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	description	The following generally relates to grating-based x-ray imaging, which, herein, refers to grating-based phase contrast imaging, which provides three contrasts in a scanned object—attenuation, phase, and dark-field, and thus can also be referred as grating-based phase contrast and/or dark-field contrast imaging. More particularly, the following relates to an interferometer grating support for grating-based x-ray imaging and/or a support bracket for the interferometer grating support, and is described with particular application to computed tomography (CT). In conventional CT imaging, contrast is obtained through the differences in the absorption cross-section of the constituents of the scanned object. This yields good results where highly absorbing structures such as bones are embedded in a matrix of relatively weakly absorbing material, for example the surrounding tissue of the human body. However, in cases where different forms of tissue with similar absorption cross-sections are under investigation (e.g., mammography or angiography), the X-ray absorption contrast is relatively poor. Consequently, differentiating pathologic from non-pathologic tissue in an absorption radiograph remains difficult for certain tissue compositions. Grating-based x-ray imaging overcomes this limitation. Grating-based x-ray imaging utilizes X-ray gratings, which allow acquisition of X-ray images in phase contrast, which provides additional information about the scanned object. Another advantage of grating-based x-ray imaging is that it is also sensitive to small-angle scattering, often called dark-field contrast. Dark-field contrast is generated by small structures like alveoli in the lung or the fine sponge-type structure in bones. Grating-based x-ray imaging uses three gratings, a source grating close to the X-ray source, an absorber grating close to the detector, and a phase or absorber grating disposed depending on whether configured with conventional, inverse, or symmetric geometry. Certain distances between gratings, grating shapes, grating locations, etc. need to be established and maintained for imaging. Unfortunately, this may be difficult. For example, there is a limited amount of free space in which the gratings can be added. Furthermore, in addition to the gratings, other X-ray beam conditioning components are between the X-ray tube output window and the examination area. This includes a low energy filter, a bow-tie shaped attenuator, and a beam collimator. Hence, these other components must also be considered and may further limit the space for the gratings. In view of at least the foregoing, there is an unresolved need for an approach to facilitate meeting and/or maintaining the requirements for the gratings for grating-based x-ray imaging. Aspects described herein address the above-referenced problems and others. In one aspect, an interferometer grating support of an imaging system configured for grating-based x-ray imaging includes at least two elongate supports separated from each other by a non-zero distance. The grating support further includes a first arc shaped grating affixed to a first end of the at least two elongate supports. The grating support further includes a second arc shaped grating affixed to a second end of the at least two elongate supports. In another aspect, an imaging system configured for grating-based x-ray imaging includes a gantry, a radiation source, a detector array disposed across an examination region from the radiation source; a grating support disposed between the radiation source and the examination region, and an interferometer. The interferometer includes a source grating G0, a phase or absorber grating G1, and absorber grating G2. The grating support supports gratings G0 and G1. The grating G2 is disposed between the examination region and the detector array. In another aspect, a non-transitory computer readable medium is configured with computer executable instructions which when executed by a processor of a computer cause the processor to: move a grating support, which supports G0 and G1 gratings of an interferometer and a bowtie filter, into a region between a low energy photon filter and a beam collimator, which are between a radiation source and an examination region, for a grating-based x-ray imaging scan. Those skilled in the art will recognize still other aspects of the present application upon reading and understanding the attached description. FIG. 1 schematically illustrates an imaging system 100, such as a CT scanner, which is configured for grating-based x-ray imaging. The imaging system 100 includes a generally stationary gantry 102, which houses a rotating gantry 104 that is rotatably supported by the stationary gantry 102 via a bearing or the like and that rotates around an examination region 106 about a z-axis. A radiation source 108 (e.g., an X-ray tube), which produces a focal spot 110, is rotatably supported by the rotating gantry 104, rotates with the rotating gantry 104, and emits radiation (via the focal spot 110) that traverse the examination region 106. A radiation sensitive detector array 112 is located opposite the radiation source 108 across the examination region 106. The radiation sensitive detector array 112 detects radiation traversing a field of view 114 and an object 115 therein and generates a signal (projection data) indicative thereof. An X-ray imaging interferometer is also rotatably supported by the rotating gantry 104 and rotates with the rotating gantry 104. The X-ray imaging interferometer includes three gratings. In FIG. 1, an interferometer grating support (“grating support”) 118 supports two of the gratings, and a third grating, an absorber grating (G2) 120, is located between the examination region 106 and the radiation sensitive detector array 112. FIG. 2 shows an example in which the grating support 118 supports a source grating (G0) 202 and a phase or absorber grating (G1) 204. As described in greater detail below, the grating support 118 is configured so that the space between the G0 grating 202 and the G1 grating 204 is sufficient for high phase-contrast and dark-field sensitivity, the relative position of the G0 grating 202 to the G1 grating 204 is precise, and the placement has suitable geometrical accuracy and stability, including while rotating. Furthermore, the grating support 118 allows for a geometrically calibration G0 and G1 (e.g., a rotation between the gratings) outside the system 100, e.g., in a calibration and/or other step. Continuing with FIG. 2, disposed between the G0 grating 202 and the G1 grating 204 is a conventional bow-tie filter 206. This example also shows a low x-ray energy photon filter 208 between an X-ray window 210 of the source 108 and the grating support 118, and an x-ray beam collimator 212 between the grating support 118 and the examination region 106. As described in greater detail below, in one non-limiting embodiment, a support bracket supports the grating support 118 and the low energy photon filter 208 and/or the beam collimator 212. Additionally or alternatively, as described in greater detail below, the support bracket also supports one or more other beam conditioning components, which is/are alternatively positioned (in alternative to the grating support 118) between the low energy photon filter 208 and the beam collimator 212, via electro-mechanical control. FIG. 2 also shows the relative geometry of the gratings. In this example, a distance 214 between the G0 grating 202 and the G1 grating 204 is less than a distance 216 between the G1 grating 204 and the G2 grating 116. That is, the G1 grating 204 is closer to the G0 grating 202 than the G2 grating 116. A distance 218 is between the G0 grating 202 and the G2 grating 116. A distance 220 is a distance between the focal spot 110 and the detector array 112. This configuration is considered inverse geometry. Inverse, conventional and symmetric configurations are discussed in Donath et al., “Inverse geometry for grating-based x-ray phase-contrast imaging,” Journal of Applied Physics,” 106, 054703, 2009. An example of suitable distances and pitches is described in patent application publication US 2015/0117598 A1, filed Dec. 4, 2014, and entitled “Grating-Based Differential Phase Contrast Imaging,” which is incorporated herein by reference in its entirety. Returning to FIG. 1, a reconstructor 122 reconstructs the signals generated by the array 112. In one instance, the reconstructor 122 is configured to generate a conventional CT image. In another instance, the reconstructor 122 is configured to generate a dark field image. In another instance, the reconstructor 122 is configured to generate phase images. In yet another instance, the reconstructor 122 is configured to generate phase images and a dark field image. In another instance, the reconstructor 122 is configured to generate a conventional CT image and dark field image. In another instance, the reconstructor 122 is configured to generate a conventional CT image and phase images. In another instance, the reconstructor 122 is configured to generate a conventional CT image, a dark field image and phase images. An example of reconstruction of conventional CT, dark field and/or phase images is described in patent application publication US 2015/0117598 A1, filed Dec. 4, 2014, and entitled “Grating-Based Differential Phase Contrast Imaging,” which is incorporated herein by reference in its entirety. Another example of x-ray imaging is described in U.S. Pat. No. 9,084,528 B2, filed Dec. 3, 2010, and entitled “Phase Contrast Imaging,” which is incorporated herein by reference in its entirety. Another example of dark field imaging is described in patent application publication US 2015/0124927 A1, filed May 13, 2013, and entitled “Dark field computed tomography imaging,” which is incorporated herein by reference in its entirety. A subject support 124, such as a couch, supports the object 115 in the field of view 114 before, during and/or after scanning a subject or object. A general-purpose computing system or computer serves as an operator console 126. The console 126 includes a human readable output device such as a monitor and an input device such as a keyboard, mouse, etc. Software resident on the console 126 allows the operator to interact with and/or operate the imaging system 100 via a graphical user interface (GUI) or otherwise. This includes selecting an imaging protocol, e.g., a grating-based x-ray imaging protocol, initiating scanning, etc. In one instance, as described in greater detail below, the console 126 sends a signal which cause the grating support 118 and the G2 grating 120 to move into position for a grating-based x-ray imaging scan or a position for a conventional CT scan. FIGS. 3 and 4 schematically illustrates a non-limiting example of the grating support 118. FIG. 3 schematically illustrates the grating support 118 by itself, and FIG. 4 schematically illustrates the grating support 118 in connection with the radiation source 108, the G2 grating 116, and the detector array 112. The relative size and/or location of the components are not limiting and are provided for explanatory purposes. The grating support 118 includes at least two elongate supports 302 and 304 that are separated from each other in a direction 306, which is transverse to a vertical line 308 from a center of the focal spot 110 to the detector array 112, by a non-zero distance at least equal to a length of the bowtie filter 206. The at least two supports 302 and 304 are symmetrically disposed about the vertical line 308 and taper. The non-zero distance varies from a distance 310 at an end 312 of the grating support 118 which is disposed adjacent the nearer the focal spot 110 to a distance 314 at an opposing end 316 of the grating support 118, which is farther from the focal spot 110. The non-zero distance varies linearly. In a variation, the non-zero distance varies non-linearly. The non-zero distance is at least large enough so that the bowtie filter 206 fits there between. The illustrated size and shape of the at least two supports 302 and 304 is not limiting. The G0 grating 202 is coupled at the end 312 of the grating support 118. The G0 grating 202 can be coupled thereto via a fastener such as an adhesive (e.g., glue), a screw, a rivet, a clamp, and the like. In this embodiment, the G0 grating 202 is arc shaped and follows a circle 318 having a center or midpoint 320 at a center of the focal spot 110. The G1 grating 204 is coupled to the opposing end 316 of the grating support 118. Likewise, the G1 grating 204 can be coupled via a fastener such as an adhesive (e.g., glue), a screw, a rivet, a clamp, and the like. In this embodiment, the G1 grating 204 is also arc shaped and follows a circle 322 (which is concentric to the circle 318) sharing the center or midpoint 320. The G0 and G1 gratings 202 and 204 can be pre-formed with the arc shape and/or bent during installation on the at least two supports 302 and 304. In this embodiment, the G0 and G1 gratings 202 and 204 are separated from each other along the line 308 by a distance of ten centimeters (10 cm). In a variation, this distance is twenty centimeters (20 cm). In a variation, this distance is value between eight and thirty centimeters (8-30 cm). Generally, the separation corresponds to the Talbot distance. In one instance, this distance is static. In another instance, this distance is variable and can be manually and/or automatically adjusted. The grating support 118 includes a material with a temperature expansion coefficient such that the G0 and G1 gratings 202 and 204 maintain their positions. A suitable material is a nickel-iron alloy having a low coefficient of thermal expansion such as Invar®, a product of Imphy Alloys, France, and/or product. Furthermore, the grating support 118 can maintain the suitable positions under centrifugal forces of a CT scanner (e.g., 2 g to 6 g, 4 g, etc.). A volume 324 bound by the G0 grating 202 and the bow-tie filter 206 is free of any x-ray attenuating material. A volume 326 bound by the G1 grating 204, the at least two supports 302 and 304, and the bow-tie filter 206 is also free of any x-ray attenuating material. A suitable bow-tie filter 206 includes a conventional bowtie filter that combines strong attenuation areas with reduced beam hardening. In one instance, this includes a bowtie filter that is relatively thick such as seven centimeters (7 cm) of a low Z material such as Teflon®, a product of Chemours, USA. In another embodiment, the bowtie filter may be made of a different material and/or have a different thickness. In yet another instance, the bowtie filter 206 is omitted. The bowtie filter 206 can be part of an assembled grating support 118 and/or installable therein. FIGS. 5, 6 and 7 illustrate non-limiting variations of the grating support 118. The grating support 118 in FIG. 5 is substantially similar to the grating support 118 in FIGS. 3 and 4, except that the grating support 118 in FIG. 5 includes at least one wall 502. The illustrated wall 502 is shaped to follow a perimeter of the G0 and G1 gratings 202 and 204 and the at least two supports 302 and 304. In other embodiments, the wall 502 is otherwise shaped. Furthermore, the grating support 118 can include the wall 502 on only one side of the grating support 118 or on both side of the grating support 118. Furthermore, the wall 502 shape does not have to follow the perimeter of the G0 and G1 gratings 202 and 204 and the at least two supports 302 and 304. For example, in a variation, the wall 502 is rectangular. The grating support 118 in FIG. 6 is substantially similar to the grating support 118 in FIGS. 3 and 4, except that the grating support 118 in FIG. 6 includes support members 602 and 604, with the member 602 at and along the G0 grating 202 and the member 604 at and along the G1 grating 204. In another embodiment, the grating support 118 can include more or less support members. In one instance, at least one of the support members 602 and 604 facilitates holding the G0 or G1 gratings 202 and 204 in place. In another embodiment, at least one of the support members 602 and 604 does not facilitate holding the G0 or G1 gratings 202 and 204 in place. The grating support 118 in FIG. 7 is substantially similar to the grating support 118 in FIGS. 3 and 4, except that with the grating support 118 in FIG. 7 the at least two supports 302 and 304 are part of a single support 702, which includes top, middle and bottom legs 704, 706 and 708, all extending between the at least two supports 302 and 304, and another support 710, extending like the at least two supports 302 and 304 from the top leg 704 through the intermediate leg 706 to the bottom leg 708. In another embodiment, the grating support 118 can include a combination of the FIGS. 3-7 and/or another configuration(s). FIG. 8 illustrates embodiment in which the grating support 118 is supported in the system 100 by a bracket 802. In this example, the bracket 802 supports the grating support 118 at a static position. The bracket 802 also supports the low energy x-ray photon filter 208 and the beam collimator 212. In a variation, at least one of the low energy x-ray photon filter 208 and the beam collimator 212 is alternatively supported by a component other than the bracket 802. A distance 804 is between the focal spot 110 and the G0 grating 202 (no visible). In one instance, the grating support 118 is releasably affixed to the bracket 802 and can be readily removed therefrom, e.g., to replace the grating support 118 and/or a component thereof (e.g., the bowtie filter 206). In another instance, the bracket 802 is releasably affixed in the system 100 and can be readily removed therefrom, e.g., to replace the bracket 802 and/or a component thereof (e.g., the grating support 118). The bracket 802 can be affixed to the source 108 and/or the rotating gantry 104 (FIG. 1). FIG. 8 also shows the distance 214 between the G0 grating 202 and the G1 grating 204. FIG. 9 illustrates an alternative support bracket 902. The alternative support bracket 902 is configured to support the grating support 118 and one or more alternative x-ray beam conditioners such as bowtie filters 904 and 906. In this example, the bowtie filters 904 and 906 have different geometry corresponding to different size, shape, etc. objects and/or subjects. In a variation, the support bracket 902 is configured to support more or less and/or other x-ray beam conditioning components. The grating support 118 and the bowtie filters 904 and 906 are affixed in an assembly 908. The assembly 908 is translatably coupled to at least one rail 910 via at least one bearing 912. A controller (not visible) controls a motor (not visible) to drive a drive system (not visible) such as a lead screw, ball screw, gear(s), chain, etc. to translate the assembly 908 to move at least between: 1) a position (shown) in which the bowtie filter 904 is between blades 914 of the collimator 212 and the low energy photon filer 208 (not visible); 2) a position in which the bowtie filter 906 is between the blades 914 and 916 of the collimator 212 and the low energy photon filer 208, and 3) a position in which the grating support 118 is between blades 914 of the collimator 212 and the low energy photon filer 208. The particular one of the alternative x-ray beam conditioners positioned between the blades 914 of the collimator 212 and the low energy photon filer 208 depends on the particular scan to be performed. For example, where a grating-based x-ray imaging scan is to be performed, which can be selected at the console 126 (FIG. 1) during scan planning for a subject, the console 126 transmits a signal that causes the controller to control the motor to drive the drive system to translate the assembly 908 to position the grating support 118 between the blades 914 of the collimator 212 and the low energy photon filer 208. For a non-grating-based x-ray imaging scan (or conventional scan), the console 126 transmits a signal that causes the controller to control the motor to drive the drive system to translate the assembly 908 to position the bowtie filter 904 or 96 between the blades 914 of the collimator 212 and the low energy photon filer 208. The blades 914 and 916 of the collimator 212 are translatably affixed to at least one other rail 918 via at least one bearing 920. A controller (not visible) controls a motor 922 to drive a drive system (not visible) such as a lead screw, ball screw, gear(s), chain, etc. to translate the blades 914 and 916. The blades 914 and 916 of the collimator 212, in one instance, move to a first position where the blades 914 and 916 contact each other and block x-rays from passing to the examination region 106 (FIG. 1). The blades 914 and 916 of the collimator 212, in another instance, move away from each other alternatively to one of a plurality of predetermined positions, each corresponding to a different distance between the blades 914 and 916 and a different beam width. The blades 914 and 916 of the collimator 212 can also be moved together in coordination in a same direction. In one instance, at least the grating support 118 is releasably affixed to the support bracket 902 and can be readily removed therefrom, e.g., to replace the grating support 118 and/or a component thereof (e.g., the bowtie filter 206). Additionally or alternatively, at least one of the collimator 212 and/or the low energy photon filer 208 is releasably affixed to the bracket 902 and can be readily removed therefrom, e.g., to replace the collimator 212 and/or the low energy photon filer 208. Additionally or alternatively, the bracket 902 is releasably affixed in the system 100 and can be readily removed therefrom, e.g., to replace the bracket 902 and/or a component supported thereby. The illustrated support bracket 902 is shaped similar to a box with a bottom 924, four sides 926 (a front side is rendered transparent so that the grating support 118 and other components can be seen), and a top (which is rendered transparent so that the grating support 118 and other components can be seen). This configuration is non-limiting, and other structural configurations, such as non-box shaped, are contemplated herein. The illustrated support bracket 902 also includes mounting members 928 and 930. The bracket 902 can be affixed to the source 108 and/or the rotating gantry 104 (FIG. 1). Other mounting members are contemplated herein. For a configuration in which the system 100 is configured with the support bracket 902, the G2 grating 120 is configured to move in the beam path between the examination region 106 and the detector array 112 and out of the beam path between the examination region 106 and the detector array 112. For example, for a grating-based x-ray imaging scan, the G2 grating 120 is moved into a region between the examination region 106 and the detector array 112 and in the beam path, and for a conventional CT scan, the G2 grating 120 is moved out the region between the examination region 106 and the detector array 112 and one of the bowtie filters 904 or 906 is moved into the region between the examination region 106 and the detector array 112 and in the beam path. The G2 grating 120 can be moved via an electro-mechanical system, which may include a controller, a motor, a drive system, and/or other components. FIG. 10 illustrates an example method in accordance with an embodiment described herein. It is to be appreciated that the ordering of the acts is not limiting. As such, other orderings are contemplated herein. In addition, one or more acts may be omitted and/or one or more additional acts may be included. At 1002, an input signal indicating a grating-based x-ray imaging scan is to be performed is received at the console 126 of the imaging system 100. At 1004, the grating support 118, which includes the gratings G0 and G1 202 and 204 and the bowtie filter 206, is positioned between the low energy photon filter 208 and the collimator 212, via electro-mechanical control. At 1006, the grating G2 116 is positioned between the examination region 106 and the detector array 112. At 1008, a radiation source 108 is controlled to emit x-ray radiation. At 1010, a detector array 112 is controlled, in coordination with the control of the radiation source 108, to detect emitted x-ray radiation traversing the examination region 106 and generate a signal indicative thereof. At 1012, the signal is reconstructed to generate a phase contrast image(s) and/or a dark field image(s). FIG. 11 illustrates an example method in accordance with an embodiment described herein. It is to be appreciated that the ordering of the acts is not limiting. As such, other orderings are contemplated herein. In addition, one or more acts may be omitted and/or one or more additional acts may be included. At 1102, a radiation source 108 is controlled to emit x-ray radiation, which traverses the grating support 118, which includes the gratings G0 and G1 202 and 204 and the bowtie filter 206, the examination region 106, and the grating G2 116. At 1104, a detector array 112 is controlled to detect emitted x-ray radiation traversing the examination region 106 and generate a signal indicative thereof. At 1106, the signal is reconstructed to generate a phase contrast image(s) and/or a dark field image(s). The above may be implemented by way of computer readable instructions, encoded or embedded on computer readable storage medium, which, when executed by a computer processor(s), cause the processor(s) to carry out the described acts. Additionally or alternatively, at least one of the computer readable instructions is carried by a signal, carrier wave or other transitory medium, which is not computer readable storage medium. The invention has been described with reference to the preferred embodiments. Modifications and alterations may occur to others upon reading and understanding the preceding detailed description. It is intended that the invention be constructed as including all such modifications and alterations insofar as they come within the scope of the appended claims or the equivalents thereof.
049869582	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel assembly and, more particularly, to a fuel assembly suitable for use in a boiling water reactor. 2. Description of the Related Art The core of such a boiling water reactor is provided with a plurality of fuel assemblies which are spaced apart from one another at predetermined intervals and in which a plurality of control rods which are inserted between adjacent fuel assemblies. The fuel assembly has an upper tie plate, a lower tie plate and a plurality of fuel rods whose opposite ends are supported by the upper and lower tie plates. Each of the fuel rod includes a multiplicity of fuel pellets. A channel box is mounted on the upper tie plate to surround a fuel bundle. The maximum power in the core provided with such fuel assemblies is obtained by multiplying the product of the following three kinds of peaking and the average power of the fuel assemblies within the core. A first peaking from among the three kinds of peaking is a radial power peaking which is the proportion of the maximum power of the fuel assemblies within the reactor core to the average power of fuel assemblies. A second peaking is an axial power peaking which is the proportion of the maximum power to the average power of the reactor core in the vertical direction thereof. A third peaking is a local power peaking which is the proportion of the maximum power of the fuel rods in the fuel assembly to the average rods power in the fuel assembly. The power P of each fuel rod in the fuel assembly is given by EQU P=.phi..multidot..delta..sub.r .multidot.N where .phi. is the thermal neutron flux in the position of the fuel rod, .delta..sub.r is the fission cross section of a fissile material and N is the density of atoms in the fissile material in the fuel rod (hereinafter referred to as "fuel atoms"). In order to efficiently burn the fuel and to prolong its burn-up period, it is necessary to increase the so-called infinite multiplication factor of the fuel assembly. As is known, to increase the infinite multiplication factor, it is effective to increase the density of fuel atoms in a region in which thermal neutron flux level is high, as well as to decrease the density of fuel atoms in a region in which thermal neutron flux level is low. In the above-described boiling water reactor, the thermal neutron flux level is high in the periphery of the fuel assembly, but is low in the central portion due to the non-uniform distribution of a moderator for neutrons, the neutron absorption effect of the fuel rod itself and so forth. Accordingly, it is desirable that a fuel assembly of the type which is used in the boiling water reactor be formed such that the density of fuel atoms in the periphery of the fuel assembly is greater than that in the central portion. The fuel assembly disclosed in Japanese Patent Unexamined Publication No. 58-26292 is known as a fuel assembly capable of satisfying such a demand. The fuel assembly disclosed in Japanese Patent Unexamined Publication No. 58-26292 is constructed in the following manner. A plurality of fuel rods for use in a reactor which employs a fissile material as fuel are incorporated in the fuel assembly in parallel to one another and in an integral form. The average density of the fissile material in the fuel rods in the periphery of the fuel assembly is selected so as to be greater than the average density of the fissile material in the fuel rods in the central portion of the fuel assembly. In a manner similar to that disclosed in U.S. Pat. No. 4,229,258, the proportion of fissile material contained in each of the fuel rods is changed in the axial direction so that the infinite multiplication factor in the upper portion of the fuel assembly becomes greater than the infinite multiplication factor in the lower portion of the fuel assembly. Thus, the infinite multiplication factor of the overall fuel assembly is increased and the burn-up period of the fuel assembly is consequently prolonged. Recently, fuel with a high degree of burn-up has been developed and there has been a trend toward an increase in the enrichment of a fuel pellet of the type which is loaded in a fuel rod. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to provide a fuel assembly whose axial power peaking can be suppressed and whose fuel economy is improved by the effective utilization of neutrons. It is another object of the present invention to provide a fuel assembly such that a decrease of its infinite multiplication factor can be suppressed. A first feature of the present invention resides in the fact that, the proportion of fuel rods whose enrichment in their lower regions is greater than the average enrichment in the lower region of the fuel assembly among the fuel rods located in the periphery of a fuel assembly, is smaller than the proportion of fuel rods whose enrichment in their upper regions is greater than the average enrichment in the upper region of the fuel assembly among the fuel rods located in the periphery of a fuel assembly. A second feature of the present invention resides in the fact that, in the upper region of a fuel assembly, the proportion of fuel rods whose enrichment in their upper regions is greater than the average enrichment in the upper region of the fuel assembly is not less than 50 percent of the total number of fuel rods located in the periphery of the fuel assembly, whereas, in the lower region of the fuel assembly, the proportion of fuel rods whose enrichment in their lower regions is greater than the average enrichment in the lower region of the fuel assembly is not greater than 20 percent of the total number of fuel rods located in the periphery of the fuel assembly. In accordance with the first feature of the present invention, at least the fuel rods whose fuel enrichment in the upper portions thereof is greater than the average enrichment in the upper region of the fuel assembly are present in the periphery of the upper region of the fuel assembly. Accordingly, since the neutrons in the periphery of the fuel assembly, in which neutron flux level is high, can be effectively utilized, good fuel economy can be achieved. Among the fuel rods located in the periphery of the fuel assembly, the proportion of fuel rods whose enrichment in their respective lower regions are greater than the average enrichment in the lower region of the fuel assembly is less than the proportion of fuel rods whose enrichment in their respective upper regions are greater than the average enrichment in the upper region of the fuel assembly. Accordingly, it is possible to decrease the local power peaking in the lower region of the fuel assembly which has a low void fraction, in particular, the local power peaking in the periphery of the lower region. In accordance with the second feature of the present invention, in the upper region of the fuel assembly, at least 50 percent of the fuel rods located in the periphery of the fuel assembly are fuel rods whose enrichment in their respective upper regions are greater than the average enrichment in the upper region of the fuel assembly. Accordingly, since neutrons in the periphery in which neutron flux level is high can be effectively utilized, good fuel economy can be achieved. With this arrangement at least 50 percent of the fuel rods located in the periphery of the fuel assembly and has enrichment in their respective upper regions greater than the average enrichment in the upper region of the fuel assembly. Accordingly, the increment of the infinite multiplication factor of the fuel assembly does not rapidly decrease. Further, the proportion of fuel rods whose enrichment in their respective lower regions are greater than the average enrichment of the lower region of the fuel assembly among the fuel rods located in the periphery of the fuel assembly does not exceed 20 percent. Accordingly, it is possible to diminish the local power peaking in the lower region of the fuel assembly having a low void fraction, in particular the local power peaking in the periphery of the fuel assembly, and hence the axial power peaking. In addition, owing to the above-noted functions, the quantity of fissile material in a new fuel assembly (the exposure of fuel assembly is zero) to be loaded in a reactor core can be increased, and therefore the exposure of fuel can be increased.
062164457	summary	TECHNICAL FIELD The invention relates generally to plasma thrusters and more particularly to a miniature pulsed plasma thruster capable of efficiently generating very small impulse bits at low levels of power and DC ignition voltages. BACKGROUND OF THE INVENTION Space vessels such as spaceships and satellites utilize thrusters to achieve motion in space. A thruster operates on the principle that a force generated in one direction generates an equal force in the opposite direction. By emitting a reaction-mass, a thruster accelerates a spacecraft in the opposite direction. A thruster may be used as a small rocket engine for orbit correction or as the main propulsion of the spacecraft. Older conventional thrusters used chemical propulsion, which utilized liquid and/or solid propellants. Electric thrusters, which accelerate gases by electrical heating and/or by electric and magnetic field forces, can outperform chemical propulsion systems, in part, because of their high specific impulse (Isp) values. Advantages of electric thrusters include high efficiency and performance, low weight, increased spacecraft orbiting lifetimes, reduced overall costs, and a savings in fuel mass. Advances in onboard electric power sources and smaller more efficient electronic devices have expanded the use of electric thrusters in spacecraft applications. Electric thrusters that convert electrical energy into kinetic energy may be grouped into three categories: electro thermal propulsion, electrostatic or ion propulsion, and electromagnetic propulsion. Within the electromagnetic propulsion category is the Pulsed Plasma Thruster (PPT), which accelerates the propellant plasma via interaction with an electric arc. Multiple government and civil entities are developing small and micro sized spacecraft that can benefit from PPTs for space missions. Such spacecraft will require major reductions in thrust levels and/or impulse bits to ensure proper and precise control of the spacecraft. Many missions, in particular those that require significant mission propulsion energies and/or acceleration, will require specific impulses beyond those available from chemical rockets. Because present electric rockets cannot efficiently operate a very low level of power and impulse bits they are not well suited for such missions. While PPTs are at a high state of development, they generally require high levels of voltage and power to initiate the plasma breakdown and are also very inefficient at low powers when operated at values of expelled propellant velocities of interest to space missions. For example, experimental PPTs have been operated at energy levels down to about 2 joules (J) per pulse requiring the use of high voltage charging supplies which can range from 2,000 to 8,000 volts depending on the design. Also, efficiencies of PPTs decrease with decreasing power and presently, are less than 10 percent efficient when operated at values of propellant velocities of interest to space systems. The inefficiencies result in significant increases in power to achieve desired levels of impulse bits. An example of such a thruster is shown in FIG. 1 and denoted generally as 10. The thruster 10 fits into the class of propellant devices that operates using an all gas propellent although an all solid solution could also be utilized. In particular, the thruster 10 utilizes a low atomic weight liquid propellant such as water or monopropellant hydrazine (N.sub.2 H.sub.4) or a mixture of two liquids such as water and hydrazine which is stored in the tank 12 and flows through a conduit 14 leading to an opening 16 that forms the feeding mechanism of the thruster 10. The liquid propellent within the tank 12 may be pressurized by high pressure helium in the tank 20, in a manner well known to those of ordinary skill in the art. The liquid propellent flows through the conduit 14 via the opening 16 and reaches a passage 18 within the thruster 10. The passage 18 leads to a small opening 22 which is sized to provide the correct flow velocity for the liquid propellent and reduce back flow into the passage 18. In the passage 18, the liquid propellent is partially or fully atomized and partially evaporated, so that there is a two phase flow of liquid and gas into the thruster 10. The liquid propellent is disassociated into low atomic weight elemental constituents thereof by an electric discharge that forms a plasma arc within the thruster 10. The liquid gas and plasma flow from an open end 24 of the passage 18 into the thrust nozzle 30 which, as shown, is shaped as a cone or bell having a curved confining surface, to provide high efficiency and conversion of the high pressure plasma into a directed supersonic flow having high momentum. This discharge of plasma is established primarily by the use of a high voltage DC (HVDC) power supply 32 which is coupled to electrodes 34 and 36 of the thruster 10. In particular, the thruster 10 operates when liquid from the tank 12 flows into the passage 18 and a high voltage ignition signal supplied by the HVDC power supply 32 is applied at terminals 34 and 36 at a predetermined frequency, such as 200 pulses per second, for example. This ignition voltage can vary but according to one design ranges from 2,000 volts to 8,000 volts. The ignition signal supplied by the HVDC power supply 32 causes a discharge to be established in the passage 18 between the electrodes 34 and 36 at a time when partially atomized fluid is entering the thrust nozzle 30 through the opening 24. The velocity and mass flow rate of liquid flowing through the passage 18 and the repetition rate and energy of the plasma discharge between the electrodes 34 and 36 are matched to achieve optimum operation. Typically, the HVDC power supply 32 raises the voltage of the thruster 10 until an electrical breakdown occurs between the electrodes 34 and 36. The requirement, however, that the HVDC supply 32 generate high levels of ignition voltages makes the thruster 10 unsuitable for many propulsion applications where small spacecraft are involved. The HVDC supply 32 can be large and not well suited for such applications. Moreover due to its size, the HVDC supply 32 makes it difficult to achieve small and precise maneuvers for some spacecraft missions. For many space mission applications, where small space systems are involved and which require extremely precise control, the use of high power and/or high voltage ignition circuits is impractical. Examples of such missions are those which require extremely precise ephemeris control and those which are otherwise penalized by high thrust, such as missions which require multiple acceleration and deceleration maneuvers. Thus a PPT that is able to efficiently operate without a high voltage ignitor system and at power levels several orders of magnitude less than prior art designs would be advantageous. SUMMARY OF THE INVENTION The present invention is a pulsed plasma thruster (PPT) capable of operating at low levels of power and impulse bits that is suitable for use in space applications where the space system is small and precise control of the spacecraft is required. The PPT of the present invention is capable of delivering reliable ignition of a spark breakdown at DC voltages less than 300 volts with reliable transfer of a spark to a useful plasma arc. The ablation, combustion and acceleration of the Polytetra Fluorethylene (PTFE) fuel propellent is precisely controlled with the use of miniaturized PPT and power processor components. The efficiency of the thruster is increased by the independent introduction of vapor (such a from a subliming solid) at optimal locations and times during the operational cycle. According to one embodiment, disclosed is a PPT having optimally located solids capable of producing high vapor pressures for purposes of enhancing both ignition and efficiency. Heat generating elements, such as micro-heaters, are placed adjacent to the solids and configured to generate heat that causes the solids to sublime. The PPT includes an igniter section that forms a passageway from the solid to a thrust discharge chamber. In one embodiment, the ignition chamber includes a plurality of holes which are sized and spaced for optimally guiding vapors to the thrust discharge chamber for purposes of enabling arc ignitions at low voltages. In one embodiment, solids are also located within the thrust discharge chamber and, via the use of heat generating elements, independently introduce vapors into the thrust discharge chamber in order to enhance PPT efficiency at desired values of propellant velocities. The thrust discharge chamber includes a set of properly spaced and shaped electrode plates which provide for transfer of an initial spark to a useful plasma arc in the gap defined by the electrodes plates. A solid propellent, such as PTFE, is provided within the thrust discharge chamber and arranged so that the plasma arc traveling through the thrust discharge chamber will ablate the PTFE and accelerate the plasma formed from ablated PTFE and the independently introduced vapor from high vapor pressure solids, as used. A power processing unit provides the DC ignition voltage necessary to cause a spark to occur in the gap between the electrode plates. In one embodiment, the power processor unit has a variable output that operates in three segments: an open circuit to constant voltage segment, a constant voltage segment, and a constant current segment. A high vapor pressure between the electrode plates is created when the heat generating means heats the solid to assist in ignition and transition of a spark to a useful plasma arc. Micro-heaters can also be embedded in, or at the edges of, the PTFE propellent and its temperature varied to control the amount of PTFE ablated to provide more control of the impulse generated by the PPT. Micro-heaters embedded in the solids, located in the ignitions section and/or the thrust discharge chamber, independently provide a source of vapor to the thrust discharge chamber to provide additional and independent control of the efficiency and impulse of the PPT. In one embodiment the electrode plates are equally spaced about a central axis through the thrust discharge chamber. In another embodiment, the PPT includes a means of varying the spacing between the electrode plates as a function of axial distance. In an other embodiment, slightly radioactive electrodes are used. In these ways ignition voltages and required power levels are achieved that are several orders of magnitude smaller than those previously obtainable. Also disclosed is a method of operating a pulsed plasma thruster comprising the steps of heating a subliming solid to create a high pressure vapor and directing that high pressure vapor in the direction of a thrust discharge chamber through an ignition chamber. Next, a DC ignition signal is applied to electrodes coupled to the thrust discharge chamber that sparks a breakdown of a fuel propellent and causes a transition of the spark to a useful plasma arc. The DC ignition signal is applied in a way that its shape and magnitude are controlled. In one embodiment the DC ignition signal is controlled in three segments corresponding to an open circuit to constant voltage segment, a constant voltage segment and a constant current segment. The high pressure vapor is directed to the thrust discharge chamber so that pressure is created between two electrode plates. The vapor can be fed uniformly to control ignition and breakdown of the fuel propellent. The spacing between the electrode plates may be adjusted to control the amount of the fuel propellent ablated. A source of ultraviolet radiation may be focused on the vapor to provide additional excitation energy that helps ignite the vapor from the subliming solid. A technical advantage of the invention is the enablement of reliable ignitions at voltages more than an order of magnitude less that previously obtainable. This enables small and light-weight PPTs and power supplies and, therefore, much lighter PPT systems than previously obtainable. Another advantage is the efficient enablement of impulse bits several orders of magnitude less than previously obtainable. This enables the deployment of PPTs suitable for space propulsion applications involving small spacecraft systems and for missions which require extremely precise control of the spacecraft.
	description	This application claims priority of German application Serial No. 103 06 668.3, filed Feb. 13, 2003, the complete disclosure of which is hereby incorporated by reference. a) Field of the Invention The invention is directed to an arrangement for the generation of intensive short-wavelength radiation based on a plasma, wherein high-energy excitation radiation is directed to a target flow in the vacuum chamber and, by means of a defined pulse energy, completely transforms portions of the target flow into a dense, hot plasma which emits particularly short-wavelength radiation in the extreme ultraviolet (EUV) range, i.e., in the wavelength region of 1 nm to 20 nm. b) Description of the Related Art The invention is used as a light source of short-wavelength radiation, preferably for EUV lithography in the production of integrated circuits. However, it can also be used for incoherent light sources in other spectral regions from the soft x-ray region to the infrared spectral region. In order to produce increasingly faster integrated circuits, it is necessary for the width of the individual structure on the chip to be increasingly smaller. Since the resolution in optical methods (optical lithography) is proportional to the wavelength of the light that is used, development is toward increasingly smaller wavelengths. An area with very good prospects for the future is EUV lithography (wavelength around 13.5 nm). In the interest of economy, a determined throughput of wafers must be ensured, which necessitates a light source having a high minimum output at a defined efficiency of the imaging optics. At the present time, there are no light sources in the wavelength region around 13.5 nm that would be capable of providing the required outputs. Also, the selection of light sources which could potentially be capable of this is very limited. Based on the present state of knowledge, laser-produced plasmas, discharge plasmas and synchrotrons are the most promising radiation sources for EUV lithography. Sources based on a plasma have the advantage that they can be incorporated relatively easily in existing production processes. “Mass-limited” targets were developed in order to limit unwanted particle emission in laser-produced plasmas which could sharply reduce the life of the plasma facing optics in particular. These mass-limited targets substantially reduce the amount of debris produced. In this connection, mass-limited means that the available target material is completely transformed into plasma by interaction with the energy beam. Since the amount of material available for generating radiation is therefore limited, the amount of energy in the beam pulse is exactly that amount needed for optimal conversion of, e.g., laser photons into EUV photons. Accordingly, at a given pulse repetition rate of the energy beam, the average output that can be coupled in is fixed and, at a determined conversion efficiency, so also is the maximum EUV output that can be generated. The maximum pulse repetition rate of the energy beam is given in that the target is disturbed through the plasma generation, and a minimum time interval between the individual laser pulses which depends on the transport speed of the target flow is therefore necessary. Target concepts that have already been suggested include: a continuous material jet (target jet) comprising, e.g., condensed xenon (e.g., according to WO 97/40650 A1); a dense droplet mist comprising microscopically small droplets (e.g., WO 01/30122 A1); cluster targets (e.g., U.S. Pat. No. 5,577,092); macroscopic droplets (e.g., EP 0 186 491 B1); and ice crystals through the use of a spray (U.S. Pat. No. 6,324,256). In all of the known target concepts, the amount of material available for an excitation pulse is small, so that the maximum energy of the individual pulse is limited. The transport speed of the target material and the diameter of the target jet can also not be increased to an unlimited extent for physical reasons (hydrodynamics), so that the pulse repetition rate of the energy beam is limited also. Since the average output is given by the product of individual pulse energy and repetition rate of the excitation signal, there is an upper limit for the EUV output that can be generated. Accordingly, with conventional targets it is not possible to reach the high average outputs in the EUV spectral region that are required by the semiconductor industry. It is the primary object of the invention to find a novel possibility for generating radiation generated from plasma, particularly EUV radiation, in which the individual pulse energy coupled into the plasma and, therefore, the usable radiation output are appreciably increased while retaining the advantages of mass-limited targets. In an arrangement for generating intensive radiation based on plasma, containing a target generator with a nozzle for metering and orientation of a target flow for plasma generation and a vacuum chamber, wherein a high-energy excitation radiation is directed to the target flow in the vacuum chamber and the target flow is completely converted piece by piece by means of a defined pulse energy of the excitation radiation into a plasma having a high conversion efficiency for the intensive radiation in a desired wavelength range, the above-stated object is met according to the invention in that the nozzle of the target generator is a multiple-channel nozzle with a plurality of separate orifices, wherein the orifices generate a plurality of target jets, the excitation radiation for generating plasma being directed simultaneously portion by portion to the target jets. The individual orifices of the nozzle are advantageously arranged in such a way that a radiation spot focused by the excitation radiation on all of the target jets exiting the nozzle is covered spatially essentially uniformly by parallel target jets, all of the target jets being completely irradiated over their diameter. The individual orifices of the nozzle can advisably be arranged in at least one row. It is particularly advantageous with respect to minimizing the coupling losses of the excitation radiation that the individual orifices of the nozzle are arranged in such a way that the target jets fill up the radiation spot of the excitation radiation without gaps and without overlapping, wherein the orifices of the nozzle are arranged so as to be offset to the direction of the excitation radiation for target jets appearing adjacent to one another in the radiation spot. For this purpose, the individual orifices of the nozzle are preferably arranged along a straight line which encloses an angle between 45° and 90° with the incident direction of the excitation radiation. In another advantageous construction, the individual orifices of the nozzle are arranged in a plurality of rows at an offset to one another. In this connection, the orifices can advisably be provided as parallel rows with an equal spacing between the orifices in the nozzle, wherein the rows lie one behind the other with respect to the incident direction of the excitation radiation and are arranged so as to be offset relative to one another by a fraction of the spacing between the orifices depending upon the quantity of rows arranged one behind the other. The orifices of the nozzle are preferably arranged in two parallel rows which are oriented orthogonal to the direction of the excitation radiation and are offset relative to one another by one half of the orifice spacing. In another suitable construction, the rows of orifices intersect, and intersecting rows share their first or last orifice as a common orifice representing the intersection point and are oriented in a mirror-symmetric manner relative to the incident direction of the excitation radiation at the same angle of intersection. It is particularly advisable that two intersecting rows of orifices are oriented in a V-shaped manner relative to the incident direction of the excitation radiation. The V-shape can be oriented with the tip in the incident direction of the excitation radiation or with the opening in the incident direction of the excitation radiation. An energy beam pulsed in a desired manner is advantageously provided as excitation radiation for the energy input into the target jets, wherein the energy beam has a focus whose cross-sectional area covers the width of all adjacent target jets simultaneously. The energy beam is preferably generated by a pulsed laser. However, a particle beam, particularly an electron beam or ion beam, can also be used in a suitable manner. An energy beam in the form of a laser beam is advisably focused through cylindrical optics on the target jets on a focus line which is oriented orthogonal to the direction of the target jets. In another constructional variant, the energy beam can also be composed of a plurality of individual energy beams which are arranged in a row orthogonal to the direction of the target jets to a quasi-continuous focus line by suitable optical elements and strike the target jets simultaneously. In another advisable arrangement for plasma excitation, the energy beam is composed of a plurality of individual energy beams, each of which is focused on a target jet and all target jets are irradiated simultaneously. A laser with beam-splitting optical elements or a plurality of synchronously operated lasers can be used for generating the row of individual energy beams. In each of the excitation variants mentioned above, the energy beam is advisably optimized with respect to the efficiency with which it couples energy into the plasma through the use of double pulses comprising a pre-pulse and a main pulse or multiple pulses. In the area of the interaction with the excitation beam, the target jets proceeding from the orifices of the multiple-channel nozzle are preferably continuous liquid jets, liquid jets which fall in droplet form at the latest in the area of interaction with the excitation radiation, or jets which pass into the solid aggregate state when exiting from the nozzle into the vacuum chamber. The target jets are preferably generated from condensed xenon. However, target jets comprising an aqueous solution of metallic salts are also suitable. The arrangement for generating plasma-generated radiation is advantageously used as a radiation source in the wavelength regions between soft x-ray radiation and the infrared spectral region. It is preferably used for the generation of EUV radiation in the wavelength region between 1 nm and 20 nm for devices for semiconductor lithography, particularly for EUV lithography, in the region of 13.5 nm. The invention proceeds from the basic idea that particularly the radiation outputs from a plasma-based radiation which are required in semiconductor lithography can not be achieved with conventional target preparation because of the mass limitation of the targets and because of the necessary target tracking (target flow). Since the quantity of material that is available for generating radiation after leaving the nozzle is limited and the target size can not be increased to any extent desired, only a limited amount of energy of the excitation radiation can at best be coupled into the plasma emitting the desired radiation. This seemingly insurmountable barrier of limited energy conversion is overcome, according to the invention, through the construction of a nozzle with a plurality of individual orifices in that the efficiency with which the excitation energy is coupled into plasma is increased and transmission losses are minimized at the same time. The nozzle contains a plurality of channels which serve to generate a plurality of individual target jets in an interaction chamber (vacuum chamber) and to irradiate the individual jets simultaneously with high-energy excitation radiation (e.g., laser beam, electron beam, etc.) in order to generate a spatially expanded, homogeneous plasma. With the arrangement according to the invention, it is possible to generate radiation, particularly EUV radiation, generated from plasma with a high average output, wherein the individual pulse energy that can be coupled into the plasma and, therefore, the usable radiation output are appreciably increased in spite of the mass limitation of the target. The invention will be described more fully in the following with reference to embodiment examples. In its basic variant, the arrangement according to the invention comprises a vacuum chamber 1, a target generator 2 which generates a bundle of parallel target jets 3 by means of a nozzle 21 having a plurality of individual orifices 22, and an excitation radiation source 4 which is focused orthogonally on the target jets 3 and forms a radiation spot 41 over all of the target jets 3. The target jets 3 enter the vacuum chamber 1 through the individual orifices 22 of the nozzle 21. In the vacuum chamber 1, they are converted into plasma by bombardment with high-energy excitation radiation from the radiation source 1 which delivers an energy beam 42 (laser beam, electron beam or ion beam) and irradiates all of the target jets 3 simultaneously. The plasma emits light in the relevant spectral region, preferably in the extreme violet (EUV) region. The target jets 3 are liquid when they enter the vacuum chamber 1, but can be liquid, continuous bet), discontinuous (droplet flow) or solid (frozen) in the area of interaction with the energy beam 42. One possibility consists in using liquefied gases, preferably xenon for generating EUV. Other possible target materials are metallic salts in aqueous solution. Solid target jets 3 are generated by suitably cooled target material in that the target jets are frozen when entering the vacuum chamber 1 and are brought in this state into the area of interaction with the energy beam. The amount of target material available for an individual pulse of the energy beam 42 and, therefore, the optimal individual pulse energy for the generation of EUV radiation is higher by a factor corresponding to the quantity of individual orifices 22 of the nozzle 21 at the identical exit speed of the target material and identical diameter of the individual orifices 22 compared to a conventional single-channel nozzle. In this example, the orifices 22 are arranged in such a way that the transmission losses for the incident energy beam 42 are minimal, i.e., the entire focused radiation spot 41 is completely covered by the target jets 3 arranged on gaps. This can be achieved, e.g., in that the individual orifices are arranged so as to be spatially offset. In principle, a kind of “watering can nozzle” with orifices 22 arranged in a defined manner is used according to the invention. However, its peculiarity consists in that there are no nozzle orifices 22 which are arranged one behind the other or which substantially overlap in the direction of the energy beam 42. Due to the expansion of the diameters of the target jets 3 during conversion into plasma, even small gaps can remain between the target jets 3 in the projection of the radiation spot 41 of the energy beam 42. FIG. 2 shows four essential variants of the arrangement of orifices 22 of the nozzle 21 in partial views a to d. FIG. 2a is a top view showing a pattern of orifices 22 as an arrangement of two parallel rows 23 which are offset relative to one another by half of the spacing of the orifices 22 within each row 23. With three parallel rows 23, the offset would be decreased to a third of the spacing of the orifices 22 as will be described more fully in the following with reference to FIG. 4. In another variant according to FIG. 2b, two rows 23 are arranged at opposite angles to the incident direction 43 of the energy beam 42. The two rows 23 share an orifice 22 of the nozzle 21, and the intersection 24 of the two rows 23 is given by this orifice 22 at the same time. The angle relative to the incident direction 43 of the energy beam 42 is identical in terms of amount for both rows 23 and varies depending on the diameter of the orifices 22 and a (possibly intentional) gap formation or slight overlapping of the exiting target jets 3 in the projection of the radiation spot 41 (as is shown in FIG. 1). The pattern of orifices 22 corresponds to a V-shape which can be oriented with the intersection 24 of the rows 23 (i.e., with the tip of the V) in the direction of the energy beam 42 as is shown in FIG. 2b or can be oriented opposite to the incident energy beam 42. FIG. 2c shows a possibility in which the orifices 22 are arranged in only one row 23. In order to avoid gaps between the target jets 3, the row 23 is inclined by an angle relative to the incident direction 43 of the energy beam 42 according to the same criteria as in FIG. 2b. In case gaps between the target jets 3 are permissible or desirable (see, e.g., the statements referring to FIG. 6), the angle can be very large or exactly 90°. Otherwise, the selected angle is preferably around 45°. Finally, without implying any lack of further possibilities, FIG. 2d shows a combination of the nozzle patterns from FIG. 2a and FIG. 2b. This arrangement can be described as parallel rows 23 arranged one behind the other with different distances between the orifices 22 or also as V-shapes which continue transverse to the energy beam 42. In essence, however, the pattern is more accurately described as a zigzag pattern oriented transverse to the incident direction 43 of the energy beam 42. Here, two parallel families 25 and 26 of orifices 22 arranged in the direction opposite to the incident direction 43 of the energy beam 42 intersect, and the intersection points 24 are shared orifices 22 as was already described with respect to the V-shape. One possibility for coupling energy into the target consists in that the target jets 3 generated by the multiple-channel nozzle 21 are irradiated by a laser as energy beam 42 in such a way that the radiation spot 41 corresponding to the laser focus (also often called the laser waist) is at least as large as the width of the entire bundle of target jets 3 (shown in FIG. 3). In a case such as that described above, FIG. 4 shows the top view of a nozzle 21 with three parallel rows 23 of orifices 22 arranged one behind the other and the impinging light cone 44, shown schematically, of the laser waist as focused part of the energy beam 42. As is clearly shown, the rows 23 are each displaced in a parallel manner by about one third of the (uniform) distance between the orifices 22 without overlapping of the target jets 3 exiting therefrom in the light cone 44. However, due to the expansion of the diameters of the target jets 3 when converted into plasma, small gaps can also remain between the target jets 3 in the projection of the radiation spot 41 of the energy beam 42. This ensures that all of the target jets 3 receive the same radiation output of the energy beam 42 and are accordingly optimally excited and can be converted into plasma. Strictly speaking, the excitation of the target jets 3 is quasi-simultaneous because the target jets 3 from the rear rows 23 of nozzle orifices 22 are actually reached later by the pulse of the energy beam 42 in the propagation direction of the energy beam 42. However, this may be ignored as it relates to plasma generation and will be described as simultaneous hereinafter. The plasmas (not shown) generated from the target jets 3 merge as a result of the simultaneous excitation of all target jets 3 into one extended plasma with multiplied radiation power (corresponding to the quantity of target jets 3) in the desired wavelength region (e.g., EUV radiation) if other known factors of the energy input (radiation power per target mass, optimized excitation through suitable temporal pulse shape, etc.) for the individual mass-limited target jets 3 are chosen. In FIG. 5, the radiation spot 41 for the plasma generation in the entire bundle of target jets 3 is generated by spatial multiplexing in which the excitation radiation comprises a plurality of individual beams 45 in a linear row arrangement 46 which are combined from a plurality of identical lasers or, through beam splitting, from one to a few lasers and bombard the target synchronously with respect to time. This has the advantage that the pulse energy of the individual laser does not need to be as high as in the case of a laser with a large diameter of the focused radiation spot 41. As a result, the foci of the individual beams 45 are arranged one above the other spatially and form a type of line focus 47. On the other hand, adjacent focusing of individual beams 45 of lasers is also worthy of consideration insofar as—corresponding to the view in FIG. 6—every target jet 3 is struck by exactly one individual beam 45, so that the arrangement of target jets 3 without gaps is less critical in the design of the nozzle 21 and the orifices 22 can be arranged in only one row. This is important particularly for applications in which the character of a point light source should not be dispensed with for the resulting radiation. In this case, the desired radiation should be coupled out of the plasma orthogonal to the direction of the target jets 3 and to the incident direction 43 of the individual beams 45. Consequently, the transmission losses and accordingly also the in-coupling losses for an individual row 23 of orifices 22 in the nozzle 21 can be minimized in that the individual target jets 3 are irradiated synchronously by a respective individual beam 45 (of a laser). In addition, the coupling of energy into the target is improved in that a smaller pre-pulse is radiated into the target jets 3 prior in time to the main energy pulse, so that a so-called pre-plasma is “smeared” over the width of the target jets 3 which are arranged at a distance from one another. The energy of the main pulse can be coupled into this pre-plasma very effectively, so that the transmission losses of excitation radiation are minimized in spite of the use of individual target jets 3 and the generation of radiation from the plasma is extensively homogeneous. As can be seen from the view according to FIG. 7, it is likewise possible and useful to employ a true line focus 47 for the irradiation of the target jets 3. The line focus 47 can be generated during laser excitation, e.g., simply by means of cylindrical optics. A line focus 47 of this kind, particularly for large-area bundles of target jets 3 resulting in large-area plasma, can have considerable importance when the homogeneity of the plasma is important for generation of radiation, since a uniform energy input into each target jet 3 is carried out in this configuration. FIG. 8 shows yet another variant of the arrangement of target jets 3 using a nozzle 21, according to FIG. 2c, in which there are no transmission losses of excitation radiation in an individual energy beam 42. Although there is only a single row 23 of orifices 22 of the nozzle 21 and the row 23 between the orifices 22 must compulsorily have spaces, the absence of gaps in the bundle of target jets 3 is brought about in this case in that the row 23 of nozzle orifices 22 encloses an angle a with the normal plane 48 of the incident energy beam 42, so that the spacing present per se between the orifices 22 of the nozzle 21 does not appear in the projection of the radiation spot 41 of the excitation radiation on the bundle of target jets 3 that is rotated in this manner. Therefore, through selection of the angle α, the transmission losses can be minimized in a suitable manner or the area-dependent coupling in of energy can be adjusted to a maximum. Further, as an added advantage, a larger area of the radiating plasma results also orthogonal to the directions of the target jets 3 and energy beam 42. Other design variants of the invention (particularly with respect to the nozzle variations according to FIGS. 2a to 2d) are readily possible without departing from the framework of this invention. The examples described above were based on parallel target jets 3 which are arranged without gaps and which enable relatively large target masses while retaining mass limitation. Further, other possible configurations with intersecting or overlapping target jets or a plurality of bundles of target jets 3 from variously positioned nozzles are not outside the scope of the invention. In particular, nozzle shapes and target arrangements which are not shown or described explicitly in the drawings are also to be considered as clearly belonging to the teaching according to the invention provided that they rely on the principle of multiplication of the radiation yield through the use of a plurality of mass-limited targets and the synchronous excitation thereof without inventive activity. While the foregoing description and drawings represent the present invention, it will be obvious to those skilled in the art that various changes may be made therein without departing from the true spirit and scope of the present invention. Reference Numbers 1 vacuum chamber 2 target generator 21 nozzle 22 orifices 23 row 24 intersection 25, 26 parallel families 3 target jets 4 excitation radiation source 41 focused radiation spot (of the excitation radiation) 42 energy beam 43 incident direction 44 light cone 45 individual beam (of the excitation radiation) 46 linear arrangement (of the individual beam foci) 47 line focus 48 normal plane (of the energy beam)
	description	The present application hereby claims priority under 35 U.S.C. §119 on German patent application number DE 103 55 616.8 filed Nov. 28, 2003, the entire contents of which are hereby incorporated herein by reference. The invention generally relates to an apparatus for radiation image recording. Preferably, it relates to one including a radiation receiver to which radiation can be applied and which converts the incident radiation to an electrical charge which represents a measure of the incident radiation and which can be read line-by-line via a reading device. Apparatuses such as these are known, for example, as X-ray recording devices. The radiation which is emitted from the X-ray source passes through the examination object and strikes the radiation receiver, which converts the radiation that is incident there to a local electrical charge. This charge represents a measure of the locally incident radiation. This electrical charge can be read line-by-line, that is to say in a defined reading direction, via a reading device. The signals which are detected and produced in the process are then processed to form a radiation image, which can be output on a monitor. The radiation which is passed through the object can be distinguished by two radiation components. Firstly the primary radiation, which strikes the radiation receiver without being scattered by the object, and secondly the secondary radiation, referred to as scattered radiation, which is scattered in the object and then strikes the radiation receiver with a scattered incidence direction. This scattered radiation is disadvantageous, since it makes the image quality poorer. It is known for scattered beam grids to be used in order to reduce the scattered radiation, and these grids are connected immediately upstream of the radiation receiver. A scattered beam grid of a normal type comprises a large number of linear absorption elements which are incorporated in a carrier material, as a rule thin lead absorption laminates, which absorb the scattered radiation. Thus, while the primary radiation passes through the scattered beam grid essentially without any impediment, the majority of the secondary radiation is absorbed by the scattered beam grid. However, one disadvantage is the fact that the regularity of the arrangement of the absorption elements, which all run parallel to one another, and the fact that the stored charge is likewise read in a geometrically standard form, specifically line-by-line, makes it possible for so-called Moiré effects to occur. This is an interference phenomenon which has a disadvantageous effect on the quality of the radiation image that is produced. U.S. Pat. No. 6,282,264 B1 relates to a digital, two-dimensional X-ray detector which can be moved to different positions in order to allow different X-ray protocols to be carried out. The system for positioning the digital detector comprises a detector which in turn comprises a digital X-ray detector arrangement and a scattered beam grid. DE 101 47 949 A1 discloses a method for production and fitting of a collimator to a Gamma detector for nuclear medicine. U.S. Pat. No. 4,602,157 describes a device for production of X-ray records, in which a storage film is used as a radiation receiver for the production of X-ray records. An embodiment of the invention is based on a problem of specifying an apparatus which offers the capability to reduce Moiré effects in a radiation image recording apparatus having a radiation receiver which can be read line-by-line and having a line scattered beam grid. In order to solve this problem for an apparatus, an embodiment of the invention provides for the absorption elements to be positioned at an angle to the line-by-line reading direction. While, in the case of known apparatuses, the absorption elements, which run in straight lines, are parallel to the reading direction, an embodiment of the invention provides the absorption elements to be effectively twisted with respect to the reading direction so that they are at an angle to the reading direction, that is to say they are no longer parallel to it. This is because it has been found that one reason for the occurrence of Moiré effects is the parallelity between the absorption elements and the reading direction. If the two are now rotated with respect to one another according to an embodiment of the invention, then the formation of Moiré effects can be reduced as a result of the irregularity that this results in. This effect can be achieved with any desired scattered beam grids, that is to say even when using multiple line grids with a very large number of lines per square centimeter, as well as focused or unfocused grids. The angle through which the two apparatus elements must be rotated with respect to one another should, according to an embodiment of the invention, be ≧5° and ≦90°. The grid itself can expediently be moved with respect to the radiation receiver. Thus, the grid is moved backwards and forwards continuously while recording the radiation image, and this serves to further reduce Moiré effects. According to a first embodiment invention alternative, the scattered beam grid can be arranged such that it is rotated with respect to the fixed-position radiation receiver. In this embodiment, the radiation receiver remains in a defined position with respect to the apparatus, that is to say it is not changed from its previous arrangement. In fact, the scattered beam grid is moved to a new position, in which the angled geometry according to the invention is assumed. In this case, it is expedient for the grid to be designed such that it can be inserted into a conventional grid drawer, and when in the inserted position is rotated with respect to the radiation receiver. This refinement according to an embodiment of the invention makes it possible to use the conventional grid drawer mechanical system, that is to say to use known grid drawers, without, for example, having to modify the scattered beam grid recording or the guide mechanisms etc. there. Furthermore, this also makes it possible to convert already existing apparatuses, after which no design changes need be carried out. As an alternative to the embodiment with an unchanged radiation receiver and a newly positioned grid, the configuration can also be reversed. Thus, the radiation receiver may be arranged rotated with respect to the fixed-position scattered beam grid. For example, it is feasible to mount the radiation receiver such that it can itself be rotated about a axis at right angles to the scattered beam grid plane, in order in this way to produce the angled arrangement according to an embodiment of the invention. In addition, it is possible to design the grid drawer such that it can be rotated or to accommodate the scattered beam grid itself in the grid drawer such that it can be rotated. By way of example, a digital solid-state detector may be used as the radiation receiver for the apparatus according to an embodiment of the invention, in which a pixel matrix is provided which is read line-by-line by means of associated reading electronics. Alternatively, a storage film can also be used as the radiation receiver, which is read in a separate reading device. FIG. 1 shows an outline sketch of an apparatus 1 according to an embodiment of the invention, including a radiation source 2 via which radiation can be emitted and can be supplied to an object 3. The radiation which passes through the object 3 strikes a scattered beam grid 4, which is followed by a radiation detector 5, in the illustrated example a solid-state radiation detector, by way of example. The operation of the radiation source 2 and of the radiation receiver 5 is controlled by a central control device 6, including the reading operation of the radiation receiver in which the radiation causes electrical charge to be released locally and to be generated as a function of the extent of the locally incident radiation. In a digital solid-state detector, the charge, which is generated on a pixel basis, is read pixel-by-pixel and line-by-line by associated reading electronics. The signals which are produced in this case are passed to the control device 6, which processes them and produces a radiation image, which can be output on a monitor 7. FIG. 2 shows an enlarged illustration of the arrangement of the scattered beam grid 4 with respect to the radiation receiver 5. As described, the radiation receiver 5 has a pixel matrix which is read line-by-line. The arrows 8 illustrate an example of the reading direction. The scattered beam grid 4 includes a carrier 9 in which a large number of linear absorption laminates 10 which run in straight lines are integrated. These may either run completely parallel to one another, as is the case with an unfocused beam grid. However, they may also be tilted somewhat with respect to one another towards the edges, so that the scattered beam grid is focused with respect to the focus of the radiation source 2. In any case, it can be seen that the reading direction, represented by the arrows 8, and the absorption elements 10 are at an angle α to one another. The scattered beam grid 4 is, as can be seen, arranged rotated with respect to the solid-state detector 5. The misalignment between the reading direction and the direction of the absorption element, that is to say the fact that they no longer run parallel to one another, makes it possible to reduce the occurrence of Moiré effects. A further contribution to this is the fact that the scattered beam grid 4 can be moved with respect to the radiation receiver 5, as is indicated by the double-headed arrow A, and this is also expediently controlled via the control device 6. The scattered beam grid 4 is in this case moved in a direction at right angles to the reading direction, as indicated by the arrows 8. However, it would also be feasible to move the scattered beam grid in a direction at right angles to the direction of the absorption elements 10. However, it is not necessary for the grid to be moveable, and a refinement with a stationary grid is also feasible. The scattered beam grid 4 should in this case be designed such that it can be inserted into a conventional grid drawer, so that on the one hand it is possible to make use of already known guide elements or inserts for the grid drawer, while on the other hand it is possible to retrofit already existing apparatuses according to an embodiment of the invention. The radiation receiver 5 remains in its original position within the apparatus or within the apparatus frame. As an alternative to this, it is feasible not to change the position of the scattered beam grid 4, as is done by the scattered beam grid used in conventional apparatuses, but in contrast to rotate the radiation receiver 5. This can be done in a simple way by the capability to rotate the radiation receiver itself about an axis at right angles to the plane of the scattered beam grid. As an alternative to the described embodiment of the radiation detector as a solid-state image detector, it is also possible to use a storage film as the radiation detector 5. This is exposed to radiation, and charges are also generated locally there. However, the reading process does not make use of receiver-end reading electronics, but of a separate reading device, to which the storage film must be passed after the image has been recorded. It would, of course, also be feasible to integrate a reading device such as this in the apparatus. Exemplary embodiments being thus described, it will be obvious that the same may be varied in many ways. Such variations are not to be regarded as a departure from the spirit and scope of the present invention, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
	abstract	Modular flow control systems include several differently-shaped structures to achieve desired flow characteristics in fluid flow. Systems include one or many plates held in desired positions by a retainer within the flow. The plates are uniquely shaped based on their position, or vice versa, to shape flow in a desired manner. The plates may fill an entire flow area or may extend partially throughout the area. Plates can take on any shape and are useable in systems installed in any type of flow conduit. When used in a PCCS upper manifold in a nuclear reactor, a chevron plate directly below the inlet divides flow along the entire upper manifold. Perforated plates allow flow to pass at ends of the PCCS upper manifold. The plates can be installed along a grooved edge during an access period and held in static position by filling the length of the PCCS upper manifold.
	abstract	One embodiment relates to an ion implanter. The ion implanter includes an ion source to generate an ion beam, as well as a scanner to scan the ion beam across a surface of a workpiece. The ion implanter also includes an array of absorption and radiation elements arranged to absorb energy of the scanned ion beam and radiate at least some of the absorbed energy away from the propagation direction. A detection element (e.g., an infrared detector) is arranged to detect energy (e.g., in the form of heat) radiated by the array of absorption and radiation elements and to determine a beam profile of the scanned ion beam based on the detected energy.
	summary
	claims	1. A multi-leaf collimator for collimating a beam of a radiotherapeutic apparatus, comprising a plurality of elongate narrow leaves arranged side-by side and supported in a frame, the frame having upper and lower formations for guiding each leaf and ridges which extend into the leaves on the upper and lower edges of the leaves, thereby to allow the leaves to move in a longitudinal direction, the upper and lower formations being aligned so that the sides of the leaves when fitted are at a non-zero angle to the beam direction, the upper and lower ridges being located on the upper and lower edges of the leaves so that a line joining their centres is at a non-zero angle to the sides of the leaf, tilted relative to the sides, opposite to that of the beam. 2. The multi-leaf collimator according to claim 1 in which the upper formations comprise channels into which the ridges extend. 3. The multi-leaf collimator according to claim 1 in which the lower formations comprise channels into which the ridges extend. 4. The multi-leaf collimator according to claim 2 in which the channels are defined between a pair of ridges. 5. The multi-leaf collimator according to claim 1 in which an outer face of the upper ridges is aligned with a side face of the leaf. 6. The multi-leaf collimator according to claim 1 in which an outer face of the lower ridges is aligned with a side face of the leaf. 7. A radiotherapeutic apparatus, comprising;a source of radiation, anda multi-leaf collimator for shaping the radiation emitted by the source,the multi-leaf collimator comprising a plurality of elongate narrow leaves arranged side-by side and supported in a frame, the frame having upper and lower formations for guiding each leaf and ridges which extend into the leaves on the upper and lower edges of the leaves, thereby to allow the leaves to move in a longitudinal direction, the upper and lower formations being aligned so that the sides of the leaves when fitted are at a non-zero angle to the beam direction, the upper and lower ridges being located on the upper and lower edges of the leaves so that a line joining their centres is at a non-zero angle to the sides of the leaf, tilted relative to the sides in a sense opposite to that of the beam. 8. The radiotherapeutic apparatus according to claim 7 in which the upper formations comprise channels into which the ridges extend. 9. The radiotherapeutic apparatus according to claim 7 in which the lower formations comprise channels into which the ridges extend. 10. The radiotherapeutic apparatus according to claim 8 in which the channels are defined between a pair of ridges. 11. The radiotherapeutic apparatus according to claim 7 in which an outer face of the upper ridges is aligned with a side face of the leaf. 12. The radiotherapeutic apparatus according to claim 7 in which an outer face of the lower ridges is aligned with a side face of the leaf.
	abstract	A fluoride sintered body suitable for a moderator which moderates high-energy neutrons so as to generate neutrons for medical care with which an affected part of the deep part of the body is irradiated to make a tumor extinct comprises MgF2 of a compact polycrystalline structure having a bulk density of 2.90 g/cm3 or more and as regards mechanical strengths, a bending strength of 10 MPa or more and a Vickers hardness of 71 or more.
051587386	summary	BACKGROUND OF THE INVENTION 1. Technical Field The invention relates to a method of controlling a pressurized water nuclear reactor in which control bars in the core are repositioned when a monitoring or operating parameter representative of the difference between the current power of the core and the power demanded (such as the mean temperature of the core) departs from a given range, called "dead band", the repositioned bars being selected so as to avoid increasing any difference between the axial power offset and a reference value; the terms "axial power offset" designate the ratio between the difference of the neutron fluxes in the upper and lower halves of the core and the sum of the fluxes, or designate another parameter representative of the imbalance of the fluxes along the path of travel of the cooling water through the core. 2. Prior Art A control method of the above-defined type is already known (EP-A-0,051,542 or FR-A-2,493,582). The control bars contain a material which highly absorbs neutrons without giving rise to fissile isotopes (hafnium, for example), in an amount such that the bars have an anti-reactivity or bar worth sufficient for load follow (usually about 1000 pcm when the bars are totally inserted in the core). The bars are generally formed by clusters of rods each having a sheath containing neutron absorbing material pellets. EP-A-0,051,542 proposes a control law as follows: if the operating parameter is outside the dead band, computing the direction and displacement speed to be given to a group of bars selected responsive to the axial offset (to avoid increasing the differential between the latter and the reference value) as a function of the value and of the sign of the operating parameter; if the operating parameter is within the dead band, repositioning a group of bars to reduce the axial offset, only if the difference between the current value of the latter and the reference value exceeds a predetermined threshold, then compensating for the repositioning by varying the boron concentration. The prior art method requires the use, in addition to the control bars (and shut-down bars which, in normal operation, are always removed from the core and are inserted to shut down the reactor and keep it shut down) of boron in the form of a compound soluble in the cooling water; the boron content is modified to compensate for the reduction of reactivity, due particularly to the progressive depletion of the fuel, and to greatly increase anti-reactivity in case of a serious accident. The initial boron content must consequently be very high. Often the boron content of the water is also varied to regulate the power of the reactor and more particularly to compensate for variations of the xenon effect, the control clusters being repositioned only to vary reactivity during rapid operating transients. The use of boron dissolved in the water forming the primary coolant has advantages. The anti-reactivity which it introduces is distributed evenly throughout the core. On the other hand, it also has serious drawbacks. The presence of boron results in an appreciable production of liquid effluents which must be processed with a complex installation. Boric acid corrodes some materials, particularly the zirconium-base alloy sheaths. Another disadvantage is related to the fact that it would be dangerous to rely solely on injection of boron for shut-down of the reactor in case of a serious incident since, due to its construction, the boron injection system has an appreciable time constant. If soluble boron is used as essential control element, it is nevertheless necessary for the absorbent bars to have sufficient anti-reactivity for an emergency shut-down of the reactor. Load follow-up requires the possibility of rapidly reducing the boron content. That becomes impossible when the boron content for normal operation has been reduced to a low value because of the depletion of the core. Methods have also been proposed for reducing the maximum boron content required in the water forming the primary coolant and/or the variations in the boron content during operation. According to FR-A-2,547,447, groups of control bars are displaced and, possibly, the boron concentration in the primary circuit is modified when it is necessary to bring the reactor condition from a state .PHI. (expressing the actual power and axial distribution of the reactor) to a reference state .PHI.c, taking into account the results of a calculation. This calculation consists in determining the variation to be given to external parameters (particularly the position of the control clusters and the boron concentration) by an iterative calculation which involves predicting a coupling relation between the external parameters and the state of the reactor, taking into account internal uncontrollable parameters, such as the moderation coefficient. Once the coupling relation has been determined, optimum variations of the external parameters are determined to approximate the reference state .PHI.c. But FR-A-2,547,447 does not teach how the coupling relation can be determined and seems to take into consideration only the axial power distribution, whereas it is important not to neglect the radial power distribution, and particularly the risk of appearance of power peaks. Another approach for reducing the required boron concentration variations to compensate fuel depletion, hence the initial boron content, consists in varying the energy spectrum of the neutrons during an operating cycle of the core, starting from an epithermic spectrum. FR-A-2,496,319 relates to such a method, in which "grey" bars, i.e., bars having a moderate neutron absorption, are removed as the core is depleted. The bars are then replaced by water which increases the moderation ratio and shifts the energy spectrum of the neutrons closer to the thermal range. The power of the reactor is controlled by means of "black" bars. To that end, the local neutron flux is measured in several zones of the core with a large number of fixed detectors and a combination of displacements of the bars is chosen which gives the required reactivity variation while disturbing to a minimum the power distribution profile, as a function of the power demanded. This method involves an extremely complex calculation, using data from a very large number of neutron flux detectors placed in the core, and yet this method does not completely overcome the problem of using boron as a soluble compound for controlling the reactor. Still other methods for controlling nuclear reactors plants are known which attempt to minimize or decrease the difference between the actual axial offset and a prescribed value. Such a method is disclosed in European patent application No. 0,097,488. SUMMARY OF THE INVENTION It is an object of the invention to provide a method for controlling a pressurized water reactor, making it possible to follow the load demand variations, typically without modifying the boron content of the water forming the primary coolant, possibly with a zero boron content, as long as the reactor is in normal condition. It is a more specific object to make it possible to maintain both the operating parameter close to its reference value, e.g., by maintaining the mean temperature close to a reference temperature, and the axial power offset close to a reference value, without modifying the soluble boron content under normal operation, even for shut-down at a temperature which may be regarded as "intermediate". It is an ancillary object to avoid disturbing the radial power distribution to arrive at the above results. To this end, there is provided a method of the above-defined kind--the neutron absorbing control bars having sufficient anti-reactivity or worth compensate for the entire reactivity variations occuring during normal operation of the reactor and in case of an incident requiring emergency shut-down of the reactor as long as the coolant is at or close to its normal operating temperature--wherein: when the operating parameter is outside the dead band and/or when the offset of the axial power distribution exceeds a reference value, a simulation procedure is used for predicting which of the bars are to be displaced to bring said operating parameter and/or said offset back to their normal values while minimizing an enthalpy increase factor in the core, the enthalpy increase being defined as the difference between the value of the enthalpy (binomial function of the temperature) at the outlet of the core and the enthalpy at the inlet of the core, possibly at a prior time, and the enthalpy increase factor being defined as the ratio between the maximum value of the increase and its mean value in the core (or in a predetermined sector of the core). The operating safety of the reactor requires a redundancy of the means for counteracting the reactivity variations and for shut-down of the neutron reaction in the case of failure of some bars. In the case of control without boron, this result may in particular be attained by providing: "black" bars whose purpose is solely to cause shut-down of the reactor and which are completely removed from the core during normal operating conditions, and "grey" control bars, i.e., bars whose individual anti-reactivity is intermediate between that of transparent bars made of a material with low neutron absorption and that of the black bars, having totally independent handling systems. If the "grey" control bars as a whole have sufficient anti-reactivity or "worth", the redundancy is such that an emergency shut-down remains possible even in the case of a failure of one of the systems of bars. In the case of a spectrum variation reactor, the sum of the anti-reactivity of the shut-down bars and of the anti-reactivity of the control bars must in addition be sufficient so that, when all these bars are inserted into the core, criticality is avoided even when the temperature of the water forming the coolant has decreased to an intermediate value from the normal operating value. The injection of boron is no longer necessary except for keeping the reactor shutdown when the coolant is cold. Because a large number of "grey" control bars (generally each having an anti-reactivity substantially half that of the black bars, e.g., 75 pcm instead of 150 pcm) then becomes necessary, it is advantageous to distribute the bars into two sets, each of the bars of one set (or its control mechanism) being coaxial with a bar of the other set (or its control mechanism). Thus, the number of penetrations through the lid of the vessel of the reactor is reduced. The control method of the invention provides numerous advantages. Because there is no need for much boron in the cooling water during normal operation, the coefficient of reactivity variation as a function of the temperature is always highly negative; this is useful in all accidents tending to increase the temperature of the core. The high anti-reactivity value of the bars means that there is no longer any risk of the reactor becoming critical should there be a break in the steam piping. The production of tritium is reduced. The primary effluents are reduced. The chosen method for predicting the bar (or bars) to be repositioned makes it possible to avoid or attenuate the radial distribution peak factors of the neutron flux, while making "load follow" operation of the reactor possible. The invention also provides a reactor adapted to be controlled by the above-defined method.
	summary
	abstract	A patient alignment system for a radiation therapy system. The alignment system includes multiple external measurement devices which obtain position measurements of components of the radiation therapy system which are movable and/or are subject to flex or other positional variations. The alignment system employs the external measurements to provide corrective positioning feedback to more precisely register the patient and align them with a radiation beam. The alignment system can be provided as an integral part of a radiation therapy system or can be added as an upgrade to existing radiation therapy systems.
	claims	1. An x-ray device, comprising:an x-ray radiation source;a coherence grating;a phase grating; andan x-ray detector made of a number of pixels disposed in a matrix-like manner; anda lens grating assembled from prisms, wherein the lens grating is disposed between the phase grating and the x-ray detector and the lens grating includes two sub-gratings arranged in an optical axis direction, of which a first sub-grating deflects x-ray beams which have experienced a phase shift by the phase grating and a second sub-grating deflects x-rays beams which passed the phase grating without being influenced. 2. The x-ray device of claim 1, wherein a focus plane is assigned to the lens grating and wherein the x-ray detector is positioned in the focus plane. 3. The x-ray device of claim 1, further comprising:an absorption grating, positioned between the lens grating and the x-ray detector. 4. The x-ray device of claim 3, wherein a focus plane is assigned to the lens grating and wherein the absorption grating is positioned in the focus plane. 5. The x-ray device of claim 1, wherein the prisms include a triangular or trapezoidal base area. 6. The x-ray device of claim 1, wherein the prisms include a regular arrangement. 7. The x-ray device of claim 6, wherein the regular arrangement of prisms comprises prisms with different base areas. 8. The x-ray device of claim 6, wherein, in each case, a plurality of prisms mesh in such a way that elongate meandering structures are formed in an optical axis direction. 9. The x-ray device of claim 1, wherein the prisms are formed onto a base plate. 10. The x-ray device of claim 9, wherein at least one lateral face of the prisms is inclined with an angle of inclination of between 5° and 15° with respect to the surface normal of the base plate. 11. The x-ray device of claim 1, wherein the prisms are embodied as slanted prisms. 12. The x-ray device of claim 1, wherein the lens grating is assembled from a number of clessidra lenses. 13. The x-ray device of claim 1, wherein gold, nickel or silicon is used as the main material for the lens grating. 14. The x-ray device of claim 1, wherein the x-ray device is for phase-contrast imaging in the medical sector. 15. The x-ray device of claim 1, wherein the lens grating includes an arrangement of positive lenses, each lens configured to focus x-ray radiation to precisely one pixel of the x-ray detector. 16. The x-ray device of claim 1, wherein the lens grating comprises a regular arrangement of columns of positive lenses focusing in one dimension, wherein each one of the columns of positive lenses focuses x-ray radiation in the scope thereof onto precisely one column of pixels of the x-ray detector.
	summary
	claims	1. A passive reactivity control nuclear fuel device for a nuclear reactor core, the passive reactivity control nuclear fuel device comprising:a multiple-walled fuel chamber includingan inner wall chamber configured to position nuclear fuel in a molten fuel state within a high neutron importance region of the nuclear reactor core, the inner wall chamber being further configured to allow at least a portion of the nuclear fuel to move in a molten fuel state into a lower neutron importance region of the nuclear reactor core while remaining within the inner wall chamber as temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition, the movement of the nuclear fuel in a molten fuel state to the lower neutron importance region increasing negative reactivity feedback in the nuclear reactor core, andan outer wall chamber containing the inner wall chamber, a gap between the outer wall chamber and the inner wall chamber thermally isolating the inner wall chamber. 2. The passive reactivity control nuclear fuel device of claim 1 further wherein thermal isolation of the inner wall chamber contributes to maintaining the nuclear fuel in a molten state. 3. The passive reactivity control nuclear fuel device of claim 1 further comprising:a duct containing the outer wall chamber and configured to flow a heat conducting fluid through the duct and in thermal communication with the outer wall chamber. 4. The passive reactivity control nuclear fuel device of claim 1, wherein movement of the nuclear fuel in a molten fuel state to the lower neutron importance region of the nuclear reactor core decreases reactivity within the nuclear reactor core. 5. The passive reactivity control nuclear fuel device of claim 1, wherein the nuclear fuel is stored in a solid fuel state within the inner wall chamber when temperature of the nuclear fuel does not satisfy a nuclear fuel melting temperature condition. 6. The passive reactivity control nuclear fuel device of claim 1, wherein the melting temperature of the nuclear fuel exceeds a flow temperature of a heat conducting fluid within a duct containing the outer wall chamber. 7. The passive reactivity control nuclear fuel device of claim 1, wherein the inner wall chamber is expandable under increased internal temperature of the inner wall chamber. 8. The passive reactivity control nuclear fuel device of claim 1, wherein the nuclear fuel includes a solid porous fertile nuclear fuel and a bonding material. 9. The passive reactivity control nuclear fuel device of claim 1, wherein the nuclear fuel includes solid porous fertile nuclear fuel, a bonding material, and fissile nuclear fuel. 10. The passive reactivity control nuclear fuel device of claim 1, wherein the nuclear fuel in a molten fuel state includes a solution of fissile nuclear fuel and a nuclear translucent carrier medium, the nuclear translucent carrier medium being formed from a melted bonding material. 11. The passive reactivity control nuclear fuel device of claim 1, wherein the inner wall chamber is not in physical contact with the outer wall chamber when the inner wall chamber has not expanded under increased internal temperature of the inner wall chamber. 12. The passive reactivity control nuclear fuel device of claim 1, wherein the inner wall chamber radiates heat from within the inner wall chamber to a heat conducting fluid flowing outside the outer wall chamber when the inner wall chamber has expanded under increased internal temperature of the inner wall chamber. 13. The passive reactivity control nuclear fuel device of claim 1, wherein the inner wall chamber conducts heat from within the inner wall chamber to a heat conducting fluid flowing outside the outer wall chamber when the inner wall chamber has expanded to physically contact the outer wall chamber under increased internal temperature of the inner wall chamber. 14. The passive reactivity control nuclear fuel device of claim 1, wherein the inner wall chamber conducts heat from within the inner wall chamber to a heat conducting fluid flowing outside the outer wall chamber when the inner wall chamber has expanded to allow physical contact between the outer wall chamber and contacts affixed to the inner wall chamber under increased internal temperature of the inner wall chamber. 15. The passive reactivity control nuclear fuel device of claim 1, wherein transfer of heat from the inner wall chamber to a heat conducting fluid flowing outside the outer wall chamber reduces the temperature of the nuclear fuel and transitions the nuclear fuel to a solid fuel state. 16. The passive reactivity control nuclear fuel device of claim 1, further comprising:one or more thermally conductive contacts affixed to the inner wall chamber and in thermal communication with the nuclear fuel, the thermally conductive contacts configured to physically contact the outer wall chamber when the inner wall chamber expands. 17. The passive reactivity control nuclear fuel device of claim 1, wherein the inner wall chamber conducts heat from within the inner wall chamber to a heat conducting fluid flowing outside the outer wall chamber when the inner wall chamber has expanded to physically contact the outer wall chamber under increased internal temperature of the inner wall chamber. 18. The passive reactivity control nuclear fuel device of claim 1, wherein a gap between the inner wall chamber and the outer wall chamber is filled at least in part by a tag gas. 19. The passive reactivity control nuclear fuel device of claim 1, wherein the inner wall chamber includes a plenum into which the nuclear fuel in a molten fuel state expands as temperature of the nuclear fuel in the molten fuel state increases. 20. A nuclear reactor having a nuclear reactor core comprising:a passive reactivity control nuclear fuel device located in the nuclear reactor core, the passive reactivity control nuclear fuel device includinga multiple-walled fuel chamber includingan inner wall chamber configured to position nuclear fuel in a molten fuel state within a high neutron importance region of the nuclear reactor core, the inner wall chamber being further configured to allow at least a portion of the nuclear fuel to move in a molten fuel state into a lower neutron importance region of the nuclear reactor core while remaining within the inner wall chamber as temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition, the movement of the nuclear fuel in a molten fuel state to the lower neutron importance region increasing negative reactivity feedback in the nuclear reactor core, andan outer wall chamber containing the inner wall chamber, a gap between the outer wall chamber and the inner wall chamber thermally isolating the inner wall chamber; anda duct containing the multiple-walled fuel chamber and configured to flow a heat conducting fluid through the duct and in thermal communication with the outer wall chamber. 21. The nuclear reactor of claim 20, wherein movement of the nuclear fuel in a molten fuel state into the lower neutron importance region of the nuclear reactor core decreases reactivity within the nuclear reactor core. 22. The nuclear reactor of claim 20, wherein the nuclear fuel is stored in a solid fuel state within the inner wall chamber when temperature of the nuclear fuel does not satisfy a nuclear fuel melting temperature condition. 23. The nuclear reactor of claim 20, wherein the melting temperature of the nuclear fuel exceeds a flow temperature of the heat conducting fluid within the duct. 24. The nuclear reactor of claim 20, wherein the inner wall chamber is expandable under temperature of the inner wall chamber. 25. The nuclear reactor of claim 20, wherein the inner wall chamber is not in physical contact with the outer wall chamber when the inner wall chamber has not expanded under increased internal temperature of the inner wall chamber. 26. The nuclear reactor of claim 20, wherein the inner wall chamber radiates heat from within the inner wall chamber to the heat conducting fluid flowing outside the outer wall chamber when the inner wall chamber has expanded under increased internal temperature of the inner wall chamber. 27. The nuclear reactor of claim 20, wherein the inner wall chamber conducts heat from within the inner wall chamber to the heat conducting fluid flowing outside the outer wall chamber when the inner wall chamber has expanded to physically contact the outer wall chamber under increased internal temperature of the inner wall chamber. 28. The nuclear reactor of claim 20, wherein the inner wall chamber conducts heat from within the inner wall chamber to the heat conducting fluid flowing outside the outer wall chamber when the inner wall chamber has expanded to allow physical contact between the outer wall chamber and contacts affixed to the inner wall chamber under increased internal temperature of the inner wall chamber. 29. The nuclear reactor of claim 20, wherein transfer of heat from the inner wall chamber to the heat conducting fluid flowing outside the outer wall chamber reduces the temperature of the nuclear fuel and transitions the nuclear fuel to a solid fuel state. 30. A nuclear reactor having a nuclear reactor core comprising:a multiple-walled fuel chamber includingan inner wall chamber configured to contain the nuclear reactor core and to position nuclear fuel in a molten fuel state within a high neutron importance region of the nuclear reactor core, the inner wall chamber being further configured to allow at least a portion of the nuclear fuel to move in a molten fuel state into a lower neutron importance region of the nuclear reactor core while remaining within the inner wall chamber as temperature of the nuclear fuel satisfies a negative reactivity feedback expansion temperature condition, the movement of the nuclear fuel in a molten fuel state to the lower neutron importance region increasing negative reactivity feedback in the nuclear reactor core, andan outer wall chamber containing the inner wall chamber, a gap between the outer wall chamber and the inner wall chamber thermally isolating the inner wall chamber.
060977906	claims	1. A pressure partition, comprising: a thin film for dividing a predetermined space into two spatial zones; and supporting means for supporting said film at an outside peripheral portion thereof, said supporting means having a curved surface for producing curvature in the outside peripheral portion of said film, wherein said curved surface is disposed at one of the two spatial zones having a lower pressure as compared with the other, and said curved surface has a convex shape with respect to a plane intersecting said film. dividing a predetermined space into two spatial zones by use of a thin film; supporting an outside peripheral portion of the film so that, due to a pressure difference between the two spatial zones, the film is deformed to follow a curved surface portion of a support; and exposing a substrate with X-rays passed through the film. dividing a predetermined space into two spatial zones by use of a thin film; supporting an outside peripheral portion of the film so that, due to a pressure difference between the two spatial zones, the film is deformed to follow a curved surface portion of a support; exposing a substrate with X-rays passed through the film; and developing the exposed substrate. a thin film for dividing a predetermined space into two spatial zones; and supporting means for supporting said film at an outside peripheral portion thereof, said supporting means having a curved surface for producing curvature in the outside peripheral portion of said film, along a predetermined curvature plane, wherein said curved surface has a curvature radius which increases toward the center of said film. a pressure partition comprising (i) a thin film for dividing a predetermined space into two spatial zones, and (ii) supporting means for supporting said film at an outside peripheral portion thereof, said supporting means having a curved surface for producing curvature in the outside peripheral portion of said film, along a predetermined curvature plane, wherein said curved surface has a curvature radius which increases toward the center of said film; and substrate holding means for holding a substrate to be exposed with X-rays being extracted through said pressure partition. providing a pressure partition that includes (i) a thin film for dividing a predetermined space into two spatial zones, and (ii) supporting means for supporting the film at an outside peripheral portion thereof, the supporting means having a curved surface for producing curvature in the outside peripheral portion of the film, along a predetermined curvature plane, wherein the curved surface has a curvature radius which increases toward the center of the film; holding a substrate to be exposed with X-rays being extracted through the pressure partition; and transferring a pattern onto a substrate to manufacture a device. dividing a predetermined space into two spatial zones by use of a thin film; and supporting an outside peripheral portion of the film so that, due to a pressure difference between the two spatial zones, the film is deformed to follow a curved surface portion of a support. 2. A pressure partition according to claim 1, wherein said curved surface has a curvature radius which is larger than the value of the curvature radius to be defined when a tension stress .sigma.f to be produced at the outside peripheral portion of said film by flexure thereof along said curved surface becomes equal to a difference between tension stresses .sigma..sub.1 and .sigma..sub.2, to be produced at the center portion and the outside peripheral portion of the film, respectively, by deflection of the film due to a pressure difference between the two spatial zones. 3. A pressure partition according to claim 1, wherein said curved surface has a curvature radius which increases toward the center of said film. 4. An exposure method, comprising the steps of: 5. A device manufacturing method, comprising the steps of: 6. A pressure partition, comprising: 7. An X-ray exposure apparatus, comprising: 8. An X-ray exposure apparatus according to claim 7, wherein said curved surface has a curvature radius which is larger than the value of the curvature radius to be defined when a tension stress .sigma.f to be produced at the outside peripheral portion of said film by flexure thereof along said curved surface becomes equal to a difference between tension stresses .sigma..sub.1 and .sigma..sub.2, to be produced at the center portion and the outside peripheral portion of the film, respectively, by deflection of the film due to a pressure difference between the two spatial zones. 9. A device manufacturing method comprising: 10. A device manufacturing method according to claim 9, wherein the curved surface has a curvature radius which is larger than the value of the curvature radius to be defined when a tension stress .sigma.f to be produced at the outside peripheral portion of the film by flexure thereof along the curved surface becomes equal to a difference between tension stresses .sigma..sub.1 and .sigma..sub.2, to be produced at the center portion and the outside peripheral portion of the film, respectively, by deflection of the film due to a pressure difference between the two spatial zones. 11. A partitioning method, comprising the steps of: 12. A method according to claim 11, wherein the curved surface portion of the support has a convex shape with respect to a plane intersecting the film. 13. A method according to claim 11, wherein the curved surface has a curvature radius which is larger than the value of the curvature radius to be defined when a tension stress .sigma.f to be produced at the outside peripheral portion of the film by flexure thereof along the curved surface becomes equal to a difference between tension stresses .sigma..sub.1 and .sigma..sub.2, to be produced at the center portion and the outside peripheral portion of the film, respectively, by deflection of the film due to a pressure difference between the two spatial zones. 14. A method according to claim 11, wherein the curved surface has a curvature radius which increases toward the center of the film.
	description	This application is a continuation of application Ser. No. 11/130,504, filed May 17, 2005 now U.S. Pat. No. 7,275,109, entitled “System and Method for Information Handling System Thermal Diagnostics” and naming Drew Schulke, Barry Kahr, Vinod Makhija, Adolfo Montero, Hasnain Shabbir as inventors, which is hereby incorporated by reference in its entirety. 1. Field of the Invention The present invention relates in general to the field of information handling system manufacture, and more particularly to a system and method for information handling system thermal diagnostics. 2. Description of the Related Art As the value and use of information continues to increase, individuals and businesses seek additional ways to process and store information. One option available to users is information handling systems. An information handling system generally processes, compiles, stores, and/or communicates information or data for business, personal, or other purposes thereby allowing users to take advantage of the value of the information. Because technology and information handling needs and requirements vary between different users or applications, information handling systems may also vary regarding what information is handled, how the information is handled, how much information is processed, stored, or communicated, and how quickly and efficiently the information may be processed, stored, or communicated. The variations in information handling systems allow for information handling systems to be general or configured for a specific user or specific use such as financial transaction processing, airline reservations, enterprise data storage, or global communications. In addition, information handling systems may include a variety of hardware and software components that may be configured to process, store, and communicate information and may include one or more computer systems, data storage systems, and networking systems. Information handling systems are generally built from a large variety of components and subsystems. Manufacture of information handling systems relies on appropriate integration of these various components and subsystems to function at a level deemed acceptable for an end-user environment. For example, thermal subsystems, such as the heat sinks, fans, thermal grease and other components involved in removing excess heat from an information handling system housing, generally must remove enough thermal energy to maintain components within an operating temperature range. If an information handling system thermal solution fails to remove sufficient thermal energy, a variety of detrimental impacts will usually occur. For instance, cooling fans will tend to run at high speeds for extended time periods thus generating increase operating noise, excessive cooling fan wear, increased power consumption and reduced internal battery life in the case of portable systems. As another example, automatic CPU throttling occurs with greater frequency to reduce thermal output of the CPU, and also reducing system performance. In some situations, a thermal shutdown occurs if temperatures become too extreme, resulting in data loss, user inquiries to technical support, and increased warranty and repair costs. Additionally, information handling systems that run at higher temperatures are often uncomfortable to users to handle. In order to avoid thermal subsystem difficulties, information handling system manufacturers typically test each system for proper thermal operation before shipping the systems to customers. One technique for testing thermal subsystem operation is to run the information handling system with the cooling fans forced off until the system reaches a predefined temperature and then forcing the cooling fans on again to determine if the cooling fans cool the system to a predetermined reduced temperature within a given time period. Properly operating thermal subsystems will reach the reduced temperature in the set time while inadequate thermal subsystems will fail to reach the reduced temperature or take an excessive time period to do so. Although such testing ensures that the thermal subsystem meets minimum requirements, the time to run the test often exceeds ten minutes, more that half of the time typically used to perform overall system testing. Increased testing time for each system increases the number of testing racks needed for testing systems as well as the power consumed by system testing. Further, testing of thermal subsystems by forcing fans on and off does not mimic any actual end-user environment and thus does not represent a realistic view of thermal performance. Therefore a need has arisen for a system and method which more quickly and efficiently tests information handling system thermal subsystem performance. In accordance with the present invention, a system and method are provided which substantially reduce the disadvantages and problems associated with previous methods and systems for testing thermal subsystem performance. A thermal diagnostics module operating in firmware monitors one or more thermal parameters of an information handling system during one or more manufacturing activities, such as the maximum temperature zone reached by the information handling system. The monitored thermal parameter is compared with an expected value to determine proper operation or failure of the thermal subsystem of the information handling system. More specifically, a thermal diagnostics module is embedded in firmware of a manufactured information handling system, such as in the embedded controller. A thermal diagnostics engine of a manufacture rack enables the thermal diagnostics module to monitor thermal parameters of an information handling system for one or more manufacturing activities, such as during hardware diagnostics, during imaging and/or during final diagnostics. For instance, the thermal diagnostics module stores the highest temperature zone reached during a manufacturing activity and provides the stored value to the thermal diagnostics engine after the manufacturing activity is complete. The detected thermal parameter is compared with an expected value for that information handling system performing the manufacturing activity to determine if the thermal subsystem is operating correctly. If the detected value exceeds the expected maximum value, the information handling system fails the thermal test while, if the detected value is less than the expected maximum value the information handling system passes the thermal test and may be shipped to an end user. Expected thermal parameter values are, for instance, determined with values measured from a properly operating system performing the manufacturing activity. The present invention provides a number of important technical advantages. One example of an important technical advantage is that background monitoring of thermal performance during other system manufacturing operations provides more realistic testing conditions and reduces manufacturing time by eliminating dedicated thermal performance testing. For instance, tracking maximum temperature zone zones reached during image installation with the BIOS and comparing the measured readings with expected readings provides a closer comparison to end user operating conditions than does operation with the cooling fan forced off. Thermal performance monitoring through BIOS firmware, such as a module running on the embedded controller, operates without interference to the manufacture process. Reading the thermal performance from the firmware after the manufacture process is complete takes minimal time and has a greater likelihood of detecting thermal subsystem failures than does a dedicated thermal subsystem test that also takes an additional ten minutes or more to perform. Background monitoring of thermal parameters during information handling system manufacture activities verifies proper operation of a thermal subsystem without dedicated thermal testing. For purposes of this disclosure, an information handling system may include any instrumentality or aggregate of instrumentalities operable to compute, classify, process, transmit, receive, retrieve, originate, switch, store, display, manifest, detect, record, reproduce, handle, or utilize any form of information, intelligence, or data for business, scientific, control, or other purposes. For example, an information handling system may be a personal computer, a network storage device, or any other suitable device and may vary in size, shape, performance, functionality, and price. The information handling system may include random access memory (RAM), one or more processing resources such as a central processing unit (CPU) or hardware or software control logic, ROM, and/or other types of nonvolatile memory. Additional components of the information handling system may include one or more disk drives, one or more network ports for communicating with external devices as well as various input and output (I/O) devices, such as a keyboard, a mouse, and a video display. The information handling system may also include one or more buses operable to transmit communications between the various hardware components. Referring now to FIG. 1, a block diagram depicts a system for background thermal diagnostics during information handling system manufacture activities. Information handling system 10 has an application layer 12, operating system layer 14 and a hardware layer 18. Hardware layer 18 includes a number of components to process information, such as a CPU 20, hard disk drive 22, RAM 24 chipset 26 and embedded controller 28. In addition, hardware layer 18 includes a thermal subsystem that removes excess heat generated by operation of the hardware component, such as a cooling fan 30 and heat sink 32. Cooling fan 30 forces a cooling airflow through the housing 34 than contains the components, especially across heat sink 32 which draws heat away from certain components, such as CPU 20. Embedded controller 28 interfaces with cooling fan 30 to alter the operating speed of cooling fan 30 as the temperature changes within housing 34. In addition, embedded controller and chipset 26 coordinate communication between various processing components and I/O devices, such as a keyboard and peripherals. For instance, firmware instructions such as in a BIOS 38 manage communications between processing components at a physical level and manage basic operating parameters, such as fan speed to maintain a desired temperature. Operating system layer 14 runs over the firmware and hardware layers to interface application layer 12 with desired computing resources. Information handling systems 10 are built at a manufacture rack 40 by first assembling hardware components and then loading software components, such as the operating system and applications. Once the hardware components are assembled, a hardware diagnostics module run hardware diagnostics to detect component failures. After proper hardware component operation is confirmed, an image engine 44 copies a software image onto the assembled information handling system and sets the system up to operate applications for end users. An application diagnostics module 46 then runs final checks on the completed system to ensure compatibility between the assembled hardware components and the loaded applications. Completed systems are shipped to end users and typically serviced by the manufacturer through a warranty period. Identifying system errors on a hardware, firmware or software level before systems are shipped reduces warranty to cost and improves the customer experience. In order to confirm the proper operation of the thermal subsystem, a thermal diagnostics engine 48 associated with manufacture rack 40 interfaces with each manufactured information handling system 10. Thermal diagnostics engine 48 reads thermal parameters from each information handling system 10 and compares the read thermal parameters with expected thermal parameters found in an expected thermal parameter database 50. The thermal parameters are monitored on each information handling system 10 with a thermal diagnostics module 52 operating in firmware layer 16, such as in conjunction with BIOS 38 on embedded controller 28. Thermal diagnostics engine 48 enables thermal diagnostics module 52 at the start of a predetermined manufacturing activity so that thermal diagnostics module 52 operates in the background as the manufacturing activity takes place to monitor and store one or more thermal parameters. For instance, thermal diagnostics module 52 is initiated at the application of power to information handling system 10 to track maximum temperature zone reach in housing 34 during the manufacture process, including hardware diagnostics, image building and completed system diagnostics. Thermal diagnostics engine 48 reads the maximum temperature zone at the end of the manufacture process and compares the detected maximum temperature zone with an expected maximum temperature zone, such as the temperature reached by a similar information handling system with a properly operating thermal subsystem. If the expected maximum temperature zone is exceeded, the system fails and is sent for analysis while, if the expected maximum temperature zone is not exceeded, the system passes and is shipped to the end user. Thermal diagnostics module 52 may track temperature during any or all of the hardware diagnostics, image building and application diagnostics, and may track other thermal parameters, such as cooling fan speed. Referring now to FIG. 2, a flow diagram depicts a process for background thermal diagnostics during information handling system manufacture activities. The process begins at step 54 with the assembly of hardware components into an information handling system. At step 56, the thermal diagnostics module is embedded in firmware of the information handling system, such as with instructions saved to the embedded controller. The thermal diagnostics module may be flashed as part of firmware instructions loaded to the assembled information handling system or may be preloaded into the embedded controller before assembly of the components. At step 58, the information handling system is powered up and at step 60 the thermal diagnostics module is enabled to monitor thermal parameters. The thermal diagnostics module is, for instance, enabled during a predetermined portion of the manufacture process so that thermal parameters are detected and stored that correlate with expected values taken from a properly-functioning system during similar activities. At step 62, the manufacturing activity is performed and the thermal diagnostics module monitors thermal parameters during the activity, such as the maximum temperature zone reached. At step 64 the thermal parameter is read from the thermal diagnostics module and, at step 66, compared with an expected value. If, at step 68, the detected thermal parameter does not exceed the expected value, the process completes at step 70 with the disabling of the thermal diagnostics module. If at step 68 the detected thermal parameter exceeds an expected value, the process continues to step 72 for failure of the thermal test by the system. Referring now to FIG. 3, an information handling system manufacturing time line with background thermal diagnostics is depicted. The information handling system manufacture process begins at step 74 with the building of hardware into an assembled information handling system. The assembled information handling system proceeds through hardware diagnostics at step 76 to ensure proper operation of the hardware and imaging at step 78 to load software applications. At step 80, the completed system is subjected to final diagnostics before shipping to an end user to ensure compatibility and proper operation of the completed software and hardware components. Monitoring of thermal parameters at step 82 is performed during one or more of the manufacturing activities. For instance, hardware diagnostics, imaging and final diagnostics each have thermal parameters that are expected to be reached and may be used to compare with detected thermal diagnostics by selecting the point along the manufacturing time line at which the thermal diagnostics module is enabled and disable. Minimal if any interruption is introduced to the manufacturing activities by the monitoring of thermal parameters with firmware running the background of the main activities, such as loading and testing applications with the CPU. Although the present invention has been described in detail, it should be understood that various changes, substitutions and alterations can be made hereto without departing from the spirit and scope of the invention as defined by the appended claims.
	description	This is a continuation application, under 35 U.S.C. §120, of copending International Application No. PCT/EP2006/006465, filed Jul. 4, 2006, which designated the United States; this application also claims the priority, under 35 U.S.C. §119, of German Patent Application DE 10 2005 035 486.6, filed Jul. 26, 2005; the prior applications are herewith incorporated by reference in their entirety. The invention relates to a fuel assembly for a pressurized water reactor. It is known from a large number of inspection results that the fuel assemblies of a pressurized water reactor bend during their service life. The reasons therefor can, for example, be anisotropy in the thermal expansion or an increase in length of the fuel rod cladding tubes or the control rod guide tubes induced by radioactive radiation. In the worst case, those bends can result in sluggishness of the control rod guide tubes or in problems in exchanging fuel assemblies. However, besides systematic bends in certain positions in the core, increased or decreased cracks between the individual fuel assembles or between fuel assembles can be created in many cases in unknown locations in the core which are located on the edge of the core and the core baffle, which influence the fuel-moderator ratio. Such a bending or deformation observed in practice is shown in the diagram of FIG. 7. In that diagram, the magnitude of the bending d measured in mm is plotted against the height h in m of the fuel assembly, measured from the lower rod holder plate, as is generated for example for an irradiated 18×18 fuel assembly. The figure shows that the bending in question is substantially a C-shaped curved bending (basic mode), which is superimposed to a certain extent with bends having higher modes, mainly with the next highest mode, in the form of an S-shaped bend. In order to decrease the extent of such bends, the prior art attempted to mechanically construct the fuel assemblies in a more stable manner and to decrease the hold-down forces. Alternatively, International Publication No. WO 2005/059924 A2, corresponding to U.S. Patent Application Publication No. US 2006/0285628 A1, has proposed to purposely influence the forces acting on the fuel assemblies by using differently constructed edge webs so as to enable optimum construction of the core despite bending which occurs. It is accordingly an object of the invention to provide a fuel assembly for a pressurized water reactor, which overcomes the hereinafore-mentioned disadvantages of the heretofore-known devices of this general type and which exhibits decreased bending during operation. With the foregoing and other objects in view there is provided, in accordance with the invention, a fuel assembly for a pressurized water reactor. The fuel assembly comprises upper and lower regions, a plurality of mutually axially separated spacers disposed in the upper and lower regions, and a multiplicity of fuel rods extended in a longitudinal direction and guided in the spacers. The spacers of the upper region have a lower flow resistance (cross-flow resistance) in a transverse direction perpendicular to the longitudinal direction than the spacers of the lower region. The invention is based on the observation that the cooling water flowing in the longitudinal or axial direction of the fuel assembly is influenced by the substantially C-shaped curved bending of the cross-flow components of the fuel assembly described above. These cross-flow components which run perpendicular to the vertical are in the lower region of the fuel assembly, that is in the region in which, as viewed from the direction of the flowing cooling water, the extent of the bend, i.e. the departure from an ideal vertical line, increases as opposed to the cross-flow components which adjust due to the decreasing bending in the region above the maximum bending. In accordance with another especially simple advantageous feature of the invention, a spacer having an edge which is formed by edge webs effects the different cross-flow resistances of the spacers of the upper and lower region in such a way that the edge webs of the spacers of the upper region, as viewed in a transverse direction, cover a smaller area than the edge webs of the spacers of the lower region. This results in a significantly decreased cross-flow resistance of the spacers in the upper region. In accordance with a further preferred feature of the invention, in a spacer which is constructed from a plurality of intersecting inner webs, the inner webs of the spacers of the upper region, as viewed in a transverse direction, also cover a smaller area than the inner webs of the spacers of the lower region. Using this measure, the “transparency” of the spacers of the upper region is additionally increased with respect to the “transparency” of the spacers of the lower region. Basically, the smaller area coverage can result from the fact that the height of the respective edge webs or inner webs of the spacers of the upper region is smaller than the height of the respective edge webs or inner webs of the spacers of the lower region. In accordance with a concomitant feature of the invention, alternatively or in addition, the edge webs and possibly the inner webs of the spacers of the upper region are provided with openings which are larger than openings that are possibly present in the edge webs and the inner webs of the spacers of the lower region. Basically, however, another embodiment is conceivable in which exclusively the edge webs and possibly also the inner webs of the upper region are provided with openings. 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 fuel assembly for 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. Referring now to the figures of the drawings in detail and first, particularly, to FIG. 1 thereof, there is seen a fuel assembly 2 of a pressurized water reactor in which a multiplicity of fuel rods 6 that extend in an axial or longitudinal direction 4 are guided in a plurality of mutually axially separated spacers 8-I, 8-II. A deformation in the form of a C-shaped curved bending, deflection or sagging in an operating condition includes an elastic part and a part that becomes increasingly plastic with increasing operating time. Since the fuel assembly 2 is not surrounded by a casing or box, cooling water K flowing at the fuel assembly 2 can flow along upward between adjacent fuel assemblies between adjacent spacers 8-I, 8-II in the fuel assembly 2 and enable a desired horizontal cross-exchange of cooling water. In the fuel assembly 2, which is bent in the shape of a (backward or mirror-reversed) C, systematic cross currents Q which are generated due to its bent shape, are opposed in a lower region I by cross currents Q generated in an upper region II. While the cross currents created in the lower region I exert a force on the fuel assembly 2 that results in reducing the amount of bending in this lower region I, the opposing cross currents Q produce an increase in bending so that in practice the superimposition of the C-shaped arcuate bend described above by using FIG. 7 takes the form of an S-shaped deformation. These cross currents occurring in the upper region II of the fuel assembly 2 consequently lead to an unstable behavior because their extent increases as do the forces exerted by them on the fuel assembly 2 with increasing bending. The invention is thus based on the concept that the amount of forces created in the upper region II and the resulting tendency toward instability and toward creating a plastic deformation can be decreased if care is taken to subject the spacers 8-II provided in the upper region II of the cross current Q to a lower flow resistance than the spacers 8-I located in the lower region I. In other words: in the case of the lower spacers 8-I, a higher resistance against cross currents is advantageous since the forces generated by these cross currents decrease bending, while the cross forces exerted in the upper region II on the spacers 8-II should be as low as possible in order to minimize their influence on the amount of bending. FIG. 1 shows a situation in which the border between the upper region I and the lower region II does not run exactly in the middle of the fuel assembly 2 so that in the embodiment using nine spacers 8-I, 8-II, the five lower spacers 8-I are assigned to the lower region I and the remaining four spacers 8-II are assigned to the upper region II. The border between the lower region I and the upper region II differs installation dependently from fuel assembly type to fuel assembly type, and should be located approximately in the region of maximum bending. According to FIG. 2, a spacer 8-I of the lower region I is constructed from a plurality of intersecting or crossing inner webs 10. The edge of the spacer 8-I is formed by an edge web 12. The intersecting inner webs 10 and edge webs 12 form square grid cells 14, through which the fuel rods 6 are guided. In the simplified representation of the figure, nubs and spring elements disposed on the inner webs 10 and the edge webs 12 for storage of the fuel assemblies and, if necessary, existing guide or twist vanes or in double wall spacers axially running flow channels, are not shown from reasons of clarity. The figure shows that the edge webs 12 and the inner webs 10 of the spacer 8-I of the lower region are closed, i.e. it contains no access openings and, viewed in this way in each transverse direction 16, 18, they cover a large surface and impart a high flow resistance so that the vertically flowing cooling water exerts a high transverse force as a result of the bending of the fuel assembly generated by the inclination or skewing of one of the edge webs against the streaming cooling water, to compensate for this bending. On the other hand, in the case of FIG. 3, both the inner webs 10 and the edge webs 12 of a spacer 8-II of the upper region are provided at the same usual overall height with openings 20 which result in a lower flow resistance in a transverse direction with respect to the spacer 8-I (FIG. 2), and permit a cross current of the cooling water in the spacer 8-II as well, so that the transverse forces exerted by the cooling water on the spacers 8-II can be correspondingly decreased. Alternatively to the embodiment shown in FIG. 3, a reduced degree of coverage of a spacer 8-II of the upper region can also be achieved according to FIG. 4 in such a way that the height h-II of the inner and edge webs 10 and 12 is decreased. The decreased height h-II is illustrated in the figure by using the spacer 8-I (drawn in a dotted line) of the lower region with a greater height h-I. In the embodiment according to FIGS. 5 and 6, both the spacers 8-I of the lower region and the spacers 8-II of the upper region are provided with openings 20-I and 20-II in the edge webs 12. In this case the areas of the openings 20-II of the spacer 8-II of the upper region are greater than the areas of the openings 20-I of the spacer 8-I of the lower region. In addition to the embodiments shown in FIGS. 5 and 6, the inner webs 10 can also be provided with openings, and in this case the openings provided in the inner webs of the spacer of the lower region are smaller than the openings provided in the inner webs of the spacer 8-II of the upper region.
	claims	1. A method of providing a nuclear fission igniter for initiating a nuclear fission deflagration wave in a nuclear deflagration wave reactor, the method comprising:inserting at least one nuclear fission igniter into at least one cavity of a housing of the nuclear fission deflagration wave reactor for initiating at least one nuclear fission deflagration wave in the nuclear fission deflagration wave reactor, the nuclear fission deflagration wave reactor comprising fertile nuclear fuel;shielding the at least one nuclear fission igniter;providing a sufficient amount of neutrons from the at least one nuclear fission igniter to the fertile nuclear fuel to convert the fertile nuclear fuel to fissile nuclear fuel and to initiate and maintain a steady-state deflagration wave; andremoving the at least one nuclear fission igniter from the nuclear fission deflagration wave reactor after initiation of the at least one nuclear fission deflagration wave and obtaining the steady-state deflagration wave. 2. The method of claim 1, wherein the at least one nuclear fission igniter includes:a portion of nuclear fission fuel material insertable in the nuclear fission deflagration wave reactor, wherein:the portion of nuclear fuel material has a keffective less than 1 when the at least one nuclear fission igniter is outside the nuclear fission deflagration wave reactor; andthe portion of nuclear fission fuel material is arranged to establish a keffective of at least 1 when the at least one nuclear fission igniter is installed in the nuclear fission deflagration wave reactor. 3. The method of claim 1, wherein shielding the at least one nuclear fission igniter shields against neutrons and radiation, the method further comprising removing the shielding from the nuclear fission igniter prior to removing the at least one nuclear fission igniter from the nuclear fission deflagration wave reactor. 4. The method of claim 1, further comprising transporting the at least one nuclear fission igniter to at least one nuclear fission deflagration wave reactor core. 5. The method of claim 1, further comprising removing decay heat from the at least one nuclear fission igniter. 6. A method of providing a nuclear fission igniter for initiating a nuclear fission deflagration wave in a nuclear fission deflagration wave reactor core, the method comprising:placing at least one nuclear fission igniter in at least one nuclear fission deflagration wave reactor core, the core further comprising fertile nuclear fuel;providing a sufficient amount of neutrons from the at least one nuclear fission igniter to at least a portion of the fertile nuclear fuel in the reactor core to convert the fertile nuclear fuel to fissile nuclear fuel and to initiate the nuclear fission deflagration wave;propagating the nuclear fission deflagration wave due to continued conversion of the fertile nuclear fuel to fissile nuclear fuel; andremoving the at least one nuclear fission igniter from the at least one nuclear fission deflagration wave reactor core upon obtaining a steady-state condition of the nuclear fission deflagration wave. 7. The method of claim 6, further comprising:if nuclear shielding material is present around the at least one nuclear fission igniter, removing the nuclear shielding material from the at least one nuclear fission igniter prior to providing a sufficient amount of neutrons from the at least one nuclear fission igniter. 8. The method of claim 6, wherein the at least one nuclear fission igniter includes:a portion of nuclear fission fuel material insertable in the nuclear fission deflagration wave reactor core, wherein:the portion of nuclear fission fuel material has a keffective less than 1 when the nuclear fission igniter is outside the nuclear fission deflagration wave reactor core; andthe portion of nuclear fission fuel material is arranged to establish a keffective of at least 1 when the nuclear fission igniter is installed in the nuclear fission deflagration wave reactor core. 9. The method of claim 8, wherein placing the at least one nuclear fission igniter includes mating a plurality of channels defined on an outer surface of the portion of nuclear fission fuel material with a plurality of coolant channels defined in the nuclear fission deflagration wave reactor core. 10. The method of claim 6, wherein placing the at least one nuclear fission igniter places a plurality of housed nuclear fission igniters in one nuclear fission deflagration wave reactor core. 11. The method of claim 6, wherein placing the at least one nuclear fission igniter places a plurality of housed nuclear fission igniters in a plurality of nuclear fission deflagration wave reactor cores. 12. The method of claim 6, further comprising, if at least one decay heat removal device is present, removing the at least one decay heat removal device from the at least one nuclear fission igniter. 13. The method of claim 6, if the at least one nuclear fission igniter is in a housing body, further comprising removing the at least one nuclear fission igniter from the housing body prior to providing a sufficient amount of neutrons from the at least one nuclear fission igniter. 14. The method of claim 6 wherein placing the at least one nuclear fission igniter in the at least one nuclear fission deflagration wave reactor core includes:placing the at least one nuclear fission igniter having a second nuclear fuel material different from a first nuclear fuel material of the nuclear fission deflagration wave reactor core. 15. The method of claim 14, wherein propagating the nuclear fission deflagration wave includes removing neutron absorbing material from at least one of the first nuclear fission fuel material and the second nuclear fission fuel material. 16. The method of claim 14, wherein propagating the nuclear fission deflagration wave includes adding neutron moderating material to at least one of the first nuclear fission fuel material and the second nuclear fission fuel material. 17. The method of claim 14, wherein propagating the nuclear fission deflagration wave includes adding neutron reflecting material to at least one of the first nuclear fission fuel material and the second nuclear fission fuel material. 18. The method of claim 14, wherein propagating the nuclear fission deflagration wave includes adding neutron multiplicative material to at least one of the first nuclear fission fuel material and the second nuclear fission fuel material. 19. The method of claim 14, wherein initiating the nuclear fission deflagration wave includes providing neutrons from the nuclear fission igniter to fertile material in the first nuclear fission fuel material.
051280930	abstract	A hydraulic system for a control rod drive (CRD) includes a variable output-pressure CR pump operable in a charging mode for providing pressurized fluid at a charging pressure, and in a normal mode for providing the pressurized fluid at a purge pressure, less than the charging pressure. Charging and purge lines are disposed in parallel flow between the CRD pump and the CRD. A hydraulic control unit is disposed in flow communication in the charging line and includes a scram accumulator. An isolation valve is provided in the charging line between the CRD pump and the scram accumulator. A controller is operatively connected to the CRD pump and the isolation valve and is effective for opening the isolation valve and operating the CRD pump in a charging mode for charging the scram accumulator, and closing the isolation valve and operating the CRD pump in a normal mode for providing to the CRD through the purge line the pressurized fluid at a purge pressure lower than the charging pressure.
043607365	description	DETAILED DESCRIPTION OF THE INVENTION FIG. 1 is a simplified showing of the relationship between a nuclear reactor vessel 10 and a surrounding primary shield 12. The primary shield 12 defines a reactor cavity 14. The walls of the primary shield 12 are spaced from the reactor vessel 10 to define an annular space 16 having an open upper end 18. The reactor vessel 10 has an annular ledge 20 which is adjacent to and radially inwardly disposed from an annular ledge 22 on the primary shield 12. The upper end 18 between the annular ledges 20 and 22 is spanned by a form of the radiation shield of this invention which is generally indicated by the number 24. It comprises a container 26 formed of a thin flexible material, such as rubber or plastic, filled with a radiation attenuating liquid 28. The radiation attenuating liquid 28 is preferably a hydrogeneous liquid. The liquid serves as a moderator and absorber for neutron radiation emanating from the reactor vessel 10. As shown in FIG. 2, the radiation shield 24 also comprises means 30 connecting opposing walls 32 and 34 of the container 26 to maintain the distance therebetween when the container 26 is filled with the radiation attenuating liquid 28. Since the radiation shield 24 is preferably collapsible for storage, the means 30 are preferably flexible, permitting the opposing walls 32 and 34 to approach each other when the container 24 is not filled with a radiation attenuating liquid. In the illustrated embodiment, the means 30 are drop stitches. FIG. 3 shows a second embodiment of the subject invention. In this embodiment, the radiation shield 36 is rectangular parallelepipedal in shape--that is, it is shaped like a water mattress. An intersecting grid of drop stitches 38 is provided to maintain the distance between the major walls of the container when it is filled with a radiation attenuating fluid--or, put another way, to prevent the major surfaces of the radiation shield from bulging. As is well known in the textile art, drop stiches are threads which extend between spaced pieces of fabric and are interlaced with the threads in the spaced pieces of fabric. FIG. 4 shows a third embodiment of the subject invention. In this embodiment, the radiation shield 40 has parallel walls 42 and 44 which are each initially formed from two plies of material joined (as by stitching, heat welding, or cementing) along the nodes 46. The inner plies are cut between the nodes 46, bent inwardly, and joined along the lines 48. If desired, inserts may be placed between the inner plies, and the inner plies from each side may be joined to the inserts, thereby increasing the spacing of the outer plies. The connections between the outer plies, known as "wing tabs," also serve to maintain the distance between the major walls of the container when it is filled with a radiation attenuating fluid. CAVEAT While the present invention has been illustrated by detailed descriptions of three preferred embodiments thereof, it will be obvious to those skilled in the art that various changes in form and detail can be made therein without departing from the true scope of the invention. For that reason, the invention must be measured by the claims appended hereto and not by the foregoing preferred embodiments.
053713630	claims	1. A device for sensing radiation on an interior pipe surface having a substantially circular cross-section, the device comprising: a carriage, movable through the pipe, having a front end, a back end, a longitudinal central axis and radii extending between said longitudinal central axis and the pipe; at least two guide arms coupled to said carriage, each having a wheel rotatably mounted thereon, said guide arms being biased along a radius of said carriage toward the pipe so that said wheels contact the pipe and position said central axis of said carriage concentrically within the pipe; a set of pistons mounted on said carriage equiangularly about said central axis within a single plane and adapted for radial extension and retraction, each piston having a carriage end and a free end spaced from said carriage end; a radiation sensor mounted on said free end of each piston for detecting radiation on the interior pipe surface when said set of pistons are extended; a rack connected to said set of pistons and a rotatable gear coupled to said carriage and cooperatively dimensioned to engage said rack, whereby said gear rotates to move said rack and rotate said set of retracted pistons and sensors one half of the angle between adjacent pistons to cover a complete circumferential strip on the interior of the pipe; a first cable means coupled to said back end of said carriage and electrically connected to said sensors for transmitting sensor data out of the pipe; and a second cable coupled to said front end of said carriage for discretely pulling said carriage through the pipe, whereby between moves said sensors cover a complete circumferential strip on the interior of the pipe at each location in the geometry required to meet pre-determined criteria. a pair of radiation sensors mounted on said free end of each piston for sensing radiation when said set of pistons are extended; each of said pistons including a central piston axis and a piston plane that intersects said central piston axis and said carriage central axis; whereby each pair of sensors has one sensor located on one side of the respective piston plane and the other sensor located on the other side of the piston plane symmetrical with the one sensor. a first carriage movable through the pipe and having a front end, a back end, and a first set of radiation sensors mounted equiangularly about the central axis for sensing radiation on the interior pipe surface; a second carriage coupled a first distance from said back end of said first carriage and having a second set of radiation sensors mounted equiangularly about the central axis for sensing radiation on the interior pipe surface, said second set of sensors being rotated in a first direction one-third of the angle between adjacent sensors of said first set of sensors; a third carriage with a front end coupled a second distance from said second carriage and having a back end, and a third set of sensors mounted equiangularly about the central axis for sensing radiation on the interior pipe surface, said third set of sensors being rotated in a first direction two-thirds of the angle between adjacent sensors of said first set of sensors; a first cable coupled to said back end of said third carriage and electrically connected to said sensors for transmitting sensor data out of the pipe; and a second cable coupled to said front end of said first carriage for pulling said carriages through the pipe, whereby said sensors cover a complete circumferential strip on the interior pipe surface. a carriage movable through the pipe having a longitudinal central axis and radii extending between said longitudinal central axis and the pipe; means for positioning said carriage centrally within the pipe; a set of radiation sensors mounted about said central axis for detecting radiation on the interior pipe surface; indexing means for rotating said set of radiation sensors a fraction of the angle between adjacent sensors, so that a circumferential strip on the interior of the pipe is sensed; and cable means coupled to said carriage for moving said carriage through the pipe and transmitting sensor data out of the pipe. a set of pneumatic pistons each having a carriage end attached to said carriage and a free end spaced from said carriage end. each piston has a pair of sensors mounted at its free end, one sensor of each pair being on one side of said respective piston plane and the other sensor of each pair being on the other side of said respective piston plane. a rack connected to said set of pistons; and a rotatable gear coupled to said carriage and cooperatively dimensioned to engage said rack and rotate said retracted pistons and said sensors. at least two spring loaded guide arms coupled to said carriage, each guide arm having a wheel rotatably mounted thereon for contacting the interior pipe surface, said guide arms being biased toward the pipe so that the carriage central axis is concentrically positioned within the pipe. two carriages coupled in spaced relation along said central axis and adapted for movement through the pipe; two sets of sensors, each set being mounted on one of said two carriages for detecting radiation on the interior pipe surface; each set of sensors having an angular displacement, about the longitudinal central axis, with respect to the other sets of sensors, the angular displacement being dependent on: a) the number of carriages, and b) the number of sensors per set, so that a complete circumferential strip the entire interior pipe surface is covered as said carriages are moved through the pipe. a carriage adapted for movement through the pipe; a set of radiation sensors mounted on said carriage for detecting radiation on an interior pipe surface; means for positioning said set of radiation sensors to cover a complete circumferential strip on the interior pipe surface; and means for transmitting the radiation sensor readings out of the pipe and recording the sensor readings to establish a detailed radiological survey of the interior pipe surface. 2. The device according to claim 1, additionally comprising: 3. A device having a longitudinal central axis sensing radiation on an interior pipe surface having a substantially circular cross-section, the device comprising: 4. A device for detecting radiation on an interior pipe surface, comprising: 5. The device according to claim 4, wherein said set of sensors are mounted equiangularly within a single plane disposed perpendicular to said carriage central axis. 6. The device according to claim 5, further comprising means for radially extending and retracting said set of sensors. 7. The device according to claim 6, wherein said set of sensors is movable between an extended position for sensing radiation and a retracted position for rotation by said indexing means and movement by said cable means. 8. The device according to claim 7, wherein said means for radially extending and retracting said set of sensors comprises: 9. The device according to claim 8, wherein each piston has a sensor mounted at its free end. 10. The device according to claim 9, wherein each piston includes a central piston axis and a piston plane that intersects said central piston axis and said carriage central axis; and 11. The device according to claim 10, wherein the sensors of each pair are mounted symmetrically about said piston plane with respect to each other, with each sensor facing generally away from said piston plane. 12. The device according to claim 11, wherein said indexing means comprises: 13. The device according to claim 12, wherein said retracted pistons and said sensors are rotated one half the angle between adjacent pistons. 14. The device according to claim 13, wherein said means for positioning comprises: 15. A device having a longitudinal central axis for detecting radiation on an interior pipe surface comprising: 16. The device according to claim 15, wherein said sensors of each set are mounted symmetrically about the longitudinal central axis. 17. The device according to claim 16, wherein each set of sensors includes two sensors disposed at 180.degree. to each other, whereby the angular displacement between adjacent sets is 90.degree., i.e., (360.degree..div.[2.times.2]). 18. The device according to claim 16, wherein each set of sensors includes three sensors disposed at 120.degree. to each other, whereby the angular displacement between adjacent sets is 60.degree., i.e., (360.degree..div.[2.times.3]). 19. The device according to claim 16, wherein the device includes three carriages and each set of sensors includes three sensors disposed at 120.degree. to each other, whereby the angular displacement between adjacent sensors is 40.degree., i.e. (360.degree..div.[3.times.3]). 20. A device for detecting radiation within a pipe, comprising:
	claims	1. A method of producing actinium by using liquefied radium, the method comprising:a loading step of moving the liquefied radium from a vial to load the liquefied radium into a reaction space inside a chamber;a step of producing actinium through a nuclear reaction process by irradiating a particle beam to the liquefied radium in the reaction space inside the chamber; andan unloading step of moving a product comprising the liquefied radium and actinium to the vial,wherein, when the liquefied radium is loaded into the reaction space inside the chamber, a gas containing radon is moved to the vial through a first flow path connected to an upper side of the reaction space, and the moved gas is discharged from the vial through a second flow path. 2. The method of claim 1, further comprising step of separating actinium from the product. 3. The method of claim 2, further comprising a reloading step of transferring pure liquefied radium obtained by separating actinium from the product to the reaction space of the chamber. 4. The method of claim 2, further comprising condensing radon to discard radon. 5. The method of claim 2, further comprising diluting radon with external air to discharge the diluted radon. 6. The method of claim 2, wherein the loading step comprises moving a preset amount of radium to the reaction space. 7. The method of claim 6, wherein the loading step comprises moving the preset amount of radium to the reaction space by using a syringe pump. 8. The method of claim 2, wherein the unloading step comprises unloading the product by flowing in an inert gas into the reaction space of the chamber. 9. The method of claim 2, wherein the radium is liquefied by using an organic solution. 10. The method of claim 9, wherein the organic solution includes NO3 or Cl2. 11. The method of claim 2, further comprising a step of refining the separated actinium. 12. The method of claim 7, wherein the preset amount of radium from the syringe pump moves to the reaction space through a third flow path, and the product comprising the liquefied radium and actinium moves from the reaction space to the vial through a fourth flow path, both of the third flow path and the fourth flow path including a flow path connected to a lower side of the reaction space. 13. The method of claim 1, further comprising:a step of transferring the product along a third flow path from the vial to an actinium separating and refining unit. 14. The method of claim 1, wherein, while performing the unloading step, a gas within the vial is discharged along the second flow path coupled between the vial and a radon collection unit.
	claims	1. A method for appraising axle wear of a robot arm of an industrial robot, which comprises the steps of:taking a bi-directional torque profile of at least one axle of the robot arm during at least one working cycle of the industrial robot and providing the torque profile to an evaluation device for an analysis;with the evaluation device, analyzing the torque profile for portions of the torque profile that exceed a previously fixed torque band;with the evaluation device, determining current axle wear by assessing a frequency and/or a curve profile of the portions of the torque profile;with the evaluation device, appraising axle wear of the robot arm based on the current axle wear for determining maintenance requirements; andstoring the torque profile within the evaluation device for later use by a user. 2. The method according to claim 1, which further comprises performing one of:with the evaluation device, measuring the torque profile; andreading out the torque profile from a data memory of the evaluation device. 3. The method according to claim 1, which further comprises, with the evaluation device, analyzing a ratio of a maximum torque value in a specific portion of the torque profile to an averaged torque value in a previously defined time period within the working cycle considered for assessing the axle wear. 4. The method according to claim 1, which further comprises, with the evaluation device, analyzing at least one curve profile of a portion of the torque profile for assessing the axle wear. 5. The method according to claim 4, which further comprises, with the evaluation device, analyzing a slope of the curve profile at a time directly before and possibly after an extreme, taken from the latter up to at least a next-following point of inflection of the curve profile. 6. The method according to claim 1, wherein the evaluation device uses axle-specific parameters for assessing the axle wear. 7. The method according to claim 6, which further comprises determining the axle-specific parameters empirically or by a neural method. 8. The method according to claim 1, which further comprises representing at least one of the torque profiles and a torque band on a display device. 9. The method according to claim 1, which further comprises, with the evaluation device, appraising an absolute axle wear or axle state by taking into account the current axial wear together with a number of working cycles completed so far. 10. The method according to claim 1, which further comprises, with the evaluation device, estimating a time period until a wear limit for the axle is reached by taking into account the current axial wear and/or a number of working cycles completed so far. 11. A system for determining axle wear of a robot arm of an industrial robot, comprising:a data module containing data of a bi-directional torque profile of at least one axle during at least one working cycle of the industrial robot;an analysis module for analyzing portions of the torque profile that exceed a previously fixed torque band; andan assessment module for interpreting a frequency and/or a curve profile of the portions of the torque profile as axle wear of the robot arm, said assessment module, said data module, and said analysis module coupled to each other for exchanging the data with each other, said assessment module storing the axle wear of the robot arm and the torque profile for later use by a user. 12. The system according to claim 11, wherein at least one of said data module, said analysis module and said assessment module, is disposed in a robot controller. 13. The system according to claim 11, further comprising an evaluation device to be connected to a robot controller, at least one of said data module, said analysis module and said assessment module is disposed in said evaluation device. 14. The system according to claim 11, wherein the torque profile can be read out from a robot controller as direct or indirect values. 15. The system according to claim 11, wherein said data module, said analysis module and said assessment module are in each case computer program products each contained in a computer-readable medium.
	abstract	A radiation source of a radiation system of a lithographic projection apparatus includes a primary jet nozzle 10 constructed and arranged to eject a primary gas or liquid 15 in a first direction; a supply 11 for the primary gas or liquid which is to be brought into an excited energy state when ejected from the primary nozzle 10 and is to emit ultraviolet electromagnetic radiation when falling back to a lower energy state; an exciting mechanism such as a laser 30 for bringing the primary gas or liquid into the excited energy state; a secondary jet nozzle 20 constructed and arranged to eject a secondary gas or liquid 25 in the first direction and positioned aside, possibly enclosing, the primary jet nozzle 10; and a supply 21 for the secondary gas or liquid.
049892266	description	DETAILED DESCRIPTION Referring to FIG. 1, there is shown a single-crystal silicon substrate or wafer 1 having highly polished, oppositely facing surfaces 2 and 3. The silicon substrate 1 is initially prepared so that the surfaces 2 and 3 are generally parallel with the so-called [110] crystal planes of the substrate. Such substrates are commercially available and are known as [110] silicon wafers. Although the substrate is shown as being generally rectangular, for the method of forming curved surfaces to be described herein, other shapes such as circular, oval or the like could also be selected, depending upon the needs and interests of the user. Advantageously, thickness variation in the substrate 1 will be less than five micrometers (microns) over a two centimeter surface distance. Shown covering the bottom surface 3, sides, and part of the top surface 2 is a layer of silicon nitride 4. Ridges 5 of silicon nitride are formed on the top surface 2 of the substrate using known film etching techniques. For example, the substrate 1 would typically be first thoroughly cleaned such as in a bath of a solution of sulfuric acid and hydrogen peroxide. After rinsing with water, the substrate is placed in a 900.degree. C. oven so that a layer of silicon dioxide may be dry-grown on the substrate surfaces to a thickness of between five and twenty nm. This oxide layer serves as a stress buffer for the substrate to prevent cracking thereof when later subjected to silicon nitride deposition. Following growth of the silicon dioxide layer (not specifically shown in FIG. 1), the substrate is covered with a silicon nitride layer 4 which will serve several purposes including development of a stress to bend the substrate, acting as a mask to enable selective etching of the substrate, and protecting the side 3 of the substrate opposite the side to be etched. The nitride layer 4 may be deposited at a temperature between 800.degree. and 900.degree. C., using well known low pressure chemical vapor deposition (LPCVD) techniques, to a thickness of about 0.24 microns. The deposited nitride layer develops a tensile stress as will be discussed further later on. It should be understood that the parameters for deposition of the nitride layer could also be successfully employed. Over the nitride layer 4 on one side of the substrate, a photoresist layer is deposited such as by spinning. A mask, containing the pattern to be etched into the substrate 1, is then used to expose the pattern in the photoresist layer. The etching pattern to be used consists of a series of side-by-side, generally parallel grooves, which will facilitate bending the substrate to produce the desired curvature. The width and spacing of the grooves, as well as the ultimate depth, all contribute to determining the amount of bending which will be produced in the substrate. To facilitate the etching of grooves in the silicon crystal substrate 1 in the desired shape (generally parallel side walls), it is advantageous to align those portions of the mask corresponding to the grooves with the lines of intersection between the [111] planes of the substrate crystal perpendicular to the surface and the surface plane, (corresponding to a <110> plane) of the substrate (these imaginary lines of intersection in the substrate surface are called traces). The etching process will occur much faster in the <110> crystal direction than in the <111> direction to thus allow for development of grooves in the substrate having generally parallel sidewalls. After exposure of the mask pattern in the photoresist layer, the photoresist is developed to remove it from those areas where the grooves are to be produced. These areas leave areas of silicon nitride exposed for subsequent removal. Before removal of the exposed nitride areas, a protective layer of photoresist is applied over the nitride layer on the other side of the substrate. The exposed silicon nitride areas are then removed, for example, by use of a conventional plasma chamber. To completely remove the exposed nitride and also the underlying silicon dioxide, the substrate is placed in a standard solution of buffered hydrofluoric acid. A stripping solution may then be used to remove all remaining photoresist material. The condition of the substrate after completing these steps is as shown in FIG. 1, and the substrate is now in a condition where deep grooves may be etched in the substrate itself. Etching of grooves in the silicon crystal substrate is carried out by placing the substrate in a 44% weight/weight solution of potassium hydroxide and water mixed in a 5:2 ratio. This solution serves to etch approximately six hundred times faster in the <110> direction than in the <111> direction and the result is the formation of grooves having substantially vertical side walls (ribs). The etching process continues until the desired thickness 11 (FIG. 2) of the silicon substrate at the bottom of the grooves is achieved. Since the silicon nitride layer 4 on the bottom of the substrate 1 develops a tensile stress with respect to the substrate, the substrate slowly bends as the groove etching process takes place, as shown in FIG. 2, to produce a generally concave curvature on the bottom surface. As earlier indicated, the degree or radius of curvature of the substrate is dependent upon a number of factors such as groove depth and width, rib thickness, substrate thickness 11, and thickness of and stress produced by the silicon nitride layer 4. The inter-relationship and effect of these factors on curvature are known, see Woodbury, R. C. et al, "Curved Silicon Substrates for Multilayer Structures", SPIE Vol. 691 X-Ray Imaging II (1986). To mechanically strengthen the substrate of FIG. 2, a backing or potting material may be placed between ribs 12 developed by etching the grooves. Such potting material may be a conventional polymeric (e.g. epoxy) adhesive which upon hardening would strengthen the substrate and maintain the curved surface (or interface) 3 in the desired shape. It might be noted that by strengthening the substrate in the manner described, further bending of the substrate may be induced, and this should be taken into account when doing the initial bending. If the resulting substrate structure of FIG. 2 is to be used for focusing visible light, the functional surface 7 of the silicon nitride layer 4 would be covered with a reflective thin film coating 13, such as aluminum, gold, or a dielectric coating. If it were to be used to focus x-rays, a periodic-multilayer coating 14 would be applied to the concave side of the substrate. Use of the substrate structure as a Bragg angle diffractor would not require a special additional coating, but would require bending of the structure to produce a surface curvature which would accommodate Bragg angle diffraction requirements. The above-described method and process for producing a curved (cylindrical) surface on a substrate is one of a number of processes which might be used. Another embodiment of the method of the present invention suitable for achieving non-cylindrical bending (i.e., bending about more than one axis) could include the steps described above up to the bending of the substrate and before application of additional films, such as reflective coatings, to the concave surface. At this point, the substrate could next be subjected to high pressure, low temperature oxidation of the exposed portions of silicon for the purpose of achieving oxide growth. Producing oxide growth at lower temperatures reduces susceptability to slip of substrate crystal planes. High pressure, of about 10 atmospheres to 100 atmospheres, is used so that oxidation of the silicon can proceed rapidly enough to cause the formation of a silicon dioxide layer on the sides of the ribs 12 (FIG. 2) and at the bottoms of the grooves 15, all at lower temperatures, e.g., below 700.degree. C. Since silicon dioxide when applied to a silicon substrate produces compressive stresses, the silicon dioxide layers produced as discussed above operate to produce compressive stresses parallel to the ribs 12 and this causes the substrate to bend, with an arc of curvature in the plane of the ribs (rather than in the plane of curvature shown in FIG. 2). The result is a noncylindrical bending, i.e., a bending about more than one axis. After development of a silicon dioxide layer, other coatings such as reflective coatings could be added to the working surface. Still another embodiment of the method of the present invention involves substantially the same steps described in the first embodiment except that the initial silicon dioxide film is ultimately used to produce the etching pattern in the substrate and is thermally grown on the substrate to a thickness of between 0.7 and 2 microns. Such thermal-growth techniques are well known in the art. After growth of the silicon dioxide layer, the mask pattern is produced directly in the silicon dioxide layer, without the use of silicon nitride. Grooves in the silicon are then etched in a standard fashion. After etching, a silicon dioxide layer is thermally grown on all exposed surfaces of the substrate and then silicon dioxide is removed from the working or functional surface to allow the compressive stresses produced by the silicon dioxide on the etched side to bend the substrate, thereby yielding the desired concave curvature on the working side. It is to be understood that the above-described arrangements are only illustrative of the application of the principles of the present invention. Numerous modifications and alternative arrangements may be devised by those skilled in the art without departing from the spirit and scope of the present invention and the appended claims are intended to cover such modifications and arrangements.
	description	This application is a divisional of U.S. application Ser. No. 14/982,047, filed on Dec. 29, 2015, the entire contents of which are hereby incorporated by reference. The present disclosure relates to a pipe restraint device and/or a reactor pressure vessel including the same. Conduit structures such as pipes may be used to supply fluids to a reactor pressure vessel. For example, conduit structures may be welded to nozzle structures. The nozzle structure may be arranged to transport fluid inside a reactor pressure vessel. Depending on the fluid supplied through the conduit structure and/or the operational environment, the conduit structure may deteriorate over time due to corrosion, vibrational fatigue, and/or other factors. Accordingly, as part of regular maintenance, conduit structures may be examined to inspect for damage and/or weakness. A conduit structure may burst if the internal pressure of fluid inside the conduit structure is greater than the strength of the conduit structure at a particular location. In some reactor pressure vessels, the joint between a conduit structure and a nozzle structure may be adjacent to safety related components. Accordingly, in some reactor pressure vessels, a cooling system pool and/or bio-shield wall may be positioned between the safety related components and the conduit structure to limit and/or prevent damage to the safety related components if the conduit structure bursts near the joint between the conduit structure and the nozzle. However, the cooling system pool and bio-shield wall may have a large footprint and take up valuable space surrounding the reactor pressure vessel. At least one example embodiment relates to a restraint device for a conduit structure and/or a reactor pressure vessel including the same. According to an example embodiment, a reactor pressure vessel includes a reactor pressure vessel body, a nozzle structure connected to the reactor pressure vessel body, a conduit structure connected to the nozzle structure, and a restraint device attached around a portion of the conduit structure. The restraint device includes collar parts that have cross-sections corresponding to respective segments of a periphery of the portion of the conduit structure, brackets attached to the nozzle structure, and rods connecting the brackets to the collar parts. The collar parts are connected end-to-end to each other such that a cross-section of the collar parts connected to each other corresponds to the periphery of the portion of the conduit structure. The collar parts are pinned to each other. The brackets are spaced apart from each other around a periphery of the nozzle structure. The conduit structure may be a pipe. The portion of the conduit structure may have an outer diameter that is greater than the outer diameter of a different location of the pipe, and the portion of the conduit structure may be one of integrally formed with the pipe and attached to the pipe. The collar parts may each define threaded holes facing the brackets. The rods may be threaded rods and fit in the threaded holes. The collar parts may be configured to be pivoted around the portion of the conduit structure when the collar parts are unpinned from each other and the rods are removed from the threaded holes. The collar parts may include a first collar part and the second collar part. A size of the first collar part may be different than a size of the second collar part. The restraint device may include one of Belleville washers between the portion of the conduit structure and at least one of the collar parts. The Belleville washers may be configured to absorb loads if the conduit structure breaks. The restraint device may include engineered-crush material between the portion of the conduit structure and at least one of the collar parts. The engineered-crush material may be configured to absorb loads if the conduit structure breaks. The rods may extend parallel to an axial direction of the conduit structure. The collar parts may each include a protruded portion at one end and a recessed portion at an other end. The one end of each of the collar parts may define an opening that crosses through the protruded portion. The other end of each of the collar parts may define a hole that crosses through the recessed portion. The pins may extend through the openings of the protruded portions and the holes of the recessed portions to mate the protruded portion of each of the collar parts to the recessed portion of a corresponding one of the collar parts. The collar parts may be configured to be unpinned from each other if the pins are removed from through the openings of the protruded portions and the holes of the recessed portions. The brackets may be clevis brackets. The clevis brackets may secured to the nozzle structure using clevis pins. The restraint device may include locking nuts that secure the rods to the clevis brackets and the collar parts. According to an example embodiment, a restraint device includes a plurality of collar parts connected end-to-end to each other such that a cross-section of the collar parts connected to each other defines a through hole, brackets spaced apart from the collar parts, and rods connected to the collar parts and the brackets. The collar parts are pinned to each other. The collar parts each include a side that defines a threaded hole. The collar parts may each have a curved cross-section. The collar parts connected to each other may form a tube shape. The collar parts may each include a protruded portion at one end and a recessed portion at an other end. Two of the collar parts may be different sizes. The one end of the collar parts may define an opening that crosses through the protruded portion. The other end of the collar parts may define a hole that crosses through the recessed portion. The pins may extend through the openings of the protruded portions and the holes of the recessed portions to mate the protruded portion of each of the collar parts to the recessed portion of a corresponding one of the collar parts. The collar parts may be configured to be unpinned from each other if the pins are removed from through the openings of the protruded portions and the holes of the recessed portions. The restraint device may further include one of Belleville washers attached to a surface of at least one of the collar parts. The Belleville washers may be in the through-hole if the collar parts are connected to each other. The restraint device may further include engineered-crush material attached to a surface of at least one of the collar parts. The engineered-crush material may be in the through-hole if the collar parts are connected to each other. The rods may extend to the brackets in a direction that is parallel to an axial direction of the through hole defined by the collar parts connected to each other. The brackets may be clevis brackets. At least one example embodiment relates to a method of attaching a restraint device to a conduit structure. According to an example embodiment, a method of attaching a restraint device to a conduit structure is provided. The conduit structure is connected to a nozzle structure that includes brackets on an outer surface of the nozzle structure. The method includes inserting a first end of rods into the brackets such that a remaining part of each of the rods extends from the brackets over a portion of the conduit structure, connecting collar parts to the rods, and pinning the collar parts to each other end-to-end such that the collar parts pinned to each other to wrap around the portion of the conduit structure. The collar parts each include a side that defines a threaded hole. The connecting collar parts to the rods includes inserting a second end of each of the rods into a corresponding threaded hole among the threaded holes defined by the collar parts. The method may further include inserting one of Belleville washers between the portion of the conduit structure and at least one of the collar parts. The method may further include inserting engineered-crush material between the portion of the conduit structure and at least one of the collar parts. The brackets may be clevis brackets connected to the nozzle structure using clevis pins. At least one example embodiment also relates to a method of inspecting an area of a portion of a conduit structure that is covered by a restraint device. According to an example embodiment, a method of inspecting an area of a portion of a conduit structure that is covered by a restraint device is provided. The conduit structure is connected to a nozzle structure that includes brackets on an outer surface of the nozzle structure. The restraint device includes collar parts that are pinned to each other end-to-end around the portion of the conduit structure. The collar parts are connected to the brackets by threaded bolts that are inserted in threaded holes defined by the collar parts. The collar parts each include a protruded portion at one end and a recessed portion at an other end. The protruded portion of each of the collar parts is mated to the recessed portion of a different one of the collar parts. The one end of the collar parts defines an opening that crosses through the protruded portion. The other end of the collar parts defines a hole that crosses through the recessed portion. The restraint device includes pins that are inserted through the openings of the protruded portions and the holes of the recessed portions. The method includes removing the threaded bolts from the threaded holes of the collar parts, unpinning two collar parts from each other by removing the pins that are used to pin the two collar parts to each other, and rotating the collar parts that remain pinned to each other around the portion of the conduit structure to expose the area of the conduit structure. Example embodiments will now be described more fully with reference to the accompanying drawings, in which some example embodiments are shown. Example embodiments, may, however, be embodied in many different forms and should not be construed as being limited to the embodiments set forth herein; rather, these example embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the scope of example embodiments to those of ordinary skill in the art. In the drawings, like reference numerals in the drawings denote like elements, and thus their description may be omitted. It should be understood that when an element or layer is referred to as being “on,” “connected to,” “coupled to,” or “covering” another element or layer, it may be directly on, connected to, coupled to, or covering the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled to” another element or layer, there are no intervening elements or layers present. Like numbers refer to like elements throughout the specification. As used herein, the term “and/or” includes any and all combinations of one or more of the associated listed items. It should be understood that, although the terms first, second, third, etc. may be used herein to describe various elements, components, regions, layers and/or sections, these elements, components, regions, layers, and/or sections should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer, or section from another region, layer, or section. Thus, a first element, component, region, layer, or section discussed below could be termed a second element, component, region, layer, or section without departing from the teachings of example embodiments. Spatially relative terms (e.g., “beneath,” “below,” “lower,” “above,” “upper,” and the like) may be used herein for ease of description to describe one element or feature's relationship to another element(s) or feature(s) as illustrated in the figures. It should be understood that the spatially relative terms are intended to encompass different orientations of the device in use or operation in addition to the orientation depicted in the figures. For example, if the device in the figures is turned over, elements described as “below” or “beneath” other elements or features would then be oriented “above” the other elements or features. Thus, the term “below” may encompass both an orientation of above and below. The device may be otherwise oriented (rotated 90 degrees or at other orientations) and the spatially relative descriptors used herein interpreted accordingly. The terminology used herein is for the purpose of describing various embodiments only and is not intended to be limiting of example embodiments. As used herein, the singular forms “a,” “an,” and “the” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “includes,” “including,” “comprises,” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. Example embodiments are described herein with reference to cross-sectional illustrations that are schematic illustrations of idealized embodiments (and intermediate structures) of example embodiments. As such, variations from the shapes of the illustrations as a result, for example, of manufacturing techniques and/or tolerances, are to be expected. Thus, example embodiments should not be construed as limited to the shapes of regions illustrated herein but are to include deviations in shapes that result, for example, from manufacturing. Thus, the regions illustrated in the figures are schematic in nature and their shapes are not intended to illustrate the actual shape of a region of a device and are not intended to limit the scope of example embodiments. Unless otherwise defined, all terms (including technical and scientific terms) used herein have the same meaning as commonly understood by one of ordinary skill in the art to which example embodiments belong. It will be further understood that terms, including those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. FIG. 1 illustrates a perspective view of a restraint device attached to a conduit structure according to an example embodiment. FIG. 2 illustrates a side view of the restraint device attached to the conduit structure in FIG. 1. FIGS. 3-4 are sectional views of the restraint device attached to the conduit structure in FIG. 1. Referring to FIGS. 1-4, a restraint device 100 according to an example embodiment may include a plurality of collar parts. The restraint device 100 described with reference to FIGS. 1-4 is a separate and distinct structure from the conduit structure 10 and nozzle structure 20 in FIGS. 1-4. The example shown in FIGS. 1-4 includes a first collar part 30 and a second collar part 35, but example embodiments are not limited thereto and the number of collar parts may be an integer greater than or equal to 2. The collar parts, such as the first collar part 30 and the second collar part 35, may be formed of stainless steel, low alloy steel, and/or other metal alloys. However, example embodiments are not limited thereto and other materials may be suitable for forming the collar parts. The collar parts may be different sizes. For example, a width of the first collar part 30 may be greater than a width the second collar part 35, or a width of the second collar part 35 may be greater than a width of the first collar part 30. Also, the first collar part 30 may correspond to a greater portion of the outer periphery of the conduit structure 10 compared to the second collar part 35 and vice versa. One of ordinary skill in the art would appreciate that the material of the collar part and/or dimensions (e.g., thickness) may be selected based on design considerations and the environment where the collar parts are installed. The collar parts may be connected end-to-end to each other. A cross-section of the collar parts may define a through-hole if the collar parts are connected end-to-end to each other. For example, as shown in FIG. 1, the first collar part 30 and second collar part 35 may be connected end-to-end to each other by inserting a protruded portion P of the first collar part 30 into a recessed portion R of the second collar part 35 and by inserting a protruded portion P of the second collar part 35 into a recessed portion R of the first collar part 30. The structures of the first collar part 30 and the second collar part 35 are described later in more detail with reference to FIGS. 5-6 of the present application. The collar parts may be pinned to each other. Additionally, the pins used to secure the collar parts to each other may be removed. For example, as shown in FIG. 2, a pin 40 may be used to secure the protruded portion P of the first collar part 30 to the recessed portion R of the second collar part 35. Similarly, a pin 40 may be used to secure the protruded portion P of the second collar part 35 to the recessed portion R of the first collar part 30. The pin 40 may be formed of the same material as the first collar part 30 and/or second collar part 35. Alternatively, the pin 40 may be formed of a different material than the collar parts 30 and 35. When the collar parts are connected end-to-end to each other, the collar parts may define a collar C. The collar C may be arranged around a portion of the conduit structure 10. The conduit structure 10 may be a pipe, or similar structure for transporting a fluid, and may be connected to the nozzle structure 20. For example, the conduit structure 10 may be connected to the nozzle structure 20 by welding the conduit structure 10 to the nozzle structure 20. In some embodiments, the conduit structure 10 may be a pipe that is configured to deliver a fluid (e.g., a steam and/or water liquid mixture) to a reactor pressure vessel body. The nozzle structure 20 may be connected to the reactor pressure vessel body and configured to deliver the fluid to the reactor pressure vessel body. The conduit structure 10 and/or nozzle structure 20 may be formed of stainless steel, low alloy steel, and/or other metal alloys. However, example embodiments are not limited thereto and other materials for forming the conduit structure 10 and/or nozzle structure 20 may be suitable. The restraint device 100 may attach around a portion of a conduit structure 10. Once attached to the portion of the conduit structure 10, the restraint device 100 may be detached from around the portion of the conduit structure 10. The collar parts such as the first collar part 30 and second collar part 35 may have cross-sections corresponding to respective segments of a periphery of the conduit structure 10. For example, as shown in FIG. 1, in a non-limiting example where the conduit structure 10 may be a tubular pipe, the first collar part 30 may have a curved cross-section that is sized to wrap around a first portion of the conduit structure 10, and the second collar part 35 may have a curved cross-section that is sized to wrap around a second portion of the conduit structure 10. If the first collar part 30 and second part 35 are connected to end-to-end to each other, a cross section of the collar parts 30 and 35 connected to each other may correspond to a periphery (e.g., outer diameter) of the conduit structure 10. Additionally, the collar parts 30 and 35 may be sized to provide a clearance between the periphery (e.g., outer diameter) of the conduit structure 10 and the surface of the collar parts 30 and 35 when the collar parts 30 and 35 wrap around the conduit structure 10. The clearance may be in a range from ⅛ of an inch to 2 inches, but is not limited thereto. The restraint device 100 may include brackets 60. The brackets 60 may be attached to the nozzle structure 20 and/or may be detached from the nozzle structure 20. The brackets 60 may be spaced apart from the collar parts 30 and 35. The brackets 60 may be spaced apart from each other around a periphery of the nozzle structure 20. As shown in FIG. 4, rods 70 (or bolts) may be connected to the brackets 60 and the collar parts 30 and 35. In other words, opposite ends of the rods 70 may be connected to the brackets 60 and the collar parts 30 and 35, respectively. In FIGS. 1-4, a non-limiting example is shown where each of the collar parts 30 and 35 are connected to one of the brackets 60. However, in different implementations, the collar parts may be connected to a plurality of the brackets 60 and/or different numbers of the brackets 60, respectively. For example, one of ordinary skill in the art would recognize that the restraint device 100 shown in FIGS. 1-4 may alternatively include a plurality of the brackets 60 (e.g., 2 or more) connected to the first collar part 30 and/or a plurality of the brackets 60 (e.g., 2 or more) connected to the second collar part 35. Additionally, the number of brackets 60 connected to the first collar part 30 may be different than the number of brackets 60 connected to the second collar part 35. The threaded rods 70 may be inserted into the collar parts 30 and 35. For example, FIG. 5 of the present application illustrates a side of the first collar part 30 may define a threaded hole TH and FIG. 6 of the present application illustrates that a side of the second collar part 35 may define an opening O′. The opening O′ may be a threaded opening O′. The rod 70 shown in FIG. 4 may be a threaded rod. A first end of the rod 70 may be threaded and may be inserted into the threaded hole TH of the first collar part 30 and/or inserted into the opening O′ of the second collar part 35 in order to secure the rod 70 to the first collar part 30 and/or secure the rod 70 to the second collar part 35. A locking nut 65 may be placed around the rod 70 to further secure the rod 70 to the first collar part 30 and/or secure the rod 70 to the second collar part 35. The locking nut 65 may contact a corresponding one of the collar parts such as the first collar part 30 and/or the second collar part 35. When the collar parts such as the first collar part 30 and second collar part 35 are connected end-to-end and wrapped around the conduit structure 10, the threaded hole TH (see FIG. 5) of the first collar part 30 and the opening O′ of the second collar part 35 (see FIG. 6) may face the brackets 60 attached to the nozzle structure 20. The rods 70 may be threaded at ends and may fit in the threaded hole TH (see FIG. 5) of the first collar part 30 and/or the configured to fit in the opening O′ of the second collar part 35 (see FIG. 6). The brackets 60 may be clevis brackets and may be attached to the nozzle structure using a clevis connection 50. A clevis pin 55 may secure each of the brackets 60 to a corresponding one of the clevis connections 50. The brackets 60, clevis connections 50, and/or clevis pins 55 each may be formed of stainless steel, low alloy steel, and/or other metal alloys, but are not limited thereto and other materials may be suitable. The conduit structure 10 may include a raised surface that is configured to limit and/or reduce break loads if the conduit structure 10 breaks near the joint between the conduit structure 10 and the nozzle structure 20. For example, referring to FIG. 3, the portion 15 of the conduit structure 10 where the restraint device 100 may attach around may have an outer dimension and/or a wall thickness that is greater than an outer dimension and/or wall thickness of a different location of the conduit structure 10 where the restraint device 100 is not attached around. For example, if the conduit structure 10 is a pipe, the portion 15 of the pipe 10 may have an outer diameter and/or wall thickness that is greater than an outer diameter and/or wall thickness of a different location of the pipe. The portion 15 of the conduit structure 10 (e.g., pipe) may be integrally formed with the conduit structure 10 (e.g., pipe) or attached to the conduit structure 10. For example, the wall of the conduit structure 10 may be thicker at the portion 15 of the conduit structure 10 compared to other locations of the conduit structure 10. Alternatively, another structure may be welded to the outer periphery of the conduit structure 10 to define the portion 15 of the conduit structure 10, or secured to the outer periphery of the conduit structure 10 using other methods to define the portion 15 of the conduit structure 10. Referring to FIG. 4, a second end of each of the rods 70 may be threaded and may fit in a threaded opening of a corresponding one of the brackets 60 to secure the rods 70 to the brackets 60. Locking nuts 65 may be attached around the rods 70 and tightened to further secure the rods 70 to the brackets 60. Two locking nuts 65 may be spaced apart from each other along each of the rods 70 to secure respective ends of the rods 70 to the collar parts (e.g., 30 and 35) and the brackets 60 respectively. By inserting respective ends of the rods 70 into the collar parts 30 and 35 and the brackets 60, the rods 70 may be arranged to extend parallel to an axial direction of the conduit structure 10. If the rods 70 are not parallel to the axial direction of the conduit structure 10, then the rods 70 may create a moment in the combined structure of conduit structure 10 connected to the nozzle structure 20 and the rods 70 connected to the collar parts 30 and 35 and the brackets 60. The collar parts 30 and 35 in FIGS. 1-4 may be configured to be pivoted around the portion (e.g., portion 15 in FIG. 3) of the conduit structure 10 when the collar parts 30 and 35 are unpinned from each other and the rods 70 are removed from the collar parts 30 and 35. As shown in FIGS. 1 and 3, Belleville washers 45 may be placed between an outer surface of the conduit structure 10 and an inner surface of the collar parts 30 and 35. The Belleville washers 45 may be configured to absorb loads if the conduit structure 10 breaks. The Belleville washers 45 may be formed of the same materials as the collar parts 30 and 35. FIG. 5 is a perspective view of a first collar part of a restraint device according to an example embodiment. Referring to FIG. 5, the first collar part 30 may include a first surface S1 that is opposite a second surface S2. A side of the first collar part 30 may define a threaded hole TH. The threaded hole TH may extend though the side of the first collar part 30 or only partially into the side of the first collar part 30. The first collar part 30 may have a cross-section that corresponds to a segment of a conduit structure. For example, if the conduit structure is curved, the first collar part 30 may have a curved cross-section that corresponds to a segment of a curved shaped (e.g., circle or ellipse, but not limited thereto). The first collar part 30 includes a protruded portion P at one end and a recessed portion R at an other end. The one end of the first collar part 30 may define an opening O that crosses through the protruded portion P. The other end of the first collar part 30 may define a hole H that crosses through the recessed portion. The opening O and hole H may be the same size. Even though FIG. 5 illustrates only one threaded hole TH defined in the side of the first collar part 30, example embodiments are not limited thereto. The number of threaded holes TH defined in the side of the first collar part 30 may be an integer greater than one. For example, the number of threaded holes TH may be greater than or equal to the number of rods 70 that will be inserted in the first collar part 30. When the first collar part 30 defines a plurality of threaded holes TH, the threaded holes TH may be spaced apart from each other. Similarly, the first collar part 30 could be modified to include a plurality of protruded portions P spaced apart from each other at the one end and/or a plurality of the recessed portions R spaced apart from each other at the other end. FIG. 6 is a perspective view of a second collar part of a restraint device according to an example embodiment. Referring to FIG. 6, a side of the second collar part 35 may define an opening O′ and the opening O′ may be threaded. In other words, the opening O′ may be the same as or similar in structure to the threaded hole TH defined in the first collar part 30. The opening O′ may extend though the side of the second collar part 36 or only partially into the side of the second collar part 35. The second collar part 36 may have a cross-section that corresponds to a segment of a conduit structure. For example, the second collar part 36 may have a curved cross-section that corresponds to a segment of a curved shaped (e.g., circle or ellipse, but not limited thereto). The second collar part 35 may include a protruded portion P at one end and a recessed portion R at an other end. The one end of the second collar part 35 may define an opening O that crosses through the protruded portion P. The other end of the second collar part 35 may define a hole H that crosses through the recessed portion. The opening O and hole H may be the same size. Even though FIG. 6 illustrates only one opening O′ defined in the side of the second collar part 35, example embodiments are not limited thereto. The number of openings O′ defined in the side of the second collar part 35 may be an integer greater than one. For example, the number of openings O′ may be greater than or equal to the number of rods 70 that will be inserted in the second collar part 35. When the second collar part 35 defines a plurality of openings O′, the openings O′ may be spaced apart from each other. FIG. 7 illustrates a sectional view of a restraint device attached to a conduit structure according to an example embodiment. Referring to FIG. 7, a restraint device 200 according to an example embodiment may be the same as (or substantially the same as) the restraint device 100 described previously with respect to FIGS. 1-4, except the restraint device 200 shown in FIG. 7 may include engineered-crush materials 47 between the collar parts 30 and 35 instead of the Belleville washers 45 (see FIG. 3). The restraint device 200 described with reference to FIG. 7 is a separate and distinct structure from the conduit structure 10 and nozzle structure 20 in FIG. 7. The engineered-crush materials 47 may be designed to be expendable and/or replaceable parts for one-time use. The engineered-crush materials 47 may be configured to absorb loads if the conduit structure 10 (e.g., a pipe) breaks and/or bursts. The engineered-crush materials 47 may be made from metals, high quality metal alloys, and/or engineered composite materials. For example, suitable alloys for forming the engineered-crush materials 47 include 300-series stainless steels and nickel alloys such as Alloys 600, 625, 718, X-750 or 925, but are not limited thereto. The engineered-crush materials 47 may be formed of using a high quality spring wire as a feed material. For example, several material specifications such as ASTM A-228 music wire or ASTM A679 high-tensile hard drawn wire may be used as the high quality spring wire as a feed material for forming the engineered crush materials 47. The engineered crush materials 47 may be formed from composite materials selected based on their desired properties (e.g., relative stiffness, tensile strength, insulating, and/or non-magnetic). For example, the desired stiffness and/or tensile strength for engineered crush materials 47 may be a design parameter determined through empirical study. Galvanic corrosion may be observed in environments where dissimilar metals and a solute (e.g., water) exist. Accordingly, the engineered-crush materials 47 may be formed using an insulating material having non-magnetic properties in order to limit and/or reduce problems such as galvanic corrosion. The engineered crush materials 47 may be formed in several configurations and structural arrangements. For example, the engineered crush materials 47 may have a form or pattern that is an array of regular cells such as a honeycomb. Alternatively, the engineered-crush material 47 may have an irregular form such as a spun metal-wire pad (e.g., similar to a scrubbing or abrasive pad) or a metal foam. Processing controls may be used to limit the range and variation of gaps or hollow spaces formed between solid portions of the engineered crush materials. For example, one example of a processing control may include using hollow refractory-metal (e.g., tungsten) beads and an interspace metallic or composite material that are bonded together by relatively conventional metal casting method or a hot isostatic-press method. Pre-manufactured foams of various densities can also be post-processed, for example by partially pressing a lower density foam to create a uniformly denser material. The various processes may be use to form pre-engineered full-crush compression lengths with a controlled loading rate and ultimate load capacity. Additionally, 3D-printing or additive manufacturing techniques may be used to form engineered crush materials 47 of finished dimensions that combine both intricate and variable cellular patterns and densities with multiple alloyed or blended materials, including some composites. By using 3D-printing, parts of engineered-crush materials 47 may be created with unique material compositions. For example, one approach may include forming an engineered crush material 47 that includes a metal cellular structure or a metal foam with integrated composite-coated beads containing a soft material. The soft material may be one of graphite powder, chopped filaments, elastomers or polymers (e.g., nitrile-butadiene rubber, neoprene, ethylene-propylene-diene-monomer [EPDM], or fluoroelastomer [FKM]) where the encapsulated soft-material can be squeezed out during the crush event so that it acts as a version of hydraulic brake or damper. Because a part formed from the engineered crush materials 47 may be formed in two or more pieces for one-time use, and is expected to be replaced after an event, this discharge of soft material may be an acceptable behavior. In some example embodiments, when one of the above-described restraint devices is attached around a pipe connected to a nozzle structure of a nuclear reactor, the soft material in the engineered crush materials 47 would need to formed from accepted nuclear-grade materials or from materials approved for nuclear applications. FIG. 8 is a perspective view of a restraint device 300 attached to a conduit structure according to an example embodiment. Referring to FIG. 8, the restraint device 300 shown in FIG. 8 may be the same as (or substantially the same as) the restraint devices 100 and 200 previously described with reference to FIGS. 1-4, 5-6, and 7, except for the number of collar parts attached around the conduit structure 10. The restraint device 300 described with reference to FIG. 8 is a separate and distinct structure from the conduit structure 10 and nozzle structure 20 in FIG. 8. Unlike the restraint devices 100 and 200, the plurality of collar parts in the restraint device 300 may include 3 collar parts: a first collar part 31, a second collar part 33, and a third collar part 37. The collar parts 31, 33, and 37 may be different sizes. The collar parts 31, 33, and 37 may be pinned to each other using the pins 40 or to be unpinned from each other by removing the pins 40. The collar parts 31, 33, and 37 may be connected end-to-end by inserting the protruded portion P of one of the collar parts 31, 33, and 37 into the recessed portion R of a different one of the collar parts 31, 33, and 37. Rods may be connected between the collar parts 31, 33, and 37 and brackets 60 attached to the nozzle structure 20. Referring to FIGS. 1-4, 5-6, and 7, the first collar part 30 and the second collar part 35 may be pinned together if the protruded portion P of the collar parts 30 and 35 are mated to the corresponding recessed portions of the collar parts 30 and 35, based on inserting pins through the openings O of the protruded portions P and the holes H of the recessed portions. The collar parts 30 and 35 may be unpinned from each other by removing the pins 40 from through the openings O of the protruded portions P and the holes H of the recessed portions R. Referring to FIG. 8, the collar parts 31, 33, and 37 may be pinned to each other and/or unpinned from each other similar to the collar parts 30 and 35 described with reference to FIGS. 1-4, 5-6, and 7. According to some example embodiments, various methods may be used to attach any one of the restraint devices 100, 200, and/or 300 described above with reference to FIGS. 1-4, 5-6, 7, and 8 to a conduit structure 10 connected to a nozzle structure 20. The nozzle structure 20 may include brackets 60 on an outer surface of the nozzle structure 20. For example, referring to FIGS. 1-6 and/or 7, in an example embodiment, the method may including inserting a first end of the rods 70 into the brackets 60 such that a remaining part of each of the rods 70 extends from the brackets 60 to over a portion of the conduit structure 10, and connecting the collar parts 30 and 35 to the rods 70. The brackets 60 may be clevis brackets connected to the nozzle structure 20 using clevis pins 55. The first collar part 30 and the second collar part 35 may define a threaded hole TH and an opening O′, respectively. The opening O and hole H may be the same size and similar (or the same) in structure. The connecting collar parts 30 and 35 to the rods 70 may include inserting a second end of each of the rods 70 into a corresponding threaded hole TH (and/or opening O′) among the threaded holes TH (and/or openings O′) defined by the collar parts 30 and 35. For example, FIG. 4 illustrates the second end of the rods 70 may be inserted into the collar parts 30 and 35. Then, the collar parts 30 and 35 may be connected end-to-end to each other and arranged so the collar parts 30 and 35 wrap around the portion of the conduit structure 10 and form the collar C (see FIG. 2). At this time, the collar parts 30 and 35 may be pinning using the pins 40 to each other end-to-end such that the collar parts 30 and 35 pinned to each other wrap around the portion of the conduit structure 10. For example, as shown in FIGS. 1 and/or 5, the first collar part 30 and second collar part 35 may be connected end-to-end to each other by inserting a protruded portion P of the first collar part 30 into a recessed portion R of the second collar part 35 (see FIG. 6) and by inserting a protruded portion P of the second collar part 35 (see FIG. 6) into a recessed portion R of the first collar part 30. The pins 40 may be inserted through the openings defined by the protruded portions P and the holes H defined by the recessed portions R, respectively, of the first and second collar parts 30 and 35 when the first and second collar parts 30 and 35 are connected end-to-end to each other. Optionally, in some example embodiments, the method may further include inserting one of Belleville washers 45 (see FIG. 3) and engineered-crush material 47 (see FIG. 7) between the portion of the conduit structure 10 and at least one of the collar parts 30 and 35. For example, the Belleville washers 45 and/or engineering-crush material 47 may be placed on the conduit structure 10 before the collar parts 30 and 35 are connected end-to-end and arranged to wrap around the portion of the conduit structure 10. In some example embodiments, locking nuts 65 may be placed on the rods 70 to secure the first end of the rods 70 to the brackets 60 and/or to secure the second end of the rods to the collar parts 30 and 35. In an example embodiment, a method of attaching the restraint device 300 to the conduit structure 10 connected to the nozzle structure may be performed similar to the method of attaching the restraint devices 100 and 200 to the conduit structure 10 connected to the nozzle structure 20. However, because the restraint device 300 in FIG. 8 includes three collar parts 31, 33, and 37 instead of the two collar parts 30 and 35 for the restraint devices 100 and 200 in FIGS. 1-4, 5-6, and 7, there are several differences. For example, when attaching the restraint device 300 to the conduit structure 10, respective ends of the rods 70 are connected into the three collar parts 31, 33, and 37 and corresponding brackets 60. The collar parts 31, 33, and 37 are connected to end-to-end to each other to wrap around the portion of the conduit structure 10, then the pins 40 are placed through the recessed portions and protruded portions of the collar parts 31, 33, and 37 mated to each other in order to further secure the collar parts 31, 33, and 37 to each other. Optionally, the method may further include inserting one of Belleville washers 45 (see FIG. 3) and engineered-crush material 47 (see FIG. 7) between the portion of the conduit structure 10 and at least one of the collar parts 31, 33, and 37. Alternatively, in an example embodiment, the collar parts (e.g., 30 and 35) may be connected end-to-end to each other around the portion of the conduit structure 10. Then, pins 40 may be inserted through the protruded portions P and recessed portions R of the collar parts to pin the collar parts to each other. Then, respective ends of rods 70 may be connected to the collar parts and brackets 60 attached to the nozzle structure 20. Also, locking nuts 65 may be used to the secure the rods 70 to the collar parts and the brackets 60. According to some example embodiments, various methods may be used to inspect an area of a conduit structure 10 that is covered by one of the restraint devices 100, 200, and/or 300 described above with reference to FIGS. 1-6, 7, and 8. For example, as described above, any one of the restraint devices 100, 200, and 300 may be attached to a conduit structure 10 connected to a nozzle structure 20 that includes brackets 60 on an outer surface of the nozzle structure 20. Any one of the restraint devices 100, 200, and/or 300 may include collar parts (e.g., 30 and 35 for the restraint devices 100 and 200, or the collar parts 31, 33, and 37 for the restraint device 300) that are pinned to each other end-to-end around the portion of the conduit structure 10. The collar parts may be connected to the brackets 60 by threaded rods 70 (or bolts) that are inserted in threaded holes TH (and/or openings O′) that are defined by the collar parts. The collar parts may each include a protruded portion and one end and a recessed portion at an other end. The protruded portion of each of the collar parts may be mated to the recessed portion of a different one of the collar parts. The one end of the collar parts may define an opening that crosses through the protruded portion P (see FIG. 5). The other end of the collar parts may define a hole H that crosses through the recessed portion R (see FIG. 6). The restraint devices 100, 200, and 300 may include pins 40 that inserted through the openings of the protruded portions and the holes of the recessed portions. In an example embodiment, the method of inspecting the area of the portion of the conduit structure that is covered by one of the restraint devices 100, 200, and/or 300 may include removing the threaded rods 70 (or bolts) from the threaded holes TH (or openings O′) of the collar parts, unpinning two collar parts from each other by removing the pins 40 that are used to pin the two collar parts to each other, and rotating the collar parts that remain pinned to each other around the portion of the conduit structure to expose the area of the conduit structure 10. For example, referring to FIG. 8, in order to inspect the area of the conduit structure 10 that is covered by the third collar part 37, the rod 70 connected between the third collar part 37 and the corresponding bracket 60 may be removed from the third collar part 37. Then, the pin 40 that connects the recessed portion of the third collar part 37 to the protruded portion P of the second collar part 33 may be removed. Then, the pin 40 that connects the protruded portion P of the third collar part 37 to the recessed portion R of the first collar part 31 may be removed. Next, the third collar part 37 may be separated from the first collar part 31 and the second collar part 33 to expose the area of the conduit structure 10 that was previously covered by the third collar part 37 and also leave in place the first and second collar parts 31 and 33 connected to each other around part of the conduit structure 10. The first and second collar parts 31 and 33, which remain pinned to each other around part of the portion of the conduit structure 10 and expose the area that was previously covered by the third collar part 37, may be rotated (or pivoted) in a clockwise direction or a counterclockwise direction around the conduit structure 10. If the first and second collar parts 31 and 33 are rotated a clockwise direction by an amount corresponding to the size of the first collar part 31, then the area of the conduit structure 10 that was previously covered by the first collar part 31 may be exposed and inspected and the second collar part 33 may cover at least part of the area of the conduit structure 10 that was previously covered by the third collar part 37. Alternatively, if the first and second collar parts 31 and 33 are rotated (or pivoted) in a counterclockwise direction by an amount corresponding to the size of the second collar part 33, then the area of the conduit structure 10 that was previously covered by the second collar part 33 may be exposed and inspected and the first collar part 31 may cover at least part of the area of the conduit structure 10 that was previously covered by the third collar part 37. FIG. 9 is a sectional view of a reactor pressure vessel connected to a restraint device attached to a conduit structure according to an example embodiment. A nuclear reactor pressure vessel assembly is described in U.S. patent application Ser. No. 14/751,690 (filed on Jun. 26, 2015), the entire contents of which is incorporated herein in by reference. Although the nuclear reactor pressure vessel in FIG. 9 is illustrated without top head (e.g., reactor vessel head), one of ordinary skill in the art would appreciate that a top head may be connected to a top of the reactor body B shown in FIG. 9 in order to enclose the contents within the reactor body B. Referring to FIG. 9, the nuclear reactor pressure vessel 1000 may include a body B that surrounds a core inlet region 114, a shroud 104, a reactor core 112, stand pipes SP, steam separators 118, a steam dryer 102, and other components. The body B may be the vertical wall of the reactor pressure vessel 1000. The reactor core 112 is over the core inlet region 114. The steam separators 118 are over the reactor core 112 and the stand pipes SP. The steam dryer 102 may be connected on top of the steam separators 118. A nozzle structure such as the reactor pressure vessel main steam nozzle 20 (hereinafter main stream nozzle 20) may be connected to an opening defined in the body B. A conduit structure 10 such as a pipe may be outside the reactor body B and connected (e.g., welded) to the main steam nozzle 20. The conduit structure 10 connected to the main steam nozzle 20 may be configured to remove one or more fluids (e.g., steam) from the reactor pressure vessel 1000. For example, the main steam nozzle 20 may be arranged to transport fluid from the reactor pressure vessel 1000. A feedwater nozzle 122 may be connected to a feedwater opening defined in the body B. A conduit structure 125 such as a main feedwater pipe 125 may be outside the reactor body B and connected (e.g., welded) to the feedwater nozzle 122. The main feedwater pipe 125 connected to the feedwater nozzle 122 may be configured to supply one or more fluids (e.g., water and/or steam) to the reactor pressure vessel 1000. For example, the feedwater nozzle 122 may be arranged to transport fluid inside the reactor pressure vessel 1000. One of the restraint devices 100, 200, and 300 according to example embodiments described above in FIGS. 1-6, 7, and 8 (and/or variations thereof) may be attached around a portion of the conduit structure 10 that is outside the body B and adjacent to the joint between the conduit structure 10 and the main steam nozzle 20. Although not illustrated, various safety related components may be arranged outside of the body B, near the joint between the conduit structure 10 and the main steam nozzle 20. By attaching one of the above-described restraint devices 100, 200, and 300 around the conduit structure 10, the restraint device may protect the safety-related components from fluids if the conduit structure 10 bursts and/or breaks and may take up a smaller footprint than a cooling system pool and/or bio-shield wall used in general reactor pressure vessels. Additionally, the restraint devices 100, 200, and 300 are configured to limit and/or contain loads created by a break in the conduit structure 10 without overloading other structures. For example, the conduit structure 10 may include a portion 15 (see FIG. 3) with a raised surface to limit and/or restrict loads created from a break in the conduit structure 10. Also, Belleville washers 45 and/or engineered-crush material 47 may be positioned between the conduit structure 10 and the collar parts wrapped around the conduit structure 10 in order to absorb loads if the conduit structure 10 breaks or bursts. Additionally, because the collar parts may be connected end-to-end to each other around a portion of the conduit structure 10, the collar parts may be configured to at least partially contain a break in the conduit structure 10 at a location surrounded by the collar parts (e.g., 31 and 35). Additionally, the restraint devices 100, 200, 300 may be assembled and/or disassembled using a simplified process. Thus, in some example embodiments, the restraint devices 100, 200, 300 may be attached to the conduit structure 10 connected to the main steam nozzle 20 using a simplified process. Additionally, for maintenance inspection, the restraint devices 100, 200, and 300 may be quickly disassembled to gain access to locations of the conduit structure 10 and/or nozzle structure 20. Alternatively, for maintenance inspection and/or for responding to a conduit structure burst, in some example embodiments, one or more of the collar parts of the restraint devices 100, 200, and 300 may be removed and the remaining collar parts may be rotated (or pivoted) to inspect a location of the conduit structure 10 and/or at least partially contain a location of conduit structure burst or break. One of ordinary skill in the art would appreciate that the restraint devices 100, 200, 300 described above is not limited to being attached around the conduit structure 10 and may be used in other applications as well. For example, one of the restraint devices 100, 200, and 300 according to example embodiments described above in FIGS. 1-6, 7, and 8 (and/or variations thereof) may be attached around a portion of the main feedwater pipe 125 that is outside the body B and adjacent to the joint between the main feedwater pipe 125 and the feedwater nozzle 122. By attaching one of the above-described restraint devices 100, 200, and 300 around the main feedwater pipe 125, the restraint device may protect the safety-related components from fluids if the main feedwater pipe 125 bursts and/or breaks and may take up a smaller footprint than a cooling system pool and/or bio-shield wall used in general reactor pressure vessels. Additionally, the restraint devices 100, 200, and 300 are configured to limit and/or contain loads created by a break in the main feedwater pipe 125 without overloading other structures. For example, similar to the conduit structure 10, the main feedwater pipe 125 may include a portion with a raised surface to limit and/or restrict loads created from a break in the main feedwater pipe 125 (see the portion 15 on the conduit structure 10 in FIG. 3). Also, Belleville washers 45 and/or engineered-crush material 47 may be positioned between the main feedwater pipe 125 and the collar parts wrapped around the main feedwater pipe 125 in order to absorb loads if the main feedwater pipe 125 breaks or bursts. Additionally, because the collar parts may be connected end-to-end to each other around a portion of the main feedwater pipe 125, the collar parts may be configured to at least partially contain a break in the main feedwater pipe 125 at a location surrounded by the collar parts. Additionally, the restraint devices 100, 200, 300 may be assembled and/or disassembled using a simplified process. Thus, in some example embodiments, the restraint devices 100, 200, 300 may be attached to the main feedwater pipe 125 connected to the feedwater nozzle 122 using a simplified process. Additionally, for maintenance inspection, the restraint devices 100, 200, and 300 may be quickly disassembled to gain access to locations of the main feedwater pipe 125 and/or feedwater nozzle 122. Alternatively, for maintenance inspection and/or for responding to a conduit structure burst, in some example embodiments, one or more of the collar parts of the restraint devices 100, 200, and 300 may be removed and the remaining collar parts may be rotated (or pivoted) to inspect a location of the main feedwater pipe 125 and/or at least partially contain a location of main feedwater pipe 125 burst or break. While a number of example embodiments have been disclosed herein, it should be understood that other variations may be possible. Such variations are not to be regarded as a departure from the spirit and scope of the present disclosure, and all such modifications as would be obvious to one skilled in the art are intended to be included within the scope of the following claims.
	claims	1. A modular container system for radioactive waste comprising:a plurality of enclosure envelopes each of which defines a cavity configured to receive radioactive waste; anda plurality of modular shielding inserts configured to be positioned in the cavity of each of the plurality of enclosure envelopes;wherein each of the plurality of enclosure envelopes has approximately the same size cavity;wherein the plurality of enclosure envelopes have different grades to accommodate different activity levels of radioactive waste and/or containment requirements;wherein the different grades of the plurality of enclosure envelopes differ structurally from each other; andwherein the plurality of modular shielding inserts include different grades of shielding inserts having different thicknesses and/or being made of different material to accommodate the different activity levels of radioactive waste. 2. The modular container system of claim 1 wherein each of the plurality of enclosure envelopes comprises a lid forming at least part of the enclosure envelope, wherein the lids for the plurality of enclosure envelopes have different grades to accommodate the different activity levels of radioactive waste and/or containment requirements. 3. The modular container system of claim 2 wherein the different grades of the lid vary structurally from each other. 4. The modular container system of claim 1 wherein at least one grade of the plurality of enclosure envelopes comprises a lid forming at least part of the enclosure envelope, wherein an interior side of the lid is coupled to a shielding insert and wherein the shielding insert can be decoupled from the lid from an exterior side of the lid. 5. The modular container system of claim 1 wherein at least one grade of the plurality of enclosure envelopes is made of stainless steel. 6. The modular container system of claim 1 wherein at least one grade of the plurality of enclosure envelopes is made of carbon steel. 7. The modular container system of claim 1 comprising:a plurality of modular containers each of which includes a different grade of the plurality of enclosure envelopes; anda reusable transport overpack sized to enclose any of the plurality of modular containers during transport. 8. The modular container system of claim 1 wherein the plurality of enclosure envelopes includes a first enclosure envelope configured to be used with a first class of radioactive waste and a second enclosure envelope configured to be used with a second class of radioactive waste that is more radioactive than the first class of radioactive waste. 9. The modular container system of claim 8 wherein the plurality of enclosure envelopes includes a third enclosure envelope configured to be used with a third class of radioactive waste that is more radioactive than the second class of radioactive waste. 10. The modular container system of claim 1 wherein the plurality of modular shielding inserts includes a first set of modular shielding inserts configured to be used with radioactive waste having a first activity level and a second set of modular shielding inserts configured to be used with radioactive waste having a second activity level that is greater than the first activity level. 11. The modular container system of claim 1 wherein the plurality of modular shielding inserts includes a first set of modular shielding inserts configured to be used with a first class of radioactive waste and a second set of modular shielding inserts configured to be used with a second class of radioactive waste that is more radioactive than the first class of radioactive waste. 12. A modular container for radioactive waste comprising:a main body;a lid coupled to the top of the main body, the lid and the main body forming an enclosed cavity configured to receive radioactive waste; anda plurality of modular shielding inserts configured to be positioned in the cavity;wherein the plurality of modular shielding inserts include different grades of shielding inserts having different thicknesses and/or being made of different material to accommodate different activity levels of radioactive waste; andwherein the plurality of modular shielding inserts are separate from any support frameworks used to hold radioactive waste that may be present in the modular container. 13. The modular container of claim 12 comprising a shielding insert coupled to an interior side of the lid, wherein the shielding insert can be decoupled from the lid from an exterior side of the lid. 14. The modular container of claim 12 wherein the plurality of modular shielding inserts includes a first set of modular shielding inserts configured to be used with radioactive waste having a first activity level and a second set of modular shielding inserts configured to be used with radioactive waste having a second activity level that is greater than the first activity level. 15. The modular container of claim 12 wherein the main body is made of stainless steel. 16. The modular container of claim 12 wherein the main body is made of carbon steel. 17. A modular container system comprising:a plurality of the modular containers recited in claim 12 each of which includes a different grade of the lid and the main body to accommodate different activity levels of radioactive waste; anda reusable transport overpack sized to enclose any of the plurality of modular containers during transport. 18. A modular container system for radioactive waste comprising:a plurality of standardized enclosure envelopes having different grades that differ structurally from each other to accommodate different activity levels of radioactive waste and/or containment requirements; anda plurality of modular shielding inserts configured to be positioned in the cavity of each of the plurality of standardized enclosure envelopes;wherein each of the plurality of standardized enclosure envelopes defines a cavity configured to receive radioactive waste;wherein the different grades of the plurality of standardized enclosure envelopes define approximately the same sized cavity; andwherein the plurality of modular shielding inserts include different grades of shielding inserts having different thicknesses and/or being made of different material to accommodate the different activity levels of radioactive waste. 19. The modular container system of claim 18 wherein each of the plurality of standardized enclosure envelopes comprises a lid forming at least part of the standardized enclosure envelope, wherein the lids for the plurality of standardized enclosure envelopes have different grades to accommodate the different activity levels of radioactive waste and/or containment requirements. 20. The modular container system of claim 19 wherein the different grades of the lids vary structurally from each other. 21. The modular container system of claim 18 wherein at least one grade of the plurality of standardized enclosure envelopes comprises a lid forming at least part of the standardized enclosure envelope, wherein an interior side of the lid is coupled to a shielding insert and wherein the shielding insert can be decoupled from the lid from an exterior side of the lid. 22. The modular container system of claim 18 wherein at least one grade of the plurality of standardized enclosure envelopes is made of stainless steel. 23. The modular container system of claim 18 wherein at least one grade of the plurality of standardized enclosure envelopes is made of carbon steel. 24. The modular container system of claim 18 comprising:a plurality of modular containers each of which includes a different grade of the plurality of standardized enclosure envelopes; anda reusable transport overpack sized to enclose any of the plurality of modular containers during transport. 25. The modular container system of claim 18 wherein the plurality of enclosure envelopes includes a first enclosure envelope configured to be used with a first class of radioactive waste and a second enclosure envelope configured to be used with a second class of radioactive waste that is more radioactive than the first class of radioactive waste. 26. The modular container system of claim 25 wherein the plurality of enclosure envelopes includes a third enclosure envelope configured to be used with a third class of radioactive waste that is more radioactive than the second class of radioactive waste. 27. The modular container system of claim 18 wherein the plurality of modular shielding inserts includes a first set of modular shielding inserts configured to be used with radioactive waste having a first activity level and a second set of modular shielding inserts configured to be used with radioactive waste having a second activity level that is greater than the first activity level. 28. The modular container system of claim 18 wherein the plurality of modular shielding inserts includes a first set of modular shielding inserts configured to be used with a first class of radioactive waste and a second set of modular shielding inserts configured to be used with a second class of radioactive waste that is more radioactive than the first class of radioactive waste. 29. A modular container system for radioactive waste comprising:a plurality of enclosure envelopes each of which defines a cavity configured to receive radioactive waste;wherein each of the plurality of enclosure envelopes has approximately the same size cavity;wherein the plurality of enclosure envelopes have different grades to accommodate different activity levels of radioactive waste and/or containment requirements;wherein the different grades of the plurality of enclosure envelopes differ structurally from each other;wherein at least one grade of the plurality of enclosure envelopes comprises a lid forming at least part of the enclosure envelope, an interior side of the lid being coupled to a shielding insert; andwherein the shielding insert can be decoupled from the lid from an exterior side of the lid. 30. The modular container system of claim 29 wherein each of the plurality of enclosure envelopes comprises a lid forming at least part of the enclosure envelope, wherein the lids for the plurality of enclosure envelopes have different grades to accommodate the different activity levels of radioactive waste and/or containment requirements. 31. The modular container system of claim 30 wherein the different grades of the lid vary structurally from each other. 32. The modular container system of claim 29 wherein at least one grade of the plurality of enclosure envelopes is made of stainless steel. 33. The modular container system of claim 29 wherein at least one grade of the plurality of enclosure envelopes is made of carbon steel. 34. The modular container system of claim 29 comprising:a plurality of modular containers each of which includes a different grade of the plurality of enclosure envelopes;a reusable transport overpack sized to enclose any of the plurality of modular containers during transport. 35. The modular container system of claim 29 wherein the plurality of enclosure envelopes includes a first enclosure envelope configured to be used with a first class of radioactive waste and a second enclosure envelope configured to be used with a second class of radioactive waste that is more radioactive than the first class of radioactive waste. 36. The modular container system of claim 35 wherein the plurality of enclosure envelopes includes a third enclosure envelope configured to be used with a third class of radioactive waste that is more radioactive than the second class of radioactive waste. 37. A modular container system for radioactive waste comprising:a plurality of standardized enclosure envelopes having different grades that differ structurally from each other to accommodate different activity levels of radioactive waste and/or containment requirements;wherein at least one grade of the plurality of standardized enclosure envelopes comprises a lid forming at least part of the standardized enclosure envelope, an interior side of the lid being coupled to a shielding insert; andwherein the shielding insert can be decoupled from the lid from an exterior side of the lid. 38. The modular container system of claim 37 wherein each of the plurality of enclosure envelopes comprises a lid forming at least part of the enclosure envelope, wherein the lids for the plurality of enclosure envelopes have different grades to accommodate the different activity levels of radioactive waste and/or containment requirements. 39. The modular container system of claim 38 wherein the different grades of the lid vary structurally from each other. 40. The modular container system of claim 37 wherein at least one grade of the plurality of enclosure envelopes is made of stainless steel. 41. The modular container system of claim 37 wherein at least one grade of the plurality of enclosure envelopes is made of carbon steel. 42. The modular container system of claim 37 comprising:a plurality of modular containers each of which includes a different grade of the plurality of enclosure envelopes;a reusable transport overpack sized to enclose any of the plurality of modular containers during transport. 43. The modular container system of claim 37 wherein the plurality of enclosure envelopes includes a first enclosure envelope configured to be used with a first class of radioactive waste and a second enclosure envelope configured to be used with a second class of radioactive waste that is more radioactive than the first class of radioactive waste. 44. The modular container system of claim 43 wherein the plurality of enclosure envelopes includes a third enclosure envelope configured to be used with a third class of radioactive waste that is more radioactive than the second class of radioactive waste.
	description	The present invention relates to a scintillator, a method of forming the same, and a radiation detection apparatus. Some radiation detection apparatuses (or radiation imaging apparatuses) are configured to convert radiation into light using a scintillator and detect the light using photoelectric conversion elements. A scintillator sometimes varies in characteristics in accordance with irradiation with radiation. Such a phenomenon is also called “bright burn” (see Japanese Patent Laid-Open No. 2016-88988). Japanese Patent Laid-Open No. 2016-88988 discloses, as an example of a method of suppressing bright burn, a method of letting a scintillator include atoms as monovalent cations more than an activator agent for improving the luminous efficiency of the scintillator. However, such a composition will cause a deterioration in the crystallinity of the scintillator or a reduction in the transmission efficiency of light in the scintillator. The present invention provides a technique advantageous in both suppressing bright burn and improving the quality of a scintillator. One of the aspects of the present invention provides a scintillator having a columnar crystal structure vapor-deposited on a substrate, wherein each column of the crystal structure contains an alkali halide metal compound as a host material, and further contains, as an additive, a compound of a precious metal as a metal having lower ionization tendency than hydrogen (H), with the additive having a lower melting point than the host material. Further features of the present invention will become apparent from the following description of exemplary embodiments with reference to the attached drawings. The preferred embodiments of the present invention will be described below with reference to the accompanying drawings. Note that the respective drawings are merely illustrated for the purpose of describing structures or configurations, and the dimensions of the illustrated respective members do not necessarily reflect actual dimensions. In addition, the same reference numerals denote the same elements in the respective drawings, and a repetitive description will be omitted. FIGS. 1A and 1B are schematic views for explaining a method of evaluating bright burn. As shown in FIG. 1A, bright burn is evaluated with respect to a radiation detection apparatus AP obtained by bonding a scintillator 2 vapor-deposited on a substrate 1 onto a sensor substrate (sensor unit) 3 on which a plurality of photoelectric conversion elements are arrayed. The scintillator 2 generates light (scintillation light) upon receiving radiation. The sensor substrate 3 detects this light. Assume that the radiation detection apparatus AP can detect radiation with this configuration. The scintillator 2 is generally formed on the substrate 1 by a vapor deposition method under a nearly vacuum environment (for example, 0.01 Pa or less) using a vapor deposition apparatus, and has a columnar (needle-like) crystal structure in this case. Each column of the crystal structure includes an alkali halide metal compound as a host material. Assume that cesium iodide (CsI) is used as the host material in this case. In addition, in this case, each column of the scintillator 2 contains thallium (Tl) as an activator agent for improving luminous efficiency. Note that the host material that can be used is not limited to the one exemplified in this case. For example, it is possible to use another type of fluorescent material such as sodium iodide (NaI) or potassium iodide (KI). In addition, the activator agent that can be used is not limited to the one exemplified in this case. For example, it is possible to use another type of activator agent such as europium (Eu) or indium (In). FIG. 1B shows a state in which a radiation shielding member 4 is arranged on the radiation detection apparatus AP. Referring to FIG. 1B, a portion of the scintillator 2 which is not covered by the radiation shielding member 4 is defined as a “non-covered portion 21” and a portion of the scintillator 2 which is covered by the radiation shielding member 4 is defined as a “covered portion 22”. When the radiation detection apparatus AP is irradiated with radiation in this state, the radiation enters the non-covered portion 21, and no radiation enters the covered portion 22. In this case, after the end of irradiation with radiation, a characteristic (sensitivity or conversion efficiency from radiation to light) difference sometimes occurs between the portions 21 and 22. More specifically, carriers (electron-hole pairs) are generated at the non-covered portion 21 which radiation has entered, and recombine to generate scintillation light. At this time, at the non-covered portion 21, such carriers are sometimes unintentionally trapped at an energy trap level (to be simply referred to as a trap level hereinafter) originating from lattice defects or the like. This can cause recombination at an unexpected timing after the end of irradiation with radiation or unexpected characteristic variation at the time of further irradiation with radiation. Such a phenomenon is called bright burn. More specifically, a trap level is an energy level that can be formed in a band gap (valence band—conduction band energy band) in the crystal structure of the scintillator 2. This is an energy level at which carriers can be trapped. For example, a trap level can be formed by, for example, a lattice defect (so-called iodine leakage) caused by the leakage of one or more iodine atoms mainly in the crystal structure of the scintillator 2 made of cesium iodide. In addition, a trap level can be formed because of the presence of thallium as an activator agent. In general, a trap level caused by the presence of thallium is an energy level “deeper (at a position near the middle of the band gap) than a trap level originating from a lattice defect. When, therefore, a lattice defect is present near thallium, carriers are trapped at a trap level for a relatively long period of time. This causes the above bright burn. Bright burn sometimes remains for, for example, several hours to several days after irradiation with radiation. The following literatures can give additional explanations to the above description: Kazuo Sakai et al., “Determination of Electronic Properties of Deep Level Impurities in Semiconductor”, Seisan-Kenkyu, Volume 25, Issue 7, pp. 278-287, July 1973 Tsugunori Okumura, “DLTS: Deep Level Transient Spectroscopy”, HYBRIDS, Vol, 7, No. 5, pp. 29-36, 1991 As described above, bright burn can occur after the end of irradiation with radiation, and a characteristic difference can occur between the portions 21 and 22. Bright burn is evaluated by measuring the luminance of the scintillator 2 when it is irradiated with radiation having relatively low radiation intensity (dose) after so-called “burning” is performed by irradiating the scintillator 2 with radiation having relatively high radiation intensity. In this specification, an evaluation value BB(t) of bright burn is expressed as:BB(t)={a(t)/b(t)}/{a(0)/b(0)}−1where a(0): the luminance value (per unit volume; the same hereinafter) of the non-covered portion 21 before burning b(0): the luminance value of the covered portion 22 before burning a(t): the luminance value of the non-covered portion 21 after the lapse of a time t since burning b(t): the luminance value of the covered portion 22 after the lapse of a time t since burning According to the above mathematic expression, a(0)/b(0) represents the luminance value ratio between the non-covered portion 21 and the covered portion 22 before burning. Assume that in this case, the luminance distribution of the scintillator 2 is uniform between the non-covered portion 21 and the covered portion 22.a(0)/b(0)=1 Subsequently, as shown in FIG. 1B, the radiation shielding member 4 was placed on the substrate 1, and burning was performed. Thereafter, the radiation shielding member 4 was removed, and the luminance values of the non-covered portion 21 and the covered portion 22 after the lapse of the time t were measured to obtain a(t)/b(t). In this case, when the above bright burn has occurred,a(t)/b(t)>1andBB(t)>0In contrast to this, when bright burn has been suppressed or reduced,BB(t)≈0That is, as the evaluation value BB(t) decreases, bright burn is suppressed or reduced more, and hence the quality of the scintillator 2 is high. When the bright burn evaluation value BB(t) increases, a signal obtained by a given shooting operation may be superimposed on a signal obtained by the immediately preceding shooting operation. This may cause afterimage and artifacts in images obtained by shooting, and hence may cause a deterioration in the quality of images. Such a problem can occur when, for example, radiography is continuously performed (so-called continuous radiography is performed). In this case, when the change amount of luminance value between the non-covered portion 21 and the covered portion 22 after burning is sufficiently smaller (for example, 1/10 or less) than noise (noise component, so-called dark noise, originating from a dark current) in the photoelectric conversion elements on the sensor substrate 3, the change amount of luminance value is buried in noise and becomes difficult to discriminate. For this reason, when the S/N ratio of the photoelectric conversion elements on the sensor substrate 3 in general use is set to 30 dB (20×log10(S/N)=30, that is, S/N≈33), the target value of the evaluation value BB(t) is preferably set to 0.3% or less. FIG. 2 is a schematic view for explaining a method of forming the scintillator 2 according to this embodiment. Although described in detail later, according to this embodiment, in order to suppress or reduce the bright burn described above, the scintillator 2 further includes an additive having a lower melting point than the host material (to be sometimes simply referred to as an “additive” hereinafter in the specification). As this additive, a compound of a precious metal as a metal having lower ionization tendency than hydrogen (H) is used. Such precious metals include gold (Au), silver (Ag), platinum (Pt), palladium (Pd), rhodium (Rh), iridium (Ir), ruthenium (Ru), osmium (Os), copper (Cu), and mercury (Hg). At least one of them is used. When a precious metal is copper or silver, a corresponding compound is, for example, an iodide such as copper iodide or silver iodide or a bromide such as copper bromide or silver bromide. The scintillator 2 can be formed by using a known vapor deposition apparatus 5. Vapor deposition processing by the vapor deposition apparatus 5 is performed by using electron beam vapor deposition as a suitable method. In this embodiment, the vapor deposition apparatus 5 includes a chamber 50, a holding unit 51, and evaporation units 52A, 52B, and 52C. The chamber 50 provides a space for performing vapor deposition. A controller (not shown) can control the pressure and temperature inside the chamber 50. When performing vapor deposition, the controller maintains the inside of the chamber 50 in a nearly vacuum state (0.01 Pa or less) and at a desired temperature (for example, about 80° C. to 140° C.). The holding unit 51 rotatably holds the substrate 1 as a vapor deposition processing target as indicated by the arrow in FIG. 2, and rotates the substrate 1 in vapor deposition processing. The evaporation unit 52A reserves cesium iodide as a source material (evaporation source material) in a crucible, heats the material up to a temperature equal to or higher than its melting point in vapor deposition processing, and emits the vaporized material toward the substrate 1 held by the holding unit 51. The evaporation unit 52B reserves thallium iodide as a source material in a crucible, heats the material up to a temperature equal to or higher than its melting point in vapor deposition processing, and emits the vaporized material toward the substrate 1. The evaporation unit 52C reserves copper as a source material in a crucible, heats the material up to a temperature equal to or higher than its melting point in vapor deposition processing, and emits the vaporized material toward the substrate 1. The evaporation units 52A to 52C emit vaporized materials in parallel. Although described in detail later, this operation will form the scintillator 2 including an activator agent and additives on the substrate 1 so as to have a columnar crystal structure. The present inventors have found from extensive studies that bright burn is suppressed or reduced by letting the scintillator 2 contain the above additives. The mechanism of this effect is considered as follows. That is, according to this embodiment, the additives contained in the scintillator 2 are coupled to the trap level or cancel the effect of the trap level. Alternatively, the additives provide carriers (free electrons) that can be trapped at the trap level so as to let the trap level capture the carriers in advance. This allows carriers (electron-hole pairs), generated at the time of subsequent irradiation with radiation, to properly recombine to generate scintillation light without being trapped at the trap level. As a result, the bright burn described above is suppressed or reduced. The additives contained in the scintillator 2 can be checked by, for example, X-ray diffraction. Because the scintillator 2 has deliquescence, for example, the scintillator 2 is dissolved in water and then vaporized and dried to obtain the powder of the scintillator 2. In this embodiment, copper is used as the above precious metal. When X-ray diffraction is performed for this powder, copper as a pure metal is not detected, while CuI (melting point of 605° C.), Cs3Cu2I5 (melting point of 390° C.), and CsCu2I3 (melting point of 383° C.) are detected. That is, the above additives are copper compounds (CuI, Cs3Cu2I5, and CsCu2I3), each of which has a lower melting point than cesium iodide as the host material (melting point of 621° C.). In this embodiment, the above additives do not have higher melting point than the host material, and hence are not contained at least as granular or powdery impurities as a result of vapor deposition processing by the vapor deposition apparatus 5. In other words, elements (atoms) constituting additives are considered to be incorporated as constituent atoms of the columnar crystal structure of the scintillator 2 in the crystal structure. Accordingly, these additives are not deposited as solids. This improves the crystallinity of the scintillator 2. Accordingly, the light transmission characteristic of the scintillator improves, that is, the quality of the scintillator 2 improves. Experimental results based on several conditions will be described below with reference to FIG. 3. FIG. 3 shows a comparative example and first to sixth experimental examples. The comparative example corresponds to a comparative example containing no precious metal additives. As the comparative example, the scintillator 2 was formed, which has a columnar crystal structure containing cesium iodide as a host material and thallium as an activator agent. More specifically, the evaporation units 52A and 52B respectively reserve cesium iodide and thallium iodide, vaporize them, and emit them to the substrate 1. As the substrate 1, a substrate was prepared, which was obtained by forming an aluminum film (Al with a thickness of 200 nm) as a reflecting layer on a silicon substrate with a predetermined thickness and stacking a silicon oxide film (SiO2 with a thickness of 100 nm) on the aluminum film. Vapor deposition processing was performed under the conditions that the pressure inside the chamber 50 was 0.01 Pa or less, the temperature of the substrate 1 was about 80° C. to 140° C., and the rotational speed of the substrate 1 by the holding unit 51 was 60 rpm. Assume that the evaporation unit 52C is not installed/driven in the comparative example. After the vapor deposition processing, when the temperature of the substrate 1 having undergone processing decreased to room temperature, SEM (scanning electron microscope) observation and ICP (inductively coupled plasma) analysis were performed with respect to the scintillator 2 formed on the substrate 1. In the comparative example, a columnar crystal structure with a film thickness of about 750 μm and a thallium concentration of about 0.42 mol % was obtained as the scintillator 2. MTF (Modulation Transfer Function) evaluation at spatial frequency 2 LP/mm (line pairs/mm) based on the edge method was performed with respect the scintillator 2 described above by using radiation quality RQAS complying with the international standards. For comparison with the second experimental example to be described later, the MTF evaluation value of the comparative example was set to “100” in FIG. 3. In addition, the bright burn evaluation described above with reference to FIG. 1B was performed with respect to the scintillator 2 described above. First of all, in the state shown in FIG. 1B (the radiation shielding member 4 is arranged), the scintillator 2 was irradiated (burnt) with radiation under radiation irradiation conditions including a tube voltage of about 80 kV and a dose of about 2.9 mGy. Subsequently, the radiation shielding member 4 was removed, and the scintillator 2 was irradiated with radiation through a copper plate with a thickness of 0.6 mm under the conditions that a tube voltage was about 70 kV and a dose was about 2 μGy, after the lapse of 2.5 minutes, 10 minutes, and 30 minutes. With this operation, the bright burn evaluation value BB (2.5 min), the bright burn evaluation value BB (10 min), and the bright burn evaluation value BB (30 min) were obtained. For the sake of comparison, the bright burn evaluation value after the lapse of 2.5 min was set to “100” in FIG. 3. In this case, the bright burn evaluation value after the lapse of 10 min (that is, BB(10 min)/BB(2.5 min)×100) was 95. In addition, the bright burn evaluation value after the lapse of 30 min (that is, BB(30 min)/BB(2.5 min)×100) was 91. The first experimental example corresponds to an experimental example of this embodiment including additives. In the first experimental example, the evaporation unit 52C is driven, together with the evaporation units 52A and 52B. The evaporation unit 52C reserves copper, vaporizes the copper, and emits it toward the substrate 1. Other conditions are the same as those in the comparative example. With this operation, the scintillator 2 further containing a copper compound as an additive was formed. As a result of SEM observation and ICP analysis, in the first experimental example, a columnar crystal structure having a film thickness of about 720 μm, a thallium concentration of about 0.45 mol %, and an additive concentration of 3 ppm was obtained as the scintillator 2. In the first experimental example, MTF evaluation and bright burn evaluation were performed according to the same procedure as in the comparative example. In the first experimental example, the MTF evaluation value was 112. In addition, in the first experimental example, the bright burn evaluation values after the lapse of 2.5 min, 10 min, and 30 min were 60, 51, and 38, respectively. That is, bright burn was suppressed or reduced to about 60% as compared with the comparative example. The second experimental example corresponds to an experimental example of this embodiment containing more additives than the first experimental example. As a result of SEM observation and ICP analysis, in the second experimental example, a columnar crystal structure having a film thickness of about 585 μm, a thallium concentration of about 0.75 mol %, and an additive concentration of 10 ppm was obtained as the scintillator 2. In the second experimental example as well, MTF evaluation and bright burn evaluation were performed according to the same procedure as in the comparative example. In the second experimental example, the MTF evaluation value was 127. In addition, in the second experimental example, the bright burn evaluation values after the lapse of 2.5 min, 10 min, and 30 min were 46, 39, and 36, respectively. That is, bright burn was suppressed or reduced. The third experimental example corresponds to an experimental example of this embodiment containing more additives than the second experimental example. As a result of SEM observation and ICP analysis, in the third experimental example, a columnar crystal structure having a film thickness of about 655 μm, a thallium concentration of about 0.43 mol %, and an additive concentration of 30 ppm was obtained as the scintillator 2. In the third experimental example as well, MTF evaluation and bright burn evaluation were performed according to the same procedure as in the comparative example. In the third experimental example, the MTF evaluation value was 111. In addition, in the third experimental example, the bright burn evaluation values after the lapse of 2.5 min, 10 min, and 30 min were 34, 32, and 30, respectively. That is, bright burn was suppressed or reduced. The fourth experimental example corresponds to an experimental example of this embodiment containing more additives than the third experimental example. As a result of SEM observation and ICP analysis, in the fourth experimental example, a columnar crystal structure having a film thickness of about 830 μm, a thallium concentration of about 0.54 mol %, and an additive concentration of 160 ppm was obtained as the scintillator 2. In the fourth experimental example as well, MTF evaluation and bright burn evaluation were performed according to the same procedure as in the comparative example. In the fourth experimental example, the MTF evaluation value was 139. In addition, in the fourth experimental example, the bright burn evaluation values after the lapse of 2.5 min, 10 min, and 30 min were 39, 35, and 20, respectively. That is, bright burn was suppressed or reduced. The fifth experimental example corresponds to an experimental example of this embodiment containing more additives than the fourth experimental example. As a result of SEM observation and ICP analysis, in the fifth experimental example, a columnar crystal structure having a film thickness of about 720 μm, a thallium concentration of about 0.55 mol %, and an additive concentration of 180 ppm was obtained as the scintillator 2. In the fifth experimental example as well, MTF evaluation and bright burn evaluation were performed according to the same procedure as in the comparative example. In the fifth experimental example, the MTF evaluation value was 146. In addition, in the fifth experimental example, the bright burn evaluation values after the lapse of 2.5 min, 10 min, and 30 min were 40, 35, and 11, respectively. That is, bright burn was suppressed or reduced. The sixth experimental example corresponds to an experimental example of this embodiment containing more additives than the fifth experimental example. As a result of SEM observation and ICP analysis, in the sixth experimental example, a columnar crystal structure having a film thickness of about 650 μm, a thallium concentration of about 1.37 mol %, and an additive concentration of 240 ppm was obtained as the scintillator 2. In the sixth experimental example as well, MTF evaluation and bright burn evaluation were performed according to the same procedure as in the comparative example. In the sixth experimental example, the MTF evaluation value was 161. In addition, in the sixth experimental example, the bright burn evaluation values after the lapse of 2.5 min, 10 min, and 30 min were 16, 11, and 10, respectively. That is, bright burn was suppressed or reduced. As described above, according to this embodiment, each column of the scintillator 2 with the columnar crystal structure contains an alkali halide metal compound as a host material, and also contains a compound of a precious metal as an additive having a lower melting point than the host material. This prevents carriers (electron-hole pairs), generated at the time of irradiation with radiation, from being unintentionally trapped at a trap level originating from, for example, a lattice defect in the scintillator 2. Accordingly, this embodiment can suppress or reduce bright burn. This is especially advantageous for a crystal structure that contains an activator agent (thallium in the embodiment) as another additive and can have a “deep” trap level. In addition, it is considered that using a material having a lower melting point than a host material as the above additive allows the element of the additive to be incorporated as a constituent atom of the columnar crystal structure into the crystal structure of the scintillator 2 at the time of vapor deposition. In this case, the additive is not deposited. Therefore, the embodiment can improve the crystallinity of the scintillator 2 and hence is advantageous in improving the quality of the scintillator 2. In this case, increasing the additive concentration may reduce the luminance when the scintillator 2 receives radiation. Referring to FIG. 3, as is obvious from the experimental results of the first to sixth experimental examples, the first experimental example indicates that setting the additive concentration to 3 ppm will suppress or reduce bright burn. Accordingly, there is no need to let the scintillator 2 excessively contain an additive. For example, setting the additive concentration to 240 ppm or less, preferably 160 ppm or less, and more preferably 30 ppm or less can suppress or reduce bright burn while maintaining the luminance of the scintillator 2. On the other hand, in order to properly suppress or reduce bright burn, for example, the additive concentration is preferably set to 3 ppm or more, and preferably 10 ppm or more. In summary, letting the scintillator 2 contain a compound of a precious metal as an additive can improve both the crystallinity and quality of the scintillator 2. On the other hand, excessively increasing the additive concentration sometimes reduces the luminance (the luminance of scintillation light) of the scintillator 2. Accordingly, the scintillator 2 may contain the above additive at a concentration at which the luminance of scintillation light is maintained. For example, the additive concentration may be decided such that a decrease in the luminance of the scintillator 2 including the additive becomes 20% or less, and preferably 10% or less, of a decrease in the luminance of the scintillator that does not contain the additive. The above scintillator can be applied to a radiation detection apparatus (radiation imaging apparatus) that detects radiation. As radiation, X-rays are typically used. However, α-rays, β-rays, or the like may be used. FIG. 4 shows an example of the usage of the radiation detection apparatus. Radiation 611 generated by a radiation source 610 is transmitted through a chest 621 of an object 620 such as a patient and enters a radiation detection apparatus 630. The radiation 611 that has entered the apparatus 630 contains internal information of the patient 620. The apparatus 630 acquires electrical information corresponding to the radiation 611. This information is converted into a digital signal. For example, a processor 640 then performs predetermined signal processing for the digital signal. A user such as a doctor can observe a radiation image corresponding to this electrical information on a display 650 in, for example, a control room. The user can transfer the radiation image or the corresponding data to a remote place via a predetermined communication means 660. The user can also observe this radiation image on a display 651 in a doctor room as another place. The user can also record the radiation image or the corresponding data on a predetermined recording medium. For example, a processor 670 can also record the radiation image or the corresponding data on a film 671. Although several preferred examples have been described above, the present invention is not limited to them, and the examples may be partly changed without departing from the spirit of the present invention. In addition, it is obvious that each term in this specification is merely used to explain the present invention, and the present invention is not limited to the strict meaning of the term. The present invention can include equivalents of the terms. While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments. The scope of the following claims is to be accorded the broadest interpretation so as to encompass all such modifications and equivalent structures and functions. This application claims the benefit of Japanese Patent Applications No. 2017-217513, filed on Nov. 10, 2017 and No. 2018-167216, filed on Sep. 6, 2018, which are hereby incorporated by reference herein in their entirety.
059995831	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The invention provides a method for analyzing operation of an electromagnetic drive mechanism 22 for nuclear control rods 24, shown generally in FIG. 1, in a manner that permits detection of performance problems including not only failure of components, but also deterioration of performance over time. By collecting and storing data on the performance of the components and comparing present performance to previously stored historical data, the invention permits detection of impending problems before a failure actually occurs. The control rods as shown in FIG. 1 are attached in clusters 26, each cluster being commonly driven by a drive rod 28 disposed in a vertical extension housing 32 of the reactor core pressure vessel 34 containing the fuel rod assemblies 36 into which the control rods 24 are advanced or from which the control rods are retracted for variable damping of nuclear flux. The moving parts of the mechanism are within the pressure envelope of the reactor and the electromagnetic coils 42 for driving the movable parts are disposed around and about each of the extensions. FIG. 2 shows one drive rod mechanism with the extension housing partly cut away, and FIG. 3 is a detailed view, partly in section, showing exemplary grippers that or operable in sequences to engage, lift and/or lower the drive rod when the associated coils of the drive mechanism are energized. This arrangement is substantially as disclosed in U.S. Pat. No. 5,009,834--Tessaro, which is hereby incorporated with respect to the mechanical and electromagnetic aspects of the control rod drive. The drive mechanism comprises stationary grippers 44 and movable grippers 46 for engaging the drive rod 28, and a lifting armature 48 by which the movable grippers are lifted or allowed to fall along the longitudinal axis of the drive rod 28. Each is operated by a corresponding electromagnetic coil 54, 56, 58. The grippers are arranged normally to release the drive rod 28, for example being mounted to pivot clear of the drive rod or spring biased to retract, when not electromagnetically forced to engage. Thus, when neither of the stationary and movable gripper coils 54, 56 is energized, the corresponding grippers 44, 46 release their hold on the drive rod, which falls by gravity, allowing the control rods 24 to drop into the nuclear core. At other times the coils are energized for either holding drive rod 28 and the associated control rods 24 in position or for stepping them up or down in response to signals from a controller (not shown) that regulates the output level of the reactor. FIG. 3 shows an exemplary mounting of a movable gripper, in particular one of three grippers that are spaced circumferentially around drive rod 28 for bearing radially inwardly to engage ridges or grooves 68 on rod 28 or outward to clear the ridges or grooves. The same reference numbers are used throughout the drawings to identify corresponding elements. The drive mechanism has at least one stationary gripper coil 54, at least one movable gripper coil 56, each having an independently driven gripper 44, 46, and at least one lifting armature 48 driven by a lift coil 58 for displacing the movable gripper relative to the stationary gripper. Each coil is coupled to a coil current driver controlled by a timing circuit that is wired or programmed to effect a series of switching operations for achieving coil current sequences as shown in FIG. 4 (for lowering the drive rod) and FIG. 5 (for lifting the drive rod) by one step at a time. The current drivers 62 and timing circuit 64 are shown generally in FIG. 6. Current drivers 62 provide current to coils 54, 56, 58 for effecting sequences of holding and moving operations that cause the control rod drive rod 28 to be raised or lowered by one increment during the sequences shown in FIGS. 4, and 5, each step taking about 1.7 s to complete and any number of sequences being executed one after another depending on the needs of the reactor for more or less nuclear flux. The holding and moving operations include phases in which the coils are energized individually, and other phases in which the coils are energized in combinations. The coil currents having nominal amplitudes at different times in the cycle (e.g., full-on to initially engage, part-on for holding, and off) and nominal timing relationships. FIG. 4 is a time plot showing the nominal current levels and nominal timing relationships for steps in which drive rod 28 and associated control rods 24 are lowered or advanced into the spaces between the nuclear fuel rods in the core; and FIG. 5 represents raising or retracting control rods 24 from the core. Lifting (FIG. 5) is accomplished beginning from a situation in which stationary gripper 54 is energized for holding drive rod 28, and movable gripper 46 resides in its lower position but is disengaged from drive rod 28 because movable gripper coil 56 and lift coil 58 are both de-energized. During the raising or "out" step, movable gripper 46 is latched onto drive rod 28 by energizing movable gripper coil 56; stationary gripper coil 54 is then de-energized and stationary gripper 44 releases rod 28; lift armature 48 is operated to lift movable gripper 46 together with the drive rod by an increment equal to the armature's span of movement; stationary gripper 44 is again engaged; and finally the movable gripper coil and armature coil are de-energized, and the mechanism returns to its start position. The timing circuit 64 has suitable gating, timing and/or state circuits that move through this sequence with each step, in particular by sending a signal to the appropriate current driver(s) 62 at the appropriate times. Current drivers maintain the required coil current, for example, using a current sensing resistor 72 coupled in a feedback loop for maintaining the current level indicated by the "send" signal from the timing circuit. Each gripper preferably comprises a plurality of circumferentially spaced toothed bodies that are brought radially inwardly by electromagnetic force to engage in annular slots or ridges 68 of the drive rod when engaging. When the respective coils are de-energized, the toothed grippers move radially outwardly to release rod 28. For a lowering step, again starting from a time when stationary gripper 44 is holding the drive rod, the first step is to energize lift coil 58 to cause armature 48 to raise movable gripper 46 (which is de-energized at the time) to a higher point along the drive rod 28; movable gripper coil 56 is then energized and movable gripper 46 engages the drive rod while held by armature 48 at this higher point; stationary gripper 44 is released, then armature coil 58 is de-energized. The drive rod 28 and the control rods 24 coupled to it, drops by gravity as movable gripper 46 falls back to its original position. Stationary gripper 44 is then energized, and finally movable gripper 46 is de-energized to resume the situation preceding the step. Activation and deactivation of the grippers and the armature require a discrete time interval to permit the coil current to be established or cut off or for a mechanical motion to be completed, before the next motion is commenced. The necessary times can be nominally established, allowing for a safety margin, and conventionally are programmed into timing circuit 64. However, with wear and potentially with electrical failures, the mechanism may deteriorate to the point that it cannot operate correctly or operate at nominal timing. Wear and electrical failure can cause sudden failure or operation can deteriorate over time. According to the invention, the operational status of the control rod drive mechanism is monitored by sensing current signals in coils 54, 56, 58 during the sequence of lifting and lowering operations, and analyzing the current signals both against nominal operational thresholds and also against historical data that is accumulated, stored, and compared with data as it is collected during present operations. In this manner, the operational status of the mechanism can be assessed, and impending failure modes can be identified or even predicted. The invention thus provides ongoing diagnostic checking as well as data that can be used, for example over a plant-wide network, for assessing and planning maintenance and engineering. During stepping operations, and preferably continuously, the coil current levels to each of the gripper coils 54, 56 and the armature coil 58 are sampled, digitized and stored to provide coil current data samples over time. This is accomplished as shown in FIGS. 6 and 7 using current sensing means to develop a signal representing coil current, which is digitized by an analog to digital converter 74, operated repetitively to collect samples. The coil current data samples can be stored in raw form, and preferably are processed to generate coil current data representing a measure of at least one of: a current amplitude, a time of current variation indicating a change in coil inductance, and an ac ripple. The coil current data is compared to the nominal current amplitudes and timing relationships, and deviations therefrom are identified and indicated to the operators. For obtaining the samples, each of the coils is coupled to an associated current sensor such as a resistor in series with the coil, an inductor responsive to the coil field, or an inductive loop around the coil, etc. For ac operation, the signal can be coupled through a rectifier and filtered by an RC combination to obtain a voltage signal representing the level of current in the coil. The voltage signal can be sampled via an analog to digital converter triggered by a clock signal from an oscillator, or responsive to a logic device such as a processor 78 programmed repetitively to select and sequentially sample signals developed from a plurality of coils. In the event that a separate clock oscillator (not shown) is associated with the analog to digital converter, or if control computer 78 controls sampling, then a failure of the clock oscillator 76 of the initial timing circuit can be detected by deterioration of timing of the resulting switching operations, detected by computer 78 (or vice versa). Sampling is preferably accomplished at a frequency of at least ten times the ac power frequency to enable assessment of the extent of ripple in the current signal, which is indicative of the operational status of the power supply (not shown) and the current drivers 62 to the coils (e.g., loading). The coil current data can be stored in a raw form or processed to develop factors representative of signal attributes, which are then stored in memory 82, or both. The raw data and/or processed attribute factors, generally termed the coil current data, are stored in the computer memory as a historical log, for example on a disk drive. During the collection and processing of data in later cycles, the most recent coil current data is compared to the previous historical coil current data. By sensing for and indicating variations, e.g., exceeding a predetermined threshold of variation, trends occurring over time can be monitored, and impending problems can be predicted. Referring to FIG. 4, there are certain particular attributes that are advantageously monitored and compared to their historical values. These include the average level of the current signals maintained by the switching controller, the timing of the switching cusps in the signal upon turn-on and turn-off of coil driving current, the extent of ac ripple, the slope of the rising and falling current signal traces, and the occurrence of characteristic notches. The current waveforms for the stationary and movable gripper coils 54, 56 each contain a readily detectable notch 84 occurring with the mechanical pull-in of the associated gripper, due to increase in inductance, until current drive regulation by driver 62 re-establishes the nominal current level due to feedback control. At the bottom of notch 84, the slope of the current waveform changes direction, which is readily detectable when comparing sample values to immediately preceding sample values, or by calculating a running average or slope of a predetermined number of immediately preceding sample values. The current traces for all the coils have inductive exponential charging and discharging slopes, but likewise have readily detectable transitions between the respective current levels representing turn-on and turn-off. The timing of switching can be identified by comparing each sample to previous values or averages leading up to the level change. For proper operation, the switch-on edges 86, switch-off edges 88 and gripper pull-in notches 84 must occur at the proper times, namely in the correct sequence and with sufficient spacing in time that earlier needed operations occur and are completed before later operations depending on the earlier ones commence. For example, for stepping upwardly, stationary gripper 44 cannot be released until movable gripper 46 has pulled in, or else the drive rod could drop. Lifting armature 48 cannot be activated until movable gripper 46 has pulled in and stationary gripper 44 is released. By noting the occurrence of the pull-in gripper notches as well as the time spacing between switching operations, the operational status of the control rod drive mechanism can be monitored. FIG. 7 generally indicates the steps undertaken to obtain and analyze current data repetitively. In the event that comparison of present sample data and historical data shows that a gripper pull-in notch 84 has abruptly begun to occur earlier, the gripper mechanical fittings may be getting loose. If the gripper pull-in notch becomes later, the gripper coil drive arrangement is suspect, or the mechanical fittings may be binding. These attributes can be assessed, as well as the ability of the current drive circuits to maintain predetermined current levels, whether a coil has become open circuited (leading to zero current) or shorted across adjacent windings (reduced inductance and electromagnetic power), etc. For making these assessments, the nominal and measured current amplitudes, the presence and occurrence of the gripper pull-in notch 84 said notch at nominal and measured delay times and amplitudes following application of a current to the associated gripper coil, are each assessed. The amplitudes and delays as compared to nominal and historical data are used by processor 78 in analyzing the data according to programmed processing steps, to identify mechanical impairment of the gripper, degradation of magnetic flux of the driven coils and in general to assess whether the control rod drive mechanism continues to operate as designed. Preferably, the current monitoring steps are only one aspect of a monitoring device that is programmed to localize defective or failing components based on the specific results of monitoring. For this purpose, it is advantageous to provide additional measurements apart from the coil currents, for use in conjunction with coil current data to localize problems. By suitably monitoring various status signals, for example using relays or other switched means coupled along the power distribution path from the mains to the coils, problems can be localized to the circuits or elements at which a failure has occurred. For example, a status monitor relay or switching circuit can provide a status input to the apparatus of the invention representing the presence of a signal on each phase of the mains, on the output side of any circuit breakers or similar interrupters coupled to the mains, on the outputs of a regulated power supply that feeds the current regulating circuits and at points in the control and logic circuits that trigger switching. As noted above, a timing fault in one of clock oscillator 76 driving the timing circuit and the timing reference (e.g., clock) of the processor 78 can be detected from changes in timing. Alternatively, the clock oscillator signal can be digitized together with the current signal, or its cycles counted, to determine whether switch-on edges 86 and switch-off edges 88 occur in correct synchronization with the clock signal. Current or voltage can be sensed at a plurality of points between an ac power source and the control rod drive coils to assess the respective switching devices, power regulators, controllers and the like by monitoring for the presence of current or voltage or for comparing current of voltage levels to nominal levels for identifying electrical or mechanical failure points, whereupon the failure point is logged, made the subject of a warning message or used to trigger an alarm or signal to a remote apparatus. By monitoring the presence and/or level of voltages and currents, including not only two or more coil current levels but also other voltages such as power supply outputs, and by monitoring the timing of switching operations and the occurrence of notches due to gripper or armature pull-in, it is possible readily to determine and indicate various fault conditions. In a preferred embodiment, the conditions include: power cabinet thyristor failure; PA1 power cabinet circuit interrupter operation (e.g., fuse); PA1 power cabinet loss of AC phase; PA1 drive mechanism physical impairment of movement; PA1 drive mechanism coil flux degradation; PA1 controller clock oscillator frequency shift; PA1 controller clock counter malfunction; PA1 controller to power cabinet data transmission error/failure; and, PA1 controller decoder malfunction. The apparatus of the invention can be embodied in a portable unit for periodic testing or permanently installed as a part of the control rod drive system. In addition, the invention is operable for online diagnostic testing during operations and/or can be part of a larger diagnostic system, for example wherein the apparatus communicates data to a plant diagnostic system or preventive maintenance system. The invention having been disclosed in connection with the foregoing variations and examples, additional variations will now be apparent to persons skilled in the art. The invention is not intended to be limited to the variations specifically mentioned, and accordingly reference should be made to the appended claims rather than the foregoing discussion of preferred examples, to assess the scope of the invention in which exclusive rights are claimed.
	claims	1. A method comprising:providing an upper housing of a nail lamp comprising a portion having a translucent material;coupling a lower housing to the upper housing, wherein an enclosed space is formed between the upper and lower housings;providing a display panel capable of displaying at least two digits;positioning a first printed circuit board in the enclosed space between the upper and lower housings, wherein the first printed circuit board comprises electronic circuitry comprising a control circuit that is coupled to one or more buttons, accessible from an exterior of the nail lamp, and the display, andby way of the one or more buttons, a user can select a curing time, which will be displayed on the display panel;coupling a second printed circuit board to the first printed circuit board in the enclosed space between the upper and lower housings, wherein the second printed circuit board comprises a plurality of interior-illuminating light emitting diodes that are coupled to the control circuit of the first printed circuit board,light emitted by the interior-illuminating light emitting diodes is directed through apertures into a treatment chamber of the nail lamp, andwhen on, the interior-illuminating light emitting diodes emit ultraviolet light; andcoupling a plurality of exterior-illuminating light emitting diodes to the control circuit of the first printed circuit board, wherein light emitted by the exterior-illuminating light emitting diodes strikes a surface of the translucent material, visible from the exterior of the nail lamp,when on, the exterior-illuminating light emitting diodes emit non-ultraviolet light, the interior-illuminating light emitting diodes emit light in a first direction, the exterior-illuminating light emitting diodes emit light in a second direction, and the first direction is toward the treatment chamber and the second direction is away from the treatment chamber; andcoupling an internal rechargeable battery pack to the first printed circuit board, wherein the rechargeable battery pack comprises a USB port and a battery gauge; andcoupling an exterior power connector to the first printed circuit board, wherein power input via the exterior power connector is used to power the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes, and to recharge the internal rechargeable battery pack,when power is not connected to the exterior power connector, the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes are powered by the internal rechargeable battery pack, andthe rechargeable battery pack comprises a battery pack power connector, and when the battery pack is removed from the nail lamp, the battery pack can be charged via the battery pack power connector. 2. The method of claim 1 comprising:coupling a detection sensor to the control circuit, wherein after the user has selected a curing time, the detection sensor detects the presence of a hand in the treatment chamber, and when a hand is placed in the treatment chamber, the control circuit turns on the interior-illuminating light emitting diodes and the exterior-illuminating light emitting diodes. 3. The method of claim 2 wherein while the interior-illuminating light emitting diodes are on, the display panel shows a time remaining for the interior-illuminating light emitting diodes to be on, andafter the selected curing time has elapsed, the control circuit turns off the interior-illuminating light emitting diodes, even when the hand remains in the treatment chamber. 4. The method of claim 2 wherein when the interior-illuminating light emitting diodes are on and the hand is removed from the treatment chamber, the detection sensor detects the removal of the hand from the treatment chamber, and the control circuit turns off the interior-illuminating light emitting diodes, even before the selected curing time has elapsed. 5. The method of claim 1 wherein while the interior-illuminating light emitting diodes are on, the display panel shows a time remaining for the interior-illuminating light emitting diodes to be on, andafter the selected curing time has elapsed, the control circuit turns off the interior-illuminating light emitting diodes, even when the hand remains in the treatment chamber. 6. The method of claim 1 wherein the USB port supplies power to an external device other than the nail lamp. 7. The method of claim 1 wherein the battery gauge indicates a level of charge of the rechargeable battery pack. 8. The method of claim 1 wherein the curing time selected by the user can be a predetermined curing time of 30 seconds or 60 seconds. 9. The method of claim 1 wherein the buttons comprise at least three buttons. 10. The method of claim 1 wherein the interior-illuminating light emitting diodes are in recessed openings. 11. The method of claim 1 wherein the interior-illuminating light emitting diodes comprise at least one 1-watt light emitting diode. 12. The method of claim 1 wherein the interior-illuminating light emitting diodes emit ultraviolet light in a range from about 340 nanometers to about 410 nanometers. 13. The method of claim 1 wherein while the exterior-illuminating light emitting diodes are on, a color of the light emitted by the exterior-illuminating light emitting diodes changes to be different colors comprising at least red, green, and blue shades. 14. A method comprising:providing an upper housing of a nail lamp comprising a portion having a translucent material;coupling a lower housing to the upper housing, wherein an enclosed space is formed between the upper and lower housings;providing a display panel capable of displaying at least two digits;positioning a first printed circuit board in the enclosed space between the upper and lower housings, wherein the first printed circuit board comprises electronic circuitry comprising a control circuit that is coupled to one or more buttons, accessible from an exterior of the nail lamp, and the display, andby way of the one or more buttons, a user can select a curing time, which will be displayed on the display panel;coupling a second printed circuit board to the first printed circuit board in the enclosed space between the upper and lower housings, wherein the second printed circuit board comprises a plurality of interior-illuminating light emitting diodes that are coupled to the control circuit of the first printed circuit board,light emitted by the interior-illuminating light emitting diodes is directed through apertures into a treatment chamber of the nail lamp, andwhen on, the interior-illuminating light emitting diodes emit ultraviolet light; andcoupling a plurality of exterior-illuminating light emitting diodes to the control circuit of the first printed circuit board, wherein light emitted by the exterior-illuminating light emitting diodes strikes a surface of the translucent material, visible from the exterior of the nail lamp,when on, the exterior-illuminating light emitting diodes emit non-ultraviolet light, the interior-illuminating light emitting diodes emit light in a first direction, the exterior-illuminating light emitting diodes emit light in a second direction, and the first direction is toward the treatment chamber and the second direction is away from the treatment chamber; andcoupling an internal rechargeable battery pack to the first printed circuit board, wherein the rechargeable battery pack comprises a USB port and a battery gauge that indicates a level of charge of the rechargeable battery pack;coupling an exterior power connector to the first printed circuit board, wherein power input via the exterior power connector is used to power the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes, and to recharge the internal rechargeable battery pack,when power is not connected to the exterior power connector, the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes are powered by the internal rechargeable battery pack, andthe rechargeable battery pack comprises a battery pack power connector, and when the battery pack is removed from the nail lamp, the battery pack can be charged via the battery pack power connector; andcoupling a detection sensor to the control circuit, wherein after the user has selected a curing time, the selected curing time is displayed on the display panel, the detection sensor detects the presence of a hand in the treatment chamber, and when a hand is placed in the treatment chamber, the control circuit turns on the interior-illuminating light emitting diodes and the exterior-illuminating light emitting diodes, andwhen the interior-illuminating light emitting diodes are on and the hand is removed from the treatment chamber, the detection sensor detects the removal of the hand from the treatment chamber, and the control circuit turns off the interior-illuminating light emitting diodes, even before the selected curing time has elapsed. 15. The method of claim 14 wherein the USB port supplies power to an external device other than the nail lamp. 16. The method of claim 14 wherein the interior-illuminating light emitting diodes are in recessed openings. 17. The method of claim 14 wherein the interior-illuminating light emitting diodes comprise at least one 1-watt light emitting diode. 18. The method of claim 14 wherein the interior-illuminating light emitting diodes emit ultraviolet light in a range from about 340 nanometers to about 410 nanometers. 19. The method of claim 14 wherein while the exterior-illuminating light emitting diodes are on, a color of the light emitted by the exterior-illuminating light emitting diodes changes to be different colors comprising at least red, green, and blue shades. 20. A method comprising:providing an upper housing of a nail lamp comprising a portion having a translucent material;coupling a lower housing to the upper housing, wherein an enclosed space is formed between the upper and lower housings;providing a display panel capable of displaying at least two digits;positioning a first printed circuit board in the enclosed space between the upper and lower housings, wherein the first printed circuit board comprises electronic circuitry comprising a control circuit that is coupled to one or more buttons, accessible from an exterior of the nail lamp, and the display, andby way of the one or more buttons, a user can select a curing time, which will be displayed on the display panel;coupling a second printed circuit board to the first printed circuit board in the enclosed space between the upper and lower housings, wherein the second printed circuit board comprises a plurality of interior-illuminating light emitting diodes that are coupled to the control circuit of the first printed circuit board,light emitted by the interior-illuminating light emitting diodes is directed through apertures into a treatment chamber of the nail lamp, andwhen on, the interior-illuminating light emitting diodes emit ultraviolet light; andcoupling a plurality of exterior-illuminating light emitting diodes to the control circuit of the first printed circuit board, wherein light emitted by the exterior-illuminating light emitting diodes strikes a surface of the translucent material, visible from the exterior of the nail lamp,when on, the exterior-illuminating light emitting diodes emit non-ultraviolet light, the interior-illuminating light emitting diodes emit light in a first direction, the exterior-illuminating light emitting diodes emit light in a second direction, and the first direction is toward the treatment chamber and the second direction is away from the treatment chamber; andcoupling an internal rechargeable battery pack to the first printed circuit board, wherein the rechargeable battery pack comprises a USB port and a battery gauge that indicates a level of charge of the rechargeable battery pack;coupling an exterior power connector to the first printed circuit board, wherein power input via the exterior power connector is used to power the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes, and to recharge the internal rechargeable battery pack,when power is not connected to the exterior power connector, the electronic circuitry of the first printed circuit board, interior-illuminating light emitting diodes, and exterior-illuminating light emitting diodes are powered by the internal rechargeable battery pack, andthe rechargeable battery pack comprises a battery pack power connector, and when the battery pack is removed from the nail lamp, the battery pack can be charged via the battery pack power connector; andcoupling a detection sensor to the control circuit, wherein after the user has selected a curing time, the selected curing time is displayed on the display panel, the detection sensor detects the presence of a hand in the treatment chamber, and when a hand is placed in the treatment chamber, the control circuit turns on the interior-illuminating light emitting diodes and the exterior-illuminating light emitting diodes,when the interior-illuminating light emitting diodes are on and the hand is removed from the treatment chamber, the detection sensor detects the removal of the hand from the treatment chamber, and the control circuit turns off the interior-illuminating light emitting diodes, even before the selected curing time has elapsed, andwhen the interior-illuminating light emitting diodes are on and the hand remains in the treatment chamber, after the selected curing time has elapsed, the control circuit turns off the interior-illuminating light emitting diodes.
049869590	claims	1. An expandable top nozzle subassembly for a nuclear fuel assembly, said top nozzle subassembly comprising: (a) an upper structure including a top plate and a sidewall enclosure rigidly connected to and depending below an outer peripheral edge of said top plate; (b) a lower adapter plate disposed below said top plate of said upper structure and within said sidewall enclosure thereof, said adapter plate and sidewall enclosure being slidably movable relative to one another so as to vertically move said sidewall enclosure past an outer peripheral edge of said adapter plate as said top plate moves toward and away from said adapter plate; (c) interengagable means on a lower edge of said sidewall enclosure and on said outer peripheral edge of said adapter plate for capturing and retaining said adapter plate within said sidewall enclosure upon movement of said sidewall enclosure relative to said adapter plate and therewith said top plate which is attached to said sidewall enclosure away from said adapter plate; and (d) a plurality of resiliently-yieldable biasing devices disposed in said sidewall enclosure and extending between and engaging said top plate and said adapter plate, said devices being movably displaceable between compressed and expanded states in response respectively to application and removal of a hold-down force on said upper structure in the direction of said adapter plate for permitting and causing movement of said sidewall enclosure relative to and past said outer peripheral edge of said adapter plate so as to move said top plate toward and away from said adapter plate and thereby said top nozzle subassembly between compressed and expanded conditions, only said biasing devices extending between and engaging both said top plate and said adapter plate such that the amount of reduction in the height of said top nozzle subassembly in moving from its expanded to compressed condition is only limited by the amount of displacement said biasing devices can undergo in moving from their expanded to compressed states. said top plate has a hole defined therethrough within each of said recesses in said top plate; and said subassembly further comprises a guide member secured to said top plate in each of said holes and extending within each of said coil springs for guiding movement of said spring between its expanded and compressed states along a linear path, said guide member being of a predetermined length such that said guide members are located in spaced relation remote from said adapter plate when said biasing devices are in said expanded states and are located adjacent to said adapter plate when said biasing devices are in said compressed states. (a) an upper structure including a top plate and a sidewall enclosure rigidly connected to and depending below an outer peripheral edge of said top plate; (b) a lower adapter plate disposed below said top plate of said upper structure and within said sidewall enclosure thereof, said adapter plate and sidewall enclosure being slidably movable relative to one another so as to vertically move said sidewall enclosure past an outer peripheral edge of said adapter plate as said top plate moves toward and away from said adapter plate, said lower adapter plate being stationarily secured to said upper ends of said guide thimbles in spaced relation above upper ends of said fuel rods; (c) interengagable means on a lower edge of said sidewall enclosure and on said outer peripheral edge of said adapter plate for capturing and retaining said adapter plate within said sidewall enclosure upon movement of said sidewall enclosure relative to said adapter plate and therewith said top plate which is attached to said sidewall enclosure away from said adapter plate; and (d) a plurality of resiliently-yieldable biasing devices disposed in said sidewall enclosure and extending between and engaging said top plate and said adapter plate, said devices being movably displaceable between compressed and expanded states in response respectively to application and removal of a hold-down force on said upper structure in the direction of said adapter plate for permitting and causing movement of said sidewall enclosure relative to and past said outer peripheral edge of said adapter plate so as to move said top plate toward and away from said adapter plate and thereby said top nozzle subassembly between compressed and expanded conditions, only said biasing devices extending between and engaging both said top plate and said adapter plate such that the amount of reduction in the height of said top nozzle subassembly in moving from its expanded to compressed condition is only limited by the amount of displacement said biasing devices can undergo in moving from their expanded to compressed states. said top plate has a hole defined therethrough within each of said recesses in said top plate; and said subassembly further comprises a guide member secured to said top plate in each of said holes and extending within each of said coil springs for guiding movement of said spring between its expanded and compressed states along a linear path, said guide member being of a predetermined length such that said guide members are located in spaced relation remote from said adapter plate when said biasing devices are in said expanded states and are located adjacent to said adapter plate when said biasing devices are in said compressed states. 2. The top nozzle subassembly as recited in claim 1, wherein said top plate has an inner peripheral edge defining a large central opening. 3. The top nozzle subassembly as recited in claim 1, wherein said top plate has a plurality of corner portions and at least one recess formed in a lower surface of said top plate at each of said corner portions and facing toward said adapter plate. 4. The top nozzle subassembly as recited in claim 3, wherein said adapter plate has a plurality of corner portions and at least one recess formed in an upper surface of said adapter plate at each of said corner portions and facing toward said top plate, each recess of said adapter plate being aligned below one of said recesses of said top plate. 5. The top nozzle subassembly as recited in claim 4, wherein said adapter plate has a series of flow openings defined therethrough within each of said recesses in said adapter plate. 6. The top nozzle subassembly as recited in claim 4, wherein said biasing devices are a plurality of coil springs each disposed between said top plate and adapter plate and being seated at its opposite upper and lower ends in respectively aligned pairs of said recesses of said top plate and adapter plate and movable between expanded and compressed states. 7. The top nozzle subassembly as recited in claim 6, wherein: 8. The top nozzle subassembly as recited in claim 1, wherein said sidewall enclosure of said upper structure is composed of generally planar vertical wall portions rigidly interconnected together at their opposite vertical edges. 9. The top nozzle subassembly as recited in claim 1, wherein said interengagable means on said lower edge of said sidewall enclosure of said upper structure is a retaining structure which projects inwardly from said sidewall enclosure. 10. The top nozzle subassembly as recited in claim 9, wherein said retaining structure is composed of a series of spaced fingers. 11. The top nozzle subassembly as recited in claim 9, wherein said interengagable means on said outer peripheral edge of said adapter plate is an undercut seat structure having a cross-sectional configuration which interfits in overlying relation with the cross-sectional configuration of said inwardly-projecting retaining structure of said sidewall enclosure. 12. In a nuclear fuel assembly including a bottom nozzle, a plurality of guide thimbles having upper and lower ends and being attached at said lower ends to said bottom nozzle and extending upwardly therefrom, an array of upstanding fuel rods extending along and spaced from said guide thimbles and spaced at their lower ends above said bottom nozzle, and a plurality of support grids axially spaced along and connected to said guide thimbles for supporting said array of upstanding fuel rods, an expandable top nozzle subassembly which permits increased fuel rod growth and burnup, said top nozzle subassembly comprising: 13. The top nozzle subassembly as recited in claim 12, wherein said top plate has an inner peripheral edge defining a large central opening and aligned above said outer perimeter of said guide thimbles. 14. The top nozzle subassembly as recited in claim 12, wherein said top plate at each of said corner portions thereof has at least one recess formed in a lower surface of said top plate and facing toward said adapter plate. 15. The top nozzle subassembly as recited in claim 14, wherein said adapter plate at each of said corner portions thereof has at least one recess formed in an upper surface of said adapter plate and facing toward said top plate, each recess of said adapter plate being aligned below one of said recesses of said top plate. 16. The top nozzle subassembly as recited in claim 15, wherein said adapter plate has a series of flow openings defined therethrough within each of said recesses in said adapter plate. 17. The top nozzle subassembly as recited in claim 15, wherein said biasing devices are a plurality of coil springs each disposed between said top plate and adapter plate and being seated at its opposite upper and lower ends in respectively aligned pairs of said recesses of said top plate and adapter plate and movable between expanded and compressed states. 18. The top nozzle subassembly as recited in claim 17, wherein: 19. The top nozzle subassembly as recited in claim 12, wherein said sidewall enclosure of said upper structure is composed of generally planar vertical wall portions rigidly interconnected together at their opposite vertical edges. 20. The top nozzle subassembly as recited in claim 12, wherein said interengagable means on said lower edge of said sidewall enclosure of said upper structure is a retaining structure which projects inwardly from said sidewall enclosure. 21. The top nozzle subassembly as recited in claim 20, wherein said retaining structure is composed of a series of spaced fingers. 22. The top nozzle subassembly as recited in claim 20, wherein said interengagable means on said outer peripheral edge of said adapter plate is an undercut seat structure having a cross-sectional configuration which interfits in overlying relation with the cross-sectional configuration of said inwardly-projecting retaining structure of said sidewall enclosure.
	summary
046997490	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates to a method and apparatus for controlling a nuclear reactor under dropped control rod conditions, and more particularly for shutting down the reactor only if the dropped rod condition causes the axial power distribution to exceed prescribed limits. 2. Prior Art One means for controlling the reactivity of a commercial nuclear reactor such as a pressurized water reactor (PWR) is through insertion of control rods into the reactor core. The control rods absorb neutrons to control the number of fission reactions. Since the control rods are inserted into and withdrawn from the upright, generally cylindrical core along a vertical path, they have a direct effect on the axial distribution of the fission reactions, and hence the power generated, in the core. Skewing of the power generated in the core in the axial direction due to the effect of the control rods is commonly measured in terms of a quantity such as axial offset or axial shape index which reference skewing of power toward the top and bottom of the core respectively. Operational constraints placed on the axial distribution of power in the core are translated into limits on axial offset or axial shape index which, if exceeded, lead to tripping or shutting down of the reactor through full insertion of all the control rods. PWRs have both full length control rods which extend all the way through the core and part length rods which cover only portions of the core. The full length rods may be inserted to any depth in the core while the part length rods are either fully inserted or fully retracted. In those reactors in which the part length rods are manipulated during power changes, the position of these rods makes a substantial difference in the critical limits on axial offset or axial shape index. Both the full length and part length control rods are inserted and retracted in groups consisting of rods located symmetrically about the vertically oriented axis of the generally cylindrical core such that normal movement of the control rods does not cause an imbalance in the radial distribution of power. However, the rods are incrementally stepped into and out of the core by electromechanical jacks which can, on occasion, malfunction resulting in the dropping of a rod into the core, thereby distorting the axial distribution of power. The nature of the operation of a PWR is such that the reactor attempts to make up for the local loss of reactivity caused by the dropped rod by increasing the power elsewhere in the core so that the demand placed upon the reactor is still met. This in turn, can lead to local limits being exceeded in these other parts of the core. One type of protection system provided on PWRs monitors the neutron flux and trips the reactor when a negative rate of change of flux in excess of a preselected value is detected. Such a negative rate of change in neutron flux can for example, indicate a dropped rod since the inserted rod reduces the local reactivity and it takes time for the power to increase elsewhere in the core and thus, return the power to the demanded level. The control rod drives in PWRs are such that dropping of control rods may occur during an operating cycle. The current protection system for these plants will usually respond to a dropped rod by tripping the reactor. The combined effect of several trips could result in a significant capacity factor loss. It is not necessary, however, to trip the reactor if local power peaks can be maintained below design limits. Accordingly, commonly owned U.S. Pat. No. 4,399,095 proposes that while the reactor should be tripped upon the occurence of a very large negative flux change, for a more moderate drop in power the reactor can continue to operate as long as the power does not exceed the reduced power level initially resulting from the dropped rod by a preselected amount. It also calls for limits on rod withdrawal and a rollback in turbine power to maintain reactor power below the new limit. It is a primary object of the present invention to provide a method and apparatus for controlling a nuclear reactor which permits the reactor to operate at full power with a dropped rod as long as local peak power in the core does not exceed design limits. SUMMARY OF THE INVENTION The above object and others are realized by the invention which derived from our analysis of dropped rod incidents and our determination that local power peaking limits will be exceeded only if the dropped rod condition results in skewing of the axial power distribution, as measured for instance by the axial offset, by an amount which exceeds specified limits. More specifically, in accordance with the invention, when a dropped rod condition is detected, the plant is permitted to operate at the demanded power level, even 100% power, as long as a preselected axial power distribution limit is not exceeded. However, if the axial power distribution limit is exceeded, the reactor is shut-down. In plants where the part length rods are manipulated during power changes, separate limits are established for axial power distribution for the fully inserted and fully retracted positions of these rods. The dropped rod condition is detected by a negative rate of change of the neutron flux which is greater than a present limit. A negative rate of change in flux which exceeds a second, more negative limit, which is indicative of a severe abnormal condition, results in an immediate reactor trip regardless of the axial power distribution,
	summary
	description	Next, a description is given of an embodiment of the present invention. FIG. 1 are schematic views showing a configuration for a SPM measuring unit of the present invention. FIG. 1A is an upper view and FIG. 1B is a front view. As with the related art SPM, a probe support table 6 and a probe 7 are fitted to a scanner 1 moveable in an XYZ direction, and a sample 8 is located on a sample table 9. The surface of the sample 8 can then be scanned while detecting mutual physical interaction between the probe 7 and the sample 8. Although not shown in FIG. 1, a mechanism for sensing mutual interaction is also incorporated, as with the SPM of the related art. An X displacement sensor 3, Y displacement sensor 4, and Z displacement sensor 5 are also incorporated into this embodiment so that movement of the probe 7 can be detected. It is therefore possible to read in the amount of displacement in the X, Y and Z directions while scanning using the scanner 1. In this embodiment, a sensor counter electrode 2 is fitted to the scanner 1 as it is assumed that the displacement sensors are electrostatic capacitance sensors, but interferometers or optical sensors etc. may also be utilized as sensors. FIG. 2 is a block view showing an overall configuration for a SPM of this embodiment. A SPM controller 14 controls a SPM measuring unit 13. Further, output values for each displacement sensor are sent to operation/display means 16 fitted to the SPM controller 14. This means that it is necessary to synchronize driving of the scanner 1 and reading out the sensor output during scanning, so that signals can therefore be processed in an effective manner by processing using the SPM controller 14. The operation/display means 16 controls the whole of the SPM and is a computer and program for displaying data. In this embodiment, the output data of the X, Y and Z sensors is sent to image correction processor 15 from the operation/display means 16 and processed. The aforementioned SPM obtains data arrayed in such a manner that there is the same number of elements for each of the X, Y and Z sensor output values. The output values 17(a) for X displacement sensor 3, Y-displacement output values 18(a) and Z-displacement output values 19 are shown schematically as respective data arrays in FIG. 3. In the case of scanning a certain region by repeating an action of moving a distance corresponding to one pixel in the Y direction after scanning one line in the X direction, values for each row for X are displayed as lines increasing incrementally in single units as shown approximately in the X displacement sensor output value line profile 17(b), and each column for Y is shown increasing in single units as shown by the Y displacement sensor output value line profile 18(b). FIG. 3 shows ideal scanning results, and in reality the results will include various errors due to scanner hysteresis etc. The Z displacement sensor output values 19 have displacement sensor values showing a height corresponding to the surface shape of the scanned sample stored for each element of the array. There is therefore a problem as to whether or not the output values of the X, Y and Z sensors correctly express scanner displacement. For example, as shown in FIG. 1, if the angle of fitting the X, Y and Z displacement sensors deviates from an ideal angle assumed beforehand, errors will occur. In this case, it is therefore necessary to carry out some kind of compensation to ensure that the displacements shown by the sensor values are correct. FIG. 4 shows example compensation. Consider the case where, as shown in FIG. 4, the X and Y displacement sensor axes are taken as U and V, so that the respective angles deviate from the XY axes constituting ideal axes by just angles a and B. The X and Y axes are set taking into consideration the X Y deviation sensor data shown in FIG. 3. In this case, it is necessary to correct (U, V) on the displacement sensor axes to the ideal XY axes, and it is possible to express these equations as follows. x=uxc2x7cos xcex1+vxc2x7sin xcex2 y=xe2x88x92uxc2x7sin xcex1+vxc2x7cos xcex2 A correct sensor value can then be obtained by calculating the values for each point for the X Y displacement sensor value based on these equations. This processing is carried out on a computer after obtaining the array of displacement sensor values and this can of course be added to the correction function as electrical signal processing following the displacement sensor output. Correction can also be carried out in the same way when the fitting angle of the Z displacement sensor becomes displaced. Next, a case is considered where sensor values drift in response to changes in temperature, etc. This drift can be easily corrected if the drift is expressed as a function corresponding to elapsed time. For example, consider the case where displacement sensor output increases linearly in a unitary manner in response to time. In this case, if the amount of drift is taken to be D, the elapsed time is taken to be T, the gradient is taken to be a, and a section is taken to be b, then a function expressing the amount of drift can be represented by: D(T)=axc2x7T+b When intervals, constituted by units of time, at which data is sampled are taken to be xcex94T, and an amount of drift per unit time is taken to be xcex94D, then: xcex94D=axc2x7xcex94T Correction can then be achieved in a straightforward manner by simply subtracting the amount of drift from increases in the sensor value per unit time. Correction can also be easily achieved in a similar manner if drift in the displacement sensor values is obtained as a function D (T) of time. An image that can be said to be true in shape can then be obtained by plotting points in XYZ space taking the respective displacement sensor output values obtained in the above manner as coordinates. However, this makes the amount of data substantial and also means that the load placed on the computer carrying out the processing and on the electrical circuit for signal processing is substantial. Further, as image data such as bit maps handled by computers etc., it is most convenient if the XY coordinates of individual points of an image express scanner displacement as is or that the intensity of these points expresses displacement in the Z-direction. The means for obtaining this kind of image are the aforementioned image correction processor 15. FIG. 5 shows an outline view for the case where points are plotted in an XY plane based on the XY displacement sensor output values. If it is taken that slight variations exist with respect to X and Y, then this gives the kind of sensor value XY plot shown in FIG. 5. An operation where values for Z corresponding to coordinates of data 21 arrayed lined up in equal intervals depicted in the background of the points are interpolated based on this data is the image correction processing of this invention. Data based on three arrays for X, Y and Z can be handled as a single item of data by obtaining this arrayed data in advance. This means that data can be used in an efficient manner and that transfer to image formats such as bit maps generally employed by computers can be achieved in a straightforward manner. A rough description of the flow is now given based on the flowchart shown in FIG. 6. An outline view of a correction method is shown in FIG. 7. First, at a target point selection process 22, the XY coordinates of a point of an array of equally spaced data intended to be obtained is obtained. These XY coordinates are the target point shown in FIG. 7. A group of the three closest points to these coordinates as shown by the sensor value A, sensor value B and sensor value C of FIG. 7 are then selectively extracted from the group of sensor values. This process is carried out at a near point choosing process 23 of FIG. 6. Next, at a triangle determining process 24, this group of three close points is made to form a triangle in the XY plane and a determination is made as to whether or not the target point is present within this triangle. An equation expressing a plane in three dimensional space constituted by this group of three points is then obtained (approximation calculation process 25) and a Z value for the target point can then be obtained (correction value calculation process 26) by inputting the XY coordinates of the target point into this equation. This process is repeated until completion is determined by a processing end determination process 27, i.e. repeated by just the number of elements of arrayed data constituting the correction results, so that a corrected image is obtained. In FIG. 6, after choosing each print of the corrected image as a target point, three points close to this point are detected, and a determination is made as to whether or not these three points form a triangle. However, there is also a method whereby whether or not the target point is present within a triangle is detected after dividing the group of XY sensor values into a triangle by linking each point. This method is shown in the flowchart of FIG. 8. In this case, dividing up into triangles is carried out at a triangle dividing process 30 and the widely used Delaunay triangular dividing method is given as an example of this method. In his case, it is first necessary to make a Voronoi diagram, as sown in FIG. 9. It is taken that each of the points (hereinafter referred to as generatrix points) in FIG. 9 are located on a plane based on the XY sensor values. Polygons encompassing each point are referred to as Voronoi polygons and the boundary of each polygon consists of two equal vertical lines of line segments linking each generatrix. An apex of a Voronoi polygon, referred to as a Voronoi point, is always the interaction of three sides. This means that there are always three generatrix points located about the periphery of a Voronoi point. A triangle connecting the three points is referred to as a Delaunay triangle. It is therefore possible to effectively divide a plane up into triangles if points for all of the Delaunay triangles are shown collectively in FIG. 10 and this is referred to as a Delaunay diagram. The above method is the Delaunay triangular dividing method but this method is also advantageous with respect to the precision of the approximation calculations carried out thereafter because Delaunay triangles give shapes relatively close to equilateral triangles. This method can also be generally utilized in a wide variety of fields including structural analysis and image processing etc. and is advantageous from the point of view of performance. However, with this method it is necessary to store and process Voronoi points and Delaunay triangles in advance, which increases the load placed on the storage capacity etc. of the computer used due to the processing in FIG. 6. As a result of this, there is a possibility that the process of FIG. 6 will not be selected and acquired depending upon the performance of the computer used. After the aforementioned triangular dividing, as shown in FIG. 8, a corrected image is obtained by repeating a continuous flow of calculating XY coordinates for a target point (target point selection process 31), choosing a Delaunay triangle including the target point (near triangle selection process 32), calculating an approximation from the three points constituting the Delaunay triangle (approximation calculation process 33), and calculating correction values form the approximation (correction value calculation process 34) until completion is determined at the processing completion determination process 35. In the processes in FIG. 6 and FIG. 8, highly accurate correction is possible by carrying out the respective planar approximations but it is necessary to obtain equations expressing planes for all of the points and there are therefore cases where this may take time. The processing speed can therefore be increased by adopting a method where a Z displacement sensor value for the nearest point is substituted for the Z value for the target point or where Z displacement sensor values for a number of groups in the vicinity of the target point is averaged and then substituted for the Z value for the target point, but precision will be sacrificed. A method shown in the outline view in FIG. 11 can also be considered for the image correction processing. A group of four sensor values surrounding a target point and comprising a quadrangle are chosen as shown in FIG. 11 by the near point choosing process 23 of FIG. 6. Next, a straight line passing through the target point parallel to the Y axis is drawn by the approximation calculation process 25 with respect to a straight line connecting sensor value A and sensor value B, and a straight line connecting sensor value C and sensor value D, with X and Z coordinates being obtained for points of intersection a and b where the line passing through the target point intersects the other two straight lines. It is then possible to obtain a Z value for the target point from an approximation for a straight line linking the points of intersection a and b. In the embodiment described above, a description is given of a method of obtaining an image of a highly accurate shape based on all of the sensor values but it is also possible to measure various characteristics other than height with a SPM such as light, frictional force, and surface potential, etc. In this case it is also possible to simultaneously record this characteristic information in advance together with the X and Y sensor values for use in place of the arrayed data for the Z sensor values so that characteristic images that are highly accurate in the XY direction can be obtained. As an example of this, a schematic view of a configuration for the case where the SPM measuring unit shown in FIG. 1 is utilized as a scanning near field microscope is shown in FIG. 12. In FIG. 12, a point of distinction with FIG. 1 is that an optical probe 100 made from a light propagating body such as an optical fiber is used in order to illuminate the sample 8 with light, and a condensing lens 103 and light source 102 are added in order to ensure that light is incident at the probe 100. Light passing through the sample 8 is guided towards a light detector 106 by a mirror 104 and a condenser lens 105 so that the optical characteristics of the sample 8 can be measured. It is therefore necessary for a sample table 101 used here to be of a shape and material that does not block light that passes through the sample 8. Optical characteristic information obtained by a light detector 106 is saved as arrayed data as with the aforementioned Z sensor values so that an optical characteristic image that is highly accurate with respect to positioning in the X and Y directions can be obtained. If displacement in the Z direction is microscopic so that sufficient precision can be obtained without employing a sensor, then it is possible to obtain a shape image by performing correction taking a drive signal in a Z direction inputted to a scanner as data expressing the height direction, as with the related probe microscope. As described above, a scanning probe microscope of the present invention comprises microscopic driving means for driving a sample or probe microscopically in X, Y and Z directions, displacement detection means capable of measuring displacement of the microscopic driving means in the X, Y and z directions, and image correction means for recording values outputted by each displacement detection means as arrayed data during scanning of a sample with a probe, and making an output image from the recorded arrayed data with the relative positions with respect to the X, Y and Z directions corrected. With this construction, the actual shape of the sample etc. can be repeatedly reproduced with a high degree of accuracy without being influenced by hysteresis or non-uniform operation of a piezoelectric element or being influenced by environmental conditions. As a result, a SPM can be utilized in a measuring apparatus for measuring the surface conditions of a semiconductor or recording medium to a high degree of accuracy.
039768341	abstract	An emergency core cooling system for a nuclear reactor in which an emergency cooling injection manifold is integrally formed with the guide structure which guides control elements into the reactor core. The guide structure comprises two vertically spaced plates each of which substantially overlies the entire core and which are interconnected by a control element guidance means. A third plate is supported in vertical spaced relationship from one of the plates of the guide structure to define the manifold therebetween. Means are provided for substantially sealing the plenum from the main coolant flow path of the reactor. Means are also provided for introducing emergency coolant into the injection manifold and for dispersing coolant fluid therein into the core in the event of a loss of coolant accident.
	summary
051475987	description	DETAILED DESCRIPTION OF THE INVENTION In the following description, like references characters designate like or corresponding parts throughout the several views Also in the following description, it is to be understood that such terms as "forward", "rearward", "left", "right", "upwardly", "downwardly", and the like, are words of convenience and are not to be construed as limiting terms. In General Referring now to the drawings, and particularly to FIGS. 1 and 2, there is shown a pressurized water nuclear reactor (PWR), being generally designated by the numeral 10. The PWR 10 includes a reactor pressure vessel 12 which houses a nuclear reactor core 14 composed of a plurality of elongated fuel assemblies 16. The relatively few fuel assemblies 16 shown in FIG. 1 is for purposes of simplicity only. In reality, as schematically illustrated in FIG. 2, the core 14 is composed of a great number of fuel assemblies. Spaced radially inwardly from the reactor vessel 12 is a generally cylindrical core barrel 18 and within the barrel 18 is a former and baffle system, hereinafter called a baffle structure 20, which permits transition from the cylindrical barrel 18 to a squared off periphery of the reactor core 14 formed by the plurality of fuel assemblies 16 being arrayed therein. The, baffle structure 20 surrounds the fuel assemblies 16 of the reactor core 14. Typically, the baffle structure 20 is made of plates 22 joined together by bolts (not shown). The reactor core 14 and the baffle structure 20 are disposed between upper and lower core plates 24, 26 which, in turn, are supported by the core barrel 18. The upper end of the reactor pressure vessel 12 is hermetically sealed by a removable closure head 28 upon which are mounted a plurality of control rod drive mechanisms 30. Again, for simplicity, only a few of the many control rod drive mechanisms 30 are shown. Each drive mechanism 30 selectively positions a rod cluster control mechanism 32 above and within some of the fuel assemblies 16. A nuclear fission process carried out in the fuel assemblies 16 of the reactor core 14 produces heat which is removed during operation of the PWR 10 by circulating a coolant fluid, such as light water with soluble boron, through the core 14. More specifically, the coolant fluid is typically pumped into the reactor pressure vessel 12 through a plurality of inlet nozzles 34 (only one of which is shown in FIG. 1). The coolant fluid passes downward through an annular region 36 defined between the reactor vessel 12 and core barrel 18 (and a thermal shield 38 on the core barrel) until it reaches the bottom of the reactor vessel 12 where it turns 180 degrees prior to flowing up through the lower core plate 26 and then up through the reactor core 14. On flowing upwardly through the fuel assemblies 16 of the reactor core 14, the coolant fluid is heated to reactor operating temperatures by the transfer of heat energy from the fuel assemblies 16 to the fluid. The hot coolant fluid then exits the reactor vessel 12 through a plurality of outlet nozzles 40 (only one being shown in FIG. 1) extending through the core barrel 18. Thus, heat energy which the fuel assemblies 16 impart to the coolant fluid is carried off by the fluid from the pressure vessel 12. Due to the existence of holes (not shown) in the core barrel 18, coolant fluid is also present between the barrel 18 and baffle structure 20 and at a higher pressure than within the core 14. However, the baffle structure 20 together with the core barrel 18 do separate the coolant fluid from the fuel assemblies 16 as the fluid flows downwardly through the annular region 36 between the reactor vessel 12 and core barrel 18. As briefly mentioned above, the reactor core 14 is composed of a large number of elongated fuel assemblies 16. Turning to FIG. 3, each fuel assembly 16, being of the type used in the PWR 10, basically includes a lower end structure or bottom nozzle 42 which supports the assembly on the lower core plate 26 and a number of longitudinally extending guide tubes or thimbles 44 which project upwardly from the bottom nozzle 42. The assembly 16 further includes a plurality of transverse support grids 46 axially spaced along the lengths of the guide thimbles 44 and attached thereto The grids 46 transversely space and support a plurality of fuel rods 48 in an organized array thereof. Also, the assembly 16 has an instrumentation tube 50 located in the center thereof and an upper end structure or top nozzle 52 attached to the upper ends of the guide thimbles 44. With such an arrangement of parts, the fuel assembly 16 forms an integral unit capable of being conveniently handled without damaging the assembly parts. As seen in FIGS. 3 and 4, each of the fuel rods 48 of the fuel assembly 16 has an identical construction insofar as each includes an elongated hollow cladding tube 54 with a top end plug 56 and a bottom end plug 58 attached to and sealing opposite ends of the tube 54 defining a sealed chamber 60 therein. A plurality of nuclear fuel pellets 62 are placed in an end-to-end abutting arrangement or stack within the chamber 60 and biased against the bottom end plug 58 by the action of a spring 64 placed in the chamber 60 between the top of the pellet stack and the top end plug 56. Prior Art Inteoral Fuel Burnable Absorber Rods In the operation of a PWR it is desirable to prolong the life of the reactor core 14 as long as feasible to better utilize the uranium fuel and thereby reduce fuel costs. To attain this objective, it is common practice to provide an excess of reactivity initially in the reactor core 14 and, at the same time, provide means to maintain the reactivity relatively constant over its lifetime. As mentioned earlier, one prior art approach to achieving these objectives is to use fuel rods which are referred to as integral fuel burnable absorber (IFBA) rods, one being shown in FIG. 4. Such IFBA rods are provided in the prior art VANTAGE 5 nuclear fuel assembly manufactured and marketed by the assignee herein. The IFBA rod is a fuel rod 48 which has some fuel pellets 62 containing a burnable absorber or poison material. Specifically, end-to-end arrangements, or strings, of fuel pellets 62A containing no poison material are provided at upper and lower end sections of the fuel pellet stack of the fuel rod 48 and a string of the fuel pellets 62B with the poison material is provided at the middle section of the stack. As seen in FIGS. 5 and 6, each fuel pellet 62A containing no burnable absorber is in the shape of a solid right cylindrical body of nuclear fuel or fissionable material, such as enriched uranium dioxide. As seen in FIGS. 7 and 8, each fuel pellet 62B containing burnable absorber is composed of a solid right cylindrical body 66 serving as a substrate of the nuclear fuel or fissionable material, such as enriched uranium dioxide, and a thin cylindrical circumferential coating 68 on the exterior continuous outer surface 70 of the body 66. The coating 68 is preferably zirconium diboride (ZrB.sub.2), in which the boron-10 isotope is an effective neutron absorber; alternatively the coated fuel pellets 62B can be composed of a burnable absorber or poison material, such as gadolinia, mixed integrally with the enriched uranium fuel. The zirconium provides the cohesive matrix for holding the boron together to prevent fragmentation of the coating as the burnable absorber is burned up. Composite Fuel Burnable Absorber Arrangement of the Invention As described earlier, one problem in the case of the above-described IFBA rods with using the same burnable absorber, zirconium diboride, for controlling both power peaking and moderator temperature coefficient is that a large number of IFBA rods have to be employed, resulting in a higher residual penalty. The present invention avoid the drawback of IFBA rods by using two different absorber materials in a composite nuclear fuel and burnable absorber rod which has the same construction as the IFBA rod 48 except for the composition of the burnable absorber coated fuel pellets 62B. In the composite rod, two burnable absorber materials are used: one material, namely a boron-bearing material such as zirconium diboride, is tailored primarily for controlling power peaking; and the other material, namely an erbium-bearing material such as erbium oxide, is tailored primarily for controlling moderator temperature coefficient. The result is a significant reduction in the number of composite fuel and burnable absorber rods that need to be used, and consequently a reduction in the residual penalty without any loss in peaking factor or moderator temperature coefficient control. Boron in the zirconium diboride coated on the nuclear fuel is the preferred material for power peaking control in view of its advantages of no moderator displacement and very low residual penalty. Erbium coated on or mixed in the nuclear fuel is the preferred material for moderator temperature coefficient control. Erbium has a large resonance around 0.5 ev, which leads to a strong negative contribution to moderator temperature coefficient. As the spectrum hardens due to the increase in water temperature and the reduction in the moderator density, the harder spectrum leads to a larger resonance absorption. The contribution to moderator temperature coefficient is strong enough that even a low concentration of erbium in selected fuel rods, would eliminate the need for additional zirconium diboride or other burnable absorber materials for moderator temperature coefficient control. The low concentration of erbium, coupled with its good depletion characteristics, would lead to low residual penalty. Thus, erbium would control the moderator temperature coefficient directly through resonance absorption. Without it, the coefficient will have to be controlled indirectly through reduction of soluble boron in water by absorptions in an increased number of IFBA rods. At the same time, a smaller number of IFBA rods will be used to control the power peaking. The combination of zirconium diboride and erbium, used in the same cycle, takes advantage of the strength of both of these absorbers in the most appropriate manner. Turning now to FIGS. 9-12, there are illustrated the various embodiments of the two burnable absorber materials, boron-bearing material and erbium-bearing material, incorporated with nuclear fuel for use in the reactor core 14, in accordance with the principles of the present invention. Preferably, the fuel 72 has a substrate 74 of fissionable material, such as enriched uranium dioxide, configured as a cylindrical body or pellet having a continuous outer cylindrical circumferential surface 76. In the first embodiment shown in FIG. 9, the fuel 72A has the erbium-bearing burnable absorber material, such as erbium oxide and represented by the dashed lines, interspersed or mixed with the substrate 74A of fissionable material. The boron-bearing burnable absorber material, zirconium diboride, is provided in the form of an outer coating 78A on the outer surface 76 of the substrate 74 of the fuel 72A. In the second embodiment shown in FIG. 10, the fuel 72B has an outer coating 78B in the form of a sputtered mixture of erbium oxide and zirconium diboride. In the third embodiment shown in FIG. 11, the fuel 72C has an outer coating 78C composed of two coating layers 80 and 82, the inner layer 80 being zirconium diboride and the outer layer 82 being erbium boride. In the fourth embodiment shown in FIG. 12, the fuel 72D has an outer coating 78D also composed of two coating layers 80 and 82. However, now the inner layer 80 is erbium oxide and the outer layer 82 is zirconium diboride. Various methods of applying the coatings can be used. Examples of different methods which can be used are disclosed in above-cited U.S. Pat. No. 3,427,222, the disclosure of which is incorporated herein by reference. Referring to FIG. 2, there is shown one exemplary embodiment of an arrangement in the nuclear reactor core 14 of first and second groups of fuel rods, in accordance with the present invention, for controlling power peaking and moderator temperature coefficient factors. For purposes of brevity, in FIG. 2 the locations of fuel rods of the first group are identified by the letter "x", whereas the locations of fuel rods of the second group are identified by the letter "o". It will be noted that the first and second groups of fuel rods are illustrated in separate fuel assemblies 16. However, it should be understood that fuel rods from both groups can be contained in the same fuel assemblies. The fuel rods in the first group at locations "x" contain fissionable material but are free of any burnable absorber material, whereas the fuel rods of the second group at locations "o" contain both fissionable material and the two burnable absorber materials. As described above, the two burnable absorber materials can be provided as separate coatings or a mixture. Preferably, the one burnable absorber material is the erbium-bearing material such as erbium oxide and the other is the boron-bearing material such as zirconium diboride. Alternatively, the erbium-bearing material can be interspersed or mixed with the fissionable material. The fissionable material preferably contains enriched uranium dioxide. It is thought that the present invention and many of its attendant advantages will be understood from the foregoing description and it will be apparent that various changes may be made in the form, construction and arrangement thereof without departing from the spirit and scope of the invention or sacrificing all of its material advantages, the form hereinbefore described being merely a preferred or exemplary embodiment thereof.
	summary
	claims	1. A method of reducing the storage time of spent nuclear fuel, the method comprising:providing a spent nuclear fuel rod; andirradiating, by a gamma ray free electron laser (FEL), the spent nuclear fuel rod along a longitudinal axis of the spent nuclear fuel rod with substantially collimated gamma ray photons having energy levels of about 10 MeV to about 15 MeV for a predetermined time period to initiate a photofission reaction in remaining fertile fissile material in the spent nuclear fuel rod. 2. A method of reducing the storage time of spent nuclear fuel, the method comprising:providing a sample of spent nuclear fuel; andplacing the sample of spent nuclear fuel in a nuclear reactor with active nuclear material and control material; andremoving portions of the control material until the reactor reaches near criticality;irradiating, after the removing, the spent nuclear fuel with substantially collimated gamma ray photons having energy levels of about 10 MeV to about 15 MeV for a predetermined time period to initiate a photofission reaction in remaining fertile fissile material in the spent nuclear fuel. 3. The method of claim 2, further comprising:extracting power from the nuclear reactor, wherein the extracted power includes power due to the photofission reaction;converting the power from the nuclear reactor into electricity; andemploying the electricity to provide power to a gamma ray source that provides the substantially collimated gamma ray photons having energy levels of about 10 MeV to about 15 MeV. 4. The method of claim 3, wherein the gamma ray source is a gamma ray free electron laser (FEL). 5. The method of claim 4, wherein the predetermined time period is about 1 to about 10 hours. 6. A method of reducing the storage time of spent nuclear fuel rods, the method comprising:placing a spent nuclear fuel rod in a nuclear reactor with a plurality of active nuclear fuel rods and a plurality of control rods;removing one or more of the plurality of control rods until the reactor reaches near criticality; andirradiating the spent nuclear fuel rod, in the nuclear reactor, with substantially collimated gamma ray photons having energy levels of about 10 MeV to about 15 MeV for a predetermined time period to initiate a photofission reaction in remaining fertile fissile material in the spent nuclear fuel rod. 7. The method of claim 6, wherein the irradiating the spent nuclear fuel rod comprises irradiating the spent nuclear fuel rod along its longitudinal axis. 8. The method of claim 6, wherein the irradiating the spent nuclear fuel rod comprises irradiating the spent nuclear fuel rod with a gamma ray free electron laser (FEL). 9. The method of claim 6, further comprising:extracting power from the nuclear reactor that includes power due to the photofission reaction in the remaining fertile fissile material in the spent nuclear fuel rod;converting the power from the nuclear reactor into electricity; andemploying the electricity to provide power to a gamma ray source that provides the substantially collimated gamma ray photons having energy levels of about 10 MeV to about 15 MeV. 10. The method of claim 9, wherein the gamma ray source is a gamma ray free electron laser (FEL). 11. The method of claim 10, wherein the predetermined time period is about 1 to about 10 hours. 12. The method of claim 2, further comprising extracting power from the nuclear reactor, wherein the extracted power includes power due to the photofission reaction. 13. The method of claim 6, further comprising extracting power from the nuclear reactor, wherein the extracted power includes power due to the photofission reaction.
043222676	summary	BACKGROUND OF THE INVENTION This invention relates to an apparatus for controlling a residual heat removal system used for a nuclear reactor, which can safely cool the reactor within a short time after it is shut down. To begin with, the outline of a typical nuclear power plant will be explained. A reactor is placed in a container vessel and the heat generated through nuclear reactions in the reactor core turns the coolant water into steam. The steam is taken out through a main stream conduit externally of the container to drive a main turbine. The main turbine in turn drives a generator coupled directly to the main turbine so that electric power is generated. The steam, after having driven the main turbine, is condensed through a condenser into water. The condensed water is fed back as coolant water through a condensate pump and a feedwater pump into a reactor vessel. Thus, a nuclear power plant includes a closed loop of coolant water. When a fault occurs inside or outside the reactor, several control rods are immediately inserted into the reactor, that is, the reactor is scrammed (the nuclear chain reaction in the fuel is stopped). Simultaneously with scramming, isolation valves provided in the main steam conduit immediately inside and outside the container vessel are closed, depending on the nature of fault, to prevent radioactive materials from escaping from the reactor vessel. With the isolation valves closed, the reactor core can no longer be cooled by the main cooling system including the main turbine. Since a reactor continues to generate decay heat for more than ten hours after scram, an auxiliary cooling system must be provided for the reactor which takes out the residual heat from the reactor to cool the reactor down when the isolation valves have been closed. Such an auxiliary cooling system is a residual heat removal system (hereinafter referred to simply as RHR system) with which the invention is concerned. The RHR system comprises a closed loop which is started upon the closure of the isolation valves, the reactor steam is first led to a heat exchanger to be condensed into water and the condensed water is fed as coolant into the reactor vessel by a pump. This pump is so designed as to be driven by a turbine actuated by the reactor steam since in an emergency there is a large possibility that the power source in the plant is out of use and therefore the RHR system must operate without resorting to the plant power source. The steam, having done work on the turbine, is exhausted into another vessel. A make-up water reservoir communicates with the part of the pipes between the heat exchanger and the feedwater pump so as to prevent cavitation in the pump when the flow of water out of the heat exchanger decreases. Most of the above mentioned components of the RHR system are housed in the container vessel and the control of the system is performed by three separately provided control devices as follows. (a) Device for controlling the flow of the condensed water: This control device operates the heat exchanger inlet valve to control the internal pressure P.sub.H of the heat exchanger to a preset value (P.sub.H).sub.ref in order that the flow W.sub.H of the condensed water through the exchanger per unit time may be stabilized. (b) Device for controlling the flow of feed water: This device controls the aperture of the steam inlet valve of the turbine to control the flow W.sub.F of feed water to a preset value (W.sub.F).sub.ref in order that the coolant water may be fed into the reactor vessel at a constant rate. (c) Device for controlling the flow of make-up water: This serves to supply make-up water to the pump when the reactor-side pressure P.sub.S at the junction of the feedwater pipe and the make-up water pipe falls below a preset value (P.sub.S).sub.ref. Normally, (P.sub.S).sub.ref >P.sub.S and the flow of make-up water W.sub.C =0 so that W.sub.H =W.sub.F. According to this RHR system, since the flow W.sub.TB of water resulting from steam which has driven the turbine is exhausted, the level L.sub.R of the reactor water falls as measured by the expression (1) given below. ##EQU1## Here, L.sub.RO indicates the initial reactor water level, A.sub.R the cross sectional area of the reactor vessel, t the time for which the reactor is being operated and V.sub.f the specific volume of the reactor water, the reactor water meaning saturated water. According to a test calculation for a boiling water reactor having a rated output of 1,100,000 KW, the reactor water level L.sub.R falls about two meters down in several hours after scram and thereafter the emergency core cooling system ECCS as a safety mechanism other than the RHR system starts operating so that a large amount of cooling water is injected into the reactor vessel to resume the initial level. This is a preferable in view of the safety of the reactor since the safety is double assured by the RHR system and the ECCS. However, the flood of the cooling water causes thermal impacts on the reactor core assembly and the reactor vessel, resulting in causing deterioration thereof. It is therefore preferable if the residual heat can be removed by the RHR system alone. The problems caused by the supercooling due to the operation of the ECCS arises mainly from the fall of the reactor water level due to the operation of the RHR system. On the other hand, the RHR system must not only remove the residual heat but also observe the preset rate of the fall of, for example, the reactor water temperature to protect the members in the reactor vessel from thermal impacts. The following expression (2) denotes the rate of the fall of the reactor water temperature, i.e.-.DELTA.Temp/.DELTA.t, as one of the main temperature fall rate, calculated from the energy balance for a reactor with its ECCS out of operation. ##EQU2## In the expression (2), Q.sub.R indicates the decay heat in the reactor, T.sub.emp the temperature of the reactor water, M.sub.f the weight of the entire reactor water, i.sub.g the enthalpy of steam, i.sub.f the enthalpy of the reactor water (saturated water), and i.sub.F the enthalpy of the cooling water. In this case, it is clear that W.sub.H (i.sub.g -i.sub.F)=W.sub.F (i.sub.g -i.sub.F), both quantities indicating an amount of heat required to turn feed water at the flow rate of W.sub.H =W.sub.F into steam, and that the quantity W.sub.TB (i.sub.g -i.sub.f) denotes an amount of heat required to turn the condensed water at the flow rate of W.sub.TB into steam. For example, the rate of the fall of the reactor water temperature must be maintained at a present value, e.g. 55.degree. C./hour, to keep the residual thermal stress in, for example, the container vessel smaller than an allowable limit. However, since the decay heat Q.sub.R decreases with time, the temperature fall rate increases when W.sub.F is kept constant, as seen from the expression (2), until it exceeds 55.degree. C./hour. Accordingly, the operator must change the preset value (W.sub.F).sub.ref for the coolant water flow from time to time by manual setting in order that the temperature fall rate may not exceed the maximum allowable value 55.degree. C./hour. If (W.sub.F).sub.ref is so set as to correspond to 30.degree. C./hour whereby the rate may not exceed 55.degree. C./hour, the problem of supercooling can be solved, but too much time is required to remove the residual heat. SUMMARY OF THE INVENTION One object of this invention is to provide an apparatus for controlling an RHR system for a reactor, which can suppress the fluctuation of the reactor water level. Another object of this invention is to provide an apparatus for controlling an RHR system for a reactor, capable of observing the preset rate of the fall of the reactor temperature. Still another object of this invention is to provide an apparatus for controlling an RHR system for a reactor, capable of satisfying the requirements for the reactor water level and the reactor temperature fall rate. According to this invention, which has been made to attain the above objects, there is provided a system in which the steam generated in the reactor vessel is led to the heat exchanger to be condensed into cooling water and the cooling water is returned to the reactor core via the control valve and the pump driven by the turbine actuated by reactor steam so as to cool the reactor core, wherein a make-up water supply tank is provided which communicates via a non-return or check valve with the outlet of the control valve and when the reactor water level lowers, the control valve is closed to decrease the pressure P.sub.s at the outlet of the control valve, and the lowering of the reactor water level is compensated by supplying make-up water from the tank when the pressure P.sub.s becomes lower than the pressure P.sub.c at which the check valve is opened.
051261014	summary	BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for cleaning up reactor coolant in a boiling water reactor plant and, more particularly, to a reactor-coolant cleanup apparatus suitable for use in mitigating radiation exposure which may occur during scheduled inspections due to the presence of a piping provided for taking out reactor coolant at the bottom of a reactor pressure vessel, as well as to a method of controlling such an apparatus. 2. Description of the Related Art As disclosed in Japanese Patent Unexamined Publication No. 58-201094, a conventional type of reactor-coolant cleanup system for use in a boiling water reactor plant is in general arranged such that reactor coolant is extracted from its reactor pressure vessel through a piping connected to the lowest portion of the reactor pressure vessel and a piping branching off a primary loop recirculation piping. The reactor coolant flows in both of these pipings intermingle with each other within a primary containment vessel and is, in turn, passed through a heat exchanger, a pump, and a cleanup device which constitutes part of the reactor-coolant cleanup system. Thereafter, this reactor coolant intermingles with the flow of water fed through a reactor feedwater piping, and is returned to the reactor pressure vessel. The piping disposed at the lowest portion of the reactor pressure vessel performs the following functions. The first function is to discharge the crud component accumulated at the bottom portion of the reactor pressure vessel from the reactor pressure vessel together with the reactor coolant. The second function is to completely discharge the reactor coolant from the reaction pressure vessel for the purposes of inspection or modification. The third function is to circulate low-temperature reactor coolant stagnating at a lower portion of the reactor pressure vessel by means of the reactor-coolant cleanup system (without utilizing any recirculation system) when the reactor is in a hot stand-by state in which the normal running of the reactor is not carried out. The piping connected to the lowest portion of the reactor pressure vessel is arranged to discharge the reactor coolant from the inside of a core shroud surrounding a reactor core directly into the exterior of the reactor pressure vessel. For this reason, if an accident such as breakage should occur in such a piping, the reactor coolant is fed into the reactor core through an emergency core cooling system. However, even after the reactor core has been flooded, the discharge of the reactor coolant through the piping is continued. Accordingly, it is impossible to form the piping from a pipe having a sufficiently large diameter, and the diameter of this piping is commonly one-fourth to one-fifth the diameter of a piping provided for taking out water in the recirculation piping. As a result, the crud component contained in the reactor coolant tends to easily stick to the inner surface of the piping and there is a tendency for the dose rate of the piping to increase. The outlet piping and the inlet piping of the primary loop recirculation piping are connected to the reactor pressure vessel in the outside of the reactor core shroud (not shown). Accordingly, even in a case where the primary loop recirculation piping is partially broken, after the reactor core has been flooded by the operation of the emergency core cooling system, the reactor coolant in the reactor core is not discharged through the recirculation piping directly into the exterior of the reactor pressure vessel. It is, therefore, possible to increase the diameter of the recirculation piping in order to prevent the crud component from sticking to the inner surface of the recirculation piping. Further, the piping connected to the lowest portion of the reactor pressure vessel is located at a structurally lower position. It follows, therefore, that the proportion of the length of horizontally extending pipe portions to the overall length of such a piping is large. This fact also causes the crud component contained in the reactor coolant to stick to the inner surface of the piping and, hence, increases the dose rate of the piping. As described above, in the prior art, the crud component in the reactor coolant sticks to the inner surface of the piping connected to the lowest portion of the reactor pressure vessel to cause an increase in the dose rate of the piping. This increase in the dose rate constitutes a radiation source which brings about an increase in the dose rate of the surroundings within the primary containment vessel during scheduled inspections. In the prior art, however, no consideration is given to this problem, and it has been impossible, therefore, to avoid the problem that workers who need to enter the primary containment vessel for the purposes of scheduled inspections may undergo serious radiation exposure. In order to mitigate this radiation exposure, it has been proposed that a shielding made of lead, iron, or the like be employed. Although this proposal utilizes a method of installing a lead plate or an iron plate directly onto the piping, it is necessary to install a support for preventing the weight of the shielding from being applied directly to the piping, and the installation of this kind of support incurs an increase in cost. Moreover, the installation of this support inevitably narrows the working space in the primary containment vessel and, therefore, leads to a deterioration in the efficiency of operation during scheduled inspections. SUMMARY OF THE INVENTION It is, therefore, an object of the present invention to mitigate the radiation exposure of workers during scheduled inspections by reducing the dose rate of a piping connected to the lowest portion of a reactor pressure vessel without deteriorating the function of the piping. To achieve the above object, since the sticking of the crud component contained in reactor coolant to the inner surface of the piping leads to an increase in the dose rate of the piping, it is necessary to prevent the crud component from sticking to the inner surface of this piping. Moreover, it is necessary that the dose rate be reduced by using a shielding made of lead, iron, or the like. In accordance with the present invention, there is provided a structure for preventing the sticking of the crud component by utilizing the phenomenon in which, as the flow velocity in the piping becomes smaller or as the proportion of horizontal pipe portions is increased, the crud component more easily sticks to the inner surface of the piping. Moreover, the present invention utilizes the steel plate itself of the reactor pressure vessel as a shielding without the need of employing an additional shielding. In accordance with the present invention, a piping, which has heretofore been connected to the lowest portion of the reactor pressure vessel and extended downward therefrom, is disposed inside the reactor pressure vessel and is arranged to extend into the exterior of the reactor pressure vessel at a position which is higher than the lowest portion of the reactor pressure vessel.
	claims	1. A material for a nuclear fusion reactor, the material consisting essentially of:an alloy including two or more substances selected from the group consisting of Be12M or Be13M, Be17M2 and Be;wherein M is a metal element selected from the group consisting of Ti, V, Mo, W, Zr, Nb and Ta; andwherein a composition ratio x of M to Be is in a range of 2.0≦x≦15.0 (at %). 2. The material for a nuclear fusion reactor according to claim 1,wherein a composition ratio x of M to Be is in a range of 7.7<x<10.5 (at %). 3. The material for the nuclear fusion reactor of claim 1, wherein the alloy is produced by casting; andwherein a crystal grain size of the alloy is no more than 50 μm. 4. The material for the nuclear fusion reactor of claim 1, wherein the alloy is produced by powder metallurgy; andwherein a crystal grain size of the alloy is no more than 50 μm. 5. A plasma facing material for a nuclear fusion reactor comprising the material for the nuclear fusion reactor of claim 1.
055263852	description	DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to the figures of the drawing in detail and first, particularly, to FIG. 1 thereof, there is seen a simplified, sectional view of a nuclear reactor pressure vessel 1 (referred to below as a pressure vessel) of a pressurized-water nuclear power station which is constructed, for example, for a thermal reactor output of 3765 MW corresponding to an electrical gross output of 1300 MW. A reactor core 2 which is assembled from fuel assemblies, of which only a single fuel assembly 3 is shown, is cooled by light water which enters through inlet branches 4 and flows downwards in an annular space 5 (as is seen by flow arrows f1). Cooling water flows from a lower plenum 6, through a perforated lower grate 7, upwards through cooling channels of the fuel assemblies 3 (as is seen by flow arrows f2) in which it is heated, and then flows from an upper plenum 8 through outlet branches and through a so-called hot primary circuit line 10 (shown sectionally) that is connected thereto, to a non-illustrated steam generator, where it releases its heat through heat-exchanging tubes to a secondary coolant. The cooling water flow through the reactor core 2, the upper plenum 8 and the outer branches 9 is made clear by the flow arrows f2 that were already mentioned above. The cooled cooling water, which is also referred to as the primary coolant, is pumped back from the steam generator, through a non-illustrated so-called cold primary circuit line, to the inlet branch 4 of the pressure vessel 1, so that a continuous circulation is established in normal operation. In normal operation, the primary coolant is under a pressure of about 158 bar in the primary circuit and therefore also within the pressure vessel 1, and the coolant temperature at the outlet branch 9 is about 329.degree. C. The reactor pressure vessel 1 with its internals is constructed for this pressure and temperature stress plus a safety margin. The reactor pressure vessel 1 is formed of a pot-shaped lower vessel part 1A with a bottom hemisphere 11 and an annular flange 12 at its upper end, to which a domed cover 1B having a counter-flange 13 is bolted to make a seal (cover bolts are not shown, but bolt penetration openings 14 are shown). Only the most important internals will be mentioned, namely a lower screen barrel 15 and the already-mentioned lower grate 7 which is disposed above the lower screen barrel at a small distance and which forms a bottom of a core vessel 16. The core vessel 16 is suspended by a support flange 16.1 on a ring shoulder 17 of the annular flange 12 and has a lower part which takes up the core 2 with the individual fuel assemblies 3. The core 2 is covered by an upper grid plate 18 on which a guide structure 19 having an upper support plate 19.1 is supported. Control rods 20, which can be lowered or raised for reactivity control by non-illustrated control rod drives and are disposed above the cover 1B, dip into some of the fuel assemblies. In a four-loop unit, four outlet branches 9 and four inlet branches 4 are alternately located in a plane 21--21 and distributed over the periphery of the pressure vessel 1. The coolant, which is held under a supercritical pressure and is therefore liquid, not only covers the core 2, but also fills the upper plenum 8 approximately up to the upper support plate 19.1 in normal operation. This therefore also ensures effective cooling of those internals which, although they do not themselves generate any heat (such as the fuel assemblies 3), are subject to so-called gamma-heating by gamma-radiation. If the water level in the pressure vessel drops due to an extremely improbable failure of all cooling devices and emergency cooling devices, the component temperature (normally about 400.degree. C.) begins to rise and heat is increasingly released, in particular by radiation and conduction, to the pressure vessel 1, in particular if the water level has fallen down to the upper grid plate 18 or even a little below that. This overheating is utilized in the still relatively early stage by the safety device according to the invention for reliably preventing a failure of the pressure vessel 1 due to overpressure in the event of the insufficient core cooling. As is seen in FIG. 1 in conjunction with FIG. 2, for this purpose, a pressure pipe 23 passes through a wall 22 of the pressure vessel 1 in a pressure-tight manner, it extends into the interior of the pressure vessel 1, which is indicated as a whole with reference numeral 24, and it has at least one pressure compensation opening 26 which is disposed in the interior 24 of the pressure vessel and is sealed by a fusible sealing body 25. The pressure pipe 23 is a blow-off pipe and the pressure compensation opening 26 is a pressure relief opening, which is shown as a plurality of pressure compensation openings 26 in a perforated pipe head 27 in FIG. 2. According to FIGS. 1 and 2, the pressure pipe 23 with the perforated pipe head 27 is sealed by means of the fusible sealing body 25, which is positioned underneath the reactor core 2, preferably within the lower core structure or grate 7, and in particular directly underneath a grid plate 7.1, on which the fuel assemblies 3 rest with their lower ends or bottom plates. The perforated pipe head 27 with its fusible sealing body 25 thus forms a heat sensor which can very quickly react to an overheating of the core. For this purpose, the fusible sealing body 25 is formed of a melting solder which melts at a limit temperature in the region of, for example, 600.degree. to 700.degree. C. and unblocks the pressure compensation openings 26, but keeps the pressure compensation openings 26 sealed during normal operation. A brazing solder based on a silver alloy with a high silver content of, for example, 50% is particularly suitable as the melting solder, because such a brazing solder does not show any fatigue phenomena up to or almost up to its response temperature and withstands forces caused by a differential pressure. In addition, such a solder is resistant to radiation. The pressure pipe 23 is guided with a first pipe section 23.1 vertically downwards from the perforated pipe head 27 through the lower grate 7 and the adjacent screen barrel 15, that is to say within the interior of the bottom hemisphere 11. The pressure pipe 23 then has a first bending point 23a and is laid in an arc at a distance from the inner periphery as a second pipe section 23.2 up to the annular space 5 between the outer periphery of the core vessel 16 and the inner periphery of the lower pressure vessel part 1A, where it is laid vertically upwards from a second bending point 23b as a straight pipe piece 23.3 up to a third bending point 23c. At the third bending point 23c, the direction of the pressure pipe 23 changes from vertically parallel to the axis to horizontally perpendicular to the axis, and the pressure pipe is laid outwards through a non-illustrated pressure-tight penetration with an outer pipe piece 23.4 that leads to non-illustrated a blow-off vessel. The perforated pipe head 27 shown in FIG. 2 is sealed at its end surface by a pipe plug 28. The perforated pipe head 27 is preferably provided with a plurality of the mutually adjacent pressure compensation openings 26 in a pipe shell wall 29 thereof. This plurality of pressure compensation openings 26 is sealed by the fusible sleeve 25 that was already mentioned above and is soldered to the pipe shell wall 29. The fusible sleeve 25 is fittingly seated at a narrowed end 30 of the pressure pipe 23 and is axially secured by bearing against a shoulder 31 formed by the narrowing. A plurality of mutually adjacent rings 32 of the pressure compensation openings 26, which are three in the present case, are coaxial with the pipe. Each ring 32 includes four pressure compensation openings 26 distributed over the periphery of the pressure pipe 23. As is shown, the pipe plug 28 has a conical profile with a rounded tip, and it is inserted into the end of the pressure pipe 23 and fixed by a girth weld 33. The pressure pipe 23 according to FIGS. 1 and 2 (and also according to FIG. 3 to be explained below) is a blow-off pipe, so that the openings 26 are blow-off openings. Outside the pressure vessel 1, the pressure pipe 23 leads to a non-illustrated blow-off valve which discharges or feeds the blow-off steam into a blow-off vessel. This blow-off valve can open, preferably under pressure control, in such a way that it opens when a control pressure that is taken from the arriving pressure pipe 23 reaches a minimum value, for example 30 bar. In normal operation, the interior of the pressure pipe 23 is unpressurized, or normal atmospheric pressure prevails therein. In the second illustrative embodiment according to FIGS. 3 and 4, the pressure pipe 23 is sealingly guided in a suspended configuration through a cover branch or support 34 of the pressure vessel 1 and extends with the perforated pipe head 27, that is sealed by means of the fusible sealing body or the fusible sleeve 25, into the interior 24 of the pressure vessel 1 (as is seen in FIG. 1). The cover branch 34 is extended downwards by a guard pipe 35 that is conically widened at its end, and the perforated pipe 23 is provided along its length with guide rings 36 by means of which it is guided for axially sliding under the action of heat on the inner periphery of the guard pipe 35 or of the cover branch 34. At the outer end of the cover branch 34, a pressure-tight penetration for the pressure pipe 23 is provided in which a penetration housing 37 has a lower end that is bolted to the upper end of the cover branch 34 and is welded to be pressure-tight by a girth weld 38. The penetration housing 37 forms a receptacle for a conical ring gasket 39 and a nut 40, pressing the ring gasket 39 into a tight seating with a securing nut 41. As is seen in FIG. 4, a first sealing ring 62 is held with a lower rounded end 63 thereof against a collar 61 of the pressure pipe 23, which is provided with a conical all-around seating surface 60. The rounded end is also forced against a conical surface 64 on the inner periphery of the penetration housing 37. An upper end of the first sealing ring 62 is of a conical/rounded shape. A rounded part 62a is forced against the pressure pipe 23. A second sealing ring 65 is forced with a downward-projecting rounded-conical end 65a against an all-around conical surface 62b of the first sealing ring 62, with the rounded part being held against the conical inner peripheral surface 64 of the penetration housing 37. Thus, two respective all-around sealing seats 63/60, 63/64 and 62/23, 65/64 of the two sealing rings 63/65 result, on the outer periphery of the pressure pipe 23 and on the inner periphery (inner peripheral surface 64) of the penetration housing 37 relative to the pressure pipe 23 and the penetration housing 27, respectively, as well as an all-around sealing seat 62b/65a between the respective first and second sealing rings 62 and 65. A blow-off line 43 is pressure-tightly flanged by a ring flange 43.2 to a ring flange 42 of the penetration housing 37. The perforated pipe head 27 in the example according to FIG. 3 is of the same construction as that according to FIG. 2. The advantage of the safety device according to FIGS. 1 and 2 as compared with that according to FIG. 3 is that, during a change of a fuel assembly and unbolting of the vessel cover 1B, the pressure pipe 23 does not have to be removed, as is the case in the example according to FIG. 3. In this example, it is advantageous that the pressure pipe 23 can be taken up to the upper grid plate or up to a point close to this grid plate, so that overheating of the core can be detected very rapidly at an early stage. In the third illustrative embodiment according to FIGS. 5 and 6, a pressure pipe 230 is a pressure control pipe, by means of which a valve 44, which is provided externally of the vessel for reducing the system pressure, can be triggered. For this purpose, the pressure pipe 230 is pressure-tightly guided through a cover branch or support 34 (in this connection, see FIG. 3). In the vicinity of a pressure-tight connection 45 to a pressure control line 46, a pressure-tight bolting and weld is provided analogously to FIG. 3. The pressure control line 46 is connected to a control piston 47 of the blow-off valve 44 which is constructed, for example, as a three-way valve, and the system pressure being applied through a line 48 to the blow-off valve 44 is diverted by the blow-off valve 44 through a line 49 to the non-illustrated blow-off vessel, when the blow-off valve is shifted into its open position by a control pressure applied to the control piston 47. The pressure control pipe 230 can have a smaller diameter than the pressure pipe 23 (see FIGS. 1 to 3). As is seen in FIG. 6, this pressure control pipe also has a "heat sensor" in the form of a fusible sealing body 50 being formed of a melting solder which melts at a limiting temperature in the region from, for example, 600.degree. to 700.degree. C. and unblocks the pressure control line 230, but keeps a pressure compensation opening 51 sealed during normal operation. In particular, the pressure control pipe 230 seen in FIG. 6 is sealed at an end thereof extending into the interior of the pressure vessel 1 seen in FIG. 5, by a cover 52. The pressure control pipe 230 has a shell wall in which at least the one pressure compensation opening 51 is formed and inside which a spherical metal body 53 is embedded in the fusible sealing body 50. It is particularly advantageous if the pressure compensation opening 51 is an oblique opening as shown, having an opening axis 51' which is oriented obliquely inwards, so that in the event of fusion, the spherical body 53 drops into the interior of the pressure control pipe 230. Embedding of the spherical body 53 on both sides is shown, i.e. the melting solder 50 seals the pressure compensation opening 51 both outside the spherical body 53 and inside the latter. In FIG. 5 (in which components that are identical to FIG. 1 bear the same reference numerals), it is shown that the pressure control pipe 230 is guided parallel to the axis of the control rods 20, as a measuring lance in a manner of speaking, through the guide structure 19 and the upper grid plate 18 disposed on the underside thereof, to the head of a fuel assembly 3, where it is fitted into a corresponding receiving bore 54 with the required thermal play. In this region, an excessive temperature is very quickly detected by the perforated pipe head 270 when the coolant level (in the event of a highly improbable failure of the cooling devices and emergency cooling devices of the nuclear reactor) falls down to the level of the lower grid plate 18 or even lower. When this temperature reaches the limit value of, for example, about 700.degree. C., the fusible sealing body 50 melts and the spherical bodies 53 are thrust by the differential pressure into the pressure control pipe 230, so that the pressure can then be compensated for as far as the control piston 47 through the pressure compensation openings 51 which are then free. This control piston opens the blow-off valve 44, the indirectly controlled pressure compensation into the blow-off vessel can start, and it continues until the lower limit value (below 30 bar) has been reached.
041490878	claims	1. A recharging device for a nuclear reactor including a drum, a recharging box having a recharging mechanism and a recharging channel for connecting the drum to the recharging box, said recharging device comprising: a drum body; a holder pivotably mounted in said drum body and rotatable about a holder axis; stationary axial tubular sockets arranged in said holder in a number of rows, concentrically with the axis of the holder for receiving fuel assemblies; a recharging channel having pipes for recharging fuel assemblies abutting said drum body and arranged coaxially with said tubular sockets over one socket in each row; a recharging box; means for connecting the recharging box to said drum body so that the box communicates with said drum body through said pipes of said recharging channel, the recharging box including a recharging mechanism arranged in said recharging box for recharging of fuel assemblies and having a grip for holding fuel assemblies during recharging, the grip being movable to described a trajectory; said tubular sockets being so arranged in rows in said holder that the axis of at least one of said sockets in each row intersects with the trajectory described by said grip of said recharging mechanism in the course of its movement; said pipes of said recharging channel, abutting said drum body at points of intersection between a socket axis and a point on the trajectory described by said grip of said recharging mechanism; and means for rotating said holder to position different tubular sockets in alignment with said pipes. 2. A recharging device as claimed in claim 1 wherein three rows of tubular sockets are concentrically arranged within said holder. 3. A recharging device as claimed in claim 2 wherein the grip describes a straight trajectory and wherein the pipes of the recharging channel are aligned in a straight line. 4. A recharging device as claimed in claim 2 wherein the grip of the recharging mechanism describes an arcuate-shape trajectory and wherein the pipes of the recharging channel are aligned with points on the arcuate-shaped trajectory.
052727408	claims	1. An radioactivity trapping agent contained in a nuclear fuel based on sintered uraniferous oxides, for trapping the radioactivity of fission products which appear in the course of irradiation of said fuel, comprising an oxygenated compound stable at high temperatures, including, in combination, at least two metallic oxides and at least one oxide of a non-radioactive isotope of a radioactive fission product which appears during the irradiation, and whose radioactivity is to be trapped. 2. A trapping agent according to claim 1 wherein in the stable oxygenated compound the metallic oxides are selected from the group consisting of Al.sub.2 O.sub.3, CeO.sub.2, Nb.sub.2 O.sub.5, SiO.sub.2, TiO.sub.2, UO.sub.2, V.sub.2 O.sub.3, Y.sub.2 O.sub.3 and ZrO.sub.2. 3. A trapping agent according to either one of claims 1 and 2 wherein the metallic oxide is a silico-aluminate, silico-zirconate, silico-niobate or silico-cerate. 4. A trapping agent according to claims 1 or 2 wherein the stable oxygenated compound is pollucite or zeolite containing Cs. 5. A trapping agent according to claims 1 or 2, wherein characterised in that the stable oxygenated compound additionally contains a stable defined compound of an alkali metal and/or alkaline earth metal other than the fission product to be trapped. 6. A trapping agent according to claim 1 or 2, wherein said agent is included in nuclear fuel elements comprising a sintered uraniferous oxide surrounded by a metal sheath. 7. A trapping agent according to claim 6 wherein said agent is included in the sintered uraniferous oxide, the oxide being in pellet form. 8. A trapping agent according to claim 6 wherein said agent coats the sintered uraniferous oxide, the oxide being in pellet form. 9. A trapping agent according to claim 6 wherein said agent internally coats said sheath. 10. A trapping agent according to claim 6 wherein said agent is included in the fuel elements by at least two means selected from the group consisting of inclusion in the oxide, coating the oxide which is in pellet form, and internally coating the sheath. 11. A trapping agent according to claim 5 wherein said stable oxygenated compound comprises Rb, Na or K for Cs or Ca, Ba or Mg for Sr. 12. A nuclear fuel comprising sintered uraniferous oxides which produce radioactive fission products during irradiation of said fuel, and a trapping agent for the radioactivity of said fission products, said trapping agent comprising a high temperature-stable oxygenated compound including, in combination, at least two metallic oxides and at least one additional oxide which is an oxide of a non-radioactive isotope of a radioactive fission product whose radioactivity is to be trapped.
	summary
	claims	1. A system for detecting resonant fluorescence comprising:a light emitting diode (LED) configured to emit pulsed photoemissions towards a target in response to a pulsed signal;a photodiode configured to (1) receive resonant fluorescence emissions from the target, the resonant fluorescence emissions a response to the pulsed photoemissions, and (2) generate a current in response to the received resonant fluorescence emissions; andan amplifier system having first and second stages, wherein the first stage is configured to receive (1) the current from the photodiode, and (2) a gating signal as a function of the pulsed signal, the first stage further configured so that the gating signal gates the first stage to have a first output with (1) a first gain when the LED is activated to emit one of the pulsed photoemissions, and (2) a second gain when the LED is deactivated, wherein the second stage is configured to receive control signals and the first output of the first stage, the second stage having a second output and having a gain and offset configured to respond to the control signals to produce a linear dynamic range for a signal at the second output of the second stage that is an analog of the resonant fluorescence emissions from the target. 2. The system of claim 1 further comprising a controller programmed to generate the pulsed signal and the control signals. 3. The system of claim 1 further comprising an analog-to-digital converter for digitizing the second output of the second stage. 4. The system of claim 1, wherein the first stage comprises a transimpedance amplifier receiving the current and generating a voltage proportional to the current. 5. The system of claim 4, wherein the first stage comprises a first operational amplifier having a positive input selectively coupled to a ground potential through a first resistor/capacitor network setting a first input source impedance, the photodiode coupled between a negative input of the first operational amplifier and a supply voltage, and a second resistor/capacitor network selectively coupled from the negative input to an output of the first operational amplifier setting the first gain of the first stage and a second input source impedance. 6. The system of claim 5, wherein a first analog switch selectively couples resistors of the first resistor/capacitor network to the positive input of the first operational amplifier in response to the pulsed signal. 7. The system of claim 5, wherein a second analog switch selectively couples resistors of the second resistor/capacitor network to the negative input of the first operational amplifier in response to the pulsed signal thereby decreasing the first gain during stimulated emissions from the LED and increasing the first gain during resonance fluorescence emissions from the target. 8. The system of claim 1, wherein the second stage comprises a second operational amplifier having a positive input coupled to the first output of the first stage, a negative input coupled through a first resistor to an offset voltage and a three terminal voltage divider network including selectively coupled parallel resistors connected in series with a single resistor, one terminal of the voltage divider network is coupled to the second output of the second stage, a second terminal of the voltage divider network is coupled to a ground potential and a third terminal of the voltage divider network is coupled to the negative input of the second operational amplifier. 9. The system of claim 8, wherein the parallel resistor network comprises analog switches for selectively connecting resistors of the parallel resistor network to the negative terminal of the second operational amplifier, the analog switches selectable in response to the control signals. 10. The system of claim 8 further comprising an analog-to-digital converter having an input coupled to the second output of the second stage and digital outputs generating a digital signal. 11. The system of claim 8 further comprising a programmable offset voltage generator having an output generating the offset voltage in response to the control signals. 12. The system of claim 6, wherein the resistors are selectively connected in parallel with the capacitor in first resistor/capacitor network in response to the control signals and the values of the resistors and capacitor are sized to minimize the differences in impedances seen by charge injection at the inputs of the first operational amplifier when the gain of the first amplifier stage is gated by the pulse signal thus minimizing response time of the system. 13. The system of claim 12, wherein the output of the offset generator is isolated from the first resistor with a low output impedance buffer stage. 14. The system of claim 8, wherein the offset generator is programmed with parallel resistor network selectively connected in a voltage divider network in response to the control signals. 15. A method for detecting resonant fluorescent emissions from a target, comprising:irradiating the target with light from a pulsed light source, thereby causing the target to emit resonant fluorescent emissions, the pulsed light source receiving a signal that activates and de-activates the pulsed light source to gate the light ON and OFF;receiving the resonant fluorescent emissions from the target by a photoconductor to thereby produce a current modulated by the received resonant fluorescent emissions;coupling the current from the photoconductor to an amplifier system comprising a first stage amplifier that converts the current to a voltage output and a second stage amplifier with programmable gain and offset that receives the voltage output and produces an amplifier output;reducing a gain and balancing source impedances of the first stage amplifier in response to the signal that activates the pulsed light source ON; andincreasing the gain and balancing source impedances of the first stage amplifier in response to the signal deactivating the pulsed light source from ON to OFF. 16. The method of claim 15 further comprising:analyzing the amplifier output for cut-off and saturation;optimizing a dynamic range of the amplifier system;adjusting digitally the programmable gain of the second stage amplifier to optimize the dynamic range, andadjusting digitally the offset of the second stage amplifier to optimize the dynamic range. 17. The method of claim 16 further comprising converting the amplifier output to a digital signal using an analog-to-digital converter. 18. The method of claim 17, further comprising storing the digital signal in a controller as an analog of the resonant fluorescent emission. 19. The method of claim 15, wherein the photoconductor is a photodiode. 20. The method of claim 15, wherein the balancing of source impedances of the first stage amplifier minimizes a settling time of the amplifier system.
	claims	1. In a heat exchanger tube and shell structure, a generally flat support plate having a plurality of individual tube receiving apertures formed therein, at least three members integral with the plate defining each of the apertures, the integral members protruding inwardly toward the center of the respective aperture and forming bights between at least adiacent pairs of the members in order to provide a predetermined flow area when the tube that is individual to the respective aperture is lodged in place, the flow area having an inlet and an outlet, the members having beveled and sections at the inlet and the outlet, the inwardmost end of each of the integral members forming a flat land, said protruding integral member flat lands restraining but not all contacting the outer surface of the individual tube that is to be received within the respective aperture. 2. A heat exchanger tube and shell structure according to claim 1 wherein each of the apertures has an hourglass configuration. claim 1 3. A heat exchanger tube and shell structure according to claim 1 wherein the beveled end sections have a chamfer angle of about 11 degrees. claim 1 4. A heat exchanger tube and shell structure according to claim 1 wherein the inwardmost end of each of the integral members includes a tube contact section formed between the beveled end sections. claim 1 5. A heat exchanger tube and shell structure according to claim 4 wherein the tube contact section is about 0.75 inches in length. claim 4 6. A heat exchanger tube and shell structure according to claim 1 wherein the plate is formed from SA-240 410S stainless steel material. claim 1
047740493	abstract	A method and apparatus for monitoring and generating on-line, real time displays of two and three dimensional nuclear reactor core power distributions and off-line, periodically updated summaries of three dimensional nuclear reactor core power and burnup distributions is disclosed. The method and apparatus makes use of information obtained from inlet sensors and core-exit thermocouples to produce enthalpy rise values. Flux measurements are combined with enthalpy to produce power values. In one aspect of the invention, deviations from reference values are classified and displayed on a two-dimensional color graphics terminal where the various classifications are displayed according to a color code which enables a rapid and convenient method of analysis of the dynamics of the reactor operation.
053012127	claims	1. Apparatus for vertical, stepwise displacement of a component, said apparatus comprising (a) a raising device consisting of metal plates assembled in the form of a frame and fixed to jack boxes, each containing a jack, so as to displace said raising device both ways in a direction perpendicular to a plane of said frame; and (b) a plurality of modular lifting elements each consisting of metal plates assembled in the form of a frame, the shape and dimensions of said frame constituting the modular lifting element allowing it to be introduced into said frame of said raising device in a direction perpendicular to said frame, the modular element introduced into said frame of said raising device being in an assembly position allowing it to be fastened to said raising device, the frame of said raising device comprising orifices passing through said metal plates of said frame and each of said modular lifting elements comprising orifices coming into alignment with orifices of said frame of said raising device in the assembly position of a modular lifting element and of the raising device, connecting means consisting of keys being capable of being introduced into the aligned orifices of said frame of said raising device and of said modular lifting element. 2. Apparatus according to claim 1, wherein each of said modular lifting elements in the form of a frame has corners comprising a tubular column, to which two metal plates of the frame of the modular lifting element are fastened, said columns comprising means for fastening said modular lifting element to said frame of said raising device and means intended for interacting with corresponding means of the columns of a second modular lifting element, in order to ensure stable stacking of modular lifting elements.
	abstract	Methods and systems for correcting position errors for a multi-leaf collimator (MLC) are provided. A method may include determining a first position for each of the plurality of leaves. The information associated with the first position may include a first movement direction and a first angle. A movement of the each of the plurality of leaves along the first movement direction may be configured to move toward or away from a center of the radiation field. The method may also include determining an offset value associated with the first position based on the first angle and the first movement direction; and determining a target position of the each of the plurality of leaves based on the offset value.
	description	FIG. 1 shows in schematic vertical cross section an image information reading apparatus (sheet-like member processing apparatus) 12 which incorporates a light-shielding mechanism 10 according to the present invention. As shown in FIG. 1, the image information reading apparatus 12 has an apparatus housing 12a including a front wall (control wall) which supports on its upper portion a touch panel 14 that functions as controls and a display monitor. The apparatus housing 12a accommodates therein a plurality of, e.g., four, cassette loading regions 20a through 20d for removably holding respective cassettes 18, disposed below the touch panel 14. Each of the cassettes 18 comprises a casing 24 for housing a stimulable phosphor sheet (sheet-like member) 22, and a lid 28 by which an opening 26 in the casing 24 is openably closed. The cassette 18 has a lock means (not shown) for locking the lid 28 in a closed position on the casing 24. A vertically movable sheet feeder 30 is vertically movably disposed behind the cassette loading units 20a through 20d. The vertically movable sheet feeder 30 can selectively be aligned with any one of the cassette loading units 20a through 20d for removing a stimulable phosphor sheet 22 from the cassette 18 in the corresponding one of the cassette loading units 20a through 20d and returning a stimulable phosphor sheet 22 from which radiation image information is read and erased back into the cassette 18. The vertically movable sheet feeder 30 has a vertically. movable base 32 on which there are mounted a suction cup 34 movable into the cassette 18 with the lid 28 being open in one of the cassette loading units 20a through 20d, and a feed roller pair 36 for receiving and feeding the stimulable phosphor sheet 22 attracted by the suction cup 34. The image information reading apparatus 12 has an erasing unit 44 and a reading unit 46 disposed below the vertically movable sheet feeder 30 in the apparatus housing 12a and connected thereto by a feed system 42. The feed system 42 comprises a plurality of roller pairs 48 which jointly make up a vertical feed path extending downwardly from the vertically movable sheet feeder 30. The erasing unit 44 is disposed on the vertical feed path. The erasing unit 44 has a casing 50 which houses a vertical array of erasing light sources 52. The casing 50 includes an upper panel 50a having a first opening (inlet and outlet) 54 defined therein for guiding the stimulable phosphor sheet 22 into and out of the casing 50 therethrough, and a lower panel 50b having a second opening (outlet and inlet) 56 defined therein for guiding the stimulable phosphor sheet 22 out of and into the casing 50 therethrough. Each of the first and second openings 54, 56 is of an elongate rectangular shape. The light-shielding mechanism 10 according to the present invention is associated with the second opening 56. As shown in FIGS. 2 through 5, the light-shielding mechanism 10 has charge-eliminating brushes disposed on a feed path for the stimulable phosphor sheet 22 for contacting and eliminating electric charges from the stimulable phosphor sheet 22. In the illustrated embodiment, the charge-eliminating brushes include first and second charge-eliminating brushes 58a, 58b, and third and fourth charge-eliminating brushes 60a, 60b. The first and second charge-eliminating brushes 58a, 58b are disposed one on each side of the second opening 56, i.e., one on each side of the stimulable phosphor sheet 22, and mounted on an inner (upper) surface of the lower panel 50b by respective attachment plates 62a, 62b disposed therebetween. First and second guide plates 64a, 64b are fixed respectively to upper surfaces of the first and second charge-eliminating brushes 58a, 58b. The third and fourth charge-eliminating brushes 60a, 60b are disposed one on each end of the second opening 56, i.e., one on each edge of the stimulable phosphor sheet 22, and mounted on an outer (lower) surface of the lower panel 50b. The third and fourth charge-eliminating brushes 60a, 60b are oriented in directions perpendicular to the first and second charge-eliminating brushes 58a, 58b. The first and second charge-eliminating brushes 58a, 58b comprise respective plates 66a, 66b disposed one on each side of the stimulable phosphor sheet 22, i.e., the second opening 56, and longer than the transverse dimension of the stimulable phosphor sheet 22 in the transverse direction thereof which is perpendicular to the direction in which the stimulable phosphor sheet 22 is fed, and respective bristle assemblies 68a, 68b having ends embedded in the respective plates 66a, 66b and projecting toward each other. The bristle assemblies 68a, 68b comprise bristles set at a density ranging from 3,000 to 5,000 bristles/inch, preferably from 3,500 to 4,400 bristles/inch, and having a thickness ranging from 10 D (denier) to 300 D, preferably from 50 D to 200 D. The density of the bristles is about 2.5 times the density of the bristles of general charge-eliminating brushes. The bristles may be made of any of various materials, particularly a material that is not detrimental to the stimulable phosphor sheet 22 upon contact therewith, e.g., composite fibers of acrylonitrile and copper sulfide. The third and fourth charge-eliminating brushes 60a, 60b are of the same structure as the first and second charge-eliminating brushes 58a, 58b. Those parts of the third and fourth charge-eliminating brushes 60a, 60b which are identical to those of the first and second charge-eliminating brushes 58a, 58b are denoted by identical reference numerals with suffixes c, d. As shown in FIG. 1, the reading unit 46 is disposed near the lower end of the erasing unit 44. The reading unit 46 comprises an auxiliary scanning feeding mechanism 70 for delivering a stimulable phosphor sheet 22 from a cassette 18 in an auxiliary scanning direction indicated by the arrow A, an optical system 72 for applying a laser beam L as it is deflected in a main scanning direction (substantially perpendicular to the auxiliary scanning direction) to the stimulable phosphor sheet 22 as it is delivered in the auxiliary canning direction, and a light guiding system 74 for photoelectrically reading light which is emitted from the stimulable phosphor sheet 22 when the stimulable phosphor sheet 22 is exposed to the laser beam L. The auxiliary scanning feeding mechanism 70 has first and second roller pairs 76, 78 rotatable in synchronism with each other. Each of the first and second roller pairs 76, 78 has a pair of rollers that can be moved toward and away from each other. The light guiding system 74 comprises a light guide 80 extending along a main scanning line on the stimulable phosphor sheet 22 where the laser beam L is applied, and a photomultiplier 82 mounted on an upper end of the light guide 80. Operation of the image information reading apparatus 12 thus constructed will be described below. A cassette 18 which stores a stimulable phosphor sheet 22 which carries radiation image information of a subject such as a human body recorded by an exposure device (not shown) is introduced into the apparatus housing 12a along the cassette loading region 20a, for example. As the cassette 18 is introduced, the leading end of the cassette 18 pushes open a shutter 29, and enters the interior space of the apparatus housing 12a. After respective cassettes 18 have been inserted into the cassette loading units 20a through 20d, the vertically movable sheet feeder 30 is actuated to move the vertically movable base 32 into horizontal alignment with the cassette loading unit 20a, for example. Then, the first stimulable phosphor sheet 22 in the cassette 18 is attracted by the suction cup 34, and removed thereby from the cassette 13 out of the opening 26. Substantially at the same time that the leading end of the stimulable phosphor sheet 22 is gripped by the feed roller pair 36, the stimulable phosphor sheet 22 is released from the suction cup 34. The stimulable phosphor sheet 22 is transferred from the feed roller pair 36 to the feed system 42, and then delivered downwardly to the erasing unit 44 by the roller pairs 48 of the feed system 42. In the erasing unit 44, the stimulable phosphor sheet 22 is introduced into the casing 50 through the first opening 54. When the stimulable phosphor sheet 22 is thereafter fed out of the casing 50 through the second opening 56, both surfaces of the stimulable phosphor sheet 22 are held in contact with the first and second charge-eliminating brushes 58a, 58b, and both edges of the stimulable phosphor sheet 22 are held in contact with the third and fourth charge-eliminating brushes 60a, 60b, as shown in FIG. 4. Therefore, electric charges in the stimulable phosphor sheet 22 are effectively eliminated by the first and second charge-eliminating brushes 58a, 58b and the third and fourth charge-eliminating brushes 60a, 60b. Subsequently, the stimulable phosphor sheet 22 is fed to the reading unit 46 by the feed system 42. In the reading unit 46, as shown in FIG. 1, while the stimulable phosphor sheet 22 is being fed in the auxiliary 5 scanning direction indicated by the arrow A by the first and second roller pairs 76, 78 of the auxiliary scanning feeding mechanism 70, the laser beam L emitted from the optical system 72 is applied to the recording surface of the stimulable phosphor sheet 22. Radiation image information stored in the stimulable phosphor sheet 22 is now photoelectrically read by the light guiding system 74. The stimulable phosphor sheet 22 from which the radiation image information has been read by the reading unit 46 is fed back upwardly into the erasing unit 44 by the feed system 42. The leading end of the stimulable phosphor sheet 22 which is fed upwardly is introduced into the casing 50 while being held in contact with the first and second charge-eliminating brushes 58a, 58b and the third and fourth charge-eliminating brushes 60a, 60b of the light-shielding mechanism 10 at the second opening 56. The erasing light sources 52 of the erasing unit 44 are energized to erase remaining radiation image information from the stimulable phosphor sheet 22. In the illustrated embodiment, the bristles of the bristle assemblies 68a-68d of the first through fourth charge-eliminating brushes 58a, 58b, 60a, 60b are set at a density ranging from 3,000 to 5,000 bristles/inch, preferably from 3,500 to 4,400 bristles/inch, and have a thickness ranging from 10 D to 300 D, preferably from 50 D to 200 D. When the trailing end of the stimulable phosphor sheet 22 moves off the bristle assemblies 68a-68d into the casing 50, the second opening 56 is blocked against entry of light by the bristle assemblies 68a-68d, as shown in FIG. 5. When the erasing light sources 52 are energized in the casing 50, erasing light emitted from the erasing light sources 52 is reliably prevented from leaking from the second opening 56 along the feed system 42 to the reading unit 46. The light-shielding mechanism 10 is much simpler than the conventional light-shielding structures such as a laby-rinth structure, can effectively be reduced in size, and can be manufactured highly inexpensively. The light-shielding mechanism 10 is mainly composed of the first through fourth charge-eliminating brushes 58a, 58b, 60a, 60b whose bristles have a density that is about 2.5 times the density of the bristles of general charge-eliminating brushes. The light-shielding mechanism 10 can thus perform a charge-eliminating function and a light-shielding function with a highly simple arrangement. As described above, the bristles of the bristle assemblies 68a-68d of the first through fourth charge-eliminating brushes 58a, 58b, 60a, 60b are set at a density ranging from 3,000 to 5,000 bristles/inch, preferably from 3,500 to 4,400 bristles/inch, and have a thickness ranging from 10 D to 300 D, preferably from 50 D to 200 D. The bristles may be made of composite fibers of acrylonitrile and copper sulfide. Consequently, the light-shielding mechanism 10 has a sufficient light-shielding effect, and is not detrimental to the stimulable phosphor sheet 22, allowing the stimulable phosphor sheet 22 to be used efficiently. If the diameters of the bristles of the bristle assemblies 68a-68d were larger, then they would tend to be detrimental to the stimulable phosphor sheet 22. If the diameters of the bristles of the bristle assemblies 68a-68d were smaller, then they would be liable to be broken or otherwise damaged due to a reduced mechanical strength. The stimulable phosphor sheet 22 from which remaining radiation image information has been erased is delivered up-wardly from the erasing unit 44 by the feed system 42, and thereafter sent back into the empty cassette 18 in the cassette loading unit 20a by the vertically movable sheet feeder 30. In the illustrated embodiment, the light-shielding mechanism 10 is associated with the second opening 56 in the casing 50 of the erasing unit 44. However, another light-shielding mechanism 10 may also be associated with the first opening 54. Moreover, still another light-shielding mechanism 10 may be incorporated in an area on the feed path for the stimulable phosphor sheet 22 where unwanted light, e.g., extraneous light, would otherwise be likely to be applied to the stimulable phosphor sheet 22. In the illustrated embodiment, the light-shielding mechanism 10 is incorporated in the image information reading apparatus 12 which reads radiation image information from the stimulable phosphor sheet 22 and erases remaining radiation image information from the stimulable phosphor sheet 22. However, the light-shielding mechanism 10 may be incorporated in an image information reproducing apparatus for reproducing radiation image information on a photo-graphic photosensitive medium such as a photographic film or the like. In the light-shielding mechanism for use in the sheet-like member processing apparatus, the discharge-eliminating brushes are disposed on the feed path for the sheet-like member, and the bristles of the discharge-eliminating brushes are set at a density ranging from 3,000 to 5,000 bristles/inch, and have a thickness ranging from 10 denier to 300 denier. The discharge-eliminating brushes thus constructed have an effective light-shielding capability. The light-shielding mechanism is simple in construction and inexpensive to manufacture, and is capable of reliably preventing the sheet-like member from being irradiated with unwanted light. Although a certain preferred embodiment of the present invention has been shown and described in detail, it should be understood that various changes and modifications may be made therein without departing from the scope of the appended claims.
047755083	description	DETAILED DESCRIPTION OF THE INVENTION As shown in the FIGURE, and in accordance with the present invention, a composite fuel cladding tube 1 is provided having two concentric layers, each composed of a different zirconium base alloy. The outer layer 10 is composed of a conventional high strength zirconium base alloy known for its excellent corrosion resistance in aqueous environments. This first alloy may be either Zircaloy-2 or Zircaloy-4. The Zircaloy-2 or 4 utilized preferably conforms to the chemistry specification published in ASTM B350-80 Table 1 for UNS 60802 (Zircaloy-2) or UNS 60804 (Zircaloy-4). In addition the oxygen content of these alloys should be between 900 and 1600 ppm. Metallurgically bonded to and located within the outer layer is a second cylindrical layer 20 having the composition shown in Table I, below. TABLE I ______________________________________ Preferred Preferred Composition Composition A Composition B (wt. %) (wt. %) (wt. %) ______________________________________ Sn .1-.3 .1-.3 .1-.3 Fe .05-.2 .05-.2 .05-.2 Nb .05-.4 .05-.4 .05-.4 Ni .03-.1 <70 ppm .03-.1 Cr total Ni + Cr .03-.1 <200 ppm O 300-1200 ppm 300-700 ppm 300-700 ppm Fe + Ni + Cr <.25 <.25 <.25 Zr Balance* Balance* Balance* ______________________________________ *Zirconium is essentially the balance except for impurities (other than oxygen), which are maintained below 2000 ppm. This inner layer has been provided to give the fuel cladding tube improved resistance to the propagation of PCI related cracks in pile. The alloy selected for this layer (as shown in Table I) contains minimal amounts of tin, iron, niobium and nickel (as noted in the table chromium may be substituted for some or all of the nickel) in order to assure that the aqueous corrosion resistance of the inner layer is at least substantially the same as the corrosion resistance of the Zircaloy outer layer. Upper limits have been provided for these elements to assure that the inner layer material maintains sufficient ductility during in pile usage to stop the propagation of PCI related cracks. At the levels shown in the table the total iron, nickel and chromium contents, as well as their individual values, have been limited to assure that the amount of precipitates formed by these elements is not excessive, thereby minimizing any adverse effects these elements may have on PCI related performance, while providing a sufficient level of precipitates to assure the desired aqueous corrosion resistance. In one of the preferred compositions shown in Table I chromium may completely replace the nickel in the inner layer composition. For applications such as in heavy water reactors, this low nickel composition is preferred since chromium has a significantly lower thermal neutron capture cross section compared to that of nickel. At the levels specified for tin and niobium, these elements in addition to enhancing aqueous corrosion resistance also provide some solid solution strengthening. It is critical that the niobium content be kept below 0.4 wt.% in order to minimize niobium containing precipitates. In order to provide greater assurance in this regard it is preferred that the maximum niobium content be no greater than 0.2 wt.%. Increasing oxygen increases the hardness of the inner layer alloy and is believed to adversely affect the ability of the layer to resist PCI crack propagation in pile. Oxygen is therefore kept below 1200 ppm. Preferably the oxygen content of the inner layer is between about 300 to 1000 ppm, and more preferably between 300 and 700 ppm. The lower limit on oxygen content has been selected on the basis that any further improvement in PCI performance obtained by decreasing the oxygen further is believed to be limited and therefore cannot be justified in view of the significant additional costs involved in reducing the oxygen content further. While it has been noted that the total impurities in the inner layer are maintained below 2000 ppm, it is preferred that it be below 1500 ppm and that individual impurity contents be within the maximum levels specified by ASTM B350-80 Table 1 UNS R60001, where applicable. ASTM B350-80, in its entirety, is hereby incorporated by reference. Electron beam melting of the zirconium starting material to be used in the inner layer alloy, may be performed to reduce total impurity content. The thickness of the inner layer 20 is less than the thickness of the outer layer 10, and is preferably about 0.002 to about 0.006 and more preferably about 0.003 to 0.005 inches. The outer layer 20 forms the bulk of the cladding and provides the cladding with its required mechanical properties. The required thickness of this outer layer may thus be determined by conventional procedures used by those of ordinary skill in the art of nuclear fuel element design. Complete metallurgical bonding between the inner and outer layer is preferably obtained by a combination of hot working, annealing and cold working steps. The invention will be further clarified by the following example which is intended to be purely exemplary of the present invention. Melt an alloy having the nominal composition shown in Table II by consumable electrode vacuum arc melting the required alloying additions with commercially available zirconium. Arc melting is preferably performed at least twice. It should be understood that the cladding chemistry requirements set forth in this application may be met by performing chemical analyses at the ingot stage of manufacture for alloying elements and impurities, and subsequently, at an intermediate stage of manufacture, such as near the co-extrustion stage, for the interstitial elements, oxygen, hydrogen and nitrogen. Chemical analysis of the final size cladding is not required. TABLE II ______________________________________ Nominal Composition of Inner Layer Material ______________________________________ Sn 0.2 wt. % Fe 0.1 wt. % Nb 0.1 wt. % Ni 0.05 wt. % Cr 0.05 wt. % O 300 ppm Zr remainder, with incidental impurities ______________________________________ Fabricate the resulting ingot by conventional Zircaloy primary fabrication techniques, including a beta solution treatment step, into tubular starting components for the inner layer. Tubular Zircaloy starting components for the outer layer are conventionally fabricated from ingots meeting the requirements of ASTM B350-80 for grade R60802 or R60804 and having an oxygen content between about 900 and 1600 ppm. These tubular starting components, for both the inner and outer layers, may have a cold worked, hot worked, alpha annealed, or beta quenched micro-structure. The inside diameter surface of the outer layer starting component, as well as the outside diameter surface of the inner layer starting component are then machined to size, such that the clearance between the components when nested inside of each other is minimized. After machining, the components are cleaned to remove, as nearly as possible, all surface contamination from the surfaces to be bonded. The components are then nested inside of each other, and the annulus formed at the interface of the adjacent components is vacuum electron beam welded shut, such that a vacuum is maintained in the annulus after welding both ends of the nested components. At this stage, the unbonded tube shell assembly is ready to be processed according to the known extrusion, cold pilgering and annealing processes utilized to fabricate cladding tubes made completely of Zircaloy. Conventional Zircaloy lubricants, cleaning, straightening, and surface finishing techniques may be used in conjunction with any of the processes, both conventional and new, described in copending application Ser. Nos. 343,788 and 343,787 both filed on Jan. 29, 1982, and in U.S. Pat. No. 4,450,016 which are all hereby incorporated by reference. All of the foregoing fabrication processes will result in complete and continuous metallurgical bonding of the layers, except for minor, insignificant areas of unavoidable bond-line contamination. Beta treatment, either by laser or induction heating, while not required to practice the present invention, is preferred. When used, such treatment would be performed either between the next to last and last cold pilgering passes preferably as a surface treatment (as described in U.S. patent application 343,788) or just prior to the next to last cold pilger pass preferably as a through wall beta treatment. After beta treatment all intermediate, as well as the final anneals, should be performed below about 600.degree. C. and more preferably at or below about 550.degree. C. These low temperature anneals are used to preserve the enhanced corrosion resistance imparted by the beta treatment. Most preferably, the aqueous corrosion resistance of the outer layer and inner layer are characterized by a grey or substantially black, adherent corrosion film and a weight gain of less than about 200 mg/dm.sup.2, and more preferably less than about 100 mg/dm.sup.2 after a 24-hour, 500.degree. C., 1500 psi steam test. Whether or not beta treatment has been used, the final anneal, after the final cold pilgering pass, may be one in which the zirconium alloy inner layer is stress relieved (i.e. without significant recrystallization), partially recrystallized, or fully recrystallized. Where a full recrystallization final anneal is performed, the resulting average equiaxed grain size is no larger than about 1/4, and more preferably between about 1/10 and 1/30, the inner layer wall thickness and the Zircaloy outer layer has been at least fully stress relief annealed. After the final anneal, conventional Zircaloy tube cleaning, straightening, and finishing steps are performed. The lined cladding is loaded with fissile fuel material. Preferably the fuel materials used are in the form of cylindrical pellets and may have chamferred edges and/or concavedly dished ends. Preferably those pellets are composed of UO.sub.2 and are about 95% dense. The uranium in these pellets may be enriched or natural uranium. These pellets may also contain a burnable absorber such as gadolinium oxide or a boron containing compound. The resulting fuel element may be one of any of the known commercial pressurized water, boiling water, or heavy water reactor designs, preferably containing helium within the sealed fuel rod. Other embodiments of the present invention will be apparent to those skilled in the art from a consideration of this specification or practice of the invention disclosed herein. It is intended that the specification and examples be considered as illustrative only, with the true scope and spirit of the invention being indicated by the following claims.
	abstract	A magnetic shunt assembly (12) for an exposure apparatus (10) includes a magnetic shunt assembly (12). The apparatus (10) includes an optical assembly (24)(26), a stage (44), a first mover assembly (16) that moves the stage (44) in a first gap (37). The first mover assembly (16) is surrounded by a magnetic field. The magnetic shunt assembly (12) is positioned near the optical assembly (24)(26) approximately between the optical assembly (24)(26) and the mover assembly (16). The magnetic shunt assembly (12) is made of a material having a relatively high magnetic permeability. The magnetic shunt assembly (12) can provide a low magnetic reluctance path that redirects at least a portion of the magnetic field from the first mover assembly (16) away from the gap (37).
	summary
	abstract	A method and apparatus for modifying an existing nuclear reactor moveable in-core detector system to insert and withdraw target specimens from a reactor core during reactor operation without practically impeding the moveable in-core detector system's ability to obtain flux maps of the core throughout the reactor's operation. The apparatus provides a separate drive unit and delivery cable that is independent of the detector drive system, but uses most of the same core delivery conduits to access the core. A specimen holder is remotely detachable from the delivery cable when appropriately positioned and can be remotely reattached for withdrawal after a scheduled period of radiation.
	claims	1. An X-ray convergence element, in which X-rays entering from an entrance-side opening end of a tubular body are reflected on an inner surface of the tubular body, and the reflected X-rays exit from an exit-side opening end of the tubular body while being converged, the X-ray convergence element, comprising:an X-ray blocking member positioned adjacent the entrance-side opening end, having a diameter smaller than a diameter of the entrance-side opening end, a thickness of the X-ray blocking member, along a central axis of the tubular body, being different in a radial direction, and the center of the X-ray blocking member being arranged on the center axis of the tubular body,wherein a configuration of the varying side radial surface of the X-ray blocking member reflects incident X-rays to be equal to or greater than a total reflected optimal angle of the inner surface of the tubular body to enable reflected X-rays to pass through the tubular body. 2. The X-ray convergence element according to claim 1, further comprising:an annular member fixed in proximity to the entrance-side opening end; anda plurality of supporting members extending from the annular member toward the center of the X-ray blocking member to support the X-ray blocking member. 3. The X-ray convergence element according to claim 2, wherein the X-ray blocking member is an elongated plate-like body, a diameter of which being narrowed toward the X-ray entering side along the center axis. 4. The X-ray convergence element according to claim 2, wherein the X-ray blocking member has an X-ray incident surface that is a part of a spherical surface. 5. The X-ray convergence element according to claim 1, wherein the X-ray blocking member forms a spherical body;further comprising a plurality of fixing members for fixing the X-ray blocking member to the tubular body between the inner surface of the tubular body and a surface of the X-ray blocking member. 6. The X-ray convergence element according to claim 5, wherein the fixing members are spaced from each other with a predetermined distance in the circumferential direction of the tubular body, and are stick-like bodies arranged approximately parallel to each other in the axial direction of the tubular body. 7. The X-ray convergence element according to claim 1, further comprising an X-ray transmitting sheet for fixing the X-ray blocking member at the entrance-side opening end. 8. An X-ray irradiation device, comprising:the X-ray convergence element according to claim 1 for converging X-rays irradiated from an X-ray source; andan irradiating unit for irradiating the X-rays converged by the X-ray convergence element. 9. An X-ray convergence element in which X-rays entering from an entrance-side opening end of a tubular body are reflected on an inner surface of the tubular body, and the reflected X-rays exit from an exit-side opening end of the tubular body while being converged, the X-ray convergence element comprising:an X-ray blocking member having a diameter smaller than a diameter of the entrance-side opening end, a thickness of the X-ray blocking member, along a central axis of the tubular body, being different in a radial direction, and wherein the X-ray blocking member forms a spherical body further comprising a plurality of fixing members for fixing the X-ray blocking member to the tubular body between the inner surface of the tubular body and a surface of the X-ray blocking member, wherein the fixing members are spherical bodies arranged so as to be spaced from each other in the circumferential direction of the tubular body. 10. An X-ray convergence element, in which X-rays entering from an entrance-side opening end of an elongated glass tubular body are reflected on an inner surface of the elongated glass tubular body, and the reflected X-rays exit from an exit-side opening end of the elongated glass tubular body while being converted, the X-ray convergence element comprising:an X-ray blocking member, positioned adjacent the entrance-side opening end, having a diameter smaller than a diameter of the opening end, a thickness of the X-ray blocking member, along a central elongated glass axis of the tubular body, being different in a radial direction, and the center of the X-ray blocking member being arranged on the center axis of the elongated glass tubular body wherein a configuration of the varying side radial surface of the X-ray blocking member reflects incident X-rays to be equal to or greater than a total reflected optimal angle of the inner surface of the elongated glass tubular body to enable reflected X-rays to pass through the elongated glass tubular body. 11. An X-ray convergence element, in which X-rays entering from an entrance-side opening end of an elongated glass tubular body are reflected on an inner surface of the elongated glass tubular body, and the reflected X-rays exit from an exit-side opening end of the elongated glass tubular body while being converted, the X-ray convergence element comprising:an X-ray blocking member, positioned adjacent the entrance-side opening end, having a diameter smaller than a diameter of the opening end, a thickness of the X-ray blocking member, along a central axis of the elongated glass tubular body, being different in a radial direction, and the center of the X-ray blocking member being arranged on the center axis of the elongated glass tubular body wherein a configuration of the varying side radial surface of the X-ray blocking member reflects incident X-rays to be equal to or greater than a total reflected optimal angle of the inner surface of the elongated glass tubular body to enable reflected X-rays to pass through the elongated glass tubular body; andmeans for positioning the X-ray blocking member at the entrance-side opening of the elongated glass tubular body including an annular metal flange mounted on the entrance-side opening end to suspend the X-ray blocking member across the entrance-side opening end.
	claims	1. A leakage prevention seal sealing a space between a rotating shaft rotating about an axis and a housing surrounding the rotating shaft from a radial outer side so as to regulate a flow of high-temperature pressurized water in the space from the upstream side to the downstream side in an axial direction, the leakage prevention seal comprising:a first seal ring which surrounds the rotating shaft and which contacts with an upstream side surface of the housing along a circumferential direction in the rotating shaft;a second seal ring, which, on the upstream side of the first seal ring, surrounds the rotating shaft and which contacts with an upstream surface of the first seal ring along the circumferential direction in the rotating shaft; anda heat-driven section which, when high-temperature pressurized water reaches the heat-driven section, reduces the diameter of both the first seal ring and the second seal ring and causes the inner peripheral surfaces of both the first seal ring and the second seal ring to be in contact with the rotating shaft,wherein the first seal ring has a closed loop shape to form a first gap extending over a first range in a circumferential direction between the rotating shaft and the first seal ring during the reduction in diameter,wherein the second seal ring forms a second gap, which allows the high-temperature pressurized water to leak to the downstream side, over a second range in the circumferential direction during the reduction in diameter, andwherein the circumferential positions of both the first range and the second range are different. 2. The leakage prevention seal according to claim 1, further comprising a first gap positioning unit determining the circumferential position of the first range where the first gap is formed by applying a force in a radial direction to the first seal ring. 3. The leakage prevention seal according to claim 2, further comprising a pressing unit pressing the second seal ring toward the first seal ring. 4. The leakage prevention seal according to claim 3,wherein the first seal ring includes:a ring main body extending in the circumferential direction of the rotating shaft; anda pair of soft members disposed at both respective ends of the ring main body, formed of a material softer than the material of the ring main body, and brought into contact with each other during the reduction in diameter. 5. The leakage prevention seal according to claim 4,wherein the heat-driven section reduces the diameter of the first seal ring at a first temperature and reduces the diameter of the second seal ring at a second temperature, andwherein the first temperature is lower than the second temperature. 6. The leakage prevention seal according to claim 5,wherein the second seal ring has a closed loop shape when reduced in diameter, andwherein the second gap extends over the second range between the second seal ring and the rotating shaft. 7. The leakage prevention seal according to claim 6, further comprising a second gap positioning unit determining the circumferential position of the second range where the second gap is formed by applying a force in the radial direction to the second seal ring. 8. The leakage prevention seal according to claim 5,wherein the second seal ring has a C shape for both circumferential ends to face each other in the circumferential direction during the reduction in diameter, andwherein the second gap is formed between both of the ends of the second seal ring. 9. A pump for a nuclear reactor cooling material comprising:a rotating shaft rotating about an axis;a housing surrounding the rotating shaft from a radial outer side; anda leakage prevention seal according to claim 8 sealing a space between the rotating shaft and the housing so as to regulate a flow of high-temperature pressurized water in the space from the upstream side to the downstream side in the axial direction. 10. The pump for a nuclear reactor cooling material according to claim 9,wherein an annular groove recessed to the radial outer side and extending in a circumferential direction is formed in an inner peripheral surface of the housing,wherein the first seal ring and the second seal ring are arranged to be accommodated in the annular groove, andwherein the surface of the annular groove facing the upstream side is an abutting surface.
	abstract	A charged particle beam apparatus is provided which has high resolving power and a wide scanning region (observation field of view). The apparatus has a unit for adjusting the focus, a unit for adjusting astigmatism, a unit for controlling and detecting scanning positions and a controller operative to control the focus adjustment and astigmatism adjustment at a time in interlocked relation to the scanning positions, thereby assuring compatibility between the high resolving power and the observation view field of a wide area.
041475909	claims	1. Nuclear propulsion apparatus comprising: a. means for compressing incoming air; b. nuclear fission reactor means for heating said air; c. means for expanding a portion of the heated air to drive said compressing means; d. said nuclear fission reactor means being divided into a plurality of radially extending segments; e. means for directing a portion of the compressed air for heating through alternate segments of said reactor means and another portion of the compressed air for heating through the remaining segments of said reactor means; and f. means for further expanding the heated air from said drive means and the remaining heated air from said reactor means through nozzle means to effect reactive thrust on said apparatus. a. means for compressing incoming air; b. nuclear fission reactor means for heating said air; c. means for expanding a portion of the heated air to drive said compressing means; d. said nuclear fission reactor means being divided into a plurality of radially extending segments; e. means for directing a portion of the compressed air for heating in one direction through alternate segments of said reactor means and another portion of the compressed air in the opposite direction for heating through the remaining segments of said reactor means to balance fluid forces on said reactor means; f. means for further expanding the heated air from said drive means and the remaining heated air from said reactor means through nozzle means to effect reactive thrust on said apparatus; g. said nuclear fission reactor means being a right circular cylinder in shape with the cross sections of said segments being circular sectors; and h. pressure vessel means enclosing said segments to permit maintenance of circle arc geometry when the radius of said reactor means changes as a result of thermal growth. 2. The apparatus of claim 1 in which the partially expanded air from said drive means is further expanded through an annularly disposed thrust nozzle and the remaining heated air directly from said reactor means is expanded through a central thrust nozzle. 3. The apparatus of claim 2 in which the heated air for said drive means is derived from reactor means segments with air flow in one direction and the remaining heated air is derived from the remaining reactor means segments in the opposite direction. 4. The apparatus of claim 3 in which a portion of the compressed air prior to heating is mixed with heated air about to be expanded in said drive means. 5. Nuclear apparatus comprising: 6. The apparatus of claim 5 in which said pressure vessel means consists of multi-layered, thin-walled arc-shaped wall sections at the periphery of each reactor segment and resilient joint means located at adjoining reactor segments to interconnect adjoining wall sections. 7. The apparatus of claim 6 in which the fuel for said reactor means consists of tube-like elements extending parallel to the axis of said reactor means and in the direction of air flow through each said segment. 8. The apparatus of claim 7 in which the downstream end of each segment is provided with means to support said fuel elements against movement caused by fluid pressure. 9. The apparatus of claim 8 in which said support means includes a grid-like lattice structure and means to cool said structure and prevent overheating of the reactor end support structure. 10. The apparatus of claim 9 having air-cooled shielding means surrounding said pressure vessel means. 11. The apparatus of claim 5 in which said reactor means is provided with a hollow hub and means within said hub for exercising control over the reactivity of said reactor means. 12. The apparatus of claim 5 having means for directing air flow as aforesaid, said ducting means performing the additional function of providing some shielding for said reactor means.
	summary
	claims	1. A recycled fuel assembly storage basket comprising:a plurality of rectangular first plate members being stacked with long side ends thereof abutting to each other;a plurality of connecting members extended in a direction towards which the first plate members are stacked, attached to a side surface of each of the first plate members being stacked, connecting the first plate members, and projecting from the side surface;a plurality of rectangular second plate members both of whose long side ends have recesses into which the connecting members are fitted; anda recycled fuel assembly stored in a space surrounded by the first plate members and the second plate members. 2. The recycled fuel assembly storage basket according to claim 1, wherein each of the first plate members and the second plate members has a through hole penetrating in a longitudinal direction. 3. The recycled fuel assembly storage basket according to claim 1, wherein a cross-section of each of the connecting members perpendicular to the longitudinal direction is a trapezoid, and an upper base of the cross-section comes into contact with the side surface of each of the first plate members. 4. The recycled fuel assembly storage basket according to claim 3, wherein a cross-section of each of the recesses in the second plate members perpendicular to the longitudinal direction is a trapezoid, and an upper base side of the cross-section comes into contact with the side surface of each of the first plate members. 5. The recycled fuel assembly storage basket according to claim 1, wherein the second plate members and the connecting members are made of different materials. 6. The recycled fuel assembly storage basket according to claim 1, wherein the connecting members are divided at different positions in the direction towards which the first plate members are stacked. 7. The recycled fuel assembly storage basket according to claim 1, wherein the connecting members are attached to the first plate members by a fastening member. 8. The recycled fuel assembly storage basket according to claim 7, wherein a through hole is provided at a side of each of the connecting members, and the fastening member penetrates through the through hole. 9. The recycled fuel assembly storage basket according to claim 7, further comprising a load supporting unit that supports a load of the second plate members between the fastening member and the connecting member, and between the fastening member and the first plate members. 10. The recycled fuel assembly storage basket according to claim 9, further comprising a rotation suppressing member that suppresses rotation of the load supporting unit at least one of between the load supporting unit and the first plate members, and between the load supporting unit and the second plate members. 11. The recycled fuel assembly storage basket according to claim 7, further comprising a reinforcement member made of a material having higher stiffness than that of the first plate members inside the through hole of the first plate members, the reinforcement member being connected with the fastening member. 12. The recycled fuel assembly storage basket according to claim 1, whereina groove extending in the direction towards which the first plate members are stacked is formed on the side surface of each of the first plate members, andthe connecting member is fitted into the groove. 13. A recycled fuel assembly storage container comprising:a trunk having an opening portion and a cavity;a lid attached to the opening portion and sealing the cavity; andthe recycled fuel assembly storage basket of claim 1 which is disposed in the cavity. 14. A method for manufacturing a recycled fuel assembly storage basket comprising:stacking a plurality of rectangular first plate members with long side ends thereof abutting to each other;forming a plurality of plate member joint bodies by connecting the first plate members with connecting members attached to a side surface of each of the first plate members and projecting from the side surface;disposing side surfaces of the plate member joint bodies so as to face each other, and placing the connecting members opposite from each other; andinserting the connecting members placed opposite from each other into recesses formed at both of long side ends of a rectangular second plate member.
	description	1. Field of the Invention The present invention relates to a data networking system and a method for networking data, and in particular, a system and method for automatically managing machine tool data and providing the data to a remote terminal over a network. 2. Background Art The ever-increasing emphasis on product quality continues to put pressure on manufacturers to find new ways to produce high quality products without increasing production time or otherwise increasing manufacturing costs. Inherent in this high quality, low cost dichotomy is a need to reduce scrap, while obtaining the longest possible life from manufacturing tools and equipment. Thus, increasing the number of tooling changes and/or decreasing the time between machine tool maintenance may increase product quality, but it may result in an unnecessary increase in tooling costs and/or lost production time. Over time, manufacturers have developed systems and methods of predictive and preventative maintenance. Such systems may include a scheduled tool change based on a number of parts produced, or scheduled machine down time, during which bearings and other components may be replaced prior to their having an adverse effect on product quality. In order to implement these systems in a cost effective manner, or to reduce the frequency of these preventative maintenance tasks, decision-makers need information. In particular, information that is indicative of historical trends is useful, so that accurate predictions can be made regarding future production runs. In addition, the ability to isolate particular problem areas is also useful; this helps to concentrate efforts where they will have the most impact and produce the most benefit. Toward this end, manufacturers have continued to analyze machine tools and their associated components in an effort to gather information they can use to make efficacious decisions regarding their production systems and processes. One type of machine tool analysis used is a vibration analysis. Information gathered from this type of analysis may be indicative of a variety of different production problems. One system and method of characterizing a machining process using vibrational signatures of machines is described in U.S. Pat. No. 5,663,894, issued to Seth et al. on Sep. 2, 1997. Seth et al. describes characterizing the vibrational signatures of machines by discriminating vibrational activity at various positions on the machines. This is done both with and without machining loads. Both time and frequency domain analysis may then be stored in a database for future comparison and tracking. In addition to gathering vibration data with and without machining loads, it may also be desirable to associate vibration data with particular operations performed on a machine. Once this data is gathered, it would then be desirable to collect it for storage on a network server that can be accessed by one or more terminals remotely located from the machining area. In general, traditional monitoring systems are based on individual tool condition analysis, and are used primarily for tool breakage. Templates are used, but trend analysis is not performed. Because data, such as vibration data, can occupy a large amount of storage space, and bandwidth when it is being transferred, it would also be desirable to reduce the size of the data, while still providing operation specific, and even tool specific, data that can be used to evaluate the machining operations. One advantage of the present invention is that it provides a data networking system and method which allows machine operation data, at the tool specific level or beyond, to be examined remotely from the machining environment. Another advantage of the present invention is that it provides a data networking system and method which reduces the size of the raw data to conserve data storage space and bandwidth, while still providing operation specific machine tool data to an end user. The invention further provides a data management and networking system for automatically retrieving and storing data from a machine tool for distribution to a remote terminal over a network. The machine tool is operable to perform at least one machining operation on a workpiece, and has at least one sensor operatively connected to it for sensing a machine operation parameter. The at least one sensor has a first processing unit operatively connected to it for receiving data related to the machine operation parameter. The machine tool further has a controller operatively connected to it and configured to output data related to the at least one machining operation to the first processing unit. The system includes a data storage unit for storing data for subsequent retrieval. The system also includes a second processing unit configured to automatically collect the machine operation data and the machine operation parameter data from the first processing unit. The second processing unit is also configured to apply an algorithm to the machine operation parameter data to generate at least one parametric representation of the machine operation parameter data. The second processing unit is further configured to associate the at least one parametric representation with respective machining operation data, and to send the associated parametric representation and machining operation data to the data storage unit. The invention also provides a data management and networking system for automatically retrieving and storing data from a machine tool for distribution to a remote terminal over a network. A machine tool is operable to perform at least one machining operation on a workpiece. The at least one machining operation includes machining time and non-machining time. The machine tool has at least one sensor operatively connected to it for sensing a machine operation parameter, and for outputting signals related to the machine operation parameter to a first processing unit. The machine tool also has a controller operatively connected to it and configured to output signals related to the at least one machining operation to the first processing unit. The system includes a data storage unit for storing data for subsequent retrieval. The system also includes a second processing unit configured to automatically collect the machining operation data and the machine operation parameter data from the first processing unit, and to separate out at least some data related to non-machining time. The second processing unit is further configured to apply an algorithm to the separated machine operation parameter data to generate at least one parametric representation of the separated machine operation parameter data, and to associate the machining operation data and the at least one parametric representation and to send the associated data to the data storage unit. The invention further provides a method for managing and networking data for a machine tool. The method includes performing a machining operation on a first workpiece, the machining operation including machining time and non-machining time. A machine operation parameter is sensed while the machining operation is being performed. Data related to the sensed machine operation parameter is captured, and data related to the machining operation is also captured. At least some data related to non-machining time is separated out, and an algorithm is applied to the separated machine operation parameter data to generate at least one parametric representation of the separated machine operation parameter data. The at least one parametric representation is associated with respective machining operation data, and the associated parametric representation and machining operation data is stored for subsequent retrieval by a remote terminal over a network. Elements of a data management system 10 for a machine tool are illustrated in FIG. 1. One such data management system is described in U.S. Pat. No. 6,845,340, entitled “System and Method For Machining Data Management,” issued on Jan. 18, 2005, and incorporated herein by reference. A portion of a machine tool 11 includes a bed 12 and a spindle 14. The machine tool 11, shown in FIG. 1, is a computer numerical control (CNC) milling machine. As will be readily discerned from the description below, the present invention can be used with any type of machine tool operable to perform at least one machining operation on a workpiece. Mounted in the spindle 14 is a cutting tool 16, which is used to machine a workpiece 18. Attached to the spindle 14 is a vibration sensor 20 that is configured to sense vibrations in the spindle 14 and output signals related to the vibrations to a first processing unit 22. The vibration sensor 20 may be chosen from any one of a number of types of vibration sensors, such as an accelerometer, a velocity sensor, or any other suitable sensor capable of sensing vibrations. Of course, other types of sensors may be used—i.e., ones that sense machine operation parameters other than vibrations. For example, a current sensor may be used to measure changes in the amount of current the machine tool 11 draws during various machining operations. Similarly, a thermocouple, or other type of temperature sensor, could be used to detect changes in temperature of some portion of the machine tool 11. The spindle speed, torque, or feed rate could also be sensed to provide information relating to the machining operations. Indeed, any sensor capable of sensing a machine operation parameter can be used to send signals to the first processing unit 22. The first processing unit 22 may be conveniently mounted directly on a portion of the machine tool 11, and includes a processor 24 and a memory 26. The processor 24 may be programmed to perform specific instruction sets on data, such as vibration data received from the sensor 20. A controller, such as a PLC 28, is also attached to the machine tool 11, and may be programmed with information specific to the machine tool 11, or specific to a machining process or cycle performed by the machine tool 11. The processor 24 and the memory 26 are both operatively connected to the sensor 20 and the PLC 28, such that data may be transferred among them. As noted above, the PLC 28 may be programmed with information regarding particular machining operations. It is configured to output signals related to the machining processes to the first processing unit 22. For example, if a set of machining operations are being performed on the workpiece 12, and completion of this set of operations constitutes a machining cycle, the PLC 28 can, among other things, output signals to the first processing unit 22 delineating different portions of the machining cycle. Thus, the PLC 28 may send a tool pickup signal each time a different tool is used in a set of machining operations. The PLC 28 may also send signals indicating when a particular cutting tool, such as the cutting tool 16, is performing a particular machining operation. In addition, the PLC 28 may communicate to the first processing unit 22 when the machine tool 11 is idling, and may further communicate time related data such as the number of machining cycles performed or the number of the workpiece being machined. Thus, by outputting signals related to the machining operations, the PLC 28 may communicate to the first processing unit 22 tool-specific data, idling data, and time related data, just to name a few. Of course, the specific information output from the PLC 28 to the processing unit 22 may vary, depending on the type and quantity of information desired. FIG. 2 shows a data management and networking system 30 in accordance with the present invention. The system 30 includes an operator interface 32 operatively connected between the first processing unit 22 and a second processing unit, or machine PC 34. The machine PC 34 can be a personal computer attached to a machine tool, such as the machine tool 11, or it may be a specialized processing unit, particularly configured for use with the machine tool. The machine PC 34 has at least two software applications loaded onto it. The first, a dynamic link library (DLL) 36, is configured to automatically collect data from the first processing unit 22. The DLL 36 can be configured to automatically collect data from the first processing unit 22 at some predetermined interval, thereby eliminating the need for a manual download. For example, it may be desirable to have the DLL 36 collect data at a rate that is faster than the machining operation cycle time. After the DLL 36 collects the data, the data can be cleared from the memory 26 of the first processor 22, thereby freeing data storage space. The DLL 36 may perform a number of functions on the data collected from the first processing unit 22. For example, the data collected from the first processing unit 22 may include machine operation parameter data, such as raw vibration data measured with the sensor 20 shown in FIG. 1. Because raw data, such as vibration data, can consume very large amounts of storage space, and bandwidth when the data is transferred over a network, it is desirable to reduce the size of the data being stored and transferred, without losing the information that will be useful to a production control decision maker. The DLL 36 addresses this issue by generating at least one parametric representation of the machine operation parameter data, such as the raw vibration data. For example, the DLL 36 may include an algorithm which is applied to raw vibration data to generate one or more statistical parameters. Such parameters may include a maximum, a minimum, an average, an average root mean square (RMS), a maximum RMS, a minimum RMS, and an RMS summation. In addition, the DLL 36 may apply an algorithm to the preprocessed data that optimizes, for example, a kurtosis, a kurtosis average, a kurtosis maximum, a kurtosis minimum, and a kurtosis standard deviation. Like the RMS values, the kurtosis values are readily calculated using known statistical formulas. The DLL 36 may also apply an algorithm to the raw vibration data that transforms the data into a frequency domain. By performing a frequency spectrum analysis, the raw vibration data can be analyzed by its frequency, such that a parametric representation of the raw vibration data can be in the form of frequency band amplitudes. That is, a frequency spectrum generated from the raw vibration data can be divided into frequency ranges, or bands, and the amplitude of these bands used as a parametric representation of the raw data. Similarly, the frequency spectrum data can be used to generate energy bands instead of frequency bands if it is desirable to represent the raw data in terms of its energy, rather than its frequency. The DLL 36 communicates with a data bridge application 38, which is used to associate the parametric representation with respective machining operation data such that analysis of individual machining operations, and even individual tool operations, is possible. This process is explained more fully below in conjunction with FIG. 3. The data bridge application 38 also verifies that data related to the machining operation is valid. By generating the parametric representation of the machine operation parameter data, such as the raw vibration data, the size of the data that needs to be stored and transferred over a network is greatly reduced. In addition to generating the parametric representation, the size of the data can be further reduced by separating out that portion of the machining operation that is non-machining time. During a given machining operation, there may be times when the workpiece is not actually being machined. For example, a spindle may move from one location on a workpiece to another location without cutting, or otherwise removing, any material from the workpiece. The machining operation may still be in process, even during the time when the workpiece is not being cut. A machine tool, such as the machine tool 11, may also include automatic tool changing, such that a cutting tool is removed from a workpiece, the spindle is moved to a tool changing location, and the cutting tool is exchanged for another. All of this time constitutes non-machining time. In order to further reduce the size of the data stored and transferred over a network for the machine tool analysis, it may be desirable to separate some or all of this non-machining time. This function can be performed by the data bridge application 38. Of course, it may be desirable to retain at least some of the non-machining time to provide an indication of the operation of the machine tool and its components when it is not cutting a workpiece. Such information can be useful for preventative maintenance purposes. In such a case, the data related to the non-machining time can be sampled at a predetermined frequency such that the relevant data is available, but much of the non-machining time is not used, thereby conserving storage space and bandwidth. Once the data bridge application 38 generates the statistical parameter or parameters, and selectively filters out redundant data, it associates the data with respective machining operation data and sends the associated data to a data storage unit, such as a database server 40 residing on a network server 42. The network server 42 also includes a data collection portion 44, which initially collects the data from the machine PC 34, and then provides it to the database server 40. The database server 40 stores the structured data received from the machine PC 34 so that it can be accessed by remote terminals 46, 48 linked to the server 42 by a network 50. It is understood that a hardwire connection between the network server 42 and the terminals 46, 48 is not required; rather, a network, such as the network 50, may be a wireless network. A network, such as the network 50, may also utilize, for example, telephone lines or fiber-optic cables to effect the connection between the terminals 46, 48 and the server 42. In addition to the data collection described above, a second processing unit, such as the machine PC 34, can also be configured to automatically collect, from the first processing unit 22, data related to operation of the machine tool under predetermined conditions, wherein no work is performed on a workpiece. For example, a machine tool, such as the machine tool 11, can be programmed to move the spindle 14, pick up a tool, such as the tool 16, rotate the tool 16 at various predetermined speeds, and even idle, while the sensor 20 picks up the vibrations and sends the signals to the first processing unit 22. Where a spindle, such as a spindle 14, moves along slides (not shown) on the machine tool 11, the spindle 14 can be made to move to the extremities of each slide, which may be along axes at various orientations. The data collected by the sensor 20, and sent to the first processing unit 22, can then be automatically collected by the machine PC 34 and sent to the network server 42. This data may provide important information regarding the health of the machine tool itself, the spindle, the bearings, and the slide. It may also provide information regarding the cross transmissivity between the various slides. This data provides information regarding how much vibration is transferred from one slide to another as the spindle is being moved. Thus, the present invention contemplates a database server, such as the database server 40, being provided with data related to machining operations, and data related to non-machining operations, of a machine tool. Also shown in FIG. 2 is a third processing unit 52, which is configured similarly to the first processing unit 22. In particular, the third processing unit 52 receives inputs from a sensor and a PLC operatively connected to a second machine tool 53. An operator interface 54 provides a link between the third processing unit 52 and a fourth processing unit, or second machine PC 56. Data that is collected by the second machine PC 56 from the third processing unit 52 is sent to the network server 42. The network server is configured to associate the data from the two machine PC s 34, 56, which facilitates analysis of a specific machining operation that is performed on different machine tools. Thus, data from different workpieces that are machined on the same machine tool can be provided to the network server 42. In addition, data from the machining of different workpieces that are machined on different machine tools can also be provided to the network server 42. This data is then associated with related data, such that trends can be analyzed from the remote terminals 46, 48, and production control decisions can be made. FIGS. 3A and 3B show a sample of machining operation data and machine operation parameter data that can be collected from a machine tool, such as the machine tool 11 shown in FIG. 1. The upper portion of FIG. 3A shows a signal provided by the PLC 28 that indicates machining operations performed by eight different tools. In addition, the waveform of the signal provided by the PLC 28 also shows when the machining operation is between tools. The lower portion of FIG. 3A shows raw vibration data in a time domain, correlated with the signals from the PLC 28. Thus, FIG. 3A provides an example of data that would be output from the sensor 20 and PLC 28 to the first processing unit 22. As shown in FIG. 3B, an additional level of detail for the correlated PLC signals and vibration data is available. In particular, FIG. 3B shows vibration data and PLC signals for tool 6, which indicate eight separate machining steps, or “hits”. Each of the eight hits indicates machining of some feature on a workpiece, such as the workpiece 18 shown in FIG. 1. Between each of eight hits is non-machining time, indicated by the valleys in the PLC signal and the areas of small amplitude on the vibration signal. Using this information, a machine PC, such as the machine PC 34, configured in accordance with the present invention, can automatically collect data related to a particular tool, or even particular hits within a tool, while separating out non-machining time, and calculating a statistical parameter that represents the raw vibration data without the unwieldy size associated with the raw data. By separating out at least some of the non-machining time data, the separated data can be represented by a single value, thereby significantly reducing the band width required for data transmission. FIG. 4 shows trend lines that may be generated using data from the database server 40 and accessed by the remote terminals 46, 48. In particular, the parametric representation of the raw vibration data is shown on the ordinate as a kurtosis value. The abscissa indicates the number of cycles, although the data may be also shown in a time domain or with an abscissa that indicates the number of parts machined. The upper trend line 58 represents data collected while a workpiece, such as the workpiece 18, was being machined. Conversely, the lower trend line 60 represents data collected when the machine tool was idling, and no machining was being performed. This type of graphical data output can be helpful to a production control decision maker, particularly when it is combined with some predetermined maximum allowable value—i.e., predetermined alarm values. For example, in FIG. 4, the maximum value shown on the graph for the kurtosis of the vibration data is just over 0.45. A machine PC, such as the machine PC 34, can also collect alarm data from the first processing unit 22 and send it to the network server 42. Thus, an alarm value for the operation shown in FIG. 4 may be set at a value such as 0.45. The production control decision maker can than readily determine when the alarm value is exceeded, by examining a trend line, such as the trend line 58. FIGS. 5A-5D illustrate trend lines generated for various machine tools. For example, FIG. 5A shows a comparison of two trend lines for the same tool (Tool 1) used on different machines within the same facility. This can provide a means for directly comparing the cutting performance of two machines at the same plant. FIG. 5B also compares two machines at the same facility, but the trend lines represent “spindle health”—i.e., the data shown here was collected during non-machining time. Finally, FIGS. 5C and 5D show comparisons of machine tools at different facilities. To utilize a system, such as the system 30, the following steps may be employed. A machining operation is performed on a first workpiece, and vibration data is sensed by a vibration sensor and captured by a first processing unit. Data related to the machining operation is also captured by the first processing unit, upon receiving signals from a PLC. At least some data related to non-machining time is separated out, and at least one parametric representation of the separated data is generated. The generated parametric representation is then associated with respective machining operation data, so that information specific to a particular tool, or even a particular hit within a tool, is available on a network server. This process can be repeated for additional workpieces, on the same machine, on different machines within the same facility, or even on different machines in different facilities. Because the present invention manages the raw machining data to employ the use of parametric representations and the separation of non-machining time, information that would otherwise be inaccessible because of storage and communication problems, is now available over a network system so that many machine tools, within a single plant, or even different plants, can be examined together to provide an overall picture of a machining process. Further, given the level of detail that can be achieved, individual steps within a particular tool can also be examined across many different machines at many different facilities. While the best mode for carrying out the invention has been described in detail, those familiar with the art to which this invention relates will recognize various alternative designs and embodiments for practicing the invention as defined by the following claims.
RE0367605	description	DETAILED DESCRIPTION OF THE INVENTION The following discussion will begin with a description of the system utilized to produce the ion beams. This system has two major subsystems, the pulsed power source and the ion diode. The discussion will then continue with descriptions of a number of examples of ion beam treatments to various materials. The present invention provides an ion beam generator capable of high average power and repetitive operation over an extended number of operating cycles for treating large surface areas of materials at commercially attractive costs. In particular, the ion beam generator of the present invention can produce high average power (1 kW-4 MW) pulsed ion beams at 0.1-2.5 MeV energies and pulse durations or lengths of from about 10 nanoseconds (ns)-2 microseconds (.mu.s) or longer as necessary for the particular application. The ion beam generator can directly deposit energy in the top 50 micrometers (.mu.m) of the surface of a material. The depth of treatment can be controlled by varying the ion energy and species as well as the pulse length. FIG. 1 schematically illustrates irradiating a material with ion beams in accordance with the principles of the present invention. Although this process can be used to implant ions to the extent that the chemical composition of the implanted region is altered, normally the process will be utilized to deposit energy into the top surface of the material and will not significantly change the atomic composition of the material. As such the process will either heat or ablate the near surface using typically 3.times.10.sup.13 ions/cm.sup.2 per pulse. Such a dose will represent only approximately 10.sup.-5 -10.sup.-3 atomic percent of the sample density. Deposition of ion beam energy 11 in a thin near surface layer 13 causes melting of the layer with relatively small energies (typically 1-10 J/cm.sup.2) and allows rapid cooling of the melted layer by thermal diffusion into the underlying substrate 17 as depicted in FIG. 1. FIG. 2 is a graph which represents the effects whereby, when high energy ions come to rest in a material, the energy is deposited preferentially near the end of the range of penetration into the material. FIG. 2 is a graph showing the so-called Bragg peak for a 0.9 MeV proton beam, plotting electron volts per Angstrom as a function of depth in microns. At higher energy intensities (.gtoreq.10-20 J/cm.sup.2), this process can cause rapid ablation of the substrate. This in turn can be used to deposit a polycrystalline or nanocrystalline layer onto another substrate or to redeposit such a layer on the original substrate. This is shown schematically in FIGS. 5A and 5B which depict rapid ablation and redeposition onto the same material specimen and rapid ablation from one material surface with deposition onto a second material surface, respectively. FIG. 5A shows a production process with the material 54 moving from left to right as indicated by the arrow 55. Ions 50 from the ion beam source 25 ablate the material 54 to form particles 52 which rise above the material 54 and then redeposit back onto the material 54. In FIG. 5B the high energy ions 50 from the ion beam source 25 ablate the first material 60 creating ablated particles 52 which then fall onto the second material 62 which is moving in the direction of the arrow 55. Of course, either ablation process could also be conducted on stationary materials. These higher intensity pulses can also be used to induce shock hardening of much deeper regions of the irradiated substrate. The relatively small energy densities needed for treatment together with the high instantaneous powers available using the present invention allow large surface areas (50 to more than 1000 cm.sup.2) to be treated with a single ion beam pulse, greatly reducing or eliminating the portions of the treated material which are subject to edge effects at the transition between treated and untreated areas. The relatively short ion beam pulse lengths, preferably .ident.200 ns for use with metals, developed by the ion beam generator limit the depth of thermal diffusion, thus allowing the treated/melted region to be localized to a selected depth. Typical cooling rates of the present invention (10.sup.8 -10.sup.10 K/sec) are sufficient to cause amorphous layer formation in some materials, fine grain structures in some materials, the production of non-equilibrium microstructures (nano-crystalline and metastable phases), and the formation of new alloys by rapid quenching and/or liquid phase mixing of layers of different materials. Such rapid thermal quenching (>10.sup.8 K/sec) can significantly improve smoothness, corrosion, wear and hardness properties of the treated near surface layer. The ion beam generator of the present invention is composed of two major components: a high energy, pulsed power system (shown in FIG. 3) and an ion beam source 25 (shown in FIG. 4), both capable of high repetition rates and both having extended operating lives. The Pulsed Power Source The first of these components is a compact, electrically efficient, repetitively pulsed, magnetically switched, pulsed power system capable of 10.sup.9 pulse operating cycles aof the type described by H. C. Harjes, et al. Pro 8th IEEE Int. Pulsed Power Conference (1991), and D. L. Johnson et al., "Results of Initial Testing of the Four Stage RHEPP Accelator" pp. 437-440 and C. Harjes et al., "Characterization of the RHEPP 1 .mu.s Magnetic Pulse Compression Module", pp. 787-790, both reprinted in the Digest of Technical Papers of the Ninth IEEE International Pulsed Power Conference, June, 1993, all of which is incorporated by reference herein. These references in conjunction with the discussion herein below place fabrication of such a pulsed power source within the skill of the art. A block diagram of a power system produced according to the teachings of the present application is shown in FIG. 3. From the prime power input, several stages of magnetic pulse compression and voltage addition are used to deliver a pulsed power signal of up to 2.5 MV, 60 ns FWHM, 2.9 kJ pulses at a rate of 120 Hz to an ion beam source for this particular system. The power system converts AC power from the local power grid into a form that can be used by an ion beam source 25. Referring to FIG. 3, in one embodiment of the invention, the power system comprises a motor 5 which drives an alternator 10. The alternator 10 delivers a signal to a pulse compression system 15 which has two subsystems, a 1 .mu.s pulse compressor 12 and a pulse forming line 14. The pulse compression system 15 provides pulses to a linear inductive voltage adder (LIVA) 20 which delivers the pulses to the ion beam source 25. The alternator 10 according to one embodiment is a 600 kW, 120 Hz alternator. In the unipolar mode, it provides 210 A rms at a voltage of 3200 V rms with a power factor of 0.88 to the magnetic switch pulse compressor system 15. The alternator is driven by a motor connected to the local 480V power grid. The particular alternator used herein was designed by Westinghouse Corporation and fabricated at the Sandia National Laboratories in Albuquerque, N.M. It is described in detail in a paper by R. M. Caifo et al., "Design and Test of a Continuous Duty Pulsed AC Generator" in the Proceedings of the 8th IEEE Pulsed Power Conference, pp. 715-718, June, 1991, San Diego, Calif. This reference is incorporated herein in its entirety. This particular power system was selected and built because of its relative ease in adaptability to a variety of loads. Other power sources may be used and may indeed be better optimized to this particular use. For example, a power supply of the type available for Magna-Amp, Inc. comprising a series of step-up transformers connected to the local power grid feeding through a suitably-sized rectifier could be used. The present system however has been built and performs reasonably well. In one embodiment, the pulse compression system 15 is separated into two subsystems, one of which is a common magnetic pulse compressor 12 composed of a plurality of stages of magnetic switches (i.e., saturable reactors) the operation of which is well known to those skilled in the art. This subsystem is shown in more detail in FIG. 3A. The basic operation of each of the stages is to compress the time width (transfer time) of and to increase the amplitude of the voltage pulse received from the preceeding stage. Since these are very low loss switches, relatively little of the power is wasted as heat, and the energy in each pulse decreases relatively little as it moves from stage to stage. The specific subsystem used herein is described in detail by H. C. Harjes, et al., "Characterization of the RHEPP 1 .mu.s Magnetic Pulse Compression Module", 9th IEEE International Pulsed Power Conference, pp. 787-790, Albuquerque, N.M., June, 1993. This paper is incorporated by reference herein in its entirety. These stages as developed for this system are quite large. In the interest of conserving space, it would be possible to replace the first few stages with appropriately designed silicon control rectifiers (SCR's) to accomplish the same pulse compression result. These stages 12 convert the output of the alternator 10 into a 1 .mu.s wide LC charge waveform which is then delivered to a second subsystem 14 comprising a pulse forming line (PFL) element set up in a voltage doubling Blumlein configuration. The PFL is a triaxial water insulated line that converts the input LC charge waveform to a flat-top trapezoidal pulse with a design 15 ns rise/fall time and a 60 ns FWHM. The construction and operation of this element is described in detail by D. L. Johnson et al. "Results of Initial Testing of the Four Stage RHEPP Accelerator", 9th IEEE International Pulsed Power Conference, pp. 427-440, Albuquerque, N.M., June, 1993. This paper is also incorporated by reference in its entirety. A cross sectional view of the PFL is shown in FIG. 3B. The pulse compression system 15 can provide unipolar, 250 kV, 15 ns rise time, 60 ns full width half maximum (FWHM), 4 kJ pulses, at a rate of 120 Hz, to the linear inductive voltage adder (LIVA) (20). In a preferred embodiment, the pulse compression system 15 should desirably have an efficiency >80% and be compressed of high reliability components with very long lifetimes (.about.10.sup.9 -10.sup.10 pulses). Magnetic switches are preferably used in all of the pulse compression stages, MS1-MS5, because they can handle very high peak powers (i.e., high voltages and currents), and because they are basically solid state devices with a long service life. The five compression stages used in this embodiment as well as the PFL 14 are shown in FIG. 3A. The power is supplied to the pulse compression system 15 from the alternator 10 and is passed through the magnetic switches, MS1-MS5, to the PFL 14. The PFL is connected to the linear induction voltage adder (LIVA) 20 described below. The second and third magnetic switches, MS2 and MS3, are separated by a step-up transformer T1 as shown. Switch MS6 is an inversion switch for the PFL. The pulse forming line (PLF) element 14 is shown in schematically in FIG. 3A and in cross section in FIG. 3B. MS6 in FIG. 3A corresponds to the inversion switch 302 shown in FIG. 3B located on the input side of the tri-axial section 314 of the PFL. Output switches 304 and charging cores 306 are also shown. The regions 310 are filled with deionized water as the dielectric. The interior region 308 is filled with air and oil cooling lines, not shown, for the output switches 304. The output of the PFL is fed in parallel to each of the individual LIVA stages 20, with the positive component flowing through conductors 316 and the shell 318 of the PFL serving as ground. The positive conductors 316 are connected to each of the LIVA stages. The LIVA (20) is preferably liquid dielectric insulated. It is connected to the output of the PFL and can be configured in different numbers of stages to achieve the desired voltage for delivery to the ion beam source. The LIVA 20 can deliver nominal 2.5 MV, 2.9 kJ, pulses at a rate of 120 Hz to the ion beam source 25 when configured with 10 stages of 250 kV each. For most of the ion beam treatments, the LIVA was configured with four stages of 250 kV each, such that the LIVA delivered a total of 1.0 MV to the ion beam source. However, this voltage can be increased or decreased by changing the number of stages in the LIVA to match the particular material processing need. This nominal output pulse of the LIVA 20 is the same as the provided to it by the PFL, namely, trapezoidal with 15 ns rise and fall times and 60 ns FWHM. FIG. 3C shows a cross section of the four stage LIVA. The four stages, 320, 322, 324, and 326, are stacked as shown and fed the positive pulses from the PFL via the cables 321, 323, 325, and 327. The stages are separated by gaps 330 and surrounded by transformer oil for cooling. The output from each of the LIVA stages adds to deliver a single total pulse to the ion beam source shown here schematically as 25 which is located within a vacuum chamber 332, shown in partial view. As with the PFL, the outside shell of the LIVA is connected to ground. The power system P (FIG. 3) as described, can operate continuously at a pulse repetition rate of 120 Hz delivering up to 2.5 kJ of energy per pulse in 60 ns pulses. The specific power system described here can deliver pulsed power signals of about 20-1000 ns duration with ion beam energies of 0.25.2.5 MeV. The power system can operate at 50% electrical efficiency from the wall plug to energy delivered to a matched load. The power system P uses low loss pulse compression stages incorporating, for example, low loss magnetic material and solid state components, to convert AC power to short, high voltage pulses. The ability to produce voltages from 250 kV to several MV by stacking voltage using a plurality of inductive address incorporating low loss magnetic material is a principle feature when high voltages are needed, although it is also possible to use a single stage pulse supply, eliminating the need for the adder. The power system can operate at relatively low impedances (<100.OMEGA.) which also sets it apart from many other repetitive, power supply technologies, such as transformer-based systems. This feature allows high treatment rates and the treatment of large areas (5 to more than 1000 cm.sup.2) with a single pulse so as to reduce edge effects occurring at the transition between treated and untreated areas. The Ion Diode The second component of the present invention is an ion beam source 25 (shown in FIG. 4). The ion beam source is capable of operating repetitively and efficiently to utilize the pulsed power signal from the power system efficiently to turn gas phase molecules into a high energy pulsed ion beam. A precursor of the ion beam source is an ion diode described generally by J. B. Greenly et al, "Plasma Anode Ion Diode Research at Cornell: Repetitive Pulse and 0.1 TW Single Pulse Experiments", Proceedings of 8th Intl. Conf. on High Power Particle Beams (1990) all of which is incorporated by reference herein. Although this reference ion diode differs significantly from the ion diode utilized in the present system, the background discussion in this reference is of interest. An ion beam source 25, according to the principles of the present invention, is shown in FIG. 4. The ion beam source 25 is preferably a magnetically-confined anode plasma (MAP) source. FIG. 4 is a partially cross-sectional view of one symmetric side of the ion beam or MAP source 25. The ion beam or MAP source 25 produces an annular ion beam K which can be brought to a broad focus symmetric about the axis X--X 400 shown. In the cathode electrode assembly 30 slow (1 ms rise time) magnetic field coils 414 produce magnetic flux S (as shown in FIG. 4A) which provides the magnetic insulation of the accelerating gap between the cathodes 412 and the anodes 410. The anode electrodes 410 also act as magnetic flux shapes. The slow coils 414 are cooled by adjacent water lines, not shown, incorporated into the structure supporting the cathodes 412 and the slow coils 414. The main portion of the MAP structure shown in this Figure is about 18 cm high and wide. The ion beam or MAP source 25 operates in the following fashion: a fast gas valve assembly 404 located in the anode assembly 35 produces a rapid (200 .[.ms.]. .Iadd..mu.s.Iaddend.) gas puff which is delivered through a supersonic nozzle 406 to produce a highly localized volume of gas directly in front of the surface of a fast driving coil 408 located in an insulating structure 420. After pre-ionizing the gas with a 1 .[.ms.]. .Iadd..mu.s .Iaddend.induced electric field, the fast driving coil 408 is fully energized, inducing a loop voltage of 20 kV on the gas volume, driving a breakdown to full ionization, and moving the resulting plasma toward the flux filled shaping anode electrodes 410 in about 1.5 .[.ms.]. .Iadd..mu.s .Iaddend.to form a thin magnetically-confined plasma layer. The pre-ionization step is a departure from the earlier MAP reference which showed a separate conductor located on the face of a surface corresponding to the insulating structure 420 herein. Since this conductor was exposed to the plasma, it broke down frequently. One of the inventors herein discovered that the separate pre-ionizing structure was unnecessary. The gas can be effectively pre-ionized by placing a small ringing capacitor in parallel with the fast coil. The field oscillators produced by this ringing circuit pre-ionize the gas in front of the anode fast coil. We have also discovered that, prior to provision of the main pulse to the fast coil, it is beneficial to have the ability to adjust the configuration of the magnetic field in the gap between the fast coil and the anode to adjust the initial position of plasma formation in the puffed gas pulse prior to the pre-ionization step. This is accomplished by the provision of a slow bias capacitor and a protection circuit both being installed in parallel with the fast coil and isolated therefrom by a controllable switch. A slow bias field is thus created prior to pre-ionization of the gas by the fast coil. After pre-ionization the fast coil is then fully energized as described above to completely breakdown the gas into the plasma. After this pulse the field collapses back into the fast coil which is connected to a resistive load which is in turn connected to a heat sink, not shown. In this manner heat build up in the fast coil is avoided. The fast coils 408 have been redesigned from the reference fast coils in several ways as well as the heat sinking mentioned above. The gap between the fast coil and the anode electrodes 410 has been reduced with the result that the amount of necessary magnetic energy has been decreased by over 50%. The lower energy requirement permits repetitive use at higher frequencies and reduces the complexity of the feed system voltages for the fast coils. The design of the new flux-shaping anode electrode assembly has also contributed to these beneficial results. The pulsed power signal from the power system is then applied to the anode assembly 35, accelerating ions from the plasma to form an ion beam K. The slow (S) and fast (F) magnetic flux structures, at the time of ion beam extraction, are shown in FIG. 4A. The definite separation between the flux from the fast coil from the flux from the slow coil is shown therein. This is accomplished by the flux-shaping effects of the anodes 410 and also by the absence of a slow coil located in the insulating structure 420 as was taught in the earlier MAP reference paper. The slow coils in the present system are located only in the cathode area of the MAP. This anode flux shaping in conjunction with the location of slow coils in the cathode assembly is different from that shown in the MAP reference paper and permits the high repetition rate, sustained operation of the MAP diode disclosed herein. This design allows the B=0 point (the separatrix) to be positioned near the anode surface, resulting in an extracted ion beam with minimal rotation. This minimal rotation is necessary for effective delivery of the beam to the material to be treated. FIG. 4B is a detailed view of the gas valve assembly 404 and the passage 425 which conducts the gas from the valve 404 to the area in front of the fast coil 408. The passage 425 has been carefully designed to deposit the gas in the localized area of the fast coil with a minimum of blow-by past this region. The gas valve flapper 426 is operated by a small magnetic coil 428 which opens and closes the flapper 426 upon actuation from the MAP control system. The flapper valve is pivoted on the bottom end 427 of the flapper. The coil 428 is mounted in a high thermal conductivity ceramic support structure 429 which is in turn heat sinked to other structure, not shown. This heat sinking is necessary for the sustained operating capability of the MAP. The gas is delivered to the valve from a plenum 431 behind the base of the flapper. The vacuum in the nozzle 406 rapidly draws the gas into the MAP once the flapper 426 is opened. The function of the nozzle is to produce a directed flow of gas only in the direction of flow and not transverse to it. Such transverse flow would direct gas into the gap between the anode and the cathode which would produce detrimental arcing and other effects. The reduction of the fast coil-anode gap discussed above makes the design of the nozzle very important to the successful operation of the MAP. Fortunately, gas flow design tools are available and were used to develop a nozzle with improved gas flow (higher mach number) and minimal boundary effects. This improved nozzle has an enlarged opening into the gas between the fast coil and the near edge of the anode which tapers from 9 to 15 mm instead of the straight walled 6 mm conduit in the reference MAP. The operating pressure of the gas in the puff valve has been increased from the range of 5-25 psig to the range of 35-40 psig. Experiments have confirmed much improved MAP operation as a result of this new design. The ion diode of this invention is distinguished from prior art ion diodes in several ways. Due to its low gas load per pulse, the vacuum recovery within the MAP allows sustained operation up to and above 100 Hz. As discussed above, the magnetic geometric is fundamentally different from previous ion diodes. Prior diodes produced rotating beams that were intended for applications in which the ion beam propagates in a strong axial magnetic field after being generated in the diode. The present system requires that the ion beam be extracted from the diode to propagate in field-free space a minimum distance of 20-30 cm to a material surface. The magnetic configurations of previous ion diodes are incapable of this type of operation because those ion beams were forced by the geometries of those diodes to cross net magnetic flux and thus rotate. Such beams would rapidly disperse and be useless for the present purposes. By moving the slow coils (the diode insulating magnetic field coils) to the cathode side of the diode gap eliminated the magnetic field crossing for the beam but required a total redesign of the magnetic system for the anode plasma source. The modifications to the fast coil discussed above result in an energy requirement that is 5-10 times less than previous configurations. The modifications include: the elimination of a slow coil on the anode side of the diode and its associated feeds, better control over the magnetic field shaping and contact of the anode plasma to the anode electrode structure through the use of the partially field-penetrable electrodes, the elimination of the separate pre-ionizer coil from the prior ion diodes, the circuit associated with the fast coil to provide "bias" current to adjust the magnetic field to place the anode plasma surface on the correct flux surface to eliminate beam rotation and allow optimal propagation and focusing of the beam, and the redesign of the gas nozzle to better localize the gas puff which enable the fast coil to be located close to the diode gap which in turn reduces the energy requirements and complexity of the fast coil driver. The plasma can be formed using a variety of gas phase molecules. The system can use any gas (including hydrogen, helium, oxygen, nitrogen fluorine, neon, chlorine and argon) or vaporizable liquid or metal (including lithium, beryllium, boron, carbon, sodium, magnesium, aluminum, silicon, phosphorous, sulfur, and potassium) to produce a pure source of ions without consuming or damaging any component other than the gas supplied to the source. The ion beam K propagates 20-30 cm in vacuum (.about.10.sup.-3) to a broad focal area (up to 1000 cm.sup.2) at the target plane, not shown, where material samples are placed for treatment and can thermally alter areas from 5 cm.sup.2 to over 1000 cm.sup.2. The ion beam or MAP source 25 is capable of operating at repetitive pulse rates of 100 Hz continuously with long component lifetimes >10.sup.6. The ion beam or MAP source 25, according to the principles of the present invention, draws ions from a plasma anode rather than a solid dielectric surface flashover anode used in present single pulse ion beam sources. Use of a flashover anode typically introduces a variety of contaminants to the surface of the material, often with detrimental results. One of the significant advantages of the using the improved MAP source disclosed herein is that one has precise control over the components in the ion beam by controlling the composition of the gas source. The present invention combines the pulsed power supply P and the MAP ion source 25 to obtain a system for repetitively generating pulsed high voltage ion beams in a manner that allows the use of this technology for the efficient treatment of surfaces in commercial applications. In particular, the ion voltage is in the range 0.1-2.5 MeV per ion, the energy per pulse is as large as 2.5 kJ, and the ion source impedance is significantly less than 100.OMEGA., allowing the pulse width to be as small as 30 ns. These numbers are characteristic of the present embodiment, and may be superseded by design changes obvious to worker in the art. The detailed description of the new class of ion beam generators having been completed, attention now turns to the many applications made possible and practical in an industrial sense by said generators. There are three broad classes of surface effects upon which the aforementioned applications depend. These are: a) Surface Smoothing; b) Evaporation and Ablation from a Surface, and; c) Generation and Quenching of Non-Equilibrium Surface Structure. Other types of effects exist, and are not intended to be removed from the scope of the claims, but the effects listed above illustrate the enormous breadth of the present invention. Surface Smoothing has a sphere of influence far wider than the innocuous name would suggest. Every surface has an energy (or surface tension) raising the energy of the atoms which make up to the surface above the energy they would have if located in the bulk of the material. Accordingly, given the opportunity any surface structure which increases the surface area (thereby increasing the number of surface atoms) will adjust by moving material around to reduce the total surface area. As described in the Background section, Surface Smoothing is driven by the surface tension of the molten surface following surface heating by the ion beam, but before sufficient heat has conducted into the body of the material to allow the near-surface regions to resolidify. During this time, the surface morphology will become less jagged and smoother, the improvement limited primarily by the duration of surface melting. Another effect which can add to the smoothing of the surfaces of fine-grain sintered materials, such as ceramics or materials resulting from powder metallurgy, via ion beam surface melting. In these cases, when proper process parameters are used, a glass or alloy surface may be formed, thereby eliminating the grain structure from the surface in favor of a smooth glassy surface. Note further that the glass or alloy need not be equilibrium forms of the material, as the rapid quenching will preserve many forms of molecular solid solutions which do not exist in the relevant equilibrium phase diagram. The process conditions for Surface Smoothing are not onerous, so long as the near-surface region of the material does melt to some depth. In contrast to some of the techniques to be described later. Surface Smoothing can often be carried out in a number of smaller ion pulses, each one melting the surface, thereby allowing said surface to become a little smoother. Having described how to smooth a surface using ion beam surface heating, the range of applications of Surface Smoothing must be described. Again, these examples are simply for illustration, and there is no intent to limit the present invention to a scope inferior to that of the attached claims. The simple process of smoothing a surface, e.g., to remove surface defects resulting from etching or machining, is straightforward. Example 1 describes the removal of etching defects on a copper surface using the Surface Smoothing process. The surface initially consisted of canyons and mountains some 3-5 .mu.m in height having sharp edges and points. Following Surface Smoothing, the surface exhibited surface roughness only on a size scale of less than 0.5 .mu.m. Example 2 described the polishing of machining marks from a machinable titanium alloy. The marks were originally some 5 .mu.m, the remnants of a precision machining operation. The process of Surface Smoothing reduced the surface roughness to less than 0.1 .mu.m, again removing the sharp, abrupt initial features and leaving only a gently rolling surface. This polishing of machining marks will also be useful in polishing of diamond-turned optics, allowing such polishing to be executed without danger of changing the carefully controlled surface generated by the machining process, thus greatly reducing the cost of such optical elements. Another application will be in the treatment of machine tool surfaces, so that a minimum of machine marks may be made in the first place. Example 3 describes the smoothing of an Al.sub.2 O.sub.3 ceramic surface by conversion of the surface to a glassy layer. Such a process should be useful on a wide range of ceramics and other materials having a pronounced grainy structure. There are certain materials, such as most stainless steels, which do not form glassy layers. They can, however, be melted to form a solid layer of metal in these circumstances, said layer of metal having a very-fine-grained structure. Surface Smoothing makes two primary alterations in surface morphology, it reduced the average surface roughness and it reduces the surface area of the body treated. Both of these effects have clear applications. The phenomenon of adhesion between two materials is now well-understood. However, it is clear that the more surface area upon which two materials meet, the more adhesive force will exist between them. In fact, the function of many adhesives is not only to stick to the surfaces of both bodies being glued together, but also to maximize the area of contact by flowing into small grooves and crevasses before hardening. The increase in surface area which occurs in this process is enormous, and also increases with time, explaining why fast-curing epoxies are generally not as strong as their slower-curing cousins. If one produces a surface which is (approximately) maximally smooth using Surface Smoothing, the result will be a surface which will experience minimal adhesive forces to another body in contact. In other words, Surface Smoothing is another approach to non-stick surfaces. Note that a non-stick surface need not be a low-friction surface, as the one refers to the force required to start the body into motion and the other to the force needed to keep it in motion some moving. Another general result of the Surface Smoothing process, resulting directly from reduction in surface roughness, is reduction of wear between two elements in contact and in relative motion. As discusses in the Background section, the amount of material lost in a given time to adhesive wear should be a linear function of the surface roughness of the two elements. Although that estimate is oversimplified, it is clear that less wear will result from the mechanical interaction of two surfaces after Surface Smoothing has been performed, beyond any surface hardening which might also have taken place. Related to the above is the fact that a smooth surface can increase the working toughness of a material, although the actual micro-properties of that material are not altered. The materials used for mechanical applications are rarely, if ever, completely homogeneous. Among other defects, incipient surface cracks provide sites for failure of the element under stress. If the surface of such a body is essentially smoothed, all incipient cracks are located below the surface, and thus have two closed ends rather than one. Such cracks are nearly twice as resistant to growth as is a crack which intersects the surface. Thus, a smooth surface gives a tougher part. Corrosion resistance can also be increased through the use of Surface Smoothing. Increased surface area, cracks, and other defects associated with rough surfaces increase the rate of corrosive processes, including in particular pitting, stress corrosion, and attack by microbiological organisms. A number of processes exist which directly attack the chemistry of corrosion, such as formation of a layer of corrosive-resistant surface alloy, but all such techniques work better if the surface is also smooth and relatively free of cracks. This is the role of Surface Smoothing in preventing corrosion. Several examples have been investigated, which will be discussed in the section on Non-Equilibrium Surface Structures. An application of Surface Smoothing closely related to the above is that of passivation or protection of welds against corrosion. Exposed welds, particularly between dissimilar materials, offer fertile ground for corrosive processes. The reason is at least two-fold. Generally, the region of the weld is rather heterogeneous in composition and structure. Any corrosive process is thus likely to act with different rates in different regions, resulting in a surface of increasing micro-roughness as corrosion continues. Also, the initial surface of a weld is usually very rough, having many flaws and cracks on a small size scale. The effect of Surface Smoothing following the welding process thus acts to ameliorate both effects, resulting in a more corrosion-resistant weld. A final illustration of the use of Surface Smoothing is in application to amorphous magnetic materials. When a thin layer of a magnetic material is considered, the surface roughness can have a significant effect of magnetic properties, including coercive field and dc hysteresis losses. An example of great industrial significance is METGLAS.TM., a class of magnetic alloys produced by shooting a jet of the molten alloy at a spinning metal wheel which cools the alloy into a ribbon quickly enough that the resulting structure is amorphous. One negative aspect of this means of production is that the side of the ribbon opposite the wheel has a very rough surface. This roughness also limits the thickness of material that can be commercially produced, limiting the high frequency range of METGLAS.TM. applications. Surface cracking of the METGLAS.TM. ribbon also limits the thickness of material that can be produced commercially, increasing the cost of METGLAS.TM. cores for power distribution and related applications. As a result, although the potential of METGLAS.TM. in power handling devices is enormous, it has not yet realized that potential. Surface Smoothing is a technique capable of smoothing and even forming METGLAS.TM., with the hoped-for improvement in magnetic properties, as described in Example 4. The technique of Surface Smoothing can, of course, be applied to any amorphous or fine-grained material, with beam kinetic energy and ion species tailored to obtain the proper cooling rate. Due to the extremely rapid quench rate, Surface Smoothing can also be used to produce or modify new magnetic materials not accessible using existing techniques. A related technique can be applied to thin layers of amorphous or nanocrystailine material, given only that these layers are deposited on a substrate having high thermal conductivity (roughly speaking, metals and ceramics rather than polymers and insulators). The physics behind the design of a smoothing treatment is the same as above, except that the heat from the ion pulse is conducted into the substrate instead of into the bulk of a thick sample. Examples of such processes include smoothing e.g., plasma spray deposited films, filling in pinhole defects in the amorphous film, and precisely controlling the grain size of fine-grain films by melting and recrystallization. Having described a number of applications for the process of Surface Smoothing as made possible by the present invention, attention is now focused on Evaporation and Ablation from a Surface (EAS for short). One of the most important applications of EAS is the simple task of cleaning surfaces. Simple, that is, except that one wants to consistently clean a surface to an environmentally-limited amount of contamination, without the use of EPA- of OSHA-regulated solvents, preferably immediately before using the clean surface (e.g., in welding, flux-free soldering, vacuum deposition, and the like). If cleaning is also extended to the removal of, for example, oxide layers from a metal surface, it becomes clear that cleaning can be an essential and difficult part of the manufacturing process. The process of EAS has many uses in this domain. A conventional form of cleaning is degreasing parts prior to some assembly step, such as welding, soldering, gluing, etc. As will be shown in Example 5 below, a 100 nm thick layer of conventional lubricating oil is easily removed from a stainless steel surface using a single pulse of about 1-2 J/cm.sup.2, a very small dosage for the present class of ion beam generators. Note that no attempt is made to restrict the beam to the contaminant layer alone, as an extremely low beam energy would be required, owing to the low density and small thickness of the contaminant. Rather, the ion species and the energy of the beam is adjusted to superheat a thin layer of the metal surface, which then vaporizes the hydrocarbon contaminant before the bulk of the steel can cool the surface. A further extension of cleaning a surface is the rapid and thorough sterilization of surfaces subjected to appropriate EAS treatment. Such techniques are likely to have impact in the manufacture of the pre-sterilized medical implements. The technique described above is quite general, and may be used on any form of contamination that has a significantly lower boiling point than the substrate material. In fact, in cases where a natural passivating layer, e.g., a surface oxide, must be removed before soldering, for example, can take place, and the relative characteristics of the bulk material and the surface passivating layer are as outlined above, the passivating layer can be removed by superheating the underlying material. In most cases, however, the materials encountered in both natural and artificial surface layers have higher vaporization points than do the materials they protect. In such cases, the EAS technique can still be used to remove the surface layer provided only that loss of a few microns of the underlying material is acceptable. This is accomplished by ablating the surface layers of the underlying material, taking along the unwanted overlayer. The total energy required for ablation is generally quite high (>10 J/cm.sup.2), and should be restricted to as thin a layer of material as is reasonable (perhaps 0.5-1.0 .mu.m). These numbers, like all specific numbers appearing in the specification, depend to some extent on the ion species used and the type of bulk material being processed. Note particularly the difference caused by attempting to treat a polymer substrate, whose thermal conductivity is perhaps 1000-10000 times smaller than that of a metal alloy. The ablation temperature will be about the same, and the energy contained in a given layer is perhaps 10-20% that of an equivalent metal layer, owing to the lower density of the polymer. As a result, the characteristic time to remove energy from a heated surface layer will be on the order of 10 times that for a typical metal. In addition, the range of ions in the polymer is much greater for a given beam kinetic energy than in normal structural metals. The net effect is that a much greater thickness (say, .times. times the distance in the metal, for example) will be heated by a beam of given kinetic energy. As the characteristic time depends quadratically on this thickness and inversely on the thermal conductivity, the characteristic time in polymer heating will be .about.(10.sup.2 -10.sup.3).times..sup.2 longer than that in a metal. Extremely rapid quenching thus cannot be produced on a polymer surface by the techniques of the present invention. The time required for heating, however, is limited only by the maximum peak power of the ion beam generator. The EAS techniques therefore apply to polymers, whereas most of the Surface Smoothing and Non-Equilibrium processes do not. If an patterned ion-absorbing mask or compound is used to prevent the ion pulse from affecting certain areas of the element being treated, a surface having a pattern of varying surface properties can be generated. Such a pattern can range from removing an oxide layer in certain areas to obtain patterned etching of a surface by chemical action to direct etching of ablated patterns in large scale solar cells to manufacture of patterned printed circuit boards. The EAS process offers the advantage of limiting the use of solvents and powerful acids in such procedures. When a higher level of pulse power (>>10J/cm.sup.2), is deposited in a thin surface layer (.about..mu.m in thickness), violent ablation occurs. The expanding gases accelerate the evaporated layer outward from the body of the material at extreme velocity, generating as a result of momentum conservation a strong pressure wave in the material. As most materials exhibit a nonlinear stress-strain relationship, the pressure wave rapidly sharpens into a shock wave. As this shock wave propagates inward through the material, it generates dislocations, twinning planes, and complex systems of these structure defects, thereby dissipating its power and eventually (within perhaps 100 .mu.m or more) ceases to exist as a cohesive entity. This damaged region, however, has undergone a phenomenon known as shock-hardening, an extreme form of work-hardening. Even though the direct heating action of the ion beam may be limited to the first few .mu.m, the shock hardening effect penetrates much deeper, offering a surface treatment which cannot be directly obtained using the present invention. EAS uses the pulsed ion beam generators of the present invention to rapidly vaporize material from the surface of a body. This vaporized material can be used as a source material for vapor deposition processes, having the advantage that chemical compositions will not be charged by segmentation effects due to the phase diagram of the alloy system or chemical reactions with a resistive heating element, as is often used in vapor phase deposition. In addition, the vapor deposition will take place in a very short period of time (<1 .mu.s). As a result the heat of adsorption will rapidly conduct away into the bulk of the substrate, and one will again obtain a rapidly quenched material, given only that the substrate has large thermal conductivity. The large surface area that the ion beam generators of the present invention can vaporize makes this approach available to large-scale manufacturing efforts. Another effect associated with EAS used in this mode has been observed. A layer of material a few .mu.m thick is vaporized within the period of a few tens of nanoseconds. This converts a metal layer having a given density into a plasma which initially has very nearly the same density, as it has not yet had time to expand away from the bulk of the material. The energy distribution of this layer follows a Boltzmann distribution, meaning that a significant percentage of the vaporized material has kinetic temperatures significantly less than the average temperature of the plasma. Because of this, and because the plasma is so close to a relatively cool conducting surface, a small amount of the vaporized material redeposits on the surface from which it came. In doing so, that surface acquires a structure which is extremely rough on a nanoscale, particularly having numerous protuberances much smaller than a .mu.m in size, possessing unique properties. EAS processes can be used for many other manufacturing purposes, and presentation of these examples is not intended to limit the scope of the invention beyond the limitations outlined in the attached claims. The final major class of processes made practical for large-scale manufacturing by the new category of pulsed ion beam generators made possible by the current invention is the production of non-equilibrium surface structures (NESS for short). The name is a bit misleading, as some near-equilibrium applications also come under this title, but the general concept is that one heats a surface having an initial structure rapidly to some depth with a pulsed ion beam, the heat is rapidly lost to conduction into the material, and the result is a product surface having a structure with different properties than those of the initial structure. As the structure of many of the product surfaces is non-equilibrium, that term is used herein to describe the whole family of processes. A good example of the production and retention of high-temperature structures is offered by Example 6, in which an NESS-type process is applied to the surface of a tool steel component. (Such a process is not limited to the hardening of steel.) The hardness of the surface roughly tripled, but the important point is how this increase in hardness came about. X-ray and electron microscope analysis of the untreated surface shows the simple co-ferrite phase with a significant density of cementite precipitates. However, the treated surface showed the presence of small crystallites of austenite, the possible presence of martensite, and no carbide precipitates. This is significant in that austenite is stable only at high temperatures, and that the equilibrium structure at room temperature is a mixture of ferrite and cementite (Fe.sub.3 C precipitates). At high temperature, the carbon dissolves into the matrix, producing austenite in the process. The NESS process has thus quenched a high-temperature phase structure so that it exists at room temperature. Conventionally hardened tool steels are composed either of a very fine grain pearlite or of tempered martensite. The structure obtained from the NESS treatment differs from these, thus providing another surface microstructure useful for hardening steel alloys. Other precipitates than carbon, of course, can be dissolved and retained in a non-equilibrium solid solution using the NESS technique, and other materials than steel can be successfully treated. Another approach toward hardening the surface of steel (or other alloys) is to add elements, usually carbon and/or nitrogen, which encourages the formation of high-hardness carbides and nitrides in the near-surface region. The NESS process offers an alternate approach to the usual process of addition, which involves long periods of diffusion in hot environments. For carburization, it is possible to start by depositing a glassy layer of carbon on the surface to be treated (this deposition may use an EAS process, but need not). The layer of carbon and a suitable thickness of the underlying metal would then be melted by the pulse of an ion beam, whereupon the carbon would dissolve into the steel. Further heat treatment may be necessary to obtain optimal surface conditions, depending on the starting alloys. A similar technique which may work for nitriding would require deposition of a layer of a high-temperature nitride, such as titanium or vanadium nitride. (The titanium or vanadium also improve the properties of the resulting steel. However, this hardening process is not limited to these two elements, but may use any nitride which can withstand the high process temperatures without volatilizing.) The remainder of the process is carried out as for carbon above, save that further thermal treatment are generally not useful in nitridization. Other elements can be introduced into the surface layers of a compatible body using this type of NESS technique. The beneficial effects of Surface Smoothing on corrosion resistance was discussed earlier. Additional phenomena more closely related to the NESS processes are also of value in holding back corrosion. This is illustrated in Example 7, in which a stainless steel surface is treated with a mixed carbon-hydrogen ion beam pulse from an early device utilizing a flashover ion source. Although this technology is primitive compared to that offered by the current invention, in particular not allowing industrial scale-up, it did prove adequate to demonstrate the increase of corrosion resistance. When 304 stainless steel is annealed at high temperatures as described in the Example, chromium-depleted regions form near the grain boundaries of the metal. The chromium precipitates out in large chromium carbide particles in the interiors of the grains. The chromium-depleted regions are intrinsically more susceptible to corrosion, and the chromium carbide particles present intergranular surfaces which are also particularly susceptible to corrosion. As a result, 304 stainless steel, when subjected to the described heat treatment, becomes extremely susceptible to corrosion, primarily preferential grain boundary corrosion. When the heat-treated surface is subjected to a 0.3 MeV. .about.300 ns pulse of mixed ions with a total energy of 2-3 J/cm.sup.2, the rapid melting and recrystallization removed the chromium-depleted grain boundaries and caused the chromium carbide particles to redissolve in the metal. This treatment was observed to increase corrosion resistance essentially back to the pre-heat treatment level. Similar work aimed at studies of pitting susceptibility of 316L and 316F stainless steels has also been undertaken with similar results. Aluminum alloys have also been subjected to NESS processes to increase their corrosion resistance. Again, the pulsed ion beam used was a mix of carbon and hydrogen ions accelerated to 0.7 MeV. The pulses were .about.100 ns wide, and the total energy of each pulse was .about.2-3 J/cm.sup.2. Exposure testing for the alloys used was conducted in a saturated salt fog environment. The alloys treated have included 2024-T3, 6061-T6, and 7075-T6. In all cases the NESS treatment increased the corrosion resistance of the samples. This should be true for all structural aluminum alloys. Another approach to increasing corrosion resistance through NESS treatment can be illustrated best by considering a carbon steel (i.e., low chromium content). Such steels are extremely susceptible to corrosion, rusting in moist air, disintegrating over time in saline environments, and failing even more quickly in more hostile conditions. The addition of chromium to such steels produces stainless steels, which do not share this extreme sensitivity to environment. However, stainless steel is expensive, especially considering that the mechanical properties of stainless steels are suboptimal, and that the property of being "stainless" need only exist at the surface of the element. NESS treatment can help to solve this problem by mixing a surface-deposited layer of chromium with the near-surface regions of the steel element. The result will be an element having the superior mechanical properties of carbon steel combined with an outer layer of stainless steel perhaps 5-20 .mu.m thick (depending on conditions) which is both smooth and uniform, thus providing excellent corrosion resistance. This sort of technique is extendible to many metal alloy systems, including welds, the scope of which are well-known to practitioners in the metallurgical arts. The Examples referred to above will now be described in detail. These Examples are not intended to limit the scope of the claims appended in any manner, but rather to illustrate their application in specific instances. EXAMPLE 1 A sample of nominally pure Cu was etched in 1 molar nitric acid for one minute. Scanning electron microscopy (SEM) analysis of the resulting surface showed a roughened surface with hillocks and "sharp" features approximately 3-5 .mu.m in height. These samples were treated using a single pulse of an ion beam generated using a RHEPP prototype power source and a flashover ion source. (In a flashover ion source an electrical discharge volatilizes the surface of a polymer, resulting in the generation of mixed carbon and hydrogen ions.) The beam kinetic energy was 1.0 MeV, the pulse width was approximately 60 ms, and the total pulse energy density at the treated surface was .about.3J/cm.sup.3. Post-treatment SEM analysis revealed a smoother surface with more gradual changes in surface configuration and an average surface roughness of .about.0.5 .mu.m. In this example the Cu surface was molten for .about.500 ns. The driving force of surface tension during this period was clearly sufficient to produce nearly complete removal of the original surface morphology. EXAMPLE 2 A piece of Ti-6Al-4V alloy (a common machinable titanium alloy) was machined using conventional precision machining techniques, leaving a nominally flat surface with machining marks producing a surface roughness of .about.5 .mu.m. This surface was treated by exposure to four pulses, each pulse having a beam kinetic energy of .about.3.0-0.4 MeV, a duration of .about.400 ns, and a total pulse energy density of .about.7 J/cm.sup.2. SEM analysis of the treated surface revealed surface roughness had been reduced to .about.0.1 .mu.m. The time the metal surface was liquid was again some 250-500 ns, suggesting that the effect of multiple pulses in the smoothing process is additive, i.e., that more pulses give a smoother surface. EXAMPLE 3 One side of an alumina (Al.sub.2 O.sub.3 ceramic) sample was polished using submicron abrasive grit suspensions. Following characterization of the surface with an SEM, the polished surface was subjected to a single ion pulse having a beam kinetic energy of .about.1.0 MeV, a beam duration of .about.60 ns, and a total pulse energy density of .about.10 J/cm.sup.2. Post-treatment analysis showed evidence for melting and resolidification resulting in reduction of surface porosity. There remained, however, some microcracking on a 0.1 .mu.m size scale. It is considered likely that further treatment would yield a uniformly smooth surface. EXAMPLE 4 Because of its unique magnetic properties, various amorphous magnetic alloys known by the registered trademark (Allied-Signal, Inc.) METGLAS.TM. are desirable in high frequency applications, including pulsed power supplies and control. These materials are made by spraying the molten alloy on a cooled rotating wheel, thereby quenching the material at .about.10.sup.6 .degree.K/sec and forming an amorphous ribbon having thicknesses in the range of 15-50 .mu.m. Due to hydrodynamic instabilities during the cooling process, one side of such ribbons has significant ripples in thickness having a period similar to the thickness of the ribbon. This non-uniformity is important for two reasons. First, the magnetic properties at high frequencies are a function of the thickness of the ribbon; hence the variation in thickness limits the performance of devices constructed of non-uniform ribbon. Second, the size scale of the surface roughness is sufficient that when the ribbon is formed into a coil, or similar structure, the layer of insulation between alternate layers of ribbon must be very thick to prevent formation of short-circuits. The thick insulation reduced the density of magnetic material in a given construct, lowering performance and increasing the physical dimensions of the ultimate device. An experiment was performed to discover if Surface Smoothing with ion beam pulses could even out the non-uniformities of a METGLAS.TM. surface while retaining the unique magnetic properties which result from the amorphous structure. METGLAS.TM. 2605CO material was chosen for the test, as it is perhaps most widely used in commercial applications at this time. The nominal composition of METGLAS.TM. 2605CO is Fe.sub.56 Co.sub.18 B.sub.15 Si.sub.1, and it is produced using the wheel-quenching technique described above. A sample was selected, and subjected to a single 2 J/cm.sup.2 pulse of mixed carbon and hydrogen ions from a flashover source. The beam kinetic energy was .about.0.6 MeV, and the pulse width was .about.60 ns. The resulting surface was virtually flat. A second concern, of course, was that the nanostructure which helps to give METGLAS.TM. 2605CO its unique properties might be damaged by remelting and quenching at a rate different than encountered in the original manufacture. Tests have shown that the amorphous structure of the original METGLAS.TM. is unchanged by the ion pulse treatment. EXAMPLE 5 A 0.1 .mu.m layer of machining fluid (a hydrocarbon mixture) was applied to the surface of a sample of 304 stainless steel. The surface was examined using x-ray photo-emission spectroscopy (XPS) to verify the thickness of the hydrocarbon layer. The sample was then exposed to three ion pulses, each having a total energy density of 2-3 J/cm.sup.2, a beam kinetic energy of 0.5-0.75 MeV, and a pulse duration of .about.50 ns. Following treatment, XPS was again performed, and showed only that amount of hydrocarbon expected from atmospheric contamination (about a monolayer). The surface cleaning was thus totally successful. EXAMPLE 6 A sample of 0-1 tool steel was subjected to ion pulses to determine if the surface could be hardened thereby. The sample was subjected to a single pulse having a beam kinetic energy of .about.1 MeV, a duration of .about.40 ns, and a surface energy density of .about.5 J/cm.sup.2. On recovery, the top few microns of the sample showed only fine grains on the order of 20 nm in size, compared to the initial material which had grain size on the order of 1 .mu.m in size. The initial material had a significant density of iron carbide precipitates, whereas the surface layers did not, having apparently redissolved the carbon into the iron matrix. Hardness testing on the samples was done using micro-indentation techniques. A Knoop indentor tip was pressed into the samples with a 25 gram load, producing indentations about 5 .mu.m in thickness. A direct reduction of this data showed that the untreated surface had a Knoop hardness of 330, while the treated surface has a Knoop hardness of 900, roughly three times higher. Further, indentation hardness tests are influenced by the hardness of the material out to a distance of perhaps 10 time the size of the indentations. Since the treated layer is only .about.7 .mu.m thick, this means that it is actually much harder than the indentation testing revealed. .theta.-2.theta. x-ray diffraction measurements were taken of the treated and untreated surfaces. The untreated surface shows only a sharp peak corresponding to large ferrite grains (the Fe.sub.3 C precipitates would not diffract at the angles examined). The treated surface, however, showed three interesting differences from the untreated surface. First, austenite peaks appeared, showing that high-temperature species had been successfully recovered in the rapid quench. Second, the diffraction peaks were all quite broad, in agreement with the observation that the grain size in the treated material was very small. Finally, the ferrite peak in the treated sample is asymmetric, suggesting the existence of lattice strains consistent with the presence of martensite. It is likely that all of these effects combine to increase the hardness of the surface of the treated sample. EXAMPLE 7 Four flat samples of 304 stainless steel were prepared to determine if ion beam pulses could eliminate preferential grain boundary corrosion due to heat treatment. All samples were held at 1100.degree. C. for 24 hours, and then quenched in cold water. Two of the samples were sensitized to corrosive action by heating them at 600.degree. C. for 100 hours, followed by cooling in air. This second anneal produces precipitation of chromium carbide particles, formed through depletion of the grain boundaries of the metal of their chromium, a well-known problem in the application of stainless steels having too much carbon. All samples were polished to a mirror finish. Two of the samples, one from each group of annealing conditions, were subjected to four pulses each having a surface energy density of .about.3 J/cm.sup.2, a beam kinetic energy of .about.0.3 MeV, and a duration of .about.300 ns. Each pulse was a combination of carbon and hydrogen ions, the ions source using flashover technology. The degree of sensitization was determined using potentiokinetic reactivation in a 0.5M H.sub.2 SO.sub.4 plus 0.01M KSCN solution held at 30.degree. C. The charge per unit area Q/A required for reactivation is a measure of the susceptibility of the surface of the corrosive effects of this solution. The sample exposed only to the 1100.degree. C. anneal had a Q/A value of 0.018 Coulombs/cm.sup.2. The sample having the same heat treatment but also exposed to the ion beam pulse had a Q/A value of 0.057 and 0.084 Coulombs/cm.sup.2 (on separate measurements), suggesting that the beam treated surface was somewhat more susceptible to corrosion. The more important results, however, are on the samples which had undergone both annealing cycles. The sample which only received both annealing cycles had a Q/A value of 0.825 and 0.817 Coulombs/cm.sup.2 (again two measurements were made), an enormous increase from the value of 0.018 for the sample which only received the high-temperature anneal. This huge difference in corrosive sensitivity explains why temperatures in the 600.degree. C. range are avoided in application of most stainless steels. However, when such a sample is treated with the above described ion beam pulse schedule, the Q/A value dropped to 0.027 and 0.028 Coulombs/cm.sup.2, a value nearly as low as the original material. One example of why this result is important lies in the problem of welding stainless steel for applications in which corrosive environments are to be encountered. In welding there will clearly be a zone of material which will slowly cool from a temperature in the sensitization range (roughly 400.degree.-800.degree. C.). This zone will be somewhat sensitized to corrosion, although not to the extreme of the experimental sample described above. Unless the entire assembly can be subjected to high-temperature annealing when complete, most stainless steels will not be practical choices for corrosive environments. When stainless steels must be welded now, a steel is chosen having so little carbon that the grain boundary sensitization process cannot occur, thus solving the corrosion problem. However, low-carbon steels are generally soft and weak by comparison to other possibilities, so this choice is a compromise. The ion beam pulse surface modification technology described herein will reduce the number of design compromises required, in this problem and in many others. The capacity of the present invention for producing high energy, high average power pulsed ion beams results in a new, low cost, compact surface treatment technology capable of high volume commercial applications and new treatment techniques not possible with existing systems. Having thus described the present invention with the aid of specific examples, those skilled in the art will appreciate that other similar combinations of the capabilities of this technology are also possible without departing from the scope of the claims attached herewith.
	summary
	claims	1. A computer implemented method for modelizing a nuclear reactor core, comprising the steps of:partitioning, by a computer processor, the core in cubes to constitute nodes of a grid for computer implemented calculation,calculating, by the computer processor, neutron flux by using an iterative solving procedure of at least one eigensystem, components of an iterant of the eigensystem corresponding either to a neutron flux, to a neutron outcurrent or to a neutron incurrent, for a respective cube to be calculated,wherein a control parameter is varied to impact a neutron eigenvalue μ through a perturbed interface current equation and drive the neutron eigenvalue μ towards 1,the perturbed interface current equation being defined by j out + δ ⁢ ⁢ j out = ( μ + δ ⁢ ⁢ μ ) ⁢ c 1 ⁡ ( ϕ + δϑ ⁢ ∂ ϕ ∂ ϑ ) + Ω ^ ⁢ Y ^ ⁡ ( j out + δ ⁢ ⁢ j out ) where jout designates the neutron outcurrent, Φ designates the neutron flux, θ designates the control parameter, Ŷ is a coupling operator, {circumflex over (Ω)} is a mono-directional current throughflow operator, and c1 is an operator depending on the cube properties, the control parameter being a parameter of the model representing a feature of the nuclear reactor core. 2. The method of claim 1 wherein the control parameter θ is given by a determinative output of the following equation: ϑ ( new ) = ϑ ( prev ) + 〈 ω † \| r out ( prev ) 〉 〈 ω † \| c 1 ⁢ ∂ ϕ ∂ ϑ 〉 wherein ω† is a weighting function,rout is given by: jout−c1φ+{circumflex over (Ω)}Ŷjout. 3. The method of claim 2 wherein the control parameter represents a boron concentration of the nuclear reactor core. 4. The method of claim 2 wherein the control parameter represents a rod insertion depth for a group of selected control rods of the nuclear reactor core. 5. The method of claim 1 wherein the control parameter is a neutron eigenvalue λ, and wherein, during an iteration of the iterative solving procedure, the neutron eigenvalue λ is varied to drive the neutron eigenvalue μ towards 1, and wherein the variation of the neutron eigenvalue λ is an application of a variation a δλ to λ, such that λ is driven to λ+δλ, which impacts the neutron eigenvalue μ through the perturbed interface current equation. 6. The method of claim 5, wherein the neutron eigenvalue λ is preconditioned prior to the iteration of the eigensystem solving procedure according to: λ ( new ) = λ ( prev ) + 〈 ω † \| r out ( prev ) 〉 〈 ω † \| c 1 ⁢ ∂ ϕ ∂ λ 〉 where ω† is a weighting function,rout is given by: jout−c1φ+{circumflex over (Ω)}Ŷjout. 7. The method of claim 6 wherein the partial operator derivative ∂ ϕ ∂ λ is iteratively solved through application of: [ ∂ ϕ ~ ∂ λ ] ( new ) = s + 2 ⁢ λ ⁢ ⁢ B ^ ⁡ [ ∂ ϕ ~ ∂ λ ] ( old ) - λ 2 ⁢ B ^ 2 ⁡ [ ∂ ϕ ~ ∂ λ ] ( old ) where ⁢ ⁢ ∂ ϕ ∂ λ ≅ ∂ ϕ ~ ∂ λ {circumflex over (B)}({circumflex over (R)}−ŜLD)−1{circumflex over (F)}s={circumflex over (B)}({circumflex over (R)}−ŜLD)−1ĜŶjout=({circumflex over (R)}−ŜLD)−1{circumflex over (F)}({circumflex over (R)}−ŜLD)−1ĜŶjout {circumflex over (R)} designates a removal operator, ŜLD is a lower-diagonal part of an inscatter operator Ŝ, {circumflex over (F)} is a production operator, and Ĝ is an incurrent operator. 8. The method of claim 1 further comprising a step of building the nuclear reactor core on the basis of the calculated neutron flux. 9. The method of claim 1 further comprising a step of operating the nuclear reactor core on the basis of the calculated neutron flux. 10. A nontransitory computer readable medium comprising a computer program for controlling a computer to:partition the core in cubes to constitute nodes of a grid for computer implemented calculation, andcalculate neutron flux by using an iterative solving procedure of at least one eigensystem, components of an iterant of the eigensystem corresponding either to a neutron flux, to a neutron outcurrent or to a neutron incurrent, for a respective cube to be calculated,wherein a control parameter is varied to impact a neutron eigenvalue μ through a perturbed interface current equation and drive the neutron eigenvalue μ towards 1,the perturbed interface current equation being defined by j out + δ ⁢ ⁢ j out = ( μ + δ ⁢ ⁢ μ ) ⁢ c 1 ⁡ ( ϕ + δϑ ⁢ ∂ ϕ ∂ ϑ ) + Ω ^ ⁢ Y ^ ⁡ ( j out + δ ⁢ ⁢ j out ) where jout designates the neutron outcurrent, Φ designates the neutron flux, θ designates the control parameter, Ŷ is a coupling operator, {circumflex over (Ω)} is a mono-directional current throughflow operator, and c1 is an operator depending on the cube properties, the control parameter being a parameter of the model representing a feature of the nuclear reactor core. 11. The nontransitory computer readable medium of claim 10 further controlling the computer to operate the nuclear reactor core on the basis of the calculated neutron flux. 12. A method for at least one of operating and building a nuclear reactor core comprising:modelizing a nuclear reactor core by performing the computer implemented steps of:partitioning, by a computer processor, the core in cubes to constitute nodes of a grid for computer implemented calculation,calculating, by the computer processor, neutron flux by using an iterative solving procedure of at least one eigensystem, components of an iterant of the eigensystem corresponding either to a neutron flux, to a neutron outcurrent or to a neutron incurrent, for a respective cube to be calculated; andat least one of operating and building the nuclear reactor core on the basis of the calculated neutron flux,wherein a control parameter is varied to impact a neutron eigenvalue μ through a perturbed interface current equation and drive the neutron eigenvalue μ towards 1,the perturbed interface current equation being defined by j out + δ ⁢ ⁢ j out = ( μ + δ ⁢ ⁢ μ ) ⁢ c 1 ⁡ ( ϕ + δϑ ⁢ ∂ ϕ ∂ ϑ ) + Ω ^ ⁢ Y ^ ⁡ ( j out + δ ⁢ ⁢ j out ) where jout designates the neutron outcurrent, Φ designates the neutron flux, θ designates the control parameter, Ŷ is a coupling operator, {circumflex over (Ω)} is a mono-directional current throughflow operator, and c1 is an operator depending on the cube properties, the control parameter being a parameter of the model representing a feature of the nuclear reactor core. 13. The method of claim 12 wherein the control parameter θ is given by a determinative output of the following equation: ϑ ( new ) = ϑ ( prev ) + 〈 ω † \| r out ( prev ) 〉 〈 ω † \| c 1 ⁢ ∂ ϕ ∂ ϑ 〉 wherein ω† is a weighting function,rout is given by: jout−c1φ+{circumflex over (Ω)}Ŷjout. 14. The method of claim 13 wherein the control parameter represents a boron concentration of the nuclear reactor core. 15. The method of claim 13 wherein the control parameter represents a rod insertion depth for a group of selected control rods of the nuclear reactor core. 16. The method of claim 12 wherein the control parameter is a neutron eigenvalue λ, and wherein, during an iteration of the iterative solving procedure, the neutron eigenvalue λ is varied to drive the neutron eigenvalue μ towards 1, and wherein the variation of the neutron eigenvalue λ is an application of a variation δλ to λ, such that λ is driven to λ+δλ, which impacts the neutron eigenvalue μ through the perturbed interface current equation. 17. The method of claim 16, wherein the neutron eigenvalue λ is preconditioned prior to the iteration of the eigensystem solving procedure according to: λ ( new ) = λ ( prev ) + 〈 ω † \| r out ( prev ) 〉 〈 ω † \| c 1 ⁢ ∂ ϕ ∂ λ 〉 where ω† is a weighting function,rout is given by: jout−c1φ+{circumflex over (Ω)}Ŷjout. 18. The method of claim 17 wherein the partial operator derivative ∂ ϕ ∂ λ is iteratively solved through application of: [ ∂ ϕ ~ ∂ λ ] ( new ) = s + 2 ⁢ ⁢ λ ⁢ ⁢ B ^ ⁡ [ ∂ ϕ ~ ∂ λ ] ( old ) - λ 2 ⁢ B ^ 2 ⁡ [ ∂ ϕ ~ ∂ λ ] ( old ) where ⁢ ⁢ ∂ ϕ ∂ λ ≅ ∂ ϕ ~ ∂ λ {circumflex over (B)}=({circumflex over (R)}−ŜLD)−1{circumflex over (F)}s={circumflex over (B)}({circumflex over (R)}−ŜLD)−1ĜŶjout=({circumflex over (R)}−ŜLD)−1{circumflex over (F)}({circumflex over (R)}−ŜLD)−1ĜŶjout {circumflex over (R)} designates a removal operator, ŜLD is a lower-diagonal part of an inscatter operator Ŝ, {circumflex over (F)} is a production operator, and Ĝ is an incurrent operator.
053496159	summary	BACKGROUND OF THE INVENTION The invention relates to a device for the retention of core melt-through-in the event of a core melt-through accident in light-water reactors and also to a reactor plant having such a device. Because of the afterheat of the reactor core, which is produced because of the radioactive fission products, the core melts if the cooling water empties from the reactor pressure vessel because of an accident; the molten mass of the core penetrates the wall of the pressure vessel. If there is no retention device to collect the molten mass, then the foundation of the building is also breached by the molten mass, with the concrete being decomposed because of the high melting temperature (over 2500.degree. C.) with the formation of hydrogen, carbon monoxide, carbon dioxide and water vapour. The molten mass of the core is essentially composed of uranium oxide, zirconium and steel in the ratio of roughly 6:1:3. Various safety concepts have been developed to prevent the hypothetical consequences of serious accidents in light-water reactors, in particular of core melt-through accidents. Thus for example a core melt-through retention device ("core catcher") has been proposed, in which a shaft-like collecting basin for the molten mass is provided beneath the reactor core (R. Hammond, J. Dooley, 1982 "Retrofitting Core Catcher to Nuclear Plants", NUREG/CR-2941; or U.S. Pat. No. 4,036,688). This known device consists of an upper section, which is cylindrical (diameter: 3.5-5 mm, height: 10-15 m) and a lower section, which tapers conically downwards (height: 20-25 m). The upper section is lined with highly refractory material and the lower section is constructed as a water-cooled, double-walled steel crucible. This crucible is filled with a siliceous or oxidic ceramic bulk material. With the cooling system provided there is the danger of the inner crucible wall being perforated by the molten mass, as a result of which radioactive fission products of the molten mass can be released into the atmosphere. SUMMARY OF THE INVENTION The object of the invention is to create inside the containment a collecting basin for the molten mass of the core, which is constructed as a crucible for the safe and long-term retention of the molten mass at high temperatures. The molten mass of the core collected in the crucible of the device according to the invention is cooled in the cooling basin by sump water, which comes partly from the broken primary water circuit. The water vaporised on cooling condenses on the walls of the containment and flows back into the containment sump again. The crucible lining should be as inert as possible with respect to the molten mass of the core. When the molten mass solidifies a solid layer--a "secondary crucible"--is constructed in the edge zones of the crucible, which produces a protective action for the wall of the retention device. Until the formation of this secondary crucible, the material of the lining can only react with the molten mass to a limited extent. It is therefore advantageous if a non-oxidising ceramic is chosen for the crucible lining. So that the protective secondary crucible is quickly formed, the heat has to be conducted away easily by the lining. High-temperature isostatic pressed boron nitride--"HIP-BN"--meets these requirements (thermal conductivity: 49 W/m.multidot.K at 20.degree. C.; 28 W/m.multidot.K at 800.degree. C.) and offers various other advantages. Thanks to the boron a recriticality of the molten mass of the core can be prevented. Boron nitride (BN) has a poor wettability with respect to the molten mass of the core. The melting point of BN is high; it is roughly 3000.degree. C. BN is characterised by a good thermal fatigue resistance and a good compressive strength. BN is resistant in air up to a temperature of 1000.degree. C. With regard to construction the simplest method is to construct the protuberances on the crucible vat as circular cylindrical cooling tubes. Low-alloy steel can be used for the external crucible wall. On the bottom of the vat between the cooling tubes is advantageously provided a thick guard plate, with which the lining can be protected against the impact of the molten mass of the core. This guard plate is melted by the molten mass of the core if the requirements are met (i.e. in the event of a core melt-through accident). The crucible lid, which forms a water-tight seal for the crucible, can be composed of steel plates, for example by horizontal plates being welded to vertical plates disposed in a honeycomb, which protrude into the interior of the crucible vat. The honeycomb lid reinforcement can be placed on the guard plate of the base of the vat. With the retention of the molten mass of the core if the requirements are met, first of all the kinetic energy of the falling molten mass of the core is converted into deformation energy; then the crucible lid is melted through. The volume of the crucible has such dimensions that the crucible is filled by the molten mass to roughly 10 cm above the vat base, for example. The cooling basin may be provided as the deepest part of the containment sump; it can be constructed as a cavity in the foundation plate of the containment. The crucible lid guarantees that no water penetrates into the crucible, even if it is flooded by incoming primary water. The cooling basin is always filled with water. A distinction can be made between two ways in which the reactor pressure vessel may malfunction, which are referred to by the designations "low pressure path" and "high pressure path" respectively. In the case of the low pressure path the molten mass of the core flows through a melted-open perforation in the reactor vessel. In the case of the high pressure path the lower spherical section of the reactor pressure vessel is centrifuged away with the molten mass of the core located therein. In order to control the high pressure path, a collecting structure has to be provided between the reactor pressure vessel and the retaining device, with which the retaining device can be screened from the wall piece blown off the pressure vessel. This collecting structure is advantageously constructed in a funnel shape so that the molten mass can be directed into the central region of the retaining device. The steam produced during the cooling of the retention device filled with molten mass can freely spread in the interior of the containment. Thanks to the condensation of the steam on the walls an equilibrium pressure can be balanced out; this depends on the heat dissipation of the containment to the atmosphere. It is possible for the pressure to rise to an unacceptable level. In order to redress such a pressure build-up, the containment has to be connected to a filtered pressure relief device (device for the filtered relief of pressure).
	summary
	summary
046506306	claims	1. The process of producing a fusion reaction in a plasma-free environment comprising the steps of continuously pumping an evacuated vessel to a hard vacuum of the order of 10.sup.-7 atmospheres, producing a DC magnetic field, in said vessel; producing a first sharply focused homogeneous beam of positive hydrogen isotope ions of non-plasma form having a first energy and causing said first beam of ions to move along a given path in said evacuated vessel, producing a second sharply focused homogeneous beam of negative hydrogen isotope ions of non-plasma form having a second energy and causing said second beam of ions to move along a path coincident with but opposite in direction to said first path, said coincident path extending over a distance comprising a major portion of the total distance travelled by said first and second beams of ions; said first and second energies having values sufficient to produce a fusion reaction between said ions of said first and second beams which collide with one another but not so high to cause said colliding ions to fly apart, and heating a heat exchange fluid with at least a fraction of the energy produced by fusion of colliding ions and thereafter extracting useful energy from said heated heat exchange fluid. 2. The process of claim 1 wherein said path is a straight line. 3. The process of claim 1 wherein said path is curved. 4. The process of claim 1 wherein said path is circular. 5. The process of claim 1, 2, 3 or 4 wherein said ions of said first beam are deuterium and said ions of said second beam are tritium. 6. The process of claim 1 wherein said heat exchange fluid is liquid lithium. 7. Apparatus for producing energy from the fusion of ions of first and second sharply focused homogeneous ion beams is a plasma-free environment comprising: an evacuated chamber which has a hard vacuum therein of the order of 10.sup.-7 atmospheres and means for continuously drawing said hard vacuum in said chamber; means for producing a constant DC magnetic field in said vessel; first ion source means for producing said first ion beam to have a first energy, a first electrical charge and a non-plasma form and injecting said first ion beam into said chamber, said first ion beam moving along a given path within said chamber; second ion source means for producing said second ion beam to have a second energy, a second electrical charge of a polarity opposite to said first electrical charge and a non-plasma form and injecting said second ion beam into said chamber, said second ion beam moving along a path coincident with at least a major portion of the length of said given path within said chamber and directed oppositely to said first ion beam; the ions of said first and second ion beams having respective energies to maximize the probability of a fusion reaction between colliding ions of the respective beams in the absence of a plasma; and heat exchange means connected to said chamber to extract from said chamber energy which is produced by fusion reactions between the ions of said beams. 8. The apparatus of claim 7 wherein said path is a straight line. 9. The apparatus of claim 7 wherein said path is a curved line. 10. The apparatus of claim 7 wherein said path is a circle. 11. The apparatus of claim 7, 8, 9 or 10 wherein said ions of said first and second beams are of deuterium and tritium respectively.
052895130	claims	1. A method of making a lattice member, comprising the steps of: (a) controllably moving conveyor means for conveying a plurality of interior and a plurality of exterior strap members therealong; (b) advancing each interior and each exterior strap member into alignment with a deflector vane piercing die by controllably moving the conveyor means; (c) actuating the deflector vane piercing die, so that each interior and each exterior strap member is pierced to form a deflector vane thereon; (d) advancing each interior and each exterior strap member into alignment with a deflector vane drawing die by controllably moving the conveyor means; (e) actuating the deflector vane drawing die, so that the deflector vane is drawn into a predetermined curvature; (f) advancing a pair of the exterior strap members into alignment with a trihedral drawing die by controllably moving the conveyor means; and (g) actuating the trihedral drawing die to draw each exterior strap member, so that each of the pair of exterior strap members obtains a trihedral-shaped cross section. (a) advancing each interior and each exterior strap member into alignment with a spring drawing die by controllably moving the conveyor means; and (b) actuating the spring drawing die, so that each interior and each exterior strap member is drawn to form a spring member thereon. (a) joining the pair of exterior strap members to form a unitary outer strap member having a hexagon-shaped cross section; (b) joining the interior strap members so as to form a plurality of intersecting first and second inner strap members defining a plurality of rhombic-shaped rod cells and a plurality of generally rhombic-shaped thimble cells; and (c) joining the first and second inner strap members to the interior of the outer strap member. (a) advancing each interior and each exterior strap member into alignment with a trimming die by controllably moving the conveyor means; and (b) actuating the trimming die, so that each interior and each exterior strap member is trimmed. (a) advancing each exterior strap member into alignment with a coining die by controllably moving the conveyor means: and (b) actuating the coining die, so that each exterior strap member is coined. (a) controllably moving a motorized conveyor along a predetermined circuit extending through the die machine by operating a pre-programmed computer for conveying a plurality of interior and a plurality of exterior strap members along the circuit, each interior and each exterior strap member engaging the conveyor; (b) successively advancing each interior and each exterior strap member along the circuit and into coaxial alignment with a preselected pneumatically actuatable deflector vane piercing die by controllably moving the conveyor; (c) selectively pneumatically actuating the deflector vane piercing die by operating the computer, so that each interior and each exterior strap member is pierced to form a plurality of deflector vanes thereon; (d) successively advancing each interior and each exterior strap member along the circuit and into coaxial alignment with a preselected pneumatically actuatable deflector vane drawing die by controllably moving the conveyor; (e) selectively pneumatically actuating the deflector vane drawing die by operating the computer, so that each deflector vane is drawn into a predetermined curvature for forming a plurality of curved deflector vanes in each interior and each exterior strap member as said deflector vane drawing die is actuated; (f) successively advancing each of the interior and each of the exterior strap members along the circuit and into alignment with a preselected pneumatically actuatable spring drawing die by controllably moving the conveyor; and (g) selectively pneumatically actuating the preselected spring drawing die by operating the computer to draw a plurality of raised portions extending from each interior and exterior strap member, so that the raised portions define a plurality of spring members in each interior and each exterior strap member as said spring drawing die is actuated. (h) successively advancing a preselected pair of exterior strap members along the circuit and into alignment with a preselected pneumatically actuatable trihedral drawing die by controllably moving the conveyor; (i) selectively pneumatically actuating the preselected trihedral drawing die by operating the computer to successively draw each of the exterior strap members, so that each exterior strap member obtains a regular trihedral-shaped transverse cross section; (j) joining the pair of trihedral-shaped exterior strap members one to another by activating a laser welding device so that the trihedral-shaped exterior strap members form a unitary outer strap member defining a regular hexagon in transverse cross section, the outer strap member having an interior wall; (k) joining the interior strap members one to another by activating the laser welding device so as to form a plurality of intersecting first and second inner strap members defining a plurality of rhombic-shaped rod cells and a plurality of generally rhombic-shaped thimble cells, the first and second inner strap members each having end portions; (l) surrounding the plurality of first and second inner strap members with the outer strap member; and (m) joining the end portions of each of the first and second inner strap members to the interior wall of the outer strap member by activating the laser welding device. (a) successively advancing each interior and each exterior strap member along the circuit and into alignment with a preselected pneumatically actuatable trimming die by controllably moving the conveyor; and (b) selectively pneumatically actuating the preselected trimming die by operating the computer, so that each interior and each exterior strap member is pierced to trim each interior and each exterior strap member. (a) successively advancing each exterior strap member along the circuit and into alignment with a preselected pneumatically actuatable coining die by controllably moving the conveyor; and (b) selectively pneumatically actuating the preselected coining die by operating the computer, so that each exterior strap member is drawn to coin each exterior strap member. (a) an outer strap member having a hexagonal transverse contour; (b) a plurality of parallel first inner strap members extending transversely interiorly of said outer strap member, each of said first inner strap, strap members having end portions thereof attached to said outer strap member; (c) a plurality of parallel second inner strap members extending transversely interiorly of said outer strap member, each of said second inner strap members having end portions thereof attached to said outer strap member, each of said second inner strap members intersecting each of said first inner strap members at a predetermined angle with respect thereto for defining a plurality of rhombic-shaped rod cells and a plurality of generally rhombic-shaped thimble cells for receiving respective ones of a plurality of fuel rods and thimble tubes; and (d) deflector means associated with each rod cell and attached to said outer strap member and to each of said first and second inner strap members for deflecting a component of a fluid stream onto the fuel rods. (a) an outer strap member having a hexagonal transverse cross section formed by engaging a pair of exterior strap members with a computer controlled conveyor, successively advancing each of the pair of exterior strap members into coaxial alignment with a trihedral drawing die by controllably moving the conveyor, actuating the trihedral drawing die to draw each of the exterior strap members into a trihedron by operating a computer, joining the exterior strap members by activating a laser welding device so that the pair of exterior strap members define a hexagon in transverse cross section to form said outer strap member; (b) a plurality of parallel first inner strap members joined to said outer strap member by activating the laser welding device, each of said first inner strap members extending transversely interiorly of said outer strap member; (c) a plurality of parallel second inner strap members joined to said outer strap member by activating the laser welding device, each of said second inner strap members extending transversely interiorly of said outer strap member, each of said second inner strap members intersecting each of said first inner strap members at a predetermined angle with respect to each of said first inner strap members for defining a plurality of rhombic-shaped rod cells and a plurality of generally rhombic-shaped thimble cells; and (d) deflector means associated with each of the rod cells and attached to said first inner, second inner, and outer strap members for deflecting a component of a fluid flowing past said strap members, said deflector means formed by engaging said first inner, second inner, and outer strap members with the conveyor, advancing each of said first inner, second inner, and outer strap members into alignment with a deflector vane piercing die by controllably moving the conveyor, actuating the deflector vane piercing die by operating the computer so that each strap member is pierced to form said deflector means on each strap member, advancing each of said first inner, second inner, and outer strap members into alignment with a deflector vane drawing die by controllably moving the conveyor, actuating the deflector vane drawing die by operating the computer so that said deflector means is drawn into a predetermined curvature. (a) an outer strap member having a regular hexagonally-shaped transverse contour formed by engaging a preselected pair of exterior strap members with a computer controlled motorized conveyor extending along a predetermined circuit extending through a progressive die machine, successively advancing the pair of exterior strap members along the circuit and into coaxial alignment with a preselected pneumatically actuatable trihedral drawing die by controllably moving the conveyor, selectively pneumatically actuating the trihedral drawing die by operating the computer to successively draw each exterior strap members into a regular trihedron, joining the exterior strap members by activating a laser welding device so that the exterior strap members define a regular hexagon in transverse cross section, said outer strap member having at least one elongate side panel; (b) a plurality of elongate parallel first inner strap members each having end portions thereof joined to said outer strap member by activating a laser welding device, each of said first inner strap members extending transversely interiorly of said outer strap member parallel to the side panel of said outer strap member; (c) a plurality of elongate parallel second inner strap members each having end portions thereof joined to said outer strap member by activating the laser welding device, each of said second inner strap members extending transversely interiorly of said outer strap member, each of said second inner strap members intersecting each of said first inner strap members at a predetermined angle with respect to each of said first inner strap members, so that a plurality of rhombic-shaped rod cells are defined to receive respective ones of the fuel rods and so that a plurality of generally rhombic-shaped thimble cells are defined to receive respective ones of the thimble tubes, whereby the plurality of fuel rods and the plurality of thimble tubes are maintained in spaced parallel array as the fuel rods and the thimble tubes are received through their respective rod cells and thimble cells; and (d) a plurality of deflector vanes associated with each of the rod cells and integrally attached to each of said first and second inner strap members and to said outer strap member, each of said deflector vanes being formed by engaging said first and second inner strap members and said outer strap members with the conveyor, engaging each of said first, second and outer strap members with the conveyor, successively advancing each of said first, second and outer strap members along the circuit and into coaxial alignment with a preselected pneumatically actuatably deflector vane piercing die by controllably moving the conveyor, selectively pneumatically actuating the deflector vane piercing die by operating the computer so that each first, second and outer strap member is pierced to form the plurality of said deflector vanes on each first, second and outer strap member, successively advancing each of said first, second and outer strap members along the circuit an into coaxial alignment with a preselected pneumatically actuatable deflector vane drawing die by controllably moving the conveyor, selectively pneumatically actuating the deflector vane drawing die by operating the computer so that each of said deflector vanes is drawn into a predetermined curvature. 2. The method of claim 1, further comprising the steps of: 3. The method of claim 2, further comprising the steps of: 4. The method of claim 1, further comprising the step of trimming each interior and each exterior strap member. 5. The method of claim 4, wherein said step of trimming each interior and each exterior strap member comprises the steps of: 6. The method of claim 1, further comprising the step of coining each exterior strap member. 7. The method of claim 6, wherein said step of coining each exterior strap member comprises the steps of: 8. In a progressive die machine, a method of making a lattice member for a fuel assembly, the method comprising the steps of: 9. The method of claim 8, further comprising the steps of: 10. The method of claim 8, further comprising the steps of: 11. A lattice member made by the method of claim 8, comprising: 12. The lattice member according to claim 11, further comprising a plurality of resilient spring members associated with each fuel rod and formed from the outer strap member and from each of the first and second inner strap members, each of said spring members engaging its respective fuel rod for supporting the fuel rod. 13. A lattice member, comprising: 14. The lattice member according to claim 13, wherein said outer strap member, each of said first inner strap members and each of said second inner strap members further comprise resilient spring means formed therefrom by advancing each of said strap members into alignment with a spring drawing die and actuating the spring drawing die to draw a raised portion from each of said strap members. 15. A lattice member for a fuel assembly, the lattice member capable of maintaining a plurality of elongate fuel rods and plurality of elongate thimble tubes in spaced parallel array, the lattice member comprising: 16. The lattice member according to claim 15, wherein said outer strap member, each of said first inner strap members and each of said second inner strap members further comprise a plurality of resilient spring members formed therefrom by successively advancing each strap member along the circuit and into coaxial alignment with a preselected pneumatically actuatable spring drawing die by controllably moving the conveyor and selectively pneumatically actuating the spring drawing die by operating the computer to draw a plurality of raised portions outwardly extending from each strap member.
	description	1. Field of the Invention The present invention relates to a method of reducing corrosion of a nuclear reactor structural material composed of a stainless steel or a nickel-base alloy, which is used in a nuclear power plant such as boiling water reactor (BWR). 2. Related Art In a boiling water reactor (BWR) plant widely operated in the world, the cooling water contains a high concentration of oxidizing species or oxidizers such as oxygen and hydrogen peroxide which are generated by radiolysis of reactor water. Therefore, it is known that stress corrosion cracking (SCC) or intergranular stress corrosion cracking (IGSCC) occurs to a material such as a stainless steel or a nickel-base alloy used as a material constituting a nuclear reactor structure (which is called as a nuclear reactor structural material hereinlater) in the nuclear power plants. The generation of such SCC or IGSCC and the crack growth depend on the electrochemical corrosion potential (ECP). The electrochemical corrosion potential is decreased by reducing the concentration of oxygen and hydrogen peroxide, thereby suppressing the stress corrosion cracking and the crack growth. In order to prevent such stress corrosion cracking (SCC) or intergranular stress corrosion cracking (IGSCC) (which may be merely referred to as SCC hereinlater), the following operations or techniques have been performed in nuclear power plants around the world. That is, in a hydrogen water chemistry (HWC), a concentration of oxygen and hydrogen peroxide in a nuclear reactor water is reduced by injecting hydrogen in the feed water. On the other hand, a noble metal such as Pt and Rh is deposited or adhered to the surface of a nuclear reactor structural material in advance, and the hydrogen is injected (see, for example, “Genshirosui kagaku hando bukku” (Handbook of nuclear reactor water chemistry) edited by Atomic Energy Society of Japan, Corona Publishing Co., Ltd., Dec. 27, 2000, p. 210, and Japanese Patent No. 2624906). In addition, for example, Japanese Unexamined Patent Application Publication No. HEI 07-270592 discloses an anticorrosion technique in which titanium oxide, which is known as a photocatalyst, is deposited to a material. Japanese Unexamined Patent Application Publication No. 2001-4789 discloses a technique combined a photocatalyst, a noble metal, and hydrogen injection. In the known methods of reducing corrosion described above, the following inconveniences or problems have been provided. For example, it is known that the reactor water in a nuclear reactor becomes a reducing condition by the hydrogen injection. The reactor water contains nitrogen compounds composed of radioactive nitrogen (N-16) generated by nuclear transformation of oxygen. These compounds including soluble substances such as a nitrate ion and a nitrite ion are changed into volatile ammonia under the reducing atmosphere in the reactor water. Unfortunately, the resultant ammonia flows into a main steam, thereby increasing the dose rate in the turbine system. Furthermore, since the injected hydrogen flows into an off-gas system, it is necessary to carry out a reaction to recombine the hydrogen with oxygen, and therefore, additional equipment is required. On the other hand, the noble metal chemical addition is advantageous in that even a small amount of hydrogen injection can reduce the corrosion, compared with the hydrogen injection mentioned above. However, in order to allow a noble metal to adhere to a nuclear reactor structural material, a solution containing the noble metal must be injected in the nuclear reactor water. As a result, the noble metal also adheres to the surface of a fuel cladding tube composed of a zirconium alloy. This adhesion causes corrosion of the fuel material or increases the amount of hydrogen absorption. In addition, at a portion to which the noble metal is deposited, when the hydrogen molar concentration is double or more of the oxygen molar concentration, the corrosion potential of the material drastically decreased. As a result, the material shows a very low potential, for example, −500 mV. Such a significant decrease in the corrosion potential impairs the stability of the oxide film formed on the surface of the material. As a result, radioactive metal oxides on the surface of the film or in the film are released in the reactor water. Moreover, when the above noble metal chemical addition is performed in nuclear power plants, a large amount of noble metal adheres to a zirconium oxide film of the fuel. As a result, this adhesion increases the oxidation and hydrogenation of the fuel material. Furthermore, when the recombination of hydrogen with oxygen is performed on the surface of the noble metal, and the oxygen concentration in the reactor water is decreased, the dose rate in the turbine system is increased. As described above, the noble metal chemical addition causes negative effects in the water quality conservation, the decrease in the flowing of radioactivity and the increase in burn-up of the fuel. In order to eliminate such negative effects, the development of a method of decreasing the injection amount of the noble metal or a method using an alternative substance of the noble metal is desired. On the other hand, in the anticorrosion methods using a photocatalyst, the inconveniences or problems caused in the hydrogen injection or the noble metal chemical addition do not occur. However, as described in Japanese Unexamined Patent Application Publication No. HEI 07-270592, No. 2001-4789, and No. 2001-276628, in order to reduce the corrosion, SCC mitigation using a photocatalyst require light or radiation to excite the photocatalyst. Therefore, the application range of anticorrosion is limited to a structural material in the reactor such as a shroud, and unfortunately, a sufficient anticorrosion effect cannot be expected in other components such as primary loop recirculation system piping. In consideration of the above circumstances encountered in the prior art, it is an object of the present invention to provide a method of reducing corrosion of a nuclear reactor structural material, in which an amount of hydrogen injection for preventing stress corrosion cracking is decreased to thereby suppress the flowing of radioactivity into a turbine system, to decrease an amount of excessive hydrogen in an off-gas system, to suppress melting of metal oxides in the vicinity of a noble metal, the melting being caused by the adhesion of the noble metal, and also to reduce a corrosion of a fuel material so as to suppress the increasing in the amount of hydrogen absorption. Another object of the present invention is to provide a method of reducing corrosion of a nuclear reactor structural material in a nuclear reactor, particularly, BWR, plants, capable of suppressing the stress corrosion cracking by decreasing an electrochemical corrosion potential of the material under a condition of reducing the amount of hydrogen injection for suppressing the material corrosion. These and other objects can be achieved according to the present invention by providing, in one aspect, a method of reducing corrosion of a material constituting a nuclear reactor structure comprising the steps of: injecting a solution or a suspension containing a substance generating an excitation current by an action of at least one of radiation, light and heat existing in a nuclear reactor, or a metal or a metallic compound forming the substance generating an excitation current under a condition in a nuclear reactor; depositing the substance generating the excitation current to a surface of the material of the nuclear reactor structure; and injecting hydrogen in a nuclear reactor water while controlling a hydrogen concentration in a feed water to thereby control a corrosion potential. In the method of this aspect, it may be desired that the corrosion potential is controlled in a range of −0.4 V vs. SHE to −0.1 V vs. SHE. The notation “V vs. SHE” represents the potential measured by using a standard hydrogen electrode (SHE) as a standard. The substance generating the excitation current may be at least one of substances selected from TiO2, ZrO2, ZnO, WO3, PbO, BaTiO3, Bi2O3, SrTiO3, Fe2O3, FeTiO3, KTaO3, MnTiO3, SnO2, and Nb2O5. The solution or the suspension may be injected in at least one of a feed water system, an outlet of a reactor water clean-up system, a primary loop recirculation system and a residual heat removal system. The hydrogen may be injected in at least one of a feed water system, an outlet of a reactor water clean-up system, a primary loop recirculation system and a residual heat removal system. It may be desired that the solution or the suspension is injected when the nuclear reactor is started up or when the nuclear reactor is shut down, and the hydrogen is injected while the nuclear reactor is operated. Hydrogen may be added to the solution or the suspension in advance, and the solution or the suspension is injected in the cooling water while the nuclear reactor is operated. The adhesion amount of the substance generating the excitation current on the surface of the nuclear reactor structural material is preferably in a range of 10 to 200 μg/cm2. The hydrogen concentration in a feed water of hydrogen to be injected in the cooling water of the nuclear reactor is 0.2 to 1 ppm. The adhesion amount of the substance generating the excitation current on a surface of the nuclear reactor structural material is monitored, and the hydrogen concentration in a feed water is controlled in accordance with the adhesion amount. According to the method of reducing corrosion of a nuclear reactor structural material of the present invention in the above aspect, the electrochemical corrosion potential can be controlled to an adequate potential with a small amount of hydrogen injection. Therefore, the corrosion of the nuclear reactor structural material can be effectively reduced, while preventing the increase in dose rate in the turbine system or the flowing of hydrogen into the off-gas system. In another aspect of the present invention, there is also provided a method of reducing corrosion of a material constituting a nuclear reactor structure comprising the steps of: applying a substance generating an excitation current and a noble metal to a surface of a material constituting a nuclear reactor structure in advance; and controlling a concentration of oxidizing chemical species and a concentration of reducing chemical species in a nuclear reactor water so that a molar ratio of H2/O2 is less than a value of 2 in which a catalytic reaction to recombine the oxidizing chemical species with the reducing chemical species is not accelerated by the noble metal. In preferred embodiments of this aspect, it may be desired that the substance generating the excitation current is at least one of compounds selected from TiO2, ZrO2, ZnO, WO3, PbO, BaTiO3, Bi2O3, SrTiO3, Fe2O3, FeTiO3, KTaO3, MnTiO3, SnO2, and Nb2O5. The noble metal is preferably at least one of elements selected from Pt, Pd, Ir, Rh, Os, and Ru. The substance generating an excitation current and the noble metal is applied by at least one of methods selected from chemical injection, flame coating, spraying, plating, and vapor deposition. A concentration of oxidizing chemical species and a concentration of reducing chemical species in a nuclear reactor water may be controlled so that a molar ratio of H2/O2 is less than a value of 2 by injecting hydrogen from a feed water system or a condensate system. A hydrogen concentration in the feed water or the condensate system is not less than 0.07 ppm and less than 0.16 ppm. The noble metal is applied before the application of the substance generating the excitation current. The substance generating the excitation current and the noble metal are applied at the same time or before the application of the noble metal. An electrochemical corrosion potential of the nuclear reactor structural material composed of a stainless steel is preferably controlled to be −0.23 V vs. SHE or less. An electrochemical corrosion potential of the nuclear reactor structural material composed of a nickel-base alloy is preferably controlled to be −0.1 V vs. SHE or less. According to this aspect, the stress corrosion cracking can be also suppressed by decreasing an electrochemical corrosion potential of the material under a condition that the amount of hydrogen injection for suppressing the material corrosion is reduced. In addition, the dose rate in the turbine system which was a problem in the prior art can be effectively prevented from increasing, thus being advantageous. The nature and further characteristic features of the present invention will be made more clear from the following descriptions made with reference to the accompanying drawings. Preferred embodiments of a method of reducing corrosion of a nuclear reactor structural material according to the present invention will be described in detail with reference to the accompanying drawings. A first embodiment of the method of reducing corrosion of a material constituting a nuclear reactor structure (which may be called hereunder “nuclear reactor structural material”) according to the present invention will be first described with reference to FIGS. 1 to 4. FIG. 1 shows a circulating system of reactor water in a nuclear power plant. This reactor water circulating system includes a reactor pressure vessel 10, a feed water system piping 1, a primary loop recirculation (PLR) system piping 2, a reactor water clean-up (RWCU) system piping 3, and a residual heat removal (RHR) system piping 4. Examples of a nuclear reactor structural material forming the reactor pressure vessel 10 include materials of a shroud 6 shown in FIG. 1, a core support plate, and a grid plate. The method of reducing corrosion of a nuclear reactor structural material of the present invention can be applied to such materials. A feed water pump 7 is disposed in the feed water system piping 1. This feed water pump 7 sends cooling water from the feed water system piping 1 to the reactor pressure vessel 10. A part or portion of the cooling water circulates in the primary loop recirculation (PLR) system piping 2 with a primary loop recirculation (PLR) pumps 8. A part or portion of the cooling water in the primary loop recirculation (PLR) system piping 2 circulates in the reactor water clean-up (RWCU) system piping 3 with a reactor water clean-up (RWCU) system pump 9. In addition, a part or portion of the cooling water in the primary loop recirculation (PLR) system piping 2 circulates the residual heat removal (RHR) system piping 4 with a residual heat removal (RHR) system pump 12. A heat exchanger E and a filter deminelizer F are disposed in the reactor water clean-up (RWCU) system piping 3 to purify the cooling water. Injection points or sections 13, 14, 15, and 16 are disposed in the feed water system piping 1, the primary loop recirculation (PLR) system piping 2, the reactor water clean-up (RWCU) system piping 3, and the residual heat removal (RHR) system piping 4, respectively, so as to connect an injection system of titanium oxide and hydrogen thereto. FIG. 2 is an illustration showing the structure of the injection system of titanium oxide and hydrogen. This injection system of titanium oxide and hydrogen includes a hydrogen gas injection unit 19 and a titanium oxide solution injection unit 20. This injection system is connected to at least one or one portion of the feed water system piping 1, the primary loop recirculation (PLR) system piping 2, the reactor water clean-up (WCU) system piping 3, and the residual heat removal (RHR) system piping 4. Each of the injection points 13, 14, 15, and 16 includes a pair of a hydrogen injection point 17 and a titanium oxide injection point 18. The hydrogen gas injection unit 19 is connected to the hydrogen injection point 17, and the titanium oxide solution injection unit 20 is connected to the titanium oxide injection point 18. Accordingly, a hydrogen gas and a titanium oxide solution can be supplied at the same time or separately. The hydrogen injection point 17 and the titanium oxide injection point 18 may be disposed adjacently or separately. Instead of the steel cylinder equipment shown in FIG. 2, the hydrogen gas injection unit 19 may be, for example, electrolysis equipment of water to form a supply system of hydrogen. A titanium oxide solution in the titanium oxide solution injection unit 20 is injected from the titanium oxide injection point 18 with an injection pump 21 and then circulates in the nuclear reactor with reactor water. As a result, titanium oxide adheres to the surfaces of the nuclear reactor structural materials such as shroud 6. On the other hand, the hydrogen gas is injected from the hydrogen injection point 17 and also circulates in the nuclear reactor with the reactor water. The amount of the hydrogen gas injection can be controlled with a flow control valve 22. Thus, the hydrogen concentration can be controlled with the volume of water flowing in the piping. The injection of the titanium oxide solution and hydrogen gas can be performed at any time, for example, when the nuclear reactor is started up, when the nuclear reactor is shut down, or while the nuclear reactor is operated. Hydrogen gas may be added to the titanium oxide solution in advance. The resultant solution may be injected in the cooling water to supply hydrogen gas and titanium oxide at the same time. FIG. 3 schematically shows a mechanism of an oxidation-reduction reaction on the surface of the titanium oxide adhering to a nuclear reactor structural material. The titanium oxide 26 adhering to the surface of the structural material 25 composed of a stainless steel is excited with heat so as to generate an electron 27 (e−) and a hole 28 (h+). A part of electrons 27 and holes 28 are recombined. However, in the presence of hydrogen, the oxidizing reaction of the hydrogen with the hole 28 is accelerated. As a result, an anode current on the surface of the structural material 25 is increased. FIG. 4 shows an Evans diagram with which a corrosion potential of a material is defined. The corrosion potential is defined at a point where an anode current and a cathode current are balanced. According to the method of reducing corrosion of a nuclear reactor structural material of the present invention, when the titanium oxide and the hydrogen are injected in the cooling water, as schematically shown in FIG. 4, the anode current represented by the broken line is increased to that represented by the continuous line. As a result, the potential at the intersection of the anode current and the cathode current moves in the negative direction, and the corrosion potential is decreased. Accordingly, corrosion of the nuclear reactor structural material is reduced. A second embodiment of the present invention will be described hereunder with reference to FIGS. 5 to 10. FIG. 5 shows a circulating system of cooling water in a nuclear power plant. In this circulating system, equipment for setting test pieces for sampling is connected to the circulating system shown in FIG. 1. In FIG. 5, the same components as those in FIG. 1 have the same reference numerals. The description of the structure composed of the same components is omitted herein. Referring to FIG. 5, test pieces 31 for monitoring the adhesion amount are disposed in a branch line formed in the vicinity of the injection point 14 of the primary loop recirculation (PLR) system pipe 2. Valves 32 and 33 (e.g., stop valves), which can isolate the test pieces 31 from the circulating system during sampling, are disposed at the upstream and the downstream of the branch line including the test pieces 31. The adhesion amount of the titanium oxide to the structural material is monitored in the following manner. A titanium oxide solution is injected while the valves 32 and 33 are opened. After a predetermined period of time, the valves 32 and 33 are closed and the test pieces 31 are then removed. The adhesion amount of titanium oxide to the test pieces 31 is evaluated by fluorescent X-ray analysis or Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Regarding hydrogen injection, the hydrogen concentration in cooling water can be controlled by regulating the flow volume of hydrogen gas. The reasons or grounds for the numerical limitation in the method of reducing corrosion of a nuclear reactor structural material of the present invention are as follows. FIG. 6 shows a relationship between a generation ratio of stress corrosion cracking (SCC) of nickel-base alloys (Alloy 600 and Alloy 182) and the corrosion potential. The generation ratio of SCC is evaluated using three kinds of experimental methods including a uniaxial constant load (UCL) tensile test, a creviced U-bent beam test, and a creviced bent beam test. Alloy 600 and Alloy 182 are typical nickel-base alloys used as nuclear reactor structural materials. As shown by an arrow in FIG. 6, when the corrosion potential of the above nickel-base alloys is −100 mV vs. SHE (−0.1 V vs. SHE) or less, the generation of SCC is suppressed under all the three kinds of the test conditions. FIG. 7 shows a relationship between a crack growth rate of sensitized type 304 stainless steel and the corrosion potential, the relationship being obtained by a cracking growth test. FIG. 7, which is cited from Corrosion vol. 53, No. 4, April 1997, pp. 306-311, shows data of type 304 stainless steel at a temperature of 288° C. Referring to FIG. 7, in the condition of 0.1 μS/cm corresponding to the water quality in a BWR (shown by symbol □ in FIG. 7), when the corrosion potential is −100 mV vs. SHE (−0.1 V vs. SHE) or less, the cracking growth rate is sufficiently as low as 10−8 mm/s or less. FIG. 8 shows a potential-pH diagram of iron (at 290° C.). As shown in FIG. 8, in neutral pH=5.6 at 290° C., an iron oxide Fe2O3 is stable in the range of −400 mV vs. SHE (−0.4 V vs. SHE) or more of the corrosion potential. For these reasons, in the method of reducing corrosion of a nuclear reactor structural material according to the present invention, the range of corrosion potential is limited from −0.4 V vs. SHE to −0.1 V vs. SHE. According to 1998 JAIF International Conference on Water Chemistry in Nuclear Power Plant Proceeding (p. 226), when the amount of hydrogen injection exceeds 1 ppm, the form of the iron oxide changes from stable Fe2O3 to Fe3O4. Therefore, the amount of hydrogen injection is preferably 1 ppm or less. Furthermore, in order to suppress the flowing of radioactive nitrogen into a turbine system, the amount of hydrogen injection is preferably 1 ppm or less. As described above, preferably, the corrosion potential is controlled in the range of −0.4 V vs. SHE to −0.1 V vs. SHE in terms of the advantage of corrosion reduction. In addition, in order to solve the problem of the flowing of radioactive nitrogen, the amount of hydrogen injection is controlled to 1 ppm or less. The present inventors evaluated the effect of corrosion prevention in the method of reducing corrosion of a nuclear reactor structural material of the present invention. FIG. 9 shows a relationship between the amount of the hydrogen injection and the corrosion potential and also shows a measurement result of the change in corrosion potential of a stainless steel to the amount of the hydrogen supply. In this evaluation, the adhesion amount of titanium oxide was changed. FIG. 9 also shows data of a stainless steel treated with a noble metal as a comparative example. Referring to the measurement result shown in FIG. 9, in the stainless steels treated with titanium oxide, the change in corrosion potential caused by hydrogen supply was gradual, compared with that of the stainless steel treated with a noble metal. However, the corrosion potential was obviously decreased as the amount of hydrogen injection increased. In the stainless steel having 10 μg/cm2 of titanium oxide, when the amount of hydrogen injection was 1 ppm, the corrosion potential was decreased to −0.1 V vs. SHE. On the other hand, in the stainless steel having 200 μg/cm2 of the titanium oxide, when the amount of hydrogen injection was 0.2 ppm, the corrosion potential was decreased to −0.1 V vs. SHE. This result shows that the increase in the adhesion amount of titanium oxide decreased the corrosion potential. In addition, even when the amount of hydrogen supply was 0.5 ppm or more, the corrosion potential was not decreased to −0.4 V vs. SHE or less. In view of the above considerations, in the method of reducing corrosion of a nuclear reactor structural material of the present invention, the adhesion amount of titanium oxide is limited from 10 to 200 μg/cm2. The amount of hydrogen injection is limited from 0.2 to 1 ppm. FIG. 10 shows a relationship between the adhesion amount of the titanium oxide, the amount of the hydrogen injection, and the corrosion potential. As shown in FIG. 10, the corrosion potential depends on the adhesion amount of the titanium oxide and the amount of the hydrogen injection. Accordingly, the adhesion amount of the titanium oxide is controlled in the range of 10 to 200 μg/cm2, and the amount of the hydrogen injection is controlled in the range of 0.2 to 1 ppm. Thus, the electrochemical corrosion potential (ECP) can be controlled in the range of −0.4 V vs. SHE to −0.1 V vs. SHE. As mentioned above, according to the described embodiments, the nuclear reactor is operated under the conditions of the adhesion or application amount of the titanium oxide and the amount of the hydrogen injection described above. As a result, problems such as the flowing of radioactive nitrogen, the release of radioactive metal oxides into the reactor water, and excessive hydrogen in an off-gas system, which are encountered in the prior art, can be prevented, and the stress corrosion cracking of the nuclear reactor structural material can be also suppressed. The following is another embodiment of a method of reducing corrosion of a material constituting a nuclear reactor structure according to the present invention of an aspect which may be more general than the first and second embodiments mentioned above though the subject gist thereof is identical. In this another embodiment of the present invention, too, a substance generating an excitation current is added or deposited to the surface of the nuclear reactor structural material, and a noble metal is applied or deposited to the material. The concentration of oxidizing chemical species and the concentration of reducing chemical species in the nuclear reactor water are controlled under a condition in which the noble metal is deposited. In the above aspect of the present invention, the concentration of the reducing chemical species in the nuclear reactor water is controlled as follows. The molar ratio represented by H2/O2 is controlled to be less than the value of 2 (i.e., less than 0.16 ppm of the hydrogen concentration in a feed water) in which recombining catalytic reactions of various chemical species are not accelerated. Thus, the electrochemical corrosion potential (ECP) is decreased under the reducing atmosphere corresponding to a trace of the hydrogen injection. The noble metal adhering to the surface of the material achieves a role to take out the excitation current efficiently. At least one of elements selected from Pt, Pd, Ir, Rh, Os, and Ru is used as the noble metal. A semiconductor is used as a typical substance excited with heat or light for generating an excitation current. At least one of compounds selected from TiO2, ZrO2, ZnO, WO3, PbO, BaTiO3, Bi2O3, SrTiO3, Fe2O3, FeTiO3, KTaO3, MnTiO3, SnO2, and Nb2O5 is used as the semiconductor. The substance generating an excitation current and the noble metal are applied or deposited to the nuclear reactor structural material by at least one of methods or treatments selected from chemical injection, flame spray coating, spraying, plating, and vapor deposition. When a material having a semiconductor thereon is disposed, i.e., exposed, in a high temperature water or under an environment of ultraviolet irradiation, an excitation current is generated on the surface of the material. The potential on the surface of the material is referred to as electrochemical corrosion potential (ECP). This ECP is an indicator of the stress corrosion cracking (SCC) susceptibility of the material. For example, in the high temperature water at 280° C., when the electrochemical corrosion potential is −230 mV (vs. SHE) or less, the stress corrosion cracking does not occur. In addition, a test result of the cracking growth under the same environment shows that the decrease in the potential significantly decreases the crack growth rate. The electrochemical corrosion potential of a material is defined by two reactions, i.e., a reaction between reactants and a reaction of the material itself in the environment in which the material is exposed. For example, in the BWR plants, the former is an electrochemical reaction of oxygen, hydrogen peroxide, and hydrogen generated by radiolysis of water, and the electrochemical reaction is performed on the surface of the material. The latter is an elution reaction of the material itself. The electrochemical corrosion potential, which is determined on the basis of a mixed potential theory, is a potential wherein the cathode current is equal to the anode current. Among the above reactants, oxygen and hydrogen peroxide contribute to the cathode reaction, whereas the hydrogen and the elution reaction of the material contribute to the anode reaction. The standard oxidation-reduction potential in each electrochemical reaction is determined by the concentration of each reactant, the temperature, and the pH in the environment etc. The potential of the cathode reaction is higher than that of the anode reaction. Therefore, the acceleration of the cathode reaction increases the electrochemical corrosion potential. This also indicates that the increase in the concentration of oxygen and hydrogen peroxide increases the electrochemical corrosion potential. On the other hand, the increase of the anode reaction decreases the electrochemical corrosion potential. Methods of reducing the cathode reaction includes a known method of controlling corrosion with a deoxidant and a method of decreasing the concentration of oxygen and hydrogen peroxide by hydrogen injection. On the other hand, a method of reducing corrosion by increasing the anode reaction includes a known method of decreasing the potential by allowing a noble metal to adhere to increase the hydrogen reaction. In the method utilized for the present embodiment, the electrochemical corrosion potential is changed by increasing the anode current. A typical substance which increases the anode current is an n-type semiconductor. The thermal excitation of a general semiconductor is represented by the following formula:ni=n0exp(−εg)/(2kBT)wherein ni represents a concentration of the pair of an electron and a hole generated by thermal excitation, n0 represents a constant relating to the concentration of the electron at the top of the valence band, εg represents a band gap, kB represents Boltzmann constant, and T represents a temperature. In this embodiment, in particular, an n-type semiconductor is preferably used as the substance generating an excitation current. Accordingly, the excited electrons become an anode current for decreasing the electrochemical corrosion potential. As described above, TiO2 is used as a typical n-type semiconductor in this method. The band gap of TiO2 is about 3 eV. This indicates that, under ultraviolet irradiation, TiO2 is excited with light having the wavelength of 410 nm or less. In other words, when Cherenkov light is generated in a nuclear reactor core, this light is also usable. However, if the excitation current cannot be taken out efficiently, the electrons and the holes generated by the excitation are recombined. In this case, since the anode current is not increased, the electrochemical corrosion potential is not changing. According to the technique used as the countermeasure in general industries, the yield of the excitation current is improved by allowing a noble metal typified by Pt for adhering in the vicinity of the substance generating the excitation current. In an environment of the reactor water in BWR plants, however, an observation is reported in which the electrochemical corrosion potential is unintentionally increased with Pt under an oxidizing condition without hydrogen injection. Accordingly, it is necessary to consider the balance between the improvement of the yield of the excitation current due to the adhesion of the noble metal and the effect in which the pressure Pt itself increases the electrochemical corrosion potential. In order to suppress the increase in the electrochemical corrosion potential with Pt itself, it is effective to control the nuclear reactor water to be a reducing condition. A specific indicator to achieve this purpose, resides in that the molar ratio of hydrogen to oxygen in the reactor water exceeds 2. However, when the molar ratio of hydrogen to oxygen in the reactor water is a value of 2 or more, N-16 in the reactor water is reduced and changed to a chemical form which easily flows into a vapor phase. In this case, the flowing of N-16 into a turbine system is increased. As a result, the dose rate in the turbine system during the plant operation will be increased. In order to reduce this negative effect, it is effective to shift the balance between hydrogen and oxygen in the reactor water to a reducing side such that the molar ratio represented by H2/O2 is less than a value of 2. The increase in the electrochemical corrosion potential due to the noble metal can be suppressed by slightly changing the concentration of oxidizing chemical species and the concentration of reducing chemical species in the reactor water in the nuclear power plant (BWR). In addition, the recombination reaction of an electron and a hole after the generation of the excitation current can be suppressed using the noble metal. As a result, the electrochemical corrosion potential of the material can be effectively decreased. According to the described embodiment, a substance, which is typified by an n-type semiconductor for generating an excitation current, and a noble metal are applied or deposited to the surface of the nuclear reactor structural material. In this state, the concentration of oxidizing chemical species and the concentration of reducing chemical species in the nuclear reactor water are controlled in an appropriate range. This method can reduce the electrochemical corrosion potential of the material without increasing the dose rate in the turbine system. Examples of the method for reducing corrosion of a nuclear reactor structural material according to the above embodiment of the present invention will be described specifically with reference to FIGS. 11 to 13. Firstly, a result of a slow strain rate test (SSRT) of a sensitized type 304 stainless steel at 280° C. will be described with reference to FIG. 11. FIG. 11 shows a fracture surface ratio in the SSRT of test pieces having TiO2 thereon and having TiO2 and Pt thereon. FIG. 11 also shows advantage or advantageous function in a reducing condition. In FIG. 11, the ordinate represents a ratio of the area generating intergranular stress corrosion cracking (IGSCC) to the total fracture surface area after testing, i.e., a fracture surface ratio (%). When this value is high, the test piece is more susceptible to the stress corrosion cracking (SCC). The abscissa represents the kind of various test pieces. In the test pieces, to which no specific description of the condition is given, the water quality was an oxidizing condition simulating an environment in the core of the BWR, and on the contrary, in the test piece, to which the specific description of the reducing condition is given, the water quality was a slightly reducing condition simulating an environment in the core of the BWR wherein 0.1 ppm of hydrogen was injected from the feed water. A test piece composed of type 304 stainless steel, to which no coating or application was made, was used as a reference material. In addition, a test piece composed of type 304 stainless steel having TiO2 thereon, and test pieces composed of type 304 stainless steel having TiO2 and Pt thereon were used. Referring to FIG. 11, the stress corrosion cracking (SCC) fracture surface ratio was significantly decreased by allowing TiO2 and Pt to adhere to the type 304 stainless steel and controlling the condition to be a reducing condition. The change in the chemical form of nitrogen compounds in the case where TiO2 and Pt adhere will be described with reference to FIG. 12. In the known techniques using hydrogen injection and a noble metal chemical addition, the increase in the dose rate is observed in a main steam piping. This is because the chemical form of radioactive nitrogen compounds in the reactor water changes to a reduced form such as ammonia and nitrogen monoxide. FIG. 12 shows the test result in a laboratory for tracking the change in the form of nitrogen compounds. In FIG. 12, reference symbol {circle around (1)} represents an example using a reference material (type 304 stainless steel) with no hydrogen injection, reference symbol {circle around (2)} represents an example using type 304 stainless steel in 1.5 ppm of H2 injection (hydrogen water chemistry (HWC)), reference symbol {circle around (3)} represents an example using a noble metal in 0.15 ppm HWC condition (noble metal chemical addition (NMCA)), and reference symbol {circle around (4)} represents an example using a type 304 stainless steel having TiO2 and Pt thereon in 0.1 ppm HWC condition. It was confirmed that nitrogen oxides were oxidized to nitric acid under the conditions of the present Example. As shown in FIG. 12, the result shows the fact that the amount of flowing of nitrogen compound into the vapor phase could be decreased. The hydrogen concentration-dependency of the electrochemical corrosion potential shown by a test piece having TiO2 and Pt thereon will be described with reference to FIG. 13. FIG. 13 summarizes the result of the water-chemistry-dependency of the electrochemical corrosion potential (ECP) of a test piece composed of type 304 stainless steel having TiO2 and Pt thereon, the result being measured by a laboratory test. In FIG. 13, the ordinate represents the electrochemical corrosion potential and the abscissa represents the hydrogen concentration in the feed water. Under the normal water chemistry (NWC) for the reactor water, the electrochemical corrosion potential of type 304 stainless steel shown by a reference material a in FIG. 13 was about 0.15 V vs. SHE. In FIG. 13, the area in which the molar ratio of H2/O2 is less than the value of 2 corresponds to the area in which the hydrogen concentration in the feed water is less than 0.16 ppm. In this area, the catalytic reaction to recombine oxidizing chemical species with reducing chemical species is not accelerated by a noble metal. Referring to FIG. 13, in a test piece b having only TiO2 thereon, although the electrochemical corrosion potential was reduced to about −0.2 V vs. SHE regardless of the condition, the electrochemical corrosion potential was not reduced to −0.23 V vs. SHE, which was a threshold e for suppressing the IGSCC of the stainless steel. In a test piece c having only Pt thereon, when the hydrogen concentration in the feed water was less than 0.1 ppm, the electrochemical corrosion potential was barely reduced. The electrochemical corrosion potential was reduced in the range from 0.1 to 0.2 ppm of the hydrogen concentration. However, 0.16 ppm of the hydrogen concentration was required in order to reduce the electrochemical corrosion potential to −0.23 V vs. SHE. In contrast, in a test piece d having TiO2 and Pt thereon, which corresponded to the present Example, when the amount of the hydrogen injection was at least 0.07 ppm, the electrochemical corrosion potential was −0.23 V vs. SHE or less. This phenomenon could not be achieved with the test piece b having only TiO2 thereon and the test piece c having only Pt thereon. This result indicates that the IGSCC of the structural material could be suppressed. Accordingly, the hydrogen concentration in the feed water should be at least 0.07 ppm and less than 0.16 ppm. This condition can suppress the stress corrosion cracking, and in addition, does not accelerate the catalytic reaction to recombine oxidizing chemical species with reducing chemical species by a noble metal. It is to be noted that the present invention is not limited to the described embodiments and many other changes and modifications may be made without departing from the scopes of the appended claims.
	description	Priority is claimed to Japanese Patent Application No. 2011-099461, filed Apr. 27, 2011, and International Patent Application No. PCT/JP2012/058231, the entire content of each of which is incorporated herein by reference. 1. Technical Field The present invention relates to a charged particle beam irradiation apparatus that irradiates an irradiated body with a charged particle beam. 2. Description of the Related Art A charged particle beam irradiation apparatus that irradiates a charged particle beam is used in a radiation therapy apparatus that performs cancer therapy by irradiating a tumor area of a patient with, for example, a proton beam. As such a radiation therapy apparatus, for example, a radiation therapy apparatus described in the related art is known. The radiation therapy apparatus described in the related art is provided with a radiation generation section which generates a radiation which is irradiated to the body surface of a tested object, a multi-leaf collimator which determines an irradiation field of the radiation irradiated from the radiation generation section, and a CCD camera which photographs the tested object through an opening portion of the multi-leaf collimator, and performs predetermined processing on the basis of a captured image obtained by the CCD camera. According to an embodiment of the present invention, there is provided a charged particle beam irradiation apparatus including: an irradiation section configured to irradiate an irradiated body with a charged particle beam; a multi-leaf collimator configured to set an irradiation range of the charged particle beam which is irradiated from the irradiation section; an imaging section that is provided so as to be able to advance and retreat with respect to an irradiation axis of the charged particle beam which is irradiated from the irradiation section, between the irradiation section and the multi-leaf collimator, and directly images an opening portion of the multi-leaf collimator; and a drive section configured to move the imaging section between an imaging position corresponding to an irradiation area which includes the irradiation axis of the charged particle beam and a retreated position away from the irradiation area. In the related art, an installation position of a CCD camera is fixed and an opening portion of a multi-leaf collimator is imaged through two half mirrors by the CCD camera. For this reason, a captured image obtained by the CCD camera is sometimes distorted. Further, there is also a mounting error or the like of the two half mirrors. For this reason, a problem in that the captured image of the CCD camera is different from an actual image can arise. Accordingly, in order to confirm whether the shape of the opening portion of the multi-leaf collimator is shaped as planned, with an image, it is necessary to carry out complicated processing such as performing some sort of error correction processing on output image data of the CCD camera. It is desirable to provide a charged particle beam irradiation apparatus in which it is possible to obtain a clear captured image of an opening portion of a multi-leaf collimator. In the charged particle beam irradiation apparatus according to an embodiment of the present invention, before the charged particle beam is irradiated from the irradiation section to the irradiated body, the opening portion of the multi-leaf collimator is imaged by the imaging section and whether the shape of the opening portion of the multi-leaf collimator is a shape as planned is confirmed with an image. Usually, the imaging section is located at the retreated position away from the irradiation area that includes the irradiation axis of the charged particle beam which is irradiated from the irradiation section. When imaging by the imaging section is performed, the imaging section is moved from the retreated position to the imaging position corresponding to the irradiation area which includes the irradiation axis of the charged particle beam by the drive section. Then, the opening portion of the multi-leaf collimator is imaged by the imaging section at the imaging position. Due to making the imaging section be able to advance and retreat with respect to the irradiation axis of the charged particle beam which is irradiated from the irradiation section in this manner, it is not necessary to dispose a half mirror between the multi-leaf collimator and the imaging section unlike a case where the installation position of the imaging section is fixed, and therefore, it is possible to directly image the opening portion of the multi-leaf collimator. For this reason, a problem such as distortion occurring in the captured image of the imaging section is prevented. In this way, it is possible to obtain a clear captured image of the opening portion of the multi-leaf collimator. Preferably, the imaging section is mounted on a mounting bracket that can advance and retreat with respect to the irradiation axis of the charged particle beam, the drive section moves the mounting bracket between the imaging position and the retreated position, and a shield wall for protecting the imaging section from the charged particle beam is provided closer to the side of the irradiation axis of the charged particle beam than the imaging section in the mounting bracket when the mounting bracket is at the retreated position. By providing the shield wall for protecting the imaging section from the charged particle beam in this manner, charged particle beam damage to the imaging section during the irradiation of the charged particle beam is suppressed. In this case, preferably, a light source section configured to irradiate light to the opening portion of the multi-leaf collimator may be further mounted on the mounting bracket. By providing the light source section in this manner, in a state where the mounting bracket is at the imaging position, light is directly irradiated toward the opening portion of the multi-leaf collimator from the light source section, and therefore, when imaging the opening portion of the multi-leaf collimator by the imaging section, the opening portion of the multi-leaf collimator is illuminated. Accordingly, it is possible to obtain a clear captured image of the opening portion of the multi-leaf collimator. It is preferable that the light source section be mounted on the mounting bracket so as to be located on the irradiation axis of the charged particle beam when the mounting bracket is at the imaging position. In the charged particle beam irradiation apparatus, there is a case where an irradiated body collimator is disposed below the multi-leaf collimator. The irradiated body collimator is made for each irradiated body and has an opening portion matching an irradiation target (an affected area) of the irradiated body. Furthermore, since the irradiated body collimator is artificially replaced each time the irradiated body is changed, artificial error should not occur in amounting direction. In this case, since in a state where the mounting bracket is at the imaging position, light is irradiated toward the irradiated body through the opening portion of the irradiated body collimator from the light source section with the irradiation axis of the charged particle beam as the center, the shape of the shadow of light which reaches the irradiated body becomes a shape similar to the opening portion of the irradiated body collimator. Accordingly, by comparing the shape of the shadow of the light with the shape of the irradiation target captured in an image or a photograph in advance, it is possible to reliably perform confirmation of a mounting direction of the irradiated body collimator. According to an embodiment of the present invention, it is possible to obtain a clear captured image of the opening portion of the multi-leaf collimator. In this way, even if complicated error correction processing or the like is not performed on especially output image data of the imaging section, it becomes possible to confirm whether the shape of the opening portion of the multi-leaf collimator is a shape as planned, with an image. Hereinafter, a preferred embodiment of a charged particle beam irradiation apparatus according to an embodiment of the present invention will be described in detail referring to the drawings. FIG. 1 is a perspective view showing a charged particle beam therapy apparatus provided with a charged particle beam irradiation apparatus according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of the charged particle beam therapy apparatus shown in FIG. 1. In each drawing, a charged particle beam therapy apparatus 1 is, for example, an apparatus for performing cancer therapy by irradiating a charged particle beam P with respect to a tumor area (an irradiation target) B that is an affected area in the body of a patient A. As the charged particle beam, for example, a proton beam, a heavy particle beam, or the like can be used. The charged particle beam therapy apparatus 1 is provided with a rotating gantry 3 provided so as to surround a treatment table 2, and a charged particle beam irradiation apparatus 4 which is mounted on the rotating gantry 3 and can rotate around the treatment table 2 by the rotating gantry 3. In addition, the charged particle beam therapy apparatus 1 is further provided with a cyclotron (an accelerator) 5. The cyclotron 5 is installed at a position away from the rotating gantry 3 and accelerates and emits a charged particle beam generated at an ion source (not shown). The charged particle beam emitted from the cyclotron 5 is supplied to the charged particle beam irradiation apparatus 4 through a beam transport system (not shown). In addition, it is also possible to rotate the cyclotron 5 integrally with the rotating gantry 3. The charged particle beam irradiation apparatus 4 has a scatterer 6, a ridge filter 7, a multi-leaf collimator 8, and a patient collimator (an irradiated body collimator) 18 which are disposed in order in an irradiation direction of the charged particle beam P. The scatterer 6, the ridge filter 7, and the multi-leaf collimator 8 are mounted on a casing 4a of the charged particle beam irradiation apparatus 4. The scatterer 6 is formed of a lead plate or the like and is for expanding the charged particle beam supplied from the cyclotron 5 into a wide beam. The ridge filter 7 is for adjusting dose distribution of the charged particle beam expanded by the scatterer 6. Specifically, the ridge filter 7 imparts a spread-out Bragg peak (SOBP) to the charged particle beam so as to correspond to the thickness (the length in the irradiation direction) of the tumor area B of the patient A. The scatterer 6 and the ridge filter 7 configure an irradiation section which irradiates the charged particle beam P. The multi-leaf collimator 8 is for setting an irradiation range (an irradiation field) of the charged particle beam P in accordance with the shape of the tumor area B of the patient A. Specifically, the multi-leaf collimator 8 has a pair of leaf groups 8a and 8b which includes a large number of leafs made of, for example, brass. The leaf groups 8a and 8b are disposed so as to face each other. An opening portion 8c through which the charged particle beam P passes is formed between the leaf groups 8a and 8b. The position and the shape of the opening portion 8c can be changed by individually advancing or retreating the leaves of the leaf groups 8a and 8b in a longitudinal direction. In addition, the multi-leaf collimator 8 is used, for example, in a case where the tumor area B of the patient A is large. The patient collimator 18 is detachably mounted on the casing 4a of the charged particle beam irradiation apparatus 4 on the lower side of the multi-leaf collimator 8. The patient collimator 18 is for setting an irradiation range of the charged particle beam P in accordance with the shape of the tumor area B of the patient A, similar to the multi-leaf collimator 8. The patient collimator 18 is made for each patient A and has an opening portion 18a through which the charged particle beam P passes. The opening portion 18a has dimensions and a shape matching the tumor area B of the patient A. When the multi-leaf collimator 8 is used, the patient collimator 18 is removed from the casing 4a. In addition, when the patient collimator 18 is used, the opening portion 8c of the multi-leaf collimator 8 is more increased than the actual tumor area B. A collimator shape confirmation unit 9 which can advance and retreat with respect to an irradiation axis Q of the charged particle beam P is disposed between the ridge filter 7 and the multi-leaf collimator 8. The collimator shape confirmation unit 9 is distant from the multi-leaf collimator 8 by, for example, about 400 mm. In addition, the distance between the multi-leaf collimator 8 and a target (the body surface of the patient A) of the charged particle beam P is, for example, about 100 mm. The collimator shape confirmation unit 9 has a flat plate-shaped mounting bracket 10, as shown in FIGS. 2 and 3. In addition, FIG. 3 is a diagram of the collimator shape confirmation unit 9 when viewed from the multi-leaf collimator 8 side. An imaging camera (imaging section) 11 and a projector (a light source section) 12 are mounted adjacently to each other on the back surface of the mounting bracket 10. The imaging camera 11 is configured by, for example, a CCD camera. The imaging camera 11 is for imaging the opening portion 8c of the multi-leaf collimator 8 in order to confirm the shape of the opening portion 8c of the multi-leaf collimator 8. The projector 12 is configured to have, for example, an LED and irradiates light (visible light, ultraviolet rays, or the like) toward the opening portion 8c of the multi-leaf collimator 8. In this way, when the opening portion 8c of the multi-leaf collimator 8 is imaged by the imaging camera 11, the opening portion 8c is illuminated by the projector 12. Furthermore, if light is irradiated toward the multi-leaf collimator 8 from the projector 12 in a state where the patient collimator 18 is mounted on the casing 4a, the light reaches the body surface of the patient A through the opening portion 8c of the multi-leaf collimator 8 and the opening portion 18a of the patient collimator 18. Accordingly, whether the mounting direction of the patient collimator 18 is right or wrong can be determined by visually confirming the shape of light (shadow) which reaches the body surface of the patient A and also by comparing the shape with a photograph or image data of the tumor area B of the patient A. Furthermore, a shield wall 13 for protecting the imaging camera 11 and the projector 12 from the charged particle beam P is mounted at a position on the side of the irradiation axis Q of the charged particle beam P with respect to the imaging camera 11 and the projector 12 on the back surface of the mounting bracket 10. The shield wall 13 is formed of a lead plate or the like. Slide sections 14 are respectively provided at both end portions of the mounting bracket 10. Furthermore, guide rods 15 passing through the slide sections 14 and extending in a direction perpendicular to the irradiation axis Q of the charged particle beam P are respectively disposed on both sides of the mounting bracket 10. The guide rods 15 are fixed to the casing 4a. In this way, the collimator shape confirmation unit 9 can move along each guide rod 15 between an imaging position (refer to a two-dot chain line in FIG. 3) corresponding to an irradiation area R which includes the irradiation axis Q of the charged particle beam P and a retreated position away from the irradiation area R which includes the irradiation axis Q of the charged particle beam P. In addition, usually, the collimator shape confirmation unit 9 is at the retreated position as shown in FIG. 3. In this case, it is preferable that the projector 12 be mounted on the mounting bracket 10 such that a light outlet of the projector 12 is located on the irradiation axis Q of the charged particle beam P when the collimator shape confirmation unit 9 is at the imaging position, as shown in FIG. 4A. In this way, since the opening portion 8a of the multi-leaf collimator 8 is efficiently illuminated, confirmation of the image of the opening portion 8a by the imaging camera 11 can be accurately performed. Furthermore, since the shape of light which reaches the body surface of the patient A through the opening portion 18a of the patient collimator 18 becomes a shape similar to the opening portion 18a, the patient collimator 18 being correctly mounted on the casing 4a can be confirmed by comparing the shape of the light with the shape of the tumor area B of the patient A captured in an image or a photograph in advance. Furthermore, in a state where the collimator shape confirmation unit 9 is at the retreated position, as shown in FIG. 4B, the imaging camera 11 is disposed on the side opposite to the irradiation axis Q of the charged particle beam P with respect to the projector 12 and the shield wall 13 is disposed on the side of the irradiation axis Q of the charged particle beam P with respect to the projector 12. In this way, it is possible to sufficiently protect the imaging camera 11 and the projector 12 from the charged particle beam P by the shield wall 13. In addition, the shield wall 13 may have a structure to surround, for example, the imaging camera 11 and the projector 12, or the like, rather than a structure in which the shield wall 13 is disposed closer only to the side of the irradiation axis Q of the charged particle beam P than the projector 12. In addition, the charged particle beam irradiation apparatus 4 further has a drive section 16 which enables the collimator shape confirmation unit 9 to reciprocate between the retreated position and the imaging position, and a controller 17 connected to the imaging camera 11, the projector 12, and the drive section 16, as shown in FIG. 3. The drive section 16 is configured to include an air cylinder, an air source, an electromagnetic valve, and the like. In this case, a piston of the air cylinder is connected to the slide section 14 on one side. Furthermore, in addition to this, the drive section 16 may be configured to include a ball screw, an electromagnetic motor, and the like. The controller 17 controls the projector 12 and the drive section 16 and also determines whether or not the charged particle beam P is irradiated to the tumor area B in the body of the patient A, on the basis of a captured image of the imaging camera 11. FIG. 5 is a flowchart showing the details of processing procedure which is executed by the controller 17. This processing is used in a case where the patient collimator 18 is not mounted on the casing 4a, and is executed immediately before the charged particle beam P is irradiated to the tumor area B in the body of the patient A. In FIG. 5, first, the drive section 16 is controlled so as to move the collimator shape confirmation unit 9 from the retreated position to the imaging position (procedure S101). Subsequently, the projector 12 is controlled so as to irradiate light toward the opening portion 8c of the multi-leaf collimator 8 from the projector 12 (procedure S102). Subsequently, an image of the opening portion 8c of the multi-leaf collimator 8 captured by the imaging camera 11 is input (procedure S103). Subsequently, whether the shape of the opening portion 8c of the multi-leaf collimator 8 is a shape as planned is determined by comparing image data of the opening portion 8c of the multi-leaf collimator 8 with shape data of the opening portion 8c of the multi-leaf collimator 8 planned by a therapy planning device (not shown) (procedure S104). When it is determined that the shape of the opening portion 8c of the multi-leaf collimator 8 is the shape as planned, determination to carry out irradiation of the charged particle beam P is made (procedure S105) and the result is notified to a main control device (not shown). On the other hand, when it is determined that the shape of the opening portion 8c of the multi-leaf collimator 8 is not the shape as planned, determination not to carry out irradiation of the charged particle beam P is made (procedure S106) and the result is notified to the main control device. Then, after execution of procedures S105 and S106, the drive section 16 is controlled so as to move the collimator shape confirmation unit 9 from the imaging position to the retreated position (procedure S107). When the determination to carry out the irradiation of the charged particle beam P is made in procedure S105, thereafter, the charged particle beam P is irradiated to the tumor area B in the body of the patient A. At this time, since the imaging camera 11 and the projector 12 that are susceptible to a radiation are protected from the charged particle beam P by the shield wall 13, the charged particle beam P hardly damages the imaging camera 11 and the projector 12. As described above, in this embodiment, when the opening portion 8c of the multi-leaf collimator 8 is imaged by the imaging camera 11, the collimator shape confirmation unit 9 having the imaging camera 11 is moved from the retreated position to the imaging position, and therefore, it is not necessary to dispose a half mirror between the multi-leaf collimator 8 and the imaging camera 11 unlike a case where the installation position of the imaging camera 11 is fixed, and the opening portion 8c of the multi-leaf collimator 8 can be directly imaged by the imaging camera 11. For this reason, a problem such as the captured image of the imaging camera 11 being distorted by a half mirror does not arise and it is possible to obtain the captured image in which the contour shape of the opening portion 8c of the multi-leaf collimator 8 is clear. In this way, since whether or not the contour shape of the opening portion 8c of the multi-leaf collimator 8 is a shape as planned can be correctly confirmed, it becomes possible to effectively search a defect or the like in the multi-leaf collimator 8. Further, since it is not necessary to intricately correct output image data of the imaging camera 11 in order to confirm the contour shape of the opening portion 8c of the multi-leaf collimator 8, complicated image processing or arithmetic processing need not be performed. In addition, the present invention is not limited to the above-described embodiment. For example, the accelerator is not limited to a cyclotron, but another accelerator (a synchrotron, a synchro-cyclotron, a linac, or the like) may be used. Further, the present invention is not limited to a configuration using a rotating gantry, but a fixed irradiation method may also be adopted in which the charged particle beam irradiation apparatus 4 is fixed with respect to the treatment table 2. The scatterer 6 and/or the ridge filter 7 is not necessarily required and may be omitted. The distance between the collimator shape confirmation unit 9 and the multi-leaf collimator 8 is not limited to about 400 mm, but the distance may be different from that. Furthermore, the distance between the multi-leaf collimator 8 and the patient is not limited to about 100 mm, but the distance may be different from that. The projector 12 is not limited to an LED, and another luminous body (for example, a fluorescent lamp or an incandescent lamp) may be used. The imaging camera 11 is not limited to a CCD camera, but another camera (for example, CMOS camera) may be used. Further, the present invention is not limited to a configuration in which both the imaging camera 11 and the projector 12 are mounted on the single mounting bracket 10, but a bracket for mounting the imaging camera 11 and another bracket for mounting the projector 12 may be separately provided. The shield wall 13 is not limited to a configuration in which the shield wall 13 is mounted on the mounting bracket 10, but the shield wall 13 may be mounted on another component (for example, the casing 4a). In short, it is only required for the configuration that the imaging camera 11 and/or the projector 12 can be protected from a radiation when the imaging camera 11 and/or the projector 12 is at the retreated position. The mounting bracket 10 is not limited to a configuration in which the mounting bracket 10 moves between the imaging position and the retreated position in a linear movement, but a configuration in which the mounting bracket 10 moves while drawing another trajectory (for example, a configuration in which a rotary shaft is mounted on one end of an arm and a bracket is mounted on the other end of the arm) may be used. The projector 12 is not limited to a configuration in which the light outlet of the projector 12 is located on the irradiation axis Q when the collimator shape confirmation unit 9 is at the imaging position, but the projector 12 may be configured so as not to be located on the irradiation axis Q. Furthermore, in the above-described embodiments, the mounting bracket 10 on which the imaging camera 11 and the projector 12 are mounted has a flat plate shape. However, the shape of the mounting bracket 10 may be a box shape, a frame shape, or the like. Furthermore, a configuration is made such that the collimator shape confirmation unit 9 in which the imaging camera 11, the projector 12, and the shield wall 13 are mounted on the mounting bracket 10 can advance and retreat with respect to the irradiation axis Q of the charged particle beam P. However, a configuration may be made such that only the imaging camera 11 can advance and retreat with respect to the irradiation axis Q of the charged particle beam P. Furthermore, a configuration is made such that whether the shape of the opening portion 8c of the multi-leaf collimator 8 is a shape as planned and whether irradiation of the charged particle beam P is performed are determined by the controller 17. However, the present invention is not particularly limited thereto, but an operator may confirm whether the shape of the opening portion 8c of the multi-leaf collimator 8 is a shape as planned, by viewing the captured image of the opening portion 8c of the multi-leaf collimator 8, and then determining whether the irradiation of the charged particle beam P is performed. Further, direct imaging as referred to in the above-described embodiments means that imaging is performed without using reflection by a half mirror or the like, and it goes without saying that a sheet or the like can be sandwiched between the multi-leaf collimator 8 and the imaging camera 11 in order to make a captured image clearer. The embodiment of the present invention can be used in a charged particle beam irradiation apparatus. It should be understood that the invention is not limited to the above-described embodiment, but may be modified into various forms on the basis of the spirit of the invention. Additionally, the modifications are included in the scope of the invention.
	summary
	claims	1. A fluorescent screen configured to convert an X-ray into visible light, comprisinga gadolinium oxysulfide phosphor activated with praseodymium and cerium,wherein the phosphor contains praseodymium having a concentration of 0.01 mass % or more and 0.3 mass % or less and cerium having a concentration of 5 ppm or more and 30 ppm or less,wherein an average particle diameter of the phosphor is 10 μm or more and 20 μm or less, andwherein a weight per unit area of the phosphor is 300 mg/cm2 or more and 380 mg/cm2 or less. 2. The screen according to claim 1, wherein the concentration of the praseodymium is 0.03 mass % or more and 0.2 mass % or less. 3. The screen according to claim 1, wherein the concentration of the cerium is 10 ppm or more and 25 ppm or less. 4. The screen according to claim 1, wherein the weight is 300 mg/cm2 or more and 350 mg/cm2 or less. 5. The screen according to claim 1, wherein the average particle diameter is 13 μm or more and 18 μm or less. 6. The screen according to claim 1, wherein a Wadell's sphericity of the phosphor is 0.8 or more and 0.96 or less. 7. An X-ray detector configured to detect a transmitted X-ray from a target, comprising the screen according to claim 1. 8. The detector according to claim 7, further comprisinga photodiode configured to convert the visible light into an electrical signal. 9. An X-ray inspection apparatus, comprising:an X-ray irradiator configured to irradiate an X-ray to a target;an X-ray detector configured to detect a transmitted X-ray through the target; anda display configured to display an image of the inside of the target in accordance with an intensity of the transmitted X-ray detected by the X-ray detector,wherein the detector includes the detector according to claim 7.
052767205	abstract	An improved emergency cooling system and method is disclosed that may be adapted for incorporation into or use with a nuclear BWR wherein a reactor pressure vessel (RPV) containing a nuclear core and a heat transfer fluid for circulation in a heat transfer relationship with the core is housed within an annular sealed drywell and is fluid communicable therewith for passage thereto in an emergency situation the heat transfer fluid in a gaseous phase and any noncondensibles present in the RPV, an annular sealed wetwell houses the drywell, and a pressure suppression pool of liquid is disposed in the wetwell and is connected to the drywell by submerged vents. The improved emergency cooling system and method has a containment condenser for receiving condensible heat transfer fluid in a gaseous phase and noncondensibles for condensing at least a portion of the heat transfer fluid. The containment condenser has an inlet in fluid communication with the drywell for receiving heat transfer fluid and noncondensibles, a first outlet in fluid communication with the RPV for the return to the RPV of the condensed portion of the heat transfer fluid and a second outlet in fluid communication with the drywell for passage of the noncondensed balance of the heat transfer fluid and the noncondensibles. The noncondensed balance of the heat transfer fluid and the noncondensibles passed to the drywell from the containment condenser are mixed with the heat transfer fluid and the noncondensibles from the RPV for passage into the containment condenser. A water pool is provided in heat transfer relationship with the containment condenser and is thermally communicable in an emergency situation with an environment outside of the drywell and the wetwell for conducting heat transferred from the containment condenser away from the wetwell and the drywell.
050842315	summary	BACKGROUND OF THE INVENTION The present invention relates to fission reactors and, more particularly, to a refueling mast for a fission reactor. A major objective of the present invention is to provide a refueling mast which is suitable for a boiling water reactor and which is both economical and durable. Nuclear fission reactors promise to provide abundant energy with far less strain on the environment than fossil fuels. However, since fissionable fuels are hazardous materials, great care must be taken in their transit. This care is especially important within a reactor complex, where fuel elements are transferred between storage area and reactor core. The transfer must be mechanized so that operators are not exposed to radiation. In some boiling water reactor complexes, fuel elements are in the form of rods which are inserted into a core where the heat-generating fission reaction takes place. Spent fuel elements are transferred to a storage area and fresh fuel elements are transferred from the storage area to the core. The reactor core is situated in a reactor vessel and submersed in water which is circulated to provide for heat transfer. The storage area is also submersed in water in a separate tank, in part because water shields radiation emitted from a fuel element. Typically, the storage tank and the reactor vessel are separated by a barrier, e.g., of concrete. Transfer of fuel elements can be effected using a trolley, a movable bridge which is moved along tracks and spans the region including the reactor vessel and the storage area. A fuel grapple is used to engage fuel assemblies so that they can be laterally transferred from one area and to release them once they are securely positioned at their destination. Fuel element transfer requires vertical as well as lateral transfer. Typically, the fuel elements in storage are at a different depth than the fuel elements in the core. Furthermore, fuel elements must be lifted over the barrier between the storage and reactor vessel areas. A gate is typically placed in this barrier, but it provides an opening which is sufficient only to avoid a need to lift a fuel element in transit out of the water. Vertical movement can be effected using a "refueling mast", typically a vertically telescoping assembly including nested tubes. The outer tube is fixed, nested inner tubes extend downward from and retract into the outer tube. To transfer fuel elements in and out of the core, the refueling mast must permit precise positioning and orienting of the grapple even when the mast is fully extended. In other words, the mast should be sufficiently rigid so that the drag induced by relative movement through water does not bend or twist the mast significantly. This rigidity is desirable to reduce settling time after lateral moves and to improve the operator's "feel" and control over fuel assembly position. In addition, the refueling mast should be sufficiently strong to resist impact damage during possible accidental collisions with vessel components. Such damage can require repair or replacement of the refueling mast, in either case, causing expense and down-time for the reactor complex. Some refueling masts incorporate telescoping steel tubes having square cross-sections. The walls of the tubes can be 1/2" to 1/3" thick, providing strength and rigidity. The square cross sections contribute to torsional rigidity. Because precision, corrosion-resistant, square tubing is not widely available, these refueling masts are very expensive. In addition, the several thick square tubes constituted very massive refueling mast. A more lightweight and economical refueling mast has been fabricated by welding small cylindrical trusses together, defining a skeletal "tube" of triangular cross-section. While formed of readily available cylindrical tubing, these refueling masts do incur the added cost of hand welding the trusses together. More seriously, these trussed refueling masts are readily damaged by accidental impacts and require repair and/or replacement more frequently than is desirable. What is needed is a more economical refueling mast which provides the strength required to resist impact damage, and the translational and torsional rigidity to limit bending and twisting of the mast due to hydrodynamic drag. A method is desired for forming such a mast using readily available components and relatively inexpensive assembly procedures. SUMMARY OF THE INVENTION In accordance with the present invention, a refueling mast comprises cylindrical telescoping tubes with grooved longitudinal (vertical) tracks formed in the outer surface of each of the inner tubes. Grooved guide rollers on each of the outer tubes engage respective grooved tracks of the next inner tube to provide a centralizing action and to prevent relative rotation between the tubes at the roller to tube interface. The grooved tracks can be cold formed by rolling roller dies longitudinally along the outer surface of a cylindrical tube repeatedly. The pressure applied to the rollers is increased with successive transversals until the grooves are formed in the cylinders as desired. In addition to forming the track grooves, the process can flatten and harden the steel tubes along the tracks. The track grooves, the engagement of the guide rollers, the flattening and the hardening all contribute to torsional rigidity. Tracks on successive tubes can be radially aligned upon assembly of the refueling mast to ensure a compact nesting of tubes. The precision, corrosion-resistant, cylindrical tubes to which this method is applied are readily available, and thus are available at relatively low cost. The process of forming the track grooves is relatively inexpensive compared to the assembly of a "tube" from trusses. The desired strength and translational rigidity is provided by the steel tubes. Moreover, the system of track grooves and rollers provides a highly compact design that further increase mast rigidity, provides smoother operational tracking, and improves operator visibility. The enclosed assembly significantly reduces exposures by shielding a bridge operator from contaminated lower sections and by minimizing water drip. These and other features and advantages of the present invention are described below with reference to the following drawings.
	claims	1. A method of regulating a dose of energy produced during stroboscopic firing of an EUV light source configured to generate an energy dose target within one or more packet comprising:(a) setting by a laser controller a dose servo value for a current packet;(b) timing by the laser controller a trigger to pulse a laser beam to irradiate a droplet during the current packet;(c) sensing EUV energy generated by irradiation of the droplet;(d) accumulating by the laser controller the sensed EUV energy with EUV energy generated by irradiation of one or more preceding droplet during the current packet;(e) repeating steps (b), (c), and (d) when the accumulated EUV energy within the current packet is less than an adjusted dose target based on the energy dose target and an accumulated dose error; and(f) mistiming by the laser controller the trigger to pulse the laser beam to not irradiate another droplet during the current packet. 2. The method of claim 1 wherein the dose servo value is equal to 0. 3. The method of claim 1 wherein the dose servo value is not equal to 0. 4. The method of claim 1 wherein the adjusted dose target is equal to the dose target plus the dose servo value. 5. The method of claim 1 further comprising:(g) calculating by the laser controller a dose error for the current packet;(h) accumulating by the laser controller the dose error for the current packet with a dose error for one or more preceding packet;(i) calculating by the laser controller a new adjusted dose target for a next packet based on the energy dose target and the accumulated dose error; and(j) calculating by the laser controller a new dose servo value for the next packet. 6. The method of claim 5 wherein the dose error for the current packet is equal to the dose target for the current packet minus the accumulated EUV energy for the current packet. 7. The method of claim 5 wherein the accumulated dose error comprises the dose error for the current packet and the dose error for one or more preceding packet. 8. The method of claim 5 further comprising repeating steps (a)-(j) for the next packet wherein the adjusted dose target for the next packet is the new adjusted dose target. 9. The method of claim 5 further comprising repeating steps (a)-(j) for the next packet wherein the dose servo value for the next packet is the new dose servo value. 10. The method of claim 9 wherein the new dose servo value is equal to the dose error for the current packet multiplied by a gain. 11. A system for regulating a dose of energy produced during stroboscopic burst-firing of an EUV light source configured to generate an energy dose target within one or more packet comprising:a drive laser configured to pulse a laser beam when a trigger is received;a sensor configured to sense EUV energy generated by irradiation of a droplet; anda controller configured to:(a) set a dose servo value for a current packet;(b) time the trigger to pulse the laser beam to irradiate a droplet during the current packet;(c) accumulate sensed EUV energy generated by irradiation of the droplet with EUV energy generated by irradiation of one or more preceding droplet during the current packet;(d) repeat steps (b) and (c) when the accumulated EUV energy within the current packet is less than an adjusted dose target based on the energy dose target and an accumulated dose error; and(e) mistime the trigger to pulse the laser beam to not irradiate another droplet during the current packet. 12. The system of claim 11 wherein the dose servo value is equal to 0. 13. The system of claim 11 wherein the dose servo value is not equal to 0. 14. The system of claim 11 wherein the adjusted dose target is equal to the dose target plus the dose servo value. 15. The system of claim 11 wherein the controller is further configured to:(f) calculate a dose error for the current packet;(g) accumulate the dose error for the current packet with a dose error for one or more preceding packet;(h) calculate a new adjusted dose target for a next packet based on the energy dose target and the accumulated dose error; and(i) calculate a new dose servo value for the next packet. 16. The system of claim 15 wherein the dose error for the current packet is equal to the dose target for the current packet minus the accumulated EUV energy for the current packet. 17. The system of claim 15 wherein the accumulated dose error comprises the dose error for the current packet and the dose error for one or more preceding packet. 18. The system of claim 15 further comprising repeating steps (a)-(i) for the next packet wherein the adjusted dose target for the next packet is the new adjusted dose target. 19. The system of claim 15 further comprising repeating steps (a)-(i) for the next packet wherein the dose servo value for the next packet is the new dose servo value. 20. The system of claim 19 wherein the new dose servo value is equal to the dose error for the current packet multiplied by a gain.
051685132	abstract	This is a process for aligning an x-ray lithography system including an x-ray mask and a work piece with an alignment mark. A zone plate lens is used in the x-ray mask. X-rays are directed through the zone plate lens to the alignment mark to detect when the lens is aligned with the mark by emission of photoelectrons generated by the work piece in response to the x-rays. The change of current when the x-ray beam crosses a feature on the alignment mark is detected by a properly biased zone plate or grating. The alignment mark can be an etched slot or a metal feature.
053295641	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT The drawing of FIG. 1 illustrates a typical open cycle nuclear reactor and coolant system. Coolant tank 10 contains pressurized coolant that is released to coolant pump 12 through coolant line 14. Coolant pump 12 directs coolant through coolant line 14 to nuclear reactor 16. In an open cycle reactor designed for use in outer space the coolant exits reactor 16 through exhaust line 18 and may be used for providing propulsive thrust and/or providing power in conjunction with dynamic conversion devices. When reactor 16 and coolant pump 12 are shut down, it is necessary to remove decay heat from reactor 16. This is accomplished by incorporating passive cooling system 20 into the nuclear reactor coolant system. Passive cooling system 20 is generally comprised of coolant tanks 22, check valves 24, and flow control means 26. Coolant tanks 22 are in fluid communication with coolant line 14 by means of inlet lines 28 and exhaust lines 30. Check valves 24 positioned in inlet lines 28 allow coolant to flow from coolant line 14 into coolant tanks 22 while preventing coolant flow from coolant tanks 22 into inlet lines 28. Flow control means 26 is positioned in exhaust lines 30 to provide a predetermined coolant flow rate from each coolant tank 22 into exhaust lines 30, coolant line 14, and to reactor 16. Each flow control means 26 provides for a different rate of coolant flow. The flow rate of each flow control means 26 is determined by the known decay heat rate of reactor 16. This allows the coolant flow rate from tanks 22 to match the decay heat rate of the reactor to prevent under or over cooling after reactor 16 is shutdown and coolant pump 12 is inoperative. Each flow control means 26 may be a control valve or a fixed orifice. During normal operations of reactor 16, coolant from coolant tank 10 is received by coolant pump 12. Coolant pump 12 forces the coolant through coolant line 14 to reactor 16 and into inlet lines 28. Check valves 24 allow coolant to flow into coolant tanks 22 until the coolant pressure therein equals the discharge pressure of coolant pump 12. Check valves 24 also prevent the back flow of coolant through inlet lines 28 when the coolant pump discharge pressure decreases. When reactor 16 is shut down, coolant pump 12 is also shut down as a normal function of system operation. Coolant pressure in coolant line 14 then drops to a level below that in coolant tanks 22. At that time, flow control means 26 allow flow of coolant from coolant tanks 22 into coolant line 14. Due to the pressure from coolant tanks 22, the coolant travels to reactor 16, removes decay heat, and exits through exhaust line 18. Each flow control means 26 provides for a different rate of flow. The flow rate of each control means 26 is determined in relation to the known decay heat rate of reactor 16 and the volume and number of coolant tanks 22 to be used. In this manner, the initial coolant flow from all of coolant tanks 22 provides sufficient coolant for the higher level of decay heat immediately after reactor shutdown. As the pressure in coolant tanks 22 is reduced, or the tanks successively empty, the reduced coolant flow is sufficient for lower levels of heat removal required during the later stages of decay heat removal. Thus, the decay heat rate of the reactor is matched to prevent under or over cooling and to provide the proper rate of cooling. This provides a passive cooling system for removal of decay heat that is automatically filled with coolant during normal reactor operations and begins operation at reactor and coolant pump shutdown without the need for complicated controls that may easily malfunction. Because many varying and differing embodiments may be made within the scope of the inventive concept herein taught and because many modifications may be made in the embodiment herein detailed in accordance with the descriptive requirement of the law, it is to be understood that the details herein are to be interpreted as illustrative and not in a limiting sense.
043354670	abstract	A liquid metal reactor comprising a vessel containing the core and liquid metal, at least one heat exchanger ensuring a heat-exchange between said liquid metal and a second fluid, a first duct connecting said vessel with the inlet of said exchanger and a second duct connecting said vessel with the outlet of said exchanger. Means are provided for restricting the movement of said exchanger in two directions perpendicular to the direction of said first duct.
050911430	description	DETAILED DESCRIPTION OF PREFERRED EMBODIMENT Hereinafter, the present invention will be described in connection with a preferred embodiment by referring to FIGS. 1-3. In FIG. 1, a reactor pressure vessel 1 constituting a natural circulation reactor is disposed within a reactor container 7 supported on a base concrete mat 15. The reactor container 7 includes a drywell 8, a pressure suppressing chamber 9, a coolant pool 10 within the pressure suppressing chamber, a pedestal 11, vent pipes 12 as more clearly illustrated in FIG. 4, and horizontal vents 16. The drywell 8 is communicated with the pressure suppressing chamber 9 through passage holes 20. A peripheral pool 13 disposed on the outer side of the reactor container 7 is connected to a make-up coolant line 22 for the peripheral pool 13, and also communicated with the exterior through a vent pipe 14 for the peripheral pool 13. The reactor pressure vessel 1 is connected to an accumulated coolant injection system 17, a residual heat removal and cleaning system 18, and a residual heat removal system 19 through respective pipes. The accumulated coolant injection system 17 is actuated in response to a reduction of the reactor pressure down to a certain level upon breakage of any pipe connected to the reactor pressure vessel 1, for injecting a coolant into the reactor pressure vessel 1. The residual heat removal systems 18, 19 have respective pumps 23, 24 and heat exchangers 25, 26, and are actuated in an emergency type situation in response to a full reduction of the reactor pressure upon breakage of any pipe connected to the reactor pressure vessel, for removing the decay heat generated from the reactor core. At this time, the residual heat removal system 19 injects a coolant from the coolant pool 10 within the pressure suppressing chamber 10 into the reactor pressure vessel 1. As illustrated in FIG. 3, the reactor pressure vessel 1, which is shown as having a metallic wall, includes a group of fuel control rods 2, a reactor core 3, a steam chimney 4, and a steam drier 5. A coolant 6 is filled in the reactor pressure vessel 1 so that the reactor core 3 is submerged under the coolant 6. Steam produced from the reactor core 3 flows into a turbine through the steam drier 5 and a main steam pipe (not shown) both positioned above the coolant 6. In this embodiment, as described in detail below, the reactor core 3 is installed below the level of the coolant as established when the amount of the coolant 6 within the reactor pressure vessel 1 is reduced down to 60% of the total capacity. Moreover, under the state where the reactor pressure vessel 1 is installed in the reactor container 7, the reactor core 3 is preferably positioned below the passage holes 20 as seen from FIG. 1. This means a feature that the position of the reactor core 3 in the present invention is lower than that in the prior art. In the natural circulation reactor thus constructed, the coolant 6 in the reactor pressure vessel 1 would be flushed in response to abrupt decompression within the reactor pressure vessel and discharged to the outside thereof, on the supposition of breakage X of any pipe of large diameter connected to the reactor pressure vessel 1 as shown in FIG. 2. The discharged amount of the coolant is about 40% of the total amount of the coolant before discharge of vapor (i.e., before breakage of any pipe of large diameter). Theoretical calculation is as follows. EQU e=(ET-EW)/(ES-EW) where e: evaporation rate of coolant PA0 ET: enthalpy of coolant (Kcal/Kg) PA0 ES: enthalpy of steam at atmospheric pressure (Kcal/Kg) PA0 EW: enthalpy of water at atmospheric pressure (Kcal/Kg) Since the pressure within the reactor pressure vessel is 80 ata during normal operation and the atmospheric pressure is 1 ata, ET, ES and EW are given by 313.314 Kcal/Kg, 639.15 Kcal/Kg and 100.092 Kcal/Kg, respectively. Therefore, the evaporation rate of coolant e is given by: ##EQU1## In other words, more than 60% of the total amount of coolant remains. Accordingly, on the supposition of breakage X of a pipe of large diameter connected to the reactor pressure vessel 1 as shown in FIG. 2; the reactor core 3 installed below the level of the coolant as established when the amount of the coolant is reduced down to 60%, will be kept submerged under coolant even after the coolant 6 is flushed. Afterward, the coolant starts evaporating due to the decay heat from the reactor core, causing a level of the coolant to be further lowered. On the other hand, at the time when the pressure within the reactor is reduced down to 5 atg, the accumulated coolant injection system 17 is actuated to inject the coolant from the accumulated coolant injection tank into the reactor pressure vessel 1 for keeping the reactor core 3 submerged under coolant. Thereafter, when the interior of the reactor pressure vessel is fully decompressed down to the atmospheric pressure, the residual heat removal systems 18, 19 now come into operation so that the reactor pressure vessel is brought into a long-term cooling mode. Since then, the residual heat removal system 19 operates to inject the coolant from the coolant pool 10 within the pressure suppressing chamber into the reactor pressure vessel 1 through the heat exchanger 23, thereby raising a level of the coolant in the reactor pressure vessel. The injected coolant is flown out from the broken part of the pipe to the outside of the reactor pressure vessel 1, while keeping the reactor core 3 submerged under coolant, and then accumulated in a lower drywell 21 surrounding a lower portion of the reactor pressure vessel 1. Once the coolant level in the lower drywell 21 reaches the passage holes 20, the coolant continuously flows out of the passage holes 20 into the pressure suppressing chamber 9 through the vent pipes 12 and the horizontal vents 16. With such circulation of the coolant, the coolant levels in both the pressure suppressing chamber 9 and the lower drywell 21 are maintained nearly at a level of the passage holes 20 as shown in FIG. 2. Most of the coolant at a low temperature injected into the reactor pressure vessel 1 from the residual heat removal system 19 flows downwardly along the outer surface of the steam chimney 4, and then passes through the reactor core 3 upwardly from its bottom while being increased in the temperature by removing the decay heat of the reactor core 3. A portion of the coolant 6 injected from the residual heat removal system 19 into the reactor pressure vessel 1 bypasses the reactor core, and flows out from the broken part of the pipe directly as it remains at a low temperature. Accordingly, the coolant flown out and accumulated in the lower drywell 21 surrounding the lower portion of the reactor pressure vessel 1 has a temperature lower than that of the coolant in the reactor pressure vessel 1. In the prior art where a reactor core is positioned above a level of the coolant in a lower drywell, it is not only required to inject a sufficiently ample amount of coolant for compensating a portion of the coolant injected from a residual heat removal system 19 into a reactor pressure vessel that bypasses the reactor core to flow toward the broken part of the pipe without passing through a steam chimney downwardly, but also forced for a heat exchanger of a residual heat removal system to cool the coolant at a low temperature that enters a pressure suppressing chamber through passage holes from the lower drywell as it remains at a low temperature without acting to cool the reactor core. Consequently, the efficiency of the heat exchanger is lowered and the low temperature of the coolant is not utilized sufficiently for cooling the reactor core. In the foregoing embodiment of the present invention, when the coolant level in the lower drywell 21 increases up to the passage holes 20 with outflow of the coolant incidental to injection from both the accumulated coolant injection system 17 and the residual heat removal system 19, the reactor core 3 is positioned below a level of the coolant in the lower drywell 21 because the passage holes 20 are located above the reactor core 3. With such arrangement, even though the coolant injected from the residual heat removal system 19 is flown out of the reactor pressure vessel 1 in a state of low temperature while bypassing the reactor core 3, the coolant accumulated in the lower drywell 21 can be utilized to indirectly cool the reactor core 3 from the outer side of the reactor pressure vessel 1 via the wall thereof through heat exchange with the coolant 6 of higher temperature in the reactor pressure vessel. In this manner, the coolant which has flown out bypassing the reactor core 3 also contributes to cooling of the reactor core, thereby improving removal efficiency of the decay heat. Furthermore, the coolant heated to a higher temperature through heat exchange with the coolant in the reactor pressure vessel 1 tends to move toward the upper portion of the coolant pool residing in the lower drywell 21, so that the coolant of higher temperature selectively flows into the pressure suppressing chamber 9 through the passage holes 20, and this increases a temperature of the coolant in the pressure suppressing chamber 9. Accordingly, the coolant of higher temperature is subjected to heat exchange in the residual heat removal system 19, with the result that heat exchange efficiency of the residual heat removal system 19 is improved, allowing a heat exchanger of small size to offer the sufficient effect. According to the present invention, as stated abOVe, since the reactor core can be maintained submerged under coolant even in the event of breakage of any pipe connected to the reactor pressure vessel, it is ensured to eliminate a possibility that the top portion of the reactor core is exposed temporarily during an intermediate period before actuation of the accumulated coolant injection system to start injecting of the coolant into the reactor pressure vessel after the end of flushing. In addition, with the core in the reactor pressure vessel positioned below a level of the passage holes for the lower drywell, the coolant of low temperature flowing out of the reactor pressure vessel and accumulated in the lower drywell after the completion of flushing serves to cool the wall surface of the reactor pressure vessel from its outside, thereby in turn cooling the reactor core. Thus, the decay heat generated in the reactor core can be removed reliably and efficiently.
	abstract	A reactor service manipulator delivery system supported on a remotely operated trolley that travels on top of a track attached to the steam dam of a BWR shroud. The trolley has a mast and pulley system designed to manipulate a TV camera for inspection of various reactor components inboard and outboard of the shroud at the same time that fuel is being moved within the core during a refueling operation so that refueling can be performed in parallel with the inspection.
	abstract	An isotope production system that includes a cyclotron having a magnet yoke that surrounds an acceleration chamber. The cyclotron is configured to direct a particle beam from the acceleration chamber through the magnet yoke. The isotope production system also includes a target system that is located proximate to the magnet yoke. The target system is configured to hold a target material and includes a radiation shield that extends between the magnet yoke and the target location. The radiation shield is sized and shaped to attenuate gamma rays emitted from the target material toward the magnet yoke. The isotope production system also includes a beam passage that extends from the acceleration chamber to the target location. The beam passage is at least partially formed by the magnet yoke and the radiation shield of the target system.
	abstract	The present invention relates to components in an ion implanter that may see incidence of the ion beam, such as a beam dump or a beam stop. Such components will be prone to the ions sputtering material from their surfaces, and sputtered material may become entrained in the ion beam. This entrained material is a source of contamination. The present invention provides an ion implanter comprising power supply apparatus and an ion-receiving component. The component has an opening that receives ions from an ion beam such that ions strike an internal surface. The power supply apparatus is arranged to provide an electrical bias to the internal surface to decelerate the ions prior to their striking the surface, thereby mitigating the problem of material being sputtered from the surface.
053902173	description	DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Now, the present invention will be described in detail. The carbon fibers useful for the present invention may be of any type, such as polyacrylonitrile (PAN) type or pitch type carbon fibers or carbon fibers prepared by a gas phase growing method. However, high performance pitch-type carbon fibers having high thermal conductivity in the axial direction of fibers, are particularly preferred. The C/C composite materials of the present invention are obtainable by using such carbon fibers. (I) In a case where carbon fibers are oriented substantially in the thickness direction, the ratio of the thermal coductivity in the thickness direction to the thermal conductivity in a direction perpendicular to the thickness direction is at least 2, and the thermal conductivity in the thickness direction is at least 3 W/cm.multidot..degree.C., such C/C composite material can be prepared by the following method. Firstly, long carbon fibers are impregnated with a thermosetting resin, followed by heating to partially cure the thermosetting resin. Such thermosetting resin includes, for example, a phenol resin, a furan resin, an epoxy resin and an unsaturated polyester resin. A phenol resin, particularly a resol-type phenol resin, is preferred. Such thermosetting resin is used usually as dissolved and diluted with a solvent, for example, an alcohol such as ethanol, a hydrocarbon such as hexane, or acetone. The concentration of the thermosetting resin solution is usually within a range of from 10 to 70% by weight, preferably from 20 to 60% by weight. When a curing agent is required as in the case of a furan resin or an epoxy resin, such curing agent is also added to the solution. Such curing agent is added in an amount suitable for the particular resin used. As a method for impregnating long carbon fibers to such thermosetting resin solution, a simple method of dipping the carbon fibers in the solution, may be employed. However, in the case of a long fiber robing, a method of continuously passing it through a tank filled with the solution, is preferred from the viewpoint of the efficiency of the treatment. Further, in this case, it is preferred to apply supersonic waves of a level of from 10 to 50 KHz to the tank filled with the solution, whereby an adverse effect of irregular treatment due to e.g. air bubbles among monofilaments or among weave openings, can be prevented. The carbon fibers impregnated with the thermosetting resin solution is, for instance, passed through rollers to remove an excess solution and then subjected to heat treatment. By the heat treatment, the thermosetting resin is thermally cured. The conditions for the heat treatment vary depending upon the type of the thermosetting resin used. However, the heat treatment is conducted usually at a temperature of from 50.degree. to 300.degree. C., preferably from 80.degree. to 200.degree. C. for from 0.2 to 5 hours, preferably from 0.2 to 2 hours. In such a case, it is preferred to gradually raise the temperature to the prescribed temperature in order to avoid abrupt release of the solvent from the thermosetting resin solution coated on the carbon fibers. The heat treatment is preferably conducted by continuously passing the carbon fibers through a heating furnace, from the viewpoint of the efficiency of the treatment. Then, the obtained fiber/resin composite is cut into pieces having a length longer than the thickness of the desired C/C composite material. The length is selected usually within a range slightly longer than the thickness of the desired product and may, for example, be selected within a range of from 15 to 100 mm. The composite pieces are then aligned in one direction so that they will be substantially parallel to one another. Then, a pressure is exerted to the aligned pieces in a direction perpendicular to the longitudinal direction of the fibers, followed by heating and molding. For example, by supplying the composite pieces to a mold by means of a funnel-form feader, the composite pieces are aligned substantially in parallel to one another in the mold, then a pressure is exerted in a direction perpendicular to the longitudinal direction of the fibers under heating at a temperature required for the curing of the resin, to cure the resin and obtain a molded product. Then, the molded product is introduced into a container so that it is surrounded by coke breeze. Then, the container is introduced into an electric furnace, and the temperature is raised to a level of 100.degree. C., if necessary, under a nitrogen gas stream, for carbonization. If necessary, the carbonized product is introduced into a graphitization furnace and subjected to heat treatment at a temperature of at least 2,000.degree. C. under an inert atmosphere. Then, obtained carbonized product or graphitized product is impregnated with a petroleum-type or coal-type pitch or with a thermosetting resin such as a phenol resin or a furan resin, followed by carbonization, after curing the resin in the case where the thermosetting resin is employed. In such case, the thermosetting resin is used usually as dissolved in a solvent such as an alcohol, acetone or anthracene oil to have a proper viscosity. Further, in such case, it is preferred to employ an impregnation method under pressure. For example, a molded carbonized or graphitized product and pitch are introduced into a low pressure reactor (autoclave), which is then heated under vacuum to dissolve the pitch. After the carbonized or graphitized product is immersed in the molten pitch, nitrogen gas is introduced, and the temperature is raised under a low pressure to a level of from 550.degree. to 600.degree. C. Then, the reactor is cooled, and the densified product of the carbonized or graphitized product is withdrawn, and it is carbonized at a temperature of up to 100.degree. C. in the same manner as described above and, if necessary, graphitized. The above-mentioned so-called densification is repeated to obtain a high density C/C composite material having a specific gravity of at least 1.6. If the densification or the resin content in the fiber/resin composite is inadequate, or if the temperature raising rate for carbonization or graphitization is too high, the strength of the fibers in a direction perpendicular to the longitudinal direction of the fibers, tends to be low. In some cases, the fibers are likely to break. Therefore, it is necessary to select proper conditions. The C/C composite material thus obtained is an anisotropic material having high heat conductivity and electrical conductivity in the direction of the thickness. In order to improve the strength in a direction perpendicular to the thickness direction, the obtained C/C composite material may be wound by long carbon fibers or by a carbon material such as a C/C composite material, depending upon the particular purpose. Further, a plurality of composite materials may be bonded by means of e.g. a resin composed essentially of a phenol resin, and the bonded product is again heated to a temperature range at which the C/C composite materials were finally treated, to firmly bond the plurality of pieces of the C/C composite materials to obtain a composite material having a desired size. In the present invention, this C/C composite material may be reinforced in both the thickness direction and the direction perpendicular thereto, by bonding a metal to one side of the C/C composite material, which is substantially perpendicular to the thickness direction of the composite material. Various metals may be employed depending upon the particular purposes of application of the resulting C/C composite materials. However, it is usual to select the metal from, for example, Ti, Cu, Fe, Ni, Cr and alloys thereof. When heat resistance is required, Ti or an alloy of Ti is preferred. For example, in the case of Ti, such an alloy preferably contains A1 or V. Such metal is employed usually in the form of a thin plate having a thickness of at most about 5 mm, preferably from 0.1 to 1 mm. The bonding may be conducted by a usual method such as vacuum soldering, diffusion bonding or HIP (hot isostastic press). (II) In a case where at least 50% of carbon fibers are oriented substantially in the thickness direction, the ratio of the thermal conductivity in the thickness direction to the thermal conductivity in a direction perpendicular to the thickness direction and to the plane of orientation of the fibers in the thickness direction, is at least 1.2, preferably at least 1.5, and the thermal conductivity in the thickness direction is at least 1.5 W/cm.multidot..degree.C., preferably at least 1.8 W/cm.multidot..degree.C., such C/C composite material can be obtained by the following method using woven fabrics, short fibers, webs or non-woven fabrics. (A) A case where woven fabric is used: As the woven fabric, a plain weave fabric, a satin fabric or a twill fabric may be employed. Firstly, such woven fabric is impregnated with a thermosetting resin. The type and the concentration of the thermosetting resin may be selected in the same manner as described above with respect to (I). The method of impregnating the woven fabric of carbon fibers to such thermosetting resin solution may also be the same as described above with respect to (I). After the impregnation, the woven fabric is dried in a drier to remove the solvent. The fiber/resin composite thus obtained, is then cut into pieces having a desired size. For example, the woven fabric is passed through rolls to impregnate an alcohol solution of a phenol resin, and the impregnated fabric is then passed through rolls to remove an excess resin and then introduced in a drier kept at a temperature lower by 10.degree. C. than the boiling point of the alcohol to remove the alcohol. Then, the fabric is cut by a cutter into pieces having a size slightly larger than the cross section in the thickness direction of the desired product. The cut pieces of the composite are overlayed one on another in a mold frame having a size slightly larger than the desired product, to fill the mold, and molded. For example, the cut pieces of the composite are piled one on another, and a pressure is exerted in the direction of piling, and the temperature is raised for molding and curing the resin to obtain a molded product. The conditions for the heat curing treatment vary depending upon the type of the thermosetting resin used. Usually, however, the heat treatment is conducted at a temperature of from 50.degree. to 300.degree. C., preferably from 80.degree. to 200.degree. C. for from 0.2 to 5 hours, preferably from 0.2 to 2 hours. Then, the molded product is introduced into a container, followed by carbonization and, if necessary, graphitization, in the same manner as in the case of the above-mentioned (I). Then, by repeating the so-called densification in the same manner as in the case of the above (I), a high density C/C composite material having a specific gravity of at least 1.6 can be obtained. The C/C composite material thus obtained is an anisotropic material having a thermal conductivity of at least 1.5 W/cm.multidot..degree.C. (usually less than 3.0 W/cm.multidot..degree.C.) and excellent electrical conductivity, in the thickness direction. (B) Another embodiment in which woven fabric is used: Woven fabrics of carbon fibers impregnated with a thermosetting resin were overlayed one on another, followed by molding, curing and carbonization, and the carbonized product is impregnated with pitch or a thermosetting resin, followed by carbonization and, if necessary, graphitization, to obtain the desired C/C composite material. This material is then cut into pieces having a size, in the plane of the woven fabric of this C/C composite material, larger than the cross section in the thickness direction of the desired product. The cut pieces of the composite material are bound or bonded in such a form wherein the plane direction agrees i.e. the plane of each woven fabric is in the thickness direction of the desired product. They may be bound by winding long fibers made of carbon fibers thereon. Otherwise, they may be bound by a C/C composite material or a usual carbon material, so that there will be no space between the overlayed pieces. Further, the pieces may be bonded by means of e.g. a resin composed essentially of a phenol resin, and they are heated to a temperature level at which the C/C composite material was finally treated, to bond the plurality of the cut pieces of the C/C composite material to one another. (C) A case where short fibers or non-woven fabric is used: (i) Short carbon fibers are fibrillated to form a web by a conventional method. This web is used instead of the woven fabric of (A) and treated in the same manner as in (A) to obtain a C/C composite material wherein the direction of the majority of fibers of the web (the direction of the plane of the web) is in the same direction as the thickness direction of the desired product. PA1 (ii) A non-woven fabric of carbon fiber prepared from long carbon fibers by a usual method is used instead of the woven fabric of (A) and treated in the same manner as in (A) to obtain a C/C composite material wherein the direction of the plane of the non-woven fabric is in the same direction as the thickness direction of the desired product. (D) A case where a web formed from short fibers and subjected to needling is used: A product obtained by needling the web obtained in (C) in the thickness direction of the web, is used instead of the web, and it is treated in the same manner as in (C) to obtain a C/C composite material wherein the direction of the plane of the web is in the same direction as the thickness direction of the desired C/C composite material. Further, in the present invention, in the above method (C) (i) or (D) (preferably (D)), it is possible to obtain a product wherein the thermal conductivity in the thickness direction and the thermal conductivity in a direction perpendicular to the thickness direction and parallel to the plane of each web or felt, are at least 3 W/cm.multidot..degree.C., by increasing the number of densification operation (at least about 6 or 7 times) or needling operation, or by conducting graphitization at a relatively high temperature (at least about 2,900.degree. C.)) for applications wherein heat is effectively conducted in two directions i.e. in the thickness direction and one direction perpendicular to the thickness direction. In the present invention, such C/C composite material is used as the main constituting material for the first wall to be disposed to face a plasma of a nuclear fusion reactor, and it is disposed so that one side which is substantially perpendicular to the thickness direction, faces the plasma. The C/C composite material is positioned to extend, in its thickness direction between the high temperature plasma region and the external low temperature region. Further, in the present invention, it is preferred to bond or bind, by metallurgical bonding or by mechanical binding, a metal to one side of the C/C composite material which is substantially perpendicular to the thickness direction of the C/C composite material. Particularly preferred is the metallurgically bonding. The metal is usually selected from, for example, Ti, Cu, Fe, Ni, Mo, Cr and alloys thereof. As an alloy system, for example in the case of Ti, it is preferred that the alloy contains A1 or V. Such metal is used usually in the form of a thin plate having a thickness of at most about 5 mm, preferably from 0.1 to 0.3 mm. However, a stainless steel plate having a thickness of not more than about 50 mm, may be employed as the substrate directly or with inter-position of the above thin plate. The bonding may be made by a conventional method such as vacuum soldering, diffusion bonding or HIP (hot isotactic press). The C/C composite material of the present invention has high heat conductivity and electrical conductivity in at least one direction including the thickness direction and thus is capable of effectively removing or conducting heat. Further, when a metal is bonded as mentioned above, the thermal shock resistance in both the thickness direction and the direction perpendicular thereto is high. Now, the present invention will be described in further detail with reference to Examples. However, it should be understood that the present invention is by no means restricted to such specific Examples. EXAMPLE 1 Long fibers of pitch-originated carbon fiber ("Dialead" manufactured by Mitsubishi Kasei Corporation, 4,000 filaments, fiber diameter: 10 .mu.m) were immersed in an ethanol solution of a phenol resin, and then they were introduced into a drier to remove ethanol at 70.degree. C. and then heated to a temperature of at least 100.degree. C. to half-cure the phenol resin. The fiber/resin composite thus obtained (tow prepreg) (carbon fiber/resin=56/44 in weight ratio) was cut into pieces having a length of 40 mm. The pieces were rod-like and rigid with the fibers fixed with the resin. The cut pieces of the composite were aligned in one direction in a mold so that they were in parallel to one another, so as to fill the mold in the form larger than the size of the desired C/C composite material. Then, a low pressure is exerted at 150.degree. C., and the temperature was raised to 250.degree. C. over a period of one hour and held at 250.degree. C. for one hour for molding and curing. The size after the molding was 101.9.times.102.5.times.40.1 Then, this molded product was introduced into a container packed with coke breeze and heated to 1,000.degree. C. over a period of about 50 hours in a state covered with the-coke breeze, for carbonization of the resin. Then, this carbonized composite and solid pitch were introduced into an autoclave, and the temperature was raised to 250.degree. C. under a reduced pressure condition. Then, nitrogen was permitted to bring the atmosphere to a positive pressure. Then, the temperature was raised to 500.degree. C. in 8 hours and then held at 500.degree. C. for 5 hours. The pressure during the temperature raising, was maintained at a constant level by adjusting the valve attached to the autoclave. The autoclave was cooled, and the composite material was taken out and carbonized to a temperature of 1,000.degree. C. in the same manner as the carbonization of the molded product. The above autoclave treatment and the subsequent carbonization treatment were repeated in a total of three times. Then, the product was introduced into a graphitization furnace and heated to 2,800.degree. C. in an argon atmosphere and then cooled to obtain a C/C composite material. The C/C composite material thus obtained had a bulk density of 1.8 g/cm.sup.3, and the thermal conductivities in the thickness direction (the same direction as the fiber axis) and in a direction perpendicular thereto, were measured by a laser flash method thermal coefficient measuring device (manufactured by Shinkuriko). The thermal conductivity in the thickness direction was 3.70 W/cm.multidot..degree.C., and the thermal conductivity in the direction perpendicular to the thickness direction was 0.31 W/cm.multidot..degree.C. The ratio was 12.0. This product did not break even when rapidly introduced into the graphitization furnace heated at a temperature of 2,500.degree. C., and was superior also in the thermal shock resistance. EXAMPLE 2 A C/C composite material was prepared in the same manner as in Example 1 except that the size after the molding was 122.times.137.times.44 mm, and the autoclave treatment and the subsequent carbonization treatment were repeated in a total of 4 times. The bulk density of the C/C composite material thus obtained, was 1.83 g/cm.sup.3. The thermal conductivity in the thickness direction was 3.61, and the thermal conductivity in the direction perpendicular to the thickness direction was 0.51. The ratio was 7.08. This C/C composite material did not break even when rapidly introduced into a graphitization furnace heated at a temperature of 2,500.degree. C., and it was excellent also in the thermal shock resistance. EXAMPLE 3 Eight satin fabric sheets (260 g/m.sup.2) of pitch fibers ("Dialead", 3,000 filaments, fiber diameter: 10 .mu.m) were impregnated in an ethanol solution of a phenol resin (phenol resin/ethanol=1/4 ) and then introduced into a drier maintained at a temperature of 70.degree. C. to remove ethanol. Then, the obtained composite was cut into pieces of 22.times.105 mm. The pieces of the composite were overlayed one on another in a thickness of about 95 mm in a direction perpendicular to the plane of 22.times.105 mm to obtain a size larger than the size of the desired C/C composite material. Then, a low pressure was exerted at 150.degree. C., and the temperature was raised to 250.degree. C. over a period of one hour, and maintained at 250.degree. C. for one hour for molding and curing. The size of the molded product thus obtained was 103.2.times.93.4.times.21.9 mm. Then, this molded product was introduced into a container packed with coke breeze and heated to 1,000.degree. C. over a period of about 50 hours in a state covered with coke breeze, for carbonization. Then, the carbonized composite material and solid pitch were introduced into an autoclave, and the temperature was raised to 250.degree. C. under a reduced pressure condition. Then, nitrogen gas was introduced to bring the atmosphere in a positive pressure, and the temperature was raised to 500.degree. C. over a period of 8 hours and then maintained at 500.degree. C. for 5 hours. The pressure during the temperature raise, was maintained at a constant level by means of a valve attached to the autoclave. The autoclave was cooled, and the composite material was taken out and carbonized to a temperature of 1,000.degree. C. in the same manner as in carbonization of the molded product. The above-mentioned autoclave treatment and the subsequent carbonization treatment were conducted in a total number of three times, and the product was introduced into a graphitization furnace and heated to a temperature of 2,800.degree. C. in an argon atmosphere and then cooled to obtain a C/C composite material. The bulk density of the C/C composite material thus obtained was 1.62 g/cm.sup.3. The thermal conductivity in the thickness direction was 1.63 W/cm.multidot..degree.C., and the thermal conductivity in a direction perpendicular thereto and perpendicular to the plane of the woven fabric, was 0.23 W/cm.multidot..degree.C. The ratio of the thermal conductivities was 7.0. (The orientation in the thickness direction of the carbon fibers was about 50%.) EXAMPLE 4 The same satin fabric of pitch-originated carbon fibers as used in Example 3 was impregnated in an ethanol solution of a phenol resin in the same manner as in Example 3, dried, molded into a flat plate and cured. Then, this product was heated at 1,000.degree. C., and then usual pitch impregnation method was repeated to densify the product. Finally, graphitization was conducted at 2,800.degree. C. Then, this flat plate C/C composite material having a thickness of 10 mm was cut into pieces having a width of 20 mm and a length of 100 mm. Twenty pieces thus obtained were overlayed one on another so that their flat surfaces were in contact one another, and they were bonded by a phenol resin. Further, they were wound by carbon fibers to obtain C/C composite material having a width of 100 mm, a length of 200 mm and a thickness of 20 mm. The thermal conductivity in the thickness direction of this product was 1.64 W/cm.multidot..degree.C., and the ratio of the thermal conductivity in the thickness direction to the thermal conductivity in a direction perpendicular to the thickness direction and perpendicular to the bonding surfaces, was 7.5. (The orientation in the thickness direction was about 50%.) EXAMPLE 5 Pitch-originated fibers ("Dialead", 3,000 filaments, fiber diameter: 10 .mu.m) were cut to obtain short fibers, which were then fibrillated to obtain a web. The web was cut into pieces of 30 mm.times.150 mm. The pieces were impregnated in an ethanol solution of a phenol resin. Then, these pieces were overlayed one on another to obtain a thickness of about 100 mm, and a C/C composite material was prepared in the same manner as in Example 3. The thermal conductivity in the thickness direction of the C/C composite material thus obtained was 1.64. The ratio of the thermal conductivity in the thickness direction to the thermal conductivity in a direction perpendicular to the thickness direction and parallel to the laminating direction, was about 6.5. (The orientation of the planes of webs in the thickness direction was about 100%.) EXAMPLE 6 The same web as obtained in Example 5 was subjected to needling, to obtain a felt in which fibers were oriented in the thickness direction of the web. By using this felt, a C/C composite material was obtained in the same manner as in Example 5, and the thermal conductivity was measured in the same manner as in Example 5. The thermal conductivity in the thickness direction was 1.64, and the ratio was 6.0. (The orientation of the planes of webs in the thickness direction was about 93%.) EXAMPLE 7 A C/C composite material was prepared in the same manner as in Example 3 except that since the desired size for the C/C composite material was large, the composite was cut into pieces having a size of 45.times.110 mm, and the size of the molded product obtained by overlaying to increase the carbon fiber content in the finally obtainable C/C composite material, was changed to 112.times.105.times.46 mm, and the autoclave treatment and the subsequent carbonization treatment were conducted four times in total. The bulk density of the composite material thus obtained was 1.82 g/cm.sup.3. The thermal conductivity in the thickness direction was 2.14 W/cm.multidot..degree.C., and the thermal conductivity in a direction perpendicular to the thickness direction and to the plane of each woven fabric, was 0.34 W/cm.multidot..degree.C. The ratio of the thermal conductivities was 6.0. (The orientation of the carbon fibers in the thickness direction was about 50%.) EXAMPLE 8 A C/C composite material was prepared in the same manner as in Example 7 except that the temperature for heat treatment was changed to 3,000.degree. C. in Example 7. The bulk density of the composite material thus obtained was 1.84 g/cm.sup.3. The thermal conductivity in the thickness direction was 2.95 W/cm.multidot..degree.C., and the thermal conductivity in a direction perpendicular to the thickness direction and to the plane of each woven fabric, was 0.37 W/cm.multidot..degree.C. The ratio of the thermal conductivities was about 8.0. EXAMPLE 9 A C/C composite material was obtained in the same manner as in Example 5 except that in Example 5, the thickness of lamination was increased to increase the carbon fiber content in the finally obtainable C/C composite material. The bulk density of the composite material was 1.85 g/cm.sup.3. The thermal conductivity in the thickness direction was 1.72 W/cm.multidot..degree.C., and its ratio to the thermal conductivity (0.39) in a direction perpendicular to the thickness direction and to the bonding surface, was about EXAMPLE 10 A C/C composite material was obtained in the same manmer as in Example 9 except that in Example 9, the temperature for heat treatment was changed to 3,000.degree. C. The bulk density of the composite material thus obtained was 1.83 g/cm.sup.3, and the ratio of the heat conductivities was about 4.9 (2.19/0.45). EXAMPLE 11 A C/C composite material was prepared in the same manner as in Example 6 except that in Example 6, the number of needling was increased to increase the proportion of fibers oriented in the thickness direction of the webs, and the autoclave treatment and the subsequent carbonization treatment were conducted five times in total. The bulk density of the composite material thus obtained was 1.72 g/cm.sup.3. The thermal conductivity in the thickness direction was 1.66, and its ratio to the thermal conductivity (1.17) in a direction perpendicular to the thickness direction and to the direction of lamination was about 1.4. EXAMPLE 12 A C/C composite material was prepared in the same manner as in Example 11 except that in Example 11, the temperature for heat treatment was changed to at least about 2,900.degree. C. The bulk density of the composite material thus obtained was 1.73 g/cm.sup.3, and the ratio of the heat conductivities was about 1.2 (1.84/1.53). EXAMPLE 13 A C/C composite material was prepared in the same manner as in Example 6 except that in Example 6, the densification treatment was conducted 8 times, and the temperature of graphitization was changed to at least about 2,900.degree. C. The thermal conductivity in the thickness direction and the thermal conductivity in a direction perpendicular to the thickness direction and to the direction of lamination, were 3.3 W/cm.multidot..degree.C. and 3.1 W/cm.multidot..degree.C., respectively. Further, the thermal conductivity in a direction perpendicular to the thickness direction and parallel to the direction of lamination, was 0.57 W/cm.multidot..degree.C. EXAMPLE 14 By using the C/C composite material obtained in Example 1, a pure Ti plate was bonded to one side of the composite material which is substantially perpendicular to the thickness direction of the composite material. Namely, on a pure Ti plate (melting point: about 1,675.degree. C. having a thickness of about 0.3 mm, a Cu solder was placed, and the above C/C composite material was placed thereon. Then, a weight of about 1 kg was placed thereon. In a vacuum furnace, the temperature was raised over a period of about one hour and maintained at about 1,050.degree. C. for 5 hours to obtain a desired C/C composite material having Ti bonded thereto. The obtained C/C composite material had adequate reinforcing effects also in a direction perpendicular to the thickness direction. EXAMPLE 15 A C/C composite material was prepared in the same manner as in Example 14 except that in Example 14, the size after the molding was 122.times.137.times.44 mm and the autoclave treatment and the subsequent carbonization treatment were conducted four times in total. The bulk density of the C/C composite material thus obtained was 1.83 g/cm.sup.3. The thermal conductivity in the thickness direction was 3.61, and the thermal conductivity in the direction perpendicular to the thickness direction was 0.51. The ratio of the thermal conductivities was 7.08. This C/C composite material did not break even when introduced rapidly into a graphitization furnace heated to a temperature of 2,500.degree. C., and it was excellent in the thermal shock resistance. Then, a pure Ti plate was bonded to one side of this C/C composite material in the same manner as in Example 14. The C/C composite material thus obtained had adequate reinforcing effects also in a direction perpendicular to the thickness direction. EXAMPLE 16 FIG. 1 illustrates a first embodiment of the first wall of a nuclear fusion reactor according to the present invention. The first wall 1 comprises the C/C composite material 2 prepared in Example 1, which is vacuum-soldered to a substrate 3. Namely, the composite material 2 is bonded to a stainless steel substrate 3 having a thickness of 10 mm by a copper solder with interposition of a Ti plate 7 having a thickness of 1 mm and a solder portion 4. The substrate 3 is provided with cooling tubes 5 to improve the cooling effects. In this Figure, the plasma-facing side 6 is disposed to face the plasma of the nuclear fusion reactor. In this manner, the composite material of the present invention is used as the first wall. FIG. 2 illustrates a second embodiment of the first wall of the present invention. In this embodiment, the C/C composite material 2 obtained in Example 1 was used, and a thin metal plate 7' (pure Ti plate) was bonded to one side which is substantially perpendicular to the thickness direction. Namely, on a pure Ti plate (melting point: 1,675.degree. C.) 7 having a thickness of about 1 mm, a copper solder was placed, and the above C/C composite material was placed thereon. A weight of about 1 kg was placed thereon. In a vacuum furnace, the temperature was raised over a period of 1 hour and maintained at about 1,050.degree. C. for 5 hours to obtain a C/C composite material having Ti bonded thereto with the solder portion 4 interposed therebetween. Then, the thin metal plate 7 of this C/C composite material was mechanically connected to the substrate 3 by e.g. a bolt. Reference numeral 8 indicates a fixing plate, and numeral 9 indicates a connector. The substrate 3 may be provided with cooling tubes as in the first embodiment. Reference numeral 6 indicates the plasma-facing side. FIG. 3 illustrates a third embodiment of the first wall of the present invention. In this embodiment, the C/C composite materials 2 and 2' are bonded around a cooling tube 5 with a solder portion 4 interposed therebetween. The plasma-facing side is disposed to face the plasma of the nuclear fusion reactor. Thus, the composite materials of the present invention are used as the first wall. EXAMPLE 17 A C/C composite material having a metal bonded thereto was prepared in the same manner as in Example 16 except that in the first embodiment of Example 16, the C/C composite material obtained in Example 3 was used, and a Mo plate having a thickness of 2 mm was used as the material for interposition. It was used as the first wall. Further, a C/C composite material for the first wall was prepared in the same manner as in Example 16 except that in the second embodiment of Example 16, the C/C composite material obtained in Example 3 was bonded to a Mo plate (melting point: about 2,620.degree. C.) having a thickness of 2 mm to obtain a C/C composite material having Mo bonded thereto. The C/C composite material of the present invention has large heat conductivity and electrical conductivity in the thickness direction and thus is useful for application where heat or electrical conductivity in one direction is required. For example, it is useful as a material for a heat exchanger whereby heat removal or heat conduction is carried out by contacting one flat surface with a cooling jacket, or as a material for a switch. Further, the first wall made of the C/C composite material of the present invention has particularly excellent properties as the first wall, since the surface temperature, the vapor pressure and the sublimation loss are maintained at low levels even when exposed to a high heat load for a long period of time.
	description	This application is a national phase of International Application No. PCT/EP2006/067499 entitled “POWDER DISPENSER, NOTABLY FOR PELLETIZER AND METHOD FOR MAKING NUCLEAR FUEL PELLETS”, which was filed on Oct. 17, 2006, and which claims priority of French Patent Application No. 05 53175, filed Oct. 19, 2005. The present invention relates to a powder dispenser, notably used for feeding a device for making pellets of nuclear fuel, for example of the MOX (mixture of plutonium oxide and uranium oxide) type, and a method for making said pellets using such a dispenser. The making of nuclear fuel pellets includes the following steps: filling a mould or die having the shape of a pellet, by means of a dispenser, displacing the dispenser in order to release the thereby filled mould, and then pressing via first and second punches which penetrate the mould, evacuating the pellets. The longest step in this making method is the one for filling the die. Thus, when it is sought to reduce the cycle time for making pellets, it is sought to reduce the time required for filling the die. A casing is known as a powder dispenser or shoe, including four side walls and an upper wall to which a pipe feeding powder is connected, said casing being suitable to move on a table in which orifices are provided which form a mould for pressing the pellets. However, the use of MOX powder poses a particular problem because of the fineness of the MOX particles. Indeed, MOX powder has poor flow behaviour, i.e. a poor capacity for continuous flow. The particles then tend to form clusters and to form bridges of powder which block the flow of the powder and therefore its distribution in the dies. A non-homogeneous distribution of the powder then occurs in the die. The consequence of this is that pellets are made which do not have the sought mass and/or have too dispersed densities. The characteristics of the pellets should be controlled so as to ensure maximum operating safety when assemblies of nuclear fuel including said pellets are used in nuclear reactors. Additionally, adhesion of the powder to the walls of the shoe causes a lengthening of the cycle time. Accordingly, an object of the present invention is to provide a powder dispenser which ensures that pellets are made with homogeneous characteristics. An object of the present invention is also to provide a dispenser with which the cycle time for making nuclear fuel pellets may be reduced. The aforementioned objects are achieved by a powder dispenser, suitable to move on a die, including a casing into which powder is fed; inside the casing, surfaces are provided, tilted relative to the direction of displacement of the shoe for grouping the powder along preferential axes. In other words, the dispenser according to the present invention includes an increased displacement surface as compared with the earlier dispensers, in order to increase impulses applied to the powder. The subject-matter of the present invention is mainly a powder dispenser including a casing which includes on an upper wall, means for connecting to at least one powder feed pipe connected to a hopper, said dispenser being suitable to impart to the powder a reciprocal movement on a plane along a determined displacement direction, and means for grouping the powder along distinct axes substantially parallel to the displacement direction, in order to fill the dies for pressing pellets, each die being positioned on a distinct grouping axis, the grouping means being borne by walls of the casing perpendicular to the displacement direction and having a sawtooth section along a plane parallel to the displacement plane. In an advantageous example, the dispenser includes downstream grouping means and upstream grouping means according to the direction of displacement. The downstream grouping means are advantageously shifted transversely relative to the upstream grouping means by a tooth half-width, so that a tooth tip is facing a bottom part between two consecutive teeth. The dispenser according to the present invention advantageously includes longitudinal guide means suitable to cooperate with guide means borne by the displacement plane. These means for guiding the dispenser and those of the plane may form a slide, the guide means may then include an axial protrusion on each transverse side of the casing, capable of sliding in an axial groove fixed relative to the plane. Advantageously, the axial protrusion is oriented towards the casing and at least one of the protrusions is removable. According to the present invention, the dispenser is advantageously connected to displacement means for causing reciprocal movement along the displacement direction via two rotationally fixed arms through a first end on each of the side faces of the casing respectively, and rotationally mobile through a second end opposite to the first end, said arms each including a cylinder. In an exemplary embodiment, the grouping means are respectively borne by a mobile plate relative to the casing. Advantageously, the dispenser includes means capable of causing said plates to vibrate relative to the dies along the displacement direction. These excitation means may for example include a vibrator or be of the piezoelectric type. These vibration means may include a shaft firmly attached through one end to a plate and through a second end to a means for actuating a reciprocal movement along the displacement direction, and suspension means. The suspension means may for example include a spring pressed between the shaft and the casing. The dispenser may further include a sealing means interposed between the plates and the wall of the casing facing each other, for example an elastomeric ring with an axis substantially coinciding with that of the arm. The suspension means may also be an elastomeric ring interposed between the plate and the wall of the casing facing each other, and also form the sealing means. The elastomeric ring may be adhesively bonded onto the casing and the plate, or firmly attached to the casing and to the plate by vulcanization. The ring may also be force-fitted on a first protruding ring of the casing and on a second protruding ring of the plate. In a particular example, the ring is maintained between two metal sheet plates so as to form a sandwich plate. The metal sheets may include windows facing the passage of the ring and in which the window of the metal sheet on the casing side is smaller than the one on the plate side. For example, the metal sheet in contact with the plate is welded and/or riveted on the latter and includes ends folded back at right angles. The dispenser advantageously includes a face forming a pusher having the shape of a nose, sliding on the slide plane intended to push the pellets after their formation. The object of the present invention is also a device for making pellets including a table comprising dies, upper and lower punches intended to press the powder in the dies, a dispenser according to the present invention, means for controlling the displacement of the dispenser according to a reciprocal movement along the first displacement direction, means for conveying the powder into the dispenser, the dies being positioned at least along one row, the distance separating the dies being equal to the distance separating the bottom parts of the teeth, the dispenser being positioned on the dies so that, during a displacement, each bottom part between two teeth covers a die. The row is advantageously perpendicular to the direction of displacement. Advantageously, the device includes two rows of parallel dies, the dies of each row being equidistant from each other and the dies of the first row being shifted relative to the dies of the second row by half of the distance separating the dies of the second row. For example, each row includes seven dies. The conveying means include at least one feed pipe connecting a hopper to the dispenser. The feed pipe may extend in the direction of the rows of dies. The device according to the present invention may include a means for collecting the content of the dispenser after a die filling cycle. This collecting means may also include at least one orifice provided in the table connected through a pipe to suction means, the orifice being under the dispenser when the latter is in a particular emptying position. Further, this device may advantageously include means for putting the powder collected by the collecting means in the hopper. Advantageously, the table can move along an axis perpendicular to its planar face. The device also includes rails into which the axial protrusions of the dispenser penetrate according to a particular example. The subject-matter of the present invention is also a method for making pellets including the following steps: filling dies with powder by means of a powder dispenser provided with grouping means along distinct axial directions corresponding to the positioning of the dies, pressing the powder in the dies, evacuating the pellets. In a particular example, the shoe may have a reciprocal movement according to a sinusoidal law during the filling step. In another particular example, the shoe has a reciprocal movement according to a triangular law during the filling step. Further, the grouping means may be set into vibration. Additionally, evacuation of the pellets is advantageously carried out by lowering the die and by having the pellets pushed by the dispenser. The method may also include an additional step for emptying the dispenser. In FIG. 1, a device may be seen for making pellets including a table 2, provided with at least one die 4 provided with an orifice in which the powder to be pressed will be positioned, a shoe or powder distributor 6 intended to move above the die 4, a feed hopper 8 connected to the shoe via a pipe 10 and a means 12 for displacing the shoe 6 along an X axis, this means 12 advantageously applying a reciprocal movement according to the arrows 14 and 15. The shoe 6 is formed by a casing including an upper wall 16 and side walls 18, the pipe 10 being connected to the upper surface 16. The device also includes a valve 20 interposed between the hopper and the feed pipe 10 so as to control the supply of the shoe with powder. When the valve 20 is open, the powder contained in the hopper 8 flows into the pipe 10 so as to reach the shoe 6. The shoe 6, under the action of the displacement means 12, will have a longitudinal reciprocal movement along the X axis according to the arrows 14 and 15 and will dispense the powder in the die 4. In the illustrated example, a single die is visible, but several dies may be provided. In FIG. 2, a detailed illustration may be seen of a shoe according to the present invention, including a casing 22 with a substantially rectangular shape, formed by the side walls 18 and the upper wall 16. The side walls include walls 18.1 and 18.2 perpendicular to the X axis, the wall 18.2, a so-called front wall, preceding the rear wall 18.1 in the direction indicated by the arrow 14. Walls 18.3, 18.4 parallel to the X direction, together connect the ends of the front and rear walls respectively. The shoe 6 is capable of sliding on the table 2along the X axis, between an extreme retracted position in which the shoe does not cover the dies 4, and an extreme advanced position (position D), allowing evacuation of the pellets. Table 2in the illustrated example includes fourteen dies or moulds positioned in first R1 and second R2 rows substantially parallel to the Y axis. In the illustrated example, the rows are shifted relative to each other so that the dies are not aligned along axes parallel to the X or first displacement axis. Thus, when looking along the arrow 14, the orifices of the dies of the first row are between two orifices of dies of the second row except for the orifices on the extreme left of R1 and on the extreme right of R2 (FIG. 2). More or less than fourteen dies and more than two rows may also be provided depending on the desired flow rates and pellet sizes. According to the present invention, the shoe 6 includes inner plates 19, 23 provided with means for grouping the powder along distinct paths, so as to displace and impulse the powder towards each die by means of a significant shoe surface. With this, the adhesion of the powder and its adherence to the walls may be reduced. These means are formed by cavities delimited by surfaces 30, 32 tilted relative to the X or first displacement axis. In the illustrated example the internal plates are of substantially identical geometry, we shall describe the wall 19. The plate 19 has a sawtooth section along a plane parallel to the plane of the table 2, the teeth including tips 21 connected by bottom parts 25. The end of the sawteeth may be more or less rounded. The plate 19 is positioned relative to the table so that the dies are aligned with the bottom parts 25 between the teeth when looking along the arrow 14. The bottom parts 25 are advantageously delimited by an arc of circle, avoiding retention of powder. Advantageously, the plate 23 has the same dimensions as the plate 19. The plate 23 is facing the plate 19. Advantageously, the teeth of the plate 23 are shifted along the Y axis relative to the teeth of the plate 19. Advantageously, the shift is a tooth half-width. In the illustrated example, the profile of the plate 19 and of the plate 23 are complementary. Advantageously, the plates 19, 23 are removable and fixed inside the casing. Thus, their replacement does not require replacement of the entire shoe. For this purpose, the upper wall of the casing is also removable. It may also be provided that the grouping means 19, 23 be directly formed in the inner faces of the side walls of the casing. The casing is for example made of CuZn and the grouping means for example of polymer. The feed tubes 10 open out into the upper wall of the casing substantially between the contours of the plates 19, 23. In the illustrated example, the shoe is fed by four feed tubes 10 regularly distributed along an axis Y perpendicular to the X axis. Provision may be made for more or less feed tubes. For example, six tubes may be provided opening out at right angles to the six bottom parts 25 of the wall 19 or 23, or else twelve tubes opening out at right angles to each bottom part 25. In the illustrated example, four separate flexible pipes are used. But provision may be made for using a single feed tube 10 of an elongated shape and extending along the Y axis all along the upper surface of the casing thereby allowing a continuous feed all along the path delimited by the sawteeth. The device according to the present invention also includes longitudinal guide means 33 allowing an accurate displacement of the shoe along the direction X relative to the table 2. The means 33 include an axial protrusion 34 borne by the shoe cooperating with a longitudinal groove 36 borne by the table 2, and visible in FIG. 5. In FIG. 5, the detail of the axial protrusion 34 and of the groove 36 may be seen. Advantageously, the axial protrusion 34 is directed towards the casing and penetrates into the groove 36 or rail interposed between this protrusion 34 and a wall 18.3,18.4 of the casing. For mounting the shoe on the table, provision is made for at least one of the axial protrusions 34 attached on either side on the side walls 18.3,18.4 of the casing being removable, as this may be seen in FIG. 2. It may be provided that the groove 36 be borne by the shoe and the protrusion 34 be borne by the table. The shoe is maintained in contact with the table, and in particular with the dies, advantageously by mechanical means such as a spring. But the use of pneumatic means, for example a pneumatic actuator, may be provided. Also advantageously, the hopper is for example fed by a suction system with a vacuum pump, or a mechanical one of the vibrating chute and worm screw type. By using a shoe according to the present invention, it is possible to limit retention of the powder inside the shoe and the risks of packing the powder. Effective filling of the first and second rows is then obtained with increased flow rates. The shoe, during the filling, is displaced according to a reciprocal movement, along the arrows 14 and 15 along the X axis. With reference to FIG. 6, this movement is for example obtained by means of two cylinders 38 each mounted through one end 39, rotatably on the side walls 18.3,18.4 of the casing of the shoe and also mounted so as to be rotationally mobile through a second end opposite to the first end, on an actuating device (not shown). Advantageously, the table is mounted so as to be mobile along a vertical axis Z, orthogonal to the X direction and to the Y direction. Because the actuator is rotatably mounted through both of these ends, both on the shoe and on the actuating device, the shoe entirely follows the displacement of the table. The reciprocal movement of the shoe advantageously is of the sinusoidal or triangular type. By using a displacement mode of the sine wave type, it is possible to attain a flow rate of the order of 9 grams of powder per second and by using a triangular law for the displacement of the shoe, flow rates of the order of 8 grams per second may be achieved. The shoe also includes at a longitudinal end a nose 40 intended for pushing the pellets towards a conveyer after pressing (not shown). According to a press model, a shaking axis and a shaking amplitude on either side of this axis are defined. The shaking axis corresponds to the central axis between the two rows of dies and the shaking amplitude ensures that the dies are covered by the powder from the shoe. By modulating the position of the shaking axis, i.e. by making its position asymmetrical relative to both rows of dies, it is possible to adjust a possible filling asymmetry between the front row and the rear row. We shall detail the filling of the dies of the first row R1, the filling of the dies of the second row R2 being carried out in a symmetrical way. When the means 19 move in the direction 15, the sawtooth profile of the grouping means 19 gathers the powder between each pair of teeth, the powder is displaced along the teeth towards the bottom parts 25. As the bottom parts 25 are aligned with the dies 4 of the first row R1 and positioned at the rear of the first row R1 before the filling, the latter encounter the dies 4 of the row R1, the powder gathered in the bottoms 25 at a certain instant, is at right angles to the dies 4 of the row R1 and falls into the latter. The filling of the dies is accomplished all the better since the powder is considerably impulsed by the means 19 providing a large surface for displacing the powder. The same phenomenon occurs for the second row R2, when the means 23 moves in the direction 15. All the powder required for making a pellet does not fall in one go into each die, but the filling is carried out over several passages by the reciprocal displacement of the shoe. Good filling homogeneity may be obtained by this filling in several steps. Further, the conjugate reciprocal movement of the shoe and the upward movement of the table create a phenomenon of suction of the powder towards the inside of the dies. As the lower punch is fixed, an upward movement of the table generates an increase in the free volume of the dies causing suction of the powder. In FIGS. 7-9, an alternative embodiment of a dispenser according to the present invention may be seen, including a shoe 106 which differs from the shoe 6 of FIGS. 2-6, in that the grouping means are mobile relative to the casing. The dispenser according to FIG. 7 includes a plate 119 bearing grouping means according to the present invention, the plate 119 being attached to a first end 104 of an arm 102 capable of being displaced along the X direction in a reciprocal movement along the arrow 105. The arm is attached through a second end to an actuating device (not shown) capable of applying low amplitude displacements to the arm so as to set the grouping means 119 into vibration along the X direction. Under the action of the arm, the grouping means move along the X direction inside the casing. The dispenser also includes suspension means 110, in the illustrated example, formed by two helical springs 112 in series, reactively mounted between the arm 102 and a cage 108 fixed relative to the casing. With the suspension means, the powder may be caused to vibrate at low frequencies and with a high amplitude, which causes a homogenous distribution of the powder over the whole surface of the shoe. These movements may be combined or linked with vibrations of lower amplitude and/or with a lower frequency, aiming at breaking the cohesion of the powder, in order to fluidify it and fill the dies properly. The dispenser also includes a sealing means 114 between the casing and the grouping means in order to prevent the powder from being placed between the walls of the casing and the grouping plates. These sealing means in the illustrated example include an elastomeric ring, substantially coaxial with the arm 102. In the illustrated example in FIG. 8, the ring 114 forms both sealing means and suspension means 110, the dimensions of the ring being determined in order to fulfil both of these functions. Advantageously, the elastomeric material used withstands temperatures substantially comprised between 50° C. and 130° C. and radiations. The ring is for example made by cutting it out in an elastomeric plate. The ring is attached to the casing and to the grouping means, for example, by adhesive bonding or by vulcanization. The ring may also be force-fitted onto protruding parts of the casing and of the grouping means, for example rings with an outer diameter larger than the inner diameter of the elastomeric ring. Making the suspension means in the shape of a cut-out ring in a sandwich material plate including an elastomeric layer 116 hemmed in between two metal sheet plates 118 may be also be contemplated (FIGS. 9A and 9B). The metal sheets of the suspension means may be welded (FIG. 9B) and/or riveted (FIG. 9A) on the casing and the plates 119. Only a plate provided with grouping means is illustrated in FIGS. 7, 8, 9A and 9B, but a device provided with two vibrating plates facing each other like in the dispenser of FIG. 2, does not depart from the scope of the present invention. An excitator may be provided for each plate or a single excitator for both plates, the plates being for example rigidly connected. Advantageously (cf. FIGS. 9A and 9B), the metal sheet in contact with the grouping means includes ends 120 folded back at right angles in order to follow the side contours of the grouping means, and an elastomeric layer overlapping from the rear face of the grouping means. In this way, the suspension means 110 also prevent any intrusion of powder between the grouping means and the casing. In one embodiment, shaking of the powder is only caused by the vibration of the grouping means, the shoe no longer performing a reciprocal movement for shaking the powder. On the one hand, the stresses on the arms provided with cylinders described earlier may be thereby reduced, the latter then being only used for large amplitude displacements for placing the shoe in the positions A to D illustrated in FIG. 6, for example allowing the shoe to be removed for the pressing. On the other hand, there is also a reduction in the cycle time for making the pellets, since the powder is directly impulsed. Further, as the shoe remains permanently above both rows of dies, the time for filling the dies is shorter than in the system where the shoe performs round trips between the upstream and downstream dies. A dispenser which provides shaking of the powder both by a reciprocal movement of the shoe and by causing vibration of the grouping means does not depart from the scope of the present invention. Advantageously, the excitator is provided outside the shoe, facilitating maintenance. Further, with this external arrangement, risks of failure for lack of ventilation may be avoided. The grouping means capable of vibrating, are preferably localized as near as possible to the dies in order to break cohesion of the powder where it should be evacuated. The excitator for example includes an electromagnetic excitation device, for example a vibrator or it is of the piezoelectric excitator type. The use of vibrators has the advantage of allowing wide frequency and amplitude ranges. Any type of excitators, for example of the magnetic type, may be adequate. The device for making pellets include, as described earlier, means for controlling the displacement of the shoe and also for controlling the excitator according to determined cycles so as to ensure repeatability of the filling of the dies. Strong amplitude vibrations may be provided at the beginning of the cycle and then vibrations of lower amplitude and/or vibrations of variable frequency. A method for making pellets applying the dispenser according to the present invention will now be described in relationship with the positions A to E of the shoe illustrated in FIG. 6. According to the present invention, the making method includes the following steps: a) placing the shoe on the dies (position A), the shoe including means for grouping the powder along distinct axes, b) filling the matrices by shaking the grouping means, c) removing the shoe (position B), d) compressing the powder, e) evacuating the pellets (position C). During step b), the valve 20 is open allowing the powder contained in the hopper to flow into the casing of the shoe through the pipes 10. Next, the casing of the shoe performs reciprocal movements (for example seven or eight round trips) and/or the grouping means are set into vibration providing uniform distribution of powder and preventing cohesion of the powder particles. During this filling, the lower punch may be moved so as to cause a suction effect. During step c), the shoe has a displacement, rearwards on the table 2, of large amplitude, relative to the reciprocal movements during the shaking, so as to completely clear the dies for the approach of the upper punch. During step d), the powder is pressed between the upper punch and the lower punch during a determined time. A change in the displacement velocity of the upper punch may be provided during the pressing. During step e), the table moves downwards causing ejection of the pellets from the dies, and then the shoe performs a large amplitude movement forwards in order to push the pellets towards a conveyer positioned at the front end of the table. The method may include an additional step for emptying the shoe, the latter is then placed in an emptying position (position D), above orifices connected to means for sucking up the powder remaining in the shoe. Next at the end of the cycle, the shoe is placed in a waiting rest position (position E). For positions C to E, the table is in the low position. By means of the shoe according to the present invention, a gain of several seconds may be achieved on the time for filling the dies.
043671845	description	DETAILED DESCRIPTION In the past nuclear reactor fuels containing highly enriched uranium (as much as 93% U.sup.235) have been used, but as mentioned hereinbefore such fuels are undesirable because the uranium can easily be used in atomic weapons. The use of uranium of lower enrichment for reactor fuel involves manufacturing problems that are difficult to solve. For example, fuel microspheres made of highly enriched uranium may have a low density, whereas microspheres made of uranium containing less U.sup.235 must have a high density. In addition, the form of the uranium in reactor fuel microspheres is of crucial importance. Microspheres consisting of UO.sub.2 alone are unacceptable because under operational conditions in a reactor this material adversely affects a pyrolytic carbon coating that is applied to the microspheres for a purpose not important to an understanding of this invention. A composition consisting of UC.sub.2 and UO.sub.2 can be used to form dense reactor fuel microspheres that are not easily processed to supply fissile material for weapons. However, such UC.sub.2 /UO.sub.2 microspheres must contain at least 15 mole percent UO.sub.2 to prevent attack by fission products generated in the microspheres upon a SiC coating that is applied to the latter in addition to the previously mentioned carbon coating. An optimal combination of UO.sub.2 and UC.sub.2 prevents deterioration of both of the coatings. In accordance with this invention, microspheres having the desired composition of UO.sub.2 and UC.sub.2 and a high density are manufactured by a sintering process involving carbothermic reduction of UO.sub.2 to UC.sub.2 in an atmosphere consisting of CO and an inert gas. It is an important advantage of the invention that this manufacturing process occurs in such a way that neither uranium oxycarbide or uranium monocarbide is included in the fuel composition, since each of these compounds can cause damage, under operational conditions in a reactor, to the aforementioned pyrolytic carbon coating applied to fuel microspheres. The preferred process of this invention can best be understood by reference to FIGS. 1 and 2 which illustrate the phase relationships of the U-C-O system between 1300.degree. and 1750.degree. C., the components in some of the phase regions of the diagram not being identified because they are not involved in the process. For use in a high temperature, gas-cooled reactor a composition consisting of 1 to 30 mole percent UC.sub.2 is desirable. A percentage of UC.sub.2 as high as 55 would be acceptable, but the required density of microspheres is difficult to achieve for UC.sub.2 concentrations greater than 30%. The desired UC.sub.2 -UO.sub.2 composition range is located along the line joining UC.sub.2 and UO.sub.2 on the phase diagram and is represented by a narrow rectangular area at the lower portion of this tie line. The UC.sub.2 phase actually contains a minor amount of oxygen and has a composition of UC.sub.1.83 O.sub.0.075. Three phase fields are involved in a carbothermic reduction process which occurs in the portion of the diagram where the desired UC.sub.2 /UO.sub.2 composition range is located. One compatibility triangle includes the phases UO.sub.2, UC.sub.2, and carbon, the UC.sub.2 containing a minor amount of oxygen as stated above. A composition within this triangle would not be acceptable for use as fuel in a high temperature, gas-cooled reactor because of the free carbon therein, which would drastically reduce the density of sintered microspheres formed of the composition. A second compatibility triangle of interest includes the previously mentioned UC.sub.2 and UO.sub.2 phases plus uranium oxycarbide, the latter being represented as UC.sub.x O.sub.y. A composition within this triangle is unacceptable because of the presence of UC.sub.x O.sub.y, since, as stated earlier, uranium oxycarbide can cause damage to the pyrolytic carbon coating applied to fuel microspheres. The last compatibility triangle that must be considered in connection with the invention is the region that includes UC.sub.x O.sub.y and UO.sub.2. A microsphere composition in this two-phase region is again unacceptable because of the presence of UC.sub.x O.sub.y. The reaction occurring during the carbothermic reduction process involved in this invention is represented by the following equation: EQU UO.sub.2 +4C=UC.sub.2 +2CO The composition after calcination of microspheres usable in the carbothermic reduction process of the invention can include 45 to 97 mole percent UO.sub.2 and 3 to 55 mole percent free carbon. This range is located along the line joining C and UO.sub.2 on the phase diagram and is represented by a bracket at the lower portion of the tie line. Microspheres having a UO.sub.2 --C composition within the stated range (which will be referred to hereinafter as precursor microspheres) have been formed by a process similar to the process described in an article titled "The KEMA U(VI) Process for the Production of UO.sub.2 Microspheres," which was published by J. Kanij, A. Noothout and O. Votocek in May, 1973, in connection with a symposium relating to sol-gel processes for forming nuclear fuel. The solutions used in the above-identified KEMA process can be used to form precursor microspheres, which by means of this invention can be converted into nuclear fuel microspheres usable in a high temperature, gas-cooled reactor, by adding carbon black to the KEMA components. However, the steps that have been used to form precursor microspheres usable in the process of this invention are described in the following paragraph only as an example of a suitable method for making the precursor microspheres, and other means can optionally be used to produce microspheres within the UO.sub.2 -C range stated above. To obtain precursor microspheres, 0.2 gram of a dispersing agent (e.g., Marasperse CB or Marasperse CBOS-6) can be dissolved in 171 ml of a 3.12 molar solution of hexamethylenetetramine and water and then 5.37 grams of carbon black having an average particle size of 24.times.10.sup.-3 .mu.m and a surface area of 138 m.sup.2 /g (e.g., carbon black available from Cabot Corporation under the name Black Pearls L) is added while the solution is being agitated by a Branson ultrasonic vibrator, the temperature of the solution being held below 30.degree. C. during dispersion of the carbon. The temperature of the hexamethylenetetramine-carbon mixture is reduced to 5.degree. C. and it is then mixed with 175 ml of an aqueous solution containing acid-deficient uranyl nitrate (2.43 molar) and urea (3.04 molar), the temperature of the uranyl nitrate-urea solution being at -5.degree. C. prior to mixing. The resulting mixture is discharged from a vibrating nozzle into trichloroethylene at a temperature of 65.degree. C. to form microspheres having a diameter in the range of 300-400 microns, in accordance with known procedures used in the sol-gel process of forming nuclear fuel microspheres. Preferably the microspheres thus formed are aged in the trichloroethylene for 20 minutes, and after being separated from the liquid they are dried by use of an air stream, washed with 0.5 molar ammonium hydroxide, again purged with air, and finally heated in an oven at 250.degree. C. to complete drying. The dried microspheres are calcined at 450.degree. C. to convert UO.sub.3 therein to UO.sub.2 and thereby provide precursor microspheres having a composition of UO.sub.2 and free carbon within the range given above. In accordance with this invention, microspheres having a UO.sub.2 -C composition within the stated range are sintered at 1550.degree. C. in a continuously flowing atmosphere consisting of argon and carbon monoxide, the molar percentage of CO in the atmosphere being varied in a manner described hereinafter. Since the CO-Ar atmosphere is continuously removed from the furnace in which the UO.sub.2 -C microspheres are sintered, the carbothermic reduction reaction proceeds toward UC.sub.2. In the portion of the U-C-O phase diagram shown in FIG. 2, the letter a designates a microsphere composition of UO.sub.2 and free carbon which is suitable as an initial composition for forming microspheres in accordance with the invention (namely, a composition in the middle of the range of UO.sub.2 -C usable in the process of the invention). As the carbothermic reduction of the initial UO.sub.2 /C composition proceeds, the composition of the microspheres will change to include different amounts of UO.sub.2, UC.sub.2, and free C, these compositions lying on the broken line between points a and b. The amount of free C in the microspheres will gradually decrease until point b is reached, when the microspheres will contain only UC.sub.2 and UO.sub.2. The composition of the microspheres can also be varied along the broken line between points b, c and d, and beyond point d, as determined by partial pressure of CO in the CO/inert gas atmosphere present in the furnace in which the microspheres are sintered. This dependence of the composition of the microspheres on the CO partial pressure in the furnace atmosphere is depicted in FIG. 3, wherein the initial composition of UO.sub.2 +free C is represented as point a. The composition moves into the three-phase region UO.sub.2 +UC.sub.2 +C (toward point b in FIG. 2) only if the partial pressure of CO(P.sub.CO) in the furnace atmosphere is less than level 1 in FIG. 3. According to the Gibbs phase rule, there is one degree of freedom within the three-phase region. Therefore for a given temperature, the equilibrium pressure of CO is constant and independent of the quantities of the three solid phases. When the tie line joining UC.sub.2 and UO.sub.2 is reached at point b, the equilibrium CO pressure will drop to a lower level (at point b' in FIG. 3). The equilibrium CO pressure over the three-phase region UC.sub.x O.sub.y +UO.sub.2 +UC.sub.2 is also constant (level 2 in FIG. 3 between points b' and c). The reaction will proceed into this three-phase region only if the P.sub.CO in the furnace atmosphere is less than level 2 in FIG. 3. The reaction will continue into the two-phase region UO.sub.2 +UC.sub.x O.sub.y if the P.sub.CO in the furnace is less than level 2. The Gibbs phase rule shows that there are two degrees of freedom in a two-phase region. Therefore at any temperature P.sub.CO over the UO.sub.2 and UC.sub.x O.sub.y will vary as the quantity of the two solid phases varies (line c--d in FIG. 3). Therefore the final composition of microspheres sintered in an atmosphere containing CO can be controlled by regulating the partial pressure of CO in the gas stream entering the sintering furnace. If the P.sub.CO is above level 1, no reaction will occur. If the P.sub.CO is between level 1 and level 2, UO.sub.2 and UC.sub.2 will be produced. If the P.sub.CO is between level 2 and level 3, the reaction will proceed into the UO.sub.2 +UC.sub.x O.sub.y phase region. FIG. 4 illustrates the above-described process conditions with greater particularity. Thermodynamic data for the U-C-O system show that atmospheres containing from about 1.2 to 1.9% CO will produce the phases UO.sub.2 and UC.sub.2 at 1550.degree. C. A sintering atmosphere containing less than 1.2% CO will produce UO.sub.2 and UC.sub.x O.sub.y while an atmosphere containing more than 1.9% CO will produce no reaction and leave UO.sub.2 and carbon in microspheres placed in such an atmosphere. Thus at a temperature of 1550.degree. C. the value 1.9% CO corresponds to level 1 of FIG. 3 and the value 1.2% CO corresponds to level 2 of FIG. 3. In accordance with this invention microspheres having the composition of UO.sub.2 and free carbon represented by point a in FIG. 2 are initially sintered in a furnace under a flowing gas consisting of about 0.5 to 1 mole percent CO and 99% to 99.5% Ar, which causes the microsphere composition to change to UO.sub.2 plus UC.sub.x O.sub.y. This process step produces microspheres of very high density (approaching 11 g/cm.sup.3). It would not be desirable to change the composition of the microspheres to UO.sub.2 +UC.sub.2 directly by use of an atmosphere comprising between 1.2 to 1.9% CO because microspheres so produced would have an unacceptable low density (5-8g/cm.sup.3). It would appear from examination of FIG. 4 that a second sintering period at 1550.degree. C. under an atmosphere containing more than 1.9% CO would change the composition of the microspheres back to UO.sub.2 +free carbon. However, it has been found that sintering the microspheres which have been converted to UO.sub.2 +UC.sub.x O.sub.y at a temperature of 1550.degree. C. under an atmosphere consisting of 3 mole percent CO and 97 mole percent Ar instead produces microspheres containing UC.sub.2 and UO.sub.2 within the desired composition range of 1-30 mole percent UC.sub.2 and 70-99 mole percent UO.sub.2. Furthermore these microspheres have the required high density in the range of about 10.2 to 11.0 g/cm.sup. 3. A sintering furnace used in forming reactor fuel microspheres in accordance with this invention can consist of a tube furnace having a diameter of 3.8 cm. Molybdenum carbide crucibles can be used to hold the microspheres to prevent any reaction between UO.sub.2 -UC.sub.2 and the crucible. The microspheres in the furnace are exposed to a flowing atmosphere containing accurately controlled amounts of CO and Ar. Microspheres containing between 45 to 97 mole percent UO.sub.2 and between 3 to 55 mole percent free carbon are first sintered at 1550.degree. C. in a flowing atmosphere consisting of 1 mole percent CO and 99 mole percent Ar for 4 hours. The microspheres are then sintered at 1550.degree. C. in a flowing atmosphere consisting of 3 mole percent CO and 97 mole percent Ar for an additional 4 hours. By way of example, the following microsphere compositions were obtained by the above-described process steps. ______________________________________ INI- INI- TIAL TIAL FINAL FINAL FINAL MOLE MOLE MOLE MOLE DENSITY SAMPLE % UO.sub.2 % C % UO.sub.2 % UC.sub.2 g/cm.sup.3 ______________________________________ 1 69.9 30.1 88.9 11.1 10.29 2 60.4 39.6 83.5 16.5 10.22 3 54.9 45.1 79.7 20.3 10.72 4 53.2 46.8 77.5 22.5 10.64 ______________________________________ The composition of the UO.sub.2 -UC.sub.2 microspheres obtained by the described process steps was established by chemical analysis and x-ray diffraction procedures.
	claims	1. A transportation assembly for transporting radioactive material, comprising:(a) an outer container having first and second ends, wherein the outer container defines an inner cavity, the outer container having an inner shell, wherein at least a portion of the inner shell comprises a plurality of layers including at least one layer of chopped fiberglass mat, at least one layer of aramid fabric, and at least one layer of a double bias glass fabric, the inner shell further including at least one stiffening member disposed at either of the first and second ends of the outer container, wherein the stiffening member is substantially transverse to a longitudinal axis extending from the first end to the second end; and(b) an inner container disposed within the inner cavity of the outer container. 2. The assembly of claim 1, wherein the assembly is designed and configured to transport fissile material. 3. The assembly of claim 1, wherein the outer container further includes an outer shell. 4. The assembly of claim 3, wherein the outer container further includes an intermediate liner disposed between the inner shell and the outer shell. 5. The assembly of claim 3, wherein the outer shell is galvanized carbon steel or stainless steel. 6. The assembly of claim 4, wherein the intermediate liner is polyurethane foam. 7. The assembly of claim 1, wherein at least a portion of the inner shell includes at least seven layers, including double bias glass fabric, chopped fiberglass, aramid fabric, double bias glass fabric, chopped fiberglass, aramid fabric, and double bias glass fabric. 8. The assembly of claim 1, wherein at least a portion of the inner shell includes at least ten layers, including double bias glass fabric, chopped fiberglass, aramid fabric, four layers of double bias glass fabric, chopped fiberglass, aramid fabric, and double bias glass fabric. 9. The assembly of claim 1, wherein the outer container includes first and second ends and wherein at least a portion of the inner shell at either of the first and second ends further includes a stiffening member. 10. The assembly of claim 1, wherein the inner container has a body and a lid, and wherein the inner container includes a clamshell closure system to secure the lid to the body. 11. The assembly of claim 10, wherein the outer container includes at least one recessed area in the inner cavity to receive the clamshell closure system. 12. The assembly of claim 1, wherein the inner container has a body and a lid, and wherein the inner container includes a ceramic gasket disposed between the body and the lid. 13. The assembly of claim 1, wherein the outer container includes first and second portions couplable to one another at an interface and a ceramic gasket disposed at the interface. 14. The assembly of claim 13, wherein the ceramic gasket is a silicone-coated ceramic gasket. 15. The assembly of claim 13, wherein the first and second portions, when coupled to one another at the interface, are securable to one another by a plurality of latches and a plurality of fasteners. 16. The assembly of claim 1, wherein the outer container includes at least one forklift pocket for transportation of the assembly by a forklift. 17. An outer container to provide protection for an inner container for transporting radioactive material, the outer container comprising first and second portions defining an inner cavity, the first and second portions both having an inner shell, wherein at least a portion of the inner shell comprises a plurality of layers including at least one layer of chopped fiberglass mat, at least one layer of aramid fabric, and at least one layer of a double bias glass fabric, wherein the inner shell further includes at least one stiffening member disposed in either of the first and second portions of the outer container, the stiffening member being oriented in a plane substantially transverse to a longitudinal axis extending through the outer container. 18. The outer container of claim 17, wherein at least a portion of the inner shell includes at least seven layers, including double bias glass fabric, chopped fiberglass, aramid fabric, double bias glass fabric, chopped fiberglass, aramid fabric, and double bias glass fabric. 19. The outer container of claim 17, wherein at least a portion of the inner shell includes at least ten layers, including double bias glass fabric, chopped fiberglass, aramid fabric, four layers of double bias glass fabric, chopped fiberglass, aramid fabric, and double bias glass fabric. 20. The outer container of claim 17, further comprising first and second ends, wherein at least a portion of the inner shell at either of the first and second ends further includes a stiffening member. 21. An outer container to provide protection for an inner container for transporting radioactive material, the outer container comprising:(a) first and second portions coupled to one another at an interface, wherein the first and second portions define an inner cavity, the first and second portions each having an inner shell, wherein at least a portion of the inner shell comprises a plurality of layers including at least one layer of chopped fiberglass mat, at least one layer of aramid fabric, and at least one layer of a double bias glass fabric, wherein the inner shell further includes at least one stiffening member disposed in either of the first and second portions of the outer container, the stiffening member being oriented substantially transverse to a longitudinal axis extending through the outer container; and(b) an outer container closure system for securing the first and second portions to one another, wherein the outer container closure system includes a plurality of latches and a plurality of fasteners. 22. The outer container of claim 21, wherein the outer container includes at least one forklift pocket for transportation of the assembly by a forklift. 23. A method of transporting radioactive material, comprising:(a) placing an inner container into an outer container, wherein the inner container contains the radioactive material, and the outer container includes first and second portions defining an inner cavity, the first and second portions both having an inner shell, wherein at least a portion of the inner shell comprises a plurality of layers including at least one layer of chopped fiberglass mat and, at least one layer of aramid fabric, and at least one layer of a double bias glass fabric, wherein the inner shell further includes at least one stiffening member disposed in either of the first and second portions of the outer container, the stiffening member being oriented in a plane substantially transverse to a longitudinal axis extending through the outer container; and(b) securing the first and second portions of the outer container using an outer container closure system, wherein the outer container closure system includes a plurality of latches and a plurality of fasteners.
	abstract	The invention relates to a rotary encoder comprising internal error control with a monitoring unit comprising at least a computing module, a verification means, a memory unit and an alarm unit. The invention also relates to a method for checking a rotary encoder when said encoder is in operation, the rotary encoder generating at least one measuring signal pair representative of the amount of rotation. In order to be able to determine the functioning of the rotary encoder, even when said rotary encoder is stationary, it is provided according to the present invention that a characteristic value should be created in the monitoring unit from current amplitude values of the measuring signal pair, said characteristic value being used in a comparison with at least one quality value representative of the functional states of the rotary encoder.
044773773	summary	INTRODUCTION The present invention relates to recovery of cesium ions from mixtures thereof with other ions by establishing a separate basic source phase containing the ions to be separated, including cesium ions, a separate recipient phase and a liquid membrane phase containing a macrocyclic polyphenol (calixarene) ligand in a liquid membrane solvent interfacing with said source and recipient phases, maintaining the interface contact for a period of time long enough to transport a substantial part of the cesium ions from the source phase to the recipient phase and recovering the cesium ions from the recipient phase. The process may be referred to as the selective transport of Cs+ through a liquid membrane by a macrocyclic polyphenol or calixarene ligand. BACKGROUND OF THE INVENTION The cyclic polyphenols comprising a ring of monomer units having the structures depicted in the drawing, first reported by A. Zinke and E. Ziegler, Chem. Ber., 77, 264-272 (1944), are somewhat similar in structure to the cyclic polyethers and other macrocyclic ligands which are characterized by their size-related selectivity in binding cations noted in J. D. Lamb, R. M. Izatt, J. J. Christensen, D. J. Eatough, COORDINATION CHEMISTRY OF MACROCYCLIC COMPOUNDS, edited by G. A. Melson, Plenum, pages 145-217 (1979). The synthetic chemistry of compounds of this type has received careful study, expecially by Gutsche and his coworkers, who have designated these compounds calixarenes, C. D. Gutsche, R. Muthukrishnan, J. Org. Chem. 43, pages 4905-4906 (1978). Synthesis of cyclic heptamers of similar structure has been reported by H Kammerer and G. Happel, Makromol.Chem. 181, pages 2049-2062 (1980) and of cyclic pentamers by A. Ninagwa and H. Matsuda, Makromol.Chem.Rat.Comm.3, pages 65-67 (1982). The oligomeric hexameric and tetrameric compounds depicted in the drawing have been described by C. D. Gutsche, B. Dhawan, K. H. No and R. Muthukrishnan, J. Am. Chem.Soc.,103, pages 3782-3792 (1981). Such compounds are Bronsted-Lowry acids which E. M. Choy, D. F. Evans, E. L. Cussler, J. Am.Chem.Soc.,96, pages 7085-7090 (1974) used successfully to drive the flux of Na+ against the concentration gradient of monensen. SUMMARY OF THE INVENTION The invention is based on the discovery that calixarenes are very effective as membrane carriers of cesium cations. They are characterized by a high degree of transport selectivity for Cs+ over other alkali metal cations, a low solubility in water, which minimizes loss to adjacent water phases, and the formation of neutral cation complexes through loss of a proton so that the anion does not need to accompany the cation through the membrane. This latter property makes it possible to couple the transport of cations in the reverse flux of protons through the membrane.
047114363	claims	1. A retention strap for holding in assembled relationship before welding a grid assembly comprising mating, perpendicular inner straps, and outer straps extending about said inner straps, comprising four bars, each of generally "H" shape, and including a pair of end posts connected together by a cross member, each post having openings therethrough located above and below the connecting cross member, means for hingedly connecting first and second said bars and means for hingedly connecting third and fourth said bars to provide pairs of hinged bars, and means for releasably connecting two said pairs of bars. 2. A retention strap as in claim 1, said means for hingedly connecting two of said bars comprising hinge elements extending from a said post of each bar, said hinge elements being in vertically spaced relation and the pivotal axis of said hinge elements being spaced from the adjacent edges of said posts. 3. The retention strap of claim 1, said means for releasably connecting two pairs of bars comprising vertically spaced means for connecting adjacent bars with a space between the adjacent edges of adjacent bars. 4. The retention strap of claim 2, said means for releasably connecting two pairs of bars comprising vertically spaced means for connecting adjacent bars with a space between the adjacent edges of adjacent bars.
	abstract	A plasma doping method, even though a plasma doping treatment is repeated, can make a dose from a film to a silicon substrate uniform for each time. The method includes preparing a vacuum chamber having a film containing an impurity formed on an inner wall thereof such that, when the film is attacked by ions in plasma, the amount of an impurity to be doped into the surface of a sample by sputtering is not changed even though the plasma containing the impurity ions is repeatedly generated in the vacuum chamber; placing the sample on the sample electrode; and irradiating the plasma containing the impurity ions so as to implant the impurity ions into the sample, and doping the impurity into the sample by sputtering from the film containing the impurity fixed to the inner wall of the vacuum chamber.
	claims	1. A plasma generation system comprisinga shock coil having an annular disc shaped body bounded by an outer ring formed about an outer periphery of the body and an annular hub formed about an inner periphery of the body and a coil of parallel wound wires attached to a face of the body, anda Laval nozzle for introducing gas to the shock coil, the nozzle comprising an annular disc-shaped nozzle body coupled about an inner periphery of the nozzle body to the hub and forming with the hub about an outer periphery of the nozzle body a radially oriented annular nozzle outlet positioned adjacent the inner periphery of the body of the shock coil, wherein the nozzle is oriented to radially discharge a gas across the surface of the coil from the inner toward the outer periphery of the body of the shock coil, wherein when a gas is discharged across the surface of the coil and the coil is energized an annular plasma is ejected from the surface of the coil. 2. The plasma generation system of claim 1 wherein the coil of parallel wound wires is a single-turn coil. 3. The plasma generation system of claim 2 wherein the coil of parallel wound wires is a multi-strand coil. 4. The plasma generation system of claim 1 wherein the wires of the coil of parallel wound wires begin adjacent an outer radius of the body at angularly spaced points and encircle the face of the body one turn ending at an inner radius of the body. 5. The plasma generation system of claim 4 wherein the wires of the coil of parallel wound wires begin at the perimeter of the body. 6. The plasma generation system of claim 1 wherein a face of the nozzle body facing the hub forms an annular shaped gas plenum and a constricting-expanding nozzle with a face of the hub. 7. The plasma generation system of claim 6 further comprising a plurality of gas channels formed in the hub and in communication with the gas plenum. 8. The plasma generation system of claim 7 further comprising a valve seat ring having a plurality of valve seats aligned with the plurality of gas channels. 9. The plasma generation system of claim 1 further comprising a shroud coupled to the outer ring. 10. The plasma generation system of claim 1 wherein the shock coil is configured to fire the wires in a synchronized manner. 11. The plasma generation system of claim 1 wherein the wires are combined into a plurality of groups of wires that are azimuthally symmetric about the surface of the shock coil.
062781251	abstract	A shielded radiation assembly provides easy access to a radiation treatment space while minimizing radiation leakage. The shielded radiation assembly includes a support structure and a radiation shield supported on the support structure. A radiation emitting device is movably supported on the support structure for movement independent of the radiation shield. The radiation shield may be flexible, including a plurality of radiation shielding sections which are supported by the support structure. The radiation shielding section may be formed of the radiation absorbing material.
	claims	1. A radioactive gas monitor comprising:a detection unit that detects radiation emitted from radioactive nuclides contained in sample gas; anda measurement unit that processes a signal transmitted from the detection unit and outputs an engineering value corresponding to radioactive concentration, whereinthe detection unit has a detection tube through which the sample gas flows, a first detector to which a first concentration measurement range within all required measurement ranges of radiation is allocated, a second detector to which a second concentration measurement range within all required measurement ranges of radiation is allocated, wherein concentrations in the second concentration measurement range are higher than concentrations in the first concentration measurement range, and a shield which shields the detection tube, the first detector, and the second detector from environmental radiation,the measurement unit has a first measurement unit which processes a signal transmitted from the first detector and a second measurement unit which processes a signal transmitted from the second detector,the shield has at least one detector installing hole having a central axis orthogonal to a central axis of the detection tube, andat least the first detector between the first detector and the second detector is arranged inside the detector installing hole, and an inner diameter of the detection tube and a relative position between the detection tube and the first detector are determined so that the measurement range of the first detector and the measurement range of the second detector are overlapped with each other. 2. The radioactive gas monitor according to claim 1, whereinthe shield has one detector installing hole, anda radiation sensor of a columnar scintillation detector used as the first detector is arranged inside the detector installing hole, and a cylindrical ionization chamber used as the second detector is arranged side by side in parallel with the detection tube. 3. The radioactive gas monitor according to claim 2, whereinthe second measurement unit includes a logarithmic amplifier which inputs a DC current output from the cylindrical ionization chamber and outputs a voltage by converting the DC current into the voltage proportional to a logarithm of the DC current. 4. The radioactive gas monitor according to claim 2, whereinthe columnar scintillation detector has a preamplifier which converts a current pulse output from the radiation sensor into an analog voltage pulse, and the preamplifier is installed outside the shield. 5. The radioactive gas monitor according to claim 2, whereina collimator which narrows down radiation incident on the radiation sensor arranged inside the detector installing hole is disposed inside the detector installing hole. 6. The radioactive gas monitor according to claim 2, whereina detector temperature sensor is attached to a radiation sensor of the columnar scintillation detector, andbased on a temperature signal input from the detector temperature sensor, the first measurement unit performs temperature compensation on an engineering value corresponding to radioactive concentration. 7. The radioactive gas monitor according to claim 1, whereinthe shield has two detector installing holes arranged so as to oppose each other across the detection tube, anda radiation sensor of a columnar scintillation detector used as the first detector is arranged inside one detector installing hole, and a radiation sensor of a fibrous scintillation detector used as the second detector is arranged inside the other detector installing hole. 8. The radioactive gas monitor according to claim 7, whereinthe columnar scintillation detector has a preamplifier which converts a current pulse output from the radiation sensor into an analog voltage pulse, and the preamplifier is installed outside the shield. 9. The radioactive gas monitor according to claim 7, whereinthe radiation sensor of the fibrous scintillation detector has a light guide which is optically bonded to a scintillation fiber which is cut to have a predetermined length, and a photomultiplier tube which is optically bonded to the light guide. 10. The radioactive gas monitor according to claim 7, whereinthe fibrous scintillation detector has a preamplifier which converts a current pulse output from the radiation sensor into an analog voltage pulse, and the preamplifier is installed outside the shield. 11. The radioactive gas monitor according to claim 7, whereina collimator which narrows down radiation incident on the radiation sensor arranged inside the detector installing hole is disposed inside the detector installing hole. 12. The radioactive gas monitor according to claim 7, whereina detector temperature sensor is attached to a radiation sensor of the columnar scintillation detector, andbased on a temperature signal input from the detector temperature sensor, the first measurement unit performs temperature compensation on an engineering value corresponding to radioactive concentration. 13. The radioactive gas monitor according to claim 7, whereina detector temperature sensor is attached to a radiation sensor of the fibrous scintillation detector, andbased on a temperature signal input from the detector temperature sensor, the second measurement unit performs temperature compensation on an engineering value corresponding to radioactive concentration. 14. The radioactive gas monitor according to claim 1, whereinthe detection unit includes a sample gas temperature sensor which detects a temperature of sample gas flowing through the detection tube, and a sample gas pressure sensor which detects a pressure of the sample gas flowing through the detection tube, andthe measurement unit obtains a sample gas temperature and a sample gas pressure, based on a temperature signal input from the sample gas temperature sensor and a pressure signal input from the sample gas pressure sensor. 15. The radioactive gas monitor according to claim 14, wherein based on the sample gas temperature and the sample gas pressure, the measurement unit outputs an engineering value corresponding to radioactive concentration by converting the engineering value into a predetermined temperature and pressure.
	description	This application is a continuation of U.S. Ser. No. 11/154,085 filed Jun. 16, 2005, which application is a continuation of U.S. Ser. No. 10/619,702 filed Jul. 15, 2003, which claims priority to U.S. provisional patent application Ser. No. 60/396,322 filed Jul. 17, 2002, the disclosures of which are incorporated herein by reference. The disclosed methods and apparatus relate generally to the construction and use of magnetic focusing and correction elements for modifying the intensity distribution of ions within ribbon beams and more particularly to precision correction of the angle of incidence of ions used for implanting and doping in semiconductor devices. The process of ion implantation is useful in semiconductor manufacturing as it makes possible the modification of the electrical properties of well-defined regions of a silicon wafer by introducing selected impurity atoms, one by one, at a velocity such that they penetrate the surface layers and come to rest at a specified depth below the surface. It makes possible the creation of three-dimensional electrical circuits and switches with great precision and reproducibility. The characteristics that make implantation such a useful processing procedure are threefold: First, the concentration of introduced dopant atoms can be accurately measured by straight-forward determination of the incoming electrical charge that has been delivered by charged ions striking the wafer. Secondly, the regions where the above dopant atoms are inserted can be precisely defined by photo resist masks that make possible precision dopant patterning at ambient temperatures. Finally, the depth at which the dopant atoms come to rest can be adjusted by varying the ion energy, making possible the fabrication of layered structures. Systems and methods are desired for enhancing the ion implantation process. The ion species presently used for silicon implantation include arsenic, phosphorus, germanium, boron and hydrogen having energies that range from below 1 keV to above 80 keV. Ion currents ranging from microamperes to multi-milliamperes are needed. Tools providing implant currents greater than about 0.5 mA are commonly referred to as ‘high-current’ implanters. Trends within the semiconductor industry are moving towards implantation energies below 1 keV and control of angle of incidence below 1.degree. Typically, an ion implanter for introducing such dopant materials into silicon wafers and other work pieces may be modeled into four major systems: First, an ion source where the charged ions to be implanted are produced. Secondly, an acceleration region where the energy of the ions is increased to that needed for a specified implant procedure. Thirdly, an optical ion transport system where the ion ensemble leaving the source is shaped to produce the desired implant density pattern and where unwanted particles are eliminated. Finally, an implant station where individual wafers are mounted on the surface of an electrostatic chuck or a rotating disc that is scanned through the incoming ion beam and where a robot loads and unloads wafers. One aspect of the present invention aims towards enhancing or improving ion beam transport systems. A recent improvement for ion implanter design has been the introduction of ribbon beam technology. Here, ions arriving at a work piece are organized into a stripe that coats the work piece uniformly as it is passed under the ion beam. The cost advantages of using such ribbon beam technology are significant: For disc-type implanters, ribbon-beam technology eliminates the necessity for scanning motion of the disc across the ion beam. For single-wafer implanters the wafer need only be moved under the incoming ribbon beam along a single dimension, greatly simplifying the mechanical design of end-stations and eliminating the need for transverse electromagnetic scanning. Using a correctly shaped ribbon beam, uniform dosing density is possible across a work piece with a single one-dimensional pass. The technical challenges of generating and handling ribbon beams are non trivial because the ribbon beam/end station arrangement must produce dose uniformities better than 1%, angular accuracies better than 1 degree and operate with ion energies below 1 keV. U.S. Pat. No. 5,350,926 entitled “High current ribbon beam ion implanter” and U.S. Pat. No. 5,834,786, entitled “Compact high current broad beam ion implanter”, both issued to White et al., present some features of ribbon beam technology. White et al. have also reviewed some of the problems of generating ribbon beams in an article entitled “The Control of Uniformity in Parallel Ribbon Ion Beams up to 24 Inches in Size” presented on page 830 of the 1999 Conference Proceedings of Applications of Accelerators in Research and Industry”, edited by J. L. Dugan and L Morgan and published by the American Institute of Physics (1-56396-825-August 1999). By its very nature, a ribbon beam has a large width/height aspect ratio. Thus, to efficiently encompass such a beam traveling along the Z-axis, a focusing lens for such a beam must have a slot-like characteristic with its slot extending along the X-axis and its short dimension across the height of the ribbon (the Y-direction). The importance of this is that, while the focal lengths of a magnetic quadrupole lens in each dimension are equal but of opposite sign, the angular deflections of the ribbon's boundary rays in the width and height dimensions can be very different. In addition, the magnetic field boundaries of the lens can be close to the ion beam permitting local perturbations introduced along these boundaries to have deflection consequences that are effectively limited to a small region of the ribbon beam. While in principle it is feasible to generate a wanted shape of ribbon beam directly from an ion source, in a practical situation full-length ribbon extraction may not be feasible. Often it is desirable to generate a modest-length ribbon at the source and expand it to the width required for implantation, using ion-optical expansion. Another aspect of the present invention is directed towards extracting ions from an ion source in the form of a multiplicity of individual beamlets whose central trajectories are parallel and arranged in a linear manner. Such geometry provides a precise definition of the origin and angular properties for each beamlet. Those skilled in the art will recognize that these principles remain valid even if multiple parallel rows of beamlets are used or if the central trajectories of the beamlets are not parallel when they leave the source region or if a slit-geometry is chosen for ion extraction. Furthermore, those skilled in the art will recognize that focusing and deflection elements will be needed to transport the ions between an ion source and a work piece where the particles are to be implanted. For focusing lenses to operate as ideal focusing elements it is desirable that, to first order, the angular deflection introduced to the trajectory of individual beamlets be proportional to the beamlets distance from the lens symmetry axis; namely, the magnitude of the deflecting fields should increase linearly with distance from the central trajectory of the ion beam. Quadrupole lenses satisfying the linearity requirement described above and having high length to height aspect ratio have been described by W. K. Panofsky et al. in the journal Review of Scientific Instruments volume 30, 927, (1959), for instance. Basically, their design consists of a rectangular high permeability steel frame with each of the long sides of the frame supporting a single uniformly wound coil. To generate a quadrupole field the top and bottom coils are wound equally spaced along each of the long sides of the steel frame members with the currents through the coils being excited in opposite directions when viewed from one end of the rectangular array. A north pole at the end of one bar sees a south pole facing it. On the short sides of the rectangular frame, additional coils are used to buck the magnetostatic potential at both ends of each long side preventing magnetic short circuits through the end-bars. For quadrupole field generation the opposing ampere-turns along each vertical bar are equal to the ampere-turns along each of the long bars. The currents passing through these two bucking coils will be equal but generate fields in opposing directions. For many focusing applications the correction of aberrations and the compensation of non-linear spreading of a low energy beam is critical so that the possibility for producing deviations from a linear growth of magnetic field away from the center is desirable. A method for introducing the necessary multipole components to the field has been described by Enge '328 in U.S. Pat. No. 3,541,328, particularly, the method described in this document for producing multipole focusing fields in the space between two iron cores between which ions are passed. A series of independently excitable windings, each having a coil distribution appropriate for generating a specific multipole, are wound along each of the iron cores. In the journal Nuclear Instruments and Methods, volume 136, 1976, p 213-224 H. J. Scheerer describes the focusing characteristics of such a dual rod design in accordance with the description in U.S. Pat. No. 3,541,328. Specifically, in FIG. 6 of this patent it can be seen the coils for each multipole are connected in series and powered as a single unit. The Panofsky quadrupoles and Enge multipole generators were both conceived for transmitting ions through a beam transport system where the parameters of the ion transport elements are fixed for a single experiment or measurement. They suffer disadvantages when active control of the deflecting fields is needed to correct beam parameters. First, neither design generates a dipole field contribution where the B-field is along the long axis of the rectangle. Secondly, the symmetry point (x=0) is usually established from the geometry of the coils and of the steel yokes so there is no easy way to introduce steering about the y-axis by moving the center of the lens-field distribution. In an embodiment of the present invention, a rectangular steel window frame construction provides the magnetic supporting structure needed for producing the wanted deflection fields. A feature of the present embodiment is that the windings along the long-axis bars consist of a large number of independently excited short sections. This concept allows high-order multipoles to be generated without dedicated windings and the central point of any multipole contribution can be translated along the transverse x-axis. Additional coils around the end bars are essential for eliminating magnetic short circuits when multipole components are being generated. However, these end-bar coils can also be excited independently in a manner that allows the production of a pure dipole field between the long-axis bars at right angles to the long dimension of the rectangle. Finally, when the coils on the end bars are switched off, dipole fields can be generated along the long axis of the window frame. In another embodiment of the present invention, local variations in ion density or the shape of the ribbon beam at the exit from the source are corrected by locally modifying the deflecting fields. These corrections can be made under computer control and on a time scale that is only limited by the decay rate of eddy currents in the steel. The input beam parameters needed for control involves position-sensitive faraday cups for measuring the intensity and angle distribution of ions within said ribbon beam allowing discrepancies from the wanted distribution to be corrected by modifying the deflection fields. While each of the applications of such lens variations will be discussed further, it should be appreciated that, because of linear superposition of fields in free space, the currents necessary to produce a particular type of correction can be calculated individually. This process can be repeated for each type of correction needed with the complete solution being produced by superposition. Such concurrent introduction of a selected group of multipole fields into a single beam transport element has been described by White et al. in the journal Nuclear Instruments and Methods volume A 258, (1987) pp. 437-442 entitled “The design of magnets with non-dipole field components”. The fundamental concept underlying the present invention is the creation of a region filled with magnetic fields that encompasses all trajectories comprising a ribbon beam. The d.c. magnetic fields having a magnitude and direction throughout the region that is appropriate to introduce the wanted deflections of all beamlets constituting the ribbon beam. Within the constraints implied by Maxwell's equations, magnetic field configurations can be chosen that provide controlled changes in the angular coordinates of beamlets and produce superposed corrections for: (1) angular errors, (2) differential intensity errors, (3) uniform steering about axes normal to both (y.sub.0, z.sub.0) and (x.sub.0, z.sub.0) planes, (4) the introduction of linear positive and negative focusing, (5) specialized deflection fields for aberration correction. Other objects and advantages will become apparent herinafter in view of the specifications and drawings. The unique properties of the system according to the present invention will be better elucidated by reference to a practical example. In this example, a pair of quadrupole lenses are used to expand an initially parallel set of beamlets to a broader set of parallel beamlet trajectories. FIG. 1 illustrates the beam coordinate system used in the following discussions. Three representative sections, 120, across a ribbon beam are shown. The X-axis is always aligned with the surfaces, 120, at right angles to the beamlets, 130, comprising the ribbon beam and along the surface's long axis. The Z-axis, 110, is tangential to the central trajectory, of the ribbon beam and remains coincident with the central trajectory throughout the length of the ion optical transport system, causing it to change direction as the central trajectory, 110, changes direction. At each point along the beam path the Cartesian Y-axis lies also in the surface, 120, and along the ribbon beam's cross-sectional narrow dimension. FIG. 2 shows the essential structure of an ion beam expander, 200, that optically couples an ion source, 201, having narrow width, to produce a ribbon height at a work piece or wafer, 220, that allows simultaneous ribbon beam implantation across the whole wafer width in a single traverse of the wafer 220, using linear reciprocating motion, 221. A short ribbon beam generated by the ion source 201, in the form a group of beamlets arranged in a linear array, 210, is expanded so that its width at a converging lens, 250, matches that needed at a work piece, 220, being implanted. The beam expander, 200, further comprises a diverging lens, 230, followed by a free-space drift region, 240, where the individual ion beamlets drift apart before they are collimated back to parallelism by the larger width converging lens, 250. In the preferred embodiment the work piece, 220, passes under an expanded ribbon beam pattern, 260, at constant velocity with the angle of incidence being adjustable by rotating the wafer about an axis, 270, to modify the ion impact angle, .theta. When the wafer is rotated about the axis, 270, to large angles, the beam width can be adjusted by modifying the expansion ratio to minimize beam wastage. For the geometry of FIG. 2 the ion density should be constant across the width of the ribbon beam. However, for geometries such as those of a rotating disc type implanter, the ion density within the ribbon beam must vary with implant radius. In this case, it will be clear that to produce doping uniformity at the work piece the ribbon beam ion density will generally require active correction across the ribbon beam. FIG. 3 shows the basic features of lens correctors according to the embodiment of the present invention. A high-permeability rectangular steel structure, 310, aligned with its long axis parallel to the width of a ribbon beam, 320, (X-coordinate) and with its geometric center coincident with the geometric center of the ribbon beam, supports coils, 330, 340, that are used to generate the wanted magnetic fields within a gap, 312, through which the ions forming the ribbon beam, 320, are directed. Individual coils, 330, 340, shown schematically, are distributed along both long-axis bars, 314, 316, of the rectangular steel structure, 310, with individual controllable power supplies establishing the current through each of the coils via the circuits, 350 and 351. While, for clarity, the individual coils, listed as 330 and 340, are shown with considerable separation, in practice the coils should be as close together as is practical to allow the magnetic field on the axis of beam region, 322, to vary smoothly. For some applications where the coils, 330, and 340, must have large cross section to minimize power dissipation, thin ferromagnetic plates (not shown) can be used to separate individual coils and relay the scalar potentials nearer to the ion beam boundaries. Alternatively, the coils 330 and 340 may be connected together as a continuous coil. End coils, 332 and 342, shown in FIG. 3, are not necessarily divided into multiple elements. Their primary function is to establish appropriate magnetostatic potentials that prevent magnetic short circuits between the upper and lower steel bars, 314, and 316. During quadrupole operation equal and opposite ampere-turns must be generated by coils, 332 and 342, to the ampere turns applied along the long axes of the rectangular structure. To make possible the production of several deflection modes the current directed through the end coils, 332 and 342, should be reversible and adjustable with precision. During the generation of dipole magnetic fields along the X-axis, coils 332 and 342, may be turned off. FIG. 4, illustrates a cross-section as viewed along the line A-A′, in the x-direction, shown in FIG. 3 with the addition of a surrounding vacuum enclosure. It can be seen that small high permeability steel tabs, 420 and 422, mentioned earlier, transfer the magnetostatic potential generated along each bar, 314 and 316, to the boundaries of the ion beam region, 322. The straight section of the steel tabs, 420 and 422, should be located as close as possible to the ion beam to localize the position resolution of correcting field components. Without reservations, the projections shown in FIG. 5 show the preferred embodiment of a lens-corrector enclosure. The design goal for the enclosure is to avoid exposure of the vacuum environment to the coils and their insulation. Also, to avoid vacuum to air feed-throughs for power feed and water-cooling channels. Basically, a magnetic lens/corrector can operate at ambient atmospheric pressure inside such an enclosure, 510. It has vacuum on the outside, 500, and ambient atmospheric pressure or liquid cooling on the inside, 510. The enclosure must have a depth along the Z-axis adequate to contain a coil structure as described in FIGS. 3 and 4 and sufficient magnetic path length along the ion beam that the ions can be deflected through the wanted correction angle. While those skilled in the art will recognize that there are many methods of fabricating the enclosure, 510, in the present embodiment the enclosure is machined from a suitable block of aluminum jig-plate. During operation the enclosure, 510, is bolted to a housing that is part of an implantation system's vacuum envelope, 530. Such a construction serves to define the position of the corrector element with respect to other optical elements that are part of the beam transport components used in an implanter. The corrector lens shown in FIG. 3 or 4 may be connected to the ambient atmosphere via connecting holes, 540 and 542. Through these holes, 540 and 542, pass electric power leads for each of the coils plus air or liquid cooling for the coils. The enclosure, 510, is made vacuum tight by attaching a simple plate, 550, to the flat surface, 560, sealed with O-rings, 552. The cross section view of FIG. 6 illustrates an assembled structure of a typical lens-corrector, 600, where like elements are described in previous embodiments. The rectangular high permeability bar structure, 314 and 316, is the basis of the rectangular window frame. It will be seen that for ease of wiring and cooling the steel bars may be fabricated from appropriate steel tubing that will allow easy access for the wiring and cooling lines. The Z-axis of the ribbon beam plane passes through the open center, 322, of the corrector. Power and cooling are introduced through the penetrations, 542. The electrical connections are arranged using the distribution panel, 610. FIG. 7 illustrates the background to the generation of a quadrupole field in the region between rectangular bars, 314 and 316, and how such a distribution can be modified to correct for aberrations. Assuming that a uniform current sheet, j.sub.z(x), 701, 702, is produced as illustrated by the modules around the surface of each bar, these current sheets will generates a magnetic field, B.sub.x(x), in the immediate surface of the winding given byB.sub.x(x)=.mu..sub.0.multidot.j.sub.z(x) (1) To generate a pure quadrupole field, j.sub.z(x) is constant for all values of x. Applying Ampere's theoremB.sub.y(x)=(.mu..sub.0/d).multidot.j(x).multidot.x (2) Where d is the distance from each bar to the center line, 710. Thus, for uniform currents flowing in the manner shown by the arrows in FIG. 7 a north pole generated at the end of one bar sees a south pole immediately opposite on the adjacent steel bar with the magnetic field B.sub.y(x) being zero at the center of the x-dimension, measured between the vertical steel connecting bars, 721, 722, and increasing linearly from the center to each end changing sign at the center Those skilled in the art will recognize, because of superposition, that within the resolution limit of the geometry and assuming no saturation of the steel, whatever multipole is required can be excited by choosing the appropriate distribution of the current density, j(x). Clearly, individual windings having constant current and variable pitch can provide the needed variations in j(x) as has been disclosed in U.S. Pat. No. 3,541,328. However, it is realized that whatever multipole is needed can be excited by using a single group of windings provided the single winding layer is divided into a large number of short individually excited coils, 330 and 340, as illustrated in FIG. 3. Some Specific Geometries FIG. 8 is a graphical representation for understanding the generation of multipole fields that can be introduced by a lens corrector according to the embodiment of the present invention. Because excitation currents are d.c., or do not change rapidly with time, it is unnecessary to include vector potentials in the field description. Such a simplification allows the use of magnetostatic potentials, alone, for calculating the magnetic B-fields (the magnetic induction). The usefulness of this approach is that under these conditions the same equations are satisfied for magnetostatic fields as are satisfied for electrostatic fields with the driving potential for magnetostatic fields being ampere-turns rather than volts. However, it should be emphasized that such an analysis must not include the regions of current excitation which surrounds individual steel bars. Referring to equation (2) it can be seen that for quadrupole generation the difference between the magnetic potentials generated along each bar increases linearly from one end of the lens to the distant end. Thus, assuming uniformly spaced windings and equal currents through each winding, the loci of the associated magnetostatic equipotentials along each bar are straight lines that pass through zero at the center of each bar, because of symmetry. The B.sub.y(x) fields, which are produced between the bars, 314 and 316, described in FIG. 3, are excited by the negative gradient of the magnetostatic potential difference. As the distance between the high permeability steel tabs, 420 and 422, described in FIG. 4, is constant along the width of the lens/corrector, the difference between the magnetostatic potentials of each bar allows B.sub.y(x) to be calculated directly. Using this same presentation, FIGS. 9a and 9b show schematically the manner in which expansion (or contraction) of a ribbon beam ensemble can be accomplished. In FIG. 9a the magnetostatic equipotentials, 910 and 912, associated with a diverging lens, 930, in FIG. 9b produce a reduced-size ribbon beam, 950, starting from a fully expanded beam, 960, produced by equipotentials, 920 and 922. A simple linear change of all of the currents through all of the elementary coils, 330 and 340, allows expansion of the width of the ribbon beam to appropriate size before the ribbon beam impacts the wafer, 970. In FIGS. 10a and 10b, an individual beamlet, 980, is assumed to leave an ion source, 901, with intensity lower than anticipated for the remainder of the beamlets. To compensate for the reduced local ion density in the ribbon beam the fan-out pattern produced by the diverging lens, 930, is locally compressed around the attenuated beamlet, 980, by reducing the angular spacing between trajectories, 982, and 984. When satisfactory uniformity has been achieved at the entrance to lens 940, the overall spread of the fan is modified, as shown in FIGS. 9a and 9b, to allow uniform implantation of the whole work piece. It can be seen from the magnetostatic potential plot that for both bars forming the diverging lens, 930, the magnetostatic potentials, 924 and 926, no longer increase linearly from the center of each bar but rather has been reduced locally, at 925 and 927, to introduce a non-linearity in deflection angles for trajectories 984 and beyond that restores uniformity of implant intensity along the width of the ribbon beam. If necessary, angle corrections to compensate for this non-linear deflection can be introduced in lens, 940. There is a one-to-one correspondence between position along the final ribbon beam and the coil location along the first quadrupole bar allowing the computer correction algorithm to be simple and straight forward. FIGS. 11a and 11b show a method for introducing ribbon beam shifts along the x-direction or a rotation around the y-axis normal to the X-Z plane of FIG. 11b. Basically, to introduce a parallel shift all of the individual coils along both bars of the lens/corrector, 930, are electrically energized to produce a zero, 990, that is offset from the nominal center of the lens, 930. A compensating correction needed for the lens 990. To produce rotation about the y-axis the collimating currents through the lens 940, are adjusted appropriately to not return the output trajectories to being parallel to the ions leaving the source, 901. The principles used for producing the above offset in an alternate embodiment of the present invention are illustrated in FIG. 12. The coils, 330 and 340, illustrated in FIG. 3 and distributed along the bars, 314, and 316, are not energized and are left from the drawing to minimize confusion. The bucking coils, 332, 342, produce a uniform strip of magnetic B.sub.y-field, 328, that in the median plane is wholly parallel to the direction of the y-axis. Thus, there is no B.sub.x-field component along the x-direction so that it is not possible to induce motion out of the X-Z plane. Steering about the Y direction is fully decoupled from lens action and steering about the X-direction. FIGS. 13a and 13b, show a method for generating uniform B-fields along the x-direction. In FIG. 13a a pair of magnetostatic potentials, 1310 and 1316 are generated each having equal magnitude and direction along the individual bars with respect to one end. This can be achieved by energizing the coil collection, 330 and 340, shown in FIG. 3, uniformly and with the same hand. While the contribution to the magnetostatic potential from both bars would ideally be equal, it is possible for them to be unequal, as is shown in FIG. 13a. In practice, without exceptions, superposition allows all of these previously described field arrangements to be added together to produce a combination deflection structure that produces focusing, corrections of aberrations, corrections for differential variations in source output, and local steering across the ribbon ion beam around both X and Y axes. The constraint is that saturation should be minimal in the ferromagnetic members. A Useful Lens/Corrector Geometry. FIG. 14 illustrates the design of a lens/corrector assembly consisting of two independent elements, 1430 and 1431, between which a ribbon beam can be directed through the slot, 322. Such a lens/corrector assembly, which is topologically identical to the rectangular steel bar structure illustrated in FIG. 3, has useful characteristics for insertion into the vacuum region of a beam-transport pipe and into the fringe field regions of a magnetic deflector where the vertical steel parts of the rectangular bar structure, 310, in FIG. 3, would short circuit the poles producing the magnetic deflection field. In principle, the vertical bars, 312, illustrated in FIG. 3, together with their associated windings, 332 and 334, have been severed at the central symmetry-point of each of the bucking windings. Referring again to FIG. 14, the bucking windings associated with the cut-away upper bar are labeled 1400, 1401. The windings that produce the focusing field are labeled 1410. After severance it should be arranged that the same current continues to pass through the resulting ‘half-windings’, 1400, 1401, so that when a lens/corrector is used in lens mode each resultant half winding will produce half the ampere turns as the original windings 332 and 334, illustrated in FIG. 3. Each element has three independently wound excitation coils that, if necessary, can themselves be wound as a collection of independent coils, 330, such as those shown in FIG. 3, to allow the introduction of multipole correction fields. Just as in the structure presented in FIG. 3 where the ampere-turns around the whole bar structure must integrate to zero, the symmetry of the independent element array, 1430 and 1431, requires that along the length of each element the total magnetostatic potential must integrate to zero. FIG. 14 illustrates the cross section of a quadrupole designed according to the above prescription. A ferromagnetic bar is located at the center of each element. This bar need not have a cylindrical cross section, but those skilled in the art will recognize that the cross-sectional area must be adequate to avoid saturation. Three independent winding sections, 1400, 1401 and 1410, are wrapped around each bar. To allow multipole generation and aberration correction the individual winding sections can themselves consist of a group of individually excited coils as was illustrated in FIG. 3, item 330. Ferromagnetic extension tabs, 420, introduced in the manner shown in FIG. 4, transfer the magnetostatic potential, generated along the length of the central steel bar, close to the boundary of the ribbon ion beam. The effect is to minimize the volume of magnetic field that must be produced and the needed ampere turns. Also, to improve the spatial resolution of the lens/corrector fields at an ion beam boundary in the lens aperture. Without reservations the bars and associated coil structures are enclosed within closed tubes, 1430, 1435, manufactured from a suitable non-magnetic material having rectangular cross section. This enclosing tube structure permits the outside walls of the tube to be in vacuum while power leads to the coils and air or water cooling is readily accessible through the ends, 1460 and 1461. A useful feature of the lens/corrector presented in FIG. 14 is while the total magnetostatic potential generated along each element must integrate to zero, it is not essential to pass equal currents through the windings within the elements 1430 and 1431. An unbalance in current ratio between the two elements changes the position of the neutral axis of the lens causing it to move in the Y-direction an introduce steering of an ion beam about the X-axis. Hydrogen Implanter: FIG. 15, a further embodiment of the present invention, shows the principles of a high current H.sup.+ implanter for implanting ions into large-diameter semiconductor wafers using the ion transport elements described earlier. A suitable ion source, 10, produces a ribbon array of beamlets, 12, with all beamlets having the same energy, between 10 keV and 100 keV. A multipole corrected diverging lens, 20, introduces diverging angles into the array, 22, of beamlets to produce the necessary ribbon width. A momentum-dispersing magnetic field, 30, with its B-field vector in the plane of the diverging beamlets and approximately at right angles to the central beamlet of the array, deflects the ions at right angles to the plane of said ribbon beam allowing ions heavier than H.sup.+ to be collected into a cup, 40; this arrangement eliminates deuterium and other molecular contributions. A second multipole-corrected lens, 50, collimates the array of the diverging beamlets and returns the beamlets to parallelism. A platen supports a wafer, 60, and uniformly scans it, across the beam. This novel yet simple system employs no electromagnetic beam scanning. The advantages are short length, low cost, a simple optical path and small footprint. FIG. 16 shows the manner in which multiple-use coils can be mounted along a short section of one of the high permeability bars, 1617, to provide the high magnitude ampere-turns that are needed for exciting some deflection modes. It can be seen that continuous high-current capacity water-cooled coils, 1616, are wrapped as an under layer directly around a cylindrical magnetic core, 1617. Individually excitable coils, 1618, as shown in FIG. 3 as items 330 and 340, also surround the high permeability steel bar, 1615, to provide focusing and aberration corrections. Individual steel tabs 420, transfer the magnetostatic potentials to the region near to the beam. Any additional changes in the details, materials, and arrangement of parts, herein described and illustrated, can be made by those skilled in the art. Accordingly, it will be understood that the following claims are not to be limited to the embodiment disclosed here, and can include practices otherwise than those described, and are to be interpreted as broadly as allowed under the law.

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