleaved straps defining a plurality of hollow cells for respectively receiving a plurality of fuel rods, at least some of said straps being disposed in pairs thereof so as to form springs in pairs thereof being positioned in back-to-back relationships between adjacent ones of said cells, said springs in each pair thereof being configured to normally assume expanded positions in which they are displaced away from one another to engage fuel rods received in said respective cells and being deflectible to retracted positions in which they are displaced toward one another to allow loading of the fuel rods in said respective cells without engaging said springs, a spring retainer apparatus for facilitating the loading of said fuel rods into said cells of said fuel assembly grid, comprising: 7. The spring retainer apparatus as recited in claim 6, wherein said mating means on said holder bars are in the form of aligned notches defined in said bars of said first and second spring retainer assemblies. 8. The spring retainer apparatus as recited in claim 6, wherein said bifurcated end on each of said posts defines two spaced pairs of spaced apart fingers adapted to receive said pair of springs therebetween and engage said spring pair at two displaced locations therealong for retaining them in their retracted positions. 9. The spring retainer apparatus as recited in claim 6, wherein each member in said plurality thereof supported by a respective one holder bar is rigidly connected to and extends from said bar in a generally parallel relationship with respect to the other members of said plurality thereof supported by said bar. 10. The spring retainer apparatus as recited in claim 6, wherein said bifurcated terminal end of each member defines a pocket adapted to receive said pair of springs therein and retain said springs in their retracted positions and a convergently-tapered entrance to said pocket for facilitating insertion of said springs when in their retracted positions into said pocket. 11. The spring retainer apparatus as recited in claim 6, wherein said bifurcated terminal end of each member defines a pocket adapted to receive said pair of springs therein and retain said springs in their retracted positions and a convergently-tapered entrance to said pocket for causing deflection of said springs from their normal expanded positions to their retracted positions and facilitating insertion of said retracted springs into said pocket. 12. For use with a fuel assembly having a least one grid formed of interleaved straps defining a plurality of hollow cells for respectively receiving a plurality of fuel rods, at least some of said straps being disposed in pairs thereof so as to form springs in pairs thereof being positioned in back-to-back relationships between adjacent ones of said cells, said springs in each pair thereof being configured to normally assume expanded positions in which they are displaced away from one another to engage fuel rods received in said respective cells and being deflectible to retracted positions in which they are displaced toward one another to allow loading of the fuel rods in said respective cells without engaging said springs, a spring retainer method for facilitating the loading of said fuel rods into said cells of said fuel assembly grid, comprising the steps of: 13. The spring retainer method as recited in claim 12, wherein said moving of said holder bars toward said strap pairs causes deflection of said springs from normal expanded positions to retracted positions and retention of said retracted springs in their retracted positions.
	abstract	A method for fabricating a collimator assembly is provided. The collimator assembly includes a first collimator grid having a first surface and an opposing second surface, wherein the first collimator grid defines a plurality of cells. Each cell of the plurality of cells is aligned in a first direction and extends between the first surface and the second surface. The method includes coupling a reinforcing layer to the first collimator grid such that the reinforcing layer extends substantially perpendicular to the first direction.
	claims	1. A method of determining nuclear fusion irradiation coordinates for calculating irradiation coordinates of energy lines when the energy lines are irradiated onto nuclear fusion fuel, comprising:virtually arranging a predetermined number of electric charges at a predetermined number of initial coordinates on a spherical surface set by using random numbers by an information processing device;analyzing coordinates of the predetermined number of electric charges arranged at the initial coordinates in time series based on coulomb forces acting among the predetermined number of electric charges by constraining the coordinates onto the spherical surface by the information processing device;determining a timing at which potential energies of the predetermined number of electric charges were stabilized based on the coordinates analyzed in the coordinate analysis step by the information processing device;deriving coordinates of the predetermined number of electric charges at the timing determined in the potential evaluation step as irradiation coordinates of the energy lines in a case where nuclear fusion fuel is arranged at the center of the spherical surface by the information processing device; andarranging a predetermined number of energy line sources at positions within a nuclear fusion device corresponding to the irradiation coordinates when the nuclear fusion fuel is arranged at the center of the spherical surface. 2. The method of determining nuclear fusion irradiation coordinates according to claim 1, wherein in the step of determining the timing at which potential energies of the predetermined number of electric charges were stabilized, it is determined whether or not a temporal change of the sum of potential energies of the predetermined number of electric charges at the timing is not more than a predetermined value.
046613110	claims	1. A nuclear power plant comprising: a reactor pressure vessel positioned in an underground cavity; a small high-temperature pebble bed reactor disposed within the reactor pressure vessel and having spherical operating elements passing through a reactor core; means for addition, removal, and circulation of operating elements associated with said reactor including: means for discharging said operating elements from said core, depletion measuring means for separating depleted operating elements based on degree of depletion, and means for sorting and removal of operating element fragments, located under the reactor in a divided loading space; means for conveying operating elements to said reactor core including an insertion block means for inward transfer of operating elements located in said divided loading space and connected to said depletion measuring means for sorting; means for adding fresh operating elements located outside of said cavity and connected to said insertion block means; means for distributing said operating elements to said reactor core, disposed laterally outside said pressure vessel above said reactor core; and a first conduit connecting the insertion block means with the means for distributing. an extraction block means for outwardly transferring used operating elements; a second conduit connecting the depletion measuring means with the extraction block means; a collector vessel disposed outside of the underground cavity; a third conduit connecting the extraction block means with the collector vessel; a fourth conduit connecting the means for adding and the means for conveying. (a) a reactor pressure vessel; (b) a small high-temperature pebble bed reactor disposed within the reactor pressure vessel and having a core including spherical operating elements for passing through the core several times; (c) a heat exchanging apparatus disposed within the reactor pressure vessel; (d) a divided loading space; (e) means disposed in the divided loading space for adding fresh operating elements to said reactor; (f) a collector vessel for collecting used operating elements, disposed in the divided loading space; (g) a horizontal conduit for gaining access to the divided loading space; (h) a vertical shaft for gaining access to the divided loading space; (i) means disposed within the divided loading space for removal of operating elements, said means including a discharge device, a depletion measuring device for separating depleted operating elements based on degree of depletion, and a means for sorting and removal of element fragments; and (j) means disposed within the divided loading space for conveying operating elements, said means including an inward transfer of fresh operating elements from the addition device and the inward transfer of partially depleted operating elements from the depletion measuring device. (a) a distributor for distributing the operating elements, disposed above the reactor core, outside and to the side of the reactor pressure vessel; (b) a first coonduit connecting the inward transfer block with the distributor; (c) an outwad transfer block for outwardly transferring used operating elements; (d) a second conduit connecting the depletion measuring device with the outward transfer block; (e) a third conduit connecting the outward transfer block with the collector vessel. 2. A nuclear power plant as recited in claim 1 further comprising: 3. A nuclear power plant as recited in claim 2, wherein a column of operating elements is always present in said fourth conduit. 4. A nuclear reactor as recited in claim 2, wherein said operating elements comprise one-half spherical fuel elements and one-half spherical graphite elements. 5. A nuclear power plant according to claim 4, wherein said means for addition, removal and circulation of said operating elements further fully replaces said graphite elements with fresh elements during operation of the reactor after a period of "n-1" years, where "n" is the service life of the graphite elements in years. 6. A nuclear power plant with a small high-temperature pebble bed reactor disposed in an underground cavity, comprising: 7. A nuclear power plant as recited in claim 6 further comprising: 8. A nuclear reactor as recited in claim 7, wherein said operating elements comprise one-half spherical fuel elements and one-half spherical graphite elements. 9. A nuclear power plant according to claim 8, wherein said means for adding fresh operating elements and means for removal of operating elements further fully replaces said graphite elements with fresh elements during operation of the reactor after a period of "n-1" years, where "n" is the service life of the graphite elements in years.
	description	The present invention relates to a radioisotope generator for medical applications, preferably positioned in a shielded box, said box preferably being made at least partially from a dense material, for example tungsten or lead, comprising an eluent reservoir and a chromatographic column connected to one another by a first eluent transmission duct, said chromatographic column having a stationary phase loaded with a parent radioisotope disintegrating spontaneously into a daughter radioisotope. This radioisotope generator is used, inter alia, in the field of nuclear medicine to produce a radioisotope eluate (daughter radioisotope) from a source (i.e., a chromatographic column having a stationary phase loaded with parent radioisotopes that disintegrate spontaneously into daughter radioisotopes that are designed to be eluted by an eluent). These daughter radioisotopes in the eluate are designed to be used as such or to bond to a molecule, for example a biocompatible molecule (protein, antibody, etc.) so as to form a radio-marked molecule, resulting from the combination of the daughter radioisotope with the molecule, which is generally next administered to a patient by injection, typically in the form of a solution or a liquid suspension, when the molecule is biocompatible. The administration of the radioisotope or the radio-marked molecule makes it possible in that case to diagnose or treat certain cancers, depending on the choice of the radioisotope and/or biocompatible molecule. In the particular context of the preparation of a solution or a suspension comprising a radioisotope or a radio-marked biocompatible molecule designed to be administered to a patient, many constraints arise. Indeed, it is first necessary to make sure that the production and withdrawal of the eluate comprising the daughter radioisotopes, as well as the marking reaction of the biocompatible molecule by the daughter radioisotope to form the radio-marked molecule, is done under sterile conditions. Next, in order for the marking reaction to be as effective as possible, it is important to have an eluate that has a high degree of purity in daughter radioisotopes, i.e., an eluate highly concentrated in daughter radioisotopes and in which the presence of contaminants that may cause interference in or inhibit the marking reaction is low enough not compromise that marking reaction. Unfortunately, the phenomenon of passage of the parent radioisotopes through the stationary phase of the column, or breakthrough, is often inherent to the working of the generator described below and is problematic. In fact, this phenomenon corresponds to unwanted driving by the eluent of parent radioisotopes that detach from (or do not attach to) the stationary phase and find themselves in the eluate at the outlet of the chromatographic column. This results in an eluate that comprises a mixture of parent and daughter radioisotopes, and which, after the marking reaction, is administered to the patient and may be toxic if the parent radioisotope activity in the solution or suspension comprising the radio-marked biocompatible molecule is too high. Within the meaning of the present invention, the term “parent radioisotope(s)” refers to the radioisotope initially loaded on the stationary phase as well as the intermediate-generation radioisotopes that will supply the daughter radioisotope. Indeed, in some cases, the decomposition of the parent radioisotope produces a compound with a very short half-life that in turn decomposes into a daughter radioisotope of interest. These radioisotopes of a higher generation than the daughter radioisotopes of interest are called “parent radioisotopes”. Within the meaning of the present invention, “daughter radioisotope(s)” refers to the radioisotope(s) resulting from the decomposition that will be the eluted radioactive molecule of interest for uses in nuclear medicine, biomedical research and diagnostics. One solution to reduce this “breakthrough” is to produce an elution of the stationary phase of the column with a significant volume of eluent to next re-concentrate the eluate resulting from such a solution using a re-concentrator in order to increase the concentration thereof in daughter radioisotopes and decrease the activity thereof in parent radioisotopes to a threshold value that cannot be exceeded and for which toxic effects of that radioisotope cannot manifest in the individual receiving the solution or the suspension comprising the radio-marked biocompatible molecule from the re-concentrated eluate. In this method, which takes place before the marking reaction with a biocompatible molecule, the re-concentrator is placed downstream from the generator and connected to the generator at the outlet of the chromatographic column. During the re-concentration, the daughter radioisotopes, circulated by a vector solution (typically a physiological saline solution), are retained by a stationary phase that has a specific affinity with these radioisotopes, such that only the latter are retained by this stationary phase. The stationary phase is further deliberately chosen so that a small volume of solution suffices, for example using physiological serum (approximately 1.5 ml to 5.0 ml) and thus makes it possible to have a re-concentrated eluate with a limited volume but in which the activity in daughter radioisotopes is high enough and the activity in parent radioisotopes is low enough to be compatible with the aforementioned medical applications. However, this re-concentration step is costly, since it requires establishing an additional re-concentration system, and long enough to observe a significant loss in the performance of the daughter radioisotope activity in the re-concentrated eluate thus obtained, which constitutes a loss of profitability of the generator, and an additional risk of contamination. Another solution lies in producing, from the generator, a fractionated solution well known by those skilled in the art, which consists of collecting eluate by predetermined volume fractions and retaining and joining the fractions in which, on the one hand, the parent radioisotope activity is deemed low enough, and on the other hand, the daughter radioisotope activity is high enough for medical applications. Unfortunately, like the re-concentration step, the fractionated solution has the drawback of being a long enough method, since it is necessary, between each fraction, to interrupt the flow of eluate to identify the parent radioisotope activity. This is reflected in a significant loss of performance of the daughter radioisotope activity performance in the eluate thus obtained, which constitutes a loss of profitability of the generator, and again a risk of contamination. The fractionated solution, to be effective, then requires the use of a maintenance system that makes it possible to determine the correct fractionating and allows the real-time measurement of the parent and daughter radioisotope activities in each fraction, which constitutes an alternative at least as complex as the re-concentration step. Next, the establishment of a fractionated elution of the stationary phase is also problematic when it involves producing an eluate loaded with daughter radioisotopes under sterile conditions. In that case, it is in fact necessary to ensure that each container, designed each to receive an eluate fraction, is sterile, and that the step for pooling the fractions comprising the daughter radioisotopes is done under sterile conditions, which constitutes a non-negligible logistical, and de facto costly, constraint. There is therefore a need to have a generator that makes it possible to reduce this breakthrough phenomenon and to obtain, directly after elution, a sterile eluate in which the parent radioisotope activity is low enough and the daughter radioisotope activity is high enough, such that this eluate is directly usable and implemented in the form of a solution of radio-marked molecules. Document US 2011/0280770 proposes to meet this need by providing a generator comprising an elution line connecting the chromatographic column to the first eluent reservoir (upstream) and to the eluate outlet (downstream). This elution line comprises a first pinch valve arranged to regulate the flow of eluent from the reservoir toward the column, and a second pinch valve placed on a bypass of the elution line. This duration procures a loading line for parent radioisotope (62Zn) concentrated in a liquid phase. In this context, the second pinch valve therefore makes it possible to selectively regulate the arrival of 62Zn radioisotope in the column. A third pinch valve is present on the elution line, at the eluate outlet, downstream from the chromatographic column. This third line is intended to make it possible to regulate the flow at the outlet of the column toward a second eluate reservoir. However, the generator according to document US 2011/0280770 still has a complex design, since operation requires the continuous monitoring, during the elution of the stationary phase of the column, using controls, on the one hand, of at least two flow rates: the 62Zn loading flow rate from the bypass line toward the column and the eluent outlet flow rate from the eluent reservoir toward the column, and on the other hand, volumes of solution loaded with parent radioisotopes and eluent. Other devices are also known from documents US 2003/0127395 and U.S. Pat. No. 4,585,941 and describe systems depending on a pumping system to perform. the elution process. The aim of the present invention is to provide a radioisotope generator whose design is simplified and which therefore allows easier use, under sterile conditions, than the generator described in document US 2011/0280770 while eliminating the problem of breakthrough. According to the present invention, this aim is achieved by having a generator as described above, characterized in that it comprises a second duct and a valve housed between an upstream part of the first eluent duct and a downstream part of the first eluent duct, and connecting said second duct to said upstream part of the first eluent duct and to the downstream part of the first eluent duct, said valve having a first position in which the second duct is in fluid communication with said upstream part of the first eluent duct and a second position in which the second duct is in fluid communication with said downstream part of the first eluent duct, said second duct having a bypass segment for a predetermined volume of eluent, said segment being defined directly between said valve and a segment end, said predetermined eluent volume being a sufficient volume to obtain, when said sufficient volume crosses through the chromatographic column, under the action of a driving force of the eluent, an eluate comprising a parent radioisotope activity comprised in a value range from 0.0% to 30.0% relative to a daughter radioisotope activity of said eluate. The presence of the second duct in fluid communication, via the valve, with the first duct connecting the eluent reservoir to the chromatographic column, makes it possible to have a generator that is completely sterile once the reservoir, the first and second ducts and the valve are sterilized beforehand before being interconnected to one another to form a closed elution line and connected to the chromatographic column of the generator. Alternatively, the various aforementioned elements are interconnected and the resulting elution line is next sterilized as a whole. Furthermore, the generator according to the invention only requires monitoring one valve to generate an eluate that is directly usable for medical applications, the withdrawn volume being predetermined by the predetermined length and diameter of the bypass segment. Indeed, when the user wishes to perform an elution, he first positions the valve in its first position, which is a position in which the second duct is in fluid communication with said upstream part of the first eluent duct so as to charge the bypass segment with eluent through a predetermined and sufficient eluent volume. Next, when the bypass segment is filled with eluent, the user positions the valve in its second position, in which the second duct is in fluid communication with said downstream part of the first eluent duct, and the eluent is discharged from the bypass segment toward the chromatographic column. Once the elution is complete, the activity of the daughter radioisotope, which does not cease to be generated in the column from the parent radioisotope loaded on the column, increases to reach an activity threshold value that cannot be exceeded and that is governed by an equilibrium between the parent radioisotope and the daughter radioisotope. A cycle is thus formed, and it is the frequency between the successive elutions that determines the respective parent and daughter radioisotope activities in the eluate obtained for each of these successive elutions. The predetermined volume here corresponds to the sufficient and optimal volume to elute, in very large majority, the daughter radioisotope resulting from the disintegration and a minimal fraction of parent radioisotope, thus reducing the breakthrough phenomenon. Indeed, the predetermined volume makes it possible to obtain, after elution of the column, an eluate in which the measured daughter radioisotope activity is comprised in a value range from 60.0% to 100.0%, preferably from 70.0% to 100.0%, more particularly greater than 80.0% relative to the daughter radioisotope activity present on the column at the time of the elution, whereas the parent radioisotope activity in the eluate is comprised in value range from 0.0% to 30.0% relative to the daughter radioisotope activity of said eluate. The generator according to the present invention therefore makes it possible, for each elution with a sufficient predetermined eluent volume, to obtain an elution profile of the daughter radioisotope that is quite surprising. Indeed, as explained above, in the existing wet generator systems, i.e., for which the elution is done continuously, the elution profile of the daughter radioisotope traditionally has a first fraction comprising a majority of the parent radioisotope preceding a second fraction comprising a majority of the daughter radioisotope. On the contrary, in the context of the present invention, it has surprisingly been observed that the activity of the parent radioisotope [in] the eluate is reduced enough for this eluate to be directly usable in the aforementioned medical applications. Thus, with the generator according to the present invention, for an elution with the predetermined sufficient volume of eluent, it is also easy, and under sterile conditions, not only to monitor the parent radioisotope activity in the eluate, but also to have a sufficient daughter radioisotope activity, so as to obtain an eluate that is directly usable in medical applications. Indeed, the eluate obtained by the passage of the predetermined volume of eluent in the chromatographic column of the generator according to the invention has an elution peak of the daughter radioisotope that is narrow and substantially lacks parent radioisotopes by optimization of the synchronization between the elution and the complete generation of daughter radioisotopes on the stationary phase depending on the secular disintegration cycle of the parent radioisotopes. During the lifetime of the generator, the daughter isotope solutions of interest are recovered through a series of loading and unloading operations of the segment, alternating, until the eluent contained in the reservoir is exhausted: it therefore involves a discontinuous elution that consists of a series of elutions with a sufficient volume of eluent. In this context, each elution is associated with a withdrawal of a volume of eluate intended for an appropriate medical use. Between each elution, the user will be sure to dry the column, for example by pumping sterilized ambient air from the segment end or from a free end of the second duct toward the eluate outlet. The drying makes it possible to discharge a residual volume of excess eluent present in the column, and thus to minimize the risk of seeing the parent radioisotope migrate toward the eluate outlet of the column between two successive elutions. The choice of the sufficient predetermined volume is determined by the elution profile of the radioisotopes, and therefore: (i) by the physicochemical properties of the chromatographic column and the eluent; (ii) as well as by the pair of parent and daughter radioisotopes used. The generator according to the invention therefore constitutes a similar design and usage alternative to the solutions proposed in the state of the art, and in particular to the solution provided by conventional dry generators, for which it is systematically necessary to load the column manually by injecting a predetermined volume of eluent, this type of generator by definition not comprising an eluent reservoir. Indeed, the difficulty inherent to the use of this type of generator [lies] in the fact that it is necessary to ensure a sterile connection for each eluent injection in the column in order to avoid contamination risks. Preferably, said reservoir is situated above said chromatographic column, said segment end, which can be a free end of the second duct, being positioned at a sufficient height, measured from an apical end of the chromatographic column, such that the gravitational force has a sufficient intensity to allow a flow of the eluent through the withdrawal segment. Advantageously, at least one bypass segment part connected to said valve is inclined relative to a horizontal plane by an angle α having a predetermined value such that its sine value is greater than 0 and less than or equal to 1, and its cosine value is between −1 and 1. In this way, the intensity of the gravitational force that acts on the eluent withdrawn toward the withdrawal segment is first determined by the drop height, measured from the apical end of the chromatographic column, from the bypass segment toward the chromatographic column, and additionally, by the angle α whose value determines the incline of the second part connected to said valve. The incline thus allows a gravitational flow of the sufficient predetermined volume of eluent. Optionally, the generator according to the invention comprises means for blocking the eluent in fluid communication with said bypass segment, so as to block the passage of said volume of eluent beyond said segment end. The presence of the blocking means makes it possible on the one hand to precisely determine the withdrawn volume, and on the other hand, optionally to avoid the overflow of said eluent volume by said free end of the second duct. Advantageously, said free end is connected to a second sterile filter with an inverse polarity relative to that of said eluent. Said segment end can also be directly connected to a first sterile filter with a polarity opposite that of said eluent, said first sterile filter being said blocking means of the eluent. In this way, the air that penetrates inside the second duct and the bypass segment is sterilized, which has the advantage of providing a sterile generator whereof the eluate obtained directly is appropriate for medical use. Preferably, the generator according to the invention comprises a pumping means arranged to be connected hermetically to an eluate outlet and designed to pump, once said valve is in its second position and after elution of the stationary phase of the chromatographic column by said sufficient volume of eluent, a fluid from the segment end or from the free end of the second duct toward the eluate outlet, said fluid being a remaining fraction of said sufficient volume of eluent present in the column or ambient air pumped from said free end or said segment end of said second duct. As an example, the pumping means can be a vacuum container or an actuator comprising a piston mounted in a cylinder, said cylinder having a first end communicating with said eluate outlet of the chromatographic column, said piston being extended by an arm that extends outside said cylinder through an orifice present on a second cylinder end, opposite the first cylinder end, said piston having a first idle position and a fluid pumping position, said piston, when it is set in motion between said first idle position and the pumping position, generating a pumping force for the fluid. The pumping means makes it possible, after each elution, to discharge the excess eluent present in the column and optionally to dry the latter so as to obtain a column that is dried or weakly impregnated with eluent. By making it possible to discharge this excess eluent fragment present in the column, one thus minimizes the risk of having the parent radioisotope migrate toward the eluate outlet of the column between two successive elutions. Other embodiments of the generator according to the invention are provided in the appended claims. The invention further relates to an elution method for a chromatographic column of a radioisotope generator comprising an eluent reservoir and connected to the chromatographic column by a first eluent duct, said chromatographic column having a stationary phase impregnated with eluent and loaded with a parent radioisotope disintegrating spontaneously into a daughter radioisotope, said method comprising the following steps: withdrawing a predetermined volume in a withdrawal segment of a second eluent duct connected to an upstream part of the first eluent duct and a downstream part of the first eluent duct by a valve, said withdrawal segment being defined directly between the valve and a segment end, the withdrawal being done when the valve is in a first position in which the second duct is in fluid communication with said upstream part of the first eluent duct; and an elution, under the action of a driving force of the eluent, of said predetermined volume of eluent from said withdrawal segment toward said chromatographic column when the valve is in a second position in which the second duct is in fluid communication with said downstream part of the first eluent duct, a step for drying the column by pumping sterilized ambient air from the segment end or from a free end of the second duct toward the eluent outlet,said predetermined eluent volume being a sufficient volume to obtain, when said sufficient volume crosses through the chromatographic column, an eluate comprising a parent radioisotope activity comprised in a value range from 0.0% to 30.0% relative to a daughter radioisotope activity of said eluate. Preferably, the method comprises a step for blocking the eluent, after said injection step, so as to block the passage of said volume of eluent past said segment end. The method may further comprise a bleeding step, carried out before the drying step, when the valve is in its second position and after elution of the stationary phase of the chromatographic column by the sufficient eluent volume, which consists of pumping a remaining fraction of the sufficient volume of eluent present in the column. Alternatively, the parent radioisotope activity is comprised in a value range from 0.0% to 20%, advantageously from 0.0% to 10%, more preferably from 0.0% to 5.0%, still more preferably from 0.0% to 2.0%, more advantageously from 0.0% to 1.0%, relative to the daughter radioisotope activity of said eluate. Advantageously, the parent radioisotope activity is equal to 0.0 mCi. Other embodiments of the method according to the invention are provided in the appended claims. In these figures, similar elements bear the same references. The radioisotope generator 1 according to the invention shown in FIG. 1 comprises an eluent reservoir 2 and a chromatographic column 3 connected to one another by a first eluent transmission duct 4, such that the eluent contained in the reservoir 2 is in fluid communication with the chromatographic column 3. The chromatographic column 3 comprises a stationary phase impregnated with eluent and loaded with a parent radioisotope disintegrating spontaneously into a daughter radioisotope. The first eluent transmission duct 4 connects an eluent inlet 5 positioned upstream from the stationary phase 2 to an eluent outlet 6 of the reservoir 2. The radioisotope generator 1 further comprises a second duct 7 and a valve 8 connecting an upstream part 4′ of the first eluent duct and a downstream part 4″ of the first eluent duct. The upstream part 4′ connects the eluent outlet 6 of the reservoir 2 to a first inlet 8′ of the valve 8, while the downstream part 4″ connects a second inlet 8″ of the valve 8 to the eluent inlet 5 of the chromatographic column 3. The valve 8 further connects an end 7′ of the part connected to the second duct 7 to the upstream part 4′ and downstream part 4″ of the first eluent duct 4. The second duct 7 is placed in fluid communication with the valve 8 by means of a connection between the end 7′ of the connected part of the second duct 7 and a third inlet 8′″ of the valve 8. In this context, the valve 8 has a first position in which the second duct 7 is in fluid communication with the upstream part 4′ of the first eluent duct 4 and a second position in which the second duct 7 is in fluid communication with the downstream part 4″ of the first eluent duct 4. The second duct 7 further has a bypass segment 9 for a predetermined volume v of eluent. The segment 9 is defined directly between the valve 8 and a segment end 9′. Typically, the predetermined volume v of eluent is defined by a bypass segment length and a bypass segment diameter. In the first embodiment as described in FIG. 1, the segment 9 is defined between the end 7′ of the connected part of the second duct 7 and the segment end 9′. In particular, the segment end is connected to a blocking means 17 of the eluent in fluid communication with the bypass segment 9, so as to block the passage of the eluent volume beyond the segment end 9′. The blocking means 17 can for example be a sterile filter with a polarity opposite that of the eluent whose function is to allow ambient air to pass in the bypass segment 9 and to block the passage of the eluent in a defined direction from the end 7′ of the connected part of the second duct 7 toward the segment end 9′. Preferably, the generator 1 is placed in a shielded box C for example at least partially made from a dense material, for example tungsten or lead. The box C comprises a first access opening 10 to the reservoir 2 and an outlet opening 11 positioned downstream from an eluate outlet 12 of the chromatographic column 3 and arranged to be crossed through by a second eluate outlet duct 12′ arranged to connect the eluate outlet 12 of the column 3 to an eluate container 13 arranged to be positioned in a chamber 14 arranged in the box and positioned downstream from the outlet opening 11. Preferably, the eluate container 13 and/or the chamber 14 comprise(s) shielding made from a dense material, for example tungsten or lead. In the first embodiment as illustrated in FIG. 1, the reservoir 1 is positioned above the chromatographic column 3. The end 9′ of the bypass segment 9, which can for example be a free and 15 of the second duct 7, is positioned at a predetermined height H, measured from an apical end 16 of the chromatographic column 3. Optionally, at least one bypass segment part 9 connected to the valve 8 is inclined relative to a horizontal plane h by an angle α defined between the horizontal plane h and a line d secant to the horizontal plane h. Advantageously, the angle α has a predetermined value such that its sine value is greater than 0 and less than or equal to 1 and its cosine value is comprised between −1 and 1. During the operation of the first embodiment of the generator (FIG. 1), the valve 8 is first positioned in its first position. The eluent flows from the reservoir 2 through the upstream part 4′ of the first duct 4 toward the second duct 7. The bypass segment 9 fills, under the effect of the gravitational force that acts on a volume V of eluent contained in the reservoir 2, by the predetermined volume v of eluent according to a bypass flow rate at a value predetermined by the length of the bypass segment diameter 9. The air contained in the segment is driven toward the sterile filter 17 by the eluent. The travel of the eluent from the reservoir toward the free end 15 is stopped by the presence of the sterile filter 17. The height H and the value of the angle α make it possible to determine a sufficient intensity value of the gravitational force that acts on the sufficient volume vs of eluent withdrawn so as to allow the flow of the sufficient volume of eluent through the segment 9. Once the predetermined volume v of eluent is withdrawn from the reservoir, the valve is next positioned in its second position. The eluent flows from the withdrawal segment 9 through the chromatographic column 3 according to an elution flow rate determined by the pressure drop of the chromatographic column 3. The predetermined volume v of eluent is a sufficient volume Vs to obtain, when the sufficient volume crosses under the action of a driving force of the eluent, which may for example be a drawing-off force of the eluent generated by a pump system connected to the outlet of the chromatographic column 3 at the determined elution flow rate, an eluate comprising a parent radioisotope activity comprised in a value range from 0.0% to 30.0% relative to a daughter radioisotope activity of said eluate. The parent radioisotope activity in the eluate is preferably comprised in a value range from 0.0% to 20.0%, more preferably from 0.0% to 10.0% relative to the daughter radioisotope activity of said eluate. More preferably, the parent radioisotope activity is comprised in a value range from 0.0% to 5.0% relative to the daughter radioisotope activity of said eluate. Still more preferably, the parent radioisotope activity is comprised in a value range from 0.0% to 2.0% relative to the daughter radioisotope activity of said eluate. More advantageously, the parent radioisotope activity is comprised in a value range from 0.0% to 1.0% relative to the daughter radioisotope activity of said eluate. Quite advantageously, the parent radioisotope activity is preferably equal to 0.0 mCi. FIGS. 2a and 2b illustrate part of two separate alternatives of a second embodiment of the generator 1 according to the invention. The second embodiment copies the features of the first embodiment and, additionally, a pumping means MP arranged to be connected hermetically to the eluate outlet 12. The pumping means MP can for example be a vacuum container. Alternatively, the pumping means MP can be an actuator 18 comprising a piston 19 mounted in a cylinder 20 (FIG. 2a). The cylinder 20 has a first end 21 communicating with the eluate outlet 12 of the chromatographic column 3. The piston 19 is extended by an arm 22 that extends outside the cylinder 20 through an orifice 23 present on a second cylinder end 24, opposite the first cylinder end 21. The piston has a first idle position R and a pumping position P (see FIG. 2b by equivalence). During operation, after a first elution and before a second subsequent elution, the first valve 8 is kept in its second elution position and the pumping means MP is hermetically connected to the eluate outlet 12 while ensuring that the valve 8 is positioned in its second position. Preferably, the eluate outlet is extended by a needle that is connected to a vacuum capsule by piercing a tight wall covering a fluid inlet orifice present on the capsule. Once the needle penetrates the capsule, a residual volume of said eluent volume that is free, i.e., that is not retained in the stationary phase of the column, and that stagnates in the column, is automatically suctioned in the capsule. By making it possible to evacuate this residual excess eluent volume present in the column, one thus minimizes the risk of having the parent radioisotope migrate toward the eluate outlet of the column between two successive elutions. Once this free eluent is suctioned, ambient air is next expelled from the free end 15 or the segment 9 end 9′ of the second duct 7 so as to dry the excess eluent fraction. The suctioning of the free eluent and the passage of air in the column therefore make it possible to bleed and dry the latter so as to obtain, between two elutions, a column that is dried or weakly impregnated with eluent. Once the bleeding and drying of the column are done, the capsule is disconnected from the eluate outlet 12 and the eluate container 13 is once again connected to the column. Similarly to the vacuum capsule, the container comprises a tight wall designed to be crossed through by the needle positioned in the extension of the eluate outlet 12 of the column 3. A new elution is next done first by positioning the first valve 8 in its first position to load the bypass segment 9 with eluent, and next by positioning the first valve 8 in its second elution position. This new elution is next followed by a new bleeding and drying step. Thus, once a first elution is complete, the activity of the daughter radioisotope, which does not cease to be generated in the column from the parent radioisotope loaded on the column, increases to reach an activity threshold value that cannot be exceeded and that is governed by a secular equilibrium between the parent radioisotope and the daughter radioisotope. A cycle is thus formed, and it is the frequency between each successive elution (second, third, etc. elution) after the first elution that determines the respective parent and daughter radioisotope activities in the eluate obtained for each of these successive elutions. Furthermore, the actuator 18 can be hermetically connected by a second valve 25 to the eluate outlet 12 (FIG. 2b). The second valve 25 has an elution position in which the third duct 12′ is in fluid communication with the eluate container 13 via a fourth duct 12″ connecting the eluate container 13 to the valve, and a bleeding position in which the third duct 12′ is in fluid communication with the pumping means. During operation, after a first elution and before a second subsequent elution, the second valve 25, initially in its elution position, is positioned in its bleed position, while the first valve 8 is kept in its second elution position. The piston is next set in motion between its first idle position R and its second pumping position P, which generates a pumping force of the remaining fraction of the sufficient volume of eluent. The remaining fraction of the sufficient volume of eluent is therefore conveyed from the chromatographic column 3 toward the cylinder 20 of the actuator 18, which fills with eluent. If the piston is kept in motion and when the free eluent is suctioned from the column, ambient air is next pumped from the free end 15 or the segment 9 end 9′ of the second duct 7 so as to drive the excess eluent fractions in order to obtain a column that is maximally impregnated with eluent. Once the bleeding and drying of the column are done, the second valve 25 is positioned in its first position and a new elution is done by first positioning the first valve 8 in its first position to load the bypass segment 9 with eluent, and next by positioning the first valve 8 in its second elution position. This new elution will next be followed by a new bleeding and drying step. The generator according to a third embodiment (FIG. 3) further comprises a pressure switch 15′ connected to the free end 15 of the second duct or to the segment 9 end 9′. In this third embodiment of the generator according to the invention, the pressure switch 15′ makes it possible to monitor the elution flow rate of the sufficient volume of eluent as well as a bleed flow rate, i.e., a pumping flow rate of the eluent, and a drying flow rate, i.e., a pumping flow rate of the air through the column, and to determine any operating anomalies of the generator. For each of the embodiments of the generator described above, the choice of the sufficient predetermined volume is determined by the elution profile of the radioisotopes and therefore: (i) by the physicochemical properties of the chromatographic column and the eluent; (ii) and by the pair of parent and daughter radioisotopes used. In reference to FIGS. 1 and 2, the present invention also pertains to an elution method for a chromatographic column 3 of a radioisotope generator 1 comprising an eluent reservoir 2 and connected to a chromatographic column 3 by a first eluent duct 4, said chromatographic column 3 having a stationary phase impregnated with eluent and loaded with a parent radioisotope disintegrating spontaneously into a daughter radioisotope. The method according to the invention comprises the following steps: withdrawing a predetermined volume in a withdrawal segment 9 of a second eluent duct 7 connected to an upstream part 4′ of the first eluent duct 4 and a downstream part 4″ of the first eluent duct 4 by a valve 8, said withdrawal segment 9 being defined directly between the valve 8 and a segment end 9′. The withdrawal is done when the valve 8 is in a first position in which the second duct 7 is in fluid communication with said upstream part 4′ of the first eluent duct; and an elution step, under the action of a driving force of the eluent, of said predetermined volume of eluent from said withdrawal segment 9 toward said chromatographic column 3 when the valve 8 is in a second position in which the second duct 7 is in fluid communication with said downstream part 4″ of the first eluent duct 4. The method further comprises a step for drying the column by pumping ambient air from the segment 9 and 9′ or from a free end 15 of the second duct 17 toward the eluate outlet 12. The ambient air is sterilized by passing through the sterile filter 17 present on the second duct 7. A bleeding step can be carried out before the drying step. This bleeding step is performed when the valve 8 is in its second position and after elution of the stationary phase of the chromatographic column 3 by the sufficient volume of eluent, which consists of pumping a remaining fraction of the sufficient volume of eluent present in column 3. In this method, the predetermined volume of eluent is a sufficient volume to obtain, when the sufficient volume crosses through the chromatographic column 3, an eluate comprising a parent radioisotope activity comprised in a value range from 0.0% to 30.0% relative to a daughter radioisotope activity of the eluate. Preferably, the method comprises a step for blocking the eluent, after said injection step, so as to block the passage of said eluent volume past said segment end 9′. The blocking step is ensured by the presence of a sterile filter 17 with a polarity opposite that of the eluent whose function is to allow air to pass in the bypass segment 9 and to block the passage of the eluent in a defined direction from the end 7′ of the connected part of the second duct 7 toward the segment end 9′. The method according to the invention makes it possible preferably to obtain a parent radioisotope activity that is comprised in a value range from 0.0% to 20% relative to the daughter radioisotope activity of said eluate. Advantageously, the parent radioisotope activity is comprised in a value range from 0.0% to 10% relative to the daughter radioisotope activity of said eluate. More preferably, the parent radioisotope activity is comprised in a value range from 0.0% to 5.0% relative to the daughter radioisotope activity of said eluate. Still more preferably, the parent radioisotope activity is comprised in a value range from 0.0% to 2.0% relative to the daughter radioisotope activity of said eluate. More advantageously, the parent radioisotope activity is comprised in a value range from 0.0% to 1.0% relative to the daughter radioisotope activity of said eluate. Advantageously, the parent radioisotope activity is equal to 0.0 mCi. The results relative to the operation of the generator according to the present invention are described below for illustrative purposes and should in no way be considered limiting. These results are relative to loading and elution tests of the generator according to the invention for different parent/daughter radioisotope pairs and different stationary phases. Operational Mode Loading of the Generator Test 1 pertains to the 99Mo/99mTc pair (parent/daughter) on a first titanium-based stationary phase of a first generator according to the invention done in aqueous phase with an acid pH. The activity loaded on the stationary phase was 27.9 mCi during the loading time T0. Test 2 pertains to the 99Mo/99mTc pair and a second aluminum-based stationary phase of a second generator according to the invention done in aqueous phase with an acid pH. The activity loaded of the stationary phase was 57.8 mCi at the loading time T0. Elution Test For tests 1 and 2, the reservoir consists of a pouch of NaCl saline solution concentrated at 0.9 vol %. The two generators were diluted daily for a determined period in order to monitor the elution performance and the release rates of 99Mo in each of the eluates withdrawn daily (breakthrough). Results The elution performance Y (in %) is understood in the context of the present invention as the ratio of the activity of the 99mTc [A(99mTc)el in mCi] in the eluate and the activity of the 99mTc [A(99mTccol mCi] that is present on the column at the time of the elution and is calculated using the following formula:Y(in %)=100×[A(99mTc)el/A(99mTc)col] The 99Mo release rates are given in % and correspond of the following ratio: R=100×[A(99Mo)el/A(99mTc)el], where A(99Mo)el represents the 99Mo activity in the eluate. The results relative to tests 1 and 2 are provided in tables 1 and 2 below: TABLE 1.099Mo/99mTc pair on TiO2 - test 1Time TY (in %)R (%)T099<1.4 10−6T0 + 1 day91<1.6 10−6T0 + 2 days93<2.0 10−6T0 + 8 days95<1.9 10−6T0 + 9 days95<3.2 10−7T0 + 10 days95<1.4 10−6T0 + 11 days97<1.6 10−6T0 + 13 days94<6.4 10−6T0 + 14 days96<6.9 10−6T0 + 15 days98<6.8 10−6T0 + 16 days98<7.1 10−6T0 + 17 days95<9.0 10−6T0 + 21 days94<3.0 10−6T0 + 22 days94<2.1 10−6The specifications of the European pharmacopeia (Monographs for sodium pertechnetate (99mTc) for injection produced by fission “Eur. Phar. 0124” and Monographs for sodium pertechnetate (99mTc) for injection not produced by fission “Eur. Phar. 0283”) provide a threshold value not to be exceeded of approximately 0.1%. TABLE 299Mo/99mTc pair on Al2O3 - test 2Time TY (in %)R (in %)T092<4.4 10−4T0 + 1 day100<3.1 10−4T0 + 2 days100<2.3 10−4T0 + 3 days100<1.2 10−4T0 + 6 days100<3.3 10−4T0 + 7 days101<4.5 10−5T0 + 9 days99<2.8 10−4T0 + 10 days101<6.3 10−5T0 + 13 days99<5.0 10−5T0 + 14 days99<2.7 10−5The specifications of the European pharmacopeia (Monographs for sodium pertechnetate (99mTc) for injection produced by fission “Eur. Phar. 0124” and Monographs for sodium pertechnetate (99mTc) for injection not produced by fission “Eur. Phar. 0283”) provide a threshold value not to be exceeded of approximately 0.1%. Based on tests 1 and 2 and a reference test, the values illustrated in Table 3 are found: TABLE 3Pair // stationary phaseY (in %)R (in %)68Ge/68Ga // TiO2§ >70%§§§ 10−4-10−6§§§§99Mo/99mTc // TiO2§§ ~95%~10−6-10−799Mo/99mTc // Al2O3§§~100% 10−4-10−5§Values measured at time T = T0§§Average values§§§Y (in %) = 100 × [A(68Ga)el/A(68Ge)col]§§§§R = 100 × [A(68Ge)el/A(68Ga)el], where A(68Ge)el represents the activity of 68Ge in the eluate.The specifications of the European pharmacopeia (Monographs for sodium pertechnetate (99mTc) for injection produced by fission “Eur. Phar. 0124”; Monographs for sodium pertechnetate (99mTc) for injection not produced by fission “Eur. Phar. 0283” and Monographs for “Gallium solution (68Ga) (Chloride) for radioactive labeling” “Eur Phar 2464”) provide a threshold value not to be exceeded of approximately 0.1%. As shown by the results provided above, the parent radioisotope activity detected in the eluate is on average lower by a factor of 10−6 -10−8 relative to the daughter radioisotope activity in the same eluate, which means a parent radioisotope activity of less than 1.0% relative to the daughter radioisotope activity of the eluate, which is quite remarkable. Of course, the present invention is in no way limited to the embodiments described above, and changes may be made thereto without going beyond the scope of the appended claims. For example, the generator according to the present invention may be used in applications other than use for pharmaceutical or medical purposes. Furthermore, although the description discloses a generator comprising a valve, it is understood that the present invention is not limited to a generator comprising only one valve, but also covers other embodiments in which several valves fluidly connect the withdrawal segment to the reservoir and the column. As an illustration, a fourth embodiment in which the generator comprises a first valve connecting the withdrawal segment to the reservoir and a second valve connecting the same segment to the chromatographic column can of course be considered as an equivalent implementation of the generator according to the invention.
062333062	summary	The invention relates to an apparatus for irradiating an object by means of X-rays, including an X-ray source for producing X-rays for irradiating the object, which X-ray source is provided with a bundle of capillary tubes which conduct X-rays, the end of the bundle which is intended as an exit for the X-rays being provided with an X-ray transparent X-ray window. An apparatus of this kind is known from European patent No. 0 244 504 B 1. X-ray irradiation apparatus can be used in a large number of fields of application. A first example of such an application is X-ray analysis where the composition and/or the structure of materials is analyzed. The object to be irradiated is then formed by a specimen of the material to be analyzed by means of the apparatus. Generally speaking, two analysis techniques are feasible: X-ray fluorescence and X-ray diffraction. In the case of X-ray fluorescence, a specimen is irradiated by means of a polychromatic X-ray beam. The irradiation excites the various elements present in the specimen which then emit X-rays (fluorescent radiation) which is characteristic of the constituent elements. The elementary composition of the specimen can be determined by detection and analysis of this fluorescent radiation. In the case of X-ray diffraction, the specimen is generally irradiated by means of a monochromatic X-ray beam which is deflected (diffracted) only at given angles because of the regularity of the crystal structure of the components present in the specimen. The diffraction angles then offer information as regards the crystal structure of the constituents of the specimen. Another example of a field of application of X-ray irradiation apparatus is X-ray lithography where very small structures for microelectronics are formed on a substrate or masks are manufactured for the exposure of such structures. The object to be irradiated is then formed by said substrate or the mask to be manufactured. Another example of a field of application for X-ray irradiation apparatus is medical therapy or diagnostics where it is often important to apply X-rays to a very accurately defined region of the human body. The object to be irradiated is then formed by the tissue to be irradiated. In all of said applications the X-rays required for irradiating the object to be examined or treated can be generated by means of an X-ray tube. In such an X-ray tube the X-rays are generated by electron bombardment of an anode so that X-rays are produced in the anode. Because this process must take place in vacuum, the X-ray tube is necessarily constructed so as to include a vacuum tight housing. In order to conduct the X-rays out of the X-ray tube, the housing is provided with a window opening which is situated near the anode and serves to conduct the X-rays produced out of the tube. In generally known conventional X-ray tubes this window opening is covered by an X-ray transparent X-ray window which is usually made of beryllium. Even though the choice of beryllium as the window material is based on the attractive properties of beryllium in respect of the absorption of X-rays, such absorption cannot be ignored. This holds notably in the case of X-rays having a comparatively long wavelength, for example of the order of magnitude of from 1 nm to 10 nm. It could be attempted to reduce the absorption by the window by making the window thinner, but the strength of the material imposes a limit in this respect. The thickness that can nowadays be achieved for beryllium X-ray windows is of the order of magnitude of 50 .mu.m. In order to withstand the pressure of the ambient atmosphere on the X-ray window, such thin windows are supported by a supporting grid. Because of the lack of solidity and the high brittleness of beryllium, it is not very likely that these windows can be constructed to be much thinner yet. Other materials for X-ray windows, for example foils of a synthetic material, cannot be used because of the comparatively high temperature whereto the window is exposed during operation of the X-ray tube. In the apparatus described in the cited European patent No. 0 244 504 capillary tubes for total reflection of X-rays on the interior thereof are combined so as to form a bundle having a length of approximately from 0.5 mm to 1.0 mm. The capillary tubes in this bundle have a diameter of from approximately 10 .mu.m to 20 .mu.m, the bundle comprising as many as one hundred thousand capillary tubes so that it has a plate-like external appearance. This plate-like bundle is provided on one side with a thin layer of, for example aluminium or magnesium of a thickness of the order of magnitude of 5 .mu.m. This thin layer is bombarded by a thin electron beam so that it serves as an X-ray target, the energy of the electron beam being of the order of magnitude of 20 keV. The diameter of the electron beam is approximately 5 .mu.m, so that it is smaller than the diameter of each of the capillary tubes in the bundle. The other side of the plate-like bundle is provided with a thin layer of, for example beryllium, carbon or a higher polymer with an aluminum coating having a thickness of the order of magnitude of 2 .mu.m in order to transmit the X-rays generated in the former layer and to intercept any electrons. The latter layer bears on the grid which is formed by the ends of the capillary tubes in the bundle. Granted, this known structure is suitable for generating X-rays having a comparatively long wavelength. However, generating X-rays of comparatively long wavelength is a process with a low efficiency, i.e. a comparatively high power of the generating electron beam is required so as to generate a low X-ray intensity. Because the thin layer acting as the X-ray target is not provided with cooling means for discharging the heat dissipated in this layer, only a small electric power can be applied to this layer by the electron beam. The X-ray power of this structure, therefore, is very limited. It is an object of the invention to provide an X-ray irradiation apparatus in which the X-ray source is suitable to produce X-rays of comparatively long wavelength and an intensity which suffices to operate the X-ray irradiation apparatus in practical circumstances. To this end, the apparatus according to the invention is characterized in that the X-ray source includes an X-ray tube having a vacuum tight housing which is provided with a window opening for conducting the X-rays produced by the tube to the exterior of the housing, that one end of the bundle is provided on the window opening in a vacuum tight manner and that the capillary tubes at that end of the bundle are directed towards the location where the X-rays are generated, that the interior of the capillary tubes is in vacuum contact with the vacuum space of the X-ray tube which is situated within the housing, and that the X-ray transparent X-ray window seals the interior of the capillary tubes from the environment in a vacuum tight manner. A bundle of X-ray conducting capillary tubes is known per se, for example from a contribution to the Proceedings of SPIE, Vol. 3115 (1997), entitled "Polycapillary Focusing Optic For Low-Energy-X-Ray Fluorescence" by Ira Klotzky and Qi-Fan Xiao. The conductive properties of such capillary tubes is based on the well-known phenomenon concerning total reflection of X-rays on the interior of the capillary tubes. Because of the total reflection, only an insignificant loss of intensity occurs, so that these capillary tubes can be used to conduct the X-rays in a loss-free manner. The capillary tubes are assembled so as to form a bundle in known manner in that at one end (the end to be connected to the X-ray tube) of this bundle the capillary tubes are enclosed by a bonding material, for example a synthetic material. Thus, the gaps between the capillary tubes are filled in an airtight manner and at the same time an envelope is formed on the outer side of the bundle; this envelope can also be used for connecting the bundle to the X-ray tube. Such connection can be realized, for example by providing the window opening of the tube with a tubular raised edge in which said envelope can be fitted in a vacuum tight manner. Long-wave X-rays are strongly absorbed by gases, notably air. Therefore, the interior of the capillary tubes is in vacuum contact with the interior of the X-ray tube which is situated within the housing, so that any gas present in said capillary tubes cannot absorb the long-wave X-rays. The end of the bundle which faces the anode of the X-ray tube can then be shaped in such a manner that maximum X-ray power is taken up by the bundle. For example, in the case of a more or less point-shaped X-ray focus (a focal spot of comparatively small dimensions in practical circumstances) all capillary tubes of the bundle can be directed towards said focus. The other end of the bundle may have an appearance adapted to the intended application of the X-ray analysis apparatus; for example, the capillary tubes at that end can all be directed towards one point again, so that the total power conducted by the bundle is concentrated onto said one point, or an X-ray focal line of a desired shape can be formed. Because of the small cross-section of the capillary tubes, the ends thereof at the exit side of the bundle constitute a surface which may serve as a fine-meshed supporting grid for the X-ray window, so that the thickness of the X-ray window may be much smaller than that of the X-ray window in customary X-ray tubes. The thickness of the X-ray window amounts to less than one micrometer in one embodiment of the invention. When a bundle serving as a fine-meshed supporting grid consists of capillary tubes of a diameter which is customary for such X-ray optical fibers (i.e. of the order of magnitude of from 10 .mu.m to 100 .mu.m), this thickness of the X-ray window can be realized without special effort. The X-ray window in another embodiment of the invention is made of a synthetic foil. For this synthetic foil use could be made of polypropylene or polyethylene naphtalate (PEN). These materials are synthetic materials containing practically exclusively elements having a low atomic number (carbon and hydrogen) so that the material of these windows absorbs only a comparatively small amount of long-wave X-rays. When said material is not commercially available as a foil of the desired thickness, it should be subjected to a treatment aimed at realizing such a small thickness prior to the manufacture of the window. This can be achieved by stretching the available foil. Said PEN, however, can be purchased in the desired thickness. A polymer X-ray window of small thickness is also marketed by MOXTEK and bears the product identification AP1.3; these windows have a polymer thickness of 300 nm, so that they can also be used for the above purpose. The X-ray window of another embodiment yet of the invention is made of diamond. Like the above-mentioned synthetic materials, diamond, consisting exclusively of carbon, has a comparatively low absorptivity for long-wave X-rays. Moreover, diamond is chemically very resistant; this may be of advantage for a variety of applications. The manufacture of diamond layers of small thickness is known per se, for example from the published German patent application ("Offenlegungsschrift") No. 39 27 132 A1.
049884760	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of a method of and an apparatus for evaluating deformations of channel boxes in accordance with the present invention will be explained below with reference to the accompanying drawings. As shown in FIG. 1, the present apparatus includes a display device 1 and a computing and processing device 2. The computing and processing device 2 consists of a computing section 2a, a procedure storing section 2b, an intermediate-data storing section 2c, an image-data outputting section 2d and an input section 2e. Data created by the computing and processing device 2 is displayed on a display screen of an image output device 4 in the form of a picture, characters and the like. An input device is denoted by 3. The illustrated apparatus also includes memory devices 5, 6, 7 and 8. The memory devices 5, 6, 7 and 8 respectively store therein data of core characteristics, data of measured deformations of channel boxes, data of material properties and shapes, and data of set loading patterns. FIGS. 2 to 5 are tables showing the contents of the data stored in the respective memory devices 5, 6, 7 and 8. The data of core characteristics, shown in FIG. 2, includes core names, core types, the three-dimensional distribution of fast neutron flux and so on. The data of measured deformations of a channel box, shown in FIG. 3, includes the name of each fuel-assembly label, the degree of exposure of each fuel assembly, and the measured values of bulge and bow. The data of set loading patterns, shown in FIG. 4, includes a map of fuel-assembly labels, a map of channel-box labels and so on for each cycle. The data of material properties and shapes, shown in FIG. 5, includes the Poisson's ratio, the flexural rigidity, the Young's modulus and the like of a channel-box material. FIG. 6 shows a procedure employing a method of and an apparatus for evaluating deformations of channel boxes in accordance with this embodiment o the basis of the above-described data. FIG. 7 is a block diagram which functionally represents this procedure. FIGS. 8 to 11 show in detail the procedures of individual portions of the procedure shown in FIG. 6. The procedure for evaluating deformations of channel boxes in accordance with this embodiment will be explained in sequence. Referring to FIG. 1, the process first proceeds to Step 21, in which the data of core characteristics, shown in FIG. 2, is inputted through the input device 3 and stored in the memory device 5. Likewise, the data of measured deformations of a channel box, shown in FIG. 3, is stored in the memory device 6. The data of material properties and shapes, shown in FIG. 4, is stored in the memory device 7, and the data of a set loading pattern, shown in FIG. 5, is stored in the memory device 8. FIG. 12 shows an example of a display provided when the data of material properties and shapes, stored in the memory device 7, is outputted to the image output device 4. FIG. 13 shows an example of a display on the image output device 4. In this display example, a result is plotted which is obtained by axially measuring creep deformation and exposure bow which occurs in a particular channel box after the third exposure cycle, and the particular channel box is shown as being identified with a channel number 413 and core-array position coordinates (4, 11) from among all the seven hundred and sixty-four channel boxes disposed in a core. The process of outputting the above-described data to the image output device 4 is executed in accordance with an output command which is inputted through a keyboard (not shown) provided on the input device 1. Then, in Step 23, setting of the exposure cycle and the loading pattern for a channel box whose deformation is to be estimated is carried out. In Step 24, the process jumps to the subroutine shown in FIG. 8. In this subroutine, the estimated deformation of the channel box whose conditions were set in Step 23 is calculated for each axial position as well as for each radial position by employing the measured-deformation data and an analytic model in the computing section 2a. The results of these calculations are stored in the intermediate-data memory section 2c. The procedure for performing these calculations is explained in detail below with reference to FIG. 8. First of all, the distribution of the fast neutron flux in the core is read from the data of core characteristics stored in the memory device 5. Moreover, the map of fuel-assembly labels and the map of channel-box labels are read from the set loading pattern stored in the memory device 8 so that the computing and processing device 2 is made to recognize the correspondence between fuel assemblies as or channel boxes and respective loading positions in the core. On the basis of the data thus read, calculations on fast neutron flux .phi. are performed (Step 24A). The result of a core-characteristic calculation program is employed as the fast neutron flux .phi.. However, since the fast neutron flux .phi. corresponding to the midpoint of each fuel assembly in the core is already given, the fast neutron flux .phi. at each side surface of the channel box, in which the fuel assembly is loaded, is obtained by interpolating the fast neutron flux .phi. between adjacent fuel assemblies. Fast-neutron fluence FU is calculated with the following equation (Step 24B): EQU FU=.phi..sup.. t (9) where .phi. : fast neutron flux, and t : exposure time. Then, regarding a channel box which has been actually loaded in the nuclear reactor and extracted therefrom after exposure for the purpose of measuring its deformation, the measured value of the deformation is read from the memory device 6 (Step 24C) and the read value is used as an initial value. With respect to a channel box whose measured value is not available, an estimated value obtained by calculations is employed. Moreover, the data of material properties and shapes is read from the memory device 7. In addition, the amount of bulge and the amount of bow are calculated in Steps 24D and 24E, respectively. Thereafter, the total sum of these deformations is obtained (Step 24F). These calculations are performed for each of the channel boxes of all the fuel assemblies loaded in the core (Step 24G). Moreover, the above calculations are performed for all the loaded fuel assemblies in each cycle having a set cycle period, for example, in each of the first to fifth cycles (Step 24H). The total deformation D(z) of the channel boxes calculated in the flow chart of FIG. 8 is given by the following equation: EQU D(z)=.delta..sub.O +.delta.+.DELTA..delta.+X(z) .delta..sub.O : initial deformation, .delta. : elastic deformation, .DELTA..delta. : increment of bulge, and X(z) : displacement due to bowing. The analysis method is explained in detail below. The deformation of a channel box is represented by the sum of bulge and bow. The bulge at an axial position z is represented by the sum of the elastic deformation .delta. and the increment .delta..DELTA. of the bulge for a time interval .DELTA.'t. These amounts .delta. and .DELTA..delta. are obtained from the following equations: ##EQU1## EQU .DELTA..delta.=R.epsilon..DELTA.t (2) where P : load resulting from differential pressure, L : width of the channel box, and R : radius of curvature of the bow (mm). Flexural rigidity D and the creep rate .epsilon. of a zircalloy are obtained from the following equations: ##EQU2## where E : Young's modulus, .upsilon. : Poisson's ratio, d : thickness of the channel box, T : temperature of the channel box (K), .phi. : fast neutron flux (1/mm.sup.2. s) (En>1Mev), and .sigma. : tensile stress. The fast neutron flux .phi. in equation (4) is the one obtained by the calculations performed in Step 24A of the procedure shown in FIG. 8. As described previously bowing results from the irradiation growth of the zircalloy. If a bending moment which is applied to a channel box due to the irradiation growth in the axial direction z of the same is represented by Mx in the x direction, displacement X(z) due to bowing in the x direction at a position z in the axial direction is obtained from the following equation based on the beam theory: ##EQU3## where Ix : second moment of area with respect to the X axis The bowing moment Mx and irradiation growth strain .epsilon.j (.DELTA.H/H) are obtained from the following equations, respectively: ##EQU4## where .DELTA.S.sub.j : area of a finely divided region of the channel box, H : height of the channel box, A : constant (=1.435.times.10.sup.-13), t : exposure time (S), and FU.sub.j : fast-neutron fluence. The fast-neutron exposure FU.sub.j in equation (7) is the one obtained by the calculations performed in Step 24B. By solving equation (5) by employing equations (6) and (7), the displacement X(z) due to bowing is obtained. The total displacement D(z) of the channel box which is the sum of bow and bulge is obtained from the following equation: EQU D(z)=.delta..sub.O +.delta.+.DELTA..delta.+X(z) (8) A load P which is derived from a differential the fast-neutron flux .phi. and a temperature T is obtained by nuclear calculations and hydrothermal calculations, and is stored as data of core nuclear properties. The width L, the height H and the thickness d of the channel box as well as the Young's modulus E and the Poisson's ratio .TM. of the zircalloy are stored as data of material properties. As data of the measured value of initial deformation of the channel box, .delta.0 in equation (8) is stored. The results of the above calculations on bulge, bow and deformation are transferred to and stored in the intermediate-data storing section 2c. Then, on the basis of the results of the calculations on the deformation of the channel box, stored in the intermediate-data storing section 2c, the computing and processing section 2a uses the subroutine of FIG. 9 to determine whether or not interference has occurred between the channel box 9 and the control rod 12 (hereinafter referred to simply as "interference judgment" as required), the channel box 9 being a channel box in which set assemblies are loaded (step 25 in FIG. 6). In the flow chart of FIG. 9, the data obtained from the intermediate-data storing section 2c in Step 24 of FIG. 6 that is, the results of the calculations performed on the deformation of the channel boxes of all the loaded fuel assemblies during the set cycle period are read out (Step 25A). Then, channel boxes which are to be subjected to the above interference judgment are selected in a predetermined sequence. This sequence is stored in memory (Step 25B). With respect to all the fuel assemblies loaded in the core, whether or not the control rods interfere with the associated channel boxes is determined (Step 25C). The above interference judgment is made as to each of the four blades of each cross-shaped control rod in units of cells each consisting of four assembly channel boxes as shown in FIG. 24. FIG. 24 is a cross-sectional view showing the arrangement of the cross-shaped control rod and channel boxes each of which accommodates a fuel assembly. As shown in the figure, each cell unit includes the four channel boxes 9, the control rod 12, control-rod rollers 13, and fuel channel boxes A, B, C and D. If the four fuel assemblies in the cell are represented by A, B, C and D, respectively, and if the inner side surfaces of each of the channel boxes are respectively called a side 1, a side 2, a side 3 and a side 4 in the clockwise direction as viewed in FIG. 24 with the side 1 corresponding to the upper side surface as viewed in this figure, judgment is made as to the interferences between a side A-3 and a side B-1, between a side B-4 and a side C-2, between a side C-1 and a side D-3, between a side C-1 and a side D-3, and between a side D-2 and a side A-4. The interference judgment is made as to each of the areas of the channel box which have been divided in the axial direction thereof. For example, the state shown in FIG. 25a is not regarded as interference, but the state shown in FIG. 25b is regarded as interference. Referring back to FIG. 9, selection of a channel box which is to be subjected to interference judgment and interference judgment as to the channel box are automatically performed in the computing and processing section 2a (Step 25D). The above interference judgment is made as to each of the fuel assemblies loaded in the core for all the specified operating cycles (Step 25C). The obtained results of the interference judgement are transferred to and stored in the intermediate-data storing section 2c (Step 25F). Then, these results of the interference judgment and the results of the associated calculation are displayed in the form of a table or a figure (Step 26 in FIG. 6). FIG. 11 shows in detail the procedure of a displaying portion of the flow chart shown in FIG. 6. In this portion, the results of the interference judgment and the results of the associated calculation are read from the intermediate-data storing section 2c. Subsequently, an operator specifies a display region through the input device 1 in order to determine a position in the core which corresponds to the result to be displayed. When the results of the calculation and the judgment are to be displayed, a particular region in the core can be specified from among the following three regions: 1) a region corresponding to all the channel boxes in the core; 2) a region corresponding to the channel boxes positioned in a specified partial region in the core (1/2 core or 1/4 core); and 3) a region corresponding to an arbitrary single channel box. Moreover, after a particular display region has been determined, the operator likewise selects and specifies a desired display method through the input device 1. It is possible to select the display method between two kinds of methods: one method utilizes a table, while the other method utilizes a figure. On the basis of information representing these specifications, the computing section 2a creates image data, and this image data is output through the image-data output section dd to the image output device 4 for display purposes. FIG. 14 shows a display example in which the result of judgment is outputted in a table form. FIG. 14 illustrates a display of axial deformations of a particular channel box after the third cycle of exposure has been completed, this channel box being identified with a channel number 413 and core position coordinates (11, 9). In the display output shown in FIG. 14, the status of deformation of one arbitrarily set channel box, and the results of interference judgment as to the same are collectively outputted in a table form. FIG. 15 shows a display example in which the same information is output in the form of a figure. In the display output shown in FIG. 15, the status of deformation of the arbitrary set channel box, namely, bend and bulge are displayed on corresponding figures each of which simulates the channel box. FIG. 16 shows a display example of the deformations of a plurality of channel boxes after the seventh cycle has been completed, the channel boxes being located at different positions in a partial region which corresponds to 1/4 of the overall region in a core A. In the display output shown in FIG. 16, the statuses of deformations of the respective channel boxes in the partial region which has been set in the core A, loading positions in the core A and the number of exposure cycles are collectively outputted in a table form. FIG. 17 shows a display example in which the same information is outputted in the form of a figure. In the display output shown in FIG. 17, the statuses of deformations of the channel boxes in the partial region (1/4 core) which has been set in the core A are represented in different colors each indicating a different degree of maximum deformation, and the thus-colored statuses are displayed on a figure which simulates the partial region in the core A. FIG. 18 shows another display example in which the result of judgment is output in a table form. FIG. 18 is a display example which shows data of particular channel boxes, located at five positions at which interference has occurred, from among all the channel boxes in the core A which have passed the sixth cycle. In the display output shown in FIG. 18, the statuses of deformations of the channel boxes which have interfered with associated control rods from among all the channel boxes in the core A, the loading positions of the channel boxes in question and the number of exposure cycles are collectively outputted in a table form. FIG. 19 shows a display example in which the same information is outputted in the form of a figure. In the display output shown in FIG. 19, the positions of the channel boxes which have interfered with associated control rods from among all the channel boxes in the core A are displayed on a figure which simulates the entire region of the core A. In the entire procedure, if no interference occurs between any channel box and the associated control rod in the set core region and during the set cycle period as shown in FIG. 6, the process is completed. On the other hand, if interference occurs between a particular channel box and the associated control rod, the core loading position at which it is estimated that the channel box in question does not interfere with the associated control rod, a shuffling pattern and a loading direction are reset (Step 28 in FIG. 6). FIG. 10 shows a subroutine for this resetting. First of all, the results of interference judgment obtained in Step 25 of FIG. 6 are read from the intermediate-data storing section 2c (Step 28A). A loading pattern according to which the fuel-assembly channel boxes which have caused interference are to be moved is reset (Step 28B). Several resetting methods are prepared so that the operator can select a desired method on a display screen. For example, information such as that shown in FIG. 21 is displayed on the screen of the display device 4. The operator selects the required rule while viewing the display screen. The selected rule is inputted to the computing section 2a through the input device 3. Typical examples of the rules are as follows: (1) a rule that channel boxes which have caused interference are moved to the positions of interchangeable assemblies which have been used for exposure in the same exposure cycle; (2) a rule that two side surfaces which oppose an associated control rod are not altered in position in each cell; (3) a rule that a channel box in question is moved to a position in the core and a position in a cell so that a side surface, which bow in a protrusive manner from the first cycle through an (n-1)th cycle which preceded an n.sup.th cycle in which interference occurred, is made to face outwardly of the core in the n.sup.th cycle; and (4) a rule that a channel box in question is moved to the position in a cell at which the direction of bowing occurring during the exposure time of the n.sup.th cycle is a direction away from an associated control rod. Then, a channel box which satisfies the rule selected by the operator is automatically selected from among all the channel boxes by the computing and processing section 2a (Step 28C). At this time, a plurality of interchangeable channel boxes which can satisfy the selected rule are present and a single channel box is therefore selected from among them. In this selection, the computing and processing section 2a may automatically select the required rule, or the operator may select the desired rule while viewing a guidance displayed on the display screen. In the case of automatic selection by the computing and processing section 2a, a channel box whose deformation occurring from the first cycle through the (n-1)th cycle is at a minimum is selected from among the channel boxes which satisfy a specified rule. In the case of manual selection by an operator, the display device is caused to display a guidance which informs the operator of the positions in the core at which channel boxes, which satisfy the specified rules, are loaded, and the operator selects the desired channel box on the basis of the guidance. In one typical guidance method, on the basis of set rules, a target core position which conforms to each of the rules and core positions which satisfy all the rules are displayed. FIG. 20 shows a display example of the guidance. FIG. 20 is a display example obtained by specifying the core A and a 1/4 core region, and shows the position of a channel box which caused interference after the third cycle as well as interchangeable positions. In this embodiment, on the basis of these guidances, the operator selects another channel box to be substituted for a channel box which has caused interference, so as to realize an optimum loading pattern. Data of the thus-selected channel box is inputted through the input device 3 to the computing and processing section 2a. Thereafter, the channel box selected in Step 28C is substituted for the channel box which has caused interference (Step 28D). Thus, the selected channel box which has been loaded in the position of the channel box which made interference is loaded in the position of the channel box which suffered interference. The above operations are repeated for all the channel boxes which have caused interference (Step 28E). When the positions to which all the channel boxes that have made interference are to be moved are found, the result of this resetting is transferred to and stored in the intermediate-data storing section 2c (Step 28F). The loading pattern obtained by such resetting is displayed on the display screen and, at the same time, is stored in the intermediate-data storing device 2c. FIG. 22 shows an example of the display. FIG. 22 shows a display example in which channel boxes in the core A have been reset in accordance with certain rules. When the processing in Step 28 of FIG. 6 is completed, Steps 24, 25 and 28 in FIG. 6 are repeated on the basis of a method of using the reset channel boxes, thereby maximizing the number of channel boxes which do not interfere with associated control rods throughout a set exposure period. If it is judged here that no matter how the loading position of the channel box which has been used for exposure is set in the reactor, interference with an associated control rod will occur during an exposure period, a display which indicates that the channel box cannot be used is provided on the display screen and, in addition, detailed information such as the shuffling pattern, the loading direction and the operating hysteresis of the channel box in question is displayed on the display screen. As described above, in the above-described embodiment, in the step of resetting a loading pattern on the basis of the results of judgment as to interference between a channel box and an associated control rod, a guidance for a loading pattern which causes no interference is displayed on the display screen, the guidance being based on previously set restricting conditions and rules. An operator determines an optimum loading pattern while viewing the guidance. However, in the process of resetting a loading pattern, the resetting pattern may be stored in the memory device 8 so that it can be automatically selected. As another embodiment, a procedure such as that shown in FIG. 26 is available. The contents of processing carried out in each step are substantially the same as the contents of processing executed in the aforesaid embodiment. However, by repeating Steps 23, 24, 25 and 26 in FIG. 6 with respect to all the channel boxes loaded in a core in each cycle throughout the loading period thereof, it is possible to set the loading patterns of all the channel boxes for each cycle. As described above, in the above-described embodiment, in the step of resetting a loading pattern on the basis of the results of judgment as to interference between a channel box and an associated control rod, a guidance for a loading pattern which causes no interference is displayed on the display screen, the guidance being based on previously set restricting conditions and rules. An operator determines an optimum loading pattern while viewing the guidance. However, in the process of resetting a loading pattern, the resetting pattern may be stored in the memory device 8 so that it can be automatically selected. The use of a method of and an apparatus for evaluating deformations of channel boxes in accordance with the present invention makes it possible to precisely estimate deformations of channel boxes during their loading period in a reactor and, on the basis of the result of this estimation, judgment is made as to whether each channel box has interfered with an associated control rod or not. If interference is estimated to occur, the loading positions, the shuffling pattern, and the loading directions of the channel boxes in question are reset so as to prevent interference. In this manner, it is possible to maximize, while insuring safety, the number of channel boxes which can be used even when the loading period in the reactor is extended. Accordingly, it is possible to reduce the fuel cycle cost and the number of waste channel boxes. It is, therefore, possible to suppress an increase in the space required to store the waste channel boxes. Briefly stated, in accordance with the present invention, it is possible to provide a method of and an apparatus for evaluating deformations of channel boxes, both of which make it possible to readily judge whether or not interference has occurred between each channel box and an associated control rod during the loading period in a reactor. With the method and apparatus described above, it is possible to select and set a channel-box using method in which the number of channel boxes which do not interfere with associated control rods can be maximized.
046845020	abstract	An alignment sleeve capture arrangement in the top nozzle of a fuel assembly includes an internal cylindrical wall defining a bore through the upper hold-down plate of the top nozzle below and in communication with a passageway therein through which extends an alignment sleeve of the top nozzle which is used to attach it to the guide thimble of the fuel assembly. The bore has an inside diameter larger than the inside diameter of the passage so as to form a cavity surrounding an upper position of the alignment sleeve which extends axially through the bore as well as the passageway. Also, the arrangement includes an annular shoulder on the upper hold-down plate surrounding the alignment sleeve upper portion and defining an upper limit of the cavity. The shoulder forms a transition between the larger inside diameter of the bore and the smaller inside diameter of the passageway. Additionally, an annular retainer is attached to the upper hold-down plate and spaced below the shoulder. The retainer surrounds the alignment sleeve upper portion and has a neck portion with a central hole through which the alignment sleeve extends and defines a lower limit of the cavity. Lastly, the arrangement includes a bearing ring encircling and attached to the alignment sleeve upper portion and having an outside diameter less than the inside diameter of the cavity and greater than respective inside diameters of the shoulder and retainer neck portion which define the upper and lower limits of the cavity such that the bearing ring can slide within the cavity with the alignment sleeve between the upper and lower limits thereof as the upper hold-down plate moves along the alignment sleeve and will retain the alignment sleeve slidably attached to the hold-down plate when the sleeve is detached from the guide thimble upper end portion. The retainer also has a hollow body portion with one end attached to the hold-down plate and an opposite end integrally connected with the neck portion, the retainer body portion defining a portion of the cavity.
054406005	claims	1. A stator core comprising a plurality of elements laminated together in a circumferential array, each of said elements being arranged between a pair of adjacent elements and having first and second planar radial surfaces which lie in respective radial planes intersecting a centerline axis of said stator core, said first planar radial surface of each one of said elements being in contact and opposing said first planar radial surface of an adjacent one of said elements, and said second planar radial surface of each one of said elements being in contact and opposing said second planar radial surface of an adjacent one of said elements, said first and second planar radial surfaces being disposed at an acute angle relative to each other, each of said elements having a key-shaped profile with a generally square back and an elongated shank, said square back being radially inward of said elongated shank, each of said elements further comprising: 2. A core according to claim 6 wherein: said perimeter extends completely around said element along both said inner and outer edges; and adjacent ones of said elements are disposed in back-to-back pairs with each pair being in abutting contact completely around said perimeter thereof, and next adjacent elements being in abutting contact completely along said elevations thereof. 3. A core according to claim 2 wherein each of said elements is a sheet metal component having a depression, said depression forming said central recess on said first side and said central elevation on said second side. 4. A stator core comprising a plurality of elements laminated together in a circumferential array, each of said elements being sandwiched between a pair of adjacent elements and having first and second planar radial surfaces which lie in respective radial planes intersecting a centerline axis of said stator core, said first planar radial surface of each one of said elements being in contact and opposing said second planar radial surface of an adjacent one of said elements, said first and second planar radial surfaces being disposed at an acute angle relative to each other, each of said elements being a solid wedge with no gaps in the volume between said first and second planar radial surfaces. 5. The stator core as defined in claim 4, wherein each of said elements has a radially inner edge and a radially outer edge, said radially inner edges forming an radially inner bore of said stator core and said radially outer edges forming a radially outer circumference of said stator core. 6. The stator core as defined in claim 4, wherein each of said elements has a key-shaped profile with a generally square back and an elongated shank, said square back being radially inward of said elongated shank. 7. The stator core as defined in claim 4, wherein each of said elements is a plate having a tapered thickness, said thickness increasing linearly in a radial direction. 8. The stator core as defined in claim 7, wherein each of said plates is made of iron. 9. The stator core as defined in claim 4, wherein each of said elements is a plate of constant thickness with a depression formed therein, said first planar radial surface comprising a planar surface on the perimeter of a recess formed on one side of said respective element by said depression and said second planar radial surface comprising a planar surface on a projection formed on the other side of said respective element by said depression. 10. A linear flow electromagnetic induction pump comprising an inner stator and an outer stator for impelling liquid metal through an annular flow channel therebetween, each of said inner and outer stators comprising a multiplicity of alternately stacked stator cores and stator coils, wherein each stator core of said inner stator comprises a plurality of elements laminated together in a circumferential array, each of said elements being sandwiched between a pair of adjacent elements and having first and second planar radial surfaces which lie in respective radial planes intersecting a centerline axis of said stator core, said first planar radial surface of each one of said elements being in contact and opposing said second planar radial surface of an adjacent one of said elements, said first and second planar radial surfaces being disposed at an acute angle relative to each other. 11. The linear flow electromagnetic induction pump as defined in claim 10, wherein each of said elements has a radially inner edge and a radially outer edge, said radially inner edges forming an radially inner bore of said stator core and said radially outer edges forming a radially outer circumference of said stator core. 12. The linear flow electromagnetic induction pump as defined in claim 10, wherein each of said elements has a key-shaped profile with a generally square back and an elongated shank, said square back being radially inward of said elongated shank. 13. The linear flow electromagnetic induction pump as defined in claim 10, wherein each of said elements is a plate having a tapered thickness, said thickness increasing linearly in a radial direction. 14. The linear flow electromagnetic induction pump as defined in claim 13, wherein each of said plates is made of iron. 15. The linear flow electromagnetic induction pump as defined in claim 9, wherein each of said elements is a plate of constant thickness with a depression formed therein, said first planar radial surface comprising a planar surface on the perimeter of a recess formed on one side of said respective element by said depression and said second planar radial surface comprising a planar surface on a projection formed on the other side of said respective element by said depression.
054405980	summary	TECHNICAL FIELD The present invention relates to nuclear reactors and particularly to an arrangement and use of neutron absorbing materials such as gadolinia in the fuel rods of the bundle to enhance plutonium utilization in the reactor. BACKGROUND Increasingly, there is interest in the capabilities of nuclear reactors to transform and thereby destruct through reactor burnup large quantities of weapons grade plutonium. It is common, e.g. in boiling water reactors, to employ fissionable material, such as uranium and minor amounts of other fissionable materials, such as plutonium or thorium in the fuel pellets. Additionally, neutron absorbers are frequently used in the nuclear fuel pellets to control the inherent excess reactivity of the fuel in the core to achieve greater efficiency and economy and to prolong the service life of the fuel. For example, in boiling water reactors, uranium, which has initial excessive reactivity, is combined with a depletable neutron absorber, commonly referred to as a burnable poison, such as gadolinium. This initial excessive fuel reactivity is tempered by the introduction of the depletable neutron absorber which progressively expends its capacity to absorb neutrons. Thus, the burnable poison absorbs excess neutrons to level or stabilize the fuel reactivity rate during the period of initial excessive reactivity and then subsequently absorbs neutrons at a decreasing rate approximately commensurate with the diminishing reactivity of the fuel whereby a substantially constant rate of reactivity is maintained. In a typical boiling water reactor, the vast majority of the fuel rods of a fuel bundle comprise fissile uranium material with only a very few of the rods having a combination of the fissile uranium and a burnable poison, such as gadolinium. While plutonium has previously been considered as an alternate fuel for boiling water reactors, as well as a combination of fissile uranium and plutonium with a burnable poison, for example, see U.S. Pat. No. 5,089,210 of common assignee herewith, it has been commonly believed that there is a severe limitation with respect to the quantity of plutonium which may be used in boiling water reactors. Particularly, it has previously been thought that no more than about one-quarter of the fuel rods in a reactor may be loaded with plutonium or mixed oxide fuel without unacceptable operational consequences. Also, reactor designers heretofore believed the presence of plutonium would interfere with the effectiveness of the gadolinium reactivity control. This is indeed the case when gadolinium is loaded into 10 to 20% of the rods, as is typical in reactors of this type. Hence, use of plutonium as a fuel in nuclear reactors has been inhibited by these and other considerations. DISCLOSURE OF THE INVENTION In accordance with the present invention, it has been found that a combination of urania, plutonia and gadolinia may be employed in the fuel rods in a manner to enhance utilization of plutonia, as a fuel for the nuclear reactor, provided the fuel rods are specifically arranged in each fuel bundle in conjunction with an extensive use of burnable poison in the fuel bundle. More particularly, it has been found that if the gadolinium is disposed in the interior fuel rods in combination with fissile uranium and plutonium and the exterior rods forming the perimeter of the fuel bundle are void of gadolinium, plutonium usage as a fuel in the reactor may be enhanced without destabilizing the power level of the reactor. The plutonium is preferably contained in all of the fuel rods of the bundle in various percentages. As well known, the reactivity of a fuel bundle containing enriched uranium and gadolinium over time produces a characteristic reactivity curve, which each fuel bundle must approximate if overall steady-state power levels in the nuclear reactor are to be maintained. By combining the fissile materials of uranium and plutonium with gadolinium, the burnable poison, in a typical fuel bundle arrangement, a characteristically different reactivity curve than the desired curve is produced. It has been found, however, that by arranging the individual fuel rods containing the uranium, plutonium and burnable poison in an interior array of the rods and effecting more extensive use of the burnable poison, the characteristic reactivity curve of a typical enriched uranium fuel bundle with modest use of the burnable poison in largely separated fuel rods, may be approximated enabling steady-state power levels in the reactor. That is, the fuel bundle design containing the plutonium fuel desired to be transformed has reactivity characteristics which closely resemble the reactivity characteristics normally associated with enriched uranium fuel. In a preferred embodiment according to the present invention, there is provided a nuclear fuel bundle comprising a plurality of fuel rods arranged in a generally square array, each of the rods having a predetermined concentration of fissile material with at least a majority of the rods including plutonium, a predetermined number of the rods having a concentration of a material for absorbing neutrons, the predetermined number of rods constituting an interior array thereof, all of which predetermined number of rods lie within a surrounding exterior array of fuel rods of the plurality thereof, the predetermined number of rods in the interior array thereof being in excess of 20% of the total number of the plurality of rods in said fuel bundle. In a further preferred embodiment according to the present invention, there is provided a nuclear fuel bundle comprising a plurality of fuel rods arranged in the bundle, each of the rods having a predetermined concentration of fissile material with at least a majority of the rods including plutonium and a predetermined number of the rods having a concentration of material for absorbing neutrons. The fuel bundle also has a reactivity curve substantially corresponding to the reactivity curve illustrated in FIG. 4c. In a still further preferred embodiment according to the present invention, there is provided in a nuclear reactor core having a plurality of fuel bundles, at least a first bundle of the plurality thereof containing a plurality of fuel rods having a concentration of enriched uranium with certain of the rods thereof having a concentration of a burnable poison, the first bundle having a reactivity curve substantially corresponding to the reactivity curve of FIG. 2c and at least a second bundle of the plurality thereof containing a plurality of fuel rods each having a concentration of enriched uranium and plutonium and certain of the rods of the second bundle forming an interior array thereof having a concentration of burnable poison surrounded by an exterior array of rods void of the burnable poison, the second bundle having a reactivity curve substantially corresponding to the reactivity curve of FIG. 4c. Accordingly, it is a primary object of the present invention to provide, in a nuclear reactor, enhanced usage of plutonium as a reactor fuel.
	description	The present disclosure relates generally to nuclear reactors and more specifically to devices for securing core shrouds in nuclear reactors. Boiling water reactors have a core shroud that holds the fuel in proper alignment with the control rod drives so that the plant can shut down safely. The core shroud has circumferential welds that hold cylinders of the shroud together to maintain alignment. Some of these circumferential welds have indications which require some type of repair to allow continued safe operation. U.S. Pat. No. 5,402,570 discloses a method for repairing boiling water reactor shrouds using a plurality of tie rods that apply vertical compressive forces to the shrouds. U.S. Pat. No. 5,809,100 discloses a method and tool for measuring a preload on tie rods applying forces to nuclear reactor core shrouds. FIG. 1 shows a perspective view of a shroud comprising a larger shroud cylinder 114 positioned above a smaller shroud cylinder 112. The shroud further includes a disc section (middle ring) connecting the larger shroud cylinder 114 to the smaller shroud cylinder 112 through two circumferential welding conventionally named H2 and H3 welds. FIG. 1 furthermore shows a plurality of blocks 110 that are bolted across the H2 and H3 welds to secure the smaller shroud cylinder 112 and the larger shroud cylinder 114 to each other. These repairs include (i) a multitude—e.g., approximately twelve, of these blocks (ii) with bolts 116 fixing blocks 110 to cylinders 112, 114 passing entirely through cylinders 112, 114. Both features (i) and (ii) are needed to achieve the axially and radially support for the shroud cylinders in operation. A securing device is provided for installing on an outer circumferential surface of a nuclear reactor core shroud and in contact with an inner circumferential surface of a pressure vessel. The securing device includes a base configured for contacting the outer circumferential surface of the nuclear reactor core shroud. The securing device also includes a radial extender including an actuator, a stationary support section fixed to the base and a movable contact section. The radial extender is configured such that the movable contact section is movable along the stationary support section by the actuator to force the movable contact section radially into the inner circumferential surface of the pressure vessel. A method for installing a securing device on an outer circumferential surface of a nuclear reactor core shroud and in contact with an inner circumferential surface of a pressure vessel is provided. The method includes fixing a base of the securing device to outer circumferential surface of the nuclear reactor core shroud; and moving an actuator of the securing device to force a movable contact section of the securing device along a stationary support section of the securing device to force the movable contact section radially into the inner circumferential surface of the pressure vessel. One problem with conventional techniques is that they are very expensive to implement, due to excessive time required for installation and the expense of the hardware to be fabricated for the repair. Another problem with the conventional technique represented in FIG. 1 is that the through holes in the shroud cylinders impact the tightness of the shroud and the bolts emerging inside the shroud cylinders impact the fluid flow inside of shroud cylinders. The present disclosure provides a securing device with lateral support to reduce the quantity of repairs needed to provide the securing device for safe operation. The securing device of the present disclosure utilizes underwater threading of a blind hole to allow the bases of the securing device to be bolted directly to the core shroud without making a through hole, reducing the bypass fluid flow inside the core shroud that is associated with repairs that go entirely through the wall of the shroud. Advantages of the securing device of the present disclosure may be as follows: providing axial and radial support for welds on the core shroud with a minimal number of securing devices installed (potentially only four securing devices of the present disclosure circumferentially spaced at 90 degree increments, compared with approximately twelve as shown in FIG. 1); attaching the securing devices of the present disclosure to the shroud does not increase bypass fluid flow within the shroud; and the tapered wedge design of the securing devices of the present disclosure allows the lateral support of the securing device to be adjusted during installation for optimal fit with respect to the pressure vessel, allowing for thermal expansion during operation (belleville washers may be utilized to allow compliance on the lateral supports). FIG. 2 schematically shows a nuclear reactor core shroud assembly 10 that is surrounded by a nuclear reactor pressure vessel in a nuclear reactor. Shroud assembly 10 is centered on a vertically extending longitudinal center axis CA. As used herein, the terms circumferential, radial, axial and derivatives thereof are defined with respect to center axis, unless otherwise specified. Shroud assembly 10 includes a shroud 12 that surrounds nuclear fuel assemblies and is surrounded by a plurality of jet pump assemblies 14 that are provided in an annular space, known as a downcomer annular, radially between shroud 12 and the pressure vessel. Each jet pump assembly 14 includes two jet pumps 16 that are coupled to a riser pipe 18 by a ram's head 20. Water enters riser pipe 18, passes through ram's head 20 and is then driven downward into an inlet mixer 22 by drive nozzles 24. FIGS. 3 and 4 show perspective views of a securing device 30 in accordance with an embodiment of the present invention installed on an outer circumferential surface 32 of shroud 12 above jet pump assemblies 14. FIG. 4 shows how securing device 30 is wedged radially between outer circumferential surface 32 of shroud 12 and an inner circumferential surface 34 of pressure vessel 36. As shown in FIGS. 3 and 4, shroud 12 includes a first cylindrical section 38 and a second cylindrical section 40 having an outer diameter that is less than first cylindrical section 38. First cylindrical section 38 is positioned above second cylindrical section 40. Shroud 12 further includes a disc section 42 connecting first cylindrical section 38 to second cylindrical section 40. Disc section 42 extends radially inward from first cylindrical section 38 to second cylindrical section 40. Sections 38, 40, 42 together define outer circumferential surface 32 of shroud 12, with section 38 defining a first outer circumferential surface section 32a, section 40 defining a second outer circumferential surface section 32b, and disc section 42 defining a third outer circumferential surface section 32c. Sections 38, 42 have the same outer diameter, which is greater than the outer diameter of section 40. Disc section 42 is fixed to first cylindrical section 38 by a first weld 44—known as the H2 weld—and is fixed to second cylindrical section 40 by a second weld 46—known as the H3 weld. Over time, welds 44, 46 have indications which require some type of repair to allow continued safe operation of shroud 12. Securing devices 30 are applied to shroud 12 to radially secure sections 38, 40, 42 with respect to each other to allowed continued operation of shroud 12. As shown in FIGS. 3 and 4, securing device 30 includes a stepped base 48 that is configured for contacting outer circumferential surface 32 of shroud 12. Base 48 includes a first radial contact section 50 having a contact surface 50a configured for radially contacting first outer circumferential surface section 32a and for radially contacting third outer circumferential surface section 32c. Base 48 also includes a second radial contact section 52, which is radially offset from first radial contact section 50, having a contact surface 52a configured for radially contacting second outer circumferential surface section 32b. Base 48 further includes an axial contact section 54, which connects radial contact sections 50, 52, having a contact surface 54a configured for axially contacting a lower radially extending surface 42a of disc section 42. Securing device 30 further includes a radial extender 56 configured for pressing against inner circumferential surface 34 of pressure vessel 36 to wedge securing device 30 radially between outer circumferential surface 32 of shroud 12 and inner circumferential surface 34 of pressure vessel 36. Radial extender 56 includes a first portion in the form of a stationary support portion 58 rigidly fixed to base 48 and a second portion in the form of a movable contact portion 60 that is radially movable with respect to base 48 by an actuator 62 of radial extender 56. As described further below, stationary support portion 58 includes a sloped surface 64 (FIGS. 5a, 5b) and movable contact portion 60 includes a sloped surface 66 (FIGS. 5a, 5b). Portions 58, 60 are configured such that axial movement of movable contact portion 60 by actuator 62 moves movable contact portion 58 radially with respect to base 48 and stationary support portion 58. The axial movement of movable contact portion 60 varies a radial distance between contact surface 50a of base 48 and a contact surface 56a of radial extender 56. Base 48 includes a plurality of holes 50b, 52b passing radially therethrough. More specifically, first radial contact section 50 includes two holes 50b passing radially therethrough and second radial contact section 52 includes two holes 52b passing radially therethrough. Holes 50b pass from contact surface 50a to an outer surface 50c of first radial contact section 50 and holes 52b pass from contact surface 52a to an outer surface 52c of second radial contact section 50. Each of holes 50b, 52b receives a respective fastener 68, 70, which in a preferred embodiment are bolts, for mounting securing device 30 on shroud 12. Each of fasteners 68, 70 includes a respective threaded shank 68a, 70a (FIGS. 5a, 5b) that extends through the respective hole 50b, 52b into a respective one of a plurality of threaded blind holes 72, 74 formed in shroud 12 such that the threads of shanks 68a, 68b and holes 72, 74 intermesh to fix securing device 30 to shroud 12. In particular, first cylindrical section 38 includes two threaded holes 72 formed therein extending from outer circumferential surface section 32a into first cylindrical section 38, without breaching an inner circumferential surface 38a of section 38, and second cylindrical section 40 includes two threaded holes 74 formed therein extending from outer circumferential surface section 32b into second cylindrical section 40, without breaching an inner circumferential surface 40a of section 40. FIGS. 5a, 5b show exploded views of securing device 30. As shown in FIGS. 5a, 5b, base 48 is formed integrally as a single piece with stationary support portion 58. Stationary support portion 58 protrudes radially from outer surface 50c of first radial contact section 50 and forms a first wedge part 51 including three walls 76, 78, 80 extending from outer surface 50c that define a receptacle 82 configured for receiving a first end 60a of movable contact portion 60. First and second walls 76, 78 define identical side walls of support portion 58 and third wall 80 defines a bottom wall. Third wall 80 includes a threaded axially extending hole 84 passing entirely therethrough axially and configured for receiving a portion of actuator 62. Walls 76, 78 each have a tapered irregular prism shape such that walls 76, 78 become progressively larger in the radial direction as walls 76, 78 extend downward toward bottom wall 80. Walls 76, 78, 80 together form sloped surface 64 of support portion 58. In particular, each of walls 76, 78 includes a respective sloped surface section 76a, 78a that extends further away from first radial contact section 50 as surface sections 76a, 78a extend downward. In the embodiment shown in FIGS. 5a, 5b, wall 80 also includes a sloped surface section 80a that is coincident and coextensive with surface sections 76a, 78a; however, in other embodiments surface section 80a may have a different shape. Movable contact portion 60 includes a first end 60a for moving axially and vertically within receptacle 82 and a second end 60b configured for contacting inner circumferential surface 34 of pressure vessel 36 via contact surface 56a. First end 60a includes an insertion section 86 that is axially slidable within receptacle 82 between side walls 76, 78 and toward and away from bottom wall 80. Insertion section 86 includes a radially elongated slot 87 passing axially therethrough that is configured for receiving actuator 62. Insertion section 86 is connected to a second wedge part 89 and laterally between side walls 88, 90 of second wedge part 89 that form sloped surface 66. Walls 88, 90 each include a sloped surface section 88a, 90a forming sloped surface 66. Walls 88, 90 are shaped such that sloped surface 66 has a complementary shape to sloped surface 64, causing sloped surface 64 to rest flush against sloped surface 66 while movable contact portion 60 is being moved axially and radially by actuator 62. Contact portion 60 further includes an arm 92 extending radially from wedge part 89 to a stop 94, which is provided on second end 60b, that includes contact surface 56a, which defines a radial outermost surface of securing device 30. Actuator 62 is formed as a bolt including a head 96 and a threaded shank 98. Actuator 62 is centered on insertion section 86 between walls 88, 90 by a washer 100. Washer 100 includes a square base 102 configured for sliding in contact with lateral surfaces of walls 88, 90 as actuator 62 is moved between radial ends of elongated slot 87. Actuator 62 is axially movable in elongated slot 87 due to a radial length of slot 87 being greater than a diameter of shank 98. Base 102 contacts a radially inner surface of an outer wall 104 of wedge part 89 when actuator 62 is at a radially outermost position of actuator 62. Outer wall 104 extends laterally between side walls 88, 90. During the axial movement of actuator 62, base 102 moves radially along walls 88, 90 and toward or away from outer wall 104. Washer 100 further includes a cylindrical centering wall 106 extending axially upward from base 102 that is configured for receiving head 96 to align actuator 62. FIG. 6 shows a top plan view of securing device 30 with portions 58, 60 connected together by actuator 62. In the view in FIG. 6, actuator 62 is at a radially innermost position of actuator 62, such that a radially innermost contact surface 86a of insertion section 86 contacts outer surface 50c of first radial contact section 50. As shown in the view in FIG. 6, wedge part 89 radially overlaps wedge part 51. FIGS. 7a to 7d illustrate how the actuator 62 is moved axially within hole 84 and radially in elongated slot 87 to vary the radial extent of securing device 30. FIGS. 7a and 7b illustrate actuator 62 in a first position in which securing device 30 is in a radially contracted position, with FIG. 7a showing a side view of securing device 30 and FIG. 7b showing a cross-sectional side view of securing device 30. In the position shown in FIGS. 7a, 7b, second wedge part 89 is positioned at a top of wedge part 51 and actuator 62 is positioned such that a bottom of shank 98 is in hole 84 and a top of shank 98 is positioned in elongated hole 87 spaced away from both a radially inner edge 87a and a radially outer edge 87b of elongated hole 87. FIGS. 7c and 7d illustrate actuator 62 in a second position in which securing device 30 is in a radially extended position, with FIG. 7c showing a side view of securing device 30 and FIG. 7d showing a cross-sectional side view of securing device 30. In the position shown in FIGS. 7c, 7d, second wedge part 89 is positioned near a bottom of wedge part 51 and actuator 62 is positioned such that a bottom of shank 98 is below hole 84 and a top of shank 98 is positioned in elongated hole 87 in contact with radially inner edge 87a. In order to move from the position in FIGS. 7a, 7b, where securing device 30 has a minimum radial length L1, to the position in FIGS. 7c, 7d, where securing device 30 has a maximum radial length L2, actuator 62 is rotated such that shank 98 moves axially downward in hole 84 via the engagement of the helical threads of shank 98 and the helical threads of hole 84. As actuator 62 is moved axially downward, sloped surface 66 of movable contact portion 60 slides along sloped surface 64 of stationary support portion 58, causing movable contact portion 60 to move radially outward away from base 48. The movement of movable contact portion 60 radially outward away from base 48 allows contact surface 56a of stop 94 to press against inner circumferential surface 34 of pressure vessel 36, forcing contact surface 50a of first radial contact section 50 radially against first outer circumferential surface section 32a of shroud 12 and forcing contact surface 52a of second radial contact section 52 radially against second outer circumferential surface section 32b of shroud 12. A method of installing securing device 30 on shroud 12 first includes machining threaded holes 72, 74 in shroud 12. Then, the method includes aligning holes 50b, 52b of base 48 with the respective holes 72, 74 in shroud and installing fasteners 68, 70 through the respective holes 50b, 52b and into the respective holes 72, 74 such that base 48 is fixed to shroud 12. Next, actuator 62 is actuated axially downward such that sloped surface 66 of movable contact portion 60 moves along sloped surface 64 of stationary support portion 58 and movable contact portion 60 is forced radially outward against inner circumferential surface 34 of pressure vessel 36. A plurality of securing devices 30 are circumferentially spaced from each other on shroud 12 to support the alignment of sections 38, 40, 42 of shroud 12 with respect to each other and with respect to the vessel 36. A thermal expansion of shroud 12 and pressure vessel 36 may be compensated with a series of Belleville washers that can either be below movable contact portion 60 or above movable contact portion 60 on actuator 62. The location of the washers can be determined as the thermal analysis is completed to see the differential growth characteristics. In the preceding specification, the invention has been described with reference to specific exemplary embodiments and examples thereof. It will, however, be evident that various modifications and changes may be made thereto without departing from the broader spirit and scope of invention as set forth in the claims that follow. The specification and drawings are accordingly to be regarded in an illustrative manner rather than a restrictive sense. In particular, in BWR reactors shroud, any linking two shroud cylinders assembled through disc section and welding lines can be secured by using the security device and the method of the present invention.
	summary
	description	In accordance with principles of present invention, examples of systems and methods for absorbing neutrons in spent nuclear fuel storage racks are depicted in FIGS. 3-16 and described in detail herein. FIGS. 3-4 depict one embodiment of a neutron absorber 300 for insertion into a cell of a spent nuclear fuel storage rack, for example, Flux Trap Nuclear Fuel Storage Rack 10 (FIG. 1) or Eggcrate Nuclear Fuel Storage Rack 100 (FIG. 2). Neutron absorber 300 has a chevron shape as best depicted in FIG. 4. Further, neutron absorber 300 is formed of a metal composite which includes neutron absorbing material, for example, boron carbide or a metal boron alloy. Such alloys may include alloys of aluminum, magnesium, titanium, aluminum/magnesium or aluminum/titanium, in combination with boron, for example. Stainless steel/boron alloys may also be used. Besides boron carbide and elemental boron, any element with a high thermal neutron absorption cross section may be substituted for boron. Further, neutron absorber 300 may be formed of materials occurring as a compound in either amorphous or crystalline powder form which has a fairly uniform particle size distribution, for example, gadolina (Gd2O3) and erbia (Er2O3). Referring to FIGS. 3-4, neutron absorber 300 is formed about a height of a cell of a spent nuclear fuel storage rack. Also, neutron absorber 300 includes a first portion 320 and a second portion 325 which have an angle 330 between them. Neutron absorber 300 is adapted to be deformed to cause angle 330 to decrease from its static position, for example, from greater than 90 degrees to less than 90 degrees. Neutron absorber 300 may be formed of a material having a modulus of elasticity of 10xc3x97106 psi to 20xc3x97106 psi, for example. This elastic deformability and its chevron shape allow neutron absorber 300 to be inserted into a cell 410 of a flux trap spent fuel storage rack 400 and attached between two walls of the cell, as depicted in FIG. 5. The higher the modulus of elasticity the greater the frictional locking force which is exerted on cell wall 410 when neutron absorber 300 is inserted therein. Also, first portion 320 and second portion 325 may be formed of a unitary material or they may be formed separately and attached to each other, for example, via standard TIG welding or by friction stir welding. Further, neutron absorber 300 may also include notches 310 adapted to receive one or more stresses to cause the deformation of neutron absorber 300. Also, notches 310 may serve as capture points to lock neutron absorbers in place between the two walls of the cell of the spent nuclear fuel storage rack. For example, some cell walls have xe2x80x9cdimplesxe2x80x9d (not shown) stamped on their faces, as is known to those skilled in the art, and notches 310 may be configured to engage such xe2x80x9cdimples.xe2x80x9d In another example, a rack may include weldments and spacer rods which notches 310 may engage. Further, a rack may include other features protruding toward an interior of a cell which notches 310 may engage. Referring to FIG. 5, cell 410 includes a first wall 420 and a second wall 425. Neutron absorber 300 may be elastically deformed from an unstressed condition in which angle 330 is greater than a cell angle 423 between first wall 420 and second wall 425 to a stressed condition wherein angle 330 is less than cell angle 423. Neutron absorber 300 in this stressed condition may be inserted into cell 410 and placed adjacent to first wall 420 and second wall 425. The stress may be released thus attaching neutron absorber 300 to first wall 420 and second wall 425, as depicted in FIG. 5. A pressure friction fit caused by the release of the stress and the elastic return of first portion 320 and second portion 325 of neutron absorber 300 causes neutron absorber 300 to attach to first wall 420 and second wall 425 and remain in place. This pressure friction fit results because neutron absorber 300 does not completely return elastically to its pre-deformation position due to the presence of first wall 420 and second wall 425. Specifically, the elastic nature of the material of neutron absorber 300, which would return first portion 320 and second portion 325 to their pre-deformation position if first wall 420 and second wall 425 were not present, causes potential energy to be stored. Thus, a force tending to cause this elastic return instead causes the friction fit which attaches neutron absorber 300 to first wall 420 and second wall 425. Further, an additional neutron absorber 301 may be inserted into cell 410 opposite neutron absorber 300, as shown in FIG. 5. Also, the frictional forces between neutron absorber 300 and first wall 420 and second wall 425 provide restraining forces sufficient to reduce or eliminate movement of neutron absorber 300 when fuel is inserted into or removed from cell 410, as is understood by those skilled in the art. For example, neutron absorber 300 may have a modulus of elasticity of 15xc3x97106 psi and in such a case, 1,075 pounds may be required to move or pull neutron absorber 300 in a vertical direction, that is, out of cell 410. In another example, neutron absorber 300 may have a modulus of elasticity of 20xc3x97106 psi which may require a force of 1,440 pounds to move neutron absorber 300 in a vertical direction out of cell 410. Neutron absorber 300 may also be installed into an eggcrate style fuel storage rack 500, as depicted in FIG. 6, in the same manner as described above for fluxtrap spent fuel storage rack 400. Neutron absorber 300 thus located in cell 510 adjacent a second cell 512 and a third cell 514 neutronically decouples cell 510 from these other cells. Another embodiment of a neutron absorber 600 for insertion into a cell of a spent fuel storage rack is illustrated in FIGS. 7-8. Neutron absorber 600 is chevron shaped and includes a first portion 610 and a second portion 620, which are connected to a third portion 630, for example, by standard TIG welding or by friction stir welding. Any welds between third portion 630 and first portion 610 or second portion 620 may be continuous or non-continuous. First portion 610 and second portion 620 are adapted to absorb neutrons and may include, for example, boron or another material in a metal alloy matrix capable of absorbing neutrons, as described above for neutron absorber 300. Third portion 630 is adapted to elastically deform to allow neutron absorber 600 to be attached to first wall 420 and/or second wall 425 of cell 410 and may be formed of the same alloy materials as first portion 610 and second portion 620, for example, but without the neutron absorber component (e.g., boron). Specifically, third portion 630 is deformable to allow an angle 625 between first portion 610 and second portion 620 to be decreased to less than cell angle 423, as described above for absorber 300. A release of the stress utilized to cause this deformation allows a friction fit between neutron absorber 600, (i.e. first portion 610, second portion 620, and third portion 630), and first wall 420 and second wall 425. The friction fit results from first wall 420 and second wall 425 preventing a full elastic return of first portion 610, second portion 620, and third portion 630 to their static angular positions relative to one another. The force resulting from stored potential energy due to the deformation of third portion 630 causes the frictional fit when the stress is released. Neutron absorber 600 also includes notches 640 adapted to receive grippers 710 of a neutron absorber installation tool 700 as depicted in FIGS. 9-12. Notches 640 may also serve to engage portions of first wall 420 and second wall 425 to lock neutron absorber 600 in position abutting these cell walls. Installation tool 700 includes a plurality of cylinders 720 adapted to apply stresses at a plurality of notches 640 via grippers 710. Such stresses may be utilized to deform neutron absorber 600 or portions thereof For example, FIG. 12 depicts neutron absorber 600 having third portion 630 deformed by installation tool 700 such that an angle 625 between first portion 610 and second portion 620 is less than an angle between two cell walls of a cell of a fuel storage rack (not shown). These cell walls may, for example, have angles of ninety degrees therebetween and thus a deformation of third portion 630 might cause angle 625 to be less than ninety degrees. Also, referring to FIG. 9, installation tool 700 includes a supporting mast 740 which connects and supports cylinders 720. By applying a stress to several pairs of notches 640 using grippers 710, an entire length of neutron absorber 600 may be deformed. Further, neutron absorber 600 may be lifted and manipulated using installation tool 700. FIG. 13 illustrates neutron absorber 600 attached to installation tool 700 being inserted into a cell 750 of a fuel storage rack. FIG. 14 depicts neutron absorber 600 in a deformed position held by installation tool 700 in cell 750, wherein angle 625 is less than an angle 775 between a first cell wall 760 and a second cell wall 770. FIG. 15 illustrates neutron absorber 600 attached to first cell wall 760 and second cell wall 770 after release of the stress on notches 640 by installation tool 700. Advantageously, installation tool 700 is formed of materials which can be easily decontaminated, for example, stainless steel. It will be understood by those skilled in the art that installation tool 700 could be used to deform and install neutron absorber 300, 600 or a neutron absorber of any other shape or size which includes notches or other means to receive a stress. Also, it will be understood by those skilled in the art that neutron absorber 600 and neutron absorber 300 could be formed in any shape or size to conform to cell walls of spent fuel storage racks of various shapes or sizes. Moreover, neutron absorber 300 and neutron absorber 600 could be formed to include more than two portions such as first portion 320 and second portion 325, corresponding to more than two cell walls, e.g., first wall 420 and second wall 425. Further, notches 310 and notches 640 may be formed in neutron absorber 300 and neutron absorber 600 at any number of locations to serve as capture points for engaging cell walls having various characteristics. Yet, further, neutron absorber 300 and neutron absorber 600 may include other features for engaging cell walls. One method of inserting a neutron absorber into a cell of a fuel storage rack is described as follows with reference to FIGS. 3-4 and 16. A magazine 800 mounted to a spent fuel storage rack bridge 805 holds a plurality of neutron absorbers 300 in a pool 810 containing water and a spent fuel storage rack 850. Installation tool 700 is located in pool 810 connected to a drive assembly 860 located above pool 810 controlled by a controller (not shown) programmed by a user at a control console 870. The user may program the controller to control drive assembly 860 to three dimensionally align installation tool 700. Further, the controller (not shown) may be programmed by the user to cause drive assembly 860 to cause installation tool 700 to align grippers 710 with notches 310 and apply a stress to notches 310. Thus, the user may cause angle 330 between first portion 320 and second portion 325 to be less than an angle between two cell walls of a cell 855 of fuel storage rack 850. The controller may be programmed to cause installation tool 700 to be lifted from magazine 800 together with neutron absorber 300. Drive assembly 860 may thus cause neutron absorber 300 to be inserted into a cell 855 of spent fuel storage rack 850. Neutron absorber 300 may be manipulated against two walls of cell 855 through programming of the controller by the user and the stress exerted by grippers 710 on notches 310 may be released. Thus, neutron absorber 300 may be attached to the walls of cell 855 via a frictional fit, as described above. This process may be repeated for each cell of fuel cell storage rack 850. It will be understood by those skilled in the art that this method may be utilized for installation of neutron absorber 600 or neutron absorbers of any other shape or size, for example, those which include notches to receive installation tool 700. It will also be understood by those skilled in the art that cylinder 720 of installation tool 700 may utilize pneumatic, hydraulic, or other means of applying forces to neutron absorber 300 or neutron absorber 600. The embodiments described herein are just examples. There may be many variations to the method and/or devices described herein without departing from the spirit of the invention. For instance, the operational steps may be performed in a differing order, or steps may be added, deleted or modified. All of these variations are considered a part of the claimed invention. Although preferred embodiments have been depicted and described in detail herein, it will be apparent to those skilled in the relevant art that various modifications, additions, substitutions and the like can be made without departing from the spirit of the invention and these are therefore considered to be within the scope of the invention as defined in the following claims.
054085098	abstract	A method and apparatus for positioning stud affecting apparatus comprising: sequentially positioning a plurality of flange cover sectors about the flange of a nuclear pressure vessel; rotating each flange cover sector until the entire flange is covered by said flange cover sectors; moving a caddy containing stud affecting tools including stud tensioners and stud drive tools into a position adjacent a point on the flange of the nuclear reactor pressure vessel; moving apparatus sector vessels containing stud affecting apparatus to a point on the flange of the nuclear pressure vessel and positioning them on a specific flange cover sector; rotating all flange cover sectors to bring another flange cover sector into registration with the caddy; sequentially moving the apparatus sectors onto each flange cover sector by rotating the flange cover sectors; and actuating the stud affecting tools to perform the appropriate function to tension or untension the studs and/or to remove and/or to insert studs into the pressure vessel to enable removal of the dome and servicing of the nuclear pressure vessel.
	claims	1. An electric generator, comprising:a stator and a rotor positioned within the stator, wherein the stator and rotor are configured to generate electric current when the rotor is rotated; anda high energy photon source positioned and configured to irradiate at least a portion of conductors in the rotor or stator. 2. The electric generator of claim 1, wherein:the stator generates a magnetic field when the electric generator is operating; andthe rotor comprises armature windings configured to generate electric current when the rotor is rotated. 3. The electric generator of claim 2, wherein the high energy photon source is positioned within the rotor armature windings and configured to irradiate at least the armature windings. 4. The electric generator of claim 3, wherein the high energy photon source is configured as a sleeve that fits within the rotor inside of the armature windings. 5. The electric generator of claim 2, wherein the high energy photon source is positioned between the rotor and the stator and configured to irradiate the armature windings. 6. The electric generator of claim 5; wherein the high energy photon source is configured as a sleeve that fits between the rotor and the stator. 7. The electric generator of claim 2, wherein:the stator comprises field and compensating windings; andthe high energy photon source is positioned and configured to irradiate the field and compensating windings. 8. The electric generator of claim 1, wherein the high energy photon source comprises cobalt-60. 9. The electric generator of claim 1, wherein the high energy photon source comprises cesium-137. 10. The electric generator of claim 1, wherein the high energy photon source generates X-ray or γ-ray photons. 11. The electric generator of claim 1, wherein the high energy photon source is positioned and configured to irradiate the rotor or stator conductors so that the rotor or stator conductors are exposed to and absorb high energy photons to create an electron avalanche process that boosts the electric current generation. 12. A method of manufacturing an electric generator having a rotor and a stator, comprising:positioning a source of high energy photons within the electric generator so as to irradiate current generating conductors in one or both of the rotor or the stator so that the rotor or stator conductors are exposed to and absorb high energy photons to create an electron avalanche process that boosts the electric current generation. 13. The method of manufacturing an electric generator of claim 12, wherein positioning the source of high energy photons within the electric generator comprises positioning the source of high energy photon within the rotor so as to irradiate at least armature windings within the rotor. 14. The method of manufacturing an electric generator of claim 12, wherein positioning the source of high energy photons within the electric generator comprises positioning the source of high energy photon between the rotor and the stator. 15. The method of manufacturing an electric generator of claim 12, wherein the high energy photon source generates X-ray or γ-ray photons. 16. An electric generator, comprising:a stator and a rotor positioned within the stator, wherein the stator and rotor are configured to generate electric current when the rotor is rotated, wherein the suitor generates a magnetic field when the electric generator is operating and the rotor comprises armature windings configured to generate the electric current when the rotor is rotated; anda high energy photon source positioned and configured to irradiate at least a portion of conductors in the rotor or stator,wherein:the high energy photon source is positioned within the rotor armature windings and configured to irradiate at least the armature windings;the high energy photon source is positioned between the rotor and the stator and configured to irradiate at least the armature windings; orthe stator comprises field and compensating windings, and the high energy photon source is positioned and configured to irradiate the field and compensating windings.
	summary
	claims	1. A method for adjusting a collimator of an X-ray source having a radiation source therein, comprising:detecting, via a 3D camera, an arrangement of an X-ray detector with respect to the X-ray source;automatically determining an adjustment for the collimator based on a position of the X-ray detector determined with respect to the X-ray source;moving the radiation source with respect to the collimator; andautomatically adjusting the collimator based on the adjustment determined for the collimator, wherein the 3D camera is mechanically connected to the X-ray source and is configured to move together with the X-ray source,wherein an image generated by the 3D camera includes an irradiation area of the X-ray source, andwherein the image generated by the 3D camera includes the X-ray detector. 2. The method of claim 1, wherein the X-ray detector comprises a mobile X-ray detector to allow a free exposure arrangement of the X-ray detector. 3. The method of claim 2, wherein the automatically adjusting of the collimator comprises at least one of:automatically adjusting a height of a light field of the collimator,automatically adjusting a width of the light field of the collimator, andautomatically adjusting a rotation of the light field of the collimator. 4. The method of claim 1, wherein the automatically adjusting of the collimator comprises at least one of:automatically adjusting a height of a light field of the collimator,automatically adjusting a width of the light field of the collimator, andautomatically adjusting a rotation of the light field of the collimator. 5. The method of claim 1, wherein the detecting of the arrangement of the X-ray detector with respect to the X-ray source comprises detecting a position of the X-ray detector, and whereinan adjustment for the X-ray source is automatically determined based on the position of the X-ray detector detected, anda position of the X-ray source is automatically adjusted based on the adjustment for the X-ray source determined. 6. The method of claim 1, further comprising:outputting a warning indicating when an optimal adjustment of the collimator cannot be achieved with arrangement of the X-ray detector detected with respect to the X-ray source. 7. A non-transitory computer program product storing a computer program, the computer program being loadable into a memory of a processing device of an X-ray device, and including program code sections to cause the processing device to execute the method of claim 1 when the computer program is executed in the processing device. 8. A non-transitory computer readable media storing computer executable instructions for, when executed by a processor, perform the method of claim 1. 9. A method for adjusting a collimator of an X-ray source, comprising:detecting, via a 3D camera, an arrangement of an X-ray detector with respect to the X-ray source to determine a position of the X-ray detector detected with respect to the X-ray source;automatically determining an adjustment for the collimator based on the position of the X-ray detector determined with respect to the X-ray source; andautomatically adjusting the collimator based on the adjustment determined for the collimator,wherein the detecting of the arrangement of the X-ray detector with respect to the X-ray source comprises;capturing an image comprising the X-ray detector and the X-ray source,automatically computing, based on the image captured, at least one of:a distance between the X-ray detector and the X-ray source, andan orientation of the X-ray detector with respect to the X-ray source. 10. The method of claim 9, wherein the X-ray detector comprises a mobile X-ray detector to allow a free exposure arrangement of the X-ray detector. 11. The method of claim 10, wherein the automatically adjusting of the collimator comprises at least one of:automatically adjusting a height of a light field of the collimator, andautomatically adjusting a width of the light field of the collimator. 12. The method of claim 9, further comprising:outputting a warning indicating when an optimal adjustment of the collimator cannot be achieved with arrangement of the X-ray detector detected with respect to the X-ray source. 13. A non-transitory computer program product storing a computer program, the computer program being loadable into a memory of a processing device of an X-ray device, and including program code sections to cause the processing device to execute the method of claim 9 when the computer program is executed in the processing device. 14. A non-transitory computer readable media storing computer executable instructions for, when executed by a processor, perform the method of claim 9. 15. An X-ray device, comprising:an X-ray source including a collimator, a radiation source and an actuator configured to move the radiation source with respect to the collimator;a capturing device including a 3D camera and configured to detect an arrangement of an X-ray detector with respect to the X-ray source,wherein the capturing device is mechanically connected to the X-ray source and is configured to move together with the X-ray source,wherein an image generated by the capturing device includes an irradiation area of the X-ray source, andwherein the image generated by the 3D camera includes the X-ray detector, anda processor configured todetermine an adjustment for the collimator based on a detected position of the X-ray detector with respect to the X-ray source, andadjust the collimator based on the adjustment determined for the collimator. 16. An X-ray device, comprising:an X-ray source including a collimator;an X-ray detector; andat least one processor configured todetect, via a 3D camera, an arrangement of the X-ray detector with respect to the X-ray source by automatically computing, based on an image captured by the 3D camera including the X-ray detector and the X-ray source, at least one of:a distance between the X-ray detector and the X-ray source, andan orientation of the X-ray detector with respect to the X-ray source;automatically determine an adjustment for the collimator based on a position of the X-ray detector determined with respect to the X-ray source; andautomatically adjust the collimator based on the adjustment determined for the collimator.
	claims	1. A charged particle beam drawing apparatus, comprising:a drawing portion for drawing patterns corresponding to figures included in a drawing data, in a drawing area of a workpiece, by irradiating the workpiece with a charged particle beam, wherein the workpiece is formed by applying a resist to an upper surface of the workpiece;a proximity effect correcting map forming portion for forming a proximity effect correcting map having meshes, so that the figures included in the drawing data are placed in the proximity effect correcting map;a representative figure forming portion for forming representative figures, wherein area of a representative figure in a mesh is equal to gross area of figures in the mesh;a proximity effect correction dose calculating portion for calculating a proximity effect correction dose of the charged particle beam in each mesh, on the basis of area of each representative figure in each mesh;a figure area changing portion for changing area of at least one figure, before the representative figures are formed by the representative figure forming portion, if it is necessary to change the proximity effect correction dose of the charged particle beam for drawing at least one pattern corresponding to the at least one figure; anda proximity effect correction dose changing portion for changing the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the at least one figure, calculated by the proximity effect correction dose calculating portion, if it is necessary to change the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the at least one figure. 2. The charged particle beam drawing apparatus according to claim 1, wherein if a correction error appears to the at least one pattern locally in a unit drawing area, the figure area changing portion changes area of the at least one figure corresponding to the at least one pattern, and proximity effect correction dose changing portion changes the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the at least one figure. 3. The charged particle beam drawing apparatus according to claim 2, wherein if a first figure and a second figure are placed in a same mesh of the proximity effect correcting map, wherein changing the proximity effect correction dose of the charged particle beam for drawing at least one pattern corresponding to the first figure is necessary, and changing the proximity effect correction dose of the charged particle beam for drawing at least one pattern corresponding to the second figure is unnecessary, the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the first figure is obtained by the proximity effect correction dose calculating portion and the proximity effect correction dose changing portion, and the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the second figure is obtained by the proximity effect correction dose calculating portion, respectively. 4. The charged particle beam drawing apparatus according to claim 3, wherein if the first figure and the second figure are placed in the same mesh of the proximity effect correcting map, the representative figure forming portion forms a representative figure in the same mesh, wherein area of the representative figure is equal to gross area of the first figure and the second figure, after the area of the first figure is changed by the figure area changing portion, and the proximity effect correction dose changing portion changes the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the first figure, calculated by the proximity effect correction dose calculating portion on the basis of the area of the representative figure. 5. The charged particle beam drawing apparatus according to claim 4, wherein if the first figure and the second figure are placed in the same mesh of the proximity effect correcting map, the proximity effect correction dose calculating portion calculates the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the second figure on the basis of the area of the representative figure. 6. A proximity effect correction method of a charged particle beam drawing apparatus for drawing patterns corresponding to figures included in a drawing data, in a drawing area of a workpiece, by irradiating the workpiece with a charged particle beam, wherein the workpiece is formed by applying a resist to an upper surface of the workpiece, comprising:forming a proximity effect correcting map having meshes by a proximity effect correcting map forming portion, so that the figures included in the drawing data are placed in the proximity effect correcting map;forming representative figures by a representative figure forming portion, wherein area of a representative figure in a mesh is equal to gross area of figures in the mesh;calculating a proximity effect correction dose of the charged particle beam in each mesh, on the basis of area of each representative figure in each mesh, by a proximity effect correction dose calculating portion;changing area of at least one figure by a figure area changing portion, before the representative figures are formed by the representative figure forming portion, if it is necessary to change the proximity effect correction dose of the charged particle beam for drawing at least one pattern corresponding to the at least one figure; andchanging the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the at least one figure, calculated by the proximity effect correction dose calculating portion, by a proximity effect correction dose changing portion, if it is necessary to change the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the at least one figure. 7. The proximity effect correction method of the charged particle beam drawing apparatus according to claim 6, wherein if a correction error appears to the at least one pattern locally in a unit drawing area, the figure area changing portion changes area of the at least one figure corresponding to the at least one pattern, and proximity effect correction dose changing portion changes the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the at least one figure. 8. The proximity effect correction method of the charged particle beam drawing apparatus according to claim 7, wherein if a first figure and a second figure are placed in a same mesh of the proximity effect correcting map, wherein changing the proximity effect correction dose of the charged particle beam for drawing at least one pattern corresponding to the first figure is necessary, and changing the proximity effect correction dose of the charged particle beam for drawing at least one pattern corresponding to the second figure is unnecessary, the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the first figure is obtained by the proximity effect correction dose calculating portion and the proximity effect correction dose changing portion, and the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the second figure is obtained by the proximity effect correction dose calculating portion, respectively. 9. The proximity effect correction method of the charged particle beam drawing apparatus according to claim 8, wherein if the first figure and the second figure are placed in the same mesh of the proximity effect correcting map, the representative figure forming portion forms a representative figure in the same mesh, wherein area of the representative figure is equal to gross area of the first figure and the second figure, after the area of the first figure is changed by the figure area changing portion, and the proximity effect correction dose changing portion changes the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the first figure, calculated by the proximity effect correction dose calculating portion on the basis of the area of the representative figure. 10. The proximity effect correction method of the charged particle beam drawing apparatus according to claim 9, wherein if the first figure and the second figure are placed in the same mesh of the proximity effect correcting map, the proximity effect correction dose calculating portion calculates the proximity effect correction dose of the charged particle beam for drawing the at least one pattern corresponding to the second figure on the basis of the area of the representative figure.
	claims	1. A charged-particle beam system comprising:a source of a beam of charged particles;an objective lens;an aberration corrector for correcting third-order spherical aberration, the aberration corrector being mounted between the source of the beam and the objective lens, the aberration corrector defining an image point; anda transfer lens for correcting fifth-order spherical aberration and third-order chromatic aberration, the transfer lens being so placed that a principal plane of the transfer lens is located at the image point of the aberration corrector. 2. A charged-particle beam system as set forth in claim 1, wherein strength of said transfer lens is so set that an aberration generation point in the aberration corrector is projected at a front focal point of the objective lens or at a coma-free point. 3. A charged-particle beam system as set forth in claim 1 or 2, wherein said aberration corrector corrects the third-order spherical aberration, and wherein the charged-particle beam system has a function of correcting the fifth-order spherical aberration and third-order chromatic aberration while holding a trajectory of the beam of the charged particles assumed when the third-order spherical aberration was corrected. 4. A charged-particle beam system as set forth in claim 3, wherein the charged-particle beam system has a function of adjusting strength of said transfer lens such that the fifth-order spherical aberration and third-order chromatic aberration are corrected. 5. A charged-particle beam system as set forth in claim 3, wherein the charged-particle beam system has a function of controlling strength of said transfer lens to adjust resolution of a scanned image. 6. A charged-particle beam system as set forth in claim 3, wherein the charged-particle beam system has a function of controlling strength of said transfer lens to adjust contrast of a scanned image. 7. A charged-particle beam system comprising:a source of a beam of charged particles;a deceleration objective lens;an aberration corrector for correcting third-order spherical aberration, the aberration corrector being mounted between the source of the beam and the objective lens, the aberration corrector defining an image point; andan additional accelerating lens for correcting fifth-order spherical aberration and third-order chromatic aberration, the additional accelerating lens having a principal plane placed at the image point of the aberration corrector. 8. A charged-particle beam system as set forth in claim 7, wherein strength of said additional accelerating lens is so set that an aberration generation point in the aberration corrector is projected at a front focal point of the objective lens or at a coma-free point. 9. A charged-particle beam system as set forth in claim 7 or 8, wherein said aberration corrector corrects the third-order spherical aberration, and wherein the charged-particle beam system has a function of correcting the fifth-order spherical aberration and third-order chromatic aberration while holding a trajectory of the beam of the charged particles assumed when the third-order spherical aberration was corrected. 10. A charged-particle beam system as set forth in claim 9, wherein the charged-particle beam system has a function of adjusting strength of said additional accelerating lens such that the fifth-order spherical aberration and third-order chromatic aberration are corrected. 11. A charged-particle beam system comprising:a source of a beam of charged particles;an objective lens of a superimposed electric and magnetic field type;an aberration corrector for correcting third-order spherical aberration, the aberration corrector being mounted between the source of the beam and the objective lens, the aberration corrector defining an image point; andan additional accelerating lens for correcting the fifth-order spherical aberration and third-order chromatic aberration, the additional accelerating lens having a principal plane placed at the image point of the aberration corrector. 12. A charged-particle beam system as set forth in claim 11, wherein strength of said additional accelerating lens is so set that an aberration generation point in the aberration corrector is projected at a front focal point of the objective lens or at a coma-free point. 13. A charged-particle beam system as set forth in claim 12, wherein said aberration corrector corrects the third-order spherical aberration, and wherein the charged-particle beam system has a function of correcting the fifth-order spherical aberration and third-order chromatic aberration while holding a trajectory of the beam of the charged particles assumed when the third-order spherical aberration was corrected. 14. A charged-particle beam system as set forth in claim 13, wherein the charged-particle beam system has a function of adjusting strength of said additional accelerating lens such that the fifth-order spherical aberration and third-order chromatic aberration are corrected. 15. A charged-particle beam system as set forth in any one of claims 1, 7 and 11, wherein the aberration corrector is composed of four stages of electrostatic multipole elements and two stages of magnetic quadrupole elements for superimposing a magnetic potential distribution on an electric potential distribution created by two central stages of electrostatic quadrupole elements of the four stages, the magnetic potential distribution being analogous to the electric potential distribution, and wherein said charged-particle beam system further includes an objective lens for focusing the beam of charged particles onto a specimen, means for applying a decelerating voltage to the specimen, a manipulation portion permitting a human operator to modify the accelerating voltage of the beam or the working distance between the objective lens and the specimen, and a control portion for controlling the multipole elements based on manipulation of the manipulation portion or on settings.
	summary
049922327	summary	This invention relates to boiling water nuclear reactors (BWRs) operating under hydrogen water chemistry conditions. More particularly, a technique for restricting the levels of increase of radiation in the main steam lines due to N-16 production where hydrogen water chemistry is utilized to minimize intergranular stress corrosion cracking (IGSCC) is disclosed. BACKGROUND OF THE INVENTION Boiling water reactors (BWRs) operating over long periods of time have stainless steel components which are subject to IGSCC. The injection of hydrogen into the feedwater of BWRs has been demonstrated as an effective means of suppressing the stress corrosion cracking of these stainless steel components. Under normal water chemistry conditions, the oxygen concentration is approximately 200 parts per billion (ppb) and the hydrogen concentration is approximately 10 ppb. Under hydrogen water chemistry conditions, the concentrations necessary to prevent ISGCC are in the range of 2-15 ppb oxygen and 100 ppb hydrogen. These concentrations are approximate and vary among reactors. To inspect for the presence of stress corrosion, non-destructive testing is used. Such non-destructive testing of piping joints requires plant shutdown while the inspection occurs. Thus, even the threat of IGSCC costs the plant expensive down time. Unfortunately, and coincident with this hydrogen treatment, higher levels of radiation in the main steam lines and turbines have been observed. These higher levels of radiation in the more heavily shielded plants have not caused a significant problem. Heavily shielded turbines, condensers and steam piping have prevented the radiation from finding its way through to operating personnel and occupied areas. Unfortunately, many plants include heavy shielding in the turbine, condenser and steam piping side of the plant which is only adequate to limit dose rates under normal water chemistry. This being the case, the increased levels of radiation have tended to limit the use of hydrogen water chemistry to prevent stress corrosion. BWR operation under normal water chemistry produces a small fraction of N-16 formed by the n,p reaction of 0-16 and exists in a chemical form which tends to be volatile. As this fraction is transported in the aqueous phase in the reactor and the water coolant is converted to steam, a portion of the volatile fraction is swept into the steam phase and transported to the turbine. N-16 is a radioactive nuclide whose half-life is approximately 7 seconds. In its decay, high energy gamma radiation of 6 and 7 MeV is emitted. Thus, during normal plant operation a significant radiation field emanates from the steam lines and turbine. Because of the intensity and relatively high energy of the gamma radiation, significant shielding is required to limit the radiation field intensity. In spite of the shielding, the influence of the N-16 source can be measured even at significant distances from the source. We have discovered as a part of the present invention that the observed radiation levels are caused at least in part by the N-16 being converted into volatile nitrogen compounds, including ammonia, which are transported in the steam phase. Under hydrogen water chemistry conditions, a larger fraction of the N-16 is converted to a volatile form. Thus, the radiation levels in the steam phase increase significantly when compared to the levels without hydrogen addition. Dependent on the reactor, the levels have been measured by us to increase from 1.2 to 5 times at the hydrogen concentration necessary to prevent IGSCC in the recirculation system. For some plants the increase is sufficient to exceed safety dose rate limits not only close to the source, but also in surrounding buildings and grounds and at site boundaries. This is perceived as one of the most detrimental aspects of hydrogen water chemistry. Thus, it would be highly desirable if a method could be found to limit the N-16 volatility, i.e., the quantity transported to the steam. SUMMARY OF THE INVENTION The present invention generally provides a method for operating boiling water reactors with hydrogen water chemistry under conditions limiting the level of released radiation which has heretofore accompanied such chemistry. More specifically, by inhibiting the transfer of gaseous nitrogen compounds from the liquid phase to the steam phase, the release of radioactive N-16 into less shielded portions of the reactor system may be reduced. Various approaches for inhibiting such transfer are employed, depending in part on the operating mode of the reactor. Three operational modes are employed providing varying levels of hydrogen protection. First, the boiling water reactors may be operated with full plant protection where feed water hydrogen concentration is sufficient to prevent IGSCC or irradiation assisted stress corrosion cracking (IASCC) in all parts of the primary reactor system, including all stainless steel components in both the recirculation system and in the reactor vessel. Second, the reactors may be operated with selective protection where hydrogen is introduced only at certain critical regions within the reactor, providing localized protection within those regions. Operating with selective protection allows less total hydrogen to be introduced, generating less N-16 than is generated with full protection. The critical regions for hydrogen introduction will generally include (a) the recirculation system, (b) the core bypass region, i.e., the region not contained within the boundary of the fuel assemblies and the region immediately above the fuel core, more particularly the region of the top fuel guide, and (c) the lower plenum region of the reactor vessel which includes the bottom of the vessel up to the region just above the fuel support plate. Third, the boiling water reactor may be operated with partial protection where the hydrogen concentration is lower than that required to attain the lowest electrochemical potential in order to completely inhibit IGSCC. Such mode of operation partially arrests crack growth and decreases the fraction of volatile N-16. In the first category, the approach is either to chemically decrease the quantity of volatile N-16 species transferred into the steam phase, to physically decrease the quantity of volatile N-16 species transferred into the steam phase, or to delay transport of the volatile N-16 species in the steam phase to the main steam line to the turbine for a sufficient time to allow substantial decay of the radiation. The second and third categories involve the use of less hydrogen and hence less volatile N-16 formation. FULL PROTECTION First, formation of volatile nitrogen compounds may be chemically inhibited. This may be accomplished by altering reaction paths leading to the formation of volatile N-16 with small amounts of additives particularly free-radical scavengers and/or increasing the pH of the reactor feed water to an acidic level. Thus, the present invention provides for the introduction of trace quantities (ppb concentrations) of a species, to inhibit, suppress, or alter the reaction path of the radioactive nitrogen leading to the formation of a volatile species, e.g., ammonia, and/or enhancing the reaction path leading to a non-volatile species, e.g., a nitrite. Examples of possible additives are nitrous oxide, carbon dioxide, nitrite, nitrate, low molecular weight alcohols, or ketones, copper, zinc or vanadium, etc., not excluding other possibilities. Alternatively, a slight increase of the pH is effective to reduce the volatility of the ammonia. A change in pH may also alter the reaction paths leading to the formation of volatile nitrogen compounds. In this latter instance, the formation of volatile N-16 species is inhibited. Usually, the pH of the boiler feed water will be increased to the range from about 7.0 to 8.6 as measured at room temperature (normally, the feedwater will have a pH in the range from about 6.1 to 8.1). This may be accomplished by appropriate balancing of the anionic and cationic ion exchange resin used in the boiler water treatment facility. Secondly, the N-16 transport to the steam phase can be limited by physical means. It is recognized that the N-16 is formed in two regions of the core: (1) within the envelope of the fuel bundle channel, i.e., the in-channel region, and (2) in the region outside the fuel bundle region, i.e., the bypass region. Essentially all the boiling occurs within the in-channel region and essentially none in the bypass region. In addition, the flow rate is much faster and hence the residence time in the in-channel region is much shorter than that in the bypass region, while the volumes of water in both regions are comparable. Thus, a significant portion of the N-16 formation occurs in the bypass region. Because the residence time of the water in the bypass region is significant compared with the half life of N-16, a decrease in the flow rate will decrease the total production of N-16 at the core exit, which constitutes one physical method of control. A second physical method involves limiting the contact time between the steam and water. This will decrease the net transfer of the volatile N-16 species from the liquid to the steam phase and, hence, limit the N-16 steam phase concentration. This approach may be achieved by physically altering the region above the core. A third method involves increasing the retention time of the N-16 in the steam by several seconds which is significant compared to the half-life. This may be accomplished by a physical means of providing an increased volume for the steam as close to the reactor vessel as possible. This volume could be shielded. An alternate method may involve a chemical method of adsorption onto a matrix material for a long enough time (seconds) to effect a significant delay relative to the second half-life. SELECTIVE AND PARTIAL PROTECTION The concentration of hydrogen required to achieve protection of the recirculation system stainless steel components varies significantly among plants. (See, FIG. 2). Such variation is attributed to differences in the effectiveness of hydrogen utilized to promote hydrogen-oxygen recombination in the downcomer region. Thus, methods which can promote the efficiency of hydrogen utilization will decrease the total hydrogen utilization and diminish the amount of volatile N-16 generated and transported into the steam phase. Reducing the hydrogen concentration required can be beneficial in reducing the N-16 steam phase activity depending on the ultimate hydrogen concentration required (see FIG. 3). This can be accomplished by methods such as catalyzing the hydrogen-oxygen recombination reaction, for example by increasing radiation in the downcomer region, or possibly by surface catalysis. It is also recognized that hydrogen injected into the feed water, the usual region of injection, is only partially available to the downcomer region. That is, the hydrogen bearing water partitions at the top of the jet pump such that a portion goes into the jet pump and hence directly into the core, which bypasses the downcomer region. Therefore, if the hydrogen is injected below the inlet to the jet pumps, the total quantity is available for the downcomer region. Since this can result in a corresponding decrease in the total amount of hydrogen added (and going into the core region) less volatile N-16 will be formed. To ensure an adequate concentration of hydrogen in the bypass region of the core while limiting the volatile N-16 production, hydrogen can be injected directly into bypass regions. Such hydrogen injection in combination with the techniques described for enhancing hydrogen utilization in the downcomer region, will reduce the overall hydrogen addition and hence reduce the volatile N-16 concentration. Under such operation, both the recirculation system and the core bypass region would be protected from IGSCC and IASCC with only relatively small increases in the volatile N-16 concentration. In the lower plenum region, a sufficiently low oxygen concentration may be attained in this region by the addition of hydrogen e.g., via feedwater addition, and catalyzing the recombination reaction by either increased radiation in this region or in the vicinity of the jet pumps or by surface catalysis, as in the downcomer region described above. For partial protection, it is possible to operate at a somewhat higher electrochemical potential so that the crack growth rate is reduced but not stopped. This would require less hydrogen and hence decreased formation of volatile forming of N-16. Under either full or partial suppression, it also appears very likely that the fraction of ammonia (N-16) transferred to the steam phase can be affected by other changes in physical parameters. Among these, changes in the water level in a reactor core may be effective in reducing the N-16 level in the steam phase to compensate at least partially for the increase in radiation levels brought about by operation under hydrogen water chemistry. Other parameters include but are not limited to recirculation flow rate, axial power distribution, and axial steam void distribution.
043137938	claims	1. A machine for permanently removing stiff instrument guide tubing from a nuclear reactor, comprising: (a) a frame; (b) a reel carried on said frame, the reel including a circular cartridge detachably connected to the outer rim of the reel, the cartridge having a substantially continuous helical groove extending around the circumference of the cartridge, the groove having an effective diameter approximately equal to that of the outer diameter of the tube; (c) means for capturing one end of the tube on the reel; (d) means for selectively driving the reel relative to the frame in either circumferential direction; (e) a plurality of cam rollers carried by said frame and closely spaced around the circumference of said reel, said rollers being mounted in fixed relationship to the reel, whereby the cam rollers provide sufficient friction between the groove and the tube so that the tube can be tightly wound onto or wound off from the reel; (f) means carried by the frame adjacent to the reel for straightening the tube as it winds onto or off of the reel. 2. The machine recited in claims 1 wherein the means for capturing one end of the tube include wall means in the reel forming a slot through at least one groove. 3. The machine of claim 1 further including means for selective moving said reel out of and into alignment with said cam rollers, whereby access may be had to the means for capturing the tube in said reel. 4. The machine of claim 1 wherein said cam rollers are free to rotate. 5. The machine of claim 1 wherein said cam rollers have an outer surface made of non-metallic material. 6. The machine of claim 1 wherein the perpendicular distance between the base of the groove and the cam roller is no greater than about 25 percent more than the diameter of the tube. 7. The machine of claim 1 wherein a lead shield is carried by the frame and disposed around the reel and cam rollers. 8. The machine recited in claim 1 wherein the means for selectively driving the reel relative to the frame include a hub at the center of the reel and forming an integral part thereof, a drive shaft perpendicularly secured to the hub, and a motor for rotating the drive shaft. 9. The machine of claim 8 further including means for selectively moving said reel out of and into alignment with said cam rollers, including a split taper bushing connecting the hub to the drive shaft, and bearing means between the drive shaft and the frame for permitting selective displacement of the drive shaft in the direction of the shaft axis.
039765431	description	SPECIFIC EMBODIMENT OF THE INVENTION The assembly is a preset temperature actuated bistable device for automatically removing the restraint on a neutron absorber allowing the absorber to insert into the core of a liquid sodium cooled fast breeder nuclear reactor thus preventing core overheating due to excessive power for a given coolant flow. Referring to FIG. 1, a neutron absorber 10, hexagonal in cross section, is surrounded by a slightly larger doublewall hexagonal tube having an inner tube 12 and an outer tube 13. The annulus therebetween is filled with two rows of fuel pins 15 some of which are interrupted to allow space for circular "L" shaped flanges 14 made of stainless steel and welded to three sides of the inner tube 12 at the same elevation on the tube. The outer tube 13 has holes 19 therein within which circular flanges 14 fit tightly; a lip 14a on each flange forms a smooth continuous surface with the surrounding outer tube 13. This minimizes interference with sodium coolant flow around the outer tube 13 and allows the tubes 12 and 13 to be placed adjacent to other hexagonal tubes, not shown, in the reactor core which contain similar absorbers, control rods, or fuel rods. Each circular flange 14 contains a bimetallic disk 16 and a nickel-chromium-iron alloy helical spring 17 trapped compressively between the flange and the disk. The lip 14a is only wide enough to support the spring 17; a hole 14b defined by the lip 14a insures intimate contact between the sodium coolant and the disk 16 so that heat transfer will be improved. The hole 14b also facilitates inspection of the disk 16 and spring 17. Each bimetallic disk 16 is shaped as a spherical cap and is made of a layer 18 of molybdenum on the inside or normally convex side of the disk and a layer 20 of stainless steel on the outside or normally concave side of the disk. This relationship of concave and convex sides will hereinafter be described as the closed position of the disk 16. These materials are chosen for the difference in their thermal coefficients of expansion which gives the switching action as well as for their compatibility with high temperature liquid sodium coolant and a low tendency to interdiffuse at high temperatures; other suitable material combinations, such as a nickel-chromium-alloy on the outside with molybdenum or a molybdenum-titanium alloy on the inside are also suitable. As shown in FIG. 2, the inside or normally convex side of the disk 16 has a spherical depression 22 formed in it; its radius is slightly larger than the radius of a metal ball 24 made of cobalt alloy tool material whereby a smooth sliding fit is obtained between the depression 22 and the ball 24. The ball 24 is rotatably retained in the depression 22 by a retainer 26 formed as part of the material of the inside layer 18. The cross section of the retainer 26 is substantially right triangular where one right triangular leg is integral with the inside layer 18 and the other right triangular leg is curved slightly to match the radius of the depression 22 whereby the ball 24 is rotatably retained. In the embodiment shown, the depression 22 is large enough so that it penetrates completely through the inside layer 18 of the disk 16, thus defining a hole 23 in the inside layer 18 with the shape of a zone of a sphere, and a spherical depression 25 in the outside layer 20. However, this is not critical; depending upon the size of the ball 24 in relation to the disk 16, the spherical depression 22 may or may not penetrate through the inside layer 18 and into the outside layer 20. The ball 24 is thus trapped in the disk 16 and faces a port 28 in the side of the inner tube 12 which is located concentrically with a line normal to the plane of the side and passing through the center of the ball 24. The disk 16 is urged toward the inner tube 12 by the spring 17. The ball 24 is large enough to project partially through the port 28 in the closed position to the inside of the hexagonal tube 12 as shown in FIG. 1. The absorber 10 is supported solely by means of the conical bottom 30 thereof resting upon the metal ball or balls 24. As shown in FIG. 4, a thin layer or foil of fissionable metal 34 may be disposed in the bimetallic disk 16. Fissions at a rate proportional to reactor power will then take place in the disk 16, thus generating heat within the disk itself to raise the temperature of the disk in addition to relying on heat addition from core components or coolant. If desired, the fissionable material may be in the form of a metal oxide 36, dispersed as nodules in at least one of the layers 18 and 20 of the disk 16 as depicted in FIG. 5. The addition of fissionable material in either form is not necessary to the invention, but can be used to decrease the response time of the disk 16 in the event of a dangerous power increase. The exact distribution and quantity of material used depend on other core parameters, such as type of coolant, location of the assemblies in the core, neutron spatial and energy distributions, reactor power, etc. Referring to FIG. 3, upon reaching a preset temperature in the range of about 550.degree.C. to 770.degree.C. (the exact temperature being determined by the difference in thermal expansion coefficients and diameters and thicknesses of the two metals in the bimetallic disk 16), the difference in thermal expansion coefficients gives rise to imbalanced thermal stresses, which cause at least one disk 16 to switch so that the inside layer 18 is now concave and the outside layer 20 is now convex. Thus concave and convex sides will now be reversed. This position of the disk 16 will be referred to hereinafter as the open position. The disk 16 does not bend or retract gradually from the closed to the open position or vice versa. The generally spherical shape of the disk 16 gives it a bistable characteristic, that is, it has two stable states; all other states are unstable. When the preset temperature is attained by heating the disk 16, the disk will, if in the closed position, snap abruptly to the open position. Conversely, if the preset temperature is attained by cooling the disk 16, the disk will, if in the open position, snap abruptly to the closed position. For this reason, bimetallic disks are used, for instance, as contacts in electrical switches. The lateral displacement is sufficient to pull the ball 24 from the inside of the inner tube 12. The conical bottom 30 of the absorber 10 also exerts a force which tends to push the ball 24 out of the tube 12. The absorber 10 is sufficiently smaller than the tube 12 so that removal of any one ball 24 will allow the absorber 10 to slip off the remaining two balls 24 and be inserted into the nuclear reactor core. When the absorber 10 has been fully inserted into the core, it will be below the disks 16 as shown by FIG. 3. When the actual temperature is again below the preset temperature, any open disk 16 will switch to the closed position due to the imbalanced thermal stresses, which tend to produce an opposite effect when the actual temperature falls below the preset temperature. Hence, the spring 17 is required so that when the absorber 10 is lifted into position for another use, as shown in FIG. 1, a top chamfered edge 32 on the top of the absorber 10 will gradually push the disks 16 back against the springs 17 until the absorber 10 has been lifted above the disks, when the spring will push the closed disks 16 back into position so that the absorber 10 may be rested on the balls 24.
	summary
	abstract	A method and system is provided to determine or estimate components that may have to be maintained before a molding system that has those components is caused to be stopped by problems with those components. Cycle times that each correspond to the time of the cycle of each operation of the molding system and operation times of the steps performed by the components, which operation times affect the cycle times, are measured and stored. Based on the sum of the operation times that exceed a predetermined time or the sum of the number of operation times that exceed the predetermined time, any step that may cause a problem among the steps of the components, which affect the cycle time, is determined.
052375943	abstract	A nuclear apparatus for obtaining qualitative and quantitative information related to an element of earth formation surrounding a borehole, comprising: (1) a neutron source for irradiating the formation with neutrons of sufficient energy to activate atoms of at least a given element; (2) at least two (preferably four) detectors longitudinally spaced from said source, for detecting the gamma rays emitted during the activation reaction; (3) means for assigning a maximum number of counts for each detector and for establishing a relationship between these maximum number of counts and the corresponding instant of time counts for each detector; and (4) means for deriving from the relationship qualitative information related to the element.. The relationship is approximately a straight line, the slope of which is representative of the element of interest. The amplitude of the counts is representative of the quantity of the activated element and of the radial distance between the activated atoms and the borehole.
048448567	summary	FIELD OF THE INVENTION The invention relates to a process for automatic regulation of the soluble boron content of the cooling water of a pressurized water nuclear reactor. BACKGROUND OF THE INVENTION Pressurized water nuclear reactors have a core consisting of assemblies arranged vertically and side-by-side in a vessel containing pressurized water which is responsible for cooling the core and transporting the heat from this core to the steam generators. The steam provided by the steam generators makes it possible to drive a turbine which is itself responsible for driving a turbo-alternator producing electric current. Depending on the needs of the electricity network and on the manner in which the power station is coupled to other nuclear power stations, it is necessary to ensure the control of the nuclear reactor to obtain from this reactor at any time a power corresponding to the power demanded. The control of the reactor is usually ensured by the vertical displacement, inside the core, of control rods which absorb the neutrons. In the most frequent modes of control of a pressurized water nuclear reactor, the movement of a control group consisting of highly absorbing rods is controlled automatically by employing as a regulating parameter the deviation between the real mean temperature of the core and a reference temperature which is a linear function of the power which the nuclear reactor has to supply to the turbine. However, in all the modes of control of a pressurized water nuclear reactor, it is necessary to have available an additional means for controlling the nuclear reactor. This additional means consists of a system for boration and dilution of the reactor cooling water, i.e., a system of means making it possible to vary the soluble boron content of the nuclear reactor cooling water, which can be introduced in the form of boric acid or, on the contrary, diluted by introducing pure water. The increase in the soluble boron content makes it possible, in fact, to increase the absorption of the neutrons by the cooling fluid and hence to reduce the reactor power. The dilution obviously has an opposite effect. The system for boration and dilution of the reactor cooling water makes it possible to complement the action of the groups of control rods and, in particular, to correct the long-term effects due to the variations in reactor reactivity. These long-term effects which accompany the variations in reactor reactivity include in particular the formation and the disappearance of xenon through a nuclear reaction in the reactor core. The appearance and the conversion of xenon have, in themselves, a major influence on the reactivity and on the axial distribution of power in the reactor core. The axial distribution of power in the reactor core, i.e. the distribution of power in the vertical direction, is in fact neither homogeneous nor constant for a variety of reasons, the main ones of which are that the control rods employed for controlling the reactor are generally inserted only over a part of the height of the core, that this insertion varies over time, and that the density of the cooling water and the concentration of xenon in the reactor core are not constant along its height. One of the objectives sought after in the course of reactor control is to avoid the power distribution in the core being excessively imbalanced between the upper part and the lower part of the core. To control the axial distribution of power in the core, there are usually available means for measuring the neutron flux at various heights in the core and means for calculating a parameter expressing the imbalance of power in the core, called "axial power inbalance .DELTA.I" and defined as follows: EQU .DELTA.I=P.sub.H -P.sub.B where P.sub.H is the power in the high half of the core, P.sub.B the power in the low half of the core and .DELTA.I the axial power imbalance expressed as a percentage of the nominal power. More precisely, a determination is made of the deviation in the value of the axial imbalance measured relative to a reference axial power imbalance .DELTA.I ref which corresponds to the value of the .DELTA.I measured at 100% of the reactor power, the control rods being virtually drawn out and the xenon being at equilibrium throughout the reactor core. In addition to the regulation of power with control rods comprising, in particular, the movement of a control group as a function of the deviation in the core temperature relative to a reference temperature, there is in operation a manual control of the boron content of the cooling water to make it possible to conform to the instructions for positioning the control rods as a function of the reactor power level. These positioning instructions are established so as to maintain the deviation in the power imbalance relative to the reference imbalance in a zone of small amplitude around the zero value. The means for boration and the means for dilution are controlled manually by an operator. This partly manual mode of control can be considered as relatively satisfactory in the case where the power station is employed at a constant power level or with very slow variations in power levels. During an operation of the power station following loading, when the variations in power are more numerous and faster, the necessary actions of boration or dilution are most frequent. It can then be very useful to have available a means of automatic control of the actions of boration and dilution. In U.S. Pat. No. 3,570,562, a part of the primary cooling water is diverted continuously into a measuring assembly permitting the momentary boron concentration in this primary water to be determined. The boron concentration is adjusted automatically by virtue of a regulator, as a function of the power demanded from the reactor, the permitted boron concentration limits, and the position of the control rods in the reactor core. Such a system of automatic regulation is, however, complex because it requires the continuous determination of the boron concentration in the cooling fluid and the establishment of a correlation between the required value of the concentration and the value of various control parameters of the reactor. In French Pat. No. 2,392,472, there is described a system for automatic boration and dilution based on the comparison between the mean temperature of the core and the reference temperature representing the power demanded by the turbine from the nuclear reactor. In the case of a mode of reactor control such as described in French Pat. No. 2,395,572 owned by the present assignee, methods of automatic control of the boron content such as described above would not be applicable. In the control process described in French Pat. No. 2,395,572, groups of control rods having reduced anti-reactivity are moved within the core, only as a function of the power demanded from the turbine. A group of highly absorbing control rods which is different from the power regulation groups is moved as a function of the deviation between the mean temperature of the core and the reference temperature. This temperature regulation group is moved in a manner which is totally independent of the power regulation groups, between control boundaries defined by the operating mode of the reactor and the state of change in the reactor core. To maintain the regulating group between these control boundaries, the concentration of boron in the primary fluid is varied either manually or automatically when the regulating group moves to reach one of the control boundaries. There is therefore no automatic regulation of the concentration of soluble boron in the cooling water so long as the regulating group does not move so as to reach or go beyond these control limits. Furthermore, the axial power distribution which is disturbed to a lesser degree than in other modes of control by the power regulating groups, is not controlled automatically. SUMMARY OF THE INVENTION The object of the invention is therefore to offer a process for automatic regulation of the content of soluble boron in the cooling water of a pressurized water nuclear reactor whose control is ensured by the vertical movement of control rods absorbing the neutrons in the core of the reactor consisting of assemblies arranged vertically and side-by-side and by the regulation of the content of soluble boron in the pressurized water by virtue of means of boration and means of dilution of this water, the control rods comprising at least one regulating group consisting of highly absorbing rods which are moved automatically as a function of the deviation between the mean temperature of the core and a reference temperature which is a function of the power which the reactor has to supply and of means associated with the reactor for determining the axial power imbalance in the core and the deviation of this axial imbalance relative to a reference imbalance corresponding to the minimum insertion of the control rods into the core and to the equilibrium of the xenon concentration in this core, this regulating process being capable of acting with certainty following a simple principle to assist the regulating group and permit a sufficiently homogeneous power distribution to be maintained in the core whatever the power program demanded from the reactor. To this end: operating regions of the means of boration and the means of dilution, respectively, are determined a priori, corresponding to pairs of values of two control parameters, namely a parameter which is characteristic of the position of the regulating group in the core and the deviation in the axial power imbalance relative to the reference imbalance, taking account of the operating conditions of the reactor and the safety standards, and that, in a continuous manner, during the operation of the reactor: a determination is made of the momentary value of the deviation in the axial power imbalance relative to the reference imbalance and the momentary value of the parameter which is characteristic of the position of the regulating group in the core, forming a pair of values of the control parameters, in the case where the means of boration and the means of dilution are initially at rest, the operation of the means of boration or the means of dilution is triggered if the pair of values of the control parameters corresponds to an operating region of the means of boration or the means of dilution, respectively, and these means are maintained at rest if the pair of values does not correspond to an operating region, and, in the case where the means of boration or the means of dilution are initially operating, the operation of these means is maintained so long as the pair of values of the control parameters corresponds to an operating region of these means of boration or of dilution.
047284854	abstract	Method for regulating the pressure of the primary circuit of a pressurized water nuclear reactor during shut-down phases, by use of an installation comprising, as a branch circuit to the primary circuit, a volume control circuit with a discharge valve and a charging valve. When the liquid level in the pressurizer approaches the top, a constant flow rate is maintained at the charging valve, the flow rate of the discharge valve is regulated by direct measurement of the primary pressure, successive sprinklings through the valve follow and the reduction in discharge flow rate is detected until further sprinkling has no further effect on the discharge flow rate.
	abstract	A radiation measurement device includes a radiation detector generating an analog signal containing pulse components, an A/D converter converting the analog signal into sampled data, an n-th power pulse discrimination unit calculating n-th power values of the sampled data to discriminate the pulse component, where n is two or more, and a pulse counter counting a number of the discriminated pulse components.
	description	This application claims priority to U.S. Provisional Application Ser. No. 61/678,702, filed Aug. 2, 2012, which is hereby incorporated by reference herein in its entirety. Nuclear fuel assemblies for powering nuclear reactors generally comprise large numbers of fuel rods that are contained in discrete fuel rod assemblies. These assemblies typically comprise a bottom end fitting or nozzle, a plurality of fuel rods extending upwardly therefrom and spaced from each other in a square or triangular pitch configuration, spacer grids situated periodically along the length of the assembly for support and orientation of the fuel rods, a plurality of control guide tubes interspersed throughout the assembly, and a top end fitting or cap. Once assembled, the fuel rod assembly can be installed within and removed from the reactor as a unit. When the nuclear fuel rods have expended a large amount of their available energy, they are considered to be “spent,” and the fuel rod assembly is removed from the reactor and temporarily stored in an adjacent pool until they can be transported to an interim storage facility, reprocessing center, or to a permanent storage facility or repository. Even though the rods are considered to be spent, they are still highly radioactive and hazardous both to people and property. There are a number of options available for storing and disposing of the radioactive spent fuel rods. In one such option, the fuel rod assemblies are contained within a dry storage system that can be transported offsite to another facility. In such systems, the fuel rod assemblies are typically placed, without water, within cylindrical canisters, which are then placed within transport casks. Transportable canister-based dry spent fuel storage systems must comply with multiple federal regulatory requirements, including both storage and transport requirements. Systems that are licensed for storage must meet safety design conditions imposed by 10 CFR Part 72, while systems that are licensed for transport must meet more challenging safety design conditions that are imposed by 10 CFR Part 71 (Part 71 hereafter). These parts are the sections of the Code of Federal Regulations that stipulate the requirements that must be complied with to obtain U.S. Nuclear Regulatory Commission (NRC) certification for the storage and transport of spent fuel. In order to achieve NRC certification under Part 71 for transport of a dry storage system for spent fuel, the storage system must be designed such that nuclear criticality cannot be achieved under normal operations and postulated accident conditions. Nuclear criticality is a condition in which the effective neutron multiplication factor of the fuel array, keff, is greater than or equal to 1.0 and a nuclear chain reaction becomes self-sustaining. According to the requirements, nuclear criticality must not be achieved even if the storage system is flooded with a neutron moderator, like water, in an optimal condition that enhances the potential for criticality. Notably, no regulatory credit is given for designing the system to ensure that water intrusion is not realistically possible. The requirement to prevent criticality even in the presence of a neutron moderator typically forces dry storage and transport system designers to produce systems that incorporate expensive neutron absorber material in the spaces between the fuel rod assemblies. The neutron absorber material ensures that, even with a neutron moderator present, keff remains less than or equal to 0.95 and the system is not able to sustain a nuclear chain reaction. Unfortunately, such designs have relatively low fuel storage capacity and are expensive because of the need for the neutron absorber material. Furthermore, these systems are not perfectly suitable to be placed in a permanent repository because of exceedingly large dimensions, typical neutron absorber degradation uncertainties, and other canister material degradation concerns under long-term disposal conditions. The net result is that the cost per spent fuel assembly stored, transported, and disposed of is greatly increased. From the above discussion, it can be appreciated that it would be desirable to have a transportable dry storage system and method that have higher spent fuel storage capacity and/or that remove the need for expensive neutron absorber material. As described above, it would be desirable to have a transportable dry storage system and method that have higher spent fuel storage capacity and/or that remove the need for expensive neutron absorber materials. Examples of such systems and methods are described in the following disclosure. In some embodiments, spent fuel rods are separated from their fuel rod assemblies and the freed rods are placed within a dry storage canister that, for example, can be placed in a storage or transport cask or in a repository. Because the fuel rods are separated from the fuel rod assembly, the rods can be placed within the storage canister with a much higher packing density. As a consequence, there is less space between the rods and, therefore, less danger of the system reaching nuclear criticality if a neutron moderator such as water were to enter the canister. Because of this, there is no need to provide expensive neutron absorber material within the canister. Furthermore, because of the limited open spacing, there is minimal risk for the rods to become geometrically reconfigured within the canister, a desirable feature when analyzing transport accident conditions to meet regulatory requirements. In the following disclosure, various specific embodiments are described. It is to be understood that those embodiments are example implementations of the disclosed inventions and that alternative embodiments are possible. All such embodiments are intended to fall within the scope of this disclosure. As described above, in order to satisfy federal safety requirements, fuel rod assemblies are typically placed within cylindrical canisters along with expensive neutron absorber material, resulting in low spent fuel storage capacity and high costs. An alternative way to satisfy such requirements is to package spent fuel in a manner in which there are few voids between the rods that a neutron moderator material, such as water, can fill so as to reduce the potential for nuclear criticality. Accordingly, neutron absorber material is unnecessary. In addition to increasing spent fuel storage capacity and removing the need for expensive neutron absorber material, such a design may enable credits to be awarded for the effects of burnup on the nuclear fuel to decrease criticality. As nuclear fuel is used, it builds up fission products that reduce its capability to support a self-sustaining chain reaction. This process is referred to as “burnup” and it is measured in terms of megawatt days per ton. Once burnup is sufficient to prevent further power development, the fuel is typically termed “spent fuel.” Possible credits could include (a) a reasonable credit for reduction in the amount of effective fissile material content of the fuel, resulting from that material being consumed by protracted fissioning during power operations, (b) a reasonable credit for effective neutron absorption by the actinides that are present in the spent fuel, and (c) a reasonable credit for effective neutron absorption by the fission products that are present in the spent fuel. One way of achieving the above-described goals is to remove spent fuel rods from their fuel rod assemblies and place the freed rods within a dry storage canister with very little space between the rods. Doing this provides several benefits. First, the spent fuel rods will have a higher packing density within the canister and therefore a higher storage capacity can be obtained. In addition, because there is very little space between the rods, the risks associated with ingress of water or another neutron moderator are reduced and no expensive neutron absorber material is required. Furthermore, because there is less risk associated with nuclear criticality in the event of compromise of the canister, the canister can be made of relatively inexpensive materials. When increasing the packing density in this manner, steps can be taken to ensure that the heat generated by the spent fuel rods is dissipated, especially from the center of the canister, which is farthest from the canister walls. FIGS. 1-8 illustrate various canister designs that can be used to achieve both high rod packing density as well as desirable heat dissipation. FIGS. 1 and 2 illustrate a first embodiment of a dry storage canister 10 in which free spent fuel rods (i.e., rods separated from their fuel rod assemblies) can be stored in a dry condition (i.e., without the presence of water). As shown in FIG. 1, the canister 10 generally comprises an elongated outer housing 12 in which is provided an internal basket 14 that is adapted to receive spent fuel rods and dissipate their heat. The shape and dimensions of the outer housing 12 can depend upon the size and nature of the rods it is to store and/or the size and nature of a container (e.g., cask) in which the canister is to be placed. In some embodiments, however, the outer housing 12 is cylindrical, approximately 165 to 210 inches long, and has a diameter of approximately 12 to 24 inches. The walls of the outer housing 12 can be made of a strong metal material, such as stainless steel, and can be approximately ¼ to ½ inches thick. As shown in FIG. 1, the internal basket 14 divides the interior space of the outer housing 12 into multiple storage compartments or cells 16 in which spent fuel rods, such as rods 18, can be provided. As is apparent from FIG. 1, the cells 16 extend along the length direction of the housing 12 from one end of the housing to the other. FIG. 2 shows the configuration of the basket 14 more clearly. In the example shown in FIG. 2, the basket 14 comprises a central tube 20 from which radially extend multiple divider walls 22 that create a “pie piece” configuration for the cells 16. The divider walls 22 extend to the housing 12. Between the distal ends of the divider walls 22 extend end walls 24. With such a configuration, each cell 16 of the basket 14 is generally triangular and is defined by the central tube 20, two divider walls 22, and an end wall 24. The various components of the internal basket 14, including the central tube 20, the divider walls 22, and the end walls 24, can be made of a metal or alloy materials having high thermal conductivity (e.g., 200 to 380 W/(m·k)). Example materials include aluminum alloys and copper. When the spent fuel has aged for many years and has lower residual heat, the basket 14 can be made of materials with lower thermal conductivity and higher strength, such as steel, to further increase packing density. The thickness and materials of these components can be selected based upon the strength that is needed as well as the amount of heat dissipation that is required. In some embodiments, however, the walls of the basket 14 are approximately ¼ to ⅝ inches thick. The number of divider walls 22 that the basket 14 includes can be varied based upon the size and number of cells 16 that are desired. In the illustrated example, however, the basket 14 comprises eight divider walls 22 that form eight separate cells 16. In FIG. 2, only one of the storage cells 16 is shown filled with spent fuel rods 18. As is clear from the figure, the rods 18 are tightly packed within the cell 16 such that there is very little space between them. In some embodiments, the rods 18 contact each other along much of or all of their lengths. By way of example, a packing density of approximately 5 to 6 spent fuel rods per squared inch can be achieved within each cell 16 for rods of typical dimensions (e.g., 0.382 to 0.45 inches in diameter). In the illustrated example, 271 rods 18 are shown contained within the filled cell 16, in which case the canister 10, with an approximate radius of 12 inches would be able to store 2,168 such rods in total. The internal basket 14 is configured to not only provide structural support to the spent fuel rods 18 but also to dissipate heat generated by the rods, particularly in the center of the canister, which is farthest from the walls of the outer housing 12. The basket 14 achieves this with the dividing walls 22, which transfer heat from the center of the canister 10 to the outer housing 12, which acts like a heat sink. The pie-piece configuration of the cells 16 increases this heat transfer by increasing the amount of basket material in the center of the canister 10 while simultaneously reducing the concentration of rods 18 in that location. In other words, the ratio of the mass of the heat-dissipating basket material to the mass of the fuel rod material increases as the canister 10 is traversed from the walls of the outer housing 12 to the center of the canister. The central tube 20 also reduces the density of the spent fuel rod material near the center of the canister 10. In addition, the central tube 20 acts as a load distribution cell that spreads loads imposed upon the canister 10, for example, if the canister is impacted because of an accident. In addition, the central tube 20 can provide space for a drain tube (not shown) that is used to drain residual water that drips down to the bottom of the canister from the fuel rods during a draining and drying process performed prior to sealing of the canister 10. FIG. 3 illustrates an alternative dry storage canister 30 that is similar in many ways to the canister 10 shown in FIGS. 1 and 2. The canister 30 also generally comprises an elongated outer housing 32 and an internal basket 34 that defines multiple storage cells 36 having a pie-piece configuration. In the embodiment of FIG. 3, however, each cell 36 is provided with corrugated dividers 38 that further dissipate heat generated by the spent fuel rods 18. The dividers 38 can therefore also be made of a material having high thermal conductivity, such as aluminum alloys or copper. If the spent fuel has lower residual heat, lower thermal conductivity and higher strength materials, such as steel, can be used. As is apparent in FIG. 3, the corrugated dividers 38 separate the spent fuel rods 18 into multiple discrete rows of rods that are generally perpendicular to the radial direction of the canister 10. With such a configuration, the dividers 38 separate the rods 18 of one row from the rods of adjacent rows. In addition, because each divider 38 is corrugated, each rod 18 within each row can be, if desired, separated from adjacent rods within its own row depending upon the configurations of the corrugations. In addition to dissipating heat from the rods 18, the dividers 38 can facilitate packing of the free fuel rods 18 into their cells 36. For example, the rods 18 and dividers 38 can be combined together separate from the canister 30 and later placed together as a preformed unit into a cell 36 of the canister. Alternatively, the dividers 38 can be positioned within the cell 36 and can be used to guide the various free rods 18 into their respective positions within the cell 36. FIGS. 4 and 5 illustrate a third embodiment of a dry storage canister 40. As shown in FIG. 4, the canister 40 generally comprises an elongated outer housing 42 in which is provided an internal basket 44 that is adapted to receive spent fuel rods 18. In some embodiments, the shape, dimensions, and material of the outer housing 42 can be similar to those described above in relation to the outer housing 12 shown in FIGS. 1 and 2. The internal basket 44 forms multiple cylindrical storage cells 46. As is apparent from FIG. 4, the cells 46 generally extend along the length direction of the outer housing 42 from one end of the housing to the other. FIG. 5 shows the configuration of the basket 44 more clearly. In the example shown in FIG. 5, the basket 44 comprises twelve storage cells 46 each formed by a cylindrical tube 48 of the basket. Although twelve cells 46 are shown in FIG. 5, it is noted that a larger or smaller number of cells could be used. By way of example, the tubes 48 can have a diameter of approximately 4 to 6 inches and also can be made of metal materials that have high thermal conductivity. Example materials include, aluminum alloys and copper. Again, if the spent fuel has lower residual heat, lower thermal conductivity and higher strength materials, such as steel, can be used. The thickness of the walls and materials of the cylindrical tubes 48 can be selected based upon the strength that is needed as well as the amount of heat dissipation that is required. In some embodiments, however, the walls of the tubes 48 are approximately ⅛ to ¼ inches thick. In FIG. 5, nine of the storage cells 46 are shown filled with spent fuel rods 18. As is clear from the figure, the rods 18 are tightly packed within the cells 46 such that there is very little space between the rods. In some embodiments, the rods 18 contact each other along much of or all of their lengths. By way of example, a packing density of approximately 4 to 5 spent fuel rods per square inch can be achieved within each cell 46. In the illustrated example, 108 rods are shown contained within the filled cells 46, in which case the canister 40 would be able to store 1,296 such rods in total. Spacing between the cylindrical tubes 48 is maintained by one or more spacer disks 50 that extend between the outer surfaces of the tubes. In some embodiments, one such spacer disk 50 can be positioned at least at each end of the canister 40. The spacer disks 50 can, for example, be made of the same thermally-conductive material from which the tubes 48 are made. As is further shown in FIG. 5, the internal basket 44 can further comprise elongated peripheral plates 52 that are positioned at the edges of the spacer disks 50 and extend along the length direction of the canister 40. When provided, the plates 52 provide further structural integrity to the basket 44. It is also noted that, instead of basket 44, solid aluminum cylinders having bored cylindrical channels to receive cylindrical tubes 48 could be used to separate the tubes and provide for increased heat dissipation. Although corrugated dividers similar to those described above can be provided within the storage cells 46, if desired, it is noted that they are not likely required because the distance from the outer wall of the cylindrical tubes 48 to the centers of the tubes is not great. FIGS. 6 and 7 illustrate a third embodiment of a dry storage canister 60. As shown in FIG. 6, the canister 60 generally comprises an elongated outer housing 62 in which is provided an internal basket 64 that is adapted to receive spent fuel rods 18. In some embodiments, the shape, dimensions, and material of the outer housing 62 can be similar to those described above in relation to the outer housing 12 shown in FIGS. 1 and 2. The internal basket 64 defines multiple rectangular storage cells 66. As is apparent from FIG. 6, the cells 66 generally extend along the length direction of the outer housing 62 from one end of the housing to the other. FIG. 7 shows the configuration of the basket 64 more clearly. In the example shown in FIG. 7, the basket 64 comprises seven storage cells 66 each formed by a rectangular (e.g., square) tube 68 of the basket. Although seven cells 66 are shown in FIG. 7, it is noted that a larger or smaller number of cells could be used. By way of example, the tubes 68 can have cross-sectional (height and width) dimensions of approximately 4 to 6 inches and also can also be made of metal material that have high thermal conductivity. Example materials include aluminum alloys and copper. If the spent fuel has a lower residual heat, lower thermal conductivity and higher strength materials, such as steel, can be used. The thickness of the walls of the tubes 68 can be selected based upon the strength that is needed as well as the amount of heat dissipation that is required. In some embodiments, however, the walls of the tubes 68 are approximately ¼ to ⅜ inches thick. In FIG. 7, one of the storage cells 66 is shown filled with spent fuel rods 18. As is clear from the figure, the rods 18 are tightly packed within the cells 66 such that there is very little space between the rods. In some embodiments, the rods 18 contact each other along much of or all of their lengths. By way of example, a packing density of approximately 4 to 5 rods of spent fuel per square inch can be achieved within each cell 66. In the illustrated example, 225 rods 18 are shown contained within the filled cells 66, in which case the canister 60 would be able to store 1,575 such rods in total. Spacing between the rectangular tubes 68 is maintained by one or more spacer disks 70 that extend between the outer surfaces of the tubes. In some embodiments, one such spacer disk 70 can be positioned at least at each end of the canister 60. In some embodiments, the spacer disks 70 can be made of the same thermally-conductive material from which the tubes 68 are made. It is also noted that, instead of spacer disks 70, the basket 64 could comprise a solid cylindrical member having drilled rectangular channels adapted to receive tubes 68 could be used to separate the tubes and provide for increased heat dissipation. FIG. 8 illustrates a further dry storage canister 80 that is similar in many ways to the canister 60 shown in FIGS. 6 and 7. Accordingly, the canister 80 generally comprises an elongated outer housing 82 and an internal basket 84 that defines multiple storage cells 86. In the embodiment of FIG. 8, however, each cell 86 is provided with corrugated dividers 88 that further dissipate heat generated by the spent fuel rods 18. The dividers 88 can therefore also be made of a material having high thermal conductivity, such as aluminum alloys or copper. If the spent fuel has lower residual heat, lower thermal conductivity and higher strength materials, such as steel, can be used. As is apparent in FIG. 8, the corrugated dividers 88 separate the spent fuel rods 18 into multiple discrete rows of rods. With such a configuration, the dividers 88 separate the rods 18 of one row from the rods of adjacent rows. In addition, because each divider 88 is corrugated, each rod 18 within each row can be, if desired, separated from adjacent rods within its own row. Aside from dissipating heat from the rods 18, the dividers 88 facilitate packing of the free rods into their cell 86. For example, the rods 18 and dividers 88 can be combined together separate from the canister 80 and later placed together as a preformed unit into a cell 86 of the canister. Alternatively, the dividers 88 can be positioned within the cell 86 and can be used to guide the various free rods 18 into their respective positions within the cell 86. Irrespective to the nature of the canisters that are used to store the spent fuel rods 18, the canisters can be placed in a storage or transport cask. FIG. 9 illustrates an example storage cask 90 in which multiple canisters 92 have been provided. In this example, the walls of the cask 90 are made of concrete. In other cases, such as when the cask is a transport cask, the walls of the cask can be made of other materials, such as stainless steel and/or lead. The dry storage systems described in this disclosure provide numerous advantages over conventional storage systems. As noted above, much higher packaging density can be achieved and a large amount of void space is removed to limit the amount of neutron moderator (e.g., water) that can intrude, and reconfiguration of the fuel within the canister under transport and long-term disposal conditions. This eliminates need for expensive neutron absorber material. Because of the design of the canister baskets, improved heat removal can be achieved providing for a more uniform heat profile for the canisters in a geologic repository. Because of the high packing density, better shielding can be achieved with the outer rods shielding the inner rods, especially if the inner rods are hotter, high burnup fuel rods. In addition, the canister designs are relatively simple, which provides advantages in terms of structural analysis and ease of implementation. Furthermore, higher safety margins of storage can be achieved while simultaneously reducing costs. Additionally, damaged fuel rods can be managed more easily. Finally, the designs present a configuration strategy that supports efficient spent fuel packaging, fuel reprocessing, transport, and disposal, as well as standardization of storage, transport, and disposal systems.
049884760	claims	1. A method of evaluating deformations of a channel box of a fuel assembly having been used for exposure in a nuclear reactor core having an array of fuel assemblies, comprising the steps of: finding initial deformations of said channel box which has been deformed during past exposure; specifying a position in said array at which said channel box is adapted to be located; calculating estimated deformations of said channel box during a next exposure cycle from data of core characteristics, data of shape and material properties of channel boxes, data of loading patterns, and said initial deformations; and judging whether said calculated deformations are agreeable or not. 2. A method as set forth in claim 1, wherein said estimated deformations are calculated for every channel box in said nuclear reactor core. 3. A method as set forth in claim 2, wherein control rods are provided in said nuclear reactor core, each of said control rods being associated with channel boxes in one group unit, with said judging step determining whether or not any one of said channel boxes in one group unit interferes with the associated control rod due to said estimated deformations. 4. A method of evaluating deformations of channel boxes of fuel assemblies having been used for exposure in a nuclear reactor core, said fuel assemblies being divided in groups each having a predetermined number of said fuel assemblies and including a control rod, comprising the steps of: finding initial deformations of said channel boxes; reading data of core characteristics, data of material properties and shapes of said channel boxes, data of positions of said channel boxes and said control rods, data of loading patterns and said initial deformations; calculating estimated deformations of channel boxes in a next exposure cycle from said read data; judging whether or not said channel boxes interfere with said associated control rods in accordance with said estimated deformations; displaying results of the interference; resetting loading positions, loading directions and a loading pattern causing no interference, if interference is estimated to occur; and displaying said reset loading positions, directions and pattern. 5. A method as set forth in claim 4, further comprising the steps of maximizing a number of channel boxes which do not interfere with the associated control rods, wherein said maximizing step is carried out in such a way that said calculating step, said judging step and said resetting step are repeated in accordance with said reset loading pattern so as to maximize a number of channel boxes which do not interfere with said associated control rods. 6. A method as set forth in claim 5, wherein said calculating step, said judging step, said resetting step and said maximizing step are repeated so as to set a loading pattern of said channel boxes loaded in said reactor core, with which it is estimated that no interference occurs during said next exposure cycle. 7. A method as set forth in claim 4, wherein said initial deformations are obtained by measuring said channel boxes. 8. A method as set forth in claim 4, wherein said initial deformations of said channel boxes are calculated from said data of core characteristics, said data of material properties and shapes of said channel boxes, said data of loading patterns and data of past exposure applied to said channel boxes. 9. An apparatus for evaluating deformation of channel boxes of fuel assemblies having been used for exposure in a nuclear reactor core; comprising memory means for storing therein data of core characteristics, data of material properties and shapes of said channel boxes, data of initial deformations of said channel boxes, and data of loading patterns; a computing and processing means for calculating estimated deformations of said channel boxes during a next exposure cycle in accordance with said data delivered from said memory means with the use of arithmetic expressions; and a display means for displaying a result of calculation made by said computing and processing means. 10. An apparatus as set forth in claim 9, wherein said nuclear reactor core includes control rods each associated with one unit group of said fuel assemblies having a predetermined number, and said computing and processing means is adapted to judge whether said channel boxes interfere with said associated control rods.
	claims	1. An apparatus adapted to select at least one band of wavelengths from diverging incident synchrotron x-ray radiation in a given range of wavelengths with an energy resolution in a range from about 0.5 parts in 10000 to about five parts in 10000 and optical efficiency in a range from about 50 percent to about 90 percent. 2. An apparatus comprising:a first crystal adjustably oriented relative to diverging incident synchrotron x-ray radiation whereina band of emitted wavelengths of the first crystal includes at least one band of wavelengths narrower than a range of wavelengths of the incident synchrotron x-ray radiation, anda surface curvature of the first crystal is adapted to focus emitted radiation in a first plane;a second crystal adjustably oriented relative to radiation emitted from the first crystal whereina band of emitted wavelengths of the second crystal includes the at least one band of wavelengths, andthe second crystal is asymmetrically cut whereby parallel faces of a lattice structure of the second crystal are oriented at a first predetermined angle from a surface of the second crystal; andan aperture disposed to block radiation emitted from the second crystal having wavelengths outside the at least one band of wavelengths. 3. An apparatus as recited in claim 2, wherein the second crystal is disposed to receive at least the band of emitted wavelengths of the first crystal. 4. An apparatus as recited in claim 3, wherein the second crystal is adapted to rotate so that radiation emitted by the second crystal is directed in a similar direction and spatially offset from the incident synchrotron x-ray radiation. 5. An apparatus as recited in claim 2, wherein the first crystal is asymmetrically cut whereby parallel faces of a lattice structure of the first crystal are oriented at a second predetermined angle from a surface of the first crystal. 6. An apparatus as recited in claim 5, wherein the second predetermined angle is about seven degrees. 7. An apparatus as recited in claim 5, wherein a surface curvature of the second crystal is adapted to focus emitted radiation in a second plane perpendicular to the first plane. 8. An apparatus as recited in claim 7, wherein the first predetermined angle is oriented so that a band of emitted wavelengths of the first crystal has a width in a range from about 0.5 parts in 10000 to about five parts in 10000 of a wavelength included in the at least one band of wavelengths. 9. An apparatus as recited in claim 7, further comprising a mirror with a curved surface adapted to position a vertical focus of radiation emitted from the second crystal in the band of emitted wavelengths of the second crystal. 10. An apparatus as recited in claim 2, wherein the band of emitted wavelengths of the second crystal has a width in a range from about 0.5 parts in 10000 to about five parts in 10000 of a wavelength included in the at least one band of wavelengths. 11. An apparatus as recited in claim 2, wherein the band of emitted wavelengths of the second crystal has an energy flux in a range from about 50 percent to about 90 percent of an energy flux in a corresponding band of wavelength in the incident radiation. 12. An apparatus as recited in claim 2, further comprising a mirror with a curved surface adapted to reject high order harmonics of at least one of the band of emitted wavelengths of the first crystal or the band of emitted wavelengths of the second crystal.
	claims	1. A fast reactor having a reflector control system, comprising:a reactor vessel which is filled with a liquid metal coolant;a reactor core including a fuel assembly, which is placed at a central position of the reactor vessel; anda neutron reflector including a region, which is placed at an upper side thereof and at which a neutron absorber or a neutron transmitting material having a neutron reflection ability lower than that of the liquid metal coolant is placed and a reflection region which is placed at a lower side thereof and provided outside the reactor core so as to be moved in a vertical direction in an installed state of the fast reactor for adjusting leakage of neutrons from the reactor core so as to control a reactivity thereof,wherein said neutron reflector is moved in an upward direction in accordance with a change in reactivity caused by burn-up of a fuel, and the reflection region includes an upper sub-region and a lower sub-region both with higher fast-neutron reflection ability than that of the liquid metal coolant, the lower sub-region contains a material with a higher fast-neutron reflection ability than that of the upper sub-region. 2. The fast reactor according to claim 1, wherein said lower sub-region is a region from a bottom end of the neutron reflector to a place substantially two-fifths of the height thereof. 3. The fast reactor according to claim 1, wherein said lower sub-region comprises a material having a larger neutron scattering cross-section for fast neutrons having an energy of substantially 0.1 to 1 MeV as compared to that of the upper sub-region. 4. The fast reactor according to claim 1, wherein said neutron reflector is composed of steel containing at least one of chromium and nickel, and the lower sub-region includes at least one of chromium and nickel at a higher content as compared to that of the upper sub-region of the neutron reflector. 5. The fast reactor according to claim 1, wherein said upper sub-region is made of a material different from that of said lower sub-region. 6. The fast reactor according to claim 5, wherein said upper sub-region is composed of steel containing at least one of chromium and nickel, and the lower sub-region region includes at least one of chromium and nickel at a higher content as compared to that of the upper sub-region. 7. The fast reactor according to claim 1, wherein the lower sub-region has a higher fast-neutron reflection ability as compared with that of the upper sub-region prior to neutron exposure of said reflector. 8. A fast reactor having a reflector control system, comprising:a reactor vessel which is filled with a liquid metal coolant;a reactor core located in the reactor vessel including a fuel assembly; anda neutron reflector provided outside the reactor core so as to be moved in a vertical direction and which includes a first neutron absorbing or transmitting material located at an upper side thereof having a neutron reflection ability lower than that of the liquid metal coolant, a first neutron reflection material located below said first absorbing or transmitting material, and a second neutron reflection material located below said first neutron reflection material,wherein the first and second neutron reflection materials both have a higher fast-neutron reflection ability than that of the liquid metal coolant, and the first neutron reflection material is different from the second neutron reflection material. 9. The fast reactor according to claim 8, wherein said first and second materials are located in a region between a bottom end of the neutron reflector and substantially two-fifths of the height thereof. 10. The fast reactor according to claim 8, wherein each of said first and second materials comprises a material having a large neutron scattering cross-section for fast neutrons having an energy of substantially 0.1 to 1 MeV. 11. The fast reactor according to claim 8, wherein said first material is composed of steel containing at least one of chromium and nickel, and the second neutron reflection material includes at least one of chromium and nickel at a higher content as compared to that of the first neutron reflection material. 12. The fast reactor according to claim 8, wherein the second material has a higher fast-neutron reflection ability as compared with that of the first material prior to neutron exposure of said reflector.
	claims	1. A method for preparing alpha sources of polonium, comprising:providing a sample of polonium in a solution;introducing a controlled amount of sulfide and a controlled amount of copper for forming an insoluble sulfide salt in the solution, in order to co-precipitate polonium from the solution; andfiltering out the precipitates that contain the alpha sources of polonium. 2. The method of claim 1, wherein the controlled amount of copper is in the range of about 1 μg to about 100 μg. 3. The method of claim 2, wherein the controlled amount of copper is in the range of about 30 μg to about 70 μg. 4. The method of claim 3, wherein the controlled amount of copper is about 50 μg. 5. The method of claim 1, wherein there is a time period of at least about 10 min after introducing the sulfide and the copper, before filtering out the precipitates. 6. The method of claim 5, wherein the time period is no more than about 3 hours. 7. The method of claim 1, wherein the polonium is provided in an acidic solution. 8. The method of claim 7, wherein the solution comprises hydrochloric acid. 9. The method of claim 8, wherein the hydrochloric acid is in the solution at a concentration in the range of about 0.01 M to about 2 M. 10. The method of claim 9, wherein the hydrochloric acid has a concentration in the range of about 0.1 M to about 1 M. 11. The method of claim 10, wherein the hydrochloric acid has a concentration of about 1 M. 12. The method of claim 1, wherein the polonium is provided in a controlled amount of solution that is in the range of about 5 mL to about 20 mL. 13. The method of claim 12, wherein the controlled amount of solution is about 10 mL. 14. The method of claim 1, wherein filtering out the precipitates comprises filtering the sample of polonium using a vacuum box. 15. The method of claim 14, further comprising preparing multiple alpha sources from multiple samples of polonium in parallel, using the vacuum box. 16. The method of claim 1, further comprising drying the precipitates after the filtering and mounting the precipitates on a disc for counting by alpha spectrometry.
	abstract	A nuclear reactor includes a reactor pressure vessel and a nuclear reactor core comprising fissile material disposed in a lower portion of the reactor pressure vessel. The lower portion of the reactor pressure vessel is disposed in a reactor cavity. An annular neutron stop is located at an elevation above the uppermost elevation of the nuclear reactor core. The annular neutron stop comprises neutron absorbing material filling an annular gap between the reactor pressure vessel and the wall of the reactor cavity. The annular neutron stop may comprise an outer neutron stop ring attached to the wall of the reactor cavity, and an inner neutron stop ring attached to the reactor pressure vessel. An excore instrument guide tube penetrates through the annular neutron stop, and a neutron plug comprising neutron absorbing material is disposed in the tube at the penetration through the neutron stop.
047132140	claims	1. In a fast neutron nuclear reactor cooled by a liquid metal and comprising a vessel containing said liquid metal coolant and a support structure, a device of purifying the liquid metal coolant comprising (a) an external cylindrical envelope fixed to the support structure; (b) an assembly of annular and coaxial chambers separated by cylindrical casings disposed vertically inside said cylindrical envelope; (c) a pump connected to said assembly of chambers and disposed with respect to said vessel for circulating the liquid metal through said chambers; (d) a filter cartridge disposed at the central part of said assembly of chambers; (e) a channel disposed at the central part of said filter cartridge for collecting the purified liquid metal; (f) an economizer exchanger contained in a first chamber of said assembly of chambers connected to said pump to receive liquid metal to be purified and to said channel to receive purified liquid metal; (g) cooling means connected to a second chamber for cooling the liquid metal before its purification by passage through the filter wherein said chambers are all disposed one inside the other, their casings being fixed at their lower parts, on one horizontal plate supported by said external envelope, such that they are freely expandable independent of each other, said assembly of chambers comprising from said external envelope inwards; the inner chamber (16) being a chamber for the entry and the cooling of the liquid metal to be purified, communicating through its lower part with the outlet of the pump for circulating the liquid metal to be purified (6) and through its upper part with the chamber for cooling and purifying (22) the liquid metal. 2. The purifying device as claimed in claim 1, wherein the economizer-exchanger consists of two adjacent coaxial annular chambers (14, 16) separated by a metallic shell (15) across which the heat exchanges take place, the outer chamber (14) being a chamber for reheating and discharging the purified liquid metal and communicating through its lower part with the lower part of the degassing chamber (12) and with an outlet duct (45) for the purified metal and through its upper part with the basin for collecting the purified liquid metal (44), 3. The purifying device as claimed in claim 1, wherein the economizer exchanger consists of tubes (60) arranged along the axial direction, inside an annular chamber (61) comprised between the internal cylindrical shell (13) of the degassing chamber (12) and the thermal insulation wall (18) joined at its upper part to the basin for collecting the purified liquid metal (44) and at its lower part to the degassing chamber (12) and to the duct for discharging the purified metal (45), inside which the purified and cooled liquid metal circulates, the tubes (60) being connected at one of their ends to the outlet of the pump for circulating the liquid metal (6) to be purified and at their other end to the annular chamber (22) for cooling and purifying the liquid metal. 4. The purifying device as claimed in claim 1 wherein the economizer exchanger consists of an assembly of double coaxial tubes (70) arranged helically inside a chamber (71) filled with thermal insulation material, comprised between the internal cylindrical shell (72) of the degassing chamber (12) and the external cylindrical shell (73) of the cooling chamber (20), the internal tube of the double coaxial tube (70) being joined at its lower part to the discharge of the pump for circulating liquid metal (6) and at its upper part to the annular chamber for cooling and purifying (22), and the outer part of the double coaxial tubes (70) communicating at its upper part with the basin for collecting the purified liquid metal (44) and at its lower part with the degassing chamber (12) and with the duct for discharging the purified liquid metal (45). 5. The purifying device as claimed in claim 2, wherein plates for stiffening and deflecting the liquid metal (55, 56) are arranged vertically inside the two adjacent coaxial annular chambers (14, 16) forming the economizer exchanger over the entire length of these chambers for stiffening of the structure and guiding the liquid metal. 6. The purifying device as claimed in claim 2, wherein the first chamber (16), the second chamber (20) and the chamber (22) containing the filter are closed at their upper part by a set of horizontal plates (37 and 38) placing the first chamber (16) in communication with the chamber (22) containing the filter and insulating the second chamber (20) from the liquid metal to be purified, openings ("a and 38 a) being provided in these plates (37 and 38) and passage shafts (39) being arranged in the region of these openings (37a and 38a) for introducing into the cooling chamber (20) devices for heat withdrawal (40) forming part of the external means for cooling this chamber. 7. The purifying device as claimed in any one of claims 2, 5 and 6 wherein the means for cooling (40) the purified liquid metal in the cooling chamber (20) consist of heat pipes which are immersed in the liquid metal filling this chamber and are connected outside the purifying device to a heat exchanger (41) of the air-cooled type. 8. The purifying device as claimed in claim 1, wherein the means for cooling the purified fluid filling the cooling chamber consist of hairpin tubes (75) which are filled with liquid sodium for exchange and are immersed with their lower part in the liquid metal filling the cooling chamber (20) and entering with their upper part into a device for cooling by air (76). 9. The purifying device as claimed in any one of claims 2, 5 and 6, wherein the various cylindrical shells of the annular chambers are all fixed at their lower part on a single base plate (10) pierced with openings (10a) for the passage of the liquid metal to be purified, a chamber for entry (30) of the liquid metal communicating with the openings (10a) in the base plate (10) being arranged under this plate (10) and communicating with the outlet of the pump for circulating the liquid metal (6). 10. The purifying device as claimed 1 in claim 1, wherein the cylindrical shells (19, 21, 23) defining the chambers for cooling (20) and for purifying (22) are joined to a first horizontal base plate (10d) and the cylindrical shells (15, 17, 11, 13) of the economizer exchanger and of the degassing chamber (12) are joined to at least one horizontal base plate (10b) which is different from the first plate (10d). 11. The purifying device as claimed in claim 10, wherein the pump (6) is arranged above the base plate (10b) supporting the cylindrical shells (15, 17, 11, 13) of the economizer exchanger and of the degassing chamber (12), all of the components of the purifying device being above this lower base plate (10b). 12. The purifying device as claimed in any one of claims 2, 5 and 6, which device is of the integrated type and is arranged inside a casing (1) filled with an inert gas. 13. The purifying device as claimed in claim 2, wherein an electromagnetic regulating pump (86) is arranged between the degassing chamber (12) and the chamber for discharge of the purified liquid metal (14) so as to propel the liquid metal in this chamber (14) up to a level above the upper end of the internal cylindrical shell (13) of the degassing chamber (12).
	summary
050158635	abstract	This invention relates to a shielding material used as a radiation shield of a container containing radioactive wastes. A radiation shield with an excellent heat-transferring property is fabricated from composite particles (A) obtained by coating core particles (a) of radiation-shielding property with a metal (b) of high thermal conductivity. Composite particles are formed into a certain shape of radiation shield by hot-press forming or other forming or packed into the internal space of radioactive waste container or the shield container cavity to compose a radiation shield.
047056630	abstract	In a nuclear reactor fuel element for receiving mutually parallel rods, the improvement includes a rectangular grid-shaped spacer including planar webs crossing and facing the rods defining grid mesh openings receiving the rods, the webs including two outer webs forming an outer corner of the spacer and defining a corner grid mesh opening at the outer corner, the outer corner having an outward curve being curved in a direction parallel to the longitudinal direction of the rods, the outer webs having edges at the curve transverse to the rods being drawn inward toward the rods in the corner grid mesh opening forming a bevel in longitudinal direction of the rod.
041705173	description	DESCRIPTION OF THE PREFERRED EMBODIMENT This invention provides a new reactor vessel to cavity seal arrangement that forms a permanent flexible seal between the reactor vessel and the reactor cavity floor effecting a water-tight seal for the refueling canal during refueling operations while accommodating material expansions and contractions that occur during normal reactor operations, without destroying the water-tight integrity of the seal. The invention can best be understood by reference to the plan view of a reactor containment illustrated in FIG. 1 which shows a nuclear steam generating system of the pressurized water type incorporating the permanent water tight seal ring of this invention. A pressurized vessel 10 is shown which forms a pressurized container when sealed by its head assembly 12. The vessel has coolant flow inlet means 14 and coolant flow outlet means 16 formed integral with and through its cylindrical walls. As is known in the art, the vessel 10 contains a nuclear core (not shown) consisting mainly of a plurality of clad nuclear fuel elements which generate substantial amounts of heat depending primarily upon the position of control means, the pressure vessel housing 18 of which is shown. The heat generated by the reactor core is conveyed from the core by coolant flow entering through inlet means 14 and exiting through outlet means 16. The flow exiting through outlet means 16 is conveyed through hot leg conduit 20 to a heat exchange steam generator 22. The steam generator 22 is of the type wherein heated coolant flow is conveyed through tubes (not shown) which are in heat exchange relationship with water which is utilized to produce steam. The steam produced by the steam generator 22 is commonly utilized to drive a turbine (not shown) for the production of electricity. The flow is conveyed from the steam generator 22 through conduit 24 to a pump 26 from which it proceeds through cooled leg conduit 28 to inlet means 14. Thus, it can be seen that a closed recycling primary or steam generating loop is provided with coolant piping communicably coupling the vessel 10, the steam generator 22, and the pump 26. The generating system illustrated in FIG. 1 has three such closed fluid flow systems or loops. The number of such systems should be understood to vary from plant to plant, but commonly two, three or four are employed. Within the containment 42 the reactor vessel 10 and head enclosure 12 are maintained within a separate reactor cavity surrounded by a concrete wall 30. The reactor cavity is divided into a lower portion 32 which completely surrounds the vessel structure itself and an upper portion 34 which is commonly utilized as a refueling canal. In prior art designs, air flow communication was maintained between the lower reactor vessel well 32 and the refueling canal 34 to assist cooling of the concrete walls of the reactor cavity and the excore detectors embedded within the concrete walls. The air flow was facilitated by exhaust fans positioned within the containment 40 outside of the concrete barrier 30. During refueling operations, the reactor vessel flange 36 was sealed to the reactor cavity shelf 40 by a clamped gasket seal ring which prevented leakage of refueling water to the cavity space directly below the reactor vessel. Such seals, however, required considerable time be allotted for their installation and could not be fastened into place until the reactor cooled down. Furthermore, installation of the seal cut off the air path which facilitated circulation of the cooling medium around the lower portion of the vessel cavity. This invention expedites refueling procedures by providing a permanent reactor vessel to cavity seal 38 between the reactor vessel flange 36 and the cavity shelf 40 which accommodates the normal material expansions and contractions experienced during reactor operation while maintaining the water-tight integrity of the seal essential during refueling operations. In addition, a structural modification to the cavity wall around the nozzle locations 14 and 16 facilitates air flow in the lower portion of the reactor cavity, which enables cooling to occur during refueling operations as well as during reactor operations. Continuous air cooling is accomplished through the designed enlarged apertures 44 surrounding the coolant piping exiting through the cavity walls 30. The seal ring of this invention can better be appreciated by reference to FIG. 2 which shows a cross-section of the seal and its interface with the reactor cavity shelf and the reactor vessel flange. In its preferred form, the seal is constructed as a 0.25 inch thick stainless steel annular ring having a quarter-circle cross-section with an approximate eight inch radius. At one end the seal 38 is welded to the reactor vessel flange 36 and at the other end to an angle 46, covering an edge of the reactor shelf 40, which is secured by an anchor 48 embedded in the concrete of the cavity wall 30. Thus, the permanent seal 38 maintains the water-tight integrity of the refueling canal 34 and isolates the portion of the reactor vessel well 32 encompassing the vessel 10. The particular design of this invention has been shown to exhibit the flexibility and durability of accommodating over 400 cycles of expansion and contraction, far exceeding the number required to satisfy normal reactor operations and refueling requirements throughout reactor life. Thus, the containment arrangement of this invention expedites refueling operations by removing the present necessity of testing and/or replacing seal O-rings at refueling and the sealing and raising of seal plates, thus increasing the efficiency of reactor operations. Furthermore, the vessel well cooling system can be continuously operated to assure that the excore detectors and concrete cavity walls are continuously maintained below their specified temperature limits, thereby assuring the continued reliability of the containment equipment.
051568187	summary	BACKGROUND OF THE INVENTION AND PRIOR ART A wide range of radioactive waste processes are known for the isolation of a variety of low level wastes (LLW) and intermediate level wastes (ILW) by the use of volume reduction, and solidification. The resulting product of these processes, which may be substantially uncontaminated, slightly contaminated, or remain highly contaminated, is then usually packaged in drums or other containers for disposal. Ideally, radioactive waste should be as substantially reduced in volume as is commercially practical due to the excessively high costs of disposal or storage. Typically, this is accomplished by tight packing into containers such as metal drums or the like. Such containers suffer from various disadvantages including the fact that they are usually round and therefore a considerable amount of storage space is lost due to the dead space between the containers. Additionally, such containers are known to bulge or corrode over time. One improved method of reducing the volume of radioactive waste is uniaxial centrifugal casting thereof as is disclosed in U.S. Pat. No. 4,897,221 issued Jan. 30, 1990 to Frank Manchak, Jr. Other uniaxial centrifugal waste casting methods are disclosed in U.S. application Ser. No. 328,020 filed Mar. 23, 1989 by Frank Manchak, Jr., et al, and in U.S. application Ser. No. 384,087 filed as a CIP of Ser. No. 328,020 on Jul. 21, 1989. These applications both disclose the use of reinforcing cages which are used in the casting mold. It is now suspected, although not scientifically proven, that high density packing of radioactive waste not only reduces the volume to be stored, but also that such high density packing also provides greater inherent radiation shielding and reduced radiation leakage as compared to less dense packing. For some radioactive materials, high density packing is also suspected to reduce the radioactive half life, i.e., enhance the rate of radioactive decay. A high density packing process and apparatus is desired so that hazardous radioactive waste can be more densely and rapidly compacted into a radiation shielded dense monolithic form having strength and structural integrity for transport and which can be monitored for radiation compliance and, if necessary, provided with additional radiation barrier material before leaving the centrifugal casting apparatus. As referred to herein, the term "castable radioactive materials" is meant to comprise a hardenable mixture of radioactive waste materials and other waste materials mixed as necessary with one or more hardenable materials such as polyorganic compounds or cementitious materials or the like. As used herein, the terms "monolith", "cast monolith" and "monolithic form" are intended to refer to a solidified casting having one or more layers of radiation encapsulating material on the exterior thereof. Such monoliths may be provided, as taught herein, either by casting the entire monolith including shell layers of impact resistant and radiation shielding materials and the hazardous waste at the jobsite or, in the alternative, by using pre-formed shells and merely casting the waste at the jobsite. In pre-formed shells are used, provision must be made for casting additional radiation barrier material inside of the pre-formed shells if jobsite conditions dictate. SUMMARY OF THE INVENTION In a first embodiment, the present invention provides a method of isolating hazardous radioactive waste for disposal comprising the steps of: a) injecting a flowable charge of heat curable radiation shielding material into a rotatable mold, said charge being of volume calculated to provide a radiation barrier wall of selected minimum thickness on all interior surfaces of said mold; PA0 b) rotating said mold to centrifugally distribute said radiation shielding material on the interior surfaces of said mold; PA0 c) heating the walls of said mold during rotation thereof to cure and solidify said radiation barrier wall; PA0 d) filling the cured radiation barrier wall with castable radioactive waste material while rotating said mold to centrifugally compact and cast said radioactive waste material inside of said barrier wall to form a monolith comprised of said cast waste material and barrier wall; PA0 e) removing said mold from said monolith; PA0 f) detecting the amount of leakage radiation emitted by said monolith; PA0 g) applying additional radiation shielding material to the exterior surface of said monolith if the detected leakage radiation exceeds a predetermined threshold level; and PA0 h) transporting said monolith to a storage area. PA0 a) a bifurcated centrifugal casting mold having at least two separable mold parts and fluid inlet and fluid outlet ports aligned along a first axis, said mold being supported for rotation about said first axis; PA0 b) means for supporting a completed cast monolith in said apparatus with the mold parts removed therefrom; PA0 c) powered drive means for rotating said mold and said monolith about said first axis; PA0 d) mold removal means aligned along a second axis substantially perpendicular to said first axis for removing the separate parts of said bifurcated casting mold from a cast monolith while leaving said monolith supported in said apparatus for rotation about said first axis; PA0 e) means for injecting a charge of radiation shielding material into said mold and for filling said mold with castable radioactive waste material; PA0 f) means for heating said mold during rotation of said mold about said first axis; PA0 g) means for detecting radiation emitted by a cast monolith comprised of an external barrier of said radiation shielding material substantially encapsulating cast radioactive waste; and PA0 h) means for applying additional radiation shielding material to said monolith if needed. PA0 a) placing a hardened pre-formed shell of impact resistant radiation shielding material in a rotatable mold; PA0 b) making a preliminary determination of the probable radioactivity of waste material to be cast in said shell; PA0 c) injecting a flowable charge of hardenable radiation shielding material into said shell if the preliminary determination of radioactivity exceeds a threshold value, said charge being of volume calculated to provide said shell with an additional radiation barrier wall of selected minimum thickness on all interior surfaces of said shell; PA0 d) rotating said mold and said shell to centrifugally distribute said additional radiation shielding material on the interior surfaces of said shell; PA0 e) curing said additional radiation shielding material by heating said material during rotation of the mold to harden and solidify said additional radiation shielding material inside said shell; PA0 f) filling the shell with castable radioactive waste material while rotating said mold to centrifugally compact and cast said radioactive waste material inside of said shell to form a monolith comprised of said cast waste material and said shell; PA0 g) removing said mold from said monolith; PA0 h) detecting the amount of leakage radiation emitted by said monolith; PA0 i) applying additional radiation shielding material to the exterior surface of said monolith if the detected leakage radiation exceeds a predetermined threshold level; and PA0 j) transporting said monolith to a storage area. PA0 a) a bifurcated centrifugal casting mold having at least two separable mold parts, said mold being supported for rotation about said first axis; PA0 b) means for supporting a completed cast monolith in said apparatus with the mold parts removed therefrom; PA0 c) powered drive means for rotating said mold and said monolith about said first axis; PA0 d) mold removal means aligned along a second axis substantially perpendicular to said first axis for removing the separate parts of said bifurcated casting mold from a cast monolith while leaving said monolith supported in said apparatus for rotation about said first axis; PA0 e) means for injecting a charge of radiation shielding material into a pre-formed shell placed in said mold and for filling said shell with castable radioactive waste material; and PA0 f) means for heating the interior of said shell during rotation of said mold about said first axis. The present invention further provides, in a first embodiment, an apparatus for isolating hazardous castable radioactive waste for disposal comprising: Preferably, centrifugal casting of the radiation barrier shielding material is accomplished by simultaneously rotating the casting mold about two mutually perpendicular axes so that a particularly dense radiation shielding barrier wall is formed which will contain the radioactive waste material. Separable mold parts are then removed from the cast monolith while still leaving the monolith supported for rotation in the centrifugal casting apparatus. Additional radiation shielding and/or structural integrity are attained, if necessary, by winding a strand of fiber composite material about the formed monolith. In a second embodiment, the invention provides a method of isolating hazardous radioactive waste for disposal comprising the steps of: In the second embodiment, the invention also provides apparatus for isolating hazardous castable radioactive waste for disposal comprising: Further advantages of the preferred embodiments of the methods and apparatus disclosed herein include the fact that costly metal storage drums or steel reinforced concrete drums and the attendant corrosion thereof are eliminated; and that a means for removal of heat generated by radioactive decay and latent chemical reaction in the cast monolith is shown wherein a heat removal pipe, preferably ceramic, may be inserted into the substantially completed cast monolith before final completion of the monolith.
	abstract	Embodiments include an imaging system that includes a collimator support base and a detector assembly. The collimator support base is configured to interchangeably accept a slit aperture collimator and a pinhole aperture collimator. The slit aperture collimator has either a corresponding septa assembly or a corresponding crossed-slit collimator. The detector assembly is configured to detect collimated gamma rays emanating from a subject in a field of view of the imaging system and generate one or more signals in response to the detected gamma rays. Methods of adjusting performance of imaging systems are also provided.
	abstract	A stage device to be used in a vacuum includes: a gas supply unit for generating a gas; a base member having upper, lower, right, and left surfaces; a slider formed in a frame shape surrounding the base member and having surfaces facing the respective surfaces of the base member, and disposed to be movable; and an air bearing configured to float the slider by supplying the gas to a space between the base member and the slider. The slider includes: an air chamber provided on the surface facing the base member for accumulating air, and the base member includes thereinside a slider-moving air flow passage configured to guide the gas from an inlet port to an outlet port for supplying the gas to the air chamber of the slider.
053274725	summary	CROSS-REFERENCE TO RELATED APPLICATION This application is a continuation of International Application PCT/DE91/00133, filed Feb. 20, 1991. The invention relates to a boiling water reactor, having a pressure vessel, a steam turbine connected to the pressure vessel, at least one nuclear reactor fuel assembly and controllable absorber elements disposed in a reactor core in the pressure vessel, the fuel assembly including an elongated fuel assembly case with mutually parallel side walls laterally closing off the fuel assembly, an inlet end for liquid coolant and an outlet end for a liquid/steam mixture of the coolant, and fuel rods containing nuclear fuel and being disposed side by side and parallel to the case walls, the absorber elements being disposed outside the fuel assembly, the fuel rods being disposed in lengthwise rows and crosswise rows intersecting the lengthwise rows in such a manner that they reach through meshes of a grid extending practically at right angles to the side walls, and each four fuel rods disposed in two adjacent lengthwise rows and two adjacent crosswise rows forming one flow subchannel for the coolant, being parallel to the side walls. The invention also relates to a fuel assembly for the boiling water reactor. The structures of fuel assemblies for boiling water reactors described above are conventional and are used in the invention as well. They are therefore part of the fuel assembly and the reactor of the invention. In the boiling water reactor core, the liquid coolant enters the fuel assembly case at a lower or inlet end and leaves it as a liquid/steam mixture at an upper or outlet end of the case. Since an increasing proportion of the coolant, which simultaneously acts as a moderator, is in the form of steam in the upper part of the fuel assembly, the vertical flow in the reactor core must be channelled in such a way that sufficient moderator is present there as well. To this end, tubes for the liquid coolant (water tubes) can be used, which replace one or more fuel rods. Such a water tube may also have a larger cross section than an individual fuel rod, so that it extends over the cross section of a plurality of meshes in the grid, or it may have some other cross section (such as cross-shaped). The case walls also serve to channel the vertical flow and in particular must prevent coolant vapor from accumulating on the absorber elements because of an uncontrolled horizontal flow, which would interfere with the proper course and control of the reactions in the reactor That kind of horizontal flow is even considered desirable for pressurized water reactors, because it brings about a temperature equalization between hotter and cooler regions of the fuel assembly and improves cooling. Such a horizontal flow, which in a boiling water fuel assembly is largely suppressed by the case walls and in any event is kept away from the absorber elements between the fuel assemblies, can therefore be generated in a pressurized water fuel assembly by suitable baffles or vanes in the flow subchannels. Such vanes may be disposed at the ribs of spacers, which are necessary in any event to fix the mutual spacing of the fuel rods, or on the ribs of their own mixing grids, as is shown, for instance, in FIGS. 1 and 2 of German Published, Non-Prosecuted Application DE-OS 15 64 697. That produces a circular flow around the individual fuel rods by means of which all of the flow subchannels bordering a fuel rod communicate with one another. The superimposition of the individual circular flows then leads to horizontal flows, which pass transversely through the entire fuel assembly. The same circular flows also develop in the grid structures of pressurized water reactors as is shown in FIGS. 1, 8 and 9 of U.S. Pat. No. 4,224,107. In German Published, Non-Prosecuted Application DE--OS 2 157 742, it is proposed that four vanes be disposed in propeller-like fashion in each flow subchannel of a pressurized away from the coolant flow, tapering and protruding obliquely from the wall of the water tube into the interstices between the adjacent fuel rods. Such baffles deflect the liquid film on the water tube wall and mix it turbulently with the hot liquid/steam mixture of the coolant flowing between the fuel rods. However, that kind of turbulence increases the pressure loss in the vertical flow and can therefore largely cancel out or even overcome the advantages of improved cooling that are sought. In contrast, in pressurized water reactors, the creation of a mixture of liquid and steam is prevented by a high pressure in the reactor core, so that even at the hot outlet end of the fuel assembly, there is sufficient liquid moderator available, and dryout of the fuel rods need not be feared. A fuel assembly case, which would merely represent unnecessary consumption of material and addition neutron absorption, is not present, and the absorber elements are distributed as uniformly as possible over the cross section of the fuel assembly. As a result, completely different flow conditions prevail, In particular, a horizontal flow between adjacent flow subchannels of a fuel assembly and between adjacent fuel assemblies themselves can form. The absorber elements are disposed outside the fuel assemblies, in interstices between the individual fuel assemblies. Normally, a film of water is located on the surface of the fuel rods, which carries heat produced in the nuclear-heated fuel rods, leads to evaporation of the liquid coolant in the upper part of the fuel assembly, and transfers heat into the interior of the interstices between adjacent fuel rods. The interstices form flow subchannels for the vertical flow in the reactor core. If the output of the fuel assembly is excessive, this water film can tear away or dry out. A boiling transition or dryout of the rods is then said to have occurred. Such an occurrence worsens the heat transfer from the rods to the coolant, and undesirable local overheating of the fuel rods occurs. On the other hand, in the upper part of the fuel assembly as well, there is still a considerable proportion of the coolant in the form of liquid droplets and a liquid film creeping along the case walls and along a water tube if applicable, which could be utilized to improve cooling in the event of high outputs. U.S. Pat. No. 4,749,543 has therefore proposed that grooves ("flow trippers") be machined on the insides of the case walls, at which grooves a film of liquid is rendered turbulent. According to German Petty Patent DE-G 88 02 565.9, in a boiling water reactor with a central water tube, baffles are attached to the side of a spacer facing water reactor, in order to produce turbulence in the flow subchannels and to produce a greater heat transfer at the fuel rods. In U.S. Pat. No. 4,725,403, for the same purpose, one additional sheath is mounted on the spacer ribs, which has two vanes on its side facing away from the coolant flow that are inclined toward one another in such a way that a swirl is imposed upon the pressurized water reactor coolant flowing through the additional sheath. According to German Published, Non-Prosecuted Application DE 35 19 421 A1, the additional sheath itself is also wound spirally within itself, and it has four such vanes, which are bent outward in the direction of the desired swirl. However, such vanes of pressurized water reactors represent a considerable flow resistance and therefore cause a pressure drop, worsening the utilization of the reactor, so that the desired improvement practically does not ensue. Therefore, if such vanes are used at all in pressurized water reactors to produce a horizontal flow, particular care must be taken to ensure that the vertical flow turbulence, which is unavoidable at such vanes, and the attendant pressure loss, are kept as small as possible. According to Published European Application No. 0 291 748, corresponding to U.S. Pat. No. 4,844,860, an especially low pressure loss arises at the vanes of a gridlike spacer if the vanes at the intersections are bent in pairs toward one another and are welded together in such a way that one pair of diagonally disposed triangles, aimed at the fuel rods, is created in each flow channel. That produces swirling flows which cosine to make horizontal flows extending diagonally through the pressurized water fuel assembly. In boiling water reactors, if a horizontal flow should develop at all, it is interrupted at the case walls in any event, so that it need not be expected that any substantial improvement would be attainable by using vanes to generate a horizontal flow. Instead, it is precisely in boiling water reactors, that the pressure loss in the flow subchannels is especially critical. It is accordingly an object of the invention to provide a boiling water nuclear reactor and a nuclear reactor fuel assembly for the boiling water reactor, which overcome the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which utilize the liquid portion of the coolant contained in the liquid/steam mixture to increase the output of the fuel assembly and to prevent dryout. It has surprisingly been found that vanes or similar baffles, which are used in pressurized water reactors to produce and reinforce horizontal flows and are intended to generate as little turbulence as possible in the vertical flow, are so advantageous in boiling water reactors, precisely because of this turbulence, that the disadvantage of the increased pressure loss is acceptable. Horizontal flows only play a subordinate role, because they are deflected by the case walls and have to be kept away from the absorber elements. With the foregoing and other objects in view there is provided, in accordance with the invention, a boiling water reactor, comprising a pressure vessel, a steam turbine connected to the pressure vessel, a reactor core disposed in the pressure vessel, at least one nuclear reactor fuel assembly disposed in the reactor core, and controllable absorber elements disposed in the reactor core outside the at least one fuel assembly; the at least one fuel assembly including an elongated fuel assembly case with mutually parallel side walls laterally closing off the fuel assembly, an inlet end for liquid coolant, an outlet end for a liquid/steam mixture of the coolant, fuel rods containing nuclear fuel being disposed side by side and parallel to the side walls of the case, and a grid extending practically or substantially perpendicularly to the side walls of the case, the grid having grid meshes formed therein through which the fuel rods extend; the fuel rods being disposed in lengthwise rows and in crosswise rows intersecting the lengthwise rows, and each four of the fuel rods disposed in two adjacent lengthwise rows and in two adjacent crosswise rows forming one flow subchannel being parallel to the side walls of the case for coolant flowing in a given direction, the flow subchannels defining a center axis and side walls of the flow subchannels; and at least two vanes disposed in each of at least a plurality of the flow subchannels, the vanes being tapered in the given direction, being three-dimensionally curved or at least bent to form an angle with respect to the center axis, for creating a swirl in the coolant around the center axis. In accordance with another feature of the invention, the at least two vanes are four vanes disposed in each of the plurality of flow subchannels, the four vanes being substantially or practically rotationally symmetrical about the center axis. In accordance with a further feature of the invention, the grid is formed of ribs having edges facing away from the coolant flow, and the vanes are disposed on the edges of the ribs. In accordance with an added feature of the invention, the ribs have retaining elements fixing a spacing between the fuel rods and the side walls of the case. In accordance with an additional feature of the invention, all of the vanes are disposed and formed substantially rotationally symmetrically in one direction about the center axis in one of the flow subchannels, and all of the vanes are disposed and formed substantially rotationally symmetrically in an opposite direction in the flow subchannels adjacent the one flow subchannel. With the objects of the invention in view, there is also provided a nuclear reactor fuel assembly of a boiling water reactor, comprising an elongated case having an interior, mutually parallel side walls laterally closing off the interior, an inlet end for a liquid coolant flow, and an outlet end for a liquid/steam mixture of the coolant; a grid extending substantially perpendicularly to the side walls of the case, the grid having mutually parallel first lengthwise ribs and mutually parallel second crosswise ribs meeting the first ribs at intersections, the ribs having lateral surfaces being parallel to each other and to the side walls of the case, the ribs having edges facing toward the coolant flow, and the ribs defining grid meshes therebetween; fuel rods containing nuclear fuel being disposed side by side and parallel to the side walls of the case, each of the fuel rods passing through a respective one of the grid meshes, and the fuel rods being disposed in lengthwise rows and in crosswise rows intersecting the lengthwise rows; each four of the fuel rods disposed in two adjacent lengthwise rows and in two adjacent crosswise rows forming one flow subchannel being parallel to the side walls of the case for conducting the coolant flow in a given direction, the flow subchannels defining a center axis and side walls of the flow subchannels; and two vanes being disposed at one of the intersections in each of at least a plurality of the flow subchannels, the two vanes being disposed on the edges of the first ribs facing away from the coolant flow at two sides of the second ribs, and the vanes being tapered in the given direction and being curved, for instance three-dimensionally curved or at least bent in order to form an angle with respect to the center axis in different directions for creating a swirl in the coolant around the center axis. In accordance with another feature of the invention, there are no controllable absorber elements disposed in the interior of the case. In accordance with a further feature of the invention, there are provided two three-dimensionally curved further vanes tapering in the flow direction and being disposed on the edge of the second rib facing away from the coolant flow; one of the further vanes being disposed on each respective side of the first rib, and the further vanes being curved toward different meshes than the vanes on the first rib. In accordance with an added feature of the invention, there is no intersection of one of the second ribs and one of the first ribs between an intersection of the first rib and the second rib and one of the further vanes. With the objects of the invention in view, there is additionally provided a nuclear reactor fuel assembly, comprising an elongated case having an interior, mutually parallel side walls laterally closing off the interior, an inlet end for a liquid coolant flow, an outlet end for a liquid/steam mixture of the coolant; fuel rods containing nuclear fuel being disposed side by side and parallel to each other and to the side walls of the case, the fuel rods being disposed in lengthwise rows and in crosswise rows intersecting the lengthwise rows; a grid extending substantially perpendicularly to the side walls of the case, the grid having mutually parallel sheaths seated in spaces and forming meshes of the grid being penetrated by the fuel rods, the sheaths having ends facing away from the coolant flow; each four of the sheaths containing the fuel rods in two adjacent lengthwise rows and in two adjacent crosswise rows forming one flow subchannel being parallel to the side walls of the case for coolant flowing in a given direction, the flow subchannels defining a center axis and side walls of the flow subchannels; and one vane being disposed on each respective end facing away from the coolant flow of at least two of each four of the sheaths forming a flow subchannel, the vanes being diagonally opposite in the flow subchannel, being tapered in the given direction, and being inwardly curved (for instance bent or curved) three-dimensionally into the flow subchannel and rotationally symmetrical with respect to the center axis, for creating a swirl in the coolant around the center axis. In accordance with a concomitant feature of the invention, the sheaths include main sheaths and additional sheaths parallel to the main sheaths in the flow subchannels, the additional sheaths have the ends facing away from the coolant flow, and the vanes are formed onto the ends of the additional sheaths facing away from the coolant flow. The swirl generated by the vanes attached to the coolant outflow end of the grid in the cross section of the fuel assembly case spins the water droplets in the two-phase coolant mixture out of the flow subchannel in the direction of the outer surface of the fuel rods. There, even at an elevated output of the nuclear fuel assembly, they form a water film that prevents a dryout of the rods and an attendant poor heat transfer. It is also seen that the film of water is formed on the outer surface of the fuel rods to an increased extent, in order to increase the allowable output of the nuclear fuel assembly. 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 boiling water nuclear reactor and a nuclear reactor fuel assembly for the boiling water 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. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
043326390	abstract	A failed element detection and location system for use in a nuclear reactor, for example, a liquid metal fast breeder reactor (LMFBR), which utilizes a large number of fuel pins in an active core and which circulates a continuous stream of liquid metal heat exchanging fluid such as liquid sodium past the pins is disclosed herein. This system first collects a combined sample of the fluid just as the latter passes through at least a selected group of containers, each housing a plurality of the fuel pins. This combined sample is detected for the presence or absence of a predetermined contaminant, specifically neutrons, resulting from the failure (break) in one or more of the fuel pins. In the event that the contaminant is detected in the combined sample, individual samples of fluid are collected, one at a time, as the fluid just passes through the selected group of containers. These individual samples are also detected for the presence or absence of the contaminant, thereby indicating the fuel pin container or containers responsible for the presence of the contaminant.
062394304	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a particle beam apparatus, and more particularly to a particle beam apparatus with an energy filter. 2. Discussion of Relevant Art Particle beam apparatuses in the form of transmission electron microscopes with energy filters are known, for example, from U.S. Pat. Nos. 4,740,704, 4,760,261 and 5,449,914. The energy filters described in these documents are dispersive, that is, a charged particle entering the filter undergoes, on passing through the filter, a deflection which depends on the particle energy. The filter described in U.S. Pat. No. 4,740,704 is used by the inventors employer' in the transmission electron microscope 912 Omega manufactured and sold by LEO Elektronenmikroskopie GmbH. In the 912 Omega, the filter is arranged in the imaging beam path between the specimen to be investigated and the projection screen or the camera on which the specimen is electron-optically imaged. With such an energy filter on the imaging side, the energy loss which the particles have undergone in the specimen can be analyzed. At the same time, the imaging errors which depend on the energy, the chromatic aberrations, are reduced in the imaging beam path, since only particles with a reduced energy bandwidth contribute to the imaging. For the correction of chromatic imaging errors, both in scanning electron microscopes and also in transmission electron microscopes, it is known from U.S. Pat. No. 5,319,207 to provide a mirror corrector in the illumination beam path between the electron source and the specimen to be investigated. The mirror corrector consists of a magnetic beam deflector and an electrostatic mirror which images into each other the two planes of symmetry within the magnetic beam deflector. Although the beam deflector has dispersive properties, the corrector is non-dispersive overall, that is, particles entering the corrector undergo, after passing completely through the corrector, no deflection which is dependent on the particle energy. Such correctors are however relatively expensive and up to now have not been commercially offered. As an alternative to a corrector, it is known from an article by H. Rose in Optik (Optics), Vol. 85 (No. 3), pp. 95-98 (1990), to provide an energy filter in the illuminating beam path of a transmission electron microscope. The energy filtering which is effected permits at least the energy-dependent errors to be reduced, because of the small energy bandwidth of the particles that contribute to subsequent imaging. Although here also the filter has dispersive elements for the splitting of the particle beam according to energy, the filter is overall free from dispersion, so that the particles entering the filter again undergo, after completely passing through the filter, no deflection which depends on energy. The freedom from dispersion of the whole filter is attained in that the filter is symmetrical about a midplane, and the dispersion in both of the mutually symmetrical filter portions is exactly opposed. This freedom of the filter from dispersion insures that small voltage fluctuations at the filter do not lead to a drift of the beam behind the filter. Dispersion-free filters however have the disadvantage that the dispersion that can be attained in the energy selection plane, in which the energy selection takes place by means of a slit diaphragm, is relatively small. And since the dispersion is in general dependent on the particle energy and decreases with increasing particle energy, the particle energy within the filter has to be relatively low when high energy sharpness is to be attained. In the article, the starting point was a particle energy of 3 keV, and in later work by H. Rose a significant energy region of 3-5 keV was specified. At low particle energies within the filter, however, a broadening of the energy bandwidth results because of the so-called Boersch effect. Since the Boersch effect has significant effects particularly in intermediate images of the particle source within the filter, because of the higher particle density in such intermediate images, the use was already proposed by H. Rose of a filter with exclusively astigmatic intermediate images within the filter. Furthermore, a raster electron microscope with a dispersive energy filter between the source and the objective is known from Japanese Patent JP 62-93848. In the system described there, the filter is however only used for the production of a relative signal, so that the negative influence of the noise of the electron source on the subsequently produced picture can be eliminated by quotient formation between the actual secondary electron measurement signal and the relative signal. SUMMARY OF THE INVENTION The present invention has as its object to provide a particle beam apparatus in which the particle beam that is used for further imaging or picture production can have a high energy sharpness, and in which the influence of the Boersch effect is small. This object is attained by a particle beam apparatus having a particle beam producer, an objective, and an energy filter that has dispersion and is arranged between the particle beam producer and the objective. The energy filter images a first input plane achromatically into a first output plane and a second input plane dispersively into a second output plane. The particle beam producer is imaged into the first input plane. In the particle beam apparatus according to the invention, an energy filter is arranged on the illumination side, between the particle beam producer and an objective, as in the above-mentioned article. In contrast to the arrangement according to the above-mentioned article, this energy filter has a dispersion: that is, the particles that have passed through the whole filter have, at the end of the filter, a deflection which is dependent on their kinetic energy. A so-called imaging energy filter is concerned here, which images a first input plane achromatically into a first output plane, and simultaneously images a second input plane dispersively into a second output plane. The particle beam producer--or, more precisely, the surface of the particle beam producer that emits particles--is imaged in the first input plane of the energy filter, in the particle beam apparatus according to the invention, so that in spite of the dispersion of the energy filter, energy fluctuations of the particle beam do not lead to any drift of the image of the particle beam producer in and beyond the second output plane. Since dispersive energy filters have a higher dispersion than dispersion-free energy filters, the average particle energy in the particle beam apparatus according to the invention can be chosen to be higher, at the same energy sharpness of the energy-filtered particle beam, than according to the state of the art. Because of this higher average particle energy, which can be between 5 and 35 keV, and should preferably amount to about 8-20 keV, the negative influence of the Boersch effect is markedly reduced. The energy selection by a corresponding slit type selection diaphragm can take place, in the particle beam apparatus according to the invention, in the output side region of the energy filter or beyond the energy filter in the second output plane. The imaging of the particle beam producer in the first input plane preferably takes place with enlargement, such that by means of the energy selection beyond the energy filter, no cutting down of the aperture of the particle beam takes place in the subsequent beam path. In an advantageous embodiment example of the invention, the particles are already accelerated to a relatively high energy before they enter the energy filter, and pass through both the energy filter and the succeeding imaging stages with the same energy, and are braked to the smaller desired end energy only in the objective, or between the objective and the specimen to be investigated. This embodiment of the particle beam apparatus according to the invention can in particular be constructed as a low voltage scanning electron microscope, in which the particle beam is focused by the objective on the specimen to be investigated. To scan the specimen, a deflecting device is then provided in the region of the objective, and with it the particle beam focus can be deflected in two mutually orthogonal directions. The target energies in such low voltage scanning electron microscopes are between 10 eV and 10 keV. A detector for the detection of secondary electrons emitted from the specimen to be investigated is provided between the objective and the filter in such a low voltage scanning electron microscope. A further detector can be provided for the detection of back-scattered particles from the specimen, the beam path of these back-scattered particles being preferably coupled sideways out of the energy filter. For the separation of the directly back-scattered particles from those particles which have undergone an energy loss, a further slit diaphragm can be arranged between the filter and the detector for the detection of the back-scattered particles. As an alternative to the embodiment as a low voltage scanning electron microscope, the particle beam apparatus according to the invention can also be constructed as a high energy transmission electron microscope. In this case, the particle beam would be accelerated to the desired high target energy directly after exiting the energy filter. The dispersion of the energy filter should be in the region between 5-20 .mu.m/eV, preferably between 10 and 15 .mu.m/eV, at the average particle energy within the filter. If the dispersion of the filter is less than 5-10 .mu.m/eV, no sufficient energy sharpness can be attained, or slit widths of the selection diaphragm are required which are too small. If the upper boundary value of 15-20 .mu.m/eV is exceeded, the aperture of the particle beam behind the selection diaphragm then becomes too large, with the consequence that the subsequent electron optical imaging elements produce greater aperture errors, so that the gain in resolution possible by the reduction of the chromatic errors is further compensated or even over-compensated.
	abstract	A parallel nanotomography imaging system is provided having an x-ray source, which is preferably a laser-based x-ray source that generates x-rays that are collected using a collector optic and are received in a composite objective assembly. The composite objective assembly includes plural micro-objectives, each imaging the target. The x-ray image is received by an x-ray image formation and acquisition apparatus, and processed and/or displayed.
	description	This application is a divisional of U.S. patent application Ser. No. 12/677,465, filed May 11, 2010, which will issue on Aug. 18, 2015 as U.S. Pat. No. 9,109,722, which is the U.S. National Stage of International Application No. PCT/CA2008/001601, filed Sep. 10, 2008, which in turn claims the benefit of U.S. Provisional application No. 60/971,423, filed Sep. 11, 2007, each of which applications are incorporated by reference in their entirety herein. This invention relates generally to a method of repositioning annular elements (spacers) that are constrained to move longitudinally in relation to a tube with which they are associated, the spacers being located on one side of the tube wall such that they are not directly accessible by mechanical repositioning means. The present invention is especially applicable to the repositioning of spacers in a nuclear reactor, such as a CANDU® reactor. In a CANDU® nuclear reactor, the pressure tubes which contain the fuel bundles are each positioned within a calandria tube. It is necessary to have an annular space maintained between the pressure tube and the calandria tube to allow for the circulation of gases which thermally insulate the hot pressure tube from the relatively colder calandria tube and the heavy water moderator which flows in the space outside the calandria tube. The annular space is maintained by annulus spacers, which are one component that make up a CANDU® reactor fuel channel. These spacers maintain the radial spacing between two coaxial tubes, an inner pressure tube and an outer calandria tube, and help the calandria tubes support the inner pressure tubes. There are both loose-fitting and snugfitting annulus spacers, which differ in design. A loose-fitting spacer comprises a closely coiled spring made from a square cross section wire, assembled on a circular girdle wire to form a torus. The girdle wire of the loose-fitting spacer is welded to form a continuous loop of fixed size. The minor diameter of the loose-fitting spacer is such that it is slightly larger than that of the outside diameter of a pressure tube. As such, the spacer fits loosely around the pressure tube. The spacer stays in its installed position by friction alone and not by spring tension. Loose-fitting spacers were used in earlier CANDU® reactors. A snug-fitting spacer comprises a closely coiled spring made from a square cross section wire, assembled on a circular girdle wire to form a torus. The girdle wire is not welded, therefore the effective minor diameter of the spacer can be increased by applying tension to extend the coiled spring. The design of the snug-fitting spacer is such that the coil spring is under some tension when installed on a pressure tube, resulting in a snug fit. The design of the annulus spacer is such that they are not fixed rigidly in position. The spacer is held in position by spring tension and friction. Snug fitting spacers typically maintain their initial desired position, however, it may be possible that a spacer may move from its desired position, or, during the course of operation of a reactor, it may be desirable to move the position of a spacer. Typically, four spacers are used in a fuel channel, each spacer being positioned at a different axial position. To provide the required support, the annulus spacers must be located at the proper position; if a spacer is out of position, the hot pressure tube may come into contact with the cooler calandria tube. Such contact between the inner pressure tube and the outer calandria tube is unacceptable. During installation of spacers in such a reactor, or, as suggested above, during its operation, spacers may be displaced from their required positions with the result that the pressure tubes will lack the necessary configuration of supports to carry the distributed load in operation of the reactor, and serious problems may arise from sagging of these tubes. It is therefore desirable to have some way of detecting and repositioning (if necessary) the spacers after installation or even after the reactor has been operating for some time. The optimal position of a spacer may change slightly during the operating life of a reactor. The original installed spacer position is based on the support conditions throughout the reactor life. However, it may be desirable to reposition the spacers late in the reactor life to better suit the end of life conditions. Repositioning spacers late in life may extend the operating life of a reactor by some years, resulting in a significant economic benefit. These annulus spacers are located between the pressure tubes and the calandria tubes and are not directly accessible by mechanical means. Since the spacer position is not fixed mechanically, it is desirable to have a means to detect their position. U.S. Pat. No. 4,613,477 (“U.S. '477) discloses a method for repositioning garter springs, used as annulus spacers between the coolant tubes and calandria tubes of fluid cooled nuclear reactors. Such garter springs are not directly accessible by mechanical means. In the method of U.S. '477, an electromagnetic coil is advanced along the selected fuel channel to a position adjacent the garter spring, and a current pulse is passed through the coil thereby to exert an electromagnetic repulsive force on the garter spring having a component in the direction of the required displacement. This technique is applicable to the loose-fitting spacers which have the welded girdle wire. The welded girdle wire of the loose-fitting spacer forms a continuous electrical circuit that is necessary for the electromagnetic-based technique. The electromagnetic technique does not work on the tight-fitting spacer, because the non-welded girdle wire does not provide a continuous electrical path within the spacer. A need remains for an apparatus and method for detecting and repositioning tight-fitting annulus spacers. This background information is provided for the purpose of making known information believed by the applicant to be of possible relevance to the present invention. No admission is necessarily intended, nor should be construed, that any of the preceding information constitutes prior art against the present invention. In accordance with one aspect of the present invention, there is provided a method of detecting an annulus spacer having an inner cylindrical surface in contact with an inner tube and an outer cylindrical surface in contact with a generally coaxial outer tube, which method comprises the steps of: vibrationally isolating a section of the inner tube; vibrating the wall of said inner tube within said isolated section; measuring vibration in the wall at a minimum of two axial positions within said isolated section, and detecting a reduction in the vibration level of the wall at one or more of said axial positions in comparison to the remaining axial position(s), wherein the reduction in vibration is indicative of the presence of the annulus spacer at or near the axial position at which said reduction in vibration was detected. In accordance with another aspect of the present inventions, there is provided a method of axially repositioning an annulus spacer having an inner cylindrical surface in contact with an inner tube and an outer cylindrical surface in contact with a generally coaxial outer tube, which method comprises the steps of: vibrationally isolating a section of the wall of the inner tube adjacent to the annulus spacer; causing said annulus spacer to go from a loaded condition to an unloaded condition such that it is only in contact with said inner tube; vibrating the annulus spacer by vibrating the isolated section of the wall at a desired frequency such that the annulus spacer is displaced longitudinally from an initial position to a required position, whereby the vibration of the annulus spacer produces accelerations sufficient to overcome the tension of the annulus spacer on the inner tube. In accordance with another aspect of the present invention there is provided an apparatus for detecting and/or repositioning an annulus spacer having an inner cylindrical surface in contact with an inner tube and an outer cylindrical surface in contact with a generally coaxial outer tube, comprising: a tool head having a first end and a second end; a first and a second clamping block assembly at said first and second ends, respectively, of said tool head; one or more piezo-actuators associated with said tool head and operable to vibrate said inner tube; and two or more accelerometers associated with said tool head for measuring vibration of said inner tube. The apparatus and methods of the present invention are useful for detection and/or repositioning of one or more annulus spacers surrounding a first tube that is positioned within, and generally coaxial with, a second tube (e.g., see FIG. 1). In the example depicted in FIG. 1, the annulus spacer maintains the radial spacing between the first tube (e.g., an inner tube) and the second tube (e.g., an outer tube). Typically more than one annulus spacer work together to maintain the radial spacing between the first tube and the second tube. In a specific example of the present invention, the inner tube is a pressure tube, the outer tube is a calandria tube and the spacer is a snug-fitting annulus spacer, as would be found in a CANDU® nuclear reactor. In another specific example, the spacer is a loose-fitting annulus spacer. As will be readily appreciated by the skilled worker, the apparatus and methods of the present application can be used in other applications in which an inner tube is positioned within and coaxial with an outer tube and the tubes maintained in spaced relation by one or more annulus spacers. As will be described in more detail below, there is provided an apparatus and method for detecting an annulus spacer, repositioning an annulus spacer or detecting and repositioning an annulus spacer. The methods are based on the use of an apparatus, such as a tool head, that is inserted inside a pressure tube. In the case of a nuclear reactor, such as a CANDU® reactor, the apparatus (tool head) is inserted in a pressure tube when the reactor is shut down. FIG. 2 depicts an example of an arrangement of components within a CANDU® reactor. The apparatus (tool head) is delivered into the pressure tube using standard, existing delivery machines. The delivery machine is positioned at one end of the fuel channel and can form a sealed connection with the fuel channel end. The delivery machine is able to remove the closure plug from the end of the fuel channel to allow access to the pressure tube. The delivery machine can introduce tooling into a CANDU® fuel channel and position it at any length along the fuel channel. The delivery machine provides a mechanical interface for positioning the tool and provides for service connections to the tool, such as electrical power, control/feedback signals, pneumatic supply, or hydraulic supply. An example of a suitable delivery machine is the AECL Fuel Channel Inspection System. Tool Head Referring now to FIGS. 3A and 3B, tool head 100 is sized for insertion within a first tube, such as pressure tube 200 in a nuclear reactor, and comprises actuators and sensors used for annulus spacer detection, repositioning, and detection/repositioning. Tool head 100 is configured for operative association with a delivery machine (not shown), and is suitable for use in a wet environment as would be present in pressure tube 200 and outer calandria tube 400, for example, in a CANDU® reactor. Tool head 100 comprises clamping block assembly 2, coupling 16, piezo-actuator 6, accelerometer 8 and eddy current gap probe 10. Clamping Block Assembly. As shown in FIGS. 3A and 3B, tool head 100 includes clamping block assemblies 2 at a first end and at a second end of tool head 100. Each clamping block assembly 2 is removably attachable to coupling 16, and is adapted for rotation about coupling 16. Each clamping block assembly 2 includes clamping member(s) 20, which are moveable from a retracted position to an extended position. In the retracted position, clamping member(s) 20 do not impede movement of tool head 100 within pressure tube 200. In the extended position, clamping member(s) 20 engage the inner surface of pressure tube 200. Desirably, clamping member(s) 20 do not damage, or do not damage beyond acceptable tolerances, the inner surface of pressure tube 200. Each clamping block assembly 2 and clamping member(s) 20 are operable for use in pressure tube jacking (discussed further below) and are also used to vibrationally isolate a section of pressure tube 200 between each clamping block assembly 2 at the first and second end of pressure tube 200 (discussed further below). Coupling 16 is actuated by hydraulic pressure supplied from the delivery machine. Actuation of the coupling 16 produces a moment between clamping block assembly 2 and the tool head 100. When clamping block assembly 2 is clamped to pressure tube 200 and coupling 16 is actuated, the moment is applied to pressure tube 200. This moment applied to pressure tube 200 effectively lifts pressure tube 200 away from calandria tube 400. This operation may be used to remove any load on an annulus spacer 12 and cause annulus spacer 12 to come out of contact with calandria tube 400. Removal of the load from an annulus spacer 12 is required in order to allow the annulus spacer 12 to be freely moved. Piezo-Actuator. Tool head 100 includes piezo-actuator 6, which is operable to apply vibrations to the inside surface of pressure tube 200. Typically only one piezo-actuator 6 is included in a tool head. However, more than one piezo-actuator 6 can be incorporated in tool head 100 if desired and/or if necessary. Piezo-actuator 6 includes bearing pad 22 that is movable from a retracted position to an extended position. In the retracted position, bearing pad 22 does not impede movement of tool head 100 within pressure tube 200. In the extended position, bearing pad 22 is brought into contact with the inner wall of pressure tube 200. The position of piezo-actuator 6 with respect to the clamping block assembly 2 affects the ability of the piezo-actuator 6 to provide power to vibrate the pressure tube in the desired mode. Piezo-actuator 6 has limitations with respect to its travel (or stroke) and the force that it can apply. The amount of force and stroke required to vibrate pressure tube 200 is dependent on the location of piezo-actuator 6 with respect to the mode shape, and therefore, also with respect to the clamping block assemblies 2, which define the length of the segment of the vibrating pressure tube, and thereby affect the modes of vibration. There is a location or a location range that allows piezo-actuator 6 to better produce the desired mode shape or shapes. In general, a balance has to be achieved between force and stroke. Typically, a location that requires less stroke also requires more force, and vice versa. The performance characteristics of piezo-actuator 6 is matched to the force and stroke requirements of the particular mode shape or shapes. When bearing pad 22 is in contact with the inner wall of pressure tube 200, piezo-actuator 6 is operable to vibrate a portion of pressure tube 200 in a controlled manner. Piezo-actuator 6 is controlled using an amplifier (not shown) and signal generator (not shown), such that it can be made to operate at a desired frequency. The frequency of vibration of piezo-actuator 6 selected will depend on a variety of non-limiting factors such as operating conditions, materials used, user preference, regulatory requirements and/or the like. In one embodiment, piezo-actuator 6 generates vibrations at a natural frequency of pressure tube 200. In one embodiment, piezo-actuator 6 generates vibrations in the frequency range of about 100 Hz to about 1500 Hz. In one embodiment, piezo-actuator 6 generates vibrations at approximately 400 Hz, which corresponds to the (1,1) mode. In one embodiment, piezo-actuator 6 generates vibrations at approximately 625 Hz, which corresponds to the (2,1) mode. In one embodiment of the invention, piezo-actuator 6 generates vibrations at approximately 1096 Hz, which corresponds to the (3,1) mode. As noted above, each clamping block assembly 2 and assembly clamping members 20 are operable to vibrationally isolate the section of pressure tube 200 between each clamping block assembly 2, at the first and second ends of pressure tube 200. Prior to actuation of piezo-actuator 6, assembly clamping members 20 may be moved to the extended position, contacting the inner surface of pressure tube 200. When assembly members 20 are in the extended position, the portion of pressure tube 200 between each clamping block assembly 2 is vibrationally isolated from the remainder of pressure tube 200. As used herein, vibrationally isolated is understood to mean that vibrations produced by piezo-actuator 6 within the portion of pressure tube 200 bounded by clamping members 20, are kept apart or away from the remainder of pressure tube 200 so as to minimize or eliminate the effect of vibrations on the remainder of pressure tube 200. Accelerometers. Tool head 100 includes accelerometers 8, which detect vibrations of pressure tube 200. Accelerometer(s) 8 may also be used to detect impacts between annulus spacer 12 and the outer surface of pressure tube 200 during movement of annulus spacer 12 (discussed further below). The number and positioning of accelerometer(s) 8 in tool head 100 vary with the intended use. The accelerometers are typically used in pairs, with a pair consisting of two accelerometers 8 located at generally the same axial position in the tool, with one accelerometer 8 positioned to measure acceleration at the vertical top of the pressure tube 200 and one accelerometer 8 positioned to measure acceleration at the vertical bottom of the pressure tube 200. There are typically at least six accelerometers 8 (i.e. three accelerometer pairs), however, additional accelerometer 8 pairs may be used. Desirably, tool head 100 includes twelve accelerometers 8 mounted as six pairs. In the embodiment of FIG. 3A, tool head 100 includes twelve accelerometers 8. The embodiment of FIGS. 3A and 3B provide three accelerometer 8 pairs on either side of the axial centerline of the tool, allowing the tool head to measure the position of annulus spacer 12 on either side of the tool head centre, which corresponds to the antinode locations for j=2 modes. In other embodiments, there are only six accelerometers 8 (three pairs) located on one side of the tool axial centre. In a specific embodiment of the invention, the tool incorporates means for moving the accelerometers axially within the tool to improve the detection resolution. This may be accomplished by mounting accelerometers 8 in a moveably attached component within tool head 100 which may be moved axially within tool head 100 by any standard mechanical means such as an electric motor and leadscrew or a hydraulic cylinder. Eddy Current Gap Measurement Probe. Tool head 100 also includes eddy current gap measurement probe 10 to obtain measurements to confirm that annulus spacer 12 is in the unloaded position following pressure tube jacking. Such use of eddy current gap measurement probe 10 is known to the skilled worker. In the embodiment of FIGS. 3A and 3B, tool head 100 includes two eddy current gap probes 10 to enable the gap above and below the pressure tube 200 to be measured simultaneously. In other embodiments, there is only one eddy current gap probe 10 to measure the gap below the pressure tube. In a specific embodiment of the invention, tool head 100 includes three eddy current gap probes 10 to measure the gap above, below, and to one side of the pressure tube. Umbilical Tool head 100 is configured for operative association with umbilical 30. Umbilical 30 includes appropriate electrical cables and hydraulic and/or pneumatic hoses to connect tool head 100 to an out-of-reactor power unit and control system (not shown). Out-of-reactor power unit includes a hydraulic power supply (pump, valves) and electrical power supplies. This unit is a source of power and amplification, and may be positioned adjacent to the reactor, proximal to the services for the delivery machine. Control Station. Tool head 100 is operable from a control station (not shown), which is desirably located in a low radiation environment, away from the reactor. The control station includes such items as signal conditioning for transducers, means for data acquisition and an operator interface. Special purpose software is included to control tool head 100 and analyse the data resulting from annulus spacer 12 detection, movement and/or detection and movement processes. Dedicated procedures, outlined for example in user manuals, are included to guide/instruct operators in annulus spacer 12 detection and/or annulus spacer 12 repositioning. It will be clear that tool head 100 can be included as a kit, to retrofit existing machines. Methods During operation of a reactor, it may be possible for annulus spacer(s) 12 to move axially along pressure tube 200. This movement of annulus spacer(s) 12 can result from vibration and/or thermal cycling of the reactor. When axial movement of annulus spacer(s) 12 occurs, it may be necessary or desirable to reposition annulus spacer(s) 12. Alternatively or additionally, it is possible that initial placement of annulus spacer(s) 12 is not optimal or desired, and here again it may be necessary or desirable to reposition annulus spacer(s) 12, from a first position to a second position. Tool head 100 may be used for (i) detecting annulus spacer(s) 12, (ii) repositioning annulus spacer 12, and/or (iii) detecting annulus spacer 12 during repositioning. Vibration-based techniques are used for both detection and repositioning of annulus spacer 12. The following discussion provides details of methods of using the apparatus of the present invention to detect and/or reposition an annulus spacer; however, it will be clear that variations can be made to the following methods while not deviating from the present invention. Such methods are within the scope of the present application. Annulus Spacer Detection Detection of annulus spacer 12 is achieved by monitoring changes in the response of the pressure tube 200 vibrations caused by the presence of annulus spacer 12. Tool head 100 is inserted in pressure tube 200 to an initial position. The initial position may be close to a position where a user expects annulus spacer 12 to be. Alternatively, if for example the user does not have knowledge of where annulus spacer 12 is anticipated to be, the initial position of tool head 100 can be an arbitrary position within pressure tube 200. After the tool head is positioned at the selected location, clamping members 20 are actuated to move into contact with and apply pressure to the wall of the inner tube in such a manner that a section of the inner tube is vibrationally isolated from the remainder of the tube. The vibrational isolation is used to establish a consistent environment for detection of changes without effecting the remainder of the tube. The isolated section is subsequently vibrated through the action of the piezo-actuator and acceleration measurements are taken at three or more axial locations to determine the frequency response. The measurements from the different axial locations are compared and a relative change in the frequency response indicates the presence of a loaded spacer. FIG. 5 depicts plots of the first and second axial mode shapes for a clamped-clamped beam. As used herein, “clamped-clamped beam” can be established with tool head 100 positioned in the desired location of pressure tube 200, each clamping block assembly 2 is actuated to move assembly clamping member 20 from the retracted position to the extended position, thereby vibrationally isolating a portion of pressure tube 200. FIG. 6 depicts the circumferential and axial mode shapes for a clamped-clamped beam with a circular cross-section. Detection of the position of annulus spacer 12 is based on the differences in the vibration responses at the top and bottom of pressure tube 200 vibrating in the vicinity of a loaded annulus spacer 12. Annulus spacer 12 primarily contacts calandria tube 400 near the bottom of the tube, and transmits force to the pressure tube 200 primarily at this location. Detection is achieved by exciting a random vibration in pressure tube 200 using piezo-actuator 6 and measuring the response of pressure tube 200 at both a top position and a bottom position of pressure tube 200 using accelerometers 8 at three or more axial locations. The acceleration is monitored at the natural frequencies of the pressure tube section, where the expected maximum accelerations are highest. The presence of annulus spacer 12 alters the local acceleration and deflection of the pressure tube wall, primarily at the bottom of pressure tube 200. This produces an asymmetry in the circumferential mode shape. In use, tool head 100 is positioned inside pressure tube 200 and random vibrations are excited using tool piezo-actuator 6. A comparison between the pressure tube acceleration at the top position and the bottom position is performed at multiple axial positions to identify spacer location(s). This is illustrated in the views provided in FIG. 4. View A depicts a simplified axial cross section view of a beam mode in a pressure tube. Acceleration measurements are taken at the top position and the bottom position, designated at and ab, respectively, in FIG. 4. View B shows a simplified view of the ‘modified’ beam mode as it is affected by the reactionary force from a loaded annulus spacer 12. The presence of annulus spacer 12 is determined by comparing measurement at and ab at various axial locations along pressure tube 200. In the absence of annulus spacer 12, the absolute value of at and ab are approximately equal. However, when a loaded annulus spacer 12 is present, there is a difference between at and ab. The value of ab is reduced typically in the range of 20-40% compared to the value of at. At any given frequency, the ratio of the absolute value of the acceleration measured at the top and bottom of the pressure tube is defined as the frequency response function at that frequency. FIG. 7 depicts a plot of the frequency response function spectra for a section of pressure tube, with and without the presence of a loaded annulus spacer. The plot of FIG. 7 shows that there are significant differences in the frequency response function with and without a loaded spacer in certain frequency ranges. This relationship allows spacer detection to be achieved by analyzing the accelerations within an identified frequency range or ranges. FIG. 8 is a plot depicting the frequency response ratio as a function of axial position along the pressure tube for frequencies in the range of the (1,1) mode. The loaded annulus spacer is located at the 450 mm axial position of a 800 mm long pressure tube section. The testing was done with an annulus spacer load of 400 N. The plotted frequency response function exhibits a minima of approximately 0.6 at the axial location corresponding to the annulus spacer. FIG. 9 depicts a plot of the frequency response ratio as a function of axial position along the pressure tube for frequencies in the range of the (2,1) mode. The loaded annulus spacer is located at the 450 mm axial position. The plotted frequency response function exhibits a minima of approximately 0.76 at the axial location corresponding to the annulus spacer. Pressure Tube Jacking After some period of operation of a reactor, annulus spacer 12 is in contact with pressure tube 200 and outer calandria tube 400 (a loaded condition). For repositioning of annulus spacer 12, it is necessary to bring annulus spacer 12 out of contact with calandria tube 400 (an unloaded condition), to free annulus spacer 12 for movement. Moving annulus spacer 12 from a loaded condition to an unloaded condition is carried out by applying a moment of force to pressure tube 200 using tool head 100. This procedure is also known to the skilled worker as pressure tube jacking or jacking. Eddy current gap probe(s) 10 is/are used to measure the pressure tube-to-calandria tube gap, to confirm that annulus spacer 12 is in the unloaded condition. Thus, eddy current gap probe(s) 10 may also be used to determine if it is necessary to apply a moment of force to pressure tube 200. Tool head 100 is configured to apply a moment of force to pressure tube 200, using clamping block assembly 2. As noted above, clamping block assembly 2 is operable for rotation about coupling 16. To apply a moment of force, tool head 100 is positioned within pressure tube 200 and assembly members 20 are moved to the extended position. Each clamping block assembly 2 is rotated (in opposite direction to one another) and a moment of force is applied in the vertical plane parallel to the pressure tube axis. The applied moment of force effectively lifts inner pressure tube 200 off outer calandria tube 400, thereby taking annulus spacer 12 out of contact with calandria tube 400 and freeing annulus spacer 12 for movement. Thus, by applying the moment of force to pressure tube 200, annulus spacer 12 is moved from the loaded condition to the unloaded condition. Such pressure tube jacking is also used in the case of a type of annulus spacer known as a loose-fit spacer. Annulus Spacer Repositioning Repositioning of annulus spacer 12 is achieved by vibrating a section of the pressure tube in a controlled manner. To reposition annulus spacer 12, tool head 100 is positioned within pressure tube 200 at a desired location with respect to annulus spacer 12. Desirably, the position of annulus spacer 12 is determined as discussed above. Once tool head 100 is positioned in the desired location, each clamping block assembly 2 is actuated to move assembly clamping member 20 from the retracted position to the extended position, thereby vibrationally isolating a portion of pressure tube 200. This vibrational isolation provides a standard fixed length of pressure tube 200 located between the two clamping block assemblies 20 for the vibration-based repositioning of annulus spacer 12. Tool head 100 is used to apply a moment of force to pressure tube 200, to raise the pressure tube and remove the load from the annulus spacer 12. In some instances, if the annulus spacer were normally in the unloaded condition, it is possible to move a snug-fitting annulus spacer 12 without jacking the pressure tube. The unloading of annulus spacer 12 is confirmed by measuring the pressure tube-to-calandria tube gap using eddy current gap probe 10. Eddy current gap probe 10 provides information used to determine the amount of moment necessary to apply to pressure tube 200. Once in position, and annulus spacer 12 is in the unloaded position, bearing pad 22 within piezo-actuator 6 is moved from the retracted position to the extended position. Piezo-actuator 6 is operable to vibrate the pressure tube 200 at the desired frequency. The frequency of vibration is selected to match a natural frequency of the isolated pressure tube section. Typically the (2,1) mode is used for spacer repositioning as this mode provides for the highest efficiency in terms of power provided by the piezo-actuator versus peak pressure tube acceleration produced. However, other higher modes such as (2,2) and (2,3) may be used. For a water-filled pressure tube with an active vibrating length of 800 mm, frequencies of 626 Hz, 793 Hz and 1096 Hz correspond to the (2,1), (2,2) and (2,3) modes, respectively. The frequency of vibration of piezo-actuator 6 selected will depend on a variety of non-limiting factors such as operating conditions, actual pressure tube size, damping effects of the tool head, user preference, regulatory requirements and/or the like. The frequency of vibration produced may be adjusted to match the actual natural frequency by monitoring the pressure tube acceleration produced during actuation. The vibrations cause annulus spacer 12 to vibrate as well. These vibrations in annulus spacer 12 produce accelerations that are high enough to overcome the spring tension in the spacer and allow the spacer to lift off of the surface of the pressure tube. Desirably, tool head 100 is positioned to initially place annulus spacer 12 between a node and an anti-node of the mode shape generated by the vibrations. The vibrations typically cause annulus spacer 12 to move away from an anti-node and towards a node (FIG. 4). This is shown graphically in FIG. 4, which shows two axial mode shapes of a clamped-clamped beam. The relative position of annulus spacer 12 with respect to the mode shape determines the direction of spacer movement. A variety of mode shapes may be used. The greater the mode number desired for use, the greater the amount of power that is required to produce an equivalent acceleration. Annulus Spacer Monitoring During Repositioning In one example, the movement of annulus spacer 12 is monitored during movement of annulus spacer 12. This is carried out using accelerometers 8 to detect the high frequency impacts between annulus spacer 12 and pressure tube 200 as annulus spacer 12 vibrates during movement. Multiple accelerometers at different positions on tool head 100 are used. The difference in the time when the impact is detected by the accelerometers and the magnitude of the impact is used to determine spacer location and movement. FIG. 10 is a graph depicting acceleration as a function of time, detected at accelerometers 8 positioned at various positions on tool head 100. (Each of the three accelerometers 8 is designated 1, 2, and 3). The data were taken from a single annulus spacer 12 impact with the pressure tube 200. In this example, accelerometer 3 was located 27 mm axially from the annulus spacer 12 and near the pressure tube top. Accelerometer 2 was located 76 mm axially from annulus spacer 12 and also near the pressure tube top. Accelerometer 1 was located 87 mm axially from annulus spacer 12 and was located near the pressure tube bottom. It will be noted from the graph that the start of the acceleration response occurred later in time the further away from the impact accelerometer 8 was located. The wave front moves at approximately 1700 m/s. The initial acceleration peak is reduced the further away the accelerometer is from the annulus spacer impact. The time delay and the reduction in amplitude may be used to determine the position of annulus 12 spacer impact. Kits It will be clear that tool head 100, and/or components of tool head 100, can be included as a kit. Such a kit may optionally include instructions for use and/or software for operating tool head 100. All publications, patents and patent applications mentioned in this Specification are indicative of the level of skill of those skilled in the art to which this invention pertains and are herein incorporated by reference to the same extent as if each individual publication, patent, or patent applications was specifically and individually indicated to be incorporated by reference. The invention being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the invention, 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.
	claims	1. A method of evaluating proposed solutions to a nuclear reactor constraint problem, comprising:providing an objective function definition generic to a constraint problem,configuring the generic objective function into a nuclear reactor constraint problem objective function having channel deformation of control blades as a constraint,the nuclear reactor constraint problem objective function being a sum of optimization parameters and constraint parameters,each optimization parameter including a multiple of a credit term and an associated credit weight, the credit term being a numerical value associated with the optimization parameter, the credit weight being a numerical value corresponding to a relative importance of the associated credit term,each constraint parameter including a multiple of a penalty term and an associated penalty weight, the penalty term being a numerical value associated with a violation of a constraint, at least one penalty term including a summation of a number of control blades affected by the channel deformation, the penalty weight being a numerical value corresponding to a relative importance of the associated penalty term, at least one penalty weight being a numerical value corresponding to a relative importance of the control blades affected by the channel deformation, the channel deformation being at least one of bowing, bulging and twisting of a channel,the channel having walls surrounding a fuel bundle;receiving, for each proposed solution to the nuclear reactor constraint problem, a value of at least one variable in at least one credit term in the configured objective function at the processor, the credit term variable being related to the proposed solution;receiving, for each proposed solution to the nuclear reactor constraint problem, a value of at least one variable in at least one penalty term in the configured objective function at the processor, the penalty term variable being related to the proposed solution;generating, using the processor, a figure of merit for each of the proposed solutions to the nuclear reactor constraint problem based on the credit term variable and the penalty term variable using the configured objective function; anddetermining a desired one of the proposed solutions to the nuclear reactor constraint problem based on the generated figures of merit. 2. The method of claim 1, further comprising:implementing the desired proposed solution to the nuclear reactor constraint problem, based on the evaluation, in order to optimize performance of the nuclear reactor, the determining the desired one of the proposed solutions being accomplished by using the figures of merit to evaluate the relative strength of the proposed solutions. 3. A method of evaluating proposed solutions to a nuclear reactor constraint problem, comprising:providing an objective function definition generic to a constraint problem,configuring the generic objective function into an application specific objective function having channel deformation of control blades as a constraint,the application specific objective function being a sum of optimization parameters and constraint parameterseach optimization parameter including a multiple of a credit term and an associated credit weight, the credit term being a numerical value associated with the optimization parameter, the credit weight being a numerical value corresponding to a relative importance of the associated credit term,each constraint parameter including a multiple of a penalty term and an associated penalty weight, the penalty term being a numerical value associated with a violation of a constraint, at least one penalty term including a summation of a number of control blades affected by the channel deformation, the penalty weight being a numerical value corresponding to a relative importance of the associated penalty term, at least one penalty weight being a numerical value corresponding to a relative importance of the control blades affected by the channel deformation, the channel deformation being at least one of bowing, bulging and twisting of a channel, the channel having walls surrounding a fuel bundle;generating, using the processor, a figure of merit for each of the proposed solutions to the nuclear reactor constraint problem based on the credit term variable and the penalty term variable using the application specific objective function; anddetermining a desired one of the proposed solutions to the nuclear reactor constraint problem based on the generated figure of merit. 4. The method of claim 3, further comprising:implementing the desired proposed solution to the nuclear reactor constraint problem, based on the evaluation in order, to optimize performance of the nuclear reactor, the determining the desired one of the proposed solutions being accomplished by using the figures of merit to evaluate the relative strength of the proposed solutions. 5. An apparatus for evaluating proposed solutions to a nuclear reactor constraint problem, comprising:a memory storing an application specific objective function configured based on a generic objective function definition generic to a constraint problem,the application specific objective function having channel deformation of control blades as a constraint,the application specific objective function definition being a sum of optimization parameters and constraint terms,each optimization parameter including a multiple of a credit term and an associated credit weight, the credit term being a numerical value associated with the optimization parameter, the credit weight being a numerical value corresponding to a relative importance of the associated credit term,each constraint parameter including a multiple of a penalty term and an associated penalty weight, the penalty term being a numerical value associated with a violation of a constraint, at least one penalty term including a summation of a number of control blades affected by the channel deformation, the penalty weight being a numerical value corresponding to a relative importance of the associated penalty term, at least one penalty weight being a numerical value corresponding to a relative importance of the control blades affected by the channel deformation based on criteria for channel deformation,the channel deformation being at least one of bowing, bulging and twisting of a channel, the channel having walls surrounding a fuel bundle;an interface receiving, for each proposed solution to the nuclear reactor constraint problem, a value of at least one variable in at least one credit term of the application specific objective function and receiving a value of at least one variable in at least one penalty term of the application specific objective function, the credit term variable and the penalty term variable being related to the proposed solution; anda processor generating a figure of merit for each of the proposed solutions to the nuclear reactor constraint problem based on the credit term variable and the penalty term variable using the application specific objective function, the processor configured to determine a desired one of the proposed solutions to the nuclear reactor constraint problem based on the generated figures of merit. 6. The apparatus of claim 5, wherein the processor is further configured to implement the desired proposed solution to the nuclear reactor constraint problem, based on the evaluation, in order to optimize performance of the nuclear reactor, the processor configured to determine the desired one of the proposed solutions by using the figures of merit to evaluate the relative strength of the proposed solutions. 7. A method of generating a solution to an optimization problem, comprising:generating, using a processor, candidate solutions to a nuclear reactor constraint problem;generating, using the processor, objective function values using a configured objective function, the configured objective function being configured from an objective function definition generic to the constraint problem,the configured objective function having channel deformation of control blades as a constraint,the configured objective function being a sum of optimization parameters and constraint parameters,each optimization parameter including a multiple of a credit term and an associated credit weight, the credit term being a numerical value associated with the optimization parameter, the credit weight being a numerical value corresponding to a relative importance of associated credit terms,each constraint parameter including a multiple of a penalty term and an associated penalty weight, the penalty term being a numerical value associated with a violation of a constraint, at least one penalty term including a summation of a number of control blades affected by the channel deformation, the penalty weight being a numerical value corresponding to a relative importance of the associated penalty term, at least one penalty weight being a numerical value corresponding to a relative importance of the control blades affected by the channel deformation,the channel deformation being at least one of bowing, bulging and twisting of a channel, the channel having walls surrounding a fuel bundle; andassessing convergence on a desired solution to the nuclear reactor constraint problem based on the objective function values. 8. The method of claim 7, further comprising:implementing the desired solution, based on the assessment, if the objective function value is acceptable, the assessing the convergence on the desired solution including determining a strength of the candidate solutions by evaluating the objective function values. 9. A method of configuring an objective function and implementing proposed solution, the method automated by a processor, comprising:providing an objective function configured for a constraint problem,the objective function being a sum of optimization parameters and constraint parameters,each optimization parameter including a multiple of a credit term and an associated credit weight, the credit term being a numerical value associated with the optimization parameter, the credit weight being a numerical value corresponding to a relative importance of the associated credit term,each constraint parameter including a multiple of a penalty term and an associated penalty weight, the penalty term being a numerical value associated with a violation of a constraint, at least one penalty term including a summation of a number of control blades affected by the channel deformation, the penalty weight being a numerical value corresponding to a relative importance of the associated penalty term, at least one penalty weight being a numerical value corresponding to a relative importance of the control blades affected by the channel deformation;defining the credit terms based on user input,the channel deformation being at least one of bowing, bulging and twisting of a channel, the channel having walls surrounding a fuel bundle;generating a merit based on the credit term and penalty term using the objective function; andimplementing a proposed solution, if the figure of merit is acceptable.

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