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	abstract	A transmission electron microscope is capable of correcting, with high efficiency and high accuracy, an electron energy loss spectrum extracted from each of measured portions included in an electron energy loss spectral image with two axes representing the amount of an energy loss and positional information on a measured portion. The transmission electron microscope has an electron spectroscope and a spectrum correction system. The spectrum correction system corrects a spectrum extracted from each measured portion included in an electron energy loss spectral image acquired from a sample based on a difference between a spectrum extracted from a standard portion of a standard spectral image and a spectrum extracted from a portion different from the standard portion.
053135075	abstract	An apparatus for attaching a key member to a nuclear fuel assembly grid and detaching the same therefrom is disclosed. The apparatus includes a supply and recovery mechanism, an inserting and removing mechanism, and a rotating mechanism. The supply and recovery mechanism operates to supply the key member to a prescribed position adjacent to the grid and recover the same. The inserting and removing mechanism is disposed between the supply and recovery mechanism and the grid, and operates to insert the key member supplied from the supply and recovery mechanism into the grid and remove the key member from the grid to recover the same to the supply and recovery mechanism. The rotating mechanism is disposed adjacent to the inserting and removing mechanism, and operates to rotate the key member inserted in the grid in a prescribed direction about the longitudinal axis to attach the same to the grid and rotate the same in a direction opposite to the prescribed direction to detach the same from the grid.
	description	The present invention relates to a differential evacuation system suitable for use in the manufacture of semiconductor wafers or the like using a photolithography technique. Conventionally, semiconductor devices such as semiconductor memories are manufactured by a method using a reduced projection exposure apparatus in which a circuit pattern drawn on a reticle or a mask is projected onto a wafer or the like through a projection optical system to transfer the circuit pattern to the wafer. The smallest size (resolution) of a circuit pattern that can be transferred by the reduced projection exposure apparatus is proportional to the wavelength of light used for exposure. Therefore, the shorter the wavelength, the higher the resolution. Accordingly, the wavelength of light used for exposure is becoming shorter and shorter with the increasing demand for finer semiconductor devices. Thus, progressively shorter wavelengths of ultraviolet light have been put into use for exposure, i.e. KrF excimer laser (wavelength: about 248 nm), and ArF excimer laser (wavelength: about 193 nm). The photolithography using such ultraviolet light, however, cannot comply with the demand for even finer semiconductor devices. Under these circumstances, there has recently been developed a reduced projection exposure apparatus using extreme ultraviolet (EUV) light having a shorter wavelength than those of ultraviolet light, i.e. a wavelength of the order of 10 nm to 15 nm (such a reduced projection exposure apparatus will hereinafter be referred to as “an EUV exposure apparatus”). A laser-produced plasma (LPP) light source, for example, is used as an EUV light source of an EUV exposure apparatus. The LPP light source utilizes EUV light having a wavelength of the order of 13.5 nm, for example, which is emitted from a high-temperature plasma generated by applying high-intensity pulsed laser to a target material placed in a vacuum chamber. Examples of target materials used for this purpose include xenon (Xe) gas, droplet, cluster, etc. tin (Sn) droplet, and lithium (Li) droplet. The target material is supplied into the vacuum chamber by a droplet generator or other similar means. In the EUV exposure apparatus, a light generation section having the EUV light source and a section subsequent to the light generation section, in which optical processing, e.g. exposure, is performed by using EUV light generated in the light generation section, are different from each other in service conditions. The LPP light source generates a plasma by applying high-luminance pulsed laser light to a target in an EUV light generation chamber, thereby generating EUV light. During the laser irradiation, scattering particles and ions known as debris are undesirably produced from the target. The debris contaminates and damages a mirror that converges EUV light, causing a degradation of the reflectance. To reduce the degradation of the reflectance of the EUV light converging mirror by the debris, a buffer gas, e.g. He, is conventionally supplied into the light generation chamber. Accordingly, the pressure in the light generation chamber is about 10 Pa. On the other hand, the pressure in an apparatus that applies EUV light to a mask to perform exposure is required to be about 10−7 Pa. Patent Literature 1 (FIG. 12) proposes a differential evacuation system that realizes the pressure difference between the light generation chamber and the exposure apparatus. An EUV exposure apparatus in Patent Literature 1 includes a light generation chamber having an EUV light source and an illumination optical chamber in which optical processing, e.g. exposure, is performed by using light generated in the light generation chamber. A turbomolecular pump is installed between the light generation chamber and the illumination optical chamber. The rotating shaft of the turbomolecular pump is made hollow to allow light to pass through the hollow inside of the rotating shaft, thereby forming a chamber connecting passage. The two chambers are evacuated individually, and at the same time, the turbomolecular pump is driven to evacuate gas molecules leaking through the chamber connecting passage from the high-pressure side chamber toward the low-pressure side chamber, thereby introducing light generated in the light generation chamber into the illumination optical chamber through the chamber connecting passage while maintaining a large pressure difference between the two chambers. The reason why the chamber connecting passage is evacuated by the turbomolecular pump installed between the two chambers as stated above is that a large pressure difference cannot be maintained between the two chambers simply by connecting together the two chambers, which are evacuated individually, through the chamber connecting passage. It should be noted that the chamber connecting passage cannot be closed with a filter because EUV light is passed therethrough (it is difficult to produce a filter material having a high transmittance in the wavelength region of EUV light). In the differential evacuation system disclosed in the following Patent Literature 1, however, only one turbomolecular pump can be installed. Therefore, when a large differential pressure is required, it is necessary to greatly increase the external size of the turbomolecular pump to increase the pump capacity, or to reduce the conductance of the chamber connecting passage provided in the turbomolecular pump (i.e. the passage diameter is reduced to increase the resistance to the passage of gas molecules). However, the turbomolecular pump has a special structure and hence a high production cost. If the turbomolecular pump is increased in size, the production cost becomes higher. On the other hand, it is difficult to reduce the conductance because it is necessary to sufficiently ensure a desired optical path. [Patent Literature 1] Japanese Patent Application Publication No. 2004-103731 The present invention has been made in view of the above-described circumstances. An object of the present invention is to provide a differential evacuation system capable of easily maintaining, at a low cost, a large differential pressure between a light generation chamber having an EUV light source and an illumination optical chamber in which optical processing, e.g. exposure, is performed by using light generated in the light generation chamber, and yet capable of sufficiently ensuring a desired optical path. The invention of claim 1 of this application is a differential evacuation system including a light generation chamber that generates light, an illumination optical chamber in which optical processing is performed by using the light generated in the light generation chamber, and a chamber connecting passage serving as a light passage that connects together the light generation chamber and the illumination optical chamber to guide the light generated in the light generation chamber into the illumination optical chamber. The chamber connecting passage has a flow path constricting portion with the smallest inner diameter and is increased in inner diameter at portions thereof that are at opposite sides, respectively, of the flow path constricting portion. One or a plurality of vacuum pumps are attached to a position of the chamber connecting passage that is closer to one of the light generation chamber and the illumination optical chamber that is higher in pressure than the other than at least the flow path constricting portion. The invention of claim 2 of this application is a differential evacuation system as set forth in claim 1, in which an enlarged-diameter part is provided at a position of the chamber connecting passage that is closer to one of the light generation chamber and the illumination optical chamber that is higher in pressure than the other than at least the flow path constricting portion, and the one or plurality of vacuum pumps are attached to the enlarged-diameter part. The enlarged-diameter part is structured to have an inner diameter larger than those of portions of the chamber connecting passage that are at opposite sides, respectively, of the enlarged-diameter part. The invention of claim 3 of this application is a differential evacuation system as set forth in claim 2, in which the plurality of vacuum pumps are attached to a side of the enlarged-diameter part. The invention of claim 4 of this application is a differential evacuation system as set forth in claim 2, in which the plurality of vacuum pumps are attached to the outer peripheral surface of the enlarged-diameter part. The invention of claim 5 of this application is a differential evacuation system as set forth in claim 1, in which one or a plurality of pipes are connected to a position of the chamber connecting passage that is closer to one of the light generation chamber and the illumination optical chamber that is higher in pressure than the other than at least the flow path constricting portion, and the vacuum pumps are attached to the pipes, respectively. The invention of claim 6 of this application is a differential evacuation system including a light generation chamber that generates light, an illumination optical chamber in which optical processing is performed by using the light generated in the light generation chamber, and a chamber connecting passage serving as a light passage that connects together the light generation chamber and the illumination optical chamber to guide the light generated in the light generation chamber into the illumination optical chamber. The chamber connecting passage has a flow path constricting portion with the smallest inner diameter and is increased in inner diameter in a conical tube shape at portions thereof that are at opposite sides, respectively, of the flow path constricting portion. One or a plurality of vacuum pumps are attached to each of the portions that are at opposite sides, respectively, of the flow path constricting portion. The invention of claim 7 of this application is a differential evacuation system as set forth in claim 6, in which the portions of the chamber connecting passage that are at opposite sides, respectively, of the flow path constricting portion are provided with enlarged-diameter parts, respectively, and the one or plurality of vacuum pumps are attached to each of the enlarged-diameter parts. The invention of claim 8 of this application is a differential evacuation system as set forth in claim 7, in which the plurality of vacuum pumps are attached to a side of each of the enlarged-diameter parts. The invention of claim 9 of this application is a differential evacuation system as set forth in claim 7, in which the plurality of vacuum pumps are attached to the outer peripheral surface of each of the enlarged-diameter parts. The invention of claim 10 of this application is a differential evacuation system as set forth in claim 6, in which one or a plurality of pipes are connected to each of the portions of the chamber connecting passage that are at opposite sides, respectively, of the flow path constricting portion, and the vacuum pumps are attached to the pipes, respectively. The invention of claim 11 of this application is a differential evacuation system including a light generation chamber that generates light, an illumination optical chamber in which optical processing is performed by using the light generated in the light generation chamber, and a chamber connecting passage serving as a light passage that connects together the light generation chamber and the illumination optical chamber to guide the light generated in the light generation chamber into the illumination optical chamber. The chamber connecting passage has a flow path constricting portion with the smallest inner diameter and is increased in inner diameter from the flow path constricting portion toward at least one of the light generation chamber and the illumination optical chamber. An enlarged-diameter part is provided at an intermediate position of the chamber connecting passage, and one or a plurality of vacuum pumps are attached to the enlarged-diameter part. The invention of claim 12 of this application is a differential evacuation system as set forth in claim 11, in which the plurality of vacuum pumps are attached to a side of the enlarged-diameter part. The invention of claim 13 of this application is a differential evacuation system as set forth in claim 11, in which the plurality of vacuum pumps are attached to the outer peripheral surface of the enlarged-diameter part. According to the inventions of claims 1 to 5, a flow path constricting portion is provided at an intermediate position of the chamber connecting passage. Therefore, the conductance of the chamber connecting passage can be reduced. Because the chamber connecting passage has a configuration in which portions that are at opposite sides, respectively, of the flow path constricting portion are increased in inner diameter, it is possible to sufficiently ensure an optical path diverging in opposite directions away from each other from the point of convergence of light passing through the chamber connecting passage by making the light convergence point coincident with the flow path constricting portion. Further, because evacuation is performed at an optimal position in the chamber connecting passage, it is possible to perform even more effective evacuation by the vacuum pumps. According to the invention of claim 2, the vacuum pumps are attached to an enlarged-diameter part provided at an intermediate position of the chamber connecting passage. Therefore, it is possible to easily install a plurality of vacuum pumps and hence possible to increase the differential pressure between the light generation chamber and the illumination optical chamber. According to the invention of claim 3, the vacuum pumps can be installed so as not to project outward, which allows a reduction in the external size of the differential evacuation system. Particularly, if the vacuum pumps are installed on a side of the enlarged-diameter part in such a manner as to be circumferentially spaced from each other, it is possible to easily increase the number of vacuum pumps installed. According to the invention of claim 4, the vacuum pumps can be favorably disposed in a situation where there is a space in the radial direction of the enlarged-diameter part but there is no much space in the axial direction of the enlarged-diameter part. According to the inventions of claims 6 to 10, a flow path constricting portion is provided at an intermediate position of the chamber connecting passage. Therefore, the conductance of the chamber connecting passage can be reduced. Because the chamber connecting passage is increased in inner diameter in a conical tube shape at portions thereof that are at opposite sides, respectively, of the flow path constricting portion, it is possible to sufficiently ensure an optical path diverging in opposite directions away from each other from the point of convergence of light passing through the chamber connecting passage by making the light convergence point coincident with the flow path constricting portion. Further, because the vacuum pumps are installed at portions of the chamber connecting passage that are at opposite sides, respectively, of the flow path constricting portion, it is possible to easily install a large number of vacuum pumps and hence possible to easily increase the differential pressure between the light generation chamber and the illumination optical chamber. According to the invention of claim 7, the vacuum pumps are attached to enlarged-diameter parts provided at intermediate positions, respectively, of the chamber connecting passage. Therefore, it is possible to easily install a plurality of vacuum pumps and hence possible to increase the differential pressure between the light generation chamber and the illumination optical chamber. According to the invention of claim 8, the vacuum pumps can be installed so as not to project outward, which allows a reduction in the external size of the differential evacuation system. Particularly, if the vacuum pumps are installed on a side of each enlarged-diameter part in such a manner as to be circumferentially spaced from each other, it is possible to easily increase the number of vacuum pumps installed. According to the invention of claim 9, the vacuum pumps can be favorably disposed in a situation where there is a space in the radial direction of the enlarged-diameter parts but there is no much space in the axial direction of the enlarged-diameter parts. According to the invention of claim 11, a flow path constricting portion is provided at an intermediate position of the chamber connecting passage. Therefore, the conductance of the chamber connecting passage can be reduced. Because the chamber connecting passage is increased in inner diameter from the flow path constricting portion toward at least one of the light generation chamber and the illumination optical chamber, it is possible to sufficiently ensure an optical path diverging in opposite directions away from each other from the point of convergence of light passing through the chamber connecting passage by making the light convergence point coincident with the flow path constricting portion. Further, because the vacuum pumps are attached to an enlarged-diameter part provided at an intermediate position of the chamber connecting passage, it is possible to easily install a plurality of vacuum pumps and hence possible to increase the differential pressure between the light generation chamber and the illumination optical chamber. According to the invention of claim 12, the vacuum pumps can be installed so as not to project outward, which allows a reduction in the external size of the differential evacuation system. Particularly, if the vacuum pumps are installed on a side of the enlarged-diameter part in such a manner as to be circumferentially spaced from each other, it is possible to easily increase the number of vacuum pumps installed. According to the invention of claim 13, the vacuum pumps can be favorably disposed in a situation where there is a space in the radial direction of the enlarged-diameter part but there is no much space in the axial direction of the enlarged-diameter part. Embodiments of the present invention will be explained below in detail with reference to the accompanying drawings. FIG. 1 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-1 according to a first embodiment of the present invention. As shown in the figure, the differential evacuation system 1-1 has a light generation chamber 10 accommodating a plasma 11 serving as a light source that generates (emits) EUV light, an illumination optical chamber 100 in which optical processing (e.g. exposure processing for semiconductor manufacture) is performed by using EUV light generated in the light generation chamber 10, and a chamber connecting passage 150 serving as a light passage that connects together the light generation chamber 10 and the illumination optical chamber 100 to guide light generated in the light generation chamber 10 into the illumination optical chamber 100. The light generation chamber 10 has a nozzle (target material supply means) 13 that supplies a target material (e.g. xenon (Xe) gas, droplet, cluster, etc., tin (Sn) droplet, or lithium (Li) droplet) toward the position of the plasma 11, a converging mirror 15 having a concave reflecting surface, a buffer gas introducing tank 17 installed outside the light generation chamber 10 and filled with a buffer gas, e.g. helium (He), a nozzle 18 that blows the buffer gas from the buffer gas introducing tank 17 to the neighborhood of the surface of the converging mirror 15, a transmitting window 19 attached to the outer peripheral wall of the light generation chamber 10 to transmit laser light, and a vacuum pump 21 attached to the light generation chamber 10 to maintain the inside of the light generation chamber 10 at a predetermined low pressure. The center of the converging mirror 15 is provided with a light-passing hole 15a that passes laser light introduced from the transmitting window 19. The inside of the light generation chamber 10 is maintained at a pressure of the order of about several Pa by driving the vacuum pump 21 in order to generate EUV light and to reduce the deterioration of the converging mirror 15 due to debris reaching the same. The illumination optical chamber 100 has an optical element 101, e.g. a reflecting mirror, and a plurality of mirrors for illumination installed therein. An exposure apparatus (not shown) for semiconductor manufacture or the like is installed in the stage subsequent to the optical element 101 and the illumination mirrors. The exposure apparatus transfers the pattern of a mask illuminated with EUV light onto a wafer. Examples of the exposure apparatus include a projection exposure apparatus that transfers by exposure a circuit pattern formed on a mask onto an object to be processed by the step-and-scan method or the step-and-repeat method using EUV light (e.g. a wavelength of 13.4 nm) as illumination light for exposure, for example. A vacuum pump 103 is attached to the illumination optical chamber 100 to maintain the inside of the illumination optical chamber 100 at a predetermined degree of vacuum. The inside of the illumination optical chamber 100 is maintained at a vacuum below 1×10−3 Pa by the vacuum pump 103 and kept under an He or other buffer gas atmosphere to prevent the contamination of the optical element 101 and other components and to maintain the reflectance of the mirror for EUV and also to prevent the attenuation of EUV light in the optical path. He and other similar buffer gases do not block EUV light at a low pressure. The chamber connecting passage 150 is formed in a tubular configuration in which it has a flow path constricting portion 151 with the smallest inner diameter and in which portions that are at opposite sides, respectively, of the flow path constricting portion 151 are increased in inner diameter. More specifically, the portions of the chamber connecting passage 150 that are at opposite sides, respectively, of the flow path constricting portion 151 are increased in inner diameter in a conical tube shape. The term “conical tube shape” refers to a shape (trumpet-like shape) in which the chamber connecting passage 150 gradually changes in inner diameter from a small inner diameter passage portion toward a large inner diameter passage portion. That is, the chamber connecting passage 150 is tapered in conformity with the converging angle (NA: Numerical Aperture) of EUV light 203, which will be described later. The chamber connecting passage 150 has an enlarged-diameter part 160 provided at an intermediate position (a position near the flow path constricting portion 151 of the chamber connecting passage 150 and closer to the light generation chamber 10 than the flow path constricting portion 151). The enlarged-diameter part 160 has an inner diameter larger than those of portions of the chamber connecting passage 150 that are at opposite sides, respectively, of the enlarged-diameter part 160. FIG. 2 is a partly sectioned view as seen in the direction of the arrows A-A in FIG. 1. As shown in FIGS. 1 and 2, the enlarged-diameter part 160 is in the shape of a circular box, the inside of which is a closed space. The enlarged-diameter part 160 is provided so that its center axis coincides with the center axis of the chamber connecting passage 150. The enlarged-diameter part 160 has a plurality (four) of vacuum pumps 170 installed on one of mutually opposing right and left sides thereof (i.e. the side that faces the light generation chamber 10). The vacuum pumps 170 are equally spaced on a circumference centered at the center axis of the enlarged-diameter part 160. The vacuum pumps 170 are all commercially available turbomolecular pumps of the same structure. The vacuum pumps 170 are attached to the enlarged-diameter part 160 so that the rotating shaft of each vacuum pump 170 is parallel to the center axis of the chamber connecting passage 150. The vacuum pumps 170 as installed in this orientation can be disposed in a space-saving manner because the vacuum pumps 170 do not project outward and allow a reduction in the external size of the differential evacuation system 1-1. It is also possible to easily install a large number of vacuum pumps 170 on the enlarged-diameter part 160 in such a manner as to be circumferentially spaced from each other and hence possible to easily increase the differential pressure between the chambers 10 and 100. In the differential evacuation system 1-1 arranged as stated above, pulsed laser 201 emitted from a laser generator (not shown) and transmitted through a condenser lens passes through the transmitting window 19 and the light-passing hole 15a and is converged on a target material (e.g. tin) supplied from the nozzle 13 to generate a plasma 11. The plasma 11 emits EUV light 203, which is reflected and converged by the converging mirror 15 in order to increase the light utilization efficiency before being introduced into the chamber connecting passage 150. The above-described plasma 11 produces scattering particles known as debris together with EUV light. The adhesion of the scattering particles to the surface of the converging mirror 15 is suppressed by blowing the buffer gas from the nozzle 18 onto the surface of the converging mirror 15. Thus, the contamination and damage of the converging mirror 15 are reduced. The EUV light introduced into the chamber connecting passage 150 is converged on a point located in the center of the flow path constricting portion 151 of the chamber connecting passage 150, thereby preventing the chamber connecting passage 150 from blocking the EUV light. The EUV light having passed through the chamber connecting passage 150 and introduced into the illumination optical chamber 100 is reflected by the optical element 101, before being introduced into an exposure apparatus (not shown) for semiconductor manufacture or the like. As has been stated above, in this embodiment, the inside of the light generation chamber 10 is maintained under an He or other buffer gas atmosphere of a low pressure of several Pa by the vacuum pump 21, while the inside of the illumination optical chamber 100 is maintained at a vacuum below 1×10−3 Pa by the vacuum pump 103. Therefore, gas molecules move through the chamber connecting passage 150 from the light generation chamber 10 toward the illumination optical chamber 100. A rise in the pressure in the illumination optical chamber 100 undesirably causes an increase in the optical path length of EUV light in the illumination optical chamber 100 and the exposure apparatus (not shown), resulting in an increase in the attenuation of the EUV light, which makes it impossible to perform exposure on the wafer. In this regard, the differential evacuation system 1-1 has a flow path constricting portion 151 with a reduced inner diameter provided at an intermediate position of the chamber connecting passage 150. Accordingly, the conductance of the chamber connecting passage 150 is small, so that it is difficult for gas molecules to pass through the chamber connecting passage 150. In addition, a part of gas molecules moving through the chamber connecting passage 150 are evacuated by driving the vacuum pumps 170. Consequently, it is possible to effectively reduce the number of gas molecules moving through the chamber connecting passage 150 from the light generation chamber 10 toward the illumination optical chamber 100 and hence possible to increase the differential pressure between the two chambers 10 and 100. Accordingly, the pressure in the illumination optical chamber 100 can be maintained at a lower level. As a result, there is substantially no attenuation of EUV light in the illumination optical chamber 100 and the exposure apparatus (not shown), thus allowing exposure on the wafer. Particularly, in this embodiment, the vacuum pumps 170 are attached to the enlarged-diameter part 160. Therefore, it is possible to easily install a plurality of commercially available vacuum pumps 170 (having no special structure). Thus, the evacuation capacity can be increased easily. Even if the differential pressure between the light generation chamber 10 and the illumination optical chamber 100 is large, it is possible to easily cope with this situation. It should be noted that because the chamber connecting passage 150 has a configuration in which portions that are at opposite sides, respectively, of the flow path constricting portion 151 are increased in inner diameter, specifically in a conical tube shape, it is possible to sufficiently ensure an optical path diverging in opposite directions away from each other from the point of convergence of light passing through the chamber connecting passage 150 by making the light convergence point coincident with the flow path constricting portion 151. Further, in this embodiment, the enlarged-diameter part 160 is installed at a position in the chamber connecting passage 150 near the flow path constricting portion 151 and closer to the light generation chamber 10, which is the higher in pressure of the two chambers 10 and 100. Therefore, it is possible to perform even more effective evacuation by the vacuum pumps 170. In general, turbomolecular pumps have a constant evacuation rate in the pressure region below several Pa irrespective of the suction pressure. Therefore, installing turbomolecular pumps at a higher-pressure position enables a larger amount of leaking gas to be evacuated at a small evacuation rate. Because the amount of leaking gas is determined by the conductance of the chamber connecting passage 150 between the light generation chamber 10 and the enlarged-diameter part 160 and the differential pressure, the enlarged-diameter part 160 is disposed at a position near the flow path constricting portion 151 in order to reduce the amount of leaking gas to be evacuated by the vacuum pumps 170 (i.e. to prevent the pressure in the light generation chamber 10 from being influenced by the evacuation). In other words, it is preferable, from the viewpoint of obtaining a necessary differential pressure with a vacuum pump system having as small a capacity as possible (with as small a number of vacuum pumps as possible), to determine an optimum installation position of the enlarged-diameter part 160 somewhere between the light generation chamber 10 and the flow path constricting portion 151 while taking into account the amount of leaking gas and the evacuation rate required of the pump system. In addition, because the flow path conductance is correlated with the pressure in the flow path, as the pressure reduces, the conductance decreases and eventually assumes a constant value irrespective of the pressure in a molecular flow region. Therefore, vacuum evacuation performed at an intermediate position of piping causes a pressure reduction and a decrease in the conductance in a portion of the piping downstream of the position where evacuation is performed. Accordingly, the position for vacuum evacuation, i.e. the installation position of the enlarged-diameter part 160, is preferably set near the light generation chamber 10, which is a high pressure-side chamber, and within a range in which the pressure in the light generation chamber 10 is not influenced by the evacuation of gas from the enlarged-diameter part 160. For this reason, the installation position of the enlarged-diameter part 160 is determined at the above-described position. FIG. 3 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-2 according to a second embodiment of the present invention. In the differential evacuation system 1-2 shown in FIG. 3, the members or portions identical or equivalent to those of the differential evacuation system 1-1 shown in FIGS. 1 and 2 are denoted by the same reference numerals as those used in FIGS. 1 and 2. It should be noted that the second embodiment is the same as the first embodiment shown in FIGS. 1 and 2 except the following points (the same shall apply in the following third to eighth embodiments). The differential evacuation system 1-2 shown in FIG. 3 differs from the above-described differential evacuation system 1-1 only in that another one set of an enlarged-diameter part 160-2 and four vacuum pumps 170-2 is installed at the chamber connecting passage 150 in addition to the enlarged-diameter part 160 and the four vacuum pumps 170. The enlarged-diameter part 160-2 has the same configuration and structure as the enlarged-diameter part 160. The four vacuum pumps 170-2 also have the same configuration and structure as the four vacuum pumps 170. The enlarged-diameter part 160-2 is installed at an intermediate position of the chamber connecting passage 150, more specifically, at a position near the flow path constricting portion 151 of the chamber connecting passage 150 and closer to the illumination optical chamber 100 than the flow path constricting portion 151. The above-described arrangement doubles the number of vacuum pumps 170 and 170-2 usable for evacuation and therefore allows effective evacuation. Accordingly, the system can easily cope with a large differential pressure between the light generation chamber 10 and the illumination optical chamber 100. It should be noted that in the following embodiments, including this, the suffix “−2” as attached to the reference numerals “160” and “170” refers to an enlarged-diameter part and vacuum pumps installed closer to one of the two chambers 10 and 100 that is lower in pressure than the other. FIG. 4 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-3 according to a third embodiment of the present invention. The differential evacuation system 1-3 shown in FIG. 4 differs from the foregoing differential evacuation system 1-1 in that the position of the enlarged-diameter part 160 installed in the chamber connecting passage 150 is near the flow path constricting portion 151 of the chamber connecting passage 150 and closer to the illumination optical chamber 100 than the flow path constricting portion 151, and in that two superconducting magnets 23 are used to prevent ions and other debris from reaching the converging mirror 15 instead of blowing a buffer gas onto the surface of the converging mirror 15, thereby reducing the degradation of the reflectance of the converging mirror 15. In this embodiment, a magnetic field is generated in a direction perpendicular to the optical axis of the converging mirror 15. Ion debris is moved in the magnetic field direction shown by the broken lines, thereby preventing ions from reaching the surface of the converging mirror 15. It is necessary in order to effectively generate such a large magnetic field to maintain a high vacuum below 1×10−5 Pa. With this arrangement, the light generation chamber 10 needs to be maintained at a lower pressure than the illumination optical chamber 100. In first embodiment, the illumination optical chamber 100 is lower in pressure than the light generation chamber 10, and therefore, the enlarged-diameter part 160 is installed at a position closer to the light generation chamber 10 than the flow path constricting portion 151. However, in a case where the light generation chamber 10 is lower in pressure than the illumination optical chamber 100 as in this embodiment, the enlarged-diameter part 160 should preferably be installed at a position closer to the illumination optical chamber 100. It should be noted that, depending upon cases, the enlarged-diameter part 160 may be installed at the position defined in this embodiment even when the illumination optical chamber 100 is lower in pressure than the light generation chamber 10 as in the first embodiment. Further, both the enlarged-diameter parts 160 and 160-2 shown in FIG. 3 may be installed at a position closer to the light generation chamber 10 than the flow path constricting portion 151 or may be installed at a position closer to the illumination optical chamber 100 than the flow path constricting portion 151, although such arrangements are not illustrated. FIG. 5 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-4 according to a fourth embodiment of the present invention. The differential evacuation system 1-4 shown in FIG. 5 differs from the differential evacuation system 1-2 shown in FIG. 3 only in that one of the two enlarged-diameter parts 160 and 160-2 installed in the chamber connecting passage 150, i.e. the enlarged-diameter part 160, is formed in the shape of a substantially umbrella-shaped (substantially conical) box projecting substantially perpendicularly from the conical tube-shaped wall of the chamber connecting passage 150, and that all the rotating shafts of the four vacuum pumps 170 attached to the enlarged-diameter part 160 are set substantially parallel to the wall (outer peripheral side wall) of the chamber connecting passage 150. The vacuum pumps 170 as installed in this orientation can also be disposed in a space-saving manner because the vacuum pumps 170 do not project outward and allow a reduction in the external size of the differential evacuation system 1-4, as in the case of the foregoing embodiments. It is also possible to easily install a large number of vacuum pumps 170 on the enlarged-diameter part 160 in such a manner as to be circumferentially spaced from each other as in the case of the foregoing embodiments. It should be noted that although in this embodiment only the rotating shafts of the vacuum pumps 170 at one side of the flow path constricting portion 151 are installed substantially parallel to the wall of the chamber connecting passage 150, the rotating shafts of the vacuum pumps 170-2 at the other side of the flow path constricting portion 151 may also be installed substantially parallel to the wall of the chamber connecting passage 150. The vacuum pumps 170 of the differential evacuation systems 1-1 and 1-3 according to the first and third embodiments may also be installed with their rotating shafts extending substantially parallel to the wall of the chamber connecting passage 150. FIG. 6 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-5 according to a fifth embodiment of the present invention. FIG. 7 is a partly sectioned view as seen in the direction of the arrows B-B in FIG. 6. The differential evacuation system 1-5 shown in FIGS. 6 and 7 differs from the above-described differential evacuation system 1-3 shown in FIG. 4 in that enlarged-diameter parts 160 and 160-2 are provided at opposite sides, respectively, of the flow path constricting portion 151 of the chamber connecting passage 150 and that a plurality of vacuum pumps 170 and 170-2 (in this embodiment, four equally spaced vacuum pumps 170 and four equally spaced vacuum pumps 170-2) are attached to the respective outer peripheral surfaces of the enlarged-diameter parts 160 and 160-2. This arrangement also allows a reduction in the conductance of the chamber connecting passage 150 and makes it possible to ensure sufficiently an optical path diverging in opposite directions away from each other from the point of convergence of light and to easily install a large number of vacuum pumps 170 and 170-2 on the enlarged-diameter parts 160 and 160-2, as in the case of the foregoing embodiments. Further, the differential evacuation system 1-5 is suitable for use in a situation where there is a space in the radial direction of the enlarged-diameter parts 160 and 160-2 but there is no much space in the axial direction of the enlarged-diameter parts 160 and 160-2 (i.e. in the direction of the center axis of the chamber connecting passage 150). It should be noted that, in the first to fourth embodiments also, the vacuum pumps 170 (170-2) may be attached to the outer peripheral surface of the enlarged-diameter part 160 (160-2) as in this embodiment. FIG. 8 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-6 according to a sixth embodiment of the present invention. FIG. 9 is a partly sectioned view as seen in the direction of the arrows C-C in FIG. 8. The differential evacuation system 1-6 shown in FIGS. 8 and 9 differs from the above-described differential evacuation system 1-2 shown in FIG. 3 in that, unlike in the differential evacuation system 1-2, no enlarged-diameter parts 160 and 160-2 are provided at opposite sides, respectively, of the flow path constricting portion 151 of the chamber connecting passage 150 but a plurality of pipes 25 and 25-2 (in this embodiment, four equally spaced pipes 25 and four equally spaced pipes 25-2) are radially connected to portions of the chamber connecting passage 150 that are at opposite sides, respectively, of the flow path constricting portion 151 and vacuum pumps 170 and 170-2 are connected to the pipes 25 and 25-2. With this arrangement, although the advantageous effects produced by providing the enlarged-diameter parts 160 and 160-2 cannot be obtained, it is possible to reduce the conductance of the chamber connecting passage 150 and to sufficiently ensure an optical path diverging in opposite directions away from each other from the point of convergence of light, as in the case of the foregoing embodiments. In a case where vacuum pumps 170 are provided only at one side of the flow path constricting portion 151, the vacuum pumps 170 should preferably be installed at a position closer to one of the two chambers that is higher in pressure than the other, as in the first embodiment. Although in this embodiment a plurality (four) of vacuum pumps 170 (or 170-2) are installed, the number of vacuum pumps 170 (or 170-2) installed may be selected to be a plural number other than four or one according to need. FIG. 10 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-7 according to a seventh embodiment of the present invention. FIG. 11 is a partly sectioned view as seen in the direction of the arrows D-D in FIG. 10. The differential evacuation system 1-7 shown in FIGS. 10 and 11 differs from the above-described differential evacuation system 1-6 shown in FIG. 8 in that the light generation chamber 10 has the same arrangement as that of the light generation chamber 10 shown in FIG. 4, and in that the pipes 25 and 25-2 are bent in the axial direction (i.e. in the direction of the center axis of the chamber connecting passage 150) and further that the vacuum pumps 170 and 170-2 are attached to the respective distal ends of the pipes 25 and 25-2, thereby installing the rotating shafts of the vacuum pumps 170 and 170-2 in parallel to the center axis of the chamber connecting passage 150. The vacuum pumps 170 and 170-2 as installed in this orientation do not project outward (radially) and allow a reduction in the external size of the differential evacuation system 1-7, in the same way as described in connection with the first embodiment. FIG. 12 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-8 according to an eighth embodiment of the present invention. The differential evacuation system 1-8 shown in FIG. 12 differs from the above-described differential evacuation system 1-1 shown in FIG. 1 in that the chamber connecting passage 150 is formed in a tubular configuration in which the inner diameter of the chamber connecting passage 150 increases toward one of the two chambers 10 and 100 from the flow path constricting portion 151 where the inner diameter is the smallest. More specifically, the chamber connecting passage 150 has a configuration in which a portion thereof at one side of the flow path constricting portion 151 is increased in inner diameter in a conical tube shape (i.e. a configuration in which the flow path constricting portion 151 is connected to the illumination optical chamber 100, and the chamber connecting passage 150 expands in a conical tube shape toward the light generation chamber 10). In addition, an enlarged-diameter part 160 is provided at an intermediate position of the chamber connecting passage 150 (i.e. a position near the flow path constricting portion 151 of the chamber connecting passage 150). The enlarged-diameter part 160 has an inner diameter larger than those of portions of the chamber connecting passage 150 that are at opposite sides, respectively, of the enlarged-diameter part 160. The enlarged-diameter part 160 and a plurality (four) of vacuum pumps 170 attached to the enlarged-diameter part 160 are arranged in the same way as in the first embodiment. The differential evacuation system 1-8 arranged as stated above can also provide advantageous effects as in the case of the first embodiment. That is, it is possible to reduce the conductance of the chamber connecting passage 150 by the flow path constricting portion 151, and to sufficiently ensure an optical path diverging in opposite directions away from each other from the point of convergence of light passing through the chamber connecting passage 150 by making the light convergence point coincident with the flow path constricting portion 151. It is also possible to easily install a plurality of vacuum pumps 170 by attaching them to the enlarged-diameter part 160 provided at an intermediate position of the chamber connecting passage 150 and hence possible to increase the differential pressure between the light generation chamber 10 and the illumination optical chamber 100. The differential evacuation system 1-8 also has a plurality of vacuum pumps 170 attached to one side of the enlarged-diameter part 160. Therefore, the vacuum pumps 170 can be installed so as not to project outward, which allows a reduction in the external size of the differential evacuation system 1-8. It should be noted that the vacuum pumps 170 may be attached to the outer peripheral surface of the enlarged-diameter part 160 as in the differential evacuation system 1-5 shown in FIGS. 6 and 7. The differential evacuation system 1-8 arranged in this way is suitable for use in a situation where there is a space in the radial direction of the enlarged-diameter part 160 but there is no much space in the axial direction of the enlarged-diameter part 160 as in the case of the differential evacuation system 1-5. Although some embodiments of the present invention have been described above, the present invention is not limited to the foregoing embodiments but can be modified in a variety of ways without departing from the appended claims and the scope of the technical idea described in the specification and the accompanying drawings. It should be noted that any configuration or structure that offers the operation/working-effect of the invention in this application is within the scope of the technical idea of the invention in this application even if it is not directly mentioned in the specification or the drawings. For example, although in the foregoing embodiments the present invention is used in an exposure apparatus for semiconductor manufacture, the present invention is not limited thereto but may also be used for other applications, e.g. a reflectance measuring device, a wavefront measuring device, a microscope, a shape measuring device, a clinical device, a chemical composition analyzer, a structure analyzer, and so forth. Although the foregoing embodiments use turbomolecular pumps as vacuum pumps, it is also possible to use vacuum pumps of various other structures. Further, various changes may be made to the position and number of enlarged-diameter parts 160 installed and the position and number of vacuum pumps 170 installed, needless to say. For example, vacuum pumps 170 (170-2) may be attached to both the right and left sides of the enlarged-diameter part 160 (160-2). Although the chamber connecting passage 150 used in the foregoing embodiments is in the shape of a conical tube, it is possible to adopt any of various other shapes in place of the conical tube shape, for example, a shape in which a circular cylindrical tube is increased in inner diameter for every predetermined length (i.e. the inner diameter is increased stepwise). In short, the chamber connecting passage 150 may have any shape, provided that its inner diameter gradually increases from the flow path constricting portion 151. Further, although the foregoing embodiments use He gas as an example of buffer gas blown onto the surface of the converging mirror 15 in order to prevent the degradation of the reflectance of the converging mirror 15, the buffer gas used in the present invention is not limited to He gas. It is possible to use any gas (Ar, Ne, etc.) that has a high transmittance for EUV light. It is also possible to use any gas (e.g. HBr, HCl, etc.) that etches Sn adhered to the surface of the converging mirror 15 and that has a high transmittance for EUV light. FIG. 1 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-1. FIG. 2 is a partly sectioned view as seen in the direction of the arrows A-A in FIG. 1. FIG. 3 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-2. FIG. 4 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-3. FIG. 5 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-4. FIG. 6 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-5. FIG. 7 is a partly sectioned view as seen in the direction of the arrows B-B in FIG. 6. FIG. 8 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-6. FIG. 9 is a partly sectioned view as seen in the direction of the arrows C-C in FIG. 8. FIG. 10 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-7. FIG. 11 is a partly sectioned view as seen in the direction of the arrows D-D in FIG. 10. FIG. 12 is a schematic view showing the arrangement of a main part of a differential evacuation system 1-8. 1-1: differential evacuation system 10: light generation chamber 11: plasma 13: nozzle 15: converging mirror 15a: light-passing hole 17: buffer gas introducing tank 18: nozzle 19: transmitting window 21: vacuum pump 23: superconducting magnet 100: illumination optical chamber 101: optical element 103: vacuum pump 150: chamber connecting passage 151: flow path constricting portion 160: enlarged-diameter part 160-2: enlarged-diameter part 170: vacuum pump 170-2: vacuum pump 203: EUV light 1-2: differential evacuation system 1-3: differential evacuation system 1-4: differential evacuation system 1-5: differential evacuation system 1-6: differential evacuation system 25, 25-2: pipe 1-7: differential evacuation system 1-8: differential evacuation system
051679051	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical nuclear power plant includes a nuclear reactor core for producing heat and a steam generator in fluid communication with the nuclear reactor core for generating steam. The steam generator includes inlet and outlet primary nozzles attached to the steam generator. At times it is necessary to perform maintenance in the steam generator. To safely and satisfactorily perform this maintenance, it is prudent first to seal or block the inlet and outlet primary nozzles of the steam generator. Disclosed herein is a foldable nozzle dam having a foldable extrusion-resistant seal or gasket for sealing the primary nozzles of the nuclear steam generator. Before describing the subject matter of the present invention, it is instructive first to generally describe the structure and operation of a typical nuclear reactor and associated steam generator. Therefore, referring to FIG. 1, there is illustrated a nuclear reactor vessel, generally referred to as 10, having a lower portion 20 and a closure head 30 mounted atop lower portion 20. Lower portion 20 houses a nuclear reactor core 40 for producing heat. Reactor vessel 10 is disposed in a reactor cavity 50 that is defined by a reactor vessel enclosure 60. Reactor cavity 50 is partitioned into an upper cavity portion 70 for enclosing closure head 30 and a lower cavity portion 80 sealingly isolated from upper cavity portion 70 for enclosing lower portion 20. Reactor core 40 is surrounded by a primary fluid (e.g., demineralized borated water) circulating through reactor vessel 10 for removing the heat produced by reactor core 40. In addition, the exterior of closure head 30 is surrounded by a refueling pool 90 (e.g., demineralized borated water) substantially filling upper cavity portion 70 for providing a biological shield so that nuclear radiation from reactor core 40 is attenuated during refueling of reactor core 40. Of course, during refueling operations, closure head 30 is removed from lower portion 20 in a manner well known in the art to provide access to reactor core 40. Still referring to FIG. 1, a steam generator, generally referred to as 100 is disposed near reactor vessel 10 for generating steam, as described more fully hereinbelow. Interconnecting reactor vessel 10 and steam generator 100 is a pipe 110 that is in fluid communication with the primary fluid surrounding reactor core 40 and through which pipe 110 the primary fluid is pumped, as shown by the direction of the arrows in FIG. 1. In this regard, a reactor coolant pump 120 is interconnected with pipe 110 for pumping the primary fluid through pipe 110, through reactor core 40 and through steam generator 100. Referring to FIG. 2, there is shown steam generator 100 with parts removed for clarity. Steam generator 100 comprises a vertically-oriented shell 130 defining a cavity 140 therein. Shell 130 has a generally dome-shaped upper shell portion 150, a generally cylindrical hull portion 160 integrally attached to upper shell portion 150 and a generally bowl-shaped lower shell portion or channel head 170 integrally attached to hull portion 160. Disposed in cavity 140 are a plurality of vertically-oriented inverted U-shaped heat transfer tubes 180 for conducting the radioactive primary fluid therethrough. Each U-shaped tube 180 defines a pair of vertical tube leg portions 190a and 190b interconnected by a U-bend tube portion 200 integrally formed therewith. Each tube leg portion 190a and 190b has a pair of open tube ends 210a and 210b, respectively, for passage of the primary fluid therethrough. Moreover, disposed in cavity 140 near lower shell portion 170 is a horizontal tube sheet 220 having a plurality of apertures for receiving and for vertically supporting each open tube end 210a/210b, which open tube ends 210a/210b are suitably attached to tube sheet 220, such as by welding. Referring yet again to FIG. 2, disposed in lower shell portion 170 is a vertical divider plate 230 for dividing lower shell portion 170 into an inlet plenum chamber 240 and an outlet plenum chamber 250. Moreover, formed through lower shell portion 170 and in communication with inlet plenum chamber 240 and outlet plenum chamber 250 are a plurality of relatively small diameter access ports or manway openings 260 (only two of which are shown) for providing access to inlet and outlet plena 240/250 so that maintenance can be performed in steam generator 100. Such maintenance may be to inspect any of the tubes 180 for degradation and/or to repair any degraded tubes 180. Of course, manway openings 260 are capable of being sealingly covered by suitable manway covers and seals (not shown) during operation of steam generator 100. As illustrated in FIG. 2, integrally attached to lower shell portion 170 is a conduit, such as inlet primary nozzle 270, and another conduit, such as outlet primary nozzle 280, in fluid communication with inlet plenum chamber 240 and with outlet plenum chamber 250, respectively. Each of the primary nozzles 270 and 280 has an inside surface 283 defining an open end 286 of diameter larger than the diameter of manway openings 260, the open end 286 defining an annular depending shoulder or rim 288 therearound (see FIG. 4). As shown in FIG. 2, integrally attached to upper shell portion 150 is a feedwater nozzle 290 for passage of non-radioactive secondary fluid or feedwater (i.e., demineralized water) into cavity 140 of steam generator 100. In addition, integrally attached to the top of upper shell portion 150 is a main steam line nozzle 300 for passage of steam therethrough. Moreover, attached to hull portion 260 and horizontally disposed in cavity 140 are a plurality of circular spaced-apart tube support plates 310 (only four of which are shown) having holes therethrough for receiving each tube leg portion 190a/190b so that each tube 180 is laterally supported thereby. Each support plate 310 also has a plurality of unobstructed additional holes therethrough for passage of the non-radioactive secondary fluid. During operation of steam generator 100, the primary fluid, which is heated by reactor core 40, is pumped from reactor core 40, through one segment of pipe 110, through inlet primary nozzle 270 and into inlet plenum chamber 240. The primary fluid then flows through open tube end 210a, through tube 180, out the other open tube end 210b and into outlet plenum chamber 250, whereupon the primary fluid exits steam generator 100 through outlet primary nozzle 280 and is returned by another segment of pipe 110 to reactor core 40. As the primary fluid flows through tubes 180, secondary fluid simultaneously enters cavity 140 through feedwater nozzle 290 to surround tubes 180. It will be appreciated that as the primary fluid flows through tubes 180, it gives up its heat to the secondary fluid surrounding tubes 180. A portion of the secondary fluid surrounding heat transfer tubes 180 is converted to steam which rises upwardly to exit steam generator 100 through main steam line nozzle 300. The steam is then transported to a turbine-generator (not shown) for producing electricity in a manner well known in the art of steam-powered electricity production. Such a typical nuclear steam generator is more fully disclosed in U.S. Pat. No. 4,079,701 entitled "Steam Generator Sludge Removal System" issued Mar. 21, 1978 to Robert A.l Hickman et al., the disclosure of which is hereby incorporated by reference. Referring briefly to FIG. 3, there is shown the subject matter of the present invention, which is a circular foldable nozzle dam 320 having an extrusion-resistant seal or gasket, nozzle dam 320 being disposed in inlet plenum chamber 240 and across open end 286 of inlet primary nozzle 270 to block or seal inlet primary nozzle 270, as more fully described hereinbelow. It will be appreciated that although nozzle dam 320 is shown disposed in inlet plenum chamber 240 and across the open end of inlet primary nozzle 270, nozzle dam 320 may also be disposed in outlet plenum chamber 250 and across the open end of outlet primary nozzle 280 to block or seal outlet primary nozzle 280. Thus, although the description of the invention refers to sealing or blocking inlet primary nozzle 270, it will be understood that the invention may be used to seal or block outlet primary nozzle 280 as well. Turning now to FIGS. 4 and 5, a generally annular ring member or bracket 330 is permanently sealingly attached, such as by welding, to rim 288 of inlet primary nozzle 270, for reasons described more fully hereinbelow. Bracket 330 is permanently attached to rim 288 and remains attached to rim 288 as steam generator 100 is operated (i.e., generates steam) in the manner disclosed hereinabove. For this purpose, annular bracket 330 defines a generally circular opening 340 centrally transversely therethrough for passage of the primary fluid during operation of steam generator 100. Bracket 330 has a top surface 343 thereon having a multiplicity of grooves 346 (only two of which are shown in FIG. 5) formed therein for reasons provided hereinbelow. Grooves 346 provide a roughened top surface 343 for reasons more fully described hereinbelow. Moreover, bracket 330 may be "INCONEL", stainless steel or the like, to resist stress corrosion cracking during operation of steam generator 100. Bracket 330 is preferably fabricated of stress corrosion resistant material because stress corrosion cracking of bracket 330 may lead to creation of fluid flow paths therethrough such that inlet primary nozzle 270 is not sealed when nozzle dam 320 is installed in the manner more fully described hereinbelow. More specifically, the "INCONEL" material may comprise by weight approximately 76.0% nickel, 0.08% carbon, 0.5% manganese, 8.0% iron, 0.008% sulfur, 0.25% copper and 15.5% chromium. Bracket 330 also has an integral periphery portion 350 extending circumferentially therearound. The bottom of periphery portion 350 of bracket 330 is sealingly attached to rim 288, such as by welding. Bracket 330 may also have a slot 355 (see FIG. 8) extending around the bottom thereof for pressure testing the soundness of the weldment that sealingly attaches the bottom of periphery portion 350 to rim 288. In this regard, a source of pressurized gas (not shown) is connected to a channel 357 that is in gas communication with slot 355. The pressurized gas (e.g., nitrogen) is passed through channel 357 and flows into slot 355. If the weldment is not sound, the gas will leak from slot 355 and across the bottom of bracket 330 and will be detected by means known in the art. Alternatively, if the weldment is not sound, the gas will leak from slot 355 and a maximum stable or equilibrium value for the gas pressure will not be obtainable. If the weldment is sound, the gas will not leak from slot 355 and a plug (not shown) will be welded into channel 357 to permanently seal channel 357. As shown in FIGS. 4 and 5, formed through periphery portion 350 are a plurality of spaced-apart threaded transverse holes 360 disposed circumferentially around periphery portion 350 at predetermined intervals. In addition, bracket 330 may be formed of a plurality of mating sections, such as half section 370a and 370b, sealingly joined, such as by welding, at their interface 380. In one embodiment of the invention, bracket 330 is formed of section 370a and 370b in order to pass each section 370a/370b separately through the relatively small diameter manway 260 and yet dispose the assembled sections 370a/370b that comprise bracket 330 completely circumferentially around open end 286 of inlet primary nozzle 270. Bracket 330 provides a foundation or support means for supporting nozzle dam 320, as described in more detail hereinbelow. Referring to FIGS. 6, 7, 17 and 18, mounted atop bracket 330 is foldable nozzle dam 320 for sealingly covering opening 340 of bracket 330. As described in more detail hereinbelow, nozzle dam 320 is foldable for passing through the relatively small diameter manway 260 and unfoldable for being disposed completely across opening 340 of bracket 330. In this regard, nozzle dam 320 comprises a generally arcuate-shaped first wing or first side section 390a hingedly connected by a pair of hinge assemblies, generally referred to as 400, to a generally arcuate-shaped second wing or second side section 390b. A handle 395, which is adapted to be grasped by hand or by a suitable tool (not shown), is attached to each side section 390a and 390b for outwardly and inwardly pivoting side sections 390a and 390b about hinge assembly 400. In use, side sections 390a and 390b are capable of being pivoted about hinge assembly 400 such that they are deployable in the same plane with respect to each other in order to cover opening 340. Each side section 390a and 390 b defines a generally rectangular cut-out 405 (best seen in FIG. 16) open on one side for maneuvering nozzle dam 320 through manway 260. As shown in FIGS. 6, 7, 8 and 8A, each side section 390a and 390b defines an integral semi-circular periphery portion 410 having a plurality of spaced-apart smooth bores 420 therethrough. Bores 420 are formed such that they are capable of being coaxially aligned with threaded holes 360 of bracket 330, for reasons provided immediately hereinbelow. Each bore 420 is capable of matingly receiving therethrough clamping means, such as an externally threaded elongated shank portion 430 belonging to a fastener or bolt 440, for removably fastening or bolting nozzle dam 320 to bracket 330. Each bolt 440 has a bolt head 450 integral therewith so that bolt 440 may be turned to threadably engage hole 360 for tightly connecting nozzle dam 320 to bracket 330. Moreover, interposed between periphery portion 410 and bolt head 450 is an adjustable positioning block 460 connected to periphery portion 410 by a shoulder screw 470 and having a threaded bore therethrough for threadably receiving bolt 440 to connect nozzle dam 320 to bracket 330. The adjustable feature of positioning block 460 allows it to align bolt 440 with bore 420 and hole 360. Each positioning block 460 is adjustable in the sense that it can be rotated in a 360.degree. circle about shoulder screw 470, as shown by the dotted circular arrow in FIG. 8A, and moved laterally with respect to shoulder screw 470, as shown by the straight solid arrow in FIG. 8A. In addition, as best seen in FIG. 8, disposed between positioning block 460 and bolt head 450 may be a set of leaf springs 480 for longitudinally tensioning bolt 440 so that bolt 440 snugly intimately engages the threads of hole 360. Referring again to FIGS. 6 and 7, a generally rectangular center section 490 is matingly disposed in opening 405 defined by side section 390a and 390b for completely covering opening 405, center section 490 having integral arcuate-shaped end portions 500 capable of being bolted to bracket 330 by a plurality of spaced-apart bolts 505. Each arcuate-shaped end portion 500 has the same radius as the radius of side sections 390a and 390b. When center section 490 is bolted to bracket 330 and to side sections 390a and 390b, nozzle dam 320 assumes a rigid generally circular and planar configuration for completely covering opening 350 of bracket 330. Thus, nozzle dam 320 functions as a cover plate for covering opening 350 of bracket 330. The configuration of nozzle dam 320, when fully assembled, is sufficiently structurally sound to block, the column of water present in nozzle 270 or 280 during reactor refueling operations. Moreover, in the preferred embodiment of the invention, a handle 510 having a hole 520 therethrough extends along each longitudinal side of center section 490 to provide means for removably disposing center section 490 in opening 405. As best seen in FIGS. 7, 8, 8B and 8C, interposed between top surface 343 of bracket 330 and nozzle dam 320 is extrusion-resistant seal means, such as a foldable extrusion-resistant seal member or gasket 530, for providing a fluid-tight seal between nozzle dam 320 and bracket 330 so that fluid will not pass through opening 340 of bracket 330. Of course, it will be appreciated that sealing opening 340 in this manner also seals inlet primary nozzle 270. As disclosed in more detail hereinbelow, seal member 530 has an integral periphery portion 540 therearound having a plurality of spaced-apart transverse apertures 550 therethrough for receiving shank portion 430 of each bolt 440 and 505. As disclosed hereinabove, sections 390a, 390b and 490 comprising nozzle dam 320 are drawn toward top surface 343 of bracket 330 as bolts 440 and 505 pass through bore 420 and threadably engage hole 360. Bolts 440 and 505 may be torqued to a value of approximately 175.+-.25 foot-pounds force so that bolts 440/505 are neither undertorqued nor overtorqued. As sections 390a, 390b and 490 are drawn toward bracket 330, a compressive force will act perpendicularly on each opposing face or side of seal member 530 because seal member 530 is interposed between sections 390a, 390b, 490 and bracket 330. This compressive force acting perpendicularly against each side of seal member 530 will tend to cause aperture 550 of seal member 530 to extrude laterally outwardly away from shank portion 430 of bolt 440 and bolt 505 and assume a generally oval shape. Such extrusion of aperture 550 laterally away from shank portion 430 as sections 390a, 390b and 490 are tightly connected to bracket 330 will tend to enlarge the annular gap or fluid flow path defined by aperture 550 that surrounds shank portion 430 (see FIG. 8C). Such enlargement of the gap defined by aperture 420 will tend to decrease the surface area "A" to a smaller area "A'", which area "A" is available for sealing, between bracket opening 340 and aperture 550 (see FIGS. 8B and 8C). Excessive extrusion may result in a portion of aperture 550 overlapping opening 340 such that any fluid present in opening 340 will easily flow through that portion of aperture 550 overlapping opening 340. This is undesirable because such enlargement of the gap or flow path will compromise the ability of seal member 530 to perform its intended function of providing a nozzle dam 320 that is fluid-tight. Thus, according to the invention, seal member 530 is configured to be extrusion-resistant so that seal member 530 will not excessively laterally extrude away from bolts 440 and 505 in a manner that excessively enlarges the fluid flow path defined by apertures 550 surrounding bolts 440 and 505, as described in more detail hereinbelow. It should be understood that aperture 550 may experience some limited extrusion laterally away from shank portion 430 as sections 390a, 390b and 490 are tightly connected to bracket 330. However, such limited extrusion will not be sufficient to cause any portion of aperture 550 to overlap opening 340. Turning now to FIGS. 9, 10, 11, and 12, seal member 530 comprises a plurality of layers laminated or bonded together. In the preferred embodiment of the invention, seal member 530 comprises a generally annular first layer 560a. First layer 560a is sealingly bonded, such as by a suitable adhesive, to the underside of a generally circular second layer 560b. Second layer 560b is sealingly attached, such as by a suitable adhesive, to periphery portion 410 of first side section 390a and to periphery portion 410 of second side section 390b of nozzle dam 320. In addition, second layer 560b is circular and extends across the diameter of nozzle dam 320 for covering opening 405 so that fluid cannot pass through opening 405. First layer 560a, which may be EPDM (ethylene propylene diene monomer) rubber, has a Shore A durometer hardness of between approximately 40 and 60, and preferably a durometer hardness of approximately 50. Second layer 560b, which also may be EPDM rubber, has a Shore A durometer hardness of between approximately 60 and 80, and preferably a durometer hardness of approximately 70. The dual hardness of seal member 530 allows it to be extrusion-resistant and also allows it to intimately engage top surface 343 of bracket 330 for creating a seal between nozzle dam 320 and bracket 330. It will be appreciated that the relatively harder material of second layer 560b resists extrusion and the relatively softer material of first layer 560a assists in maintaining seal member 530 in intimate sealing engagement with top surface 343. As best seen in FIG. 12, first layer 560a is relatively soft for intimately engaging the grooves 346 formed in top surface 343 of bracket 330. The intimate engagement of first layer 560a with grooves 346 provides a multiplicity of obstructions or ridges that oppose the migration or leakage of the primary fluid along the interface of first layer 560a and top surface 343 of bracket 330. Such ridges will tend to increase the pressure drop of any fluid that would tend to migrate or leak across the interface, thereby reducing the rate of or eliminating such leakage. That is, if the primary fluid should tend to migrate along this interface, the pressure of the fluid at the interface will tend to drop as it traverses grooves 346. Such a pressure drop will tend to further limit or eliminate the migration or leakage at the interface because the pressure driving the fluid along the interface will decrease as the fluid migrates or leaks along the interface. Moreover, the intimate frictional engagement of first layer 560a and grooves 346 assists in resisting extrusion and in maintaining seal member 530 in sealing intimate engagement with top surface 343 of bracket 330 so that the fluid path defined by aperture 550 surrounding shank portion 430 is not enlarged as nozzle dam 320 is bolted to bracket 330. Referring now to FIGS. 13 and 14, there is shown an alternative embodiment of seal member 530, referred to as seal member 580, comprising a plurality of molded regions 590a/590b rather than laminated layers 560a and 560b. In this alternative embodiment of the invention, seal member 580 comprises a generally annular first region 590a. First region 590a is sealingly molded, such as by a press-cure process, to the underside of a generally circular second region 590b. Second region 590b is sealingly attached, such as by a suitable adhesive, to periphery portion 410 of first side section 390a and to periphery portion 410 of second side section 390b of nozzle dam 320. In addition, second region 590b extends across the diameter of nozzle dam 320 for covering opening 405 defined by side sections 390a, 390b so that fluid cannot pass through opening 405. First region 590a, which may be EPDM rubber, has a Shore A durometer hardness of between approximately 40 and 60, and preferably a durometer hardness of approximately 50. Second region 590b, which may be EPDM rubber, has a Shore A durometer hardness of between approximately 60 and 80, and preferably a durometer hardness of approximately 70. Referring briefly to FIG. 15, yet another embodiment of seal member 530 is shown. In this alternative embodiment, seal member 530, including layers 560a and 560b associated therewith, has truncated sides 600 to easily accommodate hinge assembly 400 (see FIGS. 17 and 18). Referring to FIGS. 16, 17, and 18, side sections 390a and 390b, which are pivotably hingedly connected together, are there shown in a folded state to pass through the relatively small diameter of manway opening 260 of steam generator 100. As disclosed hereinabove, the diameter of open end 286 of inlet primary nozzle 270 may be larger than the diameter of manway opening 260. Thus, nozzle dam 320 is foldable to pass through manway opening 260 and unfoldable to be disposed completely across opening 340 of bracket 330, such that it also covers open end 286 of inlet primary nozzle 270. Moreover, seal member 530 or 580 is also foldable because seal member 530 or 580 is sealingly permanently attached to foldable nozzle dam 320 in the manner previously described. As best seen in FIGS. 17 and 18, hinge assembly 400 includes a pivot pin 610 for allowing first side section 390a and second side section 390b of nozzle dam 320 to pivot thereabout. As disclosed hereinabove, first side section 390a, second side section 390b and center section 490 are capable of being securely locked in the same transverse plane with respect to each other to cover opening 286 of bracket 330 (as best seen in FIG. 7) when center section 490 is bolted to side sections 390a and 390b by bolts 505. By way of example only and not by way of limitation, steam generator manway opening 260 may have a diameter of approximately 16 inches and open end 286 of inlet primary nozzle 270 (or outlet primary nozzle 280) may have a diameter of approximately 38 inches. Thus, the diameter of manway opening 260 is substantially smaller than the diameter of open end 286 of inlet primary nozzle 270. Moreover, the outside diameter of bracket 330 may be approximately 41.5 inches and the inside diameter of bracket 330 may be approximately 38.5 inches. Thus, in the preferred embodiment, bracket 330 has an inside diameter slightly greater than the diameter of open end 286 for surrounding open end 286. When mounted atop bracket 330, the diameter of nozzle dam 320 may be roughly 42 inches in its unfolded state. However, in its folded state, each side section 390a/390b generally defines a half-circle having a radius of roughly 21 inches and has cut-out 405 for allowing nozzle dam 320 to be maneuvered through manway opening 260. The annular first layer 560a of laminated seal member 530, which intimately engages top surface 343 of bracket 330 and which is adhesively attached to second layer 560b, has an inside diameter of approximately 34 inches and an outside diameter of roughly 42 inches in the preferred embodiment. The second layer 560b of laminated seal member 530, which is adhesively attached to sections 390a and 390b, has a diameter of roughly 42 inches in the preferred embodiment. Moreover, the first layer 560a may have a transverse thickness of approximately 0.188 inches and the second layer 560b may have a transverse thickness of approximately 0.125 inches resulting in a laminated seal member 530 having a total transverse thickness of approximately 0.313 inches. In the alternative embodiment of the invention, the first region 590a of molded seal member 580, which intimately engages top surface 343 of bracket 330, has an inside diameter of approximately 34 inches and an outside diameter of approximately 42 inches. The second region 590b of molded seal member 580 has a diameter of roughly 42 inches in the preferred embodiment. The transverse thickness of molded seal member may be approximately 0.313 inches. Moreover, the threaded holes 360 in bracket 330 may have a diameter of approximately 0.750 inch and the smooth bores in nozzle dam 320 may have a diameter of approximately 0.937 inch. The threaded bore in each positioning block 460 has a diameter of approximately 0.750 inch. The apertures in seal member 530 (or seal member 580) may have a diameter of approximately 0.937 inch. OPERATION In use, bracket 330 cooperates with nozzle dam 320 and seal member 530 or 580 to sealingly block or cover open end 286 of primary nozzles 270 or 280 so that maintenance can be simultaneously performed in steam generator 100 as reactor core 40 is refueled. In this regard, reactor core 40 is first shut down and the level of water in refueling pool 90 is drained, in a manner well understood in the art, to a level that is below the elevation of inlet and outlet primary nozzles 270/280. It will be appreciated that draining refueling pool 90 to a level that is below the elevation of inlet and outlet nozzles 270/280 also drains heat transfer tubes 180 and plenum chambers 240/250. Next, the manway covers (not shown) are removed from the relatively small diameter manway openings 260 for providing access to the steam generator plena (e.g., inlet plenum chamber 240). At this point, first side section 390a and second side section 390b are folded inwardly toward each other about pivot pin 610, which belongs to hinge assembly 400, so that sections 390a/390b can be maneuvered through the relatively small diameter manway opening 260. Once inside inlet plenum chamber 240, sections 390a/390b are unfolded outwardly to an outstretched configuration, using handles 395, for mounting sections 390a/390b on bracket 330 to cover opening 340 of bracket 330. Of course, it will be understood that bracket 330 will have been previously sealingly attached to open end 286 of nozzle 270. In this regard, each section 370a/370b of bracket 330 will have been separately passed through manway opening 260 and matingly attached together, such as by welding, at the interface 380 thereof. Alternatively, bracket 330 may be a unitary one-piece member sealingly attached to open end 286 of nozzle 270 during manufacture of steam generator 100. Sections 390a/390b are mounted atop bracket 330, using handles 395, such that smooth bores 420 of sections 390a/390b are roughly aligned with threaded holes 360 of bracket 330. Adjustable positioning block 460 is caused to pivot about shoulder screw 470 and/or moved laterally with respect to shoulder screw 470 until bolt 440 is coaxially aligned with hole 360. Once bores 420 are coaxially aligned with holes 360, bolts 440 are caused to pass through bores 420 and threadably engage holes 360 for removably clamping or connecting sections 390a/390b to bracket 330. Next, center section 490 is passed through manway opening 260 and matingly disposed, using handles 510, to cover cut-outs 405 defined by side sections 390a/390b. At this point, center section 490 is attached to side sections 390a/390b by bolts 505 that threadably engage holes 360. Once sections 390a, 390b and 490 are properly aligned, all bolts are uniformly torqued in a controlled manner to predetermined torque values. In this manner, side sections 390a/390b and center section 490 form the rigid circular nozzle dam 320 used for covering opening 340 of bracket 330. As described hereinabove, interposed between nozzle dam 320 and bracket 330 is extrusion-resistant seal member 530 or 580, which is adhesively attached to side section 390a/390b, for providing a fluid-tight seal between nozzle dam 320 and bracket 330. As sections 390a, 390b and 490 comprising nozzle dam 320 are drawn toward top surface 343 of bracket 330 when bolts 440 and 505 threadably engage holes 360, a compressive force will act perpendicularly on each opposing face or side of seal member 530 because seal member 530 is interposed between sections 390a, 390b, 490 and bracket 330. This compressive force acting perpendicularly against each side of seal member 530 will tend to cause aperture 550 of seal member 530 to extrude laterally outwardly away from shank portion 430 of each bolt 440 and bolt 505. Such extrusion of aperture 550 laterally away from shank portion 430 as sections 390a, 390b and 490 are tightly clamped to bracket 330 will tend to enlarge the annular gap or fluid flow path surrounding shank portion 430. Such enlargement of the gap will tend to decrease the surface area "A", which is available for sealing, between bracket opening 340 and aperture 420. Excessive extrusion may result in a portion of aperture 420 overlapping opening 340 such that any primary fluid present in opening 340 will easily flow through that portion of aperture 420 overlapping opening 340. This is undesirable because enlargement of such a flow path will compromise the ability of seal member 530 to perform its intended function of providing a nozzle dam 320 that is fluid-tight. Thus, according to the invention, the extrusion-resistant configuration of seal member 530 results in a seal member 530 that will resist lateral extrusion away from bolts 440 and 505 that would otherwise enlarge the fluid flow path surrounding bolts 440 and 505. More specifically, first layer 560a is relatively soft for intimately engaging the grooves 346 formed in top surface 343 of bracket 330. The engagement of first layer 560a with grooves 346 of bracket 330 assists in creating a fluid-tight seal in the manner previously described. Therefore, it will be appreciated that the relatively softer material of first layer 560a (or first region 590a) assists in maintaining seal member 530 in intimate sealing engagement with bracket surface 343 as the relatively harder material of second layer 560b (or second region 590b) resists extrusion of seal member 530 laterally away from bolt 440 (or bolt 505). In addition, as disclosed hereinabove, the intimate engagement of first layer 560a with grooves 346 provides a multiplicity of obstructions or ridges that oppose migration or leakage of the primary fluid along the interface of first layer 560a and top surface 343 of bracket 330. In this regard, such ridges will tend to increase the pressure drop of any fluid that would migrate across the interface, thereby reducing the rate of such leakage. Moreover, it will be appreciated that the relative softness of first layer 560a or first region 590a will allow it to fill any indentations or imperfections in top surface 343 of bracket 330 to further enhance the sealing of nozzle dam 320. In addition, it should also be understood that apertures 550 are punched through seal member 530 or 580 after seal member 530 or 580 is mounted on the nozzle dam assembly such that apertures 550 will precisely align with their associated bolts. After nozzle dam 320 is suitably installed in inlet primary nozzle 270 in the manner disclosed hereinabove, upper cavity portion 70 of reactor cavity 50 is refilled with water and closure head 30 is removed, in a manner well known in the art, to provide access to reactor core 40 for refueling reactor core 40. However, as upper cavity portion 70 is refilled, the primary fluid will not rise into inlet plenum chamber 240 or outlet plenum chamber 250 because nozzle dam 320 seals or blocks openings 286 of primary nozzles 270/280. At this point, maintenance may be simultaneously performed in steam generator plena 240/250 as reactor core 40 is refueled. After reactor core 40 is refueled and after maintenance is performed in steam generator 100, nozzle dam 320 is removed from steam generator 100 substantially in the reverse order of its installation in steam generator 100. Although the invention is fully illustrated and described herein, it is not intended that the invention as illustrated and described be limited to the details shown, because various modifications may be obtained with respect to the invention without departing from the spirit of the invention or the scope of equivalents thereof. For example, bracket 330 may be deleted and nozzle dams 320 removably clamped or connected directly to rim 288 of nozzles 270/280. In such a modification of the invention, rim 288 will have a prepared mating surface and threaded holes therein to receive bolts 440. A further modification to the present invention would be to eliminate the grooves 346 in bracket 330, if desired. An additional modification to the present invention would be to provide a seal member 530 made of extrusion-resistant other than homogeneous EPDM. Yet another modification to the present invention would be to provide a seal member comprising relatively soft EPDM rubber but having a multiplicity of extrusion-resistant "NYLON" or like fibers homogeneously dispersed or specifically located therein. Moreover, although the invention was conceived during an investigation directed towards a foldable nozzle dam having a foldable extrusion-resistant seal or gasket for sealing the open ends of steam generator primary nozzles, the invention may have other uses, such as to seal the open ends of any similar conduit. Therefore, what is provided is a foldable nozzle dam having a foldable extrusion-resistant seal or gasket for sealing conduits, such as the primary nozzles of a nuclear steam generator.
042119286	description	The storage unit 20 shown in FIGS. 2 and 4-8, inclusive, has a mass 23 of radiation-shielding material through which a straight tube 24 provides a straight passage 25. At a first end the tube 24 is fitted with a coupling assembly, generally indicating by reference 30, for manipulating means. This coupling assembly may take any form that is suitable for safety and operational requirements that are current at the time of use; for example, as shown in one of the above-referenced U.S. Pat. Nos. 3,147,383 or 3,593,594. The coupling assembly 30 which is illustrated is described and claimed in a copending joint application of one of the present inventors and another, Ser. No. 964078, filed concurrently with this application, and assigned to the same assignee as the present application. At a second end the tube 24 is fitted with a shutter 40 having a hole 42 through it which can be placed in register with the passage 25. The shutter 40 is movable transverse to the passage 25, between first and second limits. In FIGS. 2 and 5, the shutter is shown in a first limit, blocking the passage. In FIG. 7, the shutter is shown in the second limit, with the hole 42 in register with the passage 25. Radioactive material 31 (FIG. 3) is housed in a capsule 32 which has a pivotal member 33 connected to it via a pin 34. The capsule is connected by a ball joint 36 to the leader 11, at the other end of which is the female part 98 of the cable connector 9. The leader 11 is made of a chain of cylindrical members 37 of the same diameter all coupled together via ball-joint links 38 having the same diameter. The cable connector has a portion 39 of reduced diameter for locking engagement in the coupling assembly 30 when the radioactive material is to be held in the stored position. The latch portion 39 is locked in a slot (not shown) in a block 31 that is slidably retained in the coupling assembly. Details of the locking mechanism are set forth in the above-identified co-pending application, and forming no part of the present invention will not be repeated in this specification. Forward of the leader 11, toward the shutter 40, the capsule 32 is connected via a cylindrical member 37 and ball-joint link 38 to a shutter-control plug 44 having a diameter which is larger than the diameter of the cylindrical members 37. The tube 24 is enlarged internally at a portion 46 adjacent the shutter, and stops short of the shutter. A shutter latch tube 48 fits telescopically within the enlarged portion 46, for slidable motion toward and away from the shutter. The latch tube 48 has a portion at the end 50 confronting the shutter which is enlarged in diameter externally to essentially the same outer diameter as the straight tube 24, and a coil spring 52 surrounds the latch tube between a shoulder 54 on the enlarged end 50 and the confronting end 56 of the straight tube 24. At the inner end 58 remote from the shutter 40 the latch tube has a portion of reduced inner diameter providing a shoulder 60 against which the inner end 62 of the shutter control plug 44 can bear. When the radioactive material 31 is returned to the stored position, as by manipulating the crank assembly 7 to withdraw it back from the snout 8, the shutter control plug 44 can be operated to pull the shutter latch tube 48 back from the shutter against the action of the spring 52, by continuing to apply cranking force in the direction of withdrawal. The shutter 40 is slidably mounted in its support 66 and is urged by springs 68 to a position in its first limit, shown in FIGS. 2, 4 and 5. Whenever the latch tube 48 is pulled away from the shutter the shutter 40 is free to take up a position in its first limit. The shutter can be placed in its second limit, shown in FIG. 7, by pulling (upward in the drawings) on the knob 70, which is connected to the shutter by a rod 72. When the shutter is open the knob 70 extends up above the main body of the storage unit, and is shown in dashed line in FIG. 2, acting as a tell-tale. A safety feature is provided for preventing movement of the shutter to the open limit when the guide tube 6C for the snout 8 is not coupled to the storage unit. A connector 74 for that guide tube is represented by dashed lines in FIGS. 2, 5, 6 and 7. This connector couples to a nipple 76 which is a permanent part of the storage unit and is internally bored to provide a continuation 78 of the passage 25. The shutter 40 is fitted with a latch-pin 80 having a stem 82 (shown in FIG. 6) which extends through a hole 67 forward of the shutter housing 66 where it can be pushed by the connector 74 as it is fitted to the nipple 76. The latch pin has a main body that is urged by a spring 84 into a recess 86 in the back wall of the shutter. A slot 88 in the shutter provides a slide-way for the stem 82 when the latch pin is pushed back from the recess 86. When the guide tube 6C is connected, then the shutter 40 can be opened. When the shutter is opened, by pulling up on the knob after connecting the guide tube coupler 74 to the nipple 76, the hole 42 is moved into register with the passage 25. An annular recess 90 around the hole in the back wall of the shutter has an internal diameter large enough to accept the enlarged end 50 of the shutter latch tube 48. To reduce sliding friction against the back wall of the shutter that end is desirably internally bevelled. The spring 52 urges the latch tube into the recess 90. To avoid permanently compressing the spring 52 with the shutter control member 44 when the capsule 32 is put in the stored position, cranking force at the crank assembly is preferably relaxed after the latch tube 48 has been pulled away from the shutter and the shutter has moved to the closed position, and before the coupler 9 is uncoupled and the leader 11 locked in the coupling assembly 10 of the system. The latch portion 39 of the coupler portion 98 shown in FIG. 2 is long enough to slide in the direction of the passage 25 when the coupler is locked in the coupling assembly 30.
	description	1. Field of the Invention The present invention relates to a fuel assembly for a small-sized nuclear reactor using a coolant such as a liquid metal, and particularly, to a fuel assembly including a plurality of grids provided to a fuel bundle. 2. Related Art Generally, in the nuclear reactor of the type mentioned above, a fuel assembly is supported in a reactor core while being attached to a support member. In a nuclear reactor using a coolant such as a liquid metal, the coolant is circulated around a plurality of fuel pins included in the fuel assembly supported in the reactor core. In this case, if the nuclear reactor is small-sized, the fuel assembly is configured to store the fuel pins in a wrapper tube to enable the circulation of the coolant with no need for a drive source. The wrapper tube includes an entrance nozzle at a lower end thereof for introducing the coolant, and an operation handling head at an upper end thereof. The wrapper tube includes therein grids for supporting the fuel pins in the radial direction of the wrapper tube, and liner tubes inserted in the wrapper tube for fixedly holding the respective grids in the axial direction of the wrapper tube. The intervals in the radial direction of the fuel pins are kept by the grids. Meanwhile, the intervals in the axial direction of the grids are kept by a tie rod, the liner tubes, or the like (see Japanese Unexamined Patent Application Publication No. HEI 6-174882, for example). With reference to FIGS. 8 to 11, a conventional example of a fuel assembly 100 will be described. In FIGS. 8 and 9, a plurality of fuel pins 101 are incorporated in a wrapper tube 103, with the pin intervals in the radial direction of the fuel pins 101 kept by grids 102. Each of the fuel pins 101 is fixed at a lower portion thereof by a lower pin support plate 105 and at an upper portion thereof by an upper pin support plate 106. From a coolant inlet 108 of an entrance nozzle 104 provided at a lower position, the coolant such as a liquid metal flows in and moves upward. Then, the coolant flows out from a coolant outlet 109 of a handling head 107. In the thus configured fuel assembly 100, ring-shaped grids are used as the grids 102 having a low pressure drop. Further, as illustrated in FIG. 10, liner tubes 110 each formed by a thin hexagonal tube are provided on the inner surface side of the wrapper tube 103, i.e., outside a fuel bundle such that the liner tubes 110 and the grids 102 are alternately stacked. Thereby, the intervals in the axial direction of the grids 102 are kept. Since the flow passage area around the fuel bundle is large, the cladding temperature of the fuel in a central area of the fuel bundle becomes relatively high. Therefore, there arises a need to keep the cladding temperature equal to or lower than a cladding temperature limit, and thus the thermal efficiency is decreased. To suppress this phenomenon, as illustrated in FIG. 11, there has been known a technique of providing the liner tubes 110 with peripheral flow preventing projections, which are formed by bending peripheral walls of the liner tubes 110. As described above, there has been proposed in the conventional fuel assembly to provide the liner tubes with the peripheral flow preventing projections formed by bending the peripheral walls of the liner tubes, for example. According to the proposal, however, it is not necessarily easy to sufficiently suppress the peripheral flow. To suppress the peripheral flow in the fuel assembly as much as possible, it is necessary to reduce the flow passage area formed between the wrapper tube and peripherally disposed ones of the fuel pins to be approximately equal to the flow passage area surrounded by other ones of the fuel pins disposed toward the center from the peripherally disposed ones of the fuel pins. Specifically, it is necessary to secure the flow passage area formed between the wrapper tube and the peripherally disposed fuel pins to be approximately equal to the flow passage area surrounded by other ones of the fuel pins disposed in a triangular array inside the peripherally disposed ones of the fuel pins. The present invention was conceived in light of the above-described circumferences, and an object of the present invention is to provide a fuel assembly which achieves a high thermal efficiency and a stable lifetime performance by preventing an unnecessary flow of a coolant in a peripheral flow passage formed between peripherally disposed fuel pins and a wrapper tube and by causing the coolant to effectively flow toward interiorly disposed fuel pins. To achieve the above object, the present invention provides a fuel assembly charged in a reactor core of a nuclear reactor using a liquid metal as a coolant. The fuel assembly includes a wrapper tube, grids, and peripheral flow suppressing members. The wrapper tube, which is vertically disposed, includes an entrance nozzle at a lower end thereof for introducing the coolant and an operation handling head at an upper end thereof, and stores therein a plurality of fuel pins. The grids support the plurality of fuel pins in the wrapper tube in the radial direction of the wrapper tube. The peripheral flow suppressing members, formed by a plurality of blocks, are inserted in the wrapper tube to fixedly hold the grids in the axial direction of the wrapper tube. The peripheral flow suppressing members suppress a flow of the coolant, and are disposed in a peripheral flow passage extending between peripherally disposed ones of the fuel pins and the wrapper tube over a length corresponding to a heat generation length, which is a length range in the axial direction of the fuel pins storing a radioactive fuel material. In a preferable embodiment of the fuel assembly according to the present invention, each of the peripheral flow suppressing members may be formed by blocks, which are disposed in the peripheral flow passage, and each of which has such a cross section that reduces the flow passage area of the peripheral flow passage to be approximately equal to the flow passage area of a region on the center side from the peripherally disposed ones of the fuel pins. Further, it is preferable that a plurality of the blocks are stacked along the axial direction of the grids, and that groups of the stacked blocks keep relative positions in the axial direction of the grids. Furthermore, the blocks may be disposed in a ring shape to face the inner circumferential surface of the wrapper tube, and a peripheral wall of each of the blocks may be formed with a coolant circulation hole for communicating a coolant flow passage on the inner circumferential side of the block with the peripheral flow passage on the outer circumferential side of the block. The fuel assembly may further include sleeves disposed to cover outer circumferential portions of the peripherally disposed ones of the fuel pins outside the range of the heat generation length, and to keep relative positions between the grids. A lower portion of the handling head may be provided with a spring for pressing down one of the sleeves, and downward pressing force of the spring may press and hold the grids and the peripheral flow suppressing members from the above with elastic force via the sleeve. According to the present invention having the above-described characteristics, the peripheral flow suppressing members are provided in the space extending between the peripherally disposed ones of the fuel pins and the wrapper tube over the length corresponding to the major heat generation length of the fuel pins. Thereby, it is possible to suppress the unnecessary flow of the coolant from being formed in an outer circumferential area in the fuel assembly and also possible to cause the coolant to effectively flow toward the interiorly disposed fuel pins. Accordingly, it is possible to provide a fuel assembly having a high thermal efficiency and a stable lifetime performance. Further characteristics of the present invention will be made clearer from the following description of embodiments with reference to the attached drawings. An embodiment of a fuel assembly according to the present invention will be described below with reference to FIGS. 1 to 7. A schematic overall configuration of the fuel assembly will be first described with reference to FIG. 1. FIG. 1 is a cross-sectional view illustrating an overall configuration of a fuel assembly 10. The fuel assembly 10 is configured to include an entrance nozzle 4 at a lower end of a vertically disposed wrapper tube 3 for introducing a coolant, to include an operation handling head 7 at an upper end of the wrapper tube 3, and to store a plurality of fuel pins 1 in the wrapper tube 3. The pin intervals of the fuel pins 1 in the radial direction of the wrapper tube 3 are kept by grids 2, and each of the fuel pins 1 is fixedly supported at a lower end portion thereof by a lower pin support plate 5 and at an upper end portion thereof by an upper pin support plate 6. The coolant such as a liquid metal flows in from a coolant inlet 8 of the entrance nozzle 4 and moves upward. Then, the coolant flows out from a coolant outlet 9 of the handling head 7. The above-described configuration further includes peripheral flow suppressing members 12 for suppressing the flow of the coolant in a peripheral flow passage 11, which extends between peripheral fuel pins 1a and the wrapper tube 3 over a length corresponding to a major heat generation length of the fuel pins 1. In the above, the major heat generation length refers to a length range in the axial direction of the fuel pins 1, which stores a radioactive fuel material. In the example illustrated in FIG. 1, the range of the major heat generation length corresponds to the range from the lower pin support plate 5 to a grid 2a disposed at an approximately intermediate height position of the wrapper tube 3. In the range from the grid 2a located at the intermediate height position to the upper pin support plate 6, a gas plenum is formed. Therefore, this range is outside the range of the heat generation length. Each of the peripheral flow suppressing members 12 is formed by a plurality of blocks 13 provided in the peripheral flow passage 11 (FIG. 1 illustrates only a right half of each of the blocks 13). The block 13 is configured to have such a cross section that reduces the flow passage area of the peripheral flow passage 11 to be approximately equal to the flow passage area of a region on the center side from the peripheral fuel pins 1a. Further, the blocks 13 are configured to be stacked in the vertical direction to keep the relative positions in the axial direction of the grids 2 in accordance with the settings of the vertical thickness and the number of stacks of the blocks 13. Each of the peripheral fuel pins 1a of a predetermined number is provided with a sleeve 14 at a portion thereof outside the range of the heat generation length such that the sleeve 14 covers the fuel pin 1a and keeps the relative position between the corresponding grids 2. Furthermore, a lower portion of the handling head 7 is provided with a spring 15 for pressing down one of the sleeves 14 disposed at the uppermost positions. Thus, the sleeves 14, the grids 2 and the blocks 13 are pressed and held from the upper side by the spring 15 with elastic force. With reference to FIGS. 2 to 4, the configuration of the blocks 13 will now be described in detail. FIG. 2 is a side view illustrating an overall configuration of one of the blocks 13, and FIG. 3 is a plan view of FIG. 2. FIG. 4 is a partial cross-sectional view illustrating the IV section of FIG. 3 on an enlarged scale. The block 13 has a predetermined vertical thickness as illustrated in FIG. 2 and has a regular hexagonal planar shape as illustrated in FIG. 3. The planar shape corresponds to the inner circumferential surface of the wrapper tube 3 indicated by a virtual line in FIG. 3. To obtain this shape, the block 13 is processed by wire electrical discharge processing, for example. As illustrated in FIG. 3, the inner circumferential surface of the block 13 is formed with convexities 16 in the form of circular arcs in accordance with the outer circumferential surfaces of the fuel pins 1 held inside the block 13. As a configuration for providing a plurality of the fuel pins 1, the example of FIG. 3 illustrates a configuration in which each of the sides of the block 13 includes eight convexities 16 to hold the peripherally disposed ones of the fuel pins 1. FIG. 5 illustrates an example of a configuration in which the convexities 16 of the block 13 are omitted for simplification and four fuel pins 1 are disposed on each of the sides of the block 13. As illustrated in FIGS. 2 and 4, both sides of each of the corners on the outer surface of the block 13 are provided with latch holes 17 formed by vertically extending groove holes, in which positioning pins are inserted. The vertically stacked blocks 13 are latched to the latch holes 17 inserted with latch pins 18. Accordingly, the blocks 13 can be positioned in the radial direction. Further, as illustrated in FIGS. 2 and 4, the peripheral wall of the block 13 is formed with a coolant circulation hole 20 for communicating a coolant flow passage 19 on the inner circumferential side of the block 13 with the peripheral flow passage 11 on the outer circumferential side of the block 13. In the described configuration, therefore, the inner circumferential side and the outer circumferential side of the block 13 are communicated with each other through the coolant circulation hole 20, and the coolant freely flows through the coolant circulation hole 20 to thereby equalize the pressure of the coolant between the inner circumferential side and the outer circumferential side. The configuration of the sleeves 14 will now be described with reference to FIGS. 1, 5, and 6. FIG. 5 is a cross-sectional view (i.e., a transverse cross-sectional view) of FIG. 1 taken along the line V-V, and FIG. 6 is a cross-sectional view (i.e., a vertical cross-sectional view) of FIG. 5 taken along the line VI-VI. As illustrated in FIG. 5, the sleeves 14 are larger in diameter than the fuel pins 1 and disposed on the inner circumferential side of the respective corners of the wrapper tube 3. For example, the sleeves 14 are installed in a disposition in contact with the corners on the inner surface of the wrapper tube 3, while being fitted to cover portions of six peripheral fuel pins 1a outside the range of the heat generation length. As illustrated in FIG. 1, each of the sleeves 14 is set to have a predetermined length in the axial direction (i.e., a vertical length) for keeping the relative positions between the corresponding grids 2. The relative positions between the vertically disposed grids 2 can be kept by making the upper and lower ends of the sleeve 14 in contact with the grids 2. In FIG. 5, six sleeves 14 are disposed at the corners. However, at least three sleeves 14 can sufficiently keep the relative positions between the grids 2. FIG. 7 illustrates an enlarged view of the configuration of the spring 15 which presses down the uppermost sleeve 14. As illustrated in FIG. 7, an upper spring retainer 21 is provided at a lower end position of the handling head 7, and a retaining rod 22 perpendicularly projects downward from the center of the lower surface of the upper spring retainer 21. The retaining rod 22 is inserted in an upper end portion of the uppermost disposed sleeve 14. Further, the above-described spring 15, such as a compression coil spring, for example, is provided around the retaining rod 22 to generate the downward pressing force. Meanwhile, the upper end of the uppermost sleeve 14 is provided with a spring bearing member 23 to receive the downward pressing force applied by the spring 15. As described above, in the present configuration, the handling head 7 is provided with the retaining rod 22, and the sleeve 14 is pressed downward via the spring 15 and the spring bearing member 23. Thereby, the peripheral flow preventing blocks 13, the sleeves 14, and the grids 2 are pressed and held downward. That is, as a device for keeping the relative positions between the grids 2 in the range outside the range of the heat generation length, the sleeves 14 larger in diameter than the fuel pins 1 are fitted to cover the fuel pins 1. Therefore, it is possible to press and hold the grids 2 and the like with the elastic force via the sleeves 14 and the spring 5 without interrupting the expansion in the axial direction of the fuel pins 1. Accordingly, the sleeves 14, the grids 2 and the blocks 13 can be pressed and held from the above with the elastic force. As described above, in the present configuration, each of the peripheral flow suppressing members 12 is formed by the blocks 13, which are disposed in the peripheral flow passage 11 formed in the gap between the wrapper tube 3 and the peripheral fuel pins 1a facing the wrapper tube 3, and each of which has the cross section that reduces the flow passage area of the peripheral flow passage 11 to be approximately equal to the flow passage area of the region surrounded by the centrally disposed ones of the fuel pins 1 forming a triangular array. Further, the blocks 13 are stacked to keep the relative positions in the axial direction of the grids 2. Furthermore, to keep regular intervals between the positions in the axial direction of the grids 2 that hold the fuel pins 1 at regular intervals, a plurality of the peripheral flow preventing blocks 13 are stacked between adjacent ones of the grids 2 in a heat generation unit of the reactor core to keep the grids 2 at predetermined positions. In addition, to suppress the peripheral flow, a part of each of the blocks 13 in contact with the fuel pins 1 is formed into such a shape that follows the shapes of the fuel pins 1 to close the flow passage along the fuel pins 1 facing the wrapper tube 3. Further, each of the blocks 13 is drilled with the coolant circulation hole 20 for communicating the gap formed between the wrapper tube 3 and the block 13 with the space inside the block 13. Thereby, a difference in pressure is eliminated between the space inside the block 13 and the gap formed between the wrapper tube 3 and the block 13, so that the deformation of the block 13 is prevented. Further, in the present configuration, as the device for keeping the relative positions between the grids 2 in the range outside the range of the heat generation length, the sleeves 14 larger in diameter than the fuel pins 1 are fitted to cover the fuel pins 1 for supporting the grids 2. Furthermore, the grids 2, the sleeves 14 and the blocks 13 are held while being pressed from the upper side via the spring 15 supported by the handling head 7. As described above, according to the present embodiment, it is possible to prevent an unnecessary flow of the coolant in an outer circumferential area in the fuel assembly and also possible to cause the coolant to effectively flow toward the interiorly disposed ones of the fuel pins. Further, the grids are fixed at appropriate positions in the axial direction by the peripheral flow suppressing members, each of which is formed by the peripheral flow preventing blocks or the like. Furthermore, the peripheral flow is suppressed, and the temperature distribution in the fuel assembly is planarized to suppress fuel cladding temperature. Accordingly, the lifetime of the fuel can be extended. Further, in such a configuration that the grids, the peripheral flow preventing blocks, and the sleeves are pressed from the direction of the handling head without interrupting the expansion in the axial direction of the fuel pins, it is possible to prevent the fuel pins from being applied with the load for pressing the components. The present invention is not limited to the embodiments described above, but other alterations and modifications can be made as long as not departing from the scope of the appended claims of the invention.
052271307	claims	1. A fuel assembly (1) for a nuclear reactor of pressurized-water type, comprising a number of fuel rods (2) which are retained into a bundle by means of spacers (3) arranged along the fuel rods (2) as well as a top nozzle (4) and a bottom nozzle (5) between the fuel rods (2), between which the guide tubes (13) with associated fuel rods (2) are fixed, said top nozzle (4) and bottom nozzle (5) being provided with a plurality of openings for a coolant flow to the fuel rods (2), wherein at least the lower part of the fuel assembly (1) is provided with a partial fuel box (7) surrounding the bundle and extending from the bottom nozzle (5) and at least up past the lowermost, ordinary spacer (3) of the bundle, however with a length smaller than half the length of the bundle. 2. A fuel assembly (1) according to claim 1, wherein also the upper part of the fuel assembly (1) is provided with a partial fuel box (6) extending from the top nozzle (4) and at least down past the uppermost, ordinary spacer (3) of the bundle. 3. A fuel assembly (1) according to claim 1, wherein the partial fuel boxes (6, 7) at the same time constitute a frame for the spacers they surround. 4. A fuel assembly (1) according to claim 1, wherein the walls of the partial boxes (6, 7) are also retained by partial spacers (10, 11). 5. A fuel assembly (1) according to claim 1, wherein the walls of the partial fuel boxes (6, 7) are provided with a number of holes (6). 6. A fuel assembly (1) according to claim 5, wherein the holes (17) in the wall of a fuel box (6, 7) are arranged displaced in relation to the holes (17) in an adjacent wall of another fuel box (6, 7) in the reactor core. 7. A fuel assembly (1) according to claim 1, wherein the openings in the top and/or bottom nozzle (4, 5) are provided with manually or automatically actuated throttling members for control of the coolant flow through the fuel assembly (1).
050664530	description	In the FIGS. like parts have like numerals. Referring now to FIG. 1, part of a Fast Reactor nuclear fuel assembly 10 is shown which conventionally comprises a wrapper 12 of hexagonal cross-section and a plurality of fuel pins 14 arranged lengthwise within the wrapper 12 at a position intermediate the upper end 16 of the wrapper 12 and the lower end 18 of the wrapper 12. The fuel pins 14 are shown located in known manner between an upper support grid 20 and a lower support grid 22, and the fuel pins 14 are spaced apart in a hexagonal array, for example by spacer grids or fins (not shown) so as to allow coolant to flow between the fuel pins 14. The lower end 18 of the wrapper 12 is provided with a flow restrictor in the form of a known gag 26 of cylindrical form comprising a series of perforated plates 28 and meshes 29 located within a hollow cylinder 31 and disposed one on top of the other so as to provide a number of ducts in the form of passageways 30 (only three are shown) which extend lengthwise of the wrapper 12. A tapered inlet 32 is provided at the lower end 18 and, in use, liquid sodium coolant flows into the wrapper 12 in the direction of arrow "A" via the inlet 32, upwardly through the passageways 30 in the gag 26 and then upwardly around the fuel pins 14 before exiting from the wrapper 12 at the upper end 16. A circular mixer plate 35 has a radiused lower corner 36, and a sharp upper corner which assists in mixing the coolant in the upper end 16. Typically, in a breeder fuel element the fuel comprises an array of breeder pins 14. The heat output of the breeder pins 14 starts at a low level, eg 9wg.sup.-1 and builds up over time and accumulated neutron radiation dose to about 25Wg.sup.-1 after 600 days. Thus the variation in fuel assembly power output can rise from about 0.3 MW at the start to about 1.5 MW at 2% burn-up before it is withdrawn from the reactor. A variable flow control device 40 is provided in the nuclear fuel assembly 10 and comprises a cylindrical member 41 having a circular flange 42 from which a number of cylindrical pegs 48, 49, 50 respectively (only three are shown) depend which are locatable in only some of the passageways 30. The pegs 48, 49, 50 differ in length so that longitudinal displacement of the pegs 48, 49, 50 opens or closes one or more of the passageways 30. A hollow cylindrical housing 52 extends upwardly from the flange 42, and a tubular portion 53 extends from the housing 52 through the region of the fuel pins 14 and terminates in a closed end 54 below the mixer plate 35. A support arm 55 is secured to and extends from the wrapper 12, and passes through openings 56 in the side of the housing 52 and through a cavity 57. Collars 58, 59 secured to the arm 55 locate either side of the housing 52 and maintain the alignment of the housing 52 and thereby the pegs 48, 49, 50 with the gag 26. The arm 55 supports a rod 60 which extends upwardly inside the tubular portion 53 to abut the closed end 54. A compression spring 61 acting between the underside of the arm 55 and the base of the cavity 57 biases the member 41 downwardly against the upthrust of the liquid sodium on the pegs 48, 49, 50, so that the rod 60 is forced against the closed end 54. The rod 60 is made from a material that exhibits greater neutron-induced growth under neutron irradiation than the material of the tubular portion 53. Consequently, in operation under neutron irradiation, the rod 60 grows and bears against the end 54 and forces the flow control device 40 upwardly, thereby progressively withdrawing the pegs 48, 49, 50 from the passageways 30 to increase coolant flow through the gag 26. The number of pegs 48, 49, 50 is selected to allow a required number of passageways 30 to remain permanently open, so that a required minimum flow of coolant is provided along the fuel pins 14. The function of the mesh 29 is to provide a basic restriction to flow in the passageways 30, and the size of the mesh 29 needs to be selected in conjunction with the number of and diameter of the passageways 30 to provide a required flow rate of the coolant through the gag 26. The rod 60 may be made from a material such as PE16 Nimonic nickel alloy, or from an austenitic stainless steel such as AISI321 which has a typical composition: 0.05 C, 17.5 Cr, 9.5 Ni, 0.5 Mo, 1.0 Mn, 0.4 Ti, 0.3 Si PA1 0.11 C, 11.0 Cr, 0.65 Ni, 0.7 Mo, 1.0 Mn, 0.4 Si, 0.4 Nb, 0.3 V, 0.005 B max The stainless steel may be mechanically treated, eg cold worked, to vary its initial neutron-induced growth property, for example to delay the onset of neutron induced growth. The rod 60 may be of composite form and comprise several cylindrical sections, e.g., 60a, 60b, 60c, (FIG. 1a) having different neutron-induced growth properties and placed one upon the other, to provide a required extension of the composite rod 60 under a specified neutron radiation. Preferably, the relatively high growth sections would be located at the position of the greatest neutron radiation in the core of the reactor. In order to provide an initial dwell period, as shown in FIG. 1b the rod 60 might be shorter than the tubular portion 53 to define a gap 63 (shown exaggerated for clarity, so that a predetermined amount of growth of the rod 60 would be necessary before the rod 60 abutted and supported the tubular portion 53 at the closed end 54. A stop, for example the arm 55 abutting the upper ends of the openings 56, would be necessary to arrest the downward movement of the tubular portion 53 under the bias of the spring 61. The member 41 or at least the tubular portion 53 may be made from a ferritic martensitic steel such as AISI 410 or Firth Vickers 448, which have a typical composition: It will be appreciated that alternative materials may be used for the tubular portion 53 and the rod 60, and alternative arrangements may be possible, for example as shown in FIG. 2. In FIG. 2, a nuclear fuel assembly 70 is shown similar in many respects to the assembly 10 of FIG. 1, but having a central rod 72 of a material such as Fv448 which exhibits low neutron-induced growth. The upper end of the rod 72 is held by a clamp 74 to the bore 76 of a tube 78 made from a material such as PE16 Nimonic, or AISI 321 steel. The tube 78 is fixed to the lower support grid 22 and has a flange 79 that locates on the underside of the lower support grid 22. The lower end of the rod 72 is joined to a variable flow control device 80 similar in many respects to the device 40 of FIG. 1, in having a number of cylindrical pegs 81, 82, 83 respectively (only three being shown). The pegs 81, 82, 83 locate in passageways 30 in a gag 26a identical to the gag 26 of FIG. 1 except that the topmost mesh 29 of FIG. 1 is omitted and an upper perforated plate 28a fitted instead of the upper two plates 28 of FIG. 1. The outermost pegs 81, 83 terminate, as shown more clearly in FIG. 3, in central tongues 81a, 83a having radiused ends and joined by curved shoulders 84 to the cylindrical portions of the pegs 81, 833 so as to maintain the alignment of the flow control device 80 with the gag 26a when the cylindrical portions of the pegs 81, 83 are withdrawn from the passageways 300 without imposing a serious restriction on coolant flow through the passageways 30. In operation, the greater neutron-induced growth of the tube 78 lifts the rod 72 which consequently raises the variable flow control device 80 so to withdraw the pegs 81, 82, 83 progressively from the passageways 30. Although the invention has been described in relation to a fuel assembly for a Fast Reactor, it may have applications in fuel assemblies for alterative nuclear reactors. It will be appreciated that pegs 81,82, 83 having tongues 81a, 82a, 83a respectively may be used in the fuel assembly 10 of FIG. 1, which would allow the collars 58, 59 to be dispensed with.
043080987	claims	1. A method of monitoring an operating parameter of a nuclear reactor system at a first location within the reactor containment over a given extended period of time and electrically communicating the information embodied in an analog signal representative of the monitored parameter generated at the first location over the given extended period of time to a remote second location substantially free of the high level of electromagnetic interference encountered in the ambient environment of a nuclear facility, which maximizes noise rejection comprising the steps of: continuously monitoring the operating parameter of the reactor within the reactor containment over the given period of time; generating the analog electrical output which is representative of the parameter monitored over the given time period at the first location; electrically, digitally sampling the analog output within the ambient environment of the nuclear facility, at a predetermined number of discrete coordinates along the analog signal respectively on either side of a preselected number of discrete points on the analog signal sufficient to provide a digital representative reproduction of the information being communicated; electrically transmitting the digital samples of the discrete coordinates from the ambient environment of the nuclear facility to the second remote location; electrically averaging at the second remote location the predetermined number of coordinates sampled on either side of each discrete point to obtain an electrical representation of the averaged values for the respective discrete points; and electrically situating at the second location the respective average values in the appropriate locations for the corresponding discrete points in the digital representative reproduction of the analog signal.
047117540	abstract	A method and apparatus for impacting a surface with a desired kinetic impact energy wherein an impacting device which can apply a variable impact energy corresponding to the magnitude of an input control signal is provided and placed adjacent the surface to be impacted. Thereafter, an input control signal of a preset magnitude is applied to the impact device to initiate an impact, the kinetic energy of the impact is determined, the value of the determined kinetic energy is compared with a value corresponding to the desired kinetic impact energy, the results of the comparison are indicated, the preset magnitude of the signal used for the control signal is adjusted to reduce any difference noted as a result of the comparison, and the process is repeated until a repeatable impact of the desired impact energy is determined and indicated. Preferably, the impacting device is a solenoid whose plunger provides the impact, the input control signal is an input voltage applied across the solenoid coil, and the impact energy is determined by measuring the velocity of the plunger just prior to impact by: sampling the magnitude of a signal, whose magnitude is proportional to the distance moved by said plunger, at uniform time increments; subtracting the sampled values from successive sampling times to provide difference values; and, upon detecting a zero difference value, indicating that impact has occurred, utilizing the immediately previously provided difference value as a measure of the velocity of the plunger just prior to impact, and thus of the kinetic impact energy.
043691617	summary	BACKGROUND OF THE INVENTION The invention concerns a rack and pinion mechanism for moving a unit absorbing neutrons, movable vertically in a nuclear reactor for controlling the power and for emergency shutdown of the reactor. PRIOR ART In nuclear reactors, the regulation of power and emergency shutdown of the reactor are generally obtained by inserting control rods, constituted by tubes containing a material strongly absorbent of neutrons, inside the core. Power regulation is obtained by progressive movements of the control rods to increase their degree of insertion in the reactor core if power is required to be decreased or, conversely, by movements to reduce the degree of insertion of the control rods if power is required to be increased. These movements of inserted control rods in the vertical direction from the upper part of the core are made downwards in the first case and upwards in the second case. When the emergency shutdown is tripped, the control rods are caused to fall under the effect of gravity to their position of maximum engagement in the core. Movements of the control rods are generally effected by mechanisms disposed in the upper part of the reactor in engagement with a control shaft extending the control rods upwards into a region distant from the reactor core. The association with the control shafts of racks disposed in the longitudinal direction of these shafts, either machined directly in the shaft or added to this shaft, to move the control rods by the setting in rotation of a pinion engaged with the rack solid with the control rod has already been envisaged. These rack and pinion apparatuses can allow precise movements of the control rods during control of the reactor to be effected, if the pinion is driven in a precisely controlled way. Similarly, it is possible to halt the control rods in a precise position, from the moment the pinion can be kept rotationally stationary. This assumes a suitable motorization of the pinion driving the rack, the means for driving the pinion being associated with a control allowing movements of the control rods to be effected in both directions according to movements with well defined amplitude. To trip the emergency shutdown, however, it is necessary to disengage the rack from its driving means so as not to obstruct the fall of the rods under the effect of their own weight. To allow these emergency shutdowns, means for driving the pinion step by step have been proposed, allowing locking in position and releasing of the pinion at the moment of emergency shutdown. Such apparatuses, of the pawl type, are complicated, however, and their operation is entirely discontinuous. Systems for engaging and disengaging the pinion have also been proposed, allowing release of the rack at the moment of emergency shutdown, but such apparatuses assume movable mounting of the pinion which complicates the apparatus and makes its working less reliable. SUMMARY OF THE INVENTION The object of the invention is therefore a rack and pinion mechanism for moving a unit absorbing neutrons, movable vertically in a nuclear reactor for controlling the power and for emergency shutdown of the reactor, comprising a vertical control shaft whose lower part is connected to the absorbent unit and whose upper part has a rack disposed in the longitudinal direction of the shaft and a pinion driven in rotation by a motor apparatus, in engagement with the rack so as to move the control shaft and the absorbent unit in both directions, this mechanism having to allow precise movements of the control rods and the halting of these rods in well defined positions and the falling of the rods for emergency shutdown of the reactor controlled by a simple apparatus preventing disengagement of the rack and pinion. To this end, the pinion permanently in engagement with the rack is mounted to rotate on a shaft connected to the motor apparatus for setting the pinion in rotation and disposed perpendicularly to the control shaft, and a clutch device solid with the shaft in rotation is mounted to move in translation on this shaft between a disengagement position in which the pinion and the clutch device are brought into contact and connected by a mechanical means allowing the rotary movement of the shaft to be transmitted to the pinion, the translatory movement of the clutch device in the axial direction of the shaft being controlled by a push-rod connected to an actuating member with vertical movement which is maneuverable from the upper part of the apparatus. For a full understanding of the invention, an embodiment of the rack and pinion mechanism according to the invention will now be described by way of example, with reference to the attached drawings.
044184220	claims	1. An aiming device for fasteners of an implanted bone nail, said device being suitable for use with a Roentgen ray source having an exit window emitting a radiation beam, said device comprising: a reception socket (7) for receiving a fastener aiming sleeve (32); support means (25) for said reception socket; and mounting means (3,12) for joining said support means with the housing (21) of the Roentgen ray source (4), said support means comprising means for positioning said reception socket spaced from the exit window (22) of the Roentgen ray source and approximately in the center of the radiation beam of the source. 2. The device according to claim 1 wherein said reception socket has a hole in the bottom thereof, said socket being adjustable with respect to said support means (25). 3. The device according to claim 2 wherein said support means includes a fork-like element (26, 28, 29) having a pair of prongs joined to a common portion, wherein said reception socket is mounted on said common portion, and wherein said mounting means (12, 3) has a pair of sleeves (38, 39) for receiving the prongs of the fork. 4. The device according to claim 3, characterized in that at least one locking element (8) is mounted on the mounting means for securing the fork-like element (26, 28, 29) in selected positions. 5. The device according to claim 4, characterized in that the mounting means comprises a base plate (12) connectable to the Roentgen ray source housing and a bracket plate (3) which is pivotally mounted on the base plate (12) and contains the sleeves (38 and 39). 6. The device according to claim 5, characterized in that, on the base plate, a manually operable locking mechanism (14) is mounted and the pivotable bracket plate (3) includes a locking portion (64) which can be brought into interlocking engagement with the locking mechanism (14). 7. The device according to claim 5, characterized in that the locking element is an eccentric locking cam (8) connected with a rotary shaft (43) journalled in said mounting means and placed in an opening area of each of said sleeves (38 and 39) and the rotary shaft (43) is connected to a bell crank linkage arranged on the bracket plate (3). 8. The device according to claim 7, characterized in that a pivotable arm (45) is connected to the rotary shaft (43) and to an actuating portion (46 and 47) which, in turn, is pivotally connected to a second pivotable arm (48), said second arm being rigidly connected to a second rotary shaft (50) journalled in said bracket plate (3) and on which shaft is fixed eccentric retaining plates (52, 53), said second shaft having a handle (9) for rotating same. 9. The device according to claim 8, characterized in that the eccentric plates (52, 53) are arranged in such a way that in the locking position they are in self-locking engagement with resilient shoes (62 and 63) on the pivotable bracket plate (3). 10. The device according to claim 9, characterized in that at least portions of bracket plate (3) and base plate (12) lie parallel when in the locking position and that adjusting screws (65, 66) for said resilient shoes are mounted such that they extend through bracket plate (3) when in the locking position and are forced onto the base plate (12), thereby to compensate for any clearance existing between the bracket plate (3) and base plate (12).
	abstract	A thermal neutron shield comprising boron shielding panels with a high percentage of the element Boron. The panel is least 46% Boron by weight which maximizes the effectiveness of the shielding against thermal neutrons. The accompanying method discloses the manufacture of boron shielding panels which includes enriching the pre-cursor mixture with varying grit sizes of Boron Carbide.
	claims	1. A method for reporting and monitoring of system components and for detecting at least one of errors and potential problems in components of a bulk fuel distribution facility comprising:configuring stand alone software modules of the bulk fuel distribution facility;configuring fuel product hardware of the bulk fuel distribution facility, wherein configuring fuel product hardware comprises configuring supervisory control and data acquisition (SCADA) system hardware, meters, pump valves, level instruments, pre-set hardware, a load rack, and a carrier terminal;configuring software modules associated with the fuel product hardware of the bulk fuel distribution facility;checking the stand alone software modules, fuel product hardware, and software modules associated with fuel product hardware for at least one of errors and potential problems; andreviewing results determined by the checking of the stand alone software modules, fuel product hardware, and software modules associated with fuel product hardware for at least one of errors and potential problems. 2. The method of claim 1, further comprising storing the results in a memory. 3. The method of claim 1, further comprising transmitting the results over a computer network. 4. The method of claim 1, further comprising installing software modules and hardware for monitoring and controlling the bulk fuel distribution facility, wherein installing software modules and hardware for monitoring and controlling further comprises installing at least one of a fuel distribution facility controller, SCADA system software and hardware, meters, pump valves, level instruments, pre-set hardware and software, load racks, an accounting module, and a carrier terminal. 5. The method of claim 1, wherein configuring stand alone software modules further comprises configuring a fuel distribution facility controller, SCADA system software, and an accounting module. 6. The method of claim 1, further comprising accessing the results by a web browser. 7. The method of claim 1, further comprising requesting access to the results with a batch file module. 8. The method of claim 1, further comprising automatically transmitting the results over a distributed computer network based on a schedule. 9. A method for reporting and monitoring of system components and for detecting at least one of errors and potential problems in components of a bulk fuel distribution facility comprising:configuring stand alone software modules of the bulk fuel distribution facility;configuring fuel product hardware of the bulk fuel distribution facility;configuring software modules associated with the fuel product hardware of the bulk fuel distribution facility;checking the stand alone software modules, fuel product hardware, and software modules associated with fuel product hardware for at least one of errors and potential problems, wherein checking comprises comparing the hardware and software system information to one or more validation rules, wherein comparing the hardware and software system information to one or more validation rules further comprises comparing software versions found in components of the bulk fuel distribution facility with software versions stored in a table; andreviewing results determined by the checking of the stand alone software modules, fuel product hardware, and software modules associated with fuel product hardware for at least one of errors and potential problems. 10. The method of claim 9, further comprising storing the results in a memory. 11. The method of claim 9, further comprising transmitting the results over a computer network. 12. The method of claim 9, further comprising installing software modules and hardware for monitoring and controlling the bulk fuel distribution facility, wherein installing software modules and hardware for monitoring and controlling further comprises installing at least one of a fuel distribution facility controller, supervisory control and data acquisition (SCADA) system software and hardware, meters, pump valves, level instruments, pre-set hardware and software, load racks, an accounting module, and a carrier terminal. 13. The method of claim 9, wherein configuring stand alone software modules further comprises configuring a fuel distribution facility controller, supervisory control and data acquisition (SCADA) system software, and an accounting module. 14. The method of claim 9, further comprising accessing the results by a web browser. 15. The method of claim 9, further comprising requesting access to the results with a batch file module. 16. The method of claim 9, further comprising automatically transmitting the results over a distributed computer network based on a schedule. 17. The method of claim 9, wherein configuring fuel product hardware comprises configuring supervisory control and data acquisition (SCADA) system hardware, meters, pump valves, level instruments, pre-set hardware, a load rack, and a carrier terminal.
	abstract	A CT imaging system and a method for determining a CT collimator slit profile. The method includes determining a profile of two opposite edges of the collimator slit in a longitudinal direction thereof based on the following: a vertical distance between a focus of a radiation source to the collimator slit, a vertical distance between the focus and the radiation detector, an inclination angle between adjacent detector elements, a length of each detector element, a desired width of projection on the radiation detector by the radiation rays passing through the slit whose longitudinal edge profile is to be determined, and an offset angle of a connecting line from a point on a longitudinal center line of the slit to the focus relative to a plane passing said focus and perpendicular to the slit.
053496248	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to the drawing in detail, FIG. 1 depicts X-ray tube 10 generating an X-ray beam 12 with sufficient flux and energy to form images of a soil sample 14 pursuant to the present invention. As shown, the soil sample is positioned within an analysis zone between an imaging device 16 and the point source 18 of radiation from X-ray tube 10 along an axis 20 to the image plane 22 of the imaging device. Controlled scanning movement relative to the X-ray beam 12 is imparted to the soil sample 14 along perpendicular scanning axes 24 and 26 intersecting the beam axis 20. Magnification of X-ray images formed on plane 22, on the other hand, is controlled by movement 28 along axis 20 imparted to the soil sample as denoted in FIG. 1. Thus, a controllably scanned and magnified x-ray image of the soil sample is formed at the image plane 22 by generation of the microfocused X-ray beam 12 through equipment associated with X-ray tube 10, such as an X-ray machine operating under a voltage of 80 kv and current of 35 ma. Such a commercially available X-ray machine is marketed, for example, by Feinfocus U.S.A., Inc., as model FSX-100.25. As shown in FIG. 2, the soil sample 14 undergoing examination within the analysis zone between X-ray tube 10 and the image plane 22 is a body of soil 30 contaminated by heavy metal particles 32, including extremely small particles less than one millimeter and as small as 10 microns in size. The contaminated soil body 30 occupies a cylindrical volume formed within a container 34 having circular retainer lids 36 at opposite axial ends. Because the contaminant particles 32 have a significantly higher X-ray absorption coefficient than the low absorption coefficient for the soil alone, the X-ray image 38 of the soil sample as shown in FIG. 3 includes high contrast image feature portions 32' corresponding to the contaminant particles 32. Accordingly, measurement of the size and location of each image portion 32' within its image 38 will provide accurate and useful analysis data from which the size and distribution of the contaminant particles 32 within the body of soil 30 is calculated, based on the geometrical parameters of the soil sample 14 and analysis zone as hereinbefore described with respect to FIG. 1. According to actual analyses performed pursuant to the present invention, the cylindrical soil samples 14 utilized had a diameter (d) of 1/2 inch and a thickness (t) between 0.2 and 0.4 inches. The soil in such sample without contamination had an X-ray absorption coefficient between approximately 0.1 and 0.5 cm.sup.2 /g, which is substantially lower than the X-ray absorption coefficient of the contaminants. The X-ray image 38 as depicted in FIG. 3 may be recorded on photographic film or captured by electronic means through the imaging device 22. Magnification of the X-ray image is varied to accommodate the size range of the contaminant particles to be detected for measurement purposes, up to a maximum magnification factor of about 250:1 under microfocus X-ray capabilities of presently available X-ray machines. Detection of contaminant particles as small as 10 microns is thereby made possible. Detection of the contaminant particles, as dark spot image portions 32' depicted in FIG. 3, may be further enhanced by electronic image processing. The scanning movement imparted to the soil sample 14 as hereinbefore described is utilized to obtain measurement data from which the location of the particles 32 may be calculated. Alternatively, a stream of soil may be moved through the analysis zone for intermittent examination of soil samples. The contaminant particle size and location data so obtained may be digitized and fed to automatic computer controlled equipment for subsequent physical separation of the particles. The X-ray images or views may also be captured and measured electronically to provide digitized data on contaminant particle size and location by computer programmed calculation. The foregoing sample analysis method is depicted in FIG. 4, wherein block 40 represents a source of contaminated soil fed to a sample analysis zone 42 irradiated by the microfocus X-ray beam from source 10 to produce the image display represented by block 44. Scanning and image magnification control respectively denoted by blocks 46 and 48 is exercised as hereinbefore explained in order to enable measurement of magnified image features through a system denoted by block 50. The measurement data output of the system 50 is then utilized to calculate in situ size and location for contaminant particles through a computer program, as denoted by block 52, in order to obtain a data readout 54. As also denoted in FIG. 4 by block 56, the size and location data output of program 52 controls operation of particle separation apparatus to which the contaminant soil is fed after passage through the sample analysis zone 42, in order to obtain separated contaminant particles 58 and contaminant-free soil 60. The particle separation apparatus 56 may utilize, for example, an air stream vacuum technique to produce a stream of the contaminant-free soil denoted by block 60. As a result of the foregoing described method, specific in-situ data on size and shape of contaminant particles is produced, and because of soil sample scanning, precise particle location data is provided as the basis for more efficient use of a particle separation technique as well as to drastically reduce the duration and equipment cost for soil sample assessment. Numerous other modifications and variations of the present invention are possible in light of the foregoing teachings. It is therefore to be understood that within the scope of the appended claims the invention may be practiced otherwise than as specifically described.
048150142	abstract	A computer based system aids an operator in proceeding step-by-step through procedures for a complex process facility. At each step, monitored plant parameter values are used to evaluate relevant plant status and recommend action to be taken. The status and recommended action are presented to the operator on a display device together with prompts for generating appropriate responses. The step logic is carried out repetitively to provide the operator with feedback and to verify operator actions. The complete display picture including operator responses, and other plant conditions monitored in parallel with the current step, is logged for later review. An online review feature permits review of plant conditions and operator actions while the operator continues to execute the procedure. High-level textual statements of all steps of a current procedure can be reviewed and prior steps can be executed or re-executed.
	abstract	An X-ray photoelectron spectroscopy analysis system for analysing an insulating sample 20, and a method of XPS analysis. The system comprises an X-ray generating means 30 having an exit opening 32 and being arranged to generate primary X-rays 46,56 which pass out of the exit opening in a sample direction towards a sample surface 22 for irradiation thereof. It has been found that the X-ray generating means in use additionally generates unwanted electrons 258 which may pass out of the exit opening substantially in the sample direction and cause undesirable sample charging effects. The system further comprises an electron deflection field generating means 380,480,580 arranged to generate a deflection field upstream of the sample surface. The deflection field is configured to deflect the unwanted electrons away from the sample direction, such that the unwanted electrons are prevented from reaching the sample surface.
	abstract	A laser ignition/ablation propulsion system that captures the advantages of both liquid and solid propulsion. A reel system is used to move a propellant tape containing a plurality of propellant material targets through an ignition chamber. When a propellant target is in the ignition chamber, a laser beam from a laser positioned above the ignition chamber strikes the propellant target, igniting the propellant material and resulting in a thrust impulse. The propellant tape is advanced, carrying another propellant target into the ignition chamber. The propellant tape and ignition chamber are designed to ensure that each ignition event is isolated from the remaining propellant targets. Thrust and specific impulse may by precisely controlled by varying the synchronized propellant tape/laser speed. The laser ignition/ablation propulsion system may be scaled for use in small and large applications.
047050713	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 there is shown a steam control valve 10 for a power plant steam chest 12. The steam chest 12 includes a hollow elongated central member 14. Central member 14 has a steam inlet means 16 passing therethrough in predetermined position as shown in FIG. 1. The central member 14 also has a steam outlet means 18 passing therethrough in predetermined position. Steam inlet means is at a relatively higher pressure than the steam outlet means. For example the pressure at the steam inlet 16 may be 1000 psia and the pressure at the steam outlet 18 200 psia, for example. In a nuclear power plant the throttle valve controls the flow of steam from the steam generator to the steam chest as is known in the art. The central member has control valve aperture means 22 passing therethrough in predetermined position. The control valve 10 includes a cylindrical outer housing means 24 having a lip member 26 affixed to the upper end 28 thereof. The lip member 26 has an outside diameter such as 40 inches which is greater than the control valve aperture 22 which typically has a diameter of 25 inches. The outer housing 24 passes through the control valve aperture and is maintained in predetermined position by the lip member 26. The outer housing 24 includes a bottom muffler portion 30. The bottom muffler portion 30 has eight window opening means therethrough 32 of predetermined dimensions such as 9.times.6.5 and spaced about the circumference of the bottom muffler portion. The bottoms 34 of the window openings 32 are a predetermined distance such as 4.0 inches above the bottom 36 of the bottom muffler portion 30. The bottom muffler portion 30 of the outer housing 24 has an initial inside diameter such as 20 inches which is greater than the final inside diameter which is 19.4 inches of the remaining portion of the outer housing 24 above the muffler portion. A movable plug 38 is provided for controllably sealing the high pressure inlet means 16 from the relatively low pressure outlet means 18 as is known in the art. The movable plug 38 is coaxially aligned with the outer housing 24 and is slidable within the interior 40 of the outer housing. Shaft means 42 for moving the plug is provided as is known in the art. The shaft means 42 for moving the plug is affixed at one end 41a to the plug in predetermined position as shown in FIGS. 1 and 2. The shaft means 42 is affixed at the other end 41b to lifting means 43 which is conventional. The plug 38 preferably has groove means 44 therein about the circumference thereof in predetermined position as shown in FIG. 2. Circular seal ring means 46 is provided preferably split pressure rings. The circular seal ring means 46 is sized to be insertable into the groove means. The steam control valve 10 is described thus far as conventional. The improvement comprises a bottom ring portion 48. The prior art bottom ring portion is shown in FIGS. 2 and 3. As discussed previously the bottom ring portion of the prior art comprised a plurality of flowholes 49 disposed therethrough and upper band 51 without flowholes adjacent the window openings. The bottom ring portion of the present invention is shown in FIGS. 4-8. The bottom ring portion 48 of the present invention has a plurality of pockets 50 therein about the inner circumference 52 thereof. Each of the tapered pockets 50 is of predetermined dimensions such as about 5 inches wide, 3.8 inches high and 1.8 inches deep at the top of the ring. Each of the pockets is aligned with one of the window openings 32. As shown in FIG. 6 each of the pockets 50 has a steam exit portion 52 having an initial central diameter 54 substantially equal to the inside diameter of the bottom muffler portion 30 of the outer housing 24. Each of the pockets 50 has a final central diameter 56 at the steam entrance portion 58 of the pocket 50 a predetermined amount larger than the initial central diameter of the steam exit portion 30 of the outer housing 24 with the steam entrance portion 58 of each of the pockets 50 being disposed with in bottom 34 of the aligned window openings 32. The exit portion 52 of the pocket 50 being a predetermined distance such as 0.20 inches above the bottom of the outer housing 24. A channel 60 is provided at the bottom of the muffler portion for engaging said central member 14 as shown in FIGS. 5 and 6 in the same manner as in the prior art. With reference to FIGS. 4 and 5 utilizing the present invention when the plug 38 is initially lifted by the lifting means 43, steam at the high pressure inlet 16 flows through the window openings 32 and through the pockets 50. As the plug is raised the steam flow through the pockets is increased without damaging vibration of the outer housing means and plug. Preferably the wall portion 62 of the ring portion 48 from the entrance portion 58 to the exit portion 52 of each of the pockets is offset from the vertical. The entrance portion 58 to the exit portion 52 is typically at an angle offset 26.degree. from the vertical as shown in FIG. 6. Preferably the side portions 64 of the ring portion 48 proximate said pockets have a predetermined curvature such as a 1.25 inches radius.
	description	The present application claims the benefit of U.S. Provisional Patent Application No. 62/641,756, tilted “REFLECTORS FOR MOLTEN CHLORIDE FAST REACTORS,” filed Mar. 12, 2018, the entire disclosure of which is incorporated by reference herein. The utilization of molten fuels in a nuclear reactor to produce power provides significant advantages as compared to solid fuels. For instance, molten fuel reactors generally provide higher average core power densities compared to solid fuel reactors, while at the same time having reduced fuel costs due to the relatively high cost of solid fuel fabrication. Molten fluoride fuel salts suitable for use in nuclear reactors have been developed using uranium tetrafluoride (UF4) mixed with other fluoride salts as well as using fluoride salts of thorium. Molten fluoride salt reactors have been operated at average temperatures between 600° C. and 860° C. Binary, ternary, and quaternary chloride fuel salts of uranium, as well as other fissionable elements, have been described in co-assigned U.S. patent application Ser. No. 14/981,512, titled MOLTEN NUCLEAR FUEL SALTS AND RELATED SYSTEMS AND METHODS, which application is hereby incorporated herein by reference. In addition to chloride fuel salts containing one or more of UCl4, UCl3F, UCl3, UCl2F2, and UClF3, the application further discloses fuel salts with modified amounts of 37Cl, bromide fuel salts such as UBr3 or UBr4, thorium chloride fuel salts, and methods and systems for using the fuel salts in a molten fuel reactor. Average operating temperatures of chloride salt reactors are anticipated between 300° C. and 800° C., but could be even higher, e.g., >1000° C. In one aspect, the technology relates to a reflector assembly for a molten chloride fast reactor (MCFR) including: a support structure including a substantially cylindrical base plate, a substantially cylindrical top plate, and a plurality of circumferentially spaced ribs extending between the base plate and the top plate, wherein the support structure is configured to encapsulate a reactor core for containing nuclear fuel; and a plurality of tube members disposed within the support structure and extending axially between the top plate and the bottom plate, wherein the plurality of tube members are configured to hold at least one reflector material to reflect fission born neutrons back to a center of the reactor core. In an example, each tube member of the plurality of tube members includes a substantially similar diameter. In another example, the plurality of tube members includes two or more tube members having different diameters. In yet another example, each tube member of the plurality of tube members are disposed within the support structure so that adjacent tube members are abutted to each other at a tangency location. In still another example, the plurality of tube members include two or more tube members having different wall thicknesses. In an example, an interstitial space is defined between the plurality of tube members, and wherein a packing fraction of the at least one reflector material relative to the plurality of tube members and the interstitial space is greater than, or equal to, 70%. In another example, the packing fraction is greater than, or equal to, approximately 87%. In yet another example, the interstitial space is configured to hold fuel salt or coolant fluid. In still another example, the interstitial space is devoid of material. In an example, the plurality of tube members are packed within the support structure and devoid of welds. In another example, the at least one reflector material includes liquid lead and/or graphite. In another aspect, the technology relates to a reflector assembly for a MCFR including: at least one reflector structure, wherein the at least one reflector structure is circumferentially arrangeable in a substantially cylindrical shape that encapsulates a reactor core for containing nuclear fuel; and one or more tank sections disposed within the at least one reflector structure, wherein the one or more tank sections are configured to hold at least one reflector material to reflect fission born neutrons back to a center of the reactor core. In an example, the at least one reflector structure defines a longitudinal axis, and wherein the at least one reflector structure includes two or more tank sections of the one or more tanks sections, each of the two of more tank sections axially aligned along the longitudinal axis. In another example, each of the two or more tanks sections are formed by individual and separable reflector structures. In yet another example, the reflector assembly further includes a support structure that holds the at least one reflector structure in the substantially cylindrical shape. In another aspect, the technology relates to a method of reflecting fission born neutrons back to a center of a reactor core containing high temperature nuclear fuel, the method including: encapsulating the reactor core within a reflector assembly, the reflector assembly including a plurality of tank sections circumferentially arrangeable in a substantially cylindrical shape such that the reactor core is located therein; and disposing at least one reflector material into the plurality of tank sections. In an example, the at least one reflector material is a first reflector material, and the method further includes replacing at least a portion of the first reflector material with a second reflector material. In another example, the first reflector material is liquid lead and the second reflector material is graphite. In yet another example, the plurality of tank sections include a plurality of tube members disposed within a support structure, and the method further includes channeling a fuel salt through an interstitial space that is defined between the plurality of tube members. In still another example, the plurality of tank sections is supported by a support structure, and the method further includes extracting the reflector assembly from the reactor core via the support structure and replacing at least a portion of the plurality of tank sections. This disclosure describes various configurations and components of a molten fuel fast or thermal nuclear reactor. For the purposes of this application, embodiments of a molten fuel fast reactor that use a chloride fuel will be described. However, it will be understood that any type of fuel salt, now known or later developed, may be used and that the technologies described herein may be equally applicable regardless of the type of fuel used, such as, for example, salts having one or more of U, Pu, Th, or any other actinide. Note that the minimum and maximum operational temperatures of fuel within a reactor may vary depending on the fuel salt used in order to maintain the salt within the liquid phase throughout the reactor. Minimum temperatures may be as low as 300-350° C. and maximum temperatures may be as high as 1400° C. or higher. FIG. 1 illustrates, in a block diagram form, some of the basic components of a molten fuel reactor. In general, a molten fuel reactor 100 includes a reactor core 104 containing a fissionable fuel salt 106 that is liquid at the operating temperature. Fissionable fuel salts include salts of any nuclide capable of undergoing fission when exposed to low-energy thermal neutrons or high-energy neutrons. Furthermore, for the purposes of this disclosure, fissionable material includes any fissile material, any fertile material or combination of fissile and fertile materials. The fuel salt 106 may or may not completely fill the core 104, and the embodiment shown is illustrated with an optional headspace 102 above the level of the fuel salt 106 in the core 104. The size of the reactor core 104 may be selected based on the characteristics and type of the particular fuel salt 106 being used in order to achieve and maintain the fuel in an ongoing state of criticality, during which the heat generated by the ongoing production of neutrons in the fuel causes the temperature of the molten fuel to rise when it is in the reactor core 104. The performance of the reactor 100 is improved by providing one or more reflectors 108 around the core 104 to reflect neutrons back into the core. Additionally, the reflectors 108 may shield components positioned radially outward from the core 104. The molten fuel salt 106 is circulated between the reactor core 104 and one or more primary heat exchangers 110 located outside of the core 104. The circulation may be performed using one or more pumps 112. The primary heat exchangers 110 transfer heat from the molten fuel salt 106 to a primary coolant 114 that is circulated through a primary coolant loop 115. In an embodiment the primary coolant may be another salt, such as NaCl—MgCl2, lead, or other liquid metal. Other coolants are also possible including Na, NaK, Na mixtures, supercritical CO2, liquid lead, and lead bismuth eutectic. In an embodiment, a reflector 108 is between each primary heat exchanger 110 and the reactor core 104 as shown in FIG. 1. For example, in an embodiment a cylindrical reactor core 104, having a diameter of 2 meters (m) and a height of 3 m or greater, is oriented vertically so that the flat ends of the cylinder are on the top and bottom respectively. The entire reactor core 104 is surrounded by reflectors 108 between which are provided channels for the flow of fuel salt 106 into and out of the reactor core 104. Eight modular reflectors 108 and primary heat exchangers 110 are distributed azimuthally around the circumference of the reactor core 104, with each primary heat exchanger 110 provided with pumps to drive circulation of the fuel salt 106. In alternative embodiments, a different number of reflectors 108 and primary heat exchangers 110 may be used. For example, embodiments having 2, 3, 4, 5, 6, 8, 12, and 16 reflectors and primary heat exchangers are contemplated. In the embodiment shown in FIG. 1, in normal (power generating) operation, the fuel salt is pumped from the reactor core 104, through the primary heat exchanger 110, and cooled fuel salt is returned back to reactor core 104. Heated primary coolant 114 from the primary heat exchangers 110 is passed to a power generation system 120 for the generation of some form of power, e.g., thermal, electrical or mechanical. The reactor core 104, primary heat exchangers 110, pumps 112, molten fuel circulation piping (including other ancillary components that are not shown such as check valves, shutoff valves, flanges, drain tanks, etc.) and any other components through which the molten fuel circulates or contacts during operation can be referred to as the fuel loop 116. Likewise, the primary coolant loop 115 includes those components through which primary coolant circulates, including the primary heat exchangers 110, primary coolant circulation piping (including other ancillary components that are not shown such as coolant pumps 113, check valves, shutoff valves, isolation valves, flanges, drain tanks, etc.). Salt-facing elements of the heat exchanger 110 and the primary coolant loop 115 may be clad to protect against corrosion. Other protection options include protective coatings, loose fitting liners, or press-fit liners. In an embodiment, cladding on the internal surface of the tubes is molybdenum that is co-extruded with the base heat exchanger tube material. For other fuel salt contacting surfaces (exterior surfaces of the tube sheets and exterior surface of the shell), the cladding material is molybdenum alloy. Nickel and nickel alloys are other possible cladding materials. Niobium, niobium alloys, and molybdenum-rhenium alloys may be used where welding is required. Components in contact with primary cooling salt may be clad with Alloy 200 or any other compatible metals, such as materials meeting the American Society of Mechanical Engineers' pressure vessel code. The tube primary material may be 316 stainless steel or any other compatible metals. For example, in an embodiment, Alloy 617 is the shell and tube sheet material. The molten fuel reactor 100 further includes at least one containment vessel 118 that contains the fuel loop 116 to prevent a release of molten fuel salt 106 in case there is a leak from one of the fuel loop components. The containment vessel 118 is often made of two components: a lower, vessel portion 118v that takes the form of a unitary, open-topped vessel with no penetrations of any kind; and an upper, cap portion 118h referred to as the vessel head that covers the top of the vessel portion 118v. All points of access to the reactor 100 are from the top through the vessel head 118h. One advantage of the above described reactor 100 is in its operational mode and fuel cycle flexibility. For example, after an initial enriched fuel load, the reactor can utilize a fast spectrum burn (high-energy neutrons) to achieve a low parasitic absorption, breed & burn behavior. Breed & burn behavior is generally a mode of operation where the reactor conversion ratio exceeds 1.0 and more fissile fuel is bred than burned. This additional fissile fuel can be removed and used in subsequent daughter reactors so as to reduce the need for further fuel enrichment. After the breed & burn operations, the reactor can also utilize a thermal spectrum burn (higher neutron absorption) to achieve high parasitic absorption, burn behavior. Burn behavior is generally a mode of operation where the reactor conversion is lower than 1.0 and more fissile fuel is burned than bred. Additionally, the reactor may also operate with a reactor conversion ratio of about 1.0 so that the fissile fuel which is bred is burned. To enable a more efficient reactor process in each operational mode, the reflectors 108 may be selectively configureable with different reflector materials so that the energy spectrum of which neutrons are reflected back into the core 104 can be shifted. For example, at the beginning of the reactor life, the reflectors 108 may include fast neutron reflector materials so that the neutrons are high-energy and a fast spectrum burn is achieved. Fast neutron reflector materials are typically large atomic weight elements that have a low neutron absorption cross-section, such as, but not limited to lead, lead oxide, lead bismuth, and tungsten. Then, toward the end of the reactor life, the reflector may transition to include reflector materials that are neutron moderators so that the neutrons are lower-energy and a thermal spectrum burn is achieved. Neutron moderator materials for softening the energy spectrum are typically small atomic weight elements, such as, but not limited to, graphite, beryllium, lithium, zirconium-hydride (ZrH), and non-graphite carbon. Broadly speaking, this disclosure describes multiple alterations and component configurations that improve the performance of the reactor 100 described with reference to FIG. 1. For example, reflectors are described below that are configured to contain one or more reflector materials, e.g., a material that acts as a fast neutron reflector (for example, liquid lead) and/or a material that acts as a neutron moderator (for example, graphite, or a liquid containing graphite). Generally, the reflector materials are contained inside structural components which form the reflectors. In some examples, the structural components may be connected to a reflector material circuit that enables the required or desired liquid reflector material to be circulated (e.g., via natural circulation or by active pumping) through the reflector without removal of the reflector from the containment vessel. In other examples, the structural components may be removed from the containment vessel to replace and/or insert the required or desired reflector material. Generally, the bulk portion of the reflectors 108 may be formed, but is not required to be formed, from one or more molybdenum alloy, one or more zirconium alloys (e.g., any of the ZIRCALOY™ alloys such as Zircaloy-2 and Zircaloy-4), one or more niobium alloys, one or more zirconium-niobium alloys (e.g., M5 and ZIRLO), one or more zirconium silicides (e.g., Zr3Si2), one or more magnesium peroxides (e.g., MgO2), one or more nickel alloys (e.g., HASTELLOY™ N) or high temperature ferritic, martensitic, or stainless steel, steel, and the like. Other specific steel materials include, stainless steels including aluminum-containing stainless steels, advanced steels such as FeCrAl alloys, Alloy 617, HT9, oxide-dispersion strengthened steel, T91 steel, T92 steel, HT9 steel, 316 steel, 304 steel, an APMT (Fe-22 wt. % Cr-5.8 wt. % Al), and Alloy 33 (a mixture of iron, chromium, and nickel, nominally 32 wt. % Fe-33 wt. % Cr-31 wt. % Ni). Similar to the salt-facing elements of the reactor, the reflector material elements of the reflector may be clad to protect against corrosion. Other protection options include protective coatings, loose fitting liners, or press-fit liners. In an embodiment, cladding on the internal and/or exterior surface of the tubes is molybdenum. The cladding material may also include molybdenum alloy, nickel, and nickel alloys, while niobium, niobium alloys, and molybdenum-rhenium alloys may be used where welding is required. Components may also use subsurface ceramic coatings. For example, in an embodiment, Alloy 617 is the material the reflector is formed out of. FIG. 2A is a partial perspective view of an exemplary reflector assembly 200 for use in the molten fuel reactor 100 (shown in FIG. 1). FIG. 2B is a partial longitudinal cross-sectional view of the reflector assembly 200. Referring concurrently to FIGS. 2A and 2B, the reflector assembly 200 includes a lower reflector 202 and a central reflector 204, while an upper reflector is not shown for clarity. The lower reflector 202 is disposed within a flow guide 206 that enables the fuel salt flow to be channeled from the primary heat exchanger back into a reactor core 208 as described above. The central reflector 204 includes a plurality of reflector structures 210 that are circumferentially arranged about a longitudinal axis 212 to encapsulate the reactor core 208 in a substantially cylindrical shape. In the example, there are 8 reflector structures 210 that form the cylindrical core. Although, other configurations are also contemplated. By making the reflector structures 210 modular, the central reflector 204 is more easily replaced (e.g., periodically every 4-5 years) so as to increase overall reactor performance, efficiency, and availability during its life-cycle. At least one tank section 214 is disposed within the reflector structure 210 and is configured to hold at least one reflector material 216 so that fission born neutrons are reflected back to a center of the reactor core 208. In the example, the reflector structure 210 forms a single tank section 214 such that the entire reflector structure 210 is a large tank configured to hold the reflector material 216. Because of the high hydrostatic pressure forces generated by the reflector material 216, for example, liquid lead which is a dense material, the walls of the reflector structure/tank are relatively thick as compared to other reflector configurations described below. In one example, the reflector structure/tank may be formed with Alloy 617 having a wall thickness of approximately 100 millimeters (mm) or greater. In other examples, the reflector structure/tank may include internal reinforcement members so as to increase the strength thereof and prevent the walls from buckling under the hydrostatic pressure loads. Depending on the fuel cycle operation of the reactor core, each of the reflector structures 210 may contain a similar reflector material 216 (e.g., liquid lead for a fast spectrum burn or graphite for a thermal spectrum burn). In other examples, two or more of the reflector structures 210 may contain a different reflector material 216 so that the energy spectrum reflection of the reflector assembly can be specifically modified to a fuel cycle operation as required or desired. Due to the modularity of the reflector structures 210, the reflector material 216 may be changed out during the replacement of the central reflector 204 as needed for the life-cycle of the reactor. Additionally or alternatively, the tank sections 214 may be coupled to a reflector material circuit (not shown) that drains spent reflector material from the tank sections 214 and pumps new reflector material (either the same material or a different material) into the tank sections 214 without needing to remove the reflector structures 210 from the containment vessel. In another example, the reflector structure 210 may be internally divided such that two or more tank sections 218 are formed within the reflector structure and configured to hold the reflector material 216 as illustrated in FIG. 2B. The tank sections 218 are axially aligned along the longitudinal axis 212 so as to lower the hydrostatic pressure forces generated by the reflector material 216 such that the thickness of the reflector structure/tank walls may be reduced. Each tank section 218 may have a similar reflector material, or a different reflector material, and/or coupled to the reflector material circuit as described above. Alternatively, the reflector structure 210 may be divided along the longitudinal axis 212 such that the tank sections 218 may extend axially along the reactor core 208. In other examples, the reflector structure 210 may be divided such that two or more individual and separable tank sections 220 form the reflector structure as illustrated in FIG. 2A. The tank sections 220 lower the hydrostatic pressure forces generated by the reflector material 216 as described above and are configured to be axially stacked to form the reactor core 208. By further compartmentalizing the reflector structure 210 the modularity of the reflector assembly 200 is further increased. Each tank section 220 may have a similar reflector material, or a different reflector material, and/or coupled to the reflector material circuit as described above. Alternatively, the reflector structure 210 may be divided along the longitudinal axis 212 such that the tank sections 220 may extend axially along the reactor core 208. FIG. 2C is a perspective view of a support structure 222 for use with the central reflector 204 of the reflector assembly 200 (shown in FIG. 2A). FIG. 2D is a circumferential cross-sectional view of the support structure 222 shown in FIG. 2C. Referring concurrently to FIGS. 2C and 2D, the support structure 222 holds the reflector structures 210 in place within the reactor core and enables the central reflector 204 to be lifted from the containment vessel for maintenance and/or replacement. The support structure 222 is formed from solid components made of high temperature alloys (e.g., Alloy 617). In the example, the support structure 222 is a frame that includes a substantially cylindrical base plate 224, a substantially cylindrical top plate 226, and a plurality of circumferentially spaced ribs 228 that extend between the plates 224, 226. Each reflector structure 210 is secured within this frame. In some examples, one or more restraint hoops 230 may be positioned around the outer perimeter of the central reflector 204 in order to support the assembly for lateral loads. Additionally, the ribs 228 may extend above the top plate 226 to form exit flow channels for the fuel salt during reactor operation as described above. FIG. 3A is a perspective view of a central reflector 300 for another reflector assembly. FIG. 3B is a top view of the central reflector 300. Referring concurrently to FIGS. 3A and 3B, certain components of the reflector assembly are described above and, as such, are not described further. As described above, the central reflector 300 includes a plurality of reflector structures 302 that are circumferentially arranged about a longitudinal axis to encapsulate a reactor core 304 in a substantially cylindrical shape. In this example, however, the reflector structure 302 includes a grid pattern of radial members 306 and circumferential members 308. For example, the radial members 306 and circumferential members 308 may be 6.25 mm thick plates. This grid pattern forms a plurality of tank sections 310 that are configured to hold at least one reflector material within the reflector structure 302. Each tank section 310 may selectively contain a reflector material to configure the energy spectrum reflection of the reflector assembly for any fuel cycle operation as required or desired. In the example, the radial members 306 are spaced approximately 4.4° apart from one another and the circumferential members 308 are spaced approximately 100 mm apart from one another. It is appreciated that any other spacing as required or desired may also be utilized. In one example, the reflector structure 302, radial members 306, and circumferential members 308 may be formed (e.g., cast or additively manufactured) as a monolithic piece. In another example, the radial members 306 and circumferential members 308 may be welded, friction fit, or brazed within the reflector structure 302. In some examples, not every tank section 310 may include a reflector material. At least one tank section 310 may be devoid of a reflector material and is only a void space. In another example, at least one tank section 310 may contain a fuel salt or a coolant salt that enables heat to be removed from the reflector assembly. Selectively locating voids and/or fuel salt tanks within the reflector structure further enables the energy spectrum reflection of the reflector assembly to be configured as required or desired. FIG. 4A is a perspective view of another central reflector 400. FIG. 4B is a top view of the central reflector 400. Referring concurrently to FIGS. 4A and 4B, certain components of the central reflector are describe above in reference to FIGS. 3A and 3B and, as such, are not described further. As described above, the central reflector 400 includes a plurality of reflector structures 402 having a grid pattern of radial members 404 and circumferential members 406 forming a plurality of tank sections 408 to encapsulate a reactor core 410 in a substantially cylindrical shape. In this example, however, the reflector structure 402 includes a first circumferential end 412 and a second circumferential end 414. Each circumferential end 412, 414 is formed as a curved surface that corresponds to a curved surface of an adjacent reflector structure. By forming the reflector structures 402 with curved ends, a straight line seam between the reflector structures is removed so that there is not a straight line exit path for neutrons to follow. This further reduces parasitic loss of neutrons from the reactor core 410 during operation. FIG. 5A is a partial longitudinal cross-sectional view of another reflector assembly 500. FIG. 5B is a partial axial cross-sectional view of the reflector assembly 500. Referring concurrently to FIGS. 5A and 5B, certain components of the reflector assembly are described above and, as such, are not described further. As described above, the reflector assembly 500 includes a lower reflector 502 disposed within a flow guide 504, a central reflector 506 including a plurality of reflector structures 508 circumferentially arranged about a longitudinal axis, and an upper reflector that is not shown for clarity. In this example, however, the reflector structures 508 are fabricated from monolithic blocks of tungsten or tungsten carbide and defined within the blocks are a plurality of tank sections 510 that are configured to hold at least one reflector material within the reflector structure 508. Each tank section 510 may selectively contain a reflector material, a fuel salt, or a void space to configure the energy spectrum reflection of the reflector assembly 500 for any fuel cycle operation as required or desired and as described above. The tank sections 510 may be substantially circular in cross-section with wall sections that separate each tank section being as thin as 1 mm. In other examples, the tank sections 510 may have any other cross-sectional profile as required or desired (e.g., hexagonal). Additionally, a support structure 512 is illustrated with a base plate 514, a top plate 516, and a plurality of circumferentially spaced ribs 518 that extend between the plates 514, 516. The support structure 512 provides support for each of the tank sections 510 and enables the central reflector 506 to be lifted from the containment vessel for maintenance and/or replacement. FIG. 6 is a partial perspective view of another reflector assembly 600. Certain components of the reflector assembly are described above and, as such, are not described further. As described above, the reflector assembly 600 includes a lower reflector 602 disposed within a flow guide 604, a central reflector 606 circumferentially arranged about a longitudinal axis, and an upper reflector that is not shown for clarity. In this example, however, the central reflector 606 is formed by a support structure 608 including a base plate (not shown), a top plate 610, and a plurality of circumferentially spaced ribs 612. A plurality of tube members 614 are disposed within the support structure 608 between the base plate and the top plate 610. The tube members 614 extend along the longitudinal axis and are substantially parallel to the ribs 612. In this example, the tube members 614 form the tank sections and are configured to hold at least one reflector material within the central reflector 606. Each tube member 614 may selectively contain a reflector material, a fuel salt, or a void space to configure the energy spectrum reflection of the reflector assembly 600 for any fuel cycle operation as required or desired and as described above. The tube members 614 may be packed such that adjacent tube members 614 are abutted to each other at tangency locations so as to increase the packing fraction and reduce the interstitial space between the tube members 614. The packing fraction is defined as the amount of reflector material relative to the tube member walls and the interstitial space. In one example, the tube members 614 all are similarly sized and shaped and may have approximately 1 mm thick walls and an approximately 100 mm diameter. In other examples, the tube members 614 may have any other shape and/or size as required or desired, including different sizes and/or shapes. For example, the tube members may be formed as hexagonal ducts so as to further increase the packing fraction. FIG. 7A is a partial perspective view of another reflector assembly 700. FIG. 7B is a perspective view of a support structure 702 for use with the reflector assembly 700. FIG. 7C is an axial cross-sectional view of the reflector assembly 700. FIG. 7D is a partial enlarged cross-section view of the reflector assembly 700. Referring concurrently to FIGS. 7A-7D, certain components of the reflector assembly are described above and, as such, are not described further. As described above, the reflector assembly 700 includes a lower reflector 704 disposed within a flow guide 706, a central reflector 708 circumferentially arranged about a longitudinal axis, and an upper reflector that is not shown for clarity. The central reflector 708 is formed by the support structure 702 that includes a base plate 710, a top plate 712, and a plurality of circumferentially spaced ribs 714. A plurality of tube members 716 are disposed within the support structure 702 forming the tank sections and configured to hold at least one reflector material within the central reflector 708. In this example, however, two or more of the tube members 716 have different diameters. The tube members 716 extend between and supported by the base plate 710 and the top plate 712 while substantially parallel to the ribs 714. That is, the tube members 716 are connected at the top and bottom of the support structure so as to support the reflector material contained therein. For example, each tube member 716 may include a cap at each end for connecting to the support structure 702. The base and/or top plates 710 may include a plurality of recesses 718 that correspond to each tube member 716 so that the tube members are supported therein. By using the support structure 702, the central reflector 708 may be easily removed from the containment vessel and replaced at scheduled intervals. In some examples, the tube members 716 may be in flow communication with a reflector material circuit (not shown) to receive the reflector material as required or desired and as described above. The ribs 714 divide the support structure 702 into 8 sectors 720, each with the same volume. The tube members 716 are arranged in each sector 720 such that the packing pattern of the tube members 716 are repeated in every sector 720 and as illustrated in FIG. 7C. The tube members 716 are bundled together within the support structure 702 such that welds are not required to hold the tube members together. For example, the tube members 716 may be manufactured with Alloy 617. Additionally, a first tube 722 having a radius of approximately 296 mm with a wall thickness of 4 mm is positioned at the center of the sector 720. A second tube 724 is positioned radially outward of the first tube 722 and has a radius of approximately 132 mm with a wall thickness of 2 mm. A third tube 726 is positioned radially inward of the first tube 722 and has a radius of approximately 98 mm with a wall thickness of 1.5 mm. A fourth tube 728 is positioned between the second tube 724 and the third tube 726 and has a radius of approximately 70 mm with a wall thickness of 1 mm. A number of other tubes 730 that have radii of between 7 mm and 53 mm with a wall thickness of 1 mm are packed between tubes 722, 724, 726, and 728. As such all the tube members are abutted to each other and to the ribs 714 at tangency locations. The space between the tube members defines an interstitial space 732. This configuration forms a packing fraction, defined as the amount of reflector material relative to the tube member walls and the interstitial space, as greater than, or equal to, 80%. More specifically, the packing fraction is greater than, or equal to, approximately 87%. This enables for large quantities of reflector material, while reducing wall thicknesses to between 1 mm and 4 mm. Furthermore, circular shapes facilitated the thinnest structural walls in order to reduce parasitic loss due to the capture of neutrons. However, wall thicknesses may be between 1 mm and 100 mm as required or desired. In alternative examples, any other packing configuration of the tube members (e.g., a configuration of tube members having radii larger and/or smaller than described above) may be used that enables the central reflector 708 to function as described herein. For example, configurations may form a packing fraction that is greater than, or equal to, 60%, a packing fraction that is greater than, or equal to 70%, or a packing fraction that is greater than, or equal to 75% as required or desired. The interstitial space 732 may be configured to form a void having no material or hold a fuel such a fuel salt or a coolant salt. For example, since the central reflector 708 forms the reactor core, components of the reflector will absorb heat and will need to be cooled. As such, the base plate 710 may include one or more orifices so that a portion of the fuel salt flow is channeled through the central reflector 708, via one or more of the interstitial spaces 732, and then exit through an orifice in the top plate 712 and rejoin the main flow at the exit channel located above the central reflector 708. This system increases criticality of the reactor, and thus, overall performance by providing addition fission neutrons in the reactor core. Additionally, the fuel salt generates its own hydrostatic pressure within the central reflector 708 and counteracts a portion of the reflector material hydrostatic forces within the tube members 716. In other examples, the interstitial space 732 may be configured to receive another coolant salt flow from the primary cooling circuit or a separate cooling circuit so as to remove heat from the central reflector 708. As such, the reflector assembly 700 may at least be partially cooled by the fluid in the interstitial space 732. In further examples, one or more of the tube members 716 may be configured to channel fuel salt or another coolant salt therethrough as required or desired. Both the fuel salt and the reflector material (e.g., liquid lead) are corrosive, and thus, require metal cladding or a corrosion inhibitor to protect against corrosion as described above. As described above, depending on the fuel cycle operation of the reactor core, each of the tube members 716 may contain a similar reflector material (e.g., liquid lead for a fast spectrum burn and/or graphite for a thermal spectrum burn). While during reflector operation, some or all of the tube members 716 may be changed out so as to contain a different reflector material. This enables the energy spectrum reflection of the reflector assembly to be specifically modified to a fuel cycle operation as required or desired. As described above, the reflector material may be changed or replace via a reflector material circuit. In other examples, one or more of the tube members may be formed from solid and/or liquid material and removed and replaced from the support structure. For example and in any of the examples described herein, the reflector material may include, but is not limited to, multitube liquid lead, liquid lead, lead, lead oxides (PbO), lead sulfides (PbS), stainless steel (e.g. SS316, SS309, SS3310, etc.), tungsten, tungsten carbides, desalloy, zirconium silicides (ZrSi2, Zr3Si2, etc.), zirconium sulfides (ZrS2), zirconium oxides (ZrO2), depleted uranium, HT-9, magnesium oxides (MgO), silicon carbides (SiC), ferrous sulfides (FeS), barium oxides (BaO), and alkaline earth lead compounds (Ba2Pb, Sr2Pb, etc.). FIG. 8 illustrates a flowchart of an exemplary method 800 of reflecting fission born neutrons back to a center of a reactor core containing high temperature nuclear fuel. To begin, the reactor core is encapsulated within a reflector assembly (operation 802). For example, the reflector assembly includes a plurality of tank sections that are circumferentially arrangeable in a substantially cylindrical shape such that the reactor core is located within. At least one reflector material is then disposed into the plurality of tank sections (operation 804). In some examples, during operation of the reactor core at least a portion of the first reflector material is replaced by a second reflector material (operation 806). For example, the first reflector material may be liquid lead so as to enable a fast spectrum operation and the second reflector material may be graphite so as to enable a thermal spectrum operation later in the reactor life-cycle. In other examples, the plurality of tank sections may include a plurality of tube members disposed within a support structure and during operation of the reactor core a fuel salt is channeled through an interstitial space defined between the plurality of tube members (operation 808) for cooling the reflector assembly. In another example, the plurality of tank sections are supported by a support structure and the method further includes extracting the reflector assembly from the reactor core via the support structure and replacing at least a portion of the plurality of tank sections (operation 810). In addition to those described above, further examples are disclosed in the following numbered clauses: 1. A reflector assembly for a molten chloride fast reactor (MCFR) comprising: a support structure comprising a substantially cylindrical base plate, a substantially cylindrical top plate, and a plurality of circumferentially spaced ribs extending between the base plate and the top plate, wherein the support structure is configured to encapsulate a reactor core for containing nuclear fuel; and a plurality of tube members disposed within the support structure and extending axially between the top plate and the bottom plate, wherein the plurality of tube members are configured to hold at least one reflector material to reflect fission born neutrons back to a center of the reactor core. 2. The reflector assembly of clause 1 or any clause that depends from clause 1, wherein each tube member of the plurality of tube members comprises a substantially similar diameter. 3. The reflector assembly of clause 1 or any clause that depends from clause 1, wherein the plurality of tube members comprises two or more tube members having different diameters. 4. The reflector assembly of clause 3 or any clause that depends from clause 3, wherein each tube member of the plurality of tube members are disposed within the support structure so that adjacent tube members are abutted to each other at a tangency location. 5. The reflector assembly of clause 3 or any clause that depends from clause 3, wherein the plurality of tube members comprises two or more tube members having different wall thicknesses. 6. The reflector assembly of clause 3 or any clause that depends from clause 3, wherein an interstitial space is defined between the plurality of tube members, and wherein a packing fraction of the at least one reflector material relative to the plurality of tube members and the interstitial space is greater than, or equal to, 70%. 7. The reflector assembly of clause 6 or any clause that depends from clause 6, wherein the packing fraction is greater than, or equal to, approximately 87%. 8. The reflector assembly of clause 6 or any clause that depends from clause 6, wherein the interstitial space is configured to hold fuel salt or coolant fluid. 9. The reflector assembly of clause 6 or any clause that depends from clause 6, wherein the interstitial space is devoid of material. 10. The reflector assembly of clause 1 or any clause that depends from clause 1, wherein the plurality of tube members are packed within the support structure and devoid of welds. 11. The reflector assembly of clause 1 or any clause that depends from clause 1, wherein the plurality of tube members are formed from Alloy 617. 12. The reflector assembly of clause 1 or any clause that depends from clause 1, wherein the plurality of tube members are clad in at least one of niobium, molybdenum, or ceramic substrate. 13. The reflector assembly of clause 1 or any clause that depends from clause 1, wherein the at least one reflector material comprises liquid lead and/or graphite. 14. A reflector assembly for a MCFR comprising: at least one reflector structure, wherein the at least one reflector structure is circumferentially arrangeable in a substantially cylindrical shape that encapsulates a reactor core for containing nuclear fuel; and one or more tank sections disposed within the at least one reflector structure, wherein the one or more tank sections are configured to hold at least one reflector material to reflect fission born neutrons back to a center of the reactor core. 15. The reflector assembly of clause 14 or any clause that depends from clause 14, wherein the at least one reflector structure forms a single tank section of the one or more tank sections. 16. The reflector assembly of clause 14 or any clause that depends from clause 14, wherein the at least one reflector structure defines a longitudinal axis, and wherein the at least one reflector structure comprises two or more tank sections of the one or more tanks sections, each of the two of more tank sections axially aligned along the longitudinal axis. 17. The reflector assembly of clause 16, wherein each of the two or more tanks sections are formed by individual and separable reflector structures. 18. The reflector assembly of clause 14 or any clause that depends from clause 14, wherein the one or more tank sections are formed by a grid pattern of a plurality of radial members and a plurality of circumferential members, each disposed within the at least one reflector structure. 19. The reflector assembly of clause 18, wherein the at least one reflector structure comprises two circumferential ends, and wherein the two circumferential ends comprise curved surfaces. 20. The reflector assembly of clause 14 or any clause that depends from clause 14, wherein the at least one reflector structure is monolithically formed with the one or more tank sections defined therein. 21. The reflector assembly of clause 14 or any clause that depends from clause 14, further comprising a support structure that holds the at least one reflector structure in the substantially cylindrical shape. 22. A method of reflecting fission born neutrons back to a center of a reactor core containing high temperature nuclear fuel, the method comprising: encapsulating the reactor core within a reflector assembly, the reflector assembly including a plurality of tank sections circumferentially arrangeable in a substantially cylindrical shape such that the reactor core is located therein; and disposing at least one reflector material into the plurality of tank sections. 23. The method of clause 22 or any clause that depends from clause 22, wherein the at least one reflector material is a first reflector material, the method further comprising replacing at least a portion of the first reflector material with a second reflector material. 24. The method of clause 23, wherein the first reflector material is liquid lead and the second reflector material is graphite. 25. The method of clause 22 or any clause that depends from clause 22, wherein the plurality of tank sections include a plurality of tube members disposed within a support structure, the method further comprising channeling a fuel salt through an interstitial space that is defined between the plurality of tube members. 26. The method of clause 22 or any clause that depends from clause 22, wherein the plurality of tank sections is supported by a support structure, the method further comprising extracting the reflector assembly from the reactor core via the support structure and replacing at least a portion of the plurality of tank sections. It is to be understood that this disclosure is not limited to the particular structures, process steps, or materials disclosed herein, but is extended to equivalents thereof as would be recognized by those ordinarily skilled in the relevant arts. It should also be understood that terminology employed herein is used for the purpose of describing particular examples only and is not intended to be limiting. It must be noted that, as used in this specification, the singular forms “a,” “an,” and “the” include plural referents unless the context clearly dictates otherwise. It will be clear that the systems and methods described herein are well adapted to attain the ends and advantages mentioned as well as those inherent therein. Those skilled in the art will recognize that the methods and systems within this specification may be implemented in many manners and as such is not to be limited by the foregoing exemplified examples and examples. In this regard, any number of the features of the different examples described herein may be combined into one single example and alternate examples having fewer than or more than all of the features herein described are possible. While various examples have been described for purposes of this disclosure, various changes and modifications may be made which are well within the scope contemplated by the present disclosure. Numerous other changes may be made which will readily suggest themselves to those skilled in the art and which are encompassed in the spirit of the disclosure.
	summary
047737999	abstract	For sampling a section of a tube in a nuclear fuel assembly comprising a skeleton formed by two end-pieces joined by tubes fixed to the end-pieces an opening for the extraction of the section through the upper end-piece is cut out with a milling cutter. Through the inside and by means of a cutting tool, the spacer tube is cut off at a level beneath the junction with the upper end-piece by means of a rotary tool introduced through the upper end-piece and the latter is extracted through the opening.
	claims	1. A container filling system, comprising:a shielding material that substantially blocks radioactivity and substantially defines a chamber;a conduit extending through the shielding material into the chamber;a container securing unit that is disposed in the chamber proximal to the conduit and is adapted to receive a container via the conduit; anda solution delivery device that is disposed in the chamber and is adapted to meter an aliquot from a radioactive stock solution and inject the aliquot from said stock solution into the container. 2. The system of claim 1, wherein the container securing unit includes a port adapted to receive the container. 3. The system of claim 1, wherein the container securing unit includes multiple ports that are each adapted to receive a container. 4. The system of claim 1, wherein the ports include an insert. 5. The system of claim 1, wherein at least one of the container securing unit and the conduit are adapted to move with respect to each other in a first plane. 6. The system of claim 1, wherein the container securing unit and the conduit are adapted to move with respect to each other in a first plane and a second plane. 7. The system of claim 1, further comprising a locator that is disposed in the chamber and is adapted to direct placement of a container. 8. The system of claim 1, further comprising a pair of locators that are each disposed in the chamber and adapted to direct placement of a shipping container and a radioactive stock solution vessel. 9. The system of claim 1, further comprising a dispensing arm that is disposed in the chamber and adapted to receive a solution delivery device. 10. The system of claim 1, further comprising a guide that is disposed in the chamber and adapted to engage a radioactive stock solution container. 11. The system of claim 1, further comprising a receiver that is disposed in the chamber and adapted to engage a cap of a container shipping vial. 12. The system of claim 1, further comprising a tapered guide member that is disposed in the chamber proximal to the container securing unit and adapted to direct a container filling needle into a container. 13. The system of claim 1, further comprising a rod that is adapted to pass through the conduit and engage the container. 14. The system of claim 1 wherein the solution delivery device is movable via rotation about an axis between a position proximal to said container securing unit and a position proximal to a stock solution vessel. 15. The system of claim 1, further comprising a receiver that is adapted to engage a container and remove it from the container securing unit. 16. A method for filling one or more containers, comprising:providing the system of claim 1;placing a first container in the container securing unit via the conduit;metering an aliquot from a radioactive stock solution; andinjecting the aliquot into the container. 17. The method of claim 16, further comprising at least one of:moving either the conduit or the container receiving unit in a first plane and placing a second container in the container securing unit;indexing either the conduit or the container receiving unit and placing a second container in the container securing unit; andengaging the conduit and the container receiving unit and placing the container in the container securing unit. 18. The method of claim 16, further comprising disposing a needle proximate a radioactive stock solution container. 19. The method of claim 18, wherein at least one of a needle and a tapered guide lid is placed above the radioactive stock solution. 20. The method of claim 16, where metering of the aliquot is effected through operation of a computer control means. 21. The method of claim 16, wherein the aliquot has a volume of about 1 μL to about 10,000 μL. 22. The method of claim 16, further comprising:placing at least one further container in the container securing unit via the conduit;metering at least one further aliquot from a radioactive stock solution; andinjecting at least one further aliquot into the at least one further container. 23. The method of claim 22, wherein the first container and at least one further container are injected with different radioactive solutions, or wherein the first container and at least one further container are injected with different doses of the same radioactive solution. 24. The method of claim 16, further comprising at least one of:guiding a needle into a container;placing a cap upon the container;tamping a cap upon the container using a rod passing through the conduit;engaging the container and removing it from the container securing unit;uncapping a container shipping vial;engaging the container and placing it in the container shipping vial;capping the container shipping vial;placing an aluminum seal on a capped container shipping vial; andcrimping an aluminum seal on a capped container shipping vial. 25. The method of claim 16, further comprising determining the dose contained in a container shipping vial including at least one container having an aliquot. 26. The method of claim 25, wherein a dose calibrator is used to determine the dose contained in the container shipping vial. 27. A system comprising:the system of claim 1; andat least one of:a logic device that controls the solution delivery device; anda tapered guide lid that is positioned over the radioactive stock solution. 28. The system of claim 27, further comprising a shipping container that is adapted to receive a container shipping vial, wherein the shipping container and container shipping vial have substantially similar shapes at their interface.
047599014	claims	1. A nuclear reactor installation located in the cavity of a pressure vessel equipped with a vessel roof and a nuclear reactor contained in said vessel, a core contained within the reactor is traversed from top to bottom by a cooling gas and is surrounded by a thermal side shield, within the pressure vessel is a plurality of main loops each containing a heat exchanger, a blower and two gas conducting conduits connecting the heat exchanger pipe and the blower with the reactor core, several auxiliary loops connected by means of two gas conducting conduits with the reactor core for removal of decay heat, such as is generated by a rapid insertion of control rods into the core, each auxiliary loop comprising: bundled heat pipes made up of a plurality of independent, parallel heat pipes each with a heat absorbing part located within the pressure vessel and a heat emitting part located outside the pressure vessel; means for blowing cooling gas, causing the gas to flow, associated with said heat pipes; means for interrupting the flow of cooling gas associated with said means for blowing; a heat sink associated with the heat emitting part of the heat pipes of each bundle; an external cooling loop associated with each heat sink; each cooling loop serially including a circulating pump and a cooling tower; wherein the heat emitting part of the heat pipes of each bundle terminates in a reservoir located above the pressure vessel, said reservoir being said heat sink, being filled with water and being connected to said external cooling loop. at least one evaporator line exiting from each reservoir; and a safety valve connected to each evaporator line. 2. A nuclear reactor installation as in claim 1, wherein the bundled heat pipes are located in an annular space formed by the wall of the cavity and the thermal side shield, and wherein the heat absorbing parts of the heat pipes in a bundle are also arranged in the annular space; each heat pipe further comprises a center part connecting said heat emitting part and said heat absorbing part, serving to transport heat, said center part being installed in a vertical passage through the roof of said pressure vessel. 3. A nuclear reactor installation as in claim 1 further comprising: 4. A nuclear reactor installation as in claim 1, wherein the bundled heat pipes are located in an annular space formed by the wall of the cavity and the thermal side shield, and wherein the heat absorbing parts of heat pipes in a bundle are also arranged in the annular space; each heat pipe further comprises a center part connecting said heat emitting part and said heat absorbing part, serving to transport heat, said center part being installed in a vertical passage through the roof of said pressure vessel.
	abstract	The invention pertains to a nuclear fuel rod for a nuclear reactor. The fuel rod has a cladding. The cladding's external surface has a surface texture that includes a rib. The rib coils around the circumference of the cladding. The rib length forms a sequence of continuous rib loops uniformly spaced along an axial length of the cladding. The ratio of rib height to cladding diameter is greater than or equal to 0.0134 and less than or equal to 0.0268. The ratio of rib height to rib width is greater than or equal to 0.8 and less than or equal to 1.2. A pitch measured between adjacent rib loops is greater than or equal to 9× rib height and less than or equal to 12× rib height. The rib enhances fuel rod heat transfer in a region downstream of grid mixing vanes, where turbulence is dissipated.
043009832	abstract	A method and arrangement for containing the core melt flowing from a nuclear reactor into a core catcher below the core wherein the core melt is permitted to gradually penetrate layers of a core catcher materials of inorganic reactor soluble oxides or salts disposed in the core catcher which core catcher materials are dissolved by the oxidic part of the core melt, and the molten solution, after solidification and after being cooled down to a temperature at which hydrogen generating reactions do not take place, is leached with water and rinsed out of the core catcher without the need for humans to be present in the reactor containment and to be exposed to radiation.
	description	The present invention relates to an apparatus for making measurement and inspection of a pattern based on design data on a semiconductor device or the like and the image obtained by a scanning electron microscope. More particularly, it relates to a pattern measurement apparatus for adding identification information to line segments within the electron-microscope image, and managing the pattern-forming line segments based on the identification information. In recent years, the design data on a semiconductor device has increasingly come into use for the measurement on the semiconductor device by the scanning electron microscope (: SEM). In JP-A-2006-66478 (corresponding to US 2006/0045326), the following embodiment is explained: A pattern matching is performed between line segments based on the design data and contour lines of patterns obtained by the scanning electron microscope. Then, a pattern is measured which is identified by this pattern matching. Moreover, in JP-A-2000-177961 (corresponding to U.S. Pat. No. 6,768,958), the following embodiment is explained: Pattern edge of a mask pattern on the electron-microscope image is stored into a database, using a standard format such as GDSII. In JP-A-7-130319 (corresponding to U.S. Pat. No. 5,523,567), there is disclosed a technology for forming an extremely-low-magnification image by mutually connecting a plurality of field-of-views to each other. A SEM image itself is merely two-dimensional luminance information. Accordingly, the edge represented on the SEM image has none of information about what the edge itself indicates. Consequently, when identifying a pattern of measurement purpose or the like, it becomes necessary to perform position identification by the pattern matching as is explained in JP-A-2006-66478. Meanwhile, in accompaniment with the microminiaturization of semiconductor devices in recent years, the measurement based on an even-higher-magnification image has become more and more requested. For example, in order to grasp an extent of the pattern correction by OPC (Optical Proximity Correction), it is required to measure a certain part of the pattern which will be modified as a result of being influenced by the OPC pattern. If, however, the measurement is made using the high magnification needed for evaluating a location like this, there occurs the following problem: Namely, it becomes increasingly difficult to involve, within the field-of-view, the entire pattern, or a range of the pattern needed at least for identifying configuration of the pattern. The acquisition of an image with a high magnification, on the other hand, results in the acquisition of the image in only a narrow field-of-view. As a consequence, it has been found difficult to establish mutual compatibility between the high-magnification observation for high-resolution implementation and the observation in a wide region. In the explanation in JP-A-2000-177961 as well, no disclosure is made concerning a proposal which would be able to simultaneously solve mutually incompatible problems like this. Furthermore, according to the technology disclosed in JP-A-7-130319, on the contrary, such a processing as thinning out scanning lines is performed in order to form the extremely-low-magnification image. Accordingly, this technology is unsuitable for accomplishment of the purpose of the high-magnification observation for high-resolution implementation. One of the main objects of the present invention is to establish the mutual compatibility between the measurement with a high magnification and the measurement in a wide region. Another object thereof is to provide a pattern measurement apparatus which, even in the case of the edge information based on a SEM image, makes it possible to implement the management of the edge information that is equivalent to the management of the design data. As an aspect for accomplishing the above-described objects, the following pattern measurement apparatus is proposed: Namely, the pattern measurement apparatus adds identification information to each of fragments which constitute a pattern within the image obtained by the SEM, and stores the identification information in a predetermined storage format. Here, the identification information is added to each fragment for distinguishing between one fragment and another fragment. According to the above-described configuration, it turns out that the identification information is added to each fragment on the SEM image which has possessed no specific identification information originally. As a consequence, it becomes possible to implement the management of the SEM image based on the identification information. Giving an example, a case is considered where a superimposed image is formed by mutually connecting images of a plurality of field-of-views to each other. In this case, at the time of the formation, the mutual connection between the field-of-views is performed in such a manner that fragments having identification information which is common to the field-of-views are mutually connected to each other. Consequently, at the time of forming the mutually-connected image, this method allows implementation of the mutual connection based on high-accuracy position alignment with no shift appearing between the field-of-views. In Description of the INVENTION, the explanation will be given concerning more concrete configuration and effects of the present invention. Other objects, features and advantages of the invention will become apparent from the following description of the embodiments of the invention taken in conjunction with the accompanying drawings. Hereinafter, the explanation will be given below concerning the following embodiment: A side-by-side checking (i.e., comparison) is made between the edge portion of a SEM (: Scanning Electron Microscope) image formed by an electron microscope and the design data, thereby adding identification information to the SEM edge which constitute each fragment of the pattern. In FIG. 1, the SEM edge is extracted from a SEM image formed by an electron microscope, then making a side-by-side checking between each line segment of the SEM edge and the design data. The design data includes a variety of information about the pattern. In the present embodiment, however, information specific to each line segment constituting the pattern is extracted in particular out of this variety of information. Then, the information extracted is applied as the identification information for each fragment. FIG. 2 is a diagram for explaining an embodiment where the identification information is added to the SEM edge. If the identification information about each line segment of the pattern is stored in the original design data, it is all right just to use this information. If, however, the identification information is not stored therein, it is possible to allocate the identification information for each line segment thereto in accordance with a predetermined rule. FIG. 2 is the diagram for explaining the embodiment of such a case. FIG. 2 is the explanatory diagram for explaining the embodiment where the identification information is added to each fragment of the SEM edge in accordance with a predetermined algorithm. Namely, FIG. 2 is the diagram for explaining the following embodiment: After a matching between the design data 201 and the line segments 202 based on the SEM edge has been performed, the identification information specific to each line segment is automatically allocated to each line segment. This allocation is performed based on position information (i.e., Top, Left, Bottom, Right) within the field-of-view of the line segments, and an algorithm of allocating numbers sequentially in a counter-clockwise direction from the line segment existing on the leftmost side. Incidentally, the line segments 202 are formed by converting the SEM edge into a contour line (i.e., contour-line conversion). The outline of the contour-line conversion will be described later. Moreover, in order to judge which of line segments of the design data 201 each fragment constituting the line segments 202 is associated with, positions of the line segments 202 are determined which are the closest to a plurality of measurement points 203 allocated to each fragment of the design data 201. Based on identification information on the line segments of the design data 201 to which the measurement points 203 belong, the identification information is added to each line segment of the line segments 202. Also, a boundary between the respective line segments of the line segments 202 may be determined by drawing a straight line such that, as illustrated in, e.g., FIG. 3, the vertex angle of the design data 201 is divided into two, and determining the boundary between the line segments depending on to which of the two-divided regions each line segment 202 belong. As explained above, the identification information is added to each line segment of the SEM edge on the basis of the design data. This addition of the identification information makes it possible to easily implement inspections and measurements in which each line segment is used. In the explanation hereinafter, their concrete examples will be explained in detail using the accompanying drawings. Of course, it is needless to say that the above-described identification-information addition method to the line segments 202 is merely one example, and that a variety of modifications can be made within a range of not departing from the spirit of the present invention. Incidentally, in the present embodiment, the processing of adding the identification information has been applied to the SEM edge which is converted into the contour line. The technology for implementing the contour-line conversion is, e.g., as follows: FIG. 4 is a diagram for explaining the correspondence relationship between a white band 401 of a pattern on the SEM image and luminance-profile peak positions of the white band 401. In FIG. 4, right-half of the edge portion of the pattern is displayed on the SEM image. In the present embodiment, the contour-line conversion of the SEM edge is executed as follows: Luminance-signal extraction regions 402 are set such that the regions 402 include the white band 401. Then, the luminance distribution is determined in a direction intersecting the pattern edge. Finally, the contour-line conversion of the SEM edge is executed by mutually connecting the luminance-distribution peak positions 403 or locations having a predetermined luminance to each other. As illustrated in FIG. 4, the white band 401 on the SEM image is image information which has its own width, and has a convex-shaped luminance distribution. In the present embodiment, in order to make the comparison with the design data, the white band is converted into the line-segment information as is the case with the design data. Incidentally, the white band is the image information which occurs in a pattern having gradient or protrusion, and which is characteristic of a charged-particle beam apparatus typical of which is SEM. As illustrated in FIG. 4, the white band is showed up in white on the SEM image. Incidentally, the contour-line conversion technology explained in the present embodiment is, after all, merely one example. Namely, various types of conversion technologies are applicable, as long as they are technologies capable of converting the white band or SEM edge into a narrow line, and tracing situation of the white band or the like with a high accuracy. The line-segment information to which the identification information is added as described above is stored into a storage medium in a standard format such as, e.g., GDSII. In the present embodiment, GDSII is also used as the format of the design data on the original semiconductor device. In this way, the SEM-edge information is registered in the same format as that of the original design data. This registration scheme makes it possible to address the SEM-edge information in the same way as in the design data. This point will be described later. Hereinafter, referring to the drawings, the explanation will be given below concerning the more concrete practical embodiments. FIG. 5 is a diagram for explaining the overview of a scanning electron microscope for acquiring a SEM image. Hereinafter, referring to FIG. 5, the explanation will be given below regarding the scanning electron microscope (which, hereinafter, will be referred to as “SEM” in some cases). A voltage is applied between a cathode 1 and a first anode 2 by a high-voltage control power-supply 20 which is controlled by a control processor 30. A primary electron beam 4 is derived from the cathode 1 by this applied voltage as a predetermined emission current. An acceleration voltage is applied between the cathode 1 and a second anode 3 by the high-voltage control power-supply 20 controlled by the control processor 30. The primary electron beam 4 emitted from the cathode 1 is accelerated by this acceleration voltage, thereby being caused to travel toward a subsequent-stage lens system. The primary electron beam 4 is converged by a convergence lens 5 which is current-controlled by a lens control power-supply 21 controlled by the control processor 30. Then, an unnecessary region of the primary electron beam 4 is removed by a diaphragm plate 8. After that, the primary electron beam 4 is converged onto a sample 10 as an infinitesimal spot by a convergence lens 6 which is current-controlled by a lens control power-supply 22 controlled by the control processor 30, and an objective-lens control power-supply 23 controlled by the control processor 30. The objective lens 7 can assume various configuration modes such as in-lens scheme, out-lens scheme, and snorkel scheme (semi in-lens scheme). Also, retarding scheme is possible which decelerates the primary electron beam 4 by applying a negative voltage to the sample 10. Moreover, each lens may also be configured with an electrostatic-type lens including a plurality of electrodes to which a controlled voltage is applied. The primary electron beam 4 is scanned two-dimensionally on the sample 10 by a scanning coil 9 which is current-controlled by a scanning-coil control power-supply 24 controlled by the control processor 30. A secondary signal 12 such as secondary electrons, which is generated from the sample 10 by the irradiation with the primary electron beam 4, travels to a top portion of the objective lens 7. After that, the secondary signal 12 is separated from the primary electrons by an orthogonal-electromagnetic-field generation device 11 for separating the secondary signal, then being detected by a secondary-signal detector 13. The signal detected by the secondary-signal detector 13, after being amplified by a signal amplifier 14, is transferred to an image memory 25 to be displayed on an image display 26 as the sample image. A two-stage deflection coil (objective-lens-used aligner) 16, which is deployed at the same position as that of the scanning coil 9, makes it possible to two-dimensionally control the pass-through position of the primary electron beam 4 with respect to the objective lens 7. Here, the coil 16 is current-controlled by an objective-lens-used-aligner control power-supply 27 controlled by the control processor 30. A stage 15 is capable of displacing the sample 10 in at least two directions (i.e., X direction and Y direction) within a plane perpendicular to the primary electron beam 4. This displacement makes it possible to change the scanning region by the primary electron beam 4 on the sample 10. A pointing device 31 allows specification of the position of the sample image displayed on the image display 26, and acquisition of the information thereabout. An input device 32 allows specifications of image grabbing conditions (i.e., scanning rate, and images' totalized number-of-pieces), field-of-view correction scheme, and output and saving of the images. Incidentally, address signals corresponding to memory positions in the image memory 25 are generated inside the control processor 30, or inside a control computer set up separately. Then, the address signals, after being analog-converted into analog signals, are supplied to the scanning-coil control power-supply 24. When the image memory 25 has, e.g., 512×512 pixels, the address signals in the X direction are digital signals which repeat from 0 to 512. Also, the address signals in the Y direction are digital signals which repeat from 0 to 512, and which are incremented by 1 when the address signals in the X direction attain to from 0 to 512. These digital address signals are converted into the analog signals. The addresses of the image memory 25 and addresses of deflection signals for scanning the electron beam are in a one-to-one correspondence with each other. As a result, the two-dimensional image of a deflection region of the electron beam by the scanning coil 9 is recorded into the image memory 25. Additionally, the signals inside the image memory 25 can be read one after another in time sequence by a read-address generation circuit which is synchronized with a read clock. The signals read in correspondence with the addresses are analog-converted, then becoming luminance modulation signals of the image display 26. Also, the apparatus explained in the present embodiment is equipped with a function of forming a line profile based on the detected secondary electrons or reflected electrons. The line profile is formed based on the electron detection amount at the time when the primary electron beam 4 is scanned one-dimensionally or two-dimensionally on the sample 10, the luminance information on the sample image, or the like. The line profile thus obtained is used for, e.g., the size measurement on a pattern formed on a semiconductor wafer or the like. Incidentally, in FIG. 5, the explanation has been given assuming that the control processor 30 is integrated with the scanning electron microscope, or is in a configuration compatible therewith. It is needless to say, however, that the configuration is not limited thereto. Namely, the processing explained so far may be performed by a processor which is provided separately from the scanning electron microscope. At this time, the following appliances become necessary: A transmission medium for transmitting the detection signal detected by the secondary-signal detector 13 to the control processor 30 as an image, or transmitting a signal to the objective-lens control power-supply 23 or the scanning-coil control power-supply 24 from the control processor 30, and an input/output terminal for inputting/outputting the signals transmitted via the transmission medium. Moreover, the apparatus in the present embodiment is equipped with a function of storing in advance, as a recipe, conditions (i.e., measurement locations, optical conditions of the scanning electron microscope, and the like) at the time of observing, e.g., a plurality of points on the semiconductor wafer, and making the measurement and observation in accordance with the contents of the recipe. Also, a program for performing a processing which will be explained hereinafter may be registered into a storage medium, and the program may be executed by a processor for supplying necessary signals to the scanning electron microscope and the like. Namely, the embodiment which will be explained hereinafter is about the program employable in a charged-particle beam apparatus such as the scanning electron microscope that is capable of acquiring the image, or an explanation as a program product. Furthermore, the design data on the circuit pattern of a semiconductor device represented in the GDS format or OASIS format may be stored into the control processor 30. Then, a design-data management unit 33 for converting the design data into data needed for the control over the SEM may be connected to the control processor 30. The design-data management unit 33 is equipped with a function of generating the recipe for controlling the SEM on the basis of the inputted design data. Also, the unit 33 is equipped with a function of processing the design data on the basis of the signal transmitted from the control processor 30. Also, the processing which will be explained hereinafter may be performed using a processor which is provided inside the design-data management unit 33. In addition, in substitution for the control processor 30, the scanning electron microscope may also be controlled using the processor provided inside the design-data management unit 33. Additionally, in the explanation of the present embodiment, the design-data management unit 33 will be explained as a separated unit provided separately from the control processor 30. Its configuration, however, is not limited thereto. Namely, the design-data management unit 33 may also be integrated with the control processor 30, for example. In the present embodiment, the sample 10 is assumed to be a wafer which is deployed in the semiconductor-product fabrication processes. A resist pattern formed on the wafer by the lithography process is used. As a comparison target with this resist pattern, the design data on the circuit pattern of a semiconductor device is used which turns out to be the original of this resist pattern. The design data on the circuit pattern of a semiconductor device refers to an ideal pattern configuration at the time when the circuit of the semiconductor device is finally formed on the wafer. Incidentally, in the explanation hereinafter, the semiconductor wafer is selected as the inspection target. The configuration, however, is not limited thereto, as long as the design data and a target to be evaluated form a pair. The explanation hereinafter is also effective to a mask pattern which is formed on a glass substrate, and which is used when exposing the semiconductor pattern on a wafer, and a pattern which is formed on such a glass substrate as liquid-crystal panel. Also, regarding the type of the design data on a circuit pattern, whatever type is all right as long as software for displaying the design data on a circuit pattern is capable of displaying its format scheme and addressing the design data as graphics data. FIG. 6 is a diagram for explaining a basic flow of the processing, which ranges from the acquisition of the SEM image to the verification of a pattern using the predetermined-formatted contour-line information formed based on the SEM image acquired (in the present embodiment, the GDS format is used as the predetermined format). This processing is executed in the design-data management unit 33 explained in FIG. 5, or in the control processor 30. Also, in the design-data management unit 33, or in the control processor 30 (the unit 33 and the processor 30, in some cases, are referred to as simply “control unit”, which is a term including both of them). The contour-line conversion of a pattern configuration also makes it possible to extract configuration abnormality or defect configuration of a peripheral pattern including this pattern. Also, generating this contour line as the format of the pattern design data makes it possible to use the evaluation and verification technologies used in the various types of design methodologies. This feature has allowed implementation of high-accuracy yield management and enhancement in the semiconductor fabrication processes. Moreover, by representing the contour line of a pattern configuration by using the design data having a hierarchical structure, it becomes possible to represent the contour line in such a manner that the contour line is in a correspondence relationship with the structure of the design data on the circuit. This feature allows the good-or-bad of the verification result on the contour line to be directly reflected on the design data, thereby making it possible to confirm, predict, and amend the design data. Accordingly, it becomes possible to address a design unsuccessfulness more swiftly, and to make a contribution to the yield enhancement. By intimately coordinating the recipe generation system originating from the design data and the image acquisition scheme based on the design data, the contour-line conversion is performed while being caused to be related with the design data which became the original of the fabrication. This feature allows implementation of high-accuracy configuration reproduction or high-accuracy extraction of the defect configuration. Additionally, in the explanation hereinafter, not being limited to a transferred pattern of the silicon, mention will also be made to application of a semiconductor mask pattern. Hereinafter, the explanation will be given below concerning the concrete function of each configuration component explained in FIG. 6. (1) Outline of Recipe Generation Unit In a recipe generation unit, measurement coordinates and the design data are inputted which correspond to the pattern design data for fabricating a semiconductor pattern. Then, a recipe for making the measurement is generated automatically. These measurement points includes coordinates of a critical point at the time of the lithography and processing, critical points of circuit-performance-associated factors (element characteristics, wiring delay, and via), CAA/DRC, and the like. These measurement points are inputted, then generating the recipe for the photographing (i.e., scanning by the scanning electron microscope). Namely, positions of measurement targets, photographing magnification, and alignment pattern position (AP) and autofocus position (AF) for achieving a measurement field-of-view are generated automatically. In the recipe generation unit, the design data is used as reference for the inspection. This feature allows implementation of determination of the measurement positions and field-of-view range with the design data used as the reference, and implementation of an enhancement in preciseness in the photographing of the measurement data with configuration of the range used as the reference. Hereinafter, the explanation will be given below concerning a recipe generation technologies which is preferable for extracting, from an image for the measurement/inspection target, a contour configuration which represents configuration of the image accurately. Hereinafter, the detailed description will be given below regarding optimization of the photographing field-of-view positions for the measurement and inspection, and an optimization technology for its photographing conditions. concerning the optimization technology for the photographing field-of-view positions (i.e., acquisition of a panorama image based on measurement points) When an inspection target pattern is converted into a contour line to perform its configuration evaluation, a contour line of panorama synthesis is generated. As will be explained hereinafter, this contour line of the panorama synthesis is generated by combining FOVs (: Field-Of-Views) at the respective measurement points with each other. This contour line makes it possible to generate the contour line of the inspection target in a wide range while maintaining accuracy of the contour line of each FOV in a sub-nanometer unit. Also, since the contour-line generation processing is performed on each FOV basis, the parallel processing calculation becomes executable. This parallel calculation allows implementation of speeding-up of the processing. In this recipe generation, when extracting the contour line from the image of the photographing result, it is required to take into consideration the connection at the boundary on each field-of-view basis, and to perform a setting of the FOVs where an overlap amount to some extent is predicted and added. This setting of the FOVs allows implementation of a high-accuracy connection portion in the connection of the contour lines on each field-of-view basis. Using the drawing, this setting will be explained hereinafter. (1-1) Case of Measuring a Pattern which Spread over a Plurality of FOVs In accompaniment with the microminiaturization of semiconductor devices in recent years, the request made for the measurement apparatus in the measurement accuracy and reproducibility has become more and more strict. With respect to a pattern which is becoming increasingly microminiaturized, more microscopic information needs to be acquired by narrowing the FOVs (i.e., heightening the magnification). On the other hand, narrowing the FOVs sometimes results in the case where the measurement target pattern cannot be involved within a single FOV. Also, when evaluating for the doness of the pattern, in some cases, it is necessary to evaluate not only a single pattern but also its relationship with another pattern existing in proximity to the single pattern. Concretely, when a plurality of patterns are formed in proximity to each other, in some cases, it is necessary to evaluate modifications of the patterns caused by the proximate correction effect. In view of the above-described problems, in the present embodiment, the introduction will be given below concerning the recipe generation technology for generating the following recipe: Namely, by superimposing a plurality of FOVs on each other to form a large FOV, this recipe allows formation of an image where a pattern so large as to extend off a single FOV can be displayed, or an image where the relative relationship between a plurality of patterns can be identified accurately. Concretely, a large-region image can be formed as follows: The region of a measurement/inspection target (when performing the evaluation including an adjacent pattern, a region including the target pattern and the adjacent pattern) is determined. Next, with respect to the large region determined, a plurality of small field-of-views are calculated where the inspection target image can be photographed with a high accuracy. Finally, the large-region image can be formed by combining these small field-of-views (FOVs) with each other. Incidentally, in the present embodiment, the connectivity between the FOVs is taken into consideration. As a result of this, as illustrated in FIG. 7, size of the FOVs is determined such that the FOVs 701 are overlapped with each other. Since the equivalent configurations are represented in an overlapped portion 702, the accurate position alignment can be performed by, e.g., a pattern matching between these configurations. Furthermore, in the present embodiment, the contour-line conversion is performed with respect to the SEM edge, then performing the position alignment between the FOVs such that its line segments are overlapped with each other. This feature allows execution of the exceedingly-high-accuracy position alignment between the FOVs. Also, as described earlier, the identification information is added to each contour line in the present embodiment. Accordingly, even in the case of, e.g., a sample where a plurality of same patterns are arranged, a side-by-side comparison of the identification information on each contour line is made between the adjacent FOVs. This execution of the side-by-side comparison makes it possible to implement the accurate superimposition between the FOVs while preventing a mix-up between the patterns. In particular, in each contour line used in the present embodiment, the identification information is added thereto based on the design data. Consequently, even in the case of different FOVs, the identification information on each contour line can be made common thereto as long as each contour line is of the same pattern. This allows implementation of the high-superimposition-accuracy-based superimposition between the FOVs without necessitating extra time and labor. Also, if sizes of the individual FOVs are nonuniform, in the image after the superimposition, a variation in the measurement accuracy occurs for each location thereof. This situation requires that the photographing be performed with a uniform magnification for each FOV. Also, maintaining a stable length-measuring accuracy for a plurality of measurement targets requires that the images be acquired with the use of an identical magnification always. In the present embodiment, in view of the conditions like this, a proposal is made concerning a recipe setting method which makes it possible to address a change in size of the pattern by changing the number of the FOVs while keeping unchanged the size of each FOV capable of ensuring a desired measurement accuracy. Namely, when determining the acquisition number of the FOVs so that a desired measurement pattern will be involved therein, only the FOV acquisition number-of-pieces is automatically changed while keeping the size of each FOV unchanged in correspondence with the setting of the size of a region which involves the measurement pattern. In this way, by giving a higher priority to the determination of the size of each FOV, it becomes possible to stably maintain the measurement accuracy independently of the size of the pattern. Also, a similar effect can also be obtained by changing the acquisition number-of-pieces and the size of the superimposition regions in correspondence with the size of the pattern. In this case, the acquisition number-of-pieces is determined so that a region involving the entire pattern will be involved. Simultaneously, it is advisable to change the size of the superimposition regions in order to adjust the size of the image to be formed. Based on the references described so far, in the design-data management unit 33 or the control processor 30 explained in FIG. 5, the factors such as the image acquisition number-of-pieces and the size of the superimposition regions are determined automatically, then being stored into the recipe for controlling the scanning electron microscope. As described above, it is desirable to determine the size of each FOV in advance, and to determine the factors such as the image acquisition number-of-pieces and the size of the superimposition regions with the information on the size of each FOV used as the reference. If, however, there exists other circumstances to which a higher priority is to be given, changing the size of each FOV is executable. (1-2) Case of Measuring and Observing a Certain Region Selectively with High Magnification In evaluating the finished quality of the semiconductor device, consider the following occasion: A simulation based on the design data is performed, and a sample involving a critical region where there is a possibility of occurrence of a defect or the like is measured and inspected based on this simulation result. On this occasion, in some cases, the more detailed measurement and observation is made regarding this critical region as compared with other regions. In order to automatically creating a recipe for measuring the sample like this, a proposal is made concerning an algorithm where the degree of risk obtained based on the simulation result is quantified on each measurement-region basis, and where the size of each FOV is automatically determined in accordance with the degree of risk thus quantified. Namely, as illustrated in FIG. 8, each FOV is automatically determined as follows: The detailed measurement is made on a region 801 with a high degree of risk by using a small FOV; whereas the approximate measurement is made on an otherwise region by using a large FOV (not illustrated). Determining each FOV in accordance with the rule like this allows implementation of the determination of each FOV which makes it possible to establish mutual compatibility between the high measurement accuracy and an enhancement in the measurement efficiency. Incidentally, in quantifying the degree of risk, the various conditions on the formation of the semiconductor device are taken into consideration, and weights can be assigned to their coefficients in this way. The factors such as the setting of size of the superimposition regions are automatically determined based on the rules explained in (1-1-1). (1-3) Case of Determining FOVs with Circuit-Associated Meaning Taken into Consideration A large number of plural elements are formed on a semiconductor device. Of these elements, there exist elements which have a different meaning in circuit terms, such as gate unit of a transistor, gate extension unit thereof, intersection unit thereof with diffusion layer, polysilicon wiring thereof, diffusion sharing unit thereof with adjacent transistor, and the like. Accordingly, it is conceivable that the evaluation of the pattern is performed based on the design data and in each circuit unit. FIG. 9 is a diagram for explaining an embodiment where the FOVs are automatically set based on the design data and depending on the type of an arbitrarily set pattern. As illustrated in FIG. 9, each FOV is allocated in such a manner that each FOV involves the pattern selectively. Also, since the design data involves data on a circuit to which the pattern belongs, each FOV is allocated at an appropriate position based on selection of the circuit data, position of the pattern configuring the circuit, information on the configuration, and the size of a desired FOV set in advance. Additionally, if the FOV in an appropriate size can be allocated from the circuit-associated importance and the measurement accuracy in view of the purpose of the measurement, it becomes possible to establish mutual compatibility between maintaining of the high measurement accuracy and efficiency implementation of the measurement. Consequently, in the present embodiment, a proposal is made concerning a method for classifying the regions on each circuit-type basis, and changing the size of a FOV to be applied on each region basis. As an example, it is conceivable to set an algorithm for setting in advance the weights-assignment coefficients on each circuit-importance basis, and determining the size of each FOV in correspondence with the weights-assignment coefficients. For example, it is advisable to determine in advance the size of each FOV in correspondence with the set weights-assignment coefficients, and to set the number and positions of the FOVs so that a desired pattern or desired region will be involved therein. Since the FOV in the same size is allocated to the circuits of the same type, it becomes possible to make the measurements based on the same accuracy. More concretely, an assembly of a plurality of transistors is evaluated in a circuit-associated unit, thereby being able to be also used for, e.g., characterization (i.e., characteristics evaluation of cell) of a standard cell or the like. FIG. 9 is the diagram for conceptually explaining the embodiment where the appropriate FOVs are allocated to the design data depending on the type of the circuit. Also, the allocation of the FOVs as illustrated in FIG. 9 is performed in a hierarchical structure illustrated in such a conceptual diagram as FIG. 10. The recipe is automatically set so that a low-magnification FOV is allocated to a location such as a mere wiring unit where high accuracy is not requested relatively, and so that a high-magnification FOV is allocated to an important location such as a transistor where performance of the semiconductor element is determined. Also, the low-magnification section is also used for the addressing. In the meaning in circuit terms, the respective FOVs are classified into the locations of a transistor to be measured, i.e., the locations such as gate unit, gate extension unit, intersection unit with diffusion layer, polysilicon wiring, diffusion sharing unit with adjacent transistor, and the like. From the conditions on the measurement magnification calculated in advance from the design-rule with respect to this classification, each magnification, i.e., each FOV region, is determined and deployed automatically. Consequently, the recipe can be generated where the magnification differs depending on the differences in the patterns to be measured, and where the respective FOVs are overlapped with each other. (2) Outline of Image Acquisition Unit In the image acquisition unit, the images of the measurement/inspection target are sequentially acquired in accordance with the recipe generated by the recipe generation unit. An image for the alignment is acquired using the design data (which, hereinafter, will be referred to as “CAD (Computer Aided Design) data” as an example of the design data in some cases). Then, using this image, the positioning of the location is performed using the CAD data. Next, a high-magnification image of the measurement target position is acquired, then superimposing the CAD data on the high-magnification image. At this time, if an error occurs in the positioning in the high-magnification image, the matching of the CAD data is performed again to make the position correction. After that, the correspondence information on the acquired image with the CAD position is managed. In the present embodiment, the images of the pattern which becomes the inspection target are acquired with a high accuracy, using the design data (e.g., GDS data) which becomes the original of the pattern fabrication. Namely, since the image acquisition is performed based on the design data, there exists a one-to-one correspondence relationship between the inspection images and the design data. This correspondence relationship makes it possible to immediately determine to which position in the design data the image belongs. Accordingly, inspecting the image makes it possible to judge, based on the design data, what type of influences the good-or-bad of the image exerts on the design (e.g., circuit performance and yield). In this way, in the present inspection scheme, the image recording scheme which has the correspondence relationship with the design data is employed. This image recording scheme makes it facilitate to convert the contour line into the design data. This conversion of the contour line into the design data will be described later. (3) Outline of Edge Detection Unit In the edge detection unit, the edge representing the pattern is detected based on the acquired image acquired by the image acquisition unit. In this detection, a region for detecting the profile on each pixel basis is set with the line segments of the CAD data used as the reference. Then, the edge points are detected according to the edge detection scheme of the length-measuring SEM. At this time, in order to recognize a deformation of the pattern (i.e., pattern cut or short-circuit), the correspondence relationship between the corresponding portion and the CAD line segment is detected, then extracting the collapse. Moreover, an averaging processing is applied to the point string detected, thereby performing a smoothing as the contour line. In the edge detection unit, the following edge detection is performed. (3-1) Edge Detection Based on Line-Profile Formation Hereinafter, the explanation will be given below regarding a method of extracting the SEM edge from a line profile (which, hereinafter, will be referred to as merely “profile” in some cases) obtained by the electron-beam scanning), and performing the line-segment conversion (which is referred to as “contour-line conversion” in some cases) of the SEM edge. The contour line in the present embodiment is formed in accordance with the following steps: 1) An approximate contour line is formed, using an image processing. In this case, as illustrated in, e.g., FIG. 11, the image processing is performed whereby the line segments will be formed along the white band of the SEM edge. 2) A length-measuring box is set so that pixels which form the line segment will be involved in the box. The profile is formed by scanning the electron beam inside the set length-measuring box. Also, the length-measuring boxes are set in an arbitrary number along the formation direction of the contour line. The formation direction of the profile is determined using the design data as the original, and based on a prediction of the transfer of the actual pattern. 3) The profile calculation is performed inside the length-measuring boxes, thereby selecting the line-segment-converted edge points accurately. Then, the contour line is formed in such a manner that the edge points are mutually connected to each other. In this case, peak positions of the formed line profile, or the profile positions equivalent to a predetermined luminance threshold value (Th) are selected, then being defined as the edge points. (3-2) Noise Elimination Processing at the Time of Edge Detection When the contour-line conversion is performed, the edge information on the original image is sometimes lost. As a result, in some cases, the appropriate contour-line conversion becomes difficult. Hereinafter, based on the illustration in FIG. 12, the explanation will be given below concerning steps for connecting such edge points to each other appropriately. 1) First, the white band of the image which configures the edge is detected. 2) After the two-valued conversion is performed with a threshold value 1 (Th1), the narrow-line conversion of the edge is carried out (noise is small). 3) After the two-valued conversion is performed with a threshold value 2 (Th2), the narrow-line conversion of the edge is carried out (noise is large). 4) Portions where the edge is judged to be lost with Th1, and where the edge is judged to exist with Th2 are detected as being loss points. 5) The edge existence ratio is detected in the loss-point interval. 6) If the edge existence ratio is larger than a constant value, the loss points are connected to each other. Performing the processing as described above allows implementation of the appropriate connection of the loss-point interval. (3-3) Elimination Processing of Beard-Like Noise When the edge detection is performed, as illustrated in FIG. 13, a line segment which extends from the edge just like a beard occurs in some cases, despite the fact that this phenomenon is not directly related with the edge. Hereinafter, the explanation will be given below regarding steps for eliminating the noise like this. 1) First, the narrow-line conversion of the SEM edge is performed. 2) The beard position is detected by the template processing. 3) The end-point position is detected by the template processing. 4) A pixel signal between the beard position and the end-point position is eliminated, thereby performing the elimination of the beard portion. (3-4) Concrete Pattern-Collapse Judgment In the edge detection for the purpose of implementing the contour-line generation, it is necessary to recognize a configuration collapse of the pattern corresponding to the design data (i.e., pattern whose configuration does not coincide with the design data). In the present method, the profile calculation on each pixel basis is performed where the design data is used as the reference. Accordingly, in the case of a pattern which is significantly retreated or expanded with respect to the design data, or in the case of a division configuration or connection configuration which differs from the design data, the distance between the line segments, which are the design data, and the edge points, which are employed as the target, is comparatively large. As a result, in some cases, the accurate profile calculation becomes impossible, and thus the accurate contour-line construction becomes impossible. In the present method, in order to solve these problems, optimization of the edge detection is implemented by performing the following processings: 1) Calculating an approximate contour line is performed in the above-described noise elimination and loss elimination processes, using the image processing. At this time, a rough contour configuration is determined based on the judgment on a general signal amount on each pixel basis. 2) The correspondence relationship is determined between the above-described approximate contour line and the line segments of the design data corresponding to the proximity. In this way, a classification is made regarding the retreat or expansion due to the difference in the distance, and the division or connection which does not correspond to the line segments of the design data. 3) With respect to the accurate edge detection of the pattern-collapse portion, from the above-described classification, the position of a profile calculation region is defined as the approximate edge position. In this way, the optimization of the profile calculation region is performed. (3-5) Case of Forming Contour Line by Processing Line Segments not Existing in Design Data In the transferred pattern on a semiconductor wafer, planarization of the plane or surface (i.e., CMP (: Chemical Mechanical Polishing) processing) needs to be performed in order to maintain the fabrication yield highly. On account of this, in the wiring region or the like, in many cases, a dummy wiring pattern which does not function as the wiring pattern is transferred to a region of loose wiring pattern, depending on the degree of congestion of the wiring (i.e., dummy film). Since this pattern is not the pattern which configures the circuit, it does not exist as the design data generally. Also, since this pattern is designed for the purpose of filling the loose region, it is embedded in a configuration which is larger than the wiring pattern as the circuit. In the present contour-line extraction, a processing is performed where the dummy pattern like this larger than the wiring pattern is excluded from the extraction targets based on the design rule. Also, in recent years, automatic generation of the dummy pattern has become increasingly executable in the design automatization processing (EDA (: Electronic Design Automation)) by performing a simulation on the planarization processing based on the wiring density. Consequently, in the present contour-line extraction processing, if there exists the data used for the above-described dummy-pattern generation, the dummy pattern and the actual pattern are caused to correspond to each other by making reference to this configuration data. In this way, recognizing the dummy pattern is performed, thereby making it possible to exclude the dummy pattern from the contour-line extraction. (3-6) Addition of Identification Information to Multilayered Contour Line In the semiconductor fabrication processes, finished qualities of the elements and wiring exist as inspection target patterns on each process basis. For example, as illustrated in FIG. 14, a diffusion region and a gate pattern exist as transfer patterns directly after the gate fabrication process of a transistor. Also, in the wiring process in each later, pattern of the wiring layer and contact pattern exist in a mixed manner. In the processing of the edge detection in the contour-line extraction, the correspondence relationship with the design data, which is designed for each later which becomes the target, is calculated. This calculation makes it possible to identify whether the edge is the diffusion-region pattern or the gate-layer pattern, thereby allowing the edge points to be classified in correspondence with the design data in each later. On account of this, as the above-described identification information for the line segments, it is advisable to add the layer information together therewith. This layer information makes it possible to exclude the diffusion-region pattern and to extract a contour line for performing an inspection of the gate layer alone, or makes it possible to inspect both the diffusion layer and the gate layer simultaneously. (4) Outline of Configuration-Conversion/GDS Generation Unit In the configuration-conversion/GDS generation unit, the correspondence relationship between the respective edge points detected and the corresponding CAD-data line segments is calculated. The string of these points is sorted for each CAD-data line segment, then converting the sorted points into a closed polygon in such a manner as to become a continuous universal. Using this result, a cell structure as GDS data is generated on each FOV basis. Also, this cell is deployed in the coordinate space on the design data, thereby representing, as the GDS, the contour-line data corresponding to the hierarchical design data. The high-accuracy contour-line configuration extracted from the inspection target has the correspondence relationship with the design data which became the original of the pattern's fabrication. As a result, by representing the contour-line configuration in the same scheme as that of the GDS, i.e., the scheme of the design data, various utilizations of the contour-line configuration become implementable. By representing the contour line of the pattern configuration by using the design data having the hierarchical structure, it becomes possible to represent the contour line in such a manner that the contour line is in the correspondence relationship with the structure of the design data on the circuit. This feature allows the good-or-bad of the verification result on the contour line to be directly reflected on the design data, thereby making it possible to confirm, predict, and amend the design data. Accordingly, it becomes possible to address a design unsuccessfulness more swiftly. Also, by representing the pattern configuration as the contour-line-converted GDS, integration with the design data becomes implementable. Accordingly, the design data and the configuration of the fabrication pattern resulting therefrom can be managed in the same environment. Consequently, the design data and the fabrication pattern can be confirmed simultaneously. This simultaneous confirmation allows an optimum design for the fabrication to be easily implemented in the design process (i.e., data amendment or the like). Also, by converting the pattern configuration into the GDS, the data processing by the respective types of EDA general-purpose tools becomes easier to execute. Consequently, the EDA processing becomes implementable where the pattern configuration is dealt with in the same way as the design data. Also, by representing the pattern configuration as the hierarchical GDS, the hierarchical-GDS pattern is deployed on the design layout in a manner of being caused to correspond to each other. This deployment makes it easier to generate a panorama configuration on which the FOVs in the respective measurement regions are pasted, thereby allowing implementation of respective types of pattern verifications in a wide range. (4-1) Integration of SEM Image with Design Data by Predetermined-Format Conversion Hereinafter, the explanation will be given below regarding the following embodiment: The contour line of the pattern configuration from a pattern or a mask image on the wafer which becomes the inspection target is converted into a predetermined format (GDS format in the present embodiment), then being managed as graphics data. The integration of the circuit and layout and library, the integration with the measurement recipe (i.e., wide range, adjacent FOV), the hierarchy-converted representation, or the recipe linked with the design structure, and contour-line D/B management are performed, and these factors are formed into integrated and managed data. This formation makes it possible to make full use of the following respective types of EDA systems: (4-1-1) Data Processing by Respective Types of EDA General-Purpose Tools By converting the inspection-target pattern into the GDS as the contour line, the pattern becomes processable by the already-existing automatization system of semiconductor design. Namely, in the design environment, graphics is used as the design data which represents a semiconductor pattern. This graphics is schematically used as the semiconductor transfer pattern. In this way, the processings are performed in a pseudo manner by the respective types of verifications and analysis software. The contour line of an inspection-target pattern obtained by the present method is processed as the accurate semiconductor pattern by the respective types of verifications and analysis software. This processing allows implementation of the high-accuracy verifications and analyses, thereby making it possible to promote the optimization of construction of the design environment in which the fabrication facilitation in the design process is taken into consideration. (4-1-2) Pasting Technology of a Plurality of FOVs by Using Design Data (i.e., Panorama-Image Generation) In order to accomplish the high-accuracy Implementation, the contour line of an inspection-target pattern needs to be formed based on an image which is acquired with such a high magnification as one-million times to two-million times. Accordingly, its FOV is an extremely narrow region. On the other hand, inspecting a wide region is desirable from the viewpoint of the position relationship with adjacent pattern and the configuration dependence. In the present embodiment, in order to measure and inspect a wide region with an accuracy which is almost equal to the one of an image acquired with a high magnification, the introduction will be give below concerning a technology of forming a wide-region contour line by mutually connecting a plurality of FOVs to each other. Concretely, as was explained in (1), by forming a wide-region contour-line image by mutually connecting images acquired with a high magnification to each other, it becomes possible to measure and inspect the wide region with a high accuracy. Also, by making a relative position adjustment between the FOVs in such a manner that the contour lines formed based on the luminance information are overlapped with each other, it becomes possible to form an exceedingly-high-accuracy large-region contour-line image. Also, the identification information is added to each contour line which constitutes each side, then being used for the verification at the time of the superimposition. As a result of this, even if similar patterns are adjacent o each other, it becomes possible to implement the accurate superimposition between the FOVs without mixing up the similar patterns. (4-2) Outline of GDS-File Conversion of Contour Line FIG. 15 is a flowchart for explaining processes of converting, into a GDS file, the contour line determined from the SEM edge. The contents of the D/B of the detected edge are converted into a memory structure for the contour-line conversion processing. This memory structure stores therein information such as the detected edge obtained at the time of the image acquisition using the design data, design graphics line-segments, and superimposition correction coefficient. Here, the correspondence relationships (i.e., distance and angle) between the respective design graphics line-segments and the detected edge points are determined, using these pieces of information. This memory structure stores therein all of the line segments of the design graphics of the field-of-view (FOV) corresponding to one image acquisition. In the above-described processing, all of the edge points and all of the graphics line-segments are caused to correspond to each other. The same number is allocated to these line segments as the graphics number on each closed-polygon basis. After the above-described establishment of the correspondence relationships between the edge points and the line segments is terminated, the respective line segments are sorted on each graphics basis. Next, a plurality of line-segment groups represented by one graphics number are sorted based on the line-segment number. This sorting specifies an arrangement of the respective line segments in accordance with the sequence of respective vertex points which configure one closed polygon. As this arrangement, a clockwise direction and a counterclockwise direction exist in a two-dimensional coordinate space. The following point characterizes the representation by this rule: The case where the inner side of the graphics represented by the closed polygon indicates the area (i.e., the pattern portion as semiconductor) is defined as the clockwise direction. Contrary thereto, the case where the outer side of the graphics resented by the closed polygon indicates the area is defined as the counterclockwise direction. As a consequence of the above-described sorting on each line-segment basis within the graphics, the sorting of the respective edge points corresponding to each line segment (i.e., direction of the vertex-points string of the design graphics) is executable. The sorting of the edge points is performed which is caused to correspond to this direction (i.e., clockwise direction or counterclockwise direction) on each line-segment basis. As a consequence of the above-described sorting, the respective edge points are generated which correspond to the respective design graphics line-segments on each design graphics line-segment basis which configure the closed polygon. Accordingly, the contour-line configuration representing the closed polygon can be generated finally. Also, in some cases, the contour-line configuration of the photographed image is cut off by the field-of-view (FOV) frame. In this case, clipping of the contour line by the FOV is performed, thereby converting the edge points into the closed polygon. (4-3) Outline of Sampling Density (i.e., Configuration Stabilization) When the contour line is generated in the coordinate space of the design data using the edge points extracted from the image, a difference generally occurs in the resolution between pixels within the field-of-view of the image and the coordinate space of the design data. For example, if the pixel resolution of the image photographed with a magnification of twelve hundred thousand times is equal to 512 pixels, one pixel is equivalent to 2 to 3 nm. Accordingly, if the contour line is represented in the coordinate space of the design data with this resolution, it turns out that the contour line is mapped into the coordinate space of a 2-to-3-nm unit. Consequently, the spacing therebetween is connected by a straight line, which causes an error to occur. Since the resolution of the design data can generally be represented in 0.1 nm to 1.0 nm, there exists the need of representing the contour-line configuration approximately with this resolution. In the present technique, as illustrated in FIG. 16, after the contour-line conversion is performed based on each coordinate position, a threshold value for averaging the respective vertex points is determined. Then, the smoothing is performed with this threshold value used as the reference. (4-4) Parallel Processing In the present technique, for the purpose of constructing the high-accuracy contour-line configuration in a wide-region photographing range, the scheme is employed where the wide region is photographed such that the wide region is divided into high-magnification field-of-views (FOVs). As a consequence of these factors, the above-described contour-line conversion processing becomes executable independently in a unit of the acquired images. Accordingly, each resultant contour-line conversion processing becomes executable by mutually-independent processing apparatuses. Namely, the parallel processing as illustrated in FIG. 17 becomes implementable. This parallel processing is characterized by a data structure and a processing scheme which allow implementation of the high-speed processing proportional to the number of the processing apparatuses. Namely, the processings on each FOV basis are paralleled. In order to construct the final wide-region contour-line configuration, deployment coordinates of the respective FOVs are used which exist on the wide-region design data used in the measurement. The use of the deployment coordinates makes it possible to construct the hierarchy-structured design data accurately. (4-5) Hierarchy-Formation Processing of Contour Line Hereinafter, the explanation will be given below regarding an embodiment where the contour-line-converted SEM edge is managed in a cell unit equivalently to the design data. FIG. 18 is a conceptual diagram of such a data structure. In the present technique, the contour-line configuration on each field-of-view basis can be represented as the cell, i.e., the unit of the design data. The design data line-segments used at the time of the image acquisition, and graphics of the other layers (graphics of layers of wiring layer, contact layer, and the like) on the design related with the line segments can be stored into this cell in a manner of being overlapped with each other. This makes it possible to manage the design data and the contour-line configuration as one cell. Namely, the semiconductor transfer configuration and the design data which became its original can be managed as the same data. Also, in the recipe used for the photographing, the position in each measurement is represented as the position on the chip, i.e., the coordinate system of the design. Consequently, by deploying the above-described FOV cells at the positions on the chip hierarchically, it becomes possible to deal with the FOV cells as the pattern contour configuration on the chip. Moreover, in the photographing recipe, the image acquisition is performed by describing a photographing condition of a plurality of chips on the wafer. Accordingly, the design data can be created where the chips on which the contour lines are deployed are deployed as the wafer coordinate system. Also, based on the above-described data structure, the contour-line configuration of a plurality of wafers can be formed into the hierarchical structure as the GDS. This makes it possible to implement the unified management of the contour-line configuration as the data ranging from the element level to the lot level, thereby allowing the pattern configuration to be made full use of in the respective types of yield analyses and statistical managements. (4-6) Panorama-Conversion Processing of Contour Lines In the above-described contour-line generation technology, as described earlier, it is possible to construct the large-region panorama contour line which is constructed by combining and deploying the contour lines of the respective FOVs in accordance with the panorama-image acquisition recipe and the design-data representation of the contour lines (i.e., GDS conversion or the like). In generating the panorama contour line, the following correction is made regarding the contour-line connection between the FOVs, thereby implementing the high-accuracy panorama contour-line generation. (4-6-1) Correction of Connection Portion between FOVs (Overlapping Direction of FOVs) In the contour-line extraction of each FOV, in a proximity to the FOV boundary, the accuracy of the image for the contour-line detection is low due to the property of an electron beam at the time of the image acquisition. As a result, the extracted contour lines lack reliability in some cases. In the technology introduced in this column, in the contour-line connection processing in a proximity to the FOV boundary, an overlapped amount of the contour lines in the boundary portion is detected from the overlapped images of the FOVs optimized by the recipe at the time of the photographing. Then, coordinates of the overlapped portions are corrected based on the overlapped amount detected, thereby correcting the accuracy of the contour-line generation in the FOV boundary portion. (4-6-2) Connection Between Contour Lines When deploying the contour line of each FOV into its higher-order hierarchy, the deployment is performed using the coordinates (i.e., coordinates at which the FOV should be deployed) of the design data managed by the photographing recipe described earlier. On account of this, the coordinates are represented by the design-data coordinate system. Accordingly, it turns out that, when the design data (graphics) of each FOV is deployed, the connection between the FOVs is established accurately. Due to the property of the electron beam, however there is a possibility that a several-pixel shift occurs in the position of the contour line within each FOV acquired by the image acquisition. Consequently, in some cases, a several-nanometer shift occurs resultantly in the contour line deployed into the higher-order hierarchy. In the present technique, in addition to the above-described correction in the overlapping direction, the subtle shift between the contour lines in the overlapped portions is corrected with a difference with the design data used as the parameter. Namely, a difference is calculated between the contour line existing in one of the overlapped portions of the FOVs and the line segments of the design data corresponding to the contour line. Similarly, a difference is also calculated between the contour line in the other overlapped portion and the corresponding region. Then, the correction is made so that the respective differences become equal to each other. Moreover, based on its correction amount, the coordinates configuring the contour lines are corrected. Next, this correction is made with respect to the up-and-down and right-to-left FOVs which are adjacent to the FOVs in question, respectively, thereby making the two-dimensional coordinate correction. As a consequence, the contour lines in the adjacent FOVs can be connected to each other accurately. (4-6-3) Grouping of Closed Polygon In the panorama contour line, when one closed polygon is represented as the contour line, the closed polygon is represented by the coordinate system of the design data. As a result, its configuration coordinate-points string becomes an enormous one. Accordingly, in some cases, the string exceeds a limit which can be represented as the design data (such as GDS). Also, even within the range of the limit, when processing the configuration coordinate-points string in the contour-line processing application systems the representative of which is the EDA tool, it becomes necessary to process the string in such a manner that the string is divided. This is because the configuration coordinate-points string is the enormous one. With respect to the case like this, in the present technique, the contour line configuring the closed polygon on the FOV boundary can be divided so as to be formed into the closed polygon. In this case, the same group number (graphics number) is added to one divided contour line which spreads across between the FOVs. This group number allows the application systems to recognize that the contour line is the same divided contour line. Incidentally, because of the division of the contour line, a line segment (segment of FOV) which does not exist originally in the pattern occurs in the divided contour line. This line segment is recognized by the application systems from the presence or absence of the addition of the above-described group number and the FOV boundary information, then being able to be processed (i.e., eliminated if required). For example, in an application of the OPC model correction where a comparatively wide region is employed as its target, this divided line segment is recognized by the system of the OPC processing portion. This recognition makes it possible to easily reconstruct the contour line as the closed polygon. Also, if the electrical connection is represented by a single layer such as the wiring pattern, recognizing the above-described group number makes it possible to represent equipotential between the patterns. When short-circuit between patterns at the judgment on the short-circuit detection of a pattern, this representation of the equipotential is usable for an application such as neglecting a short-circuit pattern at the same potential. (5) Concerning Outline of GDS Utilization Unit The GDS utilization unit performs respective types of verifications, using the contour line formed as described above. These verifications are as follows: (5-1) OPC Simulation by Contour-Line Conversion of Mask Configuration Hereinafter, the explanation will be given below regarding an embodiment where the high-accuracy OPC (: Optical Proximity Correction) simulation is performed based on the contour-line conversion of a semiconductor mask configuration. The OPC simulation is as follows: The optical proximity effect is expected, and a pattern for correcting this effect is formed using the design data, i.e., a mask pattern, or mask data which becomes an original of the mask fabrication. In accompaniment with the progress in the micromachining, however, a difference between the design data and an actually-produced mask configuration is becoming more and more conspicuous. As a result, an error in the simulation has become significant, and thus the optimum correction is becoming increasingly difficult to make. In view of this situation, the exceedingly-high-accuracy contour line of the mask configuration generated by the present technique is used as the data for the simulation. This method makes it possible to accomplish basically the same accuracy as the one of the simulation using the actual mask configuration, thereby allowing implementation of the high-accuracy OPC model correction and model verification. Also, the contour-line data in the present technique is represented with the GDS or the like as the scheme of the design data. This representation allows the conventional simulation environment to be made full use of with no modification added thereto. Furthermore, the contour line of the mask configuration, the contour line obtained as a result of the OPC simulation, and the pattern contour line transferred onto the wafer pattern are superimposed on each other as the design data. This superimposition allows implementation of the high-accuracy verification on the fabrication facilitation of the design data. (5-2) CAA There exists a simulation technology of analyzing the design data, calculating correlation in defect size with respect to the pattern density (i.e., wiring width and wiring spacing), and anticipating a critical area for the defect in layout (hereinafter, this simulation technology will be referred to as “CAA”). Instead of the design data, the CAA calculation is performed using the contour-line configuration extracted by the present technique. This allows implementation of the accurate yield prediction and calculation of the correlation with the defect size. (5-3) Model High-Accuracy Correction of Circuit Library As the circuit performance simulation (mainly Tr element), Spice has been generally used from conventionally. Consider a case where the operation model is defined in a pseudo manner by using resistance value and capacity value calculated from the design data, and where the model correction is made by generating and actually measuring the test circuit. This case is a task which necessitates exceedingly extra time and labor. Simultaneously, acquirable measurement data is small in amount, which has made it difficult to enhance the accuracy. Also, regarding the standard cell (Stdcell) used in ASIC or the like, there occurs the necessity for compensation for the strict electrical characteristics (i.e., characterization of cell) of the cell (DEM library) for implementing the manufacturing facilitation design (DFM library) in recent years. The use of the contour line which represents the high-accuracy pattern configuration allows the high-accuracy implementations of not only the Tr characteristics within the cell, but also the electrical parameters such as the resistance value and capacity value of the wiring. In particular, by presenting sheet resistance (Rs) which allows the recognition in the wiring's length direction represented by the design data, it becomes possible to implement higher-accuracy wiring resistance extraction (LPE). As a result, back annotate to the cell library becomes executable. The following are the main usages which can be optimized by reproducing the actual device configuration using the high-accuracy contour line in the present technique: 1) the characterization of the DFM library, 2) prediction of leakage current at the Tr gate, 3) physical parameter extraction for Signal Integrity→crosstalk and IR drop, 4) reliability verification→antenna effect, electro migration, hot electron, 5) physical wiring length→strict delay parameter for circuit simulator (timing verification). (5-4) Pattern Finished-Quality Inspection and Defect Inspection By reproducing the pattern configuration as the design data with a high accuracy, it becomes possible to use the programs such as DRC (: design rule check) and ERC (: electrical connectivity check). Also, as illustrated in FIG. 19, the contour lines represent the two-dimensional configuration. Accordingly, the pattern check can be made regarding the wiring spacing and wiring width in an arbitrary angle direction (i.e., oblique direction) other than the horizontal and vertical directions. This makes it possible to evaluate finished quality of the actual pattern configuration, thereby allowing execution of the high-accuracy verification of the pattern. Also, in the present technique, the technique of the “pattern-collapse recognition” described earlier makes it possible to detect a residual pattern such as SRAF or side rope which does not exist in the design data, and to judge the disappearance-surviving pattern as an abnormal pattern. Consequently, this judgment is usable for the inspection of a pattern abnormality within the field-of-view. (5-5) GDS-Based Length Measurement and Superimposition Display As illustrated in FIG. 20, the GDS data which represents the contour line generated in the present technique can be displayed on a CAD display device. This display allows the high-accuracy silicon pattern configuration or mask configuration to be displayed in a manner of being superimposed on the design data which became the original of these configurations. In particular, by performing the superimposition display of the respective contour-line configurations of the design data, the mask, and the silicon pattern, it becomes possible to perform the high-speed visual-check evaluation where the correlation relationship among them is taken into consideration. Also, by measuring coordinate values of the contour line on the CAD display device, it becomes possible to make the length measurement easily on the CAD display device without using the length-measuring SEM. Also, by performing the superimposition display of the image data which became the original of the contour-line generation and the above-described configurations, it becomes possible to easily make the evaluation of the correlation relationship between the image of pattern configuration and the design data. Moreover, when the identification information is added to each line segment of the SEM edge on the basis of the design data, information on each line segment at the time when the pattern is grasped as a closed graphics is added as the identification information. The addition of this information makes it possible to facilitate the setting of measurement locations. Hereinafter, referring to FIG. 21, the explanation will be given below concerning a concrete embodiment of this information. FIG. 21 illustrates a state where a plurality of equivalent line patterns are arranged within the FOV. In recent years, the technology referred to as “DPT (: Double Patterning Technology)” is becoming more and more employed. This technology is a type of exposure technologies using an optical exposure apparatus (which, hereinafter, will be referred to as “stepper” in some cases). In this technology, the exposure processing is performed in a manner of being divided into two times, thereby allowing the pattern formation of a sample which has an inter-pattern spacing incapable of being exposed by one-time exposure. The embodiment in FIG. 21 indicates the data obtained based on the electron microscope image of a sample which lies in a state where a first-time-exposed pattern (A) and a second-time-exposed pattern (B) are arranged alternately. In this data, identification information (L, R) is added to each line segment (only the right-and-left information on the line patterns in the present embodiment). Also, information (A1, B1, A2, B2, . . . in the present embodiment) for identifying each line is added thereto. Namely, each line segment can be identified from another line segment by co-using the identification information for identifying each line and the identification information for identifying the position of each line segment within each line. By adding the identification information like these to each line segment, it becomes possible to facilitate the setting of measurement locations to be used in the measurement of a semiconductor device, such as, e.g., pattern width, pattern pitch, and inter-space interval. Also, if a measurement result is judged to be obviously different and apart from the corresponding ideal value, the setting of making re-measurement or more-detailed measurement on the corresponding location is easily implementable. It should be further understood by those skilled in the art that although the foregoing description has been made on embodiments of the invention, the invention is not limited thereto and various changes and modifications may be made without departing from the sprit of the invention and the scope of the appended claims.
	description	Pursuant to 35 U.S.C. §119(a), this application claims the benefit of earlier filing date and right of priority to Korean Application No. 10-2013-0011994, filed on Feb. 1, 2013, the contents of which is incorporated by reference herein in its entirety. 1. Field of the Disclosure The present disclosure relates to a multi stage safety injection device capable of injecting coolant into a reactor vessel step by step when a reactor accident occurs, and a passive safety injection system having the same. 2. Description of the Related Art A Reactor can be classified according to the configuration of a safety system or the installation location of a main component. According to the characteristics of a safety system, a reactor can be classified into i) an active reactor using an active force such as a pump or the like, and ii) a passive reactor using a passive force such as gravity force, pressure force or the like. And also according to the installation location of main components (a steam generator, a pressurizer, and a pump impeller), a reactor can be divided into i) a loop type reactor in which main components are installed out of the reactor vessel, and ii) an integral reactor in which main components are installed within the reactor vessel. When an accident occurs in a reactor, passive tanks with various types are used to supply emergency cooling water to a reactor vessel. i) A nitrogen pressurized safety injection tank (accumulator) for rapidly supplying coolant to a reactor during a large break loss of coolant accident, in which a large line is fractured to outflow a large amount of coolant, is used in domestic and abroad commercial loop type water reactors, and ii) a core makeup tank using a gravitational head of water subsequent to making a pressure balance between the reactor and tank is used in addition to a nitrogen pressurized safety injection tank in the U.S. Westinghouse passive loop type reactors such as AP600, AP1000 and so on. In the integral reactor, main components such as pumps and steam generators or the like are installed within the reactor vessel contrary to the commercial loop type water reactor, and thus there are no large lines for connecting the main components. Accordingly, in the lines which connecting a reactor vessel and systems such as a chemical and volume control system, a safety injection system, a shutdown cooling system, a safety valve, and the like, have small size in integral reactor. Due to these characteristics, a large break loss of coolant accident, where large lines are fractured, is eliminated fundamentally. Furthermore, in the integral reactor, main components are installed into a reactor vessel, where a large amount of coolant exists. Accordingly, when an accident, a loss of coolant accident due to a break such as a line fracture or the like, occurs in the integral reactor, the pressure and water level within the reactor vessel are slowly decreased compared to those of a loop type reactor. Even the integral reactor has such characteristics, in general, the integral reactor requires i) a high flow rate of coolant safety injection at the initial stage of the accident in which the core level is relatively fast decreased, ii) a medium flow rate of coolant safety injection at the early and middle stages of the accident in which the coolant discharge flow rate is relatively large due to a high internal pressure of the reactor vessel, and iii) a low flow rate of coolant safety injection at the middle and late stages of the accident in which the coolant discharge flow rate is greatly reduced due to a decreased pressure of the reactor vessel. It is noted that a high flow rate of the integral reactor is quite smaller compared to a flow rate required in the commercial loop type reactor. However, a nitrogen pressurized safety injection tank in the related art has been typically designed to quickly inject a high flow rate of coolant in a safe manner when the internal pressure of the reactor vessel is rapidly decreased, and a core makeup tank in the related art has been designed to safely inject at a single mode flow rate along a predetermined passage due to a gravitational head of water subsequent to making a pressure balance between the reactor vessel and core makeup tank. As a result, in order to compensate such a disadvantage in the related art, various type systems are used in a complicated manner in a reactor according to the required characteristic of safety injection during an accident. For instance, i) a pressure balance core makeup tank (safety injection at high pressure), a pressurized safety injection tank (safety injection at medium pressure), an in-containment refuelling water storage tank (safety injection at low pressure), and the like are used in a complicated manner in a passive safety system such as passive pressurized water reactors AP600, AP1000 and the like, and ii) a pressurized safety injection tank (safety injection at medium pressure), a high-pressure safety injection pump, a low-pressure safety injection pump, and the like are used in a complicated manner in an active safety system. Accordingly, a device for simplifying safety injection facilities that have been configured in a complicated manner according to the required characteristic of safety injection into the reactor to effectively inject coolant will be taken in to consideration. An aspect of the present disclosure is to simplify a safety injection facility that has been configured in a complicated manner. Another aspect of the present disclosure is to provide a safety injection facility in which a flow rate of coolant injection is varied according to the required characteristic of safety injection into the reactor when an accident occurs. In order to accomplish the foregoing aspects, a multi stage safety injection device according to an embodiment of the present disclosure may include a safety injection tank formed to contain coolant to be injected into a reactor vessel by a gravitational head of water when an accident occurs in which the pressure or water level of the reactor vessel is decreased, a pressure balance line connected to the reactor vessel and safety injection tank to form a pressure balance state between the reactor vessel and the safety injection tank, and a set of safety injection lines connected to the safety injection tank and the reactor vessel to inject coolant to the reactor vessel in a pressure balance state between the reactor vessel and the safety injection tank, and connected to the safety injection tank with different heights to reduce a flow rate of coolant injected into the reactor vessel step by step according to the water level reduction of the safety injection tank. According to an example associated with the present disclosure, the safety injection line may form a total flow resistance being increased step by step according to the water level reduction of the safety injection tank to decrease a flow rate of coolant injected into the reactor vessel. It is based on a principle in which a flow resistance of total summed passages decreases in case of safety injection with two summed passages than that with only one passage, and further decreases in case of three summed passages than that with two summed passages. According to another example associated with the present disclosure, the safety injection line may include a first safety injection line connected to a lower end part of the safety injection tank to continuously provide an injection passage for coolant filled within the safety injection tank is injected into the reactor vessel, and at least one second safety injection line connected to the safety injection tank at a location higher by a predetermined height from the first safety injection line to provide an injection passage for coolant until the water level of the safety injection tank becomes lower than a predetermined water level. According to another example associated with the present disclosure, the multi stage safety injection device may further include a plurality of orifices, at least one of which is installed for each of the safety injection line to act as a flow resistance of coolant injection, and configured to increase a total flow resistance step by step according to the water level reduction of the safety injection tank. It is intended to give a suitable flow resistance for each of the safety injection lines, thereby performing suitable coolant injection step by step according to the required characteristic of the reactor when an accident occurs. According to another example associated with the present disclosure, the multi stage safety injection device may further include an isolation valve installed at the pressure balance line to block the flowing of coolant from the reactor vessel into the safety injection tank during a normal plant operation, and assigned to be open by a control signal generated from the pressure or water level reduction of the reactor vessel to implement coolant injection in a pressure balance state between the reactor vessel and the safety injection tank by a gravitational head of water when an accident occurs. According to another example associated with the present disclosure, the multi stage safety injection device may further include an isolation valve installed at the safety injection line to block the flowing of coolant from the safety injection tank to the reactor vessel in a pressure balanced state with the reactor vessel during a normal plant operation, and assigned to be open by a control signal generated from the pressure or water level reduction of the reactor vessel to implement coolant injection from the safety injection tank to the reactor vessel when an accident occurs. Furthermore, in order to implement the forgoing task, according to the present disclosure, there is disclosed a passive safety injection system. The passive safety injection system may include a core makeup tank connected to a reactor vessel to maintain a pressure balance state with the reactor vessel and inject coolant to the reactor vessel when an accident occurs in which the pressure or water level of the reactor vessel is decreased, and a multi stage safety injection device connected to the reactor vessel to inject coolant step by step to the reactor vessel at a pressure lower than that of the core makeup tank following to the injection of the core makeup tank, wherein the multi stage safety injection device includes a safety injection tank formed to contain coolant to be injected into a reactor vessel by a gravitational head of water when an accident occurs in which the pressure or water level of the reactor vessel is decreased, a pressure balance line connected to the reactor vessel and the safety injection tank to form a pressure balance between the reactor vessel and the safety injection tank, and connected to the reactor vessel and the core makeup to form a pressure balance state between the reactor vessel and the core makeup tank, and a set of safety injection lines connected to the safety injection tank and the reactor vessel to inject coolant to the reactor vessel in a pressure balance state between the reactor vessel and the safety injection tank, and connected to the safety injection tank with different heights to reduce a flow rate of coolant injected into the reactor vessel step by step according to the water level reduction of the safety injection tank. According to an example associated with the present disclosure, the passive safety injection system may further include an isolation valve installed at the pressure balance line to block the flowing of coolant from the reactor vessel into the safety injection tank during a normal plant operation, and assigned to be open by a control signal generated from the pressure or water level reduction of the reactor vessel to implement coolant injection in a pressure balance state between the reactor vessel and the safety injection tank by a gravitational head of water when an accident occurs. Hereinafter, a multi stage safety injection device associated with the present disclosure and a passive safety injection system having the same will be described in more detail with reference to the accompanying drawings. Even in different embodiments according to the present disclosure, the same or similar reference numerals are designated to the same or similar configurations, and the description thereof will be substituted by the earlier description. Unless clearly mentioned otherwise, expressions in the singular number used in the present disclosure may include a plural meaning. FIGS. 1 through 7 are views illustrating a multi stage safety injection device associated with an embodiment of the present disclosure, and FIGS. 8 through 15 are views illustrating a multi stage safety injection device associated with another embodiment of the present disclosure. FIG. 1 is a conceptual view illustrating a multi stage safety injection device 100 associated with an embodiment of the present disclosure. The multi stage safety injection device 100 is connected to a reactor vessel 12, and formed to inject coolant to the reactor vessel 12 using a passive force when a loss of coolant accident occurs due to a break such as a line fracture. However, the injection flow rate of coolant required according to the passage of time subsequent to an accident may not be constant, and thus the multi stage safety injection device 100 is designed to convert the flow rate of coolant being injected according to the passage of time. The multi stage safety injection device 100 may include a safety injection tank 110, a pressure balance line 120 and a set of safety injection lines 130. The safety injection tank 110 is formed to accommodate coolant therein. Coolant stored within the safety injection tank 110 is injected from the safety injection tank 110 to the reactor vessel 12 due to a gravitational head of water when a loss of coolant accident occurs in which the pressure or water level of the reactor vessel 12 is decreased. Gravitational head of water, as a water head determined by a location in the gravitational field, is energy formed by the safety injection tank 110 disposed at a higher location than that of the reactor vessel 12. Accordingly, coolant injection from the safety injection tank 110 to the reactor vessel 12 is carried out due to a gravitational head of water which is a passive force, and thus additional energy is not needed to be supplied from the outside. A space excluding coolant within the safety injection tank 110 is filled with a gas (typically, nitrogen is used). The pressure balance line (reactor pressure balance pipe) 120 is connected to the reactor vessel 12 and safety injection tank 110 to form a pressure balance between the reactor vessel 12 and safety injection tank 110. When the pressure balance line 120 is open, fluid such as steam or water moves from the reactor vessel 12 having a relatively high pressure to the safety injection tank 110, and thus the reactor vessel 12 and safety injection tank 110 makes a pressure balance to each other. Coolant injection from the safety injection tank 110 to the reactor vessel 12 is carried out due to a gravitational head of water, and thus a pressure balance between the safety injection tank 110 and reactor vessel 12 should be first formed to inject coolant. An orifice (not shown) may be installed in the pressure balance line 120 to adjust a flow rate of fluid being introduced from the reactor vessel 12 into the safety injection tank 110. An isolation valve 121 may be provided in the pressure balance line 120. The isolation valve 121 provided in the pressure balance line 120 is in a closed state during a normal plant operation to block fluid from being introduced from the reactor vessel 12 into the safety injection tank 110. Accordingly, during a normal plant operation, the reactor vessel 12 and safety injection tank 110 maintains an isolated state due to the isolation valve 121, and thus the pressure thereof is not in a balanced state. The isolation valve 121 is open by a control signal of the relevant system generated from the pressure or water level reduction of the reactor vessel when a reactor accident occurs. When fluid is introduced from the reactor vessel 12 into the safety injection tank 110 to form a pressure balance between the reactor vessel 12 and the safety injection tank 110, coolant injection due to a gravitational head of water is started from the safety injection tank 110. When a single isolation valve 121 is installed therein, the entire multi stage safety injection device 100 may not be operated due to a failure of the isolation valve 121, and therefore, a plurality of isolation valves 121 may be installed in a plurality of branch lines 122 operating independently from each other, respectively, as illustrated in the drawing. Furthermore, the isolation valve 121 installed in the pressure balance line 120 may be open by a control signal generated from the pressure or water level reduction of the reactor vessel 12, and thus designed to receive power backup using a battery or the like to be prepared for power loss (AC). When the isolation valve 121 is installed in the pressure balance line 120, a pressure between the reactor vessel 12 and the safety injection tank 110 is not balanced unless the isolation valve 121 is open and the pressure of the reactor vessel 12 is higher than that of the safety injection tank 110 to close the check valve 132, and thus coolant is not injected into the reactor vessel 12 from the safety injection tank 110 even when an additional isolation valve (not shown) is not installed in the safety injection line. The safety injection line 130 is connected to the safety injection tank 110 and reactor vessel 12 to inject coolant within the safety injection tank 110 into the reactor vessel 12. When a pressure between the reactor vessel 12 and the safety injection tank 110 is balanced due to the pressure balance line 120, coolant filled within the safety injection tank 110 is injected into the reactor vessel 12 through the safety injection line 130. According to the present disclosure, a set of safety injection lines 130 are connected to the safety injection tank 110 with different heights to decrease a flow rate of coolant injected into the reactor vessel 12 according to the water level reduction of the safety injection tank 110. A first safety injection line 130a is connected to a lower end part of the safety injection tank 110 to provide an injection passage until almost of the coolant within the safety injection tank 110 is injected into the reactor vessel 12. A second safety injection line 130b is connected to the safety injection tank 110 at a location higher by a predetermined height from the first safety injection line 130a to provide an injection passage for coolant until the water level of the safety injection tank becomes less than a predetermined water level. A height difference between first safety injection line 130a and second safety injection line 130b connected to the safety injection tank may be varied according to the required characteristic of coolant safety injection into the reactor. When the injection of coolant into reactor vessel 12 from the safety injection tank 110 is started, the injection of coolant is carried out through the first safety injection line 130a and second safety injection line 130b at first, but the injection of coolant through the second safety injection line 130b is no more carried out when the water level of coolant becomes less than the connected location between the second safety injection line 130b and the safety injection tank 110 (the installation height of the second safety injection line 130b denotes a location 130b′ at which the second safety injection line 130b is connected to the safety injection tank 110 unless otherwise clearly different in its context in the present disclosure). Accordingly, the entire flow rate of coolant injected into the reactor vessel 12 decreases as much as the flow rate of coolant that has been injected through the second safety injection line 130b. Even when coolant is injected through the first safety injection line 130a and second safety injection line 130b, a water head difference decreases as decreasing the water level within the safety injection tank 110, and thus the flow rate of coolant injection decreases to a certain extent. Similarly, even when the safety injection of coolant is carried out only by the first safety injection line 130a, a flow rate of coolant injection gradually decreases according to the water level reduction of the safety injection tank 110. However, the decrease speed of an injection flow rate in case where coolant is injected only through the first safety injection line 130a is slower than that in case where coolant is injected through the first safety injection line 130a and second safety injection line 130b. It is because the injection flow rate of coolant itself in the former case is less than that in the latter case. At a moment when the injection of coolant is no more carried out through the second safety injection line 130b due to the water level reduction of the safety injection tank 110, the flow rate of coolant being injected into the reactor vessel 12 suddenly decreases at a fast rate. It is because one injection passage of coolant is removed in addition to a simple reduction of its water head difference. The first safety injection line 130a and second safety injection line 130b may be merged at any one position prior to being injected into the reactor vessel 12 as illustrated in the drawing. A check valve 132 may be installed in a safety injection line 130c into which the first safety injection line 130a and second safety injection line 130b are merged. The check valve 132 is a device for blocking coolant from flowing backward from the reactor vessel 12 to the safety injection tank 110. The check valve 132 is open by a gravitational head of water when coolant is injected from the safety injection tank 110 to the reactor vessel 12 due to the occurrence of a reactor accident. The design pressure of the safety injection tank 110 is determined by a pressure making a balance to the reactor vessel 12. When the isolation valve 121 is installed in the pressure balance line 120 and the check valve 132 is installed in the safety injection line 130c, a pressure between the reactor vessel 12 and the safety injection tank 110 does not form a balance prior to the isolation valve 121 being open during an accident, and thus the design pressure of the safety injection tank 110 may be designed to be lower than that of the reactor vessel 12. An orifice 131 is installed in the safety injection line 130 to act as a flow resistance of coolant. For the multi stage safety injection device 100, at least one orifice 131 may be installed for each of the safety injection lines 130 to adjust an injection flow rate of coolant step by step. The orifice 131 forms a suitable flow resistance for each of the safety injection lines 130 to perform suitable coolant injection step by step according to the required characteristic of the reactor. A flow resistance of total summed passages decreases in case of safety injection with two or three summed passages than that with only one passage. Here, the degree of decreasing a flow resistance of total passages may be set according to the flow resistance of the orifice 131. As illustrated in the drawing, when the second safety injection line 130b is connected to the safety injection tank 110 at a higher location than that of the first safety injection line 130a, a relatively small total flow resistance is formed by a second orifice 131b installed in the second safety injection line 130b than that of a first orifice 131a installed in the first safety injection line 130a, thereby allowing a relatively higher flow rate of coolant to flow through the safety injection line 130. A flow rate of coolant in case where the safety injection is carried out only through the first safety injection line 130a is less than that in case where safety injection is carried out through the first safety injection line 130a and second safety injection line 130b at the same time. Because an additional flow rate is generated by the second injection line 130b, when the injection of coolant is carried out through the combined paths of the first safety injection line 130a and the second injection line 130b. The reason of setting the injection flow rate of coolant as described above is to expand an injection time in case of performing a relatively low flow rate of safety injection, thereby performing safety injection for a long period of time (more than about 72 hours in case of a passive safety injection system). The safety injection lines 130a, 130b are connected to the safety injection tank 110 with different heights from each other, and thus coolant is no more introduced from the second safety injection line 130b when the water level within the safety injection tank 110 is reduced below than the location of 130b′. Accordingly, for the multi stage safety injection device 100, safety injection from the safety injection tank 110 to the reactor vessel 12 may be carried out with multiple stages, and a size of the safety injection tank 110, a height of the safety injection line, and a flow resistance of the orifice are set according to the characteristics of safety injection required by a reactor, thereby injecting coolant in a continuous and successive manner for a long period of time required by the reactor. Safety injection facilities in the related art that have been configured in a complicated manner has a problem such as a delay or overlap of time for making a pressure balance for each safety injection tank during the process of performing the switching of safety injection flow rates, but according to a multi stage safety injection device 100 presented in the present disclosure, the flow rate switching of coolant is successively carried out in a state that a pressure balance is made between the safety injection tank 110 and the reactor vessel 12, thus not causing a problem such as a delay or overlap of time during the flow rate switching subsequent to starting the operation of the safety injection tank 110. Furthermore, the multi stage safety injection device 100 is a passive safety injection system, thereby enhancing the reliability and stability compared to an active safety injection system. Hereinafter, the operation of a multi stage safety injection device installed in an integral reactor and other system arrangements during a normal plant operation or the occurrence of an accident will be described. FIG. 2 is a conceptual view illustrating the normal plant operation state of an integral reactor 10 installed with a multi stage safety injection device 100 illustrated in FIG. 1. For the integral reactor 10, the reactor vessel 12 is disposed within a containment building (container) 11. For the integral reactor 10, main components such as reactor coolant pumps 12a, a pressurizer 12b, steam generators 12c, and the like are installed within the reactor vessel 12 as described above. Water is supplied to the steam generator 12c through a feedwater line 13a from the feedwater system 13 located out of the containment building 11, and water receives energy from nuclear fission produced in the core 12d to become high temperature and high pressure steam, and moves to a turbine system 14 located out of the containment building 11 through a steam line 14a. During a normal plant operation, isolation valves 13b, 14b installed in the feedwater line 13a and steam line 14a are in an open state. A passive residual heat removal system 15 is installed out of the containment building 11, and connected to the steam line 14a and feedwater line 13a to remove heat from the reactor vessel 12 when an accident occurs. However, during a normal plant operation of the integral reactor 10, an isolation valve 15a is maintained in a closed state. An automatic depressurization system 16 is installed within the containment building 11, and connected to the reactor vessel 12 to reduce a pressure of the reactor vessel 12 when an accident occurs. However, in the automatic depressurization system 16, the automatic depressurization valves 16a are also maintained in a closed state during a normal plant operation of the integral reactor 10 similarly to the passive residual heat removal system 15. A passive safety injection system 200 is installed within the containment building 11, and connected to the reactor vessel 12 to inject coolant into reactor vessel 12. The passive safety injection system 200 is generally composed of multi trains. The passive safety injection system 200 may include the multi stage safety injection device 100 and core makeup tank 210, and both isolation valves 121, 211 are maintained in a closed state during a normal plant operation of the integral reactor 10. During a normal plant operation of the integral reactor 10, a containment building isolation valve 17 is in an open state, and the passive safety injection system 200, passive residual heat removal system 15 and automatic depressurization system 16 do not operate. FIG. 3 is a conceptual view illustrating the operation of a safety facility when a loss of coolant accident occurs in the integral reactor 10 illustrated in FIG. 2. When a loss of coolant accident such as line fracture or the like occurs in which coolant is discharged and thus the pressure or water level of the reactor vessel 12 is decreased, the containment building isolation valve 17 is closed, and the isolation valve 13b installed in the feedwater line 13a and the isolation valve 14b installed in the steam line 14a are also closed by a control signal of the relevant system to stop the operation of the feedwater system 13 and turbine system 14. The isolation valve 15a of the passive residual heat removal system 15 is open by the relevant control signal. Coolant within the condensation heat exchanger 15e (contained within emergency cooling tank 15d) is introduced into the feedwater line 13a through the check valve 15b and orifice 15c to transfer residual heat from the reactor vessel 12, and returned to the steam line 14a to remove residual heat using the condensation heat exchanger 15e. Similarly, the valves 16a of the automatic depressurization system 16 are open by the relevant control signal to reduce a pressure of the reactor vessel 12, thereby smoothly performing safety injection from the passive safety injection system 200. The core makeup tank 210 is connected to the reactor vessel 12 by the pressure balance line 120 to maintain a pressure balance state with the reactor vessel 12, and connected to the reactor vessel 12 by the safety injection line 130c to inject coolant to the reactor vessel 12 when an accident occurs. Accordingly, the core makeup tank 210 is connected to the reactor vessel 12 by the pressure balance line 120 and safety injection line 130c, but the function of each line is totally different. A portion for connecting the reactor vessel 12 and core makeup tank 210 from the pressure balance line 120 is open all the time, and thus the reactor vessel 12 and core makeup tank 210 maintain a pressure balance state. Accordingly, the design pressure of the core makeup tank 210 is high at a level of the reactor vessel 12. The isolation valve 211 installed between the core makeup tank 210 and safety injection line 130c is open by a control signal generated from the pressure or water level reduction of the reactor vessel 12, and pressure balance type safety injection due to the water level of the core makeup tank 210 is started into the reactor vessel 12. Coolant is passed through the isolation valve 211, check valve 212 and orifice 213 and injected into the reactor vessel 12, and the flow rate at this time is suitably established by the orifice 213. Safety injection due to the core makeup tank 210 is carried out at a relatively high flow rate compared to that of the multi stage safety injection device 100 which will be described later. When the pressure or water level of the reactor vessel 12 is further reduced due to cooling of the reactor vessel 12, discharging from the fractured portion and the like, a control signal is generated from the relevant system to open the isolation valve 121 installed in the pressure balance line 120, thereby forming a pressure balance between the reactor vessel 12 and the safety injection tank 110. The isolation valve 121 installed in the pressure balance line 120 is designed to be open subsequent to the pressure or water level of the reactor vessel being reduced to a certain extent, and thus the design pressure of the safety injection tank 110 is designed to be lower than that of the core makeup tank 210, and the coolant injection into the reactor vessel 12 is also carried out at a pressure lower than that of the core makeup tank 210. Referring to FIG. 1, the injection of coolant due to the multi stage safety injection device 100 may be divided into two stages. When coolant injection due to the core makeup tank 210 is set to as a high flow rate of safety injection, coolant injection due to the multi stage safety injection device 100 may be carried out with two stages at a pressure lower than that of the core makeup tank 210, and thus each stage can be divided into a medium flow rate of safety injection and a low flow rate of safety injection. The medium flow rate of safety injection is carried out through the first safety injection line 130a and second safety injection line 130b of the multi stage safety injection device 100 at a pressure condition lower than that of the high flow rate of safety injection of the core makeup tank 210, and the low flow rate of safety injection is carried out through the first safety injection line 130a from a time point at which the coolant level of the safety injection tank 110 is reduced than that of the installation location of the second safety injection line 130b. A high flow rate of safety injection due to the core makeup tank 210 and a medium and low flow rate of safety injection due to the multi stage safety injection device 100 may denote relative flow rates, respectively, and each flow rate may be set according to the safety injection characteristics required by the reactor. The reason of requiring multi stage safety injection from a high to a low flow rate is due to the accident characteristics of the reactor. In particular, for the integral reactor 10, the water level of the core relatively fast decreases when an accident occurs, and thus a high flow rate of coolant is required to be rapidly injected. The passive safety injection system 200 implements a high flow rate of safety injection by the core makeup tank 210. Subsequent to the occurrence of an accident, the internal pressure of the reactor vessel is still high with a relatively high coolant discharge flow rate from the early to middle stages of the accident, but the pressure of the reactor decreases with a relatively low coolant discharge flow rate from the middle to late stages of the accident, and thus a medium and a low flow rate of safety injection are required, respectively. For the passive safety injection system 200, a medium and a low flow rate of safety injection are carried out step by step by the multi stage safety injection device 100. Referring to FIG. 3, the inside of the core makeup tank 210 is vacant and thus a high flow rate of safety injection due to the core makeup tank 210 has been previously completed. The coolant level within the safety injection tank 110 is positioned below a location at which the second safety injection line 130b is connected to safety injection tank 110, and thus it is seen that a medium flow rate of safety injection has been completed, and a lower flow rate of safety injection is carried out only through the first safety injection line 130a. Hereinafter, a medium and a low flow rate of safety injection processes by means of the multi stage safety injection device 100 will be described with reference to FIGS. 4 through 6. FIG. 4 is a conceptual view illustrating the pressure balance step when a loss of coolant accident occurs in the multi stage safety injection device 100 illustrated in FIG. 1. When the isolation valve 121 installed in the pressure balance line 120 is open by a control signal, fluid is introduced from the reactor vessel 12 to the safety injection tank 110 through the pressure balance line 120. The multi stage safety injection device 100 is a safety facility using a pressure balance method between the reactor vessel 12 and the safety injection tank 110, and therefore, a pressure balance should be formed between the safety injection tank 110 and the reactor vessel 12 before to start coolant injection from the safety injection tank 110. When fluid is introduced from the reactor vessel 12, an upper portion within the safety injection tank 110 is filled with nitrogen gas that has been filled therein in advance and the steam. A pressure between the reactor vessel 12 and safety injection tank 110 is gradually balanced according to the introduction of fluid, and the opening of the check valve 132 installed in the safety injection line 130 and safety injection is started by a gravitational head of water of the safety injection tank 110. FIG. 5 is a conceptual view illustrating a coolant injection step (medium flow rate of injection step) in the multi stage safety injection device 100 subsequent to FIG. 4. When safety injection by means of the multi stage safety injection device 100 is started, a medium flow rate of safety injection is carried out through the first safety injection line 130a and second safety injection line 130b until the water level of the safety injection tank 110 is reduced than the installation height 130b′ of the second safety injection line 130b. The first orifice 131a installed in the first safety injection line 130a is configured to inject a predetermined flow rate of coolant according to the characteristics of the reactor required when coolant is injected in a single mode, and the second orifice 131b installed in the second safety injection line 130b is formed to inject a predetermined flow rate of coolant according to the characteristics of the reactor required when coolant is injected through both the first safety injection line 130a and second safety injection line 130b. Accordingly, the flow rate of coolant injected through both the first safety injection line 130a and second safety injection line 130b is higher than that only through the first safety injection line 130a. A gravitational head of water is gradually decreased by the water level reduction of the safety injection tank 110 even while implementing a medium flow rate of safety injection by means of the first safety injection line 130a and second safety injection line 130b, and the flow rate of coolant injected into the reactor vessel 12 is gradually reduced. The flow rate of coolant injected into the reactor vessel 12 is only gradually decreased but not instantaneously and rapidly reduced until the water level of the safety injection tank 110 is reduced than the installation height 130b′ of the second safety injection line 130b. However, when the water level of the safety injection tank 110 is reduced lower than the installation height 130b′ of the second safety injection line 130b, the flow rate of coolant injected into the reactor vessel 12 is instantaneously and rapidly reduced. FIG. 6 is a conceptual view illustrating a coolant injection step (low flow rate of injection step) in the multi stage safety injection device 100 subsequent to FIG. 5. Since the water level of the safety injection tank 110 is reduced lower than the installation height 130b′ of the second safety injection line 130b, the injection of coolant is no more carried out through the second safety injection line 130b, but a low flow rate of safety injection is carried out only through the first safety injection line 130a. A flow resistance is formed by the first orifice 131a installed in the first safety injection line 130a, and thus the amount of coolant injected into the reactor vessel 12 is adjusted to a low flow rate by the first orifice 131a. According to the progress of a low flow rate of safety injection, the water level of coolant in the safety injection tank 110 is gradually reduced, and a gravitational head of water thereof is gradually decreased but not instantaneously and rapidly reduced, as the amount of coolant injected through the first safety injection line 130a is relatively small, and thus the speed of decreasing a gravitational head of water and the speed of reducing an injection flow rate of coolant are very slow. A low flow rate of safety injection may continue until almost of the coolant within the safety injection tank 110 is injected into the reactor vessel 12, and be maintained up to a time point (about 72 hours) that requires safety injection with no operator's action or emergency AC power in a passive reactor. Hereinafter, a change of flow rate of coolant safety injection in time by means of the multi stage safety injection device 100 and core makeup tank 210 illustrated in FIGS. 1 through 6 will be described with reference to FIG. 7. FIG. 7 is a graph illustrating an injection flow rate of coolant in time in the multi stage safety injection device 100 and core makeup tank 210 described in FIGS. 1 through 6. The horizontal axis denotes a flow of time from a moment at which a loss of coolant accident or the like occurs, and the vertical axis denotes a flow rate of coolant injection by means of the multi stage safety injection device and core makeup tank. At the early stage of an accident, the water level of the core in a reactor vessel is relatively fast decreased, and thus a high flow rate of safety injection is carried out in the core makeup tank. The flow rate is gradually decreased due to a decrease of head of water of the core makeup tank even while implementing a high flow rate of safety injection. A medium and a low flow rate of safety injection by means of the multi stage safety injection device are carried out subsequent to the early stage of an accident. The operation and injection time of the core makeup tank and multi stage safety injection device are varied according to the accident condition of a reactor, and thus a delay of safety injection start time using the multi stage safety injection device or a coolant injection overlap phenomenon of the core makeup tank and multi stage safety injection device during a pressure balance process subsequent to the operation of the multi stage safety injection device is an unavoidable physical phenomenon. However, when flow rate switching, that is the medium flow rate to the low flow rate, is carried out within the multi stage safety injection device, the overlap or delay of coolant injection does not occur as illustrated in the drawing. When a medium flow rate of safety injection by means of the multi stage safety injection device is started, safety injection is reduced compared to a case of a high flow rate of safety injection. Furthermore, the flow rate of coolant injection is gradually decreased due to a decrease of head of water while implementing a medium flow rate of safety injection by means of the multi stage safety injection device. When the water level of the safety injection tank is reduced than the installation height of the second safety injection line, a flow rate of coolant injection is instantaneously and rapidly decreased to implement a low flow rate of safety injection. The reduction of flow rate continues even while implementing a low flow rate of safety injection, but the reduction speed is very slow and continual safety injection is carried out to maintain it for a period of time required by the reactor. As described above, a multi stage safety injection device according to the present disclosure may be formed to decrease a flow rate of coolant injection step by step according to the required safety injection characteristics of a reactor, thereby injecting coolant for a long period of time. Hereinafter, a multi stage safety injection device associated with another embodiment of the present disclosure will be described with reference to FIGS. 8 through 16. The redundant description previously illustrated in FIGS. 1 through 7 will be substituted by the earlier description. FIG. 8 is a conceptual view illustrating the multi stage safety injection device 300 associated with another embodiment of the present disclosure. The multi stage safety injection device 300 is formed to inject coolant into the reactor vessel 22 when an accident occurs, and may include a safety injection tank 310, a pressure balance line 320, and a safety injection line 330. The safety injection tank 310 is formed to accommodate coolant to be injected into the reactor vessel 22 when an accident occurs in which the pressure or water level of the reactor vessel 22 is decreased. The safety injection tank 310 is all filled with coolant (boric acid solution). The pressure balance line 320 is connected to the reactor vessel 22 and safety injection tank 310 to form a pressure balance between the reactor vessel 22 and the safety injection tank 310. It is different from the multi stage safety injection device 100 illustrated in FIG. 1 in that an isolation valve is not installed in the pressure balance line 320. Accordingly, the pressure balance line 320 is always maintained in an open state, and when the pressure of the reactor vessel 22 is changed not only when an accident occurs but also during a normal plant operation, fluid is introduced from the reactor vessel 22 to the safety injection tank 310 to maintain a pressure balance within a short period of time. For the pressure balance line 320, an orifice (not shown) may be installed to limit a flow rate of fluid introduced from the reactor vessel 22 according to the design characteristics. When a pressure balance between the reactor vessel 22 and the safety injection tank 310 is maintained as described above, the design pressure of the safety injection tank 310 should be designed to be high at a level of the reactor vessel 22. The safety injection line 330 is connected to the safety injection tank 310 and reactor vessel 22 to inject coolant into the reactor vessel 22 in a pressure balance state between the reactor vessel 22 and the safety injection tank 310 in an accident. A set of safety injection lines 330 are connected to the safety injection tank 310 with different heights to reduce a flow rate of coolant injected into the reactor vessel 22 step by step according to the water level reduction of the safety injection tank 310. As illustrated in FIG. 8, the safety injection line 330 may include a first safety injection line 330a connected to a lower end part of the safety injection tank 310, a second safety injection line 330b connected to a lateral surface of the safety injection tank 310 at a location higher by a predetermined height from the first safety injection line 330a, and a third safety injection line 330c connected to a lateral surface of the safety injection tank 310 at a location higher by a predetermined height from the second safety injection line 330b. As coolant is injected into the reactor vessel 22 from the safety injection tank 310 when an accident occurs, the water level of the safety injection tank 310 is gradually decreased. When coolant injection is first started, coolant is injected through the first safety injection line 330a, second safety injection line 330b and third safety injection line 330c. When the coolant level of the safety injection tank 310 is lower than the installation height of the third safety injection line 330c as implementing coolant injection, coolant is no more introduced to the third safety injection line 330c, and coolant is injected only through the first safety injection line 330a and second safety injection line 330b. Then, when coolant is started not to be introduced to the third safety injection line 330c, the injection flow rate of coolant is instantaneously and rapidly decreased. When the water level of the safety injection tank 310 is lower than the installation height of the second safety injection line 330b as further implementing coolant injection, coolant is no more introduced to the second safety injection line 330b, and coolant is injected only through the first safety injection line 330a. Similarly, when coolant is started not to be introduced to the second safety injection line 330b, the injection flow rate of coolant is instantaneously and rapidly decreased. An injection flow rate in case where coolant is injected through all the first safety injection line 330a, second safety injection line 330b and third safety injection line 330c may be referred to as a high flow rate of safety injection, and an injection flow rate in case where coolant is injected through the first safety injection line 330a and second safety injection line 330b as a medium flow rate of safety injection, and an injection flow rate in case where coolant is injected only through the first safety injection line 330a as a low flow rate of safety injection. A high, a medium and a low flow rate are relative values, respectively, and may be differently designed according to the size of the safety injection tank 310, the installation height of the safety injection lines 330, and the flow resistance of each of the safety injection lines 330. The orifice 331 is installed in the safety injection line 330 to act as a flow resistance. For a high, a medium and a low flow rate of safety injection of the multi stage safety injection device 300, the orifice 331 forms a suitable flow resistance based on the required characteristics of a reactor according to the installation height of the safety injection line 330 connected to the safety injection tank 310, thereby injecting coolant at a suitable flow rate. The flow resistance of a first orifice 331a is set to a low flow rate condition when the first safety injection line 330a is operated in a single mode in FIG. 8, and the flow resistance of a second orifice 331b is set to a medium flow rate condition when the first safety injection line 330a and second safety injection line 330b are operated at the same time, and the flow resistance of a third orifice 331c is set to a high flow rate condition when the first safety injection line 330a, second safety injection line 330b and third safety injection line 330c are operated at the same time. Accordingly, when implementing a high flow rate of safety injection, coolant injected through the third safety injection line 330c, second safety injection line 330b and first safety injection line 330a is larger than that through the first safety injection line 330a and second safety injection line 330b, and when implementing a medium flow rate of safety injection, coolant injected through the second safety injection line 330b and first safety injection line 330a is larger than that through the first safety injection line 330a. The reason of forming the orifice 331 with different flow resistances is to provide a high, medium and low flow rate stages of safety injection and different periods of time required for coolant injection. A relatively high flow rate of coolant should be rapidly injected when an accident occurs whereas a relatively low flow rate of coolant is required to be injected for a long period of time at the middle and late stages of the accident. In the multi stage safety injection device 300, the orifices 331 are formed to have different flow resistances, and thus designed to adjust the injection amount and injection time of coolant required for a flow of time subsequent to the consequence of a reactor accident. An isolation valve 333 is provided in a safety injection line 330d into which the first safety injection line 330a, second safety injection line 330b and third safety injection line 330c are merged. The isolation valve 333 is maintained in a closed state in a normal plant operation to block coolant from being introduced from the safety injection tank 310 into the reactor vessel 22. The isolation valve 333 is open by a control signal of the relevant system when an accident occurs. The reactor vessel 22 and safety injection tank 310 have been in a pressure balance state, and thus coolant injection is started from the safety injection tank 310 along with the opening of the isolation valve 333. The isolation valve 333 may be designed to receive backup by a battery or the like to be prepared for power loss (AC), and a plurality of isolation valves 333 may be installed for a plurality of branch lines 334, respectively, to prevent the operation of the entire multi stage safety injection device 300 from being stopped due to a single failure of the isolation valves. In some embodiments, a check valve 332 is installed between the reactor vessel 22 and safety injection tank 310. FIG. 9 is a conceptual view illustrating the normal plant operation state of an integral reactor installed with the multi stage safety injection device 300 illustrated in FIG. 8. The multi stage safety injection device 300 is installed within a containment building 21 of the integral reactor 20, and connected by the pressure balance line 320 and safety injection line 330. The safety injection tank 310, composed of multi trains generally, is installed at a location higher than that of the reactor vessel 22 for coolant injection due to a gravitational head of water. During a normal plant operation, an isolation valve is in a closed state in the multi stage safety injection device 300. The integral reactor 20 illustrated in FIG. 9 is different from the integral reactor 10 illustrated in FIG. 2 in that the core makeup tank does not exist, and the safety injection line 330 of the multi stage safety injection device 300 is added, and the isolation valve 333 is installed in the safety injection line 330 other than the pressure balance line 320. The safety injection tank 310 is connected to the reactor vessel 22 through the pressure balance line 320, and the pressure balance line 320 is always open, the design pressure of the safety injection tank 310 is high at a level of the reactor vessel 22. Accordingly, the safety injection tank 310 designed with a high pressure is in charge of the function of the core makeup tank that has injected a high flow rate of coolant to the reactor vessel 22 when an accident occurs in FIG. 2. Three safety injection lines 330 are installed therein for a high, a medium and a low flow rate of multi stage safety injections. For the integral reactor 20, the reactor vessel 22 is disposed within a containment building (container) 21. For the integral reactor 20, main components such as reactor coolant pumps 22a, a pressurizer 22b, steam generators 22c, and the like are installed within the reactor vessel 22 as described above. Water is supplied to the steam generator 22c through a feedwater line 23a from the feedwater system 23 located out of the containment building 21, and water receives energy from nuclear fission produced in the core 22d to become high temperature and high pressure steam, and moves to a turbine system 24 located out of the containment building 21 through a steam line 24a. During a normal plant operation, isolation valves 23b, 24b installed in the feedwater line 23a and steam line 24a are in an open state. A passive residual heat removal system 25 is installed out of the containment building 21, and connected to the steam line 24a and feedwater line 23a to remove heat from the reactor vessel 22 when an accident occurs. However, during a normal plant operation of the integral reactor 20, an isolation valve 25a is maintained in a closed state. An automatic depressurization system 16 is installed within the containment building 21, and connected to the reactor vessel 22 to reduce a pressure of the reactor vessel 22 when an accident occurs. However, in the automatic depressurization system 26, the automatic depressurization valves 26a are also maintained in a closed state during a normal plant operation of the integral reactor 20 similarly to the passive residual heat removal system 25. During a normal plant operation of the integral reactor 10, a containment building isolation valve 27 is in an open state, and the passive safety injection system 300, passive residual heat removal system 25 and automatic depressurization system 26 do not operate. FIG. 10 is a conceptual view illustrating the operation of a safety facility when a loss of coolant accident occurs in the integral reactor 20 illustrated in FIG. 9. When a loss of coolant accident such as line fracture 27a or the like occurs and the pressure or water level of the reactor vessel 22 is reduced, the isolation valve 333 installed in the safety injection line 330 is open by a control signal of the relevant system, and safety injection is started from the multi stage safety injection device 300 into the reactor vessel 22. The coolant level of the safety injection tank 310 is between the second safety injection line 330b and third safety injection line 330c in FIG. 10, and thus coolant is no more injected into the third safety injection line 330c, and through this it is seen that a high flow rate of safety injection stage has been already finished. Safety injection is carried out through the first safety injection line 330a and second safety injection line 330b, and therefore, FIG. 10 illustrates a medium flow rate of safety injection stage. FIG. 11 is a conceptual view illustrating the pressure balance step when a loss of coolant accident occurs in the multi stage safety injection device 300 illustrated in FIG. 8. When a control signal is generated by the relevant system when an accident occurs, the isolation valve 333 installed in the safety injection line 330 is open by the control signal, and the safety injection of coolant due to a gravitational head of water is started. Fluid is introduced from the reactor vessel 22 into the safety injection tank 310 through the pressure balance line 320, and thus the reactor vessel 22 and safety injection tank 310 maintains a pressure balance state. FIG. 12 is a conceptual view illustrating a coolant injection step (high flow rate of injection step) in the multi stage safety injection device 300 subsequent to FIG. 11. When an accident occurs, coolant within the safety injection tank 310 is injected into the reactor vessel 22 through the first safety injection line 330a, second safety injection line 330b and third safety injection line 330c. Total flow resistance decreases in the case of injecting coolant through three passages of the first safety injection line 330a, second safety injection line 330b and third safety injection line 330c compared to the case of injecting coolant through only one passage of the first safety injection line 330a, and therefore, a high flow rate of coolant is injected into the reactor vessel 22 when an accident occurs. A gravitational head of water is gradually decreased by the water level reduction of coolant until the coolant level of the safety injection tank 310 is reduced than the installation height 330c′ of the third safety injection line 330c, and therefore a flow rate of coolant injection is gradually reduced. Then, a flow rate of coolant injection is instantaneously and rapidly reduced at a moment at which the coolant level of the safety injection tank 310 is reduced lower than the installation height 330c′ of the third safety injection line 330c. FIG. 13 is a conceptual view illustrating a coolant injection step (medium flow rate of injection step) in the multi stage safety injection device 300 subsequent to FIG. 12. The coolant level of the safety injection tank 310 is reduced lower than the installation height 330c′ of the third safety injection line 330c, and therefore coolant is not injected through the third safety injection line 330c, but a medium flow rate of safety injection is carried out through the first safety injection line 330a and second safety injection line 330b. The coolant level of the safety injection tank 310 is continuously reduced while implementing a medium flow rate of safety injection, and the amount of coolant injection from the safety injection tank 310 into the reactor vessel 22 is gradually decreased. At a moment at which the coolant level of the safety injection tank 310 is reduced than the installation height 330b′ of the second safety injection line 330b, coolant is no more introduced through the second safety injection line 330b and a flow rate of coolant injected into the reactor vessel 22 is instantaneously and rapidly reduced. FIG. 14 is a conceptual view illustrating a coolant injection step (low flow rate of injection step) in the multi stage safety injection device 300 subsequent to FIG. 13. The water level of the safety injection tank 310 is reduced lower than the installation height 330b′ of the second safety injection line 330b, and therefore safety injection from the safety injection tank 310 into the reactor vessel 22 is carried out only through the first safety injection line 330a, thereby implementing a low flow rate of safety injection. A flow resistance in the case of implementing coolant injection only through one passage of the first safety injection line 330a is relatively greater than that in the case of implementing coolant injection through two passages of the first safety injection line 330a and second safety injection line 330b or the case of implementing coolant injection through three passages of the first safety injection line 330a, second safety injection line 330b and third safety injection line 330c, and therefore a low flow rate of safety injection can be carried out for a long period of time. The low flow rate of safety injection continues until almost of the coolant of the safety injection tank 310 is injected into the reactor vessel 22, and the injection time can be adjusted according to the design of the safety injection tank 310. At present, a time required for the operation of a safety system with no operator's action or emergency AC power in the passive reactor 20 is about 72 hours. FIG. 15 is a conceptual view illustrating a modified example of the multi stage safety injection device illustrated in FIG. 8. The multi stage safety injection device 300 has the same configuration as that of the multi stage safety injection device 300 illustrated in FIG. 8, but it is different from FIG. 8 in that the third safety injection line 330c is first merged to the second safety injection line 330b prior to being merged to the safety injection line 330d in the multi stage safety injection device 300 illustrated in FIG. 15. FIG. 16 is a graph illustrating an injection flow rate of coolant in time in the multi stage safety injection device 300 described in FIGS. 8 through 15. A high, a medium and a low flow rate of safety injection are all carried out from the safety injection tank in the multi stage safety injection device to inject a high flow rate of coolant within a short period of time when an accident occurs. Subsequently, a medium flow rate of safety injection is carried out at the early and middle stages of the accident to implement safety injection for a longer period of time than that of the high flow rate stage. Finally, a low flow rate of safety injection is carried out for a long period of time while smoothly decreasing the injection speed thereof at the middle and late stages of the accident. The multi stage safety injection of coolant by means of a multi stage safety injection device may implement flow rate switching in a state that a pressure balance between the reactor vessel and the safety injection tank has been made, and therefore, coolant may be continuously and successively injected without causing a problem of delay or overlap in the coolant injection during the process of flow rate switching as shown in FIG. 16. The foregoing multi stage safety injection device may inject coolant with a single safety injection tank in multiple stages according to the safety injection characteristics required for a reactor. Accordingly, a reactor having the multi stage safety injection device may effectively use coolant within the safety injection tank and thus additional safety injection facilities may not be required for each pressure condition, thereby simplifying facilities as well as reducing the economic cost. The present disclosure can be applied to not only a integral reactor but a loop type reactor for changing a performance of the core makeup tank to multi stage. In the loop type reactor, a reactor vessel correspond to a reactor coolant system. A passive safety injection system including a multi stage safety injection device may be formed with a fully passive type, and thus safety functions can be carried out only using natural forces contained in the system, such as gas pressure or gravity force, without using an active device such as a pump and also without an operator's action for a period of time required for the passive system when an accident occurs. Therefore, an emergency AC power system is not required, which enhances the reliability of the safety injection system and enhances the safety of a reactor. The configurations and methods according to the above-described embodiments will not be applicable in a limited way to the foregoing multi stage safety injection device and passive safety injection system having the same, and all or part of each embodiment may be selectively combined and configured to make various modifications thereto. According to the present disclosure having the foregoing configuration, it may be possible to simplify various safety injection facilities used in a complicated manner due to the required safety injection characteristics of a reactor as a single type facility. Furthermore, according to the present disclosure, the flow rate of coolant injected into the reactor vessel may be decreased step by step according to the water level reduction of the safety injection tank subsequent to starting coolant injection, and thus coolant can be injected only with a single type facility according to the required safety injection characteristics of a reactor being varied according to the passage of time subsequent to an accident.
	summary
	claims	1. A method comprising:providing an internal control rod drive mechanism (CRDM) including an electric motor and a support surface including sealed electrical connectors electrically connected with the electric motor to deliver electrical power to the electrical motor;installing the internal CRDM inside a nuclear reactor, the installing including placing the support surface of the internal CRDM onto a support element inside the nuclear reactor, the placing causing sealed electrical connectors disposed on the support element to mate with the sealed electrical connectors on the support surface of the internal CRDM;wherein the nuclear reactor contains coolant water and the installing is performed with the internal CRDM submerged in the coolant water and the seals of the sealed electrical connectors of the internal CRDM and the support element are effective to prevent coolant water ingress into the sealed electrical connectors. 2. The method of claim 1 wherein the providing comprises:welding the electrical connectors onto ends of mineral-insulated cables (MI cables) providing power to the electric motor to form the sealed electrical connectors of the internal CRDM. 3. The method of claim 1 wherein the installing further comprises:after the placing is performed, purging space between the mated sealed electrical connectors of the internal CRDM and the support element through a purge line using an inert gas. 4. The method of claim 3 wherein the installing further comprises:sealing off the purge line after the purging to trap residual inert gas in the space between the mated sealed electrical connectors of the internal CRDM and the support element. 5. The method of claim 1 wherein the sealed electrical connectors of the internal CRDM and the support element are sealed glass connectors, sealed ceramic connectors, or sealed glass ceramic connectors. 6. The method of claim 1 wherein the installing further comprises:during the placing, providing compliance springs between sealed electrical connectors disposed on the support element and the mating sealed electrical connectors on the support surface of the internal CRDM.
	description	This application is the U.S. National Phase of International Application No. PCT/US2013/033767, filed Mar. 25, 2013, which claims priority to U.S. Provisional Patent Application No. 61/615,048, filed Mar. 23, 2012. The contents of the foregoing applications are incorporated herein by reference in their entireties. The disclosed scenarios relates generally to the field of plasma physics and, in particular, to methods and apparati for confining plasma to facilitate nuclear fusion for the purpose of producing power. Nuclear fusion reactors have been proposed to produce electrical power from the fusion of atomic particles such as deuterium, tritium, and helium. Generally, in fusion, light nuclei bind to produce fast moving, heavy particles, which contain vast quantities of energy. This process only occurs at temperatures of hundreds to thousands of million Kelvin such that the Coulomb force, which repulses the positively charged nuclei, is overcome. Reactivity, or the rate of fusion, is a function of temperature. The most important fusion reactions for practical reactors are as follows.D+T→α(3.6 MeV)+n(14.1 MeV), (Equation 1)D+3He→4He(3.7 MeV)+p(14.7 MeV), and (Equation 2)D+D→3He(0.8 MeV)+n(2.5 MeV), (Equation 3)where D is deuterium, T is tritium, α is a helium nucleus, n is a neutron, p is a proton, and 3He and 4He are helium-3 and helium-4, respectively. The associated kinetic energy of each product is indicated in parentheses. The D-T reaction produces most of its energy in neutrons, which means that electrical energy can only be produced by using the neutron radiation to heat a working fluid, mach like in a fission reactor. Due to temperature limitations, that conversion can only be about 30% efficient. An advantage of the D-T fuel mixture is that it produces net power at the lowest temperatures, of only 5-10 keV (1 keV=11.6 million K, and is a more convenient unit of temperature). However, the energetic neutrons liberated in this reaction represent a significant threat to the reactor's structure as the neutron flux degrades the electrical, mechanicals and thermal properties of the reactor components and also leaves many of their materials radioactive. Some of these energetic neutrons can be used to breed tritium, a scarce material. Thus, the D-T fuel mixture poses significant challenges with radiation damage, material activation, and fuel availability. Pursuing a D-T reactor would require substantial research and development of nuclear materials and tritium breeding as well as several meters worth of shielding to protect reactor components and personnel from neutron radiation. The D-D fusion reactions are very attractive because the abundance of deuterium obviates the need to breed tritium. Moreover, the neutrons generated are fewer in number and lower in energy than from D-T per unit of energy produced. By selective treatment of D-D fusion's daughter products—removing the T from the plasma before it fuses but burning the prompt and decay-formed 3He, a technique called He-catalyzed D-D fusion—the neutron production can be reduced to 7% of the D-T level, per unit of energy produced. The D-3He reaction termed aneutronic, as it produces relatively few neutrons and requires none for breeding. The energy from the charged reaction products can be directly converted to electrical power at a much higher efficiency than D-T. However, higher temperatures, of 50-100 keV, are required to achieve the same reactivity as D-T. Both reactions admit D-D side reactions, which for a D-3He reactor is the only source of neutron production. A known method for decreasing this neutron generation is lowering the reactant concentration ratio of D:3He from 1:1 to 1:9. In a thermal plasma with 100 keV ion temperatures, this causes neutron production to drop from 2.6% to 0.5% of D-T's per unit of energy produced. This reduces the level of neutron shielding required to under a meter. However, the lower D concentration reduces the power density by a factor of 4.5, adversely affecting the economics. Another highly appealing aneutronic fuel is proton-boron-11 (p-11B), however, many doubt its viability because at the plasma temperatures required for p-11B fusion, over 200 keV, the fusion power generated is calculated to be less than the power required to sustain the high plasma temperature. In addition to a fuel source, fusion reactors must incorporate a heating process, confinement method, and energy conversion system. Fusion reactors can be broadly classified as those that use magnetic confinement and those that use inertial confinement. In the former, magnetic fields from external coils or produced by plasma currents confine hot plasma, allowing for fusion to occur. In inertial confinement, by contrast, external particle beams or lasers compress the reactants to produce fusion. Dozens of magnetic geometries that have been proposed for fusion reactors. While the tokamak is the most widely used configuration, other topologies include stellarators, dipoles, theta-pinch, magnetic mirrors, and field-reversed configurations. A critical parameter for comparing these geometries is β, the ratio of magnetic pressure to plasma pressure. The stellarators and tokamaks are low-β devices, meaning that larger, heavier, and more expensive magnetic coils are needed. Field-reversed configurations and dipoles have β's closer to unity, making them cheaper and less complex. A high β is crucial for burning aneutronic fuels since they require such high temperatures and pressures. The International Thermonuclear Experimental Reactor (ITER) is the culmination of current tokamak research. It is designed to burn D-T and requires plasma temperatures of 10-30 keV. It uses injection of energetic beams for plasma heating and requires a minimum plasma dimension of 2.8 meters. ITER's total dimensions are 30 meters in height with a 30 meter diameter. It converts the highly energetic neutrons to electricity and is therefore prone to radiation damage and a maximum efficiency of 30%. However, aneutronic D-3He would require an even larger tokamak-type reactor to achieve the required plasma temperatures. Thus, plasma heating methods are a critical consideration for reactor design. Colliding beams, induced currents, and radio waves, have all been proposed for plasma heating and are used in experimental devices. The use of colliding beams for heating a toroidal reactor is disclosed by Jassby (U.S. Pat. No. 4,065,351). This proves infeasible for advanced aneutronic fuels, such as D-3He. Hacsi (U.S. Paten Application Publication No. 2008/0095293) discloses a C-Pinch geometry for a thermonuclear fusion device. A plasma-ring generator is provided where a multitude of capacitors discharge across arc-points arranged in a circular or other configuration to cause a plasma-ring or plasma-structure with a circulating electric current to be formed. This provides a novel method of heating a plasma but does not solve the inherent plasma confinement issues. Monkhorst et al (U.S. Pat. No. 6,611,106) discloses a plasma-electric power generation system for direct conversion of fusion product energy to electric power. Plasma ions are magnetically confined in the FRC while the plasma's electrons are electrostatically confined in a deep energy well, created by tuning an externally applied magnetic field. In this configuration, the ions must have adequate densities and temperatures so that upon collision they are fused together by the nuclear force, thus forming fusion products that emerge in the form of an annular beam. Energy is removed from the fusion product ions as they spiral past electrodes of an inverse cyclotron converter. Rostoker et al. (U.S. Pat. No. 7,015,646) and Rostoker et al. (U.S. Pat. No. 7,126,284) disclose a system and method for containing plasma and forming a field-reversed configuration (FRC) magnetic topology in which plasma ions are contained magnetically in stable, non-adiabatic orbits in the FRC. As in Monkhorst, the electrons are contained electrostatically in a deep energy well, created by tuning an externally applied magnetic field. The simultaneous electrostatic confinement of electrons and magnetic confinement of ions avoids anomalous transport and facilitates classical containment of both electrons and ions. Moreover, the fusion fuel plasmas that can be used with this confinement system and method are not limited to neutronic fuels only, but also advantageously include advanced fuels. Rostoker '646, Rostoker '284 and Monkhorst disclose a method that combines electrostatic and magnetic confinement. While a confinement method is illustrated in detail, a heating method is not proposed. The cited patents do not address the practical issues of plasma heating and stable confinement within a small-size FRC reactor for burning aneutronic fuel. Other FRCs lack proven methods to heat electrons and drive plasma currents. Rotating magnetic fields (RMF), powered by RF, can heat small plasmas. However, the even-parity configuration (RMFe, Rotating Magnetic Field, even-parity) has been shown to have poor energy confinement resulting in the need for a larger FRC. An improved field reversed magnetic field configuration fusion reactor system is disclosed. The reactor system includes a reactor chamber, and a gas injection system for injecting fuel into the reactor chamber for fusion reactions. A plurality of radio frequency (RF) antennae are configured to generate an odd-parity rotating magnetic field capable of heating the fuel to a temperature sufficient to cause a plasma of fuel ions to fuse. The magnetic field that includes an open field region and a closed field region and a toroidal current is generated within the plasma around a null line, at which the magnitude of the magnetic field is zero. Superconducting flux coils around the reactor chamber in which a current is induced the odd-parity rotating magnetic field. The induced current generates a confinement field that confines the plasma. A direct energy conversion system that extracts energy from a plurality of products from fusion reactions in the plasma. Alternatively, an indirect energy conversion system may also be deployed. A method for generating power from a field reversed magnetic field configuration fusion reactor system is disclosed. The method includes injecting ionized fuel plasma into a plasma chamber. Radio frequency antennae generate an odd-parity rotating, magnetic field that heats the plasma by producing, in the plasma, periodic co-streaming ion beams. The effects of the odd-parity rotating magnetic field heat the plasma sufficiently to cause the ionized fuel to under go fusion reactions. The energy of the products of the fusion reactions are directly and/or indirectly converted into electricity. In the following description, for purposes of explanation, specific numbers, materials and configurations are set forth in order to provide a thorough understanding of the invention. It will be apparent, however, to one having ordinary skill in the art, that the invention may be practiced without these specific details. In some instances, well-known features may be omitted or simplified so as not to obscure the disclosed scenarios. Furthermore, reference in the specification to “one embodiment” or “an embodiment” means that as particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the invention. The appearances of the phrase “in an embodiment” in various places in the specification are not necessarily all referring to the same embodiment. During the course of this description like numbers will be used to identify like elements according to the different views, which illustrate the invention. The disclosed scenarios decreases neutron production in D-3He-fueled FRC while improving power density. The disclosed scenarios embraces a more stable alternative to convention FRC systems and can reduce neutron production of D-3He plasmas below 1%, while maintaining a higher D:3He ratio, hence higher power density. It relies on odd-parity RMF (RMFo) heating to generate periodic, beam-like, high-energy ion energy distributions in a steady state FRC device. For an FRC reactor to burn its D-3He fuel mixture, the plasma ions must be heated to over 50 keV. If energetic neutral-beam injection were used for heating, the plasma would have to be over 4 meters in diameter in order to absorb the energy of the neutral beams. Such a large reactor would produce power in the range of 1 GW. With RF heating, on the other hand, power can be absorbed over shorter distances. RF heating allows the size of the reactor to be reduced by about a factor of 100 in volume and 10 in radius, to 0.5 m in diameter. A smaller volume translates to a proportionally lower power, near 10 MW, suitable for compact power systems. A field-reversed configuration is produced in a cylindrical vessel by the following means. An axial magnetic field is applied to the plasma creating azimuthal electric currents in the ionized gas. These currents then serve to support the magnetic field itself. The direction of the applied field is then reversed. The currents in the ionized gas continue to maintain the original magnetic field within a region around the center of the plasma, and the magnetic field lines “heal” themselves into a self-consistent configuration. The result is a spheriodal-shaped region within the plasma whose magnetic field is in a direction opposite, or reversed, relative to the applied field. Energetic Ion Beams Fusion reaction cross sections, σij, depend on the relative velocity or center-of-mass (CM) energy, ECM, of the colliding nuclei, species i and j. In a thermal plasma of temperature Tth, collisions occur with an average CM energy comparable to Tth. For D-T, most fusion events arise from particles with energy near 6 Tth. For thermal plasmas, the energy-averaged fusion reaction rates, <σv>ij, peak at different temperatures for each fuel mixture: near 60 keV for D-T, 250 keV for D-3He, 600 keV for p-11B, and 1 MeV for D-D. However, because the fusion power Pf˜n2<σv>ij while β˜nT/B2, a fusion-device-specific limit on β causes the maximum Pf far thermal plasmas to be produced at temperatures where <σv>ij˜T2, i.e. considerably below the peak, Tp. The same equations show that Pf˜β2B4 and a strong benefit accrues from higher β and B. It has long been appreciated that the plasma-parameter requirements for net fusion power gain could be relaxed by promoting beam-target interactions, that is, forming a plasma with a fraction of one reacting species having a high, nearly monoenergetic energy Eb near the peak of reactivity while the other species is relatively stationary. Both beam-like, that is, collimated, and isotropic velocity distributions with energy Eb were considered. For energetic beam-like distributions, particle pairs in the beam have a low CM energy, characterized by transverse temperature T⊥<<Eb; fusion reactions within a beam are infrequent. However, if the beam encounters an oppositely directed beam or a nearly static ensemble of a fusible species, increasing fusion power could be produced if Eb was raised towards the σv peak at Ep. Fusion reaction rates versus CM energy—not versus temperature—are shown in FIG. 2 for three fusible pairs. Below the peak, the D-T 24 and D-3He 20 pairs show strong increases in rate with ECM, far stronger than D-D 22 shows. In the range 0.2Ep<E<0.8Ep, σv grows ˜ECM4 for D-T 24 and D-3He 20, and higher fusion power is possible in a two-component plasma constrained by β. Beam particles passing through plasma lose energy to both the plasma's electrons and ions. A beam formed by injection of energetic particles will continually lose energy and only transiently be near the peak in σv. Quantitatively, the fusion probability of a beam particle as it slows down from an injection energy near Ep to the bulk plasma temperature is about 1% or less. A slow, though adiabatic, plasma compression may be a one-time means to compensate for the beam losing energy to the bulk plasma. To reduce the beam's energy loss to plasma electrons to an acceptable level requires a minimum electron temperature, Te>Eb/20˜30 keV for a 600 keV D beam circulating in a 3He plasma. The β limit requires the beam density, nb, to be considerably lower than the bulk plasma density, ne. Plasmas with nbEb˜ne(Te+Ti), where Ti is the ion temperature of the bulk plasma, have sufficiently improved power production that the fusion events produced by the beam would generate more energy than was necessary to produce the beam and sustain the plasma. A neutral-beam-heated D-T-fueled tokamak operated with compression seemed ideally suited to demonstrate beam-enhanced fusion-power production. We assert that important improvements can be gained in the two-component concept by changing several of their choices: from beam heating to RF heating, from D-T to D-3He fuel, from a single compression to a rapid, periodic, RF acceleration-deceleration, and from the tokamak geometry to the FRC geometry. The overarching improvement we seek is a sizeable decrease in neutron production while maintaining net power production at a power density comparable to or in excess of D-T's. The choice of D-3He as fuel eliminates the need for neutrons to breed tritium and, in doing so, eliminates the need for extensive and lengthy R&D programs for nuclear-materials testing and tritium breeding and would also alleviate reactor-siting restrictions associated with radioactivity. Though D-3He has a 10-times lower <σv> than D-T at the same plasma temperature, the same or higher fusion power density can be achieved because the 10-fold higher β of the FRC compared to the tokamak allows higher plasma temperature at the same plasma density or higher density at the same temperature. Additionally, with the same magnet technology, a 50% higher magnetic field strength is possible in the linear FRC than in the donut-shaped tokamak. As describe below, the advantage gained by the approach in the disclosed scenarios arises from the novel RF plasma-heating technique's ability to produce in the plasma, in steady-state, periodic, collimated co-propagating on beams of the two species with different peak energy for each species. D+ ions will have half the peak energy as 3He+2 ions. The CM energy between the two beams will be near Ep/3 and the time-averaged beam densities near ne/10. This will reduce the D-D fusion rate by lowering the D's effective temperature to T⊥ but raise the D-3He fusion rate above the value estimated for a temperature based on the average energy, Eav. Rider (4 Physics of Plasmas 1039, 1997) pointed out that the large ratio of the 90 Coulomb-Spitzer scattering to fusion cross-sections made it difficult to maintain different ion temperatures for each ion species. Below an explanation of how the novel RF applied to an FRC causes a periodic acceleration then deceleration of each ion, is presented. This is the highly efficient recirculation of power suggested by Rider to remedy this criticism. Rf-Created Ion Beams in an FRC Ion heating by RMFo is highest near the O-point null line 10, near the center of the plasma's magnetic axis, where it creates a time-varying azimuthal electric field. This periodically accelerates ions into betatron orbits 12 and then decelerates them back into cyclotron orbits 14. Choosing the RMFo's ωRMF and amplitude properly allows ions to be pumped up, repeatedly, to energies near the peak in the D-3He fusion cross-section and then returned to the bulk temperature. This is a conservative process and satisfies the recirculating energy criterion derived by Rider, described below. In a D-3He plasma, the trajectories of RMFo-accelerated ions are predicted to form two betatron orbit streams close to the FRC's O-point null line 10: a D stream 12 and an 3He stream. The deuterium stream ions have half the peak energy of the 3He ions, causing non-zero relative velocity between them. The transverse temperature of each beam is considerably lower than the beam's peak energy, hence deuterium ions collide with each other at a far lower center of mass energy than with 3He; accordingly, the D-D neutron production rate falls and fp is reduced. Further reductions can be gained from the differential in the energy-dependent fusion rates. In a scenario, the bulk plasma has an average energy of 70 keV and the RMFo increases the 3He by about 100 keV 20,a then it will increase the D+ by about 50 keV 22,b and D-T reactivity will be suppressed 24. Thus, several effects—centrally peaked betatron orbits, low transverse beam temperature, reduced D-to-3He ratio, and higher 3He energy—combine to decrease fp below 0.2% for a RMFo-heated D-3He-fueled FRC. Add to these effects that D-3He fusion produces neutrons that have only one-sixth of the energy of those produced by burning D-T and the larger surface to volume ratio (∝1/radius) for a small FRC compared to a large tokamak (25 cm vs. 10 m) and an additional 240-fold reduction of neutron power load on the wall is obtained. Overall, the shielding requirements for the disclosed scenarios, of a small, clean reactor are far less than for a D-T fueled larger fusion engine. The r-z cross section of a generic FRC is shown schematically in FIG. 3. On the magnetic axis, a circle of a radius ro, measured from the major axis 31 to the O-point 40, in the FRC's midplane, z=0, the magnitude of the magnetic field, \|B\|, is zero. This null line allows a particular type of rapidly circulating charged-particle trajectory called a betatron orbit, see FIG. 1, an orbit whose curvature reverses direction as it crosses the null. Odd-parity radiofrequency rotating magnetic fields (RMFo) applied to FRC plasmas can heat both electrons and ions and, in doing so, promote their trajectories into shapes called punctuated betatron orbits (PBO), see FIG. 1, wherein the fast betatron orbit is terminated by slowly counter-drifting cyclotron orbits. In an RMFo-heated plasma, the betatron segment of the orbit does not have constant energy. Going from punctuation point to punctuation point, the particle's energy quickly grows and then, just as quickly, decreases. This accel/decel pattern repeats periodically and rapidly, once per RMFo period. The cause is the RMFo's (rotating) azimuthal electric field, εφ pointing in opposite directions on opposite sides of the FRC. Advantageously, the cyclotron segments of the orbits are further removed radially from the null line than are the betatron segments. These cyclotron orbits may be either far inside or far outside ro, as shown FIG. 1. In this plot the particle trajectory, viewed along the major axis, is traced in the frame-of-reference rotating at the RMFo angular speed, ωRMF. The betatron segments lie inside the crescent of angular extent φPBO created by the cyclotron orbits. This locked behavior shows that PBOs have a time-average azimuthal speed of ωRMFro. The spatial separation reduces the frequency of impacts of the fast betatron segments with the slower cyclotron segments. The cause of the radial distillation is the εφ×Bz radial drift executed by cyclotron orbits, where Bz is the FRC's axial field. The value of a PBO particle's peak azimuthal energy, Wφ\|max, is approximately proportional to ζωRMFBRMFroφPBO, where ζ is the charge on the particle. Accordingly, 3He+2 will have twice the energy as D+ but, because of 3He's greater mass, its peak azimuthal velocity will only be 15% faster than D's. About 1/3 of the particles will have velocity within 80% of the maximum. The ratio of a betatron-orbit particle's radial to azimuthal energy, Wr/Wφ, will depend on the initial position and velocity of an ion relative to the RMFo's phase. In a scenario, Wr/Wφ\|max˜1/2 for one PBO. In other scenarios, Wr/Wφ˜1/3 is common, though values as small as 1/200 and as large as 1/1 have been seen in simulations. The value of Wr/Wφ at a collision depends on the azimuthal extent of the PBO crescent, φPBO, in the RMF frame, its radial excursion, ΔrPBO, and at which point the collision occurs. Examination of a set of simulations has allowed us to estimate Ecm for D+-3He+2 collisions due to crossing PBOs. For a 25-cm radius FRC with Ba=100 kG and BRMF=0.4 kG, the maximum energy attained by D+ and 3He+2 are 0.4 MeV and 0.8 MeV, respectively. Long□duration trajectory simulations allow us to generate the particle distribution function. We find the Tav˜120 keV from the definition 2Eav/3. Excluding the betatron section of the orbit lowers Tav to ˜56 keV. From these considerations, we estimate the collisions of beam-like D-3He will have Ecm˜240 keV while the D-D collisions will have Ecm˜140 keV. In a scenario, the D-3He fusion rate is increased by a factor of 2 above those due to the background plasma temperature while decreasing the D-D-produced neutrons a factor of 0.7. About 5 MW of fusion power would be generated, with a power density over 10 MW/m3, a power in the neutron channel ˜0.4% of the total, and a wall loading ˜1 MW/m2. Recirculating Power: The Rider Criterion Rider (4 Physics of Plasmas 1039, 1997) has pointed out that a high level of recirculating power, far greater than the fusion power, is required to sustain particle distributions far from Maxwellian, such as the PBOs described above, which would produce enhanced fusion power. The RMFo method does have high recirculating power, as measured by the electrical Q, about 100, of its antenna circuit. For an absorbed RF power of 2 MW, estimated for a 5 MW net-fusion-power-producing FRC/RMF reactor, the circulating power between the antenna and the RF tank is 200 MW. For beam-enhanced D-3He, Rider estimated that the ratio of recirculating power to fusion power needed must exceed 20 to sustain beam-like ion distributions. The disclosed scenarios satisfies his criterion. This level of recirculating power pales in comparison with that estimated from the instantaneous acceleration of ions into the betatron segment of the PBOs. The acceleration to Eav˜300 keV occurs for about 10% of the ions in 1 ms. For a 25-cm reactor with ni˜2×1014 cm−3, the instantaneous power required to accelerate the particles is 6Pi˜0.1V ni EavωRMF˜4×1012 W. At the same time, however, ions are being decelerating and give nearly the same amount of power back to the RMF antennae. This may be likened to a container holding a gas so tenuous that the gas particles infrequently collide with each other. One wall of the container will experience an outward force; the opposite wall will experience an oppositely directed force. No net energy will be expended maintaining the gas in the container. During a single RMF period, ca 1 ms, a 3He+2 ion with energy near 300 keV in a plasma with a D+ density of 2×1014 cm−3 has a probability of 10−7 for fusing and 10−5 for undergoing 90° scattering. If the scattered ions are moved out of the crescent, they will no longer gain energy from or lose energy to the RMF. Instead, they will behave like the “classic” hot ion in the two-component method, possibly fusing but more likely heating the lower temperature background plasma. Along this cooling trajectory they may re-enter the crescent. If not, these ions will lose energy predominantly to the electrons, helping to maintain them above the minimum temperature previously noted. Once cooled to the near the average plasma energy, these ions may again be pumped into PBOs. The FRC geometry is shown in FIG. 3. Field shaping coils 30 create a linear open field region (OFR) 32. The eponymous reverse field region is divided from the OFR by the separatrix 34 and forms a closed poloidal field region (CFR) 36. A toroidal current 38, centered on the O-point null line 40, is formed through the axis of the CFR. The FRC reactor machine is shown in FIG. 4. This diagram shows the critical parts of the reactor core. Fuel is injected 42 and diffuses through the core chamber. The fuel is ionized prior to entry into the FRC. The anti-parallel components of the RMFo field 44 are created by the RF antennas 46. The direction of the RMFo is opposite on the two sides of the mid-plane, hence the name odd-parity. The relative phasing of the waveforms going to the antennas arranged around the plasma results in the rotating magnetic field. The RMF waveguides and antennas are shown 46. Radio-frequency waveguides can be of many types and are well-known technology. The antenna is the port for the waveguide carrying the radio-frequency waves. The axial flux coils 48 are passive superconducting coils, in which the rotating plasma induces currents that magnetically confine the plasma. These coils provide magnetic pressure while allowing the RMFo from external coils to penetrate the plasma. The internal structure of the plasma 50 is shown in FIG. 4 and is defined by the field-reversed configuration. A radiation shield, for reflecting, attenuating, and absorbing, neutrons, Bremsstrahlung, and synchrotron radiation, is shown in 52. The energy flow is shown in FIG. 5. The diagram shows how energy and particles flow into and out of the reactor. A fuel atom of species 1 (n1) originates in 54 and enters the plasma 56. A second fuel atom (n2) originates in 58 and enters the plasma 56. The fusion reaction 56 converts the reactants into the fusion products and produces power. The reaction also produces Bremsstrahlung x-rays, synchrotron radiation and some neutrons from the D-D side reaction. The ion products pass through the scrape-off-layer 60 and are converted to electricity with through the direct conversion system 62 and exit the system while the power is sent to the power bus 64. The neutrons that are produced in the fusion side reactions hit the shielding wall 66. The plasma 56 is heated by the RMFo RF heating system 68, which is powered by the power bus 64, produced by either in the heat engine 70 or the direct conversion system 62. The superconducting coils 72 are cooled by the refrigeration system 76. The refrigeration system 76 also runs from the power bus 64. Power is generated from waste heat and x-rays by the heat engine 70. This power can be recirculated to heat the plasma and ionize incoming gas or delivered to the power grid. The shielding wall, 66, absorbs the neutron flux, any emitted synchrotron radiation that is not reflected back into the plasma, and Bremsstrahlung. The refrigeration system 76 cools the superconducting coil 72 and removes waste heat. Only a small portion of the total waste heat is removed by the refrigerator 76. Net power is available from the power bus 78. This power is delivered to the power grid. Although the scenarios herein has been described with reference to particular embodiments, it is to be understood that these embodiments are merely illustrative of the principles and applications of the disclosed scenarios. It is therefore to be understood that numerous modifications may be made to the illustrative embodiments and that other arrangements may be devised without departing from the spirit and scope of the disclosed scenarios as defined by the appended claims.
	abstract	Disclosed herein is a spacer grid for a nuclear fuel assembly which is formed from grid strips of an improved structure, thus reducing flow-induced high-frequency vibration. The spacer grid has dimples or grid springs for supporting fuel rods and is formed from a plurality of grid strips assembled in a lattice shape to form lattice cells. Each of the grid strips has at least one slot formed in a planar portion of the grid strip separately from the dimple or grid spring. Therefore, characteristics of the vibration of the spacer grid can be set in a variety of different manners so that flow-induced high-frequency vibration can be reduced.
046719261	abstract	A fuel assembly for a boiling water reactor has a bundle of fuel rods consisting of a top tie plate and a bottom part which, together with a plurality of fuel rods, constitutes a rigid unit. The fuel rod bundle is surrounded by a fuel channel (1), to which there is attached a fixing member (2) cast in stainless steel. The fixing member (2) is attached to a vertical projection (3), extending from the top tie plate, by means of a bolt (4) which is loaded with a tensile force and a sleeve (10) which is loaded with a compressive force and which surrounds the bolt and is arranged in the fixing member, the coefficients of thermal expansion of the bolt and the sleeve being less than that of the fixing member.
	summary
	summary
	claims	1. Apparatus for reducing back-scattered x-rays incident on a person working with a patient on an operating table, the patient being exposed to x-rays from an x-ray source while on the table so that the back-scattered x-rays result from x-rays from the source being incident on the patient and/or table, the apparatus comprising an upper x-ray shield panel and a lower x-ray shield panel arrangement, the upper x-ray shield panel and the lower x-ray shield panel arrangement having thicknesses between front and back faces thereof and respectively having lower and upper edges in close enough proximity to each other to substantially attenuate the back-scattered x-rays incident on (a) the front face of the upper x-ray shield panel, (b) the lower x-ray shield panel arrangement, and (c) a gap between the edges while the front faces of the upper x-ray shield panel and lower x-ray shield panel arrangement are aligned, the upper shield panel being transparent to visible optical energy and pivotable about a vertical axis relative to the lower shield panel arrangement to enable one or both hands and one or both forearms of a person standing behind the back faces of the upper and lower shield panels to extend through an open region between the lower and upper edges resulting from pivoting of the upper x-ray shield panel relative to the lower x-ray shield panel arrangement about the vertical axis, the upper x-ray shield panel and lower x-ray shield panel arrangement together having a height and widths sufficiently greater than the height and width of the person standing behind the back faces so as to substantially prevent the back-scattered x-rays incident on the front faces of the upper x-ray shield panel and the lower x-ray shield panel arrangement while the front faces are aligned from being incident on the portion of the person behind the back faces. 2. The apparatus of claim 1 wherein the upper x-ray shield panel and the lower x-ray shield panel arrangement have aligned vertically extending edges that are substantially coincident with the vertical axis, and further including another x-ray shield panel having front and back faces and a vertically extending edge in sufficiently close proximity with the aligned vertically extending edges of the upper x-ray shield panel and lower x-ray shield panel arrangement to substantially attenuate the back-scattered x-rays incident on the aligned vertically extending edges of the upper x-ray shield panel and the lower x-ray shield panel arrangement and the vertically extending edge of the another x-ray shield panel, the front face of the another x-ray shield panel being positionable at a non-zero angle relative to the front faces of the upper x-ray shield panel and the lower x-ray shield panel arrangement. 3. The apparatus of claim 2 wherein the another x-ray shield panel has a height substantially equal to the combined heights of the upper x-ray shield panel and the lower x-ray shield panel arrangement. 4. The apparatus of claim 3 wherein the vertically extending edge of the another x-ray shield panel is pivotable relative to the aligned vertically extending edges of the upper x-ray shield panel and the lower x-ray shield panel arrangement. 5. The apparatus of claim 4 wherein the another x-ray shield panel has a horizontal extent substantially at a right angle to the faces and a first segment extending slightly beyond the front faces toward the operating table and a second segment extending by a substantial distance beyond the back faces away from the operating table. 6. The apparatus of claim 5 wherein the lower x-ray shield panel arrangement includes a single x-ray shield panel. 7. The apparatus of claim 5 wherein the lower x-ray shield panel arrangement includes first and second x-ray shield panels, the first x-ray shield panel having an upper edge corresponding with the upper edge of the lower x-ray shield panel arrangement and a lower edge, the second x-ray shield panel having an upper edge below the lower edge of the first x-ray shield panel and a lower edge in close proximity to the floor or on the floor, the first and upper x-ray shield panels being arranged to be able to have different vertical positions so that the gap between the upper edge of the first x-ray shield panel and the lower edge of the upper x-ray shield panel is maintained constant at the different vertical positions, the first and second x-ray shield panels being arranged so that the upper and lower edges of the second x-ray shield panel are maintained at the same vertical position while the first and upper x-ray shield panels are at all of the different vertical positions and the upper edge of the second x-ray shield panel is above the lower edge of the first x-ray shield panel at all of the different vertical positions. 8. The apparatus of claim 7 further including a pulley arrangement to which the upper and first x-ray shield panels are drivingly connected so the upper and first x-ray shield panels can be driven to the different vertical positions, the pulley arrangement including a wheel and a counterweight, the counterweight being on a side of the wheel different from the upper and first x-ray shield panels, the counterweight having a weight approximately equal to the combined weights of the upper and first x-ray shield panels. 9. The apparatus of claim 2 wherein the vertically extending edge of the another x-ray shield panel is pivotable relative to the aligned vertically extending edges of the upper x-ray shield panel and the lower x-ray shield panel arrangement. 10. The apparatus of claim 2 wherein the another x-ray shield panel has a horizontal extent substantially at a right angle to the faces and a first segment extending slightly beyond the front faces toward the operating table and a second segment extending by a substantial distance beyond the back faces away from the operating table. 11. The apparatus of claim 1 wherein the lower x-ray shield panel arrangement includes a single x-ray shield panel. 12. The apparatus of claim 1 wherein the lower x-ray shield panel arrangement includes first and second x-ray shield panels, the first x-ray shield panel having an upper edge corresponding with the upper edge of the lower x-ray shield panel arrangement and a lower edge, the second x-ray shield panel having an upper edge below the lower edge of the first x-ray shield panel and a lower edge in close proximity to the floor or on the floor, the first and upper x-ray shield panels being arranged to be able to have different vertical positions so that the length of the gap between the upper edge of the first x-ray shield panel and the lower edge of the upper x-ray shield panel is maintained constant at the different vertical positions, the first and second x-ray shield panels being arranged so that the upper and lower edges of the second x-ray shield panel are maintained at the same vertical position while the first and upper x-ray shield panels are at all of the different vertical positions and the upper edge of the second x-ray shield panel is above the lower edge of the first x-ray shield panel at all of the different vertical positions. 13. The apparatus of claim 12 further including a pulley arrangement to which the upper and first x-ray shield panels are drivingly connected so the upper and first x-ray shield panels can be driven to the different vertical positions, the pulley arrangement including a pulley and a counterweight, the counterweight being on a side of the pulley different from the upper and first x-ray shield panels, the counterweight having a weight approximately equal to the combined weights of the upper and first x-ray shield panels. 14. The apparatus of claim 1 in combination with at least one of the tables and the x-ray source. 15. A method of reducing back-scattered x-rays incident on a person working with a patient on an operating table, the patient being exposed to x-rays from an x-ray source while on the table so that the back-scattered x-rays result from x-rays from the source being incident on the patient and/or table, the apparatus comprising an upper x-ray shield panel and a lower x-ray shield panel arrangement, the upper x-ray shield panel and the lower x-ray shield panel arrangement having thicknesses between front and back faces thereof and respectively having lower and upper edges in close enough proximity to each other to substantially attenuate the back-scattered x-rays incident on the front faces of the upper x-ray shield panel, the lower x-ray shield panel arrangement and a gap between the edges while the front faces of the upper x-ray shield panel and lower x-ray shield panel arrangement are aligned, the upper shield panel being transparent to visible optical energy and pivotable about a vertical axis relative to the lower shield panel arrangement to enable one or both hands and one or both forearms of a person standing behind the back faces of the upper and lower shield panels to extend through an open region between the lower and upper edges resulting from pivoting of the upper x-ray shield panel relative to the lower x-ray shield panel arrangement about the vertical axis, the upper x-ray shield panel and lower x-ray shield panel arrangement together having a height and widths sufficiently greater than the height and width of the person standing behind the back faces so as to substantially prevent the back-scattered x-rays incident on the front faces of the upper x-ray shield panel and the lower x-ray shield panel arrangement while the front faces are aligned from being incident on the person, the method comprising causing the upper x-ray shield panel to be turned toward the table and maintaining the lower x-ray shield panel arrangement substantially parallel to an edge of the table while the patient is exposed to x-rays from the x-ray source to form the open region, extending one or both hands and one or both forearms through the open region while the patient is exposed to x-rays from the x-ray source while the remainder of the person is behind the back faces. 16. The method of claim 15 wherein the lower x-ray shield panel arrangement includes first and second x-ray shield panels, the first x-ray shield panel having an upper edge corresponding with the upper edge of the lower x-ray shield panel arrangement and a lower edge, the second x-ray shield panel having an upper edge below the lower edge of the first x-ray shield panel and a lower edge in close proximity to the floor or on the floor, the first and upper x-ray shield panels being arranged to be able to have different vertical positions so that the length of the gap between the upper edge of the first x-ray shield panel and the lower edge of the upper x-ray shield panel is maintained constant at the different vertical positions, the first and second x-ray shield panels being arranged so that the upper and lower edges of the second x-ray shield panel are maintained at the same vertical position while the first and upper x-ray shield panels are at all of the different vertical positions and the upper edge of the second x-ray shield panel is above the lower edge of the first x-ray shield panel at all of the different vertical positions, the method further comprising causing the lower edge of the upper x-ray shield panel to abut an upper surface of the patient on the operating table while the patient is exposed to x-rays from the x-ray source and one or both hands and one or both forearms of the person extend through the open region while the remainder of the person is behind the back faces.
055925200	abstract	A window in the control rod for a nuclear reactor has flanges along its opposite sides. A latch handle has slots along its opposite sides. The latch handle is sized and configured such that in a first angular orientation, the latch handle may be received within the plane and peripheral confines of the window and, upon rotation of the latch handle through 90.degree. into a second orientation, engages the slotted sides of the latch handle with the flanges of the window to capture the latch handle within the window while simultaneously enabling linear vertical movement of the latch handle relative to the window. The latch handle is then attached to a shaft for operating a coupling mechanism between the control rod and the control rod drive.
	summary
	description	This application is related to the following co-pending U.S. patent application Ser. No. 12/549,447, entitled “SYSTEM AND METHOD FOR MANAGING WIND TURBINES” assigned to the same assignee as this application and filed herewith, the entirety of which is incorporated by reference herein. The invention relates generally to wind turbine systems and, more particularly, to systems and methods for management of wind turbines. Wind turbines are increasingly gaining importance in the area of renewable sources of energy generation. A wind turbine generally includes a wind rotor having turbine blades that transform wind energy into rotational motion of a drive shaft, which in turn is utilized to drive a rotor of an electrical generator to produce electrical power. In recent times, wind turbine technology has been applied to large-scale power generation applications. Modern wind power generation systems typically take the form of a wind turbine farm (or wind-farm) having multiple such wind turbines that are operable to supply power to a transmission system providing power to a utility system. Of the many challenges that exist in harnessing wind energy, one is maximizing wind turbine performance. One of the factors that affect the wind turbine performance is down time due to tripped wind turbines on account of a fault, or unsuitable operating conditions, such as environmental conditions among others. On detection of a fault or unsuitable conditions, the wind turbines are tripped to avoid damage to the wind turbines. Currently, human intervention is required to assess the causes for the wind turbine being tripped and then reset the wind turbine to start operating again. Consequently, long down times of the wind turbine are experienced to have trained personnel to assess, analyze and reset or restart the tripped wind turbine. Typically, service engineers review the turbine fault logs from a remote location and reset the turbine. In certain instances, a physical inspection or review of the wind turbine may be required to identify the cause of a fault, or to reset the wind turbine, in such cases field service engineers diagnose the faults, fix the root cause for problem and thereafter reset the turbine. The review and reset process for each individual wind turbine usually requires a substantial time from the service engineers. Further, in wind-farms having hundreds or thousands of wind turbines, the review and reset process for each wind turbine that is tripped can be logistically challenging, and in certain cases, may require a substantial turn around time from the service engineers, during which time the wind turbines will be non-operational. The non-operational time of wind turbines may translate in to significant loss of productivity for the wind-farm. Maintaining a staff of multiple service engineers to handle an eventuality of multiple wind turbines requiring support on the wind-farms increases the costs of supporting the maintenance staff significantly. The aforementioned systems require that manual analysis be conducted on the turbine data for detecting root causes for faults in the wind turbine and the wind turbines are reset through manual commands from service team, either remotely or locally at site. This process leads to substantive down times of wind turbines, causing losses on account of less productivity. Further, maintaining a support staff to analyze fault logs and turbine data; accordingly service the wind turbines further leads to additional maintenance costs. Therefore, a need exists for an improved wind turbine management system that may address one or more of the problems set forth above. In accordance with one aspect of the invention, a wind turbine management system is provided. The wind turbine management system includes a wind turbine operable to generate electricity using wind energy. The wind turbine comprises operational characteristics related to the operation of the wind turbine. A control server comprises a wind turbine management module. The wind turbine management module is configured to implement the steps of receiving operational information on the operational characteristics of the wind turbine, analyzing the operational information based on a set of rules, and determining whether a fault of the wind turbine is resettable. According to an aspect, the set of rules are configurable, and may be configured based on operational parameters or characteristics such as historical data, heuristic data, engineering data for the wind turbine, environmental factors, wind turbine configuration, among several others. The system further includes a network that operably couples the wind turbine and the management module. Further, a rule configuration module is accessible via the network. In accordance with an aspect of the invention, a method of wind turbine management is provided. The method includes receiving operational information on operational characteristics of a wind turbine. The operational information comprises operational data. The operational information is analyzed based on a set of rules, and a determination is made as to whether a fault of the wind turbine is resettable. In accordance with another aspect of the invention, a method of wind turbine management is provided. The method includes receiving and analyzing operational information on operational characteristics of a wind turbine. The operational information is analyzed based on a set of rules, and a determination is made as to whether advanced operational information is required. Advanced operational information is received and analyzed based on the set of rules, and a determination is made as to whether a fault of the wind turbine is resettable. As described in detail below, embodiments of the present invention provide systems and methods for managing wind turbines. Wind turbines are managed based on a number of operational parameters of the wind turbine and the environmental conditions. Due to certain operational faults, a wind turbine may be tripped for the safety of the wind turbine. Some non-limiting examples of the conditions that may cause trip of the wind turbine include wind gust conditions, temperatures in mechanical components such as gears, bearings and others, exceeding a threshold value, excess voltage or excess current faults, faults in converter and certain other hardware units, faults in generator and rotor speed sensors, tower vibrations, grid event fault. Wind turbines may trip due to several reasons, including faults induced by transient operating conditions, unsuitable environmental conditions, among other conditions. Many cases of wind turbines being tripped are due to a “soft fault” or a “resettable fault.” A soft fault may be due to a fault that is transient in nature, or in general, a fault causing a trip of the wind turbine after which the wind turbines may be safely reset within a short time interval. Some non-limiting examples of the operational conditions inducing soft faults include wind gust conditions, temperatures in mechanical components such as gears, bearings and others, exceeding a threshold value, excess voltage or excess current faults, faults in converter and certain other hardware units, faults in generator and rotor speed sensors, tower vibrations, grid event fault. The system includes a set of rules to analyze the nature of the fault, and determine whether the fault is resettable. A “hard fault” is a fault that causes trip of the wind turbine and requires an on-site intervention for the wind turbine. Systems and methods disclosed herein provide for, including other features, identifying and automatically resetting a tripped wind turbine in case of soft faults. Further, advanced diagnostic logs are generated for experts to study and reduce trip resolution time. In case of hard faults, in addition to a detailed diagnostic log, an error message is generated indicating that on-site maintenance for the wind turbine is required. FIG. 1 illustrates a block diagram representation of a wind farm 100 according to an embodiment of the present invention. The wind farm 100 comprises multiple wind turbine modules 1101, 1102 . . . 110N, each of the multiple wind turbine modules 110 being communicably coupled to a farm server 120. Each of the wind turbine modules, for example, the wind turbine module 1101 comprises a wind turbine 102, a controller 104, and an interface computer 106. The controller 104 is configured to receive operational information associated with the wind turbine 102 and the wind turbine module 110. The controller 104 is also configured to control the operations of the wind turbine module 110 including tripping or resetting the wind turbine 102, among others. The interface computer 106 may be configured to receive data from the controller 104 and act as an interface between the controller 104 and the server 120. In some embodiments, the interface computer 106 is configured to accesses and processes additional or advanced operational information of the wind turbine 110. The interface computer 106 is further configured to store and retrieve the advanced or additional information of the wind turbine module 110, among other functions. The farm server 120 is configured to receive and process operational information for each of the wind turbine modules 1101 . . . 110N. The wind turbine module 110 and the farm server 120 may be communicably coupled through a wire, cable, optical fiber and the like. However, one of ordinary skill would recognize that other ways of coupling communicably, such as, through a wireless link facilitated by various types of well-known network elements, such as hubs, switches, routers, and/or the like, would result in equally valid embodiments of the present invention. Generally, the wind turbine 102 is employed to harness wind energy and convert the wind energy into other useful forms, for example, electricity. In one embodiment, the wind turbine 102 converts the wind energy to kinetic energy that is provided to a generator (not shown in the figures). The generator converts the kinetic energy to electricity, which may then be supplied to a power grid. The wind turbine 102 may further include various other components to support the functionality, monitoring, maintenance and other functions of the wind turbine 102. Other such components include, but are not limited to, components such as sensors, circuitry, converter, gears, bearing, rotors, and such components are not shown for the sake of simplicity. The controller 104 is configured to monitor and control all such components and the wind turbine 102 of the wind turbine module 110. The controller 104 is any type of programmable logic controller that comprises a Central Processing Unit (CPU), various support circuits and a memory. The CPU of the controller 104 may comprise one or more commercially available microprocessors or microcontrollers that facilitate data processing and storage, or may comprise an application specific processing circuit. Various support circuits facilitate operation of the CPU and may include clock circuits, buses, power supplies, input/output circuits and/or the like. The memory includes a Read Only Memory (ROM), Random Access Memory (RAM), disk drive storage, optical storage, removable storage, and the like for storing a control program or for storing data relating to status information. The controller 104 cooperates with the interface computer 106 to generate operational information 130, which may be resident on the interface computer 106, or the farm server 120, or both. In some embodiments, the controller 104 is configured to perform the functions of the interface computer 106. Further, the interface computer 106 and the farm server 120 are examples of computers that are generally known in the art. As used herein, the term ‘computer’ will be meant to include a central processing unit (CPU) configured to execute programmable instructions, a memory configured to store data including programmable instructions, support circuits that facilitate the operation of the CPU. The CPU may comprise one or more commercially available microprocessors or microcontrollers that facilitate data processing and storage. The memory includes a Read Only Memory, Random Access Memory, disk drive storage, optical storage, removable storage, and the like. Various support circuits facilitate operation of the CPU and may include clock circuits, buses, power supplies, input/output circuits and/or the like. The memory may further include data and software packages, such as an operating system (not shown), application software packages, and operational information, among others. The computers also include an input and output interface to interact with other computers or electronic devices. Computers may function as servers, clients to a server, interface computers, storage system, and may serve several other functions. In general, various devices may be categorized as computers, and such devices include a laptop computer, a desktop computer, a Personal Digital Assistant (PDA) and the like. The interface computer 106 stores the operational information 130 associated with the components of the wind turbine module 110, while the farm server 120 is configured to control the entire wind farm 100 comprising the individual wind turbine modules 1101 . . . 110N. The farm server 120 is further configured to send operational information pertaining to the individual wind turbine modules 110, and receive operating instructions for the individual wind turbine modules 110. For this purpose, the farm server 120 may communicate with other devices, for example, over a communications network (not shown). In certain embodiments, the interface computer 106 aggregates all operational information from controller 104. The operational information comprises the operational information 130, which may be routinely communicated to the farm server 120 by the computer 106. The operational information 130 includes information of the wind turbine, such as, information on specific values of operational characteristics or parameters such as baseline control parameters, input messages, park or wind farm configuration, error status including error codes from trip time to shutdown time, error history for wind turbine modules or components therein, parametric data pertaining to various operational parameters of the wind turbine modules, wind turbine configuration, wind turbine status, condition/status flags, sensor data among several others. The operational parameters or characteristics may also include environmental configuration, wind turbine configuration among others. Other non limiting examples of operational information include data on parameters such as temperature profile, wind speed, wind speed profile, hardware faults in components such as converters, among others, voltage generated, current generated, accuracy of sensors such as rotor speed sensors, tower vibrations, grid event, among several other parameters associated with one or more components of the wind turbine module 110. Such operational information 130 is advantageously utilized, according to several techniques discussed herein, in automatically resetting the tripped wind turbine 102 and/or the tripped wind turbine module 110. The operational information 130 is routinely monitored for managing the wind turbines. Further, the operational information 130 is a subset of the operational information gathered and/or stored by the controller 104, the interface computer 106 and the farm server 120. FIG. 2 illustrates a block diagram representation of a system 200 for managing wind turbines according to an embodiment of the present invention. The system 200 includes a wind turbine farm 202, similar to the wind farm 100 as discussed above, the wind farm 202 comprising a farm server 210. The system 200 further comprises a control server 220 for managing the wind turbines, a monitor 230 for accessing the server 220, and rules 240 stored on a device 242. The farm server 210, the server 220, the monitor 230 and the device 242 are communicably coupled to each other through a network 250. In an alternate embodiment, the server 220, the monitor 230 and the device 242 are integrated in the farm server 210. Various components of the system 200 may be arranged and/or integrated in various feasible permutation and/or combination variations. All such variations will occur readily to those skilled in the art, and are included within the scope and spirit of the present invention. The farm server 210 includes operational information (for example, the operational information 130 of FIG. 1), and as such, the farm server 210 communicates the operational information for each of the wind turbine module on the wind farm 202 to the server 220, over the network 250. The farm server 210 is further configurable to receive and process operating instructions from the server 220, over the network 250, for each of the wind turbine modules 1101 . . . 110N. For example, the farm server 210 is configured to receive operational information from the interface computers 106, and is further configured to send the operational information to the control server 220. The farm server 210 is also configured to receive operating instructions from the control server 220. The control server 220 is a computer, such as those generally known in the art. The control server 220 includes a CPU 214, support circuits 216 and a memory 218. The memory 218 includes an operating system 222 and various software packages, such as a management module 224 configured to manage the wind turbines on the wind turbine farm 202, for example, providing monitoring output messages, auto-reset instructions, diagnostic recommendations, among other functions. The memory 218 further includes a rules engine 226 for configuring the rules 240, for example based on operating conditions of the wind turbine and/or analysis of wind turbine faults. In certain embodiments, the farm server 210 is a Supervisory Control And Data Acquisition (SCADA) module, running on, for example, Win NT, VisuPro, or Mark Series platforms, among several others known in the art. The monitor 230 is a computer, such as those generally known in the art. Generally, the monitor 230 is utilizable to access, monitor or control the server 220, for example, by service personnel for the wind turbines. Service personnel may include site maintenance staff or wind turbine experts for supporting the operations at a wind farm or multiple wind farms. The service personnel may instruct to reset a particular wind turbine through the server 220 by sending reset instructions over the network 250, to a controller (e.g., the controller 104 of FIG. 1) of that particular wind turbine. In one or more embodiments, the service personnel may advise physical maintenance activities and/or take other corrective actions in case of possible faults in the wind turbines. The management module 224 includes software code (e.g., processor executable instructions) that when executed, is configured to analyze operational information and determine the fault within the wind turbine. The management module 224 is configured to receive and process operational information, in order to determine if a tripped wind turbine may be automatically reset and further, providing instructions to reset a tripped wind turbine. The management module 224 is also configured to provide enhanced diagnostics on a tripped or a faulty wind turbine to the service personnel. The management module 224 is further configured to analyze the operational information with respect to the rules relating to the operation of the wind turbines, for example, the rules 240 that are accessible to the management module 224 over the network 250. In the embodiment illustrated by FIG. 2, the rules 240 are comprised in a device 242 communicably coupled to the network 250. However, one of ordinary skill would recognize that other arrangements of the rules 240, such as maintaining the rules 240 on the control server 220, or any other device on the network 250 would result in equally valid embodiments of the present invention. According to various embodiments, the rules 240 are utilized by the management module 224 to analyze and determine the fault within the wind turbine. For example, the rules 240 may specify a safe range of threshold value of temperatures of various wind turbine components or regions, frequency of occurrence of the errors according to which a tripped wind turbine may be made operational. More specifically, if the temperature of gear box crosses an upper threshold limit, the wind turbine 102 may get damaged or may cease to operate. Accordingly, the controller 104 is configured to trip the wind turbine 102. However, it has been advantageously determined that the wind turbine being tripped due to crossing the temperature thresholds in the gearbox and bearings may be safely reset once the temperature gets below the predetermined safety limit. The rules 240 specify such safety limits or temperature threshold values, and other knowledge on temperature thresholds and several other parameters pertaining to the operation of the wind turbines, the impact of operating conditions, among several other factors. According to an aspect, the set of rules are configurable, and may be configured based on operational information such as historical data, heuristic data, engineering data for the wind turbine, environmental factors, wind turbine configuration, among several others. For example, the rules are configurable to include the knowledge of various conditions to be met for auto-reset of the wind turbine, for generating diagnostic information related to component conditions, baseline parameter mismatching and warning messages (conveyed to service engineer in advance, e.g. days ahead of next maintenance cycle). As another example, the rules 240 may specify the lower and upper limit of electrical parameters such as voltage and current levels that are acceptable. Accordingly, if the wind turbine is tripped due to the voltage and/or the current levels in the wind turbine circuits crossing a particular threshold value, the management module 224 consults the rules 240 and monitors the wind turbine to ascertain if the voltage and/or the current levels have stabilized within the acceptable upper and lower thresholds. It has been advantageously observed that typically, the voltage and/or the current values stabilize within the upper and the lower thresholds within a short duration after a transient behavior. While only a few examples have been mentioned above, it is appreciated here that the management module 224 is configured to analyze the operational information of the wind turbine in light of the rules 240. The management module 224 is further configured to determine, after a time interval of a wind turbine being tripped, whether the operational parameters of the tripped wind turbine are within permissible ranges of threshold values. In case the operational parameters have stabilized within the corresponding threshold values, the management module 224 is configured to reset the wind turbine (e.g. the wind turbine 102) by instructing the controller 104. The time interval, according to certain embodiments, ranges from about a few seconds to about a few minutes, depending on the nature of the fault. Occasionally, the operational information may be insufficient to perform analysis. As such, the management module 224 may request for advanced operational information, from the wind turbine module (e.g., the wind turbine module 110 of FIG. 1). The advanced operational information is over and above the operational information routinely received by the management module 224. The farm server 210, in turn, communicates the request to a computer (e.g., the computer 106 of FIG. 1) of the wind turbine module. As discussed, the computer 106 aggregates extensive operational information, from which routine operational information is communicated to the control server 220. Based on request for advanced operational information, the computer 106 is configured to communicate the advanced operational information to the control server 220. In certain embodiments, the computer 106 may, based on request by the management module 224, extract advanced operational information of the wind turbine module, such as current operating or environmental conditions, for example, current wind speed, wind gust data, and the like. The additional or advanced operational information provides the management module 224 to make an enhanced assessment of the conditions prevalent at the wind turbine module 110. For example, the management module 224 may determine that a wind turbine was tripped because wind speed profile crossed a pre-defined threshold due to a gust of wind. The management module 224, in such conditions, may continue to monitor the current wind speed profile to ascertain the time at which the wind speed profile is within the acceptable thresholds. Additionally, the management module 224 may request for data that indicates if any damage was done to the wind turbine or other associated components by the wind gust that caused the trip of the wind turbine. Another example related to asymmetric generator current, in which the turbine is tripped if asymmetric current is found in any of the generator phases. In such cases, the management module 224 checks whether the threshold parameter that indicates the limit for asymmetric generator current, is set correctly in the turbine. If the parameter is set to an incorrect value, the management module 224 gives a diagnostic message indicating that the asymmetric generator current threshold is set to an incorrect value, and instructs that the threshold be changed to the correct value. In a next step, using snapshot current measurements in the generator phases, the management module 224 determines which phase is defective. Further, the management module 224 checks whether the fault occurred within a permissible number of times, limited by a pre-defined frequency limit. If the fault has occurred permissible number of times, the management module 224 sends an auto-reset command for the turbine to reset. If the fault occurred more than the permissible number, the management module 224 generates a service request for a service engineer. As another example, the management module 224 may determine that an electrical system tripped due to a surge in the voltage and/or the current in the circuits. The management module 224 may continue monitoring the operational information to identify when the voltage and/or current values have stabilized within the corresponding threshold limits. In case, it is identified that the voltage and/or the current values have not stabilized at expected ranges, or, in any case, are abnormal, the management module 224 may request advanced operational information to ascertain causes for the abnormality. For example, using additional information, the management module 224 ascertains, in conjunction with the rules 240 that certain circuit components may be malfunctioning, causing the abnormality. In such cases, the management module 224 communicates a warning and/or a detailed diagnostic log for the expert to perform corrective actions. In several cases, an enhanced diagnosis of the wind turbine operational conditions, as described above, allow for an automatic reset of the wind turbine 102 in cases for which an automatic reset that has not been feasible earlier. In other cases, a detailed fault log is generated for the trained personnel, thereby considerably reducing the analysis time burden on the personnel, and consequently reducing the mean time to return to service for the wind turbines. According to an embodiment of the present invention, a method for managing a wind turbine comprises receiving operational information of a wind turbine. The operational information is analyzed based on a set of rules. In case of a wind turbine being tripped, the analysis determines whether the trip of the wind turbine is resettable, that is, if the fault causing the trip is a soft fault or a hard fault. According to another embodiment of the invention, a method for managing a wind turbine comprises receiving operational information of a wind turbine. The operational information is analyzed based on a set of rules. In certain embodiments, it may be determined by analyzing the operational information received routinely that advanced operational information is required to analyze the wind turbine performance and/or faults therein. In such cases, advanced operational information is retrieved from the wind turbine, based on the initial analysis of operational information received routinely. The advanced operational information is then received and used for conducting an enhanced diagnostic analysis of the wind turbine. This process of receiving advanced operational information may be iterated as required. According to various embodiments, the advanced operational information includes sensor data of the wind turbine up to the trip. In certain other embodiments, the advanced operational information further includes sensor data after the wind turbine has tripped. The enhanced diagnostic analysis is helpful in determining whether the trip of the wind turbine is resettable. If a resettable fault is determined, the wind turbine is reset. If, however, the fault is not resettable, a detailed diagnostic report is generated for further manual analysis, for example, by service personnel. Referring now to FIG. 3, a flow chart representing steps involved in a method 300 for automatically resetting a wind turbine, for example, the wind turbine 102 is illustrated. The method 300 may be implemented by a management module (e.g., the management module 224 of FIG. 2) resident on the server 220. The management module 224 processes operational information (e.g., the operational information 130 of FIG. 1) of the wind turbine 102 to provide an automatic reset to the tripped wind turbine. It is appreciated here that while the method embodiments discussed herein may refer to elements from FIG. 1 and FIG. 2, such embodiments are not limited to the system elements of FIG. 1 and FIG. 2. The method 300 starts at step 302 and proceeds to step 304 at which the operational information of the wind turbine is received. In one embodiment, a control server (e.g., the control server 220 of FIG. 2) receives the operational information of the wind turbine from a farm server (e.g., the farm server 120 of FIG. 1 and the farm server 210 of FIG. 2). For example, a line voltage fault may occur within the wind turbine due to which the wind turbine is tripped. In general, the line voltage fault may occur due to a defective relay output, grid voltage error and/or the like. Accordingly, the management module 224 receives the operational information such as, frequency of the occurrence of the fault, one or more consecutive voltages after the trip time of the wind turbine, among other operational information. At step 306, the operational information is analyzed with respect to rules, for example, the rules 240 of FIG. 2. In one embodiment, the management module 224 analyzes the operational information 130 of the wind turbine modules 110 to determine if the fault that caused the wind turbine to be tripped is resettable. To accomplish whether the fault is resettable, the operational information is compared with respect to the rules. According to an embodiment, in the line voltage fault example, the rules are configured to define that for the wind turbine to be reset automatically after the trip, the frequency of occurrence of the line voltage fault should be less than ten instances over the last twenty-four hours and/or less than twenty instances over the last seven days. In another embodiment, the configured rules define that the three consecutive voltages from the time since the wind turbine tripped should be in range of 200 Volts and 400 Volts. According to certain embodiments, the management module 224 analyzes the received operational information with the rules defined for a corresponding fault that caused the wind turbine to be tripped. In other words, the management module 224 analyzes whether the operational information of the tripped wind turbine lies within the threshold limits as defined in the rules corresponding to the fault that caused the wind turbine to be tripped. If the operational information indicates that the operational parameters lie within the threshold limits, the fault is identified as resettable. According to one embodiment, faults that have not occurred frequently, and the magnitude of such faults is within a predetermined tolerance limit are typically resettable. If, however, the operational information indicates that the operational parameters of the wind turbine breach the threshold limits corresponding to a particular fault or the frequency with which such faults have occurred, the wind turbine is not reset. According to certain embodiments, a request for changing the operational parameter to a correct value is sent to service team. Specifically, at step 308, a determination is made as to whether the fault is resettable. If, at the step 308, it is determined that the fault is not resettable (option “NO”), the method 300 proceeds to step 314. If at the step 308, it is determined that the fault is resettable (option “YES”), then the method 300 proceeds to step 310. At the step 310, safety conditions for the wind turbine to be operational are assessed. If the safety conditions are satisfied, the wind turbine is reset at step 312, such that the wind turbine becomes operational. In one embodiment, the management module may provide an instruction to a controller (e.g., the microcontroller 106 of FIG. 1) of the wind turbine, to reset the wind turbine. The method 300 proceeds to step 314. At the step 314, a diagnostic fault analysis log is generated. The log is utilizable by an expert, or service personnel. According to one embodiment, a detailed diagnostic report on the wind turbine is generated, and the service personnel are alerted. In one embodiment, the management module alerts the expert regarding the fault of the wind turbine. For example, if the frequency of the occurrence of the above mentioned line fault voltage is more than the limits defined within the rules (frequency>=six for last seven days), it is determined that the fault causing the wind turbine to trip is not resettable. Accordingly, the management module alerts the expert regarding the fault of the wind turbine, additionally providing the expert with a diagnostic log of the operational parameters pertaining to the fault. In another embodiment, the expert analyzes the fault of the wind turbine. The method 300 ends at step 316. According to various embodiments of the method 300, the operational information is received for monitoring various faults due to which a wind turbine may be tripped. For example, for trips due to storm/gust of wind are generated once the slope of wind speed profile crosses a pre-defined threshold. The trips due to such can be reset once wind becomes steady and the average wind speed is below a predetermined safety threshold. According to an embodiment, the rules are configured to define the average wind speed threshold at 5 m/s. In other embodiments, the rules are configured to define the average wind speed threshold at 8 m/s. As discussed below, the rules are configurable based upon various operating configuration factors including the operational information, environmental conditions, wind farm configuration, turbine configuration, among others, the rules provide different threshold values for different operating configurations. As discussed, wind turbine may be tripped due to temperature in the gearbox and bearings crossing the temperature thresholds and the turbine can be safely reset once the temperature is below the predetermined safety limit. Another instance of faults causing the wind turbine to be reset relate to converter and other similar hardware units of the wind turbine module. According to an embodiment, the wind turbine may be reset, for example, if the frequency of occurrence of such fault in given period (1 hour/1 day/1 week/1 month) does not exceed more than the pre-decided threshold value for that period. Faults in generator and rotor speed sensors may also cause the wind turbine to be tripped. For trips due to such faults, according to an embodiment, the speed sensors are checked for allowable percentage error, and if the difference among the speed sensors falls below a pre-determined threshold value, the turbine may be reset. Further, the wind turbine may be tripped due to wind turbine tower vibrations. The wind turbine may also be tripped in case of a grid event, such as a fault in the grid, or the grid being tripped, among others. According to an embodiment, the wind turbine may be reset after the grid is restored, and sufficient time has elapsed. Faults as discussed above, and several other faults of the wind turbine module and corresponding threshold values will occur readily to those skilled in the art. The various techniques disclosed herein are configured to provide operational information relating to such faults and provide an automatic reset of the wind turbine, and all such variations lie within the scope and spirit of the present invention. FIG. 4 is a flow chart representing steps involved in a method for automatically resetting a wind turbine according to another embodiment of the present invention. The method 400 starts at step 402 and proceeds to step 404 at which operational information of the wind turbine is received. In one embodiment, a control server (e.g., the control server 220 of FIG. 2) receives the operational information of the wind turbine from a farm server (e.g., the farm server 104 of FIG. 1 or the farm server 210 of FIG. 2). At step 406, the operational information is analyzed with respect to rules (e.g., the rules 240 of FIG. 2). The analysis of operational information may reveal whether the fault that caused the wind turbine to be tripped is a resettable fault. The analysis of operational information with respect to the rules may further determine whether advanced operational information of the wind turbine needs to be requested, for further analysis of the fault that caused the wind turbine to be tripped, and/or resetting the tripped wind turbine. At step 408, a determination is made as to whether the fault is resettable. If it is determined that the fault is resettable (option “YES”), the method 400 proceeds to step 410. At the step 410, the safety conditions for making the wind turbine operational are assessed. If the safety conditions are satisfied, the wind turbine is reset to start operating at step 412. If, however, at the step 408, it is determined that the fault is not resettable (option “NO”), the method 400 proceeds to step 414. At the step 414, a determination is made as to whether advanced operational information needs to be requested in order to analyze further, the fault that caused the wind turbine to be tripped. It may be determined that advanced operational information may also be required to reset the tripped wind turbine. If at the step 414, it is determined that advanced operational information does not need to be requested (option “NO”), the method 400 proceeds to step 422. In certain cases, for example, it may be determined that the fault that caused the wind turbine to be tripped is a fault that may not be reset without appropriate intervention by the service personnel. In such cases, the method 400 generates an enhanced diagnostic fault analysis log at the step 422. The enhanced diagnostic fault analysis log is utilizable by the service personnel to identify the nature of the fault and plan an appropriate remedial action, advantageously, in a shorter response time. If, however, at the step 414, it is determined that advanced operational information needs to be requested (option “YES”), the method 400 proceeds to step 416, at which advanced operational information is received. At step 418, the advanced operational information is analyzed based on the rules. The analysis at the step 418 determines whether the fault that caused the wind turbine to be tripped may be reset. Accordingly, a determination is made at step 420, as to whether the wind turbine is resettable. If it is determined that the wind turbine is not resettable (option “NO”), then the method 400 proceeds to step 422, at which an enhanced diagnostic fault log is generated. If at step 420, however, it is determined that the wind turbine is resettable (option “YES”), the method 400 proceeds to step 410, at which safety conditions for operating the wind turbine are assessed. If the safety conditions for operating the wind turbine are met at the step 410, the method proceeds to step 412, at which the wind turbine is reset to resume operation. The method 400 then proceeds to step 422 at which an enhanced diagnostic fault log is generated. In one embodiment, the management module alerts the expert regarding the fault of the wind turbine. The method 400 ends at step 426. With respect to the method 400, according to one embodiment, the management module 224 analyzes the operational information of the wind turbine. For example, a wind turbine, the wind turbine 102, may be tripped due to a temperature fault in gearbox and/or bearings of the wind turbine. In general, the temperature fault may occur if the temperature of the wind turbine 102 crosses a particular temperature threshold value. In such a condition, the management module analyzes the operational information 130 relating to the temperature of the gearbox and/or the bearings of the wind turbine 130 with respect to the rules. In this embodiment, the operational information 130 may not be sufficient to determine as to whether the wind turbine can be reset. Accordingly, the management module 224 determines whether the operational information 130 received is sufficient to reset the tripped wind turbine 102. The determination whether the operational information is sufficient or advanced operational information is required is based on analysis of the fault that caused the wind turbine to be tripped, the operational information 130 received and the rules 240. According to an embodiment of the invention, the rules are configurable. As discussed, the rules are configured based various operating configuration factors, including, but not limited to operational information of the wind turbine, environmental conditions, farm configuration, wind turbine configuration, among others. The rules are configured to determine threshold values according to various operating configuration factors. FIG. 5 illustrates a method 500 for configuring rules based on operating configuration of the wind turbine. As discussed, operating configuration of the wind turbine comprises several factors, including but not limited to, operational information of the wind turbine, trip and reset history of the wind turbine, engineering information of the wind turbine, farm configuration, wind turbine configuration, environmental conditions, and conditions or factors that affect the operational health of the wind turbine and/or the wind-farm. The method 500 starts at step 502, and proceeds to step 504 at which operating configuration information and/or fault analysis logs for a wind turbine are obtained. At step 506, the rules are analyzed based on the fault analysis logs and the operating configuration information. According to an embodiment, at the step 506 the fault analysis logs and the operating configuration are compared to assess whether the rules (including threshold parameters) need to be reconfigured for the existing operating configuration of the wind turbine. According to an embodiment, the analysis may indicate that a particular error that causes the wind turbine to trip is occurring due to a threshold value that is low for the operating configuration of the wind turbine. For example, it may be determined that in some geographic regions the environment is particularly windy, and the frequency of a wind turbine tripping due to wind gusts is higher than in other geographical regions. In other cases, it may be determined that particular seasons are windier than other seasons for the same geographical region. In such cases, if the threshold for frequency of wind turbine trip within a particular time interval is configured according to comparatively less windy geographical region (less windy season), the wind turbine will trip more than the threshold frequency in case of windy geographic regions (or windy seasons). In such cases, therefore, the wind turbine will not be automatically reset, even though the conditions are favorable for reset and/or the fault may be resettable. Based on such analysis, it may be determined that the threshold frequency and other rules needs to be reconfigured according to the analysis of the fault analysis log and the operating configuration information for the wind turbine. At this stage, a set of potential reconfigured rules may be defined in accordance with the analysis. Accordingly, at step 508, a determination is made at step as to whether the rules need to be reconfigured. If it is determined that the rules do not need to be reconfigured, (option “NO”), then the method 500 proceeds to step 514. If at step 508, however, it is determined that the rules need to be reconfigured (option “YES”), the method 500 proceeds to step 510, at which safety conditions for operating the wind turbine are assessed. If the safety conditions are satisfied according to potential reconfigured rules, at step 512 the potential reconfigured rules are defined as the new existing rules. In one embodiment, the management module 224 may update the rules (e.g., the rules 240 of FIG. 2) of the wind turbine. The method 500 proceeds to step 514. At the step 514, a flag for service engineers is generated, and the flag may include an enhanced diagnostic fault log comprising details of the analysis at the step 506, and/or defining the rules according to the step 512. Advantageously, the rules are easily configurable to accommodate additional learning from the field, i.e. learning about operational information, environmental conditions, farm and turbine configurations, and the like. Accordingly, while some specific threshold values have been discussed as examples, those skilled in the art will readily appreciate that various embodiments as discussed, provide for application of rules that are configurable according to operating configuration, in order to determine if a turbine can be reset. Further, according to some embodiments, the service engineer/team configures (or reconfigures) rules based on operational information for the wind turbine. The reconfigured rules may be deployed for a test period, updated, reconfigured, and then incorporated as defined existing rules in the wind turbine management system 200. Operating/operational characteristics or operating/operational parameters generally refer to characteristics/parameters of the wind turbine, wind turbine configuration, farm configuration, environmental conditions, among information on several other parameters pertinent to the operation of a wind farm. The terms “operational information” and “advanced (or additional) operational information” includes operational information of the various operating parameters/operating characteristics of the wind turbine, and data on any other operational configuration pertinent to the operation of the wind turbine. Those skilled in the art will appreciate that although various embodiments disclosed herein have been discussed with respect to the environment illustrated by FIG. 1 and FIG. 2, such embodiments are not limited to the arrangements illustrated by FIG. 1 and FIG. 2. For example, in one embodiment, the farm server 210 and the control server 220 may be a single computer. In other embodiments, the rules 240 may reside on the control server 220. In yet other embodiments, the monitor 230 may not be included, and service personnel may access the control server 220 directly. In other embodiments, the management module 224 comprises the functionality of the rules engine 226. In other contemplated embodiments, the rules engine 226 may reside on the device 242. It is further contemplated in certain embodiments that the interface computer 106 may also provide the functionality of the monitor 230, and vice versa. These and other obvious variations of the various computer components and/or functions as disclosed herein will appear readily to those skilled in the art, and all such variations are included within the scope and spirit of the present invention. Further, it is appreciated here that the term “network” as discussed herein includes all communications network capable of communicating data to devices communicably coupled to the network. Non limiting examples of such communications network include Local Area Networks, application specific networks, storage networks, the Internet, networks on the communication channels including the PSTN, CDM, GSM networks, among others. The various embodiments disclosed herein offer several advantages in managing the wind turbine systems. According to an advantage, providing an automatic reset reduces the mean return time to service (MRTS) for the wind turbines, considerably improving the performance of a wind turbine farm. Further, creating detailed and enhanced (based on the nature of the fault) diagnostic logs may help service personnel identify and remedy the wind turbine faults in considerably less time. Further, generation of enhanced diagnostic logs reduces the number of personnel required for managing wind turbines. While only certain features of the invention have been illustrated and described herein, modifications and changes will occur to those skilled in the art. It is, therefore, to be understood that the appended claims are intended to cover all such modifications and changes as fall within the true spirit of the invention.
	description	This application claims priority to U.S. Provisional Application Ser. No. 60/544,098, filed on Feb. 12, 2004. This work has been funded in whole or in part by U.S. government funding. The government may have certain rights in the invention. The present invention relates generally to mass spectrometry, and more specifically to optically patterning laser profiles for laser desorption and/or ionization of species for mass spectroscopic analysis. It was recognized in the early 1960s that by generating ions in a spatially resolved region of a surface, one could obtain atomic or molecular weight maps, or images (of ion mass-to-charge (m/z)), based on the spatial distribution of analyte and mass spectrometry detection. (R. Castaing and G. Slodzian, Microanalysis by Secondary Ionic Emission, J. Microsc. 1, 395-410 (1962)). For many years, imaging mass spectrometry was largely limited to secondary ion mass spectrometry (SIMS) whereby secondary analyte ions are produced by impinging the surface with a focused beam (<1 μm) of high-energy particles (e.g., keV Cs+or Ga+) (see M. L. Pacholski and N. Winograd, Imaging with Mass Spectrometry, Chem. Rev. 99, 2977-3005 (1999)), or by using laser microprobe mass spectrometry (LMMS) in which UV photons are used to provide direct ablation and photoionization of the analyte in a spatially-resolved mode. (L. Van Vaeck, H. Struyf, W. Van Roy, and F. Adams, Organic and Inorganic Analysis with Laser Microprobe Mass Spectrometry. Part I: Instrumentation and Methodology, Mass Spectrom. Rev. 13, 189-208 (1994); L. Van Vaeck, H. Struyf, W. Van Roy, and F. Adams, Organic and Inorganic Analysis with Laser Microprobe Mass Spectrometry. Part II: Applications, Mass Spectrom. Rev. 13, 209-232 (1994)). However, both techniques are primarily limited to the analysis of atomic ions and small molecules (typically<500 amu) and ultimately provide spatial imaging resolution that directly depends on the focusing properties of the optics (i.e., ion or photon optical elements) used to define the ionizing beam. The general principle of LMMS is illustrated in FIG. 1 (prior art), which shows a molecular weight map for an organic dye patterned onto a nitrocellulose membrane. FIG. 1 depicts an imaging mass map by LDI-TOFMS of crystal violet (hexamethyl-pararosanaline, m/z=372) deposited onto nitrocellulose. in the shape of an ampersand “&.” FIG. 1A is the optical microscopy image of the deposited material. FIG. 1B is the corresponding image obtained by LDI-TOFMS where white and black circles represent mass spectra with a signal-to-noise of less than and greater than 10 at m/z 372, respectively. Each mass spectrum represents the average of 10 laser shots and the laser spot (ellipse, ca. 50×90 μm) was translated in 95 μm increments to produce the resulting 780-pixel image. The analyte was interrogated by laser desorption/ionization time-of-flight mass spectrometry (LDI-TOFMS) by rastering the sample (via micropositioners) with respect to the laser spot (nitrogen laser, 337 nm) in 95 μm increments. In the late 1980s, the development of matrix assisted laser desorption/ionization (MALDI) provided a means to generate gas-phase ions of large intact biomolecules (ca. 102 to 106 amu) from solid samples. (M. Karas, D. Bachmann, U. Bahr, F. Hillenkamp, Matrix-Assisted Ultraviolet Laser Desorption of Non-Volatile Compounds, Int. J Mass Spectrom. Ion. Proc. 78, 53-68 (1987)). MALDI consists of incorporating analyte molecules into the crystal lattice of a UV or IR absorbing matrix, whereby matrix and analyte molecules are desorbed and ionized upon irradiation of the sample at the appropriate matrix-absorbing wavelength. Caprioli and coworkers have described imaging mass spectrometry of peptides and proteins in thin (ca. 10-20 μm) tissue sections based on MALDI-TOFMS techniques (Caprioli U.S. Pat. No. 5,808,300; incorporated by reference herein). In this method, a homogenous layer of matrix is applied to the tissue section and then a full mass spectrum is recorded at each spatial location by moving the sample relative to the MALDI laser. (R. M. Caprioli, T. B. Farmer, and J. Gile, Molecular Imaging of Biological Samples: Localization of Peptides and Proteins Using MALDI-TOFMS,” Anal. Chem. 69, 4751-4760 (1997)). By using conventional optical arrangements (i.e., an apertured primary laser beam and field lens, the final shape of the laser beam at the sample target is defined by the slit function of the aperture and exhibits a spatial resolution limited by the diffraction properties of the optics used (in practice, typically 10-20 μm for typical ultraviolet operation). This can be described by Equation 1:d=1.22×λ/NA (1) where d is the diffraction limited focus diameter, λ is the wavelength, and NA is the numerical aperture of the lens. (See for example, D. Malacara and Z. Malacara, “Diffraction in Optical Systems,” Chapter 9 in Handbook of Lens Design, Marcel Dekker Inc., New York (1994)). Recent advances in MALDI optics include the application of near-field scanning optical microscopy (NSOM; See for example, E. Betzig, J. K. Trautman, T. D. Harris, J. S. Weiner, and R. L. Kostelak, Breaking the Diffraction Barrier: Optical Microscopy on a Nanometric Scale, Science 251, 1468-1470 (1991) and references therein). This techniques help to overcome diffraction-limited spatial resolution. The use of NSOM techniques for LMMS was recently demonstrated for the analysis of small organic ions, such as dihydroxybenzoic acid and acetylcholine D (see A. Kossakovski, S. D. O'Connor, M. Widmer, J. D. Baldeschwieler and J. L. Beauchamp, Spatially Resolved Chemical Analysis with an NSOM-based Laser Desorption Microprobe, Ultramicrosc. 71, 111-115 (1998)), for anthracene and bis(phenyl-N,N-diethyltriazene) ether (see R. Stöckle, P. Setz, V. Deckert, T. Lippert, A. Wokaun, and R. Zenobi, Nanoscale Atmospheric Pressure Laser Ablation-Mass Spectrometry, Anal. Chem. 73, 1399-1402 (2001)), and for peptides and oligosaccarhides by MALDI with a spatial resolution<500 nm (see B. Spengler and M. Hubert, Scanning Microprobe Matrix-Assisted Laser Desorption Ionization (SMALDI) Mass Spectrometry: Instrumentation for Sub-Micrometer Resolved LDI and MALDI Surface Analysis, J. Am. Soc. Mass Spectrom. 13, 735-748 (2002)). Note that NSOM techniques require the physical aperture of the transmitted light be placed at a distance substantially closer to the image plane (i.e., sample surface) than the wavelength of transmitted light. For example, at UV wavelengths commonly used in MALDI applications, the aperture must be placed less than ca. 350 mn from the target surface. Experimentally, this is exceedingly challenging in MALDI where the sample topography can easily exceed micrometer(s) deviation in elevation unless stringent and difficult sample preparation procedures are used. Further, NSOM techniques are currently limited to generating symmetrical (typically round) spot shapes at the image plane (i.e., sample target) and cannot be easily changed to user defined dimensions or shape. In 1986, Hornbeck described an innovative optical element for the spatial patterning of light based on digital micro-mirror arrays (DMAs) (Hornbeck, U.S. Pat. No. 4,566,935; incorporated by reference herein). The DMA consists of highly reflective aluminum micro-mirror elements (e.g., 10-20 μm on each side) that are typically constructed in an array (e.g., 1024×768 mirrors) format. By addressing each individual mirror via a bias voltage, the relative angle of each mirror (ca. +10° to −10°, relative to normal of the array) can be positioned via a torsion hinge and rapidly switched (ca. 10-20 μs) representing an “on” or “off” state. DMA devices have found widespread application in video imaging, projection, and telecommunications, and have more recently been used in analytical spectroscopy (see D. Dudley, W. Duncan, and J. Slaughter, Emerging Digital Micromirror Device (DMD) Applications, White Paper, DLP Products New Applications, Texas Instruments, Inc. Plano, Tex. 75086). For example, Winefordener and colleagues have described using a linear DMA array (2×420 mirror array) to construct a flat-field visible wavelength spectrometer. (E. P. Wagner II, B. W. Smith, S. Madden, J. D. Winefordner, and M. Mignardi, Construction and Evaluation of a Visible Spectrometer Using Digital Micromirror Spatial Light Modulation, Appl. Spectrosc. 49, 1715-1719 (1995)). In this instrument, light dispersion and collimation is achieved by a Rowland-type curved grating spectrograph and wavelength selectivity is obtained by placing a DMA at the focus plane of the spectrograph and selectively reflecting portions the spectrum onto a photomultiplier tube detector. Later, Fateley and coworkers described the use of DMAs for constructing Hadamard transform masks for multiplexed Raman imaging (see R. A. DeVerse, R. M. Hammaker, and W. G. Fateley, Hadamard Transform Raman Imagery with a Digital Micro-Mirror Array, Vib. Spectrosc. 19, 177-186 (1999); W. G. Fateley, R. M. Hammaker, and R. A. DeVerse, Modulations Used to Transmit Information in Spectrometry and Imaging, J. Mol. Struct. 550-551, 117-122 (2000)), and multiplexed near infrared flat-field spectroscopy (see R. A. DeVerse, R. M. Hammaker, and W. G. Fateley, Realization of the Hadamard Multiplex Advantage Using a Programmable Optical Mask in a Dispersive Flat-Field Near-Infrared Spectrometer, Appl. Spectrosc. 54, 1751-1758 (2000)). By using a DMA to affect a dynamic Hadamard matrix mask, limitations of moving fixed optical matrix masks could be overcome (e.g., slow translation times, positioning errors, differences in axial position owing to stacked masks, and fixed mask element sizes). Importantly, the Hadamard transform provided enhanced signal-to-noise over conventional scanning techniques (ca. a factor of 12-14) in good agreement with that predicted from theory (see F. C. A. Dos Santos, H. F. Carvalho, R. M. Goes, and S. R. Taboga, Structure, Histochemistry, and Ultrastructure of the Epithelium and Stroma in the Gerbil (Meriones unguiculatus) Female Prostate, Tissue & Cell 35, 447-457 (2003)). The present invention is directed to a novel arrangement of optical devices for the rapid patterning of laser profiles used for desorption and/or ionization sources in analytical mass spectrometry. Specifically, the new optical arrangement provides for a user-defined laser pattern at the sample target that can be quickly (μs-timescale) changed to different dimensions (or shapes) for subsequent laser firings. For each firing, the pattern of light can be constructed so that noncongruent regions are irradiated simultaneously, for ionizing multiple regions of interest or for providing a multiple ion sources for multiple mass spectrometers. The large number of wavelets constituting the light pattern can be used to project a conjugate perspective distorted image to eliminate perspective foreshortening at the image plane. Further, the laser profile can be repositioned on the target sample rather than conventional means of mechanically moving the sample target to analyze different spatial regions of the sample. The rapid patterning of laser profiles, according to the present invention, will significantly impact many areas of mass spectrometry ranging from imaging mass spectrometry (e.g., by patterning the laser spot to irradiate a region of interest) to increased throughput when coupled with high repetition rate laser technology. In one aspect of the present invention, there is a method for inspecting a sample comprising the steps of providing a wavefront of photons from a photon source; transforming the wavefront of photons into a uniform intensity profile; selectively varying the spatial distribution of photons within the uniform intensity profile to construct a photon pattern; focusing the photon pattern on at least a portion of a sample; and, desorbing, and optionally ionizing, at least a portion of the sample. In some embodiments, the method further comprises mass spectrometric analysis of the sample after the step of desorbing. In some embodiments, the method further comprises ion mobility spectrometric analysis of the sample after the step of desorbing. In some embodiments of the method, the step of providing comprises generating photons from a radiation source selected from the group consisting of a laser, a Nernst glower, a globar, an arc discharge, a plasma discharge, a hollow cathode lamp, a synchrotron, a flashlamp, a resistively heated source, and any combination thereof. In some embodiments of the method, the step of transforming comprises using one or more refractive homogenizer optical elements. In some embodiments of the method, the one or more refractive homogenizer optical elements is selected from the group consisting of a prism homogenizer, a crossed-cylindrical lens array, an off-axis cylindrical lens, and any combination thereof. In some embodiments of the method, the step of transforming comprises using one or more non-refractive homogenizer optical elements. In some embodiments of the method, the one or more non-refractive homogenizer optical elements is selected from the group consisting of a reflective non-refractive optical element, a diffractive non-refractive optical element, and any combination thereof. In some embodiments of the method, the step of transforming comprises using a waveguide. In some embodiments of the method, the waveguide is a fiber optic. In some embodiments of the method, the step of selectively varying comprises using a component selected from the group consisting of a digital micro-mirror array, a variable slit, an optical mask, and any combination thereof. In some embodiments of the method, the sample is biological tissue. In some embodiments of the method, the biological tissue is plant or animal tissue. In some embodiments of the method, the sample is a laser microcapture dissection sample. In some embodiments of the method, the sample is selected from the group consisting of a protein, a nucleotide, a nucleic acid, a deoxynucleic acid, a protein microarray, a nucleotide microarray, a nucleic acid microarray, a deoxynucleic acid microarray, an immobilized biological material, a patterned biological material, and any combination thereof. In some embodiments of the method, the sample is selected from the group consisting of inorganic samples, semiconductors, ceramics, polymers, composites, metals, alloys, glasses, fibers, and any combination thereof. In some embodiments of the method, the method further comprises the step of correcting said spatial distribution for perspective distortion. In some embodiments of the method having a correcting step, the step of correcting comprises using selected photon patterns for said step of focusing, said selected photon patterns designed to eliminate perspective distortion. In some embodiments of the method having a correcting step, the step of correcting comprises calibrating for perspective distortion using an image captured by a CCD array. In another aspect of the present invention, there is an apparatus for inspecting a sample, the apparatus comprising a source for providing a wavefront of photons, the source having sufficient power to desorb, and optionally ionize, at least a portion of the sample; means for transforming the wavefront of photons into a uniform intensity profile, the means for transforming being fluidly coupled to the source; means for selectively varying the spatial distribution of photons within the uniform intensity profile to construct a photon pattern, the means for selectively varying being fluidly coupled to the means for transforming; and, means for focusing the photon pattern onto the sample, the means for focusing being fluidly coupled to the means for selectively varying. In some embodiments of the apparatus, the apparatus further comprises a mass spectrometer fluidly coupled to said sample such that at least a portion of material desorbed and optionally ionized from said sample enters said mass spectrometer In some embodiments of the apparatus, the apparatus further comprises an ion mobility spectrometer fluidly coupled to said sample such that at least a portion of material desorbed and optionally ionized from said sample enters said ion mobility spectrometer In some embodiments of the apparatus, the source is selected from the group consisting of a laser, a Nernst glower, a globar, an arc discharge, a plasma discharge, a hollow cathode lamp, a synchrotron, a flashlamp, a resistively heated source, and any combination thereof. In some embodiments of the apparatus, the means for transforming comprises one or more refractive homogenizer optical elements. In some embodiments of the apparatus, the one or more refractive homogenizer optical elements is selected from the group consisting of a prism homogenizer, a crossed-cylindrical lens array, an off-axis cylindrical lens, and any combination thereof. In some embodiments of the apparatus, the means for transforming comprises one or more non-refractive homogenizer optical elements. In some embodiments of the apparatus, the one or more non-refractive homogenizer optical elements is selected from the group consisting of a reflective homogenizer optical element, a diffractive homogenizer optical element, and any combination thereof. In some embodiments of the apparatus, the means for selectively varying is selected from the group consisting of a digital micro-mirror array, a variable slit, an optical mask, and any combination thereof. In some embodiments of the apparatus, the means for selectively varying is a digital micro-mirror array. In another aspect of the present invention, there is a method for inspecting a sample comprising the steps of providing a plurality of wavefronts of photons from a plurality of photon sources; transforming the plurality of wavefronts into a plurality of uniform intensity profiles; selectively varying the spatial distribution of photons within the uniform intensity profiles to construct a plurality of photon patterns; focusing the plurality photon patterns onto a sample; and, desorbing, and optionally ionizing, at least a portion of the sample to form a plurality of packets of desorbed and optionally ionized material. In some embodiments of the method, the method further comprises the step of mass spectrometric analysis of the sample after the step of desorbing, the step of mass spectrometric analysis being performed with one or more mass spectrometers. In some embodiments of the method, the method further comprises the step of ion mobility analysis of the sample after the step of desorbing, the step of ion mobility spectrometric analysis being performed with one or more ion mobility spectrometers. In some embodiments of the method, the step of providing comprises generating photons from a radiation source selected from the group consisting of a laser, a Nernst glower, a globar, an arc discharge, a plasma discharge, a hollow cathode lamp, a synchrotron, a flashlamp, a resistively heated source, and any combination thereof. In some embodiments of the method, the step of transforming comprises using one or more refractive homogenizer optical elements. In some embodiments of the method, the one or more refractive homogenizer optical elements is selected from the group consisting of a prism homogenizer, a crossed-cylindrical lens array, an off-axis cylindrical lens, and any combination thereof. In some embodiments of the method, the step of transforming comprises using one or more non-refractive homogenizer optical elements. In some embodiments of the method, the one or more non-refractive homogenizer optical elements is selected from the group consisting of a reflective non-refractive optical element, a diffractive non-refractive optical element, and any combination thereof. In some embodiments of the method, the step of transforming comprises transforming using a waveguide. In some embodiments of the method, the waveguide is a fiber optic. In some embodiments of the method, the step of selectively varying comprises using a component selected from the group consisting of a digital micro-mirror array, a variable slit, an optical mask, and any combination thereof. In some embodiments of the method, the sample is biological tissue. In some embodiments of the method, the biological tissue is plant or animal tissue. In some embodiments of the method, the sample is a laser microcapture dissection sample. In some embodiments of the method, the sample is selected from the group consisting of a protein, a nucleotide, a nucleic acid, a deoxynucleic acid, a protein microarray, a nucleotide microarray, a nucleic acid microarray, a deoxynucleic acid microarray, an immobilized biological material, a patterned biological material, and any combination thereof. In some embodiments of the method, the sample is selected from the group consisting of inorganic samples, semiconductors, ceramics, polymers, composites, metals, alloys, glasses, fibers, and any combination thereof. In some embodiments of the method, the method further comprises the step of correcting said spatial distribution for perspective distortion. In some embodiments of the method having a correcting step, the step of correcting comprises using selected photon patterns for said step of focusing, said selected photon patterns designed to eliminate perspective distortion. In some embodiments of the method having a correcting step, the step of correcting comprises calibrating for perspective distortion using an image captured by a CCD array. In some embodiments of the method, the plurality of photon patterns are noncongruent photon patterns. In another aspect of the present invention, there is a method for inspecting a sample comprising the steps of providing a wavefront of photons from a photon source; transforming the wavefront of photons into a uniform intensity profile; selectively varying the spatial distribution of photons within the uniform intensity profile to construct a photon pattern; focusing the photon pattern on at least a portion of a sample; desorbing, and optionally ionizing, at least a portion of the sample to form a desorbed sample; and, thereafter performing mass spectrometry, or ion mobility spectrometry, or a combination of ion mobility spectrometry and mass spectrometry on at least a portion of the desorbed and optionally ionized sample. The present invention is directed to a system and method which a novel arrangement of optical devices for the rapid patterning of laser profiles used for desorption and/or ionization sources in analytical mass spectrometry. Specifically, the new optical arrangement provides for a user-defined laser pattern at the sample target that can be quickly (μs-timescale) changed to different dimensions (or shapes) for subsequent laser firings. Alternatively, the laser profile can be repositioned on the target sample rather than conventional means of moving the sample target to analyze different spatial regions of the sample. The rapid patterning of laser profiles, according to the present invention, will significantly impact many areas of mass spectrometry ranging from imaging mass spectrometry (e.g., by patterning the laser spot to irradiate a region of interest) to increased throughput when coupled with high repetition rate laser technology. Optical arrangements of the present invention, are used for rapidly patterning a laser spot on to a target sample for the purpose of desorbing and/or generating ions to be analyzed by mass spectrometry techniques (see FIG. 2). Briefly, the primary laser beam is expanded and shaped by use of a beam expander and beam shaping lenses. The conditioned beam is then passed through a homogenizer array(s) to produce a beam wavefront of equal intensity across the cross section of the beam. This light is then reflected on the DMA. Based on the desired pattern applied to the individual mirrors of the DMA, the patterned light is focused onto the sample target by means of a field lens. The present invention differs from the prior art in that an innovative optical arrangement comprising a DMA is used to spatially pattern light onto a sample target surface for the purposes of desorption and/or ionization of material for mass spectrometric analysis. By defining the dimensions and shape of the laser radiation at the surface, one can precisely control the sample interrogation region in imaging mass spectrometry techniques. For example, complex shapes, such as individual cells in a tissue section (e.g., exhibiting diseased vs. healthy morphology), can be easily selected for selective irradiation and subsequent mass analysis. Further, spatial resolution can be significantly enhanced (ca. 0.5 to 2 μm) over conventional MALDI imaging mass spectrometry (ca. 10 to 20 μm), by using the small spatial mirror elements of the DMA rather than slits to aperture the laser radiation. A second application of this optical arrangement is to rapidly (ca. 10 to 20 μs) raster laser irradiation across the sample, at a high repetition rate, for increased throughput and enhanced sensitivity in mass spectrometric applications. This is in contrast with conventional methods of physically repositioning the sample target with respect to the static optical arrangements typically used. The foregoing has outlined rather broadly the features and technical advantages of the present invention in order that the detailed description of the invention that follows may be better understood. Additional features and advantages of the invention will be described hereinafter which form the subject of the claims of the invention. It should be appreciated by those skilled in the art that the conception and specific embodiment disclosed may be readily utilized as a basis for modifying or designing other structures for carrying out the same purposes of the present invention. It should also be realized by those skilled in the art that such equivalent constructions do not depart from the spirit and scope of the invention as set forth in the appended claims. The novel features which are believed to be characteristic of the invention, both as to its organization and method of operation, together with further objects and advantages will be better understood from the following description when considered in connection with the accompanying figures. It is to be expressly understood, however, that each of the figures is provided for the purpose of illustration and description only and is not intended as a definition of the limits of the present invention. As used herein, “a” or “an” means one or more, unless otherwise indicated. The singular encompasses the plural and the plural encompasses the singular. As used herein, the term “fluidly coupled”, with respect to two or more optical components refers to the flow of light or matter between the components, so that the light and/or matter output of one component is substantially the input of one or more other components. As used herein, “inspecting” or “inspection”, in the context of performing work on a sample, is defined in its broadest terms, and includes, but is not limited to, inspection of the entire sample or the inspection of one or more selected portions or spatial regions of a sample. Although the term “inspection” may include both the sampling of material and the subsequent analysis of the sampled material, it also includes sampling of the material itself without any further chemical analysis. As an example, the laser desorption of part of a sample constitutes an inspection of that part of the sample, regardless of whether or not that desorbed portion is subsequently further analyzed (with, for example, a mass spectrometer, or some other analytical instrument or technique). In those cases where “inspection” of a material does not include chemical analysis of the material, “inspection” is synonymous with “sampling” of material. The present invention is directed to one or more novel arrangements of optical devices for the rapid patterning of laser profiles used for desorption and/or ionization sources in analytical mass spectrometry. Specifically, the new optical arrangement provides for a user-defined laser pattern at the sample target that can be quickly (μs-timescale) changed to different dimensions (or shapes) for subsequent laser firings. Alternatively, the laser profile can be repositioned on the target sample dynamically by optics rather than conventional means of mechanically moving the sample target relative to static optics for analyzing different spatial regions of the sample. The present invention is also directed to methods of spatially interrogating samples with spatially-resolved light for the purpose of desorbing and/or ionizing at least some of the sample for mass spectral analysis. In some embodiments, a laser is used as the source of light. In some embodiments, a digital micro-mirror array is used to impart a spatial component to such light. In some embodiments, beam conditioning optics and/or beam homogenizing optics are employed. In some embodiments, a matrix material or substance is employed to assist in the desorption and/or ionization process as in, for example, MALDI techniques. The present invention is also directed to a system for spatially interrogating samples for mass spectrometric analysis. In some embodiments, such systems comprise the integration of traditional laser desorption mass spectrometers and techniques with one or more digital micro-mirror arrays (DMA), the latter providing spatial attributes to the incident laser beam. Such systems may comprise a host of additional optics for the conditioning and homogenizing of the incident laser beam. Additionally, the DMA is capable of being addressed in a user-defined and programmable manner. In some embodiments, the system may comprise a device for optically identifying the targeted region and, hence, the spatial properties of the incident beam. Suitable DMAs, for use according to the present invention, include the Discovery 1100 series DMA (e.g., the Discovery 1100 UV) available from Productivity Systems, Inc., Richardson, Tex. The optical arrangement of the present invention is preferably comprised of six major components: a high intensity light source (e.g., laser), primary beam conditioning optics, beam homogenizer optics, a post-homogenization collimation lens, a digital micro-mirror array (DMA), and a lens to focus the patterned light image onto the target sample stage of a mass spectrometer. Briefly, the primary laser radiation is expanded to generate a collimated beam of light. Conditioning optics can provide for the shaping of the incident radiation to optimally illuminate the homogenizer and/or array (e.g., the DMA). The primary beam is then directed through optical elements for spatial light intensity homogenization (e.g., refractive homogenizer optical elements (prism homogenizers, crossed-cylindrical lens arrays, off-axis cylindrical lenses, etc.), or non-refractive homogenizer optical elements (reflective, diffractive, etc.)) to transform the wavefront from a non-uniform intensity profile to a uniform intensity profile which is directed to a DMA. The means for transforming the wavefront to one having uniform intensity profile are those beam homogenizer optics described above as well as others known to those of skill in the art. FIG. 2 describes the optical platform and light profiles in one embodiment of the present invention. Referring to FIG. 2A, the primary beam of radiation is first expanded and shaped to the proximal dimensions of the DMA. The light is then passed through a beam homogenizer(s), reflected from the programmed pattern of the DMA and then focused onto the sample target for desorption and/or ionization. A field objective lens is shown in FIG. 2A as a means for focusing, however, any suitable means, known to those of skill in the art may be used. Other lenses and other focusing optics and/or elements, known to those of skill in the art, may be used as well. Another non-limiting example of such means for focusing is a parabolic mirror. Referring to FIG. 2B, a hypothetical illustration of the intensity profile of the light wavefront at different regions in this optical arrangement is shown. The points labeled (i), (ii), and (iii) in FIG. 2B correspond to those regions labeled in FIG. 2A. The result in (iii) is a wavefront having a uniform intensity profile (also referred to herein, as a “uniform intensity profile”). Thus, the patterned laser spot of the present invention provides for a spatially-resolved region of a sample to be interrogated. Although the means for selectively varying the spatial distribution of photons within a uniform intensity profile to construct a photon pattern is preferably a DMA, a variable slit, an optical mask, or any combination of these optical components. These means may also be any equivalent optical elements known to those of skill in the art. The DMA is operated by loading a series of patterns into on-board memory and each is then performed in a defined temporal sequence. Based on the state of each mirror element in the array (typically 1024×768 individual mirrors) the light directed toward the mass spectrometer is the pattern of reflected light from the DMA. Subsequent collimation and field optics can be used to focus the laser pattern to a spot on the sample target. FIG. 3 illustrates light patterning for the selective desorption/ionization of targeted material for a representative embodiment wherein a thin tissue section of gerbil stroma and epethial cells is immobilized onto a sample target. FIG. 3A illustrates the selective targeting of a single fibroblast cell. FIG. 3B illustrates the selective targeting of four normal stroma cells situated proximal to the fibroblast. The latter case illustrates that the light pattern for desorption does not need to be congruent. Using optical microscopy, the position and morphology of cells on the target is imaged. Based on the optical image a pattern is applied to the DMA to select a single, or several, cells for ionization (e.g., to independently analyze cells displaying diseased vs. healthy morphologies). Note that the pattern(s) need not be congruent, i.e., several regions of the sample target can be irradiated simultaneously in a single or for multiple shots (FIG. 3B). In this manner, the sample can be quickly screened for biomarkers of diseased vs. healthy state, similar to conventional imaging MALDI MS. By patterning light to selectively probe histological regions of interest, the described optics can be used in a manner similar to that of Laser Capture Microdissection (LCM) (see P. M. Conn, Ed., Methods in Enzymology-Laser Capture Microscopy and Microdissection, Vol. 356, Academic Press, New York, (2002)). However, unlike conventional LCM techniques that use a raster-mode of laser operation, the present innovation can irradiate an entire region or outline of the target sample directly. By utilizing the preferred embodiment in an LCM-mode, LCM-MS experiments can be performed rapidly in that LCM sample preparation is not decoupled from the MS analysis as it is in conventional LCM. By moving the laser radiation relative to the target sample plate, challenges associated with mechanically moving the sample plate are overcome. For example, by using mechanical micropositioners to move the sample plate relative to the laser spot, moving parts can quickly wear giving rise to hysteresis and the need for frequent recalibration for precise positioning. In contrast, the bi-state micromirrors of the DMA must only be calibrated once for spatial position on the target plate. In contrast to conventional MALDI optics, a further advantage, in terms of spatial resolution, is obtained by beam homogenization and DMA patterning of light. Because of the size of the individual micromirrors (ca. 13 μm) the effective aperture size can be reduced significantly by using only a few mirrors coupled with focusing optics. Further, by homogenizing the laser beam, differences in fluence at the sample target and corresponding signal intensity will be minimized. The latter is particularly important for spatial accuracy in MALDI imaging mass spectrometry, for example, in the determination of differential protein expression in different tissue regions (e.g., diseased vs. healthy), rapidly identifying and mapping tumor-specific markers in biopsies, (see P. Chaurand and R. M. Caprioli, Direct Profiling and Imaging of Peptides and Proteins from Mammalian Cells and Tissue Sections by Mass Spectrometry,” Electrophoresis 23, 3125-3135 (2002)), or for imaging the spatial distribution of pharmaceuticals in targeted tissue. A further challenge in contemporary imaging MS experiments arises from viewing and irradiating the sample stage from oblique angles relative to normal of the MALDI target. In most cases this occurs owing to practical considerations whereby it is most convenient to sample and focus the ions directly normal to the target stage, and difficulties associated with directing the laser and imaging optics collinear with the ion beam. This arrangement is depicted in FIG. 4A where the laser radiation and the target imaging optics (e.g. a charge coupled device of “CCD”) are focused to the MALDI target at +30° and −30° relative to normal of the MALDI target. If, for example, a square target spot to be irradiated is viewed orthogonal to the MALDI stage it would appear as in FIG. 4B, left. However, owing to the oblique angle used for irradiation and viewing, a square projected onto the stage would appear as a trapezoid (FIG. 4B, center), and the “true” square sample spot to be irradiated would appear at the imaging optics to be an inverted trapezoid relative to the irradiation (FIG. 4B, right). Clearly, the extent of image foreshortening, or perspective distortion, for projection or viewing directly depends on the relative viewing polar coordinates and the oblique viewing angle (ψ). The size of the perspective foreshortened object (projected or imaged) also varies inversely both with the distance of the object in the target imaging plane (DMA to MALDI target) and CCD imaging plane (MALDI target to CCD). The imaging foreshortening owing to the oblique projection and imaging angles can be described algebraically based on geometrical optics (see J. A. McLean, M. G. Minnich, A. Montaser, J. Su, and W. Lai, Optical Patternation: A Technique for Three-Dimensional Aerosol Diagnostics, Anal. Chem. 72, 4796-4804 (2000); and W. Lai, S. Alfini, and J. Su, Development of an Optical Pattemator for the Quantitative Characterization of Liquid Sprays. 10th International Symposium on Applications of Laser Techniques to Fluid Dynamics, Lisbon, Portugal, July 2000). Briefly, the trigonometric relation between the DMA and the MALDI target (or MALDI target and CCD array) can be described by: x DMA = X DMA ⁢ L DMA h DMA ⁢ 1 1 - ( Y DMA ⁢ sin ⁢ ⁢ ψ DMA ) / h DMA ⁢ ⁢ and ⁢ ⁢ y DMA = Y DMA ⁢ L DMA ⁢ cos ⁢ ⁢ ψ DMA h DMA ⁢ 1 1 - ( Y DMA ⁢ sin ⁢ ⁢ ψ DMA ) / h DMA ( 2 ) where (xDMA, yDMA) are the coordinates of the image on the DMA, (XDMA, YDMA) are the coordinates of the patterned irradiation in the MALDI target plane, ψDMA is the oblique irradiation angle, LDMA is the distance between the DMA and focusing field lens, and hDMA is the distance from the center of the field lens to the center of the irradiated scene (FIG. 4C). Although the equations describing the perspective distortion from the MALDI target to the CCD image plane are identical (i.e. projection or imaging), a distinction is made owing to potential differences in the experimental arrangements for oblique angle (ψDMA vs. ψCCD), lens-to-projection distance (LDMA vs. LCCD), and image-to-lens distance (hDMA vs. hCCD). In both cases, the magnitude of (Y sin ψ/h) for practical experimental arrangements is <<1 and thus a MacLaurin binomial series expansion of Eqns. 2 can be performed: x = XL h ⁢ ( 1 + sin ⁢ ⁢ ψ h ⁢ Y + sin 2 ⁢ ψ h 2 ⁢ Y 2 + sin 3 ⁢ ψ h 3 ⁢ Y 3 + … ⁢ ) ⁢ ⁢ and ⁢ ⁢ y = YL ⁢ ⁢ cos ⁢ ⁢ ψ h ⁢ ( 1 + sin ⁢ ⁢ ψ h ⁢ Y + sin 2 ⁢ ψ h 2 ⁢ Y 2 + sin 3 ⁢ ψ h 3 ⁢ Y 3 + … ⁢ ) ( 3 ) In the limit of projection or imaging approaching a geometry orthogonal to the target (ψ→0), the first-order approximation of Eqn. 3 is exact. By using oblique projection and imaging angles, the first-order approximation introduces an error of relatively small magnitude (0-5% in spatial dimensions across a target 30 cm from the projected object or imaging camera at angles of 15° to 60°, respectively). By preferably first calibrating, and subsequently correcting for perspective distortion in the image captured by, preferably, the CCD array (other image capture methods are applicable), a simultaneous calibration and correction can be applied to the DMA array whereby the foreshortened patterned irradiation is corrected by projecting a conjugate distorted image from the DMA so that a “true” sample is irradiated on the MALDI target plate. Such calibration and correction methods are known to those of skill in the art and are those commonly used in the field of particle imaging velocimetry, and in the filed of optical patternation, among others. Importantly, the calibration for correcting imaging foreshortening needs to be performed only once for a particular optical arrangement. All subsequent image corrections can be performed dynamically, because the micromirrors of the DMA do not exhibit hysteresis due to their bistable state (“on” or “off”) and thus only require initial calibration of spatial position on the sample target. Owing to the potentially large demagnification of the individual micromirrors of the DMA (i.e. 100s of nm in the diffraction limit of the field lens) the “true” image will be limited in pixelation resolution to ˜100s of nm, which is still within an acceptable range for most imaging applications. An embodiment of the present invention is derived by intentionally generating noncongruent patterns of light for purposes of simultaneously generating a plurality of ion sources. In this manner, the plurality of ion sources can be used for injecting a multiple ion packets into a plurality of mass analyzers such as a mass analyzer array (see for example Ref. 22). E. Badman and R. Graham Cooks, A Parallel Miniature Cylindrical Ion Trap Array, Anal. Chem. 72, 3291-3297 (2000). Thus, the effective plurality of ion sources allows for multiplexed simultaneous analysis of multiple ion packets, or for parallel mass analysis in a spatially-resolved mode owing to the correspondence of position from which the ions were generated and the mass analyzer utilized for detection. It should be recognized by those skilled-in-the-art that the present invention can be used in conjunction with any system for which a tailored pattern of uniform light is desired. For example, the method and system for patterning light detailed herein can be used for the generation of desorbed neutral atoms or molecules, or for ionizing atoms or molecules in a spatially-resolved mode for use by a variety of gas, liquid, or solid methods (e.g. mass spectrometry, ion mobility, ion mobility-mass spectrometry, photoaffinity labeling, etc.). All patents and publications referenced herein are hereby incorporated by reference. It will be understood that certain of the above-described structures, functions, and operations of the above-described embodiments are not necessary to practice the present invention and are included in the description simply for completeness of an exemplary embodiment or embodiments. In addition, it will be understood that specific structures, functions, and operations set forth in the above-described referenced patents and publications can be practiced in conjunction with the present invention, but they are not essential to its practice. It is therefore to be understood that the invention may be practiced otherwise than as specifically described without actually departing from the spirit and scope of the present invention as defined by the appended claims. Although the present invention and its advantages have been described in detail, it should be understood that various changes, substitutions and alterations can be made herein without departing from the spirit and scope of the invention as defined by the appended claims. Moreover, the scope of the present application is not intended to be limited to the particular embodiments of the process, machine, manufacture, composition of matter, means, methods and steps described in the specification. As one of ordinary skill in the art will readily appreciate from the disclosure of the present invention, processes, machines, manufacture, compositions of matter, means, methods, or steps, presently existing or later to be developed that perform substantially the same function or achieve substantially the same result as the corresponding embodiments described herein may be utilized according to the present invention. Accordingly, the appended claims are intended to include within their scope such processes, machines, manufacture, compositions of matter, means, methods, or steps. U.S. Pat. No. 4,566,935 L. J. Hornbeck, Spatial Light Modulator and Method (Jan. 28, 1986). U.S. Pat. No. 5,808,300 R. M. Caprioli, Method and apparatus for imaging biological samples with MALDI MS (Sep. 15, 1998). U.S. Pat. No. 6,046,808 W. G. Fateley, Radiation Filter, Spectrometer, and Imager Using a Micro-Mirror Array (Apr. 4, 2002). U.S. Pat. No. 2003/0073145 A1 R. Caprioli, Methods and Apparatus for Analyzing Biological Samples by Mass Spectrometry (Apr. 17, 2003) PCT WO 02/27285 A1 W. G. Fateley, R. Coifinan, F. Geshwind, and R. A. Deverse, System and Method for Encoded Spatio-Spectral Information Processing (Apr. 4, 2002).
051788250	description	DESCRIPTION OF THE PREFERRED EMBODIMENT Referring to FIG. 1A, a fuel bundle of this invention is illustrated. The fuel bundle includes a lower tie plate 14, an upper tie plate 16 and a handle 18 for manipulating the bundle. As is common in the prior art, a channel 20 extends between the upper and lower tie plates and surrounds a group of fuel rods R. Fuel rods R are typically arrayed in rows and columns. By way of example, the arrays can includes matrices of rods from 7 by 7 to 12 by 12 arrays. Indeed, the preferred embodiment includes in FIGS. 5 and 6, a 9 by 9 array and in FIGS. 7 and 8, a 10 by 10 array. Following the suggestion of the prior art, a detailed construction of the fuel rods at their points of transition can be best seen with respect to FIG. 1B, a section taken at the point of transition between fuel rods having larger, bottom diameter fuel tubes and upper smaller diameter fuel tubes. Those having skill in the art will realize that rods R are sealed top and bottom. Bottom tubes 24 contain a column of relatively large diameter pellets. Top tube 22 contains a column of smaller diameter pellets. Reducers 23 form a smooth surface lacking discontinuities for transition between the large diameter tubes 24 and the smaller diameter tubes 22. Referring further to FIG. 1B, a lower spacer L is illustrated. Lower spacer L is shown schematically functioning to keep the large diameter tubes 24 spaced apart, one from another and from the channel structure 20. Upper smaller diameter tubes 22 are shown with a spacer U. It is the function of spacer U to keep the smaller diameter tubes spaced apart one from another and from the channel 20. As will hereinafter be seen, upper spacers U and lower spacers L constitute an array of ferrules (illustrated in FIGS. 2A-2B, 3) or alternately an Inconel grid structure (illustrated in FIG. 4). In either case, a problem at the spacers is created by the tapered rods R. Simply stated, it is from time to time necessary in the life span of a fuel bundle B to remove, inspect and/or replace fuel rods R. Such removal requires partial disassembly of the fuel bundle including removal of upper tie plate 16 and handle 18. Thereafter, the rods are lifted upwardly from the fuel bundle array. In such lifting, it can be seen that upper spacers U have a dual function. First, the springs in the upper spacer U must be sufficiently resilient to bias the smaller diameter fuel tubes 22 against stops in the spacer. Secondly, the spacers must permit the larger diameter rods 24 to be removed. It will be appreciated that fuel bundle B could be inverted for the removal, inspection and/or replacement of fuel rods. Lower tie plate 14 could be removed followed by all fuel rods being withdrawn in an ordinary fashion from the bottom of the fuel bundle. It is the purpose of this invention to obviate the necessity of such inversion during fuel rod removal. Referring to FIGS. 2A-2B, a dimensional analysis with respect to round ferrules F is illustrated. Referring to FIG. 2A, a ferrule F having a nominal thickness of 0.020 is shown containing a fuel rod having a diameter of 0.460 inches. The rod illustrated is shown at large tube 24. A uniform clearance of 0.033 is shown. As is common in the art, ferrule F is provided with stops 30 and a spring 32 which biases rod 24 into the stops. Uniform matrix spacing of the large diameter portion 24 of the fuel rod R occurs. With respect to FIG. 2B, a ferrule F is illustrated having larger stops 31. Larger stops 31 are configured so as top center a 0.420 inch diameter fuel rod R at smaller diameter portion 22. Such biasing occurs via a spring 32 and results in a 0.053 inch clearance uniformly around the ferrule. Referring to FIG. 2C, the ferrule F of FIG. 2B is shown with the large diameter tube 24 placed within it. Specifically, the large diameter tube (which is 0.460 inches in diameter) ends up with only 0.0055 inches of clearance with respect to the ferrule F. Furthermore, those having skill in the art can understand that there is virtually no space available for spring 32. As a practical matter, the design of FIG. 2C is not feasible. Given manufacturing tolerances, both directed to the ferrule F, stops 31 and the diameter of the fuel rod R at the large fuel diameter tube 24, it would be expected by those having skill in the art that interfering contact would occur with such an arrangement. Finally referring to FIG. 2D, a compromise is illustrated. Stops 34 having a 0.0439 inch radial dimension are illustrated with respect to rod R at larger diameter portion 24. Adjacent spring 32 it can be seen that a clearance of 0.0180 inches in clearance is allowed. Removal of a large diameter rod portion 24 from such a ferrule is practicable against the bias of spring 32. The question then becomes what net effect does a ferrule having the dimensions of 2D have with respect to the larger diameter rod portions 24 and the smaller diameter rod portions 22. This is illustrated with respect to FIG. 3. Referring to FIG. 3, 2 side-by-side ferrules F are illustrated. It will be seen that the orientation of the spring and stops is the same in the two ferrules. Specifically referring to upper ferrule F, it can be seen that stops 34 are at the top. Referring to lower ferrule F, stops 34 are identically and symmetrically placed with respect to the top. This orientation is used for all the spacer cells in the preferred embodiment of this invention. In the preferred embodiment, the upper and lower spacer cells are identical. In FIG. 3 the small diameter portion of the fuel rods in the upper spacers are shown as continuous lines. The large diameter portions of the fuel rods in the lower spacers are shown as dashed lines. When the lower large diameter portion of a fuel rod is inserted or withdrawn through the upper spacers, its position is also shown by the dashed lines. It is known that ferrule F surrounding fuel rods can have beneficial flow effects as to passing coolant. Specifically, the ferrules F can function to channel water to flow against the outside surface of the fuel rods R so that boiling within the fuel bundle optimally occurs. The design clearances illustrated in FIG. 2D will produce this desirable effect. Referring to FIG. 4, an Inconel grid-type spacer G is illustrated. The Inconel grid spacer G includes stops 60 and spring portions 62. In the upper grid G, rod R at small diameter portion 22 is shown biased by spring 62 against stops 60. In FIG. 4, at the lower grid G, large diameter rod R at large tube 24 is schematically shown at broken lines 24. The necessary movement of springs 62 to permit passage of such a rod is illustrated. Again, offset of the centers of the rods at the large diameter tube 22 and small diameter tube 24 is illustrated. As before, it can be seen that the respective centers 51, 52 of the large diameter rod portion and small diameter rod portion 22 are offset, one with respect to the other. Referring to FIGS. 5A and 6A the solution is illustrated for a spacer consisting of circular ferrules. FIG. 5A illustrates the upper spacers, and FIG. 6A the lower spacers. The channel cross section 20 is the same for both locations. The spacer band 40 is shown together with some of the ferrules. An enlarged view of a ferrule and fuel rod is also shown in FIGS. 5B and 6B illustrating the offset X of the ferrule center relative to the fuel rod center in each case. For both the lower and upper spacers, the array of fuel rods is centered in the channel. The centers of the upper small diameter part of the fuel rods are directly above the centers of the lower large diameter part of the fuel rods. Because the fuel rod centers are offset relative to the spacer cells, the spacers must be offset with respect to the channel. The spacers are located in the channel by spacer band stops 70, 71, 72. Since the relative displacement of rod centers an cell centers is in the vertical direction of the figure, stops 70 have the same height on the upper and lower spacers. In FIG. 5A, the fuel rod diameter is small, and the ferrules are displaced downward (in the plane of the Fig.) relative to the fuel rod centers. The spacer band stops 71 at the top are larger than the stops 72 at the bottom. In FIG. 6A, the situation is reversed for the lower spacers, and the upper band stops 73 are smaller than the lower band stops 74. With such a scheme, the respective centers of the large diameter tubes 24 and the small diameter tubes 20 exactly overly one another. It will be realized that this precise overlying cannot occur while a fuel rod is being withdrawn. Specifically, when the larger diameter portion 24 of rod R is in the upper spacer U, displacement of the center 51 in an upper spacer U must inevitably occur with respect to a lower spacer L. It will be remembered, however, that such rods are flexible. Specifically, and during rod removal for inspection, flexibility of the rods will accommodate the movement described herein. Referring to FIGS. 7A and 8A, the solution for the Inconel grid-type spacer can be seen to be precisely identical. Referring to FIGS. 7A and 8A, stops 70 on sides have equal heights for the upper and lower spacers. In FIG. 7A the upper spacer stops 91 are larger than stops 92, while on FIG. 8A the upper spacer stops 93 are smaller than stops 94. An enlarged view of a cell and fuel rod is shown for each case in FIGS. 7B and 8B respectively illustrating the offset X of the cell center relative to the fuel rod center in each case. DESCRIPTION OF THE ALTERNATIVE EMBODIMENT In the alternate embodiment the upper spacers are identical to those of the preferred embodiment. The lower spacers are centered in he channel, and the lower portions of the fuel rods are centered in the cells, as in the prior art. FIG. 9A shows a ferrule type spacer with the fuel rods centered in the ferrules, and FIG. 10A shows an Iconel grid spacer with the fuel rods centered in the cells. In both cases the stops on the bands are of equal size on all four sides.
	description	The present invention relates to apparatus and method for performing cavitation peening, and, more particularly, the present invention relates to cavitation peening within a narrow annulus. Peening is a process of introducing mechanical stress into the surf e layer of a part to compress and strengthen it against future fractures and wear. Peening can be performed in a variety of manners, including shot peening, laser peening and cavitation peening. Cavitation peening involves the application of bubbles onto the surface with the part in a liquid environment. The collapsing of the bubbles imparts impactive forces to the part. One difficulty with prior cavitation peening apparatus and methods is the difficulty in peening within narrow spaces because the peening nozzle does not fit with such tight spaces. While the present invention may be used in a variety of industries, the environment of nuclear power plant will be discussed herein for illustrative purposes. A nuclear power plant has a nuclear reactor housed within a pressure vessel and a reactor coolant system (RCS) for removing heat from the reactor and to generate power. Nozzles are attached to the vessels and/or piping for a number of purposes, such as for connecting piping and instrumentation, providing vents, and securing control element mechanisms and heater elements. The nuclear industry is required to perform inspections of such nozzles, as well as their welds, due to the emergence of primary water stress corrosion cracking (PWSCC). Stress corrosion cracking occurs in a material due to a combination of a corrosive environment and tensile forces placed on the material. Cracking can be induced in materials in different ways including cold forming, welding, grinding, machining, and heat treatment as well as other physical stresses placed on the material. Stress corrosion cracking in nuclear reactor environments is a significant phenomenon that must be carefully monitored for successful operation of a nuclear power plant facility. Without careful monitoring for PWSCC, material defects may begin and may ultimately damage the material. If cracking continues, the materials may be damaged to such an extent that the materials must be removed from service and replaced. In the nuclear reactor environment, such replacement of components is extremely undesirable due to radiological concerns related to worker and facility safety, as well as overall plant economic concerns. Thus, what is needed is an apparatus and method of mitigating or preventing the initiation of stress corrosion cracking. A sealing member is provided to create a sealed region about an annulus formed between an inner body, such as a thermal sleeve, and an outer body, such as a control rod drive nozzle. Liquid is introduced into the sealed region to create a flooded region, which is pressurized to a desired level. A nozzle is provided into the flooded region, the nozzle being configured to fit within the annulus. Pressurized fluid is ejected from the nozzle, causing the formation of cavitation bubbles. The nozzle flow causes the cavitation bubbles to settle on the surfaces forming the annulus. The collapsing impact of the cavitation bubbles imparts compressive stress in the materials of the surfaces forming the annulus. Tooling is provided to maneuver the nozzle within the flooded region so that all desired portions of the surfaces are treated. The instant invention is an apparatus and method for cavitation peening within narrow spaces, such as the annulus between an inner body and an outer body. The nozzle of the present invention has an elongate body configured to fit within the annulus. The body has a first end with a first width and a first thickness, and a second end with a second width and a second thickness. The body is tapered in both width and thickness such that the second width is greater than the first width and the second thickness is greater than the first thickness. The body further has an arcuate profile configured to fit with the annulus. A discharge orifice is located in the narrow first end of the body. The nozzle also includes a base coupled to the body at the second end of the body. The base defines an inlet for connecting to a source of peening fluid. The base and the body define a flow path therethrough to the discharge orifice. A primary target application for the instant invention is the mitigation of the inner diameter (ID) surfaces of pressurized water reactor (PWR) reactor vessel closure head (RVCH) control rod drive housing (CRDH) nozzles. Residual tensile stresses in nozzle material, weld material, and base metal cladding contribute to and exacerbate PWSCC. Changing the stress state from tensile to compressive can prevent PWSCC initiation, mitigating the need for costly and time consuming repairs. Peening provides asset life extension through elimination of the degradation process by imparting residual compressive stress to an object. A thermal sleeve is incorporated into the design of many CRDH nozzles which restricts access to the inside surface of the CRDH nozzle. FIG. 1 shows a cross-sectional view of a typical arrangement for a CRDH nozzle 1 with a thermal sleeve 2 passing through a reactor pressure vessel head 4, and FIG. 2 shows a close-up cross-sectional view of the CRDH nozzle 1, thermal sleeve 2, and reactor pressure vessel head 4 of FIG. 1. The inside diameter of the CRDH nozzle 1 and the outside diameter of the thermal sleeve 2 form an annulus 3 therebetween. Due to the limited access, any work involving the inside diameter of the CRDH nozzle 1 usually requires removal of the thermal sleeve 2. Reattachment of the thermal sleeve 2 is generally required after work is completed. Such removal and reattachment of the thermal sleeve processes are costly, time consuming, and introduce risk. This invention allows for mitigation of stresses within the annulus 3 surfaces and eliminates the need to remove the thermal sleeve 2. The cavitation peening process consists of directing a nozzle at the work surface through which water at high pressure and high velocity is discharged through a small orifice. Vapor bubbles are formed in the resulting high velocity water jet stream as it contacts the water at lower pressure. The pressure within each bubble is below the vapor pressure of the surrounding water medium. The bubbles collapse at the surface, generating high pressure shock waves on the work surface which impart compressive stresses on the surface. Typically, the process requires a back pressure to prevent the bubbles from prematurely collapsing. A seal is installed about the base of the CRDH nozzle 1, sealing the annular gap so that the region can be flooded with water and pressurized to the desired back pressure (1 to 100 psi or greater, depending on the specific application). A cavitation peening nozzle penetrates the seal allowing access to the annular gap for delivery of the cavitation water jet stream. The cavitation peening process initiates and the peening nozzle (peening head) is driven to rotate by tooling around the axis of the CRDH nozzle 1 so that the entire ID surface of the CRDH nozzle 1 can be peened. As the peening head rotates the peening nozzle also actuates vertically up and down as needed for the optimal process effectiveness. In this manner, the cavitation peening process is implemented without having the entire component submerged in water. Preferably, the peening nozzle water pressure is approximately 50 ksi to 60 ksi with a back pressure of approximately 30 psi to 50 psi. These operational parameters allow for preferred cavitation bubble size, as well as a preferred amount of shock pressure being imparted to the treatment surface upon collapse of the cavitation bubbles. However, such operational conditions cause the nozzle to vibrate during use. This vibration can cause the nozzle to fail. Thus, a robust nozzle design is necessary. FIG. 3 shows a first view of a preferred nozzle 10 of the present invention, and FIG. 4 shows a second view of the nozzle 10. The nozzle 10 includes a body 11 having a proximal end 12 including a discharge orifice 15 and a distal end 13. To provide support and durability, the body 11 is tapered such that the nozzle distal end 13 has a greater width than does the proximal end 12. Preferably, the distal end width is two to four times the proximal end width. While the thickness of the nozzle 10 must be minimized so that the nozzle 10 will fit within the annulus 3, in a preferred embodiment the thickness is also tapered such that the distal end 13 has a greater thickness than does the proximal end 12. The maximum thickness of the nozzle 10 preferably is less than ⅛ inch to allow for insertion into and peening of the annulus surfaces. The nozzle 10 further includes a base 14 at the distal end 13. The base 14 provides gripping surfaces so that the nozzle 10 can be gripped and retained by tooling to position and maneuver the nozzle 10. FIG. 8 shows an example of such tooling 20. The tooling includes a body 21 defining an enclosed area. A base plate 22 is rotationally coupled to the body 21, allowing for rotation of the body 21. A ring bearing is used to maintain the water-tight integrity of the base plate to body junction. A carriage assembly 23 connects the nozzle 10 to a lead screw 24, allowing for vertical movement of the nozzle 10. An additional drive allows for rotation of the carriage assembly 23 and nozzle 10. The carriage assembly 23 may also be movable radially relative to the body 21, to allow for peening of annuluses of varying diameter. The nozzle base 14 further includes an orifice 16 which allows a source of peening fluid to be attached. The orifice 16 is fluidly connected to the discharge orifice 15 via a passageway 17 (see FIG. 5) internal to the nozzle body 11. Preferably, the peening fluid is provided by a metallic tube 25 that can withstand the pressures imposed by the high pressure peening fluid. To allow for vertical displacement of the nozzle 10, the tubing 25 may be provided in a coil, with the coil stack positioned such that its central axis is vertical, parallel to the lead screw and perpendicular to the base plate 22. Thus, the coil central axis is parallel to or collinear with the longitudinal axis of the tooling body 21. As the nozzle 10 is moved upward (that is, away from the base plate 22), the coil is elastically deformed such that the spacing between adjacent coils is increased. Downward movement of the nozzle 10 returns the coils to their default position. The tubing coil 25 allows for linear movement of the nozzle 10 along the coil central axis. FIG. 6 shows an orifice insert 15 for the nozzle 10, and FIG. 7 shows a cross-sectional view of the orifice insert 15. The insert 15 includes a body 31 having a threaded central portion 32. A head 33 is provided at a proximal end of the insert 15. The head 33 preferable includes engagement surfaces, such as a hex head bolt, configured to be engaged by a tool to allow the threaded portion 32 to be coupled with corresponding threading in the nozzle body 11. A seal 34 is provided at a distal end of the insert 15. Preferably, the seal 34 is formed of a polymer material. When the insert 15 is in its operational position within the nozzle body 11, the seal 34 abuts corresponding surfaces of the nozzle body 11. This ensures a water-tight seal between the orifice insert 15 and the nozzle body 11. A bore 35 is provided centrally within the insert 15 to define a flow path therethrough. A jewel member (not shown) having a bore therethrough may be positioned in the proximal tip of the insert 15. Cavitation peening requires that the nozzle and surface to be treated are in a liquid environment. Rather than placing the entire reactor pressure vessel head underwater, which would require substantial time and effort, as well as the creation of a large amount of waste water that must be disposed of, a seal assembly is used. FIG. 9 shows one such seal assembly 40. The seal assembly 40 includes a housing 41 that is configured to surround and enclose the tooling 20 and nozzle 10. The body 41 includes an actuated proximal end 42 and a closed distal end 43. The proximal end 42 contains three flat sealing surfaces 44 that open to avoid thermal sleeve funnels during installation and close to seal against the bottom of the CRDH nozzle 1. A gasket or seal 45 is molded into the sealing surfaces 44 to ensure water tight integrity of the seal assembly 40. Another alternative for the seal assembly 40 can be found in co-owned U.S. patent application Ser. No. 14/554,525 filed on even date herewith, which application is incorporated by reference herein in its entirety. Stainless steel, such as 18-8 stainless steel, is a preferred material for the tooling 20 and seal assembly 40. Stainless steel, such as 17-4 PPH stainless steel, is a preferred material for the nozzle 10. Silicone is a preferred material for the seal 45. In use, the reactor pressure vessel head is removed from the reactor and placed in a storage position within the containment building. (This is a routine step that is performed during refueling outages to allow access to the fuel rods and reactor core.) The nozzle 10 is coupled to the tooling 20, which is positioned within the seal assembly 40. The coupled assembly is then positioned about a CRDH nozzle 1 and thermal sleeve 2 to be serviced such that the seal 45 contacts the outer surface of the CRDH nozzle 1 or the inner surface of the head 4. The body 41 thus surrounds the tooling 20, CRDH nozzle 1, and thermal sleeve 2, forming a sealed region about the bottom of the CRDH nozzle 1. Liquid, such as water, is then introduced into the sealed region, forming a flooded region. This may be accomplished in a known manner, such as by connecting a source of water to the seal body 41 through a valve and opening the valve. The sealed region is then pressurized to a predetermined pressure level, such as approximately 30 psi to 50 psi. This may be accomplished by continuing to supply water to the flooded region, raising the liquid level until the weight thereof results in the desired pressure level. This may entail raising the liquid level well into the annulus 3. The tooling 20 is then engaged to insert the nozzle 10 within the annulus. This is shown in FIG. 11. The nozzle body 11 is curved to matingly correspond to the curves of the CRDH nozzle 1 and thermal sleeve 2. Preferably, the inside surface 11A of the nozzle body 11 has a greater radius of curvature than does the outer surface 11B of the nozzle body 11. In the specific embodiment used in conjunction with the CRDH nozzle 1 and thermal sleeve 2 discussed herein, the inner surface 11A radius of curvature may be approximately 2 in. while the outer surface radius of curvature may be approximately 1.13 in. The radii of curvature are chosen to match the space in which the nozzle 10 is to be used, which in this example is the annulus 3. The low profile thickness of the nozzle body 11 allows it to fit within the annulus 3. Optionally, the tooling 20 may be used to shift the thermal sleeve 20 within the CRDH nozzle 1 to a position diametrically opposed to the nozzle 10, providing additional clearance for inserting the nozzle within the annulus 3. The tooling may include a chuck 26 to grip the inner diameter of the thermal sleeve 2 and shift it in a direction away from the nozzle 10. With the nozzle 10 positioned, flow of the pressurized peening fluid is initiated causing the peening process to begin. The pressurized flow through the nozzle 10 causes cavitation bubbles to form. The flow is directed substantially parallel to the surface(s) to be treated with a standoff distance (that is, the distance between the nozzle discharge orifice 15 and area of the surface to be treated) of approximately 5 in. to 7 in. The collapsing impact of the cavitation bubbles imparts compressive stress in the materials of the surfaces forming the annulus 3. The tooling 20 is used to maneuver the nozzle 10 circumferentially around and vertically up and down about the thermal sleeve 2 to treat all desired surfaces thereof. The nozzle 10 is also inserted within the annulus 3 to treat the outer surface of the thermal sleeve 2 and the inner surface of the CRDH nozzle 1. The nozzle 10 has an elongate shape, preferably having a longitudinal length of approximately 5 in. to 6 in., allowing it to extend well within the annulus 3. The nozzle length and standoff distance allow peening to 10 in. or more within the annulus 3. Operational parameters such as peening nozzle water pressure, flow rate, back pressure, peening nozzle position, and peening nozzle velocity can be qualified by performing cavitation peening of a mock-up example assembly, and then destructively inspecting the mock-up parts to measure the compressive residual stresses imparted thereto. These parameters are measured and recorded during use, and these recordings provided to the customer, thereby ensuring that the intended surfaces were actually treated as intended. While the preferred embodiments of the present invention have been described above, it should be understood that they have been presented by way of example only, and not of limitation. It will be apparent to persons skilled in the relevant art that various changes in form and detail can be made therein without departing from the spirit and scope of the invention. Thus the present invention should not be limited by the above-described exemplary embodiments, but should be defined only in accordance with the following claims and their equivalents. Furthermore, while certain advantages of the invention have been described herein, it is to be understood that not necessarily all such advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught herein without necessarily achieving other advantages as may be taught or suggested herein.
	summary
	description	This application is a divisional of U.S. patent application Ser. No. 13/450,150, filed Apr. 18, 2012, which claims the benefit of U.S. Provisional Patent Application No. 61/476,624, filed Apr. 18, 2011, the entireties of which are incorporated herein by reference. The present invention relates generally to systems and methods of removing thermal energy from pools of liquid, and specifically to systems and methods of removing thermal energy from spent nuclear fuel pools that are self-powered and autonomous. The spent fuel pool (SFP) in a nuclear power plant serves to store used spent nuclear fuel discharged from the reactor in a deep pool (approximately 40 feet deep) of water. In existing systems, the decay heat produced by the spent nuclear fuel is removed from the SFP by circulating the pool water through a heat exchanger (referred to as the Fuel Pool Cooler) using a hydraulic pump. In the Fuel Pool Cooler, the pool water rejects heat to a cooling medium which is circulated using another set of pumps. Subsequent to it's cooling in the Fuel Pool cooler, the pool water is also purified by passing it through a bed of demineralizers before returning it to the pool. In existing systems, the satisfactory performance of the spent fuel cooling and clean up system described above is critically dependent on pumps which require electric energy to operate. As the events at the Fukushima Dai-ichi showed, even a redundant source of power such as Diesel generators cannot preclude the paralysis of the classical fuel pool cooling system. In order to insure that the decay heat produced by the fuel stored in the SFP is unconditionally rejected to the environment, the present invention introduces a heat removal system and method that does not require an external source of electric energy or equipment that can be rendered ineffective by an extreme environmental phenomenon such as a tsunami, hurricane, earthquake and the like. These, and other drawbacks, are remedied by the present invention. An autonomous and self-powered system of cooling a pool of liquid in which radioactive materials are immersed is presented. The inventive system utilizes a closed-loop fluid circuit through which a low boiling point working fluid flows. The closed-loop fluid circuit of the inventive system, in accordance with the Rankine Cycle: (1) extracts thermal energy from the liquid of the pool into the working fluid; (2) converts a first portion of the extracted thermal energy into electrical energy that is used to power one or more forced flow units that induce flow of the working fluid through the closed-loop fluid circuit; and (3) transfers a second portion of the extracted thermal energy to a secondary fluid, such as air. In this way, the inventive system operates without the need for any electrical energy other than that which is generates internally in accordance with the Rankine Cycle. In one embodiment, the invention can be an autonomous self-powered system for cooling radioactive materials, the system comprising: a pool at least partially filled with a liquid and radioactive materials immersed in the liquid; a closed-loop fluid circuit comprising a working fluid having a boiling temperature that is less than a boiling temperature of the liquid, the closed-loop fluid circuit comprising, in operable fluid coupling, an evaporative heat exchanger at least partially immersed in the liquid, a turbogenerator, and a condenser; one or more forced flow units operably coupled to the closed-loop fluid circuit to induce flow of the working fluid through the closed-loop fluid circuit; and the closed-loop fluid circuit converting thermal energy extracted from the liquid of the pool into electrical energy that powers the one or more forced flow units; wherein the evaporative heat exchanger comprises: a top header, a bottom header, a downcomer tube defining a first passageway between the top and bottom headers, and a plurality of heat exchange tubes each forming a second passageway between the top and bottom headers; a working fluid inlet extending into the downcomer tube for introducing a liquid phase of the working fluid into the first passageway; and a working fluid outlet for allowing a vapor phase of the working fluid to exit the evaporative heat exchanger. In another embodiment, the invention can be a vertical evaporative heat exchanger for immersion in a heated fluid comprising: a tubeside fluid circuit comprising: a top header; a bottom header; a core tube forming a downcomer passageway between the top header and the bottom header, the core tube having a first effective coefficient of thermal conductivity; a plurality of heat exchange tubes forming passageways between the bottom header and the top header, the plurality of the heat exchange tubes having a second effective coefficient of thermal conductivity that is greater than the first effective coefficient of thermal conductivity; a working fluid in the tubeside fluid circuit; an inlet for introducing a liquid phase of the working fluid into the tubeside fluid circuit; an outlet for allowing a vapor phase of the working fluid to exit the top header; and wherein transfer of heat from the heated fluid to the working fluid induces a thermosiphon flow of the liquid phase of the working fluid within the tubeside fluid circuit. 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 following description of the preferred embodiment(s) is merely exemplary in nature and is in no way intended to limit the invention, its application, or uses. While the invention is exemplified in FIGS. 1-6 as being used to cool pools of liquid in which radioactive materials are immersed (such as spent nuclear fuel, high level radioactive waste or low level radioactive waste), the invention is not so limited and can be used to cool any body of liquid in need of cooling. Referring first to FIG. 1, an autonomous self-powered cooling system 1000 according to an embodiment of the present invention is schematically illustrated. The autonomous self-powered cooling system 1000 generally comprises a closed-loop fluid circuit 100, an electrical circuit 200, and a pool of liquid 50. Radioactive materials 20 are immersed in the pool of liquid 50, which in the exemplified embodiment is a spent fuel pool. Radioactive materials 20, such as spent nuclear fuel, generate a substantial amount of heat for a considerable amount of time after completion of a useful cycle in a nuclear reactor. Thus, the radioactive materials 20 are immersed in the pool of liquid 50 to cool the radioactive materials 20 to temperatures suitable for dry storage. In embodiments where the radioactive materials 20 are spent nuclear fuel rods, said spent nuclear fuel rods will be supported in the pool of liquid 50 in fuel racks located at the bottom of the pool of liquid 50 and resting on the floor. Examples of suitable fuel racks are disclosed in United States Patent Application Publication No. 2008/0260088, entitled Apparatus and Method for Supporting Fuel Assemblies in an Underwater Environment Having Lateral Access Loading, published on Oct. 23, 2008, and United States Patent Application Publication No. 2009/0175404, entitled Apparatus or Supporting Radioactive Fuel Assemblies and Methods of Manufcturing the Same, published on Jul. 9, 2009, the entireties of which are hereby incorporated by reference. As a result of being immersed in the pool of liquid 50, thermal energy from the radioactive materials 20 is transferred to the pool of liquid 50, thereby heating the pool of liquid 50 and cooling the radioactive materials. However, as the pool of liquid 50 heats up over time, thermal energy must be removed from the pool of liquid 50 to maintain the temperature of the pool of liquid 50 within an acceptable range so that adequate cooling of the radioactive materials 20 can be continued. As discussed in greater detail below, the closed-loop fluid circuit 100 extends through the pool of liquid 50. A working fluid 75 is flowed through the closed-loop fluid circuit 100. The closed-loop fluid circuit 100 extracts thermal energy from the pool of liquid 50 (into the working fluid 75) and converts the extracted thermal energy into electrical energy. The electrical energy generated by said conversion powers the electrical circuit 200, which in turn powers forced flow units 190, 151 (described below) that induce flow of the working fluid 75 (FIG. 2) through the closed-loop circuit 100. The aforementioned extraction and conversion of thermal energy into electrical energy is accomplished by the closed-loop fluid circuit 100 in accordance with the Rankine Cycle. In certain specific embodiments, and depending on the identity of the liquid 50 to be cooled and the working fluid 75 being used, the closed-loop fluid circuit 100 can accomplish the extraction and conversion of thermal energy into electrical energy in accordance with the Organic Rankine Cycle. In order to cool the pool of liquid 50 prior to the liquid 50 of the pool evaporating/boiling, the working fluid 75 is preferably a low boiling-point fluid (relative to the liquid 50 of the pool). More specifically, the working fluid 75 is selected so that it has a boiling temperature that is less than the boiling temperature of the liquid 50 of the pool. It is appreciated that the temperature at which a liquid boils/evaporates is dependent on pressure and that the liquid 50 of the pool and the working fluid 75 may be subject to different pressures in certain embodiments of the invention. Furthermore, as discussed in greater detail below, the working fluid 75 is evaporated/boiled in an evaporative heat exchanger 110 that is immersed in the pool of liquid 50. In certain such embodiments, the liquid 50 of the pool will be under a first pressure and the working fluid 75 in the evaporative heat exchanger 110 will be under a second pressure that is greater than first pressure. Thus, in such an embodiment, the working fluid 75 is selected so that the boiling temperature of the working fluid 75 at the second pressure is less than the boiling temperature of the liquid 50 of the pool at the first pressure. In one specific embodiment, the first pressure will be atmospheric pressure and the second pressure will be in a range of 250 psia to 400 psia. In one embodiment, the liquid 50 of the pool is water. As used herein, the term “water” includes borated water, demineralized water and other forms of treated water or water with additives. Suitable working fluids 75 include, without limitation, refrigerants. Suitable refrigerants may include, without limitation, ammonia, sulfur dioxide, chlorofluorocarbons, hydrochlorofluorocarbons, hydrofluorocarbons, haloalkanes, and hydrocarbons. One particularly suitable refrigerant that can be used as the working fluid 75 is tetraflouroethane, commonly known as HFC-134a. The exemplified embodiment of the closed-loop fluid circuit 100 generally comprise an evaporative heat exchanger 110, a turbogenerator 130, a condenser 150, a working fluid reservoir 170, and a hydraulic pump 190. The aforementioned components 110, 130, 150, 170, 190 of the closed-loop fluid circuit 100 are operably and fluidly coupled together using appropriate piping, joints and fittings as is well-known in the art to form a fluid-tight closed-loop through which the working fluid 75 can flow through in both a liquid phase 75A and a vapor phase 75B. The working fluid 75 is in the liquid phase 75A between a working fluid outlet 153 of the condenser 150 and a working fluid inlet 111 of the evaporative heat exchanger 110. The working fluid 75 is in the vapor phase 75B between a working fluid outlet 112 of the evaporative heat exchanger 110 and a working fluid inlet 152 of the condenser 150. As discussed in greater detail below, the evaporative heat exchanger 110, which is immersed in the liquid 50 of the pool, converts the working fluid 75 from the liquid phase 75A to the vapor phase 75B by transferring thermal energy from the liquid 50 of the pool into the working fluid 75. Conversely, the condenser 150 converts the working fluid 75 from the vapor phase 75B to the liquid phase 75A by transferring thermal energy from the working fluid 75 into a secondary fluid (which can be air that is rejected to the environment in certain embodiments). In the exemplified embodiment, the autonomous self-powered system 1000 further comprises two forced flow units that induce flow of the working fluid 75 through the closed-loop fluid circuit 100, namely the hydraulic pump 190 (which is considered part of the closed-loop fluid circuit 100) and a blower 151 which, when operated, forces cooling air to flow over heat exchange tubes 154 (as shown in FIG. 6) of the condenser 150. The hydraulic pump 190 directly induces flow of the working fluid 75 through the closed-loop fluid circuit 100 by drawing the liquid-phase 75A of the working fluid 75 from the working fluid reservoir 170 and forcing the liquid-phase 75A of the working fluid 75 into the evaporative heat exchanger 110. The blower 151 indirectly induces flow of the working fluid 75 through the closed-loop fluid circuit 100 by increasing air flow over the heat exchange tubes 154 of the condenser 150 (the working fluid 75 being the tubeside fluid in the condenser 150), thereby increasing the extraction of thermal energy from the working fluid 75 in the condenser 150 and promoting increased condensation and a thermo-siphon flow effect of the working fluid 75. In certain embodiments of the invention, more or less forced flow units can be incorporated into the autonomous self-powered system 1000 as desired. For example, in certain embodiments, the blower 151 may be omitted while, in certain other embodiments, the hydraulic pump 90 may be omitted. For example, if the condenser 50 were a natural draft air-cooled condenser (see FIGS. 4-5B), the blower 151 may be omitted. Furthermore, in certain embodiments where the condenser 50 is not an air cooled condenser, but is for example a shell and tube heat exchanger, a hydraulic pump that is used to force flow of the secondary fluid through the condenser 50 can be a forced flow unit. Irrespective of the exact number and identity of the forced flow units that are used to induce flow of the of the working fluid 75 through the closed-loop fluid circuit 100, all of said forced flow units are powered only by electrical energy generated through the conversion of the thermal energy that is extracted from the liquid 50 of the pool. More specifically, in the exemplified embodiment, both the hydraulic pump 190 and the blower 151 are operably and electrically coupled to the electrical circuit 200, which is powered solely by the electrical energy generated by the turbogenerator 130 (discussed in greater detail below). Thus, the autonomous self-powered system 1000 can operate to cool the liquid 50 of the pool for an indefinite period of time and completely independent of any outside sources of electrical energy, other than that electrical energy that is generated through the conversion of the thermal energy extracted from the liquid 50 of the pool. Stated simply, the thermal energy of the liquid 50 of the pool is the sole source of energy required to drive the cooling system 1000. Referring still to FIG. 1, the general operation cycle of the autonomous self-powered system 1000 will be described. The working fluid reservoir 170 stores an amount of the liquid phase 75a of the working fluid 75 to charge and control the quantity of the working fluid 75 in the thermal cycle at start up. The working fluid reservoir 170 also provides the means to evacuate the closed-loop fluid circuit 100 of air and to fill the closed-loop fluid circuit 100 with the required amount of the working fluid 75. In certain embodiments, the working fluid reservoir 170 is needed only at the beginning of the system operation (start up) to insure that the proper quantity of the working fluid 75 is injected into the thermal cycle. The hydraulic pump 190 is located downstream of the working fluid reservoir 170 in the exemplified embodiment. However, in alternate embodiments, the hydraulic pump 190 can be located upstream of the working fluid reservoir 170. Once started, the hydraulic pump 190 draws the liquid phase 75A of the working fluid 75 from the working fluid reservoir 170, thereby drawing the liquid phase 75A of the working fluid 75 into the working fluid inlet 191 of the hydraulic pump 190. As the hydraulic pump 190 operates, the liquid phase 75A of the working fluid 75 is expelled from the working fluid outlet 192 of the hydraulic pump under pressure. The expelled liquid phase 75A of the working fluid 75 is forced into the evaporative heat exchanger 110 via the working fluid inlet 111 of the evaporative heat exchanger 110. The evaporative heat exchanger 110 is at least partially immersed in the liquid 50 of the pool so that thermal energy from liquid 50 can be transferred to the working fluid 70 while in the evaporative heat exchanger 110. In the exemplified embodiment, the evaporative heat exchanger 110 is full immersed in the liquid 50 of the pool. Furthermore, the evaporative heat exchanger 110 is located at a top of the pool of liquid 50, which tends to be hotter than the bottom of the pool of liquid 50 due to temperature differentials in the liquid 50 (hot fluids rise). In one embodiment, the evaporative heat exchanger 110 is mounted to one of the sidewalls 55 of the pool of liquid 50 so that the evaporative heat exchanger 110 does not interfere with loading and unloading operations that take place within the pool of liquid 50 for the radioactive materials 20. The details of one embodiment of the evaporative heat exchanger 110, including the operation thereof, will now be described with reference to FIGS. 1 and 2 concurrently. Of course, the invention is not so limited, and the evaporative heat exchanger 110 can take on other structural embodiments in other embodiments of the invention. The evaporative heat exchanger 110 generally comprises a core tube 113 (which acts as a downcomer tube in the exemplified embodiment), a plurality of heat exchange tubes 114, a working fluid bottom header 115, and a working fluid top header 116, which collectively define a tubeside fluid circuit. The working fluid bottom header 115 comprises a bottom tube sheet 117 while the working fluid top header 116 comprises a top tube sheet 118. In one embodiment, the bottom and top headers 115, 116 and the core pipe 113 are constructed of a corrosion resistant alloy, such as stainless steel. The bottom and top tube sheets are constructed of an aluminum clad stainless steel. The heat exchange tubes 114 are constructed of aluminum (as used herein the term “aluminum” includes aluminum alloys) and are welded to the aluminum cladding of the bottom and top tube sheets 117, 118 to make leak tight joints. The core pipe 113 will be welded to the stainless steel base metal of the bottom and top tube sheets 117, 118. Of course, other materials and construction methodologies can be used as would be known to those of skill in the art. The core tube 113 extends from the working fluid outlet header 116 to the working fluid inlet header 115, thereby forming a fluid-tight path between the two through which the liquid phase 75A of the working fluid 75 will flow. More specifically, the core tube 113 is connected to the lower and upper tube sheets 117, 118 of the working fluid headers 115, 116. The working fluid inlet 111 extends into the core tube 113 and introduces cool liquid phase 75A of the working fluid 75 into a top portion of the core tube 113. The core tube 113 is formed of a material that has a low coefficient of thermal conductivity (as compared to the material of which the heat exchange tubes 114 are constructed), such as steel. The core tube 113 may also comprise a thermal insulating layer, which can be an insulating shroud tube, to minimize heating of the liquid phase 75A of the working fluid 75 in the core tube 113 by the liquid 50 of the pool. Irrespective of the materials and/or construction of the core tube 113, the core tube 113 has an effective coefficient of thermal conductivity (measured from an inner surface that is contact with the working fluid 75 to an outer surface that is in contact with the liquid 50 of the pool) that is less than the effective coefficient of thermal conductivity of the heat exchange tubes 114 (measured from an inner surface that is contact with the working fluid 75 to an outer surface that is in contact with the liquid 50 of the pool) in certain embodiments of the invention. As discussed in detail below, this helps achieve an internal thermosiphon recirculation flow of the liquid phase 75A of the working fluid 75 within the evaporative heat exchanger 110 itself (indicated by the flow arrows in FIG. 2). The plurality of heat exchange tubes 114 form a tube bundle that circumferentially surrounds the core tube 113. The plurality of heat exchange tubes 114 are arranged in a substantially vertical orientation. The heat exchange tubes 114 are constructed of a material having a high coefficient of thermal conductivity to effectively transfer thermal energy from the liquid 50 of the pool to the working fluid 75. Suitable materials include, without limitation, aluminum, copper, or materials of similar thermal conductivity. In one embodiment, the heat exchange tubes 114 are finned tubes comprising a tube portion 119 and a plurality of fins 120 extending from an outer surface of the tube portion 119 (shown in FIG. 6). In the exemplified embodiment, each heat exchange tube 114 comprises four fins 120 extending from the tube portion 119 at points of 90 degree circumferential separation. During operation of the autonomous self-powered system 1000, cool liquid phase 75A of the working fluid 75 enters the evaporative heat exchanger 110 via the working fluid inlet 111 as discussed above. The liquid phase 75A of the working fluid 75 is considered “cool” at this time because it had been previously cooled in the condenser 50. As the cool liquid phase 75A of the working fluid 75 enters the evaporative heat exchanger 110, it is introduced into the core tube 113. The cool liquid phase 75A of the working fluid 75 flows downward through the core tube and into the bottom header 115, thereby filling the bottom header 115 and flowing upward into the plurality of heat exchange tubes 114. As the liquid phase 75A of the working fluid 75 flows upward in the plurality of heat exchange tubes 114, thermal energy from the liquid 50 of the pool that surrounds the plurality of heat exchange tubes 114 is conducted through the plurality of heat exchange tubes 114 and into the liquid phase 75A of the working fluid 75, thereby heating the liquid phase 75A of the working fluid 75. The warmed liquid phase 75A of the working fluid 75 then enters the top header 116 where it is drawn back into the core tube 113 by a thermosiphon effect. As a result, the liquid phase 75A of the working fluid 75 is recirculated back through the aforementioned cycle until the liquid phase 75A of the working fluid 75 achieves the boiling temperature of the working fluid 75, thereby being converted into the vapor phase 75B of the working fluid 75. The vapor phase 75B of the working fluid 75 rises within the evaporative heat exchanger 110 and gather within a top portion of the top header 116 where it then exits the evaporative heat exchanger 110 via the working fluid outlet(s) 112. The internal design of the evaporative heat exchanger 110 promotes recirculation of the working fluid 117 and separation of the vapor phase 75B from the liquid phase 75A in the top header 116 (as shown in FIG. 2). As mentioned above, the evaporative heat exchanger 110 is pressurized to a supra-atmospheric pressure. In one embodiment, the pressure within the evaporative heat exchanger 110 is between 250 psia to 400 psia, with a more preferred range being between 280 psia and 320 psia, with approximately 300 psia being most preferred. Pressurization of the evaporative heat exchanger 110 is achieved through properly positioned valves as would be known to those of skill in the art. In one embodiment, the working fluid 75 and the pressure within the evaporative heat exchanger 110 are selected so that the working fluid evaporates at a temperature between 145° F. and 175° F., and more preferably between 155° F. and 165° F. Referring solely now to FIG. 1, the pressurized vapor phase 75B of the working fluid 75 exits the working fluid outlet 112 of the evaporative heat exchanger 110 and enters the working fluid inlet 131 of the turbogenerator 130. The pressurized vapor phase 75B of the working fluid 75 produced in the evaporative heat exchanger 110 then serves to energize a suitably sized turbogenerator 130. In other words, the turbogenerator 130 converts a first portion of the thermal energy extracted from the liquid 50 of the pool (which is now in the form of kinetic energy (velocity head) and/or potential energy (pressure head) of the vapor flow) to electrical power, as would be understood by those of skill in the art. As used herein, the term “turbogenerator” includes a device and/or subsystem that includes a turbine and electrical generator either in directed or indirect connection. The term “turbogenerator” is intended to include any device and/or subsystem that can convert the pressurized vapor phase 75B of the working fluid 75 into electrical energy. As the vapor phase 75B of the working fluid 75 passes through the turbogenerator 130 it is partially depressurized as it exits the working fluid outlet 132 of the turbogenertaor still in the vapor phase 75B. At this point, the vapor phase 75B of the working fluid 75 may be at a pressure between 200 psia and 270 psia. As mentioned above, the forced flow units (which in the exemplified embodiment are the hydraulic pump 190 and the blower 151) are operably and electrically coupled to the turbogenerator 130 by the electrical circuit 130 via electrical lines 201. All of the forced flow units are powered solely by the electrical energy generated by the turbogenerator 130 as discussed above. Moreover, in many instances, the turbogenerator 130 will generate surplus electrical energy. Thus, the autonomous self-powered system 1000 may further comprise a rechargeable electrical energy source 202, such as a battery, operably and electrically coupled to the turbogenerator 130 by the electrical circuit 200. In certain embodiments, the rechargeable electrical energy source 202 will be operably coupled to a controller so that certain valves, sensors, and other electrical components can be operated even when the turbogenerator 130 is not running. Referring still to FIG. 1, the partially depressurized vapor phase 75B of the working fluid 75 that exits the turbogenerator 130 enters the working fluid inlet 152 of the condenser 150. The condenser 150 transfers a sufficient amount of thermal energy from the partially depressurized vapor phase 75B of the working fluid 75 to a secondary fluid so that the depressurized vapor phase 75B of the working fluid 75 is converted back into the liquid phase 75A of the working fluid 75. The condensed liquid phase 75A of the working fluid 75 exits the condenser 150 via the working fluid outlet 153 of the condenser where it flows back into the working fluid reservoir 170 for recirculation through the closed-loop fluid circuit 100. In one embodiment, the condenser 150 is an air-cooled condenser and, thus, the secondary fluid is air that is expelled to the environment. In other embodiments, the condenser 150 can be any type of heat exchanger than can remove thermal energy from the partially depressurized vapor phase 75B of the working fluid 75, including without limitation, a shell and tube heat exchanger, a plate heat exchanger, a plate and shell heat exchanger, an adiabatic heat exchanger, a plate fin heat exchanger, and a pillow plate heat exchanger. Referring to FIGS. 1 and 3 concurrently, an example of induced flow air cooled-condenser 150 that can be used in the system 1000 is exemplified. The induced flow air cooled-condenser 150 comprises a plurality of heat exchange tubes 154 (FIG. 6) positioned within an internal cavity formed by a housing 159. The working fluid 75 is the tubeside fluid and flows through the plurality of heat exchange tubes 154. The plurality of heat exchange tubes 154 are arranged in a substantially vertical orientation and are finned as discussed above with respect to the heat exchange tubes 114 of the evaporative heat exchanger 110, and as shown in FIG. 6. The induced flow air cooled-condenser 150 comprises a cool air inlet 155 and a warmed air outlet 156. The warmed air outlet 156 is at a higher elevation than the cool air inlet 155. The plurality of heat exchange tubes 154 are located in the cavity of the housing at an elevation between the elevation of the cool air inlet 155 and an elevation of the warmed air outlet 156. As such, in addition to the air flow within the housing 159 being forced by operation of the blower 151, which is located within the warmed air outlet 156, additional air flow will be achieved by the natural convective flow of the air as it is heated (i.e., the chimney effect). As warmed air exists the condenser 150 via the warmed air outlet 156, additional cool air is drawn into the cool air inlet 155. The induced flow air cooled-condenser 150, in certain embodiments, is located outside of the containment building in which the pool of liquid 50 is located. Referring now to FIGS. 4-5B concurrently, an example of natural draft air cooled-condenser 250 that can be used in the system 1000 is exemplified. Of note, the flow of air over the heat exchanger tubes 154 (which are also vertically oriented) is accomplished solely by natural convection (i.e., the chimney effect) and, thus, the blower 151 is not required. However, in certain embodiments, the blower 151 can be incorporated into the natural draft air cooled-condenser 250 as desired to accommodate for situations where the ambient air may reach elevated temperatures that could negatively affect adequate heat removal from the working fluid 75. Of further note, the natural draft air cooled-condenser 250 comprises a working fluid inlet header 260 comprising a plurality concentrically arranged toroidal tubes. Similarly, the natural draft air cooled-condenser 250 also comprises a working fluid outlet header 261 comprising a plurality concentrically arranged toroidal tubes. The plurality of heat exchange tubes 154 form a tube bundle that extends from the toroidal tubes of the working fluid inlet header 260 to the toroidal tubes of the working fluid outlet header 261. As with the air-cooled condenser 150, the natural draft air cooled-condenser 250 comprises a cool air inlet 255 and a warmed air outlet 256. The warmed air outlet 256 is at a higher elevation than the cool air inlet 255. The plurality of heat exchange tubes 254 are located in the cavity of the housing 259 at an elevation between the elevation of the cool air inlet 255 and an elevation of the warmed air outlet 256. The system 1000 of the present invention can be used to remove heat from any pool of water. In particular, it can be used to reject the decay heat from a spent fuel pool. Because the inventive system 1000 does not require any external active components such as pumps, motors, or electric actuators/controllers, it can be engineered as an autonomous system that is not reliant on an external energy source to function. Thus, the inventive system 1000 is safe from an extreme environmental event such as a tsunami. It is evident that several of the systems 1000 can be deployed in a single pool of liquid if desired. The inventive system 1000 can be retrofit to existing plants for use both as an emergency cooling system under station blackout scenarios and as an auxiliary system to provide operational flexibility during corrective and elective maintenance (particularly during outages). The inventive system 1000 can also be incorporated into the plant design for new build projects to operate as the primary cooling system, thereby removing station blackout as a possible threat to spent fuel pool safety. As used throughout, ranges 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 referenced 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. While the invention has been described with respect to specific examples including presently preferred modes of carrying out the invention, those skilled in the art will appreciate that there are numerous variations and permutations of the above described systems and techniques. It is to be understood that other embodiments may be utilized and structural and functional modifications may be made without departing from the scope of the present invention. Thus, the spirit and scope of the invention should be construed broadly as set forth in the appended claims.
	abstract	A direct-write electron beam lithography system employing a patterned beam-defining aperture to enable the generation of high current-density shaped beams without the need for multiple beam-shaping apertures, lenses and deflectors is disclosed. Beam blanking is accomplished without the need for an intermediate crossover between the electron source and the wafer being patterned by means of a double-deflection blanker, which also facilitates proximity effect correction. A simple type of “moving lens” is utilized to eliminate off-axis aberrations in the shaped beam. A method for designing the patterned beam-defining aperture is also disclosed.
054948630	abstract	The present invention relates to a process for nuclear waste disposal. In it, a glass forming mixture including an aqueous solution of one or more metal alkoxides, alcohol, and solubilized, low level radioactive waste having a pH effective to hydrolyze the one or more metal alkoxides is formed. The one or more metal alkoxides in the glass forming mixture are converted to a network of corresponding one or more metal oxides. A gel is then formed from the glass forming mixture containing the network of one or more metal oxides. The gel is dried and sintered under conditions effective to form a densified glass.
050769936	claims	1. Contraband detection apparatus comprising: means for irradiating an object under investigation with a collimated pulsed beam of fast neutrons having a pulse width of less than 5 nanoseconds; first detecting means for detecting gamma rays emitted from said object as a result of interactions between a neutron from said pulsed beam of fast neutrons and an atomic nucleus within said object; identifying means for identifying a particular atomic element which gives rise to a particular detected gamma ray; locating means for determining the approximate location within said object of the origin of each gamma ray detected by said detecting means without the necessity of detecting associated particles; and second detection means responsive to said irradiating means, identifying means and locating means for detecting a distribution and concentration of at least one atomic element within said object indicative of the presence of contraband. measuring means for measuring the energy of each detected gamma ray, and means responsive to said measured energy for identifying the particular atomic element from which the detected gamma ray originated. means for generating a highly collimated pulsed beam of fast neutrons, and means for moving said object relative to said beam so that said fast neutrons enter a prescribed volume of said object. means for generating a recurring short pulse of less than five nanoseconds of directed fast neutrons; means for scanning an object under investigation for the presence of contraband with said recurring short pulse of directed fast neutrons, each of said fast neutrons possibly reacting with a particular atomic nucleus present within said object, thereby generating gamma rays having an energy characteristic of the particular atomic nucleus with which said fast neutrons react; means for detecting the gamma rays produced by neutrons in reaction with atomic nuclei, said detection means including means for detecting the energy of a particular gamma ray and the time of its detection relative to the time of generation of said short pulse of fast neutrons; and means for determining a particular volume element, or voxel, within said object from which a particular detected gamma ray originated without the necessity of detecting associated particles, such as alpha particles, that may be generated by the means for generating the fast neutrons, said detected gamma ray thereby providing a direct indication of the particular atomic nucleus in said particular voxel; the particular atomic nuclei, present in a sample of the voxels within said object providing a direct indication of the abundances and distributions of particular elements within said object; a prescribed abundance and distribution of particular elements within said object providing a direct indication of the presence of contraband within said object. (a) means for scanning an object under investigation with a pulsed beam of highly collimated fast neutrons by controllably directing said pulsed beam at a prescribed volume of said object, said pulsed beam of highly collimated fast neutrons having a pulse width of less than 5 nanoseconds; (b) means for detecting gamma rays having prescribed energies emitted from said prescribed volume of said object as a result of interactions between pulsed fast neutrons from said pulsed beam of fast neutrons and atomic nuclei of particular elements within said object, said prescribed energies corresponding to atomic elements commonly found in contraband; and (c) means responsive to said detecting means for ascertaining whether a distribution and concentration of at least one atomic element indicative of contraband exists within said prescribed volume, said means performing its contraband detecting function without the necessity of detecting associated particles, such as alpha particles, that may be generated coincident with the pulsed fast neutrons. (a) directing a pulsed beam of fast neutrons, laterally limited, towards an object under investigation said pulsed beam having a pulse width of less than 5 nanoseconds; and (b) detecting gamma rays having prescribed energies emitted from a prescribed volume of said object as a result of interactions between pulsed fast neutrons from said pulsed beam of fast neutrons and atomic nuclei of a particular elements within said prescribed volume, said prescribed energies corresponding to atomic elements commonly found in contraband. 2. The contraband detection apparatus as set forth in claim 1 wherein said identifying means comprises: 3. The contraband detection apparatus as set forth in claim 2 wherein said irradiating means comprises: 4. The contraband detection apparatus as set forth in claim 3 wherein said irradiating means further includes means for creating relative motion between said object and said pulsed beam so that a plurality of prescribed volumes within said object are irradiated in turn with said pulsed beam, whereby a desired portion of said object comprising said plurality of prescribed volumes has said pulsed beam pass therethrough. 5. The contraband detection apparatus as set forth in claim 3 wherein said locating means includes means for measuring the time of flight of a particular neutron within said pulsed beam up to the approximate time at which said particular neutron interacts with an atomic nucleus within said object, said time of flight measurement providing a measure of the depth at which said particular gamma ray was produced within said object. 6. The contraband detection apparatus as set forth in claim 5 wherein said time of flight measurement means includes means for measuring the time between the generation of a pulsed neutron within said beam and the detection of a gamma ray resulting from the interaction of said pulsed neutron with an atomic nucleus, said measured time including both the time of flight of said pulsed neutron from its source to its interaction with the atomic nucleus, and the time of flight of said gamma ray from said nucleus to the time of its detection by said detecting means, the time of flight of said neutron being much greater than the time of flight of said gamma ray. 7. The contraband detection apparatus as set forth in claim 6 further including correction means for correcting said time of flight measurement to minimize the effects of the time of flight of said gamma ray, whereby said time of flight measurement includes primarily the time it takes said pulsed neutron to travel from its source to the atomic nucleus with which it interacts. 8. The contraband detection apparatus as set forth in claim 6 wherein said time of flight measurement means includes means for measuring the time between the detection of a gamma ray and the generation of a pulsed neutron. 9. The contraband detection apparatus as set forth in claim 5 wherein said second detection means includes means for electronically creating a density image of particular elements within said object indicative of contraband, said density image being created directly from the identity of said atomic elements identified by said identifying means and the location of said atomic elements determined by said locating means. 10. The contraband detection apparatus as set forth in claim 9 wherein the particular elements within said object indicative of contraband comprise oxygen, nitrogen or carbon. 11. The contraband detection apparatus as set forth in claim 10 wherein the particular elements within said object indicative of contraband further include hydrogen or chlorine. 12. The contraband detection apparatus as set forth in claim 10 wherein the contraband detected by said apparatus is selected from the group comprising explosives or narcotics. 13. A contraband detection system comprising: 14. The contraband detection system as set forth in claim 13 wherein said gamma ray detecting means comprises an array of detectors positioned proximal said object. 15. The contraband detection system as set forth in claim 13 wherein said voxel determining means comprises means for measuring the approximate time of flight of a particular pulse of high energy neutrons within said short pulse of directed high energy neutrons from the time said particular pulse is generated until a neutron within said pulse interacts with an atomic nucleus, the location of said voxel thus being determinable from the known kinematics associated with said short pulse of directed high energy neutrons and said measured time of flight. 16. The contraband detection system as set forth in claim 15 wherein said means for measuring the time of flight includes electronic means for measuring the time between the generation of a particular pulse of high energy neutrons and the detection of a gamma ray by said gamma ray detecting means. 17. The contraband detection system as set forth in claim 16 wherein said recurring short pulse of high energy neutrons is generated every T seconds, and wherein said electronic measuring means measures the time between the detection of a gamma ray by said gamma ray detecting means, and the subsequent generation of the next pulse of high energy neutrons. 18. The contraband detection system as set forth in claim 13 wherein said means for scanning comprises means for controllably directing a specified number of short pulses of said high energy neutrons at respective volumes of said object fronting said high energy neutron generating means, said short pulses of high energy neutrons penetrating into said object through said respective volumes. 19. The contraband detection system as set forth in claim 18 wherein said scanning means includes means for creating controlled relative motion between said object and said directed high energy short pulse neutron generating means, whereby said respective volumes of said object have a short neutron pulse pass therethrough in a controlled fashion. 20. A system for detecting contraband comprising: 21. The system for detecting contraband as set forth in claim 20 wherein said scanning means includes means for determining the approximate time of flight of a burst of pulsed fast neutrons within said pulsed beam of fast neutrons up until the time of interaction with atomic nuclei within said object, said interaction causing said gamma rays to be produced, said time of flight providing a measure of the depth within said object at which the gamma rays originated, and hence a measure of the depth within the object along a path of said pulsed beam of fast neutrons at which a particular atomic element, commonly found in contraband, is located, said time of flight thereby defining a particular volume element, or voxel, of the object within which said particular atomic element is found. 22. The system for detecting contraband as set forth in claim 21 wherein said means for ascertaining the distribution and concentration of said at least one atomic element indicative of contraband includes means for combining the time-of-flight information determined by said scanning means with the detected gamma ray information from said gamma ray detecting means to produce a two-dimensional energy-time spectrum, from which two-dimensional energy-time spectrum the approximate location of specified atomic elements within said object can be fairly deduced. 23. A method of detecting contraband comprising the steps of: 24. The method of detecting contraband as set forth in claim 23 further including repeating steps (a) and (b) for a sufficiently large number of prescribed volumes of the object under investigation so as to ascertain whether a distribution and concentration of at least one atomic element indicative of contraband exists within said object. 25. The method of detecting contraband as set forth in claim 24 wherein step (b) includes measuring the energy of the detected gamma rays and the time at which the gamma rays are detected relative to the time at which the pulsed fast neutrons are generated, and obtaining a two-dimensional energy-time spectrum from said energy and time measurements for the prescribed volume of said object receiving said pulsed beam of fast neutrons. 26. The method of detecting contraband as set forth in claim 25 wherein said step of measuring the time at which gamma rays are detected comprises determining the approximate time of flight of a burst of pulsed neutrons in said laterally limited pulsed beam of fast neutrons up until the time said burst interacts with atomic nuclei and causes a gamma ray to be produced, and correlating said time of flight to an approximate depth within said object where the atomic nuclei are located along the path of said pulsed neutron beam, said correlation allowing said two-dimensional energy-time spectrum to be effectively converted into a two-dimensional energy-location spectrum.
	claims	1. A detector for an electron column, which is made of conductive material in a mesh form, made from an arrangement of one or more conductive wires, or a conductive plate shape, and which is located and used directly above a sample, wherein the detector directly receives and transmits electrons generated by an electron beam in an electron column to an outside without amplifying the detected electrons, as a transmission of data about the electric current, and wherein the electron beam is radiated through a space between the conductive wires. 2. The detector as set forth in claim 1, wherein the detector has a two-dimensional or three-dimensional structure formed of one conductive wire. 3. A method of detecting electrons generated by an electron beam in an electron column, the method comprising steps for:receiving directly electrons generated by an electron beam in an electron column, andtransmitting the electrons directly to an outside, as a transmission of data about the electric current, without amplifying the detected electrons. 4. The method as set forth in claim 3, wherein the detector comprises a detector for an electron column, which is made of conductive material in a mesh form, made from an arrangement of one or more conductive wires, or a conductive plate shape, and which is located and used directly above a sample. 5. The method as set forth in claim 3, wherein the detector is wired through a conductive part of a sample using a sample current method and performs detection. 6. The method as set forth in claim 5, wherein the detection is performed by applying negative voltage to the sample. 7. The method as set forth in claim 3, wherein the detector detects electrons from electron beams which are generated by a plurality of electron columns, and the detector performs detection while the electron columns are sequentially operated. 8. The method as set forth in claim 3, wherein the detector comprises a detector for an electron column, which is made of conductive material in a mesh form, made from an arrangement of one or more conductive wires, or a conductive plate shape, and which is located and used directly above a sample, and wherein the detector has a two-dimensional or three-dimensional structure formed of one conductive wire. 9. The method as set forth in claim 4, wherein the detector detects electrons from electron beams which are generated by a plurality of electron columns, and the detector performs detection while the electron columns are sequentially operated. 10. The method as set forth in claim 5, wherein the detector detects electrons from electron beams which are generated by a plurality of electron columns, and the detector performs detection while the electron columns are sequentially operated. 11. The method as set forth in claim 6, wherein the detector detects electrons from electron beams which are generated by a plurality of electron columns, and the detector performs detection while the electron columns are sequentially operated. 12. The method as set forth in claim 8, wherein the detector detects electrons from electron beams which are generated by a plurality of electron columns, and the detector performs detection while the electron columns are sequentially operated.
	summary
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	summary
	abstract	An RI manufacturing apparatus includes: an accelerator which accelerates charged particles; a target which is irradiated with the charged particle accelerated by the accelerator, thereby manufacturing a radioactive isotope; a built-in shield that may be a wall body which surrounds the accelerator and the target to shield radiation; and a target shield that may be a wall body which is disposed between the built-in shield and the accelerator and surrounds the target to shield the radiation.
045444994	summary	BACKGROUND OF THE INVENTION Cooling, operational and waste water from the daily operation of nuclear power plants and fuel rod holding tanks is contaminated with a number of radioactive isotopes which are present in the water in very low concentrations but which nonetheless are highly radioactive and toxic to human life. Since the volumes of contaminated water are extremely large, it is neither possible nor economically feasible to store away this water permanently. Instead, the water must be re-used or released back into the environment. Safe disposal or re-use of the contaminated water can only be conducted if a sufficient quantity of radioactive isotopes are removed from it to reach permissible levels. The method of ion exchange is the most promising and most in use today because of the large volume reduction of waste material. The radioactive isotopes present in contaminated nuclear reactor water occur as cations, anions or solids, and any complete disposal system must handle all three species. Radioactive isotopes present in typical reactor cooling water are listed in Table 1. This water also generally contains non-radioactive isotopes of boron (400 ppm), sodium (150 ppm) and chlorine (5 ppm). The most dangerous cations from the stand point of high concentrations and long-half lives are Cs, Co and Sr. These are removed with the other dissolved cations by a cation exchanger. In copending applications U.S. Ser. No. 959,222 filed Nov. 9, 1978 and U.S. Ser. No. 039,595, filed May 16, 1979, each entitled Fixation By Ion Exchange of Toxic Materials In a Glass Matrix and each by C. J. Simmons, J. H. Simmons, P. B. Macedo, and T. A. Litovitz the removal of radioactive cations from reactor cooling systems using a porous glass cation exchanger is disclosed. The anions present in solution consist primarily of I.sup.131 which has a half-life of 8 days but which poses a significant threat to life due to its affinity for and high reconcentration in animal and human metabolic processes. Most other anion isotopes are also short-lived and due to this rapid decay, they have a stronger tendency to damage their ion-exchange hosts than do the cation isotopes. After 3 months, the majority of the non-metal anions have generally decayed to stable isotopes, however many of the longer-lived metal isotopes form anionic complexes such as chromates, cerates, and molybdates, which remain radioactive for longer time periods. For example, the half-lives of Cr.sup.51, Ce.sup.144, and Te.sup.99 are 26 days, 290 days and 200,000 years respectively. Today, organic anion resins are used in nuclear reactors, however, they are readily decomposed by radioactivity, they cannot be dried, they are not compatible for use in mixed beds with the new types of glass cation exchangers coming on the market, and they cannot be put into a long-term chemically stable form, thus causing a serious danger to the environment through premature release of the radioactive isotopes. The present invention is directed to the disposal of both poisonous radioactive anions such as radioactive iodide, chromate, molybdate, cerate and technetium, and non-poisonous or non-radioactive isotopes. The non-poisonous anions must be removed from nuclear waste streams to protect parts which are in contact with the streams. Exemplary parts are fuel elements, tubing, heat-exchangers, reactor vessels. Chloride is the predominant non-radioactive anion which must be removed. The present invention discloses the use of an especially prepared porous glass medium as an anion exchanger. The glass anion exchanger is far superior to the organic exchangers available today for the following reasons. It is insensitive to radiation (such as from short-lived isotopes). It is compatible with the new glass cation exchangers and can be used in mixed-bed exchanger media with them. It can be dried, thus reducing the dissemination of radioactive isotopes after use. It can be heated to permanently fixate radioactive isotopes within its pores and produce a long-term chemically stable form which will resist premature dissemination of radioactive isotopes into the environment. Finally, as can be seen from Table 1, and Table 4, there are a large number of radioactive isotopes which occur as solids. These solids are dangerous and have long half-lives such as Co.sup.60 with 5 years. These solids do not chemically bond to the ion exchange media, however they remain entrapped between the grains of the ion exchanger by simple filtering action. As a result, they are effectively removed from the water by the ion exchange media. If the media are organic resins, they are encased in cement or bitumen, neither of which have a good long-term chemical stability, and the filtered solids are the first to be released to the environment, thus causing a serious health hazzard. If the media are the anion-exchanged glasses disclosed here, it is possible to heat them to moderate temperatures and cause sintering of the ion exchange powder, thus permanently fixating these toxic, radioactive solids in the glass structure and effectively isolating them from the environment. TABLE 1 ______________________________________ Typical radioactive isotopes in reactor cooling water typical concentration .gamma.-emitters .mu.Ci/ml chemical form ______________________________________ Co--57 1.3 .times. 10.sup.-5 cation, solid Cr--51 3.5 .times. 10.sup.-4 anion I--131 2.0 .times. 10.sup.-4 anion Cs--134 1.1 .times. 10.sup.-3 cation Cs--137 1.8 .times. 10.sup.-3 cation Zr--95 7.1 .times. 10.sup.-5 solid Nb--95 8.6 .times. 10.sup.-5 solid Co--58 6.7 .times. 10.sup.-3 cation, solid Fe--59 2.6 .times. 10.sup.-4 cation, solid Ba--La--140 1.2 .times. 10.sup.-5 cation Cs--136 3.1 .times. 10.sup.-5 cation Mn--54 6.9 .times. 10.sup.-4 cation, solid Co--60 3.5 .times. 10.sup.-3 cation, solid Non .gamma.-emitters Sr--90 cation Y--9D cation H--3 cation, anion C--14 cation, anion, solid Other .gamma.-emitter isotopes found in trace amounts Np--239 Ce--144 anion, solid Ce--139 anion, solid Sn--113 anion Zn--69M cation, solid Co-- 138 cation W--187 solid I--133 anion As--76 anion Cs--134 cation Nb--97 solid Mo--99 anion Zr--97 solid I--132 anion I--134 anion Ag--110M solid Zu--65 cation, solid Na--22 cation Cu--64 cation, anion, solid Na--24 cation K--40 cation Ni--65 cation, solid K--42 cation Cl--38 anion Mn--56 cation, solid Rb--88 cation I--135 anion ______________________________________ The two most popular types of commercial reactors, both of which produce low level wastes, are the Boiling Water Reactor (B.W.R.) and the Pressurized Water Reactor (P.W.R.). In a typical Pressurized Water Reactor (P.W.R.), pressurized light water circulates through the reactor core (heat source) to an external heat sink (steam generator). In the steam generator, where primary and secondary fluids are separated by impervious surfaces to prevent contamination, heat is transferred from the pressurized primary coolant to secondary coolant water to form steam for driving turbines to generate electricity. In a typical Boiling Water Reactor (B.W.R.), light water circulates through the reactor core (heat source) where it boils to form steam that passes to an external heat sink (turbine and condenser). In both reactor types, the primary coolant from the heat sink is purified and recycled to the heat source. The primary coolant and dissolved impurities are activated by neutron interactions. Materials enter the primary coolant through corrosion of the fuel elements, reactor vessel, piping, and equipment. Activation of these corrosion products adds radioactive nuclides to the primary coolant. Corrosion inhibitors, such as lithium, are added to the reactor water. A chemical shim, boron, is added to the primary coolant of most P.W.R.'s for reactivity control. These chemicals are activated and add radionuclides to the primary coolant. Fission products diffuse or leak from fuel elements and add nuclides to the primary coolant. Radioactive materials from all these sources are transported around the system and appear in other parts of the plant through leaks and vents as well as in the effluent streams from processes used to treat the primary coolant. Gaseous and liquid radioactive wastes (radwaste) are processed within the plant to reduce the radioactive nuclides that will be released to the atmosphere and to bodies of water under controlled and monitored conditions in accordance with federal regulations. The principal methods or unit operations used in the treatment of liquid radwaste at nuclear power plants are filtration, ion exchange, and evaporation. Liquid radwastes in a P.W.R. are generally segregated into five categories according to their physical and chemical properties as follows: a. Clean Waste includes liquids which are primarily controlled releases and leaks from the primary coolant loop and associated equipment. These are liquids of low solids content which are treated in the reactor coolant treatment system. PA0 b. Dirty or Miscellaneous Waste includes liquids which are collected from the containment building, auxiliary building, and chemical laboratory; regeneration solutions from ion-exchange beds; and solutions of high electrical conductivity and high solids content from miscellaneous sources. PA0 c. Steam Generator Blowdown Waste is condensate from the steam that is removed (blowdown) periodically to prevent excessive solids buildup. PA0 d. Turbine Building Drain Waste is leakage from the secondary system that is collected in the turbine building floor sump. PA0 e. Detergent Waste includes liquids from the laundry, personnel decontamination showers, and equipment decontamination. PA0 a. High-Purity Waste includes liquids of low electrical conductivity (<50 .mu.mho/cm) and low solids content, i.e., reactor coolant water that has leaked from the primary reactor system equipment, the drywell floor drain, condensate demineralizer backwash, and other sources of high-quality water. PA0 b. Low-Purity Waste includes liquids of electrical conductivity in excess of 50 .mu.mho/cm and generally less than 100 .mu.mho/cm; i.e., primarily water from floor drains. PA0 c. Chemical Waste includes solutions of caustic and sulfuric acid which are used to regenerate ion exchange resins as well as solutions from laboratory drains and equipment decontamination. PA0 d. Detergent Waste includes liquids from the laundry and personnel decontamination showers. Liquid radwastes in a B.W.R. are generally segregated into four categories according to their physical and chemical properties as follows: The liquid radwastes from both types of reactors are highly dilute solutions of radioactive cations, anions and other dissolved radioactive materials as well as undissolved radioactive particles of finely divided solids. A practical process for disposing of radioactive materials in a dry solids form having high resistance to leaching and other forms of chemical attack would not only be suitable for the disposal of radioactive nuclear wastes, but also for the fabrication of radioactive sources useful in industry, medicine, and in the laboratory. Heretofore, there did not exist any practical, foolproof means for the safe disposal, storage and immobilization of pernicious radioactive waste material. Present day storage containers do not provide sufficient isolation and immobilization of such radioactive material, sufficient long-term resistance to chemical attack by the surroundings, and sufficient stability at high temperatures. Currently low level radioactive waste, that is radioactive waste generated at reactor sites, is disposed of in the following manner: (A) The dead ion exchange resin containing radioactive waste is mixed with cement or bitumen and cast in forty gallon barrels. (B) The bottoms from evaporators which contain the radioactive contaminated boric acid and the solutions used to regenerate the ion exchange columns are mixed with cement powder or bitumen and cast in forty gallon barrels. (C) The filters containing particulate forms of radioactive waste are usually encased in cement or bitumen in barrels. These cement or bitumen barrels are transported to low level radioactive waste sites and buried six to twenty feet deep in the ground. At least one of the sites is in the United States eastern states and exposed to substantial rainfall. In Europe, these barrels are buried at sea. In both cases water will first corrode the metal then the cement and will relatively quickly expose the radioactive ions for leaching into the ground water or sea water. Because the U.S. burials are only a few feet deep, the contaminated water can readily intermix with streams, lakes and rivers, thus, entering the ecosphere. The rationale for this practice is the assumption that upon sufficient dilution the radioactivity becomes harmless. Some of the most serious nuclear wastes are cesium and strontium which are biologically similar to sodium and calcium. They have thirty year half-lives indicating that they should be isolated from the ecosphere for at least three hundred years (ten half-lives). At Bikini, the experts assumed that dilution had made the island inhabitable after decades in which no atomic explosions were performed, yet when the population was returned to the island its health was deleteriously effected. It has since been realized that plants and animal life biologically reconcentrate these radioactive elements back up to dangerous levels. Thus, the "safe" concentration of radioactive waste must be much lower than accepted values and a more durable substitute for cement is needed. In one aspect, the present invention presents a safe alternative to the cement-solidification of low level waste. U.S. Pat. No. 3,640,888 teaches the production of neutron sources by encapsulating californium-252 in glass using the steps of packing an open-ended vitreous tube with a porous powder of quartz having an organic liquid ion exchange material sorbed thereon, passing an aqueous solution containing californium-252 cation through the powdered quartz, drying and heating the powdered quartz and tube in air to oxidize and volatilize the organic liquid ion exchange material resulting in the non-volatile oxide of californium-252, and then fusing the tip and powder contents to form a vitreous body containing the californium-252 oxide. The patent, however, does not disclose, teach or suggest the use of porous glass or silica having aminoorganosilyloxy groups bonded to silicon and/or having hydrous metal oxides bonded to silicon through divalent oxygen linkages wherein hydroxyl groups are exchanges for radioactive anions in aqueous solution nor does it disclose or suggest any method or technique for concentrating and safely disposing of radioactive wastes. As will be apparent hereinafter from the various aspects of applicants' contributions to the art, there are provided novel methods to obtain novel compositions and articles for the containment of pernicious and dangerous radioactive materials over extraordinarily long periods of time. Unlike melting glass containment procedures, the methods of the invention need not involve any steps which would expose radioactive material to high temperatures, e.g., above about 900.degree. C., thereby eliminating the environmental hazard due to possible volatilization of radioactive material into the atmosphere. Belgian Pat. No. 839,705, issued July 16, 1976 and German Offenlegungsschrift No. 2,611,495, published July 10, 1976 correspond substantially to U.S. Pat. No. 4,110,096, issued Aug. 29, 1978 to Pedro B. Macedo named as an inventor herein and Theodore A. Litovitz. These patents and Offenlegungsschrift contain essentially the same disclosures but there is no disclosure of porous glass forms having sufficient ion exchange capabilities to bind practical amounts of radioactive anions to the glass to thereby concentrate and contain said radioactive anions in the manner taught herein. The presence of silica gel in the pores can be advantageous in this invention as providing more surface area and a higher proportion of silicon-bonded hydroxyl groups and ultimately higher amounts of organofunctionalsiloxy bonded hydroxyl groups or hydrated metal oxide groups for ion exchange with radioactive anions. U.S. Pat. No. 4,110,096 also discloses oxides or salts of heavy metals such as zirconium, lead, and thorium as dopants for the porous glass. The dopants are precipitated in the pores, the porous glass is washed in water or an acidic solution, dryed and sintered. However, there is no teaching or suggestion of binding a hydrous metal oxide to silicon of a porous glass or porous silica gel through divalent oxygen linkages prior to heating to sintering temperatures and thereafter reacting the resulting product with radioactive or toxic anions. In an article by Amphlett et al, entitled, "Synthetic Inorganic Ion-Exchange Materials-II Hydrous Zirconium Oxide And Other Oxides," J. Inorg. Nucl. Chem., Vol. 6, pp. 236 to 245 (1958), hydrous oxides, such as hydrous zirconium oxide, are disclosed as anion exchangers in acid and neutral solution and as cation exchangers in alkaline solution. The Amphlett et al article is herein incorporated by reference in its entirety. There is no teaching or suggestion in the Amphlett et al article of binding the hydrous metal oxide to the silicon atoms of a porous glass or porous silica gel through divalent oxygen linkages and reacting the resulting product with radioactive or toxic anions. U.S. Pat. No. 2,943,059 discloses porous glass ion exchange glass for removal of the radioactive ions cesium and strontium: anions are not specifically mentioned. The glass composition must contain at least 10% titanium dioxide, zirconium dioxide, or hafnium dioxide and at least 20% PO.sub.2.5 which combines in a unique manner with the above three oxides. The reference does not teach or render obvious a porous glass or silica gel having an SiO.sub.2 content of at least 82% by weight (SiO.sub.2 is an optional ingredient). The high silica content is needed in the present invention for obtaining a glass of high durability. Also, hydration of the hydrous metal oxide groups to form an anion exchange medium is not disclosed. Collapsing of the porous structure after ion exchange is not disclosed. U.S. Pat. No. 3,843,341 teaches forming porous glass beads which may contain more than 96% by weight silica and impregnating them with various metal salts, including nitrates, followed by heat decomposing the metal salt to form the corresponding metal oxide, e.g., titanium dioxide and tin oxide. The porous products may contain greater than 96% by weight silica. The product is used as a catalyst and the hydrated form is not specified. U.S. Pat. No. 3,923,688 teaches a high silica porous glass (at least 96% by weight SiO.sub.2) which can be used as a catalyst support, a filter, a cation exchanger, or an anion exchanger. When used as a catalyst support, zirconium oxide, which apparently has a catalytic effect and/or imparts thermal stability to the catalyst, is deposited within the pores of the glass by decomposition of zirconium nitrate. A porous glass having hydrous zirconium oxide bonded thereto is not disclosed as an anion exchanger. Production of a cation exchanger, however, is disclosed wherein sodium ions are placed on the surface of the porous glass. Conversion of the glass to an anion exchanger by attaching hydrous metal oxides to the glass surface is not disclosed. Also, treatment of the porous glass with an organosilane is disclosed. The product is disclosed as being also useful as a support for chromatographic separations. However, anion exchangers having hydrated aminoorganosilyloxy groups at the surface of the porous glass are not disclosed. Furthermore, removal of radioactive ions from aqueous radwaste solutions are not disclosed and there is no mention of collapsing the pores of the glass. U.S. Pat. No. 4,025,667 discloses porous glass having a coating of zirconium oxide thereon. The zirconium oxide coating may be silanized with an organofunctionalsilane coupling agent. The organofunctional portion of the silane coupling agent is used to immobilize enzymes. Removal of radioactive ions from radwastes is not disclosed. In addition, the pores of the porous glass are not subsequently collapsed. The reference does not teach hydrating the zirconium oxide coated glass to form an anion exchange medium having ion exchangeable hydroxyl groups attached to the zirconium ion. U.S. Pat. No. 3,969,261 discloses ion exchangers comprising porous silica gel beads, or other porous silica supports having a tertiary aminoalkylsilane bonded to oxygen of the silica gel to produce .tbd.SiOSi.tbd. bonds. These ion exchangers are made by reacting a (dialkylamino)alkoxysilane with the hydroxyl groups of a silica gel which can also contain hydroxides of titanium, zirconium and thorium. Neither removal of radioactive ions from radwastes nor subsequent collapsing the pores is disclosed. U.S. Pat. No. 4,118,316 discloses high silica porous glass beads of carefully controlled pore size which are reacted with an aminoalkylsilane, such as gamma-aminopropyltriethoxysilane. The resulting product is then quaternarized with a hydrocarbon halide or tertiary amine to introduce quaternary ammonium moieties on the beads. The quaternary ammonium moieties are used to separate cation polymers into molecular weight fractions. Hydration of the amino group of the aminoalkylsilane to produce anion exchange groups is not disclosed. Neither removal of radioactive ions nor subsequent collapsing of the pores of the porous glass is disclosed. The 1979-80 Pierce Handbook & General Catalog, pages 355-379 discloses controlled pore porous glass supports for chromatography and more specifically discloses silylated aminoalkyl controlled pore glass supports for solid phase sequencing of large peptide fragments. This reference, however, fails to disclose, teach or suggest the removal of radioactive anions from aqueous radwaste solutions or subsequent collapsing of the porous structure. U.S. Pat. No. 3,709,833 discloses porous silica glass forms which can contain zirconium oxide and which are primarily useful as catalyst supports. This patent does not disclose, teach or suggest that the porous silica glass forms disclosed therein can be used as anion exchangers nor does it disclose the removal of radioactive anions from aqueous radwaste solutions or the containerizing or burying of same underground or underwater or the collapsing of the pores containing the radioactive anions. U.S. Pat. No. 2,614,135 discloses porous silica gels treated with aminoorganosilane to produce a product suitable for removing oil from oil-polluted waters. U.S. Pat. 2,990,243 teaches the removal of fission products and/or plutonium from solutions by adsorbing the fission product and/or plutonium on a titanated silica gel. U.S. Pat. No. 2,893,824 also teaches a titanated silica gel. However, none of these references teach or suggest using a porous silica gel having an interconnected porous structure and having organofunctionalsiloxy groups bonded to silicon of the silica gel and/or hydrous polyvalent metal oxide groups bonded to silicon of the silica gel through divalent oxygen linkages as a backfill for nuclear waste disposal sites. None of the afore-mentioned prior art references disclose, teach or suggest the removal of radioactive anions from an aqueous radwaste through the use of a silica gel or a porous silica glass containing at least 82 mol percent silica and having hydrated organofunctionalsiloxy groups bonded to silicon of the glass or gel and/or a hydrated polyvalent metal oxide bonded to silicon of the glass or gel or deposited within the pores thereof. These references fail to disclose or suggest the containerizing and burial underground or underwater of the containerized silica gel or porous glass impregnated with radioactive anions internally bonded therein. The references also fail to disclose or suggest collapsing of the pores of the silica gel or porous glass to encase the radioactive anions therein to provide articles useful as radiation sources or suitable for burial. Furthermore, the references fail to disclose, teach or suggest the use of silica gel or porous glass containing the hydrated organofunctionalsiloxy groups and/or hydrated polyvalent metal oxides as backfill for stored nuclear waste materials. In addition, there is no disclosure or suggestion in any of these references of the ionic bonding of polyvalent metal oxides to porous silica glass or silica gel by first exchanging the protons of the silicon-bonded hydroxyls with an alkali metal, e.g., sodium, or ammonium, cations followed by replacement of the alkali metal or ammonium cations with the polyvalent metal cations. SUMMARY OF THE INVENTION The invention relates to the concentration of toxic, e.g., radioactive anions, such as chromate or molybdate anions, and/or corrosive anions, such as, CL.sup.-, and the like and immobilization of same for extremely long periods of time. This invention is based in part on the preparation of an ion exchange medium which is a porous silica glass or silica gel, having a large internal surface area which is modified with hydrous polyvalent metal oxides and/or organofunctionalsiloxy groups, so as to provide the capability of ionically bonding to said surface area radioactive ions that contact same. As used in the specification and claims, the term "hydrous polyvalent metal" means metal cations having a valence of at least two, whose oxides can be hydrated and which, in the hydrated form, exhibit anion exchange capabilities by removal of hydroxyl groups (--OH) bonded to the polyvalent metal cation. This invention also contemplates passing of a liquid stream to be purified through a bed of porous silicate glass anion exchange medium having interconnected pores and having hydrous organofunctionalsiloxy groups, preferably cationic in nature, e.g., aminoalkylsiloxy groups, and/or having hydrous polyvalent metal oxides bonded to silicon atoms of the porous glass through divalent oxygen linkages. Corrosive, toxic, poisonous, and/or radioactive anions of the liquid undergo an anion exchange reaction with said porous glass anion exchange medium whereby hydroxyl groups of the hydrated hydrous polyvalent metal oxide groups or hydroxyl groups bonded to the functional groups of said organofunctionalsiloxy groups are replaced by said corrosive, toxic, poisonous, and/or radioactive anions. When the organofunctionalsiloxy groups are anionic, e.g., carboxyorganosiloxy groups, radioactive cations in the liquid are removed. Some of the radioactive anions likely to be found in nuclear plant coolants are those containing radioactive iodide, chronium, molybdenum, and technetium. Non-radioactive, non-poisonous anions which corrode or foul processing equipment, such as chloride, sulphate, and nitrate, are also removed by the ion exchangers of the present invention. The resulting porous glass containing the radioactive anions and/or cations is then containerized in concrete or bitumen and disposed or underground or underwater. The resulting porous glass containing said radioactive anions and/or cations can then be heated to collapse the pores, if desired. The resulting collapsed product: (a) can be used as a radioactive source for sewage treatment or for medical and laboratory equipment or, (b) can be stored, containerized and/or disposed of by underground burial or burial at sea. In another aspect of the present invention, the porous, non-radioactive silicate glass and/or silica gel anion exchange medium is used alone or in combination with a porous glass or porous silica gel cation exchange medium as described herein and/or in the copending application Ser. Nos. 959,222, filed Nov. 9, 1978 and 39,595, filed May 16, 1979, as a backfill for underground nuclear waste disposal sites to protect against attack by water that may enter the site as by seepage or flood, and as an overpack within cannisters to protect the radwaste solids against attack by water. DETAILED DESCRIPTION OF THE INVENTION The novel methods of this invention for removing radioactive ions from media (usually an aqueous solution) containing them involves contacting said media with an ion exchange porous silica glass or silica gel which has bonded to the silicon of the inner surfaces of the pores thereof or otherwise immobilized therein non-radioactive hydrated organofunctional siloxy groups, preferably hydroxyl ammonium organosiloxy groups, e.g., hydroxyl ammonium alkylenesiloxy groups of the formula: ##STR1## or carboxyorganosiloxy groups, e.g., carboxyalkylenecarbonylaminoalkylenesiloxy groups. ##STR2## or non-radioactive, hydroxyl polyvalent metal groups, e.g., ##STR3## groups. In the above formulas, n is an integer of 1 to 18, preferably 3 to 8; the remaining two valences of the silicon atom to which the --C.sub.n H.sub.2n.sup.-- group is bonded are joined to a hydrocarbon radical, and/or through oxygen to silicon of the glass, and/or to another --C.sub.n H.sub.2n NH.sub.3.sup.+ OH.sup.- group in the case of the hydroxyl ammonium alkylenesiloxy groups or another --C.sub.n H.sub.2n NHC.sub.n H.sub.2n COO.sup.- H.sup.+ of the carboxyalkylenecarbonylaminoalkylenesiloxy groups; M is a polyvalent metal having a valence of 2 to 5, preferably 3 or 4, and most preferably is a tetravalent metal as shown in the formula, e.g., zirconium; and the remaining valences of M, not bonded to the .tbd.SiO-- or OH.sup.- groups as shown, are bonded ionically to OH.sup.- groups and/or through oxygen to silicon of the glass, or through oxygen to other M atoms. The pH of the radioactive aqueous solution being treated with the ion exchange porous glass or silica gel can range from about 4 to about 10, preferably from about 6 to about 8, for the hydroxyl ammonium organosiloxy group containing porous glass or silica gel, from about 4 to about 12, preferably about 6 to about 10, for the carboxyalkylenecarbonylaminoalkylenesiloxy group containing porous glass or silica gel; and from about 4 to about 10, preferably about 6 to about 8, for the hydroxyl polyvalent metal oxy group containing porous glass or silica gel. The radioactive aqueous solution, e.g., a coolant stream, contains radioactive anions and cations. The non-radioactive hydroxyl anions of the above-described group bonded on the surfaces of the porous glass or silica gel, in particular, those bonded to the inner surfaces of the myriad of interconnecting pores, are displaced by the radioactive anions of the radioactive aqueous solution forming such groups as .tbd.SiOSiC.sub.n H.sub.2n NH.sub.3.sup.+ I.sup.-, and/or .tbd.SiOM.sup.+ I.sup.-, (using radioactive iodine anion as an example). In the case of carboxyorganosiloxy groups, bonded to the inner surfaces of the myriad pores of the porous glass or silica gle, the non-radioactive carbonyloxy-bonded protons are displaced by radioactive cations of the radioactive aqueous solution forming such groups as .tbd.SiOSiC.sub.n H.sub.2n NHC(O)C.sub.n H.sub.2 COO.sup.31 Cs.sup.+ (using radioactive cesium cation as an example). Thus, the radioactive anions and/or cations are chemically bonded to silicon of the glass or silica gel through ammonium alkylenesiloxy linkages, or metal oxy linkages in the case of anions and oxycarbonylalkylenecarbonylaminoalkylenesiloxy linkages in the case of cations. The invention is especially suitable for "decontaminating" radioactive waste streams which contain minute but dangerous levels of anionic as well as cationic radioactive species therein, especially radioactive streams such as the radioactive primary coolant water of the boiling water reactor system, the radioactive secondary coolant water (which drives the turbine) in the pressurized water reactor system, and generally the liquid radwastes exemplified previously which accumulate during the operation of such systems, by contacting the ion exchange porous glass described herein with such streams thus chemically binding radioactive anionic species through ammonium organosiloxy groups or metal oxy groups, and binding radioactive cationic species through oxycarbonyloxyganosiloxy groups, to the Si of the glass. The preferred methods contemplated by the practice of the invention utilize the ion exchange silicate glass described herein rather than a silica gel since much lesser amounts of silica dissolve into the coolant water system from the glass than from the gel. This can be of special importance since the (primary and secondary) coolant waters are contained in a closed circulating system and a build-up of silica in these coolant waters is not desirable. (When liquid radwaste is to be discarded as in a river, the silica build-up does not appear to be a problem.) In addition, flowrates through a porous silicate glass are considerably higher than through a porous silica gel. However, the ion exchange silica gels can be more advantageous for use as backfilling materials pursuant to this invention. The ion exchange porous silica glass or gel can be made and used in the shape of various preforms, such as the small, short rods or small spheres or powders, or other particulate forms can be employed to remove radioactive anions or cations from highly dilute solutions of same by the present invention. For example, solutions containing as little as 1 ppt (parts per trillion) based on weight, i.e., 1 wt. part, radioactive anions or cations can be purified by contacting such solutions with the porous glass preforms in the manner described herein. This contact can take place in an ion exchange column packed with the ion exchange porous silicate glass preforms and the radioactive anion and cation-containing solution and stirred therein for a period of time that permits the maximum exchange of the radioactive anions of the solution for the non-radioactive hydroxyl anion attached to the silicon-bonded organofunctionalsilyloxy group or metal oxy groups and/or of the radioactive cations of the solution for the non-radioactive proton attached to the oxycarbonyl group of the carboxyalkylsiloxy group. Dilute solutions having less than 0.001 microcurie radioactivity per ml as well as more concentrated solutions, e.g., those having as high as 1 millicurie or more radioactivity per ml are efficiently treated by this invention. Radioactive materials which can be chemically bound or fixed in the porous ion exchange glass or silica gel matrix according to this invention include radioactive elements (naturally occuring isotopes and man-made isotopes and existing as liquids or solids dissolved or dispersed in liquids or gases), in the form of the anion, such as radioactive chromate, molybdate, technetium, iodide (I.sup.131) and in the form of negatively charged complexes containing radioactive metals such as iron. Especially suitable in the practice of the invention are radioactive wastes from nuclear reactors, spent reactor fuel reprocessing plants, spent fuel storage pools or other radioactive waste producing processes. Non-radioactive, corrosive anions which can be removed from waste streams such as these, or from other process streams by chemical bonding or fixation in the glass matrix include chloride, nitrate, and sulphate ions. The radioactive cations that can be removed by the carboxyalkylsiloxy modified porous silica glass or gel are those listed in the above-identified copending application, Ser. Nos. 959,222 and 39,595. In a typical nuclear reactor there are several sources of radwaste as described hereinabove that must be safely contained. These include highly dilute liquid waste streams which can contain dispersed radioactive solids as well as dissolved radioactive anions, concentrated liquid wastes which can contain radioactive cations, radioactive anions and radioactive solids (such wastes are the result of the boiling down of primary coolant containing boric acid as a chemical shim and the boiling down of used regeneration solutions from the regular ion exchange beds customarily used); and/or radioactive gases such as radioactive krypton and/or radioactive iodine. Therefore, one use of our invention is in the provision of a total radwaste disposal system wherein the porous ion exchange glass having interconnected pores and organofunctionalsiloxy groups bonded to silicon of the glass and/or having hydrous metal oxides bonded to silicon of the glass through divalent oxygen linkages is packed into an anion exchange column which preferably is a fusible glass column. It is preferred that the porous ion exchange glass be finely divided and sieved to a suitable size to maximize the rate of flow of the radwaste stream through and between the particles of the porous ion exchange glass and to also minimize the ion exchange time. First, the dilute radwaste stream is passed through the column and the radioactive anions in solution are anion exchanged with the hydroxyl groups of the silicon-bonded organofunctionalsiloxy groups and/or hydroxyl groups of the silicon-bonded hydrous metal oxide groups in the porous glass to chemically bond the radioactive anions to the glass. The liquid radwaste stream can also be contacted with a porous cation exchange glass such as those disclosed in the above-mentioned copending applications, Ser. Nos. 959,222 and 39,595 and/or the porous carboxyorganosiloxy glasses described herein. The contact with the porous cation exchange glass can be carried out in different beds of the same column that contains the porous anion exchange glass or in a separate column. If the dilute radwaste stream is to be re-used as primary coolant, it is conventional to add lithium ions as a corrosion inhibitor. Therefore, it can be advantageous to also utilize a porous cation exchange glass having silicon-bonded lithium oxy groups, preferably in a separate column or bed, so that lithium ions (which do not become radioactive as do sodium ions) are released to the coolant stream as radioactive cations are removed from it. Additionally, dispersed radioactive solids in the dilute radwaste stream can be mechanically filtered onto the porous anion and/or cation exchange glass particles in the column or columns as the stream percolates through and between the particles. In order to maintain the ratios of solids in the radwaste stream to the porous ion exchange glass small enough to maintain the filtering action as the solids accumulate on the porous ion exchange glass particles, fresh porous ion exchange glass particles can be added to the column or columns, from time to time or the bed can be up-flowed. After the column has been exhausted of its ion exchange capacity by the dilute liquid radwaste stream, it can be dried and, if desired and available, a concentrated liquid radwaste (containing concentrated boric acid, for example, at a temperature of 100.degree. C.) can be added to the column. Thus, the pores of the porous ion exchange glass can be further stuffed with the radioactive solids, cations and anions contained by the concentrated radwaste. The particles can be dried to deposit the radioactive solids, cations and anions within the pores of the porous glass using techniques taught in U.S. Pat. No. 4,110,096. Thereafter, the column can be evacuated and radioactive gases can be introduced and together they are heated to collapse the pores of the loaded porous ion exchange glass and to collapse the glass column thereby immobilizing and containing the exchanged radioactive anions, the radioactive solids on the exterior of the porous glass particles, the radioactive solids, anions and/or cations deposited in the pores of the porous glass and the radioactive gas contained by the glass column. Suitable pressure differentials can be used to facilitate the collapsing of the glass column. Heating can be continued to cause the porous glass particles to stick to each other to further trap interstitial radioactive solids between the particles. Upon cooling there results a highly durable solid which effectively contains the radioactive waste introduced into the glass column. Some of the nuclear reactor streams may be acidic because some elements in the radwaste appear as cations, e.g., rubidium, strontium, the lanthanides, and actinides cations, which, of course, have to be immobilized also. One way to accomplish this is to pass the acidic radwaste stream through a porous glass cation exchange column, collapsing the pores, and disposing of the collapsed product all as described in said copending applications Ser. Nos. 39,595 and 959,222. This invention can be employed for concentrating and immobilizing radioactive anions and/or cations in a glass for extremely long time storage. When applicable, silicate glass loaded with radioactive anions bonded to silicon through organofunctional-siloxy linkages or through hydrous polyvalent metal oxy linkages, and/or cations bonded to silicon of the glass or gel through oxycarbonylorganosiloxy groups, can be appropriately packaged in containers, e.g., steel, concrete, urea-formaldehyde formulations, bitumen, etc., and buried beneath the earth's surface or dumped into the ocean. Alternatively, the radioactivity of the sintered glass containing the bonded radioactive anions can be utilized in suitable devices or instruments for a variety of purposes, such as, destroying microorganisms, e.g., in the preservation of food, or in sterilizing sewage sludge or for any other purpose where radioactivity can be employed constructively. The typical concentrations of radioactive anions and cations in a typical reactor cooling water are given in Table 1 hereinabove. A typical PWR coolant water includes the following non-radioactive materials: TABLE 2 ______________________________________ Boron up to 4000 ppm* Lithium as .sup.7 Li, ppm 0.2 to 6 ppm Total silica as SiO.sub.2 200 ppb** (max) Chlorides as Cl.sup.- 0.2 ppm (max) Hydrogen as H.sub.2, Std 20-40 cc/Kg H.sub.2 O Total Dissolved Gases, 100 Std cc/Kg H.sub.2 O Total suspended solids 1 ppm (max) ______________________________________ ppm = parts per million *ppb = parts per billion Advantages of the present invention include the fact that conventional organic ion-exchange resins used in PWR and BWR systems to "decontaminate" coolant water and radwaste streams decompose or lose their stability during operation especially when the resin acquires or is exposed to radiation of certain levels of intensity, e.g., 10.sup.8 rad. Such decomposition or loss of stability is not manifest in the utilization of the ion exchange porous silicate glasses or silica gels described herein. Additionally, it has been observed that one unit volume of said porous ion exchange glass or gel can "concentrate" the radioactive ionic species contained in upwards of thousands, possibly millions of unit volumes of BWR coolant and/or PWR coolant and/or liquid radwaste on a calculated basis. With molecular stuffing techniques wherein maximum concentration is manifest by merely introducing and causing precipitation of ionic species from two or perhaps three unit volumes of liquid radwaste per unit volume of said glass. Also, the ionic exchange porous glass or gel in particulate form, e.g., bead, powder, flakes, etc., conveniently containerized, for example, in a column is highly efficient inasmuch as it allows much greater throughputs of PWR coolant, BWR coolant, and/or liquid radwaste which contacts a greater surface area of glass than is the case when utilizing comparably dimensioned organic ionic exchange resin columns. Silicate glass as formed by the phase-separation and acid leaching process as described more fully hereinafter contains large amounts of silicon-bonded hydroxyl groups and so does silica gel. These hydroxyl groups exchange readily with other anions only under highly acidic conditions. Because of this, it is difficult or impractical to utilize such glasses to process most types of radioactive wastes especially those of the type that decompose, precipitate or are otherwise adversely affected by acidic agents. Furthermore, in most cases, radioactive wastes, such as those resulting from reactor operation are highly dilute aqueous solutions. The adjustment of such solutions to a low enough pH to provide effective ion exchange with silicon-bonded hydroxyl groups of the glass requires the addition of large amounts of an acidic substance and, in those cases where the reclaimed water is to be recycled back to the reactor, the pH needs to be subsequently raised again which requires the addition of large amounts of alkaline materials. Thus, ion exchange treatment techniques utilizing porous silicate glass or silica gel containing silicon-bonded hydroxyl groups and no other ion exchange groups is at best uneconomical and impractical. In contrast, it has been unexpectedly found that, when the protons of the silicon-bonded hydroxyl groups are replaced with hydroxyl ammonium organosiloxy groups and/or hydrous polyvalent metal oxide groups, the radioactive anions readily exchange with the hydroxyl groups of the hydroxyl ammonium organosiloxy groups and/or the hydroxyl groups of the hydrated metal oxide groups at acid, neutral or moderately alkaline pH. Thus, it is unnecessary to adjust the pH of the radioactive material being impregnated into the pores of the porous ion exchange silicate glass or silica gel. In a similar manner, the carboxyorganosiloxy porous glass or silica gel can be used to remove radioactive cations from radioactive solutions without special pH adjustments. It has also been unexpectedly found that radioactive anions can be substantially completely removed from very dilute solutions or dispersions thereof in water. For example, water containing radioactive anions can be purified down to a few parts per billion of radioactive anions by treatment with porous silicate glass having the above-described hydroxyl-containing groups bonded to silicon linkages. It has also been unexpectedly found that the impregnation of porous ion exchange silicate glass requires a relatively short period of time for effecting reasonably extensive ion exchange. The porous ion exchange silica glass or gel loaded with ionicly bound radioactive anions and/or cations resulting from the present invention, can be stored, or packaged or "containerized" in suitable containers or forms, i.e., in concrete, metal, or plastic containers or disposed of as by underground burial or by burial at sea, and/or the pores thereof can be collapsed by heating thereby fixing and/or mechanically encapsulating the radioactive anions within a resultant chemically inert, non-porous glass product. When heating to collapse the pores, the impregnated porous glass can be first dried to remove liquid, such as any solvents and/or volatile materials (water) in the pores and/or it can be washed to remove any solvents or unreacted materials residing within the pores or on the surface of the glass followed by drying to remove the washing solvent. The temperature used for drying can be between 50.degree. C. and 200.degree. C. and higher and lower temperatures can be used. The sintering or pore collapsing temperature used depends upon the glass composition and usually falls into the range of about 800.degree. C. to about 1000.degree. C. although higher or lower temperatures can be used depending upon the particular glass composition. The sintered silicate glass or silica gel compositions or articles of this invention have high chemical durability to aqueous corrosion and have sufficiently low radioisotope diffusion coefficient values to provide protection of the environment from the release of radioactive material such as radioactive isotopes, nuclear waste materials, etc., which are chemically bound and/or physically encapsulated or entrapped therein. Such glass or silica gel compositions are characterized by at least 82 mol percent of SiO.sub.2. The glass compositions containing the radioactive anions or cations according to this invention are characterized by a radiation activity illustratively above one millicurie, preferably greater than one curie, per cubic centimeter of said compositions. When highly dilute radwastes are treated with the porous silicate glass or silica gel pursuant to this invention for the purpose of concentrating and immobilizing the radwaste for storage, the radiation activity of the resulting loaded porous silicate glass may not reach the level of one millicurie per cubic centimeter of the porous silicate glass and may remain below 1 microcurie per cc., when it becomes expedient for other reasons to store, or package in suitable containers, or dispose of as by burial, and/or to collapse the pores of the glass. In concentrating and immobilizing radioactive anions in dilute radwastes, the porous silicate glass can be loaded up to 10 microcuries per cc. or more but usually is loaded up to 1 microcurie per cc. of said porous glass. The radioactive material is typically in the form of radioactive anions that: (a) are ionically bonded to the nitrogen atoms of hydrated aminoalkylsiloxy groups which, in turn, are bonded to the silicon atoms of the porous glass, as illustrated by the formula: ##STR4## for the anion I.sup.-.sub.131 or (b) have replaced hydroxyl groups of a silicon-bonded hydrated hydrous polyvalent metal oxide, i.e., are ionically bonded to the polyvalent metal as illustrated by the formulas: ##STR5## and/or ##STR6## represents a crystal of zirconia deposited within the pores of the silica glass or gel and m is an integer. In the case of carboxyalkylenecarbonylaminoalkylenesiloxy groups bonded to silicon of the porous glass or silica gel, radioactive cations become bonded ionically to the carbonyloxy group as illustrated by the formula: ##STR7## for the cation Cs.sup.+.sub.137. In one aspect, the amount of radioactive material contained in the resulting radioactively loaded glass composition is at least 1 ppb (part per billion based on weight). In the practice of the novel methods whereby liquid radwaste is "decontaminated", a plurality, of the radioactive species listed herein become bonded to the silicon of the glass through organosiloxy groups or metal oxy groups. The porous silica glass and gel compositions should contain at least 82 mol percent SiO.sub.2, most preferably greater than 89 mol percent SiO.sub.2, each on a dry basis, to: (a) provide high chemical durability to aqueous corrosion, and (b) provide low radioisotope diffusion coefficient values. Some of the organofunctionalsiloxy groups, e.g., hydroxyl ammoniumorganosiloxy groups or carboxyorganosiloxy groups, or hydroxyl polyvalent metal groups can be bonded through oxy groups to boron of the silica glass. After ion exchange with radioactive ions, therefore, some of the radioactive ions are ionically bonded to boron of the glass through the above-mentioned groups. In some cases, a large proportion of the polyvalent metal oxide is simply deposited within the pores of the silica glass or gel with little, if any, bonding of the polyvalent metal by oxy linkages to silicon of the glass or gel. It is believed that, based on current observations, at least some of the polyvalent metal atoms are joined to silicon by oxy linkages in most cases. From a practical standpoint, the upper limit of radioactive material contained in the silicate glass or silica gel composition will be governed, to a degree, by such factors as: the SiO.sub.2 concentration in the composition, by the concentration and type of other ingredients which may be present in the composition such as B.sub.2 O.sub.3, Al.sub.2 O.sub.3, TiO.sub.2, P.sub.2 O.sub.5, zirconia, thorium oxide, lead oxide, alkali metal oxides and GeO.sub.2, and/or other network formers, by the type of radioactive material, by the volume fraction of the porous glass or silica gel precursor, by the various techniques employed to fix and/or encapsulate the radioactive material in the composition and other factors. A typical range of radioactive anion content (or cation content in the case of the carboxyalkylsiloxy-containing silica glass or gel) is about 1 ppb to about 20,000 ppm, preferably about 10 ppb to about 1000 ppm, in the porous glass. In one embodiment of this invention, the silicate glass containing the radioactive anions bonded to silicon pursuant to this invention can be further contained within a collapsed glass article of a variety of shapes or forms, e.g., glass tube, having enhanced containment properties and characterized by an outer glass clad whose composition is at least about 90 mol percent silica, preferably greater than about 95 mol percent, and whose inner core contains the radioactive materials. The high silica content of the glass clad imparts to the articles a considerably greater chemical durability and resistance to leaching by ground waters. The inner core has a lower silica concentration of the order of at least about 70 mol percent silica, preferably about 82 mol percent, and most preferably about 89 mol percent, based on dry weights. The pores of the inner core can also be collapsed, if desired. In this embodiment the porous ion exchange silica glass or gel loaded with inoicly bound radioactive anions and/or cations resulting from the methods of the present invention, are placed, before or after drying and/or pore collapse, within a fusible glass tube or container, preferably made of high silica glass. In the case, mentioned hereinbefore, wherein the porous ion exchange silica glass or gel forms are contained within a fusible glass tube thereby forming an ion exchange column, the resulting loaded column after ion exchange can be heated as is to first dry, then collapse the pores of said forms and then collapse the tube. In either case, the outer fusible glass tube or container is collapsed around the core of loaded glass or silica gel preforms by heating to a sufficiently high temperature, e.g., 1200.degree. C. or lower to 1500.degree. C. or higher. Various techniques such as applying vacuum or pressure to facilitate collapse of the tube or container can be used as are disclosed in copending application Ser. No. 959,220, filed Nov. 9, 1978 by Macedo et al, and the continuation-in-part application, Ser. No. 34,567, the disclosures of which are incorporated herein by reference. The porous ion exchange silicate glass or gel having interconnected pores and having organofunctionalsiloxy groups bonded to silicon of the glass or gel and/or having hydrous polyvalent metal oxides bonded to silicon of the glass or gel through divalent oxygen linkages can be used as a backfill for underground radioactive waste disposal sites and as an overpack material in the cannister, both to prevent or retard the dissemination of radioactive materials into the environment. The porous cation exchange silica glasses or gels of copending application Ser. Nos. 959,222, filed Nov. 9, 1978 and 39,595, filed May 16, 1979 can also be used mixed with the porous anion exchange glasses or gels described herein or can be used in separate sections of the backfill area. In burying radioactive nuclear waste, particularly high level nuclear waste, typically a mine or mine shaft are dug which are large enough for people and equipment to transport and bury the nuclear waste containers in the mine. Once the nuclear waste cylinders, such as high level nuclear waste glass cylinders, or other solidified nuclear waste system are in position in the mine, the mine and mine shaft are closed up by backfilling. Bentonite has been reported to serve as a good backfill material because it can act as an ion exchanger which can slow down the diffusion of ions from the nuclear waste container caused by the penetration of water into the material container. However, bentonite only acts as an ion exchanger for cations. Overpack material is placed either adjacent to the high-level radioactive waste solids inside the cannister or inside a second cannister which encloses the first cannister containing the radwaste solid. The overpack material can be disposed in the first or second cannister or both and serves the same functions as the backfill by acting as a buffering material, a source of silica and an ion exchange material for the radioactive isotopes as desdribed below. Therefore, the word "backfill" throughout this description refers both generally to the overpack material and backfill material. The porous glass or silica gel having interconnected pores and aminoorganosiloxy groups bonded to silicon and/or having hydrous metal oxides bonded to silicon through divalent oxygen linkages act as anion exchangers and can also act as cation exchangers. The hydroxyl groups bonded to the organofunctionalsiloxy groups and/or metal oxy groups ion exchange with the radioactive anions. However, unreacted silicon-bonded hydroxyl groups of the glass will serve as cation exchangers by exchanging the hydrogen atom of the hydroxyl group for the radioactive cation. The proportion of silicon bonded hydroxyl groups to the organofunctionalsiloxy groups and/or metal oxy groups in the glass can be controlled as described above. Furthermore, as disclosed in the above-mentioned article by Amphlett et al insoluble hydrous oxides such as zirconium oxide, thorium oxide, and titanium oxide behave as anion exchangers in acid and neutral solution and cation exchangers in alkaline solution. In addition, to achieve both cation and anion exchange capacity: porous glass or silica gel cation exchangers such as disclosed in copending U.S. application Ser. No. 959,222 and copending U.S. application Ser. No. 39,595 can be used as a backfill with the porous glass or silica gel anion exchangers having organofunctionalsiloxy groups and/or hydrous metal oxy groups. Additionally, porous glass or porous silica gel having an interconnected porous structure and having substantially only hydroxyl groups bonded to the surface silicon atoms can be used as a backfill. The use of a porous ion exchange silicate glass or silica gel as a backfill for nuclear waste disposal sites has the advantage over backfilling with dirt or bentonite of impending the attack of the nuclear waste containers by water. First, if the porous glass or porous silica gel is originally backfilled into the mine in a very dry state, it will swell when contacted by water flowing towards the nuclear waste containers thereby closing up any holes or passage ways through the porous glass backfill. Second, as water percolates through the porous glass or silica gel, the silica will dissolve and form a saturated solution. Therefore, if the water penetrates through the backfill and contacts the radioactive nuclear waste glass: the dissolution rate of the radioactive nuclear waste glass would be very slow, if at all. The radioactive nuclear waste glass may be at a slightly higher temperature than the backfill. The higher glass temperature would heat the in-flowing water rendering it slightly unsaturated. The nuclear waste glass could then dissolve in the unsaturated solution but its dissolution rate would be very significantly lower than with a dirt or bentonite backfill. Of course, if the water flow was so great as to result in an unsaturated solution, the nuclear waste glass would be attacked even if its temperature were the same or lower than the temperature of the backfill porous glass or porous silica gel. However, as discussed above, once the nuclear waste glass or silica gel is attacked and dissolved: the radioactive anions and/or cations being leached from it would be ion exchanged with the porous silica glass or silica gel. Thus, there would be a major delay between the dissolution of the nuclear waste glass and the motion of ions out of the burial site. Furthermore, because the porous glass or porous silica gel can act as both a cation and anion exchanger it will buffer the water to a neutral pH thereby minimizing the dissolution rate of the glass. The ability to trap radioactive anions migrating from the nuclear waste mine is very important. Technetium is the most serious long term problem in radioactive nuclear waste disposal sites because of its very long half-life (over 200,000 years). However, backfilling with a porous anion exchange silicate glass or silica gel having an interconnected porous structure and having organofunctionalsiloxy group and/or hydrous metal oxide groups bonded to silicon of the porous glass or silica gel impedes the migration of technetium anions from the waste site by anion exchanging the radioactive technetium for the non-radioactive hydroxyl groups of the organofunctionalsiloxy groups and/or hydrous metal oxide groups. The lower liquid flow rates through porous ion exchange silica gels, discussed above, are advantageous in backfilling applications even though they are less advatangeous than the porous glasses in the treatment of a nuclear waste process stream. The lower flow rates obtained with the porous silica serve to slow down the attack by water flowing toward the buried nuclear waste and also slow down the outward flow of water which has penetrated and attacked the nuclear waste. Porous silica gels are commercially available and can be modified to have anion exchange properties as described above in connection with the porous silicate glass anion exchange media. The literature adequately describes the preparation of the porous silicate glass compositions. Suitable glass compositions which may be utilized in the novel methods generally contain SiO.sub.2 as a major component, have a large surface area and have large amounts of silicon-bonded hydroxyl groups on their surfaces. In the practice of various embodiments of the invention the SiO.sub.2 content of the porous glass or silica gel is at least about 82 mol percent SiO.sub.2, preferably at least about 89 mol percent SiO.sub.2. Such glasses are described in the literature, see U.S. Pat. Nos. 2,106,744; 2,215,036; 2,221,709; 2,272,342; 2,326,059; 2,336,227; 2,340,013; 4,110,093 and 4,110,096, for example. The disclosures of the last two mentioned patents are incorporated hereby by reference. The porous silicate glass compositions can also be prepared in the manner described in U.S. Pat. No. 3,147,225 by forming silicate glass frit particles, dropping them through a radiant heating zone wherein they become fluid while free falling and assume a generally spherical shape due to surface tension forces and thereafter cooling them to retain their glassy nature and spherical shape. In general, the porous silicate glass can be made by melting an alkali-borosilicate glass, phase-separating it into two interconnected glass phases and leaching one of the phases, i.e., the boron oxide and alkali metal oxide phase, to leave behind a porous skeleton comprised mainly of the remaining high silicate glass phase. The principal property of the porous glass is that when formed it contains a large inner surface area covered by silicon-bonded hydroxyl groups. We prefer to use porous glass made by phase-separation and leaching because it can be made with a high surface area per unit volume and has small pore sizes to give a high concentration of silicon-bonded hydroxyl surface groups, and because the process of leaching to form the pores leaves residues of hydrolyzed silica groups in the pores thus increasing the number of silicon-bonded hydroxyl surface groups present. The porous silicate glass may be in the shape of a suitable geometric or non-geometric container such as a cylinder, or it may be in particulate form such as powder, beads, spheroid, etc., desirably contained in a suitable container or conforming to the shape of the container such as a column, nylon bag, cube, plate-like membrane, cylinder, sphere, etc., and thereafter (or prior thereto) treated so that the protons of the silcon-bonded hydroxyl groups are replaced with hydroxyl ammonium organosiloxy groups and/or hydrous metal oxide groups and/or carboxyorganosiloxy groups. As mentioned above the hydrous polyvalent metal oxy groups may be simply deposited within the pores with little bonding to silicon. The proportion or concentration of silicon-bonded hydroxyl groups on the porous silicate glass surfaces can be regulated by regulating the surface area of the porous silicate glass during its preparation as is well-known in the art. Generally, the surface area is controlled by the temperature and time at temperature during the phase-separation portion of the preparation of the porous silicate glass. Thus, the longer the time at the temperature and/or the higher the temperature used in the phase-separation, the greater the pore diameter and, therefore, the smaller the surface area per gram in the resulting porous silicate glass. Conversely, the surface area, and thus the proportion of surface .tbd.SiOH groups available for reaction with the organofunctionalsilane and/or hydrous metal oxide can be increased by lowering the time and/or temperature of the heat treatment used to induce phase-separation. The silicon content of the borate rich phase formed in the manufacture of porous glass precipitates as silica gel during the leaching of the porous glass and this precipitate greatly increases the surface area and the proportion of silicon-bonded hydroxyl groups available for reaction with the organofunctionalsilane or hydrous metal oxide. Thus, an additional technique for increasing the surface area and the proportion of silicon-bonded hydroxyl groups is to start with a composition which will produce large quantitites of a silica gel precipitate. This can be accomplished by increasing the amount of silica initially used in the composition from which the glass is made. Any other techniques known by the skilled worker for increasing, or decreasing if desired, the proportion of surface .tbd.SiOH groups can be used to provide a porous glass having the desired proportion of surface silicon-bonded hydroxyl groups available for reaction with the organofunctionalsilanes and/or hydrous polyvalent metal oxides. The above-described porous silicate glass having surface hydroxyl groups bonded to silicon is then converted into the anion exchangers utilized in the processes of the present invention. In a first approach, a water soluble organofunctional silane is reacted with the silicon-bonded hydroxyl groups of the glass. Suitable and preferable water soluble organofunctional silanes useful in the present invention are presented by the structural formula: EQU [HR"NC.sub.n H.sub.2n ].sub.c Si(OR).sub.a (R').sub.b wherein a is in integer of 1 through 3, b is an integer of 0 through 2, c is an integer of 1 through 3, preferably 1, a+b+c is equal to four, n is an integer from 1 through 10, preferably 2 to 4, R is an alkyl group, such as a C.sub.1 -C.sub.6 alkyl group, and preferably is methyl or ethyl, and R' is a monovalent hydrocarbon group, preferably having 1 to 10 carbon atoms, R" is hydrogen, alkyl of 1 to 10 carbon atoms or aminoalkyl, H.sub.2 NC.sub.n H.sub.2n --, or carboxyalkylcarbonyl HOOCC.sub.n H.sub.2n C(O).sup.-. Exemplary of the monovalent hydrocarbon groups that are represented by R' are the C.sub.1 -C.sub.10 alkyl groups (for example the methyl, ethyl, isopropyl, and n-butyl groups); the aryl groups (for example the phenyl and naphthyl groups); the aralkyl groups (for example, the benzyl and the phenylethyl groups); the alkaryl groups (for example, the styryl, tolyl, n-hexylphenyl groups), and the cycloalkyl groups (for example, the cyclohexyl group). Preferably R' is an alkyl group. Methyl and ethyl are the most preferred R' groups. However, other organofunctional silanes having groups capable of anion exchange reaction and having groups which are readily hydrolyzable can be utilized. For example, water soluble organofunctional silanes having more than one amino groups can be used. Hydrolyzable organofunctional silanes of the above formula are commercially available as "silane coupling agents." The preferred water soluble organofunctional silanes for use in the present invention are gamma-aminopropyltriethoxysilane and N-beta-(aminoethyl)gamma-aminopropyltrimethoxy silane. These two compounds are known commercially as Union Carbide's A-1100 and A-1120 silane coupling agents, respectively. The --OR in the above formula are readily hydrolyzable and readily react with the silicon-bonded hydroxyl groups on the glass surfaces, for example, as represented by: ##STR8## wherein R, R" and n are as defined hereinabove and the remaining valences of the silane silicon not bonded to the C.sub.n H.sub.2n group or the --OR group or glass are bonded to hydrocarbon groups, R', and/or bonded to other silicon atoms of the glass through divalent oxygen (resulting from reaction of second or third --OR groups) if present in the silane with silicon-bonded hydroxyl groups of the glass. The reaction is preferably carried out in the presence of ammonium hydroxide at a pH in the range of from about 7 to about 11. The porous glass is soaked, for example, in an aqueous ammonium hydroxide solution of the aminoorganosilane for about 1 hour to about 24 hours at a temperature in the range of 0.degree. C. to 30.degree. C. The ammoniacal solution typically contains from 1% to 10% by weight of the organofunctional silane. Soaking at higher temperatures decreases the stability of the silane. The soaked rods are then dried under vacuum at a temperature of from about 0.degree. C. to about 30.degree. C. for between about 2 hours to 24 hours. The dried rods are then heated from the drying temperature to between about 200.degree. C. to 450.degree. C. to secure the bonding between the silane and the glass surface. Hydration of the amino group, i.e., where R" is hydrogen or alkyl, can then be accomplished by contacting with water or by contacting with the aqueous solution to be treated; said hydration being represented by: ##STR9## In the case where R" is aminoalkyl --C.sub.n H.sub.2n NH.sub.2, the hydration is represented by: ##STR10## Where R" is carboxyalkyl, the carboxy group may be converted to an ester or salt group before or during the reaction with the silicon-bonded hydroxyl groups of the glass and then reconverted back to the carboxy group, --COO.sup.- H.sup.+, by slight to moderate acidification. In a second approach, insoluble hydrous inorganic polyvalent metal oxides which exhibit anion exchange properties involving surface hydroxyl groups are incorporated into the pores of the porous glass structure. Exemplary of the insoluble hydrous metal oxides are ZrO.sub.2, PbO.sub.2, ThO.sub.2, TiO.sub.2, Mg.sub.2 O, Al.sub.2 O.sub.3, and SnO.sub.2. Of these, ZrO.sub.2 and PbO.sub.2 are preferred. In this approach, the soluble nitrate salt of the hydrous metal oxide, such as Zr(NO.sub.3).sub.4 is deposited inside the porous glass by the molecular stuffing process as described in detail in U.S. Pat. No. 4,110,096 by P. S. Macedo and T. A. Litovitz herein incorporated by reference in its entirety. Various guidelines for stuffing porous glass rods are set forth at column 16, line 45 to column 17, line 29. Briefly the stuffing process would involve immersing the porous glass in an aqueous solution of the metal nitrate to diffuse the metal nitrate into the pores and drying in an oven to precipitate the metal nitrates. Drying temperatures in the range of about 100.degree. C. to about 150.degree. C. and drying times of about 1.5 hours to about 12 hours are suitable. The concentration of the metal nitrate in the aqueous solution is typically between about 2% to 70% by weight based on the weight of the solution. During the molecular stuffing process at least a portion of the metal nitrate, such as zirconium nitrate, reacts with the glass to replace the silicon-bonded hydroxyl group. This reaction in its simplest form can be represented by: ##STR11## In the above formula, x is an integer of 2 to 4, preferably 3 through 4, and represents the valence of the metal cation, M. Of course more than one nitrate group --NO.sub.3 of the polyvalent metal nitrate molecule can react with more than one silicon-bonded hydroxyl group such that the polyvalent metal is bonded through oxy groups to more than one silicon atom of the glass. The silicon-bonded (or boron-bonded) nitrate is then decomposed by heating the stuffed porous glass at a temperature from about 200.degree. C. to about 700.degree. C. for about 0.5 to 12 hrs. The portion of the precipitated metal nitrate which does not react with the glass and which is entrapped within the pores is also converted to the oxide during the nitrate decomposition step. The oxides are then hydrated by treatment with water anion exchangeable hydroxyl groups to the metal as represented by the formula: ##STR12## wherein x and M are as previously defined, a is an integer of 1 to 3, b is an integer of 1 to 3 and (a+b) is an integer not greater than x and (x-a-b)+represents the remaining valence of M not bonded through oxygen to silicon as well as similar reactions involving boron sites on the glass or gel surface. Alternatively, the hydration can be performed by the aqueous solution to be treated, such as the radioactive waste stream. Alternatively, the anchoring of the insoluble polyvalent metal salts to the silica matrix of the porous glass or silica gel can be accomplished by first reacting the porous glass or porous silica gel with the hydroxide of an alkali metal, a Group Ib metal and/or ammonium to bond the cations of said metal or ammonium to silicon atoms of said glass or silica gel through divalent oxygen linkages and then reacting the resulting intermediate porous cation exchange silica glass or gel (containing alkali metal, Group Ib metal and/or ammonium cations bonded to silicon of the glass or gel through oxy linkages) with the polyvalent metal nitrate. Suitable alkali metal, Group IB and/or ammonium cation exchange mediums and method for making them are disclosed in copending applications Ser. No. 39,595, filed May 16, 1979 and Ser. No. 959,222, filed Nov. 9, 1979. The disclosures of both applications relate to both the identity and methods for making the porous glass or porous silica gel cation exchangers are incorporated herein by reference. The preferred intermediate cation exchange porous glass or porous silica gel has sodium ions bonded to silicon of the glass or gel through divalent oxygen linkages. It can be prepared, for example, by replacing the protons of the .tbd.SiOH groups of the porous glass or porous silica gel with sodium derived from a sodium salt, such as NaNO.sub.3 in an NH.sub.4 OH medium. The porous intermediate cation exchange glass or silica gel can be easily reacted with the nitrate salt of the hydrous polyvalent metal oxide in an acidic aqueous medium having a pH of from about 0.5 to about 6. In the reaction, metal nitrate groups, --M(NO.sub.3).sub.x-1, are exchanged for said alkali metal, Group Ib metal and/or ammonium cations bonded to silicon atoms of the glass through divalent oxygen linkages to anchor or bond the polyvalent metal nitrate group to the silica glass or gel structure, which can be represented as: ##STR13## M, x, a and b are as defined above. The nitrate groups attached to the metal cation, M, are replaced by hydroxyl groups by treating the M(NO.sub.3).sub.x-1 exchanged rod with an aqueous ammonium hydroxide solution at a temperature of from about 10.degree. C. to about 60.degree. C. for between about 1 hour and 12 hours to yield a porous silica glass or porous silica gel having anion exchange properties involving surface hydroxyl groups. Subsequently, the porous glass or silica gel is preferably washed with water to remove excess ammonium hydroxide. Alternatively, the nitrate could also be decomposed to the oxide and the oxide then hydrated as described as the second approach hereinabove. The proportions of anion exchangeable hydroxyl groups bonded to silicon of the porous glass or silica gel through the organofunctionalsiloxy groups and/or through the metal oxy groups can be replaced by several techniques. Of course, the proportion of silicon-bonded hydroxyl groups in the porous glass or silica gel will determine generally the maximum amount of silicon-bonded organofunctionalsiloxy groups and/or polyvalent metal oxy groups obtainable. The amount of these groups, in turn, will determine the maximum amount of said anion-exchangeable hydroxyl groups obtainable. Longer times of contact of the organofunctional silane and/or metal nitrate with the porous glass or silica gel will increase the proportion of silicon-bonded organofunctionalsiloxy groups and polyvalent metal oxy groups, respectively. Also, the smaller the particle size of the porous glass or silica gel, the greater the proportion of the silicon-bonded organofunctionalsiloxy and/or metal oxy groups within a given time. Longer times of contact with the ammonium hydroxide during the hydration step will increase the proportion of said anion-exchangeable hydroxyl groups. Any other suitable technique can be used to regulate the proportion of anion-exchangeable hydroxyl groups bonded to silicon of the porous glass or silica gel through the organofunctionalsiloxy groups and/or through the metal oxy groups to the desired level. The porous ion exchange silicate glass contains about 0.1 mol percent to about 10 mol percent, preferably about 0.5 mol percent to about 4 mol percent of non-radioactive anion exchangeable hydroxyl groups bonded to said organofunctionalsiloxy and/or polyvalent metal oxy groups or cation exchangeable protons bonded to oxycarbonylalkyleneaminoalkylenesiloxy groups. The surface to weight ratios for the porous silicate glass employed in our invention are at least about 0.1 m.sup.2 /g to at least several thousand m.sup.2 /g, e.g., 10,000 m.sup.2 /g, preferably at least upwards of 100 m.sup.2 /g. Desirably, the surface to weight ratio of the starting silicate glass ranges from about 5 to about 1500 m.sup.2 /g.
	claims	1. A method of reflective x-ray diffraction measurement of the crystal orientation of a sample, comprising:using a low power x-ray source, and detector, rigidly coupled together in a combination for coordinated rotation over the sample;using a polycapillary collimating x-ray optic coupled to the x-ray source to produce a parallel x-ray beam on the sample from the x-ray source;locating the sample in a sample movement path in and out of which the sample is moveable during measurement;taking reflective x-ray diffraction data at multiple, discrete and unique phi angles wherein the detector detects diffracted x-rays from the sample wherein the sample, and the source/detector combination are re-positioned relative to each other at each of said multiple phi angles, whereby said multiple phi angles are defined by a rotation, over a range of at least twenty degrees, about an axis projecting out of a surface of the sample;automatically rotating the source/detector combination relative to the sample to automatically achieve the multiple, discrete and unique phi angles;providing a pole figure representation. across said multiple phi angles, of said crystal orientation of the sample; andtaking respective reflective x-ray diffraction data at respective discrete positions of the sample, automatically rotating the source/detector combination relative to the sample to automatically achieve multiple, discrete and unique phi angles at each discrete position, and providing a respective pole figure representation across said multiple phi angles for each discrete position. 2. The method of claim 1, wherein the multiple phi angles comprise at least one angle of at least 25 degrees. 3. The method of claim 1, wherein diffraction data are taken at not fewer than four unique phi angles. 4. The method of claim 1, wherein diffraction data are taken at not greater than twenty phi angles. 5. The method of claim 1, wherein the pole figure represents the crystal alignment, and a full width half maximum value is calculated from the pole figure for crystal alignment quantification. 6. The method of claim 1, wherein said taking is carried out continuously along a length of the article, and the sample continuously moves along said length in the sample movement path between the source and detector during said taking. 7. The method of claim 1, wherein the sample is in the form of a tape or sheet, linearly passing through a measurement zone between the source and detector. 8. The method of claim 7, wherein the sample is at least a portion of a superconducting tape. 9. The method of claim 1, wherein the sample is at least a portion of a superconducting tape.
	claims	1. A turning device for turning a container about a turning axis comprising:a stationary holding member;a movable holding member mounted on the stationary holding member while being rotatable about the turning axis with respect to the stationary holding member;two bearing members which are spaced apart along the turning axis and which are configured for receiving the container therebetween with the container bearing on the two bearing members and being allowed to rotate about the turning axis with respect to the bearing members, at least one of the bearing members being supported by the movable holding member such that the at least one bearing member is rotatable about the turning axis with respect to the movable holding member,the turning device being configured such that the at least one bearing member supported by the movable holding member does not rotate about the turning axis relative to the stationary holding member when the movable holding member rotates about the turning axis relative to the stationary holding member. 2. The turning device according to claim 1 further comprising a clamp capable of holding the at least one bearing member mounted on the movable holding member so as to prevent the at least one bearing member from rotating around the turning axis when the movable holding member is rotating about the turning axis relative to the stationary holding member. 3. The turning device according to claim 2, wherein the clamp is supported at least in part by the movable holding member. 4. The turning device according to claim 2, wherein the clamp comprises a synchronizing shaft mounted on the movable holding member so as to be rotatable about the synchronization axis parallel to the turning axis, the synchronizing shaft being driven to revolve circularly about the turning axis on account of the rotation of the movable holding member and driven to rotate about an axis of the synchronizing shaft by a mechanical linkage with each bearing member. 5. The turning device according to claim 4, wherein each mechanical linkage comprises includes one synchronizing gear comprising a planet wheel with an axis being the turning axis and in fixed rotational connection with the bearing member and a satellite wheel, the satellite wheels of the two synchronizing gears being connected in rotation by the synchronizing shaft. 6. The turning device according to claim 5, wherein the satellite wheel of each synchronizing gear is mounted on the synchronizing shaft and is in fixed rotational connection with the synchronizing shaft. 7. The turning device according to claim 1, wherein the movable holding member is rotatable through 360° about the turning axis relative to the stationary holding member. 8. The turning device according to claim 1, wherein the movable holding member supports one bearing member in cantilevered overhang position relative to the other bearing member, the other bearing member being located between the bearing member supported in cantilevered overhang position by the movable holding member and the stationary holding member. 9. The turning device according to claim 8, wherein the movable holding member comprises a proximal portion and a distal portion spaced apart along the turning axis and located on each side of the receiving space, the proximal portion is mounted on the stationary holding member so as to be rotatable about the drive axis, and the distal portion is in cantilevered overhang position and supports the bearing member. 10. The turning device according to claim 1, wherein one of the bearing members is attached to the stationary holding member. 11. The turning device according to claim 1, wherein the stationary holding member comprises a stationary support shaft extending along the turning axis, one of the bearing members being attached to one end of the stationary support shaft. 12. The turning device according to claim 11, wherein the movable holding member is mounted so as to rotate on the support shaft. 13. The turning device according to claim 1, further comprising at least one rotating drive arm for a container received so as to be supported on the bearing members, the at least one rotating drive arm integrally attached to the movable holding member. 14. The turning device according to claim 1, wherein the turning device is capable of turning a nuclear fuel assembly container. 15. The turning device according to claim 1, wherein the turning device is capable of being operated under water. 16. A turning assembly comprising:a nuclear fuel assembly container; andthe device according to claim 1. 17. A nuclear power generating plant comprising:the turning assembly according to claim 16.
	description	This application claims priority and benefit under 35 U.S.C. § 119 to U.S. application Ser. No. 62/098,943, entitled “Automatic Hydropneumatic Actuation Device,” filed on Dec. 31, 2014, and incorporated herein by reference in its entirety. Light water nuclear fission reactors employ neutron absorbing materials to control the reactivity within the reactor core. The temperature within the reactor core may increase due to a loss of coolant flow. The coolant flow may be provided by a pump, and the loss of coolant flow may occur due to a pump shutting down (e.g., due to a loss of power thereto, due to mechanical failure, etc.). A loss of pump flow may be difficult for the nuclear reactor to control without component damage. Reactor designs that rely on the temperature increase of the coolant (i.e., a thermal feedback, etc.) to insert negative reactivity may be subject to a significant time delay between the temperature increase and the corresponding negative reactivity response. Disclosed embodiments include a control assembly for a nuclear reactor having a pump, a nuclear reactor, a method of manufacturing a control assembly for a nuclear reactor, and a method of operating a nuclear fission reactor having a reactor core. In the following detailed description, reference is made to the accompanying drawings, which form a part hereof. In the drawings, the use of similar or the same symbols in different drawings typically indicates similar or identical items, unless context dictates otherwise. The illustrative embodiments described in the detailed description, drawings, and claims are not meant to be limiting. Other embodiments may be utilized, and other changes may be made, without departing from the spirit or scope of the subject matter presented here. One skilled in the art will recognize that the herein described components (e.g., operations), devices, objects, and the discussion accompanying them are used as examples for the sake of conceptual clarity and that various configuration modifications are contemplated. Consequently, as used herein, the specific exemplars set forth and the accompanying discussion are intended to be representative of their more general classes. In general, use of any specific exemplar is intended to be representative of its class, and the non-inclusion of specific components (e.g., operations), devices, and objects should not be taken as limiting. The present application uses formal outline headings for clarity of presentation. However, it is to be understood that the outline headings are for presentation purposes, and that different types of subject matter may be discussed throughout the application (e.g., device(s)/structure(s) may be described under process(es)/operations heading(s) and/or process(es)/operations may be discussed under structure(s)/process(es) headings; and/or descriptions of single topics may span two or more topic headings). Hence, the use of the formal outline headings is not intended to be in any way limiting. Given by way of overview, illustrative embodiments include: a control assembly for a nuclear reactor having a pump, a nuclear reactor, a method of manufacturing a control assembly for a nuclear reactor, and a method of operating a nuclear fission reactor having a reactor core. Embodiments of this new hydropneumatic actuator provide a rapid, passive (e.g., without electronic control, etc.) response to an undesirable loss of fluid (e.g., a loss of flow, a loss of pressure) condition (e.g., due to a pump or other fluid flow device shutting down, leak in the system, etc.). The hydropneumatic actuator directly reacts to the loss of flow rather than reacting directly to applied higher pressures or reacting indirectly (and in a delayed manner) to an input such as a sensor sensing the desired (or undesired condition) and sending a signal through a controller to actuate the actuator or waiting for a material property to physically react to a thermal condition such as in the thermally-responsive actuator. Accordingly, the hydropneumatic actuator provides a mechanical motion directly in response to loss of fluid condition (e.g., flow, pressure, etc.). By way of example, the hydropneumatic actuator may be provided as part of a control assembly for a nuclear reactor having a pump, the hydropneumatic actuator providing a rapid, passive response to an undesirable loss of flow without scram event. In one embodiment, the nuclear reactor is a large fast spectrum, sodium-cooled reactor. The loss of flow without scram event may be particularly difficult for such reactors to endure due to the rapid rise in temperature that occurs. Embodiments of the hydropneumatic actuator respond to pump flow within the cooling system of the nuclear reactor to fully withdraw a neutron modifying material when the pump flow reaches a minimum flow rate and then rapidly insert the neutron modifying material upon loss of flow below a firing condition flow rate. The hydropneumatic actuator may thereby rapidly insert negative reactivity to avoid adverse temperature effects (e.g., sodium boiling, etc.) when a loss of flow occurs without triggering a scram (e.g., in response to a loss of pump flow without scram condition, etc.). In other embodiments the hydropneumatic actuator responds to insert a neutron modifying material when the pump flow reaches a reduced flow rate and then rapidly withdraws the neutron modifying material upon loss of flow. The hydropneumatic actuator may thereby rapidly remove positive reactivity to avoid adverse temperature effects when loss of flow occurs without triggering a scram. In some embodiments the neutron modifying material includes a fissionable material. In some embodiments the neutron modifying material includes an absorber and a fissionable material. A description of FIGS. 45-51 is provided before FIGS. 1-44 in order to provide an introduction and context to the disclosure contained herein. The subsequent description of FIGS. 1-44 provides additional details of the present implementations. FIG. 45 illustrates an apparatus 4500 including a nuclear reactor 4502 with a reactor core 4504. Nuclear reactor 4502 further includes a fluid pump 4506 configured to pump a fluid through fluid flow path 4508. The fluid may include without limitation a compressible fluid or a coolant fluid. The fluid pressure in fluid flow path 4508 is indicated by fluid pressure indicators 4510. In FIG. 45, fluid pressure indicators 4510 represent a high fluid flow pressure. In an implementation, high fluid flow pressure 4510 corresponds to normal operation of pump 4506, such as when nuclear reactor 4502 is undergoing normal operation. Expanded view 4512 illustrates the interior of reactor core 4504 and is divided into three regions: a control assembly region 4514, a fuel region 4516, and a lower region 4518. In an implementation, fuel region 4516 contains at least some nuclear fissile material capable of sustaining a nuclear fission reaction. Regions 4514, 4516, and 4518 are not necessarily drawn to scale in FIGS. 45-50, and may be relatively larger or smaller with respect to each other than the scale depicted herein. Expanded view 4512 depicts two ducts 4520 with similar or identical structures contained therein as described in more detail below. Housings 4520 are merely illustrative, and core 4504 may have any number of ducts 4520, including ducts 4520 that contain the same or different components with respect to each other. Further, in FIGS. 45-50, like elements are referred to with the same numerals where convenient, but not all like elements are labeled in FIGS. 45-50 to enhance clarity and readability. Ducts 4520 are in fluid communication with fluid flow path 4508. In an implementation, fluid flowing from pump 4506 may enter ducts 4520 from the bottom as indicated by fluid flow arrows 4522. In an implementation, fluid flow arrows 4522 indicate a fluid pressure consistent with normal operation of pump 4506. Ducts 4520 contain a cup 4526 disposed therein with an open end oriented toward the fluid flow 4522 and an opposing closed end. Disposed within the cup 4526 is a member 4524 slidably moveable along the axis of fluid flow 4522 and through a plug 4528. In implementations, member 4524 further includes a first piston 4530 disposed below plug 4528 and a second piston 4532 disposed within, and slideably coupled to, cup 4526. In an implementation, member 4524 includes a neutron modifying material, such as a neutron absorption bundle 4534 on its distal end. In an implementation, a loading assembly includes cup 4526, plug 4528, and first piston 4530. As explained in more detail below, when fluid flow 4522 increases to satisfy a loading condition (e.g., a minimum flow rate or flow pressure), the fluid passes through plug 4528 and first piston 4530 to force member 4524 in a loaded position shown in FIG. 45. As fluid flow 4522 increases, compressed fluid, and therefore energy, is stored in a firing assembly, which cooperates with the loading assembly. In an implementation, fluid flow 4536 passes between cup 4526 and inner wall of duct 4520 to return to fluid flow path 4508 and into pump 4506 when the member is in the loaded position shown in FIG. 45. FIG. 46 illustrates an apparatus 4600 including a nuclear reactor 4602 with a reactor core 4604. Nuclear reactor 4602 further includes a fluid pump 4606 configured to pump a fluid through fluid flow path 4608. The fluid may include without limitation a compressible fluid or a coolant fluid. The fluid pressure in fluid flow path 4608 is indicated by fluid pressure indicators 4610. In FIG. 46, fluid pressure indicators 4610 represent a reduced fluid flow pressure. In an implementation, reduced fluid flow pressure 4610 corresponds to impaired or diminished operation of pump 4606, such as when nuclear reactor 4602 is not undergoing normal operation. Expanded view 4612 illustrates the interior of reactor core 4604 and is divided into three regions: a control assembly region 4614, a fuel region 4616, and a lower region 4618. In an implementation, a firing assembly includes second piston 4624 and cup 4622. In FIG. 46, reduced fluid flow 4620 satisfies a firing condition for the firing assembly such that member 4626 is forced downward out of the loaded position by the expansion of fluid 4628 against cup 4630. The firing condition may be satisfied by any fluid pressure in duct 4634 below a predetermined amount. When member 4626 is fired out of the loaded position, neutron modifying materials 4632 are forced downward by the release of stored energy into fuel region 4616. In some implementations, neutron modifying materials 4632 are neutron absorption bundles. FIG. 47 illustrates an apparatus 4700 including a nuclear reactor 4702 with a reactor core 4704. Nuclear reactor 4702 further includes a fluid pump 4706 configured to pump a fluid through fluid flow path 4708. The fluid pressure in fluid flow path 4708 is indicated by fluid pressure indicators 4710. In FIG. 47, fluid pressure indicators 4710 represent a high fluid flow pressure. In an implementation, high fluid flow pressure 4710 corresponds to normal operation of pump 4706, such as when nuclear reactor 4702 is undergoing normal operation. Expanded view 4712 illustrates the interior of reactor core 4704 and is divided into three regions: a control assembly region 4714, a fuel region 4716, and a lower region 4718. FIG. 47 depicts ducts 4720 in fluid communication with fluid flow path 4708 and accepting fluid flow 4722. FIG. 47 depicts member 4724 coupled to first piston 4726 and second piston 4728 disposed within cup 4730 in a loaded position due to the pressure of fluid flow 4722. In the loaded position, the loading assembly stores energy from compressed fluid in cup 4730 and is held in the loaded position due to the force of fluid flow 4722 on at least first piston 4726 as explained in more detail below. In the loaded position, fluid flow 4732 continues to flow around cup 4730 and back into fluid flow path 4708 and into pump 4706. In an implementation, fuel material 4734 is attached to the distal end of member 4724, and disposed within fuel region 4716 when the assembly is in the loaded position. FIG. 48 illustrates an apparatus 4800 including a nuclear reactor 4802 with a reactor core 4804. Nuclear reactor 4802 further includes a fluid pump 4806 configured to pump a fluid through fluid flow path 4808. The fluid pressure in fluid flow path 4808 is indicated by fluid pressure indicators 4810. In FIG. 48, fluid pressure indicators 4810 represent a reduced fluid flow pressure. In an implementation, reduced fluid flow pressure 4810 corresponds to impaired or diminished operation of pump 4806, such as when nuclear reactor 4802 is not undergoing normal operation. Expanded view 4812 illustrates the interior of reactor core 4804 and is divided into three regions: a control assembly region 4814, a fuel region 4816, and a lower region 4818. In FIG. 48, reduced fluid flow (not shown in expanded view 4812) satisfies a firing condition for the firing assembly such that member 4820 is forced downward out of the loaded position by the expansion of fluid 4822 against cup 4824. In an implementation, the action of the firing assembly forces fuel material 4826 at the distal end of member 4820 out of fuel region 4816 and into lower region 4818. FIG. 49 illustrates an apparatus 4900 including a nuclear reactor 4902 with a reactor core 4904. Nuclear reactor 4902 further includes a fluid pump 4906 configured to pump a fluid through fluid flow path 4908. In FIG. 49, fluid pressure indicators 4910 represent high fluid flow pressure. In an implementation, high fluid flow pressure 4910 corresponds to normal operation of pump 4906, such as when nuclear reactor 4902 is undergoing normal operation. Expanded view 4912 illustrates the interior of reactor core 4902 and is divided into three regions: a control assembly region 4914, a fuel region 4916, and a lower region 4918. FIG. 49 depicts the assembly in the loaded position with energy stored by the firing assembly due to the pressure of fluid flow 4920. Member 4922 has attached to its distal end fuel material 4926 disposed in fuel region 4916 when the member is in the loaded position. Control material 4924 is also attached to member 4922, and is disposed above fuel material 4926 in control assembly region 4914 when the member is in the loaded position. FIG. 50 illustrates an apparatus 5000 with reduced flow 5002 through fluid flow path 5004. Expanded view 5006 illustrates the interior of the reactor core, and is divided into three regions: a control assembly region 5008, a fuel region 5010, and a lower region 5012. Reduced fluid flow 5002 satisfies a firing condition for the firing assembly such that member 5012 is forced downward out of the loaded position by the expansion of fluid 5014 against cup 5016. In an implementation, the action of the firing assembly forces fuel material 5015 out of fuel region 5010 and into lower region 5012, and forces control material 5017 out of control region 5008 and into fuel region 5010. FIG. 51 is a plot 5100 of fluid pressure 5102 against time according to one implementation. As fluid pressure rises to point 5104, a loading condition is satisfied, thus moving the apparatus into the loading position. As fluid pressure continues to climb past point 5104, the loading assembly continues to accumulate stored energy as fluid pressure increases against the cup. Further on, as fluid pressure begins to drop, a firing condition is satisfied at point 5106. Once the firing condition has been satisfied, the firing assembly releases the stored energy in a direction opposite the direction of loading to move the member and any materials, such as absorption bundles or fuel materials attached thereto. According to the embodiment shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, a hydropneumatic actuator, shown as hydropneumatic actuator 100, includes a first piston, shown as piston 102, a plug, shown as plug 104, and a housing, shown as housing 106. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, housing 106 has an inner volume, and piston 102 is disposed within the inner volume. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, plug 104 is disposed within housing 106 and spaced from piston 102. In one embodiment, plug 104 may be fixed to housing 106 (e.g., welded to housing 106, etc.) although it is to be appreciated that plug 104 may be fixed in other appropriate manners, which may include removably fixing plug 104 to housing 106 or even reducing or limiting movement of plug 104 such as with friction or other techniques. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, hydropneumatic actuator 100 includes an inlet, shown as inlet 108, and an outlet, shown as outlet 110. Inlet 108 and outlet 110 may define ports through which a fluid (e.g., a liquid, etc.) may be provided as part of a hydraulic system. In one embodiment, housing 106 defines coolant flow path 112 (e.g., a coolant flow path along which a pump provides a coolant flow, etc.) between inlet 108 and outlet 110. According to the embodiment shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, piston 102 may be slidably coupled to housing 106. Referring to FIG. 8 and FIG. 9, a seal 114 may be provided between the piston 102 and the housing 106. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, hydropneumatic actuator 100 includes a rod, shown as rod 116, that is at least partially disposed within the inner volume of housing 106. In one embodiment, piston 102 is coupled (e.g., fixed, etc.) to rod 116. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, rod 116 has first end 118. First end 118 of rod 116 may be configured to engage a remote device. The remote device is associated with a hydraulic system (e.g., a hydraulic system that hydropneumatic actuator 100 forms a portion of, etc.), according to one embodiment. Hydropneumatic actuator 100 provides an output, shown as output 120. In FIG. 1, output 120 is a linear output corresponding with the linear movement of piston 102. Hydropneumatic actuator 100 may provide the linear output along any appropriate line or direction. In some embodiments, the linear output is provided along at least one of an axial centerline defined by piston 102, an axial centerline defined by housing 106, and an axial centerline defined by rod 116. In other embodiments, hydropneumatic actuator 100 provides the linear output along still another direction as may be appropriate in many applications. In still other embodiments, hydropneumatic actuator 100 provides still another type of output 120 (e.g., a rotational output, etc.) to form a type of rotary actuator through any appropriate mechanism including rack and pinion and oscillating vane. According to one embodiment, piston 102 and plug 104 define pairs of cooperating apertures. The pairs of cooperating apertures define at least portions of converging-diverging passages, according to the embodiment shown in FIG. 1 and FIG. 5. The converging-diverging passages may define a nearly-ideal Venturi geometry. In one embodiment, piston 102 and plug 104 define a plurality of aperture sets each including a pair of cooperating apertures, the plurality of aperture sets forming at least portions of a plurality of converging-diverging passages. According to various embodiments, the piston 102 and plug 104 may have only a single pair of cooperating apertures. The number of apertures provided in the piston 102 and plug 104 may vary, and may not correspond in number to each other. By way of example, the piston 102 may have greater, fewer, or the same number of apertures as the plug 104. For example, a pair of cooperating apertures may include a single aperture of piston 102 matched with multiple apertures of plug 104, or vice versa. As shown in FIG. 1 and FIG. 5, piston 102 defines first apertures (e.g., a first group of apertures, etc.), shown as converging openings 122, and plug 104 defines second apertures (e.g., a second group of apertures, etc.), shown as diverging openings 124. One of the converging openings 122 defined at least partially by piston 102 and one of the diverging openings 124 defined at least partially by plug 104 define a pair of cooperating apertures. Each of the pairs of cooperating apertures may form at least a portion of a converging-diverging passage formed when piston 102 and plug 104 are in contact with one another (e.g., as shown in FIG. 3, FIG. 5, FIG. 8, and FIG. 9). As shown in FIG. 1, piston 102 and plug 104 each define six converging openings 122 and six diverging openings 124, respectively. In other embodiments, piston 102 and plug 104 each define more or fewer converging openings 122 and diverging openings 124, respectively. For example, piston 102 may have a single converging openings 122 and plug 104 may have a single diverging openings 124. Alternatively, piston 102 may have multiple converging openings 122 while plug 104 has a single diverging openings 124 and vice versa. Converging openings 122 and diverging openings 124 may be shaped to combine into one or more passages having a constricted section, such as in a Venturi tube when piston 102 and plug 104 are in contact with one another as shown in FIG. 5, FIG. 8, and FIG. 9. FIG. 8 may be a detail view of FIG. 5 and shows a configuration where the piston 102 and plug 104 are in contact with one another. Such a configuration may occur after a fluid flow is provided along coolant flow path 112. In FIG. 8, converging openings 122 extends between an inlet end, shown as inlet end 802, and a throat, shown as inlet throat 804. Diverging openings 124 extends between a throat, shown as outlet throat 806, and an outlet end, shown as outlet end 808. The opening area of the inlet throat 804 of converging openings 122 may have an opening area that is less than the inlet end 802 of the converging openings 122. The diverging openings 124 may be shaped in any appropriate way and may have an outlet throat 806 which has an opening area that is smaller than the opening area at the outlet end 808 of the diverging openings 124. In some embodiments, as shown in FIG. 8, the converging opening area at the inlet throat 804 of converging openings 122 may be aligned and/or have an opening area that is substantially similar to that of the opening area at the outlet throat 806 of diverging openings 124. The fluid flow along fluid coolant flow path 112 may travel through inlet end 802 of the converging openings 122 towards the inlet throat 804 and then into the outlet throat 806 of the diverging openings 124 towards the outlet end 808. In one embodiment, the flow through converging openings 122 and diverging openings 124 has a constant flow rate. The pressure of the fluid flow through converging openings 122 and diverging openings 124 may decrease between inlet end 802 and inlet throat 804 (e.g., due to the reduced area and greater velocity, etc.) and then increase between outlet throat 806 and outlet end 808 (e.g., due to the larger area and reduced velocity, etc.). Specifically, the fluid pressure at inlet end 802 may be greater than the fluid pressure at inlet throat 804; the fluid pressure at outlet throat 806 may be less than the fluid pressure at outlet end 808. The greater pressure at inlet end 802 relative to the pressure at inlet throat 804 generates forces tending to biasing force piston 102 towards plug 104; the greater pressure at outlet end 808 relative to the pressure at outlet throat 806 generates a biasing force tending to biasing force piston 102 toward plug 104. As a result of fluid flow through both the converging and diverging openings of the first piston and plug respectively, the piston 102 and plug 104 are pulled together. The pressure of a fluid flow along coolant flow path 112 through converging openings 122 and diverging openings 124 may be nearly equal at outlet end 808 and inlet end 802 (i.e., the discharge pressure may recover to nearly its inlet value, etc.). In one embodiment, inlet throat 804 of converging openings 122 has a cross-sectional area that is equalized with a cross sectional area of outlet throat 806 of diverging openings 124 although it is to be appreciated that any size, shape, and/or alignment may be appropriate as one of skill in the art will recognize. As shown in FIG. 8 and FIG. 9, the cross-sectional area of converging openings 122 transitions nonlinearly between inlet end 802 and inlet throat 804. By way of example, the cross-sectional area of converging openings 122 may transition between inlet end 802 and inlet throat 804 according to a conic section including parabolic, elliptical, circular, hyperbolic, or other nonlinear profiles. In other embodiments, the cross-sectional area of converging opening transitions linearly or even in stepwise fashion between inlet end 802 and inlet throat 804. As shown in FIG. 8 and FIG. 9, the cross-sectional area of diverging openings 124 transitions linearly between outlet throat 806 and outlet end 808. Piston 102 defines surface 202 facing substantially toward plug 104, and plug 104 defines surface 126 facing substantially toward piston 102, according to the embodiment shown in FIG. 8 and FIG. 9. Surface 202 and surface 126 may define a pair of mating surfaces (e.g., surfaces having a shape, profile, or other features that substantially correspond with one another, etc.). As shown in FIG. 8 and FIG. 9, surface 202 engages (e.g., mates with, cooperates with, etc.) surface 126 when piston 102 is positioned in the configuration shown in FIG. 8 and FIG. 9. In one embodiment, inlet throat 804 of converging openings 122 and outlet throat 806 of diverging openings 124 are disposed along surface 202 and surface 126, respectively. Although FIG. 8 and FIG. 9 show the mating surface 202 and surface 126 as substantially planar outside of the inlet throat 804 and outlet throat 806, it is to be appreciated that any appropriate surface structure, texture, and/or shaping may be used as appropriate. As shown in FIG. 8 and FIG. 9, piston 102 includes a body portion that defines the converging openings 122 and plug 104 includes a body portion that defines the diverging openings 124. Converging openings 122 and diverging openings 124 (i.e., the converging-diverging passage, the pair of cooperating apertures, etc.) are spaced from peripheries of piston 102 and plug 104, according to one embodiment. Converging openings 122 and diverging openings 124 may be cast, machined, or otherwise formed into the body portions of piston 102 and plug 104. The body portions of piston 102 and plug 104 may be formed of a single piece or multiple pieces according to various embodiments. Referring to FIG. 4, in some embodiments, hydropneumatic actuator 100 may comprise additional features including hysteresis device 402, expansion device 404, and locking mechanism 406. Hysteresis device 402 may provide a driving force that may operate independent of the biasing force, withdrawing the neutron modifying material during various coolant flow conditions. In some embodiments, hysteresis device 402 receives a hysteresis control signal to provide the driving force. In some embodiments, hysteresis device 402 is a spring mechanism. The spring mechanism may be compressed and latched, such that the hysteresis control signal unlatches the spring mechanism and the spring mechanism may return to its free length; thus, providing the driving force. In some embodiments, hysteresis device 402 may be positioned above hydropneumatic actuator 100. Referring to FIG. 4, in some embodiments, expansion device 404 may be provided. In some embodiments, expansion device 404 may be located in the fluid 144. In some embodiments, expansion device 404 may engage with another element, such as housing 106 or cup 130. Expansion device 404 may receive an engagement control signal to remain engaged with those other elements until a separate disengagement control signal may be received, allowing expansion device 404 to return to the contracted state. In some embodiments, expansion device 404 may be comprised of a thermal expansive material. Thus, in those embodiments, as the temperature of the coolant rises, expansion device 404 may reach the expanded state. In some embodiments, expansion device 404 may be a bellows. Referring to FIG. 4, in some embodiments, locking mechanism 406 may be provided. In some embodiments, locking mechanism 406 may be located below piston 102. Locking mechanism 406 may engage with another element, such as rod 116 and may prevent the motion of rod 116. In those embodiments the neutron modifying material may be prevented from being withdrawn or inserted, depending on the conditions that may be present when the locking mechanism 406 is engaged. In some embodiments, locking mechanism 406 has a locked state and an unlocked state. In further embodiments, locking mechanism 406 may receive a locking control signal to transition from the locked state to the unlocked state or an unlocking control signal to transition to the unlocked state. In some embodiments, locking mechanism 406 may prevent motion of rod 116, or another element, via a frictional force. In other embodiments, locking mechanism 406 may comprise a ferromagnetic material, and thus prevent movement of rod 116, or another element, by a magnetic force. Referring to FIG. 7, in some embodiments, hydropneumatic actuator 100 may further comprise flow restricting device 702. Flow restricting device 702 may be positioned to restrict coolant flow. In some embodiments, flow restricting device 702 may be positioned above the second piston 128 in fluid 144. In some embodiments, flow restricting device 702 may be a bimetallic strip, with the characteristics to restrict coolant flow based on operating temperatures. Referring to FIG. 10, in one embodiment, piston 102 defines a first sidewall that forms converging openings 122. Plug 104 defines a second sidewall that forms diverging openings 124. Converging openings 122 and diverging openings 124 are thereby positioned at peripheries of piston 102 and plug 104. In FIG. 10, piston 102 and plug 104 are shown in contact with one another. Housing 106 has an inner surface that forms a portion of the converging-diverging passage (i.e., piston 102, plug 104, and housing 106 cooperate to form the converging-diverging passage, etc.). Piston 102 and plug 104 may be cast, machined, or otherwise formed to have sidewalls that form portions of converging openings 122 and diverging openings 124. According to various embodiments, multiple converging-diverging passages may be formed between the piston 102 and plug 104 using the housing 106 to provide a portion of the structure of the passages. Converging-diverging passages formed at least partially by housing 106 may be considered inverted relative to those defined by only piston 102 and plug 104. In other embodiments, the cross-sectional area of diverging openings 124 transitions nonlinearly between outlet throat 806 and outlet end 808. By way of example, the cross-sectional area of diverging openings 124 may transition between outlet throat 806 and outlet end 808 according to a conic section or other nonlinear profiles, linear profiles, or even in step-wise fashion. Any combination of linear and non-linear cross sections may be used as appropriate to produce a Venturi effect in the piston 102 and/or plug 104. According to the embodiment shown in FIG. 1, FIG. 2, FIG. 3, FIG. 5, and FIG. 6, hydropneumatic actuator 100 includes a second piston 128 and a cup 130 (e.g., reservoir, etc.). The second piston 128 and cup 130 combine to form a biasing member. The biasing member or individual components thereof may be included or excluded as would be appropriate to one of skill in the art. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, piston 102 and the biasing member components are positioned on opposing sides of plug 104. In one embodiment, cup 130 is coupled to housing 106 (e.g., with one or more structural members, etc.). As shown in FIG. 1, cup 130 has a sidewall that defines an interior space, and second piston 128 is disposed within the interior space of cup 130. In one embodiment, cup 130 has an internal diameter of 148 millimeters although other sizes may be appropriate as needed. The biasing member is positioned to apply a force that actuates rod 116 and piston 102 in response to a loss of flow along coolant flow path 112, according to the embodiment shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7. As shown in FIG. 1, rod 116 includes an opposing second end, shown as opposing second end 132. In one embodiment, second piston 128 is coupled to opposing second end 132 of rod 116. Rod 116 and second piston 128 may thereby move in unison within housing 106 and cup 130. As shown in FIG. 1, rod 116 includes a transition, shown as tapered portion 134, that is coupled to second piston 128. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8, FIG. 9, FIG. 11 and FIG. 12, cup 130 is positioned along coolant flow path 112. In other embodiments, the biasing member is otherwise at least one of positioned along, disposed along, and in fluid communication with coolant flow path 112. Cup 130 includes a sidewall having an open end, shown as open end 810 (see, e.g., FIG. 8), and an enclosed end, shown as enclosed end 602 (see, e.g., FIGS. 6 and 7), according to the embodiment shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, FIG. 7, FIG. 8 and FIG. 9. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, second piston 128 includes a body that separates the interior space of cup 130 into a first region, shown as first region 136, and a second region, shown as second region 138. First region 136 may be exposed to (e.g., in confronting relation with, directly exposed to, open to, etc.) coolant flow path 112 (e.g., the portion of coolant flow path 112 within housing 106 and outside of cup 130, etc.). In one embodiment, open end 810 of cup 130 has an opening configured to fluidly couple first region 136 and a fluid (e.g., liquid, gas, etc.) associated with coolant flow path 112. In the embodiment shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, second piston 128 is slidably coupled to the sidewall of cup 130 with a seal, shown as seal 140. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, second piston 128 defines a plurality of orifices, shown as orifices 142, that place first region 136 in fluid communication with second region 138. A fluid (e.g., liquid, gas etc.), shown as fluid 144, is disposed within a first portion, shown as fluid portion 146, of second region 138. By way of example, a fluid associated with coolant flow path 112 may enter fluid portion 146 of second region 138 through orifices 142 and define fluid 144. In one embodiment, fluid 144 includes a liquid coolant. By way of example, the liquid coolant may include liquid sodium. As shown in FIG. 1, FIG. 5, FIG. 6, and FIG. 7, second piston 128 includes a body portion that defines the entirety of each orifices 142. In other embodiments, second piston 128 and a sidewall of cup 130 cooperate to define orifices 142. By way of example, the sidewall of cup 130 may have a cross-sectional dimension (e.g., diameter, etc.) that is larger than a corresponding cross-sectional dimension of second piston 128 thereby forming a gap that places first region 136 in fluid communication with second region 138, particularly fluid portion 146. The gap is configured (e.g., sized, shaped, positioned, oriented, etc.) to restrict a flow of fluid 144 therethrough, according to one embodiment. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, a second portion, shown as resilient portion 148, of second region 138 contains a resilient member. By way of example, the resilient portion 148 may contain a compressible fluid (e.g., a liquid, a gas, etc.), shown as compressible fluid 150. In one embodiment, compressible fluid 150 is different from the fluid 144 associated with the coolant flow path 112. In some cases, compressible fluid 150 includes argon gas (e.g., pure argon gas, a mixture of argon gas and one or more other gases, etc.) compressible fluid 150 may include an identifying material (e.g., such that compressible fluid 150 is tagged, colored, selectively reactive, etc.) to facilitate identification of a leak of compressible fluid 150. Fluid portion 146 interacts with resilient portion 148 at an interface, shown as interface 152. Interface 152 may include a plate, membrane, or other device that separates fluid 144 from compressible fluid 150. In other embodiments, interface 152 defines the boundary where compressible fluid 150 within resilient portion 148 directly contacts a surface of fluid 144 within fluid portion 146. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, cup 130 is configured to contain compressible fluid 150 within second region 138 (e.g., within resilient portion 148 of second region 138, etc.). By way of example, cup 130 may include a sidewall having one or more panels that are joined to form a fluid tight chamber. By way of another example, cup 130 may be formed of a material (e.g., a metal, a polymeric material, etc.) that lacks pores large enough for compressible fluid 150 to escape therethrough. In one embodiment, compressible fluid 150 is disposed within resilient portion 148. The compressible fluid may be contained by a sidewall of cup 130 and fluid 144 within fluid portion 146 of second region 138. In one embodiment, a pressure of compressible fluid 150 disposed within resilient portion 148 varies with the pressure of fluid 144 within fluid portion 146 of second region 138. By way of example, an increase in the pressure of fluid 144 within fluid portion 146 (e.g., due to an increase in the pressure of a fluid associated with coolant flow path 112, etc.) may increase the pressure of compressible fluid 150 within resilient portion 148. In other embodiments, second piston 128 does not define the plurality of orifices 142, and resilient portion 148 defines at least a majority of second region 138. A compressible fluid within resilient portion 148 may be contained by a sidewall of cup 130 and a surface of second piston 128. In other embodiments, the biasing member of hydropneumatic actuator 100 includes another device or another arrangement of components. By way of example, the biasing member may include a spring (e.g., a mechanical spring, a resilient solid, etc.) disposed within resilient portion 148 of second region 138. A plate may be coupled (e.g., with a seal, etc.) to a sidewall of cup 130, and the spring may be coupled to the plate and to cup 130 (e.g., enclosed end 602 of cup 130, etc.). By way of another example, the biasing member may include a combination of a spring and a gas spring (e.g., both a compressible fluid and a spring disposed within resilient portion 148 of second region 138, etc.). In still other embodiments, the biasing member includes still other components that may be still otherwise arranged. As shown in FIG. 8, plug 104 defines a bore, shown as bore 812, that receives rod 116. According to the embodiment shown in FIG. 8 and FIG. 9, rod 116 is slidably coupled to bore 812 of plug 104 with a seal, shown as seal 502. In one embodiment, at least a portion of rod 116 has a cross-sectional shape (e.g., along a plane within which plug 104 extends, in a plane that is orthogonal to a longitudinal axis of rod 116, etc.) that mates with (e.g., engages, cooperates with, etc.) a cross-sectional shape of bore 812 (e.g., within a plane that corresponds with the specified plane of rod 116, etc.) bore 812 may have a uniform cross-sectional shape through the thickness of plug 104 or may have a specified cross-sectional shape along only a portion of the thickness of plug 104 (e.g., top and bottom thereof, etc.), according to various embodiments. Rod 116 may have a specified cross-sectional shape along the entire length thereof or along only a portion of the length thereof (e.g., a portion of the length that interfaces with plug 104 as piston 102 and rod 116 translate between the first orientation and the second orientation, etc.), according to various embodiments. The specified cross-sectional shape of piston 102 and the specified cross-sectional shape of plug 104 may rotationally align piston 102 and plug 104, thereby reducing the risk of misalignment between converging openings 122 and diverging openings 124. According to one embodiment, hydropneumatic actuator 100 includes a sensor positioned to provide sensing signals relating to the position of at least one or any combination of piston 102, rod 116, and second piston 128. As shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, hydropneumatic actuator 100 includes a position indicator, shown as magnet 154. A sensing device interfaces with magnet 154 to facilitate determining the position of piston 102, rod 116, and second piston 128, according to one embodiment. In other embodiments, hydropneumatic actuator 100 includes another device configured to monitor the position of at least one of piston 102, rod 116, and second piston 128. In still other embodiments, hydropneumatic actuator 100 includes a fluid level sensor positioned to provide sensing signals relating to the fluid level within cup 130. A processing circuit may evaluate the sensing signals to identify a leak of compressible fluid 150 from cup 130. By way of example, the processing circuit may compare a current fluid level within cup 130 with a target fluid level within cup 130 (e.g., for the first orientation, for the second orientation, etc.). A current fluid level within cup 130 that is greater than a target fluid level within cup 130 may indicate a leak of compressible fluid 150 from cup 130. In one embodiment, piston 102, rod 116, and second piston 128 are selectively repositionable within housing 106 and cup 130 between a first orientation (e.g., the orientation shown in FIG. 1, the orientation shown in FIG. 2, etc.) and a second orientation (e.g., the orientation shown in FIG. 3, etc.) piston 102, rod 116, and second piston 128 may be positioned in the first orientation when a fluid flow having a characteristic (e.g., pressure, flow rate, etc.) exceeding (which in some cases may be less than) a threshold level is provided along coolant flow path 112. By way of example, the first orientation may relate to an initial state (e.g., startup state, quiescent state, etc.) of a pump positioned to provide a fluid flow along coolant flow path 112. In the first orientation, the fluid portion 146 may have a height of 50 millimeters (e.g., with a volume of 0.0008 cubic meters, etc.) and resilient portion 148 may have a height of 810 millimeters (e.g., with a volume of 0.0137 cubic meters, etc.) such that second region 138 has a combined height of 860 millimeters with a gas-to-liquid volume ratio of 17.1. A fluid flow provided along coolant flow path 112 having a characteristic (e.g., pressure, flow rate, etc.) exceeding (which in some cases may be greater than) the threshold level actuates piston 102, rod 116, and second piston 128 into the second orientation from the first orientation during a startup phase. By way of example, the fluid flow may interface with piston 102 to translate piston 102, rod 116, and second piston 128 within housing 106 and cup 130 (e.g., in an upward direction according to the orientation shown in FIG. 2, etc.). In one embodiment, second piston 128 translates 500 millimeters within cup 130 between the first and second orientations although any length of translation may be appropriate. Piston 102 and rod 116 may also translate a substantially similar distance, such as 500 millimeters, between the first and second orientations. In the second orientation, the fluid portion 146 may have a height of 250 millimeters (e.g., with a volume of 0.0041 cubic meters, etc.) and resilient portion 148 may have a height of 110 millimeters (e.g., with a volume of 0.0018 cubic meters, etc.) such that second region 138 has a combined height of 360 millimeters with a gas-to-liquid volume ratio of 0.439. It is to be appreciated that any volume, length and size of the above components and their movements may be adjusted as appropriate for the application and size, desired force and reaction time and range of the system. The threshold level may be related to the forces applied to first end 118 of rod 116 (e.g., weight forces, forces applied by a remote device, etc.). The force with which piston 102 is actuated may be related to the pressure of the fluid flow and the cross-sectional area of piston 102. The rate at which piston 102, rod 116, and second piston 128 translate within housing 106 and cup 130 (e.g., the rate of ascent according to the orientation shown in FIG. 2, FIG. 3, FIG. 5, and FIG. 6, etc.) may be reduced by the compression of compressible fluid 150 within cup 130. After initial compression, fluid 144 may flow through orifices 142 from fluid portion 146 of second region 138 into first region 136 until a new volume of resilient portion 148 is achieved. Piston 102, rod 116, and second piston 128 may continue to translate until piston 102 engages plug 104 (e.g., contacts plug 104, abuts plug 104, in communication with plug 104, etc.). In one embodiment, piston 102 engages plug 104 when disposed in the second orientation thereby placing converging openings 122 and diverging openings 124 in direct fluid communication. By way of example, fluid flowing from converging openings 122 may flow directly into diverging openings 124. In one embodiment, pressure variations within the converging-diverging passages secure piston 102 and rod 116 in the second orientation during normal operation of the hydraulic system (e.g., during normal operation of a pump providing a fluid flow along coolant flow path 112, during normal operation of a nuclear reactor associated with the hydraulic system, etc.). By way of example, a fluid flow along coolant flow path 112 and through the converging-diverging passages generates a suction force (e.g., due to the Venturi effect, etc.) between piston 102 and plug 104 that retains piston 102, rod 116, and second piston 128 in the second orientation. The suction force may be generated due to pressure differentials within, between, and/or proximate converging openings 122 and diverging openings 124 (e.g., at inlet throat 804 and outlet throat 806, etc.). In one embodiment, the suction forces retain piston 102, rod 116, and second piston 128 in the second orientation to reduce the risk of undesirable movement of first end 118 of rod 116 during routine variations in the fluid flow along coolant flow path 112 (e.g., due to routine pump speed changes, etc.). As shown in FIG. 1, FIG. 5, FIG. 8, and FIG. 9, the converging-diverging passages are disposed along coolant flow path 112. The fluid may thereby flow through the converging-diverging openings, through open end 810 of cup 130, and around cup 130 along coolant flow path 112. Fluid flow may also occur through orifices 142 of second piston 128 such that fluid 144 may have a pressure equal to that of the fluid flow along coolant flow path 112. Fluid 144 may act upon compressible fluid 150 by way of interface 152 such that compressible fluid 150 has a pressure that is related to (e.g., equal to, etc.) the pressure of the fluid flow along coolant flow path 112. After initial actuation of piston 102, rod 116, and second piston 128 (e.g., due to the pressure applied by the pump reaching the threshold level, etc.), compressible fluid 150 may compress due to an increase in the characteristic (e.g., pressure, etc.) of the fluid flow along coolant flow path 112. Such compression may continue, thereby decreasing the volume of resilient portion 148, until the characteristic of the fluid flow reaches a normal operating range (e.g., a target range, a range of pressures, stable and/or substantially equalized state, etc.). In one embodiment, the pressure of a fluid such as a gas within resilient portion 148 is equal to the pressure of the fluid flow along coolant flow path 112 during normal operation of the hydraulic system. A fluid flow having a characteristic (e.g., pressure, etc.) within the normal operating range may be provided along coolant flow path 112 during normal operation of the hydraulic system with which hydropneumatic actuator 100 is associated (e.g., during a pressurization phase, etc.). By way of example, the hydraulic system may include a pump (which may be any flow device or mechanism for moving fluid including a mechanical pump, a gravity pump, etc.) positioned to provide a fluid flow along coolant flow path 112. The pressure of the fluid flow provided by the pump may vary within the normal operating range. The normal range is greater than the threshold level, according to one embodiment, thereby reducing the likelihood that piston 102 may disengage from plug 104 during normal operation of the hydraulic system (e.g., during normal operation of the pump, etc.). By way of example, the threshold level may be between 25% and 30% of the normal range (e.g., between 25% and 30% of a lower bound of the normal range, between 25% and 30% of a midpoint of the normal range, between 25% and 30% of an upper bound of the normal range, etc.). During normal operation of the hydraulic system, piston 102, rod 116, and second piston 128 may remain in the second orientation. Compressible fluid 150 may also be in a compressed state. Various conditions may generate a loss of flow along coolant flow path 112. The loss of flow along coolant flow path 112 or a loss of pump flow (e.g., a loss of flow along coolant flow path 112 otherwise provided by a pump, etc.) may define a loss of flow condition. The loss of flow condition may include a total loss of flow (e.g., with a pressure equal to zero, with a flow rate equal to zero, etc.). In other embodiments, the loss of flow condition includes a characteristic of the fluid flow equaling or falling below a breakaway value (e.g., a breakaway pressure, a breakaway flow rate, etc.). The loss of flow condition may occur due to mechanical or other failure of the flow device (e.g., pump, etc.) providing the flow along coolant flow path 112, due to a loss of power to the flow device providing the flow along coolant flow path 112, due to a failure of another component of the hydraulic system with which hydropneumatic actuator 100 is associated (e.g., due to a hydraulic line rupturing, due to a fitting leaking, etc.), or for still other reasons. The pressure and flow rate of the fluid flow along coolant flow path 112 may decrease (e.g., due to pump coast down, etc.) at a characteristic rate. In one embodiment, the pressure at inlet 108 (e.g., below second piston 128 according to the orientation shown in FIG. 2, FIG. 3, FIG. 5, and FIG. 6, etc.) may follow the pump coast down or other reduction to the square of the flow rate of the fluid flow along coolant flow path 112. In one embodiment, the biasing member, which includes the resilient member that in some cases includes compressible fluid 150, stores energy during the pressurization phase that is released in response to the loss of flow condition during an actuation phase. The biasing member may be configured to apply a force that actuates piston 102, rod 116, and second piston 128 in response to the loss of flow condition. By way of example, the pressure, volume, or other characteristic of compressible fluid 150 may be specified (e.g., in an initial state, with piston 102, rod 116, and second piston 128 in the first orientation, with piston 102, rod 116, and second piston 128 in the second orientation, etc.) to provide a target force that actuates piston 102, rod 116, and second piston 128 in response to the loss of flow condition due to the loss of pressure force holding piston 102, rod 116 and second piston 128 in the operational second position. In one embodiment, the target force applied by compressible fluid 150 overcomes the coast down or decreased suction force associated with the pressure variations within the converging-diverging passages in response to the loss of flow condition. The target force may cooperate with weight forces or other forces acting in the same direction. The biasing member thereby actuates piston 102, rod 116, and second piston 128 into the first orientation from the second orientation. In one embodiment, at least one of piston 102 and plug 104 includes a feature configured to prevent adhesion there between (e.g., sticking, welding-type phenomena, etc.). By way of example, the feature may include a micro-spacer at least one of sized and positioned to prevent the entirety of surface 202 from contacting the entirety of surface 126. Hydropneumatic actuator 100 may thereby apply output 120. The hydraulic system may employ output 120 to actuate a remote device in response to the loss of flow condition. In one embodiment, output 120 is used to actuate a switch, an alarm, a valve, another mechanical device, another electromechanical device, or any other appropriate warning or security device. Such a warning or security device may provide an alert relating to the loss of flow condition, may disengage another component of the hydraulic system (e.g., turn off a pump in response to a loss of flow condition initiated due to a ruptured hydraulic line, turn off a valve disposed immediately downstream of hydropneumatic actuator 100, etc.), or may perform still another function (e.g., actuate a remote component, etc.). In one embodiment, first end 118 of rod 116 engages the mechanical device, the electromechanical device, or the other remote component. By way of example, first end 118 of rod 116 may be coupled to the mechanical device, the electromechanical device, or the other remote component. By way of another example, first end 118 of rod 116 may selectively engage (e.g., depress, contact, etc.) the mechanical device, the electromechanical device, or the other remote component in response to the condition of the fluid flow along coolant flow path 112. According to the embodiment shown in FIG. 1, FIG. 2, FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7, orifices 142 are configured (e.g., sized, shaped, positioned, oriented, etc.) to restrict a flow of fluid 144 therethrough during the actuation phase. In one embodiment, the loss of flow condition involves a loss of pressure of the fluid flow along coolant flow path 112 and up-flow of second piston 128 (e.g., the side of second piston 128 oriented towards inlet 108, etc.) that decreases according to a profile of pressure versus time. From the normal operating range, the pressure of the fluid flow along the flow path may decrease (e.g., linearly, exponentially, logarithmically, otherwise nonlinearly, etc.). The pressure of fluid 144 within fluid portion 146 and the pressure of compressible fluid 150 within resilient portion 148 is related to (which can include equal to, etc.) the pressure of the fluid flow along coolant flow path 112. In one embodiment, the pressure of fluid 144 within fluid portion 146 and the pressure of compressible fluid 150 within resilient portion 148 are equal to the pressure of the fluid flow along coolant flow path 112 at the onset of the loss of flow condition. The pressure of the fluid flow along coolant flow path 112 and toward inlet 108 of second piston 128 (e.g., according to the orientation shown in FIG. 2, FIG. 3, FIG. 5, and FIG. 6, etc.) may decay rapidly. Such rapid decay may be characterized by a time constant. A reduction in the pressure of the fluid flow along coolant flow path 112 relative to the pressure of fluid 144 within fluid portion 146 and the pressure of compressible fluid 150 within resilient portion 148 may induce a pressure differential across second piston 128 and initiate a fluid flow of fluid 144 through orifices 142. The configuration of orifices 142 restricts the flow of fluid 144 into first region 136 such that compressible fluid 150 applies a force to second piston 128, rod 116, and piston 102 (e.g., toward inlet 108 or below according to the orientation shown in FIG. 3). At least one of the force due to the fluid flow acting on piston 102 (e.g., relating to the pressure of the fluid flow and the cross-sectional area of piston 102, etc.); the weight forces of piston 102, rod 116, and second piston 128; and the suction forces due to the fluid flow through the converging-diverging passages oppose the force generated by compressible fluid 150. The fluid flow along coolant flow path 112 (e.g., pressure, flow rate, etc.) continues to decay, thereby increasing the pressure differential across second piston 128, until it reaches the breakaway value, where the force applied by compressible fluid 150 overcomes the opposing forces. The opposing forces may be due to at least one of the fluid flow acting on piston 102; the weight forces of piston 102, rod 116, and second piston 128 (if gravity can assist in that orientation of the device); the suction forces due to the fluid flow through the converging-diverging passages; and the force applied by an optional spring or other biasing member. The biasing member may thereafter rapidly actuate or translate (e.g., accelerate, etc.) Piston 102, rod 116, and second piston 128 toward the first orientation such that hydropneumatic actuator 100 provides output 120. After actuation of piston 102, rod 116, and second piston 128 into the first orientation, an applied fluid flow along coolant flow path 112 having a characteristic greater than the threshold value may again actuate piston 102, rod 116, and second piston 128 into the second orientation. In one embodiment, hydropneumatic actuator 100 may thereby seamlessly transition between providing output 120 in a first direction (e.g., toward outlet 110 or above according to the orientation shown in FIG. 3) and providing output 120 in a second direction (e.g., toward inlet 108 or downward according to the orientation shown in FIG. 2). hydropneumatic actuator 100 may respond to a loss of flow condition and thereafter return to normal operation without needing to be reset, reconfigured, or replaced. By way of example, the response of hydropneumatic actuator 100 to a loss of flow condition is automatic and passive (e.g., mechanical and independent of electronic feedback, etc.), and the return of hydropneumatic actuator 100 to normal operation after a loss of flow condition is resolved is also automatic and passive. Operation of hydropneumatic actuator 100 may not require the use of electricity, and as such would provide a response even in the event of a loss of electricity that results in a reduction or loss of fluid flow in coolant flow path 112. Referring next to the embodiment shown in FIG. 13 and FIG. 14, a hydraulic system, shown as hydraulic system 1300, includes hydropneumatic actuator 100. As shown in FIG. 13 and FIG. 14, flow device 1302 is coupled to hydropneumatic actuator 100. By way of example, flow device 1302 may include a pump, a high pressure reservoir, or still another device. In one embodiment, flow device 1302 provides a fluid flow along a flow path. By way of example, flow device 1302 may provide a fluid flow to inlet 108 of hydropneumatic actuator 100. Hydropneumatic actuator 100 defines coolant flow path 112 between inlet 108 and outlet 110. Accordingly, the fluid flow provided to inlet 108 is provided at outlet 110. According to the embodiment shown in FIG. 13, hydropneumatic actuator 100 provides output 120 to remote device 1304 that is associated with hydraulic system 1300. According to the embodiment shown in FIG. 14, hydraulic system 1300 includes remote device 1304. Output 120 provided by hydropneumatic actuator 100 varies based on the fluid flow along coolant flow path 112, according to one embodiment. By way of example, a rod disposed within an inner volume of a housing of hydropneumatic actuator 100 may have an end that is configured to engage remote device 1304. In one embodiment, hydropneumatic actuator 100 is configured to actuate remote device 1304 at a rate that is greater than a characteristic coast down rate associated with flow device 1302 (e.g., a flow provided due to the inertia of a pump, etc.). The actuation rate of remote device 1304 (e.g., within six to twelve seconds, etc.) may occur faster than actuation using a thermal response (e.g., within twelve to twenty-four seconds, etc.). As shown in FIG. 14, remote device 1304 includes a valve (e.g., a ball valve, etc.). Accordingly, hydropneumatic actuator 100 may provide output 120 to close the valve in direct response to a loss of flow condition. The valve may thereby operate within hydraulic system 1300 as a check valve. Flow from the valve may be used to power various other hydraulic components. In still other embodiments, hydropneumatic actuation operates as a blowout preventer (e.g., in an underwater oil system, etc.) where a downstream loss of pressure actuates a valve. In other embodiments, remote device 1304 includes a warning or security device which may include one or more of a switch, an alarm, another mechanical device, or another electromechanical device. Such warning or security devices may provide an alert relating to the loss of flow condition, may disengage another component of the hydraulic system (e.g., turn off flow device 1302 in response to a loss of flow condition initiated due to a ruptured hydraulic line, turn off a valve disposed immediately downstream of hydropneumatic actuator 100, turn off another valve, etc.), or may perform still another function (e.g., actuate a remote component, etc.). Output 120 actuates remote device 1304, according to one embodiment. In still other embodiments, hydraulic system 1300 includes other hydraulic components (e.g., rotational actuators, linear actuators, etc.) coupled to flow device 1302. By way of example, the other hydraulic components may be coupled to flow device 1302 in series with hydropneumatic actuator 100. The fluid flow may be provided from outlet 110 of hydropneumatic actuator 100 to operate such devices (e.g., directly, with one or more intermediate valves, etc.). In other embodiments, the fluid flow is provided to operate such devices and thereafter flows to inlet 108. By way of another example, the other hydraulic components may be coupled to flow device 1302 in parallel with hydropneumatic actuator 100. By way of example, the fluid flow along coolant flow path 112 may be only a portion of the total fluid output provided by flow device 1302. Such parallel plumbing of hydropneumatic actuator 100 may facilitate retrofitting hydropneumatic actuator 100 into existing hydraulic system 1300. Referring next to the embodiment shown in FIG. 15, FIG. 16, FIG. 17, FIG. 18, FIG. 19, FIG. 20, FIG. 21, and FIG. 22, hydropneumatic actuator 100 forms a portion of a control assembly 1500 for a nuclear reactor, shown as nuclear reactor 2100. In one embodiment, nuclear reactor 2100 includes a fuel assembly having a duct containing nuclear fuel. As shown in FIG. 21, the nuclear fuel is disposed within a fuel region, shown as fuel region 2102. In one embodiment, fuel region 2102 extends between a first bound (e.g., upper bound, etc.), shown as first bound 2104, and a second bound (e.g., lower bound, etc.), shown as second bound 2106. Nuclear reactor 2100 may include a pump in fluid communication with the duct of the fuel assembly and housing 106 of hydropneumatic actuator 100. In one embodiment, the pump is configured to provide a coolant flow along a coolant flow path. Housing 106 of hydropneumatic actuator 100 may have an inner volume that defines at least a portion of the coolant flow path (i.e., coolant flow path 112 may define a portion of the coolant flow path along which the pump of nuclear reactor 2100 provides a coolant flow, etc.). As shown in FIG. 15, FIG. 16, FIG. 17, FIG. 18, FIG. 19, FIG. 20, FIG. 21, and FIG. 22, the control assembly 1500 includes remote device 1304. In one embodiment, remote device 1304 includes a neutron modifying material. As shown in FIG. 19 and FIG. 20, first end 118 of rod 116 is configured (e.g., shaped, etc.) to engage the neutron modifying material. A coolant flow along coolant flow path 112 and through the converging-diverging passages generates a suction force (e.g., due to the Venturi effect, etc.) between piston 102 and plug 104 that secures piston 102, rod 116, second piston 128, and the neutron modifying material during normal operation of nuclear reactor 2100 (e.g., during normal, uninterrupted operation of a coolant pump associated with nuclear reactor 2100, etc.). By way of example, a coolant flow above the threshold level may elevate the neutron modifying material from fuel region 2102, and the suction forces may retain the neutron modifying material in such a withdrawn position relative to fuel region 2102. The suction forces may retain the neutron modifying material even as the coolant flow experiences pressure variations within a normal range (e.g., unintended variations, variations to accommodate different power levels of nuclear reactor 2100, etc.). In one embodiment, the biasing member of hydropneumatic actuator 100 (e.g., compressible fluid 150 within cup 130, etc.) is positioned or otherwise configured to apply a force that selectively repositions piston 102, rod 116, and the neutron modifying material in response to a loss of pump flow without scram condition. By way of example, the biasing member of hydropneumatic actuator 100 (e.g., compressible fluid 150 within cup 130, etc.) may be positioned or otherwise configured to apply a force that inserts the neutron modifying material into fuel region 2102 in response to a loss of pump flow without scram condition. The force applied by compressible fluid 150 may overcome the suction forces associated with the pressure variations within the converging-diverging passages in response to the loss of pump flow without scram condition (e.g., facilitated by orifices 142 defined at least partially by second piston 128 restricting a flow of the liquid coolant therethrough, etc.). The control assembly 1500 may thereby rapidly introduce the neutron modifying material into the fuel region 2102 of nuclear reactor 2100 to rapidly introduce negative reactivity therein. Referring still to the embodiment shown in FIG. 15, FIG. 16, FIG. 17, FIG. 18, FIG. 19, FIG. 20, FIG. 21, and FIG. 22, housing 106 includes a duct, shown as duct 1502, and an insert, shown as duct insert 1504. In one embodiment, duct 1502 has a hexagonal cross-sectional shape. Duct insert 1504 may have an internal cross-sectional shape that corresponds with that of piston 102 and plug 104 (e.g., circular, etc.) and an external cross-sectional shape that corresponds with that of duct 1502. Duct insert 1504 may thereby prevent bypass flow along duct 1502 around piston 102 and plug 104. Duct insert 1504 may be welded to duct 1502. In other embodiments, housing 106 does not include duct insert 1504. By way of example, piston 102 and plug 104 may have a cross-sectional shape (e.g., hexagonal, etc.) that corresponds with the cross-sectional shape of duct 1502 (e.g., hexagonal, etc.). FIG. 23, FIG. 24, FIG. 25, FIG. 26, FIG. 27, FIG. 28, FIG. 29, FIG. 30, FIG. 31, FIG. 32, FIG. 33, FIG. 34, FIG. 35, FIG. 36, FIG. 37, FIG. 38, FIG. 39, FIG. 40, FIG. 41, FIG. 42, FIG. 43, and FIG. 44 are a series of flowcharts depicting implementations. For ease of understanding, the flowcharts are organized such that the initial flowcharts present implementations via an example implementation and thereafter the following flowcharts present other implementations and/or expansions of the initial flowchart(s) as either sub-component operations or additional component operations building on one or more earlier-presented flowcharts. Those having skill in the art will appreciate that the style of presentation utilized herein (e.g., beginning with a presentation of a flowchart(s) presenting an example implementation and thereafter providing additions to and/or further details in subsequent flowcharts) generally allows for a rapid and easy understanding of the various process implementations. In addition, those skilled in the art will further appreciate that the style of presentation used herein also lends itself well to modular and/or object-oriented program design paradigms. FIG. 23, FIG. 24, FIG. 25, FIG. 26, FIG. 27, FIG. 28, FIG. 29, FIG. 30, and FIG. 31 provide illustrative flow diagrams for a method of manufacturing a control assembly for a nuclear reactor, shown as method 2300, according to one embodiment. Although the method is presented as a sequence of steps for illustrative purposes, this sequence does not limit the scope of the claimed methods, and those of ordinary skill in the art will be aware of modifications and variations that may be made to the order, timing, etc. of the sequence. Referring to FIG. 23, method 2300 starts at start block 2302. At block 2304, a coolant flow path is defined within an inner volume of a duct. At block 2306, a plug is fixed to the duct. At block 2308, a first piston is slidably coupled to the duct. In one embodiment, the plug and the first piston define a pair of cooperating apertures that forms at least a portion of a converging-diverging passage. At block 2310, a neutron modifying material is coupled to the first piston with a rod. At block 2312, a converging-diverging passage is positioned along the coolant flow path such that pressure variations within the converging-diverging passage secure the first piston, the rod, and the neutron modifying material during normal operation of the nuclear reactor. At block 2314, a biasing member is positioned to apply a force to the rod and the first piston. In one embodiment, the force releases the first piston, the rod, and the neutron modifying material in response to a loss of pump flow without scram condition. In one embodiment, method 2300 stops at done block 2316. In other embodiments, method 2300 continues. Additional and modified method steps are set forth below by way of non-limiting example. Referring to FIG. 24, a first aperture of the pair of cooperating apertures is associated with the first piston and a second aperture of the pair of cooperating apertures is associated with the plug, the first aperture and the second aperture defining at least a portion of a converging opening and at least a portion of a diverging opening at block 2402. Referring to FIG. 25, associating the first aperture of the pair of cooperating apertures and associating the second aperture of the pair of cooperating apertures at block 2402 may include extending the converging opening between an inlet end and a throat and extending the diverging opening between a throat and an outlet end at block 2502. Referring to FIG. 26, a pair of mating surfaces are defined on the plug and the first piston and the throat of the converging opening and the throat of the diverging opening are positioned along the pair of mating surfaces at block 2602. Referring to FIG. 27, associating the first aperture of the pair of cooperating apertures and associating the second aperture of the pair of cooperating apertures at block 2402 may include defining the first aperture within a first body of the first piston and defining the second aperture within a second body of the plug such that the pair of cooperating apertures is spaced from peripheries of the plug and the first piston at block 2702. Referring to FIG. 28, associating the first aperture of the pair of cooperating apertures and associating the second aperture of the pair of cooperating apertures at block 2402 may include defining the first aperture on a first sidewall of the first piston and defining the second aperture on a second sidewall of the plug such that the pair of cooperating apertures is positioned at peripheries of the plug and the first piston at block 2802. Referring to FIG. 29, in some embodiments, positioning the converging-diverging passage along the coolant flow path at block 2312 includes associating a plurality of aperture sets with the plug and the first piston at block 2902. Referring to FIG. 30, the first piston and the plug are rotationally aligned by defining a bore within the first piston and positioning the rod within the bore at block 3002. In one embodiment, at least a portion of the rod has a cross-sectional shape that mates with a cross-sectional shape of the bore. Referring to FIG. 31, positioning a biasing member to apply a force to the rod and the first piston at block 2314 may include coupling a second piston to the rod and positioning the second piston within an interior space of a cup. FIG. 32, FIG. 33, FIG. 34, FIG. 35, FIG. 36, FIG. 37, FIG. 38, FIG. 39, FIG. 40, FIG. 41, FIG. 42, FIG. 43, and FIG. 44 provide illustrative flow diagrams for a method of operating a nuclear fission reactor having a reactor core, shown as method 3200, according to one embodiment. Although the method is presented as a sequence of steps for illustrative purposes, this sequence does not limit the scope of the claimed methods, and those of ordinary skill in the art will be aware of modifications and variations that may be made to the order timing, operation, etc. of the sequence. Referring to FIG. 32, method 3200 starts at start block 3202. At block 3204, coolant flows along a coolant flow path in the nuclear fission reactor. At block 3206, nuclear fuel is fissioned within a fuel region of the reactor core. At block 3208, energy from the coolant flow is stored in a resilient member. At block 3210, a neutron modifying material is inserted into the reactor core using the stored energy in response to the coolant flow falling below a threshold rate. In one embodiment, method 3200 ends at done block 3212. In other embodiments, method 3200 continues. Additional method steps are set forth below by way of non-limiting example. Referring to FIG. 33, the neutron modifying material is withdrawn from the reactor core during an initial startup phase at block 3302. Referring to FIG. 34, the neutron modifying material is maintained in a withdrawn position when the coolant flow is within a target range at block 3402. Referring to FIG. 35, flowing coolant along a coolant flow path in the nuclear fission reactor at block 3204 may include engaging a pump from an initial quiescent state at block 3502. Referring to FIG. 36, the neutron modifying material is withdrawn in response to the coolant flow exceeding a threshold flow rate at block 3602. Referring to FIG. 37, the neutron modifying material is maintained in a withdrawn position when the coolant flow is within a target range at block 3702. Referring to FIG. 38, the neutron modifying material is inserted at a rate that is greater than a characteristic coast down rate associated with the pump at block 3802. Referring to FIG. 39, inserting the neutron modifying material into the reactor core using the stored energy at block 3210 may include inserting the neutron modifying material in response to a loss of flow without scram condition at block 3902. Referring to FIG. 40, the neutron modifying material is passively inserted at block 4002. Referring to FIG. 41, the neutron modifying material is inserted independent of thermal feedback from the reactor core at block 4102. Referring to FIG. 42, the neutron modifying material is inserted mechanically and independent of electronic feedback relating to a condition of the reactor core at block 4202. Referring to FIG. 43, the position of the neutron modifying material is monitored at block 4302. Referring to FIG. 44, storing energy from the coolant flow in a resilient member at block 3208 may include pressurizing a gas within a reservoir at block 4402. According to one embodiment, a control assembly for a nuclear reactor having a pump includes a duct having an inner volume and defining a coolant flow path, a plug fixed to the duct, a rod disposed within the inner volume and having a rod end that is configured to engage a neutron modifying material, a first piston disposed within the inner volume, slidably coupled to the duct, and coupled to the rod, and a biasing member coupled to the rod and the first piston. In one embodiment, the biasing member is positioned to apply a biasing force that repositions the first piston, the rod, and the neutron modifying material in response to a loss of pump flow without scram condition. In one embodiment, the biasing member is positioned to apply a first biasing force that positions the first piston, the rod, and the neutron modifying material into the fuel region; and a second biasing force that repositions the first piston, the rod, and the neutron modifying material out of the fuel region in response to a loss of pump flow without scram condition. In one embodiment the neutron modifying material increases positive reactivity in the fuel region. In one embodiment, the neutron modifying material includes a first neutron modifying material and a second neutron modifying material. In one embodiment, the first neutron modifying material includes a neutron absorber, and the second neutron modifying material includes fissionable material. In one embodiment the neutron absorber is positioned into the fuel region ahead of the fissionable material. In one embodiment, the plug and the first piston define a pair of mating surfaces. In one embodiment, a throat of a converging opening and a throat of a diverging opening are disposed along the pair of mating surfaces. In one embodiment, the first piston defines a first sidewall that forms at least a portion of a first aperture and the plug defines a second sidewall that forms at least a portion of a second aperture. The first aperture and the second aperture define a pair of cooperating apertures positioned at peripheries of the plug and the first piston. In one embodiment, the duct has an inner surface. The inner surface may form a portion of a converging-diverging passage. In one embodiment, the rod and the first piston are selectively repositionable within the duct between a first orientation and a second orientation. The first piston contacts the plug when disposed in the second orientation thereby placing the pair of cooperating apertures into direct fluid communication. In one embodiment, the plug and the first piston define a plurality of aperture sets each including a pair of cooperating apertures. The plurality of aperture sets forms at least portions of a plurality of converging-diverging passages. In one embodiment, the plug defines a bore that receives the rod. At least a portion of the rod has a cross-sectional shape that mates with a cross-sectional shape of the bore thereby rotationally aligning the first piston and the plug. In one embodiment, the biasing member includes a cup having a sidewall with a cross-sectional dimension that is larger than a corresponding cross-sectional dimension of a second piston thereby forming a gap that places a first region of the cup in fluid communication with a second region of the cup. In one embodiment, the gap may be configured to restrict a flow of the liquid coolant there through such that a biasing force applied by a compressible fluid contained within the cup overcomes a suction force associated with pressure variations within the converging-diverging passage in response to a loss of pump flow without scram condition. According to another embodiment, a nuclear reactor includes a fuel assembly including a duct containing nuclear fuel, a pump in fluid communication with the duct of the fuel assembly, and a control assembly. The pump is configured to provide a coolant flow along a coolant flow path. The control assembly includes a duct having an inner volume that defines at least a portion of the coolant flow path, a plug fixed to the duct, a neutron modifying material coupled to a rod, a first piston disposed within the inner volume, slidably coupled to the duct, and coupled to the rod, and a biasing member coupled to the first piston, the rod, and the neutron modifying material. In one embodiment, the biasing member is positioned to apply a biasing force that inserts the neutron modifying material into a fuel region of the fuel assembly in response to a loss of pump flow without scram condition. In one embodiment, the biasing member is positioned to apply a first biasing force to positions a neutron modifying material into the fuel region of the fuel assembly; and a second biasing force that repositions the neutron modifying material out of the fuel region of the fuel assembly in response to a loss of pump flow without scram condition. In one embodiment the neutron modifying material increases positive reactivity in the fuel region. In one embodiment, the neutron modifying material includes a first neutron modifying material and a second neutron modifying material. In one embodiment, the first neutron modifying material includes a neutron absorber, and the second neutron modifying material includes fissionable material. In one embodiment the neutron absorber is positioned into the fuel region ahead of the fissionable material. In one embodiment, the first piston defines a first sidewall that forms at least a portion of a first aperture and the plug defines a second sidewall that forms at least a portion of a second aperture. The first aperture and the second aperture define a pair of cooperating apertures positioned at peripheries of the plug and the first piston. In one embodiment, the duct of the control assembly has an inner surface. The inner surface of the duct may form a portion of a converging-diverging passage. In one embodiment, the plug and the first piston define a plurality of aperture sets each including a pair of cooperating apertures. The plurality of aperture sets forms at least portions of a plurality of converging-diverging passages. In one embodiment, the plug defines a bore that receives the rod. At least a portion of the rod may have a cross-sectional shape that mates with a cross-sectional shape of the bore thereby rotationally aligning the first piston and the plug. In one embodiment, the biasing member includes a cup. A second piston may separate an interior space of the cup into a first region and a second region. In some embodiments, the cup defines an opening configured to fluidly couple the first region and a liquid coolant associated with the coolant flow path. In one embodiment, the biasing member includes a compressible fluid disposed within the second region of the cup. The compressible fluid may be configured to apply a biasing force that inserts the neutron modifying material into the fuel region of the fuel assembly in response to the loss of pump flow without scram condition. The pressure of the compressible fluid may vary with a pressure of the liquid coolant. In one embodiment, the compressible fluid may be configured to apply a first biasing force to position a neutron modifying material into the fuel region; and second biasing force to reposition the neutron modifying material out of the fuel region in response to a loss of pump flow without scram condition. In one embodiment the neutron modifying material increases positive reactivity in the fuel region. In one embodiment, the neutron modifying material includes a first neutron modifying material and a second neutron modifying material. In one embodiment, the first neutron modifying material includes a neutron absorber, and the second neutron modifying material includes fissionable material. In one embodiment the neutron absorber is positioned into the fuel region ahead of the fissionable material. In one embodiment, the second piston is slidably coupled to a sidewall of the cup. The second piston may define an orifice that places the first region of the cup in fluid communication with the second region of the cup. The orifice may be configured to restrict a flow of the liquid coolant there through such that the biasing force applied by the compressible fluid overcomes a suction force associated with the pressure variations within the converging-diverging passage in response to the loss of pump flow without scram condition. In one embodiment, the sidewall of the cup has a cross-sectional dimension that is larger than a corresponding cross-sectional dimension of the second piston thereby forming a gap that places the first region of the cup in fluid communication with the second region of the cup. The gap may be configured to restrict a flow of the liquid coolant there through such that the biasing force applied by the compressible fluid overcomes a suction force associated with the pressure variations within the converging-diverging passage in response to the loss of pump flow without scram condition. According to still another embodiment, a method of manufacturing a control assembly for a nuclear reactor includes defining a coolant flow path within an inner volume of a duct, fixing a plug to the duct, slidably coupling a first piston to the duct, the plug and the first piston defining a pair of cooperating apertures that forms at least a portion of a converging-diverging passage, coupling a neutron modifying material to the first piston with a rod, positioning the converging-diverging passage along the coolant flow path such that pressure variations within the converging-diverging passage secure the first piston, the rod, and the neutron modifying material into a first position during normal operation of the nuclear reactor, and positioning a biasing member to apply a biasing force to the rod and the first piston, the biasing force repositioning the first piston, the rod, and the neutron modifying material into a second position in response to a loss of pump flow without scram condition. In one embodiment, the neutron modifying material includes an absorber, and wherein, the first position is outside of a fuel region and the second position is within the fuel region. In one embodiment, the neutron modifying material includes fissile material wherein, the first position is within the fuel region, and the second position is outside of the fuel region. In one embodiment, the neutron modifying material includes an absorber and fissile material wherein, the in the first position the fissile material is within the fuel region and in the second position the absorber is within the fuel region. According to one embodiment, the method includes associating a first aperture of the pair of cooperating apertures with the first piston and a second aperture of the pair of cooperating apertures with the plug, the first aperture and the second aperture defining at least a portion of a converging opening and at least a portion of a diverging opening. According to one embodiment of the method, the associating step includes extending the converging opening between an inlet end and a throat and extending the diverging opening between a throat and an outlet end. The throat of the converging opening may have a cross-sectional area that is equalized with a cross-sectional area of the throat of the diverging opening. According to one embodiment of the method, the associating step includes defining a pair of mating surfaces on the plug and the first piston and positioning the throat of the converging opening and the throat of the diverging opening along the pair of mating surfaces. According to one embodiment, the method includes defining the first aperture within a first body of the first piston and defining the second aperture within a second body of the plug such that the pair of cooperating apertures is spaced from peripheries of the plug and the first piston. According to one embodiment of the method, the associating step includes defining the first aperture on a first sidewall of the first piston and defining the second aperture on a second sidewall of the plug such that the pair of cooperating apertures is positioned at peripheries of the plug and the first piston. In one embodiment, the duct has an inner surface. The inner surface may form a portion of the converging-diverging passage. According to one embodiment, the method includes associating a plurality of aperture sets with the plug and the first piston, the plurality of aperture sets each including a pair of cooperating apertures. The plurality of aperture sets may form at least portions of a plurality of converging-diverging passages. According to one embodiment, the method includes rotationally aligning the first piston and the plug by defining a bore within the plug and positioning the rod within the bore, at least a portion of the rod having a cross-sectional shape that mates with a cross-sectional shape of the bore. According to one embodiment of the method, the positioning the biasing member step includes coupling a second piston to the rod and positioning the second piston within an interior space of a cup. The second piston may include a piston body that separates the interior space of the cup into a first region and a second region. According to yet another embodiment, a method of operating a nuclear fission reactor having a reactor core includes flowing coolant along a coolant flow path in the nuclear fission reactor, fissioning nuclear fuel within a fuel region of the reactor core, storing energy from the coolant flow in a resilient member, and inserting a neutron modifying material into the reactor core using the stored energy in response to the coolant flow falling below a threshold flow rate. According to one embodiment, the method includes withdrawing the neutron modifying material from the reactor core during an initial startup phase. According to one embodiment, the method includes maintaining the neutron modifying material in a withdrawn position when the coolant flow is within a target range. According to one embodiment, the method includes inserting the neutron modifying material during an initial start-up phase. According to one embodiment, the method includes maintaining the neutron modifying material in an inserted position when the coolant flow is within target range. According to another embodiment, the method includes repositioning the neutron modifying material in a withdrawn position when the coolant flow is out of a target range. In one embodiment, the flowing coolant step includes engaging a pump from an initial quiescent state. According to one embodiment, the method includes withdrawing the neutron modifying material in response to the coolant flow exceeding a second threshold flow rate. In one embodiment, the second threshold flow rate is between 25% and 30% of the first threshold flow rate. According to one embodiment, the method includes maintaining the neutron modifying material in a withdrawn position when the coolant flow is within a target range. According to one embodiment, the method includes inserting the neutron modifying material at a rate that is greater than a characteristic coast down rate associated with the pump. According to one embodiment of the method, the insertion step includes inserting the neutron modifying material in response to a loss of coolant flow without scram condition. According to one embodiment, the method includes passively inserting the neutron modifying material. According to one embodiment, the method includes inserting the neutron modifying material independent of thermal feedback from the reactor core. According to one embodiment, the method includes inserting the neutron modifying material mechanically and independent of electronic feedback relating to a condition of the reactor core. According to one embodiment, the method includes monitoring the position of the neutron modifying material. According to one embodiment of the method, the storing energy step includes pressurizing a gas within a reservoir. With respect to the use of substantially any plural and/or singular terms herein, those having skill in the art can translate from the plural to the singular and/or from the singular to the plural as is appropriate to the context and/or application. The various singular/plural permutations are not expressly set forth herein for sake of clarity. The herein described subject matter sometimes illustrates different components contained within, or connected with, different other components. It is to be understood that such depicted architectures are merely exemplary, and that in fact many other architectures may be implemented which achieve the same functionality. In a conceptual sense, any arrangement of components to achieve the same functionality is effectively “associated” such that the desired functionality is achieved. Hence, any two components herein combined to achieve a particular functionality can be seen as “associated with” each other such that the desired functionality is achieved, irrespective of architectures or intermediate components. Likewise, any two components so associated can also be viewed as being “operably connected”, or “operably coupled,” to each other to achieve the desired functionality, and any two components capable of being so associated can also be viewed as being “operably couplable,” to each other to achieve the desired functionality. Specific examples of operably couplable include but are not limited to physically mateable and/or physically interacting components, and/or wirelessly interactable, and/or wirelessly interacting components, and/or logically interacting, and/or logically interactable components. In some instances, one or more components may be referred to herein as “configured to,” “configured by,” “configurable to,” “operable/operative to,” “adapted/adaptable,” “able to, “conformable/conformed to,” etc. Those skilled in the art will recognize that such terms (e.g., “configured to”) can generally encompass active-state components and/or inactive-state components and/or standby-state components, unless context requires otherwise. While particular aspects of the present subject matter described herein have been shown and described, it will be apparent to those skilled in the art that, based upon the teachings herein, changes and modifications may be made without departing from the subject matter described herein and its broader aspects and, therefore, the appended claims are to encompass within their scope all such changes and modifications as are within the true spirit and scope of the subject matter described herein. It will be understood by those within the art that, in general, terms used herein, and especially in the appended claims (e.g., bodies of the appended claims) are generally intended as “open” terms (e.g., the term “including” should be interpreted as “including but not limited to,” the term “having” should be interpreted as “having at least,” the term “includes” should be interpreted as “includes but is not limited to,” etc.). It will be further understood by those within the art that if a specific number of an introduced claim recitation is intended, such an intent will be explicitly recited in the claim, and in the absence of such recitation no such intent is present. For example, as an aid to understanding, the following appended claims may contain usage of the introductory phrases “at least one” and “one or more” to introduce claim recitations. However, the use of such phrases should not be construed to imply that the introduction of a claim recitation by the indefinite articles “a” or “an” limits any particular claim containing such introduced claim recitation to claims containing only one such recitation, even when the same claim includes the introductory phrases “one or more” or “at least one” and indefinite articles such as “a” or “an” (e.g., “a” and/or “an” should typically be interpreted to mean “at least one” or “one or more”); the same holds true for the use of definite articles used to introduce claim recitations. In addition, even if a specific number of an introduced claim recitation is explicitly recited, those skilled in the art will recognize that such recitation should typically be interpreted to mean at least the recited number (e.g., the bare recitation of “two recitations,” without other modifiers, typically means at least two recitations, or two or more recitations). Furthermore, in those instances where a convention analogous to “at least one of A, B, and C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, and C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). In those instances, where a convention analogous to “at least one of A, B, or C, etc.” is used, in general such a construction is intended in the sense one having skill in the art would understand the convention (e.g., “a system having at least one of A, B, or C” would include but not be limited to systems that have A alone, B alone, C alone, A and B together, A and C together, B and C together, and/or A, B, and C together, etc.). It will be further understood by those within the art that typically a disjunctive word and/or phrase presenting two or more alternative terms, whether in the description, claims, or drawings, should be understood to contemplate the possibilities of including one of the terms, either of the terms, or both terms unless context dictates otherwise. For example, the phrase “A or B” will be typically understood to include the possibilities of “A” or “B” or “A and B.” With respect to the appended claims, those skilled in the art will appreciate that recited operations therein may generally be performed in any order. Also, although various operational flows are presented in a sequence(s), it should be understood that the various operations may be performed in other orders than those which are illustrated, or may be performed concurrently. Examples of such alternate orderings may include overlapping, interleaved, interrupted, reordered, incremental, preparatory, supplemental, simultaneous, reverse, or other variant orderings, unless context dictates otherwise. Furthermore, terms like “responsive to,” “related to,” or other past-tense adjectives are generally not intended to exclude such variants, unless context dictates otherwise. Those skilled in the art will appreciate that the foregoing specific exemplary processes and/or devices and/or technologies are representative of more general processes and/or devices and/or technologies taught elsewhere herein, such as in the claims filed herewith and/or elsewhere in the present application. While various aspects and embodiments have been disclosed herein, other aspects and embodiments will be apparent to those skilled in the art. The various aspects and embodiments disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope and spirit being indicated by the following claims. An example apparatus includes a duct configured to conduct a fluid in a first direction, a loading assembly disposed within the duct and configured to move a member in the first direction into a loaded position when pressure of the fluid in the duct satisfies a loading condition, and a firing assembly operably coupled to the loading assembly and disposed within the duct. The firing assembly and the loading assembly are configured to store energy when the member is in the loaded position and to release the stored energy and move the member out of the loaded position in a second direction opposite the first direction when the pressure of the fluid in the duct satisfies a firing condition. Another example system of any preceding system includes a plug fixed to the duct and a first piston coupled to the member disposed within and slidably coupled to the duct. Another example system of any preceding system a member disposed within the duct and having an end that is configured to engage a neutron modifying material. Another example system of any preceding system includes a plug and a first piston that define a pair of cooperating apertures that forms at least a portion of a converging-diverging passage. Another example system of any preceding system includes a converging-diverging passage is disposed along a fluid flow path such that pressure variations within the converging-diverging passage secure the first piston and the member when the pressure of the fluid in the duct satisfies the loading condition. Another example system of any preceding system includes a pair of cooperating apertures includes a first aperture defined at least partially by the first piston and a second aperture defined at least partially by the plug, the first aperture and the second aperture defining at least a portion of a converging opening and at least a portion of a diverging opening. Another example system of any preceding system includes the converging opening extends between an inlet end and an inlet throat, the diverging opening extends between an outlet throat and an outlet end, and the inlet throat of the converging opening has an inlet throat cross-sectional area that is equalized with an outlet throat cross-sectional area of the outlet throat of the diverging opening. Another example system of any preceding system includes a first piston that includes a first body that defines the first aperture and the plug includes a second body that defines the second aperture such that the pair of cooperating apertures is spaced from peripheries of the plug and the first piston. Another example system of any preceding system includes a firing assembly includes a cup and a second piston, wherein the cup has a sidewall that defines an interior space, and the second piston is disposed within the interior space of the cup. Another example system of any preceding system includes a member that has an opposing second end, wherein the second piston is coupled to the opposing second end of the member, and a second piston includes a piston body that separates the interior space of the cup into a first region and a second region, and a member that is positioned along the fluid flow path, and a cup that has an open end such that the first region is exposed to the fluid flow path. Another example system of any preceding system includes a cup that is configured to contain a compressible fluid within the second region. The example system also includes a cup that defines an opening configured to fluidly couple the first region and a liquid coolant associated with the fluid flow path. The example system also includes a pressure of the compressible fluid that varies with the pressure of the liquid coolant. Another example system of any preceding system includes a second piston that is slidably coupled to the sidewall of the cup. The example system also includes a second piston that defines an orifice that places the first region in fluid communication with the second region. The example system also includes an orifice that is configured to restrict a flow of the fluid therethrough such that the release of stored energy applied by the firing assembly overcomes a suction force associated with the pressure variations within the converging-diverging passage when the pressure of the fluid in the duct satisfies a firing condition. Another example system of any preceding system includes a hysteresis device positioned to apply a driving force independent of the release of stored energy by the firing assembly. Another example system of any preceding system includes that the hysteresis device is configured to receive a hysteresis control signal, and the hysteresis device initiates the driving force in response to receiving the hysteresis control signal. Another example system of any preceding system includes a hysteresis device that is a spring mechanism. Another example system of any preceding system includes an expansion device that has a contracted state and an expanded state, and is positioned to provide a resisting force in the expanded state. Another example system of any preceding system includes that the expansion device is an engaging member that maintains the expansion device in the expanded state. Another example system of any preceding system includes that the expansion device is configured to receive an engagement control signal, and the engaging member maintains the expansion device in the expanded state in response to receiving the engagement control signal. Another example system of any preceding system includes that the expansion device is configured to receive a disengagement control signal, and the engaging member disengages and allows the expansion device to return to the contracted state in response to the disengagement control signal. Another example system of any preceding system includes that the expansion device comprises a thermal expansive material. Another example system of any preceding system includes that the expansion device further comprises a bellows. Another example system of any preceding system includes a locking mechanism that has a locked state and an unlocked state so that when the locking mechanism is in the locked state, it engages the loading assembly. Another example system of any preceding system includes a locking mechanism in the locked state engages the member and inhibits movement of the member relative to the duct. Another example system of any preceding system includes a locking mechanism that is configured to receive a locking control signal, and the locking mechanism enters and maintains the locked state in response to receiving the locking control signal. Another example system of any preceding system includes a locking mechanism that is configured to receive an unlocking control signal, and the locking mechanism enters and maintains the unlocked state in response to the unlocking control signal. Another example system of any preceding system includes a locking mechanism constructed of a ferromagnetic material. Another example system of any preceding system includes a flow restricting device, such that the firing assembly releases the stored energy in response to movement of the flow restricting device. Another example system of any preceding system includes a flow restricting device that moves in response to a change in temperature. An example system includes a nuclear reactor including a fuel assembly including a fuel assembly duct containing nuclear fuel, a pump in fluid communication with the fuel assembly duct of the fuel assembly, such that the pump is configured to provide a coolant flow along a coolant flow path. Another example system of any preceding system includes a control assembly including a control assembly duct configured to conduct coolant along at least a portion of the coolant flow path, a firing assembly disposed within the control assembly duct, and configured to release stored energy when the pressure of the coolant in the coolant flow path satisfies a firing condition. Another example system of any preceding system includes a control assembly including a plug fixed to the control assembly duct, a neutron modifying material coupled to a member, a first piston disposed within and slidably coupled to the control assembly duct, and coupled to the member, such that the firing assembly is coupled to the first piston and the member, and the release of stored energy inserts the neutron modifying material into a fuel region of the fuel assembly when the pressure of the coolant in the coolant flow path satisfies the firing condition. Another example system of any preceding system includes a configuration such that the plug and the first piston define a pair of cooperating apertures that forms at least a portion of a converging-diverging passage. Another example system of any preceding system includes a configuration such that the converging-diverging passage is disposed along the coolant flow path is such that pressure variations within the converging-diverging passage secure the neutron modifying material in a withdrawn position until the pressure of the coolant in the coolant flow path satisfies the firing condition. Another example system of any preceding system includes a pair of cooperating apertures including a first aperture defined at least partially by the first piston and a second aperture defined at least partially by the plug, such that the first aperture and the second aperture define at least a portion of a converging opening and at least a portion of a diverging opening. Another example system of any preceding system includes a configuration such that the converging opening extends between an inlet end and an inlet throat, and the diverging opening extends between an outlet throat and an outlet end, and the inlet throat of the converging opening has an inlet throat cross-sectional area that is equalized with an outlet throat cross-sectional area of the outlet throat of the diverging opening. Another example system of any preceding system includes a first piston that includes a first body defining the first aperture and the plug includes a second body defining the second aperture such that the pair of cooperating apertures is spaced from peripheries of the plug and the first piston. Another example system of any preceding system includes a firing assembly including a cup and a second piston, such that the cup has a sidewall that defines an interior space, and the second piston is disposed within the interior space of the cup. Another example system of any preceding system includes a member that has a first end and an opposing second end, and the neutron modifying material is coupled to the first end of the member. The example system also includes a second piston that is coupled to the opposing second end of the member, such that the second piston includes a piston body that separates the interior space of the cup into a first region and a second region. The example system also includes a cup that has an open end such that the first region is exposed to the coolant flow path. Another example system of any preceding system includes coolant that is configured to store the stored energy that inserts the neutron modifying material into the fuel region of the fuel assembly when the pressure of the coolant in the coolant flow path satisfies the firing condition. Another example system of any preceding system includes a second piston that is slidably coupled to the sidewall of the cup, such that the second piston defines an orifice that places the first region in fluid communication with the second region. The example system also includes an orifice that is configured to restrict a flow of the coolant therethrough such that the release of stored energy applied by the coolant overcomes a suction force associated with the pressure variations within the converging-diverging passage when the pressure of the coolant in the coolant flow path satisfies the firing condition. Another example system of any preceding system includes a control assembly including a hysteresis device positioned to apply a driving force. Another example system of any preceding system includes a hysteresis device that is configured to receive a hysteresis control signal, such that the hysteresis device initiates the driving force in response to receiving the hysteresis control signal. Another example system of any preceding system includes a hysteresis device that is a spring mechanism. Another example system of any preceding system includes a control assembly including an expansion device, such that the expansion device has a contracted state and an expanded state, and the expansion device is positioned to provide a resisting force in the expanded state. Another example system of any preceding system includes and expansion device including an engaging member, such that the engaging member maintains the expansion device in the expanded state. Another example system of any preceding system includes an expansion device configured to receive an engagement control signal, such that the engaging member maintains the expansion device in the expanded state in response to receiving the engagement control signal. Another example system of any preceding system includes an expansion device that is configured to receive a disengagement control signal, such that the engaging member disengages and allows the expansion device to return to the contracted state in response to the disengagement control signal. Another example system of any preceding system includes an expansion device constructed of a thermal expansive material. Another example system of any preceding system including an expansion device that includes a bellows. Another example system of any preceding system includes a locking mechanism that has a locked state and an unlocked state, such that the locking mechanism in the locked state engages the control assembly. Another example system of any preceding system includes a locking mechanism that, in the locked state, engages the control assembly to inhibit movement of the firing assembly relative to the duct. Another example system of any preceding system includes a locking mechanism that is configured to receive a locking control signal, such that the locking mechanism enters and maintains the locked state in response to receiving the locking control signal. Another example system of any preceding system includes a locking mechanism that is configured to receive an unlocking control signal, such that the locking mechanism enters and maintains the unlocked state in response to the unlocking control signal. Another example system of any preceding system includes a locking mechanism constructed of at least a ferromagnetic material. Another example system of any preceding system includes a control assembly that includes a flow restricting device, such that the firing assembly releases stored energy in response to movement of the flow restricting device. Another example system of any preceding system includes a flow restricting device that moves in response to a change in temperature. An example method includes defining a coolant flow path within an inner volume of a duct, fixing a plug to the duct, slidably coupling a first piston to the duct. The plug and the first piston define a pair of cooperating apertures that forms at least a portion of a converging-diverging passage. The example method further includes coupling a neutron modifying material to the first piston with a member, positioning the converging-diverging passage along the coolant flow path such that pressure variations within the converging-diverging passage secure the first piston, the member, and the neutron modifying material during normal operation of the nuclear reactor, and positioning a biasing member to apply a biasing force to the member and the first piston, such that the biasing force releases the first piston, the member, and the neutron modifying material in response to a loss of pump flow without scram condition. Another example method of any preceding method includes associating a first aperture of the pair of cooperating apertures with the first piston and a second aperture of the pair of cooperating apertures with the plug, such that the first aperture and the second aperture defining at least a portion of a converging opening and at least a portion of a diverging opening.
	description	The invention is generally related to medical isotopes and, more particularly, to a medical isotope production reactor. Technetium-99m (t1/2 6.02 hr) is the most widely used radioisotope in nuclear medicine, accounting for more than 80% of all diagnostic nuclear medicine procedures. Technetium-99m (99mTc) is almost exclusively produced from the decay of its 66-hour parent 99Mo. Projected world demand for 99Mo by the year 2008 was estimated at approximately 11,000 to 12,000 Ci per week (6 days pre-calibrated). The most common method of 99Mo production is based on neutron irradiation in a nuclear reactor of a U—Al alloy or electroplated target enriched to 93 wt % 235U. After irradiation, the 99Mo is extracted from the other fission products by radiochemical methods. Although the specific activity achieved by this method is several tens of kilocuries per gram of molybdenum, large amounts of radioactive wastes are generated as byproducts of the fission process and the problem of long-lived fission product management is the major disadvantage in the production of 99Mo by this method. The use of aqueous homogeneous solution reactors or water boiler reactors presents an attractive alternative to the conventional target irradiation method of producing 99Mo in that solution reactors eliminate the need for targets and can operate at much lower power than required for a target reactor to produce the same amount of 99Mo. Specifically, the use of solution reactors for the production of medical isotopes is potentially advantageous because of their low cost, small critical mass, inherent passive safety, and simplified fuel handling, processing and purification characteristics. These advantages stem partly from the fluid nature of the fuel and partly from the homogeneous mixture of the fuel and moderator. In general, homogeneous reactor systems are superior to heterogeneous reactor systems in their inherent safety characteristics which arise from their greater radiolytic gas production per energy release, thereby resulting in a considerably larger prompt negative temperature coefficient of reactivity. However, the modularity of heterogeneous reactor systems provides a greater degree of freedom and versatility in the fuel arrangement. If practical methods for handling a radioactive aqueous fuel system are implemented, the inherent simplicity of a heterogeneous-homogeneous combinatorial reactor should result in considerable economic gains in the production of medical isotopes. The advantages of utilizing homogeneous reactor technology for medical isotope production applications has prompted several countries, including the U.S., Russia, and China, to initiate programs to assess the feasibility of applying this technology on a commercial basis. U.S. Pat. No. 5,596,611 discloses a uranyl nitrate homogeneous reactor (100 kW to 300 kW) for the production of 99Mo. The reactor is immersed in a containment pool which serves as a heat removal media for the sensible and decay heat generated in the reactor. The reactor vessel is finned to enhance the heat transfer to the containment pool. The reactor operates in a continuous mode in which the radioactive waste products are recirculated back into the reactor. A portion of the uranyl nitrate solution from the reactor is directly siphoned off and passed through columns of alumina to fix some of the fission products, including 99Mo, on the alumina. The 99Mo and some fission products on the alumina column are then removed through elution with a hydroxide and the 99Mo is either precipitated out of the resultant elutent with alpha-benzoinoxime or passed through other columns. U.S. Pat. No. 5,910,971 discloses a small (20 kW to 100 kW) dedicated uranyl sulfate homogeneous reactor for the production of 99Mo which operates in a batch mode for a period of several hours to a week. After shutdown and following a cool-down period, the resultant solution is pumped through a solid sorbent material that selectively adsorbs the 99Mo. The uranyl sulfate and all fission products not adhering to the sorbent are returned to the reactor vessel. The reactor uses internal cooling coils for heat removal. Although homogeneous reactor system concepts offer many advantages and greater flexibility for the production of 99Mo, potential power instabilities, which result from radiolytic bubble formation and thermal agitation, generate reactivity variations that can impair continuous stable operation. As a result, static solution reactor systems are power limited and, therefore, the specific activity of the 99Mo achievable, is limited by solution cooling constraints and potential thermal instabilities. The present invention is drawn to a combinatorial heterogeneous-homogeneous reactor configuration in which an array or groups of homogeneous fuel assemblies are interlinked together in a heterogeneous lattice. The present invention removes the limitation of a homogeneous reactor by providing a reactor concept that utilizes the inherent advantages of homogeneous fuel elements but in a heterogeneous fuel lattice arrangement that limits the power density of any one homogeneous fuel element and yet forms a reactor arrangement that is capable of producing any product demand of interest. The present invention provides a method for producing medical isotopes by the use of a modular reactor core comprised of homogeneous fuel assemblies arranged in a regular rectangular or triangular pitch lattice. The aqueous fuel solution is contained within individual fuel assemblies that are right circular cylinders clad in corrosion-resistant alloys such as stainless steel, zircalloy, zircalloy alloys, or other metal alloys that are resistant to corrosive fissile environments but preserve neutron economy. The fuel assemblies are supported below by a core plate that is tied directly to the lower reactor support structure. The bottom of each assembly can open into a common plenum area which provides a hydrodynamic communication/coupling path between the individual assemblies in the lattice. Alternately, the fuel assemblies can be isolated hydrodynamically from one another. The fuel assemblies are supported above by an upper plate that is welded to each assembly tube. The top of each assembly opens to a common upper plenum which provides a means of thermodynamic pressure equalization among the four assemblies in the reactor core lattice. The present provides a liquid fuel reactor concept where no fuel is circulated outside the core region. The present invention provides a homogenous fuel element that combines the inherent safety characteristics with a heterogeneous lattice array which limits the power density of any one homogeneous fuel assembly. The present invention provides a homogeneous fuel element with individual heat removal, reflux condenser, and sweep gas circuits which are modular and removable from the core lattice for maintenance purposes. The various features of novelty which characterize the invention are pointed out with particularity in the claims annexed to and forming part of this disclosure. For a better understanding of the present invention, and the operating advantages attained by its use, reference is made to the accompanying drawings and descriptive matter, forming a part of this disclosure, in which a preferred embodiment of the invention is illustrated. As seen in FIG. 1, the invention is generally indicated by numeral 10. The combinatorial heterogeneous-homogeneous reactor arrangement 10 is generally comprised of three major subsystems, namely the reactor core 12, the reactor cooling system 14 (FIG. 6), and the reactor gas management system 16 (FIG. 9). Unlike a reactor with uranium pellets in clad fuel rods used in the production of energy to produce electricity, this medical isotope production reactor uses a liquid fuel solution that circulates through the core. The reactor core 12 is comprised of a modular heterogeneous lattice such as graphite, beryllium, water, steel or some other neutron reflecting material that minimizes neutron leakage and optimizes neutron economy which has a plurality of removable homogeneous fuel assemblies 18. The fuel assemblies 18 within the lattice are interlinked at a common upper plenum 19 to insure system thermodynamic stability. The fuel assemblies 18 are typically grouped into symmetric subunits, as best seen in FIG. 4, which can be interlinked at a common lower plenum 21 to provide a means for promoting free convection circulation among the fuel assemblies 18 in the subgroup of FIG. 4. Alternately, all fuel assembly subgroups may be interlinked through the common lower plenum 21 to allow for free convection circulation and intercommunication of fluid fuel among all of the fuel assemblies 18 through out the core lattice. From this it can be understood that lower plenum 21 is common to a group of symmetric subunits of fuel assemblies in one embodiment and common to all fuel assemblies in another embodiment. The spacing between fuel assemblies 18 or assembly subgroups and, thus, the amount of interspersed neutron reflecting lattice material such as graphite, beryllium, water, steel, or some other neutron reflecting material that minimizes neutron leakage and optimizes neutron economy between fissile units can be adjusted by design to regulate the desired neutron interaction between homogenous fuel assemblies and, thus, the net design power level and isotope production capability of the reactor. The reactor core 12 lattice geometric configurations can be of any regular array such as a rectangular array on a square pitch, a hexagonal array on a triangular pitch, or some other commonly used lattice geometric arrangement. The market demand for the product and, thus, the reactor power level will dictate the number of required fuel assemblies and the lattice configuration. FIG. 2 illustrates a sixteen fuel assembly array on a square pitch where the lattice fuel assemblies 18 are grouped in subunits consisting of four fuel assemblies. FIG. 3 illustrates another lattice pattern in which seven fuel assemblies 18 are arranged on a triangular pitch lattice with a sub-grouping configuration in which one fuel assembly is shared among the three fuel sub-groups. Regardless of the lattice structure, the individual fuel assemblies 18 within the reactor core 12 are grouped into symmetric subunits with each fuel assembly 18 being a self-contained cylindrical vessel 23 (FIG. 5) which houses the fissile fuel solution. FIG. 4 illustrates a typical four fuel assembly subunit of a regular array square pitch lattice such as that illustrated in FIG. 1. For ease of explanation and illustration, reference is made to FIG. 5, which illustrates a single homogeneous fuel assembly 18. Each fuel assembly 18 includes the following. Cooling coil circuits 20 in the lower section are immersed in the liquid fuel solution. Reflux condenser circuit 22 in the upper section condenses entrained water vapor and solution spray. Sweep gas circuit 24 dilutes the radiolytic gases to insure that the gas mixture remains below the hydrogen lower flammability limit (<4% by volume H2). A concentric umbilical tube 26 provides a means for cooling water inlet and outlet flow lines 28, 30 for the fission heat removal cooling coils 20 and reflux condenser 22, sweep gas inlet 32, and line 34 used for condensed water return, acid addition, and fresh fuel solution replenishment for each operating cycle. The umbilical tube 26 is welded to the assembly flange 36 which is bolted to the upper dome head structure 38 and so is removable. The fuel assembly cooling coil circuits 20 shown in FIG. 5 remove sensible and decay heat produced in each homogeneous fuel assembly. The cooling coil circuits 20 are comprised of a series of corrosion resistant tubing sections constructed of material such as stainless steel, zircalloy, or zircalloy alloys, or other metal alloys that are resistant to corrosive fissile environments but preserve neutron economy. The cooling coil circuits comprise a series of either helical, serpentine, or other combinations of curved and straight tubing sections whose number of turns as well as the spatial location are arranged to insure maximal uniform heat removal throughout the fuel assembly with minimal pressure drop. Each coil section can be linked to a corresponding reflux coil condenser circuit 22 in the upper portion of each fuel assembly which serves to condense entrained water vapor and solution spray out of the sweep gas mixture. Condensation of the water vapor and solution spray reduces the deposition of entrained uranium on exposed surfaces of the reactor gas management system. Each cooling and reflux coil condenser circuit 20, 22 is a continuous coil that is welded to a concentric inlet and outlet header 28, 30 housed in the assembly central umbilical support tube 26. The common upper plenum is designed to provide: (1) a large solution-gas interface to reduce solution entrainment in the solution vapor/radiolytic gases escaping the solution surface; (2) a large volume to accommodate an emergency fluid expansion without affecting the solution-gas interface; and (3) a large volume for the sweep gas to mix, dilute, and cool the radiolytic gas emerging from the fuel solution surface. The individual homogeneous fuel assemblies 18 in each subunit share a common lower plenum 21 with the other fuel assemblies in the subgroup or with all of the fuel assemblies within the lattice as a means for promoting free convection circulation throughout the lattice subgroup or the lattice as a whole. The upper plenum of each homogeneous fuel assembly 18 opens into a common upper plenum 19 shared by all fuel assemblies 18 within the reactor core 12. This insures proper equilibration of the radiolytic and carrier gas emanating from each homogeneous fuel assembly and thereby providing for overall core thermodynamic stability. The reactor core cooling system 14 is schematically illustrated in FIG. 6 and generally comprised of a decay tank 40 for the 16N generated by neutron activation of the primary coolant passing through the reactor core 12, a surge tank 42 (on the inlet side of pumps 44) which serves as a coolant reservoir and provides expansion space for the system, redundant, variable-speed, primary coolant pumps 44, and a packaged, high-efficiency chilled water system 46. These components are in fluid communication with each other and the reactor core 12 via fluid lines 48. The dome of surge tank 42 is swept with air using lines 50 to remove the hydrogen generated from the radiolytic decomposition of primary coolant. The volumetric flow of air is designed to maintain the hydrogen concentration in the air to approximately 2% by volume to prevent a fire hazard. The packaged chilled water system 46 is designed to maintain the inlet reactor cooling water temperature to the reactor at 4 to 6 degrees Celsius. The flow rate through the reactor core 12 can be varied according to the inlet temperature to maintain the desired differential temperature, thereby accommodating different reactor loadings ranging from decay heat removal to full power operation. The reactor gas management system 16 is best seen in FIG. 5 and 9 and is designed to provide (1) a dilution gas flow that mixes with the radiolytic gases to insure that hydrogen content in the gas mixture remains below the lower flammability limit and (2) cooling for the radiolytic gas mixture to assist in removal of water vapor, solution spray, and any uranium entrained in the radiolytic gas emanating from the solution surface. The sweep gas, which can be air, nitrogen, oxygen, or an equivalent, enters the upper portion of each fuel assembly via a perforated nozzle 52. This disperses the gas above the fuel surface (It is seen in FIG. 5 that the level of the liquid fuel solution is at approximately the mid-point of the fuel assembly 18.) in a turbulent pattern to enhance intermixing of the radiolytic gas mixture rising from the fuel surface with the cooler sweep gas exiting the perforated nozzle 52. The nozzle 52 disperses the gas that passes through the concentric umbilical tube 26 from the sweep gas inlet 32 between the central control rod 54 and the umbilical tube 26. As seen in FIG. 9, the sweep gas inlet header 56 for each subunit of fuel assemblies 18 originates from the outlet of the tube of the reactor gas management system 16. The reactor gas management system 16, best seen in FIG. 9, is generally comprised of an entrainment trap 58, hydrogen recombiner equipment 60, a gas cooler-condenser 62, a pressure regulating valve 64, and, if necessary, a blower. The radiolytic gas loops from all of the fuel assembly subunits utilize a common radioactive gas disposal arrangement. The entrainment trap 58 is comprised of a silver activated metal (stainless steel) sponge which removes entrained liquid, iodine vapors, solid radioactive daughters of the fission gas, and activated particulates in the sweep gas. The metal sponge presents a large catalytic surface area for the capture of fission fragments and other particulates. The metal sponge is housed in a metal chamber located on each of the parallel gas lines leaving the reactor and prior to the inlet to the hydrogen recombiner equipment 60. The hydrogen recombiner equipment 60 associated with each subunit of fuel assemblies 18 (best seen in FIG. 10 with only one of the parallel units being shown for ease of illustration) recombines hydrogen and oxygen formed by radiolytic dissociation of water in the fuel solution during core operation. Each catalytic chamber is comprised of an axial bed 68 containing catalytic particles encased in a metal housing 70 with a steel shot flashback shield (not seen) on the inlet 72 and exit 74 to the chamber sized to serve as an explosion trap that quenches the hydrogen-oxygen flames at the recombiner inlet and exit and sufficient heat capacity to stop combustion. The axial bed is provided with substrate particles 76 (alumina, carbon, silica, etc.) having a precious metal coating 78 (palladium, platinum, etc.) which serves as the active catalyst. The particles 76 can be wet-proofed with a hydrophobic coating 80, such as Teflon®, which repels water but allows a surrounding envelope of gaseous reactants to be retained on the particle surface. The gas mixture flow into the axial bed 68 can be driven by a blower not shown or can be used in a natural circulation mode. The natural circulation mode may be assisted by a heater (not shown) at the inlet 72. The heater also serves to remove any residual water not vaporized. The natural circulation mode is also assisted by the extended chimney 82 above the exit 74 of the axial bed 68. In the unlikely event that a hydrogen deflagration/detonation were to occur, the increased pressure would activate pressure relief mechanisms 84 at each end of metal housing 70 to isolate the axial bed 68 and vent the burning contents to a pressure relief container 86, thereby minimizing potential reactivity excursions. The heat of the recombination reaction is removed in the gas cooler-condenser 62, illustrated in more detail in FIG. 11, which is fluid communication with the gas discharge from recombiner 60. Multiple condensing coils 88 are preferably provided with baffles to increase coil surface area and turbulence. The cooler-condensers 62 are configured to provide a gravity drain flow 90 of the condensate back to the reactor 10 to preserve radiolytic mass balance. Depending on the uranyl salt employed as the fuel base, acid addition to the returning condensate flow may be required to insure the pH remains within specification. A pressure regulation valve 64 is used to insure that the reactor pressure remains at its operating value. A pressure regulating system 94, schematically illustrated in FIG. 12, is optional and contingent on the use of uranyl nitrate as the fuel solution. The pressure regulation valve of the cooler-condenser 62 maintains the reactor gas management system 16 and, therefore, the pressure in the reactor 10 at a constant pressure by bleeding any non-condensable gas to a HEPA filter/charcoal bed 96. The filter bed 96 removes residual iodine in the gas stream which is then compressed by a positive displacement compressor 98 and directed into a noble gas holding tank 100. The air, nitrogen/nitrogen oxide, and noble gas mixture is compressed by use of a positive displacement compressor 98. The contents of the holding tank 100 are eventually discharged to the NOx removal system 102 and radioactive gas disposal system 104 prior to being released to the environment. The NOx removal system 102 functions to remove residual NOx from the gas mixture, thereby preventing potential corrosion of downstream equipment and acid contamination of the environment. The radioactive gas disposal system 104 removes radioactive isotopes of xenon and krypton from the gas stream by holding up these noble gases for a time sufficient to permit decay of these isotopes to levels which are permissible for elevated release. The procedure implemented in the concept to remove NOx from the gas stream is to pass the gas mixture through a catalytic bed which contains zeolite or inorganic oxide substrate particles coated with ceria (cerium oxide), silica gel, or the equivalent. The catalytic action of the active coating removes a large percentage of any NOx formed from the radiolytic decomposition of the uranyl nitrate fuel base. The scrubbed gas mixture is then passed to the off-gas system which includes a set of HEPA filters and adsorption beds that contain sufficient quantities of adsorbing material to adsorb all of the xenon and all but krypton-85. The inert noble gas, nitrogen, and oxygen are monitored for radioactive content and released, if within specification, via the stack. The 99Mo processing system, schematically illustrated in FIG. 13, includes a sequence of processing steps in which: the fuel solution, which has been discharged from the reactor after a pre-specified irradiation period, (1) is stored in a first arrangement of columns 108 where the chemical state (fuel concentration, pH, temperature, etc.) of the irradiated fuel solution is adjusted and mixed to insure optimal conditions for high efficiency 99Mo extraction with a selected sorbent are obtained; (2) is passed through a second arrangement of columns 110 containing an inorganic or a solid polymer sorbent 112 to extract the 99Mo from the fuel solution; (3) is eluted with a concentrated base solution; and (4) purified with conventional exchange chromatography columns 116 (purification columns). The second columns 110 are connected in such a manner as to allow for parallel processing of the irradiated fuel solution. The sorbent 112 used in second columns 110 (separator columns) is preferably either an inorganic sorbent that is a hydrated metal complex or silver activated carbon or equivalent, or a solid polymer sorbent such as α-benzoin-oxime or maleic anhydride copolymer. The piping configuration and valve network is arranged to permit: (1) rinsing of the separation columns 110 with distilled water and/or acid to remove residual reactor fuel solution and trace fission products, and (2) elution of the 99Mo adsorbed on the separation columns 110 with a strong base (concentrated sodium or ammonium hydroxide) and passed to purification columns 116 (e.g. silver activated carbon/zirconium oxide, etc.) where the trace anions (135I, 103Ru, 132Te, etc.) are removed. The purified product is then converted to MoO3 by evaporation 118 and certified 120 for product purity. The certified product is then packaged and transported to a 99mTc-generator site for integration with the medical dispensing units. During the 99Mo processing sequence, the fuel solution is passed through the separation columns 110 and collected in criticality safe storage columns 122 (FIG. 14). The fuel solution is then sent to the fuel cleanup in batch mode to remove the fission product impurities from actinides. The fuel cleanup arrangement, schematically illustrated in FIG. 14, is comprised of a series of liquid-liquid extraction centrifugal contactors and/or pulse columns which are grouped into extraction 124, scrubbing 126, and stripping 128 sections. In the extraction section 124 the uranium and plutonium are extracted by multistage countercurrent contact with 30% V/O tributyl phosphate (TBP) in a paraffinic hydrocarbon diluent. Fission products, which have much lower distribution coefficients than uranium and plutonium, remain largely in the aqueous phase and leave the extraction section in the aqueous raffinate. Americium and curium, which are predominately trivalent, are similar to the rare-earth fission products in that they have relatively low distribution coefficients and thus remain in the raffinate 130 with the fission products. Neptunium is partly in the extractable hexavalent state and partly in the pentavalent state. However, in the fuel clean system concept, all the neptunium is converted to the hexavalent state to insure that the plutonium remains with the organic extract. Typically in the extraction section 124 centrifugal contactors are employed to disperse the phases and minimize the holdup, thereby reducing the potential for solvent degradation from intense fission product radioactivity. In the scrubbing section 126 the small quantities of fission products carried by the organic solvent leaving the extraction section 124 are removed from the organic solvent by countercurrent washing with aqueous nitric acid. The fission product impurities join the aqueous raffinate 130 from the extraction section. In the stripping section 128 the uranium and plutonium in the organic phase are back extracted to the aqueous by dilute (˜0.01M) nitric acid. The organic solvent form is then washed in the wash section 132 successively with 0.2M sodium carbonate and dilute nitric acid to remove trace radiolytic and hydrolytic decomposition products and then reused in the fuel cleanup arrangement. The aqueous raffinate stream 130 containing the fission products is passed to an aqueous waste management/processing arrangement schematically illustrated in FIG. 15 that receives many different feed streams that are differentiated primarily by their radioactivity content. The low-level waste streams are typically neutralized, if necessary, and concentrated in a simple flash or vapor compression evaporator to produce low-level waste concentrates and water. The volume of the waste concentrates is contingent on the salt content. Low-salt level waste can be greatly reduced in volume by evaporation without precipitation of the solids, whereas high-salt waste streams can only moderately be reduced in volume. The water is decontaminated (simple wire-mesh entrainment separators achieve a decontamination factor of several thousand) and returned to the fuel cleanup process. The highly radioactive stream feed to the aqueous waste management/processing arrangement encompasses the bulk of the fission products which reside in the raffinate stream 130 of the fuel cleanup arrangement. This aqueous phase contains many curies per liter and must be cooled to prevent self-boiling. The long term activity of the fission products are segregated into intermediate Class C and low level Class A streams by selectively removing the Cs and Sr from the raffinate stream with ion exchange resins and disposing the resin as Class C waste. The fission products remaining in the raffinate stream are passed to a waste concentrator that concentrates the waste to a concentration level that is commensurate with a stabilization process and disposal as Class A waste. Because of potential self-heating of the fission products, the evaporator and bottom storage tanks are provided with cooling means. As best seen in FIG. 7, reactivity control authority for each homogeneous fuel assembly is provided by control rods 133 that are inserted into the fuel solution through thimbles 134 which are sealed at the bottom. Lateral and vertical motion of the thimbles 134 is constrained at the upper and lower plenums 19, 21. Some of the control rods 133 function strictly as safety rods 133S while the remainder of the rods 133 serve as both power regulating/dampening and safety shutdown rods. The control rods 133 in each fuel assembly are clustered with their corresponding control rods 133 in the adjacent fuel assemblies 18 into safety rod and power regulating/dampening groups as illustrated by lines 135. Additionally, the rod clusters for each subunit are arranged in symmetric groups to insure that the core reactivity changes are uniform and symmetric. All core reactivity changes are performed by adjusting the positions of the rod clusters in fine increments (notch-by-notch). The control rod cluster withdrawal movements are constrained to notch movements by mechanical electrical interlocks with the maximum rod speed being limited. The axial position of each rod cluster is controlled by a rack and pinion drive mechanism, or equivalent, which is actuated through a rear-reduction unit by a reversible, 3-phase, variable reluctance electric motor 136. The control rod drive mechanism and rod element assembly are separate parts that are coupled by a direct current magnet 137 located at the linkage between the cluster drive mechanism and each control rod element. The electromagnets of all control elements are wired so that when a valid scram signal is received, all the electromagnets are de-energized simultaneously, and the control rods fall freely by gravity into the core and then are decelerated for the last two inches by the air cushioning effect of the control rod piston riding in the cylinder formed by the walls of the rod housing. FIG. 8 schematically illustrates a secondary means of bringing the nuclear reactor to sub-criticality and to maintain sub-criticality as the reactor cools. A suitable liquid neutron poison (gadolinium nitrate, sodium pentaborate, etc.) is injected into the cooling coils. The liquid injection makes possible an orderly and safe shutdown in the event that not enough control rods can be inserted into the reactor core to accomplish shutdown in the normal manner. The secondary shutdown arrangement is sized to counteract the positive reactivity effect of shutting down from rated power to cold shutdown condition. The shutdown operation occurs either under pneumatic pressure 138 or an explosively actuated squib valve 139 or a positive displacement pump operating in conjunction with a motor operated injection valve. The secondary shutdown arrangement includes a solution tank 140 containing the neutron poison material, a test water tank 141, and associated local piping, valves, and controls. While specific embodiments and/or details of the invention have been shown and described above to illustrate the application of the principles of the invention, it is understood that this invention may be embodied as more fully described in the claims, or as otherwise known by those skilled in the art (including any and all equivalents), without departing from such principles.
	claims	1. A reactor vessel thermal load reducing system comprising:a reactor vessel having a reactor vessel wall and being partially filled with liquid coolant to an operating coolant liquid surface level between a bottom and a top of said reactor vessel wall, wherein said reactor vessel wall has the following vertically defined points:Point A at said bottom of the wall,Point C at said operating coolant liquid surface level,Point E at said top of the wall,Point B between Point A and Point C, andPoint D between Point C and Point E;a guard vessel located circumferentially outside and adjacent to said reactor vessel; anda reactor vessel wall temperature difference minimizing means, said means comprisinga heat conductive member circumferentially located directly adjacent to said reactor vessel wall;solid heat insulation material distributed on the inside of said reactor vessel wall from point D to point C but not from point B to point A;solid heat insulation material distributed on the outside of said guard vessel from a point horizontally adjacent to point B to a point horizontally adjacent to point D;wherein during steady state operation of said reactor, said heat conductive member receives a net amount of heat radiation from said reactor vessel wall from point B to point C, and said heat conductive member radiates a net amount of heat to said reactor vessel wall from point C to point D;wherein said heat conductive member is a member attached to said guard vessel wall; andwherein said heat conductive member has a higher heat conduction coefficient than said reactor vessel wall; andwherein said heat conductive member reduces the thermal stress on said reactor vessel wall that would otherwise be caused by the rapid increase of the liquid coolant temperature being raised during reactor startup from 200° C. to 550° C. 2. The reactor vessel thermal load reducing system according to claim 1, wherein said heat conductive member is 12% Cr steel.
039473201	summary	This invention relates to fuel elements for a neutronic reactor. In particular it pertains to the structural make-up of material containing fissionable isotope for a nuclear reactor. Reference is made to my copending application, Ser. No. 721,108, filed Jan. 9, 1947 now U.S. Pat. No. 2,975,117 issued Dec. 19, 1960 and to the copending application of Leo Szilard, Ser. No. 698,334, filed Sept. 20, 1946, now U.S. Pat. 3,103,475 issued Sept. 10, 1963, for a showing of the type of reactors involved. This invention involves a partial departure from conventional fuel elements having a single cylindrical body of material containing a fissionable isotope, such as uranium. Such a body is difficult and costly to manufacture because of the necessity to machine to precise dimensions. Also the body develops undesirable elongated crystals in the direction of rolling operation preceding the step of machining. Further, uranium is a relatively poor heat conductor. An object of this invention is to provide a structure for material containing fissionable isotope for a reactor, which structure can be manufactured cheaply and easily by such simple operations as stamping or upsetting without a need for machining to accurate size. Another object is the provision of a structural make-up for material containing fissionable isotope which does not exhibit a pronounced tendency to grow in a single direction. A further object is to provide a structure of a fuel element for a reactor which structure has improved heat conductivity. This permits the heat of fission generated in the fissionable isotope to be dissipated more repeatedly and consequently the reactor to be operated at a higher specific power. Other objects and advantages of this invention will, in part, be obvious and appear hereinafter.
	summary
052456447	summary	The invention relates to a spacer for a fuel assembly of a pressurized water reactor, having a first group of first webs standing on end, extending parallel to one another in a plane and being slit on one long side thereof, a second group of second webs standing on end, extending at right angles thereto and being slit on the other long side thereof, and a plug-in connection between each one web of the first group and one respective web of the second group, in which the webs are inserted into one another by means of the slits and form a grid. As discussed in further detail below with regard to the first drawing figure, in such a device spacer webs and especially guide lugs formed thereon cause a high pressure loss. It is accordingly an object of the invention to provide a spacer for a fuel assembly of a pressurized water reactor, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which keeps the pressure loss at the spacer as low as possible by means of different provisions. In particular, this is accomplished according to the invention by dispensing with insertion buttons and attaining a given fixation of the plug-in connections for welding through the use of impressions on the webs themselves. With the foregoing and other objects in view there is provided, in accordance with the invention, a spacer for a fuel assembly of a pressurized water reactor, comprising a first group of first webs standing on end and extending parallel to one another in a plane, each of the first webs having longer sides and shorter sides, one of the longer sides of each of the first webs having a slit formed therein with a narrowed point and an impressed indentation; a second group of second webs standing on end and extending at right angles to the first webs, each of the second webs having longer sides and shorter sides, another of the longer sides of each of the second webs having a slit formed therein with a narrowed point and an impressed indentation; each respective one of the first webs being connected to a respective one of the second webs to form a grid by inserting the webs into each other at the slits and locking the narrowed point of one web into place in the impressed indentation of another web with a plug-in connection. In accordance with another feature of the invention, the impressed indentation of one web has lateral beads serving as guide surfaces for the longer side having the slit of the other web, in each of the plug-in connections. In accordance with a further feature of the invention, each of the webs has two lateral pinches forming the narrowed point. In accordance with an added feature of the invention, each of the webs has a pinch forming the impressed indentation, and the lateral beads are formed of material positively displaced by pinching. In accordance with a concomitant feature of the invention, the webs are welded together. 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 spacer for a fuel assembly of a pressurized water reactor, it is nevertheless not intended to be limited to the details shown, since various modifications and structural changes may be made therein without departing from the spirit of the invention and within the scope and range of equivalents of the claims. The construction and method of operation of the invention, however, together with additional objects and advantages thereof will be best understood from the following description of specific embodiments when read in connection with the accompanying drawings.
047028831	claims	1. In a nuclear fuel assembly having at least one control rod guide thimble and a top nozzle, said guide thimble including an upper extension member, said top nozzle including an upper hold-down plate having a passageway slidably receiving an upper end portion of said extension member, an improved structure for removably attaching said upper hold-down plate on said guide thimble upper extension member, comprising: (a) means defining a recess on said upper end portion of said extension member; (b) a stop member having upper and lower portions, said stop member lower portion adapted to connect onto and disconnect from said extension member upper end portion, said stop member upper portion having an outside diameter greater than that of said stop member lower portion and extending above said extension member upper end portion when said stop member lower portion is connected onto the same, said stop member also having a ledge formed thereon at a transition between its upper and lower portions which defines an upper limit of said recess when said stop member is connected onto said extension member upper end portion; and (c) an element mounted in said upper hold-down plate and extending therefrom into said passageway of said plate and said recess of said extension member upper end portion, said element being positioned to slide upwardly along said recess until making engagement with said ledge on said stop member when said stop member is connected onto said extension member upper end portion for limiting upward movement of said upper hold-down plate along said guide thimble, said element being positioned to slide upwardly along and past said recess when said stop member has been disconnected from said extension member upper end portion for allowing removal of said upper hold-down plate from said guide thimble. said upper end portion of said extension member has means defining a threaded section on the interior thereof; said stop member lower portion has a complementary threaded section defined on the exterior thereof adapted to thread into said threaded section of said extension member upper end portion for releasably connecting said stop member into said guide thimble extension member. (a) means defining an axially extending recess on the exterior of said upper end portion of each of said guide thimble extension members, said recess terminating at an upper terminal edge of said extension member upper end portion; (b) means defining a threaded section on the interior of said upper end portion of each of said guide thimble extension members; (c) a plurality of stop members each having upper and lower portions, said each stop member lower portion having a threaded section defined on the exterior thereof adapted to thread into and unthread from said threaded section of one of said extension member upper end portions, said stop member upper portion having an outside diameter greater than that of said stop member lower portion, said stop member also having an overhanging ledge formed thereon at a transition between its upper and lower portions which defines an upper end of said recess on said one extension member upper end portion when said stop member is threaded therein; and (d) a plurality of elements mounted in said upper hold-down plate and each extending therefrom into one of said passageways of said plate and said recess of one of said extension member upper end portions, said each element being positioned to slide upwardly along said corresponding recess until making engagement with said ledge on one of said stop members when said stop member is threaded into said corresponding extension member upper end portion for limiting upward movement of said upper hold-down plate along said guide thimble, said each element being positioned to slide upwardly along and past said corresponding recess when said one stop member has been unthreaded from said corresponding extension member upper end portion for allowing removal of said upper hold-down plate from said guide thimble. 2. The improved attaching structure as recited in claim 1, wherein said stop member upper portion has an outside diameter substantially the same as the outside diameter of said upper end portion of said guide thimble extension member which adapts said stop member upper portion to be slidably receivable in said upper hold-down plate passageway. 3. The improved attaching structure as recited in claim 1, wherein: 4. The improved attaching structure as recited in claim 1, wherein said recess terminates at an upper terminal edge of said guide thimble extension member upper end portion. 5. In a nuclear fuel assembly having a plurality of control rod guide thimbles and a top nozzle, said guide thimbles each including an upper extension member, said top nozzle including an upper hold-down plate having a plurality of passageways slidably receiving upper end portions of said respective extension members of said guide thimbles, an improved structure for removably attaching said upper hold-down plate on said guide thimble upper extension members, comprising: 6. The improved attaching structure as recited in claim 5, wherein said upper portion of each of said stop members has an outside diameter substantially the same as the outside diameter of said upper end portion of each of said guide thimble extension members which adapts said each stop member upper portion to be slidably receivable in one of said upper hold-down plate passageways.
	abstract	A lid frame for a nuclear fuel assembly shipping container and a shipping container for nuclear fuel assemblies are provided. The shipping container includes a lower container having a cradle, an upper container detachably coupled to the lower container, and a base frame coupled to the cradle with at least one nuclear fuel assembly placed thereon. The lid frame includes a plurality of supports installed apart from each other so as to surround the nuclear fuel assembly placed on the base frame, a plurality of clamps separated from each other, coupled to the supports so as to be perpendicular to the supports, rotatably hinged to the base frame, and clamping the nuclear fuel assembly, and a plurality of gap compensators coupled to inner surfaces of the supports in order to compensate for a gap between the inner surfaces of the supports and the nuclear fuel assembly.
	summary
	description	1. Field of the Invention The present invention concerns a fastening device for a diaphragm for x-ray radiation as well as a computed tomography apparatus having a radiation source with a diaphragm for x-ray radiation mounted on such a fastening device. 2. Description of the Prior Art X-ray computed tomography apparatuses known from German OS 102 42 920 and German OS 102 44 898 have comprise a rotatable frame on which an x-ray source and an x-ray detector are disposed opposite one another. A patient bed on which the patient is positioned is moved through a patient opening of the rotary frame to acquire, for example, diagnostic x-ray images of a patient, with a number of x-ray projections of a body region of the patient being acquired from different projection directions. Slice images of the body region of the patient or volume representations can be reconstructed from the acquired x-ray projections of the body region. In a diagnostic examination with an x-ray computed tomography apparatus, the patient is located on a patient bed in the patient opening of the rotary frame, or move through the patient opening. In order to alleviate feelings of spatial confinement as well as to enable more space for the medical personnel in the region of the patient opening for medical measures, as well as also to make it easier to examine particularly corpulent persons by means of x-ray computed tomography, there is a desire to enlarge the patient opening. The outer diameter of the rotating rotary frame, however, should not be enlarged. At the same time, the rotation speed of the rotary frame should be increased in order to develop new application fields for computed tomography, for example in cardiology. Both the enlargement of the patient opening and the increase of the rotation speed of the rotary frame require design changes to presently-used x-ray computed tomography apparatuses. A known radiator diaphragm 1 associated with an x-ray source arranged on a rotary frame is shown in FIG. 1. Conventionally it is arranged with a filter unit 2 (separated by a non-load bearing intermediate plate 3) in a housing requiring a relatively large space. The housing 4 is conventionally fashioned from a several millimeter thick steel plate and, apart from openings for the passage of x-ray radiation, is provided with an x-ray-shielding material. The non-load bearing intermediate plate 3 that separates the filter unit 2 from the radiator diaphragm 1 is fastened in the supporting and scatter-radiation-sealed housing 4 with angle supports 5, as can be seen in the section view of FIG. 2. The massive housing 4 has not only a high space requirement on the rotary frame, which is disadvantageous with regard to the size of the patient opening, but also has a mass of several kilograms, which is also disadvantageous with regard to angular momentum on the rotary frame. High centrifugal forces must be accommodated by the fastening means with which the housing is fastened on the rotary frame. An object of the present invention is to provide a fastening device for a diaphragm for x-ray radiation, preferably for a computed tomography apparatus, which has an optimally low space requirement with an optimally low dead weight. This object is achieved in accordance with the invention by a fastening device for a diaphragm for x-ray radiation, having a base plate with an opening for the passage of x-ray radiation that can accommodate load forces, and at least one covering device disposed to enclose a space at the base plate, whereby a diaphragm can be contained in the space. According to the invention the conventional massive housing for the diaphragm for x-ray radiation is thus foregone, and instead a base plate that can be attached to the rotary frame is used the diaphragm for x-ray radiation being arranged at the base plate. The base plate is designed, with regard to the material used and the material strength, such that it can accommodate the load forces necessary for retention of the diaphragm. A covering device that is arranged on the base plate is provided for incorporation of the diaphragm. Since the inventive fastening device essentially has only a base plate and a covering device, it can be constructed more easily than the known diaphragm housings and moreover requires a smaller space, such that the aforementioned requirements are met, both to enlarge the patient opening of the computed tomography apparatus and (as a consequence of the reduced mass) to achieve an increase of the rotation speed of the rotary frame of the computed tomography apparatus. According to a preferred embodiment of the invention, at least one side wall is present on at least one side of the base plate, and the covering device is attached to the base plate and/or to the side wall to enclose the space. In an embodiment of the invention at least one side wall is present on each side of the base plate and the fastening device has a second covering device so that spaces for accommodation of components are present on both sides of the base plate in order to achieve a shaping of the x-ray beam as well as to be able to influence the intensity and the spectrum of the x-ray radiation. The inventive fastening device thereby allows the components to be arranged relatively close to the x-ray source. In a preferred embodiment of the invention two side walls are on each side of the base plate on both sides of the opening, providing a U-shaped profile on both sides of the base plate. The U-shaped profiles can be sealed with the covering device. The U-shaped profile is particularly inflexible with regard to deformation. The side walls on both sides of the base plate preferably are arranged such that a double-U-shaped profile results. The description of the side walls as being present on both sides of the opening encompasses the side walls being attached at the edges of the opening, thus in the opening. In an embodiment of the invention, the covering devices for sealing of the U-shaped profiles of the base plate are likewise fashioned U-shaped. As a consequence of the provision of two spaces in the fastening device, in a variant of the invention the diaphragm for x-ray radiation can be arranged in a space that can be sealed with a covering device and a beam filter for x-ray radiation can be arranged in the other space that can be sealed with a covering device. In one embodiment of the invention, the covering devices each have an opening for the passage of x-ray radiation therethrough. Moreover, the covering devices are thin-walled to save weight such that, although they are dimensionally stable and suitable for sealing a space, they can themselves accommodate no load forces for retention of components such as diaphragms or filter devices. In another embodiment of the invention, the covering devices are fashioned of a self-supporting material that is permeable to x-ray radiation, and this material is provided with a layer of an x-ray-shielding material (preferably lead). A weight saving is achieved in this manner, as is a scatter-radiation-sealed closure of the spaces. Likewise for weight-saving, the base plate and/or the side walls can be composed of aluminum. The base plate and the side walls can form one unit, for example in the form of a cast part. The side walls alternatively can be attached to the base plate by known fastening means, for example with screws. For scatter-radiation the side walls can have a layer of an x-ray-radiation-shielding material (preferably lead). The above object also is achieved by a computed tomography apparatus having a rotary frame on which an x-ray source and an x-ray detector are mounted opposite one another, and a diaphragm which is arranged on a fastening device, associated with the x-ray source of the type described above. The x-ray computed tomography apparatus shown in FIG. 3 has an acquisition unit with an x-ray source 11 from the focus F of which x-ray radiation originates that is shaped into a fan-shaped x-ray beam 12 with a fan angle α by a diaphragm explained below and not explicitly shown in FIG. 3. Moreover, the acquisition unit has an x-ray detector 13 that, in a known manner, has a number of rows of detector elements successively arranged in the direction of the system axis Z of the computed tomography apparatus. The x-ray source 11 and the x-ray detector 13 are disposed opposite one another on a rotary frame 18, which is the rotatable part of the gantry of the computed tomography apparatus. In the exemplary embodiment, a patient P is shown on a patient bed 16 of the computed tomography apparatus. The patient bed 16 can be displaced in the direction of the system axis Z of the computer tomography apparatus, whereby this patient bed 16 moves through a patient opening 17 of the rotary frame 18 of the computed tomography apparatus. The rotary frame 18 is mounted such that it can rotate around the system axis Z of the computed tomography apparatus and is rotated around the system axis Z in the (φ-direction to scan the patient P with x-ray radiation. X-ray projections of a body region of the patient P are acquired from different projection directions. The x-ray beam 12 irradiates an imaging field 10 of a circular cross section. The data of the x-ray projections acquired with the x-ray detector 13 are supplied to a computer 14 with which slice images or volume representations of acquired body regions of the patient P can be reconstructed in a known manner from the measurement data and displayed on a display device 19. The rotary frame 18 is driven by a motor 15 in a manner schematically shown in FIG. 3 As can be seen from FIG. 3, an inventive fastening device for the mentioned diaphragm (which is shown only schematically in FIG. 3) is associated with the x-ray source 11 on the rotary frame 18. As can be seen from FIGS. 4 and 5, the fastening device 20 has a base plate 21 with an opening 22. According to the exemplary embodiment shown in FIGS. 4 and 5, two side walls are respectively provided on each side of the base plate 21, thus on the upper side and the lower side, and in fact both sides of the opening 22, such that (as can be seen from FIG. 6) a double-U profile of the fastening device results. In the exemplary embodiment, the side walls 23 through 26 are respectively attached to the base plate 21 with screws (not shown in detail). The side walls 23 and 24 are arranged in a slot in the base plate 21 that is preferably produced via milling. The unit composed of the base plate 21 and the side walls 23 through 26 also can be manufactured as one piece, for example as a cast unit. Given a separate execution of the side walls 23 through 26 from the base plate 21, the side walls 23 through 26 can be connected to the base plate 21 with other fastening means or connection methods, for example by welding. The base plate 21 as well as the side walls 23 through 26 are formed of solid aluminum in the case of the present exemplary embodiment. The base plate 21 as well as the side walls 23 through 26 preferably exhibit a thickness of 5 to 10 mm. Fashioning the base plate 21 and of the side walls 23 through 26 from aluminum has the advantage that aluminum is a material that can be easily processed and exhibits a relatively low dead weight. The execution of the fastening device with a double-U profile has the advantage that it is very rigid with regard to deformation. For protection from scatter radiation, in the exemplary embodiment both sides of the base plate 21 and the inner side of the side walls 23 through 26 are provided with x-ray-shielding material 47 layer of lead in the present case, as shown in FIG. 6. As can be seen from FIGS. 6 and 7, in the exemplary embodiment a filter 30 for filtering the x-ray radiation is disposed on the upper side of the base plate 21 between the side walls 23 and 24. The filter 13 is a known filter formed, for example, from aluminum, titanium or stainless steel that serves for filter of the x-ray radiation depending on the desired examination type. A diaphragm 31 that has a number of diaphragm plates that can be moved relative to one another to shape the x-ray beam is disposed on the underside of the base plate 21 between the side walls 25 and 26. Diaphragms that can be arranged on the fastening device are known, for example, from German OS 102 44 898 and German OS 102 42 920. The filter 30 and the diaphragm 31 each can be fastened (for example with screws) both to the base plate 21 and to the side walls 23, 24, or 25, 26, for fixing to the fastening device 20. To enclose the ray filter 30 and the diaphragm 31, covering devices 40 and 41 are provided which are fashioned U-shaped in the exemplary embodiment. The covering devices 40 and 41 respectively have openings 42 and 43 for the unhindered passage of x-ray radiation. The covering devices 40, 41 are thin-walled in the exemplary embodiment such that, although these are dimensionally stable, they can accommodate no load forces with regard to the diaphragm 31 or the filter 30, which is not necessary since the load forces are completely accommodated by the base plate 21 and the side walls 23 through 26. As a result of the thin-walled execution of the covering devices 40, 41, which are preferably fashioned from a metallic material, the weight of the fastening device can be reduced. For protection from scatter radiation, in the exemplary embodiment the covering devices 40 and 41 are provided on their inner sides with an x-ray-shielding material, preferably with a layer of lead, which likewise is no explicitly shown in the figures. If the covering devices 40 and 41 are ultimately connected (for example screwed together) with the side walls 23 and 24 and 25 and 26, a scatter radiation-sealed closure ensues of the spaces in which the filter 30 or the diaphragm 31 are disposed. The fastening device 20 provided with the filter 30 and the diaphragm 31 can ultimately be fastened to suitable mountings (not shown in the figures) of the rotary frame 18 with the base plate 21 in association with the x-ray source 11, as is schematically shown in FIG. 3. The supports 44, 45 of the base plate 21 that can be seen in FIG. 7 that serve for attachment of the base plate 21 and thus the fastening device 20 to the rotary frame 18. Space is saved and weight is reduced by the inventive fastening device 20 in comparison to a diaphragm box of a conventional computed tomography apparatus, such that the requirements are met to execute the patient opening larger in comparison to the patient opening of conventional computed tomography apparatuses and to reduce the mass on the rotary frame 18, which has an advantageous effect for higher rotation speeds of the rotary frame 18. As an alternative to the fastening device described in the exemplary embodiment, the side walls of the fastening device on the upper side and lower side can be arranged offset from one another by 90° such that, although a double-U profile does not result, a U-shaped profile results both on the upper side and on the lower side, so a high deformation rigidity still can be attained. As another alternative, side walls do not necessarily have to be present. Instead, the diaphragm and/or the filter can be fastened only to the base plate and be enclosed with a corresponding hollow cuboid-shaped covering device (preferably open at the top). The covering devices in this case preferably have notches in order to be able to simply attach covering devices to the base plate, for example by means of screws. In the variants with side walls, the side walls do not have to be arranged on both sides of the base plate. In the event that a filter is not necessary, one or more side walls that serve for attachment of a diaphragm can be arranged, for example, only on one side of the base plate. Moreover, it can be sufficient for only one side wall to be present on each side, which side wall serves together with the base plate for the arrangement of a filter or a diaphragm. A number of side walls for attachment of a diaphragm or a ray filter can also be present on each side of the base plate. The base plate as well as the side walls thereby do not necessarily have to be fashioned from aluminum. Rather, other metals or dimensionally stable materials that can provide the load forces necessary for a diaphragm or a filter are also suitable as materials for the base plate and the side walls. Furthermore, the coating of the base plate as well as the side walls (insofar as the side wall material is not itself x-ray-shielding) does not necessarily have to ensue with lead. Other x-ray-shielding materials can be used for the coating. The side walls need exhibit no coating with an x-ray-shielding material if shielding plates made from an x-ray-shielding material are associated with the side walls. The shielding plates are, for example, applied to the side walls or are even part of the covering devices. The covering devices likewise do not necessarily have to be fashioned U-shaped, but rather, dependent on the number of the side walls, can exhibit a shape that is suitable for closure of the space accommodating the ray filter or the diaphragm. Dependent on the material used for the covering device, the suitable wall thickness is selected that ensures the necessary dimensional stability for the covering devices. The covering devices also do not necessarily have to be coated with lead, but alternatively can be provided (to the extent necessary) with a different x-ray-shielding material. Although modifications and changes may be suggested by those skilled in the art, it is the intention of the inventors to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of their contribution to the art.
	abstract	The invention describes a product and a method for generating electrical power directly from nuclear power. More particularly, the invention describes the use of a liquid semiconductor as a means for efficiently converting nuclear energy, either nuclear fission and/or radiation energy, directly into electrical energy. Direct conversion of nuclear energy to electrical energy is achieved by placing nuclear material in close proximity to a liquid semiconductor. Nuclear energy emitted from the nuclear material, in the form of fission fragments or radiation, enters the liquid semiconductor and creates electron-hole pairs. By using an appropriate electrical circuit an electrical load is applied and electrical energy generated as a result of the creation of the electron-hole pairs.
	summary
040455262	summary	This invention relates to a process for the preparation of graphite-clad or graphite-coated nuclear fuel rods. More particularly, the invention relates to a process for the preparation of excellent integrated graphite-coated nuclear fuel rods for high temperature gas-cooled reactors, the graphite-coated rods being prepared by integrally molding a material for the nuclear fuel rod and a material for the graphite coat or sheath for the nuclear fuel rod and baking the integrally molded mass. Conventional rod-type, for example, cylindrically-shaped nuclear fuel compacts or rods, comprising coated particulate nuclear fuel, have heretofore been prepared by charging a mixture of the coated nuclear fuel particles, graphite powder and a binder therefor into a metallic molding die, compressing the mixture in its axial direction to obtain a molding thereof and baking the molding. Such conventional methods are impossible to thereby prepare fuel rods which are very large in length as compared with their diameter; moreover, these rods when each housed in a graphite sleeve for use in atomic reactors will constitute resistance to heat transfer in gaps between the rods and sleeves, and they will therefore be caused to be heated to excessively high temperatures when in use. This invention eliminates such drawbacks. The graphite-sheathed nuclear fuel rods, which are final products, of this invention consist essentially of a nuclear fuel rod and a graphite sheath (or coat) therefor which have been integrated by the use of specific integrally molding and subsequently baking techniques according to this invention. The integration of the fuel rod and graphite sheath in the final product of this invention when using the final product in the reactor, will be conducive to ensuring a decreased heat resistance at the portion between the rod and sheath and also to ensuring a less difference in irradiation shrinkability between the rod and sheath thereby preventing them from peeling from each other with the result that the final products have satisfactory heat characteristics and a high capability of specific heat dissipation. The integral structure of the final products of this invention gives the advantages and effects as detailed below. It enables the final products not only to exchange heat directly with a cooling gas when they are used but also to obtain high densification thereon whereby they have an increased strength and heat conductivity. It also enables the final products to be mechanically processed safely without exposing the nuclear fuel particles of the rod because the rod is covered with the graphite coat, that is the graphite-clad one.
	abstract	An ion beam irradiating apparatus has a field emission electron source 10 which is disposed in a vicinity of a path of the ion beam 2, and which emits electrons 12. The field emission electron source 10 is placed in a direction along which an incident angle formed by the electrons 12 emitted from the electron source 10 and a direction parallel to the traveling direction of the ion beam 2 is in the range from −15 deg. to +45 deg. (an inward direction of the ion beam 2 is +, and an outward direction is −).
	abstract	A system and method for storing high level waste. In one aspect, the invention is a system comprising: an outer shell having an open top end and a hermetically closed bottom end; an inner shell forming a cavity, the inner shell positioned inside the outer shell so as to form a space between the inner shell and the outer shell; at least one passageway connecting the space and a bottom portion of the cavity; at least one passageway connecting an ambient atmosphere and a top portion of the space; a lid positioned atop the inner shell, the lid having at least one passageway connecting the cavity and the ambient atmosphere; and a seal between the lid and the inner shell so at form a hermetic lid-to-inner shell interface.
	abstract	An X-ray analyzer includes an X-ray source, a straight tube type multi-capillary, a flat plate spectroscopic crystal, a parallel/point focus type multi-capillary X-ray lens, and a Fresnel zone plate. A qualitative analysis is performed over an area on the sample, the flat plate spectroscopic crystal and the Fresnel zone plate are removed from the X-ray optical path, and X-rays are collected by the multi-capillary lens and the sample is irradiated. When analyzing the chemical morphology of an element, the multi-capillary lens retracts from the optical path, the source rotates, and the flat plate spectroscopic crystal and the Fresnel zone plate are inserted on the optical path. A narrow sample area is irradiated by the Fresnel zone plate with X-rays having energy extracted from the flat plate spectroscopic crystal. This makes it possible to carry out accurate qualitative analysis on the sample and perform detailed analysis of more minute parts.
061309265	abstract	A cyclotron and a target system containing rotating foils composed of target nuclide to undergo nuclear reactions with the beam from the cyclotron are integrated into one unit such that the foils intercept the orbit of the accelerating beam in the cyclotron. Accordingly, the beam strikes the foils to undergo nuclear reaction therein and to correspondingly lose a small portion of its energy in its passage through the foils. The transmitted beam from the foils gains the lost energy to the foils as it circulates in the accelerating zone of the cyclotron and subsequently re-strikes the foils. This process of continuing strikes results in accumulation of the beam current striking the foils and proportionally increases the rate of nuclear reactions. Since the beam after striking the foils is re-circulated and regains the energy loss to the foils, the integrated unit is termed the Recyclotron. The targets are designed to dissipate the heat from the beam load primarily by radiation. The Recyclotron seems to be an ideal machine for producing neutrons for Boron Neutron Capture Therapy by accelerating a beam of proton and using beryllium foils. It may also be used for generating other secondary nuclear particles from charged particles other than proton. The Recyclotron may also be used to enhance generation of a radionuclide from a target that has a high melting point and can be made into a thin foil. Specific example is generation of palladium 103 from a beam of proton striking rhodium 103 foils.
	summary
	summary
	description	This application is the National Stage application under 35 U.S.C. 371 of PCT Application No. PCT/US2006/60087 filed on 19 Oct. 2006 which claimed priority to U.S. Provisional Patent Application 60/729,161, filed 21 Oct. 2005, both of which are hereby incorporated by reference in their entirety. This work was supported by U.S. DOE Contract DE-AC02-05CH11231 and NIBIB Public Health Service Grant R01 EB00339. The government has certain rights in this invention. 1. Field of the Invention The present invention relates to methods and devices for the discovery and identification of new semiconductor materials as detector materials, and semiconductor materials which have been identified using these methods. 2. Description of the Related Art The discovery of new semiconductors triggers new applications in fields as diverse as optoelectronics, sensors, detectors and power electronics. The exploration for new semiconductor materials increases the chances of finding a heavy-atom compound that can be grown as large crystals with little carrier trapping. It well may be that the current list of known compounds (e.g. HgI2, PbI2, CZT, TlBr, AlSb) does not contain the best possible materials. Furthermore new materials may become candidates for heavy-atom, ultra-fast, luminous semiconductor scintillators and allow radiative transition [e.g. donor band-acceptor CdS(In, Te)] and have a small band gap such as 200,000 photon/MeV limit. While it is generally recognized that materials with a small band gap are semiconductors and those with a large band gap are insulators, there are notable exceptions, such as diamond. X-ray diffraction measurements have been made for over 100,000 crystalline materials and the results fill the Inorganic Crystal Structure and Powder Diffraction Databases, but bandgaps have been measured for only a small percentage of them. Even so, the bandgap alone is not a useful characteristic for identifying semiconductors because the bandgap range between 1.5 and 3.5 eV that contains many useful semiconductors also contains insulators. A temperature-dependent electrical conductivity is not useful for identifying semiconductors because only semiconductors with bandgaps below 1.5 eV exhibit appreciable thermal ionization at reasonable temperatures. Furthermore, temperature-dependent electrical conductivity is not useful because it is negligible in undoped semiconductors with band gaps above 1.5 eV but can be large for insulators that exhibit ionic conductivity. For example NaCl is not a semiconductor because holes are spontaneously trapped on the Cl2−Vk center but the electrical conductivity is high due to motion of the Cl− ions. Moreover, many insulators have large ionic conductivities that increase with temperature. A successful semiconductor radiation detector material should have good stopping power, can be obtained as large crystals at low cost, have acceptable carrier mobilities and lifetimes, and operate at ambient temperatures. Despite the fact that available detector materials fall short of these goals, the list of candidate materials has not grown substantially during the past 25 years. Many thousands of compounds can be prepared in crystalline form, but only a small fraction have been explored as detector materials. There is a need to identify semiconductor detector materials in the early stages of exploration, when samples are not available as single crystals, but only as crystalline powders. The band gaps can be estimated by measuring reflectance, but this alone does not determine which are semiconductors. The defining characteristic of a semiconductor (for circuits and nuclear detectors) is electron and hole mobility. Thus, a semiconductor is a non-metal in which electron and hole carriers are mobile, and an insulator is a non-metal in which electrons or holes spontaneously trap. To function as a semiconductor detector both charge carriers (electrons and holes) must be mobile in an electric field. If either charge carrier is trapped by the spontaneous formation of a defect (e.g. a Vk center) in the material, the material will become polarized and ineffective as a detector. Herein are described methods and devices for the discovery and identification of new semiconductor materials based on the mobility of internally created electrons and holes. In one embodiment, the present invention provides a method for identifying new semiconductor materials based on the mobility of internally created electrons and holes. The present method was designed for the early stages of exploration of new compounds, when samples are not available as single crystals, but as crystalline powders. In a preferred embodiment, the method comprises the steps of (1) providing a layer of a compound in crystalline powder form; (2) applying pressure to the crystalline compound to provide contact between the microcrystals in the crystalline compound; (3) applying electrical voltage and measuring the conductivity; (4) applying electrical voltage and measuring the conductivity while irradiating the compound to create electron-hole pairs; and (5) determining the ionization current due to the movement of internally generated electron and hole carriers. In another embodiment, the present invention provides a device for applying pressure to a crystalline compound, applying electrical voltage and measuring the conductivity, repeating application of electrical voltage and measuring the conductivity while irradiating the compound to create electron-hole pairs and then determining ionization current due to the movement of internally generated electron and hole carriers. In another embodiment, the present invention provides for new semiconductor materials BiOI, PbIF, PbBiO2I, PbBiOI, Pb3O2I2, Pb5O4I2, Bi2GdO4Cl, BiPbO2Cl, and BiPbO2Br discovered using the methods and devices described herein. These materials can be used for optoelectronics and radiation detectors. In another embodiment, the present invention provides for new semiconductor materials discovered using the process and methods and pressure cell described herein. In modern usage, semiconductor materials are valued for their ability to conduct internal electrons and holes over macroscopic distances and used as circuit elements and nuclear detectors. The present method describes a method and device for determining which materials possess this property by measuring the change in their electrical conductivity during exposure to ionizing radiation. In accord with this and the notion that all pure inorganic materials in a specific crystal structure can be classified as either metals, semiconductors or insulators, the term “semiconductor materials” are defined herein as a non-metallic solid in which electrons and holes are mobile, and an “insulator” as a solid in which electrons or holes are self trapped. Unlike semiconductors, metals have partially filled valence bands and are electrically conductive at temperatures approaching 0 K. In one embodiment, the present invention provides a method for identifying new semiconductor materials based on the mobility of internally created electrons and holes. The present method was designed for the early stages of exploration of new compounds, when samples are not available as single crystals, but as crystalline powders. In a preferred embodiment, the method comprises the steps of (1) providing a compound in crystalline powder form; (2) applying pressure to the crystalline compound to provide contact between the microcrystals in the crystalline compound; (3) applying electrical voltage and measuring the conductivity; (4) applying electrical voltage and measuring the conductivity while irradiating the compound to create electron-hole pairs; and (5) determining ionization current due to the movement of internally generated electron and hole carriers. The method is based on the need to determine whether these semiconductor materials have the ability to detect radiation. The final step of determining the ionization current due to the movement of internally generated electron and hole carriers is generally carried out by subtracting the ionization current measured in step 3 from the ionization current in the presence of radiation measured in step 4. The ionization current is preferably direct current (“dc”) applied. In one embodiment, the present method comprises the following steps: (1) produce powders by solid state reactions or precipitation; (2) insert powder in a pressure cell and compress with 1 ton/cm2 to provide contact between micro-crystals of the powder; (3) measure dc current vs. voltage without ionizing radiation; (4) measure dc current vs. voltage with 60Co ionizing radiation (450 Ci source at 8 cm, 1500 rad/min); and (5) subtract currents to determine ionization current due to the movement of internally generated electron and hole carriers. The method step (1) further comprising the step of checking the crystal phase of the crystalline powders by x-ray diffraction. In another embodiment, the present invention provides a device for carrying out the method comprising a metal pressure cell containing two metal anvils and means for applying pressure to a thin layer of crystalline compound placed in the space between the anvils, an electrical contact to apply electrical voltage to one metal anvil, and an electrical contact on the opposite anvil to measure the conductivity across the crystalline compound, and an electrical ground. The pressure cell and the metal anvils can be made of materials such as stainless steel or titanium. In another embodiment, the device further comprises an insulator to prevent any contacts between the two metal anvils or within the pressure cell. The insulator is preferably a non-conducting inflexible material or polymer to insure that conductivity only occurs through the crystalline compound compressed between the two anvils. In a preferred embodiment, the device is as shown in FIG. 2, comprising a stainless steel pressure cell containing (a) two titanium anvils encased in an inflexible non-conducting polymer, such as DELRIN (DuPont), wherein the two anvils do not make contact except at the area where the thin layer of crystalline compound is placed, (b) an electrical contact to conduct bias voltage to the first anvil, (c) an electrical contact connecting the second anvil to an ammeter, (d) an electrical ground, (e) means for applying pressure to the compound placed between the anvils, such as two large screws having springs between the screw heads and the pressure cell. The inflexible non-conducting polymer is electrically insulating and acts to confine the powder during compression. In one embodiment, the pressure applied to the crystalline compound to provide contact between the microcrystals in the crystalline compound is at least 0.5 N/mm2, preferably about 1 ton/cm2. Referring to FIG. 2, the pressure cell further comprises such means for compression as screws that compress springs with a force of 30 lbs each, so the total force applied is 180 lbs to the 3 mm Titanium anvils, and the pressure is 2000 lbs (1 ton) per square cm, or 13,000 lbs per square inch. A layer of crystalline powder is provided and placed in the pressure cell between the two anvils and compressed. In a preferred embodiment, the powder layer is 0.5-1.0 mm thick after compression; the volume is about 5-10 cubic mm and the weight of powder is about 25-50 mg. The semiconductor materials to be tested should be provided in crystalline powder form. The powders can be produced by solid state reactions or precipitation, for example. The crystal phase of the powders can be confirmed by such methods as x-ray diffraction. X-ray diffraction measurements have been made for over 100,000 crystalline materials and the results found in the Inorganic Crystal Structure and Powder Diffraction Databases. New semiconductor materials to be tested can also be looked up these databases, synthesized and then confirmed that the correct crystalline form has been achieved by observing that the x-ray diffraction pattern is the same as provided in the database. Formulas of materials that may be prove to be semiconductor detector materials generally are high density materials (i.e., having a density of 7 or 8 or higher), possess good stopping power (e.g., stopping gamma rays), and have a high atomic number. More preferred materials possess both high density and high atomic number. Electrical voltage is applied across the crystalline compound in the pressure cell at a range of applied voltages, and conductivity is measured. In general, the applied voltages can be from 0 volts to 100 volts. In a preferred embodiment, one electrical contact connects a direct current (dc) power supply to one anvil in the pressure cell, while another electrical contact connects the other opposite anvil to an ammeter that can measure currents as small as 1 pA. The irradiation of the compound to create electron-hole pairs is carried out using a source for generating ionizing radiation. The amount of ionizing radiation is not critical, but measurements would be more difficult with a source having a much lower radiation activity level than about 450 Curie (Ci) or 1500 rad/min ionizing radiation. In some embodiments, it may be preferred to use a source which generates 4500 Ci. In one embodiment, the source is a Cobalt-60 cancer therapy unit used to generate gamma rays. In a preferred embodiment, the source is placed in close proximity to the pressure cell such that the crystalline compound is exposed to the ionizing radiation until equilibrium current is reached. When a source producing about 450 Ci is used, the time for exposure is about 10 minutes. In a preferred embodiment, close proximity is about 3-10 cm, more preferably, about 8 cm, depending on the strength of the source. The increase in steady-state current produced by the ionizing radiation is directly related to the mobility-lifetime product of the carrier that has the greatest trapping (usually the holes). The step of determining ionization current due to the movement of internally generated electron and hole carriers is carried out by subtracting the measured currents to determine the ionization current due to the movement of internally generated electron and hole carriers. The current resulting from the internal generation of electrons and holes is described by the Hecht equation (K. Hecht, Zeitschrift für Physik (Berlin), 77, 235 (1932)):I=I0d′/d[1−exp(−d/d′)]where I0 is the rate of electron-hole pair production and d is the sample thickness. The average drift distance before trapping is given by d′=μτE, where μ and τ are the carrier mobility and lifetime, respectively, and E is the electrical field strength. Detrapping and retrapping may occur, increasing the effective carrier lifetime τ. In a crystalline semiconductor powder most of the carriers recombine in the material, and d′<<d, whereby the equation reduces to I=I0, d′/d=I0μτV/d2. Thus, if trapping is negligible, d′>>d and I≈I0. If trapping is severe, d′<<d and I≈I0[d′/d]=I0 μtV/d2. If either carrier self traps, d′≈0 and I≈0. In an insulator, d′=0 and I=0. Although carrier trapping is severe in semiconductor powder samples, if the rate of internal generation of electrons and hold is sufficiently high, the resulting steady state conductivity can be measured. On the other hand, if even one carrier is self-trapped, the internally generated carriers are not mobile and steady-state conductivity is negligible. The ionization current measured for semiconductors has little quantitative significance, since there can be severe trapping on microcrystal surfaces, however, the present methods and devices are intended for use in screening new semiconductor materials. Some semiconductor samples may have such severe trapping that the ionization current is not measurable, however such severe trapping could indicate a sample not worthy of further investigation. Furthermore, it may be difficult to measure the ionization current in samples with high background current (e.g. ionic conductivity). For example, there may exist samples where radiation damage increases the ionic conductivity, although this has not yet been observed. Semiconductor materials discovered by this process can then be evaluated using known methods in the art of purification, synthesis and crystallization for obtaining crystals useful as detector materials. In a preferred embodiment, the present invention provides for new semiconductor materials useful for detecting radiation, discovered using the methods and device described herein. In a specific embodiment, the new semiconductor materials discovered using the methods and pressure cell described herein are BiOI, PbIF, BiPbO2I, PbBiOI, Pb3O2I2, Pb5O4I2, Bi2GdO4Cl, BiPbO2Cl, and BiPbO2Br. Pressure cell and Validation of the DC Ionization Conductivity Methods Using Known Semiconductor Materials and True Insulators In this example we placed the sample between two titanium anvils in a pressure cell as shown in FIG. 1 and the electrical conductivity is measured for a range of applied voltages. The measurements were then repeated during irradiation by 1.2 MeV gamma rays from a 450 Curie Co-60 cancer therapy unit placed 8 cm from the cell for about 10 minutes, the amount of time for equilibrium current to be reached. The measurements were taken without radiation present (OFF) and during irradiation by the Co-60 source (ON). The difference in the ionization current in the present of radiation can be observed in the graph. It is this difference in height that is plotted on the graphs shown in FIGS. 5, 6 and 8. After the voltage is applied the material polarizes and reaches a steady current. When the source is turned on, traps fill and the current increases to an equilibrium level. At this point, the rate of generation of electron-hole pairs is equal to the rate of trapping and recombination. When the source is removed the current drops to the initial level as the carriers detrap. The samples used were either the highest purity materials obtained from chemical suppliers or synthesized in our laboratory from highest purity available starting materials. For all samples the crystal phase was checked by x-ray diffraction and a weighed amount was used to produce a compressed thickness of approximately 1 mm (volume 7 mm3). After a powder sample is pressed between the titanium anvils, the electrical conductivity is measured for a range of applied voltages (source off) and then the measurements are repeated during irradiation by 1.2 MeV Co-60 gamma rays from a 450 Ci cancer therapy unit (source on). The dose rate was 1,500 rad/min. The currents were measured using a Keithley model 617 electrometer. FIG. 3 shows the source-dependent steady-state currents of the known semiconductors ZnO (band gap 3.37 eV), CdS (2.49 eV), ZnTe (2.3 eV), GaAs (1.5 eV), HgI2 (2.2 eV), PbI2 (2.5 eV) and diamond (5.4 eV) increases linearly with applied voltage as expected. All currents reported here are steady state values. The relationship between ionization current and voltage is nearly linear as expected from the Hecht equation for the case where d′<<d. The numbers in the parentheses are the accepted room-temperature energy gaps. The relationship is linear as expected from the Hecht equation for the case where d′<<d. Variations between samples are due to differences in μτ products. Since most of the trapping is on the microcrystal surfaces, the observed current values are not indicative of what would be collected from single crystals. Referring now to FIG. 4, the corresponding current of true insulators BiOF, Lu2SiO5, Bi2SiO5, SiO2, and are consistent with zero. No measurable current is shown. Tables I lists the density, experimentally measured band gap and currents I(off) and I(on) measured at 100 V with the source off and on, respectively for materials studied in which the materials were not identified as semiconductors. Table I lists materials whose ionization current is too small to be identified as semiconductors. Band gaps were taken from W. H. Strehlow and E. L. Cook, “Compilation of energy band gaps in elemental and binary compound semiconductors and insulators,” J Phys Chem Ref Data, vol. 2, pp. 163-199, 1973, or were determined in our laboratory from measurements of reflectance vs. wavelength. While hole hopping is known to occur for CsI, the resulting current is well below those in Table II. TABLE IMATERIALS NOT IDENTIFIED AS SEMICONDUCTORSρEGI(off)aI(on)bCompound(gm/cm3)(eV)(nA)(nA)Bi4Ge3O127.14.22.502.51Bi2SiO57.90.140.16BiOF9.274.774.6CsI4.76.20.580.67Lu2SiO57.46.41.431.40PbBr26.73.210971093PbCl25.93.9113110PbF27.85.011501151SiO22.68.41.011.02 DC Ionization Conductivity Methods Used to Identify New Semiconductor Materials Referring now to FIG. 5, using the device of Example 1, the sample of crystalline BiPbO2Cl was placed between two titanium anvils in a pressure cell as shown in FIG. 2 and the electrical conductivity is measured at the applied voltages of 2V and 100V as a function of time. Tables II also lists the density, experimentally measured band gap and currents I(off) and I(on) measured at 100 V with the source off and on, respectively for materials studied in which the materials were identified as semiconductors. In Table II many materials exhibit significant I(off) values due to ionic conduction and n- or p-type doping. The large currents seen for the semiconductors ZnO and ZnTe are due to the latter. Band gaps were taken from W. H. Strehlow and E. L. Cook, “Compilation of energy band gaps in elemental and binary compound semiconductors and insulators,” J Phys Chem Ref Data, vol. 2, pp. 163-199, 1973, or were determined in our laboratory from measurements of reflectance vs. wavelength. Table II lists materials whose ionization current increases with voltage and thereby identified as semiconductors. TABLE IIMATERIALS IDENTIFIED AS SEMICONDUCTORSρEGI(off)aI(on)bCompound(gm/cm3)(eV)(nA)(nA)BiGdO4Cl8.42.7733904BiPbO2Cl8.32.714.352.7BiPbO2Br8.62.817.525.3BiPbO2I8.62.76.1703BiOI8.12.11.804.11CdS4.82.54.9650diamond3.55.40.043.6GaAs5.31.514171894HgI26.42.210.478Pb3O2I27.62.72.527Pb5O4I22.70.811.24PbFI7.43.05.59.3PbI26.12.54.022.6PbO9.62.70.312.37ZnO5.73.410,50013,100ZnS4.13.85.075.59ZnTe5.82.3482,000493,000*New determination as semiconductorsaCurrent at 100 V with source offbCurrent at 100 V with source on Table II also shows the raw data in table format of the ionization current measured at a 100V for various materials, without radiation present (I(off)) and during irradiation (I(on)). The difference between the measured conductivity with the radiation OFF or ON is shown. The formula of the compound and its identity as a semiconductor as determined by the process is indicated by the asterisk. The other materials were not identified as a semiconductor material by the method. The measured current for each material (e.g., I(on) and I(off)) at the various voltages is not shown. However, FIG. 6 shows the ionization current (I(on)−I(off)) measured at various voltages as a function of voltage for new semiconductor materials: BiOI, PbIF, PbBiO2I, PbBiOI, Pb3O2I2, Pb5O4I2, Bi2GdO4Cl, BiPbO2Cl, and BiPbO2Br. Because this method uses the difference between the source on and source off conditions, it cannot be used for samples whose ionic conductivity is much larger than the ionization conductivity. The present structures, embodiments, examples, methods, and procedures are meant to exemplify and illustrate the invention and should in no way be seen as limiting the scope of the invention. Various modifications and variations of the described pressure cell, methods of making, and applications and uses thereof of the invention will be apparent to those skilled in the art without departing from the scope and spirit of the invention. Any patents or publications mentioned in this specification are indicative of levels of those skilled in the art to which the invention pertains and are hereby incorporated by reference to the same extent as if each was specifically and individually incorporated by reference.
	claims	1. A corrosion-resistant structure for a high-temperature water system comprising:a structural material; anda corrosion-resistant film consisting of at least one chemical compound selected from the group consisting of La2(CO3)3, La(CH3COO)3 and La2(C2O4)3, deposited on a surface in a side that comes in contact with a cooling water having a temperature of 20° C. or higher and 350° C. or lower, of the structural material which constitutes the high-temperature water system that passes a cooling water of high temperature therein. 2. The corrosion-resistant structure for the high-temperature water system according to claim 1, wherein the structural material is at least one structural material selected from the group consisting of a carbon steel, a copper alloy and a Ni-based alloy. 3. The corrosion-resistant structure for the high-temperature water system according to claim 1, wherein a deposition amount of the at least one chemical compound is 1 μg/cm2 or more and 200 μg/cm2 or less. 4. The corrosion-resistant structure for the high-temperature water system according to claim 1, wherein an oxide film of the structural material is formed on a surface of the structural material, and the corrosion-resistant film is formed on a surface of the oxide film. 5. The corrosion-resistant structure of claim 1, wherein the corrosion-resistant film consists of La2(CO3)3. 6. The corrosion-resistant structure of claim 1, wherein the corrosion-resistant film consists of La(CH3COO)3. 7. The corrosion-resistant structure of claim 1, wherein the corrosion-resistant film consists of La2(C2O4)3. 8. The corrosion-resistant structure of claim 1, wherein the structural material is a carbon steel surface and the corrosion-resistant film is a uniform and continuous film covering the surface of the carbon steel. 9. The corrosion-resistant structure of claim 8, further comprising:an oxide film between the surface of the carbon steel and the corrosion-resistant film. 10. The corrosion-resistant structure of claim 1, wherein the corrosion-resistant film consists of at least one chemical compound in an amount of 20 μg/cm2 to 120 μg/cm2.
	claims	1. A charged particle beam apparatus, comprising:a stage for placing a sample thereon;a detector detecting secondary charged particles generated due to irradiate a primary charged particle beam to the sample;an objective lens that focuses the primary charged particle beam on the sample and having an opening through which the primary charged particle beam passes; anda power supply unit applying a negative voltage to the sample,wherein the objective lens includes:a first magnetic pole member that is disposed around the opening and has a terminal portion at a sample side thereof that functions as an upper magnetic pole member of the objective lens;a second magnetic pole member that supplies a magnetic flux to the first magnetic pole member and is formed with a hollow interior;a coil that is disposed within the second magnetic pole member and supplies a magnetic flux to the second magnetic pole member; anda third magnetic pole member that is disposed between the stage and the second magnetic pole member, has the opening and functions as lower magnetic pole member of the objective lens, andwherein a potential lower than that of the second magnetic pole member is supplied to the third magnetic pole member. 2. The charged particle beam apparatus according to claim 1, further comprising:means for supplying a retarding potential to the sample,wherein a potential higher than the retarding potential is supplied to the third magnetic pole member. 3. The charged particle beam apparatus according to claim 2,wherein a potential difference between a potential at the sample and a potential at the third magnetic pole member is within 100V. 4. The charged particle beam apparatus according to claim 3,wherein the potential at the third magnetic pole member is equal to the potential at the sample. 5. The charged particle beam apparatus according to claim 2,wherein an accelerating potential for accelerating the primary charged particle beam is applied to the first magnetic pole member. 6. The charged particle beam apparatus according to claim 1, further comprising:means for electrically isolating the second magnetic pole member and the third magnetic pole member from oath other. 7. The charged particle beam apparatus according to claim 1, wherein the second magnetic pole member is brought to a ground potential. 8. The charged particle beam apparatus according to claim 1,wherein a bottom of the second magnetic pole member has a conical shape with the opening, and wherein the third magnetic pole member is realized with a magnetic plate disposed in parallel with a conical surface of the conically-shaped bottom with a predetermined gap left from the conical surface. 9. The charged particle beam apparatus according to claim 1, further comprising:an electrostatic adsorption device that holds the sample. 10. The charged particle beam apparatus according to claim 9,wherein the electrostatic adsorption device includes:an internal electrode that is opposed to the sample with a dielectric between them;a contact electrode that applied a retarding voltage to the sample; andmeans for retaining a potential difference between a potential at the contact electrode and a potential at the third magnetic pole member at a value falling within −±100V. 11. The charged particle beam apparatus according to claim 1, further comprising:a cooling member for the third magnetic pole member. 12. The charged particle beam apparatus according to claim 1, further comprising:means for acquiring a shaded image of a portion of irradiation of the primary charged particle beam. 13. The charged particle beam apparatus according to claim 1,wherein the third magnetic pole member has two magnetic plates of an upper magnetic plate and a lower magnetic plate; andwherein the lower magnetic plate is brought to a same potential as a potential at the sample.
	abstract	A miniature mechanical shutter having a chamber, a shutter member having an aperture formed therethrough that is mounted to the chamber to allow translation and rotation about an axis. A pair of cap members are disposed on opposing ends of the shutter member to support the shutter member during the translation and rotation. The shutter further comprising a plurality of magnet members, such that a first of the plurality of magnet members is disposed in a first end of the shutter member, a second of the plurality of magnet members is disposed in a second end of the shutter member opposite the first end, and a third of the plurality of magnets members is disposed external to the chamber. At least one of the plurality of magnet members is responsive to an electrical impulse to translate and/or rotate the shutter member between an opened position and a closed position.
	description	This application claims the benefit of U.S. provisional application 60/740,024, filed on Nov. 28, 2005, entitled “X-ray Collimator for Imaging with Multiple Sources and Detectors”, and hereby incorporated by reference in its entirety. This invention relates to X-ray imaging. In many applications of X-ray imaging, and especially in medical imaging applications, it is highly desirable to minimize the total X-ray dose delivered during imaging to the subject or object being imaged. Since X-rays travel substantially in straight lines, X-rays emitted from the X-ray source (or sources) directed away from any X-ray detector in the system are useless for imaging. Such useless radiation is typically blocked by providing an X-ray collimator near the X-ray source that passes radiation directed toward the detector(s) and blocks other radiation. Various X-ray imaging systems have been considered in the art, and a corresponding variety of X-ray collimation approaches for imaging have also been considered. For example, in U.S. Pat. No. 4,315,157, an imaging approach having a single X-ray source and multiple well-separated detectors is considered. A collimator is employed to block radiation that otherwise would pass through the patient and strike the dead spaces between the detectors. Fan beam systems (e.g., as in U.S. Pat. No. 6,229,870) are commonly employed, where a collimator having vanes defines several parallel thin fan-shaped beams. Conventional X-ray collimators typically provide vanes to define fan beams and/or high aspect ratio channels to define narrow beams, e.g., as considered in US 2004/0120464. Collimators having a large rectangular aperture matched in shape to a rectangular detector array are considered in US 2004/0028181. In U.S. Pat. No. 5,859,893, a system having multiple source locations and multiple detectors is considered. The corresponding collimator has independent high aspect ratio channels defining beam paths from each source to each detector. However, when an X-ray imaging system has multiple sources and multiple detectors, conventional X-ray collimation approaches (e.g., providing independent channels for each source to detector path) can encounter a hitherto unappreciated difficulty. More specifically, providing such independent channels in the collimator can lead to a situation where the X-ray source spacing is forced to be undesirably large. Accordingly, it would be an advance in the art to provide an X-ray collimator for multi-source, multi-detector imaging systems that can provide reduced source spacing. Reduced source spacing for multi-source, multi-detector X-ray imaging systems is provided by allowing channels within an X-ray collimator to intersect within the body of the collimator. As a result, the channels are not independent, and the source spacing can be significantly reduced. Although such collimators have a much more “open” structure than conventional collimators having independent channels, they can still provide efficient collimation performance (e.g., predicted leakage <5%). Several high attenuation layers having through holes and stacked together can provide collimators according to the invention, where the through holes combine to form the intersecting channels. FIG. 1 shows a transverse view of an X-ray imaging system 100 according to an embodiment of the invention. In this example, an X-ray source (or source array) emits X-rays from multiple source locations 108. Typically the source locations are disposed on a substrate and cooling layer 106 (e.g., when a transmission target is employed). X-rays emitted from source locations 108 pass through substrate 106 and through a field of view 102 (which may include, e.g., a patient) and are received by well-separated detectors (typically detector arrays) 110, 112, and 114. Imaging system 100 includes a collimator 104, which substantially absorbs X-rays emitted from any of source locations 108 that are directed away from any of the detectors (i.e., detectors 110, 112, and 114). As indicated above, such absorption of undetectable X-rays that are useless for imaging is highly desirable. Collimator 104 can be designed to pass X-rays passing through the collimator from each source location at a set of predetermined angles θ corresponding to the detectors. These predetermined angles are unique for each source location and vary gradually from one source location to the next. FIG. 2 shows an X-ray collimator according to an embodiment of the invention. In the example of FIG. 2, collimator 104 includes high attenuation layers 202, 204, 206, 208 and 210 arranged in a layer by layer stack to provide collimator 104 having an input face 216 and an output face 218. Each high attenuation layer includes two or more through holes, and the through holes in the high attenuation layers combine to form four or more channels extending through collimator 104 from input face 216 to output face 218. Some of these channels are identified with dashed lines on FIG. 2, such as channels 222, 224, and 220. In preferred embodiments of the invention, the channels taper such that they are larger at the output face than at the input face, e.g., as shown by dotted lines 214. In this manner, the channel shapes can follow the natural divergence of the X-rays as they propagate away from source locations 108. High attenuation layers 202, 204, 206, 208, and 210 are preferably made of X-ray absorbing material (e.g., including high-Z elements). Suitable materials for the high attenuation layers include but are not limited to brass, tungsten, lead, molybdenum, and mixtures or alloys thereof. Although the example of FIG. 2 shows five high attenuation layers, the invention can be practiced with any number of high attenuation layers greater than two. A key aspect of the invention is that these channels are not independent. More specifically, at least two channels intersect within the collimator at a location other than at the input face or output face (e.g., the intersection of channels 220 and 222). Typically, as shown in the example of FIG. 2, there will be numerous such internal intersections of channels. In many cases, a channel will also have multiple internal intersections with other channels (e.g., channel 220 has internal intersections with channel 222 and with channel 224). Such intersecting, non-independent collimator channels allow for a much closer source location spacing than the conventional approach of independent channels that have no intersections within the body of a thick collimator. Good collimation performance can be obtained with this approach. Such good performance is surprising, since the collimator of FIG. 2 is much more “open” in structure than conventional collimators having independent channels. Collimator performance calculations have been performed. In these calculations, the following parameters were assumed. A brass (μ=6.735 cm−1 at 80 keV) collimator having a thickness of 4 cm was employed. A configuration having three detectors was assumed, the detector angles θ being 0°, 17° and −17° at the central source location of the source array. Each source location was assumed to emit 80 keV X-rays in a +/−60° arc. A leakage factor L=NU/ND was defined, where NU is the number of undetectable primary photons passing through the imaging filed of view, and ND is the number of detectable primary photons passing through the imaging field of view. For a 2.5 mm source location spacing, L=0.1685. For a 3 mm source location spacing, L=0.021. In practice, it is desirable for L to be less than 0.05, so this goal is easily reached with the 3.0 mm source location spacing. Leakage decreases as source separation increases, as shown on FIG. 7, which is a plot of L as a function of source location spacing for this numerical example. FIG. 3 shows a top view of layer 210 of collimator 104, which is shown in a side view on FIG. 2. Several sets of through holes are present in layer 210, and are indicated as sets 302, 304, and 306. Each such set corresponds to a different axial location in imaging system 100. In this example, the collimator channels only intersect in transverse planes (e.g., as shown on FIG. 2). Axial collimation is provided by the height of the holes in sets 302, 304, and 306, and may restrict the X-rays to all or only part of the axial extent of the detectors, depending on the imaging application. Conventional layer fabrication and assembly methods are suitable for fabricating and assembling the high attenuation layers of collimators according to the invention. For example, these layers can be made by precision drilling methods, such as laser drilling, mechanical drilling or chemical etching. Each layer would have its own pattern, and could further include features for facilitating precision alignment, such as alignment holes in each layer. Pins can be inserted through such alignment holes during assembly to keep the layers aligned. A high attenuation layer having through holes with sloped edges (e.g., high attenuation layer 210 on FIG. 2) can be provided by fabricating the high attenuation layer as a laminate, each layer of the laminate having through holes which gradually change size and/or shape from one layer to the next to provide a stepwise approximation to the sloped hole edge. FIGS. 4a-b show X-ray collimators according to alternate embodiments of the invention. In these embodiments, high attenuation layers providing relatively small levels of X-ray attenuation (e.g., 204 and 208 on FIG. 2) are removed from the collimator, thereby simplifying collimator design and fabrication without appreciably altering performance. FIG. 4a shows a configuration where omitted high attenuation layers are replaced by air gaps 402 and 404. FIG. 4b shows a configuration where omitted high attenuation layers are replaced with transparent layers 406 and 408, which do not provide significant X-ray attenuation, relative to the high attenuation layers. Low Z materials are suitable for the transparent layers, although high-Z materials can also be employed if the combination of density and thickness of the high-Z material is such that X-ray absorption is relatively small in the transparent layer. Suitable materials for such transparent layers include, but are not limited to low density plastics, fiber material, carbon fiber, and microspheres in an epoxy matrix. Sufficiently thin layers of Al can also be employed as transparent layers, since Al is relatively X-ray transparent compared to most other common metals. Embodiments of the invention can provide a great deal of flexibility in controlling the pattern of X-rays delivered to a field of view by an X-ray imaging system. In particular, any one source location can be collimated to deliver X-rays to one, some or all of the detectors. FIG. 5 shows an X-ray collimator according to an embodiment of the invention having a differing number of collimator channels per X-ray source location. In this example, most source locations provide X-rays to three detectors, as on FIG. 2. However, source location 502 provides X-rays to only two detectors, and source location 504 provides X-rays to only one detector. The hole patterns in layers 202′, 204′, 206′, 208′, and 210′ can be changed as shown on FIG. 5 in order to accomplish this and similar modifications. Embodiments of the invention can also be employed to provide differing levels of attenuation for the collimator channels. Such differing attenuation can be provided by adding a filter layer to the basic collimator structure of FIG. 2, to provide independently predetermined levels of X-ray attenuation for channels covered by the filter layer. One application of channel-dependent filtering is to attenuate detectable X-rays traversing through the outer portions relative to the inner portions of the field of view 102. This technique, which is implemented in conventional computed tomography systems by employing a “bow-tie” filter, provides a more uniform X-ray intensity distribution exiting the field of view. One or more filter layers can be employed, and the filter layer or layers can be disposed at the collimator input face, the collimator output face, and/or at an intermediate location. FIGS. 6a-c show X-ray collimators according to several embodiments of the invention including a filter layer. FIG. 6a shows an embodiment of the invention having a filter layer 602 disposed at the collimator input face. FIG. 6b shows an embodiment of the invention having a filter layer 604 disposed at the collimator output face. FIG. 6c shows an embodiment of the invention having a filter layer 606 disposed at an intermediate location between the collimator input and output faces. The per channel attenuation provided by a filter layer can be set by appropriately selecting the composition and/or thickness of the filter layer material in the channel path. Filter layers such as 602, 604, and 606 can be fabricated with the same materials and with the same methods as described above in connection with the high attenuation layers. The preceding description of the invention has been by way of example as opposed to limitation, and the invention can also be practiced by making various modifications to the given examples. For example, the preceding examples implicitly relate to an X-ray imaging geometry where collimation with intersecting channels is done in the transverse direction. Collimation with intersecting channels can be done in the axial direction in addition to or alternatively to such collimation in the transverse direction. The invention is broadly applicable to various kinds of X-ray imaging systems, including but not limited to computerized tomography systems, x-ray fluoroscopy systems, and tomosynthesis systems. More generally, the invention is applicable in any situation where multiple source locations are to be collimated to provide efficient irradiation of a field of view in a system having several detectors or detector arrays.
053612850	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a schematic side sectional elevation showing a sleeve cutting tool 1 according to the present invention. This tool basically comprises two concentrically arranged shafts 2, 4 which are reciprocal with respect to one another. Both shafts 2, 4 are hollow. The outer shaft 2 supports the inner shaft 4 concentrically therein and in a manner which allows the inner shaft to rotate relative thereto. Selectively inflatable upper and lower bladder assemblies 6, 8 are supported on the shaft assembly. These bladder assemblies 6, 8 are connected with a source of pneumatic or hydraulic pressure via conduits. Note that only the conduit 7 which supplies the upper bladder assembly which extends all the way up the hollow inner shaft and which is illustrated as extending out of the top of the inner shaft 4 and curving back down to the upper bladder assembly 6, is shown. An EDM cutting head 10 is supported between the upper and lower bladder assemblies 6, 8. The cutting head 10 is in a drive connection with the inner shaft 4 so as to be synchronously rotatable therewith. In the embodiments of the invention, the inner shaft 4 is connected with a hydraulic motor 12 which can drive the shaft in either rotational direction. The motor 12 is controlled by a switching control (not shown) which reverses the direction the motor is driving the shaft each 360.degree. to 370.degree. rotation (for example). While it is possible to continuously drive the shaft 4 only in one rotational direction, it is preferred to induce the above type of oscillation in that it simplifies the electrical connection between the base 11 and the EDM cutting head. For example, the oscillation eliminates the need for brushes and the like to maintain constant electrical communication between the base of the cutting tool and the cutting head. The cutting head 10 includes a hydraulically operated motor 13 (see FIG. 7, for example) which allows the cutting electrode 14 to be displaced with respect to the axis of rotation of the inner shaft 4 and thus allows the eccentricity of the cutting electrode 14 to be varied. In the situation illustrated in FIG. 1, it is assumed that a crack has been detected in a portion of the nozzle 16 which is covered with a thermal sleeve 18. In accordance with this detection, the cutting tool 1 is inserted into the thermal sleeve 18 so that the cutting electrode 14 is located at a level which is between the crack and the site where the thermal sleeve 18 is welded to the nozzle. The upper and lower bladder assemblies 6,8 are inflated so that the tool 1 is retained in place and the cutting tool is temporarily secured in place. The EDB cutting process is then initiated. In FIG. 1, the cutting electrode 14 has been gradually displaced laterally until such time as the EDM cutting action has cut almost through the thermal sleeve 18 which is fitted within the nozzle. After the thermal sleeve 18 is cut all the way through, the cutting electrode 14 is retracted to a position of minimal projection, the upper and lower bladder assemblies 6, 8 are deflated and the sleeve cutting tool is removed. Following this, the free end portion of the thermal sleeve 18 is pulled from the nozzle 14, thus exposing the portion of the 16 nozzle in which the crack is formed. Following the removal of the thermal sleeve, the crack removal tool 20 is inserted into the nozzle 16. As shown in FIG. 2 the crack removal tool 20 basically comprises upper and lower bladder assemblies 22, 24 which are larger than those provided on the sleeve cutting tool. In this arrangement the lower bladder assembly 24 is supported on the outer shaft 26 while the upper bladder assembly 22 is slidably disposed on the inner shaft 28. The cutting head (hereinafter referred to as the crack removal head) 30 and a crack detection sensor 32 are mounted on the inner shaft so as to be displaceable relative to the lower bladder assembly 24. Although not clear from this figure, the inner shaft 28 is arranged to be displaceable through a relatively large distance with respect to the outer shaft (see FIG. 12 for example). The reason for this is that, when the crack removing tool 20 is inserted into the nozzle 16, it is impossible to see the crack or to determine when it has been removed. Accordingly, the crack detector 32 is provided. In this instance, the detector is an eddy current type detection. The crack detector 32 is energized and moved both axially and rotationally, until such time as the crack or flaw is located. After the position of the crack is identified, the inner shaft 28 is displaced (upwardly as seen in the drawings) through a predetermined distance which locates the crack removal electrode 34 immediately opposite the crack. EDM cutting is then initiated and the metal around the crack is removed. Since the amount of metal which is being removed cannot be measured while the tool is in position, the metal removal is continued for a predetermined time. This time is determined by empirical data from which it is able to relatively accurately estimate how much metal is removed per unit time. After the predetermined time (for example, 1 hour) the EDM cutting is stopped and the inner shaft 28 retracted to return the crack sensor 32 to the crack site. If the crack is still detected, the EDM cutting electrode 34 is moved back into position and metal is removed for another predetermined period of time. These cutting/checking steps are repeated until such time as the crack is no longer detected. However, since the accuracy of the crack detector 32 is limited, after the crack is detected as having been eliminated, the metal removal procedure is repeated once more but for a shorter period of time (e.g. 40 mins) to ensure total removal. When this last metal removal process is completed, the bladder assemblies 22, 24 are deflated and the tool 20 is extracted from the nozzle. Depending on the amount of metal which has been removed, it may be necessary to fill the newly created void with a suitable weld material or the like. If desired, the crack removal tool can be reinserted and the surface of the weld material smoothed via EDM cutting to exactly the required ID. The cut-off portion of the thermal sleeve 18 can be reinserted and butt-welded to the portion still fixed within the nozzle, thus completing the repair. It will be noted that in addition to the 360.degree. to 370.degree. oscillation, it is possible to reciprocally move the metal removal electrode 34 up and down while the rotational motion is taking place to remove long cracks. It is also possible to use different shaped metal removal electrodes of the nature depicted in FIGS. 5 and 6, for example. The type (for example, shape) can be selected based on the width and length of the crack that needs be removed. As will be appreciated by those skilled in the art of EDM, it is necessary to continuously supply a flow of dielectric fluid between the interface defined between the electrode and the surface of work piece being cut. This fluid, along with pressurized fluid(s) which controls the operation of the hydraulic motor 36 used to determine the lateral displacement of the crank removal electrode 34, is supplied via conduits which are passed upwardly through the interior of the hollow inner shaft 28. It will be understood that a similar conduiting arrangement is provided in the sleeve cutting tool 1. In the case of the crack removal tool, two motors 40, 42 are required at the base. One motion 40 is for inducing rotational motion and the other motion 42 is for producing reciprocal or axial motion 42. The control of the hydraulic motors 12, 13, 36, 40, 42 of the cutting and removal tools 1, 20 is controlled by controllers (no numerals) which are operatively connected with the tools in the representative manner shown in FIGS. 1 and 2. In this instance, de-ionized water is used as the dielectric fluid and is constantly circulated through the space defined between the inflatable bladder assemblies. In the case of the crack removal electrodes shown in FIGS. 5 and 6, through bores 38 are formed therein in a manner which allows the dielectric fluid to be supplied to the cutting site. It is worth noting at this point that the motors which are used to provide rotational and reciprocal motion are preferably hydraulic or pneumatically operated types as differentiated from electrically operated motors. The reason for this is that even though the lower inflatable bladders provide a reasonable seal with the inner surfaces of the thermal sleeve or nozzle, still some leakage occurs and the need to hermetically seal the motors and the like is avoided. In order to establish a satisfactory electrical connection necessary for performing EDM, it is possible to provide a leaf spring like contacts at the upper ends of the tools, preferably at a location above the upper bladder assemblies. The electrodes used in the above types of sleeve cutting and crack removal tools can be made of materials such as copper-tungsten, tungsten and graphite. In the case of the thin sharp edged sleeve cutting electrode, the former two materials can be used. In the case of the crack removal electrodes, the latter two types of material can find application. It is of course within the scope of the invention that a number of different materials or composites can be used and as such the invention is not specifically limited to the same. FIG. 3 shows an example of the shape (as seen in plan) of the thin cutting electrode used in the sleeve cutting tool. FIGS. 7 and 8 show upper and lower portions respectively of a preferred embodiment of the sleeve cutting tool according to the present invention. In this figure, elements designated in FIG. 1 are designated by like numerals. FIGS. 9 to 12 show details of the crack removal tool according to a preferred embodiment of the device. FIGS. 9 and 10 show the crack removal head in its upper and lower positions. As the upper bladder member is slideably supported on the inner shaft, it is preferred to move the crack removal head to its uppermost position at the time of insertion and to inflate the upper bladder. The crack removal head is then lowered to its lowermost position and the lower bladder is then inflated. This separates the upper and lower bladders and improves the alignment of the tool within the nozzle. It should also be noted that it is within the scope of the invention to reduce the diameters of the crack removal device and adapt the same for use a thermal sleeve should a crack be discovered in a portion which is not readily removed through the use of the sleeve cutting tool.
	summary
046684662	claims	1. An apparatus for measuring the spring force imposed on a fuel rod when disposed through a cell in a support grid of a fuel assembly which contains at least one spring-like element, said apparatus comprising: (a) means for generating an increasing force at a first location external of said grid cell; (b) means for transmitting said increasing force from said first location and applying said increasing force at a second location displaced from said first location and internal of said grid cell to said at least one spring-like element disposed in said cell; and (c) means for measuring the level of said increasing force at the instance the application of said force causes deflection of said spring-like element to occur; (d) said transmitting and applying means including a pair of front and rear elongated members, each having a mid-section and upper and lower end portions extending in opposite directions from said mid-section, said members being connected together at their mid-sections for pivotal movement such that as said upper end portions of said members being juxtaposed in spaced apart relation to one another are moved toward and away from each other said lower end portions of said members also being juxtaposed in spaced apart relation to one another are moved away from and toward each other, said lower end portions of said members being adapted to fit into a grid cell while said upper end portions of said member extend upwardly therefrom. a pair of transversely spaced tabs attached to said rear bar at its mid-section and extending outwardly from a side thereof facing said front bar, said tabs having respective aligned holes defined therethrough; means defining a hole through said mid-section of said front bar; and a pivot pin extending through said aligned holes in said spaced tabs on said rear bar and through said hole in said front bar and mounting said front bar on said tabs for pivotal movement relative to said rear bar. a shaft rotatably connected to one of said upper end portions of said elongated members and threadably connected to the other thereof; and a knob attached to an end of said shaft for facilitating rotation of said shaft in either of two opposite directions in order to move said upper end portions of said elongated members toward and away from each other. an adjustable stop attached to one of said members for engaging said grid so as to provide correct positioning of said lower end portions of said members in said grid cell for application of said increasing force to said spring-like element in said cell. guide means coupled between said upper end portions of said elongated members to assist in maintaining alignment of said members with one another as they are pivotally moved relative to one another. a guide pin anchored in said upper end portion of one of said elongated members and extending transversely toward said upper end portion of the other of said members; and a guide bore formed through said upper end portion of the other of said members for slidably receiving said guide pin therethrough as said members are pivotally moved relative to one another. limit means connected to said upper end portion of one of said elongated members and extending transversely toward said upper end portion of the other of said elongated members for engagement therewith upon relative pivotal movement of said elongated members toward one another, said limit means being adjustable for presetting the minimum displacement between said upper end portions of said elongated members and thereby defining a maximum force which can be applied at said lower end portions of said elongated members to said spring-like element in said grid cell. means coupled to at least one of said members for sensing the level of said increasing force being applied to said spring-like element within said grid cell; means coupled to at least one of said members for sensing when said deflection of said spring-like element occurs; and means coupled to said force level sensing means and said spring deflection sensing means for indicating the level of force at the instance said deflection of said spring-like element occurs. a circuit element attached to and electrically insulated from said lower end portion of one of said elongated members; and a set screw attached to said lower end portion of the other of said elongated members, said set screw being adjusted to preset the displacement between said lower end portions of said elongated members and being disposed in contact with said circuit element when said elongated members are initially inserted into said grid cell. (a) a pair of front and rear elongated members, each having a mid-section and upper and lower end portions extending in opposite directions from said mid-section, said members being pivotally connected together at their mid-sections such that as said upper end portions of said members being juxtaposed in spaced apart relation to one another are moved toward and away from each other said lower end portions of said members also being juxtaposed in spaced apart relation to one another are moved away from and toward each other; (b) means disposed on said lower end portion of at least one of said members and being operable to coact with said lower end portion of the other of said members to preset a minimum displacement between said members at said respective lower end portions thereof and thereby a minimum combined cross-sectional dimension of said members at their lower end portions such that when said lower end portions of said members are inserted into a grid cell they simulate a fuel rod disposed through said cell having a predetermined outside diamter; (c) means coupling said upper end portions of said members together and being operable to apply a progressively increasing force so as to draw said upper end portions toward one another and thereby, via said pivotal connection of said members, push said lower end portions apart from one another when deflection of said spring-like element positioned within said grid cell in engagement with at least one of said lower end portions of said members occurs; (d) means coupled to at least one of said members for sensing the level of the increasing force being applied to said spring-like element within said grid cell; (e) means coupled to at least one of said members for sensing when said deflection of said spring-like element occurs; and (f) means coupled to said force level sensing means and said spring deflection sensing means for indicating the level of force at the instance said deflection of said spring-like element occurs. an adjustable stop attached to one of said members for engaging said grid so as to provide correct positioning of said lower end portions of said members in said grid cell for application of said increasing force to said spring-like element in said cell. guide means coupled between said upper end portions of said elongated members to assist in maintaining alignment of said members with one another as they are pivotally moved relative to one another. limit means connected to said upper end portion of one of said elongated members and extending transversely toward said upper end portion of the other of said elongated members for engagement therewith upon relative pivotal movement of said elongated members toward one another, said limit means being adjustable for presetting the minimum displacement between said upper end portions of said elongated members and thereby defining a maximum force which can be applied at said lower end portions of said elongated members to said spring-like element in said grid cell. 2. The measuring apparatus as recited in claim 1, wherein said increasing force is applied to said spring-like element at said second location in a direction generally perpendicular to a central axis of said grid cell along which said fuel rod is inserted through said cell. 3. The measuring apparatus as recited in claim 1, wherein said elongated members include a pair of front and rear bars, said upper and lower end portions of said rear bar extending in opposite directions from said mid-section thereof and in generally linear alignment with one another, said upper and lower end portions of said front bar extending in opposite directions from said mid-section thereof and in a transversely offset relationship in which said upper end portion of said front bar is spaced remote from said upper end portion of said rear bar while said lower end portion of said front bar is spaced adjacent to said lower end portion of said rear bar. 4. The measuring apparatus as recited in claim 3, wherein said elongated members further include: 5. The measuring apparatus as recited in claim 1, wherein said generating means includes a rotatable member coupling said upper end portions of said elongated members together and being operable to apply said increasing force at said first location so as to draw said upper end portions toward one another and thereby, via said pivotal connection of said members, push said lower end portions apart from one another when deflection of said spring-like element positioned within said grid cell in engagement with at least one of said lower end portions of said members occurs. 6. The measuring apparatus as recited in claim 5, wherein said rotatable member includes: 7. The measuring apparatus as recited in claim 1, further comprising: 8. The measuring apparatus as recited in claim 1, further comprising: 9. The measuring apparatus as recited in claim 8, wherein said guide means includes: 10. The measuring apparatus as recited in claim 1, further comprising: 11. The measuring apparatus as recited in claim 10, wherein said limit means is a set screw threadably received through said upper end portion of said one elongated member. 12. The measuring apparatus as recited in claim 1, wherein said transmitting and applying means further includes adjustable means disposed on said lower end portion of at least one of said elongated members and being operable to coact with said lower end portion of the other of said elongated members to preset a minimum displacement between said members at said respective lower end portions thereof and thereby a minimum combined cross-sectional dimension of said members at their lower end portions such that when said lower end portions of said members are inserted into a grid cell they simulate a fuel rod disposed through said cell having a predetermined outside diameter. 13. The measuring apparatus as recited in claim 1, wherein said measuring means includes: 14. The measuring apparatus as recited in claim 13, wherein said force level sensing means is a strain gauge attached to said lower end portion of one of said elongated members. 15. The measuring apparatus as recited in claim 13, wherein said spring deflection sensing means includes a pair of electrical contacts coupled between said lower end portions of said members and being capable of breaking contact with one another when said application of said increasing force to said spring-like element causes deflection of said spring-like element to occur. 16. The measuring apparatus as recited in claim 15, wherein said pair of electrical contacts includes: 17. An apparatus for measuring the spring force imposed on a fuel rod when disposed through a cell in a support grid of a fuel assembly which contains at least one spring-like element, said apparatus comprising: 18. The measuring apparatus as recited in claim 17, further comprising: 19. The measuring apparatus as recited in claim 17, further comprising: 20. The measuring apparatus as recited in claim 17, further comprising:
	claims	1. A nuclear fuel spacer grid for supporting a plurality of elongated fuel rods within a nuclear fuel assembly, comprising: a plurality of windowless grid strips, each grid strip having an axial slot for allowing the plurality of grid strips to be intersected to define a plurality of cells for receiving a fuel rod; and a coolant mixing vane extending from upper and lower ends of each of the plurality of grid strips, each of the coolant mixing vanes having a convex portion and a concave portion wherein the concave portion forms a swirling motion of coolant in the nuclear fuel assembly and the convex portion supports a fuel rod within a cell with convex portions of mixing vanes on other of the plurality of grid strips forming the cell. 2. The nuclear fuel spacer grid according to claim 1 , wherein the convex portion and concave portion of each coolant mixing vane are opposed to each other in the convex and concave direction for swirling upwardly flowing coolant within the fuel assembly and forming an active swirling motion of the coolant at a position around each intersection of the grid strips. claim 1 3. The nuclear fuel spacer grid according to claim 1 , wherein each of the coolant mixing vanes elastically supports the fuel rod at the convex portion used as a spring. claim 1 4. The nuclear fuel spacer grid according to claim 3 , wherein the coolant mixing vanes form a fuel rod supporting structure capable of supporting a fuel rod at four upper support points and at four lower support points. claim 3 5. The nuclear fuel spacer grid according to claim 2 , wherein the coolant mixing vanes of each grid strip are different from each other in structure, thus reducing a pressure drop of coolant flowing on the vanes and forming a more active swirling motion of the coolant, within the fuel assembly. claim 2 6. The nuclear fuel spacer grid according to claim 2 , wherein the coolant mixing vanes of each grid strip are individually provided with a hole capable of reducing the pressure difference between the coolant flowing on the concave portion and convex portion of said coolant mixing vanes. claim 2
	summary
	summary
	description	Reference will now be made in detail to the description of the invention as illustrated in the drawings with like numerals indicating like parts throughout the several views. As described in detail hereinafter, the present invention provides storage systems and methods utilizing non-welded closure techniques. Although the present invention will be described herein in relation to the storage of SNF, it should be understood that the teachings of the present invention are not so limited and, in particular, the present invention may be utilized in various other storage applications. Referring now to FIG. 1, a preferred embodiment of the storage system 100 will now be described in detail. As depicted therein, storage system 100 incorporates a canister 110 which includes an outer wall or shell 112 and a bottom (not shown) that cooperate to define an interior 114 which is suitable for the storage of materials therein. Additionally, a closure lid 116 is adapted to be received within an open end 117 of the canister and form a seal therewith for containing materials within the interior of the canister. Preferably, one or more compression members or links 118 (described in detail hereinafter) are provided for urging or forcing the closure lid into sealing engagement with the canister. In some embodiments, an outer lid 120 cooperates with a open end 117 of the canister so that a redundant seal of the storage system is provided. Preferably, the outer lid is retained in sealing engagement with the distal end of the canister by a hold-down member 122 (described in detail hereinafter). As depicted in FIG. 2, the canister 110, closure lid 116 and compression links 118, and, in embodiments so provided, outer lid 120 and hold-down member 122, cooperate to provide a non-welded closure system 100. System 100 may, in some embodiments, offer one or more advantages over classical bolted closures which typically require a flanged surface or ledge. Such a ledge typically protrudes beyond the shell of a canister or, in other embodiments, encroaches upon the opening of the canister, in order to provide a significantly strong and sizable surface to allow bolts, which are adapted to secure the lid to the canister, to be placed therethrough. In regard to bolted closures utilizing flanges that extend beyond the canister shell, such a configuration typically provides access to the full opening of the canister; however, typically only a single lid closure may be utilized. In regard to those embodiments which utilize flanges which encroach upon the opening of the canister, such a configuration tends to preclude the use of outer or peripheral regions of the canister interior. Referring now to FIG. 2, the embodiment of the closure lid 116 depicted therein is adapted to permit a basket or other suitable structure to receive a material to be stored, such as SNF, for example. A basket for storing SNF, for example, typically comprises vertical and lateral support members which may be combined with neutron absorbers. These features provide structural support to the SNF so that a correct, predetermined geometry of the SNF is maintained under both normal and accident conditions, thereby ensuring that heat transfer and nuclear critically requirements are maintained. Various configurations of baskets and other material support structures may be utilized to perform the aforementioned functionality as may be required based upon the particular application, with all such configurations considered well within the scope of the present invention. Referring now to FIGS. 3 and 4, closure lid 116 and its associated components will now be described in greater detail. As shown in FIG. 3, closure lid 116 cooperates with canister shell 112 to form an annular space or region 130. Compression links 118 are adapted to be inserted between the canister shell 112 and closure lid 116 within the annular region 130. As shown in greater detail in FIG. 4, once a compression link 118 is inserted within the annular region 130, the compression link preferably is urged radially outwardly so that an upper or engagement surface 132 of the compression link is positioned below a closure lid-retention surface 134 formed in canister shell 112. Preferably, urging of the compression link radially outwardly is facilitated by inserting a backing ring or wedge 136 between a surface of the closure lid and an exterior surface of the compression link, thereby allowing a portion of the compression link to be received within retention recess 142 of the canister shell 112. Once appropriately positioned with the retention recess, drive bolt 144 of the compression link may be driven so that a distal end 146 of the drive bolt is urged downwardly toward the closure lid. Preferably, although not required, that portion of the closure lid which is intended to receive or engage the distal end 146 of the drive bolt is configured with a hardened surface which is adapted to resist substantial deformation in response to engagement of the drive bolt. In some embodiments, the functionality of the hardened surface may be achieved by one or more bearing members or inserts 148. Such an insert may be formed of metal or any other suitable material. In some embodiments, insert 148 may include a bolt-receiving recess 150 for properly positioning the distal end 146 of the drive bolt. So provided, once the bolt is driven so that the distal end of the drive bolt engages the insert, downward force of the bolt is transferred to the closure lid, thereby urging a seating surface 152 of the closure lid against a closure lid-receiving ledge 154. Additionally, in reaction to the downward force of the bolt, the outer retaining member 155 of the compression link is urged upwardly so that the engagement surface 132 engages the closure lid-retention surface 134, thereby retaining the closure lid in its locked or sealed position. In order to facilitate a more secure sealing of the closure lid, some embodiments may incorporate a gasket 156 which is adapted to engage in a sealing relationship with the closure lid and the canister shell, such as by being received within a gasket recess 158 of the closure lid and engaging a surface defining the recess as well as seating surface 152 of the canister shell. So provided, engagement of the compression link with the closure lid and canister shell places axial, tensile force in that portion of the canister shell located between the closure lid-retention surface and the closure lid-receiving ledge, while exerting a compressive force on the closure lid. This is accomplished with the bolts of the compression links not being attached to or through the seating surface of the closure lid or the closure lid-receiving ledge of the canister shell. Referring now to FIGS. 5 and 6, outer lid 120 and its associated components will now be described. As shown in FIG. 5, outer lid 120 is adapted to cooperate with canister shell 112 so that closure lid 116 is disposed between the outer lid and the interior of the canister. Although capable of numerous configurations, outer lid 120 preferably incorporates a hold down-receiving recess 170 formed along an upper edge thereof and an opposing seating surface 174 which is adapted to engage a distal end of the canister shell. Seating surface 174 may incorporate a gasket recess 178 which is adapted to receive a gasket 180 for promoting sealing engagement of the outer lid with the canister shell. Additionally, an alignment protrusion 179 may be provided on a underside of the outer lid that is adapted to be received by the annular region 130, so that the outer lid may be appropriately aligned with the closure lid and canister shell. Preferably, lid hold-down member 122 incorporates an upper ring 182 which is adapted to be received about the distal end of the canister shell and the outer lid, with an outer lid hold-down ledge 184 protruding from an inner surface of the ring. The hold-down ledge 184 is adapted to be received by the hold-down receiving recess 170 of the outer lid. A plurality of connectors 192, e.g., bolts, depend from the ring, with each of the connectors engaging a lid hold-down segment 194. Each lid hold-down segment is configured as an arcuate segment with an inner diameter which is appropriately configured so that each segment may be received about an exterior surface of the canister shell. In order to facilitate sealing engagement of the outer lid with the canister shell, each lid hold-down segment preferably incorporates an outer lid-retaining ledge 196 which extends inwardly from its respective segment. The aforementioned outer lid-retaining ledges are adapted to engage within a compression recess 198 formed in an outer surface of the canister shell. So configured, when the connectors are tightened, each lid hold-down segment is urged toward the ring, thereby causing the outer lid-retaining ledge 196 to engage the compression recess 198 of the canister and the outer lid hold-down ledge 184 of the ring 182 to engage the hold-down receiving recess 170 of the outer lid. Thus, when so tightened, the outer lid is held in compression against the canister shell. The foregoing description has been presented for purposes of illustration and description. It is not intended to be exhaustive or to limit the invention to the precise forms disclosed. Modifications or variations are possible in light of the above teachings. The embodiment or embodiments discussed, however, were chosen and described to provide the best illustration of the principles of the invention and its practical application to thereby enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations, are within the scope of the invention as determined by the appended claims when interpreted in accordance with the breadth to which they are fairly and legally entitled.
	abstract	Systems and/or methods of waste disposal use human-made caverns that are constructed within deep geological formations. A given human-made cavern may be constructed by first drilling out a vertical wellbore to a deep geological formation. Then a bottom portion of the vertical wellbore is jet drilled using an abrasive jetting fluid to form a launch chamber of void volume, that is sized to fit a reaming tool in its deployed open configuration. A reaming tool, in a closed configuration, is then inserted into the vertical wellbore for landing in the launch chamber. The reaming tool is then deployed into its open configuration while in the launch chamber. Reaming operations then occur from the launch chamber directed downwards within the deep geological formation, forming a given human-made cavern. The newly formed human-made cavern may be conditioned and/or configured for receiving amounts of the waste for long-term disposal and/or storage.
050680811	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an assembly method for a nuclear fuel assembly, capable of preventing scratches from occurring on outer peripheral surfaces of nuclear fuel rods when the nuclear fuel assembly is assembled, and to a grid in the nuclear fuel assembly for supporting the fuel rods. 2. Prior Art FIG. 10 of the attached drawings depicts an example of a nuclear fuel assembly which is mounted on a nuclear reactor such as a pressurized water reactor or the like. In this assembly, a pair of top and bottom nozzles 1 and 2 are arranged in facing relation to each other and in vertically spaced relation to each other. A plurality of control-rod guide thimbles 3 extend between and are securely fixed to the top and bottom nozzles 1 and 2. A plurality of grids 4 are secured to intermediate portions of the respective control-rod guide thimbles 3 in vertically spaced relation to each other. As shown in FIGS. 11 through 13, each of the grids 4 is formed as follows. That is, a plurality of straps 7, each in the form of a thin strip sheet, are assembled perpendicularly to each other into a grid by mutual fitting of slits 8 which are formed in the straps 7 in longitudinally equidistantly spaced relation to each other. A plurality of grid cells 5 are defined in each of the grids 4. A pair of dimples 9 and 9 and a pair of springs 10 and 10 for supporting a fuel rod 6 are formed on the wall surface of each of the grid cells 5 in opposed relation to each other. The fuel rod 6 inserted in the grid cell 5 is supported in urging relation to the dimples 9 by the springs 10. An assembly method of the nuclear fuel assembly constructed above will next be described. First, the grids 4 are arranged in vertically spaced relation to each other at a predetermined spacing. The control-rod guide thimbles 3 are then inserted into and fixed to predetermined grid cells 5 of each of the grids 4, respectively. Subsequently, the fuel rods 6 are inserted into corresponding grid cells 5 in each of the grids 4 which are supported by the control-rod guide thimbles 3, with the fuel rod 6 in sliding contact with the dimples 9 and the springs 10. In this manner, the fuel rods 6 are fixedly arranged in corresponding grid cells 5 through the dimples 9 and the springs 10. After insertion of all the fuel rods 6, the pair of top and bottom nozzles 1 and 2 are fixedly mounted respectively to the opposite ends of the control-rod guide thimbles 3. In the aforesaid assembly method of the nuclear fuel assembly, when the fuel rods 6 are inserted respectively into the grid cells 5 in each of the grids 4, the outer peripheral surface of each of the fuel rods 6 is clamped between the dimples 9 and the springs 10, and the fuel rod 6 must be inserted into the corresponding grid cells 5, while the fuel rod 6 resists the resilient force of the springs 10. Thus, there is a problem that the outer peripheral surface of the fuel rod 6 is scratched by the springs 10 and the dimples 9 along its longitudinal direction. SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an assembly method for a nuclear fuel assembly, capable of preventing scratches from occurring on an outer peripheral surface of each fuel rod upon assembling of the nuclear fuel assembly. Another object of the invention is to provide a combination of a grid in the above-mentioned nuclear fuel assembly and a plurality of elongated key members. According to a first aspect of the invention, there is provided an assembly method of a nuclear fuel assembly, comprising the steps of: preparing a plurality of grids each of which comprises a plurality of elongated straps intersected with each other to define a plurality of grid cells therein, and a plurality of pairs of dimples and springs formed on the straps for supporting a plurality of fuel rods, each pair of dimples and spring being disposed in facing relation to each other, on wall sections of the straps, which cooperate with each other to define one of the grid cells, the pair of dimples and spring projecting into the grid cell; subsequently inserting a deflecting jig into one of the grid cells defined in each of the grids, the deflecting jig being in the form of a rod having a diameter capable of being enlarged; subsequently enlarging the diameter of the deflecting jig to urge the spring associated therewith against resilient force of the spring to deflect the spring away from the dimples associated therewith; subsequently inserting a plurality of elongated key members, respectively along a longitudinal direction of the straps forming the grid, into the grid cells through a plurality of openings which are defined at intersections between the straps, each of the key members being formed with a plurality of hooks which are spaced a predetermined spacing from each other along the longitudinal direction of the key member; subsequently rotating each of the key members about its axis to cause the hooks of the key member to project from a wall surface of the strap associated with the key member, through the openings, in a direction opposite to the projecting direction of the springs formed on the strap; subsequently moving the key member forwardly in the longitudinal direction of the strap to engage the hooks of the key member with the wall surface of the strap, thereby fixedly mounting the key member to the strap to maintain the springs deflected; subsequently releasing the urging of the spring due to the deflecting jig to withdraw the same from the grid cell and, subsequently, inserting the fuel rods respectively into the grid cells; subsequently moving the key member rearwardly to release retention of the springs due to the hooks of the key member thereby bringing the springs into pressure contact with the fuel rods, respectively; and withdrawing the key members from the grid cells. According to a second aspect of the invention, there is provided a combination of a grid in a nuclear fuel assembly and a plurality of elongated key members, the grid comprising a plurality of elongated straps intersected with each other to define a plurality of grid cells therein, a plurality of pairs of dimples and springs formed on the straps for supporting a plurality of fuel rods, and a plurality of openings which are defined at intersections among the straps, each pair of dimples and spring being disposed in facing relation to each other, on wall sections of the straps, which cooperate with each other to define one of the grid cells, the pair of dimples and spring projecting into the grid cell, and each of the elongated key members being provided for maintaining the springs deflected respectively away from the dimples, the key member being capable of being inserted into the grid cells through the openings along a longitudinal direction of a corresponding one of the straps. According to the assembly method of the nuclear fuel assembly and the combination of the grid and the elongated key members, when the fuel rods are inserted respectively into the grid cells of the grid, the deflecting jig is inserted into the grid cells and is enlarged in diameter to deflect the springs away from the dimples facing thereto, the key member is inserted into the grid cells through the openings formed at intersections among the straps, and the key member is rotated and moved forwardly whereby the hooks of the key member are engaged with the wall surface of the strap, to maintain the springs deflected. Under such condition, the distance between the spring and the dimples facing thereto becomes larger than the diameter of the fuel rod. Therefore, the fuel rods do not slide in contact with the springs and dimples and the outer peripheral surfaces of the respective fuel rods are not clamped between the spring and the dimples. Accordingly, no scratches occur on the outer peripheral surfaces of the fuel rods. In addition, since, when the fuel rods ar inserted respectively into the grid cells, the fuel rods are not clamped between the springs and the dimples, no unreasonable tension force is applied to the fuel rods, and it is possible to reduce a power source for inserting the fuel rods respectively into the grid cells. Thus, it is possible to made an inserting unit and so on compact.
	abstract	A neutron spectrometer is provided by a series of substrates covered by a solid-state detector stacked on an absorbing layer. As many as 12 substrates that convert neutrons to protons are covered by a layer of absorbing material, acting as a proton absorber, with the detector placed within the layer to count protons passing through the absorbing layer. By using 12 detectors the range of neutron energies are covered. The flat embodiment of the neutron spectrometer is a chamber, a group of detectors each having an absorber layer, with each detector separated by gaps and arranged in an egg-crate-like structure within the chamber. Each absorber layer is constructed with a different thickness according to the minimum and maximum energies of neutrons in the spectrum. In this arrangement, each of the 12 surface facets provides a polyethylene substrate to convert neutrons to protons, covered by a layer of absorbing material, acting as a proton absorber, with the detector stacked on the absorbing layer to count protons passing through the absorbing layer.
	summary
	abstract	A method for working on a defective heating element of a pressurizer comprising a tank lying flat along a longitudinal axis and elongate heating elements extending within the tank, and at least one spacer plate through which the heating elements pass and which is capable of maintaining a transverse spacing between the heating elements is provided. The method includes cutting at least one spacer plate around the heating element so as to detach said heating element from said spacer plate, and then extracting the heating element from the tank in one single piece.
	description	This is a continuation application of U.S. application Ser. No. 13/171,704, filed Jun. 29, 2011 which claims priority to Japanese Patent Application No. 2010-148471 filed on Jun. 30, 2010. The entire disclosures of all of these applications are hereby incorporated by reference. The present invention relates to a treatment planning system, a device for calculating a scanning path and a particle therapy system, particularly the particle therapy system for treating an affected area of a patient by irradiating the affected area with an ion beam of, for example, protons or carbon ions and the treatment planning system used for a particle therapy system. Particle therapy is conducted by irradiating target tumor cells with a particle beam. Among the radiant rays used in particle therapy, x rays are most widely used. Recently, however, demand has been rising for particle therapy in which particle rays (ion beam), typically a proton beam or a carbon ion beam capable of achieving high target dose conformity, are used. In particle therapy, excessive irradiation or inadequate irradiation may cause adverse effects on normal tissues or may lead to recurrence of a tumor. It is therefore required to irradiate a target tumor region with an ion beam for a specified dose with maximum accuracy and conformity. In the field of particle therapy, use of a scanning irradiation method has been increasing so as to realize high dose conformity. In a scanning irradiation method, a fine ion beam is used to completely irradiate the inside of a tumor to achieve a high dose only on a tumor region. The scanning irradiation method does not basically require patient-specific devices such as a collimator for forming ion beam dose distribution into a tumor shape, so that it is possible to form dose distribution into various patterns. In the scanning irradiation method, to irradiate an arbitrary position inside a tumor, it is necessary to control the depth to which an ion beam reaches (beam range) and the irradiation position on a plane perpendicular to the direction of beam travel (on a lateral plane). The range of an ion beam can be controlled by varying the beam energy using an accelerator or a range shifter. The irradiation position on a lateral plane can be arbitrarily controlled by bending the direction of beam travel using two sets of scanning magnets. In the scanning irradiation method, unlike in cases where an entire tumor is irradiated with spread x-rays at a time, divided regions of a tumor are irradiated with a beam in turn. Therefore, when a beam is irradiated to a target which moves, for example, due to respiration or heart beat, the relative distance between irradiation positions changes to differ from the distance assumed at the time of planning, possibly making a planned dose distribution unavailable. In a method used to avoid the above problem, movement of an irradiation target is observed and an ion beam is irradiated only when the target is in a specific position. In other methods also proposed, reducing the difference between a planned dose distribution and a real dose distribution is attempted by controlling the number of times of irradiation or the scanning path. In the method proposed in Japanese Patent No. 4273502, for example, a same target position is irradiated plural number of times so as to average dose errors caused by movement of the target and thereby reduce the dose distribution error relative to a planned dose distribution. Furthermore, according to non-patent literature (S Water, R Kreuger, S Zenklusen, E Hug and A J Lomax, “Tumour tracking with scanned proton beams assessing the accuracy and practicalities,” Phys. Med. Biol. 54 (2009) 6549-6563), aligning a main direction of ion beam scanning with the direction of target movement brings a real dose distribution closer to a planned dose distribution. With existing treatment planning systems, it has been difficult to arbitrarily set an ion beam scanning direction. In existing treatment planning systems, a scanning direction is determined regardless of the direction of target movement as follows. Irradiation position control in lateral directions is performed using two sets of scanning magnets which scan an ion beam in mutually perpendicular directions. The speeds of scanning by the two scanning magnets are not the same. Generally, the scanning magnet positioned upstream along the direction of beam travel can perform scanning at a higher speed. A scanning path is formed such that, first, scanning is made in the direction of fast scanning by one of the scanning magnets until an end of the target is reached, then such that, after the scanning position is moved a little in the direction of scanning by the other scanning magnet, fast scanning is resumed in the direction of fast scanning. Generally, this process is repeated to form a zig-zag scanning path. This type of scanning path is formed, for example, in the method disclosed in Japanese Unexamined Patent Application Publication No. 2009-66106. To scan an ion beam in the same direction as the direction of target movement, the treatment planning system to be used is required to grasp the movement of a target and determine a scanning direction which coincides with the direction of target movement. Since an ion beam can be irradiated to a patient from an arbitrary direction by an irradiation device, the scanning direction has to be determined by taking into consideration the direction of beam irradiation even when the movement of the target is unchanged. For the operator of a treatment planning system, determining a scanning direction in such a situation is difficult. As described above, existing treatment planning systems and devices for calculating s scanning path do not provide any means by which the operator can specify, in a simple manner, a scanning direction taking into consideration three-dimensional movement of a target and a specified irradiation direction. The above problem can be solved by the feature of the independent claims. The dependent claims relate to advantageous embodiments of the invention. A treatment planning system for creating a treatment plan for particle therapy can comprising: an input device; an arithmetic device for performing arithmetic processing based on a result of input to the input device and creating treatment plan information (scanning path information); and a display device for displaying the treatment plan information. In the treatment planning system, the arithmetic device calculates a scanning path by setting a pre-specified optional direction as a main direction for scanning irradiation positions with an ion beam using a scanning magnet. The arithmetic device calculates: based on multiple tomography images of multiple states of a target region, a position of a specific region; extracts a direction of movement of the position of the specific region; and applies the direction extracted and projected on an ion beam scanning surface as the direction of movement of the target. With the device for calculating a scanning path according to the invention it is possible to realize a dose distribution of a very high uniformity in the irradiation target area. According to the present invention, treatment planning data which can realize dose distribution with improved uniformity can be created. Embodiments of the present invention will be described below with reference to drawings. A treatment planning system (or a scanning path creation system) according to a preferred embodiment of the present invention will be described below with reference to drawings. First, a particle therapy system for which the treatment planning system is used will be described with reference to FIGS. 3 and 4. FIG. 3 shows an overall structure of the particle therapy system. An ion beam generator 301 includes an ion source 302, a preaccelerator 303, and an ion beam accelerator 304. Even though the ion beam accelerator of the present embodiment is assumed to be a synchrotron-type ion beam accelerator, the present embodiment is also applicable to other types of ion beam accelerators including cyclotron-type accelerators. The synchrotron-type ion beam accelerator 304 includes, as shown in FIG. 3, a bending magnet 305, an accelerator 306, an extraction radiofrequency device 307, an extraction deflector 308, and a quadruple magnet (not shown) which are arranged along the beam orbit thereof. With reference to FIG. 3, how an ion beam generated by the ion beam generator 301 making use of the synchrotron-type ion beam accelerator 304 is emitted toward a patient will be described below. The ion particles (for example, protons or heavy ions) supplied from the ion source 302 are accelerated by the preaccelerator 303 and is sent to the synchrotron 304 that is a beam accelerator. The synchrotron 304 includes the accelerator 306. The accelerator 306 accelerates the ion beam by applying a radiofrequency wave to a radiofrequency acceleration cavity (not shown) provided in the accelerator 306 in synchronization with the period at which the ion beam circling inside the synchrotron 304 passes the accelerator 306. The ion beam is accelerated in this way until it reaches a predetermined energy level. When, after the ion beam is accelerated to a predetermined energy level (for example, 70 to 250 MeV), an emission start signal is outputted from a central control unit 312 via an irradiation control system 314, radiofrequency power from a radiofrequency power supply 309 is applied, by an extraction radiofrequency electrode installed in the extraction radio frequency device 307, to the ion beam circling in the synchrotron 304, causing the ion beam to be emitted from the synchrotron 304. A high energy beam transport line 310 connects the synchrotron 304 and a beam delivery system (nozzle) 400. The ion beam extracted from the synchrotron 304 is led, via the high energy beam transport line 310, to the beam delivery system 400 installed at a gantry 311. The gantry 311 is for allowing an ion beam to be irradiated onto a patient 406 from an arbitrary direction. The gantry 311 can rotate, in its entirety, into any direction around a bed 407 on which the patient 406 lies. The beam delivery system 400 is for shaping the ion beam to be finally irradiated onto the patient 406. Its structure differs depending on the irradiation method employed. A passive scattering method and a scanning method are among typical irradiation methods. The present embodiment uses the scanning method. In the scanning method, a fine ion beam transported through the high energy beam transport line 310 is irradiated as it is onto a target and is scanned three-dimensionally making it possible to consequently form a high dose region on the target only. FIG. 4 shows a structure of the beam delivery system 400 employing the scanning method. The roles and functions of components of the beam delivery system 400 will be briefly described below with reference to FIG. 4. The beam delivery system 400 is provided with scanning magnets 401 and 402, a dose monitor 403, and a beam position monitor 404 arranged in the mentioned order from the upstream side. The dose monitor measures the amount of the ion beam passing therethrough. The beam position monitor can measure the position passed through by the ion beam. The information provided by these monitors enables the irradiation control system 314 to perform control to keep the ion beam irradiated to a predetermined position in a predetermined amount. The direction of travel of the fine ion beam transported from the ion beam generator 301 through the high energy beam transport line 310 is bent by the scanning magnets 401 and 402. These scanning magnets are provided so as to cause magnetic flux lines to be generated perpendicularly to the direction of travel of the ion beam. Referring to FIG. 4, for example, the scanning magnet 401 bends the ion beam in a scanning direction 405 and the scanning magnet 402 bends the ion beam perpendicularly to the scanning direction 405. Using these two scanning magnets, the ion beam can be moved to an arbitrary position in a plane perpendicular to the direction of travel thereof so as to irradiate a target 406a. The irradiation control system 314 controls, via a scanning magnet field strength control device 411, the amounts of current applied to the scanning magnets 401 and 402. The scanning magnets 401 and 402 have currents supplied from scanning magnet power supplies 410 allowing magnetic fields of strengths corresponding to the amounts of currents supplied to be generated so as to arbitrarily set the degree of bending of the ion beam. The relationships between the ion beam, degree of beam bending, and amounts of currents are held as a table in a memory 313 included in the central control unit 312 to be referred to as required. When the scanning method is used for ion beam irradiation, an ion beam can be scanned in two ways. In one way, discrete scanning is made in which an irradiation position is moved and stopped repeatedly. In the other way, an irradiation position is continuously changed. In discrete scanning, a predetermined amount of ion beam is irradiated at a fixed position which is referred to as a spot. Supply of the ion beam is then suspended and the amounts of currents applied to the scanning magnets are changed so as to move the irradiation position. After the irradiation position is moved, irradiation of the ion beam is resumed. When, in this process, high-speed scanning is possible, the ion beam need not necessarily be suspended. In the method in which the ion beam irradiation position is continuously moved, the irradiation position is changed while irradiation of the ion beam is maintained. Namely, the irradiation position is changed by continuously changing the degrees of excitation of the scanning magnets while the ion beam irradiation is maintained so as to scan the entire part of the irradiation field. In this method, the irradiation amount can be changed over different irradiation positions by changing either or both of the speed of scanning effected by the scanning magnets and the amount of ion beam current. A treatment planning system according to a preferred embodiment of the present invention will be described below with reference to FIG. 5. A treatment planning system 501 is connected, via network, to a data server 502 and the central control unit 312. The treatment planning system 501 includes, as shown in FIG. 6, an input device 602, a display device 603, a memory 604, an arithmetic processing unit 605, and a communication device 606. The arithmetic processing unit 605 is connected to the input device 602, display device 603, memory (storage device) 604, and communication device 606. Prior to treatment, images for use in treatment planning are taken. As images used for treatment planning, computed tomography (CT) data is most popular. CT data used for treatment planning is three-dimensional data composed using images of a patient taken by irradiation from plural directions. With image taking growing higher in speed recently, computed tomography makes it possible to acquire plural sets of CT data on plural states (referred to as phases) of even a patient's site periodically moving due to respiration by taking plural images of the site in different phases caused by respiratory movement. This computed tomography is referred to as four-dimensional computed tomography (4DCT). 4DCT imaging makes it possible to observe movement due to, for example, respiration of a target by comparing CT data on different phases of the site. When using such a method, to make movement of the target observable with increased accuracy, a marker such as a metal ball may be implanted in the target. CT data taken using a CT system (not shown) is stored in the data server 502. The treatment planning system 501 uses the CT data. FIG. 1 is a flowchart for treatment planning. When treatment planning is started (step 101), the treatment planning system 501 reads required CT data from the data server 502 in accordance with instructions from a medical physicist (or doctor) operating the treatment planning system 501. Namely, the treatment planning system 501 copies (stores) the CT data from the data server 502 to the memory 604 via the network connected to the communication device 606. When the CT data has been read, the operator, while checking the CT data displayed on the display device 603, inputs data on a region to be specified as a target for each slice of the CT data using the input device 602 that may be, for example, a mouse. When, like in the case of 4DCT, there are plural data sets acquired by imaging a same site, an image may be synthesized from plural images and the above target selection operation may be performed using the synthesized image. A set of synthesized image can be obtained, for example, by comparing the CT values of each set of corresponding spots, each representing a same position, of plural images and selecting a highest luminance value for each position. When region data has been inputted for each slice of the CT data, the operator registers the inputted regions in the treatment planning system (step 102) causing the regions inputted by the operator to be stored as three-dimensional position information in the memory 604. In cases where there are other regions to be also assessed and controlled, for example, when there are critical organs requiring doses on them to be minimized, the operator also registers the positions of such critical organs. FIG. 7 shows a state with a target region 702 inputted, by an operator using the display device 603, on a slice 701 including CT data. Next, the operator specifies the direction of irradiation that is determined by the angles of the gantry 311 and bed 407. For irradiation from plural directions, specify plural sets of angles. The other parameters to be determined by the operator to perform ion beam irradiation include the dose (prescription dose) to be irradiated on each region registered in step 102 and the distance between adjacent spots. The prescription doses to be determined as irradiation parameters also include, besides the dose to be irradiated on each target, a tolerable dose for each critical organ. The distance between adjacent spots is initially determined automatically to be approximately the same as the beam size of the ion beam, but it can be changed by the operator. The operator is required to set these irradiation parameters (step 103). In addition to the above parameters, the direction of target movement is specified using a feature function of the treatment planning system according to the present embodiment. How to specify the direction of target movement will be described below with reference to FIGS. 8 and 9. As shown in FIG. 8, for ion beam irradiation, the gravitational center of the target region 702 is assumed to be positioned to coincide with an isocenter (rotational center of the gantry 311) 801. A spot position is defined on coordinates in a plane (isocenter plane) 804 perpendicular to a straight line (beam center axis) 803 which includes the isocenter 801 and connects a scanning center (beam source) 802 and the isocenter 801. In the following, the plane 804 will be referred to as the isocenter plane and the straight line 803 will be referred to as the beam center axis. For example, when there is a spot at position 805 on the isocenter plane 804, the currents applied to the scanning magnets 401 and 402 are adjusted to make the ion beam pass the position 805 on the isocenter plane 804. As a result, the trajectory of the ion beam becomes like a straight line 806. How far the ion beam reaches depends on the beam energy. The following description will be based on an example case in which 4DCT data is taken making use of an implanted marker. Effects similar to those generated in the following example case can also be obtained without using any marker by having an arbitrary feature point in an image specified by the operator. The treatment planning system 501 searches all CT slice images provided by the 4DCT data for each phase stored in the memory 604 and determines a marker position in each slice. This may be done directly by the operator when automatic searching is difficult. Consequently, the marker position in the CT data for each phase is determined. This process is illustrated in FIG. 9. In FIG. 9, points 902 and 903 each represent a marker position in a phase. Linearly connecting the marker positions in all phases determines a three-dimensional marker trajectory 904. The marker is positioned such that the marker trajectory represents movement of a target. Next, the marker positions, including the points 902 and 903, in all phases are projected on the isocenter plane 804. In FIG. 9, point 905 represents the point 902 projected on the isocenter plane 804. Thus, projecting all marker positions on the isocenter 804 determines a marker trajectory 906 projected on the isocenter plane 804. The projection result is displayed on the display device 603 of the treatment planning system 501. This is illustrated in FIG. 10. Points 1001, 1002, 1003, 1004, 1005, and 1006 represent the marker positions in corresponding phases projected on the isocenter plane 804. Based on the displayed marker positions, the arithmetic processing unit 605 of the treatment planning system 501 automatically calculates the direction of target movement. For example, the arithmetic processing unit 605 calculates the distances between multiple points 1001 to 1006 and determines two points, the distance between which is larger than the distance between any other combined two points. In the case of the example shown in FIG. 10, points 1001 and 1004 are selected as the two points most spaced apart and the direction along line 1007 connecting points 1001 and 1004 is defined as the direction of target movement. In cases where an ion beam is emitted only when the marker is inside a specific region, it is possible to extract only the points corresponding to the phases with the marker in such a specific region and perform calculations as described above. The direction of target movement determined by calculation is also displayed on the display device 603 of the treatment planning system 501. An example of the direction display is shown in FIG. 11. In FIG. 11, an arrowed direction 1101 represents the calculated direction of target movement. This display appears together with a display of the isocenter plane 804 shown in FIG. 10. Or, the arrow 1101 may be displayed overlapped with a display like the one shown in FIG. 10. The coordinate systems 1008 shown in FIGS. 10 and 1102 shown in FIG. 11 both used to define directions are common. The operator can manually modify, as required, the direction referring to the coordinate systems. Namely, the direction can be changed by inputting, on the input screen 1103, an x-direction component and a y-direction component of the arrow 1101. It is also possible to directly change the arrow direction on the display screen using an input device such as a mouse (step 104). The direction of target movement may be determined after marker positions are projected on a plane as described above, but it may also be determined without projecting marker positions. Namely, referring to FIG. 9, out of all the points including points 902 and 903, two the distance between which is longer than the distance between any other combination of two points are selected and the direction along a line connecting the selected two points is determined as the direction of target movement. In the example case shown in FIG. 9, the direction along a line connecting points 902 and 903 is determined as the direction of target movement. Projecting the direction thus determined on the isocenter plane 804 determines the direction of target movement on the isocenter plane. An advantage of the above method of determining the direction of target movement without projecting marker positions on a plane is that components of target movement in a direction perpendicular to the isocenter plane 804 can also be calculated. The dose distribution caused by an ion beam becomes a Gaussian-like distribution along a direction perpendicular to the direction of travel of the ion beam. The dose distribution along the direction of travel of the ion beam, however, shows a sharp peak immediately before the ion beam stops. Generally, therefore, the movement of a target along the direction of travel of the ion beam, i.e. a direction perpendicular to the isocenter plane 804, affects the dose distribution more than the movement of a target along a lateral direction. When the component of target movement in a direction perpendicular to the isocenter plane 804 is also displayed on the display screen shown in FIG. 11, the operator can modify the direction of beam irradiation that is determined by the angles of the gantry 311 and bed 407 so as to make the component of target movement perpendicular to the isocenter plane 804 smaller than a maximum allowable value. After the above parameters are determined, the treatment planning system 501 automatically performs calculations (step 105). In the following, details of calculations the treatment planning system 502 performs following the flowchart shown in FIG. 2 will be described. First, the treatment planning system 501 determines positions to be irradiated with an ion beam. In cases where a discrete scanning method is used, discrete spot positions are calculated. In cases where an ion beam is to be irradiated continuously, a scanning path is calculated. Even though, the following description of the present embodiment is based on a discrete scanning method, a continuous scanning method may also be used. Effects similar to those of the present embodiment can also be obtained using a continuous scanning method which can be regarded as a method in which discrete positions to be irradiated with an ion beam are very closely arranged along a scanning path. When plural irradiation directions (determined by the angles of the gantry 311 and bed 407) are specified, the operation performed for a single irradiation direction is repeated for the plural irradiation directions. The treatment planning system 501 starts selecting spot positions based on the CT data stored in the memory 604 and the region information inputted by the operator (step 201). As described in the foregoing, the positions to be irradiated with an ion beam are determined on the coordinates on the isocenter plane 804. Referring to FIG. 8, assume that the point 805 on the isocenter plane 804 is selected as a position to be irradiated. The treatment planning system 501 seeks an energy level which, when an ion beam is irradiated along the straight line 806 connecting the beam source 802 and point 805, causes the ion beam to stop approximately in a target range and selects the energy level (not necessarily singular) for use in irradiating the point 805. This process for energy level selection is performed for every irradiation position set on the isocenter plane. As a result, the combinations of positions to be irradiated on the isocenter plane and energy levels to be used are determined. In this way, the spots to be actually irradiated with an ion beam are determined. On the isocenter plane 804, the positions to be irradiated are selected such that the distance between adjacent positions does not exceed the value specified in step 103. In an easiest way, positions may be arranged to form a square lattice such that positions mutually adjacent along a side are spaced apart from each other by a predetermined distance along the side. The treatment planning system 501 of the present embodiment can select the direction determined in step 104 as the axis of the above lattice, i.e. as the direction along which the positions to be irradiated are linearly arranged. FIG. 12 is a conceptual illustration of the process leading to selection of spots. The direction 1101 determined in step 104 is also shown in FIG. 12. The treatment planning system 501 first sets plural straight lines parallel with the direction 1101 (step 202). Straight line 1201 represents one of the plural straight lines. The straight lines are spaced apart by the distance selected in step 103. Next, irradiation positions are set on each of the plural straight lines (step 203). The distance between irradiation positions adjacent to each other on a same straight line equals the distance between straight lines adjacent to each other. In FIG. 12, the irradiation positions thus set, including 1202 and 1203, are circularly represented, and it is seen that they are arranged to form a square lattice with its axis represented by the direction 1101. Finally, a beam energy level which causes, when the irradiation positions are irradiated with an ion beam, the ion beam to stop inside the target range is selected (step 204). The irradiation positions for which the ion beam stops outside the target range are not irradiated with the ion beam. Referring to FIG. 12, the irradiation positions, including 1202, represented by white circles are not irradiated with the ion beam. Only the irradiation positions, including 1203, represented by black circles, are irradiated with the ion beam. Broken line 1204 represents the target range contour at the depth where the ion beam of a certain energy level stops. In cases where scanning is performed discretely and ion beam emission is suspended during the time after a spot is irradiated with an ion beam until the next spot starts being irradiated, the consequential dose distribution is not dependent on the scanning path. In such cases, the scanning path may be determined after the dose is determined for each spot. In the present embodiment, however, the scanning path is determined at this stage with consideration that, when a different scanning method is adopted, it becomes necessary to calculate dose distribution taking into consideration the scanning path. Namely, in the present embodiment, the scanning path is determined in step 205 regardless of the scanning method to be used. The scanning path is determined to be along the straight lines set in step 202. Referring to FIG. 13, the spots, including point 1203, to be irradiated with a certain beam energy level are represented by black circles. The scanning path begins with the straight line 1301 that is the top line among the straight lines set to be parallel with the direction defined by the operator. The ion beam scanning advances from spot to spot first along the straight line 1301. When the last spot on the straight line 1301 is reached, scanning moves to the next straight line adjacent to the straight line 1301 and the direction of scanning is reversed. This process is repeated until all the spots on straight line 1302 have been scanned. Consequently, the scanning path is zigzagged as indicated by arrow 1303. The operation for determining a scanning path is performed for the spots to be irradiated with each of the selected beam energy levels. When the operation is completed for every energy level, the scanning paths for all spots to be irradiated have been determined (step 206). This is repeated for every irradiation direction in cases where irradiation is to be made in plural directions (step 207). When all spot positions and a scanning path for them have been determined, the treatment planning system 501 starts calculation for irradiation amount optimization (step 208). This calculation determines the irradiation amount for each spot so as to approach the target dose distribution set in step 103. For this type of calculation, an objective function is widely made use of. The objective function represents an error quantified relatively to a target dose distribution determined using spot-by-spot irradiation amounts as parameters. The objective function is defined such that its value is smaller when the target dose distribution is approached closer. An irradiation amount for each spot which minimizes the function value is sought by iterative calculation and is determined as an optimum irradiation amount. When the irradiation amount for each spot has been determined through iterative calculation, the treatment planning system 501 calculates dose distribution based on the finalized spot positions and spot irradiation amounts (step 209). The calculation results are displayed on the display device 603 (step 210). The operator checks the calculation results and determines whether the dose distribution meets the target conditions. Not only the dose distribution but also the spot positions and scanning path calculated by the treatment planning system 501 can also be checked on the display device 603 (step 106). When the dose distribution or the scanning path is found undesirable, the operator returns to step 103 and changes the settings of irradiation parameters such as the irradiation direction, prescription dose, or distance between spots. Even when the operator returns to step 103 and changes parameter settings, the direction of target movement determined in step 104 is retained. According to the new conditions specified by the operator, the scanning path and the dose distribution are updated through steps 201 and 209, and the new results are displayed on the display device 603. When the displayed results are determined desirable, treatment planning is finished (step 107). The irradiation conditions acquired are stored, via network, in the data server 502 (steps 108 and 109). When irradiating an ion beam, the central control unit 312 reads the corresponding treatment planning data stored in the data server 502. If necessary at that time, the data can be converted into a format readable by the central control unit 312. The central control unit 312 specifies conditions for ion beam irradiation such as the ion beam energy to be irradiated, scanning positions, and irradiation amounts. The irradiation control system 314 irradiates an ion beam based on the conditions specified by the central control unit 312. According to the present embodiment, it is possible to input movement of a patient's affected area and generate treatment planning data to cause an ion beam to be scanned mainly in a direction coinciding with the direction of the movement, so that treatment planning data which can realize dose distribution with improved uniformity can be provided. Even though, in the first embodiment, the direction of target movement is extracted using 4DCT images, effects similar to those of the first embodiment can also be obtained according to a second embodiment of the invention by having the direction of target movement directly specified by the operator using ordinary CT data without using any 4DCT image. The second embodiment will be described below. The operation according to the second embodiment is the same as in the first embodiment up to step 103 shown in FIG. 1. The operation differing from the first embodiment will be described in the following. In the second embodiment, the direction of target movement is determined, in step 104, by the operator without using any 4DCT data. In cases where the direction of movement of a specific organ caused, for example, by respiration or heart beat is not considered to vary much, the operator may directly specify the direction of target movement without checking the target position, for example, using a marker, i.e. saving the operation for extracting the direction of target movement. The operator specifies the direction of target movement in a three-dimensional coordinate system, for example, like the one shown in FIG. 14, based on CT data. In FIG. 14, the foot-to-head direction is defined as z axis, and x and y axes are set to be perpendicular to the z axis, respectively. When the target is determined to move in the foot-to-head direction, the operator specify a three-dimensional direction in the coordinate system. For example, the operator inputs coordinate value (x, y, z)=(0, 0, 1) from an input screen like the one shown in FIG. 11. When the direction of target movement is determined, the treatment planning system projects the direction specified in the coordinate system shown in FIG. 14 on the isocenter plane 804 and calculates the direction projected on the isocenter plane 804. When the direction on the isocenter plane 804 is determined, the operation of and subsequent to step 105 can be performed in the same way as in the first embodiment. Since the present embodiment requires no marker position to be determined for each phase, the operation to be performed by the operator is reduced. According to the present embodiment, it is possible to input movement of a patient's affected area and generate treatment planning data to cause an ion beam to be scanned mainly in a direction coinciding with the direction of the movement, so that treatment planning data which can realize dose distribution with improved uniformity can be provided. In the first and second embodiments, spots are arranged on straight lines parallel with a specified direction. In that way, when the specified direction is changed, the spot positions are also changed making it necessary to perform the operations beginning with step 203 shown in FIG. 2. When a discrete scanning method in which ion beam irradiation is stopped during scanning is used, the dose distribution is not dependent on the scanning path as long as the spot positions remain unchanged. In this case, it is possible, unlike in the first and second embodiments, to change only the scanning path portion that begins at a predetermined spot into an arbitrary direction. Such a method will be described below as a third embodiment. FIG. 15 shows the flow of operation, according to the third embodiment, corresponding to the automatic calculation performed by the treatment planning system 501 (step 105 shown in FIG. 1). After automatic calculation is started (step 1501), spot positions are selected (step 1502), the irradiation amount is optimized for each spot (step 1503), and dose distribution is calculated (step 1504) as done by an existing treatment planning system without taking the scanning direction into consideration. In the method of the present embodiment, the scanning path is changed after dose distribution is calculated in step 1504. First, the direction of target movement specified in step 104 shown in FIG. 1 is read (step 1505). Subsequently, a scanning path is set as described below for spots to be irradiated with a same level of beam energy and from a same irradiation direction (step 506). When a scanning path is specified, the arithmetic processing unit 605 of the treatment planning system 501 prepares a function for converting the path into an appropriate value. For example, the function may be defined based on the total scanning distance along the scanning path such that its value is smaller when the scanning direction is closer to the direction specified in step 104. Out of various scanning paths, the one that makes the value of the defined function smallest is searched for, for example, using a simulated annealing algorithm, as an optimum scanning path. An example is shown in FIG. 16 in which reference numeral 1601 represents a state with an unchanged scanning path for spots to be irradiated with a same level of beam energy. Spot positions are represented by black circles and an arrow 1602 represents an initial scanning path. The scanning path 1602 has been set without taking into consideration the direction of target movement. Reference numeral 1603 represents a state with a scanning path changed based on a specified direction of target movement. The spot positions are not different between the two states. In the state 1603, however, a direction of target movement 1604 is specified and it is seen that a scanning path 1605 has been set to cause scanning to proceed mostly along the specified direction. This is performed for every level of beam energy to be irradiated and every irradiation direction (determined by the angles of the gantry 311 and bed 407) (steps 1507 and 1508). Finally, the irradiation parameters including the scanning path information thus determined are outputted and the operation is ended (steps 1509 and 1510). In the method of the present embodiment, the scanning path can be changed after the spot positions and the irradiation amount for each spot are determined. The scanning path can therefore be changed outside the treatment planning system. For example, there can be a case in which the scanning path is changed using the central control unit 312 immediately before ion beam irradiation. The treatment planning data generated by the treatment planning system 501 is stored in the data server 502. In performing ion beam irradiation, the data stored in the data server 502 is read by the central control unit 312. At that time, the central control unit can display the scanning path on the display device 315 and provide an interface for changing the scanning path, thereby allowing the operator to change the scanning path using an input device (not shown) provided for the central control device. By inputting instructions for changing the scanning path on a screen like the one shown in FIG. 11 or in a coordinate system like the one shown in FIG. 14, the operator can change the scanning path as done in step 1506. According to the present embodiment, an ion beam scanning path can be changed by observing the state of a target immediately before starting ion beam irradiation, so that the movement of the target to be irradiated can be well reflected in treatment to be performed. Even though a scanning path can be changed immediately before starting ion beam irradiation by the methods of the first and second embodiments, too, the method of the present embodiment makes it possible to change only the scanning path without affecting the dose distribution. Thus, the present embodiment has advantages in that the scanning path can be changed requiring less time for calculation and in that advisability of the treatment plan after a change in the dose distribution can be checked (step 107) in a simple manner. According to the present embodiment, it is possible to input movement of a patient's affected area and generate treatment planning data to cause an ion beam to be scanned mainly in a direction coinciding with the direction of the movement, so that treatment planning data which can realize dose distribution with improved uniformity can be provided.
054220475	claims	1. A method for making fuel particles having metal carbides dispersed in a spherical graphite skeleton comprising: a) adding aqua-mesophase to an alkaline solution to form a first solution, b) adding a metal salt to said first solution to form a fuel solution, c) adding said fuel solution to an oil bath to form an emulsion of aqueous spheres in oil and heating and stirring same until said spheres with said metal salts dispersed therein, dry to form solid spheres, d) filtering said solid spheres out of said oil bath and rinsing and drying same, e) heating said solid spheres to between 700.degree.-1100.degree. C. for 1-24 hours to carbonize them to amorphous carbon and convert said metal salts to metal oxides, f) heating said solid spheres to between 2000-3000 C. for 1-8 hours to graphitize said carbon and to convert said metal oxides to metal carbides to form said fuel particles and g) depositing a carbon-based coating on said fuel particles. 2. The method of claim 1 wherein said metal salt is a fertile or fissle metal salt, which salt has a metal selected from the group consisting of uranium, plutonium and thorium. 3. The method of claim 1 wherein said oil is one selected from the group consisting of coconut oil, vegetable oil, linseed oil, olive oil, and silicone oil. 4. The method of claim 1 wherein before adding said fuel solution to said oil bath, a surfactant is added to said oil bath and stirred therein. 5. The method of claim 4 wherein said surfactant is one selected from the group consisting of PVA, stearic scid, sodium alkyl sulfate, trisodium phosphate and sodium aryl sulfonate. 6. The method of claim 4 wherein sufficient surfactant is added to said oil bath to size the spheres so formed, to between 100-500 microns.
046541926	claims	1. In a nuclear reactor having a core, a safety rod for downward insertion into and upward withdrawal from said core, a drive shaft for supporting and operating said safety rod, and drive means connected to said drive shaft for operating said shaft; apparatus for releasably supporting said safety rod, said apparatus comprising an upper adapter adapted to be affixed to the upper end of said safety rod, said upper adapter having a retention means, a lower portion on said drive shaft and having a hollow interior for housing said upper adapter, a bimetallic means supported within said hollow interior of said lower portion and having at least one ledge which engages said retention means to support said upper adapter, said bimetallic means being a substantially cylindrical bimetallic member for receiving said upper adapter in a generally coaxial relation, said substantially cylindrical bimetallic member comprising an inner layer and an outer layer, said inner layer having a greater coefficient of thermal expansion than said outer layer, said supporting ledge projecting inwardly on said inner layer for supporting said retention means, and said substantially cylindrical bimetallic member being provided with a split extending in a substantially axial direction, increasing temperature of said generally cylindrical bimetallic member being effective to cause said member to deform by opening at said split whereby said supporting ledge disengages from said retention means to release said upper adapter for downward movement with said safety rod into said core. in which said hollow interior of said drive shaft is provided with a shoulder which supports said substantially cylindrical bimetallic member. in which said substantially cylindrical bimetallic member has a mounting portion which is affixed to said lower portion of said drive shaft by fastening means. in which said inner layer is made of an austenitic stainless steel, and said outer layer is made of a high chrome steel. in which said retention means takes the form of a downwardly facing shoulder on said upper adapter for supporting engagement by said ledge. in which said ledge tapers in width from said split toward a diametrically opposite portion of said substantially cylindrical bimetallic member. 2. Apparatus according to claim 1, 3. Apparatus according to claim 1, 4. Apparatus according to claim 1, 5. Apparatus according to claim 1, 6. Apparatus according to claim 1,
	description	The present application is a national phase entry under 35 U.S.C. §371 of International Application No. PCT/EP2011/068900, filed Oct. 27, 2011, published in French, which claims priority from French Patent Application No. 1058851, filed Oct. 27, 2010, the disclosures of which are incorporated by reference herein. The invention relates to the field of online material analysis. The material analysed by these means can be in the form of an aerosol or gas charged with particles making up this material forming smoke. More particularly, the invention relates to the field of optical analysis systems for the study of particles formed by pyrolysis inside a characterisation cell. The cell forming the subject matter of the invention can be associated with various known characterisation means such as: laser-induced fluorescence; fluorescence spectrometry; absorption spectrometry; Raman spectrometry; infrared spectrometry. By way of non-limiting example, the following description is based on the use of laser-induced breakdown spectrometry, or LIBS analysis. This method consists in focussing a pulsed laser beam into a reactional mixture to be analysed and forming plasma which is analysed by emission spectrometry. This determines the composition of said reactional mixture. This technique is applied in the description hereinbelow to control of smoke coming from the production of nanometric particles by laser pyrolysis. A LIBS system for LIBS analysis is illustrated in FIG. 1 and comprises a nanoparticle synthesis reactor A5, a LIBS cell A1, a laser A2 for emitting a laser beam, a lens A3 for converging the laser beam inside the LIBS cell A1, an optical system A4 for collecting signals coming from the LIBS cell A1, and a spectrometer A7. Production of nanometric particles within the reactor A5 is based on the interaction of crossed flows between a beam emitted by a laser, for example a carbon dioxide CO2 power laser, and a reactional mixture. The beam excites vibrational states of the molecules (so-called precursors) of the reactional mixture. The energy transmitted from the beam to the molecules is redistributed to the entire reactional mixture by collision. There is then very rapid elevation of the temperature of the reactional mixture which causes thermal decomposition of the molecules, resulting in a so-called “supersaturated” vapour in radicals and in energy. Nanoparticles then form from the radicals by homogeneous germination. The nanoparticles grow by a phenomenon of collision/coalescence growth. Dissociation and formation of nanoparticles take place in a overlapping volume between the beam and the flow of the reactional mixture observable by way of the production of a flame at this point. When the nanoparticles exit from this volume, they undergo a quenching effect which stops their growth. The nanoparticles are then guided to the LIBS cell A1 through an entry conduit A6. The LIBS cell A1 comprises a reaction chamber and four arms: a first arm A11 forming inlet orifice A111 for the smoke; a second arm A12 facing the first and forming outlet orifice A121 for evacuating of smoke; a third arm A13 closed by a window A131 through which the laser beam intended to form a plasma enters; and a fourth arm A14 closed by a cache A141 and facing the third arm A13 is not used. The LIBS cell A1 also comprises a viewing window A15 for observing the plasma with the naked eye. In the LIBS cell A1, the nanoparticles behave as a gas and therefore expand inside the reaction chamber and occupy all the space available and form, smoke. Inside the reaction chamber, the laser beam Flaser generated by the laser A2 is focussed by the lens A3. When the laser beam Flaser is focussed in the mixture to be analysed there is vaporisation of nanoparticles causing ejection of atoms and forming plasma which expands. During expansion of the plasma, atoms de-energise, causing the emission of light. This light is then received by the optical system A4 which is adapted and placed to the same side as the laser A2. This light is then analysed by the spectrometer A7 connected to the optical system A4 via fibre optics A8 adapted to transport the signal. On drawback of this LIBS cell results from the fact that the nanoparticles behave as a gas within the reaction chamber. This is why the analysis window A131 of the third arm A13 becomes clogged. The clogged analysis window A131 acts as a filter which blocks part of the laser beam Flaser. Not all the energy of the laser beam Flaser is therefore efficient and only a portion thereof can be used to form the plasma. The formed plasma is therefore less energetic and emits a lower signal. This already weakened signal is further attenuated when it passes back through the analysis window A131 of the third arm towards the optical system A4. Another drawback, still linked to the gaseous behaviour of the smoke, is the clogging of the viewing window A15 tending to obstruct observation of the plasma with the naked eye. Yet another drawback is that the formed plasma is not limited to the focal point of the laser beam Flaser, that is to say where the latter is the most highly concentrated. In fact, as particles are present throughout the reaction chamber, secondary plasmas Plsec can form between the focal point of the laser beam, where the main plasma Plpr forms, and the analysis window A131 through which the laser beam Flaser enters the reaction chamber, as illustrated in FIG. 2. The secondary plasmas Plsec can be located outside the observation zone by the optical system A4. Another drawback of the LIBS cell A1 hereinabove is instability of the signals acquired by the optical system A4 and by the spectrometer A7, the origin of which is numerous. The aim of the invention is to overcome at least one of the drawbacks of the prior art presented hereinabove by way of example. To this aim, the invention provides to a characterisation cell for smoke analysis by optical spectrometry, comprising: a reaction chamber; an inlet orifice for the inlet of smoke inside the reaction chamber; an outlet orifice for the evacuation of smoke from the reaction chamber; an analysis window for the entry of a laser beam intended to form the plasma inside the reaction chamber;characterised in that the system also comprises: a fan for ensuring scanning of inert gas in the vicinity of the analysis window, and a shielding injector for shielded injection of smoke inside the reaction chamber, the shielding being ensured by a jet of inert gas around the smoke. The advantage is that the signal obtained at output (light emitted by the plasma and passing through the analysis window) is stabilised relative to the prior art. Other optional and non-limiting features of the cell are: the cell also comprises an arm extending from the reaction chamber and one free end of which is closed by the analysis window, this arm being formed by two parts of different straight cross-sections, the largest cross-section part being arranged to the side of the analysis window and the smallest cross-section part being arranged to the side of the reaction chamber to form a Venturi and ensure overpressure to the side of the window; the flow rate of inert gas generated by the fan and optionally the Venturi is adjustable; the flow rate of inert gas generated by the coaxial shielding injector is adjustable; the injector is a circular double nozzle having two coaxial orifices, a first having a disc-shaped cross-section for the inlet of smoke and a second having a ring-shaped cross-section which encloses the first for the inlet of inert gas; and a viewing window is provided for observation of the plasma produced inside the reaction chamber during its operation. The invention also relates to a characterisation system comprising a cell such as that described hereinabove and also a collector downstream of the outlet orifice of the cell recovering the powder after analysis of the latter and a pressure regulator for keeping the pressure constant in the reaction chamber of the cell. Other optional and non-limiting features of the system are: the pressure regulator comprises a regulation valve placed downstream of the collector to compensate the loss of charge due to clogging of the filters of the latter; the regulation valve is connected to a pressure probe placed in the cell for its servo-control; and the fan also ensures scanning of inert gas in the vicinity of the viewing window. In reference to FIGS. 3 and 4, an example embodiment of a proposed characterisation cell is described hereinbelow. In this example, the characterisation cell is a LIBS system. The LIBS cell for smoke analysis by plasma created by laser comprises a LIBS cell 1. The LIBS cell 1 comprises a reaction chamber in which the plasma is formed, a first arm 11 with at its free end an inlet orifice 111 for the inlet of the smoke inside the reaction chamber, a second arm 12 with at its free end an outlet orifice 121 for the evacuation of the smoke from the reaction chamber. The inlet 111 and outlet 121 orifices can be opposite and are arranged advantageously respectively on the upper part and the lower part of the LIBS cell 1. The LIBS cell 1 further comprises a third arm 13 closed by an analysis window 131 for entry of a laser beam Flaser intended to form the plasma inside the reaction chamber. Facing the third arm 13 a fourth arm 14 closed by a cache 141 can be provided. The four arms 11, 12, 13 and 14 can be advantageously arranged in to a cross, where the beam entering via the analysis window 131 intersects the smoke entering via the inlet orifice 111 and exiting via the outlet orifice 121 opposite the latter. The laser beam Flaser can ablate the material forming the LIBS cell 1. The fourth arm 14 is therefore selected longer than the third arm 13. Thus chance for the particles which result from ablation by the laser beam Flaser of the cache 141 of the fourth arm 14 to pollute the measurements made of the smoke is decreased. The LIBS cell 1 can also comprise a viewing window 15 to allow an operator to observe the interior of the reaction chamber with the naked eye or by means of a viewing device, for example a video camera connected to a monitor. This viewing window 15 can be arranged on the LIBS cell 1 so that the viewing angle through the viewing window 15 is perpendicular to the incident direction of the laser beam Flaser inside the reaction chamber and/or the arrival flow of the smoke via the inlet orifice 111. The LIBS cell also comprises a fan 16 for ensuring scanning of inert gas near at least the analysis window 131. This reduces the quantity of smoke in the vicinity of the analysis window 131, therefore decreasing clogging of the analysis window 131. The fan 16 can be a pump connected by tubes to an inert gas tank, for example argon, on one side, and on the other side to an intake orifice 132 for inert gas located in the third arm 13 in the vicinity of its end closed by the analysis window 131. To increase the efficiency of the flow of inert gas in the vicinity of the analysis window 131, the third arm 13 can have the form of a Venturi, as illustrated in FIG. 4, i.e. the third arm 13 is divided into two different cross-section parts S1, S2. The first part 134, to the side of its free end, has a cross-section S1 larger than the cross-section S2 of the second part 135 to the side of the reaction chamber. Overpressure ΔP is then generated in the first part 134, further limiting the quantity of smoke in the vicinity of the analysis window 131. The fan 16 can also be connected to an intake orifice located in the vicinity of the end of the fourth arm 14 which is closed by a cache. This helps balance the flow of argon gas inside the LIBS cell 1. The fan 16 can also be connected to an intake orifice located in the vicinity of the viewing window 15. This also reduces the clogging of the viewing window 15. In this case, to balance out the flow of inert gas inside the LIBS cell 1, scanning can also be ensured in the same way to the side opposite the viewing window 15. The flow rate of inert gas of the fan 16 can be adjustable. The LIBS cell further comprises injector 17 for the coaxial shielded injection of the smoke also the reaction chamber, the shielding being ensured by a jet of inert gas coaxial a the smoke and enclosing the latter. The shielding of the smoke confines the latter inside the reaction chamber. Therefore, the nanoparticle smoke will not tend to occupy all the space available inside the LIBS cell 1 and especially towards the analysis window 131 and the viewing window 15. This also prevents the formation of secondary plasmas outside the focal point of the laser beam Flaser. As illustrated in FIG. 5, the injector 17 can be a double nozzle 17 with truncated cone shape having two coaxial orifices 171 and 172, a first 171 with a disco-shaped cross-section in for the inlet of smoke Fu and a second 172 with a ring-shaped cross-section enclosing the first 171 orifice for the inlet of the inert gas. In this way the injected inert gas encloses the smoke which is confined inside the cylinder formed by the inert gas. The inert gas is for example argon Ar. The LIBS cell 1 can form part of a LIBS system also comprising a LIBS collector 18 downstream of the outlet orifice 121 of the LIBS cell 1 and a pressure regulator 19 for keeping the pressure constant in the reaction chamber. The pressure regulator 19 can be a regulation valve placed downstream of the LIBS collector 18 to compensate the loss of charge due to clogging of the filters of the latter. The regulation valve LIBS 19 is connected to a pressure probe S1 placed inside the LIBS cell 1 for measuring the pressure therein. A servo-control is provided for controlling the regulation valve LIBS 19 as a function of the pressure measured inside the LIBS cell 1. The regulation valve LIBS 19 opens progressively as the LIBS collector 18 is clogged by smoke. The LIBS system further comprises a reactor 5 for the generation of smoke such as described in the technological background section. The outlet of the reactor 5 is connected to a pump 9 which creates a flow of smoke. As it leaves the reactor 5, the smoke is led in part to the LIBS cell 1 and in part to a collector 51 of the reactor. Arranged at the outlet of the collector 51 is a regulation valve 52 for regulating the pressure inside the reactor 5 which must be kept constant. The regulation valve 52 is connected to a pressure probe S2 placed inside the reactor 5 for measuring the pressure therein. A servo-control is provided for controlling the regulation valve 52 as a function of the pressure measured inside the reactor 5. The regulation valve 52 opens progressively as the filters of the collector 51 of the reactor 5 become clogged due to nanoparticles. The collectors 18 and 51 collect nanoparticles of the smoke so that they are not rejected into the atmosphere. The gas flows leaving the regulation valves 19 and 52 are combined and directed to the pump 9. The presence of the regulation valve LIBS 19 is needed to conserve a stable observed signal. In fact, in the absence of the regulation valve LIBS 19, the clogging of the collector 51 of the reactor causes opening of the regulation valve 52, which boosts the flow rate in the path outside LIBS cell and decreases the flow rate in the path of the LIBS cell. At the same time, the LIBS collector 18 also clogs up, which varies the pressure in the path of the LIBS cell and therefore inside the LIBS cell 1. The drop in flow rate and the variation in pressure in the path of the LIBS cell make the resulting plasma instable. Example of Operation In operation, the pressure inside the reactor 5 is kept below atmospheric pressure to prevent the produced nanoparticles from escaping into the ambient atmosphere, for example, the pressure is servo-controlled at 900 mbar. The reactor 5 is parameterised to give production of 400 g/h of nanoparticles. The pump 9 sets a rate of 160 m3/h. A loss of excessive charge between the path outside LIBS and the path of the LIBS cell should be avoided. Indeed, this is harmful for stability of the plasma to be generated. The pressure inside the LIBS cell 1 can be servo-controlled at 850 mbar. The overall flow rate of inert gas (argon) used for scanning the windows 131 and 15 and shielding the smoke is 30 L/min, distributed as follows: 20 L/min for scanning the windows 131 and 15 and 10 L/min for shielding the smoke. The laser 2 used is a nanosecond laser of Nd:YAG type. The energy per pulse of the laser 2 is set at 50 mJ. A converging lens 3 is positioned between the laser 2 and the analysis window 131. The laser 2 and the converging lens 3 are positioned so that the focal point of the laser beam Flaser emitted by the laser 2 is at the junction of the four arms 11, 12, 13 and 14, or under the inlet flow of the smoke, and opposite the viewing window 15 if the latter is provided on the LIBS cell 2. The signal emitted by the plasma is collected by the optical system 4 placed at outlet, facing the analysis window 131. The optical system 4 sends the collected signal to a spectrometer 7 which analyses the spectrum of the signal emitted (which is the light of the plasma). The dimensions of the cell are (from the end of the arms to the centre of the cell, that is, where the plasma is created): first arm 11: 53 mm second arm 12: 160 mm third arm 13: 50 mm fourth arm 14: 100 mmComparative Test Comparative tests were conducted on a LIBS cell, the dimensions of which are specified hereinabove for measuring the combined effect of the shielding and of the scanning. FIG. 6 illustrates a graph illustrating the intensity of the measured signal (in arbitrary unit) as a function of the scanning flow rate used (in L/min) for four different elements: silicon Si, hydrogen H, argon Ar and carbon C. The intensity of the signal for silicon Si and hydrogen H shows up on the scale of ordinates to the left. The intensity of the signal for argon Ar and carbon C shows up on the scale of ordinates to the right. The shielding flowrate is selected such that the combined flow rate of the shielding and of the scanning is 30 L/min. So if the scanning flow rate is 0 L/min, the shielding flow rate is 30 L/min. If the scanning flow rate is 10 L/min, the shielding flow rate is 20 L/min. FIG. 6 therefore shows that with shielding alone (scanning flow rate is zero), the intensities of the signals for the four elements are much lower than for a shielding flow rate of 10 L/min (or a scanning flow rate of 20 L/min). This FIG. 6 also shows that with scanning alone (shielding flow rate is zero), the intensities of the signals for the four elements are lower than for a shielding flow rate of 10 L/min (or a scanning flow rate of 20 L/min). The conditions of shielding flow rate at 10 L/min and scanning flow rate at 20 L/min are close to the optimum and produce signal intensities close to the maximum. FIG. 7 shows the combined effect of shielding and scanning on the repeatability of the signal. The repeatability is given in ordinates for four elements (same as for FIG. 6) and is expressed in relative standard deviation of the intensity of lines and calculated over fifty spectra, one spectrum resulting from integration of the signal over thirty shots by a laser. The lower the standard deviation the better the repeatability. The shielding flow rate is selected such that the combined flow rate of shielding and scanning is 30 L/min. It is noticed that the repeatability of the measured signals is better when the shielding and the scanning are combined relative to the use of the shielding alone or the scanning alone with a low value translating considerable repeatability. When the scanning flow rate is 20 L/min and that of shielding is 10 L/min the repeatability is close to the minimum. Both FIGS. 6 and 7 therefore show that the effect of shielding alone and of scanning alone are not added together, but much more, signal quality is unexpectedly improved. Even though the description has been given in reference to a LIBS cell, the invention is not limited to the latter and also relates to other cells and especially those adapted for the following spectrometries: laser-induced fluorescence; fluorescence spectrometry; absorption spectrometry; Raman spectrometry; and infrared spectrometry.
	claims	1. An apparatus comprising:a pressurized water reactor (PWR) including a nuclear reactor core comprising fissile material disposed in a reactor pressure vessel also containing primary coolant water;a pressurizer integral with or operatively connected with the reactor pressure vessel and configured to control pressure in the reactor pressure vessel; anda decay heat removal system including a pressurized passive condenser and a pump driven by a turbine in which steam from the pressurizer drives the turbine and exhausts into the pressurized passive condenser and the pump is connected to suction water from the pressurized passive condenser into the reactor pressure vessel. 2. The apparatus of claim 1 further comprising:a pressurizer power operated relief valve configured to control discharge of steam bypassing the turbine into the pressurized passive condenser to control pressure in the pressurizer. 3. The apparatus of claim 1 further comprising:a pressurizer block valve configured to activate the decay heat removal system by opening to admit steam from the pressurizer to the turbine. 4. The apparatus of claim 1 further comprising:a pressurizer block valve configured to activate the decay heat removal system by opening to admit steam from the pressurizer to the turbine;a pressurizer power operated relief valve downstream of the pressurizer block valve and configured to control discharge of steam into the pressurized passive condenser to control pressure in the pressurizer; anda steam turbine control valve downstream of the pressurizer block valve and configured to throttle steam into the turbine. 5. The apparatus of claim 1 further comprising:a common shaft, the pump and the turbine being mounted on the common shaft so that the shaft provides direct mechanical coupling via which the turbine drives the pump. 6. The apparatus of claim 1 wherein the pressurizer comprises an integral pressurizer. 7. The apparatus of claim 1 further comprising:a steam generator configured to heat sink the PWR by flow of secondary coolant water in thermal communication with the primary coolant water; anda pressurizer block valve configured to activate the decay heat removal system in response to a loss of heat sinking by the steam generator by opening to admit steam from the pressurizer to the turbine. 8. The apparatus of claim 7 wherein the steam generator comprises an internal steam generator disposed inside the reactor pressure vessel.
048760609	claims	1. A control blade for use in nuclear reactors comprising: an upper structure means; a lower structure means; a central tie rod means for connecting integrally said upper and lower structure means together, having radial projections so as to exhibit a substantially cross-shaped cross-section; a sheath plate means having a substantially U-shaped cross-section and secured to the end of each projection of said central tie rod means; and neutron absorber means charged in each of said sheath plate means; said neutron absorber means being divided into a plurality of neutron absorber elements along the axis of said central tie rod means, each neutron absorber element being composed of a pair of neutron absorber plates or sheets spaced from and opposing each other; a supporting spacer means disposed for supporting said opposing neutron absorber plates; and a water gap for guiding the flow of a moderator defined between said neutron absorber plates, wherein said supporting spacer means comprises a plurality of supporting spacers disposed between said opposing neutron absorber plates, each of said supporting spacers including a spacing portion engaging with inner surfaces of said opposing neutron absorber plates and supporting portions projecting from centers of both ends of the spacing portions, said opposing neutron absorber plates being provided with holes in such a manner that said supporting portions of said spacers loosely penetrate said holes of said absorber plates and are secured to walls of said sheath plate means. 2. A control blade for use in nuclear reactors according to claim 1, wherein the thicknesses of said neutron absorber elements are so varied that the thickness of the whole neutron absorber means is progressively decreased along the length of said control blade means from the end near said upper structure towards means the end near said lower structure means, whereby the neutron absorption characteristics are progressively decreased along the length of said control blade means from the end near said upper structure means towards the end near said lower structure means. 3. A control blade for use in nuclear reactors according to claim 2, wherein the variation of the thicknesses of said neutron absorber elements is conducted such that the reduction in the thickness of the whole neutron absorber means is effected in a stepped manner along the length of said control blade means from the end near said upper structure means towards the end near said lower structure means. 4. A control blade for use in nuclear reactors according to claim 1, wherein the neutron absorption characteristics are varied at least in the neutron absorber element adjacent to said upper structure means, such that the end of said neutron absorber element remote from said central tie rod means exhibit greater neutron absorption than other portions of said neutron absorber element. 5. A control blade for use in nuclear reactors according to claim 1, wherein said neutron absorber elements are engaged and supported by supporting protrusions protruding from each of said central tie rod means at a predetermined spacing in the direction of axis of said central tie rod means. 6. A control blade for use in nuclear reactors according to claim 1, wherein an auxiliary handle is provided in said neutron absorber element adjacent to said upper structure means, at a portion near said central tie rod means. 7. A control blade for use in nuclear reactors according to claim 1, wherein water passage holes are formed in corresponding portions of the walls of said sheath plate means and said neutron absorber plates so as to allow a moderator to be introduced into said water gap. 8. A control blade for use in nuclear reactors according to claim 1, wherein said neutron absorber plate or sheet is made of a metallic neutron absorber plate or sheets, the opposing neutron absorber plates being spaced from each other by spacers which serve to preserve said water gap between said opposing neutron absorber plates. 9. A control blade for use in nuclear reactors according to claim 1, wherein said neutron absorber element includes a plurality of metallic neutron absorber plates or sheets disposed such as to oppose to each other in the thicknesswise direction of said wing, said neutron absorber plates being spaced from each other and held by supporting spacers so as to define therebetween said water gap. 10. A control blade use in nuclear reactors according to claim 1, wherein adjacent neutron absorber elements are partially overlapped at their adjacent ends. 11. A control blade for use in nuclear reactors according to claim 1, wherein the linear gap formed between adjacent neutron absorber elements is covered by the neutron absorber plate or sheet which opposes to this gap in the direction of thickness of said wing. 12. A control blade use in nuclear reactors according to claim 1, wherein the linear gaps formed between the respective adjacent neutron absorber elements are so positioned that they do not occupy the same horizontal plane. 13. A control blade for use in nuclear reactors according to claim 1, wherein said spacers are arranged in a zig-zag or staggered manner in the direction of axis of said central tie rod means. 14. A control blade for use in nuclear reactors according to claim 1, wherein each of the linear gaps formed the neutron absorber plates or sheets of adjacent neutron absorber elements is masked by the opposing neutron absorber plate. 15. A control blade for use in nuclear reactors according to claim 1, wherein said neutron absorber plate is a hafnium metal plate. 16. A control blade for use in nuclear reactors according to claim 1, wherein said sheath plate means is locally and inwardly dimpled so as to form a water passage between the inner surface of each wall of said sheath plate means and the outer surface of the adjacent neutron absorber plate, and wherein said central tie rod means is chamferred at its side surfaces, said sheath plate means being provided with water passage holes dispersed in the vicinity of the chamferred portion of said central tie rod means. 17. A control blade for use in nuclear reactors according to claim 1, wherein the side surfaces of said upper and lower structure means facing said neutron absorber plates or sheets are chamferred and said sheath plate means is provided with water passage holes dispersed in the vicinity of the chamferred portions of said upper and lower structure means. 18. A control blade for use in nuclear reactors according to claim 1, wherein said water gap between the opposing neutron absorber plates or sheets is preserved by wire-type spacers disposed between said neutron absorber plates. 19. A control blade for use in nuclear reactors according to claim 1, wherein wire-type spacers are disposed between said opposing neutron absorber plates or sheets in the region near the outer end of said wing, so as to extend in the direction of axis of said central tie rod means. 20. A control blade according to claim 1, wherein said sheath plate means are provided with holes located in alignment with corresponding holes of said opposing absorber plates respectively so that said supporting portions of said supporting spacers loosely penetrating the holes of the neutron absorber plates are fitted in the holes formed in the walls of said sheath plate means to be secured thereto so as to provide outer flat surfaces for said sheath plate means. 21. A control blade according to claim 1, wherein washer-like members are further disposed between said sheath plate means and said neutron absorber plates in a loose engagement with said supporting portions of said supporting spacer means. 22. A control blade according to claim 1, wherein said supporting spacers are disposed between said opposing neutron absorber plates with substantially equal intervals in a widthwise direction of each of said sheath plate means. 23. A control blade according to claim 1, wherein said supporting spacers are disposed between said opposing neutron absorber plates with substantially constant intervals in an axial direction of said central tie rod means, the intervals being slightly reduced between adjacent spacer means belonging to adjacent neutron absorber elements.
042138248	abstract	An improved containment for radiation shielding and pressure suppression is presented. The arrangement, which is particularly suited for marine propulsion application, includes, in a preferred embodiment, a double wall containment shell including water as a biological shield, a divided wet well arrangement and means for precluding discontinuity of the radiation shielding effect due to shifting of the liquid in the wet well at various ship attitudes.
	claims	1. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor;an overpack lid positioned atop the overpack body to enclose the open top end of the cavity;an air inlet vent for introducing cool air into the cavity, the air inlet vent comprising an annular air inlet plenum and an annular air inlet passageway, the annular air inlet plenum extending radially inward from an outer surface of the overpack body to the annular air inlet passageway, the annular air inlet passageway extending upward from the annular air inlet plenum to an opening in the floor; andan air outlet vent in the overpack lid for removing warmed air from the cavity. 2. The system of claim 1 wherein the annular air inlet passageway has an inverted truncated cone-shape. 3. The system of claim 1 wherein the annular air inlet plenum circumferentially surrounds the axis. 4. The system of claim 1 wherein the annular air inlet plenum extends horizontally from the outer surface of the overpack body at an axial height below the floor, the annular air inlet passageway extending upward from the air inlet plenum to the opening in the floor at an oblique angle to the vertical axis. 5. The system of claim 1 further comprising a plurality of plates disposed within the annular air inlet plenum, each of the plates extending along a reference line that is tangent to a first reference circle having a center point coincident with the vertical axis. 6. The system of claim 1 wherein the annular air inlet plenum extends from a substantially 360° opening in the outer surface of the overpack body. 7. The system of claim 1 wherein the air inlet vent is configured so that aerodynamic performance of the air inlet vent is substantially independent of an angular direction of a horizontal component of an air-stream applied to the outer surface of the overpack body. 8. The system of claim 7 wherein the air outlet vent is configured so that aerodynamic performance of the air outlet vent is substantially independent of an angular direction of a horizontal component of an air-stream applied to the outer surface of the overpack body. 9. The system of claim 8 wherein the air outlet vent comprises an annular passageway extending from an annular opening in a bottom surface of the overpack lid to an annular opening in an outer sidewall surface of the overpack lid. 10. The system of claim 1 wherein the overpack body comprises a cylindrical wall, a bottom block disposed within the cylindrical wall, and a base structure at a bottom end of the cylindrical wall, the base structure comprising a base plate and an annular plate arranged in a spaced relation to the base plate to form the annular air inlet plenum therebetween, the bottom block comprising a columnar portion that extends through a central hole of the annular plate and rests atop the base plate, the annular air inlet passageway formed within the bottom block and circumferentially surrounding the columnar portion. 11. The system of claim 1 further comprising a hermetically sealed canister for containing the high level radioactive waste positioned within the cavity, an annular gap existing between an outer surface of the canister and an inner wail surface of the overpack body, the annular gap forming an annular air flow passageway between the annular air inlet passageway and the air outlet vent. 12. The system of claim 1 wherein the annular air inlet passageway extends from a first end located a first radial distance from the vertical axis to a second end located a second radial distance from the vertical axis, wherein the second radial distance is greater than the first radial distance. 13. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor, the overpack body comprising an air inlet vent for introducing cool air into a bottom portion of the cavity, the air inlet vent comprising a substantially horizontal annular air inlet plenum that circumferentially surrounds the vertical axis, the substantially horizontal annular air inlet plenum extending radially inward from a substantially 360° opening in an outer surface of the overpack body;an overpack lid positioned atop the overpack body to enclose the open top end of the cavity, the overpack lid comprising an air outlet vent for removing warmed air from the cavity; andthe air inlet vent configured so that aerodynamic performance of the air inlet vent is substantially independent of an angular direction of a horizontal component of an air-stream applied to the outer surface of the overpack body. 14. The system of claim 13 wherein the air outlet vent is configured so that aerodynamic performance of the air outlet vent is substantially independent of an angular direction of a horizontal component of an airstream applied to the outer surface of the overpack body. 15. The system of claim 13 wherein the air inlet vent further comprises an oblique annular air inlet passageway and the substantially horizontal annular air inlet plenum is located at an axial height below the floor, the oblique annular air inlet passageway circumferentially surrounding the vertical axis and extending upward from the substantially horizontal annular air inlet plenum to an opening in the floor. 16. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor, the overpack body comprising an air inlet vent for introducing, cool air into a bottom portion of the cavity;an overpack lid positioned atop the overpack body to enclose the open top end of the cavity, the overpack lid comprising an air outlet vent for removing warmed air from the cavity;the air inlet vent configured so that aerodynamic performance of the air inlet vent is substantially independent of an angular direction of a horizontal component of an air-stream applied to the outer surface of the overpack body; andwherein the overpack body comprises a cylindrical wall, a bottom block disposed within the cylindrical wall, and a base structure at a bottom end of the cylindrical wall, the base structure comprising a base plate and an annular plate arranged in a spaced relation to the base plate to form the annular air inlet plenum therebetween, the bottom block comprising a columnar portion that extends through a central hole of the annular plate and rests atop the base plate, the annular air inlet passageway formed within the bottom block and circumferentially surrounding the columnar portion. 17. The system of claim 13 wherein the air inlet vent and the air outlet vent are substantially axisymmetric. 18. A system for storing high level radioactive waste comprising:an overpack body extending along a vertical axis and having a cavity for storing high level radioactive waste, the cavity having an open top end and a floor, the overpack body comprising an air inlet vent for introducing cool air into a bottom portion of the cavity;an overpack lid positioned atop the overpack body to enclose the open top end of the cavity, the overpack lid comprising an air outlet vent, for removing, warmed air from a top portion of the cavity; andthe air inlet vent comprising a first section extending from an outer surface of the overpack body to a first radial distance from the vertical axis and a second section extending, from the first radial distance to an opening in the floor at a second radial distance from the vertical axis, the second radial distance being greater than the first radial distance. 19. The system of claim 18 wherein the first section of the air inlet vent is an annular plenum that extends substantially horizontal and the second section is an annular passageway that extends oblique to the vertical axis. 20. The system of claim 19 wherein the overpack body comprises a cylindrical wall, a bottom block disposed within the cylindrical wall, and a base structure at a bottom end of the cylindrical wall, the base structure comprising a base plate and an annular plate arranged in a spaced relation to the base plate to form the annular plenum therebetween, the bottom block comprising a columnar portion that extends through a central hole of the annular plate and rests atop the base plate, the annular passageway formed within the bottom block and circumferentially surrounding the columnar portion.

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