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	description	The present application claims priority based on Japanese Patent Application No. 2005-102859, filed on Mar. 31, 2005, the entire content of which is incorporated herein by reference. This invention relates to a mobile working apparatus for doing works such as inspections and machining operations on structures such as nuclear reactor structures and a working method of operating such an apparatus. Intra-nuclear-reactor working apparatuses are generally used for intra-reactor operations such as inspections, examinations and preventive maintenances of the inner surface of nuclear reactor pressure vessels and intra-reactor structures. Particularly, when the weld line found on the bottom of an annular part sandwiched between the pressure vessel inner wall and the shroud of a boiling water nuclear reactor is the target of operation, the operation faces various problems such as a limited working space and a long working time because it is difficult to access the target that is located in a very narrow area. Various intra-nuclear-reactor working apparatuses have been proposed to carry out such an operation in a short period of time and secure a larger working space. Firstly, an intra-nuclear-reactor working apparatus comprising a slim self-propelled apparatus main body that is adapted to move on a shroud support plate, adhering to the wall surface of a nuclear reactor pressure vessel, a shroud support cylinder or a jet pump by suction, in order to inspect the weld line found on the bottom of an annular part is known (See Japanese Patent Application Laid-Open Publication No. Hei 11-174192, the entire content of which being incorporated herein by reference). The apparatus has an inspection mechanism section that includes an airtight chamber for maintaining the orientation by buoyancy, a wall surface pushing means using a thruster and flowing water, a traveling means such as a crawler and inspection means such as various sensors. Thus, the apparatus runs by means of the crawler arranged at the bottom of the apparatus as it adheres to the wall surface so as to be guided by and move along the wall surface. Additionally, the apparatus gauges the distance from the inspection apparatus to a lateral surface of a jet pump diffuser by means of a non-contact range finder and identifies its relative position. At the same time, it identifies its absolute position on the shroud support plate from the distance covered by the crawler. Secondly, intra-nuclear-reactor working apparatuses adapted to move on a shroud support plate between a shroud support cylinder and a jet pump adaptor by means of a pair of crawlers in order to inspect a weld line and clean a target area are also known (See Japanese Patent Application Laid-Open Publication Nos. Hei 11-109082, Hei 10-221484 and Hei 9-15376, the entire contents of which being incorporated herein by reference). The apparatus described in Japanese Patent Application Laid-Open Publication No. Hei 11-109082 comprises a traveling mechanism section that is dimensioned to allow the apparatus to move in a narrow area and an independent inspection unit including an inspection camera and an ultrasonic search device, in which the inspection unit is coupled to and pulled by the traveling mechanism section. The apparatus described in Japanese Patent Application Laid-Open Publication Nos. Hei 10-221484 and Hei 9-15376 comprises a similar traveling mechanism section that is dimensioned to allow the apparatus to move in a narrow area and adapted to move on a shroud support plate by means of the nozzle mounted thereon for sucking and cleaning operations. These apparatuses can clean a region right below the jet pump riser pipe pinched by a jet pump adaptor. Thirdly, an intra-nuclear-reactor working apparatus comprising a guide section formed so as to match the radius of curvature of the outer surface of a jet pump diffuser and a positioning mechanism for rigidly securing the apparatus by extruding an extrusion member toward a nuclear reactor pressure vessel to apply reaction force to the guide section for the purpose of ultrasonic inspection of detecting flaws of the welded sections of the lower ends of a jet pump adaptor at the bottom of an annular part is also known (See Japanese Patent Application Laid-Open Publication No. Hei 11-326291, the entire contents of which being incorporated herein by reference). Unlike the above-described mobile inspection apparatus, this inspection apparatus is rigidly secured to a jet pump diffuser and is adapted to drive the inspection head for the purpose of ultrasonic inspection of detecting flaws by means of the head drive mechanism mounted in it. This apparatus is adapted to be rigidly and reliably secured to improve the accuracy of the inspection head scanning operation and hence the accuracy of inspection. When, for example, inspecting the weld line of an intra-reactor structure such as a shroud in the water in a nuclear reactor by means of any of the known intra-nuclear-reactor working apparatuses by ultrasonic means, a phased array ultrasonic probe or the like is mounted on a vehicle that is designed to move, adhering to the wall surface by sucking, for the purpose of conveying and positioning the probe and examining the target of inspection. Additionally, a scanning mechanism having a certain degree of freedom of adjustment is employed and mounted on the vehicle for the purpose of remotely adjusting the operating position and the attitude of the probe in the inspection. With such a combination of a vehicle and a scanning mechanism, it is possible to examine weld lines having a large radius of curvature such as those of both the inside and the outside of a shroud without giving rise to any interference of the scanning mechanism with the intra-reactor structures including the shroud and the jet pump, because the inspection sensor requires adjustment only to a slight extent. Furthermore, the risk of interference with the intra-reactor structures is low, if the scanning mechanism is fitted to the bottom side or the top side of the adhering and moving vehicle to increase the overall dimensions. Additionally, the combination of the adhering and traveling vehicle and the scanning mechanism can also be used for operations other than inspections such as cleaning operations, grinding operations and polishing operations as well as operations for improving stresses by means of laser peening involving a small reaction force. Laser peening refers to a preventive security treatment of irradiating a laser beam to or near a weld line in water in order to transform the tensile residual stress of the surface of a structure into compressive residual stress. However, the use of a combination of a vehicle and a scanning mechanism for operations including those of examining the weld lines of shroud support cylinders and shroud support plates and the weld lines of nuclear reactor pressure vessels and shroud support plates that are found in narrow areas such as the bottom of an annular part entails the following problems. When examining such weld lines, for example, the inspection sensor has to be made to follow the fillet-welded section showing a radius of curvature of about 15 mm so that the probe is required to change its position and attitude to a large extent. However, the space where a scanning mechanism can operate is dimensionally limited, and hence it is necessary to check the configuration, the structure and the dimensions of the scanning mechanism so that the inspection sensor may not interfere with the jet pump adaptor, if the position and the attitude of the inspection sensor are changed to a large extent. Additionally, a sensing line is arranged between the shroud and the jet pump at the side of the shroud of the bottom of the annular part. Therefore, the overall length of the adhering and moving vehicle and that of the scanning mechanism mounted on it have to be reduced so that they may not interfere with the jet pump sensing line and the bracket anchoring it when they are moved peripherally along the shroud. With the method of identifying the absolute position on the shroud support as described in Japanese Patent Application Laid-Open Publication No. Hei 11-174192 that is referred to above as prior art, it is conceivable that a traveling error occurs when the crawler slips in a region that is not covered by the jet pump diffuser. Additionally, in the area where the gap between the jet pump diffuser and the shroud support cylinder and the wall of the nuclear reactor pressure vessel is smallest, the gauging distance of the non-contact range finder relative to the moving distance along the wall surface is small, and thus a gauging error can occur depending on the adhering condition of the inspection apparatus to the wall surface. Therefore, it is reasonable to have apprehension of a degraded accuracy of gauging the traveling distance. While all the intra-nuclear-reactor working apparatuses described in Japanese Patent Application Laid-Open Publication Nos. Hei 11-109082, 10-221484 and 9-15376 can move in narrow areas, they require means for highly accurately identifying the absolute position of a spot on the shroud support plate. With the intra-nuclear-reactor working apparatus described in Japanese Patent Application Laid-Open Publication No. Hei 11-326291, it is necessary that the apparatus for conveying and positioning the working equipment needs to be self-propelled in order to cover a large working area in a short period of time for the intra-nuclear-reactor working apparatus. In view of the above-identified problems of the prior art, it is therefore an object of the present invention to provide a working apparatus and a working method that are adapted to perform accurate positioning operations in a narrow environment, such as, in the water in the nuclear reactor and complex scanning operations for various pieces of working equipment such as inspection sensors and can secure a large working area within a short period of time and reduce the overall working hours. In order to attain the object, according to an aspect of the present invention, a working apparatus for doing works on a structure is provided. The apparatus comprises: a working equipment to be placed vis-a-vis the structure to do a work; an operation mechanism to be mounted by the working equipment and adapted to actively move the working equipment relative to the structure; and an adhering/traveling module coupled to the operation mechanism and adapted to adhere to the structure so as to have weight of the working apparatus borne by the structure and travel/move on the structure for positioning. According to another aspect of the present invention, a working method for doing works on a structure is provided. The method comprises: bringing in a working apparatus having an operation mechanism mounted by a working equipment and an adhering/traveling module; having the working apparatus adhere to the wall surface of the structure and the weight of the working apparatus borne by the structure; having the working apparatus travel and move along the wall surface; having the adhering/traveling module gauge the traveled quantity relative to the wall surface; and having the working apparatus perform a scanning operation on the structure by means of the operation mechanism. Now, first and second embodiments of an intra-nuclear-reactor working apparatus and a working method according to the present invention will be described referring to the accompanying drawings. The first embodiment of the present invention will be described by referring to FIGS. 1 through 4D. This embodiment will be described in terms of ultrasonic inspection of detecting flaws as an example of operation. FIG. 1 is a conceptual schematic illustration showing how an intra-nuclear-reactor working apparatus 20 that is adapted to ultrasonic inspection of detecting flaws is arranged on the bottom of the annular part between a shroud intermediate trunk 1 and a shroud lower trunk 4, which are intra-reactor structures of a boiling water nuclear reactor, and the wall of the nuclear reactor pressure vessel 2. The object of flaw detection may be an H8 horizontal weld line 10 that is the weld line of a shroud support cylinder 6 and a shroud support plate 7 or an H9 horizontal weld line 11 that is the weld line of the nuclear reactor pressure vessel 2 and the shroud support plate 7. Referring to FIG. 1, the intra-nuclear-reactor working apparatus 20 is arranged on the shroud support plate 7 along the inner wall of the nuclear reactor pressure vessel 2 for the purpose of inspecting the H9 horizontal weld line 11. A cable (not shown) is connected to the intra-nuclear-reactor working apparatus 20 so as to connect the latter to a control/operation section (not shown) which may typically be arranged on the operation floor or on the fuel exchanger. FIGS. 2A and 2B illustrate the arrangement in the intra-nuclear-reactor working apparatus 20. As shown in the drawings, the intra-nuclear-reactor working apparatus 20 generally includes: a scanning mechanism 21 for actively driving the working equipment including a flaw detecting probe to move relative to the intra-reactor structures, and adhering/traveling modules 22 arranged at the opposite lateral sides of the scanning mechanism 21. A phased array ultrasonic probe 23 is arranged under the center of the scanning mechanism 21 so as to operate as an ultrasonic flaw detecting sensor. The phased array ultrasonic probe 23 is driven to rotate around a horizontal axis by a timing belt 31 and a rotary shaft drive motor 30, which is a drive source. The rotary mechanism (the rotary shaft drive motor 30 and the timing belt 31) is linked to a rocking shaft base 32 that operates as the center 33 of the rocking motion by way of a rotary shaft core, which is typically a pin, so as to swing the rotary mechanism 30 around the center 33 of the rocking motion by means of the timing belt 35, using a rocking shaft drive motor 34 as a drive source. The rocking shaft base 32 is vertically movably linked to a vertical shaft base 36 by way of a linear guide 37 so that it is driven to move up and down by means of a timing belt 39, a ball screw and a nut 40, using a vertical shaft drive motor 38 as a drive source. Each of the adhering/traveling modules 22 comprises a thruster 41 that is driven to rotate by a drive motor (not shown), a traveling wheel 42 to be used for moving horizontally along the wall surface after adhering to the wall surface, a motor 43 and a timing belt 44 for driving the traveling wheel 42, a distance gauging roller 45 and a rotary sensor 46 for gauging the horizontal traveling distance and a ball caster 26 for supporting the weight of the intra-nuclear-reactor working apparatus when it moves on the shroud support plate 7. A float 24 is arranged at an upper part of the scanning mechanism 21 so as to position the center of buoyancy above the center of gravity in water and hence the intra-nuclear-reactor working apparatus can hold its attitude without toppling down in water. A ball caster 25 is arranged on the float 24 in order to hold the apparatus away from the wall surface by a certain distance when the latter adheres to the wall surface. Thus the ball caster 25 and the two traveling wheels 42 receive the reaction force of the wall surface when the adhering/traveling modules 22 adhere to the wall surface. The distance gauging rollers 45 are also held in contact with the wall surface. Thus, the rollers are brought into contact with the wall surface by the right force exerted to them typically by springs (not shown) and rotate when the apparatus runs horizontally. The scanning mechanism 21 is provided with an inclination sensor 27, which detects the inclination thereof in lateral directions relative to the wall surface that the working apparatus is adhering to as viewed from the rear side of the working apparatus and monitors if the rotary shaft of the phased array ultrasonic probe 23 is horizontal or not. Now, the sequence of operation of arranging this embodiment of intra-nuclear-reactor working apparatus 20 on the shroud support plate 7, which is an intra-reactor structure, and carrying out an inspection will be described below by referring to FIG. 3. The intra-nuclear-reactor working apparatus 20 is suspended by the cable of a lift apparatus (not shown) and lowered from above the nuclear reactor so as to be put near one of the access hole covers 12 arranged respectively at azimuths 0° and 180° positions of the nuclear reactor. In the instance of FIG. 3, the intra-nuclear-reactor working apparatus 20 is put near the azimuth 0° of the nuclear reactor. As the intra-nuclear-reactor working apparatus 20 is lowered to the level of the shroud upper trunk, passing by the feed water sparger, and made to enter the annular part, it is driven to approach the side of the shroud intermediate trunk 1 or the side of the wall of the nuclear reactor pressure vessel 2 depending on the position of the target of inspection by the propelling force generated by the revolutions of the two thrusters 41. If the H8 horizontal weld line 10 is the target of inspection, the intra-nuclear-reactor working apparatus 20 that is being suspended is lowered toward the shroud intermediate trunk 1 and the shroud lower trunk 4 until it is laid on the shroud support plate 7 without touching the shroud support ring 5. Then, the two thrusters 41 are driven to make the apparatus adhere to the shroud support cylinder 6. Once the apparatus is placed on the shroud support plate 7, the apparatus is driven to move to the original position for starting the inspection. The intra-nuclear-reactor working apparatus 20 placed on the shroud support plate 7 is driven to move horizontally as the two traveling wheels 42 that are held in contact with the shroud support cylinder 6 are driven to rotate by the horizontal drive force acquired relative to the shroud support cylinder 6. The position where the access hole cover 12 and the intra-nuclear-reactor working apparatus 20 are brought to contact with each other is selected as original position. Then, the intra-nuclear-reactor working apparatus 20 is driven to move along the shroud support cylinder 6 as shown in FIG. 3, passing through the gap between the shroud support cylinder 6 and the jet pump adaptors 9, traveling at least within a range of about 90°, in order to inspect the H8 horizontal weld line 10. At a selected position of inspection, the apparatus performs a scanning operation by means of the scanning mechanism 21 for the inspection, while it is being remotely controlled for the position and the attitude of the phased array ultrasonic probe 23 relative to the H8 horizontal weld line 10, which is the inspection target. When the scanning operation is finished for a scanning range, the apparatus moves peripherally to the next scanning range. The peripheral distance that is covered by the scanning operation is constantly and continuously gauged by the distance gauging roller 45. If the intra-nuclear-reactor working apparatus 20 is inclined laterally as viewed from behind, or as detected by the inclination sensor 27, it means that the phased array ultrasonic probe 23 is not arranged in parallel with the shroud support plate 7. If the angle of inclination exceeds a tolerance range, it is regulated so as to be found within the tolerance range by adjusting the extent by which the ball casters 26 project. If, on the other hand, the H9 horizontal weld line 11 at the side of the wall of the nuclear reactor pressure vessel 2 is the target of inspection, the intra-nuclear-reactor working apparatus 20 is arranged at the side of the wall of the nuclear reactor pressure vessel 2 in a similar manner, and the position where the access hole cover 12 and the intra-nuclear-reactor working apparatus 20 are brought to contact with each other is selected as original position. Then, the intra-nuclear-reactor working apparatus 20 is driven to move along the wall of the nuclear reactor pressure vessel 2 as shown in FIG. 3, passing through the gap between the wall of the nuclear reactor pressure vessel 2 and the jet pump adaptors 9, traveling at least within a range of about 90°, in order to inspect the H8 horizontal weld line 10. The H8 horizontal weld line 10 and the H9 horizontal weld line 11 are inspected by placing the intra-nuclear-reactor working apparatus 20 at a total of eight positions to repeat the above sequence of operation. Now, the operation of each of the drive mechanisms of the scanning mechanism 21 for inspecting the H8 horizontal weld line 10 by means of the phased array ultrasonic probe 23 will be described below by referring to FIGS. 4A through 4D. Referring firstly to FIG. 4A, the phased array ultrasonic probe 23 is irradiating an ultrasonic wave onto an ultrasonic wave irradiating position 57 on the shroud support cylinder 6 along an ultrasonic wave irradiation axis 56 that is schematically illustrated in FIG. 4A. At this time, the distance from the center 55 of rotation of the probe to the shroud support cylinder 6 is gauged by a distance sensor such as an ultrasonic sensor fitted to a lateral side of the phased array ultrasonic probe 23. The gauging direction is same as the flaw detecting direction of the phased array ultrasonic probe 23. In other words, the distance is gauged while the phased array ultrasonic probe 23 is held horizontally as shown in FIG. 4A. If necessary, on the basis of the outcome of the distance gauging operation, the rocking mechanism comprising the rocking shaft drive motor 34 and the timing belt 35 is driven to regulate the distance from the center 55 of rotation of the probe to the shroud support cylinder 6. The flaw detecting direction (the orientation of the ultrasonic wave irradiation axis 56 or the direction of ultrasonic wave irradiation) of the probe is corrected by the rotary mechanism comprising the rotary shaft drive motor 30 and the timing belt 31, while the vertical position is corrected by the vertical drive mechanism comprising the vertical shaft drive motor 38, the timing belt 39, the ball screw and the nut 40. The distance from the center 55 of rotation of the probe to the shroud support plate 7 is gauged by rotating the phased array ultrasonic probe 23 from the state of FIG. 4A so as to direct the gauging direction of the distance sensor downward. If necessary, on the basis of the outcome of the distance gauging operation, the vertical drive mechanism is driven to regulate the distance from the center 55 of rotation of the probe to the shroud support plate 7. Thereafter, the distance from the center 55 of rotation of the probe to the shroud support cylinder 6 is gauged once again for the purpose of assurance. If the distance error exceeds a tolerance range, the above-described procedure of adjustment and correction is repeated. In this way, the distance from the center 55 of rotation of the probe to the shroud support cylinder 6 and the distance from the center 55 of rotation of the probe to the shroud support plate 7 are regulated. Then, referring to FIG. 4B, an ultrasonic flaw detecting operation is conducted on the shroud support cylinder 6 by lowering the phased array ultrasonic probe 23 by means of the vertical drive mechanism and scanning the shroud support cylinder 6 down to the ultrasonic wave irradiating position 58. Thereafter, as shown in FIG. 4C, an ultrasonic flaw detecting operation is conducted on the welded part by rotating the phased array ultrasonic probe 23 around the center 55 of rotation of the probe along the curvature of a fillet-welded bead 50 until the ultrasonic wave irradiation axis 56 is directed to the bottom surface, while keeping a predetermined distance to the fillet-welded bead 50. If the surface of the fillet-welded bead 50 does not show the profile of a ¼ circle, it is possible to scan the fillet-welded bead 50, while keeping a predetermined distance to the latter, by providing the intra-nuclear-reactor working apparatus 20 with a mechanism for projecting a slit laser beam and observing the surface profile, acquiring profile data and controlling the vertical drive mechanism, the rocking mechanism and the rotary mechanism so as to follow the profile of the bead. Then, an ultrasonic flaw detecting operation is conducted on the shroud support plate 7 by operating the vertical drive mechanism, the rocking mechanism and the rotary mechanism so as to constantly direct the ultrasonic wave irradiation axis 56 perpendicularly relative to the shroud support plate 7 and scanning the shroud support plate 7 down to an ultrasonic wave irradiating position 60. Thus, with this embodiment of intra-nuclear-reactor working apparatus 20, it is possible to scan a fillet-welded section, while remotely regulating the relative position and the attitude of the inspection sensor in the operation of inspecting a horizontal weld line of an intra-nuclear-reactor structure. As a pair of adhering/traveling modules 22 are arranged at the opposite sides of the scanning mechanism 21, it is possible to reliably hold the phased array ultrasonic probe 23 along a horizontal weld line and hence highly reliably inspect the horizontal weld line. Furthermore, since the height of the inspection apparatus is reduced, it is possible to move it on the shroud support plate 7 without allowing it to interfere with jet pump sensing lines 80. Additionally, since the apparatus travels while adhering to the shroud support cylinder 6, it is possible to apply it to a nuclear reactor where the shroud lower trunk 4 is inclined without modifying the configuration thereof. Still additionally, since separable adhering/traveling modules 22 are provided, it is possible to apply the apparatus to the undulations of the wall surface that may vary between the shroud side and the nuclear reactor pressure vessel 2 side and also to the curvature of the nuclear reactor that may vary from reactor to reactor by changing the angle of coupling between the scanning mechanism 21 and the adhering/traveling modules 22. The scanning mechanism 21 has a simple configuration and it is possible for the scanning mechanism 21 to perform a scanning operation along a fillet-welded section without interfering with the jet pump adaptors 9 in a narrow area. Additionally, it is possible to reduce the time necessary for preparation and adjustment so as to consequently reduce the overall working hours because the position and the attitude of the scanning mechanism 21 can be adjusted depending on the output of the phased array ultrasonic probe 23. The adhering/traveling modules 22 adhere to the wall of the shroud support cylinder 6 or that of the nuclear reactor pressure vessel 2 by means of the thrusters 41 to move horizontally by the traveling wheels 42 and directly gauge the traveled distance relative to the wall surface by means of distance gauging rollers 45 so that they can be continuously and accurately position themselves along a horizontal weld line. Therefore, it is possible to easily identify the position to be inspected and reliably perform an inspection. Since the adhering/traveling modules 22 have respective distance gauging rollers 45 to make the number of distance gauging rollers 45 equal to two, the traveled distance can be gauged accurately if one of them slips. Additionally, if the wall surface to which they are adhering has undulations such as vertical weld lines and one of the distance gauging rollers 45 rides on a protrusion, it is possible to accurately gauge the traveled distance by the other distance gauging roller 45. A washing water discharging nozzle, a polishing brush, a grinding jig or a laser peening head may be mounted in this embodiment of the present invention in place of the phased array ultrasonic probe 23. Then, it is possible to perform a cleaning operation, a polishing operation, a grinding operation or a stress improving operation by means of an appropriate one of the working jigs or heads. With this embodiment, it is possible to perform an inspection, a cleaning operation, a polishing operation, a grinding operation or a laser peening operation to a weld line that is found on the bottom of a very narrow annular part in a process of working on a structure in the nuclear reactor pressure vessel immersed in water. More specifically, it is possible to make the phased array ultrasonic probe 23 or some other inspection sensor or the working equipment follow a fillet-welded section of a radius of curvature of about 15 mm in a very narrow environment. Thus, it is possible to continuously position itself in a peripheral direction on a shroud support plate 7 and highly accurately gauge the traveled distance relative to a horizontal weld line to consequently improve the quantity of inspection. Additionally, it can secure a large working area within a short period of time and reduce the overall working hours. Now, the second embodiment of intra-nuclear-reactor working apparatus according to the present invention will be described below. In this embodiment, the rotary mechanism of the scanning mechanism 21 is a slider crank mechanism that is formed by means of a translation mechanism such as a ball screw and a pair of links. FIGS. 5A and 5B illustrate a scanning operation of this embodiment that comprises a slider crank mechanism. Referring to FIGS. 5A and 5B, the phased array ultrasonic probe 23 is fitted to a probe holder 69 that is rotatable around a center 55 of rotation of the probe and coupled to a nut 67 by means of a link 68. The nut 67 is driven to move up and down by means of a bevel gear 65, a ball screw 66 and a rotary shaft drive motor 30, which is a drive source. Referring to FIG. 5A, the phased array ultrasonic probe 23 is irradiating an ultrasonic wave onto an ultrasonic wave irradiating position 61 on the shroud support cylinder 6 along an ultrasonic wave irradiation axis 56 that is schematically illustrated in FIG. 5A. As the nut 67 is raised from this state, as shown in FIG. 5B, the probe holder 69 is lifted by the link 68 to rotate the phased array ultrasonic probe 23 around the center 55 of rotation of the probe and the embodiment performs an ultrasonic flaw detecting operation along the curvature of the fillet-welded bead 50, while keeping a predetermined distance to the fillet-welded bead 50. Since the slider crank mechanism of this embodiment is formed by means of a translation mechanism including a ball screw 66 and a nut 67, and a pair of links 68, this embodiment provides an advantage of reducing the rotary angle of the phased array ultrasonic probe 23 relative to the same rotary angle of the rotary drive motor 30, if compared with the first embodiment where the phased array ultrasonic probe 23 is driven to rotate by a timing belt 31 shown in FIGS. 2A and 2B. Therefore, it is possible to reduce the rotary backlash of the phased array ultrasonic probe 23 and to improve the accuracy of rotation. Now, the third embodiment of intra-nuclear-reactor working apparatus according to the present invention will be described below. In this embodiment, the mechanism constituting members and the strength holding members of the intra-nuclear-reactor working apparatus 20, the scanning mechanism 21 and the working equipment are formed by using a polymeric resin material. Specific examples of materials that can be used for this embodiment include polyamide type resins, polyimide type resins, polyether-ether-ketone resins and polyether-sulfone-resins that are excellent in terms of resistance against radioactive rays, water-absorbing property, mechanical strength and thermal resistance. All or part of these materials may be used for the above mechanism composing members and the strength holding members. Thus, with this embodiment, it is possible to replace polymeric resin materials in place of metal materials in order to reduce the weight of the various pieces of equipment including the intra-nuclear-reactor working apparatus 20 and the scanning mechanism 21 in water. As a result, the float 24 arranged in an upper part of the scanning mechanism 21 can be dimensionally reduced to consequently reduce the overall dimensions of the apparatus. As the apparatus is made lightweight and downsized, it can be handled easily and it can pass through narrow areas so that the reliability of operation of the apparatus is also improved. The present invention is not limited to the above-described embodiments, which may be modified in various different ways without departing from the scope of the present invention. For example, while the above described embodiments of the intra-nuclear-reactor working apparatus and working method are adapted to be used in nuclear reactors, the present invention can broadly be applied to various working apparatus and various working methods. Additionally, while the above-described embodiments of working apparatus and working method are adapted to operations in water, they can be modified in various different ways as pointed out below. For example, while the operation mechanisms including the adhering/traveling modules 22 and related mechanisms may be housed in a water-tight case or the like and adapted to perform adhering/traveling operations in water, the working equipment of a working apparatus according to the present invention may be separated from them and put in air so as to operate in air. As another example, the adhering/traveling modules 22 and the thrusters 41 may be dimensionally raised to use a large drive source and a large drive mechanism for the thrusters 41 so that the thrusters 41 may acquire a sufficiently large air flow rate to produce a large adhering force in air as they are driven to rotate at high speed. With such an arrangement, a working apparatus and a working method according to the present invention may be applied to works in air.
041815696	abstract	A liquid metal cooled fast breeder nuclear reactor has power setback means for use in an emergency. On initiation of a trip-signal a control rod is injected into the core in two stages, firstly, by free fall to effect an immediate power-set back to a safe level and, secondly, by controlled insertion. Total shut-down of the reactor under all emergencies is avoided.
056298722	summary	The present invention is concerned generally with a system and method for reliably monitoring industrial processes having nonwhite noise characteristics. More particularly, the invention is concerned with a system and method for removal of nonwhite noise elements or serially correlated noise, allowing reliable supervision of an industrial process and/or operability of sensors monitoring the process. Conventional parameter-surveillance schemes are sensitive only to gross changes in the mean value of a process, or to large steps or spikes that exceed some threshold limit check. These conventional methods suffer from either large numbers of false alarms (if thresholds are set too close to normal operating levels) or a large number of missed (or delayed) alarms (if the thresholds are set too expansively). Moreover, most conventional methods cannot perceive the onset of a process disturbance or sensor deviation which gives rise to a signal below the threshold level for an alarm condition. In another conventional monitoring method, the Sequential Probability Ratio Test ("SPRT") has found wide application as a signal validation tool in the nuclear reactor industry. Two features of the SPRT technique make it attractive for parameter surveillance and fault detection: (1) early annunciation of the onset of a disturbance in noisy process variables, and (2) the SPRT technique has user-specifiable false-alarm and missed-alarm probabilities. One important drawback of the SPRT technique that has limited its adaptation to a broader range of nuclear applications is the fact that its mathematical formalism is founded upon an assumption that the signals it is monitoring are purely Gaussian, independent (white noise) random variables. It is therefore an object of the invention to provide an improved method and system for continuous evaluation and/or modification of industrial processes and/or sensors monitoring the processes. It is another object of the invention to provide a novel method and system for statistically processing industrial process signals having virtually any form of noise signal. It is a further object of the invention to provide an improved method and system for operating on an industrial process signal to remove unwanted serially correlated noise signals. It is still an additional object of the invention to provide a novel method and system utilizing a pair of signals to generate a difference function to be analyzed for alarm information. It is still a further object of the invention to provide an improved method and system including at least one sensor for providing a real signal characteristic of a process and a predicted sensor signal allowing formation of a difference signal between the predicted and real sisal for subsequent analysis free from nonwhite noise contamination. It is also an object of the invention to provide a novel method and system wherein a difference function is formed from two sensor signals, and/or pairs of signals and nonwhite noise is removed enabling reliable alarm analysis of the sensor signals. It is yet an additional object of the invention to provide an improved method and system utilizing variable pairs of sensors for determining both sensor degradation and industrial process status. Other objects, features and advantages of the present invention will be readily apparent from the following description of the preferred embodiments thereof, taken in conjunction with the accompanying drawings described below.
048511846	description	Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a reactor building 1 of a pressurized water reactor including a steel safety containment 2, which is a so-called secondary shielding in the form of a sphere having a diameter of 50 meters, for example. The upper portion of the sphere 2 is enclosed by a hemispherical roof portion 3 of the reactor building 1. Below the equator of the sphere, the reactor building is in the form of a vertical cylinder 4 extending to a base plate 5 of the reactor building, which is sunk into soil 6. In a construction which is in the form of heavily reinforced concrete, the thickness D of the reactor building wall 3, 4 is 2 meters, for example. This assures that aircraft striking the reactor building 1 will be unable to do serious damage, which could lead to rupturing of the safety containment 2 enclosing the radioactive components. A so-called valve room or fixture chamber 10, which includes valves or fixtures for shutting off fresh-steam lines leading out of the safety containment 2, is connected to the outside wall 4 of the reactor building 1. Since these valves or fixtures have to be protected from destruction, walls 11 of the valve room or fixture chamber 10 which, for instance, are of block-like form, are at least as thick as those of the reactor building 1. In a typical rectangular building, for example, the emergency supply or feed building of a reactor plant has edges and corners, like those of the valve room or fixture chamber, which represent exposed regions in case of impact. The upper outer corner 12 of the valve room or fixture chamber 10 is double-layered in a region 14, according to the invention. An outer shell 16 extends parallel to an inner shell 15, which has a shape approximately equivalent to that of the original wall 11 and has half the wall thickness thereof, the shells being spaced apart by the thickness of the shell or layer 15, forming a hollow space 17. The outer shell 16 is formed of concrete reinforced with steel fibers or filaments and is thus virtually homogeneously resilient. As FIG. 1 clearly shows, the outer surface 18 of the shell 16 protrudes beyond the surface or plane 19 of the wall 11 by approximately one-half of the original wall thickness, or in other words one meter beyond the plane 19 of the wall 11. The hollow space 17 has three parts due to the fact that it is subdivided by two supports 20 and 21. Rigid expanded plastic in the form of a filler material having a damping action, is accommodated in the hollow space 17. The result of this structure is that if loads are brought to bear on the exposed wall region of the corner 12 from the outside, forces can be transmitted into the valve room or fixture chamber 10 and from it into the reactor building 1 only after attenuation. In the embodiment of FIG. 2, the corner 12 is again provided with a double-layered wall region 14. However, the outer shell 16 in this embodiment is only supported by a single support 23, resulting in a hollow space 17 having two chambers. The hollow space 17 contains metal mesh bodies acting as the damping filler material However, the chambers in the hollow space 17 can also be in the form of prefabricated thin-walled molded articles, without being filled with damping material. As shown in FIG. 3, at the corner 12 of the valve room or fixture chamber 10, the inner shell 15 of the double-layered wall region 14 has practically the same wall thickness as the wall 11, although it has an outer rounded portion 24. The outer shell 16 is raised beyond the outer rounded portion 24, although without an internal support, resulting in a single-chambered intermediate space 17. In the embodiment illustrated in FIG. 4, the reactor building 1 is double-layered in a region 25 of a roof 26, which forms a corner 27. In this embodiment, an inner shell 28 of the double-layered region 25 is reduced to one-half the original thickness of solid walls 29. An outer shell 30 has a rounded portion parallel to the inner shell 28 which is in alignment with the outside of the walls 29. A hollow space 31 is again filled with damping material. Despite the "weakening" of the wall in the region 25 , sufficient resistance to penetration from the outside is obtained. In addition, external forces that are capable of engaging the exposed corner 27 are diminished, so that only slight acceleration forces are triggered in the interior of the reactor building 1. In the embodiment illustrated in FIG. 5, a region 35 of the reactor building 1 is shown at the level of an internal ceiling 36, on which components 37 are supported. For instance, the ceiling 36 encloses a room 38 having electrical systems, represented by cable lines 39. An outer shell 40 of the double-layered region 35 is rounded in shape, so that it protrudes convexly beyond the surface of the reactor building 1. Once again, the intermediate space 41 contains a filler material. FIG. 6 shows that the reactor building 1 can also be double-layered over a greater height in a region 50 in the vicinity of the ceiling 36. As a result, both the ceiling 36 as well a ceiling 51 located below it are protected. An outer shell 52 of fiber-reinforced concrete, together with an inner shell 53 of steel-reinforced concrete, contain two hollow spaces 54 and 55 bordering on one another and containing a damping material. A support 56 located between the hollow spaces 54 and 55 is dimensioned in such a way that no significant forces can be transmitted if there is a direct action from outside, because the inner shell 53 has the greater resiliency when the load is imposed. In the embodiment illustrated in FIG. 7, the reactor building 1 is protected in the vicinity of a corner 60 and a load-bearing ceiling 61 located below it, by prefabricated building elements. A building element 63 associated with the corner 60 has a structure with a rectangular cross section adapted to the corner. Two layers or shells 64 and 65 are both formed of steel fiber-reinforced concrete that is very tough. A hollow space 66 therebetween contains a filler material. The building element 63 is seated sufficiently firmly on the reactor building 1 merely by virtue of its own weight. At that location the building element 63 forms a damping protective layer, which prevents impact strains from being induced into the building 1 upon external action exerted upon the exposed point. A building element 70 associated with the ceiling 61 covers the attachment of the ceiling 61 to a vertical concrete wall 71. The building element is engaged in a corresponding recess 73 with a dovetail-like protrusion 72 at the ceiling 61. A gap 75 remaining after the insertion can be filled up in order to increase strength and to attain a form-locking connection of the building element 70. A form-locking connection is one which is connects two elements together due to the shape of the elements themselves, as opposed to a force-locking connection, which locks the elements together by force external to the elements. However, other fastenings of the building elements 63, 70 to the reactor building 1 are also conceivable.
	summary
	description	The present invention relates to devices for magnetizing laser plasmas with pulsed magnetic fields. More particularly, the invention relates to a device for magnetizing a laser plasma with a pulsed magnetic field comprising a vacuum chamber, in which a target able to generate a laser plasma during an interaction of the target with a laser pulse is placed, and a winding that is powerable electrically in order to generate a pulsed magnetic field in the laser plasma. It is known in the art that the interaction between a high-power laser pulse and a solid or gaseous target allows a plasma, commonly referred to as a laser plasma, to be generated. The generation of this plasma is accompanied by the emission of an intense beam of charged particles. Such a beam has many applications, such as for example in the probing of physical effects, in inertial fusion or even in the generation of intense radiation. To generate a laser plasma, the laser pulse must be of high intensity and focused on a focal spot of small transverse size on the target. It is therefore necessary to provide a vacuum chamber, at least in the terminal leg of the laser pulse, the high intensity and small transverse size of the pulse tending to ionize any gas that is located on its path, in particular ambient air, leading to the risk of damage to the laser optics, loss of power from the laser pulse and endangerment of personnel present in the vicinity. Such intense beams of charged particles are usually highly divergent and it is desirable to be able to focus them in the aforementioned applications. It is known that generating a high-strength pulsed magnetic field in a laser plasma allows the focus of the beams of charged particles to be improved, the charged particles then being subjected to a rotary movement about the magnetic field lines, this movement usually being characterized by a Larmor radius. The document “Laser-driven Magnetic-Flux Compression in High-Energy-Density Plasmas” by O. V. Gotchev et al. (Physical Review Letters, vol. 103, 215004) describes an exemplary device for magnetizing a laser plasma with a pulsed magnetic field comprising coils placed in a vacuum chamber, on either side of and in very close proximity to the target, the coils thus being suitable for generating a magnetic field of 5 to 9 tesla in the target when a sufficiently large current, of about 80 kA, is made to flow therethrough. Such devices have a number of drawbacks. The heat produced by the flow of current through the coils leads to their destruction and it is therefore necessary to replace the coils each time the laser is fired. The rate at which the laser may be fired is therefore decreased. The destruction of the coils may damage the optics for focusing the laser pulse, which are themselves also generally placed in the vacuum chamber, and at the very least implies frequent cleaning of the vacuum chamber. Since the instantaneous magnetic field is determined by measuring the current flowing through the coils, then by applying a calculation taking account of the geometry of the coils, the gradual destruction of the coils as the magnetic field is generated makes the calculation of the magnetic field unreliable because the geometry of the coils changes over time in a way that is difficult to predict. The maximum duration and strength of the pulsed magnetic field are limited by the destruction of the coils and it is difficult to generate pulsed magnetic fields of more than 10 tesla and of more than 300 nanoseconds with such a device. The high currents flowing through the coils mean that electrical leads especially designed for vacuums (“vacuum feedthroughs”) have to be used in order to prevent the electrical supplies of the coils generating electrical arcs in the vacuum chamber. There is therefore a need for a device for magnetizing a laser plasma with a pulsed magnetic field that solves at least some of the aforementioned problems. For this purpose, according to the invention, such a device for magnetizing a laser plasma with a pulsed magnetic field is characterized in that the winding is placed in a re-entrant chamber containing a cooling fluid. By virtue of these arrangements, the device for magnetizing a laser plasma with a pulsed magnetic field may generate pulsed magnetic fields of more than 10 tesla, ranging up to 40 tesla and beyond, with durations of more than 300 nanoseconds, thereby allowing a beam of charged particles to be better focused. This focus may furthermore be kept stable for a long time. The firing rate of the laser may be increased since it is no longer necessary to change elements of the winding after each firing of the laser. The risk of damage to the optics, elements of the chamber and personnel is decreased. The magnetic field generated in the laser plasma may be determined and controlled precisely and reliably. It is not necessary to use special vacuum leads to supply the winding with power. In preferred embodiments of the invention, recourse may optionally furthermore be made to one and/or other of the following arrangements: the re-entrant chamber comprises an axial vacuum through-duct comprising two axial ends, each of the axial ends being in communication with the vacuum chamber; the winding comprises at least one coil encircling the axial vacuum through-duct; the winding comprises two coils encircling the axial vacuum through-duct, said coils being separated by a central plate; the re-entrant chamber furthermore comprises at least one radial vacuum through-duct comprising two radial ends, each of the radial ends being in communication with the vacuum chamber; the radial vacuum through-duct is located in the central plate separating the two coils; the target is placed substantially in the middle of the winding; the target is placed substantially at one end of the winding; the cooling fluid is either a gas or a cryogenic fluid, in particular liquid nitrogen or liquid helium; the re-entrant chamber comprises a weakly conductive vacuum-resistant material, in particular a stainless steel; the pulsed magnetic field is a magnetic field the strength of which is higher than a few tesla, preferably higher than about ten tesla and preferably higher than forty tesla; the device furthermore comprises a laser source for emitting a laser pulse able to interact with the target in order to generate the laser plasma, and the laser pulse possesses a power substantially comprised between one gigawatt and one petawatt and especially between one terawatt and about one hundred terawatts; the laser pulse possesses a duration substantially comprised between about ten femtoseconds and about ten nanoseconds and especially between about ten femtoseconds and about ten picoseconds. Other features and advantages of the invention will become apparent from the following description of a plurality of embodiments thereof, which are given by way of nonlimiting example and with regard to the appended drawings. In the various figures, identical or similar elements are designated by the same references. FIGS. 1 to 4 illustrate a device 1 for magnetizing a laser plasma with a pulsed magnetic field according to one embodiment of the invention. Such a device 1 comprises a laser source 2. This laser source 2 is able to emit a laser pulse 3 that has a high power, for example comprised between one gigawatt and one petawatt (depending on whether the pulses are short or long) and especially between one terawatt and about one hundred terawatts per centimeter square when it is focused into a focal spot of small size, as detailed below. This laser pulse 3 has a duration substantially comprised between about ten femtoseconds and about ten nanoseconds. It may for example have an energy of a few joules and a duration of a few nanoseconds. In other embodiments, the intensity of the laser pulse may be lower, for example a few millijoules, and the duration of the laser pulse may also be shorter, for example a few femtoseconds. The laser source 2 may comprise one or more laser oscillators and optical elements 27 such as for example lenses, crystals and/or gratings. The laser pulse 3 propagates in a propagation direction X. The device 1 comprises a vacuum chamber 4 in which a target 5 able to generate a laser plasma 6 during an interaction of the laser pulse 3 with the target 5 is placed. The target 5 may be a solid, liquid or gaseous target, for example an aluminum film of 15 microns thickness, as described in “Ultrafast laser-driven microlens to focus and energy-select mega-electron volt protons” by T. Toncian et al. (SCIENCE, vol. 312, 21 Apr. 2006) and the references cited in this article. It may extend substantially in a plane of extension YZ, for example a plane perpendicular to the propagation direction X. An interaction between the pulse 3 and the target 5 may be obtained by focusing at least partially said pulse onto a front side of the target 5, by means of optical focusing devices, into a focal spot of small size, for example of about 6 microns full-width at half maximum (FWHM) intensity. The laser pulse 3 creates a laser plasma 6 on the front side of the target by ionizing target atoms located in the focal spot. The laser pulse 3 heats the target 5 and communicates to the electrons of said target a substantial amount of thermal energy that may cause some of said electrons to pass through the target and to escape therefrom via the back side, said back side being the side of the target opposite the front side in a thickness direction X′ of the target, said thickness direction X′ for example being substantially perpendicular to the plane of extension YZ of the target In one embodiment, the thickness direction X′ of the target 5 and the propagation direction of the laser pulse X may be substantially collinear. In another embodiment, the propagation direction X of the laser will possibly be inclined to the thickness direction of the target X′, for example by 45° or more. The laser pulse 3 therefore generates a movement of electrons through the thickness of the target 5 which forms a beam of electrons that is made to move substantially in the thickness direction X′ of the target 5. By extending out of the target on the back side, these electrons may create high electrical fields on said back side (of the order of one teravolt per meter). These electrical fields may in particular be sufficiently strong to tear ions from the back side (for example impurities trapped on the opposite surface) and thus create a beam 7 of charged particles. The energy of said charged particles (of charge typically of the order of a few picocoulombs to a few nanocoulombs) may for example be as high as sixty to one hundred megaelectronvolts and doses may for example be of the order of 10^11 to 10^13 particles per pulse. In the case of electrons (when gaseous targets are used) the energy may reach a few gigaelectronvolts. One pulse of such a beam 7 may for example last less than a picosecond, i.e. substantially the duration of the first laser pulse, and the current generated may thus be about a few kiloamperes to a few hundred kiloamperes. The beam of electrons made to move through the thickness of the generating target by the laser pulse may be divergent. The beam 7 of charged particles created may thus itself also be divergent. It is thus necessary to focus said beam 7 of particles in order to be able to use it in a number of applications, including the aforementioned. The device 1 thus also comprises a winding 8 (or electromagnet) able to generate a pulsed magnetic field 9 in the plasma laser 6. The pulsed magnetic field 9 is a magnetic field the strength of which is higher than a few tesla. Thus, for example in the example in FIG. 1, the strength of the pulsed magnetic field 9 is higher than about ten tesla and about forty tesla. In this way, the focus of the beam 7 of particles is improved. In the example in FIG. 1, the winding 8 is powered by a suitable electrical power supply 25, by means of a supply cable 27. The electrical power supply 25 is for example able to deliver 30 to 50 kilojoules, by delivering a current of at least 50 kiloamperes, typically 100 kiloamperes, under a voltage of 16 kilovolts to the winding 8. The winding 8 is placed in a re-entrant chamber 10 containing a cooling fluid 11. The re-entrant chamber 10 is a chamber penetrating substantially into the interior of the vacuum chamber 4. In FIG. 1, the re-entrant chamber 10 penetrates the vacuum chamber 4 in a vertical direction Z perpendicular to the propagation direction X. The cooling fluid 11 may be a gas such as for example air as in the embodiment in FIGS. 1 and 2. In other embodiments, the cooling fluid 11 may be a cryogenic fluid such as for example liquid nitrogen or liquid helium as in the embodiment in FIG. 3. Any other liquid, water, solvents or oils of any type may be used whether making direct contact with the electromagnet or not. The cooling fluid 11 may be placed so as to make contact with the winding 8 in order to allow the winding 8 to be cooled. As a variant, a capillary tube, in which a second cooling fluid is made to flow, may be placed making contact with the winding 8. In this variant embodiment, the re-entrant chamber may contain a cooling fluid 11 that is for example air. In the embodiment illustrated in FIGS. 1 to 4, the target 5 is placed substantially in the middle of the winding 8. As a variant, the target 5 may be placed substantially at one end of the winding 8. In this way the target 5 is more easily accessible. In the embodiment in FIG. 1, the re-entrant chamber 10 comprises an axial duct 12. The axial duct 12 is a vacuum through-duct. It comprises two axial ends 13, 14, each in communication with the vacuum chamber 4. In the example in FIG. 1, the axial duct 12 extends between its two axial ends 13, 14 substantially in the propagation direction X. The axial duct 12 is placed in the vacuum chamber on the axis of the laser so as to be passed through by the laser pulse 3. Thus, in the embodiment illustrated in FIG. 1, the target 5 is located in the axial duct 12 and for example located substantially in the middle of the axial duct 12. In the example in FIG. 1, the winding 8 comprises two coils 15, 16 encircling the axial vacuum through-duct 12. As a variant, a single coil 15 may be provided, as illustrated in the embodiment in FIG. 3. In the embodiment in which two coils 15, 16 are provided, the coils may be separated by a central plate 17. The central plate 17 is designed to contain the magnetic pressure generated by the winding 8. The central plate 17 is for example made of stainless steel insulated by sheets of epoxy resin, for example sheets of epoxy resin adhesively bonded to one or both sides of a plate made of stainless steel. The central plate may for example be located substantially in the middle of the axial duct 12. The central plate may for example be located substantially level with the target 5 In one embodiment, more particularly illustrated in FIG. 2, the re-entrant chamber 10 furthermore comprises at least one radial vacuum through-duct 18. The radial duct 18 comprises two axial ends 19, 20, each in communication with the vacuum chamber 4. In the example in FIG. 1, the radial duct 18 extends between its two axial ends 19, 20 substantially in a transverse direction Y that is substantially perpendicular to the propagation direction and to the vertical direction Z. In the embodiment in FIGS. 1 to 4, the radial duct 18 transects the axial duct 12 in a zone of intersection 21. The radial duct 18 may for example be located substantially in the middle of the axial duct 12. The radial duct 18 may for example be located substantially level with the target 5. In the example in FIG. 1, the zone of intersection 21 is thus located substantially in the middle of the axial duct 12 and level with the target 5. In this way, a device 25 for diagnosing the laser plasma 6 may access the laser plasma by means of the radial duct 18, as illustrated in the embodiment in FIG. 4. Such a diagnosing device 25 for example comprises at least one laser beam 26 able to pass through the laser plasma 6 and to be emitted and collected by modules 27. In the embodiment illustrated in FIG. 1, the radial vacuum through-duct 18 is located in the central plate 17 separating the two coils 15, 16. In this way, the magnetic discontinuity created by the radial duct 18 in the pulsed magnetic field is minimized. The axial and radial ducts 12, 18 are dimensioned with diameters and angular apertures that are large enough to accommodate the spatial footprint of the one or more respective laser beams. The elements of the re-entrant chamber 10, and especially the central plate G, are made, at least in part, from a material, possibly a composite, that is not, or not very, magnetic and that is mechanically strong enough to resist the magnetic pressure and the vacuum and sufficiently electrically nonconductive that losses due to induction are not excessively high—a stainless steel for example. The vacuum chamber 4 may be equipped with a window 22 allowing said beam 7 of particles to exit the vacuum chamber. The vacuum chamber 4 may be equipped with a collimator 23 allowing peripheral particles or radiation to be stopped at the exit of the device. The vacuum chamber 4 may be equipped with a module for stopping radiation, for example comprising a material of high atomic number such as iron, lead or uranium. The vacuum chamber 4 may also be equipped with a beam-deviating module allowing the beam of charged particles to be separated from radiation having a similar propagation direction, for example a magnetic-field-based deviating module. The vacuum chamber 4 may be placed and kept under vacuum by means of one or more vacuum pumps 24.
061005347	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will now be explained based on embodiments with reference to the drawings. (1) First Embodiment Referring to FIG. 1, there is illustrated an microscopic area scanning apparatus according to a first embodiment of the present invention. In FIG. 1, three hollow-cylindrical piezoelectric elements 101 (two are shown in the figure) are vertically fixed at an interval of 120 degrees on a horizontal circumferential plane of a table 105 such that their top free ends are equal in height to one another. Each of the hollow cylindrical piezoelectric elements 101 each have a ball 102 axially held on the top free end by bolt. This ball 102 is slidably fitted by upper and lower halves of exactly the same two ball retainers 103 having a hole in an bottomless cup form. The ball 102 and the ball retainer 103, at least one of them, is formed by a surface film of a soft metal or a solid lubricant in order to provide smoothness at a surface thereof. With this structure, there is no necessity of applying a lubricating oil or grease to the ball 102 and the ball retainer 103. Consequently, it is possible to prevent drift or creep from occurring due to the lubricating oil or grease. The use in a vacuum is also available. The ball is desirably formed of phosphor bronze or stainless steel (SUS304 or the like) polished at the surface to have a surface film 108 formed by ion plating of a soft metal such as gold, silver, or lead. The surface film 108 may be alternatively formed by sputtering with molybdenum disulfide as a solid lubricant. Besides, a copper-based alloy (sintered bearing alloy) containing a solid lubricant may be used. Meanwhile, the ball retainer 103 may use a SKS material (alloy tool steel) polished at a surface, an SUJ material (bearing steel) plated by a hard chromium plating, or a surface-polished stainless steel (SUS304 or the like). Although in this embodiment the surface film 108 is provided on the surface of the ball 102, a surface film 108 may be formed on the ball retainer 103 similarly to the ball 102. The upper and lower ball retainers 103 are press-fitted in respective holders 106a. Each of these two holders 106a is provided with a flange 106b. The both flanges 106b have bolts arranged, at right and left symmetric locations, to penetrate through a gap defined therebetween. The flange 106b uses a plate material of a stainless steel (SUS304-CSP) or a spring phosphor bronze to have an elasticity. This elasticity is desirably given to such a degree that a resonant frequency is not lowered for the microscopic area scanning apparatus. With such a structure, the gap between the two flanges 106b is adjusted by tensioning the bolts 106 to thereby control the exerted pressure to the ball 102. This allows a frictional force acting between the surface film 108 of the ball 102 and the ball retainer 103 to be controlled to a desired magnitude. As this frictional force is intensified, a coupling rigidity of the ball 102, the surface film 108 and the ball retainer 103 increases to increase the resonant frequency in XYZ directions of the microscopic area scanning apparatus. A sample stage 104 is fixed to one inner point of a ring member 107. The fixed position of the sample stage 104 to the ring member 107 is fixed with one ball retainer 103. The remaining two ball retainers 103 are fixed to the ring member 107. The ring member 107 is designed to have a rigidity with respect to a radial direction lower than that of the sample stage 104. The ring member 107 also has a rigidity with respect to a Z direction equivalent to a rigidity of the sample member 104 with respect to the Z direction. In this structure, errors in XY directions of the hollow cylindrical piezoelectric elements are absorbed by radial deflection of the ring member 107. The ring member 107 has its rigidity low in a radial direction but high in a height direction, having no effects upon resonant frequency with respect to the Z direction. The sample stage 104 is substantially of a rigid member, and uses a material that is light in weight without deviation in mass. The sample member 104 is formed desirably of an aluminum alloy (e.g. A6061, A5052) or a thin stainless plate (e.g. SUS304) in a disc form with a rib for enhancing rigidity. This structure provides a higher resonant frequency characteristic in Z direction than the conventional structure to the microscopic area scanning apparatus while scanning in X and Y directions as the conventional. (2) Second Embodiment At Referring to FIG. 2, there is illustrated a second embodiment of a microscopic area scanning apparatus of the present invention. In FIG. 2, three hollow-cylindrical piezoelectric elements 101 are vertically fixed at an interval of 120 degrees on a horizontal circumferential plane of a table 105 such that their top free ends are equal in height to one another. The hollow cylindrical piezoelectric elements 101 each have a ball 102 comprising a magnetic material axially held on the top free end by adhesion. This ball 102 is fitted and covered on a ball retainer 103 formed of a permanent magnet material having a hole in a bottomless cup form. The ball 102 and the ball retainer 103, at least one of them, is formed by a surface film of a soft metal or solid lubricant in order to provide smoothness at a surface thereof. In this embodiment, a surface film 108 is formed on the ball retainer 103. In this structure, there is no necessity of applying a lubricating oil or grease to the ball 102 and the ball retainer 103. Consequently, it is possible to prevent drift or creep from occurring due to the lubricating oil or grease. The use in a vacuum is also available. The ball 102 uses a magnetic material such as a ferromagnetic material, desirably a ferromagnetic stainless steel (SUS420J2, SUS440C, etc.) having a polished surface and electroless plated with nickel. The ball retainer 103 uses a permanent magnetic material high in holdability, desirably a neodymium (Nd) based material polished and nickel plated to have a surface film formed thereon of gold, silver, lead, molybdenum disulfide or the like, or a samarium-cobalt (Sm--Co) based material polished to form thereon a surface film 108 of gold, silver, lead, molybdenum disulfide or the like. Although in this embodiment formed the surface film 108 is formed on the ball retainer 103, the ball 102 may be formed, at a surface, with a surface film 108 using a soft metal such as gold, silver or lead or a solid lubricant such as molybdenum disulfide. Where the ball 102 is of a permanent magnet or electromagnet and the ball retainer 103 is of a magnetic material as discussed above, the ball 102 can be exerted by pressure due to a magnetic force acted by between the ball 102 and the ball retainer 103. If the ball 103 is made of an electromagnet, the frictional force between the ball 102 and the ball retainer 103 can be adjusted to a desired degree by controlling a magnetic force applied between the ball 102 and the ball retainer 103. A sample stage 104 is fixed to one inner point of a ring member 107. The fixed position of the sample stage 104 to the ring member 107 is fixed with one ball retainer 103. The remaining two ball retainers 103 are fixed to the ring member 107. The ring member 107 is designed to have a rigidity with respect to a radial direction lower than that of the sample stage 104. The ring member 107 also has a rigidity with respect to a Z direction equivalent to a rigidity of the sample stage 104 with respect to the Z direction. In this structure, errors in XY directions of the hollow cylindrical piezoelectric elements are absorbed by radial deflection of the ring member 107. The ring member 107 has its rigidity low in a radial direction but high in a height direction, having no effects upon resonant frequency with respect to the Z direction. The sample stage 104 is substantially of a rigid member, and uses a material that is light in weight without deviation in mass. The sample member 104 is formed desirably of an aluminum alloy (e.g. A6061, A5052) or a thin stainless plate (e.g. SUS304) in a disc form with a rib for enhancing rigidity. This structure provides a higher resonant frequency characteristic in Z direction than the conventional structure to the microscopic area scanning apparatus while scanning in X and Y directions as the conventional. Referring to FIG. 3, there is shown a typical view in operation of the microscopic area scanning apparatus of the first embodiment of the present invention. To scan over the sample stage 104 in an arrow direction as viewed in the figure, the three hollow cylindrical piezoelectric elements 101 (two in number in the figure) may be moved by bending in a same amount and in a same direction. On this occasion, each of the balls 102 placed at the respective free end of the hollow cylindrical piezoelectric members moves along a circular path about the fixed end of the hollow cylindrical piezoelectric member 101. The ball 102 is in a slidable linear contact with the ball retainer 103 through the surface film 108. The movement of the hollow cylindrical piezoelectric element 101 due to inclination, i.e. the movement of the ball 102 due to inclination, is absorbed by sliding between the ball 102 and the ball retainer 103. Thus, the circular-path motion of the ball 102 is transformed into linear motion in the ball retainer 103. The ball 102 is in linear contact with the ball retainer 103 through the surface film 108. The linear contact allows the ball 102 to be applied by a force, thus providing a high Z-directional coupled rigidity as compared with connection by an elastic hinge. Also, the frictional slide with the ball 102 and the ball retainer 103 exhibits an extremely low frictional coefficient of approximately 0.002-0.003. This value is as low as approximately one-tenth of surface-contact frictional coefficient (approximately 0.3). There is no tendency of causing smoothless motion (hereinafter referred to as stick-slip phenomenon), with a capability of precise movement. Thus, the combination of the ball 102 and the ball retainer 103 is preferred as an element for the microscopic range scanning apparatus. Therefore, it is possible to scan over the sample stage 104 with smoothness without causing stick-slip phenomenon during its movement from a start of scan, i.e. the state of FIG. 1 to a mid-process of scan, i.e. the state of FIG. 3. Referring to FIG. 4, there is illustrated a perspective view of a displacement-error absorbing means as one structural example of the microscopic area scanning apparatus of the present invention. The displacement-error absorbing means has a structure that a ring member 107 inscriptively fixed with a sample stage 104, wherein one ball retainer 103 fixed to a fixing portion for the ring member 107 and the sample stage 104 and remaining two ball retainers 103 fixed to the ring member 107. The error caused in horizontal displacement of the hollow cylindrical piezoelectric elements encountered during X-Y scanning is absorbed by radial deflection of the ring member 107. Since the rigidity of the ring member 107 is low in a radial direction but high in a height direction, the deflection in the ring member 107 has no effect upon the resonant frequency in the Z direction. As explained above, this invention is a microscopic area scanning apparatus used for scanning over a sample placed on a scanning probe microscope (SPM) that is represented by an atomic force microscope (AEM) or a scanning near optical field microscope (SNOM), wherein at least three hollow cylindrical piezoelectric elements are provided each of which is driven in three XYZ directions by one of divided electrodes. The microscopic area scanning apparatus comprises: three or more hollow cylindrical piezoelectric elements arranged on a circumference of a common plane; a plurality of balls each axially provided at a free end of the hollow cylindrical piezoelectric element; ball retainers each for rotatably and slidably holding a plurality of a respective ball in contact therewith; a sample stage fixed to the ball retainers; and a table for fixing the hollow cylindrical piezoelectric elements on the circumference of the common plane. Therefore, the present invention has an effect to solve the problem raised by the conventional microscopic area scanning apparatus, and realize a microscopic area scanning apparatus satisfying both of a wide scanning range and a high z-direction resonant frequency.
048805963	description	DETAILED DESCRIPTION OF THE INVENTION The present invention is directed to a self-actuated reactor shutdown system (SASS). While the invention is particularly applicable for use in a liquid metal fast breeder (LMFBR), it can be utilized in other types of reactors, such as the gas-cooled fast reactor (GCFR). A SASS is defined as a control rod system that can scram the reactor automatically without either a signal from an external control circuit or an operator action. Initiation of the scram in accordance with the present invention is entirely from direct sensing of coolant temperature and/or an over-power condition. Particular requirements of a SASS are as follows: 1. It must be capable of operating automatically. PA0 2. It must be fail-safe, such that no malfunction of the SASS can cause a hazardous condition. PA0 3. It must not impose excessive restrictions on normal operation of the reactor. PA0 4. It must have as little as possible adverse effect upon plant availability. PA0 5. It must contribute substantially to the overall safety of the reactor. The SASS of this invention satisfies each of the above requirements and employs an electromagnetic latch mechanism and a thermionic diode to activate a control rod scram without a signal from the reactor operating control system. The use of electromagnetic latch mechanisms to retain absorber elements such that during normal operation the control rod is held above the reactor core and is dropped into the core upon release of the latch mechanism by gravitational force on the absorber element, are known in the art as pointed out above. While the present invention utilizes this known principal of operation, the invention also incorporates the use of a thermionic device which is responsive to high coolant temperature and/or high neutron flux (over-power) conditions of the reactor. The diode functions to control an electromagnet which, in turn, releases the absorber element, whereby the SASS of this invention provides a system responsive to both coolant temperature and neutron flux. The SASS incorporating the present invention cannot be overridden by external control either from operators or plant control systems with the intent to hold off a scram. Further, the SASS of this invention is able to be restored to operational or cocked condition only by deliberate operator action, and only when the reactor conditions have been corrected and will permit reactivation. In addition, the SASS of this invention is responsive to scram signals generated by the plant protective systems. Referring now to FIGS. 1A and 1B, a SASS incorporating the present invention is illustrated. As known in the art and illustrated in the drawings, the control rods or elements of the SASS are positioned within a fuel bundle containing a plurality of fuel rods or assemblies. The fuel bundles are located in the core of the reactor, while the control rod or neutron absorber element of that bundle is maintained in a location exterior of the reactor core region under normal reactor operating conditions. As shown in FIGS. 1A-1B and 2, the SASS or control assembly generally indicated at 10 is positioned centrally within a fuel bundle composed of a plurality of reactor fuel rods or assemblies 11. The control assembly 10 is encased in guide tube 12 which extends through the reactor core region indicated at 13 and secured in the core at the lower end of the guide tube as known in the art. Guide tube 12 is provided at the lower end 14 with a plurality of coolant inlet openings 15 through which reactor coolant under pressure is directed upwardly as indicated by the flow arrows. Movably located within the upper end 16 of guide tube 12 are an absorber assembly (control rod) 17 and a main driveline assembly 18, which are spaced from the inner surface of the guide tube so as to provide for coolant flow therebetween as indicated by flow arrows. Absorber assembly 17, containing neutron absorbing material as known in the art, is provided with a plurality of openings 19 in the lower and upper ends thereof to allow coolant to flow therethrough, as indicated by flow arrows. Secured to the upper end of absorber assembly 17 is a magnet armature 20 which cooperates with an electromagnet 21 secured to the main driveline 18 to retain the absorber assembly in its ready or cocked position exterior of core region 13 as shown, when electromagnet 21 is energized. Positioned in guide tube 12 below the core region 13 is a control assembly snubber or kinetic energy absorbing means 22 which retards the downward movement of the absorber assembly 17 after it passes into the core region. As pointed out above, the direct holding of a reactor control (absorber) rod by an electromagnet secured to the end of a control drive similar to the apparatus of FIGS. 1A and 1B thus far described is known. In operation of the apparatus thus far described, the electromagnet 21 is lowered by the driveline 18 to contact the magnet armature 20 on the top of the control rod or absorber assembly 17, and the electromagnet 21 is energized by application of electrical current from a power source, whereby the assembly 17 is attracted to the electromagnet and is withdrawn from the core region 13 by driveline 18 and positioned in its ready or cocked location above the core region as shown. Release (scram) of the absorber assembly 17 is obtained by reducing the holding power of the electromagnet 21. For example, such release may be obtained by a known method where the reactor undergoes a thermal transient and the coolant is heated above normal thereby heating the electromagnet to a calibrated curie point, causing the magnet to release the control rod. Release via the curie point approach is effective but slow. The main driveline 18 is actuated by a mechanically driven system supported on the reactor top shield. A variety of such mechanical drive systems are known, such as electrically driven racks and pinions, roller nut and ball nut screws. The driveline 18 is usually sealed by bellows that allow the linear movement to be translated through the reactor containment boundary. Release of the absorber element 17 in accordance with the present invention provides a substantially higher speed of response and involves a thermionic device such as one or more thermionic diodes illustrated in FIGS. 3 and 4. The thermionic device is attached electrically in parallel with the electromagnet and when the device conducts it shorts the electromagnet current causing it to lose its holding power. The thermionic switched electromagnetic latch of the present invention as illustrated in FIGS. 1A and 1B consists of a flux sensing thermionic switch 23 located above and electrically connected in parallel, as described hereinafter, with the electromagnet 21 and a temperature sensing thermionic switch 24 mounted on main driveline 18 above the top guide tube 18. Note that FIG. 2 illustrates three switches 24 positioned around driveline 18. Thermionic switch 24 is also connected electrically in parallel, as hereinafter described, with electromagnet 21 and is located above the coolant outlet 25 of the fuel assemblies 11 so that heated coolant indicated by the flow arrows passing through coolant outlet 25 is directed onto temperature sensing switch 24. A neutron shield 26 for flux sensing thermionic switch 23 is positioned about the switch by a neutron shield drive rod 27 operatively connected to the drive mechanism, not shown, for operating the main driveline 18 described above. Neutron shield 26, for example, may be constructed of material such as depleted uranium. Main driveline 18 is provided with a plurality of coolant outlets 28 such that coolant from inlet 15 passes under pressure up through guide tube 12, through openings 19 and around absorber assembly 17, around electromagnet 21, around thermionic switch 23, upwardly through main driveline 18, and exits via coolant outlets 28. The flux sensing thermionic switch 23, which can be electrically identical to temperature sensing switch 24, is located within the control assembly 10 so that it will not be in direct contact with high temperature coolant from the fuel assemblies 11. As shown in FIG. 2, a plurality of temperature sensing thermionic switches 24 can be placed around or along the driveline 18, or the switches 24 can be supported on extensions or arms over the fuel assembly coolant outlets 25. Also, ducts may be provided to direct the coolant flow from outlets 25 onto the temperature sensing thermionic switch 24. It is within the scope of this invention to utilize a plurality of flux sensing thermionic switches 23 within the control assembly 11 to provide for redundancy, set point, and position adjustment. Also, the flux sensing thermionic switch 23 can be placed in a different location than that illustrated, if needed, to more accurately adjust the detection ability. The thermionic switches 23 and 24 of FIGS. 1A and 1B control assembly are embodied in FIGS. 3 and 4 as a thermionic diode indicated generally at 30. The diode 30 consists of a sealed container 31 having therein an emitter 32 and a collector plate 33 separated by a gap 34, with a uranium blanket 35 positioned around emitter 32 which causes heating of the diode due to neutron flux, and a quantity of thermionic material 36 located within sealed container 31. Emitter 32 and collector plate 33 are connected to an electrical potential, as illustrated in FIG. 5, via electrical leads 37 and 38, respectively, which extend through insulators 39 in container 31. The uranium blanket 35 may be replaced by a quantity of uranium attached to the emitter 32. By way of example, the diode 30 may be constructed of the following material: container 31 is of stainless steel; emitter 32 is of molybdenum, with a diameter of 0.750 in. and wall thickness of 0.050 in.; collector plate 33 is of molybdenum, with a diameter of 0.450 in. and wall thickness of 0.10 in.; gap 34 is in the range of 0.10 in.; uranium blanket 35 has a wall thickness of 0.10 in.; thermionic material 36 may be cesium or other metalic vapors at operational temperatures. The electric leads 37 and 38 are of copper; and the insulators 39 are of alumina. The thermionic material 36 is tailored to ionize at a selected temperature, for example, in the range of 1000.degree. F. to 1100.degree. F. An electrical potential, from power supply 40, such as 10 to 15 volts, is applied to the emitter 32 and collector plate 33 and when the ionization temperature of the thermionic material 36 is reached, due to reactor over-power conditions (high neutron flux) or coolant temperature, the material changes from high resistance to low resistance thereby conducting more of the available current and, in effect, short-circuits the electromagnet 21 in FIG. 1A which is connected in parallel with the diode 30, via the control circuit illustrated in FIG. 5. FIG. 5 schematically illustrates an embodiment of an electric circuit interconnecting the electromagnet and the thermionic switch means with an external power supply. As shown, the thermionic switches or diodes 23 and 24 are connected in parallel with electromagnet 21 and to current limited, regulated D.C. power supply 40. It has thus been shown that the present invention provides a self-actuating shutdown system (SASS) for nuclear reactors, particularly and LMFR, which is responsive to low coolant flow and/or high neutron flux (over-power) conditions of the reactor. The SASS of this invention satisfies each of the requirements outlined above for such a system. While a particular embodiment of the invention has been illustrated and described, modifications will become apparent to those skilled in the art, and it is intended to cover in the appended claims all such modifications as come with the scope of the invention.
	abstract	A multi-modular power plant includes a plurality of on-site nuclear power modules that generate a power plant output, and a number of power plant systems which operate using electricity associated with a house load of the power plant. A switchyard associated with the power plant may electrically connect the power plant to a distributed electrical grid. The distributed electrical grid may be configured to service a plurality of geographically distributed consumers. Additionally, the switchyard may electrically connect the power plant to a dedicated electrical grid. The dedicated electrical grid may provide electricity generated from the power plant output to a dedicated service load, and the power plant output may be equal to or greater than a combined load of the dedicated service load and the house load. At least a portion of the power plant output may be distributed to both the power plant systems and the dedicated electrical grid.
	description	The present application hereby claims priority under 35 U.S.C. §119 on German patent application number DE 10 2009 004 119.2 filed Jan. 8, 2009, the entire contents of which are hereby incorporated herein by reference. At least one embodiment of the invention generally relates to a sensor unit for an X-ray detector, in particular a computed tomography scanner. At least one embodiment of the invention furthermore generally relates to a method for producing such a sensor unit. A computed tomography scanner (CT) usually comprises a so-called gantry, with an X-ray beam source (X-ray tube) and a radially opposite (X-ray) detector being attached thereto. The gantry is intended to rotate around an object to be irradiated, with the X-ray radiation emitted and modified during the penetration of the object being detected by the detector. The detector is generally assembled from a plurality of individual detector modules. Each detector module comprises a sensor unit which in turn has a scintillator for converting the X-ray radiation into visible light and photodiodes for detecting this light. The scintillator is normally formed from a plurality of scintillator pixels, usually in the form of cubic elements of scintillating material. The scintillator pixels are generally arranged in an array, that is to say in a matrix arranged in a checkerboard fashion in rows and columns. Narrow interspaces (so-called septa), filled with a light reflecting and/or absorbing material, are in each case formed between the individual pixels; these septa are used to delimit the individual pixels in respect of one another in terms of radiation. A method for producing such a scintillator is disclosed in, for example, DE 198 49 772 A1. Accordingly, elongate scintillator elements are firstly layered next to and above one another in parallel and bonded to form a block whilst forming the septa. Subsequently, the block is cut into slices, transversely with respect to the longitudinal direction of extent of the scintillator elements, such that the individual slices have the desired array structure. Within the scope of the sensor unit, each scintillator pixel has one photodiode associated with it. In a conventional sensor unit—as is described, for example, in DE 10 2005 014 187 A1—these photodiodes are arranged in an array matched to the pixel structure of the scintillator, with the array being fitted to the outer side of the scintillator facing away from the X-ray tube. Each sensor unit is often also assigned a collimator which is used to suppress scattered beams of the X-ray radiation impinging on the scintillator. The collimator is usually formed from a stack of thin tungsten sheets which are attached to a support plate in an upright fashion in respect of the latter. This support plate is usually fitted to an inner side of the scintillator intended to face the X-ray tube. Here, the collimator sheets are respectively arranged approximately flush with the septa, as a result of which the X-ray radiation is incident on the scintillator pixels in a directed fashion. Since the collimator sheets should not shadow the scintillator pixels in the process, very exact positioning of the former in respect of the scintillator is necessary. Exact positioning of the collimator sheets is difficult, particularly in the case of very small pixels and very narrow septa of the scintillator. In at least one embodiment of the invention, a production method for a sensor unit of an X-ray detector is specified which permits particularly precise positioning of the collimator sheets in respect of the scintillator. Furthermore, in at least one embodiment of the invention, a sensor unit is specified in which the collimator sheets are positioned particularly precisely in respect of the scintillator. In respect of the production method of at least one embodiment, individual scintillator strips are firstly produced from a plurality of scintillator pixels adjoining one another along one dimension. A photodiode strip, made of a plurality of photodiodes in turn adjoining one another along one dimension, is in each case attached (in particular adhesively bonded) to a longitudinal side of each of the individual scintillator strips. Here, respectively one photodiode is arranged adjoining respectively one scintillator pixel for readout purposes. The combination of scintillator strips and photodiode strips is referred to as a sensor strip in the following text. The sensor strips are now respectively mounted individually on an outer side of the support plate of a collimator. In principle, the collimator is assembled as described above, that is to say it comprises a stack of collimator sheets attached to an inner side of the support plate. In the process, the individual collimator sheets are aligned substantially perpendicularly with respect to the support plate, and parallel with respect to one another. The side of the support plate intended to face the X-ray tube is referred to as the inner side of the support plate. Accordingly, the side of the support plate intended to face away from the X-ray tube is referred to as the outer side of the support plate. Here, “individual” means that the sensor strips are not directly interconnected during assembly. Thus, according to at least one embodiment of the invention, provision is made for assembling the scintillator column by column from the sensor strips which are initially available as individual elements, with each of the sensor strips being individually attached to the support plate of the collimator. As a result of individually attaching the sensor strips on the support plate, it is possible for each sensor strip—and hence the individual scintillator pixels—to be positioned very precisely in respect of the collimator sheets. In particular, it is possible for the scintillator strips to be aligned flush with the interspaces between the collimator sheets in a very precise fashion and so the X-ray radiation can impinge on the scintillator strips in an unimpeded fashion. Since each sensor strip is attached separately to the support plate, it moreover is possible for a defective sensor strip to be replaced in a comparatively simple fashion. The positioning of the sensor strips in respect of the collimator being very precise also results in the possibility of being able to produce such a sensor unit made of collimator and scintillator with comparatively narrow scintillator strips (corresponding to small scintillator pixels) and narrow septa. This indirectly affords the possibility of an improved image resolution of the detector. Since the sensor strips are prefabricated as individual elements, the photodiode strips can also be adjusted with respect to the scintillator strips, and hence the photodiodes can be adjusted with respect to the scintillator pixels, in a particularly simple and precise fashion. In particular, this can advantageously be carried out with the aid of a stop. Moreover, the production of the sensor strips can be automated particularly well. In the process, there is no, or only very little, risk of damaging the light-sensitive surface of the photodiodes. The individual production of the sensor strips moreover also affords the possibility of reducing the waste during the production of the sensor units since each sensor strip can be checked separately in respect of both the stability of the connection between the photodiode strip and scintillator strip and in respect of the functionality thereof. In particular, the individual sensor strips are respectively aligned substantially parallel to the collimator sheets and are respectively arranged flush with the interspaces formed between two collimator sheets. Expediently each of the sensor strips respectively has the same number of scintillator pixels. Overall, in an expedient refinement, a (substantially rectangular) scintillator is therefore formed on the outer side of the support plate, the individual scintillator pixels of which scintillator being arranged in an array structure of rows and columns. In an advantageous embodiment of the method, the sensor strips are, during the assembly on the support plate, aligned with a stop which is fixed in respect of the collimator sheets. This benefits the automation of the production method. Here, the collimator sheets themselves preferably form the stop, in particular by the collimator sheets being integrated into the support plate such that a narrow side of each sheet in each case at least partly protrudes beyond the outer side of the support plate. Advantageously, the sensor strips—at least the respective scintillator strip thereof—are applied laterally to the collimator sheet serving as a stop in this embodiment. As a result, this very simply precludes (the surface of the scintillating material of) the sensor strips from lying in the shadow of the respectively associated collimator sheet. When assembling the sensor strips, the photodiode strips can in principle be arranged either on a side of the scintillator strip (parallel to the support plate) facing away from the support plate in the assembled state or on a side face of the scintillator strip (perpendicular to the support plate) adjacent to the support plate in the assembled state. However, in a particularly advantageous embodiment of the method, each sensor strip is respectively oriented during the assembly such that the respective photodiode strip is basically aligned perpendicularly with respect to the support plate, and hence it is aligned parallel to the collimator sheets. In the process, the photodiode strips are in particular arranged approximately flush with the collimator sheets. Hence the photodiode strips are protected in a particularly effective fashion from the X-ray radiation. In a further advantageous embodiment of the method, during the assembly on the support plate provision is made for the interspaces formed between the individual sensor strips to be filled after the sensor strips are fixed on the support plate, in particular using a casting resin, for example epoxy resin. This subsequently forms a particularly stable combination of the individual sensor strips and the sensor unit. In an embodiment of the production method which can be implemented particularly easily, the photodiode strips are adhesively bonded to the scintillator strip using an optically transparent adhesive in order to form the sensor strips. The scintillator strips are preferably made from substantially cube-shaped scintillator pixels. Here, in preferred dimensioning, the individual cubes each have edge lengths of approximately 0.5 to 3 mm. In the process, individual beams of scintillator material are expediently firstly lined up parallel to and at a certain distance from one another in order to produce the scintillator strips. The individual beams are connected to form a palette by filling the interspaces with a light reflecting and/or absorbing material, for example a polymer which is liquid at first. Said palette is subsequently separated out, in particular sawed, into the individual scintillator strips in the transverse direction in respect of the individual beams. Each emerging scintillator strip therefore is subdivided along the length thereof into—cuboid—scintillator pixels delimited in respect of one another. In an advantageous embodiment of the production method, the sides of each scintillator pixel not intended to adjoin a photodiode are already provided with a reflector lacquer before the sensor strip is produced and thus, possibly, before the scintillator strip is produced as well. Since each scintillator strip is initially available as a separate individual part, the application of the reflector lacquer on the entire side face thereof (and hence on the outside side faces of the scintillator pixels thereof) in particular can be carried out particularly well. As intended, the reflector lacquer reflects the visible light emitted by the individual scintillator pixels. This increases the radiation intensity incident on the photodiode. In respect of the sensor unit of at least one embodiment, provision is made for a sensor unit with a support plate on which, firstly, a stack of collimator sheets is attached (in each case substantially perpendicularly to same) and on which, secondly, a plurality of sensor strips are attached. Here, each sensor strip is respectively formed by a scintillator strip and a photodiode strip. Moreover, each of the sensor strips is individually positioned, in particular substantially parallel in respect of the collimator sheets, respectively flush with the interspaces of said sheets and attached to the support plate. Such a sensor unit is preferably used for a detector in a computed tomography scanner. In the case of a sensor unit in which the photodiode strips are aligned perpendicularly with respect to the support plate, said strips are in each case basically enclosed between two scintillator strips. The readout of the scintillator pixels is therefore performed laterally. The photodiode strips are in this case preferably arranged flush with the collimator sheets. In the process, the individual photodiode strips are expediently dimensioned such that a narrow side thereof provided in each case for contacting the photodiodes protrudes beyond the adjacent scintillator strip or strips. Therefore, the photodiodes can be contacted from an outer side of the scintillator facing away from the support plate. As a result of being able to contact the photodiodes on the outer side of the scintillator, the sensor unit of this design is particularly suitable for a flat-panel detector of a CT. Such a flat-panel detector is made of a multiplicity of detector modules arranged adjacently to one another, over an area, with a very small spacing (in both a plurality of rows and a plurality of columns). Here, the electronics of each detector module required for the readout of the photodiodes are preferably arranged in turn in a vertical arrangement—perpendicular with respect to the scintillator surface—on the outer side of the scintillator, as intended. Equivalent parts and dimensions are always provided with the same reference signs in all figures. Various example embodiments will now be described more fully with reference to the accompanying drawings in which only some example embodiments are shown. Specific structural and functional details disclosed herein are merely representative for purposes of describing example embodiments. The present invention, however, may be embodied in many alternate forms and should not be construed as limited to only the example embodiments set forth herein. Accordingly, while example embodiments of the invention are capable of various modifications and alternative forms, embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that there is no intent to limit example embodiments of the present invention to the particular forms disclosed. On the contrary, example embodiments are to cover all modifications, equivalents, and alternatives falling within the scope of the invention. Like numbers refer to like elements throughout the description of the figures. It will be understood that, although the terms first, second, etc. may be used herein to describe various elements, these elements should not be limited by these terms. These terms are only used to distinguish one element from another. For example, a first element could be termed a second element, and, similarly, a second element could be termed a first element, without departing from the scope of example embodiments of the present invention. As used herein, the term “and/or,” includes any and all combinations of one or more of the associated listed items. It will be understood that when an element is referred to as being “connected,” or “coupled,” to another element, it can be directly connected or coupled to the other element or intervening elements may be present. In contrast, when an element is referred to as being “directly connected,” or “directly coupled,” to another element, there are no intervening elements present. Other words used to describe the relationship between elements should be interpreted in a like fashion (e.g., “between,” versus “directly between,” “adjacent,” versus “directly adjacent,” etc.). The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of example embodiments of the invention. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. As used herein, the terms “and/or” and “at least one of” include any and all combinations of one or more of the associated listed items. It will be further understood that the terms “comprises,” “comprising,” “includes,” and/or “including,” when used herein, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. It should also be noted that in some alternative implementations, the functions/acts noted may occur out of the order noted in the figures. For example, two figures shown in succession may in fact be executed substantially concurrently or may sometimes be executed in the reverse order, depending upon the functionality/acts involved. Spatially relative terms, such as “beneath”, “below”, “lower”, “above”, “upper”, and the like, may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It will be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, term such as “below” can encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein are interpreted accordingly. Although the terms first, second, etc. may be used herein to describe various elements, components, regions, layers and/or sections, it should be understood that these elements, components, regions, layers and/or sections should not be limited by these terms. These terms are used only to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of the present invention. FIG. 1 illustrates a computed tomography scanner 1 in a roughly schematic, simplified illustration. The computed tomography scanner 1 comprises a basically annular gantry 2 which can rotate about an isocentric axis I of the computed tomography scanner 1 (indicated by a double-headed arrow 3). Attached to the gantry 2 is, firstly, an X-ray tube 4 and, secondly, a detector 5 for detecting the X-ray radiation 6 emanating from the X-ray tube 4, the detector lying substantially opposite to said X-ray tube. A patient is, as intended, positioned in the region of the isocentric axis I (within the gantry 2) for irradiation purposes with the aid of a patient couch 7. The detector 5 is assembled from a multiplicity of basically cube-shaped detector modules 8. Each detector module 8 firstly comprises a sensor unit 10 respectively on a top side 9 intended to face the X-ray tube 4, which sensor unit in turn comprises a scintillator 11 (FIG. 2) for converting the X-ray radiation 6 into visible light. A multiplicity of photodiodes 12 (FIG. 3) are integrated into each sensor unit 10 for the purpose of detecting the visible light. Secondly, each detector module 8 comprises an elongate electronics unit 13 intended to face away from the X-ray tube 4, which electronics unit inter alia contacts the photodiodes 12 for readout purposes. In an assembled state shown in the present illustration, the individual detector modules 8 are, in respect of the gantry 2, fitted adjacent to one another over an area in a plurality of rows Z in an axial direction 14 and in a plurality of columns Y in a tangential direction 15, wherein all sensor units 10 together form a detector area 16. In respect of the respectively associated sensor unit 10, the electronics units 13 are arranged offset toward the outside in a radial direction 17. FIG. 2 illustrates a side view of one of the sensor units 10 separately from the others. For orientation purposes, the radial direction 17 and the tangential direction 15 are illustrated in accordance with the intended installed situation as per FIG. 1. Here, the axial direction 14 points into the plane of the drawing. The sensor unit 10 comprises a rectangular support plate 20. The inner side 21 thereof is intended to face the X-ray tube 4, while the outer side 22 thereof opposite thereto is intended to face away from the X-ray tube 4. A collimator 23 made of a stack of tungsten collimator sheets 24 is attached to the support plate 20 on the inner side 21. Here, the individual collimator sheets 24 are aligned approximately parallel with respect to one another, with each collimator sheet 24 sticking out from the support plate 20 at a substantially right angle. The X-ray radiation 6 is, as intended, incident in a substantially perpendicular fashion on the support plate 20 in the interspaces 25 formed between the collimator sheets 24 (in the tangential direction 15). For attachment purposes, each collimator sheet 24 is, on a narrow side 26, led through openings 28 of the support plate 20 in a substantially accurately fitting fashion with in each case a plurality of finger-like protrusions 27, and hence said collimator sheet is fixed. Each protrusion 27 in this case protrudes beyond the support plate 20 on the outer side 22 of the latter. The scintillator 11 is attached to the outer side 22 of the support plate 20. The scintillator 11 is assembled from a multiplicity of photodiode strips 32 and scintillator strips 33. In the process, each photodiode strip 32 and each scintillator strip 33 is aligned along the axial direction 14. The photodiode strips 32 and scintillator strips 33 are respectively arranged alternately next to one another and are interconnected in the tangential direction 15. Here, the width BS (in the tangential direction 15) of each scintillator strip 33 approximately corresponds to the width BZ of an interspace 25. The thickness SF (again in the tangential direction 15) of each photodiode strip 32 approximately corresponds to the thickness SK of the individual collimator sheets 24. Each scintillator strip 33 is in each case arranged on the other side of an interspace 25. As a result of the above-mentioned dimensioning, the scintillator strip 33 in this case respectively lies in the region irradiated by the X-ray radiation 6, while the photodiode strips 32 are at least partly protected from the X-ray radiation 6 by the collimator sheets 24. A narrow side 35 of the photodiode strips 32 respectively protrudes beyond the scintillator strips 33 on an outer side 34 of the scintillator 11 facing away from the support plate 20. The photodiodes 12 integrated in the photodiode strip 32 can be contacted by way of the electronics unit 13 on this narrow side 35. In order to produce the sensor unit 10 as per FIG. 2, the method illustrated on the basis of FIGS. 3 and 4 is applied. In the process, as illustrated in FIG. 3, a photodiode strip 32 and a scintillator strip 33 are initially joined to form a so-called sensor strip 40. A multiplicity of photodiodes 12 are arranged adjacent to one another on the photodiode strip 32 (along the length thereof). The side of the photodiode strip 32 on which the light-sensitive surfaces of the photodiodes 12 are attached is referred to as the front side 41 thereof. The side of the photodiode strip opposite to the front side is referred to as the backside 42 of the photodiode strip. On the front side 41, the photodiodes 12 are arranged laterally offset with respect to the longitudinal direction in the region of a first narrow side 43, while the narrow side 35 of the photodiode strip 32 opposite thereto has electrical contacts (not illustrated in any more detail) affixed to it for connecting the photodiodes 12 to the electronics unit 13. The scintillator strip 33 is assembled from a multiplicity of cube-shaped scintillator pixels 44 which are arranged adjacent to one another in the longitudinal direction of the scintillator strip 33. Here, the number of scintillator pixels 44 corresponds to the number of photodiodes 12 on one of the photodiode strips 32. Each scintillator pixel 44 is formed by a cube of scintillating material. Two adjoining scintillator pixels 44 are in this case respectively delimited—optically—from one another in the longitudinal direction by a so-called septum 45. Each scintillator pixel 44—possibly even before the production of the scintillator strip 33—is covered by a layer 46 (FIG. 4) of reflector lacquer on five sides, which lacquer reflects the visible light being generated in the pixel. The side 47 of each scintillator pixel 44 respectively not coated by reflector lacquer (FIG. 4) in each case faces the front side 48 of the scintillator strip 33 (not visible here). This front side 48 of the scintillator strip 33 is adhesively bonded onto the front side 43 of the photodiode strip 32 in the region of the photodiodes 12 using an optically transparent adhesive. During the bonding process, the photodiode strip 32 is, using a stop, aligned in respect of the scintillator strip 33 such that respectively one scintillator pixel 44 is arranged on respectively one photodiode 12. In the process, the height HF of the photodiode strip 32 is greater than the height HS of the scintillator strip 33. Accordingly, the narrow side 35 of the photodiode strip 32 protrudes beyond the scintillator strip 33. The height HS of the scintillator strip 33 (or of a scintillator pixel 44) approximately corresponds to the width B of a photodiode 12. FIG. 4 shows that, during the assembly, a side face 50 adjoining the front side 48 of the scintillator strip 33 is aligned approximately flush with the narrow side 43 of the photodiode strip 32, wherein the layer 46 of reflector lacquer protrudes beyond the photodiode strip 32 on this side. FIG. 4 also shows that a plurality of sensor strips 40 produced as per FIG. 3 are finally adhesively bonded onto the support plate 20 and in the process form the scintillator 11 or the sensor unit 10. In the process, the individual sensor strips 40 are respectively aligned along the protrusions 27 serving as stops with an edge 51 of the coated side face 50 facing away from the photodiode strip 32. The coated side face 50 is adhesively bonded onto the support plate 20 in a planar fashion. In principle, it is also feasible in this case for the sensor strips 40—in the case of suitable dimensioning of the photodiode strips 32—to be adhesively bonded onto the support plate 20 such that the photodiode strips 32 are arranged on the side of the sensor strip 40 facing away from the support plate 20. Subsequently, the interspace 52 respectively existing between two sensor strips 40 is filled with a casting resin. Hence, the individual scintillator pixels 44 are arranged on the support plate 20 in an array structure. In the process, the individual scintillator pixels 44 are delimited from one another by the septa 45 in the longitudinal direction (which corresponds to the axial direction 14); by contrast, they are basically delimited from one another by the photodiode strips 32 in the transverse direction (tangential direction 15). As a result of the presented production method, each scintillator strip 33 is in each case arranged very precisely in the region of an interspace 25 of the collimator 23. The patent claims filed with the application are formulation proposals without prejudice for obtaining more extensive patent protection. The applicant reserves the right to claim even further combinations of features previously disclosed only in the description and/or drawings. The example embodiment or each example embodiment should not be understood as a restriction of the invention. Rather, numerous variations and modifications are possible in the context of the present disclosure, in particular those variants and combinations which can be inferred by the person skilled in the art with regard to achieving the object for example by combination or modification of individual features or elements or method steps that are described in connection with the general or specific part of the description and are contained in the claims and/or the drawings, and, by way of combineable features, lead to a new subject matter or to new method steps or sequences of method steps, including insofar as they concern production, testing and operating methods. References back that are used in dependent claims indicate the further embodiment of the subject matter of the main claim by way of the features of the respective dependent claim; they should not be understood as dispensing with obtaining independent protection of the subject matter for the combinations of features in the referred-back dependent claims. Furthermore, with regard to interpreting the claims, where a feature is concretized in more specific detail in a subordinate claim, it should be assumed that such a restriction is not present in the respective preceding claims. Since the subject matter of the dependent claims in relation to the prior art on the priority date may form separate and independent inventions, the applicant reserves the right to make them the subject matter of independent claims or divisional declarations. They may furthermore also contain independent inventions which have a configuration that is independent of the subject matters of the preceding dependent claims. Further, elements and/or features of different example embodiments may be combined with each other and/or substituted for each other within the scope of this disclosure and appended claims. Still further, any one of the above-described and other example features of the present invention may be embodied in the form of an apparatus, method, system, computer program, computer readable medium and computer program product. For example, of the aforementioned methods may be embodied in the form of a system or device, including, but not limited to, any of the structure for performing the methodology illustrated in the drawings. Even further, any of the aforementioned methods may be embodied in the form of a program. The program may be stored on a computer readable medium and is adapted to perform any one of the aforementioned methods when run on a computer device (a device including a processor). Thus, the storage medium or computer readable medium, is adapted to store information and is adapted to interact with a data processing facility or computer device to execute the program of any of the above mentioned embodiments and/or to perform the method of any of the above mentioned embodiments. The computer readable medium or storage medium may be a built-in medium installed inside a computer device main body or a removable medium arranged so that it can be separated from the computer device main body. Examples of the built-in medium include, but are not limited to, rewriteable non-volatile memories, such as ROMs and flash memories, and hard disks. Examples of the removable medium include, but are not limited to, optical storage media such as CD-ROMs and DVDs; magneto-optical storage media, such as MOs; magnetism storage media, including but not limited to floppy disks (trademark), cassette tapes, and removable hard disks; media with a built-in rewriteable non-volatile memory, including but not limited to memory cards; and media with a built-in ROM, including but not limited to ROM cassettes; etc. Furthermore, various information regarding stored images, for example, property information, may be stored in any other form, or it may be provided in other ways. Example embodiments 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 present 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. Transfer device for a nuclear installation between a first chamber and a second chamber separated by a wall comprising a curved surface comprising:a barrel door comprising a cylindrical body and having an outer periphery, the cylindrical body defining an inner space, the inner space accessible by an opening that is oriented on a side of the first chamber or on a side of the second chamber, the inner space configured to receive materials to produce nuclear fuel, the barrel door movable around an axis;at least one sealing means in contact with the curved surface of the wall and the outer periphery of the barrel door to form a seal between the wall and the outer periphery of the barrel door, the at least one sealing means comprising:a seal carrier; anda seal attached to the seal carrier;wherein the seal carrier is removably fixed on the wall, andwherein the seal is in contact with the outer periphery of the barrel door. 2. Device set forth in claim 1, wherein the seal carrier comprises a T groove receiving the seal. 3. Device set forth in claim 1, wherein the seal carrier is made of stainless steel. 4. Device as set forth in claim 1, wherein the seal is made of a material that is resistant to flames and hot gas. 5. Device as claimed in claim 4, wherein the seal is made of intumescent material. 6. Device as set forth in claim 1, wherein the sealing carrier is made of several parts. 7. Device as set forth in claim 1, comprising a first pressure drop means able to increase travel of gases between the chambers, said first means being mounted on an upper end of the door, substantially in a plane orthogonal to the axis of rotation of the door. 8. Device as claimed claim 7, wherein the first pressure drop means is formed by a steel angle assembly. 9. Device set forth in claim 7, wherein the first pressure drop means is formed by several arcs of a circle placed end to end. 10. Device as set forth in claim 1, comprising a second pressure drop means, positioned along a generatrix of the outer periphery of the transfer mechanism. 11. Device as claimed in claim 10, wherein the second pressure drop means comprises an elongated element made of steel, with a substantially circular transversal section. 12. Device as set forth in claim 1, wherein the door comprises a first axis projecting from a first side and a second axis projecting from a second side, around which the door is able to rotate. 13. Device as set forth in claim 1, wherein the door is driven in rotation using at least one electric motor. 14. Device set forth in claim 1, wherein the at least one sealing means is configured to confine flames and hot gas in the first chamber for a determined length of time to prevent passage of the flames and hot gas into the second chamber. 15. Device set forth in claim 4, wherein the material is resistant to hot gases that are at least the temperature of the flames.
	claims	1. An X-ray reflecting device comprising a plural number of X-ray reflecting elements, each of said X-ray reflecting elements comprising:a body composed of a silicon plate; anda plurality of slits formed in said body through an etching process in such a manner as to penetrate from a front surface to a back surface of said body, each of said slits having a wall surface serving as an X-ray reflecting surface,wherein said plurality of X-ray reflecting elements are arranged side-by-side in a horizontal direction in such a manner as to allow said slits in the respective X-ray reflecting elements to be located in a given positional relationship with each other to allow X-rays incident from one side of the X-ray reflecting device to be collected through the X-ray reflecting device and focused onto a narrow zone on a side opposite to said one side. 2. An X-ray reflecting element comprising:a body composed of a metal plate; anda plurality of slits formed in said body through an X-ray LIGA process in such a manner as to penetrate from a front surface to a back surface of said body, each of said slits having a wall surface serving as an X-ray reflecting surface to allow X-rays incident from one side of the X-ray reflecting element to be collected through the X-ray reflecting element and focused onto a narrow zone on a side opposite to said one side. 3. An X-ray reflecting device comprising a plural number of X-ray reflecting elements, each of said X-ray reflecting elements comprising:a body composed of a metal plate; anda plurality of slits formed in said body through an X-ray LIGA process in such a manner as to penetrate from a front surface to a back surface of said body, each of said slits having a wall surface serving as an X-ray reflecting surface,wherein said plurality of X-ray reflecting elements are arranged side-by-side in a horizontal direction in such a manner as to allow said slits in the respective X-ray reflecting elements to be located in a given positional relationship with each other to allow X-rays incident from one side of the X-ray reflecting device to be collected through the X-ray reflecting device and focused onto a narrow zone on a side opposite to said one side.
	description	This invention provides improved image contrast grids for use in x-ray imaging applications. As described in detail below, the image contrast grids have improved rejection ratios and also reduced fill factors, i.e., increased open aperture ratios. Accordingly, the grids can improve image quality. In addition, the grids can provide increased efficiency and thus reduce the required dosage of source radiation that is needed to obtain an image of an object. In addition, the grids can have fine structures that reduce or even eliminate the need for the use of a Bucky system during imaging. This invention also provides methods of making the image contrast grids that are economical, controllable and reproducible. The methods can provide consistent grid structures in a cost-efficient manner. This invention also provides methods of using the image contrast grids in imaging systems for imaging objects such as bodies. FIG. 7 shows an exemplary embodiment of an image contrast, or antiscatter, grid 224 according to this invention. The image contrast grid 224 comprises a body 260 that includes a plurality of openings 262. The body 260 forms a continuous matrix. In various exemplary embodiments, the openings 262 have an elongated, generally cylindrical configuration. An x-ray absorbing material 264 is formed in the openings 262 in the body 260. As shown, in some exemplary embodiments of the image contrast grids 224 according to this invention, the x-ray absorbing material 264 can be formed to substantially fill the openings 262. In these exemplary embodiments, the x-ray absorbing material 264 can fill the openings along the entire length of the openings 262 as shown. Alternatively, the x-ray absorbing material 264 can fill the openings 262 only along selected portions of their length. For example, the x-ray absorbing material 264 can be formed only near the top surface 266 of the body 260. In other exemplary embodiments of the image contrast grids 224 according to this invention, the x-ray absorbing material can be formed only on the side walls 268 defining the openings 262. For example, in such exemplary embodiments, the x-ray absorbing material can form a hollow-cylindrical configuration in the openings 262. In such exemplary embodiments, the x-ray absorbing material 264 can cover only portions of, or substantially the entire, side walls 268. In various exemplary embodiments of the image contrast grids according to this invention, the openings 262 formed in the body 260 have a quasi-periodic arrangement. However, in other exemplary embodiments of the image contrast grid 224, the openings 262 can be formed in different patterns. For example, in the exemplary embodiment of the image contrast grid 324 shown in FIG. 8, the openings 362 of the body 360 have a regular pattern. Other regular patterns of openings in the image contrast grids can also be formed. Furthermore, in other exemplary embodiments of the image contrast grids according to this invention, the openings can be randomly formed. FIG. 9 illustrates an exemplary embodiment of an image contrast grid 424 having randomly formed openings 462 in the body 460. In the image contrast grid 224 shown in FIG. 7, the x-ray absorbing material 264 completely fills the openings 262 along their entire lengths. Thus, the x-ray absorbing material 264 forms solid columns of x-ray absorbing material in the matrix of the body 260. The columns of the x-ray absorbing material 264 have a generally cylindrical shape. The body 260 can have any suitable configuration. A typical configuration for imaging applications is the illustrated generally rectangular shape. The body 260 includes the top surface 266, a bottom surface 270 and side surfaces 272. However, other configurations of the body 260, such as square configurations, can also be formed. The dimensions of the body 260 can be varied to provide the desired cross-sectional area A of the top surface 266 and height h. The body 260 can comprise any suitable material that is substantially transparent to x-rays. These materials can be inorganic and/or organic. Exemplary inorganic materials suitable for forming the body 260 include aluminum, aluminum alloys such as aluminum-nickel alloys, and metal oxides such as aluminum oxide. The body 260 can also be formed of any suitable organic material. Exemplary plastics that can be used to form the body 260 include, for example, acrylics, such as polymethylmethacrylate (PMMA), and epoxies, such as SU-8 epoxy, which is commercially available from Shell Chemical Company. The size of the openings formed in these materials may be different than those openings formed in metallic materials such as aluminum. Other materials that can be used to form the body 260 include semiconductor materials, such as silicon. Silicon provides the advantage that it can be etched to form the openings 262 using well-known dry and wet etching techniques and other processes. The x-ray absorbing material 264 that is formed in the openings 262 of the body 260 can be any suitable material that absorbs x-rays substantially without scattering the x-rays. The x-ray absorbing material 264 is applied in the openings 262 to absorb Compton-scattered x-rays that are scattered by the object to be imaged. Exemplary x-ray absorbing materials include lead, gold, platinum, tin, silver and mercury. Many exemplary embodiments of the image contrast grids 224 use lead as the x-ray absorbing material 264 because lead has excellent x-ray absorbing properties. In addition, lead is inexpensive and can be easily applied in the openings due to its low melting point. The amount that the openings 262 in the body 260 of the image contrast grid 224 are filled by the x-ray absorbing material 264 can be characterized, for example, by two different factors. First, the fill amount can be characterized by the fill factor F. The fill factor F is defined as the ratio of the cross-sectional area of the x-ray absorbing material Ax-ray absorbing material to the total cross-sectional area of the image contrast grid Agrid, in a plane parallel to the plane of the top surface 266 of the image contrast grid 224, as follows: F=Ax-ray absorbing material/Agrid In general, at a given fill factor F, the detail of the image formed using the image contrast grid can be improved by increasing the pitch of the openings, which is the spacing between the openings. Second, the fill amount of the openings 262 in the body 260 can be characterized by the open aperture ratio O, which reflects the cross-sectional area of the openings 262 that is not filled with the x-ray absorbing material 264. The open aperture ratio is defined as the ratio of the total cross-sectional area of the open, non-filled portions of the openings Aopen to the total cross-sectional area of the image contrast grid Agrid, in a plane parallel to the plane of the top surface 266 of the image contrast grid 224, as follows: O=Aopen/Agrid The open aperture ratio O and the fill factor F are related as: O+F=l The fill factor F, or the open aperture ratio O, affect the imaging performance of the image contrast grid 224 by affecting the amount of absorption of the x-rays by the x-ray absorbing material 264 formed in the openings. That is, because the x-ray absorbing material affects the percentage of the x-rays that pass through an object and impinge on the top surface 268 of the image contrast grid 224 in a direction normal to the top surface 268, the fill amount of the openings 262 by the x-ray absorbing material 264 affects the percentage of these normal x-rays that can be absorbed by the image contrast grid 224. Accordingly, increasing the fill factor F, or decreasing the open aperture ratio O, of the image contrast grid 224 thus increases the amount of the x-ray absorbing material 264 that can absorb the normal x-rays. Likewise, decreasing the fill factor F, or increasing the open aperture ratio O, of the image contrast grid 224 decreases the amount of the x-ray absorbing material 264 that can absorb the normal x-rays. In accordance with this invention, the image contrast grids 224 can provide lower fill factors F, and thus higher open aperture ratios O, than those provided by known image contrast grids, such as the image contrast grid 124 shown in FIG. 6. Open aperture ratios O approaching one are preferred. Accordingly, the image contrast grids 224 according to this invention absorb a lower percentage of the normal x-rays that impinge on them after having passed through an object to be imaged. The columns of the x-ray absorbing material 264 shown in FIG. 7 have a diameter d and an inter-column spacing (pitch) P. A typical value for the diameter d is from about 0.1 xcexcm to about 100 xcexcm for body materials such as aluminum. A typical value of the pitch P is from about 0.2 xcexcm to about 200 xcexcm. A typical height h for the body is from about 10 xcexcm to about 2000 xcexcm. In various exemplary embodiments, the column diameter d satisfies the relationship: xe2x80x830.1 xcexcm less than dxe2x89xa60.5P. For non-metallic materials such as PMMA, the opening diameter d can typically be from about 10 xcexcm to about 1000 xcexcm. The image contrast grid 224 can be formed using various exemplary embodiments of the methods according to this invention. A first exemplary embodiment of a method according to this invention comprises patterning the material of the body using conventional photolithographic techniques. For example, the openings can be formed in the masked body by wet or dry etching techniques, as described in U.S. Pat. No. 6,177,236, incorporated herein by reference in its entirety. The etching processes can form a pattern of openings 262 in the body 260 having a staggered arrangement. The openings 262 can have the cylindrical shape shown in FIG. 7. The openings 262 can alternatively have other cross-sectional shapes, such as square, rectangular, triangular, hexagonal or the like. In various exemplary embodiments of the image contrast grid 224, the height of the x-ray absorbing material 264 in the openings 262 is thicker than the absorption length of the x-rays. For typical x-ray applications, a height of 0.5-1 mm of lead is sufficient. For other materials, the desired height is related to the atomic number Z of the element. In various exemplary embodiments, the desired height is inversely proportional to Z3. After the openings 262 are formed in the body material 260 by dry or wet etching or some other suitable technique, the x-ray absorbing material 264 is applied in the openings 262. An exemplary technique for applying the x-ray absorbing material 264 in the openings 262 is to dip the body 260 into a bath of a molten metal. For example, the body material, such as aluminum, can be wetted with the x-ray absorbing material, such as lead, by dipping the aluminum into a molten lead bath. During the dipping process, the lead flows into the openings 262. The melted x-ray absorbing material 264 can partially or substantially completely fill the openings. Various factors that influence the fill amount of the melted x-ray absorbing material 264 into the openings 262 include the size of the openings 262, the length of the openings 262, and the amount of time the body 260 is dipped into the melted x-ray absorbing material 264. To enhance the flow of the x-ray absorbing material 264 into the openings 262, a flux may be utilized in various exemplary embodiments of the dipping process. Fluxes can be especially advantageous for openings that have a small diameter and/or a relatively long length, and where a high fill amount of the x-ray absorbing material 264 is desired in the openings 262. The flow of the x-ray absorbing material 264 into the openings 262 can also be enhanced by applying pressure to the melted x-ray absorbing material 264 so that the melted x-ray absorbing material 264 is injected into the openings under pressure. Alternatively, in other exemplary embodiments, a pressure gradient can be formed across the thickness of the body 260, to enhance the filling of the openings 262 by the x-ray absorbing material 264. For example, a low pressure can be created at a surface of the body 260, such as, for example, by a vacuum pump. An elevated pressure can be applied at an opposite surface of the body, to increase the pressure gradient across the body 260. Typically, the pressure gradient is created in the thickness direction of the body 260. As stated above, in various exemplary embodiments, the side walls 268 of the openings 262 in the body 260 can be coated with the x-ray absorbing material 264 along only a portion of the length of the side walls 268, instead of partially or substantially completely filling the openings 262 with the x-ray absorbing material. Coating only the side walls 268 of the openings 262 with the x-ray absorbing material 264 can significantly improve the imaging performance of the image contrast grid 224, by increasing the open aperture ratio O. Any suitable physical, chemical or electrochemical coating process can be used to coat the side walls 268 of the openings 262 of the body 260 with the x-ray absorbing material 264. Exemplary coating processes include physical vapor vacuum deposition, electrochemical deposition, chemical vapor deposition, chemical liquid deposition and the like. The coating process forms a coating on the side walls 268 that has a suitable thickness and length to provide the desired level of coverage for x-ray absorption by the image contrast grid 224. The coating thickness of the x-ray absorbing material 264 formed on the side walls 268 of the openings 262 is preferably no greater than about the radius of the openings 262. The coatings of the x-ray absorbing material 264 on the side walls 268 of the openings 262 improves the imaging performance of the image contrast grids by providing a higher open aperture ratio O. That is, the resulting hollow coatings, having, e.g., a hollow cylinder configuration, provide a higher open aperture ratio O than is achieved by reducing the diameter d and filling the openings 262 to a greater level, to provide the same desired open aperture ratio O. Other exemplary embodiments of the methods of forming the image contrast grids comprise coating the openings 262 in the body 260 with the x-ray absorbing material 264 by using any suitable electroplating technique. These embodiments are particularly useful for forming image contrast grids 224 having a random pattern of the openings 262. In still other exemplary embodiments of the methods of forming image contrast grids according to this invention, an etching process, such as an anodic etching process, can be used in combination with photolithography to form the openings 262 in the body 224. For example, as described in U.S. Pat. No. 6,177,236, the body is anodically etched using a suitable etching solution to form micropores. The micropores are separated from each other by thin walls. For aluminum, the walls between the micropores comprise aluminum oxide. The micropores typically have a diameter of 0.3 xcexcm or less. The micropores may then be filled with the x-ray absorbing material 264 to form an image contrast grid. In other embodiments, the micropores formed by anodic etching are aggregated, and the thin walls separating the micropores are removed. Oxide etching using any suitable oxide etch solution for the material forming the body can be employed to selectively remove the thin walls after a suitable application of photoresist or other patterned masking material. The mask and photoresist can be removed during the oxide etching step by suitable selection of the oxide etch, or can alternatively be removed in a separate step, or left. By combining anodic etching and oxide etching processes, the resulting openings formed in the body are suitably sized to allow the x-ray absorbing material to be applied into the openings. The exemplary methods according to this embodiment can be used to form random opening patterns. Other exemplary embodiments of the methods of forming the image contrast grids 224 comprise the use of a photoimagable material. The photoimagable material can be, for example, PMMA or SU-8. The photoimagable material is patterned with holes 262 and is coated or filled with the x-ray absorbing material 264 using any suitable coating process such as sputtering, or by chemical or electrochemical processes. Alternatively, a seed layer of a conductive material can be deposited on the photoimagable material and any suitable x-ray absorbing material 264 can then be applied over the seed layer by any suitable process. For example, lead can be applied over the seed layer by an electroplating process. The image contrast grids 224 with an opening diameter of less than about 10 xcexcm also have improved scatter rejection, while leaving at most a minimal trace of the image contrast pattern on the final image. Accordingly, because the openings have a small size, the Bucky system does not need to be used during imaging for the image contrast grids 224 formed according to these embodiments. An important aspect of imaging is achieving a suitable focus of the image. For some imaging applications, a parallel column structure as illustrated in FIG. 7 is not completely satisfactory. That is, because the x-rays that arrive at the imager are focused on the x-ray source, a focused image contrast grid having a focal length that equals the distance between the grid and the source is used. Micromachined openings, such as the openings formed in the body material by etching processes, typically grow in a direction substantially normal to the top surface of the body. Accordingly, this opening orientation produces parallel devices having an infinite focal length. According to this invention, it is desirable that the x-rays that pass through the object strike the top surface of the image contrast grid 224 at an angle normal to the top surface. The x-rays that strike the top surface at a normal angle have a high level of transmission through the image contrast grid 224. In contrast, the x-rays that strike the top surface at an acute angle of less than 90xc2x0 are highly attenuated, i.e., absorbed. The rejection ratio R is related to the amount of x-rays that are absorbed versus the amount of x-rays that are transmitted at a given angle of incidence of the x-rays. The rejection ratio R is given by: R(xcex8)=A(xcex8)/T(xcex8) where: A(xcex8) is the absorption of the x-rays at an angle of incidence of xcex8 of the x-rays; and T(xcex8) is the transmission of the x-rays at an angle of incidence of xcex8 of the x-rays. Accordingly, the rejection ratio R decreases toward zero as the amount of x-rays that are absorbed decreases and the amount transmitted increases. The rejection ratio R increases toward infinity as the amount of x-rays that are absorbed increases and the amount transmitted decreases. The image contrast grids 224 according to this invention can provide increased rejection ratios R, corresponding to a high level of x-ray transmission and a low level of x-ray absorbance. As stated above, the rejection ratio R is dependent on the angle of incidence of the x-rays on the top surface of the image contrast grid 224. FIG. 10 illustrates the relationship between the angle of incidence of x-rays on the top surface of the image contrast grid versus the rejection ratio R of the x-rays for an image contrast grid 224 according to this invention (curve A), and for a conventional image contrast grid having a sandwich structure such as the image contrast grid 124 shown in FIG. 6 (curve B). As shown, the rejection ratio R increases as the angle of incidence of the x-rays increases, reflecting a higher percentage of the x-rays being absorbed as opposed to being transmitted. Because the image contrast grids can provide improved levels of x-ray transmission, the dose that is delivered to patients during medical imaging procedures is significantly reduced because fewer orthogonal x-rays are absorbed by the image contrast grids. As shown in FIGS. 11 and 12, to provide the desired level of focus during imaging procedures, various exemplary embodiments of the image contrast grids 524 according to this invention have a contoured top surface 566 at which the x-rays impinge on the image contrast grid. As shown in FIGS. 11 and 12, the top surface 566 includes surface regions 5662, 5664, 5666 and 5668, each oriented at a different angle relative to the direction N; i.e., the surface regions are skewed relative to the normal N. The surface region 5662 is perpendicular to the normal N, while the surface regions 5664, 5666 and 5668 are oriented at different acute angles relative to the direction N. Consequently, the x-rays 5322, 5324, 5326 and 5328 strike each respective surface region 5662, 5664, 5666 and 5668, at an angle of about 90xc2x0. By orienting the surface regions 5662, 5664, 5666 and 5668 in this manner, the level of x-ray transmission increases, and the corresponding rejection ratio R for each of these surface regions approaches zero. Accordingly, the overall rejection ratio R of the image contrast grid 524 also increases. According to this invention, the top surface 566 of the image contrast grid 524 can be contoured by any suitable process. For example, the top surface 566 of the body can be stamped. Alternatively, the upper surface 566 of the body can be contoured by any suitable milling procedure. For example, a milled pattern can be formed in the upper surface 566 using a milling machine, such as a computer-controlled milling machine that can provide precise patterns. Aluminum materials are relatively soft and can be easily machined and contoured. As shown in FIG. 12, the pattern formed in the contoured top surface 566 of the body can include concentric rings. Each ring can form one of the surface regions 5662, 5664, 5666 and 5668 that is orthogonal to the focal point. The distance between the rings can be varied to provide the desired pattern. When the body material is etched or anodized, the pores grow substantially orthogonal to the local surface orientation. Accordingly, the openings 5622, 5624, 5626 and 5628 associated with the respective surface regions 5662, 5664, 5666 and 5668 are generally parallel to each other. However, the openings 5622, 5624, 5626 and 5628 have different orientations from each other. Thus, the x-ray absorbing material 5622, 5624, 5626 and 5628 formed in the respective openings 5622, 5624, 5626 and 5628 does not form an entirely parallel structure of columns or x-ray absorbing material configurations. The rings are formed in the top surface of the body with a desired pitch p, which is the distance between the rings. The pitch of the rings can be varied to affect the sensitivity of the grid geometry to misalignment. For a one-degree variation across the grid, the pitch is preferably smaller than the focal length f divided by 30 (i.e., p=f/30). This pitch p can be easily achieved in various exemplary embodiments of the methods of this invention, even for short focal lengths f that correspond to a small desired pitch p. Image quality considerations can, in some applications of the image contrast grids, require a finer pitch. The various exemplary embodiments of the micromachined image contrast grids 224-524 of this invention provide advantages over known grid structures. First, the image contrast grids 224-524 according to this invention can achieve a two-dimensional antiscatter geometry. Second, the openings, and the x-ray material formed in the openings, provide an increased open aperture ratio O. For example, the open aperture ratio of the image contrast grids can be at least about 90%. In contrast, known image contrast grids have an open aperture ratio of only about 80%. Third, as explained above, the Bucky system typically does not need to be used during use of the image contrast grids according to this invention because the openings can be formed with sufficiently small sizes to not be visible in most imaging modes. For example, the image contrast grids can be formed with up to about 1000 openings per mm. In contrast, known image contrast grids 224-524 have less than 10 openings per mm. However, in some applications, the particular focusing system that is used can cause image artifacts. If desired, these artifacts can be removed by using the Bucky system. In other exemplary embodiments, the above-described methods can be used to form the body of the image contrast grid from an x-ray absorbing material rather than from an x-ray transparent material. The openings in the body are then filled with an x-ray transparent material to form a complementary structure to those of the above-described embodiments. The openings in the body can be partially filled by the x-ray transparent material. The x-ray transparent material can be formed substantially only on the walls of the openings. If the openings are left unfilled, then the body formed of the x-ray absorbing material would require an x-ray transparent support structure such as an aluminum plate. If the openings are filled with aluminum or plastic or any other suitable x-ray transparent materials having desirable structural properties, then the body will be self-supporting. Such structures are capable of high open aperture ratios, typically above 90%. In further exemplary embodiments, the above-described embodiments can be modified by the use of casting processes to reduce the cost of making the image contrast grids, or to transfer a pattern from one material to another material. It is contemplated that the image contrast grids 224-524 can be used in different applications. For example, another exemplary application for collimating structures for x-rays is in single photon emission computer tomography (SPECT) cameras. In these devices, the collimator allows a two-dimensional x-ray detector to function as a camera, by detecting photons based on their direction rather than just on the locations at which they strike the imager. The imaging, therefore, does not depend on a pointlike x-ray source for forming images. In this application in SPECT cameras, a radioisotope is administered to a patient before undergoing imaging. The radioisotope has a characteristic x-ray or gamma ray emission spectrum. The radioisotope concentrates within a particular organ or structure within the patient""s body, and a computed tomography approach is used to reconstruct a three-dimensional image of the concentrated region. However, SPECT camera performance is dependent on, and is often limited by, the performance of the collimator. For SPECT cameras, the x-ray absorbing material formed in the openings will typically have a height of 5 mm to 5 cm for some medical imaging procedures, depending on the particular radioisotope that is used. While the invention has been described in conjunction with the specific embodiments described above, it is evident that many alternatives, modifications and variations are apparent to those skilled in the art. Accordingly, the preferred embodiments of the invention as set forth above are intended to be illustrative and not limiting. Various changes can be made without departing from the spirit and scope of the invention.
	summary
046559981	abstract	In a liquid metal cooled nuclear reactor with a nuclear fuel assembly in a coolant-containing primary vessel housed within a concrete containment vault, there is thermal insulation to protect the concrete, the insulation being disposed between vessel and concrete and being hung from metal structure secured to and projecting from the concrete, the insulation consisting of a plurality of adjoining units each unit incorporating a pack of thermal insulating material and defining a contained void co-extensive with said pack and situated between pack and concrete, the void of each unit being connected to the voids of adjoining units so as to form continuous ducting for a fluid coolant.
063234971	description	DETAILED DESCRIPTION The invention is described below in connection with an ion implantation system. However, the invention can be used with other systems or processes that use beams of energetic, charged particles, such as electron beam imaging systems. Thus, the invention is not limited to the specific embodiments described below. FIG. 1 is a schematic block diagram of an ion implantation system 100 in accordance with the invention. The ion implantation system 100 includes a beam generator 1 that generates and directs a beam 2 toward a semiconductor wafer 3. The beam generator 1 can include various different types of components and systems to generate a beam 2 having desired characteristics. The beam 2 can be any type of charged particle beam, such as an energetic ion beam used to implant the semiconductor wafer 3. The semiconductor wafer 3 can take various physical shapes, such as the common disk shape. The semiconductor wafer 3 can include any type of semiconductor material or any other material that is to be implanted using the beam 2. A beam current, i.e., an amount of charge carried by particles in the beam 2 to the wafer 3, is measured by a detector 4. The detector 4 can be any type of device that detects a level of the beam 2 current. For example, the detector 4 can be a Faraday cup or other device, as are well known in the art. The detector 4 can be fixed in place or movable and can be positioned in a variety of different ways, such as along the beam 2 path to the wafer 3, adjacent the wafer 3 as shown in FIG. 1, behind the wafer 3, etc. Other types of devices to measure the beam 2 current, such as devices that use calorimetery or beam-induced magnetic field measurement can be used, if desired, as the detector 4. The detector 4 outputs a signal representing the detected beam 2 current to a controller 5. The controller 5 can be or include a general purpose computer or network of general purpose computers that are programmed to perform desired input/output and other functions. The controller 5 can also include other electronic circuitry or components, such as application specific integrated circuits (e.g., ASICs), other hardwired or programmable electronic devices, discrete element circuits, FPGAs, etc. The controller 5 can also include devices, such as user input/output devices (keyboards, touch screens, user pointing devices, displays, printers, etc.), communication devices, data storage devices, mechanical drive systems, etc., to perform desired functions. The controller 5 also communicates with a wafer drive 6 that is capable of moving the wafer 3 relative to the beam 2, e.g., the wafer drive 6 can scan the wafer 3 across the beam 2 to implant the wafer 3. The wafer drive 6 can include various different devices or systems to physically move the wafer 3 in a desired way. For example, the wafer drive 6 can include servo drive motors, solenoids, screw drive mechanisms, one or more air bearings, position encoding devices, mechanical linkages, robotic arms or any other components to move the wafer 3 as are well-known in the art. The beam 2 is transported from the beam generator 1 to the wafer 3 in a relatively high vacuum environment created in a housing 8 by a vacuum system 7. By high vacuum, it is meant that low pressure exists in the housing 8. Conversely, low vacuum refers to a relatively higher pressure in the housing 8. The vacuum in the housing 8 is maintained using well-known systems, such as vacuum pumps, vacuum isolation valves, pressure sensors, etc. The vacuum system 7 may communicate with the controller 5, e.g., to provide information to the controller 5 regarding the current vacuum level in one or more portions of the housing 8. The beam 2 is shown in FIG. 1 to follow a straight path from the beam generator 1 to the wafer 3. However, the beam 2 may follow a curved path with one or more deflections within the generator 1 and/or between the beam generator 1 and the wafer 3. The beam 2 can be deflected, for example, by one or more magnets, lenses or other ion optical devices. Prior to implantation, the wafer drive 6 can move the wafer 3 away from the beam 2 so that the beam 2 is not incident on the wafer 3. The beam generator 1 then generates a beam 2 and the detector 4 detects a reference level for the beam current while a vacuum level within the housing 8 is at a desired level and/or is stable. As one example, the vacuum level at which the reference level for the beam current is determined may be a highest vacuum level generated by the vacuum system 7 within the housing 8. Of course, the reference level for the beam current may be determined for other vacuum-levels within the housing 8. The detector 4 outputs a signal to the controller 5 that can be used by the controller 5 as the reference level for the beam current, or the controller 5 can process the signal to generate a reference level for the beam current. For example, the detector 4 may output an analog signal that represents a number of detected ions, and the controller 5 may convert the analog signal to a digital number that is stored within the controller 5. The stored digital number may be used as a reference level for the beam current. During implantation, the beam 2 is incident on at least a portion of the wafer 3. The beam 2 can be scanned across the wafer 3 and/or the wafer 3 can be scanned across the beam 2 by the wafer drive 6. For example, the beam 2 may be scanned by the beam generator 1 in a plane parallel to the paper in FIG. 1, while the wafer 3 is moved in a direction perpendicular to the paper by the wafer drive 6. Materials in or on the wafer 3, such as photoresist on the surface of the wafer 3, may outgas or otherwise produce materials when impacted by particles in the beam 2. This causes a vacuum fluctuation within the housing 8 that can cause the vacuum level to decrease near the wafer 3 and along the beamline. This decrease in vacuum level can cause an increase in the number of charge exchanging collisions that occur for particles in the beam 2 traveling to the wafer 3. As discussed above, the charge exchanging collisions, i.e., collisions between energetic particles in the beam 2 and materials released by outgassing or volatilization at the wafer 3, cause the charge of individual particles in the beam 2 to be changed. For example, singly positively charged ions in the beam 2 can be neutralized by collisions along the beamline, or the positively charged ions may be doubly positively charged. Although the charge of the ions can be altered, the energy of the particles is not substantially changed. Therefore, although the charge of some particles may be altered so that the detector 4 does not detect the presence of the particles, the particles may impact the wafer 3 and contribute to the overall impurity dosing of the wafer 3. Thus, the detector 4 may output a signal during implantation that indicates a decrease in beam current even though the total dosing of the wafer 3 is not affected. The controller 5 can recognize, i.e., operate based on an assumption, that the detected decrease in beam current, or a portion of a detected decrease in beam current, has been caused by vacuum fluctuations during implantation, but that the total dose implanted in the wafer 3 is not being affected. Thus, the controller 5 can detect a vacuum fluctuation based on a detected decrease in beam current. It should be understood that the beam current may vary during implantation due to other factors, such as ion source variations, and that the controller 5 may determine that some portion of a detected beam current decrease has been caused by vacuum fluctuations, while another portion of the decrease has been caused by other factors, e.g., variations at the ion source. The controller 5 may adjust certain implantation parameters to correct for variations in beam current that are not due to vacuum fluctuations, as is known in the art and not described here. In addition, outgassing may vary with time, and the controller 5 may determine that the contribution of vacuum fluctuation to detected beam current decrease as compared to other factors may vary over time during implantation. In such cases the controller 5 may use an adjusted measured beam current that reflects only the contribution of vacuum fluctuation, and not the contribution of other factors, for purposes of controlling implantation. The controller 5 may sense a decrease in beam current, but not necessarily adjust specific implantation parameters, such as a beam 2 scan rate, wafer 3 scan rate, etc. Instead, the controller 5 may output a signal to the vacuum system 7 indicating that a rise in vacuum pressure has been detected and that the vacuum level within the housing 8 should be adjusted accordingly. This signal to the vacuum system 7 may be provided in addition to measured vacuum level signals provided by pressure sensors to the vacuum system 7. Thus, based on the signal from the controller 5, the vacuum system 7 may begin adjusting the vacuum level within the housing 8 before a decrease in vacuum level is detected by pressure sensors associated with the vacuum system 7. Alternately, the controller 5 may compare a detected beam current level provided by the detector 4 during implantation with the stored reference level for the beam current and use the difference between the two values to control either the beam 2 or the wafer drive 6. For example, the controller 5 may determine (based on stored information) that the decrease in beam current detected by the detector 4 during implantation is largely due to vacuum fluctuations along the beam line. Further, the controller 5 can determine that a portion of the detected decrease in beam current due to charge exchanging collisions does not affect the total dose delivered to the wafer 3, while another portion of the detected decrease in beam current does contribute to a decrease in the total dose delivered to the wafer 3. For example, some charge exchanging collisions may neutralize beam particles without affecting the particles' kinetic energy. The neutralized particles will not be detected by the detector 4, but still contribute to the total dose implanted in the wafer 3. Other collisions caused by the vacuum fluctuation may cause the charge and kinetic energy of a particle to be altered, or cause the particle to follow a trajectory that prevents the particle from being implanted in the wafer 3. These latter collisions cause a decrease in detected beam current, and also a decrease in the total dose implanted in the wafer 3. The controller 5 can scale the difference value between the detected beam current and the reference value for the beam current, so that a total dose delivered to the wafer 3 is adjusted to a desired level. The difference value can also be normalized, e.g., by dividing the difference value by the reference value. For example, the controller 5 may control the wafer drive 6 to move the wafer 3 more slowly across the beam 2 path based on the scaled and normalized scaled reference value. The scaling factors used by the controller 5 can be determined empirically and stored in the controller 5. Thus, when a particular difference value is determined by the controller 5, a corresponding scaling factor can be retrieved and used to adjust the difference value to appropriately control the beam 2 or movement of the wafer 3. The controller 5 may also control for implantation non-uniformity in two dimensions caused by vacuum fluctuation. For example, vacuum fluctuation may cause implantation non-uniformity in two dimensions at the wafer 3, e.g., non-uniformity along the beam scan direction parallel to the paper in FIG. 1 and non-uniformity along the wafer scan direction perpendicular to the paper in FIG. 1. Thus, the controller 5 may control the beam scan rate and the wafer scan rate to control for non-uniformity in both directions. Different scale factors may also be used to control the beam scan rate and the wafer scan rate, respectively. FIG. 2 shows a more detailed schematic block diagram of an ion implantation system 100 in accordance with the invention. An ion source 11 generates ions and supplies an ion beam 2. As is known in the art, the ion source 11 may include an ion chamber and a gas box containing a gas to be ionized. The gas is supplied to the ion chamber where it is ionized. The ions thus formed are extracted from the ion chamber to form the ion beam 2. The ion beam 2 may have an elongated cross section and may be ribbon-shaped, with a long dimension of the beam 6 cross section preferably having a horizontal orientation, or the beam 2 may have a circular cross-section. An extraction power supply and extraction electrode 12 accelerate ions from the ion source 11. The extraction power supply may be adjustable, for example, from about 0.2 to 80 keV. Thus, ions from the ion source 11 may be accelerated to energies of about 0.2 to 80 keV by the extraction electrode 12. The construction and operation of ion sources are well-known to those skilled in the art. The ion beam 2 passes through a suppression electrode and a ground electrode (not shown) to a mass analyzer 13. The mass analyzer 13 includes a resolving magnet that deflects ions in the ion beam 2 such that ions of a desired ion species pass through a resolving aperture 14 and undesired ion species do not pass through the resolving aperture 14. In a preferred embodiment, the mass analyzer 13 resolving magnet deflects ions of the desired species by 90.degree.. Ions of the desired ion species pass through the resolving aperture 14 to a scanner 15 (which is not required for systems using a ribbon-beam) positioned downstream of the mass analyzer 13. The scanner 15 may include scanning electrodes as well as other electrodes (not shown) for controlling the beam 2. Ions in the ion beam 2 are scanned and then pass through an angle corrector magnet 16. The angle corrector magnet 16 deflects ions of the desired ion species and converts the ion beam 2 from a diverging ion beam to a nearly collimated ion beam 2 having substantially-parallel ion trajectories. In a preferred embodiment, the angle corrector magnet 16 deflects ions of the desired ion species by 70.degree.. An end station 17 supports one or more semiconductor wafers in the path of the ion beam 2 such that ions of the desired species are implanted into the semiconductor wafers (not shown). The end station 17 may include a cooled electrostatic platen and a wafer drive 6 for moving wafers perpendicular to the long dimension of the ion beam 2 cross section, so as to distribute ions over the wafer surface. The ion implantation system 100 may include additional components known to those skilled in the art. For example, the end station 17 typically includes automated wafer handling equipment for introducing wafers 3 into the ion implantation system 100 and for removing wafers after implantation. The end station 17 may also include a dose measuring system, an electron flood gun and other known components. It will be understood that the entire path traversed by the ion beam 2 is evacuated during ion implantation. Additional details of the ion implantation system 100 are not provided here since they are well-known in the art and are not necessarily important to the invention. The components of the ion implantation system 100 are controlled by a controller 5. Thus, the controller 5 can monitor the ion implantation process and take steps to adjust various aspects of the process, such as the rate at which ions are produced from the ion source 11, the scan rate of the ion beam 2, the scan rate of the wafer relative to the ion beam 2 at the end station 17, etc. FIG. 3 is a schematic diagram of a portion of the ion implantation system 100 in FIG. 2 from the resolving aperture 14 to the end station 17, and shows the beam 2 path from the resolving aperture 14 to the semiconductor wafer 3 in the end station 17. The ion beam 2 path is conceptually divided into three regions, where Region I is upstream of the angle corrector magnet 16, Region II is within the angle corrector magnet 16, and Region III is downstream of the angle corrector magnet 16. In Region I, the beam 2 is a diverging beam. In Region II, the angle corrector magnet 16 deflects the charged articles in the beam 2 by approximately 70.degree. and collimates the beam. Thus, the beam 2 in Region III is a substantially collimated beam such that ions in the beam are all incident on the wafer 3 surface at substantially the same angle. Before implantation of the wafer 3 begins, the controller 5 controls the wafer drive 6 to move the wafer 3 out of the path of the beam 2. The beam current of the ion beam 2 is then measured by one or more of the detectors 41, 42 and 43. The detector 41 is a profiler or traveling Faraday cup that is moved transverse to the beam 2 near the plane where the beam 2 is incident on the wafer 3. Use of this type of traveling Faraday detector 41 is well-known, and a signal produced by the detector 41 is used to determine uniformity of the beam 2. The beam current can also be measured by a Faraday detector 42 that is positioned adjacent the wafer 3 during implantation. Since the detector 42 is positioned adjacent the wafer 3, the detector 42 can detect the beam current either before the wafer 3 is positioned for implantation or during implantation of the wafer 3. A third detector 43 can also be used to detect beam current. Since the detector 43 is positioned downstream of the wafer 3 during implantation, the detector 43, which is typically a Faraday-type detector, is typically used before implantation to measure a total dose expected to be implanted in the wafer 3. It should be understood that although the detectors 41-43 in this example are Faraday-type detectors, other types of detectors for sensing the beam current, such as those using calorimetry or beam induced magnetic field measurement, may be used in addition to, or in place of, the detectors 41-43. In addition, it is not necessary to use all three detectors 41-43. For example, the detectors 41 and 43 may be eliminated or not used to detect the beam current to control the implantation process with respect to vacuum fluctuation. Thus, only the detector 42 may be used to detect beam current. In the following example, only the detector 42 is used to detect the ion beam current and control the implantation process during vacuum fluctuation. When a vacuum level within the end station 17 and along the beam line is at a desired reference level, e.g., when the wafer 3 is positioned away from the beam 2 path and the vacuum along the beam line is at a relatively high and uniform level, the detector 42 detects the beam current of the ion beam 2. This detected current measured when the vacuum level is at a reference level is used by the controller 5 as a reference value for the ion beam current. The reference value for the ion beam current is not necessarily determined when the wafer 3 is out of the beam 2 path. That is, the reference value for the ion beam current may be a detected beam current when the wafer 3 is in a position to be implanted, and the vacuum along the beamline is at a desired level, e.g., at the beginning of implantation of the wafer 3. Alternately, the controller 5 may use an empirically determined reference value for the beam current that is stored within the memory of the controller 5. After implantation of the wafer 3 begins, substances in or on the wafer 3, such as photoresist, may be begin to outgas or otherwise release particles. This particle release causes a fluctuation in the vacuum level near the wafer 3 and along the beam line, e.g., along the beam path back to the resolving aperture 14. As discussed above, a decrease in the vacuum level along the beamline can cause an increase in the number of charge exchanging collisions between ions in the beam 2 and other particles, such as those released from the wafer 3. These charge exchanging collisions can cause ions in the beam 2 to become neutralized. Neutral particles are not acted on by the angle corrector magnet 16, and thus the neutral particles follow a straight line path from the point at which the particle was neutralized. Charge exchanging collisions can occur anywhere along the beamline, and the location of the charge exchanging collision typically determines whether the neutralized particle impacts the wafer 3 and contributes to the overall dose implanted in the wafer 3. In this example, charge exchanging collisions that neutralize ions in the beam 2 and that occur upstream of a line 9 cause the neutralized particles to not impact the wafer 3 or to be measured as contributing to the beam current. However, charge exchanging collisions that neutralize ions in the beam 2 and that occur downstream of the line 9 result in the neutralized particles impacting the wafer 3. The path of neutralized particles in FIG. 3 is shown by dashed line trajectories. Since the detector 42 cannot detect neutralized particles, the detector 42 detects a decrease in beam current, even though some of the neutralized particles that undergo charge exchanging collisions downstream of the line 9 contribute to the overall dose of the wafer 3. Charge exchanging collisions that occur upstream of the line 9 are termed non-line of sight collisions, while collisions that occur downstream of the line 9 are termed line of sight collisions, since the neutralized particles have a line of sight to the wafer and contribute to the dose of the wafer 3. Neutralizing of particles in the beam 2 when the vacuum level drops along the beamline causes the detector 42 to detect a decrease in the beam current. A difference .DELTA.I between the reference value for the beam current I.sub.ref and the measured beam current I.sub.m, is contributed to by both non-line of sight collisions and line of sight collisions that neutralize particles in the beam 2. Thus, the beam current difference .DELTA.I is a function of both the line of sight collisions and non-line of sight collisions. Since the line of sight collisions contribute to the overall dose of the wafer 3, the controller 5 cannot simply either increase the beam current of the beam 2 so that the measured current I.sub.m is equal to the reference value I.sub.ref or adjust the scan rate of the wafer 3 to compensate for the beam current difference .DELTA.I, without taking into account the neutralized particles that are implanted in the wafer 3, but do not contribute to the detected beam current. Accordingly, the difference value .DELTA.I is scaled using an appropriate scale factor, and the scaled value is used to control the wafer scan rate, beam current, or other implantation parameters to achieve a desired dose of the wafer 3. Preferably, the scan rate of the wafer 3 is adjusted. Scale factors may generally represent an estimation of the percentage amount of a detected decrease in measured beam current I.sub.m that is caused by non-line of sight collisions. Scale factors can be determined empirically, e.g., an appropriate scale factor may be determined based on a measured beam current I.sub.m and the actual dose implanted in the wafer 3 during an actual implantation process. Scale factors may also be determined by mathematically modeling an implantation process. For example, scale factors may be based on calculated distancedensity products that are obtained from implantation system models. Neutral particle densities, e.g., from outgassing products and other sources, may be calculated based on a model of the vacuum system, and the beam path lengthneutral particle density may be determined for line-of-sight and non-line-of-sight paths. Based on the relative values of these distance*density products, the scale factors for the implantation system may be derived. An empirical approach may be more accurate than a modeling approach for determining scale factors, but using an empirical approach may be more time consuming. As one example of how a scale factor may be used, if a 50% decrease in beam current is detected, e.g., a difference value .DELTA.I is normalized by dividing .DELTA.I by the reference value I.sub.ref giving .DELTA.I/I.sub.ref =0.5, and half of the detected decrease in beam current is caused by non-line of sight collisions and the other half of the detected decrease in beam current is caused by line of sight collisions, the wafer scan rate may be decreased by 1/4 of its original value (adjusted by a scale factor of 0.25) to achieve a desired dose rate for the wafer 3. That is, although the detected beam current I.sub.m is half the reference value for the beam current I.sub.ref, only 1/2 of the decrease in detected beam current need be compensated for since 1/2 of the detected decrease in beam current is caused by neutralized particles that still contribute to the overall dose of the wafer 3. Thus, a 25% increase in detected beam current I.sub.m or a 25% decrease in the wafer scan rate may be used to compensate for the non-line of sight collisions causing an overall decrease in the dosing of the wafer 3. The above example is an overly simplified example used to describe one aspect of the invention. It should be understood that other differences in detected beam current and a reference value for the beam current may be determined, and that other ratios of charge exchanging collisions that do and do not contribute to the overall wafer 3 dose may be encountered. In addition, non-uniformity effects in two dimensions may be compensated for by the controller 5. For example, empirically-derived scale factors may be used to adjust both a beam scan rate and a wafer scan rate to adjust for non-uniform dosing in both the beam scan and wafer scan directions that is caused by vacuum fluctuations. Of course, the scale factors may be derived mathematically, e.g., by modeling beam paths and neutral particle densities in the corrector magnet 16 to estimate the beam scan direction and wafer scan direction non-uniformity and scan rates to adjust for the non-uniformity in two directions. The controller 5 can use the determined beam current difference .DELTA.I for other purposes, such as controlling the vacuum system in the ion implantation system 100 to compensate for the vacuum fluctuations during implantation. The controller 5 may also use the beam current difference information to control other parameters of the implantation process, such as to control scanning of the beam 2, e.g., by adjusting a scanning waveform applied to scan plates in the scanner 15, etc. Control of scanning of the beam 2 may be used to adjust for horizontal non-uniformity, i.e., implantation non-uniformity in the wafer 3 in a direction perpendicular to the wafer scan direction. The controller 5 can also use the determined beam current difference information to make adjustments for beam non-uniformity effects of the vacuum fluctuations along the beam line. As can be seen in FIG. 3, ions on the outside of the beam envelope travel a longer distance from the resolving aperture 14 before reaching the line 9 than ions traveling on the inside of the beam envelope. Thus, ions traveling on the outside of the beam envelope may have a higher probability of experiencing a charge exchanging collision before reaching the line 9. This alone may result in underdosing one side of the wafer 3 (e.g., the right side of the wafer 3 in FIG. 3) compared to the other side. However, ions traveling along the inside of the beam envelope travel some distance from the line 9 before reaching Region III. If an ion experiences a charge exchanging collision between the line 9 and Region III, the neutralized particle is no longer steered by the angle corrector magnet 16 and follows a straight line path toward a portion of the wafer 3 further to the right than the ion would have originally impacted. This tends to cause extra dosing of the right side of the wafer 3, and may nearly counteract charge exchanging collisions that more frequently occur along outer paths of the beam 2. The inventor has found that the effects of vacuum fluctuations on beam uniformity in the arrangement shown in FIG. 3 typically have a relatively small effect on implant uniformity. However, in other configurations, vacuum fluctuations may have a greater effect on implant uniformity. In those cases, the controller 5 may adjust the beam parameters to counteract the effects of vacuum fluctuation. FIG. 4 shows a flowchart of steps of a method for adjusting ion implantation parameters based on an ion beam current reference value and a measured beam current. In step S10 an ion beam is generated. The ion beam can be generated in any one of several well-known ways in the art and can include any type of desired ion species at any desired energy. The ion beam typically includes substantially only one ion species, but the beam may include different ion species, if desired. In step S10, a reference value for the ion beam current is determined. The ion beam current is a measure of an amount of charge carried by particles in the beam per unit area or for a total cross-sectional area of the beam over a period of time. The reference value can be a measured beam current when the vacuum level within an ion implantation system is at a desired level. For example, the ion beam current may be measured before implantation of a wafer has begun, when the vacuum level within the ion implantation system and along an ion beam path is relatively high and stable. In step S30, a material, such as a semiconductor wafer, is implanted using the ion beam generated in step S10. Implantation of the material can be performed by directing the ion beam at a desired angle toward the semiconductor wafer such that energetic particles in the beam are implanted in the material. In step S40, the ion beam current is measured during implantation. The beam current can be measured using any desired beam current measuring device, such as a Faraday cup, a detector that uses calorimetry or beam-induced magnetic field measurements, or other detector. The ion beam current can be measured at a position adjacent the material being implanted or along the beam path to the material being implanted. In step S50, ion implantation parameters are adjusted based on the reference value for the ion beam current and the measured beam current during implantation. For example, the difference between the reference value and the measured current can be determined and ion implantation parameters can be adjusted based on the difference value. Various different ion implantation parameters can be adjusted based on the difference value. For example, the wafer scan rate can be adjusted, e.g., decreased, to accommodate for a decrease in dosing level resulting from vacuum fluctuations along the beam path during implantation. Other ion implantation parameters can be adjusted, such as the beam current, the beam scan rate or frequency, beam uniformity, the evacuation rate of a vacuum system used to control the vacuum level along the beamline, etc. The difference value between the reference value for the beam current and the measured beam current during implantation can be scaled to account for non-line of sight collisions that contribute to a decrease in detected beam current and a decrease in wafer dosing, and line of sight collisions that contribute to a decrease in detected beam current, but do not affect wafer dosing. Thus, the difference value can be scaled and implant parameters can be adjusted so that a desired dose is delivered to the semiconductor material. While the invention has been described in conjunction with specific embodiments thereof, it is evident that many alternatives, modifications and variations will be apparent to those skilled in the art. Accordingly, preferred embodiments of the invention as set forth herein are intended to be illustrative, not limiting. Various changes may be made without departing from the invention.
	abstract	An X-ray microscope apparatus includes an X-ray generator, a photocathode disposed on a path of X-rays for producing electrons when irradiated with X-rays generated by the X-ray generator, an electron image enlarging device having an acceleration anode for accelerating electrons produced by the photocathode and a magnetic lens for enlarging and focusing an electron beam of electrons emitted by the photocathode, an electron beam detecting device for detecting the electron beam focused thereon by the electron image enlarging device; and an image processing device for processing an electron image formed by the electron beam detecting device. The X-ray microscope apparatus can be formed in compact construction.
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	claims	1. A magnetohydrodynamic stirrer for mixing liquid, comprising:a conduit having a longitudinal axis,said conduit comprising two opposing solid walls, each extending along said longitudinal axis and each abutting a solid floor;a magnet, electromagnet, or both disposed in proximity to said conduit;at least three interior electrodes disposed within said conduit,a first of said interior electrodes contacting one of said two opposing walls and contacting said floor, said first of said interior electrodes extending along said longitudinal axis,a second of said interior electrodes contacting the other of said two opposing walls and contacting said floor, said second of said interior electrodes extending along said longitudinal axis, anda third of said interior electrodes being disposed on said floor of said conduit at a distance from said two opposing walls; anda controller in operational engagement with said interior electrodes,said controller, during operation, being capable of the application of a potential, a current, or both between at least two of said interior electrodes so as to give rise to flow of a liquid along said longitudinal axis within said conduit during operation of said stirrer. 2. The magnetic stirrer of claim 1, wherein at least one of the interior electrodes is moveable. 3. The magnetohydrodynamic stirrer of claim 1, wherein at least one of said interior electrodes is a pin. 4. The magneto hydrodynamic stirrer of claim 1, wherein said conduit comprises an inlet and an outlet. 5. The magnetohydrodynamic stirrer of claim 1, wherein at least one of said interior electrodes is characterized as being linear in configuration. 6. The magnetohydrodynamic stirrer of claim 1, wherein at least one of said interior electrodes is characterized as being circular. 7. The magnetohydrodynamic stirrer of claim 1, wherein said controller is capable of effecting application of a periodic potential, current, or both between at least two of said interior electrodes so as to give rise to chaotic advection within a liquid disposed within said conduit during operation of said stirrer. 8. The magnetohydrodynamic stirrer of claim 1, wherein said controller is capable of effecting application of a non-periodic potential, current, or both between at least two of said interior electrodes so as to give rise to chaotic advection within a liquid disposed within said conduit during operation of said stirrer. 9. The magnetohydrodynamic stirrer of claim 1, wherein said magnet or electromagnet is disposed exterior to said conduit. 10. The magnetohydrodynamic stirrer of claim 1, wherein a portion of said conduit comprises a magnetic material. 11. The magnetohydrodynamic stirrer of claim 1, wherein said conduit further comprises a ceiling. 12. The magnetohydrodynamic stirrer of claim 11, wherein at least one of said interior electrodes is essentially flush with said floor or ceiling of said conduit. 13. The magnetohydrodynamic stirrer of claim 1, wherein said controller is in operational engagement with said magnet or electromagnet and said controller, during operation, modulates the application of a magnetic field from said magnet or electromagnet.
	claims	1. A coupling structure of a fuel assembly comprising:a latch sleeve having a projecting portion formed at an upper end portion thereof;an upper nozzle having formed therein a latch sleeve installation hole configured to receive the upper end portion of the latch sleeve;a lock key, installed inside the latch sleeve installation hole, comprises an opening portion formed in a bottom surface of the lock key, the opening portion having a shape corresponding to the projecting portion, in which the latch sleeve and the lock key are coupled to each other to form the coupling structure of the fuel assembly by rotating the lock key with the upper end portion of the latch sleeve inserted into the lock key;a flange portion formed at a portion of the latch sleeve arranged below the projecting portion; anda gap portion formed at a portion of the latch sleeve arranged between the projecting portion and the flange portion, whereinthe coupling structure of the fuel assembly comprises a screw coupling means for screw-coupling the lock key to the upper nozzle side with a male screw thread formed on a side surface of the lock key,the flange portion is configured to contact a bottom surface of the upper nozzle,the gap portion is configured to accommodate a receiver portion of the lock key, andthe screw coupling means is a position adjustment means for filling a vertical gap between the receiver portion and the bottom surface of the projecting portion by moving the lock key up by rotating the lock key with the male thread formed on the lock key being screw coupled with the upper nozzle side so that a vertical play is eliminated at a fitting portion between the lock key and the latch sleeve. 2. The coupling structure of a fuel assembly according to claim 1 characterized in that the screw coupling means screw-couples the lock key and the latch sleeve installation hole with a female screw thread formed on an inner surface of the latch sleeve installation hole. 3. The coupling structure of a fuel assembly according to claim 1 characterized in thatthe screw coupling means includes a cylindrical thick-walled pipe installed in the latch sleeve installation hole, the thick-walled pipe having a female screw thread thread formed in an inner surface thereof, andthe screw coupling means screw-couples the lock key and the thick-walled pipe by installing the lock key in the thick-walled pipe. 4. The coupling structure of a fuel assembly according to claim 1, wherein the screw coupling means does not comprise a detachable nut. 5. A coupling method for a coupling structure of a fuel assembly comprising:a latch sleeve having a projecting portion formed at an upper end portion thereof;an upper nozzle having formed therein a latch sleeve installation hole into which the upper end portion of the latch sleeve is inserted, a lock key which is installed inside the latch sleeve installation hole, and which has an opening portion formed in a bottom surface thereof, the opening portion having a shape corresponding to the projecting portion;a screw coupling means for screw-coupling the lock key to the latch sleeve installation hole by a male thread formed on a side surface of the lock key and a female thread formed on an inner surface of the latch sleeve installation hole;a flange portion formed at a portion of the latch sleeve arranged below the projecting portion and configured to contact a lower surface of the upper nozzle;a gap portion formed at a portion of the latch sleeve arranged between the projecting portion and the flange portion; anda receiver portion formed in the opening portion and configured to enter the gap portion, in which the latch sleeve and the lock key are coupled to each other by rotating the lock key with the upper end portion of the latch sleeve being inserted into the lock key so that the projecting portion and the receiver portion are placed over each other,the coupling method comprising:performing position adjustment using the screw coupling means to fill a vertical gap between an upper surface of the receiver portion and a bottom surface of the projecting portion by moving the lock key up by rotating the lock key with the male thread being screw coupled with the female screw so that a vertical play is eliminated at a fitting portion between the lock key and the latch sleeve.
046831118	claims	1. A gas circulator for a nuclear reactor, comprising: a stator; a rotor having a rotor shaft with a first end and a second end; an impeller attached to the first end of the rotor shaft; a first radial active magnetic bearing positioned proximate the first end of the rotor shaft; a first radial backup bearing positioned proximate the first end of the rotor shaft; a second radial active magnetic bearing positioned proximate the second end of the rotor shaft; a second radial backup bearing positioned proximate the second end of the rotor shaft; an axial active magnetic bearing positioned between the first and second ends of the rotor shaft; and an axial backup bearing positioned between the first and second ends of the rotor shaft; wherein two of the backup bearings are located within a sealed chamber. supporting the circulator radially with a first active magnetic bearing and a second active magnetic bearing; supporting the circulator axially with a third active magnetic bearing; providing a first backup bearing for the first active magnetic bearing; providing a second backup bearing for the second active magnetic bearing; providing a third backup bearing for the third active magnetic bearing; and locating the second and third backup bearings in a sealed chamber. a nuclear reactor contained within a primary system pressure boundary; a gas coolant for the nuclear reactor; and a gas circulator including a stator, a rotor having a rotor shaft with a first end and a second end, an impeller attached to the rotor shaft at the first end of the rotor shaft, a first radial active magnetic bearing positioned proximate the first end of the rotor shaft, a first radial backup bearing positioned proximate the first end of the rotor shaft, a second radial active magnetic bearing positioned proximate the second end of the rotor shaft, a second radial backup bearing positioned proximate the second end of the rotor shaft, an axial active magnetic bearing positioned between the first and second ends of the rotor shaft, an axial backup bearing positioned between the first and second ends of the rotor shaft; wherein the gas circulator is contained within the primary system pressure boundary. pumping a coolant through the nuclear reactor with a pump; supporting the pump radially with two active magnetic bearings; supporting the pump axially with an active magnetic bearing; providing backup bearings for the radial active magnetic bearings; providing a backup bearing for the axial active magnetic bearing; and enclosing one radial backup bearing and the axial backup bearing in a sealed chamber. 2. A gas circulator as defined in claim 1, wherein the chamber contains a lubricant. 3. A gas circulator as defined in claim 2, wherein the lubricant is a solid lubricant. 4. A gas circulator as defined in claim 2, wherein the lubricant is a liquid lubricant. 5. A gas circulator as defined in claim 1, wherein the second radial backup bearing and the axial backup bearing are located within the chamber. 6. A gas circulator as defined in claim 5, wherein the second radial backup bearing is an antifriction bearing and wherein the axial backup bearing is an antifriction bearing. 7. A gas circulator as defined in claim 5, wherein the first radial backup bearing includes a graphite bushing mounted on the stator. 8. A gas circulator as defined in claim 7, wherein the first radial backup bearing further includes a metal sleeve mounted on the rotor shaft. 9. A gas circulator as defined in claim 5, wherein the axial backup bearing and second radial backup bearing are spaced apart sufficiently to permit the backup bearings to provide substantially all radial support for the rotor when the first and second radial active magnetic bearings are deenergized. 10. A gas circulator as defined in claim 5, wherein the sealed chamber is defined by an inner member, an outer member, and sealing means for forming a seal between the inner and outer members, the outer member being substantially annular and at least part of the inner member being located within the outer member. 11. A gas circulator as defined in claim 10, wherein one of the rotor shaft and the inner member has a bore and the other of the rotor shaft and the inner member has an extension with a first end and a second end, the extension extending into the bore, a clearance existing between the extension and the bore when the active magnetic bearings are energized. 12. A gas circulator as defined in claim 11, wherein the rotor shaft has the bore and the inner member has the extension, the first end of the extension extending into the bore, the second end of the extension being connected to the inner member. 13. A gas circulator as defined in claim 12, wherein the second end of the extension is beveled and the rotor shaft is correspondingly beveled. 14. A gas circulator as defined in claim 12, wherein the first end of the extension is beveled and the rotor shaft is correspondingly beveled. 15. A gas circulator as defined in claim 11, wherein the inner member has the bore and the rotor shaft has the extension, the first end of the extension extending into the bore, the second end of the extension being connected to the second end of the rotor shaft. 16. A gas circulator as defined in claim 15, wherein the second end of the extension is beveled and the inner member is correspondingly beveled. 17. A gas circulator as defined in claim 10, further comprising means for braking the rotor. 18. A gas circulator as defined in claim 17, wherein the means for braking the rotor includes a first flange connected to the rotor shaft, a second flange connected to the inner member, and means for loading the first flange and the second flange at their respective beveled contacting surfaces. 19. A gas circulator as defined in claim 10, wherein the chamber contains a liquid lubricant, and wherein means for preventing the liquid lubricant from traveling toward the rotor shaft are located within the chamber. 20. A gas circulator as defined in claim 19, wherein the preventing means includes a ring which by centrifugal force urges the liquid lubricant away from the rotor shaft. 21. A gas circulator as defined in claim 5, further comprising control means for adjusting the position of the rotor while the rotor is rotating. 22. A gas circulator as defined in claim 21, wherein the control means includes means for sensing rotor vibrations and means for reducing rotor vibrations. 23. A method for using a circulator for a gas-cooled nuclear reactor, comprising the steps of: 24. A method as defined in claim 23, further comprising the step of electrically driving the circulator. 25. A method as defined in claim 23, wherein the supporting steps and the providing steps are performed within a primary system pressure boundary for the nuclear 26. A method as defined in claim 23, further comprising the step of introducing a lubricant into the 27. A method as defined in claim 26, wherein the introducing step includes introducing a solid lubricant into the chamber. 28. A method as defined in claim 26, wherein the introducing step includes introducing a liquid lubricant into the chamber. 29. A method as defined in claim 23, further comprising the step of supplying a braking mechanism for the circulator. 30. A method as defined in claim 23, further comprising the step of installing the circulator with a rotor shaft in a substantially horizontal orientation. 31. A method as defined in claim 23, further comprising the step of installing the circulator with a rotor shaft in a substantially vertical orientation. 32. A method as defined in claim 31, wherein the locating step includes locating both of the second and third backup bearings in a sealed chamber positioned proximate the bottom of the rotor shaft. 33. A method as defined in claim 32, wherein each providing step includes providing an antifriction backup bearing. 34. A nuclear reactor system, comprising: 35. A nuclear reactor system as defined in claim 34, wherein the rotor shaft has a substantially vertical orientation. 36. A nuclear reactor system as defined in claim 35, wherein the second radial backup bearing and the axial backup bearing are located within a sealed chamber. 37. A nuclear reactor system as defined in claim 36, wherein the first radial backup bearing includes a graphite bushing mounted on the stator, wherein the second radial backup bearing is an antifriction bearing, and wherein the axial backup bearing is an antifriction bearing. 38. A nuclear reactor system as defined in claim 37, wherein the first radial backup bearing further includes a metal sleeve mounted on the rotor shaft. 39. A nuclear reactor system as defined in claim 34, further comprising control means for controlling the active magnetic bearings to adjust the position of the rotor. 40. A nuclear reactor system as defined in claim 39, wherein the control means includes means for suppressing rotor vibrations. 41. A nuclear reactor system as defined in claim 34, wherein the active magnetic bearings include windings and wherein the windings are sealed off from the gas coolant. 42. A method for operating a nuclear reactor, comprising the steps of: 43. A method as defined in claim 42, wherein the pumping step includes pumping a gas coolant through the nuclear reactor. 44. A method as defined in claim 42, wherein the pumping step includes pumping the coolant with an electrically driven pump. 45. A method as defined in claim 42, wherein the pumping step includes pumping the coolant with a pump having a substantially vertical shaft. 46. A method as defined in claim 42, wherein the pumping step includes pumping the coolant with a pump having a substantially horizontal shaft. 47. A method as defined in claim 42, further comprising the step of introducing a lubricant into the chamber. 48. A method as defined in claim 47, wherein the introducing step includes introducing a solid lubricant into the chamber. 49. A method as defined in claim 47, wherein the introducing step includes introducing a liquid lubricant into the chamber. 50. A method as defined in claim 42, wherein the providing and enclosing steps are performed within a primary system pressure boundary for the nuclear reactor. 51. A method as defined in claim 42, wherein each active magnetic bearing includes a stator, further comprising the step of sealing off the stators of the active magnetic bearings from the coolant.
052271285	description	DESCRIPTION OF THE PREFERRED EMBODIMENT(S) Illustrated schematically in FIG. 1 is an exemplary boiling water reactor (BWR) 10 which includes a reactor pressure vessel 12 partially filled with a liquid coolant, or water, 14 which is suitably recirculated through the pressure vessel 12 and upwardly through a reactor core 16 therein. The core 16 includes a plurality of vertically extending fuel assemblies or bundles 18 which are conventionally effective for the heating coolant 14 to generate steam which is discharged from the pressure vessel 12 for powering a conventional steam turbine-generator (not shown), for example. As shown in more particularity in FIGS. 2 and 3, each of the fuel assemblies 18 includes a first, or upper tie plate 20 spaced vertically or longitudinally from a second, or lower tie plate 22, and parallel thereto. In this exemplary embodiment, the tie plates 20, 22 are generally square in configuration and support therebetween a plurality of laterally spaced apart nuclear fuel rods 24 which extend longitudinally therebetween and are joined thereto. As shown in FIG. 3, the fuel rods 24 are disposed in a conventional 4.times.4 matrix for example, with any other suitable matrix also being usable. In accordance with one feature of the present invention, a plurality of laterally spaced apart hollow control rods or tubes 26 extend longitudinally between the upper and lower tie plates 20, 22 and are joined thereto as described in more detail below. As shown in FIG. 3, the control rods 26 are laterally spaced apart from each other in a 3.times.3 matrix, for example with each control rod 26 being disposed equidistantly at the center between four adjacent ones of the fuel rods 24. The number of control rods 26 and their spacing in the fuel bundle 18 may be conventionally selected for suitably shaping the reactivity of the fuel rods 24 during operation. The lower tie plate 22 includes a lower manifold 28 therein which is suitably joined in flow communication with all of the control rods 26 at their lower ends. A generally closed reservoir 30 is disposed below the lower tie plate 22 and fixedly joined thereto in flow communication with the lower manifold 28 by a transfer tube 32 and contains a conventional neutron absorbing control liquid 34. The reservoir 30 is fixedly joined at its upper end to the lower tie plate 22 by the transfer tube 32 so that it is removable from the reactor core 16 as a unit together with the fuel assembly 18 when the fuel assembly 18 is removed therefrom. Means shown generally at 36 are provided for pumping the control liquid 34 from the reservoir 30 through the lower manifold 28 and into the control rods 26 for selectively varying the level L of the control liquid 34 in the control rods 26 for correspondingly varying the reactivity of the fuel rods 24. The control liquid 34 may be any conventional neutron absorber or poison such as mercury or sodium pentaborate in a water solution which is effective for absorbing neutrons from the fuel rods 24 during operation in substantially the same manner as conventional solid control rods. By varying the level L of the control liquid 34 in the several control rods 26 simultaneously, a maximum amount of neutrons may be absorbed by the control liquid 34 as it fills the control rods 26 to a maximum level L.sub.max at about the same elevation as the top of the fuel rods 24, and a minimum amount, or substantially no neutrons are absorbed, when the level L is lowered down to the lower tie plate 22 at the bottom ends of the fuel rods 24. The level L of the control liquid 24 may also be selectively disposed at intermediate positions therebetween as desired. In this way, the level L of the control liquid 34 is used to control reactivity of the fuel rods 24 in a manner similar to the amount of insertion of conventional solid control rods in a nuclear reactor core. A significant advantage of the present invention is that the fuel assembly 18 includes a closed system for the control liquid 34 as an integral part thereof so that each individual fuel assembly 18 may be separately removed from the reactor core 16 as required for replacement or reversal as described in more detail below. Since the control liquid 34 is contained in such a closed system, additional piping or connections are not required for its operation, and, therefore, they need not be disassembled in order to allow the fuel assembly 18 to be removed from the core 16. As shown in FIG. 2, the fuel assembly 18 preferably further includes a lower housing 38 fixedly or interrally joined to the lower tie plate 22 and surrounding the reservoir 30. The housing 38 extends downwardly from the lower tie plate 22 and past the reservoir 30, and includes a lower nosepiece 40 for channeling the coolant 14 into the lower housing 38 and around the reservoir 30. As shown in FIGS. 2 and 4, the lower nosepiece 40 is generally conical in configuration and is sized for insertion into a complementary aperture or seat 42 extending vertically through a lower core plate 16a of the reactor core 16 which is disposed at the bottom of the core 16 below an upper core plate 16b disposed at the top of the core 16. As shown in more particularity in FIG. 4, the lower nosepiece 40 includes a central hub 44 having three equiangularly spaced apart spokes or ribs 46 extending outwardly therefrom which are integrally formed with the lower housing 38. The spaced apart ribs 46 allow the coolant 14 to enter the lower nosepiece 40 through the seat 42 for flow upwardly inside the lower housing 38. The lower tie plate 22 as shown in FIGS. 2 and 5 includes a plurality of laterally spaced apart inlets 48 extending therethrough at respective ones of the fuel rods 24, and disposed in flow communication with the inside of the housing 38 for channeling the coolant 14 received from the lower nosepiece 40 through the lower tie plate 22 and upwardly therefrom along the several fuel rods 24. The coolant 14 is, therefore, allowed to flow upwardly through the lower tie plate 22 and around each of the fuel rods 24 to provide cooling thereof. As shown in more particularity in FIGS. 5 and 6, each of the inlets 48 includes an enlarged portion, or counterbore 48a into which the lower end 24a of an individual fuel rod 24 may be seated. In order to allow the coolant 14 to flow upwardly through the inlet 48 and past the fuel rod lower end 24a, the lower end 24a includes three radially extending and equiangularly spaced apart grooves 50 which extend therein longitudinally through the counterbore 48a and suitably upwardly therepast for providing a continuous flowpath upwardly through the lower tie plate 22 for channeling the coolant 14. Accordingly, the lower tie plate 22 has a generally checkerboard configuration for mounting the spaced apart fuel rods 24, while allowing the lower manifold 28 to extend between adjacent fuel rods 24 for channeling the control liquid 34 to the spaced apart control rods 26 also mounted thereto. This is best shown in FIG. 3, and may be manufactured using conventional casting techniques. In order to effectively seal the control liquid 34 within the housing 30 while allowing pumping thereof, a conventional, metal lower bellows 52 is disposed inside the reservoir 30 as shown in more particularity in FIG. 7 in flow communication with the lower manifold 28. The lower bellows 52 includes a flat top 52a disposed against the inside surface of the top of the reservoir 30 and in flow communication with the transfer tube 32 by being suitably welded thereto, for example. The bellows 52 further includes a flat, imperforate bottom 52b spaced below the top 52a, and a corrugated, annular side wall 52c which is also imperforate and extends integrally between the bellows top 52a and bottom 52b for containing the control liquid 34 therein without leaking therefrom upon elastic compression of the bellows side wall 52c during operation. More specifically, the bellows 52 is suitably compressed for pumping the control liquid 34 upwardly through the transfer tube 32 and into the lower manifold 28 for raising the level L of the control liquid 34 in the control rods 26. The bellows 52 may be compressed by any suitable means including pneumatic or hydraulic pressure, or by a suitable driven piston 54 disposed inside the reservoir 30 and adjacent to the bellows 52 as shown in the exemplary embodiment illustrated in FIG. 7. The piston 54 is selectively translatable upwardly, inside the reservoir 30 for selectively compressing the bellows 52 to pump the control liquid 34 into the lower manifold 28, or downwardly for allowing the bellows 52 to uncompress for allowing gravity to return the control liquid 34 back into the bellows 52 within the reservoir 30. Referring to FIGS. 1, 2 and 7, the pumping means 36 in this exemplary embodiment includes a conventional actuator 56 having a selectively extendable, elongate plunger or rod 58 positionable through an aperture 60 in the lower nosepiece 40 and into the reservoir 30, and joined to the piston 54 in abutting contact therewith, for example. Alternatively, the rod 58 may be fixedly joined to the piston 54. As shown in phantom in FIG. 7, when the plunger 58 is fully withdrawn, the piston 54 is disposed at the bottom of the reservoir 30, and the bellows 52 is uncompressed and has its maximum volume which receives the control liquid 34 from all of the several control rods 26 to lower the control liquid 34 to its minimum level. In order to raise the level L of the control liquid 34 in the control rod 26, the actuator 56 is actuated for extending the plunger 58 upwardly inside the reservoir 30 for translating upwardly the piston 54 as shown in solid line in FIG. 7 to selectively compress the lower bellows 52 to pump the control liquid 34 into the control rods 26 to correspondingly raise the level L thereof. The actuator 56 may be any conventional actuator powered pneumatically, hydraulically, or electrically for suitably extending and retracting the plunger 58. The actuators 56 as shown in FIG. 1 are preferably disposed entirely inside the reactor pressure vessel 12 below the reactor core 16, with the only penetration of the pressure vessel 12 being suitable conduits 62 for powering the actuators 56. The seals therefore required for the conduits 62 extending through the pressure vessel 12 are simpler than those which would be required for sealing the translatable plunger 58 if the actuators 56 were instead mounted outside the pressure vessel 12 below the lower head thereof. Referring again to FIG. 7, the reservoir 30 is preferably spaced radially inwardly from the side wall of the housing 38 to define therebetween an annular metering orifice 64 for suitably metering flow of the coolant 14 from the lower nosepiece 40 and to the lower tie plate inlets 48. Furthermore, the reservoir 30 is spaced longitudinally below the lower tie plate 22 to define therebetween an access channel 66 for allowing the coolant 14 to flow upwardly from the metering orifice 64 around the reservoir 30 and into the lower tie plate inlets 48. The transfer tube 32 allows the reservoir 30 to be spaced from the lower tie plate 22 while still providing flow communication between the lower bellows 52 and the lower manifold 28 for channeling the control liquid 34 therebetween. Referring again to FIG. 2, each of the fuel assemblies 18 is preferably top-and-bottom symmetrical as shown for being functionally reversible in the reactor core 16 so that after an initial burn cycle of the fuel rods 24, the fuel bundles 18 may be removed from the core 16, turned upside down and reinstalled into the core 16 for further operation for another portion of the burn cycle. By configuring the fuel bundles 18 to be symmetrical, the control liquid 34 in the control rods 26 may be identically varied. More specifically, the upper tie plate 20 is configured identically to the lower tie plate 22 and similarly includes an upper manifold 28u joined in flow communication with an upper reservoir 30u through an upper transfer tube 32u. Disposed inside the upper reservoir 30u is a corresponding upper bellows 52u, with a corresponding upper piston 54u being disposed thereabove. An upper housing 38u surrounds the upper reservoir 30u and is formed integrally with the upper tie plate 20, and includes an upper nosepiece 40u extending upwardly therefrom. The upper nosepiece 40 u may serve as the lifting bail for withdrawing from and inserting into the reactor core 16 the fuel assembly 18. The fuel assembly 18 need not be top-and-bottom symmetrical with the upper bellows 52u and related components, but may have the control rods 26 simply ending in the upper tie plates 20. The control rods 26 may be simply initially evacuated, to allow the level L of the control liquid 34 to be selectively varied within the control rods 26. Alternatively, the control rods 26 may include a conventional inert gas such as nitrogen which is compressed into the tops of the control rods 26 as the control fluid 34 is pumped into the control rods 26. As shown in FIG. 2, the symmetrical fuel assembly 18 may be similarly operated with either the upper bellows 52u being evacuated, or containing an inert gas, and being effective for providing a reservoir for containing excess control fluid 34 pumped upwardly therein upon compression of the lower bellows 52. In the exemplary embodiment illustrated in FIG. 2, the control rods 26 preferably include a non-neutron absorbing displacable fluid 68 which is displacable upwardly from the control rods 26 as the control liquid 34 is pumped therein. As described above, the displacable fluid 68 may be an inert gas such as nitrogen, or a gas moderator such as hydrogen or ammonia, or preferably a liquid nuclear moderator such as water or Deuterium based water. For the displacable fluid 68 in liquid form illustrated in FIG. 2, it is preferably immiscible with the control liquid 34 to prevent the mixing thereof and ensure the proper functioning of the control liquid 34. As a liquid moderator, the displacing fluid 68 is effective for moderating neutrons emitted from the fuel rods 26 for slowing the neutrons to thermal neutron energy levels for increasing reactivity of the core 16. Accordingly, with the control liquid 34 pumped into the control rods 26, neutrons from the fuel rods 24 will be absorbed, whereas when the control liquid 34 is removed from the control rods 26 and replaced by the liquid moderator 68, the neutrons from the fuel rods 24 will be slowed and thus moderated. The upper bellows 52u, therefore, is effective for storing the liquid moderator 68 upon displacement thereof from the control rods 26 by the control liquid 34 pumped therein. Accordingly, a completely contained closed system for the control liquid 34 is provided in each fuel assembly 18. The control rods 26 are arranged in a suitable between the fuel rods 24 to distribute the neutron absorbing control liquid 34 in the most efficient manner to avoid flux peaking in the fuel rods 24 and approach the ideal condition of completely homogeneous distribution. Furthermore, the control rods 26 are suitably and permanently sealed, by welding for example, into the lower and upper manifolds 28, 28u at both ends thereof, and are integral with the upper and lower tie plates 20, 22 in the preferred embodiment. The control liquid containment system is, therefore, removable along with each fuel assembly 18 without the need to disconnect any fluid carrying conduits thereto. The components for carrying the control liquid 34 may be made of any suitable and conventional material such as Zircaloy, stainless steel and/or inconel, which have material properties suitable for the lifetime of a fuel assembly in the nuclear reactor 10. Suitable techniques may be used to ensure that the bellows 52, 52u and the control rods 26 have not ruptured and developed leaks. For example, periodic sampling of the coolant 14 may be performed to test for any leaking control liquid 34. Alternatively, a reduction in the mechanical load required to displace the lower bellows 52 upwardly may be used to infer a rupture of the lower bellows 52 or significant leak of the control liquid 34 from the system since resistance to translation upwardly of the bellows 52 in a normal system increases relative thereto. While there have been described herein what are considered to be preferred embodiments of the present invention, other modifications of the invention shall be apparent to those skilled in the art from the teachings herein, and it is, therefore, desired to be secured in the appended claims all such modifications as fall within the true spirit and scope of the invention.
	summary
	abstract	Method of three-dimensional image reconstruction and transmission electron microscope capable of producing three-dimensional images. When a TEM image is taken at each tilt angle of a specimen, the amount of defocus Δf is switched to plural amounts Δf1, Δf2, and Δf3, in turn. When a three-dimensional image is reconstructed, image data stored in the image memory is sent to a CRT. TEM images acquired with the amounts Δf1, Δf2, and Δf3 are displayed on the CRT. One optimum TEM image is selected at each tilt angle of the specimen. A three-dimensional image reconstruction circuit reconstructs a three-dimensional image based on the selected TEM images.
	description	This application is a continuation of U.S. application Ser. No. 13/885,582, which was the National Stage of International Application No. PCT/IB10/02914, filed Nov. 15, 2010. Nuclear reactors generate energy from a nuclear chain reaction (i.e., nuclear fission) in which a free neutron is absorbed by the nucleus of a fissile atom in a nuclear fuel, such as Uranium-23 5 (235U). When the free neutron is absorbed, the fissile atom splits into lighter atoms, and releases more free neutrons to be absorbed by other fissile atoms, resulting in a nuclear chain reaction, as is well understood in the art. Thermal energy released from the nuclear chain reaction is converted into electrical energy through a number of other processes also well known to those skilled in the art. The advent of nuclear power reactors adapted to burn nuclear fuel having low fissile content levels (e.g., as low as that of natural uranium) has generated many new sources of burnable nuclear fuel. These sources include waste or recycled uranium from other reactors. This is not only attractive from a cost savings standpoint, but also based upon the ability to essentially recycle spent uranium back into the fuel cycle. Recycling spent nuclear fuel stands in stark contrast to disposal in valuable and limited nuclear waste containment facilities. For these and other reasons nuclear fuel and nuclear fuel processing technologies that support the practices of recycling nuclear fuel and burning such fuel in nuclear reactors continue to be welcome additions to the art. In some embodiments of the present invention, a fuel bundle for a nuclear reactor is provided, and comprises a plurality of fuel elements each including a first fuel component of recycled uranium; and a second fuel component of at least one of depleted uranium and natural uranium blended with the first fuel component, wherein the blended first and second fuel components have a first fissile content of less than 1.2 wt % of 235U. Some embodiments of the present invention provide a fuel bundle for a nuclear reactor, wherein the fuel bundle comprises a first fuel element including recycled uranium, the first fuel element having a first fissile content of no less than 0.72 wt % of 235U; and a second fuel element including at least one of depleted uranium and natural uranium, the second fuel element having a second fissile content of no greater than 0.71 wt % of 235U. In some embodiments, any of the fuel bundles and methods just described are utilized in a pressurized heavy water reactor, wherein the fuel bundles are located within one or more tubes of pressurized water that flow past the fuel bundles, absorb beat from the fuel bundles, and perform work downstream of the fuel bundles. Other aspects of the present invention will become apparent by consideration of the detailed description and accompanying drawings. Before any embodiments of the invention are explained in detail, it is to be understood that the invention is not limited in its application to the details of embodiment and the arrangement of components set forth in the following description or illustrated in the accompanying drawings. The invention is capable of other embodiments and of being practiced or of being carried out in various ways. A number of nuclear fuels according to various embodiments of the present invention are disclosed herein. These fuels can be used in a variety of nuclear reactors, and are described herein with reference to pressurized heavy water reactors. Such reactors can have, for example, pressurized horizontal or vertical tubes within which the fuel is positioned. An example of such a reactor is a Canadian Deuterium Uranium (CANDU) nuclear reactor, a portion of which is shown schematically in FIG. 5. Other types of reactors can have un-pressurized horizontal or vertical tubes with holes in them. Pressurized heavy water nuclear reactors are only one type of nuclear reactor in which various nuclear fuels of the present invention can be burned. Accordingly, such reactors are described herein by way of example only, it being understood that the various fuels of the present invention can be burned in other types of nuclear reactors. Similarly, the various fuels of the present invention described herein can be positioned in any form within a nuclear reactor for being burned. By way of example only, the fuel can be loaded into tubes or can be contained in other elongated forms (each of which are commonly called “pins” or “elements”, referred to herein only as “elements” for sake of simplicity). Examples of elements used in some embodiments of the present invention are indicated at 22 in FIGS. 1-4, and are described in greater detail below. In the case of fuel contained within tubes, the tubes can be made of or include zirconium, a zirconium alloy, or another suitable material or combination of materials that in some cases is characterized by low neutron absorption. Together, a plurality of elements can define a fuel bundle within the nuclear reactor. Such fuel bundles are indicated schematically at 14 in FIG. 5. The elements of each bundle 14 can extend parallel to one another in the bundle. If the reactor includes a plurality of fuel bundles 14, the bundles 14 can be placed end-to-end inside a pressure tube 18. In other types of reactors, the fuel bundles 14 can be arranged in other manners as desired. With continued reference to FIG. 5, when the reactor 10 is in operation, a heavy water coolant 26 flows over the fuel bundles 14 to cool the fuel elements and remove heat from the fission process. The nuclear fuels of the present invention are also applicable to pressure tube reactors with different combinations of liquids/gasses in their heat transport and moderator systems. In any case, coolant 26 absorbing heat from the nuclear fuel can transfer the heat to downstream equipment (e.g., a steam generator 30), to drive a prime mover (e.g., turbine 34) to produce electrical energy. Canadian Patent Application No. 2,174,983, filed on Apr. 25, 1996, describes examples of fuel bundles for a nuclear reactor that can comprise any of the nuclear fuels described herein. The contents of Canadian Patent Application No. 2,174,983 are incorporated herein by reference. The various nuclear fuels of the present invention can be used (e.g., blended) in conjunction within one or more other materials. Whether used alone or in combination with other materials, the nuclear fuel can be in pellet form, powder form, or in another suitable form or combination of forms. In some embodiments, fuels of the present invention take the form of a rod, such as a rod of the fuel pressed into a desired form, a rod of the fuel contained within a matrix of other material, and the like. Also, fuel elements made of the fuels according to the present invention can include a combination of tubes and rods and/or other types of elements. As described in greater detail below, fuels according to various embodiments of the present invention can include various combinations of nuclear fuels, such as depleted uranium (DU), natural uranium (NU), and reprocessed or recycled uranium (RU). As used herein and in the appended claims, references to “percentage” of constituent components of material included in nuclear fuel refers to percentage weight, unless specified otherwise. Also, as defined herein, DU has a fissile content of approximately 0.2 wt % to approximately 0.5 wt % of 235U (including approximately 0.2 wt % and approximately 0.5 wt %), NU has a fissile content of approximately 0.71 wt % of 235U, and RU has a fissile content of approximately 0.72 wt % to approximately 1.2 wt % of 235U (including approximately 0.72 wt % and approximately 1.2 wt %). Recycled Uranium Reprocessed or recycled uranium (RU) is manufactured from spent fuel created from nuclear power production using light water reactors (LWRs). A fraction of the spent fuel is made up of uranium. Therefore, chemical reprocessing of spent fuel leaves behind separated uranium, which is referred to in the industry as reprocessed or recycled uranium. Natural Uranium (NU) contains only the three isotopes 234U, 235U, and 238U. However, after irradiation in a LWR and cooling, the resulting RU has an isotopic composition different from natural uranium. In particular, RU includes four additional types of uranium isotopes that are not present in natural uranium: 236U and 232U, 233U, and 237U (generally considered impurities). Accordingly, the presence of these four additional isotopes can be considered a signature for RU. It should also be understood that the isotopic composition of RU is dependent on many factors, such as the initial 235U content in the fuel prior to irradiation (i.e., fresh fuel), the origin(s) of the fuel, the type of reactor in which the fuel was burned, the irradiation history of the fuel in the reactor (e.g., including burnup), and the cooling and storage periods of the fuel after irradiation. For example, most irradiated fuels are cooled for at least five years in specially engineered ponds to ensure radiological safety. However, the cooling period can be extended to 10 or 15 years or longer. RU often includes chemical impurities (e.g., Gadolinum) caused by fuel cladding, fuel doping, and separation and purification methods used on the RU. These chemical impurities can include very small quantities of transuranic isotopes, such as Plutonium-238 (238Pu), 239Pu, 240Pu, 241Pu, 242Pu, Neptunium-23 7 (237Np), Americium-241 (241A m), Curium-242 (242Cm) and fission products, such as Zirconium-95/Niobium-95 (95Zr/95Nb), Ruthenium-103 (103Ru), 106Ru, Cesium-134 (134Cs), 137Cs, and Technetium-99 (99Tc). Other impurities often present in RU include: Aluminum (Al), Boron (B), Cadmium (Cd), Calcium (Ca), Carbon (C), Chlorine (Cl), Chromium (Cr), Copper (Cu), Dysprosium (Dy), Flourine (F), Iron (Fe), Magnesium (Mg), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), Nitrogen (N), Phosphorous (P), Potassium (K), Silicon (Si), Sodium (Na), Sulphur (S), and Thorium (Th). Depleted Uranium As stated above, depleted uranium (DU) has a fissile content of approximately 0.2 wt % to approximately 0.5 wt % of 235U (including approximately 0.2 wt % and approximately 0.5 wt %). DU is uranium primarily composed of the isotopes Uranium-23 8 (238U) and Uranium-235 (235U). In comparison, natural uranium (NU) is approximately 99.28 wt % 238U, approximately 0.71 wt % 235U, and approximately 0.0054 wt % percent 234U. DU is a byproduct of uranium enrichment, and generally contains less than one third as much 235U and 234U as natural uranium. DU also includes various impurities, such as: Aluminum (Al), Boron (B), Cadmium (Cd), Calcium (Ca), Carbon (C), Chlorine (Cl), Chromium (Cr), Copper (Cu), Dysprosium (Dy), Flourine (F), Gadolinium (Gd), Iron (Fe), Magnesium (Mg), Manganese (Mn), Molybdenum (Mo), Nickel (Ni), Nitrogen (N), Phosphorous (P), Potassium (K), Silicon (Si), Sodium (Na), Sulphur (S), and Thorium (Th). Blended Fuel It will be appreciated that in many applications, the uranium content of many nuclear fuels is too high or too low to enable such fuels to be burned in a number of nuclear reactors. Similarly, the constituent components of RU (234U, 235U, 236U, and 238U) and the above-described impurities (232U, 233U, and 237U) typically found in RU can prevent RU from being a viable fuel in many reactors. However, the inventors have discovered that by blending RU with DU, the fissile content of 235U in the resulting nuclear fuel can be brought into a range that is acceptable for being burned as fresh fuel in many nuclear reactors, including without limitation pressurized heavy water nuclear reactors (e.g., pressurized heavy water nuclear reactors having horizontal fuel tubes, such as those in CANDU reactors). Similar results can be obtained by blending RU with NU to reduce the fissile content of 235U in the resulting nuclear fuel to an acceptable range for being burned as fresh fuel. Whether blended with DU or NU, RU can be blended using any method known in the art, such as but not limited to using an acid solution or dry mixing. In some embodiments, the nuclear reactor fuel of the present invention includes a first fuel component of RU and a second fuel component of DU that have been blended together to have a combined fissile content of less than 1.2 wt % of 235U. In such fuels, the RU can have a fissile content of approximately 0.72 wt % of 235U to approximately 1.2 wt % of 235U. In other embodiments, the RU in such fuels can have a fissile content of approximately 0.8 wt % of 235U to approximately 1.1 wt % of 235U. In other embodiments, the RU in such fuels can have a fissile content of approximately 0.9 wt % of 235U to approximately 1.0 wt % of 23SU. In still other embodiments, the RU in such fuels can have a fissile content of approximately 0.9 wt % of 235U. In each of these embodiments, the DU of such fuels can have a fissile content of approximately 0.2 wt % of 23SU to approximately 0.5 wt % of 235U. Accordingly, by blending lower 235U fissile content DU with the higher 235U fissile content RU, the resulting blended RU/DU nuclear fuel can have a fissile content of less than 1.0 wt % of 235U in some embodiments. In other embodiments, the resulting blended RU/DU nuclear fuel can have a fissile content of less than 0.8 wt % of 235U. In other embodiments, the resulting RU/DU nuclear fuel can have a fissile content of less than 0.72 wt % of 235U. In still other embodiments, the resulting RU/DU nuclear fuel can have a fissile content of approximately 0.71 wt % of 235U, thereby resulting in a natural uranium equivalent fuel generated by blending RU and DU. In some embodiments, the nuclear reactor fuel of the present invention includes a first fuel component of RU and a second fuel component of NU that have been blended together to have a combined fissile content of less than 1.2 wt % of 235U. In such fuels, the RU can have a fissile content of approximately 0.72 wt % of 235U to approximately 1.2 wt % of 235U. In other embodiments, the RU in such fuels can have a fissile content of approximately 0.8 wt % of 235U to approximately 1.1 wt % of 235U. In other embodiments, the RU in such fuels can have a fissile content of approximately 0.9 wt % of 235U to approximately 1.0 wt % of 235U. In still other embodiments, the RU in such fuels can have a fissile content of approximately 0.9 wt % of 235U. Accordingly, by blending lower 235U fissile content NU with the higher 235U fissile content RU, the resulting blended RU/NU nuclear fuel can have a fissile content of less than 1.0 wt % of 235U in some embodiments. In other embodiments, the resulting blended RU/DU nuclear fuel can have a fissile content of less than 0.8 wt % of 235U. In other embodiments, the resulting RU/NU nuclear fuel can have a fissile content of less than 0.72 wt % of 235U. In still other embodiments, the resulting RU/NU nuclear fuel can have a fissile content of approximately 0.71 wt % of 235U, thereby resulting in a natural uranium equivalent fuel generated by blending RU and NU. In some embodiments, RU is blended with both DU and NU to produce fuels having the same 235U fissile contents or content ranges described above in connection with blended RU/DU and blended RU/NU nuclear fuels. In such cases, the 235U fissile contents and content ranges of RU, and the 235U fissile contents and content ranges of DU can be the same as those described above. The nuclear fuels according to the various embodiments of the present invention can include a burnable poison (BP). For example, any of the nuclear fuels described herein can include a blend of RU and DU with a burnable poison (BP), or a blend of RU and NU with a burnable poison (BP). The burnable poison can be blended with the various RU/DU blends, RU/NU blends, and RU/DU/NU blends described herein. Fuel Bundle Constructions Nuclear fuel blending (as described above) is a powerful manner of producing fresh nuclear fuels from otherwise unusable RU. However, such blending is only one technique by which RU can be utilized for burning in many types of reactors, including pressurized heavy water reactors. In many applications, the blended RU fuels described herein can be used with great efficiency in fuel bundles depending at least in part upon the locations of such blended fuels in the fuel bundles. Also, RU can even be successfully utilized in fuel bundles without necessarily being blended as described above. Instead, when RU is included in particular locations in a fuel bundle, has certain 235U fissile contents, and/or is used with targeted combinations of DU and/or NU, the resulting fuel bundle has highly desirable characteristics. These characteristics include greater fuel burnup control and low coolant void reactivity (described below), FIGS. 1-4 illustrate various embodiments of a nuclear fuel bundle for use in a nuclear reactor, such as the pressurized heavy water reactor 10 shown schematically in FIG. 5. In particular, each of FIGS. 1-4 illustrates a cross-sectional view of a number of embodiments of a fuel bundle 14 positioned in a pressure tube 18. The fuel arrangements illustrated in each of FIGS. 1-4 are provided by way of example, it being understood that other fuel arrangements within the fuel bundles of FIGS. 1-4 are possible, and fall within the spirit and scope of the present invention. It should also be noted that the characteristics (including 235U fissile contents and 235U fissile content ranges) of the various fuels described in connection with FIGS. 1-4 below (RU, DU, NU, RU/DU blends, RU/NU blends, and RU/DU/NU blends) are provided above. Heavy water coolant 26 is contained within the pressure tube 18, and occupies subchannels between the fuel elements 22 of the fuel bundle 14. The fuel elements 22 can include a central element 38, a first plurality of elements 42 positioned radially outward from the central element 38, a second plurality of elements 46 positioned radially outward from the first plurality of elements 42, and a third plurality of elements 50 positioned radially outward from the second plurality of elements 46. It should be understood that in other embodiments, the fuel bundle 14 can include fewer or more elements, and can include elements in configurations other than those illustrated in FIGS. 1-4. For example, the fuel elements 22 can be positioned parallel to one another in one or more planes, elements arranged in a matrix or array having a block shape or any other cross-sectional shape, and elements in any other patterned or patternless configuration. The pressure tube 18, the fuel bundle 14, and/or the fuel elements 22 can also be configured in various shapes and sizes. For example, the pressure tubes 18, fuel bundles 14, and fuel elements 22 can have any cross-sectional shapes (other than the round shapes shown in FIGS. 1-5) and sizes desired. As another example, the fuel elements 22 within each fuel bundle 14 can have any relative sizes (other than the uniform size or two-size versions of the fuel elements 22 shown in FIGS. 1-4). In the embodiments of FIGS. 1 and 2, a 37-element fuel bundle is illustrated in which all of the fuel elements 22 have a uniform cross-sectional size (or diameter, in the case of elements having a round cross-sectional shape). The first plurality of elements 42 in each of FIGS. 1 and 2 includes six elements arranged in parallel with one another in a generally circular pattern. The second plurality of elements 46 in each of FIGS. 1 and 2 includes twelve elements also arranged in parallel with one another in a generally circular pattern. The third plurality of elements 50 in each of FIGS. 1 and 2 includes eighteen elements also arranged in parallel with one another in a generally circular pattern. The central element 38, the first plurality of elements 42, the second plurality of elements 46, and the third plurality of elements 50 are arranged concentrically such that all of the elements 22 are in parallel with one another. It should be understood that the lines included in FIGS. 1 and 2 indicating the generally circular position of the elements 22 is for illustration purposes only, and does not necessarily indicate that elements 22 are tethered together or otherwise coupled in a particular arrangement. In the embodiments of FIGS. 3 and 4, a 43-element fuel bundle 14 is illustrated. The first plurality of elements 42 in each of FIGS. 3 and 4 includes seven elements arranged in parallel with one another in a generally circular pattern. The second plurality of elements 46 in each of FIGS. 3 and 4 includes fourteen elements arranged in parallel with one another in a generally circular pattern. The third plurality of elements 50 in each of FIGS. 3 and 4 includes twenty-one elements arranged in parallel with one another in a generally circular pattern. The central element 38, the first plurality of elements 42, the second plurality of elements 46, and the third plurality of elements 50 are arranged concentrically such that all of the elements 22 are in parallel with one another. The central element 38 and each of the first plurality of elements 42 have a first cross-sectional size (or diameter, in the case of elements having a round cross-sectional shape), and each of the second plurality 46 and third plurality 50 of elements have a second cross-sectional size (or diameter, in the case of elements having a round cross-sectional shape) different from the first cross-sectional size. In particular, the first cross-sectional size is greater than the second cross-sectional size. In this regard, the term “cross-sectional shape” refers to the cross-sectional shape generated by a plane passing through the body referred to in an orientation that is perpendicular to a longitudinal axis of the body. It should also be understood that the lines included in FIGS. 3 and 4 indicating the generally circular position of the elements 22 is for illustration purposes only and does not necessarily indicate that elements are tethered together or otherwise coupled in a particular arrangement. In some embodiments, each of the fuel elements 22 of FIGS. 1-4 includes a tube filled with nuclear fuel. The tube can be made of or include zirconium, a zirconium alloy, or another suitable material or combination of materials that in some cases is characterized by low neutron absorption. The tube can be filled with one or more materials, such as nuclear fuel alone or in combination with other materials. The material(s) can be in pellet form, powder form, or in another suitable form or combination of forms. In other embodiments, each of the fuel elements 22 includes a rod formed from one or more materials (e.g., nuclear fuel alone or in combination with other materials), such as nuclear fuel contained within a matrix of other material. Also, in some embodiments, the fuel elements 22 in a bundle 14 can include a combination of tubes and rods and/or other fuel-containing elements, and the fuel elements 22 can take on other configurations suitable for the particular application. As shown in FIGS. 1-4, the fuel elements 22 can include various combinations of nuclear fuels, such as depleted uranium (DU), natural uranium (NU), and reprocessed or recycled uranium (RU). With reference first to FIG. 1, the fuel bundle 14 illustrated therein includes 37 elements. The central element 38 of FIG. 1 includes a blend of RU and DU having a first fissile content (i.e., (RU/DU)1) and/or a blend of DU and a burnable poison (BP) and/or DU. As described above, a blend (generally designated herein by the use of a slash “/” herein) of materials can be created using any method known in the art, such as but not limited to using an acid solution or dry mixing of the subject materials. Returning to FIG. 1, the first plurality of elements 42 includes a blend of RU and DU having a second fissile content (i.e., (RU/DU)2). The second plurality of elements 46 includes a blend of RU and DU having a third fissile content (i.e., (RU/DU)3) and/or NU having a first fissile content (i.e., NU1). The third plurality of elements 50 includes a blend of RU and DU having a fourth fissile content (i.e., (RU/DU)4) and/or NU having a second fissile content (i.e., NU2). In the embodiments illustrated in FIG. 1, (as well as those of other figures of the present application), materials that have been blended together are referred to with a slash “/”. However, in each such case, alternative fuel arrangements for such elements include the use of fuel elements 22 each having only one of the fuels noted, but used in combination with fuel elements 22 having the other fuel noted. The use of such elements 22 of different fuel types (e.g., in the same ring of elements 22) can be provided in place of or in addition to elements 22 having a blend of fuel types as described above. For example, the ring of (RU/DU)2 elements 22 in FIG. 1 indicates that each illustrated element 22 in the first plurality of elements 36 is a blend of RU and DU. However, alternatively or in addition, the first plurality of elements 36 can instead include one or more elements of RU and one or more elements of DU. The resulting fuel elements 22 containing RU or DU can be arranged in various configurations, such as in an alternating pattern with changing circumferential position about the fuel bundle 14. In some embodiments, the 235U fissile content of the RU/DU blends included in the fuel bundle 14 of FIG. 1 are approximately the same (from ring to ring, or with changing radial distance from the center of the fuel bundle 14). In other embodiments, the 235U fissile content of the RU/DU blends included in the fuel bundle 14 change from ring to ring, or with changing radial distance from the center of the fuel bundle 14. For example, the RU/DU blend included in at least one of the central element 38, the first plurality of elements 42, the second plurality of elements 46, and the third plurality of elements 50 in FIG. 1 can have a fissile content different than a fissile content of a blend included in one or more of the other elements. In some embodiments, an (RU/DU)1 blend included in the central element 38 of FIG. 1 generally has a lower percentage of 235U than the (RU/DU)2 blend included in the first plurality of elements 42, the (RU/DU)2 blend included in the first plurality of elements 42 generally has a lower percentage of 235U than any (RU/DU)3 blend included in the second plurality of elements 46, and any (RU/DU)3 blend included in the second plurality of elements 46 generally has a lower percentage of 235U than any (RU/DU)4 blend included in the third plurality of elements 50. Therefore, the 235U fissile content of the nuclear fuel included in the fuel bundle 14 can increase in an outward radial direction from the center of the fuel bundle 14. In other embodiments, however, the 235U fissile content decreases in an outward radial direction from the center of the fuel bundle 14. Similarly, the fissile content of any NU used in the embodiments of FIG. 1 can be approximately the same or varied with changing distance from the center of the fuel bundle 14. For example, any NU1 included in the second plurality of elements 46 can generally have a lower percentage of 235U than any NU2 included in the third plurality of elements 50. Alternatively, any NU2 included in the third plurality of elements 50 can generally have a lower percentage of 235U than any NU1 included in the second plurality of elements 46. Furthermore, in some embodiments, the particular fissile content of a particular fuel element 22 can be varied throughout one or more of the plurality of elements 42, 46, and 50 (e.g., in a circumferential direction within the fuel bundle 14) or along the longitudinal length of the fuel bundle 14. Also, a BP can be included in any or all of the fuel elements 22 of FIG. 1, such as in the center element 38 as illustrated. The following fuel bundle arrangements are based upon the fuel bundle embodiments illustrated in FIG. 1, and are presented as examples of fuel bundles having particularly desirable characteristics, but are not to be considered limiting to the scope of the present invention or the other possible embodiments contemplated by FIG. 1. As used herein, the term “ring” includes a center element alone. Center element: RU/DU 1st ring of elements 42: RU/DU 2nd ring of elements 46: RU/DU 3rd ring of elements 50: RU/DU Center element: (RU/DU)1 1st ring of elements 42: (RU/DU)2 2nd ring of elements 46: (RU/DU)3 3rd ring of elements 50: (RU/DU)4 Wherein (RU/DU)2 has a 235U fissile content greater than that of (RU/DU)1, (RU/DU)3 has a 23SU fissile content greater than that of (RU/DU)1 and/or (RU/DU)2, and/or wherein (RU/DU)4 has a 235U fissile content greater than that of (RU/DU)1, (RU/DU)2, and/or (RU/DU)3. Center element: (RU/DU)1 1st ring of elements 42: (RU/DU)2 2nd ring of elements 46: (RU/DU)3 3rd ring of elements 50: NU Wherein (RU/DU)2 has a 235U fissile content greater than that of (RU/DU)1, and wherein (RU/DU)3 has a 235U fissile content greater than that of (RU/DU)1 and/or (RU/DU)2. Center element: (RU/DU)1 1st ring of elements 42: (RU/DU)2 2nd ring of elements 46: NU 3rd ring of elements 50: (RU/DU)3 Wherein (RU/DU)2 has a 235U fissile content greater than that of (RU/DU)1, and wherein (RU/DU)3 has a 235U fissile content greater than that of (RU/DU)1 and/or (RU/DU)2. Center element: (RU/DU)1 1st ring of elements 42: (RU/DU)2 2nd ring of elements 46: NU 3rd ring of elements 50: NU Wherein (RU/DU)2 has a 235U fissile content greater than that of (RU/DU)1 FIG. 2 illustrates another embodiment of a 37-element fuel bundle 14. The central element 38 of FIG. 2 includes RU having a first fissile content (i.e., RU1) and/or DU having a first fissile content (i.e., DU1). The first plurality of elements 42 of FIG. 2 includes RU having a second fissile content (i.e., RU2) and/or DU having a second fissile content (i.e., DU2). The second plurality of elements 46 includes RU having a third fissile content (i.e., RU3). The third plurality of elements 50 includes RU having a fourth fissile content (i.e., RU4). The 235U fissile contents of the RU included in each fuel element 22 can be approximately the same and/or can be varied. In those embodiments where the 235U fissile content of the RU in FIG. 2 varies, this change can be with radial distance from the center of the fuel bundle and/or with circumferential position within the fuel bundle 14, and can exist between any or all of the rings shown in FIG. 2, and/or between any or all circumferential positions of any ring. For example, in some embodiments, the RU1 included in the central element 38 generally has a lower percentage of 235U than the RU2 included in the first plurality of elements 42, the RU2 blend included in the first plurality of elements 42 generally has a lower percentage of 235U than the RU3 included in the second plurality of elements 46, and/or the RU3 included in the second plurality of elements 46 generally has a lower percentage of 235U than the RU4 included in the third plurality of elements 50. Therefore, in some embodiments, the 235U fissile content of nuclear fuel of the fuel bundle 14 increases in an outward radial direction from the center of the fuel bundle 14. However, in other embodiments, the 235U fissile content decreases in an outward radial direction from the center of the fuel bundle 14. It is to be understood that even when the fissile content of RU included in the fuel bundle 14 of FIG. 2 is varied in any of the manners described above, each fuel element 22 still has a 235U fissile content generally between and including approximately 0.72 wt % to approximately 1.2 wt % of 235U. By way of example only, the fissile content of the RU1 included in the central element 38 is chosen from the range defined above for RU, and the fissile content of the RU2 included in the first plurality of elements 42 is also chosen from the same range defined, but can be different from the fissile content chosen for the central element 38. Similarly, the fissile content of any DU used in the embodiments of FIG. 2 can be approximately the same or varied—either with radial distance from the center of the fuel bundle 14 or with change in circumferential position within the fuel bundle 14. Again by way of example only, any DU1 included in the central element 38 can generally have a lower percentage of 235U than any DU2 included in the second plurality of elements 42. Alternatively, any DU2 included in the second plurality of elements 42 can generally have a lower percentage of 235U than any DU1 included in the central element 38. Furthermore, in some embodiments, the particular fissile content of a particular fuel element 22 can be varied throughout one or more of the plurality of elements 42, 46, and 50 (e.g., in a circumferential direction within the fuel bundle 14) or along the longitudinal length of the fuel bundle 14. Also, a BP can be included in any or all of the fuel elements 22 of FIG. 2. The following fuel bundle 14 arrangement is based upon the fuel bundle embodiments illustrated in FIG. 2, and is presented as an example of a fuel bundle 14 having particularly desirable characteristics, but is not to be considered limiting to the scope of the present invention or the other possible embodiments contemplated by FIG. 2. As used herein, the term “ring” includes a center element alone. Center element: DU1 1st ring of elements 42: DU2 2nd ring of elements 46: RU1 3rd ring of elements 50: RU2 Wherein DU2 has a 235U fissile content greater than that of DU1, and wherein RU2 has a 235U fissile content greater than that of RU1. The embodiments of FIG. 3 are substantially similar to the embodiments of FIG. 1 described above, except that the fuel bundle 14 is a 43-element fuel bundle, and has non-uniformly sized fuel elements 22, as described above. Since the distribution of nuclear fuel in the central, first, second, and third pluralities of elements 38, 42, 46, and 50, respectively, is similar to FIG. 1, reference is hereby made to the description accompanying FIG. 1 above for more detail regarding the embodiments (and possible alternatives thereto) shown in FIG. 3. The following fuel bundle arrangements are based upon the fuel bundle embodiments illustrated in FIG. 3, and are presented as examples of fuel bundles having particularly desirable characteristics, but are not to be considered limiting to the scope of the present invention or the other possible embodiments contemplated by FIG. 3. As used herein, the term “ring” includes a center element alone. Center element: RU/DU 1st ring of elements 42: RU/DU 2nd ring of elements 46: RU/DU 3rd ring of elements 50: RU/DU Center element: RU/DU 1st ring of elements 42: RU/DU 2nd ring of elements 46: RU/DU 3rd ring of elements 50: NU Center element: RU/DU 1st ring of elements 42: RU/DU 2nd ring of elements 46: NU 3rd ring of elements 50: RU/DU Center element: DU/BP 1st ring of elements 42: (RU/DU)1 2nd ring of elements 46: (RU/DU)2 3rd ring of elements 50: (RU/DU)3 Wherein (RU/DU)2 has a 235U fissile content greater than that of (RU/DU)1, and wherein (RU/DU)3 has a 235U fissile content greater than that of (RU/DU)2 and/or (RU/DU)1. Center element: DU 1st ring of elements 42: (RU/DU)1 2nd ring of elements 46: (RU/DU)2 3rd ring of elements 50: (RU/DU)3 Wherein (RU/DU)2 has a 235U fissile content greater than that of (RU/DU)1, and wherein (RU/DU)3 has a 235U fissile content greater than that of (RU/DU)2 and/or (RU/DU)1. Center element: DU/BP 1st ring of elements 42: (RU/DU)1 2nd ring of elements 46: (RU/DU)2 3rd ring of elements 50: NU Wherein (RU/DU)2 has a 235U fissile content greater than that of (RU/DU)1. Center element: DU/BP 1st ring of elements 42: (RU/DU)1 2nd ring of elements 46: NU 3rd ring of elements 50: (RU/DU)2 Wherein (RU/DU)2 has a 235U fissile content greater than that of (RU/DU)1. The embodiment of FIG. 4 is substantially similar to the embodiment of FIG. 2 described above, except that the fuel bundle 14 is a 43-element fuel bundle, and has non-uniformly sized fuel elements 22, as described above. Since the distribution of nuclear fuel in the central, first, second, and third pluralities of elements 38, 42, 46, and 50, respectively, is similar to FIG. 2, reference is hereby made to the description accompanying FIG. 2 above for more detail regarding the embodiments (and possible alternatives thereto) shown in FIG. 4. The following fuel bundle arrangements are based upon the fuel bundle embodiments illustrated in FIG. 4, and are presented as examples of fuel bundles having particularly desirable characteristics, but are not to be considered limiting to the scope of the present invention or the other possible embodiments contemplated by FIG. 4. As used herein, the term “ring” includes a center element alone. Center element: DU/BP 1st ring of elements 42: RU 2nd ring of elements 46: RU 3rd ring of elements 50: RU Center element: DU 1st ring of elements 42: RU 2nd ring of elements 46: RU 3rd ring of elements 50: RU Center element: DU 1st ring of elements 42: DU 2nd ring of elements 46: RU 3rd ring of elements 50: RU The embodiments of FIGS. 3 and 4 provide examples of how the particular number of fuel elements, the fuel element arrangement (e.g., rings of elements in the illustrated embodiments), fuel element sizes, and relative fuel element sizes can change while still embodying the present invention. In some embodiments, the 235U fissile content of nuclear fuel decreases in an outward radial direction from the center of the fuel bundle 14. In other embodiments, the 235U fissile content increases in an outward radial direction from the center of the fuel bundle 14. In heavy water cooled reactors, the rate of neutron multiplication increases when coolant voiding occurs. Coolant voiding occurs, for example, when coolant starts to boil. Coolant void reactivity is a measure of the ability of a reactor to multiply neutrons. This phenomenon is due to positive coolant void reactivity, and can occur in all reactors for different scenarios. The present invention can provide a significant reduction in coolant void reactivity, and can also provide a negative fuel temperature coefficient and/or a negative power coefficient. The embodiments described above and illustrated in the figures are presented by way of example only and are not intended as a limitation upon the concepts and principles of the present invention. As such, it will be appreciated by one having ordinary skill in the art that various changes in the elements and their configuration and arrangement are possible without departing from the spirit and scope of the present invention. For example, in various embodiments described and/or illustrated herein, RU and DU blends are further blended with different types of nuclear fuel or other materials to produce nuclear fuels having desired fissile contents. For example, the RU and DU can be blended (alone or as an RU/DU blend) with slightly enriched uranium (SEU) and low enriched uranium (LEU). As defined herein, SEU has a fissile content of approximately 0.9 wt % to approximately 3 wt % of 235U (including approximately 0.9 wt % and approximately 3 wt %), and LEU has a fissile content of approximately 3 wt % to approximately 20 wt % of 235U (including approximately 3 wt % and approximately 20 wt %). Also, the embodiments described herein may be used with pressure tubes larger or smaller than those used in current pressure tube reactors and may also be used in future pressure tube reactors. Furthermore, the present invention can be employed in fuel bundles having a different number and arrangement of elements, and is not limited to 43-element and 37-element fuel bundle designs and arrangements, such as those illustrated by way of example in FIGS. 1-4. For example, although the embodiments of FIGS. 3 and 4 utilize two different element sizes in the illustrated fuel bundles 14, whereas the embodiments of FIGS. 1 and 2 utilize uniform element sizes across the illustrated fuel bundles 14, it will be appreciated that any of the fuel bundles described herein can have the same or differently-sized elements in different rings and/or different circumferential positions within the fuel bundles while still falling within the spirit and scope of the present invention. As another example, larger element sizes need not necessarily be located only in the first and/or second rings of a fuel bundle 14. In other embodiments, such relatively larger element sizes are located in radially outer rings of the fuel bundle 14 (e g., the radially outermost ring and/or ring adjacent thereto).
	description	FIG. 2 shows the structure of a short-wave exposure system assumed in the present invention. FIG. 3 illustrates an exemplary representative spectrum of exposure light employed in this short-wave exposure system. Referring to FIGS. 2 and 3, this system reflects synchrotron radiation 2 having a critical wavelength of 8.46 xc3x85 emitted from a radiation generator (SR device) 1 having a deflecting magnetic field of 4.5 T and electron acceleration energy of 0.7 GeV twice through rhodium mirrors 3 having an oblique incidence angle of 1xc2x0 and transmits the synchrotron radiation 2 through a beryllium window 4 of 20 xcexcm and an X-ray mask 5 prepared by forming an X-ray absorber pattern on a diamond mask substrate having a thickness of 2 xcexcm for thereafter irradiating a resist surface 6 provided on a substrate with this synchrotron radiation 2. For the purpose of comparison, FIG. 3 also shows an exemplary spectrum in a conventional X-ray exposure system employing silicon carbide mirrors and a silicon carbide mask substrate having a thickness of 2 xcexcm. The conventional X-ray exposure system mainly employs light having a wavelength longer than 7 xc3x85 on an absorption edge of silicon. On the other hand, the short-wave exposure system according to the present invention employs light of a wavelength, including that shorter than 7 xc3x85, up to about 3 xc3x85. While a system employing X-rays emitted from a radiation generator is mainly described, the present invention is not restricted to the X-rays emitted from the radiation generator but a similar effect is attained also in an exposure technique employing another X-ray source such as a plasma X-ray source. Further, a similar effect is attained also in an exposure technique employing an electron beam substantially identical in energy to the X-rays. Exposure with short-wave X-rays has been regarded as difficult in relation to the X-ray proximity exposure technique since it has been regarded that the range of secondary electrons generated in a resist irradiated with exposure light decides the resolution limit, which in turn is reduced due to reduction of the wavelength. The resolution of an optical image is increased in proportion to the square root of the shortened exposure wavelength, and increased by reducing the distance between the mask and the wafer. On the other hand, it has been regarded that blurring is caused on a short-wave side due to secondary electrons consisting of photoelectrons and Auger electrons and there is a limit resulting from the blurring limiting the resolution, i.e., a resolution limit resulting from the secondary electrons. The resolution limit resulting from the secondary electrons has recently been changed to a higher resolution side and corrected to a direction enabling reduction of the wavelength through experiments and calculations. However, the resolution is influenced by both of the resolution limit resulting from Fresnel diffraction and that resulting from the secondary electrons, and hence it has been concluded as difficult to increase the resolution by reducing the wavelength of the exposure light. In other words, the present invention aims at solving the problem of limitation of the resolution caused by blurring resulting from secondary electrons in a resist irradiated with exposure light. An object of the present invention is to increase the resolution by short-wave exposure by solving this problem. In exposure with light having energy by far higher than that necessary for chemical reaction in the X-ray proximity exposure technique or the like or with accelerated electrons or ions, i.e., high-energy exposure, secondary electrons such as photoelectrons and Auger electrons generated in a resist irradiated with the exposure light excite chemical reaction of the resist for forming a pattern. In other words, the electrons secondarily generated in the resist are important for exposure. The electrons generated upon irradiation with exposure light have been studied in detail. As to values generally employed for deciding blurring resulting from secondary electrons in evaluation of the resolution in the X-ray proximity exposure shown in FIG. 1, the energy of the exposure wavelength has been regarded as the energy of generated electrons as such, for obtaining the straight lines of the resolution limits in consideration of the ground range of the electrons in the resist etc. This is because values substantially accounting for the experimental fact have been obtained in an exposure waveband longer than the conventionally employed wavelength of 7 xc3x85. It has been found out that the situation is remarkably changed by an element forming the resist in the inventive exposure waveband including the wavelength shorter than 7 xc3x85. The present invention has been proposed on the basis of recognition obtained by studying secondary electrons generated from an element forming the resist in detail. Absorption edges of various light elements are present in the exposure waveband for the short-wave exposure including X-rays having a wavelength shorter than 7 xc3x85 mainly assumed in the present invention, i.e., the energy band up to about 3 KeV. The situation of the generated photoelectrons and Auger electrons remarkably vary around the absorption edges. This has been utilized to propose the present invention. In other words, the present invention has been proposed not by directly employing the energy of the conventionally employed exposure light as the energy of electrons for deciding blurring but by noting that blurring is decided by the energy of electrons generated in a resist in practice and re-evaluating the resolution limit. FIG. 4 shows energy levels of secondary electrons generated from elements irradiated with X-rays. Referring to FIG. 4, the horizontal axis shows the wavelengths (xc3x85) of the applied X-rays, and the vertical axis shows the energy levels (eV) of the generated secondary electrons. While photoelectrons and Auger electrons are generated by X-ray irradiation, the energy of the photoelectrons is obtained by subtracting binding energy of excited electrons from the energy of the exposure wavelength. The energy of the Auger electrons is obtained by further subtracting binding energy of outer-shell electrons from the energy difference between excited levels and the levels of the outer-shell electrons. If the binding energy of the outer-shell electrons is small, the energy of the Auger electrons substantially matches with the energy of simultaneously generated characteristic X-rays. The ratio of generating not secondary electrons but X-rays is shown by a value referred to as a fluorescence yield. The fluorescence yield in this energy band is about 2 to 3 percent, and those generated in the resist exposed with the X-rays can be substantially regarded as secondary electrons. Electrons generated in the resist exposed with the X-rays in the first place are secondary electrons consisting of photoelectrons and Auger electrons, with no generation of electrons having higher energy. The photoelectrons and Auger electrons as well as characteristic X-rays are absorbed by the resist again for generating low-energy electrons sensitizing the resist with lower energy than that of the secondary electrons generated in the first place. Blurring resulting from secondary electrons is increased in proportion to the energy, and hence low-energy electrons generated from the resist re-absorbing the secondary electrons and the characteristic X-rays generated from the photoelectrons and the Auger electrons absorbed by the resist do not reduce the resolution as compared with the secondary electrons generated in the first place. The photoelectrons and the Auger electrons must be regarded as the factor limiting the resolution in the X-ray exposure technique. In other words, the energy of electrons to be employed in the straight lines of the resolution resulting from the secondary electrons in FIG. 1 is not the energy of the exposure light but the energy of the secondary electrons consisting of photoelectrons and Auger electrons shown in FIG. 4 at the maximum. This electron energy decides the resolution limit caused by blurring resulting from secondary electrons. PMMA (polymethyl methacrylate) forming a representative resist consists of hydrogen, carbon and oxygen. Absorption edges (i.e., binding energy of electrons) of these elements are on a low-energy side, and hence the energy of photoelectrons obtained as the difference between the energy of the applied X-rays and the binding energy is close to the energy of the exposure wavelength not only in the waveband of the conventional X-ray exposure but also in the waveband for the short-wave exposure. So far as an organic resist mainly composed of carbon similar to PMMA is employed, therefore, the energy of electrons employed in the straight lines of resolution resulting from secondary electrons shown in FIG. 1 is close to the energy of the exposure wavelength. Consequently, it follows that the generally employed relation between the wavelengths and the resolution substantially holds also in the organic resist mainly composed of carbon similar to PMMA. When a resist material having an X-ray absorption edge in the vicinity of the exposure waveband is irradiated with X-rays, however, the situation of generated secondary electrons is remarkably changed. For example, bromine has an X-ray absorption edge in the vicinity of 8 xc3x85, and the quantity of generated secondary electrons is abruptly increased on an immediate short-wave side of the absorption edge. The energy of photoelectrons included in the secondary electrons, obtained by subtracting the binding energy of electron levels on the absorption edge from the energy of the X-rays employed for exposure, is abruptly reduced on the short-wave side of the absorption edge, not to exceed the energy on the absorption edge up to about 4 xc3x85. The energy of Auger electrons, in the range of 1.2 to 1.4 KeV, corresponds to a wavelength of 9 to 10 xc3x85. Also when the energy of the exposure wavelength is increased to about 4 xc3x85, electrons having higher energy than that corresponding to 9 to 10 xc3x85 are generated only in a small quantity. The present invention thus reduces blurring resulting from secondary electrons generated in a resist by short-wave exposure for forming a pattern of high resolution. Means of the present invention, described with reference to bromine in the above, are now described. [Means 1] An exposing method of condensing or magnifying X-rays generated from an X-ray source through an X-ray mirror in a beam line, thereafter transmitting the X-rays through a window member serving as a vacuum barrier and further transmitting the X-rays through an X-ray mask consisting of a mask substrate and an absorber pattern formed thereon for irradiating a resist with the X-rays serving as exposure light employs a resist having a main absorption waveband in the wave range of 3 xc3x85 to 13 xc3x85 and containing an element generating Auger electrons having energy in the range of at least about 0.51 KeV and not more than 2.6 KeV upon exposure. Also when the wavelength is reduced, blurring of electrons is hardly increased due to generation of Auger electrons having constant energy. Further, the energy of photoelectrons is lower than the energy of photoelectrons generated from a conventional resist mainly consisting of carbon, oxygen, nitrogen and hydrogen, and hence blurring of photoelectrons can also be reduced as compared with the case of employing the conventional resist. [Means 2] A resist containing an element mainly generating Auger electrons in the range of at least about 0.51 KeV and not more than 2.6 KeV upon exposure with an electron beam having an acceleration voltage of at least 1.5 KeV is employed. Also when the acceleration voltage is increased, blurring of electrons is hardly increased due to generation of Auger electrons having constant energy. [Means 3] A resist containing an element, mainly absorbing exposure light, generating Auger electrons having energy higher than the energy of photoelectrons is employed. Electrons generated from the resist upon exposure include Auger electrons having constant energy and photoelectrons having lower energy than the Auger electrons. Consequently, a pattern of high resolution can be formed with small blurring of electrons also when the wavelength of the exposure light is reduced. [Means 4] A resist having a main absorption waveband in the wave range of 3 to 13 xc3x85 and containing an element generating Auger electrons having energy higher than the energy of photoelectrons upon exposure is employed while selecting the wave range where the Auger electrons have higher energy than the photoelectrons for exposure. The energy of generated photoelectrons is limited to be lower than the energy of Auger electrons, and hence the quantity of high-energy electrons is reduced. Further, blurring of electrons can be reduced and a pattern of high resolution can be formed. [Means 5] A resist having a main absorption waveband in the wave range of 3 to 13 xc3x85 and containing an element generating Auger electrons having energy higher than the energy of photoelectrons upon exposure is employed while performing exposure in the wave range where the energy of photoelectrons is substantially equal to or not more than the energy of Auger electrons of carbon. Blurring of electrons is further suppressed due to employment of electrons having extremely low energy, for obtaining a pattern of ultrahigh resolution. [Means 6] A resist having a main absorption waveband in the wave range of 3 to 1.3 xc3x85 and containing an element generating Auger electrons having energy in the range of about 0.51 KeV to 2.6 KeV is employed while performing exposure in the wave range where the energy of photoelectrons is not more than 1.4 KeV. The energy of photoelectrons is smaller than the energy corresponding to the wavelength of 13 xc3x85 also in the short-wave range, and hence blurring of electrons can be reduced. The constant energy of Auger electrons is not increased also when the wavelength is reduced. [Means 7] An X-ray exposing method condensing or magnifying X-rays generated from an X-ray source in a beam line comprising an X-ray mirror and thereafter transmitting the X-rays through a window member serving as a vacuum barrier for transferring an X-ray mask pattern to a resist exposes the resist with an illumination optical system comprising a wavelength sweeper capable of changing a wavelength without changing an optical axis to a condensing X-ray mirror or a magnifying X-ray mirror in the beam line. The exposure wave range can be selected without changing the material for or the X-ray oblique incidence angle of the condensing X-ray mirror or the magnifying X-ray mirror already built into the system. The wavelength sweeper is now described. Reflectance against a short wavelength is reduced when an X-ray oblique incidence angle in an X-ray mirror is increased. In this regard, the wavelength sweeper cuts a short-wave component by controlling the oblique incidence angle. The wavelength sweeper is an illumination optical system combined with at least two X-ray mirrors for cutting an X-ray wave component of a short-wave range without changing the original optical axis of the X-rays. FIG. 5 is a block diagram showing a wavelength sweeper of a system employing three X-ray mirrors 7, 8 and 9. The distance L between the first and second X-ray mirrors 7 and 8 along the X-axis direction is constant. The distance L between the second and third X-ray mirrors 8 and 9 is also constant along the X-axis direction. The first and third X-ray mirrors 7 and 9 are fixed in position, and have rotation mechanisms about an axis perpendicular to the plane of FIG. 5. The second X-ray mirror 8 has a function of making translation along the y-axis direction. The position of the second X-ray mirror 8 and the angle of the third X-ray mirror 9 are so adjusted that oblique incidence angles in the second and third X-ray mirrors 8 and 9 reach 2xcex1 and xcex1 respectively when X-rays enter the first X-ray mirror 7 at an oblique incidence angle xcex1. Thus, the optical axes of the X-rays entering the first X-ray mirror 7 and outgoing from the third X-ray mirror 9 can be substantially equalized with each other. The position of the second X-ray mirror 8 and the angle of the third X-ray mirror 9 are so adjusted that oblique incidence angles in the second and third X-ray mirrors 8 and 9 reach 2xcex2 and xcex2 respectively when the first X-ray mirror 7 is so rotated that the X-rays enter the first X-ray mirror 7 at an oblique incidence angle xcex2. Therefore, the optical axes of the X-rays can be substantially equalized with each other. Thus, the oblique incidence angles in the X-ray mirrors 7, 8 and 9 can be adjusted while leaving the optical axes of the X-rays substantially unchanged, so that the wave range of the X-rays can be selected through difference in reflectance varying with the oblique incidence angles. [Means 8] An exposing method of condensing or magnifying X-rays generated from an X-ray source through a beam line comprising an X-ray mirror and thereafter transmitting the X-rays through an X-ray filter and a window member serving as a vacuum barrier for transferring an X-ray mask pattern to a resist employs a beam line comprising an illumination optical system formed by combining at least two plane mirrors having surface coating materials varying with positions of the surfaces of the mirrors. A short-wave component can be reduced without changing a condensing or magnifying X-ray mirror. [Means 9] A resist contains a material selected from a group consisting of fluorine, iodine and germanium. The absorption edge of such an element is on a side longer than 10 xc3x85, and hence a pattern is formed with secondary electrons having lower energy than photoelectrons of carbon with respect to conventional X-ray exposure light of 7 to 10 xc3x85, thereby improving resolution. [Means 10] A resist having a main absorption waveband in the wave range of 3 to 13 xc3x85 or containing an element generating Auger electrons having energy in the range of at least about 0.51 KeV and not more than 2.6 KeV upon exposure with an electron beam of at least 1.5 KeV is employed for forming a resist pattern on a substrate and fabricating a semiconductor device by working the resist pattern. [Function] A technique of improving resolution by reducing a wavelength includes a method of reducing an irradiation wavelength and a method of reducing a wavelength absorbed by a resist while leaving the irradiation wavelength intact. An object of the present invention implementing improvement of resolution by obtaining an optical image having high resolution through exposure with X-rays having a short wavelength is to reduce blurring resulting from secondary electrons in a resist. Therefore, the present invention proposes a method of controlling the energy of secondary electrons generated in the resist by selecting the element forming the resist and a wave range. FIGS. 4 and 6 illustrate excitation wavelength dependence of energy of photoelectrons and Auger electrons generated from candidate elements for forming the resist. The energy of photoelectrons, increased as the excitation wavelength is reduced, is abruptly reduced once on a short-wave side of the absorption edge of each element. On the other hand, the energy of Auger electrons takes a constant value on the short-wave side of the absorption edge. In other words, generated electron energy is not increased on an immediate short-wave side of the absorption edge also when the wavelength for exposure is reduced but it follows that Auger electrons taking a constant value and photoelectrons having energy lower by at least one digit are generated. In any case, the energy of these electrons generated in the resist irradiated with X-rays is generally reduced as compared with the energy of the X-rays applied for exposure, and the electrons of this energy provide blurring influencing the resolution. The quantity absorbed by the resist is reduced as the energy of electrons is increased, and low-energy electrons are readily absorbed by the resist. These factors influence the resolution, to come to decide blurring resulting from secondary electrons. FIG. 7 shows results of evaluation of influence exerted on resolution by electrons, having various energy levels, generated in a resist at different ratios. It is assumed that four types of electrons having different energy levels are generated at different ratios. Referring to FIG. 7, the vertical axis shows stored energy in the resist, and the horizontal axis shows the arrival ranges of electrons, i.e., resolution. High-energy electrons cause blurring over a wide range and exert influence between patterns, while low-energy electrons have high absorption power in the resist with a small arrival range and small blurring resulting from secondary electrons, to influence the pattern quality. Observing the stored energy in the resist containing low-energy electrons, it follows that a stored energy distribution profile having a sharp spire by the low-energy electrons is obtained. When setting a slice level in a development process to this spire part, it follows that a high-resolution pattern is obtained. When the ratio of low-energy electrons is large, it follows that the slice level range is wide to spread selection ranges for the resist material and development conditions. It is consequently obvious that the range of conditions for obtaining a high-resolution pattern is so wide that a high-resolution pattern can be readily obtained. Observing this relation, it is understood that not only the range of high-energy electrons but electrons of a low-energy range may rather strongly influence the resolution, and electrons of optimum energy most influencing the resolution are present. The influence by high-energy electrons is observed as influence on an adjacent pattern in a case of a high-density pattern, to influence the resolution. Results of study of influence exerted on resolution by two types of electrons having different energy levels are now shown. Images of absorbed energy in a resist were obtained while fixing the energy of the first electrons to 1.4 KeV and varying the energy of the second electrons in the range of 0.1 KeV to 2.5 KeV. FIG. 8 shows a case of a mask pattern having lines and spaces of 50 nm, and FIG. 9 shows a case of a mask pattern having spaces of 50 nm. X-ray intensity on the resist was set to zero on a mask line part and to 1 on a mask space part. In both cases, the images of absorbed energy are gradually steepened as the energy of the electrons is increased from 0.1 KeV, to exhibit the highest contrast around the electron energy of 0.7 KeV to 1.4 KeV. When the energy exceeds 2.1 KeV, blurring is rather increased When forming a pattern with electrons such as Auger electrons having constant energy and photoelectrons increased in energy due to reduction of the wavelength, the photoelectrons may strongly contribute to improvement of the resolution if the energy thereof is lower than that of the Auger electrons. Thus, there is combination of energy levels of photoelectrons and Auger electrons most increasing the resolution. This combination of the electron energy levels varies with the pattern dimension and the energy of the Auger electrons. In view of a wave band shorter than 20 xc3x85 as to the energy levels of secondary electrons of the elements shown in FIG. 6, absorption edges of iodine, fluorine, germanium, bromine, silicon, sulfur, phosphorus and chlorine are present on a short-wave side in this order and the energy levels of Auger electrons generated from these elements are increased in this order. However, wavelengths reducing energy of photoelectrons shift toward the short-wave side in this order of elements. In other words, it follows that wavelengths reducing the energy levels of photoelectrons generated in the resists can be selected in this order of the elements by selectively reducing the exposure wavelength, and the resolution can be improved in consideration of reduction of Fresnel diffraction due to the capability of reducing the wavelength. The ratio of generation of electrons of each energy level is decided by the element contained in the resist, the ratio of the element and the wavelength spectrum of the exposure light. In other words, it follows that the ratio of electrons generated in the resist is decided by X-ray absorption power in the resist at each wavelength, i.e., the X-ray absorption spectrum of the resist. This is because the quantity of generated electrons is increased as the quantity of absorption of X-rays is increased. The absorption spectrum of the resist is not much dependent on the binding state of a compound but decided by the absorption spectrum of each element and the weight ratio of the element in the resist in an energy band of a level assumed in X-ray exposure. FIGS. 10 and 11 show results of ratios of photoelectrons and Auger electrons resulting from absorption edges present in the exposure waveband among secondary electrons generated in resists exposed with X-rays. FIG. 10 shows results in a system employing platinum mirrors, and FIG. 11 shows results in a system employing rhodium mirrors. In each system, the ratios of the electrons are low in resists containing elements such as PMMA, fluorine and iodine having no absorption edges in the exposure waveband. In the remaining resists containing elements having absorption edges in the exposure waveband, the ratios of electrons related to the absorption edges present in the exposure waveband are increased to exceed 90% as the thicknesses of membranes are increased, i.e., as the average exposure wavelengths are reduced. Under standard conditions employing a diamond membrane of 2 xcexcm in thickness, the ratios of electrons related to absorption edges in the exposure waveband are increased as the wavelengths of the absorption edges are increased in order of bromine, silicon, phosphorus, sulfur and chlorine. A large quantity of electrons related to absorption edges in the exposure waveband indicates that the resist contains a large quantity of photoelectrons having low energy among the secondary electrons, to enable improvement of the resolution. As to the ratios of photoelectrons and Auger electrons of respective energy levels, content dependence of elements contained in the resists was studied. FIG. 12 shows X-ray spectra in bromine-containing PMMA resists, for example, having various weight ratios of bromine. All specific gravity levels were set to 1, and film thicknesses were set to 1 xcexcm. The ratios of photoelectrons and Auger electrons are also decided by the spectrum of excited exposure light. FIG. 13 shows wavelength dependence of absorbed energy levels in a case of employing a system including platinum mirrors. FIG. 14 shows wavelength dependence of absorbed energy levels in a case of employing a short-wave exposure system including rhodium mirrors. Diamond membranes of 2 xcexcm in thickness were obtained. Referring to FIG. 12, it is understood that absorbance on a shorter-wave side of the absorption edge of bromine is increased when the ratio of bromine is increased in the bromine-containing PMMA resist. As shown in FIGS. 13 and 14, therefore, the ratio of absorbed energy on the shorter-wave side of the absorption edge can be increased by exposing a resist of a material including an absorption edge in the exposure waveband. In the case of the bromine-containing PMMA resist, the ratios of photoelectrons and Auger electrons having low energy generated from bromine atoms in an exposure wave range on a shorter wave-side of the absorption edge of bromine are increased. Consequently, resolution is not deteriorated but can expectedly be rather improved also in short-wave exposure. The weight ratio of bromine in a resist prepared by brominating PHS (polyhydroxystyrene) was varied in the range of 0% to 50.2% for measuring specific gravity. FIG. 15 shows the results of measurement (experimental values) along with results of calculation (calculated values). The specific gravity is increased as the bromination ratio is increased such that the specific gravity reaches about 1.8 times that of a general PHS resist when the Br weight ratio is 50%, and a resist of about 2.5 times can also be obtained at the maximum. Similar relation holds as to the effect of bromination also in novolac resin or another polymeric resist such that the specific gravity is increased as the bromine content is increased and a resist having specific gravity of almost three times can also be obtained. In this waveband, X-ray absorbance is increased in proportion to the specific gravity, and hence it follows that a resist having sensitivity higher by at least one digit as compared with a PHS resist containing no bromine can be expected depending on the exposure wavelength as a result of the bromine content and as a result of the effect on the absorption edge of bromine and the effect of the increased specific gravity. FIG. 16 shows this relation. Light prepared by condensing synchrotron radiation emitted from a radiation generator having deflecting magnetic field intensity of 4.5 T and acceleration energy of 0.7 GeV through a beam line employing two rhodium mirrors having an oblique incidence angle of 1xc2x0 and transmitting the synchrotron radiation through a beryllium window of 20 xcexcm in thickness serving as a vacuum barrier and a diamond mask substrate of 2 xcexcm in thickness was employed for exposure. Energy absorbed by a resist of 0.2 xcexcm in thickness was obtained. It follows that light of 4 to 8 xc3x85 is mainly employed for exposure at this exposure wavelength. As clearly understood from FIG. 4, it follows that the energy of photoelectrons resulting from L shells of bromine having an absorption edge at 8 xc3x85 is lower than the energy of Auger electrons under this condition. Electrons resulting from orbits other than the L shells and those resulting from carbon, oxygen and hydrogen are also generated as a matter of course, and hence FIG. 17 shows results of ratios of electrons resulting from L shells of bromine. It is understood that the ratio of electrons already exceeds 60% in a resist having a bromine weight ratio of 40%, i.e., that prepared by replacing one of eight hydrogen components forming hydroxystyrene with bromine, and the ratio of electrons reaches 70% when two hydrogen components are replaced. In other words, it can be said that electrons generated by exposure in this waveband and related to resolution mainly result from L shells of bromine. Among the 70% of secondary electrons, Auger electrons of bromine have the maximum energy of about 1.4 KeV, which is by far lower than the energy of photoelectrons of carbon exceeding 2 KeV in this waveband. Therefore, it follows that a pattern of high resolution can be formed by employing a bromine-containing resist for exposure employing light in the waveband of 4 to 8 xc3x85. Also in the bromine-containing resist, no electrons result from L shells of bromine when the resist is irradiated with light having a wavelength longer than 8 xc3x85 but only resolution substantially similar to that in a resist containing no bromine can be expected. While the system employing X-rays emitted from a radiation generator has been mainly described, the present invention is not restricted to the X-rays from the radiation generator but a similar effect is attained also when employing another X-ray source including a plasma X-ray source due to the principle of the present invention. Ratios of photoelectrons and Auger electrons resulting from absorption edges present in an exposure waveband were obtained as to other elements. FIGS. 10 and 11 shows the results, which were obtained as to a case of employing rhodium mirrors similar to those in the first embodiment and a case of employing platinum mirrors having an oblique incidence angle of 1xc2x0. Referring to each of FIGS. 10 and 11, the horizontal axis plots the thickness of a diamond film forming a mask substrate, for obtaining thickness dependence of the substrate. When the thickness of the diamond film is increased, it follows that the diamond film is employed as an X-ray filter for cutting a long-wave side and performing short-wave exposure. Therefore, a similar effect is attained also in a filter employing another material such as beryllium or boron nitride in place of diamond. The ratio of secondary electrons resulting from an absorption edge of each element present in an absorption waveband is increased on a short-wave side not only in the case of rhodium mirrors but also in the case of platinum mirrors. A ratio of electrons exceeding 60% is implemented not only in bromine but also in silicon or phosphorus when the thickness of the diamond film is at least 2 xcexcm, and it is understood that there is a condition satisfying the electron ratio of at least 60% also in sulfur or chlorine. It follows that exposure of low photoelectron energy is implemented at least under this condition. When performing exposure with light on a slightly shorter-wave side of the absorption edge of an element contained in a resist, photoelectrons of low energy are generated in the resist to enable improvement of resolution. Therefore, combination of irradiation light for exposure and the element contained in the resist is important. FIGS. 18A and 18B show absorption spectra to resists in a case of employing novolac resin prepared by replacing two hydrogen components with bromine as a base polymer of a bromine-containing resist. In an illumination optical system employing rhodium (Rh) mirrors or ruthenium (Ru) mirrors having an oblique incidence angle of 1xc2x0, light in the band of 4 to 8 xc3x85 can be effectively utilized to enable high-speed exposure. In an optical system employing platinum (Pt) mirrors or osmium (Os) mirrors having an oblique incidence angle of 1xc2x0, on the other hand, it follows that light in the band of 6 to 8 xc3x85 is mainly utilized, and photoelectron energy of bromine in this waveband can be reduced below that of Auger electrons of carbon, and it follows that pattern transfer of ultrahigh resolution can be implemented. In order to select an irradiation wavelength for exposure in response to an element contained in a resist without changing a condensing/magnifying mirror, a method employing a wavelength sweeper comprising beryllium (Be) mirrors having a variable incidence angle was studied. A beam line including two cobalt (Co) mirrors having an incidence angle of 89.1xc2x0 was employed as an illumination optical system while setting a wavelength sweeper formed by three plane mirrors of beryllium (Be) in front of the cobalt (Co) mirrors. The wavelength was selected with the wavelength sweeper capable of varying a cut wavelength on a short-wave side by changing the incidence angle in the beryllium (Be) mirrors. FIG. 19 shows spectra of irradiation light for exposure obtained through the aforementioned wavelength sweeper. The wavelength of the applied light can be continuously changed in the range of about 3 xc3x85 to at least 8 xc3x85 by simply changing the incidence angle in the variable beryllium (Be) mirrors without changing a condensing/magnifying mirror. FIG. 20 shows absorption spectra in a brominated PHS resist, similar to that employed in the first embodiment, exposed in this illumination system. The short-wave side can be arbitrarily adjusted through the wavelength sweeper, and this means that the maximum energy of photoelectrons resulting from L shells of bromine can be freely adjusted. In other words, the energy of photoelectrons resulting from L shells of bromine can be reduced below that of Auger electrons of carbon by cutting the wavelength at 6 xc3x85. Further, the energy of photoelectrons resulting from L shells of bromine can be reduced below that of Auger electrons of itself by cutting the wavelength at 4 xc3x85. FIG. 21 shows spectra of absorbed energy in resists, containing various elements, exposed in an exposure apparatus employing an illumination optical system including a beam line employing two cobalt mirrors having an incidence angle of 89.1xc2x0 and a wavelength sweeper similarly to the fourth embodiment. A radiation generator having a deflecting magnetic field of 4.5 T and electron acceleration energy of 0.8 GeV was employed. Each resist was normalized to contain 100% of the element with specific gravity of 1. The incidence angle in beryllium mirrors of the wavelength sweeper and the thickness of a diamond filter were varied with the element. Direct light from cobalt mirrors having an incidence angle of 89.10 was employed for a chlorine-containing resist with a diamond filter having a thickness of 13 xcexcm and specific gravity of 3.52. Light obtained by reflecting light from cobalt mirrors three times by a wavelength sweeper having beryllium mirrors to have an incidence angle of 89.5xc2x0 was employed for a sulfur-containing resist with a diamond filter having a thickness of 10 xcexcm. The incidence angle to beryllium mirrors was set to 89.15xc2x0 and the thickness of a diamond filter was set to about 2 xcexcm for a bromine-containing resist. Thus, absorbed energy was substantially equally set to around 0.3 W in each resist, and the average absorption wavelength was changed from 7.93 xc3x85 to 4.31 xc3x85 in each resist. This indicates that resolution can be improved from 50 nm to 37 nm in consideration of Fresnel diffraction without changing the throughput by changing the resist material while keeping the distance between a mask and a wafer at 10 xcexcm, and a thick diamond mask substrate can be utilized on a high resolution side. The maximum object resides in that only a constant wave range on an immediate short-wave side from the absorption edge of each resist is absorbed into the resist. In other words, the resolution is improved by utilizing only a part having low energy of photoelectrons resulting from the absorption edge. Only the material for filters employed in systems similar to those in the aforementioned fifth embodiment was changed from diamond to beryllium to obtain absorbed energy levels. Mask substrates were prepared from diamond substrates of 2 xcexcm in thickness. FIG. 22 shows results in cases from direct exposure to passage through a beryllium filter of 100 xcexcm having specific gravity of 1.86. FIG. 23 shows results in a case of employing germanium filters provided on mask substrates. The beryllium filter can obtain a spectrum substantially equal to that obtained through a diamond filter with a thickness larger by about one digit. It is understood that the thickness of a germanium filter can be reduced by about 1 digit as compared with a diamond filter. It follows that the thickness of a beryllium filter utilized as a window member serving as a vacuum barrier can be increased while the thickness of a germanium filter applied to a mask can be reduced. The material applied to the mask substrate is not restricted to germanium but a substantially similar effect can be attained also in a polymer film or a boron nitride substrate employed as a filter, as confirmed by calculation from the X-ray absorption coefficient of each material. A method of varying the surface materials for mirrors was employed as a method of cutting a short-wave side of exposure light without utilizing a wavelength sweeper. FIG. 24 shows examples thereof. All mirrors were set to an oblique incidence angle of 1xc2x0, and only surface materials were varied with resist materials. In other words, mirrors of nickel, rhodium and silicon carbide were employed for chlorine-, phosphorus- and bromine-containing resists respectively. It is obvious in principle that filters can be employed for optimization similarly to the aforementioned fifth and sixth embodiments, and the thicknesses of mask substrates of diamond, silicon carbide etc. were varied in this embodiment. FIG. 25 shows an optical system employed for the method of changing the surface materials for mirrors. Referring to FIG. 25, two plane mirrors 10 and 11 having variable mirror positions and a constant incidence angle are combined with each other. Surface coating materials are varied with positions of the plane mirrors 10 and 11 irradiated with X-rays. FIG. 26 shows exemplary mirror surface coating materials varying with the mirror positions. When the mirrors 10 and 11 are vertically moved, the various mirror surface materials reflect light to change the cut wavelength in this optical system. This optical system can change the cut wavelength while changing neither the optical axis nor the mirrors 10 and 11. While the optical system employs two mirrors 10 and 11 in this embodiment, an optical system not changing an optical system can be implemented with a single or at least three mirrors due to the constant incidence angle. While movable mirrors fixed to the oblique incidence angle of 1xc2x0 are employed in the seventh embodiment, the oblique incidence angle is not restricted to 1xc2x0 but a similar effect can be expected with a deeper or shallower angle depending on the material. A metal such as beryllium or boron nitride belonging to the group 2 or 4 of the periodic table having no absorption edge in the target wave range of the present invention can be utilized as the material for mirrors of a wavelength sweeper selecting a wavelength by changing the incidence angle. However, the reflection characteristics of mirrors having a surface material of a metal belonging to the group 5 or 6 of the periodic table is influenced by an absorption edge and hence an optical system capable of arbitrarily selecting a wavelength by only changing the incidence angle cannot be implemented with such a material. When wavelength dependence of reflectance is optimally selected for such a mirror surface material, however, an optical system acting similarly to a wavelength sweeper can be implemented and is important in a sense. The structure of a mirror moving mechanism is simplified in a point that the direction of movement of optical elements is one-dimensional, and light of a short wavelength can be obtained through a mirror system having a deep incidence angle. Consequently, advantages such as miniaturization of mirrors can be implemented only according to the present invention. A method employing a filter material is shown as a method of cutting short-wave light and obtaining exposure light having the optimum wavelength. FIG. 27 shows an embodiment in cases of bromine- and silicon-containing resists. This figure shows spectra of X-rays absorbed by bromine-containing resists of 0.2 xcexcm in thickness exposed through an exposure apparatus having an illumination optical system employing two rhodium mirrors having an oblique incidence angle of 1xc2x0. This illumination system applies light of about 4 to 10 xc3x85 to mask surfaces. When exposing the bromine-containing resists with this exposure apparatus, the peaks of absorbed light are in the range of 4 to 8 xc3x85 in a diamond filter of 12 xcexcm in thickness. FIG. 27 also shows an example implementing a waveband having low photoelectron energy by cutting a short-wave side. In an example employing a silicon carbide filter of 12 xcexcm in thickness, the quantity of light having a wavelength shorter than 7 xc3x85 is remarkably reduced in energy absorbed in the resist, for performing optimization to the bromine-containing resist utilizing light in the band of 7 to 8 xc3x85. FIG. 27 also shows an example employing gold as a filter material for a silicon-containing resist. The optimum wavelength for the silicon-containing resist can be selected in the range of 7 to 5.5 xc3x85 by employing the gold filter of 0.4 xcexcm in thickness. While the thickness of the silicon carbide filter is 12 xcexcm in this example, a similar result was obtained through a silicon carbide filter of 10 xcexcm in exposure with a diamond mask of 2 xcexcm in thickness. FIG. 28 shows a case of an exposure apparatus of an illumination system having platinum mirrors. This apparatus, connected to a light source having a deflecting magnetic field of 3.29 T and acceleration energy of 0.585 GeV, is approximately optimum for a silicon-containing resist, and can be used as such. FIG. 28 shows that remarkable improvement is attained also with respect to a bromine-containing resist by simply changing a diamond substrate mask to a silicon carbide substrate mask of 2 xcexcm. As hereinabove described, the short-wave side can be cut by employing the absorption edge of the element, for implementing exposure with the optimum wavelength. The absorption edge of silicon effectively functions as a filter and hence silicon carbide or silicon nitride is effective in the case of a bromine-containing resist, and it is effective to apply this material not only to a filter but also to a mask substrate. When employing a mask of a substrate, such as a diamond mask, transparent up to a short wavelength, a material such as tantalum or tungsten having an absorption edge in the vicinity of 7 xc3x85 is suitable as the filter material. As to a silicon-containing resist, a material having an absorption edge in the vicinity of 6 xc3x85 is suitable as the filter material for selecting the optimum wavelength among metals such as rhenium, osmium, iridium, platinum and gold belonging to the group 6. This material is applied to a mask substrate or a window member serving as a vacuum barrier by vacuum deposition or sputtering. A metal such as zirconium, niobium, molybdenum, ruthenium, rhodium, palladium or silver belonging to the group 5 or an alloy of this metal is effective for optimizing the wavelength for exposing a sulfur-containing resist. This embodiment is particularly effective in the point that the wavelength can be optimized through a filter every resist material when an exposure system employing an optical system including light of the necessary waveband is already present. Illumination light for exposure optimum for an element contained in a resist can be obtained by employing the aforementioned system of the fourth embodiment. FIG. 29 shows results of application to resists containing chlorine and sulfur. This figure indicates that the exposure wavelength can be optimized through a mask of a diamond substrate of 10 xcexcm. FIG. 30 shows absorption spectra of not only the resists containing chlorine and sulfur but also those containing phosphorus, silicon and bromine. Not only wavelength sweepers but also the thicknesses of diamond filters are so varied that the quantities of absorption in the resists are substantially similar to each other. According to these results, it follows that the average wavelength of absorbed light is reduced from 7.6 xc3x85 to about 4.1 xc3x85 and the resolution of an optical image is improved. The energy of photoelectrons is low on a short-wave side of an absorption edge and apparently effective for high resolution, while the bandwidth of exposure light is more important. In other words, the energy of photoelectrons generated on an immediate short-wave side is extremely low and hence the quantity of energy stored in the resist is small, and it follows that contribution to the resolution is decided by electrons other than the noted photoelectrons. Therefore, it is important to select not only the optimum wavelength but also the optimum waveband not only in view of high-speed exposure but also in view of high resolution. In this embodiment, mask contrast, which is 2.35 in a mask employing a tantalum absorber of 0.3 xcexcm in thickness with respect to a bromine-containing resist, is increased to 6.21 in a case of a silicon-containing resist. In other words, it follows that mask contrast similar to that in the case of 0.3 xcexcm with respect to the bromine-containing resist can be obtained when employing the silicon-containing resist with a thin absorber of about 0.1 xcexcm in thickness. Illumination light for exposure having a shorter wavelength than a system including two cobalt mirrors having an incidence angle of 89.1xc2x0 can be implemented by employing a beam line system including a condensing/magnifying mirror having a shallower oblique incidence angle. FIG. 31 shows examples of illumination light in a case of employing cobalt mirrors having different oblique incidence angles. Illumination light having a wavelength reduced to about 1 xc3x85 can be obtained in a cobalt mirror system having an oblique incidence angle of 0.5xc2x0, i.e., an incidence angle of 89.5xc2x0. As to mirror surface materials capable of reducing wavelengths by reducing oblique incidence angles, not only cobalt but also metals such as nickel, copper and iron belonging to the group 4 and alloys thereof can also provide similar illumination light by employing different oblique incidence angles. Further, mirrors of metals such as tantalum, tungsten, osmium, iridium, platinum and gold belonging to the group 6 and alloys thereof can also provide short-wave illumination light including light of a shorter wavelength than 2 xc3x85 with deeper oblique incidence angles although reflectance is slight reduced. FIG. 32 shows an example cutting satellite peaks on short-wave sides in a system employing platinum mirrors having an oblique incidence angle of 1xc2x0 and a wavelength sweeper. FIG. 33 shows energy absorption spectra of brominated PHS resists, employed in the aforementioned first embodiment, exposed with light emitted from a radiation generator (0.7 GeV and 4.5 T) and reflected twice by rhodium mirrors having an oblique incidence angle of 1xc2x0. FIG. 34 shows energy absorption spectra of resists in a case of employing platinum mirrors in place of the rhodium mirrors. The thickness of a beryllium window in the exposure system was 20 xcexcm, and that of a diamond substrate was 2 xcexcm. It is understood that absorption on a shorter-wave side of the absorption edge (7.8 xc3x85) of bromine is remarkably increased as the bromine weight ratio is increased. The quantity of energy absorbed in the brominated PHS resist having a bromine weight ratio of about 50% was 7 to 8 times in the case of the exposure system employing rhodium mirrors and 5 to 6 times in the case of the exposure system employing platinum mirrors as compared with a PHS resist containing no bromine. This indicates that sensitivity can be improved by employing a resist containing a material such as bromine having an absorption edge in the exposure wave range. Increase of absorption of a component having a shorter wavelength than the absorption edge of bromine remarkably changes the quantities of energy of photoelectrons and Auger electrons generated in the exposed resist. A material, such as a PHS resist, containing no bromine, mainly consisting of carbon, oxygen and hydrogen and having no absorption edge in the exposure wave range generates Auger electrons having low energy and photoelectrons having energy close to that of the exposure light. The energy of photoelectrons is increased as the exposure wavelength is reduced, and hence it follows that blurring of electrons influencing resolution is increased. Bromine has an absorption edge in the exposure wave range, and hence low-energy photoelectrons from L shells and Auger electrons from M shells, having energy of about 1.4 KeV corresponding to a wavelength of about 9 xc3x85, are generated due to exposure light on an immediate short-wave side of the absorption edge (7.8 xc3x85) of bromine. While photoelectrons and Auger electrons from other electron levels are also generated as a matter of course, the energy thereof is smaller than that of the Auger elections from the M shells, and blurring of electrons is smaller. In the case of short-wave exposure light, the energy of Auger electrons remains unchanged and hence blurring of electrons also remains unchanged. The energy of photoelectrons is gradually increased and substantially equalized with that of Auger electrons with exposure light of about 4 xc3x85. The energy of photoelectrons is lower than that of Auger electrons and blurring of electrons is also small as compared with the Auger electrons up to 4 xc3x85. In bromine, therefore, electrons having lower energy than the energy (about 1.4 KeV) of the Auger electrons from the M shells are generated also when the wavelength is reduced from about 7.8 xc3x85 to 4 xc3x85, and hence blurring of electrons influencing resolution is suppressed also when the wavelength is reduced, whereby high resolution is obtained. When absorption on a shorter-wave side of the absorption edge of bromine is increased in a bromine-containing resist, this indicates that absorption of the exposure light by bromine gets dominant as compared with carbon, oxygen and hydrogen. This particularly indicates generation of a large quantity of electrons having lower energy than the energy of Auger electrons corresponding to the wavelength of 9 xc3x85 with respect to exposure light from the absorption edge (7.8 xc3x85) of bromine up to 4 xc3x85. When employing a brominated PHS resist having a high bromine weight ratio, therefore, it can be expected that blurring of secondary electrons resulting from reduction of the wavelength is suppressed as compared with a PHS resist mainly made of carbon, oxygen and hydrogen. The thickness of a diamond film of an X-ray mask membrane was varied from 1 xcexcm to 100 xcexcm for studying the effect of reduction of the wavelength. FIG. 35 shows absorption spectra in a brominated PHS resist having a bromine weight ratio of 50% in a case of a short-wave exposure system employing rhodium mirrors having an oblique incidence angle of 1xc2x0, and FIG. 36 shows those in a case of a short-wave exposure system employing platinum mirrors. The absorption spectra are normalized and plot with reference to maximum absorption intensity. It is understood that a long-wave component is gradually cut and the wavelength is reduced when the thickness of the diamond film is increased from 1 xcexcm to 100 xcexcm. The average absorption wavelength is reduced from 6.57 xc3x85 to 4.17 xc3x85 in the case of the short-wave exposure system employing rhodium mirrors, and can be reduced from 6.85 xc3x85 to 3.44 xc3x85 in the case of the short-wave exposure system employing platinum mirrors. The relation between energy levels of electrons generated from brominated PHS resists irradiated with exposure light reduced in wavelength and the quantities of absorption in the resists was investigated. FIG. 37 is a graph plotting the ratios of absorption by Auger electrons and photoelectrons having lower energy levels than the energy (about 1.4 KeV) of Auger electrons of bromine with respect to the total quantity of energy absorbed by the resists in the short-wave exposure system employing rhodium mirrors according to this embodiment while varying the thickness of the diamond film. FIG. 38 shows results in the short-wave exposure system employing platinum mirrors in place of the rhodium mirrors. If this ratio is in excess of 0.5, it means that the ratio of electrons having lower energy than Auger electrons of bromine is large in the absorbed energy in the resist. In other words, this is an index showing the ratio of electrons having lower energy than the energy (1.4 KeV) corresponding to the wavelength of about 9 xc3x85 in the total quantity of absorption, and if this ratio is in excess of 0.5, it means that the resist dominantly absorbs electrons exerting small influence on blurring among the total quantity of absorption. If this ratio is smaller than 0.5, it means that the resist dominantly absorbs electrons exerting large influence on blurring. Referring to FIG. 37, the ratio of absorption of electrons having energy of not more than 1.4 KeV is reduced from 0.5 in the PHS resist when the thickness of the diamond film exceeds 2 xcexcm to reduce the wavelength in the system employing rhodium mirrors, and reaches a low level of about 0.1 when the thickness of the diamond film is 100 xcexcm to further reduce the wavelength. This indicates that high-energy electrons exerting remarkable influence on blurring are dominantly absorbed in the resist. The ratio is remarkably increased in the bromine-containing PHS resist as compared with the PHS resist as the bromine weight ratio is increased. While this ratio is reduced when the thickness of the diamond film is increased to increase the short-wave component, a value of at least 0.5 is obtained in the brominated PHS resist having a bromine weight ratio of 50% also when the thickness of the diamond film is 100 xcexcm while low-energy electrons exerting small influence on blurring occupy a ratio of at least 50% of absorption also in the case of an average absorption wavelength of 4.17 xc3x85, and it is understood that blurring of electrons can be suppressed also when the wavelength is reduced. According to the present invention, the energy of Auger electrons is higher than that of photoelectrons and the ratio of absorption of low-energy electrons is dominant in the exposure wave range so that a pattern of high resolution can be obtained while suppressing blurring of electrons also when the wavelength is reduced. In a resist containing a material having an absorption edge in the exposure wave range, it follows that the ratios of Auger electrons having constant energy and photoelectrons having lower energy are remarkably increased on a shorter-wave side of the absorption edge. In the range where the energy of photoelectrons is not in excess of the energy of Auger electrons, blurring of the photoelectrons is lower than that of the Auger electrons also when the wavelength is reduced, and hence a pattern having high resolution is obtained The energy of Auger electrons of bromine is higher than that of photoelectrons in the range of about 8 xc3x85 to 4 xc3x85, and the quantity of absorption is large due to the shorter wave range than the absorption edge. Further, the exposure wave range of the exposure system employing rhodium mirrors is mainly longer than 4 xc3x85 and substantially matches with the wave range where the energy of Auger electrons of bromine exceeds that of photoelectrons. Therefore, the combination of the bromine-containing resist and the exposure system employing rhodium mirrors is particularly effective since absorption of low-energy electrons is dominant and blurring of electrons can be kept low. If the bromine weight ratio is lower than 37.7%, however, the ratio of absorption of electrons having energy of not more than 1.4 KeV may be reduced below 0.5 when the thickness of the diamond film is increased. Thus, the ratio of high-energy electrons is gradually increased when the wavelength is reduced, and hence the optimum wave range depends on the bromine weight ratio. When resolution necessary for the pattern is increased, blurring of electrons must be further reduced. Therefore, the optimum exposure wave range must be selected in response to the necessary pattern dimension. Referring to FIG. 36, the aspect changes in the case of platinum mirrors since the exposure light contains a component having a wavelength shorter than 4 xc3x85. Absorption by low-energy electrons is large as compared with a PHS resist containing no bromine, similarly to the case of rhodium mirrors. The quantity of light of a wavelength of about 6 to 8 xc3x85 is large when the thickness of the diamond film is up to about 10 xcexcm, and hence the energy of photoelectrons from bromine is low. When the thickness of the diamond film is further increased to reduce the wavelength, however, it follows that the ratio of a component having a wavelength shorter than 4 xc3x85 is increased in the case of platinum mirrors as compared with the case of rhodium mirrors. In bromine, the energy of Auger electrons is not changed by the exposure light having a wavelength shorter than 4 xc3x85, while the energy of photoelectrons exceeds that of Auger electrons to increase blurring of electrons. Thus, it is understood that the ratio of absorption by electrons having energy higher than 1.4 KeV is rapidly increased in the bromine-containing PHS resist when the wavelength is reduced in the case of platinum mirrors. The ratio is reduced to about 0.3 when the thickness of the diamond film is 100 xcexcm. Therefore, the system employing platinum mirrors is preferably employed in an exposure wave range exhibiting an average absorption wavelength substantially longer than 4 xc3x85. It has been shown that conditions capable of forming a pattern having high resolution with low energy of photoelectrons and Auger electrons, i.e., with small blurring by secondary electrons, can be implemented by employing a resist containing an element having an absorption edge in the vicinity of the exposure waveband. It is obvious from the principle of the present invention that the ratio of the element having the absorption edge in the vicinity of the exposure waveband in the resist is important. While the effect in view of X-ray absorptivity is increased as the quantity of the element having the absorption edge in the vicinity of the exposure waveband is increased, influence is exerted on other elements to be considered such that solubility of the resist is reduced as the bromination ratio is increased, and hence it follows that there is an optimum value. In the case of a bromine-containing resist, the atomic weight of bromine is large and hence a resist containing 1 to 4 elements per monomer is preferable. In the case of silicon, the atomic weight is small and hence it follows that a larger quantity is preferable. Therefore, a resist such as siloxane resist containing silicon in the polymer skeleton and including side chains having a small molecular weight or containing silicon also in side chains is preferable. A more desirable effect is attained by introducing bromine into the siloxane resist. Energy of electrons generated by exposure has been considered as to silicon having an absorption edge at about 7 xc3x85. Auger electrons having energy of about 1620 eV and low-energy photoelectrons are generated with reference to light having a wavelength slightly shorter than the absorption edge (6.9 xc3x85) of silicon. In other words, Auger electrons having energy corresponding to a wavelength of about 7.6 xc3x85 are generated at the maximum, and hence blurring of electrons can be reduced also when the wavelength is reduced. When the wavelength is further reduced, the energy of photoelectrons is gradually increased while the energy of Auger electrons remains constant, to be substantially equal to the energy of the Auger electrons at an exposure wavelength of about 3.6 xc3x85. In other words, the energy of electrons generated from silicon is lower than the energy corresponding to the wavelength of about 7.6 xc3x85 with reference to the exposure light in the range of about 6.9 xc3x85 to about 3.6 xc3x85, and hence blurring of electrons is not increased but a pattern of high resolution is obtained also when the wavelength is reduced. Therefore, it is an effective method for improvement of resolution to limit the main exposure wave range to this range. The energy of photoelectrons exceeds that of Auger electrons and blurring of electrons is gradually increased when the wavelength is further reduced. In order to study resolution in siloxane resist or polysilazane resist containing silicon, the ratio of absorption by electrons having lower energy than that of Auger electrons of silicon with respect to total absorbed energy was obtained. Such ratios were obtained as to cases of employing rhodium mirrors similar to those in the exposure system according to the aforementioned first embodiment, nickel mirrors having an incidence angle of 1xc2x0 and platinum mirrors having an incidence angle of 1xc2x0. FIG. 39 is a graph showing energy absorption spectra with respect to a silicon-containing resist having specific gravity of 1 g/cm3 and a thickness of 0.35 xcexcm. The thickness of a diamond mask substrate is 2 xcexcm. Absorption on a shorter wave side of the absorption edge of silicon is strong, and the absorption wave range is 3.5 xc3x85 to 7 xc3x85 in the case employing nickel mirrors. Similarly, the absorption wave ranges are 4 xc3x85 to 7 xc3x85 in the case employing rhodium mirrors, and 2.5 xc3x85 to 7 xc3x85 in the case employing platinum mirrors. The ratios of electrons having lower energy than Auger electrons of silicon with respect to total absorbed energy were 0.86 in the case of nickel mirrors, 0.86 in the case of rhodium mirrors and 0.81 in the case of platinum mirrors respectively. In each exposure system, the ratio of absorption by Auger electrons exceeds 0.8. Thus, the ratio of electrons having lower energy than the energy corresponding to the wavelength of 7.6 xc3x85 is dominant with respect to the quantity of absorption in the resist also in the exposure wave range including light having a wavelength shorter than 7 xc3x85, and high resolution can be expected. A method employing polysilane or polysilene as a resist was employed for increasing the silicon content. The silicon content can be set to 48.3% at the maximum in dimethyl polysilane, and can be increased up to 65.1% in methyl polysilene. Photosensitivity was supplied by a method similar to that for a general chemically amplified resist, and alkali solubility was supplied by a method of introducing a hydroxyphenyl group or a hydroxydifluoromethyl group. In a fourteenth embodiment, energy and absorption of Auger electrons and photoelectrons in a case of employing a resist containing germanium are considered. Auger electrons having energy of about 1150 eV and low-energy photoelectrons are mainly generated with reference to light having a slightly shorter wavelength than the absorption edge (9.9 xc3x85) of germanium. In other words, Auger electrons having energy (1150 eV) corresponding to the wavelength of about 10.8 xc3x85 are generated at the maximum, and hence blurring of electrons can be reduced also when the wavelength is reduced. When the wavelength is further reduced, the energy of Auger electrons remains constant while the energy of photoelectrons is gradually increased to be substantially equal to the energy of the Auger electrons at an exposure wavelength of about 5 xc3x85. In other words, the energy of electrons generated from silicon is lower than the energy corresponding to the wavelength of about 10.8 xc3x85 with reference to exposure light in the range of about 10 xc3x85 to 5 xc3x85, and hence blurring of electrons is not increased but a pattern of high resolution can be obtained also when the wavelength is reduced. When the wavelength is further reduced, the energy of photoelectrons exceeds that of Auger electrons, to gradually increase blurring of electrons. The energy of photoelectrons generated at a wavelength up to 4.4 xc3x85 is lower than the energy (1396 eV) of Auger electrons of bromine. In other words, the energy of photoelectrons generated with reference to the exposure light of 4.4 xc3x85 is substantially identical to the energy corresponding to the wavelength of 9 xc3x85, and germanium generates only electrons having energy lower than about half the energy of the exposure light. Thus, it is understood that blurring of electrons may be small and resolution may be improved also when the energy of photoelectrons is in excess of that of Auger electrons due to reduction of the wavelength, if the energy of generated photoelectrons is low. Resolution of a germanium-containing resist (C8H8O+Ge) prepared by adding germanium to a PHS resist was studied. The specific gravity of the resist was 1.17 g/cm3 when the germanium weight ratio was 0%, and 1.6 g/cm3 when the germanium weight ratio was 37.7%. The thickness of the resist film was 0.2 xcexcm. The ratio of absorption by electrons having lower energy than the energy of Auger electrons of germanium was obtained with respect to the quantity of absorbed energy in the germanium-containing resist having the germanium weight ratio of 37.7% in the exposure system according to the aforementioned first embodiment. FIG. 40 plots this ratio with respect to diamond films having thicknesses of 1xcexcm to 100 xcexcm. The average wavelength, reduced when the thickness of the diamond film is increased, is about 6.2 xc3x85 if the thickness of the diamond film is 20 xcexcm, and about 4.7 xc3x85 if the thickness of the diamond film is 50 xcexcm. In the germanium-containing resist having the germanium weight ratio of 37.7%, about 50% is absorption by electrons having energy of not more than 1150 eV corresponding to the wavelength of 10.8 xc3x85 also when the thickness of the diamond film is 20 xcexcm bringing the average absorption wavelength of 6.2 xcexc, and it is understood that the energy of electrons influencing resolution is kept low and blurring is kept small also when the wavelength is reduced. With respect to exposure light having a wavelength longer than 5 xc3x85, the energy levels of Auger electrons and photoelectrons generated from germanium are not more than 1150 eV, i.e., lower than the energy (1396 eV) of Auger electrons of bromine. When mainly employing an exposure wave range of 10 xc3x85 to 5 xc3x85, therefore, resolution may be increased if the germanium-containing resist is employed, since blurring of electrons is smaller than that in the case of employing a bromine-containing resist. In order to add germanium to the resist, germanium-containing molecules may be bonded to resist molecules, or surface-treated nanograins may be added to the resist. When mixing germanium-containing fullerene, an already existing resist can be employed for short-wave exposure. In a fifteenth embodiment, energy levels and absorption quantities of Auger electrons and photoelectrons in a case of employing a resist containing iodine having absorption edges on a longer-wave side of germanium are considered. M shells of iodine have a plurality of absorption edges between 13 xc3x85 and 20 xc3x85, and Auger electrons having energy of about 510 eV and low-energy photoelectrons are mainly generated at least with reference to light having a wavelength slightly shorter than 13 xc3x85. In other words, Auger electrons having energy corresponding to a wavelength of about 24 xc3x85 are generated at the maximum and hence blurring of electrons generated by exposure light having a shorter wavelength than the absorption edges can be reduced. When the wavelength is further reduced, the energy of Auger electrons remains constant while the energy of photoelectrons is gradually increased and substantially equalized with the energy of Auger electrons in an exposure wave range of about 11 to 8.5 xc3x85. In other words, the energy of electrons generated from iodine is lower than the energy corresponding to the wavelength of about 24 xc3x85 with reference to exposure light in the range of about 24 xc3x85 to at least 11 xc3x85, and hence blurring of electrons is not increased but a pattern of high resolution is obtained also when the wavelength is reduced. When the wavelength is further reduced, the energy of photoelectrons exceeds that of Auger electrons, to gradually increase blurring of electrons. Still the energy of photoelectrons generated at a wavelength of up to 6.1 xc3x85 is lower than the energy (1396 eV) of Auger electrons of bromine. In other words, the energy of generated photoelectrons is substantially identical to the energy corresponding to the wavelength of 9 xc3x85 and Auger electrons have lower energy with reference to the exposure light of 6.1 xc3x85, and hence blurring of electrons is suppressed. Also when the energy of photoelectrons is higher than that of Auger electrons, therefore, it may be possible to reduce blurring of electrons and improve resolution if the energy of generated photoelectrons is low. It has been shown in this embodiment that blurring of electrons can be reduced as compared with a conventional resist also when adding an element having no absorption edge in the exposure wave range. This is because absorption edges of iodine, not present in the exposure wave range, are present on a shorter-wave side of those of hydrogen, oxygen and carbon. The absorption edge of fluorine is also present on a shorter-wave side of those of hydrogen, oxygen and carbon, and hence blurring of electrons can be reduced also when employing a fluorine-containing resist. While such a situation can take place also when employing a resist containing bromine, phosphorus, sulfur or silicon in a case of reducing the wavelength, it is obvious from the above embodiments that blurring of electrons is reduced as compared with the conventional resist in this case. The specific function of the present invention is to reduce blurring of electrons generated by X-rays. According to the present invention, therefore, blurring of generated electrons can be reduced also in exposure employing an electron beam or an ion beam having energy substantially identical to that of soft X-rays. When irradiating a bromine-containing resist with an electron beam having an acceleration voltage of 1 KeV to 4 KeV corresponding to the energy of an X-ray wavelength of about 3 xc3x85 to 13 xc3x85, preferably an acceleration voltage of at least 1.5 KeV, for drawing a pattern, the energy of incident electrons is higher than that corresponding to the absorption edge (1.59 KeV) of bromine and hence incident electrons colliding with bromine partially generate Auger electrons and photoelectrons having lower energy than the incident electrons. Therefore, blurring of electrons in the resist is reduced while resolution of the pattern is increased. When employing incident electrons having higher energy than that corresponding to the absorption edge of each element in a resist containing silicon, phosphorus, sulfur or chlorine in place of bromine, it follows that spreading of electrons in the resist can be suppressed. Incident electrons are scattered while gradually losing energy in the case of the electron beam, and hence an electron scattering cross section is large in an element such as iodine or bromine having a large atomic number, i.e., an element having a large number of electrons around the atomic nucleus while the scattering probability of electrons tends to increase in the resist containing iodine or bromine for effectively suppressing the range of electrons. Also when drawing a pattern with an electron beam having a high acceleration voltage of 50 KeV to 100 KeV, incident electrons partially generate Auger electrons and photoelectrons having lower energy than the incident electrons, and hence blurring of electrons in the resist is reduced and resolution of the pattern is increased. Further, the energy of secondary electrons generated in the resist is gradually reduced while repeating scattering, and a similar effect of improving resolution can be expected when the energy reaches 1.6 KeV to 4 KeV. Thus, it is understood that resolution is improved when drawing the pattern on a resist containing an element having an absorption edge corresponding to the energy of about 1.6 KeV to 4 KeV also with an electron beam having a high acceleration voltage of 50 KeV to 100 KeV. Synchrotron radiation emitted from a radiation generator having deflection field intensity of 4.5 T and acceleration energy of 0.7 GeV was condensed in a beam line employing two rhodium mirrors having an oblique incidence angle of 1xc2x0 and passed through a beryllium window of 20 xcexcm in thickness serving as a vacuum barrier and a diamond mask substrate of 2 xcexcm in thickness, for applying this light to a substrate coated with a brominated PHS resist of 0.2 xcexcm in thickness having a bromine content of 50 wt. %. It was possible to form a resist pattern having a pattern dimension of 50 nm when the distance between an X-ray mask and the substrate coated with the resist was 10 xcexcm, and it was possible to form a resist pattern having a pattern dimension of 35 nm when the distance between the X-ray mask and the substrate coated with the resist was 5 xcexcm . A semiconductor device was fabricated by etching a substrate through such a resist pattern serving as a mask, washing the substrate, forming a new film on the substrate and thereafter repeating application of the resist, exposure, working, washing and film formation. Bromine has an absorption edge at about 8 xc3x85 and hence the energy of Auger electrons generated from the brominated PHS resist irradiated with exposure light having a wavelength in the range of 4 xc3x85 to 8 xc3x85, shorter than the absorption edge, is higher than that of photoelectrons. Therefore, blurring of electrons is not increased also when short-wave exposure is performed, and a fine pattern can be formed following improvement of an optical image due to Fresnel diffraction. A finer semiconductor device having a high degree of integration can be fabricated by working such a resist pattern. According to the present invention, as hereinabove described, blurring resulting from secondary electrons generated in a resist subjected to short-wave exposure can be reduced for enabling formation of a high-resolution pattern. Although the present invention has been described and illustrated in detail, it is clearly understood that the same is by way of illustration and example only and is not to be taken by way of limitation, the spirit and scope of the present invention being limited only by the terms of the appended claims.
	abstract	Spent fuel rods are stored in a container. In order to improve the retention capacity of the barriers for radioactive emitters (radionuclides), the spent fuel rods are embedded in a bulk fill of zeolite and/or activated charcoal.
	claims	1. An apparatus for deionizing water, comprising: a secondary cooling water system for a PWR nuclear power plant which contains in the system a steam generator and a condenser, and which has a mixture of an anion exchange resin and a gel-type cation exchange resin having a crosslinking degree of about 12 to 16% therein. 2. An apparatus of claim 1 wherein the anion exchange resin and the cation exchange resin forms a bed. claim 1 3. An apparatus of claim 1 wherein the cation exchange resin has a crosslinking degree of about 14%. claim 1 4. An apparatus of claim 1 wherein the cation exchange resin comprises a plurality of particles having a substantially uniform particle diameter. claim 1 5. An apparatus of claim 1 wherein the secondary cooling water system further comprises a prefilter in an upstream of the mixture. claim 1 6. An apparatus of claim 5 wherein the prefilter comprises at least one of a filter assembly containing hollow-fiber membranes, a filter assembly containing a precoatable filter element and a filter assembly containing a pleated, filter element. claim 5 7. An apparatus of claim 1 wherein the mixture of the anion exchange resin and the gel-type cation exchange resin has a rate of elution of a total organic carbon of less than 0.03 g-TOC/m 3 -MR/hr. claim 1
	abstract	Method and system are disclosed for determining conditions of components that are removably coupled to articles of personal protection equipment (PPE) by tracking the components against predetermined criteria.
049820982	summary	The present application claims priority of Japanese Patent Application Nos. 62-018986 filed on Jan. 29, 1987, 62-058071 filed on Mar. 13, 1987, and 62-066699 and 62-066700 respectively filed on Mar. 20 1987. FIELD OF THE INVENTION AND RELATED ART STATEMENT The present invention relates to speed compensated intensifying screens to be used for diagnostic examination of various parts of the human body and for use in the X-ray radiography. More particularly, this invention relates to speed compensated intensifying screen for producing clear images of various given human organ on one X-ray radiograph film as in the radiography of the chest, of the jaws in general and the periphery thereof in dentistry and surgery specilizing in the therapy of the oral cavity. In the application of the radiography to medical diagnosis, the practice of using a sensitive film in combination with an intensifying screen is generally resorted to. The intensifying screen is generally configurated by superposing on a substrate such as of paper or plastic material, a layer of a phosphor capable of emitting light under X-ray excitation and a thin protective film for protecting the layer of phosphor in the order mentioned. In the X-ray radiography, two such intensifying screens and one X-ray film interposed between the intensifying screens are used as held fast in a cassette. In the conventional intensifying screen, the speed of the layer of phosphor is substantially uniform throughout the entire area of a given plane. When the intensifying screen of this nature is used in the X-ray radiography of a part of the human body such as the chest which contains a plurality of organs exhibiting widely varied absorption coefficients to the X-rays, it is difficult to produce a clear image of all such component organs. In recent years, the development of so-called intensifying screens which have formed within one intensifying screen a plurality of regions possessing different degrees of speed has been gathering momentum. So far, the following inventions have been proposed, for example. (1) An intensifying screen set which combines an intensifying screen of full size and an intensifying screen formed in the shape conforming to a particular part requiring higher speed (Japanese Patent Application Disclosure SHO No. 59(1984)-83,099). (2) An intensifying screen set which combines an intensifying screen of ordinary run and a sheet adapted to effect partial absorption or reflection of the light emitted from the intensifying screen (Japanese Patent Application Disclosure SHO No. 61(1986)-155,900). (3) An intensifying screen which has formed within a layer of phosphor a pattern capable of partially absorbing the light emitted from the layer of phosphor (Japanese Patent Application Disclosure SHO No. 62(1987)-24,200). (4) An intensifying screen which has interposed between a layer of phosphor and a protective film a pattern layer capable of partially absorbing or reflecting the light emanating from the layer of phosphor (Japanese Patent Application Disclosure SHO No. 62(1987)-231,200). The invention of (1), however, entails a disadvantage that discontinuity of speed occurs along the borderline between the part of higher speed and the remaining part and the borderline is suffered to appear as a line pattern in the produced X-ray radiograph. The method which resorts to the partial absorption or reflection of the light emanating from the layer of phosphor as in the inventions of (2) through (4) is effected by directly printing in a pertinent pattern on the film or layer of phosphor a pigment or other similar coloring substance capable of absorbing the light emanating from the phosphor. In the method of this principle, the following measure is taken to prevent the borderline between a colored part and a non-colored part from appearing in the produced X-ray radiograph. An original photoengraving plate is produced by preparing a plurality of films colored as varied in density according to a given intensifying pattern, superposing these films in such a manner that the composite density will continually decrease in the direction from the light passing part to the light absorbing part, and photographing the composite surface of the superposed films. Then, a printing plate is produced from the original photoengraving plate and a light absorbing layer is formed thereon as by gravure printing to give rise to a gradient change of density from the light absorbing part to the light passing part. Indeed this method enables borderlines of change of density arising in the stage of printing to be reduced to a gradient change so delicate as to elude notice by unaided eyes. It nevertheless has a disadvantage that the borderlines are suffered to appear as line patterns in the produced X-ray radiograph. As an intensifying screen of special grade which, unlike the aforementioned intensifying screen of ordinary grade, has formed therein a speed distribution conforming specifically to the part of the human body selected as an object for radiography, an X-ray intensifying screen having formed in the central part thereof strips of high-speed part corresponding to the mediastinum (Japanese Patent Application Disclosure SHO 56(1981)-73,400), for example, has been introduced to the art. The exclusive intensification of the central part as taught by this invention, however, falls short of producing on one X-ray radiograph a clear image of the hilum of the lung, i.e. the trachease, the bronchi, and the periphery thereof, and the mediastinum, inclusive of the lungfield because the upper and lower regions of one and the same mediastinum have different X-ray absorption coeffient and also because the mediastinum and the lungfield have different absorption coefficient. To cope with this particular problem, there has been proposed an intensifying screen for use in the X-ray radiography of the chest, which has speed elaborately varied to suit the various organs concerned, namely the lungfield region, the upper region of the mediastinum, the lower region of the mediastinum, and the right and left regions of the hilum of the lung, for example (Japanese Patent Application Disclosure SHO No. 62(1987)-231,199). Owing to the presence of the heart beneath the lower region of the mediastinum, for example, the X-ray radiograph of the chest produced by using this intensifying screen still contains a vague portion in the otherwise clear image. In the circumstances, the desirability of further improvement in the intensifying screen has been finding enthusiastic recognition. Further, since this intensifying screen for use in the X-ray radiography of the chest has speed varied for each of the regions concerned, it has a disadvantage that the borderlines of difference in density are suffered to appear as line patterns in the produced image similarly to the disadvantage mentioned above. The existing intensifying screens of the kind having speed corrected to suit the particular part of the human body as an object for radiography are mainly intended for use in the X-ray radiography of the chest. Notwithstanding the X-ray radiography naturally constitutes itself a highly efficient means for the diagnostic examination of the head and for the diagnosis in the domains of dentistry and surgery specializing in the oral cavity, no intensifying screen has yet been developed which has speed corrected to suit these parts of the human body as an object for radiography. In the diagnostic examination of the head, for example, such special X-ray radiography as "Mr. Towne's method" has found popular utility. The Mr. Towne's method consists in taking radiograph of the head of a given patient in the front-to-back direction, suits the purpose of radiography of the occipital bone in its entirely, and serves as an important means for the diagnosis of diseases in the head as because of the ability thereof to project the backbone on the interior of the occipital foramen. This particular direction of radiography is also advantageous for cerebral angiography. The X-ray radiography of the head has had no alternative to date but to use an intensifying screen which has uniformly distributed has yet been developed which is intended exclusively for the X-ray radiography of the head. In the cross section of the head in the direction of radiography, therefore, the distance of transmission of X-rays in the head differs widely in the central part and in the part near the scalp. It is only the backbone, the central part of the occipital bone, etc. aimed at by the X-ray radiography that are radiographed clearly enough to serve for the purpose of actual diagnosis. The part near the scalp permits excessive transmission of X-rays and fails to form an image fit for diagnosis in the X-ray radiograph Thus, the Mr. Towne's method suffers from a disadvantage that the range of the head allowed to form in the X-ray radiograph a clear image fit by any measure for the diagnosis is rather limited Further in the X-ray radiography of the upper and lower jaws and the periphery thereof which is utilized for diagnosis in the domains of dentistry and surgery specializing in the oral cavity, intensifying screens having uniformly distributed speed in the layer of phosphor are used for the same reason as described above. Owing to the presence of the cervical vertebra exhibiting a notably different absorption coefficient to X-rays, no accurate diagnosis is obtained because not proper radiographic density is obtained only in the part corresponding to the cervical vertebra As a solution to this problem, the practice of making necessary correction on the X-ray apparatus side by adjusting the intensity of X-rays in terms of voltage or amperage thereby substantially equalizing the density of the part corresponding to cervical vertebra with that of the remaining part is also used. This method has a disadvantage that the apparatus itself is expensive and is devoid of versatility. OBJECT AND SUMMARY OF THE INVENTION An object of this invention, therefore, is to provide speed compensated intensifying screens which effect highly desirable correction of speed proper to the part of the human body subjected to radiography without suffering borderlines of change of density, therefore, ensures satisfactory radiography for the purpose of diagnosis. Another object of this invention is to provide an speed compensated intensifying screen for use in the X-ray radiography of the chest, which gives proper correction of speed on an X-ray radiograph so as to produce on the film a clear image of the part of the human body necessary for diagnostic examination of the chest such as, for example, the lungfield, the hilum of the lung, and the mediastinum and, at the same time, prevents the borderlines of change in density in the light-absorbing layer from standing out in the produced image. A further object of this invention is to provide a speed compensated intensifying screen for use in the X-ray radiography of the head, which gives proper correction of speed on an X-ray radiographic film so as to produce on the film a clear image of not only the backbone and the occipital bone, i.e. essential parts for the X-ray radiography of the head, but also such peripheral parts as the part near the scalp and, at the same time, prevents the borderlines of change of density in the light-absorbing layer intended for correction of speed from standing out in the produced image. Yet another object of this invention is to provide a speed compensated intensifying screen for use in the X-ray radiography of the upper and lower jaws and the periphery thereof, which gives a proper correction of speed on an X-ray radiograph being used in the X-ray radiography of the upper and lower jaws and the periphery thereof so as to produce on the film a clear image of the entire aspect of the pertinent parts inexpensively and safely while precluding the occurrence of a difference in density due to the shadow produced by the cervical vertebra and, at the same time, prevents the borderlines of change in density in the light-absorbing layer intended for correction of speed from standing out in the image. This invention is directed to a speed compensated intensifying screen for radiography, comprising a substrate, a layer of phosphor formed on the substrate, a protective layer formed on the layer of phosphor, and a light-absorbing layer serving to absorb the light emitted from the aforementioned layer of phosphor proportionately to the part of the human body subjected to radiography, in which intensifying screen is characterized by the fact that the aforementioned layer of phosphor is enabled by the aforementioned light-absorbing layer to create therein a plurality of regions differing in speed and the speed across each of the boundaries of the aforementioned plurality of regions of speed is continuously varied. The plurality of regions of speed in the present invention are fixed in accordance with the particular part of the human body subjected to radiography. The ratio of change of speed across each of the borderlines between the plurality of regions of speed, i.e. the speed gradient per unit length in a minute increment, is so continuous that no visible line will appear in the produced X-ray radiograph. This rule is similarly applicable to the change of speed which takes place within each of the regions of speed. When the continuity of the change in speed is measured with a densitometer, even in the conventional intensifying screen on which the change in speed is imparted by superposition of films containing a given image in gradually varied levels of density, breaks in the continuity of the change in density cannot be expressed in definite numerical values because of noises inevitably generated during the measurement. When this intensifying screen is used in X-ray radiography, the produced X-ray radiograph clearly shows line patterns evincing the presence of breaks of continuity of the change in speed. It is thus difficult to express the continuity of the change in speed. It is, however, possible to quantify the continuity of the change in speed based on the presence or absence of line patterns to be visibly found in the X-ray radiograph. As one concrete embodiment of the present invention, an intensifying screen for use in the X-ray radiography of the chest. In this intensifying screen for the X-ray radiography of the chest, the plurality of regions differing in speed created by the light-absorbing layer in the layer of phosphor substantially comprise, as illustrated in FIG. 1, for example, a region A substantially corresponding to the lower part of the mediastinum and located substantially in the central part, a trapezoidal region B of high speed continuously diverging from the bottom part of the region A toward the abdomen side, a region C corresponding to the right hilum of the lung and a region D corresponding to the left hilum of the lung with the speed substantially continuously lowered from the opposite lateral sides of the region A toward the right and left lungfields, a region E located in the upper part of the region A and corresponding to the upper part of the mediastinum with the speed substantially continuously lowered upwardly and to the opposite sides, a region F and a region G with the speed substantially continuously lowered from the opposite sides of the region B toward the right and left lungfields, a region H corresponding to the right lungfield, and a region I corresponding to the left lungfield and, further, the speed across each of the borderlines of the aforementioned plurality of regions of speed is continuously varied. The regions A through I of speed in the intensifying screen for the X-ray radiography of the chest possess such a positional relationship as illustrated in FIG. 1. This positional relationship need not be strictly defined but may be accepted so long as it approximates what is illustrated in FIG. 1. Properly, the magnitudes of speed in these regions are such that where the magnitude of speed in the regions A and B taken as 100, the magnitude of speed in the regions H and I corresponding to the lungfield is not more than 50, and the magnitudes of speed in the regions H and I. In the regions C, D, F, and G, the speed is substantially continuously lowered from the boundaries of the regions A and B toward the right and left lungfields and, in the region E, the speedis continuously lowered from the boundary of the region A upwardly and toward the right and left lungfields as indicated by the arrows of solid line in FIG. 1. In a preferred speed distribution, regions A' and B' indicated by a dotted line in FIG. 1 are formed as more restricted regions of high speed and the regions A and B excluding the regions A' and B' have the change of speed thereof smoothened as a whole so as to permit a slight decrease of the speed toward the lungfield and upwardly. By creating the regions of speed corresponding to the pertinent internal organs and thereby effecting corrections of speed properfor the organs, the regions of such organs as the lungfield, the hilums of the lung, and the mediastinum areenabled to be radiographed in clear contrast on one X-ray radiograph. Moreover, the boundaries of the regions of speed are not suffered to stand out in the produced image and the diagnostic examination can be carried out accurately. As another typical embodiment of the present invention, an intensifying screen forthe X-ray radiography of the head can be cited. In this intensifying screen for the X-ray radiography of the head, the light-absorbing layer enables the layer of phosphor to create therein a plurality ofregions differing in speed and the plurality of regions substantially comprise, as illustrated in FIG. 2, a substantially elliptical region J of high speed located substantially in the central part relative to the longitudinal cross section of the head, a region L of low speed corresponding to the outside of the contour of the head, and a region K corresponding to the head except for the region J of high speed and possessing a magnitude of speed intermediate between the magnitude of speed of the region J of high speed and the magnitude of speed of the region L and the speed across each of the borderlines of the regions of speed is continuously varied. The positional relationship of the regions of speed in the intensifying screen for the X-ray radiography of the head need not be strictly defined but may be accepted so long as it approximates what is illustrated in FIG. 2. For example, it is desired to be fixed as follows. In the case of an ordinary intensifying screen measuring 300 mm.times.250 mm and used for the X-ray radiography of the head, a region J of high speed substantially shaped like an ellipsis possessing a major axis in the range of 80 to 120 mm and a minor axis in the range of 40 to 80 mm is formed substantially in the central part, a region K corresponding to the head is formed around the region J, and a region L of low speed is formed outside the contour of the head. Properly, the magnitudes of speed of the plurality of regions of speed are desired to be such that when the magnitude of speed in the region J of high speed is taken as 100, the magnitude of speed in the region L of low speed outside the contour of the head is not more than 50, and the magnitude of speed in the region K is intermediate between the magnitude of speed in the region J and the magnitude of speed in the region of L. In a desirable speed distribution, the speed in the region K is substantially continuously lowered radially from the region J of high speed to the region L of low speed as indicated by the arrow in the diagram. By creating such regions of speed as described above, the differences in the absorption coefficient of X-rays due to the differences in the distance of X-ray transmission in the cross section of the head in the direction of the X-ray radiography and the differences in the absorption coefficient of X-ray among the different organs concerned are corrected so that the central part of the head to the part near the scalp are all radiographed in clear contrast in one X-ray radiograph. The borderlines between the plurality of regions of speed are not suffered to stand out in the produced image and the diagnostic examination can be carried out accurately. As still another typical embodiment of the present invention, an intensifying screen for X-ray radiography of the upper and lower jaws and the periphery thereof is cited. In this intensifying screen for the X-ray radiography of the upper and lower jaws and the periphery thereof, the light-absorbing layer enables the layer of phosphor to create therein a plurality of regions differing in speed and the plurality of regions differing in speed substantially comprise, as illustrated in FIG. 3, for example, a belt-like region M of high speed extending from the central part of one end to the central part of the other end and substantially corresponding to the position of the cervical vertebra and another region N as illustrated in FIG. 3 and the speed across each of the borderlines between the plurality of regions of speed is continuously varied. The belt-like region M of high speed in the intensifying screen for the X-ray photography of the upper and lower jaws and the periphery thereof is desired, in an ordinary intensifying screen measuring 150 mm.times.300 mm, 150 mm.times.303 mm, 200 mm.times.300 mm, or 200 m.times.300 mm and intended for use in the X-ray radiography of the upper and lower jaws and the periphery thereof, to be located along the center line extending from the center of one major side to the center of the other major side in a width in the range of 5 to 40 mm on either side of the center line. The magnitudes of speed in the regions of speed are desired to be such that when the magnitude of speed in the belt-like region M is taken as 100, the magnitude of speed in the other region N is in the range of 40 to 80. Further, these regions are desired to be given a similar change of speed as indicated within the range of speed correction ratio of any of the three types, Type 1 through Type 3, shown in the graph of speed distribution of FIG. 3. If the speed of the other region N is less than 40 where that of the belt-like region M of high speed is 100, the produced X-ray radiograph shows unduly high contrast and suffers from lack of uniformity of density. If the speed of the region N exceeds 80, the effect of this invention is not manifested fully because no sufficient correction of speed is effected. In the actual use for the X-ray radiography, this intensifying screen for the X-ray radiography of the upper and lower jaws and the periphery thereof is used as nipped between to intensifying screens. If the intensifying screen possessing such a high speed correction ratio as Type 3 of FIG. 4 is used in combination with intensifying screens having no speed correction and receiving the light from the phosphor uniformly, the effect of the invention is similarly obtained because the amount of light impinging on the X-ray film gives rise to a speed distribution of Type 2, for example. By forming a region of high speed in the position corresponding to the cervical vertebra as described above, the upper and lower jaws and the periphery thereof are enabled to be radiographed in uniform density. The light-absorbing layer in the intensifying screen of the present invention may be formed by any of the following procedures. (1) A layer for absorbing the light emitted from the phosphor is formed on the surface of a layer of phosphor, in a shape conforming with the shape of the part of the human body subjected to radiography. (2) A layer for absorbing the light emitted from the phosphor is formed inside a layer of phosphor, in a shape conforming with the shape of the part of the human body subjected to radiography. (3) A layer for absorbing the light emitted from the phosphor is formed on the surface of a protective layer, in a shape conforming with the shape of the part of the human body subjected to radiography. In all the methods described above, the method of (2) proves to be particularly effective because the produced light-absorbing layer provides a high ratio of speed correction, possesses highly desirable adhesiveness to the X-ray film, exhibits satisfactory granularity of texture, and enjoys high sharpness of image. Where the light-absorbing layer is formed by the procedure of (2), the intensifying screen of the present invention is manufactured as follows. First, as illustrated in FIG. 5, a first layer 14a of phosphor is formed on a substrate 12 made of plastic film such as polyester or non-woven fabric by applying on the substrate 12 a paste prepared by adding a phosphor such as CaW0.sub.4, Gd.sub.2 0.sub.2 S:Tb, or BaFCl:Eu to an organic binder and subsequently drying the applied layer of the paste. Then, on a plastic film such as of polyester, a light-absorbing layer 16 is formed by applying on the plastic film a pigment capable of absorbing the light emitted from the phosphor used in the layer 14a of phosphor in such a manner that the applied layer of the pigment will give rise to a plurality of regions of speed, depending on the particular part of the human body subjected to radiography. During the formation of this light-absorbing layer 16, the application of the pigment is so regulated that the density is continuously changed across each of the borderlines between the regions of speed. For the formation of the light-absorbing layer 16 mentioned above, the following two procedures are available. (1) The relevant part of the body of a person of standard body type is radiographed at the focal point and at points separated by gradually increased intervals from the focal point until fine details of the part and the osteal components blur out along their peripheries, to prepare a set of photogravure plates of varying shade. A printing plate is produced from the photogravure plates. A light-absorbing layer is formed by applying a coating material with the aid of the plate using the printing technique such as the gravure printing. (2) As illustrated in FIG. 6, a light-shielding plate 20 provided with an opening 22 conforming with a desired region of high speed is set in place and a planar light source 24 is disposed directly on or at a prescribed distance upward from the light-shielding plate 20. A sensitive film 26 is disposed at a prescribed distance downward from the light-shielding plate 20. Then, a collimated beam of light (indicated by the arrow z in the diagram) is projected downwardly from above the planar light source 24 to effect exposure of the sensitive film 26. In this case, the light emanating from the planar light source 24 is converted into scattered light (indicated by the arrow y in the diagram), depending on the positional relation between the light-shielding plate 20 and the planar light source 24 and that between the light-shielding plate 20 and the sensitive film 26. Since the sensitive film 26 is exposed to the scattered light, continuous change in density is produced along the borderline between the opening corrsponding to the region of high speed and the remaining part. A light-absorbing layer is formed in the same manner as in (1) above, using as a photogravure plate the sensitive film which has been exposed as described above. Thereafter, the light-absorbing layer 16 is mounted, on the layer 16 and a second layer 14b of phosphor is likewise mounted on the first layer 14a- of phosphor and a protective film 18 is superposed on the second layer 14b of phosphor to complete an intensifying screen aimed at. Owing to the presence of the light-absorbing layer incorporated in the layer of phosphor in the manner described above, the speed correction ratio could be easily varied, when necessary, by simply adjusting the position at which the light-absorbing layer is formed, namely by varying the thickness of the first layer of phosphor and that of the second layer of phosphor. Optionally, the light-absorbing layer 16 may be directly superposed on the first layer 14a of phosphor instead of on the plastic film. When an intensifying screen is manufactured by using a light-absorbing layer formed by either of the procedure described above, the change in speed across each of the borderlines between the plurality of regions of speed is rendered continuous. As a result, these borderlines are not suffered to stand out as line patterns in the image. Thus, the intensifying screen ensures production of X-ray radiographs of quality.
052767191	claims	1. A hydraulic control rod drive for a nuclear reactor, with a piston/cylinder drive associated with a control rod and a reactor plenum enclosing the drive, comprising: a) two hollow bodies together forming a cylinder-piston unit and defining an inner space; b) means for supplying a working fluid through one of said hollow bodies; c) a first one of said hollow bodies being stationary and a second one of said hollow bodies being disposed coaxially with respect to said first hollow body and defining an annular gap therebetween so as to allow axial movement of said second hollow body; said second hollow body forming a carrier body for control elements of a control rod; d) said first hollow body having a lower region with a working fluid supply channel formed therein; e) means for lifting, lowering or suspending said second hollow body by feeding working fluid through said supply channel to said inner space and removing the working fluid from said inner space via a throttle passage; f) a positional measurement system for said second hollow body with an ultrasonic measurement path, including an ultrasound reflector disposed at an upper end of said second hollow body, and an ultrasonic transducer rigidly mounted above and remote from said ultrasound reflector; and g) means for venting said inner space, said venting means being in the form of a venting channel configuration disposed at an upper end in said second hollow body, said venting channel configuration having channels opening into the reactor plenum at a given distance from said ultrasonic measurement path, so as not to cause density fluctuations in the working fluid disposed in said ultrasonic measurement path. a movable cylinder having control rod elements disposed thereon; a stationary piston rigidly mounted in the fuel assembly, said piston having a bottom, an open top, and an axial opening formed therein for allowing communication between said bottom and said open top; said cylinder being disposed coaxially around said piston and defining a gap therebetween so as to allow axial movement of said cylinder; means for supplying a working fluid to said piston for lifting, lowering or suspending said cylinder; means for measuring a vertical displacement of said cylinder; and means for venting said gap between said piston and said cylinder. 2. The hydraulic control rod drive according to claim 1, wherein said throttle passage is formed by said annular gap. 3. The control rod drive according to claim 1, wherein said first hollow body is a hollow piston being open at an upper end thereof, said second hollow body is a hollow cylinder coaxially surrounding and covering said first hollow body and defining said annular gap therebetween, and whereby an axial position of said hollow cylinder relative to said hollow piston is determined by an amount of working fluid supplied through said hollow piston into said hollow cylinder. 4. The control rod drive according to claim 3, including a cross-shaped attachment part having a central channel part and cross legs extending away from said central channel part, said cross-shaped attachment part being disposed on the upper end of said hollow cylinder and having said venting channel configuration formed therein, said venting channel configuration including radial channels originating from said central channel part, communicating with an interior of said hollow cylinder, extending through said cross legs, and opening into the reactor plenum. 5. The control rod drive according to claim 4, wherein the control elements of the control rod are absorber plates disposed around said hollow cylinder in a cross-shaped configuration and having distal edges facing away from said hollow cylinder, said radial channels opening into the reactor plenum approximately in the region of said distal edges. 6. The control rod drive according to claim 3, wherein the control elements of the control rod are embodied as cross-shaped absorber plates extending radially from said hollow cylinder, including a head plate disposed on said hollow cylinder and having said venting channel configuration formed therein, said head plate having a diameter approximately corresponding to a diameter of said hollow cylinder, said venting channel configuration including channels being T-shaped as seen in axial section, and including outlet pipes having outlet openings and communicating with said channels, said outlet openings being disposed at a given distance from said ultrasonic measurement path. 7. The control rod drive according to claim 1, wherein said venting means are a venting channel configuration disposed at an upper end in said second hollow body, said venting channel configuration including venting channels extending at an angle of between 5.degree. and 10.degree. relative to the horizontal. 8. The control rod drive according to claim 1, including first annular protrusions and recesses formed about the outer circumference of said first hollow body, second annular protrusions and recesses formed on an inner surface of said second hollow body, said first and second annular protrusions and recesses defining annular gaps therebetween, said annular gaps forming the throttle passage for the working fluid emanating from the inner space of said first and second hollow bodies. 9. In a nulcear reactor having a fuel assembly with a control rod and a reactor plenum enclosing the fuel assembly, a hydraulic control rod drive, comprising: 10. The control rod drive according to claim 9, wherein said measuring means include an ultrasonic reflector disposed on said cylinder, and an ultrasonic transducer rigidly mounted above said cylinder in alignment with a longitudinal axis of said cylinder. 11. The control rod drive according to claim 9, wherein said venting means are in the form of a venting channel formed in an upper end of said cylinder for allowing working fluid with gas bubbles to escape from said cylinder.
048636827	summary	FIELD OF THE INVENTION This invention relates to austenitic stainless steel compositions for service in environments of high irradiation such as in the interior of a nuclear fission reactor. The invention is particularly concerned with an austenitic stainless steel alloy composition having both a high resistance to irradiation promoted corrosion and reduced long term irradiation induced radioactivity. BACKGROUND OF THE INVENTION Stainless steel alloys, especially those of high chromium-nickel type, are commonly used for components employed in nuclear fission reactors due to their well known good resistance to corrosive and other aggressive conditions. For instance, nuclear fuel, neutron absorbing control units, and neutron source holders are frequently clad or contained within a sheath or housing of stainless steel of Type 304 or similar alloy compositions. Many such components, including those mentioned, are located in and about the core of fissionable fuel of the nuclear reactor where the aggressive conditions such as high radiation and temperature are the most rigorous and debilitating. Solution or mill annealed stainless steels are generally considered to be essentially immune to intergranular stress corrosion cracking, among other sources of deterioration and in turn, failure. However, stainless steels have been found to degrade and fail due to intergranular stress corrosion cracking following exposure to high irradiation such as typically encountered in service within and about the core of fissionable fuel of water cooled nuclear fission reactors. Such irradiation related intergranular stress corrosion cracking failures have occurred notwithstanding the stainless steel metal having been in the so-called solution or mill annealed condition, namely having been treated by heating up to within a range of typically about 1,850.degree. to about 2,050.degree. F., then rapidly cooled as a means of solutionizing carbides and inhibiting their nucleation and precipitation out into grain boundaries. Accordingly, it is theorized that high levels of irradiation resulting from a concentrated field or extensive exposure, or both, are a significantly contributing cause of such degradation of stainless steel, due among other possible factors to the irradiation promoting segregation of the impurities therein. Efforts have been made to mitigate intergranular stress corrosion cracking of stainless steels which have not been desensitized by solution or mill annealing, or irradiated, including the development of "stabilized" alloys. For example, alloys have been developed containing a variety of alloying elements which are intended to form stable carbides. Such stabilizing carbides should resist solutionizing at annealing temperatures of at least 1900.degree. F. whereby the carbon is held so that the subsequent formation of chromium carbide upon exposure to high temperatures is prevented. Included among the alloying elements proposed are titanium, niobium and tantalum. An example of one type of such a stainless steel alloy is marketed under the designation of Type 348. The Metals Handbook, Ninth Ed., Vol. 3, page 5, American Society for Metals, 1980 gives the alloy composition for Type 348 in weight percent as follows: ______________________________________ C Mn Si Cr Ni P S Cu Nb + Ta ______________________________________ 0.08 2.00 1.00 17.0- 9.0- 0.045 0.03 0.2 10 .times. % C max. max. max. 19.0 13.0 max. max. max. min. ______________________________________ SUMMARY OF THE INVENTION This invention comprises a stainless steel alloy composition having specific ratios of alloying elements for service where exposed to irradiation. The austenitic stainless steel alloy composition provides resistance to the degrading effects of the irradiation, and is of reduced long term irradiation induced radioactivity. OBJECTS OF THE INVENTION It is a primary object of this invention to provide an austenitic stainless steel alloy composition having effective resistance to the deleterious effects attributable to prolonged exposure to high levels of radiation. It is also an object of this invention to provide an austenitic stainless steel alloy composition which essentially maintains its physical and chemical integrity when subjected to high levels of irradiation over long periods. It is a further object of this invention to provide an austenitic stainless steel alloy composition which provides effective resistance to irradiation promoted intergranular stress corrosion cracking. It is a still further object of this invention to provide an austenitic stainless steel alloy composition which minimizes the long term imposed radioactivity resulting from exposure to extensive high levels of irradiation in service. It is an additional object of this invention to provide an austenitic stainless steel alloy composition which exhibits low radiation emissions following its irradiation whereby it can be disposed of at low costs.
059441909	claims	1. A radiopharmaceutical capsule safe, comprising: a safe comprising a safe bottom and a safe lid, said safe bottom and said safe lid each being formed from radiopaque material, said safe bottom having a vial bottom-receiving cavity formed therein and said safe lid having a vial cap-receiving cavity formed therein; and a capsule vial comprising a vial bottom and a vial cap securable to said vial bottom, said vial cap being formed from radiotransmissive material and said vial bottom being configured to receive a radiopharmaceutical capsule therein; wherein said vial bottom-receiving cavity and said vial bottom are cooperatively configured such that said vial bottom is receivable within said vial bottom-receiving cavity and wherein said vial cap-receiving cavity and said vial cap are cooperatively configured such that said vial cap is receivable within said vial cap-receiving cavity; whereby said capsule vial can be encased completely within said safe to contain radiation emitted by said radiopharmaceutical capsule when said safe lid is engaged with said safe bottom, and whereby said radiopharmaceutical capsule can be assayed while environmentally sealed within said vial capsule by removing said safe lid from engagement with said safe bottom; wherein both the vial cap and the vial bottom are releasably lock-engageable respectively with said safe bottom and said safe wherein said vial bottom has two or more bottom tabs extending outwardly therefrom, said vial cap has two or more cap tabs extending outwardly therefrom, and said vial cap and said vial bottom are threadably engageable with each other; and wherein said safe bottom has two or more lower slots extending along the vial bottom-receiving cavity to receive the bottom tabs and said safe lid has two or more upper slots extending along the vial cap-receiving cavity to receive the cap tabs; whereby said vial cap can be disengaged from said vial bottom by rotating said safe lid relative to said safe bottom. providing a safe comprising a safe bottom and a safe lid, each being formed from radiopague material, said safe bottom and said safe lid being engageable with each other; providing a capsule vial comprising a vial bottom and a vial cap, said vial cap being formed from radiotransmissive material and being engageable with said vial bottom wherein at least one of the vial cap and the vial bottom is releasably lock-engageable respectively with said safe bottom and said safe lid; disposing said vial bottom in a vial bottom-receiving cavity formed in said safe bottom; disposing said vial cap in a vial cap-receiving cavity formed in said safe lid; disposing a radiopharmaceutical capsule in said vial bottom; engaging said vial cap to said vial bottom; and engaging said safe lid to said safe bottom; and further comprising disposing activated charcoal in said vial bottom-receiving cavity before disposing said vial bottom in said vial bottom-receiving cavity. 2. The radiopharmaceutical capsule safe of claim 1, wherein the upper slots have circumferentially oriented upper tab-engaging slot extensions which permit limited rotation of said safe lid relative to said vial cap. 3. The radiopharmaceutical capsule safe of claim 2, wherein said upper tab-engaging slot extensions are oriented such that the cap tabs are positioned within said upper tab-engaging slot extensions when said safe lid is rotated to disengage said vial cap from said vial bottom, whereby said vial cap is retained within said vial cap-receiving cavity when disengaged from said vial bottom. 4. The radiopharmaceutical capsule safe of claim 1, wherein the lower slots have circumferentially oriented lower tab-engaging slot extensions which permit limited rotation of said vial bottom relative to said safe bottom. 5. The radiopharmaceutical capsule safe of claim 4, wherein said lower tab-engaging slot extensions are oriented such that the bottom tabs are positioned within said lower tab-engaging slot extensions when said safe lid is rotated to disengage said vial cap from said vial bottom, whereby said vial bottom is retained within said vial bottom-receiving cavity when said safe bottom is inverted to dispense a radiopharmaceutical capsule contained within said vial bottom. 6. The radiopharmaceutical capsule safe of claim 1, further comprising an upper lock ring positioned in a lower portion of said vial cap-receiving cavity, and wherein said upper slots are formed in said upper lock ring. 7. The radiopharmaceutical capsule safe of claim 1, further comprising a lower lock ring positioned in an upper portion of said vial bottom-receiving cavity, and wherein said lower slots are formed in said lower lock ring. 8. The radiopharmaceutical capsule safe of claim 2, further comprising an upper lock ring positioned in a lower portion of said vial cap-receiving cavity, and wherein said upper slots and said upper tab-engaging slot extensions are formed in said upper lock ring. 9. The radiopharmaceutical capsule safe of claim 1, further comprising a lower lock ring positioned in an upper portion of said vial bottom-receiving cavity, and wherein said lower slots and said lower tab-engaging slot extensions are formed in said lower lock ring. 10. The radiopharmaceutical capsule safe of claim 1, further comprising an outer jar in which said safe is received, said outer jar comprising a jar bottom in which said safe bottom is received and a jar cap engageable with said jar bottom and configured to cover said safe lid. 11. The radiopharmaceutical capsule safe of claim 10, wherein said jar bottom has a retaining member which retains said safe bottom within said jar bottom. 12. The radiopharmaceutical capsule safe of claim 11, wherein said retaining member comprises an annular retaining ring disposed near an upper, open portion of said jar bottom. 13. A method of packaging a radiopharmaceutical capsule, said method comprising the steps: 14. The method of claim 13, wherein said vial cap is disposed in said vial cap-receiving cavity before said vial cap is engaged with said vial bottom, whereby said vial cap is engaged with said vial bottom generally simultaneously with said safe lid being engaged with said safe bottom. 15. The method of claim 13, further comprising providing a jar comprising a jar bottom and a jar cap, disposing said safe bottom in said jar bottom, and securing said jar cap to said jar bottom over said safe lid. 16. The method of claim 12 wherein both the vial cap and the vial bottom are releasably lock-engageable respectively with said safe bottom and said safe lid.
	description	Priority to Korean patent application number 10-2019-0089190 filed on Jul. 23, 2019 the entire disclosure of which is incorporated by reference herein, is claimed. The present disclosure relates to a method of producing actinium by using liquefied radium and, more specifically, to a production method capable of producing actinium by performing a nuclear reaction of liquefied radium. Ac-225 is produced while two neutrons are escaping from the radium-226 target material when accelerating and colliding a proton with a radium-226 target material by a nuclear reaction of 226Ra(p, 2n)225Ac to produce actinium-225, i.e., a radioactive medicine for treatment. A Ra-226 material used at this time generally includes a powder-type target among solid targets. A Ra-226 powder to which the proton has been irradiated passes through a series of separation and refinement processes in order to separate Ac-225 which is included in the powder and has been produced by performing a nuclear reaction. To this end, a method of producing Ac-225 may comprise melting Ra-226 into a liquefied form, passing a liquefied Ra-226 through separation and refinement processes, and performing a process of preparing the powder type Ra-226 to reuse a powder type Ra-226 for producing Ac-225 again. A method of producing Ac-225 by using such a powder type Ra-226 is disclosed in U.S. Pat. No. 6,680,993. However, such a conventional technique makes a quantitative loss of Ra-226 according as Ra-226 is changed into a powder form and a liquefied form in a series of processes for producing Ac-225. Due to problems that Ra-226 has a long half-life of about 1,600 years at present, and releases radon, i.e., an inert gas in the decay process, there have been difficulties in disposal and storage of Ra-226, and, for this reason, additional production has been suspended. Therefore, it is desirable that a loss of Ra-226 is minimized in the process of producing Ac-225 by using Ra-226 which has not been left much in the world. The purpose of the present disclosure is to provide a method of producing actinium using liquefied radium, the method for minimizing loss of Ra-226 which may be generated in the process of producing Ac-225 by performing a nuclear reaction using conventional Ra-226. To achieve the purpose, the present disclosure may provide a method of producing actinium by using liquefied radium, the method comprising a step of moving the liquefied radium to load the liquefied radium into a reaction space inside a chamber, a step of producing actinium through a nuclear reaction process by irradiating a particle beam to the liquefied radium of the reaction space inside the chamber, and an unloading step of moving a product comprising the liquefied radium and actinium to the outside of the chamber. Meanwhile, the method of producing actinium using liquefied radium may further comprise a separation step of separating actinium from the product. Further, the method of producing actinium using liquefied radium may comprise a reloading step of moving remaining liquefied radium obtained by separating actinium from the product to the reaction space of the chamber. Moreover, the method of producing actinium using liquefied radium may further comprise a radon discharge step of discharging radon included in the product while performing the loading step or the unloading step. Further, the radon discharge step enables radon to be discarded by condensing radon. Additionally, the radon discharge step enables radon to be discharged after diluting radon with external air. Meanwhile, the loading step enables a preset amount of radium to be moved to the reaction space. Moreover, the loading step enables the preset amount of radium to be moved to the reaction space by using a syringe pump. On the other hand, the unloading step enables the product to be unloaded by flowing in an inert gas into the reaction space of the chamber. Meanwhile, the radium can be liquefied by using an organic solution. Moreover, the organic solution may be NO3 or Cl2. Moreover, the method of producing actinium using liquefied radium may further comprise a step of refining separated actinium, the step which is performed after the step of separating actinium. A method of producing actinium by using liquefied radium according to the present disclosure can minimize loss of Ra-226 according to the state change of Ac-225 by producing Ac-225 using Ra-226 of a liquefied state, moving the produced Ac-225 in a liquefied state after Ac-225 is produced, and separating Ac-225 and reusing Ra-226 thereby enabling a nuclear reaction process of Ac-225 to be performed. Further, a method of producing actinium by using liquefied radium according to the present disclosure has an effect of enabling safety to be improved by including a radon collection unit which is capable of discharging and isolating radon produced from Ra-226, thereby preventing radiation exposure due to radon. Hereinafter, a method of producing actinium by using liquefied radium according to an embodiment of the present disclosure will be described in detail with reference to the accompanying drawings. Names of respective elements in the description of the following embodiments can be referred to as other names in the art. However, if there are functional similarities and identities in the elements, the elements can be said to have equivalent configurations although modified embodiments are adopted. Further, marks added to the respective elements are described for convenience of explanation. However, illustration contents on drawings having these marks described thereon do not limit the respective elements to the scope within the drawings. Similarly, if there are functional similarities and identities in the elements although partially modified embodiments adopt configurations on the drawings, the elements can be said to have equivalent configurations. Further, when the elements are recognized as elements which should be naturally included by looking at a general technician level of the field of the art, the explanations thereof are omitted. FIG. 1 is a flowchart of a method of producing actinium by using liquefied radium, i.e., an embodiment according to the present disclosure. As illustrated in FIG. 1, a method of producing actinium by using liquefied radium according to the present disclosure may comprise a loading step (S100), an actinium production step (S200), an unloading step (S300), a radon discharging step (S400), and an actinium separating and refining step (S500), and a reloading step (S600). The loading step (S100) corresponds to a step of moving liquefied radium to a reaction space inside a chamber. Here, radium may be liquefied using an organic solution, and, for example, radium may be moved in a liquefied state in which ions such as Cl2 or NO3 are bonded. The loading step (S100) may be performed by a method of moving the liquefied radium to the reaction space by applying a pressure to liquefied radium outside the chamber. For example, a syringe pump may be provided such that a predetermined amount of the liquefied radium can be moved in a repeated loading step (S100). Meanwhile, the radon discharging step (S400) may be simultaneously performed in the loading step (S100). The radon discharging step (S400) corresponds to a step of transferring the separated radon to a separate space by separating from a product radon, i.e., a radioactive gas generated while radium is being decayed. Radon is consistently generated while radium is being naturally decayed, and radon may be naturally discharged from a vial in the process of transferring liquefied radium or liquefied product. For example, the radon discharging step (S400) may be performed by ventilating a gas only from a vial. When transferring liquefied radium through a flow path of one side by using a syringe pump specifically in the loading step (S100), gas existing inside the flow path and chamber is moved to a vial through a flow path of the other side, gas including radon is discharged from the vial through a flow path connected to one side of the vial, and then a radon disposal step such as collection of radon may be performed. The radon disposal step enables the volume-reduced radon to be disposed as radioactive waste after reducing volume of radon by condensing radon from a gas discharged at an extremely low temperature. Further, since a half-life of radon is turned out to be 3.82 days, the radon gas may be discharged to the outside when radioactivity of the radon gas is weakened to a reference numerical value or less measured by radiometry after several cycles of the half-life by storing a radon gas for a predetermined time, or the radon gas may be discharged to the outside by diluting the radon gas with a sufficient amount of air. The actinium production step (S200) corresponds to a step of irradiating a particle beam accelerated from a particle accelerator to a reaction space inside the chamber when loading of liquefied radium is completed within a chamber. The actinium production step (S200) may be performed by adjusting energy or flux of the particle beam considering overall performance of an apparatus including volume of the liquefied radium inside the chamber, irradiation areas of beams, cooling performance of the chamber, pressure within the chamber, and others. When a particle beam is irradiated, a p,2n nuclear reaction occurs in Ra-226 of a liquefied state, and Ac-225 is generated. Although the particle beam is irradiated to produce actinium within the reaction space, all of Ra-226 of a liquefied state is not entirely subjected to a nuclear reaction process, but only some of Ra-226 of a liquefied state is subjected to the nuclear reaction process and converted into Ac-225. The unloading step (S300) is performed to discharge a liquefied product from the chamber when the nuclear reaction process is completed. For example, the unloading step (S300) may comprise discharging liquefied radium and liquefied actinium, i.e., a product to the outside of the chamber by blowing an inert gas such as He gas that is a Group 18 element into the reaction space. The aforementioned radon discharging step (S400) may be performed even in the unloading step (S300). The gas may be naturally discharged in the process of transferring the liquefied radium to the vial by blowing liquefied radium into a vial with the inert gas. Specifically, when blowing the He gas, i.e., the inert gas into the chamber such that a liquefied product can be moved, the liquefied product is transferred to the vial through a flow path connected to one side of the chamber, and a gas containing radon is discharged to the outside of the vial in response thereto. The aforementioned radon discharging step (S400) corresponds to a step of discharging radon, i.e., a radioactive gas generated while radium is being decayed. While radium is being naturally decayed, radon is consistently generated, and these processes can be performed several times in the overall production process. The radon discharging step (S400) may comprise enabling the liquid radium or liquid product to be discharged to the outside of the vial by the generation of a pressure difference in the process of transferring a liquid radium or liquid product. The actinium separating and refining step (S500) corresponds to a step of separating and refining actinium in a radon-separated product. The actinium separating and refining step (S500) may be performed after transferring actinium from the vial to a space for separating and refining actinium, e.g., a space such as a glove box or hot-cell. The separation of actinium is performed by separating liquefied actinium and liquefied radium. The refinement of actinium is a step of refining the separated-liquefied actinium such that the refined-liquefied actinium can be used for medical purposes. Since separated actinium contains other impurities, high purity actinium can be produced by removing the impurities. The reloading step (S600) corresponds to a step of loading the pure liquefied radium again after moving a residual material obtained by separating liquefied actinium from a product, i.e., pure liquefied radium to a chamber such that the pure liquefied radium can be used again in the nuclear reaction process. The reloading step (S600) also can be performed by moving a fixed quantity of the pure liquefied radium to the chamber by using a syringe pump in the same manner as in the loading step (S100), or can be performed by flowing helium. Meanwhile, although a step has not been expressed as a separate step, the step may comprise enabling the separated-liquefied radium to be disposed in a pure liquefied radium state by removing impurities from the separated-liquefied radium before reloading separated-liquefied radium in the chamber. Further, the separated-liquefied radium with an increased volume can be concentrated by a solution which is added in the process of separating actinium and radium. A method of producing actinium by using liquefied radium 1 according to the present disclosure as described above enables pure liquefied radium to be used again in the nuclear reaction process after separating actinium produced after performing a nuclear reaction process using radium of a liquefied state. On the other hand, although it has not been described above, a beam line connected to a chamber 100 can be maintained in a vacuum state, and the chamber 100 can be isolated from the beam line such that a liquefied target can be moved independently from the beam line in a reaction space 110 within the chamber 100. The chamber 100 includes a foil 101 which is formed of a metallic material in an irradiation path of a particle beam 10 to isolate the chamber 100 from the beam line, and the foil 101 may be formed to seal each of the beam line and the chamber 100. Meanwhile, since heat is generated when the particle beam 10 is irradiated if the foil 101 seals respective opening portions of the beam line and the chamber 100 in a connection part of the beam line and the chamber 100, a separate cooling unit for cooling the connection part of the beam line and the chamber 100 may be provided. However, since such a configuration is a configuration which is generally used in an apparatus for producing a radioactive material by using a liquefied target, a more detailed description thereof will be omitted. FIG. 2 is a block diagram illustrating a concept of an actinium production apparatus in which an actinium production method according to the present disclosure is performed. FIG. 3 is an embodiment in which the configuration of FIG. 2 is embodied. As illustrated, a method of producing actinium by using liquefied radium according to the present disclosure may be performed by using an actinium production apparatus including a chamber 100, a syringe pump 300, a vial 200, a radon collection unit 500, a helium source 400, and an actinium separating and refining unit 600. As described above, the vial 200 is a space for temporarily loading liquefied radium 1 and a nuclear reaction product, and the liquefied radium 1 may be moved from the vial 200 to the chamber 100 through the syringe pump 300. After a nuclear reaction process is performed in the chamber 100, the liquefied radium 1 and liquefied actinium 2 are moved to the vial 200. A gas is discharged from one side of the vial 200 to maintain pressure according as the syringe pump is operated, or a helium gas is supplied. The discharged gas is moved through a separate flow path, and radon can be collected or condensed while the discharged gas is passing through the radon collection unit 500. Specifically, when pressure in a flow path is increased by the operation of the syringe pump 300 or the helium source 400 in a loading process or an unloading process, gas is finally discharged from one side of the vial 200. The discharged gas can be moved to the radon collection unit 500 through the flow path. As a product produced by performing a nuclear reaction process is transferred to the actinium separating and refining unit 600, the liquefied actinium 2 and the liquefied radium 1 are separated from each other in the actinium separating and refining unit 600. After refining the separated-liquefied actinium 2 in an actinium refinement unit 700, passing the separated-liquefied radium 1 through a refinement process, and moving the separated-liquefied radium 1 passing through the refinement process to the vial 200 again, a nuclear reaction process is prepared. Meanwhile, for example, although radium chloride (RaCl2) as the liquefied radium 1 and actinium chloride (AcCl3) as the liquefied actinium 2 have been described with illustration in the present embodiment, this is an example only, and actinium liquefied using various organic liquids may be used. Hereinafter, performing a method of producing actinium by using liquefied radium 1 according to the present disclosure will be described in detail with reference to FIG. 4 to FIG. 10. FIG. 4 and FIG. 5 are conceptual diagrams illustrating a loading step. As illustrated in FIG. 4, the loading step comprises receiving the liquefied radium 1 by allowing the syringe pump 300 to suck a fixed quantity of liquefied radium 1 contained in the vial 200. At this time, quantity of the liquefied radium 1 sucked by the syringe pump 300 may be determined by considering quantity of the liquefied radium 1 contained in the chamber 100 and quantity of the liquefied radium 1 which is stagnant in a flow path from the syringe pump 300 to the chamber 100. As illustrated in FIG. 5, the liquefied radium 1 is loaded in the chamber 100 after the liquefied radium 1 is moved along the flow path when the liquefied radium 1 is extruded by the syringe pump 300. Further, according as the liquefied radium 1 is contained in the chamber 100, a gas containing radon is moved to the vial through an upper flow path in FIG. 5, the gas containing radon is discharged through a flow path provided in one side of the vial such that the gas containing radon passes through the radon collection unit 500, and radon can be collected in the radon collection unit 500. FIG. 6 is a conceptual diagram illustrating a step of producing actinium. A valve between the syringe pump 300 and the chamber 100 may be closed to prevent movement of the liquefied radium 1 when the liquefied radium 1 is loaded in the chamber 100. Further, a valve between the chamber 100 and the helium source 400 may be closed to prevent backflow of a radioactive material due to pressure increased during a nuclear reaction process. Thereafter, the nuclear reaction process is performed by irradiating a particle beam to the reaction space 110. Meanwhile, when the valve between the helium source 400 and the chamber 100 is opened, the helium source is operated to enable pressure inside the reaction space 110 to be maintained. FIG. 7 is a conceptual diagram illustrating an unloading step. When performing an unloading process, a valve is operated to open a flow path facing the vial 200 from the reaction space 110, and a product is moved to the vial 200 by blowing a helium gas 4 into the reaction space 110. At this time, it is preferable to blow a sufficient amount of helium into the reaction space 110 such that the product is not remained in the reaction space 110 and a flow path from the reaction space 110 to the vial 200. On the other hand, the helium gas 4 is flown in the reaction space 110 through a flow path connected to an upper side of the reaction space 110, and the liquefied radium 1 can be moved through a flow path connected to a lower side of the reaction space 110. Accordingly, when blowing the helium gas 4 into the reaction space 110, a product of a liquefied state can be naturally discharged from the lower side of the reaction space 110 to the outside of the chamber 100. FIG. 8 is a conceptual diagram illustrating a step of discharging radon 3 when performing the unloading step. As illustrated in FIG. 8, according as a liquefied product is flown in the vial while performing the unloading step, gas within the vial 200 is discharged along a flow path such that the gas within the vial 200 discharged along the flow path passes through the radon collection unit 500. Thereafter, the radon collection unit 500 collects the gas of radon 3 only from gas mixed together with a helium gas 4 and gas of radon 3, and discharges a remaining gas to the outside. When radon is collected, the collected radon may be disposed as radioactive waste in a liquefied state as described above. Further, although it has not been illustrated in FIG. 8, when the radon collection unit 500 is not provided, radon is stored for a predetermined time, or is diluted with a sufficient amount of air to enable the diluted radon to be discharged to the outside. FIG. 9 is a conceptual diagram illustrating a step of transferring a liquefied product to separate and refine actinium. As illustrated in FIG. 9, the liquefied product is transferred from the vial to a space for refinement and separation to separate and refine actinium. Specifically, the product is transferred to the actinium separating and refining unit 600 by opening only a flow path between the vial 200 and the actinium separating and refining unit 600 and blowing the helium gas 4 into the vial 200. The liquefied radium 1 and the liquefied actinium 2 may be separated from each other in the actinium separating and refining unit 600. Refinement of actinium comprises performing an appropriate refinement process comprising removing impurities from the separated actinium such that the separated actinium can be used for medical purposes after transferring separated actinium. FIG. 10 illustrates a figure of moving liquefied radium 1 before performing a reloading step. After disposing remaining liquefied radium 1 having the liquefied actinium 2 separated therefrom into pure liquefied radium through a refinement process, and concentrating liquid increased in the process of separating radium from actinium to prepare a preset fixed quantity of radium, the preset fixed quantity of radium is transferred to the vial 200 again. Thereafter, the processes can be repeatedly performed by starting a production process from the loading step. Meanwhile, the reloading process may be configured such that, when the pure liquefied radium is loaded into the vial in the reloading step, gas is discharged to the outside according to pressure increased inside a flow path in a manner similar to those of the loading step and the unloading step. Therefore, according as fluid is flown in the loading, unloading and reloading steps, radon is naturally discharged from the vial. The pure liquefied radium can be transferred using the helium gas during the reloading process. However, a method of transferring the pure liquefied radium is an example only, the pure liquefied radium may be transferred by various methods in addition to a method of using the helium gas. As illustrate above, a method of producing actinium by using liquefied radium according to the present disclosure can minimize loss of radium by producing actinium through a nuclear reaction process using radium of a liquefied state, and performing the nuclear reaction process by circulating radium in a liquefied state without performing a separate chemical change in a repeated production process. Further, a method of producing actinium by using liquefied radium according to the present disclosure has an effect of enabling safety to be improved by discharging radon generated during handling of radon, thereby preventing exposure to radiation due to radon gas.
044144750	claims	1. Shielding container assembly for storing weak to medially active waste in a storage barrel, comprising a plurality of shielding containers each having massive concrete walls in a substantially square cross section surrounding the storage barrel, each shielding container having two pairs of oppositely-disposed sections, one of said pairs having symmetrical projections formed thereon with a given shape extended outward from said substantially square cross section and the other of said pairs having recesses with said given shape formed therein extended into said substantially square cross section, each of said projections being releasably anchored in a respective one of said recesses of an adjacent shielding container when stacking said shielding containers in a horizontal row. 2. Shielding container assembly according to claim 1, wherein said projections and chamfers are disposed at corners of said shielding container. 3. Shielding container assembly according to claim 2, wherein said projections and chamfers are in the form of symmetrical pairs. 4. Shielding container assembly according to claim 1, wherein said shielding container has a clearance space formed therein for receiving said storage barrel, said space extending through the total height of said shielding container. 5. Shielding container assembly according to claim 4, wherein said clearance space has a cylindrical cross section and is centrally disposed in said substantially square cross section of said sheilding container. 6. Shielding container assembly according to claim 1, wherein said shielding container has top and bottom surfaces thereon, said surfaces having raised portions formed thereon and having recesses formed therein in which said raised portions fit. 7. Shielding container assembly according to claim 6, wherein said raised portions are disposed at four corners of said square cross section of said shielding container. 8. Shielding container assembly according to claim 6 or 7, wherein said shielding container has undercuts formed therein at said recesses for attachment of gripper tools. 9. Shielding container assembly according to claim 8, including reinforcements being disposed in said undercuts and extended into said shielding container. 10. Shielding container assembly according to claim 1, including a storage chamber having straight walls with recesses formed therein, said projections being extended into said recesses. 11. Shielding container assembly for storing weak to medially active waste in a storage barrel, comprising a plurality of shielding containers each having massive cast iron walls in a substantially square cross section surrounding the storage barrel, each shielding container having two pairs of oppositely-disposed sections, one of said pairs having symmetrical projections formed thereon with a given shape extended outward from said substantially square cross section and the other of said pairs having recesses with said given shape formed therein extended into said substantially square cross section, each of said projections being releasably anchored in a respective one of said recesses of an adjacent shielding container when stacking said shielding containers in a horizontal row.
	summary
046831061	summary	FIELD OF THE INVENTION The invention relates to wiring installations located above the top cover of a nuclear reactor, in particular a pressurized water nuclear reactor, in the reactor containment building. BACKGROUND OF THE INVENTION A number of electrical devices are located in a nuclear reactor building and require electric connection wires and cables. Such devices include measuring sensors, particularly sensors for measuring the position of the control clusters in the reactor core and thermo-couples for measuring the temperature of the core, and mechanisms for actuating the neutron absorption clusters for controlling and stopping the core. The cables are numerous and cumbersome, in particular above the cover of the reactor vessel. By way of example, for a nuclear reactor with four loops, the number of control and shutdown clusters may be as high as seventy-three and the number of thermo-couples as high as fifty-two. For each control cluster, cable is required for powering the cluster actuating mechanism and a cable for the sensor measuring the position of the cluster; each thermo-couple is connected to a cable. That makes a total of one hundred and ninety-eight cables. To date, the cables have been disposed as follows: each cable has a first section connecting the electric device and a fixed connector installed above the cover. A second section extends from the fixed connector to another fixed connector installed on a connector plate remote from the reactor; all second sections of the cables are distributed in two half rings and then extend from the reactor as a single harness supported by a bridge disposed between the reactor and the plate installed at a distance therefrom. Such a cabling installation has disadvantages. Positioning the cables is a long and delicate operation since a single section extends from a fixed connector situated above the cover to the plate situated at a distance from the reactor, and is consequently very long and difficult to handle. The diameter of the section may be such that it cannot easily be bent, and the small space available above the cover cannot accomodate an excess cable length; the length of each cable is therefore adjusted on the spot during installation thereof, the removable connectors situated at the ends of the cables are consequently mounted on the spot, under difficult conditions. Once installed, the cable has further drawbacks: for removing the cover from the reactor the cables must be disconnected from the plate remote from the core and the bridge must be raised along with the cables which it supports. Furthermore, changing a cable during the lifetime of the reactor is a difficult operation since the large number of cables means that the bridge supports several layers of cables: handling of the cables in the lower part of the harness which extends across the bridge is difficult in the hostile environment due to radioactivity from the core. The difficulties are still greater when the number of sensors measuring the position of the clusters is increased to achieve redundancy (for example to four) for reliability. This means installing four sensors which transmit the same information to four different processing systems. In this case, and to comply with the safety standards, the electric power supplies for these measuring systems must be different in origin and spatially separated. Similarly, the paths for the transmission cables must be different and minimum distances, of about 300 mm if these paths are open, are required between the paths followed by these cables. Referring to the above example, with redundant sensors for measuring the position of the clusters, the number of cables for measuring the positions of the clusters, which was seventy-three, now becomes two hundred and ninety-two. Added to the cable supplying power to the cluster actuating mechanisms and to those carrying temperature signals from thermocouples, a total of four hundred and seventeen cables must be installed above the cover. Taking into account the minimum distances imposed by installation regulations, the volume required for the cables is appreciably greater than the volume of cables used to date since the amount of cables is about three times greater than that used at present. There is consequently a need for a wiring arrangement making it possible to increase the number of sensors measuring the position of the control clusters so that they may be redundant and free of the above-mentioned disadvantages. SUMMARY OF THE INVENTION It is an object of the invention to provide an improved wiring installation for connection of electric devices which are placed above the cover of the reactor and inside a nuclear reactor building, the devices being e.g., sensors for measuring the position of the control clusters and actuators for the mechanisms controlling these clusters of thermo-couples. It is a more specific object to provide an installation suitable for accommodating a very high number of cables, in particular cables associated with redundant electric devices, and which allows cables to be readily fitted and changed during the lifetime of the reactor, and the cover of the reactor to be removed without difficulties. For that purpose, there is provided an installation for cabling electric devices placed inside a nuclear reactor building, such as sensors for measuring the position of the clusters controlling the core, actuators for the mechanisms controlling these clusters or thermo-couples comprising: associated with each of the electric devices, at least a first cable extending from the device and whose end opposite the device is connected to a fixed connector installed above the top cover of the reactor, the arrangement of the fixed connectors corresponding to similar electric devices being similar, corresponding to each of the first cables, a second cable having a mobile connector at each of its ends and connectable on the one hand to the fixed connector installed above the top cover and on the other hand to a connector fixed to a plate installed at a distance from the reactor, means for supporting the assembly of the second cables from the fixed connectors installed above the top cover to the connectors fixed to said plate. According to the invention, each of the second cables is formed from several sections: a first section having two mobile connectors for connection on the one hand to a fixed connector installed above the top cover and on the other hand to a fixed input connector in a sealed conduit installed horizontally above the top cover. a second section inside the conduit, connected both to the input connector in the conduit and to a fixed output connector of the conduit, a third section having two mobile connectors for connection both to the fixed output connector of the conduit and to the connector fixed on the plate installed at a distance from the core. Preferably, the conduits are installed in at least one plane perpendicular to the axis of a reactor, the conduits in each plane being parallel to each other. The input connectors for each conduit may be disposed on the lateral parts of the conduit and the output connectors at the ends of the conduit. Preferably, each conduit is divided longitudinally into two independent compartments each comprising a lateral part and an end of the conduit. Furthermore, associated with each fixed connector installed above the top, is an input connector into a neighboring conduit, so that all the first sections connecting, to their input connector, fixed connectors corresponding to similar electric devices are of the same length. In the case where several electric devices are redundant, conduit input connectors situated in separate conduits are associated with the fixed connectors situated above the top cover at the ends of the first cables relative to these devices. Preferably, all third sections of those second cables which extend in the same direction from mutually parallel conduits are supported by the same bridge up to the same plate at a distance from the core.
046997598	description	DETAILED DESCRIPTION OF THE INVENTION In the following description, like reference characters designate like or corresponding parts throughout the several views. Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like, are words of convenience and are not to be construed as limiting terms. In General Referring now to the drawings, and particularly to FIG. 1, there is shown an elevational view of a reconstitutable nuclear fuel assembly, represented in vertically foreshortened form and being generally designated by the numeral 10. Basically, the fuel assembly 10 includes a lower end structure or bottom nozzle 12 for supporting the assembly on the lower core plate (not shown) in the core region of a reactor (not shown), and a number of longitudinally extending guide tubes or thimbles 14 which project upwardly from the bottom nozzle 12. The assembly 10 further includes a plurality of transverse grids 16 axially spaced along the guide thimbles 14 and an organized array of elongated fuel rods 18 transversely spaced and supported by the grids 16. Also, the assembly 10 has an instrumentation tube 20 located in the center thereof and an upper end structure or top nozzle 22 removably attached to the upper ends of the guide thimbles 14, in a manner fully described below, to form an integral assembly capable of being conventionally handled without damaging the assembly parts. As mentioned above, the fuel rods 18 in the array thereof in the assembly 10 are held in spaced relationship with one another by the grids 16 spaced along the fuel assembly length. Each fuel rod 18 includes nuclear fuel pellets 24 and the opposite ends of the rod are closed by upper and lower end plugs 26,28 to hermetically seal the rod. Commonly, a plenum spring 30 is disposed between the upper end plug 26 and the pellets 24 to maintain the pellets in a tight, stacked relationship within the rod 18. The fuel pellets 24 composed of fissile material are responsible for creating the reactive power of the nuclear reactor. A liquid moderator/coolant such as water, or water containing boron, is pumped upwardly through the fuel assemblies of the core in order to extract heat generated therein for the production of useful work. To control the fission process, a number of control rods 32 are reciprocally movable in the guide thimbles 14 located at predetermined positions in the fuel assembly 10. The top nozzle 22 has a lower adapter plate 34 with a plurality of passageways 36 (only one being shown) formed through the adapter plate. The guide thimbles 14 which receive the control rods 32 have their uppermost end portions 38 coaxially positioned within the adapter plate passageway 36. Specifically, operatively associated with the top nozzle 22 is a rod cluster control mechinism 40 havng an internally threaded cylindrical member 42 with a plurality of radially extending flukes or arms 44. Each arm 44 is interconnected to one or more control rods 32 such that the control mechanism 40 is operable to move the control rods 32 vertically in the guide thimbles 14 to thereby control the fission process in the fuel assembly 10, all in a well-known manner. Double Lock Joint Structure for Releasably Attaching Top Nozzle to Guide Thimbles Referring now to FIGS. 2 through 5, there is seen the improved features of the present invention for releasably connecting the lower adapter plate 34 of the top nozzle 22 to the upper end portions 38 of the guide thimbles 14 for facilitating access to the fuel rods 18 of the fuel assembly 10. The improved features of the present invention comprise components of a double lock joint structure, generally designated 46. As depicted in FIGS. 2 through 5, the double lock joint structure 46 includes axially extending slots 48, being four in number in the illustrated embodiment, defined in each guide thimble upper end portion 38 which permit inward elastic collapse thereof to a compressed position upon application of sufficient forces directed radially inward toward a central axis A of the upper end portion 38. The upper end portion 38 elastically returns outward to an expanded position upon removal of the radially inward directed forces thereto. These forces are imposed on the upper end portion 38 of each guide thimble 14 whenever the adapter plate 34 is applied to it. The joint structure 46 also includes means preferably taking the shape of axially spaced upper and lower annular bulges 50,52 formed circumferentially in the upper end portion 38. The upper annular bulge 50 has an outside diametric size greater than the inside diametric size of a given adapter plate passageway 36 when the guide thimble upper end portion 38 is at its expanded position. On the other hand, the outside diametric size of the upper bulge 50 reduces to less than the inside diametric size of the adapter plate passageway 36 when the upper end portion 38 is collapsed to its compressed position due to application of the radially inward directed forces thereto during insertion and withdrawal into and from the adapter plate passageway 36. However, in the case of the annular bulge 52, it has an outside diametric size which is greater than the inside diametric size of the one adapter plate passageway 36 when the guide thimble upper end portion 38 is at either one of its expanded and collapsed positions. For locking the guide thimble upper end portion 38 to the adapter plate 34, the upper annular bulge 50 is axially displaced from the lower annular bulge 52 through a distance approximately equal to that between top and bottom surfaces 54,56 of the adapter plate 34. Therefore, after insertion of the upper end portion 38 of the guide thimble 14 through the adapter plate passageway 36, as shown in FIG. 5, the upper annular bulge 50 is located above the adapter plate 34 adjacent to and in contact with the top surface 54 thereof, the lower annular bulge 52 is located below the adapter plate 34 adjacent to and in contact with the bottom surface 56 thereof and the adapter plate 34 is placed in a captured position between the upper and lower annular bulges 50,52. Further, the joint structure 46 includes a locking tube 58 removably inserted into each guide thimble upper end portion 38 to a locking position therein which maintains the upper end portion in its expanded position and the adapter plate 34 in the captured position between the upper and lower annular bulges 50,52. Removal of the locking tube 58 withdraws it to an unlocking position which permits the upper end portion 38 to inwardly collapse to its compressed position upon removal of the adapter plate 34 from the upper end portion. The upper end portion 38 can also be collapsed to its compressed position upon insertion of the adapter plate 34 back on the guide thimble 14. For securing the locking tube 58 at its locking position in the upper end portion 38 of the guide thimble 14, the tube includes upper and lower axially, and circumferentially, displaced protuberances 60,62 in the form of short segments adapted to mate with the upper and lower annular bulges 50,52 of the guide thimble upper end portion 38. Also, a top annular flange 64 on the tube 58 is located above the upper protuberance 60 for facilitating gripping of the tube for insertion and removal of the tube into and from the guide thimble upper end portion 38. While the upper and lower bulges 50,52 are illustrated as each extending circumferentially about the upper end portion 38, it should be understood that each bulge need not be continuous about the upper end portion, but can be in the form of a series of short segments similar to the protuberances 60,62 of the locking tube 58. Likewise, it should be understood that when the upper and lower bulges 50,52 are continuous as is illustrated, the upper and lower protuberances 60,62 of the locking tube 58 can extend continuously about the tube similar to the upper and lower bulges, instead of being short segments. It is thought that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material adavantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.
	abstract	The invention provides a positive/negative phase shift bimetallic zone plate and production method thereof, wherein the positive/negative phase shift bimetallic zone plate comprises: a first metallic material having a positive phase shift; a second metallic material having a negative phase shift at a working energy point; wherein the first metallic material and the second metallic material are alternately arranged, so that the second metallic material replaces the blank portion in a cycle of a traditional zone plate.
052456447	description	Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a plan view of a prior art spacer, in which a first group of first webs 1 standing on end and extending parallel to one another is disposed at right angles to a second group of second webs 2 that are also standing on end and extending parallel, in the plane of the spacers. The webs 1 are split on the one or lower longer sides thereof, for instance, while the webs 2 have corresponding slits on the other or upper longer sides thereof, so that there is a plug-in connection 3 between each web 1 and a web 2 in which the webs intersect and are inserted into one another in the slits. In order to keep the webs in the illustrated position until they are welded together, and to lend greater stability to the welded connection, the webs of the prior art device have beads or so-called insertion buttons, between which the other web is engaged and guided. FIG. 1 also shows contact bumps 4 and springs 5, between which fuel rods of a fuel assembly are held. Flow lugs that are formed onto the webs in order to guide a coolant flow are not shown. In French or Belgian reactors, for instance, the flow lugs point into the openings of the grid formed by the spacer webs, on the trailing side of the spacer. In the prior art devices, the spacer webs and in particular the guide lugs formed onto them cause a high pressure loss. As mentioned above, it is an object of the invention to keep the pressure loss at the spacers as low as possible by means of different provisions. Therefore, according to the invention, the insertion buttons are omitted and a certain fixation of the plug-in connections for welding is attained only by means of impressions on the webs themselves. FIG. 2 shows a web 10 of the spacer of the invention, which has applicable insertion slits 11 on one side, defining web tabs beyond the slits. The insertion slit 11 is narrowed at one point, as a result of pinching-in of an impression or impressed indentation 12 on both sides. An arrow 13 indicates an insertion direction for the other web. At that location, the web has beads 14, which are formed from the material of the web and which bulge laterally when an indentation 15 is formed by pressing inward. The beads 14 provide guidance for insertion of the slit in the web of the other group, by forming a funnel tapering in the insertion direction. FIG. 3 shows a corresponding cross section taken along the line III--III of FIG. 2. FIG. 4 shows a corresponding longitudinal section taken along the line IV--IV. In FIG. 5, a web is shown with a plurality of such insertion slits. The novel plug-in connection is produced as follows: when the webs are inserted, the narrowed portion of one slit first scrapes over the smooth surface of the intersecting web, until a tab of the movable web is engaged by the funnel formed by the lateral beads 14 and thrust into the intended position. As it is thrust further, the movable web tab is then guided laterally, until the portion of the slit that is narrowed by the impressions 12 locks into place in the corresponding indentation 15 of the other web. The webs are then welded together.
	claims	1. A nuclear reactor containment system and containment protection system comprising:a containment vessel comprising a cylindrical steel shell that surrounds a wet well, the containment vessel defining containment space configured for housing a nuclear reactor containing a nuclear fuel core emitting heat, the reactor disposed in the wet well;a containment enclosure structure surrounding the containment vessel and comprising a hollow cylindrical steel shell; anda concrete foundation comprised of a bottom slab supporting the cylindrical shell of the containment vessel and vertically extending sidewalls rising from the slab forming a top base mat supporting the containment enclosure structure, a lower portion of the containment vessel being positioned inside the sidewalls of the concrete foundation below the base mat and an upper portion of the containment vessel extending upwards from the base mat;a water-filled annular reservoir formed between the containment vessel and containment enclosure structure for serving as the heat sink for the heat generated inside the containment space, the annular reservoir extending circumferentially around a perimeter of the upper portion of the containment vessel above the base mat and the lower portion of containment vessel extending below the annular reservoir;wherein the annular reservoir is configured to cool the containment vessel by receiving heat generated within the containment vessel. 2. The system of claim 1, wherein the annular reservoir contains water for cooling the containment vessel. 3. The system of claim 2, wherein the upper portion of the containment vessel above the base mat includes substantially radial heat transfer fins disposed in the annular reservoir and extending between the containment vessel and containment enclosure structure. 4. The system of claim 3, further comprising a circumferential rib attached to the containment vessel, the heat transfer fins having bottom ends coupled to the circumferential rib, wherein the circumferential rib is seated on the foundation. 5. The system of claim 2, wherein the containment vessel includes an internal surface which contains extended surface area defined by a plurality of radial fins to enhance capture of heat energy from the containment space. 6. The system of claim 2, wherein the air cooling system is operable to draw outside ambient air into the annular reservoir through the air conduits to cool the containment vessel by natural convection. 7. The system of claim 2, wherein wetted portions of the annular reservoir are coated or lined with a corrosion resistant material. 8. The system of claim 1, wherein a portion of the water in the annulus is evaporated and vented to atmosphere through the containment enclosure structure in the form of water vapor. 9. The system of claim 1, further comprising an air cooling system including a plurality of vertical inlet air conduits spaced circumferentially around the containment vessel in the annular reservoir, the air conduits being in fluid communication with the annular reservoir and outside ambient air external to the containment enclosure structure. 10. The system of claim 1, further comprising an upper annulus formed above the annular reservoir between the containment vessel and containment enclosure structure, the upper annulus in fluid communication with the annular reservoir and a vent to atmosphere. 11. The system of claim 10, further comprising head space formed between a top head of the containment vessel and a top of the containment enclosure structure, the head space forming a plenum in fluid communication with the vent to atmosphere and the upper annulus. 12. The system of claim 1, wherein the containment vessel includes a shell having a diametrically enlarged top portion which overhangs lower smaller diameter portions of the shell. 13. The system of claim 12, further comprising a plurality of vertical support columns circumferentially spaced around the perimeter of the containment vessel, the support columns engaging and operable to help support the top portion of the containment vessel. 14. The system of claim 1, wherein the containment enclosure structure has sidewalls comprised of substantially radially spaced apart inner and outer concentric shells having concrete disposed in the annular space formed between the shells. 15. The system of claim 1, wherein the containment enclosure structure includes a top dome spaced vertically apart from a top head of the containment vessel. 16. The system of claim 15, wherein the top head of the containment vessel is of radially symmetric curvilinear contour for maximum impact resistance. 17. A nuclear reactor containment system comprising:a containment vessel comprising a cylindrical steel shell configured for housing a nuclear reactor containing a nuclear fuel core emitting heat;a containment enclosure structure surrounding the containment vessel and comprising a hollow cylindrical steel shell;a water filled annulus formed between the containment vessel and containment enclosure structure for cooling the containment vessel;a plurality of substantially radial fins protruding outwards from the containment vessel and located in the water filled annulus;a concrete foundation comprised of a bottom slab supporting the cylindrical shell of the containment vessel and vertically extending sidewalls rising from the slab forming a top base mat supporting the containment enclosure structure, a lower portion of the containment vessel being positioned inside the sidewalls of the concrete foundation below the base mat and an upper portion of the containment vessel extending upwards from the base mat;the water filled annulus extending circumferentially around a perimeter of the upper portion of the containment vessel above the base mat and the lower portion of containment vessel extending below the water filled annulus;wherein the water filled annulus is configured to cool the containment vessel by receiving heat generated within the containment vessel by the fuel core which is transferred to the water filled annulus via the substantially radial fins;wherein the water in the annulus is heated and a portion is evaporated and vented to atmosphere through the containment enclosure structure in the form of water vapor. 18. The system of claim 17, further comprising an air cooling system including a plurality of vertical inlet air conduits spaced circumferentially around the containment vessel in the annulus, the air conduits being in fluid communication with the annular reservoir and outside ambient air external to the containment enclosure structure, wherein when a thermal energy release incident occurs inside the containment vessel and water in the annulus is substantially depleted by evaporation, the air cooling system being operable to draw outside ambient air into the annulus through the air conduits to cool the containment vessel by natural convection. 19. A nuclear reactor containment system comprising:a containment vessel including a cylindrical shell having an outer cylindrical wall, the cylindrical shell configured for housing a nuclear reactor containing a nuclear fuel core emitting heat;a cylindrical containment enclosure structure surrounding the containment vessel and comprising a hollow cylindrical steel shell, the cylindrical containment having an inner cylindrical wall that faces the outer cylindrical wall;an annular reservoir containing water and formed between the outer cylindrical wall and the inner cylindrical wall, the annular reservoir for cooling the containment vessel;a concrete foundation comprised of a bottom slab supporting the cylindrical shell of the containment vessel and vertically extending sidewalls rising from the slab forming a top base mat supporting the containment enclosure structure, a lower portion of the containment vessel being positioned inside the sidewalls of the concrete foundation below the base mat and an upper portion of the containment vessel extending upwards from the base mat;the annular reservoir extending circumferentially around a perimeter of the upper portion of the containment vessel above the top base mat and the lower portion of containment vessel extending below the annular reservoir;a plurality of external substantially radial fins protruding outwards from the containment vessel into the annular reservoir and extending between outer cylindrical wall and the inner cylindrical wall; andan air cooling system including a plurality of vertical inlet air conduits spaced circumferentially around the containment vessel in the annular reservoir, the air conduits being in fluid communication with the annular reservoir and outside ambient air external to the containment enclosure structure;wherein the radial fins have bottom ends attached to and supported by a circumferential annular rib attached to the outer cylindrical wall of the containment vessel and protruding radially outwards beyond the outer cylindrical wall, the circumferential annular rib seated on the top base mat of the foundation;wherein the annular reservoir is configured to cool the containment vessel by receiving heat generated within the containment vessel via the fins and transferring the heat to the annular reservoir.
055263887	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The invention is generally related to a nuclear reactor fuel assembly and more particularly to debris filters used in fuel assemblies. 2. General Background Commercial nuclear reactors include multiple fuel assemblies. Each fuel assembly is comprised of a number of fuel rods radially spaced apart in a parallel array by grid assemblies spaced along the length of the fuel rods. Each grid assembly is formed in an eggcrate design by multiple metal strips that criss-cross at right angles to form individual cells for each of the fuel rods. The strips are provided with tabs that project into the cells against the fuel rods. The tabs serve the purposes of holding the fuel rods in their respective radial positions and providing maximum surface area contact of the fuel rods with coolant flowing through the cells. Control rod guide thimble tubes also extend through selected cells in the grid assembly and are attached at their upper and lower ends respectively to an upper end fitting and a lower end fitting. The upper and lower end fittings are also commonly referred to in the industry as nozzle plates since they are rigid plates that provide structural integrity and load bearing support to the fuel assembly and are provided with flow apertures therethrough for coolant flow. The lower end fitting or nozzle plate is positioned directly above openings in the lower portion of the reactor where coolant flows up into the reactor to the core. The ligaments between apertures in the end fittings coincide with the ends of the fuel rods and limit upward or downward movement of the fuel rods. Debris such as metal particles, chips, and turnings is generated during manufacture, installation, and repair of the reactor, piping, and associated cooling equipment. The size and complexities of the equipment prevent location and removal of all such debris before operations are commenced. Also, some of this debris may not become loose matter in the system until the system is put into operation. It has been recognized that this debris presents a greater problem to the system than previously thought. These small pieces of debris have been found to lodge between the walls of the grid cells and the fuel rods. Movement and vibration of the lodged debris caused by coolant flow results in abrasion and removal of cladding on the fuel rods. This in turn leads to detrimental effects such as corrosion of the fuel rods and failure to retain radioactive fission gas products. Such damage, although not critical to safety of the surrounding environment, can reduce operating efficiency by the need to suspend operation while replacing damaged fuel rods. One approach to stopping debris from travelling up into the clad area of the fuel rods has been to use the lower end fitting as a debris filter. Another approach has been to use the standard lowermost spacer grid or a special anti-debris grid structure to catch or stop the upward movement of debris. However, to prevent fretting failures of the fuel rods in this area, the fuel rod must have a solid cross section. This is accomplished by using a longer than normal lower end plug in the fuel rod. This approach includes the disadvantages of increased expense and reduced fuel rod plenum volume which adversely affects the duration of fuel rod burnup. It can be seen that a need exists for a debris filter capable of filtering debris of a size which may lodge between the grid cell walls and the fuel rods. An important consideration besides that of filtration is that a substantial coolant pressure drop across the filter must be avoided in order to maintain an adequate coolant flow over the fuel rods for heat removal therefrom. SUMMARY OF THE INVENTION The invention addresses the above need. What is provided is a debris resistant fuel rod sleeve that is received over the lower end of a fuel rod. The sleeve extends above the top of the lowermost spacer grid. Openings are spaced apart around the circumference of the sleeve to correspond to the location of hard stops in the spacer grid. The hard stops are received in the openings and retain the sleeves in position during operation and during reconstitution or recaging if necessary. The outboard side of the peripheral sleeves may be provided with top and bottom lead in features to prevent hang-ups.
	claims	1. An x-ray microscope system comprising:an x-ray illumination beam generating system comprising:an x-ray source; anda beam-splitting grating, wherein said x-ray illumination beam generating system produces a plurality of x-ray micro-beams through the Talbot effect, the plurality of x-ray micro-beams having a depth-of-focus, an axis of propagation and a predetermined intensity profile normal to said axis for a predetermined x-ray energy;a mount configured to support an object to be examined within the depth-of-focus, the mount configured to move the object relative to said plurality of x-ray micro-beams; andat least one x-ray pixel array detector for detecting x-rays resulting from interaction of said plurality of x-ray micro-beams with said object, said detector comprising a plurality of pixels within said depth-of-focus. 2. The x-ray microscope system of claim 1, wherein the beam-splitting grating is a π phase-shifting grating or a π/2 phase-shifting grating at said predetermined x-ray energy. 3. The x-ray microscope system of claim 1, wherein the x-ray source comprises:an emitter for an electron beam; anda transmission x-ray target comprising a plurality of discrete microstructures comprising a first material having a first mass density and a substrate comprising a second material having a second mass density lower than the first mass density. 4. The x-ray microscope system of claim 3, wherein the energy of the electron beam is greater than 1.1 times of the predetermined x-ray energy. 5. The x-ray microscope system of claim 3, wherein the electron beam is incident upon the target at an oblique angle. 6. The x-ray microscope system of claim 1, wherein the x-ray source is a microfocus x-ray source or an extended x-ray source used in combination with an absorption grating. 7. The x-ray microscope system of claim 1, further comprising at least one filter so that the full width half maximum of the bandwidth of the plurality of x-ray micro-beams is 30% centered at the predetermined x-ray energy. 8. The x-ray microscope system of claim 1, wherein the mount is configured to translate the object in two orthogonal directions. 9. The x-ray microscope system of claim 8, wherein the mount is further configured to rotate the object about a direction perpendicular to the axis of propagation. 10. The x-ray microscope system of claim 1, wherein the detector is a CCD-based detector and is aligned such that centers of the pixels are aligned to centers of the x-ray micro-beams. 11. The x-ray microscope system of claim 1, further comprising an analysis system configured to display and analyze output signals from the detector. 12. The x-ray microscope system of claim 1, further comprising a mask positioned to block a predetermined number of the x-ray micro-beams. 13. The x-ray microscope system of claim 1, further comprising a mask positioned upstream of the detector to block a predetermined number of the x-ray micro-beams transmitted through the object. 14. The x-ray microscope system of claim 1, in which the system achieves submicron spatial resolution. 15. The x-ray microscope system of claim 1, wherein each pixel comprises an actively detecting area at a center of the pixel, the actively detecting area comprising less than 50% of a total area of the pixel. 16. The x-ray microscope system of claim 1, further comprising an attenuating grating placed upstream of the detector and positioned to absorb x-rays between the x-ray micro-beams to increase the intensity ratio between x-ray micro-beams and the regions between the x-ray micro-beams. 17. A method for measuring the x-ray transmission of an object, the method comprising:producing an x-ray Talbot interference pattern comprising a plurality of anti-nodes and having a depth-of-focus;positioning an x-ray array detector comprising a plurality of pixels such that the plurality of pixels are within the depth-of-focus of the x-ray Talbot interference pattern; andpositioning an object to be examined within the depth-of-focus such that x-rays of at least some of the anti-nodes transmitted through the object to be examined are detected by the detector. 18. The method of claim 17, further comprising blocking at least some of the x-rays transmitted through the object from being detected by the detector. 19. The method of claim 17, further comprising blocking at least some x-rays of the x-ray Talbot interference pattern from reaching the object. 20. The method of claim 19, wherein said blocking comprises positioning a mask in front of the object. 21. The method of claim 20, wherein the mask is positioned within the depth-of-focus.
	claims	1. A cylindrical neutron generator, comprising:a cylindrical RF-driven ion source, a cylindrical unintermittent plasma formed in the ion source by a R-F driven antenna;a cylindrically-shaped radial ion extractor system, said extractor system disposed coaxially about the ion source to radially extract ions from the ion source; and,a cylindrical neutron generating solid target having an uninterrupted solid surface that is disposed coaxially as an electrically continuous cylinder inside and spaced from the ion source to receive ions extracted from the ion source by said cylindrical extractor system, whereby said target becomes loaded with impinging ions from the ion source to produce ion induced neutron generating reactions. 2. Apparatus for detecting fissile materials, comprising:a cylindrical neutron generator of claim 1;a moderator surrounding the neutron generator to slow the neutrons to thermal neutrons;a shield surrounding parts of the moderator to prevent neutrons from escaping in undesired directions;an associated neutron detector for detecting neutrons produced by thermal neutron reaction with fissile materials. 3. Apparatus for borehole instrumentation, comprising:a cylindrical neutron generator of claim 1;an associated gamma ray detector for detecting gamma rays produced by neutron reaction with features surrounding the borehole. 4. The cylindrical neutron generator of claim 1 further comprising a RF antenna disposed within the ion source. 5. The cylindrical neutron generator of claim 4 further comprising: a matching network connected to the RF antenna; anda RF power supply connected to the matching network. 6. The cylindrical neutron generator of claim 1 wherein the ion source further comprises a cylindrical extraction system with a plurality of axially extending slots. 7. The cylindrical neutron generator of claim 6 wherein the extraction system comprises a cylindrical extraction electrode disposed in a circumferential portion of the plasma formed in the ion source that is cylindrically positioned toward the target with respect to other portions of the plasma, and the cylindrical extraction electrode having a plurality of axially extending slots. 8. The cylindrical neutron generator of claim 7 wherein the extraction system further comprises a cylindrical plasma electrode outside and spaced apart from the extraction electrode and having a plurality of axially extending slots aligned with the slots in the extraction electrode. 9. The cylindrical neutron generator of claim 1 wherein the plasma ion source is a deuterium ion source or a deuterium and tritium ion source. 10. The cylindrical neutron generator of claim 1 wherein the plasma ion source is a multicusp plasma ion source. 11. The cylindrical neutron generator of claim 1 wherein the target has a titanium surface. 12. The cylindrical neutron generator of claim 1 further comprising a vacuum chamber disposed to contain said target. 13. Apparatus for detecting explosives, comprising:a cylindrical neutron generator of claim 1;a moderator surrounding the neutron generator to slow the neutrons to thermal neutrons;a shield surrounding the moderator except for a front neutron escape portion to prevent neutrons from escaping in undesired directions;an associated gamma ray detector for detecting gamma rays produced by thermal neutron reactions with explosives. 14. A cylindrical neutron generator comprising:a cylindrical RF-driven ion source, a cylindrical unintermittent plasma formed in the ion source by a R-F driven antenna;a cylindrical neutron generating solid target having an uninterrupted solid surface that is disposed coaxially as an electrically continuous cylinder inside and spaced from the ion source; anda means for radially extracting ions from the ion source and impinging the extracted ions upon the target. 15. The cylindrical neutron generator of claim 14 further comprising an RF antenna disposed within the ion source. 16. The cylindrical neutron generator of claim 15 further comprising:a matching network connected to the RF antenna; andan RF power supply connected to the matching network. 17. The cylindrical neutron generator of claim 14 wherein the extracting means comprises a cylindrical extraction system with a plurality of axially extending slots. 18. The cylindrical neutron generator of claim 17 wherein the extracting means comprises a cylindrical extraction electrode disposed in a circumferential portion of the plasma formed in the ion source that is cylindrically positioned toward the target with respect to other portions of the plasma, and the cylindrical extraction electrode having a plurality of axially extending slots. 19. The cylindrical neutron generator of claim 18 wherein the extracting means comprises a cylindrical plasma electrode inside and spaced apart from the extraction electrode and having a plurality of axially extending slots aligned with the slots in the extraction electrode. 20. The cylindrical neutron generator of claim 14 wherein the plasma ion source is a deuterium ion source or a deuterium and tritium ion source. 21. The cylindrical neutron generator claim 14 wherein the plasma ion source is a multicusp plasma ion source. 22. The cylindrical neutron generator of claim 14 wherein the target has a titanium surface. 23. The cylindrical neutron generator of claim 14 further comprising a vacuum chamber disposed to contain the target. 24. Apparatus for detecting explosives, comprising:a cylindrical neutron generator of claim 14;a moderator surrounding the neutron generator to slow the neutrons to thermal neutrons;a shield surrounding the moderator except for a front neutron escape portion to prevent neutrons from escaping in undesired directions; andan associated gamma ray detector for detecting gamma rays produced by thermal neutron reactions with explosives. 25. The cylindrical neutron generator of claim 23, further comprising a detector to detect a neutron reaction produced particles, said detector being disposed outside said vacuum chamber. 26. The cylindrical neutron generator of claim 1 wherein the plasma ion source is a deuterium ion source. 27. The cylindrical neutron generator of claim 14 wherein the plasma ion source is a deuterium ion source.
054597684	summary	CROSS-REFERENCE TO RELATED APPLICATION This application is a Continuation of International Application Serial No. PCT/DE93/00180, filed Mar. 2, 1993. BACKGROUND OF THE INVENTION Field of the Invention The invention relates to a safety device against overpressure failure of a nuclear reactor pressure vessel in case of insufficient cooling of the core. If the extremely improbable failure of all of the cooling devices of the reactor core is assumed in a nuclear power station in general, and in a pressurized-water reactor nuclear power station in particular, there is a risk of the reactor core overheating. In a pressurized-water nuclear power station, an unacceptable overpressure in the primary circuit is prevented by the pressurizer system containing spray and pressure relief devices. A pressurizer relief tank serves to condense the steam blown off upon opening of the pressurizer valves, relief valves and safety valves and of the volume control system safety valves. The pressurizer relief tank is filled with water to about two thirds, above which there is a nitrogen cushion. In the case of pressurized-water reactors, the primary circuit is at a pressure of, e.g., 158 bar (normal operation). German Published, Non-Prosecuted Application DE 35 26 377 A1, corresponding to U.S. Pat. No. 4,777,013, describes a high-temperature reactor with a reactor pressure vessel and a safety valve, being constructed as a spring valve, for limiting the pressure in the reactor pressure vessel in case of core heat-up accidents. The reactor pressure vessel is lined on its inside with a liner connected to a liner-cooling system. The valve spring of the safety valve is formed of a material having an elastic force which decreases with increasing temperature. When the safety valve is open, the valve spring is exposed to outflowing gas and is connected to the liner-cooling system for the purpose of cooling. The invention is based on the concept of substantially reducing the popping or blow-off response pressure in the cooling circuit of a nuclear reactor as a function of temperature, especially in the primary circuit of a pressurized-water reactor, so that in the very unlikely case of the reactor core overheating, the primary-circuit pressure is automatically reduced to values below 30 bar. SUMMARY OF THE INVENTION It is accordingly an object of the invention to provide a safety device against overpressure failure of a nuclear reactor pressure vessel, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type, which permits the above-mentioned criterion to be met and which thus forms a barrier against overpressure failure of the nuclear-reactor pressure vessel in the case of overheating of the core. With the foregoing and other objects in view there is provided, in accordance with the invention, in a nuclear reactor having an interior, a pressure vessel, a coolant conducting surface exposed to primary pressure, such as a wall or pipeline of the pressure vessel, and a core, a safety device against overpressure failure of the pressure vessel upon insufficient cooling of the core, comprising a differential-pressure-loaded pressure relief valve being set in the coolant conducting surface, the pressure relief valve having a hollow guide cylinder, a closure piece in the form of a differential-pressure piston being constructed as a hollow body and being longitudinally displaceable in the hollow guide cylinder between a closure position and an opening position, and a fusible stop sealing and retaining the differential-pressure piston in the closure position, the fusible stop melting due to a threshold temperature heat flow reaching the fusible stop upon reaching an upper threshold temperature in the interior of the reactor, for permitting the differential-pressure piston to move into the opening position. In accordance with another feature of the invention, the pressure relief valve has seating surfaces, the differential-pressure piston has sealing surfaces, and the fusible stop is disposed between the sealing surfaces and the seating surfaces. In accordance with a further feature of the invention, the differential-pressure piston has peripheral piston surfaces, the guide cylinder has an inner periphery with guide surfaces, and the fusible stop is additionally disposed between the peripheral piston surfaces and the guide surfaces. In accordance with an added feature of the invention, the pressure relief valve has a valve body with a wall and an inner periphery and the guide cylinder has an outer periphery, defining an annular duct remaining free as an overflow duct between the inner and outer peripheries; the pressure relief valve has vanes being disposed in the annular duct and joined to the wall of the valve body for holding the guide cylinder in a centered position in the valve body; and the overflow duct has an inlet cross section being normally sealed by the differential-pressure piston in the closure position and being cleared and released in the opened position. In accordance with an additional feature of the invention, the guide cylinder has an end facing away from the differential-pressure piston, and the end has a bottom with a pressure relief orifice formed therein. The main advantages which can be achieved by means of the invention are that, when a certain threshold temperature in the reactor core is reached, which is distinctly below the failure temperature of the reactor pressure vessel, the fusible stop is caused to melt and the closure piece is thus released. The system pressure (reactor pressure) causes the preferably employed differential-pressure piston to be displaced in its guide cylinder as far as a piston end stop. After the piston end stop is reached, the system pressure is reduced through the relief cross section which is thus opened, to values below 30 bar. In accordance with yet another feature of the invention, the pressure relief valve is set into the wall of a primary coolant pipe near the nuclear reactor pressure vessel. In accordance with yet a further feature of the invention, the pressure relief valve is set into the wall of the pressure vessel at the level of the primary coolant pipe sockets and in wall sections between them. In accordance with yet an added feature of the invention, the pressure relief valve is connected to a pressurizer discharge line opening into a pressurizer relief tank. In accordance with a concomitant feature of the invention, with correspondingly lower cross-sectional dimensions of the pressure relief valve and the lines connected thereto, the pressure relief line is alternatively constructed as a control line for a separate relief valve. Among fusible alloys, silver solder alloys have been found to be particularly advantageous and they are stable and radiation-resistant in a temperature range up to approximately 700.degree. C. 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 safety device against overpressure failure of a nuclear reactor pressure vessel, 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.
	claims	1. A high energy photon source comprising: A. a vacuum chamber, B. at least two electrodes located within said vacuum chamber and defining an electrical discharge region and arranged to create high frequency plasma pinches at a pinch site upon electrical discharge, C. a working gas comprising an active gas and a buffer gas, said buffer gas being a noble gas, and said active gas being chosen to provide light at least one spectral line, D. a working gas supply system for supplying a working gas to said discharge region, E. a pulse power source for providing electrical pulses and voltages high enough to create electrical discharge between said at least one pair of electrode, and F. a conical nested debris collector with surfaces aligned with light rays extending out from the pinch site toward the radiation collector-director. 2. A high energy photon source as in claim 1 wherein said pulse power source is programmable to provide electrical pulses at frequencies of at least 1000 Hz. claim 1 3. A high energy photon source as in claim 1 wherein said active gas is lithium vapor. claim 1 4. A high energy photon source as in claim 1 wherein said active gas is lithium hydride. claim 1 5. A high energy photon source as in claim 1 and further comprising a light pipe arranged to transmit radiation collected and directed by said collector-director. claim 1 6. A high energy photon source as in claim 1 wherein said buffer gas is argon. claim 1 7. A high energy photon source as in claim 1 wherein said buffer gas is radon. claim 1 8. A high energy photon source as in claim 1 wherein said at least two electrodes are three disk shaped electrodes defining two outer electrodes and an inner electrode, said two inner electrodes during operation being at a polarity opposite said inner electrode. claim 1 9. A high energy photon source as in claim 1 wherein said conical nested debris collector is fabricated as a part of said radiation collector-director. claim 1 10. A high energy photon source as in claim 9 wherein said material is lithium. claim 9 11. A high energy photon source as in claim 1 wherein said active gas is a vapor of a metal defining a melting point and further comprising a heating means to maintain said radiation collector and said debris collector at a temperature in excess of the melting point of said metal. claim 1 12. A high energy photon source as in claim 11 wherein said lithium is located in one of said two electrodes. claim 11 13. A high energy photon source as in claim 1 wherein said active gas is produced by heating of a material. claim 1 14. A high energy photon source as in claim 13 and further comprising a position adjustment means to adjust said lithium relative to said central electrode tip. claim 13 15. A high energy photon source as in claim 1 and further comprising a blast shield comprised of electrical insulator material positioned to limit elongation of said plasma pinches wherein said blast shield comprises a hole located so as to permit extreme ultraviolet light rays from said pinch to pass through said blast shield. claim 1 16. A high energy photon source as in claim 15 wherein said hole is beveled to permit increased off axis collection of the light rays. claim 15 17. A high energy photon source as in claim 1 wherein said two electrodes are configured coaxially to define a central electrode defining an axis and an outer electrode comprised of an array of rods. claim 1 18. A high energy photon source as in claim 17 wherein said array of rods are arranged to form in a generally cylindrical shape. claim 17 19. A high energy photon source as in claim 17 wherein said array of rods are arranged to form a generally conical shape. claim 17 20. A high energy source as in claim 1 and further comprising a beam splitter for transmitting extreme ultraviolet radiation and reflecting visible light. claim 1 21. A high energy source as in claim 20 wherein said window is comprised of a sheet of a solid material having a thickness of less than 1 micron. claim 20 22. A high energy source as in claim 20 wherein said material is chosen from a group of materials consisting of beryllium, zerconium and silicon. claim 20 23. A high energy source as in claim 1 and further comprising a preionizer for preionizing said working gas. claim 1 24. A high energy source as in claim 23 wherein said preionizer is a RF driven spark gap. claim 23 25. A high energy source as in claim 23 wherein said preionizer comprises a spiker circuit. claim 23 26. A high energy source as in claim 23 wherein said preionizer is a DC spark gap ionizer. claim 23 27. A high energy source as in claim 26 wherein said preionizer is a RF driven surface discharge. claim 26 28. A high energy source as in claim 26 wherein said preionizer is a corona discharge. claim 26 29. A high energy source as in claim 1 and further comprising a vacuum chamber window for transmitting extreme ultraviolet radiation and reflecting visible light. claim 1 30. A high energy source as in claim 29 wherein said window is comprised of a sheet of a solid material having a thickness of less than 1 micron. claim 29 31. A high energy source as in claim 29 wherein said material is chosen from a group of materials consisting of beryllium and silicon. claim 29 32. A high energy photon source as in claim 29 and further comprising a focusing means for focusing said radiation on to said windows. claim 29 33. A high energy photon source as in claim 1 and further comprising an external reflection radiation collector-director for collecting radiation produced in said plasma pinches and for directing said radiation in a desired direction. claim 1 34. A high energy photon source as in claim 33 wherein said metal is lithium. claim 33 35. A high energy photon source as in claim 34 wherein said two electrodes are configured coaxially to define a central electrode defining an axis and a central tip and said lithium is positioned along said axis. claim 34 36. A high energy photon source as in claim 33 wherein said electrodes are comprised of an electrode material and said collector-director is coated with the same electrode material. claim 33 37. A high energy photon source as in claim 36 wherein said buffer gas is helium. claim 36 38. A high energy photon source as in claim 36 wherein said electrode material is tungsten. claim 36 39. A high energy photon source as in claim 38 wherein said electrode material is silver. claim 38
044980116	abstract	The invention concerns a device for the receiving, moving and radiation-shielding of vessels filled with expended reactor fuel elements. The device consists of a protective container having a base, a cylindrical protective jacket and a cover made from concrete. At the lower rim of the jacket there are lateral air ducts which open into the annular space between protective jacket and fuel element vessel. In the area of the upper jacket edge, lateral air outlet ducts are provided. For facilitating the loading of the device with fuel element containers and its transportation, the base is constructed in the form of a separate movable pallet. The fuel element container can be placed on this pallet, and the protective jacket over it. The air outlet ducts in the area of the cover are arranged in an inclined or angular fashion. The base is provided with a raised center platform for supporting the fuel element vessel. Also, centering means is provided for the correct seating of the protective jacket with respect to the base.
	abstract	Systems, articles of manufacture, and associated computer-executed methods determine an optimum temporal segmentation for automated information technology (IT) management. A computer-executed method detects changes in a performance metric in an automated information technology (IT) management system comprising defining a plurality of temporal segments as sets of contiguous time samples wherein time samples within a segment are mutually more similar in terms of performance metric behavior than time samples in previous and subsequent segments, and discovering the segments using an information-theoretical approach. Detecting changes in the performance metric can further comprise associating cost with the segments that is lesser for homogeneous metric behavior and greater for heterogeneous metric behavior within a segment, and finding segmentation that minimizes the cost using dynamic programming.
	claims	1. A method for analyzing target interrogation data, the method comprising:irradiating a target with neutrons;collecting target interrogation data, wherein the target interrogation data comprises spectra that is representative of the contents of the target;performing a primary analysis of the spectra according to a least squares analysis to determine a first set of elemental intensities representative of the contents of the target;performing a secondary analysis of the spectra utilizing the first set of elemental intensities by comparing the first set of elemental intensities from the target to a second set of elemental intensities for known spectra wherein the secondary analysis is a tertiary hypothesis test; andclassifying the contents of the target based on the secondary analysis comparison. 2. The method according to claim 1, wherein classifying the target further comprises the step of determining whether the target contains explosives, chemical warfare agents, or illicit drugs. 3. The method according to claim 1, wherein spectra is emitted from at least one element of the target selected from the group consisting of H, C, N, O, S, Cl, Fe, Al, Si, and P. 4. The method according to claim 1, further comprising the step of providing a library of spectra for at least one element. 5. The method according to claim 1, further comprising the step of plotting a receiver operating characteristic curve. 6. The method according to claim 1, wherein the spectra are gamma ray spectra. 7. A method for analyzing target interrogation data, the method comprising:irradiating a target with neutrons;collecting target interrogation data, wherein the target interrogation data comprises spectra that is representative of the contents of the target;performing a primary analysis of the spectra according to a principal component analysis to determine a first set of vectors representative of the contents of the target;performing a secondary analysis of the spectra utilizing the first set of vectors by comparing the first set of vectors from the target to a second set of vectors for known spectra; andclassifying the contents of the target based on the secondary analysis comparison. 8. The method according to claim 7, wherein the secondary analysis is a generalized likelihood ratio test or support vector machines. 9. The method according to claim 7, wherein classifying the target further comprises the step of determining whether the target contains explosives, chemical warfare agents, or illicit drugs. 10. The method according to claim 7, wherein spectra is emitted from at least one element of the target selected from the group consisting of H, C, N, O, S, Cl, Fe, Al, Si, and P. 11. The method according to claim 7, further comprising the step of plotting a receiver operating characteristic curve. 12. The method according to claim 7, wherein the secondary analysis is a binary hypothesis test. 13. The method according to claim 7, wherein the secondary analysis is a tertiary hypothesis test. 14. The method according to claim 7, wherein the spectra are gamma ray spectra. 15. An interrogation system for determining the contents of a target comprising:at least one pulsed neutron generator;at least one detector configured to provide spectra representative of the target;a primary analysis application to perform a least squares analysis of the spectra to determine a first set of elemental intensities representative of the contents of the target; anda secondary analysis application to perform an analysis of the spectra utilizing the first set of elemental intensities by comparing the first set of elemental intensities from the target to a second set of elemental intensities for known spectra wherein the secondary analysis is a tertiary hypothesis test;wherein the system classifies the contents of the target based on the secondary analysis application comparison. 16. The interrogation system according to claim 15, wherein the system classifies the target to determining whether the target contains explosives, chemical warfare agents, or illicit drugs. 17. The interrogation system according to claim 15, wherein spectra is emitted from at least one element of the target selected from the group consisting of H, C, N, O, S, Cl, Fe, Al, Si, and P. 18. The interrogation system according to claim 15, further comprising a library of spectra for at least one element. 19. The system according to claim 15, wherein the secondary analysis application plots a receiver operating characteristic curve. 20. The system according to claim 15, wherein the spectra are gamma ray spectra. 21. An interrogation system for determining the contents of a target comprising:at least one pulsed neutron generator;at least one detector configured to provide spectra representative of the target;a primary analysis application to perform a principal component analysis to determine a first set of vectors representative of the contents of the target; anda secondary analysis application to perform an analysis of the spectra utilizing the first set of vectors be comparing the first set of vectors from the target to a second set of vectors for known spectra;wherein the system classifies the contents of the target based on the secondary analysis application comparison. 22. The interrogation system according to claim 21, wherein the secondary analysis application utilizes a generalized likelihood ratio test or support vector machines. 23. The interrogation system according to claim 21, wherein the system classifies the target to determining whether the target contains explosives, chemical warfare agents, or illicit drugs. 24. The interrogation system according to claim 21, wherein spectra is emitted from at least one element of the target selected from the group consisting of H, C, N, O, S, Cl, Fe, Al, Si, and P. 25. The interrogation system according to claim 21, wherein the secondary analysis application plots a receiver operating characteristic curve. 26. The interrogation system according to claim 21, wherein the secondary analysis application utilizes a binary hypothesis test. 27. The interrogation system according to claim 21, wherein the secondary analysis utilizes a tertiary hypothesis test. 28. The system according to claim 21, wherein the spectra are gamma ray spectra.
	summary
	description	This application is a Continuation application of U.S. application Ser. No. 10/898,592 filed on Jul. 26, 2004, now U.S. Pat. No. 7,268,356 which is Continuation application of U.S. application Ser. No. 10/699,853 filed on Nov. 4, 2003, now U.S. Pat. No. 6,794,663 which is a Continuation application of U.S. application Ser. No. 09/985,537 filed on Nov. 5, 2001 now U.S. Pat. No. 6,664,552. Priority is claimed based on U.S. application Ser. No. 10/898,592 filed on Jul. 26, 2004, which claims the priority of U.S. application Ser. No. 10/699,853 filed on Nov. 4, 2003, which claims the priority date of U.S. application Ser. No. 09/985,537 filed on Nov. 5, 2001, which claims the priority dates of Japanese applications 2000-342372 and 2001-204768 filed on Nov. 6, 2000 and Jul. 5, 2001, respectively, all of which is incorporated by reference. The present invention relates to method and apparatus specimen fabrication for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer or a device or preparing the micro sample to be separated by using a focused ion beam. Electronic parts such as a semiconductor memory typified by a dynamic random access memory, a microprocessor, a semiconductor device such as a semiconductor laser, and a magnetic head are required to be manufactured in a high yield since decrease in the manufacturing yield due to occurrence of a defect causes profit deterioration. Consequently, early detection/measure of/against a defect, a foreign matter, and poor processing as causes of a failure are big tasks. For example, at a site of manufacturing a semiconductor device, energies are put into finding a failure by a careful test and analyzing the cause of the failure. In an actual electronic part manufacturing process using a wafer, a wafer being processed is tested, the cause of an abnormal portion such as a defect in a circuit pattern or a foreign matter is tracked down, and a measurement to be taken is examined. Usually, to observe a fine structure of a sample, a scanning electron microscope (hereinbelow, abbreviated as SEM) with high resolution is used. However, as the packing density of a semiconductor device is becoming higher, an object cannot be observed with the resolution of the SEM. Therefore, in place of the SEM, a transmission electron microscope (hereinbelow, abbreviated as TEM) having higher observation resolution is used. Conventional TEM sample fabrication is accompanied by a work of making a sample into small pieces by cleaving, cutting, or the like. When the sample is a wafer, in most cases, the wafer has to be cut. Recently, there is a micro area processing method of irradiating a sample with an ion beam and applying an action that particles constructing the sample are released from the sample by sputtering, that is, a method of using a process with a focused ion beam (hereinbelow, abbreviated as FIB). According to the method, first, a strip pellet having a thickness of sub millimeters including an area to be observed is cut from a sample such as a wafer by using a dicer or the like. A part of the strip pellet is processed with an FIB into a thin film state to thereby prepare a TEM sample. The feature of the sample for TEM observation processed with the FIB is that a part of a specimen is processed to a thin film having a thickness of about 100 nm for the TEM observation. Although the method enables a requested observation area to be positioned with accuracy of a micrometer level and to be observed, still, the wafer has to be cut. Although monitoring a result of a process during fabrication of a semiconductor device or the like has an big advantage from the viewpoint of managing the yield, a wafer is cut for preparation of a sample as described above and a piece of the wafer is not subjected to a following process but is discarded. In recent years, particularly, the diameter of a wafer is increasing to reduce the price of manufacturing a semiconductor device. Specifically, the number of semiconductor devices which can be manufactured from a single wafer is increased to reduce a unit price. However, it increases the price of the wafer itself, an added value increases as the manufacturing process advances and, further, the number of semiconductor devices lost by discarding a wafer increases. Therefore, the conventional test method accompanying cutting of the wafer is very uneconomical. To deal with the problem, there is a method of preparing a sample without cutting a wafer. The method is disclosed in Japanese Patent Application No. H05-52721, “Method of separating sample and method of analyzing sample separated by the separating method” (known technique 1). According to the method, as shown in FIGS. 2(a) to 2(g), first, the posture of a sample 2 is maintained so that the surface of the sample 2 is irradiated with an FIB 1 at the right angle and scanned with the FIB 1 in a rectangular shape, and a rectangular hole 7 having a required depth is formed in the surface of the sample (FIG. 2(a)). Subsequently, the sample 2 is tilted and a bottom hole 8 is formed. The tilt angle of the sample 2 is changed by a specimen stage (not shown) (FIG. 2(b)). The posture of the sample 2 is changed, the sample 2 is disposed so that the surface of the sample 2 becomes perpendicular to the FIB 1 again, and a trench 9 is formed (FIG. 2(c)). By driving a manipulator (not shown), the tip of a probe 3 at the end of the manipulator is made come into contact with a portion to be separated in the sample 2 (FIG. 2(d)). A deposition gas 5 is supplied from a gas nozzle 10, and an area including the tip of the probe 3 is locally irradiated with the FIB 1 to form an ion beam assist deposition film (hereinbelow, simply called deposition film 4). The separation portion in the sample 2 and the tip of the probe 3 which are in contact with each other are connected to each other by the deposition film 4 (FIG. 2(e)). The peripheral portion is trenched with the FIB 1 (FIG. 2(f)), and a micro sample 6 as a sample separated from the sample 2 is cut. The cut separated sample 6 is supported by the connected probe 3 (FIG. 2(g)). The micro sample 6 is processed with the FIB 1 and the area to be observed is walled, thereby obtaining a TEM sample (not shown). According to the method, a micro sample including a requested analysis area is separated from a sample such as a wafer by using a process with an FIB and means for carrying the micro sample. The micro sample separated by the method is introduced to any of various analyzers and can be analyzed. A similar sample fabricating method is disclosed in Japanese Patent Application Laid-Open No. H09-196213, “Apparatus and method for preparing micro sample” (known technique 2). According to the method, as shown in FIGS. 9(a) to 9(j), first, the FIB 1 is emitted to form marks 403 and 404 for identifying a target position and, after that, rectangular holes 401 and 402 are formed on both outer sides of the marks 403 and 404 in the sample 2 (FIG. 9(a)). Subsequently, a trench 406 is formed with the FIB 1 (FIG. 9(b)). The specimen stage is tilted and the surface of the sample is obliquely irradiated with the FIB 1, thereby forming a tapered trench 408, and an extraction sample 407 which is connected to the sample 4 only via a residual area 405 is formed (FIG. 9(c)). The tilted specimen stage is returned to the original position and the probe 3 is controlled by a probe controller so as to come into contact with a part of the extraction sample 407. The residual area 405 of the extraction sample 407 will be cut with an FIB later. In consideration of a probe drift or the like, it is desirable to cut the residual area 405 in short time, so that the volume of the residual area 405 has to be low. Consequently, due to a fear that the residual area 405 is destroyed by the contact of the probe 3, the probe 3 is made contact while preventing a damage as much as possible by using the probe controlling method. The probe 3 and the extraction sample 407 which are in contact with each other are fixed by using a deposition film 409 (FIG. 9(d)). Subsequently, the residual area 405 is cut with the FIB 1 (FIG. 9(e)). In such a manner, the extraction sample 407 is cut out, and the probe 3 is lifted by the probe driving apparatus to extract the extraction sample 407 (FIG. 9(f)). Subsequently, the cut extraction sample 407 is allowed to come into contact with a trench 411 formed in an extracted sample holder (FIG. 9(g)). At this time, the extraction sample 407 has to come into contact at a sufficiently low speed so that the extraction sample 407 is not destroyed or is not come off from the connected portion with the deposition film 409, so that the contacting method is necessary. After making the extraction sample 407 contact with the trench 411, they are fixed by using a deposition film 412 (FIG. 9(h)). After the fixing, the probe 3 connection portion is irradiated with the FIB, and sputtering is performed to separate the probe from the extraction sample 407 (FIG. 9(i)). In the case of preparing a TEM sample, finally, the FIB 1 is emitted again to finish an observation area 410 so that the thickness of the observation area 410 becomes about 100 nm or less (FIG. 9(j)). In the case of preparing a sample for analysis or measurement, the finishing process for making the observation area thin (FIG. 9(j)) is not always necessary. The example of employing the method of extracting a micro sample by the sample fabricating apparatus has been described above. There is also a method of processing the shape of a micro sample by the sample fabricating apparatus, taking out the base from the sample fabricating apparatus, and extracting the micro sample by another mechanism in atmosphere. For example, such a method is described by L. A. Giannuzzi et al., “Focused Ion Beam Milling and Micromanipulation Lift-Out for Site Specific Cross-Section TEM Specimen Preparation”, Material Research Society, Symposium Proceeding Vol. 480, pp. 19 to 27 (known technique 3). Similarly, it is also descried by L. R. Herlinger, “TEM Sample Preparation Using a Focused Ion Beam and a Probe Manipulator”, Proceedings of the 22nd International Symposium for Testing and Failure Analysis, pp. 199 to 205 (known technique 4). According to such a method, as shown in FIG. 3(a), both sides of a target position on a wafer 208 are processed in a stair shape with the FIB 1 to form a sample membrane 207, a specimen stage is tilted to change the angle formed between the FIB 1 and the surface of the sample, and the sample is irradiated with the FIB 1. As shown in FIG. 3(b), the periphery of the sample membrane 207 is cut with the FIB 1, thereby separating the sample membrane 207 from the wafer. The wafer is taken out from an FIB system, a glass stick is allowed to approach the process portion in the atmosphere, the sample membrane 207 is attracted by the glass stick by using static electricity and is separated from the wafer, the glass stick is moved above a mesh 209 and is attracted by the mesh 209 by using static electricity or disposed so that the process face faces a transparent attachment. As described above, the processed micro sample in the system may not be taken out in the system. Even when most of the outer shape of the micro sample is processed with an ion beam, the separated micro sample is introduced into the TEM, and can be analyzed. By using any of the methods, without cutting a wafer, only a micro sample or a membrane sample for test is extracted from a sample, and the wafer from which the sample is extracted can be returned to the next process. Therefore, unlike the conventional techniques, there is no semiconductor device which is lost by the cutting of a wafer, the manufacturing yield of the semiconductor device is increased in total, and the manufacturing cost can be reduced. In the case of forming a hole by using sputtering of irradiating the surface of a sample with an ion beam and observing a section of the hole by an FIB system or a scanning electron microscope (SEM), the section is formed at an end of an ion beam scan range. However, the actually formed section is not perfectly perpendicular to the surface of a sample due to flare of a processing beam and re-deposition of a sputtered substance, and a slight taper exists. An FIB system having a mechanism of tilting a specimen stage can prevent the taper by tilting a sample by an angle corresponding to the taper, for example, about 0.5 degree and irradiating the tilted sample with an ion beam and form an observation section having higher perpendicularity. The method is described as, for example, processing of a sample section of a transmission electron microscope (TEM), in “Electron and ion beam handbook, Third Edition”, Japan Society for the Promotion of Science, 132 commission, Nikkan Kogyo Shinbun Sha, pp. 459 and 460 (known technique 5). The conventional methods have the following problems. Specifically, to form the bottom hole 8 in the first known technique, to form the tapered trench 408 in the second known technique, and to cut the periphery of the sample membrane 207 in the fourth known technique, the posture or tilt angle of the sample 2 is changed as a necessary process by the specimen stage. However, as the diameter of a wafer increases, the specimen stage also becomes larger. Consequently, a problem such that it takes time to tile a large stage with high accuracy and, as a result, sample fabrication time becomes longer arises. Due to heavy weight of the specimen stage itself, the eucentric is not maintained before and after the tilting and the sample position relative to the ion beam irradiating optical system moves, so that the focal point of the FIB is relatively largely deviated from the surface of the sample, the surface of the sample cannot be observed, and a problem such that the ion beam irradiating optical system has to be re-adjusted also occurs. The function of tilting the specimen stage causes increase in the size of the specimen stage itself and in the size of a specimen chamber for housing the specimen stage. The trend of the diameter of a wafer is shifting from 200 mm to 300 mm. When the diameter of a wafer is further increased to 400 mm, the size of the stage has to be increased and the problem which occurs in association with the tilt of the specimen stage has to be solved. In contrast, when the function of tilting the specimen stage of the system can be eliminated, miniaturization of the whole system can be realized and a problem such as a deviation of the sample position accompanying a tilt of the sample is solved. However, by the above-described conventional methods, fabrication of a sample for analyzing, observing or measuring a micro area by separating a micro sample from an original sample (wafer) or preparing the micro sample to be separated cannot be realized. Originally, the change in the tilt angle or posture of a sample is required due to existence of the fixed idea that the surface of a sample has to be irradiated with ion beams in at least two directions at different angles to separate a micro sample from an original sample or prepare the micro sample to be separated. The tilting of the stage denotes here turning of a stage around a line segment included in or parallel to the stage plane as an axis. It will be simply described as tilting of a stage hereinlater. By an FIB controller in which a specimen stage has the tilting function, an FIB can be emitted at an arbitrary angle, and can eliminate the taper as in the known technique 5. On the other hand, the function of tilting a specimen stage can be omitted from the system, the miniaturization of the whole system is realized, and the program such as a deviation of the sample position which occurs in association with the tilting of a sample can be solved. However, according to the conventional methods, it is difficult to emit an FIB at an arbitrary angle. A method of obliquely irradiating the surface of a sample with an ion beam to form a hole, thereby enabling an observation section to be formed is disclosed as “Section observing method” in Japanese Patent Application Laid-Open No. H03-166744 (known technique 6). Although a process of forming a vertical section by the method is described, a method of optionally changing an irradiation angle without tilting a specimen stage is not mentioned. Consequently, it is difficult to eliminate the taper. In consideration of the problems, a first object of the invention is to provide a sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from an original sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated without tilting a specimen stage by breaking down the conventional fixed idea. A second object is to provide a sample fabricating apparatus suitable for achieving the first object. A third object is to realize a sample fabricating apparatus and a sample fabricating method which can form a section by irradiation with an FIB at an arbitrary angle in a certain range even when a not-tilting specimen stage is used. Terms used in the specification will be defined as follows. A requested section is a section the operator of the apparatus intends to prepare. A set section denotes a section obtained when it is assumed that a set ion beam scanning area is ideally processed without an influence of a beam diameter, re-deposition, or the like. A formed section is a section actually formed with an FIB. A formed-section edge is a cross line between the formed section and the surface of a sample. A set-section edge is a cross line between the set section and the surface of a sample. A scanning-area edge is one of the sides of an ion bean scanning area. A requested-section edge is a cross line of a requested section and the surface of a sample. A requested-section edge normal direction is a direction of a normal line in a sample surface of a requested section edge, which extends from the sample to a process space. A requested section normal direction is a direction of a normal line of a requested section, which extends from the inside of the sample to a process space. A requested depression angle is an angle formed between the requested-section normal direction and the sample surface. The requested depression angle is positive in the case where the requested-section normal line direction extends from the sample surface to the inside of the sample, and is negative in the case where the requested-section normal line direction extends from the inside of the sample to the surface of the sample (corresponding to an elevation angle). A set-section depression angle is an angle formed between the set-section normal line direction and the sample surface. The set-section depression angle is positive when the set-section normal line direction extends from the sample surface to the inside of the sample and is negative when the set-section normal line direction extends from the inside of the sample to the surface of the sample (corresponding to an elevation angle). The first object of the invention is achieved as follows. Basic aspects of the invention to break down the conventional fixed idea that the tilt angle or the posture of a sample has to be changed are as follows. (1) An ion beam processing method for separating a requested portion in a sample or preparing the requested portion by irradiating the sample with an ion beam from a plurality of directions while fixing an angle formed between a sample placement face and an optical axis of an ion beam to the sample. According to the invention, the ion beam processing method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. (2) A sample separating method for irradiating a sample with an ion beam while setting an angle formed between the optical axis of the ion beam emitted to the sample and the surface of the sample to be larger than 0 degree and smaller than 90 degrees and irradiating a requested portion in the sample with the ion beam while fixing an angle formed between the optical axis of the ion beam emitted to the sample and the sample surface to thereby separate the requested portion or prepare the requested portion to be separated. According to the invention, the sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. (3) A sample separating method for irradiating a sample with an ion beam while setting an angle formed between the optical axis of the ion beam emitted to the sample and the sample surface to be a range from 30 degrees to 75 degrees, and irradiating a requested portion in the sample with the ion beam while fixing the angle formed between the optical axis of the ion beam emitted to the sample and the sample surface, thereby separating the requested portion or preparing the requested portion to be separated. According to the invention, the sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. Particularly, by setting the FIB irradiation angle in the range from 30 degrees to 75 degrees, the surface of the sample can be observed excellently, and the shape of the micro sample is formed to be suitable for fabrication. (4) The object is also realized by a sample fabricating method for separating a micro sample from a sample or preparing the micro sample to be separated by using a sample fabricating apparatus including at least a focused ion beam irradiating optical system, secondary particle detecting means for detecting secondary particles generated from a sample irradiated with the focused ion beam, and a specimen stage on which a specimen base is placed, in which the sample is irradiated with the focused ion beam by setting the angle formed between the optical axis of the focused ion beam emitted to the sample and the sample surface to be larger than 0 degree and smaller than 90 degrees, and the sample is turned by using a sample surface normal line as a turning axis and is irradiated with the ion beam while fixing the angle formed between the optical axis of the focused on beam to the sample and the sample surface. That is, an aspect of the invention for breaking down the conventional fixed idea is to include an operation of turning a specimen stage around the line normal to the sample surface as a turning axis into the sample fabricating method in accordance with an object. According to the invention, the sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. Also in the case of an apparatus in which the specimen stage has the tilting function, the time required to tilt the stage is unnecessary so that the sample fabricating time is made relatively short. The problem such that the sample surface cannot be observed before and after the specimen stage is tilted is also reduced. (5) In the sample fabrication method of (4), the requested portion in the sample is supported by a probe. According to the invention, the sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. By supporting the micro sample by the probe and extracting the micro sample from the specimen base, the section of the micro sample can be observed in detail, and the position of processing the section can be controlled with high precision. As the method of supporting the micro sample, any method can be used as long as the micro sample can be supported such as fixing by using a deposition film, fixing by using static electricity, or the like. (6) A sample fabricating method for observation, analysis, or measurement, including: a step of forming a sample connected to a specimen base via a residual area by a step of forming a rectangle hole by irradiating the sample with a focused ion beam while setting an angle formed between the optical axis of the focused ion beam emitted to the sample and the sample surface to be larger than 0 degree and smaller than 90 degrees, a step of turning the sample by using a sample surface normal line as a turning axis, and a step of forming a tapered trench in the surface of the specimen base by emitting a focused ion beam after the turn; a step of fixing the connected sample to a requested portion of transfer means by making a requested portion in the connected sample contact with the requested portion of the transfer means, and forming a deposition film in an area including the contact portion by irradiating the area with a focused ion beam while supplying a deposition gas; and a step of cutting the residual area by emitting a focused ion beam. According to the invention, the sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. The section of the micro sample can be observed in detail, and the section process position can be controlled with high precision. (7) A sample fabricating method for observation, analysis, or measurement, including: a step of forming a membrane by forming a rectangle hole by emitting a focused ion beam while setting an angle formed between the optical axis of the focused ion beam emitted to the sample and the sample surface to be larger than 0 degree and smaller than 90 degrees; a step of turning the sample by using a sample surface normal line as a turning axis, and a step of separating the sample membrane or preparing the sample membrane to be separated by emitting a focused ion beam after the turn. According to the invention, the sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. Since a process of forming an ion beam assist deposition film or the like is not included, the sample fabrication time can be shortened. (8) In the sample fabricating method in any of (3), (4), (5), (6), and (7), in order to separate at least two micro samples or prepare the micro samples to be separated, the peripheral area of each of micro samples is processed to some midpoint of all the processes, the sample is turned, and the process of the peripheral area of each of the micro samples is sequentially continued. According to the invention, the sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. Particularly, a plurality of samples can be prepared with high throughput. The second object of the invention is achieved as follows. (9) A sample fabricating apparatus including at least a focused ion beam irradiating optical system and a specimen stage on which a specimen base is placed, for separating a micro sample from the specimen base or preparing the micro sample to be separated, wherein an angle formed between an almost center axis of a mechanical column including the focused ion beam irradiating optical system and the sample placement face of the specimen stage is fixed, and the apparatus has a separator for separating a desired portion in the sample and a probe for supporting the separated sample. According to the invention, the sample fabricating method for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample without tilting a specimen stage can be realized. By supporting the micro sample by the probe and extracting the micro sample from the specimen base, the section of the micro sample can be observed in detail, and the sample fabricating apparatus capable of controlling the section process position with high precision can be realized. As the method of supporting the micro sample, any method can be used as long as the micro sample can be supported such as fixing by using a deposition film, fixing by using static electricity, or the like. (10) A sample fabricating apparatus for separating a micro sample from a specimen base or preparing the micro sample to be separated, including at least a focused ion beam irradiating optical system, secondary particle detecting means for detecting secondary particles generated from a sample irradiated with the focused ion beam, and a specimen stage on which a specimen base is placed, wherein the angle formed between the optical axis of the focused ion beam emitted to the sample and the sample surface is larger than 0 degree and smaller than 90 degrees, the specimen stage has the function of turning around a sample surface normal line as a turn axis, and the apparatus has the function of determining, after the turn, the position irradiated with the focused ion beam for separating a sample or preparing the sample to be separated by using image displaying means for displaying a secondary particle image formed by secondary particles generated from the sample irradiated with the focused ion beam or an electron beam emitted from an electron beam emitting system separately provided. According to the invention, the sample fabricating apparatus for preparing a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated without tilting the specimen stage, which is suitable from the viewpoints that operations of the apparatus can be automated and the burden on the operator can be lessened and can prepare a sample in which a damage in the sample surface is little in a short time can be realized. (11) A sample fabricating apparatus for separating a micro sample from a specimen base or preparing the micro sample to be separated, including at least a focused ion beam irradiating optical system, secondary particle detecting means for detecting secondary particles generated from a sample irradiated with the focused ion beam, and a specimen stage on which a specimen base is placed, wherein the angle formed between the optical axis of the focused ion beam emitted to the sample and the sample surface is larger than 0 degree and smaller than 90 degrees, the specimen stage has the function of turning around a sample surface normal line as a turn axis, and the apparatus has the function of determining, after the turn, the position irradiated with the focused ion beam for separating a sample or preparing the sample to be separated by using a result of performing an image process on a secondary particle image formed by secondary particles generated from the sample irradiated with the focused ion beam or an electron beam emitted from an electron beam emitting system separately provided. According to the invention, the sample fabricating apparatus for preparing a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated without tilting the specimen stage, which is suitable from the viewpoints that operations of the apparatus can be automated and the burden on the operator can be lessened and can prepare a sample in which a damage in the sample surface is little in a short time can be realized. (12) A sample fabricating apparatus for separating a micro sample from a specimen base or preparing the micro sample to be separated, including at least a focused ion beam irradiating optical system, secondary particle detecting means for detecting secondary particles generated from a sample irradiated with the focused ion beam, and a specimen stage on which a specimen base is placed, wherein the angle formed between the focused ion beam irradiating optical system and the sample surface is in a range from 30 degrees to 75 degrees, the specimen stage has a turning function around a normal line to the sample surface as a rotation axis, and the apparatus includes a transfer means for transferring an extracted micro sample which is a desired portion separated from the specimen base to another member, and a holding means of a sample holder on which the extracted micro sample is placed. The sample fabricating apparatus is suitable for fabricating a sample for analyzing, observing, and measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated without tilting the specimen stage. Particularly, by irradiating the focused ion beam at an angle from 30 degrees to 75 degrees, the surface of the sample can be observed excellently, and the shape of the micro sample is suitable for easy fabrication. The sample fabricating apparatus capable of fabricating a sample in shorter time can be realized. (13) A sample fabricating apparatus for separating a micro sample from a specimen base or preparing the micro sample to be separated, including at least a focused ion beam irradiating optical system, secondary particle detecting means for detecting secondary particles generated from a sample irradiated with the focused ion beam, and a specimen stage on which a specimen base is placed, in which the angle formed between the optical axis of the focused ion beam emitted to the sample and the sample surface is 45 degrees, the specimen stage has a function of turning around a sample surface normal line as a rotation axis, and the apparatus includes a transfer means for transferring an extracted micro sample which is a requested portion separated from the specimen base to another member, and a holding means of a sample holder on which the extracted micro sample is placed. According to the invention, the sample fabricating apparatus for preparing a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or by preparing the micro sample to be separated without tilting the specimen stage can be realized. The apparatus is suitable for separating a sample or preparing the sample to be separated since the angle of the focused ion beam can be set to 45 degrees in both of the cases of observing the sample surface and a section of the sample by irradiation with the focused ion beam under the same conditions. Further, the sample fabricating apparatus capable of preparing a sample having little damage in its surface in a short time can be realized. (14) In the sample fabricating apparatus in any of (10), (11) (12), and (13), the optical axis of the focused ion beam emitted to the sample almost coincides with the mechanical center axis of an objective lens almost symmetrical with respect to the center as a component of the focused ion beam irradiating optical system. According to the invention, the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated without tilting the specimen stage can be realized by mechanically specifying the angle formed between the objective lens almost symmetrical with respect to the center as a component of the focused ion beam irradiating optical system and the surface of the specimen stage, so that designing of the apparatus can be simplified. (15) A sample fabricating apparatus including at least a focused ion beam irradiating optical system, secondary particle detecting means for detecting secondary particles generated from a sample irradiated with the focused ion beam, and a specimen stage on which a specimen base is placed, in order to separate a micro sample from the specimen base or preparing the micro sample to be separated, for irradiating a peripheral area of the micro sample in the specimen stage with the focused ion beam from a plurality of incident directions to thereby separate the micro sample or prepare the micro sample to be separated, in which the focused ion beam irradiating optical system is provided with a focused ion beam tilting function of changing the optical axis of the focused ion beam emitted to the sample by at least 15 degrees. According to the invention, the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated without tilting the specimen stage can be realized by the focused ion beam tilting function capable of changing the incident direction of the focused ion beam at least by 15 degrees. Particularly, the focused ion beam incident angle can be selected in preparation of a sample, so that various sample fabricating methods and various sample shapes can be realized. (16) In the sample fabricating apparatus of (15), the focused ion beam tilting function capable of changing the optical axis of the focused ion beam emitted to the sample by at least 15 degrees is realized by a mechanism of varying the tilt angle with respect to the specimen stage of a mechanical column including the focused ion beam irradiating optical system. According to the invention, the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated without tilting the specimen stage can be realized by the mechanism of varying the tilt angle with respect to the specimen stage of the mechanical column including the focused ion beam irradiating optical system. Particularly, the focused ion beam incident angle can be selected in preparation of a sample, so that various sample fabricating methods and various sample shapes can be realized. (17) In the sample fabricating apparatus of (15), the focused ion beam tilting function capable of changing the optical axis of the focused ion beam emitted to the sample by at least 15 degrees is realized by an electric deflecting mechanism. According to the invention, the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated without tilting the specimen stage can be realized by the electric deflecting mechanism. Particularly, the mechanical apparatus configuration is simplified, the manufacturing cost can be reduced, and the focused ion beam incident angle can be selected in preparation of a sample, so that various sample fabricating methods and various sample shapes can be realized. (18) In the sample fabricating apparatus in any of (10), (11) (12), (13), (14), (15), (16), and (17), the specimen stage has a fixed tilt angle using a line segment included in the stage plane or a line segment parallel to the stage plane as a tilt axis. According to the invention, since the specimen stage does not have the tilting function, miniaturization of the whole apparatus can be realized, and the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, and measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated can be realized. (19) In the sample fabricating apparatus in any of (9), (10), (11), (12), (13), (14), (15), (16), and (17), the specimen stage is constructed by combining a stage which is turned at a specific fixed angle and a stage which can be turned at an arbitrary angle. According to the invention, since the specimen stage does not have the tilting function, miniaturization of the whole apparatus can be realized, and the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, and measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated can be realized. Particularly, the apparatus is suitable for saving the time necessary for positioning and increasing the throughput of sample preparation. (20) In the sample fabricating apparatus in any of (9), (10) (11), (12), (13), (14), (15), (16), and (17), the specimen stage is constructed by combining a stage which is turned at a fixed angle that is at least one of 90 degrees and 180 degrees and a stage which can be turned at an arbitrary angle. According to the invention, since the specimen stage does not have the tilting function, miniaturization of the whole apparatus can be realized, and the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, and measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like or preparing the micro sample to be separated can be realized. Particularly, the apparatus is suitable for saving the time necessary for positioning and increasing the throughput of sample preparation. The third object of the invention is achieved by the following. (21) A sample fabricating apparatus for forming a sample section in a sample by ion beam processing, including an ion beam optical system constructed by an ion source, a lens for condensing ions emitted from the ion source, and a deflector, an ion beam optical system controller for controlling the ion beam optical system, a detector for detecting secondary particles generated from a sample irradiated with an ion beam, a specimen stage for holding the sample, and a specimen-stage position controller for controlling the position of the specimen stage, in which an angle formed between the optical axis of the ion beam emitted from the ion beam optical system and the sample surface is fixed and formation of a sample section is controlled in correspondence with a set-section depression angle. Thus, also in the apparatus in which the tilting of the specimen stage with respect to the ion beam optical system cannot be changed, a section at an arbitrary tilt angle can be formed. (22) A sample fabricating apparatus for forming a sample section in a sample by ion beam processing, including an ion beam optical system constructed by an ion source, a lens for condensing ions emitted from the ion source, and a deflector, an ion beam optical system controller for controlling the ion beam optical system, a detector for detecting secondary particles generated from a sample irradiated with an ion beam, a specimen stage for holding the sample, and a specimen-stage position controller for controlling the position of the specimen stage, in which the ion beam optical system controller has a construction that an angle formed between the optical axis of the ion beam emitted from the ion beam optical system and the sample surface is larger than 0 degree and smaller than 90 degrees, and controls an ion beam scan by the deflector in correspondence with a set-section depression angle of a set section. Thus, the FIB irradiating angle at the time of processing a section can be arbitrarily set. (23) In the sample fabricating apparatus in each of (21) and (22), the ion beam optical system controller controls the deflector on the basis of angle information that a requested depression angle is projected to a plane including, as a normal line, the optical axis of the ion beam in correspondence with a set-section depression angle of a set section. Thus, the ion beam processing set angle is controlled and the FIB irradiating angle at the time of processing a section can be arbitrarily set. (24) In the sample fabricating apparatus in each of (21) and (22), the ion beam optical system controller controls the deflector on the basis of angle information that a set-section depression angle is projected to a plane including, as a normal line, the optical axis of the ion beam in correspondence with a set-section depression angle of a set section, and the specimen-stage position controller controls turning in the specimen stage plane of the specimen stage. Thus, a section at an arbitrary depression angle can be easily formed in an arbitrary processing position by turning a sample. (25) In the sample fabricating apparatus in any of (21) to (24), angle information that a set-section depression angle of a set section is projected to a plane including, as a normal line, the optical axis of the ion beam is displayed on a display for displaying secondary particle information detected by the secondary particle detector and is set. With the configuration, the operator can visually make processing setting corresponding to a requested FIB irradiating angle. (26) In the sample fabricating apparatus in each of (21) and (22), in correspondence with parameters of coordinates of a requested-section edge, a requested-section normal line direction, and a size, parameters equivalent to the parameters, or a combination of those parameters, the ion beam optical system controller controls the ion beam deflector, and the specimen-stage position controller controls turn in the specimen stage plane of the specimen stage. With the configuration, processing setting corresponding to section forming parameters desired by the operator can be automated. (27) In the sample fabricating apparatus in any of (21) to (26), an input apparatus for setting a requested-section depression angle of a requested section or a parameter equivalent to the requested-section depression angle is provided. With the configuration, the operator can easily set the depression angle of the requested section. (28) A sample fabricating method for irradiating a sample with an ion beam from an oblique direction to prepare a section by sputtering, including a step of setting a depression angle of a section requested to be observed in a sample, a step of determining a scanning-area edge of an ion beam in corresponding to the depression angle and setting a scanning area, and a step of processing the scanning area with the ion beam. Only by deflecting the ion beam, a section at an arbitrary tilt angle in a certain range can be formed. (29) In the sample fabricating method of (28), by preparing a sample from a step of obtaining a turn angle of the requested section and a step of determining a turn angle of the sample in correspondence with the depression angle and the turn angle of the requested section, and setting turn in the specimen stage plane of the specimen stage, a section at an arbitrary tilt angle in a certain range in the requested section position can be formed. (30) In a sample fabricating apparatus for forming a sample section in a sample held on a specimen stage by processing with a charged particle beam by using a charged particle beam optical system for condensing, scanning and deflecting a charged particle beam emitted from a charged particle source, an angle formed between the optical axis of the charged particle beam emitted from the charged particle beam optical system and a surface of the specimen stage is fixed, and formation of a sample section is controlled by turning of the specimen stage in the specimen stage plane. (31) In a sample fabricating apparatus for forming a sample section in a sample held on a specimen stage by processing with a charged particle beam by using a charged particle beam optical system for condensing, scanning and deflecting a charged particle beam emitted from a charged particle source, an angle formed between the optical axis of the charged particle beam emitted from the charged particle beam optical system and a surface of the sample is fixed, and the scanning and deflection of the charged particle beam optical system is controlled in correspondence with an angle formed between a direction of a normal line of a section which is set for forming a sample section requested to be observed in the sample and the surface of the sample. An embodiment of a sample fabricating apparatus according to the invention includes at least: a focused ion beam irradiating optical system disposed so that a focused ion beam is emitted at an angle formed between the surface of a sample on a stage and the optical axis of a focused ion beam, larger than 0 degree and smaller than 90 degrees; secondary electron detecting means for detecting secondary electrons generated from the sample irradiated with the focused ion beam; and a specimen stage of a structure having no tilting mechanism. Concrete embodiments will be described hereinbelow. A schematic configuration of a sample fabricating apparatus as an embodiment of the invention will be describe by referring to FIG. 4. A sample fabricating apparatus 17 has a vacuum chamber 41 in which an ion beam irradiating optical system 35 constructed by an ion source 32, a beam limiting aperture 33, an ion beam scanning electrode 34, an ion beam lens 31, and the like; a secondary electron detector 36 for detecting secondary electrons and secondary ions emitted from a sample irradiated with an FIB; a deposition-gas supplying source 37 for supplying an original material gas to form a deposition film in an ion beam irradiation area; the probe 3 attached at the tip of a manipulator 42; a specimen stage 39 on which a specimen base 38 such as a semiconductor wafer or a semiconductor chip is placed; a sample holder 40 for fixing a micro sample as a part extracted from the specimen base 38, and the like are disposed. In this case, the ion beam irradiating optical system 35 is mounted relative to the stage 39 so that the angle formed by an almost center axis of an objective lens 44 and the surface of the sample becomes almost 45 degrees. The specimen stage 39 has the function of turning around a line segment perpendicular to the surface of a sample as a rotation axis. As apparatuses for controlling the apparatus, a stage controller 61 mainly including an electric circuit and an arithmetic unit, a manipulator driver 62, an amplifier 63 for the secondary electron detector, a deposition gas controller 64, an FIB controller 65, a central processing unit 74, and the like are disposed. The central processing unit 74 has the function of recognizing the shape of a sample by performing an image process on a secondary electron image formed by secondary electrons generated from the sample irradiated with the FIB. The central processing unit 74 also has the function of irradiating a desired position in the sample shape with the FIB 1 by the FIB controller 65 on the basis of sample shape information. An operation of the sample fabricating apparatus will now be described. First, ions released from the ion source 32 are emitted to the specimen base 38 via the beam limiting aperture 33, ion beam lens 31, and objective lens 44. The FIB 1 is narrowed so that its diameter becomes a few nm to about 1 micrometer on the sample. When the specimen base 38 is irradiated with the FIB 1, atoms constructing the surface of the sample are released to the vacuum by a sputtering phenomenon. By making a scan with the FIB 1 by using the ion beam scanning electrode 34, processing at a micrometer level to a sub-micrometer level can be performed. By irradiating the specimen base 38 with the FIB 1 while introducing a deposition gas into the specimen chamber, a deposition film can be formed. In such a manner, the specimen base 38 can be processed by skillfully using the sputtering or deposition with the FIB 1. The deposition film formed by the irradiation with the FIB 1 is used to connect the contact portion at the tip of the probe 3 and the sample or to fix the extracted sample to a sample holder 40. A scan with the FIB 1 is performed, secondary electrons and secondary ions emitted from the sample are detected by the secondary electron detector 36, and the intensities of the detected secondary electrons and secondary ions are converted to the luminance of an image, thereby enabling the specimen base 38, the probe 3, and the like to be observed. A sample fabricating method as an embodiment of the invention will now be described by referring to FIGS. 1(a) to 1(f). To understand FIGS. 1(a) to 1(f), as a supplement, refer to FIG. 8A showing a rectangular hole 501 fabricated when the FIB irradiation axis is normal to the surface of a sample and FIG. 8B showing a rectangular hole 502 fabricated when the FIB irradiation axis is at 45 degrees from the surface of a sample. A sample is prepared as follows. First, a mark indicative of the fabrication position of a membrane for TEM observation and a protection film are formed on the base. Subsequently, a rectangle whose one side is in the direction of projection of the optical axis of an FIB to the base surface onto the surface of the sample is scanned with the FIB 1 on the specimen base to thereby form two rectangular holes 101 (FIG. 1(a)) having a depth of about 15 .mu.m and tapered in the depth direction and a trench 102 similarly tapered in the depth direction (FIG. 1(b)). The FIB optical axis is tilted by 45 degrees from the surface of the sample. Subsequently, by using the axis perpendicular to the surface of the sample as a rotation axis, the sample is turned by about 180 degrees. By performing an image process on a secondary electron image formed by secondary electrons generated from the sample irradiated with the FIB 1, the two rectangular holes and the trench formed so far are recognized. The FIB irradiation position is controlled by the FIB controller 65 on the basis of the sample shape information, and a trench 103 similarly tapered in the depth direction is formed (FIG. 1(c)). Subsequently, by driving the probe controller, the tip of the probe 3 is made come into contact with the micro sample 6 on the base. After that, a deposition gas is supplied from the gas nozzle, an area including the tip portion of the probe 3 is locally irradiated with the FIB 1, and a deposition film 105 is formed to connect the portion separated from the base and the probe 3 which are in contact (FIG. 1(d)). By cutting a residual area 104 with the FIB 1, the micro sample 6 enters a state supported by the probe 3 connected (FIG. 1(e)). By moving the probe 3 upward, the micro sample 6 can be extracted (FIG. 1(f)). The following processes are similar to those in the conventional technique. Specifically, the specimen stage is operated while the probe is stopped above the specimen surface, thereby moving the micro sample onto a sample mesh. The micro sample is fixed to the sample mesh by using a deposition film. The probe is cut with the FIB so as to be separated from the micro sample. Finally, the observation area in the micro sample is thinned to a thickness of about 100 nm with the FIB, thereby completing the TEM sample. In the method, to form the trench tapered in the depth direction in FIG. 1(c), the sample is turned by about 180 degrees. Alternately, the trench may be also formed by turning the sample by about 90 degrees by using the axis perpendicular to the surface of the sample as a rotation axis. The shape of the micro sample in this case is as shown in FIG. 5(a). The shape of the micro sample formed by turning the sample by about 180 degrees is as shown in FIG. 5(b). The order of formation of the two rectangular holes (FIG. 1(a)), the trench (FIG. 1(b)) similarly tapered in the depth direction, and the trench (FIG. 1(c)) formed by turning the sample by about 180 degrees or 90 degrees is not limited. In the embodiment, by performing image processing on a secondary electron image formed by secondary electrons generated from the sample irradiated with the FIB, the two rectangular holes and the trenches formed so far are recognized and the FIB irradiation position is controlled by the FIB controller on the basis of the sample shape information. The operation can be therefore automated and the burden on the operator can be lessened. However, it is not always necessary to use an image processor. The operator of the apparatus can control the FIB irradiation position by observing a secondary electron image on an image display. In the case of forming a plurality of micro samples, each of the samples can be fabricated in accordance with the order. First, two rectangular holes 101 (FIG. 1(a)) having a depth of about 15 .mu.m and tapered in the depth direction and the trench 102 (FIG. 1(b)) similarly tapered in the depth direction are formed in necessary positions in each of a plurality necessary number of samples. By using an axis perpendicular to the surface of the sample as a rotation axis, the sample is turned by about 180 degrees. Subsequently to the positioning of the samples, the trench 103 tapered in the depth direction is formed in each of the samples (FIG. 1(c)). The probe controller is driven to fabricate a plurality of micro samples 6 as TEM samples in accordance with the order by using the probe 3. In such a manner, the turning operation requiring relatively long time can be reduced. Thus, a plurality of samples can be fabricated with throughput higher than that in the case of fabricating each of the samples in accordance with the order. In the foregoing embodiment, in the series of processes of separating the micro sample from the specimen base, the angle formed between the FIB and the sample surface is 45 degrees and unchanged. That is, the process of tilting the stage is not included. According to the embodiment, therefore, even when the function of tilting the specimen stage is omitted to reduce the size of the whole apparatus, preparation of a sample for analyzing, observing, or measuring a micro area by separating a micro sample from a sample or preparing the micro sample to be separated can be realized. Also in the case of the apparatus in which the specimen stage has the tilting function different from the embodiment, the invention is valid. The time required to tilt the stage is unnecessary, so that the sample preparation time becomes relatively shorter. A problem such that the surface of the sample cannot be observed before and after the specimen stage is tilted is reduced. In the embodiment, a micro sample is extracted from the specimen base at the time of forming a membrane for the TEM sample, so that the section of the micro sample can be observed in detail, and the section processing position can be controlled with high precision. According to the embodiment, the sample fabricating apparatus for preparing a sample for analyzing, observing, or measuring a micro area by separating a micro sample from a sample or preparing the micro sample to be separated, which is suitable from the viewpoints that operations of the apparatus can be automated and the burden on the operator can be lessened is provided. In the embodiment, the specimen stage is constructed by combining a stage which turns at a predetermined fixed angle and a stage which can be turned at an arbitrary angle. The stage which is turned at the fixed angle is turned by 180 degrees or 90 degrees as described above. The stage which is turned at an arbitrary angle is operated by adjusting a processing position on a sample or the like. Generally, the precision for determining the turn angle of the stage which turns at an arbitrary angle is at most 0.01 degree. As in the embodiment, in the case where fine positioning is necessary after the turn, precision is insufficient. However, in the stage having the function of only the turning at a specified fixed angle, the turn precision can be further increased. Therefore, the operation for turning the stage by a fixed angle to adjust the process position after the turn of 180 degrees or 90 degrees in the embodiment is suitable to shorten the time required for the positioning and to increase the throughput of preparing the sample. In the embodiment, the FIB optical axis is set to 45 degrees from the surface of a sample. In the case of observing both the surface of a sample and a sample section by the irradiation with an FIB, the FIB irradiation angle is 45 degrees in both cases, and both of them can be observed under similar conditions. Thus, 45 degrees is suitable for separating a sample or preparing a sample to be separated. However, the angle is not limited to 45 degrees. At an angle smaller than 90 degrees, an affect of the invention can be obtained. When the FIB optical axis is tilted from the surface of a sample by an angle less than 30 degrees, a process area for separating a micro sample is enlarged and the sample surface is wasted. When the angle becomes 75 degrees or more, the angle from the surface of an actually processed wall face becomes nearly 90 degrees and the process depth for separating the micro sample increases. There are cases such that the process time becomes longer and, further, the micro sample cannot be separated. In order to separate a micro sample, therefore, the angle formed between the sample irradiation axis of a beam and the surface of the sample is preferably in a range from 30 degrees to 75 degrees. Although the designing of the apparatus is simplified by setting the angle formed between an almost mechanical center axis of the objective lens in the focused ion beam irradiating system and the surface of the specimen base to 45 degrees so that the angle formed between the FIB optical axis and the surface of the sample becomes 45 degrees, even when the angle other than 45 degrees is set, the FIB optical axis can be tilted by 45 degrees from the sample surface by tilting the ion beam. In the embodiment, a semiconductor wafer having a flat shape is used as an example of the sample. The invention is valid for, not necessarily a flat sample, but a sample of an arbitrary shape. In the above, the angle formed between the surface of a sample and the ion beam sample irradiation axis has been described. In the case of a sample of an arbitrary shape, it is sufficient to fix an angle with a face on which a sample is to be placed of the specimen stage to prepare a sample. For example, the invention can be also applied to what is called micro machining for separating a micro part from a sample in accordance with the invention and connecting the separated micro part with another micro part to thereby fabricate a fine mechanical structure, a fine device, or the like. The sample fabricating apparatus suitable for carrying out the example has a structure in which an angle formed between an almost center axis of a mechanical column including a focused ion beam irradiating optical system and the face on which a sample is placed of the specimen stage is fixed and is characterized by including means for separating a requested portion in a sample and a probe for supporting the separated sample. In a semiconductor wafer having a flat shape as a sample, the sample placement face and the surface of a sample are parallel to each other. Obviously, the angle formed between the sample irradiation axis of the focused ion beam and the sample surface and the angle formed between the sample irradiation axis of the focused ion beam and the sample placement face of the specimen stage are the same. In the embodiment, the sample is scanned with a focused ion beam. At this time, the angle of a focused ion beam incident on the sample slightly varies depending on the scan position, but the change in the incident angle of an ion beam in association with such scanning is not included in a change in the angle between the sample irradiation axis of the focused ion beam and the surface of the sample. That is, when the sample is scanned with the focused ion beam, it is assumed that the angle formed between the sample irradiation axis of the focused ion beam and the surface of the sample can be fixed. The sample irradiation axis of the focused ion beam denotes a center line of an ion beam incident on the surface of a sample when the scanning is stopped and there is no deflection by a scan electrode. Another sample fabricating method as an embodiment of the invention will now be described by referring to FIGS. 6(a) to 6(d) A sample fabricating apparatus similar to the apparatus shown in FIG. 4 is used. First, a mark indicative of the fabrication position of a membrane for TEM observation and a protection film are formed on a specimen base. A rectangle whose one side is in the direction of projection of the irradiation axis of an FIB to the base surface onto the surface of the sample is scanned with the FIB 1 on the specimen base to form two rectangular holes 301 (FIG. 6(a)) having a depth of about 15 .mu.m and tapered in the depth direction. In this case, a membrane between the two rectangular holes 301 is a sample as a target and the thickness of the membrane is about 100 nm. Subsequently, membrane both ends 302 are cut. By using the axis perpendicular to the surface of the sample as a rotation axis, the sample is turned by about 90 degrees. By performing an image process on a secondary electron image formed by secondary electrons generated from the sample irradiated with the FIB 1, the two rectangular holes 301 formed so far are recognized. The FIB irradiation position is controlled by the FIB controller 65 on the basis of the sample shape information, the bottom of a sample membrane 303 is cut with the FIB 1 as shown in FIG. 6(c) to thereby separate the sample membrane 303 from the specimen base. Alternately, the sample membrane 303 is not separated and the process is finished while leaving a residual area which can be broken by a little impact as a preparation for separation in a post process. After that, the specimen base is taken out from the sample fabricating apparatus and, by using static electricity of a glass stick 304 in atmosphere, the sample membrane 303 is moved from the specimen base onto a TEM sample holder. When the sample membrane 303 as a micro sample is not completely separated, an impact is given to the micro sample residual area by the glass stick 304, the sample membrane 303 is separated from the specimen base. After that, by similarly using the static electricity of the glass stick 304, the sample membrane 303 is moved from the specimen base onto the TEM sample holder. The method and apparatus for specimen fabrication for processing most of the outer shape of a micro sample with an ion beam without taking out the sample membrane 303 as a micro sample in the apparatus are also included in the invention. Although at least one of both sides of the sample membrane is cut in FIG. 6(b) before the sample is turned by about 90 degrees in the method, it may be cut after the turn. The order of fabrication of the two rectangular holes, cutting of both sides of the sample membrane, cutting of the bottom of the sample membrane, and the like is not limited. Although image processing is used in the embodiment, in a manner similar to the first embodiment, the operator of the apparatus may observe a secondary electron image and control an FIB irradiation position. In the foregoing embodiment, in the series of processes of separating a sample from a specimen base or preparing the sample to be separated, the angle formed between the FIB and the surface of a sample is 45 degrees and is unchanged. That is, the process of tilting the stage is not included. According to the embodiment, therefore, even if the function of tilting the specimen stage is eliminated to reduce the size of the whole apparatus, preparation of a sample for analyzing, observing, or measuring a micro area by separating a micro sample from the sample or preparing the micro sample to be separated can be realized. Also in the case of an apparatus in which the specimen stage has the tilting function in a manner different from the embodiment, the time required to tilt the stage is unnecessary and the sample fabrication time is made relatively short. A problem such that the surface of a sample cannot be observed before and after the specimen stage is tilted is also reduced. In the embodiment, a micro sample exists in the specimen base at the time of preparing a membrane for the TEM sample, so that the precision of the section processing position is relatively lower as compared with the first embodiment. However, the processes of operating the probe, forming an ion beam assist deposition film for adhering a probe and a micro sample, and the like are not included, so that the sample preparation time can be shortened. In a manner similar to the first embodiment, the FIB irradiation angle is not always limited to 45 degrees. When the angle is smaller than 90 degrees, the effects of the invention can be obtained. FIG. 7 is a schematic configuration diagram of a sample fabricating apparatus having an electron beam irradiating apparatus as an embodiment of the invention. A sample fabricating apparatus 17 has a vacuum chamber 41 in which an ion beam irradiating optical system 35, a secondary electron detector 36, a deposition-gas supplying source 37, a probe 3, a specimen stage 39, and the like are disposed in a manner similar to the sample fabricating apparatus of the second embodiment. Similarly, the ion beam irradiating optical system 35 is mounted relative to the stage 39 so that the angle formed between the FIB optical axis and the surface of the sample becomes 45 degrees. The specimen stage has the function of turning around a line segment perpendicular to the surface of a sample as a rotation axis. In the apparatus, an electron beam irradiating system constructed by a field emission electron gun 81 for emitting an electron beam, an electron beam lens 82, an electron scanning electrode 83, and the like is mounted. As apparatuses for controlling the apparatus, not only a stage controller 61, a manipulator driver 62, an amplifier 63 for the secondary electron detector, a deposition gas controller 64, and an FIB controller 65 but also an electron gun controller 91, an electron beam irradiating optical system controller 92, an electron beam scanning controller 93, a central processing unit 74, and the like are disposed. The central processing unit 74 has the function of recognizing the shape of a sample by performing an image process on a secondary electron image formed by secondary electrons generated from the sample irradiated with the FIB or an electron beam 84. The central processing unit 74 also has the function of irradiating a desired position of the sample shape with the FIB 1 by the FIB controller 65 on the basis of sample shape information and the function of irradiating a desired position of the sample shape with the electron beam 84 by the electron gun controller 91. The operation of the ion beam irradiating optical system 35 is similar to that of the second embodiment. An operation of emitting an electron beam will now be described. An electron source of the electron beam irradiating apparatus is a field emission electron gun 81 and an arbitrary position in the specimen base 38 can be aimed by an electron scanning electrode 83. A process area 42 irradiated with an FIB can be also scanned and irradiated with the electron beam 84. For the operation, preparation is made as follows. First, the FIB 1 is condensed to a spot and emitted to a sample. The irradiation trace in the spot shape is scanned with the electron beam 84, secondary electrons are detected, and the spot-shaped irradiation trace is observed, thereby clarifying the relation between the irradiation position of the FIB 1 and the electron beam irradiation position. The relation is stored in the central processing unit 74. Therefore, on the basis of the stored information, the process position of the FIB 1 can be automatically irradiated with an electron beam, and the process status can be observed. All the above-described controls are performed by the central processing unit 74. The sample fabricating method is similar to each of the methods described in the first and second embodiments. In the first and second embodiments, the image process on a secondary electron image formed by secondary electrons generated from a sample irradiated with an FIB is used for controlling the irradiation position of the FIB. However, in the apparatus of the third embodiment, a secondary electron image formed by secondary electrons generated from a sample irradiated with an electron beam can be used. When the sample irradiated with an electron beam is observed, as compared with preparation of a sample only with irradiation of the FIB, the number of damages in the surface of a sample is much smaller, and the sample preparation in shorter time can be realized. According to the third embodiment, in a manner similar to the first and second embodiments, obviously, the sample fabricating apparatus for fabricating a sample for analyzing, observing, or measuring a micro area by separating a micro sample from a sample or preparing the micro sample to be separated, which is suitable from the viewpoint that the operation of the apparatus can be automated and the burden on the operator can be lessened is provided. A schematic configuration diagram of a sample fabricating apparatus as an embodiment of the invention will be described by referring to FIGS. 10(a) and 10(b). In the fourth embodiment, a focused ion beam tilting function capable of changing a focused ion beam incident direction by at least 15 degrees is realized by a mechanism of varying a tilt angle with respect to a specimen stage of a mechanical column including the focused ion beam irradiating system. A sample fabricating apparatus 17 has a vacuum chamber 41 in which an ion beam irradiating optical system 35 constructed by an ion source 32, a beam limiting aperture 33, an ion beam scanning electrode 34, an ion beam lens 31, and the like; a secondary electron detector 36 for detecting secondary electrons and secondary ions emitted from a sample irradiated with the FIB; a deposition-gas supplying source 37 for supplying an original material gas to form a deposition film in an ion beam irradiation area; a probe 3 attached at the tip of a manipulator 42; a specimen stage 39 on which a specimen base 38 such as a semiconductor wafer or a semiconductor chip is placed; a sample holder 40 for fixing a micro sample as a part extracted from the specimen base 38, and the like are disposed. The ion beam irradiating optical system 35 is constructed so as to set the angle of the FIB irradiation axis tilted from the specimen base surface in a range from 75 degrees to 90 degrees. In the embodiment, the ion beam irradiating optical system 35 and the vacuum chamber 41 are connected to each other via a bellows 45, and deformation of the bellows is used. FIG. 10(a) shows a state where the angle of the FIB irradiation axis from the surface of the specimen base is 90 degrees, and FIG. 10(b) shows a state where the angle is 75 degrees. As apparatuses for controlling the apparatus, a stage controller 61 mainly including an electric circuit and an arithmetic unit, a manipulator driver 62, an amplifier 63 for the secondary electron detector, a deposition gas controller 64, an FIB controller 65, a central processing unit 74, and the like are disposed. FIGS. 12(a) to 12(d) show a sample fabricating method according to the fourth embodiment. Conventionally, the tapered trench 408 is formed by tilting the specimen stage and obliquely irradiating the surface of a sample with the FIB 1. In place of tilting the specimen stage, it is sufficient to tilt the ion beam irradiating optical system 35 as shown in FIG. 10(b) and form the tapered trench 408 as shown in FIG. 12(c). The other processes are similar to those in the conventional technique. According to the embodiment, the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a semiconductor device, or the like and preparing the micro sample to be separated without tilting the specimen stage is realized by a focused ion beam tilting function capable of changing a focused ion beam incident direction by at least 15 degrees. In particular, according to the embodiment, since the focused ion beam incident angle can be selected in preparation of a sample, various sample fabricating methods and sample shapes can be realized. A schematic configuration of a sample fabricating apparatus as an embodiment of the invention will now be described by referring to FIG. 11. In the fifth embodiment, a focused ion beam deflecting function capable of changing a focused ion beam incident direction at least by 15 degrees is realized by electric deflection. A sample fabricating apparatus 17 has a vacuum chamber 41 in which an ion beam irradiating optical system 35, a secondary electron detector 36, a deposition-gas supplying source 37, a probe 3, a specimen stage 39, a sample holder 40, and the like are disposed in a manner similar to the third embodiment. In this case, a deflector 51 for changing angle is further disposed between the objective lens 44 and the specimen stage 39. By an ion beam deflecting action of the deflector 51, the angle of the FIB optical axis with respect to the specimen base surface can be set so as to be changed in a range from 75 degrees to 90 degrees. As apparatuses for controlling the apparatus, a stage controller 61 mainly including an electric circuit and an arithmetic unit, a manipulator driver 62, an amplifier 63 for the secondary electron detector, a deposition gas controller 64, an FIB controller 65, a central processing unit 74, and the like are disposed. The sample fabricating method according to the fifth embodiment is shown in FIGS. 12(a) to 12(d). Conventionally, the tapered trench 408 is formed by tilting the specimen stage to obliquely irradiate the surface of a sample with the FIB 1. In place of tilting the specimen stage, it is sufficient to tilt the ion beam irradiation axis relative to the sample as shown in FIG. 11 by the deflector 51 for changing angle and form the tapered trench 408 as shown in FIG. 12(c). The other processes are similar to those in the conventional technique. According to the fifth embodiment, the sample fabricating apparatus capable of fabricating a sample for analyzing, observing, or measuring a micro area by separating a micro sample including a requested specific area from a sample of an electronic part such as a semiconductor wafer, a device, or the like or preparing the micro sample to be separated is realized by an electric deflecting action of the deflector for changing angle capable of changing a focused ion beam incident direction by at least 15 degrees. In particular, the mechanical apparatus configuration is simplified, the apparatus manufacturing cost can be reduced and, further, the focused ion beam incident angle can be selected in preparation of a sample. Thus, various sample fabricating methods and sample shapes can be realized. FIG. 13 is a configuration block diagram showing an embodiment of a sample fabricating apparatus according to the invention. The sample fabricating apparatus has: a specimen stand 1002 which is movable but is not tilted on which a sample 1 such as a semiconductor wafer or a semiconductor chip is placed; a specimen-stage position controller 1003 for controlling the position of the specimen stand 1002 to specify the position of observing and processing the sample 1001; an ion-beam irradiating optical system 1005 for irradiating a peripheral portion of the observation position of the sample 1001 with an ion beam 1004 to form a hole for observation; an electron-beam irradiating optical system 1007 for emitting an electron beam 1006 for observing the peripheral portion of the sample 1001; and a secondary-electron detector 1008 for detecting secondary particles (for example, secondary electrons) from the sample 1001. The configuration of the ion-beam irradiating optical system 1005 is as follows. An acceleration voltage with respect to the ground potential is applied to an ion source 1009 for generating ions by a power source 1010 for acceleration voltage. When emission of ions of the ion source 1009 is unstable, Joule's heating is performed by a power source 1011 for Joule's heating to improve the state of the ion source 1009. In an extractor 1012 for generating an ion extracting electric field, an extraction voltage is applied from an extractor power source 1013 to the ion source 1009. Flare of the extracted ion beam is limited by an aperture 1014. The aperture 1014 has the same potential as that of the extractor 1012. An ion beam passed through the aperture 1014 is condensed by a condenser lens 1016 to which a condensing voltage is applied by a condenser-lens power source 1015. The condensed ion beam scans while being deflected by a deflector 1018 to which a deflector power source 1017 is applied. The deflector power source 1017 is constructed by power sources 1019 and 1020 for deflection in the X direction and power sources 1021 and 1022 for deflection in the Y direction. Potentials Vx/2 and Vx/2 of the same absolute value and opposite polarities are applied to counter electrodes in the X direction in the power sources 1019 and 1020. Potentials Vy/2 and Vy/2 are similarly set in the Y direction for the power sources 1021 and 1022. The deflected ion beam is condensed onto the surface of the sample 1001 by an objective lens 1024 to which an objective voltage is applied from an objective-lens power source 1023. The power source 1010 for acceleration voltage, extractor 1013, condenser-lens power source 1015, deflector power source 1017, and objective-lens power source 1023 are controlled by a controller 1025 for ion-beam irradiating optical system. The optical axis of the ion beam of the ion-beam irradiating optical system 1005 is tilted relative to the surface of the sample 1. The electron-beam irradiating optical system 1007 is constructed by an electron source 1026 for generating electrons, a deflector 1027 for deflecting and scanning an electron beam, and the like. The controller 1025 for ion-beam irradiating optical system, specimen-stage position controller 1003, a controller 1028 for electron-beam irradiating optical system for controlling the electron-beam irradiating optical system 1007, a monitor 1029 for displaying information detected by the secondary-electron detector 1008, and the like are controlled by a central processing unit 1030. The specimen stage 1002, ion-beam irradiating optical system 1005, electron-beam irradiating optical system 1007, secondary-electron detector 1008, and the like are disposed in a vacuum chamber 1031. FIG. 14 shows an example of processing a sample in the ion-beam irradiating optical system tilted for observing a section. In the configuration, an ion-beam irradiating optical axis 1035 is tilted from an axis 1040 perpendicular to the surface of the sample 1001. A tilt angle 1041 is set to an angle θ larger than 0° and smaller than 90°. 1036 denotes an optical-axis projected line which is the ion-beam irradiating optical axis 1035 projected on the surface of the sample. A processed hole 1039 is formed here to observe a formed section 1038. It is now assumed that a requested-section edge 1037 as a cross line of the formed section 1038 and the sample surface is parallel to the optical-axis projected line 1036 as shown in FIG. 14. At this time, the ion beam process setting is made by, as shown in FIG. 15, setting an ion-beam scan area 1046 on a secondary electron image 1045 in the monitor 1029. In this case, the requested-section edge 1037 is parallel to the optical-axis projected line 1036 (imaginary line which does not exist on the secondary electron image). FIG. 16 shows a sample processed section in this case. In this case, the ion beam 1004 is emitted in parallel with a requested section 1052 to form the processed hole 1039. If ideal processing is realized, the formed section coincides with the requested section 1052. However, in reality, there are an influence of the ion beam flare, re-deposition, and the like, a section 1052 having a process taper angle at is formed. Consequently, a positional deviation occurs with the distance in the depth direction, and there is the possibility that the accurate section cannot be observed, so that the following improvement is necessary. As shown in FIG. 17, when an ion beam 1055 is emitted while being tilted only by a tilt angle corresponding to the taper angle to form a processed hole 1054, a section 1056 is formed accurately in the position of the requested section 1052. In other words, it is sufficient to adjust the set section depression angle αd of a set section 1058 so as to coincide with the tilt angle αt corresponding to the taper angle in FIG. 16. In order to realize the tilting by the not-tilting specimen stage, process setting shown in FIGS. 18(a) and 18(b) is made. In FIG. 18(a), setting is made so that a deflection scan area end 1061 (which is a set-section edge) of an ion-beam scan area 1062 forms a rotation angle 1063 for fabrication (in this case, expressed as Φd) with respect to the optical-axis projected line 1036. As shown in FIG. 18(b), it is also possible to turn the whole secondary electron image 1045 by Φd and display the turned image. In this case, the imaginary optical-axis projected line 1036 is turned by Φd. An ion-beam scan area 1066 and a deflection scan area end (which is a set-section edge) 1065 are seen to be perpendicular on the secondary electron image 1045 in a manner similar to FIG. 15. Consequently, it is easier for the operator to make the fabrication setting. Φd is calculated by the controller 1025 for ion-beam irradiating operation system by Formula 1 to thereby automatically set the scan of the deflector 1018.1d=arctan(tan d(sin)2−(tan d.times. cos)2) Formula 1 Since the ion beam optical axis tilt angle θ is determined in the apparatus, the rotation angle φd of fabrication setting with respect to the set section depression angle ad is unconditionally determined. In this case, −θ.ltoreq.αd.ltoreq.+θ is satisfied. FIG. 19 shows the process at this time. A set-section edge 1071 of a processed hole 1072 is deviated from the optical-axis projected line 1036 by an angle 1074 (expressed as a rotation angle βd of set-section edge). βd is expressed by Formula 2.2d=arcsin(tan d tan) Formula 2 The relation between βd and Φd is simply expressed as Formula 3.βd=arctan(cos θ.times. tan Φd) Formula 3 That is, as shown in FIG. 20(a), in FIG. 15 showing the secondary electron image in the case where the process rotation angle Φd is 0°, when the state where a direction 1081 of the section processed structure is parallel to the optical-axis projected line 1036 is a turn reference (0° in this case) of the specimen stage 3, as shown in FIG. 20B, when the specimen stage is turned by βd, the set-section edge 1071 coincides with the direction 1081 of section processed structure, and a requested observation section can be prepared. As described above, since the process rotation angle Φd is determined by the set-section depression angle αd, the specimen stage rotation angle βr determined from the rotation angle βd of the set-section edge is also unconditionally determined with respect to the set-section depression angle ad. Consequently, by calculating Formula 2 by a sample position controller 1018, turning of the specimen stage in the direction of the structure from which a section is extracted can be automatically controlled. The flow of the above setting operations is expressed by a flow chart shown in FIG. 21. First, the depression angle αd of the set section is input by the user (1091). For example, as shown in FIG. 22A, by inputting the depression angle αd of the set section to a set area 1101 for set-section depression-angle on a monitor 1029, it is transmitted to a controller 1025 for ion-beam irradiating optical system via the central processing unit 1030. Subsequently, the user sets a requested-section edge (1093). For example, as shown in FIG. 22(a), the requested-section edge is set by designating a start point (Xs, Ys) 1103 and an end point (Xe, Ye) 1104 of the requested-section edge 1102 on the secondary electron image 45. The target position can be also set from CAD (Computer-Aided Design) data of device designing. In this case, a lower layer wiring position which is not in the top surface of a sample can be also set. In the CAD data, in the step of setting the requested-section edge (1093), the start point (Xs, Ys) 1103 and the end point (Xe, Ye) 1104 of the required-section edge 1102 can be also numerically set as coordinate information. The arrow 1105 in FIG. 22(a) expresses the requested-section edge normal direction. In the direction of the arrow, an ion beam processed hole is formed. On the basis of the above information, first, an ion beam scan range is determined. A case of tilting the ion beam scan itself for capturing a secondary electron image as described by referring to FIG. 18(b) will be described. First, the rotation angle Φd for fabrication is calculated by Formula 1 (1092). By scanning an ion beam while being deflected by the rotation angle Φd for fabrication, deflection coordinates (Xi, Yj) before the scanning the ion beam are converted to (Xij, Yij) expressed by Formulae 4 and 5.Xij=Xi cos Φd+Yj sin Φd Formula 4Yij=−Xi sin Φd+Yj cos Φd Formula 5 (i=1 to n, j=1 to m) for defining the ion beam scan area are determined from the requested-section edge (Xs, Ys) and (Xe, Ye) and a requested-section depth Zd (1095). For example, as shown in FIG. 22A, the requested-section depth Zd set in 1094 is input to a set area 1106 for the requested-section depth on the monitor 1029 and is thereby transmitted via the central processing unit 1030 to the controller 1025 for ion-beam irradiating optical system. (i=1 ton, j=1 to m) are determined from the length of the processed hole determined from the length of the requested-section edge and the width of the processed hole determined from the section observation angle and the requested-section depth Zd. Deflector voltages corresponding to (Xij, Yij) are calculated by Formulae 6 and 7 (1096).Vxij=kx.times.Xij Formula 6Vyij=ky.times.Yij Formula 7 where kx and ky are coefficients of deflection in the X and Y directions, respectively, and are determined in the apparatus on the basis of the power source 1010 for acceleration voltage, the length of the deflector 1018, distance between the counter electrodes, distance between the deflector 1018 and the sample 1001, and the like. The voltage (Vxij, Vyij) is applied from the deflector power source 1017 to control the voltage of the deflector 1018. At this time, as shown by 1065 in FIG. 18(b), the set-section edge becomes perpendicular on the secondary electron image 1036. The specimen stage rotation angle βr necessary to make the requested-section edge 1102 coincide with the set-section edge 1065 by the turning of the specimen stage 1002 is calculated by the specimen-stage position controller 1003 by Formula 8, and the specimen stage 2 is turned.βr=arctan(cos θ×Φd)−arctan(cos θ×Xs−Xe over Ys−Ye) Formula 8 At this time, on the secondary electron image 1045, as shown in FIG. 22(b), an ion-beam scanning area 1108 is set as an area surrounded by (X11, Y11) 1109, (X1m, Y1m) 1110, (Xn1, Yn1) 1111, and (Xnm, Ynm) 1112 with respect to a requested-section edge 1107. By scanning the area with an ion beam so as to be processed, a requested section is formed. If there is a process error due to flare of the ion beam and it is a problem, the deflection scan area end formed by a line segment connecting the (X11, Y11) 1109 and (X1m, Y1m) 1110 is moved to the right direction only by an amount of the error from the requested section 1107 in FIG. 22(b) and is set. In such a manner, the formed section becomes the requested section 1107. An actual process example in the case where the ion beam optical axis tilt angle θ is 45° will now be described. Table 1 shows set values (in degrees, calculated to one digit to the right of the decimal) of the process rotation angle Φd and the rotation angle βd of the set-section edge with respect to the depression angle αd of the set section ranging from −45° to +45° by calculating Formulae 1 and 2. 1TABLE 1 Rotation angle Set-section Process of the depression angle rotation angle set-section edge αd (degree) Φd (degree) βd (degree) −45 −90 −90 −40 −65.4 −57.0 −30 −45 −35.3 −20 −28.9 −21.3 −10 −14.2 −10.2 0 0 0 10 14.2 10.2 20 28.9 21.3 30 45 35.3 40 65.4 57.0 45 90 90 FIG. 26 shows the relation between the depression angle of the actually formed section and the depression angle ad of the set section when the process is performed under those conditions. If the process is ideally performed, an experimental value 1141 is supposed to coincide with an ideal line 1142, but they do not coincide with each other in reality. The deviation is caused by a taper formed in the process. In order to form an accurate requested section, therefore, the following flow for automatically correcting the taper angle at is necessary. The taper angle αt depends on not only ion beam energy, a sample material, and the like, but also the optical axis tilt angle θ of the ion beam and the requested-section depression angle αe. Consequently, when the taper angle is expressed as αt (αe, θ), by using the set-section depression angle ad expressed by the following Formula 9 to deflect Φd of Formula 1 and controlling βr in Formula 8 by turning the specimen stage, the formed section and the requested section can be made coincide with each other.αd=αe+αi(αe,θ) Formula 9 That is, by employing a table using αe and θ in the taper angle αt (αe, θ) as parameters, the section can be automatically formed in the requested section position. When θ is 45°, the table is as shown in Table 2. 2 TABLE 2 Requested-section depression Taper angle αe (degree) αt (degree) −45 3.4 −40 3.8 −30 4.6 −20 5.4 −10 6.2 0 7.0 10 7.7 20 8.5 30 9.3 40 10.1 45 10.5 As described above, with the configuration of the invention, by automatically controlling the rotation angle Φd of process setting and the rotation angle βr of the specimen stage, the tilt irradiation angle αd of an ion beam can be arbitrarily selected, and taper eliminating process or the like is also facilitated. In a seventh embodiment, an example where a shape to be actually processed for forming a section is a rectangle will be described. Since the ion beam scanning area described in the sixth embodiment has a rectangular shape as shown in FIG. 18(a), the shape actually processed on the sample surface is a parallelogram as shown by 1151 in FIG. 27(a). Reference numerals 1153, 1154, and 1155 are metal lines of a device and an object is to process the positions of the metal lines 1153 and 1154. A formed-section edge 1152 is processed so as to cross perpendicular to the metal lines 1153 and 1154. In this case, a processed edge 1156 other than the formed section edges is formed obliquely with respect to the formed-section edge 1152 and there is a case such that the metal line 1155 which is inherently unnecessary to be processed is also processed. Consequently, in some cases, a process as shown in FIG. 27(b) is desired. Specifically, the processed shape on the sample surface is set to a rectangle as shown by 1157, and a processed edge 1159 other than a formed-section edge 1158 is made parallel to the metal line 1153 and the like, thereby enabling only the target metal lines 1153 and 1154 to be processed. In order to realize the process, it is sufficient to make process setting shown in FIG. 28. FIG. 28 corresponds to FIG. 18(b) and shows that the whole secondary electron image 1161 is turned by Φd. In this case, although a scanning-area edge 1163 is set in a manner similar to the set-section edge 1065 in FIG. 18(b), a scanning area 1162 is set in a parallelogram different from the rectangular-shaped scanning area 1066. An interior angle γ (shown in degrees) of the parallelogram indicated by 1164 is expressed by Formula 10.γ=90−Φd+arctan {(cos θ)2×tan Φd} Formula 10 As described above, by performing a process by setting the scanning area 1162 in the parallelogram shape, the rectangular process of FIG. 27(b) can be realized, so that an arbitrary tilt process can be realized without processing an unnecessary area. In an eighth embodiment, an example of applying the sample fabricating apparatus according to the invention to a membrane sample for TEM observation, energy dispersive X-ray spectrometry (EDX), or electron energy loss spectroscopy (EELS) will be described. The membrane for TEM observation is requested to be thin in order to improve observation resolution and is usually processed to a thickness of about 100 nm. However, in the case of irradiating an observation section with an ion beam in parallel as described in the sixth embodiment, when the TEM membrane is processed, tapered membrane sections 1115 and 1116 as shown in FIG. 23 are formed. Consequently, a sample has a thickness distribution in the depth direction with respect to a requested observation section 1117. In this case, an extra structure is also included in a deep area, so that the observation accuracy deteriorates. Further, in the case of using the EDX or EELS for analyzing a composition element, quantitativeness of the signal amount of an X-ray and an electron beam is important. In the case of a sample of which film thickness varies as shown in FIG. 23, the quantitative analysis of compositions cannot be carried out. In order to solve the problem, as described in the sixth embodiment, the rotation angle Φd of processing setting of an ion beam is controlled by the controller 1025 for ion-beam irradiating optical system, and the requested observation section 1117 is obliquely irradiated with an ion beam 1121, thereby enabling a membrane section 1122 to be formed in parallel with the requested observation section 1117, as shown in FIG. 24(a). Similarly, by setting the rotation angle βd of process setting of the ion beam in the opposite direction, a tilted ion beam 1124 shown in FIG. 24(b) can be emitted, so that a membrane section 1125 can be formed. Thus, an observation membrane having high uniformity in film thickness can be formed. As described above, with the configuration of the embodiment, by automatically controlling the rotation angle Φd of process setting and the rotation angle βr of the specimen stage, the tilt irradiation angle αd of an ion beam can be arbitrarily selected, and a membrane having high thickness uniformity can be formed. Thus, the embodiment is effective at improving the observation accuracy of the TEM observation and making quantitative analysis of EDX or EELS. In a ninth embodiment, an example of applying the sample fabricating apparatus according to the invention to a sample for analyzing the composition in the depth direction of Auger electron spectroscopy (AES) or secondary ion mass spectroscopy (SIMS) will be described. In the case of analyzing a composition in the depth direction of a sample portion in which the composition is uniform in the direction parallel to the surface of the sample by AES or SIMS, by analyzing a section formed at a small angle to improve the resolution in the depth direction, the depth resolution can be improved. FIGS. 25(a) and 25(b) show a method of preparing a section suitable for such analysis. An ion beam 1131 is emitted while being deflected by the ion beam deflecting control described in the sixth embodiment to form a hole 1133. By forming a section 1132 in such a manner, the sample internal structure exposed in the section is wider than that in the sample depth direction. The formed section 1132 is irradiated with an electron beam 1134, Auger electrons are detected and dispersed, and an in-plane composition distribution in the formed section 1132 is obtained, thereby obtaining a composition distribution in the depth direction of the sample 1001. The method can be also used for element analysis in the depth direction by the SIMS by emitting an ion beam in place of the electron beam 1134, detecting secondary ions, and performing mass spectrometry. As described above, by forming the tapered section at a small angle by the sample fabricating apparatus, the resolution of analysis of composition in the depth direction of AES, SIMS, or the like can be also improved. Although the embodiment has been described by using the process with an ion beam as an example, the invention can be applied to a process using, not necessarily the ion beam, but a charged particle beam which can be processed. In the sample fabricating method according to the invention, in the series of processes for separating a micro sample from a specimen stage, the angle formed between the FIB and the sample surface is not changed, so that the process for tilting the stage is not included. In the sample fabricating method of the invention, therefore, even when the function of tilting the specimen stage is omitted to reduce the size of the whole apparatus, preparation of a sample for analyzing, observing, or measuring a micro area by separating a micro sample from a sample or preparing the micro sample to be separated can be realized. Also in the case of the apparatus in which the specimen stage has the tilting function, time required to tilt the stage is unnecessary, so that sample fabrication time is made relatively short. The problem such that the sample surface cannot be observed before and after the specimen stage is tilted can be also reduced. According to the invention, the sample fabricating apparatus for preparing a sample for analyzing, observing, or measuring a micro area by separating a micro sample from a sample or preparing the micro sample to be separated, which is suitable from the viewpoint that the operation of the apparatus can be automated and the burden on the operator can be lessened is provided. According to the invention, with the configuration of the apparatus using the not-tilted specimen stage effective at reducing the apparatus manufacturing cost, an ion beam can be emitted at an arbitrary angle and a very accurate section can be formed, so that the precision of FIB or SEM observation can be increased. A sample membrane having uniform film thickness can be formed, so that it is effective at improving the precision of the TEM observation and making quantitative analysis of EDX and EELS.
	abstract	A lifting support for a boiling water reactor nuclear fuel assembly comprising a grappling head configured to allow attachment to a lifting device, a body with an upper end and a lower end, the upper end connected to the grappling head, the body configured to be inserted into a water channel of a boiling water reactor nuclear fuel assembly, and an end connected to the lower end, the end configured to be accepted by the nuclear fuel assembly.
	abstract	A stage system includes a first stage movable along a reference plane, containing a vertical direction, and in the vertical direction or in a first direction close to the vertical direction, a second stage movable in a second direction intersecting with the first direction and relative to the first stage, a first driving mechanism for moving the first stage in the first direction, a second driving mechanism for moving the second stage in the second direction, a countermass movable in the first direction, and a third driving mechanism for moving the countermass in a direction opposite to the first direction.
	summary
	abstract	The present invention concerns a nuclear reactor, preferably a pool-type nuclear reactor cooled by liquid metal or molten salts, having a core formed of a bundle of fuel elements and immersed in a primary fluid for cooling the core; the fuel elements are provided with expanders acting in a direction perpendicular to the axes of the fuel elements and having low thermal expansion elements which engage alternatively with high thermal expansion elements to amplify the radial expansion of respective end elements which, when a predetermined temperature is exceeded, engage with each other and space the fuel elements from one another and in particular their active part to introduce negative reactivity into the core.
	description	This application is a U.S. national stage application under 35 U.S.C. § 371 of PCT Application No. PCT/US2016/030809, filed May 4, 2016, which claims the benefit of U.S. Provisional Application No. 62/156,604, filed May 4, 2015, the entireties of which are incorporated herein by reference. The present invention relates generally to an apparatus for supporting spent nuclear fuel, and more specifically to a fuel basket for spent nuclear fuel and a container implementing the same. There are two different types of fuel baskets that dominate the industry: flux trap baskets and non-flux trap baskets. Flux trap baskets require an additional empty space between each fuel cell, which results in the flux trap baskets having a reduced capacity relative to non-flux trap baskets. The size of the flux trap baskets are governed by the number of cells, the size of the cells, and the thickness of the material used to form the baskets. It may be possible to increase capacity (increase the number of cells) by decreasing the thickness of the material used to form the basket while not increasing the overall area of the basket. However, material thickness is dictated by the structural resistance required to withstand regulatory normal conditions, off-normal conditions, and accident events. Thus, there is great hesitancy in the industry to reduce the material thickness, and in fact such thickness reductions without additional modification may not pass required agency approvals. Thus, a need exists for an improvement in flux trap fuel baskets that enables the wall thickness of the baskets to be decreased, thereby increasing overall capacity and performance. The present application is directed to an apparatus for supporting spent nuclear fuel. The apparatus may include a basket apparatus that is designed to be inserted into a cavity of a container. The basket apparatus may be formed by arranging a plurality of slotted plates in an intersecting manner, although other designs for the basket apparatus that do not include use of such slotted plates may also be used to form the basket apparatus. The slotted plates may form fuel cells for storing fuel assemblies with spent nuclear fuel rods therein and flux trap spaces between adjacent ones of the fuel cells. Furthermore, the apparatus may include reinforcement members positioned in the flux traps to increase the structural strength of the basket apparatus. In one aspect, the invention may be an apparatus for supporting spent nuclear fuel, the apparatus comprising: a plurality of wall plates arranged in an intersecting manner to define a basket apparatus extending along a longitudinal axis, the basket apparatus comprising a plurality of fuel cells and a plurality of flux traps between adjacent ones of the fuel cells; and a plurality of reinforcement members positioned in the flux traps and extending between opposing ones of the wall plates that form the flux traps. In another aspect, the invention may be an apparatus for supporting spent nuclear fuel, the apparatus comprising: a plurality of wall plates forming a basket apparatus comprising a plurality of fuel cells and a plurality of flux traps between adjacent ones of the fuel cells; the basket apparatus extending along a longitudinal axis and comprising a top-most axial portion, a bottom-most axial portion, and a middle portion; a first set of reinforcement members positioned in lower portions of the flux traps formed by the bottom-most axial portion of the basket apparatus, the reinforcement members of the first set extending between sections of opposing ones of the wall plates that form the lower portions of the flux traps; a second set of reinforcement members positioned in upper portions of the flux traps formed by the top-most axial portion of the basket apparatus, the reinforcement members of the second set extending between sections of opposing ones of the wall plates that form the upper portions of the flux traps; and a plurality of fuel assemblies disposed in the fuel cells, each of the fuel assemblies comprising a plurality of spent nuclear fuel rods supported between two end caps. In yet another embodiment, the invention may be an apparatus for supporting spent nuclear fuel, the apparatus comprising: a plurality of wall plates forming a basket apparatus comprising a plurality of fuel cells and a plurality of flux traps between adjacent ones of the fuel cells, the wall plates comprising reinforcement slots; a plurality of reinforcement members, each of the reinforcement members comprising a body portion and first and second flange portions protruding from opposite sides of the body portion; the reinforcement members positioned in the flux traps so that: (1) the first and second flange portions nest within the reinforcement slots of opposing ones of the wall plates that form the flux traps; and (2) the body portion abuts outer surfaces of the opposing ones of the wall plates, thereby maintaining a fixed distance between the outer surface of the opposing ones of the slotted wall plates. In still another embodiment, the invention may be an apparatus for supporting spent nuclear fuel, the apparatus comprising: a plurality of wall plates forming a basket apparatus that extends along a longitudinal axis and comprises a plurality of fuel cells and a plurality of flux traps between adjacent ones of the fuel cells; and a plurality of reinforcement members positioned in the flux traps and extending between opposing ones of the wall plates that form the flux traps, the reinforcement members arranged in a plurality of longitudinal groups, each of the longitudinal groups comprising a subset of the reinforcement members arranged in a spaced apart manner along a group axis that is substantially parallel to the longitudinal axis. Further areas of applicability of the present invention will become apparent from the detailed description provided hereinafter. It should be understood that the detailed description and specific examples, while indicating the preferred embodiment of the invention, are intended for purposes of illustration only and are not intended to limit the scope of the invention. The features and benefits of the invention are illustrated and described herein by reference to exemplary embodiments. This description of exemplary embodiments is intended to be read in connection with the accompanying drawings, which are to be considered part of the entire written description. Accordingly, the disclosure expressly should not be limited to such exemplary embodiments illustrating some possible non-limiting combination of features that may exist alone or in other combinations of features. In the description of embodiments disclosed herein, any reference to direction or orientation is merely intended for convenience of description and is not intended in any way to limit the scope of the present invention. Relative terms such as “lower,” “upper,” “horizontal,” “vertical,”, “above,” “below,” “up,” “down,” “top” and “bottom” as well as derivatives thereof (e.g., “horizontally,” “downwardly,” “upwardly,” etc.) should be construed to refer to the orientation as then described or as shown in the drawing under discussion. These relative terms are for convenience of description only and do not require that the apparatus be constructed or operated in a particular orientation. Terms such as “attached,” “affixed,” “connected,” “coupled,” “interconnected,” and similar refer to a relationship wherein structures are secured or attached to one another either directly or indirectly through intervening structures, as well as both movable or rigid attachments or relationships, unless expressly described otherwise. As used throughout, any ranges disclosed herein are used as shorthand for describing each and every value that is within the range. Any value within the range can be selected as the terminus of the range. In addition, all references cited herein are hereby incorporated by reference in their entireties. In the event of a conflict in a definition in the present disclosure and that of a cited reference, the present disclosure controls. Throughout the disclosure set forth herein, for certain of the components described several iterations of that component are depicted. For clarity and to avoid clutter, only some depictions of that component will be numbered. Referring first to FIG. 1, a container 100 for storing spent nuclear fuel is illustrated. The container 100 generally comprises a container body 110 and a container lid 120 coupled to the container body 110. In certain embodiments, the container 100 may be a ventilated vertical overpack (“VVO”), which is a massive structure made principally from steel and concrete to store canisters loaded with spent nuclear fuel or other high level waste. Although the structural details of the container 100 are not described herein, it should be appreciated that the container 100 is specifically designed and is formed of specifically selected materials to provide extreme radiation blockage of both gamma and neutron radiation emanating from the high level radioactive waste stored therein. Specifically, the high level radioactive waste or spent nuclear fuel that is stored within the container 100 emits gamma and neutron radiation that must be blocked from reaching the environment due to its harmful effects. This blockage of harmful radiation is achieved with the container 100 structure and design and the structure and design of other components located within and surrounding the container 100. Furthermore, the high level radioactive waste or spent nuclear fuel that is stored within the container 100 may be extremely hot. Thus, the container 100 may also be specifically designed to facilitate a convective/no force cooling of any high level radioactive waste containers stored therein, although other techniques including forced air cooling may also be used in other embodiments. The container 100 may include casks, dual-purpose metal casks, multi-purpose canisters (MPCs), silo systems, or any other storage, repository, or transport system that contains a fuel basket structure. The specific structure of the container 100 is not to be limiting of the present invention in all embodiments unless specifically stated as such. Thus, various different container configurations are possible and may be used in accordance with the invention described herein. Referring to FIGS. 1, 2A, and 2B concurrently, the container body 110 has an inner surface 111 that defines a cavity 112. The container body 110 may be formed of a single layer of material or multiple different layers as illustrated. A basket apparatus 200, also referred to herein and known in the art as a fuel basket, is positioned within the cavity 112. The invention may in some embodiments be directed to an apparatus for supporting spent nuclear fuel, which apparatus may be the basket apparatus 200 by itself, or the basket apparatus 200 when disposed within the container 100. When used to support and store spend nuclear fuel, the basket apparatus 200 is positioned within the cavity 112 of the container 100 and forms a plurality of fuel cells 210 and a plurality of flux traps 220 between adjacent ones of the fuel cells 210. Thus, the basket apparatus 200 described herein is known in the art as a flux trap basket. As discussed in more detail below, the flux traps 220 are spaces or gaps between the adjacent fuel cells 210 that may be left empty or filled with a moderator, such as water, to assist in the shielding of radiation. The design of basket apparatuses generally, and the basket apparatus 200 specifically, is dictated by the requirement to manage reactivity control in compliance with prescribed regulatory limits. Basket assemblies having flux traps are required under the standards of certain regulatory bodies and under certain circumstances (such as when highest reactivity fuel or fresh fuel is being stored). This is because basket assemblies that use flux traps are better configured to deal with high levels of radiation in nuclear fuel than basket assemblies without flux traps due to the additional radiation protection provided by the flux trap spaces and any moderator substances such as water contained therein. FIG. 2A illustrates the cavity 112 of the container 100 with the basket apparatus 200 therein but without any spent nuclear fuel located within the basket apparatus 200. FIG. 2B illustrates the cavity 112 of the container 100 with the basket apparatus 200 therein and with fuel assemblies 300 positioned within the fuel cells 210 of the basket apparatus 200. In some embodiments each of the fuel cells 210 are sized and configured to hold no more than one of the fuel assemblies 300 therein. Furthermore, in some embodiments the flux traps 220 have a cross-sectional size and shape that is insufficient to contain any of the fuel assemblies 300 therein. Thus, the fuel assemblies 300 may be stored in the fuel cells 210, but may not be stored in the flux traps 220. Rather, the flux traps 220 always remain as a space that is free of the fuel assemblies 300. In the exemplified embodiment a fuel assembly 300 comprising a plurality of spent nuclear fuel rods 310 is positioned and supported within each of the fuel cells 210. The fuel rods 310 are illustrated generically using grayscale, but the fuel rods 310 may be rods having a circular or other transverse cross-sectional shape and the spent nuclear fuel is disposed within the fuel rods 310. In the exemplified embodiment each of the fuel cells 210 contains one or more fuel assemblies 300, each containing a plurality of the spent nuclear fuel rods 310. However, the invention is not to be so limited in all embodiments and some of the fuel cells 210 may be left empty in alternative embodiments. In the exemplified embodiment, each of the fuel assemblies 300 comprises a first end cap 301, a second end cap 302, and the spent nuclear fuel rods 310 extending between the first and second end caps 301, 302. The fuel assemblies 300 may also include one or more tie rods 303 for coupling the first and second end caps 301, 302 to one another. Although only one tie rod 303 is illustrated as being associated with each of the fuel assemblies 300 in the exemplified embodiment, in alternative embodiments each fuel assembly 300 may include multiple tie rods 303 and may also include tie plates to assist in holding the fuel rods 310 securely in place. In the exemplified embodiment, the first end cap 301 is located in an upper portion of the basket apparatus 200 and the second end cap 302 is located in a lower portion of the basket apparatus 200. The first and second end caps 301, 302 may be tie plates or other structures. In the exemplified embodiment, the first and second end caps 301, 302 extend axially beyond the terminal ends of the spent nuclear fuel rods 301. Stated another way, there exists a transverse axis or plane that intersects the first end caps 301 without intersecting any of the fuel rods 310 (or specifically the nuclear fuel stored therein) and separately there exists a transverse axis or plane that intersects the second end caps 302 without intersecting any of the fuel rods 310 (or specifically the nuclear fuel stored therein). Referring briefly to FIGS. 2A and 5A concurrently, in certain embodiments each of the fuel cells 210 may have a length L1 and a width W1. Similarly, each of the flux traps 220 (or at least the portion of each of the flux traps 220 that is adjacent to an individual one of the fuel cells 210) may have a length L2 and a width W2. In the exemplified embodiment, the width W1 of the fuel cells 210 is greater than the width W2 of the flux traps 220 and the length L1 of the fuel cells 210 is the same as the length L2 of the flux traps 220. As a result, the fuel cells 210 have a greater cross-sectional area than the flux traps 220. The fuel cells 210 and the flux traps 220 may have heights that extend the entirety of the height of the basket apparatus 200, although the flux traps 220 may be at least partially interrupted by the intersecting wall plates that are used to form the basket apparatus 200 as described in more detail below. Referring to FIGS. 3, 4, 5A, and 8 concurrently, the basket apparatus 200 will be described in accordance with an embodiment of the present invention. The basket apparatus 200 is formed by a plurality of wall plates 400 that are arranged in an intersecting manner to form and define the basket apparatus 200. More specifically, referring to FIG. 8, each of the wall plates 400 is a slotted wall plate such that the wall plates 400 may be interlocked with one another in an intersecting manner to form the basket apparatus 200. In the exemplified embodiment, each of the wall plates 400 comprises an upper edge 401, a lower edge 402, a plurality of plate slots 403 formed into each of the upper and lower edges 401, 402, and a plurality of reinforcement slots 404 formed into at least one of the upper and lower edges 401, 402. Although the plate slots 403 are illustrated as being formed into each of the upper and lower edges 401, 402 of the wall plates 400, the invention is not to be so limited and for some of the wall plates 400, for example the upper-most wall plates in the basket apparatus 200, the wall plates 400 may include plate slots 403 in the lower edge 402 but not also in the upper edge 401. The plate slots 403 in each of the wall plates 400 are sized and configured to receive an intersecting one of the wall plates 400 to form the basket apparatus 200. Thus, the plate slots 403 may be positioned and designed to achieve a desired overall basket apparatus structure. In the exemplified embodiment, the reinforcement slots 404 are illustrated as being formed into both of the upper and lower edges 401, 402 of the wall plates 400. However, the invention is not to be so limited in all embodiments and the reinforcement slots 404 may be formed into only the upper edges 401 or only the lower edges 402 of the wall plates 400 in other embodiments. As will be described in greater detail below, the reinforcement slots 404 provide a location at which a reinforcement member 500 may be coupled to the wall plate 400. Thus, the reinforcement slots 404 are only needed on edges of the wall plates 400 that are intended to retain one of the reinforcement members 500. In some embodiments, some of the wall plates 400 are configured to retain a reinforcement member 500 and therefore will include reinforcement slots 404 in at least one of its upper or lower edges 401, 402 while others of the wall plates 400 will not include any reinforcement slots because such wall plates 400 may not perform any function related to the reinforcement members 500. Furthermore, in some embodiments the reinforcement slots 404 are not needed and the reinforcement members 500 may be coupled to the wall plates 400 without being retained within reinforcement slots 404. Nonetheless, in some embodiments for simplicity the wall plates 400 may all be formed identical with reinforcement slots 404 regardless of whether they are used to retain a reinforcement member 500. In the exemplified embodiment, the plate slots 403 have a first height H1 and the reinforcement slots 404 have a second height H2. The heights of the plate slots 403 and the reinforcement slots 404 are measured from the upper or lower edge 401, 402 into which the plate and reinforcement slots 403, 404 are formed to a terminal end of the plate and reinforcement slot 403, 404. In the exemplified embodiment, the second height H2 of the reinforcement slots 404 is less than the first height H1 of the plate slots 403. As seen in FIG. 8, the plate slots 403 and the reinforcement slots 404 of the wall plates 400 are arranged in a pattern comprising a repeating sequence of reinforcement slot, plate slot, plate slot. Of course, other arrangements are possible depending upon the overall desired shape of the basket apparatus 200. In the exemplified embodiment, the reinforcement slots 404 are formed between a first closely spaced pair of the plate slots 403a and a second closely spaced pair of the plate slots 403b. Specifically, the wall plate 400 has sets of two of the plate slots 403 that are closely spaced. The space in between the intersecting wall plates 400 that are positioned within each set of two closely spaced plate slots forms one of the flux traps 220 of the basket apparatus 200. The space in between adjacent ones of the sets of two of the plate slots 403 that are used to form the flux traps 220 is a portion of the wall plate 400 that is intended to form a part of one of the fuel cells 210. In the exemplified embodiment, the reinforcement slots 404 are centrally positioned between each set of two closely spaced plate slots 403. However, the invention is not to be so limited in all embodiments and other arrangements and positioning of the plate slots 403 and the reinforcement slots 404 relative to one another may be possible in other embodiments. Referring to FIGS. 3, 4, and 5A concurrently, the basket apparatus 200 is illustrated that has been formed by a plurality of the wall plates 400 being arranged in an intersecting manner as has been described in detail above. Specifically, the basket apparatus 200 is formed by placing a first set of the wall plates 400 in a parallel and spaced apart arrangement. Then, a second set of the wall plates 400 are positioned in a parallel and spaced apart arrangement that is orthogonal to the orientation of the first set of wall plates 400. Next, the plate slots 403 of the wall plates 400 of the first set are aligned with the plate slots 403 of the wall plates 400 of the second set, and the intersecting/orthogonal wall plates 400 are coupled to one another by inserting the wall plates 400 of the first set into the plate slots 403 of the wall plates 400 of the second set and vice versa. Thus, the plate slots 403 of each of the wall plates 400 receive an intersecting one of the wall plates 400 therein. This operation continues as the basket apparatus 200 is built up axially, which results in the assembly of the basket apparatus 200. As noted herein above, the basket apparatus 200 comprises a plurality of fuel cells 310 for storing fuel assemblies of spent nuclear fuel therein and a plurality of flux traps 220 between adjacent ones of the fuel cells 210. In the exemplified embodiment, there is a flux trap 220 between each adjacent pair of the fuel cells 210. However, the invention is not to be so limited in all embodiments and the basket apparatus 200 may be a combination flux trap/non-flux trap basket such that not every adjacent fuel cell 210 is separated by one of the flux traps 220. In the exemplified embodiment, each of the wall plates 400 has an inner surface 410 and an outer surface 411. For a first one of the wall plates 400 and a second one of the wall plates 400, the inner surfaces 410 of the first and second ones of the wall plates 400 face one another. For the second one of the wall plates 400 and a third one of the wall plates, the outer surfaces 411 of the second and third ones of the wall plates 400 face one another. The inner surfaces 410 of the wall plates 400 bounds a portion of one of the fuel cells 210. Specifically, in the exemplified embodiment the inner surfaces 410 of four wall plates 400 collectively form or bound one of the fuel cells 210. The outer surfaces 411 of the wall plates 400 bounds a portion of one of the flux traps 220. Specifically, in the exemplified embodiment the outer surfaces 411 of two adjacently positioned wall plates 400 collectively form one of the flux traps 220. Thus, in one embodiment each wall plate 400 forms, defines, or bounds a portion of one of the fuel cells 210 and a portion of one of the flux traps 220. In one alternative embodiment, the peripheral wall plates 400 may only define a portion of one of the fuel cells 210 and not also a portion of one of the flux traps 220, as shown in FIG. 5A. In another alternative embodiment, the peripheral-most wall plates 400 may only define a portion of one of the flux traps 220 and not also a portion of one of the fuel cells 210, as shown in FIG. 5B. The flux traps 220 are designed to have a particular width W2 to facilitate decreasing radiation and eliminating the danger of criticality. In some embodiments, the flux traps 220 have a width W2 between 20 mm and 30 mm, more specifically between 22 mm and 28 mm, and still more specifically approximately 26 mm. However, the invention is not to be so limited in all embodiments and the exact width of the flux traps 220 may be outside of the range noted herein depending on radiation levels of the fuel assemblies to be stored therein. As described above, in the exemplified embodiment the wall plates 400 form and define the flux traps 220. In some embodiments, the wall plates 400 have a wall thickness t of between 7 mm and 14 mm, and more specifically approximately 10 mm. Of course, thicknesses of the wall plates 400 outside of the aforementioned range may also be permissible in some embodiments. In certain embodiments, the wall plates 400 have a thickness t and the flux traps 220 have a width W2. There are two walls plates 400 that bound each of the flux traps 220, such that the combined thickness of the flux traps 220 and the walls bounding them is 2t+W2. In previous basket apparatuses, the wall thickness t has been maintained at a predetermined minimum value to ensure that reactivity control is maintained below regulatory limits regardless of the level of reactivity of the fuel stored therein and to ensure proper thermal conductivity. Furthermore, the wall thickness t has been selected to ensure that it can withstand regulatory normal, off-normal, and accident conditions (i.e., structural rigidity). One major consideration in fuel basket design is that it must withstand inertial impact loads, such as a severe inertial loading event that might cause a free fall in the horizontal direction leading to an impact with a hard surface or a sudden tip-over of the cask from a vertical orientation. Under such events, the fuel assembly 300 bearing on the wall plate 400 acts to deform it and the wall plate 400 must be adequately stiff to withstand the exerted load. Thus, two important considerations for the structural resistance of the wall panel 400 are: (1) ensuring that deflection is maintained below acceptable limits for reactivity control; and (2) ensuring that the wall panels 400 are not compromised. These are some of the many factors that go into determining the appropriate wall thickness t. Regardless, in order to ensure safe operation, and to also maximize capacity, t is selected to be a specific value and 2t+W2 is selected to be a specific value. Using the inventive concepts described below, it has been found that the value of t may be decreased while maintaining 2t+W2 at the same level, thereby increasing the width of the flux traps 220 and increasing the volume of water that can be placed within the flux trap spaces. Alternatively, it has been found that the value of t may be decreased without increasing the width of the flux traps 220, thereby increasing the overall capacity of the flux trap fuel apparatus 200 relative to those previously known and used. Furthermore, the value of t may be decreased while the value of W2 is increased but less than the decrease in the value of t, which results in an increase in capacity while also increasing the width of the flux trap spaces for enhanced performance. Even with these modifications to the values of t and W2, the structural rigidity and other performance characteristics and regulatory requirements remain met due to the inclusion of the reinforcement members 500 which will be described in greater detail below. Specifically, the reinforcement members 500 are located within the flux traps 220 and span between and abut the outer surfaces 411 of the wall plates 400 that bound the flux traps 220, which significantly reduces the amount of deflection of the wall panels 400 because the reinforcement members 500 will reinforce the wall panels 400 and maintain the width W2 of the flux trap 220. Thus, the reinforcement members 500 provide a means to reduce the wall panel 400 thickness and maintain adequate structural strength and thermal performance in the basket apparatus 200. Still referring to FIGS. 3, 4 and 5A, as noted above the wall plates 400 are arranged in an intersecting manner to define the basket apparatus 200. The basket apparatus 200 extends along a longitudinal axis A-A. The fuel cells 210 and the flux traps 220 are formed by the spaces between the intersecting wall plates 400, with the larger cross-sectional area spaces forming the fuel cells 210 and the relatively smaller cross-sectional area spaces forming the flux traps 220. In this embodiment, the fuel cells 210 have square or rectangular cross-sectional shapes, although the invention is not to be so limited in all embodiments. Furthermore, as illustrated in these figures, the reinforcement slots 500 are positioned in the flux traps 220 and extend between opposing ones of the wall plates 400 that form the flux traps 220. Specifically, the reinforcement slots 500 extend between, and may abut and be coupled directly via welding, bolting, or the like, to the outer surfaces 411 of the wall plates 400 that face one another and form the flux traps 220. Specifically, the wall plates 400 are arranged in pairs of closely spaced wall plates 400 that have opposing outer surfaces 411 that face one another that form the flux traps 220. Thus, the flux traps 220 are formed or defined by the outer surfaces 411 of two closely spaced parallel wall plates 400, and more specifically by the opposing outer surfaces 411 thereof that face one another. The pairs of closely spaced wall plates 400 are spaced apart from other pairs of closely spaced wall plates 400 by a distance (the width W1 of the fuel cells 210) that is greater than the distance (the width W2 of the flux traps 220) between the closely spaced wall plates 400 (because the width W1 of the fuel cells 210 is greater than the width W2 of the flux traps 220). The spaces between the pairs of closely spaced wall plates 400 form the fuel cells 210. More specifically, each of the fuel cells 210 is formed in the space between by two parallel wall plates 400 extending in a first direction and the space between two parallel wall plates 400 extending in a second direction that is orthogonal to the first direction. In the exemplified embodiment, each of the fuel cells 210 except for the outermost fuel cells 210 is surrounded by flux traps 220 and the outermost fuel cells 210 are surrounded on two sides by flux traps 220. Referring to FIG. 6, in such an embodiment, when the basket apparatus 200 is positioned within the cavity 112 of the container 100, a basket spacer 250 may be included that circumscribes the basket apparatus 200. Specifically, the basket spacer 250 may be positioned between the inner wall 111 of the container body 110 and the basket apparatus 200 to maintain proper spacing between the basket apparatus 200 and the inner wall 111 of the container body 110. In some embodiments, the basket spacer 250 may be spaced apart from the basket apparatus 200 using reinforcement members 251 to form additional flux traps 252 between the basket apparatus 200 and the basket spacer 250. In an alternate embodiment shown in FIG. 5B, each of the fuel cells 210 may be completely surrounded by the flux traps 220. In still other embodiments, the basket apparatus 200 may be a combination flux trap/non-flux trap fuel basket such that there are rows of flux traps 220 in both directions that the wall plates 400 extend centrally located within the basket apparatus 200 but the outer regions of the basket apparatus 200 are free of flux traps. Thus, variations are possible within the scope of the present invention. Referring briefly to FIG. 9, the reinforcement member 500 is illustrated in accordance with one embodiment of the present invention. In the exemplified embodiment, the reinforcement member 500 comprises a body portion 501, a first flange portion 502, and a second flange portion 503. The first and second flange portions 502, 503 protrude from opposite sides of the body portion 501. Thus, in the exemplified embodiment the reinforcement member 500 is a “T” shaped member. The reinforcement members 500 may be a T-shaped plate. Furthermore, in some embodiments the reinforcement members 500 may comprise a flat plate that extends substantially orthogonal to the opposing ones of the wall plates 400 between which the reinforcement member 500 extends. Of course, the invention is not to be so limited in all embodiments and the reinforcement member 500 may have a different shape. For example, in some embodiments the reinforcement members 500 may be cruciform shaped rather than T-shaped. Such cruciform shaped reinforcement members 500 will readily fit within the reinforcement slot 404 in the upper edge 401 of one wall plate 400 and an aligned reinforcement slot 404 in the lower edge 402 of another wall plate 400 that is axially adjacent to the one wall plate 400. Thus, this will increase the structural rigidity in the slotted wall plate basket apparatus 200. This will be more readily understood upon reading the discussion of the assembly of the basket apparatus 200 below. FIGS. 11A-11D show alternative embodiments for the reinforcement members 500a-d, particularly showing their transverse cross-sectional shapes. Thus, the reinforcement members 500A may be I-shaped as shown in FIG. 11A, the reinforcement members 500B may be C-shaped as shown in FIG. 11B, the reinforcement members 500C may be Z-shaped as shown in FIG. 11C, or the reinforcement members 500D may be square/rectangular shaped. Combinations of differently shaped reinforcement members 500 may also be utilized in the same basket apparatus 200 in some embodiments. Furthermore, although in FIGS. 11A-11D the reinforcement members 500A-D are illustrated as having a particular length, this is not to be limiting of the invention in all embodiments. As discussed in greater detail below, the reinforcement members 500 described herein may have an axial height that is less than the height of the basket apparatus 200, and several of the reinforcement members 500 may be coupled to the basket apparatus 200 in a transversely aligned and axially spaced apart manner to provide the necessary structural rigidity to the basket apparatus 200. This may be desirable because it leaves a greater volume of the flux trap 220 space open. Alternatively, the reinforcement members 500 may have a height that is sufficient to enable a single reinforcement member 500 to extend the entire height of the basket apparatus 200. This may be desirable for ease of assembly and manufacturing. This will be discussed below with reference to FIGS. 13 and 14. Referring to FIGS. 10A-10C, assembly of the basket apparatus 200 from the wall plates 400 and coupling of the reinforcement members 500 thereto will be described in accordance with one embodiment of the present invention. As noted above, the wall plates 400 are arranged in an intersecting manner. Specifically, a first set of the wall plates 400 are positioned in a parallel and spaced apart manner. Then, a second set of the wall plates 400 are positioned in a parallel and spaced apart manner orthogonal to the first set of wall plates 400. The second set of wall plates 400 are positioned atop of the first set of wall plates 400 with the plate slots 403 of the first and second sets of the wall plates 400 axially aligned with one another so as to cooperatively secure the first set of wall plates 400 to the second set of wall plates 400. Each parallel grouping of the wall plates 400 forms an axial section of the basket apparatus 200. This process continues until the basket apparatus 200 has a desired overall height. FIG. 10A illustrates the basket apparatus 200 partially assembled with two of the wall plates 400 positioned in preparation for being assembled onto others of the wall plates 400 that are already assembled in the partially formed basket apparatus 200. Within the assembled portion of the basket apparatus 200, some of the reinforcement members 500 are visible secured to the wall plates 400 via the reinforcement slots 404 thereof. In some embodiments, the reinforcement members 500 may be included throughout the basket apparatus 200 nested within each of the reinforcement slots 404. Thus as each layer (or axial segment) of the basket apparatus 200 is formed, reinforcement members 500 may be coupled to the wall plates 400 of that layer so that the reinforcement members 500 are interspersed throughout the basket apparatus 200. In others of the embodiments, some of the reinforcement slots 404 of the wall plates 400 that are assembled into the basket apparatus 200 may include reinforcement members 500 therein while others may not include reinforcement members 500. Thus, the structural arrangement of the basket apparatus 200 formed using the intersecting wall plates 400 permits variation in the positioning of the reinforcement members 500 as desired. The reinforcement members 500 do not need to be located at every reinforcement slot 404 so long as there are a sufficient number of them to ensure that the flux traps 220 (i.e., the gaps between the outer surfaces 411 of the wall plates 400) do not close under loading events as described above. Specifically, a sufficient number of the reinforcement members 500 should be included in the basket apparatus 200 to prevent the wall plates 400 from deflecting towards one other during loading or other non-normal conditions. In FIG. 10A, some of the reinforcement members 500 are illustrated exploded away from the basket apparatus 200 and from the wall plates 400 that are about to be assembled onto the basket apparatus 200. The two wall plates 400 that are not yet assembled will be positioned so that their plate slots 403 will engage the plate slots 403 of the wall plates 400 directly below. This engagement of the plate slots 403 of the axially adjacent plates 400 secures the plates 400 together to form the basket apparatus 200. The axially adjacent plates 400 may also be welded or bolted together for an additional structural rigidity, although this is not required in all embodiments and the interaction of the plate slots 403 alone may be sufficient without additional welding or bolting. FIG. 10B illustrates the basket apparatus 200 with the wall plates 400 that were previously not formed onto the basket apparatus 200 assembled. In FIG. 10B, the reinforcement members 500 are illustrated exploded away from the basket apparatus 200 in preparation for coupling thereto. Referring to FIGS. 10B and 10C concurrently, after the wall plates 400 are assembled, the reinforcement members 500 are positioned within the reinforcement slots 404. Specifically, each of the reinforcement members 500 is sized and shaped to be secured to the wall plates 400 and to fit within the flux trap 220. In the exemplified embodiment, the first and second flange portions 502, 503 of the reinforcement members 500 are positioned so as to nest within the reinforcement slots 404 of opposing ones of the wall plates 400 between which the reinforcement member 500 extends. In that regard, the wall plates 400 that form the flux traps 220 each have at least one of the reinforcement slots 404 formed therein. Specifically, as noted above two adjacent ones of the wall plates 400 form each of the flux traps 220. The two adjacent wall plates 400 each have a plurality of the reinforcement slots 404 formed therein such that the reinforcement slots 404 on one of the wall plates 400 forming/defining the flux trap 220 are aligned with the reinforcement slots 404 on the other one of the wall plates 400 forming/defining the same flux trap 220. Thus, the first flange portion 502 of the reinforcement member 500 nests within the reinforcement slot 404 of one of the wall plates 400 and the second flange portion 503 of the reinforcement member 500 nests within the reinforcement slot 404 of an opposing one of the wall plates 400. As a result, the body portions 501 of the reinforcement members 500 extend into the flux trap 220 that spans between the two wall plates 400 that the first and second flange portions 502, 503 of the reinforcement member 500 are coupled to. The two wall plates 400 that the reinforcement connector 500 couples to collectively define one of the flux traps 220, and thus the reinforcement member 500 is located within the flux trap 220. More specifically, with the first and second flange portions 502, 503 of the reinforcement member 500 nested within the reinforcement slots 404 of the opposing or adjacent wall panels 400, the body portion 501 of the reinforcement member 500 extends into the flux trap 220 and abuts the outer surfaces 411 of the opposing wall plates 400 that face one another. In this manner, the body portions 501 of the reinforcement members 500 maintain a fixed distance between the opposing ones of the wall plates 400 between which the reinforcement member 500 extends. Due to the body portions 501 of the reinforcement members 500 abutting the outer surfaces 411 of the opposing wall plates 400 that form the flux traps 220 (which may be each flux trap in some embodiments), the reinforcement members 200 work in tandem to increase the structural strength of the basket apparatus 200 and prevent deflection of the wall panels 400 as described herein. FIG. 10C illustrates the basket apparatus 200 with one of the reinforcement members 500 positioned within every pair of reinforcement slots 404 formed into adjacent ones of the wall panels 400 forming the flux traps 220. Of course, there does not need to be a reinforcement member 500 within every pair of reinforcement slots 404 in all embodiments, and some of the reinforcement slots 404 may be left empty and free of a reinforcement member 500 therein. In the exemplified embodiment, each of the fuel cells 210 is defined by an enclosed geometry formed by a portion of four of the wall plates 400 (although it may be more than four of the wall plates 400 depending on the shape of the fuel cells 210). In the exemplified embodiment, for each of the portions of the four wall plates 400 that form the fuel cells 210, the reinforcement members 500 are centrally located along that portion of the wall plate 400. Stated another way, each of the fuel cells 210 extends along an axis B-B (see FIG. 2A) that is substantially parallel to the longitudinal axis A-A of the basket apparatus 200. For each adjacent pair of the fuel cells 210, a longitudinal reference plane that extends between and includes the fuel axes B-B of the adjacent pair of the fuel cells 210 intersects at least one of the reinforcement members 500. This occurs due to the central location of the reinforcement members 500 along the portion of the wall plates 400 forming each fuel cell 210. Of course, the invention is not to be so limited in all embodiments and the reinforcement members 500 may be positioned at other locations along the wall panels 400, an example of which is shown in FIGS. 7A and 7B and described below. As noted above, in certain embodiments each of the wall panels 400 that is used to form the basket apparatus 200 is an identical construction. Thus, each of the wall panels 400 may include the reinforcement slots 404 for retaining the reinforcement members 500. In some embodiments the reinforcement members 500 may be coupled to each of the wall panels 400 at each of the reinforcement slots 404. Thus, the reinforcement members 500 may be positioned throughout the basket apparatus 200 along its axial height. However, the structure of the basket apparatus 200 using the wall panels 400 allows for a great deal of variation. Specifically, the reinforcement members 500 may only be coupled to some of the wall panels 400 and/or at some of the reinforcement slots 404. Referring to FIGS. 8 and 9, in one embodiment the wall panels 400 may have a height H3 measured between the upper and lower edges 401, 402. Furthermore, the reinforcement members 500 may have a height H4. The height H4 of the reinforcement members 500 may be less than the height H3 of the wall panels 400. In one embodiment, the height H4 of the reinforcement members 500 may be less than or equal to one-half of the height H3 of the wall panels 400. This enables one of the reinforcement members 500 to nest within the reinforcement slot 404 in the upper edge 401 of the wall panel 400 while another one of the reinforcement members 500 nests within the reinforcement slot 404 in the lower edge 401 of the same wall panel 400 that is aligned with the reinforcement slot 404 in the upper edge 401 without the reinforcement members 500 overlapping one another. FIGS. 2A and 2B illustrate one embodiment of the internal features of the container 100 with the basket apparatus 200 therein. In this embodiment, the reinforcement members 500 are positioned only at the top end of the basket apparatus 200 and at the bottom end of the basket apparatus 200. Specifically, in this embodiment the reinforcement members 500 comprise a first set 520a of the reinforcement members located adjacent a top end of the basket apparatus 200 and a second set 520b of the reinforcement members located adjacent a bottom end of the basket apparatus 200. The first and second sets 520a, 520b may be separate and distinct components in some embodiments. In this embodiment a first transverse reference plane C-C (transverse to the longitudinal axis A-A of the basket apparatus 200) exists that intersects each of the reinforcement members 500 of the first set 520a of reinforcement members. A second transverse reference plane D-D (transverse to the longitudinal axis A-A of the basket apparatus 200) exists that intersects each of the reinforcement members 500 of the second set 520b of reinforcement members. Furthermore, a third transverse reference plane E-E (transverse to the longitudinal axis A-A of the basket apparatus 200) exists axially between the first and second transverse reference planes C-C, D-D. In the exemplified embodiment, due to the reinforcement members 500 being located only at the top and bottom ends of the basket apparatus 200, the third transverse reference plane E-E does not intersect any of the reinforcement members 500. By positioning the reinforcement members 500 at the top and bottom of the basket apparatus 200 only, it is possible that the reinforcement members 500 are not transversely aligned with any of the spent nuclear fuel. Specifically, as seen in FIG. 2B, the fuel rods 310 do not extend the entire length of the fuel cell 210, but rather extend between the first and second end caps 301, 302. Thus, the fuel rods 310 extend from a first end 311 that is spaced from a top-most end 206 of the basket apparatus 200 to a second end 312 that is spaced from a bottom-most end 205 of the basket apparatus 200. The first set 520a of reinforcement members 500 are located within the axial space between the first end 311 of the fuel rods 310 and the top-most end 206 of the basket apparatus 200. The second set 520b of reinforcement members 500 are located within the axial space between the second end 312 of the fuel rods 310 and the bottom-most end 205 of the basket apparatus 200. Thus, in this embodiment no portion of the fuel rods 310 is aligned with the reinforcement members 500. Stated another way, there is no transverse plane that intersects a portion of the fuel rods 310 and one or more of the reinforcement members 500. This arrangement may be advantageous for the following reasons. The fuel rods 310 are known to emanate radiation in the transverse direction. The reinforcement members 500 take up some of the valuable volume of the flux traps 220 that would otherwise be filled with water or some other modulator/radiation shielding material. Because the reinforcement members 500 are not aligned with the fuel rods 310 in this embodiment, the reinforcement members 500 do not interfere with the radiation shielding and the full width of the flux traps 220 that is adjacent to the fuel rods 310 in the transverse direction is available for radiation shielding (either by itself or via being filled with a radiation shielding material). Of course, additional reinforcement members 500 may be included within the flux traps in axial alignment with the reinforcement members 500 of the first and second sets 520a, 520b to provide additional structural rigidity to the basket apparatus 200 in some embodiments. Referring to FIGS. 2A, 2B, and 3 concurrently, the above will be described in a different way with specific mention of the wall plates 400. In the exemplified embodiment, the wall plates 400 include a plurality of first wall plates 400a, a plurality of second wall plates 400b, and a plurality of third wall plates 400c. The first wall plates 400a form a top-most axial section of the basket apparatus 200. The third wall plates 400c form a bottom-most axial section of the basket apparatus 200. The second wall plates 400b form one or more middle axial sections of the basket apparatus 200. Each axial section of the basket apparatus 200 is defined by a plurality of the wall plates 400 that are all intersected by the same transverse reference plane. In this embodiment, it may be the case that the second wall plates 400b are formed of a metal matrix material having neutron absorbing particular reinforcement. Thus, the second wall plates 400b may be formed of a material that shields against neutron radiation. Furthermore, in this embodiment the first and third wall plates 400a, 400c may be formed of stainless steel. Stainless steel does not shield against neutron radiation to the same degree that the metal matrix of the second wall plates 400b does. Thus, in this embodiment it is preferable to not include fuel rods in transverse alignment with the first and third wall plates 400a, 400c. Furthermore, in this same embodiment, the reinforcement members 500 may also be formed of stainless steel. In one embodiment, the reinforcement members 500 formed of stainless steel may be located only in portions of the flux traps that are formed by the top-most axial section (i.e., the first wall plates 400a) and the bottom-most axial section (i.e., the third wall plates 400c) of the basket apparatus 200. In this embodiment, the end caps 301, 302 may be transversely aligned with the top-most axial section formed by the first wall plates 400a and the bottom-most axial section formed by the third wall plates 400c. However, it may be preferable that the fuel rods 310 do not extend into the top-most axial section and the bottom-most axial section of the basket apparatus 200. In embodiments that use wall plates 400 formed of stainless steel and reinforcement members 500 formed of stainless steel, the reinforcement members 500 may be welded to the steel plates 400. Furthermore, in all embodiments disclosed herein it is possible for the reinforcement members 500 to be welded, bolted, combinations thereof, or otherwise mechanically fastened to the wall plates 400 defining the flux trap 220 within which the reinforcement members 500 are positioned either alternative to or in addition to the reinforcement members 500 nesting within the reinforcement slots 404 as disclosed herein. Referring briefly to FIGS. 7A and 7B, the basket apparatus 200 is illustrated with an alternative arrangement of reinforcement members 700. The basket apparatus 200 and the reinforcement members 700 are identical to the similar structures/components described above except with regard to the differences specifically noted herein below. First, in this embodiment the reinforcement members 700 are not illustrated with flanges that interact with slots in the wall plates 400. Rather, in this embodiment the reinforcement members 700 are illustrated such that they are fastened to the wall plates 400 via welding, bolting, or the like as described herein above. Of course, this arrangement of the reinforcement members 700 may also be coupled to the wall plates 400 using flanges and slots are described above. In this embodiment, the reinforcement members 700 are illustrated as flat rectangular plates rather than T-shaped plates because there is no longer a need for the T-flanges. Of course, other shapes are possible and fall within the scope of this disclosure. For example, the reinforcement members 700 may include additional material/flanges to ensure a proper weld or bolted engagement between the reinforcement members 700 and the wall plates 400. Another difference between this embodiment and those previously described is in the positioning and arrangement of the reinforcement members 700 within the flux traps 220. Specifically, in this embodiment rather than having one reinforcement member 700 (or a plurality of axially spaced reinforcement members) positioned within each flux trap 220 space at the center-point of that particular flux trap 220 space, this embodiment includes two reinforcement connectors 700 within each flux trap 220 space situated symmetrically from the mid-plane of the portion of the wall plates 400 defining the flux trap 220. Thus, multiple of the reinforcement members 700 may be positioned within one of the flux traps 220 that bounds one side of a single fuel cell 210. In the exemplified embodiment, the two reinforcement members 700 that are positioned within a single flux trap 220 space are equidistantly spaced from the center-point of that flux trap 220 space. However, variations in the arrangement, positioning, and number of the reinforcement members 700 within a single flux trap space 220 are possible. Although variations are possible, in certain embodiments it is preferable that the reinforcement members 500, 700 described herein be positioned into abutting contact with side surfaces of the wall plates 400 that define the flux traps 220 and the fuel cells 210 rather than the corners thereof. Stated another way, each of the fuel cells 210 has a polygonal shape, which is a square in the exemplified embodiment (although other shapes are possible). The polygonal shape of the fuel cells 210 has a plurality of sides and a plurality of corners. The reinforcement members 500, 700 are positioned adjacent to and aligned with the sides of fuel cells 210 (or the sides of the plates that define the fuel cells 210) rather than the corners of the fuel cells 210. This is because the reinforcement members 500, 700 are intended to prevent these walls frin deflecting or moving towards one another during certain conditions. The reinforcement members 500, 700 would not achieve this purpose if positioned at the corners of the fuel cells 210 rather than along the sides of the fuel cells 210. The flux traps 220 may be considered to extend transversely in intersecting directions orthogonal to the longitudinal axis A-A of the basket apparatus 200 along the entire length and width of the basket apparatus 200. As used herein, a single flux trap space refers to a portion of the flux traps that bound a portion of one of the fuel cells 210. Specifically, each fuel cell 210 (or at least each fuel cell 210 other than the peripheral-most fuel cells) is bounded by portions of four flux traps 220. Those portions of the four flux traps are each referred to herein as a single flux trap. Thus, in the embodiment of FIGS. 7A and 7B, there are two reinforcement members 700 positioned within each of the portions of the four flux traps 220 that bound each of the fuel cells 210. Referring briefly to FIG. 12, an alternative basket apparatus 800 is illustrated. In FIG. 12, the basket apparatus 800 is not formed from slotted plates as with the previously described embodiments. Rather, in the exemplified embodiment the basket apparatus 800 is formed from a plurality of distinct elongated tubes 801 with square-shaped transverse-cross sections. Of course, as with the previously described embodiments, the transverse cross-sectional shape of the elongated tubes is not to be limiting in all embodiments and they may be triangular, rectangular, hexagonal, or the like in alternative embodiments. The elongated tubes 801 have inner surfaces that define a fuel cell 804 for the storage of fuel assemblies as has been described above. The elongated tubes 801 are arranged in an adjacent and spaced apart manner so that each of the elongated tubes 801 is at least partially, if not fully, surrounded by a flux trap 802. In the exemplified embodiment, two reinforcement members 803 are depicted within each portion of the flux trap space 802 that surrounds one of the elongated tubes 801. The two reinforcement members 803 are offset from the center-point of the flux trap 802 within which they are positioned similar to the arrangement described with reference to FIGS. 7A and 7B above. Of course, the invention is not to be so limited and a single reinforcement member or more than two reinforcement members may be disposed within each portion of the flux trap space 802 as has been described in detail herein above. Thus, FIG. 12 is mainly intended to illustrate a different form of a basket assembly that is formed by elongated tubes rather than by slotted plates. All other features described above and below are applicable to both the embodiments that utilize slotted plates and those that utilize elongated tubes to form the basket assemblies. Referring to FIG. 13, the fuel basket 200 is illustrated with a portion thereof exploded away so that the positioning of the reinforcement members 500 may be seen. In this embodiment, the fuel basket 200 is illustrated as being formed by separate tubes that are coupled together in a spaced apart manner thereby forming the flux traps therebetween. However, this same discussion is applicable to the embodiments described above whereby the basket apparatus 200 is formed by the wall plates 400. Thus, although in this embodiment the reinforcement slots, plate slots, and the like are omitted, they may be included in other embodiments and thus the description related to FIG. 13 is not intended to be limited to the specific embodiment shown, but rather may be relevant to all embodiments described herein. In this embodiment, the reinforcement members 500 are arranged in groupings 510a-d (also referred to herein as longitudinal groups). Each grouping 510a-d is aligned along a longitudinal axis that is parallel to the longitudinal axis of the basket apparatus 200. Furthermore, in this embodiment each grouping 510a-d comprises a plurality of the reinforcement members 500 (distinct, separate components) that are axially spaced apart along the height of the basket apparatus 200. Stated another way, in this embodiment each of the groupings 510a-d comprises a subset of the reinforcement members 500 that are arranged in a spaced apart manner along an axis of that grouping 510a-d (also referred to herein as a group axis) that is substantially parallel to the longitudinal axis A-A of the basket apparatus 200. Each of the reinforcement members 500 may be coupled to the basket apparatus 200 in any number of ways. Specifically, the reinforcement members 500 may be coupled to the basket apparatus 200 utilizing the flange/slot arrangement described above with particular reference to FIGS. 10A-10C. Alternatively, the reinforcement members 500 may be coupled to the basket apparatus 200 via welding, bolting, combinations thereof, or other similar techniques. Thus, in this embodiment the groupings 510a-d of the reinforcement members 500 are positioned within the flux traps 220 in an axially spaced apart manner along the height of the basket apparatus 200. As a result, the reinforcement members 500 take up less space within the flux traps 220 than if the reinforcement members 500 were not axially spaced apart. This may be desirable because maintaining a larger volume of empty space (either left empty or filled with a modulator) within the flux traps 220 may result in greater reactivity control and greater radiation shielding. The exact number of reinforcement members 500 within each of the groupings 500a-d and the exact spacing between the reinforcement members 500 is not limiting of the present invention in all embodiments. These design considerations may be made to achieve an appropriate balance between flux space volume, structural rigidity, deformation resistance, and the like. This arrangement utilizing groupings 510a-d of the reinforcement members 500 arranged in an axially spaced manner along an axis that is parallel to the longitudinal axis A-A of the basket apparatus 200 is also shown in cross-section in FIG. 2C. Specifically, referring to FIG. 2C, in one embodiment a plurality of the reinforcement members 500 (i.e., a grouping 500a-d of the reinforcement members 500) may be positioned within each flux trap 220 in an axially spaced apart manner. Thus, the reinforcement members 500 may form a non-continuous support structure for the walls that define the flux trap 220. In another embodiment, the reinforcement members 500 may be elongated such that the body portion 501 of the reinforcement members 500 extends along a majority of or an entirety of the length of the flux trap 220. In such embodiment, rather than having a plurality of axially spaced apart reinforcement members 500, there may be a single elongated reinforcement member 500 within the flux trap 220 that extends along most or the entirety of the height of the flux trap 220. However, in some embodiments it may be preferable to use the plurality of spaced apart reinforcement members 500 because this may take up less of the flux trap 220 space, leaving more of the flux trap 220 space available for water or the like to provide radiation shielding. Referring to FIG. 14, an alternative arrangement of the fuel basket 200 with reinforcement members 600 is illustrated. Again, although the fuel basket 200 is illustrated as being formed by separate tubular structures, the invention is not to be so limited and the concepts described below with reference to FIG. 14 may be applied to any flux trap fuel basket, including those formed using slotted plates described above. The difference between this embodiment and those previously described, and specifically the embodiment described with reference to FIG. 13, is that the reinforcement members 600 are much taller than those previously described. Specifically, in this embodiment the basket apparatus 200 has a height H5 and the reinforcement members 600 have a height H6. In one embodiment, the height H6 of the reinforcement members 600 is the same as the height H5 of the basket apparatus 200. In another embodiment, the height H6 of the reinforcement members 600 may be slightly less than the height H5 of the basket apparatus 200. Thus, in this embodiment the reinforcement members 600 are singular structures that extend along the entire height of the basket apparatus 200 within the flux trap spaces thereof. The reinforcement members 600 extend from a top end 601 to a bottom end 602. In some embodiments the reinforcement members 600 may be welded, bolted, or otherwise affixed to the basket apparatus 200 only at the tops and bottoms of the reinforcement members 600 adjacent the top and bottom ends 601, 602 of the reinforcement members 600. This may be sufficient to maintain the reinforcement member 600 within the flux trap without dislodging even during load situations. Thus, it is not necessary in all embodiments to make a connection between the reinforcement members 600 and the basket apparatus 200 along the entire length of the reinforcement members 600. Of course, in some embodiments the reinforcement members 600 may be coupled (welded, bolted, or the like) to the basket apparatus 200 along additional points of contact between the top and bottom ends 601, 602 of the reinforcement members 600. Furthermore, combinations of the configuration of the groupings 510a-d of reinforcement members 500 shown in FIG. 13 and the reinforcement members 600 shown in FIG. 14 are also possible in some embodiments. Specifically, some of the flux trap spaces may have groupings 510a-d of the reinforcement members 500 and others of the flux trap spaces may have unitary reinforcement members 600 extending along the entire axial height of the flux trap spaces. As noted above, the elongated reinforcement members 600 may be utilized in a basket apparatus 200 that is formed from slotted plates as discussed above. In such an embodiment, the reinforcement members 600 may extend from an upper-most wall plate 400 in the basket apparatus 200 to a bottom-most plate 400 in the basket apparatus 200. In this embodiment, the reinforcement members 600 may be physically coupled to only the upper-most wall plate 400 and the bottom-most wall plate 400 while not also being physically coupled to the wall plates 400 therebetween. Specifically, the reinforcement members 600 in this alternative embodiment may be welded, bolted, or the like to the upper-most wall plate 400 and to the lower-most wall plate 400. While the reinforcement member 600 will also abut and extend along all of the wall plates 400 between the upper and lower-most wall plates 400 in the basket apparatus 200, the reinforcement member 600 may not be physically welded, bolted, or the like to those additional wall plates 400. Of course, in alternative embodiments the reinforcement member 600 may be physically secured (via bolting, welding, mechanical mating, or the like) to more than just the upper and lower-most wall plates 400 in the basket apparatus 200. In some embodiments the basket apparatuses may be formed entirely of neutron absorber material (i.e., the plates forming the basket apparatus may have a built-in neutron absorber material). In such embodiments, it may be preferable to add a stainless steel plate to the bottom and top of the basket apparatus (where the fuel rods are not located) so that the stainless steel plates form the bottom and top portions of the basket apparatus. Furthermore, in such embodiments it may be preferable to utilize a set of axial strips at the basket edges to join the top and bottom grids. The reinforcement members described herein may be made of stainless steel so that they can be welded to the top and bottom portions of the basket apparatus. Stainless steel reinforcement members may be preferable because they enable a thinner wall with equivalent strength, thereby leaving more of the flux space available for being filled with a moderator for criticality control. The reinforcement member 500 described herein enables the panel thickness of the wall panels 400 to be reduced while allowing the structural response of the wall panels 400 to provide the required resistance during all regulatory loading events during storage, transport, or disposal because the reinforcement member 500 prevents wall deflection even with a thinner wall). The reactivity control is improved in this design since a small fraction of the removed wall panel 400 volume may be maintained as free-space for water influx during flooding events while the remainder of the volume is removed to allow a more compact basket design. The fact that the flux-trap basket apparatus 200 in this embodiment has thinner wall panels 400 compared to the non-flux trap basket design does not adversely affect the thermal performance since there are two panels between adjacent fuel assemblies, providing the same or more material for thermal conductivity. While the inventive concepts described herein have been illustrated with a basket apparatus made up of square shaped fuel cells, the fundamental design concept disclosed herein is also applicable to fuel cells of rectangular and hexagonal cross section, and the like. Furthermore, while the inventive concepts described herein have been described with reference to flux trap fuel baskets, they may also be used in combination flux trap/non-flux trap iterations. While the foregoing description and drawings represent some example systems, it will be understood that various additions, modifications and substitutions may be made therein without departing from the spirit and scope and range of equivalents of the accompanying claims. In particular, it will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, sizes, and with other elements, materials, and components, without departing from the spirit or essential characteristics thereof. In addition, numerous variations in the methods/processes described herein may be made. One skilled in the art will further appreciate that the invention may be used with many modifications of structure, arrangement, proportions, sizes, materials, and components and otherwise, used in the practice of the invention, which are particularly adapted to specific environments and operative requirements without departing from the principles of the present invention. The presently disclosed embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims and equivalents thereof, and not limited to the foregoing description or embodiments. Rather, the appended claims should be construed broadly, to include other variants and embodiments of the invention, which may be made by those skilled in the art without departing from the scope and range of equivalents of the invention.
	claims	1. A hydrostatic packing seal for a system for sealing a shaft of primary motor-driven pump units of nuclear reactors, the hydrostatic packing seal comprising:a rotary active surface attached to the shaft and a floating active surface, wherein the floating active surface is configured to move axially to follow axial displacements of the shaft, and wherein the rotary active surface and the floating active surface face each other and are separated by a water film,wherein said rotary active surface or said floating active surface has at least one surface structured by an array of asperities to prevent the deposition of iron oxide fouling said at least one surface of said rotary active surface or said floating active surface, each asperity having lateral dimensions between 10 nm and 5 μm, a height between 10 nm and 5 μm, and a distance between two consecutive asperities being between 10 nm and 5 μm, said asperities being holes or pillars. 2. The hydrostatic packing seal according to claim 1, wherein the asperities are holes. 3. The hydrostatic packing seal according to claim 1, wherein the asperities are pillars. 4. The hydrostatic packing seal as claimed in claim 3, wherein at least one of the pillars has a form factor less than 2. 5. The hydrostatic packing seal according to claim 1, wherein the asperities are nanometric asperities that have lateral dimensions between 10 nm and 1 μm and a height between 10 nm and 1 μm, with the distance between two consecutive asperities being between 10 nm and 1 μm. 6. The hydrostatic packing seal according to claim 1, wherein the asperities are micronic asperities that have lateral dimensions between 1 μm and 5 μm and a height between 1 μm and 5 μm, with the distance between two consecutive asperities being between 1 μm and 5 μm.
	description	The present invention relates to a particle accelerating structure, and more particularly to a structure suitable for both increasing the energy of and raising a repetition frequency of a particle beam periodically emitted from the structure. The particle stream emitting from an RF accelerating structure may be used for multiple purposes, for example medical treatment, non-destructive investigation of solid objects, and the like. An example of a particle accelerator suitable for application of the present invention is a radio-frequency (“RF”) accelerator using a photocathode which typically comprises a conductive housing defining a cavity, a photocathode for emitting photoelectron into the cavity, and a wave guide for generating an RF electric field in the cavity. As light is periodically applied to the photocathode, photoelectrons are emitted into the cavity intermittently. These photoelectrons are converged and accelerated by an RF electric field generated in the cavity. The RF electric field is applied synchronously with application of light to the photocathode. A typical RF accelerator is described in U.S. Pat. No. 6,094,010 to Washio, which is incorporated herein by reference. Such accelerating structures generally include a housing made from a conducting material such as copper. The housing defines a cavity. A photocathode is mounted on an inner surface of the housing. Into the cavity is fed light (laser) via a window, and illuminates the surface of the photocathode. Photoelectrons are emitted from the photocathode into the cavity. Such a housing may include one or more cells, dividing the cavity into a plurality of sub-cavities which are separated from each other by toroidal shaped discs (known in the art as “irises”). The sub-cavities are sized and configured to resonate in a particular harmonic mode which corresponds to the frequency of a particular electromagnetic field induced in the irises, with the result that a strong longitudinal electric field is generated along a longitudinal central axis of the housing. Once a longitudinal electric field has been established in this way, the photoelectrons are accelerated along the longitudinal axis to emerge from an exit port. The resulting stream of photoelectrons may used for any of the multiple purposes known in the art. In general, it is desirable to operate an RF accelerating structure at the highest power possible. Very high duty factor, high gradient photo-injectors and RF cavities in general are a critical component of the next generation of applications in high energy electron beam-based physics. Today, there is a compelling need for these applications, which include linear colliders, x-ray free-electron lasers, inverse Compton scattering sources, as well as associated imaging or analysis applications of interest to homeland security. The key issue for high average power, normal conducting, photo-injectors and RF accelerating structures is to effectively cool the housing structure. Thermal management of very high duty factor, high gradient RF structures is crucial to their performance. A significant percentage of the applied RF power is deposited on the walls of the housing in specific locations depending on the magnitude and the direction of the electromagnetic fields in that location. This heating presents significant thermal engineering problems. The large amount of power dissipated in the structure can cause “hot spots” and local thermo-mechanical distortions which may lead to detrimental changes in RF properties and beam quality. One of the most challenging parts of an accelerator housing to be cooled are the “irises” which protrude into the cavity of the housing. Another challenging aspect to be cooled is the so-called RF coupler, which is a thin walled interface between the waveguide and the cavity. Accordingly, the problem of thermal gain has been approached by providing channels within the housing structure, and forcing water to flow through the channels in combination with cooling the water on the outside of the housing by conventional heat dissipation means such as by radiator. However, the prior art is limited in the method for creating, and configuring the channels used for cooling the housing structure. One method currently used to incorporate cooling channels into RF structures is achieved by drilling elongate cylindrical holes into the structure for example, as described in U.S. Pat. No. 6,094,010 to Washio, which is incorporated herein by reference, and where it is specifically described how cylindrical holes are provided to cool the irises of an RF accelerator. It will be readily understood that because these channels are drilled, they are limited to linear configurations, and are connected to each other at sharp angles. It will be understood that this kind of configuration greatly limits the cooling uniformity and rate of cooling in that fluid flow is dramatically slowed by the sharp changes in direction (discontinuities in flow gradient), thereby reducing the rate at which heat can be extracted. Another method that has been used to introduce cooling channels into RF structure is to braze sections of the structure together with pre-machined, curve shaped channels cut out in each section. However, brazing multiple components to form high gradient RF structures is a delicate and expensive step, and many braze cycles are needed to build an effective cooling structure. Moreover, the resulting structure is not uniform or homogeneous, which adversely affects the efficiency at which heat can be extracted from the housing by water in the channels. Thus, there is a need for a method and structure for fabricating an RF housing having a channel system with gentle changes in direction, suitable for cooling the RF housing structure. There is a further need for an RF housing structure having such channel system, that has a uniform and homogeneous configuration, that is not a collection of components, with sections cut out, brazen together. The present invention addresses these and other needs. According to a preferred embodiment of the invention, there is described an RF accelerator that has improved cooling characteristics over the prior art. In a preferred embodiment, the RF accelerator has a conductive housing defining a cavity. The housing comprises cells which have a substantially homogeneous composition, wherein assembly of the housing is not achieved by brazing together sheets of metal having cutout shapes for forming an internal flow path. A cathode for emitting particles is provided. A wave guide is provided, coupled to the cavity for guiding a micro wave into the cavity. An opening is disposed in a wall of the conductive housing for guiding the photoelectrons emitted into the cavity out from the cavity to form an electron beam. A flow path through which coolant flows to forcibly cool the conductive housing is configured to extend through the housing. The conductive housing comprises a cylinder having an inner circumferential surface of a cylindrical shape and a protrusion having a through hole in which the protrusion comprises a toroid like extension from the inner circumferential surface defined by the cylinder toward a center axis of the conductive housing. The flow path enters an external wall of the conductive housing from an outer circumferential surface, and circulates around the through hole defined in the central area of the protrusion, and then returns to the outer circumferential surface of the conductive housing. The flow path comprises a curved portion that in a preferred embodiment comprises at least a semi circle. In a preferred embodiment, the flow path is configured to conform to the external geometry of the housing, whereby a substantially constant thickness of housing material separates the flow path from the exterior of the housing over a length of the flow path. In another aspect, the flow path has no sharp turns. In yet another aspect, the flow path is not circular in cross section, but may have an elongate cross section. In a further aspect, the walls of the flow path have a surface roughness (Ra) of between 800 to 1200 micro inches in order to cause turbulent flow of the cooling fluid in the channel, thereby increasing the heat conduction from the housing. Preferably, the housing is fabricated by a metal additive manufacturing technique, wherein a metal is deposited in layers using a directed material fabrication process controlled by a computer. The metal additive manufacturing technique uses an electron beam to melt metal feedstock in order to build up the layers of material, preferably copper, or an alloy of copper. In a final aspect, the surface that is exposed to the radiofrequency field is subjected to processing after fabrication in order to achieve surface roughness of less than 63 micro inches. Such a surface is advantageous in order to prevent breakdown of the microwave field. These and other advantages of the invention will become more apparent from the following detailed description thereof and the accompanying exemplary drawings. With reference to the drawings, which are provided by way of exemplification and not limitation, preferred embodiments of the invention are described below. Prior to describing the embodiments of the invention, however, known technology used in effectuating the invention will be described. Turning now to a method of effectuating the present invention, a method of constructing a housing for an RF accelerator will be described that is capable of manufacturing structure capable of overcoming the shortcomings of the prior art. Metal additive fabrication technologies, such as Electron Beam Melting (EBM), have been described for example in U.S. Pat. No. 5,786,562 (Larson), U.S. Pat. No. 6,112,804 (Sachs et al.), U.S. Pat. No. 6,391,251 (Keicher et al.), U.S. Pat. No. 6,401,001 (Jang et al.). The contents of each of these patents is incorporated herein by reference. These technologies employ rapid prototyping layer methods to allow for virtually any three dimensional geometry to be physically constructed, including the provision of channels and openings. The metal additive fabrication techniques used in carrying out the present invention are capable of producing structure in the form of fully dense metal components that are homogenous in metallurgical structure, having no seams or joints, with properties similar to or better than that of conventionally machined materials, and which include a curved channel system that does not include sharp changes of direction or gradient discontinuities. Using the above described metal additive fabrication techniques, the present invention describes preferred cooling channel configurations for improving the thermal cooling characteristics of an RF accelerator housing structure. These cooling channels have enhanced cooling uniformity, in that they provide gentle changes in flow direction, thus reducing hot spots. The cooling channels allow increased flow rate for a given pressure in a homogeneous metal structure by using smooth bends in the channels, as apposed to the intersections with sharp changes in direction (gradient discontinuities) used previously. Specifically, with reference to FIGS. 1-5 a preferred embodiment of a housing structure for an RF accelerator is described. FIGS. 1-5 shows a preferred embodiment of the present invention. An RF injector is generally identified by the numeral 20. A housing 22 is positioned at the center of the injector to define a cavity 25, and may comprise a half cell 24 and a full cell 26. More cells may be added, depending on requirements for acceleration. The cells 24, 26 may be joined to each other by brazing. In an alternative embodiment, using the method of fabrication described above, the cells may be fabricated as a single unitary structure. A wave guide 23 provides an entry point for RF wave introduction to the housing. The half cell 24 defines a half cell sub-cavity 36, and the full cell 26 defines a full cell sub-cavity 38. As described above, the resonant frequency of these sub-cavities is utilized to accelerate photon particles which are directed by an external magnetic field set up in the cell structures to exit from the downstream port 34. Accessory ports 28, 30, 32 are provided as tuning ports or vacuum pump out ports, as needed. At the rear of the housing, a cathode 44 is provided as the source of photoelectrons for acceleration through the exit port 34. Each cell, 24, 26 includes a constriction or “iris” having a narrowed opening 46, 48. Each “iris” may be imagined to be formed as a toroid that protrudes into an otherwise cylindrical interior of the housing, and adjoined continuously to the housing. Thus, the internal radius of the housing reduces to a local minimum at the openings 46, 48 of each toroid. This configuration permits enhanced intensification of the electric field for accelerating photoelectrons through the cavities 36, 38 and finally out of the exit port 34. Of importance to the invention is the presence of cooling channels 40, 42 which are utilized to circulate water around the cells 24, 26 for cooling during operation. As exemplified in FIG. 2, the channels 40, 42 may be positioned substantially in the toroidal portions of the housing, where the heating effect induced by the magnetic field is greatest. The shape of each channel, made according to the method of fabrication of the present invention described above, is configured to provide a superior cooling effect to the cells 24, 26 and the housing generally. The cross sectional shape of a channel is not limited to being circular, but in a preferred embodiment may be elongate, with an elongate axis extending radially outwardly from the center of the housing. This aspect provides for a greater surface area contact between fluid and metal cell. Furthermore, as seen in FIG. 2 a channel may be positioned to extend over the majority of the radius of the solid portion of the toroid in which it is positioned, having one point of entry for fluid flow, and one point of exit. With these characteristics, as seen in FIG. 2, the cross sectional configuration of the channel may conform to the cross sectional geometry of the toroidal portion of the cell 26, allowing a substantially constant thickness of metal to surround the channel, at least on the radially interior portion of the housing 22. Moreover, as exemplified in FIG. 3, the path of a channel through a cell may be substantially curved, preferably with no discontinuity in the gradient of the walls defining the direction of fluid flow. FIG. 3 exemplifies the path of channel 42 through the cell 26, and in a preferred embodiment has only continuously and evenly curved walls without rapid changes in direction, or discontinuities in flow gradient, allowing fluid to flow through the cell 26 at an enhanced speed, allowing for improved heat extraction during operation. In this plan sectional view of the channel 42, the channel is seen to substantially conform to the circumferential exterior surfaces (internal and external) of the cell 26 over a substantial portion of the length of the channel within the cell, allowing a substantially constant thickness of metal to separate the channel 42 from an exterior circumferential surface. These combined characteristics provide for an improved heat extraction capability of the channel 42. In a preferred embodiment, the cell is formed from copper, or an alloy of copper. However, any metal suitable for manufacturing in the described way may also be used. In another aspect of the invention, exemplified in FIGS. 4-5, a cooling channel 60 is provided around the waveguide coupling hole 62, which receives a heavy thermal load in a small area. The coupling inlet hole 62 is an opening in the housing that provides a connection between the cavity 25 and the wave guide 23 for admission of microwaves to the cavity. The coupling inlet hole 62 may have an oval shape to maximize the coupling of the RF power into the RF structure. In a preferred aspect, the cooling circuit 60 conforms to the shape of the coupling hole 62 to enhance the efficiency of cooling this area. In a preferred embodiment, the cooling channel 60 has no discontinuities in flow gradient, and surrounds the coupling hole 62. In a preferred aspect, the invention is directed to the surface roughness of the cooling channels. Because high surface roughness causes turbulent flow which is superior for cooling at a given flow rate, the present invention may have cooling channels in which dimples are introduced during manufacture, such that the resulting surface has a roughness of at least 1000 micro inches Ra, and preferably in the range of 800 to 1200 micro inches Ra. In a final aspect of the present invention, the interior surface walls of the cells that are exposed to the radiofrequency field are subjected to processing after fabrication in order to achieve surface roughness of preferably less than 63 micro inches. This may be achieved by a simple machining process. Without such treatment, the radiofrequency field may cause local heating on the surface and reduce the efficiency of the accelerator. The foregoing method and structure address certain shortcomings in the prior art. By fabricating the housing and the channels according to the method of the present invention, channels having a novel configuration are introduced that provides enhanced cooling, and therefore enhanced operation of the RF accelerator. Thus, it will be apparent from the foregoing that, while particular forms of the invention have been illustrated and described, various modifications can be made without parting from the spirit and scope of the invention.
049901834	abstract	The present invention relates to a process for producing steel in a ladle furnace in which the molten steel is stirred by injection of an inert gas in the lower part of the furnace. According to the invention, the stirring of the bath of steel is effected by the injection of gaseous argon so as to distribute in a homogeneous manner the additives added and the metal temperature in the course of the treatment, while there is simultaneously injected liquid argon above the surface of the bath in the region of intumescence. In this way, substantially any increase in the concentration of nitrogen of the bath of steel in the course of the treatment is avoided. In some cases, and in particular when wires of the type filled with silico-calcium are employed, a reduction in the concentration of nitrogen in the bath of steel is found.
	claims	1. An ion source for use with an ion implant device, the ion source comprising:(a) an ionization chamber defined by a plurality of side walls defining an ionization volume, one of said sidewalls including an ion extraction aperture for enabling an ion beam to be extracted from said ionization chamber along a predetermined axis defining an ion beam axis;(b) a source of electrons external to the chamber and an aligned beam receptor configured relative to and outside said ionization chamber to cause an electron beam to be directed across the ionization volume of said ionization chamber in a direction generally perpendicular to said ion beam axis for ionizing gas in the ionization chamber; and(c) a gas source in fluid communication with said ionization chamber for supplying a cluster molecule feed gas or a monatomic feed gas; wherein the source of electrons ionizes the cluster feed gas by direct electron, impact ionization and ionizes the monatomic feed gas by way of a plasma. 2. An ion source for use with an ion implant device, the ion source comprising:(a) an ionization chamber defined by a plurality of side walls defining an ionization volume, one of said sidewalls including an ion extraction aperture for enabling an ion beam to be extracted from said ionization chamber along a predetermined axis defining an ion beam axis;(b) a source of electrons external to the chamber and an aligned beam receptor configured relative to and outside said ionization chamber to cause an electron beam to be directed across the ionization volume of said ionization chamber in a direction generally perpendicular to said ion beam axis for ionizing gas in the ionization chamber; and(c) a gas source in fluid communication with said ionization chamber for supplying a cluster molecule feed gas or a monatomic feed gas; andwherein the source of electrons ionizes the cluster feed gas by direct electron impact ionization and ionizes the monatomic feed gas by arc discharge. 3. An ion source for use with an ion implant device, the ion source comprising:(a) an ionization chamber defined by a plurality of side walls defining an ionization volume, one of said sidewalls including an ion extraction aperture for enabling an ion beam to be extracted from said ionization chamber along a predetermined axis defining an ion beam axis and an entrance port, d3, for;(b) a source of electrons external to the chamber and an aligned beam receptor configured relative to and outside said ionization chamber to cause an electron beam to be directed across the ionization volume of said ionization chamber in a direction generally perpendicular to said ion beam axis for ionizing gas in the ionization chamber and disposed at a distance, d1, from the chamber; and(c) a gas source in fluid communication with said ionization chamber for supplying a cluster molecule feed gas or a monatomic feed gas; wherein d1 is less than d3. 4. An ion source for use with an ion implant device, the ion source comprising:(a) an ionization chamber defined by a plurality of side walls defining an ionization volume, one of said sidewalls including an ion extraction aperture for enabling an ion beam to be extracted from said ionization chamber along a predetermined axis defining an ion beam axis;(b) a source of electrons external to the chamber and an aligned beam receptor configured relative to and outside said ionization chamber to cause an electron beam to be directed across the ionization volume of said ionization chamber in a direction generally perpendicular to said ion beam axis for ionizing gas in the ionization chamber, disposed at a distance, d1, from the chamber, wherein the source of electrons has a characteristic dimension, d2; and(c) a gas source in fluid communication with said ionization chamber for supplying a cluster molecule feed gas or a monatomic feed gas;wherein d1 is less than d2. 5. An ion source for use with an ion implant device, the ion source comprising:(a) an ionization chamber defined by a plurality of side walls defining an ionization volume, one of said sidewalls including an ion extraction aperture for enabling an ion beam to be extracted from said ionization chamber along a predetermined axis defining an ion beam axis;(b) a source of electrons external to the chamber and an aligned beam receptor configured relative to and outside said ionization chamber to cause an electron beam to be directed across the ionization volume of said ionization chamber in a direction generally perpendicular to said ion beam axis for ionizing gas in the ionization chamber;(c) a gas source in fluid communication with said ionization chamber for supplying a cluster molecule feed gas or a monatomic feed gas;(d) pressure barrier enclosing a portion of the source of electrons;(e) a vacuum pump to modify the gas pressure proximate to the source of electrons. 6. An for use with an ion implant device the ion source comprising:an ionization chamber having an electron entrance aperture; a source of feed gas in fluid communication with said ionization chamber; and an electron emitter formed from a cathode disposed outside said ionization chamber at a distance d1 from said ionization chamber, wherein said distance d1 is selected to cause a plasma to be generated, wherein said electron emitter is selectively mountable at a second distance d2, wherein the distance d2 is selected to cause said ion source to operate in a direct electron mode and wherein the distance d1 results in said ion source operating in a direct electron impact mode forming a dual mode ion source. 7. The ion source as recited in claim 6, wherein said cathode is a directly heated cathode. 8. The ion source as recited in claim 6, wherein said cathode is an indirectly heated cathode. 9. The ion source as recited in claim 6, further including a source for generating magnetic flux. 10. The ion source as recited in claim 9, wherein said electron emitter generates a beam of electrons generally parallel to a first axis and said magnetic flux is parallel to said first axis. 11. The ion source as recited in claim 9, wherein said magnetic flux is in the same direction as said electron beam. 12. The ion source as recited in claim 9, wherein said magnetic flux is in a direction opposite said electron beam. 13. The ion source as recited in claim 6 further including an electron repeller configured to repel electrons from said electron emitter back into said ionization chamber. 14. The ion source as recited in claim 6 further including a beam dump configured to prevent electrons from said electron emitter back into said ionization chamber.
046769463	summary	FIELD OF THE INVENTION This invention relates to thermal insulating blankets and in particular to insulating blankets useful in containment buildings of nuclear power plants. BACKGROUND OF THE INVENTION First-generation nuclear power plants utilized metallic, reflective-type insulation for pipes and equipment located inside the containment buildings. It was found that this reflective insulation did not produce the promised reduction in heat loss and resulted in reduced efficiency and increased operating costs. Further, during maintenance shutdowns this fragile metal insulation was damaged by foot traffic and/or handling making it difficult or impossible to reinstall. Since each piece was custom-made, replacements could not be readily obtained during the scheduled shutdown period. In addition, this insulation did not lend itself to easy inspection of pipe welds, which must be performed at regular intervals. As a result of these problems, nuclear power plants began to replace this metal insulation with removable blankets, particularly in areas where inspection of pipe welds was required. A potential problem arises, however, with use of blanket insulation during a loss of coolant accident (LOCA). During a LOCA, the blankets may be subjected to high energy liquid jets (i.e., subcooled liquid or steamwater mixtures at high pressure) which enter the containment area. If the jet stream impinges on the blankets, the fibrous blanket material may be torn lose generating debris which can clog the protective screen of the emergency core cooling system (ECCS) sump and thereby impair recirculation of water from the sump. The first blanket system accepted by the United States Nuclear Regulatory Commission consists of a two-inch thick blanket of very light density glass fiber fillers totally encapsulated in a glass fiber cloth envelope. The blankets are used in either single or double layer construction depending upon the pipe temperature. The cloth envelopes are formed with sewn seams and, in the case of double layer construction, the seams in the two layers are staggered with respect to one another. Velcro fastenings are used to attach the blankets to the pipes and/or adjacent blankets. An outer jacket of 26-gauge (0.01875 inch thick) stainless steel fastened by suitcase latches is sometimes used to protect the blankets. These fragile blankets are intended to be completely destroyed in the event of a LOCA with the hope that the residue from the blankets will be small enough so as not to block the sump screen and, if necessary, to pass through the recirculating pump. Another known insulating blanket used in nuclear containment buildings consists of a glass fiber filler layer having a waterproof sheet of ERCO-SIL 36S (sold by Eastern Refractories Company, Inc., Belmont, Mass.) on its outer surface (i.e., disposed away from the pipe). The remaining sides of the filler layer are covered by glass fiber cloth. Metal clips consisting of stainless steel hog rings connect the cloth to the waterproof sheet. This design is much stronger than the first design and is intended to resist damage during a LOCA. Other known insulating blankets used in nuclear containment buildings are described in Durgin, W. W., and Noreika, J. F., "The Susceptibility Of Fibrous Insulation Pillows To Debris Formation Under Exposure To Energetic Jet Flows," NUREG/CR-3710 (SAND 83-7008), Alden Research Laboratory and Sandia National Laboratory, U.S. Nuclear Regulatory Commission, Washington, D.C. 20555. A first blanket described therein consists of 16 lb/ft.sup.3 mineral wool with a cover of asbestos cloth coated with one-half mil of Mylar (registered trademark of E. I. DuPont de Nemours & Co., Wilmington, Del.). A second consists of 11 lb/ft.sup.3 needle packed fiberglass layers covered with stainless knitted mesh on one side (close to the pipe) and silicone glass cloth on the other (outer) side. A third consists of 11 lb/ft.sup.3 needle packed fiberglass layers covered with 18 ounce fiberglass cloth. These three blankets were tested for damage and failure (loss of blanket material) under jet streams of up to 65 psi applied at an angle of 45.degree. and 90.degree. . The third blanket exhibited the greatest resistance to damage and failure. In the field of thermal and acoustic insulation blankets for exhaust systems in gas transfer plants, oil rigs, refineries and the like, it has been suggested to provide an insulation blanket comprising a ceramic fiber core approximately one and one-half inches in thickness, a thin lead sheet adjacent the core for noise insulation, a thin stainless steel foil/fiberglass cloth laminate between the core and insulated object for excluding moisture, a silicone rubber coated fiberglass cloth completely surrounding the core and other layers, and a flexible stainless steel mesh stocking enveloping the entire assembly to provide additional protection (U.S. Pat. No. 4,442,585). These blankets are wrapped tightly around pipes by means of lacing anchors and second layers are provided around the joints to render the edges significantly impermeable to thermal and acoustic radiation. SUMMARY OF THE INVENTION It is an object of this invention to provide a thermal insulating blanket useful for insulating pipes and equipment inside the containment building of a nuclear power plant and which will resist damage during a loss of coolant accident (LOCA). Another object is to provide an insulating blanket having an outer casing that will dissipate the force of a high force liquid stream striking the blanket so as to prevent the blanket from tearing. A further object is to provide an insulating blanket which if torn during a LOCA will not clog the protective screen of the emergency coolant recirculating sump. Another object is to provide an insulating blanket that will be cut into small pieces if torn by a high force liquid stream. Another object is to provide removable and reusable, flexible blanket insulation for pipes and equipment. According to this invention an insulating blanket is provided having an inner surface positionable adjacent the object to be insulated and an opposing outer surface. The blanket consists of a filler layer of thermal insulating fibers, a waterproof sheet covering one surface of the filler layer, and a wire mesh casing surrounding the filler layer and sheet to form the blanket. The waterproof sheet is positioned between the outer surface of the blanket and the filler layer. The wire mesh casing serves to dissipate high force liquid jet streams which may strike the outer surface of the blanket during a LOCA. Further, if the jet stream tears the blanket, the wire mesh serves to cut up the filler layer as it passes through the mesh so that the torn blanket pieces will not clog the protective screen of the emergency coolant recirculating sump. In a preferred embodiment, a flexible wire mesh septum lies in substantially parallel relationship between two layers of glass fiber wool or ceramic fiber wool. The mesh septum increases the strength of the blanket and aids in cutting up the filler layer as it passes through the septum if torn by a high force liquid stream. A flexible waterproof sheet, consisting of a fine wire mesh screen embedded in silicone rubber, covers the outer surface of the filler layer. A flexible wire mesh casing surrounding the filler layer and waterproof sheet has of from about 40 to about 100 regularly spaced apertures per square inch and is made from stainless steel or Inconel wire having a diameter of from about 0.005 to about 0.015 inches. More preferably, the casing consists of knitted Inconel mesh having about 60 apertures per square inch and made from about 0.011 inch diameter wire. According to the process of the invention, a thermal insulating blanket is applied to pipes and equipment in the containment building of a nuclear power station. The insulation resists damage if struck by a high force liquid stream during a LOCA and is cut into small pieces which will not clog the protective screens of the emergency coolant sump if torn during a LOCA. The insulating blanket has an inner surface positioned adjacent the pipes and equipment and an opposing outer surface, and consists of a layer of thermal insulating fibers and a wire mesh casing covering at least one surface of the filler layer to form the outer surface of the blanket. The casing dissipates high force liquid streams which strike the outer surface of the blanket and cuts up the filler layer as it passes through the casing if torn by a jet stream.
	description	1. Field The present invention relates generally to the inspection of nuclear fuel rods and, more particularly, to the inspection of a nuclear fuel pellet stack within a hermetically sealed fuel rod cladding to detect missing pellet surfaces and pellet-to-pellet gaps. 2. Related Art The large nuclear reactors utilized for power generation employ an array of a large number fuel rods containing nuclear fuel. Each rod comprises a metal tube or a sheath which may be from 8 to 15 feet (2.4-4.6 m) long and up to one-half inch (1.27 cm) in diameter, and which contains a stack of cylindrical fuel pellets of suitable fissionable material such as uranium oxide. The upper end of the tube is empty of fuel pellets and forms a plenum for a gas or other fluid under substantial pressure which fills the top of the rod and also a small clearance space around the fuel pellets. The fuel rods are supported in parallel groups in fuel assemblies which may typically contain upwards of 300 fuel rods, and the complete nuclear reactor is made up of a large number of these fuel assemblies arranged in a suitable configuration in an active core. The metal tubes of the fuel rods, also known as cladding, constitute the primary containment boundary for the radioactive nuclear fuel, and inspection of the internal components of the rod that can affect the rod's integrity is of primary importance. In the manufacture of the fuel rods, the tubing itself and the end cap welds are carefully inspected and helium leak tested. Since a nuclear reactor may contain upwards of 40,000 fuel rods, a probability exists that some number of defective rods will be present even with a highly effective manufacturing quality control program. It is also desirable to inspect the fully loaded fuel pellet stack for defects such as missing pellet surfaces and pellet-to-pellet gaps which can ultimately compromise the cladding's integrity or affect core performance. The temperature differences on the outer cladding surface of an assembled fuel rod can result from differences in the radial thermal resistance between the cladding inside diameter and the fuel pellet outer surface due to a missing pellet surface or a pellet-to-pellet gap. It is important to detect conditions such as this that might ultimately result in breaches of the cladding which could lead to fission products leaking into the reactor coolant and can result in many conditions that increase operating costs. These conditions include: (1) high radiation readings in the primary cooling system; (2) increased volume of liquid radioactive waste; (3) increased volume of solid radioactive waste due to more frequent demineralizer bed replacement; (4) increased costs for disposal of spent fuel assemblies due to special handling and additional decontamination; and (5) increased exposure to personnel. These increased costs outweigh the costs incurred by testing assemblies. Once identified, a leaking fuel rod may be extracted from the fuel assembly and replaced with a dummy rod to allow the eventual reload of the assembly in the core. To the extent failure mechanisms can be located in advance of placing the fuel assemblies in the core, the costs of replacing defective rods can be minimized. Accordingly, it is an object of this invention to provide a means of nondestructively inspecting a fuel pellet stack sealed within the cladding of a nuclear fuel rod. Further, it is an object of this invention to provide such an inspection method that can be performed efficiently, with minimal effort and expense. These and other objects are achieved by the inventions claimed hereafter which provide a method of detecting defects in nuclear fuel within a fuel rod cladding which include the step of heating at least a portion of the fuel rod to a temperature substantially above the ambient temperature, preferably in a range of between 80 to 120 degrees centigrade. The temperature over the surface of the cladding is then measured as the cladding is cooled, preferably in an ambient environment. Variations are then noted in the temperature measured over the surface of the cladding to determine defects in the fuel stack. In one embodiment, the heating step is performed in a soaking chamber that covers at least a portion of the fuel rod and preferably, the temperature is measured with an infrared receiver such as an infrared camera. Preferably, the fuel rod is rotated as it passes in front of the infrared camera. In another embodiment, the method includes a second heating step after the initial heating step wherein the second heating step heats the surface of the rod for a time period substantially shorter than the initial heating step and before the measuring step. The second heating step may be performed by a radiant heat source, and desirably the rod is moved past the radiant heat source. In still another embodiment, the measuring step is performed in a reduced pressure environment, i.e., below atmospheric pressure and desirably, the noting step occurs at approximately between 60 and 180 seconds after the heating step is completed. A typical nuclear fuel rod is shown by way of example in FIG. 1. The fuel rod 10 comprises a metal tubular cladding 12 of a suitable alloy such as Zircaloy capable of withstanding the severe conditions to which it is subjected during operation, and is usually of considerable length, such as from 8 to 15 feet (2.4-4.6 m) and a relatively small diameter which may be in the order of ½ inch (12.7 mm). The tube 12 is filled for most its length with nuclear fuel pellets 14 which may be made of uranium oxide or other suitable nuclear fuel, and which are of a diameter to fit closely within the tube 12 with a very small radial clearance. The tube 12 is closed at top and bottom by upper and lower end caps 18 and 16, respectively, which are welded in place to form a leak-tight closure. The fuel pellets 14 are disposed in a vertical column extending through most of the length of the tube 12 but with an empty space or plenum 22 at the top. A spring 20 is disposed in this plenum to hold the column of fuel pellets in position. The plenum in the top of the tube 12, and the small clearance between the pellets 14 and the tube 12, are filled with a fluid which is usually gas, and which usually will contain fission products during and after operation within the reactor. This fluid in the tube 12 is normally maintained under substantial pressure typically in the order of 100 to 300 psi (7-21 kg/cm2) at the beginning of fuel assembly life (prior to operation within a reactor core) and further increases during operation as fission products are generated in the fuel. As the fuel pellets 14 are loaded into the cladding 12, there may develop increased gaps between the pellets or missing pellet surfaces such as chips or scars which can affect the temperature distribution over the cladding and detract from the optimum performance of the fuel rod. Therefore, it is desirable to be able to inspect for such defects after the pellets have been loaded into the cladding and, preferably after the cladding has been sealed and pressurized. The embodiments set forth hereafter provide such an inspection technique that is performed by thermal imaging the outer cladding surface with an infrared camera and utilizes the temperature differences over the cladding to identify fuel stack defects. The temperature differences are set up as a result of the differences in the radial thermal resistance between the cladding inside diameter surface and the fuel pellet outer surface due to the missing pellet surfaces or pellet-to-pellet gaps. FIG. 2 is a schematic illustration of some apparatus which may be employed in carrying out the steps of the methods claimed hereafter. In accordance with one embodiment, the fuel rod 10 is soaked at a given temperature preferably at or between 80 to 120° C. in a soaking chamber 24, preferably covering at least a portion of the fuel rod over which the fuel pellets extend or which is expected of having a defect. Then the fuel rod 10 is extracted from the soaking chamber 24 and the cladding surface 12 is heated for a short period of time of approximately 60 sec., while moving past a radiant heat source 26. Then the rod is moved while rotating past an infrared camera 28. Though not required, preferably the latter steps are conducted in a reduced pressure environment, i.e., below atmospheric pressure, to reduce the convective heat transfer. However, the clad temperature difference should be detectable for at least 2 min. at natural convection in air. The output of the infrared camera 28 can be operated upon by a processor 32 controlled by a computer 36 to establish a comparison of the temperature differences, and recorded by a recorder 34. The variable radial thermal resistance will affect heat transfer from the fuel pellets 14 to the cladding 12 resulting in cladding temperature differences on the outside surface of the cladding. The thermal image will be evaluated by the software in the computer 36 to account for pellet eccentric positioning and pellet missing surfaces within the cladding. Finite element analysis is used to provide the optimal soaking temperature as well inputs for software evaluation of the temperature data. In an alternate embodiment, the fuel rod 10 may be soaked at a higher temperature up to 120° C. and then extracted from the soaking chamber and then moved while rotating past the infrared camera 28. Preferably, this is also done in a reduced pressure environment to reduce convective heat transfer. A proof of principle was conducted for the thermal image inspection method claimed hereafter using a transient finite element analysis of the fuel rod with a heat up time of 60 seconds and a cool down time of 120 seconds as figuratively illustrated in the graphical representation shown in FIG. 3. The power source is able to increase the fuel rod outer surface temperature by approximately 100° C. during the 60-second heat up time. Natural convection in air is used for the cool down part of the cycle. The fuel rod temperature distributions for a fuel rod with no defects, (FIGS. 4A and 4D), a fuel rod with a missing pellet surface length of 60 mils and a depth of 10 mils (FIGS. 4B and 4E) and a fuel rod with a missing pellet surface length of 60 mils and a depth of 20 mils (FIGS. 4C and 4F) at 60 seconds (FIGS. 4A-4C) and 180 seconds (FIG. 4D-4F) are graphically illustrated in FIGS. 4A-4F. The fuel rod surface temperature distributions at 60 seconds and 180 seconds are graphically illustrated in FIGS. 5A and 5B, respectively. The clad outer surface temperature differences relative to a fuel rod with no missing pellet surface and a fuel rod with a pellet stack defect are shown in FIG. 6. FIG. 6 shows the method's sensitivity to defect depth. The graph in FIG. 6 shows two areas along the cladding surrounding pellet defects of different depths relative to adjacent areas that surround no pellet defect. One defect is approximately 10 mils and results in and approximately 1.5° C. difference relative to the adjacent cladding area covering no defect. The second defect has a depth of approximately 20 mils and produces approximately a 1° C. difference. This difference can be easily detected by a modern thermal image device. Thus, the methods claimed herein provide a practical means of inspecting a nuclear fuel pellet stack in a sealed fuel rod for missing pellet surfaces and pellet-to-pellet gaps. 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. For example, it should be appreciated that this process could be performed continuously with the fuel rods passing through a heating zone with a velocity of, for example, approximately 10″/min and moving to a temperature detection zone where the temperature is monitored by one or more temperature detection devices such as cameras surrounding the rod. 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	In the metal billet to be used for hot dilation forming, a forward side with respect to the pressing direction has a quadrate section and its diagonal length is not more than an inner diameter of a container. Moreover, a backward side with respect to the pressing direction has a circular section and its diameter is substantially same as the inner diameter of the container. The metal billet is heated to a temperature suitable for press working and is set into a container for press forming. While a center of a workpiece of the metal billet is being bored by a boring punch to be operated by a pressing machine, the metal billet is hot-dilated so that a bottomed container for a cask is formed.
	claims	1. A system for scanning a moving target comprising:a scanning zone located between a radiation source and a radiation source detector;a first sensor located adjacent to the scanning zone for starting the scanning once the moving target has entered the scanning zone and stopping the scanning once the moving target has exited the scanning zone; anda shutter comprising at least one shielding block driven by a dual solenoid configuration, wherein the shutter is located near the radiation source, wherein the first sensor sends a signal to the shutter to open, allowing radiation to pass from the radiation source through the scanning zone when the moving target is present in the scanning zone and to close, stopping the emission of radiation, when the moving target is no longer present in the scanning zone. 2. The system in claim 1 wherein the first sensor distinguishes between a first portion of the moving target passing through the scanning zone and a second portion of moving target passing through the scanning zone, wherein the first portion of the moving target does not trigger the first sensor to initiate a scan and the second portion of the moving target does trigger the first sensor to initiate the scan. 3. The system in claim 1 wherein the radiation source emits gamma-rays and the radiation source detector detects gamma-rays. 4. The system in claim 1 wherein the radiation source detector includes at least one detector array including a plurality of gamma-ray detectors. 5. The system in claim 4 wherein the at least one detector array is comprised of 20-60 gamma-ray detectors. 6. The system in claim 4 wherein the gamma-ray detectors are scintillation counter-type detectors. 7. The system of claim 1 wherein the shutter fails-safe to a closed position. 8. The system of claim 1 wherein at least one radiation sensor senses radiation levels outside the scanning zone. 9. The system of claim 1 wherein the radiation from the radiation source is detected by the radiation source detector and is used to image the contents of the moving target using photon counting. 10. A method for scanning a moving target comprising:creating a scanning zone for the moving target to pass through, where the scanning zone is located between a radiation source and a radiation source detector;positioning a first sensor adjacent to the scanning zone for sensing when to start and stop the scanning process when a moving target has entered the scanning zone;sending a signal from the first sensor to a shutter when the moving target has entered the scanning zone, wherein the shutter comprises at least one shielding block driven by a dual solenoid configuration;opening the shutter to allow radiation from the radiation source to pass through the scanning zone when the moving target is present; andclosing the shutter to stop the emission of radiation when the moving target is no longer present in the scanning zone. 11. The method in claim 10 further comprising, distinguishing between a first portion of the moving target passing through the scanning zone and a second portion of the moving target passing through the scanning zone, wherein the first portion of the moving target does not trigger the first sensor to initiate the scan and the second portion of the moving target does trigger the first sensor to initiate the scan. 12. The method in claim 10 further comprising, emitting gamma rays from the radiation source towards the moving target and detecting gamma-rays that pass through the moving target. 13. The method of claim 10 further comprising, sensing radiation levels outside of the scanning zone. 14. The method of claim 10 further comprising, imaging the contents of the moving target using photon counting. 15. A system for scanning a moving target comprising:a scanning zone located between a radiation source and a radiation source detector, wherein the radiation from the radiation source is detected by the radiation source detector, further wherein the radiation source detector includes at least one detector array employing a plurality of scintillation counter-type, gamma-ray detectors;a first sensor located adjacent to the scanning zone for starting the scanning once the moving target has entered the scanning zone and stopping the scanning once the moving target has exited the scanning zone; anda shutter comprising at least one shielding block driven by a dual solenoid configuration, wherein the shutter is located near the radiation source, wherein the first sensor sends a signal to the shutter to open to allow radiation to pass from the radiation source through the scanning zone when the moving target is present in the scanning zone and to close, stopping the emission of radiation, when the moving target is no longer present in the scanning zone. 16. The system of claim 15 wherein the at least one detector array is coupled to a preamplifier within a 16-channel data processing circuit. 17. The system of claim 16 wherein the data processing circuit is coupled to a discriminator. 18. The system of claim 17 wherein the discriminator is coupled to a pulse generator that generates pulses for each photon received into the at least one detector array; further wherein the pulse generator is coupled to a line driver. 19. The system in claim 18 wherein a computer receives the pulses from the data processing circuit and the pulses are processed to generate an image of the moving target.
	abstract	A system and method for trapping a charged particle is disclosed. A time-varying periodic multipole electric potential is generated in a trapping volume. A charged particle under the influence of the multipole electric field is confined to the trapping volume. A three electrode configuration giving rise to a 3D Paul trap and a four planar electrode configuration giving rise to a 2D Paul trap are disclosed.
	abstract	The radiation monitor includes: a shutter; a calculation section; an AC solenoid; a temperature switch which is attached to the AC solenoid; a circuit protector which has a contact and is connected in series to the AC solenoid; and a mode selection switch connected in series to the AC solenoid. The shutter is maintained in a closed state when the mode selection switch is set to a normal mode; the mode selection switch is changed from the normal mode to a check radiation source mode, thereby flowing an AC current through the AC solenoid to change the shutter from the closed state to an opened state; and the contact of the temperature switch is reversed from the opened state to the closed state, thereby disconnecting the contact of the circuit protector to interrupt the AC current that flows through the AC solenoid.
049884735	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates generally to spent fuel storage and, more particularly, is concerned with a self-latching reactivity-reducing device for allowing placement of a spent fuel assembly in a fuel storage facility. 2. Description of the Prior Art In a typical nuclear reactor, the reactor core includes a large number of fuel assemblies each of which is composed of top and bottom nozzles with a plurality of elongated transversely spaced guide thimbles extending longitudinally between the nozzles and a plurality of transverse support grids axially spaced along the guide thimbles. Also, each fuel assembly is composed of a plurality of elongated fuel elements or rods transversely spaced apart from one another and from the guide thimbles and supported by the transverse grids between the top and bottom nozzles. The fuel rods each contain fissile material and are grouped together in an array which is organized so as to provide a neutron flux in the core sufficient to support a high rate of nuclear fission and thus the release of a large amount of energy in the form of heat. A liquid coolant is pumped upwardly through the core in order to extract some of the heat generated in the core for the production of useful work. At the end of their useful life, spent fuel assemblies are removed from the reactor core and replaced with fresh fuel assemblies. Because of the lack of any permanent off-site spent fuel disposal facility at the present time, nuclear power plant utilities are forced to store all spent fuel assemblies in pools at on-site fuel storage facilities. However, these on-site storage facilities were originally designed to hold only a fraction of the fuel used over the operating life of the plant. Spent fuel storage pool reactivity, K-eff, is limited in most nuclear plants by technical specifications to being less than 0.95. These technical specifications thus limit the ability to increase the number of spent fuel assemblies which can be stored on-site The spent fuel pool reactivity limit is also at odds with modern nuclear fuel management strategies. Most utilities are increasing the U-235 enrichments of the fuel that is used. This increase allows the utilities to reduce the total number of fuel assemblies they need to buy and store. There exist several options to increasing storage capability or fuel enrichment limits. These options range from very expensive reracking operations to a criticality safety reanalysis. One of the most effective methods available today is called "burnup credit" analysis. In this form of criticality safety analysis, calculations are performed to show that a fuel assembly can be safely stored after it has accumulated a minimum amount of burnup. The minimum amount of burnup is dependent on the initial U-235 enrichment of the assembly in question. At high enrichments the burnup requirement may be very large. The burnup requirement is often large enough to preclude the storage of a significant number of fuel assemblies. Each of the problems described above could be overcome by reducing the reactivity of the fuel assemblies to be stored. One technique is to insert neutron absorber or poison rods into the spent fuel assembly to reduce the reactivity of the fuel assembly so that it can be stored in the on-site fuel storage facility. Representative of this technique is the approach disclosed in European Pat. application No. 0,061,043 to Kuhnel et al and French Pat. application No. 2,544,541 to Foussard. Each of these publications discloses the use of a device attachable to the top nozzle of the spent fuel assembly for locking a cluster of poison rods against removal in the fuel assembly. One drawback of the locking devices disclosed in the cited publications stems from their reliance upon the exercise of some human effort in rendering them effective, and from their relatively easy accessibility at the top of the fuel assembly. If it is too easy to unlock or unfasten the devices and remove the cluster of poison rods, then these arrangements might be considered as removable under current regulatory standards. The current regulatory standards do not allow credit to be taken for removable neutron absorbers. Thus, simply putting conventional neutron absorber or poison rods into a spent fuel assembly and locking them in the fuel assembly at its top nozzle may not be sufficient to meet current standards. Consequently, a need exists for an improved approach to lowering reactivity in a spend fuel assembly so as to permit its placement in an on-site fuel storage facility. SUMMARY OF THE INVENTION The present invention provides a self-latching reactivity-reducing device designed to satisfy the aforementioned needs. Several of these devices placed in guide thimbles of a spent fuel assembly greatly reduce the nuclear reactivity of the fuel assembly. This would allow spent nuclear fuel to be stored in spent fuel storage racks that would otherwise be too reactive. The reactivity-reducing device of the present invention is insertable fully in a guide thimble of the spent fuel assembly and incorporates self-latching means which is effective, upon full insertion of the device, to automatically render the device non-removable without the use of an independent tool. The self-latching means is located at a region along the device adjacent the lower end of the fuel assembly where it is inaccessible from the top of the fuel assembly and thus unlatchable without the assistance of the independent tool. Accordingly, the present invention is directed to a reactivity-reducing device for insertion in a guide thimble of a spent nuclear fuel assembly. The reactivity-reducing device comprises: (a) an elongated rod having leading and trailing ends and containing neutron absorber material, the rod being insertable in the guide thimble to place its trailing end adjacent an upper end portion of the guide thimble and its leading end adjacent a lower end portion of the guide thimble; and (b) means mounted at the leading end of the rod for self-latching with the lower end portion of the guide thimble upon completion of insertion of the rod into the guide thimble and being unlatchable from the guide thimble without the use of an independent tool. Further, the rod has a central passage defined therein extending between and open at least at the trailing end thereof, the passage providing the only way for reaching the self-latching means by the independent tool for unlatching the same. The reactivity-reducing device also includes means removably attached to the trailing end of the rod for closing the passage therethrough and rendering the self-latching means at the leading end of the rod inaccessible by the independent tool from the trailing end of the rod such that the rod is non-removably installed in the guide thimble. More particularly, the self-latching means includes a plurality of latch members mounted for pivotal movement between displaced latching and releasing positions at the leading end of the rod, and a plurality of actuating levers respectively attached to the latch members and engagable by the independent tool when inserted through the passage for moving the levers and thereby the latch members from their latching to releasing positions once the closing means has been removed from the rod trailing end. Also, the self-latching means includes means coupled between the latch members and the leading end of the rod for biasing the latch members toward their latching positions. Also, the rod has a tubular portion and a head portion attached to the tubular portion at the trailing end of the rod. The tubular portion has a diameter smaller than the inside diameter of the guide thimble and the head portion has a diameter larger than the inside diameter of the guide thimble such that the head portion seats on the top nozzle for suspending the tubular portion within the guide thimble when the rod is installed in the guide thimble. Further, the head portion has means defined thereon for cooperating with an independent remover for gripping the head portion to withdrawal the rod from the guide thimble once the self-latching means has been unlatched from the guide thimble. These and other features and advantages of the present invention will become apparent to those skilled in the art upon a reading of the following detailed description when taken in conjunction with the drawings.
	description	The invention relates to a system for transferring fuel elements between an upper pool and a lower pool of a nuclear plant. A typical nuclear plant has its upper pool in a reactor building and the lower pool of a fuel-element storage unit. The reactor can be a boiling-water reactor, for example, or also a pressurized-water reactor. Fuel elements are transferred between the pools by a system or apparatus comprising a conveyor tube connecting the upper and the lower pool and extending at an acute angle to the vertical, one or more transport baskets into each of which at least one of the fuel elements can be placed for transfer through the conveyor tube, an upper transfer device in the upper pool for loading fuel elements into and unloading them from the transport baskets, and/or a lower transfer device in the lower pool for loading fuel elements into and unloading them from the transport baskets. In a nuclear plant, replacement and transfer of fuel elements has particular importance in practice. In this connection, fuel elements generally consist of a bundle of individual fuel rods, and the fuel element itself is equipped with a handle or the like so that it can be transported using suitable machines, for example in order to set it into the reactor vessel or remove it from the reactor vessel. Thus, spent fuel elements, in particular, must be removed from the reactor vessel and transported to a fuel-element storage unit, for example. Conversely, fresh fuel elements must be loaded into the reactor vessel. In practice, it is usual to fill the upper pool in the reactor building during the fuel element exchange, so that the fuel elements are transported in liquid (water). They are taken out of the open reactor vessel using a handler that can be moved above the reactor vessel and moved into the upper pool and temporarily stored, if necessary, in a buffer pool/cooling pond. From the upper pool, the fuel elements must be transported to a fuel-element storage unit, for example, using a transfer system, the storage unit also having a (lower) pool, the upper pool (for example in the reactor building) and the lower pool (for example in the fuel-element storage unit) being filled to a different liquid level, independent of one another. Transport using the transfer system takes place between these two pools through a conveyor tube mounted at an angle to the vertical. Such transfer systems are basically known from practice. In this connection, an effort is made to keep the time expenditure for a fuel element exchange as short as possible in order to reduce interruptions in the power operation of the reactor as much as possible. The reduction in the time required for the fuel element exchange has particular importance from an economic point of view. In a transfer system for fuel elements of a nuclear reactor facility known from U.S. Pat. No. 3,952,885 the fuel elements are transported through a conveyor tube oriented at an angle to the vertical. The conveyor tube leads through the safety sheath that encloses the pressurized reactor vessel of a pressurized-water reactor in a gas-tight manner. The inner pool and the outer pool are filled to the same liquid level during the fuel element exchange, so that no blocking measures in the region of the conveyor tube are necessary during transfer of the fuel elements. Transport takes place using a cable hoist and using a carriage that has two chambers, of which one accommodates a fresh fuel element for the trip there, and the other a spent fuel element for the return trip. In this connection, the carriage can pivot from a vertical transfer position into a horizontal or angled transport position. The known transfer system exclusively serves for transfer of fuel elements between two pools filled to the same liquid level. The same holds true for the transfer system known from U.S. Pat. No. 4,096,031, with which fuel elements are transported directly between the reactor vessel and a storage container mounted directly next to it, where the reactor vessel and the storage container are connected with one another by a transport tube that extends at an acute angle to the vertical. Transfer devices are provided at the end of this conveyor tube that can pivot the fuel elements from an angled transport position into a vertical transfer position. Transfer through the conveyor tube takes place using a cable hoist that directly grips the fuel element with a grab. U.S. Pat. No. 3,058,900 describes a charging apparatus for nuclear reactors in which fuel elements are transported directly between the reactor vessel and a channel that runs horizontally below the reactor vessel, the reactor vessel and the channel being connected with one another by a tube that is oriented at an angle to the vertical. For transport, a fuel element is inserted into a cartridge that can be transported through the tube, the cartridge bing provided at the top with a handle or the like so that it can be gripped by a tool. The tube can be closed off completely using a blocking element. This blocking element is opened when a fuel element exchange takes place by means of the charging apparatus. A loading and unloading apparatus for fuel elements is known from U.S. Pat. No. 4,202,729 in which the apparatus sits on the top of the reactor vessel and has two ramps extending at an angle to the vertical in opposite directions and between which the fuel elements can pivot using a pivoting apparatus. An apparatus having a similar construction is known from U.S. Pat. No. 4,440,718. It is therefore an object of the present invention to provide an improved system for handling fuel elements. Another object is the provision of such an improved system for handling fuel elements that overcomes the above-given disadvantages, in particular that provides for fast and efficient transfer of fuel elements between an upper pool and a lower pool of a nuclear plant. Particularly preferably, this transfer system is supposed to be suitable for transfer between an upper pool and a lower pool that have different liquid levels. A system for transferring fuel elements between an upper pool and a lower pool of a nuclear plant has according to the invention a conveyor tube having an upper end at the upper pool and a lower end at the lower pool and extending at an acute angle to the vertical between the ends. A plurality of transport baskets can move through the conveyor tube and each can carry at least one of the fuel elements for transport between the pools. An upper transfer device at the upper end in the upper pool can load the fuel elements into or unload them from the transport baskets, and a lower transfer device in the lower pool can load fuel elements into or unload them from the transport baskets. Each of the devices is adapted to hold two of the transport baskets. The baskets are displaceable for positioning above or below the conveyor tube and are movable during displacement through the tube between a vertical transfer position and an angled transport position. Preferably, the upper transfer device and/or the lower transfer device has two pivot frames into each of which a transport basket can be set and in which the respective transport baskets can pivot between a vertical transfer position and an angled transport position. In this connection, the pivot frames (with the transport baskets provided in them) can be mounted so as to pivot about a common (horizontal) axis. Particularly preferably, the pivot frames can be displaced together horizontally, and can be pivoted automatically during displacement by the transport baskets set into them. This can be done, for example, in that the pivot frames of the transport baskets set into them are guided in/on control rails during displacement in such a manner that the transport baskets pivot automatically, preferably in that lower control pins are guided in the control rails. Such control rails can be curved, for example. The invention first of all proceeds from the recognition that fast and efficient transfer of fuel elements through a conveyor tube can be done if the fuel elements themselves are transported through the conveyor tube not directly, but rather in transport baskets, wherein particularly preferably, a plurality of fuel elements, for example four fuel elements, can be set into each transport basket. Loading and unloading of the transport baskets with fuel elements takes place in a vertical transfer position, and transport itself takes place in an angled transport position corresponding to the angle of the conveyor tube to the vertical. The transfer device according to the invention allows fast loading and unloading of the transport baskets, and, at the same time, simple and fast loading of the transport baskets into the conveyor tube. This is because two transport baskets can be set in at the same time, in the region of the transfer device, where one transport basket is provided above/below and consequently aligned with the conveyor tube in the angled transport position, and the other transport basket can be laterally offset next to the conveyor tube, in a vertical transfer position. This brings about the possibility of loading/unloading the transport basket in the vertical transfer position while a further transport basket is in the angled transport position or even in the conveyor tube. Consequently, the transport baskets can be positioned either aligned with the conveyor tube, or positioned next to the conveyor tube for transfer by displacement of the transport baskets in the transfer device. Particularly preferably, during this displacement, pivoting of the transport baskets into the respective position, i.e. either into the transfer position or into the transport position, takes place on its own and consequently automatically. In this way, it can be sufficient to equip the transfer device merely with a displacement drive that shifts the transport baskets linearly, where then during displacement pivoting takes place automatically without an additional drive. Taking into consideration the fact that the transfer device is in the pool and consequently underwater, it is very advantageous if the number of required drives can be reduced. Nevertheless, simple, fast, and automated loading and unloading of the transport baskets, and, at the same time, rapid transfer through the conveyor tube, take place within the scope of the invention. Particularly preferably, automatic pivoting during displacement occurs in connection with the pivot frames and/or control rails described. According to another suggestion of the invention, the pivot frames can be mounted so as to pivot in a common displacement frame and can be displaced with it, the pivot frames with the transport baskets set into them being positionable by displacement of the pivot frame relative to the conveyor tube, and being automatically positioned in this connection. The displacement frame itself can be guided so as to be displaceable in a (stationary) support frame, wherein one or more of the control rails described can be connected with the support frame. It lies within the scope of the invention that merely the upper transfer device or the lower transfer device is designed for two transport baskets in the embodiment described. The remaining other transfer device can be designed for merely a single transport basket. In this case, the system is preferably operated with two transport baskets. Particularly preferably, however, both the upper transfer device and the lower transfer device are configured in the manner according to the invention, so that two transport baskets can be both in the upper transfer device and in the lower transfer device. In this case, the work is performed with (precisely) three transport baskets, where a first transport basket is in the upper transfer device, a second transport basket is in the lower transfer device, and a third transport basket is either in the conveyor tube or in one of the transfer devices. In this manner, particularly rapid transfer of the fuel elements and consequently an accelerated fuel element exchange take place, so that down time of the reactor for a fuel element exchange can be clearly reduced. This can be achieved with simple and reliable design and handling of the apparatuses described. Preferably, the transfer system is equipped with a cable hoist that has a traction cable guided through the conveyor tube for raising and lowering the transport baskets through the conveyor tube. Such a cable hoist is characterized by simple and reliable handling. It can be excellently combined with the transfer devices according to the invention. This particularly holds true when a lift carriage is guided through the conveyor tube, on which carriage the traction cable is connected and onto which a transport basket can be set for transport. The lift carriage is consequently provided underneath the transport basket during transport, so that the cable hoist, according to the invention, does not engage directly on the transport baskets, at the top, but rather (indirectly) through the lift carriage. Such an embodiment is practical, when, among other things, the conveyor tube, at its upper end, can be closed off with a blocking device, and if a cable inlet port is laterally integrated into the conveyor tube below this upper blocking element, through which inlet the traction cable passes from the tube interior to the cable winch. In this embodiment, the cable of the cable hoist is consequently introduced into the conveyor tube from the cable winch not on the end, but rather through an (upper) lateral cable inlet port, so that the cable feed into the conveyor tube takes place below an upper (fully closing) blocking element, for example a slide. This has the advantage that the upper blocking element can basically be closed again after introduction of the fuel elements into the conveyor tube, because transport is possible, using the cable hoist, even when the upper blocking element is closed. The upper blocking element consequently only has to be opened for a short period of time if the fuel elements must be lowered or raised past the upper blocking element. In connection with the lift carriage described, the possibility exists that the lift carriage does not have to move completely out of the conveyor tube at the top, but rather merely into the region of the upper end of the conveyor tube, since the lateral cable inlet port that engages on the lift carriage is provided there. Preferably, not only an upper blocking element is provided, but also a lower blocking element at the lower tube end, and these blocking elements, as fully closing blocking elements, for example as slides, can close the tube off in liquid-tight manner. Furthermore, it can be practical to integrate into the conveyor tube one or more (partially closing) blocking elements that each have a cable passage through which the traction cable can pass in the closed position. Thus, one or more, for example two partially closing intermediate blocking elements can be provided between the upper (fully closing) blocking element and the lower (fully closing) blocking element, and can be equipped, for example as ball valves, with a cable passage, for example a hole in the valve ball. A partially closing blocking element is a blocking element that, while it can be brought into a completely open position on the one hand and into a closed position on the other hand, still has a cable passage in the closed position (closing position), and consequently a correspondingly dimensioned opening (for example a groove), so that the traction cable of the cable hoist can pass through the blocking element for perfect transfer. The slight leaks that might occur due to the cable passage, in this connection, can be accepted and evened out again by appropriate pumping. The deciding factor is the fact that such leaks can be reduced to a minimum, using the partially closing blocking elements. In this connection, pneumatic actuators, for example, can be used for the blocking elements. Alternatively, however, electrical or hydraulic drives can also be used. Furthermore it is practical that the transport baskets and/or the lift carriage is/are guided on guide rails, by guide elements, for example guide rollers, which rails are mounted on the inside wall of the conveyor tube. Furthermore it can be practical to provide guide rails for at least the transport baskets, and, if applicable, also for the lift carriage, also in the region of the pivot frames. FIG. 1 shows in a simple view a nuclear reactor facility having a reactor building 1 in which an unillustrated nuclear reactor, for example a boiling-water reactor, is provided. A fuel-element storage unit 2 is provided next to the reactor building 1. An upper pool 3 filled to an upper level with liquid lies in the reactor building. A lower pool 4 filled to a lower liquid level is provided near the fuel-element storage unit 2. During a fuel element exchange, (spent) fuel elements 5, for example, are moved by a transfer system 6 out of the reactor, through the upper pool 3, and into the region of the lower pool 4 and/or conversely new fuel elements are transported upward. To remove the fuel elements 5 from the reactor vessel, a handler 7 is provided in the reactor building 1 that can remove a fuel element 5 from the reactor vessel, for example, and transport it to the transfer system 6 in the region of the upper pool 3. To this end, the handler 7 can be equipped with for example a telescoping grab 8 that can grip a handle 9 of the fuel element 5. Similarly, a handler 10 provided in the fuel-element storage unit 2 can move the fuel elements 5 away from or to the transfer system 6. The present invention concerns itself with the transfer system 6 that can transport the fuel elements 5 between the upper pool 3 of the reactor building 1 and the lower pool 4 of the fuel-element storage unit 2, the liquid level of the upper pool lying above the liquid level of the lower pool. The transfer system 6 has a conveyor tube 11 extending at an acute angle to the vertical between the upper and lower pools. Furthermore, the transfer system has a plurality of transport baskets 12, i.e. the fuel elements themselves are transported through the conveyor tube 11 not directly, but rather in the transport baskets 12, and in this embodiment four fuel elements can be set into a transport basket. Furthermore, the transfer system 6 has a cable hoist 13 in turn that has a cable winch 14, a drive 15, and a traction cable 16 and that works in the conveyor tube 11 for raising and lowering the transport baskets 12. The conveyor tube 11 is equipped with a plurality of blocking elements 17, 18, and 19 that can close off the tube passage to prevent or minimize flow of liquid from the upper pool 3 into the lower pool 4. The conveyor tube 11 is provided at its upper end with an upper fully closing blocking element 17, and, at its lower end, with a lower fully closing blocking element 18, these blocking elements 17, 18 being configured as slides. Sufficient space is available at these locations for use of slides. A plurality of further blocking elements, namely a plurality of partially closing intermediate elements 19, are provided between the upper blocking element 17 and the lower blocking element 18; in this embodiment, these are configured as ball valves. Ball valves are used at these locations because the conveyor tube 12 runs inside a concrete sleeve and relatively little space is available. The difference between the fully closing blocking elements 17 and 18 and the partially closing blocking elements 19 is that the partially closing blocking elements are provided with a cable passage 30 through which the traction cable 16 can pass in the closed position of the blocking element 19. In contrast, the fully closing blocking elements 17 and 18 are configured without such cable passages. The blocking elements 17, 18, and 19 must be opened completely to be able to move a transport basket 12 through the respective locations. The partially closing blocking elements 19 can, however, be closed after the transport basket 12 has passed because the traction cable 16 of the cable hoist passes through the cable passage 30 even in the closed valve position. The transfer system 6 furthermore has a lift carriage 20, i.e. the traction cable 16 of the cable hoist 13 does not engage the transport baskets 12, but rather is connected with the separate lift carriage 20 that engages underneath the transport basket 12, i.e. the transport basket 12 is set onto the lift carriage 20 during transfer. The advantages of this configuration will be discussed below. Furthermore, the transfer system 6 according to FIG. 2 has an upper transfer device 21 in the upper pool 3 for loading the fuel elements 5 into and/or unloading them from the baskets 12. In the lower pool 4, the transfer system 6 has a lower transfer device 22 (FIG. 3) for loading the fuel element 5 into and/or unloading them from the baskets 12. For the transfer of the fuel elements 5 from the upper pool 3 into the lower pool 4, first a transport basket 12 is loaded with fuel elements 5 by the upper transfer device 21. Then, the transport basket 12 is transported by the upper transfer device 21 through the conveyor tube 11 into the region of the lower transfer device 22, specifically using the cable hoist 13. In the lower transfer device 22, the fuel elements 5 can then (for example using the handler 10) be removed from the transport basket 12. Subsequently, the transport basket 12 (for example empty without fuel elements) can be transported back up through the conveyor tube 11, again using the cable hoist 13. In order to guarantee a rapid and thereby efficient transfer, the upper transfer device 21 and the lower transfer device 22 can each be loaded with two of the baskets 12 that can be displaced horizontally for positioning above or below the conveyor tube 11, and, during displacement can pivot, preferably automatically, between a vertical transfer position and an angled transport position. The transport baskets 12 are consequently loaded with the fuel elements 5 in the vertical transfer position and accordingly the fuel elements 5 are also removed from the transport baskets 12 in this vertical transfer position. For transport through the conveyor tube 11, the transport baskets 12 are then pivoted into the angled transport position. In this embodiment, this pivoting of the transport baskets 12 takes place automatically during displacement of the transport baskets 12. This will be explained first using the upper transfer device 21 as an example. The upper transfer device 21 is equipped with two pivot frames 23 into each of which a transport basket can be set and in which the transport baskets 12 can pivot between a vertical transfer position and an angled transport position. In this connection, the two pivot frames 23, with the transport baskets 12 provided in them, are mounted so as to pivot about a common (horizontal) axis A in opposite directions. The two pivot frames 23 can be jointly displaced horizontally, and can be automatically pivoted by the transport baskets 12 set into them, during displacement, specifically in opposite directions. To this end, the two pivot frames 23 are mounted so as to pivot in a common displacement frame 24 and can be displaced with it, the pivot frames with the transport baskets 12 set into them being positionable relative to the conveyor tube by displacement of the displacement frame 24 in the support frame 25, and, in this connection, being automatically pivotable. This is possible by means of control rails 26 that are curved in this embodiment, the pivot frames 23 or the transport baskets 12 set into them being guided in the control rails 26 during displacement such that the transport baskets 12 pivot automatically because the transport baskets 12 in this embodiment have control pins 27 on the lower side that engage into the control rails 26. In this connection, the support frame 25 has two guide rails 28 in which the displacement frame 24 is guided horizontally and linearly, specifically by a drive 29. The lower transfer device 22 is configured similarly, and also has a support frame 25, a displacement frame 24, and two pivot frames 23. Preferably, three transport baskets are provided. The method of functioning of the transfer system 6 according to the invention will now be explained using FIGS. 4 to 10a and 10b. First, the fuel elements 5 are removed from the reactor vessel using the handler 7 and transported into the region of the upper transfer device 21. There, a transport basket 12 is in a pivot frame 23, in the vertical transfer position, so that four fuel elements can be set into the transport basket 12 (see FIG. 4). This transport basket 12 is situated, in the vertical transfer position laterally offset next to the conveyor tube 11. An empty transport basket 12 is above the conveyor tube 11, for example, in the angled transport position where this empty transport basket 12 was transported upward during loading of the other transport basket from the region of the lower transfer device 22, for example. In order to now position the filled transport basket 12 above the conveyor tube 11, the displacement frame 24 with the pivot frames 23 provided in it is displaced. This is evident from a comparison of FIGS. 6a and 6b that show the upper transfer device 21 in different functional positions and in different views. The transport baskets 12 engage into the control rails 26 with their lower control pins 27, so that during displacement of the displacement frame 24, and thereby also of the pivot frames 23, these pivot frames 23 with the transport baskets 12 set into them pivot in opposite directions, so that the filled transport basket 12 is not only positioned above the conveyor tube 11, but also, at the same time, pivoted from the vertical transfer position into the angled transport position. The lift carriage 20, with which an empty transport basket 12 was previously transported from below to above, is consequently still in the region of the upper end of the conveyor tube 11, so that the filled transport basket 12 is set onto the lift carriage 20 during displacement of the displacement frame 24. The upper blocking element 17 is open, in this connection (see FIG. 5). Now the lift carriage 20, with the filled transport basket 12 set onto it, can be lowered using the cable hoist 13 (see FIGS. 7a and 7b). The lower blocking element 18 is closed, at first. The same holds true for the intermediate valves (ball valves 19) inside the conveyor tube 11. During lowering of the lift carriage 20 with the transport basket 12, the intermediate valves 19 are then individually opened step by step, in the manner of a lock system, and, after the lift carriage with transport basket 12 has moved through, are immediately closed again. This is possible because the intermediate valves 19 each have a cable passage 30 through which the traction cable 16 can pass in the closed position of this valve. In this manner, flow of liquid out of the upper pool 3 into the lower pool 4 during transport is prevented (see FIGS. 8a and 8b). Before the transport basket 12 can exit the conveyor tube 11 at the lower end, the lower slide 18 is opened. In this regard, reference is made to FIG. 9 that shows the conveyor tube 11 in a view at an angle from below. It can be seen that the transport basket 12 is lowered below the lower intermediate valve 19, where this intermediate valve 19 is closed. The lower slide 18 is opened. The lift carriage 20 with the transport basket 12 set onto it then exits from the conveyor tube 11 on the lower side, and consequently enters into the lower transfer device 22. In this regard, reference is made to FIGS. 10a and 10b. Consequently, the filled transport basket 12 is in the angled transport position in the lower transfer device 22, and furthermore, once again an empty transport basket 12 is provided in the vertical transfer position. The displacement frame 24 can be displaced again, so that the transport baskets are positioned and pivoted accordingly. The filled transport basket 12 consequently assumes the vertical transfer position, while the empty transport basket 12 assumes the angled transport position below the conveyor tube 11. Now the empty transport basket 12 can once again be transported upward with the lift carriage 20. During the same time, the filled transport basket 12 can be unloaded by the lower handler 10. This makes it clear that the fuel elements can be transferred rapidly. In particular, loading can take place in the upper transfer device, and unloading can take place in the lower transfer device, at the same time. In particular, transport of a further transport basket 12 can be done by the transfer system during loading and unloading. Consequently, at least two transport baskets are preferably provided. In this embodiment, however, three transport baskets are provided, one transport basket always being in the upper transfer device and one transport basket in the lower transfer device, while a third transport basket can be transported between the upper transfer device and the lower transfer device. FIG. 2, further shows that the traction cable 16 of the cable hoist 13 does not enter into the conveyor tube through the upper end of the conveyor tube 11, but rather that the conveyor tube 11 has below the upper slide 17 a lateral cable inlet port 31 through which the traction cable 16 passes out of the tube interior to the cable winch 14, specifically through a cable guide tube 32. This cable inlet port 31 is consequently provided below the slide 17 and, in particular, below the upper transfer device 21. Such a cable inlet port is particularly practical in connection with the lift carriage 20 that, as described, is underneath the transport baskets 12. The figures furthermore show guide rails 33 inside the conveyor tube 11. The lift carriage 20 is equipped with guide elements, namely rollers 34 that are guided in these rails 33. The transport baskets are also equipped with guide elements 35 in the form of rollers also guided in the guide rails 33. Furthermore, guide rails 36 are also provided in the region of the upper transfer device 21, as are guide rails 37 in the region of the lower transfer device. The upper transfer device 21 and the lower transfer device 22 are configured to be functionally equivalent in this embodiment. They differ, in terms of design, in specific details. This relates, for example, to the pivot frames 23. The pivot frames 23 of the upper transfer device are laterally closed on all sides, while the pivot frames 23 of the lower transfer device are open on one side. This is connected with the fact that the traction cable 16 in the lower transfer device 22 must be guided past the pivot frames 23, so pivoting of the pivot frames 23 must not be hindered by the traction cable. Finally, the figures also show that the blocking elements 17, 18, and 19 are operated pneumatically. To this end, the upper slide 17 is provided with a pneumatic actuator 38. The lower slide 18 is also provided with a pneumatic actuator 39. The ball valves 19 are also provided with linearly acting pneumatic actuators 40 that engage the valve ball 42 of the valve 19 via a crank arm 41, this valve ball 42 having the cable passage 30 as described, configured as a hole of the valve ball 42. In this embodiment, pneumatic actuators are indicated. Alternatively, however, electrical or hydraulic drives can also be is used.
	abstract	Based on determined locations of Kukharev (K) regions, and the estimated times of their formation on Earth, in the atmosphere, and in space, antimatter may be produced and collected, as described by the present invention. Due to jumps in the gravitational field, various standing waves are formed from the resonances of the gravitational tides. A wave of charged particles is formed within the K region and can be setup to collide with targets comprising heavy metal atoms (or other equivalents), the colliding thereby creating antimatter particles. These antimatter particles can then be stored in various traps and used for various purposes, e.g., energy formation.
	abstract	Illustrative embodiments provide methods and systems for migrating fuel assemblies in a nuclear fission reactor, methods of operating a nuclear fission traveling wave reactor, methods of controlling a nuclear fission traveling wave reactor, systems for controlling a nuclear fission traveling wave reactor, computer software program products for controlling a nuclear fission traveling wave reactor, and nuclear fission traveling wave reactors with systems for migrating fuel assemblies.
	description	The present invention relates to a cleaning device of a porous plate for nuclear power that cleans a tube support plate for supporting a heat exchanger tube, for example, in a steam generator used as a heat exchanger in a nuclear power plant. For example, in a pressurized water reactor (PWR), light water is used as reactor coolant and neutron moderator to be high-temperature and high-pressure water that does not boil over the entire reactor internal, the high-temperature and high-pressure water is sent to the steam generator to generate steam by heat exchange, and the steam is sent to a turbine generator to generate electricity. Moreover, the steam generator is configured so that a plurality of heat exchanger tubes having an inverted U-shape is provided inside, end portions of each heat exchanger tube are supported by a tube sheet, and an inlet side channel head and an outlet side channel head of primary cooling water are formed at a lower end portion of a body portion. Further, an inlet portion of secondary cooling water is provided in the body portion to be located above a tube bundle shroud, a gas-water separator and a moisture separator are vertically arranged side by side, and a steam outlet is provided above the gas-water separator and the moisture separator. As such a steam generator, for example, there is a steam generator described in Patent Literature 1 below. Patent Literature 1: Japanese Laid-open Patent Publication No. 2007-147138 In the above-described steam generator, the multiple heat exchanger tubes provided within the body portion are supported by the plurality of tube support plates and the tube sheet. By inserting the heat exchanger tubes into mounting holes formed in large numbers, the tube support plate supports the multiple heat exchanger tubes to prevent vibration. Moreover, since the tube support plate is manufactured so that the multiple mounting holes are machined on a disk member, cutting oil, chips, dust and the like adhere to the tube support plate, and it is not possible to directly mount the tube support plate to the body portion as it is, from the viewpoint of foreign substance management or subsidiary material management. The present invention has been made to solve the above-described problems, and an object thereof is to provide a cleaning device of a porous plate for nuclear power that can efficiently remove the adhered foreign substances. According to an aspect of the present invention, a cleaning device of a porous plate for nuclear power includes: a cleaning tank that is capable of storing a cleaning liquid therein and is capable of housing the porous plate in an upright state; a rotation device that is capable of rotating the porous plate within the cleaning tank; and an ultrasonic wave oscillation device that irradiates the porous plate within the cleaning tank with ultrasonic waves. Therefore, the porous plate is rotated by the rotation device in an upright state by being immersed in the cleaning liquid in the cleaning tank, and by irradiating with ultrasonic waves from the ultrasonic wave oscillation device, the adhered cutting oil, chips, dust and the like are removed. Thus, it is possible to efficiently remove the adhered foreign substances. Advantageously, in the cleaning device, the ultrasonic wave oscillation device includes an ultrasonic transducer that is disposed on an inner wall surface of the cleaning tank to face one of a front part and a back part of the porous plate, and a reflecting plate that is disposed on the inner wall surface of the cleaning tank to face the other of the front part or the back part, and the ultrasonic wave oscillation device is provided to be movable along a vertical direction by a moving device. Thus, since the porous plate is irradiated with ultrasonic waves from the ultrasonic transducer moving in the vertical direction while rotating, in the upright state of being immersed in the cleaning liquid in the cleaning tank, and the porous plate is irradiated with ultrasonic waves reflected from the reflecting plate, it is possible to remove cutting oil, chips, dust and the like over the entire surface of the porous plate, to improve the cleaning efficiency, and to miniaturize the ultrasonic transducers, thereby being able to miniaturize the device and reduce the cost. Advantageously, in the cleaning device, a plurality of drive rollers forming the rotation device is provided at a lower portion of the interior of the cleaning tank, and a plurality of support rollers configured to prevent collapse of the porous plate is provided at an upper portion of the interior of the cleaning tank. Thus, since the porous plate is rotatable by a plurality of drive rollers provided at the lower portion, and collapse is prevented by a plurality of support rollers provided at the upper portion, it is possible to safely and efficiently clean the porous plate. Advantageously, in the cleaning device, the support rollers include a first pair of guide rollers that supports the front part and the back part of the porous plate, and a second pair of guide rollers that supports an outer peripheral end surface of the porous plate. Thus, since the front part and the back part of the porous plate are supported by the first guide roller, and the outer peripheral end surface thereof is supported by the second guide roller, it is possible to safely support the porous plate. Advantageously, in the cleaning device, a heating device configured to heat the cleaning liquid is provided at the lower portion of the interior of the cleaning tank. Therefore, by heating the cleaning liquid in the cleaning tank using a heating device, the cleaning effect of the cleaning liquid is improved, and since the cleaning liquid is stirred by convection action, it is also possible to improve the cleaning effect of the porous plate in this respect. Advantageously, in the cleaning device, a supply path configured to supply the cleaning liquid to the interior of the cleaning tank, and a discharge path configured to discharge the cleaning liquid within the cleaning tank. Therefore, it is possible to supply the cleaning liquid to the cleaning tank from the supply path and discharge the cleaning liquid in the cleaning tank from the discharge path, thereby being able to improve the cleaning effect by circulating the cleaning liquid, and to suppress the contamination of the cleaning liquid in the cleaning tank. According to the cleaning device of the porous plate for nuclear power of the present invention, since the cleaning tank that is capable of storing the cleaning liquid therein and housing the porous plate in a upright state, a rotation device that is capable of rotating the porous plate in the cleaning tank, and an ultrasonic wave oscillation device that irradiates the porous plate in the cleaning tank with ultrasonic waves, it is possible to efficiently remove the foreign substances such as adhered cutting oil, chips, and dust. Preferred embodiments of the cleaning device of the porous plate for nuclear power of the present invention will be described below in detail with reference to the accompanying drawings. In addition, the present invention is not limited to the embodiments, and when there is a plurality of embodiments, a configuration obtained by combining each embodiment may be included. FIG. 1 is a front view of a cleaning device of the porous plate for nuclear power according to an embodiment of the present invention, FIG. 2 is a plan view of the cleaning device of the porous plate for nuclear power of this embodiment, FIG. 3 is a side view of the cleaning device of the porous plate for nuclear power of this embodiment, FIG. 4 is a cross-sectional view of the cleaning tank in the cleaning device of the porous plate for nuclear power of this embodiment, FIG. 5 is a front view illustrating a rotation device of the cleaning tank, FIG. 6 is a side view of the cleaning tank, FIG. 7 is a plan view of the cleaning tank, FIG. 8 is a schematic view of a guide roller, FIG. 9 is a schematic diagram of an auxiliary roller, FIG. 10-1 is a plan view illustrating a prepared hole of a tube support plate, FIG. 10-2 is a plan view illustrating a prepared hole and an R chamfered portion of the tube support plate, FIG. 10-3 is a plan view illustrating a broached hole of the tube support plate, FIG. 11 is a flow chart illustrating a method of manufacturing a tube support plate, and FIG. 12 is a schematic block diagram illustrating a steam generator of this embodiment. The nuclear reactor of this embodiment is a pressurized water reactor (PWR) that uses light water as reactor coolant and neutron moderator to be high-temperature and high-pressure water that does not boil through the entire reactor internal, sends the high-temperature and high-pressure water to the steam generator to generate steam by heat exchange, and sends the steam to the turbine generator to generate electricity. In a nuclear power plant having the pressurized water reactor of this embodiment, the pressurized water reactor and the steam generator are housed in a reactor containment vessel, and the pressurized water reactor and the steam generator are connected to each other via a cooling water pipe. Therefore, the primary cooling water is heated by fuel (atomic fuel), and the high-temperature primary cooling water is sent to the steam generator via the cooling water pipe. Heat exchange between the high-pressure and high-temperature primary cooling water and the secondary cooling water is performed in the steam generator, and the cooled primary cooling water is returned to the pressurized water reactor through the cooling water pipe. In the steam generator 13 applied to the nuclear power plant thus configured, as illustrated in FIG. 12, a body portion 41 has a closed hollow cylindrical shape, and a lower part thereof has a slightly smaller diameter than an upper part. A tube bundle shroud 42 having a cylindrical shape at a predetermined interval from an inner wall surface is provided in the lower part of the body portion 41. A plurality of tube support plates 43 is disposed inside the tube bundle shroud 42 in response to a predetermined height position, a tube sheet 44 is fixed below the tube support plate 43, and each of the tube support plates 43 is supported by a plurality of stay rods 45 that extends upward from the tube sheet 44. Moreover, a heat exchanger tube group 47 formed of a plurality of heat exchanger tubes 46 having an inverted U-shape is provided inside the tube bundle shroud 42, end portions of each of the heat exchanger tubes 46 are expanded and supported by the tube sheet 44, and intermediate portions thereof are supported by the tube support plates 43. Further, the body portion 41 is partitioned into an entrance chamber 49 and an exit chamber 50 by a partition 48 below the tube sheet 44, is formed with an inlet nozzle 51 and an outlet nozzle 52, one end portions of each of the heat exchanger tubes 46 are in communication with the entrance chamber 49, and the other end portions thereof are in communication with the exit chamber 50. Further, the body portion 41 is provided with a gas-water separator 53 that separates the water supply into steam and hot water above the heat exchanger tube group 47, and a moisture separator 54 that removes the moisture of the separated steam to be a state close to the dry steam. Further, a water supply tube 55 configured to perform the water supply of secondary cooling water is inserted into the body portion 41 between the heat exchanger tube group 47 and the gas-water separator 53, and a steam outlet 56 is formed in a ceiling portion. Moreover, the body portion 41 is provided with a water supply passage. The secondary cooling water supplied to the interior from the water supply tube 55 flows down between the water supply passage and the tube bundle shroud 42 and circulates upward at the tube sheet 44, and when rising inside the heat exchanger tube group 47, heat exchange between the secondary cooling water and the hot water (primary cooling water) flowing through each heat exchanger tube 46 is performed. Therefore, the primary cooling water heated by the pressurized water reactor is sent to the entrance chamber 49 of the steam generator 13 through the cooling water pipe, circulates through the multiple heat exchanger tubes 46, and leads to the exit chamber 50. Meanwhile, the secondary cooling water cooled by the condenser is sent to the water supply tube 55 of the steam generator 13 through the cooling water pipe, and is subjected to heat exchange with the hot water (primary cooling water) flowing in the heat exchanger tube 46 through the body portion 41. That is, heat exchange between the high-pressure and high-temperature primary cooling water and the secondary cooling water is performed inside the body portion 41, and the cooled primary cooling water is returned to the pressurized water reactor from the exit chamber 50 through the cooling water pipe. Meanwhile, the secondary cooling water subjected to heat exchange with the high-pressure and high-temperature primary coolant rises inside the body portion 41, is separated into steam and hot water in the gas-water separator 53, and is sent to the steam turbine through the cooling water pipe after removing the moisture of the steam in the moisture separator 54. In the steam generator 13 having the above-described configuration, a plurality of tube support plates 43 is provided at the lower part of the body portion 41 at predetermined intervals, and the tube sheet 44 is provided at the lower end portion thereof. Moreover, the end portions of the plurality of heat exchanger tubes 46 forming the heat exchanger tube group 47 are fixed to the multiple mounting holes formed on the tube sheet 44, and the intermediate portions thereof are supported by the multiple mounting holes 61 formed in each of the tube support plates 43. Since it is necessary to convey the secondary cooling water (steam) heated by the primary cooling water to the upper part, the respective mounting holes 61 of the respective tube support plates 43 have the different forms that have a plurality of notches on the outer peripheral side of the circular form as the cross-sectional shape of the heat exchanger tube 46. First, in the plurality of mounting holes 61 formed in the tube support plate 43, first, as illustrated in FIG. 10-1, by performing the prepared hole machining on the tube support plate 43 by a prepared hole machining device, a prepared hole 62 is formed. Next, as illustrated in FIG. 10-2, by performing the R chamfering on the end portion in the axial direction of the prepared hole 62 by the R chamfering device, an R chamfered portion 63 is formed. Next, as illustrated in FIG. 10-3, by broaching the prepared hole 62 by the broaching device, broached holes 64 having the different shapes are formed. Moreover, by chamfering the end portion in the axial direction of the broached holes 64 by the polishing apparatus of this embodiment, the mounting hole 61 is formed. The tube support plate 43 is cleaned after various types of machining are performed. As illustrated in FIGS. 1 to 3, a cleaning device 71 of the porous plate for nuclear power of this embodiment cleans the tube support plate as a porous plate, and has a first cleaning tank 72, a second cleaning tank 73, and a post-treatment chamber 74. The respective cleaning tanks 72 and 73, and the post-treatment chamber 74 are disposed at predetermined intervals. In this case, the cleaning liquid is stored inside the first and second cleaning tanks 72 and 73, after the prepared hole machining, the R chamfering, and broaching of the tube support plate 43 are performed, the tube support plate 43 is cleaned while being immersed in the first cleaning tank 72, and after chamfering of the tube support plate 43 is performed, the tube support plate 43 is cleaned while being immersed in the second cleaning tank 73. Meanwhile, after the first and second cleaning tanks 72 and 73 are used, rinsing and drying of the tube support plate 43 are performed in the post-treatment chamber 74. The first and second cleaning tanks 72 and 73 have substantially the same configuration, and are arranged side by side. The lower portions of the first and the second cleaning tanks 72 and 73 have a semicircular shape, and the upper portions thereof have a rectangular shape. The first and the second cleaning tanks 72 and 73 are set to have an inner diameter and a thickness capable of housing the tube support plate 43. The post-treatment chamber 74 is arranged alongside the second cleaning tank 73, similarly, the lower portion thereof has a semicircular shape, and the upper portion thereof has a rectangular shape, and the post-treatment chamber 74 is set to have an inner diameter and a thickness capable of housing the tube support plate 43. A crane 75 is arranged above the respective cleaning tanks 72 and 73 and the post-treatment chamber 74 to freely move, and the crane 75 is able to hang the tube support plate 43 by a hook 76. Moreover, the tube support plate 43 is hung and supported by the crane 75, and is conveyed among the first cleaning tank 72, the second cleaning tank 73, and the post-treatment chamber 74. In addition, a construction passage 77 and a stair 78 which allow an operator to move are provided around the respective cleaning tanks 72 and 73, and the post-treatment chamber 74. The respective cleaning tanks 72 and 73, and the post-treatment layer 74 are described here, but since each of them has substantially the same configuration, the second cleaning tank 73 will be described in detail, and the first cleaning tank 72 and the post-treatment chamber 74 will not be described. In the second cleaning tank 73, as illustrated in FIGS. 4 to 7, a cleaning tank main body 81 has a predetermined thickness so that the tube support plate 43 can be supported therein in a upright state, the lower portion thereof has a semicircular shape, and the upper portion thereof has a rectangular shape and is open. That is, the cleaning tank main body 81 includes a pair of vertical wall portions 81a, a pair of side wall portions 81b, and a lower casing portion 81c, and is formed with an opening 81d at an upper end portion thereof. Moreover, the cleaning tank main body 81 is fixed onto a base 82, is supported by a fixing bracket 83, has a width, a thickness, and a height greater than an outer diameter of the tube support plate 43, and is capable of storing the cleaning liquid therein. The cleaning tank main body 81 is provided with a rotation device 84 capable of rotating the tube support plate 43 at the lower portion thereof. In the rotation device 84, on the base 82, left and right mounts 85 are fixed adjacent to the lower casing portion 81c on one side of the vertical wall portion 81a in the cleaning tank main body 81, driven shafts 87 are each rotatably supported on the mounts 85 by support brackets 86, and driven sprockets 88 are each integrally and rotatably fixed to the respective driven shafts 87. Moreover, a chain 89 is wound around the left and right driven sprockets 88 to allow the driven sprockets 88 to synchronously rotate. Further, on the base 82, a driving motor 90 is fixed to be situated between the left and right mounts 85, and a driving sprocket 91 is mounted on the drive shaft. Moreover, a chain 92 is wound around the driving sprocket 91 and one driven sprocket 88, thereby being able to transmit the driving force. Moreover, the left and right driven shafts 87, to which the driven sprockets 88 are fixed, horizontally penetrate the left and right vertical wall portions 81a, and the driving rollers 93a are fixed inside the cleaning tank main body 81, respectively. In this embodiment, two driving rollers 93 are provided, but one drive roller, or three or more drive rollers may be provided. Therefore, when driving the driving motor 90, the driving sprocket 91 rotates, and the rotational force is transmitted to one driven sprocket 88 via the chain 92 to rotate the one driven sprocket 88. When one driven sprocket 88 rotates, the rotational force is transmitted to the other driven sprocket 88 to rotate the other driven sprocket 88. For that reason, the respective driving rollers 93 rotate via the driven shafts 87 by the rotational force of the respective driven sprockets 88, thereby being able to rotate the tube support plate 43. At the upper portion of the cleaning tank main body 81, a plurality of first guide rollers (support roller) 94 is provided which prevents the collapse in the thickness direction of the tube support plate 43. That is, as illustrated in detail in FIG. 8, in the cleaning tank main body 81, a pair of support tubes 95 extends from the opposing positions of the upper inner wall surface of each side wall portion 81b, L-shaped mounting brackets 96 are fixed to each of the leading end portions, and the first guide rollers 94 are rotatably supported to the respective mounting brackets 96 by the support shafts 97 parallel to each other, respectively. The two first guide rollers 94 come into contact with the front part and the back part of the tube support plate 43, and can rotate while supporting the tube support plate 43 to interpose the tube support plate 43 therebetween. Furthermore, at the lower portion of the cleaning tank main body 81, a plurality of second guide rollers (support roller) 98 is provided which prevents collapse in the radial direction of the tube support plate 43. That is, as illustrated in detail in FIG. 9, in the cleaning tank main body 81, a pair of support tubes 99 extends from the opposing positions of the lower inner wall surface of each side wall portion 81b, planar mounting brackets 100 are fixed to each of the leading end portions, and the second guide rollers 98 are rotatably supported by the two parallel support shafts 101 passing through the respective mounting brackets 100, respectively. The two second guide rollers 98 can rotate while supporting the outer peripheral end surface of the tube support plate 43 so as to abut against the outer peripheral end surface. The first pair of guide rollers 94 is disposed at a predetermined interval in the lateral direction at the upper portion of the cleaning tank main body 81 to interpose the outer peripheral portion of the tube support plate 43, and by rotating synchronously with the rotation of the tube support plate 43, it is possible to prevent collapse in the thickness direction of the tube support plate 43. The second pair of guide rollers 98 is disposed at a predetermined interval in the lateral direction at the lower portion of the cleaning tank main body 81 to support the outer peripheral end surface part of the tube support plate 43, and by rotating synchronously with the rotation of the tube support plate 43, it is possible to prevent collapse in the radial direction of the tube support plate 43. The cleaning tank main body 81 is provided with an ultrasonic wave oscillation device 111 that irradiates the tube support plate 43 supported therein with ultrasonic waves. That is, in the ultrasonic wave oscillation device 111, the support plate 112 is fixed to the outer wall surface of one vertical wall portion 81a of the cleaning tank main body 81, and a winch (moving device) 113 is installed on the support plate 112. In the respective winches 113, a traction rope 114 is pulled upward and enters the cleaning tank main body 81 via the guide rollers 115, and an ultrasonic transducer 116 is connected to the end portion of the traction rope 114. The ultrasonic transducers 116 are each disposed on the inner wall surface of the cleaning tank main body 81 to face the front part of the tube support plate 43 supported within the cleaning tank main body 81, and by operating the winch 113 to move the traction rope 114, the ultrasonic transducers 116 are movable in the vertical direction. Furthermore, a reflecting plate 117 is fixed to the cleaning tank main body 81 to face the ultrasonic transducer 116 along the vertical direction of the inner wall surface of the other vertical wall portion 81a. Furthermore, two water tubes 121 are disposed at the intermediate portion in the vertical direction of the cleaning tank main body 81 along the horizontal direction. The two water tubes 121 are disposed to face the front part side and the back part side of the tube support plate 43, and are supported on the inner wall surface of each side wall portion 81b. Moreover, a supply tube (supply path) 122 passing through the side wall portion 81b of the cleaning tank main body 81 from the outside is connected to one end portion of each water tube 121, and the other end portion of each water tube 121 is closed. Further, the water tube 121 is provided with injection nozzles 123 at predetermined intervals along the longitudinal direction, and the injection direction of the respective injection nozzles 123 is the tube support plate 43 side, but the upper part and the lower part thereof are provided to alternately slope (for example, 45°). Furthermore, at the intermediate portion in the vertical and horizontal directions of the cleaning tank main body 81, a first discharge tube (exhaust path) 124 is provided to pass through the side wall portion 81b from the outside. Furthermore, the cleaning tank main body 81 is provided with a second discharge tube (discharge path) 125 to pass through the bottom of the lower casing portion 81c. Moreover, a level gauge tube 126 is disposed on the side of the cleaning tank main body 81, and the lower portion of the level gauge tube 126 is connected to the lower portion of the cleaning tank main body 81 via an on-off valve 127 to be able to detect the storage amount of the cleaning liquid in the cleaning tank main body 81. Moreover, the respective discharge tubes 124 and 125 are connected to a discharge pipe 137 having an on-off valve 135 and a strainer 136 via the pipes 133 and 134 having on-off valves 131 and 132, the discharge pipe 137 is connected to the supply pipe 139 via a pump 138, and the supply pipe 139 is provided with a valve 140 and is connected to the supply tube 122. Further, a storage tank 141 that stores the cleaning liquid is provided, a return pipe 142 to the storage tank 141 from the downstream side of the pump 138 is provided, and a refill pipe 143 to the upstream side of the pump 138 from the storage tank 141 is provided. Therefore, when driving the pump 138, the cleaning liquid in the cleaning tank main body 81 is discharged from the respective discharge tubes 124 and 125 through the discharge pipe 137 after removing foreign substances in the cleaning liquid by the strainer 136, the cleaning liquid is supplied to each water tube 121 from the supply tube 122 through the supply pipe 139, and it is possible to supply the cleaning liquid into the cleaning tank main body 81 from the plurality of injection nozzles 123. Furthermore, at the lower portion of the cleaning tank main body 81, a heating device 151 that heats the cleaning liquid is provided. The heating device 151 is, for example, an electrical heater, and a heating unit 152 is inserted into the heating device 151 from the lower casing portion 81c of the cleaning tank main body 81. This heating device 151 enables the cleaning liquid in the cleaning tank main body 81 to be heated, and enables the cleaning liquid in the cleaning tank main body 81 to be stirred by generating convection in the cleaning liquid. In addition, the first cleaning tank 72 has substantially the same configuration as the above-described second cleaning tank 73, but the post-treatment chamber 74 may be provided with a shower device (rinsing device) and an air blower, although not illustrated, rather than the supply path and the discharge path of the cleaning liquid. As described above, as illustrated in FIG. 11, at step S11, the tube support plate 43 performs the prepared hole machining on the tube support plate 43 by the prepared hole machining device to form the prepared hole 62. At step S12, by performing the R chamfering on the end portion in the axial direction of the prepared hole 62 by the R chamfering device, the R chamfered portion 63 is formed. At step S13, by broaching the prepared hole 62 by the broaching device, the broached holes 64 having the different shapes are formed. At step S14, primary cleaning of the tube support plate 43 is performed by the first cleaning tank 72 of the cleaning device 71. At step S15, by chamfering the end portion in the axial direction of the broached hole 64 by the polishing apparatus, the mounting holes 61 are formed. At step S16, secondary cleaning of the tube support plate 43 is performed by the second cleaning tank 73 of the cleaning device 71. At step S17, after performing various inspections as finishing, at step S18, tertiary cleaning of the tube support plate 43 is performed by the second cleaning tank 73 of the cleaning device 71, and at step S19, the tube support plate 43 is stored. Moreover, at a predetermined time, at step S20, final cleaning of the tube support plate 43 is performed by the second cleaning tank 73 and the post-treatment chamber 74 of the cleaning device 71, and at step S21, an inserting operation of the tube support plate 43 with respect to the body portion (lower portion) 41 is performed. Here, in the primary cleaning, the secondary cleaning, and the tertiary cleaning using the cleaning device 71, the tube support plate 43 is merely immersed in the cleaning liquid in the first cleaning tank 72 or the second cleaning tank 73, and, in the final cleaning using the cleaning device 71, the tube support plate 43 rotates and is irradiated with ultrasonic waves while being immersed in the cleaning liquid of the second cleaning tank 73. That is, in the final cleaning using the cleaning device 71, as illustrated in FIGS. 4 to 7, the tube support plate 43 is lifted by the crane 75 and is inserted into the second cleaning tank 73. Then, the lower portion of the tube support plate 43 is supported by the driving roller 93 within the cleaning tank main body 81, the upper portion thereof is supported by the first guide roller 94, and the side portion thereof is supported by the second guide roller 98. In this case, a predetermined quantity of cleaning liquid is stored within the cleaning tank main body 81, and the tube support plate 43 is immersed in the cleaning liquid. In this state, by driving the driving motor 90 to rotate the driving roller 93, the supported tube support plate 43 is rotated. At this time, since the upper portion of the tube support plate 43 is interposed by the first guide rollers 94, and the side portion thereof is interposed by the second guide rollers 98, the tube support plate 43 stably rotates without collapsing. Furthermore, the tube support plate 43 rotates within the cleaning tank main body 81, and simultaneously, by operating the winch 113 to move the traction rope 114 back and forth, the ultrasonic transducer 116 is moved back and forth along the vertical direction. Then, ultrasonic waves from the ultrasonic transducer 116 are diffused at a predetermined angle and radiated to the front part of the tube support plate 43, a part of the ultrasonic waves from the ultrasonic transducer 116 reaches the reflecting plate 117 through each mounting hole 61 of the tube support plate 43, and the ultrasonic waves reflected by the reflecting plate 117 are irradiated to the back part of the tube support plate 43. Therefore, foreign substances such as cutting oil or chips or dust adhering to the front part and the back part are peeled off the tube support plate 43 by the cavitation effect. At this time, since the cleaning liquid in the cleaning tank main body 81 is heated by the heating device 151, and the cleaning liquid is stirred by the generated convection, the cleaning effect of the tube support plate 43 is improved. Further, if necessary, the pump 138 is driven to discharge the cleaning liquid in the cleaning tank main body 81 from each of the discharge tubes 124 and 125 and remove the foreign substances within the cleaning liquid by the strainer 136, and the cleaning liquid is supplied to each water tube 121 from the supply tube 122 and is injected into the cleaning tank main body 81 from the plurality of injection nozzles 123. Moreover, the cleaning liquid to the cleaning tank main body 81 is replenished according to the display of the level gauge tube 126. By cleaning the tube support plate 43 within the second cleaning tank 73 at a predetermined time, the foreign substances such as cutting oil, chips, or dust adhering to the front part and the back part are removed, and the final cleaning is completed. In addition, in the cleaning device 71, the tube support plate 43 is merely immersed in the cleaning liquid in the first cleaning tank 72, and in the post-treatment chamber 74, the rinsing process using the shower device (rinsing device) and the drying process using the air blower are merely performed on the tube support plate 43. Thus, the driving roller 93, the respective guide rollers 94 and 98, the ultrasonic transducer 111 and the like may not be provided. The cleaning device of the porous plate for nuclear power of this embodiment is provided with the cleaning tanks 72 and 73 that are capable of storing the cleaning liquid therein and capable of housing the tube support plate 43 in the upright state, the rotation device 84 that is capable of rotating the tube support plate 43 in each of the cleaning tanks 72 and 73, and the ultrasonic transducer 111 that irradiates the tube support plate 43 in the cleaning tanks 72 and 73 with ultrasonic waves. Therefore, the tube support plate 43 is immersed in the cleaning liquid in the cleaning tanks 72 and 73 and is rotated by the rotation device 84 in the upright state, and the ultrasonic waves is radiated from the ultrasonic transducer 111 to remove the adhered cutting oil, chips, dust and the like. Thus, it is possible to efficiently remove the adhered foreign substances. Further, in the cleaning device of the porous plate for nuclear power of this embodiment, as the ultrasonic wave oscillation device 111, the ultrasonic transducer 116 disposed on the inner wall surface of the cleaning tanks 72 and 73 to face the front part of the tube support plate 43, and the reflecting plate 117 disposed on the inner wall surface of the cleaning tanks 72 and 73 to face the back part of the tube support plate 43 are fixed, and the ultrasonic transducer 116 is movable along the vertical direction by the winch 113. Accordingly, since the tube support plate 43 is irradiated with the ultrasonic waves from the ultrasonic transducer 116 moving in the vertical direction while rotating and the reflecting plate 117, in the upright state of being immersed in the cleaning liquid in the cleaning tanks 72 and 73, it is possible to remove the cutting oil, chips, dust and the like over the entire surface of the tube support plate 43, thereby improving the cleaning efficiency, and the ultrasonic wave oscillation device 111 can be miniaturized, thereby miniaturizing the device and reducing the cost. Further, in the cleaning device of the porous plate for nuclear power of this embodiment, the plurality of driving rollers 93 forming the rotation device 84 is provided at the lower portion of the cleaning tanks 72 and 73, and the first guide roller 94 and the second guide roller 98 are provided at the upper portion of the cleaning tanks 72 and 73, as a plurality of support rollers that prevents the collapse of the tube support plate 43. In this case, the first guide roller 94 supports the front part and the back part of the tube support plate 43, and the second guide roller 98 supports the outer peripheral end surface of the tube support plate 43. Accordingly, the tube support plate 43 is rotatable by the plurality of driving rollers 93 provided at the lower portion, and the tube support plate 43 is supported by the first pair of guide rollers 94 provided at the upper portion and the second guide rollers 98 provided at the intermediate portion to rotate in a state of being prevented from collapsing. Accordingly, it is possible to safely and efficiently clean the tube support plate 43. Further, the cleaning device of the porous plate for nuclear power of this embodiment is provided with the heating device 151 that heats the cleaning liquid, at the lower portion of the cleaning tanks 72 and 73. Therefore, since the cleaning liquid in the cleaning tanks 72 and 73 is heated by the heating device 151, the cleaning effect of the cleaning liquid is improved, and since the cleaning liquid is stirred by convection, it is also possible to improve the cleaning effect of the tube support plate 43 in this regard. Further, the cleaning device of the porous plate for nuclear power of this embodiment is provided with the water tube 121 and the supply tube 122 that supply the cleaning liquid into the cleaning tanks 72 and 73, and the discharge paths 124, 125 that discharge the cleaning liquid in the cleaning tanks 72 and 73. Therefore, it is possible to supply the cleaning liquid to the cleaning tanks 72 and 73 and discharge the cleaning liquid in the cleaning tanks 72 and 73, thereby being able to improve the cleaning effect by circulating the cleaning liquid, and to suppress the contamination of the cleaning liquid in the cleaning tank. In addition, in the above-described embodiments, the shapes of the cleaning tanks 72 and 73 are not limited to the embodiments, and as long as it is possible to immerse the tube support plate 43 in the cleaning liquid, any shape may be used. Furthermore, the cleaning tanks 72 and 73 can house one tube support plate 43, but the cleaning tanks 72 and 73 may house a plurality of tube support plates 43. Further, in this embodiment, as the ultrasonic wave oscillation device 111, the ultrasonic transducer 116 and the reflecting plate 117 are provided, and the ultrasonic transducer 116 is movable along the vertical direction by the winch 113, but is limited to this configuration. For example, the ultrasonic transducer 116 may be disposed on each of the inner wall surfaces of the cleaning tanks 72 and 73. Furthermore, the ultrasonic transducer 116 may be fixed without being movable. In addition, the ultrasonic transducer 116 and the reflecting plate 117 may be movable by the winch 113. Further, in this embodiment, the porous plate for nuclear power was described by applying the tube support plate 43 of the steam generator 13 of the nuclear power plant having the pressurized water reactor, but is not limited thereto. For example, the porous plate for nuclear power may be applied to a flow distribution plate provided between the tube support plate 43 and the tube sheet 44 in the steam generator 13, a plurality of baffle plates fixed within a superheater and an evaporator in a nuclear power plant having a fast breeder reactor at predetermined intervals, a porous plate used in the nuclear power plant having a boiling type reactor or the like. 13 STEAM GENERATOR 41 BODY PORTION 43 TUBE SUPPORT PLATE 44 TUBE SHEET 61 MOUNTING HOLE 62 PREPARED HOLE 63 R CHAMFERED PORTION 64 BROACHED HOLE 71 CLEANING DEVICE OF POROUS PLATE FOR NUCLEAR POWER 72 FIRST CLEANING TANK 73 SECOND CLEANING TANK 74 POST-TREATMENT CHAMBER 81 CLEANING TANK MAIN BODY 84 ROTATION DEVICE 90 DRIVING MOTOR 93 DRIVE ROLLER 94 FIRST GUIDE ROLLER (SUPPORT ROLLER) 98 SECOND GUIDE ROLLER (SUPPORT ROLLER) 111 ULTRASONIC WAVE OSCILLATION DEVICE 113 WINCH (MOVING DEVICE) 116 ULTRASONIC TRANSDUCER 117 REFLECTING PLATE 122 SUPPLY TUBE (SUPPLY PATH) 124 FIRST DISCHARGE TUBE (DISCHARGE PATH) 125 SECOND DISCHARGE TUBE (DISCHARGE PATH) 151 HEATING DEVICE
06160867&	summary	FIELD OF THE INVENTION This invention pertains to X-ray reflecting mirrors, especially such mirrors used for reflecting "soft" X-rays. BACKGROUND OF THE INVENTION The complex index of refraction of substances with respect to X-rays is normally expressed as n=1-.delta.-i k (where .delta. and k are real numbers). The values of .delta. and k are usually extremely small compared to 1, and the imaginary part k of the refractive index expresses X-ray absorption by the substance. For this reason, lenses made for refraction of, for example, visible light normally cannot be used for refracting X-rays. Also, because .delta. and k are extremely small, surface reflectance of the substance is extremely low. Certain X-ray-reflecting surfaces comprise a large number of layers of substances exhibiting as high an interface-amplitude reflectance as possible. The thickness of each layer can be adjusted according to optical interference theory. The number of layers can be, e.g., in the hundreds, with matching of the phase of each reflected wave. Such a reflective surface can be made by alternately layering, on a suitable substrate, a substance exhibiting a refractive index for the X-ray wavelength used that is not significantly different from the refractive index (unity) of a vacuum, and a substance exhibiting a refractive index that is significantly different from unity. Conventional membranes used in multi-layer X-ray-reflecting mirrors include W/C (tungsten/carbon), Mo/C (molybdenum/carbon), and Mo/Si (molybdenum/silicon). Such layers can be formed using techniques for forming thin films such as sputtering, vacuum evaporation, and CVD (chemical vapor deposition). The availability of multi-layer reflecting mirrors that can reflect X-rays incident to the mirror at a zero angle of incidence allows an X-ray optical system to be made that exhibits less aberration than exhibited by systems in which the X-rays are incident on reflective surfaces at a highly skewed angle of incidence (e.g., at angles of incidence resulting in total reflection). A multi-layer X-ray-reflecting mirror normally exhibits a wavelength selectivity, in which X-rays are reflected strongly only when the Bragg formula is satisfied: 2d sin .theta.=n .lambda., where d is the period length of the multiple layers, .theta. is the angle of incidence, and .lambda. is the wavelength of the X-ray. Among such multi-layer reflective surfaces, certain Mo/Si multi-layer structures exhibit a high reflectance for X-rays on the long-wavelength side of silicon L absorption edges (.lambda.=12.6 nm). Grazing incidence mirrors can also be used as reflecting optical elements for X-rays. A grazing incidence mirror has a high reflectivity only at a small grazing angle smaller than a critical angle .theta..sup.c (for .lambda.=10 nm, the critical angle .theta..sup.3 is about 20.degree. or less). Such mirrors cannot be used in situations of near normal incidence. A multilayer mirror can be used at any incidence angle including normal incidence. Windt and Waskiewicz, "Multilayer Facilities Required for Extreme-Ultraviolet Lithography," J. Vac. Sci. Technol. B12(6):3826 (1994). Such X-ray mirrors are conventionally used in X-ray telescopes and X-ray laser resonators. X-ray-reflecting mirrors comprising multiple Mo/Si layers have potential uses in reduction projection-lithography systems that utilize "soft" X-rays (i.e., X-rays of relatively long wavelength, low energy, and little penetrative power). Mo/Si multi-layer reflecting mirrors exhibiting high reflectance for X-rays are conventionally made using a sputtering technique involving a plasma. Unfortunately, thin films made by sputtering generally exhibit internal stresses arising from compression. Such stresses are typically caused by a "peening" effect of high-speed particles (positive ions and neutral particles) in the plasma, as described in Kinbara, Sputtering Phenomena, Tokyo University Press, 1984. A multi-layer mirror structure having internal stress typically exhibits substantial warping of the reflective surface. Such warping generates wave-surface aberrations in optical systems comprising such mirrors; such aberrations significantly degrade the optical performance of such systems. Various techniques have been evaluated to reduce the internal stress in Mo/Si multi-layer membranes. For example, certain stresses apparently can be controlled by varying the thickness ratios of the molybdenum and silicon layers. Nguyen et al., OSA Proceedings On Extreme Ultraviolet Lithography, Vol. 23, p. 56, 1995. Another approach is to change the bias voltage on the substrate during formation of the layers by sputtering. Nakajima et al., Vacuum 37(1): 10-16, 1994. Yet another approach is to vary the applied high-frequency electrical power when applying the layers. Haga et al., 57.sup.th Applied Physics Conference Scientific Lecture Meeting, Abstract 7p-W-1, p. 495 (1996). Yet another approach is to impose a heat stress to the structure by elevating the temperature of the substrate when applying the layers. Wasa et al., 56.sup.th Applied Physics Conference Scientific Lecture Meeting, Abstract 26a-C-5, p. 491 (1995). Unfortunately, application of such techniques provides no real understanding of the true origin of the stresses and how they can be reliably controlled. Thus, whether or not stresses are present in a particular X-ray mirror is unpredictable, and attempts to reduce the stress after manufacture can lead to unexpected and unwanted consequences such as loss of reflectance. SUMMARY OF THE INVENTION This invention was developed with the aforementioned types of problems in mind and aims to provide multi-layer X-ray-reflecting mirrors having reduced internal stress without exhibiting a reduced reflectivity. According to one aspect of the invention, mirrors are provided for reflecting X-rays. A preferred embodiment of such a mirror comprises a substrate having a surface, and multiple alternating layers of a first material and a second material on the substrate. The first material consists essentially of a substance selected from the group consisting of Mo, Rh, Ru, Re, W, Ta, Ni, Cr, Al, and alloys of such substances. Molybdenum is preferred, especially if the mirror structure is destined for use with X-rays having a wavelength of 13 nm. The second material consists essentially of silicon (as a principal constituent) and a dopant, selected from a group consisting of B, C, and P, diffused into the silicon. The preferred dopant is B. The dopant is at a concentration that is sufficient to reduce the net internal stress in the multi-layer structure compared to an otherwise similar multi-layer structure lacking the dopant in the second material. The dopant is preferably at a concentration of at least 1.times.10.sup.18 atoms/cm.sup.3. The substrate is preferably glass but can be synthetic quartz or other suitable rigid material. The number of layers can generally be about 30 to 100, preferably at least 50, with the topmost layer preferably being of the second material. According to another aspect of the invention, methods are provided for making a mirror that is reflective to X-rays. According to a preferred embodiment, a first step comprises providing a rigid substrate (preferably glass, but any of various other rigid substrates conventionally used to support thin films may be suitable). To a surface of the substrate is applied a laminar structure consisting of a layer of a first material and a layer of a second material. The first material consists essentially of a substance selected from a group consisting of Mo, Rh, Ru, Re, W, Ta, Ni, Cr, Al, and alloys of such substances. (Mo is preferred especially if the wavelength with which the mirror structure is to be used is about 13 nm.) The second material consists essentially of silicon and a dopant, diffused into the silicon, that is selected from a group consisting of B, C, and P. The dopant is preferably at a concentration of at least 0.001 atomic percent relative to the silicon. Either the layer of the first material or the layer of the second material can be the layer actually contacting the surface of the substrate. At least one additional layer of each of the first and second materials are applied superposedly to the laminar structure. The additional layers are applied in alternating order to form a multi-layer mirror structure. The preferred dopant is boron, preferably at a concentration in the silicon of at least 1.times.10.sup.18 atoms/cm.sup.3. The number of layers in the multi-layer mirror structure is preferably in a range of 30-100 or, alternatively, at least 50. The layers are preferably applied using a sputtering technique; the topmost layer is preferably a layer of the first material. The foregoing and additional features and advantages of the present invention will be more readily apparent from the following detailed description, which proceeds with reference to the accompanying drawings.
049922319	abstract	An emergency core cooling system for spraying cooling water onto a nuclear reactor core of a nuclear reactor includes at least one header disposed in the nuclear reactor and arranged at an upper and outer circumferential position with respect to the reactor core. A plurality of spray nozzles are mounted on the at least one header for spraying cooling water onto the reactor core. The spray nozzles have a center axis and at least one of the plurality of spray nozzles is mounted on the at least one header so that the center axis thereof extends upwardly with respect to a horizontal axis whereas at least one of the remaining plurality of spray nozzles has the center axis thereof extending downwardly with respect to the horizontal axis. Cooling water is conducted to the at least one header for enabling spraying of the water in the emergency situation.
054266750	claims	1. A self-aligning seal system for maintenance service of a generally vertical aligned cylindrical housing extending upward passing through the lower portion of a nuclear reactor plant pressure vessel for embracing a rotatable shaft connecting an external motor to an internal coolant circulating pump impeller; said self-aligning seal system comprising the combination of: said self-aligning seal system comprising the combination of: 2. The self-aligning seal system of claim 1, wherein the seal guide member is provided with at least three downward extending tapered legs. 3. The self-aligning seal system of claim 1, wherein the seal guide member is provided with four downward extending tapered legs. 4. The self-aligning seal system of claim 1, wherein the central knob projecting from the closed top of the cylindrical seal unit is mounted on an extending shaft and provided with a collar stop to preclude the seal guide member from separating from the cylindrical seal unit. 5. A self-aligning seal system for maintenance service of a generally vertical aligned cylindrical support housing extending upward passing through the lower portion of a nuclear reactor plant pressure vessel for embracing and supporting a rotatable drive shaft connecting an external motor to an internal coolant water circulating pump impeller;
	summary
039322157	abstract	Vertical control rod includes an absorber formed of flexible members and suspended by a traction device below the reactor core during operation of the reactor and a tensional spring for drawing the absorber into the reactor core to shut off the reactor. The control rod is operable independently of gravity and avoids jamming of the absorber in the guide therefor.
	description	This is a continuation, under 35 U.S.C. §120, of copending International Application No. PCT/EP2012/061069, filed Jun. 12, 2012, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German Patent Application No. DE 10 2011 108 802.8, filed Jul. 29, 2011; the prior applications are herewith incorporated by reference in their entirety. The invention relates to a boiling water nuclear reactor assembly having a bayonet plate closure providing a coaxially connection between a control rod guide tube (CRGT) and a drive housing pipe (DHP). On one hand, a basic requirement is the specifically fixed bracing of the coupling of the CRGT on the DHP in order to prevent lifting of the CRGT and as a consequence thereof an undefinable bypass at the connection point. On the other hand, however, high demands must be met in terms of the mountability of the CRGT on the DHP. In boiling water reactors, specifically, the control rods required for controlling the power are guided beneath the reactor core in control rod guide tubes (CRGTs). It must be possible for those CRGTs, which are located at a great depth, to be removed without any problems, in order to reach regions of the lower plenum of the reactor vessel for servicing purposes. To that end, the CRGT locked by way of its foot plate to the respective DHP has to be unlocked and removed from the DHP. During the desired long operating times of the plant, however, deposits in the fittings of the joints lead to running difficulties, which complicate removal and make it very time-consuming. The removal is also made more difficult by the fact that the foot plates are located at a great depth (approximately 30 m) below the water level in the flooded reactor pool. In order to reach those foot plates, it is known in the prior art, for example, to couple up to seven tool rods each 4 m long to one another in the axial direction, in order to fit, at the bottom end of that rod system, the actual locking and unlocking tool, which to that end engages into a bayonet ring plate mounted rotatably on the foot plate. Those problems are clearly explained, for example, in the introductory part of the description of German Utility Model DE 201 00 351 U1. It is accordingly an object of the invention to provide a nuclear reactor assembly having a connection between a control rod guide tube and a drive housing pipe, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which retains an operationally proven bayonet locking while at the same time improving its mountability that is consistently required for operation. With the foregoing and other objects in view there is provided, in accordance with the invention, a control rod guide tube and a drive housing pipe connected coaxially thereto by a bayonet plate closure in a boiling water reactor, comprising an at least two-part form of a bayonet plate. The bayonet plate is formed of a central bayonet ring, mounted rotatably about the longitudinal axis thereof, in a conventional construction and operation as a carrier of bayonet grooves, additionally with an outer ring, which is mounted on the circumference or periphery of the bayonet ring. The configuration is such that the outer ring reaches inward underneath the circumference or periphery of the bayonet ring, and is supported on a base flange of the CRGT and therefore indirectly on the DHP with spring pressure acting permanently on the CRGT in the axial direction. The prestressed outer ring and the bayonet ring in this case form a kind of detachable coupling. In order to unlock the CRGT, the spring pressure acting permanently on the outer ring on the part of the DHP during operation is eliminated by virtue of the fact that the outer ring is pushed down using a tool. By rotation, the bayonet ring can then be unlocked on one hand and locked again on the other hand in a stress-free manner. In the locked state, the bayonet ring presses the CRGT against the contact surfaces of the DHP with a defined force indirectly by way of the outer ring, and braces the CRGT to the DHP in a rotationally locked manner. This configuration reliably prevents “floating” of the CRGT, around which the reactor coolant flushes during operation, in all transient operating procedures. The spring element provided for producing the spring pressure, preferably in the form of a disk spring, surrounds the drive housing pipe with a radial sliding fit. In order to ensure a seal at the contact, the mutual contact surfaces of the CRGT on the DHP advantageously have a planar (flat), conical envelope-like or crowned shape. The last two variants mentioned have the additional advantage of ensuring the absorption of lateral forces acting in the radial direction and thereby preventing undesired horizontal (lateral) movements of the CRGT with respect to the DHP. The bayonet ring is mounted rotatably on the drive housing pipe with axial play. This play is compensated for in normal operation by the spring pressure acting permanently on the CRGT, and is permitted only for assembly or disassembly purposes by pressing down the outer ring using a tool suitable therefor. The advantages achieved by the invention reside firstly in that the integration of a holding spring in the locking system makes it possible for the CRGT to be reliably braced to the DHP, in such a way that a secure installed position of the CRGT free of oscillation and movement is ensured in all operating states. On the other hand, the two-part bayonet plate provides a simple possibility for assembly, since the outer ring can be pressed down with an associated tool during unlocking and bracing and then the inner bayonet ring can be easily turned. 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 nuclear reactor assembly having a connection between a control rod guide tube and a drive housing pipe, 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. Referring now in detail to the figures of the drawings, which are simplified and diagrammatic, and first, particularly, to FIG. 1 thereof, there is seen a control rod guide tube (CRGT) 1 which surrounds a non-illustrated control rod of a reactor. The control rod is connected to a drive rod dipping vertically into a drive housing pipe (DHP) 2. The control rod, which is concentric with the vertical axis of the CRGT 1 and DHP 2 and dips from above downward into the CRGT 1, and the drive rod are themselves not shown, but rather are only indicated symbolically by a longitudinal axis 3. The CRGT 1 has a base end remote from the reactor core with a base flange 4 extending inward in the direction of the longitudinal axis 3 of the DHP 2. The base flange 4 is coupled to an annular protrusion 5 of the DHP 2. A conventional bayonet ring 6 and an outer ring 7 surrounding it according to the invention with a radial play fit and reaching underneath the outer periphery of the bayonet ring 6 with its inner periphery are positioned inside the CRGT 1 above its base flange 4 extending radially in the direction of the longitudinal axis 3 concentrically to the DHP 2. The outer ring 7 is therefore supported circumferentially on the base flange 4 of the CRGT 1, with the interposition of a disk spring 8 positioned concentrically with respect to the longitudinal axis 3. The disk spring 8 surrounds the DHP 2 with a radial sliding fit. The use of the disk spring 8 is suitable in the present case due to its small space requirement and large forces given small spring travels, which is why it is also used, as is known, preferably as a clamping element in apparatuses and tools. Common disk springs are annular disks shaped like a conical shell which can be subjected to loading in the axial direction. In the present case, the disk spring 8 surrounds the DHP 2 with a radial sliding fit. The operation of the present bayonet closure is known in principle from the commonly known structures. In the present case, too, the bayonet ring 6 has four annular or longitudinal slots 9 distributed uniformly over its circumference, which pass through the bayonet ring 6 parallel to the longitudinal axis 3 from a top side 10 thereof to an underside 11 thereof, as is seen in FIGS. 2 and 3. The circumferential course thereof lies on a circular arc made around the longitudinal axis 3 as a center point. The longitudinal slots 9 each end concordantly in the circumferential direction at one end in an insertion hole 12, also referred to as a locking bore, for a holding pin or fastening pin 13 assigned thereto in each case. The fastening pins 13, of which there are four in the exemplary embodiment, have shanks which run parallel to the longitudinal axis 3 of the control rod guide tube 2. They have free ends at the bottom which are fixed, for example screwed, in the base flange 4 in the assembled state. They also have ends which point upward in the direction of the CRGT 1 in the installed position, pass through the longitudinal slots 9 and are provided with radially widened locking heads 14 which, in the clamped or locked position outside the insertion holes 12 of the longitudinal slots 9, act upon a free surface of the bayonet ring 6 and, in a corresponding turned position of the DHP 2, act upon the bayonet ring 6 from above and brace it with a form-locking connection on the DHP 2, as long as an axial pressure of the disk spring 8 presses the outer ring 7 in the axial direction against the bayonet ring 6 and thereby fixes the turned position of the bayonet ring 6 (for rotation prevention). In the locked position, the bayonet ring 6 is secured against displacement upward in the axial direction by radially outwardly protruding, cam-like retaining protrusions 15. In the exemplary embodiment, four retaining protrusions 15 are distributed uniformly over the circumference, are integrally formed at the head of the DHP 2 and reach inward over the bayonet ring 6. The retaining protrusions 15 therefore form top stops for the bayonet ring 6 mounted with axial play. Since the disk spring 8 is intended to spread apart the axial distance between the outer ring 7 of the bayonet plate and the annular base flange 4 of the CRGT 1, the bayonet ring 6 is pressed upward against the retaining protrusions 15 on one hand by way of an annular step 16. On the other hand, the base flange 4 of the CRGT 1 is pressed downward against a contact surface 17 of the annular protrusion 5 on the DHP 2 acting in the manner of a bottom stop, and therefore as a whole the CRGT 1 is fixed on the DHP 2. Suitable shaping of the contact surface 17 of the annular protrusion 5 (e.g. conical, round, like a crown) and of the bearing surface of the base flange 4 shaped complementarily thereto makes it possible to realize a desired seal in this region. The fixing action can be eliminated from above through the CRGT 1 by applying pressure to the outer ring 7 using a suitable tool. As a result, the disk spring 8 is pressed together and tensioned, and the locking action of the bayonet closure generated thereby is thereby eliminated. The bayonet closure can then be unlocked without any problems. As can be seen best from FIG. 2, recesses 18 complementary to the retaining protrusions 15 at the head of the DHP 2 are located on the inner side of the bayonet ring 6 and are aligned in the unlocked state with the retaining protrusions 15, in such a way that the bayonet ring 6 can be lifted from the DHP 2 upward as required after the locking studs 13 have been removed. Since the base flange 4 of the CRGT 1 likewise has corresponding non-illustrated recesses, the CRGT 1 can be lifted completely from the DHP 2 in the unlocked state given a suitable turned position.
048658030	description	DESCRIPTION OF A PREFERRED EMBODIMENT As shown in FIG. 1 a plurality of modular conduit units 1 are screwed to one another so as to be sealed by gaskets 2 disposed at their interfaces. The conduit units as such are shown in FIG. 2. Together they form discharge conduit structure 10 providing a discharge path from the interior of a reactor safety containment to the atmosphere, generally by way of an exhaust stack associated with the reactor plant. At their sides the modular conduit units have side openings 3 and 4 bounded by flanges 5 and 6. The bottoms 7 of the modular conduit units 1 are preferably recessed so that they are somewhat lower than the lower edge of the side openings 3 and 4 as shown in FIG. 1 so as to retain therein any condensate. The flanges 5 and 6 consist of angle iron frames which are welded to the units 1. All the units 1 are supported on a support frame 8. The conduit units have attached thereto filter stages 12 each including a prefilter 9 and a main filter 11 both consisting of stainless steel fiber packs as filter elements. The filters 9 and 11 as shown in FIG. 3 are stainless steel fiber mats whose fibers may have a diameter down to 2 .mu.m. The filter stages 12 of the conduit structure 10 shown in FIG. 1 are arranged in a particular manner. The filter stages 12 are formed by identical frame members 13 and 14 which are mounted together by bolts 15 and 16 in a manner such that they are sealed with respect to one another. The frame members 13 and 14 consist of hollow sheet metal casings which have flanges 17, 18 and 19, 20 welded to the opposite ends thereof. The frame member 13 is bolted with its flange 17 to the flange 6 or, on the opposite side of the unit 1, flange 5 (see FIG. 2), with the gasket 21 sealingly disposed therebetween. Further bolting connections of the filter stages 12 are made in the same manner. A U-shaped member 22 is welded with its back side 23 to the flat face at the inner end of flange 18 such that the legs 24 of the U-shaped member project from the flange face. The edges 25 and 26 of the filter packs 9 and 11 are disposed between the projecting legs 24 of the U-shaped member 22 and the flange 19 of the adjacent frame member 14 so that, upon tightening of the bolts 16, the edges 25, 26 of the filters are firmly clamped therebetween thereby forming circumferential concentric seals 27 and 28 providing for a double seal structure. In the process the circumferential edges 25 and 26 of the filters are compressed to a fraction of their original thickness. The flanges 19 of the frame members 14 have perforated retaining plates 29 welded thereto at their inner edges so that the filters 9 and 11 may be flatly supported thereby at their flat downstream sides 30. Additional perforated plates 31 are inserted into the interior of the frame members 13 which engage the filters 9 and 11 at their curved upstream side 32. The curved upstream side 32 is further provided with a stainless steel cloth 33 which follows the curved filter surface and engages and retains the filter fibers so as to prevent fraying of the filter packs. The stainless steel cloth 33 is clamped between the flanges 18 and 19 together with the filter edges 25 and 26. The space remaining between the flanges around the filter edges 25 and 26 in the area of the bolts 16 is filled with a heat resistant sealing material which is cast into that space. The normal flow direction is given by arrow 35, that is, the discharge air is supplied to the filter stages from the curved side 32 of the filters as shown in FIG. 3, but the filter stages may also be arranged in the manner opposite to that shown in FIG. 3. The conduit unit together with the filter elements on their sides are disposed in a discharge collection chamber which is in communication with an exhaust stack so that the discharge air, after passage through the filter elements, is collected for discharge through the exhaust stack. REFERENCE NUMERALS 1: Modular conduit unit 2: Gaskets 3, 4: Side openings 5, 6: Flanges 7: Recessed bottom 8: Support frame 9: Prefilter 10: Discharge conduit structure 11: Main filter 12: Filter stages 13, 14: Frame members 15, 16: Bolts 17, 18: Flanges 19, 20: Flanges 21: Gasket 22: U-shaped member 23: Back side 24: Legs 25, 26: Edges 27, 28: Seals 29: Perforated retaining plate 30: Flat downstream side 31: Perforated plate 32: Curved filter side 33: Stainless steel cloth 34: Sealing material 35: Flow direction arrow.
	description	The method and apparatus of the invention relate to processing waste water from nuclear power reactors and other sources of water contaminated with radionuclides. In particular, the present method and apparatus are related to processing waste waters contaminated with colloidal, suspended and dissolved radionuclides. In the commercial nuclear power industry, there are primarily two types of reactor systems, namely boiling water reactors (BWR) and pressurized water reactors (PWRs). Both use water to moderate the speed of neutrons released by the fissioning of fissionable nuclei, and to carry away heat generated by the fissioning process. Water flows through the reactor core, is recycled, and inevitably becomes contaminated with iron, Fe-55, colloidal and soluble cobalt, Co-58, and Co-60, and other radionuclides. The water further becomes contaminated with organics (e.g., oils and greases), biologicals and non-radioactive colloids (e.g., iron rust). In a boiling water reactor (BWR), the water passing through the core will be used directly as steam in driving turbine-generators for the production of electricity. In a pressurized water reactor (PWR), the primary water that flows through the reactor is isolated from the secondary water that flows through the turbine generators by steam generators. In both cases, while the chemical constituents of the waste water will be different, these reactor systems will produce colloidal, suspended and dissolved solids that must be removed before the waste water may be reused or released to the environment. The presence of iron (as iron oxide from carbon steel piping) in Boiling Water Reactor (BWR) circuits and waste waters is a decades old problem. The presence and buildup of this iron in condensate phase separators (CPS) further confounds the problem when the CPS tank is decanted back to the plant. Iron carryover here is unavoidable without further treatment steps. The form of iron in these tanks, which partially settles and may be pumped to a de-waterable high integrity container (HIC), is particularly difficult and time consuming to dewater. The addition of chemicals upstream from the CPS, such as flocculation polymers, to precipitate out the iron only produces an iron form even more difficult to filter and dewater. Such chemically pretreated material contains both sub-micron particles and floc particles of sizes up to 100 microns. It is believed that the sub-micron particles penetrate into filter media, thus plugging the pores and preventing successful filtration of the larger micron particles. Like BWR iron waste waters, fuel pools, or basins, (especially during the decontamination phase) often contain colloids which make clarity and good visibility nearly impossible. Likewise, miscellaneous, often high conductivity, waste steams at various plants contain such colloids as iron, salts (sometimes via seawater intrusion), dirt/clay, surfactants, waxes, chelants, biologicals, oils and the like. Such waste streams are not ideally suited for standard dead-end cartridge filtration or cross-flow filtration via ultrafiltration media (UF) and/or reverse osmosis (RO), even if followed by demineralizers. Filter and bed plugging are almost assured. There are a number of prior art techniques used for removal of colloidal, suspended and dissolved solids, and the requirement to remove such materials from waste waters is not unique to nuclear reactors. However, the nature of nuclear reactors raises special concerns about the use of additives for chemical treatments because of the desire to avoid making radioactive wastes also chemical wastes. There are other concerns as well. The processed waste water must be quite free of radioactive contaminants if it is to be released to the environment. The radioactive material extracted from the waste water during processing must be stable or in a form that can be stabilized for disposal in a way that meets disposal site requirements, particularly with respect to preventing the leaching out of radioactive contaminates by liquid water. Finally, the volume of the waste must be minimized because of both the limited space available for disposal of radioactive waste and the high cost of its disposal. Accordingly there is a need for better ways of processing radioactive waste water containing suspended solids and dissolved ions from nuclear power reactors and other sources. The key to solving the above dilemmas is 1) to break the colloid by neutralizing the outer radius repulsive charges of similar charged colloidal particles, and 2) to cause these neutralized particles to flocculate and form a type of flocculant (floc) that is more readily filterable, and thus de-waterable. In the present invention, these tasks are carried out with the innovative application of an electro-coagulation (EC) unit to electrolytically seed the waste feed stream with a metal of choice, and without prior addition of chemicals common to ferri-floccing or flocculation/coagulation polymer addition. Once the colloid has been broken and floccing has begun, removal of the resultant floc can be carried out by standard backwashable filters, cross-flow filters (e.g., UF), or, in simple cases, dead-end filters. Such applications include low level radioactive waste (LLW) from both PWRs and BWRs, fuel pools, storage basins, salt water collection tanks and the like. For the removal of magnetic materials, such as some BWR suspended irons (e.g., boiler condensates and magnetite and hemagnetite), an electro-magnetic filter (EMF) unit may be coupled with the EC unit. For the removal of non-magnetic materials, the EC treatment may be followed by treatment with a flocculating chemical, such as a flocculating polymer like Betz-1138 which is a polyacrylamide copolymer available from the Betz Corporation. For a waste stream containing magnetic materials and one or more non-magnetic species, e.g., cesium (Cs), a magnetic seeding step for coupling the non-magnetic species to a magnetic moiety, e.g., CHFC (Cobalt hexaferricyanate), to form a magnetic chemical complex may be followed by the EMF for the effective removal of this complex. Thus, the invention provides a method, apparatus and system for removing contaminants from radioactive waste waters by using electro-coagulation in combination preferably with magnetic filtration and/or treatment with a flocculation agent. The electro-coagulation may also be used to enhance the subsequent removal of contaminants by dead end filtration, high gradient magnetic filtration (HGMF), ultra-filtration (UF), back flushable filters (BFF), and high integrity containers (HICs) that are dewaterable with sheet filters. The electro-coagulation takes place after adjustments of the pH and the conductivity of the waste water, if needed. Sacrificial metal electrodes, which may be iron but preferably are aluminum, are used in batch or continuous electrolytic processing of the waste water to seed it with positively charged metal ions that neutralize and agglomerate negatively charged ions, suspended particles and colloidal particles. The electro-coagulation (EC) process of the invention works on an electricity-based technology that passes an electric current through radioactive waste waters. Thus, electro-coagulation utilizes electrical direct current (DC) to provide cations from the sacrificial metal electrode ions (e.g., Fe or Al) that agglomerate and thereby precipitate out undesirable contaminates, including dissolved metals and non-metals, e.g., antimony (Sb). The electrical DC current is preferably introduced into the aqueous feed stream via parallel plates constructed of the sacrificial metal of choice. This process avoids the use of undesirable chemical additions (e.g., ferric chloride). Moreover, the anode and cathode will hydrolyze water molecules, liberating oxygen and hydrogen, respectively, as tiny bubbles, the latter combining with many of the dissolved ions in the water to form insoluble oxides. The oxygen and hydrogen also will cause small, light particles to float and flocculate (e.g., oils and greases) so that they can also be skimmed off or filtered out. Some of these lighter particles are biological particles such as bacteria that have been destroyed by electro-osmotic shock. The use of electro-coagulation with radionuclides has several specific advantages in addition to the fact that it will cause the precipitation or flotation of radionuclide species in the waste water. One of these is the oxidation of some species to render them stable in water. The oxidized species are then not toxic hazards and are not likely to be leached into the ground water if buried. They will generally pass the EPA TCLP test, which will result in significant cost savings in disposal. The production of oxygen through hydrolysis also acts as a bactericide and fungicide to further remove wastes other than purely radioactive wastes. In addition to radionuclides, the waste waters may be contaminated by one or more of heavy metals, colloids, clay, dirt, surfactants, cleaners, oils, greases, biologicals, and the like. As these contaminated waste waters are passed through one or more EC cells, the following four treatment reactions occur: 1. Coagulation—Ions, colloids and suspended solids will remain suspended indefinitely in solution due to their like charges, which are usually negative. Thus, they repel each other and do not allow coagulation or floccing. As contaminated water passes through the cell assembly, DC power is applied continuously, or is pulsed, to the cell electrodes. Metallic ions from the positive cell electrodes (anodes) slough off and provide bridging seeds to the suspended solids and other contaminates present. Only as much electrode seed material is supplied as there are dissolved, colloidal and/or suspended solids present, thus controlling the solids addition. The metallic seed ions cause the charge of suspended or dissolved solids, colloids, oils and greases, and the like, to be neutralized. This charge neutralization causes the contaminants to coagulate, or floc, so that they become large enough to settle or float or be filtered by standard filtration media, ultra-filtration (UF), or reverse osmosis (RO), or, if magnetic, by electro-magnetic filtration (EMF) or High Gradient Magnetic Separation (HGMS) filtration. This coagulation process does not require the addition of chemicals with the exception of those for adjusting the pH or conductivity, if required. 2. Oxidation—As waste water contaminated by heavy and/or radioactive metals is passed through the EC cell(s), the metals are reduced to an oxide. The metal ions are thereby changed from a dissolved state to a suspended state and then are precipitated from the water. Heavy metals that are thus oxidized by passing through the electric current will generally pass a TCLP test, which provides significant savings in the cost of sludge disposal. 3. Aeration—A natural byproduct of this EC process is aeration. No air or any other gases need to be injected into the process, as the dissociation products of water form tiny bubbles giving the coagulated contaminants buoyancy. Thus, after treatment of the waste water, oils and greases therein can either be skimmed off, or re-mixed and settled or filtered with the rest of the coagulated sludge. 4. Biologicals—A further advantage of this EC Process is that it is a natural biocidal process because it ruptures microorganisms and the like by electro-osmotic shock. The magnetic filter may comprise a ferromagnetic filtering medium that is temporarily magnetized when an electro-magnetic field is passed through it via a surrounding coiled electrical conductor. The medium (or media) may comprise steel sheets, screens, beads or balls, the latter being preferred. Upon de-energizing the electro-magnetic field, this filtering medium, which is preferably made of soft magnetic material (e.g. 430 stainless steel), is no longer magnetized to allow the filter to be back-flushed for removal of the coagulated contaminates by flushing them off the filtering media. Thus, the core of the magnetic filter preferably is not made of a permanently magnetizable material but of a soft magnetic material that is electro-magnetizable and then can be demagnetized by simply removing the magnetizing electrical current from the surrounding coil so that the filtering media, preferably 400 series (e.g. 430 S.S.) stainless steel balls, can be backflushed for reuse. The agglomerated particles from the EC unit can also be removed from the waster water by conventional filtration techniques. Furthermore, many of the agglomerated particles may quickly settle out and these may be removed by simply decanting the clarified water. However, the use of an EMF for removal of radioactive precipitates is particularly advantageous because once removed, these waste solids may be easily backflushed to and handled by conventional radioactive waste (radwaste) disposal systems, thereby avoiding the radioactive filter waste generated by mechanical filtering equipment. As used in this specification and the appended claims, the term electro-magnetic filtration (EMF) includes high gradient magnetic filtration and other magnetic filtration techniques that magnetically remove ferromagnetic particles or precipitates and that permit the filtered out material to be backflushed to a radwaste system. Another particular feature of the present invention is that radionuclides which are not ferromagnetic, such as cesium-137, can be removed by the addition of a magnetic complexing agent, such as cobalt hexaferricyanate, which forms a magnetic complex with the radionuclides that can be removed by a magnetic filter. Some of the advantages of the invention over conventional processes for chemical coagulation and mechanical filtration include the following: (1) Less Waste Volume is created because there is no need for post ion exchange coupled with UF or the like. (2) Provides consistent introduction of the seeding agent and only as needed, such as Fe or Al, at high throughputs. (3) Provides improved water quality for those radioisotopes that cannot be taken out by UF or standard filtration. (4) Provides operational advantages because there is no chemical introduction, no chloride introduction, and no significant pH swings. (5) Less waste volume is created as compared to using chemical coagulants such as alum or lime, and to using flocculation polymers alone. (6) The coagulant is significantly easier to dewater than chemical and purely polymer sludges because the electrocoagulated floc tends to contain less bound water, is more shear resistant, and is thus more readily filterable. (7) The EC process is capable of acting as a biocide for the destruction of biological organisms because electron flooding of the waste water eliminates the polar effect of water complexes allowing colloidal materials to precipitate, and the increase of electrons creates an osmotic pressure that ruptures bacteria, cysts, and viruses. (8) Metal oxides are formed that will pass TCLP disposal requirements. (9) The EC process is not adversely effected by oils and greases and these contaminates are removed so that the output may be sent to deadend filtration, BFF, EMF, UF or RO. (10) The EC process may be utilized without the introduction of chemicals, including polymers. (11) The process equipment has an extremely small foot print. (12) EC requires simple equipment and is easy to operate with sufficient operational latitude to handle most problems encountered on running. (13) Wastewater treated by EC gives clear, colorless and odorless water. (14) Sludge formed by EC tends to be readily settable and easy to de-water, because it is composed of mainly metallic oxides/hydroxides. Above all, it is a low sludge producing technique. (16) Flocs formed by EC are similar to chemical floc, except that EC floc tends to be much larger, contains less bound water, is acid-resistant and more stable, and therefore, can be separated faster by filtration. (17) EC produces effluent with less total dissolved solids (TDS) content as compared with chemical treatments. If this water is reused, the low TDS level contributes to a lower water recovery cost. (18) The EC process has the advantage of removing the smallest colloidal particles, because the applied electric field readily neutralizes them, thereby facilitating the coagulation. (19) The EC process avoids uses of chemicals and so there is no problem of neutralizing excess chemicals and no possibility of secondary pollution caused by chemical substances added at high concentration as when chemical coagulation of wastewater is used (20) The gas bubbles produced during electrolysis can carry certain pollutants to the top of the solution where it can be more easily concentrated, collected and removed (e.g., by skimming). (21) The electrolytic processes in the EC cell are controlled electrically and with no moving parts, thus requiring less maintenance. (22) The EC technique can be conveniently used in rural areas where electricity is not available, since a solar paned attached to the unit may be sufficient to carry out the process. The sacrificial electrodes are expended by being dissolved into the wastewater stream and eventually need to be replaced. The regularity here depends on the wastewater composition and the volume treated. For nuclear applications, replaceable canisters containing the electrodes would be used. An impermeable oxide film may be formed on the cathode leading to loss of efficiency of the EC unit. However, this does not occur if the unit for the process water is forced into turbulence and this oxide is never allowed to form. Self cleaning by periodic current application, controlled by the computer, will also prevent scaling. Reasonable levels of conductivity of the wastewater suspension is required. This can be compensated for in low conductivity applications by increasing the electrode area, increasing the residence time (eg, recycle or additional cells in series), increasing the amperage (eg, jumpering electrodes to place them in parallel), and/or adding innocuous chemicals to increase conductivity and/or pH (eg, sodium sulfate or sodium bicarbonate or baking soda). In the electrocoagulation (EC) unit of the invention, a direct current is applied to a cathode-anode system in order to destabilize any dissolved ionic or electrostatically suspended contaminants. During this electrolytic process, cationic species from the metal of sacrificial anodes dissolve into the water. These positively charged cations neutralize and thereby destabilize negatively charged contaminants and also create metal oxides and hydroxides which precipitate and bring down the neutralized contaminants as part of the precipitate. If aluminum anodes are used, aluminum oxides and hydroxides are formed. If iron anodes are used, iron oxides and hydroxides form. Aluminum anodes are preferred for the present invention because iron anodes become readily coated with iron oxide, which interferes with the electrolytic process. The formation of the metal oxides and hydroxides, and their subsequent precipitation, are similar to the processes which occur during coagulation or flocculation using alum or other chemical coagulants. The difference is that in electrocoagulation, the cations are produced by electrolytic dissolution of the anode metal instead of by adding a chemical coagulant. In addition, the activation energy provided by the application of an electrical current will promote the formation of oxides, instead of hydroxides which may be in a slimy form that may clog filters, if the electrical energy supplied by the unit exceeds the activation energy for formation of the metal oxide. The metal oxides are more stable than the hydroxides and therefore more resistant to breakdown by acids. The dissolved contaminants are incorporated into the molecular structure of these acid resistant precipitates by ion bridging and/or adsorption. Also, the weak intermolecular force known as van der Waalls' force causes these molecules to be attracted to one another and thereby coagulated into a floc. The precipitated floc is often capable of passing the requirements of the TCLP (the EPA's Toxicity Characteristic Leaking Procedure), which will significantly reduce solid waste disposal costs. In addition, during the electrolytic process, oxygen gas is produced at the anode by the electrolysis of the water molecules. Simultaneous reactions take place at the cathode producing hydrogen gas from the water molecules. These gases can cause the coagulated floc molecules to float, and can also cause flotation and coagulation of oils, greases, and biological materials, such as the residue produced by the rupturing of bacteria and other microorganisms by electro-osmotic shock. The floating floc can be skimmed off for disposal, or it may be subjected to shaking or other turbulence to degas the floc and cause it to settle with the metal precipitates. The coagulation process preferably increases the size of submicron particles to particles as large as 100 microns, preferably to an average size of at least 20 microns so that the parcipitate particles are easily removable by a standard 20 or 25 micron filter. Another important cathodic reaction involves the reduction of dissolved metal cations to the elemental state so that they plate out as a metal coating on the cathodes. Since at least some of these metals will be radioactive, the cathodes of the invention must be regenerated in place by reversing their polarity so that the process anodes become regenerating cathodes and the process cathodes become regenerating anodes to thereby unplate the metal coating from the process cathodes, and by providing a fluid flow past the regenerating anodes (i.e., the process cathodes) to carry off the unplated metal cations to a conventional radioactive waste disposal system. Referring now to FIG. 1, there is shown a radioactive water treatment system, generally designated 10, wherein the pH and the conductivity of an influent waste water stream 12 may be adjusted, if needed, in a tank 14. High pH may be adjusted downward by the introduction of an acid solution (such as sulfuric) from a tank 16, or low pH may be adjusted upward by the introduction of a base solution (such as sodium hydroxide or sodium bicarbonate) from a tank 18. To raise the waste water conductivity, an electrolytic solution (such as sodium sulfate or sodium bicarbonate) may be introduced into tank 14 from a tank 20. The conductivity also may be raised by introducing an iron component, such as magnetite into the adjusting tank 14, especially where the precipitates in the effluent water from the EC unit 26 are to be subsequently removed by the EMF unit. Some of the isotopes of concern in the waste water to be treated are transition metal activation products, such as Mn-54, Fe-55, Fe-59, Co-58, Co-60 and Zn-65, and their relatively short-lived decay progeny. The acid solution may be transferred to the adjusting tank 14 by a metering pump 17, the base solution by a metering pump 19, and the electrolytic solution by a metering pump 21. When the influent waste water is within the desired pH range from 6 to 8, preferably from 6.5 to 7.5, more preferably about 7.0, and the conductivity is in the range of 2 to 1000 μmhos, preferably at least 5.0 μmhos, more preferably at least 20 μmhos, most preferably in the range of 200 to 800 μmhos (tap water being about 200 μmhos), the adjusted waste water is transferred by a pump 24 to an electro-coagulation (EC) unit 26 having a plurality of sacrificial metal anodes 28 connected in parallel to the positive terminal of a power source 30, and a plurality of cathodes 29 connected in parallel to the negative terminal of the power source 30. The waste water fed to the EC unit 26 functions as an electrolyte 34 for carrying a current between the anodes 28 and the cathodes 29, the amount of this current depending on the conductivity of the waste water and the voltage across the terminals of the power source, which is regulated by a control panel 32. The amount of current is preferably at least 3 amps, more preferably in the range of 4 to 6 amps. As explained elsewhere, electrolytic reactions and dissolution of the metal of the sacrificial anodes 28 cause coagulation of the dissolved, colloidal and suspended contaminants in the waste water to produce precipitates in the form of floc or sediment. From the EC unit 26, the thus treated waste water flows to a floc and sediment tank 36, in which a portion of the precipitants may float as a floc F and a portion of the precipitants may settle out as a sediment S, an intermediate volume between the two being a clarified body of water C. At this point, the floating floc F may be skimmed off, the clarified water C decanted from the sediment S and sent on for further processing if needed, and the sediment S may be transferred to a dewatering container such as a high integrity container (HIC) with sheet filters and thereafter disposed of in conventional fashion. However, in many cases, further processing of the contents of tank 36 may be preferable to provide an effluent water containing even less contaminants that are present in the clarified water C. For further processing, either or both the sediment S and the floc F may be remixed with the clarified water C and the mixture transferred by a pump 38 to a conventional separation device for separating the precipitates from the waste water, such as a high gradient magnetic filtration unit, an ultrafiltration unit, a microfiltration unit, a dewaterable HIC with sheet filters, or preferably a backflushable filter (BFF), all as represented by the box 40 designated as a conventional filter in FIG. 1. The filtered precipitates separated from the waste water by conventional filter 40 are then transferred to a conventional radwaste system 42 for disposal. To further enlarge the size of the floc and sediment precipitates and any still suspended precipitates in tank 36, a flocculation polymer, such as BETZ-1138, may be added to the contents of tank 36 from a supply tank 35 via a metering pump 37. Preferably the mixture from tank 36 is transferred by pump 38 to an electro-magnetic filter (EMF) unit 44 made and operated in accordance with the invention as described below. When the magnetic field of the EMF is activated by applying to its electrical coils 46 a direct current from a power source 48, the portion of a ferro-magnetic filtering media bed 50 surrounded by the coil 46 is magnetized and thereby rendered capable of magnetically removing from the wastewater any electro-coagulated precipitates containing a ferro-magnetic component, such as iron containing precipitates where the waste water influent 12 comes from a boiling water reactor (BWR). The ferro-magnetic filtering media bed 50 is made up of a plurality of small ferro-magnetic pieces, preferably small stainless steel balls of a soft, or temporary, magnetic material (e.g. 430 S.S.) that may have a smooth or multi-faceted surface (the former being preferred). The balls are stacked in a tubular housing 52 that is made of a non-magnetizable material and passes through the center of electrical coil 46. The precipitate containing waste water preferably passes downward through the housing 52, the media bed 50 and the coil 46. The effluent from the EMF unit 44 may thereafter be sent to a recovered water tank 54 for discharge or recycle. While electric current from the power source 48 is passing through coil 46, the filtering media bed 50 is magnetized and therefore attracts and accumulates the ferro-magnetic precipitates in the waste water influent from floc tank 36. When the filtering efficiency of the EMF unit deteriorates to an unacceptable level, electrical current to coil 46 is turned off and the filtering media 50 is backflushed with a flow of uncontaminated water from a pump 56 to remove the now demagnetized precipitates from the filtering media bed 50 and carry them into a dewatering component 58, which is preferably a HIC with sheet filters or a BFF, but also may be another type of conventional filter. The clarified water recovered from dewatering container 58 may then be sent to the recovered water tank 54 for discharge or recycle. If the effluent from the EC unit as collected in tank 36 contains non-ferro-magnetic species such as cesium (Cs), this species may also be removed by the EMF unit by first adding to the contents of tank 36 a magnetic complexing agent from a magnetic seeding tank 60 via a metering pump 57. The complexing agent has a ferro-magnetic component. The complexing agent therefore forms a magnetic complex with the non-ferromagnetic species so that the EMF unit may be used for separating the resulting ferro-magnetic complex from the waste water. Where the non-ferromagnetic species is Cs, a preferred complexing agent is as cobalt hexaferricyanate. As previously indicated, the cathodic reaction involves the reduction of dissolved metal cations to the elemental state so that they plate out as a metal coating on the cathodes 29. Since at least some of these metals will be radioactive, the cathodes 29 must be periodically regenerated in place by reversing their polarity so that the process anodes 28 become regenerating cathodes and the process cathodes 29 become regenerating anodes to reverse the direction of the current flow and thereby unplate the metal coating from the process cathodes. Pump 24 may be used to provide a fluid flow past the regenerating anodes (i.e., the process cathodes) that serves as a regenerating flush 55 to carry off the unplated metal cations to a conventional radioactive waste disposal system, such as radwaste system 42. The details of a preferred embodiment of the EC unit is shown in FIG. 2, wherein the sacrificial anodes 28 are connected in parallel to the positive terminal of the power source 30 via a positive terminal 62 and a connecting wire 63. The cathodes 29, which alternate with the sacrificial anodes, are connected in parallel to the negative terminal of the power source 30 via a negative terminal 65 and a connecting wire 66. The anodes 28 and the cathodes 29 are mounted on a header or cap 69 so as to be suspended within an electrolyte chamber 68 of a housing 70, which has fluid inlet 71 and a fluid outlet 72. The fluid flow through the electrolyte chamber 68 is preferably upward in the direction of arrow 73, and the flow rate may be in the range of 1 liter per minute (lpm) to 200 gallons per minute (gpm), preferably at least 5 gpm per cell. The housing for a typical cell would be about four to six inches in diameter and about three to four feet long, and would contain about three to four anodes and about three to four cathodes. A typical production unit would comprise about 6 to 12 cells in parallel so that the overall flowrate would be preferably about 30 to 60 gpm for a PWR, BWR, fuel pool, or storage basin. Although an upflow in the direction of the arrow 73 is preferred, the waste water being treated may flow through the housing chamber 68 in either direction. Upflow through the EC unit 26 is preferred both for treatment of the waste water and for cleaning in place the electrodes 28 and 29 because the electrodes are preferably mounted and suspended down from the cap 69 such that there is less interference to fluid flow if that flow enters between the plates at their distal ends. The EC unit 26 alone will bring down as a precipitate at least 99 percent of the metal contaminants (whether present as ions, colloids and suspended particles) in the waste water influent stream of 12, so that subsequent filtration, preferably by an EMF unit of the type described, will remove from the radioactive waste water substantially all of the contaminants. Testing of an EC unit similar to that shown in FIG. 2, where measurements were made of the metals content of the influent and of the clarified water (supernate) in a settling container receiving the EC unit effluent, has demonstrated the following removal efficiencies: 99.0% to 99.9% for copper, 99.8% for iron, 99.5% for nickel, and 98.7% to 99.9% for zinc. The demonstrated removal efficiency for total suspended solids was 97.9%. A preferred embodiment of the EMF unit is shown in FIG. 3, which shows more clearly than FIG. 1 that the filtering media bed 50 comprises a plurality of small pieces, preferably stainless steel ball bearings 74, and that the longitudinal centerline of the media housing 52 is preferably aligned with the central axis of the electrical coil 46 surrounding the housing 52. Ball bearings with smooth round surfaces are preferable for use in the packed bed 50 because such a packed bed has a large void volume, which allows a high loading of ferro-magnetic precipitates. The coil 52 is made up of a continuous electrical conductor 76 that is coiled around a spool 77. The respective ends of the conductor 76 are connected to the direct current power source 48 via electrical connectors 78 and 79 and their corresponding connector wires. The EMF unit includes a support screen 80 of a mesh size large enough to provide free liquid flow but small enough to prevent passage of the filter media balls 74. Thus, screen 80 supports the filter media above the outlet 82 of the housing 52. The unit 44 is connected to the outlet of pump 38 by a conduit 84 and to the recovered water tank 54 by a conduit 87, which may also include a valve 86 for controlling the rate of fluid flow through the filtering media 50. The direction of fluid flow through the filtering media bed 50 is preferably downward as illustrated by the arrows 83 and 85 so as to facilitate a subsequent upward backwashing flow that is more effective than a downward flow for removing accumulated precipitates because the heavier crud accumulates at and near where flow enters the bed, and support screen 80 would interfere with using a downward flow to dislodge this crud. However, the EMF unit is also effective for the removal of ferro-magnetic precipitates irrespective of the direction of flow of the waste water being treated or of the backflush water. The rate of fluid flow through the EMF housing 52 may be in the range of 1 lpm to 200 gpm, depending on the overall flow rate through the production EC unit, such that the production EMF unit flow would preferably also be in the range of 30 to 60 gpm. In FIG. 4, there is shown a modified EMF housing 52′ having an end cap 90 at each end for retaining the filtering media within the housing and for connecting the housing to the influent and effluent conduits. Each housing end cap contains a wall 91 for supporting the filtering media and through which passes a flow tube 92 containing a screening member 93 for preventing passage of the individual pieces of the filtering media. Also shown is a modified filtering media comprised of multifaceted 430 stainless steel balls 74′, the facets of which are shown more clearly in FIG. 5. In FIG. 6, there is shown an alternative modification of the EMF unit wherein the filtering media is a 430 stainless steel screen 94 with a 10 micron mesh size, the punched out or woven screen apertures 95 of which are shown more clearly in FIG. 7. In FIG. 8, there is shown a further alternative embodiment of the EMF unit wherein the filtering media comprises one or more tubular sheets 97 of 430 stainless steel. The preferred parameters for electrolytic coagulation of ions and colloids and other solids suspended in radioactive waste water are: adjust waste water pH into range of 5.5 to 8.0, preferably 7.0-8.0, by adding if needed sodium hydroxide or bicarbonate of soda, adjust resistivity to μmhos per centimeter or greater, preferably 20 to 30 μmhos per centimeter (micro-siemens per centimeter, i.e., μmhos are the reciprocal of μohms and may also be referred to as micro-siemens) by adding if need sodium sulfate or sodium bicarbonate, and then apply 4 to 6, preferably 5, amps of direct current (DC) at 23-24 volts. The coagulated floc produced by these parameters can be removed by a 20 to 25 micron filter. Waste water with resistivity of less than 5 μmhos may be adjusted into the desired range by the addition of sodium sulfate or bicarbonate of soda. The effectiveness of electro-coagulation (EC) may be increased by providing greater electrode contact time by lowering the flow rate or recycling the flow, by increasing the electrode area immersed in the electrolyte, by increasing the current density between the anodes and cathodes, such as by jumpering electrodes of the same type where they are connected in series between the positive and negative terminals (thereby connecting them in parallel), and by raising the conductivity by adding sodium sulfate or bicarbonate of soda. Because radioactive metals will plate out on the cathode of the electro-coagulation apparatus, it is preferable that these electrodes be cleaned of the deposited metals while remaining in place, instead of being removed for cleaning in a decontamination facility. Such cleaning in place is preferably accomplished by a temporary current reversal during which the EC anode becomes a cathode and the EC cathode becomes an anode to accomplish electro-cleaning. This current reversal causes the plated metals to be redissolved into a waste liquor which is then back flushed to a conventional radioactive disposal system. The preferred parameters for the magnetic filter is to apply 10 amps of direct current at 36 volts to the conductor coils surrounding the core of stainless steel ball bearings 74, each preferably having a diameter of about 0.2-0.5 centimeters (cm), more preferably 7/32 inch diameter balls. The stainless steel balls used should serve as a soft magnetic core that does not stay magnetized in the absence of direct current through the surrounding coils. If a hard magnetic core is used, an alternating current must subsequently be applied to the coil to “demagnetize” the hard metal core that would otherwise retain its magnetism. Since the floc in BWR waster water contains iron, it is magnetic and can be separated from the waste water by the electromagnetic filter. If the amount of ferromagnetic material in the waste water is low, the effectiveness of electromagnetic filtering (EMF) may be enhanced by the addition of magnetite as a seeding agent to the wastewater before it is subjected to electro-coagulation. If the clarified water leaving the combined EC-EMF system has a conductivity that is too high for disposal, reuse or recycle, the conductivity may be lowered by passing the clarified water through an ion exchange system. The following is an example of the operation of the system of FIG. 1 for the treatment of radioactive waste water containing contaminants in the form of a solution or slurry comprising ions, colloidal particles and suspended solids. The slurry is fed to the adjusting tank 14, wherein its pH is adjusted from 5.5 to 7 by the addition of sodium hydroxide (or sodium bicarbonate, which adjusts both pH and conductivity) and its conductivity is adjusted from about 2 μmhos to about 100 μmhos by the addition of a saturated sodium sulfate solution or a sodium bicarbonate solution. The lower conductivity would have resulted in negligible current flow between the EC electrodes, whereas the higher conductivity will provide a current of about 4-5 amps. The adjusted influent from the adjusting tank 14 is fed to the EC unit 26 at a flow rate, and the power supply 30 is operated at a voltage, sufficient to apply a current of 1-amp-minute through the waste water as it flows through the EC unit on its way to the floc tank 36. In the floc tank 36, sufficient Betz-1138 could be added to provide about 4-10 parts per million (ppm) of this flocculation polymer, which serves to make the sediment S and the floc F in tank 36 significantly larger. However, the EC unit alone is more readily dewaterable due to having less bound water, higher sheer strength, etc. The thus treated waste water is then conveyed by pump 38 through the EMF unit 44 where this waste water passes through a packed bed of ball bearings made of 430 stainless steel and having smooth surfaces (as most preferred). A current of 7.5 amps is applied to the coils during passage of the waste water through the electro-magnetic field generated thereby. The flow rate of this water through the housing 52, and the axial length of the coil 46, are such that the residence time of the waste water within the magnetic field is about 2.5 seconds. The effectiveness of this treatment is evident by the visual clarity (clear and colorless) of the EMF effluent delivered to the recovered water tank 54, as compared with the densely clouded (opaque) suspension of red/brown precipitates of the stirred contents of floc tank 36 as it is fed to the pump 38. This treated water also has no detectable non-volatile radioactivity (there could still be some volatile tritium gas). Thereafter, the EMF unit is cleaned by turning off the current and providing a liquid flow reversal through the packed ball core by activating pump 56 to flush away the accumulated floc and convey this floc to a dewatering container 58, such as a high integrity container (HIC), or some other conventional disposal system for handling radioactive sludges. The deposited settlement from this cleaning liquid will usually meet the EPA's TCLP requirements for disposal, and therefore may usually be sealed in the HIC and shipped to a low level waste site for disposal. It will be apparent to one of ordinary skill in the art of waste treatment that many other modifications and substitutions may be made to the preferred embodiments described above without departing from the spirit and scope of the present invention as defined by the claims set forth below.
	abstract	The exposure device is able to supply only EUV radiation to a mask, while eliminating radiation other than the EUV radiation. A multi layer made from a plurality of Mo/Si pair layers is provided upon the front surface of a mirror, and blazed grooves are formed in this multi layer. Radiation which is incident from a light source device is incident upon this mirror, and is reflected or diffracted. Since the reflected EUV radiation (including diffracted EUV radiation) and the radiation of other wavelengths are reflected or diffracted at different angles, accordingly their directions of progression are different. By eliminating the radiation of other wavelengths with an aperture and/or a dumper, it is possible to irradiate a mask only with EUV radiation of high purity.
	summary
	abstract	A neutron radiation installation for treatment of different types of cancer tumours, comprising a source of neutrons (11), like a nuclear reactor or an accelerator dependent source of radiation, a conventional filter (14) for reducing the radiation energy to a suitable level for radiation treatment of cancer tumours, having low energetic neutron beams of an energy of between 1 eV and 40 keV, or preferably between 1 keV and 20 keV, and a radiation tube (22) out of which radiation beams are emitted towards a patient (10) having a cancer tumour (23), whereby an optimum radiation is obtained at a distance of between 50 and 100 cm from the output surface of the conventional filter (14), and in which the installation comprises an additional radiation filter (21) mounted between the conventional filter (14) and the output of the radiation tube, which additional filter is of a material which filters off neutrons in the epithermic spectrum from low energetic neutron beams up to an energy of about 1 keV, in particular metallic lithium, or another form of the element lithium, which has been enriched to about 95% in the isotope Li6.
	description	The present invention is composition and a method by which a composition, formed by combining a polymer base matrix, a thermally and EMI and RF wave absorptive filler, and a thermally conductive and EMI and RF wave reflective coating material is molded into a finished component that has thermally conductive and EMI and RF wave reflective properties. The composition of the present invention employs a base matrix of polymer, for example, with different types of filler material loaded therein. The base matrix is, preferably, liquid crystal polymer; however, it may be other materials. This composition is achieved through the steps of combining the base matrix material with a thermally conductive filler material and molding the composition. This process is known to result in producing polymer compositions with high thermal conductivities as compared to the base matrix alone. The base matrix is loaded with thermally conductive filler. The mix may include, for example, by volume, 40 percent base matrix and 60 percent filler material. Depending on the base matrix and filler, loading can be even higher. One of the primary reasons for employing a thermally conductive plastic composition is that it is moldable into more complex geometries to achieve better heat dissipation. Because of the versatility of the material, applications that would clearly indicate its use are extremely widespread. Many of these applications, however, require both heat dissipating and electrical insulation to be provided concurrently. By way of example, a satellite receiver dish employs a small densely packed circuit package to receive transmissions. The circuits generate a great deal of heat and are continually bombarded with EMI and RF waves. To protect the surrounding device components and satellite dish circuitry from heat buildup and malfunctions resulting from EMI and RF absorption, the circuitry of the satellite dish must be enclosed in an EMI and RF wave reflective case that can also effectively dissipate heat. Traditionally, these cases would be constructed from a metallic material with reflective properties that prevent EMI and RF and also transfer heat. The traditional casings, however, have the traditional drawbacks associated with the fabrication of metal casings as discussed earlier. In these applications, it is logical to attempt to employ thermally conductive polymers as a heat transfer solution. The drawback in the prior art is that although the polymers conduct heat, they also absorb and transfer EMI and RF waves over the same pathways used to transfer the heat. The present invention overcomes the absorption problem of the prior art allowing application of thermally conductive polymers in environments that also require EMI and RF wave shielding. The present invention provides a thermally conductive composite material that is formed by first coating the thermally conductive filler material that is to be employed. The coating of the thermally conductive filler material provides a barrier against the natural properties of the filler to absorb EMI and RF waves while conducting heat to the filler, allowing the heat transfer process to continue. The preferred embodiment of the present invention employs carbon flakes as a thermally conductive filler material. The carbon flakes are then coated with a thermally conductive yet EMI and RF wave reflective material, in the preferred embodiment. This coating is preferably copper but may be other metallic materials, such as aluminum or nickel. The coating provides EMI and RF wave shielding to the naturally conductive filler material preventing transfer of into the filler core and thus preventing EMI and RF waves transfer throughout the final composition. Once coated, the filler material is introduced to the base polymer matrix. The two components are mixed and loaded into the desired molding machine and associated mold in a fashion known in the art which need not be discussed in detail here. Once removed from the mold, the final composition is in its final shape and ready for its end use. As can be understood, the process does not eliminate the localized, introduction of EMI and RF waves into the composition or slight conductivity in localized areas within the material. The composition formed in the process of the present invention, however, prevents conduction and absorption of EMI and RF waves throughout the entire composition by interrupting the pathways within the composition over which the interference would flow. The process of the present invention can be employed for many of the various configurations used in fabricating a thermally conductive composite. Although the preferred embodiment indicates the use of carbon flake filler in a polymer base matrix, many other fillers can be employed to achieve the desired thermally conductive composition. As the type of filler varies, the method of coating the particular material remains the same and EMI reflective metallic material is employed as the coating. In view of the foregoing, a superior moldable thermally conductive composite material with EMI and RF wave reflective properties can be realized. The composition of the present invention, greatly improves over prior art attempts to provide such EMI and RF wave reflective, moldable, thermally conductive materials. In particular, the present invention provides thermal conductivity that is vastly improved over known compositions and provides insulation against the absorption EMI and RF waves that was until now unavailable in the prior art. It would be appreciated by those skilled in the art that various changes and modifications can be made to the illustrated embodiments without departing from the spirit of the present invention. All such modifications and changes are intended to be covered by the appended claims.
	summary
	claims	1. A method for repairing a photo mask, the method comprising:locating a machining probe of a repairing atomic force microscope at a defective portion of a photo mask;reciprocating the machining probe to remove the defective portion of the photo mask;using a scanning electron microscope to observe a photo mask repair process of the machining probe; andimaging in-situ a shape of a repaired photo mask using an imaging probe of an imaging atomic force microscope, the imaging probe being different from the machining probe. 2. The method as claimed in claim 1, further comprising:imaging the defective portion of the photo mask by the machining probe or the imaging probe before removing the defective portion of the photo mask. 3. The method as claimed in claim 1, wherein an end point of the photo mask repair process is determined by observing the photo mask repair process using the scanning electron microscope, andimaging of the repaired photo mask using an imaging probe is performed in higher magnification than the observing the photo mask repair process using the scanning electron microscope. 4. The method as claimed in claim 1, wherein using the scanning electron microscope to observe the photo mask repair process and imaging in-situ the shape of the repaired photo mask using the imaging probe are performed in a same vacuum chamber. 5. A method for repairing a photo mask, the method comprising:loading a photo mask in a vacuum chamber;roughly navigating a defective portion in the photo mask using an electron microscope or an optical microscope;imaging a precise location of the defective portion using a repairing atomic force microscope or an imaging atomic force microscope;locating a machining probe of the repairing atomic force microscope on the defective portion;repairing the defective portion with the machining probe;imaging in-situ a shape of the repaired photo mask using an imaging probe of the imaging atomic force microscope after the repair is finished, the imaging atomic force microscope being different from the repairing atomic force microscope;monitoring a wearing degree of the machining probe; andreplacing the machining probe with a new probe by a replacement probe loading part in the vacuum chamber. 6. The method as claimed in claim 5, further comprising:controlling an incident angle of an electron gun of the electron microscope by driving a rotation stage;wherein the electron microscope is fixed to the vacuum chamber. 7. The method as claimed in claim 5, wherein monitoring the wearing degree is performed by a micro electron column and a micro column sliding stage. 8. The method as claimed in claim 7, wherein an angle of the machining probe with respect to the micro electron column is controlled by driving a rotation stage. 9. The method as claimed in claim 5, wherein repairing the defective portion is observed in real time using the electron microscope. 10. The method as claimed in claim 5, wherein repairing the defective portion is assisted by an ion beam device.
	summary
	description	This application is based on and claims the benefit of priority of U.S. Provisional Application No. 62/907,753, filed Sep. 30, 2019, the entire contents of which are incorporated herein by reference. The present disclosure relates generally to fission reactors and structures related to the nuclear fission reactor space in fission reactors. In particular, a thermal generating structure, such as a fuel element containing a fissionable nuclear fuel composition, is encased by a containment structure, such as cladding. The thermal generating structure has an involute curve shape and a plurality of such shapes is assembled to form the cylindrical reactor layer. The involute curve shape varies based on a radial position with the cylindrical reactor layer, yet uniformity of the involute curve shapes minimizes the number of unique shapes for the fuel element (or other features, such as moderator materials and/or poisons) that are loaded into each thermal generating structure to achieve a desired reactor performance profile. The involute curve shape of the thermal generating structure allows for uniform thick fuel elements and cladding as well as uniform coolant spaces between the individual thermal generating structures. The present disclosure is particularly adapted for manufacture of at least the involute curve shape cladding structure of the thermal generating structure by an additive manufacturing process. The disclosed fission reactor is suitable for use in various applications, including as power sources on small vessels (such as space vessels and satellites), for nuclear thermal propulsion (NTP), and for isotope production. In the discussion that follows, reference is made to certain structures and/or methods. However, the following references should not be construed as an admission that these structures and/or methods constitute prior art. Applicant expressly reserves the right to demonstrate that such structures and/or methods do not qualify as prior art against the present invention. In designing new thermal generating features and structures for fission reactors, adequate cooling of each fuel element across the entire nuclear fission reactor space is often a limiting design factor. In one prior reactor design, uranium fuel has been encapsulated within rolled metal plates by, for example, a cold rolling process. With reference to the schematic illustration in FIG. 1, an arrangement of layers 1 that includes a fuel composition layer 2 between two clad layers (first clad layer 4a and second clad layer 4b) is feed into the nip of rollers 6 in a cold rolling apparatus. The cold rolling process reduces the thickness of the arrangement of layers 1 in one or more cold rolling steps from an initial thickness to a final thickness. In the process, the various layers of material (in the depicted example, the fuel composition layer 2 and the two clad layers 4a and 4b) are metallurgically bonded (indicated in FIG. 1 by a dashed line at the interface between fuel composition layer 2 and the two clad layers 4a and 4b) into a unitary layered structure 8 in which the clad layers 4a and 4b provide encapsulating layers on either side of the fuel composition layer 2 (shown in cross-section in FIG. 1). Whether formed as a strip or a plate, the unitary layered structure 8 can then be further processed using conventional metal forming techniques. In one example, such unitary layered structures 8 in the form of plates have been curved in the shape of an involute and assembled into a reactor core assembly of the High Flux Isotope Reactor (HFIR) 10, which is a nuclear research reactor located at Oak Ridge National Laboratory (ORNL) (a partial view of which is shown in FIG. 1, in cross-section). In the HFIR design, the involute shape 12 provided for uniform thick uranium/clad plates located between uniform coolant spaces. The unitary layered structures and involute shapes in the HFIR have several drawbacks that reduce the flexibility of the design. For example, to conform to neutronic and thermal management requirements, the composition of the fuel composition layer 2 is spatially non-uniform relative to the location in the plate or strip as well as are tailored based on location within the reactor core assembly. But, at the same time, the compositions and distribution of layers of the unitary layered structure are fixed upon processing, e.g., cold rolling, of the fuel composition layer 2 and the two clad layers 4a and 4b. Therefore, the structure at each location in the HFIR has to have a uniquely constructed unitary layered structure and the uniquely constructed unitary layered structure are not otherwise interchangeable. Considering the above, it would be advantageous to have more flexibility in varying the shape, location, and composition of cladded fuel elements in a reactor core assembly. Furthermore, it would be advantageous to meet the requirements for neutronic and thermal management in fission nuclear reactor design with fewer geometric and compositional variations of cladded fuel elements while also reducing complexity of component fabrication and fission nuclear reactor assembly. Additionally, a design that is modular and repetitive and is of sufficiently sized dimensions can allow application of manufacturing methods, such as additive manufacturing. Neutronics and thermal performance of fuel elements in core designs for fission nuclear reactors are influenced by, among other things, the structure, e.g., the shape, size and relative location, of fuel elements, cladding enclosing the fuel element, and coolant channels, and by the thermal transport properties of the fuel element, the cladding, and the coolant. As noted above, alternative designs are needed to increase design and manufacturing flexibility and reliability while still meeting neutronics and thermal performance of fuel elements. One example of an alternative design (shown in FIG. 2) assembles layers (a 60 degree portion 30 of a layer is shown in FIG. 2) containing a series of radially concentric fuel rings 32 into a cylindrically shaped nuclear fission reactor space. In each fuel ring 32, an edge 34a and internal webbing 34b of the fuel ring function as cladding and defines a volume that contains a fuel composition 36 having a bowtie shape. The edge 34a and webbing 34b can also define the shape of the coolant channels 38, which in FIG. 2 have a circular shape in cross-section. The volume containing the fuel composition 36 has the same cross-sectional area in each of the fuel rings 32. Similarly, the coolant channels 38 in each fuel ring 32 have the same cross-sectional area. For neutronics and thermal management purposes, each fuel ring 32 requires a different fuel composition (for a constant fuel cross-sectional area) or a different fuel shape (for a constant fuel composition). For example, a fuel composition sized to fit in ring 32b cannot be used in ring 32f and also successfully operate from the viewpoint of neutronics and thermal management. Thus, in further example, the ten ring design shown in FIG. 2 would require a number of different fuels varying in one or more of fuel composition and fuel shape. Another example of an alternative design (shown in FIGS. 3A and 3B) assembles layers (a 15 degree portion 50 of a layer is shown in FIGS. 3A and 3B) containing pockets 52 for a fuel element 54 that are distributed concentrically and radially within the portion 50. A plurality of portions 50 can be assembled into a cylindrically shaped nuclear fission reactor space. As compared to the example in FIG. 2, the example in FIGS. 3A and 3B changed the shape of the fuel element 54 from a bowtie shape to a more triangular or rectangular shape. Elliptical coolant holes 56 are located in the clad web structure 58 between each pocket 52. Similar to the example in FIG. 2, each differently sized and located fuel elements 54 require a different fuel composition or a different fuel shape and, overall, the example in FIGS. 3A and 3B would also require a sufficiently large number of different fuels varying in one or more of fuel composition and fuel shape (although changing from a bowtie shape to a more triangular or rectangular shape would simplify the manufacture of such components as well as simplify production of such components with varying fuel compositions). However, neutronics and thermal performance analysis for the design shown in FIGS. 3A and 3B demonstrated that, of the various different shapes and locations for the fuel elements, the only fuel element shape that was capable of being adequately cooled was the thinly shaped fuel element 54a at the radially outermost position, i.e., the fuel element with the largest length-to-width ratio. The above two examples demonstrate the challenges in designing thermal generating features and structures for fission reactors in which the structures satisfy neutronics and thermal performance criteria and are of sufficiently common design and/or have sufficiently few variations as to reduce manufacturing complexity and manufacturing variability (and thereby reduce the probability for manufacturing defects). In general, the disclosure is directed to a nuclear fission reactor structure in which the fuel elements containing a fissionable nuclear fuel composition are positioned along an axis of a enclosing cladding structure that has a shape of an involute curve. A plurality of such involute curve shaped cladding structures are arranged to form a ring and multiple concentric rings are arranged to form a layer of the nuclear fission reactor structure. Multiple layers are themselves assembled to form the nuclear fission reactor structure. In exemplary embodiments, the nuclear fission reactor structure is an active core region of a nuclear fission reactor. Embodiments disclosed herein include a nuclear fission reactor structure comprising a plurality of layers. Each layer of the plurality of layers includes: an inner segment body including an inner opening extending axially from a first side of the inner segment body to a second side of the inner segment body, an intermediate segment body radially outward of the inner segment body, and an outer segment body radially outward of the intermediate segment body. A first interior interface separates the inner segment body and the intermediate segment body and a second interior interface separa tes the intermediate segment body and the outer segment body. In a cross-sectional plan view in a plane perpendicular to the axially extending inner opening: the inner segment body includes a plurality of inner cladding arms having a first involute curve shape that spirally radiates outward from a first radially inner end adjacent to the inner opening to a first radially outer end at the first interior interface, the intermediate segment body includes a plurality of intermediate cladding arms having a second involute curve shape that spirally radiates outward from a second radially inner end adjacent to the first interior interface to a second radially outer end at the second interior interface, and the outer segment body includes a plurality of outer cladding arms having a third involute curve shape that spirally radiates outward from a third radially inner end adjacent to the second interior interface to a third radially outer end at a radially outer surface of the outer segment body. Embodiments disclosed herein also include a nuclear fission reactor comprising a plurality of layers as disclosed herein. The plurality of layers are assembled into a nuclear fission reactor structure with a first end surface, a second end surface, and an outer side surface connecting the first end surface to the second end surface. Also included are a radial reflector positioned about the outer side surface of the active core structure, a pressure vessel, and a coolant system in fluid communication with the active core structure through openings in the pressure vessel. Embodiments disclosed herein also include a method of fabricating a nuclear fission reactor structure as disclosed herein. The method comprises manufacturing the inner segment body, segments of the intermediate segment body, and segments of the outer segment body, wherein each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms include a plurality of chambers; assembling the inner segment body, the segments of the intermediate segment body, and the segments of the outer segment body into a layer, wherein the segment bodies are assembled by one of welding and bonding; positioning one of a fissionable fuel composition and a moderator material in the plurality of chambers to form a fuel-loaded layer; and assembling a plurality of fuel-loaded layers into the nuclear fission reactor structure. In an alternative embodiment, of a method of fabricating a nuclear fission reactor structure as disclosed herein, the method comprises manufacturing a layer including the inner segment body, the intermediate segment body, and the outer segment body as a unitary structure, wherein each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms include a plurality of chambers; positioning one of a fissionable fuel composition and a moderator material in the plurality of chambers to form a fuel-loaded layer; and assembling a plurality of fuel-loaded layers into the nuclear fission reactor structure. Additionally, although the disclosed reactor and core have complex mechanical geometries, integral and iterative manufacturing on a layer-by-layer basis using additive manufacturing techniques, such as 3D printing, of elemental metal or metal alloys enables the structure and features disclosed herein to be more easily manufactured. For ease of viewing, in some instances only some of the named features in the figures are labeled with reference numerals. FIG. 4 schematically illustrates in perspective, partial disassembled view a simplified example embodiment of a nuclear fission reactor 100. The nuclear fission reactor 100 comprises a plurality of layers 102 assembled into a nuclear fission reactor core structure 104 with a first end surface 106, a second end surface 108, and an outer side surface 110 connecting the first end surface 106 to the second end surface 108 arranged along a longitudinal axis 112 of the active core structure 104. The layers 102 are defined by an inner segment body, an intermediate segment body, an outer segment body, an first interior interface, and a second interior interface as described further herein. The nuclear fission reactor 100 also comprises a radial reflector 114 positioned about the outer side surface 110 of the active core structure 104. The active core structure 104 is shown with a cylindrical structure, but any suitable geometric shape can be utilized as long as the active core structure displays suitable neutronic and thermal management characteristics. In exemplary embodiments, the active core structure 104 has sufficient layers 102 so that the ratio of the length of the active core region (LRX) to the diameter of the active core structure (DRX) is approximately 1 (i.e. LRX/DRX=1±0.05). In general, the radial reflector 114 reduces the neutron leakage of the nuclear fission reactor 100 by scattering back into the core (or reflecting) neutrons that would otherwise escape, which increases the effective multiplication factor (keff) of the design and reduces the amount of fuel necessary to maintain criticality. A pressure vessel and a coolant system in fluid communication with the active core structure through openings in the pressure vessel (shown schematically as pressure vessel 120 and coolant system 130) are also provided. Any suitable radial reflector, pressure vessel and coolant system can be incorporated into the nuclear fission reactor 100. For example, the coolant system can be liquid-based or gas-based. When the coolant system is gas-based, the plurality of layers 102 can be assembled into the active core structure 104 by welding adjacent layers 102 together with weld joints at the outer circumferential surface, i.e., the interface corresponding to the outer side surface 110 of adjacent layers 102, and at the inner diameter surface so as to provide a gas-tight, open cylindrical shape having, in cross-section, an annulus shape. For gas-based coolant systems, having only the outermost surfaces gas-tight is sufficient as gas circulating throughout the active core region is acceptable. When the coolant system is liquid-based, the facing surfaces of adjacent layers 102 are bonded to each other such that the coolant channels are separate from each other while each providing a continuous path for coolant to traverse the active core structure from the first end to the second end. To assist in aligning features, such as coolant channels, in one layer 102 with features in an adjacent layer 102, alignment aids can be used. For example, clocking techniques can be applied that use projecting registry features on a surface of one layer 102 that mate with or insert, for example by inserting into or being received by, receiving spaces on an abutting surface of the adjacent layer 102. Other registry features can also be used including pins, notches, shaped projections and so forth. In addition, other alignment aids such as alignment channels or scribe marks can be used. Also, the alignment aids can be located at one or more of various suitable surfaces, including abutting internal surfaces and continuous outer side surfaces 110. The disclosed nuclear fission reactor structure comprises a plurality of layers, each layer including a series of concentrically arranged segment bodies and each segment body including cladding arms having an involute curve shape. FIG. 5 schematically illustrates in a top view a series of concentric segment bodies 210, 240, 270 each of which include cladding arms having a first involute curve shape, assembled into a layer 200. In exemplary embodiments, the nuclear fission reactor structure comprises an inner segment body 210, an intermediate segment body 240, and an outer segment body 270. The intermediate segment body 240 is radially outward of the inner segment body 210 and the outer segment body 270 is radially outward of the intermediate segment body 240. Interfaces separate one segment body from a sequentially, radially-adjacent segment body. For example, a first interior interface 212 separates the inner segment body 210 and the intermediate segment body 240 and a second interior interface 242 separates the intermediate segment body 240 and the outer segment body 270. The nuclear fission reactor structure includes an inner opening that axially extends from a first axial end of the nuclear fission reactor structure to a second axial end of the nuclear fission reactor structure (typically corresponding to a longitudinal axis of the nuclear fission reactor structure). This inner opening can function as a coolant channel, but can also function (in combination with or exclusive from a coolant channel) to house reactor control equipment, control rods, sensors, or radioisotope production equipment. Each layer has a corresponding inner opening that, when multiple layers are assembled into the nuclear fission reactor structure, defines a portion of the inner opening. FIG. 5 shows an embodiment of a layer 200, in a top view relative to the layer and in a cross-sectional, plan view relative to an assembled nuclear fission reactor structure, in each case in a plane perpendicular to an axis of the axially extending inner opening 202. The layer 200 includes an inner segment body 210 including an inner opening 202 extending axially from a first side 204 of the layer 200 to a second side 206 of the layer 200. The layer 200 also includes an intermediate segment body 240 radially outward of the inner segment body 210 and an outer segment body 270 radially outward of the intermediate segment body 240. The concentrically arranged segment bodies 210, 240, 270 are joined to each other to form the layer 200 at interfaces. The segment bodies can be joined and the interfaces formed by any suitable means. In some embodiments, segment bodies are joined and the interfaces formed by welding; in other embodiments, segment bodies are joined and the interfaces formed by compression fitting. In each case, a first interior interface 212 separates the inner segment body 210 and the intermediate segment body 240 and a second interior interface 242 separates the intermediate segment body 240 and the outer segment body 270. FIG. 6A shows an embodiment of an inner segment body 210, in a top view relative to the inner segment body 210 and in a cross-sectional, plan view relative to an assembled nuclear fission reactor structure, in each case in a plane perpendicular to an axis of the axially extending inner opening 202. FIG. 6B shows a magnified view of a portion P1 of inner segment body 210 shown in FIG. 6A. The inner segment body 210 includes a plurality of inner cladding arms 214 having a first involute curve shape that spirally radiates outward from a first radially inner end 216 adjacent to the inner opening 202 to a first radially outer end 218 at the outer edge 220 that will form or be part of the first interior interface 212 in the assembled layer 200. The plurality of inner cladding arms 214 include a plurality of chambers 222. The plurality of chambers 222 are distributed along the length of the inner cladding arm 214. Each chamber 222 is contained within a web 224 of the material that forms the inner segment body 210 such that, in each cladding arm 214, each chamber 222 is enclosed by the web 224 and a first chamber 222a is separated from an adjacent chamber 222b by a portion of the web 224. As described herein, the chambers 214 can contain a fissionable fuel composition (or other compositions, such as moderator materials and poisons) and the web 224 functions as cladding for the fissionable fuel composition or other compositions. One or more coolant openings 230 are located between the plurality of chambers 222 in one cladding arm 214 and the plurality of chambers 222 in an adjacent inner cladding arm 214 (such as chamber 222c in one inner cladding arm 214a and chamber 222d in adjacent inner cladding arm 214b (see FIG. 6B)). The coolant openings 230 extend through the inner cladding arm 214 in the direction of the thickness of the inner segment body 210 from a first side 204′ of the inner segment body 210 to a second side 206′ of the inner segment body 210. The coolant openings 230 can be of various forms. For example, where the web 224 of the inner segment body 210 is a unitary body, the coolant openings 230 are one or more passages, channels or other openings that can be formed in the web during initial web manufacturing, e.g., during the layer-by-layer deposition process of an additive manufacturing process, or can be formed in the web post-web manufacturing, by a material removal process such as drilling, milling, plunge milling, or using an electrical discharge machining (EDM) process. In another example, where each cladding arm 214 is formed as a unitary body and the plurality of cladding arms 214 are joined to form the inner segment body 210, the coolant openings 230 are passages or other openings that are formed by features in the edges of the inner cladding arm 214, i.e., the edges bounded by the surface of the inner cladding arm 214 forming the first side 204′ of the inner segment body 210, the surface of the inner cladding arm 214 forming the second side 206′ of the inner segment body 210, the surface of the first radially inner end 216 of the inner cladding arm 214, and the surface of the first radially outer end 218 of the inner cladding arm 214. In this regard, the edges of the cladding arm 214 can include grooves, ribs, protrusions or other surface features that, when contacted by an edge of an adjacent cladding arm 214, form one or more passages, channels or other openings. In some embodiments, the surface features are discreet areas located along the periphery of the edges; in other embodiments, the surface features extend along at least one opposing side surface either continuously or discontinuously from a first end oriented toward the first side of the inner segment body to a second end oriented toward the second side of the inner segment body. Combinations of different surface features can also be implemented. Additionally, surface features may be present on only one of the edges of the cladding arm or may be located on both edges of the cladding arm. In one example, the surface feature is a protrusion. Non-limiting examples of protrusions include features resembling bumps, knobs, or mesa-like features, both regularly and irregularly shaped. The surface feature has a top surface distal from the at least one opposing side surface from which the protrusion projects. When assembled in the segment body with an immediately adjacent cladding arm, the top surface of the protrusion contacts an opposing side surface on the immediately adjacent cladding arm and the height or projection distance of the protrusion provides a stand-off separation between the two cladding arms. This stand-off separation forms a channel between the two cladding arms. When present, in some embodiments, such surface features can be offset along the radially extending length of the cladding arm 214 such that the location of the surface features are not coincident to the portion of the web 224 separating a first chamber 222a from an adjacent chamber 222b. Combinations of different coolant openings can also be implemented. As an example, FIG. 6C illustrates a surface feature (in this case a rib 234) on an edge of a cladding arm, (in this case, an example of an inner cladding arm 214). However, surface features can similarly be present on either or both edge surfaces as well as on one or more of the inner cladding arm 214, the intermediate cladding arm 244, and the outer cladding arm 272. In some embodiments, it is preferred that the inner segment body 210 is formed as a unitary body so as to avoid a weld or other structure on the surface forming the inner diameter of the opening 202 that would otherwise be present from joining individual cladding arms 214 or groups of cladding arms 214. For ease of viewing the involute curve shape of inner cladding arm 214, an embodiment of an inner cladding arm 214 is outlined in FIG. 6A. In the illustrated embodiment, the two curving sides 232a, 232b of the involute curve shape of the inner cladding arm 214 are located at a line connecting the mid-points in the web 224 located between the plurality of chambers 222 in one cladding arm 214 and the plurality of chambers 222 in an adjacent inner cladding arm 214. The involute curve shape itself may be of constant width (i.e., where width is the distance between the two opposing curving sides 232a, 232b of the involute curve shape of the inner cladding arm 214) as a function of location along an axis of the involute curve shape extending from a midpoint of the first radially inner end 216 to a midpoint of first radially outer end 218. Alternatively, the involute curve shape may be of varying width as a function of location along an axis of the involute curve shape extending from the midpoint of the first radially inner end 216 to the midpoint of the first radially outer end 218. For example, the involute curve shape may be of a constantly increasing width or constantly decreasing width as a function of location along an axis of the involute curve shape extending from the midpoint of the first radially inner end 216 to the midpoint of the first radially outer end 218. FIG. 7A shows an embodiment of an intermediate segment body 240, in a top view relative to the intermediate segment body 240 and in a cross-sectional, plan view relative to an assembled nuclear fission reactor structure, in each case in a plane perpendicular to an axis of the axially extending inner opening 202. FIG. 7B shows a magnified view of a portion P2 of intermediate segment body 240 shown in FIG. 7A. In FIG. 7A, the intermediate segment body 240 is shown in the context of the inner segment body 210 and outer segment body 270 forming the layer 200. The intermediate segment body 240 includes a plurality of inner cladding arms 244 having a second involute curve shape that spirally radiates outward from a second radially inner end 246 adjacent to an inner opening 248, which will form or be part of the first interior interface 212 in the assembled layer 200, to a second radially outer end 250 at the outer edge 256, which will form or be part of the second interior interface 242 in the assembled layer 200. The plurality of intermediate cladding arms 244 include at least one chamber 252, alternatively a plurality of chambers 252a, 252b (see also, e.g., FIGS. 9 and 10). In FIG. 7B, the chambers 252 are only shown in two intermediate cladding arms 244, but additional intermediate cladding arms 244, alternatively all the intermediate cladding arms 244 can include one or more chambers 252. The chamber 252 extends along the length of the intermediate cladding arm 244 or, where a plurality of chambers is included, the chambers 252a, 252b are distributed along the length of the intermediate cladding arm 244. The chamber 252 (or, where a plurality of chambers is included, the chambers 252a, 252b) is contained within a web 254 of the material that forms the intermediate segment body 240 such that, in each intermediate cladding arm 244, the individual chamber 252 is enclosed by the web 254. Further, where a plurality of chambers 252 is included, a first chamber 252a is separated from an adjacent chamber 252b by a portion of the web 254 (See also FIGS. 9 and 10). As described herein, the chambers 252 can contain a fissionable fuel composition (or other compositions, such as moderator materials and poisons) and the web 254 functions as cladding for the fissionable fuel composition or other compositions. Similar to the inner segment body 210, the intermediate segment body 240 can include one or more coolant openings 258 that can be located between the chamber 252 or the plurality of chambers 252a, 252b in one intermediate cladding arm 244 and the plurality of chamber 252 or the plurality of chambers 252a, 252b in an adjacent intermediate cladding arm 244. The coolant openings 258 extend through the intermediate cladding arm 244 in the direction of the thickness of the intermediate segment body 240 from a first side 204″ of the intermediate segment body 240 to a second side 206″ of the intermediate segment body 240. Also, similar to the inner segment body 210, the coolant openings 258 associated with the intermediate segment body 240 can be of various forms (although the coolant openings 258 associated with the intermediate segment body 240 can be the same or can be different from the coolant openings 230 in the inner segment body 210). For example, where the web 254 of the intermediate segment body 240 is a unitary body, the coolant openings are one or more passages, channels or other openings that can be formed in the web during initial web manufacturing, e.g., during the layer-by-layer deposition process of an additive manufacturing process, or can be formed in the web, post-web manufacturing, by a material removal process such as drilling, milling, plunge milling, or using an electrical discharge machining (EDM) process. In another example, where each intermediate cladding arm 244 is formed as a unitary body and the plurality of intermediate cladding arms 244 are joined to form the intermediate segment body 240, the coolant openings 258 can be passages or other openings that are formed by surface features in the edges of the intermediate cladding arms 244, i.e., the edges bounded by the surface of the intermediate cladding arm 244 forming the first side 204″ of the intermediate segment body 240, the surface of the intermediate cladding arm 244 forming the second side 206″ of the intermediate segment body 240, the surface of the second radially inner end 246 of the intermediate cladding arm 244, and the surface of the second radially outer end 250 of the intermediate cladding arm 244. In this regard, the edges of the cladding arm 244 can include grooves, ribs, or other surface features that, when contacted by an edge of an adjacent intermediate cladding arm 244, form one or more passages, channels or other openings. In this regard, the edges of the intermediate cladding arm 244 can include any of the surface features described and/or shown herein with regard to the inner cladding arm 214 and FIG. 6C. When present, in some embodiments, such surface features can be offset along the radially extending length of the intermediate cladding arm 244 such that the location of the surface features are not coincident to the portion of the web 254 separating a first chamber 252a from an adjacent chamber 252b. Combinations of different coolant openings can also be implemented. In some embodiments, it is preferred that the intermediate segment body 240 is formed as a unitary body so as to avoid a weld or other structure on the surface 260 forming the inner diameter of the opening 248 that would otherwise be present from joining individual intermediate cladding arms 244 or groups of intermediate cladding arms 244. In some embodiments, one or both of the surface 260 forming the inner diameter of the opening 248 and the outer edge 256 of the intermediate segment body 240 can be a smooth surface (as seen for surface 260) or can be a ridged with a series of peaks and valleys (as seen for the surface of the outer edge 256). The form of the surface 260 forming the inner diameter of the opening 248 and of the surface of the outer edge 256 can be complementary to the surface to which they about within the assembled layer 200. However, if not fully complementary, a gap may exist that can function as a coolant channel or an adapter structure can be used to mate non-conforming surfaces at the interface. For example, the first interior interface can include a plurality of secondary coolant channels that traverse the active core structure from the first end to the second end. Alternatively, if these surfaces are not fully complementary, an adapter structure can be used to mate non-conforming surfaces at the interface. As a further alternative, a combination of secondary coolant channels and adapter structures can be implemented. For ease of viewing the involute curve shape of the intermediate cladding arm, an embodiment of an intermediate cladding arm 244 is outlined in FIG. 7A. In the illustrated embodiment, the two curving sides 262a, 262b of the involute curve shape of the intermediate cladding arm 244 are located at a line connecting the mid-points in the web 254 located between the chamber 252 or plurality of chambers 252a, 252b in one intermediate cladding arm 244 and the chamber 252 or plurality of chambers 252a, 252b in an adjacent intermediate cladding arm 244. The involute curve shape itself may be of constant width (i.e., where width is the distance between the two opposing curving sides 262a, 262b of the involute curve shape of the intermediate cladding arm 244) as a function of location along an axis of the involute curve shape extending from a midpoint of the second radially inner end 246 to a midpoint of the second radially outer end 250. Alternatively, the involute curve shape may be of varying width as a function of location along an axis of the involute curve shape extending from the midpoint of the second radially inner end 246 to the midpoint of the second radially outer end 250. For example, the involute curve shape may be of a constantly increasing width or constantly decreasing width as a function of location along an axis of the involute curve shape extending from the midpoint of the second radially inner end 246 to the midpoint of the second radially outer end 250. FIG. 8A shows an embodiment of an outer segment body 270, in a top view relative to the outer segment body 270 and in a cross-sectional, plan view relative to an assembled nuclear fission reactor structure, in each case in a plane perpendicular to an axis of the axially extending inner opening 202. FIG. 8B shows a magnified view of a portion P3 of outer segment body 270 shown in FIG. 8A. The outer segment body 270 includes a plurality of outer cladding arms 272 having a third involute curve shape that spirally radiates outward from a third radially inner end 274 adjacent to an inner opening 276, which will form or be part of the second interior interface 242 in the assembled layer 200, to a third radially outer end 278 at the outer edge 280, which will form or be part of the radially outermost edge in the assembled layer 200 (or, if additional segment bodies are included beyond the three depicted, will form or be part of a further interface in the assembled layer 200). The plurality of outer cladding arms 272 include at least one chamber 282, alternatively a plurality of chambers 282a, 282b (see also, e.g., FIGS. 9 and 10). In FIG. 8B, the chambers 282 are only shown in two outer cladding arms 272, but additional outer cladding arms 272, alternatively all the outer cladding arms 272, can include one or more chambers 282. The chamber 282 extends along the length of the outer cladding arm 272 or, where a plurality of chambers is included, the chambers 282a, 282b are distributed along the length of the outer cladding arm 272. The chamber 282 (or, where a plurality of chambers is included, the chambers 282a, 282b) is contained within a web 284 of the material that forms the outer segment body 270 such that, in each outer cladding arm 272, the individual chamber 282 is enclosed by the web 284. Further, where a plurality of chambers 282 is included, a first chamber 282a is separated from an adjacent chamber 282b by a portion of the web 284 (See also FIGS. 9 and 10). As described herein, the chambers 282 can contain a fissionable fuel composition (or other compositions, such as moderator materials and poisons) and the web 284 functions as cladding for the fissionable fuel composition or other compositions. Similar to the inner segment body 210 and intermediate segment body 240, the outer segment body 270 can include one or more coolant openings 286 that can be located between the chamber 282 or the plurality of chambers 282a, 282b in one outer cladding arm 272 and the chamber 282 or the plurality of chambers 282a, 282b in an adjacent outer cladding arm 272. The coolant openings 286 extend through the outer cladding arm 272 in the direction of the thickness of the outer segment body 270 from a first side 204′″ of the outer segment body 270 to a second side 206′″ of the outer segment body 270. Also, similar to the inner segment body 210 and intermediate segment body 240, the coolant openings 286 associated with the outer segment body 270 can be of various forms (although the coolant openings 286 associated with the outer segment body 270 can be the same or can be different from one or more of the coolant openings 58 in the intermediate segment body 240 and the coolant openings 230 in the inner segment body 210). For example, where the web 284 of the outer segment body 270 is a unitary body, the coolant openings are one or more passages, channels or other openings that can be formed in the web during initial web manufacturing, e.g., during the layer-by-layer deposition process of an additive manufacturing process, or can be formed in the web, post-web manufacturing, by a material removal process such as drilling, milling, plunge milling, or using an electrical discharge machining (EDM) process. In another example, where each outer cladding arm 272 is formed as a unitary body and the plurality of outer cladding arms 272 are joined to form the outer segment body 270, the coolant openings 286 can be passages or other openings that are formed by surface features in the edges of the outer cladding arms 272, i.e., the edges bounded by the surface of the outer cladding arm 272 forming the first side 204′″ of the outer segment body 270, the surface of the outer cladding arm 272 forming the second side 206′″ of the outer segment body 270, the surface of the third radially inner end 274 of the outer cladding arm 272 and the surface of the third radially outer end 278 of the outer cladding arm 272. In this regard, the edges of the outer cladding arm 272 can include grooves, ribs, or other surface features that, when contacted by an edge of an adjacent outer cladding arm 272, form one or more passages, channels or other openings. In this regard, the edges of the intermediate cladding arm 244 can include any of the surface features described and/or shown herein with regard to the inner cladding arm 214 and FIG. 6C. When present, in some embodiments, such surface features can be offset along the radially extending length of the outer cladding arm 272 such that the location of the surface features are not coincident to the portion of the web 284 separating a first chamber 282a from an adjacent chamber 282b. Combinations of different coolant openings can also be implemented. In some embodiments, one or both of the surface 288 forming the inner diameter of the opening 276 and the outer edge 280 of the outer segment body 270 can be a smooth surface (as seen for surface 288) or can be a ridged with a series of peaks and valleys (as seen for the surface of the outer edge 280). The form of the surface 288 forming the inner diameter of the opening 276 can be complementary to the surface to which they abut within the assembled layer 200. Also, if a further segment body is radially outward of the outer segment body 270, then the form of the surface of the outer edge 280 can be complementary to the surface to which it abuts within an assembled layer 200. However, if these surfaces are not fully complementary, a gap may exist that can function as a coolant channel. For example, the second interior interface can include a plurality of secondary coolant channels that traverse the active core structure from the first end to the second end. Alternatively, if these surfaces are not fully complementary, an adapter structure can be used to mate non-conforming surfaces at the interface. As a further alternative, a combination of secondary coolant channels and adapter structures can be implemented. For ease of viewing the involute curve shape of the outer cladding arm, an embodiment of an outer cladding arm 244 is outlined in FIG. 8A. In the illustrated embodiment, the two curving sides 292a, 292b of the involute curve shape of the outer cladding arm 272 are located at a line connecting the mid-points in the web 284 located between the chamber 282 or plurality of chambers 282a, 282b in one outer cladding arm 272 and the chamber 282 or plurality of chambers 282a, 282b in an adjacent intermediate cladding arm 272. The involute curve shape itself may be of constant width (i.e., where width is the distance between the two opposing curving sides 292a, 292b of the involute curve shape of the outer cladding arm 244) as a function of location along an axis of the involute curve shape extending from a midpoint of the third radially inner end 274 to a midpoint of the third radially outer end 278. Alternatively, the involute curve shape may be of varying width as a function of location along an axis of the involute curve shape extending from the midpoint of the third radially inner end 274 to the midpoint of the third radially outer end 278. For example, the involute curve shape may be of a constantly increasing width or constantly decreasing width as a function of location along an axis of the involute curve shape extending from the midpoint of the third radially inner end 274 to the midpoint of the third radially outer end 278. In some embodiments, when considered collectively, the first involute curve shape, the second involute curve shape, and the third involute curve shape share a common involute curve shape and, therefore, the surfaces of the inner cladding arm, the surfaces of the intermediate cladding arm, and the surfaces of outer cladding arm form a continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. For example and as seen in FIG. 9, when surfaces of the curving sides 232a, 232b of the first involute curve shape of the inner cladding arm are projected across the first interior interface 212, the projection is coincident with the surfaces of the curving sides 262a, 262b of the second involute curve shape of the intermediate cladding arm. As a result, there is one, continuous involute curve shape that contains the surfaces of the curving sides 232a, 232b of the first involute curve shape of the inner cladding arm and the surfaces of the curving sides 262a, 262b of the second involute curve shape of the intermediate cladding arm. As a further example, when the continuous involute curve shape described above is further projected across the second interior interface 242, the projection is also coincident with the surfaces of the curving sides 292a, 292b of the third involute curve shape of the outer cladding arm. As a result of this further projection, there is one, continuous involute curve shape that contains the surfaces of the curving sides 232a, 232b of the first involute curve shape of the inner cladding arm, the surfaces of the curving sides 262a, 262b of the second involute curve shape of the intermediate cladding arm, and the surfaces of the curving sides 292a, 292b of the third involute curve shape of the outer cladding arm. Also as seen in FIG. 9, each of the first involute curve shape, the second involute curve shape, and the third involute curve shape correspond to different portions of the continuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. In other embodiments, the surfaces of the curving sides 232a, 232b of the first involute curve shape of the inner cladding arm, the surfaces of the curving sides 262a, 262b of the second involute curve shape of the intermediate cladding arm, and the surfaces of the curving sides 292a, 292b of the third involute curve shape of the outer cladding arm correspond to the curvature of a continuous involute curve shape, but one or more of the segment bodies is rotated relative to an adjacent segment body. If rotated less than a quantized value that would maintain alignment of the surfaces, the rotation results in the surfaces of the curving sides being rotationally offset from the projection of the continuous involute curve shape. In such an arrangement, the surfaces of the curving sides of the involute curve shape of the cladding arm on either side of the relevant affected interface are discontinuous in that they are connected by a step change. In still other embodiments, when considered collectively, the first involute curve shape, the second involute curve shape, and the third involute curve shape have different curvatures. Therefore, the surfaces of the inner cladding arm, the surfaces of the intermediate cladding arm, and the surfaces of outer cladding arm form a discontinuous involute curve shape extending from the inner opening to the radially outer surface of the outer segment body. Such an embodiment is illustrated in the example layer 200 illustrated in FIG. 5. Although, in some embodiments, some or all of the surfaces of the inner cladding arm, the surfaces of the intermediate cladding arm, and the surfaces of outer cladding arm form a discontinuous involute curve shape, such surfaces are still collectively radially spiraling in the same direction, i.e., either in a right-handed (clockwise) direction (as seen in FIG. 5) or in a left-handed (counter-clockwise) direction. In still further embodiments, one or more (but less than all) of the first involute curve shape, the second involute curve shape, and the third involute curve shape share a common involute curve shape. Therefore, some of the surfaces of the inner cladding arm, the surfaces of the intermediate cladding arm, and the surfaces of outer cladding arm form a continuous involute curve shape extending across their respective surfaces while other of the surfaces of the inner cladding arm, the surfaces of the intermediate cladding arm, and the surfaces of outer cladding arm form a discontinuous involute curve shape extending across their respective surfaces. In the embodiments shown and described in FIGS. 6A-B, 7A-B, and 8A-B, each of the plurality of inner cladding arms, the plurality of intermediate cladding arms, and the plurality of outer cladding arms can, independently, include one or more chambers. In some embodiments, the inner cladding arms have more chambers than in any either the intermediate cladding arms or the outer cladding arms. For example and as illustrated in FIG. 5, the inner cladding arms in the inner segment body 210 each can contain six chambers 222 (see also chambers 222 in FIG. 6A) and the intermediate cladding arms and the plurality of outer cladding arms each contain one chamber (252 and 282, respectively) (see also chambers 252 in FIG. 7B and chambers 282 in FIG. 8B). As another example and as illustrated in FIG. 10, the inner cladding arms each can contain six chambers 222 (see also chambers 222 in FIG. 6A) and the intermediate cladding arms and the plurality of outer cladding arms each contain two chambers (252 and 282, respectively). In exemplary embodiments, the total number of chambers in one inner cladding arm, one intermediate cladding arm, and one outer cladding arm is ten or less. FIG. 10 also illustrates alternative embodiments of the intermediate segment body 240 and the outer segment body 270. In the alternative embodiments, a plurality of cladding arms are manufactured as unit, such as unit 300 including a plurality of intermediate cladding arms and unit 310 including a plurality of outer cladding arms. Manufacturing cladding arms as a unit is advantageous when utilizing additive manufacturing processes. Furthermore when manufactured as a unit, the units can use less material to form the web (at least in part because adjacent cladding arms can have less web material between any chambers contained in those adjacent cladding arms as compared to separate cladding arms that are then positioned adjacent to each other) and can minimize the number of welded joints needed to assembly a complete segment body. As previously noted, in the various examples of the cladding arm, the individual chambers are enclosed by the web. Typically, during manufacturing, the web forms the sides and bottom of the chamber and one side of the chamber, such as the top, is initially open to allow loading of a fissionable fuel composition (or other compositions, such as moderator materials and poisons). Subsequent to loading, the one open side of the chamber is then closed by way of a cap being attached to the web. FIG. 11 schematically illustrates an example of a cladding arm 400. In the example cladding arm 400, several features discussed herein are shown. For example, the example cladding arm 400 has a plurality of chambers (in the illustrated embodiment, three chambers 402a, 402b, 402c). Also shown is a fuel composition 404. The fuel composition 404 is shown at different points in the loading process. In one example, the fuel composition 404 is an already formed body 406 having dimensions suitable for insertion into the chamber, such as chamber 402a. Suitable dimensions includes the body 406 being sized to have thermal transfer contact between the outer surfaces of the body 406 of the fuel composition 404 and the interior surfaces of the chamber 402. Alternatively, the body 406 has a minimal stand-off distance between the outer surfaces of the body 406 of the fuel composition 404 and the interior surfaces of the chamber 402 and a thermal transfer agent, such as a salt or metal that will be molten at operating temperatures, is also loaded into the chamber 402. Also, the volume of the body 406 is sufficiently smaller than the volume of the chamber 402 to accommodate the by-products of the fission reaction and of operating at elevated temperature, such as a volume to accommodate fission gases and any change in volumes from the fission reaction as well as from any thermal expansion. As seen in association with chamber 402b, the body 406 of the fuel composition is inserted into the chamber and, as seen in association with chamber 402c, a cap 408 closes the chamber, for example, by welding the cap to the portion of the web forming the periphery of the opening of the chamber. Once closed by the cap 408, the chamber is isolated from the environment and the fuel composition 404 is enclosed by the web of the cladding arm 400 (or, if the cap is considered not part of the web after closing the chamber, enclosed by the combination of the web of the cladding arm 400 and the cap). Another example feature shown in the embodiment of the cladding arm 400 are the surface features 420 one edge 422 of the cladding arm 400. As previously described, either one or both of the edges 422,424 are bounded by the surface 426 of the cladding arm 400 that forms/will form the first side of the segment body, the surface 428 of the cladding arm 400 that forms/will form the second side of the segment body, the surface 430 of the radially inner end of the cladding arm 400, and the surface 432 of the radially outer end of the cladding arm 400. In the illustrated example in FIG. 11, the surface feature 420 is a rib that extends above the surface of edge 422. As can be readily understood from FIG. 11, when the edge 422 is contacted by an edge of an adjacent cladding arm, the surface feature 420 will cause the portion of the edge 422 to be off set from the edge of an adjacent cladding arm by a distance that corresponds to the distance that the surface feature 420 extends above the surface of edge 422, thereby forming a channel extending from the surface 426 of the cladding arm 400 that forms/will form the first side of the segment body to the surface 428 of the cladding arm 400 that forms/will form the second side of the segment body. FIG. 12 shows a layer 500 including an inner body segment 502, an intermediate segment body 504, and an outer segment body 506. Each body segment has a plurality of chambers. Located above each segment body are a plurality of fuel composition bodies 508, corresponding in shape (including involute curve shape) and number to the chambers present in the respective segment body in which the fuel composition body will be loaded. For example, fuel composition body 508a will be loaded into the radially inward chamber 510a in the inner segment body 502, fuel composition body 508g will be loaded into the radially inward chamber 510g in the intermediate segment body 504, and fuel composition body 508j will be loaded into the radially outward chamber 510j in the outer segment body 506. Furthermore, in some embodiments the fuel composition in each fuel composition body varies, resulting in chambers at different locations along the cladding arm containing different fissionable fuel compositions. Although shown and described in FIGS. 11 and 12 with respect to a fuel composition, one or more of the instances in which a fuel composition is loaded into a chamber can be substituted by a moderator material composition or a poison composition, or mixtures of a moderator material composition or a poison composition. Such a substitution can be done in accordance with a reactor neutronics design and a thermal management design. FIGS. 13A and 13B shows results of thermal analysis studies on the involute curve shape cladding arm design disclosed herein. Thermal analysis was conducted based on a fission reactor containing such an involute curve shape cladding arm design. The involute curve shape cladding arm design in FIG. 13A shows a cladding arm 600 (corresponding to an embodiment of an inner segment body cladding arm) having a first set of six fuel composition bodies 602, a cladding arm 604 (corresponding to an embodiment of an intermediate segment body cladding arm) having a second set of four fuel composition bodies 606, and with a cladding arm 608 (corresponding to an embodiment of an outer segment body cladding arm) having a third set of four fuel composition bodies 610. Overall, the thermal analysis demonstrated that there is adequate cooling on both sides of the cladding arms of each segment body to prevent the fuel composition in the chambers from melting. Amongst the cladding arms and fuel compositions in FIG. 13A, thermal analysis indicated that temperature ranged from about 1256.3 K (for cladding at the concave surface 620 and at tip 622) to up to 2504.6 K for the hottest temperature elevation, which occurred in the region of the inner segment body cladding arm located toward the radially outer end (corresponding to Section P4 in FIG. 13A and shown in magnified view in FIG. 13B as regions 630a and 630b). Region 630a is associated with the fuel composition body in chamber 602e and occurs on curved edge of the inner segment body cladding arm with a temperature of between 2227.2 K and 2504.6 K. This result was interpreted as the fuel composition body in chamber 602e expanding during operation and causing an increase in curvature of the fuel composition body resulting in the fuel composition body to no longer contact the inner surface of chamber 602e in the region 630a. Because of this gap formed between the fuel composition body and the inner surface of chamber 602e, the heat transfer decreased and the temperature increased. Note that this test did not include a thermal transfer agent, such as a salt or liquid metal buffer, the presence of which would be expected to fill the gap and improve heat transfer and reduce the temperature in region 620. However, the portion 622 of the web collocated with region 620 maintains a much lower temperature of between 1256.3 K and 1395 K. The involute curve shape cladding arms, segmented bodies and layers disclosed herein can be manufactured by any suitable process. FIGS. 14A-D is a flow diagram graphical illustrating exemplary steps in the assembly of a layer from the various portions of the segmented bodies (FIG. 14A-B, the loading of a fuel composition and/or moderator composition and poisons into the layer (FIG. 14C), and the assembly of multiple layers into a nuclear fission reactor structure (FIG. 14D). In a first manufacturing process, the involute curve shape cladding arms 700 containing a plurality of chambers and wherein a web of the involute curve shape cladding arms defines the cladding structure is manufactured by metallurgical processes. These metallurgical processes, in one example, include an additive manufacturing process. It is preferred that the structure of the inner segment body 702 be made as a unitary structure (as shown in FIG. 14A) to minimize joints on the inner diameter surface of the opening. Furthermore, using suitable additive manufacturing processes, the entire structure of a layer 720, including the features of an inner segment body 702, an intermediate segment body 704 and an outer segment body 706 structure of the inner segment body 702, can made as a unitary structure. In other aspects, the involute curve shape cladding arms forming the intermediate segment body 704 and the involute curve shape cladding arms forming the outer segment body 706 can be manufactured individually and joined into the layer or, as shown in FIG. 14A, as a unitary body forming units that are joined into the layer 720 (See FIG. 14B). Other structures of the involute curve shape cladding arms, such as the chambers, and the coolant openings, are typically manufactured at this point in the process. As for the chambers in each of the involute curve shape cladding arms, they are initially manufactured (either in the additive manufacturing process or by machining the material of the involute curve shape cladding arms) to a point where an opening remains defining the chamber, i.e., a cavity having side walls and one closed end. Joining the involute curve shape cladding arms to form the layer 720 (FIG. 14B) can be by any suitable means, including welding and bonding. After forming the layer 720, the chambers are loaded with the fissionable fuel composition 742 (or other material such as a moderator or poison) (see FIG. 14C, wherein the loading process is indicated by arrows). If desired, a thermal transfer agent is also placed into the chamber. Once the chamber is loaded, a cap is placed over the opening and is sealed, for example, by welding or by a hot isostatic pressing (HIP) process, to form the assembled involute curve shape cladding arm. A plurality of assembled layers 740 are then further assembled into a nuclear fission reactor structure 780 as shown in FIG. 14D. The layers are arranged one on top of the other with corresponding internal structures, such as coolant openings. As previously disclosed, clocking techniques using projecting registry features can be used for alignment purposes. In an example construction, up to 10 layers 740 can be assembled to form the nuclear fission reactor structure 780. Assembly of the layers 740 is by any suitable means, such as welding or bonding. In addition, a plate 782 can be placed on either end of the nuclear fission reactor structure 780. The plate can have suitable openings for, for example, to correspond to the coolant openings, to correspond to the inner opening, and/or to correspond to openings for instrumentation. The assembled nuclear fission reactor structure 780 is placed within a radial reflector 784. A radial reflector is optional based on fuel materials and core design. In some manufacturing methods or steps in manufacturing methods, portions of the involute curve shape cladding arms, the segment bodies, and/or the layers are manufactured as an integral, unitary structure using, for example, an additive manufacturing process. As used herein, additive manufacturing processes include any technologies that build 3D objects by adding material on a layer-upon-layer basis. An example of a suitable additive manufacturing process utilizes 3-D printing of a metal alloy, such as a molybdenum-containing metal alloy, Zircalloy-4 or Hastelloy X, to form the noted structural features. In other embodiments, the fissionable nuclear fuel composition and/or the thermal transfer agent and/or the moderator materials and/or poisons can be included within the integral, unitary structure when suitable multi-material, additive manufacturing processes with multiple metals within the feedstock are employed. If the molten metal is not included in the additive manufacturing process, the additive manufacturing process can be paused, a volume of molten metal placed into the fuel cavity (either in liquid or solid form) and the additive manufacturing process continued to complete the structure of the closed chamber. Other alloys that can be used when suitable multi-material, additive manufacturing processes with multiple metals within the feedstock are employed include: steel alloys, zirconium alloys, and Molybdenum-Tungsten alloys (for the shell of the reactor core); beryllium alloys (for the reflector); and stainless steel (for the containment housing). Even when not manufactured by an additive manufacturing process, the above materials can be used in manufacturing the various structures disclosed herein. Additive manufacturing techniques for the manufacture of integral and unitary structures can include the additional steps of: (a) predictive and causal analytics, (b) in-situ monitoring combined with machine vision and accelerated processing during the layer-by-layer fabrication of the structure, (c) automated analysis combined with a machine learning component, and (d) virtual inspection of a digital representation of the as-built structure. In addition, additive manufacturing technology can create complex geometries and, when coupled with in-situ sensors, machine vision imagery, and artificial intelligence, allows for tuning of the manufacturing quality as the components are built on a layer-by-layer additive basis (often, these layers are on the scale of 50 microns) and provides predictive quality assurance for the manufacture of such reactors and structures. As used herein, cladding is the outer layer of fuel containing features and is located between the coolant and the nuclear fuel. The cladding functions as a safety barrier that prevents radioactive fission fragments from escaping the fuel into the coolant and contaminating it. Some design constraints of cladding include neutron absorption, radiation resistance and temperature behavior. The cladding is typically made of a corrosion-resistant material with low absorption cross section for thermal neutrons. Example materials include Zircaloy or steel, although other materials may be used if suitable to the reactor conditions, such as metallic and ceramic systems (Be, C, Mg, Zr, O, and Si). In some embodiments, the cladding material can be isotope enriched to enhance reactive through reduction of isotopes with higher neutron absorption cross-sections, e.g., molybdenum enriched Mo-92 will have a less parasitic neutron absorption cross-section than elemental molybdenum. A suitable fissionable nuclear fuel composition applicable to the disclosed fission reactor and to be included in the heat generating source includes uranium oxide that is less than 20% enriched, uranium with 10 wt. % molybdenum (U-10Mo), uranium nitride (UN), and other stable fissionable fuel compounds. Burnable poisons may also be included. Typically, the fissionable nuclear fuel composition is in the form of a ceramic material. Suitable molten metals for inclusion in the disclosed fission reactor and to be included in the fuel cavity is sodium (Na), sodium-potassium (NaK), potassium (K), and iron (Fe). It is contemplated that various supporting and ancillary equipment can be incorporated into the disclosed fission reactor. For example, at least one of a moderator (such as a zirconium hydride (ZrH), beryllium oxide (BeO), water and graphite), a control rod (such as iridium control rod), and a scientific instrument (such as a temperature sensor or radiation detector), as well as isotope production equipment, can be incorporated into the fission reactor. Additionally, the control rods can also incorporate a neutron poison which absorbs neutrons and can be used to regulate the criticality of nuclear reactors. The neutron poison can absorb enough neutrons to shut down the fission reactor (e.g., when the control rods are completely inserted into the reactor space) or can be axially positioned to maintain criticality of the fission reactor (e.g., when the control rods are withdrawn from the reactor core a distance to allow a continuous fission chain reaction). Any suitable number of control rods and moderators can be used and suitably distributed throughout the reactor space in order to obtain one or more of a desired flux profile, power distribution, and operating profile. In exemplary embodiments, the control rods are threaded, which contribute to save axial space, maximizes control rod diameter, and allows for direct roller nut contact for reliable SCRAM operation. All or a subset of control rods can be individually controlled by independent motors to provide discrete reactivity control and/or for power shaping. FIG. 15 schematically illustrates in cross-sectional side view an embodiment of a nuclear fission reactor 800 comprising a plurality of layers 802 assembled into a nuclear fission reactor structure 804 and arranged along a longitudinal axis 806 of the nuclear fission reactor structure 804. The layers 802 are defined by an inner segment body, an intermediate segment body, an outer segment body, a first interior interface, and a second interior interface as previously disclosed and described in embodiments herein. The nuclear fission reactor 800 also comprises a radial reflector 810 positioned about the outer side surface of the nuclear fission reactor structure 804. The nuclear fission reactor structure 804 can be any suitable geometric shape as long as it displays suitable neutronic and thermal management characteristics. As noted herein, exemplary embodiments have sufficient layers 802 so that the ratio of the length of the active core region (LRX) to the diameter of the active core structure (DRX) is approximately 1 (i.e., LRX/DRX=1±0.05). In general, the radial reflector 810 reduces the neutron leakage of the nuclear fission reactor 800 by scattering back into the core (or reflecting) neutrons that would otherwise escape, which increases the effective multiplication factor (keff) of the design and reduces the amount of fuel necessary to maintain criticality. A pressure vessel 820 encloses, among other things, the nuclear fission reactor structure 804 and has openings 822 to allow the active core structure to be in fluid communication (the flow of coolant being indicated by arrows 824) with a coolant system (not shown). Some of the various ancillary equipment associated with nuclear fission reactors are also shown in FIG. 15, including a control rod assembly 830 and shut down equipment, such as poison rod 832 which can be moved axially within the inner opening of the nuclear fission reactor structure 804. As previously disclosed and described in embodiments herein, any suitable radial reflector, pressure vessel and coolant system can be incorporated into the nuclear fission reactor 800. The disclosed arrangements pertain to any configuration in which a heat generating source including a fissionable nuclear fuel composition, whether a fuel element or the fissionable nuclear fuel composition per se, is surrounded by cladding. Although generally described herein in connection with a pressurized water reactor (PWR reactors) and with water as a primary coolant, the structures and methods disclosed herein can also be applicable to other reactor systems. This includes boiling water reactors (BWR reactors), deuterium oxide (heavy water) moderator reactors such as CANDU reactors, light water reactors (LWR reactors), pebble bed reactors (PBR reactors), nuclear thermal propulsion reactors (NTP reactors), both commercial and research reactors, and utilize other primary coolants, such as helium, hydrogen, methane, molten salts, and liquid metals. Any fuel-to-clad configuration in these various reactors may produce better nuclear core safety and performance characteristics if the molten metal fuel buffer technique disclosed herein is utilized. Fission reactors disclosed herein can be used in suitable applications including, but not limited to, terrestrial power sources, remote power or off-grid applications, space power, space propulsion, isotope production, directed energy applications, commercial power applications, and desalination. While reference has been made to specific embodiments, it is apparent that other embodiments and variations can be devised by others skilled in the art without departing from their spirit and scope. The appended claims are intended to be construed to include all such embodiments and equivalent variations.
	claims	1. A grid for absorbing electromagnetic radiation comprising: a plurality of comb elements, each comb element of the plurality of comb elements having a rigid and substantially flat base upon which comb lamellae extend transversely, the comb lamellae having a height perpendicular to the base, wherein the plurality of comb elements are arranged such that the lamellae of each comb element abuts a flat surface of the flat base of an adjacent comb element to form a grid structure having apertures having an interior dimension that equals the height of the lamellae. 2. A grid for absorbing electromagnetic radiation comprising: a plurality of comb elements, each comb element of the plurality of comb elements having a rigid and substantially flat base upon which comb lamellae extend transversely on each of two opposing surfaces of the flat base, the comb lamellae having a height perpendicular to the base, and a plurality of rigid and substantially flat separating elements, wherein the plurality of comb elements are arranged such that the lamellae of each comb element abuts a flat surface of a corresponding element of the plurality of separating elements to form a grid structure having apertures having an interior dimension that equals the height of the lamellae. 3. A grid as claimed in claim 1 , characterized in that claim 1 the lamellae form a comb structure of the plurality of comb elements that is focused on a focal spot. 4. A grid as claimed in claim 1 , characterized in that claim 1 the plurality of comb elements are secured in a frame by way of grooves at edges of the frame. 5. A grid as claimed in claim 4 , characterized in that claim 4 the plurality of comb elements are glued in the grooves. 6. A grid as claimed in claim 1 , characterized in that claim 1 the plurality of comb elements absorb X-rays. 7. A focused detection system comprising: a detector that is configured to detect X-rays, and a grid for the absorption of X-rays that includes: a plurality of comb elements, each comb element of the plurality of comb elements having a rigid and substantially flat base upon which comb lamellae extend transversely, the comb lamellae having a height perpendicular to the base, wherein the plurality of comb elements are arranged such that the lamellae of each comb element abuts a flat surface of the flat base of an adjacent comb element to form a grid structure having apertures having an interior dimension that equals the height of the lamellae, such that X-rays that enter the apertures substantially normal to the grid are detected by the detector, and X-rays that enter the apertures at a non-normal angle to the grid are absorbed by the grid. 8. An X-ray apparatus which includes a grid which is arranged in front of a detector in order to absorb X-rays, wherein the grid includes: a plurality of comb elements, each comb element of the plurality of comb elements having a rigid and substantially flat base upon which comb lamellae extend transversely, the comb lamellae having a height perpendicular to the base, wherein the plurality of comb elements are arranged such that the lamellae of each comb element abuts a flat surface of the flat base of an adjacent comb element to form a grid structure having apertures having an interior dimension that equals the height of the lamellae, such that X-rays that enter the apertures substantially normal to the grid are detected by the detector, and X-rays that enter the apertures at a non-normal angle to the grid are absorbed by the grid. 9. A method of manufacturing a grid that is configured to absorb electromagnetic radiation, comprising: providing a plurality of comb elements, each comb element of the plurality of comb elements having a rigid and substantially flat base upon which comb lamellae extend transversely, the comb lamellae having a height perpendicular to the base, and arranging the plurality of comb elements such that the lamellae of each comb element abuts a flat surface of the flat base of an adjacent comb element to form a grid structure having apertures having an interior dimension that equals the height of the lamellae. 10. A method of manufacturing a grid that is configured to absorb electromagnetic radiation, comprising: providing a plurality of comb elements, each comb element of the plurality of comb elements having a rigid and substantially flat base upon which comb lamellae extend transversely on each of two opposing surfaces of the base, the comb lamellae having a height perpendicular to the base, providing a plurality of rigid and substantially flat separating elements, arranging the plurality of comb elements such that the lamellae of each comb element abuts a flat surface of a corresponding element of the plurality of separating elements, to form a grid structure having apertures having an interior dimension that equals the height of the lamellae. 11. A grid as claimed in claim 2 , characterized in that claim 2 the lamellae form a comb structure of the plurality of comb elements that is focused on a focal spot. 12. A grid as claimed in claim 2 , characterized in that claim 2 the plurality of comb elements and separating elements are secured in a frame by way of grooves at edges of the frame. 13. A grid as claimed in claim 12 , characterized in that claim 12 the plurality of comb elements and separating elements are glued in the grooves. 14. A grid as claimed in claim 2 , characterized in that claim 2 the plurality of comb elements absorb X-rays. 15. A focused detection system comprising: a detector that is configured to detect X-rays, and a grid for the absorption of X-rays that includes: a plurality of comb elements, each comb element of the plurality of comb elements having a rigid and substantially flat base upon which comb lamellae extend transversely on each of two opposing surfaces of the flat base, the comb lamellae having a height perpendicular to the base, and a plurality of rigid and substantially flat separating elements, wherein the plurality of comb elements are arranged such that the lamellae of each comb element abuts a flat surface of a corresponding element of the plurality of separating elements to form a grid structure having apertures having an interior dimension that equals the height of the lamellae, such that X-rays that enter the apertures substantially normal to the grid are detected by the detector, and X-rays that enter the apertures at a non-normal angle to the grid are absorbed by the grid. 16. An X-ray apparatus which includes a grid which is arranged in front of a detector in order to absorb X-rays, wherein the grid includes: a plurality of comb elements, each comb element of the plurality of comb elements having a rigid and substantially flat base upon which comb lamellae extend transversely on each of two opposing surfaces of the flat base, the comb lamellae having a height perpendicular to the base, and a plurality of rigid and substantially flat separating elements, wherein the plurality of comb elements are arranged such that the lamellae of each comb element abuts a flat surface of a corresponding element of the plurality of separating elements to form a grid structure having apertures having an interior dimension that equals the height of the lamellae, such that X-rays that enter the apertures substantially normal to the grid are detected by the detector, and X-rays that enter the apertures at a non-normal angle to the grid are absorbed by the grid. 17. An X-ray apparatus according to claim 16 , wherein claim 16 the height of the lamellae is tapered along a transverse axis of the base. 18. An X-ray apparatus according to claim 8 , wherein claim 8 the height of the lamellae is tapered along a transverse axis of the base. 19. A grid according to claim 1 , wherein claim 1 the height of the lamellae is tapered along a transverse axis of the base. 20. A grid according to claim 2 , wherein claim 2 the height of the lamellae is tapered along a transverse axis of the base.
	summary
046541918	summary	BACKGROUND OF THE INVENTION The present invention relates to a pressure release arrangement for a container, especially for the safety containment of a pressurized water nuclear reactor in connection with which it is utilized to provide for safe pressure release before the occurrence of a containment explosion. Pressure reduction in containers may be achieved by operational measures which, during failures, always impart certain insecurities. It is generally safer to install in the safety containment a suitable pressure relief valve which is independent of operational actions. It is the object of the present invention to provide a release valve which remains securely closed during normal operating pressures in the safety containment and which opens only just before rupture of the containment would otherwise occur since otherwise, that is, if the valve could open earlier, containment integrity during the normal, more likely accidents for which the containment was designed might be questionable. It is also to be taken into consideration that testing of the valve for proper operation is not possible when such a valve is installed since the valve opening pressure is above the operating pressure for which the containment is designed. Such a valve therefore needs to be composed of simple structural elements which can be exactly calculated by well established stress analysis techniques. SUMMARY OF THE INVENTION In a pressure release arrangement for a pressure container such as the pressure containment of a nuclear reactor, a pressure release pipe extends through the containment walls and is closed at its end within the containment by a closure plate. A drawbar is with one end operatively connected to the closure plate and with its other end to a distant point of the containment walls. Within the containment, the release pipe has a design rupture wall area adapted to be ruptured by the drawbar when the vessel walls are stretched beyond a predetermined degree so as to release the pressure to prevent explosion of the containment but to release the pressure only when absolutely necessary as evidenced by stretching of the containment walls. With this arrangement, pressure and, if contained in the containment, radioactive material are released to the environment safely and in a simple manner only when necessary to avoid a more serious accident as it would surely happen by explosion of the containment. The advantages of a relief valve controlled by stress-induced deformation of materials are as follows: During the plastic deformation of the safety containment, a substantial amount of mechanical energy is consumed. A portion of the energy can be utilized by means of the simple elements for the opening of the pressure relief valve. Auxiliary operating means are not necessary. As a result the pressure relief valve is a simple structure which is fully passively operative and insures high reliability without requiring servicing. PA1 Growing plastic deformation of the safety containment is a reliable indication that a critical state of complete rupture of the containment is approaching. PA1 In contrast, the containment pressure is a less reliable indicator since deformation occurs as a result of overpressurization and the interrelation between pressure and deformation is of complex nature with inherent inaccuracies so that the pressure at which a relief valve must be opened cannot exactly be determined. If the pressure would be used as a basis for the control of the pressure relief valves, it would be easily possible, for example, that the pressure relief valve would be permitted to open unnecessarily upon occurrence of momentary pressure peaks which, because of the mass inertia of the containment, would not generate critical deformation of the containment, resulting possibly in unnecessary release of radioactive material. PA1 Plastic deformation passes a plurality of stages at a certain pressure before the rupture of a container occurs. Selection of the particular stage at which the valve is open is therefore not critical. On the other hand, the respective pressure has only a relatively small delay period before failure of the containment would occur because of the non-linearity of the stress-strain curve. Inaccuracies of the values controlling a pressure dependent relief valve would therefore be of great influence. As a result, pressure control of the relief valve would not be advantageous. PA1 The relief valve according to the invention has no seals or gaskets which may cause leakage long before opening of the valve. There are essentially no movable components. Only the drawbar moves slightly in an opening in the operating beam until a given free motion length is accommodated. Furthermore, the valve opens only far enough to prevent a further rise in pressure in the safety containment. Undesired opening of the valve, if possible, is possible only by strong mechanical impacts. However, they can be avoided by suitable selection of the valve location or by providing protective panels.
	description	1. Field of the Invention The present invention generally relates to nuclear medicine, and systems for obtaining nuclear medical images of a patient's body organs of interest. In particular, the present invention relates to a novel collimator with variable focusing and direction of view for nuclear medicine imaging, particularly for single photon imaging including single photon emission computed tomography (SPECT). 2. Description of the Background Art Nuclear medicine is a unique medical specialty wherein radiation is used to acquire images that show the function and anatomy of organs, bones or tissues of the body. Radio pharmaceuticals are introduced into the body, either by injection or ingestion, and are attracted to specific organs, bones or tissues of interest. Such radio pharmaceuticals produce gamma photon emissions that emanate from the body. One or more detectors are used to detect the emitted gamma photons, and the information collected from the detector(s) is processed to calculate the position of origin of the emitted photon from the source (i.e., the body organ or tissue under study). The accumulation of a large number of emitted gamma positions allows an image of the organ or tissue under study to be displayed. Single photon imaging, either planar or SPECT, relies on the use of a collimator placed between the source and a scintillation crystal or solid state detector, to allow only gamma rays aligned with the holes of the collimator to pass through to the detector, thus inferring the line on which the gamma emission is assumed to have occurred. Single photon imaging techniques require gamma ray detectors that calculate and store both the position of the detected gamma ray and its energy. Two principal types of collimators have been used in nuclear medical imaging. The predominant type of collimation is the parallel-hole collimator. This type of collimator contains hundreds of parallel holes, which can be formed by casting, drilling, or etching of a very dense material such as lead. Parallel-hole collimators are most commonly attached near the detector (scintillator) with holes arranged perpendicular to its surface. Consequently, the camera detects only photons traveling nearly perpendicular to the scintillator surface, and produces a planar image of the same size as the source object. In general, the resolution of the parallel-hole collimator increases as the holes are made smaller in diameter and longer in length. The parallel-hole collimator offers greater sensitivity than a pinhole collimator, and its sensitivity does not depend on how closely centered the object is to the detector. The conventional pinhole collimator typically is cone-shaped and has a single small hole drilled in the center of the collimator material. The pinhole collimator generates a magnified image of an object in accordance with its acceptance angle, and is primarily used in studying small organs such as the thyroid or localized objects such as a joint. The pinhole collimator must be placed at a very small distance from the object being imaged in order to achieve acceptable image quality. The pinhole collimator offers the benefit of high magnification of a single object, but loses resolution and sensitivity as the field of view (FOV) gets wider and the object is farther away from the pinhole. Other known types of collimators include converging and diverging collimators. The converging collimator has holes that are not parallel; rather, the holes are focused toward the organ with the focal point being located in the center of the FOV. The image appears larger at the face of the scintillator using a converging collimator. For equivalent spatial resolution the converging collimator has higher sensitivity than the parallel-hole collimator. The gain in point sensitivity is obtained at the price of a reduced FOV. The diverging collimator results by reversing the direction of the converging collimator. The diverging collimator is typically used to enlarge the FOV, such as would be necessary with a portable camera having a small scintillator. The diverging collimator has a lower sensitivity than the parallel-hole collimator, especially with thick objects. Another type of collimator is slat collimator that has been used with a rotating laminar emission camera, also known as the rotating laminar radionuclide camera. This camera has linear collimators usually formed by mounting parallel collimating plates or slats between a line of individual detectors. Alternately, individual detector areas of a large-area detector are defined and isolated through the placement of slats. The slat collimator isolates planar spatial projections; whereas, the grid collimator of traditional scintillation detectors isolates essentially linear spatial projections. The detector-collimator assembly of a slat camera is typically rotated about an axis perpendicular to the detector face in order to resolve data for accurate two-dimensional image projection. The projection data collected at angular orientations around the subject are reconstructed into a three-dimensional volume image representation. While maintaining certain advantages, such as a better sensitivity-resolution compromise, over, e.g., traditional Anger cameras, slat detectors are burdened by some other undesirable limitations. For example, the one dimensional collimation or slat geometry used by slat detectors complicates the image reconstruction process. The slat geometry results in a plane integral reconstruction as opposed to the line integral reconstruction that is generally encountered in traditional Anger camera applications. Moreover, the geometry produces a plane integral only in a first approximation. It is well known in the art that nuclear medicine imaging of small organs, such as brain, heart, kidneys, thyroid, and the like present special problems in collecting radiation emission and creating images from the collected data. Different systems including the use of the above described collimators have been used for nuclear imaging of small organs. Although images of such organs are routinely made, there remains a need for a system and methodology for improving imaging of small organs and for overcoming the shortcomings of the prior art, such as a novel collimator for a nuclear imaging camera and a method of forming the same. The present invention solves the existing need by providing a new collimator geometry that enhances the imaging of small organs with high resolution or in an efficient manner. According to the present invention, a novel slat collimator for use in nuclear medicine imaging is provided. The slat collimator comprises a first layer comprising a plurality of spaced apart elongated slats and a second layer comprising a plurality of spaced apart elongated slats. The slats of the second layer are positioned orthogonally with respect to the slats of the first layer. The slats are constructed of a radiation attenuation material, such as tantalum, tungsten, lead and the like. In one embodiment, the collimator is a static, i.e., the spaces between the slats are not variable. The spaces can be fixed by several means, including foam, grooves in the slats and guide plates. In a second embodiment, the collimator is variable, i.e., the spaces between the slat can be varied. The spaces can be varied through several means, including springs, air bubbles and magnetic force. Pressure can be differentially applied to one end of a slat layer to control the pointing direction of the slats. The present invention is directed to a slat collimator that comprises two layers of slats. The present invention also describes a method of collimator fabrication using two stacks of slats. Also described are various techniques by which the angles of the slats can be varied to create non-parallel beam collimators. Such collimators may be advantageous in SPECT studies of small organs, such as brain, heart, kidney, thyroid, etc. The convergence of the collimator can be changed to adapt for each study. Also, the convergence can be changed in a SPECT study as the distance from the camera to the organ changes during the scan. For a given spatial resolution, the gain of sensitivity with 2D-convergence will dominate the small sensitivity loss due to the extra collimator thickness relative to a conventional hole collimator. The slat collimator of the present invention is used on a scintillation camera of the type which is used to carry out SPECT studies, i.e., is used with a nuclear imaging acquisition system for SPECT studies. The nuclear imaging acquisition system comprises the slat collimator described herein and a detector having a side which detects radiation emanating from an object after passing through said collimator. As shown in FIG. 1, a collimator in accordance with the present invention comprises two stacks of slats. The collimator comprises a first layer (100) of a plurality of elongated spaced apart slats (101a, 101b, . . . 101n) and a second layer (200) of a plurality of elongated spaced apart slats (201a, 201b, . . . 201n). The second layer (200) is positioned orthogonally with respect to said first layer (100). The slat material should be a suitable gamma ray attenuator, e.g., tantalum, tungsten, lead, etc. The slats (101a, 101b, . . . 101n) of the first layer (100) may be perpendicular to the surface of detector (not shown) or they may be at an angle greater than zero. All of the slats (101a, 101b, . . . 101n) in the first layer (100) are angled in the same direction. Similarly, the slats (201a, 201b, . . . 201n) of the second layer (200) may be perpendicular to the surface of the first layer (100) or they may be at an angle greater than zero. All of the slats (201a, 201b, . . . 201n) in the second layer (200) are angled in the same direction. By constructing collimators from two orthogonal layers of slats, similar to “Venetian blinds”, a very general collimation viewing configuration is realized. In one embodiment, the spaces (102a, 102b, . . . 102n) between the slats (101a, 101b, . . . 101n) in the first layer (100) are non-variable, i.e., fixed to produce static (non-variable) collimation. Similarly, the spaces (202a, 202b, . . . 202n) between the slats (201a, 201b, . . . 201n) in the second layer (200) are non-variable, i.e., fixed. In one aspect of this embodiment, the spaces (102a, 102b, . . . 102n; 202a, 202b, . . . 202n) between the slats (101a, 101b, . . . 101n; 201a, 201b, . . . 201n) can be filled with a low density foam materials, such as ROHACELL® rigid plastic foam material. In a second aspect, air spaces between slats could be used if slats are sufficiently rigid. The spacing of the slats (101a, 101b, . . . 101n; 201a, 201b, . . . 201n) can be fixed by mounting the slats into grooves (not shown) on the top edge of the slats (101a, 101b, . . . 101n) of the first layer (100) and on the bottom edge of the slats (201a, 201b, . . . 201n) of the second layer (200). In a third aspect, the spacing of the slats (101a, 101b, . . . 101n; 201a, 201b, . . . 201n) can be fixed by mounting the slats into grooves of slide guide plates. FIG. 2 is a cross-section view of the construction of one layer, e.g., first layer (100) using slide guide plates. As shown in FIG. 2, two slide guide plates (103a, 103b) are provided. The slide guide plates (103a, 103b) have grooves (104a, 104b . . . 104n; 105a, 105b, . . . 105n) on their inside edges into which the slats (101a, 101b, . . . 101n) are positioned. The slide guide plates (103a, 103b) are constructed out of low radiation attenuation material, such as aluminum or plastic. It can be appreciated that the spaces between slats (201a, 201b, . . . 201n) of the second layer (200) can be fixed in the same manner. In a second embodiment the spaces (102a, 102b, . . . 102n) between the slats in the first layer (100) can be varied. Similarly, the spaces (202a, 202b, . . . 202n) between the slats in the second layer (200) can be varied. As used herein, variable spaces is intended to mean that the distance between the slats (101a, 101b, . . . 101n; 201a, 201b, . . . 201n) at one end of said slates is less than the distance between slats at the other end of said slats. By varying the spaces between the slats in this manner, non-parallel beam collimators are created. In addition, the direction of view can be changed using such a variable collimator. In order for direction of view to be changed in a general manner, a means creating repulsive forces between the slats needs to be created. In one aspect of this embodiment, the slats (101a, 101b, . . . 101n; 201a, 201b, . . . 201n) can be held apart by springs. As shown in FIG. 3A, the slats (101a, 101b, . . . 101n) are held apart by springs (106a, 106b, 106c) at one end of the first layer (100) and springs (107a, 107b, 107c) at the other end of the first layer (100). The pointing direction of the slats (101a, 101b, . . . 101n) may be controlled by setting the orientation of slats at either end of the layer, such as by using springs of different sizes or by applying a force at either end of the layer. For example, springs (107a, 107b, 107c) may be larger than springs (106a, 106b, 106c) such that a direction of collimation of radiation is achieved. Alternatively, as shown in FIG. 3B, single springs (108a, 108b, . . . 108n) can be used between the slats (101a, 101b, . . . 101n). By applying a force to one end of the slats (101a, 101b, . . . 101n) in the first layer (100), direct directional control of the source slats between the ends of the array can be provided. As shown in FIG. 3B, such force can be applied by motors (109a, 109b) that push plates (110a, 110b) into one end of the slats (101a, 101b, . . . 101n) to provide directional control. In addition, by tilting the end slats the direction of view of the array can be deflected or focused. It can be appreciated that springs and similar direct directional control can be performed for the slats (201a, 201b, . . . 201n) of the second layer (200). It can further be appreciated that the directional control can be applied to only one or both of the layers of the slats. In a second aspect, slats could be held apart by a bubble-wrap between the slats. As shown in FIG. 4, slats (101a, 101b, . . . 101n) of the first layer (100) are separated by plastic (111a, 111b, . . . 111n) that contains bubbles (112a, 112b, . . . 112n) of air. By tilting the end slats, such as described above and as shown by the arrows in FIG. 4, the direction of view of the array can be deflected or focused. It can be appreciated that bubble-wrap and similar direct directional control can be performed for the slats (201a, 201b, . . . 201n) of the second layer (200). It can further be appreciated that the directional control can be applied to only one or both of the layers of the slats. In a third aspect, slats (101a, 101b, . . . 101n) of the first layer (100) could be held apart magnetically. As shown in FIG. 5, each slat (101a, 101b . . . 101c) is encompassed by a current loop. The loop wires (not shown) are attached to the slats (101a, 101b, . . . 101n). Alternate slats (e.g., 101a and 101b) have the current flowing in the opposite sense, as shown by the + and − in FIG. 5. The opposite current flow sets up a repulsive magnetic force between the slats. By tilting the end slats, such as described above, the direction of view of the array can be deflected or focused. It can be appreciated that magnetic repulsion and similar direct directional control can be performed for the slats (201a, 201b, . . . 201n) of the second layer (200). It can further be appreciated that the directional control can be applied to only one or both of the layers of the slats. In a third embodiment, the spaces in one layer, e.g., spaces (102a, 102b, . . . 102n) between the slats in the first layer (100) are non-variable, i.e., fixed, such as described above. The spaces in a second layer, e.g. spaces (202a, 202b, . . . 202n) between the slats in the second layer (200) can be varied and under direct directional control, such as described above. Alternatively, the spaces (102a, 102b, . . . 102n) between the slats in the first layer (100) can be varied and under direct directional control. The spaces in a second layer, e.g. spaces (202a, 202b, . . . 202n) between the slats in the second layer (200) are non-variable, i.e., fixed. By varying the spaces between the slats in this manner, non-parallel beam collimators are created. Such collimators may be advantageous in SPECT studies of small organs, such as brain, heart, kidney, thyroid, etc. The convergence of the collimator can be changed to adapt for each study. Also, the convergence can be changed in a SPECT study as the distance from the camera to the organ changes during the scan. To image a small organ (or region-of-interest), it is desireable to spend a greater share of the available scan time and a greater share of the available detector area detecting photons mainly from this area. An initial fast SPECT scan (or the use of two orthogonal views) would give enough information to allow the position of the organ-of-interest (ROI) to be determined. Using this position information, the collimator can be dynamically focused on the ROI during the scan for a large fraction of the total study time. Although the slat collimation system of the present invention has some drawbacks, particularly in static configuration, in comparison to foil or cast collimator, it has several advantages. The drawbacks include: The static system will be thicker (at least double) than a conventional collimator. Thus, for a given special resolution, the sensitivity will be somewhat reduced, approximately by the square of the ratio of distances from source to detector (scintillation crystal). It is made out of more costly materials. It has more complex control and calibration. The advantages include: For SPECT imaging of organs or regions significantly smaller than the typical camera field of view (FOV), the variable slat system can yield overall improvements in imaging speed (higher sensitivity). As shown in FIGS. 6A and 6B, the SPECT acquisition change have two phases of differing durations, T1 and T2. For imaging a small organ it will be advantageous to dynamically focus on the organ-of-interest for time T2 and image the entire object (no truncation) for another time period T1. Generally, T2 is much greater than T1, since the untruncated data is only needed to form the image of the organ surround at lower resolution. A SPECT acquisition commonly consists of a multiplicity of different views. Each view is defined by a specification camera position of orientation. The i-th view may have focused and unfocused temporal phases T2i and T1i. The system can focus collimators so that more (most) of the time is spent acquiring counts from the organ or region of interest and less time spent acquiring counts from the overall background. Focus can controlled to provide tight focusing on organ of interest without truncation. The focus could also be offset with respect to the center of the collimator. The use of quick prescan SPECT study, perhaps only two orthogonal planar views can suffice in many cases, allows the organ of interest to be located. Position encoders on the camera system give the position and angular orientation of each camera head (detector). Using this information together of the prescan data permits determination of the organ position for tight, dynamic focusing on the organ for the remainder of the scan. The focus of the slat collimator does not necessary have to be centered, but can be offset. This can be achieved by means of non-symmetric orientation and drive of the push plates (110a, 110b), see FIG. 3B. As disclosed above, the variable slat system can yield overall improvements in sensitivity. There are several sensitivity considerations that can be envisioned. The sensitivity (solid angle) of a convention 2D-hole collimator is given by the equation Ω = [ kD 2 L ⁡ ( D + S ) ] 2 ( Eq . ⁢ 1 ) where k is a form factor depending on hold shape, D is the size of the hole (˜across “flats” dimension), S is septal thickness and L is light. (Anger, H. O. (1964), “Scintillation Camera with Multichannel Collimators.” J Nucl Med 5:515-531.) FIG. 7A shows D and k for a square hole. FIG. 7B shows D and k for a hexagonal hole. In a stack slat collimator system, the main factor degrading sensitivity for a fixed spatial resolution will be the increased distance of the object from the camera due to the increased thickness of the collimator. The sensitivity of the stacked slat (shown representatively in FIG. 7C in which stack 1 is layer (100) and stack 2 is layer (200) will be approximately Ω = θ 1 ⁢ θ 2 = [ k 1 ⁢ D 1 2 L 1 ⁡ ( D 1 + S 1 ) ] ⁡ [ k 2 ⁢ D 2 2 L 2 ⁡ ( D 2 + S 2 ) ] ( Eq . ⁢ 2 ) where k1≈k2=√{square root over (k)} The angular sorting in x and y direction is separable and for L1=L2=L, D1=D2=D, S1=S2=S, the net solid angle of the stack collimator is approximately the same for a conventional collimator given by Eq. 1. For a fixed collimator spatial resolution, the collimator angle (shown in FIG. 8 as θ) is θ = R c ( a + b + c ) ( Eq . ⁢ 3 ) where a is the distance from the mean detection plane (in the scintillation crystal) (800) to the collimator (801), b is thickness of the collimator (801), and c is the distance from the collimator (801) to the object. Rc is the geometric spatial resolution of the collimator. If Rc, a and c are held fixed, then an increase of b implies a decrease in θ and a decrease in sensitivity. Ω1≈θ2 for conventional collimators Ω2=θxθy for stacked (layers of slats) collimator ( Ω 2 Ω 1 ) = θ x ⁢ θ y θ 2 = ( a + b 1 + c a + b 2 + c ) 2 For typical values: a=0.5 cm, c=20 cm, b1=2.5 cm, b2>2b1 or b2=2b1 (best case) ( Ω 2 Ω 1 ) = ( 23 25.5 ) 2 = 0.81 For c=16 cm (reasonable for brain imaging) ( Ω 2 Ω 1 ) = ( 19 21.5 ) 2 ≈ 0.78 Thus, with a 2D-converging slat system according to the present invention, a magnification gain >2 could easily be obtained. Hence, the small loss of sensitivity due to increased thickness of the collimator is more than offset by the gain in magnification. For SPECT imaging of organs or regions significantly smaller than the typical camera field of view (FOV), the variable slat system can yield overall improvements in imaging speed (higher sensitivity). As shown in FIGS. 6A and 6B, the SPECT acquisition can have two phases of differing durations, T1 and T2. For imaging a small organ it will be advantageous to dynamically focus on the organ-of-interest for time T2 and image the entire object (no truncation) for another time period T1. Generally, T2 is much greater than T1, since the untruncated data is only needed to form the image of the organ surround at lower resolution. A SPECT acquisition commonly consists of a multiplicity of different views. Each view is defined by a specification camera position of orientation. The i-th view may have focused and unfocused temporal phases T2i and T1i. While a preferred embodiment of the present invention has been described above, it should be understood that it has been presented by way of example only, and not limitation. Thus, the breadth and scope of the present invention should not be limited by the above described exemplary embodiment. Obviously, numerous modifications and variations of the present invention are possible in light of the above teachings. It is therefore to be understood that the invention may be practiced otherwise than as specifically described herein. As disclosed above, the variable slat system can yield overall improvements in sensitivity. There are several sensitivity considerations that can be envisioned. The sensitivity (solid angle) of a convention 2D-hole collimator is given by the equation Ω = [ kD 2 L ⁡ ( D + S ) ] 2 ( Eq . ⁢ 1 ) where k is a form factor depending on hole shape, D is the size of the hole (˜across “flats” dimension), S is septal thickness and L is light. (Anger, H. O. (1964), “Scintillation Camera with Multichannel Collimators.” J NucI Med 5:515-531.) FIG. 7A shows D and k for a square hole. FIG. 7B shows D and k for a hexagonal hole.
	description	This application claims benefit under 35 USC §119(e) to U.S. Provisional Application No. 61/552,285 filed on Oct. 27, 2011, the disclosure of which is incorporated by reference herein in its entirety for all purposes. The United States Government has rights in this invention pursuant to Contract No. DE-AC52-07NA27344 between the U.S. Department of Energy and Lawrence Livermore National Security, LLC, for the operation of Lawrence Livermore National Laboratory. This invention relates to imaging x-ray emission spectroscopy and more particularly to the accurate characterization or calibration methods applied to bent crystals, such as quartz crystals, that are used as a part of an in-situ x-ray imaging diagnostic system, such as in a fusion reactor that produces an x-ray emitting plasma. Spherically and toroidally bent crystals are used as gratings for measuring narrow-bandwidth, two dimensional x-ray images. These crystals are often used for imaging laser plasma x-ray emission with high resolution. The brightness and spectral bandwidth of the resulting x-ray images are fundamentally determined by the wavelength dependent instrument function of the crystal. Additional limits on brightness, spectral bandwidth, field of view and spatial resolution are introduced by the set-up geometry. When imaging narrow-bandwidth x-ray lines, spherically and toroidally bent crystals may provide higher spectral and spatial resolution than other x-ray imaging instruments, such as pinhole cameras or metal-mirror Kirkpatrick-Baez microscopes. Quantitative x-ray imaging involves characterization of the crystal spectrometric properties and imaging performance so that the instrumentation is properly calibrated. Due to extreme selectivity of the imaging technique, lack of calibration leads to false or even no output results. Despite the advances made in the field of x-ray imaging of laser-generated plasma, there is a need in the art to provide a more accurate and reliable method for characterizing a quartz crystal used for X-ray imaging of laser-generated plasmas. According to the invention, a method is provided for characterizing spectrometric properties (e.g., peak reflectivity, reflection curve width, and Bragg angle offset) of the Kα emission line reflected narrowly off angle of the direct reflection of a bent crystal and in particular of a spherically bent quartz 200 crystal by analyzing the off-angle x-ray emission from a stronger emission line reflected at angles far from normal incidence. The bent quartz crystal can therefore accurately image argon Kα (also denoted K-alpha) x-rays at near-normal incidence (Bragg angle of approximately 81 degrees). The method is useful for in-situ calibration of instruments employing any suitable bent crystal as a grating by first operating the crystal as a high throughput focusing monochromator on the Rowland circle at angles far from normal incidence (Bragg angle approximately 68 degrees) to make a reflection curve with the He-like x-rays such as the He-α (also denoted He-alpha) emission spectrum or “line” observed from a laser-generated plasma. A specific method for characterizing spectrometric properties of bent crystals comprises selecting a bent crystal, such as a quartz crystal, that is suitable to image selected emission lines of a target substance, positioning the bent crystal on the Rowland circle in the path of x-ray emissions from the target substance also located on the Rowland circle wherein a reflective surface of the bent crystal is disposed at approximately the Bragg angle to the path, repeating iteratively steps to build a rocking curve of x-ray reflections off-angle to the direct reflection angle, namely, exciting the target substance sufficient to generate x-ray emissions to impinge upon the bent crystal, thereupon capturing and recording intensity of a first preselected known narrow spectrum of the x-ray emissions as diverted by the bent crystal at an off-angle to x-ray emission reflections, and incrementally rotating the bent crystal about the center of rotation of its reflective surface, then using the first preselected known narrow spectrum, such as the He-alpha spectrum, to make a rocking curve at angles far from normal incidence, namely at Bragg angles near 70 degrees, that characterizes the crystal at a second preselected known narrow spectrum of a lower energy level, and characterized by a larger Bragg angle, for use as an imaging optic at the second preselected known narrow spectrum, namely the K-alpha spectrum, at angles close to normal incidence wherein the Bragg angles are 80 to 89 degrees. The exciting step is produced by laser irradiation of a supersonic argon gas jet and the x-ray emissions are from plasma produced by the laser irradiation. Preferably the bent crystal is disposed on a rotatable mount. The selected bent crystal is usable for off-angle imaging at near a 90-degree angle of reflection. The bent crystal is preferably spherically bent at a radius of curvature of equal to twice the radius of the Rowland circle. This configuration is known in the art as the Johann geometry. In the specific applications contemplated the first preselected known narrow spectrum is of the He-α emission line and the second preselected known narrow spectrum is of the Kα emission line. Numerous benefits may be achieved by using the techniques described herein. In some embodiments, by enabling in-situ characterization of the crystal used in the Laser Inertial Fusion Engine results in a smaller effective alignment error when the crystal is used for imaging. This enables better alignment of high energy, single-shot lasers used in a fusion reaction where successful laser-plasma imaging is desired. In addition, the techniques described herein can be used for characterizing the crystals that are used for imaging rare-gas x-ray lines. These and other embodiments of the invention along with many of its advantages and features are described in more detail in conjunction with the text below and attached figures. The brightest x-ray lines from most mid-Z laser plasmas are radiated from the He-α and Kα atomic transitions. Study of this x-ray line self-emission provides insight into the target physics, since the emission is determined by the population level kinetics of the plasma. Correspondingly, multi-wavelength imaging of a plasma can identify gradients in ionization state and temperature. When the crystal spectrometric properties are known, it becomes possible to determine the number of emitted photons from the detector exposure and thereby infer absolute ion populations within the plasma. Additionally, x-ray imaging of Kα fluorescence can be used to trace the transport of energetic laser-accelerated electrons within dense plasmas. Laser plasmas that emit He-α and Kα also serve as very bright, short duration (e.g., as few as between 10 and 100 picoseconds) x-ray sources for dense plasma diagnostics. Two such diagnostics are x-ray scattering, which can determine fundamental plasma properties and particle correlations, and radiography, which can measure the hydrodynamic evolution of dense matter, including phenomena such as such as shock coalescence, compression, and implosion dynamics. Spherically and toroidally bent crystals can be used for x-ray imaging in both scattering and radiography applications. In some embodiments, a measurement of the peak reflectivity, reflection curve width and the Bragg angle offset of a spherically bent quartz crystal intended for quantitative imaging of Ar Kα at 2957 eV and θB˜81°, by making a calibrated reflection curve using Ar He-α resonance line x-rays at 3140 eV and θB˜68°, is provided. FIG. 1 illustrates a configuration of a system 100 for calibrating and measuring the peak reflectivity according to an embodiment of the present invention. System 100 uses a laser source 102, a spherically bent quartz crystal 104, a diagnostic device 106, and an image plate detector 108. Spherically bent quartz crystal 104 is placed on the Rowland circle. In this configuration, the crystal functions as a grating in a high-throughput focusing monochromator. Laser plasma source 102 is used as the x-ray source to obtain an in-situ crystal characterization with no additional equipment. In some embodiments, laser source 102 may be an exciter for stimulating x-ray emission out of an Ar gas jet target. The surface averaged peak reflectivity of spherically bent quartz crystal 104 was 0.25±35% with a reflection width of 0.12 degrees and a Bragg angle offset of +0.27±0.12 degrees. The brightness of the He-α resonance line, as well as its spectral stability over a range of plasma temperatures makes it well-suited for use as an x-ray source for crystal calibration. Crystals intended for imaging Kα x-rays at near normal incidence have appropriate 2d spacings for making rocking curves with He-α in the focusing monochromator geometry as shown in Table 1 below. TABLE 1He-αres (eV),Quartz Cut2D (nm)OrderElementKα (eV), θBθB2000.42461Ar2957, 80.16°3140, 68.11°20-230.27491Ti4511, 89.37°4750, 71.74°21-310.30822Cu8048, 88.98°8392, 73.51° The in-situ rocking curve technique described above is particularly helpful for characterizing crystals intended for imaging rare gas K-shell x-rays, since in general these crystals cannot be characterized using a solid-state x-ray source without going to a different diffraction order, which alters the spectral response. In some embodiments, laser source 102 can be a Ti:Sapphire laser that provides up to 10 J of 800 nm light in pulses as short as 100 femtoseconds, for on-target intensities above 1019 W/cm2. The x-ray source can be Ar plasma formed by ultra-short pulse laser irradiation of a supersonic Ar gas jet. In some embodiments, diagnostic device 106 can be an x-ray spectrometer that monitors the source x-ray spectrum using highly oriented pyrolytic graphite (HOPG) crystal that may be cylindrically bent. For moderate photon energies, spherically bent quartz crystals with interplane spacing 2d intended for imaging Kα at Bragg angles θB close to 90° can be characterized by taking a rocking curve of the He-α emission from the same plasma at Bragg angles near 70°. In this instance, the crystal is no longer an x-ray imager but instead functions as a narrow spectral window, high-throughput monochromator, i.e. the narrow-bandwidth limit of a spectrometer. The Kα photon energies hv specified herein are those that would be observed from neutral, isolated matter. As illustrated in Table 1 above, 200 in first order is synonymous with 100 in second order. FIG. 2 illustrates an x-ray spectrum of the Ar gas jet emission that is taken using a source monitor spectrometer (e.g., diagnostic device 106 of FIG. 1 in the form of an HOPG crystal) according to an embodiment of the present invention. As illustrated in FIG. 2, spectrum of the source is shown, as used in the von Hamos geometry. As can be seen, the spectrum for the 3p-1s transition is centered at around 3.12 keV, (i.e. in the middle of the Ar K-shell spectrum), where the Bragg angle was about 36.3° and the source to crystal distance/was about 171 mm±5%. The HOPG crystal had inter-plane spacing 2d=0:67 nm, a mosaic spread of 0.8°, a width w=25.4 mm+5% and an integrated reflectivity Rint=3.0 mrad±10%. The x-rays selected by the bent crystal 104 were detected on an absolutely calibrated Fujifilm imaging plate 108. Filtering consisted of 25 μm of Be to block visible light and 84 μm of mylar to attenuate the x-rays, yielding a transmission of τF(hv=3.14 keV)=0.24+5%. The measured line width of He-α as shown in FIG. 2 consists of the natural line width ΔE/E=3×10−4 as well as contributions, in order of descending importance, from the 230 μm source size of the emitting plasma, thermal Doppler broadening, effects inherent to the crystal and the 25 μm2 pixel size of the image plate. Summing instrumental contributions in quadrature, it was estimated that there was a minimum instrument function width of 2.9 eV at 3.14 keV for a spectrometer resolution ΔE/E=9.6×10−4. This places an upper limit of ΔE at about 3.0 eV on the source function width. The He-α x-ray source brightness can be obtained by a photometric analysis of the HOPG spectra. Source monitor spectrometer throughput is given by the following equation. η sms = τ F ⁢ R int ⁢ w l 4 ⁢ ⁢ π ( 1 ) where τF is the filter transmission, Rint is the integrated reflectivity, w is the crystal width, and l is the source to crystal distance. In a particular embodiment, ηsms=8.4×10−6+12%, where the propagated uncertainty may be estimated assuming no cross correlations. The detector exposure, in units of photo-stimulated luminescence (PSL)57, is then given by N=N0ηsms CIP, where N0 is the number of photons emitted from the source into 4π and CIP(hv=3 keV)=0:002±10% PSL/(3 keV photon) is the image plate calibration factor. Using our measurement of N, we calculated that for the resonance line N0=2.1×1011 photons into 4π per joule of laser energy, for a laser to He-αres conversion efficiency of 1.0×10−4±35%. This total uncertainty may include a ±32% random uncertainty from shot-to-shot variations in the short pulse laser pulse conditions. FIG. 3 illustrates a mounting assembly 300 for a spherically bent crystal according to an embodiment of the present invention. A spherically bent quartz crystal 302 having radius of curvature, re, of about 38 cm may be held inside an adapter ring 304 within a standard kinematic mirror mount 306. An aperture of radius, ra, of about 1.4 cm, which limits the crystal solid angle, is cut into a A1 disk 308 which about 500 mm thick (thick enough to be opaque to 3 keV photons). Disk 308 is mounted about 1 mm in front of crystal 302 on a ledge built into adapter ring 304. A manual rotation stage 310 may be used to set the Bragg angle θB with an accuracy of ±2.5 arc minutes. A miniature xyz dovetail linear translation stage 312 directly underneath mirror mount 306 allows for stable linear adjustment with a minimal lever arm. Rotation of crystal 302 about its surface normal, i.e. the φ-axis, may be done by rotating adapter ring 304 manually within mirror mount 306. Crystal alignment may be performed in two steps: (1) centering the optical assembly, i.e. placing the crystal surface at the intersection of the θ and φ axes, and (2) placing crystal 302 in the chamber and alignment of the Bragg angle θB with respect to the laser plasma x-ray source. Initial alignment may be performed outside of the target chamber, using a flat mirror in place of the crystal and a continuous-wave green (543 nm) HeNe pencil-beam laser with a beam diameter of about 1 mm. An iterative procedure may be used to simultaneously (a) center the reflective surface of the flat mirror on the θ-axis, and (b) move the entire crystal mounting assembly so that the θ-axis intersects the HeNe alignment beam. (The θ axis is the axis of rotation of rotation stage 310 at the base of the crystal mounting apparatus.) The mirror used for initial alignment may be rotated to θ=0°, as measured from the surface of the mirror to the beam axis, and translated so that the beam just grazes the mirror surface. Without moving the mount base, the mirror may be then rotated 180° in θ, to return to grazing incidence but with the mirror now on the opposite side of the beam. Translation in the y-direction at xyz stage 312 combined with adjustment of the mount base may be repeated several times, until the beam is able to just graze the mirror surface at both θ=0° and θ=180°. Continuing with alignment, the flat mirror is removed and crystal 302 and adapter ring 304 is returned to the mounting hardware. Translating in y brings the center of the crystal surface back to the optical center. Next, while rotating crystal 302 about the φ axis, x and z were adjusted, along with tip and tilt of the kinematic mirror mount, to bring the pole of the spherical surface to be co-linear with the laser axis within the limits of the crystal substrate and assembly concentricity. Remaining misalignment was visible as an offset radius in the retro reflection as it traced a circle about φ but can be largely neglected due to the symmetry of the reflection angles. Next, the crystal mounting assembly is moved into the target chamber and aligned to the plasma x-ray source, placed such that crystal 302 and the plasma x-ray source both fall on the Rowland circle as shown in FIG. 1 and FIG. 2. The HeNe alignment laser sighted through the location of the target plasma at the focal point of the main laser beam. Spherically bent quartz crystal 302 was placed at 1=35.3 cm±2% away from the target. With the optical retro reflection of the alignment laser off the crystal front surface, the θ-axis was zeroed to an accuracy of half a HeNe spot diameter over about 30 cm, i.e. ±1.7 mrad, and then set the Bragg angle θB to about 67.67°±0.12°, where the propagated error can be estimated assuming no cross correlations. In this instance, crystal 302 can be considered to be a focusing monochromator, e.g., a Johann spectrometer in the limit of very narrow spectral bandwidth. The collimator and detector were then aligned using the optical reflection off the crystal surface and placed with the image plate detector (e.g., detector 108 of FIG. 1) at distance of about 32 cm from the crystal. As described below, the x-rays follow a slightly different path than the visible HeNe light because of a bias angle between the crystal lattice and the polished crystal front surface. In a particular embodiment, the detector can be about 50 mm in diameter, which can accommodate a maximum offset of about 37 mrad. The detector must be large enough to ensure that the x-rays do not walk off the sensitive region during the calibration procedure, keeping in mind that the exit angle is 2θB. The detector may be repositioned as required. Once alignment is complete, the surface of the crystal is protected from target plasma and lightweight debris. In order to accomplish this, the aperture hole can be covered with a layer of 1 μm thick Mylar foil, which is essentially transparent to 3 keV x-rays. Shielding of the detector can be provided by bricks of polyethylene, to stop laser accelerated charged particles without creating energetic x-ray fluorescence, and also using lead, which may also be used due to its opacity to x-rays over a broad range of photon energies. The bricks are placed between the plasma source and the image plate detector. Good shielding and collimation can reduce the noise and background on the image plate detector, especially when studying a rare-gas x-ray line, for which solid foil transmission-edge filters may not be available. FIG. 4A illustrates results from an arrangement of the x-ray source, the crystal and the detector on the Rowland circle. As illustrated in FIG. 4A, without misalignment, the Bragg angle offset δθ varies parabolically across the spherical surface of the crystal. FIGS. 4B and 4C illustrate that misalignments of the x-ray source, the crystal and the detector can cause substantial overall shifts in θB as well as distortions in the δθ profile. FIG. 4D illustrates the relative placement of the x-ray source, the crystal and the detector on the Rowland circle according to an embodiment of the present invention. Multi-keV x-rays can be imaged using bent crystals as diffracting optics (gratings) in either reflecting Bragg or transmitting Laue geometries, which are suitable for moderate or high photon energies, respectively. In the reflection geometry, photons with wavelength λ reflect from a crystal with inter-plane spacing d according to the Bragg condition2d sin θB=mλ (2)where θB is the angle of incidence measured from the surface and m=1;2;3 . . . is the order of reflection. Holding 2d constant, the derivative of this equation yields a convenient relation for the spectral bandwidth given by Δ ⁢ ⁢ E E = Δθ tan ⁢ ⁢ θ B ( 3 ) where the angular bandwidth Δθ is specified in radians. Spherically bent crystals used for x-ray imaging are preferentially used near normal incidence (e.g., θB˜90°) for the highest spatial resolution mainly to minimize off-axis geometric distortions and aberrations, and to achieve nearly monochromatic reflection, as is described below. Reflected signals can be considered as the convolution of a photon source function with the spectral and spatial response functions of the optics and the detector. The spectral response of a crystal to x-rays is commonly known as the instrument function, which can be studied by measuring the throughput of a collimated, narrow-bandwidth x-ray line source reflected from the crystal as it is tilted through a small range of Bragg angles. This results in a reflection curve or rocking curve of width wc, with reflectivity described byR(θ;wc;Rmax) (4)where R is the fraction of incident radiation reflected by the crystal. The instrument function is sharply peaked, often well approximated as a Lorentzian, and centered on the Bragg angle, i.e. Rmax=R(θ=θB). Equivalently, the entire reflection curve may be obtained at once if the source is fully divergent, the crystal spectral bandwidth exceeds the source spectral bandwidth and the detector is large enough. During the manufacture of bent crystals, lattice distortion may be introduced in proportion to the amount of bending. Furthermore, inaccurate polishing of the crystal flats before bending can introduce a bias angle, i.e. a misalignment of the crystal planes relative to the front surface. This can be measured in bent quartz to be up to 0.23 degrees=4 mrad (i.e. 2 mm offset measured at a distance of 2×250 mm), which means that the rocking curve can vary considerably from crystal to crystal. Specifically, the peak of the reflection curve may be shifted away from the nominal Bragg angle. Any such offset must be considered when aligning the crystal for a specific x-ray line, e.g. through the use of an “effective” 2d spacing to compensate for the offset. The number of x-ray photons N reflected by a crystal can be calculated by convolving the source photon spectrum, J, with the crystal reflection curve R (Eq. 4) over the area of the crystal. J can be obtained by de-convolving a measured source spectrum from the spectrometer instrument function. In an embodiment, J can be obtained from an x-ray spectrum simulated with the FLYCHK code and then calibrated against the measured source spectrum from FIG. 2. Plasma simulation parameters used as FLYCHK inputs are known in the art. For spherically bent crystals operated with unit magnification as described above and a circular aperture, the crystal area A=πr2a and the number of reflected photons N is given by the integral N = Asin ⁢ ⁢ θ B 4 ⁢ ⁢ π ⁢ ⁢ l 2 ⁢ ∫ ∫ J ⁡ ( λ , 2 ⅆ ) * R ⁡ ( θ , w c , R max ) ⁢ ⁢ ⅆ X ⁢ ⁢ ⅆ Z ( 5 ) θ = θ B + δθ ( 6 ) where θ is the crystal surface angle found at the point on the crystal given by the dimensionless, normalized Cartesian coordinates X=x/(2rc);Z=z/(2rc). Although the central ray is aligned to the nominal Bragg angle θB, the surface angle varies according to the offset given byδθ(X,Z,θB,ra,rc,xs,ys,zs). (7) The variation δθ depends on many factors: the location of a given differentially small reflecting element on the crystal surface, the nominal Bragg angle, the shape of the crystal (via the active area that is proportional to ra and bending radius rc) and source misalignment xs, ys, and zs. For spherically bent crystals, δθ is generally insensitive to misalignment in z but highly sensitive to misalignments in x and y. For larger values of θB such as those used herein, the variation in Bragg angle for a spherically bent crystal is essentially one dimensional and parabolic along X, with some asymmetric distortion possible due to source misalignment. The behavior of δθ is illustrated in FIGS. 4A-4C. By using Eq. 2 above to change J(X, 2d) to J(θ) we can evaluate Eq. 5 as a double-integral purely in X and Z, so long as we include 2d as a free parameter during data fitting. The total spectral bandwidth (cf. Eq. 3) can be approximated asΔθ˜max(δθ). (8) For near-normal incidence imaging, i.e. θB>80 degrees, Δθ is quite small, on the order of 10−4 degrees. In this work, farther from normal incidence and with a relatively large aperture, δθ is as large as 10−2 degrees (e.g., See FIGS. 4A-C) and Eq. 5 must be fully evaluated over the circular aperture where X2+Z2≦(ra/(2rc))2. Even so, the spectral bandwidth Δθ is narrow and at each Bragg angle the crystal may reflect only a small slice of the source spectrum. For example, the He-α resonance line from FIG. 2 is approximately 0.17 degrees wide, which is several orders of magnitude larger than Δθ. For a given Bragg angle, the spectral window is smallest if the source and crystal are both set on the Rowland circle. FIG. 5A illustrates the image plate exposures taken as part of measurement of crystal parameters according to an embodiment of the present invention used to characterize the specific crystal. FIG. 5B illustrates a calibrated reflection curve of a spherically bent quartz 200 crystal at 3.14 keV according to an embodiment of the present invention in comparison with a calculated reflection cure. The difference is instructive. Starting at 67.5 degrees, a series of laser shots were taken to build up a reflection curve, advancing the Bragg angle after each shot and always moving in the same direction to avoid backlash in the rotation stage. The photons reflected in first order (m=1) were detected on the image plate (illustrated in FIG. 5A) and were summed to obtain the number of reflected photons N(θB), as shown in FIG. 5B. Using the calibrated source spectrum with Eq. 5, iterative data fitting found best-fit values for the free parameters in Equations. 5 and 7 above as follows:2d=0.4239 mmRmax=0.25wc=0.118°xs=−0.044 mmys=−0.124 mm (9) It is to be noted that the values described above are based on a specific setup of the bent quartz crystal and other components in the system. One skilled in the art will realize that the values described above will change based on change in other parameters of the equations and setup. The difference between this calculated 2d value and that shown in Table 1 can be a Bragg angle offset due to misalignment of the crystal planes with the polished surface, and may correspond to +0.27 degrees with an uncertainty of ±0.12 degrees, as described above. Compensation for this offset is needed to achieve peak reflectivity when using the crystal for imaging. The value of the peak reflectivity Rmax, which represents the average over the entire exposed crystal surface, is somewhat higher than what has been measured for spherically bent quartz 100 using solid state x-ray sources and is much higher than the value expected for a quartz 100 flat. Bent crystals are known to have up to 20× higher reflectivity than similar flat crystals due to partial mosaicity from lattice dislocations introduced during bending. This same crystal when later characterized at one spatial point using an x-ray tube source revealed that Rmax=0.11 and wc=0.23°. The lower peak reflectivity and wider rocking curve might be explained by local variation in the crystal quality, as well as by the fact that this offline calibration was done in second order (m=2) with Fe Kα at 6.4 keV instead of in first order at 3 keV. Ordinate error bars in FIG. 5B indicate the amplitude of noise on the image plate relative to the signal amplitude. There is also a possible systematic uncertainty of ±35% from the calibration of Jusing the source monitor spectrum described above. It should also be noted that the best-fit values for source offsets xs, and ys, mentioned above are not unique. In other words, there exists an extended region in the xs−ys, plane (roughly corresponding to constant angular misalignment) within which fit error is minimized. However, from the practical point of view those parameters inherent to the crystal (e.g., 2d, Rmax, and wc and not the source misalignment during the characterization that are of concern. In the case of a typical imaging arrangement for Kα, where θB=81 degrees and the aperture radius ra=0.5 cm, the maximum Bragg angle variation Δθ is only on the order of 10−3 degrees. Therefore, the field of view for the x-ray image is limited primarily by the width wc of the rocking curve. At a typical working distance of l˜30 cm, the crystal-limited field of view (for a perfectly monochromatic source) is given by l wc˜620 μm. For a real x-ray source with non-zero line width, the angular field of view can be estimated as the convolved width of the crystal instrument function and the x-ray spectrum. As described above, operation on the Rowland circle minimizes crystal spectral bandwidth, i.e., it maximizes the crystal area that reflects a small bandwidth. This offers higher detector exposure, but also requires multi-shot operation to obtain a rocking curve and reduces the sensitivity of the resulting rocking curve to the width of the instrument function. Alternately, the crystal may be used with magnification to make a single shot rocking curve. The description above is related to characterizing a spherically bent crystal intended for imaging Kα x-ray emission from a laser plasma using spectrally-stable He-like x-rays from the same laser plasma. This has the advantage of remaining in the same reflection order for both characterization and operation, which is generally difficult to achieve in the case of rare gas x-ray lines. The resulting rocking curve provides spectrometric properties that for using the crystal for quantitative x-ray imaging. Moreover, the method and system described above helps to determine the Bragg angle offset, knowledge of which is crucial for obtaining the accurate alignment required for monochromatic imaging. Future applications of this technique may use a finer angular resolution to improve accuracy of the rocking curve and the resulting spectrometric parameters. While a number of specific embodiments were disclosed with specific features, a person of skill in the art will recognize instances where the features of one embodiment can be combined with the features of another embodiment. Also, those skilled in the art will recognize, or be able to ascertain using no more than routine experimentation, many equivalents to the specific embodiments of the inventions described herein. Such equivalents are intended to be encompassed by the following claims.
044302916	summary	BACKGROUND OF THE INVENTION This invention relates to a structure to surround the fusion plasma of a fusion reactor, or other fusion plasma containing device, said structure commonly called a blanket. Fusion reactors of all varieties produce energetic neutrons which can advantageously be captured in a blanket region or structure substantially or completely surrounding the reactor core. In a fusion-fission hybrid reactor, the blanket contains a fertile fuel intended to breed fissile fuel and to produce energy by neutron induced fission. In a pure fusion reactor, the blanket contains fertile species which capture neutrons to form valuable isotopes. In both reactor types, the blanket is cooled by a coolant by which means heat is transferred away to cool the reactor, and perhaps generate useful power. While many nuclear transformations are possibly of interest in a fusion reactor blanket, the generation of tritium from a neutron-induced nuclear reaction of lithium nuclei is especially important since tritium is a fusion reactor fuel. The design of a suitable blanket is considered a significant obstacle to the development of a practical fusion power reactor. Several concepts have been proposed encompassing liquid lithium or solid lithium compounds for tritium breeding, solid fertile fuel for fissile element breeding, and gas, liquid, and even pebble bed coolants. All have technical handicaps. A solid blanket must be replaceable for isotope recovery and for blanket repair which, it develops, is a difficult task. A liquid lithium blanket can be continually or intermittently processed for tritium recovery and can readily be used to recover heat deposited therein by conventional means. However, liquid lithium and other liquid metals in the presence of the strong magnetic fields (in magnetic confinement fusion reactors) experience magnetohydrodynamic forces which limit the serviceability of that type of blanket. Gas cooled blankets have intrinsically lower material densities which reduce the efficiencies of heat transfer. Pebble bed blankets generally require high coolant pumping power. Consequently, it is desired to provide a blanket for a fusion reactor which can be refueled on-line, has high density, and is well adapted for power and isotope production. SUMMARY OF THE INVENTION The invented blanket is a bed of solid fuel particles which serve to absorb radiation from the fusion plasma. The bed is a packed bed during reactor operation but is fluidized intermittently for fuel particle removal when desired. The particles are chosen to be UO.sub.2, UC, ThO.sub.2, Th-ZR, Li.sub.7 Pb.sub.2, L.sub.2 O or other "fuel" material as desired depending partially upon the nuclear transformation in the blanket to be achieved. The particles may be spheres, which if sized between 40 to 300 microns in diameter are termed microspheres. In some cases, it may be desired to enclose each fuel particle with a metal cladding. The bed is contained in each of a series of pressure tubes sufficient in number to substantially or completely surround the plasma region, the assembly of all such pressure tubes constituting the blanket for the reactor. During operation of the reactor, coolant, perhaps helium, flows radially through the bed of solid particles and removes blanket heat. The same coolant can be used to generate power by various processes, including the generation of steam in an external heat exchanger/steam generator. The arrangement of coolant flow through the particle bed is considered best if it is radially outward since the radial flow path is short compared to the axial length of the pressure tube and consequently minimizes coolant pumping power requirements and coolant pressure. For blanket fueling/refueling, (particle replacement), coolant flow is stopped and a second fluid, most likely of composition identical to the coolant, is passed axially upward through the particle bed. This "fluidizing" stream serves to transport the bed fuel particles out of the pressure tube for replacement and/or reprocessing. Replacement is performed intermittently during shutdown of the reactor or even during operation. On-line refueling capability is of significant advantage in a fusion-fission hybrid reactor because the rate of fission reactions in the fuel particles caused by the buildup of fissionable nuclei due to neutron reactions in fertile nuclei can be controlled by approprite removal of the enriched particles and replacement with new fertile particles. Also, in the case of a pure fusion reactor, the net yield from the reactor of radioactively decaying tritium can be increased by continuous or frequent removal and early use of the isotope. The blanket is provided with a series of staged fluidization flow distributors to allow the fluidization and/or removal of particles in stages so as to minimize the required fluidization flow pumping power.
	description	This application claim priority to U.S. Provisional Application 61/762,457 filed Feb. 8, 2013 and EP Provisional Application No. 13154537.8 filed Feb. 8, 2013, the entirety of which are hereby incorporated by reference. Any and all applications for which a foreign or domestic priority claim is identified in the Application Data Sheet as filed with the present application are hereby incorporated by reference under 37 CFR 1.57. 1. Field of the Invention The present embodiments relate to devices and methods of sample preparation for imaging systems. More specifically, the present embodiments relate to a sample preparation stage having multiple degrees of freedom allowing for in situ sample preparation and imaging. 2. Description of the Related Art Samples for electron microscope imaging require certain preparation for observation under transmitted light or electron radiation. For example, thin slices (or sections) of a sample are typically cut or milled from a bulk sample in a grid or tube. The cutting or milling can be performed by a focused ion beam (FIB) system, or within a dual beam system that includes both a FIB and an electron microscope. Examples of such dual beam systems include the Quanta 3D DualBeam systems from FEI Corporation (Hillsboro, Oreg., USA). However, after the thin slices are prepared using the FIB, the samples must then be transferred to a platform suitable for imaging. Microscopic imaging, such as scanning transmission electron microscope (STEM), can require positioning along multiple degrees of freedom in order to capture a proper image. Others have prepared stages for STEM imaging that have multiple degrees of freedom. For example, U.S. Pat. No. 7,474,419 describes a stage assembly for positioning a sample in the vicinity of a reference point. The stage assembly includes a sample table to which the sample can be mounted and a set of actuators arranged so as to effect translation of the sample table along directions substantially parallel to an X-axis perpendicular to a reference plane, a Y-axis parallel to the reference plane, and a Z-axis parallel to the reference plane. The X-axis, Y-axis and Z-axis are mutually orthogonal and passing through the reference point. In addition, U.S. Pat. No. 6,963,068 describes a manipulator that has a table that can be moved in five degrees of freedom, with three perpendicular translations and two rotations. However, techniques for manipulating samples for STEM or TEM analysis are more complex, and can require manipulating samples for both FIB milling and carving and the later STEM analysis to be performed at specific, critical temperature to prevent ice crystal formation in the sample, or undesirable thawing of the sample between manipulations. Thus, what is needed is a system that allows for complex manipulations of samples for STEM or TEM imaging without the requiring so much sample handling that the sample becomes destroyed. One embodiment is a multi-axis sample preparation stage, that includes a bulk sample holder configured to rotate a sample position about a first bulk axis parallel to the direction of the bulk sample holder and also rotate the sample position about a bulk flip axis that is perpendicular to the direction of the bulk sample holder; and a grid sample holder for holding a sample grid adjacent the bulk sample holder and configured to rotate the sample grid about a first grid axis parallel to the direction of the grid sample holder and a grid flip axis that is perpendicular to the direction of the grid sample holder. Another embodiment is a dual beam system having a focused ion beam and a scanning electron microscope. This system includes a multi-axis sample preparation stage having a bulk sample holder configured to rotate about a first bulk axis parallel to the direction of the bulk sample holder and also rotate about a bulk flip axis that is perpendicular to the direction of the bulk sample holder; and a grid sample holder adjacent the bulk sample holder and configured to rotate about a first grid axis parallel to the direction of the grid sample holder and a grid flip axis that is perpendicular to the direction of the grid sample holder. Still another embodiment is an in situ method of preparing a sample by providing the multi-axis sample preparation stage as described above, and then cutting a lamella from a sample stored in the bulk sample holder; and transferring the lamella from the bulk sample holder to a grid on the grid sample holder. Embodiments of the invention relate to sample processing systems and methods for preparing a sample for imaging in an electron microscope. One embodiment of the invention is a sample preparation and imaging stage for a dual beam electron microscope that has multiple sample locations and the ability to tilt each sample location about several axes. One embodiment of the multi-axis stage has a bulk preparation stage for manipulating a bulk sample, for example by performing a focused ion beam treatment of the bulk sample to mill or slice off a lamella of the sample for further imaging. The multi-axis stage can include a holder for a grid, tube, planchet or TEM liftout grid in order to handle a variety of sample types. In addition, the multi-axis stage may be configured to move in multiple directions with multiple degrees of freedom so that the bulk sample can be positioned under a FIB to properly mill or slice the bulk sample. In addition to the bulk preparation stage, embodiments of the multi-axis stage also include a grid stage which is configured to hold a thin structure (e.g., lamella) of the bulk sample mounted onto a grid for imaging. Thus, once cut, a lamella from the bulk sample can be transferred from the bulk stage to the grid stage by using a manipulator needle. In some embodiments, because the grid stage can move in multiple dimensions, it is possible to perform dual axis tomography where more than one angle can be viewed. Because the bulk stage and grid stage are on the same multi-axis stage, a single multi-axis stage can be used to cut a lamella and also then perform TEM scanning on the cut lamella section without venting a chamber used to transfer the lamella to the grid stage. The multi-axis stage can thus include a bulk stage with multiple degrees of freedom and a grid stage with multiple degrees of freedom along various axes which allows the components of the system to move in multiple dimensions with respect to one another. It should be realized that many different types of treatments can be applied to a sample, as discussed below. Embodiments of the invention include any type of treatment that may be used for preparing a sample for transmission electron microscope (TEM) or scanning transmission electron microscope (STEM) analysis. For example, a lamella may be prepared from a site located in a bulk sample. In this system, the bulk stage would hold a bulk sample in which a lamella site would be located. The lamella would then be prepared on the bulk stage. In addition, it should be realized that the present embodiments are not limited to any particular configuration of microscope. For example, any type of microscope that is used to capture images of a sample is within the scope of the present embodiments. Such microscopes include, for example, visible light microscopes, confocal microscopes, and infrared and near infrared microscopes. Those skilled in the art will recognize that embodiments exemplified herein with regard to an electron microscope can be readily adapted to other types of microscopes. In another embodiment, a lift out procedure may be performed. In this system, a manipulator may transfer a lamella located on the bulk stage to a grid on a grid stage. In some embodiments, the lamella may be further processed after the manipulator is removed. For example, the lamella may be milled from a thick lamella to a thin lamella using a focused ion beam. Lamella preparation can include processes such as locating a lamella site (including multiple cross sections of the sample), protective deposition (e.g., coating the lamella site with a metal cap layer), adding fiducial markers, rough milling (e.g., to create lamella about 2 μm), medium milling (e.g., to thin lamella to about 250-400 nm), fine milling (e.g., to thin the lamella to a final thickness), undercutting to release sample from the substrate, endpointing, cleaning lamella (e.g., low kV cleaning), and/or transferring the sample. With focused ion beam systems, the lamella can be positioned accurately within the instrument's mean drift (including, for example, both sample drift, due to imaging or charging, and stage drift). In addition, in some embodiments, fiducial markers can be used to improve location of a particular feature during cross-sectioning. During final thinning, the user can thin the lamella until the precut (and filled) fiducial markers are seen in a cross-section image. In some embodiments, the fiducial markers (for example, lines) can be milled at about 100 nm width, which can form a basis for judging the final thickness of the lamella. To form the fiducial markers, small beams (for example, less than about 100 pA) and relatively short dwell times can be used. These fiducial markers can be conveniently scripted. With dual-beam systems, the SEM or S/TEM (scanning transmission electron microscope) can be used to improve the registration by stopping the thinning at a particular image location. Without a dual beam for final location, the measured accuracy is on the order of 50 nm (3 sigma) for top-down FIB-prepared systems. Refinement in a small dual beam can allow a practiced operator nm-level placement. To measure placement accuracy, there are a few different metrics: the placement of the fiducial marker relative to the feature, as well as the placement of the final lamella as compared to the initial fiducial marker. Overall placement can also be judged by measuring the final placement of a known reference feature within a lamella. In some embodiments, focused ion beam methods can be used for one or more lamella preparation processes. For example, FIB techniques can be used for site-specific analysis, deposition, and ablation of materials. It will be appreciated that while an SEM uses a focused beam of electrons to image the sample in the chamber, an FIB setup uses a focused beam of ions that can be operated at low beam currents for imaging or high beam currents for site specific sputtering or milling. FIB can also be incorporated in a system with both electron and ion beam columns, allowing the same feature to be investigated using either of the beams. In some embodiments, the location of the lamella can be positioned to find an isolated feature, or to fully encapsulate a reference feature in the bulk sample. For example, where only a single feature is needed, the lamella can be prepared at a slight angle to the feature. As described herein, the bulk stage may be rotated about an axis and/or flipped about an axis such that the bulk sample is rotated or flipped for positioning the lamella location. Current FIB systems have high resolution imaging capability; this capability coupled with in situ sectioning has eliminated the need, in many cases, to examine FIB sectioned specimens in a separate SEM instrument. SEM imaging is still required for the highest resolution imaging and to prevent damage to sensitive samples. However, the combination of SEM and FIB columns onto the same chamber enables the benefits of both to be utilized. FIB can also be used to deposit material via ion beam induced deposition. For example, FIB-assisted chemical vapor deposition occurs when a gas, is introduced to a vacuum chamber and allowed to chemisorb onto the sample. By scanning an area with the beam, the precursor gas will be decomposed into volatile and non-volatile components; the non-volatile component, such as tungsten, remains on the surface as a deposition. This is useful, as the deposited metal can be used as a sacrificial layer, to protect the underlying sample from the destructive sputtering of the beam. From nanometers to hundreds of micrometers in length, metal deposition allows for metal lines to be deposited where needed. Materials such as tungsten, platinum, cobalt, carbon, gold, and the like, can be deposited. A fiducial marker or fiducial can be an object placed in the field of view of an imaging system which appears in the image produced, for use as a point of reference or a measure. A fiducial marker may be something placed into or on the sample. In some embodiments, preparation of the sample can include surface and/or buried fiducials (e.g., fixed reference points). An effective fiducial creation strategy can have a large impact on the robustness of an automated process. For example, different fiducial marker shapes can have very different behaviors. Transmission electron microscope (TEM) requires very thin samples, nowadays typically between 50 to 300 nm. The nanometer-scale resolution of FIB allows an exact thin region to be selected and prepared. In some embodiments, lower beam voltages, or further milling with a low-voltage argon ion beam after completion of the FIB process can reduce surface damage and implantation, which produce noticeable effects when using techniques such as high-resolution “lattice imaging” TEM or electron energy loss spectroscopy. In some embodiments, rough, medium, and/or fine milling can be used to adjust the size or thickness of the lamella. Decreasing FIB beam sizes can be used to improve control of the rough, medium, and/or fine milling. It will be appreciated that there is a tradeoff between slow etch time (which can cause increased drift sensitivity) and beam resolution. In some embodiments, the procedure uses 13 nA for bulk milling and undercutting, 1 nA for medium thinning, 30-100 pA for fine milling, and 3 kV-120 pA (using 1000 pA aperture) for final cleaning. However, variations such as 3 nA instead of 1 nA for medium thinning are possible, depending on user preference and the details of the available aperture strip. In transmission techniques, analysis is greatly simplified for single scattering events. In addition, the sample attenuates the beam, the attenuation a function of sample material (high-Z materials showing a higher attenuation than low-Z materials) and sample thickness. Generally, S/TEM samples have a thickness of about 80 nm. For TEM, samples generally have a thickness range from about 20 nm to about 80 nm, depending on the specific sample and TEM tool. Thickness can be measured either by cross-sectioning the thin lamella, or by measuring the electron beam attenuation. At low electron beam energies (e.g., 30 keV) thin samples can be used. At high electron beam energies (e.g., 300 keV) thicker samples can be used, for example biological material of up to about 1 μm or semiconductor materials of typically less than 100 nm may be used. In some embodiments, top-down measurement of TEM sample thickness can be influenced by the deposited protective overcoat. In some embodiments, cross-section measurements of the lamella are much more accurate and useful. In some embodiments, lamella thickness is substantially uniform. In other embodiments, samples are intentionally made with varying thickness. For example, in some embodiments, the shape of the lamella is a wedge. The process can also be simplified using the systems and methods as described herein, by setting up the system at the FIB's eucentric point. For example, tilt stage systems (e.g., the bulk stage and/or the grid stage) have an option to set the eucentric point based on the coincident point, the FIB's eucentric, or the SEM's eucentric. By setting the tool according to the FIB's eucentric point beam shift and motion during sample preparation can be avoided. It will be appreciated that the microscope can be tuned by setting beam tilt pivot points to the right level, for example, by eucentricity, precise focus, pivot point adjustment, and accurate rotation center. Sample (e.g., lamella) transfer mechanisms fall into two general types: the in situ autoprobe, and ex situ plucking with a glass rod. Each method has benefits, depending on the application target. For example, ex situ liftout is typically significantly faster. Endpointing in sample preparation generally uses a SEM signal to look at either secondary or backscattered electrons from a sample, and correlates these to thickness. In some embodiments, the method uses the brightness. For example, very thin samples become either dark or bright (depending on detector layout and source) once thinned under about 100 nm. It will be appreciated that the exact value depends on the beam energy and imaging mode. Similar techniques can be used with the integrated S/TEM detector system, with the added advantage of enhanced resolution over SEM-based techniques. The S/TEM system allows direct thickness measurements to be made from first principles, or contrast differential techniques can be used in darkfield microscopy. The system and methods disclosed herein can be used for sample preparation of cryogenically frozen samples. For example, the methods can be performed without venting the microscope chamber. FIB preparation can be used with cryogenically frozen samples in a suitably equipped instrument such as a dual beam microscope, allowing cross sectional analysis of samples containing liquids or fats, such as biological samples, pharmaceuticals, foams, inks, and food products. As discussed in more detail below, the system can further include temperature control elements for maintaining a temperature in the system. Accordingly, in some embodiments, the methods disclosed herein can be performed at room temperature, elevated temperatures, and/or at cryogenic temperatures. As used herein, the term “sample” can include any type of sample from a biological organism, but typically includes tissue, cells, viruses, cell structures, or any other biological sample of interest. The sample can be prepared for electron microscopy to be used in material science applications, such as for semiconductor materials or polymers. Electron microscopy may also be used in the biological and life sciences fields for applications such as diagnostic electron microscopy, cryobiology, protein localization, electron tomography, cellular tomography, cryo-electron microscopy, toxicology, biological production and viral load monitoring, particle analysis, pharmaceutical quality control, structural biology, 3D tissue imaging, virology, and vitrification. These separate types of applications can be performed by a range of different types of electron microscopes including, for example, transmission electron microscopes (TEM), scanning electron microscopes (SEM), reflection electron microscopes, scanning transmission electron microscopes, and low-voltage electron microscopes. Overview of Sample Preparation System FIG. 1 is a perspective view of one embodiment of a multi-axis stage 100. The multi-axis stage 100 includes a circular base 101 that is supporting a rectangular stand 103. Mounted on a left edge of the rectangular stand 103 is vertical wall 104 that holds a bulk stage 110. The bulk stage 110 is movably mounted to the vertical wall 104 and used to hold a bulk sample. The bulk stage 110 includes a bulk rotation actuator 115 configured to rotate a sample holder 118 circumferentially about a bulk rotation axis 112 as illustrated. Thus, movement of the actuator 115 results in rotational movement of the bulk sample in the sample holder 118 with 360 degrees of movement around the Y axis of the multi-axis stage 100. This allows the sample to be rotated along an axis that is parallel to the direction of the sample holder 118. In addition to this rotational movement, the bulk stage 110 also has multiple degrees of freedom about a bulk flip axis 111 which uses a flip actuator 119 mounted to the vertical wall 104 to rotate the sample holder 118 around the X axis to “flip” the sample from the front of the base stage 100 to the rear of the multi-axis stage 100 and back. This allows the bulk sample holder 118 to rotate around a line that is perpendicular to the direction of the sample holder. Rotation of a bulk sample about the bulk rotation axis 112 allows a sample treatment, such as a focused ion beam treatment, to result in a rotationally symmetric sample about the rotation axis. This can remove, or reduce, non-isotropy/inhomogeneity in the sample after ion beam treatment. Together with this angular degree of freedom (DOF) about the rotation axis, the further angular DOF provided about the bulk flip axis 111 allows a wide range of specific crystallographic orientations in the sample to be oriented along the first and/or second irradiating beam. Thus, the combined angular DOFs about the rotation axis and the flip axis allow both α-tilt and β-tilt of the sample. In a particular embodiment, the angular stroke of the sample holder 118 about the bulk flip axis is substantially 360 degrees or more. If the flip axis is arranged to be parallel to a principal axis (by suitable angular adjustment of the stage assembly about the rotation axis) of the multi-axis stage 100, and the focused beam is an ion beam, such an angular stroke allows the stage assembly to be used as a type of “ion lathe”. In such a set-up, one could manufacture various precision items, such as tips and probes that are required to have a particular cylindrical/conical profile about the flip axis. In a similar fashion, one could realize a “laser lathe”, using a laser beam as the second irradiating beam. Mounted to the rectangular stand 103 and directly adjacent the bulk stage 110 is a grid stage 150. Similar to the bulk stage, the grid stage 110 is mounted to the rectangular stand 103 so that is also provides a sample with multiple degrees of freedom about several axes. As indicated in FIG. 1, the grid stage 110 has a grid flip axis 151 and a grid rotation axis 152 that allow movement of a grid holder 156 in multiple X and Y dimensions. Rotational movement along the grid rotation axis 152 is controlled by a grid rotation actuator 154 and moves the grid holder 156 around the Y axis of the multi-axis stage 100. The allows the grid holder to rotate in a direction that is parallel to the grid holder 156. Rotational movement along the grid flip axis 151 is controlled by a flip actuator 155 which allows the grid holder to rotate about the X axis of the multi-axis stage 100. This allows the grid stage to rotate in a direction around the Y axis of the multi-axis stage 100. This multi-axis rotational movement provides several degrees of freedom for samples placed into the grid holder 156 to provide imaging of the sample. As can be realized, by having the bulk stage and the grid stage located adjacent one another and mounted to the same base, one can use this single stage for preparing samples using an ion beam, and then imaging those samples with an electron beam. In a dual beam device, the multi-axis stage can be placed within the device and then used to prepare and image samples without the requirement of removing the multi-axis stage from the dual beam device. Moreover, as discussed below, samples can be kept at a desired temperature by cooling or heating the multi-axis stage to a desired temperature and then performing all of the sample manipulations within a dual beam system without needing to expose the stage and samples to room temperature conditions. At the rear portion of the multi-axis stage 100 is a STEM stage 160 that allows transverse movement 161 of a detector holder 162 for performing a scanning transmission electron microscopy on a sample using the same multi-axis stage 100. In some embodiments, the aforementioned components can move about the axes independent of one another. At the rear portion of the multi-axis stage 100 a retractable S/TEM detector can be placed at in the detector holder 162 that can be retracted by retractor 160. The detector can also be protected by a cover to avoid, for example, radiation damage or chemical damage. In some embodiments the cover may be used in place of the retractability of the S/TEM detector. FIG. 2 is an enlarged view of one embodiment of the bulk stage 110 and the grid stage 150 showing their relationship to one another. The bulk stage includes a bulk arm 210 configured to hold a bulk sample carrier 215 with a bulk sample 220. The bulk arm 210 can rotate about the bulk stage such that the orientation of the bulk sample 220 changes. For example, the bulk arm 210 can rotate about the bulk rotation axis 112 to rotate the bulk sample 220. The bulk arm 210 can also flip about the bulk flip axis 111 to flip the bulk sample 220. Adjacent the bulk stage 110 is the grid stage 150 which is shown with a grid arm 250 configured to hold a grid plate 255 that is configured to hold a sample. The grid arm 250 can move about the grid stage with multiple degrees of freedom such that the orientation of the grid plate 255 changes over time and during electron microscopy. For example, the grid arm 250 can rotate about the grid rotation axis 152. The grid arm 250 can also flip about the grid flip axis 152 to flip the grid plate. As shown in FIG. 2, a manipulator 270 and a gas supply system 280 can be used transfer a lamella taken from the sample 220 at the bulk stage 110 and move the lamella to the grid stage 150 by methods known in the art. As shown in FIG. 3, the lamella 410 can be mounted to the grid plate 255 for further analysis. Of course, it should be realized that the present embodiments are not limited to any particular configuration of bulk sample carrier 215. For example, any type of sample carrier that used to hold a sample and allow for preparation as disclosed herein, is within the scope of the present embodiments. Similarly, it should be realized that the present embodiments are not limited to any particular configuration of the grid plate 255. For example, any type of plate that used to hold a sample and allow for further processing and/or imaging as disclosed herein, is within the scope of the present embodiments. Exemplary Methods for Sample Preparation FIG. 4 shows a flowchart illustrating an exemplary process 500 that may run within one implementation of a sample preparation system 100. Process 500 begins at block 502, where the bulk sample is loaded on the bulk stage. After the bulk sample has been loaded onto the bulk stage, the process moves to block 504, wherein a liftout grid is loaded on the grid stage. Process 500 then moves to block 506, where the bulk sample is centered on the bulk stage. For example, the bulk sample can be positioned by rotating the bulk sample arm about the bulk rotation axis and/or flipping the bulk sample arm about the bulk flip axis to properly position the bulk sample for creating a desired lamella. Once the bulk sample has been positioned, the process 500 moves to block 508, where a protective metal layer is locally deposited on the bulk sample. It should be realized that in other embodiments, the order to blocks 508 and 510 can be reversed. As discussed herein, the protective metal layer can include any material, such as, for example, platinum or tungsten. Process 500 then moves to block 510, where a region of interest on the bulk sample is determined by the user. The region of interest can include, for example, one or more isolated features and/or one or more reference features, such as a fiducial marker in the deposited protective metal layer. Alternatively, the region of interest can be marked by having previously placed the sample in an optical microscope and using a laser marker to indicate the region of interest. Once a region of interest has been located, process 500 moves to block 512, where a lamella is cut. As discussed herein, the lamella may be positioned to optimize the feature of interest location. In some embodiments, a thick lamella is cut. In one embodiment, the lamella is cut using a focusing ion beam that is targeted to cut a desired lamella from the bulk sample. As can be appreciated, the desired region is properly cut by using the multiple degrees of freedom provided by the bulk stage, as described above. Once the lamella has been cut, the lamella is transferred from the bulk stage to the grid stage by an operator. As one example, at block 514 a manipulator is inserted into the bulk sample and at block 516 the manipulator is then attached to the lamella that has been cut from the bulk sample. The manipulator can be, for example, a needle or other device configured to attach to a lamella. For example, the manipulator may be temporarily attached to the lamella to enable transport between the bulk stage and the adjacent grid stage. The manipulator then extracts the lamella at block 518. And the manipulator is retracted from the bulk sample at block 520. Process 500 then moves to block 522, where the liftout grid on the grid stage is centered. For example, the liftout grid can be positioned by rotating the grid arm about the grid rotation axis and/or flipping the grid arm about the grid flip axis. The manipulator with the lamella is then inserted at block 524 and the lamella is attached to the liftout grid at block 526. Once the lamella is attached to the liftout grid, the process 500 moves to block 528, wherein the manipulator is detached from the lamella. For example, a FIB can be used to cut the manipulator needle from the lamella. The manipulator can then be retracted at block 530. As discussed herein, in some embodiments, the lamella can be thinned from a thick lamella to a thin lamella. For example, the process 500 moves to block 532, where the thick lamella is thinned to a thin lamella by a focused ion beam. After the lamella has been transferred to the grid stage and thinned to the desired thickness, process 500 moves to decision block 540 to determine if the lamella will be examined in a small dual beam device (SDB). If a decision is made to not stay within the SDB device, then multi-axis stage 100 can be unloaded at block 560 and transferred to, for example, a TEM system at block 565. However, if a decision is made to remain with the SDB device, the sample can be directly STEM imaged. For example, the sample can undergo STEM tomography at block 550 before being unloaded at block 555. In another example, the sample can undergo STEM imaging at block 545 before being unloaded at block 555. It is noted that embodiments of the invention also cover variants of the method, in which, for example, step 502 and 504 are exchanged, or blocks 510 and 508, etc., as is clear to the person skilled in the art. Temperature Control of Multi-Axis Stage In some embodiments, the system can further include a thermal control system configured to control the temperature of the multi-axis stage 100 As shown in FIG. 5, a thermal control system 600 can be used to heat or cool the multi-axis stage 100 but still allow the stage 100 to move circularly within an imaging system. The thermal control system 600 includes a base 601 that mounts through a platform 602 via a series of connectors 604. A system of standoffs 603 may be used to raise the platform 602 to a desired level within the imaging system. The standoffs are mounted to the platform 602 through a series of pins 608. As shown, the base 601 fits within a cylindrical sleeve 610 that mates into the center of a metal ring 612. Mated to a top surface 614 of the sleeve 610 is a heat transfer body 620 including a heat transfer pipe 616 that is configured to move a heat transfer medium. In one embodiment, the heat transfer medium is cooled dry or liquid nitrogen and the temperature of the heat transfer plate 620 can be controlled by controlling the flow rate of the dry nitrogen with a flow meter (not shown) or adding a supplemental heat source, such as a thermal resistor. Thus, by controlling the type and amount of heat transfer medium circulating through the head transfer pipe 616 (and/or controlling the extra heat source), the user can control the resulting temperature of the heat transfer plate 620. Above and in thermal contact with the heat transfer plate 620 is a bearing ring 630 that has a plurality of slots 635. Each of the slots 635 in the bearing ring 630 are configured to hold thermally conductive rollers 640. Above the rollers 640 is a top plate 650. The top plate 650 includes a mounting bracket 660 and centering pin 665 that are designed to mount with the multi-axis stage 100 and provide thermal heating or cooling functionality to the multi-axis stage 100. Top plate 650 can rotate around its axis driven via the base 601. As can be envisioned, when a multi-axis stage is mounted into the mounting bracket 660, the stage can rotate in 360 degrees on top of the roller bearings (for example ball bearings or needle bearings) and still maintain thermal connectivity with the heat transfer medium that is flowing through the pipe 616. In this embodiment, all parts may be designed with a high thermal conductivity. For example, the roller bearings can be made of steel with a conductivity of 46 W/mK. The cold stage parts can be made of oxygen free copper, or other materials with a high thermal conductivity, for example, gold. In some embodiments, the temperature of the shuttle receiver can go down to −120° C., −130° C., −140° C., −150° C., −160° C., −170° C., −180° C. or less in temperature. In some embodiments, the device can be used to transfer heat such that the system is heated rather than cooled by pumping heated liquid or gas into the pipe 616. It is noted that the stage can be equipped with one roller bearing offering the needed mechanical support and degree of freedom, while the stage further shows a second roller bearing thermally connecting the stage with a stationary cooling body, cooled by, for example, liquid nitrogen. Detecting Frozen Status of Ice Another embodiment relates to determining the status of vitreous ice in samples. This normally relies on TEM electron diffraction patterns usually taken at the thin sectioned area of interest on the frozen sample. Vitreous ice status is useful for to preserving natural structural forms, such as biological cell membranes or dispersed particulates. In contrast, crystalline ice disrupts those structures or distributions. Ring patterns show that the ice is amorphous (vitreous) whereas spot patterns show the presence of hexagonal or cubic crystalline structure. Quite often the vitreous result can be in dispute due to too sharp or too dull diffraction rings, or by which TEM electron gun it was produced; W, LaB6 or FEG. When TEM sections are made one wants to know if the surrounding ice is crystalline or vitreous at that point. This helps the user know whether it is useful to continue with that sample or to start with a fresh sample. One alternate embodiment is a method that can be used in the field emission gun SEM or SEM for samples where it is important to keep the temperature below the glass transition temperature of 136K (−137 deg C.). In this embodiment, the ice sample is FIB milled to the desired thickness so that when rotated and tilted to a horizontal plane it can be observed by an analyzing detector from below using the electron beam at a desired voltage. Tilting the ice sample from the horizontal plane to either a positive or negative angle allows the analyzing detector to observe a differing transmitted orientation contrast. This differing orientation contrast comes from the lattices of the differently orientated crystals within the thin sample if a crystalline form is present. If a crystalline form is not present because the sample is vitreous then the contrast remains constant as the sample is tilted. This allows one to detect whether the sample has formed crystalline ice or not. The reason for this is that vitreous status is a state of random atomic structure and therefore will not show orientation contrast. This is a very direct and reliable way of determining the ice status of the sample when immediately made in a FEG SEM without having to make further transfer to a cryo-TEM system during which hexagonal ice contamination could compromise the result. With improvement of the SEM and Dual Beam instruments to resolve sub-nanometer resolution there are many cases where it is of little necessity to transfer to the TEM for direct resolution imaging or angular tomography. Therefore this method is convenient to verify the status of the sectioned ice within the SEM or Dual Beam instruments. The foregoing written specification is considered to be sufficient to enable one skilled in the art to practice the present embodiments. The foregoing description and Examples detail certain preferred embodiments and describes the best mode contemplated by the inventors. It will be appreciated, however, that no matter how detailed the foregoing may appear in text, the present embodiments may be practiced in many ways and the present embodiments should be construed in accordance with the appended claims and any equivalents thereof. The term “comprising” is intended herein to be open-ended, including not only the recited elements, but further encompassing any additional elements.
	description	This application is a continuation of U.S. Patent Application Ser. No. 61/616,100 filed Mar. 27, 2012, which is hereby incorporated by reference in its entirety. The idea of using radioactive materials as direct power sources for applications requiring long-lived power sources has been investigated for many decades. Nuclear power sources for deep space probes have been used on many NASA programs especially those that last for decades and where the probes will not have sufficient sunlight for solar panels to operate. Nuclear Batteries, also called atomic batteries, have been developed that attempt to exploit the heat or thermal energy of the radioactive materials as well as the alpha and beta particle emissions energy through various means. Typically these devices tend to be large in comparison to typical electrochemical batteries and also tend to suffer from the emissions of high energy particles including alpha, beta, gamma and neutrons which create human health risks. Besides space probes, small nuclear power sources have been successfully used in devices such as pace makers and remote monitoring equipment. One area of much research has to do with the direct conversion of beta emissions, i.e. electrons, emitted from radioisotopes that are targeted on a semiconductor material to develop electron-hole pairs and thus generate an electrical current in the semiconductor. All of these devices suffer from very low efficiencies due to the poor electron capture cross section of the designs as well as the semiconductor material itself. This is the same phenomenon that solar cells continue to suffer from even after decades of work and hundreds of billions of dollars of investment. Researchers have recently begun investigating nanotechnologies with which to implement nuclear power sources. Some of these include the development of micromechanical devices that vibrate or rotate in response to charge build up within the semiconducting materials. The underlying reason for pursuing the development of nuclear batteries is the much wider goal of developing long lasting, low cost power sources. Along these lines, there are many other fields of research that are producing some interesting and potentially viable power sources. In particular, fuel cells and new electrochemical battery technologies look particularly promising for small, low cost, high density and long-lived power sources but none come close to the energy density and longevity that nuclear power sources offer. Prior art describes four basic methods of converting radioisotopes into useable energy sources. Three of these require a double conversion process wherein the radioactive sources are used to first generate heat, light or mechanical energy which is then converted into electrical energy. These multiple conversion processes have extremely low efficiencies which puts them at a distinct disadvantage to compete with the fourth method which is referred to as direct conversion. Of the direct conversion methods, the two that are the most studied are the semiconductor PN junction conversion and the capacitive charge storage conversion. The semiconductor conversion processes, also known as betavoltaics, employs semiconductor technology that suffers from device degradation and very low efficiencies. The capacitive charge storage devices have problems with large size and very high voltages that can reach hundreds of thousands of volts that create materials challenges that can withstand such high voltages. These problems are magnified as the devices are scaled down. A common problem for all of the prior art is that the amount of energy that can be extracted from the radioactive material is a very low level and at a consistent output which doesn't provide a practical means to support real world applications that demand varying amounts of power at different times. Of the most relevant descriptions of a nuclear batter disclosed in prior art, Baskis, U.S. Pat. No. 5,825,839, describes a direct conversion nuclear battery utilizing separate alpha and beta sources isolated by an insulating barrier and two charge collector plates, one to collect the negative beta particles and a another plate collect the alpha particles. The two plates become charged and thereby storing the energy in the form of an electric potential the same as a capacitor stores electrical energy in the form of positive and negative charges on parallel plates. This approach utilizes the balanced alpha/beta charge approach as the present invention, but for completely different purposes. In the Baskis disclosure, a load place across the “battery” allows electrons to flow from the negative charged plate to the positively charged plate that is saturated with alpha particles. The recombination of the electrons and the alpha particles is said to produce helium gas which is vented out of the cell. However, this description does not address the recombination of “free” electrons in the metal plate combining with the alpha particles producing He gas directly. However the net effect is the same, the positive plate will become increasingly positively charged by the alpha particles producing a stored electric potential across the device. The preferred embodiment of the present invention also suggests the use of balanced alpha and beta charges for greater efficiencies, however, such a requirement is not necessary for it to operate. Additionally the present invention can store the energy of the alpha and or beta particles in chemical energy form as a chemical battery as well as in electric potential energy as in a capacitor, as described in alternative embodiments. The present invention incorporates aspects of three different energy generation and storage technologies, those being: Nuclear beta and/or alpha direct conversion, fuel cells, rechargeable electrochemical storage cells and capacitive energy storage. In the present invention, a radioisotope, or a mixture of radioisotopes, that emits beta and/or alpha particles is used as the primary energy source while an electrochemical cell is used as both a secondary energy source as well as an energy storage mechanism and a capacitor may be used as a primary storage device. This disclosure illustrates the core concepts for the construction and manufacture of the device but by no means limits the actual materials to only those used as examples and discussed herein nor the embodiments described. For example, almost any radioisotope can be used as the primary fuel source for this invention but those that are, at this time, considered safer, more optimal or more readily accessible are more desirable, especially for devices that could be used for equipment that will be in close proximity to humans or animals. As research continues and future advanced occur, it may become feasible that other radioisotopes may be well suited for use in this device and the following discussions are by no means intended to limit the invention to only the specific materials used or discussed herein. This is true for the materials used including those for the electrochemical and capacitive storage materials as well. Additionally, no limitations to the embodiments of the described invention are to be inferred. This disclosure is to be interpreted in its broadest sense as to any materials that can be used as well as to the physical embodiments in which the concepts can be applied. For instance, there are hundreds of radioactive materials that can emit alpha and or beta particles and electrochemical batteries and capacitors can be built in an unlimited number of shapes, sizes, storage capacity, energy densities or materials. There are also many rechargeable battery chemistries that can be used in said present invention and no limitations as to the type of rechargeable battery or chemistry that can be used to implement such a device is implied. Any radioisotopes or combination of radioisotopes that emit alpha and or beta particles can be used for this device. However, because the device takes advantage of both the positive charges of the alpha particle and the negative charge of the beta particle, to generate dc current directly as well as to provide a charging mechanism for the electrochemical cell, radioisotopes that produce both particles are expected to produce greater energy density and efficiencies than isotopes that produce only alpha or beta particles, however any combinations of radio isotopes or individual radioisotopes can be used. Radioisotopes that produce low energy alpha and or beta particles are particularly useful in this application since the emissions can be contained within the structure itself, thus eliminating the health issues of ionizing gamma and or neutron radiation. Isotopes that produce gamma rays and high-energy neutron are less desirable due to their associated health risks, and the inability to completely contain these emissions within the power cell itself. However, the power cell can be adapted for their use for certain applications where these issues are not a concern, for instance in generating electrical energy from nuclear waste products stored in long term storage facilities. In this case, the hazardous material is already placed in secured facilities where the high-energy emissions cannot harm persons or the environment. Using any or all available radioisotopes to generate electrical energy would be a good use for this invention. Additionally, space probes could, from a human safety standpoint, use any radioisotope material. While the invention has been described with reference to some preferred embodiments of the invention, it will be understood by those skilled in the art that various modifications may be made and equivalents may be substituted for elements thereof without departing from the broader aspects of the invention. The present examples and embodiments, therefore, are illustrative and should not be limited to such details. For the following discussion, refer to FIG. 1. The device 10, comprises a rechargeable electrochemical cell 20, such as a Lithium Ion cell, which may be comprised of a cathode plate 19 such as aluminum, a Li ion capture material 18 such as LiCoO2 (or LiMnO2, or others), an electrolyte material 17 such as a lithium salt dissolved in organic solvent with a semipermeable membrane 16 separating the anode and cathode sides of the cell, a carbon anode 14 with an plate 13 such as copper, a layer of radio isotope material or a mixture of radio isotope materials 12 which emit alpha and or beta particles, with a bonding (agent not shown) and a proton exchange membrane layer 11 that is comprised of a highly negatively charged material, and a dielectric insulating layer (not shown). These layers can be rolled up to produce a typical cylindrical battery device, referred to in the industry as a “jelly roll,” and shown in FIG. 6, or stacked on top of each other in many layers to produce irregular shapes and sizes that would be used in consumer electronic devices as shown in FIG. 2. While the secondary battery technology described herein happens to be a Li-Ion type battery, any battery storage technology compatible with this invention can be used, and a person skilled in the art of battery chemistry and technologies could easily adapt any battery technology to be useful in this invention. The amount of radioisotope material that would be needed in a particular power cell would depend upon the activity level of the particular material used and the amount of energy that the power cell would need to provide for a specific application. FIG. 2 shows a cross section a stacked cell implementation of the invention as the cells would exist relative to each other. This orientation would exist whether individual cells are stacked on top of each other or a long single cell was rolled up into a cylindrical shape. In FIG. 6, the layers of the cell would be rolled up upon themselves to create a cylindrical form similar in size and shape of common commercially available batteries such as “AA”, “AAA”, “C” and “D.” Of course any shape or size can be constructed by stacking the layers shown in FIG. 2. When stacking layers, the PEM (Proton Exchange Membrane) layer 11 would be located between the radioisotope material layer 12 and the cathode plate 19. Also note that the cathode plate 19 and the anode plate 13 are offset with respect to each other and with respect to the PEM layer 11 so as to prevent shorting the cells when they are assembled as well as to allow each cathode plates 19 to be connected together on one end or side of the cell and the anode plates 13 to be connected together on the other end or side of the cell. This also provides a means to connect the anode and cathode to the cell contacts for external connections. Theory of Operation Refer to FIG. 3 for the following discussion. A key aspect to the invention is the adoption of a proton exchange membrane 11 (PEM) similar to that used in fuel cell technologies. A common type of material used for this application is Nafion. There are a number of proton exchange membranes available that can be used in the present invention. In fuel cells, the PEM is a highly electronegative porous material that allows the positive charged “protons” to cross the membrane boundary between the anode and cathode while repelling the disassociated electrons and forcing them to flow around the cell, through an external circuit. These PEM characteristics are exploited in the present invention to allow the doubly positively charged alpha particles 23, which are approximately the same size as methanol “protons” to pass through the PEM material 11 and collect in the cathode plate 19, while forcing the beta particles 22, i.e. electrons, to flow to the anode plate 13 and collect there. The positive charges carried by the alpha particles 23 and captured by the cathode plate 19 and the negative charges carried by the beta particles 22 and captured by the anode plate 13 will migrate to their respective cathode 18 and anode 14 regions causing the cell 10 to store the charges. These charges would then cause the lithium ions 20 to migrate from the cathode 18 through the electrolyte region 17, across the separator membrane 16, further across the solid electrolyte interphase (SEI) layer 17, which is formed upon first charging, and finally to in situate themselves, intercalate, within the carbon layers of the anode 14, thus completing the charging cycle for a pair of alpha 23 and two beta 22 particles. Referring to FIG. 5, when an electrical load is placed across the anode plate 13 and cathode plate 19, an electric circuit would be completed causing electrons from the anode 14 to migrate to the anode plate 13, through the external circuit 26 and returning to the cell at the cathode plate 19. The ideal cell would be achieved when amount of radio isotopic material 12 and the external electrical load 26 were balanced where the total electrical current emanating from the radioisotope region into the anode plate 19 and cathode plate 13 were to equal the amount used by the electrical load 26. This is an ideal condition that is unlikely to ever be achieved. Normally electrical loads have varying power requirements and this is where the rechargeable electrochemical storage portion 20 of the cell 10 plays it role. It will provide additional power to the load 26 when it is needed and it will store the excess energy coming from the radio isotope material 12 for later use. If an electrical load were connected across the anode plate 13 and cathode plate 19, an electric circuit would be completed causing electrons from the anode 14 to migrate to the anode plate 13, through the external circuit 26 and returning to the cell at the cathode plate 19. The ideal cell would be achieved when amount of radio isotopic material 12 and the external electrical load 26 were balanced where the total electrical current emanating from the radioisotope region into the anode plate 19 and cathode plate 13 were to equal the amount used by the electrical load 26. This is an ideal condition that is unlikely to ever be achieved. Normally electrical loads have varying power requirements and this is where the rechargeable electrochemical storage portion 20 of the cell 10 plays it role. It will provide additional power to the load 26 when it is needed and it will store the excess energy coming from the radio isotope material 12 for later use. Referring to FIG. 4, as with any secondary electrochemical cell, the present invention can be recharged by means of an external charging circuit 25 placed across the cathode plate 19 and anode plate 13. The charging circuit 25 injects electrons 21 into the anode plate 13 which migrate into the anode carbon layer 14 and speed up the lithium ion battery charging process as shown in FIG. 3. During discharge, the beta particles 22 (electrons) emitted by the radio isotope layer 12 will flow directly through the anode plate 13 to power the external load 26 while the alpha particles will accumulate at the anode, completing the circuit. The current developed from the radioisotope material 12 will power the load reducing the draw from the stored energy of the secondary electrochemical battery cell 20. However, when the current drawn by the load 26 is less than the current developed by the radioisotope material 12, then the excess current will charge the secondary battery cell 20, thus acting as a charging circuit for the secondary electrochemical storage battery 20, the same as if the secondary battery were being charged from an external charging device 25. Because of the affinity of the anode 14 to accept electrons and the highly electronegative characteristics of the proton exchange membrane (PEM) 11, the beta particles 22 are attracted to the anode plate 13 and collect there developing an overall negative charge on the plate which is transferred to the anode carbon layer 14. The increasingly negatively charged carbon anode 14 attracts positive lithium ions 20 from the electrolyte 17 causing the migration of the lithium ions 20 from the lithium metal oxide cathode 18. At the same time, the alpha particles 22 are attracted by the overall negatively charged proton exchange membrane (PEM) 11 and migrate towards it. The PEM 11 doesn't have any binding sites for the alpha particle and its physical properties allow the alpha particles 22 to pass through it to the cathode plate 19 where they are able to bind with the cathode plate 19 and transfer their positive charges to the cathode plate 19, thereby oxidizing the cathode layer 18 and liberating more lithium ions 20 to migrate across the cell to the anode 14. Alternative Embodiments Since the radioisotope material 12 continually emits alpha and/or beta particles 22 and 23, at some point the battery will become fully charged with all Lithium ions 20 being intercalated within the carbon material of the anode 14 but the radioisotope material 12 will still be developing an electrical potential. Some of this unused electrical potential can be stored in an integral super capacitor (not shown in drawings) surrounding the entire battery device but inside the enclosure 31. The super capacitor is created by connecting one thin metal plate (not shown in drawings) to the anode plate 13, another thin metal plate (not shown in drawings) attached to the cathode plate 19 and a thin insulating material (not shown in drawings) separating said plates. However, depending upon the total energy storage capacity of the device and the system load demands, eventually one of two conditions will occur. Either the cell will be completely depleted or it will become fully charged. In the event of a full charge within the electrochemical cell and any integral capacitor of the battery, the excess energy will have to be exhausted as heat. This excess energy is most effectively released through a resistive material (not shown in drawings) around the outer surface of the cell but inside the protective metal enclosure 31 or incorporated as an integral part of said enclosure 40, so as to radiate off excess energy as heat into the surrounding environment. A built-in charging and discharging control circuit can be used to control the excess energy bleed off. A second situation exists where the device becomes completely discharged and cannot provide sufficient power for the intended load. At this point, the equipment which is powered by the device is turned off or the power cells are changed out for fresh cells. In either circumstance, the radioisotope will recharge the cell. Current lithium battery technologies limit discharge to about 40 percent. A deep discharge will damage the battery and limit its lifespan. This situation is prevented by a charge control circuit which will prevent battery damage due to overcharging or over discharge. Alternatively, a standalone self-charging nuclear capacitor is made by applying a thin layer of the radio isotope to one side of a thin metal foil then a layer of the PEM material over the radio isotope combined with a binding material followed by the second metal foil layer and finally a dielectric membrane is placed on the top of the second foil layer. These layers are then rolled up so that the two metal layers are separated by the dielectric membrane. The metal foil layers are chosen just as in any electrolytic capacitor so that the plates have a propensity to attract and store positive or negative charges. An example would be aluminum and tantalum foils. As described above, this capacitor can be implemented directly in the nuclear rechargeable electrochemical power cell by adding the capacitor layers sandwiched in the radioisotope layer. If the cell design characteristics are chosen to incorporate a high voltage capacitor to store more power, a voltage regulator would be needed to regulate the charge voltage for the electrochemical cell to protect it from damage from over charging and over voltage. A large amount of energy can be stored within this super capacitor that can be used for loads that demand very high currents for very short periods of time or if regulated can produce lower voltages for longer periods of time, or even other voltages than that of the battery. Since alpha particles possess a positive double (+2) charge, they are easily deflected by electric or magnetic fields. The electric field generated by the cell construction, with or without the high voltage capacitor may be effective in driving the alpha particles towards the cathode collector plate and thus, increasing efficiency. Similarly, the addition of a magnetic material layer that creates a magnetic field that directs the alpha particles towards the cathode may also be effective in increasing efficiency. These same phenomena may also serve to push the electrons towards the cathode as well. External Charging The inherent nature of the self-recharging battery does not preclude the capability of a fast charging in an external charging device. A nuclear battery of this design can be quickly charged by means of inserting it into an external battery charger, similar to existing battery charging devices using standard charging techniques. A self-monitoring circuit to indicate to the user the level of charge that the cell has at any given time can be incorporated into the device. Since the radioisotope would continuously charge the device, especially when it is not in use, power cells using this technology can be swapped out of equipment, set aside, and they will recharge automatically. Alternatively, they could be charged more quickly by an external charger device. The charge indicator would be powered by the device directly and would let the user know how much power is available at any given time. An electronic circuit that could control the internal and external charging and discharging characteristics of the battery could be incorporated as a safety/security aspect of the device. This circuit could be used to control the total charge of the battery as well as to disable the battery recharge system to prevent automatic self-recharging or external recharging. This functionality would be useful in a battlefield situation where the battery may be lost or stolen. In such a situation, the battery could be rendered useless, or at least prevented from recharging. Such a system can be implemented by incorporating a built in electronic chip/circuit that would enable or disable recharging or it could force discharging of the battery under specific conditions through the resistive load material used to bleed off excess power. For instance, such a condition may be where a warfighter would carry a tiny wireless control device (perhaps built into some other equipment) that would communicate with the battery controlling its functionality. Should the battery become lost or stolen and unable to communicate with some approved remote control device, the battery could automatically render itself useless, either by discharging or not allowing itself to be recharged externally or internally, thus rendering it useless to anyone but those with the correct controller devices. This same wireless control circuit could be used as a locator beacon that could be activated under any number of predefined conditions such as tampering or destruction of the cell in an attempt to obtain the nuclear materials. While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to those skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof. Thus, it is intended that the present invention cover the modifications and variations of this invention provided they come within the scope of the appended claims and their equivalents.
	description	This application is filed under the provisions of 35 U.S.C. §371 and claims the priority of International Patent Application No. PCT/US2009/037396 filed on 17 Mar. 2009 entitled “Specimen Holder Used for Mounting Samples in Electron Microscopes” in the name of David P. Nackashi, et al., which claims priority of U.S. Provisional Patent Application Nos. 61/037,115 filed on 17 Mar. 2008 and 61/085,650 filed on 1 Aug. 2008, all of which are hereby incorporated by reference herein in their entirety. The invention relates generally to specimen holders used for mounting samples in an electron microscope, e.g., a transmission electron microscope (TEM), a scanning transmission electron microscopy (STEM) and variations of the scanning electron microscopes (SEM) that use traditional TEM-type holders and stages. The specimen holder is a component of an electron microscope providing the physical support for specimens under observation. Specimen holders traditionally used for TEMs and STEMs, as well as some modern SEMs, consist of a rod that is comprised of three key regions: the end, the barrel and the specimen tip (see, e.g., FIG. 1). In addition to supporting the specimen, the specimen holder provides an interface between the inside of the instrument (i.e., a vacuum environment) and the outside world. To use the specimen holder, one or more samples are first placed on a support device. The support device is then mechanically fixed in place at the specimen tip, and the specimen holder is inserted into the electron microscope through a load-lock. During insertion, the specimen holder is pushed into the electron microscope until it stops, which results in the specimen tip of the specimen holder being located in the column of the microscope. At this point, the barrel of the specimen holder bridges the space between the inside of the microscope and the outside of the load lock, and the end of the specimen holder is outside the microscope. To maintain an ultra-high vacuum environment inside the electron microscope, flexible o-rings are typically found along the barrel of the specimen holder, and these o-rings seal against the microscope when the specimen holder is inserted. The exact shape and size of the specimen holder varies with the type and manufacturer of the electron microscope, but each holder contains these three key regions. Interfacing semiconductor-based devices with specimen holders for use in electron microscopes has seen limited commercial development. There are, however, a few applications that have either required an electrical interface between the sample and the specimen holder, or have incorporated semiconductor devices in a research environment. Several electron microscopy techniques, including Electron Beam Induced Current (EBIC), require an electrical contact between a sample and the specimen holder itself. Typically, this is done using a simple screw and metallic clip, which is gently pressed down onto the sample by tightening the screw (see, X. Zhang and D. Joy, “A simple specimen holder for EBIC imaging on the Hitachi S800,” J. Microscopy Res. and Techn. , Vol. 26(2), pp. 182-183, 1993). A wire is either soldered to the clip or looped around the screw head to provide an electrical path from the sample, through the clip, and to the specimen holder which routes the wire outside of the instrument. This approach is tedious, requiring the user to manually align the clips over the appropriate regions on the device, then manually tighten every screw that is needed to complete an electrical path to the specimen holder. Because of the small size of these screws and the sample itself, this approach takes time and requires a substantial amount of dexterity. An alternative approach (U.S. Pat. No. 5,124,645) requires a wirebond, or solder joint, to establish a more durable connection between the sample and the specimen tip of a specimen holder. These connections, however, are permanent and do not allow samples to be easily interchanged between experiments. Following an experiment, to exchange samples, the specimen holder must be placed back into a wirebond machine or soldering must again be performed to create a new electrical connection with the new sample. This approach is tedious, requires great dexterity, and is likely to damage the specimen tip after repeated use. An approach developed at the University of Illinois (U.S. patent application Ser. No. 11/192,300) addresses some of these concerns. This approach allows a semiconductor device to be mounted in a specimen tip, making as many as twelve simultaneous electrical connections between the holder and the device. A frame (generally U-shaped) aligns the device and baseplate with electrical spring contact fingers and provides a rigid surface against which the device is pressed, providing stability and forming electrical contacts between the device and the specimen holder. The baseplate is the component of the specimen tip that provides a stable surface upon which the device can be mounted, and contains electrical spring contact fingers in complementary positions to the device, which when aligned using the frame, make contacts simultaneously between the baseplate and the device. Disadvantageously, spring contact fingers such as these are delicate and more difficult to manufacture. Removing the device from the baseplate completely exposes the spring clips and presents an opportunity to accidentally bend or break these fingers, compromising the electrical connections. Considering the disadvantages of the prior art, a novel specimen holder is needed, wherein said specimen holder eliminates the need for delicate spring contact fingers and provides a simple method for repeatedly mounting and exchanging devices without disassembly or soldering. The present invention relates generally to a novel specimen holder which provides mechanical support for specimen support devices and as well as electrical contacts to the specimens or specimen support devices. In one aspect, an electron microscope specimen holder is described, said specimen holder comprising a body, a clipping means, and at least one guide mechanism. The specimen holder may further comprise a spring or a spring cantilever. In another aspect, an electron microscope specimen holder is described, said specimen holder comprising a body, a clipping means, and at least one guide mechanism, wherein the clipping means comprise an article of manufacture having a top surface, a bottom surface, a first end, a securing means, a second end, and at least one electrical contact integrated on and/or in the bottom surface of the article. The securing means may comprise one of a pivot positioned between the first end and the second end of the article; a fixed point at or near the first end of the article and wherein the article is flexible; or a set screw. The specimen holder may further comprise a spring or a spring cantilever. In each of these aspects, the specimen holder may further comprise a specimen support device mechanically secured between the clipping means and the body. The specimen support device may comprise a frame, at least one electrical lead and at least one membrane region. In still another aspect, a method of providing an electrical contact between a specimen and a specimen holder of an electron microscope is described, said method comprising: positioning a specimen on a specimen support device, wherein the specimen support device comprises a frame, at least one electrical lead and at least one membrane region; and inserting the specimen support device in a specimen holder, wherein the specimen holder comprises a body, a clipping means, and at least one guide mechanism, wherein the clipping means comprise at least one electrical contact integrated on and/or in a bottom surface of the clipping means; and wherein at least one electrical lead of the device substantially contacts at least one electrical contact of the clipping means. Yet another aspect relates to a method of using a specimen holder in electron microscopy, said method comprising: positioning a specimen support device in a specimen holder as described herein; and inserting said specimen holder in an electron microscope. Other aspects, features and advantages of the invention will be more fully apparent from the ensuing disclosure and appended claims. The present invention generally relates to novel specimen holders, methods for interfacing samples at the tip of the specimen holder, and uses of the novel specimen holder. It is to be understood that the specimen holder and specimen holder interface described herein are compatible with and may be interfaced with the semiconductor specimen support devices disclosed in U.S. Patent Application Nos. 60/916,916 and 60/974,384, which are incorporated herein by reference in their entirities. It should be appreciated by one skilled in the art that alternative specimen support devices may be interfaced with the specimen holder described herein. The specimen holder provides mechanical support for one or more specimens or specimen support devices and may also provide electrical contacts to the specimens or specimen support devices. The specimen holder can be manufactured with tips, barrels and ends of various shapes and sizes such that the specimen holder fits any manufacturer's electron microscope. As defined herein, a “spring” corresponds to any object that has a spring constant (k) and which exerts a force onto the specimen support device when it is loaded in the specimen holder. The spring may or may not observe Hooke's law (F=−kx) depending on the material of construction. As defined herein, a “hinge” connects two solid objects, in the present case the insulating clip and the mounting surface, typically allowing only a limited angle of rotation between them. Two objects connected by a hinge rotate relative to each other about a fixed axis of rotation. It is also contemplated herein that the “hinge” may be one or two fulcrums attached to the mounting surface, wherein the clip is flexible. As defined herein, a “membrane region” corresponds to unsupported material comprised, consisting of, or consisting essentially of carbon, silicon nitride, SiC or other thin films generally 1 micron or less having a low tensile stress (<500 MPa), and providing a region at least partially electron transparent region for supporting the at least one specimen. The membrane region may include holes or be hole-free. The membrane region may be comprised of a single material or a layer of more than one material and may be either uniformly flat or contain regions with varying thicknesses. The present application improves on the prior art in several ways: (1) by eliminating the required use of a delicate spring contact finger, (2) by providing a method for accommodating semiconductor devices that are of various shapes and sizes without the need to machine frames and custom parts to align different devices geometries, and (3) by providing a simple method for mounting and exchanging devices and making electrical contacts to devices without the need for partially disassembling the specimen tip (e.g., removing screws or other small parts). More specifically, rather than using spring contact fingers (bent slightly at their tips) to separately promote contact with each pad on the device, the specimen holder described herein includes at least one electrode placed on the bottom of an insulating clip, wherein the insulating clip with integrated electrode(s) provides simultaneous mechanical force to all electrodes, simultaneously presses the electrode(s) against contact pads on the device and provides mechanical force for securing the device in place for imaging. Clips and springs used in this application separately provide the mechanical force required to stabilize the device to the specimen holder, and are not used for electrical contacts between the device and the holder. Preferably, the springs are distally positioned along the insulating clip relative to the electrical contacts. This allows the electrical contacts on the clips to be manufactured using planar processes such as, but not limited to, precision machining, lithographic and/or electroplating processes. Using the specimen holder described herein, only one side of the device is required to have contact pads matching the electrode pitch and width in order to line up with the electrodes underneath the clip. This design improves upon prior art in that it allows a variety of device lengths and shapes to be mounted into the specimen tip. This specimen holder also allows a device to be mounted quickly and easily, making both physical and electrical contacts, without the need to partially disassemble the specimen tip to mount the device. One embodiment of the tip region of a specimen holder is shown is FIGS. 2A, 2B and 2C. FIG. 2A shows the tip region of a specimen holder wherein the holder tip (10000) includes a clamping mechanism in an open state ready to receive a specimen support device. FIG. 2B shows the tip region of the specimen holder of FIG. 2A wherein the holder tip (10000) is in a closed state without a specimen support device. FIG. 2C shows the tip region of the specimen holder of FIG. 2A wherein the holder tip (10000) is in an closed state with a specimen support device. In each of these figures, the clamping mechanism is comprised of a clip (10100), spring (10200), hinges (10300), set screw (10400), guide mechanism (10500), depth stop (10600), and at least one electrical contact (10700). The holder tip is comprised of a body (10025), a viewing region (10050), and the clamping mechanism. In FIG. 2C a device is loaded into the tip and held in place by the clamping mechanism. The device is generally comprised of a frame (20000), electrical leads (20100), and a membrane region (20200). In the clamping mechanism, the clip (10100) acts as a lever, the spring (10200) provides constant tension to the clip, the hinges (10300) allow the clip to pivot about the hinge, the set screw (10400) prevents the spring (10200) from being over-compressed when a device is loaded, and the guide mechanism (10500), such as guide screws, guide pins, or guide posts, provides lateral alignment to a device as it is loaded. When a device is completely loaded, the depth stop (10600) provides a means both to align the electrical contacts of the specimen holder (10700) to electrical leads of a device (20100) and to align the viewing region of the specimen holder tip (10050) with the membrane region of a device (20200). It should be appreciated by one skilled in the art that the electrical contacts of the specimen holder (10700) may extend from one length of the clip to the other or may be present in shorter sections so long as the electrical contacts are present for contact with the electrical leads of the device (20100). The resting position for the clamping mechanism is shown in FIG. 2B where a spring (10200) pushes upward at one end of the clip (10100), resulting in downward pressure created at the opposite end of the clip where the clip pivots at a set of hinges (10300). The hinge is mounted to a planar mounting surface (10800), said mounting surface extending from the barrel to at least the end of the clip and possibly further. When this mounting surface extends beyond the clip, a viewing region (10050) will typically be included therein just beyond the clip. To mount the device, downward pressure is placed on the spring end of the clip, which lifts the opposite end above the surface to a level at least as high as the thickness of the device, and typically higher, for example, greater than 1 mm (see FIG. 2A), although less than 1 mm is contemplated. The device is either placed in between the clip and the mounting surface manually, or slid underneath the clip along the mounting surface using the guide screws and depth stop as guidance. Once the device is in position, the pressure on the spring is released and the device is secured manually to the specimen tip (see FIG. 2C). Electrical contacts from the holder to the device, typically in a range from 2 to 12 electrical contacts (10700), may be provided by the integrated conducting wires or paths underneath the clip. These electrical contacts are electrically isolated from each other and from the clip itself (if the clip is made of a conductive material). When electrical pads exist on the device, the guide mechanism and depth stop will align the device with the clip to allow the electrical contacts from the clip and the pads from the device to contact one another when downward pressure on the clip is released. This will allow both mechanical pressure and electrical connections to be made in a novel, easy to operate design. The electrical contacts will extend from the clip to the barrel, down the barrel to the end, and to a connector that exists at the specimen holder end that can be mated with a plug outside the microscope and connected to a power supply to provide voltage or current through the holder and interface to the specimen support device. Each conductor will remain isolated from each other as well as the three components of the specimen holder. Another embodiment of the tip region of a specimen holder is shown in FIGS. 3A, 3B, and 3C. FIG. 3A shows the tip region of a specimen holder of the present invention where the holder tip (30000) includes a clamping mechanism in an open state ready to receive a specimen support device. FIG. 3B shows the tip region of the specimen holder of FIG. 3A where the holder tip (30000) is in a closed state without a specimen support device. FIG. 3C shows the tip region of the specimen holder of FIG. 3A where the holder tip (30000) is in a closed state with a specimen support device. In each of these figures, the clamping mechanism is comprised of a clip (30100), spring (30200), locking screw (30300), guide mechanism (30400), depth stop (30500), and at least one electrical contact (30600). The holder tip is comprised of a body (30025), a viewing region (30050), and the clamping mechanism. In FIG. 3C a device is loaded into the tip and held in place by the clamping mechanism. The device is generally comprised of a frame (20000), electrical leads (20100), and a membrane region (20200). In the clamping mechanism, the clip (30100) acts as a clamp, the spring (30200) provides constant tension to the clip, the locking screw (30300) allows the clip to move up and down parallel to the plane of the body (30025), the guide mechanism (30400), such as guide screws, guide pins, or guide posts, provide lateral alignment to a device as it is loaded. When a device is completely loaded, the depth stop (30500) provides a means both to align the electrical contacts of the specimen holder (30600) to electrical leads of a device (20100) and to align the viewing region of the specimen holder tip (30050) with the membrane region of a device (20200). It should be appreciated by one skilled in the art that the electrical contacts of the specimen holder (30600) may extend from one length of the clip to the other or may be present in shorter sections so long as the electrical contacts are present for contact with the electrical leads of the device (20100). The open position for the clamping mechanism is shown in FIG. 3B where a spring (30200) pushes upward at one end of the clip (30100), resulting in downward pressure pushing at the opposite end of the clip. The clip can be raised or lowered by a locking screw (30300) and when raised, the force exerted by the spring is enough to ensure that the front of the clip is raised enough to allow a specimen support device to be loaded into the holder. To mount the device, the locking screw is turned to raise the clip to a level at least as high as the thickness of the device, and typically higher, e.g., greater than 1 mm (see FIG. 3A), although less than 1 mm is contemplated. The device is either placed in between the clip and the surface manually, or slid underneath the clip along the surface using the guide screws and depth stop as guidance. Once the device is in position, the locking screw is turned to lower the clip so that the clip secures the device to the specimen tip (see FIG. 3C). Electrical contacts from the holder to the device, typically in a range from 2 to 12 electrical contacts (30600), may be provided by the integrated conducting wires or paths underneath the clip. These electrical contacts are electrically isolated from each other and from the clip itself (if the clip is made of a conductive material). When electrical pads exist on the device, the guide screws and depth stop will align the device with the clip to allow the electrical contacts from the clip and the pads from the device to contact one another when downward pressure on the clip is released. This will allow both mechanical pressure and electrical connections to be made in a novel, easy to operate design. The electrical contacts will extend from the clip to the barrel, down the barrel to the end, and to a connector that exists at the specimen holder end that can be mated with a plug outside the microscope and connected to a power supply. Each conductor will remain isolated from each other as well as the three components of the specimen holder. Yet another embodiment of the tip region of a specimen holder is shown in FIGS. 4A, 4B and 5A, 5B. FIGS. 4B and 5B show the tip region of a specimen holder of the present invention where the holder tip (50000) includes a flexible clamping mechanism in the resting state with a specimen support device loaded for use. FIGS. 4A and 5A show the tip region of the specimen holder of FIGS. 4B and 5B, respectively, where the holder tip (50000) is in a state ready for unloading a specimen support device. In all of these figures the flexible mechanism is comprised of a clip (50100) under which the device can be inserted, guide mechanism (50400), depth stop (50500), fulcrum (50600), fixed point (50300) and at least one electrical contact (50700). An optional set screw (50200) can be used to limit the distance that the clip can be flexed. The holder tip is comprised of a body (50025), a viewing region (50050) and a flexible clamping mechanism. The device is comprised of a frame (20000), electrical leads (20100), and a membrane region (20200). The difference between the 4A, 4B figures and the 5A, 5B figures is that in the former the fulcrum is a two-piece fulcrum and in the in latter the fulcrum is a one-piece fulcrum. To mount the device under the clip (50100), the device is first oriented between the guide screws (50400) with the device's electrical leads (20100) oriented towards the slot. Downward pressure is then applied on the top surface of the clip (50100) at a point between the fulcrum (50600) and the fixed point (50300) resulting in the clip (50100) bending upward at the end near the guide mechanism (50400), such as guide screws, guide pins, or guide posts. With this pressure applied, the device is then inserted until the leading edge of the device meets the depth stop (50500). When the device is fully inserted against the depth stop (50500), the downward force on the clip (50100) is released which secures the device under the clip (50100) by friction during imaging and analysis. Simultaneous electrical contacts are formed between the electrical contacts (50700) underneath the clip (50100) and the electrical leads (20100) allowing electrical current to be passed from the electrical contacts (50700) to the electrical leads (20100). It should be appreciated by one skilled in the art that the electrical contacts of the specimen holder (50700) may extend from one length of the clip to the other or may be present in shorter sections so long as the electrical contacts are present for contact with the electrical leads of the device (20100). Another embodiment of the tip region of a specimen holder is shown in FIGS. 6A, 6B, and 6C. FIG. 6A shows the tip region of a specimen holder of the present invention where the holder tip (60000) includes a clamping mechanism in an open state ready to receive a specimen support device. FIG. 6B shows the tip region of the specimen holder of FIG. 6A where the holder tip (60000) is in a closed state without a specimen support device. FIG. 6C shows the tip region of the specimen holder of FIG. 6A where the holder tip (60000) is in a closed state with a specimen support device. In each of these figures, the clamping mechanism is comprised of a clip (60100), spring cantilever (60200), post (60800), post hole (60400), pivots (60300), guide mechanism (60500), depth stop (60600), and at least one electrical contact (60700). The post hole (60400) allows the post (60800) to contact and/or connect to both the spring cantilever (60200) and the clip (60100) through the holder tip (60000). The holder tip is comprised of a body (60025), a viewing region (60050), and the clamping mechanism. The electrical contact(s) preferably do not flex like a spring and will not be damaged from fatigue. In FIG. 6C a device is loaded into the tip and held in place by the clamping mechanism. The device is generally comprised of a frame (20000), electrical leads (20100), and a membrane region (20200). In the clamping mechanism, the clip (60100) acts as a lever, the spring cantilever (60200) and post (60800) provide constant tension to the clip, the pivot (60300) allow the clip to pivot, and the guide mechanism (60500), such as guide screws, guide pins, or guide posts, provides lateral alignment to a device as it is loaded. When a device is completely loaded, the depth stop (60600) provides a means both to align the electrical contacts of the specimen holder (60700) to electrical leads of a device (20100) and to align the viewing region of the specimen holder tip (60050) with the membrane region of a device (20200). It should be appreciated by one skilled in the art that the electrical contacts of the specimen holder (60700) may extend from one length of the clip to the other or may be present in shorter sections so long as the electrical contacts are present for contact with the electrical leads of the device (20100). In addition the electrical contacts (60700) may consist of wires that protrude from the end of the clip, which make electrical contact to the electrical leads of the device (20100) using the bottom surface of the wire, or alternatively do not protrude from the end of the clip (see, e.g., FIG. 8 which illustrates the electrical contacts stopping at (or before) the end of the clip (60100). The resting position for the clamping mechanism is shown in FIG. 6B where a spring cantilever (60200) pushes upward on a post (60800) through a post hole (60400), which pushes upward at one end of the clip (60100), resulting in downward pressure created at the opposite end of the clip where the clip pivots at a set of pivots (60300) which may be smooth or threaded. The pivot is mounted to a mounting surface that is part of the body holder tip (60200). To mount the device, downward pressure is placed on the spring end of the clip, which lifts the opposite end above the surface to a level at least as high as the thickness of the device, and typically higher, for example, greater than 1 mm (see FIG. 6A), although less than 1 mm is contemplated. The device is either placed in between the clip and the mounting surface manually, or slid underneath the clip along the mounting surface using the guide mechanism and depth stop as guidance. Once the device is in position, the pressure on the spring is released and the device is secured manually to the specimen tip (see FIG. 6C). Electrical contacts from the holder to the device, typically in a range from 2 to 12 electrical contacts (60700 and 20100), may be provided by the conducting wires or paths and these electrical contacts may be positioned above, within, underneath and/or extended from the clip. These electrical contacts are electrically isolated from each other and from the clip itself (if the clip is made of a conductive material). When electrical pads exist on the device, the guide mechanism and depth stop will align the device with the clip to allow the electrical contacts from the clip and the pads from the device to contact one another when downward pressure on the clip is released. This will allow both mechanical pressure and electrical connections to be made in a novel, easy to operate design. The electrical contacts will be routed from the clip to the barrel, down the barrel to the end, and to a connector that exists at the specimen holder end that can be mated with a plug outside the microscope and connected to a power supply to provide voltage or current through the holder and interface to the specimen support device. Each conductor can remain isolated from each other as well as the three components that comprise the specimen holder. Further embodiments of the tip region of the specimen holder are shown in FIGS. 7 and 8. FIG. 7 shows the tip region of a specimen holder similar to FIG. 6C, wherein the holder tip (60000) is in a closed state with a specimen support device, however, the mounting surface of the holder tip only extends about as far as the electrical contacts (60700) and as such, the holder tip does not include the viewing region of FIG. 6C. FIG. 8 also shows the tip region of a specimen holder similar to FIG. 6C, however, the electrical contacts do not extend beyond the end of the clip. Specifically, in FIGS. 7 and 8, the clamping mechanism is comprised of a clip (60100), spring cantilever (60200), post (60800), post hole (60400), pivots (60300), depth stop (60600), and at least one electrical contact (60700). The post hole (60400) allows the post (60800) to contact and/or connect to both the spring cantilever (60200) and the clip (60100) through the holder tip (60000). The electrical contact(s) preferably do not flex like a spring and will not be damaged from fatigue. The holder tip is comprised of a body (60025) and the clamping mechanism. In FIG. 7, the body (60025) extends just to the edge of the electrical contacts (60700) and the specimen support device (20000) cantilevers beyond the body (60025). In FIG. 8, the electrical contacts (60700) do not extend beyond the end of the clip (60100) and the body (60025) is illustrated to extend as far as the edge of the clip (60100), wherein the specimen support device (20000) cantilevers beyond the body (60025). The embodiments in FIGS. 7 and 8 allow a rigid specimen support to extend beyond the body (60025) and still maintain mechanical contact with the body (60025) and electrical contact with the clip (60100) through the electrical contacts (60700). FIG. 7 and FIG. 8 are based upon the embodiment illustrated in FIGS. 6A, 6B and 6C, but may also be applied to the embodiments shown in FIGS. 2A, 2B, 2C, 3A, 3B, 3C, 4A, 4B, 5A and 5B, whereby the mounting surface of the holder tip only extends about as far as the electrical contacts and as such, the holder tip does not include the viewing region. The advantages of the specimen holder described herein include, but are not limited to: the ready adaptation of the specimen holder to accommodate specimen support devices having varying shapes and sizes without the need to machine frames and custom parts to align different device geometries; providing a simple method for mounting and exchanging devices and making electrical contacts to devices without the need for partially disassembling the specimen tip; allowing for interchangeable specimen tips to accommodate different specimen supports or to be used with different barrels and ends; and eliminating the use of a delicate spring contact finger. For example, the electrical contacts of the present invention may be effectuated at one of the clip (see, e.g., FIGS. 2-8) whereby there is no spring present at all or the spring is distally positioned at the other end of the clip. Although the invention has been variously disclosed herein with reference to illustrative embodiments and features, it will be appreciated that the embodiments and features described hereinabove are not intended to limit the invention, and that other variations, modifications and other embodiments will suggest themselves to those of ordinary skill in the art, based on the disclosure herein. The invention therefore is to be broadly construed, as encompassing all such variations, modifications and alternative embodiments within the spirit and scope of the claims hereafter set forth.
	description	This application is a continuation application of International Application No. PCT/CN2018/100572, filed on Aug. 15, 2018, which claims priority to Chinese Patent Application No. 201710733144.1, filed on Aug. 24, 2017; Chinese Patent Application No. 201721063911.4, filed on Aug. 24, 2017, the disclosures of which are hereby incorporated by reference. The present disclosure relates generally to a radiotherapy system, and, more particularly to a neutron capture therapy system. The background description provided herein is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure. As atomics moves ahead, such radiotherapy as Cobalt-60, linear accelerators and electron beams has been one of major means to cancer therapy. However, conventional photon or electron therapy has been undergone physical restrictions of radioactive rays; for example, many normal tissues on a beam path will be damaged as tumor cells are destroyed. On the other hand, sensitivity of tumor cells to the radioactive rays differs greatly, so in most cases, conventional radiotherapy falls short of treatment effectiveness on radio resistant malignant tumors (such as glioblastomamultiforme and melanoma). For the purpose of reducing radiation damage to the normal tissue surrounding a tumor site, target therapy in chemotherapy has been employed in the radiotherapy. While for high-radio resistant tumor cells, radiation sources with high RBE (relative biological effectiveness) including such as proton, heavy particle and neutron capture therapy have also developed. Among them, the neutron capture therapy combines the target therapy with the RBE, such as the boron neutron capture therapy (BNCT). By virtue of specific grouping of boronated pharmaceuticals in the tumor cells and precise neutron beam regulation, BNCT is provided as a better cancer therapy choice than conventional radiotherapy. BNCT takes advantage that the boron (10B)-containing pharmaceuticals have high neutron capture cross section and produces 4He and 7Li heavy charged particles through 10B(n,α)7Li neutron capture and nuclear fission reaction. As illustrated in FIG. 1, a schematic view of boron neutron capture reaction are shown, the two charged particles, with average energy at about 2.33 MeV, are of linear energy transfer (LET) and short-range characteristics. LET and range of the alpha particle are 150 keV/micrometer and 8 micrometers respectively while those of the heavy charged particle 7Li are 175 keV/micrometer and 5 micrometers respectively, and the total range of the two particles approximately amounts to a cell size. Therefore, radiation damage to living organisms may be restricted at the cells' level. When the boronated pharmaceuticals are gathered in the tumor cells selectively, only the tumor cells will be destroyed locally with a proper neutron source on the premise of having no major normal tissue damage. In accelerator-based BNCT, in one aspect, neutrons or other particles such as γ rays generated by a neutron generator are radioactive, and in another aspect, neutrons generated by the neutron generator generally need to undergo a beam shaping assembly to adjust an energy spectrum and increase neutron yield. Therefore, a reflecting assembly needs to be installed to reduce a particle leakage rate, adjust an energy spectrum, and increase neutron yield. Lead is a conventional material used for reflection or shielding. However, lead has a significant creep effect and cannot provide structural rigidity and a long service life. For BNCT, neutron beam quality depends on the beam shaping assembly and also depends on the reflecting assembly and a shielding assembly. Lead is usually used as a reflection material in the prior art. However, the creep effect of lead results in insufficient structural precision, and as a result the safety of the entire BNCT is affected. Therefore, it is really necessary to provide a new technical solution so as to solve the foregoing problem. The statements in this section merely provide background information related to the present disclosure and may not constitute prior art. To resolve the foregoing technical problem, an aspect of the present invention provides a neutron capture therapy system, so that the structural strength/precision of a beam shaping assembly can be increased without significantly affecting neutron beam quality. The neutron capture therapy system includes an accelerator configured to generate a charged particle beam; a neutron generator configured to generate a neutron beam having neutrons after irradiation by the charged particle beam; a beam shaping assembly configured to shape the neutron beam, wherein the beam shaping assembly includes a moderator configured to moderate the neutrons generated by the neutron generator to a preset energy spectrum and a reflecting assembly surrounding the moderator; wherein the reflecting assembly includes a plurality of reflectors configured to guide deflected neutrons back to the neutron beam to increase intensity of the neutrons in the preset energy spectrum and a supporting member configured to hold the reflectors. Further, the reflecting assembly includes a plurality of cells correspondingly forming a plurality of cores, each of the cells forms one of the cores, each of the cores has an accommodating space, the cores are connected to form the supporting member, and the reflectors are correspondingly disposed in the accommodating spaces of the cores. Further, the supporting member is integrally formed, and the reflectors are formed by pouring a material of the reflectors into the accommodating spaces of the cores. More particularly, a specified quantity of cores are connected to form the supporting member, the reflecting assembly further includes a top plate, a bottom plate disposed opposite to the top plate and side plates connecting to the top plate and the bottom plate and surrounding the cores, the specified quantity of cores, the reflector disposed in the accommodating spaces of the cores, the top plate, the bottom plate and the side plates correspondingly form a plurality of reflecting modules, and the reflecting modules are stacked to form the reflecting assembly surrounding the moderator. Further, at least one of materials of the cores, the top plate, the bottom plate and the side plates is made of a material with a low neutron absorption cross section and low activity with neutrons, and a proportion of a total volume of the material of the core, the top plate, the bottom plate and the side plates in a volume of the material of the reflectors is less than 10%. Further, the material of the reflectors is lead, and at least one of the materials of the cores, the top plate, the bottom plate and the side plates is lead-antimony alloy. Further, equivalent total antimony content in the lead-antimony alloy material is less than 1%. To resolve the foregoing technical problem, another aspect of the present invention provides a neutron capture therapy system, so that the structural strength/precision of a beam shaping assembly can be increased without significantly affecting neutron beam quality. The neutron capture therapy device includes a beam shaping assembly configured to shape a neutron beam having neutrons, wherein the beam shaping assembly includes a moderator configured to moderate the neutrons to a preset energy spectrum, a reflecting assembly surrounding the moderator, and a shielding assembly surrounding the reflecting assembly; wherein the shielding assembly includes a supporting member configured to hold the reflecting assembly and a plurality of shieldings arranged in the supporting member. Further, the shielding assembly includes a plurality of cells correspondingly forming a plurality of cores, each of the cells forms one of the cores, each of the cores has an accommodating space, the shieldings are correspondingly disposed in the accommodating spaces of the cores, and the cores are connected to form the supporting member. More particularly, a cross section of each of the cores is a hexagon. Further, the supporting member is integrally formed, and the shieldings are formed by pouring a material of the shieldings into the accommodating spaces of the cores. Further, a specified quantity of cores are connected to form the supporting member, a top plate, a bottom plate disposed opposite to the top plate and side plates that connect the top plate and the bottom plate and surround the cores are provided outside the supporting member, the specified quantity of connected cores, the shielding disposed in the cores, the top plate, the bottom plate, and the side plates correspondingly form a plurality of shielding modules, and the shielding modules are stacked to form the shielding assembly. Particularly, a material of the shieldings is lead, a material of the core, the top plate, the bottom plate and the side plates is a material with a low neutron absorption cross section and low activity with neutrons. Further, a proportion of a total volume of the material of the core, the top plate, the bottom plate, and the side plates in a volume of the material of the shieldings is less than 10%. Particularly, the reflecting assembly includes a plurality of reflectors configured to guide deflected neutrons back to the neutron beam to increase intensity of neutrons in the preset energy spectrum and the supporting member configured to support the reflector, a material of the reflectors is lead, and a material of the supporting member is aluminum alloy or lead-antimony alloy. To resolve the foregoing technical problem, another aspect of the present invention provides a neutron capture therapy system, so that the structural strength/precision of a beam shaping assembly can be increased without significantly affecting neutron beam quality. The neutron capture therapy device includes a beam shaping assembly configured to shape a neutron beam having neutrons, wherein the beam shaping assembly includes a moderator configured to moderate the neutrons to a preset energy spectrum and a reflecting assembly surrounding the moderator; wherein the reflecting assembly includes a plurality of reflectors configured to guide deflected neutrons back to the neutron beam to increase intensity of the neutrons in the preset energy spectrum and a plurality of cells for supporting the reflectors, the cells correspondingly form a plurality of cores, each of the cells forms one of the cores, each of the cores has an accommodating space configured to receive one of the reflectors or a material configured to shield the neutrons. Further, the cores are connected to form a supporting member, a top plate and a bottom plate disposed opposite to the top plate and side plates that connect the top plate and the bottom plate and surround the cores are provided outside the supporting member. Further, a material of the core, the top plate, the bottom plate, and the side plates is a material with a low neutron absorption cross section and low activity with neutrons, and a proportion of a total volume of the material of the core, the top plate, the bottom plate, and the side plates in a volume of a material of the reflectors is less than 10%. Particularly, the cores are connected to form a supporting member, the supporting member is integrally formed, and the material is poured into the accommodating space. Further, the cores are connected to form a supporting member, the material in the accommodating space is lead, and a material of the supporting member is aluminum alloy or lead-antimony alloy. Compared to the prior art, by means of the neutron capture therapy system in the present application, the supporting member of the reflector or/and the supporting member of the shielding assembly are disposed to support a reflection material or/and a shielding material, and alloy material with a low neutron absorption and low activity is to support lead to overcome the creep effect of the lead material, so that the structural strength of a beam shaping assembly is increased without affecting neutron beam quality. Further areas of applicability will become apparent from the description provided herein. It should be understood that the description and specific examples are intended for purposes of illustration only and are not intended to limit the scope of the present disclosure. The embodiments of the present disclosure are further described in detail below with reference to the accompanying drawings, so that those skilled in the art can implement the technical solutions according to the description. The following description of the preferred embodiments is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. A reflecting assembly needs to be installed to reduce a particle radiation leakage rate and a shielding assembly needs to be installed to provide safe shielding against radiation for particles (for example, neutrons) generated by an accelerator. Lead or a lead alloy is a conventional material for reflection or shielding. However, lead has a significant creep effect and cannot provide structural rigidity and a long service life. As shown in FIG. 2, the present disclosure provides a neutron capture therapy system 100. The neutron capture therapy system 100 includes an accelerator 200 for generating a charged particle beam P, a neutron generator 10 for generating a neutron beam N after irradiation by the charged particle beam P, a beam shaping assembly 20 for shaping a neutron beam, and a collimator 30. The beam shaping assembly 20 includes a moderator 21 and a reflecting assembly 22 surrounding the moderator 21. The neutron generator 10 is configured to generate the neutron beam N after being irradiated by a charged particle beam P. The moderator 21 moderates the neutron beam N generated by the neutron generator 10 to a preset energy spectrum. The reflecting assembly 22 guides deflected neutrons back to the neutron beam N to increase the intensity of neutrons in the preset energy spectrum. The collimator 30 concentrates neutrons generated by the neutron generator 10. In a first embodiment, the neutron capture therapy system 100 further includes a shielding assembly 40. Referring to FIG. 2, the shielding assembly 40 includes a supporting member 41 and a plurality of shieldings 42 disposed in the supporting member 41. The supporting member 41 includes a plurality of cells 43 correspondingly forming a plurality of cores 45, each cell 43 forms a core 45 having an accommodating space 44, the shieldings 42 are correspondingly disposed in the accommodating spaces 44, and the cores 45 are connected to form the supporting member 41. In a preferred embodiment, the supporting member 41 is integrally formed, and the shieldings 42 are formed by pouring the material of the shieldings 42 into the accommodating space 44 of each core 45 of the supporting member 41. Referring to FIG. 4, a specified quantity of cores 45 are connected to form the supporting member 41, and the supporting member 41 has a hexagonal cross section and facilitates formation and stacking. A top plate 46, a bottom plate 47 disposed opposite to the top plate and four side plates 48 that connect the top plate 46 and the bottom plate 47 and surround the cores 45 are provided outside the supporting member 41. The specified quantity of connected cores 45, the shielding 42 disposed in the core 45, the top plate 46, the bottom plate 47, and the side plates 48 form a shielding module 49, and shielding modules 49 are stacked to form the shielding assembly 40. In the present disclosure, to facilitate subsequent stacking of the shielding modules 49, in a preferred embodiment, the specified quantity is 20. Certainly, a person skilled in the art may adjust the quantity of the side plates according to a design requirement, for example, to 3 or 6. A specified quantity of the shielding modules is adjusted according to a design requirement, for example, to 10 or 30. The material of the shielding assembly 42 is lead, and the top plate 46, the bottom plate 47, the top plate 46, the bottom plate 47, and the side plates 48 are made of an alloy material with a low neutron absorption cross section and low neutron activity. To minimize the impact of an alloy material on neutron beam quality, the proportion of the total volume of the alloy material in the volume of the material of the shielding assembly 42 is less than 10%. In this embodiment, the reflecting assembly 22 is a structure that is made of lead and has a creep effect. The shielding assembly 40 is surrounding the reflecting assembly 22. The beam shaping assembly 20 is embedded in a shielding wall W to shield against radioactive rays generated in an irradiation room. The shielding assembly 40 is directly supported in the shielding wall W. The supporting member 41 inside the shielding assembly 40 supports the shielding 42 and at the same time reinforces the strength of the reflecting assembly 22, so that the structural strength of the entire beam shaping assembly 20 is increased. As shown in FIG. 5, in a second embodiment, the arrangement of the shielding assembly 40 in the first embodiment is directly applied to the reflecting assembly 22, the reflecting assembly 22 is disposed to be a structure that includes a supporting member 221 without the shielding assembly 40. Referring to FIG. 5, the reflecting assembly 22 includes a supporting member 221 and a plurality of reflectors 222 disposed in the supporting member 221. The supporting member 221 includes a plurality of cells 223 correspondingly forming a plurality of cores 225, and each cell 223 forms a core 225 having an accommodating space 224. The reflectors 222 are correspondingly disposed in the accommodating spaces 224 of the cores 225, and the cores 225 are connected to form the supporting member 221. In a preferred embodiment, the supporting member 221 is integrally, and the reflectors 222 are formed by pouring the material of the reflectors 222 into the cores 225 of the supporting member 221. As shown in FIG. 7, a modular design is applied for the reflecting assembly 22. Specifically, a specified quantity of cores 225 are connected to form the supporting member 221, a top plate 226, a bottom plate 227 disposed opposite to the top plate and four side plates 228 that connect the top plate 226 and the bottom plate 227 and surround the cores 225 are provided outside the supporting member 221. The specified quantity of connected cores 225, the reflector 222 disposed in the core 225, the top plate 226, the bottom plate 227, and the side plates 228 form a reflecting module 229, and reflecting modules 229 are stacked to form the reflecting assembly 22. The top plate 226, the bottom plate 227, and the four side plates 228 that are connected to the top plate 226 and the bottom plate 227 and surrounding the cores 225 are made of an alloy material with a low neutron absorption cross section and low activity, and the proportion of the total volume of the alloy material in the volume of the material of the shielding assembly 42 is less than 10%. FIG. 8 shows a third embodiment of the present disclosure. The third embodiment is different from the foregoing embodiments in that the structural design with a supporting member is configured to both the reflecting assembly and the shielding assembly. In this embodiment, the reflectors are disposed in the same manner in which the reflectors are disposed in the second embodiment, the shielding assembly is disposed in the same manner in which the shielding assembly is disposed in the first embodiment, and details are therefore not described herein again. When the beam shaping assembly 20 is embedded in the shielding wall W, the shielding assembly 40 is directly supported in the shielding wall W. In this embodiment, the supporting member 221 is disposed to support the reflectors 222 and the supporting member 41 is disposed to support the shieldings 42 without affecting neutron beam quality, to overcome the structural precision problem caused by a creep effect that occurs in the used lead material of the reflecting assembly and the shielding assembly. It should be pointed out that as discussed in the second embodiment and third embodiment, when the reflecting assembly is disposed to be a structure that has a reflecting module, the reflecting assembly 22 is surrounding the moderator 21, and an outer surface of the moderator 21 is generally cylindrical or has at least one conical structure. Therefore, when the reflecting assembly formed by stacking the reflecting modules 229 is surrounding the moderator 21, the structural combination should further be considered. The structure of the reflecting module that is directly combined with the surface of the moderator 21 is adjusted. For example, the reflecting module that is in contact with the moderator 21 is cut to attach the reflecting assembly to the outer surface of the moderator 21, so that the reflection of deflected neutrons by the reflector 222 in the reflecting assembly 22 is not affected. Each of the cores formed by the cells in the present disclosure may be any closed structure having a hole-shaped accommodating space, for example, a geometrical structure whose cross section is a square, a triangle or a hexagon, a tetrahedron, and an octahedron or a dodecahedron having a hole-shaped accommodating space, or configured to be alternatively a non-closed structure having a hole-shaped accommodating space. Examples are not enumerated herein. The lead is disposed in the hole-shaped accommodating space through pouring to be closely surrounded by the material of the cores, so that the alloy material of the cores supports the lead material. In the second embodiment and the third embodiment of the present disclosure, to facilitate stacking and manufacturing of the reflecting module and/or the shielding module, a structure whose cross section is a hexagon is configured for both the cores of the reflecting assembly and the cores of the shielding assembly. Certainly, the structure of the supporting member of the reflecting assembly may be alternatively different from the structure of the supporting member of the shielding assembly. For example, the structure of the supporting member of the cores of the shielding assembly is a geometrical shape whose cross section is a hexagon, and the structure of the supporting member of the cores of the reflecting assembly is a tetrahedron, provided that an alloy material of the supporting member can support the lead material and has low impact on neutron beam quality. Details are not described herein again. In all the foregoing embodiments, in consideration of the weight of the entire beam shaping assembly, an alloy material with light weight is applied for the cores, the top plate, the bottom plate, and the side plates that connect the top plate and the bottom plate and surround the cores, in consideration of neutron beam quality, a material with low neutron absorption cross section and low activity should further be chosen for the material of the core, the top plate, the bottom plate, and the side plates, and the proportion of the total volume of the material of the top plate, the bottom plate, the side plates, and the core in the volume of the material of the reflector or the material of the shielding is less than 10%. In the present disclosure, aluminum alloy material is preferentially chosen for the material of the top plate, the bottom plate, the side plates, and the core. Lead-antimony alloy may be alternatively applied in place of the aluminum alloy for the following reason. The neutron absorption cross section of lead-antimony alloy material is higher than that of an aluminum alloy material. However, the proportion of the total volume of the material of the top plate, the bottom plate, the side plates, and the core in the volume of the material of the reflector or the material of the shielding assembly is less than 10%, the equivalent total antimony content is less than 1%. Therefore, antimony in lead-antimony alloy material does not have significant impact on neutron beam quality. The reflectors or/and the shieldings in the beam shaping assembly of the present disclosure are made of lead having a creep effect. However, when the beam shaping assembly is embedded in the shielding wall W of the irradiation room, the supporting member made of the alloy may provide supporting to the reflectors or/and the shieldings made of the lead material with the creep effect supported in the shielding wall W. Therefore, the structural precision of the entire beam shaping assembly is increased. For the shielding assembly in the present disclosure, in one aspect, alloy is disposed to support lead, and in another aspect, the top plate, the bottom plate, and the side plates that connect the top plate and the bottom plate are disposed surrounding the lead supported by the alloy. In this way, the modular design of the shielding assembly is implemented while the structural strength of the shielding assembly is reinforced, and the structure is simple. Therefore, the shielding assembly in the present disclosure may be alternatively applied to other shielding scenarios. The beam shaping assembly for neutron capture therapy disclosed in the present disclosure is not limited to the content in the foregoing embodiments and the structures represented in the accompanying drawings. All obvious changes, replacements or modifications made to the materials, shapes, and positions of the members based on the present disclosure fall within the protection scope of the present disclosure. Although the illustrative embodiments of the present invention have been described above in order to enable those skilled in the art to understand the present invention, it should be understood that the present invention is not to be limited the scope of the embodiments. For those skilled in the art, as long as various changes are within the spirit and scope as defined in the present invention and the appended claims, these changes are obvious and within the scope of protection claimed by the present invention.
048030414	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The installation shown very diagrammatically in FIG. 1 firstly comprises guides 10 making it possible to maintain and guide in vertical position a rod A previously irradiated in the core of a fast neutron nuclear reactor. In per se known manner rod A comprises a metal can G (e.g. of stainless steel), which is tubular and in which is located a stack of pellets P constituting the nuclear fuel. These pellets P are generally formed from a mixed uranium and plutonium oxide (UO.sub.2, PuO.sub.2). However, it is readily apparent that the process according to the invention can be used no matter what the constitution of the pellets contained in the can and particularly when the mixed oxide is replaced by a carbide or by a nitride. When located in a nuclear fuel assembly, rod A also has upper and lower end fittings closing the ends of can G. The upper end fitting is removed by cutting off the can end before the rod is introduced into the installation of FIG. 1, which explains why it does not appear in the latter. As a result of the irradiation of rod A in the fast neutron reactor core, the radial clearance J which initially existed between pellets P and can G (FIG. 2a) has disappeared under the effect of the swelling of the pellets (FIG. 2b). Thus, to some extent the pellets are set in can G. The installation shown in FIG. 1 also comprises a rod raising means with a plunger or piston 12, which bears on the lower end of rod A. This plunger is progressively actuated, e.g. by means of a not shown jack, so that it progressively raises rod A along its vertical axis between guides 10 (arrow F in FIG. 1). Plunger 12 can optionally be replaced by a clamp, clip or similar device. A fixed heating device is located above the highest guide 10. At the start of a cycle, the upper end of rod A, whose can is to be replaced, is brought level with the heating device. The latter surrounds can G and makes it possible to locally raise the temperature up to its melting point without causing any deterioration of pellets P. In the represented embodiment, the heating device is constituted by an induction heating coil 14. The latter comprises at least one turn and its vertical axis coincides with that of the plunger 12 and guides 10. Coil 14 is supplied by a high frequency alternating current. Through the skin effect, it is possible to induce electric currents in the metal can G, which is a good electricity conductor. Thus, there is local heating by induction of can G, which has the effect of progressively melting the latter as rod A is raised by plunger 12. The fissile material constituting the pellets P is a poor conductor of electricity, so that the pellets are not really heated by coil 14. Preferably, in order to prevent the molten can metal from sticking again to the lower unmelted part thereof, the installation comprises means for discharging the metal as it melts. In the embodiment shown in continuous line form in FIG. 1, these means are constituted by a fixed annular deflector 16 made from a refractory material, disposed around rod A and coaxially thereto, immediately below coil 14. The upper part 16a of deflector 16 behaves in the manner of a scraper closely surrounding the still unmelted can G. For this purpose, the upper end of part 16a of the scraper is tapered, so as to permit the flow of molten metal towards an annular channel 16b constituting the lower part of deflector 16. As illustrated in FIG. 1, channel 16b is extended by a ramp 16c for removing the molten metal. According to a constructional variant shown in mixed line form in FIG. 1, deflector 16 is replaced by one or more nozzles 16' by which a neutral gas, such as argon is blown onto can G, in the immediate vicinity of coil 14. This solution also makes it possible to remove the molten metal and prevents its sticking again to the unmelted can. However, it suffers from the risk of dispersing molten metal into the cell where the installation is located. In its upper part, the installation shown in FIG. 1 comprises means making it possible to support in fixed manner a new can G', so that the latter is disposed coaxially to rod A and its lower end is as close as possible to heating coil 14. In the represented embodiment, these supporting means comprise a jacket 18, in which can G' is introduced up to a lower abutment 18a. Any upward displacement of can G' is then prevented by the putting into place of a plug 20 above jacket 18. The latter being fitted in a fixed support 22, the positioning of the new can G' with respect to the lower portion of the installation is ensured. Apart from its supporting function, the jacket 18 makes it possible to at least partly protect the new can G' against contamination from the irradiated rod A. As illustrated in FIG. 1, jacket 18 also preheats the new can G', e.g. to a temperature of approximately 600.degree. C. For this purpose, a preheating device, e.g. comprising an electrical resistor 24 helically wound around can G' is embedded in jacket 18 over the entire height of the can. This preheating device facilitates the introduction of pellets P of irradiated rod A into the new can G', whilst ensuring an expansion of said can and consequently an increase in its internal diameter. According to an essential feature of the invention, the internal diameter d.sub.2 of the unexpanded new can G' (FIG. 2c) is slightly greater than the internal diameter d.sub.1 of the preceding can G of rod A (FIG. 2c). Thus, as the object of the invention is to permit a new irradiation of the pellets P in a fast neutron nuclear reactor core, it is necessary to provide a certain radial clearance j' (FIG. 2c) between the pellets P which have already undergone at least one previous irradiation and the interior of the new can G'. As a result of this clearance j', it is clear that the preheating of the new can G' is not indispensable to the invention and soley serves to facilitate the introduction of the pellets into the can. As a result of the installation described hereinbefore, the progressive raising of rod A ensured by plunger 12 has the effect of progressively introducing the stack of pellets P into the new can G', substantially immediately after the part of the irradiated can G surrounding said pellets has been melted with the aid of coil 14. Thus, a rod can can be changed without any mechanical stressing of the nuclear fuel pellets P. The latter aspect is particularly important, because said pellets are relatively fragile. Preferably, the inactive lower end fitting E of rod A remains in place, which makes it possible to prevent a deterioration of plunger 12 by the heating coil 14. When the can change has been completed, the assembly constituted by the new can G' containing the stack of pellets P is transferred to another station, where new upper and lower end fittings are fitted in order to complete the rod. It should be noted that this process can be carried out several times in succession on the same nuclear fuel pellets. On each occasion, the swelling of the pellets under irradiation is compensated by placing them in a can, whose internal diameter is slightly increased. In this way, it is possible to eliminate the reprocessing of nuclear fuel or to only carry out said reprocessing in the case of fuel which has been subject to very high combustion levels, namely about three time the levels presently achieved following a single irradiation. For each nuclear fuel pellet recycling, it is possible to save the reprocessing costs and the transporation costs necessary for said reprocessing, the costs of the installation permitting said recycling being very small compared with that of the reprocessing. Moreover, the capital expenditure necessary for the definitive storage of the fuel or its reprocessing can be delayed for roughly 10 years with respect to the start-up of a fast neutron nuclear reactor. FIGS. 2a, 2b and 2c also show the spacing wire F and F' respectively surrounding rod A having the first can G and road A' having the new can G' within assemblies in which said rods are placed. In order that the overall dimensions of rods A and A', defined by the cylinder diameter D, which envelopes the spacing wired F and F', remains unchanged despite the diameter difference between can G and G' (internal diameters d.sub.1 and d.sub.2), it can be seen in FIGS. 2a and 2c that the diameters of the spacing wires F and F' differ. More specifically, the diameter of spacing wire f' is slightly smaller than that of spacing wire F. Obviously, the invention is not limited to the embodiment described hereinbefore and variants thereof are also covered. Thus, although the irradiated rod can is preferably eliminated by its melting, other gentle can destruction methods can also also be considered. Thus, it is possible to cut the irradiated rod can along at least two generatrixes thereof in order to separate it from the stack of pellets with applying excessive mechanical stresses thereto. In the case where the can is removed by heating, any known heating means can be used in place of the aforementioned induction heating device. However, the latter is particularly advantageous, because it induces substantially no heating of the nuclear fuel pellets. Moreover, the kinematics on the installation can be reversed, the rod A then remaining fixed whereas the heating device and the part carrying the new can move progressively along the rod axis. In the same way, any type of fuel, oxide, carbide, nitride, etc can undergo recycling in this way, as well as a random metal can material.

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